add NLnet grant 2024-12-324 to readme

different widths must make values compare not equal otherwise interning
will e.g. substitute a 0x0_u8 for a 0x0_u2

.forgejo/workflows/deps.yml

@@ -12,10 +12,10 @@ jobs:
     outputs:
       cache-primary-key: ${{ steps.restore-deps.outputs.cache-primary-key }}
     steps:
-      - uses: https://code.forgejo.org/actions/checkout@v3
+      - uses: https://git.libre-chip.org/mirrors/checkout@v3
         with:
           fetch-depth: 0
-      - uses: https://code.forgejo.org/actions/cache/restore@v3
+      - uses: https://git.libre-chip.org/mirrors/cache/restore@v3
         id: restore-deps
         with:
           path: deps
@@ -58,19 +58,19 @@ jobs:
       - name: Get SymbiYosys
         if: steps.restore-deps.outputs.cache-hit != 'true'
         run: |
-          git clone --depth=1 --branch=yosys-0.45 https://github.com/YosysHQ/sby.git deps/sby
+          git clone --depth=1 --branch=yosys-0.45 https://git.libre-chip.org/mirrors/sby deps/sby
       - name: Build Z3
         if: steps.restore-deps.outputs.cache-hit != 'true'
         run: |
-          git clone --depth=1 --recursive --branch=z3-4.13.3 https://github.com/Z3Prover/z3.git deps/z3
+          git clone --depth=1 --recursive --branch=z3-4.13.3 https://git.libre-chip.org/mirrors/z3 deps/z3
           (cd deps/z3; PYTHON=python3 ./configure --prefix=/usr/local)
           make -C deps/z3/build -j"$(nproc)"
       - name: Build Yosys
         if: steps.restore-deps.outputs.cache-hit != 'true'
         run: |
-          git clone --depth=1 --recursive --branch=0.45 https://github.com/YosysHQ/yosys.git deps/yosys
+          git clone --depth=1 --recursive --branch=0.45 https://git.libre-chip.org/mirrors/yosys deps/yosys
           make -C deps/yosys -j"$(nproc)"
-      - uses: https://code.forgejo.org/actions/cache/save@v3
+      - uses: https://git.libre-chip.org/mirrors/cache/save@v3
         if: steps.restore-deps.outputs.cache-hit != 'true'
         with:
           path: deps

.forgejo/workflows/test.yml

@@ -4,12 +4,13 @@ on: [push, pull_request]
 
 jobs:
   deps:
+    runs-on: debian-12
     uses: ./.forgejo/workflows/deps.yml
   test:
     runs-on: debian-12
     needs: deps
     steps:
-      - uses: https://code.forgejo.org/actions/checkout@v3
+      - uses: https://git.libre-chip.org/mirrors/checkout@v3
         with:
           fetch-depth: 0
       - run: |
@@ -38,10 +39,11 @@ jobs:
             z3 \
             zlib1g-dev
       - run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain 1.80.1
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain 1.89.0
           source "$HOME/.cargo/env"
+          rustup component add rust-src
           echo "$PATH" >> "$GITHUB_PATH"
-      - uses: https://code.forgejo.org/actions/cache/restore@v3
+      - uses: https://git.libre-chip.org/mirrors/cache/restore@v3
         with:
           path: deps
           key: ${{ needs.deps.outputs.cache-primary-key }}
@@ -52,9 +54,11 @@ jobs:
           make -C deps/yosys install
           export PATH="$(realpath deps/firtool/bin):$PATH"
           echo "$PATH" >> "$GITHUB_PATH"
-      - uses: https://github.com/Swatinem/rust-cache@v2
+      - uses: https://git.libre-chip.org/mirrors/rust-cache@v2
         with:
           save-if: ${{ github.ref == 'refs/heads/master' }}
       - run: cargo test
       - run: cargo build --tests --features=unstable-doc
+      - run: cargo test --doc --features=unstable-doc
       - run: cargo doc --features=unstable-doc
+      - run: FAYALITE_TEST_HASHER=always_zero cargo test --test=module --features=unstable-doc,unstable-test-hasher

Cargo.lock

@@ -2,18 +2,6 @@
 # It is not intended for manual editing.
 version = 3
 
-[[package]]
-name = "ahash"
-version = "0.8.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77c3a9648d43b9cd48db467b3f87fdd6e146bcc88ab0180006cef2179fe11d01"
-dependencies = [
- "cfg-if",
- "once_cell",
- "version_check",
- "zerocopy",
-]
-
 [[package]]
 name = "allocator-api2"
 version = "0.2.16"
@@ -301,7 +289,7 @@ checksum = "25cbce373ec4653f1a01a31e8a5e5ec0c622dc27ff9c4e6606eefef5cbbed4a5"
 
 [[package]]
 name = "fayalite"
-version = "0.2.1"
+version = "0.3.0"
 dependencies = [
  "bitvec",
  "blake3",
@@ -315,23 +303,25 @@ dependencies = [
  "num-bigint",
  "num-traits",
  "os_pipe",
+ "petgraph",
  "serde",
  "serde_json",
  "tempfile",
  "trybuild",
+ "vec_map",
  "which",
 ]
 
 [[package]]
 name = "fayalite-proc-macros"
-version = "0.2.1"
+version = "0.3.0"
 dependencies = [
  "fayalite-proc-macros-impl",
 ]
 
 [[package]]
 name = "fayalite-proc-macros-impl"
-version = "0.2.1"
+version = "0.3.0"
 dependencies = [
  "base16ct",
  "num-bigint",
@@ -345,7 +335,7 @@ dependencies = [
 
 [[package]]
 name = "fayalite-visit-gen"
-version = "0.2.1"
+version = "0.3.0"
 dependencies = [
  "indexmap",
  "prettyplease",
@@ -357,6 +347,18 @@ dependencies = [
  "thiserror",
 ]
 
+[[package]]
+name = "fixedbitset"
+version = "0.5.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d674e81391d1e1ab681a28d99df07927c6d4aa5b027d7da16ba32d1d21ecd99"
+
+[[package]]
+name = "foldhash"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
+
 [[package]]
 name = "funty"
 version = "2.0.0"
@@ -392,12 +394,13 @@ checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"
 
 [[package]]
 name = "hashbrown"
-version = "0.14.3"
+version = "0.15.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
+checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
 dependencies = [
- "ahash",
  "allocator-api2",
+ "equivalent",
+ "foldhash",
 ]
 
 [[package]]
@@ -423,9 +426,9 @@ checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"
 
 [[package]]
 name = "indexmap"
-version = "2.2.6"
+version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "168fb715dda47215e360912c096649d23d58bf392ac62f73919e831745e40f26"
+checksum = "cea70ddb795996207ad57735b50c5982d8844f38ba9ee5f1aedcfb708a2aa11e"
 dependencies = [
  "equivalent",
  "hashbrown",
@@ -472,11 +475,10 @@ checksum = "01cda141df6706de531b6c46c3a33ecca755538219bd484262fa09410c13539c"
 
 [[package]]
 name = "num-bigint"
-version = "0.4.4"
+version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
+checksum = "a5e44f723f1133c9deac646763579fdb3ac745e418f2a7af9cd0c431da1f20b9"
 dependencies = [
- "autocfg",
  "num-integer",
  "num-traits",
 ]
@@ -515,6 +517,18 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "petgraph"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a98c6720655620a521dcc722d0ad66cd8afd5d86e34a89ef691c50b7b24de06"
+dependencies = [
+ "fixedbitset",
+ "hashbrown",
+ "indexmap",
+ "serde",
+]
+
 [[package]]
 name = "prettyplease"
 version = "0.2.20"
@@ -527,9 +541,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.83"
+version = "1.0.92"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b33eb56c327dec362a9e55b3ad14f9d2f0904fb5a5b03b513ab5465399e9f43"
+checksum = "37d3544b3f2748c54e147655edb5025752e2303145b5aefb3c3ea2c78b973bb0"
 dependencies = [
  "unicode-ident",
 ]
@@ -631,9 +645,9 @@ checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
 [[package]]
 name = "syn"
-version = "2.0.66"
+version = "2.0.93"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c42f3f41a2de00b01c0aaad383c5a45241efc8b2d1eda5661812fda5f3cdcff5"
+checksum = "9c786062daee0d6db1132800e623df74274a0a87322d8e183338e01b3d98d058"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -720,6 +734,12 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
 [[package]]
 name = "version_check"
 version = "0.9.4"
@@ -871,23 +891,3 @@ checksum = "05f360fc0b24296329c78fda852a1e9ae82de9cf7b27dae4b7f62f118f77b9ed"
 dependencies = [
  "tap",
 ]
-
-[[package]]
-name = "zerocopy"
-version = "0.7.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74d4d3961e53fa4c9a25a8637fc2bfaf2595b3d3ae34875568a5cf64787716be"
-dependencies = [
- "zerocopy-derive",
-]
-
-[[package]]
-name = "zerocopy-derive"
-version = "0.7.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ce1b18ccd8e73a9321186f97e46f9f04b778851177567b1975109d26a08d2a6"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]

Cargo.toml

@@ -5,38 +5,40 @@ resolver = "2"
 members = ["crates/*"]
 
 [workspace.package]
-version = "0.2.1"
+version = "0.3.0"
 license = "LGPL-3.0-or-later"
-edition = "2021"
+edition = "2024"
 repository = "https://git.libre-chip.org/libre-chip/fayalite"
 keywords = ["hdl", "hardware", "semiconductors", "firrtl", "fpga"]
 categories = ["simulation", "development-tools", "compilers"]
-rust-version = "1.80.1"
+rust-version = "1.89.0"
 
 [workspace.dependencies]
-fayalite-proc-macros = { version = "=0.2.1", path = "crates/fayalite-proc-macros" }
-fayalite-proc-macros-impl = { version = "=0.2.1", path = "crates/fayalite-proc-macros-impl" }
-fayalite-visit-gen = { version = "=0.2.1", path = "crates/fayalite-visit-gen" }
+fayalite-proc-macros = { version = "=0.3.0", path = "crates/fayalite-proc-macros" }
+fayalite-proc-macros-impl = { version = "=0.3.0", path = "crates/fayalite-proc-macros-impl" }
+fayalite-visit-gen = { version = "=0.3.0", path = "crates/fayalite-visit-gen" }
 base16ct = "0.2.0"
 bitvec = { version = "1.0.1", features = ["serde"] }
 blake3 = { version = "1.5.4", features = ["serde"] }
 clap = { version = "4.5.9", features = ["derive", "env", "string"] }
 ctor = "0.2.8"
 eyre = "0.6.12"
-hashbrown = "0.14.3"
-indexmap = { version = "2.2.6", features = ["serde"] }
+hashbrown = "0.15.2"
+indexmap = { version = "2.5.0", features = ["serde"] }
 jobslot = "0.2.19"
-num-bigint = "0.4.4"
+num-bigint = "0.4.6"
 num-traits = "0.2.16"
 os_pipe = "1.2.1"
+petgraph = "0.8.1"
 prettyplease = "0.2.20"
 proc-macro2 = "1.0.83"
 quote = "1.0.36"
 serde = { version = "1.0.202", features = ["derive"] }
 serde_json = { version = "1.0.117", features = ["preserve_order"] }
 sha2 = "0.10.8"
-syn = { version = "2.0.66", features = ["full", "fold", "visit", "extra-traits"] }
+syn = { version = "2.0.93", features = ["full", "fold", "visit", "extra-traits"] }
 tempfile = "3.10.1"
 thiserror = "1.0.61"
 trybuild = "1.0"
+vec_map = "0.8.2"
 which = "6.0.1"

README.md

@@ -7,3 +7,11 @@ See Notices.txt for copyright information
 Fayalite is a library for designing digital hardware -- a hardware description language (HDL) embedded in the Rust programming language. Fayalite's semantics are based on [FIRRTL] as interpreted by [LLVM CIRCT](https://circt.llvm.org/docs/Dialects/FIRRTL/FIRRTLAnnotations/).
 
 [FIRRTL]: https://github.com/chipsalliance/firrtl-spec
+
+# Funding
+
+## NLnet Grants
+
+* [Libre-Chip CPU with proof of No Spectre bugs](https://nlnet.nl/project/Libre-Chip-proof/) 2024-12-324 [(progress)](https://git.libre-chip.org/libre-chip/grant-tracking/src/branch/master/nlnet-2024-12-324/progress.md)
+
+This project was funded through the [NGI0 Commons Fund](https://nlnet.nl/commonsfund), a fund established by [NLnet](https://nlnet.nl/) with financial support from the European Commission's [Next Generation Internet](https://ngi.eu) programme, under the aegis of [DG Communications Networks, Content and Technology](https://commission.europa.eu/about-european-commission/departments-and-executive-agencies/communications-networks-content-and-technology_en) under grant agreement № [101135429](https://cordis.europa.eu/project/id/101135429). Additional funding is made available by the [Swiss State Secretariat for Education, Research and Innovation](https://www.sbfi.admin.ch/sbfi/en/home.html) (SERI).

crates/fayalite-proc-macros-impl/src/fold.rs

@@ -220,6 +220,7 @@ forward_fold!(syn::ExprArray => fold_expr_array);
 forward_fold!(syn::ExprCall => fold_expr_call);
 forward_fold!(syn::ExprIf => fold_expr_if);
 forward_fold!(syn::ExprMatch => fold_expr_match);
+forward_fold!(syn::ExprMethodCall => fold_expr_method_call);
 forward_fold!(syn::ExprPath => fold_expr_path);
 forward_fold!(syn::ExprRepeat => fold_expr_repeat);
 forward_fold!(syn::ExprStruct => fold_expr_struct);

crates/fayalite-proc-macros-impl/src/hdl_bundle.rs

@@ -1,21 +1,22 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
+    Errors, HdlAttr, PairsIterExt,
     hdl_type_common::{
-        common_derives, get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedField,
-        ParsedFieldsNamed, ParsedGenerics, SplitForImpl, TypesParser, WrappedInConst,
+        ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedField, ParsedFieldsNamed, ParsedGenerics,
+        SplitForImpl, TypesParser, WrappedInConst, common_derives, get_target,
     },
-    kw, Errors, HdlAttr, PairsIterExt,
+    kw,
 };
 use proc_macro2::TokenStream;
-use quote::{format_ident, quote_spanned, ToTokens};
+use quote::{ToTokens, format_ident, quote_spanned};
 use syn::{
-    parse_quote, parse_quote_spanned,
+    AngleBracketedGenericArguments, Attribute, Field, FieldMutability, Fields, FieldsNamed,
+    GenericParam, Generics, Ident, ItemStruct, Path, Token, Type, Visibility, parse_quote,
+    parse_quote_spanned,
     punctuated::{Pair, Punctuated},
     spanned::Spanned,
     token::Brace,
-    AngleBracketedGenericArguments, Attribute, Field, FieldMutability, Fields, FieldsNamed,
-    GenericParam, Generics, Ident, ItemStruct, Path, Token, Type, Visibility,
 };
 
 #[derive(Clone, Debug)]
@@ -30,7 +31,9 @@ pub(crate) struct ParsedBundle {
     pub(crate) field_flips: Vec<Option<HdlAttr<kw::flip, kw::hdl>>>,
     pub(crate) mask_type_ident: Ident,
     pub(crate) mask_type_match_variant_ident: Ident,
+    pub(crate) mask_type_sim_value_ident: Ident,
     pub(crate) match_variant_ident: Ident,
+    pub(crate) sim_value_ident: Ident,
     pub(crate) builder_ident: Ident,
     pub(crate) mask_type_builder_ident: Ident,
 }
@@ -83,6 +86,7 @@ impl ParsedBundle {
             custom_bounds,
             no_static: _,
             no_runtime_generics: _,
+            cmp_eq: _,
         } = options.body;
         let mut fields = match fields {
             syn::Fields::Named(fields) => fields,
@@ -124,7 +128,9 @@ impl ParsedBundle {
             field_flips,
             mask_type_ident: format_ident!("__{}__MaskType", ident),
             mask_type_match_variant_ident: format_ident!("__{}__MaskType__MatchVariant", ident),
+            mask_type_sim_value_ident: format_ident!("__{}__MaskType__SimValue", ident),
             match_variant_ident: format_ident!("__{}__MatchVariant", ident),
+            sim_value_ident: format_ident!("__{}__SimValue", ident),
             mask_type_builder_ident: format_ident!("__{}__MaskType__Builder", ident),
             builder_ident: format_ident!("__{}__Builder", ident),
             ident,
@@ -426,7 +432,9 @@ impl ToTokens for ParsedBundle {
             field_flips,
             mask_type_ident,
             mask_type_match_variant_ident,
+            mask_type_sim_value_ident,
             match_variant_ident,
+            sim_value_ident,
             builder_ident,
             mask_type_builder_ident,
         } = self;
@@ -437,6 +445,7 @@ impl ToTokens for ParsedBundle {
             custom_bounds: _,
             no_static,
             no_runtime_generics,
+            cmp_eq,
         } = &options.body;
         let target = get_target(target, ident);
         let mut item_attrs = attrs.clone();
@@ -521,7 +530,7 @@ impl ToTokens for ParsedBundle {
             semi_token: None,
         }
         .to_tokens(tokens);
-        let mut mask_type_match_variant_fields = mask_type_fields;
+        let mut mask_type_match_variant_fields = mask_type_fields.clone();
         for Field { ty, .. } in &mut mask_type_match_variant_fields.named {
             *ty = parse_quote_spanned! {span=>
                 ::fayalite::expr::Expr<#ty>
@@ -563,6 +572,58 @@ impl ToTokens for ParsedBundle {
             semi_token: None,
         }
         .to_tokens(tokens);
+        let mut mask_type_sim_value_fields = mask_type_fields;
+        for Field { ty, .. } in &mut mask_type_sim_value_fields.named {
+            *ty = parse_quote_spanned! {span=>
+                ::fayalite::sim::value::SimValue<#ty>
+            };
+        }
+        ItemStruct {
+            attrs: vec![
+                parse_quote_spanned! {span=>
+                    #[::fayalite::__std::prelude::v1::derive(
+                        ::fayalite::__std::fmt::Debug,
+                        ::fayalite::__std::clone::Clone,
+                    )]
+                },
+                parse_quote_spanned! {span=>
+                    #[allow(non_camel_case_types, dead_code)]
+                },
+            ],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: mask_type_sim_value_ident.clone(),
+            generics: generics.into(),
+            fields: Fields::Named(mask_type_sim_value_fields),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let mut sim_value_fields = FieldsNamed::from(fields.clone());
+        for Field { ty, .. } in &mut sim_value_fields.named {
+            *ty = parse_quote_spanned! {span=>
+                ::fayalite::sim::value::SimValue<#ty>
+            };
+        }
+        ItemStruct {
+            attrs: vec![
+                parse_quote_spanned! {span=>
+                    #[::fayalite::__std::prelude::v1::derive(
+                        ::fayalite::__std::fmt::Debug,
+                        ::fayalite::__std::clone::Clone,
+                    )]
+                },
+                parse_quote_spanned! {span=>
+                    #[allow(non_camel_case_types, dead_code)]
+                },
+            ],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: sim_value_ident.clone(),
+            generics: generics.into(),
+            fields: Fields::Named(sim_value_fields),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
         let this_token = Ident::new("__this", span);
         let fields_token = Ident::new("__fields", span);
         let self_token = Token![self](span);
@@ -613,6 +674,32 @@ impl ToTokens for ParsedBundle {
                 }
             },
         ));
+        let sim_value_from_opaque_fields =
+            Vec::from_iter(fields.named().into_iter().map(|field| {
+                let ident: &Ident = field.ident().as_ref().unwrap();
+                quote_spanned! {span=>
+                    #ident: v.field_from_opaque(),
+                }
+            }));
+        let sim_value_clone_from_opaque_fields =
+            Vec::from_iter(fields.named().into_iter().map(|field| {
+                let ident: &Ident = field.ident().as_ref().unwrap();
+                quote_spanned! {span=>
+                    v.field_clone_from_opaque(&mut value.#ident);
+                }
+            }));
+        let sim_value_to_opaque_fields = Vec::from_iter(fields.named().into_iter().map(|field| {
+            let ident: &Ident = field.ident().as_ref().unwrap();
+            quote_spanned! {span=>
+                v.field(&value.#ident);
+            }
+        }));
+        let to_sim_value_fields = Vec::from_iter(fields.named().into_iter().map(|field| {
+            let ident: &Ident = field.ident().as_ref().unwrap();
+            quote_spanned! {span=>
+                #ident: ::fayalite::sim::value::SimValue::ty(&self.#ident),
+            }
+        }));
         let fields_len = fields.named().into_iter().len();
         quote_spanned! {span=>
             #[automatically_derived]
@@ -621,6 +708,7 @@ impl ToTokens for ParsedBundle {
             {
                 type BaseType = ::fayalite::bundle::Bundle;
                 type MaskType = #mask_type_ident #type_generics;
+                type SimValue = #mask_type_sim_value_ident #type_generics;
                 type MatchVariant = #mask_type_match_variant_ident #type_generics;
                 type MatchActiveScope = ();
                 type MatchVariantAndInactiveScope = ::fayalite::ty::MatchVariantWithoutScope<
@@ -658,6 +746,35 @@ impl ToTokens for ParsedBundle {
                 fn source_location() -> ::fayalite::source_location::SourceLocation {
                     ::fayalite::source_location::SourceLocation::caller()
                 }
+                fn sim_value_from_opaque(
+                    &self,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) -> <Self as ::fayalite::ty::Type>::SimValue {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueFromOpaque::new(*self, opaque);
+                    #mask_type_sim_value_ident {
+                        #(#sim_value_from_opaque_fields)*
+                    }
+                }
+                fn sim_value_clone_from_opaque(
+                    &self,
+                    value: &mut <Self as ::fayalite::ty::Type>::SimValue,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueFromOpaque::new(*self, opaque);
+                    #(#sim_value_clone_from_opaque_fields)*
+                }
+                fn sim_value_to_opaque<'__w>(
+                    &self,
+                    value: &<Self as ::fayalite::ty::Type>::SimValue,
+                    writer: ::fayalite::ty::OpaqueSimValueWriter<'__w>,
+                ) -> ::fayalite::ty::OpaqueSimValueWritten<'__w> {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueToOpaque::new(*self, writer);
+                    #(#sim_value_to_opaque_fields)*
+                    v.finish()
+                }
             }
             #[automatically_derived]
             impl #impl_generics ::fayalite::bundle::BundleType for #mask_type_ident #type_generics
@@ -689,11 +806,57 @@ impl ToTokens for ParsedBundle {
                 }
             }
             #[automatically_derived]
+            impl #impl_generics ::fayalite::sim::value::ToSimValue for #mask_type_sim_value_ident #type_generics
+            #where_clause
+            {
+                type Type = #mask_type_ident #type_generics;
+
+                fn to_sim_value(
+                    &self,
+                ) -> ::fayalite::sim::value::SimValue<
+                    <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                > {
+                    let ty = #mask_type_ident {
+                        #(#to_sim_value_fields)*
+                    };
+                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                }
+                fn into_sim_value(
+                    self,
+                ) -> ::fayalite::sim::value::SimValue<
+                    <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                > {
+                    let ty = #mask_type_ident {
+                        #(#to_sim_value_fields)*
+                    };
+                    ::fayalite::sim::value::SimValue::from_value(ty, self)
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::sim::value::ToSimValueWithType<#mask_type_ident #type_generics>
+            for #mask_type_sim_value_ident #type_generics
+            #where_clause
+            {
+                fn to_sim_value_with_type(
+                    &self,
+                    ty: #mask_type_ident #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#mask_type_ident #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                }
+                fn into_sim_value_with_type(
+                    self,
+                    ty: #mask_type_ident #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#mask_type_ident #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, self)
+                }
+            }
+            #[automatically_derived]
             impl #impl_generics ::fayalite::ty::Type for #target #type_generics
             #where_clause
             {
                 type BaseType = ::fayalite::bundle::Bundle;
                 type MaskType = #mask_type_ident #type_generics;
+                type SimValue = #sim_value_ident #type_generics;
                 type MatchVariant = #match_variant_ident #type_generics;
                 type MatchActiveScope = ();
                 type MatchVariantAndInactiveScope = ::fayalite::ty::MatchVariantWithoutScope<
@@ -733,6 +896,35 @@ impl ToTokens for ParsedBundle {
                 fn source_location() -> ::fayalite::source_location::SourceLocation {
                     ::fayalite::source_location::SourceLocation::caller()
                 }
+                fn sim_value_from_opaque(
+                    &self,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) -> <Self as ::fayalite::ty::Type>::SimValue {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueFromOpaque::new(*self, opaque);
+                    #sim_value_ident {
+                        #(#sim_value_from_opaque_fields)*
+                    }
+                }
+                fn sim_value_clone_from_opaque(
+                    &self,
+                    value: &mut <Self as ::fayalite::ty::Type>::SimValue,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueFromOpaque::new(*self, opaque);
+                    #(#sim_value_clone_from_opaque_fields)*
+                }
+                fn sim_value_to_opaque<'__w>(
+                    &self,
+                    value: &<Self as ::fayalite::ty::Type>::SimValue,
+                    writer: ::fayalite::ty::OpaqueSimValueWriter<'__w>,
+                ) -> ::fayalite::ty::OpaqueSimValueWritten<'__w> {
+                    #![allow(unused_mut, unused_variables)]
+                    let mut v = ::fayalite::bundle::BundleSimValueToOpaque::new(*self, writer);
+                    #(#sim_value_to_opaque_fields)*
+                    v.finish()
+                }
             }
             #[automatically_derived]
             impl #impl_generics ::fayalite::bundle::BundleType for #target #type_generics
@@ -763,8 +955,144 @@ impl ToTokens for ParsedBundle {
                     ::fayalite::intern::Interned::into_inner(::fayalite::intern::Intern::intern_sized(__retval))
                 }
             }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::sim::value::ToSimValue for #sim_value_ident #type_generics
+            #where_clause
+            {
+                type Type = #target #type_generics;
+
+                fn to_sim_value(
+                    &self,
+                ) -> ::fayalite::sim::value::SimValue<
+                    <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                > {
+                    let ty = #target {
+                        #(#to_sim_value_fields)*
+                    };
+                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                }
+                fn into_sim_value(
+                    self,
+                ) -> ::fayalite::sim::value::SimValue<
+                    <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                > {
+                    let ty = #target {
+                        #(#to_sim_value_fields)*
+                    };
+                    ::fayalite::sim::value::SimValue::from_value(ty, self)
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::sim::value::ToSimValueWithType<#target #type_generics>
+            for #sim_value_ident #type_generics
+            #where_clause
+            {
+                fn to_sim_value_with_type(
+                    &self,
+                    ty: #target #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                }
+                fn into_sim_value_with_type(
+                    self,
+                    ty: #target #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, self)
+                }
+            }
         }
         .to_tokens(tokens);
+        if let Some((cmp_eq,)) = cmp_eq {
+            let mut expr_where_clause =
+                Generics::from(generics)
+                    .where_clause
+                    .unwrap_or_else(|| syn::WhereClause {
+                        where_token: Token![where](span),
+                        predicates: Punctuated::new(),
+                    });
+            let mut sim_value_where_clause = expr_where_clause.clone();
+            let mut fields_sim_value_eq = vec![];
+            let mut fields_cmp_eq = vec![];
+            let mut fields_cmp_ne = vec![];
+            for field in fields.named() {
+                let field_ident = field.ident();
+                let field_ty = field.ty();
+                expr_where_clause
+                    .predicates
+                    .push(parse_quote_spanned! {cmp_eq.span=>
+                        #field_ty: ::fayalite::expr::ops::ExprPartialEq<#field_ty>
+                    });
+                sim_value_where_clause
+                    .predicates
+                    .push(parse_quote_spanned! {cmp_eq.span=>
+                        #field_ty: ::fayalite::sim::value::SimValuePartialEq<#field_ty>
+                    });
+                fields_sim_value_eq.push(quote_spanned! {span=>
+                    ::fayalite::sim::value::SimValuePartialEq::sim_value_eq(&__lhs.#field_ident, &__rhs.#field_ident)
+                });
+                fields_cmp_eq.push(quote_spanned! {span=>
+                    ::fayalite::expr::ops::ExprPartialEq::cmp_eq(__lhs.#field_ident, __rhs.#field_ident)
+                });
+                fields_cmp_ne.push(quote_spanned! {span=>
+                    ::fayalite::expr::ops::ExprPartialEq::cmp_ne(__lhs.#field_ident, __rhs.#field_ident)
+                });
+            }
+            let sim_value_eq_body;
+            let cmp_eq_body;
+            let cmp_ne_body;
+            if fields_len == 0 {
+                sim_value_eq_body = quote_spanned! {span=>
+                    true
+                };
+                cmp_eq_body = quote_spanned! {span=>
+                    ::fayalite::expr::ToExpr::to_expr(&true)
+                };
+                cmp_ne_body = quote_spanned! {span=>
+                    ::fayalite::expr::ToExpr::to_expr(&false)
+                };
+            } else {
+                sim_value_eq_body = quote_spanned! {span=>
+                    #(#fields_sim_value_eq)&&*
+                };
+                cmp_eq_body = quote_spanned! {span=>
+                    #(#fields_cmp_eq)&*
+                };
+                cmp_ne_body = quote_spanned! {span=>
+                    #(#fields_cmp_ne)|*
+                };
+            };
+            quote_spanned! {span=>
+                #[automatically_derived]
+                impl #impl_generics ::fayalite::expr::ops::ExprPartialEq<Self> for #target #type_generics
+                #expr_where_clause
+                {
+                    fn cmp_eq(
+                        __lhs: ::fayalite::expr::Expr<Self>,
+                        __rhs: ::fayalite::expr::Expr<Self>,
+                    ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        #cmp_eq_body
+                    }
+                    fn cmp_ne(
+                        __lhs: ::fayalite::expr::Expr<Self>,
+                        __rhs: ::fayalite::expr::Expr<Self>,
+                    ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        #cmp_ne_body
+                    }
+                }
+                #[automatically_derived]
+                impl #impl_generics ::fayalite::sim::value::SimValuePartialEq<Self> for #target #type_generics
+                #sim_value_where_clause
+                {
+                    fn sim_value_eq(
+                        __lhs: &::fayalite::sim::value::SimValue<Self>,
+                        __rhs: &::fayalite::sim::value::SimValue<Self>,
+                    ) -> bool {
+                        #sim_value_eq_body
+                    }
+                }
+            }
+            .to_tokens(tokens);
+        }
         if let (None, MaybeParsed::Parsed(generics)) = (no_static, &self.generics) {
             let static_generics = generics.clone().for_static_type();
             let (static_impl_generics, static_type_generics, static_where_clause) =
@@ -800,6 +1128,14 @@ impl ToTokens for ParsedBundle {
                 }
             }));
             quote_spanned! {span=>
+                #[automatically_derived]
+                impl #static_impl_generics ::fayalite::__std::default::Default for #mask_type_ident #static_type_generics
+                #static_where_clause
+                {
+                    fn default() -> Self {
+                        <Self as ::fayalite::ty::StaticType>::TYPE
+                    }
+                }
                 #[automatically_derived]
                 impl #static_impl_generics ::fayalite::ty::StaticType for #mask_type_ident #static_type_generics
                 #static_where_clause
@@ -822,6 +1158,15 @@ impl ToTokens for ParsedBundle {
                     };
                 }
                 #[automatically_derived]
+                impl #static_impl_generics ::fayalite::__std::default::Default
+                for #target #static_type_generics
+                #static_where_clause
+                {
+                    fn default() -> Self {
+                        <Self as ::fayalite::ty::StaticType>::TYPE
+                    }
+                }
+                #[automatically_derived]
                 impl #static_impl_generics ::fayalite::ty::StaticType for #target #static_type_generics
                 #static_where_clause
                 {

crates/fayalite-proc-macros-impl/src/hdl_enum.rs

@@ -1,20 +1,20 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
+    Errors, HdlAttr, PairsIterExt,
     hdl_type_common::{
-        common_derives, get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics,
-        ParsedType, SplitForImpl, TypesParser, WrappedInConst,
+        ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics, ParsedType, SplitForImpl,
+        TypesParser, WrappedInConst, common_derives, get_target,
     },
-    kw, Errors, HdlAttr, PairsIterExt,
+    kw,
 };
 use proc_macro2::TokenStream;
-use quote::{format_ident, quote_spanned, ToTokens};
+use quote::{ToTokens, format_ident, quote_spanned};
 use syn::{
-    parse_quote_spanned,
+    Attribute, Field, FieldMutability, Fields, FieldsNamed, FieldsUnnamed, Generics, Ident,
+    ItemEnum, ItemStruct, Token, Type, Variant, Visibility, parse_quote_spanned,
     punctuated::{Pair, Punctuated},
     token::{Brace, Paren},
-    Attribute, Field, FieldMutability, Fields, FieldsNamed, FieldsUnnamed, Generics, Ident,
-    ItemEnum, ItemStruct, Token, Type, Variant, Visibility,
 };
 
 crate::options! {
@@ -129,6 +129,9 @@ pub(crate) struct ParsedEnum {
     pub(crate) brace_token: Brace,
     pub(crate) variants: Punctuated<ParsedVariant, Token![,]>,
     pub(crate) match_variant_ident: Ident,
+    pub(crate) sim_value_ident: Ident,
+    pub(crate) sim_builder_ident: Ident,
+    pub(crate) sim_builder_ty_field_ident: Ident,
 }
 
 impl ParsedEnum {
@@ -155,7 +158,11 @@ impl ParsedEnum {
             custom_bounds,
             no_static: _,
             no_runtime_generics: _,
+            cmp_eq,
         } = options.body;
+        if let Some((cmp_eq,)) = cmp_eq {
+            errors.error(cmp_eq, "#[hdl(cmp_eq)] is not yet implemented for enums");
+        }
         attrs.retain(|attr| {
             if attr.path().is_ident("repr") {
                 errors.error(attr, "#[repr] is not supported on #[hdl] enums");
@@ -186,6 +193,9 @@ impl ParsedEnum {
             brace_token,
             variants,
             match_variant_ident: format_ident!("__{}__MatchVariant", ident),
+            sim_value_ident: format_ident!("__{}__SimValue", ident),
+            sim_builder_ident: format_ident!("__{}__SimBuilder", ident),
+            sim_builder_ty_field_ident: format_ident!("__ty", span = ident.span()),
             ident,
         })
     }
@@ -203,6 +213,9 @@ impl ToTokens for ParsedEnum {
             brace_token,
             variants,
             match_variant_ident,
+            sim_value_ident,
+            sim_builder_ident,
+            sim_builder_ty_field_ident,
         } = self;
         let span = ident.span();
         let ItemOptions {
@@ -211,6 +224,7 @@ impl ToTokens for ParsedEnum {
             custom_bounds: _,
             no_static,
             no_runtime_generics,
+            cmp_eq: _, // TODO: implement cmp_eq for enums
         } = &options.body;
         let target = get_target(target, ident);
         let mut struct_attrs = attrs.clone();
@@ -404,6 +418,133 @@ impl ToTokens for ParsedEnum {
             )),
         }
         .to_tokens(tokens);
+        let mut struct_attrs = attrs.clone();
+        struct_attrs.push(parse_quote_spanned! {span=>
+            #[allow(dead_code, non_camel_case_types)]
+        });
+        ItemStruct {
+            attrs: struct_attrs,
+            vis: vis.clone(),
+            struct_token: Token![struct](enum_token.span),
+            ident: sim_builder_ident.clone(),
+            generics: generics.into(),
+            fields: FieldsNamed {
+                brace_token: *brace_token,
+                named: Punctuated::from_iter([Field {
+                    attrs: vec![],
+                    vis: Visibility::Inherited,
+                    mutability: FieldMutability::None,
+                    ident: Some(sim_builder_ty_field_ident.clone()),
+                    colon_token: Some(Token![:](span)),
+                    ty: parse_quote_spanned! {span=>
+                        #target #type_generics
+                    },
+                }]),
+            }
+            .into(),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let mut enum_attrs = attrs.clone();
+        enum_attrs.push(parse_quote_spanned! {span=>
+            #[::fayalite::__std::prelude::v1::derive(
+                ::fayalite::__std::fmt::Debug,
+                ::fayalite::__std::clone::Clone,
+            )]
+        });
+        enum_attrs.push(parse_quote_spanned! {span=>
+            #[allow(dead_code, non_camel_case_types)]
+        });
+        let sim_value_has_unknown_variant = !variants.len().is_power_of_two();
+        let sim_value_unknown_variant_name = sim_value_has_unknown_variant.then(|| {
+            let mut name = String::new();
+            let unknown = "Unknown";
+            loop {
+                let orig_len = name.len();
+                name.push_str(unknown);
+                if variants.iter().all(|v| v.ident != name) {
+                    break Ident::new(&name, span);
+                }
+                name.truncate(orig_len);
+                name.push('_');
+            }
+        });
+        let sim_value_unknown_variant =
+            sim_value_unknown_variant_name
+                .as_ref()
+                .map(|unknown_variant_name| {
+                    Pair::End(parse_quote_spanned! {span=>
+                        #unknown_variant_name(::fayalite::enum_::UnknownVariantSimValue)
+                    })
+                });
+        ItemEnum {
+            attrs: enum_attrs,
+            vis: vis.clone(),
+            enum_token: *enum_token,
+            ident: sim_value_ident.clone(),
+            generics: generics.into(),
+            brace_token: *brace_token,
+            variants: Punctuated::from_iter(
+                variants
+                    .pairs()
+                    .map_pair_value_ref(
+                        |ParsedVariant {
+                             attrs,
+                             options: _,
+                             ident,
+                             field,
+                         }| Variant {
+                            attrs: attrs.clone(),
+                            ident: ident.clone(),
+                            fields: match field {
+                                Some(ParsedVariantField {
+                                    paren_token,
+                                    attrs,
+                                    options: _,
+                                    ty,
+                                    comma_token,
+                                }) => Fields::Unnamed(FieldsUnnamed {
+                                    paren_token: *paren_token,
+                                    unnamed: Punctuated::from_iter([
+                                        Pair::new(
+                                            Field {
+                                                attrs: attrs.clone(),
+                                                vis: Visibility::Inherited,
+                                                mutability: FieldMutability::None,
+                                                ident: None,
+                                                colon_token: None,
+                                                ty: parse_quote_spanned! {span=>
+                                                    ::fayalite::sim::value::SimValue<#ty>
+                                                },
+                                            },
+                                            Some(comma_token.unwrap_or(Token![,](ident.span()))),
+                                        ),
+                                        Pair::new(
+                                            Field {
+                                                attrs: vec![],
+                                                vis: Visibility::Inherited,
+                                                mutability: FieldMutability::None,
+                                                ident: None,
+                                                colon_token: None,
+                                                ty: parse_quote_spanned! {span=>
+                                                    ::fayalite::enum_::EnumPaddingSimValue
+                                                },
+                                            },
+                                            None,
+                                        ),
+                                    ]),
+                                }),
+                                None => Fields::Unnamed(parse_quote_spanned! {span=>
+                                    (::fayalite::enum_::EnumPaddingSimValue)
+                                }),
+                            },
+                            discriminant: None,
+                        },
+                    )
+                    .chain(sim_value_unknown_variant),
+            ),
+        }
+        .to_tokens(tokens);
         let self_token = Token![self](span);
         for (index, ParsedVariant { ident, field, .. }) in variants.iter().enumerate() {
             if let Some(ParsedVariantField { ty, .. }) = field {
@@ -430,6 +571,25 @@ impl ToTokens for ParsedEnum {
                             )
                         }
                     }
+                    #[automatically_derived]
+                    impl #impl_generics #sim_builder_ident #type_generics
+                    #where_clause
+                    {
+                        #[allow(non_snake_case, dead_code)]
+                        #vis fn #ident<__V: ::fayalite::sim::value::ToSimValueWithType<#ty>>(
+                            #self_token,
+                            v: __V,
+                        ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                            let v = ::fayalite::sim::value::ToSimValueWithType::into_sim_value_with_type(
+                                v,
+                                #self_token.#sim_builder_ty_field_ident.#ident,
+                            );
+                            ::fayalite::sim::value::SimValue::from_value(
+                                #self_token.#sim_builder_ty_field_ident,
+                                #sim_value_ident::#ident(v, ::fayalite::enum_::EnumPaddingSimValue::new()),
+                            )
+                        }
+                    }
                 }
             } else {
                 quote_spanned! {span=>
@@ -448,6 +608,18 @@ impl ToTokens for ParsedEnum {
                             )
                         }
                     }
+                    #[automatically_derived]
+                    impl #impl_generics #sim_builder_ident #type_generics
+                    #where_clause
+                    {
+                        #[allow(non_snake_case, dead_code)]
+                        #vis fn #ident(#self_token) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                            ::fayalite::sim::value::SimValue::from_value(
+                                #self_token.#sim_builder_ty_field_ident,
+                                #sim_value_ident::#ident(::fayalite::enum_::EnumPaddingSimValue::new()),
+                            )
+                        }
+                    }
                 }
             }
             .to_tokens(tokens);
@@ -529,6 +701,142 @@ impl ToTokens for ParsedEnum {
                 }
             },
         ));
+        let sim_value_from_opaque_unknown_match_arm = if let Some(sim_value_unknown_variant_name) =
+            &sim_value_unknown_variant_name
+        {
+            quote_spanned! {span=>
+                _ => #sim_value_ident::#sim_value_unknown_variant_name(v.unknown_variant_from_opaque()),
+            }
+        } else {
+            quote_spanned! {span=>
+                _ => ::fayalite::__std::unreachable!(),
+            }
+        };
+        let sim_value_from_opaque_match_arms = Vec::from_iter(
+            variants
+                .iter()
+                .enumerate()
+                .map(
+                    |(
+                        index,
+                        ParsedVariant {
+                            attrs: _,
+                            options: _,
+                            ident,
+                            field,
+                        },
+                    )| {
+                        if let Some(_) = field {
+                            quote_spanned! {span=>
+                                #index => {
+                                    let (field, padding) = v.variant_with_field_from_opaque();
+                                    #sim_value_ident::#ident(field, padding)
+                                }
+                            }
+                        } else {
+                            quote_spanned! {span=>
+                                #index => #sim_value_ident::#ident(
+                                    v.variant_no_field_from_opaque(),
+                                ),
+                            }
+                        }
+                    },
+                )
+                .chain([sim_value_from_opaque_unknown_match_arm]),
+        );
+        let sim_value_clone_from_opaque_unknown_match_arm =
+            if let Some(sim_value_unknown_variant_name) = &sim_value_unknown_variant_name {
+                quote_spanned! {span=>
+                    _ => if let #sim_value_ident::#sim_value_unknown_variant_name(value) = value {
+                        v.unknown_variant_clone_from_opaque(value);
+                    } else {
+                        *value = #sim_value_ident::#sim_value_unknown_variant_name(
+                            v.unknown_variant_from_opaque(),
+                        );
+                    },
+                }
+            } else {
+                quote_spanned! {span=>
+                    _ => ::fayalite::__std::unreachable!(),
+                }
+            };
+        let sim_value_clone_from_opaque_match_arms = Vec::from_iter(
+            variants
+                .iter()
+                .enumerate()
+                .map(
+                    |(
+                        index,
+                        ParsedVariant {
+                            attrs: _,
+                            options: _,
+                            ident,
+                            field,
+                        },
+                    )| {
+                        if let Some(_) = field {
+                            quote_spanned! {span=>
+                                #index => if let #sim_value_ident::#ident(field, padding) = value {
+                                    v.variant_with_field_clone_from_opaque(field, padding);
+                                } else {
+                                    let (field, padding) = v.variant_with_field_from_opaque();
+                                    *value = #sim_value_ident::#ident(field, padding);
+                                },
+                            }
+                        } else {
+                            quote_spanned! {span=>
+                                #index => if let #sim_value_ident::#ident(padding) = value {
+                                    v.variant_no_field_clone_from_opaque(padding);
+                                } else {
+                                    *value = #sim_value_ident::#ident(
+                                        v.variant_no_field_from_opaque(),
+                                    );
+                                },
+                            }
+                        }
+                    },
+                )
+                .chain([sim_value_clone_from_opaque_unknown_match_arm]),
+        );
+        let sim_value_to_opaque_match_arms = Vec::from_iter(
+            variants
+                .iter()
+                .enumerate()
+                .map(
+                    |(
+                        index,
+                        ParsedVariant {
+                            attrs: _,
+                            options: _,
+                            ident,
+                            field,
+                        },
+                    )| {
+                        if let Some(_) = field {
+                            quote_spanned! {span=>
+                                #sim_value_ident::#ident(field, padding) => {
+                                    v.variant_with_field_to_opaque(#index, field, padding)
+                                }
+                            }
+                        } else {
+                            quote_spanned! {span=>
+                                #sim_value_ident::#ident(padding) => {
+                                    v.variant_no_field_to_opaque(#index, padding)
+                                }
+                            }
+                        }
+                    },
+                )
+                .chain(sim_value_unknown_variant_name.as_ref().map(
+                    |sim_value_unknown_variant_name| {
+                        quote_spanned! {span=>
+                            #sim_value_ident::#sim_value_unknown_variant_name(value) => {
+                                v.unknown_variant_to_opaque(value)
+                            }
+                        }
+                    },
+                )),
+        );
         let variants_len = variants.len();
         quote_spanned! {span=>
             #[automatically_derived]
@@ -537,6 +845,7 @@ impl ToTokens for ParsedEnum {
             {
                 type BaseType = ::fayalite::enum_::Enum;
                 type MaskType = ::fayalite::int::Bool;
+                type SimValue = #sim_value_ident #type_generics;
                 type MatchVariant = #match_variant_ident #type_generics;
                 type MatchActiveScope = ::fayalite::module::Scope;
                 type MatchVariantAndInactiveScope = ::fayalite::enum_::EnumMatchVariantAndInactiveScope<Self>;
@@ -569,11 +878,41 @@ impl ToTokens for ParsedEnum {
                 fn source_location() -> ::fayalite::source_location::SourceLocation {
                     ::fayalite::source_location::SourceLocation::caller()
                 }
+                fn sim_value_from_opaque(
+                    &self,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) -> <Self as ::fayalite::ty::Type>::SimValue {
+                    let v = ::fayalite::enum_::EnumSimValueFromOpaque::new(*self, opaque);
+                    match v.discriminant() {
+                        #(#sim_value_from_opaque_match_arms)*
+                    }
+                }
+                fn sim_value_clone_from_opaque(
+                    &self,
+                    value: &mut <Self as ::fayalite::ty::Type>::SimValue,
+                    opaque: ::fayalite::ty::OpaqueSimValueSlice<'_>,
+                ) {
+                    let v = ::fayalite::enum_::EnumSimValueFromOpaque::new(*self, opaque);
+                    match v.discriminant() {
+                        #(#sim_value_clone_from_opaque_match_arms)*
+                    }
+                }
+                fn sim_value_to_opaque<'__w>(
+                    &self,
+                    value: &<Self as ::fayalite::ty::Type>::SimValue,
+                    writer: ::fayalite::ty::OpaqueSimValueWriter<'__w>,
+                ) -> ::fayalite::ty::OpaqueSimValueWritten<'__w> {
+                    let v = ::fayalite::enum_::EnumSimValueToOpaque::new(*self, writer);
+                    match value {
+                        #(#sim_value_to_opaque_match_arms)*
+                    }
+                }
             }
             #[automatically_derived]
             impl #impl_generics ::fayalite::enum_::EnumType for #target #type_generics
             #where_clause
             {
+                type SimBuilder = #sim_builder_ident #type_generics;
                 fn match_activate_scope(
                     v: <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
                 ) -> (<Self as ::fayalite::ty::Type>::MatchVariant, <Self as ::fayalite::ty::Type>::MatchActiveScope) {
@@ -592,6 +931,33 @@ impl ToTokens for ParsedEnum {
                     ][..])
                 }
             }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::sim::value::ToSimValueWithType<#target #type_generics>
+            for #sim_value_ident #type_generics
+            #where_clause
+            {
+                fn to_sim_value_with_type(
+                    &self,
+                    ty: #target #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                }
+                fn into_sim_value_with_type(
+                    self,
+                    ty: #target #type_generics,
+                ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                    ::fayalite::sim::value::SimValue::from_value(ty, self)
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::__std::convert::From<#target #type_generics>
+            for #sim_builder_ident #type_generics
+            #where_clause
+            {
+                fn from(#sim_builder_ty_field_ident: #target #type_generics) -> Self {
+                    Self { #sim_builder_ty_field_ident }
+                }
+            }
         }
         .to_tokens(tokens);
         if let (None, MaybeParsed::Parsed(generics)) = (no_static, &self.generics) {
@@ -629,6 +995,15 @@ impl ToTokens for ParsedEnum {
                     }
                 }));
             quote_spanned! {span=>
+                #[automatically_derived]
+                impl #static_impl_generics ::fayalite::__std::default::Default
+                for #target #static_type_generics
+                #static_where_clause
+                {
+                    fn default() -> Self {
+                        <Self as ::fayalite::ty::StaticType>::TYPE
+                    }
+                }
                 #[automatically_derived]
                 impl #static_impl_generics ::fayalite::ty::StaticType
                 for #target #static_type_generics
@@ -647,6 +1022,34 @@ impl ToTokens for ParsedEnum {
                     const MASK_TYPE_PROPERTIES: ::fayalite::ty::TypeProperties =
                         <::fayalite::int::Bool as ::fayalite::ty::StaticType>::TYPE_PROPERTIES;
                 }
+                #[automatically_derived]
+                impl #static_impl_generics ::fayalite::sim::value::ToSimValue
+                for #sim_value_ident #static_type_generics
+                #static_where_clause
+                {
+                    type Type = #target #static_type_generics;
+
+                    fn to_sim_value(
+                        &self,
+                    ) -> ::fayalite::sim::value::SimValue<
+                        <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                    > {
+                        ::fayalite::sim::value::SimValue::from_value(
+                            ::fayalite::ty::StaticType::TYPE,
+                            ::fayalite::__std::clone::Clone::clone(self),
+                        )
+                    }
+                    fn into_sim_value(
+                        self,
+                    ) -> ::fayalite::sim::value::SimValue<
+                        <Self as ::fayalite::sim::value::ToSimValue>::Type,
+                    > {
+                        ::fayalite::sim::value::SimValue::from_value(
+                            ::fayalite::ty::StaticType::TYPE,
+                            self,
+                        )
+                    }
+                }
             }
             .to_tokens(tokens);
         }

crates/fayalite-proc-macros-impl/src/hdl_type_alias.rs

@@ -1,15 +1,16 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
+    Errors, HdlAttr,
     hdl_type_common::{
-        get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics, ParsedType,
-        TypesParser,
+        ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics, ParsedType, TypesParser,
+        get_target,
     },
-    kw, Errors, HdlAttr,
+    kw,
 };
 use proc_macro2::TokenStream;
 use quote::ToTokens;
-use syn::{parse_quote_spanned, Attribute, Generics, Ident, ItemType, Token, Type, Visibility};
+use syn::{Attribute, Generics, Ident, ItemType, Token, Type, Visibility, parse_quote_spanned};
 
 #[derive(Clone, Debug)]
 pub(crate) struct ParsedTypeAlias {
@@ -49,10 +50,14 @@ impl ParsedTypeAlias {
             custom_bounds,
             no_static,
             no_runtime_generics: _,
+            cmp_eq,
         } = options.body;
         if let Some((no_static,)) = no_static {
             errors.error(no_static, "no_static is not valid on type aliases");
         }
+        if let Some((cmp_eq,)) = cmp_eq {
+            errors.error(cmp_eq, "cmp_eq is not valid on type aliases");
+        }
         let generics = if custom_bounds.is_some() {
             MaybeParsed::Unrecognized(generics)
         } else if let Some(generics) = errors.ok(ParsedGenerics::parse(&mut generics)) {
@@ -95,6 +100,7 @@ impl ToTokens for ParsedTypeAlias {
             custom_bounds: _,
             no_static: _,
             no_runtime_generics,
+            cmp_eq: _,
         } = &options.body;
         let target = get_target(target, ident);
         let mut type_attrs = attrs.clone();

crates/fayalite-proc-macros-impl/src/hdl_type_common.rs

@@ -1,21 +1,21 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
-use crate::{fold::impl_fold, kw, Errors, HdlAttr, PairsIterExt};
+use crate::{Errors, HdlAttr, PairsIterExt, fold::impl_fold, kw};
 use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote_spanned, ToTokens};
+use quote::{ToTokens, format_ident, quote_spanned};
 use std::{collections::HashMap, fmt, mem};
 use syn::{
-    parse::{Parse, ParseStream},
-    parse_quote, parse_quote_spanned,
-    punctuated::{Pair, Punctuated},
-    spanned::Spanned,
-    token::{Brace, Bracket, Paren},
     AngleBracketedGenericArguments, Attribute, Block, ConstParam, Expr, ExprBlock, ExprGroup,
     ExprIndex, ExprParen, ExprPath, ExprTuple, Field, FieldMutability, Fields, FieldsNamed,
     FieldsUnnamed, GenericArgument, GenericParam, Generics, Ident, ImplGenerics, Index, ItemStruct,
     Path, PathArguments, PathSegment, PredicateType, QSelf, Stmt, Token, Turbofish, Type,
     TypeGenerics, TypeGroup, TypeParam, TypeParen, TypePath, TypeTuple, Visibility, WhereClause,
     WherePredicate,
+    parse::{Parse, ParseStream},
+    parse_quote, parse_quote_spanned,
+    punctuated::{Pair, Punctuated},
+    spanned::Spanned,
+    token::{Brace, Bracket, Paren},
 };
 
 crate::options! {
@@ -26,6 +26,7 @@ crate::options! {
         CustomBounds(custom_bounds),
         NoStatic(no_static),
         NoRuntimeGenerics(no_runtime_generics),
+        CmpEq(cmp_eq),
     }
 }
 
@@ -298,7 +299,7 @@ impl ParseTypes<Expr> for ParsedExpr {
                 return Ok(ParsedExpr::Delimited(ParsedExprDelimited {
                     delim: ExprDelimiter::Group(*group_token),
                     expr: parser.parse(expr)?,
-                }))
+                }));
             }
             Expr::Paren(ExprParen {
                 attrs,
@@ -308,7 +309,7 @@ impl ParseTypes<Expr> for ParsedExpr {
                 return Ok(ParsedExpr::Delimited(ParsedExprDelimited {
                     delim: ExprDelimiter::Paren(*paren_token),
                     expr: parser.parse(expr)?,
-                }))
+                }));
             }
             Expr::Path(ExprPath {
                 attrs,
@@ -1901,8 +1902,8 @@ pub(crate) mod known_items {
     use proc_macro2::{Ident, Span, TokenStream};
     use quote::ToTokens;
     use syn::{
-        parse::{Parse, ParseStream},
         Path, PathArguments, PathSegment, Token,
+        parse::{Parse, ParseStream},
     };
 
     macro_rules! impl_known_item_body {
@@ -2044,6 +2045,7 @@ pub(crate) mod known_items {
     impl_known_item!(::fayalite::int::Size);
     impl_known_item!(::fayalite::int::UInt);
     impl_known_item!(::fayalite::int::UIntType);
+    impl_known_item!(::fayalite::reset::ResetType);
     impl_known_item!(::fayalite::ty::CanonicalType);
     impl_known_item!(::fayalite::ty::StaticType);
     impl_known_item!(::fayalite::ty::Type);
@@ -2068,11 +2070,16 @@ macro_rules! impl_bounds {
             $(
                 $Variant:ident,
             )*
+            $(
+                #[unknown]
+                $Unknown:ident,
+            )?
         }
     ) => {
         #[derive(Clone, Debug)]
         $vis enum $enum_type {
             $($Variant(known_items::$Variant),)*
+            $($Unknown(syn::TypeParamBound),)?
         }
 
         $(impl From<known_items::$Variant> for $enum_type {
@@ -2085,28 +2092,54 @@ macro_rules! impl_bounds {
             fn to_tokens(&self, tokens: &mut TokenStream) {
                 match self {
                     $(Self::$Variant(v) => v.to_tokens(tokens),)*
+                    $(Self::$Unknown(v) => v.to_tokens(tokens),)?
                 }
             }
         }
 
         impl $enum_type {
             $vis fn parse_path(path: Path) -> Result<Self, Path> {
+                #![allow(unreachable_code)]
                 $(let path = match known_items::$Variant::parse_path(path) {
                     Ok(v) => return Ok(Self::$Variant(v)),
                     Err(path) => path,
                 };)*
+                $(return Ok(Self::$Unknown(syn::TraitBound {
+                    paren_token: None,
+                    modifier: syn::TraitBoundModifier::None,
+                    lifetimes: None,
+                    path,
+                }.into()));)?
                 Err(path)
             }
+            $vis fn parse_type_param_bound(mut type_param_bound: syn::TypeParamBound) -> Result<Self, syn::TypeParamBound> {
+                #![allow(unreachable_code)]
+                if let syn::TypeParamBound::Trait(mut trait_bound) = type_param_bound {
+                    if let syn::TraitBound {
+                        paren_token: _,
+                        modifier: syn::TraitBoundModifier::None,
+                        lifetimes: None,
+                        path: _,
+                    } = trait_bound {
+                        match Self::parse_path(trait_bound.path) {
+                            Ok(retval) => return Ok(retval),
+                            Err(path) => trait_bound.path = path,
+                        }
+                    }
+                    type_param_bound = trait_bound.into();
+                }
+                $(return Ok(Self::$Unknown(type_param_bound));)?
+                Err(type_param_bound)
+            }
         }
 
         impl Parse for $enum_type {
             fn parse(input: ParseStream) -> syn::Result<Self> {
-                Self::parse_path(Path::parse_mod_style(input)?).map_err(|path| {
-                    syn::Error::new_spanned(
-                        path,
+                Self::parse_type_param_bound(input.parse()?)
+                    .map_err(|type_param_bound| syn::Error::new_spanned(
+                        type_param_bound,
                         format_args!("expected one of: {}", [$(stringify!($Variant)),*].join(", ")),
-                    )
-                })
+                    ))
             }
         }
 
@@ -2114,6 +2147,7 @@ macro_rules! impl_bounds {
         #[allow(non_snake_case)]
         $vis struct $struct_type {
             $($vis $Variant: Option<known_items::$Variant>,)*
+            $($vis $Unknown: Vec<syn::TypeParamBound>,)?
         }
 
         impl ToTokens for $struct_type {
@@ -2125,42 +2159,63 @@ macro_rules! impl_bounds {
                     separator = Some(<Token![+]>::default());
                     v.to_tokens(tokens);
                 })*
+                $(for v in &self.$Unknown {
+                    separator.to_tokens(tokens);
+                    separator = Some(<Token![+]>::default());
+                    v.to_tokens(tokens);
+                })*
             }
         }
 
         const _: () = {
             #[derive(Clone, Debug)]
-            $vis struct Iter($vis $struct_type);
+            #[allow(non_snake_case)]
+            $vis struct Iter {
+                $($Variant: Option<known_items::$Variant>,)*
+                $($Unknown: std::vec::IntoIter<syn::TypeParamBound>,)?
+            }
 
             impl IntoIterator for $struct_type {
                 type Item = $enum_type;
                 type IntoIter = Iter;
 
                 fn into_iter(self) -> Self::IntoIter {
-                    Iter(self)
+                    Iter {
+                        $($Variant: self.$Variant,)*
+                        $($Unknown: self.$Unknown.into_iter(),)?
+                    }
                 }
             }
 
             impl Iterator for Iter {
                 type Item = $enum_type;
 
-
                 fn next(&mut self) -> Option<Self::Item> {
                     $(
-                        if let Some(value) = self.0.$Variant.take() {
+                        if let Some(value) = self.$Variant.take() {
                             return Some($enum_type::$Variant(value));
                         }
                     )*
+                    $(
+                        if let Some(value) = self.$Unknown.next() {
+                            return Some($enum_type::$Unknown(value));
+                        }
+                    )?
                     None
                 }
 
                 #[allow(unused_mut, unused_variables)]
                 fn fold<B, F: FnMut(B, Self::Item) -> B>(mut self, mut init: B, mut f: F) -> B {
                     $(
-                        if let Some(value) = self.0.$Variant.take() {
+                        if let Some(value) = self.$Variant.take() {
                             init = f(init, $enum_type::$Variant(value));
                         }
                     )*
+                    $(
+                        if let Some(value) = self.$Unknown.next() {
+                            init = f(init, $enum_type::$Unknown(value));
+                        }
+                    )?
                     init
                 }
             }
@@ -2172,6 +2227,9 @@ macro_rules! impl_bounds {
                     $($enum_type::$Variant(v) => {
                         self.$Variant = Some(v);
                     })*
+                    $($enum_type::$Unknown(v) => {
+                        self.$Unknown.push(v);
+                    })?
                 });
             }
         }
@@ -2190,6 +2248,7 @@ macro_rules! impl_bounds {
                     $(if let Some(v) = v.$Variant {
                         self.$Variant = Some(v);
                     })*
+                    $(self.$Unknown.extend(v.$Unknown);)*
                 });
             }
         }
@@ -2239,9 +2298,12 @@ impl_bounds! {
         EnumType,
         IntType,
         KnownSize,
+        ResetType,
         Size,
         StaticType,
         Type,
+        #[unknown]
+        Unknown,
     }
 }
 
@@ -2252,8 +2314,11 @@ impl_bounds! {
         BundleType,
         EnumType,
         IntType,
+        ResetType,
         StaticType,
         Type,
+        #[unknown]
+        Unknown,
     }
 }
 
@@ -2264,8 +2329,10 @@ impl From<ParsedTypeBound> for ParsedBound {
             ParsedTypeBound::BundleType(v) => ParsedBound::BundleType(v),
             ParsedTypeBound::EnumType(v) => ParsedBound::EnumType(v),
             ParsedTypeBound::IntType(v) => ParsedBound::IntType(v),
+            ParsedTypeBound::ResetType(v) => ParsedBound::ResetType(v),
             ParsedTypeBound::StaticType(v) => ParsedBound::StaticType(v),
             ParsedTypeBound::Type(v) => ParsedBound::Type(v),
+            ParsedTypeBound::Unknown(v) => ParsedBound::Unknown(v),
         }
     }
 }
@@ -2277,8 +2344,10 @@ impl From<ParsedTypeBounds> for ParsedBounds {
             BundleType,
             EnumType,
             IntType,
+            ResetType,
             StaticType,
             Type,
+            Unknown,
         } = value;
         Self {
             BoolOrIntType,
@@ -2286,9 +2355,11 @@ impl From<ParsedTypeBounds> for ParsedBounds {
             EnumType,
             IntType,
             KnownSize: None,
+            ResetType,
             Size: None,
             StaticType,
             Type,
+            Unknown,
         }
     }
 }
@@ -2314,11 +2385,17 @@ impl ParsedTypeBound {
                 ParsedTypeBound::BoolOrIntType(known_items::BoolOrIntType(span)),
                 ParsedTypeBound::Type(known_items::Type(span)),
             ]),
+            Self::ResetType(v) => ParsedTypeBounds::from_iter([
+                ParsedTypeBound::from(v),
+                ParsedTypeBound::StaticType(known_items::StaticType(span)),
+                ParsedTypeBound::Type(known_items::Type(span)),
+            ]),
             Self::StaticType(v) => ParsedTypeBounds::from_iter([
                 ParsedTypeBound::from(v),
                 ParsedTypeBound::Type(known_items::Type(span)),
             ]),
             Self::Type(v) => ParsedTypeBounds::from_iter([ParsedTypeBound::from(v)]),
+            Self::Unknown(v) => ParsedTypeBounds::from_iter([ParsedTypeBound::Unknown(v)]),
         }
     }
 }
@@ -2349,9 +2426,11 @@ impl From<ParsedSizeTypeBounds> for ParsedBounds {
             EnumType: None,
             IntType: None,
             KnownSize,
+            ResetType: None,
             Size,
             StaticType: None,
             Type: None,
+            Unknown: vec![],
         }
     }
 }
@@ -2379,6 +2458,7 @@ impl ParsedBounds {
     fn categorize(self, errors: &mut Errors, span: Span) -> ParsedBoundsCategory {
         let mut type_bounds = None;
         let mut size_type_bounds = None;
+        let mut unknown_bounds = vec![];
         self.into_iter().for_each(|bound| match bound.categorize() {
             ParsedBoundCategory::Type(bound) => {
                 type_bounds
@@ -2390,15 +2470,37 @@ impl ParsedBounds {
                     .get_or_insert_with(ParsedSizeTypeBounds::default)
                     .extend([bound]);
             }
+            ParsedBoundCategory::Unknown(bound) => unknown_bounds.push(bound),
         });
-        match (type_bounds, size_type_bounds) {
-            (None, None) => ParsedBoundsCategory::Type(ParsedTypeBounds {
+        match (type_bounds, size_type_bounds, unknown_bounds.is_empty()) {
+            (None, None, true) => ParsedBoundsCategory::Type(ParsedTypeBounds {
                 Type: Some(known_items::Type(span)),
                 ..Default::default()
             }),
-            (None, Some(bounds)) => ParsedBoundsCategory::SizeType(bounds),
-            (Some(bounds), None) => ParsedBoundsCategory::Type(bounds),
-            (Some(type_bounds), Some(size_type_bounds)) => {
+            (None, None, false) => {
+                errors.error(
+                    unknown_bounds.remove(0),
+                    "unknown bounds: must use at least one known bound (such as `Type`) with any unknown bounds",
+                );
+                ParsedBoundsCategory::Type(ParsedTypeBounds {
+                    Unknown: unknown_bounds,
+                    ..Default::default()
+                })
+            }
+            (None, Some(bounds), true) => ParsedBoundsCategory::SizeType(bounds),
+            (None, Some(bounds), false) => {
+                // TODO: implement
+                errors.error(
+                    unknown_bounds.remove(0),
+                    "unknown bounds with `Size` bounds are not implemented",
+                );
+                ParsedBoundsCategory::SizeType(bounds)
+            }
+            (Some(bounds), None, _) => ParsedBoundsCategory::Type(ParsedTypeBounds {
+                Unknown: unknown_bounds,
+                ..bounds
+            }),
+            (Some(type_bounds), Some(size_type_bounds), _) => {
                 errors.error(
                     size_type_bounds
                         .Size
@@ -2415,6 +2517,7 @@ impl ParsedBounds {
 pub(crate) enum ParsedBoundCategory {
     Type(ParsedTypeBound),
     SizeType(ParsedSizeTypeBound),
+    Unknown(syn::TypeParamBound),
 }
 
 impl ParsedBound {
@@ -2425,15 +2528,18 @@ impl ParsedBound {
             Self::EnumType(v) => ParsedBoundCategory::Type(ParsedTypeBound::EnumType(v)),
             Self::IntType(v) => ParsedBoundCategory::Type(ParsedTypeBound::IntType(v)),
             Self::KnownSize(v) => ParsedBoundCategory::SizeType(ParsedSizeTypeBound::KnownSize(v)),
+            Self::ResetType(v) => ParsedBoundCategory::Type(ParsedTypeBound::ResetType(v)),
             Self::Size(v) => ParsedBoundCategory::SizeType(ParsedSizeTypeBound::Size(v)),
             Self::StaticType(v) => ParsedBoundCategory::Type(ParsedTypeBound::StaticType(v)),
             Self::Type(v) => ParsedBoundCategory::Type(ParsedTypeBound::Type(v)),
+            Self::Unknown(v) => ParsedBoundCategory::Unknown(v),
         }
     }
     fn implied_bounds(self) -> ParsedBounds {
         match self.categorize() {
             ParsedBoundCategory::Type(v) => v.implied_bounds().into(),
             ParsedBoundCategory::SizeType(v) => v.implied_bounds().into(),
+            ParsedBoundCategory::Unknown(v) => ParsedBounds::from_iter([ParsedBound::Unknown(v)]),
         }
     }
 }
@@ -3310,8 +3416,9 @@ impl ParsedGenerics {
                                 ParsedTypeBound::BoolOrIntType(_)
                                 | ParsedTypeBound::BundleType(_)
                                 | ParsedTypeBound::EnumType(_)
-                                | ParsedTypeBound::IntType(_) => {
-                                    errors.error(bound, "bound on mask type not implemented");
+                                | ParsedTypeBound::IntType(_)
+                                | ParsedTypeBound::ResetType(_) => {
+                                    errors.error(bound, "bounds on mask types are not implemented");
                                 }
                                 ParsedTypeBound::StaticType(bound) => {
                                     if bounds.StaticType.is_none() {
@@ -3323,6 +3430,12 @@ impl ParsedGenerics {
                                     }
                                 }
                                 ParsedTypeBound::Type(_) => {}
+                                ParsedTypeBound::Unknown(_) => {
+                                    errors.error(
+                                        bound,
+                                        "unknown bounds on mask types are not implemented",
+                                    );
+                                }
                             }
                         }
                         bounds.add_implied_bounds();
@@ -3648,7 +3761,10 @@ pub(crate) trait AsTurbofish {
 }
 
 impl AsTurbofish for TypeGenerics<'_> {
-    type Turbofish<'a> = Turbofish<'a> where Self: 'a;
+    type Turbofish<'a>
+        = Turbofish<'a>
+    where
+        Self: 'a;
 
     fn as_turbofish(&self) -> Self::Turbofish<'_> {
         TypeGenerics::as_turbofish(self)
@@ -3656,7 +3772,8 @@ impl AsTurbofish for TypeGenerics<'_> {
 }
 
 impl AsTurbofish for ParsedGenericsTypeGenerics<'_> {
-    type Turbofish<'a> = ParsedGenericsTurbofish<'a>
+    type Turbofish<'a>
+        = ParsedGenericsTurbofish<'a>
     where
         Self: 'a;
 
@@ -3707,15 +3824,18 @@ impl SplitForImpl for Generics {
 }
 
 impl SplitForImpl for ParsedGenerics {
-    type ImplGenerics<'a> = ParsedGenericsImplGenerics<'a>
+    type ImplGenerics<'a>
+        = ParsedGenericsImplGenerics<'a>
     where
         Self: 'a;
 
-    type TypeGenerics<'a> = ParsedGenericsTypeGenerics<'a>
+    type TypeGenerics<'a>
+        = ParsedGenericsTypeGenerics<'a>
     where
         Self: 'a;
 
-    type WhereClause<'a> = ParsedGenericsWhereClause<'a>
+    type WhereClause<'a>
+        = ParsedGenericsWhereClause<'a>
     where
         Self: 'a;
 
@@ -3932,7 +4052,8 @@ impl<P: ToTokens, U: ToTokens> ToTokens for MaybeParsed<P, U> {
 }
 
 impl<P: AsTurbofish, U: AsTurbofish> AsTurbofish for MaybeParsed<P, U> {
-    type Turbofish<'a> = MaybeParsed<P::Turbofish<'a>, U::Turbofish<'a>>
+    type Turbofish<'a>
+        = MaybeParsed<P::Turbofish<'a>, U::Turbofish<'a>>
     where
         Self: 'a;
 
@@ -3945,13 +4066,16 @@ impl<P: AsTurbofish, U: AsTurbofish> AsTurbofish for MaybeParsed<P, U> {
 }
 
 impl<P: SplitForImpl, U: SplitForImpl> SplitForImpl for MaybeParsed<P, U> {
-    type ImplGenerics<'a> = MaybeParsed<P::ImplGenerics<'a>, U::ImplGenerics<'a>>
+    type ImplGenerics<'a>
+        = MaybeParsed<P::ImplGenerics<'a>, U::ImplGenerics<'a>>
     where
         Self: 'a;
-    type TypeGenerics<'a> = MaybeParsed<P::TypeGenerics<'a>, U::TypeGenerics<'a>>
+    type TypeGenerics<'a>
+        = MaybeParsed<P::TypeGenerics<'a>, U::TypeGenerics<'a>>
     where
         Self: 'a;
-    type WhereClause<'a> = MaybeParsed<P::WhereClause<'a>, U::WhereClause<'a>>
+    type WhereClause<'a>
+        = MaybeParsed<P::WhereClause<'a>, U::WhereClause<'a>>
     where
         Self: 'a;
 

crates/fayalite-proc-macros-impl/src/lib.rs

@@ -2,15 +2,20 @@
 // See Notices.txt for copyright information
 #![cfg_attr(test, recursion_limit = "512")]
 use proc_macro2::{Span, TokenStream};
-use quote::{quote, ToTokens};
-use std::io::{ErrorKind, Write};
+use quote::{ToTokens, quote};
+use std::{
+    collections::{HashMap, hash_map::Entry},
+    io::{ErrorKind, Write},
+};
 use syn::{
-    bracketed, parenthesized,
+    AttrStyle, Attribute, Error, Ident, Item, ItemFn, LitBool, LitStr, Meta, Token, bracketed,
+    ext::IdentExt,
+    parenthesized,
     parse::{Parse, ParseStream, Parser},
     parse_quote,
-    punctuated::Pair,
+    punctuated::{Pair, Punctuated},
     spanned::Spanned,
-    AttrStyle, Attribute, Error, Item, ItemFn, Token,
+    token::{Bracket, Paren},
 };
 
 mod fold;
@@ -19,6 +24,7 @@ mod hdl_enum;
 mod hdl_type_alias;
 mod hdl_type_common;
 mod module;
+mod process_cfg;
 
 pub(crate) trait CustomToken:
     Copy
@@ -59,14 +65,20 @@ mod kw {
         };
     }
 
+    custom_keyword!(__evaluated_cfgs);
+    custom_keyword!(all);
+    custom_keyword!(any);
+    custom_keyword!(cfg);
+    custom_keyword!(cfg_attr);
     custom_keyword!(clock_domain);
+    custom_keyword!(cmp_eq);
     custom_keyword!(connect_inexact);
     custom_keyword!(custom_bounds);
     custom_keyword!(flip);
     custom_keyword!(hdl);
     custom_keyword!(hdl_module);
-    custom_keyword!(input);
     custom_keyword!(incomplete_wire);
+    custom_keyword!(input);
     custom_keyword!(instance);
     custom_keyword!(m);
     custom_keyword!(memory);
@@ -75,10 +87,12 @@ mod kw {
     custom_keyword!(no_reset);
     custom_keyword!(no_runtime_generics);
     custom_keyword!(no_static);
+    custom_keyword!(not);
     custom_keyword!(outline_generated);
     custom_keyword!(output);
     custom_keyword!(reg_builder);
     custom_keyword!(reset);
+    custom_keyword!(sim);
     custom_keyword!(skip);
     custom_keyword!(target);
     custom_keyword!(wire);
@@ -901,15 +915,346 @@ fn hdl_module_impl(item: ItemFn) -> syn::Result<TokenStream> {
     Ok(contents)
 }
 
-pub fn hdl_module(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
-    let kw = kw::hdl_module::default();
-    hdl_module_impl(syn::parse2(quote! { #[#kw(#attr)] #item })?)
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) enum CfgExpr {
+    Option {
+        ident: Ident,
+        value: Option<(Token![=], LitStr)>,
+    },
+    All {
+        all: kw::all,
+        paren: Paren,
+        exprs: Punctuated<CfgExpr, Token![,]>,
+    },
+    Any {
+        any: kw::any,
+        paren: Paren,
+        exprs: Punctuated<CfgExpr, Token![,]>,
+    },
+    Not {
+        not: kw::not,
+        paren: Paren,
+        expr: Box<CfgExpr>,
+        trailing_comma: Option<Token![,]>,
+    },
 }
 
-pub fn hdl_attr(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
-    let kw = kw::hdl::default();
-    let item = quote! { #[#kw(#attr)] #item };
-    let item = syn::parse2::<Item>(item)?;
+impl Parse for CfgExpr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        match input.cursor().ident() {
+            Some((_, cursor)) if cursor.eof() => {
+                return Ok(CfgExpr::Option {
+                    ident: input.call(Ident::parse_any)?,
+                    value: None,
+                });
+            }
+            _ => {}
+        }
+        if input.peek(Ident::peek_any) && input.peek2(Token![=]) {
+            return Ok(CfgExpr::Option {
+                ident: input.call(Ident::parse_any)?,
+                value: Some((input.parse()?, input.parse()?)),
+            });
+        }
+        let contents;
+        if input.peek(kw::all) {
+            Ok(CfgExpr::All {
+                all: input.parse()?,
+                paren: parenthesized!(contents in input),
+                exprs: contents.call(Punctuated::parse_terminated)?,
+            })
+        } else if input.peek(kw::any) {
+            Ok(CfgExpr::Any {
+                any: input.parse()?,
+                paren: parenthesized!(contents in input),
+                exprs: contents.call(Punctuated::parse_terminated)?,
+            })
+        } else if input.peek(kw::not) {
+            Ok(CfgExpr::Not {
+                not: input.parse()?,
+                paren: parenthesized!(contents in input),
+                expr: contents.parse()?,
+                trailing_comma: contents.parse()?,
+            })
+        } else {
+            Err(input.error("expected cfg-pattern"))
+        }
+    }
+}
+
+impl ToTokens for CfgExpr {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            CfgExpr::Option { ident, value } => {
+                ident.to_tokens(tokens);
+                if let Some((eq, value)) = value {
+                    eq.to_tokens(tokens);
+                    value.to_tokens(tokens);
+                }
+            }
+            CfgExpr::All { all, paren, exprs } => {
+                all.to_tokens(tokens);
+                paren.surround(tokens, |tokens| exprs.to_tokens(tokens));
+            }
+            CfgExpr::Any { any, paren, exprs } => {
+                any.to_tokens(tokens);
+                paren.surround(tokens, |tokens| exprs.to_tokens(tokens));
+            }
+            CfgExpr::Not {
+                not,
+                paren,
+                expr,
+                trailing_comma,
+            } => {
+                not.to_tokens(tokens);
+                paren.surround(tokens, |tokens| {
+                    expr.to_tokens(tokens);
+                    trailing_comma.to_tokens(tokens);
+                });
+            }
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct Cfg {
+    cfg: kw::cfg,
+    paren: Paren,
+    expr: CfgExpr,
+    trailing_comma: Option<Token![,]>,
+}
+
+impl Cfg {
+    fn parse_meta(meta: &Meta) -> syn::Result<Self> {
+        syn::parse2(meta.to_token_stream())
+    }
+}
+
+impl ToTokens for Cfg {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            cfg,
+            paren,
+            expr,
+            trailing_comma,
+        } = self;
+        cfg.to_tokens(tokens);
+        paren.surround(tokens, |tokens| {
+            expr.to_tokens(tokens);
+            trailing_comma.to_tokens(tokens);
+        });
+    }
+}
+
+impl Parse for Cfg {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        Ok(Self {
+            cfg: input.parse()?,
+            paren: parenthesized!(contents in input),
+            expr: contents.parse()?,
+            trailing_comma: contents.parse()?,
+        })
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct CfgAttr {
+    cfg_attr: kw::cfg_attr,
+    paren: Paren,
+    expr: CfgExpr,
+    comma: Token![,],
+    attrs: Punctuated<Meta, Token![,]>,
+}
+
+impl CfgAttr {
+    pub(crate) fn to_cfg(&self) -> Cfg {
+        Cfg {
+            cfg: kw::cfg(self.cfg_attr.span),
+            paren: self.paren,
+            expr: self.expr.clone(),
+            trailing_comma: None,
+        }
+    }
+    fn parse_meta(meta: &Meta) -> syn::Result<Self> {
+        syn::parse2(meta.to_token_stream())
+    }
+}
+
+impl Parse for CfgAttr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        Ok(Self {
+            cfg_attr: input.parse()?,
+            paren: parenthesized!(contents in input),
+            expr: contents.parse()?,
+            comma: contents.parse()?,
+            attrs: contents.call(Punctuated::parse_terminated)?,
+        })
+    }
+}
+
+pub(crate) struct CfgAndValue {
+    cfg: Cfg,
+    eq_token: Token![=],
+    value: LitBool,
+}
+
+impl Parse for CfgAndValue {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        Ok(Self {
+            cfg: input.parse()?,
+            eq_token: input.parse()?,
+            value: input.parse()?,
+        })
+    }
+}
+
+pub(crate) struct Cfgs<T> {
+    pub(crate) bracket: Bracket,
+    pub(crate) cfgs_map: HashMap<Cfg, T>,
+    pub(crate) cfgs_list: Vec<Cfg>,
+}
+
+impl<T> Default for Cfgs<T> {
+    fn default() -> Self {
+        Self {
+            bracket: Default::default(),
+            cfgs_map: Default::default(),
+            cfgs_list: Default::default(),
+        }
+    }
+}
+
+impl<T> Cfgs<T> {
+    fn insert_cfg(&mut self, cfg: Cfg, value: T) {
+        match self.cfgs_map.entry(cfg) {
+            Entry::Occupied(_) => {}
+            Entry::Vacant(entry) => {
+                self.cfgs_list.push(entry.key().clone());
+                entry.insert(value);
+            }
+        }
+    }
+}
+
+impl Parse for Cfgs<bool> {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        let bracket = bracketed!(contents in input);
+        let mut cfgs_map = HashMap::new();
+        let mut cfgs_list = Vec::new();
+        for CfgAndValue {
+            cfg,
+            eq_token,
+            value,
+        } in contents.call(Punctuated::<CfgAndValue, Token![,]>::parse_terminated)?
+        {
+            let _ = eq_token;
+            match cfgs_map.entry(cfg) {
+                Entry::Occupied(_) => {}
+                Entry::Vacant(entry) => {
+                    cfgs_list.push(entry.key().clone());
+                    entry.insert(value.value);
+                }
+            }
+        }
+        Ok(Self {
+            bracket,
+            cfgs_map,
+            cfgs_list,
+        })
+    }
+}
+
+impl Parse for Cfgs<()> {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        let bracket = bracketed!(contents in input);
+        let mut cfgs_map = HashMap::new();
+        let mut cfgs_list = Vec::new();
+        for cfg in contents.call(Punctuated::<Cfg, Token![,]>::parse_terminated)? {
+            match cfgs_map.entry(cfg) {
+                Entry::Occupied(_) => {}
+                Entry::Vacant(entry) => {
+                    cfgs_list.push(entry.key().clone());
+                    entry.insert(());
+                }
+            }
+        }
+        Ok(Self {
+            bracket,
+            cfgs_map,
+            cfgs_list,
+        })
+    }
+}
+
+impl ToTokens for Cfgs<()> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            bracket,
+            cfgs_map: _,
+            cfgs_list,
+        } = self;
+        bracket.surround(tokens, |tokens| {
+            for cfg in cfgs_list {
+                cfg.to_tokens(tokens);
+                <Token![,]>::default().to_tokens(tokens);
+            }
+        });
+    }
+}
+
+fn hdl_main(
+    kw: impl CustomToken,
+    attr: TokenStream,
+    item: TokenStream,
+) -> syn::Result<TokenStream> {
+    fn parse_evaluated_cfgs_attr<R>(
+        input: ParseStream,
+        parse_inner: impl FnOnce(ParseStream) -> syn::Result<R>,
+    ) -> syn::Result<R> {
+        let _: Token![#] = input.parse()?;
+        let bracket_content;
+        bracketed!(bracket_content in input);
+        let _: kw::__evaluated_cfgs = bracket_content.parse()?;
+        let paren_content;
+        parenthesized!(paren_content in bracket_content);
+        parse_inner(&paren_content)
+    }
+    let (evaluated_cfgs, item): (_, TokenStream) = Parser::parse2(
+        |input: ParseStream| {
+            let peek = input.fork();
+            if parse_evaluated_cfgs_attr(&peek, |_| Ok(())).is_ok() {
+                let evaluated_cfgs = parse_evaluated_cfgs_attr(input, Cfgs::<bool>::parse)?;
+                Ok((Some(evaluated_cfgs), input.parse()?))
+            } else {
+                Ok((None, input.parse()?))
+            }
+        },
+        item,
+    )?;
+    let cfgs = if let Some(cfgs) = evaluated_cfgs {
+        cfgs
+    } else {
+        let cfgs = process_cfg::collect_cfgs(syn::parse2(item.clone())?)?;
+        if cfgs.cfgs_list.is_empty() {
+            Cfgs::default()
+        } else {
+            return Ok(quote! {
+                ::fayalite::__cfg_expansion_helper! {
+                    []
+                    #cfgs
+                    {#[::fayalite::#kw(#attr)]} { #item }
+                }
+            });
+        }
+    };
+    let item = syn::parse2(quote! { #[#kw(#attr)] #item })?;
+    let Some(item) = process_cfg::process_cfgs(item, cfgs)? else {
+        return Ok(TokenStream::new());
+    };
     match item {
         Item::Enum(item) => hdl_enum::hdl_enum(item),
         Item::Struct(item) => hdl_bundle::hdl_bundle(item),
@@ -921,3 +1266,11 @@ pub fn hdl_attr(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream
         )),
     }
 }
+
+pub fn hdl_module(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
+    hdl_main(kw::hdl_module::default(), attr, item)
+}
+
+pub fn hdl_attr(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
+    hdl_main(kw::hdl::default(), attr, item)
+}

crates/fayalite-proc-macros-impl/src/module.rs

@@ -1,19 +1,20 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
+    Errors, HdlAttr, PairsIterExt,
     hdl_type_common::{ParsedGenerics, SplitForImpl},
     kw,
     module::transform_body::{HdlLet, HdlLetKindIO},
-    options, Errors, HdlAttr, PairsIterExt,
+    options,
 };
 use proc_macro2::TokenStream;
-use quote::{format_ident, quote, quote_spanned, ToTokens};
+use quote::{ToTokens, format_ident, quote, quote_spanned};
 use std::collections::HashSet;
 use syn::{
-    parse_quote,
-    visit::{visit_pat, Visit},
     Attribute, Block, ConstParam, Error, FnArg, GenericParam, Generics, Ident, ItemFn, ItemStruct,
     LifetimeParam, ReturnType, Signature, TypeParam, Visibility, WhereClause, WherePredicate,
+    parse_quote,
+    visit::{Visit, visit_pat},
 };
 
 mod transform_body;
@@ -377,7 +378,7 @@ impl ModuleFn {
             module_kind,
             vis,
             sig,
-            block,
+            mut block,
             struct_generics,
             the_struct,
         } = match self.0 {
@@ -439,6 +440,12 @@ impl ModuleFn {
         body_sig
             .inputs
             .insert(0, parse_quote! { m: &::fayalite::module::ModuleBuilder });
+        block.stmts.insert(
+            0,
+            parse_quote! {
+                let _ = m;
+            },
+        );
         let body_fn = ItemFn {
             attrs: vec![],
             vis: Visibility::Inherited,

crates/fayalite-proc-macros-impl/src/module/transform_body.rs

@@ -1,32 +1,40 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    fold::{impl_fold, DoFold},
+    Errors, HdlAttr,
+    fold::{DoFold, impl_fold},
     hdl_type_common::{
-        known_items, ParseFailed, ParseTypes, ParsedGenerics, ParsedType, TypesParser,
+        ParseFailed, ParseTypes, ParsedGenerics, ParsedType, TypesParser, known_items,
     },
     is_hdl_attr, kw,
-    module::{check_name_conflicts_with_module_builder, ModuleIO, ModuleIOKind, ModuleKind},
-    options, Errors, HdlAttr,
+    module::{ModuleIO, ModuleIOKind, ModuleKind, check_name_conflicts_with_module_builder},
+    options,
 };
 use num_bigint::BigInt;
 use proc_macro2::{Span, TokenStream};
-use quote::{quote, quote_spanned, ToTokens};
+use quote::{ToTokens, quote, quote_spanned};
 use std::{borrow::Borrow, convert::Infallible};
 use syn::{
-    fold::{fold_expr, fold_expr_lit, fold_expr_unary, fold_local, fold_stmt, Fold},
+    Attribute, Block, Error, Expr, ExprIf, ExprLet, ExprLit, ExprRepeat, ExprUnary,
+    GenericArgument, Ident, Item, Lit, LitStr, Local, LocalInit, Pat, Token, Type, UnOp,
+    fold::{Fold, fold_expr, fold_expr_lit, fold_expr_unary, fold_local, fold_stmt},
     parenthesized,
-    parse::{Nothing, Parse, ParseStream},
+    parse::{Parse, ParseStream},
     parse_quote, parse_quote_spanned,
     spanned::Spanned,
     token::Paren,
-    Attribute, Block, Error, Expr, ExprIf, ExprLet, ExprLit, ExprRepeat, ExprUnary,
-    GenericArgument, Ident, Item, Lit, LitStr, Local, LocalInit, Pat, Token, Type, UnOp,
 };
 
 mod expand_aggregate_literals;
 mod expand_match;
 
+options! {
+    #[options = ExprOptions]
+    pub(crate) enum ExprOption {
+        Sim(sim),
+    }
+}
+
 options! {
     pub(crate) enum LetFnKind {
         Input(input),
@@ -952,7 +960,7 @@ with_debug_clone_and_fold! {
     #[allow(dead_code)]
     pub(crate) struct HdlLet<Kind = HdlLetKind> {
         pub(crate) attrs: Vec<Attribute>,
-        pub(crate) hdl_attr: HdlAttr<Nothing, kw::hdl>,
+        pub(crate) hdl_attr: HdlAttr<syn::parse::Nothing, kw::hdl>,
         pub(crate) let_token: Token![let],
         pub(crate) mut_token: Option<Token![mut]>,
         pub(crate) name: Ident,
@@ -1109,7 +1117,7 @@ fn parse_quote_let_pat<T, R: ToTokens, C: Borrow<Token![:]>>(
     }
 }
 
-fn wrap_ty_with_expr(ty: impl ToTokens) -> Type {
+pub(crate) fn wrap_ty_with_expr(ty: impl ToTokens) -> Type {
     parse_quote_spanned! {ty.span()=>
         ::fayalite::expr::Expr<#ty>
     }
@@ -1173,7 +1181,7 @@ impl Visitor<'_> {
             Some(_) => {}
         }
     }
-    fn process_hdl_if(&mut self, hdl_attr: HdlAttr<Nothing, kw::hdl>, expr_if: ExprIf) -> Expr {
+    fn process_hdl_if(&mut self, hdl_attr: HdlAttr<ExprOptions, kw::hdl>, expr_if: ExprIf) -> Expr {
         let ExprIf {
             attrs,
             if_token,
@@ -1181,10 +1189,10 @@ impl Visitor<'_> {
             then_branch,
             else_branch,
         } = expr_if;
-        self.require_normal_module_or_fn(if_token);
-        let else_expr = else_branch.unzip().1.map(|else_expr| match *else_expr {
-            Expr::If(expr_if) => self.process_hdl_if(hdl_attr.clone(), expr_if),
-            expr => expr,
+        let (else_token, else_expr) = else_branch.unzip();
+        let else_expr = else_expr.map(|else_expr| match *else_expr {
+            Expr::If(expr_if) => Box::new(self.process_hdl_if(hdl_attr.clone(), expr_if)),
+            _ => else_expr,
         });
         if let Expr::Let(ExprLet {
             attrs: let_attrs,
@@ -1206,7 +1214,19 @@ impl Visitor<'_> {
                 },
             );
         }
-        if let Some(else_expr) = else_expr {
+        let ExprOptions { sim } = hdl_attr.body;
+        if sim.is_some() {
+            ExprIf {
+                attrs,
+                if_token,
+                cond: parse_quote_spanned! {if_token.span=>
+                    *::fayalite::sim::value::SimValue::<::fayalite::int::Bool>::value(&::fayalite::sim::value::ToSimValue::into_sim_value(#cond))
+                },
+                then_branch,
+                else_branch: else_token.zip(else_expr),
+            }
+            .into()
+        } else if let Some(else_expr) = else_expr {
             parse_quote_spanned! {if_token.span=>
                 #(#attrs)*
                 {
@@ -1586,7 +1606,7 @@ impl Visitor<'_> {
     }
 }
 
-fn empty_let() -> Local {
+pub(crate) fn empty_let() -> Local {
     Local {
         attrs: vec![],
         let_token: Default::default(),
@@ -1668,20 +1688,42 @@ impl Fold for Visitor<'_> {
                 Repeat => process_hdl_repeat,
                 Struct => process_hdl_struct,
                 Tuple => process_hdl_tuple,
+                MethodCall => process_hdl_method_call,
+                Call => process_hdl_call,
             }
         }
     }
 
-    fn fold_local(&mut self, let_stmt: Local) -> Local {
+    fn fold_local(&mut self, mut let_stmt: Local) -> Local {
         match self
             .errors
-            .ok(HdlAttr::<Nothing, kw::hdl>::parse_and_leave_attr(
+            .ok(HdlAttr::<ExprOptions, kw::hdl>::parse_and_leave_attr(
                 &let_stmt.attrs,
             )) {
             None => return empty_let(),
             Some(None) => return fold_local(self, let_stmt),
             Some(Some(HdlAttr { .. })) => {}
         };
+        let mut pat = &let_stmt.pat;
+        if let Pat::Type(pat_type) = pat {
+            pat = &pat_type.pat;
+        }
+        let Pat::Ident(syn::PatIdent {
+            attrs: _,
+            by_ref: None,
+            mutability: _,
+            ident: _,
+            subpat: None,
+        }) = pat
+        else {
+            let hdl_attr =
+                HdlAttr::<ExprOptions, kw::hdl>::parse_and_take_attr(&mut let_stmt.attrs)
+                    .ok()
+                    .flatten()
+                    .expect("already checked above");
+            let let_stmt = fold_local(self, let_stmt);
+            return self.process_hdl_let_pat(hdl_attr, let_stmt);
+        };
         let hdl_let = syn::parse2::<HdlLet<HdlLetKind<Type>>>(let_stmt.into_token_stream());
         let Some(hdl_let) = self.errors.ok(hdl_let) else {
             return empty_let();

crates/fayalite-proc-macros-impl/src/module/transform_body/expand_aggregate_literals.rs

@@ -1,45 +1,102 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
-use crate::{kw, module::transform_body::Visitor, HdlAttr};
+
+use crate::{
+    HdlAttr, kw,
+    module::transform_body::{
+        ExprOptions, Visitor,
+        expand_match::{EnumPath, parse_enum_path},
+    },
+};
 use quote::{format_ident, quote_spanned};
+use std::mem;
 use syn::{
-    parse::Nothing, parse_quote, parse_quote_spanned, spanned::Spanned, Expr, ExprArray, ExprPath,
-    ExprRepeat, ExprStruct, ExprTuple, FieldValue, TypePath,
+    Expr, ExprArray, ExprCall, ExprGroup, ExprMethodCall, ExprParen, ExprPath, ExprRepeat,
+    ExprStruct, ExprTuple, FieldValue, Token, TypePath, parse_quote_spanned,
+    punctuated::Punctuated, spanned::Spanned, token::Paren,
 };
 
 impl Visitor<'_> {
     pub(crate) fn process_hdl_array(
         &mut self,
-        hdl_attr: HdlAttr<Nothing, kw::hdl>,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
         mut expr_array: ExprArray,
     ) -> Expr {
-        self.require_normal_module_or_fn(hdl_attr);
-        for elem in &mut expr_array.elems {
-            *elem = parse_quote_spanned! {elem.span()=>
-                ::fayalite::expr::ToExpr::to_expr(&(#elem))
-            };
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        if sim.is_some() {
+            for elem in &mut expr_array.elems {
+                *elem = parse_quote_spanned! {elem.span()=>
+                    ::fayalite::sim::value::ToSimValue::to_sim_value(&(#elem))
+                };
+            }
+            parse_quote_spanned! {span=>
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_array)
+            }
+        } else {
+            for elem in &mut expr_array.elems {
+                *elem = parse_quote_spanned! {elem.span()=>
+                    ::fayalite::expr::ToExpr::to_expr(&(#elem))
+                };
+            }
+            parse_quote_spanned! {span=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_array)
+            }
         }
-        parse_quote! {::fayalite::expr::ToExpr::to_expr(&#expr_array)}
     }
     pub(crate) fn process_hdl_repeat(
         &mut self,
-        hdl_attr: HdlAttr<Nothing, kw::hdl>,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
         mut expr_repeat: ExprRepeat,
     ) -> Expr {
-        self.require_normal_module_or_fn(hdl_attr);
         let repeated_value = &expr_repeat.expr;
-        *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
-            ::fayalite::expr::ToExpr::to_expr(&(#repeated_value))
-        };
-        parse_quote! {::fayalite::expr::ToExpr::to_expr(&#expr_repeat)}
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        if sim.is_some() {
+            *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
+                ::fayalite::sim::value::ToSimValue::to_sim_value(&(#repeated_value))
+            };
+            parse_quote_spanned! {span=>
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_repeat)
+            }
+        } else {
+            *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
+                ::fayalite::expr::ToExpr::to_expr(&(#repeated_value))
+            };
+            parse_quote_spanned! {span=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_repeat)
+            }
+        }
     }
     pub(crate) fn process_hdl_struct(
         &mut self,
-        hdl_attr: HdlAttr<Nothing, kw::hdl>,
-        expr_struct: ExprStruct,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_struct: ExprStruct,
     ) -> Expr {
-        self.require_normal_module_or_fn(&hdl_attr);
         let name_span = expr_struct.path.segments.last().unwrap().ident.span();
+        let ExprOptions { sim } = hdl_attr.body;
+        if sim.is_some() {
+            let ty_path = TypePath {
+                qself: expr_struct.qself.take(),
+                path: expr_struct.path,
+            };
+            expr_struct.path = parse_quote_spanned! {name_span=>
+                __SimValue::<#ty_path>
+            };
+            for field in &mut expr_struct.fields {
+                let expr = &field.expr;
+                field.expr = parse_quote_spanned! {field.member.span()=>
+                    ::fayalite::sim::value::ToSimValue::to_sim_value(&(#expr))
+                };
+            }
+            return parse_quote_spanned! {name_span=>
+                {
+                    type __SimValue<T> = <T as ::fayalite::ty::Type>::SimValue;
+                    let value: ::fayalite::sim::value::SimValue<#ty_path> = ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_struct);
+                    value
+                }
+            };
+        }
         let builder_ident = format_ident!("__builder", span = name_span);
         let empty_builder = if expr_struct.qself.is_some()
             || expr_struct
@@ -91,12 +148,126 @@ impl Visitor<'_> {
     }
     pub(crate) fn process_hdl_tuple(
         &mut self,
-        hdl_attr: HdlAttr<Nothing, kw::hdl>,
-        expr_tuple: ExprTuple,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_tuple: ExprTuple,
     ) -> Expr {
-        self.require_normal_module_or_fn(hdl_attr);
-        parse_quote_spanned! {expr_tuple.span()=>
-            ::fayalite::expr::ToExpr::to_expr(&#expr_tuple)
+        let ExprOptions { sim } = hdl_attr.body;
+        if sim.is_some() {
+            for element in &mut expr_tuple.elems {
+                *element = parse_quote_spanned! {element.span()=>
+                    &(#element)
+                };
+            }
+            parse_quote_spanned! {expr_tuple.span()=>
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_tuple)
+            }
+        } else {
+            parse_quote_spanned! {expr_tuple.span()=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_tuple)
+            }
         }
     }
+    pub(crate) fn process_hdl_call(
+        &mut self,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_call: ExprCall,
+    ) -> Expr {
+        let span = hdl_attr.kw.span;
+        let mut func = &mut *expr_call.func;
+        let EnumPath {
+            variant_path: _,
+            enum_path,
+            variant_name,
+        } = loop {
+            match func {
+                Expr::Group(ExprGroup { expr, .. }) | Expr::Paren(ExprParen { expr, .. }) => {
+                    func = &mut **expr;
+                }
+                Expr::Path(_) => {
+                    let Expr::Path(ExprPath { attrs, qself, path }) =
+                        mem::replace(func, Expr::PLACEHOLDER)
+                    else {
+                        unreachable!();
+                    };
+                    match parse_enum_path(TypePath { qself, path }) {
+                        Ok(path) => break path,
+                        Err(path) => {
+                            self.errors.error(&path, "unsupported enum variant path");
+                            let TypePath { qself, path } = path;
+                            *func = ExprPath { attrs, qself, path }.into();
+                            return expr_call.into();
+                        }
+                    }
+                }
+                _ => {
+                    self.errors.error(
+                        &expr_call.func,
+                        "#[hdl] function call -- function must be a possibly-parenthesized path",
+                    );
+                    return expr_call.into();
+                }
+            }
+        };
+        self.process_hdl_method_call(
+            hdl_attr,
+            ExprMethodCall {
+                attrs: expr_call.attrs,
+                receiver: parse_quote_spanned! {span=>
+                    <#enum_path as ::fayalite::ty::StaticType>::TYPE
+                },
+                dot_token: Token![.](span),
+                method: variant_name,
+                turbofish: None,
+                paren_token: expr_call.paren_token,
+                args: expr_call.args,
+            },
+        )
+    }
+    pub(crate) fn process_hdl_method_call(
+        &mut self,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_method_call: ExprMethodCall,
+    ) -> Expr {
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        // remove any number of groups and up to one paren
+        let mut receiver = &mut *expr_method_call.receiver;
+        let mut has_group = false;
+        let receiver = loop {
+            match receiver {
+                Expr::Group(ExprGroup { expr, .. }) => {
+                    has_group = true;
+                    receiver = expr;
+                }
+                Expr::Paren(ExprParen { expr, .. }) => break &mut **expr,
+                receiver @ Expr::Path(_) => break receiver,
+                _ => {
+                    if !has_group {
+                        self.errors.error(
+                            &expr_method_call.receiver,
+                            "#[hdl] on a method call needs parenthesized receiver",
+                        );
+                    }
+                    break &mut *expr_method_call.receiver;
+                }
+            }
+        };
+        let func = if sim.is_some() {
+            parse_quote_spanned! {span=>
+                ::fayalite::enum_::enum_type_to_sim_builder
+            }
+        } else {
+            parse_quote_spanned! {span=>
+                ::fayalite::enum_::assert_is_enum_type
+            }
+        };
+        *expr_method_call.receiver = ExprCall {
+            attrs: vec![],
+            func,
+            paren_token: Paren(span),
+            args: Punctuated::from_iter([mem::replace(receiver, Expr::PLACEHOLDER)]),
+        }
+        .into();
+        expr_method_call.into()
+    }
 }

crates/fayalite-proc-macros-impl/src/module/transform_body/expand_match.rs

@@ -1,24 +1,121 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    fold::{impl_fold, DoFold},
-    kw,
-    module::transform_body::{with_debug_clone_and_fold, Visitor},
     Errors, HdlAttr, PairsIterExt,
+    fold::{DoFold, impl_fold},
+    kw,
+    module::transform_body::{
+        ExprOptions, Visitor, empty_let, with_debug_clone_and_fold, wrap_ty_with_expr,
+    },
 };
 use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote_spanned, ToTokens, TokenStreamExt};
+use quote::{ToTokens, TokenStreamExt, format_ident, quote_spanned};
+use std::collections::BTreeSet;
 use syn::{
-    fold::{fold_arm, fold_expr_match, fold_pat, Fold},
-    parse::Nothing,
+    Arm, Attribute, Expr, ExprMatch, FieldPat, Ident, Local, Member, Pat, PatIdent, PatOr,
+    PatParen, PatPath, PatRest, PatStruct, PatTuple, PatTupleStruct, PatWild, Path, PathSegment,
+    Token, TypePath,
+    fold::{Fold, fold_arm, fold_expr_match, fold_local, fold_pat},
     parse_quote_spanned,
     punctuated::Punctuated,
     spanned::Spanned,
     token::{Brace, Paren},
-    Arm, Attribute, Expr, ExprMatch, FieldPat, Ident, Member, Pat, PatIdent, PatOr, PatParen,
-    PatPath, PatRest, PatStruct, PatTupleStruct, PatWild, Path, PathSegment, Token, TypePath,
 };
 
+macro_rules! visit_trait {
+    (
+        $($vis:vis fn $fn:ident($state:ident: _, $value:ident: &$Value:ty) $block:block)*
+    ) => {
+        trait VisitMatchPat<'a> {
+            $(fn $fn(&mut self, $value: &'a $Value) {
+                $fn(self, $value);
+            })*
+        }
+
+        $($vis fn $fn<'a>($state: &mut (impl ?Sized + VisitMatchPat<'a>), $value: &'a $Value) $block)*
+    };
+}
+
+visit_trait! {
+    fn visit_match_pat_binding(_state: _, v: &MatchPatBinding) {
+        let MatchPatBinding { ident: _ } = v;
+    }
+    fn visit_match_pat_wild(_state: _, v: &MatchPatWild) {
+        let MatchPatWild { underscore_token: _ } = v;
+    }
+    fn visit_match_pat_rest(_state: _, v: &MatchPatRest) {
+        let MatchPatRest { dot2_token: _ } = v;
+    }
+    fn visit_match_pat_paren(state: _, v: &MatchPatParen<MatchPat>) {
+        let MatchPatParen { paren_token: _, pat } = v;
+        state.visit_match_pat(pat);
+    }
+    fn visit_match_pat_paren_simple(state: _, v: &MatchPatParen<MatchPatSimple>) {
+        let MatchPatParen { paren_token: _, pat } = v;
+        state.visit_match_pat_simple(pat);
+    }
+    fn visit_match_pat_or(state: _, v: &MatchPatOr<MatchPat>) {
+        let MatchPatOr { leading_vert: _, cases } = v;
+        for v in cases {
+            state.visit_match_pat(v);
+        }
+    }
+    fn visit_match_pat_or_simple(state: _, v: &MatchPatOr<MatchPatSimple>) {
+        let MatchPatOr { leading_vert: _, cases } = v;
+        for v in cases {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_struct_field(state: _, v: &MatchPatStructField) {
+        let MatchPatStructField { field_name: _, colon_token: _, pat } = v;
+        state.visit_match_pat_simple(pat);
+    }
+    fn visit_match_pat_struct(state: _, v: &MatchPatStruct) {
+        let MatchPatStruct { match_span: _, path: _, brace_token: _, fields, rest: _ } = v;
+        for v in fields {
+            state.visit_match_pat_struct_field(v);
+        }
+    }
+    fn visit_match_pat_tuple(state: _, v: &MatchPatTuple) {
+        let MatchPatTuple { paren_token: _, fields } = v;
+        for v in fields {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_enum_variant(state: _, v: &MatchPatEnumVariant) {
+        let MatchPatEnumVariant {
+            match_span:_,
+            sim:_,
+            variant_path: _,
+            enum_path: _,
+            variant_name: _,
+            field,
+        } = v;
+        if let Some((_, v)) = field {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_simple(state: _, v: &MatchPatSimple) {
+        match v {
+            MatchPatSimple::Paren(v) => state.visit_match_pat_paren_simple(v),
+            MatchPatSimple::Or(v) => state.visit_match_pat_or_simple(v),
+            MatchPatSimple::Binding(v) => state.visit_match_pat_binding(v),
+            MatchPatSimple::Wild(v) => state.visit_match_pat_wild(v),
+            MatchPatSimple::Rest(v) => state.visit_match_pat_rest(v),
+        }
+    }
+    fn visit_match_pat(state: _, v: &MatchPat) {
+        match v {
+            MatchPat::Simple(v) => state.visit_match_pat_simple(v),
+            MatchPat::Or(v) => state.visit_match_pat_or(v),
+            MatchPat::Paren(v) => state.visit_match_pat_paren(v),
+            MatchPat::Struct(v) => state.visit_match_pat_struct(v),
+            MatchPat::Tuple(v) => state.visit_match_pat_tuple(v),
+            MatchPat::EnumVariant(v) => state.visit_match_pat_enum_variant(v),
+        }
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatBinding<> {
         ident: Ident,
@@ -53,6 +150,15 @@ with_debug_clone_and_fold! {
     }
 }
 
+impl<P> MatchPatOr<P> {
+    /// returns the first `|` between two patterns
+    fn first_inner_vert(&self) -> Option<Token![|]> {
+        let mut pairs = self.cases.pairs();
+        pairs.next_back();
+        pairs.next().and_then(|v| v.into_tuple().1.copied())
+    }
+}
+
 impl<P: ToTokens> ToTokens for MatchPatOr<P> {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         let Self {
@@ -77,6 +183,19 @@ impl ToTokens for MatchPatWild {
     }
 }
 
+with_debug_clone_and_fold! {
+    struct MatchPatRest<> {
+        dot2_token: Token![..],
+    }
+}
+
+impl ToTokens for MatchPatRest {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self { dot2_token } = self;
+        dot2_token.to_tokens(tokens);
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatStructField<> {
         field_name: Ident,
@@ -159,9 +278,29 @@ impl ToTokens for MatchPatStruct {
     }
 }
 
+with_debug_clone_and_fold! {
+    struct MatchPatTuple<> {
+        paren_token: Paren,
+        fields: Punctuated<MatchPatSimple, Token![,]>,
+    }
+}
+
+impl ToTokens for MatchPatTuple {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            paren_token,
+            fields,
+        } = self;
+        paren_token.surround(tokens, |tokens| {
+            fields.to_tokens(tokens);
+        })
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatEnumVariant<> {
         match_span: Span,
+        sim: Option<(kw::sim,)>,
         variant_path: Path,
         enum_path: Path,
         variant_name: Ident,
@@ -173,6 +312,7 @@ impl ToTokens for MatchPatEnumVariant {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         let Self {
             match_span,
+            sim,
             variant_path: _,
             enum_path,
             variant_name,
@@ -182,7 +322,28 @@ impl ToTokens for MatchPatEnumVariant {
             __MatchTy::<#enum_path>::#variant_name
         }
         .to_tokens(tokens);
-        if let Some((paren_token, field)) = field {
+        if sim.is_some() {
+            if let Some((paren_token, field)) = field {
+                paren_token.surround(tokens, |tokens| {
+                    field.to_tokens(tokens);
+                    match field {
+                        MatchPatSimple::Paren(_)
+                        | MatchPatSimple::Or(_)
+                        | MatchPatSimple::Binding(_)
+                        | MatchPatSimple::Wild(_) => quote_spanned! {*match_span=>
+                            , _
+                        }
+                        .to_tokens(tokens),
+                        MatchPatSimple::Rest(_) => {}
+                    }
+                });
+            } else {
+                quote_spanned! {*match_span=>
+                    (_)
+                }
+                .to_tokens(tokens);
+            }
+        } else if let Some((paren_token, field)) = field {
             paren_token.surround(tokens, |tokens| field.to_tokens(tokens));
         }
     }
@@ -194,6 +355,7 @@ enum MatchPatSimple {
     Or(MatchPatOr<MatchPatSimple>),
     Binding(MatchPatBinding),
     Wild(MatchPatWild),
+    Rest(MatchPatRest),
 }
 
 impl_fold! {
@@ -202,6 +364,7 @@ impl_fold! {
         Or(MatchPatOr<MatchPatSimple>),
         Binding(MatchPatBinding),
         Wild(MatchPatWild),
+        Rest(MatchPatRest),
     }
 }
 
@@ -212,17 +375,18 @@ impl ToTokens for MatchPatSimple {
             Self::Paren(v) => v.to_tokens(tokens),
             Self::Binding(v) => v.to_tokens(tokens),
             Self::Wild(v) => v.to_tokens(tokens),
+            Self::Rest(v) => v.to_tokens(tokens),
         }
     }
 }
 
-struct EnumPath {
-    variant_path: Path,
-    enum_path: Path,
-    variant_name: Ident,
+pub(crate) struct EnumPath {
+    pub(crate) variant_path: Path,
+    pub(crate) enum_path: Path,
+    pub(crate) variant_name: Ident,
 }
 
-fn parse_enum_path(variant_path: TypePath) -> Result<EnumPath, TypePath> {
+pub(crate) fn parse_enum_path(variant_path: TypePath) -> Result<EnumPath, TypePath> {
     let TypePath {
         qself: None,
         path: variant_path,
@@ -278,8 +442,9 @@ trait ParseMatchPat: Sized {
     fn or(v: MatchPatOr<Self>) -> Self;
     fn paren(v: MatchPatParen<Self>) -> Self;
     fn struct_(state: &mut HdlMatchParseState<'_>, v: MatchPatStruct) -> Result<Self, ()>;
+    fn tuple(state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()>;
     fn enum_variant(state: &mut HdlMatchParseState<'_>, v: MatchPatEnumVariant)
-        -> Result<Self, ()>;
+    -> Result<Self, ()>;
     fn parse(state: &mut HdlMatchParseState<'_>, pat: Pat) -> Result<Self, ()> {
         match pat {
             Pat::Ident(PatIdent {
@@ -313,6 +478,7 @@ trait ParseMatchPat: Sized {
                         state,
                         MatchPatEnumVariant {
                             match_span: state.match_span,
+                            sim: state.sim,
                             variant_path,
                             enum_path,
                             variant_name,
@@ -359,6 +525,7 @@ trait ParseMatchPat: Sized {
                     state,
                     MatchPatEnumVariant {
                         match_span: state.match_span,
+                        sim: state.sim,
                         variant_path,
                         enum_path,
                         variant_name,
@@ -443,6 +610,7 @@ trait ParseMatchPat: Sized {
                     state,
                     MatchPatEnumVariant {
                         match_span: state.match_span,
+                        sim: state.sim,
                         variant_path,
                         enum_path,
                         variant_name,
@@ -462,7 +630,34 @@ trait ParseMatchPat: Sized {
             }) => Ok(Self::simple(MatchPatSimple::Wild(MatchPatWild {
                 underscore_token,
             }))),
-            Pat::Tuple(_) | Pat::Slice(_) | Pat::Const(_) | Pat::Lit(_) | Pat::Range(_) => {
+            Pat::Tuple(PatTuple {
+                attrs: _,
+                paren_token,
+                elems,
+            }) => {
+                let fields = elems
+                    .into_pairs()
+                    .filter_map_pair_value(|field_pat| {
+                        if let Pat::Rest(PatRest {
+                            attrs: _,
+                            dot2_token,
+                        }) = field_pat
+                        {
+                            Some(MatchPatSimple::Rest(MatchPatRest { dot2_token }))
+                        } else {
+                            MatchPatSimple::parse(state, field_pat).ok()
+                        }
+                    })
+                    .collect();
+                Self::tuple(
+                    state,
+                    MatchPatTuple {
+                        paren_token,
+                        fields,
+                    },
+                )
+            }
+            Pat::Slice(_) | Pat::Const(_) | Pat::Lit(_) | Pat::Range(_) => {
                 state
                     .errors
                     .error(pat, "not yet implemented in #[hdl] patterns");
@@ -497,6 +692,14 @@ impl ParseMatchPat for MatchPatSimple {
         Err(())
     }
 
+    fn tuple(state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()> {
+        state.errors.push(syn::Error::new(
+            v.paren_token.span.open(),
+            "matching tuples is not yet implemented inside structs/enums in #[hdl] patterns",
+        ));
+        Err(())
+    }
+
     fn enum_variant(
         state: &mut HdlMatchParseState<'_>,
         v: MatchPatEnumVariant,
@@ -515,6 +718,7 @@ enum MatchPat {
     Or(MatchPatOr<MatchPat>),
     Paren(MatchPatParen<MatchPat>),
     Struct(MatchPatStruct),
+    Tuple(MatchPatTuple),
     EnumVariant(MatchPatEnumVariant),
 }
 
@@ -524,6 +728,7 @@ impl_fold! {
         Or(MatchPatOr<MatchPat>),
         Paren(MatchPatParen<MatchPat>),
         Struct(MatchPatStruct),
+        Tuple(MatchPatTuple),
         EnumVariant(MatchPatEnumVariant),
     }
 }
@@ -545,6 +750,10 @@ impl ParseMatchPat for MatchPat {
         Ok(Self::Struct(v))
     }
 
+    fn tuple(_state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()> {
+        Ok(Self::Tuple(v))
+    }
+
     fn enum_variant(
         _state: &mut HdlMatchParseState<'_>,
         v: MatchPatEnumVariant,
@@ -560,6 +769,7 @@ impl ToTokens for MatchPat {
             Self::Or(v) => v.to_tokens(tokens),
             Self::Paren(v) => v.to_tokens(tokens),
             Self::Struct(v) => v.to_tokens(tokens),
+            Self::Tuple(v) => v.to_tokens(tokens),
             Self::EnumVariant(v) => v.to_tokens(tokens),
         }
     }
@@ -622,10 +832,6 @@ struct RewriteAsCheckMatch {
 }
 
 impl Fold for RewriteAsCheckMatch {
-    fn fold_field_pat(&mut self, mut i: FieldPat) -> FieldPat {
-        i.colon_token = Some(Token![:](i.member.span()));
-        i
-    }
     fn fold_pat(&mut self, pat: Pat) -> Pat {
         match pat {
             Pat::Ident(mut pat_ident) => match parse_enum_ident(pat_ident.ident) {
@@ -740,17 +946,177 @@ impl Fold for RewriteAsCheckMatch {
         // don't recurse into expressions
         i
     }
+    fn fold_local(&mut self, mut let_stmt: Local) -> Local {
+        if let Some(syn::LocalInit {
+            eq_token,
+            expr: _,
+            diverge,
+        }) = let_stmt.init.take()
+        {
+            let_stmt.init = Some(syn::LocalInit {
+                eq_token,
+                expr: parse_quote_spanned! {self.span=>
+                    __match_value
+                },
+                diverge: diverge.map(|(else_, _expr)| {
+                    (
+                        else_,
+                        parse_quote_spanned! {self.span=>
+                            match __infallible {}
+                        },
+                    )
+                }),
+            });
+        }
+        fold_local(self, let_stmt)
+    }
 }
 
 struct HdlMatchParseState<'a> {
+    sim: Option<(kw::sim,)>,
     match_span: Span,
     errors: &'a mut Errors,
 }
 
+struct HdlLetPatVisitState<'a> {
+    errors: &'a mut Errors,
+    bindings: BTreeSet<&'a Ident>,
+}
+
+impl<'a> VisitMatchPat<'a> for HdlLetPatVisitState<'a> {
+    fn visit_match_pat_binding(&mut self, v: &'a MatchPatBinding) {
+        self.bindings.insert(&v.ident);
+    }
+
+    fn visit_match_pat_or(&mut self, v: &'a MatchPatOr<MatchPat>) {
+        if let Some(first_inner_vert) = v.first_inner_vert() {
+            self.errors.error(
+                first_inner_vert,
+                "or-patterns are not supported in let statements",
+            );
+        }
+        visit_match_pat_or(self, v);
+    }
+
+    fn visit_match_pat_or_simple(&mut self, v: &'a MatchPatOr<MatchPatSimple>) {
+        if let Some(first_inner_vert) = v.first_inner_vert() {
+            self.errors.error(
+                first_inner_vert,
+                "or-patterns are not supported in let statements",
+            );
+        }
+        visit_match_pat_or_simple(self, v);
+    }
+
+    fn visit_match_pat_enum_variant(&mut self, v: &'a MatchPatEnumVariant) {
+        self.errors.error(v, "refutable pattern in let statement");
+    }
+}
+
 impl Visitor<'_> {
+    pub(crate) fn process_hdl_let_pat(
+        &mut self,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut let_stmt: Local,
+    ) -> Local {
+        let span = let_stmt.let_token.span();
+        let ExprOptions { sim } = hdl_attr.body;
+        if let Pat::Type(pat) = &mut let_stmt.pat {
+            *pat.ty = wrap_ty_with_expr((*pat.ty).clone());
+        }
+        let check_let_stmt = RewriteAsCheckMatch { span }.fold_local(let_stmt.clone());
+        let Local {
+            attrs: _,
+            let_token,
+            pat,
+            init,
+            semi_token,
+        } = let_stmt;
+        let Some(syn::LocalInit {
+            eq_token,
+            expr,
+            diverge,
+        }) = init
+        else {
+            self.errors
+                .error(let_token, "#[hdl] let must be assigned a value");
+            return empty_let();
+        };
+        if let Some((else_, _)) = diverge {
+            // TODO: implement let-else
+            self.errors
+                .error(else_, "#[hdl] let ... else { ... } is not implemented");
+            return empty_let();
+        }
+        let Ok(pat) = MatchPat::parse(
+            &mut HdlMatchParseState {
+                sim,
+                match_span: span,
+                errors: &mut self.errors,
+            },
+            pat,
+        ) else {
+            return empty_let();
+        };
+        let mut state = HdlLetPatVisitState {
+            errors: &mut self.errors,
+            bindings: BTreeSet::new(),
+        };
+        state.visit_match_pat(&pat);
+        let HdlLetPatVisitState {
+            errors: _,
+            bindings,
+        } = state;
+        let retval = if sim.is_some() {
+            parse_quote_spanned! {span=>
+                let (#(#bindings,)*) = {
+                    type __MatchTy<T> = <T as ::fayalite::ty::Type>::SimValue;
+                    let __match_value = ::fayalite::sim::value::ToSimValue::to_sim_value(&(#expr));
+                    #let_token #pat #eq_token ::fayalite::sim::value::SimValue::into_value(__match_value) #semi_token
+                    (#(#bindings,)*)
+                };
+            }
+        } else {
+            parse_quote_spanned! {span=>
+                let (#(#bindings,)* __scope,) = {
+                    type __MatchTy<T> = <T as ::fayalite::ty::Type>::MatchVariant;
+                    let __match_expr = ::fayalite::expr::ToExpr::to_expr(&(#expr));
+                    ::fayalite::expr::check_match_expr(
+                        __match_expr,
+                        |__match_value, __infallible| {
+                            #[allow(unused_variables)]
+                            #check_let_stmt
+                            match __infallible {}
+                        },
+                    );
+                    let mut __match_iter = ::fayalite::module::match_(__match_expr);
+                    let ::fayalite::__std::option::Option::Some(__match_variant) =
+                        ::fayalite::__std::iter::Iterator::next(&mut __match_iter)
+                    else {
+                        ::fayalite::__std::unreachable!("#[hdl] let with uninhabited type");
+                    };
+                    let ::fayalite::__std::option::Option::None =
+                        ::fayalite::__std::iter::Iterator::next(&mut __match_iter)
+                    else {
+                        ::fayalite::__std::unreachable!("#[hdl] let with refutable pattern");
+                    };
+                    let (__match_variant, __scope) =
+                        ::fayalite::ty::MatchVariantAndInactiveScope::match_activate_scope(
+                            __match_variant,
+                        );
+                    #let_token #pat #eq_token __match_variant #semi_token
+                    (#(#bindings,)* __scope,)
+                };
+            }
+        };
+        match retval {
+            syn::Stmt::Local(retval) => retval,
+            _ => unreachable!(),
+        }
+    }
     pub(crate) fn process_hdl_match(
         &mut self,
-        _hdl_attr: HdlAttr<Nothing, kw::hdl>,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
         expr_match: ExprMatch,
     ) -> Expr {
         let span = expr_match.match_token.span();
@@ -762,8 +1128,9 @@ impl Visitor<'_> {
             brace_token: _,
             arms,
         } = expr_match;
-        self.require_normal_module_or_fn(match_token);
+        let ExprOptions { sim } = hdl_attr.body;
         let mut state = HdlMatchParseState {
+            sim,
             match_span: span,
             errors: &mut self.errors,
         };
@@ -771,24 +1138,36 @@ impl Visitor<'_> {
             arms.into_iter()
                 .filter_map(|arm| MatchArm::parse(&mut state, arm).ok()),
         );
-        let expr = quote_spanned! {span=>
-            {
-                type __MatchTy<T> = <T as ::fayalite::ty::Type>::MatchVariant;
-                let __match_expr = ::fayalite::expr::ToExpr::to_expr(&(#expr));
-                ::fayalite::expr::check_match_expr(__match_expr, |__match_value, __infallible| {
-                    #[allow(unused_variables)]
-                    #check_match
-                });
-                for __match_variant in ::fayalite::module::match_(__match_expr) {
-                    let (__match_variant, __scope) =
-                        ::fayalite::ty::MatchVariantAndInactiveScope::match_activate_scope(
-                            __match_variant,
-                        );
-                    #match_token __match_variant {
+        let expr = if sim.is_some() {
+            quote_spanned! {span=>
+                {
+                    type __MatchTy<T> = <T as ::fayalite::ty::Type>::SimValue;
+                    let __match_expr = ::fayalite::sim::value::ToSimValue::to_sim_value(&(#expr));
+                    #match_token ::fayalite::sim::value::SimValue::into_value(__match_expr) {
                         #(#arms)*
                     }
                 }
             }
+        } else {
+            quote_spanned! {span=>
+                {
+                    type __MatchTy<T> = <T as ::fayalite::ty::Type>::MatchVariant;
+                    let __match_expr = ::fayalite::expr::ToExpr::to_expr(&(#expr));
+                    ::fayalite::expr::check_match_expr(__match_expr, |__match_value, __infallible| {
+                        #[allow(unused_variables)]
+                        #check_match
+                    });
+                    for __match_variant in ::fayalite::module::match_(__match_expr) {
+                        let (__match_variant, __scope) =
+                            ::fayalite::ty::MatchVariantAndInactiveScope::match_activate_scope(
+                                __match_variant,
+                            );
+                        #match_token __match_variant {
+                            #(#arms)*
+                        }
+                    }
+                }
+            }
         };
         syn::parse2(expr).unwrap()
     }

crates/fayalite-visit-gen/src/lib.rs

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote, ToTokens};
+use quote::{ToTokens, format_ident, quote};
 use std::{collections::BTreeMap, fs};
 use syn::{fold::Fold, parse_quote};
 

crates/fayalite/Cargo.toml

@@ -25,19 +25,23 @@ jobslot.workspace = true
 num-bigint.workspace = true
 num-traits.workspace = true
 os_pipe.workspace = true
+petgraph.workspace = true
 serde_json.workspace = true
 serde.workspace = true
 tempfile.workspace = true
+vec_map.workspace = true
 which.workspace = true
 
 [dev-dependencies]
 trybuild.workspace = true
+serde = { workspace = true, features = ["rc"] }
 
 [build-dependencies]
 fayalite-visit-gen.workspace = true
 
 [features]
 unstable-doc = []
+unstable-test-hasher = []
 
 [package.metadata.docs.rs]
 features = ["unstable-doc"]

crates/fayalite/build.rs

@@ -5,6 +5,9 @@ use std::{env, fs, path::Path};
 
 fn main() {
     println!("cargo::rustc-check-cfg=cfg(todo)");
+    println!("cargo::rustc-check-cfg=cfg(cfg_false_for_tests)");
+    println!("cargo::rustc-check-cfg=cfg(cfg_true_for_tests)");
+    println!("cargo::rustc-cfg=cfg_true_for_tests");
     let path = "visit_types.json";
     println!("cargo::rerun-if-changed={path}");
     println!("cargo::rerun-if-changed=build.rs");

crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs

@@ -2,6 +2,7 @@
 // See Notices.txt for copyright information
 //! ## `#[hdl] let` statements
 
+pub mod destructuring;
 pub mod inputs_outputs;
 pub mod instances;
 pub mod memories;

crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/destructuring.rs

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+//! ### Destructuring Let
+//!
+//! You can use `#[hdl] let` to destructure types, similarly to Rust `let` statements with non-trivial patterns.
+//!
+//! `#[hdl] let` statements can only match one level of struct/tuple pattern for now,
+//! e.g. you can match with the pattern `MyStruct { a, b }`, but not `MyStruct { a, b: Struct2 { v } }`.
+//!
+//! ```
+//! # use fayalite::prelude::*;
+//! #[hdl]
+//! struct MyStruct {
+//!     a: UInt<8>,
+//!     b: Bool,
+//! }
+//!
+//! #[hdl_module]
+//! fn my_module() {
+//!     #[hdl]
+//!     let my_input: MyStruct = m.input();
+//!     #[hdl]
+//!     let my_output: UInt<8> = m.input();
+//!     #[hdl]
+//!     let MyStruct { a, b } = my_input;
+//!     #[hdl]
+//!     if b {
+//!         connect(my_output, a);
+//!     } else {
+//!         connect(my_output, 0_hdl_u8);
+//!     }
+//! }
+//! ```

crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs

@@ -7,5 +7,5 @@
 //!
 //! `#[hdl] match` statements' bodies must evaluate to type `()` for now.
 //!
-//! `#[hdl] match` statements can only match one level of struct/enum pattern for now,
+//! `#[hdl] match` statements can only match one level of struct/tuple/enum pattern for now,
 //! e.g. you can match with the pattern `HdlSome(v)`, but not `HdlSome(HdlSome(_))`.

crates/fayalite/src/annotations.rs

@@ -12,7 +12,7 @@ use std::{
     ops::Deref,
 };
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct CustomFirrtlAnnotationFieldsImpl {
     value: serde_json::Map<String, serde_json::Value>,
     serialized: Interned<str>,
@@ -314,10 +314,8 @@ impl<T: Iterator<Item: IntoAnnotations>> Iterator for IterIntoAnnotations<T> {
 }
 
 impl<
-        T: FusedIterator<
-            Item: IntoAnnotations<IntoAnnotations: IntoIterator<IntoIter: FusedIterator>>,
-        >,
-    > FusedIterator for IterIntoAnnotations<T>
+    T: FusedIterator<Item: IntoAnnotations<IntoAnnotations: IntoIterator<IntoIter: FusedIterator>>>,
+> FusedIterator for IterIntoAnnotations<T>
 {
 }
 

crates/fayalite/src/array.rs

@@ -2,17 +2,24 @@
 // See Notices.txt for copyright information
 
 use crate::{
-    expr::{ops::ArrayIndex, Expr, ToExpr},
-    int::{DynSize, KnownSize, Size, SizeType, DYN_SIZE},
+    expr::{
+        CastToBits, Expr, HdlPartialEq, ReduceBits, ToExpr,
+        ops::{ArrayLiteral, ExprFromIterator, ExprIntoIterator, ExprPartialEq},
+    },
+    int::{Bool, DYN_SIZE, DynSize, KnownSize, Size, SizeType},
     intern::{Intern, Interned, LazyInterned},
     module::transform::visit::{Fold, Folder, Visit, Visitor},
+    sim::value::{SimValue, SimValuePartialEq},
     source_location::SourceLocation,
     ty::{
-        CanonicalType, MatchVariantWithoutScope, StaticType, Type, TypeProperties, TypeWithDeref,
+        CanonicalType, MatchVariantWithoutScope, OpaqueSimValueSlice, OpaqueSimValueWriter,
+        OpaqueSimValueWritten, StaticType, Type, TypeProperties, TypeWithDeref,
+        serde_impls::SerdeCanonicalType,
     },
     util::ConstUsize,
 };
-use std::ops::Index;
+use serde::{Deserialize, Deserializer, Serialize, Serializer, de::Error};
+use std::{iter::FusedIterator, ops::Index};
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct ArrayType<T: Type = CanonicalType, Len: Size = DynSize> {
@@ -41,15 +48,20 @@ impl<T: Type, Len: Size> ArrayType<T, Len> {
             is_storable,
             is_castable_from_bits,
             bit_width,
+            sim_only_values_len,
         } = element;
         let Some(bit_width) = bit_width.checked_mul(len) else {
             panic!("array too big");
         };
+        let Some(sim_only_values_len) = sim_only_values_len.checked_mul(len) else {
+            panic!("array too big");
+        };
         TypeProperties {
             is_passive,
             is_storable,
             is_castable_from_bits,
             bit_width,
+            sim_only_values_len,
         }
     }
     pub fn new(element: T, len: Len::SizeType) -> Self {
@@ -91,6 +103,12 @@ impl<T: Type, Len: KnownSize + Size<SizeType = Len>> ArrayType<T, Len> {
     }
 }
 
+impl<T: StaticType, Len: KnownSize> Default for ArrayType<T, Len> {
+    fn default() -> Self {
+        Self::TYPE
+    }
+}
+
 impl<T: StaticType, Len: KnownSize> StaticType for ArrayType<T, Len> {
     const TYPE: Self = Self {
         element: LazyInterned::new_lazy(&|| T::TYPE.intern_sized()),
@@ -139,6 +157,7 @@ impl<T: Type + Visit<State>, Len: Size, State: Visitor + ?Sized> Visit<State>
 impl<T: Type, Len: Size> Type for ArrayType<T, Len> {
     type BaseType = Array;
     type MaskType = ArrayType<T::MaskType, Len>;
+    type SimValue = Len::ArraySimValue<T>;
     type MatchVariant = Len::ArrayMatch<T>;
     type MatchActiveScope = ();
     type MatchVariantAndInactiveScope = MatchVariantWithoutScope<Len::ArrayMatch<T>>;
@@ -148,10 +167,8 @@ impl<T: Type, Len: Size> Type for ArrayType<T, Len> {
         this: Expr<Self>,
         source_location: SourceLocation,
     ) -> Self::MatchVariantsIter {
-        let base = Expr::as_dyn_array(this);
-        let base_ty = Expr::ty(base);
         let _ = source_location;
-        let retval = Vec::from_iter((0..base_ty.len()).map(|i| ArrayIndex::new(base, i).to_expr()));
+        let retval = Vec::from_iter(this);
         std::iter::once(MatchVariantWithoutScope(
             Len::ArrayMatch::<T>::try_from(retval)
                 .ok()
@@ -177,16 +194,106 @@ impl<T: Type, Len: Size> Type for ArrayType<T, Len> {
             Len::from_usize(array.len()),
         )
     }
+
     fn source_location() -> SourceLocation {
         SourceLocation::builtin()
     }
+
+    fn sim_value_from_opaque(&self, mut opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        let element_ty = self.element();
+        let element_size = element_ty.canonical().size();
+        let mut value = Vec::with_capacity(self.len());
+        for _ in 0..self.len() {
+            let (element_opaque, rest) = opaque.split_at(element_size);
+            value.push(SimValue::from_opaque(element_ty, element_opaque.to_owned()));
+            opaque = rest;
+        }
+        value.try_into().ok().expect("used correct length")
+    }
+
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        mut opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        let element_ty = self.element();
+        let element_size = element_ty.canonical().size();
+        let value = AsMut::<[SimValue<T>]>::as_mut(value);
+        assert_eq!(self.len(), value.len());
+        for element_value in value {
+            assert_eq!(SimValue::ty(element_value), element_ty);
+            let (element_opaque, rest) = opaque.split_at(element_size);
+            SimValue::opaque_mut(element_value).clone_from_slice(element_opaque);
+            opaque = rest;
+        }
+    }
+
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        mut writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        let element_ty = self.element();
+        let element_size = element_ty.canonical().size();
+        let value = AsRef::<[SimValue<T>]>::as_ref(value);
+        assert_eq!(self.len(), value.len());
+        for element_value in value {
+            assert_eq!(SimValue::ty(element_value), element_ty);
+            writer.fill_prefix_with(element_size, |writer| {
+                writer.fill_cloned_from_slice(SimValue::opaque(element_value).as_slice())
+            });
+        }
+        writer.fill_cloned_from_slice(OpaqueSimValueSlice::empty())
+    }
+}
+
+impl<T: Type + Serialize, Len: Size> Serialize for ArrayType<T, Len> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        SerdeCanonicalType::<T>::Array {
+            element: self.element(),
+            len: self.len(),
+        }
+        .serialize(serializer)
+    }
+}
+
+impl<'de, T: Type + Deserialize<'de>, Len: Size> Deserialize<'de> for ArrayType<T, Len> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let name = |len| -> String {
+            if let Some(len) = len {
+                format!("an Array<_, {len}>")
+            } else {
+                "an Array<_>".to_string()
+            }
+        };
+        match SerdeCanonicalType::<T>::deserialize(deserializer)? {
+            SerdeCanonicalType::Array { element, len } => {
+                if let Some(len) = Len::try_from_usize(len) {
+                    Ok(Self::new(element, len))
+                } else {
+                    Err(Error::invalid_value(
+                        serde::de::Unexpected::Other(&name(Some(len))),
+                        &&*name(Len::KNOWN_VALUE),
+                    ))
+                }
+            }
+            ty => Err(Error::invalid_value(
+                serde::de::Unexpected::Other(ty.as_serde_unexpected_str()),
+                &&*name(Len::KNOWN_VALUE),
+            )),
+        }
+    }
 }
 
 impl<T: Type, Len: Size> TypeWithDeref for ArrayType<T, Len> {
     fn expr_deref(this: &Expr<Self>) -> &Self::MatchVariant {
-        let base = Expr::as_dyn_array(*this);
-        let base_ty = Expr::ty(base);
-        let retval = Vec::from_iter((0..base_ty.len()).map(|i| ArrayIndex::new(base, i).to_expr()));
+        let retval = Vec::from_iter(*this);
         Interned::into_inner(Intern::intern_sized(
             Len::ArrayMatch::<T>::try_from(retval)
                 .ok()
@@ -218,3 +325,143 @@ impl<T: Type, L: SizeType> Index<L> for ArrayWithoutLen<T> {
         Interned::into_inner(Intern::intern_sized(ArrayType::new(self.element, len)))
     }
 }
+
+impl<Lhs: Type, Rhs: Type, Len: Size> ExprPartialEq<ArrayType<Rhs, Len>> for ArrayType<Lhs, Len>
+where
+    Lhs: ExprPartialEq<Rhs>,
+{
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<ArrayType<Rhs, Len>>) -> Expr<Bool> {
+        let lhs_ty = Expr::ty(lhs);
+        let rhs_ty = Expr::ty(rhs);
+        assert_eq!(lhs_ty.len(), rhs_ty.len());
+        lhs.into_iter()
+            .zip(rhs)
+            .map(|(l, r)| l.cmp_eq(r))
+            .collect::<Expr<Array<Bool>>>()
+            .cast_to_bits()
+            .all_one_bits()
+    }
+
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<ArrayType<Rhs, Len>>) -> Expr<Bool> {
+        let lhs_ty = Expr::ty(lhs);
+        let rhs_ty = Expr::ty(rhs);
+        assert_eq!(lhs_ty.len(), rhs_ty.len());
+        lhs.into_iter()
+            .zip(rhs)
+            .map(|(l, r)| l.cmp_ne(r))
+            .collect::<Expr<Array<Bool>>>()
+            .cast_to_bits()
+            .any_one_bits()
+    }
+}
+
+impl<Lhs: Type, Rhs: Type, Len: Size> SimValuePartialEq<ArrayType<Rhs, Len>> for ArrayType<Lhs, Len>
+where
+    Lhs: SimValuePartialEq<Rhs>,
+{
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<ArrayType<Rhs, Len>>) -> bool {
+        AsRef::<[_]>::as_ref(&**this)
+            .iter()
+            .zip(AsRef::<[_]>::as_ref(&**other))
+            .all(|(l, r)| SimValuePartialEq::sim_value_eq(l, r))
+    }
+}
+
+impl<T: Type, Len: Size> ExprIntoIterator for ArrayType<T, Len> {
+    type Item = T;
+    type ExprIntoIter = ExprArrayIter<T, Len>;
+
+    fn expr_into_iter(e: Expr<Self>) -> Self::ExprIntoIter {
+        ExprArrayIter {
+            base: e,
+            indexes: 0..Expr::ty(e).len(),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct ExprArrayIter<T: Type, Len: Size> {
+    base: Expr<ArrayType<T, Len>>,
+    indexes: std::ops::Range<usize>,
+}
+
+impl<T: Type, Len: Size> ExprArrayIter<T, Len> {
+    pub fn base(&self) -> Expr<ArrayType<T, Len>> {
+        self.base
+    }
+    pub fn indexes(&self) -> std::ops::Range<usize> {
+        self.indexes.clone()
+    }
+}
+
+impl<T: Type, Len: Size> Iterator for ExprArrayIter<T, Len> {
+    type Item = Expr<T>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.indexes.next().map(|i| self.base[i])
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.indexes.size_hint()
+    }
+
+    fn count(self) -> usize {
+        self.indexes.count()
+    }
+
+    fn last(mut self) -> Option<Self::Item> {
+        self.next_back()
+    }
+
+    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+        self.indexes.nth(n).map(|i| self.base[i])
+    }
+
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.indexes.fold(init, |b, i| f(b, self.base[i]))
+    }
+}
+
+impl<T: Type, Len: Size> DoubleEndedIterator for ExprArrayIter<T, Len> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.indexes.next_back().map(|i| self.base[i])
+    }
+
+    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+        self.indexes.nth_back(n).map(|i| self.base[i])
+    }
+
+    fn rfold<B, F>(self, init: B, mut f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.indexes.rfold(init, |b, i| f(b, self.base[i]))
+    }
+}
+
+impl<T: Type, Len: Size> ExactSizeIterator for ExprArrayIter<T, Len> {
+    fn len(&self) -> usize {
+        self.indexes.len()
+    }
+}
+
+impl<T: Type, Len: Size> FusedIterator for ExprArrayIter<T, Len> {}
+
+impl<A: StaticType> ExprFromIterator<Expr<A>> for Array<A> {
+    fn expr_from_iter<T: IntoIterator<Item = Expr<A>>>(iter: T) -> Expr<Self> {
+        ArrayLiteral::new(
+            A::TYPE,
+            iter.into_iter().map(|v| Expr::canonical(v)).collect(),
+        )
+        .to_expr()
+    }
+}
+
+impl<'a, A: StaticType> ExprFromIterator<&'a Expr<A>> for Array<A> {
+    fn expr_from_iter<T: IntoIterator<Item = &'a Expr<A>>>(iter: T) -> Expr<Self> {
+        iter.into_iter().copied().collect()
+    }
+}

crates/fayalite/src/bundle.rs

@@ -2,18 +2,25 @@
 // See Notices.txt for copyright information
 
 use crate::{
-    expr::{ops::BundleLiteral, Expr, ToExpr},
+    expr::{
+        CastToBits, Expr, ReduceBits, ToExpr,
+        ops::{ArrayLiteral, BundleLiteral, ExprPartialEq},
+    },
+    int::{Bool, DynSize},
     intern::{Intern, Interned},
+    sim::value::{SimValue, SimValuePartialEq, ToSimValue, ToSimValueWithType},
     source_location::SourceLocation,
     ty::{
-        impl_match_variant_as_self, CanonicalType, MatchVariantWithoutScope, StaticType, Type,
-        TypeProperties, TypeWithDeref,
+        CanonicalType, MatchVariantWithoutScope, OpaqueSimValue, OpaqueSimValueSize,
+        OpaqueSimValueSlice, OpaqueSimValueWriter, OpaqueSimValueWritten, StaticType, Type,
+        TypeProperties, TypeWithDeref, impl_match_variant_as_self,
     },
+    util::HashMap,
 };
-use hashbrown::HashMap;
+use serde::{Deserialize, Serialize};
 use std::{fmt, marker::PhantomData};
 
-#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, Serialize, Deserialize)]
 pub struct BundleField {
     pub name: Interned<str>,
     pub flipped: bool,
@@ -62,7 +69,7 @@ impl fmt::Display for FmtDebugInStruct {
 struct BundleImpl {
     fields: Interned<[BundleField]>,
     name_indexes: HashMap<Interned<str>, usize>,
-    field_offsets: Interned<[usize]>,
+    field_offsets: Interned<[OpaqueSimValueSize]>,
     type_properties: TypeProperties,
 }
 
@@ -82,12 +89,9 @@ impl std::fmt::Debug for BundleImpl {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("Bundle ")?;
         f.debug_set()
-            .entries(
-                self.fields
-                    .iter()
-                    .enumerate()
-                    .map(|(index, field)| field.fmt_debug_in_struct(self.field_offsets[index])),
-            )
+            .entries(self.fields.iter().enumerate().map(|(index, field)| {
+                field.fmt_debug_in_struct(self.field_offsets[index].bit_width)
+            }))
             .finish()
     }
 }
@@ -112,6 +116,7 @@ impl BundleTypePropertiesBuilder {
             is_storable: true,
             is_castable_from_bits: true,
             bit_width: 0,
+            sim_only_values_len: 0,
         })
     }
     pub const fn clone(&self) -> Self {
@@ -119,8 +124,12 @@ impl BundleTypePropertiesBuilder {
     }
     #[must_use]
     pub const fn field(self, flipped: bool, field_props: TypeProperties) -> Self {
-        let Some(bit_width) = self.0.bit_width.checked_add(field_props.bit_width) else {
-            panic!("bundle is too big: bit-width overflowed");
+        let Some(OpaqueSimValueSize {
+            bit_width,
+            sim_only_values_len,
+        }) = self.0.size().checked_add(field_props.size())
+        else {
+            panic!("bundle is too big: size overflowed");
         };
         if flipped {
             Self(TypeProperties {
@@ -128,6 +137,7 @@ impl BundleTypePropertiesBuilder {
                 is_storable: false,
                 is_castable_from_bits: false,
                 bit_width,
+                sim_only_values_len,
             })
         } else {
             Self(TypeProperties {
@@ -136,6 +146,7 @@ impl BundleTypePropertiesBuilder {
                 is_castable_from_bits: self.0.is_castable_from_bits
                     & field_props.is_castable_from_bits,
                 bit_width,
+                sim_only_values_len,
             })
         }
     }
@@ -153,14 +164,14 @@ impl Default for BundleTypePropertiesBuilder {
 impl Bundle {
     #[track_caller]
     pub fn new(fields: Interned<[BundleField]>) -> Self {
-        let mut name_indexes = HashMap::with_capacity(fields.len());
+        let mut name_indexes = HashMap::with_capacity_and_hasher(fields.len(), Default::default());
         let mut field_offsets = Vec::with_capacity(fields.len());
         let mut type_props_builder = BundleTypePropertiesBuilder::new();
         for (index, &BundleField { name, flipped, ty }) in fields.iter().enumerate() {
             if let Some(old_index) = name_indexes.insert(name, index) {
                 panic!("duplicate field name {name:?}: at both index {old_index} and {index}");
             }
-            field_offsets.push(type_props_builder.0.bit_width);
+            field_offsets.push(type_props_builder.0.size());
             type_props_builder = type_props_builder.field(flipped, ty.type_properties());
         }
         Self(Intern::intern_sized(BundleImpl {
@@ -176,7 +187,7 @@ impl Bundle {
     pub fn field_by_name(&self, name: Interned<str>) -> Option<BundleField> {
         Some(self.0.fields[*self.0.name_indexes.get(&name)?])
     }
-    pub fn field_offsets(self) -> Interned<[usize]> {
+    pub fn field_offsets(self) -> Interned<[OpaqueSimValueSize]> {
         self.0.field_offsets
     }
     pub fn type_properties(self) -> TypeProperties {
@@ -210,6 +221,7 @@ impl Bundle {
 impl Type for Bundle {
     type BaseType = Bundle;
     type MaskType = Bundle;
+    type SimValue = OpaqueSimValue;
     impl_match_variant_as_self!();
     fn mask_type(&self) -> Self::MaskType {
         Self::new(Interned::from_iter(self.0.fields.into_iter().map(
@@ -233,6 +245,28 @@ impl Type for Bundle {
     fn source_location() -> SourceLocation {
         SourceLocation::builtin()
     }
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        opaque.to_owned()
+    }
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        assert_eq!(value.size(), opaque.size());
+        value.clone_from_slice(opaque);
+    }
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        assert_eq!(self.type_properties().size(), writer.size());
+        assert_eq!(value.size(), writer.size());
+        writer.fill_cloned_from_slice(value.as_slice())
+    }
 }
 
 pub trait BundleType: Type<BaseType = Bundle> {
@@ -241,6 +275,102 @@ pub trait BundleType: Type<BaseType = Bundle> {
     fn fields(&self) -> Interned<[BundleField]>;
 }
 
+pub struct BundleSimValueFromOpaque<'a> {
+    fields: std::slice::Iter<'static, BundleField>,
+    opaque: OpaqueSimValueSlice<'a>,
+}
+
+impl<'a> BundleSimValueFromOpaque<'a> {
+    #[track_caller]
+    pub fn new<T: BundleType>(bundle_ty: T, opaque: OpaqueSimValueSlice<'a>) -> Self {
+        let fields = bundle_ty.fields();
+        assert_eq!(
+            opaque.size(),
+            fields
+                .iter()
+                .map(|BundleField { ty, .. }| ty.size())
+                .sum::<OpaqueSimValueSize>()
+        );
+        Self {
+            fields: Interned::into_inner(fields).iter(),
+            opaque,
+        }
+    }
+    #[track_caller]
+    fn field_ty_and_opaque<T: Type>(&mut self) -> (T, OpaqueSimValueSlice<'a>) {
+        let Some(&BundleField {
+            name: _,
+            flipped: _,
+            ty,
+        }) = self.fields.next()
+        else {
+            panic!("tried to read too many fields from BundleSimValueFromBits");
+        };
+        let (field_opaque, rest) = self.opaque.split_at(ty.size());
+        self.opaque = rest;
+        (T::from_canonical(ty), field_opaque)
+    }
+    #[track_caller]
+    pub fn field_from_opaque<T: Type>(&mut self) -> SimValue<T> {
+        let (field_ty, field_opaque) = self.field_ty_and_opaque::<T>();
+        SimValue::from_opaque(field_ty, field_opaque.to_owned())
+    }
+    #[track_caller]
+    pub fn field_clone_from_opaque<T: Type>(&mut self, field_value: &mut SimValue<T>) {
+        let (field_ty, field_opaque) = self.field_ty_and_opaque::<T>();
+        assert_eq!(field_ty, SimValue::ty(field_value));
+        SimValue::opaque_mut(field_value).clone_from_slice(field_opaque);
+    }
+}
+
+pub struct BundleSimValueToOpaque<'a> {
+    fields: std::slice::Iter<'static, BundleField>,
+    writer: OpaqueSimValueWriter<'a>,
+}
+
+impl<'a> BundleSimValueToOpaque<'a> {
+    #[track_caller]
+    pub fn new<T: BundleType>(bundle_ty: T, writer: OpaqueSimValueWriter<'a>) -> Self {
+        let fields = bundle_ty.fields();
+        assert_eq!(
+            writer.size(),
+            fields
+                .iter()
+                .map(|BundleField { ty, .. }| ty.size())
+                .sum::<OpaqueSimValueSize>()
+        );
+        Self {
+            fields: Interned::into_inner(fields).iter(),
+            writer,
+        }
+    }
+    #[track_caller]
+    pub fn field<T: Type>(&mut self, field_value: &SimValue<T>) {
+        let Some(&BundleField {
+            name: _,
+            flipped: _,
+            ty,
+        }) = self.fields.next()
+        else {
+            panic!("tried to write too many fields with BundleSimValueToOpaque");
+        };
+        assert_eq!(T::from_canonical(ty), SimValue::ty(field_value));
+        self.writer.fill_prefix_with(ty.size(), |writer| {
+            writer.fill_cloned_from_slice(SimValue::opaque(field_value).as_slice())
+        });
+    }
+    #[track_caller]
+    pub fn finish(mut self) -> OpaqueSimValueWritten<'a> {
+        assert_eq!(
+            self.fields.next(),
+            None,
+            "wrote too few fields with BundleSimValueToOpaque"
+        );
+        self.writer
+            .fill_cloned_from_slice(OpaqueSimValueSlice::empty())
+    }
+}
+
 #[derive(Default)]
 pub struct NoBuilder;
 
@@ -323,7 +453,19 @@ macro_rules! impl_tuple_builder_fields {
 }
 
 macro_rules! impl_tuples {
-    ([$({#[num = $num:literal, field = $field:ident] $var:ident: $T:ident})*] []) => {
+    (
+        [$({
+            #[
+                num = $num:tt,
+                field = $field:ident,
+                ty = $ty_var:ident: $Ty:ident,
+                lhs = $lhs_var:ident: $Lhs:ident,
+                rhs = $rhs_var:ident: $Rhs:ident
+            ]
+            $var:ident: $T:ident
+        })*]
+        []
+    ) => {
         impl_tuple_builder_fields! {
             {}
             [$({
@@ -335,6 +477,7 @@ macro_rules! impl_tuples {
         impl<$($T: Type,)*> Type for ($($T,)*) {
             type BaseType = Bundle;
             type MaskType = ($($T::MaskType,)*);
+            type SimValue = ($(SimValue<$T>,)*);
             type MatchVariant = ($(Expr<$T>,)*);
             type MatchActiveScope = ();
             type MatchVariantAndInactiveScope = MatchVariantWithoutScope<Self::MatchVariant>;
@@ -373,6 +516,33 @@ macro_rules! impl_tuples {
             fn source_location() -> SourceLocation {
                 SourceLocation::builtin()
             }
+            fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+                #![allow(unused_mut, unused_variables)]
+                let mut v = BundleSimValueFromOpaque::new(*self, opaque);
+                $(let $var = v.field_from_opaque();)*
+                ($($var,)*)
+            }
+            fn sim_value_clone_from_opaque(
+                &self,
+                value: &mut Self::SimValue,
+                opaque: OpaqueSimValueSlice<'_>,
+            ) {
+                #![allow(unused_mut, unused_variables)]
+                let mut v = BundleSimValueFromOpaque::new(*self, opaque);
+                let ($($var,)*) = value;
+                $(v.field_clone_from_opaque($var);)*
+            }
+            fn sim_value_to_opaque<'w>(
+                &self,
+                value: &Self::SimValue,
+                writer: OpaqueSimValueWriter<'w>,
+            ) -> OpaqueSimValueWritten<'w> {
+                #![allow(unused_mut, unused_variables)]
+                let mut v = BundleSimValueToOpaque::new(*self, writer);
+                let ($($var,)*) = value;
+                $(v.field($var);)*
+                v.finish()
+            }
         }
         impl<$($T: Type,)*> BundleType for ($($T,)*) {
             type Builder = TupleBuilder<($(Unfilled<$T>,)*)>;
@@ -423,6 +593,106 @@ macro_rules! impl_tuples {
                 BundleLiteral::new(ty, field_values[..].intern()).to_expr()
             }
         }
+        impl<$($T: ToSimValueWithType<CanonicalType>,)*> ToSimValueWithType<CanonicalType> for ($($T,)*) {
+            #[track_caller]
+            fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+                SimValue::into_canonical(ToSimValueWithType::<Bundle>::to_sim_value_with_type(self, Bundle::from_canonical(ty)))
+            }
+            #[track_caller]
+            fn into_sim_value_with_type(self, ty: CanonicalType) -> SimValue<CanonicalType>
+            {
+                SimValue::into_canonical(ToSimValueWithType::<Bundle>::into_sim_value_with_type(self, Bundle::from_canonical(ty)))
+            }
+        }
+        impl<$($T: ToSimValueWithType<CanonicalType>,)*> ToSimValueWithType<Bundle> for ($($T,)*) {
+            #[track_caller]
+            fn to_sim_value_with_type(&self, ty: Bundle) -> SimValue<Bundle> {
+                let ($($var,)*) = self;
+                let [$($ty_var,)*] = *ty.fields() else {
+                    panic!("bundle has wrong number of fields");
+                };
+                $(let $var = $var.to_sim_value_with_type($ty_var.ty);)*
+                ToSimValueWithType::into_sim_value_with_type(($($var,)*), ty)
+            }
+            #[track_caller]
+            fn into_sim_value_with_type(self, ty: Bundle) -> SimValue<Bundle> {
+                #![allow(unused_mut)]
+                #![allow(clippy::unused_unit)]
+                let ($($var,)*) = self;
+                let [$($ty_var,)*] = *ty.fields() else {
+                    panic!("bundle has wrong number of fields");
+                };
+                let mut opaque = OpaqueSimValue::empty();
+                $(let $var = $var.into_sim_value_with_type($ty_var.ty);
+                assert_eq!(SimValue::ty(&$var), $ty_var.ty);
+                opaque.extend_from_slice(SimValue::opaque(&$var).as_slice());
+                )*
+                SimValue::from_opaque(ty, opaque)
+            }
+        }
+        impl<$($T: ToSimValueWithType<$Ty>, $Ty: Type,)*> ToSimValueWithType<($($Ty,)*)> for ($($T,)*) {
+            #[track_caller]
+            fn to_sim_value_with_type(&self, ty: ($($Ty,)*)) -> SimValue<($($Ty,)*)> {
+                let ($($var,)*) = self;
+                let ($($ty_var,)*) = ty;
+                $(let $var = $var.to_sim_value_with_type($ty_var);)*
+                SimValue::from_value(ty, ($($var,)*))
+            }
+            #[track_caller]
+            fn into_sim_value_with_type(self, ty: ($($Ty,)*)) -> SimValue<($($Ty,)*)> {
+                let ($($var,)*) = self;
+                let ($($ty_var,)*) = ty;
+                $(let $var = $var.into_sim_value_with_type($ty_var);)*
+                SimValue::from_value(ty, ($($var,)*))
+            }
+        }
+        impl<$($T: ToSimValue,)*> ToSimValue for ($($T,)*) {
+            type Type = ($($T::Type,)*);
+            #[track_caller]
+            fn to_sim_value(&self) -> SimValue<Self::Type> {
+                let ($($var,)*) = self;
+                $(let $var = $var.to_sim_value();)*
+                SimValue::from_value(($(SimValue::ty(&$var),)*), ($($var,)*))
+            }
+            #[track_caller]
+            fn into_sim_value(self) -> SimValue<Self::Type> {
+                let ($($var,)*) = self;
+                $(let $var = $var.to_sim_value();)*
+                SimValue::from_value(($(SimValue::ty(&$var),)*), ($($var,)*))
+            }
+        }
+        impl<$($Lhs: Type + ExprPartialEq<$Rhs>, $Rhs: Type,)*> ExprPartialEq<($($Rhs,)*)> for ($($Lhs,)*) {
+            fn cmp_eq(lhs: Expr<Self>, rhs: Expr<($($Rhs,)*)>) -> Expr<Bool> {
+                let ($($lhs_var,)*) = *lhs;
+                let ($($rhs_var,)*) = *rhs;
+                ArrayLiteral::<Bool, DynSize>::new(
+                    Bool,
+                    FromIterator::from_iter([$(Expr::canonical(ExprPartialEq::cmp_eq($lhs_var, $rhs_var)),)*]),
+                )
+                .cast_to_bits()
+                .all_one_bits()
+            }
+
+            fn cmp_ne(lhs: Expr<Self>, rhs: Expr<($($Rhs,)*)>) -> Expr<Bool> {
+                let ($($lhs_var,)*) = *lhs;
+                let ($($rhs_var,)*) = *rhs;
+                ArrayLiteral::<Bool, DynSize>::new(
+                    Bool,
+                    FromIterator::from_iter([$(Expr::canonical(ExprPartialEq::cmp_ne($lhs_var, $rhs_var)),)*]),
+                )
+                .cast_to_bits()
+                .any_one_bits()
+            }
+        }
+        impl<$($Lhs: SimValuePartialEq<$Rhs>, $Rhs: Type,)*> SimValuePartialEq<($($Rhs,)*)> for ($($Lhs,)*) {
+            fn sim_value_eq(lhs: &SimValue<Self>, rhs: &SimValue<($($Rhs,)*)>) -> bool {
+                let ($($lhs_var,)*) = &**lhs;
+                let ($($rhs_var,)*) = &**rhs;
+                let retval = true;
+                $(let retval = retval && $lhs_var == $rhs_var;)*
+                retval
+            }
+        }
     };
     ([$($lhs:tt)*] [$rhs_first:tt $($rhs:tt)*]) => {
         impl_tuples!([$($lhs)*] []);
@@ -432,24 +702,25 @@ macro_rules! impl_tuples {
 
 impl_tuples! {
     [] [
-        {#[num = 0, field = field_0] v0: T0}
-        {#[num = 1, field = field_1] v1: T1}
-        {#[num = 2, field = field_2] v2: T2}
-        {#[num = 3, field = field_3] v3: T3}
-        {#[num = 4, field = field_4] v4: T4}
-        {#[num = 5, field = field_5] v5: T5}
-        {#[num = 6, field = field_6] v6: T6}
-        {#[num = 7, field = field_7] v7: T7}
-        {#[num = 8, field = field_8] v8: T8}
-        {#[num = 9, field = field_9] v9: T9}
-        {#[num = 10, field = field_10] v10: T10}
-        {#[num = 11, field = field_11] v11: T11}
+        {#[num = 0, field = field_0, ty = ty0: Ty0, lhs = lhs0: Lhs0, rhs = rhs0: Rhs0] v0: T0}
+        {#[num = 1, field = field_1, ty = ty1: Ty1, lhs = lhs1: Lhs1, rhs = rhs1: Rhs1] v1: T1}
+        {#[num = 2, field = field_2, ty = ty2: Ty2, lhs = lhs2: Lhs2, rhs = rhs2: Rhs2] v2: T2}
+        {#[num = 3, field = field_3, ty = ty3: Ty3, lhs = lhs3: Lhs3, rhs = rhs3: Rhs3] v3: T3}
+        {#[num = 4, field = field_4, ty = ty4: Ty4, lhs = lhs4: Lhs4, rhs = rhs4: Rhs4] v4: T4}
+        {#[num = 5, field = field_5, ty = ty5: Ty5, lhs = lhs5: Lhs5, rhs = rhs5: Rhs5] v5: T5}
+        {#[num = 6, field = field_6, ty = ty6: Ty6, lhs = lhs6: Lhs6, rhs = rhs6: Rhs6] v6: T6}
+        {#[num = 7, field = field_7, ty = ty7: Ty7, lhs = lhs7: Lhs7, rhs = rhs7: Rhs7] v7: T7}
+        {#[num = 8, field = field_8, ty = ty8: Ty8, lhs = lhs8: Lhs8, rhs = rhs8: Rhs8] v8: T8}
+        {#[num = 9, field = field_9, ty = ty9: Ty9, lhs = lhs9: Lhs9, rhs = rhs9: Rhs9] v9: T9}
+        {#[num = 10, field = field_10, ty = ty10: Ty10, lhs = lhs10: Lhs10, rhs = rhs10: Rhs10] v10: T10}
+        {#[num = 11, field = field_11, ty = ty11: Ty11, lhs = lhs11: Lhs11, rhs = rhs11: Rhs11] v11: T11}
     ]
 }
 
 impl<T: ?Sized + Send + Sync + 'static> Type for PhantomData<T> {
     type BaseType = Bundle;
     type MaskType = ();
+    type SimValue = PhantomData<T>;
     type MatchVariant = PhantomData<T>;
     type MatchActiveScope = ();
     type MatchVariantAndInactiveScope = MatchVariantWithoutScope<Self::MatchVariant>;
@@ -482,6 +753,24 @@ impl<T: ?Sized + Send + Sync + 'static> Type for PhantomData<T> {
     fn source_location() -> SourceLocation {
         SourceLocation::builtin()
     }
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert!(opaque.is_empty());
+        *self
+    }
+    fn sim_value_clone_from_opaque(
+        &self,
+        _value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert!(opaque.is_empty());
+    }
+    fn sim_value_to_opaque<'w>(
+        &self,
+        _value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        writer.fill_cloned_from_slice(OpaqueSimValueSlice::empty())
+    }
 }
 
 pub struct PhantomDataBuilder<T: ?Sized + Send + Sync + 'static>(PhantomData<T>);
@@ -528,3 +817,36 @@ impl<T: ?Sized + Send + Sync + 'static> ToExpr for PhantomData<T> {
         BundleLiteral::new(PhantomData, Interned::default()).to_expr()
     }
 }
+
+impl<T: ?Sized + Send + Sync + 'static> ToSimValue for PhantomData<T> {
+    type Type = PhantomData<T>;
+
+    #[track_caller]
+    fn to_sim_value(&self) -> SimValue<Self> {
+        SimValue::from_value(*self, *self)
+    }
+}
+
+impl<T: ?Sized + Send + Sync + 'static> ToSimValueWithType<Self> for PhantomData<T> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Self) -> SimValue<Self> {
+        SimValue::from_value(ty, *self)
+    }
+}
+
+impl<T: ?Sized> ToSimValueWithType<Bundle> for PhantomData<T> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Bundle) -> SimValue<Bundle> {
+        assert!(ty.fields().is_empty());
+        SimValue::from_opaque(ty, OpaqueSimValue::empty())
+    }
+}
+
+impl<T: ?Sized> ToSimValueWithType<CanonicalType> for PhantomData<T> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, canonical_ty: CanonicalType) -> SimValue<CanonicalType> {
+        let ty = Bundle::from_canonical(canonical_ty);
+        assert!(ty.fields().is_empty());
+        SimValue::from_opaque(canonical_ty, OpaqueSimValue::empty())
+    }
+}

crates/fayalite/src/cli.rs

@@ -8,10 +8,10 @@ use crate::{
     util::{job_server::AcquiredJob, streaming_read_utf8::streaming_read_utf8},
 };
 use clap::{
-    builder::{OsStringValueParser, TypedValueParser},
     Parser, Subcommand, ValueEnum, ValueHint,
+    builder::{OsStringValueParser, TypedValueParser},
 };
-use eyre::{eyre, Report};
+use eyre::{Report, eyre};
 use serde::{Deserialize, Serialize};
 use std::{
     error,
@@ -258,7 +258,7 @@ pub struct VerilogArgs {
         default_value = "firtool",
         env = "FIRTOOL",
         value_hint = ValueHint::CommandName,
-        value_parser = OsStringValueParser::new().try_map(which::which)
+        value_parser = OsStringValueParser::new().try_map(which)
     )]
     pub firtool: PathBuf,
     #[arg(long)]
@@ -301,7 +301,9 @@ impl VerilogArgs {
                 input.split_once(file_separator_prefix)
             {
                 let Some((next_file_name, rest)) = rest.split_once(file_separator_suffix) else {
-                    return Err(CliError(eyre!("parsing firtool's output failed: found {file_separator_prefix:?} but no {file_separator_suffix:?}")));
+                    return Err(CliError(eyre!(
+                        "parsing firtool's output failed: found {file_separator_prefix:?} but no {file_separator_suffix:?}"
+                    )));
                 };
                 input = rest;
                 (chunk, Some(next_file_name.as_ref()))
@@ -428,6 +430,13 @@ impl clap::Args for FormalAdjustArgs {
     }
 }
 
+fn which(v: std::ffi::OsString) -> which::Result<PathBuf> {
+    #[cfg(not(miri))]
+    return which::which(v);
+    #[cfg(miri)]
+    return Ok(Path::new("/").join(v));
+}
+
 #[derive(Parser, Clone)]
 #[non_exhaustive]
 pub struct FormalArgs {
@@ -438,7 +447,7 @@ pub struct FormalArgs {
         default_value = "sby",
         env = "SBY",
         value_hint = ValueHint::CommandName,
-        value_parser = OsStringValueParser::new().try_map(which::which)
+        value_parser = OsStringValueParser::new().try_map(which)
     )]
     pub sby: PathBuf,
     #[arg(long)]

crates/fayalite/src/clock.rs

@@ -4,10 +4,14 @@ use crate::{
     expr::{Expr, ToExpr},
     hdl,
     int::Bool,
-    reset::Reset,
+    reset::{Reset, ResetType},
     source_location::SourceLocation,
-    ty::{impl_match_variant_as_self, CanonicalType, StaticType, Type, TypeProperties},
+    ty::{
+        CanonicalType, OpaqueSimValueSize, OpaqueSimValueSlice, OpaqueSimValueWriter,
+        OpaqueSimValueWritten, StaticType, Type, TypeProperties, impl_match_variant_as_self,
+    },
 };
+use bitvec::{bits, order::Lsb0};
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
 pub struct Clock;
@@ -15,6 +19,7 @@ pub struct Clock;
 impl Type for Clock {
     type BaseType = Clock;
     type MaskType = Bool;
+    type SimValue = bool;
 
     impl_match_variant_as_self!();
 
@@ -36,6 +41,31 @@ impl Type for Clock {
         };
         retval
     }
+
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert_eq!(opaque.size(), OpaqueSimValueSize::from_bit_width(1));
+        opaque.bits()[0]
+    }
+
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert_eq!(opaque.size(), OpaqueSimValueSize::from_bit_width(1));
+        *value = opaque.bits()[0];
+    }
+
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        assert_eq!(writer.size(), OpaqueSimValueSize::from_bit_width(1));
+        writer.fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(
+            [bits![0], bits![1]][*value as usize],
+        ))
+    }
 }
 
 impl Clock {
@@ -55,6 +85,7 @@ impl StaticType for Clock {
         is_storable: false,
         is_castable_from_bits: true,
         bit_width: 1,
+        sim_only_values_len: 0,
     };
     const MASK_TYPE_PROPERTIES: TypeProperties = Bool::TYPE_PROPERTIES;
 }
@@ -88,9 +119,9 @@ impl ToClock for Expr<Clock> {
 }
 
 #[hdl]
-pub struct ClockDomain {
+pub struct ClockDomain<R: ResetType = Reset> {
     pub clk: Clock,
-    pub rst: Reset,
+    pub rst: R,
 }
 
 impl ToClock for bool {

crates/fayalite/src/enum_.rs

@@ -2,21 +2,31 @@
 // See Notices.txt for copyright information
 
 use crate::{
-    expr::{ops::VariantAccess, Expr, ToExpr},
+    expr::{
+        Expr, ToExpr,
+        ops::{ExprPartialEq, VariantAccess},
+    },
     hdl,
-    int::Bool,
+    int::{Bool, UIntValue},
     intern::{Intern, Interned},
     module::{
-        connect, enum_match_variants_helper, incomplete_wire, wire,
-        EnumMatchVariantAndInactiveScopeImpl, EnumMatchVariantsIterImpl, Scope,
+        EnumMatchVariantAndInactiveScopeImpl, EnumMatchVariantsIterImpl, Scope, connect,
+        enum_match_variants_helper, incomplete_wire, wire,
     },
+    sim::value::{SimValue, SimValuePartialEq},
     source_location::SourceLocation,
-    ty::{CanonicalType, MatchVariantAndInactiveScope, StaticType, Type, TypeProperties},
+    ty::{
+        CanonicalType, MatchVariantAndInactiveScope, OpaqueSimValue, OpaqueSimValueSize,
+        OpaqueSimValueSlice, OpaqueSimValueWriter, OpaqueSimValueWritten, StaticType, Type,
+        TypeProperties,
+    },
+    util::HashMap,
 };
-use hashbrown::HashMap;
-use std::{convert::Infallible, fmt, iter::FusedIterator};
+use bitvec::{order::Lsb0, slice::BitSlice, view::BitView};
+use serde::{Deserialize, Serialize};
+use std::{convert::Infallible, fmt, iter::FusedIterator, sync::Arc};
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
 pub struct EnumVariant {
     pub name: Interned<str>,
     pub ty: Option<CanonicalType>,
@@ -111,6 +121,7 @@ impl EnumTypePropertiesBuilder {
                 is_storable: true,
                 is_castable_from_bits: true,
                 bit_width: 0,
+                sim_only_values_len: 0,
             },
             variant_count: 0,
         }
@@ -129,9 +140,14 @@ impl EnumTypePropertiesBuilder {
             is_storable,
             is_castable_from_bits,
             bit_width,
+            sim_only_values_len,
         }) = field_props
         {
             assert!(is_passive, "variant type must be a passive type");
+            assert!(
+                sim_only_values_len == 0,
+                "can't have `SimOnlyValue`s in an Enum"
+            );
             type_properties = TypeProperties {
                 is_passive: true,
                 is_storable: type_properties.is_storable & is_storable,
@@ -142,6 +158,7 @@ impl EnumTypePropertiesBuilder {
                 } else {
                     type_properties.bit_width
                 },
+                sim_only_values_len: 0,
             };
         }
         Self {
@@ -149,6 +166,12 @@ impl EnumTypePropertiesBuilder {
             variant_count: variant_count + 1,
         }
     }
+    #[must_use]
+    pub fn variants(self, variants: impl IntoIterator<Item = EnumVariant>) -> Self {
+        variants.into_iter().fold(self, |this, variant| {
+            this.variant(variant.ty.map(CanonicalType::type_properties))
+        })
+    }
     pub const fn finish(self) -> TypeProperties {
         assert!(
             self.variant_count != 0,
@@ -178,7 +201,8 @@ impl Default for EnumTypePropertiesBuilder {
 impl Enum {
     #[track_caller]
     pub fn new(variants: Interned<[EnumVariant]>) -> Self {
-        let mut name_indexes = HashMap::with_capacity(variants.len());
+        let mut name_indexes =
+            HashMap::with_capacity_and_hasher(variants.len(), Default::default());
         let mut type_props_builder = EnumTypePropertiesBuilder::new();
         for (index, EnumVariant { name, ty }) in variants.iter().enumerate() {
             if let Some(old_index) = name_indexes.insert(*name, index) {
@@ -238,13 +262,14 @@ impl Enum {
 
 pub trait EnumType:
     Type<
-    BaseType = Enum,
-    MaskType = Bool,
-    MatchActiveScope = Scope,
-    MatchVariantAndInactiveScope = EnumMatchVariantAndInactiveScope<Self>,
-    MatchVariantsIter = EnumMatchVariantsIter<Self>,
->
+        BaseType = Enum,
+        MaskType = Bool,
+        MatchActiveScope = Scope,
+        MatchVariantAndInactiveScope = EnumMatchVariantAndInactiveScope<Self>,
+        MatchVariantsIter = EnumMatchVariantsIter<Self>,
+    >
 {
+    type SimBuilder: From<Self>;
     fn variants(&self) -> Interned<[EnumVariant]>;
     fn match_activate_scope(
         v: Self::MatchVariantAndInactiveScope,
@@ -307,7 +332,18 @@ impl<T: EnumType> DoubleEndedIterator for EnumMatchVariantsIter<T> {
     }
 }
 
+pub struct NoBuilder {
+    _ty: Enum,
+}
+
+impl From<Enum> for NoBuilder {
+    fn from(_ty: Enum) -> Self {
+        Self { _ty }
+    }
+}
+
 impl EnumType for Enum {
+    type SimBuilder = NoBuilder;
     fn match_activate_scope(
         v: Self::MatchVariantAndInactiveScope,
     ) -> (Self::MatchVariant, Self::MatchActiveScope) {
@@ -322,6 +358,7 @@ impl EnumType for Enum {
 impl Type for Enum {
     type BaseType = Enum;
     type MaskType = Bool;
+    type SimValue = OpaqueSimValue;
     type MatchVariant = Option<Expr<CanonicalType>>;
     type MatchActiveScope = Scope;
     type MatchVariantAndInactiveScope = EnumMatchVariantAndInactiveScope<Self>;
@@ -352,6 +389,341 @@ impl Type for Enum {
     fn source_location() -> SourceLocation {
         SourceLocation::builtin()
     }
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        opaque.to_owned()
+    }
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        assert_eq!(value.size(), opaque.size());
+        value.clone_from_slice(opaque);
+    }
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        assert_eq!(self.type_properties().size(), writer.size());
+        assert_eq!(value.size(), writer.size());
+        writer.fill_cloned_from_slice(value.as_slice())
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug, Default)]
+pub struct EnumPaddingSimValue {
+    bits: Option<UIntValue>,
+}
+
+impl EnumPaddingSimValue {
+    pub const fn new() -> Self {
+        Self { bits: None }
+    }
+    pub fn bit_width(&self) -> Option<usize> {
+        self.bits.as_ref().map(UIntValue::width)
+    }
+    pub fn bits(&self) -> &Option<UIntValue> {
+        &self.bits
+    }
+    pub fn bits_mut(&mut self) -> &mut Option<UIntValue> {
+        &mut self.bits
+    }
+    pub fn into_bits(self) -> Option<UIntValue> {
+        self.bits
+    }
+    pub fn from_bits(bits: Option<UIntValue>) -> Self {
+        Self { bits }
+    }
+    pub fn from_bitslice(v: &BitSlice) -> Self {
+        Self {
+            bits: Some(UIntValue::new(Arc::new(v.to_bitvec()))),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct UnknownVariantSimValue {
+    discriminant: usize,
+    body_bits: UIntValue,
+}
+
+impl UnknownVariantSimValue {
+    pub fn discriminant(&self) -> usize {
+        self.discriminant
+    }
+    pub fn body_bits(&self) -> &UIntValue {
+        &self.body_bits
+    }
+    pub fn body_bits_mut(&mut self) -> &mut UIntValue {
+        &mut self.body_bits
+    }
+    pub fn into_body_bits(self) -> UIntValue {
+        self.body_bits
+    }
+    pub fn into_parts(self) -> (usize, UIntValue) {
+        (self.discriminant, self.body_bits)
+    }
+    pub fn new(discriminant: usize, body_bits: UIntValue) -> Self {
+        Self {
+            discriminant,
+            body_bits,
+        }
+    }
+}
+
+pub struct EnumSimValueFromOpaque<'a> {
+    variants: Interned<[EnumVariant]>,
+    discriminant: usize,
+    body_bits: &'a BitSlice,
+}
+
+impl<'a> EnumSimValueFromOpaque<'a> {
+    #[track_caller]
+    pub fn new<T: EnumType>(ty: T, opaque: OpaqueSimValueSlice<'a>) -> Self {
+        let variants = ty.variants();
+        let size = EnumTypePropertiesBuilder::new()
+            .variants(variants)
+            .finish()
+            .size();
+        assert!(size.only_bit_width().is_some());
+        assert_eq!(size, opaque.size());
+        let (discriminant_bits, body_bits) = opaque
+            .bits()
+            .split_at(discriminant_bit_width_impl(variants.len()));
+        let mut discriminant = 0usize;
+        discriminant.view_bits_mut::<Lsb0>()[..discriminant_bits.len()]
+            .copy_from_bitslice(discriminant_bits);
+        Self {
+            variants,
+            discriminant,
+            body_bits,
+        }
+    }
+    pub fn discriminant(&self) -> usize {
+        self.discriminant
+    }
+    #[track_caller]
+    #[cold]
+    fn usage_error(&self, clone: bool) -> ! {
+        let clone = if clone { "clone_" } else { "" };
+        match self.variants.get(self.discriminant) {
+            None => {
+                panic!("should have called EnumSimValueFromBits::unknown_variant_{clone}from_bits");
+            }
+            Some(EnumVariant { ty: None, .. }) => {
+                panic!(
+                    "should have called EnumSimValueFromBits::variant_no_field_{clone}from_bits"
+                );
+            }
+            Some(EnumVariant { ty: Some(_), .. }) => {
+                panic!(
+                    "should have called EnumSimValueFromBits::variant_with_field_{clone}from_bits"
+                );
+            }
+        }
+    }
+    #[track_caller]
+    fn known_variant(&self, clone: bool) -> (Option<CanonicalType>, &'a BitSlice, &'a BitSlice) {
+        let Some(EnumVariant { ty, .. }) = self.variants.get(self.discriminant) else {
+            self.usage_error(clone);
+        };
+        let variant_bit_width = ty.map_or(0, CanonicalType::bit_width);
+        let (variant_bits, padding_bits) = self.body_bits.split_at(variant_bit_width);
+        (*ty, variant_bits, padding_bits)
+    }
+    #[track_caller]
+    pub fn unknown_variant_from_opaque(self) -> UnknownVariantSimValue {
+        let None = self.variants.get(self.discriminant) else {
+            self.usage_error(false);
+        };
+        UnknownVariantSimValue::new(
+            self.discriminant,
+            UIntValue::new(Arc::new(self.body_bits.to_bitvec())),
+        )
+    }
+    #[track_caller]
+    pub fn unknown_variant_clone_from_opaque(self, value: &mut UnknownVariantSimValue) {
+        let None = self.variants.get(self.discriminant) else {
+            self.usage_error(true);
+        };
+        value.discriminant = self.discriminant;
+        assert_eq!(value.body_bits.width(), self.body_bits.len());
+        value
+            .body_bits
+            .bits_mut()
+            .copy_from_bitslice(self.body_bits);
+    }
+    #[track_caller]
+    pub fn variant_no_field_from_opaque(self) -> EnumPaddingSimValue {
+        let (None, _variant_bits, padding_bits) = self.known_variant(false) else {
+            self.usage_error(false);
+        };
+        EnumPaddingSimValue::from_bitslice(padding_bits)
+    }
+    #[track_caller]
+    pub fn variant_with_field_from_opaque<T: Type>(self) -> (SimValue<T>, EnumPaddingSimValue) {
+        let (Some(variant_ty), variant_bits, padding_bits) = self.known_variant(false) else {
+            self.usage_error(false);
+        };
+        (
+            SimValue::from_bitslice(T::from_canonical(variant_ty), variant_bits),
+            EnumPaddingSimValue::from_bitslice(padding_bits),
+        )
+    }
+    #[track_caller]
+    fn clone_padding_from_bits(padding: &mut EnumPaddingSimValue, padding_bits: &BitSlice) {
+        match padding.bits_mut() {
+            None => *padding = EnumPaddingSimValue::from_bitslice(padding_bits),
+            Some(padding) => {
+                assert_eq!(padding.width(), padding_bits.len());
+                padding.bits_mut().copy_from_bitslice(padding_bits);
+            }
+        }
+    }
+    #[track_caller]
+    pub fn variant_no_field_clone_from_opaque(self, padding: &mut EnumPaddingSimValue) {
+        let (None, _variant_bits, padding_bits) = self.known_variant(true) else {
+            self.usage_error(true);
+        };
+        Self::clone_padding_from_bits(padding, padding_bits);
+    }
+    #[track_caller]
+    pub fn variant_with_field_clone_from_opaque<T: Type>(
+        self,
+        value: &mut SimValue<T>,
+        padding: &mut EnumPaddingSimValue,
+    ) {
+        let (Some(variant_ty), variant_bits, padding_bits) = self.known_variant(true) else {
+            self.usage_error(true);
+        };
+        assert_eq!(SimValue::ty(value), T::from_canonical(variant_ty));
+        SimValue::bits_mut(value)
+            .bits_mut()
+            .copy_from_bitslice(variant_bits);
+        Self::clone_padding_from_bits(padding, padding_bits);
+    }
+}
+
+pub struct EnumSimValueToOpaque<'a> {
+    variants: Interned<[EnumVariant]>,
+    bit_width: usize,
+    discriminant_bit_width: usize,
+    writer: OpaqueSimValueWriter<'a>,
+}
+
+impl<'a> EnumSimValueToOpaque<'a> {
+    #[track_caller]
+    pub fn new<T: EnumType>(ty: T, writer: OpaqueSimValueWriter<'a>) -> Self {
+        let variants = ty.variants();
+        let size = EnumTypePropertiesBuilder::new()
+            .variants(variants)
+            .finish()
+            .size();
+        assert_eq!(size, writer.size());
+        Self {
+            variants,
+            bit_width: size
+                .only_bit_width()
+                .expect("enums should only contain bits"),
+            discriminant_bit_width: discriminant_bit_width_impl(variants.len()),
+            writer,
+        }
+    }
+    #[track_caller]
+    fn write_discriminant(&mut self, mut discriminant: usize) {
+        let orig_discriminant = discriminant;
+        let discriminant_bits =
+            &mut discriminant.view_bits_mut::<Lsb0>()[..self.discriminant_bit_width];
+        self.writer.fill_prefix_with(
+            OpaqueSimValueSize::from_bit_width(self.discriminant_bit_width),
+            |writer| {
+                writer.fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(discriminant_bits))
+            },
+        );
+        discriminant_bits.fill(false);
+        assert!(
+            discriminant == 0,
+            "{orig_discriminant:#x} is too big to fit in enum discriminant bits",
+        );
+    }
+    #[track_caller]
+    pub fn unknown_variant_to_opaque(
+        mut self,
+        value: &UnknownVariantSimValue,
+    ) -> OpaqueSimValueWritten<'a> {
+        self.write_discriminant(value.discriminant);
+        let None = self.variants.get(value.discriminant) else {
+            panic!("can't use UnknownVariantSimValue to set known discriminant");
+        };
+        assert_eq!(
+            self.bit_width - self.discriminant_bit_width,
+            value.body_bits.width()
+        );
+        self.writer
+            .fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(value.body_bits.bits()))
+    }
+    #[track_caller]
+    fn known_variant(
+        mut self,
+        discriminant: usize,
+        value: Option<&OpaqueSimValue>,
+        padding: &EnumPaddingSimValue,
+    ) -> OpaqueSimValueWritten<'a> {
+        self.write_discriminant(discriminant);
+        let variant_ty = self.variants[discriminant].ty;
+        let variant_size = variant_ty.map_or(OpaqueSimValueSize::empty(), CanonicalType::size);
+        if let Some(value) = value {
+            if variant_ty.is_none() {
+                panic!("expected variant to have no field");
+            }
+            self.writer.fill_prefix_with(variant_size, |writer| {
+                writer.fill_cloned_from_slice(value.as_slice())
+            });
+        } else if variant_ty.is_some() {
+            panic!("expected variant to have a field");
+        }
+        if let Some(padding) = padding.bits() {
+            assert_eq!(padding.ty().type_properties().size(), self.writer.size());
+            self.writer
+                .fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(padding.bits()))
+        } else {
+            self.writer.fill_with_zeros()
+        }
+    }
+    #[track_caller]
+    pub fn variant_no_field_to_opaque(
+        self,
+        discriminant: usize,
+        padding: &EnumPaddingSimValue,
+    ) -> OpaqueSimValueWritten<'a> {
+        self.known_variant(discriminant, None, padding)
+    }
+    #[track_caller]
+    pub fn variant_with_field_to_opaque<T: Type>(
+        self,
+        discriminant: usize,
+        value: &SimValue<T>,
+        padding: &EnumPaddingSimValue,
+    ) -> OpaqueSimValueWritten<'a> {
+        let Some(variant_ty) = self.variants[discriminant].ty else {
+            panic!("expected variant to have no field");
+        };
+        assert_eq!(SimValue::ty(value), T::from_canonical(variant_ty));
+        self.known_variant(discriminant, Some(SimValue::opaque(value)), padding)
+    }
+}
+
+#[doc(hidden)]
+pub fn assert_is_enum_type<T: EnumType>(v: T) -> T {
+    v
+}
+
+#[doc(hidden)]
+pub fn enum_type_to_sim_builder<T: EnumType>(v: T) -> T::SimBuilder {
+    v.into()
 }
 
 #[hdl]
@@ -360,6 +732,79 @@ pub enum HdlOption<T: Type> {
     HdlSome(T),
 }
 
+impl<Lhs: Type + ExprPartialEq<Rhs>, Rhs: Type> ExprPartialEq<HdlOption<Rhs>> for HdlOption<Lhs> {
+    #[hdl]
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<HdlOption<Rhs>>) -> Expr<Bool> {
+        #[hdl]
+        let cmp_eq = wire();
+        #[hdl]
+        match lhs {
+            HdlSome(lhs) =>
+            {
+                #[hdl]
+                match rhs {
+                    HdlSome(rhs) => connect(cmp_eq, ExprPartialEq::cmp_eq(lhs, rhs)),
+                    HdlNone => connect(cmp_eq, false),
+                }
+            }
+            HdlNone =>
+            {
+                #[hdl]
+                match rhs {
+                    HdlSome(_) => connect(cmp_eq, false),
+                    HdlNone => connect(cmp_eq, true),
+                }
+            }
+        }
+        cmp_eq
+    }
+
+    #[hdl]
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<HdlOption<Rhs>>) -> Expr<Bool> {
+        #[hdl]
+        let cmp_ne = wire();
+        #[hdl]
+        match lhs {
+            HdlSome(lhs) =>
+            {
+                #[hdl]
+                match rhs {
+                    HdlSome(rhs) => connect(cmp_ne, ExprPartialEq::cmp_ne(lhs, rhs)),
+                    HdlNone => connect(cmp_ne, true),
+                }
+            }
+            HdlNone =>
+            {
+                #[hdl]
+                match rhs {
+                    HdlSome(_) => connect(cmp_ne, true),
+                    HdlNone => connect(cmp_ne, false),
+                }
+            }
+        }
+        cmp_ne
+    }
+}
+
+impl<Lhs: SimValuePartialEq<Rhs>, Rhs: Type> SimValuePartialEq<HdlOption<Rhs>> for HdlOption<Lhs> {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<HdlOption<Rhs>>) -> bool {
+        type SimValueMatch<T> = <T as Type>::SimValue;
+        match (&**this, &**other) {
+            (SimValueMatch::<Self>::HdlNone(_), SimValueMatch::<HdlOption<Rhs>>::HdlNone(_)) => {
+                true
+            }
+            (SimValueMatch::<Self>::HdlSome(..), SimValueMatch::<HdlOption<Rhs>>::HdlNone(_))
+            | (SimValueMatch::<Self>::HdlNone(_), SimValueMatch::<HdlOption<Rhs>>::HdlSome(..)) => {
+                false
+            }
+            (
+                SimValueMatch::<Self>::HdlSome(l, _),
+                SimValueMatch::<HdlOption<Rhs>>::HdlSome(r, _),
+            ) => l == r,
+        }
+    }
+}
+
 #[allow(non_snake_case)]
 pub fn HdlNone<T: StaticType>() -> Expr<HdlOption<T>> {
     HdlOption[T::TYPE].HdlNone()

crates/fayalite/src/expr.rs

@@ -13,10 +13,12 @@ use crate::{
     intern::{Intern, Interned},
     memory::{DynPortType, MemPort, PortType},
     module::{
-        transform::visit::{Fold, Folder, Visit, Visitor},
         Instance, ModuleIO,
+        transform::visit::{Fold, Folder, Visit, Visitor},
     },
+    phantom_const::PhantomConst,
     reg::Reg,
+    reset::{AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset},
     ty::{CanonicalType, StaticType, Type, TypeWithDeref},
     wire::Wire,
 };
@@ -108,6 +110,7 @@ expr_enum! {
         UIntLiteral(Interned<UIntValue>),
         SIntLiteral(Interned<SIntValue>),
         BoolLiteral(bool),
+        PhantomConst(PhantomConst),
         BundleLiteral(ops::BundleLiteral),
         ArrayLiteral(ops::ArrayLiteral<CanonicalType, DynSize>),
         EnumLiteral(ops::EnumLiteral),
@@ -209,7 +212,9 @@ expr_enum! {
         ModuleIO(ModuleIO<CanonicalType>),
         Instance(Instance<Bundle>),
         Wire(Wire<CanonicalType>),
-        Reg(Reg<CanonicalType>),
+        Reg(Reg<CanonicalType, Reset>),
+        RegSync(Reg<CanonicalType, SyncReset>),
+        RegAsync(Reg<CanonicalType, AsyncReset>),
         MemPort(MemPort<DynPortType>),
     }
 }
@@ -269,6 +274,20 @@ pub struct Expr<T: Type> {
 
 impl<T: Type + fmt::Debug> fmt::Debug for Expr<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        #[cfg(debug_assertions)]
+        {
+            let Self {
+                __enum,
+                __ty,
+                __flow,
+            } = self;
+            let expr_ty = __ty.canonical();
+            let enum_ty = __enum.to_expr().__ty;
+            assert_eq!(
+                expr_ty, enum_ty,
+                "expr ty mismatch:\nExpr {{\n__enum: {__enum:?},\n__ty: {__ty:?},\n__flow: {__flow:?}\n}}"
+            );
+        }
         self.__enum.fmt(f)
     }
 }
@@ -513,11 +532,7 @@ impl Flow {
         }
     }
     pub const fn flip_if(self, flipped: bool) -> Flow {
-        if flipped {
-            self.flip()
-        } else {
-            self
-        }
+        if flipped { self.flip() } else { self }
     }
 }
 
@@ -593,25 +608,42 @@ impl<T: Type> GetTarget for Wire<T> {
     }
 }
 
-impl<T: Type> ToExpr for Reg<T> {
+impl<T: Type, R: ResetType> ToExpr for Reg<T, R> {
     type Type = T;
 
     fn to_expr(&self) -> Expr<Self::Type> {
+        struct Dispatch;
+        impl ResetTypeDispatch for Dispatch {
+            type Input<T: ResetType> = Reg<CanonicalType, T>;
+            type Output<T: ResetType> = ExprEnum;
+
+            fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset> {
+                ExprEnum::Reg(input)
+            }
+
+            fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset> {
+                ExprEnum::RegSync(input)
+            }
+
+            fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset> {
+                ExprEnum::RegAsync(input)
+            }
+        }
         Expr {
-            __enum: ExprEnum::Reg(self.canonical()).intern_sized(),
+            __enum: R::dispatch(self.canonical(), Dispatch).intern_sized(),
             __ty: self.ty(),
             __flow: self.flow(),
         }
     }
 }
 
-impl<T: Type> ToLiteralBits for Reg<T> {
+impl<T: Type, R: ResetType> ToLiteralBits for Reg<T, R> {
     fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
         Err(NotALiteralExpr)
     }
 }
 
-impl<T: Type> GetTarget for Reg<T> {
+impl<T: Type, R: ResetType> GetTarget for Reg<T, R> {
     fn target(&self) -> Option<Interned<Target>> {
         Some(Intern::intern_sized(self.canonical().into()))
     }
@@ -678,6 +710,7 @@ impl<T: ToExpr + ?Sized> CastToBits for T {
 }
 
 pub trait CastBitsTo {
+    #[track_caller]
     fn cast_bits_to<T: Type>(&self, ty: T) -> Expr<T>;
 }
 
@@ -735,3 +768,27 @@ pub fn repeat<T: Type, L: SizeType>(
     )
     .to_expr()
 }
+
+impl<T: ?Sized + crate::phantom_const::PhantomConstValue> ToExpr for PhantomConst<T> {
+    type Type = Self;
+
+    fn to_expr(&self) -> Expr<Self::Type> {
+        Expr {
+            __enum: ExprEnum::PhantomConst(self.canonical_phantom_const()).intern_sized(),
+            __ty: *self,
+            __flow: Flow::Source,
+        }
+    }
+}
+
+impl<T: ?Sized + crate::phantom_const::PhantomConstValue> GetTarget for PhantomConst<T> {
+    fn target(&self) -> Option<Interned<Target>> {
+        None
+    }
+}
+
+impl<T: ?Sized + crate::phantom_const::PhantomConstValue> ToLiteralBits for PhantomConst<T> {
+    fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
+        Ok(Interned::default())
+    }
+}

crates/fayalite/src/expr/ops.rs

@@ -7,19 +7,23 @@ use crate::{
     clock::{Clock, ToClock},
     enum_::{Enum, EnumType, EnumVariant},
     expr::{
+        CastBitsTo as _, CastTo, CastToBits as _, Expr, ExprEnum, Flow, HdlPartialEq,
+        HdlPartialOrd, NotALiteralExpr, ReduceBits, ToExpr, ToLiteralBits,
         target::{
             GetTarget, Target, TargetPathArrayElement, TargetPathBundleField,
             TargetPathDynArrayElement, TargetPathElement,
         },
-        CastTo, Expr, ExprEnum, Flow, HdlPartialEq, HdlPartialOrd, NotALiteralExpr, ReduceBits,
-        ToExpr, ToLiteralBits,
     },
     int::{
         Bool, BoolOrIntType, DynSize, IntType, KnownSize, SInt, SIntType, SIntValue, Size, UInt,
         UIntType, UIntValue,
     },
     intern::{Intern, Interned},
-    reset::{AsyncReset, Reset, SyncReset, ToAsyncReset, ToReset, ToSyncReset},
+    phantom_const::{PhantomConst, PhantomConstValue},
+    reset::{
+        AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset, ToAsyncReset, ToReset,
+        ToSyncReset,
+    },
     ty::{CanonicalType, StaticType, Type},
     util::ConstUsize,
 };
@@ -262,7 +266,7 @@ impl Neg {
         };
         let result_ty = retval.ty();
         retval.literal_bits = arg.to_literal_bits().map(|bits| {
-            Intern::intern_owned(result_ty.bits_from_bigint_wrapping(-SInt::bits_to_bigint(&bits)))
+            Intern::intern_owned(result_ty.bits_from_bigint_wrapping(&-SInt::bits_to_bigint(&bits)))
         });
         retval
     }
@@ -369,7 +373,7 @@ fn binary_op_literal_bits<ResultTy: BoolOrIntType, Lhs: BoolOrIntType, Rhs: Bool
     let rhs = Rhs::bits_to_bigint(&rhs);
     let result = f(lhs, rhs)?;
     Ok(Intern::intern_owned(
-        result_ty.bits_from_bigint_wrapping(result),
+        result_ty.bits_from_bigint_wrapping(&result),
     ))
 }
 
@@ -1344,7 +1348,7 @@ macro_rules! binary_op_fixed_shift {
                     literal_bits: Err(NotALiteralExpr),
                 };
                 retval.literal_bits = lhs.to_literal_bits().map(|bits| {
-                    Intern::intern_owned(retval.ty().bits_from_bigint_wrapping($Trait::$method(
+                    Intern::intern_owned(retval.ty().bits_from_bigint_wrapping(&$Trait::$method(
                         $ty::bits_to_bigint(&bits),
                         rhs,
                     )))
@@ -1621,7 +1625,7 @@ macro_rules! impl_cast_int_op {
                     ty,
                     literal_bits: arg.to_literal_bits().map(|bits| {
                         Intern::intern_owned(
-                            ty.bits_from_bigint_wrapping($from::bits_to_bigint(&bits)),
+                            ty.bits_from_bigint_wrapping(&$from::bits_to_bigint(&bits)),
                         )
                     }),
                 }
@@ -1773,11 +1777,11 @@ impl_cast_bit_op!(CastSIntToAsyncReset, SInt<1>, #[dyn] SInt, AsyncReset, #[trai
 impl_cast_bit_op!(CastSyncResetToBool, SyncReset, Bool);
 impl_cast_bit_op!(CastSyncResetToUInt, SyncReset, UInt<1>, #[dyn] UInt);
 impl_cast_bit_op!(CastSyncResetToSInt, SyncReset, SInt<1>, #[dyn] SInt);
-impl_cast_bit_op!(CastSyncResetToReset, SyncReset, Reset, #[trait] ToReset::to_reset);
+impl_cast_bit_op!(CastSyncResetToReset, SyncReset, Reset);
 impl_cast_bit_op!(CastAsyncResetToBool, AsyncReset, Bool);
 impl_cast_bit_op!(CastAsyncResetToUInt, AsyncReset, UInt<1>, #[dyn] UInt);
 impl_cast_bit_op!(CastAsyncResetToSInt, AsyncReset, SInt<1>, #[dyn] SInt);
-impl_cast_bit_op!(CastAsyncResetToReset, AsyncReset, Reset, #[trait] ToReset::to_reset);
+impl_cast_bit_op!(CastAsyncResetToReset, AsyncReset, Reset);
 impl_cast_bit_op!(CastResetToBool, Reset, Bool);
 impl_cast_bit_op!(CastResetToUInt, Reset, UInt<1>, #[dyn] UInt);
 impl_cast_bit_op!(CastResetToSInt, Reset, SInt<1>, #[dyn] SInt);
@@ -1788,6 +1792,127 @@ impl_cast_bit_op!(CastClockToBool, Clock, Bool);
 impl_cast_bit_op!(CastClockToUInt, Clock, UInt<1>, #[dyn] UInt);
 impl_cast_bit_op!(CastClockToSInt, Clock, SInt<1>, #[dyn] SInt);
 
+impl<T: ResetType> ToReset for Expr<T> {
+    fn to_reset(&self) -> Expr<Reset> {
+        struct Dispatch;
+        impl ResetTypeDispatch for Dispatch {
+            type Input<T: ResetType> = Expr<T>;
+            type Output<T: ResetType> = Expr<Reset>;
+
+            fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset> {
+                input
+            }
+
+            fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset> {
+                input.cast_to_static()
+            }
+
+            fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset> {
+                input.cast_to_static()
+            }
+        }
+        T::dispatch(*self, Dispatch)
+    }
+}
+
+impl ExprCastTo<AsyncReset> for AsyncReset {
+    fn cast_to(src: Expr<Self>, _to_type: AsyncReset) -> Expr<AsyncReset> {
+        src
+    }
+}
+
+impl ExprCastTo<SyncReset> for AsyncReset {
+    fn cast_to(src: Expr<Self>, to_type: SyncReset) -> Expr<SyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<Clock> for AsyncReset {
+    fn cast_to(src: Expr<Self>, to_type: Clock) -> Expr<Clock> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<AsyncReset> for SyncReset {
+    fn cast_to(src: Expr<Self>, to_type: AsyncReset) -> Expr<AsyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<SyncReset> for SyncReset {
+    fn cast_to(src: Expr<Self>, _to_type: SyncReset) -> Expr<SyncReset> {
+        src
+    }
+}
+
+impl ExprCastTo<Clock> for SyncReset {
+    fn cast_to(src: Expr<Self>, to_type: Clock) -> Expr<Clock> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<AsyncReset> for Reset {
+    fn cast_to(src: Expr<Self>, to_type: AsyncReset) -> Expr<AsyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<SyncReset> for Reset {
+    fn cast_to(src: Expr<Self>, to_type: SyncReset) -> Expr<SyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<Reset> for Reset {
+    fn cast_to(src: Expr<Self>, _to_type: Reset) -> Expr<Reset> {
+        src
+    }
+}
+
+impl ExprCastTo<Clock> for Reset {
+    fn cast_to(src: Expr<Self>, to_type: Clock) -> Expr<Clock> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<AsyncReset> for Clock {
+    fn cast_to(src: Expr<Self>, to_type: AsyncReset) -> Expr<AsyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<SyncReset> for Clock {
+    fn cast_to(src: Expr<Self>, to_type: SyncReset) -> Expr<SyncReset> {
+        src.cast_to(Bool).cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<Clock> for Clock {
+    fn cast_to(src: Expr<Self>, _to_type: Clock) -> Expr<Clock> {
+        src
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprCastTo<()> for PhantomConst<T> {
+    fn cast_to(src: Expr<Self>, to_type: ()) -> Expr<()> {
+        src.cast_to_bits().cast_bits_to(to_type)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprCastTo<PhantomConst<T>> for () {
+    fn cast_to(src: Expr<Self>, to_type: PhantomConst<T>) -> Expr<PhantomConst<T>> {
+        src.cast_to_bits().cast_bits_to(to_type)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue, U: ?Sized + PhantomConstValue> ExprCastTo<PhantomConst<T>>
+    for PhantomConst<U>
+{
+    fn cast_to(src: Expr<Self>, to_type: PhantomConst<T>) -> Expr<PhantomConst<T>> {
+        src.cast_to_bits().cast_bits_to(to_type)
+    }
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct FieldAccess<FieldType: Type = CanonicalType> {
     base: Expr<Bundle>,
@@ -1812,7 +1937,8 @@ impl<FieldType: Type> FieldAccess<FieldType> {
         let field = Expr::ty(base).fields()[field_index];
         let field_type = FieldType::from_canonical(field.ty);
         let literal_bits = base.to_literal_bits().map(|bits| {
-            bits[Expr::ty(base).field_offsets()[field_index]..][..field.ty.bit_width()].intern()
+            bits[Expr::ty(base).field_offsets()[field_index].bit_width..][..field.ty.bit_width()]
+                .intern()
         });
         let target = base.target().map(|base| {
             Intern::intern_sized(base.join(TargetPathElement::intern_sized(
@@ -2604,3 +2730,47 @@ impl<T: Type> ToExpr for Uninit<T> {
         }
     }
 }
+
+pub trait ExprIntoIterator: Type {
+    type Item: Type;
+    type ExprIntoIter: Iterator<Item = Expr<Self::Item>>;
+
+    fn expr_into_iter(e: Expr<Self>) -> Self::ExprIntoIter;
+}
+
+impl<T: ExprIntoIterator> IntoIterator for Expr<T> {
+    type Item = Expr<T::Item>;
+    type IntoIter = T::ExprIntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        T::expr_into_iter(self)
+    }
+}
+
+impl<T: ExprIntoIterator> IntoIterator for &'_ Expr<T> {
+    type Item = Expr<T::Item>;
+    type IntoIter = T::ExprIntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        T::expr_into_iter(*self)
+    }
+}
+
+impl<T: ExprIntoIterator> IntoIterator for &'_ mut Expr<T> {
+    type Item = Expr<T::Item>;
+    type IntoIter = T::ExprIntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        T::expr_into_iter(*self)
+    }
+}
+
+pub trait ExprFromIterator<A>: Type {
+    fn expr_from_iter<T: IntoIterator<Item = A>>(iter: T) -> Expr<Self>;
+}
+
+impl<This: ExprFromIterator<A>, A> FromIterator<A> for Expr<This> {
+    fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> Self {
+        This::expr_from_iter(iter)
+    }
+}

crates/fayalite/src/expr/target.rs

@@ -3,18 +3,19 @@
 use crate::{
     array::Array,
     bundle::{Bundle, BundleField},
-    expr::Flow,
+    expr::{Expr, Flow, ToExpr},
     intern::{Intern, Interned},
     memory::{DynPortType, MemPort},
     module::{Instance, ModuleIO, TargetName},
     reg::Reg,
+    reset::{AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset},
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
     wire::Wire,
 };
 use std::fmt;
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct TargetPathBundleField {
     pub name: Interned<str>,
 }
@@ -25,7 +26,7 @@ impl fmt::Display for TargetPathBundleField {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct TargetPathArrayElement {
     pub index: usize,
 }
@@ -36,7 +37,7 @@ impl fmt::Display for TargetPathArrayElement {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct TargetPathDynArrayElement {}
 
 impl fmt::Display for TargetPathDynArrayElement {
@@ -45,7 +46,7 @@ impl fmt::Display for TargetPathDynArrayElement {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum TargetPathElement {
     BundleField(TargetPathBundleField),
     ArrayElement(TargetPathArrayElement),
@@ -127,6 +128,7 @@ macro_rules! impl_target_base {
         $(#[$enum_meta:meta])*
         $enum_vis:vis enum $TargetBase:ident {
             $(
+                $(#[from = $from:ident])?
                 #[is = $is_fn:ident]
                 #[to = $to_fn:ident]
                 $(#[$variant_meta:meta])*
@@ -150,19 +152,19 @@ macro_rules! impl_target_base {
             }
         }
 
-        $(
+        $($(
         impl From<$VariantTy> for $TargetBase {
-            fn from(value: $VariantTy) -> Self {
+            fn $from(value: $VariantTy) -> Self {
                 Self::$Variant(value)
             }
         }
 
         impl From<$VariantTy> for Target {
-            fn from(value: $VariantTy) -> Self {
+            fn $from(value: $VariantTy) -> Self {
                 $TargetBase::$Variant(value).into()
             }
         }
-        )*
+        )*)?
 
         impl $TargetBase {
             $(
@@ -193,30 +195,79 @@ macro_rules! impl_target_base {
                 }
             }
         }
+
+        impl ToExpr for $TargetBase {
+            type Type = CanonicalType;
+
+            fn to_expr(&self) -> Expr<Self::Type> {
+                match self {
+                    $(Self::$Variant(v) => Expr::canonical(v.to_expr()),)*
+                }
+            }
+        }
     };
 }
 
 impl_target_base! {
-    #[derive(Clone, PartialEq, Eq, Hash)]
+    #[derive(Copy, Clone, PartialEq, Eq, Hash)]
     pub enum TargetBase {
+        #[from = from]
         #[is = is_module_io]
         #[to = module_io]
         ModuleIO(ModuleIO<CanonicalType>),
+        #[from = from]
         #[is = is_mem_port]
         #[to = mem_port]
         MemPort(MemPort<DynPortType>),
         #[is = is_reg]
         #[to = reg]
-        Reg(Reg<CanonicalType>),
+        Reg(Reg<CanonicalType, Reset>),
+        #[is = is_reg_sync]
+        #[to = reg_sync]
+        RegSync(Reg<CanonicalType, SyncReset>),
+        #[is = is_reg_async]
+        #[to = reg_async]
+        RegAsync(Reg<CanonicalType, AsyncReset>),
+        #[from = from]
         #[is = is_wire]
         #[to = wire]
         Wire(Wire<CanonicalType>),
+        #[from = from]
         #[is = is_instance]
         #[to = instance]
         Instance(Instance<Bundle>),
     }
 }
 
+impl<R: ResetType> From<Reg<CanonicalType, R>> for TargetBase {
+    fn from(value: Reg<CanonicalType, R>) -> Self {
+        struct Dispatch;
+        impl ResetTypeDispatch for Dispatch {
+            type Input<T: ResetType> = Reg<CanonicalType, T>;
+            type Output<T: ResetType> = TargetBase;
+
+            fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset> {
+                TargetBase::Reg(input)
+            }
+
+            fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset> {
+                TargetBase::RegSync(input)
+            }
+
+            fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset> {
+                TargetBase::RegAsync(input)
+            }
+        }
+        R::dispatch(value, Dispatch)
+    }
+}
+
+impl<R: ResetType> From<Reg<CanonicalType, R>> for Target {
+    fn from(value: Reg<CanonicalType, R>) -> Self {
+        TargetBase::from(value).into()
+    }
+}
+
 impl fmt::Display for TargetBase {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{:?}", self.target_name())
@@ -229,6 +280,8 @@ impl TargetBase {
             TargetBase::ModuleIO(v) => TargetName(v.scoped_name(), None),
             TargetBase::MemPort(v) => TargetName(v.mem_name(), Some(v.port_name())),
             TargetBase::Reg(v) => TargetName(v.scoped_name(), None),
+            TargetBase::RegSync(v) => TargetName(v.scoped_name(), None),
+            TargetBase::RegAsync(v) => TargetName(v.scoped_name(), None),
             TargetBase::Wire(v) => TargetName(v.scoped_name(), None),
             TargetBase::Instance(v) => TargetName(v.scoped_name(), None),
         }
@@ -238,6 +291,8 @@ impl TargetBase {
             TargetBase::ModuleIO(v) => v.ty(),
             TargetBase::MemPort(v) => v.ty().canonical(),
             TargetBase::Reg(v) => v.ty(),
+            TargetBase::RegSync(v) => v.ty(),
+            TargetBase::RegAsync(v) => v.ty(),
             TargetBase::Wire(v) => v.ty(),
             TargetBase::Instance(v) => v.ty().canonical(),
         }
@@ -313,7 +368,7 @@ impl TargetChild {
     }
 }
 
-#[derive(Clone, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub enum Target {
     Base(Interned<TargetBase>),
     Child(TargetChild),

crates/fayalite/src/int/uint_in_range.rs

@@ -0,0 +1,643 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    bundle::{Bundle, BundleField, BundleType, BundleTypePropertiesBuilder, NoBuilder},
+    expr::{
+        CastBitsTo, CastTo, CastToBits, Expr, HdlPartialEq, HdlPartialOrd,
+        ops::{ExprCastTo, ExprPartialEq, ExprPartialOrd},
+    },
+    int::{Bool, DynSize, KnownSize, Size, SizeType, UInt, UIntType},
+    intern::{Intern, Interned},
+    phantom_const::PhantomConst,
+    sim::value::{SimValue, SimValuePartialEq, ToSimValueWithType},
+    source_location::SourceLocation,
+    ty::{
+        CanonicalType, OpaqueSimValueSlice, OpaqueSimValueWriter, OpaqueSimValueWritten,
+        StaticType, Type, TypeProperties, impl_match_variant_as_self,
+    },
+};
+use bitvec::{order::Lsb0, view::BitView};
+use serde::{
+    Deserialize, Deserializer, Serialize, Serializer,
+    de::{Error, Visitor, value::UsizeDeserializer},
+};
+use std::{fmt, marker::PhantomData, ops::Index};
+
+const UINT_IN_RANGE_TYPE_FIELD_NAMES: [&'static str; 2] = ["value", "range"];
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+pub struct UIntInRangeMaskType {
+    value: Bool,
+    range: PhantomConstRangeMaskType,
+}
+
+impl Type for UIntInRangeMaskType {
+    type BaseType = Bundle;
+    type MaskType = Self;
+    type SimValue = bool;
+    impl_match_variant_as_self!();
+
+    fn mask_type(&self) -> Self::MaskType {
+        *self
+    }
+
+    fn canonical(&self) -> CanonicalType {
+        CanonicalType::Bundle(Bundle::new(self.fields()))
+    }
+
+    fn from_canonical(canonical_type: CanonicalType) -> Self {
+        let fields = Bundle::from_canonical(canonical_type).fields();
+        let [
+            BundleField {
+                name: value_name,
+                flipped: false,
+                ty: value,
+            },
+            BundleField {
+                name: range_name,
+                flipped: false,
+                ty: range,
+            },
+        ] = *fields
+        else {
+            panic!("expected UIntInRangeMaskType");
+        };
+        assert_eq!([&*value_name, &*range_name], UINT_IN_RANGE_TYPE_FIELD_NAMES);
+        let value = Bool::from_canonical(value);
+        let range = PhantomConstRangeMaskType::from_canonical(range);
+        Self { value, range }
+    }
+
+    fn source_location() -> SourceLocation {
+        SourceLocation::builtin()
+    }
+
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        Bool.sim_value_from_opaque(opaque)
+    }
+
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        Bool.sim_value_clone_from_opaque(value, opaque);
+    }
+
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        Bool.sim_value_to_opaque(value, writer)
+    }
+}
+
+impl BundleType for UIntInRangeMaskType {
+    type Builder = NoBuilder;
+    type FilledBuilder = Expr<UIntInRangeMaskType>;
+
+    fn fields(&self) -> Interned<[BundleField]> {
+        let [value_name, range_name] = UINT_IN_RANGE_TYPE_FIELD_NAMES;
+        let Self { value, range } = self;
+        [
+            BundleField {
+                name: value_name.intern(),
+                flipped: false,
+                ty: value.canonical(),
+            },
+            BundleField {
+                name: range_name.intern(),
+                flipped: false,
+                ty: range.canonical(),
+            },
+        ][..]
+            .intern()
+    }
+}
+
+impl StaticType for UIntInRangeMaskType {
+    const TYPE: Self = Self {
+        value: Bool,
+        range: PhantomConstRangeMaskType::TYPE,
+    };
+    const MASK_TYPE: Self::MaskType = Self::TYPE;
+    const TYPE_PROPERTIES: TypeProperties = BundleTypePropertiesBuilder::new()
+        .field(false, Bool::TYPE_PROPERTIES)
+        .field(false, PhantomConstRangeMaskType::TYPE_PROPERTIES)
+        .finish();
+    const MASK_TYPE_PROPERTIES: TypeProperties = Self::TYPE_PROPERTIES;
+}
+
+impl ToSimValueWithType<UIntInRangeMaskType> for bool {
+    fn to_sim_value_with_type(&self, ty: UIntInRangeMaskType) -> SimValue<UIntInRangeMaskType> {
+        SimValue::from_value(ty, *self)
+    }
+}
+
+impl ExprCastTo<Bool> for UIntInRangeMaskType {
+    fn cast_to(src: Expr<Self>, to_type: Bool) -> Expr<Bool> {
+        src.cast_to_bits().cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<UIntInRangeMaskType> for Bool {
+    fn cast_to(src: Expr<Self>, to_type: UIntInRangeMaskType) -> Expr<UIntInRangeMaskType> {
+        src.cast_to_static::<UInt<1>>().cast_bits_to(to_type)
+    }
+}
+
+impl ExprPartialEq<Self> for UIntInRangeMaskType {
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        lhs.cast_to_bits().cmp_eq(rhs.cast_to_bits())
+    }
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        lhs.cast_to_bits().cmp_ne(rhs.cast_to_bits())
+    }
+}
+
+impl SimValuePartialEq<Self> for UIntInRangeMaskType {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        **this == **other
+    }
+}
+
+type PhantomConstRangeMaskType = <PhantomConst<SerdeRange<DynSize, DynSize>> as Type>::MaskType;
+
+#[derive(Default, Copy, Clone, Debug)]
+struct RangeParseError;
+
+macro_rules! define_uint_in_range_type {
+    (
+        $UIntInRange:ident,
+        $UIntInRangeType:ident,
+        $UIntInRangeTypeWithoutGenerics:ident,
+        $UIntInRangeTypeWithStart:ident,
+        $SerdeRange:ident,
+        $range_operator_str:literal,
+        |$uint_range_usize_start:ident, $uint_range_usize_end:ident| $uint_range_usize:expr,
+    ) => {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct $SerdeRange<Start: Size, End: Size> {
+            start: Start::SizeType,
+            end: End::SizeType,
+        }
+
+        impl<Start: KnownSize, End: KnownSize> Default for $SerdeRange<Start, End> {
+            fn default() -> Self {
+                Self {
+                    start: Start::SIZE,
+                    end: End::SIZE,
+                }
+            }
+        }
+
+        impl std::str::FromStr for $SerdeRange<DynSize, DynSize> {
+            type Err = RangeParseError;
+
+            fn from_str(s: &str) -> Result<Self, Self::Err> {
+                let Some((start, end)) = s.split_once($range_operator_str) else {
+                    return Err(RangeParseError);
+                };
+                if start.is_empty()
+                    || start.bytes().any(|b| !b.is_ascii_digit())
+                    || end.is_empty()
+                    || end.bytes().any(|b| !b.is_ascii_digit())
+                {
+                    return Err(RangeParseError);
+                }
+                let start = start.parse().map_err(|_| RangeParseError)?;
+                let end = end.parse().map_err(|_| RangeParseError)?;
+                let retval = Self { start, end };
+                if retval.is_empty() {
+                    Err(RangeParseError)
+                } else {
+                    Ok(retval)
+                }
+            }
+        }
+
+        impl<Start: Size, End: Size> fmt::Display for $SerdeRange<Start, End> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let Self { start, end } = *self;
+                write!(
+                    f,
+                    "{}{}{}",
+                    Start::as_usize(start),
+                    $range_operator_str,
+                    End::as_usize(end),
+                )
+            }
+        }
+
+        impl<Start: Size, End: Size> Serialize for $SerdeRange<Start, End> {
+            fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+                serializer.collect_str(self)
+            }
+        }
+
+        impl<'de, Start: Size, End: Size> Deserialize<'de> for $SerdeRange<Start, End> {
+            fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+                struct SerdeRangeVisitor<Start: Size, End: Size>(PhantomData<(Start, End)>);
+                impl<'de, Start: Size, End: Size> Visitor<'de> for SerdeRangeVisitor<Start, End> {
+                    type Value = $SerdeRange<Start, End>;
+
+                    fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                        f.write_str("a string with format \"")?;
+                        if let Some(start) = Start::KNOWN_VALUE {
+                            write!(f, "{start}")?;
+                        } else {
+                            f.write_str("<int>")?;
+                        };
+                        f.write_str($range_operator_str)?;
+                        if let Some(end) = End::KNOWN_VALUE {
+                            write!(f, "{end}")?;
+                        } else {
+                            f.write_str("<int>")?;
+                        };
+                        f.write_str("\" that is a non-empty range")
+                    }
+
+                    fn visit_str<E: Error>(self, v: &str) -> Result<Self::Value, E> {
+                        let $SerdeRange::<DynSize, DynSize> { start, end } =
+                            v.parse().map_err(|_| {
+                                Error::invalid_value(serde::de::Unexpected::Str(v), &self)
+                            })?;
+                        let start =
+                            Start::SizeType::deserialize(UsizeDeserializer::<E>::new(start))?;
+                        let end = End::SizeType::deserialize(UsizeDeserializer::<E>::new(end))?;
+                        Ok($SerdeRange { start, end })
+                    }
+
+                    fn visit_bytes<E: Error>(self, v: &[u8]) -> Result<Self::Value, E> {
+                        match std::str::from_utf8(v) {
+                            Ok(v) => self.visit_str(v),
+                            Err(_) => {
+                                Err(Error::invalid_value(serde::de::Unexpected::Bytes(v), &self))
+                            }
+                        }
+                    }
+                }
+                deserializer.deserialize_str(SerdeRangeVisitor(PhantomData))
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        pub struct $UIntInRangeType<Start: Size, End: Size> {
+            value: UInt,
+            range: PhantomConst<$SerdeRange<Start, End>>,
+        }
+
+        impl<Start: Size, End: Size> $UIntInRangeType<Start, End> {
+            fn from_phantom_const_range(range: PhantomConst<$SerdeRange<Start, End>>) -> Self {
+                let $SerdeRange { start, end } = *range.get();
+                let $uint_range_usize_start = Start::as_usize(start);
+                let $uint_range_usize_end = End::as_usize(end);
+                Self {
+                    value: $uint_range_usize,
+                    range,
+                }
+            }
+            pub fn new(start: Start::SizeType, end: End::SizeType) -> Self {
+                Self::from_phantom_const_range(PhantomConst::new(
+                    $SerdeRange { start, end }.intern_sized(),
+                ))
+            }
+        }
+
+        impl<Start: Size, End: Size> fmt::Debug for $UIntInRangeType<Start, End> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let Self { value, range } = self;
+                let $SerdeRange { start, end } = *range.get();
+                f.debug_struct(&format!(
+                    "{}<{}, {}>",
+                    stringify!($UIntInRange),
+                    Start::as_usize(start),
+                    End::as_usize(end),
+                ))
+                .field("value", value)
+                .finish_non_exhaustive()
+            }
+        }
+
+        impl<Start: Size, End: Size> Type for $UIntInRangeType<Start, End> {
+            type BaseType = Bundle;
+            type MaskType = UIntInRangeMaskType;
+            type SimValue = usize;
+            impl_match_variant_as_self!();
+
+            fn mask_type(&self) -> Self::MaskType {
+                UIntInRangeMaskType::TYPE
+            }
+
+            fn canonical(&self) -> CanonicalType {
+                CanonicalType::Bundle(Bundle::new(self.fields()))
+            }
+
+            fn from_canonical(canonical_type: CanonicalType) -> Self {
+                let fields = Bundle::from_canonical(canonical_type).fields();
+                let [
+                    BundleField {
+                        name: value_name,
+                        flipped: false,
+                        ty: value,
+                    },
+                    BundleField {
+                        name: range_name,
+                        flipped: false,
+                        ty: range,
+                    },
+                ] = *fields
+                else {
+                    panic!("expected {}", stringify!($UIntInRange));
+                };
+                assert_eq!([&*value_name, &*range_name], UINT_IN_RANGE_TYPE_FIELD_NAMES);
+                let value = UInt::from_canonical(value);
+                let range = PhantomConst::<$SerdeRange<Start, End>>::from_canonical(range);
+                let retval = Self::from_phantom_const_range(range);
+                assert_eq!(retval, Self { value, range });
+                retval
+            }
+
+            fn source_location() -> SourceLocation {
+                SourceLocation::builtin()
+            }
+
+            fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+                assert_eq!(opaque.size(), self.value.type_properties().size());
+                let mut retval = 0usize;
+                retval.view_bits_mut::<Lsb0>()[..opaque.bit_width()]
+                    .clone_from_bitslice(opaque.bits());
+                retval
+            }
+
+            fn sim_value_clone_from_opaque(
+                &self,
+                value: &mut Self::SimValue,
+                opaque: OpaqueSimValueSlice<'_>,
+            ) {
+                *value = self.sim_value_from_opaque(opaque);
+            }
+
+            fn sim_value_to_opaque<'w>(
+                &self,
+                value: &Self::SimValue,
+                writer: OpaqueSimValueWriter<'w>,
+            ) -> OpaqueSimValueWritten<'w> {
+                writer.fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(
+                    &value.view_bits::<Lsb0>()[..self.value.width()],
+                ))
+            }
+        }
+
+        impl<Start: Size, End: Size> BundleType for $UIntInRangeType<Start, End> {
+            type Builder = NoBuilder;
+            type FilledBuilder = Expr<Self>;
+
+            fn fields(&self) -> Interned<[BundleField]> {
+                let [value_name, range_name] = UINT_IN_RANGE_TYPE_FIELD_NAMES;
+                let Self { value, range } = self;
+                [
+                    BundleField {
+                        name: value_name.intern(),
+                        flipped: false,
+                        ty: value.canonical(),
+                    },
+                    BundleField {
+                        name: range_name.intern(),
+                        flipped: false,
+                        ty: range.canonical(),
+                    },
+                ][..]
+                    .intern()
+            }
+        }
+
+        impl<Start: KnownSize, End: KnownSize> Default for $UIntInRangeType<Start, End> {
+            fn default() -> Self {
+                Self::TYPE
+            }
+        }
+
+        impl<Start: KnownSize, End: KnownSize> StaticType for $UIntInRangeType<Start, End> {
+            const TYPE: Self = {
+                let $uint_range_usize_start = Start::VALUE;
+                let $uint_range_usize_end = End::VALUE;
+                Self {
+                    value: $uint_range_usize,
+                    range: PhantomConst::<$SerdeRange<Start, End>>::TYPE,
+                }
+            };
+            const MASK_TYPE: Self::MaskType = UIntInRangeMaskType::TYPE;
+            const TYPE_PROPERTIES: TypeProperties = BundleTypePropertiesBuilder::new()
+                .field(false, Self::TYPE.value.type_properties_dyn())
+                .field(
+                    false,
+                    PhantomConst::<$SerdeRange<Start, End>>::TYPE_PROPERTIES,
+                )
+                .finish();
+            const MASK_TYPE_PROPERTIES: TypeProperties = UIntInRangeMaskType::TYPE_PROPERTIES;
+        }
+
+        impl<Start: Size, End: Size> ToSimValueWithType<$UIntInRangeType<Start, End>> for usize {
+            fn to_sim_value_with_type(
+                &self,
+                ty: $UIntInRangeType<Start, End>,
+            ) -> SimValue<$UIntInRangeType<Start, End>> {
+                SimValue::from_value(ty, *self)
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+        pub struct $UIntInRangeTypeWithoutGenerics;
+
+        #[allow(non_upper_case_globals)]
+        pub const $UIntInRangeType: $UIntInRangeTypeWithoutGenerics =
+            $UIntInRangeTypeWithoutGenerics;
+
+        impl<StartSize: SizeType> Index<StartSize> for $UIntInRangeTypeWithoutGenerics {
+            type Output = $UIntInRangeTypeWithStart<StartSize::Size>;
+
+            fn index(&self, start: StartSize) -> &Self::Output {
+                Interned::into_inner($UIntInRangeTypeWithStart(start).intern_sized())
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        pub struct $UIntInRangeTypeWithStart<Start: Size>(Start::SizeType);
+
+        impl<Start: Size, EndSize: SizeType<Size = End>, End: Size<SizeType = EndSize>>
+            Index<EndSize> for $UIntInRangeTypeWithStart<Start>
+        {
+            type Output = $UIntInRangeType<Start, End>;
+
+            fn index(&self, end: EndSize) -> &Self::Output {
+                Interned::into_inner($UIntInRangeType::new(self.0, end).intern_sized())
+            }
+        }
+
+        impl<Start: Size, End: Size> ExprCastTo<UInt> for $UIntInRangeType<Start, End> {
+            fn cast_to(src: Expr<Self>, to_type: UInt) -> Expr<UInt> {
+                src.cast_to_bits().cast_to(to_type)
+            }
+        }
+
+        impl<Start: Size, End: Size> ExprCastTo<$UIntInRangeType<Start, End>> for UInt {
+            fn cast_to(
+                src: Expr<Self>,
+                to_type: $UIntInRangeType<Start, End>,
+            ) -> Expr<$UIntInRangeType<Start, End>> {
+                src.cast_bits_to(to_type)
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            ExprPartialEq<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn cmp_eq(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_eq(rhs.cast_to_bits())
+            }
+            fn cmp_ne(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ne(rhs.cast_to_bits())
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            ExprPartialOrd<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn cmp_lt(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_lt(rhs.cast_to_bits())
+            }
+            fn cmp_le(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_le(rhs.cast_to_bits())
+            }
+            fn cmp_gt(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_gt(rhs.cast_to_bits())
+            }
+            fn cmp_ge(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ge(rhs.cast_to_bits())
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            SimValuePartialEq<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn sim_value_eq(
+                this: &SimValue<Self>,
+                other: &SimValue<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> bool {
+                **this == **other
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialEq<UIntType<Width>>
+            for $UIntInRangeType<Start, End>
+        {
+            fn cmp_eq(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_eq(rhs)
+            }
+            fn cmp_ne(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ne(rhs)
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialEq<$UIntInRangeType<Start, End>>
+            for UIntType<Width>
+        {
+            fn cmp_eq(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_eq(rhs.cast_to_bits())
+            }
+            fn cmp_ne(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_ne(rhs.cast_to_bits())
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialOrd<UIntType<Width>>
+            for $UIntInRangeType<Start, End>
+        {
+            fn cmp_lt(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_lt(rhs)
+            }
+            fn cmp_le(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_le(rhs)
+            }
+            fn cmp_gt(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_gt(rhs)
+            }
+            fn cmp_ge(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ge(rhs)
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialOrd<$UIntInRangeType<Start, End>>
+            for UIntType<Width>
+        {
+            fn cmp_lt(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_lt(rhs.cast_to_bits())
+            }
+            fn cmp_le(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_le(rhs.cast_to_bits())
+            }
+            fn cmp_gt(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_gt(rhs.cast_to_bits())
+            }
+            fn cmp_ge(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_ge(rhs.cast_to_bits())
+            }
+        }
+    };
+}
+
+define_uint_in_range_type! {
+    UIntInRange,
+    UIntInRangeType,
+    UIntInRangeTypeWithoutGenerics,
+    UIntInRangeTypeWithStart,
+    SerdeRange,
+    "..",
+    |start, end| UInt::range_usize(start..end),
+}
+
+define_uint_in_range_type! {
+    UIntInRangeInclusive,
+    UIntInRangeInclusiveType,
+    UIntInRangeInclusiveTypeWithoutGenerics,
+    UIntInRangeInclusiveTypeWithStart,
+    SerdeRangeInclusive,
+    "..=",
+    |start, end| UInt::range_inclusive_usize(start..=end),
+}
+
+impl SerdeRange<DynSize, DynSize> {
+    fn is_empty(self) -> bool {
+        self.start >= self.end
+    }
+}
+
+impl SerdeRangeInclusive<DynSize, DynSize> {
+    fn is_empty(self) -> bool {
+        self.start > self.end
+    }
+}

crates/fayalite/src/intern.rs

@@ -1,9 +1,9 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 #![allow(clippy::type_complexity)]
-use crate::intern::type_map::TypeIdMap;
+use crate::{intern::type_map::TypeIdMap, util::DefaultBuildHasher};
 use bitvec::{ptr::BitPtr, slice::BitSlice, vec::BitVec};
-use hashbrown::{hash_map::RawEntryMut, HashMap, HashTable};
+use hashbrown::HashTable;
 use serde::{Deserialize, Serialize};
 use std::{
     any::{Any, TypeId},
@@ -17,7 +17,7 @@ use std::{
     sync::{Mutex, RwLock},
 };
 
-pub mod type_map;
+mod type_map;
 
 pub trait LazyInternedTrait<T: ?Sized + Send + Sync + 'static>: Send + Sync + Any {
     fn get(&self) -> Interned<T>;
@@ -316,8 +316,13 @@ pub trait Intern: Any + Send + Sync {
     }
 }
 
+struct InternerState<T: ?Sized + 'static + Send + Sync> {
+    table: HashTable<&'static T>,
+    hasher: DefaultBuildHasher,
+}
+
 pub struct Interner<T: ?Sized + 'static + Send + Sync> {
-    map: Mutex<HashMap<&'static T, ()>>,
+    state: Mutex<InternerState<T>>,
 }
 
 impl<T: ?Sized + 'static + Send + Sync> Interner<T> {
@@ -330,7 +335,10 @@ impl<T: ?Sized + 'static + Send + Sync> Interner<T> {
 impl<T: ?Sized + 'static + Send + Sync> Default for Interner<T> {
     fn default() -> Self {
         Self {
-            map: Default::default(),
+            state: Mutex::new(InternerState {
+                table: HashTable::new(),
+                hasher: Default::default(),
+            }),
         }
     }
 }
@@ -341,17 +349,16 @@ impl<T: ?Sized + 'static + Send + Sync + Hash + Eq + ToOwned> Interner<T> {
         alloc: F,
         value: Cow<'_, T>,
     ) -> Interned<T> {
-        let mut map = self.map.lock().unwrap();
-        let hasher = map.hasher().clone();
-        let hash = hasher.hash_one(&*value);
-        let inner = match map.raw_entry_mut().from_hash(hash, |k| **k == *value) {
-            RawEntryMut::Occupied(entry) => *entry.key(),
-            RawEntryMut::Vacant(entry) => {
-                *entry
-                    .insert_with_hasher(hash, alloc(value), (), |k| hasher.hash_one(&**k))
-                    .0
-            }
-        };
+        let mut state = self.state.lock().unwrap();
+        let InternerState { table, hasher } = &mut *state;
+        let inner = *table
+            .entry(
+                hasher.hash_one(&*value),
+                |k| **k == *value,
+                |k| hasher.hash_one(&**k),
+            )
+            .or_insert_with(|| alloc(value))
+            .get();
         Interned { inner }
     }
 }
@@ -742,7 +749,7 @@ pub trait MemoizeGeneric: 'static + Send + Sync + Hash + Eq + Copy {
     fn get_cow(self, input: Self::InputCow<'_>) -> Self::Output {
         static TYPE_ID_MAP: TypeIdMap = TypeIdMap::new();
         let map: &RwLock<(
-            hashbrown::hash_map::DefaultHashBuilder,
+            DefaultBuildHasher,
             HashTable<(Self, Self::InputOwned, Self::Output)>,
         )> = TYPE_ID_MAP.get_or_insert_default();
         fn hash_eq_key<'a, 'b, T: MemoizeGeneric>(

crates/fayalite/src/intern/type_map.rs

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
-use hashbrown::HashMap;
 use std::{
     any::{Any, TypeId},
     hash::{BuildHasher, Hasher},
-    ptr::NonNull,
     sync::RwLock,
 };
 
@@ -75,59 +73,36 @@ impl BuildHasher for TypeIdBuildHasher {
     }
 }
 
-struct Value(NonNull<dyn Any + Send + Sync>);
-
-impl Value {
-    unsafe fn get_transmute_lifetime<'b>(&self) -> &'b (dyn Any + Send + Sync) {
-        unsafe { &*self.0.as_ptr() }
-    }
-    fn new(v: Box<dyn Any + Send + Sync>) -> Self {
-        unsafe { Self(NonNull::new_unchecked(Box::into_raw(v))) }
-    }
-}
-
-unsafe impl Send for Value {}
-unsafe impl Sync for Value {}
-
-impl Drop for Value {
-    fn drop(&mut self) {
-        unsafe { std::ptr::drop_in_place(self.0.as_ptr()) }
-    }
-}
-
-pub struct TypeIdMap(RwLock<HashMap<TypeId, Value, TypeIdBuildHasher>>);
+pub(crate) struct TypeIdMap(
+    RwLock<hashbrown::HashMap<TypeId, &'static (dyn Any + Send + Sync), TypeIdBuildHasher>>,
+);
 
 impl TypeIdMap {
-    pub const fn new() -> Self {
-        Self(RwLock::new(HashMap::with_hasher(TypeIdBuildHasher)))
+    pub(crate) const fn new() -> Self {
+        Self(RwLock::new(hashbrown::HashMap::with_hasher(
+            TypeIdBuildHasher,
+        )))
     }
     #[cold]
-    unsafe fn insert_slow(
+    fn insert_slow(
         &self,
         type_id: TypeId,
         make: fn() -> Box<dyn Any + Sync + Send>,
-    ) -> &(dyn Any + Sync + Send) {
-        let value = Value::new(make());
+    ) -> &'static (dyn Any + Sync + Send) {
+        let value = Box::leak(make());
         let mut write_guard = self.0.write().unwrap();
-        unsafe {
-            write_guard
-                .entry(type_id)
-                .or_insert(value)
-                .get_transmute_lifetime()
-        }
+        *write_guard.entry(type_id).or_insert(value)
     }
-    pub fn get_or_insert_default<T: Sized + Any + Send + Sync + Default>(&self) -> &T {
+    pub(crate) fn get_or_insert_default<T: Sized + Any + Send + Sync + Default>(&self) -> &T {
         let type_id = TypeId::of::<T>();
         let read_guard = self.0.read().unwrap();
-        let retval = read_guard
-            .get(&type_id)
-            .map(|v| unsafe { Value::get_transmute_lifetime(v) });
+        let retval = read_guard.get(&type_id).map(|v| *v);
         drop(read_guard);
         let retval = match retval {
             Some(retval) => retval,
-            None => unsafe { self.insert_slow(type_id, move || Box::new(T::default())) },
+            None => self.insert_slow(type_id, move || Box::new(T::default())),
         };
-        unsafe { &*(retval as *const dyn Any as *const T) }
+        retval.downcast_ref().expect("known to have correct TypeId")
     }
 }
 

crates/fayalite/src/lib.rs

@@ -11,6 +11,59 @@ extern crate self as fayalite;
 #[doc(hidden)]
 pub use std as __std;
 
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __cfg_expansion_helper {
+    (
+        [
+            $($evaluated_cfgs:ident($($evaluated_exprs:tt)*) = $evaluated_results:ident,)*
+        ]
+        [
+            $cfg:ident($($expr:tt)*),
+            $($unevaluated_cfgs:ident($($unevaluated_exprs:tt)*),)*
+        ]
+        // pass as tt so we get right span for attribute
+        $after_evaluation_attr:tt $after_evaluation_body:tt
+    ) => {
+        #[$cfg($($expr)*)]
+        $crate::__cfg_expansion_helper! {
+            [
+                $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+                $cfg($($expr)*) = true,
+            ]
+            [
+                $($unevaluated_cfgs($($unevaluated_exprs)*),)*
+            ]
+            $after_evaluation_attr $after_evaluation_body
+        }
+        #[$cfg(not($($expr)*))]
+        $crate::__cfg_expansion_helper! {
+            [
+                $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+                $cfg($($expr)*) = false,
+            ]
+            [
+                $($unevaluated_cfgs($($unevaluated_exprs)*),)*
+            ]
+            $after_evaluation_attr $after_evaluation_body
+        }
+    };
+    (
+        [
+            $($evaluated_cfgs:ident($($evaluated_exprs:tt)*) = $evaluated_results:ident,)*
+        ]
+        []
+        // don't use #[...] so we get right span for `#` and `[]` of attribute
+        {$($after_evaluation_attr:tt)*} {$($after_evaluation_body:tt)*}
+    ) => {
+        $($after_evaluation_attr)*
+        #[__evaluated_cfgs([
+            $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+        ])]
+        $($after_evaluation_body)*
+    };
+}
+
 #[doc(inline)]
 /// The `#[hdl_module]` attribute is applied to a Rust function so that that function creates
 /// a [`Module`][`::fayalite::module::Module`] when called.
@@ -23,6 +76,8 @@ pub use fayalite_proc_macros::hdl_module;
 #[doc(inline)]
 pub use fayalite_proc_macros::hdl;
 
+pub use bitvec;
+
 /// struct used as a placeholder when applying defaults
 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
 pub struct __;
@@ -43,9 +98,11 @@ pub mod int;
 pub mod intern;
 pub mod memory;
 pub mod module;
+pub mod phantom_const;
 pub mod prelude;
 pub mod reg;
 pub mod reset;
+pub mod sim;
 pub mod source_location;
 pub mod testing;
 pub mod ty;

crates/fayalite/src/memory.rs

@@ -7,7 +7,7 @@ use crate::{
     array::{Array, ArrayType},
     bundle::{Bundle, BundleType},
     clock::Clock,
-    expr::{ops::BundleLiteral, repeat, Expr, Flow, ToExpr, ToLiteralBits},
+    expr::{Expr, Flow, ToExpr, ToLiteralBits, ops::BundleLiteral, repeat},
     hdl,
     int::{Bool, DynSize, Size, UInt, UIntType},
     intern::{Intern, Interned},
@@ -22,7 +22,7 @@ use std::{
     fmt,
     hash::{Hash, Hasher},
     marker::PhantomData,
-    num::NonZeroU32,
+    num::NonZeroUsize,
     rc::Rc,
 };
 
@@ -470,7 +470,7 @@ pub enum ReadUnderWrite {
     Undefined,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 struct MemImpl<Element: Type, Len: Size, P> {
     scoped_name: ScopedNameId,
     source_location: SourceLocation,
@@ -478,7 +478,7 @@ struct MemImpl<Element: Type, Len: Size, P> {
     initial_value: Option<Interned<BitSlice>>,
     ports: P,
     read_latency: usize,
-    write_latency: NonZeroU32,
+    write_latency: NonZeroUsize,
     read_under_write: ReadUnderWrite,
     port_annotations: Interned<[TargetedAnnotation]>,
     mem_annotations: Interned<[Annotation]>,
@@ -519,7 +519,12 @@ impl<Element: Type, Len: Size> fmt::Debug for Mem<Element, Len> {
         f.debug_struct("Mem")
             .field("name", scoped_name)
             .field("array_type", array_type)
-            .field("initial_value", initial_value)
+            .field(
+                "initial_value",
+                &initial_value.as_ref().map(|initial_value| {
+                    DebugMemoryData::from_bit_slice(*array_type, initial_value)
+                }),
+            )
             .field("read_latency", read_latency)
             .field("write_latency", write_latency)
             .field("read_under_write", read_under_write)
@@ -562,7 +567,7 @@ impl<Element: Type, Len: Size> Mem<Element, Len> {
         initial_value: Option<Interned<BitSlice>>,
         ports: Interned<[MemPort<DynPortType>]>,
         read_latency: usize,
-        write_latency: NonZeroU32,
+        write_latency: NonZeroUsize,
         read_under_write: ReadUnderWrite,
         port_annotations: Interned<[TargetedAnnotation]>,
         mem_annotations: Interned<[Annotation]>,
@@ -645,7 +650,7 @@ impl<Element: Type, Len: Size> Mem<Element, Len> {
     pub fn read_latency(self) -> usize {
         self.0.read_latency
     }
-    pub fn write_latency(self) -> NonZeroU32 {
+    pub fn write_latency(self) -> NonZeroUsize {
         self.0.write_latency
     }
     pub fn read_under_write(self) -> ReadUnderWrite {
@@ -707,7 +712,7 @@ pub(crate) struct MemBuilderTarget {
     pub(crate) initial_value: Option<Interned<BitSlice>>,
     pub(crate) ports: Vec<MemPort<DynPortType>>,
     pub(crate) read_latency: usize,
-    pub(crate) write_latency: NonZeroU32,
+    pub(crate) write_latency: NonZeroUsize,
     pub(crate) read_under_write: ReadUnderWrite,
     pub(crate) port_annotations: Vec<TargetedAnnotation>,
     pub(crate) mem_annotations: Vec<Annotation>,
@@ -867,7 +872,7 @@ impl<Element: Type, Len: Size> MemBuilder<Element, Len> {
             initial_value: None,
             ports: vec![],
             read_latency: 0,
-            write_latency: NonZeroU32::new(1).unwrap(),
+            write_latency: NonZeroUsize::new(1).unwrap(),
             read_under_write: ReadUnderWrite::Old,
             port_annotations: vec![],
             mem_annotations: vec![],
@@ -1030,10 +1035,10 @@ impl<Element: Type, Len: Size> MemBuilder<Element, Len> {
     pub fn read_latency(&mut self, read_latency: usize) {
         self.target.borrow_mut().read_latency = read_latency;
     }
-    pub fn get_write_latency(&self) -> NonZeroU32 {
+    pub fn get_write_latency(&self) -> NonZeroUsize {
         self.target.borrow().write_latency
     }
-    pub fn write_latency(&mut self, write_latency: NonZeroU32) {
+    pub fn write_latency(&mut self, write_latency: NonZeroUsize) {
         self.target.borrow_mut().write_latency = write_latency;
     }
     pub fn get_read_under_write(&self) -> ReadUnderWrite {
@@ -1061,7 +1066,8 @@ pub fn splat_mask<T: Type>(ty: T, value: Expr<Bool>) -> Expr<AsMask<T>> {
         | CanonicalType::SyncReset(_)
         | CanonicalType::Reset(_)
         | CanonicalType::Clock(_)
-        | CanonicalType::Enum(_) => Expr::from_canonical(Expr::canonical(value)),
+        | CanonicalType::Enum(_)
+        | CanonicalType::DynSimOnly(_) => Expr::from_canonical(Expr::canonical(value)),
         CanonicalType::Array(array) => Expr::from_canonical(Expr::canonical(repeat(
             splat_mask(array.element(), value),
             array.len(),
@@ -1077,5 +1083,64 @@ pub fn splat_mask<T: Type>(ty: T, value: Expr<Bool>) -> Expr<AsMask<T>> {
             )
             .to_expr(),
         )),
+        CanonicalType::PhantomConst(_) => Expr::from_canonical(Expr::canonical(().to_expr())),
+    }
+}
+
+pub trait DebugMemoryDataGetElement {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice;
+}
+
+impl<'a, F: ?Sized + Fn(usize, Array) -> &'a BitSlice> DebugMemoryDataGetElement for &'a F {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice {
+        self(element_index, array_type)
+    }
+}
+
+#[derive(Clone)]
+pub struct DebugMemoryData<GetElement: DebugMemoryDataGetElement> {
+    pub array_type: Array,
+    pub get_element: GetElement,
+}
+
+impl DebugMemoryDataGetElement for &'_ BitSlice {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice {
+        assert!(element_index < array_type.len());
+        let stride = array_type.element().bit_width();
+        let start = element_index
+            .checked_mul(stride)
+            .expect("memory is too big");
+        let end = start.checked_add(stride).expect("memory is too big");
+        &self[start..end]
+    }
+}
+
+impl<'a> DebugMemoryData<&'a BitSlice> {
+    pub fn from_bit_slice<T: Type, Depth: Size>(
+        array_type: ArrayType<T, Depth>,
+        bit_slice: &'a BitSlice,
+    ) -> Self {
+        let array_type = array_type.as_dyn_array();
+        assert_eq!(bit_slice.len(), array_type.type_properties().bit_width);
+        Self {
+            array_type,
+            get_element: bit_slice,
+        }
+    }
+}
+
+impl<GetElement: DebugMemoryDataGetElement> fmt::Debug for DebugMemoryData<GetElement> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.array_type.len() == 0 {
+            return f.write_str("[]");
+        }
+        writeln!(f, "[\n    // len = {:#x}", self.array_type.len())?;
+        for element_index in 0..self.array_type.len() {
+            let element = crate::util::BitSliceWriteWithBase(
+                self.get_element.get_element(element_index, self.array_type),
+            );
+            writeln!(f, "    [{element_index:#x}]: {element:#x},")?;
+        }
+        f.write_str("]")
     }
 }

crates/fayalite/src/module.rs

@@ -8,30 +8,33 @@ use crate::{
     clock::{Clock, ClockDomain},
     enum_::{Enum, EnumMatchVariantsIter, EnumType},
     expr::{
+        Expr, Flow, ToExpr,
         ops::VariantAccess,
         target::{
             GetTarget, Target, TargetBase, TargetPathArrayElement, TargetPathBundleField,
             TargetPathElement,
         },
-        Expr, Flow, ToExpr,
     },
     formal::FormalKind,
     int::{Bool, DynSize, Size},
     intern::{Intern, Interned},
     memory::{Mem, MemBuilder, MemBuilderTarget, PortName},
     reg::Reg,
+    reset::{AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset},
+    sim::{ExternModuleSimGenerator, ExternModuleSimulation},
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
-    util::ScopedRef,
+    util::{HashMap, HashSet, ScopedRef},
     wire::{IncompleteWire, Wire},
 };
-use hashbrown::{hash_map::Entry, HashMap, HashSet};
+use hashbrown::hash_map::Entry;
 use num_bigint::BigInt;
 use std::{
     cell::RefCell,
-    collections::VecDeque,
+    collections::{BTreeMap, VecDeque},
     convert::Infallible,
     fmt,
+    future::IntoFuture,
     hash::{Hash, Hasher},
     iter::FusedIterator,
     marker::PhantomData,
@@ -180,7 +183,7 @@ impl Block {
     }
 }
 
-#[derive(Clone, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct StmtConnect {
     pub lhs: Expr<CanonicalType>,
     pub rhs: Expr<CanonicalType>,
@@ -235,7 +238,7 @@ impl fmt::Debug for StmtConnect {
     }
 }
 
-#[derive(Clone, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct StmtFormal {
     pub kind: FormalKind,
     pub clk: Expr<Clock>,
@@ -284,6 +287,8 @@ pub struct StmtIf<S: ModuleBuildingStatus = ModuleBuilt> {
     pub blocks: [S::Block; 2],
 }
 
+impl Copy for StmtIf {}
+
 impl<S: ModuleBuildingStatus> StmtIf<S> {
     pub fn then_block(&self) -> S::Block {
         self.blocks[0]
@@ -315,6 +320,8 @@ pub struct StmtMatch<S: ModuleBuildingStatus = ModuleBuilt> {
     pub blocks: Interned<[S::Block]>,
 }
 
+impl Copy for StmtMatch {}
+
 impl StmtMatch {
     #[track_caller]
     fn assert_validity(&self) {
@@ -346,7 +353,7 @@ macro_rules! wrapper_enum {
         $(#[$enum_meta:meta])*
         $vis:vis enum $enum_name:ident<$T_enum:ident: $T_bound:ident = $T_enum_default:ident> {
             $(
-                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident]
+                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident $(, from = $from:ident)?]
                 $(#[$variant_meta:meta])*
                 $Variant:ident($VariantTy:ty),
             )*
@@ -358,7 +365,7 @@ macro_rules! wrapper_enum {
             $(#[$enum_meta])*
             $vis enum $enum_name<$T_enum: $T_bound = $T_enum_default> {
                 $(
-                    #[is = $is_fn, as_ref = $as_ref_fn]
+                    #[is = $is_fn, as_ref = $as_ref_fn $(, from = $from)?]
                     $(#[$variant_meta])*
                     $Variant($VariantTy),
                 )*
@@ -385,7 +392,7 @@ macro_rules! wrapper_enum {
         $(#[$enum_meta:meta])*
         $vis:vis enum $enum_name:ident<$T_enum:ident: $T_bound:ident = $T_enum_default:ident> {
             $(
-                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident]
+                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident $(, from = $from:ident)?]
                 $(#[$variant_meta:meta])*
                 $Variant:ident($VariantTy:ty),
             )*
@@ -397,22 +404,22 @@ macro_rules! wrapper_enum {
             $(#[$enum_meta])*
             $vis enum $enum_name<$T_enum: $T_bound = $T_enum_default> {
                 $(
-                    #[is = $is_fn, as_ref = $as_ref_fn]
+                    #[is = $is_fn, as_ref = $as_ref_fn $(, from = $from)?]
                     $(#[$variant_meta])*
                     $Variant($VariantTy),
                 )*
             }
         }
 
-        $(
+        $($(
             wrapper_enum! {
                 impl $T_to From<$VariantTy> for $to_type {
-                    fn from(value: $VariantTy) -> Self {
+                    fn $from(value: $VariantTy) -> Self {
                         $enum_name::$Variant(value).into()
                     }
                 }
             }
-        )*
+        )?)*
     };
     (
         #[impl()]
@@ -420,7 +427,7 @@ macro_rules! wrapper_enum {
         $(#[$enum_meta:meta])*
         $vis:vis enum $enum_name:ident<$T_enum:ident: $T_bound:ident = $T_enum_default:ident> {
             $(
-                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident]
+                #[is = $is_fn:ident, as_ref = $as_ref_fn:ident $(, from = $from:ident)?]
                 $(#[$variant_meta:meta])*
                 $Variant:ident($VariantTy:ty),
             )*
@@ -459,13 +466,15 @@ pub struct StmtWire<S: ModuleBuildingStatus = ModuleBuilt> {
     pub wire: Wire<CanonicalType>,
 }
 
+impl Copy for StmtWire {}
+
 #[derive(Hash, Clone, PartialEq, Eq, Debug)]
-pub struct StmtReg<S: ModuleBuildingStatus = ModuleBuilt> {
+pub struct StmtReg<R: ResetType, S: ModuleBuildingStatus = ModuleBuilt> {
     pub annotations: S::StmtAnnotations,
-    pub reg: Reg<CanonicalType>,
+    pub reg: Reg<CanonicalType, R>,
 }
 
-impl Copy for StmtReg {}
+impl<R: ResetType> Copy for StmtReg<R> {}
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct StmtInstance<S: ModuleBuildingStatus = ModuleBuilt> {
@@ -473,6 +482,8 @@ pub struct StmtInstance<S: ModuleBuildingStatus = ModuleBuilt> {
     pub instance: Instance<Bundle>,
 }
 
+impl Copy for StmtInstance {}
+
 wrapper_enum! {
     #[impl(
         (<S: ModuleBuildingStatus>) self: StmtDeclaration<S> = self,
@@ -481,20 +492,57 @@ wrapper_enum! {
     #[to((<S: ModuleBuildingStatus>) StmtDeclaration<S>, (<S: ModuleBuildingStatus>) Stmt<S>)]
     #[derive(Clone, PartialEq, Eq, Hash)]
     pub enum StmtDeclaration<S: ModuleBuildingStatus = ModuleBuilt> {
-        #[is = is_wire, as_ref = wire]
+        #[is = is_wire, as_ref = wire, from = from]
         Wire(StmtWire<S>),
         #[is = is_reg, as_ref = reg]
-        Reg(StmtReg<S>),
-        #[is = is_instance, as_ref = instance]
+        Reg(StmtReg<Reset, S>),
+        #[is = is_reg_sync, as_ref = reg_sync]
+        RegSync(StmtReg<SyncReset, S>),
+        #[is = is_reg_async, as_ref = reg_async]
+        RegAsync(StmtReg<AsyncReset, S>),
+        #[is = is_instance, as_ref = instance, from = from]
         Instance(StmtInstance<S>),
     }
 }
 
+impl Copy for StmtDeclaration {}
+
+impl<S: ModuleBuildingStatus, R: ResetType> From<StmtReg<R, S>> for Stmt<S> {
+    fn from(value: StmtReg<R, S>) -> Self {
+        StmtDeclaration::from(value).into()
+    }
+}
+
+impl<S: ModuleBuildingStatus, R: ResetType> From<StmtReg<R, S>> for StmtDeclaration<S> {
+    fn from(value: StmtReg<R, S>) -> Self {
+        struct Dispatch<S>(PhantomData<S>);
+        impl<S: ModuleBuildingStatus> ResetTypeDispatch for Dispatch<S> {
+            type Input<T: ResetType> = StmtReg<T, S>;
+            type Output<T: ResetType> = StmtDeclaration<S>;
+
+            fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset> {
+                StmtDeclaration::Reg(input)
+            }
+
+            fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset> {
+                StmtDeclaration::RegSync(input)
+            }
+
+            fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset> {
+                StmtDeclaration::RegAsync(input)
+            }
+        }
+        R::dispatch(value, Dispatch(PhantomData))
+    }
+}
+
 impl<S: ModuleBuildingStatus> StmtDeclaration<S> {
     pub fn annotations(&self) -> S::StmtAnnotations {
         match self {
             StmtDeclaration::Wire(v) => v.annotations,
             StmtDeclaration::Reg(v) => v.annotations,
+            StmtDeclaration::RegSync(v) => v.annotations,
+            StmtDeclaration::RegAsync(v) => v.annotations,
             StmtDeclaration::Instance(v) => v.annotations,
         }
     }
@@ -502,6 +550,8 @@ impl<S: ModuleBuildingStatus> StmtDeclaration<S> {
         match self {
             StmtDeclaration::Wire(v) => v.wire.source_location(),
             StmtDeclaration::Reg(v) => v.reg.source_location(),
+            StmtDeclaration::RegSync(v) => v.reg.source_location(),
+            StmtDeclaration::RegAsync(v) => v.reg.source_location(),
             StmtDeclaration::Instance(v) => v.instance.source_location(),
         }
     }
@@ -509,20 +559,26 @@ impl<S: ModuleBuildingStatus> StmtDeclaration<S> {
         match self {
             StmtDeclaration::Wire(v) => v.wire.scoped_name(),
             StmtDeclaration::Reg(v) => v.reg.scoped_name(),
+            StmtDeclaration::RegSync(v) => v.reg.scoped_name(),
+            StmtDeclaration::RegAsync(v) => v.reg.scoped_name(),
             StmtDeclaration::Instance(v) => v.instance.scoped_name(),
         }
     }
     pub fn sub_stmt_blocks(&self) -> &[S::Block] {
         match self {
-            StmtDeclaration::Wire(_) | StmtDeclaration::Reg(_) | StmtDeclaration::Instance(_) => {
-                &[]
-            }
+            StmtDeclaration::Wire(_)
+            | StmtDeclaration::Reg(_)
+            | StmtDeclaration::RegSync(_)
+            | StmtDeclaration::RegAsync(_)
+            | StmtDeclaration::Instance(_) => &[],
         }
     }
     pub fn canonical_ty(&self) -> CanonicalType {
         match self {
             StmtDeclaration::Wire(v) => v.wire.ty(),
             StmtDeclaration::Reg(v) => v.reg.ty(),
+            StmtDeclaration::RegSync(v) => v.reg.ty(),
+            StmtDeclaration::RegAsync(v) => v.reg.ty(),
             StmtDeclaration::Instance(v) => CanonicalType::Bundle(v.instance.ty()),
         }
     }
@@ -533,19 +589,21 @@ wrapper_enum! {
     #[to((<S: ModuleBuildingStatus>) Stmt<S>)]
     #[derive(Clone, PartialEq, Eq, Hash)]
     pub enum Stmt<S: ModuleBuildingStatus = ModuleBuilt> {
-        #[is = is_connect, as_ref = connect]
+        #[is = is_connect, as_ref = connect, from = from]
         Connect(StmtConnect),
-        #[is = is_formal, as_ref = formal]
+        #[is = is_formal, as_ref = formal, from = from]
         Formal(StmtFormal),
-        #[is = is_if, as_ref = if_]
+        #[is = is_if, as_ref = if_, from = from]
         If(StmtIf<S>),
-        #[is = is_match, as_ref = match_]
+        #[is = is_match, as_ref = match_, from = from]
         Match(StmtMatch<S>),
-        #[is = is_declaration, as_ref = declaration]
+        #[is = is_declaration, as_ref = declaration, from = from]
         Declaration(StmtDeclaration<S>),
     }
 }
 
+impl Copy for Stmt {}
+
 impl<S: ModuleBuildingStatus> Stmt<S> {
     pub fn sub_stmt_blocks(&self) -> &[S::Block] {
         match self {
@@ -714,6 +772,18 @@ impl<T: BundleType> Instance<T> {
             source_location,
         }
     }
+    pub fn from_canonical(v: Instance<Bundle>) -> Self {
+        let Instance {
+            scoped_name,
+            instantiated,
+            source_location,
+        } = v;
+        Self {
+            scoped_name,
+            instantiated: Module::from_canonical(*instantiated).intern_sized(),
+            source_location,
+        }
+    }
     pub fn containing_module_name(self) -> Interned<str> {
         self.containing_module_name_id().0
     }
@@ -958,6 +1028,14 @@ impl From<NormalModuleBody<ModuleBuilding>> for NormalModuleBody {
                                 annotations: (),
                                 reg,
                             }) => StmtReg { annotations, reg }.into(),
+                            StmtDeclaration::RegSync(StmtReg {
+                                annotations: (),
+                                reg,
+                            }) => StmtReg { annotations, reg }.into(),
+                            StmtDeclaration::RegAsync(StmtReg {
+                                annotations: (),
+                                reg,
+                            }) => StmtReg { annotations, reg }.into(),
                             StmtDeclaration::Instance(StmtInstance {
                                 annotations: (),
                                 instance,
@@ -1005,6 +1083,7 @@ pub struct ExternModuleBody<
 > {
     pub verilog_name: Interned<str>,
     pub parameters: P,
+    pub simulation: Option<ExternModuleSimulation>,
 }
 
 impl From<ExternModuleBody<Vec<ExternModuleParameter>>> for ExternModuleBody {
@@ -1012,11 +1091,13 @@ impl From<ExternModuleBody<Vec<ExternModuleParameter>>> for ExternModuleBody {
         let ExternModuleBody {
             verilog_name,
             parameters,
+            simulation,
         } = value;
         let parameters = Intern::intern_owned(parameters);
         Self {
             verilog_name,
             parameters,
+            simulation,
         }
     }
 }
@@ -1207,10 +1288,12 @@ impl<T: BundleType> fmt::Debug for DebugModuleBody<T> {
             ModuleBody::Extern(ExternModuleBody {
                 verilog_name,
                 parameters,
+                simulation,
             }) => {
                 debug_struct
                     .field("verilog_name", verilog_name)
-                    .field("parameters", parameters);
+                    .field("parameters", parameters)
+                    .field("simulation", simulation);
             }
         }
         debug_struct.finish_non_exhaustive()
@@ -1376,7 +1459,9 @@ impl TargetState {
                     })
                     .reduce(TargetWritten::conditional_merge_written)
                 else {
-                    unreachable!("merge_conditional_sub_blocks_into_block must be called with at least one sub-block");
+                    unreachable!(
+                        "merge_conditional_sub_blocks_into_block must be called with at least one sub-block"
+                    );
                 };
                 let mut written_in_blocks = written_in_blocks.borrow_mut();
                 if target_block >= written_in_blocks.len() {
@@ -1414,6 +1499,9 @@ impl TargetState {
                         })
                         .collect(),
                 },
+                CanonicalType::PhantomConst(_) => TargetStateInner::Decomposed {
+                    subtargets: HashMap::default(),
+                },
                 CanonicalType::Array(ty) => TargetStateInner::Decomposed {
                     subtargets: (0..ty.len())
                         .map(|index| {
@@ -1436,7 +1524,8 @@ impl TargetState {
                 | CanonicalType::Clock(_)
                 | CanonicalType::AsyncReset(_)
                 | CanonicalType::SyncReset(_)
-                | CanonicalType::Reset(_) => TargetStateInner::Single {
+                | CanonicalType::Reset(_)
+                | CanonicalType::DynSimOnly(_) => TargetStateInner::Single {
                     declared_in_block,
                     written_in_blocks: RefCell::default(),
                 },
@@ -1661,6 +1750,14 @@ impl AssertValidityState {
                     annotations: _,
                     reg,
                 })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
+                Stmt::Declaration(StmtDeclaration::RegSync(StmtReg {
+                    annotations: _,
+                    reg,
+                })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
+                Stmt::Declaration(StmtDeclaration::RegAsync(StmtReg {
+                    annotations: _,
+                    reg,
+                })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
                 Stmt::Declaration(StmtDeclaration::Instance(StmtInstance {
                     annotations: _,
                     instance,
@@ -1674,6 +1771,7 @@ impl AssertValidityState {
             ModuleBody::Extern(ExternModuleBody {
                 verilog_name: _,
                 parameters: _,
+                simulation: _,
             }) => {}
             ModuleBody::Normal(NormalModuleBody { body }) => {
                 let body = self.make_block_index(body);
@@ -1695,12 +1793,49 @@ impl<T: BundleType> Module<T> {
     pub fn new_unchecked(
         name_id: NameId,
         source_location: SourceLocation,
-        body: ModuleBody,
+        mut body: ModuleBody,
         module_io: impl IntoIterator<Item = AnnotatedModuleIO>,
         module_annotations: impl IntoAnnotations,
     ) -> Module<T> {
         let module_io: Interned<[_]> = module_io.into_iter().collect();
         let module_annotations = module_annotations.into_annotations().into_iter().collect();
+        match &mut body {
+            ModuleBody::Normal(_) => {}
+            ModuleBody::Extern(ExternModuleBody {
+                simulation: Some(simulation),
+                ..
+            }) => {
+                if module_io.iter().any(|io| {
+                    !simulation
+                        .sim_io_to_generator_map
+                        .contains_key(&io.module_io.intern())
+                }) {
+                    let mut sim_io_to_generator_map =
+                        BTreeMap::clone(&simulation.sim_io_to_generator_map);
+                    for io in module_io.iter() {
+                        let io = io.module_io.intern();
+                        sim_io_to_generator_map.entry(io).or_insert(io);
+                    }
+                    simulation.sim_io_to_generator_map = sim_io_to_generator_map.intern_sized();
+                }
+                if simulation.sim_io_to_generator_map.len() > module_io.len() {
+                    // if sim_io_to_generator_map is bigger, then there must be a key that's not in module_io
+                    let module_io_set = HashSet::from_iter(module_io.iter().map(|v| v.module_io));
+                    for (sim_io, generator_io) in simulation.sim_io_to_generator_map.iter() {
+                        if !module_io_set.contains(&**sim_io) {
+                            panic!(
+                                "extern module has invalid `sim_io_to_generator_map`: key is not in containing module's `module_io`:\n\
+                                key={sim_io:?}\nvalue={generator_io:?}\nmodule location: {source_location}"
+                            );
+                        }
+                    }
+                    unreachable!();
+                }
+            }
+            ModuleBody::Extern(ExternModuleBody {
+                simulation: None, ..
+            }) => {}
+        }
         let retval = Module {
             name: name_id,
             source_location,
@@ -1769,7 +1904,7 @@ impl<T: BundleType> Module<T> {
         AssertValidityState {
             module: self.canonical(),
             blocks: vec![],
-            target_states: HashMap::with_capacity(64),
+            target_states: HashMap::with_capacity_and_hasher(64, Default::default()),
         }
         .assert_validity();
     }
@@ -1842,10 +1977,10 @@ impl<CD> RegBuilder<CD, (), ()> {
 }
 
 impl<I, T: Type> RegBuilder<(), I, T> {
-    pub fn clock_domain(
+    pub fn clock_domain<R: ResetType>(
         self,
-        clock_domain: impl ToExpr<Type = ClockDomain>,
-    ) -> RegBuilder<Expr<ClockDomain>, I, T> {
+        clock_domain: impl ToExpr<Type = ClockDomain<R>>,
+    ) -> RegBuilder<Expr<ClockDomain<R>>, I, T> {
         let Self {
             name,
             source_location,
@@ -1863,7 +1998,7 @@ impl<I, T: Type> RegBuilder<(), I, T> {
     }
 }
 
-impl<T: Type> RegBuilder<Expr<ClockDomain>, Option<Expr<T>>, T> {
+impl<T: Type, R: ResetType> RegBuilder<Expr<ClockDomain<R>>, Option<Expr<T>>, T> {
     #[track_caller]
     pub fn build(self) -> Expr<T> {
         let Self {
@@ -2021,6 +2156,7 @@ impl ModuleBuilder {
             ModuleKind::Extern => ModuleBody::Extern(ExternModuleBody {
                 verilog_name: name.0,
                 parameters: vec![],
+                simulation: None,
             }),
             ModuleKind::Normal => ModuleBody::Normal(NormalModuleBody {
                 body: BuilderModuleBody {
@@ -2029,8 +2165,8 @@ impl ModuleBuilder {
                         incomplete_declarations: vec![],
                         stmts: vec![],
                     }],
-                    annotations_map: HashMap::new(),
-                    memory_map: HashMap::new(),
+                    annotations_map: HashMap::default(),
+                    memory_map: HashMap::default(),
                 },
             }),
         };
@@ -2040,7 +2176,7 @@ impl ModuleBuilder {
             impl_: RefCell::new(ModuleBuilderImpl {
                 body,
                 io: vec![],
-                io_indexes: HashMap::new(),
+                io_indexes: HashMap::default(),
                 module_annotations: vec![],
             }),
         };
@@ -2087,6 +2223,7 @@ impl ModuleBuilder {
             .builder_extern_body()
             .verilog_name = name.intern();
     }
+    #[track_caller]
     pub fn parameter(&self, name: impl AsRef<str>, value: ExternModuleParameterValue) {
         let name = name.as_ref();
         self.impl_
@@ -2099,6 +2236,7 @@ impl ModuleBuilder {
                 value,
             });
     }
+    #[track_caller]
     pub fn parameter_int(&self, name: impl AsRef<str>, value: impl Into<BigInt>) {
         let name = name.as_ref();
         let value = value.into();
@@ -2112,6 +2250,7 @@ impl ModuleBuilder {
                 value: ExternModuleParameterValue::Integer(value),
             });
     }
+    #[track_caller]
     pub fn parameter_str(&self, name: impl AsRef<str>, value: impl AsRef<str>) {
         let name = name.as_ref();
         let value = value.as_ref();
@@ -2125,6 +2264,7 @@ impl ModuleBuilder {
                 value: ExternModuleParameterValue::String(value.intern()),
             });
     }
+    #[track_caller]
     pub fn parameter_raw_verilog(&self, name: impl AsRef<str>, raw_verilog: impl AsRef<str>) {
         let name = name.as_ref();
         let raw_verilog = raw_verilog.as_ref();
@@ -2138,6 +2278,26 @@ impl ModuleBuilder {
                 value: ExternModuleParameterValue::RawVerilog(raw_verilog.intern()),
             });
     }
+    #[track_caller]
+    pub fn extern_module_simulation<G: ExternModuleSimGenerator>(&self, generator: G) {
+        let mut impl_ = self.impl_.borrow_mut();
+        let simulation = &mut impl_.body.builder_extern_body().simulation;
+        if simulation.is_some() {
+            panic!("already added an extern module simulation");
+        }
+        *simulation = Some(ExternModuleSimulation::new(generator));
+    }
+    #[track_caller]
+    pub fn extern_module_simulation_fn<
+        Args: fmt::Debug + Clone + Hash + Eq + Send + Sync + 'static,
+        Fut: IntoFuture<Output = ()> + 'static,
+    >(
+        &self,
+        args: Args,
+        f: fn(Args, crate::sim::ExternModuleSimulationState) -> Fut,
+    ) {
+        self.extern_module_simulation(crate::sim::SimGeneratorFn { args, f });
+    }
 }
 
 #[track_caller]
@@ -2170,14 +2330,12 @@ pub fn annotate<T: Type>(target: Expr<T>, annotations: impl IntoAnnotations) {
         }
         TargetBase::MemPort(v) => {
             ModuleBuilder::with(|m| {
-                RefCell::borrow_mut(unwrap!(unwrap!(m
-                    .impl_
-                    .borrow_mut()
-                    .body
-                    .builder_normal_body_opt())
-                .body
-                .memory_map
-                .get_mut(&v.mem_name())))
+                RefCell::borrow_mut(unwrap!(
+                    unwrap!(m.impl_.borrow_mut().body.builder_normal_body_opt())
+                        .body
+                        .memory_map
+                        .get_mut(&v.mem_name())
+                ))
                 .port_annotations
                 .extend(annotations)
             });
@@ -2188,6 +2346,16 @@ pub fn annotate<T: Type>(target: Expr<T>, annotations: impl IntoAnnotations) {
             reg,
         }
         .into(),
+        TargetBase::RegSync(reg) => StmtReg {
+            annotations: (),
+            reg,
+        }
+        .into(),
+        TargetBase::RegAsync(reg) => StmtReg {
+            annotations: (),
+            reg,
+        }
+        .into(),
         TargetBase::Wire(wire) => StmtWire {
             annotations: (),
             wire,
@@ -2629,3 +2797,50 @@ impl<T: Type> ModuleIO<T> {
         self.ty
     }
 }
+
+#[derive(PartialEq, Eq, Hash, Clone, Copy)]
+pub enum InstantiatedModule {
+    Base(Interned<Module<Bundle>>),
+    Child {
+        parent: Interned<InstantiatedModule>,
+        instance: Interned<Instance<Bundle>>,
+    },
+}
+
+impl InstantiatedModule {
+    pub fn leaf_module(self) -> Interned<Module<Bundle>> {
+        match self {
+            InstantiatedModule::Base(base) => base,
+            InstantiatedModule::Child { instance, .. } => instance.instantiated(),
+        }
+    }
+    fn write_path(self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            InstantiatedModule::Base(base) => fmt::Debug::fmt(&base.name_id(), f),
+            InstantiatedModule::Child { parent, instance } => {
+                parent.write_path(f)?;
+                write!(f, ".{}", instance.name_id())
+            }
+        }
+    }
+}
+
+impl fmt::Debug for InstantiatedModule {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "InstantiatedModule(")?;
+        self.write_path(f)?;
+        write!(f, ": {})", self.leaf_module().name_id())
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
+pub struct TargetInInstantiatedModule {
+    pub instantiated_module: InstantiatedModule,
+    pub target: Target,
+}
+
+#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
+pub struct ExprInInstantiatedModule<T: Type> {
+    pub instantiated_module: InstantiatedModule,
+    pub expr: Expr<T>,
+}

crates/fayalite/src/module/transform.rs

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
+pub mod deduce_resets;
 pub mod simplify_enums;
 pub mod simplify_memories;
 pub mod visit;

crates/fayalite/src/module/transform/simplify_enums.rs

@@ -5,23 +5,23 @@ use crate::{
     bundle::{Bundle, BundleField, BundleType},
     enum_::{Enum, EnumType, EnumVariant},
     expr::{
-        ops::{self, EnumLiteral},
         CastBitsTo, CastTo, CastToBits, Expr, ExprEnum, HdlPartialEq, ToExpr,
+        ops::{self, EnumLiteral},
     },
     hdl,
     int::UInt,
     intern::{Intern, Interned, Memoize},
     memory::{DynPortType, Mem, MemPort},
     module::{
-        transform::visit::{Fold, Folder},
         Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
+        transform::visit::{Fold, Folder},
     },
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
+    util::HashMap,
     wire::Wire,
 };
 use core::fmt;
-use hashbrown::HashMap;
 
 #[derive(Debug)]
 pub enum SimplifyEnumsError {
@@ -69,7 +69,9 @@ fn contains_any_enum_types(ty: CanonicalType) -> bool {
                 | CanonicalType::AsyncReset(_)
                 | CanonicalType::SyncReset(_)
                 | CanonicalType::Reset(_)
-                | CanonicalType::Clock(_) => false,
+                | CanonicalType::Clock(_)
+                | CanonicalType::PhantomConst(_)
+                | CanonicalType::DynSimOnly(_) => false,
             }
         }
     }
@@ -512,7 +514,9 @@ impl State {
             | CanonicalType::AsyncReset(_)
             | CanonicalType::SyncReset(_)
             | CanonicalType::Reset(_)
-            | CanonicalType::Clock(_) => unreachable!(),
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => unreachable!(),
         }
     }
 }
@@ -577,7 +581,9 @@ fn connect_port(
         | (CanonicalType::Clock(_), _)
         | (CanonicalType::AsyncReset(_), _)
         | (CanonicalType::SyncReset(_), _)
-        | (CanonicalType::Reset(_), _) => unreachable!(
+        | (CanonicalType::Reset(_), _)
+        | (CanonicalType::PhantomConst(_), _)
+        | (CanonicalType::DynSimOnly(_), _) => unreachable!(
             "trying to connect memory ports:\n{:?}\n{:?}",
             Expr::ty(lhs),
             Expr::ty(rhs),
@@ -665,6 +671,7 @@ impl Folder for State {
             ExprEnum::UIntLiteral(_)
             | ExprEnum::SIntLiteral(_)
             | ExprEnum::BoolLiteral(_)
+            | ExprEnum::PhantomConst(_)
             | ExprEnum::BundleLiteral(_)
             | ExprEnum::ArrayLiteral(_)
             | ExprEnum::Uninit(_)
@@ -764,7 +771,9 @@ impl Folder for State {
             | ExprEnum::ModuleIO(_)
             | ExprEnum::Instance(_)
             | ExprEnum::Wire(_)
-            | ExprEnum::Reg(_) => op.default_fold(self),
+            | ExprEnum::Reg(_)
+            | ExprEnum::RegSync(_)
+            | ExprEnum::RegAsync(_) => op.default_fold(self),
         }
     }
 
@@ -804,7 +813,7 @@ impl Folder for State {
                             .unwrap()
                             .gen_name(&format!(
                                 "{}_{}",
-                                memory.scoped_name().1 .0,
+                                memory.scoped_name().1.0,
                                 port.port_name()
                             )),
                         port.source_location(),
@@ -921,7 +930,9 @@ impl Folder for State {
             | CanonicalType::Clock(_)
             | CanonicalType::AsyncReset(_)
             | CanonicalType::SyncReset(_)
-            | CanonicalType::Reset(_) => canonical_type.default_fold(self),
+            | CanonicalType::Reset(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => canonical_type.default_fold(self),
         }
     }
 
@@ -958,8 +969,8 @@ pub fn simplify_enums(
     kind: SimplifyEnumsKind,
 ) -> Result<Interned<Module<Bundle>>, SimplifyEnumsError> {
     module.fold(&mut State {
-        enum_types: HashMap::new(),
-        replacement_mem_ports: HashMap::new(),
+        enum_types: HashMap::default(),
+        replacement_mem_ports: HashMap::default(),
         kind,
         module_state_stack: vec![],
     })

crates/fayalite/src/module/transform/simplify_memories.rs

@@ -9,16 +9,15 @@ use crate::{
     intern::{Intern, Interned},
     memory::{Mem, MemPort, PortType},
     module::{
-        transform::visit::{Fold, Folder},
         Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtWire,
+        transform::visit::{Fold, Folder},
     },
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
-    util::MakeMutSlice,
+    util::{HashMap, MakeMutSlice},
     wire::Wire,
 };
 use bitvec::{slice::BitSlice, vec::BitVec};
-use hashbrown::HashMap;
 use std::{
     convert::Infallible,
     fmt::Write,
@@ -62,6 +61,7 @@ enum MemSplit {
     Bundle {
         fields: Rc<[MemSplit]>,
     },
+    PhantomConst,
     Single {
         output_mem: Option<Mem>,
         element_type: SingleType,
@@ -76,6 +76,7 @@ impl MemSplit {
     fn mark_changed_element_type(self) -> Self {
         match self {
             MemSplit::Bundle { fields: _ } => self,
+            MemSplit::PhantomConst => self,
             MemSplit::Single {
                 output_mem,
                 element_type,
@@ -97,6 +98,7 @@ impl MemSplit {
                     .map(|field| Self::new(field.ty).mark_changed_element_type())
                     .collect(),
             },
+            CanonicalType::PhantomConst(_) => MemSplit::PhantomConst,
             CanonicalType::Array(ty) => {
                 let element = MemSplit::new(ty.element());
                 if let Self::Single {
@@ -192,6 +194,7 @@ impl MemSplit {
             | CanonicalType::AsyncReset(_)
             | CanonicalType::SyncReset(_)
             | CanonicalType::Reset(_) => unreachable!("memory element type is a storable type"),
+            CanonicalType::DynSimOnly(_) => todo!("memory containing sim-only values"),
         }
     }
 }
@@ -321,6 +324,9 @@ impl SplitMemState<'_, '_> {
                             Expr::field(Expr::<Bundle>::from_canonical(e), &field.name)
                         },
                         |initial_value_element| {
+                            let Some(field_offset) = field_offset.only_bit_width() else {
+                                todo!("memory containing sim-only values");
+                            };
                             &initial_value_element[field_offset..][..field_ty_bit_width]
                         },
                     );
@@ -339,6 +345,7 @@ impl SplitMemState<'_, '_> {
                     self.split_state_stack.pop();
                 }
             }
+            MemSplit::PhantomConst => {}
             MemSplit::Single {
                 output_mem,
                 element_type: single_type,
@@ -538,7 +545,12 @@ impl ModuleState {
             };
         loop {
             match input_element_type {
-                CanonicalType::Bundle(_) => unreachable!("bundle types are always split"),
+                CanonicalType::Bundle(_) => {
+                    unreachable!("bundle types are always split")
+                }
+                CanonicalType::PhantomConst(_) => {
+                    unreachable!("PhantomConst are always removed")
+                }
                 CanonicalType::Enum(_)
                     if input_array_types
                         .first()
@@ -612,6 +624,7 @@ impl ModuleState {
                 | CanonicalType::AsyncReset(_)
                 | CanonicalType::SyncReset(_)
                 | CanonicalType::Reset(_) => unreachable!("memory element type is a storable type"),
+                CanonicalType::DynSimOnly(_) => todo!("memory containing sim-only values"),
             }
             break;
         }
@@ -626,7 +639,7 @@ impl ModuleState {
         split_state: &SplitState<'_>,
     ) -> Mem {
         let mem_name = NameId(
-            Intern::intern_owned(format!("{}{mem_name_path}", input_mem.scoped_name().1 .0)),
+            Intern::intern_owned(format!("{}{mem_name_path}", input_mem.scoped_name().1.0)),
             Id::new(),
         );
         let mem_name = ScopedNameId(input_mem.scoped_name().0, mem_name);
@@ -743,7 +756,8 @@ impl ModuleState {
                 ..
             }
             | MemSplit::Bundle { .. }
-            | MemSplit::Array { .. } => {
+            | MemSplit::Array { .. }
+            | MemSplit::PhantomConst => {
                 let mut replacement_ports = Vec::with_capacity(input_mem.ports().len());
                 let mut wire_port_rdata = Vec::with_capacity(input_mem.ports().len());
                 let mut wire_port_wdata = Vec::with_capacity(input_mem.ports().len());
@@ -887,7 +901,7 @@ impl Folder for State {
             module,
             ModuleState {
                 output_module: None,
-                memories: HashMap::new(),
+                memories: HashMap::default(),
             },
         );
         let mut this = PushedState::push_module(self, module);

crates/fayalite/src/module/transform/visit.rs

@@ -11,12 +11,11 @@ use crate::{
     clock::Clock,
     enum_::{Enum, EnumType, EnumVariant},
     expr::{
-        ops,
+        Expr, ExprEnum, ops,
         target::{
             Target, TargetBase, TargetChild, TargetPathArrayElement, TargetPathBundleField,
             TargetPathDynArrayElement, TargetPathElement,
         },
-        Expr, ExprEnum,
     },
     formal::FormalKind,
     int::{Bool, SIntType, SIntValue, Size, UIntType, UIntValue},
@@ -28,8 +27,10 @@ use crate::{
         NormalModuleBody, ScopedNameId, Stmt, StmtConnect, StmtDeclaration, StmtFormal, StmtIf,
         StmtInstance, StmtMatch, StmtReg, StmtWire,
     },
+    phantom_const::PhantomConst,
     reg::Reg,
-    reset::{AsyncReset, Reset, SyncReset},
+    reset::{AsyncReset, Reset, ResetType, SyncReset},
+    sim::{ExternModuleSimulation, value::DynSimOnly},
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
     wire::Wire,

crates/fayalite/src/phantom_const.rs

@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    expr::{
+        Expr, ToExpr,
+        ops::{ExprPartialEq, ExprPartialOrd},
+    },
+    int::Bool,
+    intern::{Intern, Interned, InternedCompare, LazyInterned, LazyInternedTrait, Memoize},
+    sim::value::{SimValue, SimValuePartialEq, ToSimValue, ToSimValueWithType},
+    source_location::SourceLocation,
+    ty::{
+        CanonicalType, OpaqueSimValueSlice, OpaqueSimValueWriter, OpaqueSimValueWritten,
+        StaticType, Type, TypeProperties, impl_match_variant_as_self,
+        serde_impls::{SerdeCanonicalType, SerdePhantomConst},
+    },
+};
+use serde::{
+    Deserialize, Deserializer, Serialize, Serializer,
+    de::{DeserializeOwned, Error},
+};
+use std::{
+    any::Any,
+    fmt,
+    hash::{Hash, Hasher},
+    marker::PhantomData,
+    ops::Index,
+};
+
+#[derive(Clone)]
+pub struct PhantomConstCanonicalValue {
+    parsed: serde_json::Value,
+    serialized: Interned<str>,
+}
+
+impl PhantomConstCanonicalValue {
+    pub fn from_json_value(parsed: serde_json::Value) -> Self {
+        let serialized = Intern::intern_owned(
+            serde_json::to_string(&parsed)
+                .expect("conversion from json value to text shouldn't fail"),
+        );
+        Self { parsed, serialized }
+    }
+    pub fn as_json_value(&self) -> &serde_json::Value {
+        &self.parsed
+    }
+    pub fn as_str(&self) -> Interned<str> {
+        self.serialized
+    }
+}
+
+impl fmt::Debug for PhantomConstCanonicalValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.serialized)
+    }
+}
+
+impl fmt::Display for PhantomConstCanonicalValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.serialized)
+    }
+}
+
+impl PartialEq for PhantomConstCanonicalValue {
+    fn eq(&self, other: &Self) -> bool {
+        self.serialized == other.serialized
+    }
+}
+
+impl Eq for PhantomConstCanonicalValue {}
+
+impl Hash for PhantomConstCanonicalValue {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.serialized.hash(state);
+    }
+}
+
+impl Serialize for PhantomConstCanonicalValue {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        self.parsed.serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for PhantomConstCanonicalValue {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Ok(Self::from_json_value(serde_json::Value::deserialize(
+            deserializer,
+        )?))
+    }
+}
+
+pub trait PhantomConstValue: Intern + InternedCompare + Serialize + fmt::Debug {
+    fn deserialize_value<'de, D>(deserializer: D) -> Result<Interned<Self>, D::Error>
+    where
+        D: serde::Deserializer<'de>;
+}
+
+impl<T> PhantomConstValue for T
+where
+    T: ?Sized + Intern + InternedCompare + Serialize + fmt::Debug,
+    Interned<T>: DeserializeOwned,
+{
+    fn deserialize_value<'de, D>(deserializer: D) -> Result<Interned<Self>, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        <Interned<T> as Deserialize<'de>>::deserialize(deserializer)
+    }
+}
+
+/// Wrapper type that allows any Rust value to be smuggled as a HDL [`Type`].
+/// This only works for values that can be [serialized][Serialize] to and [deserialized][Deserialize] from [JSON][serde_json].
+pub struct PhantomConst<T: ?Sized + PhantomConstValue = PhantomConstCanonicalValue> {
+    value: LazyInterned<T>,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+pub struct PhantomConstWithoutGenerics;
+
+#[allow(non_upper_case_globals)]
+pub const PhantomConst: PhantomConstWithoutGenerics = PhantomConstWithoutGenerics;
+
+impl<T: Type + PhantomConstValue> Index<T> for PhantomConstWithoutGenerics {
+    type Output = PhantomConst<T>;
+
+    fn index(&self, value: T) -> &Self::Output {
+        Interned::into_inner(PhantomConst::new(value.intern()).intern_sized())
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> fmt::Debug for PhantomConst<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("PhantomConst").field(&self.get()).finish()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Clone for PhantomConst<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Copy for PhantomConst<T> {}
+
+impl<T: ?Sized + PhantomConstValue> PartialEq for PhantomConst<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.get() == other.get()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Eq for PhantomConst<T> {}
+
+impl<T: ?Sized + PhantomConstValue> Hash for PhantomConst<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.get().hash(state);
+    }
+}
+
+struct PhantomConstCanonicalMemoize<T: ?Sized, const IS_FROM_CANONICAL: bool>(PhantomData<T>);
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Copy
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Clone
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Eq
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> PartialEq
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Hash
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn hash<H: Hasher>(&self, _state: &mut H) {}
+}
+
+impl<T: ?Sized + PhantomConstValue> Memoize for PhantomConstCanonicalMemoize<T, false> {
+    type Input = Interned<T>;
+    type InputOwned = Interned<T>;
+    type Output = Interned<PhantomConstCanonicalValue>;
+
+    fn inner(self, input: &Self::Input) -> Self::Output {
+        Intern::intern_sized(PhantomConstCanonicalValue::from_json_value(
+            serde_json::to_value(input)
+                .expect("serialization failed when constructing a canonical PhantomConst"),
+        ))
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Memoize for PhantomConstCanonicalMemoize<T, true> {
+    type Input = Interned<PhantomConstCanonicalValue>;
+    type InputOwned = Interned<PhantomConstCanonicalValue>;
+    type Output = Interned<T>;
+
+    fn inner(self, input: &Self::Input) -> Self::Output {
+        PhantomConstValue::deserialize_value(input.as_json_value())
+            .expect("deserialization failed ")
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> PhantomConst<T> {
+    pub fn new(value: Interned<T>) -> Self {
+        Self {
+            value: LazyInterned::Interned(value),
+        }
+    }
+    pub const fn new_lazy(v: &'static dyn LazyInternedTrait<T>) -> Self {
+        Self {
+            value: LazyInterned::new_lazy(v),
+        }
+    }
+    pub fn get(self) -> Interned<T> {
+        self.value.interned()
+    }
+    pub fn type_properties(self) -> TypeProperties {
+        <()>::TYPE_PROPERTIES
+    }
+    pub fn can_connect(self, other: Self) -> bool {
+        self == other
+    }
+    pub fn canonical_phantom_const(self) -> PhantomConst {
+        if let Some(&retval) = <dyn Any>::downcast_ref::<PhantomConst>(&self) {
+            return retval;
+        }
+        <PhantomConst>::new(
+            PhantomConstCanonicalMemoize::<T, false>(PhantomData).get_owned(self.get()),
+        )
+    }
+    pub fn from_canonical_phantom_const(canonical_type: PhantomConst) -> Self {
+        if let Some(&retval) = <dyn Any>::downcast_ref::<Self>(&canonical_type) {
+            return retval;
+        }
+        Self::new(
+            PhantomConstCanonicalMemoize::<T, true>(PhantomData).get_owned(canonical_type.get()),
+        )
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Type for PhantomConst<T> {
+    type BaseType = PhantomConst;
+    type MaskType = ();
+    type SimValue = PhantomConst<T>;
+    impl_match_variant_as_self!();
+
+    fn mask_type(&self) -> Self::MaskType {
+        ()
+    }
+
+    fn canonical(&self) -> CanonicalType {
+        CanonicalType::PhantomConst(self.canonical_phantom_const())
+    }
+
+    fn from_canonical(canonical_type: CanonicalType) -> Self {
+        let CanonicalType::PhantomConst(phantom_const) = canonical_type else {
+            panic!("expected PhantomConst");
+        };
+        Self::from_canonical_phantom_const(phantom_const)
+    }
+
+    fn source_location() -> SourceLocation {
+        SourceLocation::builtin()
+    }
+
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert!(opaque.is_empty());
+        *self
+    }
+
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert!(opaque.is_empty());
+        assert_eq!(*value, *self);
+    }
+
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        assert_eq!(*value, *self);
+        writer.fill_cloned_from_slice(OpaqueSimValueSlice::empty())
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Default for PhantomConst<T>
+where
+    Interned<T>: Default,
+{
+    fn default() -> Self {
+        Self::TYPE
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> StaticType for PhantomConst<T>
+where
+    Interned<T>: Default,
+{
+    const TYPE: Self = PhantomConst {
+        value: LazyInterned::new_lazy(&Interned::<T>::default),
+    };
+    const MASK_TYPE: Self::MaskType = ();
+    const TYPE_PROPERTIES: TypeProperties = <()>::TYPE_PROPERTIES;
+    const MASK_TYPE_PROPERTIES: TypeProperties = <()>::TYPE_PROPERTIES;
+}
+
+type SerdeType<T> = SerdeCanonicalType<CanonicalType, SerdePhantomConst<Interned<T>>>;
+
+impl<T: ?Sized + PhantomConstValue> Serialize for PhantomConst<T> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        SerdeType::<T>::PhantomConst(SerdePhantomConst(self.get())).serialize(serializer)
+    }
+}
+
+impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for PhantomConst<T> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        match SerdeType::<T>::deserialize(deserializer)? {
+            SerdeCanonicalType::PhantomConst(SerdePhantomConst(value)) => Ok(Self::new(value)),
+            ty => Err(Error::invalid_value(
+                serde::de::Unexpected::Other(ty.as_serde_unexpected_str()),
+                &"a PhantomConst",
+            )),
+        }
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprPartialEq<Self> for PhantomConst<T> {
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprPartialOrd<Self> for PhantomConst<T> {
+    fn cmp_lt(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+
+    fn cmp_le(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+
+    fn cmp_gt(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+
+    fn cmp_ge(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> SimValuePartialEq<Self> for PhantomConst<T> {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        assert_eq!(SimValue::ty(this), SimValue::ty(other));
+        true
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValue for PhantomConst<T> {
+    type Type = PhantomConst<T>;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_value(*self, *self)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValueWithType<PhantomConst<T>> for PhantomConst<T> {
+    fn to_sim_value_with_type(&self, ty: PhantomConst<T>) -> SimValue<PhantomConst<T>> {
+        SimValue::from_value(ty, *self)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValueWithType<CanonicalType> for PhantomConst<T> {
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_value(Self::from_canonical(ty), *self))
+    }
+}

crates/fayalite/src/prelude.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 pub use crate::{
+    __,
     annotations::{
         BlackBoxInlineAnnotation, BlackBoxPathAnnotation, CustomFirrtlAnnotation,
         DocStringAnnotation, DontTouchAnnotation, SVAttributeAnnotation,
@@ -11,26 +12,32 @@ pub use crate::{
     clock::{Clock, ClockDomain, ToClock},
     enum_::{Enum, HdlNone, HdlOption, HdlSome},
     expr::{
-        repeat, CastBitsTo, CastTo, CastToBits, Expr, HdlPartialEq, HdlPartialOrd, MakeUninitExpr,
-        ReduceBits, ToExpr,
+        CastBitsTo, CastTo, CastToBits, Expr, HdlPartialEq, HdlPartialOrd, MakeUninitExpr,
+        ReduceBits, ToExpr, repeat,
     },
     formal::{
-        all_const, all_seq, any_const, any_seq, formal_global_clock, formal_reset, hdl_assert,
-        hdl_assert_with_enable, hdl_assume, hdl_assume_with_enable, hdl_cover,
-        hdl_cover_with_enable, MakeFormalExpr,
+        MakeFormalExpr, all_const, all_seq, any_const, any_seq, formal_global_clock, formal_reset,
+        hdl_assert, hdl_assert_with_enable, hdl_assume, hdl_assume_with_enable, hdl_cover,
+        hdl_cover_with_enable,
     },
     hdl, hdl_module,
-    int::{Bool, DynSize, KnownSize, SInt, SIntType, Size, UInt, UIntType},
+    int::{Bool, DynSize, KnownSize, SInt, SIntType, SIntValue, Size, UInt, UIntType, UIntValue},
     memory::{Mem, MemBuilder, ReadUnderWrite},
     module::{
-        annotate, connect, connect_any, incomplete_wire, instance, memory, memory_array,
-        memory_with_init, reg_builder, wire, Instance, Module, ModuleBuilder,
+        Instance, Module, ModuleBuilder, annotate, connect, connect_any, incomplete_wire, instance,
+        memory, memory_array, memory_with_init, reg_builder, wire,
     },
+    phantom_const::PhantomConst,
     reg::Reg,
     reset::{AsyncReset, Reset, SyncReset, ToAsyncReset, ToReset, ToSyncReset},
+    sim::{
+        ExternModuleSimulationState, Simulation,
+        time::{SimDuration, SimInstant},
+        value::{SimOnly, SimOnlyValue, SimValue, ToSimValue, ToSimValueWithType},
+    },
     source_location::SourceLocation,
     ty::{AsMask, CanonicalType, Type},
     util::{ConstUsize, GenericConstUsize},
     wire::Wire,
-    __,
 };
+pub use bitvec::{slice::BitSlice, vec::BitVec};

crates/fayalite/src/reg.rs

@@ -5,21 +5,22 @@ use crate::{
     expr::{Expr, Flow},
     intern::Interned,
     module::{NameId, ScopedNameId},
+    reset::{Reset, ResetType},
     source_location::SourceLocation,
     ty::{CanonicalType, Type},
 };
 use std::fmt;
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
-pub struct Reg<T: Type> {
+pub struct Reg<T: Type, R: ResetType = Reset> {
     name: ScopedNameId,
     source_location: SourceLocation,
     ty: T,
-    clock_domain: Expr<ClockDomain>,
+    clock_domain: Expr<ClockDomain<R>>,
     init: Option<Expr<T>>,
 }
 
-impl<T: Type + fmt::Debug> fmt::Debug for Reg<T> {
+impl<T: Type + fmt::Debug, R: ResetType> fmt::Debug for Reg<T, R> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let Self {
             name,
@@ -37,8 +38,8 @@ impl<T: Type + fmt::Debug> fmt::Debug for Reg<T> {
     }
 }
 
-impl<T: Type> Reg<T> {
-    pub fn canonical(&self) -> Reg<CanonicalType> {
+impl<T: Type, R: ResetType> Reg<T, R> {
+    pub fn canonical(&self) -> Reg<CanonicalType, R> {
         let Self {
             name,
             source_location,
@@ -59,7 +60,7 @@ impl<T: Type> Reg<T> {
         scoped_name: ScopedNameId,
         source_location: SourceLocation,
         ty: T,
-        clock_domain: Expr<ClockDomain>,
+        clock_domain: Expr<ClockDomain<R>>,
         init: Option<Expr<T>>,
     ) -> Self {
         assert!(
@@ -98,7 +99,7 @@ impl<T: Type> Reg<T> {
     pub fn scoped_name(&self) -> ScopedNameId {
         self.name
     }
-    pub fn clock_domain(&self) -> Expr<ClockDomain> {
+    pub fn clock_domain(&self) -> Expr<ClockDomain<R>> {
         self.clock_domain
     }
     pub fn init(&self) -> Option<Expr<T>> {

crates/fayalite/src/reset.rs

@@ -1,26 +1,55 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    expr::{Expr, ToExpr},
-    int::Bool,
+    clock::Clock,
+    expr::{Expr, ToExpr, ops},
+    int::{Bool, SInt, UInt},
     source_location::SourceLocation,
-    ty::{impl_match_variant_as_self, CanonicalType, StaticType, Type, TypeProperties},
+    ty::{
+        CanonicalType, OpaqueSimValueSize, OpaqueSimValueSlice, OpaqueSimValueWriter,
+        OpaqueSimValueWritten, StaticType, Type, TypeProperties, impl_match_variant_as_self,
+    },
 };
+use bitvec::{bits, order::Lsb0};
 
 mod sealed {
     pub trait ResetTypeSealed {}
 }
 
-pub trait ResetType: StaticType<MaskType = Bool> + sealed::ResetTypeSealed {}
+pub trait ResetType:
+    StaticType<MaskType = Bool>
+    + sealed::ResetTypeSealed
+    + ops::ExprCastTo<Bool>
+    + ops::ExprCastTo<Reset>
+    + ops::ExprCastTo<SyncReset>
+    + ops::ExprCastTo<AsyncReset>
+    + ops::ExprCastTo<Clock>
+    + ops::ExprCastTo<UInt<1>>
+    + ops::ExprCastTo<SInt<1>>
+    + ops::ExprCastTo<UInt>
+    + ops::ExprCastTo<SInt>
+{
+    fn dispatch<D: ResetTypeDispatch>(input: D::Input<Self>, dispatch: D) -> D::Output<Self>;
+}
+
+pub trait ResetTypeDispatch: Sized {
+    type Input<T: ResetType>;
+    type Output<T: ResetType>;
+
+    fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset>;
+    fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset>;
+    fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset>;
+}
 
 macro_rules! reset_type {
-    ($name:ident, $Trait:ident::$trait_fn:ident, $is_castable_from_bits:literal) => {
+    ($name:ident, $(#[$impl_trait:ident])? $Trait:ident::$trait_fn:ident, $is_castable_from_bits:literal, $dispatch_fn:ident) => {
         #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
         pub struct $name;
 
         impl Type for $name {
             type BaseType = $name;
             type MaskType = Bool;
+            type SimValue = bool;
 
             impl_match_variant_as_self!();
 
@@ -42,6 +71,31 @@ macro_rules! reset_type {
                 };
                 retval
             }
+
+            fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+                assert_eq!(opaque.size(), OpaqueSimValueSize::from_bit_width(1));
+                opaque.bits()[0]
+            }
+
+            fn sim_value_clone_from_opaque(
+                &self,
+                value: &mut Self::SimValue,
+                opaque: OpaqueSimValueSlice<'_>,
+            ) {
+                assert_eq!(opaque.size(), OpaqueSimValueSize::from_bit_width(1));
+                *value = opaque.bits()[0];
+            }
+
+            fn sim_value_to_opaque<'w>(
+                &self,
+                value: &Self::SimValue,
+                writer: OpaqueSimValueWriter<'w>,
+            ) -> OpaqueSimValueWritten<'w> {
+                assert_eq!(writer.size(), OpaqueSimValueSize::from_bit_width(1));
+                writer.fill_cloned_from_slice(OpaqueSimValueSlice::from_bitslice(
+                    [bits![0], bits![1]][*value as usize],
+                ))
+            }
         }
 
         impl $name {
@@ -61,13 +115,21 @@ macro_rules! reset_type {
                 is_storable: false,
                 is_castable_from_bits: $is_castable_from_bits,
                 bit_width: 1,
+                sim_only_values_len: 0,
             };
             const MASK_TYPE_PROPERTIES: TypeProperties = Bool::TYPE_PROPERTIES;
         }
 
         impl sealed::ResetTypeSealed for $name {}
 
-        impl ResetType for $name {}
+        impl ResetType for $name {
+            fn dispatch<D: ResetTypeDispatch>(
+                input: D::Input<Self>,
+                dispatch: D,
+            ) -> D::Output<Self> {
+                dispatch.$dispatch_fn(input)
+            }
+        }
 
         pub trait $Trait {
             fn $trait_fn(&self) -> Expr<$name>;
@@ -91,20 +153,21 @@ macro_rules! reset_type {
             }
         }
 
-        impl $Trait for Expr<$name> {
+        $($impl_trait $Trait for Expr<$name> {
             fn $trait_fn(&self) -> Expr<$name> {
                 *self
             }
-        }
+        })?
     };
 }
 
-reset_type!(AsyncReset, ToAsyncReset::to_async_reset, true);
-reset_type!(SyncReset, ToSyncReset::to_sync_reset, true);
+reset_type!(AsyncReset, #[impl] ToAsyncReset::to_async_reset, true, async_reset);
+reset_type!(SyncReset, #[impl] ToSyncReset::to_sync_reset, true, sync_reset);
 reset_type!(
     Reset,
     ToReset::to_reset,
-    false // Reset is not castable from bits because we don't know if it's async or sync
+    false, // Reset is not castable from bits because we don't know if it's async or sync
+    reset
 );
 
 impl ToSyncReset for bool {

crates/fayalite/src/sim/time.rs

@@ -0,0 +1,397 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use std::{
+    fmt,
+    ops::{Add, AddAssign, Sub, SubAssign},
+    time::Duration,
+};
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct SimInstant {
+    time_since_start: SimDuration,
+}
+
+impl SimInstant {
+    pub const fn checked_add(self, duration: SimDuration) -> Option<Self> {
+        let Some(time_since_start) = self.time_since_start.checked_add(duration) else {
+            return None;
+        };
+        Some(SimInstant { time_since_start })
+    }
+    pub const fn checked_duration_since(self, earlier: Self) -> Option<SimDuration> {
+        self.time_since_start.checked_sub(earlier.time_since_start)
+    }
+    pub const fn checked_sub(self, duration: SimDuration) -> Option<Self> {
+        let Some(time_since_start) = self.time_since_start.checked_sub(duration) else {
+            return None;
+        };
+        Some(SimInstant { time_since_start })
+    }
+    #[track_caller]
+    pub const fn duration_since(self, earlier: Self) -> SimDuration {
+        let Some(retval) = self.checked_duration_since(earlier) else {
+            panic!(
+                "tried to compute the duration since a later time -- durations can't be negative"
+            );
+        };
+        retval
+    }
+    pub const fn saturating_duration_since(self, earlier: Self) -> SimDuration {
+        let Some(retval) = self.checked_duration_since(earlier) else {
+            return SimDuration::ZERO;
+        };
+        retval
+    }
+}
+
+impl Add<SimDuration> for SimInstant {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn add(mut self, rhs: SimDuration) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+impl AddAssign<SimDuration> for SimInstant {
+    #[track_caller]
+    fn add_assign(&mut self, rhs: SimDuration) {
+        self.time_since_start += rhs;
+    }
+}
+
+impl Add<SimInstant> for SimDuration {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn add(self, rhs: SimInstant) -> Self::Output {
+        rhs.add(self)
+    }
+}
+
+impl Sub for SimInstant {
+    type Output = SimDuration;
+
+    #[track_caller]
+    fn sub(self, rhs: SimInstant) -> Self::Output {
+        self.duration_since(rhs)
+    }
+}
+
+impl Sub<SimDuration> for SimInstant {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn sub(self, rhs: SimDuration) -> Self::Output {
+        let Some(retval) = self.checked_sub(rhs) else {
+            panic!("SimInstant underflow");
+        };
+        retval
+    }
+}
+
+impl SubAssign<SimDuration> for SimInstant {
+    #[track_caller]
+    fn sub_assign(&mut self, rhs: SimDuration) {
+        *self = *self - rhs;
+    }
+}
+
+impl SimInstant {
+    pub const START: SimInstant = SimInstant {
+        time_since_start: SimDuration::ZERO,
+    };
+}
+
+impl fmt::Debug for SimInstant {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.time_since_start.fmt(f)
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct SimDuration {
+    attos: u128,
+}
+
+impl AddAssign for SimDuration {
+    #[track_caller]
+    fn add_assign(&mut self, rhs: SimDuration) {
+        *self = *self + rhs;
+    }
+}
+
+impl Add for SimDuration {
+    type Output = SimDuration;
+
+    #[track_caller]
+    fn add(self, rhs: SimDuration) -> Self::Output {
+        SimDuration {
+            attos: self
+                .attos
+                .checked_add(rhs.attos)
+                .expect("overflow adding durations"),
+        }
+    }
+}
+
+impl Sub for SimDuration {
+    type Output = Self;
+
+    #[track_caller]
+    fn sub(self, rhs: Self) -> Self::Output {
+        SimDuration {
+            attos: self
+                .attos
+                .checked_add(rhs.attos)
+                .expect("underflow subtracting durations -- durations can't be negative"),
+        }
+    }
+}
+
+impl SubAssign for SimDuration {
+    #[track_caller]
+    fn sub_assign(&mut self, rhs: Self) {
+        *self = *self - rhs;
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Default)]
+pub struct SimDurationParts {
+    pub attos: u16,
+    pub femtos: u16,
+    pub picos: u16,
+    pub nanos: u16,
+    pub micros: u16,
+    pub millis: u16,
+    pub secs: u128,
+}
+
+macro_rules! impl_duration_units {
+    (
+        $(
+            #[unit_const = $UNIT:ident, from_units = $from_units:ident, as_units = $as_units:ident, units = $units:ident, suffix = $suffix:literal]
+            const $log10_units_per_sec:ident: u32 = $log10_units_per_sec_value:expr;
+        )*
+    ) => {
+        impl SimDuration {
+            $(
+                const $log10_units_per_sec: u32 = $log10_units_per_sec_value;
+                pub const fn $from_units($units: u128) -> Self {
+                    Self::from_units_helper::<{ Self::$log10_units_per_sec }>($units)
+                }
+                pub const fn $as_units(self) -> u128 {
+                    self.attos / const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) }
+                }
+            )*
+            pub const fn to_parts(mut self) -> SimDurationParts {
+                $(
+                    let $units = self.attos / const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                    self.attos %= const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                )*
+                SimDurationParts {
+                    $($units: $units as _,)*
+                }
+            }
+            pub const fn from_parts_checked(parts: SimDurationParts) -> Option<Self> {
+                let attos = 0u128;
+                $(
+                    let Some(product) = const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) }.checked_mul(parts.$units as u128) else {
+                        return None;
+                    };
+                    let Some(attos) = attos.checked_add(product) else {
+                        return None;
+                    };
+                )*
+                Some(Self {
+                    attos,
+                })
+            }
+        }
+
+        impl fmt::Debug for SimDuration {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let ilog10_attos = match self.attos.checked_ilog10() {
+                    Some(v) => v,
+                    None => Self::LOG10_ATTOS_PER_SEC,
+                };
+                let (suffix, int, fraction, fraction_digits) =
+                    match Self::LOG10_ATTOS_PER_SEC.saturating_sub(ilog10_attos) {
+                    $(
+                        ..=Self::$log10_units_per_sec => {
+                            let divisor = const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                            (
+                                $suffix,
+                                self.attos / divisor,
+                                self.attos % divisor,
+                                (Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) as usize,
+                            )
+                        },
+                    )*
+                    _ => unreachable!(),
+                };
+                write!(f, "{int}")?;
+                if fraction != 0 {
+                    write!(f, ".{fraction:0fraction_digits$}")?;
+                }
+                write!(f, " {suffix}")
+            }
+        }
+
+        #[cfg(test)]
+        #[test]
+        fn test_duration_debug() {
+            $(
+                assert_eq!(
+                    format!("{:?}", SimDuration::$from_units(123)),
+                    concat!("123 ", $suffix)
+                );
+                assert_eq!(
+                    format!("{:?}", SimDuration::$from_units(1)),
+                    concat!("1 ", $suffix),
+                );
+                let mut v = SimDuration::$from_units(1);
+                if v.attos < 1 << 53 {
+                    v.attos += 1;
+                    assert_eq!(
+                        format!("{v:?}"),
+                        format!("{} {}", v.attos as f64 / 10.0f64.powf((SimDuration::LOG10_ATTOS_PER_SEC - SimDuration::$log10_units_per_sec) as f64), $suffix),
+                        "1 {} + 1 as == {} as", $suffix, v.attos,
+                    );
+                }
+            )*
+        }
+    };
+}
+
+impl_duration_units! {
+    #[unit_const = SECOND, from_units = from_secs, as_units = as_secs, units = secs, suffix = "s"]
+    const LOG10_SECS_PER_SEC: u32 = 0;
+    #[unit_const = MILLISECOND, from_units = from_millis, as_units = as_millis, units = millis, suffix = "ms"]
+    const LOG10_MILLIS_PER_SEC: u32 = 3;
+    #[unit_const = MICROSECOND, from_units = from_micros, as_units = as_micros, units = micros, suffix = "μs"]
+    const LOG10_MICROS_PER_SEC: u32 = 6;
+    #[unit_const = NANOSECOND, from_units = from_nanos, as_units = as_nanos, units = nanos, suffix = "ns"]
+    const LOG10_NANOS_PER_SEC: u32 = 9;
+    #[unit_const = PICOSECOND, from_units = from_picos, as_units = as_picos, units = picos, suffix = "ps"]
+    const LOG10_PICOS_PER_SEC: u32 = 12;
+    #[unit_const = FEMTOSECOND, from_units = from_femtos, as_units = as_femtos, units = femtos, suffix = "fs"]
+    const LOG10_FEMTOS_PER_SEC: u32 = 15;
+    #[unit_const = ATTOSECOND, from_units = from_attos, as_units = as_attos, units = attos, suffix = "as"]
+    const LOG10_ATTOS_PER_SEC: u32 = 18;
+}
+
+impl SimDuration {
+    const fn from_units_helper<const UNITS_PER_SEC: u32>(units: u128) -> Self {
+        let Some(attos) =
+            units.checked_mul(const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - UNITS_PER_SEC) })
+        else {
+            panic!("duration too big");
+        };
+        Self { attos }
+    }
+    pub const ZERO: SimDuration = SimDuration::from_secs(0);
+    pub const fn from_parts(parts: SimDurationParts) -> Self {
+        match Self::from_parts_checked(parts) {
+            Some(v) => v,
+            None => panic!("duration too big"),
+        }
+    }
+    pub const fn abs_diff(self, other: Self) -> Self {
+        Self {
+            attos: self.attos.abs_diff(other.attos),
+        }
+    }
+    pub const fn checked_add(self, rhs: Self) -> Option<Self> {
+        let Some(attos) = self.attos.checked_add(rhs.attos) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
+        let Some(attos) = self.attos.checked_sub(rhs.attos) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    pub const fn is_zero(self) -> bool {
+        self.attos == 0
+    }
+    pub const fn saturating_add(self, rhs: Self) -> Self {
+        Self {
+            attos: self.attos.saturating_add(rhs.attos),
+        }
+    }
+    pub const fn saturating_sub(self, rhs: Self) -> Self {
+        Self {
+            attos: self.attos.saturating_sub(rhs.attos),
+        }
+    }
+    pub const fn checked_ilog10(self) -> Option<i32> {
+        let Some(ilog10_attos) = self.attos.checked_ilog10() else {
+            return None;
+        };
+        Some(ilog10_attos as i32 - Self::LOG10_ATTOS_PER_SEC as i32)
+    }
+    #[track_caller]
+    pub const fn ilog10(self) -> i32 {
+        let Some(retval) = self.checked_ilog10() else {
+            panic!("tried to take the ilog10 of 0");
+        };
+        retval
+    }
+    pub const fn checked_pow10(log10: i32, underflow_is_zero: bool) -> Option<Self> {
+        let Some(log10) = Self::LOG10_ATTOS_PER_SEC.checked_add_signed(log10) else {
+            return if log10 < 0 && underflow_is_zero {
+                Some(Self::ZERO)
+            } else {
+                None
+            };
+        };
+        let Some(attos) = 10u128.checked_pow(log10) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    #[track_caller]
+    pub const fn pow10(log10: i32) -> Self {
+        let Some(retval) = Self::checked_pow10(log10, true) else {
+            panic!("pow10 overflowed");
+        };
+        retval
+    }
+    pub const fn is_power_of_ten(self) -> bool {
+        const TEN: u128 = 10;
+        const NUMBER_OF_POWERS_OF_TEN: usize = {
+            let mut n = 0;
+            while let Some(_) = TEN.checked_pow(n as u32) {
+                n += 1;
+            }
+            n
+        };
+        const POWERS_OF_TEN: [u128; NUMBER_OF_POWERS_OF_TEN] = {
+            let mut retval = [0; NUMBER_OF_POWERS_OF_TEN];
+            let mut i = 0;
+            while i < NUMBER_OF_POWERS_OF_TEN {
+                retval[i] = TEN.pow(i as u32);
+                i += 1;
+            }
+            retval
+        };
+        let mut i = 0;
+        while i < NUMBER_OF_POWERS_OF_TEN {
+            if self.attos == POWERS_OF_TEN[i] {
+                return true;
+            }
+            i += 1;
+        }
+        false
+    }
+}
+
+impl From<Duration> for SimDuration {
+    fn from(duration: Duration) -> Self {
+        Self::from_nanos(duration.as_nanos())
+    }
+}

crates/fayalite/src/sim/value/sim_only_value_unsafe.rs

@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+//! `unsafe` parts of [`DynSimOnlyValue`]
+
+use serde::{Serialize, de::DeserializeOwned};
+use std::{
+    any::{self, TypeId},
+    fmt,
+    hash::{Hash, Hasher},
+    marker::PhantomData,
+    mem::ManuallyDrop,
+    rc::Rc,
+};
+
+pub trait SimOnlyValueTrait:
+    'static + Eq + Hash + fmt::Debug + Serialize + DeserializeOwned + Clone + Default
+{
+}
+
+impl<T: 'static + Eq + Hash + fmt::Debug + Serialize + DeserializeOwned + Clone + Default>
+    SimOnlyValueTrait for T
+{
+}
+
+/// Safety: `type_id_dyn` must return `TypeId::of::<T>()` where `Self = SimOnly<T>`
+unsafe trait DynSimOnlyTrait: 'static + Send + Sync {
+    fn type_id_dyn(&self) -> TypeId;
+    fn type_name(&self) -> &'static str;
+    fn default_value(&self) -> Rc<dyn DynSimOnlyValueTrait>;
+    fn deserialize_from_json_string(
+        &self,
+        json_str: &str,
+    ) -> serde_json::Result<Rc<dyn DynSimOnlyValueTrait>>;
+}
+
+/// Safety: `type_id_dyn` is implemented correctly
+unsafe impl<T: SimOnlyValueTrait> DynSimOnlyTrait for SimOnly<T> {
+    fn type_id_dyn(&self) -> TypeId {
+        TypeId::of::<T>()
+    }
+
+    fn type_name(&self) -> &'static str {
+        any::type_name::<T>()
+    }
+
+    fn default_value(&self) -> Rc<dyn DynSimOnlyValueTrait> {
+        Rc::new(T::default())
+    }
+
+    fn deserialize_from_json_string(
+        &self,
+        json_str: &str,
+    ) -> serde_json::Result<Rc<dyn DynSimOnlyValueTrait>> {
+        Ok(Rc::<T>::new(serde_json::from_str(json_str)?))
+    }
+}
+
+/// Safety:
+/// * `type_id_dyn()` must return `TypeId::of::<Self>()`.
+/// * `ty().type_id()` must return `TypeId::of::<Self>()`.
+unsafe trait DynSimOnlyValueTrait: 'static + fmt::Debug {
+    fn type_id_dyn(&self) -> TypeId;
+    fn ty(&self) -> DynSimOnly;
+    fn eq_dyn(&self, other: &dyn DynSimOnlyValueTrait) -> bool;
+    fn serialize_to_json_string(&self) -> serde_json::Result<String>;
+    fn hash_dyn(&self, state: &mut dyn Hasher);
+}
+
+impl dyn DynSimOnlyValueTrait {
+    fn is<T: SimOnlyValueTrait>(&self) -> bool {
+        Self::type_id_dyn(self) == TypeId::of::<T>()
+    }
+
+    fn downcast_ref<T: SimOnlyValueTrait>(&self) -> Option<&T> {
+        if Self::is::<T>(self) {
+            // Safety: checked that `Self` is really `T`
+            Some(unsafe { &*(self as *const Self as *const T) })
+        } else {
+            None
+        }
+    }
+
+    fn downcast_rc<T: SimOnlyValueTrait>(self: Rc<Self>) -> Result<Rc<T>, Rc<Self>> {
+        if Self::is::<T>(&*self) {
+            // Safety: checked that `Self` is really `T`
+            Ok(unsafe { Rc::from_raw(Rc::into_raw(self) as *const T) })
+        } else {
+            Err(self)
+        }
+    }
+}
+
+/// Safety:
+/// * `type_id_dyn()` returns `TypeId::of::<Self>()`.
+/// * `ty().type_id()` returns `TypeId::of::<Self>()`.
+unsafe impl<T: SimOnlyValueTrait> DynSimOnlyValueTrait for T {
+    fn type_id_dyn(&self) -> TypeId {
+        TypeId::of::<T>()
+    }
+
+    fn ty(&self) -> DynSimOnly {
+        DynSimOnly::of::<T>()
+    }
+
+    fn eq_dyn(&self, other: &dyn DynSimOnlyValueTrait) -> bool {
+        other.downcast_ref::<T>().is_some_and(|other| self == other)
+    }
+
+    fn serialize_to_json_string(&self) -> serde_json::Result<String> {
+        serde_json::to_string(self)
+    }
+
+    fn hash_dyn(&self, mut state: &mut dyn Hasher) {
+        self.hash(&mut state);
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct DynSimOnly {
+    ty: &'static dyn DynSimOnlyTrait,
+}
+
+impl DynSimOnly {
+    pub const fn of<T: SimOnlyValueTrait>() -> Self {
+        Self {
+            ty: &const { SimOnly::<T>::new() },
+        }
+    }
+    pub fn type_id(self) -> TypeId {
+        self.ty.type_id_dyn()
+    }
+    pub fn type_name(self) -> &'static str {
+        self.ty.type_name()
+    }
+    pub fn is<T: SimOnlyValueTrait>(self) -> bool {
+        self.type_id() == TypeId::of::<T>()
+    }
+    pub fn downcast<T: SimOnlyValueTrait>(self) -> Option<SimOnly<T>> {
+        self.is::<T>().then_some(SimOnly::default())
+    }
+    pub fn deserialize_from_json_string(
+        self,
+        json_str: &str,
+    ) -> serde_json::Result<DynSimOnlyValue> {
+        self.ty
+            .deserialize_from_json_string(json_str)
+            .map(DynSimOnlyValue)
+    }
+    pub fn default_value(self) -> DynSimOnlyValue {
+        DynSimOnlyValue(self.ty.default_value())
+    }
+}
+
+impl PartialEq for DynSimOnly {
+    fn eq(&self, other: &Self) -> bool {
+        Self::type_id(*self) == Self::type_id(*other)
+    }
+}
+
+impl Eq for DynSimOnly {}
+
+impl Hash for DynSimOnly {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Self::type_id(*self).hash(state);
+    }
+}
+
+impl fmt::Debug for DynSimOnly {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "SimOnly<{}>", self.ty.type_name())
+    }
+}
+
+impl<T: SimOnlyValueTrait> From<SimOnly<T>> for DynSimOnly {
+    fn from(value: SimOnly<T>) -> Self {
+        let SimOnly(PhantomData) = value;
+        Self::of::<T>()
+    }
+}
+
+/// the [`Type`][Type] for a value that can only be used in a Fayalite simulation, it can't be converted to FIRRTL
+///
+/// [Type]: crate::ty::Type
+#[derive(Clone, Eq, PartialEq, Hash)]
+pub struct SimOnly<T: SimOnlyValueTrait>(PhantomData<fn(T) -> T>);
+
+impl<T: SimOnlyValueTrait> fmt::Debug for SimOnly<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        DynSimOnly::of::<T>().fmt(f)
+    }
+}
+
+impl<T: SimOnlyValueTrait> SimOnly<T> {
+    pub const fn new() -> Self {
+        Self(PhantomData)
+    }
+}
+
+impl<T: SimOnlyValueTrait> Copy for SimOnly<T> {}
+
+impl<T: SimOnlyValueTrait> Default for SimOnly<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// a value that can only be used in a Fayalite simulation, it can't be converted to FIRRTL
+#[derive(Clone, Eq, PartialEq, Hash, Default, PartialOrd, Ord)]
+pub struct SimOnlyValue<T: SimOnlyValueTrait>(Rc<T>);
+
+impl<T: SimOnlyValueTrait> SimOnlyValue<T> {
+    pub fn with_dyn_ref<F: FnOnce(&DynSimOnlyValue) -> R, R>(&self, f: F) -> R {
+        // Safety: creating a copied `Rc<T>` is safe as long as the copy isn't dropped and isn't changed
+        // to point somewhere else, `f` can't change `dyn_ref` because it's only given a shared reference.
+        let dyn_ref =
+            unsafe { ManuallyDrop::new(DynSimOnlyValue(Rc::<T>::from_raw(Rc::as_ptr(&self.0)))) };
+        f(&dyn_ref)
+    }
+    pub fn from_rc(v: Rc<T>) -> Self {
+        Self(v)
+    }
+    pub fn new(v: T) -> Self {
+        Self(Rc::new(v))
+    }
+    pub fn into_inner(this: Self) -> Rc<T> {
+        this.0
+    }
+    pub fn inner_mut(this: &mut Self) -> &mut Rc<T> {
+        &mut this.0
+    }
+    pub fn inner(this: &Self) -> &Rc<T> {
+        &this.0
+    }
+    pub fn into_dyn(this: Self) -> DynSimOnlyValue {
+        DynSimOnlyValue::from(this)
+    }
+}
+
+impl<T: SimOnlyValueTrait> std::ops::Deref for SimOnlyValue<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T: SimOnlyValueTrait> std::ops::DerefMut for SimOnlyValue<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        Rc::make_mut(&mut self.0)
+    }
+}
+
+#[derive(Clone)]
+pub struct DynSimOnlyValue(Rc<dyn DynSimOnlyValueTrait>);
+
+impl fmt::Debug for DynSimOnlyValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        <dyn DynSimOnlyValueTrait as fmt::Debug>::fmt(&*self.0, f)
+    }
+}
+
+impl PartialEq for DynSimOnlyValue {
+    fn eq(&self, other: &Self) -> bool {
+        DynSimOnlyValueTrait::eq_dyn(&*self.0, &*other.0)
+    }
+}
+
+impl Eq for DynSimOnlyValue {}
+
+impl Hash for DynSimOnlyValue {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        DynSimOnlyValueTrait::hash_dyn(&*self.0, state);
+    }
+}
+
+impl<T: SimOnlyValueTrait> From<SimOnlyValue<T>> for DynSimOnlyValue {
+    fn from(value: SimOnlyValue<T>) -> Self {
+        Self(value.0)
+    }
+}
+
+impl DynSimOnlyValue {
+    pub fn ty(&self) -> DynSimOnly {
+        self.0.ty()
+    }
+    pub fn type_id(&self) -> TypeId {
+        self.0.type_id_dyn()
+    }
+    pub fn is<T: SimOnlyValueTrait>(&self) -> bool {
+        self.0.is::<T>()
+    }
+    pub fn downcast<T: SimOnlyValueTrait>(self) -> Result<SimOnlyValue<T>, DynSimOnlyValue> {
+        match <dyn DynSimOnlyValueTrait>::downcast_rc(self.0) {
+            Ok(v) => Ok(SimOnlyValue(v)),
+            Err(v) => Err(Self(v)),
+        }
+    }
+    pub fn downcast_ref<T: SimOnlyValueTrait>(&self) -> Option<&T> {
+        <dyn DynSimOnlyValueTrait>::downcast_ref(&*self.0)
+    }
+    pub fn serialize_to_json_string(&self) -> serde_json::Result<String> {
+        self.0.serialize_to_json_string()
+    }
+}

crates/fayalite/src/source_location.rs

@@ -2,9 +2,8 @@
 // See Notices.txt for copyright information
 use crate::{
     intern::{Intern, Interned},
-    util::DebugAsDisplay,
+    util::{DebugAsDisplay, HashMap},
 };
-use hashbrown::HashMap;
 use std::{cell::RefCell, fmt, num::NonZeroUsize, panic, path::Path};
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -97,7 +96,7 @@ impl NormalizeFilesForTestsState {
     fn new() -> Self {
         Self {
             test_position: panic::Location::caller(),
-            file_pattern_matches: HashMap::new(),
+            file_pattern_matches: HashMap::default(),
         }
     }
 }
@@ -143,7 +142,7 @@ impl From<&'_ panic::Location<'_>> for SourceLocation {
                         map.entry_ref(file)
                             .or_insert_with(|| NormalizedFileForTestState {
                                 file_name_id: NonZeroUsize::new(len + 1).unwrap(),
-                                positions_map: HashMap::new(),
+                                positions_map: HashMap::default(),
                             });
                     file_str = m.generate_file_name(file_state.file_name_id);
                     file = &file_str;

crates/fayalite/src/testing.rs

@@ -3,9 +3,9 @@
 use crate::{
     cli::{FormalArgs, FormalMode, FormalOutput, RunPhase},
     firrtl::ExportOptions,
+    util::HashMap,
 };
 use clap::Parser;
-use hashbrown::HashMap;
 use serde::Deserialize;
 use std::{
     fmt::Write,
@@ -87,7 +87,7 @@ fn get_assert_formal_target_path(test_name: &dyn std::fmt::Display) -> PathBuf {
     let index = *DIRS
         .lock()
         .unwrap()
-        .get_or_insert_with(HashMap::new)
+        .get_or_insert_with(HashMap::default)
         .entry_ref(&dir)
         .and_modify(|v| *v += 1)
         .or_insert(0);

crates/fayalite/src/ty.rs

@@ -7,12 +7,27 @@ use crate::{
     clock::Clock,
     enum_::Enum,
     expr::Expr,
-    int::{Bool, SInt, UInt},
+    int::{Bool, SInt, UInt, UIntValue},
     intern::{Intern, Interned},
+    phantom_const::PhantomConst,
     reset::{AsyncReset, Reset, SyncReset},
+    sim::value::{DynSimOnlyValue, DynSimOnly, SimValue, ToSimValueWithType},
     source_location::SourceLocation,
+    util::{ConstUsize, slice_range, try_slice_range},
 };
-use std::{fmt, hash::Hash, iter::FusedIterator, ops::Index};
+use bitvec::{slice::BitSlice, vec::BitVec};
+use serde::{Deserialize, Deserializer, Serialize, Serializer, de::DeserializeOwned};
+use std::{
+    fmt,
+    hash::Hash,
+    iter::{FusedIterator, Sum},
+    marker::PhantomData,
+    mem,
+    ops::{Add, AddAssign, Bound, Index, Mul, MulAssign, Range, Sub, SubAssign},
+    sync::Arc,
+};
+
+pub(crate) mod serde_impls;
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
 #[non_exhaustive]
@@ -21,6 +36,23 @@ pub struct TypeProperties {
     pub is_storable: bool,
     pub is_castable_from_bits: bool,
     pub bit_width: usize,
+    pub sim_only_values_len: usize,
+}
+
+impl TypeProperties {
+    pub const fn size(self) -> OpaqueSimValueSize {
+        let Self {
+            is_passive: _,
+            is_storable: _,
+            is_castable_from_bits: _,
+            bit_width,
+            sim_only_values_len,
+        } = self;
+        OpaqueSimValueSize {
+            bit_width,
+            sim_only_values_len,
+        }
+    }
 }
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
@@ -35,6 +67,8 @@ pub enum CanonicalType {
     SyncReset(SyncReset),
     Reset(Reset),
     Clock(Clock),
+    PhantomConst(PhantomConst),
+    DynSimOnly(DynSimOnly),
 }
 
 impl fmt::Debug for CanonicalType {
@@ -50,10 +84,30 @@ impl fmt::Debug for CanonicalType {
             Self::SyncReset(v) => v.fmt(f),
             Self::Reset(v) => v.fmt(f),
             Self::Clock(v) => v.fmt(f),
+            Self::PhantomConst(v) => v.fmt(f),
+            Self::DynSimOnly(v) => v.fmt(f),
         }
     }
 }
 
+impl Serialize for CanonicalType {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serde_impls::SerdeCanonicalType::from(*self).serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for CanonicalType {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Ok(serde_impls::SerdeCanonicalType::deserialize(deserializer)?.into())
+    }
+}
+
 impl CanonicalType {
     pub fn type_properties(self) -> TypeProperties {
         match self {
@@ -67,6 +121,8 @@ impl CanonicalType {
             CanonicalType::SyncReset(v) => v.type_properties(),
             CanonicalType::Reset(v) => v.type_properties(),
             CanonicalType::Clock(v) => v.type_properties(),
+            CanonicalType::PhantomConst(v) => v.type_properties(),
+            CanonicalType::DynSimOnly(v) => v.type_properties(),
         }
     }
     pub fn is_passive(self) -> bool {
@@ -81,6 +137,12 @@ impl CanonicalType {
     pub fn bit_width(self) -> usize {
         self.type_properties().bit_width
     }
+    pub fn sim_only_values_len(self) -> usize {
+        self.type_properties().sim_only_values_len
+    }
+    pub fn size(self) -> OpaqueSimValueSize {
+        self.type_properties().size()
+    }
     pub fn can_connect(self, rhs: Self) -> bool {
         match self {
             CanonicalType::UInt(lhs) => {
@@ -143,8 +205,23 @@ impl CanonicalType {
                 };
                 lhs.can_connect(rhs)
             }
+            CanonicalType::PhantomConst(lhs) => {
+                let CanonicalType::PhantomConst(rhs) = rhs else {
+                    return false;
+                };
+                lhs.can_connect(rhs)
+            }
+            CanonicalType::DynSimOnly(lhs) => {
+                let CanonicalType::DynSimOnly(rhs) = rhs else {
+                    return false;
+                };
+                lhs.can_connect(rhs)
+            }
         }
     }
+    pub(crate) fn as_serde_unexpected_str(self) -> &'static str {
+        serde_impls::SerdeCanonicalType::from(self).as_serde_unexpected_str()
+    }
 }
 
 pub trait MatchVariantAndInactiveScope: Sized {
@@ -166,7 +243,7 @@ impl<T: 'static + Send + Sync> MatchVariantAndInactiveScope for MatchVariantWith
 }
 
 pub trait FillInDefaultedGenerics {
-    type Type: Type;
+    type Type;
     fn fill_in_defaulted_generics(self) -> Self::Type;
 }
 
@@ -178,6 +255,22 @@ impl<T: Type> FillInDefaultedGenerics for T {
     }
 }
 
+impl FillInDefaultedGenerics for usize {
+    type Type = usize;
+
+    fn fill_in_defaulted_generics(self) -> Self::Type {
+        self
+    }
+}
+
+impl<const V: usize> FillInDefaultedGenerics for ConstUsize<V> {
+    type Type = ConstUsize<V>;
+
+    fn fill_in_defaulted_generics(self) -> Self::Type {
+        self
+    }
+}
+
 mod sealed {
     pub trait TypeOrDefaultSealed {}
     pub trait BaseTypeSealed {}
@@ -195,6 +288,34 @@ macro_rules! impl_base_type {
     };
 }
 
+macro_rules! impl_base_type_serde {
+    ($name:ident, $expected:literal) => {
+        impl Serialize for $name {
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: Serializer,
+            {
+                self.canonical().serialize(serializer)
+            }
+        }
+
+        impl<'de> Deserialize<'de> for $name {
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+            where
+                D: Deserializer<'de>,
+            {
+                match CanonicalType::deserialize(deserializer)? {
+                    CanonicalType::$name(retval) => Ok(retval),
+                    ty => Err(serde::de::Error::invalid_value(
+                        serde::de::Unexpected::Other(ty.as_serde_unexpected_str()),
+                        &$expected,
+                    )),
+                }
+            }
+        }
+    };
+}
+
 impl_base_type!(UInt);
 impl_base_type!(SInt);
 impl_base_type!(Bool);
@@ -205,6 +326,16 @@ impl_base_type!(AsyncReset);
 impl_base_type!(SyncReset);
 impl_base_type!(Reset);
 impl_base_type!(Clock);
+impl_base_type!(PhantomConst);
+impl_base_type!(DynSimOnly);
+
+impl_base_type_serde!(Bool, "a Bool");
+impl_base_type_serde!(Enum, "an Enum");
+impl_base_type_serde!(Bundle, "a Bundle");
+impl_base_type_serde!(AsyncReset, "an AsyncReset");
+impl_base_type_serde!(SyncReset, "a SyncReset");
+impl_base_type_serde!(Reset, "a Reset");
+impl_base_type_serde!(Clock, "a Clock");
 
 impl sealed::BaseTypeSealed for CanonicalType {}
 
@@ -240,26 +371,48 @@ pub trait Type:
 {
     type BaseType: BaseType;
     type MaskType: Type<MaskType = Self::MaskType>;
+    type SimValue: fmt::Debug + Clone + 'static + ToSimValueWithType<Self>;
     type MatchVariant: 'static + Send + Sync;
     type MatchActiveScope;
     type MatchVariantAndInactiveScope: MatchVariantAndInactiveScope<
-        MatchVariant = Self::MatchVariant,
-        MatchActiveScope = Self::MatchActiveScope,
-    >;
+            MatchVariant = Self::MatchVariant,
+            MatchActiveScope = Self::MatchActiveScope,
+        >;
     type MatchVariantsIter: Iterator<Item = Self::MatchVariantAndInactiveScope>
         + ExactSizeIterator
         + FusedIterator
         + DoubleEndedIterator;
     #[track_caller]
     fn match_variants(this: Expr<Self>, source_location: SourceLocation)
-        -> Self::MatchVariantsIter;
+    -> Self::MatchVariantsIter;
     fn mask_type(&self) -> Self::MaskType;
     fn canonical(&self) -> CanonicalType;
     fn from_canonical(canonical_type: CanonicalType) -> Self;
     fn source_location() -> SourceLocation;
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue;
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    );
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w>;
 }
 
-pub trait BaseType: Type<BaseType = Self> + sealed::BaseTypeSealed + Into<CanonicalType> {}
+pub trait BaseType:
+    Type<
+        BaseType = Self,
+        MaskType: Serialize + DeserializeOwned,
+        SimValue: Serialize + DeserializeOwned,
+    > + sealed::BaseTypeSealed
+    + Into<CanonicalType>
+    + Serialize
+    + DeserializeOwned
+{
+}
 
 macro_rules! impl_match_variant_as_self {
     () => {
@@ -286,6 +439,7 @@ pub trait TypeWithDeref: Type {
 impl Type for CanonicalType {
     type BaseType = CanonicalType;
     type MaskType = CanonicalType;
+    type SimValue = OpaqueSimValue;
     impl_match_variant_as_self!();
     fn mask_type(&self) -> Self::MaskType {
         match self {
@@ -299,6 +453,8 @@ impl Type for CanonicalType {
             CanonicalType::SyncReset(v) => v.mask_type().canonical(),
             CanonicalType::Reset(v) => v.mask_type().canonical(),
             CanonicalType::Clock(v) => v.mask_type().canonical(),
+            CanonicalType::PhantomConst(v) => v.mask_type().canonical(),
+            CanonicalType::DynSimOnly(v) => v.mask_type().canonical(),
         }
     }
     fn canonical(&self) -> CanonicalType {
@@ -310,9 +466,636 @@ impl Type for CanonicalType {
     fn source_location() -> SourceLocation {
         SourceLocation::builtin()
     }
+    fn sim_value_from_opaque(&self, opaque: OpaqueSimValueSlice<'_>) -> Self::SimValue {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        opaque.to_owned()
+    }
+    fn sim_value_clone_from_opaque(
+        &self,
+        value: &mut Self::SimValue,
+        opaque: OpaqueSimValueSlice<'_>,
+    ) {
+        assert_eq!(self.type_properties().size(), opaque.size());
+        assert_eq!(value.size(), opaque.size());
+        value.clone_from_slice(opaque);
+    }
+    fn sim_value_to_opaque<'w>(
+        &self,
+        value: &Self::SimValue,
+        writer: OpaqueSimValueWriter<'w>,
+    ) -> OpaqueSimValueWritten<'w> {
+        assert_eq!(self.type_properties().size(), writer.size());
+        assert_eq!(value.size(), writer.size());
+        writer.fill_cloned_from_slice(value.as_slice())
+    }
 }
 
-pub trait StaticType: Type {
+#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize, Default)]
+#[non_exhaustive]
+pub struct OpaqueSimValueSizeRange {
+    pub bit_width: Range<usize>,
+    pub sim_only_values_len: Range<usize>,
+}
+
+impl OpaqueSimValueSizeRange {
+    pub fn start(&self) -> OpaqueSimValueSize {
+        OpaqueSimValueSize {
+            bit_width: self.bit_width.start,
+            sim_only_values_len: self.sim_only_values_len.start,
+        }
+    }
+    pub fn end(&self) -> OpaqueSimValueSize {
+        OpaqueSimValueSize {
+            bit_width: self.bit_width.end,
+            sim_only_values_len: self.sim_only_values_len.end,
+        }
+    }
+    pub fn is_empty(&self) -> bool {
+        let Self {
+            bit_width,
+            sim_only_values_len,
+        } = self;
+        bit_width.is_empty() && sim_only_values_len.is_empty()
+    }
+}
+
+impl From<Range<OpaqueSimValueSize>> for OpaqueSimValueSizeRange {
+    fn from(value: Range<OpaqueSimValueSize>) -> Self {
+        Self {
+            bit_width: value.start.bit_width..value.end.bit_width,
+            sim_only_values_len: value.start.sim_only_values_len..value.end.sim_only_values_len,
+        }
+    }
+}
+
+impl From<OpaqueSimValueSizeRange> for Range<OpaqueSimValueSize> {
+    fn from(value: OpaqueSimValueSizeRange) -> Self {
+        value.start()..value.end()
+    }
+}
+
+pub trait OpaqueSimValueSizeRangeBounds {
+    fn start_bound(&self) -> Bound<OpaqueSimValueSize>;
+    fn end_bound(&self) -> Bound<OpaqueSimValueSize>;
+}
+
+impl OpaqueSimValueSizeRangeBounds for OpaqueSimValueSizeRange {
+    fn start_bound(&self) -> Bound<OpaqueSimValueSize> {
+        Bound::Included(self.start())
+    }
+
+    fn end_bound(&self) -> Bound<OpaqueSimValueSize> {
+        Bound::Excluded(self.end())
+    }
+}
+
+impl<T: ?Sized + std::ops::RangeBounds<OpaqueSimValueSize>> OpaqueSimValueSizeRangeBounds for T {
+    fn start_bound(&self) -> Bound<OpaqueSimValueSize> {
+        std::ops::RangeBounds::start_bound(self).cloned()
+    }
+    fn end_bound(&self) -> Bound<OpaqueSimValueSize> {
+        std::ops::RangeBounds::end_bound(self).cloned()
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize, Default)]
+#[non_exhaustive]
+pub struct OpaqueSimValueSize {
+    pub bit_width: usize,
+    pub sim_only_values_len: usize,
+}
+
+impl OpaqueSimValueSize {
+    pub const fn from_bit_width(bit_width: usize) -> Self {
+        Self::from_bit_width_and_sim_only_values_len(bit_width, 0)
+    }
+    pub const fn from_bit_width_and_sim_only_values_len(
+        bit_width: usize,
+        sim_only_values_len: usize,
+    ) -> Self {
+        Self {
+            bit_width,
+            sim_only_values_len,
+        }
+    }
+    pub const fn only_bit_width(self) -> Option<usize> {
+        if let Self {
+            bit_width,
+            sim_only_values_len: 0,
+        } = self
+        {
+            Some(bit_width)
+        } else {
+            None
+        }
+    }
+    pub const fn empty() -> Self {
+        Self {
+            bit_width: 0,
+            sim_only_values_len: 0,
+        }
+    }
+    pub const fn is_empty(self) -> bool {
+        let Self {
+            bit_width,
+            sim_only_values_len,
+        } = self;
+        bit_width == 0 && sim_only_values_len == 0
+    }
+    pub const fn checked_mul(self, factor: usize) -> Option<Self> {
+        let Some(bit_width) = self.bit_width.checked_mul(factor) else {
+            return None;
+        };
+        let Some(sim_only_values_len) = self.sim_only_values_len.checked_mul(factor) else {
+            return None;
+        };
+        Some(Self {
+            bit_width,
+            sim_only_values_len,
+        })
+    }
+    pub const fn checked_add(self, rhs: Self) -> Option<Self> {
+        let Some(bit_width) = self.bit_width.checked_add(rhs.bit_width) else {
+            return None;
+        };
+        let Some(sim_only_values_len) = self
+            .sim_only_values_len
+            .checked_add(rhs.sim_only_values_len)
+        else {
+            return None;
+        };
+        Some(Self {
+            bit_width,
+            sim_only_values_len,
+        })
+    }
+    pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
+        let Some(bit_width) = self.bit_width.checked_sub(rhs.bit_width) else {
+            return None;
+        };
+        let Some(sim_only_values_len) = self
+            .sim_only_values_len
+            .checked_sub(rhs.sim_only_values_len)
+        else {
+            return None;
+        };
+        Some(Self {
+            bit_width,
+            sim_only_values_len,
+        })
+    }
+    pub fn try_slice_range<R: OpaqueSimValueSizeRangeBounds>(
+        self,
+        range: R,
+    ) -> Option<OpaqueSimValueSizeRange> {
+        let start = range.start_bound();
+        let end = range.end_bound();
+        let bit_width = try_slice_range(
+            (start.map(|v| v.bit_width), end.map(|v| v.bit_width)),
+            self.bit_width,
+        )?;
+        let sim_only_values_len = try_slice_range(
+            (
+                start.map(|v| v.sim_only_values_len),
+                end.map(|v| v.sim_only_values_len),
+            ),
+            self.sim_only_values_len,
+        )?;
+        Some(OpaqueSimValueSizeRange {
+            bit_width,
+            sim_only_values_len,
+        })
+    }
+    pub fn slice_range<R: OpaqueSimValueSizeRangeBounds>(
+        self,
+        range: R,
+    ) -> OpaqueSimValueSizeRange {
+        self.try_slice_range(range).expect("range out of bounds")
+    }
+}
+
+impl Mul<usize> for OpaqueSimValueSize {
+    type Output = OpaqueSimValueSize;
+
+    fn mul(self, rhs: usize) -> Self::Output {
+        self.checked_mul(rhs).expect("multiplication overflowed")
+    }
+}
+
+impl Mul<OpaqueSimValueSize> for usize {
+    type Output = OpaqueSimValueSize;
+
+    fn mul(self, rhs: OpaqueSimValueSize) -> Self::Output {
+        rhs.checked_mul(self).expect("multiplication overflowed")
+    }
+}
+
+impl Add for OpaqueSimValueSize {
+    type Output = OpaqueSimValueSize;
+
+    fn add(self, rhs: OpaqueSimValueSize) -> Self::Output {
+        rhs.checked_add(self).expect("addition overflowed")
+    }
+}
+
+impl Sub for OpaqueSimValueSize {
+    type Output = OpaqueSimValueSize;
+
+    fn sub(self, rhs: OpaqueSimValueSize) -> Self::Output {
+        rhs.checked_sub(self).expect("subtraction underflowed")
+    }
+}
+
+impl MulAssign<usize> for OpaqueSimValueSize {
+    fn mul_assign(&mut self, rhs: usize) {
+        *self = *self * rhs;
+    }
+}
+
+impl AddAssign for OpaqueSimValueSize {
+    fn add_assign(&mut self, rhs: OpaqueSimValueSize) {
+        *self = *self + rhs;
+    }
+}
+
+impl SubAssign for OpaqueSimValueSize {
+    fn sub_assign(&mut self, rhs: OpaqueSimValueSize) {
+        *self = *self - rhs;
+    }
+}
+
+impl Sum for OpaqueSimValueSize {
+    fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
+        iter.fold(OpaqueSimValueSize::empty(), Add::add)
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
+pub struct OpaqueSimValue {
+    bits: UIntValue,
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
+    sim_only_values: Vec<DynSimOnlyValue>,
+}
+
+impl OpaqueSimValue {
+    pub fn empty() -> Self {
+        Self {
+            bits: UIntValue::new(Default::default()),
+            sim_only_values: Vec::new(),
+        }
+    }
+    pub fn with_capacity(capacity: OpaqueSimValueSize) -> Self {
+        Self {
+            bits: UIntValue::new(Arc::new(BitVec::with_capacity(capacity.bit_width))),
+            sim_only_values: Vec::with_capacity(capacity.sim_only_values_len),
+        }
+    }
+    pub fn size(&self) -> OpaqueSimValueSize {
+        OpaqueSimValueSize {
+            bit_width: self.bits.width(),
+            sim_only_values_len: self.sim_only_values.len(),
+        }
+    }
+    pub fn is_empty(&self) -> bool {
+        self.size().is_empty()
+    }
+    pub fn bit_width(&self) -> usize {
+        self.bits.width()
+    }
+    pub fn bits(&self) -> &UIntValue {
+        &self.bits
+    }
+    pub fn bits_mut(&mut self) -> &mut UIntValue {
+        &mut self.bits
+    }
+    pub fn into_bits(self) -> UIntValue {
+        self.bits
+    }
+    pub fn from_bits(bits: UIntValue) -> Self {
+        Self {
+            bits,
+            sim_only_values: Vec::new(),
+        }
+    }
+    pub fn from_bitslice(v: &BitSlice) -> Self {
+        Self::from_bitslice_and_sim_only_values(v, Vec::new())
+    }
+    pub fn from_bitslice_and_sim_only_values(
+        bits: &BitSlice,
+        sim_only_values: Vec<DynSimOnlyValue>,
+    ) -> Self {
+        Self {
+            bits: UIntValue::new(Arc::new(bits.to_bitvec())),
+            sim_only_values,
+        }
+    }
+    pub fn from_bits_and_sim_only_values(
+        bits: UIntValue,
+        sim_only_values: Vec<DynSimOnlyValue>,
+    ) -> Self {
+        Self {
+            bits,
+            sim_only_values,
+        }
+    }
+    pub fn into_parts(self) -> (UIntValue, Vec<DynSimOnlyValue>) {
+        let Self {
+            bits,
+            sim_only_values,
+        } = self;
+        (bits, sim_only_values)
+    }
+    pub fn parts_mut(&mut self) -> (&mut UIntValue, &mut Vec<DynSimOnlyValue>) {
+        let Self {
+            bits,
+            sim_only_values,
+        } = self;
+        (bits, sim_only_values)
+    }
+    pub fn sim_only_values(&self) -> &[DynSimOnlyValue] {
+        &self.sim_only_values
+    }
+    pub fn sim_only_values_mut(&mut self) -> &mut Vec<DynSimOnlyValue> {
+        &mut self.sim_only_values
+    }
+    pub fn as_slice(&self) -> OpaqueSimValueSlice<'_> {
+        OpaqueSimValueSlice {
+            bits: self.bits.bits(),
+            sim_only_values: &self.sim_only_values,
+        }
+    }
+    pub fn slice<R: OpaqueSimValueSizeRangeBounds>(&self, range: R) -> OpaqueSimValueSlice<'_> {
+        self.as_slice().slice(range)
+    }
+    pub fn rewrite_with<F>(&mut self, target_size: OpaqueSimValueSize, f: F)
+    where
+        F: for<'b> FnOnce(OpaqueSimValueWriter<'b>) -> OpaqueSimValueWritten<'b>, // 'b is used as a brand
+    {
+        OpaqueSimValueWriter::rewrite_with(target_size, self, f);
+    }
+    pub fn clone_from_slice(&mut self, slice: OpaqueSimValueSlice<'_>) {
+        let OpaqueSimValueSlice {
+            bits,
+            sim_only_values,
+        } = slice;
+        self.bits.bits_mut().copy_from_bitslice(bits);
+        self.sim_only_values.clone_from_slice(sim_only_values);
+    }
+    pub fn extend_from_slice(&mut self, slice: OpaqueSimValueSlice<'_>) {
+        let OpaqueSimValueSlice {
+            bits,
+            sim_only_values,
+        } = slice;
+        self.bits.bitvec_mut().extend_from_bitslice(bits);
+        self.sim_only_values.extend_from_slice(sim_only_values);
+    }
+}
+
+impl<'a> Extend<OpaqueSimValueSlice<'a>> for OpaqueSimValue {
+    fn extend<T: IntoIterator<Item = OpaqueSimValueSlice<'a>>>(&mut self, iter: T) {
+        let Self {
+            bits,
+            sim_only_values,
+        } = self;
+        let bits = bits.bitvec_mut();
+        for slice in iter {
+            bits.extend_from_bitslice(slice.bits);
+            sim_only_values.extend_from_slice(slice.sim_only_values);
+        }
+    }
+}
+
+impl Extend<OpaqueSimValue> for OpaqueSimValue {
+    fn extend<T: IntoIterator<Item = OpaqueSimValue>>(&mut self, iter: T) {
+        let Self {
+            bits,
+            sim_only_values,
+        } = self;
+        let bits = bits.bitvec_mut();
+        for value in iter {
+            bits.extend_from_bitslice(value.bits().bits());
+            sim_only_values.extend_from_slice(value.sim_only_values());
+        }
+    }
+}
+
+impl<T: Type<SimValue = OpaqueSimValue>> ToSimValueWithType<T> for OpaqueSimValue {
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        SimValue::from_value(ty, self.clone())
+    }
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T> {
+        SimValue::from_value(ty, self)
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct OpaqueSimValueSlice<'a> {
+    bits: &'a BitSlice,
+    sim_only_values: &'a [DynSimOnlyValue],
+}
+
+impl<'a> Default for OpaqueSimValueSlice<'a> {
+    fn default() -> Self {
+        Self::empty()
+    }
+}
+
+impl<'a> OpaqueSimValueSlice<'a> {
+    pub fn from_parts(bits: &'a BitSlice, sim_only_values: &'a [DynSimOnlyValue]) -> Self {
+        Self {
+            bits,
+            sim_only_values,
+        }
+    }
+    pub fn from_bitslice(bits: &'a BitSlice) -> Self {
+        Self::from_parts(bits, &[])
+    }
+    pub fn empty() -> Self {
+        Self {
+            bits: BitSlice::empty(),
+            sim_only_values: &[],
+        }
+    }
+    pub fn size(self) -> OpaqueSimValueSize {
+        OpaqueSimValueSize {
+            bit_width: self.bit_width(),
+            sim_only_values_len: self.sim_only_values_len(),
+        }
+    }
+    pub fn is_empty(self) -> bool {
+        self.size().is_empty()
+    }
+    pub fn bit_width(self) -> usize {
+        self.bits.len()
+    }
+    pub fn bits(self) -> &'a BitSlice {
+        self.bits
+    }
+    pub fn sim_only_values(self) -> &'a [DynSimOnlyValue] {
+        self.sim_only_values
+    }
+    pub fn sim_only_values_len(self) -> usize {
+        self.sim_only_values.len()
+    }
+    pub fn to_owned(self) -> OpaqueSimValue {
+        OpaqueSimValue::from_bitslice_and_sim_only_values(self.bits, self.sim_only_values.to_vec())
+    }
+    pub fn slice<R: OpaqueSimValueSizeRangeBounds>(self, range: R) -> OpaqueSimValueSlice<'a> {
+        let start = range.start_bound();
+        let end = range.end_bound();
+        let bits_range = slice_range(
+            (start.map(|v| v.bit_width), end.map(|v| v.bit_width)),
+            self.bit_width(),
+        );
+        let sim_only_values_range = slice_range(
+            (start.map(|v| v.bit_width), end.map(|v| v.bit_width)),
+            self.sim_only_values_len(),
+        );
+        Self {
+            bits: &self.bits[bits_range],
+            sim_only_values: &self.sim_only_values[sim_only_values_range],
+        }
+    }
+    pub fn split_at(self, index: OpaqueSimValueSize) -> (Self, Self) {
+        let bits = self.bits.split_at(index.bit_width);
+        let sim_only_values = self.sim_only_values.split_at(index.sim_only_values_len);
+        (
+            Self {
+                bits: bits.0,
+                sim_only_values: sim_only_values.0,
+            },
+            Self {
+                bits: bits.1,
+                sim_only_values: sim_only_values.1,
+            },
+        )
+    }
+}
+
+#[derive(Debug)]
+pub struct OpaqueSimValueWriter<'a> {
+    bits: &'a mut BitSlice,
+    sim_only_values: &'a mut Vec<DynSimOnlyValue>,
+    sim_only_values_range: std::ops::Range<usize>,
+}
+
+#[derive(Debug)]
+pub struct OpaqueSimValueWritten<'a> {
+    _phantom: PhantomData<&'a ()>,
+}
+
+impl<'a> OpaqueSimValueWriter<'a> {
+    pub fn sim_only_values_range(&self) -> std::ops::Range<usize> {
+        self.sim_only_values_range.clone()
+    }
+    pub fn rewrite_with<F>(target_size: OpaqueSimValueSize, value: &mut OpaqueSimValue, f: F)
+    where
+        F: for<'b> FnOnce(OpaqueSimValueWriter<'b>) -> OpaqueSimValueWritten<'b>, // 'b is used as a brand
+    {
+        let OpaqueSimValueWritten {
+            _phantom: PhantomData,
+        } = f(OpaqueSimValueWriter::rewrite_helper(target_size, value));
+    }
+    pub(crate) fn rewrite_helper(
+        target_size: OpaqueSimValueSize,
+        value: &'a mut OpaqueSimValue,
+    ) -> Self {
+        let (bits, sim_only_values) = value.parts_mut();
+        let OpaqueSimValueSize {
+            bit_width,
+            sim_only_values_len,
+        } = target_size;
+        let bits = bits.bitvec_mut();
+        bits.resize(bit_width, false);
+        sim_only_values.truncate(sim_only_values_len);
+        sim_only_values.reserve_exact(sim_only_values_len - sim_only_values.len());
+        Self {
+            bits,
+            sim_only_values,
+            sim_only_values_range: 0..sim_only_values_len,
+        }
+    }
+    pub fn size(&self) -> OpaqueSimValueSize {
+        OpaqueSimValueSize {
+            bit_width: self.bit_width(),
+            sim_only_values_len: self.sim_only_values_len(),
+        }
+    }
+    pub fn bit_width(&self) -> usize {
+        self.bits.len()
+    }
+    pub fn sim_only_values_len(&self) -> usize {
+        self.sim_only_values_range.len()
+    }
+    pub fn is_empty(&self) -> bool {
+        self.size().is_empty()
+    }
+    pub fn fill_cloned_from_slice(
+        self,
+        slice: OpaqueSimValueSlice<'_>,
+    ) -> OpaqueSimValueWritten<'a> {
+        assert_eq!(self.size(), slice.size());
+        let Self {
+            bits,
+            sim_only_values,
+            sim_only_values_range,
+        } = self;
+        bits.copy_from_bitslice(slice.bits);
+        let (clone_from_src, clone_src) = slice.sim_only_values.split_at(
+            (sim_only_values.len() - sim_only_values_range.start).min(slice.sim_only_values.len()),
+        );
+        sim_only_values[sim_only_values_range.start..][..clone_from_src.len()]
+            .clone_from_slice(clone_from_src);
+        sim_only_values.extend_from_slice(clone_src);
+        OpaqueSimValueWritten {
+            _phantom: PhantomData,
+        }
+    }
+    pub fn fill_with_bits_with<F: FnOnce(&mut BitSlice)>(self, f: F) -> OpaqueSimValueWritten<'a> {
+        assert!(self.size().only_bit_width().is_some());
+        let Self {
+            bits,
+            sim_only_values,
+            sim_only_values_range,
+        } = self;
+        f(bits);
+        assert_eq!(sim_only_values.len(), sim_only_values_range.end);
+        OpaqueSimValueWritten {
+            _phantom: PhantomData,
+        }
+    }
+    pub fn fill_with_zeros(self) -> OpaqueSimValueWritten<'a> {
+        assert!(
+            self.size().only_bit_width().is_some(),
+            "can't fill things other than bits with zeros",
+        );
+        self.fill_with_bits_with(|bits| bits.fill(false))
+    }
+    pub fn fill_prefix_with<F>(&mut self, prefix_size: OpaqueSimValueSize, f: F)
+    where
+        F: for<'b> FnOnce(OpaqueSimValueWriter<'b>) -> OpaqueSimValueWritten<'b>, // 'b is used as a brand
+    {
+        let OpaqueSimValueSize {
+            bit_width,
+            sim_only_values_len,
+        } = prefix_size;
+        assert!(bit_width <= self.bit_width());
+        assert!(sim_only_values_len <= self.sim_only_values_len());
+        let next_start = self.sim_only_values_range.start + sim_only_values_len;
+        let OpaqueSimValueWritten {
+            _phantom: PhantomData,
+        } = f(OpaqueSimValueWriter {
+            bits: &mut self.bits[..bit_width],
+            sim_only_values: self.sim_only_values,
+            sim_only_values_range: self.sim_only_values_range.start..next_start,
+        });
+        assert!(self.sim_only_values.len() >= next_start);
+        self.bits = &mut mem::take(&mut self.bits)[bit_width..];
+        self.sim_only_values_range.start = next_start;
+    }
+}
+
+pub trait StaticType: Type + Default {
     const TYPE: Self;
     const MASK_TYPE: Self::MaskType;
     const TYPE_PROPERTIES: TypeProperties;

crates/fayalite/src/ty/serde_impls.rs

@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    array::Array,
+    bundle::{Bundle, BundleType},
+    clock::Clock,
+    enum_::{Enum, EnumType},
+    int::{Bool, SInt, UInt},
+    intern::Interned,
+    phantom_const::{PhantomConstCanonicalValue, PhantomConstValue},
+    prelude::PhantomConst,
+    reset::{AsyncReset, Reset, SyncReset},
+    sim::value::DynSimOnly,
+    ty::{BaseType, CanonicalType},
+};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+pub(crate) struct SerdePhantomConst<T>(pub T);
+
+impl<T: ?Sized + PhantomConstValue> Serialize for SerdePhantomConst<Interned<T>> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.0.serialize(serializer)
+    }
+}
+
+impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for SerdePhantomConst<Interned<T>> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        T::deserialize_value(deserializer).map(Self)
+    }
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename = "CanonicalType")]
+pub(crate) enum SerdeCanonicalType<
+    ArrayElement = CanonicalType,
+    ThePhantomConst = SerdePhantomConst<Interned<PhantomConstCanonicalValue>>,
+> {
+    UInt {
+        width: usize,
+    },
+    SInt {
+        width: usize,
+    },
+    Bool,
+    Array {
+        element: ArrayElement,
+        len: usize,
+    },
+    Enum {
+        variants: Interned<[crate::enum_::EnumVariant]>,
+    },
+    Bundle {
+        fields: Interned<[crate::bundle::BundleField]>,
+    },
+    AsyncReset,
+    SyncReset,
+    Reset,
+    Clock,
+    PhantomConst(ThePhantomConst),
+    DynSimOnly(DynSimOnly),
+}
+
+impl<ArrayElement, PhantomConstInner> SerdeCanonicalType<ArrayElement, PhantomConstInner> {
+    pub(crate) fn as_serde_unexpected_str(&self) -> &'static str {
+        match self {
+            Self::UInt { .. } => "a UInt",
+            Self::SInt { .. } => "a SInt",
+            Self::Bool => "a Bool",
+            Self::Array { .. } => "an Array",
+            Self::Enum { .. } => "an Enum",
+            Self::Bundle { .. } => "a Bundle",
+            Self::AsyncReset => "an AsyncReset",
+            Self::SyncReset => "a SyncReset",
+            Self::Reset => "a Reset",
+            Self::Clock => "a Clock",
+            Self::PhantomConst(_) => "a PhantomConst",
+            Self::DynSimOnly(_) => "a SimOnlyValue",
+        }
+    }
+}
+
+impl<T: BaseType> From<T> for SerdeCanonicalType {
+    fn from(ty: T) -> Self {
+        let ty: CanonicalType = ty.into();
+        match ty {
+            CanonicalType::UInt(ty) => Self::UInt { width: ty.width() },
+            CanonicalType::SInt(ty) => Self::SInt { width: ty.width() },
+            CanonicalType::Bool(Bool {}) => Self::Bool,
+            CanonicalType::Array(ty) => Self::Array {
+                element: ty.element(),
+                len: ty.len(),
+            },
+            CanonicalType::Enum(ty) => Self::Enum {
+                variants: ty.variants(),
+            },
+            CanonicalType::Bundle(ty) => Self::Bundle {
+                fields: ty.fields(),
+            },
+            CanonicalType::AsyncReset(AsyncReset {}) => Self::AsyncReset,
+            CanonicalType::SyncReset(SyncReset {}) => Self::SyncReset,
+            CanonicalType::Reset(Reset {}) => Self::Reset,
+            CanonicalType::Clock(Clock {}) => Self::Clock,
+            CanonicalType::PhantomConst(ty) => Self::PhantomConst(SerdePhantomConst(ty.get())),
+            CanonicalType::DynSimOnly(ty) => Self::DynSimOnly(ty),
+        }
+    }
+}
+
+impl From<SerdeCanonicalType> for CanonicalType {
+    fn from(ty: SerdeCanonicalType) -> Self {
+        match ty {
+            SerdeCanonicalType::UInt { width } => Self::UInt(UInt::new(width)),
+            SerdeCanonicalType::SInt { width } => Self::SInt(SInt::new(width)),
+            SerdeCanonicalType::Bool => Self::Bool(Bool),
+            SerdeCanonicalType::Array { element, len } => Self::Array(Array::new(element, len)),
+            SerdeCanonicalType::Enum { variants } => Self::Enum(Enum::new(variants)),
+            SerdeCanonicalType::Bundle { fields } => Self::Bundle(Bundle::new(fields)),
+            SerdeCanonicalType::AsyncReset => Self::AsyncReset(AsyncReset),
+            SerdeCanonicalType::SyncReset => Self::SyncReset(SyncReset),
+            SerdeCanonicalType::Reset => Self::Reset(Reset),
+            SerdeCanonicalType::Clock => Self::Clock(Clock),
+            SerdeCanonicalType::PhantomConst(value) => {
+                Self::PhantomConst(PhantomConst::new(value.0))
+            }
+            SerdeCanonicalType::DynSimOnly(value) => Self::DynSimOnly(value),
+        }
+    }
+}

crates/fayalite/src/util.rs

@@ -1,12 +1,23 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 
+pub(crate) mod alternating_cell;
 mod const_bool;
 mod const_cmp;
 mod const_usize;
 mod misc;
 mod scoped_ref;
 pub(crate) mod streaming_read_utf8;
+mod test_hasher;
+
+// allow easily switching the hasher crate-wide for testing
+#[cfg(feature = "unstable-test-hasher")]
+pub type DefaultBuildHasher = test_hasher::DefaultBuildHasher;
+#[cfg(not(feature = "unstable-test-hasher"))]
+pub(crate) type DefaultBuildHasher = hashbrown::DefaultHashBuilder;
+
+pub(crate) type HashMap<K, V> = hashbrown::HashMap<K, V, DefaultBuildHasher>;
+pub(crate) type HashSet<T> = hashbrown::HashSet<T, DefaultBuildHasher>;
 
 #[doc(inline)]
 pub use const_bool::{ConstBool, ConstBoolDispatch, ConstBoolDispatchTag, GenericConstBool};
@@ -22,10 +33,13 @@ pub use const_cmp::{
 #[doc(inline)]
 pub use scoped_ref::ScopedRef;
 
+pub(crate) use misc::chain;
 #[doc(inline)]
 pub use misc::{
-    interned_bit, iter_eq_by, BitSliceWriteWithBase, DebugAsDisplay, DebugAsRawString, MakeMutSlice,
+    BitSliceWriteWithBase, DebugAsDisplay, DebugAsRawString, MakeMutSlice, RcWriter, interned_bit,
+    iter_eq_by, slice_range, try_slice_range,
 };
 
 pub mod job_server;
+pub mod prefix_sum;
 pub mod ready_valid;

crates/fayalite/src/util/alternating_cell.rs

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::util::DebugAsDisplay;
+use std::{
+    cell::{Cell, UnsafeCell},
+    fmt,
+};
+
+pub(crate) trait AlternatingCellMethods {
+    fn unique_to_shared(&mut self);
+    fn shared_to_unique(&mut self);
+}
+
+#[derive(Copy, Clone, Debug)]
+enum State {
+    Unique,
+    Shared,
+    Locked,
+}
+
+pub(crate) struct AlternatingCell<T: ?Sized> {
+    state: Cell<State>,
+    value: UnsafeCell<T>,
+}
+
+impl<T: ?Sized + fmt::Debug + AlternatingCellMethods> fmt::Debug for AlternatingCell<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("AlternatingCell")
+            .field(
+                self.try_share()
+                    .as_ref()
+                    .map(|v| -> &dyn fmt::Debug { v })
+                    .unwrap_or(&DebugAsDisplay("<...>")),
+            )
+            .finish()
+    }
+}
+
+impl<T: ?Sized> AlternatingCell<T> {
+    pub(crate) const fn new_shared(value: T) -> Self
+    where
+        T: Sized,
+    {
+        Self {
+            state: Cell::new(State::Shared),
+            value: UnsafeCell::new(value),
+        }
+    }
+    pub(crate) const fn new_unique(value: T) -> Self
+    where
+        T: Sized,
+    {
+        Self {
+            state: Cell::new(State::Unique),
+            value: UnsafeCell::new(value),
+        }
+    }
+    pub(crate) fn is_unique(&self) -> bool {
+        matches!(self.state.get(), State::Unique)
+    }
+    pub(crate) fn is_shared(&self) -> bool {
+        matches!(self.state.get(), State::Shared)
+    }
+    pub(crate) fn into_inner(self) -> T
+    where
+        T: Sized,
+    {
+        self.value.into_inner()
+    }
+    pub(crate) fn try_share(&self) -> Option<&T>
+    where
+        T: AlternatingCellMethods,
+    {
+        match self.state.get() {
+            State::Shared => {}
+            State::Unique => {
+                struct Locked<'a>(&'a Cell<State>);
+                impl Drop for Locked<'_> {
+                    fn drop(&mut self) {
+                        self.0.set(State::Shared);
+                    }
+                }
+                self.state.set(State::Locked);
+                let lock = Locked(&self.state);
+                // Safety: state is Locked, so nothing else will
+                // access value while calling unique_to_shared.
+                unsafe { &mut *self.value.get() }.unique_to_shared();
+                drop(lock);
+            }
+            State::Locked => return None,
+        }
+
+        // Safety: state is Shared so nothing will create any mutable
+        // references until the returned reference's lifetime expires.
+        Some(unsafe { &*self.value.get() })
+    }
+    #[track_caller]
+    pub(crate) fn share(&self) -> &T
+    where
+        T: AlternatingCellMethods,
+    {
+        let Some(retval) = self.try_share() else {
+            panic!("`share` called recursively");
+        };
+        retval
+    }
+    pub(crate) fn unique(&mut self) -> &mut T
+    where
+        T: AlternatingCellMethods,
+    {
+        match self.state.get() {
+            State::Shared => {
+                self.state.set(State::Unique);
+                self.value.get_mut().shared_to_unique();
+            }
+            State::Unique => {}
+            State::Locked => unreachable!(),
+        }
+        self.value.get_mut()
+    }
+}

crates/fayalite/src/util/const_bool.rs

@@ -1,5 +1,9 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
+use serde::{
+    Deserialize, Deserializer, Serialize, Serializer,
+    de::{DeserializeOwned, Error, Unexpected},
+};
 use std::{fmt::Debug, hash::Hash, mem::ManuallyDrop, ptr};
 
 mod sealed {
@@ -9,7 +13,17 @@ mod sealed {
 /// # Safety
 /// the only implementation is `ConstBool<Self::VALUE>`
 pub unsafe trait GenericConstBool:
-    sealed::Sealed + Copy + Ord + Hash + Default + Debug + 'static + Send + Sync
+    sealed::Sealed
+    + Copy
+    + Ord
+    + Hash
+    + Default
+    + Debug
+    + 'static
+    + Send
+    + Sync
+    + Serialize
+    + DeserializeOwned
 {
     const VALUE: bool;
 }
@@ -30,6 +44,32 @@ unsafe impl<const VALUE: bool> GenericConstBool for ConstBool<VALUE> {
     const VALUE: bool = VALUE;
 }
 
+impl<const VALUE: bool> Serialize for ConstBool<VALUE> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        VALUE.serialize(serializer)
+    }
+}
+
+impl<'de, const VALUE: bool> Deserialize<'de> for ConstBool<VALUE> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let value = bool::deserialize(deserializer)?;
+        if value == VALUE {
+            Ok(ConstBool)
+        } else {
+            Err(D::Error::invalid_value(
+                Unexpected::Bool(value),
+                &if VALUE { "true" } else { "false" },
+            ))
+        }
+    }
+}
+
 pub trait ConstBoolDispatchTag {
     type Type<Select: GenericConstBool>;
 }

crates/fayalite/src/util/const_usize.rs

@@ -1,5 +1,9 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
+use serde::{
+    Deserialize, Deserializer, Serialize, Serializer,
+    de::{DeserializeOwned, Error, Unexpected},
+};
 use std::{fmt::Debug, hash::Hash};
 
 mod sealed {
@@ -8,7 +12,17 @@ mod sealed {
 
 /// the only implementation is `ConstUsize<Self::VALUE>`
 pub trait GenericConstUsize:
-    sealed::Sealed + Copy + Ord + Hash + Default + Debug + 'static + Send + Sync
+    sealed::Sealed
+    + Copy
+    + Ord
+    + Hash
+    + Default
+    + Debug
+    + 'static
+    + Send
+    + Sync
+    + Serialize
+    + DeserializeOwned
 {
     const VALUE: usize;
 }
@@ -27,3 +41,29 @@ impl<const VALUE: usize> sealed::Sealed for ConstUsize<VALUE> {}
 impl<const VALUE: usize> GenericConstUsize for ConstUsize<VALUE> {
     const VALUE: usize = VALUE;
 }
+
+impl<const VALUE: usize> Serialize for ConstUsize<VALUE> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        VALUE.serialize(serializer)
+    }
+}
+
+impl<'de, const VALUE: usize> Deserialize<'de> for ConstUsize<VALUE> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let value = usize::deserialize(deserializer)?;
+        if value == VALUE {
+            Ok(ConstUsize)
+        } else {
+            Err(D::Error::invalid_value(
+                Unexpected::Unsigned(value as u64),
+                &&*VALUE.to_string(),
+            ))
+        }
+    }
+}

crates/fayalite/src/util/misc.rs

@@ -3,7 +3,9 @@
 use crate::intern::{Intern, Interned};
 use bitvec::{bits, order::Lsb0, slice::BitSlice, view::BitView};
 use std::{
+    cell::Cell,
     fmt::{self, Debug, Write},
+    ops::{Bound, Range, RangeBounds},
     rc::Rc,
     sync::{Arc, OnceLock},
 };
@@ -94,9 +96,15 @@ pub fn interned_bit(v: bool) -> Interned<BitSlice> {
     RETVAL.get_or_init(|| [bits![0; 1].intern(), bits![1; 1].intern()])[v as usize]
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone)]
 pub struct BitSliceWriteWithBase<'a>(pub &'a BitSlice);
 
+impl<'a> Debug for BitSliceWriteWithBase<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{self:#x}")
+    }
+}
+
 impl BitSliceWriteWithBase<'_> {
     fn fmt_with_base<const BITS_PER_DIGIT: usize, const UPPER_CASE: bool>(
         self,
@@ -155,3 +163,83 @@ impl fmt::UpperHex for BitSliceWriteWithBase<'_> {
         self.fmt_with_base::<4, true>(f)
     }
 }
+
+#[derive(Clone, Default)]
+pub struct RcWriter(Rc<Cell<Vec<u8>>>);
+
+impl Debug for RcWriter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.borrow_impl(|buf| {
+            f.debug_tuple("RcWriter")
+                .field(&DebugAsDisplay(format_args!("b\"{}\"", buf.escape_ascii())))
+                .finish()
+        })
+    }
+}
+
+impl RcWriter {
+    fn borrow_impl<R>(&self, f: impl FnOnce(&mut Vec<u8>) -> R) -> R {
+        let buf = Cell::take(&self.0);
+        struct PutBackOnDrop<'a> {
+            buf: Vec<u8>,
+            this: &'a RcWriter,
+        }
+        impl Drop for PutBackOnDrop<'_> {
+            fn drop(&mut self) {
+                self.this.0.set(std::mem::take(&mut self.buf));
+            }
+        }
+        let mut buf = PutBackOnDrop { buf, this: self };
+        f(&mut buf.buf)
+    }
+    pub fn borrow<R>(&mut self, f: impl FnOnce(&mut Vec<u8>) -> R) -> R {
+        self.borrow_impl(f)
+    }
+    pub fn take(&mut self) -> Vec<u8> {
+        Cell::take(&self.0)
+    }
+}
+
+impl std::io::Write for RcWriter {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.borrow(|v| v.extend_from_slice(buf));
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        Ok(())
+    }
+}
+
+macro_rules! chain {
+    () => {
+        std::iter::empty()
+    };
+    ($first:expr $(, $rest:expr)* $(,)?) => {
+        {
+            let retval = IntoIterator::into_iter($first);
+            $(let retval = Iterator::chain(retval, $rest);)*
+            retval
+        }
+    };
+}
+
+pub(crate) use chain;
+
+pub fn try_slice_range<R: RangeBounds<usize>>(range: R, size: usize) -> Option<Range<usize>> {
+    let start = match range.start_bound() {
+        Bound::Included(start) => *start,
+        Bound::Excluded(start) => start.checked_add(1)?,
+        Bound::Unbounded => 0,
+    };
+    let end = match range.end_bound() {
+        Bound::Included(end) => end.checked_add(1)?,
+        Bound::Excluded(end) => *end,
+        Bound::Unbounded => size,
+    };
+    (start <= end && end <= size).then_some(start..end)
+}
+
+pub fn slice_range<R: RangeBounds<usize>>(range: R, size: usize) -> Range<usize> {
+    try_slice_range(range, size).expect("range out of bounds")
+}

crates/fayalite/src/util/prefix_sum.rs

@@ -0,0 +1,839 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+// code derived from:
+// https://web.archive.org/web/20250303054010/https://git.libre-soc.org/?p=nmutil.git;a=blob;f=src/nmutil/prefix_sum.py;hb=effeb28e5848392adddcdad1f6e7a098f2a44c9c
+
+use crate::intern::{Intern, Interned, Memoize};
+use std::{borrow::Cow, num::NonZeroUsize};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct PrefixSumOp {
+    pub lhs_index: usize,
+    pub rhs_and_dest_index: NonZeroUsize,
+    pub row: u32,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub struct DiagramConfig {
+    pub space: Cow<'static, str>,
+    pub vertical_bar: Cow<'static, str>,
+    pub plus: Cow<'static, str>,
+    pub slant: Cow<'static, str>,
+    pub connect: Cow<'static, str>,
+    pub no_connect: Cow<'static, str>,
+    pub padding: usize,
+}
+
+impl DiagramConfig {
+    pub const fn new() -> Self {
+        Self {
+            space: Cow::Borrowed(" "),
+            vertical_bar: Cow::Borrowed("|"),
+            plus: Cow::Borrowed("\u{2295}"), // ⊕
+            slant: Cow::Borrowed(r"\"),
+            connect: Cow::Borrowed("\u{25CF}"), // ●
+            no_connect: Cow::Borrowed("X"),
+            padding: 1,
+        }
+    }
+    pub fn draw(self, ops: impl IntoIterator<Item = PrefixSumOp>, item_count: usize) -> String {
+        #[derive(Copy, Clone, Debug)]
+        struct DiagramCell {
+            slant: bool,
+            plus: bool,
+            tee: bool,
+        }
+        let mut ops_by_row: Vec<Vec<PrefixSumOp>> = Vec::new();
+        let mut last_row = 0;
+        ops.into_iter().for_each(|op| {
+            assert!(
+                op.lhs_index < op.rhs_and_dest_index.get(),
+                "invalid PrefixSumOp! lhs_index must be less \
+                than rhs_and_dest_index: {op:?}",
+            );
+            assert!(
+                op.row >= last_row,
+                "invalid PrefixSumOp! row must \
+                not decrease (row last was: {last_row}): {op:?}",
+            );
+            let ops = if op.row > last_row || ops_by_row.is_empty() {
+                ops_by_row.push(vec![]);
+                ops_by_row.last_mut().expect("just pushed")
+            } else {
+                ops_by_row
+                    .last_mut()
+                    .expect("just checked if ops_by_row is empty")
+            };
+            if let Some(last) = ops.last() {
+                assert!(
+                    op.rhs_and_dest_index < last.rhs_and_dest_index,
+                    "invalid PrefixSumOp! rhs_and_dest_index must strictly \
+                    decrease in a row:\nthis op: {op:?}\nlast op: {last:?}",
+                );
+            }
+            ops.push(op);
+            last_row = op.row;
+        });
+        let blank_row = || {
+            vec![
+                DiagramCell {
+                    slant: false,
+                    plus: false,
+                    tee: false
+                };
+                item_count
+            ]
+        };
+        let mut cells = vec![blank_row()];
+        for ops in ops_by_row {
+            let max_distance = ops
+                .iter()
+                .map(
+                    |&PrefixSumOp {
+                         lhs_index,
+                         rhs_and_dest_index,
+                         ..
+                     }| { rhs_and_dest_index.get() - lhs_index },
+                )
+                .max()
+                .expect("ops is known to be non-empty");
+            cells.extend((0..max_distance).map(|_| blank_row()));
+            for op in ops {
+                let mut y = cells.len() - 1;
+                assert!(
+                    op.rhs_and_dest_index.get() < item_count,
+                    "invalid PrefixSumOp! rhs_and_dest_index must be \
+                    less than item_count ({item_count}): {op:?}",
+                );
+                let mut x = op.rhs_and_dest_index.get();
+                cells[y][x].plus = true;
+                x -= 1;
+                y -= 1;
+                while op.lhs_index < x {
+                    cells[y][x].slant = true;
+                    x -= 1;
+                    y -= 1;
+                }
+                cells[y][x].tee = true;
+            }
+        }
+        let mut retval = String::new();
+        let mut row_text = vec![String::new(); 2 * self.padding + 1];
+        for cells_row in cells {
+            for cell in cells_row {
+                // top padding
+                for y in 0..self.padding {
+                    // top left padding
+                    for x in 0..self.padding {
+                        row_text[y] += if x == y && (cell.plus || cell.slant) {
+                            &self.slant
+                        } else {
+                            &self.space
+                        };
+                    }
+                    // top vertical bar
+                    row_text[y] += &self.vertical_bar;
+                    // top right padding
+                    for _ in 0..self.padding {
+                        row_text[y] += &self.space;
+                    }
+                }
+                // center left padding
+                for _ in 0..self.padding {
+                    row_text[self.padding] += &self.space;
+                }
+                // center
+                row_text[self.padding] += if cell.plus {
+                    &self.plus
+                } else if cell.tee {
+                    &self.connect
+                } else if cell.slant {
+                    &self.no_connect
+                } else {
+                    &self.vertical_bar
+                };
+                // center right padding
+                for _ in 0..self.padding {
+                    row_text[self.padding] += &self.space;
+                }
+                let bottom_padding_start = self.padding + 1;
+                let bottom_padding_last = self.padding * 2;
+                // bottom padding
+                for y in bottom_padding_start..=bottom_padding_last {
+                    // bottom left padding
+                    for _ in 0..self.padding {
+                        row_text[y] += &self.space;
+                    }
+                    // bottom vertical bar
+                    row_text[y] += &self.vertical_bar;
+                    // bottom right padding
+                    for x in bottom_padding_start..=bottom_padding_last {
+                        row_text[y] += if x == y && (cell.tee || cell.slant) {
+                            &self.slant
+                        } else {
+                            &self.space
+                        };
+                    }
+                }
+            }
+            for line in &mut row_text {
+                retval += line.trim_end();
+                retval += "\n";
+                line.clear();
+            }
+        }
+        retval
+    }
+}
+
+impl Default for DiagramConfig {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl PrefixSumOp {
+    pub fn diagram(ops: impl IntoIterator<Item = Self>, item_count: usize) -> String {
+        Self::diagram_with_config(ops, item_count, DiagramConfig::new())
+    }
+    pub fn diagram_with_config(
+        ops: impl IntoIterator<Item = Self>,
+        item_count: usize,
+        config: DiagramConfig,
+    ) -> String {
+        config.draw(ops, item_count)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub enum PrefixSumAlgorithm {
+    /// Uses the algorithm from:
+    /// <https://en.wikipedia.org/wiki/Prefix_sum#Algorithm_1:_Shorter_span,_more_parallel>
+    LowLatency,
+    /// Uses the algorithm from:
+    /// <https://en.wikipedia.org/wiki/Prefix_sum#Algorithm_2:_Work-efficient>
+    WorkEfficient,
+}
+
+impl PrefixSumAlgorithm {
+    fn ops_impl(self, item_count: usize) -> Vec<PrefixSumOp> {
+        let mut retval = Vec::new();
+        let mut distance = 1;
+        let mut row = 0;
+        while distance < item_count {
+            let double_distance = distance
+                .checked_mul(2)
+                .expect("prefix-sum item_count is too big");
+            let (start, step) = match self {
+                Self::LowLatency => (distance, 1),
+                Self::WorkEfficient => (double_distance - 1, double_distance),
+            };
+            for rhs_and_dest_index in (start..item_count).step_by(step).rev() {
+                let Some(rhs_and_dest_index) = NonZeroUsize::new(rhs_and_dest_index) else {
+                    unreachable!();
+                };
+                let lhs_index = rhs_and_dest_index.get() - distance;
+                retval.push(PrefixSumOp {
+                    lhs_index,
+                    rhs_and_dest_index,
+                    row,
+                });
+            }
+            distance = double_distance;
+            row += 1;
+        }
+        match self {
+            Self::LowLatency => {}
+            Self::WorkEfficient => {
+                distance /= 2;
+                while distance >= 1 {
+                    let start = distance
+                        .checked_mul(3)
+                        .expect("prefix-sum item_count is too big")
+                        - 1;
+                    for rhs_and_dest_index in (start..item_count).step_by(distance * 2).rev() {
+                        let Some(rhs_and_dest_index) = NonZeroUsize::new(rhs_and_dest_index) else {
+                            unreachable!();
+                        };
+                        let lhs_index = rhs_and_dest_index.get() - distance;
+                        retval.push(PrefixSumOp {
+                            lhs_index,
+                            rhs_and_dest_index,
+                            row,
+                        });
+                    }
+                    row += 1;
+                    distance /= 2;
+                }
+            }
+        }
+        retval
+    }
+    pub fn ops(self, item_count: usize) -> Interned<[PrefixSumOp]> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct MyMemoize(PrefixSumAlgorithm);
+        impl Memoize for MyMemoize {
+            type Input = usize;
+            type InputOwned = usize;
+            type Output = Interned<[PrefixSumOp]>;
+
+            fn inner(self, item_count: &Self::Input) -> Self::Output {
+                Intern::intern_owned(self.0.ops_impl(*item_count))
+            }
+        }
+        MyMemoize(self).get_owned(item_count)
+    }
+    pub fn run<T>(self, items: impl IntoIterator<Item = T>, f: impl FnMut(&T, &T) -> T) -> Vec<T> {
+        let mut items = Vec::from_iter(items);
+        self.run_on_slice(&mut items, f);
+        items
+    }
+    pub fn run_on_slice<T>(self, items: &mut [T], mut f: impl FnMut(&T, &T) -> T) -> &mut [T] {
+        self.ops(items.len()).into_iter().for_each(
+            |PrefixSumOp {
+                 lhs_index,
+                 rhs_and_dest_index,
+                 row: _,
+             }| {
+                items[rhs_and_dest_index.get()] =
+                    f(&items[lhs_index], &items[rhs_and_dest_index.get()]);
+            },
+        );
+        items
+    }
+    pub fn filtered_ops(
+        self,
+        item_live_out_flags: impl IntoIterator<Item = bool>,
+    ) -> Vec<PrefixSumOp> {
+        let mut item_live_out_flags = Vec::from_iter(item_live_out_flags);
+        let prefix_sum_ops = self.ops(item_live_out_flags.len());
+        let mut ops_live_flags = vec![false; prefix_sum_ops.len()];
+        for (
+            op_index,
+            &PrefixSumOp {
+                lhs_index,
+                rhs_and_dest_index,
+                row: _,
+            },
+        ) in prefix_sum_ops.iter().enumerate().rev()
+        {
+            let live = item_live_out_flags[rhs_and_dest_index.get()];
+            item_live_out_flags[lhs_index] |= live;
+            ops_live_flags[op_index] = live;
+        }
+        prefix_sum_ops
+            .into_iter()
+            .zip(ops_live_flags)
+            .filter_map(|(op, live)| live.then_some(op))
+            .collect()
+    }
+    pub fn reduce_ops(self, item_count: usize) -> Interned<[PrefixSumOp]> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct MyMemoize(PrefixSumAlgorithm);
+        impl Memoize for MyMemoize {
+            type Input = usize;
+            type InputOwned = usize;
+            type Output = Interned<[PrefixSumOp]>;
+
+            fn inner(self, item_count: &Self::Input) -> Self::Output {
+                let mut item_live_out_flags = vec![false; *item_count];
+                let Some(last_item_live_out_flag) = item_live_out_flags.last_mut() else {
+                    return Interned::default();
+                };
+                *last_item_live_out_flag = true;
+                Intern::intern_owned(self.0.filtered_ops(item_live_out_flags))
+            }
+        }
+        MyMemoize(self).get_owned(item_count)
+    }
+}
+
+pub fn reduce_ops(item_count: usize) -> Interned<[PrefixSumOp]> {
+    PrefixSumAlgorithm::LowLatency.reduce_ops(item_count)
+}
+
+pub fn reduce<T>(items: impl IntoIterator<Item = T>, mut f: impl FnMut(T, T) -> T) -> Option<T> {
+    let mut items: Vec<_> = items.into_iter().map(Some).collect();
+    for op in reduce_ops(items.len()) {
+        let (Some(lhs), Some(rhs)) = (
+            items[op.lhs_index].take(),
+            items[op.rhs_and_dest_index.get()].take(),
+        ) else {
+            unreachable!();
+        };
+        items[op.rhs_and_dest_index.get()] = Some(f(lhs, rhs));
+    }
+    items.last_mut().and_then(Option::take)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn input_strings() -> [String; 9] {
+        std::array::from_fn(|i| String::from_utf8(vec![b'a' + i as u8]).unwrap())
+    }
+
+    #[test]
+    fn test_prefix_sum_strings() {
+        let input = input_strings();
+        let expected: Vec<String> = input
+            .iter()
+            .scan(String::new(), |l, r| {
+                *l += r;
+                Some(l.clone())
+            })
+            .collect();
+        println!("expected: {expected:?}");
+        assert_eq!(
+            *PrefixSumAlgorithm::WorkEfficient
+                .run_on_slice(&mut input.clone(), |l, r| l.to_string() + r),
+            *expected
+        );
+        assert_eq!(
+            *PrefixSumAlgorithm::LowLatency
+                .run_on_slice(&mut input.clone(), |l, r| l.to_string() + r),
+            *expected
+        );
+    }
+
+    #[test]
+    fn test_reduce_string() {
+        let input = input_strings();
+        let expected = input.clone().into_iter().reduce(|l, r| l + &r);
+        assert_eq!(reduce(input, |l, r| l + &r), expected);
+    }
+
+    fn op(lhs_index: usize, rhs_and_dest_index: usize, row: u32) -> PrefixSumOp {
+        PrefixSumOp {
+            lhs_index,
+            rhs_and_dest_index: NonZeroUsize::new(rhs_and_dest_index).expect("should be non-zero"),
+            row,
+        }
+    }
+
+    #[test]
+    fn test_reduce_ops_9() {
+        let expected = vec![
+            op(7, 8, 0),
+            op(5, 6, 0),
+            op(3, 4, 0),
+            op(1, 2, 0),
+            op(6, 8, 1),
+            op(2, 4, 1),
+            op(4, 8, 2),
+            op(0, 8, 3),
+        ];
+        println!("expected: {expected:#?}");
+        let ops = reduce_ops(9);
+        println!("ops: {ops:#?}");
+        assert_eq!(*ops, *expected);
+    }
+
+    #[test]
+    fn test_reduce_ops_8() {
+        let expected = vec![
+            op(6, 7, 0),
+            op(4, 5, 0),
+            op(2, 3, 0),
+            op(0, 1, 0),
+            op(5, 7, 1),
+            op(1, 3, 1),
+            op(3, 7, 2),
+        ];
+        println!("expected: {expected:#?}");
+        let ops = reduce_ops(8);
+        println!("ops: {ops:#?}");
+        assert_eq!(*ops, *expected);
+    }
+
+    #[test]
+    fn test_count_ones() {
+        for width in 0..=10u32 {
+            for v in 0..1u32 << width {
+                let expected = v.count_ones();
+                assert_eq!(
+                    reduce((0..width).map(|i| (v >> i) & 1), |l, r| l + r).unwrap_or(0),
+                    expected,
+                    "v={v:#X}"
+                );
+            }
+        }
+    }
+
+    #[track_caller]
+    fn test_diagram(ops: impl IntoIterator<Item = PrefixSumOp>, item_count: usize, expected: &str) {
+        let text = PrefixSumOp::diagram_with_config(
+            ops,
+            item_count,
+            DiagramConfig {
+                plus: Cow::Borrowed("@"),
+                ..Default::default()
+            },
+        );
+        println!("text:\n{text}\n");
+        assert_eq!(text, expected);
+    }
+
+    #[test]
+    fn test_work_efficient_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            PrefixSumAlgorithm::WorkEfficient.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |
+ |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |
+ | \|  | \|  | \|  | \|  | \|  | \|  | \|  | \|
+ |  @  |  @  |  @  |  @  |  @  |  @  |  @  |  @
+ |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |
+ |  | \|  |  |  | \|  |  |  | \|  |  |  | \|  |
+ |  |  X  |  |  |  X  |  |  |  X  |  |  |  X  |
+ |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |
+ |  |  | \|  |  |  | \|  |  |  | \|  |  |  | \|
+ |  |  |  @  |  |  |  @  |  |  |  @  |  |  |  @
+ |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  X  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  | \|  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  X  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  | \|  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  @  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  X  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  ●  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  ●  |  |  |  ●  |  |  |  @  |  |  |  |
+ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  | \|  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  X  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  | \|  |  |  | \|  |  |
+ |  ●  |  ●  |  @  |  ●  |  @  |  ●  |  @  |  |
+ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |
+ |  | \|  | \|  | \|  | \|  | \|  | \|  | \|  |
+ |  |  @  |  @  |  @  |  @  |  @  |  @  |  @  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_low_latency_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            PrefixSumAlgorithm::LowLatency.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  |
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ | \| \| \| \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  @  @  @  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ | \| \| \| \| \| \| \| \| \| \| \| \| \| \|  |
+ |  X  X  X  X  X  X  X  X  X  X  X  X  X  X  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  | \| \| \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  ●  @  @  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |
+ | \| \| \| \| \| \| \| \| \| \| \| \|  |  |  |
+ |  X  X  X  X  X  X  X  X  X  X  X  X  |  |  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |
+ |  | \| \| \| \| \| \| \| \| \| \| \| \|  |  |
+ |  |  X  X  X  X  X  X  X  X  X  X  X  X  |  |
+ |  |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ |  |  | \| \| \| \| \| \| \| \| \| \| \| \|  |
+ |  |  |  X  X  X  X  X  X  X  X  X  X  X  X  |
+ |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  |  |  | \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  ●  ●  ●  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |  |  |
+ | \| \| \| \| \| \| \| \|  |  |  |  |  |  |  |
+ |  X  X  X  X  X  X  X  X  |  |  |  |  |  |  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |  |
+ |  | \| \| \| \| \| \| \| \|  |  |  |  |  |  |
+ |  |  X  X  X  X  X  X  X  X  |  |  |  |  |  |
+ |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |
+ |  |  | \| \| \| \| \| \| \| \|  |  |  |  |  |
+ |  |  |  X  X  X  X  X  X  X  X  |  |  |  |  |
+ |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |
+ |  |  |  | \| \| \| \| \| \| \| \|  |  |  |  |
+ |  |  |  |  X  X  X  X  X  X  X  X  |  |  |  |
+ |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |
+ |  |  |  |  | \| \| \| \| \| \| \| \|  |  |  |
+ |  |  |  |  |  X  X  X  X  X  X  X  X  |  |  |
+ |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |
+ |  |  |  |  |  | \| \| \| \| \| \| \| \|  |  |
+ |  |  |  |  |  |  X  X  X  X  X  X  X  X  |  |
+ |  |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ |  |  |  |  |  |  | \| \| \| \| \| \| \| \|  |
+ |  |  |  |  |  |  |  X  X  X  X  X  X  X  X  |
+ |  |  |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  |  |  |  |  |  |  | \| \| \| \| \| \| \| \|
+ |  |  |  |  |  |  |  |  @  @  @  @  @  @  @  @
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_work_efficient_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            PrefixSumAlgorithm::WorkEfficient.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  |
+ |\ |  |\ |  |\ |  |\ |  |
+ | \|  | \|  | \|  | \|  |
+ |  @  |  @  |  @  |  @  |
+ |  |\ |  |  |  |\ |  |  |
+ |  | \|  |  |  | \|  |  |
+ |  |  X  |  |  |  X  |  |
+ |  |  |\ |  |  |  |\ |  |
+ |  |  | \|  |  |  | \|  |
+ |  |  |  @  |  |  |  @  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  ●  |  |  |  @  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  ●  |  ●  |  @  |  ●  |
+ |  |\ |  |\ |  |\ |  |\ |
+ |  | \|  | \|  | \|  | \|
+ |  |  @  |  @  |  @  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_low_latency_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            PrefixSumAlgorithm::LowLatency.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ ●  ●  ●  ●  ●  ●  ●  ●  |
+ |\ |\ |\ |\ |\ |\ |\ |\ |
+ | \| \| \| \| \| \| \| \|
+ ●  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |  |
+ | \| \| \| \| \| \| \|  |
+ |  X  X  X  X  X  X  X  |
+ |  |\ |\ |\ |\ |\ |\ |\ |
+ |  | \| \| \| \| \| \| \|
+ ●  ●  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |  |  |  |
+ | \| \| \| \| \|  |  |  |
+ |  X  X  X  X  X  |  |  |
+ |  |\ |\ |\ |\ |\ |  |  |
+ |  | \| \| \| \| \|  |  |
+ |  |  X  X  X  X  X  |  |
+ |  |  |\ |\ |\ |\ |\ |  |
+ |  |  | \| \| \| \| \|  |
+ |  |  |  X  X  X  X  X  |
+ |  |  |  |\ |\ |\ |\ |\ |
+ |  |  |  | \| \| \| \| \|
+ ●  |  |  |  @  @  @  @  @
+ |\ |  |  |  |  |  |  |  |
+ | \|  |  |  |  |  |  |  |
+ |  X  |  |  |  |  |  |  |
+ |  |\ |  |  |  |  |  |  |
+ |  | \|  |  |  |  |  |  |
+ |  |  X  |  |  |  |  |  |
+ |  |  |\ |  |  |  |  |  |
+ |  |  | \|  |  |  |  |  |
+ |  |  |  X  |  |  |  |  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_reduce_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            reduce_ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |
+ |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |
+ | \|  | \|  | \|  | \|  | \|  | \|  | \|  | \|
+ |  @  |  @  |  @  |  @  |  @  |  @  |  @  |  @
+ |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |
+ |  | \|  |  |  | \|  |  |  | \|  |  |  | \|  |
+ |  |  X  |  |  |  X  |  |  |  X  |  |  |  X  |
+ |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |
+ |  |  | \|  |  |  | \|  |  |  | \|  |  |  | \|
+ |  |  |  @  |  |  |  @  |  |  |  @  |  |  |  @
+ |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  X  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  | \|  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  X  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  | \|  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  @  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  X  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_reduce_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            reduce_ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ |  ●  |  ●  |  ●  |  ●  |
+ |  |\ |  |\ |  |\ |  |\ |
+ |  | \|  | \|  | \|  | \|
+ |  |  @  |  @  |  @  |  @
+ |  |  |\ |  |  |  |\ |  |
+ |  |  | \|  |  |  | \|  |
+ |  |  |  X  |  |  |  X  |
+ |  |  |  |\ |  |  |  |\ |
+ |  |  |  | \|  |  |  | \|
+ |  |  |  |  @  |  |  |  @
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ ●  |  |  |  |  |  |  |  @
+ |\ |  |  |  |  |  |  |  |
+ | \|  |  |  |  |  |  |  |
+ |  X  |  |  |  |  |  |  |
+ |  |\ |  |  |  |  |  |  |
+ |  | \|  |  |  |  |  |  |
+ |  |  X  |  |  |  |  |  |
+ |  |  |\ |  |  |  |  |  |
+ |  |  | \|  |  |  |  |  |
+ |  |  |  X  |  |  |  |  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+}

crates/fayalite/src/util/ready_valid.rs

@@ -49,6 +49,18 @@ impl<T: Type> ReadyValid<T> {
     }
 }
 
+/// This debug port is only meant to assist the formal proof of the queue.
+#[cfg(test)]
+#[doc(hidden)]
+#[hdl]
+pub struct QueueDebugPort<Element, Index> {
+    #[hdl(flip)]
+    index_to_check: Index,
+    stored: Element,
+    inp_index: Index,
+    out_index: Index,
+}
+
 #[hdl_module]
 pub fn queue<T: Type>(
     ty: T,
@@ -178,6 +190,22 @@ pub fn queue<T: Type>(
             }
         }
     }
+    // These debug ports expose some internal state during the Induction phase
+    // of Formal Verification. They are not present in normal use.
+    #[cfg(test)]
+    {
+        #[hdl]
+        let dbg: QueueDebugPort<T, UInt> = m.output(QueueDebugPort[ty][index_ty]);
+        // read the memory word currently stored at some fixed index
+        let debug_port = mem.new_read_port();
+        connect(debug_port.addr, dbg.index_to_check);
+        connect(debug_port.en, true);
+        connect(debug_port.clk, cd.clk);
+        connect(dbg.stored, debug_port.data);
+        // also expose the current read and write indices
+        connect(dbg.inp_index, inp_index_reg);
+        connect(dbg.out_index, out_index_reg);
+    }
 }
 
 #[cfg(test)]
@@ -196,13 +224,23 @@ mod tests {
             format_args!("test_queue_{capacity}_{inp_ready_is_comb}_{out_valid_is_comb}"),
             queue_test(capacity, inp_ready_is_comb, out_valid_is_comb),
             FormalMode::Prove,
-            14,
+            2,
             None,
             ExportOptions {
                 simplify_enums: Some(SimplifyEnumsKind::ReplaceWithBundleOfUInts),
                 ..ExportOptions::default()
             },
         );
+        /// Formal verification of the FIFO queue
+        ///
+        /// The strategy derives from the observation that, if we filter its
+        /// input and output streams to consider just one in every N reads and
+        /// writes (where N is the FIFO capacity), then the FIFO effectively
+        /// behaves as a one-entry FIFO.
+        ///
+        /// In particular, any counterexample of the full FIFO behaving badly
+        /// will also be caught by one of the filtered versions (one which
+        /// happens to be in phase with the offending input or output).
         #[hdl_module]
         fn queue_test(capacity: NonZeroUsize, inp_ready_is_comb: bool, out_valid_is_comb: bool) {
             #[hdl]
@@ -217,6 +255,8 @@ mod tests {
                     rst: formal_reset().to_reset(),
                 },
             );
+
+            // random input data
             #[hdl]
             let inp_data: HdlOption<UInt<8>> = wire();
             #[hdl]
@@ -225,16 +265,26 @@ mod tests {
             } else {
                 connect(inp_data, HdlNone());
             }
+
+            // assert output ready at random
             #[hdl]
             let out_ready: Bool = wire();
             connect(out_ready, any_seq(Bool));
-            let index_ty: UInt<32> = UInt::TYPE;
+
+            // The current number of elements in the FIFO ranges from zero to
+            // maximum capacity, inclusive.
+            let count_ty = UInt::range_inclusive(0..=capacity.get());
+            // type for counters that wrap around at the FIFO capacity
+            let index_ty = UInt::range(0..capacity.get());
+
+            // among all entries of the FIFO internal circular memory, choose
+            // one at random to check
             #[hdl]
-            let index_to_check = wire();
+            let index_to_check = wire(index_ty);
             connect(index_to_check, any_const(index_ty));
-            let index_max = !index_ty.zero();
-            // we saturate at index_max, so only check indexes where we properly maintain position
-            hdl_assume(clk, index_to_check.cmp_ne(index_max), "");
+            hdl_assume(clk, index_to_check.cmp_lt(capacity.get()), "");
+
+            // instantiate and connect the queue
             #[hdl]
             let dut = instance(queue(
                 UInt[ConstUsize::<8>],
@@ -245,109 +295,172 @@ mod tests {
             connect(dut.cd, cd);
             connect(dut.inp.data, inp_data);
             connect(dut.out.ready, out_ready);
-            hdl_assume(
-                clk,
-                index_to_check.cmp_ne(!Expr::ty(index_to_check).zero()),
-                "",
-            );
 
+            // Keep an independent count of words in the FIFO. Ensure that
+            // it's always correct, and never overflows.
             #[hdl]
-            let expected_count_reg = reg_builder().clock_domain(cd).reset(0u32);
-            #[hdl]
-            let next_expected_count = wire();
-            connect(next_expected_count, expected_count_reg);
-            connect(expected_count_reg, next_expected_count);
+            let expected_count_reg = reg_builder().clock_domain(cd).reset(count_ty.zero());
             #[hdl]
             if ReadyValid::firing(dut.inp) & !ReadyValid::firing(dut.out) {
-                connect_any(next_expected_count, expected_count_reg + 1u8);
+                hdl_assert(clk, expected_count_reg.cmp_ne(capacity.get()), "");
+                connect_any(expected_count_reg, expected_count_reg + 1u8);
             } else if !ReadyValid::firing(dut.inp) & ReadyValid::firing(dut.out) {
-                connect_any(next_expected_count, expected_count_reg - 1u8);
+                hdl_assert(clk, expected_count_reg.cmp_ne(count_ty.zero()), "");
+                connect_any(expected_count_reg, expected_count_reg - 1u8);
             }
-            hdl_assert(cd.clk, expected_count_reg.cmp_eq(dut.count), "");
-
-            #[hdl]
-            let prev_out_ready_reg = reg_builder().clock_domain(cd).reset(!0_hdl_u3);
-            connect_any(
-                prev_out_ready_reg,
-                (prev_out_ready_reg << 1) | out_ready.cast_to(UInt[1]),
-            );
-            #[hdl]
-            let prev_inp_valid_reg = reg_builder().clock_domain(cd).reset(!0_hdl_u3);
-            connect_any(
-                prev_inp_valid_reg,
-                (prev_inp_valid_reg << 1) | HdlOption::is_some(inp_data).cast_to(UInt[1]),
-            );
-            hdl_assume(
-                clk,
-                (prev_out_ready_reg & prev_inp_valid_reg).cmp_ne(0u8),
-                "",
-            );
+            hdl_assert(clk, expected_count_reg.cmp_eq(dut.count), "");
 
+            // keep an independent write index into the FIFO's circular buffer
             #[hdl]
             let inp_index_reg = reg_builder().clock_domain(cd).reset(index_ty.zero());
             #[hdl]
-            let stored_inp_data_reg = reg_builder().clock_domain(cd).reset(0u8);
-
-            #[hdl]
-            if let HdlSome(data) = ReadyValid::firing_data(dut.inp) {
+            if ReadyValid::firing(dut.inp) {
                 #[hdl]
-                if inp_index_reg.cmp_lt(index_max) {
+                if inp_index_reg.cmp_ne(capacity.get() - 1) {
                     connect_any(inp_index_reg, inp_index_reg + 1u8);
-                    #[hdl]
-                    if inp_index_reg.cmp_eq(index_to_check) {
-                        connect(stored_inp_data_reg, data);
-                    }
+                } else {
+                    connect_any(inp_index_reg, 0_hdl_u0);
                 }
             }
 
-            #[hdl]
-            if inp_index_reg.cmp_lt(index_to_check) {
-                hdl_assert(clk, stored_inp_data_reg.cmp_eq(0u8), "");
-            }
-
+            // keep an independent read index into the FIFO's circular buffer
             #[hdl]
             let out_index_reg = reg_builder().clock_domain(cd).reset(index_ty.zero());
             #[hdl]
-            let stored_out_data_reg = reg_builder().clock_domain(cd).reset(0u8);
-
-            #[hdl]
-            if let HdlSome(data) = ReadyValid::firing_data(dut.out) {
+            if ReadyValid::firing(dut.out) {
                 #[hdl]
-                if out_index_reg.cmp_lt(index_max) {
+                if out_index_reg.cmp_ne(capacity.get() - 1) {
                     connect_any(out_index_reg, out_index_reg + 1u8);
+                } else {
+                    connect_any(out_index_reg, 0_hdl_u0);
+                }
+            }
+
+            // filter the input data stream, predicated by the read index
+            // matching the chosen position in the FIFO's circular buffer
+            #[hdl]
+            let inp_index_matches = wire();
+            connect(inp_index_matches, inp_index_reg.cmp_eq(index_to_check));
+            #[hdl]
+            let inp_firing_data = wire();
+            connect(inp_firing_data, HdlNone());
+            #[hdl]
+            if inp_index_matches {
+                connect(inp_firing_data, ReadyValid::firing_data(dut.inp));
+            }
+
+            // filter the output data stream, predicated by the write index
+            // matching the chosen position in the FIFO's circular buffer
+            #[hdl]
+            let out_index_matches = wire();
+            connect(out_index_matches, out_index_reg.cmp_eq(index_to_check));
+            #[hdl]
+            let out_firing_data = wire();
+            connect(out_firing_data, HdlNone());
+            #[hdl]
+            if out_index_matches {
+                connect(out_firing_data, ReadyValid::firing_data(dut.out));
+            }
+
+            // Implement a one-entry FIFO and ensure its equivalence to the
+            // filtered FIFO.
+            //
+            // the holding register for our one-entry FIFO
+            #[hdl]
+            let stored_reg = reg_builder().clock_domain(cd).reset(HdlNone());
+            #[hdl]
+            match stored_reg {
+                // If the holding register is empty...
+                HdlNone => {
                     #[hdl]
-                    if out_index_reg.cmp_eq(index_to_check) {
-                        connect(stored_out_data_reg, data);
+                    match inp_firing_data {
+                        // ... and we are not receiving data, then we must not
+                        // transmit any data.
+                        HdlNone => hdl_assert(clk, HdlOption::is_none(out_firing_data), ""),
+                        // If we are indeed receiving some data...
+                        HdlSome(data_in) => {
+                            #[hdl]
+                            match out_firing_data {
+                                // ... and transmitting at the same time, we
+                                // must be transmitting the input data itself,
+                                // since the holding register is empty.
+                                HdlSome(data_out) => hdl_assert(clk, data_out.cmp_eq(data_in), ""),
+                                // If we are receiving, but not transmitting,
+                                // store the received data in the holding
+                                // register.
+                                HdlNone => connect(stored_reg, HdlSome(data_in)),
+                            }
+                        }
+                    }
+                }
+                // If there is some value stored in the holding register...
+                HdlSome(stored) => {
+                    #[hdl]
+                    match out_firing_data {
+                        // ... and we are not transmitting it, we cannot
+                        // receive any more data.
+                        HdlNone => hdl_assert(clk, HdlOption::is_none(inp_firing_data), ""),
+                        // If we are transmitting a previously stored value...
+                        HdlSome(data_out) => {
+                            // ... it must be the same data we stored earlier.
+                            hdl_assert(clk, data_out.cmp_eq(stored), "");
+                            // Also, accept new data, if any. Otherwise,
+                            // let the holding register become empty.
+                            connect(stored_reg, inp_firing_data);
+                        }
                     }
                 }
             }
 
+            // from now on, some extra assertions in order to pass induction
+
+            // sync the holding register, when it's occupied, to the
+            // corresponding entry in the FIFO's circular buffer
+            connect(dut.dbg.index_to_check, index_to_check);
             #[hdl]
-            if out_index_reg.cmp_lt(index_to_check) {
-                hdl_assert(clk, stored_out_data_reg.cmp_eq(0u8), "");
+            if let HdlSome(stored) = stored_reg {
+                hdl_assert(clk, stored.cmp_eq(dut.dbg.stored), "");
             }
 
-            hdl_assert(clk, inp_index_reg.cmp_ge(out_index_reg), "");
+            // sync the read and write indices
+            hdl_assert(clk, inp_index_reg.cmp_eq(dut.dbg.inp_index), "");
+            hdl_assert(clk, out_index_reg.cmp_eq(dut.dbg.out_index), "");
 
+            // the indices should never go past the capacity, but induction
+            // doesn't know that...
+            hdl_assert(clk, inp_index_reg.cmp_lt(capacity.get()), "");
+            hdl_assert(clk, out_index_reg.cmp_lt(capacity.get()), "");
+
+            // strongly constrain the state of the holding register
+            //
+            // The holding register is full if and only if the corresponding
+            // FIFO entry was written to and not yet read. In other words, if
+            // the number of pending reads until the chosen entry is read out
+            // is greater than the current FIFO count, then the entry couldn't
+            // be in the FIFO in the first place.
             #[hdl]
-            if inp_index_reg.cmp_lt(index_max) & out_index_reg.cmp_lt(index_max) {
-                hdl_assert(
-                    clk,
-                    expected_count_reg.cmp_eq(inp_index_reg - out_index_reg),
-                    "",
-                );
+            let pending_reads: UInt = wire(index_ty);
+            // take care of wrap-around when subtracting indices, add the
+            // capacity amount to keep the result positive if necessary
+            #[hdl]
+            if index_to_check.cmp_ge(out_index_reg) {
+                connect(pending_reads, index_to_check - out_index_reg);
             } else {
-                hdl_assert(
-                    clk,
-                    expected_count_reg.cmp_ge(inp_index_reg - out_index_reg),
-                    "",
+                connect(
+                    pending_reads,
+                    index_to_check + capacity.get() - out_index_reg,
                 );
             }
-
+            // check whether the chosen entry is in the FIFO
             #[hdl]
-            if inp_index_reg.cmp_gt(index_to_check) & out_index_reg.cmp_gt(index_to_check) {
-                hdl_assert(clk, stored_inp_data_reg.cmp_eq(stored_out_data_reg), "");
-            }
+            let expected_stored: Bool = wire();
+            connect(expected_stored, pending_reads.cmp_lt(dut.count));
+            // sync with the state of the holding register
+            hdl_assert(
+                clk,
+                expected_stored.cmp_eq(HdlOption::is_some(stored_reg)),
+                "",
+            );
         }
     }
 
@@ -430,4 +543,24 @@ mod tests {
     fn test_4_true_true() {
         test_queue(NonZero::new(4).unwrap(), true, true);
     }
+
+    #[test]
+    fn test_many_false_false() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_many_false_true() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_many_true_false() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_many_true_true() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), true, true);
+    }
 }

crates/fayalite/src/util/test_hasher.rs

@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+#![cfg(feature = "unstable-test-hasher")]
+
+use std::{
+    fmt::Write as _,
+    hash::{BuildHasher, Hash, Hasher},
+    io::Write as _,
+    marker::PhantomData,
+    sync::LazyLock,
+};
+
+type BoxDynHasher = Box<dyn Hasher + Send + Sync>;
+type BoxDynBuildHasher = Box<dyn DynBuildHasherTrait + Send + Sync>;
+type BoxDynMakeBuildHasher = Box<dyn Fn() -> BoxDynBuildHasher + Send + Sync>;
+
+trait TryGetDynBuildHasher: Copy {
+    type Type;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher>;
+}
+
+impl<T> TryGetDynBuildHasher for PhantomData<T> {
+    type Type = T;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher> {
+        None
+    }
+}
+
+impl<T: Default + BuildHasher<Hasher: Send + Sync + 'static> + Send + Sync + 'static + Clone>
+    TryGetDynBuildHasher for &'_ PhantomData<T>
+{
+    type Type = T;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher> {
+        Some(Box::new(|| Box::<DynBuildHasher<T>>::default()))
+    }
+}
+
+#[derive(Default, Clone)]
+struct DynBuildHasher<T>(T);
+
+trait DynBuildHasherTrait: BuildHasher<Hasher = BoxDynHasher> {
+    fn clone_dyn_build_hasher(&self) -> BoxDynBuildHasher;
+}
+
+impl<BH: BuildHasher<Hasher: Send + Sync + 'static>> BuildHasher for DynBuildHasher<BH> {
+    type Hasher = BoxDynHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        Box::new(self.0.build_hasher())
+    }
+
+    fn hash_one<T: Hash>(&self, x: T) -> u64 {
+        self.0.hash_one(x)
+    }
+}
+
+impl<BH> DynBuildHasherTrait for DynBuildHasher<BH>
+where
+    Self: Clone + BuildHasher<Hasher = BoxDynHasher> + Send + Sync + 'static,
+{
+    fn clone_dyn_build_hasher(&self) -> BoxDynBuildHasher {
+        Box::new(self.clone())
+    }
+}
+
+pub struct DefaultBuildHasher(BoxDynBuildHasher);
+
+impl Clone for DefaultBuildHasher {
+    fn clone(&self) -> Self {
+        DefaultBuildHasher(self.0.clone_dyn_build_hasher())
+    }
+}
+
+const ENV_VAR_NAME: &'static str = "FAYALITE_TEST_HASHER";
+
+struct EnvVarValue {
+    key: &'static str,
+    try_get_make_build_hasher: fn() -> Option<BoxDynMakeBuildHasher>,
+    description: &'static str,
+}
+
+macro_rules! env_var_value {
+    (
+        key: $key:literal,
+        build_hasher: $build_hasher:ty,
+        description: $description:literal,
+    ) => {
+        EnvVarValue {
+            key: $key,
+            try_get_make_build_hasher: || {
+                // use rust method resolution to detect if $build_hasher is usable
+                // (e.g. hashbrown's hasher won't be usable without the right feature enabled)
+                (&PhantomData::<DynBuildHasher<$build_hasher>>).try_get_make_build_hasher()
+            },
+            description: $description,
+        }
+    };
+}
+
+#[derive(Default)]
+struct AlwaysZeroHasher;
+
+impl Hasher for AlwaysZeroHasher {
+    fn write(&mut self, _bytes: &[u8]) {}
+    fn finish(&self) -> u64 {
+        0
+    }
+}
+
+const ENV_VAR_VALUES: &'static [EnvVarValue] = &[
+    env_var_value! {
+        key: "std",
+        build_hasher: std::hash::RandomState,
+        description: "use std::hash::RandomState",
+    },
+    env_var_value! {
+        key: "hashbrown",
+        build_hasher: hashbrown::DefaultHashBuilder,
+        description: "use hashbrown's DefaultHashBuilder",
+    },
+    env_var_value! {
+        key: "always_zero",
+        build_hasher: std::hash::BuildHasherDefault<AlwaysZeroHasher>,
+        description: "use a hasher that always returns 0 for all hashes,\n    \
+        this is useful for checking that PartialEq impls are correct",
+    },
+];
+
+fn report_bad_env_var(msg: impl std::fmt::Display) -> ! {
+    let mut msg = format!("{ENV_VAR_NAME}: {msg}\n");
+    for &EnvVarValue {
+        key,
+        try_get_make_build_hasher,
+        description,
+    } in ENV_VAR_VALUES
+    {
+        let availability = match try_get_make_build_hasher() {
+            Some(_) => "available",
+            None => "unavailable",
+        };
+        writeln!(msg, "{key}: ({availability})\n    {description}").expect("can't fail");
+    }
+    std::io::stderr()
+        .write_all(msg.as_bytes())
+        .expect("should be able to write to stderr");
+    std::process::abort();
+}
+
+impl Default for DefaultBuildHasher {
+    fn default() -> Self {
+        static DEFAULT_FN: LazyLock<BoxDynMakeBuildHasher> = LazyLock::new(|| {
+            let var = std::env::var_os(ENV_VAR_NAME);
+            let var = var.as_deref().unwrap_or("std".as_ref());
+            for &EnvVarValue {
+                key,
+                try_get_make_build_hasher,
+                description: _,
+            } in ENV_VAR_VALUES
+            {
+                if var.as_encoded_bytes().eq_ignore_ascii_case(key.as_bytes()) {
+                    return try_get_make_build_hasher().unwrap_or_else(|| {
+                        report_bad_env_var(format_args!(
+                            "unavailable hasher: {key} (is the appropriate feature enabled?)"
+                        ));
+                    });
+                }
+            }
+            report_bad_env_var(format_args!("unrecognized hasher: {var:?}"));
+        });
+        Self(DEFAULT_FN())
+    }
+}
+
+pub struct DefaultHasher(BoxDynHasher);
+
+impl BuildHasher for DefaultBuildHasher {
+    type Hasher = DefaultHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        DefaultHasher(self.0.build_hasher())
+    }
+}
+
+impl Hasher for DefaultHasher {
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        self.0.write(bytes)
+    }
+
+    fn write_u8(&mut self, i: u8) {
+        self.0.write_u8(i)
+    }
+
+    fn write_u16(&mut self, i: u16) {
+        self.0.write_u16(i)
+    }
+
+    fn write_u32(&mut self, i: u32) {
+        self.0.write_u32(i)
+    }
+
+    fn write_u64(&mut self, i: u64) {
+        self.0.write_u64(i)
+    }
+
+    fn write_u128(&mut self, i: u128) {
+        self.0.write_u128(i)
+    }
+
+    fn write_usize(&mut self, i: usize) {
+        self.0.write_usize(i)
+    }
+
+    fn write_i8(&mut self, i: i8) {
+        self.0.write_i8(i)
+    }
+
+    fn write_i16(&mut self, i: i16) {
+        self.0.write_i16(i)
+    }
+
+    fn write_i32(&mut self, i: i32) {
+        self.0.write_i32(i)
+    }
+
+    fn write_i64(&mut self, i: i64) {
+        self.0.write_i64(i)
+    }
+
+    fn write_i128(&mut self, i: i128) {
+        self.0.write_i128(i)
+    }
+
+    fn write_isize(&mut self, i: isize) {
+        self.0.write_isize(i)
+    }
+}

crates/fayalite/src/wire.rs

@@ -37,6 +37,18 @@ impl<T: Type> Wire<T> {
             ty: ty.canonical(),
         }
     }
+    pub fn from_canonical(v: Wire<CanonicalType>) -> Self {
+        let Wire {
+            name,
+            source_location,
+            ty,
+        } = v;
+        Self {
+            name,
+            source_location,
+            ty: T::from_canonical(ty),
+        }
+    }
     pub fn ty(&self) -> T {
         self.ty
     }

crates/fayalite/tests/hdl_types.rs

@@ -4,11 +4,17 @@ use fayalite::{
     bundle::BundleType,
     enum_::EnumType,
     int::{BoolOrIntType, IntType},
+    phantom_const::PhantomConst,
     prelude::*,
     ty::StaticType,
 };
 use std::marker::PhantomData;
 
+#[hdl(outline_generated)]
+pub struct MyConstSize<V: Size> {
+    pub size: PhantomConst<UIntType<V>>,
+}
+
 #[hdl(outline_generated)]
 pub struct S<T, Len: Size, T2> {
     pub a: T,

crates/fayalite/tests/module.rs

@@ -1,8 +1,14 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use fayalite::{
-    assert_export_firrtl, firrtl::ExportOptions, intern::Intern,
-    module::transform::simplify_enums::SimplifyEnumsKind, prelude::*, ty::StaticType,
+    assert_export_firrtl,
+    firrtl::ExportOptions,
+    int::{UIntInRange, UIntInRangeInclusive},
+    intern::Intern,
+    module::transform::simplify_enums::SimplifyEnumsKind,
+    prelude::*,
+    reset::ResetType,
+    ty::StaticType,
 };
 use serde_json::json;
 
@@ -190,10 +196,14 @@ circuit check_array_repeat:
     };
 }
 
+pub trait UnknownTrait {}
+
+impl<T: ?Sized> UnknownTrait for T {}
+
 #[hdl_module(outline_generated)]
 pub fn check_skipped_generics<T, #[hdl(skip)] U, const N: usize, #[hdl(skip)] const M: usize>(v: U)
 where
-    T: StaticType,
+    T: StaticType + UnknownTrait,
     ConstUsize<N>: KnownSize,
     U: std::fmt::Display,
 {
@@ -375,18 +385,18 @@ circuit check_written_inside_both_if_else:
     };
 }
 
-#[hdl(outline_generated)]
+#[hdl(outline_generated, cmp_eq)]
 pub struct TestStruct<T> {
     pub a: T,
     pub b: UInt<8>,
 }
 
-#[hdl(outline_generated)]
+#[hdl(outline_generated, cmp_eq)]
 pub struct TestStruct2 {
     pub v: UInt<8>,
 }
 
-#[hdl(outline_generated)]
+#[hdl(outline_generated, cmp_eq)]
 pub struct TestStruct3 {}
 
 #[hdl_module(outline_generated)]
@@ -4026,3 +4036,598 @@ circuit check_enum_connect_any:
 ",
     };
 }
+
+#[hdl_module(outline_generated)]
+pub fn check_deduce_resets<T: ResetType>(ty: T) {
+    #[hdl]
+    let cd: ClockDomain<T> = m.input(ClockDomain[ty]);
+    #[hdl]
+    let my_reg = reg_builder().reset(0u8).clock_domain(cd);
+    #[hdl]
+    let u8_in: UInt<8> = m.input();
+    connect(my_reg, u8_in);
+    #[hdl]
+    let u8_out: UInt<8> = m.output();
+    connect(u8_out, my_reg);
+    #[hdl]
+    let enum_in: OneOfThree<Reset, AsyncReset, SyncReset> = m.input();
+    #[hdl]
+    let enum_out: OneOfThree<Reset, AsyncReset, SyncReset> = m.output();
+    #[hdl]
+    let reset_out: Reset = m.output();
+    connect(reset_out, cd.rst.to_reset());
+    #[hdl]
+    match enum_in {
+        OneOfThree::<_, _, _>::A(v) => {
+            connect(
+                enum_out,
+                OneOfThree[Reset][AsyncReset][SyncReset].A(cd.rst.to_reset()),
+            );
+            connect(reset_out, v);
+        }
+        OneOfThree::<_, _, _>::B(v) => {
+            connect(enum_out, OneOfThree[Reset][AsyncReset][SyncReset].B(v))
+        }
+        OneOfThree::<_, _, _>::C(v) => {
+            connect(enum_out, OneOfThree[Reset][AsyncReset][SyncReset].C(v))
+        }
+    }
+}
+
+#[test]
+fn test_deduce_resets() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_deduce_resets(Reset);
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: Reset}
+    type Ty1 = {|A: Reset, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: Reset @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+    fayalite::module::transform::deduce_resets::deduce_resets(m.canonical().intern_sized(), false)
+        .unwrap_err();
+    let m = fayalite::module::transform::deduce_resets::deduce_resets(
+        m.canonical().intern_sized(),
+        true,
+    )
+    .unwrap();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: UInt<1>}
+    type Ty1 = {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: UInt<1> @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+    let m = check_deduce_resets(SyncReset);
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: UInt<1>}
+    type Ty1 = {|A: Reset, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: Reset @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+    let m = fayalite::module::transform::deduce_resets::deduce_resets(
+        m.canonical().intern_sized(),
+        false,
+    )
+    .unwrap();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: UInt<1>}
+    type Ty1 = {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: UInt<1> @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: UInt<1>, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+    let m = check_deduce_resets(AsyncReset);
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: AsyncReset}
+    type Ty1 = {|A: Reset, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: Reset @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: Reset, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+    let m = fayalite::module::transform::deduce_resets::deduce_resets(
+        m.canonical().intern_sized(),
+        false,
+    )
+    .unwrap();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_resets.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_resets:
+    type Ty0 = {clk: Clock, rst: AsyncReset}
+    type Ty1 = {|A: AsyncReset, B: AsyncReset, C: UInt<1>|}
+    module check_deduce_resets: @[module-XXXXXXXXXX.rs 1:1]
+        input cd: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input u8_in: UInt<8> @[module-XXXXXXXXXX.rs 4:1]
+        output u8_out: UInt<8> @[module-XXXXXXXXXX.rs 6:1]
+        input enum_in: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        output enum_out: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output reset_out: AsyncReset @[module-XXXXXXXXXX.rs 10:1]
+        regreset my_reg: UInt<8>, cd.clk, cd.rst, UInt<8>(0h0) @[module-XXXXXXXXXX.rs 3:1]
+        connect my_reg, u8_in @[module-XXXXXXXXXX.rs 5:1]
+        connect u8_out, my_reg @[module-XXXXXXXXXX.rs 7:1]
+        connect reset_out, cd.rst @[module-XXXXXXXXXX.rs 11:1]
+        match enum_in: @[module-XXXXXXXXXX.rs 12:1]
+            A(_match_arm_value):
+                connect enum_out, {|A: AsyncReset, B: AsyncReset, C: UInt<1>|}(A, cd.rst) @[module-XXXXXXXXXX.rs 13:1]
+                connect reset_out, _match_arm_value @[module-XXXXXXXXXX.rs 14:1]
+            B(_match_arm_value_1):
+                connect enum_out, {|A: AsyncReset, B: AsyncReset, C: UInt<1>|}(B, _match_arm_value_1) @[module-XXXXXXXXXX.rs 15:1]
+            C(_match_arm_value_2):
+                connect enum_out, {|A: AsyncReset, B: AsyncReset, C: UInt<1>|}(C, _match_arm_value_2) @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+}
+
+// intentionally not outline_generated to ensure we get correct macro hygiene
+#[hdl_module]
+pub fn check_cfgs<#[cfg(cfg_false_for_tests)] A: Type, #[cfg(cfg_true_for_tests)] B: Type>(
+    #[cfg(cfg_false_for_tests)] a: A,
+    #[cfg(cfg_true_for_tests)] b: B,
+) {
+    #[hdl]
+    struct S<#[cfg(cfg_false_for_tests)] A, #[cfg(cfg_true_for_tests)] B> {
+        #[cfg(cfg_false_for_tests)]
+        a: A,
+        #[cfg(cfg_true_for_tests)]
+        b: B,
+    }
+    #[hdl]
+    #[cfg(cfg_false_for_tests)]
+    let i_a: A = m.input(a);
+    #[hdl]
+    #[cfg(cfg_true_for_tests)]
+    let i_b: B = m.input(b);
+    #[hdl]
+    let w: S<UInt<8>> = wire();
+    #[cfg(cfg_false_for_tests)]
+    {
+        #[hdl]
+        let o_a: A = m.output(a);
+        connect(o_a, w.a.cast_bits_to(a));
+        connect_any(w.a, i_a.cast_to_bits());
+    }
+    #[cfg(cfg_true_for_tests)]
+    {
+        #[hdl]
+        let o_b: B = m.output(b);
+        connect(o_b, w.b.cast_bits_to(b));
+        connect_any(w.b, i_b.cast_to_bits());
+    }
+}
+
+#[test]
+fn test_cfgs() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_cfgs(UInt[8]);
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_cfgs.fir": r"FIRRTL version 3.2.0
+circuit check_cfgs:
+    type Ty0 = {b: UInt<8>}
+    module check_cfgs: @[the_test_file.rs 9962:1]
+        input i_b: UInt<8> @[the_test_file.rs 9979:20]
+        output o_b: UInt<8> @[the_test_file.rs 9992:24]
+        wire w: Ty0 @[the_test_file.rs 9981:25]
+        connect o_b, w.b @[the_test_file.rs 9993:9]
+        connect w.b, i_b @[the_test_file.rs 9994:9]
+",
+    };
+}
+
+#[hdl_module(outline_generated)]
+pub fn check_let_patterns() {
+    #[hdl]
+    let tuple_in: (UInt<1>, SInt<1>, Bool) = m.input();
+    #[hdl]
+    let (tuple_0, tuple_1, tuple_2) = tuple_in;
+    #[hdl]
+    let tuple_0_out: UInt<1> = m.output();
+    connect(tuple_0_out, tuple_0);
+    #[hdl]
+    let tuple_1_out: SInt<1> = m.output();
+    connect(tuple_1_out, tuple_1);
+    #[hdl]
+    let tuple_2_out: Bool = m.output();
+    connect(tuple_2_out, tuple_2);
+
+    #[hdl]
+    let test_struct_in: TestStruct<SInt<8>> = m.input();
+    #[hdl]
+    let TestStruct::<_> { a, b } = test_struct_in;
+    #[hdl]
+    let test_struct_a_out: SInt<8> = m.output();
+    connect(test_struct_a_out, a);
+    #[hdl]
+    let test_struct_b_out: UInt<8> = m.output();
+    connect(test_struct_b_out, b);
+
+    #[hdl]
+    let test_struct_2_in: TestStruct2 = m.input();
+    #[hdl]
+    let TestStruct2 { v } = test_struct_2_in;
+    #[hdl]
+    let test_struct_2_v_out: UInt<8> = m.output();
+    connect(test_struct_2_v_out, v);
+
+    #[hdl]
+    let test_struct_3_in: TestStruct3 = m.input();
+    #[hdl]
+    let TestStruct3 {} = test_struct_3_in;
+}
+
+#[test]
+fn test_let_patterns() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_let_patterns();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_let_patterns.fir": r"FIRRTL version 3.2.0
+circuit check_let_patterns:
+    type Ty0 = {`0`: UInt<1>, `1`: SInt<1>, `2`: UInt<1>}
+    type Ty1 = {a: SInt<8>, b: UInt<8>}
+    type Ty2 = {v: UInt<8>}
+    type Ty3 = {}
+    module check_let_patterns: @[module-XXXXXXXXXX.rs 1:1]
+        input tuple_in: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        output tuple_0_out: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
+        output tuple_1_out: SInt<1> @[module-XXXXXXXXXX.rs 6:1]
+        output tuple_2_out: UInt<1> @[module-XXXXXXXXXX.rs 8:1]
+        input test_struct_in: Ty1 @[module-XXXXXXXXXX.rs 10:1]
+        output test_struct_a_out: SInt<8> @[module-XXXXXXXXXX.rs 12:1]
+        output test_struct_b_out: UInt<8> @[module-XXXXXXXXXX.rs 14:1]
+        input test_struct_2_in: Ty2 @[module-XXXXXXXXXX.rs 16:1]
+        output test_struct_2_v_out: UInt<8> @[module-XXXXXXXXXX.rs 18:1]
+        input test_struct_3_in: Ty3 @[module-XXXXXXXXXX.rs 20:1]
+        connect tuple_0_out, tuple_in.`0` @[module-XXXXXXXXXX.rs 5:1]
+        connect tuple_1_out, tuple_in.`1` @[module-XXXXXXXXXX.rs 7:1]
+        connect tuple_2_out, tuple_in.`2` @[module-XXXXXXXXXX.rs 9:1]
+        connect test_struct_a_out, test_struct_in.a @[module-XXXXXXXXXX.rs 13:1]
+        connect test_struct_b_out, test_struct_in.b @[module-XXXXXXXXXX.rs 15:1]
+        connect test_struct_2_v_out, test_struct_2_in.v @[module-XXXXXXXXXX.rs 19:1]
+",
+    };
+}
+
+#[hdl_module(outline_generated)]
+pub fn check_struct_cmp_eq() {
+    #[hdl]
+    let tuple_lhs: (UInt<1>, SInt<1>, Bool) = m.input();
+    #[hdl]
+    let tuple_rhs: (UInt<1>, SInt<1>, Bool) = m.input();
+    #[hdl]
+    let tuple_cmp_eq: Bool = m.output();
+    connect(tuple_cmp_eq, tuple_lhs.cmp_eq(tuple_rhs));
+    #[hdl]
+    let tuple_cmp_ne: Bool = m.output();
+    connect(tuple_cmp_ne, tuple_lhs.cmp_ne(tuple_rhs));
+
+    #[hdl]
+    let test_struct_lhs: TestStruct<SInt<8>> = m.input();
+    #[hdl]
+    let test_struct_rhs: TestStruct<SInt<8>> = m.input();
+    #[hdl]
+    let test_struct_cmp_eq: Bool = m.output();
+    connect(test_struct_cmp_eq, test_struct_lhs.cmp_eq(test_struct_rhs));
+    #[hdl]
+    let test_struct_cmp_ne: Bool = m.output();
+    connect(test_struct_cmp_ne, test_struct_lhs.cmp_ne(test_struct_rhs));
+
+    #[hdl]
+    let test_struct_2_lhs: TestStruct2 = m.input();
+    #[hdl]
+    let test_struct_2_rhs: TestStruct2 = m.input();
+    #[hdl]
+    let test_struct_2_cmp_eq: Bool = m.output();
+    connect(
+        test_struct_2_cmp_eq,
+        test_struct_2_lhs.cmp_eq(test_struct_2_rhs),
+    );
+    #[hdl]
+    let test_struct_2_cmp_ne: Bool = m.output();
+    connect(
+        test_struct_2_cmp_ne,
+        test_struct_2_lhs.cmp_ne(test_struct_2_rhs),
+    );
+
+    #[hdl]
+    let test_struct_3_lhs: TestStruct3 = m.input();
+    #[hdl]
+    let test_struct_3_rhs: TestStruct3 = m.input();
+    #[hdl]
+    let test_struct_3_cmp_eq: Bool = m.output();
+    connect(
+        test_struct_3_cmp_eq,
+        test_struct_3_lhs.cmp_eq(test_struct_3_rhs),
+    );
+    #[hdl]
+    let test_struct_3_cmp_ne: Bool = m.output();
+    connect(
+        test_struct_3_cmp_ne,
+        test_struct_3_lhs.cmp_ne(test_struct_3_rhs),
+    );
+}
+
+#[test]
+fn test_struct_cmp_eq() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_struct_cmp_eq();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_struct_cmp_eq.fir": r"FIRRTL version 3.2.0
+circuit check_struct_cmp_eq:
+    type Ty0 = {`0`: UInt<1>, `1`: SInt<1>, `2`: UInt<1>}
+    type Ty1 = {a: SInt<8>, b: UInt<8>}
+    type Ty2 = {v: UInt<8>}
+    type Ty3 = {}
+    module check_struct_cmp_eq: @[module-XXXXXXXXXX.rs 1:1]
+        input tuple_lhs: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input tuple_rhs: Ty0 @[module-XXXXXXXXXX.rs 3:1]
+        output tuple_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
+        output tuple_cmp_ne: UInt<1> @[module-XXXXXXXXXX.rs 6:1]
+        input test_struct_lhs: Ty1 @[module-XXXXXXXXXX.rs 8:1]
+        input test_struct_rhs: Ty1 @[module-XXXXXXXXXX.rs 9:1]
+        output test_struct_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 10:1]
+        output test_struct_cmp_ne: UInt<1> @[module-XXXXXXXXXX.rs 12:1]
+        input test_struct_2_lhs: Ty2 @[module-XXXXXXXXXX.rs 14:1]
+        input test_struct_2_rhs: Ty2 @[module-XXXXXXXXXX.rs 15:1]
+        output test_struct_2_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 16:1]
+        output test_struct_2_cmp_ne: UInt<1> @[module-XXXXXXXXXX.rs 18:1]
+        input test_struct_3_lhs: Ty3 @[module-XXXXXXXXXX.rs 20:1]
+        input test_struct_3_rhs: Ty3 @[module-XXXXXXXXXX.rs 21:1]
+        output test_struct_3_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 22:1]
+        output test_struct_3_cmp_ne: UInt<1> @[module-XXXXXXXXXX.rs 24:1]
+        wire _array_literal_expr: UInt<1>[3]
+        connect _array_literal_expr[0], eq(tuple_lhs.`0`, tuple_rhs.`0`)
+        connect _array_literal_expr[1], eq(tuple_lhs.`1`, tuple_rhs.`1`)
+        connect _array_literal_expr[2], eq(tuple_lhs.`2`, tuple_rhs.`2`)
+        wire _cast_array_to_bits_expr: UInt<1>[3]
+        connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
+        connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
+        connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
+        wire _cast_to_bits_expr: UInt<3>
+        connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
+        connect tuple_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
+        wire _array_literal_expr_1: UInt<1>[3]
+        connect _array_literal_expr_1[0], neq(tuple_lhs.`0`, tuple_rhs.`0`)
+        connect _array_literal_expr_1[1], neq(tuple_lhs.`1`, tuple_rhs.`1`)
+        connect _array_literal_expr_1[2], neq(tuple_lhs.`2`, tuple_rhs.`2`)
+        wire _cast_array_to_bits_expr_1: UInt<1>[3]
+        connect _cast_array_to_bits_expr_1[0], _array_literal_expr_1[0]
+        connect _cast_array_to_bits_expr_1[1], _array_literal_expr_1[1]
+        connect _cast_array_to_bits_expr_1[2], _array_literal_expr_1[2]
+        wire _cast_to_bits_expr_1: UInt<3>
+        connect _cast_to_bits_expr_1, cat(_cast_array_to_bits_expr_1[2], cat(_cast_array_to_bits_expr_1[1], _cast_array_to_bits_expr_1[0]))
+        connect tuple_cmp_ne, orr(_cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 7:1]
+        connect test_struct_cmp_eq, and(eq(test_struct_lhs.a, test_struct_rhs.a), eq(test_struct_lhs.b, test_struct_rhs.b)) @[module-XXXXXXXXXX.rs 11:1]
+        connect test_struct_cmp_ne, or(neq(test_struct_lhs.a, test_struct_rhs.a), neq(test_struct_lhs.b, test_struct_rhs.b)) @[module-XXXXXXXXXX.rs 13:1]
+        connect test_struct_2_cmp_eq, eq(test_struct_2_lhs.v, test_struct_2_rhs.v) @[module-XXXXXXXXXX.rs 17:1]
+        connect test_struct_2_cmp_ne, neq(test_struct_2_lhs.v, test_struct_2_rhs.v) @[module-XXXXXXXXXX.rs 19:1]
+        connect test_struct_3_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 23:1]
+        connect test_struct_3_cmp_ne, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 25:1]
+",
+    };
+}
+
+#[hdl_module(outline_generated)]
+pub fn check_uint_in_range() {
+    #[hdl]
+    let i_0_to_1: UIntInRange<0, 1> = m.input();
+    #[hdl]
+    let i_0_to_2: UIntInRange<0, 2> = m.input();
+    #[hdl]
+    let i_0_to_3: UIntInRange<0, 3> = m.input();
+    #[hdl]
+    let i_0_to_4: UIntInRange<0, 4> = m.input();
+    #[hdl]
+    let i_0_to_7: UIntInRange<0, 7> = m.input();
+    #[hdl]
+    let i_0_to_8: UIntInRange<0, 8> = m.input();
+    #[hdl]
+    let i_0_to_9: UIntInRange<0, 9> = m.input();
+    #[hdl]
+    let i_0_through_0: UIntInRangeInclusive<0, 0> = m.input();
+    #[hdl]
+    let i_0_through_1: UIntInRangeInclusive<0, 1> = m.input();
+    #[hdl]
+    let i_0_through_2: UIntInRangeInclusive<0, 2> = m.input();
+    #[hdl]
+    let i_0_through_3: UIntInRangeInclusive<0, 3> = m.input();
+    #[hdl]
+    let i_0_through_4: UIntInRangeInclusive<0, 4> = m.input();
+    #[hdl]
+    let i_0_through_7: UIntInRangeInclusive<0, 7> = m.input();
+    #[hdl]
+    let i_0_through_8: UIntInRangeInclusive<0, 8> = m.input();
+    #[hdl]
+    let i_0_through_9: UIntInRangeInclusive<0, 9> = m.input();
+}
+
+#[test]
+fn test_uint_in_range() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_uint_in_range();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_uint_in_range.fir": r"FIRRTL version 3.2.0
+circuit check_uint_in_range:
+    type Ty0 = {value: UInt<0>, range: {}}
+    type Ty1 = {value: UInt<1>, range: {}}
+    type Ty2 = {value: UInt<2>, range: {}}
+    type Ty3 = {value: UInt<2>, range: {}}
+    type Ty4 = {value: UInt<3>, range: {}}
+    type Ty5 = {value: UInt<3>, range: {}}
+    type Ty6 = {value: UInt<4>, range: {}}
+    type Ty7 = {value: UInt<0>, range: {}}
+    type Ty8 = {value: UInt<1>, range: {}}
+    type Ty9 = {value: UInt<2>, range: {}}
+    type Ty10 = {value: UInt<2>, range: {}}
+    type Ty11 = {value: UInt<3>, range: {}}
+    type Ty12 = {value: UInt<3>, range: {}}
+    type Ty13 = {value: UInt<4>, range: {}}
+    type Ty14 = {value: UInt<4>, range: {}}
+    module check_uint_in_range: @[module-XXXXXXXXXX.rs 1:1]
+        input i_0_to_1: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        input i_0_to_2: Ty1 @[module-XXXXXXXXXX.rs 3:1]
+        input i_0_to_3: Ty2 @[module-XXXXXXXXXX.rs 4:1]
+        input i_0_to_4: Ty3 @[module-XXXXXXXXXX.rs 5:1]
+        input i_0_to_7: Ty4 @[module-XXXXXXXXXX.rs 6:1]
+        input i_0_to_8: Ty5 @[module-XXXXXXXXXX.rs 7:1]
+        input i_0_to_9: Ty6 @[module-XXXXXXXXXX.rs 8:1]
+        input i_0_through_0: Ty7 @[module-XXXXXXXXXX.rs 9:1]
+        input i_0_through_1: Ty8 @[module-XXXXXXXXXX.rs 10:1]
+        input i_0_through_2: Ty9 @[module-XXXXXXXXXX.rs 11:1]
+        input i_0_through_3: Ty10 @[module-XXXXXXXXXX.rs 12:1]
+        input i_0_through_4: Ty11 @[module-XXXXXXXXXX.rs 13:1]
+        input i_0_through_7: Ty12 @[module-XXXXXXXXXX.rs 14:1]
+        input i_0_through_8: Ty13 @[module-XXXXXXXXXX.rs 15:1]
+        input i_0_through_9: Ty14 @[module-XXXXXXXXXX.rs 16:1]
+",
+    };
+}

crates/fayalite/tests/sim/expected/array_rw.vcd

@@ -0,0 +1,283 @@
+$timescale 1 ps $end
+$scope module array_rw $end
+$scope struct array_in $end
+$var wire 8 ! \[0] $end
+$var wire 8 " \[1] $end
+$var wire 8 # \[2] $end
+$var wire 8 $ \[3] $end
+$var wire 8 % \[4] $end
+$var wire 8 & \[5] $end
+$var wire 8 ' \[6] $end
+$var wire 8 ( \[7] $end
+$var wire 8 ) \[8] $end
+$var wire 8 * \[9] $end
+$var wire 8 + \[10] $end
+$var wire 8 , \[11] $end
+$var wire 8 - \[12] $end
+$var wire 8 . \[13] $end
+$var wire 8 / \[14] $end
+$var wire 8 0 \[15] $end
+$upscope $end
+$scope struct array_out $end
+$var wire 8 1 \[0] $end
+$var wire 8 2 \[1] $end
+$var wire 8 3 \[2] $end
+$var wire 8 4 \[3] $end
+$var wire 8 5 \[4] $end
+$var wire 8 6 \[5] $end
+$var wire 8 7 \[6] $end
+$var wire 8 8 \[7] $end
+$var wire 8 9 \[8] $end
+$var wire 8 : \[9] $end
+$var wire 8 ; \[10] $end
+$var wire 8 < \[11] $end
+$var wire 8 = \[12] $end
+$var wire 8 > \[13] $end
+$var wire 8 ? \[14] $end
+$var wire 8 @ \[15] $end
+$upscope $end
+$var wire 8 A read_index $end
+$var wire 8 B read_data $end
+$var wire 8 C write_index $end
+$var wire 8 D write_data $end
+$var wire 1 E write_en $end
+$scope struct array_wire $end
+$var wire 8 F \[0] $end
+$var wire 8 G \[1] $end
+$var wire 8 H \[2] $end
+$var wire 8 I \[3] $end
+$var wire 8 J \[4] $end
+$var wire 8 K \[5] $end
+$var wire 8 L \[6] $end
+$var wire 8 M \[7] $end
+$var wire 8 N \[8] $end
+$var wire 8 O \[9] $end
+$var wire 8 P \[10] $end
+$var wire 8 Q \[11] $end
+$var wire 8 R \[12] $end
+$var wire 8 S \[13] $end
+$var wire 8 T \[14] $end
+$var wire 8 U \[15] $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b11111111 !
+b1111111 "
+b111111 #
+b11111 $
+b1111 %
+b111 &
+b11 '
+b1 (
+b0 )
+b10000000 *
+b11000000 +
+b11100000 ,
+b11110000 -
+b11111000 .
+b11111100 /
+b11111110 0
+b11111111 1
+b1111111 2
+b111111 3
+b11111 4
+b1111 5
+b111 6
+b11 7
+b1 8
+b0 9
+b10000000 :
+b11000000 ;
+b11100000 <
+b11110000 =
+b11111000 >
+b11111100 ?
+b11111110 @
+b0 A
+b11111111 B
+b0 C
+b0 D
+0E
+b11111111 F
+b1111111 G
+b111111 H
+b11111 I
+b1111 J
+b111 K
+b11 L
+b1 M
+b0 N
+b10000000 O
+b11000000 P
+b11100000 Q
+b11110000 R
+b11111000 S
+b11111100 T
+b11111110 U
+$end
+#1000000
+b1 A
+b1111111 B
+#2000000
+b10 A
+b111111 B
+#3000000
+b11 A
+b11111 B
+#4000000
+b100 A
+b1111 B
+#5000000
+b101 A
+b111 B
+#6000000
+b110 A
+b11 B
+#7000000
+b111 A
+b1 B
+#8000000
+b1000 A
+b0 B
+#9000000
+b1001 A
+b10000000 B
+#10000000
+b1010 A
+b11000000 B
+#11000000
+b1011 A
+b11100000 B
+#12000000
+b1100 A
+b11110000 B
+#13000000
+b1101 A
+b11111000 B
+#14000000
+b1110 A
+b11111100 B
+#15000000
+b1111 A
+b11111110 B
+#16000000
+b10000 A
+b0 B
+#17000000
+b0 1
+b0 A
+1E
+b0 F
+#18000000
+b11111111 1
+b1 2
+b11111111 B
+b1 C
+b1 D
+b11111111 F
+b1 G
+#19000000
+b1111111 2
+b100 3
+b10 C
+b100 D
+b1111111 G
+b100 H
+#20000000
+b111111 3
+b1001 4
+b11 C
+b1001 D
+b111111 H
+b1001 I
+#21000000
+b11111 4
+b10000 5
+b100 C
+b10000 D
+b11111 I
+b10000 J
+#22000000
+b1111 5
+b11001 6
+b101 C
+b11001 D
+b1111 J
+b11001 K
+#23000000
+b111 6
+b100100 7
+b110 C
+b100100 D
+b111 K
+b100100 L
+#24000000
+b11 7
+b110001 8
+b111 C
+b110001 D
+b11 L
+b110001 M
+#25000000
+b1 8
+b1000000 9
+b1000 C
+b1000000 D
+b1 M
+b1000000 N
+#26000000
+b0 9
+b1010001 :
+b1001 C
+b1010001 D
+b0 N
+b1010001 O
+#27000000
+b10000000 :
+b1100100 ;
+b1010 C
+b1100100 D
+b10000000 O
+b1100100 P
+#28000000
+b11000000 ;
+b1111001 <
+b1011 C
+b1111001 D
+b11000000 P
+b1111001 Q
+#29000000
+b11100000 <
+b10010000 =
+b1100 C
+b10010000 D
+b11100000 Q
+b10010000 R
+#30000000
+b11110000 =
+b10101001 >
+b1101 C
+b10101001 D
+b11110000 R
+b10101001 S
+#31000000
+b11111000 >
+b11000100 ?
+b1110 C
+b11000100 D
+b11111000 S
+b11000100 T
+#32000000
+b11111100 ?
+b11100001 @
+b1111 C
+b11100001 D
+b11111100 T
+b11100001 U
+#33000000
+b11111110 @
+b10000 C
+b0 D
+b11111110 U
+#34000000

crates/fayalite/tests/sim/expected/conditional_assignment_last.txt

@@ -0,0 +1,183 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 4,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(conditional_assignment_last: conditional_assignment_last).conditional_assignment_last::i",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(conditional_assignment_last: conditional_assignment_last).conditional_assignment_last::w",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(3), // (0x0) SlotDebugData { name: "", ty: Bool },
+                    value: 0x0,
+                },
+                1: Const {
+                    dest: StatePartIndex<BigSlots>(2), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    value: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                2: Copy {
+                    dest: StatePartIndex<BigSlots>(1), // (0x0) SlotDebugData { name: "InstantiatedModule(conditional_assignment_last: conditional_assignment_last).conditional_assignment_last::w", ty: Bool },
+                    src: StatePartIndex<BigSlots>(2), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                3: BranchIfZero {
+                    target: 5,
+                    value: StatePartIndex<BigSlots>(0), // (0x1) SlotDebugData { name: "InstantiatedModule(conditional_assignment_last: conditional_assignment_last).conditional_assignment_last::i", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:6:1
+                4: Copy {
+                    dest: StatePartIndex<BigSlots>(1), // (0x0) SlotDebugData { name: "InstantiatedModule(conditional_assignment_last: conditional_assignment_last).conditional_assignment_last::w", ty: Bool },
+                    src: StatePartIndex<BigSlots>(3), // (0x0) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                5: Return,
+            ],
+            ..
+        },
+        pc: 5,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                1,
+                0,
+                1,
+                0,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::conditional_assignment_last,
+        instantiated: Module {
+            name: conditional_assignment_last,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::conditional_assignment_last,
+                instantiated: Module {
+                    name: conditional_assignment_last,
+                    ..
+                },
+            }.i,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::conditional_assignment_last,
+                instantiated: Module {
+                    name: conditional_assignment_last,
+                    ..
+                },
+            }.i,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "conditional_assignment_last",
+        children: [
+            TraceModuleIO {
+                name: "i",
+                child: TraceBool {
+                    location: TraceScalarId(0),
+                    name: "i",
+                    flow: Source,
+                },
+                ty: Bool,
+                flow: Source,
+            },
+            TraceWire {
+                name: "w",
+                child: TraceBool {
+                    location: TraceScalarId(1),
+                    name: "w",
+                    flow: Duplex,
+                },
+                ty: Bool,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x0,
+            last_state: 0x1,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 2 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/conditional_assignment_last.vcd

@@ -0,0 +1,14 @@
+$timescale 1 ps $end
+$scope module conditional_assignment_last $end
+$var wire 1 ! i $end
+$var wire 1 " w $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+0!
+1"
+$end
+#1000000
+1!
+0"
+#2000000

crates/fayalite/tests/sim/expected/connect_const.txt

@@ -0,0 +1,136 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 2,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(connect_const: connect_const).connect_const::o",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x5,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(0), // (0x5) SlotDebugData { name: "InstantiatedModule(connect_const: connect_const).connect_const::o", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                2: Return,
+            ],
+            ..
+        },
+        pc: 2,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                5,
+                5,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::connect_const,
+        instantiated: Module {
+            name: connect_const,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::connect_const,
+                instantiated: Module {
+                    name: connect_const,
+                    ..
+                },
+            }.o,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::connect_const,
+                instantiated: Module {
+                    name: connect_const,
+                    ..
+                },
+            }.o,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "connect_const",
+        children: [
+            TraceModuleIO {
+                name: "o",
+                child: TraceUInt {
+                    location: TraceScalarId(0),
+                    name: "o",
+                    ty: UInt<8>,
+                    flow: Sink,
+                },
+                ty: UInt<8>,
+                flow: Sink,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(0),
+                ty: UInt<8>,
+            },
+            state: 0x05,
+            last_state: 0x05,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [],
+    instant: 0 s,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/connect_const_reset.txt

@@ -0,0 +1,203 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 5,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(connect_const_reset: connect_const_reset).connect_const_reset::reset_out",
+                                ty: AsyncReset,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(connect_const_reset: connect_const_reset).connect_const_reset::bit_out",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: AsyncReset,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(2), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    value: 0x1,
+                },
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x1) SlotDebugData { name: "", ty: AsyncReset },
+                    src: StatePartIndex<BigSlots>(2), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                2: Copy {
+                    dest: StatePartIndex<BigSlots>(0), // (0x1) SlotDebugData { name: "InstantiatedModule(connect_const_reset: connect_const_reset).connect_const_reset::reset_out", ty: AsyncReset },
+                    src: StatePartIndex<BigSlots>(3), // (0x1) SlotDebugData { name: "", ty: AsyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                3: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(0), // (0x1) SlotDebugData { name: "InstantiatedModule(connect_const_reset: connect_const_reset).connect_const_reset::reset_out", ty: AsyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                4: Copy {
+                    dest: StatePartIndex<BigSlots>(1), // (0x1) SlotDebugData { name: "InstantiatedModule(connect_const_reset: connect_const_reset).connect_const_reset::bit_out", ty: Bool },
+                    src: StatePartIndex<BigSlots>(4), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                5: Return,
+            ],
+            ..
+        },
+        pc: 5,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                1,
+                1,
+                1,
+                1,
+                1,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::connect_const_reset,
+        instantiated: Module {
+            name: connect_const_reset,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::connect_const_reset,
+                instantiated: Module {
+                    name: connect_const_reset,
+                    ..
+                },
+            }.reset_out,
+            Instance {
+                name: <simulator>::connect_const_reset,
+                instantiated: Module {
+                    name: connect_const_reset,
+                    ..
+                },
+            }.bit_out,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::connect_const_reset,
+                instantiated: Module {
+                    name: connect_const_reset,
+                    ..
+                },
+            }.bit_out,
+            Instance {
+                name: <simulator>::connect_const_reset,
+                instantiated: Module {
+                    name: connect_const_reset,
+                    ..
+                },
+            }.reset_out,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "connect_const_reset",
+        children: [
+            TraceModuleIO {
+                name: "reset_out",
+                child: TraceAsyncReset {
+                    location: TraceScalarId(0),
+                    name: "reset_out",
+                    flow: Sink,
+                },
+                ty: AsyncReset,
+                flow: Sink,
+            },
+            TraceModuleIO {
+                name: "bit_out",
+                child: TraceBool {
+                    location: TraceScalarId(1),
+                    name: "bit_out",
+                    flow: Sink,
+                },
+                ty: Bool,
+                flow: Sink,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigAsyncReset {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 1 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/connect_const_reset.vcd

@@ -0,0 +1,11 @@
+$timescale 1 ps $end
+$scope module connect_const_reset $end
+$var wire 1 ! reset_out $end
+$var wire 1 " bit_out $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+1!
+1"
+$end
+#1000000

crates/fayalite/tests/sim/expected/counter_async.txt

@@ -0,0 +1,376 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 4,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 10,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::cd.clk",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::cd.rst",
+                                ty: AsyncReset,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count_reg",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count_reg$next",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<1>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<5>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(7), // (0x1) SlotDebugData { name: "", ty: UInt<1> },
+                    value: 0x1,
+                },
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(6), // (0x0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(1), // (0x0) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::cd.rst", ty: AsyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                2: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(1), // (0x0) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::cd.rst", ty: AsyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                3: Const {
+                    dest: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<4> },
+                    value: 0x3,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                4: BranchIfZero {
+                    target: 6,
+                    value: StatePartIndex<BigSlots>(6), // (0x0) SlotDebugData { name: "", ty: Bool },
+                },
+                5: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                6: Add {
+                    dest: StatePartIndex<BigSlots>(8), // (0x4) SlotDebugData { name: "", ty: UInt<5> },
+                    lhs: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    rhs: StatePartIndex<BigSlots>(7), // (0x1) SlotDebugData { name: "", ty: UInt<1> },
+                },
+                7: CastToUInt {
+                    dest: StatePartIndex<BigSlots>(9), // (0x4) SlotDebugData { name: "", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(8), // (0x4) SlotDebugData { name: "", ty: UInt<5> },
+                    dest_width: 4,
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                8: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0x4) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg$next", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(9), // (0x4) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:6:1
+                9: Copy {
+                    dest: StatePartIndex<BigSlots>(2), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                10: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(0), // (0x1) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::cd.clk", ty: Clock },
+                },
+                11: AndSmall {
+                    dest: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                12: BranchIfSmallNonZero {
+                    target: 16,
+                    value: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                13: BranchIfSmallZero {
+                    target: 17,
+                    value: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                14: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(4), // (0x4) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg$next", ty: UInt<4> },
+                },
+                15: Branch {
+                    target: 17,
+                },
+                16: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                17: XorSmallImmediate {
+                    dest: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                18: Return,
+            ],
+            ..
+        },
+        pc: 18,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [
+                0,
+                0,
+                1,
+                0,
+            ],
+        },
+        big_slots: StatePart {
+            value: [
+                1,
+                0,
+                3,
+                3,
+                4,
+                3,
+                0,
+                1,
+                4,
+                4,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::counter,
+        instantiated: Module {
+            name: counter,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.count,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd.clk,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd.rst,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.count,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "counter",
+        children: [
+            TraceModuleIO {
+                name: "cd",
+                child: TraceBundle {
+                    name: "cd",
+                    fields: [
+                        TraceClock {
+                            location: TraceScalarId(0),
+                            name: "clk",
+                            flow: Source,
+                        },
+                        TraceAsyncReset {
+                            location: TraceScalarId(1),
+                            name: "rst",
+                            flow: Source,
+                        },
+                    ],
+                    ty: Bundle {
+                        /* offset = 0 */
+                        clk: Clock,
+                        /* offset = 1 */
+                        rst: AsyncReset,
+                    },
+                    flow: Source,
+                },
+                ty: Bundle {
+                    /* offset = 0 */
+                    clk: Clock,
+                    /* offset = 1 */
+                    rst: AsyncReset,
+                },
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "count",
+                child: TraceUInt {
+                    location: TraceScalarId(2),
+                    name: "count",
+                    ty: UInt<4>,
+                    flow: Sink,
+                },
+                ty: UInt<4>,
+                flow: Sink,
+            },
+            TraceReg {
+                name: "count_reg",
+                child: TraceUInt {
+                    location: TraceScalarId(3),
+                    name: "count_reg",
+                    ty: UInt<4>,
+                    flow: Duplex,
+                },
+                ty: UInt<4>,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigClock {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigAsyncReset {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x0,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<4>,
+            },
+            state: 0x3,
+            last_state: 0x2,
+        },
+        SimTrace {
+            id: TraceScalarId(3),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(3),
+                ty: UInt<4>,
+            },
+            state: 0x3,
+            last_state: 0x3,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 66 μs,
+    clocks_triggered: [
+        StatePartIndex<SmallSlots>(1),
+    ],
+    ..
+}

crates/fayalite/tests/sim/expected/counter_async.vcd

@@ -0,0 +1,217 @@
+$timescale 1 ps $end
+$scope module counter $end
+$scope struct cd $end
+$var wire 1 ! clk $end
+$var wire 1 " rst $end
+$upscope $end
+$var wire 4 # count $end
+$var reg 4 $ count_reg $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+0!
+0"
+b0 #
+b0 $
+$end
+#500000
+1"
+b11 #
+b11 $
+#1000000
+1!
+#1500000
+0"
+#2000000
+0!
+#3000000
+1!
+b100 $
+b100 #
+#4000000
+0!
+#5000000
+1!
+b101 $
+b101 #
+#6000000
+0!
+#7000000
+1!
+b110 $
+b110 #
+#8000000
+0!
+#9000000
+1!
+b111 $
+b111 #
+#10000000
+0!
+#11000000
+1!
+b1000 $
+b1000 #
+#12000000
+0!
+#13000000
+1!
+b1001 $
+b1001 #
+#14000000
+0!
+#15000000
+1!
+b1010 $
+b1010 #
+#16000000
+0!
+#17000000
+1!
+b1011 $
+b1011 #
+#18000000
+0!
+#19000000
+1!
+b1100 $
+b1100 #
+#20000000
+0!
+#21000000
+1!
+b1101 $
+b1101 #
+#22000000
+0!
+#23000000
+1!
+b1110 $
+b1110 #
+#24000000
+0!
+#25000000
+1!
+b1111 $
+b1111 #
+#26000000
+0!
+#27000000
+1!
+b0 $
+b0 #
+#28000000
+0!
+#29000000
+1!
+b1 $
+b1 #
+#30000000
+0!
+#31000000
+1!
+b10 $
+b10 #
+#32000000
+0!
+#33000000
+1!
+b11 $
+b11 #
+#34000000
+0!
+#35000000
+1!
+b100 $
+b100 #
+#36000000
+0!
+#37000000
+1!
+b101 $
+b101 #
+#38000000
+0!
+#39000000
+1!
+b110 $
+b110 #
+#40000000
+0!
+#41000000
+1!
+b111 $
+b111 #
+#42000000
+0!
+#43000000
+1!
+b1000 $
+b1000 #
+#44000000
+0!
+#45000000
+1!
+b1001 $
+b1001 #
+#46000000
+0!
+#47000000
+1!
+b1010 $
+b1010 #
+#48000000
+0!
+#49000000
+1!
+b1011 $
+b1011 #
+#50000000
+0!
+#51000000
+1!
+b1100 $
+b1100 #
+#52000000
+0!
+#53000000
+1!
+b1101 $
+b1101 #
+#54000000
+0!
+#55000000
+1!
+b1110 $
+b1110 #
+#56000000
+0!
+#57000000
+1!
+b1111 $
+b1111 #
+#58000000
+0!
+#59000000
+1!
+b0 $
+b0 #
+#60000000
+0!
+#61000000
+1!
+b1 $
+b1 #
+#62000000
+0!
+#63000000
+1!
+b10 $
+b10 #
+#64000000
+0!
+#65000000
+1!
+b11 $
+b11 #
+#66000000

crates/fayalite/tests/sim/expected/counter_sync.txt

@@ -0,0 +1,357 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 4,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 9,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::cd.clk",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::cd.rst",
+                                ty: SyncReset,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count_reg",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(counter: counter).counter::count_reg$next",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<1>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<5>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:6:1
+                0: Copy {
+                    dest: StatePartIndex<BigSlots>(2), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                1: Const {
+                    dest: StatePartIndex<BigSlots>(6), // (0x1) SlotDebugData { name: "", ty: UInt<1> },
+                    value: 0x1,
+                },
+                2: Add {
+                    dest: StatePartIndex<BigSlots>(7), // (0x4) SlotDebugData { name: "", ty: UInt<5> },
+                    lhs: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    rhs: StatePartIndex<BigSlots>(6), // (0x1) SlotDebugData { name: "", ty: UInt<1> },
+                },
+                3: CastToUInt {
+                    dest: StatePartIndex<BigSlots>(8), // (0x4) SlotDebugData { name: "", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(7), // (0x4) SlotDebugData { name: "", ty: UInt<5> },
+                    dest_width: 4,
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                4: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0x4) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg$next", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(8), // (0x4) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                5: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(1), // (0x0) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::cd.rst", ty: SyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                6: Const {
+                    dest: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<4> },
+                    value: 0x3,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                7: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(0), // (0x1) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::cd.clk", ty: Clock },
+                },
+                8: AndSmall {
+                    dest: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                9: BranchIfSmallZero {
+                    target: 14,
+                    value: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                10: BranchIfSmallNonZero {
+                    target: 13,
+                    value: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                11: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(4), // (0x4) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg$next", ty: UInt<4> },
+                },
+                12: Branch {
+                    target: 14,
+                },
+                13: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x3) SlotDebugData { name: "InstantiatedModule(counter: counter).counter::count_reg", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                14: XorSmallImmediate {
+                    dest: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                15: Return,
+            ],
+            ..
+        },
+        pc: 15,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [
+                0,
+                0,
+                1,
+                0,
+            ],
+        },
+        big_slots: StatePart {
+            value: [
+                1,
+                0,
+                3,
+                3,
+                4,
+                3,
+                1,
+                4,
+                4,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::counter,
+        instantiated: Module {
+            name: counter,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.count,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd.clk,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.cd.rst,
+            Instance {
+                name: <simulator>::counter,
+                instantiated: Module {
+                    name: counter,
+                    ..
+                },
+            }.count,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "counter",
+        children: [
+            TraceModuleIO {
+                name: "cd",
+                child: TraceBundle {
+                    name: "cd",
+                    fields: [
+                        TraceClock {
+                            location: TraceScalarId(0),
+                            name: "clk",
+                            flow: Source,
+                        },
+                        TraceSyncReset {
+                            location: TraceScalarId(1),
+                            name: "rst",
+                            flow: Source,
+                        },
+                    ],
+                    ty: Bundle {
+                        /* offset = 0 */
+                        clk: Clock,
+                        /* offset = 1 */
+                        rst: SyncReset,
+                    },
+                    flow: Source,
+                },
+                ty: Bundle {
+                    /* offset = 0 */
+                    clk: Clock,
+                    /* offset = 1 */
+                    rst: SyncReset,
+                },
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "count",
+                child: TraceUInt {
+                    location: TraceScalarId(2),
+                    name: "count",
+                    ty: UInt<4>,
+                    flow: Sink,
+                },
+                ty: UInt<4>,
+                flow: Sink,
+            },
+            TraceReg {
+                name: "count_reg",
+                child: TraceUInt {
+                    location: TraceScalarId(3),
+                    name: "count_reg",
+                    ty: UInt<4>,
+                    flow: Duplex,
+                },
+                ty: UInt<4>,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigClock {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigSyncReset {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x0,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<4>,
+            },
+            state: 0x3,
+            last_state: 0x2,
+        },
+        SimTrace {
+            id: TraceScalarId(3),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(3),
+                ty: UInt<4>,
+            },
+            state: 0x3,
+            last_state: 0x3,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 66 μs,
+    clocks_triggered: [
+        StatePartIndex<SmallSlots>(1),
+    ],
+    ..
+}

crates/fayalite/tests/sim/expected/counter_sync.vcd

@@ -0,0 +1,214 @@
+$timescale 1 ps $end
+$scope module counter $end
+$scope struct cd $end
+$var wire 1 ! clk $end
+$var wire 1 " rst $end
+$upscope $end
+$var wire 4 # count $end
+$var reg 4 $ count_reg $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+0!
+1"
+b0 #
+b0 $
+$end
+#1000000
+1!
+b11 $
+b11 #
+0"
+#2000000
+0!
+#3000000
+1!
+b100 $
+b100 #
+#4000000
+0!
+#5000000
+1!
+b101 $
+b101 #
+#6000000
+0!
+#7000000
+1!
+b110 $
+b110 #
+#8000000
+0!
+#9000000
+1!
+b111 $
+b111 #
+#10000000
+0!
+#11000000
+1!
+b1000 $
+b1000 #
+#12000000
+0!
+#13000000
+1!
+b1001 $
+b1001 #
+#14000000
+0!
+#15000000
+1!
+b1010 $
+b1010 #
+#16000000
+0!
+#17000000
+1!
+b1011 $
+b1011 #
+#18000000
+0!
+#19000000
+1!
+b1100 $
+b1100 #
+#20000000
+0!
+#21000000
+1!
+b1101 $
+b1101 #
+#22000000
+0!
+#23000000
+1!
+b1110 $
+b1110 #
+#24000000
+0!
+#25000000
+1!
+b1111 $
+b1111 #
+#26000000
+0!
+#27000000
+1!
+b0 $
+b0 #
+#28000000
+0!
+#29000000
+1!
+b1 $
+b1 #
+#30000000
+0!
+#31000000
+1!
+b10 $
+b10 #
+#32000000
+0!
+#33000000
+1!
+b11 $
+b11 #
+#34000000
+0!
+#35000000
+1!
+b100 $
+b100 #
+#36000000
+0!
+#37000000
+1!
+b101 $
+b101 #
+#38000000
+0!
+#39000000
+1!
+b110 $
+b110 #
+#40000000
+0!
+#41000000
+1!
+b111 $
+b111 #
+#42000000
+0!
+#43000000
+1!
+b1000 $
+b1000 #
+#44000000
+0!
+#45000000
+1!
+b1001 $
+b1001 #
+#46000000
+0!
+#47000000
+1!
+b1010 $
+b1010 #
+#48000000
+0!
+#49000000
+1!
+b1011 $
+b1011 #
+#50000000
+0!
+#51000000
+1!
+b1100 $
+b1100 #
+#52000000
+0!
+#53000000
+1!
+b1101 $
+b1101 #
+#54000000
+0!
+#55000000
+1!
+b1110 $
+b1110 #
+#56000000
+0!
+#57000000
+1!
+b1111 $
+b1111 #
+#58000000
+0!
+#59000000
+1!
+b0 $
+b0 #
+#60000000
+0!
+#61000000
+1!
+b1 $
+b1 #
+#62000000
+0!
+#63000000
+1!
+b10 $
+b10 #
+#64000000
+0!
+#65000000
+1!
+b11 $
+b11 #
+#66000000

crates/fayalite/tests/sim/expected/duplicate_names.txt

@@ -0,0 +1,166 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 4,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(3), // (0x6) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x6,
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(2), // (0x6) SlotDebugData { name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(3), // (0x6) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                2: Const {
+                    dest: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x5,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                3: Copy {
+                    dest: StatePartIndex<BigSlots>(0), // (0x5) SlotDebugData { name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                4: Return,
+            ],
+            ..
+        },
+        pc: 4,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                5,
+                5,
+                6,
+                6,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::duplicate_names,
+        instantiated: Module {
+            name: duplicate_names,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [],
+        uninitialized_ios: {},
+        io_targets: {},
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "duplicate_names",
+        children: [
+            TraceWire {
+                name: "w",
+                child: TraceUInt {
+                    location: TraceScalarId(0),
+                    name: "w",
+                    ty: UInt<8>,
+                    flow: Duplex,
+                },
+                ty: UInt<8>,
+            },
+            TraceWire {
+                name: "w",
+                child: TraceUInt {
+                    location: TraceScalarId(1),
+                    name: "w",
+                    ty: UInt<8>,
+                    flow: Duplex,
+                },
+                ty: UInt<8>,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(0),
+                ty: UInt<8>,
+            },
+            state: 0x05,
+            last_state: 0x05,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<8>,
+            },
+            state: 0x06,
+            last_state: 0x06,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 1 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/duplicate_names.vcd

@@ -0,0 +1,11 @@
+$timescale 1 ps $end
+$scope module duplicate_names $end
+$var wire 8 ! w $end
+$var wire 8 " w_2 $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b101 !
+b110 "
+$end
+#1000000

crates/fayalite/tests/sim/expected/enums.vcd

@@ -0,0 +1,126 @@
+$timescale 1 ps $end
+$scope module enums $end
+$scope struct cd $end
+$var wire 1 ! clk $end
+$var wire 1 " rst $end
+$upscope $end
+$var wire 1 # en $end
+$var wire 2 $ which_in $end
+$var wire 4 % data_in $end
+$var wire 2 & which_out $end
+$var wire 4 ' data_out $end
+$scope struct b_out $end
+$var string 1 ( \$tag $end
+$scope struct HdlSome $end
+$var wire 1 ) \0 $end
+$var wire 1 * \1 $end
+$upscope $end
+$upscope $end
+$scope struct b2_out $end
+$var string 1 + \$tag $end
+$scope struct HdlSome $end
+$var wire 1 , \0 $end
+$var wire 1 - \1 $end
+$upscope $end
+$upscope $end
+$scope struct the_reg $end
+$var string 1 . \$tag $end
+$scope struct B $end
+$var reg 1 / \0 $end
+$var reg 1 0 \1 $end
+$upscope $end
+$scope struct C $end
+$scope struct a $end
+$var reg 1 1 \[0] $end
+$var reg 1 2 \[1] $end
+$upscope $end
+$var reg 2 3 b $end
+$upscope $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+0!
+1"
+0#
+b0 $
+b0 %
+b0 &
+b0 '
+sHdlNone\x20(0) (
+0)
+0*
+sHdlNone\x20(0) +
+0,
+0-
+sA\x20(0) .
+0/
+00
+01
+02
+b0 3
+$end
+#1000000
+1!
+#1100000
+0"
+#2000000
+0!
+#3000000
+1!
+#4000000
+1#
+b1 $
+0!
+#5000000
+1!
+b1 &
+sHdlSome\x20(1) (
+sHdlSome\x20(1) +
+sB\x20(1) .
+#6000000
+0#
+b0 $
+0!
+#7000000
+1!
+#8000000
+1#
+b1 $
+b1111 %
+0!
+#9000000
+1!
+b11 '
+1)
+1*
+1,
+1-
+1/
+10
+11
+12
+#10000000
+0!
+#11000000
+1!
+#12000000
+b10 $
+0!
+#13000000
+1!
+b10 &
+b1111 '
+sHdlNone\x20(0) (
+0)
+0*
+sHdlNone\x20(0) +
+0,
+0-
+sC\x20(2) .
+b11 3
+#14000000
+0!
+#15000000
+1!
+#16000000

crates/fayalite/tests/sim/expected/extern_module.txt

@@ -0,0 +1,253 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 2,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(extern_module: extern_module).extern_module::i",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(extern_module: extern_module).extern_module::o",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Return,
+            ],
+            ..
+        },
+        pc: 0,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                1,
+                1,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::extern_module,
+        instantiated: Module {
+            name: extern_module,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::extern_module,
+                instantiated: Module {
+                    name: extern_module,
+                    ..
+                },
+            }.i,
+            Instance {
+                name: <simulator>::extern_module,
+                instantiated: Module {
+                    name: extern_module,
+                    ..
+                },
+            }.o,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::extern_module,
+                instantiated: Module {
+                    name: extern_module,
+                    ..
+                },
+            }.i,
+            Instance {
+                name: <simulator>::extern_module,
+                instantiated: Module {
+                    name: extern_module,
+                    ..
+                },
+            }.o,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [
+        SimulationExternModuleState {
+            module_state: SimulationModuleState {
+                base_targets: [
+                    ModuleIO {
+                        name: extern_module::i,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module::o,
+                        is_input: false,
+                        ty: Bool,
+                        ..
+                    },
+                ],
+                uninitialized_ios: {},
+                io_targets: {
+                    ModuleIO {
+                        name: extern_module::i,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module::o,
+                        is_input: false,
+                        ty: Bool,
+                        ..
+                    },
+                },
+                did_initial_settle: true,
+            },
+            sim: ExternModuleSimulation {
+                generator: SimGeneratorFn {
+                    args: (
+                        ModuleIO {
+                            name: extern_module::i,
+                            is_input: true,
+                            ty: Bool,
+                            ..
+                        },
+                        ModuleIO {
+                            name: extern_module::o,
+                            is_input: false,
+                            ty: Bool,
+                            ..
+                        },
+                    ),
+                    f: ...,
+                },
+                sim_io_to_generator_map: {
+                    ModuleIO {
+                        name: extern_module::i,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    }: ModuleIO {
+                        name: extern_module::i,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module::o,
+                        is_input: false,
+                        ty: Bool,
+                        ..
+                    }: ModuleIO {
+                        name: extern_module::o,
+                        is_input: false,
+                        ty: Bool,
+                        ..
+                    },
+                },
+                source_location: SourceLocation(
+                    module-XXXXXXXXXX.rs:4:1,
+                ),
+            },
+            running_generator: Some(
+                ...,
+            ),
+            wait_targets: {
+                Instant(
+                    20.500000000000 μs,
+                ),
+            },
+        },
+    ],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "extern_module",
+        children: [
+            TraceModuleIO {
+                name: "i",
+                child: TraceBool {
+                    location: TraceScalarId(0),
+                    name: "i",
+                    flow: Source,
+                },
+                ty: Bool,
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "o",
+                child: TraceBool {
+                    location: TraceScalarId(1),
+                    name: "o",
+                    flow: Sink,
+                },
+                ty: Bool,
+                flow: Sink,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 20 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/extern_module.vcd

@@ -0,0 +1,51 @@
+$timescale 1 ps $end
+$scope module extern_module $end
+$var wire 1 ! i $end
+$var wire 1 " o $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+0!
+1"
+$end
+#500000
+#1500000
+0"
+#2500000
+1"
+#3500000
+0"
+#4500000
+1"
+#5500000
+0"
+#6500000
+1"
+#7500000
+0"
+#8500000
+1"
+#9500000
+0"
+#10000000
+1!
+#10500000
+#11500000
+1"
+#12500000
+0"
+#13500000
+1"
+#14500000
+0"
+#15500000
+1"
+#16500000
+0"
+#17500000
+1"
+#18500000
+0"
+#19500000
+1"
+#20000000

crates/fayalite/tests/sim/expected/extern_module2.txt

@@ -0,0 +1,362 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 3,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(extern_module2: extern_module2).extern_module2::en",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(extern_module2: extern_module2).extern_module2::clk",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(extern_module2: extern_module2).extern_module2::o",
+                                ty: UInt<8>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Return,
+            ],
+            ..
+        },
+        pc: 0,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                0,
+                1,
+                101,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::extern_module2,
+        instantiated: Module {
+            name: extern_module2,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.en,
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.clk,
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.o,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.clk,
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.en,
+            Instance {
+                name: <simulator>::extern_module2,
+                instantiated: Module {
+                    name: extern_module2,
+                    ..
+                },
+            }.o,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [
+        SimulationExternModuleState {
+            module_state: SimulationModuleState {
+                base_targets: [
+                    ModuleIO {
+                        name: extern_module2::en,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::clk,
+                        is_input: true,
+                        ty: Clock,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::o,
+                        is_input: false,
+                        ty: UInt<8>,
+                        ..
+                    },
+                ],
+                uninitialized_ios: {},
+                io_targets: {
+                    ModuleIO {
+                        name: extern_module2::clk,
+                        is_input: true,
+                        ty: Clock,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::en,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::o,
+                        is_input: false,
+                        ty: UInt<8>,
+                        ..
+                    },
+                },
+                did_initial_settle: true,
+            },
+            sim: ExternModuleSimulation {
+                generator: SimGeneratorFn {
+                    args: (
+                        ModuleIO {
+                            name: extern_module2::en,
+                            is_input: true,
+                            ty: Bool,
+                            ..
+                        },
+                        ModuleIO {
+                            name: extern_module2::clk,
+                            is_input: true,
+                            ty: Clock,
+                            ..
+                        },
+                        ModuleIO {
+                            name: extern_module2::o,
+                            is_input: false,
+                            ty: UInt<8>,
+                            ..
+                        },
+                    ),
+                    f: ...,
+                },
+                sim_io_to_generator_map: {
+                    ModuleIO {
+                        name: extern_module2::clk,
+                        is_input: true,
+                        ty: Clock,
+                        ..
+                    }: ModuleIO {
+                        name: extern_module2::clk,
+                        is_input: true,
+                        ty: Clock,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::en,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    }: ModuleIO {
+                        name: extern_module2::en,
+                        is_input: true,
+                        ty: Bool,
+                        ..
+                    },
+                    ModuleIO {
+                        name: extern_module2::o,
+                        is_input: false,
+                        ty: UInt<8>,
+                        ..
+                    }: ModuleIO {
+                        name: extern_module2::o,
+                        is_input: false,
+                        ty: UInt<8>,
+                        ..
+                    },
+                },
+                source_location: SourceLocation(
+                    module-XXXXXXXXXX.rs:5:1,
+                ),
+            },
+            running_generator: Some(
+                ...,
+            ),
+            wait_targets: {
+                Change {
+                    key: CompiledValue {
+                        layout: CompiledTypeLayout {
+                            ty: Clock,
+                            layout: TypeLayout {
+                                small_slots: StatePartLayout<SmallSlots> {
+                                    len: 0,
+                                    debug_data: [],
+                                    ..
+                                },
+                                big_slots: StatePartLayout<BigSlots> {
+                                    len: 1,
+                                    debug_data: [
+                                        SlotDebugData {
+                                            name: "InstantiatedModule(extern_module2: extern_module2).extern_module2::clk",
+                                            ty: Clock,
+                                        },
+                                    ],
+                                    ..
+                                },
+                                sim_only_slots: StatePartLayout<SimOnlySlots> {
+                                    len: 0,
+                                    debug_data: [],
+                                    layout_data: [],
+                                    ..
+                                },
+                            },
+                            body: Scalar,
+                        },
+                        range: TypeIndexRange {
+                            small_slots: StatePartIndexRange<SmallSlots> { start: 0, len: 0 },
+                            big_slots: StatePartIndexRange<BigSlots> { start: 1, len: 1 },
+                            sim_only_slots: StatePartIndexRange<SimOnlySlots> { start: 0, len: 0 },
+                        },
+                        write: None,
+                    },
+                    value: SimValue {
+                        ty: Clock,
+                        value: OpaqueSimValue {
+                            bits: 0x1_u1,
+                            sim_only_values: [],
+                        },
+                    },
+                },
+            },
+        },
+    ],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "extern_module2",
+        children: [
+            TraceModuleIO {
+                name: "en",
+                child: TraceBool {
+                    location: TraceScalarId(0),
+                    name: "en",
+                    flow: Source,
+                },
+                ty: Bool,
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "clk",
+                child: TraceClock {
+                    location: TraceScalarId(1),
+                    name: "clk",
+                    flow: Source,
+                },
+                ty: Clock,
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "o",
+                child: TraceUInt {
+                    location: TraceScalarId(2),
+                    name: "o",
+                    ty: UInt<8>,
+                    flow: Sink,
+                },
+                ty: UInt<8>,
+                flow: Sink,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(0),
+            },
+            state: 0x0,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigClock {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<8>,
+            },
+            state: 0x65,
+            last_state: 0x65,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 60 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/extern_module2.vcd

@@ -0,0 +1,150 @@
+$timescale 1 ps $end
+$scope module extern_module2 $end
+$var wire 1 ! en $end
+$var wire 1 " clk $end
+$var wire 8 # o $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+1!
+0"
+b1001000 #
+$end
+#1000000
+1"
+b1100101 #
+#2000000
+0"
+#3000000
+1"
+b1101100 #
+#4000000
+0"
+#5000000
+1"
+#6000000
+0"
+#7000000
+1"
+b1101111 #
+#8000000
+0"
+#9000000
+1"
+b101100 #
+#10000000
+0!
+0"
+#11000000
+1"
+#12000000
+0"
+#13000000
+1"
+#14000000
+0"
+#15000000
+1"
+#16000000
+0"
+#17000000
+1"
+#18000000
+0"
+#19000000
+1"
+#20000000
+1!
+0"
+#21000000
+1"
+b100000 #
+#22000000
+0"
+#23000000
+1"
+b1010111 #
+#24000000
+0"
+#25000000
+1"
+b1101111 #
+#26000000
+0"
+#27000000
+1"
+b1110010 #
+#28000000
+0"
+#29000000
+1"
+b1101100 #
+#30000000
+0!
+0"
+#31000000
+1"
+#32000000
+0"
+#33000000
+1"
+#34000000
+0"
+#35000000
+1"
+#36000000
+0"
+#37000000
+1"
+#38000000
+0"
+#39000000
+1"
+#40000000
+1!
+0"
+#41000000
+1"
+b1100100 #
+#42000000
+0"
+#43000000
+1"
+b100001 #
+#44000000
+0"
+#45000000
+1"
+b1010 #
+#46000000
+0"
+#47000000
+1"
+b1001000 #
+#48000000
+0"
+#49000000
+1"
+b1100101 #
+#50000000
+0!
+0"
+#51000000
+1"
+#52000000
+0"
+#53000000
+1"
+#54000000
+0"
+#55000000
+1"
+#56000000
+0"
+#57000000
+1"
+#58000000
+0"
+#59000000
+1"
+#60000000

crates/fayalite/tests/sim/expected/memories.vcd

@@ -0,0 +1,408 @@
+$timescale 1 ps $end
+$scope module memories $end
+$scope struct r $end
+$var wire 4 ! addr $end
+$var wire 1 " en $end
+$var wire 1 # clk $end
+$scope struct data $end
+$var wire 8 $ \0 $end
+$var wire 8 % \1 $end
+$upscope $end
+$upscope $end
+$scope struct w $end
+$var wire 4 & addr $end
+$var wire 1 ' en $end
+$var wire 1 ( clk $end
+$scope struct data $end
+$var wire 8 ) \0 $end
+$var wire 8 * \1 $end
+$upscope $end
+$scope struct mask $end
+$var wire 1 + \0 $end
+$var wire 1 , \1 $end
+$upscope $end
+$upscope $end
+$scope struct mem $end
+$scope struct contents $end
+$scope struct \[0] $end
+$scope struct mem $end
+$var reg 8 9 \0 $end
+$var reg 8 I \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[1] $end
+$scope struct mem $end
+$var reg 8 : \0 $end
+$var reg 8 J \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[2] $end
+$scope struct mem $end
+$var reg 8 ; \0 $end
+$var reg 8 K \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[3] $end
+$scope struct mem $end
+$var reg 8 < \0 $end
+$var reg 8 L \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[4] $end
+$scope struct mem $end
+$var reg 8 = \0 $end
+$var reg 8 M \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[5] $end
+$scope struct mem $end
+$var reg 8 > \0 $end
+$var reg 8 N \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[6] $end
+$scope struct mem $end
+$var reg 8 ? \0 $end
+$var reg 8 O \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[7] $end
+$scope struct mem $end
+$var reg 8 @ \0 $end
+$var reg 8 P \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[8] $end
+$scope struct mem $end
+$var reg 8 A \0 $end
+$var reg 8 Q \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[9] $end
+$scope struct mem $end
+$var reg 8 B \0 $end
+$var reg 8 R \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[10] $end
+$scope struct mem $end
+$var reg 8 C \0 $end
+$var reg 8 S \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[11] $end
+$scope struct mem $end
+$var reg 8 D \0 $end
+$var reg 8 T \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[12] $end
+$scope struct mem $end
+$var reg 8 E \0 $end
+$var reg 8 U \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[13] $end
+$scope struct mem $end
+$var reg 8 F \0 $end
+$var reg 8 V \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[14] $end
+$scope struct mem $end
+$var reg 8 G \0 $end
+$var reg 8 W \1 $end
+$upscope $end
+$upscope $end
+$scope struct \[15] $end
+$scope struct mem $end
+$var reg 8 H \0 $end
+$var reg 8 X \1 $end
+$upscope $end
+$upscope $end
+$upscope $end
+$scope struct r0 $end
+$var wire 4 - addr $end
+$var wire 1 . en $end
+$var wire 1 / clk $end
+$scope struct data $end
+$var wire 8 0 \0 $end
+$var wire 8 1 \1 $end
+$upscope $end
+$upscope $end
+$scope struct w1 $end
+$var wire 4 2 addr $end
+$var wire 1 3 en $end
+$var wire 1 4 clk $end
+$scope struct data $end
+$var wire 8 5 \0 $end
+$var wire 8 6 \1 $end
+$upscope $end
+$scope struct mask $end
+$var wire 1 7 \0 $end
+$var wire 1 8 \1 $end
+$upscope $end
+$upscope $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b1 9
+b100011 I
+b1 :
+b100011 J
+b1 ;
+b100011 K
+b1 <
+b100011 L
+b1 =
+b100011 M
+b1 >
+b100011 N
+b1 ?
+b100011 O
+b1 @
+b100011 P
+b1 A
+b100011 Q
+b1 B
+b100011 R
+b1 C
+b100011 S
+b1 D
+b100011 T
+b1 E
+b100011 U
+b1 F
+b100011 V
+b1 G
+b100011 W
+b1 H
+b100011 X
+b0 !
+0"
+0#
+b0 $
+b0 %
+b0 &
+0'
+0(
+b0 )
+b0 *
+0+
+0,
+b0 -
+0.
+0/
+b0 0
+b0 1
+b0 2
+03
+04
+b0 5
+b0 6
+07
+08
+$end
+#1000000
+1#
+1(
+1/
+14
+#2000000
+1"
+0#
+b1 $
+b100011 %
+1'
+0(
+b10000 )
+b100000 *
+1+
+1,
+1.
+0/
+b1 0
+b100011 1
+13
+04
+b10000 5
+b100000 6
+17
+18
+#3000000
+b10000 9
+b100000 I
+1#
+1(
+1/
+14
+b10000 $
+b100000 %
+b10000 0
+b100000 1
+#4000000
+0#
+0(
+b110000 )
+b1000000 *
+0+
+0/
+04
+b110000 5
+b1000000 6
+07
+#5000000
+b10000 9
+b1000000 I
+1#
+1(
+1/
+14
+b1000000 %
+b1000000 1
+#6000000
+0#
+0(
+b1010000 )
+b1100000 *
+1+
+0,
+0/
+04
+b1010000 5
+b1100000 6
+17
+08
+#7000000
+b1010000 9
+b1000000 I
+1#
+1(
+1/
+14
+b1010000 $
+b1010000 0
+#8000000
+0#
+0(
+b1110000 )
+b10000000 *
+0+
+0/
+04
+b1110000 5
+b10000000 6
+07
+#9000000
+1#
+1(
+1/
+14
+#10000000
+0#
+0'
+0(
+b10010000 )
+b10100000 *
+0/
+03
+04
+b10010000 5
+b10100000 6
+#11000000
+1#
+1(
+1/
+14
+#12000000
+0#
+b1 &
+1'
+0(
+1+
+1,
+0/
+b1 2
+13
+04
+17
+18
+#13000000
+b10010000 :
+b10100000 J
+1#
+1(
+1/
+14
+#14000000
+0#
+b10 &
+0(
+b10110000 )
+b11000000 *
+0/
+b10 2
+04
+b10110000 5
+b11000000 6
+#15000000
+b10110000 ;
+b11000000 K
+1#
+1(
+1/
+14
+#16000000
+0#
+0'
+0(
+b11010000 )
+b11100000 *
+0/
+03
+04
+b11010000 5
+b11100000 6
+#17000000
+1#
+1(
+1/
+14
+#18000000
+b1 !
+0#
+b10010000 $
+b10100000 %
+0(
+b1 -
+0/
+b10010000 0
+b10100000 1
+04
+#19000000
+1#
+1(
+1/
+14
+#20000000
+b10 !
+0#
+b10110000 $
+b11000000 %
+0(
+b10 -
+0/
+b10110000 0
+b11000000 1
+04
+#21000000
+1#
+1(
+1/
+14
+#22000000
+0#
+0(
+0/
+04

crates/fayalite/tests/sim/expected/memories2.vcd

@@ -0,0 +1,363 @@
+$timescale 1 ps $end
+$scope module memories2 $end
+$scope struct rw $end
+$var wire 3 ! addr $end
+$var wire 1 " en $end
+$var wire 1 # clk $end
+$var wire 2 $ rdata $end
+$var wire 1 % wmode $end
+$var wire 2 & wdata $end
+$var wire 1 ' wmask $end
+$upscope $end
+$scope struct mem $end
+$scope struct contents $end
+$scope struct \[0] $end
+$scope struct mem $end
+$var string 1 1 \$tag $end
+$var reg 1 6 HdlSome $end
+$upscope $end
+$upscope $end
+$scope struct \[1] $end
+$scope struct mem $end
+$var string 1 2 \$tag $end
+$var reg 1 7 HdlSome $end
+$upscope $end
+$upscope $end
+$scope struct \[2] $end
+$scope struct mem $end
+$var string 1 3 \$tag $end
+$var reg 1 8 HdlSome $end
+$upscope $end
+$upscope $end
+$scope struct \[3] $end
+$scope struct mem $end
+$var string 1 4 \$tag $end
+$var reg 1 9 HdlSome $end
+$upscope $end
+$upscope $end
+$scope struct \[4] $end
+$scope struct mem $end
+$var string 1 5 \$tag $end
+$var reg 1 : HdlSome $end
+$upscope $end
+$upscope $end
+$upscope $end
+$scope struct rw0 $end
+$var wire 3 ( addr $end
+$var wire 1 ) en $end
+$var wire 1 * clk $end
+$scope struct rdata $end
+$var string 1 + \$tag $end
+$var wire 1 , HdlSome $end
+$upscope $end
+$var wire 1 - wmode $end
+$scope struct wdata $end
+$var string 1 . \$tag $end
+$var wire 1 / HdlSome $end
+$upscope $end
+$var wire 1 0 wmask $end
+$upscope $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+sHdlSome\x20(1) 1
+16
+sHdlSome\x20(1) 2
+17
+sHdlSome\x20(1) 3
+18
+sHdlSome\x20(1) 4
+19
+sHdlSome\x20(1) 5
+1:
+b0 !
+0"
+0#
+b0 $
+0%
+b0 &
+0'
+b0 (
+0)
+0*
+sHdlNone\x20(0) +
+0,
+0-
+sHdlNone\x20(0) .
+0/
+00
+$end
+#250000
+1#
+1*
+#500000
+#750000
+0#
+0*
+#1000000
+1"
+1)
+#1250000
+1#
+1*
+b11 $
+sHdlSome\x20(1) +
+1,
+#1500000
+#1750000
+0#
+0*
+#2000000
+0"
+0)
+#2250000
+1#
+1*
+b0 $
+sHdlNone\x20(0) +
+0,
+#2500000
+#2750000
+0#
+0*
+#3000000
+1"
+1%
+1'
+1)
+1-
+10
+#3250000
+sHdlNone\x20(0) 1
+06
+1#
+1*
+#3500000
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+#17000000
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+1,
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+0,
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+#20000000
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+#20500000
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+0)
+#21250000
+1#
+1*
+b0 $
+sHdlNone\x20(0) +
+#21500000
+#21750000
+0#
+0*
+#22000000

crates/fayalite/tests/sim/expected/memories3.vcd

@@ -0,0 +1,836 @@
+$timescale 1 ps $end
+$scope module memories3 $end
+$scope struct r $end
+$var wire 3 ! addr $end
+$var wire 1 " en $end
+$var wire 1 # clk $end
+$scope struct data $end
+$var wire 8 $ \[0] $end
+$var wire 8 % \[1] $end
+$var wire 8 & \[2] $end
+$var wire 8 ' \[3] $end
+$var wire 8 ( \[4] $end
+$var wire 8 ) \[5] $end
+$var wire 8 * \[6] $end
+$var wire 8 + \[7] $end
+$upscope $end
+$upscope $end
+$scope struct w $end
+$var wire 3 , addr $end
+$var wire 1 - en $end
+$var wire 1 . clk $end
+$scope struct data $end
+$var wire 8 / \[0] $end
+$var wire 8 0 \[1] $end
+$var wire 8 1 \[2] $end
+$var wire 8 2 \[3] $end
+$var wire 8 3 \[4] $end
+$var wire 8 4 \[5] $end
+$var wire 8 5 \[6] $end
+$var wire 8 6 \[7] $end
+$upscope $end
+$scope struct mask $end
+$var wire 1 7 \[0] $end
+$var wire 1 8 \[1] $end
+$var wire 1 9 \[2] $end
+$var wire 1 : \[3] $end
+$var wire 1 ; \[4] $end
+$var wire 1 < \[5] $end
+$var wire 1 = \[6] $end
+$var wire 1 > \[7] $end
+$upscope $end
+$upscope $end
+$scope struct mem $end
+$scope struct contents $end
+$scope struct \[0] $end
+$scope struct mem $end
+$var reg 8 ] \[0] $end
+$var reg 8 e \[1] $end
+$var reg 8 m \[2] $end
+$var reg 8 u \[3] $end
+$var reg 8 } \[4] $end
+$var reg 8 '" \[5] $end
+$var reg 8 /" \[6] $end
+$var reg 8 7" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[1] $end
+$scope struct mem $end
+$var reg 8 ^ \[0] $end
+$var reg 8 f \[1] $end
+$var reg 8 n \[2] $end
+$var reg 8 v \[3] $end
+$var reg 8 ~ \[4] $end
+$var reg 8 (" \[5] $end
+$var reg 8 0" \[6] $end
+$var reg 8 8" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[2] $end
+$scope struct mem $end
+$var reg 8 _ \[0] $end
+$var reg 8 g \[1] $end
+$var reg 8 o \[2] $end
+$var reg 8 w \[3] $end
+$var reg 8 !" \[4] $end
+$var reg 8 )" \[5] $end
+$var reg 8 1" \[6] $end
+$var reg 8 9" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[3] $end
+$scope struct mem $end
+$var reg 8 ` \[0] $end
+$var reg 8 h \[1] $end
+$var reg 8 p \[2] $end
+$var reg 8 x \[3] $end
+$var reg 8 "" \[4] $end
+$var reg 8 *" \[5] $end
+$var reg 8 2" \[6] $end
+$var reg 8 :" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[4] $end
+$scope struct mem $end
+$var reg 8 a \[0] $end
+$var reg 8 i \[1] $end
+$var reg 8 q \[2] $end
+$var reg 8 y \[3] $end
+$var reg 8 #" \[4] $end
+$var reg 8 +" \[5] $end
+$var reg 8 3" \[6] $end
+$var reg 8 ;" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[5] $end
+$scope struct mem $end
+$var reg 8 b \[0] $end
+$var reg 8 j \[1] $end
+$var reg 8 r \[2] $end
+$var reg 8 z \[3] $end
+$var reg 8 $" \[4] $end
+$var reg 8 ," \[5] $end
+$var reg 8 4" \[6] $end
+$var reg 8 <" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[6] $end
+$scope struct mem $end
+$var reg 8 c \[0] $end
+$var reg 8 k \[1] $end
+$var reg 8 s \[2] $end
+$var reg 8 { \[3] $end
+$var reg 8 %" \[4] $end
+$var reg 8 -" \[5] $end
+$var reg 8 5" \[6] $end
+$var reg 8 =" \[7] $end
+$upscope $end
+$upscope $end
+$scope struct \[7] $end
+$scope struct mem $end
+$var reg 8 d \[0] $end
+$var reg 8 l \[1] $end
+$var reg 8 t \[2] $end
+$var reg 8 | \[3] $end
+$var reg 8 &" \[4] $end
+$var reg 8 ." \[5] $end
+$var reg 8 6" \[6] $end
+$var reg 8 >" \[7] $end
+$upscope $end
+$upscope $end
+$upscope $end
+$scope struct r0 $end
+$var wire 3 ? addr $end
+$var wire 1 @ en $end
+$var wire 1 A clk $end
+$scope struct data $end
+$var wire 8 B \[0] $end
+$var wire 8 C \[1] $end
+$var wire 8 D \[2] $end
+$var wire 8 E \[3] $end
+$var wire 8 F \[4] $end
+$var wire 8 G \[5] $end
+$var wire 8 H \[6] $end
+$var wire 8 I \[7] $end
+$upscope $end
+$upscope $end
+$scope struct w1 $end
+$var wire 3 J addr $end
+$var wire 1 K en $end
+$var wire 1 L clk $end
+$scope struct data $end
+$var wire 8 M \[0] $end
+$var wire 8 N \[1] $end
+$var wire 8 O \[2] $end
+$var wire 8 P \[3] $end
+$var wire 8 Q \[4] $end
+$var wire 8 R \[5] $end
+$var wire 8 S \[6] $end
+$var wire 8 T \[7] $end
+$upscope $end
+$scope struct mask $end
+$var wire 1 U \[0] $end
+$var wire 1 V \[1] $end
+$var wire 1 W \[2] $end
+$var wire 1 X \[3] $end
+$var wire 1 Y \[4] $end
+$var wire 1 Z \[5] $end
+$var wire 1 [ \[6] $end
+$var wire 1 \ \[7] $end
+$upscope $end
+$upscope $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b0 ]
+b0 e
+b0 m
+b0 u
+b0 }
+b0 '"
+b0 /"
+b0 7"
+b0 ^
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+1X
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+$end
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+0A
+0L
+#15000000

crates/fayalite/tests/sim/expected/mod1.txt

@@ -0,0 +1,564 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 17,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::o.i",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::o.o",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::o.i2",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::o.o2",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::child.i",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::child.o",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::child.i2",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1: mod1).mod1::child.o2",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i2",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o2",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: SInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<4>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:4:1
+                0: Copy {
+                    dest: StatePartIndex<BigSlots>(6), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.i2", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(2), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::o.i2", ty: SInt<2> },
+                },
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.i", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(0), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::o.i", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:2:1
+                2: Copy {
+                    dest: StatePartIndex<BigSlots>(10), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i2", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(6), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.i2", ty: SInt<2> },
+                },
+                3: Copy {
+                    dest: StatePartIndex<BigSlots>(8), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(4), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.i", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX-2.rs:1:1
+                4: Const {
+                    dest: StatePartIndex<BigSlots>(16), // (0xf) SlotDebugData { name: "", ty: UInt<4> },
+                    value: 0xf,
+                },
+                5: Const {
+                    dest: StatePartIndex<BigSlots>(14), // (0x5) SlotDebugData { name: "", ty: UInt<4> },
+                    value: 0x5,
+                },
+                6: CmpLt {
+                    dest: StatePartIndex<BigSlots>(15), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(14), // (0x5) SlotDebugData { name: "", ty: UInt<4> },
+                    rhs: StatePartIndex<BigSlots>(8), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i", ty: UInt<4> },
+                },
+                7: CastToUInt {
+                    dest: StatePartIndex<BigSlots>(13), // (0xe) SlotDebugData { name: "", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(10), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i2", ty: SInt<2> },
+                    dest_width: 4,
+                },
+                // at: module-XXXXXXXXXX-2.rs:7:1
+                8: Copy {
+                    dest: StatePartIndex<BigSlots>(11), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o2", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(13), // (0xe) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX-2.rs:8:1
+                9: BranchIfZero {
+                    target: 11,
+                    value: StatePartIndex<BigSlots>(15), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX-2.rs:9:1
+                10: Copy {
+                    dest: StatePartIndex<BigSlots>(11), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o2", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(16), // (0xf) SlotDebugData { name: "", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:2:1
+                11: Copy {
+                    dest: StatePartIndex<BigSlots>(7), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.o2", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(11), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o2", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                12: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::o.o2", ty: UInt<4> },
+                    src: StatePartIndex<BigSlots>(7), // (0xf) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.o2", ty: UInt<4> },
+                },
+                // at: module-XXXXXXXXXX-2.rs:1:1
+                13: CastToSInt {
+                    dest: StatePartIndex<BigSlots>(12), // (-0x2) SlotDebugData { name: "", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(8), // (0xa) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::i", ty: UInt<4> },
+                    dest_width: 2,
+                },
+                // at: module-XXXXXXXXXX-2.rs:6:1
+                14: Copy {
+                    dest: StatePartIndex<BigSlots>(9), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(12), // (-0x2) SlotDebugData { name: "", ty: SInt<2> },
+                },
+                // at: module-XXXXXXXXXX.rs:2:1
+                15: Copy {
+                    dest: StatePartIndex<BigSlots>(5), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.o", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(9), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1.child: mod1_child).mod1_child::o", ty: SInt<2> },
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                16: Copy {
+                    dest: StatePartIndex<BigSlots>(1), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::o.o", ty: SInt<2> },
+                    src: StatePartIndex<BigSlots>(5), // (-0x2) SlotDebugData { name: "InstantiatedModule(mod1: mod1).mod1::child.o", ty: SInt<2> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                17: Return,
+            ],
+            ..
+        },
+        pc: 17,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                10,
+                -2,
+                -2,
+                15,
+                10,
+                -2,
+                -2,
+                15,
+                10,
+                -2,
+                -2,
+                15,
+                -2,
+                14,
+                5,
+                1,
+                15,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::mod1,
+        instantiated: Module {
+            name: mod1,
+            ..
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o,
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o.i,
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o.i2,
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o.o,
+            Instance {
+                name: <simulator>::mod1,
+                instantiated: Module {
+                    name: mod1,
+                    ..
+                },
+            }.o.o2,
+        },
+        did_initial_settle: true,
+    },
+    extern_modules: [],
+    state_ready_to_run: false,
+    trace_decls: TraceModule {
+        name: "mod1",
+        children: [
+            TraceModuleIO {
+                name: "o",
+                child: TraceBundle {
+                    name: "o",
+                    fields: [
+                        TraceUInt {
+                            location: TraceScalarId(0),
+                            name: "i",
+                            ty: UInt<4>,
+                            flow: Source,
+                        },
+                        TraceSInt {
+                            location: TraceScalarId(1),
+                            name: "o",
+                            ty: SInt<2>,
+                            flow: Sink,
+                        },
+                        TraceSInt {
+                            location: TraceScalarId(2),
+                            name: "i2",
+                            ty: SInt<2>,
+                            flow: Source,
+                        },
+                        TraceUInt {
+                            location: TraceScalarId(3),
+                            name: "o2",
+                            ty: UInt<4>,
+                            flow: Sink,
+                        },
+                    ],
+                    ty: Bundle {
+                        #[hdl(flip)] /* offset = 0 */
+                        i: UInt<4>,
+                        /* offset = 4 */
+                        o: SInt<2>,
+                        #[hdl(flip)] /* offset = 6 */
+                        i2: SInt<2>,
+                        /* offset = 8 */
+                        o2: UInt<4>,
+                    },
+                    flow: Sink,
+                },
+                ty: Bundle {
+                    #[hdl(flip)] /* offset = 0 */
+                    i: UInt<4>,
+                    /* offset = 4 */
+                    o: SInt<2>,
+                    #[hdl(flip)] /* offset = 6 */
+                    i2: SInt<2>,
+                    /* offset = 8 */
+                    o2: UInt<4>,
+                },
+                flow: Sink,
+            },
+            TraceInstance {
+                name: "child",
+                instance_io: TraceBundle {
+                    name: "child",
+                    fields: [
+                        TraceUInt {
+                            location: TraceScalarId(8),
+                            name: "i",
+                            ty: UInt<4>,
+                            flow: Sink,
+                        },
+                        TraceSInt {
+                            location: TraceScalarId(9),
+                            name: "o",
+                            ty: SInt<2>,
+                            flow: Source,
+                        },
+                        TraceSInt {
+                            location: TraceScalarId(10),
+                            name: "i2",
+                            ty: SInt<2>,
+                            flow: Sink,
+                        },
+                        TraceUInt {
+                            location: TraceScalarId(11),
+                            name: "o2",
+                            ty: UInt<4>,
+                            flow: Source,
+                        },
+                    ],
+                    ty: Bundle {
+                        #[hdl(flip)] /* offset = 0 */
+                        i: UInt<4>,
+                        /* offset = 4 */
+                        o: SInt<2>,
+                        #[hdl(flip)] /* offset = 6 */
+                        i2: SInt<2>,
+                        /* offset = 8 */
+                        o2: UInt<4>,
+                    },
+                    flow: Source,
+                },
+                module: TraceModule {
+                    name: "mod1_child",
+                    children: [
+                        TraceModuleIO {
+                            name: "i",
+                            child: TraceUInt {
+                                location: TraceScalarId(4),
+                                name: "i",
+                                ty: UInt<4>,
+                                flow: Source,
+                            },
+                            ty: UInt<4>,
+                            flow: Source,
+                        },
+                        TraceModuleIO {
+                            name: "o",
+                            child: TraceSInt {
+                                location: TraceScalarId(5),
+                                name: "o",
+                                ty: SInt<2>,
+                                flow: Sink,
+                            },
+                            ty: SInt<2>,
+                            flow: Sink,
+                        },
+                        TraceModuleIO {
+                            name: "i2",
+                            child: TraceSInt {
+                                location: TraceScalarId(6),
+                                name: "i2",
+                                ty: SInt<2>,
+                                flow: Source,
+                            },
+                            ty: SInt<2>,
+                            flow: Source,
+                        },
+                        TraceModuleIO {
+                            name: "o2",
+                            child: TraceUInt {
+                                location: TraceScalarId(7),
+                                name: "o2",
+                                ty: UInt<4>,
+                                flow: Sink,
+                            },
+                            ty: UInt<4>,
+                            flow: Sink,
+                        },
+                    ],
+                },
+                ty: Bundle {
+                    #[hdl(flip)] /* offset = 0 */
+                    i: UInt<4>,
+                    /* offset = 4 */
+                    o: SInt<2>,
+                    #[hdl(flip)] /* offset = 6 */
+                    i2: SInt<2>,
+                    /* offset = 8 */
+                    o2: UInt<4>,
+                },
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(0),
+                ty: UInt<4>,
+            },
+            state: 0xa,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(1),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x2,
+        },
+        SimTrace {
+            id: TraceScalarId(3),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(3),
+                ty: UInt<4>,
+            },
+            state: 0xf,
+            last_state: 0xe,
+        },
+        SimTrace {
+            id: TraceScalarId(4),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(8),
+                ty: UInt<4>,
+            },
+            state: 0xa,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(5),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(9),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(6),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(10),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x2,
+        },
+        SimTrace {
+            id: TraceScalarId(7),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(11),
+                ty: UInt<4>,
+            },
+            state: 0xf,
+            last_state: 0xe,
+        },
+        SimTrace {
+            id: TraceScalarId(8),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(4),
+                ty: UInt<4>,
+            },
+            state: 0xa,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(9),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(5),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(10),
+            kind: BigSInt {
+                index: StatePartIndex<BigSlots>(6),
+                ty: SInt<2>,
+            },
+            state: 0x2,
+            last_state: 0x2,
+        },
+        SimTrace {
+            id: TraceScalarId(11),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(7),
+                ty: UInt<4>,
+            },
+            state: 0xf,
+            last_state: 0xe,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 2 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/mod1.vcd

@@ -0,0 +1,47 @@
+$timescale 1 ps $end
+$scope module mod1 $end
+$scope struct o $end
+$var wire 4 ! i $end
+$var wire 2 " o $end
+$var wire 2 # i2 $end
+$var wire 4 $ o2 $end
+$upscope $end
+$scope struct child $end
+$var wire 4 ) i $end
+$var wire 2 * o $end
+$var wire 2 + i2 $end
+$var wire 4 , o2 $end
+$upscope $end
+$scope module mod1_child $end
+$var wire 4 % i $end
+$var wire 2 & o $end
+$var wire 2 ' i2 $end
+$var wire 4 ( o2 $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b11 !
+b11 "
+b10 #
+b1110 $
+b11 %
+b11 &
+b10 '
+b1110 (
+b11 )
+b11 *
+b10 +
+b1110 ,
+$end
+#1000000
+b1010 !
+b10 "
+b1111 $
+b1010 %
+b10 &
+b1111 (
+b1010 )
+b10 *
+b1111 ,
+#2000000