Merge remote-tracking branch 'upstream/master'

13 files changed, 1760 insertions, 46 deletions

diff --git a/passes/cmds/rename.cc b/passes/cmds/rename.cc
index 698ce7235..9b1830b7b 100644
--- a/passes/cmds/rename.cc
+++ b/passes/cmds/rename.cc
@@ -24,7 +24,7 @@
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
 
-static void rename_in_module(RTLIL::Module *module, std::string from_name, std::string to_name)
+static void rename_in_module(RTLIL::Module *module, std::string from_name, std::string to_name, bool flag_output)
 {
 	from_name = RTLIL::escape_id(from_name);
 	to_name = RTLIL::escape_id(to_name);
@@ -37,13 +37,18 @@ static void rename_in_module(RTLIL::Module *module, std::string from_name, std::
 			Wire *w = it.second;
 			log("Renaming wire %s to %s in module %s.\n", log_id(w), log_id(to_name), log_id(module));
 			module->rename(w, to_name);
-			if (w->port_id)
+			if (w->port_id || flag_output) {
+				if (flag_output)
+					w->port_output = true;
 				module->fixup_ports();
+			}
 			return;
 		}
 
 	for (auto &it : module->cells_)
 		if (it.first == from_name) {
+			if (flag_output)
+				log_cmd_error("Called with -output but the specified object is a cell.\n");
 			log("Renaming cell %s to %s in module %s.\n", log_id(it.second), log_id(to_name), log_id(module));
 			module->rename(it.second, to_name);
 			return;
@@ -108,15 +113,26 @@ struct RenamePass : public Pass {
 		log("Rename the specified object. Note that selection patterns are not supported\n");
 		log("by this command.\n");
 		log("\n");
+		log("\n");
+		log("\n");
+		log("    rename -output old_name new_name\n");
+		log("\n");
+		log("Like above, but also make the wire an output. This will fail if the object is\n");
+		log("not a wire.\n");
+		log("\n");
+		log("\n");
 		log("    rename -src [selection]\n");
 		log("\n");
 		log("Assign names auto-generated from the src attribute to all selected wires and\n");
 		log("cells with private names.\n");
 		log("\n");
+		log("\n");
 		log("    rename -wire [selection]\n");
+		log("\n");
 		log("Assign auto-generated names based on the wires they drive to all selected\n");
 		log("cells with private names. Ignores cells driving privatly named wires.\n");
 		log("\n");
+		log("\n");
 		log("    rename -enumerate [-pattern <pattern>] [selection]\n");
 		log("\n");
 		log("Assign short auto-generated names to all selected wires and cells with private\n");
@@ -124,11 +140,13 @@ struct RenamePass : public Pass {
 		log("The character %% in the pattern is replaced with a integer number. The default\n");
 		log("pattern is '_%%_'.\n");
 		log("\n");
+		log("\n");
 		log("    rename -hide [selection]\n");
 		log("\n");
 		log("Assign private names (the ones with $-prefix) to all selected wires and cells\n");
 		log("with public names. This ignores all selected ports.\n");
 		log("\n");
+		log("\n");
 		log("    rename -top new_name\n");
 		log("\n");
 		log("Rename top module.\n");
@@ -142,6 +160,7 @@ struct RenamePass : public Pass {
 		bool flag_enumerate = false;
 		bool flag_hide = false;
 		bool flag_top = false;
+		bool flag_output = false;
 		bool got_mode = false;
 
 		size_t argidx;
@@ -153,6 +172,11 @@ struct RenamePass : public Pass {
 				got_mode = true;
 				continue;
 			}
+			if (arg == "-output" && !got_mode) {
+				flag_output = true;
+				got_mode = true;
+				continue;
+			}
 			if (arg == "-wire" && !got_mode) {
 				flag_wire = true;
 				got_mode = true;
@@ -322,10 +346,12 @@ struct RenamePass : public Pass {
 			if (!design->selected_active_module.empty())
 			{
 				if (design->modules_.count(design->selected_active_module) > 0)
-					rename_in_module(design->modules_.at(design->selected_active_module), from_name, to_name);
+					rename_in_module(design->modules_.at(design->selected_active_module), from_name, to_name, flag_output);
 			}
 			else
 			{
+				if (flag_output)
+					log_cmd_error("Mode -output requires that there is an active module selected.\n");
 				for (auto &mod : design->modules_) {
 					if (mod.first == from_name || RTLIL::unescape_id(mod.first) == from_name) {
 						to_name = RTLIL::escape_id(to_name);
diff --git a/passes/hierarchy/uniquify.cc b/passes/hierarchy/uniquify.cc
index c88ecd82e..e6154e94f 100644
--- a/passes/hierarchy/uniquify.cc
+++ b/passes/hierarchy/uniquify.cc
@@ -87,6 +87,8 @@ struct UniquifyPass : public Pass {
 					smod->name = newname;
 					cell->type = newname;
 					smod->set_bool_attribute("\\unique");
+					if (smod->attributes.count("\\hdlname") == 0)
+						smod->attributes["\\hdlname"] = string(log_id(tmod->name));
 					design->add(smod);
 
 					did_something = true;
diff --git a/passes/memory/memory_bram.cc b/passes/memory/memory_bram.cc
index cf4095d06..85ed1c053 100644
--- a/passes/memory/memory_bram.cc
+++ b/passes/memory/memory_bram.cc
@@ -542,7 +542,7 @@ bool replace_cell(Cell *cell, const rules_t &rules, const rules_t::bram_t &bram,
 	}
 
 	// assign write ports
-
+	pair<SigBit, bool> wr_clkdom;
 	for (int cell_port_i = 0, bram_port_i = 0; cell_port_i < wr_ports; cell_port_i++)
 	{
 		bool clken = wr_clken[cell_port_i] == State::S1;
@@ -552,7 +552,7 @@ bool replace_cell(Cell *cell, const rules_t &rules, const rules_t::bram_t &bram,
 		pair<SigBit, bool> clkdom(clksig, clkpol);
 		if (!clken)
 			clkdom = pair<SigBit, bool>(State::S1, false);
-
+		wr_clkdom = clkdom;
 		log("      Write port #%d is in clock domain %s%s.\n",
 				cell_port_i, clkdom.second ? "" : "!",
 				clken ? log_signal(clkdom.first) : "~async~");
@@ -641,6 +641,7 @@ grow_read_ports:;
 				pi.sig_data = SigSpec();
 				pi.sig_en = SigSpec();
 				pi.make_outreg = false;
+				pi.make_transp = false;
 			}
 			new_portinfos.push_back(pi);
 			if (pi.dupidx == dup_count-1) {
@@ -718,7 +719,13 @@ grow_read_ports:;
 				if (read_transp.count(pi.transp) && read_transp.at(pi.transp) != transp) {
 					if (match.make_transp && wr_ports <= 1) {
 						pi.make_transp = true;
-						enable_make_transp = true;
+						if (pi.clocks != 0) {
+							if (wr_ports == 1 && wr_clkdom != clkdom) {								
+								log("        Bram port %c%d.%d cannot have soft transparency logic added as read and write clock domains differ.\n", pi.group + 'A', pi.index + 1, pi.dupidx + 1);
+								goto skip_bram_rport;
+							}
+							enable_make_transp = true;
+						}
 					} else {
 						log("        Bram port %c%d.%d has incompatible read transparency.\n", pi.group + 'A', pi.index + 1, pi.dupidx + 1);
 						goto skip_bram_rport;
@@ -913,17 +920,18 @@ grow_read_ports:;
 				} else {
 					SigSpec bram_dout = module->addWire(NEW_ID, bram.dbits);
 					c->setPort(stringf("\\%sDATA", pf), bram_dout);
-
-					if (pi.make_outreg) {
+					if (pi.make_outreg && pi.make_transp) {
+						log("        Moving output register to address for transparent port %c%d.%d.\n", pi.group + 'A', pi.index + 1, pi.dupidx + 1);
+						SigSpec sig_addr_q = module->addWire(NEW_ID, bram.abits);
+						module->addDff(NEW_ID, pi.sig_clock, sig_addr, sig_addr_q, pi.effective_clkpol);
+						c->setPort(stringf("\\%sADDR", pf), sig_addr_q);
+					} else if (pi.make_outreg) {
 						SigSpec bram_dout_q = module->addWire(NEW_ID, bram.dbits);
 						if (!pi.sig_en.empty())
 							bram_dout = module->Mux(NEW_ID, bram_dout_q, bram_dout, pi.sig_en);
 						module->addDff(NEW_ID, pi.sig_clock, bram_dout, bram_dout_q, pi.effective_clkpol);
 						bram_dout = bram_dout_q;
-					}
-
-					if (pi.make_transp)
-					{
+					} else if (pi.make_transp) {
 						log("        Adding extra logic for transparent port %c%d.%d.\n", pi.group + 'A', pi.index + 1, pi.dupidx + 1);
 
 						SigSpec transp_en_d = module->Mux(NEW_ID, SigSpec(0, make_transp_enbits),
diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index 26a3ca7bc..a05db2a4f 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -155,6 +155,13 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
 			new_b.append_bit(it.first.second);
 		}
 
+		if (cell->type.in("$and", "$or") && i == GRP_CONST_A) {
+			log("  Direct Connection: %s (%s with %s)\n", log_signal(new_b), log_id(cell->type), log_signal(new_a));
+			module->connect(new_y, new_b);
+			module->connect(new_conn);
+			continue;
+		}
+
 		RTLIL::Cell *c = module->addCell(NEW_ID, cell->type);
 
 		c->setPort("\\A", new_a);
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index 1f7222e49..52245ce3e 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -54,6 +54,7 @@ struct WreduceWorker
 	std::set<SigBit> work_queue_bits;
 	pool<SigBit> keep_bits;
 	dict<SigBit, State> init_bits;
+	pool<SigBit> remove_init_bits;
 
 	WreduceWorker(WreduceConfig *config, Module *module) :
 			config(config), module(module), mi(module) { }
@@ -164,6 +165,7 @@ struct WreduceWorker
 		{
 			if (zero_ext && sig_d[i] == State::S0 && (initval[i] == State::S0 || initval[i] == State::Sx)) {
 				module->connect(sig_q[i], State::S0);
+				remove_init_bits.insert(sig_q[i]);
 				sig_d.remove(i);
 				sig_q.remove(i);
 				continue;
@@ -171,6 +173,7 @@ struct WreduceWorker
 
 			if (sign_ext && i > 0 && sig_d[i] == sig_d[i-1] && initval[i] == initval[i-1]) {
 				module->connect(sig_q[i], sig_q[i-1]);
+				remove_init_bits.insert(sig_q[i]);
 				sig_d.remove(i);
 				sig_q.remove(i);
 				continue;
@@ -178,6 +181,7 @@ struct WreduceWorker
 
 			auto info = mi.query(sig_q[i]);
 			if (!info->is_output && GetSize(info->ports) == 1 && !keep_bits.count(mi.sigmap(sig_q[i]))) {
+				remove_init_bits.insert(sig_q[i]);
 				sig_d.remove(i);
 				sig_q.remove(i);
 				zero_ext = false;
@@ -387,13 +391,16 @@ struct WreduceWorker
 
 	void run()
 	{
+		// create a copy as mi.sigmap will be updated as we process the module
+		SigMap init_attr_sigmap = mi.sigmap;
+
 		for (auto w : module->wires()) {
 			if (w->get_bool_attribute("\\keep"))
 				for (auto bit : mi.sigmap(w))
 					keep_bits.insert(bit);
 			if (w->attributes.count("\\init")) {
 				Const initval = w->attributes.at("\\init");
-				SigSpec initsig = mi.sigmap(w);
+				SigSpec initsig = init_attr_sigmap(w);
 				int width = std::min(GetSize(initval), GetSize(initsig));
 				for (int i = 0; i < width; i++)
 					init_bits[initsig[i]] = initval[i];
@@ -446,6 +453,24 @@ struct WreduceWorker
 			module->connect(nw, SigSpec(w).extract(0, GetSize(nw)));
 			module->swap_names(w, nw);
 		}
+
+		if (!remove_init_bits.empty()) {
+			for (auto w : module->wires()) {
+				if (w->attributes.count("\\init")) {
+					Const initval = w->attributes.at("\\init");
+					Const new_initval(State::Sx, GetSize(w));
+					SigSpec initsig = init_attr_sigmap(w);
+					int width = std::min(GetSize(initval), GetSize(initsig));
+					for (int i = 0; i < width; i++) {
+						log_dump(initsig[i], remove_init_bits.count(initsig[i]));
+						if (!remove_init_bits.count(initsig[i]))
+							new_initval[i] = initval[i];
+					}
+					w->attributes.at("\\init") = new_initval;
+					log_dump(w->name, initval, new_initval);
+				}
+			}
+		}
 	}
 };
 
diff --git a/passes/pmgen/README.md b/passes/pmgen/README.md
index a1007dc62..223b43059 100644
--- a/passes/pmgen/README.md
+++ b/passes/pmgen/README.md
@@ -16,7 +16,7 @@ API of Generated Matcher
 ========================
 
 When `pmgen.py` reads a `foobar.pmg` file, it writes `foobar_pm.h` containing
-a class `foobar_pm`. That class is instanciated with an RTLIL module and a
+a class `foobar_pm`. That class is instantiated with an RTLIL module and a
 list of cells from that module:
 
     foobar_pm pm(module, module->selected_cells());
@@ -142,7 +142,7 @@ The `select` lines are evaluated once for each cell when the matcher is
 initialized. A `match` block will only consider cells for which all `select`
 expressions evaluated to `true`. Note that the state variable corresponding to
 the match (in the example `mul`) is the only state variable that may be used
-`select` lines.
+in `select` lines.
 
 Index lines are using the `index <type> expr1 === expr2` syntax.  `expr1` is
 evaluated during matcher initialization and the same restrictions apply as for
diff --git a/passes/sat/Makefile.inc b/passes/sat/Makefile.inc
index 6cb1ea644..fc3ac879e 100644
--- a/passes/sat/Makefile.inc
+++ b/passes/sat/Makefile.inc
@@ -9,4 +9,7 @@ OBJS += passes/sat/assertpmux.o
 OBJS += passes/sat/clk2fflogic.o
 OBJS += passes/sat/async2sync.o
 OBJS += passes/sat/supercover.o
+OBJS += passes/sat/fmcombine.o
+OBJS += passes/sat/mutate.o
+OBJS += passes/sat/cutpoint.o
 
diff --git a/passes/sat/async2sync.cc b/passes/sat/async2sync.cc
index c92db7118..d045d0dcb 100644
--- a/passes/sat/async2sync.cc
+++ b/passes/sat/async2sync.cc
@@ -39,7 +39,7 @@ struct Async2syncPass : public Pass {
 		log("reset value in the next cycle regardless of the data-in value at the time of\n");
 		log("the clock edge.\n");
 		log("\n");
-		log("Currently only $adff cells are supported by this pass.\n");
+		log("Currently only $adff and $dffsr cells are supported by this pass.\n");
 		log("\n");
 	}
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
@@ -84,7 +84,7 @@ struct Async2syncPass : public Pass {
 					bool arst_pol = cell->parameters["\\ARST_POLARITY"].as_bool();
 					Const arst_val = cell->parameters["\\ARST_VALUE"];
 
-					SigSpec sig_clk = cell->getPort("\\CLK");
+					// SigSpec sig_clk = cell->getPort("\\CLK");
 					SigSpec sig_arst = cell->getPort("\\ARST");
 					SigSpec sig_d = cell->getPort("\\D");
 					SigSpec sig_q = cell->getPort("\\Q");
@@ -120,6 +120,55 @@ struct Async2syncPass : public Pass {
 					cell->type = "$dff";
 					continue;
 				}
+
+				if (cell->type.in("$dffsr"))
+				{
+					// bool clk_pol = cell->parameters["\\CLK_POLARITY"].as_bool();
+					bool set_pol = cell->parameters["\\SET_POLARITY"].as_bool();
+					bool clr_pol = cell->parameters["\\CLR_POLARITY"].as_bool();
+
+					// SigSpec sig_clk = cell->getPort("\\CLK");
+					SigSpec sig_set = cell->getPort("\\SET");
+					SigSpec sig_clr = cell->getPort("\\CLR");
+					SigSpec sig_d = cell->getPort("\\D");
+					SigSpec sig_q = cell->getPort("\\Q");
+
+					log("Replacing %s.%s (%s): SET=%s, CLR=%s, D=%s, Q=%s\n",
+							log_id(module), log_id(cell), log_id(cell->type),
+							log_signal(sig_set), log_signal(sig_clr), log_signal(sig_d), log_signal(sig_q));
+
+					Const init_val;
+					for (int i = 0; i < GetSize(sig_q); i++) {
+						SigBit bit = sigmap(sig_q[i]);
+						init_val.bits.push_back(initbits.count(bit) ? initbits.at(bit) : State::Sx);
+						del_initbits.insert(bit);
+					}
+
+					Wire *new_d = module->addWire(NEW_ID, GetSize(sig_d));
+					Wire *new_q = module->addWire(NEW_ID, GetSize(sig_q));
+					new_q->attributes["\\init"] = init_val;
+
+					if (!set_pol)
+						sig_set = module->Not(NEW_ID, sig_set);
+
+					if (clr_pol)
+						sig_clr = module->Not(NEW_ID, sig_clr);
+
+					SigSpec tmp = module->Or(NEW_ID, sig_d, sig_set);
+					module->addAnd(NEW_ID, tmp, sig_clr, new_d);
+
+					tmp = module->Or(NEW_ID, new_q, sig_set);
+					module->addAnd(NEW_ID, tmp, sig_clr, sig_q);
+
+					cell->setPort("\\D", new_d);
+					cell->setPort("\\Q", new_q);
+					cell->unsetPort("\\SET");
+					cell->unsetPort("\\CLR");
+					cell->unsetParam("\\SET_POLARITY");
+					cell->unsetParam("\\CLR_POLARITY");
+					cell->type = "$dff";
+					continue;
+				}
 			}
 
 			for (auto wire : module->wires())
diff --git a/passes/sat/cutpoint.cc b/passes/sat/cutpoint.cc
new file mode 100644
index 000000000..048aec7f3
--- /dev/null
+++ b/passes/sat/cutpoint.cc
@@ -0,0 +1,168 @@
+/*
+ *  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 CutpointPass : public Pass {
+	CutpointPass() : Pass("cutpoint", "add hi/lo cover cells for each wire bit") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    cutpoint [options] [selection]\n");
+		log("\n");
+		log("This command adds formal cut points to the design.\n");
+		log("\n");
+		log("    -undef\n");
+		log("        set cupoint nets to undef (x). the default behavior is to create a\n");
+		log("        $anyseq cell and drive the cutpoint net from that\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		 bool flag_undef = false;
+
+		log_header(design, "Executing CUTPOINT pass.\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			if (args[argidx] == "-undef") {
+				flag_undef = true;
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		for (auto module : design->selected_modules())
+		{
+			if (design->selected_whole_module(module->name)) {
+				log("Making all outputs of module %s cut points, removing module contents.\n", log_id(module));
+				module->new_connections(std::vector<RTLIL::SigSig>());
+				for (auto cell : vector<Cell*>(module->cells()))
+					module->remove(cell);
+				vector<Wire*> output_wires;
+				for (auto wire : module->wires())
+					if (wire->port_output)
+						output_wires.push_back(wire);
+				for (auto wire : output_wires)
+					module->connect(wire, flag_undef ? Const(State::Sx, GetSize(wire)) : module->Anyseq(NEW_ID, GetSize(wire)));
+				continue;
+			}
+
+			SigMap sigmap(module);
+			pool<SigBit> cutpoint_bits;
+
+			for (auto cell : module->selected_cells()) {
+				if (cell->type == "$anyseq")
+					continue;
+				log("Removing cell %s.%s, making all cell outputs cutpoints.\n", log_id(module), log_id(cell));
+				for (auto &conn : cell->connections()) {
+					if (cell->output(conn.first))
+						module->connect(conn.second, flag_undef ? Const(State::Sx, GetSize(conn.second)) : module->Anyseq(NEW_ID, GetSize(conn.second)));
+				}
+				module->remove(cell);
+			}
+
+			for (auto wire : module->selected_wires()) {
+				if (wire->port_output) {
+					log("Making output wire %s.%s a cutpoint.\n", log_id(module), log_id(wire));
+					Wire *new_wire = module->addWire(NEW_ID, wire);
+					module->swap_names(wire, new_wire);
+					module->connect(new_wire, flag_undef ? Const(State::Sx, GetSize(new_wire)) : module->Anyseq(NEW_ID, GetSize(new_wire)));
+					wire->port_id = 0;
+					wire->port_input = false;
+					wire->port_output = false;
+					continue;
+				}
+				log("Making wire %s.%s a cutpoint.\n", log_id(module), log_id(wire));
+				for (auto bit : sigmap(wire))
+					cutpoint_bits.insert(bit);
+			}
+
+			if (!cutpoint_bits.empty())
+			{
+				for (auto cell : module->cells()) {
+					for (auto &conn : cell->connections()) {
+						if (!cell->output(conn.first))
+							continue;
+						SigSpec sig = sigmap(conn.second);
+						int bit_count = 0;
+						for (auto &bit : sig) {
+							if (cutpoint_bits.count(bit))
+								bit_count++;
+						}
+						if (bit_count == 0)
+							continue;
+						SigSpec dummy = module->addWire(NEW_ID, bit_count);
+						bit_count = 0;
+						for (auto &bit : sig) {
+							if (cutpoint_bits.count(bit))
+								bit = dummy[bit_count++];
+						}
+						cell->setPort(conn.first, sig);
+					}
+				}
+
+				vector<Wire*> rewrite_wires;
+				for (auto wire : module->wires()) {
+					if (!wire->port_input)
+						continue;
+					int bit_count = 0;
+					for (auto &bit : sigmap(wire))
+						if (cutpoint_bits.count(bit))
+							bit_count++;
+					if (bit_count)
+						rewrite_wires.push_back(wire);
+				}
+
+				for (auto wire : rewrite_wires) {
+					Wire *new_wire = module->addWire(NEW_ID, wire);
+					SigSpec lhs, rhs, sig = sigmap(wire);
+					for (int i = 0; i < GetSize(sig); i++)
+						if (!cutpoint_bits.count(sig[i])) {
+							lhs.append(SigBit(wire, i));
+							rhs.append(SigBit(new_wire, i));
+						}
+					if (GetSize(lhs))
+						module->connect(lhs, rhs);
+					module->swap_names(wire, new_wire);
+					wire->port_id = 0;
+					wire->port_input = false;
+					wire->port_output = false;
+				}
+
+				SigSpec sig(cutpoint_bits);
+				sig.sort_and_unify();
+
+				for (auto chunk : sig.chunks()) {
+					SigSpec s(chunk);
+					module->connect(s, flag_undef ? Const(State::Sx, GetSize(s)) : module->Anyseq(NEW_ID, GetSize(s)));
+				}
+			}
+		}
+	}
+} CutpointPass;
+
+PRIVATE_NAMESPACE_END
diff --git a/passes/sat/fmcombine.cc b/passes/sat/fmcombine.cc
new file mode 100644
index 000000000..cd75ca860
--- /dev/null
+++ b/passes/sat/fmcombine.cc
@@ -0,0 +1,341 @@
+/*
+ *  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"
+#include "kernel/celltypes.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct opts_t
+{
+	bool fwd = false;
+	bool bwd = false;
+	bool nop = false;
+};
+
+struct FmcombineWorker
+{
+	const opts_t &opts;
+	Design *design;
+	Module *original = nullptr;
+	Module *module = nullptr;
+	IdString orig_type, combined_type;
+
+	FmcombineWorker(Design *design, IdString orig_type, const opts_t &opts) :
+			opts(opts), design(design), original(design->module(orig_type)),
+			orig_type(orig_type), combined_type("$fmcombine" + orig_type.str())
+	{
+	}
+
+	SigSpec import_sig(SigSpec sig, const string &suffix)
+	{
+		SigSpec newsig;
+		for (auto chunk : sig.chunks()) {
+			if (chunk.wire != nullptr)
+				chunk.wire = module->wire(chunk.wire->name.str() + suffix);
+			newsig.append(chunk);
+		}
+		return newsig;
+	}
+
+	void import_prim_cell(Cell *cell, const string &suffix)
+	{
+		Cell *c = module->addCell(cell->name.str() + suffix, cell->type);
+		c->parameters = cell->parameters;
+		c->attributes = cell->attributes;
+
+		for (auto &conn : cell->connections())
+			c->setPort(conn.first, import_sig(conn.second, suffix));
+	}
+
+	void import_hier_cell(Cell *cell)
+	{
+		if (!cell->parameters.empty())
+			log_cmd_error("Cell %s.%s has unresolved instance parameters.\n", log_id(original), log_id(cell));
+
+		FmcombineWorker sub_worker(design, cell->type, opts);
+		sub_worker.generate();
+
+		Cell *c = module->addCell(cell->name.str() + "_combined", sub_worker.combined_type);
+		// c->parameters = cell->parameters;
+		c->attributes = cell->attributes;
+
+		for (auto &conn : cell->connections()) {
+			c->setPort(conn.first.str() + "_gold", import_sig(conn.second, "_gold"));
+			c->setPort(conn.first.str() + "_gate", import_sig(conn.second, "_gate"));
+		}
+	}
+
+	void generate()
+	{
+		if (design->module(combined_type)) {
+			// log("Combined module %s already exists.\n", log_id(combined_type));
+			return;
+		}
+
+		log("Generating combined module %s from module %s.\n", log_id(combined_type), log_id(orig_type));
+		module = design->addModule(combined_type);
+
+		for (auto wire : original->wires()) {
+			module->addWire(wire->name.str() + "_gold", wire);
+			module->addWire(wire->name.str() + "_gate", wire);
+		}
+		module->fixup_ports();
+
+		for (auto cell : original->cells()) {
+			if (design->module(cell->type) == nullptr) {
+				import_prim_cell(cell, "_gold");
+				import_prim_cell(cell, "_gate");
+			} else {
+				import_hier_cell(cell);
+			}
+		}
+
+		for (auto &conn : original->connections()) {
+			module->connect(import_sig(conn.first, "_gold"), import_sig(conn.second, "_gold"));
+			module->connect(import_sig(conn.first, "_gate"), import_sig(conn.second, "_gate"));
+		}
+
+		if (opts.nop)
+			return;
+
+		CellTypes ct;
+		ct.setup_internals_eval();
+		ct.setup_stdcells_eval();
+
+		SigMap sigmap(module);
+
+		dict<SigBit, SigBit> data_bit_to_eq_net;
+		dict<Cell*, SigSpec> cell_to_eq_nets;
+		dict<SigSpec, SigSpec> reduce_db;
+		dict<SigSpec, SigSpec> invert_db;
+
+		for (auto cell : original->cells())
+		{
+			if (!ct.cell_known(cell->type))
+				continue;
+
+			for (auto &conn : cell->connections())
+			{
+				if (!cell->output(conn.first))
+					continue;
+
+				SigSpec A = import_sig(conn.second, "_gold");
+				SigSpec B = import_sig(conn.second, "_gate");
+				SigBit EQ = module->Eq(NEW_ID, A, B);
+
+				for (auto bit : sigmap({A, B}))
+					data_bit_to_eq_net[bit] = EQ;
+
+				cell_to_eq_nets[cell].append(EQ);
+			}
+		}
+
+		for (auto cell : original->cells())
+		{
+			if (!ct.cell_known(cell->type))
+				continue;
+
+			bool skip_cell = !cell_to_eq_nets.count(cell);
+			pool<SigBit> src_eq_bits;
+
+			for (auto &conn : cell->connections())
+			{
+				if (skip_cell)
+					break;
+
+				if (cell->output(conn.first))
+					continue;
+
+				SigSpec A = import_sig(conn.second, "_gold");
+				SigSpec B = import_sig(conn.second, "_gate");
+
+				for (auto bit : sigmap({A, B})) {
+					if (data_bit_to_eq_net.count(bit))
+						src_eq_bits.insert(data_bit_to_eq_net.at(bit));
+					else
+						skip_cell = true;
+				}
+			}
+
+			if (!skip_cell) {
+				SigSpec antecedent = SigSpec(src_eq_bits);
+				antecedent.sort_and_unify();
+
+				if (GetSize(antecedent) > 1) {
+					if (reduce_db.count(antecedent) == 0)
+						reduce_db[antecedent] = module->ReduceAnd(NEW_ID, antecedent);
+					antecedent = reduce_db.at(antecedent);
+				}
+
+				SigSpec consequent = cell_to_eq_nets.at(cell);
+				consequent.sort_and_unify();
+
+				if (GetSize(consequent) > 1) {
+					if (reduce_db.count(consequent) == 0)
+						reduce_db[consequent] = module->ReduceAnd(NEW_ID, consequent);
+					consequent = reduce_db.at(consequent);
+				}
+
+				if (opts.fwd)
+					module->addAssume(NEW_ID, consequent, antecedent);
+
+				if (opts.bwd)
+				{
+					if (invert_db.count(antecedent) == 0)
+						invert_db[antecedent] = module->Not(NEW_ID, antecedent);
+
+					if (invert_db.count(consequent) == 0)
+						invert_db[consequent] = module->Not(NEW_ID, consequent);
+
+					module->addAssume(NEW_ID, invert_db.at(antecedent), invert_db.at(consequent));
+				}
+			}
+		}
+	}
+};
+
+struct FmcombinePass : public Pass {
+	FmcombinePass() : Pass("fmcombine", "combine two instances of a cell into one") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    fmcombine [options] module_name gold_cell gate_cell\n");
+		// log("    fmcombine [options] @gold_cell @gate_cell\n");
+		log("\n");
+		log("This pass takes two cells, which are instances of the same module, and replaces\n");
+		log("them with one instance of a special 'combined' module, that effectively\n");
+		log("contains two copies of the original module, plus some formal properties.\n");
+		log("\n");
+		log("This is useful for formal test benches that check what differences in behavior\n");
+		log("a slight difference in input causes in a module.\n");
+		log("\n");
+		log("    -fwd\n");
+		log("        Insert forward hint assumptions into the combined module.\n");
+		log("\n");
+		log("    -bwd\n");
+		log("        Insert backward hint assumptions into the combined module.\n");
+		log("        (Backward hints are logically equivalend to fordward hits, but\n");
+		log("        some solvers are faster with bwd hints, or even both -bwd and -fwd.)\n");
+		log("\n");
+		log("    -nop\n");
+		log("        Don't insert hint assumptions into the combined module.\n");
+		log("        (This should not provide any speedup over the original design, but\n");
+		log("        strangely sometimes it does.)\n");
+		log("\n");
+		log("If none of -fwd, -bwd, and -nop is given, then -fwd is used as default.\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		opts_t opts;
+		Module *module = nullptr;
+		Cell *gold_cell = nullptr;
+		Cell *gate_cell = nullptr;
+
+		log_header(design, "Executing FMCOMBINE pass.\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			// if (args[argidx] == "-o" && argidx+1 < args.size()) {
+			// 	filename = args[++argidx];
+			// 	continue;
+			// }
+			if (args[argidx] == "-fwd") {
+				opts.fwd = true;
+				continue;
+			}
+			if (args[argidx] == "-bwd") {
+				opts.bwd = true;
+				continue;
+			}
+			if (args[argidx] == "-nop") {
+				opts.nop = true;
+				continue;
+			}
+			break;
+		}
+		if (argidx+2 == args.size())
+		{
+			string gold_name = args[argidx++];
+			string gate_name = args[argidx++];
+			log_cmd_error("fmcombine @gold_cell @gate_cell call style is not implemented yet.");
+		}
+		else if (argidx+3 == args.size())
+		{
+			IdString module_name = RTLIL::escape_id(args[argidx++]);
+			IdString gold_name = RTLIL::escape_id(args[argidx++]);
+			IdString gate_name = RTLIL::escape_id(args[argidx++]);
+
+			module = design->module(module_name);
+			if (module == nullptr)
+				log_cmd_error("Module %s not found.\n", log_id(module_name));
+
+			gold_cell = module->cell(gold_name);
+			if (gold_cell == nullptr)
+				log_cmd_error("Gold cell %s not found in module %s.\n", log_id(gold_name), log_id(module));
+
+			gate_cell = module->cell(gate_name);
+			if (gate_cell == nullptr)
+				log_cmd_error("Gold cell %s not found in module %s.\n", log_id(gate_name), log_id(module));
+		}
+		else
+		{
+			log_cmd_error("Invalid number of arguments.\n");
+		}
+		// extra_args(args, argidx, design);
+
+		if (opts.nop && (opts.fwd || opts.bwd))
+			log_cmd_error("Option -nop can not be combined with -fwd and/or -bwd.\n");
+
+		if (!opts.nop && !opts.fwd && !opts.bwd)
+			opts.fwd = true;
+
+		if (gold_cell->type != gate_cell->type)
+			log_cmd_error("Types of gold and gate cells do not match.\n");
+		if (!gold_cell->parameters.empty())
+			log_cmd_error("Gold cell has unresolved instance parameters.\n");
+		if (!gate_cell->parameters.empty())
+			log_cmd_error("Gold cell has unresolved instance parameters.\n");
+
+		FmcombineWorker worker(design, gold_cell->type, opts);
+		worker.generate();
+		IdString combined_cell_name = module->uniquify(stringf("\\%s_%s", log_id(gold_cell), log_id(gate_cell)));
+
+		Cell *cell = module->addCell(combined_cell_name, worker.combined_type);
+		cell->attributes = gold_cell->attributes;
+		cell->add_strpool_attribute("\\src", gate_cell->get_strpool_attribute("\\src"));
+
+		log("Combining cells %s and %s in module %s into new cell %s.\n", log_id(gold_cell), log_id(gate_cell), log_id(module), log_id(cell));
+
+		for (auto &conn : gold_cell->connections())
+			cell->setPort(conn.first.str() + "_gold", conn.second);
+		module->remove(gold_cell);
+
+		for (auto &conn : gate_cell->connections())
+			cell->setPort(conn.first.str() + "_gate", conn.second);
+		module->remove(gate_cell);
+	}
+} FmcombinePass;
+
+PRIVATE_NAMESPACE_END
diff --git a/passes/sat/mutate.cc b/passes/sat/mutate.cc
new file mode 100644
index 000000000..c50678c51
--- /dev/null
+++ b/passes/sat/mutate.cc
@@ -0,0 +1,956 @@
+/*
+ *  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 mutate_t {
+	string mode;
+	pool<string> src;
+	IdString module, cell;
+	IdString port, wire;
+	int portbit = -1;
+	int ctrlbit = -1;
+	int wirebit = -1;
+	bool used = false;
+};
+
+struct mutate_opts_t {
+	int seed = 0;
+	std::string mode;
+	pool<string> src;
+	IdString module, cell, port, wire;
+	int portbit = -1;
+	int ctrlbit = -1;
+	int wirebit = -1;
+
+	IdString ctrl_name;
+	int ctrl_width = -1, ctrl_value = -1;
+
+	bool none = false;
+
+	int pick_cover_prcnt = 80;
+
+	int weight_cover = 500;
+
+	int weight_pq_w = 100;
+	int weight_pq_b = 100;
+	int weight_pq_c = 100;
+	int weight_pq_s = 100;
+
+	int weight_pq_mw = 100;
+	int weight_pq_mb = 100;
+	int weight_pq_mc = 100;
+	int weight_pq_ms = 100;
+};
+
+void database_add(std::vector<mutate_t> &database, const mutate_opts_t &opts, const mutate_t &entry)
+{
+	if (!opts.mode.empty() && opts.mode != entry.mode)
+		return;
+
+	if (!opts.src.empty()) {
+		bool found_match = false;
+		for (auto &s : opts.src) {
+			if (entry.src.count(s))
+				found_match = true;
+		}
+		if (!found_match)
+			return;
+	}
+
+	if (!opts.module.empty() && opts.module != entry.module)
+		return;
+
+	if (!opts.cell.empty() && opts.cell != entry.cell)
+		return;
+
+	if (!opts.port.empty() && opts.port != entry.port)
+		return;
+
+	if (opts.portbit >= 0 && opts.portbit != entry.portbit)
+		return;
+
+	if (opts.ctrlbit >= 0 && opts.ctrlbit != entry.ctrlbit)
+		return;
+
+	if (!opts.wire.empty() && opts.wire != entry.wire)
+		return;
+
+	if (opts.wirebit >= 0 && opts.wirebit != entry.wirebit)
+		return;
+
+	database.push_back(entry);
+}
+
+struct xs128_t
+{
+	uint32_t x = 123456789;
+	uint32_t y = 0, z = 0, w = 0;
+
+	xs128_t(int seed = 0) : w(seed) {
+		next();
+		next();
+		next();
+	}
+
+	void next() {
+		uint32_t t = x ^ (x << 11);
+		x = y, y = z, z = w;
+		w ^= (w >> 19) ^ t ^ (t >> 8);
+	}
+
+	int operator()() {
+		next();
+		return w & 0x3fffffff;
+	}
+
+	int operator()(int n) {
+		if (n < 2)
+			return 0;
+		while (1) {
+			int k = (*this)(), p = k % n;
+			if ((k - p + n) <= 0x40000000)
+				return p;
+		}
+	}
+};
+
+struct coverdb_t
+{
+	dict<string, int> src_db;
+	dict<tuple<IdString, IdString>, int> wire_db;
+	dict<tuple<IdString, IdString, int>, int> wirebit_db;
+
+	void insert(const mutate_t &m) {
+		if (!m.wire.empty()) {
+			wire_db[tuple<IdString, IdString>(m.module, m.wire)] = 0;
+			wirebit_db[tuple<IdString, IdString, int>(m.module, m.wire, m.wirebit)] = 0;
+		}
+		for (auto &s : m.src) {
+			src_db[s] = 0;
+		}
+	}
+
+	void update(const mutate_t &m) {
+		if (!m.wire.empty()) {
+			wire_db.at(tuple<IdString, IdString>(m.module, m.wire))++;
+			wirebit_db.at(tuple<IdString, IdString, int>(m.module, m.wire, m.wirebit))++;
+		}
+		for (auto &s : m.src) {
+			src_db.at(s)++;
+		}
+	}
+
+	int score(const mutate_t &m) {
+		int this_score = m.src.empty() ? 0 : 1;
+		if (!m.wire.empty()) {
+			this_score += wire_db.at(tuple<IdString, IdString>(m.module, m.wire)) ? 0 : 5;
+			this_score += wirebit_db.at(tuple<IdString, IdString, int>(m.module, m.wire, m.wirebit)) ? 0 : 1;
+		}
+		for (auto &s : m.src) {
+			this_score += src_db.at(s) ? 0 : 5;
+		}
+		return this_score;
+	}
+};
+
+struct mutate_queue_t
+{
+	pool<mutate_t*, hash_ptr_ops> db;
+
+	mutate_t *pick(xs128_t &rng, coverdb_t &coverdb, const mutate_opts_t &opts) {
+		mutate_t *m = nullptr;
+		if (rng(100) < opts.pick_cover_prcnt) {
+			vector<mutate_t*> candidates, rmqueue;
+			int best_score = -1;
+			for (auto p : db) {
+				if (p->used) {
+					rmqueue.push_back(p);
+					continue;
+				}
+				int this_score = coverdb.score(*p);
+				if (this_score > best_score) {
+					best_score = this_score;
+					candidates.clear();
+				}
+				if (best_score == this_score)
+					candidates.push_back(p);
+			}
+			for (auto p : rmqueue)
+				db.erase(p);
+			if (!candidates.empty())
+				m = candidates[rng(GetSize(candidates))];
+		}
+		if (m == nullptr) {
+			while (!db.empty()) {
+				int i = rng(GetSize(db));
+				auto it = db.element(i);
+				mutate_t *p = *it;
+				db.erase(it);
+				if (p->used == false) {
+					m = p;
+					break;
+				}
+			}
+		}
+		return m;
+	}
+
+	void add(mutate_t *m) {
+		db.insert(m);
+	}
+};
+
+template <typename K, typename T>
+struct mutate_chain_queue_t
+{
+	dict<K, T> db;
+
+	mutate_t *pick(xs128_t &rng, coverdb_t &coverdb, const mutate_opts_t &opts) {
+		while (!db.empty()) {
+			int i = rng(GetSize(db));
+			auto it = db.element(i);
+			mutate_t *m = it->second.pick(rng, coverdb, opts);
+			if (m != nullptr)
+				return m;
+			db.erase(it);
+		}
+		return nullptr;
+	}
+
+	template<typename... Args>
+	void add(mutate_t *m, K key, Args... args) {
+		db[key].add(m, args...);
+	}
+};
+
+template <typename K, typename T>
+struct mutate_once_queue_t
+{
+	dict<K, T> db;
+
+	mutate_t *pick(xs128_t &rng, coverdb_t &coverdb, const mutate_opts_t &opts) {
+		while (!db.empty()) {
+			int i = rng(GetSize(db));
+			auto it = db.element(i);
+			mutate_t *m = it->second.pick(rng, coverdb, opts);
+			db.erase(it);
+			if (m != nullptr)
+				return m;
+		}
+		return nullptr;
+	}
+
+	template<typename... Args>
+	void add(mutate_t *m, K key, Args... args) {
+		db[key].add(m, args...);
+	}
+};
+
+void database_reduce(std::vector<mutate_t> &database, const mutate_opts_t &opts, int N, xs128_t &rng)
+{
+	std::vector<mutate_t> new_database;
+	coverdb_t coverdb;
+
+	int total_weight = opts.weight_cover + opts.weight_pq_w + opts.weight_pq_b + opts.weight_pq_c + opts.weight_pq_s;
+	total_weight += opts.weight_pq_mw + opts.weight_pq_mb + opts.weight_pq_mc + opts.weight_pq_ms;
+
+	if (N >= GetSize(database))
+		return;
+
+	mutate_once_queue_t<tuple<IdString, IdString>, mutate_queue_t> primary_queue_wire;
+	mutate_once_queue_t<tuple<IdString, IdString, int>, mutate_queue_t> primary_queue_bit;
+	mutate_once_queue_t<tuple<IdString, IdString>, mutate_queue_t> primary_queue_cell;
+	mutate_once_queue_t<string, mutate_queue_t> primary_queue_src;
+
+	mutate_chain_queue_t<IdString, mutate_once_queue_t<IdString, mutate_queue_t>> primary_queue_module_wire;
+	mutate_chain_queue_t<IdString, mutate_once_queue_t<pair<IdString, int>, mutate_queue_t>> primary_queue_module_bit;
+	mutate_chain_queue_t<IdString, mutate_once_queue_t<IdString, mutate_queue_t>> primary_queue_module_cell;
+	mutate_chain_queue_t<IdString, mutate_once_queue_t<string, mutate_queue_t>> primary_queue_module_src;
+
+	for (auto &m : database)
+	{
+		coverdb.insert(m);
+
+		if (!m.wire.empty()) {
+			primary_queue_wire.add(&m, tuple<IdString, IdString>(m.module, m.wire));
+			primary_queue_bit.add(&m, tuple<IdString, IdString, int>(m.module, m.wire, m.wirebit));
+			primary_queue_module_wire.add(&m, m.module, m.wire);
+			primary_queue_module_bit.add(&m, m.module, pair<IdString, int>(m.wire, m.wirebit));
+		}
+
+		primary_queue_cell.add(&m, tuple<IdString, IdString>(m.module, m.cell));
+		primary_queue_module_cell.add(&m, m.module, m.cell);
+
+		for (auto &s : m.src) {
+			primary_queue_src.add(&m, s);
+			primary_queue_module_src.add(&m, m.module, s);
+		}
+	}
+
+	vector<mutate_t*> cover_candidates;
+	int best_cover_score = -1;
+	bool skip_cover = false;
+
+	while (GetSize(new_database) < N)
+	{
+		int k = rng(total_weight);
+
+		k -= opts.weight_cover;
+		if (k < 0) {
+			while (!skip_cover) {
+				if (cover_candidates.empty()) {
+					best_cover_score = -1;
+					for (auto &m : database) {
+						if (m.used || m.src.empty())
+							continue;
+						int this_score = -1;
+						for (auto &s : m.src) {
+							if (this_score == -1 || this_score > coverdb.src_db.at(s))
+								this_score = coverdb.src_db.at(s);
+						}
+						log_assert(this_score != -1);
+						if (best_cover_score == -1 || this_score < best_cover_score) {
+							cover_candidates.clear();
+							best_cover_score = this_score;
+						}
+						if (best_cover_score == this_score)
+							cover_candidates.push_back(&m);
+					}
+					if (best_cover_score == -1) {
+						skip_cover = true;
+						break;
+					}
+				}
+
+				mutate_t *m = nullptr;
+				while (!cover_candidates.empty())
+				{
+					int idx = rng(GetSize(cover_candidates));
+					mutate_t *p = cover_candidates[idx];
+					cover_candidates[idx] = cover_candidates.back();
+					cover_candidates.pop_back();
+
+					if (p->used)
+						continue;
+
+					int this_score = -1;
+					for (auto &s : p->src) {
+						if (this_score == -1 || this_score > coverdb.src_db.at(s))
+							this_score = coverdb.src_db.at(s);
+					}
+
+					if (this_score != best_cover_score)
+						continue;
+
+					m = p;
+					break;
+				}
+
+				if (m != nullptr) {
+					m->used = true;
+					coverdb.update(*m);
+					new_database.push_back(*m);
+					break;
+				}
+			}
+			continue;
+		}
+
+#define X(__wght, __queue)                               \
+    k -= __wght;                                         \
+    if (k < 0) {                                         \
+      mutate_t *m = __queue.pick(rng, coverdb, opts);    \
+      if (m != nullptr) {                                \
+        m->used = true;                                  \
+        coverdb.update(*m);                              \
+        new_database.push_back(*m);                      \
+      };                                                 \
+      continue;                                          \
+    }
+
+		X(opts.weight_pq_w, primary_queue_wire)
+		X(opts.weight_pq_b, primary_queue_bit)
+		X(opts.weight_pq_c, primary_queue_cell)
+		X(opts.weight_pq_s, primary_queue_src)
+
+		X(opts.weight_pq_mw, primary_queue_module_wire)
+		X(opts.weight_pq_mb, primary_queue_module_bit)
+		X(opts.weight_pq_mc, primary_queue_module_cell)
+		X(opts.weight_pq_ms, primary_queue_module_src)
+#undef X
+	}
+
+	std::swap(new_database, database);
+
+	int covered_src_cnt = 0;
+	int covered_wire_cnt = 0;
+	int covered_wirebit_cnt = 0;
+
+	for (auto &it : coverdb.src_db)
+		if (it.second)
+			covered_src_cnt++;
+
+	for (auto &it : coverdb.wire_db)
+		if (it.second)
+			covered_wire_cnt++;
+
+	for (auto &it : coverdb.wirebit_db)
+		if (it.second)
+			covered_wirebit_cnt++;
+
+	log("Covered %d/%d src attributes (%.2f%%).\n", covered_src_cnt, GetSize(coverdb.src_db), 100.0 * covered_src_cnt / GetSize(coverdb.src_db));
+	log("Covered %d/%d wires (%.2f%%).\n", covered_wire_cnt, GetSize(coverdb.wire_db), 100.0 * covered_wire_cnt / GetSize(coverdb.wire_db));
+	log("Covered %d/%d wire bits (%.2f%%).\n", covered_wirebit_cnt, GetSize(coverdb.wirebit_db), 100.0 * covered_wirebit_cnt / GetSize(coverdb.wirebit_db));
+}
+
+void mutate_list(Design *design, const mutate_opts_t &opts, const string &filename, const string &srcsfile, int N)
+{
+	pool<string> sources;
+	std::vector<mutate_t> database;
+	xs128_t rng(opts.seed);
+
+	for (auto module : design->selected_modules())
+	{
+		if (!opts.module.empty() && module->name != opts.module)
+			continue;
+
+		SigMap sigmap(module);
+		dict<SigBit, int> bit_user_cnt;
+
+		for (auto wire : module->wires()) {
+			if (wire->name[0] == '\\' && wire->attributes.count("\\src"))
+				sigmap.add(wire);
+		}
+
+		for (auto cell : module->cells()) {
+			for (auto &conn : cell->connections()) {
+				if (cell->output(conn.first))
+					continue;
+				for (auto bit : sigmap(conn.second))
+					bit_user_cnt[bit]++;
+			}
+		}
+
+		for (auto wire : module->selected_wires())
+		{
+			for (SigBit bit : SigSpec(wire))
+			{
+				SigBit sigbit = sigmap(bit);
+
+				if (bit.wire == nullptr || sigbit.wire == nullptr)
+					continue;
+
+				if (!bit.wire->port_id != !sigbit.wire->port_id) {
+					if (bit.wire->port_id)
+						sigmap.add(bit);
+					continue;
+				}
+
+				if (!bit.wire->name[0] != !sigbit.wire->name[0]) {
+					if (bit.wire->name[0] == '\\')
+						sigmap.add(bit);
+					continue;
+				}
+			}
+		}
+
+		for (auto cell : module->selected_cells())
+		{
+			if (!opts.cell.empty() && cell->name != opts.cell)
+				continue;
+
+			for (auto &conn : cell->connections())
+			{
+				for (int i = 0; i < GetSize(conn.second); i++) {
+					mutate_t entry;
+					entry.module = module->name;
+					entry.cell = cell->name;
+					entry.port = conn.first;
+					entry.portbit = i;
+
+					for (auto &s : cell->get_strpool_attribute("\\src"))
+						entry.src.insert(s);
+
+					SigBit bit = sigmap(conn.second[i]);
+					if (bit.wire && bit.wire->name[0] == '\\' && (cell->output(conn.first) || bit_user_cnt[bit] == 1)) {
+						for (auto &s : bit.wire->get_strpool_attribute("\\src"))
+							entry.src.insert(s);
+						entry.wire = bit.wire->name;
+						entry.wirebit = bit.offset;
+					}
+
+					if (!srcsfile.empty())
+						sources.insert(entry.src.begin(), entry.src.end());
+
+					entry.mode = "inv";
+					database_add(database, opts, entry);
+
+					entry.mode = "const0";
+					database_add(database, opts, entry);
+
+					entry.mode = "const1";
+					database_add(database, opts, entry);
+
+					entry.mode = "cnot0";
+					entry.ctrlbit = rng(GetSize(conn.second));
+					if (entry.ctrlbit != entry.portbit && conn.second[entry.ctrlbit].wire)
+						database_add(database, opts, entry);
+
+					entry.mode = "cnot1";
+					entry.ctrlbit = rng(GetSize(conn.second));
+					if (entry.ctrlbit != entry.portbit && conn.second[entry.ctrlbit].wire)
+						database_add(database, opts, entry);
+				}
+			}
+		}
+	}
+
+	log("Raw database size: %d\n", GetSize(database));
+	if (N != 0) {
+		database_reduce(database, opts, opts.none ? N-1 : N, rng);
+		log("Reduced database size: %d\n", GetSize(database));
+	}
+
+	if (!srcsfile.empty()) {
+		std::ofstream sout;
+		sout.open(srcsfile, std::ios::out | std::ios::trunc);
+		if (!sout.is_open())
+			log_error("Could not open file \"%s\" with write access.\n", srcsfile.c_str());
+		sources.sort();
+		for (auto &s : sources)
+			sout << s << std::endl;
+	}
+
+	std::ofstream fout;
+
+	if (!filename.empty()) {
+		fout.open(filename, std::ios::out | std::ios::trunc);
+		if (!fout.is_open())
+			log_error("Could not open file \"%s\" with write access.\n", filename.c_str());
+	}
+
+	int ctrl_value = opts.ctrl_value;
+
+	if (opts.none) {
+		string str = "mutate";
+		if (!opts.ctrl_name.empty())
+			str += stringf(" -ctrl %s %d %d", log_id(opts.ctrl_name), opts.ctrl_width, ctrl_value++);
+		str += " -mode none";
+		if (filename.empty())
+			log("%s\n", str.c_str());
+		else
+			fout << str << std::endl;
+	}
+
+	for (auto &entry : database) {
+		string str = "mutate";
+		if (!opts.ctrl_name.empty())
+			str += stringf(" -ctrl %s %d %d", log_id(opts.ctrl_name), opts.ctrl_width, ctrl_value++);
+		str += stringf(" -mode %s", entry.mode.c_str());
+		if (!entry.module.empty())
+			str += stringf(" -module %s", log_id(entry.module));
+		if (!entry.cell.empty())
+			str += stringf(" -cell %s", log_id(entry.cell));
+		if (!entry.port.empty())
+			str += stringf(" -port %s", log_id(entry.port));
+		if (entry.portbit >= 0)
+			str += stringf(" -portbit %d", entry.portbit);
+		if (entry.ctrlbit >= 0)
+			str += stringf(" -ctrlbit %d", entry.ctrlbit);
+		if (!entry.wire.empty())
+			str += stringf(" -wire %s", log_id(entry.wire));
+		if (entry.wirebit >= 0)
+			str += stringf(" -wirebit %d", entry.wirebit);
+		for (auto &s : entry.src)
+			str += stringf(" -src %s", s.c_str());
+		if (filename.empty())
+			log("%s\n", str.c_str());
+		else
+			fout << str << std::endl;
+	}
+}
+
+SigSpec mutate_ctrl_sig(Module *module, IdString name, int width)
+{
+	Wire *ctrl_wire = module->wire(name);
+
+	if (ctrl_wire == nullptr)
+	{
+		log("Adding ctrl port %s to module %s.\n", log_id(name), log_id(module));
+
+		ctrl_wire = module->addWire(name, width);
+		ctrl_wire->port_input = true;
+		module->fixup_ports();
+
+		for (auto mod : module->design->modules())
+		for (auto cell : mod->cells())
+		{
+			if (cell->type != module->name)
+				continue;
+
+			SigSpec ctrl = mutate_ctrl_sig(mod, name, width);
+
+			log("Connecting ctrl port to cell %s in module %s.\n", log_id(cell), log_id(mod));
+			cell->setPort(name, ctrl);
+		}
+	}
+
+	log_assert(GetSize(ctrl_wire) == width);
+	return ctrl_wire;
+}
+
+SigBit mutate_ctrl(Module *module, const mutate_opts_t &opts)
+{
+	if (opts.ctrl_name.empty())
+		return State::S1;
+
+	SigSpec sig = mutate_ctrl_sig(module, opts.ctrl_name, opts.ctrl_width);
+	return module->Eq(NEW_ID, sig, Const(opts.ctrl_value, GetSize(sig)));
+}
+
+SigSpec mutate_ctrl_mux(Module *module, const mutate_opts_t &opts, SigSpec unchanged_sig, SigSpec changed_sig)
+{
+	SigBit ctrl_bit = mutate_ctrl(module, opts);
+	if (ctrl_bit == State::S0)
+		return unchanged_sig;
+	if (ctrl_bit == State::S1)
+		return changed_sig;
+	return module->Mux(NEW_ID, unchanged_sig, changed_sig, ctrl_bit);
+}
+
+void mutate_inv(Design *design, const mutate_opts_t &opts)
+{
+	Module *module = design->module(opts.module);
+	Cell *cell = module->cell(opts.cell);
+
+	SigBit bit = cell->getPort(opts.port)[opts.portbit];
+	SigBit inbit, outbit;
+
+	if (cell->input(opts.port))
+	{
+		log("Add input inverter at %s.%s.%s[%d].\n", log_id(module), log_id(cell), log_id(opts.port), opts.portbit);
+		SigBit outbit = module->Not(NEW_ID, bit);
+		bit = mutate_ctrl_mux(module, opts, bit, outbit);
+	}
+	else
+	{
+		log("Add output inverter at %s.%s.%s[%d].\n", log_id(module), log_id(cell), log_id(opts.port), opts.portbit);
+		SigBit inbit = module->addWire(NEW_ID);
+		SigBit outbit = module->Not(NEW_ID, inbit);
+		module->connect(bit, mutate_ctrl_mux(module, opts, inbit, outbit));
+		bit = inbit;
+	}
+
+	SigSpec s = cell->getPort(opts.port);
+	s[opts.portbit] = bit;
+	cell->setPort(opts.port, s);
+}
+
+void mutate_const(Design *design, const mutate_opts_t &opts, bool one)
+{
+	Module *module = design->module(opts.module);
+	Cell *cell = module->cell(opts.cell);
+
+	SigBit bit = cell->getPort(opts.port)[opts.portbit];
+	SigBit inbit, outbit;
+
+	if (cell->input(opts.port))
+	{
+		log("Add input constant %d at %s.%s.%s[%d].\n", one ? 1 : 0, log_id(module), log_id(cell), log_id(opts.port), opts.portbit);
+		SigBit outbit = one ? State::S1 : State::S0;
+		bit = mutate_ctrl_mux(module, opts, bit, outbit);
+	}
+	else
+	{
+		log("Add output constant %d at %s.%s.%s[%d].\n", one ? 1 : 0, log_id(module), log_id(cell), log_id(opts.port), opts.portbit);
+		SigBit inbit = module->addWire(NEW_ID);
+		SigBit outbit = one ? State::S1 : State::S0;
+		module->connect(bit, mutate_ctrl_mux(module, opts, inbit, outbit));
+		bit = inbit;
+	}
+
+	SigSpec s = cell->getPort(opts.port);
+	s[opts.portbit] = bit;
+	cell->setPort(opts.port, s);
+}
+
+void mutate_cnot(Design *design, const mutate_opts_t &opts, bool one)
+{
+	Module *module = design->module(opts.module);
+	Cell *cell = module->cell(opts.cell);
+
+	SigBit bit = cell->getPort(opts.port)[opts.portbit];
+	SigBit ctrl = cell->getPort(opts.port)[opts.ctrlbit];
+	SigBit inbit, outbit;
+
+	if (cell->input(opts.port))
+	{
+		log("Add input cnot%d at %s.%s.%s[%d,%d].\n", one ? 1 : 0, log_id(module), log_id(cell), log_id(opts.port), opts.portbit, opts.ctrlbit);
+		SigBit outbit = one ? module->Xor(NEW_ID, bit, ctrl) : module->Xnor(NEW_ID, bit, ctrl);
+		bit = mutate_ctrl_mux(module, opts, bit, outbit);
+	}
+	else
+	{
+		log("Add output cnot%d at %s.%s.%s[%d,%d].\n", one ? 1 : 0, log_id(module), log_id(cell), log_id(opts.port), opts.portbit, opts.ctrlbit);
+		SigBit inbit = module->addWire(NEW_ID);
+		SigBit outbit = one ? module->Xor(NEW_ID, inbit, ctrl) : module->Xnor(NEW_ID, inbit, ctrl);
+		module->connect(bit, mutate_ctrl_mux(module, opts, inbit, outbit));
+		bit = inbit;
+	}
+
+	SigSpec s = cell->getPort(opts.port);
+	s[opts.portbit] = bit;
+	cell->setPort(opts.port, s);
+}
+
+struct MutatePass : public Pass {
+	MutatePass() : Pass("mutate", "generate or apply design mutations") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    mutate -list N [options] [selection]\n");
+		log("\n");
+		log("Create a list of N mutations using an even sampling.\n");
+		log("\n");
+		log("    -o filename\n");
+		log("        Write list to this file instead of console output\n");
+		log("\n");
+		log("    -s filename\n");
+		log("        Write a list of all src tags found in the design to the specified file\n");
+		log("\n");
+		log("    -seed N\n");
+		log("        RNG seed for selecting mutations\n");
+		log("\n");
+		log("    -none\n");
+		log("        Include a \"none\" mutation in the output\n");
+		log("\n");
+		log("    -ctrl name width value\n");
+		log("        Add -ctrl options to the output. Use 'value' for first mutation, then\n");
+		log("        simply count up from there.\n");
+		log("\n");
+		log("    -mode name\n");
+		log("    -module name\n");
+		log("    -cell name\n");
+		log("    -port name\n");
+		log("    -portbit int\n");
+		log("    -ctrlbit int\n");
+		log("    -wire name\n");
+		log("    -wirebit int\n");
+		log("    -src string\n");
+		log("        Filter list of mutation candidates to those matching\n");
+		log("        the given parameters.\n");
+		log("\n");
+		log("    -cfg option int\n");
+		log("        Set a configuration option. Options available:\n");
+		log("          weight_pq_w weight_pq_b weight_pq_c weight_pq_s\n");
+		log("          weight_pq_mw weight_pq_mb weight_pq_mc weight_pq_ms\n");
+		log("          weight_cover pick_cover_prcnt\n");
+		log("\n");
+		log("\n");
+		log("    mutate -mode MODE [options]\n");
+		log("\n");
+		log("Apply the given mutation.\n");
+		log("\n");
+		log("    -ctrl name width value\n");
+		log("        Add a control signal with the given name and width. The mutation is\n");
+		log("        activated if the control signal equals the given value.\n");
+		log("\n");
+		log("    -module name\n");
+		log("    -cell name\n");
+		log("    -port name\n");
+		log("    -portbit int\n");
+		log("    -ctrlbit int\n");
+		log("        Mutation parameters, as generated by 'mutate -list N'.\n");
+		log("\n");
+		log("    -wire name\n");
+		log("    -wirebit int\n");
+		log("    -src string\n");
+		log("        Ignored. (They are generated by -list for documentation purposes.)\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		mutate_opts_t opts;
+		string filename;
+		string srcsfile;
+		int N = -1;
+
+		log_header(design, "Executing MUTATE pass.\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			if (args[argidx] == "-list" && argidx+1 < args.size()) {
+				N = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-o" && argidx+1 < args.size()) {
+				filename = args[++argidx];
+				continue;
+			}
+			if (args[argidx] == "-s" && argidx+1 < args.size()) {
+				srcsfile = args[++argidx];
+				continue;
+			}
+			if (args[argidx] == "-seed" && argidx+1 < args.size()) {
+				opts.seed = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-none") {
+				opts.none = true;
+				continue;
+			}
+			if (args[argidx] == "-mode" && argidx+1 < args.size()) {
+				opts.mode = args[++argidx];
+				continue;
+			}
+			if (args[argidx] == "-ctrl" && argidx+3 < args.size()) {
+				opts.ctrl_name = RTLIL::escape_id(args[++argidx]);
+				opts.ctrl_width = atoi(args[++argidx].c_str());
+				opts.ctrl_value = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-module" && argidx+1 < args.size()) {
+				opts.module = RTLIL::escape_id(args[++argidx]);
+				continue;
+			}
+			if (args[argidx] == "-cell" && argidx+1 < args.size()) {
+				opts.cell = RTLIL::escape_id(args[++argidx]);
+				continue;
+			}
+			if (args[argidx] == "-port" && argidx+1 < args.size()) {
+				opts.port = RTLIL::escape_id(args[++argidx]);
+				continue;
+			}
+			if (args[argidx] == "-portbit" && argidx+1 < args.size()) {
+				opts.portbit = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-ctrlbit" && argidx+1 < args.size()) {
+				opts.ctrlbit = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-wire" && argidx+1 < args.size()) {
+				opts.wire = RTLIL::escape_id(args[++argidx]);
+				continue;
+			}
+			if (args[argidx] == "-wirebit" && argidx+1 < args.size()) {
+				opts.wirebit = atoi(args[++argidx].c_str());
+				continue;
+			}
+			if (args[argidx] == "-src" && argidx+1 < args.size()) {
+				opts.src.insert(args[++argidx]);
+				continue;
+			}
+			if (args[argidx] == "-cfg" && argidx+2 < args.size()) {
+				if (args[argidx+1] == "pick_cover_prcnt") {
+					opts.pick_cover_prcnt = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_cover") {
+					opts.weight_cover = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_w") {
+					opts.weight_pq_w = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_b") {
+					opts.weight_pq_b = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_c") {
+					opts.weight_pq_c = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_s") {
+					opts.weight_pq_s = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_mw") {
+					opts.weight_pq_mw = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_mb") {
+					opts.weight_pq_mb = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_mc") {
+					opts.weight_pq_mc = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+				if (args[argidx+1] == "weight_pq_ms") {
+					opts.weight_pq_ms = atoi(args[argidx+2].c_str());
+					argidx += 2;
+					continue;
+				}
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		if (N >= 0) {
+			mutate_list(design, opts, filename, srcsfile, N);
+			return;
+		}
+
+		if (opts.mode == "none") {
+			if (!opts.ctrl_name.empty()) {
+				Module *topmod = opts.module.empty() ? design->top_module() : design->module(opts.module);
+				if (topmod)
+					mutate_ctrl_sig(topmod, opts.ctrl_name, opts.ctrl_width);
+			}
+			return;
+		}
+
+		if (opts.mode == "inv") {
+			mutate_inv(design, opts);
+			return;
+		}
+
+		if (opts.mode == "const0" || opts.mode == "const1") {
+			mutate_const(design, opts, opts.mode == "const1");
+			return;
+		}
+
+		if (opts.mode == "cnot0" || opts.mode == "cnot1") {
+			mutate_cnot(design, opts, opts.mode == "cnot1");
+			return;
+		}
+
+		log_cmd_error("Invalid mode: %s\n", opts.mode.c_str());
+	}
+} MutatePass;
+
+PRIVATE_NAMESPACE_END
diff --git a/passes/techmap/libparse.cc b/passes/techmap/libparse.cc
index 3927a657b..991cc4498 100644
--- a/passes/techmap/libparse.cc
+++ b/passes/techmap/libparse.cc
@@ -24,6 +24,7 @@
 #include <istream>
 #include <fstream>
 #include <iostream>
+#include <sstream>
 
 #ifndef FILTERLIB
 #include "kernel/log.h"
@@ -86,15 +87,17 @@ int LibertyParser::lexer(std::string &str)
 {
 	int c;
 
+	// eat whitespace
 	do {
 		c = f.get();
 	} while (c == ' ' || c == '\t' || c == '\r');
 
-	if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_' || c == '-' || c == '+' || c == '.' || c == '[' || c == ']') {
+	// search for identifiers, numbers, plus or minus.
+	if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_' || c == '-' || c == '+' || c == '.') {
 		str = c;
 		while (1) {
 			c = f.get();
-			if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_' || c == '-' || c == '+' || c == '.' || c == '[' || c == ']')
+			if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_' || c == '-' || c == '+' || c == '.')
 				str += c;
 			else
 				break;
@@ -111,6 +114,8 @@ int LibertyParser::lexer(std::string &str)
 		}
 	}
 
+	// if it wasn't an identifer, number of array range,
+	// maybe it's a string?
 	if (c == '"') {
 		str = "";
 		while (1) {
@@ -125,9 +130,10 @@ int LibertyParser::lexer(std::string &str)
 		return 'v';
 	}
 
+	// if it wasn't a string, perhaps it's a comment or a forward slash?
 	if (c == '/') {
 		c = f.get();
-		if (c == '*') {
+		if (c == '*') {         // start of '/*' block comment
 			int last_c = 0;
 			while (c > 0 && (last_c != '*' || c != '/')) {
 				last_c = c;
@@ -136,7 +142,7 @@ int LibertyParser::lexer(std::string &str)
 					line++;
 			}
 			return lexer(str);
-		} else if (c == '/') {
+		} else if (c == '/') {  // start of '//' line comment
 			while (c > 0 && c != '\n')
 				c = f.get();
 			line++;
@@ -144,24 +150,31 @@ int LibertyParser::lexer(std::string &str)
 		}
 		f.unget();
 		// fprintf(stderr, "LEX: char >>/<<\n");
-		return '/';
+		return '/';             // a single '/' charater.
 	}
 
+	// check for a backslash
 	if (c == '\\') {
-		c = f.get();
+		c = f.get();		
 		if (c == '\r')
 			c = f.get();
-		if (c == '\n')
+		if (c == '\n') {
+			line++;
 			return lexer(str);
+		}
 		f.unget();
 		return '\\';
 	}
 
+	// check for a new line
 	if (c == '\n') {
 		line++;
 		return 'n';
 	}
 
+	// anything else, such as ';' will get passed
+	// through as literal items.
+
 	// if (c >= 32 && c < 255)
 	// 	fprintf(stderr, "LEX: char >>%c<<\n", c);
 	// else
@@ -175,14 +188,39 @@ LibertyAst *LibertyParser::parse()
 
 	int tok = lexer(str);
 
-	while (tok == 'n')
+	// there are liberty files in the wild that
+	// have superfluous ';' at the end of
+	// a  { ... }. We simply ignore a ';' here.
+	// and get to the next statement.
+
+	while ((tok == 'n') || (tok == ';'))
 		tok = lexer(str);
 
 	if (tok == '}' || tok < 0)
 		return NULL;
 
-	if (tok != 'v')
-		error();
+	if (tok != 'v') {
+		std::string eReport;
+		switch(tok)
+		{
+		case 'n':
+			error("Unexpected newline.");
+			break;
+		case '[':
+		case ']':
+		case '}':
+		case '{':
+		case '\"':
+		case ':':
+			eReport = "Unexpected '";
+			eReport += static_cast<char>(tok);
+			eReport += "'.";
+			error(eReport);
+			break;
+		default:
+			error();
+		}
+	}
 
 	LibertyAst *ast = new LibertyAst;
 	ast->id = str;
@@ -191,12 +229,11 @@ LibertyAst *LibertyParser::parse()
 	{
 		tok = lexer(str);
 
-		if (tok == ';')
+		// allow both ';' and new lines to 
+		// terminate a statement.
+		if ((tok == ';') || (tok == 'n'))
 			break;
 
-		if (tok == 'n')
-			continue;
-
 		if (tok == ':' && ast->value.empty()) {
 			tok = lexer(ast->value);
 			if (tok != 'v')
@@ -210,7 +247,12 @@ LibertyAst *LibertyParser::parse()
 				ast->value += str;
 				tok = lexer(str);
 			}
-			if (tok == ';')
+			
+			// In a liberty file, all key : value pairs should end in ';'
+			// However, there are some liberty files in the wild that
+			// just have a newline. We'll be kind and accept a newline
+			// instead of the ';' too..
+			if ((tok == ';') || (tok == 'n'))
 				break;
 			else
 				error();
@@ -225,8 +267,70 @@ LibertyAst *LibertyParser::parse()
 					continue;
 				if (tok == ')')
 					break;
-				if (tok != 'v')
-					error();
+				
+				// FIXME: the AST needs to be extended to store
+				//        these vector ranges.
+				if (tok == '[')
+				{
+					// parse vector range [A] or [A:B]
+					std::string arg;
+					tok = lexer(arg);
+					if (tok != 'v')
+					{
+						// expected a vector array index
+						error("Expected a number.");
+					}
+					else
+					{
+						// fixme: check for number A
+					}
+					tok = lexer(arg);
+					// optionally check for : in case of [A:B]
+					// if it isn't we just expect ']'
+					// as we have [A]
+					if (tok == ':')
+					{
+						tok = lexer(arg);
+						if (tok != 'v')
+						{
+							// expected a vector array index
+							error("Expected a number.");
+						}
+						else
+						{
+							// fixme: check for number B
+							tok = lexer(arg);                            
+						}
+					}
+					// expect a closing bracket of array range
+					if (tok != ']')
+					{
+						error("Expected ']' on array range.");
+					}
+					continue;           
+				}
+				if (tok != 'v') {
+					std::string eReport;
+					switch(tok)
+					{
+					case 'n':
+						error("Unexpected newline.");
+						break;
+					case '[':
+					case ']':
+					case '}':
+					case '{':
+					case '\"':
+					case ':':
+						eReport = "Unexpected '";
+						eReport += static_cast<char>(tok);
+						eReport += "'.";
+						error(eReport);
+						break;
+					default:
+						error();
+					}
+				}
 				ast->args.push_back(arg);
 			}
 			continue;
@@ -255,6 +359,14 @@ void LibertyParser::error()
 	log_error("Syntax error in liberty file on line %d.\n", line);
 }
 
+void LibertyParser::error(const std::string &str)
+{
+	std::stringstream ss;
+	ss << "Syntax error in liberty file on line " << line << ".\n";
+	ss << "  " << str << "\n";
+	log_error("%s", ss.str().c_str());
+}
+
 #else
 
 void LibertyParser::error()
@@ -263,25 +375,34 @@ void LibertyParser::error()
 	exit(1);
 }
 
+void LibertyParser::error(const std::string &str)
+{
+	std::stringstream ss;
+	ss << "Syntax error in liberty file on line " << line << ".\n";
+	ss << "  " << str << "\n";
+	printf("%s", ss.str().c_str());
+	exit(1);
+}
+
 /**** BEGIN: http://svn.clifford.at/tools/trunk/examples/check.h ****/
 
 #define CHECK_NV(result, check)                                      \
    do {                                                              \
-     auto _R = (result);                                             \
-     if (!(_R check)) {                                              \
-       fprintf(stderr, "Error from '%s' (%ld %s) in %s:%d.\n",       \
-               #result, (long int)_R, #check, __FILE__, __LINE__);   \
-       abort();                                                      \
-     }                                                               \
+	 auto _R = (result);                                             \
+	 if (!(_R check)) {                                              \
+	   fprintf(stderr, "Error from '%s' (%ld %s) in %s:%d.\n",       \
+			   #result, (long int)_R, #check, __FILE__, __LINE__);   \
+	   abort();                                                      \
+	 }                                                               \
    } while(0)
 
 #define CHECK_COND(result)                                           \
    do {                                                              \
-     if (!(result)) {                                                \
-       fprintf(stderr, "Error from '%s' in %s:%d.\n",                \
-               #result, __FILE__, __LINE__);                         \
-       abort();                                                      \
-     }                                                               \
+	 if (!(result)) {                                                \
+	   fprintf(stderr, "Error from '%s' in %s:%d.\n",                \
+			   #result, __FILE__, __LINE__);                         \
+	   abort();                                                      \
+	 }                                                               \
    } while(0)
 
 /**** END: http://svn.clifford.at/tools/trunk/examples/check.h ****/
diff --git a/passes/techmap/libparse.h b/passes/techmap/libparse.h
index cf6325570..c9ebd06c5 100644
--- a/passes/techmap/libparse.h
+++ b/passes/techmap/libparse.h
@@ -46,9 +46,17 @@ namespace Yosys
 		LibertyAst *ast;
 		LibertyParser(std::istream &f) : f(f), line(1), ast(parse()) {}
 		~LibertyParser() { if (ast) delete ast; }
+        
+        /* lexer return values:
+           'v': identifier, string, array range [...] -> str holds the token string
+           'n': newline
+           anything else is a single character.
+        */
 		int lexer(std::string &str);
-		LibertyAst *parse();
+		
+        LibertyAst *parse();
 		void error();
+        void error(const std::string &str);
 	};
 }