Merge branch 'eddie/clkpart' into xaig_dff

15 files changed, 591 insertions, 23 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 1fc139d49..d9d261fbc 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -51,6 +51,9 @@ Yosys 0.9 .. Yosys 0.9-dev
     - "synth_ice40 -dsp" to infer DSP blocks
     - Added latch support to synth_xilinx
     - Added "check -mapped"
+    - Added checking of SystemVerilog always block types (always_comb,
+      always_latch and always_ff)
+    - Added "clkpart" pass
 
 Yosys 0.8 .. Yosys 0.9
 ----------------------
diff --git a/README.md b/README.md
index db7810cb4..e46971526 100644
--- a/README.md
+++ b/README.md
@@ -371,6 +371,11 @@ Verilog Attributes and non-standard features
   for example, to specify the clk-to-Q delay of a flip-flop for consideration
   during techmapping.
 
+- The frontend sets attributes ``always_comb``, ``always_latch`` and
+  ``always_ff`` on processes derived from SystemVerilog style always blocks
+  according to the type of the always. These are checked for correctness in
+  ``proc_dlatch``.
+
 - In addition to the ``(* ... *)`` attribute syntax, Yosys supports
   the non-standard ``{* ... *}`` attribute syntax to set default attributes
   for everything that comes after the ``{* ... *}`` statement. (Reset
diff --git a/frontends/verific/verific.cc b/frontends/verific/verific.cc
index a5c4aa26a..843e7b9b4 100644
--- a/frontends/verific/verific.cc
+++ b/frontends/verific/verific.cc
@@ -130,7 +130,7 @@ RTLIL::SigBit VerificImporter::net_map_at(Net *net)
 
 bool is_blackbox(Netlist *nl)
 {
-	if (nl->IsBlackBox())
+	if (nl->IsBlackBox() || nl->IsEmptyBox())
 		return true;
 
 	const char *attr = nl->GetAttValue("blackbox");
@@ -784,15 +784,15 @@ void VerificImporter::merge_past_ffs(pool<RTLIL::Cell*> &candidates)
 		merge_past_ffs_clock(it.second, it.first.first, it.first.second);
 }
 
-void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::set<Netlist*> &nl_todo)
+void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::set<Netlist*> &nl_todo, bool norename)
 {
 	std::string netlist_name = nl->GetAtt(" \\top") ? nl->CellBaseName() : nl->Owner()->Name();
 	std::string module_name = netlist_name;
 
-	if (nl->IsOperator()) {
+	if (nl->IsOperator() || nl->IsPrimitive()) {
 		module_name = "$verific$" + module_name;
 	} else {
-		if (*nl->Name()) {
+		if (!norename && *nl->Name()) {
 			module_name += "(";
 			module_name += nl->Name();
 			module_name += ")";
@@ -1409,7 +1409,7 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::se
 
 		std::string inst_type = inst->View()->Owner()->Name();
 
-		if (inst->View()->IsOperator()) {
+		if (inst->View()->IsOperator() || inst->View()->IsPrimitive()) {
 			inst_type = "$verific$" + inst_type;
 		} else {
 			if (*inst->View()->Name()) {
@@ -1899,7 +1899,7 @@ void verific_import(Design *design, const std::map<std::string,std::string> &par
 		Netlist *nl = *nl_todo.begin();
 		if (nl_done.count(nl) == 0) {
 			VerificImporter importer(false, false, false, false, false, false, false);
-			importer.import_netlist(design, nl, nl_todo);
+			importer.import_netlist(design, nl, nl_todo, nl->Owner()->Name() == top);
 		}
 		nl_todo.erase(nl);
 		nl_done.insert(nl);
@@ -2373,6 +2373,8 @@ struct VerificPass : public Pass {
 			if (argidx > GetSize(args) && args[argidx].compare(0, 1, "-") == 0)
 				cmd_error(args, argidx, "unknown option");
 
+			std::set<std::string> top_mod_names;
+
 			if (mode_all)
 			{
 				log("Running hier_tree::ElaborateAll().\n");
@@ -2401,6 +2403,7 @@ struct VerificPass : public Pass {
 				for (; argidx < GetSize(args); argidx++)
 				{
 					const char *name = args[argidx].c_str();
+					top_mod_names.insert(name);
 					VeriLibrary* veri_lib = veri_file::GetLibrary(work.c_str(), 1);
 
 					if (veri_lib) {
@@ -2466,7 +2469,7 @@ struct VerificPass : public Pass {
 				if (nl_done.count(nl) == 0) {
 					VerificImporter importer(mode_gates, mode_keep, mode_nosva,
 							mode_names, mode_verific, mode_autocover, mode_fullinit);
-					importer.import_netlist(design, nl, nl_todo);
+					importer.import_netlist(design, nl, nl_todo, top_mod_names.count(nl->Owner()->Name()));
 				}
 				nl_todo.erase(nl);
 				nl_done.insert(nl);
diff --git a/frontends/verific/verific.h b/frontends/verific/verific.h
index 5cbd78f7b..2ccfcd42c 100644
--- a/frontends/verific/verific.h
+++ b/frontends/verific/verific.h
@@ -93,7 +93,7 @@ struct VerificImporter
 	void merge_past_ffs_clock(pool<RTLIL::Cell*> &candidates, SigBit clock, bool clock_pol);
 	void merge_past_ffs(pool<RTLIL::Cell*> &candidates);
 
-	void import_netlist(RTLIL::Design *design, Verific::Netlist *nl, std::set<Verific::Netlist*> &nl_todo);
+	void import_netlist(RTLIL::Design *design, Verific::Netlist *nl, std::set<Verific::Netlist*> &nl_todo, bool norename = false);
 };
 
 void verific_import_sva_assert(VerificImporter *importer, Verific::Instance *inst);
diff --git a/frontends/verific/verificsva.cc b/frontends/verific/verificsva.cc
index 909e9b4f1..49c0c40ac 100644
--- a/frontends/verific/verificsva.cc
+++ b/frontends/verific/verificsva.cc
@@ -36,6 +36,8 @@
 // basic_property:
 //   sequence
 //   not basic_property
+//   nexttime basic_property
+//   nexttime[N] basic_property
 //   sequence #-# basic_property
 //   sequence #=# basic_property
 //   basic_property or basic_property           (cover only)
@@ -1264,6 +1266,26 @@ struct VerificSvaImporter
 			return node;
 		}
 
+		if (inst->Type() == PRIM_SVA_NEXTTIME || inst->Type() == PRIM_SVA_S_NEXTTIME)
+		{
+			const char *sva_low_s = inst->GetAttValue("sva:low");
+			const char *sva_high_s = inst->GetAttValue("sva:high");
+
+			int sva_low = atoi(sva_low_s);
+			int sva_high = atoi(sva_high_s);
+			log_assert(sva_low == sva_high);
+
+			int node = start_node;
+
+			for (int i = 0; i < sva_low; i++) {
+				int next_node = fsm.createNode();
+				fsm.createEdge(node, next_node);
+				node = next_node;
+			}
+
+			return parse_sequence(fsm, node, inst->GetInput());
+		}
+
 		if (inst->Type() == PRIM_SVA_SEQ_CONCAT)
 		{
 			const char *sva_low_s = inst->GetAttValue("sva:low");
@@ -1590,15 +1612,25 @@ struct VerificSvaImporter
 			Instance *consequent_inst = net_to_ast_driver(consequent_net);
 
 			if (consequent_inst && (consequent_inst->Type() == PRIM_SVA_UNTIL || consequent_inst->Type() == PRIM_SVA_S_UNTIL ||
-					consequent_inst->Type() == PRIM_SVA_UNTIL_WITH || consequent_inst->Type() == PRIM_SVA_S_UNTIL_WITH))
+					consequent_inst->Type() == PRIM_SVA_UNTIL_WITH || consequent_inst->Type() == PRIM_SVA_S_UNTIL_WITH ||
+					consequent_inst->Type() == PRIM_SVA_ALWAYS || consequent_inst->Type() == PRIM_SVA_S_ALWAYS))
 			{
 				bool until_with = consequent_inst->Type() == PRIM_SVA_UNTIL_WITH || consequent_inst->Type() == PRIM_SVA_S_UNTIL_WITH;
 
-				Net *until_net = consequent_inst->GetInput2();
-				consequent_net = consequent_inst->GetInput1();
-				consequent_inst = net_to_ast_driver(consequent_net);
+				Net *until_net = nullptr;
+				if (consequent_inst->Type() == PRIM_SVA_ALWAYS || consequent_inst->Type() == PRIM_SVA_S_ALWAYS)
+				{
+					consequent_net = consequent_inst->GetInput();
+					consequent_inst = net_to_ast_driver(consequent_net);
+				}
+				else
+				{
+					until_net = consequent_inst->GetInput2();
+					consequent_net = consequent_inst->GetInput1();
+					consequent_inst = net_to_ast_driver(consequent_net);
+				}
 
-				SigBit until_sig = parse_expression(until_net);
+				SigBit until_sig = until_net ? parse_expression(until_net) : RTLIL::S0;
 				SigBit not_until_sig = module->Not(NEW_ID, until_sig);
 				antecedent_fsm.createEdge(node, node, not_until_sig);
 
diff --git a/frontends/verilog/verilog_lexer.l b/frontends/verilog/verilog_lexer.l
index 4acfb414d..c8984c2c4 100644
--- a/frontends/verilog/verilog_lexer.l
+++ b/frontends/verilog/verilog_lexer.l
@@ -188,9 +188,9 @@ YOSYS_NAMESPACE_END
 "unique0"      { SV_KEYWORD(TOK_UNIQUE); }
 "priority"     { SV_KEYWORD(TOK_PRIORITY); }
 
-"always_comb"  { SV_KEYWORD(TOK_ALWAYS); }
-"always_ff"    { SV_KEYWORD(TOK_ALWAYS); }
-"always_latch" { SV_KEYWORD(TOK_ALWAYS); }
+"always_comb"  { SV_KEYWORD(TOK_ALWAYS_COMB); }
+"always_ff"    { SV_KEYWORD(TOK_ALWAYS_FF); }
+"always_latch" { SV_KEYWORD(TOK_ALWAYS_LATCH); }
 
  /* use special token for labels on assert, assume, cover, and restrict because it's insanley complex
     to fix parsing of cells otherwise. (the current cell parser forces a reduce very early to update some
diff --git a/frontends/verilog/verilog_parser.y b/frontends/verilog/verilog_parser.y
index 77f6d2051..daea3b43a 100644
--- a/frontends/verilog/verilog_parser.y
+++ b/frontends/verilog/verilog_parser.y
@@ -141,6 +141,7 @@ struct specify_rise_fall {
 %token TOK_INTERFACE TOK_ENDINTERFACE TOK_MODPORT TOK_VAR
 %token TOK_INPUT TOK_OUTPUT TOK_INOUT TOK_WIRE TOK_WAND TOK_WOR TOK_REG TOK_LOGIC
 %token TOK_INTEGER TOK_SIGNED TOK_ASSIGN TOK_ALWAYS TOK_INITIAL
+%token TOK_ALWAYS_FF TOK_ALWAYS_COMB TOK_ALWAYS_LATCH
 %token TOK_BEGIN TOK_END TOK_IF TOK_ELSE TOK_FOR TOK_WHILE TOK_REPEAT
 %token TOK_DPI_FUNCTION TOK_POSEDGE TOK_NEGEDGE TOK_OR TOK_AUTOMATIC
 %token TOK_CASE TOK_CASEX TOK_CASEZ TOK_ENDCASE TOK_DEFAULT
@@ -156,7 +157,7 @@ struct specify_rise_fall {
 %type <ast> range range_or_multirange  non_opt_range non_opt_multirange range_or_signed_int
 %type <ast> wire_type expr basic_expr concat_list rvalue lvalue lvalue_concat_list
 %type <string> opt_label opt_sva_label tok_prim_wrapper hierarchical_id hierarchical_type_id
-%type <boolean> opt_signed opt_property unique_case_attr
+%type <boolean> opt_signed opt_property unique_case_attr always_comb_or_latch always_or_always_ff
 %type <al> attr case_attr
 
 %type <specify_target_ptr> specify_target
@@ -1581,10 +1582,28 @@ cell_port:
 		free_attr($1);
 	};
 
+always_comb_or_latch:
+	TOK_ALWAYS_COMB {
+		$$ = false;
+	} |
+	TOK_ALWAYS_LATCH {
+		$$ = true;
+	};
+
+always_or_always_ff:
+	TOK_ALWAYS {
+		$$ = false;
+	} |
+	TOK_ALWAYS_FF {
+		$$ = true;
+	};
+
 always_stmt:
-	attr TOK_ALWAYS {
+	attr always_or_always_ff {
 		AstNode *node = new AstNode(AST_ALWAYS);
 		append_attr(node, $1);
+		if ($2)
+			node->attributes[ID(always_ff)] = AstNode::mkconst_int(1, false);
 		ast_stack.back()->children.push_back(node);
 		ast_stack.push_back(node);
 	} always_cond {
@@ -1595,6 +1614,22 @@ always_stmt:
 		ast_stack.pop_back();
 		ast_stack.pop_back();
 	} |
+	attr always_comb_or_latch {
+		AstNode *node = new AstNode(AST_ALWAYS);
+		append_attr(node, $1);
+		if ($2)
+			node->attributes[ID(always_latch)] = AstNode::mkconst_int(1, false);
+		else
+			node->attributes[ID(always_comb)] = AstNode::mkconst_int(1, false);
+		ast_stack.back()->children.push_back(node);
+		ast_stack.push_back(node);
+		AstNode *block = new AstNode(AST_BLOCK);
+		ast_stack.back()->children.push_back(block);
+		ast_stack.push_back(block);
+	} behavioral_stmt {
+		ast_stack.pop_back();
+		ast_stack.pop_back();
+	} |
 	attr TOK_INITIAL {
 		AstNode *node = new AstNode(AST_INITIAL);
 		append_attr(node, $1);
diff --git a/passes/memory/memory.cc b/passes/memory/memory.cc
index 712bc2537..cee63bdd8 100644
--- a/passes/memory/memory.cc
+++ b/passes/memory/memory.cc
@@ -35,6 +35,7 @@ struct MemoryPass : public Pass {
 		log("\n");
 		log("This pass calls all the other memory_* passes in a useful order:\n");
 		log("\n");
+		log("    opt_mem\n");
 		log("    memory_dff [-nordff]                (-memx implies -nordff)\n");
 		log("    opt_clean\n");
 		log("    memory_share\n");
@@ -81,6 +82,7 @@ struct MemoryPass : public Pass {
 		}
 		extra_args(args, argidx, design);
 
+		Pass::call(design, "opt_mem");
 		Pass::call(design, flag_nordff ? "memory_dff -nordff" : "memory_dff");
 		Pass::call(design, "opt_clean");
 		Pass::call(design, "memory_share");
diff --git a/passes/opt/Makefile.inc b/passes/opt/Makefile.inc
index eb07e9452..002c1a6a1 100644
--- a/passes/opt/Makefile.inc
+++ b/passes/opt/Makefile.inc
@@ -1,6 +1,7 @@
 
 OBJS += passes/opt/opt.o
 OBJS += passes/opt/opt_merge.o
+OBJS += passes/opt/opt_mem.o
 OBJS += passes/opt/opt_muxtree.o
 OBJS += passes/opt/opt_reduce.o
 OBJS += passes/opt/opt_rmdff.o
diff --git a/passes/opt/opt_mem.cc b/passes/opt/opt_mem.cc
new file mode 100644
index 000000000..98d3551eb
--- /dev/null
+++ b/passes/opt/opt_mem.cc
@@ -0,0 +1,143 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/yosys.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct OptMemWorker
+{
+	RTLIL::Design *design;
+	RTLIL::Module *module;
+	SigMap sigmap;
+	bool restart;
+
+	dict<IdString, vector<IdString>> memrd, memwr, meminit;
+	pool<IdString> remove_mem, remove_cells;
+
+	OptMemWorker(RTLIL::Module *module) : design(module->design), module(module), sigmap(module), restart(false)
+	{
+		for (auto &it : module->memories)
+		{
+			memrd[it.first];
+			memwr[it.first];
+			meminit[it.first];
+		}
+
+		for (auto cell : module->cells())
+		{
+			if (cell->type == ID($memrd)) {
+				IdString id = cell->getParam(ID(MEMID)).decode_string();
+				memrd.at(id).push_back(cell->name);
+			}
+
+			if (cell->type == ID($memwr)) {
+				IdString id = cell->getParam(ID(MEMID)).decode_string();
+				memwr.at(id).push_back(cell->name);
+			}
+
+			if (cell->type == ID($meminit)) {
+				IdString id = cell->getParam(ID(MEMID)).decode_string();
+				meminit.at(id).push_back(cell->name);
+			}
+		}
+	}
+
+	~OptMemWorker()
+	{
+		for (auto it : remove_mem)
+		{
+			for (auto cell_name : memrd[it])
+				module->remove(module->cell(cell_name));
+			for (auto cell_name : memwr[it])
+				module->remove(module->cell(cell_name));
+			for (auto cell_name : meminit[it])
+				module->remove(module->cell(cell_name));
+
+			delete module->memories.at(it);
+			module->memories.erase(it);
+		}
+
+		for (auto cell_name : remove_cells)
+			module->remove(module->cell(cell_name));
+	}
+
+	int run(RTLIL::Memory *mem)
+	{
+		if (restart || remove_mem.count(mem->name))
+			return 0;
+
+		if (memwr.at(mem->name).empty() && meminit.at(mem->name).empty()) {
+			log("Removing memory %s.%s with no write ports or init data.\n", log_id(module), log_id(mem));
+			remove_mem.insert(mem->name);
+			return 1;
+		}
+
+		return 0;
+	}
+};
+
+struct OptMemPass : public Pass {
+	OptMemPass() : Pass("opt_mem", "optimize memories") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    opt_mem [options] [selection]\n");
+		log("\n");
+		log("This pass performs various optimizations on memories in the design.\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		log_header(design, "Executing OPT_MEM pass (optimize memories).\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++) {
+			// if (args[argidx] == "-nomux") {
+			// 	mode_nomux = true;
+			// 	continue;
+			// }
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		int total_count = 0;
+		for (auto module : design->selected_modules()) {
+			while (1) {
+				int cnt = 0;
+				OptMemWorker worker(module);
+				for (auto &it : module->memories)
+					if (module->selected(it.second))
+						cnt += worker.run(it.second);
+				if (!cnt && !worker.restart)
+					break;
+				total_count += cnt;
+			}
+		}
+
+		if (total_count)
+			design->scratchpad_set_bool("opt.did_something", true);
+		log("Performed a total of %d transformations.\n", total_count);
+	}
+} OptMemPass;
+
+PRIVATE_NAMESPACE_END
diff --git a/passes/proc/proc_dlatch.cc b/passes/proc/proc_dlatch.cc
index d9d5dfbed..a0c8351b6 100644
--- a/passes/proc/proc_dlatch.cc
+++ b/passes/proc/proc_dlatch.cc
@@ -349,6 +349,10 @@ void proc_dlatch(proc_dlatch_db_t &db, RTLIL::Process *proc)
 			continue;
 		}
 
+		if (proc->get_bool_attribute(ID(always_ff)))
+			log_error("Found non edge/level sensitive event in always_ff process `%s.%s'.\n",
+					db.module->name.c_str(), proc->name.c_str());
+
 		for (auto ss : sr->actions)
 		{
 			db.sigmap.apply(ss.first);
@@ -383,8 +387,12 @@ void proc_dlatch(proc_dlatch_db_t &db, RTLIL::Process *proc)
 	int offset = 0;
 	for (auto chunk : nolatches_bits.first.chunks()) {
 		SigSpec lhs = chunk, rhs = nolatches_bits.second.extract(offset, chunk.width);
-		log("No latch inferred for signal `%s.%s' from process `%s.%s'.\n",
-				db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str());
+		if (proc->get_bool_attribute(ID(always_latch)))
+			log_error("No latch inferred for signal `%s.%s' from always_latch process `%s.%s'.\n",
+					db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str());
+		else
+			log("No latch inferred for signal `%s.%s' from process `%s.%s'.\n",
+					db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str());
 		db.module->connect(lhs, rhs);
 		offset += chunk.width;
 	}
@@ -410,8 +418,12 @@ void proc_dlatch(proc_dlatch_db_t &db, RTLIL::Process *proc)
 			cell->set_src_attribute(src);
 			db.generated_dlatches.insert(cell);
 
-			log("Latch inferred for signal `%s.%s' from process `%s.%s': %s\n",
-					db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str(), log_id(cell));
+			if (proc->get_bool_attribute(ID(always_comb)))
+				log_error("Latch inferred for signal `%s.%s' from always_comb process `%s.%s'.\n",
+						db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str());
+			else
+				log("Latch inferred for signal `%s.%s' from process `%s.%s': %s\n",
+						db.module->name.c_str(), log_signal(lhs), db.module->name.c_str(), proc->name.c_str(), log_id(cell));
 		}
 
 		offset += width;
diff --git a/passes/techmap/clkpart.cc b/passes/techmap/clkpart.cc
new file mode 100644
index 000000000..4fa729250
--- /dev/null
+++ b/passes/techmap/clkpart.cc
@@ -0,0 +1,268 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *                2019  Eddie Hung <eddie@fpgeh.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/register.h"
+#include "kernel/sigtools.h"
+#include "kernel/celltypes.h"
+#include "kernel/rtlil.h"
+#include "kernel/log.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct ClkPartPass : public Pass {
+	ClkPartPass() : Pass("clkpart", "partition design according to clock domain") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    clkpart [options] [selection]\n");
+		log("\n");
+		log("Partition the contents of selected modules according to the clock (and optionally\n");
+		log("the enable) domains of its $_DFF* cells by extracting them into sub-modules,\n");
+		log("using the `submod` command.\n");
+		log("Sub-modules created by this command are marked with a 'clkpart' attribute.\n");
+		log("\n");
+		log("    -unpart\n");
+		log("        undo this operation within the selected modules, by flattening those with\n");
+		log("        a 'clkpart' attribute into those modules without this attribute.\n");
+		log("\n");
+		log("    -enable\n");
+		log("        also consider enable domains.\n");
+		log("\n");
+	}
+
+	bool unpart_mode, enable_mode;
+
+	void clear_flags() YS_OVERRIDE
+	{
+		unpart_mode = false;
+		enable_mode = false;
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		log_header(design, "Executing CLKPART pass (TODO).\n");
+		log_push();
+
+		clear_flags();
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			if (args[argidx] == "-unpart") {
+				unpart_mode = true;
+				continue;
+			}
+			if (args[argidx] == "-enable") {
+				enable_mode = true;
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		if (unpart_mode)
+			unpart(design);
+		else
+			part(design);
+
+		log_pop();
+	}
+
+	void part(RTLIL::Design *design)
+	{
+		CellTypes ct(design);
+		SigMap assign_map;
+
+		for (auto mod : design->selected_modules())
+		{
+			if (mod->processes.size() > 0) {
+				log("Skipping module %s as it contains processes.\n", log_id(mod));
+				continue;
+			}
+
+			assign_map.set(mod);
+
+			std::vector<RTLIL::Cell*> all_cells = mod->selected_cells();
+			std::set<RTLIL::Cell*> unassigned_cells(all_cells.begin(), all_cells.end());
+
+			std::set<RTLIL::Cell*> expand_queue, next_expand_queue;
+			std::set<RTLIL::Cell*> expand_queue_up, next_expand_queue_up;
+			std::set<RTLIL::Cell*> expand_queue_down, next_expand_queue_down;
+
+			typedef tuple<bool, RTLIL::SigSpec, bool, RTLIL::SigSpec> clkdomain_t;
+			std::map<clkdomain_t, vector<RTLIL::IdString>> assigned_cells;
+			std::map<RTLIL::Cell*, clkdomain_t> assigned_cells_reverse;
+
+			std::map<RTLIL::Cell*, std::set<RTLIL::SigBit>> cell_to_bit, cell_to_bit_up, cell_to_bit_down;
+			std::map<RTLIL::SigBit, std::set<RTLIL::Cell*>> bit_to_cell, bit_to_cell_up, bit_to_cell_down;
+
+			for (auto cell : all_cells)
+			{
+				clkdomain_t key;
+
+				for (auto &conn : cell->connections())
+				for (auto bit : conn.second) {
+					bit = assign_map(bit);
+					if (bit.wire != nullptr) {
+						cell_to_bit[cell].insert(bit);
+						bit_to_cell[bit].insert(cell);
+						if (ct.cell_input(cell->type, conn.first)) {
+							cell_to_bit_up[cell].insert(bit);
+							bit_to_cell_down[bit].insert(cell);
+						}
+						if (ct.cell_output(cell->type, conn.first)) {
+							cell_to_bit_down[cell].insert(bit);
+							bit_to_cell_up[bit].insert(cell);
+						}
+					}
+				}
+
+				if (cell->type.in(ID($_DFF_N_), ID($_DFF_P_)))
+				{
+					key = clkdomain_t(cell->type == ID($_DFF_P_), assign_map(cell->getPort(ID(C))), true, RTLIL::SigSpec());
+				}
+				else
+				if (cell->type.in(ID($_DFFE_NN_), ID($_DFFE_NP_), ID($_DFFE_PN_), ID($_DFFE_PP_)))
+				{
+					bool this_clk_pol = cell->type.in(ID($_DFFE_PN_), ID($_DFFE_PP_));
+					bool this_en_pol = !enable_mode || cell->type.in(ID($_DFFE_NP_), ID($_DFFE_PP_));
+					key = clkdomain_t(this_clk_pol, assign_map(cell->getPort(ID(C))), this_en_pol, enable_mode ? assign_map(cell->getPort(ID(E)) : RTLIL::SigSpec()));
+				}
+				else
+					continue;
+
+				unassigned_cells.erase(cell);
+				expand_queue.insert(cell);
+				expand_queue_up.insert(cell);
+				expand_queue_down.insert(cell);
+
+				assigned_cells[key].push_back(cell->name);
+				assigned_cells_reverse[cell] = key;
+			}
+
+			while (!expand_queue_up.empty() || !expand_queue_down.empty())
+			{
+				if (!expand_queue_up.empty())
+				{
+					RTLIL::Cell *cell = *expand_queue_up.begin();
+					clkdomain_t key = assigned_cells_reverse.at(cell);
+					expand_queue_up.erase(cell);
+
+					for (auto bit : cell_to_bit_up[cell])
+					for (auto c : bit_to_cell_up[bit])
+						if (unassigned_cells.count(c)) {
+							unassigned_cells.erase(c);
+							next_expand_queue_up.insert(c);
+							assigned_cells[key].push_back(c->name);
+							assigned_cells_reverse[c] = key;
+							expand_queue.insert(c);
+						}
+				}
+
+				if (!expand_queue_down.empty())
+				{
+					RTLIL::Cell *cell = *expand_queue_down.begin();
+					clkdomain_t key = assigned_cells_reverse.at(cell);
+					expand_queue_down.erase(cell);
+
+					for (auto bit : cell_to_bit_down[cell])
+					for (auto c : bit_to_cell_down[bit])
+						if (unassigned_cells.count(c)) {
+							unassigned_cells.erase(c);
+							next_expand_queue_up.insert(c);
+							assigned_cells[key].push_back(c->name);
+							assigned_cells_reverse[c] = key;
+							expand_queue.insert(c);
+						}
+				}
+
+				if (expand_queue_up.empty() && expand_queue_down.empty()) {
+					expand_queue_up.swap(next_expand_queue_up);
+					expand_queue_down.swap(next_expand_queue_down);
+				}
+			}
+
+			while (!expand_queue.empty())
+			{
+				RTLIL::Cell *cell = *expand_queue.begin();
+				clkdomain_t key = assigned_cells_reverse.at(cell);
+				expand_queue.erase(cell);
+
+				for (auto bit : cell_to_bit.at(cell)) {
+					for (auto c : bit_to_cell[bit])
+						if (unassigned_cells.count(c)) {
+							unassigned_cells.erase(c);
+							next_expand_queue.insert(c);
+							assigned_cells[key].push_back(c->name);
+							assigned_cells_reverse[c] = key;
+						}
+					bit_to_cell[bit].clear();
+				}
+
+				if (expand_queue.empty())
+					expand_queue.swap(next_expand_queue);
+			}
+
+			clkdomain_t key(true, RTLIL::SigSpec(), true, RTLIL::SigSpec());
+			for (auto cell : unassigned_cells) {
+				assigned_cells[key].push_back(cell->name);
+				assigned_cells_reverse[cell] = key;
+			}
+
+			log_header(design, "Summary of detected clock domains:\n");
+			for (auto &it : assigned_cells)
+				log("  %d cells in clk=%s%s, en=%s%s\n", GetSize(it.second),
+						std::get<0>(it.first) ? "" : "!", log_signal(std::get<1>(it.first)),
+						std::get<2>(it.first) ? "" : "!", log_signal(std::get<3>(it.first)));
+
+			for (auto &it : assigned_cells) {
+				RTLIL::Selection sel(false);
+				sel.selected_members[mod->name] = pool<IdString>(it.second.begin(), it.second.end());
+
+				RTLIL::IdString submod = stringf("%s.%s", mod->name.c_str(), NEW_ID.c_str());
+				Pass::call_on_selection(design, sel, stringf("submod -name %s", submod.c_str()));
+
+				design->module(submod)->set_bool_attribute(ID(clkpart));
+			}
+		}
+	}
+
+	void unpart(RTLIL::Design *design)
+	{
+		vector<Module*> keeped;
+		for (auto mod : design->selected_modules()) {
+			if (mod->get_bool_attribute(ID(clkpart)))
+				continue;
+			if (mod->get_bool_attribute(ID(keep_hierarchy)))
+				continue;
+			keeped.push_back(mod);
+			mod->set_bool_attribute(ID(keep_hierarchy));
+		}
+
+		Pass::call(design, "flatten");
+
+		for (auto mod : keeped)
+			mod->set_bool_attribute(ID(keep_hierarchy), false);
+
+	}
+} ClkPartPass;
+
+PRIVATE_NAMESPACE_END
diff --git a/techlibs/gowin/.gitignore b/techlibs/gowin/.gitignore
new file mode 100644
index 000000000..d6c48e90d
--- /dev/null
+++ b/techlibs/gowin/.gitignore
@@ -0,0 +1,2 @@
+brams_init.mk
+bram_init_*.vh
diff --git a/tests/arch/gowin/mux.ys b/tests/arch/gowin/mux.ys
index 4990be421..afad29a89 100644
--- a/tests/arch/gowin/mux.ys
+++ b/tests/arch/gowin/mux.ys
@@ -45,6 +45,5 @@ design -load postopt # load the post-opt design (otherwise equiv_opt loads the p
 cd mux16 # Constrain all select calls below inside the top module
 select -assert-count 20 t:IBUF
 select -assert-count 1 t:OBUF
-show
 
 select -assert-none t:LUT4 t:MUX2_LUT6 t:MUX2_LUT5 t:MUX2_LUT6 t:MUX2_LUT7 t:MUX2_LUT8 t:IBUF t:OBUF %% t:* %D
diff --git a/tests/various/svalways.sh b/tests/various/svalways.sh
new file mode 100755
index 000000000..2cc09f801
--- /dev/null
+++ b/tests/various/svalways.sh
@@ -0,0 +1,63 @@
+#!/bin/bash
+
+trap 'echo "ERROR in svalways.sh" >&2; exit 1' ERR
+
+# Good case
+../../yosys -f "verilog -sv" -qp proc - <<EOT
+module top(input clk, en, d, output reg p, q, r);
+
+always_ff @(posedge clk)
+	p <= d;
+
+always_comb
+	q = ~d;
+
+always_latch
+	if (en) r = d;
+
+endmodule
+EOT
+
+# Incorrect always_comb syntax
+((../../yosys -f "verilog -sv" -qp proc -|| true) <<EOT
+module top(input d, output reg q);
+
+always_comb @(d)
+	q = ~d;
+
+endmodule
+EOT
+) 2>&1 | grep -F "<stdin>:3: ERROR: syntax error, unexpected '@'" > /dev/null
+
+# Incorrect use of always_comb
+((../../yosys -f "verilog -sv" -qp proc -|| true) <<EOT
+module top(input en, d, output reg q);
+
+always_comb
+	if (en) q = d;
+
+endmodule
+EOT
+) 2>&1 | grep -F "ERROR: Latch inferred for signal \`\\top.\\q' from always_comb process" > /dev/null
+
+# Incorrect use of always_latch
+((../../yosys -f "verilog -sv" -qp proc -|| true) <<EOT
+module top(input en, d, output reg q);
+
+always_latch
+	q = !d;
+
+endmodule
+EOT
+) 2>&1 | grep -F "ERROR: No latch inferred for signal \`\\top.\\q' from always_latch process" > /dev/null
+
+# Incorrect use of always_ff
+((../../yosys -f "verilog -sv" -qp proc -|| true) <<EOT
+module top(input en, d, output reg q);
+
+always_ff @(*)
+	q = !d;
+
+endmodule
+EOT
+) 2>&1 | grep -F "ERROR: Found non edge/level sensitive event in always_ff process" > /dev/null