fayalite::expr::ops: add and automatically generate ops::StructuralEq

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

@@ -1133,6 +1133,7 @@ impl ToTokens for ParsedBundle {
             let mut fields_expr_ne = vec![];
             let mut fields_valueless_eq = vec![];
             let mut fields_valueless_ne = vec![];
+            let mut fields_structural_eq = vec![];
             for field in fields.named() {
                 let field_ident = field.ident();
                 let field_ty = field.ty();
@@ -1141,6 +1142,9 @@ impl ToTokens for ParsedBundle {
                     .push(parse_quote_spanned! {cmp_eq.span=>
                         #field_ty: ::fayalite::expr::HdlPartialEqImpl<#field_ty>
                     });
+                fields_structural_eq.push(quote_spanned! {cmp_eq.span=>
+                    <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                });
                 fields_value_eq.push(quote_spanned! {span=>
                     ::fayalite::expr::HdlPartialEqImpl::cmp_value_eq(
                         __lhs.#field_ident,
@@ -1188,6 +1192,7 @@ impl ToTokens for ParsedBundle {
             let expr_ne_body;
             let valueless_eq_body;
             let valueless_ne_body;
+            let structural_eq;
             if fields_len == 0 {
                 value_eq_body = quote_spanned! {span=>
                     true
@@ -1207,6 +1212,9 @@ impl ToTokens for ParsedBundle {
                 valueless_ne_body = quote_spanned! {span=>
                     ::fayalite::expr::Valueless::new(::fayalite::int::Bool)
                 };
+                structural_eq = quote_spanned! {span=>
+                    true
+                };
             } else {
                 value_eq_body = quote_spanned! {span=>
                     #(#fields_value_eq)&*
@@ -1230,12 +1238,17 @@ impl ToTokens for ParsedBundle {
                     let __rhs = ::fayalite::expr::ValueType::ty(&__rhs);
                     #(#fields_valueless_ne)|*
                 };
+                structural_eq = quote_spanned! {span=>
+                    #(#fields_structural_eq)&&*
+                };
             };
             quote_spanned! {span=>
                 #[automatically_derived]
                 impl #impl_generics ::fayalite::expr::HdlPartialEqImpl<Self> for #target #type_generics
                 #cmp_eq_where_clause
                 {
+                    const TRY_STRUCTURAL_EQ: ::fayalite::__std::primitive::bool = #structural_eq;
+
                     #[track_caller]
                     fn cmp_value_eq(
                         __lhs: Self,
@@ -1261,6 +1274,16 @@ impl ToTokens for ParsedBundle {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            if let ::fayalite::__std::result::Result::Ok(__retval) =
+                                ::fayalite::expr::ops::StructuralEq::try_new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                )
+                            {
+                                return ::fayalite::expr::ToExpr::to_expr(&__retval);
+                            }
+                        }
                         #expr_eq_body
                     }
 
@@ -1269,6 +1292,14 @@ impl ToTokens for ParsedBundle {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            return !::fayalite::expr::ToExpr::to_expr(
+                                &::fayalite::expr::ops::StructuralEq::new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                ),
+                            );
+                        }
                         #expr_ne_body
                     }
 

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

@@ -643,7 +643,9 @@ impl ToTokens for ParsedEnum {
                     #where_clause
                     {
                         #[allow(non_snake_case, dead_code)]
-                        #vis fn #ident(#self_token) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                        #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()),
@@ -929,8 +931,14 @@ impl ToTokens for ParsedEnum {
                 impl #impl_generics ::fayalite::__std::fmt::Display for #sim_value_ident #type_generics
                 #where_clause
                 {
-                    fn fmt(&self, f: &mut ::fayalite::__std::fmt::Formatter<'_>) -> ::fayalite::__std::fmt::Result {
+                    fn fmt(
-                        <#target #type_generics as ::fayalite::ty::SimValueDisplay>::sim_value_display(self, f)
+                        &self,
+                        f: &mut ::fayalite::__std::fmt::Formatter<'_>,
+                    ) -> ::fayalite::__std::fmt::Result {
+                        <#target #type_generics as ::fayalite::ty::SimValueDisplay>::sim_value_display(
+                            self,
+                            f,
+                        )
                     }
                 }
             }.to_tokens(tokens);
@@ -946,6 +954,7 @@ impl ToTokens for ParsedEnum {
             let mut variants_value_eq = vec![];
             let mut variants_expr_eq = vec![];
             let mut fields_valueless_eq = vec![];
+            let mut structural_eq: Option<TokenStream> = None;
             for (
                 variant_index,
                 ParsedVariant {
@@ -971,8 +980,23 @@ impl ToTokens for ParsedEnum {
                         .push(parse_quote_spanned! {cmp_eq.span=>
                             #field_ty: ::fayalite::expr::HdlPartialEqImpl<#field_ty>
                         });
+                    match &mut structural_eq {
+                        Some(structural_eq) => {
+                            structural_eq.extend(quote_spanned! {cmp_eq.span=>
+                                && <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                            });
+                        }
+                        None => {
+                            structural_eq = Some(quote_spanned! {cmp_eq.span=>
+                                <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                            });
+                        }
+                    }
                     variants_value_eq.push(quote_spanned! {span=>
-                        (#sim_value_ident::#variant_ident(__lhs_field, _), #sim_value_ident::#variant_ident(__rhs_field, _)) => {
+                        (
+                            #sim_value_ident::#variant_ident(__lhs_field, _),
+                            #sim_value_ident::#variant_ident(__rhs_field, _),
+                        ) => {
                             ::fayalite::expr::HdlPartialEqImpl::cmp_value_eq(
                                 __lhs.#variant_ident,
                                 ::fayalite::__std::borrow::Cow::Borrowed(__lhs_field),
@@ -1002,7 +1026,10 @@ impl ToTokens for ParsedEnum {
                             else {
                                 ::fayalite::__std::unreachable!();
                             };
-                            ::fayalite::module::connect(__retval, ::fayalite::expr::HdlPartialEqImpl::cmp_expr_eq(__lhs, __rhs));
+                            ::fayalite::module::connect(
+                                __retval,
+                                ::fayalite::expr::HdlPartialEqImpl::cmp_expr_eq(__lhs, __rhs),
+                            );
                         }
                     });
                     fields_valueless_eq.push(quote_spanned! {span=>
@@ -1043,7 +1070,10 @@ impl ToTokens for ParsedEnum {
             }
             if let Some(sim_value_unknown_variant_name) = &sim_value_unknown_variant_name {
                 variants_value_eq.push(quote_spanned! {span=>
-                    (#sim_value_ident::#sim_value_unknown_variant_name(__lhs_unknown), #sim_value_ident::#sim_value_unknown_variant_name(__rhs_unknown)) => {
+                    (
+                        #sim_value_ident::#sim_value_unknown_variant_name(__lhs_unknown),
+                        #sim_value_ident::#sim_value_unknown_variant_name(__rhs_unknown),
+                    ) => {
                         __lhs_unknown == __rhs_unknown
                     }
                 });
@@ -1060,17 +1090,26 @@ impl ToTokens for ParsedEnum {
                 }
             };
             let cmp_expr_eq_wire_name = format!("{ident}_cmp_eq");
+            let structural_eq = structural_eq.unwrap_or_else(|| {
+                quote_spanned! {span=>
+                    true
+                }
+            });
             quote_spanned! {span=>
                 #[automatically_derived]
                 impl #impl_generics ::fayalite::expr::HdlPartialEqImpl<Self> for #target #type_generics
                 #cmp_eq_where_clause
                 {
+                    const TRY_STRUCTURAL_EQ: ::fayalite::__std::primitive::bool = #structural_eq;
+
                     #[track_caller]
                     fn cmp_value_eq(
                         __lhs: Self,
-                        __lhs_value: ::fayalite::__std::borrow::Cow<'_, <Self as ::fayalite::ty::Type>::SimValue>,
+                        __lhs_value: ::fayalite::__std::borrow::Cow<'_,
+                            <Self as ::fayalite::ty::Type>::SimValue>,
                         __rhs: Self,
-                        __rhs_value: ::fayalite::__std::borrow::Cow<'_, <Self as ::fayalite::ty::Type>::SimValue>,
+                        __rhs_value: ::fayalite::__std::borrow::Cow<'_,
+                            <Self as ::fayalite::ty::Type>::SimValue>,
                     ) -> ::fayalite::__std::primitive::bool {
                         match (&*__lhs_value, &*__rhs_value) {
                             #(#variants_value_eq)*
@@ -1083,7 +1122,20 @@ impl ToTokens for ParsedEnum {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
-                        let __retval = ::fayalite::module::wire(::fayalite::module::ImplicitName(#cmp_expr_eq_wire_name), ::fayalite::int::Bool);
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            if let ::fayalite::__std::result::Result::Ok(__retval) =
+                                ::fayalite::expr::ops::StructuralEq::try_new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                )
+                            {
+                                return ::fayalite::expr::ToExpr::to_expr(&__retval);
+                            }
+                        }
+                        let __retval = ::fayalite::module::wire(
+                            ::fayalite::module::ImplicitName(#cmp_expr_eq_wire_name),
+                            ::fayalite::int::Bool,
+                        );
                         ::fayalite::module::connect(__retval, false);
                         let mut __lhs_match_variant_iter = ::fayalite::module::match_(__lhs);
                         #(#variants_expr_eq)*
@@ -1112,7 +1164,8 @@ impl ToTokens for ParsedEnum {
                 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>;
+                type MatchVariantAndInactiveScope =
+                    ::fayalite::enum_::EnumMatchVariantAndInactiveScope<Self>;
                 type MatchVariantsIter = ::fayalite::enum_::EnumMatchVariantsIter<Self>;
 
                 fn match_variants(
@@ -1125,7 +1178,9 @@ impl ToTokens for ParsedEnum {
                     ::fayalite::int::Bool
                 }
                 fn canonical(&#self_token) -> ::fayalite::ty::CanonicalType {
-                    ::fayalite::ty::CanonicalType::Enum(::fayalite::enum_::Enum::new(::fayalite::enum_::EnumType::variants(#self_token)))
+                    ::fayalite::ty::CanonicalType::Enum(::fayalite::enum_::Enum::new(
+                        ::fayalite::enum_::EnumType::variants(#self_token),
+                    ))
                 }
                 #[track_caller]
                 #[allow(non_snake_case)]
@@ -1134,7 +1189,11 @@ impl ToTokens for ParsedEnum {
                         ::fayalite::__std::panic!("expected enum");
                     };
                     let #variants_token = ::fayalite::enum_::EnumType::variants(&enum_);
-                    ::fayalite::__std::assert_eq!(#variants_token.len(), #variants_len, "enum has wrong number of variants");
+                    ::fayalite::__std::assert_eq!(
+                        #variants_token.len(),
+                        #variants_len,
+                        "enum has wrong number of variants",
+                    );
                     Self {
                         #(#from_canonical_body_fields)*
                     }
@@ -1180,7 +1239,10 @@ impl ToTokens for ParsedEnum {
                 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) {
+                ) -> (
+                    <Self as ::fayalite::ty::Type>::MatchVariant,
+                    <Self as ::fayalite::ty::Type>::MatchActiveScope,
+                ) {
                     let (#variant_access_token, scope) = v.activate();
                     (
                         match #variant_access_token.variant_index() {
@@ -1200,7 +1262,10 @@ impl ToTokens for ParsedEnum {
             impl #impl_generics ::fayalite::__std::fmt::Debug for #sim_value_ident #type_generics
             #where_clause
             {
-                fn fmt(&self, f: &mut ::fayalite::__std::fmt::Formatter<'_>) -> ::fayalite::__std::fmt::Result {
+                fn fmt(
+                    &self,
+                    f: &mut ::fayalite::__std::fmt::Formatter<'_>,
+                ) -> ::fayalite::__std::fmt::Result {
                     <#target #type_generics as ::fayalite::ty::SimValueDebug>::sim_value_debug(self, f)
                 }
             }
@@ -1213,7 +1278,10 @@ impl ToTokens for ParsedEnum {
                     &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))
+                    ::fayalite::sim::value::SimValue::from_value(
+                        ty,
+                        ::fayalite::__std::clone::Clone::clone(self),
+                    )
                 }
                 fn into_sim_value_with_type(
                     self,

crates/fayalite/src/array.rs

@@ -367,6 +367,8 @@ impl<Lhs: Type, Rhs: Type, Len: Size> HdlPartialEqImpl<ArrayType<Rhs, Len>> for
 where
     Lhs: HdlPartialEqImpl<Rhs>,
 {
+    const TRY_STRUCTURAL_EQ: bool = <Lhs as HdlPartialEqImpl<Rhs>>::TRY_STRUCTURAL_EQ;
+
     fn cmp_value_eq(
         lhs: Self,
         lhs_value: Cow<'_, Self::SimValue>,

crates/fayalite/src/bundle.rs

@@ -708,6 +708,8 @@ macro_rules! impl_tuples {
             }
         }
         impl<$($Lhs: Type + HdlPartialEqImpl<$Rhs>, $Rhs: Type,)*> HdlPartialEqImpl<($($Rhs,)*)> for ($($Lhs,)*) {
+            const TRY_STRUCTURAL_EQ: bool = true $(&& <$Lhs as HdlPartialEqImpl<$Rhs>>::TRY_STRUCTURAL_EQ)*;
+
             #[track_caller]
             fn cmp_value_eq(
                 lhs: Self,

crates/fayalite/src/expr.rs

@@ -221,6 +221,7 @@ expr_enum! {
         CastBitsTo(ops::CastBitsTo),
         ToTraceAsString(ops::ToTraceAsString),
         TraceAsStringAsInner(ops::TraceAsStringAsInner),
+        StructuralEq(ops::StructuralEq),
         ModuleIO(ModuleIO<CanonicalType>),
         Instance(Instance<Bundle>),
         Wire(Wire<CanonicalType>),
@@ -701,6 +702,7 @@ macro_rules! impl_hdl_cmp {
             impl_helper = $HdlCmpImplHelper:ident,
             $(impl_helper_base = $HdlCmpImplHelperBase:ident,)?
             impl_helper_sealed = $HdlCmpImplHelperSealed:ident,
+            $(try_structural_eq = $TRY_STRUCTURAL_EQ:ident,)?
         ]
         $vis:vis trait $HdlCmp:ident<$Rhs:ident: ValueType>:
             ValueType<Type: $HdlCmpImpl:ident<Rhs::Type> $(+ $HdlCmpImplBase:ident<Rhs::Type>)?> $(+ $HdlCmpBase:ident<Rhs>)?
@@ -729,6 +731,8 @@ macro_rules! impl_hdl_cmp {
         }
 
         $vis trait $HdlCmpImpl<$Rhs: Type>: Type $(+ $HdlCmpImplBase<$Rhs>)? {
+            $(const $TRY_STRUCTURAL_EQ: bool;)?
+
             $(#[track_caller]
             fn $cmp_value_fn(
                 $cmp_value_lhs: Self,
@@ -912,6 +916,7 @@ impl_hdl_cmp! {
     #[
         impl_helper = HdlPartialEqImplHelper,
         impl_helper_sealed = HdlPartialEqImplHelperSealed,
+        try_structural_eq = TRY_STRUCTURAL_EQ,
     ]
     pub trait HdlPartialEq<Rhs: ValueType>:
         ValueType<Type: HdlPartialEqImpl<Rhs::Type> >

crates/fayalite/src/expr/ops.rs

@@ -22,7 +22,7 @@ use crate::{
         Bool, BoolOrIntType, DynSize, IntType, KnownSize, SInt, SIntType, SIntValue, Size, UInt,
         UIntType, UIntValue,
     },
-    intern::{Intern, Interned},
+    intern::{Intern, Interned, MemoizeGeneric},
     phantom_const::{PhantomConst, PhantomConstValue},
     reset::{
         AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset, ToAsyncReset, ToReset,
@@ -2984,6 +2984,7 @@ macro_rules! impl_compare_op {
         #[to_dyn_type($lhs:ident => $dyn_lhs:expr, $rhs:ident => $dyn_rhs:expr)]
         #[to_cmp_value($lhs_compare_value:ident => $lhs_compare_value_expr:expr, $rhs_compare_value:ident => $rhs_compare_value_expr:expr)]
         #[type($Lhs:ty, $Rhs:ty)]
+        $(#[try_structural_eq = $TRY_STRUCTURAL_EQ:ident])?
         #[trait($Trait:ident)]
         $(
             struct $name:ident;
@@ -3045,6 +3046,7 @@ macro_rules! impl_compare_op {
         })*
 
         impl$(<$LhsWidth: Size, $RhsWidth: Size>)? $Trait<$Rhs> for $Lhs {
+            $(const $TRY_STRUCTURAL_EQ: bool = true;)?
             $(fn $value_method(
                 _lhs: Self,
                 $lhs_compare_value: Cow<'_, <Self as Type>::SimValue>,
@@ -3065,6 +3067,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => lhs, rhs => rhs)]
     #[to_cmp_value(lhs_value => &*lhs_value, rhs_value => &*rhs_value)]
     #[type(Bool, Bool)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqB; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeB; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3088,6 +3091,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(UIntType<LhsWidth>, UIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqU; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeU; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3112,6 +3116,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(SIntType<LhsWidth>, SIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqS; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeS; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3133,6 +3138,8 @@ impl_compare_op! {
 macro_rules! impl_compare_forwards_to_bool {
     ($ty:ident) => {
         impl HdlPartialEqImpl<Self> for $ty {
+            const TRY_STRUCTURAL_EQ: bool = true;
+
             #[track_caller]
             fn cmp_value_eq(
                 _lhs: Self,
@@ -4948,3 +4955,270 @@ impl ToExpr for SimIoForGlobal {
         }
     }
 }
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub struct StructuralEqFlags {
+    pub assume_padding_is_zeroed: bool,
+}
+
+impl StructuralEqFlags {
+    pub const DEFAULT: Self = Self {
+        assume_padding_is_zeroed: false,
+    };
+}
+
+impl Default for StructuralEqFlags {
+    fn default() -> Self {
+        Self::DEFAULT
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub enum StructuralEqError {
+    TypesAreNotEqual {
+        lhs: CanonicalType,
+        rhs: CanonicalType,
+    },
+    TypeContainsSimOnly {
+        ty: CanonicalType,
+    },
+}
+
+impl fmt::Display for StructuralEqError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::TypesAreNotEqual { lhs, rhs } => write!(
+                f,
+                "StructuralEq lhs type must be the same as rhs type:\nlhs: {lhs:#?}\nrhs: {rhs:#?}\n",
+            ),
+            Self::TypeContainsSimOnly { ty } => write!(
+                f,
+                "StructuralEq input type must not contain SimOnly type: {ty:#?}",
+            ),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct StructuralEq {
+    lhs: Expr<CanonicalType>,
+    rhs: Expr<CanonicalType>,
+    flags: StructuralEqFlags,
+    literal_bits: Result<Interned<BitSlice>, NotALiteralExpr>,
+}
+
+impl StructuralEq {
+    fn literal_eq(
+        ty: CanonicalType,
+        l: Interned<BitSlice>,
+        r: Interned<BitSlice>,
+    ) -> Result<bool, NotALiteralExpr> {
+        enum PairRefOrInternedBitSlice<'a> {
+            Ref(&'a BitSlice, &'a BitSlice),
+            Interned(Interned<BitSlice>, Interned<BitSlice>),
+        }
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize(CanonicalType);
+        impl MemoizeGeneric for MyMemoize {
+            type InputRef<'a> = (&'a BitSlice, &'a BitSlice);
+            type InputOwned = (Interned<BitSlice>, Interned<BitSlice>);
+            type InputCow<'a> = PairRefOrInternedBitSlice<'a>;
+            type Output = Result<bool, NotALiteralExpr>;
+
+            fn input_eq(a: Self::InputRef<'_>, b: Self::InputRef<'_>) -> bool {
+                a == b
+            }
+
+            fn input_borrow(input: &Self::InputOwned) -> Self::InputRef<'_> {
+                let (l, r) = input;
+                (l, r)
+            }
+
+            fn input_cow_into_owned(input: Self::InputCow<'_>) -> Self::InputOwned {
+                match input {
+                    PairRefOrInternedBitSlice::Ref(l, r) => (l.intern(), r.intern()),
+                    PairRefOrInternedBitSlice::Interned(l, r) => (l, r),
+                }
+            }
+
+            fn input_cow_borrow<'a>(input: &'a Self::InputCow<'_>) -> Self::InputRef<'a> {
+                match input {
+                    PairRefOrInternedBitSlice::Ref(l, r) => (l, r),
+                    PairRefOrInternedBitSlice::Interned(l, r) => (l, r),
+                }
+            }
+
+            fn input_cow_from_owned<'a>(input: Self::InputOwned) -> Self::InputCow<'a> {
+                let (l, r) = input;
+                PairRefOrInternedBitSlice::Interned(l, r)
+            }
+
+            fn input_cow_from_ref(input: Self::InputRef<'_>) -> Self::InputCow<'_> {
+                let (l, r) = input;
+                PairRefOrInternedBitSlice::Ref(l, r)
+            }
+
+            fn inner(self, input: Self::InputRef<'_>) -> Self::Output {
+                let (mut l, mut r) = input;
+                match self.0 {
+                    CanonicalType::UInt(_)
+                    | CanonicalType::SInt(_)
+                    | CanonicalType::Bool(_)
+                    | CanonicalType::AsyncReset(_)
+                    | CanonicalType::SyncReset(_)
+                    | CanonicalType::Reset(_)
+                    | CanonicalType::Clock(_)
+                    | CanonicalType::PhantomConst(_) => Ok(l == r),
+                    CanonicalType::Array(ty) => {
+                        let element_ty = ty.element();
+                        let element_bit_width = element_ty.bit_width();
+                        let mut eq = true;
+                        for element_index in 0..ty.len() {
+                            if !Self(element_ty).get((
+                                &l[element_bit_width * element_index..][..element_bit_width],
+                                &r[element_bit_width * element_index..][..element_bit_width],
+                            ))? {
+                                eq = false;
+                                break;
+                            }
+                        }
+                        Ok(eq)
+                    }
+                    CanonicalType::Enum(ty) => {
+                        let discriminant_bit_width = ty.discriminant_bit_width();
+                        let (l_discriminant_bits, l_body_bits) = l.split_at(discriminant_bit_width);
+                        let (r_discriminant_bits, r_body_bits) = r.split_at(discriminant_bit_width);
+                        if l_discriminant_bits != r_discriminant_bits {
+                            return Ok(false);
+                        }
+                        let mut discriminant = 0usize;
+                        discriminant.view_bits_mut::<Lsb0>()[..l_discriminant_bits.len()]
+                            .copy_from_bitslice(l_discriminant_bits);
+                        match ty.variants().get(discriminant) {
+                            Some(&EnumVariant {
+                                name: _,
+                                ty: Some(variant_ty),
+                            }) => {
+                                let variant_bit_width = variant_ty.bit_width();
+                                Self(variant_ty).get((
+                                    &l_body_bits[..variant_bit_width],
+                                    &r_body_bits[..variant_bit_width],
+                                ))
+                            }
+                            Some(EnumVariant { name: _, ty: None }) => Ok(true),
+                            None => Err(NotALiteralExpr),
+                        }
+                    }
+                    CanonicalType::Bundle(ty) => {
+                        let mut eq = true;
+                        for field in &ty.fields() {
+                            let field_bit_width = field.ty.bit_width();
+                            let l_field;
+                            let r_field;
+                            (l_field, l) = l.split_at(field_bit_width);
+                            (r_field, r) = r.split_at(field_bit_width);
+                            if !Self(field.ty).get((l_field, r_field))? {
+                                eq = false;
+                                break;
+                            }
+                        }
+                        Ok(eq)
+                    }
+                    CanonicalType::DynSimOnly(_) => unreachable!("doesn't have literal_bits"),
+                    CanonicalType::TraceAsString(ty) => Self(ty.inner_ty()).get((l, r)),
+                }
+            }
+        }
+        MyMemoize(ty).get_owned((l, r))
+    }
+    #[track_caller]
+    pub fn new(lhs: Expr<CanonicalType>, rhs: Expr<CanonicalType>) -> Self {
+        Self::with_flags(lhs, rhs, StructuralEqFlags::DEFAULT)
+    }
+    #[track_caller]
+    pub fn with_flags(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Self {
+        match Self::try_with_flags(lhs, rhs, flags) {
+            Ok(retval) => retval,
+            Err(e) => panic!("{e}"),
+        }
+    }
+    pub fn try_new(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+    ) -> Result<Self, StructuralEqError> {
+        Self::try_with_flags(lhs, rhs, StructuralEqFlags::DEFAULT)
+    }
+    pub fn try_with_flags(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Self, StructuralEqError> {
+        let ty = lhs.ty();
+        let rhs_ty = rhs.ty();
+        if ty != rhs_ty {
+            return Err(StructuralEqError::TypesAreNotEqual {
+                lhs: ty,
+                rhs: rhs_ty,
+            });
+        }
+        if ty.contains_sim_only() {
+            return Err(StructuralEqError::TypeContainsSimOnly { ty });
+        }
+        Ok(Self {
+            lhs,
+            rhs,
+            flags,
+            literal_bits: lhs.to_literal_bits().and_then(|lhs| {
+                let rhs = rhs.to_literal_bits()?;
+                if flags.assume_padding_is_zeroed {
+                    lhs == rhs
+                } else {
+                    Self::literal_eq(ty, lhs, rhs)?
+                }
+                .to_literal_bits()
+            }),
+        })
+    }
+    pub fn lhs(self) -> Expr<CanonicalType> {
+        self.lhs
+    }
+    pub fn rhs(self) -> Expr<CanonicalType> {
+        self.rhs
+    }
+    pub fn flags(self) -> StructuralEqFlags {
+        self.flags
+    }
+}
+
+impl ToLiteralBits for StructuralEq {
+    fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
+        self.literal_bits
+    }
+}
+
+impl_get_target_none!([] StructuralEq);
+
+impl ValueType for StructuralEq {
+    type Type = Bool;
+    type ValueCategory = ValueCategoryExpr;
+
+    fn ty(&self) -> Self::Type {
+        Bool
+    }
+}
+
+impl ToExpr for StructuralEq {
+    fn to_expr(&self) -> Expr<Self::Type> {
+        Expr {
+            __enum: ExprEnum::StructuralEq(*self).intern(),
+            __ty: Bool,
+            __flow: Flow::Source,
+        }
+    }
+}

crates/fayalite/src/firrtl.rs

@@ -7,7 +7,7 @@ use crate::{
     bundle::{BundleField, BundleType},
     enum_::{EnumType, EnumVariant},
     expr::{
-        ExprEnum,
+        CastToImpl, ExprEnum,
         ops::{self, VariantAccess},
         target::{
             Target, TargetBase, TargetPathArrayElement, TargetPathBundleField, TargetPathElement,
@@ -389,6 +389,7 @@ struct BlockDefinitionsCache {
     cast_bits_to_array_exprs: RefCell<HashMap<(String, Array), String>>,
     cast_bits_to_phantom_const_exprs: RefCell<HashMap<(String, PhantomConst), String>>,
     per_module_formal_inputs: RefCell<HashMap<(FormalInput, bool), String>>,
+    structural_eq_exprs: RefCell<HashMap<(String, String), String>>,
 }
 
 struct BlockDefinitions<'a> {
@@ -1774,6 +1775,143 @@ endmodule
             },
         )
     }
+    fn expr_structural_eq_bit<T: CastToImpl<Bool>>(
+        &mut self,
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        definitions: &BlockDefinitions<'_>,
+        const_ty: bool,
+    ) -> Result<String> {
+        self.expr_binary(
+            "eq",
+            Expr::<T>::from_canonical(lhs).cast_to(Bool),
+            Expr::<T>::from_canonical(rhs).cast_to(Bool),
+            definitions,
+            const_ty,
+        )
+    }
+    fn expr_structural_eq(
+        &mut self,
+        ty: CanonicalType,
+        lhs: String,
+        rhs: String,
+        definitions: &BlockDefinitions<'_>,
+        const_ty: bool,
+    ) -> Result<String> {
+        match ty {
+            CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_) => {
+                Ok(format!("eq({lhs}, {rhs})"))
+            }
+            CanonicalType::Array(ty) => {
+                if ty.len() == 1 {
+                    return self.expr_structural_eq(
+                        ty.element(),
+                        lhs + "[0]",
+                        rhs + "[0]",
+                        definitions,
+                        const_ty,
+                    );
+                } else if ty.is_empty() {
+                    return Ok(self.bool_literal(true));
+                }
+                definitions.get_or_write_definition(
+                    (lhs, rhs),
+                    |c| &c.structural_eq_exprs,
+                    |definitions, (lhs, rhs)| {
+                        let mut retval = None;
+                        for array_index in 0..ty.len() {
+                            let element_eq = self.expr_structural_eq(
+                                ty.element(),
+                                format!("{lhs}[{array_index}]"),
+                                format!("{rhs}[{array_index}]"),
+                                &definitions,
+                                const_ty,
+                            )?;
+                            retval = match retval {
+                                Some(old_eq) => {
+                                    let ident = self.module.ns.make_new("_array_structural_eq");
+                                    definitions
+                                        .add_definition_line(format_args!("wire {ident}: UInt<1>"));
+                                    definitions.add_definition_line(format_args!(
+                                        "connect {ident}, and({old_eq}, {element_eq})"
+                                    ));
+                                    Some(ident.to_string())
+                                }
+                                None => Some(element_eq),
+                            };
+                        }
+                        Ok(retval.expect("known to be Some"))
+                    },
+                )
+            }
+            CanonicalType::Enum(ty) => {
+                let lhs = self.expr_cast_enum_to_bits(
+                    lhs,
+                    ty,
+                    definitions,
+                    Indent {
+                        indent_depth: &Cell::new(0),
+                        indent: self.indent.indent,
+                    },
+                )?;
+                let rhs = self.expr_cast_enum_to_bits(
+                    rhs,
+                    ty,
+                    definitions,
+                    Indent {
+                        indent_depth: &Cell::new(0),
+                        indent: self.indent.indent,
+                    },
+                )?;
+                Ok(format!("eq({lhs}, {rhs})"))
+            }
+            CanonicalType::Bundle(ty) => {
+                let fields = ty.fields();
+                if fields.is_empty() {
+                    return Ok(self.bool_literal(true));
+                }
+                definitions.get_or_write_definition(
+                    (lhs, rhs),
+                    |c| &c.structural_eq_exprs,
+                    |definitions, (lhs, rhs)| {
+                        let mut retval = None;
+                        for field in fields {
+                            let field_ident = self.type_state.get_bundle_field(ty, field.name)?;
+                            let field_eq = self.expr_structural_eq(
+                                field.ty,
+                                format!("{lhs}.{field_ident}"),
+                                format!("{rhs}.{field_ident}"),
+                                &definitions,
+                                const_ty,
+                            )?;
+                            retval = match retval {
+                                Some(old_eq) => {
+                                    let ident = self.module.ns.make_new("_bundle_structural_eq");
+                                    definitions
+                                        .add_definition_line(format_args!("wire {ident}: UInt<1>"));
+                                    definitions.add_definition_line(format_args!(
+                                        "connect {ident}, and({old_eq}, {field_eq})"
+                                    ));
+                                    Some(ident.to_string())
+                                }
+                                None => Some(field_eq),
+                            };
+                        }
+                        Ok(retval.expect("known to be Some"))
+                    },
+                )
+            }
+            CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_) => Ok(format!("eq(asUInt({lhs}), asUInt({rhs}))")),
+            CanonicalType::PhantomConst(_) => Ok(self.bool_literal(true)),
+            CanonicalType::DynSimOnly(_) => Err(FirrtlError::SimOnlyValuesAreNotPermitted.into()),
+            CanonicalType::TraceAsString(ty) => {
+                self.expr_structural_eq(ty.inner_ty(), lhs, rhs, definitions, const_ty)
+            }
+        }
+    }
     fn expr(
         &mut self,
         expr: Expr<CanonicalType>,
@@ -2117,6 +2255,13 @@ endmodule
             ExprEnum::TraceAsStringAsInner(expr) => {
                 self.expr(Expr::canonical(expr.arg()), definitions, const_ty)
             }
+            ExprEnum::StructuralEq(expr) => {
+                let ty = expr.lhs().ty();
+                assert_eq!(ty, expr.rhs().ty());
+                let lhs = self.expr(expr.lhs(), definitions, const_ty)?;
+                let rhs = self.expr(expr.rhs(), definitions, const_ty)?;
+                self.expr_structural_eq(ty, lhs, rhs, definitions, const_ty)
+            }
             ExprEnum::ModuleIO(expr) => Ok(self.module.ns.get(expr.name_id()).to_string()),
             ExprEnum::Instance(expr) => {
                 assert!(!const_ty, "not a constant");

crates/fayalite/src/int/uint_in_range.rs

@@ -177,6 +177,8 @@ impl CastToImpl<UIntInRangeMaskType> for Bool {
 }
 
 impl HdlPartialEqImpl<Self> for UIntInRangeMaskType {
+    const TRY_STRUCTURAL_EQ: bool = true;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,
@@ -570,6 +572,8 @@ macro_rules! define_uint_in_range_type {
             HdlPartialEqImpl<$UIntInRangeType<RhsStart, RhsEnd>>
             for $UIntInRangeType<LhsStart, LhsEnd>
         {
+            const TRY_STRUCTURAL_EQ: bool = true;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,
@@ -657,6 +661,8 @@ macro_rules! define_uint_in_range_type {
         impl<Start: Size, End: Size, Width: Size> HdlPartialEqImpl<UIntType<Width>>
             for $UIntInRangeType<Start, End>
         {
+            const TRY_STRUCTURAL_EQ: bool = false;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,
@@ -676,6 +682,8 @@ macro_rules! define_uint_in_range_type {
         impl<Start: Size, End: Size, Width: Size> HdlPartialEqImpl<$UIntInRangeType<Start, End>>
             for UIntType<Width>
         {
+            const TRY_STRUCTURAL_EQ: bool = false;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,

crates/fayalite/src/module.rs

@@ -2206,6 +2206,7 @@ impl transform::visit::Visitor for AssertExprValidity<'_> {
             | ExprEnum::CastBitsTo(_)
             | ExprEnum::ToTraceAsString(_)
             | ExprEnum::TraceAsStringAsInner(_)
+            | ExprEnum::StructuralEq(_)
             | ExprEnum::FormalInput(_) => v.default_visit(self),
             ExprEnum::VariantAccess(_)
             | ExprEnum::ModuleIO(_)

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

@@ -1208,6 +1208,7 @@ impl<P: Pass> RunPass<P> for ExprEnum {
                 Ok(expr.run_pass(pass_args)?.map(ExprEnum::from))
             }
             ExprEnum::ToTraceAsString(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
+            ExprEnum::StructuralEq(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::ModuleIO(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::Instance(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::Wire(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
@@ -1653,6 +1654,35 @@ impl RunPassExpr for ops::ToTraceAsString {
     }
 }
 
+impl RunPassExpr for ops::StructuralEq {
+    type Args<'a> = [Expr<CanonicalType>; 2];
+
+    fn args<'a>(&'a self) -> Self::Args<'a> {
+        [self.lhs(), self.rhs()]
+    }
+
+    fn source_location(&self) -> Option<SourceLocation> {
+        None
+    }
+
+    fn union_parts(
+        &self,
+        _resets: Resets,
+        args_resets: Vec<Resets>,
+        mut pass_args: PassArgs<'_, BuildResetGraph>,
+    ) -> Result<(), DeduceResetsError> {
+        pass_args.union(args_resets[0], args_resets[1], None)
+    }
+
+    fn new(
+        &self,
+        _ty: CanonicalType,
+        new_args: Vec<Expr<CanonicalType>>,
+    ) -> Result<Self, DeduceResetsError> {
+        Ok(Self::with_flags(new_args[0], new_args[1], self.flags()))
+    }
+}
+
 impl RunPassExpr for ModuleIO<CanonicalType> {
     type Args<'a> = [Expr<CanonicalType>; 0];
 

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

@@ -1,28 +1,23 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    array::{Array, ArrayType},
+    bundle::{BundleField, BundleType},
-    bundle::{Bundle, BundleField, BundleType},
+    enum_::{EnumType, EnumVariant},
-    enum_::{Enum, EnumType, EnumVariant},
     expr::{
-        CastBitsTo, CastTo, CastToBits, Expr, ExprEnum, HdlPartialEq, ToExpr, ValueType,
+        ExprEnum,
-        ops::{self, EnumLiteral},
+        ops::{self, EnumLiteral, StructuralEq, StructuralEqFlags},
     },
-    hdl,
-    int::UInt,
     intern::{Intern, InternSlice, Interned, Memoize},
-    memory::{DynPortType, Mem, MemPort},
+    memory::{DynPortType, MemPort},
     module::{
-        Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
+        Block, Id, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
         transform::visit::{Fold, Folder},
     },
-    source_location::SourceLocation,
+    prelude::*,
-    ty::{CanonicalType, TraceAsString, Type},
     util::HashMap,
-    wire::Wire,
 };
-use core::fmt;
 use serde::{Deserialize, Serialize};
+use std::fmt;
 
 #[derive(Debug)]
 pub enum SimplifyEnumsError {
@@ -97,6 +92,7 @@ enum EnumTypeState {
 struct ModuleState {
     module_name: NameId,
     expr_cache: HashMap<ExprEnum, ExprEnum>,
+    source_location: SourceLocation,
 }
 
 impl ModuleState {
@@ -110,6 +106,45 @@ struct State {
     replacement_mem_ports: HashMap<MemPort<DynPortType>, Wire<CanonicalType>>,
     kind: SimplifyEnumsKind,
     module_state_stack: Vec<ModuleState>,
+    new_prefix_stmts_for_block: Vec<Stmt>,
+    new_suffix_stmts_for_block: Vec<Stmt>,
+}
+
+struct BlockScope<'a> {
+    state: &'a mut State,
+    parent_new_prefix_stmts_for_block: Vec<Stmt>,
+    parent_new_suffix_stmts_for_block: Vec<Stmt>,
+}
+
+impl<'a> BlockScope<'a> {
+    fn new(
+        state: &'a mut State,
+        new_prefix_stmts_for_block: Vec<Stmt>,
+        new_suffix_stmts_for_block: Vec<Stmt>,
+    ) -> Self {
+        let parent_new_prefix_stmts_for_block = std::mem::replace(
+            &mut state.new_prefix_stmts_for_block,
+            new_prefix_stmts_for_block,
+        );
+        let parent_new_suffix_stmts_for_block = std::mem::replace(
+            &mut state.new_suffix_stmts_for_block,
+            new_suffix_stmts_for_block,
+        );
+        Self {
+            state,
+            parent_new_prefix_stmts_for_block,
+            parent_new_suffix_stmts_for_block,
+        }
+    }
+}
+
+impl Drop for BlockScope<'_> {
+    fn drop(&mut self) {
+        self.state.new_prefix_stmts_for_block =
+            std::mem::take(&mut self.parent_new_prefix_stmts_for_block);
+        self.state.new_suffix_stmts_for_block =
+            std::mem::take(&mut self.parent_new_suffix_stmts_for_block);
+    }
 }
 
 impl State {
@@ -549,6 +584,185 @@ impl State {
             | CanonicalType::DynSimOnly(_) => unreachable!(),
         }
     }
+    fn handle_enum_structural_eq(
+        &mut self,
+        unfolded_ty: Enum,
+        folded_lhs: Expr<CanonicalType>,
+        folded_rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Expr<Bool>, SimplifyEnumsError> {
+        if flags.assume_padding_is_zeroed {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        let enum_type_state = self.get_or_make_enum_type_state(unfolded_ty)?;
+        if let EnumTypeState::Unchanged = enum_type_state {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        let module_state = self.module_state_stack.last_mut().unwrap();
+        let source_location = module_state.source_location;
+        let output_wire = Wire::new_unchecked(
+            module_state.gen_name("__enum_structural_eq"),
+            source_location,
+            Bool,
+        );
+        self.new_prefix_stmts_for_block.push(
+            StmtWire {
+                annotations: Interned::default(),
+                wire: output_wire.canonical(),
+            }
+            .into(),
+        );
+        let output_wire = output_wire.to_expr();
+        self.new_suffix_stmts_for_block.push(
+            StmtConnect {
+                lhs: Expr::canonical(output_wire),
+                rhs: Expr::canonical(false.to_expr()),
+                source_location,
+            }
+            .into(),
+        );
+        let tags_eq = match enum_type_state {
+            EnumTypeState::TagEnumAndBody(_) => StructuralEq::with_flags(
+                Expr::canonical(Expr::<TagAndBody<Enum, UInt>>::from_canonical(folded_lhs).tag),
+                Expr::canonical(Expr::<TagAndBody<Enum, UInt>>::from_canonical(folded_rhs).tag),
+                StructuralEqFlags {
+                    assume_padding_is_zeroed: true,
+                },
+            )
+            .to_expr(),
+            EnumTypeState::TagUIntAndBody(_) => {
+                let lhs = Expr::<TagAndBody<UInt, UInt>>::from_canonical(folded_lhs).tag;
+                let rhs = Expr::<TagAndBody<UInt, UInt>>::from_canonical(folded_rhs).tag;
+                lhs.cmp_eq(rhs)
+            }
+            EnumTypeState::UInt(_) => {
+                let lhs_int_tag_expr = Expr::<UInt>::from_canonical(folded_lhs)
+                    [..unfolded_ty.discriminant_bit_width()];
+                let rhs_int_tag_expr = Expr::<UInt>::from_canonical(folded_rhs)
+                    [..unfolded_ty.discriminant_bit_width()];
+                lhs_int_tag_expr.cmp_eq(rhs_int_tag_expr)
+            }
+            EnumTypeState::Unchanged => unreachable!(),
+        };
+        let mut match_arms = Vec::with_capacity(unfolded_ty.variants().len());
+        for (variant_index, variant) in unfolded_ty.variants().iter().enumerate() {
+            let block_scope = BlockScope::new(self, vec![], vec![]);
+            let this = &mut *block_scope.state;
+            let eq = if let Some(variant_ty) = variant.ty {
+                let folded_lhs =
+                    this.handle_variant_access(unfolded_ty, folded_lhs, variant_index)?;
+                let folded_rhs =
+                    this.handle_variant_access(unfolded_ty, folded_rhs, variant_index)?;
+                this.handle_structural_eq(variant_ty, folded_lhs, folded_rhs, flags)?
+            } else {
+                true.to_expr()
+            };
+            match_arms.push(Block {
+                memories: [].intern_slice(),
+                stmts: this
+                    .new_prefix_stmts_for_block
+                    .drain(..)
+                    .chain([StmtConnect {
+                        lhs: Expr::canonical(output_wire),
+                        rhs: Expr::canonical(eq),
+                        source_location,
+                    }
+                    .into()])
+                    .chain(this.new_suffix_stmts_for_block.drain(..))
+                    .collect(),
+            });
+        }
+        let match_stmt =
+            self.handle_match(unfolded_ty, folded_lhs, source_location, &match_arms)?;
+        self.new_suffix_stmts_for_block.push(
+            StmtIf {
+                cond: tags_eq,
+                source_location,
+                blocks: [
+                    Block {
+                        memories: [].intern_slice(),
+                        stmts: [match_stmt].intern_slice(),
+                    },
+                    Block {
+                        memories: [].intern_slice(),
+                        stmts: [].intern_slice(),
+                    },
+                ],
+            }
+            .into(),
+        );
+        Ok(output_wire)
+    }
+    fn handle_structural_eq(
+        &mut self,
+        unfolded_ty: CanonicalType,
+        folded_lhs: Expr<CanonicalType>,
+        folded_rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Expr<Bool>, SimplifyEnumsError> {
+        if !contains_any_enum_types(unfolded_ty) {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        match unfolded_ty {
+            CanonicalType::Array(unfolded_ty) => {
+                let unfolded_element_ty = unfolded_ty.element();
+                let mut retval = None;
+                for i in 0..unfolded_ty.len() {
+                    let element_eq = self.handle_structural_eq(
+                        unfolded_element_ty,
+                        ops::ArrayIndex::new(Expr::from_canonical(folded_lhs), i).to_expr(),
+                        ops::ArrayIndex::new(Expr::from_canonical(folded_rhs), i).to_expr(),
+                        flags,
+                    )?;
+                    retval = Some(match retval {
+                        Some(old_eq) => old_eq & element_eq,
+                        None => element_eq,
+                    });
+                }
+                Ok(retval.unwrap_or_else(|| {
+                    StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr()
+                }))
+            }
+            CanonicalType::Enum(unfolded_ty) => {
+                self.handle_enum_structural_eq(unfolded_ty, folded_lhs, folded_rhs, flags)
+            }
+            CanonicalType::Bundle(unfolded_ty) => {
+                let mut retval = None;
+                for (i, field) in unfolded_ty.fields().iter().enumerate() {
+                    let field_eq = self.handle_structural_eq(
+                        field.ty,
+                        ops::FieldAccess::new_by_index(Expr::from_canonical(folded_lhs), i)
+                            .to_expr(),
+                        ops::FieldAccess::new_by_index(Expr::from_canonical(folded_rhs), i)
+                            .to_expr(),
+                        flags,
+                    )?;
+                    retval = Some(match retval {
+                        Some(old_eq) => old_eq & field_eq,
+                        None => field_eq,
+                    });
+                }
+                Ok(retval.unwrap_or_else(|| {
+                    StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr()
+                }))
+            }
+            CanonicalType::TraceAsString(unfolded_ty) => self.handle_structural_eq(
+                unfolded_ty.inner_ty(),
+                *Expr::<TraceAsString>::from_canonical(folded_lhs),
+                *Expr::<TraceAsString>::from_canonical(folded_rhs),
+                flags,
+            ),
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => unreachable!("doesn't contain any enum types"),
+        }
+    }
 }
 
 fn connect_port(
@@ -677,6 +891,7 @@ impl Folder for State {
         self.module_state_stack.push(ModuleState {
             module_name: v.name_id(),
             expr_cache: HashMap::default(),
+            source_location: v.source_location(),
         });
         let retval = Fold::default_fold(v, self);
         self.module_state_stack.pop();
@@ -710,6 +925,18 @@ impl Folder for State {
                     op.variant_index(),
                 )?)
             }
+            ExprEnum::StructuralEq(op) => {
+                let ty = op.lhs().ty();
+                assert_eq!(ty, op.rhs().ty());
+                let folded_lhs = Expr::canonical(op.lhs()).fold(self)?;
+                let folded_rhs = Expr::canonical(op.rhs()).fold(self)?;
+                *Expr::expr_enum(self.handle_structural_eq(
+                    ty,
+                    folded_lhs,
+                    folded_rhs,
+                    op.flags(),
+                )?)
+            }
             ExprEnum::MemPort(mem_port) => {
                 if let Some(&wire) = self.replacement_mem_ports.get(&mem_port) {
                     ExprEnum::Wire(wire)
@@ -837,11 +1064,13 @@ impl Folder for State {
     }
 
     fn fold_block(&mut self, block: Block) -> Result<Block, Self::Error> {
+        let block_scope = BlockScope::new(self, vec![], vec![]);
+        let this = &mut *block_scope.state;
         let mut memories = vec![];
         let mut stmts = vec![];
         for memory in block.memories {
             let old_element_ty = memory.array_type().element();
-            let new_element_ty = memory.array_type().element().fold(self)?;
+            let new_element_ty = memory.array_type().element().fold(this)?;
             if new_element_ty != old_element_ty {
                 let mut new_ports = vec![];
                 for port in memory.ports() {
@@ -867,7 +1096,7 @@ impl Folder for State {
                         continue;
                     }
                     let wire = Wire::new_unchecked(
-                        self.module_state_stack
+                        this.module_state_stack
                             .last_mut()
                             .unwrap()
                             .gen_name(&format!(
@@ -891,7 +1120,7 @@ impl Folder for State {
                         Expr::canonical(wire.to_expr()),
                         port.source_location(),
                     );
-                    self.replacement_mem_ports.insert(port, wire.canonical());
+                    this.replacement_mem_ports.insert(port, wire.canonical());
                 }
                 memories.push(Mem::new_unchecked(
                     memory.scoped_name(),
@@ -906,10 +1135,12 @@ impl Folder for State {
                     memory.mem_annotations(),
                 ));
             } else {
-                memories.push(memory.fold(self)?);
+                memories.push(memory.fold(this)?);
             }
         }
-        stmts.extend_from_slice(&block.stmts.fold(self)?);
+        stmts.extend_from_slice(&block.stmts.fold(this)?);
+        stmts.splice(0..0, this.new_prefix_stmts_for_block.drain(..));
+        stmts.extend_from_slice(&this.new_suffix_stmts_for_block);
         Ok(Block {
             memories: Intern::intern_owned(memories),
             stmts: Intern::intern_owned(stmts),
@@ -1031,10 +1262,13 @@ pub fn simplify_enums(
     module: Interned<Module<Bundle>>,
     kind: SimplifyEnumsKind,
 ) -> Result<Interned<Module<Bundle>>, SimplifyEnumsError> {
+    // TODO: deduce StructuralEq's assume_padding_is_zeroed
     module.fold(&mut State {
         enum_types: HashMap::default(),
         replacement_mem_ports: HashMap::default(),
         kind,
         module_state_stack: vec![],
+        new_prefix_stmts_for_block: vec![],
+        new_suffix_stmts_for_block: vec![],
     })
 }

crates/fayalite/src/phantom_const.rs

@@ -384,6 +384,8 @@ impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for PhantomConst<T> {
 }
 
 impl<T: ?Sized + PhantomConstValue> HdlPartialEqImpl<Self> for PhantomConst<T> {
+    const TRY_STRUCTURAL_EQ: bool = true;
+
     #[track_caller]
     fn cmp_value_eq(
         lhs: Self,

crates/fayalite/src/sim/compiler.rs

@@ -3974,6 +3974,10 @@ impl Compiler {
                 .compile_expr(instantiated_module_or_global, Expr::canonical(expr.arg()))
                 .map_ty(TraceAsString::from_canonical)
                 .inner(),
+            ExprEnum::StructuralEq(expr) => self.compile_expr(
+                instantiated_module_or_global,
+                Expr::canonical(expr.lhs().cast_to_bits().cmp_eq(expr.rhs().cast_to_bits())),
+            ),
             ExprEnum::ModuleIO(expr) => self
                 .compile_value(TargetInInstantiatedModuleOrGlobal::from_target(
                     instantiated_module_or_global,

crates/fayalite/src/sim/value.rs

@@ -1508,6 +1508,8 @@ impl<T: SimOnlyValueTrait> ToSimValue for SimOnlyValue<T> {
 }
 
 impl HdlPartialEqImpl<Self> for DynSimOnly {
+    const TRY_STRUCTURAL_EQ: bool = false;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,
@@ -1527,6 +1529,8 @@ impl HdlPartialEqImpl<Self> for DynSimOnly {
 impl<L: SimOnlyValueTrait + PartialEq<R>, R: SimOnlyValueTrait> HdlPartialEqImpl<SimOnly<R>>
     for SimOnly<L>
 {
+    const TRY_STRUCTURAL_EQ: bool = false;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,

crates/fayalite/src/ty.rs

@@ -354,6 +354,39 @@ impl CanonicalType {
         }
         MyMemoize.get_owned((self, other))
     }
+    pub fn contains_sim_only(self) -> bool {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize;
+        impl Memoize for MyMemoize {
+            type Input = CanonicalType;
+            type InputOwned = CanonicalType;
+            type Output = bool;
+
+            fn inner(self, input: &Self::Input) -> Self::Output {
+                match input {
+                    CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_) => {
+                        false
+                    }
+                    CanonicalType::Array(ty) => ty.element().contains_sim_only(),
+                    CanonicalType::Enum(ty) => ty
+                        .variants()
+                        .iter()
+                        .any(|v| v.ty.is_some_and(CanonicalType::contains_sim_only)),
+                    CanonicalType::Bundle(ty) => {
+                        ty.fields().iter().any(|v| v.ty.contains_sim_only())
+                    }
+                    CanonicalType::AsyncReset(_)
+                    | CanonicalType::SyncReset(_)
+                    | CanonicalType::Reset(_)
+                    | CanonicalType::Clock(_)
+                    | CanonicalType::PhantomConst(_) => false,
+                    CanonicalType::DynSimOnly(_) => true,
+                    CanonicalType::TraceAsString(ty) => ty.inner_ty().contains_sim_only(),
+                }
+            }
+        }
+        MyMemoize.get_owned(self)
+    }
 }
 
 pub trait MatchVariantAndInactiveScope: Sized {
@@ -1882,6 +1915,8 @@ fn trace_as_string_cow_into_inner_value<T: Type>(
 }
 
 impl<T: HdlPartialEqImpl<U>, U: Type> HdlPartialEqImpl<TraceAsString<U>> for TraceAsString<T> {
+    const TRY_STRUCTURAL_EQ: bool = <T as HdlPartialEqImpl<U>>::TRY_STRUCTURAL_EQ;
+
     #[track_caller]
     fn cmp_value_eq(
         lhs: Self,

crates/fayalite/tests/module.rs

@@ -709,44 +709,35 @@ circuit check_enum_cmp_eq:
         input lhs: Ty0 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty0 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire _cast_enum_to_bits_expr: UInt<10>
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        match lhs:
-        match lhs: @[module-XXXXXXXXXX.rs 5:1]
             A:
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<10>(0)
-                    A:
+            B(_cast_enum_to_bits_expr_B):
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, pad(cat(_cast_enum_to_bits_expr_B, UInt<2>(1)), 10)
-                    B(_match_arm_value):
+            C(_cast_enum_to_bits_expr_C):
-                        skip
+                wire _cast_array_to_bits_expr: UInt<1>[3]
-                    C(_match_arm_value_1):
+                connect _cast_array_to_bits_expr[0], _cast_enum_to_bits_expr_C[0]
-                        skip
+                connect _cast_array_to_bits_expr[1], _cast_enum_to_bits_expr_C[1]
-            B(_match_arm_value_2):
+                connect _cast_array_to_bits_expr[2], _cast_enum_to_bits_expr_C[2]
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_to_bits_expr: UInt<3>
-                    A:
+                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]))
-                        skip
+                connect _cast_enum_to_bits_expr, pad(cat(_cast_to_bits_expr, UInt<2>(2)), 10)
-                    B(_match_arm_value_3):
+        wire _cast_enum_to_bits_expr_1: UInt<10>
-                        connect TestEnum_cmp_eq, eq(_match_arm_value_2, _match_arm_value_3) @[module-XXXXXXXXXX.rs 5:1]
+        match rhs:
-                    C(_match_arm_value_4):
+            A:
-                        skip
+                connect _cast_enum_to_bits_expr_1, UInt<10>(0)
-            C(_match_arm_value_5):
+            B(_cast_enum_to_bits_expr_B_1):
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr_1, pad(cat(_cast_enum_to_bits_expr_B_1, UInt<2>(1)), 10)
-                    A:
+            C(_cast_enum_to_bits_expr_C_1):
-                        skip
+                wire _cast_array_to_bits_expr_1: UInt<1>[3]
-                    B(_match_arm_value_6):
+                connect _cast_array_to_bits_expr_1[0], _cast_enum_to_bits_expr_C_1[0]
-                        skip
+                connect _cast_array_to_bits_expr_1[1], _cast_enum_to_bits_expr_C_1[1]
-                    C(_match_arm_value_7):
+                connect _cast_array_to_bits_expr_1[2], _cast_enum_to_bits_expr_C_1[2]
-                        wire _array_literal_expr: UInt<1>[3]
+                wire _cast_to_bits_expr_1: UInt<3>
-                        connect _array_literal_expr[0], eq(_match_arm_value_5[0], _match_arm_value_7[0])
+                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 _array_literal_expr[1], eq(_match_arm_value_5[1], _match_arm_value_7[1])
+                connect _cast_enum_to_bits_expr_1, pad(cat(_cast_to_bits_expr_1, UInt<2>(2)), 10)
-                        connect _array_literal_expr[2], eq(_match_arm_value_5[2], _match_arm_value_7[2])
+        connect eq, eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 5:1]
-                        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 TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -764,60 +755,53 @@ circuit check_enum_cmp_eq:
         input lhs: Ty1 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty1 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        match lhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr: UInt<2>
+        match lhs.tag:
             A:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(0)
-                    A:
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-                    B:
-                        skip
-                    C:
-                        skip
             B:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(1)
-                    A:
-                        skip
-                    B:
-                        connect TestEnum_cmp_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
-                    C:
-                        skip
             C:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(2)
-                    A:
+        wire _cast_enum_to_bits_expr_1: UInt<2>
-                        skip
+        match rhs.tag:
-                    B:
+            A:
-                        skip
+                connect _cast_enum_to_bits_expr_1, UInt<2>(0)
-                    C:
+            B:
-                        wire _array_literal_expr: UInt<1>[3]
+                connect _cast_enum_to_bits_expr_1, UInt<2>(1)
-                        wire _cast_bits_to_array_expr: UInt<1>[3]
+            C:
-                        wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_enum_to_bits_expr_1, UInt<2>(2)
-                        connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+        when eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1): @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+            match lhs.tag: @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                A:
-                        connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                    connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                B:
-                        connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                    connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-                        wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                C:
-                        wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                    wire _cast_bits_to_array_expr: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
+                    wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                    connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
+                    connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-                        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
+                    connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
+                    connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-                        connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
+                    connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-                        connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
+                    connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-                        connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
+                    wire _cast_bits_to_array_expr_1: UInt<1>[3]
-                        connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2])
+                    wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-                        wire _cast_array_to_bits_expr: UInt<1>[3]
+                    connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
-                        connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
+                    connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-                        connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
+                    connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-                        connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
+                    connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-                        wire _cast_to_bits_expr: UInt<3>
+                    connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-                        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 _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-                        connect TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
+                    wire _array_structural_eq: UInt<1>
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
+                    connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
+                    wire _array_structural_eq_1: UInt<1>
+                    connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
+                    connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -834,51 +818,36 @@ circuit check_enum_cmp_eq:
         input lhs: Ty0 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty0 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        when eq(lhs.tag, rhs.tag): @[module-XXXXXXXXXX.rs 1:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+            when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                skip
+            else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
-        else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+            else:
-                skip
+                wire _cast_bits_to_array_expr: UInt<1>[3]
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                connect TestEnum_cmp_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-        else when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            skip
+                connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-        else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-            skip
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-        else:
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _array_literal_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _array_structural_eq: UInt<1>
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
-            wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                wire _array_structural_eq_1: UInt<1>
-            connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
-            connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
-            connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[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 TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -894,51 +863,36 @@ circuit check_enum_cmp_eq:
         input lhs: UInt<10> @[module-XXXXXXXXXX.rs 2:1]
         input rhs: UInt<10> @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        when eq(bits(lhs, 1, 0), bits(rhs, 1, 0)): @[module-XXXXXXXXXX.rs 1:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+            when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                skip
+            else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
-        else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+            else:
-                skip
+                wire _cast_bits_to_array_expr: UInt<1>[3]
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                connect TestEnum_cmp_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            skip
+                connect _cast_bits_to_array_expr_flattened[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-            skip
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
-        else:
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _array_literal_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_flattened[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
+                connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _array_structural_eq: UInt<1>
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
-            wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                wire _array_structural_eq_1: UInt<1>
-            connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
-            connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
-            connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[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 TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
 }
@@ -4931,12 +4885,14 @@ circuit check_struct_cmp_eq:
         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]
+        wire _bundle_structural_eq: UInt<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 _bundle_structural_eq, and(eq(test_struct_lhs.a, test_struct_rhs.a), eq(test_struct_lhs.b, test_struct_rhs.b))
+        connect test_struct_cmp_eq, _bundle_structural_eq @[module-XXXXXXXXXX.rs 11:1]
+        connect test_struct_cmp_ne, not(_bundle_structural_eq) @[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_2_cmp_ne, not(eq(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]
+        connect test_struct_3_cmp_ne, not(UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 25:1]
 ",
     };
 }

crates/fayalite/tests/ui/simvalue_is_not_internable.stderr

@@ -75,7 +75,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs
@@ -214,7 +214,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs
@@ -326,7 +326,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs

crates/fayalite/visit_types.json

@@ -1055,6 +1055,15 @@
                 "global()": "Visible"
             }
         },
+        "ops::StructuralEq": {
+            "data": {
+                "$kind": "Struct",
+                "$constructor": "ops::StructuralEq::with_flags",
+                "lhs()": "Visible",
+                "rhs()": "Visible",
+                "flags()": "Opaque"
+            }
+        },
         "BlockId": {
             "data": {
                 "$kind": "Opaque"