Merge branch 'YosysHQ:master' into issue/2616

2025-04-16 13:58:47 +00:00 · 2023-07-01 11:10:27 -07:00 · 2023-07-01 11:10:27 -07:00 · f9f7a4e9db
parent 932cc67edf b5b0b7e839
commit f9f7a4e9db
35 changed files with 1399 additions and 203 deletions
--- a/15
+++ b/15
@ -2,9 +2,22 @@
 List of major changes and improvements between releases
 =======================================================

-Yosys 0.29 .. Yosys 0.29-dev
+Yosys 0.30 .. Yosys 0.31-dev
 --------------------------

+Yosys 0.29 .. Yosys 0.30
+--------------------------
+ * New commands and options
+    - Added "recover_names" pass to recover names post-mapping.
+
+ * Gowin support
+    - Added remaining primitives blackboxes.
+
+ * Various
+    - "show -colorattr" will now color the cells, wires, and 
+      connection arrows.
+    - "show -viewer none" will not execute viewer.
+
 Yosys 0.28 .. Yosys 0.29
 --------------------------
 * New commands and options
--- a/23
+++ b/23
@ -141,7 +141,7 @@ LDLIBS += -lrt
 endif
 endif

-YOSYS_VER := 0.29+44
+YOSYS_VER := 0.30+48

 # Note: We arrange for .gitcommit to contain the (short) commit hash in
 # tarballs generated with git-archive(1) using .gitattributes. The git repo
@ -157,7 +157,7 @@ endif
 OBJS = kernel/version_$(GIT_REV).o

 bumpversion:
-	sed -i "/^YOSYS_VER := / s/+[0-9][0-9]*$$/+`git log --oneline 9c5a60e.. | wc -l`/;" Makefile
+	sed -i "/^YOSYS_VER := / s/+[0-9][0-9]*$$/+`git log --oneline f7a8284.. | wc -l`/;" Makefile

 # set 'ABCREV = default' to use abc/ as it is
 #
@ -165,7 +165,7 @@ bumpversion:
 # is just a symlink to your actual ABC working directory, as 'make mrproper'
 # will remove the 'abc' directory and you do not want to accidentally
 # delete your work on ABC..
-ABCREV = 2c1c83f
+ABCREV = bb64142
 ABCPULL = 1
 ABCURL ?= https://github.com/YosysHQ/abc
 ABCMKARGS = CC="$(CXX)" CXX="$(CXX)" ABC_USE_LIBSTDCXX=1 ABC_USE_NAMESPACE=abc VERBOSE=$(Q)
@ -523,6 +523,7 @@ CXXFLAGS += -I$(GHDL_INCLUDE_DIR) -DYOSYS_ENABLE_GHDL
 LDLIBS += $(GHDL_LIB_DIR)/libghdl.a $(file <$(GHDL_LIB_DIR)/libghdl.link)
 endif

+LDLIBS_VERIFIC =
 ifeq ($(ENABLE_VERIFIC),1)
 VERIFIC_DIR ?= /usr/local/src/verific_lib
 VERIFIC_COMPONENTS ?= verilog database util containers hier_tree
@ -548,9 +549,9 @@ CXXFLAGS += -DYOSYSHQ_VERIFIC_EXTENSIONS
 endif
 CXXFLAGS += $(patsubst %,-I$(VERIFIC_DIR)/%,$(VERIFIC_COMPONENTS)) -DYOSYS_ENABLE_VERIFIC
 ifeq ($(OS), Darwin)
-LDLIBS += $(patsubst %,$(VERIFIC_DIR)/%/*-mac.a,$(VERIFIC_COMPONENTS)) -lz
+LDLIBS_VERIFIC += $(foreach comp,$(patsubst %,$(VERIFIC_DIR)/%/*-mac.a,$(VERIFIC_COMPONENTS)),-Wl,-force_load $(comp)) -lz
 else
-LDLIBS += $(patsubst %,$(VERIFIC_DIR)/%/*-linux.a,$(VERIFIC_COMPONENTS)) -lz
+LDLIBS_VERIFIC += -Wl,--whole-archive $(patsubst %,$(VERIFIC_DIR)/%/*-linux.a,$(VERIFIC_COMPONENTS)) -Wl,--no-whole-archive -lz
 endif
 endif

@ -740,13 +741,13 @@ yosys.js: $(filter-out yosysjs-$(YOSYS_VER).zip,$(EXTRA_TARGETS))
 endif

 $(PROGRAM_PREFIX)yosys$(EXE): $(OBJS)
-	$(P) $(LD) -o $(PROGRAM_PREFIX)yosys$(EXE) $(EXE_LDFLAGS) $(LDFLAGS) $(OBJS) $(LDLIBS)
+	$(P) $(LD) -o $(PROGRAM_PREFIX)yosys$(EXE) $(EXE_LDFLAGS) $(LDFLAGS) $(OBJS) $(LDLIBS) $(LDLIBS_VERIFIC)

 libyosys.so: $(filter-out kernel/driver.o,$(OBJS))
 ifeq ($(OS), Darwin)
-	$(P) $(LD) -o libyosys.so -shared -Wl,-install_name,$(LIBDIR)/libyosys.so $(LDFLAGS) $^ $(LDLIBS)
+	$(P) $(LD) -o libyosys.so -shared -Wl,-install_name,$(LIBDIR)/libyosys.so $(LDFLAGS) $^ $(LDLIBS) $(LDLIBS_VERIFIC)
 else
-	$(P) $(LD) -o libyosys.so -shared -Wl,-soname,$(LIBDIR)/libyosys.so $(LDFLAGS) $^ $(LDLIBS)
+	$(P) $(LD) -o libyosys.so -shared -Wl,-soname,$(LIBDIR)/libyosys.so $(LDFLAGS) $^ $(LDLIBS) $(LDLIBS_VERIFIC)
 endif

 %.o: %.cc
@ -797,13 +798,13 @@ ifneq ($(ABCREV),default)
 	$(Q) if test -d abc && test -d abc/.git && ! git -C abc diff-index --quiet HEAD; then \
 		echo 'REEBE: NOP pbagnvaf ybpny zbqvsvpngvbaf! Frg NOPERI=qrsnhyg va Lbflf Znxrsvyr!' | tr 'A-Za-z' 'N-ZA-Mn-za-m'; false; \
 	fi
-	$(Q) if test -d abc && ! test -d abc/.git && ! test "`cat abc/.gitcommit | cut -c1-7`" == "$(ABCREV)"; then \
+	$(Q) if test -d abc && ! test -d abc/.git && ! test "`cat abc/.gitcommit | cut -c1-7`" = "$(ABCREV)"; then \
 		echo 'REEBE: Qbjaybnqrq NOP irefvbaf qbrf abg zngpu! Qbjaybnq sebz:' | tr 'A-Za-z' 'N-ZA-Mn-za-m'; echo $(ABCURL)/archive/$(ABCREV).tar.gz; false; \
 	fi
 # set a variable so the test fails if git fails to run - when comparing outputs directly, empty string would match empty string
-	$(Q) if test -d abc && ! test -d abc/.git && test "`cat abc/.gitcommit | cut -c1-7`" == "$(ABCREV)"; then \
+	$(Q) if test -d abc && ! test -d abc/.git && test "`cat abc/.gitcommit | cut -c1-7`" = "$(ABCREV)"; then \
 		echo "Compiling local copy of ABC"; \
-	elif ! (cd abc 2> /dev/null && rev="`git rev-parse $(ABCREV)`" && test "`git rev-parse HEAD`" == "$$rev"); then \
+	elif ! (cd abc 2> /dev/null && rev="`git rev-parse $(ABCREV)`" && test "`git rev-parse HEAD`" = "$$rev"); then \
 		test $(ABCPULL) -ne 0 || { echo 'REEBE: NOP abg hc gb qngr naq NOPCHYY frg gb 0 va Znxrsvyr!' | tr 'A-Za-z' 'N-ZA-Mn-za-m'; exit 1; }; \
 		echo "Pulling ABC from $(ABCURL):"; set -x; \
 		test -d abc || git clone $(ABCURL) abc; \
--- a/backends/aiger/aiger.cc
+++ b/backends/aiger/aiger.cc
@ -736,6 +736,9 @@ struct AigerWriter
 				auto sig_qy = cell->getPort(cell->type.in(ID($anyconst), ID($anyseq)) ? ID::Y : ID::Q);
 				SigSpec sig = sigmap(sig_qy);

+				if (cell->get_bool_attribute(ID(clk2fflogic)))
+					sig_qy = cell->getPort(ID::D); // For a clk2fflogic $_FF_ the named signal is the D input not the Q output
+
 				for (int i = 0; i < GetSize(sig_qy); i++) {
 					if (sig_qy[i].wire == nullptr || sig[i].wire == nullptr)
 						continue;
--- a/backends/btor/btor.cc
+++ b/backends/btor/btor.cc
@ -728,7 +728,10 @@ struct BtorWorker
 			else
 				btorf("%d state %d %s\n", nid, sid, log_id(symbol));

-			ywmap_state(sig_q);
+			if (cell->get_bool_attribute(ID(clk2fflogic)))
+				ywmap_state(cell->getPort(ID::D)); // For a clk2fflogic FF the named signal is the D input not the Q output
+			else
+				ywmap_state(sig_q);

 			if (nid_init_val >= 0) {
 				int nid_init = next_nid++;
--- a/backends/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/cxxrtl.h
@ -1595,6 +1595,25 @@ value<BitsY> modfloor_ss(const value<BitsA> &a, const value<BitsB> &b) {
 	return r;
 }

+template<size_t BitsY, size_t BitsA, size_t BitsB>
+CXXRTL_ALWAYS_INLINE
+value<BitsY> divfloor_uu(const value<BitsA> &a, const value<BitsB> &b) {
+	return divmod_uu<BitsY>(a, b).first;
+}
+
+// Divfloor. Similar to above: returns q=a//b, where q has the sign of a*b and a=b*q+N.
+// In other words, returns (truncating) a/b, except if a and b have different signs
+// and there's non-zero remainder, subtract one more towards floor.
+template<size_t BitsY, size_t BitsA, size_t BitsB>
+CXXRTL_ALWAYS_INLINE
+value<BitsY> divfloor_ss(const value<BitsA> &a, const value<BitsB> &b) {
+	value<BitsY> q, r;
+	std::tie(q, r) = divmod_ss<BitsY>(a, b);
+	if ((b.is_neg() != a.is_neg()) && !r.is_zero())
+		return sub_uu<BitsY>(q, value<1> { 1u });
+	return q;
+
+}

 // Memory helper
 struct memory_index {
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@ -185,7 +185,7 @@ bool is_binary_cell(RTLIL::IdString type)
 		ID($and), ID($or), ID($xor), ID($xnor), ID($logic_and), ID($logic_or),
 		ID($shl), ID($sshl), ID($shr), ID($sshr), ID($shift), ID($shiftx),
 		ID($eq), ID($ne), ID($eqx), ID($nex), ID($gt), ID($ge), ID($lt), ID($le),
-		ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor));
+		ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor), ID($divfloor));
 }

 bool is_extending_cell(RTLIL::IdString type)
--- a/backends/edif/edif.cc
+++ b/backends/edif/edif.cc
@ -120,6 +120,9 @@ struct EdifBackend : public Backend {
 		log("        sets the delimiting character for module port rename clauses to\n");
 		log("        parentheses, square brackets, or angle brackets.\n");
 		log("\n");
+		log("    -lsbidx\n");
+		log("        use index 0 for the LSB bit of a net or port instead of MSB.\n");
+		log("\n");
 		log("Unfortunately there are different \"flavors\" of the EDIF file format. This\n");
 		log("command generates EDIF files for the Xilinx place&route tools. It might be\n");
 		log("necessary to make small modifications to this command when a different tool\n");
@ -132,6 +135,7 @@ struct EdifBackend : public Backend {
 		std::string top_module_name;
 		bool port_rename = false;
 		bool attr_properties = false;
+		bool lsbidx = false;
 		std::map<RTLIL::IdString, std::map<RTLIL::IdString, int>> lib_cell_ports;
 		bool nogndvcc = false, gndvccy = false, keepmode = false;
 		CellTypes ct(design);
@ -173,6 +177,10 @@ struct EdifBackend : public Backend {
 				}
 				continue;
 			}
+			if (args[argidx] == "-lsbidx") {
+				lsbidx = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(f, filename, args, argidx);
@ -184,6 +192,14 @@ struct EdifBackend : public Backend {

 		for (auto module : design->modules())
 		{
+			lib_cell_ports[module->name];
+
+			for (auto port : module->ports)
+			{
+				Wire *wire = module->wire(port);
+				lib_cell_ports[module->name][port] = std::max(lib_cell_ports[module->name][port], GetSize(wire));
+			}
+
 			if (module->get_blackbox_attribute())
 				continue;

@ -200,7 +216,7 @@ struct EdifBackend : public Backend {
 				if (design->module(cell->type) == nullptr || design->module(cell->type)->get_blackbox_attribute()) {
 					lib_cell_ports[cell->type];
 					for (auto p : cell->connections())
-						lib_cell_ports[cell->type][p.first] = GetSize(p.second);
+						lib_cell_ports[cell->type][p.first] = std::max(lib_cell_ports[cell->type][p.first], GetSize(p.second));
 				}
 			}
 		}
@ -437,7 +453,7 @@ struct EdifBackend : public Backend {
 					*f << ")\n";
 					for (int i = 0; i < wire->width; i++) {
 						RTLIL::SigSpec sig = sigmap(RTLIL::SigSpec(wire, i));
-						net_join_db[sig].insert(make_pair(stringf("(portRef (member %s %d))", EDIF_REF(wire->name), GetSize(wire)-i-1), wire->port_input));
+						net_join_db[sig].insert(make_pair(stringf("(portRef (member %s %d))", EDIF_REF(wire->name), lsbidx ? i : GetSize(wire)-i-1), wire->port_input));
 					}
 				}
 			}
@ -468,13 +484,13 @@ struct EdifBackend : public Backend {
 							log_warning("Bit %d of cell port %s.%s.%s driven by %s will be left unconnected in EDIF output.\n",
 									i, log_id(module), log_id(cell), log_id(p.first), log_signal(sig[i]));
 						else {
-							int member_idx = GetSize(sig)-i-1;
+							int member_idx = lsbidx ? i : GetSize(sig)-i-1;
 							auto m = design->module(cell->type);
 							int width = sig.size();
 							if (m) {
 								auto w = m->wire(p.first);
 								if (w) {
-									member_idx = GetSize(w)-i-1;
+									member_idx = lsbidx ? i : GetSize(w)-i-1;
 									width = GetSize(w);
 								}
 							}
--- a/backends/smt2/smt2.cc
+++ b/backends/smt2/smt2.cc
@ -626,8 +626,9 @@ struct Smt2Worker
 				}

 				bool init_only = cell->type.in(ID($anyconst), ID($anyinit), ID($allconst));
+				bool clk2fflogic = cell->type == ID($anyinit) && cell->get_bool_attribute(ID(clk2fflogic));
 				int smtoffset = 0;
-				for (auto chunk : cell->getPort(QY).chunks()) {
+				for (auto chunk : cell->getPort(clk2fflogic ? ID::D : QY).chunks()) {
 					if (chunk.is_wire())
 						decls.push_back(witness_signal(init_only ? "init" : "seq", chunk.width, chunk.offset, "", idcounter, chunk.wire, smtoffset));
 					smtoffset += chunk.width;
@ -772,7 +773,7 @@ struct Smt2Worker
 			int arrayid = idcounter++;
 			memarrays[mem] = arrayid;

-			int abits = ceil_log2(mem->size);
+			int abits = max(1, ceil_log2(mem->size));

 			bool has_sync_wr = false;
 			bool has_async_wr = false;
@ -1219,7 +1220,7 @@ struct Smt2Worker
 			{
 				int arrayid = memarrays.at(mem);

-				int abits = ceil_log2(mem->size);;
+				int abits = max(1, ceil_log2(mem->size));

 				bool has_sync_wr = false;
 				bool has_async_wr = false;
--- a/backends/smt2/smtbmc.py
+++ b/backends/smt2/smtbmc.py
@ -174,6 +174,8 @@ def help():
        further failed assertions. To output multiple traces
        covering all found failed assertions, the character '%' is
        replaced in all dump filenames with an increasing number.
+        In cover mode, don't stop when a cover trace contains a failed
+        assertion.

    --check-witness
        check that the used witness file contains sufficient
@ -1739,7 +1741,7 @@ elif covermode:
            smt_pop()
            smt.write("(define-fun covers_%d ((state |%s_s|)) (_ BitVec %d) (bvand (covers_%d state) #b%s))" % (coveridx, topmod, len(cover_desc), coveridx-1, cover_mask))

-        if found_failed_assert:
+        if found_failed_assert and not keep_going:
            break

        if "1" not in cover_mask:
--- a/backends/smt2/smtio.py
+++ b/backends/smt2/smtio.py
@ -768,7 +768,7 @@ class SmtIo:

            if self.timeinfo:
                i = 0
-                s = "/-\|"
+                s = r"/-\|"

                count = 0
                num_bs = 0
@ -1171,7 +1171,7 @@ class MkVcd:

    def escape_name(self, name):
        name = re.sub(r"\[([0-9a-zA-Z_]*[a-zA-Z_][0-9a-zA-Z_]*)\]", r"<\1>", name)
-        if re.match("[\[\]]", name) and name[0] != "\\":
+        if re.match(r"[\[\]]", name) and name[0] != "\\":
            name = "\\" + name
        return name

--- a/backends/smt2/witness.py
+++ b/backends/smt2/witness.py
@ -194,7 +194,7 @@ def aiw2yw(input, mapfile, output):

        values = WitnessValues()
        for i, v in enumerate(inline):
-            if v == "x" or outyw.t > 0 and i in aiger_map.init_inputs:
+            if outyw.t > 0 and i in aiger_map.init_inputs:
                continue

            try:
--- a/docs/source/CHAPTER_CellLib.rst
+++ b/docs/source/CHAPTER_CellLib.rst
@ -571,7 +571,7 @@ The ``$mem_v2`` cell has the following ports:
 	signals for the read ports.

 ``\RD_DATA``
-	This input is ``\RD_PORTS*\WIDTH`` bits wide, containing all data
+	This output is ``\RD_PORTS*\WIDTH`` bits wide, containing all data
 	signals for the read ports.

 ``\RD_ARST``
--- a/docs/source/CHAPTER_Memorymap.rst
+++ b/docs/source/CHAPTER_Memorymap.rst
@ -0,0 +1,654 @@
+.. _chapter:memorymap:
+
+Memory mapping
+==============
+
+Documentation for the Yosys ``memory_libmap`` memory mapper.  Note that not all supported patterns
+are included in this document, of particular note is that combinations of multiple patterns should
+generally work.  For example, `Write port with byte enables`_ could be used in conjunction with any
+of the simple dual port (SDP) models.  In general if a hardware memory definition does not support a
+given configuration, additional logic will be instantiated to guarantee behaviour is consistent with
+simulation.
+
+See also: `passes/memory/memlib.md <https://github.com/YosysHQ/yosys/blob/master/passes/memory/memlib.md>`_
+
+Additional notes
+----------------
+
+Memory kind selection
+~~~~~~~~~~~~~~~~~~~~~
+
+The memory inference code will automatically pick target memory primitive based on memory geometry
+and features used.  Depending on the target, there can be up to four memory primitive classes
+available for selection:
+
+- FF RAM (aka logic): no hardware primitive used, memory lowered to a bunch of FFs and multiplexers
+
+  - Can handle arbitrary number of write ports, as long as all write ports are in the same clock domain
+  - Can handle arbitrary number and kind of read ports
+
+- LUT RAM (aka distributed RAM): uses LUT storage as RAM
+  
+  - Supported on most FPGAs (with notable exception of ice40)
+  - Usually has one synchronous write port, one or more asynchronous read ports
+  - Small
+  - Will never be used for ROMs (lowering to plain LUTs is always better)
+
+- Block RAM: dedicated memory tiles
+
+  - Supported on basically all FPGAs
+  - Supports only synchronous reads
+  - Two ports with separate clocks
+  - Usually supports true dual port (with notable exception of ice40 that only supports SDP)
+  - Usually supports asymmetric memories and per-byte write enables
+  - Several kilobits in size
+
+- Huge RAM:
+
+  - Only supported on several targets:
+    
+    - Some Xilinx UltraScale devices (UltraRAM)
+
+      - Two ports, both with mutually exclusive synchronous read and write
+      - Single clock
+      - Initial data must be all-0
+
+    - Some ice40 devices (SPRAM)
+
+      - Single port with mutually exclusive synchronous read and write
+      - Does not support initial data
+
+    - Nexus (large RAM)
+      
+      - Two ports, both with mutually exclusive synchronous read and write
+      - Single clock
+
+  - Will not be automatically selected by memory inference code, needs explicit opt-in via
+    ram_style attribute
+
+In general, you can expect the automatic selection process to work roughly like this:
+
+- If any read port is asynchronous, only LUT RAM (or FF RAM) can be used.
+- If there is more than one write port, only block RAM can be used, and this needs to be a
+  hardware-supported true dual port pattern
+
+  - … unless all write ports are in the same clock domain, in which case FF RAM can also be used,
+    but this is generally not what you want for anything but really small memories
+
+- Otherwise, either FF RAM, LUT RAM, or block RAM will be used, depending on memory size
+
+This process can be overridden by attaching a ram_style attribute to the memory:
+
+- `(* ram_style = "logic" *)` selects FF RAM
+- `(* ram_style = "distributed" *)` selects LUT RAM
+- `(* ram_style = "block" *)` selects block RAM
+- `(* ram_style = "huge" *)` selects huge RAM
+
+It is an error if this override cannot be realized for the given target.
+
+Many alternate spellings of the attribute are also accepted, for compatibility with other software.
+
+Initial data
+~~~~~~~~~~~~
+
+Most FPGA targets support initializing all kinds of memory to user-provided values.  If explicit
+initialization is not used the initial memory value is undefined.  Initial data can be provided by
+either initial statements writing memory cells one by one of ``$readmemh`` or ``$readmemb`` system
+tasks.  For an example pattern, see `Synchronous read port with initial value`_.
+
+Write port with byte enables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Byte enables can be used with any supported pattern
+- To ensure that multiple writes will be merged into one port, they need to have disjoint bit
+  ranges, have the same address, and the same clock
+- Any write enable granularity will be accepted (down to per-bit write enables), but using smaller
+  granularity than natively supported by the target is very likely to be inefficient (eg. using
+  4-bit bytes on ECP5 will result in either padding the bytes with 5 dummy bits to native 9-bit
+  units or splitting the RAM into two block RAMs)
+
+.. code:: verilog
+
+	reg [31 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable[0])
+			mem[write_addr][7:0] <= write_data[7:0];
+		if (write_enable[1])
+			mem[write_addr][15:8] <= write_data[15:8];
+		if (write_enable[2])
+			mem[write_addr][23:16] <= write_data[23:16];
+		if (write_enable[3])
+			mem[write_addr][31:24] <= write_data[31:24];
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Simple dual port (SDP) memory patterns
+--------------------------------------
+
+Asynchronous-read SDP
+~~~~~~~~~~~~~~~~~~~~~
+
+- This will result in LUT RAM on supported targets
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+	always @(posedge clk)
+		if (write_enable)
+			mem[write_addr] <= write_data;
+	assign read_data = mem[read_addr];
+
+Synchronous SDP with clock domain crossing
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will result in block RAM or LUT RAM depending on size
+- No behavior guarantees in case of simultaneous read and write to the same address
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge write_clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+	end
+
+	always @(posedge read_clk) begin
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Synchronous SDP read first
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- The read and write parts can be in the same or different processes.
+- Will result in block RAM or LUT RAM depending on size
+- As long as the same clock is used for both, yosys will ensure read-first behavior.  This may
+  require extra circuitry on some targets for block RAM.  If this is not necessary, use one of the
+  patterns below.
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Synchronous SDP with undefined collision behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Like above, but the read value is undefined when read and write ports target the same address in
+  the same cycle
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+
+		if (read_enable) begin
+			read_data <= mem[read_addr];
+		
+		// 👇 this if block 👇
+		if (write_enable && read_addr == write_addr)
+			read_data <= 'x;
+		end
+	end
+
+- Or below, using the no_rw_check attribute
+
+.. code:: verilog
+
+	(* no_rw_check *)
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+
+		if (read_enable) 
+			read_data <= mem[read_addr];
+	end
+
+Synchronous SDP with write-first behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will result in block RAM or LUT RAM depending on size
+- May use additional circuitry for block RAM if write-first is not natively supported. Will always
+  use additional circuitry for LUT RAM.
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+
+		if (read_enable) begin
+			read_data <= mem[read_addr];
+			if (write_enable && read_addr == write_addr)
+				read_data <= write_data;
+		end
+	end
+
+Synchronous SDP with write-first behavior (alternate pattern)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- This pattern is supported for compatibility, but is much less flexible than the above
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+		read_addr_reg <= read_addr;
+	end
+
+	assign read_data = mem[read_addr_reg];
+
+Single-port RAM memory patterns
+-------------------------------
+
+Asynchronous-read single-port RAM
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will result in single-port LUT RAM on supported targets
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+	always @(posedge clk)
+		if (write_enable)
+			mem[addr] <= write_data;
+	assign read_data = mem[addr];
+
+Synchronous single-port RAM with mutually exclusive read/write
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will result in single-port block RAM or LUT RAM depending on size
+- This is the correct pattern to infer ice40 SPRAM (with manual ram_style selection)
+- On targets that don't support read/write block RAM ports (eg. ice40), will result in SDP block RAM instead
+- For block RAM, will use "NO_CHANGE" mode if available
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[addr] <= write_data;
+		else if (read_enable)
+			read_data <= mem[addr];
+	end
+
+Synchronous single-port RAM with read-first behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will only result in single-port block RAM when read-first behavior is natively supported;
+  otherwise, SDP RAM with additional circuitry will be used
+- Many targets (Xilinx, ECP5, …) can only natively support read-first/write-first single-port RAM
+  (or TDP RAM) where the write_enable signal implies the read_enable signal (ie. can never write
+  without reading). The memory inference code will run a simple SAT solver on the control signals to
+  determine if this is the case, and insert emulation circuitry if it cannot be easily proven.
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[addr] <= write_data;
+		if (read_enable)
+			read_data <= mem[addr];
+	end
+
+Synchronous single-port RAM with write-first behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Will result in single-port block RAM or LUT RAM when supported
+- Block RAMs will require extra circuitry if write-first behavior not natively supported
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[addr] <= write_data;
+		if (read_enable)
+			if (write_enable)
+				read_data <= write_data;
+			else 
+				read_data <= mem[addr];
+	end
+
+Synchronous read port with initial value
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Initial read port values can be combined with any other supported pattern
+- If block RAM is used and initial read port values are not natively supported by the target, small
+  emulation circuit will be inserted
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+	reg [DATA_WIDTH - 1 : 0] read_data;
+	initial read_data = 'h1234;
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Read register reset patterns
+----------------------------
+
+Resets can be combined with any other supported pattern (except that synchronous reset and
+asynchronous reset cannot both be used on a single read port).  If block RAM is used and the
+selected reset (synchronous or asynchronous) is used but not natively supported by the target, small
+emulation circuitry will be inserted.
+
+Synchronous reset, reset priority over enable
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+
+		if (read_reset)
+			read_data <= {sval};
+		else if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Synchronous reset, enable priority over reset
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+		if (read_enable)
+			if (read_reset)
+				read_data <= 'h1234;
+			else
+				read_data <= mem[read_addr];
+	end
+
+Synchronous read port with asynchronous reset
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+	end
+
+	always @(posedge clk, posedge reset_read) begin
+		if (reset_read)
+			read_data <= 'h1234;
+		else if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Asymmetric memory patterns
+--------------------------
+
+To construct an asymmetric memory (memory with read/write ports of differing widths):
+
+- Declare the memory with the width of the narrowest intended port
+- Split all wide ports into multiple narrow ports
+- To ensure the wide ports will be correctly merged:
+
+  - For the address, use a concatenation of actual address in the high bits and a constant in the
+    low bits
+  - Ensure the actual address is identical for all ports belonging to the wide port
+  - Ensure that clock is identical
+  - For read ports, ensure that enable/reset signals are identical (for write ports, the enable
+    signal may vary — this will result in using the byte enable functionality)
+
+Asymmetric memory is supported on all targets, but may require emulation circuitry where not
+natively supported.  Note that when the memory is larger than the underlying block RAM primitive,
+hardware asymmetric memory support is likely not to be used even if present as it is more expensive.
+
+Wide synchronous read port
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [7:0] mem [0:255];
+	wire [7:0] write_addr;
+	wire [5:0] read_addr;
+	wire [7:0] write_data;
+	reg [31:0] read_data;
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+		if (read_enable) begin
+			read_data[7:0] <= mem[{read_addr, 2'b00}];
+			read_data[15:8] <= mem[{read_addr, 2'b01}];
+			read_data[23:16] <= mem[{read_addr, 2'b10}];
+			read_data[31:24] <= mem[{read_addr, 2'b11}];
+		end
+	end
+
+Wide asynchronous read port
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Note: the only target natively supporting this pattern is Xilinx UltraScale
+
+.. code:: verilog
+
+	reg [7:0] mem [0:511];
+	wire [8:0] write_addr;
+	wire [5:0] read_addr;
+	wire [7:0] write_data;
+	wire [63:0] read_data;
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+	end
+
+	assign read_data[7:0] = mem[{read_addr, 3'b000}];
+	assign read_data[15:8] = mem[{read_addr, 3'b001}];
+	assign read_data[23:16] = mem[{read_addr, 3'b010}];
+	assign read_data[31:24] = mem[{read_addr, 3'b011}];
+	assign read_data[39:32] = mem[{read_addr, 3'b100}];
+	assign read_data[47:40] = mem[{read_addr, 3'b101}];
+	assign read_data[55:48] = mem[{read_addr, 3'b110}];
+	assign read_data[63:56] = mem[{read_addr, 3'b111}];
+
+Wide write port
+~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [7:0] mem [0:255];
+	wire [5:0] write_addr;
+	wire [7:0] read_addr;
+	wire [31:0] write_data;
+	reg [7:0] read_data;
+
+	always @(posedge clk) begin
+		if (write_enable[0])
+			mem[{write_addr, 2'b00}] <= write_data[7:0];
+		if (write_enable[1])
+			mem[{write_addr, 2'b01}] <= write_data[15:8];
+		if (write_enable[2])
+			mem[{write_addr, 2'b10}] <= write_data[23:16];
+		if (write_enable[3])
+			mem[{write_addr, 2'b11}] <= write_data[31:24];
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+True dual port (TDP) patterns
+-----------------------------
+
+- Many different variations of true dual port memory can be created by combining two single-port RAM
+  patterns on the same memory
+- When TDP memory is used, memory inference code has much less maneuver room to create requested
+  semantics compared to individual single-port patterns (which can end up lowered to SDP memory
+  where necessary) — supported patterns depend strongly on the target
+- In particular, when both ports have the same clock, it's likely that "undefined collision" mode
+  needs to be manually selected to enable TDP memory inference
+- The examples below are non-exhaustive — many more combinations of port types are possible
+- Note: if two write ports are in the same process, this defines a priority relation between them
+  (if both ports are active in the same clock, the later one wins). On almost all targets, this will
+  result in a bit of extra circuitry to ensure the priority semantics. If this is not what you want,
+  put them in separate processes.
+
+  - Priority is not supported when using the verific front end and any priority semantics are ignored.
+
+TDP with different clocks, exclusive read/write
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk_a) begin
+		if (write_enable_a)
+			mem[addr_a] <= write_data_a;
+		else if (read_enable_a)
+			read_data_a <= mem[addr_a];
+	end
+
+	always @(posedge clk_b) begin
+		if (write_enable_b)
+			mem[addr_b] <= write_data_b;
+		else if (read_enable_b)
+			read_data_b <= mem[addr_b];
+	end
+
+TDP with same clock, read-first behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- This requires hardware inter-port read-first behavior, and will only work on some targets (Xilinx, Nexus)
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable_a)
+			mem[addr_a] <= write_data_a;
+		if (read_enable_a)
+			read_data_a <= mem[addr_a];
+	end
+
+	always @(posedge clk) begin
+		if (write_enable_b)
+			mem[addr_b] <= write_data_b;
+		if (read_enable_b)
+			read_data_b <= mem[addr_b];
+	end
+
+TDP with multiple read ports
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- The combination of a single write port with an arbitrary amount of read ports is supported on all
+  targets — if a multi-read port primitive is available (like Xilinx RAM64M), it'll be used as
+  appropriate.  Otherwise, the memory will be automatically split into multiple primitives.
+
+.. code:: verilog
+
+	reg [31:0] mem [0:31];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] <= write_data;
+	end
+
+	assign read_data_a = mem[read_addr_a];
+	assign read_data_b = mem[read_addr_b];
+	assign read_data_c = mem[read_addr_c];
+
+Not yet supported patterns
+--------------------------
+
+Synchronous SDP with write-first behavior via blocking assignments
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Would require modifications to the Yosys Verilog frontend.
+- Use `Synchronous SDP with write-first behavior`_ instead
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr] = write_data;
+
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+Asymmetric memories via part selection
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Would require major changes to the Verilog frontend.
+- Build wide ports out of narrow ports instead (see `Wide synchronous read port`_)
+
+.. code:: verilog
+
+	reg [31:0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	wire [1:0] byte_lane;
+	wire [7:0] write_data;
+
+	always @(posedge clk) begin
+		if (write_enable)
+			mem[write_addr][byte_lane * 8 +: 8] <= write_data;
+
+		if (read_enable)
+			read_data <= mem[read_addr];
+	end
+
+
+Undesired patterns
+------------------
+
+Asynchronous writes
+~~~~~~~~~~~~~~~~~~~
+
+- Not supported in modern FPGAs
+- Not supported in yosys code anyhow
+
+.. code:: verilog
+
+	reg [DATA_WIDTH - 1 : 0] mem [2**ADDR_WIDTH - 1 : 0];
+
+	always @* begin
+		if (write_enable)
+			mem[write_addr] = write_data;
+	end
+
+	assign read_data = mem[read_addr];
+
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@ -42,6 +42,7 @@ Yosys manual
 	CHAPTER_Verilog.rst
 	CHAPTER_Optimize.rst
 	CHAPTER_Techmap.rst
+	CHAPTER_Memorymap.rst
 	CHAPTER_Eval.rst

 .. raw:: latex
--- a/frontends/verific/verific.cc
+++ b/frontends/verific/verific.cc
@ -112,15 +112,26 @@ void msg_func(msg_type_t msg_type, const char *message_id, linefile_type linefil
 	string message = linefile ? stringf("%s:%d: ", LineFile::GetFileName(linefile), LineFile::GetLineNo(linefile)) : "";
 	message += vstringf(msg, args);

-	if (msg_type == VERIFIC_ERROR || msg_type == VERIFIC_WARNING || msg_type == VERIFIC_PROGRAM_ERROR)
-		log_warning_noprefix("%s%s\n", message_prefix.c_str(), message.c_str());
-	else
-		log("%s%s\n", message_prefix.c_str(), message.c_str());
-
+	if (log_verific_callback) {
+		string full_message = stringf("%s%s\n", message_prefix.c_str(), message.c_str());
+		log_verific_callback(int(msg_type), message_id, LineFile::GetFileName(linefile), LineFile::GetLineNo(linefile), full_message.c_str());
+	} else {
+		if (msg_type == VERIFIC_ERROR || msg_type == VERIFIC_WARNING || msg_type == VERIFIC_PROGRAM_ERROR)
+			log_warning_noprefix("%s%s\n", message_prefix.c_str(), message.c_str());
+		else
+			log("%s%s\n", message_prefix.c_str(), message.c_str());
+	}
 	if (verific_error_msg.empty() && (msg_type == VERIFIC_ERROR || msg_type == VERIFIC_PROGRAM_ERROR))
 		verific_error_msg = message;
 }

+void set_verific_logging(void (*cb)(int msg_type, const char *message_id, const char* file_path, unsigned int line_no, const char *msg))
+{
+	Message::SetConsoleOutput(0);
+	Message::RegisterCallBackMsg(msg_func);
+	log_verific_callback = cb;
+}
+
 string get_full_netlist_name(Netlist *nl)
 {
 	if (nl->NumOfRefs() == 1) {
@ -1638,6 +1649,7 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 				cell->parameters[ID::TRANSPARENT] = false;
 				cell->parameters[ID::ABITS] = GetSize(addr);
 				cell->parameters[ID::WIDTH] = GetSize(data);
+				import_attributes(cell->attributes, inst);
 				cell->setPort(ID::CLK, RTLIL::State::Sx);
 				cell->setPort(ID::EN, RTLIL::State::Sx);
 				cell->setPort(ID::ADDR, addr);
@ -1667,6 +1679,7 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 				cell->parameters[ID::PRIORITY] = 0;
 				cell->parameters[ID::ABITS] = GetSize(addr);
 				cell->parameters[ID::WIDTH] = GetSize(data);
+				import_attributes(cell->attributes, inst);
 				cell->setPort(ID::EN, RTLIL::SigSpec(net_map_at(inst->GetControl())).repeat(GetSize(data)));
 				cell->setPort(ID::CLK, RTLIL::State::S0);
 				cell->setPort(ID::ADDR, addr);
@ -1994,7 +2007,10 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 					initval[i] = State::Sx;
 			}

-			if (initval.is_fully_undef())
+			if (wire->port_input) {
+				wire->attributes[ID::defaultvalue] = Const(initval);
+				wire->attributes.erase(ID::init);
+			} else if (initval.is_fully_undef())
 				wire->attributes.erase(ID::init);
 		}
 	}
--- a/kernel/log.cc
+++ b/kernel/log.cc
@ -59,6 +59,7 @@ bool log_quiet_warnings = false;
 int log_verbose_level;
 string log_last_error;
 void (*log_error_atexit)() = NULL;
+void (*log_verific_callback)(int msg_type, const char *message_id, const char* file_path, unsigned int line_no, const char *msg) = NULL;

 int log_make_debug = 0;
 int log_force_debug = 0;
--- a/kernel/log.h
+++ b/kernel/log.h
@ -130,6 +130,9 @@ void log_header(RTLIL::Design *design, const char *format, ...) YS_ATTRIBUTE(for
 void log_warning(const char *format, ...) YS_ATTRIBUTE(format(printf, 1, 2));
 void log_experimental(const char *format, ...) YS_ATTRIBUTE(format(printf, 1, 2));

+void set_verific_logging(void (*cb)(int msg_type, const char *message_id, const char* file_path, unsigned int line_no, const char *msg));
+extern void (*log_verific_callback)(int msg_type, const char *message_id, const char* file_path, unsigned int line_no, const char *msg);
+
 // Log with filename to report a problem in a source file.
 void log_file_warning(const std::string &filename, int lineno, const char *format, ...) YS_ATTRIBUTE(format(printf, 3, 4));
 void log_file_info(const std::string &filename, int lineno, const char *format, ...) YS_ATTRIBUTE(format(printf, 3, 4));
--- a/misc/py_wrap_generator.py
+++ b/misc/py_wrap_generator.py
@ -178,6 +178,8 @@ class WType:
 		t.cont = None
 		t.attr_type = attr_types.default
 		if str_def.find("<") != -1:# and str_def.find("<") < str_def.find(" "):
+			str_def = str_def.replace("const ", "")
+
 			candidate = WContainer.from_string(str_def, containing_file, line_number)
 			if candidate == None:
 				return None
@ -203,8 +205,12 @@ class WType:

 		prefix = ""

+		if str.startswith(str_def, "const "):
+			if "char_p" in str_def:
+				prefix = "const "
+			str_def = str_def[6:]
 		if str.startswith(str_def, "unsigned "):
-			prefix = "unsigned "
+			prefix = "unsigned " + prefix
 			str_def = str_def[9:]
 		while str.startswith(str_def, "long "):
 			prefix= "long " + prefix
@ -1285,7 +1291,7 @@ class WFunction:
 		prefix = ""
 		i = 0
 		for part in parts:
-			if part in ["unsigned", "long", "short"]:
+			if part in ["unsigned", "long", "short", "const"]:
 				prefix += part + " "
 				i += 1
 			else:
@ -1361,10 +1367,17 @@ class WFunction:
 			func.args.append(parsed)
 		return func

+	@property
+	def mangled_name(self):
+		mangled_typename = lambda code: code.replace("::", "_").replace("<","_").replace(">","_") \
+										   .replace(" ","").replace("*","").replace(",","")
+
+		return self.name + "".join(
+			f"__{mangled_typename(arg.wtype.gen_text_cpp())}" for arg in self.args
+		)
+
 	def gen_alias(self):
-		self.alias = self.name
-		for arg in self.args:
-			self.alias += "__" + arg.wtype.gen_text_cpp().replace("::", "_").replace("<","_").replace(">","_").replace(" ","").replace("*","").replace(",","")
+		self.alias = self.mangled_name

 	def gen_decl(self):
 		if self.duplicate:
@ -2190,12 +2203,15 @@ def clean_duplicates():
 			for fun in class_.found_funs:
 				if fun.gen_decl_hash_py() in known_decls:
 					debug("Multiple declarations of " + fun.gen_decl_hash_py(),3)
+
 					other = known_decls[fun.gen_decl_hash_py()]
-					other.gen_alias()
-					fun.gen_alias()
-					if fun.gen_decl_hash_py() == other.gen_decl_hash_py():
+					if fun.mangled_name == other.mangled_name:
 						fun.duplicate = True
 						debug("Disabled \"" + fun.gen_decl_hash_py() + "\"", 3)
+						continue
+
+					other.gen_alias()
+					fun.gen_alias()
 				else:
 					known_decls[fun.gen_decl_hash_py()] = fun
 			known_decls = []
--- a/passes/cmds/check.cc
+++ b/passes/cmds/check.cc
@ -112,11 +112,10 @@ struct CheckPass : public Pass {
 				for (size_t i = 0; i < all_cases.size(); i++) {
 					for (auto action : all_cases[i]->actions) {
 						for (auto bit : sigmap(action.first))
-							if (bit.wire) {
-								wire_drivers[bit].push_back(
-									stringf("action %s <= %s (case rule) in process %s",
-									        log_signal(action.first), log_signal(action.second), log_id(proc_it.first)));
-							}
+							wire_drivers[bit].push_back(
+								stringf("action %s <= %s (case rule) in process %s",
+										log_signal(action.first), log_signal(action.second), log_id(proc_it.first)));
+
 						for (auto bit : sigmap(action.second))
 							if (bit.wire) used_wires.insert(bit);
 					}
@ -134,10 +133,9 @@ struct CheckPass : public Pass {
 						if (bit.wire) used_wires.insert(bit);
 					for (auto action : sync->actions) {
 						for (auto bit : sigmap(action.first))
-							if (bit.wire)
-								wire_drivers[bit].push_back(
-									stringf("action %s <= %s (sync rule) in process %s",
-									        log_signal(action.first), log_signal(action.second), log_id(proc_it.first)));
+							wire_drivers[bit].push_back(
+								stringf("action %s <= %s (sync rule) in process %s",
+										log_signal(action.first), log_signal(action.second), log_id(proc_it.first)));
 						for (auto bit : sigmap(action.second))
 							if (bit.wire) used_wires.insert(bit);
 					}
@ -176,7 +174,8 @@ struct CheckPass : public Pass {
 							if (logic_cell)
 								topo.edge(stringf("cell %s (%s)", log_id(cell), log_id(cell->type)),
 										stringf("wire %s", log_signal(sig[i])));
-							if (sig[i].wire)
+
+							if (sig[i].wire || !cell->input(conn.first))
 								wire_drivers[sig[i]].push_back(stringf("port %s[%d] of cell %s (%s)",
 										log_id(conn.first), i, log_id(cell), log_id(cell->type)));
 						}
@ -192,7 +191,8 @@ struct CheckPass : public Pass {
 				if (wire->port_input) {
 					SigSpec sig = sigmap(wire);
 					for (int i = 0; i < GetSize(sig); i++)
-						wire_drivers[sig[i]].push_back(stringf("module input %s[%d]", log_id(wire), i));
+						if (sig[i].wire || !wire->port_output)
+							wire_drivers[sig[i]].push_back(stringf("module input %s[%d]", log_id(wire), i));
 				}
 				if (wire->port_output)
 					for (auto bit : sigmap(wire))
@ -212,6 +212,15 @@ struct CheckPass : public Pass {
 				}
 			}

+			for (auto state : {State::S0, State::S1, State::Sx})
+				if (wire_drivers.count(state)) {
+					string message = stringf("Drivers conflicting with a constant %s driver:\n", log_signal(state));
+					for (auto str : wire_drivers[state])
+						message += stringf("    %s\n", str.c_str());
+					log_warning("%s", message.c_str());
+					counter++;
+				}
+
 			for (auto it : wire_drivers)
 				if (wire_drivers_count[it.first] > 1) {
 					string message = stringf("multiple conflicting drivers for %s.%s:\n", log_id(module), log_signal(it.first));
--- a/passes/cmds/rename.cc
+++ b/passes/cmds/rename.cc
@ -139,7 +139,12 @@ static bool rename_witness(RTLIL::Design *design, dict<RTLIL::Module *, int> &ca

 		if (cell->type.in(ID($anyconst), ID($anyseq), ID($anyinit), ID($allconst), ID($allseq))) {
 			has_witness_signals = true;
-			auto QY = cell->type == ID($anyinit) ? ID::Q : ID::Y;
+			IdString QY;
+			bool clk2fflogic = false;
+			if (cell->type == ID($anyinit))
+				QY = (clk2fflogic = cell->get_bool_attribute(ID(clk2fflogic))) ? ID::D : ID::Q;
+			else
+				QY = ID::Y;
 			auto sig_out = cell->getPort(QY);

 			for (auto chunk : sig_out.chunks()) {
@ -151,7 +156,10 @@ static bool rename_witness(RTLIL::Design *design, dict<RTLIL::Module *, int> &ca
 					auto new_id = module->uniquify("\\_witness_." + name);
 					auto new_wire = module->addWire(new_id, GetSize(sig_out));
 					new_wire->set_hdlname_attribute({ "_witness_", strstr(new_id.c_str(), ".") + 1 });
-					module->connect({sig_out, new_wire});
+					if (clk2fflogic)
+						module->connect({new_wire, sig_out});
+					else
+						module->connect({sig_out, new_wire});
 					cell->setPort(QY, new_wire);
 					break;
 				}
--- a/passes/cmds/show.cc
+++ b/passes/cmds/show.cc
@ -84,7 +84,7 @@ struct ShowWorker
 	std::string nextColor()
 	{
 		if (currentColor == 0)
-			return "color=\"black\"";
+			return "color=\"black\", fontcolor=\"black\"";
 		return stringf("colorscheme=\"dark28\", color=\"%d\", fontcolor=\"%d\"", currentColor%8+1, currentColor%8+1);
 	}

@ -97,19 +97,16 @@ struct ShowWorker

 	std::string nextColor(RTLIL::SigSpec sig, std::string defaultColor)
 	{
-		sig.sort_and_unify();
-		for (auto &c : sig.chunks()) {
-			if (c.wire != nullptr)
-				for (auto &s : color_selections)
-					if (s.second.selected_members.count(module->name) > 0 && s.second.selected_members.at(module->name).count(c.wire->name) > 0)
-						return stringf("color=\"%s\"", s.first.c_str());
-		}
+		std::string color = findColor(sig);
+		if (!color.empty()) return color;
 		return defaultColor;
 	}

 	std::string nextColor(const RTLIL::SigSig &conn, std::string defaultColor)
 	{
-		return nextColor(conn.first, nextColor(conn.second, defaultColor));
+		std::string color = findColor(conn);
+		if (!color.empty()) return color;
+		return defaultColor;
 	}

 	std::string nextColor(const RTLIL::SigSpec &sig)
@ -131,12 +128,28 @@ struct ShowWorker
 		return stringf("style=\"setlinewidth(3)\", label=\"<%d>\"", bits);
 	}

-	const char *findColor(std::string member_name)
+	std::string findColor(RTLIL::SigSpec sig)
+	{
+		sig.sort_and_unify();
+		for (auto &c : sig.chunks()) {
+			if (c.wire != nullptr)
+				return findColor(c.wire->name);
+		}
+		return "";
+	}
+
+	std::string findColor(const RTLIL::SigSig &conn)
+	{
+		std::string firstColor = findColor(conn.first);
+		if (findColor(conn.second) == firstColor) return firstColor;
+		return "";
+	}
+
+	std::string findColor(IdString member_name)
 	{
 		for (auto &s : color_selections)
 			if (s.second.selected_member(module->name, member_name)) {
-				dot_escape_store.push_back(stringf(", color=\"%s\"", s.first.c_str()));
-				return dot_escape_store.back().c_str();
+				return stringf("color=\"%s\", fontcolor=\"%s\"", s.first.c_str(), s.first.c_str());
 			}

 		RTLIL::Const colorattr_value;
@ -155,8 +168,7 @@ struct ShowWorker
 			colorattr_cache[colorattr_value] = (next_id % 8) + 1;
 		}

-		dot_escape_store.push_back(stringf(", colorscheme=\"dark28\", color=\"%d\", fontcolor=\"%d\"", colorattr_cache.at(colorattr_value), colorattr_cache.at(colorattr_value)));
-		return dot_escape_store.back().c_str();
+		return stringf("colorscheme=\"dark28\", color=\"%d\", fontcolor=\"%d\"", colorattr_cache.at(colorattr_value), colorattr_cache.at(colorattr_value));
 	}

 	const char *findLabel(std::string member_name)
@ -189,6 +201,12 @@ struct ShowWorker
 		if (id[0] == '\\')
 			id = id.substr(1);

+		// TODO: optionally include autoname + print correspondence in case of ambiguity
+		size_t max_label_len = abbreviateIds ? 256 : 16384;
+		if (id.size() > max_label_len) {
+			id = id.substr(0,max_label_len-3) + "...";
+		}
+
 		std::string str;
 		for (char ch : id) {
 			if (ch == '\\') {
@ -196,7 +214,7 @@ struct ShowWorker
 				str += "&#9586;";
 				continue;
 			}
-			if (ch == '"')
+			if (ch == '"' || ch == '<' || ch == '>')
 				str += "\\";
 			str += ch;
 		}
@ -317,7 +335,7 @@ struct ShowWorker
 			}

 			code += stringf("x%d [ shape=record, style=rounded, label=\"", dot_idx) \
-					+ join_label_pieces(label_pieces) + "\" ];\n";
+					+ join_label_pieces(label_pieces) + stringf("\", %s ];\n", nextColor(sig).c_str());

 			if (!port.empty()) {
 				currentColor = xorshift32(currentColor);
@ -414,9 +432,9 @@ struct ShowWorker
 			if (wire->port_input || wire->port_output)
 				shape = "octagon";
 			if (wire->name.isPublic()) {
-				fprintf(f, "n%d [ shape=%s, label=\"%s\", %s, fontcolor=\"black\" ];\n",
+				fprintf(f, "n%d [ shape=%s, label=\"%s\", %s ];\n",
 						id2num(wire->name), shape, findLabel(wire->name.str()),
-						nextColor(RTLIL::SigSpec(wire), "color=\"black\"").c_str());
+						nextColor(RTLIL::SigSpec(wire), "color=\"black\", fontcolor=\"black\"").c_str());
 				if (wire->port_input)
 					all_sources.insert(stringf("n%d", id2num(wire->name)));
 				else if (wire->port_output)
@ -481,11 +499,11 @@ struct ShowWorker
 #ifdef CLUSTER_CELLS_AND_PORTBOXES
 			if (!code.empty())
 				fprintf(f, "subgraph cluster_c%d {\nc%d [ shape=record, label=\"%s\"%s ];\n%s}\n",
-						id2num(cell->name), id2num(cell->name), label_string.c_str(), findColor(cell->name), code.c_str());
+						id2num(cell->name), id2num(cell->name), label_string.c_str(), color.c_str(), code.c_str());
 			else
 #endif
-				fprintf(f, "c%d [ shape=record, label=\"%s\"%s ];\n%s",
-						id2num(cell->name), label_string.c_str(), findColor(cell->name.str()), code.c_str());
+				fprintf(f, "c%d [ shape=record, label=\"%s\", %s ];\n%s",
+						id2num(cell->name), label_string.c_str(), findColor(cell->name).c_str(), code.c_str());
 		}

 		for (auto &it : module->processes)
@ -555,9 +573,9 @@ struct ShowWorker
 				} else if (right_node[0] == 'x') {
 					net_conn_map[left_node].out.insert({right_node, GetSize(conn.first)});
 				} else {
-					net_conn_map[right_node].in.insert({stringf("x%d:e", single_idx_count), GetSize(conn.first)});
-					net_conn_map[left_node].out.insert({stringf("x%d:w", single_idx_count), GetSize(conn.first)});
-					fprintf(f, "x%d [shape=box, style=rounded, label=\"BUF\"];\n", single_idx_count++);
+					net_conn_map[right_node].in.insert({stringf("x%d", single_idx_count), GetSize(conn.first)});
+					net_conn_map[left_node].out.insert({stringf("x%d", single_idx_count), GetSize(conn.first)});
+					fprintf(f, "x%d [shape=box, style=rounded, label=\"BUF\", %s];\n", single_idx_count++, findColor(conn).c_str());
 				}
 			}
 		}
@ -643,6 +661,7 @@ struct ShowPass : public Pass {
 		log("    -viewer <viewer>\n");
 		log("        Run the specified command with the graphics file as parameter.\n");
 		log("        On Windows, this pauses yosys until the viewer exits.\n");
+		log("        Use \"-viewer none\" to not run any command.\n");
 		log("\n");
 		log("    -format <format>\n");
 		log("        Generate a graphics file in the specified format. Use 'dot' to just\n");
@ -903,28 +922,30 @@ struct ShowPass : public Pass {
 		#if defined(YOSYS_DISABLE_SPAWN)
 			log_assert(viewer_exe.empty() && !format.empty());
 		#else
-		if (!viewer_exe.empty()) {
-			#ifdef _WIN32
-				// system()/cmd.exe does not understand single quotes nor
-				// background tasks on Windows. So we have to pause yosys
-				// until the viewer exits.
-				std::string cmd = stringf("%s \"%s\"", viewer_exe.c_str(), out_file.c_str());
-			#else
-				std::string cmd = stringf("%s '%s' %s", viewer_exe.c_str(), out_file.c_str(), background.c_str());
-			#endif
-			log("Exec: %s\n", cmd.c_str());
-			if (run_command(cmd) != 0)
-				log_cmd_error("Shell command failed!\n");
-		} else
-		if (format.empty()) {
-			#ifdef __APPLE__
-			std::string cmd = stringf("ps -fu %d | grep -q '[ ]%s' || xdot '%s' %s", getuid(), dot_file.c_str(), dot_file.c_str(), background.c_str());
-			#else
-			std::string cmd = stringf("{ test -f '%s.pid' && fuser -s '%s.pid' 2> /dev/null; } || ( echo $$ >&3; exec xdot '%s'; ) 3> '%s.pid' %s", dot_file.c_str(), dot_file.c_str(), dot_file.c_str(), dot_file.c_str(), background.c_str());
-			#endif
-			log("Exec: %s\n", cmd.c_str());
-			if (run_command(cmd) != 0)
-				log_cmd_error("Shell command failed!\n");
+		if (viewer_exe != "none") {
+			if (!viewer_exe.empty()) {
+				#ifdef _WIN32
+					// system()/cmd.exe does not understand single quotes nor
+					// background tasks on Windows. So we have to pause yosys
+					// until the viewer exits.
+					std::string cmd = stringf("%s \"%s\"", viewer_exe.c_str(), out_file.c_str());
+				#else
+					std::string cmd = stringf("%s '%s' %s", viewer_exe.c_str(), out_file.c_str(), background.c_str());
+				#endif
+				log("Exec: %s\n", cmd.c_str());
+				if (run_command(cmd) != 0)
+					log_cmd_error("Shell command failed!\n");
+			} else
+			if (format.empty()) {
+				#ifdef __APPLE__
+				std::string cmd = stringf("ps -fu %d | grep -q '[ ]%s' || xdot '%s' %s", getuid(), dot_file.c_str(), dot_file.c_str(), background.c_str());
+				#else
+				std::string cmd = stringf("{ test -f '%s.pid' && fuser -s '%s.pid' 2> /dev/null; } || ( echo $$ >&3; exec xdot '%s'; ) 3> '%s.pid' %s", dot_file.c_str(), dot_file.c_str(), dot_file.c_str(), dot_file.c_str(), background.c_str());
+				#endif
+				log("Exec: %s\n", cmd.c_str());
+				if (run_command(cmd) != 0)
+					log_cmd_error("Shell command failed!\n");
+			}
 		}
 		#endif

--- a/passes/opt/opt_clean.cc
+++ b/passes/opt/opt_clean.cc
@ -292,10 +292,12 @@ bool rmunused_module_signals(RTLIL::Module *module, bool purge_mode, bool verbos
 	if (!purge_mode)
 		for (auto &it : module->cells_) {
 			RTLIL::Cell *cell = it.second;
-			if (ct_reg.cell_known(cell->type))
+			if (ct_reg.cell_known(cell->type)) {
+				bool clk2fflogic = cell->get_bool_attribute(ID(clk2fflogic));
 				for (auto &it2 : cell->connections())
-					if (ct_reg.cell_output(cell->type, it2.first))
+					if (clk2fflogic ? it2.first == ID::D : ct_reg.cell_output(cell->type, it2.first))
 						register_signals.add(it2.second);
+			}
 			for (auto &it2 : cell->connections())
 				connected_signals.add(it2.second);
 		}
--- a/passes/proc/proc_prune.cc
+++ b/passes/proc/proc_prune.cc
@ -91,7 +91,7 @@ struct PruneWorker
 			if (GetSize(new_lhs) == 0) {
 				if (GetSize(conn_lhs) == 0)
 					removed_count++;
-				cs->actions.erase((it++).base() - 1);
+				it = decltype(cs->actions)::reverse_iterator(cs->actions.erase(it.base() - 1));
 			} else {
 				it->first = new_lhs;
 				it->second = new_rhs;
--- a/passes/sat/clk2fflogic.cc
+++ b/passes/sat/clk2fflogic.cc
@ -80,15 +80,27 @@ struct Clk2fflogicPass : public Pass {
 		return module->Eqx(NEW_ID, {sampled_sig, sig}, polarity ? SigSpec {State::S0, State::S1} : SigSpec {State::S1, State::S0});
 	}
 	// Sampled and current value of a data signal.
-	SampledSig sample_data(Module *module, SigSpec sig, RTLIL::Const init, bool is_fine) {
+	SampledSig sample_data(Module *module, SigSpec sig, RTLIL::Const init, bool is_fine, bool set_attribute = false) {
 		std::string sig_str = log_signal(sig);
 		sig_str.erase(std::remove(sig_str.begin(), sig_str.end(), ' '), sig_str.end());
+
+
 		Wire *sampled_sig = module->addWire(NEW_ID_SUFFIX(stringf("%s#sampled", sig_str.c_str())), GetSize(sig));
 		sampled_sig->attributes[ID::init] = init;
+
+		Cell *cell;
 		if (is_fine)
-			module->addFfGate(NEW_ID, sig, sampled_sig);
+			cell = module->addFfGate(NEW_ID, sig, sampled_sig);
 		else
-			module->addFf(NEW_ID, sig, sampled_sig);
+			cell = module->addFf(NEW_ID, sig, sampled_sig);
+
+		if (set_attribute) {
+			for (auto &chunk : sig.chunks())
+				if (chunk.wire != nullptr)
+					chunk.wire->set_bool_attribute(ID::keep);
+			cell->set_bool_attribute(ID(clk2fflogic));
+		}
+
 		return {sampled_sig, sig};
 	}
 	SigSpec mux(Module *module, SigSpec a, SigSpec b, SigSpec s, bool is_fine) {
@ -213,7 +225,7 @@ struct Clk2fflogicPass : public Pass {
 					if (ff.has_clk)
 						ff.unmap_ce_srst();

-					auto next_q = sample_data(module, ff.sig_q, ff.val_init, ff.is_fine).sampled;
+					auto next_q = sample_data(module, ff.sig_q, ff.val_init, ff.is_fine, true).sampled;

 					if (ff.has_clk) {
 						// The init value for the sampled d is never used, so we can set it to fixed zero, reducing uninit'd FFs
--- a/passes/sat/sim.cc
+++ b/passes/sat/sim.cc
@ -140,6 +140,7 @@ struct SimInstance
 	dict<SigBit, pool<Wire*>> upd_outports;

 	dict<SigBit, SigBit> in_parent_drivers;
+	dict<SigBit, SigBit> clk2fflogic_drivers;

 	pool<SigBit> dirty_bits;
 	pool<Cell*> dirty_cells;
@ -270,6 +271,11 @@ struct SimInstance
 				ff.past_srst = State::Sx;
 				ff.data = ff_data;
 				ff_database[cell] = ff;
+
+				if (cell->get_bool_attribute(ID(clk2fflogic))) {
+					for (int i = 0; i < ff_data.width; i++)
+						clk2fflogic_drivers.emplace(sigmap(ff_data.sig_d[i]), sigmap(ff_data.sig_q[i]));
+				}
 			}

 			if (cell->is_mem_cell())
@ -389,6 +395,10 @@ struct SimInstance
 			auto sigbit = sig[i];
 			auto sigval = value[i];

+			auto clk2fflogic_driver = clk2fflogic_drivers.find(sigbit);
+			if (clk2fflogic_driver != clk2fflogic_drivers.end())
+				sigbit = clk2fflogic_driver->second;
+
 			auto in_parent_driver = in_parent_drivers.find(sigbit);
 			if (in_parent_driver == in_parent_drivers.end())
 				set_state(sigbit, sigval);
@ -589,7 +599,7 @@ struct SimInstance
 		}
 	}

-	bool update_ph2(bool gclk)
+	bool update_ph2(bool gclk, bool stable_past_update = false)
 	{
 		bool did_something = false;

@ -600,7 +610,7 @@ struct SimInstance

 			Const current_q = get_state(ff.data.sig_q);

-			if (ff_data.has_clk) {
+			if (ff_data.has_clk && !stable_past_update) {
 				// flip-flops
 				State current_clk = get_state(ff_data.sig_clk)[0];
 				if (ff_data.pol_clk ? (ff.past_clk == State::S0 && current_clk != State::S0) :
@ -621,7 +631,7 @@ struct SimInstance
 			if (ff_data.has_aload) {
 				State current_aload = get_state(ff_data.sig_aload)[0];
 				if (current_aload == (ff_data.pol_aload ? State::S1 : State::S0)) {
-					current_q = ff_data.has_clk ? ff.past_ad : get_state(ff.data.sig_ad);
+					current_q = ff_data.has_clk && !stable_past_update ? ff.past_ad : get_state(ff.data.sig_ad);
 				}
 			}
 			// async reset
@ -672,6 +682,8 @@ struct SimInstance
 				}
 				else
 				{
+					if (stable_past_update)
+						continue;
 					if (port.clk_polarity ?
 							(mdb.past_wr_clk[port_idx] == State::S1 || get_state(port.clk) != State::S1) :
 							(mdb.past_wr_clk[port_idx] == State::S0 || get_state(port.clk) != State::S0))
@ -701,7 +713,7 @@ struct SimInstance
 		}

 		for (auto it : children)
-			if (it.second->update_ph2(gclk)) {
+			if (it.second->update_ph2(gclk, stable_past_update)) {
 				dirty_children.insert(it.second);
 				did_something = true;
 			}
@ -1197,9 +1209,21 @@ struct SimWorker : SimShared

 	void initialize_stable_past()
 	{
-		if (debug)
-			log("\n-- ph1 (initialize) --\n");
-		top->update_ph1();
+
+		while (1)
+		{
+			if (debug)
+				log("\n-- ph1 (initialize) --\n");
+
+			top->update_ph1();
+
+			if (debug)
+				log("\n-- ph2 (initialize) --\n");
+
+			if (!top->update_ph2(false, true))
+				break;
+		}
+
 		if (debug)
 			log("\n-- ph3 (initialize) --\n");
 		top->update_ph3(true);
--- a/techlibs/gatemate/cells_bb.v
+++ b/techlibs/gatemate/cells_bb.v
@ -131,70 +131,3 @@ module CC_USR_RSTN (
 	output USR_RSTN
 );
 endmodule
-
-(* blackbox *)
-module CC_FIFO_40K (
-	output A_ECC_1B_ERR,
-	output B_ECC_1B_ERR,
-	output A_ECC_2B_ERR,
-	output B_ECC_2B_ERR,
-	// FIFO pop port
-	output [39:0] A_DO,
-	output [39:0] B_DO,
-	(* clkbuf_sink *)
-	input  A_CLK,
-	input  A_EN,
-	// FIFO push port
-	input  [39:0] A_DI,
-	input  [39:0] B_DI,
-	input  [39:0] A_BM,
-	input  [39:0] B_BM,
-	(* clkbuf_sink *)
-	input  B_CLK,
-	input  B_EN,
-	input  B_WE,
-	// FIFO control
-	input  F_RST_N,
-	input  [12:0] F_ALMOST_FULL_OFFSET,
-	input  [12:0] F_ALMOST_EMPTY_OFFSET,
-	// FIFO status signals
-	output F_FULL,
-	output F_EMPTY,
-	output F_ALMOST_FULL,
-	output F_ALMOST_EMPTY,
-	output F_RD_ERROR,
-	output F_WR_ERROR,
-	output [15:0] F_RD_PTR,
-	output [15:0] F_WR_PTR
-);
-	// Location format: D(0..N-1)X(0..3)Y(0..7) or UNPLACED
-	parameter LOC = "UNPLACED";
-
-	// Offset configuration
-	parameter [12:0] ALMOST_FULL_OFFSET = 12'b0;
-	parameter [12:0] ALMOST_EMPTY_OFFSET = 12'b0;
-
-	// Port Widths
-	parameter A_WIDTH = 0;
-	parameter B_WIDTH = 0;
-
-	// RAM and Write Modes
-	parameter RAM_MODE = "SDP"; // "TPD" or "SDP"
-	parameter FIFO_MODE = "SYNC"; // "ASYNC" or "SYNC"
-
-	// Inverting Control Pins
-	parameter A_CLK_INV = 1'b0;
-	parameter B_CLK_INV = 1'b0;
-	parameter A_EN_INV = 1'b0;
-	parameter B_EN_INV = 1'b0;
-	parameter A_WE_INV = 1'b0;
-	parameter B_WE_INV = 1'b0;
-
-	// Output Register
-	parameter A_DO_REG = 1'b0;
-	parameter B_DO_REG = 1'b0;
-
-	// Error Checking and Correction
-	parameter A_ECC_EN  = 1'b0;
-	parameter B_ECC_EN  = 1'b0;
-endmodule
--- a/techlibs/gatemate/cells_sim.v
+++ b/techlibs/gatemate/cells_sim.v
@ -733,13 +733,12 @@ module CC_BRAM_20K (
 			// SDP read port
 			always @(posedge clkb)
 			begin
-				// "NO_CHANGE" only
 				for (k=0; k < B_RD_WIDTH; k=k+1) begin
 					if (k < 20) begin
-						if (enb && !wea) A_DO_out[k] <= memory[addrb+k];
+						if (enb) A_DO_out[k] <= memory[addrb+k];
 					end
 					else begin // use both ports
-						if (enb && !wea) B_DO_out[k-20] <= memory[addrb+k];
+						if (enb) B_DO_out[k-20] <= memory[addrb+k];
 					end
 				end
 			end
@ -1274,13 +1273,12 @@ module CC_BRAM_40K (
 			// SDP read port
 			always @(posedge clkb)
 			begin
-				// "NO_CHANGE" only
 				for (k=0; k < B_RD_WIDTH; k=k+1) begin
 					if (k < 40) begin
-						if (enb && !wea) A_DO_out[k] <= memory[addrb+k];
+						if (enb) A_DO_out[k] <= memory[addrb+k];
 					end
 					else begin // use both ports
-						if (enb && !wea) B_DO_out[k-40] <= memory[addrb+k];
+						if (enb) B_DO_out[k-40] <= memory[addrb+k];
 					end
 				end
 			end
@ -1412,6 +1410,393 @@ module CC_BRAM_40K (
 	endgenerate
 endmodule

+module CC_FIFO_40K (
+	output A_ECC_1B_ERR,
+	output B_ECC_1B_ERR,
+	output A_ECC_2B_ERR,
+	output B_ECC_2B_ERR,
+	// FIFO pop port
+	output [39:0] A_DO,
+	output [39:0] B_DO,
+	(* clkbuf_sink *)
+	input  A_CLK,
+	input  A_EN,
+	// FIFO push port
+	input  [39:0] A_DI,
+	input  [39:0] B_DI,
+	input  [39:0] A_BM,
+	input  [39:0] B_BM,
+	(* clkbuf_sink *)
+	input  B_CLK,
+	input  B_EN,
+	input  B_WE,
+	// FIFO control
+	input  F_RST_N,
+	input  [14:0] F_ALMOST_FULL_OFFSET,
+	input  [14:0] F_ALMOST_EMPTY_OFFSET,
+	// FIFO status signals
+	output F_FULL,
+	output F_EMPTY,
+	output F_ALMOST_FULL,
+	output F_ALMOST_EMPTY,
+	output F_RD_ERROR,
+	output F_WR_ERROR,
+	output [15:0] F_RD_PTR,
+	output [15:0] F_WR_PTR
+);
+	// Location format: D(0..N-1)X(0..3)Y(0..7) or UNPLACED
+	parameter LOC = "UNPLACED";
+
+	// Offset configuration
+	parameter DYN_STAT_SELECT = 1'b0;
+	parameter [14:0] ALMOST_FULL_OFFSET = 15'b0;
+	parameter [14:0] ALMOST_EMPTY_OFFSET = 15'b0;
+
+	// Port Widths
+	parameter A_WIDTH = 0;
+	parameter B_WIDTH = 0;
+
+	// RAM and Write Modes
+	parameter RAM_MODE = "TDP"; // "TDP" or "SDP"
+	parameter FIFO_MODE = "SYNC"; // "ASYNC" or "SYNC"
+
+	// Inverting Control Pins
+	parameter A_CLK_INV = 1'b0;
+	parameter B_CLK_INV = 1'b0;
+	parameter A_EN_INV = 1'b0;
+	parameter B_EN_INV = 1'b0;
+	parameter A_WE_INV = 1'b0;
+	parameter B_WE_INV = 1'b0;
+
+	// Output Register
+	parameter A_DO_REG = 1'b0;
+	parameter B_DO_REG = 1'b0;
+
+	// Error Checking and Correction
+	parameter A_ECC_EN  = 1'b0;
+	parameter B_ECC_EN  = 1'b0;
+
+	integer i, k;
+
+	// 512 x 80 bit
+	reg [40959:0] memory = 40960'b0;
+
+	reg [15:0] counter_max;
+	reg [15:0] sram_depth;
+	localparam tp = (A_WIDTH ==  1) ? 15 :
+					(A_WIDTH ==  2) ? 14 :
+					(A_WIDTH ==  5) ? 13 :
+					(A_WIDTH == 10) ? 12 :
+					(A_WIDTH == 20) ? 11 :
+					(A_WIDTH == 40) ? 10 : 9;
+
+	initial begin
+		// Check parameters
+		if ((RAM_MODE != "SDP") && (RAM_MODE != "TDP")) begin
+			$display("ERROR: Illegal RAM MODE %d.", RAM_MODE);
+			$finish();
+		end
+		if ((FIFO_MODE != "ASYNC") && (FIFO_MODE != "SYNC")) begin
+			$display("ERROR: Illegal FIFO MODE %d.", FIFO_MODE);
+			$finish();
+		end
+		if ((RAM_MODE == "SDP") && (DYN_STAT_SELECT == 1)) begin
+			$display("ERROR: Dynamic offset configuration is not supported in %s mode.", RAM_MODE);
+			$finish();
+		end
+		if ((RAM_MODE == "SDP") && ((A_WIDTH != 80) || (B_WIDTH != 80))) begin
+			$display("ERROR: SDP is ony supported in 80 bit mode.");
+			$finish();
+		end
+		if ((A_WIDTH == 80) && (RAM_MODE == "TDP")) begin
+			$display("ERROR: Port A width of 80 bits is only supported in SDP mode.");
+			$finish();
+		end
+		if ((B_WIDTH == 80) && (RAM_MODE == "TDP")) begin
+			$display("ERROR: Port B width of 80 bits is only supported in SDP mode.");
+			$finish();
+		end
+		if ((A_WIDTH != 80) && (A_WIDTH != 40) && (A_WIDTH != 20) && (A_WIDTH != 10) &&
+			(A_WIDTH != 5)  && (A_WIDTH != 2)  && (A_WIDTH != 1) && (A_WIDTH != 0)) begin
+			$display("ERROR: Illegal %s Port A width configuration %d.", RAM_MODE, A_WIDTH);
+			$finish();
+		end
+		if ((B_WIDTH != 80) && (B_WIDTH != 40) && (B_WIDTH != 20) && (B_WIDTH != 10) &&
+			(B_WIDTH != 5)  && (B_WIDTH != 2)  && (B_WIDTH != 1) && (B_WIDTH != 0)) begin
+			$display("ERROR: Illegal %s Port B width configuration %d.", RAM_MODE, B_WIDTH);
+			$finish();
+		end
+		if (A_WIDTH != B_WIDTH) begin
+			$display("ERROR: The values of A_WIDTH and B_WIDTH must be equal.");
+		end
+		if ((A_ECC_EN == 1'b1) && (RAM_MODE != "SDP") && (A_WIDTH != 40)) begin
+			$display("ERROR: Illegal ECC Port A configuration. ECC mode requires TDP >=40 bit or SDP 80 bit, but is %s %d.", RAM_MODE, A_WIDTH);
+			$finish();
+		end
+		// Set local parameters
+		if (A_WIDTH == 1) begin // A_WIDTH=B_WIDTH
+			counter_max = 2 * 32*1024 - 1;
+			sram_depth  =     32*1024;
+		end
+		else if (A_WIDTH == 2) begin
+			counter_max = 2 * 16*1024 - 1;
+			sram_depth  =     16*1024;
+		end
+		else if (A_WIDTH == 5) begin
+			counter_max = 2 * 8*1024 - 1;
+			sram_depth  =     8*1024;
+		end
+		else if (A_WIDTH == 10) begin
+			counter_max = 2 * 4*1024 - 1;
+			sram_depth  =     4*1024;
+		end
+		else if (A_WIDTH == 20) begin
+			counter_max = 2 * 2*1024 - 1;
+			sram_depth  =     2*1024;
+		end
+		else if (A_WIDTH == 40) begin
+			counter_max = 2 * 1*1024 - 1;
+			sram_depth  =     1*1024;
+		end
+		else begin // 80 bit SDP
+			counter_max = 2 * 512 - 1;
+			sram_depth  =     512;
+		end
+	end
+
+	// Internal signals
+	wire fifo_rdclk = A_CLK ^ A_CLK_INV;
+	wire fifo_wrclk = (FIFO_MODE == "ASYNC") ? (B_CLK ^ B_CLK_INV) : (A_CLK ^ A_CLK_INV);
+	wire [15:0] almost_full_offset  = DYN_STAT_SELECT ? F_ALMOST_FULL_OFFSET  : ALMOST_FULL_OFFSET;
+	wire [15:0] almost_empty_offset = DYN_STAT_SELECT ? F_ALMOST_EMPTY_OFFSET : ALMOST_EMPTY_OFFSET;
+	reg  [39:0] A_DO_out = 0, A_DO_reg = 0;
+	reg  [39:0] B_DO_out = 0, B_DO_reg = 0;
+
+	// Status signals
+	reg fifo_full;
+	reg fifo_empty;
+	reg fifo_almost_full;
+	reg fifo_almost_empty;
+	assign F_FULL         = fifo_full;
+	assign F_EMPTY        = fifo_empty;
+	assign F_ALMOST_FULL  = fifo_almost_full;
+	assign F_ALMOST_EMPTY = fifo_almost_empty;
+	assign F_WR_ERROR     = (F_FULL && (B_EN ^ B_EN_INV) && (B_WE ^ B_WE_INV));
+	assign F_RD_ERROR     = (F_EMPTY && (A_EN ^ A_EN_INV));
+	wire ram_we = (~F_FULL  && (B_EN ^ B_EN_INV) && (B_WE ^ B_WE_INV));
+	wire ram_en = (~F_EMPTY && (A_EN ^ A_EN_INV));
+
+	// Reset synchronizers
+	reg  [1:0] aclk_reset_q, bclk_reset_q;
+	wire fifo_sync_rstn    = aclk_reset_q;
+	wire fifo_async_wrrstn = bclk_reset_q;
+	wire fifo_async_rdrstn = aclk_reset_q;
+
+	always @(posedge fifo_rdclk or negedge F_RST_N)
+	begin
+		if (F_RST_N == 1'b0) begin
+			aclk_reset_q <= 2'b0;
+		end
+		else begin
+			aclk_reset_q[1] <= aclk_reset_q[0];
+			aclk_reset_q[0] <= 1'b1;
+		end
+	end
+
+	always @(posedge fifo_wrclk or negedge F_RST_N)
+	begin
+		if (F_RST_N == 1'b0) begin
+			bclk_reset_q <= 2'b0;
+		end
+		else begin
+			bclk_reset_q[1] <= bclk_reset_q[0];
+			bclk_reset_q[0] <= 1'b1;
+		end
+	end
+
+	// Push/pop pointers
+	reg  [15:0] rd_pointer, rd_pointer_int;
+	reg  [15:0] wr_pointer, wr_pointer_int;
+	reg  [15:0] rd_pointer_cmp, wr_pointer_cmp;
+	wire [15:0] rd_pointer_nxt;
+	wire [15:0] wr_pointer_nxt;
+	reg  [15:0] fifo_rdaddr, rdaddr;
+	reg  [15:0] fifo_wraddr, wraddr;
+	assign F_RD_PTR = fifo_rdaddr;
+	assign F_WR_PTR = fifo_wraddr;
+
+	always @(posedge fifo_rdclk or negedge F_RST_N)
+	begin
+		if (F_RST_N == 1'b0) begin
+			rd_pointer <= 0;
+			rd_pointer_int <= 0;
+		end
+		else if (ram_en) begin
+			rd_pointer <= rd_pointer_nxt;
+			rd_pointer_int <= rd_pointer_nxt[15:1] ^ rd_pointer_nxt[14:0];
+		end
+	end
+
+	assign rd_pointer_nxt = (rd_pointer == counter_max) ? (0) : (rd_pointer + 1'b1);
+
+	always @(posedge fifo_wrclk or negedge F_RST_N)
+	begin
+		if (F_RST_N == 1'b0) begin
+			wr_pointer <= 0;
+			wr_pointer_int <= 0;
+		end
+		else if (ram_we) begin
+			wr_pointer <= wr_pointer_nxt;
+			wr_pointer_int <= wr_pointer_nxt[15:1] ^ wr_pointer_nxt[14:0];
+		end
+	end
+
+	assign wr_pointer_nxt = (wr_pointer == counter_max) ? (0) : (wr_pointer + 1'b1);
+
+	// Address synchronizers
+	reg [15:0] rd_pointer_sync, wr_pointer_sync;
+	reg [15:0] rd_pointer_sync_0, rd_pointer_sync_1;
+	reg [15:0] wr_pointer_sync_0, wr_pointer_sync_1;
+
+	always @(posedge fifo_rdclk or negedge F_RST_N)
+	begin
+		if (F_RST_N == 1'b0) begin
+			wr_pointer_sync_0 <= 0;
+			wr_pointer_sync_1 <= 0;
+		end
+		else begin
+			wr_pointer_sync_0 <= wraddr;
+			wr_pointer_sync_1 <= wr_pointer_sync_0;
+		end
+	 end
+
+	always @(posedge fifo_wrclk or negedge F_RST_N)
+	 begin
+		if (F_RST_N == 1'b0) begin
+			rd_pointer_sync_0 <= 0;
+			rd_pointer_sync_1 <= 0;
+		end
+		else begin
+			rd_pointer_sync_0 <= rdaddr;
+			rd_pointer_sync_1 <= rd_pointer_sync_0;
+		end
+	 end
+
+	always @(*) begin
+		fifo_wraddr = {wr_pointer[tp-1:0], {(15-tp){1'b0}}};
+		fifo_rdaddr = {rd_pointer[tp-1:0], {(15-tp){1'b0}}};
+
+		rdaddr = {rd_pointer[tp], rd_pointer_int[tp-1:0]};
+		wraddr = {{(15-tp){1'b0}}, wr_pointer[tp], wr_pointer_int[tp:0]};
+
+		if (FIFO_MODE == "ASYNC")
+			fifo_full = (wraddr[tp-2:0] == rd_pointer_sync_1[tp-2:0] ) && (wraddr[tp] != rd_pointer_sync_1[tp] ) && ( wraddr[tp-1] != rd_pointer_sync_1[tp-1] );
+		else
+			fifo_full = (wr_pointer[tp-1:0] == rd_pointer[tp-1:0]) && (wr_pointer[tp] ^ rd_pointer[tp]);
+
+		if (FIFO_MODE == "ASYNC")
+			fifo_empty = (wr_pointer_sync_1[tp:0] == rdaddr[tp:0]);
+		else
+			fifo_empty = (wr_pointer[tp:0] == rd_pointer[tp:0]);
+
+		rd_pointer_cmp = (FIFO_MODE == "ASYNC") ? rd_pointer_sync : rd_pointer;
+		if (wr_pointer[tp] == rd_pointer_cmp[tp])
+			fifo_almost_full = ((wr_pointer[tp-1:0] - rd_pointer_cmp[tp-1:0]) >= (sram_depth - almost_full_offset));
+		else
+			fifo_almost_full = ((rd_pointer_cmp[tp-1:0] - wr_pointer[tp-1:0]) <= almost_full_offset);
+
+		wr_pointer_cmp = (FIFO_MODE == "ASYNC") ? wr_pointer_sync : wr_pointer;
+		if (wr_pointer_cmp[tp] == rd_pointer[tp])
+			fifo_almost_empty = ((wr_pointer_cmp[tp-1:0] - rd_pointer[tp-1:0]) <= almost_empty_offset);
+		else
+			fifo_almost_empty = ((rd_pointer[tp-1:0] - wr_pointer_cmp[tp-1:0]) >= (sram_depth - almost_empty_offset));
+	end
+
+	generate
+		always @(*) begin
+			wr_pointer_sync = 0;
+			rd_pointer_sync = 0;
+			for (i=tp; i >= 0; i=i-1) begin
+				if (i == tp) begin
+					wr_pointer_sync[i] = wr_pointer_sync_1[i];
+					rd_pointer_sync[i] = rd_pointer_sync_1[i];
+				end
+				else begin
+					wr_pointer_sync[i] = wr_pointer_sync_1[i] ^ wr_pointer_sync[i+1];
+					rd_pointer_sync[i] = rd_pointer_sync_1[i] ^ rd_pointer_sync[i+1];
+				end
+			end
+		end
+		if (RAM_MODE == "SDP") begin
+			// SDP push ports A+B
+			always @(posedge fifo_wrclk)
+			begin
+				for (k=0; k < A_WIDTH; k=k+1) begin
+					if (k < 40) begin
+						if (ram_we && A_BM[k]) memory[fifo_wraddr+k] <= A_DI[k];
+					end
+					else begin // use both ports
+						if (ram_we && B_BM[k-40]) memory[fifo_wraddr+k] <= B_DI[k-40];
+					end
+				end
+			end
+			// SDP pop ports A+B
+			always @(posedge fifo_rdclk)
+			begin
+				for (k=0; k < B_WIDTH; k=k+1) begin
+					if (k < 40) begin
+						if (ram_en) A_DO_out[k] <= memory[fifo_rdaddr+k];
+					end
+					else begin // use both ports
+						if (ram_en) B_DO_out[k-40] <= memory[fifo_rdaddr+k];
+					end
+				end
+			end
+		end
+		else if (RAM_MODE == "TDP") begin
+			// TDP pop port A
+			always @(posedge fifo_rdclk)
+			begin
+				for (i=0; i < A_WIDTH; i=i+1) begin
+					if (ram_en) begin
+						A_DO_out[i] <= memory[fifo_rdaddr+i];
+					end
+				end
+			end
+			// TDP push port B
+			always @(posedge fifo_wrclk)
+			begin
+				for (i=0; i < B_WIDTH; i=i+1) begin
+					if (ram_we && B_BM[i])
+						memory[fifo_wraddr+i] <= B_DI[i];
+				end
+			end
+		end
+	endgenerate
+
+	// Optional output register
+	generate
+		if (A_DO_REG) begin
+			always @(posedge fifo_rdclk) begin
+				A_DO_reg <= A_DO_out;
+			end
+			assign A_DO = A_DO_reg;
+		end
+		else begin
+			assign A_DO = A_DO_out;
+		end
+		if (B_DO_REG) begin
+			always @(posedge fifo_rdclk) begin
+				B_DO_reg <= B_DO_out;
+			end
+			assign B_DO = B_DO_reg;
+		end
+		else begin
+			assign B_DO = B_DO_out;
+		end
+	endgenerate
+endmodule
+
 // Models of the LUT2 tree primitives
 module CC_L2T4(
 	output O,
--- a/tests/arch/anlogic/mux.ys
+++ b/tests/arch/anlogic/mux.ys
@ -26,10 +26,12 @@ proc
 equiv_opt -assert -map +/anlogic/cells_sim.v synth_anlogic # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux8 # Constrain all select calls below inside the top module
-select -assert-count 3 t:AL_MAP_LUT4
-select -assert-count 1 t:AL_MAP_LUT6
+select -assert-max 3 t:AL_MAP_LUT3
+select -assert-max 3 t:AL_MAP_LUT4
+select -assert-max 1 t:AL_MAP_LUT5
+select -assert-max 1 t:AL_MAP_LUT6

-select -assert-none t:AL_MAP_LUT4 t:AL_MAP_LUT6 %% t:* %D
+select -assert-none t:AL_MAP_LUT3 t:AL_MAP_LUT4 t:AL_MAP_LUT5 t:AL_MAP_LUT6 %% t:* %D

 design -load read
 hierarchy -top mux16
--- a/tests/arch/ecp5/mux.ys
+++ b/tests/arch/ecp5/mux.ys
@ -28,8 +28,8 @@ equiv_opt -assert -map +/ecp5/cells_sim.v synth_ecp5 # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux8 # Constrain all select calls below inside the top module
 select -assert-max 1 t:L6MUX21
-select -assert-max 7 t:LUT4
-select -assert-max 2 t:PFUMX
+select -assert-max 8 t:LUT4
+select -assert-max 3 t:PFUMX

 select -assert-none t:LUT4 t:L6MUX21 t:PFUMX %% t:* %D

--- a/tests/arch/gatemate/fsm.ys
+++ b/tests/arch/gatemate/fsm.ys
@ -15,6 +15,6 @@ cd fsm # Constrain all select calls below inside the top module
 select -assert-count 1 t:CC_BUFG
 select -assert-count 6 t:CC_DFF
 select -assert-max 5 t:CC_LUT2
-select -assert-max 4 t:CC_LUT3
+select -assert-max 6 t:CC_LUT3
 select -assert-max 9 t:CC_LUT4
 select -assert-none t:CC_BUFG t:CC_DFF t:CC_LUT2 t:CC_LUT3 t:CC_LUT4 %% t:* %D
--- a/tests/arch/ice40/rom.ys
+++ b/tests/arch/ice40/rom.ys
@ -4,5 +4,5 @@ flatten
 equiv_opt -assert -map +/ice40/cells_sim.v synth_ice40 # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd top # Constrain all select calls below inside the top module
-select -assert-count 5 t:SB_LUT4
+select -assert-max 6 t:SB_LUT4
 select -assert-none t:SB_LUT4 %% t:* %D
--- a/tests/arch/intel_alm/mux.ys
+++ b/tests/arch/intel_alm/mux.ys
@ -69,7 +69,7 @@ proc
 equiv_opt -assert -map +/intel_alm/common/alm_sim.v synth_intel_alm -family cyclonev -noiopad -noclkbuf # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux16 # Constrain all select calls below inside the top module
-select -assert-count 1 t:MISTRAL_ALUT3
+select -assert-max 1 t:MISTRAL_ALUT3
 select -assert-max 2 t:MISTRAL_ALUT5
 select -assert-max 5 t:MISTRAL_ALUT6
 select -assert-none t:MISTRAL_ALUT3 t:MISTRAL_ALUT5 t:MISTRAL_ALUT6 %% t:* %D
@ -81,8 +81,8 @@ proc
 equiv_opt -assert -map +/intel_alm/common/alm_sim.v synth_intel_alm -family cyclone10gx -noiopad -noclkbuf # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux16 # Constrain all select calls below inside the top module
-select -assert-count 1 t:MISTRAL_ALUT3
-select -assert-count 2 t:MISTRAL_ALUT5
-select -assert-count 4 t:MISTRAL_ALUT6
+select -assert-max 1 t:MISTRAL_ALUT3
+select -assert-max 2 t:MISTRAL_ALUT5
+select -assert-max 5 t:MISTRAL_ALUT6

 select -assert-none t:MISTRAL_ALUT3 t:MISTRAL_ALUT5 t:MISTRAL_ALUT6 %% t:* %D
--- a/tests/arch/nexus/mux.ys
+++ b/tests/arch/nexus/mux.ys
@ -36,8 +36,7 @@ proc
 equiv_opt -assert -map +/nexus/cells_sim.v synth_nexus # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux16 # Constrain all select calls below inside the top module
-select -assert-min 11 t:LUT4
 select -assert-max 12 t:LUT4
-select -assert-count 1 t:WIDEFN9
+select -assert-max 2 t:WIDEFN9

 select -assert-none t:IB t:OB t:VLO t:VHI t:LUT4 t:WIDEFN9 %% t:* %D
--- a/tests/arch/xilinx/mux_lut4.ys
+++ b/tests/arch/xilinx/mux_lut4.ys
@ -30,12 +30,13 @@ proc
 equiv_opt -assert -map +/xilinx/cells_sim.v synth_xilinx -family xc3se -noiopad # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd mux8 # Constrain all select calls below inside the top module
-select -assert-count 4 t:LUT1
-select -assert-count 3 t:LUT4
-select -assert-count 2 t:MUXF5
+select -assert-max 5 t:LUT1
+select -assert-max 3 t:LUT3
+select -assert-max 3 t:LUT4
+select -assert-max 3 t:MUXF5
 select -assert-count 1 t:MUXF6

-select -assert-none t:LUT1 t:LUT4 t:MUXF5 t:MUXF6 %% t:* %D
+select -assert-none t:LUT1 t:LUT3 t:LUT4 t:MUXF5 t:MUXF6 %% t:* %D


 design -load read
--- a/tests/various/constant_drive_conflict.ys
+++ b/tests/various/constant_drive_conflict.ys
@ -0,0 +1,51 @@
+read_verilog <<EOT
+module top(input A, output Y);
+	assign A = 1;
+
+	assign Y = A;
+endmodule
+EOT
+
+hierarchy -top top; proc
+
+logger -expect warning "Drivers conflicting with a constant" 1
+logger -expect log "Found and reported 1 problems." 1
+check
+logger -check-expected
+
+design -reset
+read_verilog <<EOT
+module top(input A, output Y);
+	buffer some_buffer(A, Y);
+	assign Y = 1;
+endmodule
+module buffer(input A, output Y);
+	assign Y = A;
+endmodule
+EOT
+
+hierarchy -top top; proc
+
+logger -expect warning "Drivers conflicting with a constant" 1
+logger -expect log "Found and reported 1 problems." 1
+check
+logger -check-expected
+
+design -reset
+read_verilog <<EOT
+module top(input clk, input A, output Y);
+	reg Q;
+	always @(posedge clk) Q <= A;
+
+	assign Q = 1;
+
+	assign Y = A;
+endmodule
+EOT
+
+hierarchy -top top
+
+logger -expect warning "Drivers conflicting with a constant" 1
+logger -expect log "Found and reported 1 problems." 1
+check
+logger -check-expected