diff --git a/backends/aiger/aiger.cc b/backends/aiger/aiger.cc
index dfe506c66..516e538a5 100644
--- a/backends/aiger/aiger.cc
+++ b/backends/aiger/aiger.cc
@@ -685,7 +685,7 @@ struct AigerBackend : public Backend {
 		log("invariant constraints.\n");
 		log("\n");
 		log("    -ascii\n");
-		log("        write ASCII version of AGIER format\n");
+		log("        write ASCII version of AIGER format\n");
 		log("\n");
 		log("    -zinit\n");
 		log("        convert FFs to zero-initialized FFs, adding additional inputs for\n");
diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index 66ab3878e..d6438a297 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -20,6 +20,8 @@
 
 #include "kernel/yosys.h"
 #include "kernel/sigtools.h"
+#include "kernel/celltypes.h"
+#include "kernel/utils.h"
 
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
@@ -46,9 +48,8 @@ struct XAigerWriter
 	pool<SigBit> input_bits, output_bits;
 	dict<SigBit, SigBit> not_map, ff_map, alias_map;
 	dict<SigBit, pair<SigBit, SigBit>> and_map;
-	pool<SigBit> initstate_bits;
+	//pool<SigBit> initstate_bits;
 	vector<std::pair<SigBit,int>> ci_bits, co_bits;
-	dict<IdString, unsigned> type_map;
 
 	vector<pair<int, int>> aig_gates;
 	vector<int> aig_latchin, aig_latchinit, aig_outputs;
@@ -58,11 +59,11 @@ struct XAigerWriter
 	dict<SigBit, int> ordered_outputs;
 	dict<SigBit, int> ordered_latches;
 
-	dict<SigBit, int> init_inputs;
-	int initstate_ff = 0;
-
 	vector<Cell*> box_list;
 
+	//dict<SigBit, int> init_inputs;
+	//int initstate_ff = 0;
+
 	int mkgate(int a0, int a1)
 	{
 		aig_m++, aig_a++;
@@ -76,10 +77,10 @@ struct XAigerWriter
 		{
 			aig_map[bit] = -1;
 
-			if (initstate_bits.count(bit)) {
-				log_assert(initstate_ff > 0);
-				aig_map[bit] = initstate_ff;
-			} else
+			//if (initstate_bits.count(bit)) {
+			//	log_assert(initstate_ff > 0);
+			//	aig_map[bit] = initstate_ff;
+			//} else
 			if (not_map.count(bit)) {
 				int a = bit2aig(not_map.at(bit)) ^ 1;
 				aig_map[bit] = a;
@@ -102,7 +103,7 @@ struct XAigerWriter
 		return aig_map.at(bit);
 	}
 
-	XAigerWriter(Module *module, bool zinit_mode, bool imode, bool omode, bool bmode) : module(module), zinit_mode(zinit_mode), sigmap(module)
+	XAigerWriter(Module *module, bool zinit_mode, bool imode, bool omode, bool bmode, bool holes_mode=false) : module(module), zinit_mode(zinit_mode), sigmap(module)
 	{
 		pool<SigBit> undriven_bits;
 		pool<SigBit> unused_bits;
@@ -159,19 +160,56 @@ struct XAigerWriter
 			}
 		}
 
-		for (auto bit : input_bits) {
-			if (!bit.wire->port_output)
-				undriven_bits.erase(bit);
-			// Erase POs that are also PIs
-			output_bits.erase(bit);
-		}
+		for (auto bit : input_bits)
+			undriven_bits.erase(bit);
 
 		for (auto bit : output_bits)
 			if (!bit.wire->port_input)
 				unused_bits.erase(bit);
 
+		dict<SigBit, pool<IdString>> bit_drivers, bit_users;
+		TopoSort<IdString, RTLIL::sort_by_id_str> toposort;
+		bool abc_box_seen = false;
+
 		for (auto cell : module->cells())
 		{
+			RTLIL::Module* inst_module = module->design->module(cell->type);
+			bool known_type = yosys_celltypes.cell_known(cell->type);
+
+			if (!holes_mode) {
+				toposort.node(cell->name);
+				for (const auto &conn : cell->connections())
+				{
+					if (!cell->type.in("$_NOT_", "$_AND_")) {
+						if (known_type) {
+							if (conn.first.in("\\Q", "\\CTRL_OUT", "\\RD_DATA"))
+								continue;
+							if (cell->type == "$memrd" && conn.first == "\\DATA")
+								continue;
+						}
+
+						if (inst_module) {
+							RTLIL::Wire* inst_module_port = inst_module->wire(conn.first);
+							log_assert(inst_module_port);
+
+							if (inst_module_port->attributes.count("\\abc_flop_q"))
+								continue;
+						}
+					}
+
+					if (cell->input(conn.first)) {
+						// Ignore inout for the sake of topographical ordering
+						if (cell->output(conn.first)) continue;
+						for (auto bit : sigmap(conn.second))
+							bit_users[bit].insert(cell->name);
+					}
+
+					if (cell->output(conn.first))
+						for (auto bit : sigmap(conn.second))
+							bit_drivers[bit].insert(cell->name);
+				}
+			}
+
 			if (cell->type == "$_NOT_")
 			{
 				SigBit A = sigmap(cell->getPort("\\A").as_bit());
@@ -204,59 +242,100 @@ struct XAigerWriter
 				continue;
 			}
 
-			if (cell->type == "$initstate")
-			{
-				SigBit Y = sigmap(cell->getPort("\\Y").as_bit());
-				undriven_bits.erase(Y);
-				initstate_bits.insert(Y);
-				continue;
+			//if (cell->type == "$initstate")
+			//{
+			//	SigBit Y = sigmap(cell->getPort("\\Y").as_bit());
+			//	undriven_bits.erase(Y);
+			//	initstate_bits.insert(Y);
+			//	continue;
+			//}
+
+			if (inst_module && inst_module->attributes.count("\\abc_box_id")) {
+				abc_box_seen = true;
 			}
-
-			RTLIL::Module* box_module = module->design->module(cell->type);
-			bool abc_box = box_module && box_module->attributes.count("\\abc_box_id");
-
-			for (const auto &c : cell->connections()) {
-				/*if (c.second.is_fully_const()) continue;*/
-				for (auto b : c.second.bits()) {
-					auto is_input = cell->input(c.first);
-					auto is_output = cell->output(c.first);
-					log_assert(is_input || is_output);
-					if (is_input) {
-						/*if (!w->port_input)*/ {
-							SigBit I = sigmap(b);
-							if (I != b)
-								alias_map[b] = I;
-							/*if (!output_bits.count(b))*/
-							if (abc_box)
-								co_bits.emplace_back(b, 0);
-							else if (b.wire) {
+			else {
+				for (const auto &c : cell->connections()) {
+					if (c.second.is_fully_const()) continue;
+					for (auto b : c.second.bits()) {
+						Wire *w = b.wire;
+						if (!w) continue;
+						auto is_input = cell->input(c.first);
+						auto is_output = cell->output(c.first);
+						log_assert(is_input || is_output);
+						if (is_input) {
+							if (!w->port_input) {
+								SigBit I = sigmap(b);
+								if (I != b)
+									alias_map[b] = I;
 								output_bits.insert(b);
-								if (!b.wire->port_input)
-									unused_bits.erase(b);
+								unused_bits.erase(b);
 							}
 						}
-					}
-					if (is_output) {
-						SigBit O = sigmap(b);
-						/*if (!input_bits.count(O))*/
-						if (abc_box)
-							ci_bits.emplace_back(O, 0);
-						else {
+						if (is_output) {
+							SigBit O = sigmap(b);
 							input_bits.insert(O);
-							if (!O.wire->port_output)
-								undriven_bits.erase(O);
+							undriven_bits.erase(O);
 						}
 					}
 				}
-				if (!type_map.count(cell->type))
-					type_map[cell->type] = type_map.size()+1;
 			}
 
-			if (abc_box)
-				box_list.emplace_back(cell);
 			//log_warning("Unsupported cell type: %s (%s)\n", log_id(cell->type), log_id(cell));
 		}
 
+		if (abc_box_seen) {
+			for (auto &it : bit_users)
+				if (bit_drivers.count(it.first))
+					for (auto driver_cell : bit_drivers.at(it.first))
+					for (auto user_cell : it.second)
+						toposort.edge(driver_cell, user_cell);
+
+#ifndef NDEBUG
+			toposort.analyze_loops = true;
+#endif
+			toposort.sort();
+#ifndef NDEBUG
+			for (auto &it : toposort.loops) {
+				log("  loop");
+				for (auto cell : it)
+					log(" %s", log_id(cell));
+				log("\n");
+			}
+#endif
+			log_assert(!toposort.found_loops);
+
+			for (auto cell_name : toposort.sorted) {
+				RTLIL::Cell *cell = module->cell(cell_name);
+				RTLIL::Module* box_module = module->design->module(cell->type);
+				if (!box_module || !box_module->attributes.count("\\abc_box_id"))
+					continue;
+
+				// Box ordering is alphabetical
+				cell->connections_.sort(RTLIL::sort_by_id_str());
+				for (const auto &c : cell->connections()) {
+					for (auto b : c.second.bits()) {
+						auto is_input = cell->input(c.first);
+						auto is_output = cell->output(c.first);
+						log_assert(is_input || is_output);
+						if (is_input) {
+							SigBit I = sigmap(b);
+							if (I != b)
+								alias_map[b] = I;
+							co_bits.emplace_back(b, 0);
+						}
+						if (is_output) {
+							SigBit O = sigmap(b);
+							ci_bits.emplace_back(O, 0);
+						}
+					}
+				}
+
+				box_list.emplace_back(cell);
+			}
+
+			// TODO: Free memory from toposort, bit_drivers, bit_users
+		}
+
 		for (auto bit : input_bits) {
 			RTLIL::Wire *wire = bit.wire;
 			// If encountering an inout port, then create a new wire with $inout.out
@@ -274,27 +353,23 @@ struct XAigerWriter
 					and_map[new_bit] = and_map.at(bit);
 				else if (alias_map.count(bit))
 					alias_map[new_bit] = alias_map.at(bit);
+				else
+					alias_map[new_bit] = bit;
 				output_bits.insert(new_bit);
 			}
 		}
 
 		// Do some CI/CO post-processing:
-		// Erase all POs and COs that are undriven
-		for (auto bit : undriven_bits) {
-			//co_bits.erase(bit);
+		// Erase all POs that are undriven
+		for (auto bit : undriven_bits)
 			output_bits.erase(bit);
-		}
-		// Erase all CIs that are also COs
-		//for (auto bit : co_bits)
-		//	ci_bits.erase(bit);
 		// CIs cannot be undriven
 		for (const auto &c : ci_bits)
 			undriven_bits.erase(c.first);
-
 		for (auto bit : unused_bits)
 			undriven_bits.erase(bit);
 
-		if (!undriven_bits.empty()) {
+		if (!undriven_bits.empty() && !holes_mode) {
 			undriven_bits.sort();
 			for (auto bit : undriven_bits) {
 				log_warning("Treating undriven bit %s.%s like $anyseq.\n", log_id(module), log_signal(bit));
@@ -313,30 +388,30 @@ struct XAigerWriter
 		aig_map[State::S0] = 0;
 		aig_map[State::S1] = 1;
 
-		for (auto &c : ci_bits) {
-			aig_m++, aig_i++;
-			c.second = 2*aig_m;
-			aig_map[c.first] = c.second;
-		}
-
 		for (auto bit : input_bits) {
 			aig_m++, aig_i++;
 			aig_map[bit] = 2*aig_m;
 		}
 
+		for (auto &c : ci_bits) {
+			aig_m++, aig_i++;
+			c.second = 2*aig_m;
+            aig_map[c.first] = c.second;
+		}
+
 		if (imode && input_bits.empty()) {
 			aig_m++, aig_i++;
 		}
 
-		if (zinit_mode)
-		{
-			for (auto it : ff_map) {
-				if (init_map.count(it.first))
-					continue;
-				aig_m++, aig_i++;
-				init_inputs[it.first] = 2*aig_m;
-			}
-		}
+		//if (zinit_mode)
+		//{
+		//	for (auto it : ff_map) {
+		//		if (init_map.count(it.first))
+		//			continue;
+		//		aig_m++, aig_i++;
+		//		init_inputs[it.first] = 2*aig_m;
+		//	}
+		//}
 
 		for (auto it : ff_map) {
 			aig_m++, aig_l++;
@@ -348,29 +423,29 @@ struct XAigerWriter
 				aig_latchinit.push_back(init_map.at(it.first) ? 1 : 0);
 		}
 
-		if (!initstate_bits.empty() || !init_inputs.empty()) {
-			aig_m++, aig_l++;
-			initstate_ff = 2*aig_m+1;
-			aig_latchinit.push_back(0);
-		}
+		//if (!initstate_bits.empty() || !init_inputs.empty()) {
+		//	aig_m++, aig_l++;
+		//	initstate_ff = 2*aig_m+1;
+		//	aig_latchinit.push_back(0);
+		//}
 
-		if (zinit_mode)
-		{
-			for (auto it : ff_map)
-			{
-				int l = ordered_latches[it.first];
+		//if (zinit_mode)
+		//{
+		//	for (auto it : ff_map)
+		//	{
+		//		int l = ordered_latches[it.first];
 
-				if (aig_latchinit.at(l) == 1)
-					aig_map[it.first] ^= 1;
+		//		if (aig_latchinit.at(l) == 1)
+		//			aig_map[it.first] ^= 1;
 
-				if (aig_latchinit.at(l) == 2)
-				{
-					int gated_ffout = mkgate(aig_map[it.first], initstate_ff^1);
-					int gated_initin = mkgate(init_inputs[it.first], initstate_ff);
-					aig_map[it.first] = mkgate(gated_ffout^1, gated_initin^1)^1;
-				}
-			}
-		}
+		//		if (aig_latchinit.at(l) == 2)
+		//		{
+		//			int gated_ffout = mkgate(aig_map[it.first], initstate_ff^1);
+		//			int gated_initin = mkgate(init_inputs[it.first], initstate_ff);
+		//			aig_map[it.first] = mkgate(gated_ffout^1, gated_initin^1)^1;
+		//		}
+		//	}
+		//}
 
 		for (auto it : ff_map) {
 			int a = bit2aig(it.second);
@@ -381,8 +456,8 @@ struct XAigerWriter
 				aig_latchin.push_back(a);
 		}
 
-		if (!initstate_bits.empty() || !init_inputs.empty())
-			aig_latchin.push_back(1);
+		//if (!initstate_bits.empty() || !init_inputs.empty())
+		//	aig_latchin.push_back(1);
 
 		for (auto &c : co_bits) {
 			RTLIL::SigBit bit = c.first;
@@ -517,14 +592,14 @@ struct XAigerWriter
 							symbols[stringf("%c%d", miter_mode ? 'b' : 'o', o)].push_back(stringf("%s", log_id(wire)));
 					}
 
-					if (init_inputs.count(sig[i])) {
-						int a = init_inputs.at(sig[i]);
-						log_assert((a & 1) == 0);
-						if (GetSize(wire) != 1)
-							symbols[stringf("i%d", (a >> 1)-1)].push_back(stringf("init:%s[%d]", log_id(wire), i));
-						else
-							symbols[stringf("i%d", (a >> 1)-1)].push_back(stringf("init:%s", log_id(wire)));
-					}
+					//if (init_inputs.count(sig[i])) {
+					//	int a = init_inputs.at(sig[i]);
+					//	log_assert((a & 1) == 0);
+					//	if (GetSize(wire) != 1)
+					//		symbols[stringf("i%d", (a >> 1)-1)].push_back(stringf("init:%s[%d]", log_id(wire), i));
+					//	else
+					//		symbols[stringf("i%d", (a >> 1)-1)].push_back(stringf("init:%s", log_id(wire)));
+					//}
 
 					if (ordered_latches.count(sig[i])) {
 						int l = ordered_latches.at(sig[i]);
@@ -584,17 +659,17 @@ struct XAigerWriter
 				if (holes_module && !holes_module->cell(stringf("\\u%d", box_id)))
 					holes_cell = holes_module->addCell(stringf("\\u%d", box_id), cell->type);
 				RTLIL::Wire *holes_wire;
-				int num_inputs = 0;
+				// NB: cell->connections_ already sorted from before
 				for (const auto &c : cell->connections()) {
+					log_assert(c.second.size() == 1);
 					if (cell->input(c.first)) {
 						box_inputs += c.second.size();
 						if (holes_cell) {
-							holes_wire = holes_module->wire(stringf("\\i%d", num_inputs));
+							holes_wire = holes_module->wire(stringf("\\i%d", box_inputs));
 							if (!holes_wire) {
-								holes_wire = holes_module->addWire(stringf("\\i%d", num_inputs));
+								holes_wire = holes_module->addWire(stringf("\\i%d", box_inputs));
 								holes_wire->port_input = true;
 							}
-							++num_inputs;
 							holes_cell->setPort(c.first, holes_wire);
 						}
 					}
@@ -631,12 +706,12 @@ struct XAigerWriter
 				RTLIL::Selection& sel = holes_module->design->selection_stack.back();
 				sel.select(holes_module);
 
-				Pass::call(holes_module->design, "flatten; aigmap");
+				Pass::call(holes_module->design, "flatten -wb; aigmap; clean -purge");
 
 				holes_module->design->selection_stack.pop_back();
 
 				std::stringstream a_buffer;
-				XAigerWriter writer(holes_module, false /*zinit_mode*/, false /*imode*/, false /*omode*/, false /*bmode*/);
+				XAigerWriter writer(holes_module, false /*zinit_mode*/, false /*imode*/, false /*omode*/, false /*bmode*/, true /* holes_mode */);
 				writer.write_aiger(a_buffer, false /*ascii_mode*/, false /*miter_mode*/, false /*symbols_mode*/, false /*omode*/);
 
 				f << "a";
@@ -686,12 +761,12 @@ struct XAigerWriter
 					continue;
 				}
 
-				if (init_inputs.count(sig[i])) {
-					int a = init_inputs.at(sig[i]);
-					log_assert((a & 1) == 0);
-					init_lines[a] += stringf("init %d %d %s\n", (a >> 1)-1, i, log_id(wire));
-					continue;
-				}
+				//if (init_inputs.count(sig[i])) {
+				//	int a = init_inputs.at(sig[i]);
+				//	log_assert((a & 1) == 0);
+				//	init_lines[a] += stringf("init %d %d %s\n", (a >> 1)-1, i, log_id(wire));
+				//	continue;
+				//}
 
 				if (ordered_latches.count(sig[i])) {
 					int l = ordered_latches.at(sig[i]);
@@ -716,7 +791,7 @@ struct XAigerWriter
 			RTLIL::SigBit b = c.first;
 			RTLIL::Wire *wire = b.wire;
 			int i = b.offset;
-			int a = c.second;
+			int a = bit2aig(b);
 			log_assert((a & 1) == 0);
 			input_lines[a] += stringf("input %d %d %s\n", (a >> 1)-1, i, log_id(wire));
 		}
@@ -769,7 +844,7 @@ struct XAigerBackend : public Backend {
 		log("all unsupported cells will be converted into psuedo-inputs and pseudo-outputs.\n");
 		log("\n");
 		log("    -ascii\n");
-		log("        write ASCII version of AGIER format\n");
+		log("        write ASCII version of AIGER format\n");
 		log("\n");
 		log("    -zinit\n");
 		log("        convert FFs to zero-initialized FFs, adding additional inputs for\n");
diff --git a/backends/json/json.cc b/backends/json/json.cc
index f5c687981..b4f82a3fe 100644
--- a/backends/json/json.cc
+++ b/backends/json/json.cc
@@ -130,72 +130,75 @@ struct JsonWriter
 			f << stringf("        }");
 			first = false;
 		}
-		f << stringf("\n      },\n");
+		f << stringf("\n      }");
 
-		f << stringf("      \"cells\": {");
-		first = true;
-		for (auto c : module->cells()) {
-			if (use_selection && !module->selected(c))
-				continue;
-			f << stringf("%s\n", first ? "" : ",");
-			f << stringf("        %s: {\n", get_name(c->name).c_str());
-			f << stringf("          \"hide_name\": %s,\n", c->name[0] == '$' ? "1" : "0");
-			f << stringf("          \"type\": %s,\n", get_name(c->type).c_str());
-			if (aig_mode) {
-				Aig aig(c);
-				if (!aig.name.empty()) {
-					f << stringf("          \"model\": \"%s\",\n", aig.name.c_str());
-					aig_models.insert(aig);
+		if (!module->get_blackbox_attribute()) {
+			f << stringf(",\n      \"cells\": {");
+			first = true;
+			for (auto c : module->cells()) {
+				if (use_selection && !module->selected(c))
+					continue;
+				f << stringf("%s\n", first ? "" : ",");
+				f << stringf("        %s: {\n", get_name(c->name).c_str());
+				f << stringf("          \"hide_name\": %s,\n", c->name[0] == '$' ? "1" : "0");
+				f << stringf("          \"type\": %s,\n", get_name(c->type).c_str());
+				if (aig_mode) {
+					Aig aig(c);
+					if (!aig.name.empty()) {
+						f << stringf("          \"model\": \"%s\",\n", aig.name.c_str());
+						aig_models.insert(aig);
+					}
 				}
-			}
-			f << stringf("          \"parameters\": {");
-			write_parameters(c->parameters);
-			f << stringf("\n          },\n");
-			f << stringf("          \"attributes\": {");
-			write_parameters(c->attributes);
-			f << stringf("\n          },\n");
-			if (c->known()) {
-				f << stringf("          \"port_directions\": {");
+				f << stringf("          \"parameters\": {");
+				write_parameters(c->parameters);
+				f << stringf("\n          },\n");
+				f << stringf("          \"attributes\": {");
+				write_parameters(c->attributes);
+				f << stringf("\n          },\n");
+				if (c->known()) {
+					f << stringf("          \"port_directions\": {");
+					bool first2 = true;
+					for (auto &conn : c->connections()) {
+						string direction = "output";
+						if (c->input(conn.first))
+							direction = c->output(conn.first) ? "inout" : "input";
+						f << stringf("%s\n", first2 ? "" : ",");
+						f << stringf("            %s: \"%s\"", get_name(conn.first).c_str(), direction.c_str());
+						first2 = false;
+					}
+					f << stringf("\n          },\n");
+				}
+				f << stringf("          \"connections\": {");
 				bool first2 = true;
 				for (auto &conn : c->connections()) {
-					string direction = "output";
-					if (c->input(conn.first))
-						direction = c->output(conn.first) ? "inout" : "input";
 					f << stringf("%s\n", first2 ? "" : ",");
-					f << stringf("            %s: \"%s\"", get_name(conn.first).c_str(), direction.c_str());
+					f << stringf("            %s: %s", get_name(conn.first).c_str(), get_bits(conn.second).c_str());
 					first2 = false;
 				}
-				f << stringf("\n          },\n");
+				f << stringf("\n          }\n");
+				f << stringf("        }");
+				first = false;
 			}
-			f << stringf("          \"connections\": {");
-			bool first2 = true;
-			for (auto &conn : c->connections()) {
-				f << stringf("%s\n", first2 ? "" : ",");
-				f << stringf("            %s: %s", get_name(conn.first).c_str(), get_bits(conn.second).c_str());
-				first2 = false;
-			}
-			f << stringf("\n          }\n");
-			f << stringf("        }");
-			first = false;
-		}
-		f << stringf("\n      },\n");
+			f << stringf("\n      },\n");
 
-		f << stringf("      \"netnames\": {");
-		first = true;
-		for (auto w : module->wires()) {
-			if (use_selection && !module->selected(w))
-				continue;
-			f << stringf("%s\n", first ? "" : ",");
-			f << stringf("        %s: {\n", get_name(w->name).c_str());
-			f << stringf("          \"hide_name\": %s,\n", w->name[0] == '$' ? "1" : "0");
-			f << stringf("          \"bits\": %s,\n", get_bits(w).c_str());
-			f << stringf("          \"attributes\": {");
-			write_parameters(w->attributes);
-			f << stringf("\n          }\n");
-			f << stringf("        }");
-			first = false;
+			f << stringf("      \"netnames\": {");
+			first = true;
+			for (auto w : module->wires()) {
+				if (use_selection && !module->selected(w))
+					continue;
+				f << stringf("%s\n", first ? "" : ",");
+				f << stringf("        %s: {\n", get_name(w->name).c_str());
+				f << stringf("          \"hide_name\": %s,\n", w->name[0] == '$' ? "1" : "0");
+				f << stringf("          \"bits\": %s,\n", get_bits(w).c_str());
+				f << stringf("          \"attributes\": {");
+				write_parameters(w->attributes);
+				f << stringf("\n          }\n");
+				f << stringf("        }");
+				first = false;
+			}
+			f << stringf("\n      }");
 		}
-		f << stringf("\n      }\n");
+		f << stringf("\n");
 
 		f << stringf("    }");
 	}
diff --git a/backends/verilog/verilog_backend.cc b/backends/verilog/verilog_backend.cc
index 855409d0b..9967482d6 100644
--- a/backends/verilog/verilog_backend.cc
+++ b/backends/verilog/verilog_backend.cc
@@ -187,6 +187,10 @@ void dump_const(std::ostream &f, const RTLIL::Const &data, int width = -1, int o
 {
 	if (width < 0)
 		width = data.bits.size() - offset;
+	if (width == 0) {
+		f << "\"\"";
+		return;
+	}
 	if (nostr)
 		goto dump_hex;
 	if ((data.flags & RTLIL::CONST_FLAG_STRING) == 0 || width != (int)data.bits.size()) {
@@ -340,6 +344,10 @@ void dump_sigchunk(std::ostream &f, const RTLIL::SigChunk &chunk, bool no_decima
 
 void dump_sigspec(std::ostream &f, const RTLIL::SigSpec &sig)
 {
+	if (GetSize(sig) == 0) {
+		f << "\"\"";
+		return;
+	}
 	if (sig.is_chunk()) {
 		dump_sigchunk(f, sig.as_chunk());
 	} else {
diff --git a/frontends/aiger/aigerparse.cc b/frontends/aiger/aigerparse.cc
index f2d21f1db..3fa6f5c2d 100644
--- a/frontends/aiger/aigerparse.cc
+++ b/frontends/aiger/aigerparse.cc
@@ -35,9 +35,6 @@
 
 YOSYS_NAMESPACE_BEGIN
 
-//#define log_debug log
-#define log_debug(...) ;
-
 AigerReader::AigerReader(RTLIL::Design *design, std::istream &f, RTLIL::IdString module_name, RTLIL::IdString clk_name, std::string map_filename, bool wideports)
     : design(design), f(f), clk_name(clk_name), map_filename(map_filename), wideports(wideports)
 {
@@ -368,6 +365,13 @@ void AigerReader::parse_xaiger()
                f >> s;
                log_debug("n: '%s'\n", s.c_str());
             }
+            else if (c == 'a' || c == 'i' || c == 'o' || c == 'h') {
+                uint32_t dataSize = parse_xaiger_literal(f);
+                f.ignore(dataSize);
+            }
+            else {
+                break;
+            }
         }
         else if (c == 'i' || c == 'l' || c == 'o') {
             f.ignore(1);
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 76da5a97c..3e453bd7f 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -1085,7 +1085,12 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 
 		// eval 1st expression
 		AstNode *varbuf = init_ast->children[1]->clone();
-		while (varbuf->simplify(true, false, false, stage, 32, true, false)) { }
+		{
+			int expr_width_hint = -1;
+			bool expr_sign_hint = true;
+			varbuf->detectSignWidth(expr_width_hint, expr_sign_hint);
+			while (varbuf->simplify(true, false, false, stage, 32, true, false)) { }
+		}
 
 		if (varbuf->type != AST_CONSTANT)
 			log_file_error(filename, linenum, "Right hand side of 1st expression of generate for-loop is not constant!\n");
@@ -1107,7 +1112,12 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		{
 			// eval 2nd expression
 			AstNode *buf = while_ast->clone();
-			while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
+			{
+				int expr_width_hint = -1;
+				bool expr_sign_hint = true;
+				buf->detectSignWidth(expr_width_hint, expr_sign_hint);
+				while (buf->simplify(true, false, false, stage, expr_width_hint, expr_sign_hint, false)) { }
+			}
 
 			if (buf->type != AST_CONSTANT)
 				log_file_error(filename, linenum, "2nd expression of generate for-loop is not constant!\n");
@@ -1148,7 +1158,12 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 
 			// eval 3rd expression
 			buf = next_ast->children[1]->clone();
-			while (buf->simplify(true, false, false, stage, 32, true, false)) { }
+			{
+				int expr_width_hint = -1;
+				bool expr_sign_hint = true;
+				buf->detectSignWidth(expr_width_hint, expr_sign_hint);
+				while (buf->simplify(true, false, false, stage, expr_width_hint, expr_sign_hint, true)) { }
+			}
 
 			if (buf->type != AST_CONSTANT)
 				log_file_error(filename, linenum, "Right hand side of 3rd expression of generate for-loop is not constant!\n");
diff --git a/kernel/driver.cc b/kernel/driver.cc
index c539ba569..1bc7a5935 100644
--- a/kernel/driver.cc
+++ b/kernel/driver.cc
@@ -295,6 +295,9 @@ int main(int argc, char **argv)
 		printf("    -E <depsfile>\n");
 		printf("        write a Makefile dependencies file with in- and output file names\n");
 		printf("\n");
+		printf("    -g\n");
+		printf("        globally enable debug log messages\n");
+		printf("\n");
 		printf("    -V\n");
 		printf("        print version information and exit\n");
 		printf("\n");
@@ -315,7 +318,7 @@ int main(int argc, char **argv)
 	}
 
 	int opt;
-	while ((opt = getopt(argc, argv, "MXAQTVSm:f:Hh:b:o:p:l:L:qv:tds:c:W:w:e:D:P:E:")) != -1)
+	while ((opt = getopt(argc, argv, "MXAQTVSgm:f:Hh:b:o:p:l:L:qv:tds:c:W:w:e:D:P:E:")) != -1)
 	{
 		switch (opt)
 		{
@@ -340,6 +343,9 @@ int main(int argc, char **argv)
 		case 'S':
 			passes_commands.push_back("synth");
 			break;
+		case 'g':
+			log_force_debug++;
+			break;
 		case 'm':
 			plugin_filenames.push_back(optarg);
 			break;
diff --git a/kernel/log.cc b/kernel/log.cc
index 400a549dd..9a9104e26 100644
--- a/kernel/log.cc
+++ b/kernel/log.cc
@@ -56,6 +56,10 @@ int log_verbose_level;
 string log_last_error;
 void (*log_error_atexit)() = NULL;
 
+int log_make_debug = 0;
+int log_force_debug = 0;
+int log_debug_suppressed = 0;
+
 vector<int> header_count;
 pool<RTLIL::IdString> log_id_cache;
 vector<shared_str> string_buf;
@@ -92,6 +96,9 @@ void logv(const char *format, va_list ap)
 		format++;
 	}
 
+	if (log_make_debug && !ys_debug(1))
+		return;
+
 	std::string str = vstringf(format, ap);
 
 	if (str.empty())
diff --git a/kernel/log.h b/kernel/log.h
index 759939025..e6afae716 100644
--- a/kernel/log.h
+++ b/kernel/log.h
@@ -64,6 +64,10 @@ extern int log_verbose_level;
 extern string log_last_error;
 extern void (*log_error_atexit)();
 
+extern int log_make_debug;
+extern int log_force_debug;
+extern int log_debug_suppressed;
+
 void logv(const char *format, va_list ap);
 void logv_header(RTLIL::Design *design, const char *format, va_list ap);
 void logv_warning(const char *format, va_list ap);
@@ -82,6 +86,45 @@ YS_NORETURN void log_error(const char *format, ...) YS_ATTRIBUTE(format(printf,
 void log_file_error(const string &filename, int lineno, const char *format, ...) YS_ATTRIBUTE(format(printf, 3, 4), noreturn);
 YS_NORETURN void log_cmd_error(const char *format, ...) YS_ATTRIBUTE(format(printf, 1, 2), noreturn);
 
+#ifndef NDEBUG
+static inline bool ys_debug(int n = 0) { if (log_force_debug) return true; log_debug_suppressed += n; return false; }
+#  define log_debug(...) do { if (ys_debug(1)) log(__VA_ARGS__); } while (0)
+#else
+static inline bool ys_debug(int n = 0) { return false; }
+#  define log_debug(_fmt, ...) do { } while (0)
+#endif
+
+static inline void log_suppressed() {
+	if (log_debug_suppressed && !log_make_debug) {
+		log("<suppressed ~%d debug messages>\n", log_debug_suppressed);
+		log_debug_suppressed = 0;
+	}
+}
+
+struct LogMakeDebugHdl {
+	bool status = false;
+	LogMakeDebugHdl(bool start_on = false) {
+		if (start_on)
+			on();
+	}
+	~LogMakeDebugHdl() {
+		off();
+	}
+	void on() {
+		if (status) return;
+		status=true;
+		log_make_debug++;
+	}
+	void off_silent() {
+		if (!status) return;
+		status=false;
+		log_make_debug--;
+	}
+	void off() {
+		off_silent();
+	}
+};
+
 void log_spacer();
 void log_push();
 void log_pop();
diff --git a/kernel/register.cc b/kernel/register.cc
index 64956401f..71eb6b187 100644
--- a/kernel/register.cc
+++ b/kernel/register.cc
@@ -87,6 +87,7 @@ Pass::pre_post_exec_state_t Pass::pre_execute()
 void Pass::post_execute(Pass::pre_post_exec_state_t state)
 {
 	IdString::checkpoint();
+	log_suppressed();
 
 	int64_t time_ns = PerformanceTimer::query() - state.begin_ns;
 	runtime_ns += time_ns;
diff --git a/passes/cmds/trace.cc b/passes/cmds/trace.cc
index f5305cde9..cf3e46ace 100644
--- a/passes/cmds/trace.cc
+++ b/passes/cmds/trace.cc
@@ -94,4 +94,38 @@ struct TracePass : public Pass {
 	}
 } TracePass;
 
+struct DebugPass : public Pass {
+	DebugPass() : Pass("debug", "run command with debug log messages enabled") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    debug cmd\n");
+		log("\n");
+		log("Execute the specified command with debug log messages enabled\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			// .. parse options ..
+			break;
+		}
+
+		log_force_debug++;
+
+		try {
+			std::vector<std::string> new_args(args.begin() + argidx, args.end());
+			Pass::call(design, new_args);
+		} catch (...) {
+			log_force_debug--;
+			throw;
+		}
+
+		log_force_debug--;
+	}
+} DebugPass;
+
 PRIVATE_NAMESPACE_END
diff --git a/passes/opt/opt_clean.cc b/passes/opt/opt_clean.cc
index c3b13acaf..c38e9df5e 100644
--- a/passes/opt/opt_clean.cc
+++ b/passes/opt/opt_clean.cc
@@ -137,7 +137,7 @@ void rmunused_module_cells(Module *module, bool verbose)
 
 	for (auto cell : unused) {
 		if (verbose)
-			log("  removing unused `%s' cell `%s'.\n", cell->type.c_str(), cell->name.c_str());
+			log_debug("  removing unused `%s' cell `%s'.\n", cell->type.c_str(), cell->name.c_str());
 		module->design->scratchpad_set_bool("opt.did_something", true);
 		module->remove(cell);
 		count_rm_cells++;
@@ -326,7 +326,7 @@ void rmunused_module_signals(RTLIL::Module *module, bool purge_mode, bool verbos
 	for (auto wire : maybe_del_wires)
 		if (!used_signals.check_any(RTLIL::SigSpec(wire))) {
 			if (check_public_name(wire->name) && verbose) {
-				log("  removing unused non-port wire %s.\n", wire->name.c_str());
+				log_debug("  removing unused non-port wire %s.\n", wire->name.c_str());
 			}
 			del_wires.insert(wire);
 			del_wires_count++;
@@ -336,7 +336,7 @@ void rmunused_module_signals(RTLIL::Module *module, bool purge_mode, bool verbos
 	count_rm_wires += del_wires.size();
 
 	if (verbose && del_wires_count > 0)
-		log("  removed %d unused temporary wires.\n", del_wires_count);
+		log_debug("  removed %d unused temporary wires.\n", del_wires_count);
 }
 
 bool rmunused_module_init(RTLIL::Module *module, bool purge_mode, bool verbose)
@@ -399,7 +399,7 @@ bool rmunused_module_init(RTLIL::Module *module, bool purge_mode, bool verbose)
 		}
 
 		if (verbose)
-			log("  removing redundant init attribute on %s.\n", log_id(wire));
+			log_debug("  removing redundant init attribute on %s.\n", log_id(wire));
 
 		wire->attributes.erase("\\init");
 		did_something = true;
@@ -426,7 +426,7 @@ void rmunused_module(RTLIL::Module *module, bool purge_mode, bool verbose, bool
 		}
 	for (auto cell : delcells) {
 		if (verbose)
-			log("  removing buffer cell `%s': %s = %s\n", cell->name.c_str(),
+			log_debug("  removing buffer cell `%s': %s = %s\n", cell->name.c_str(),
 					log_signal(cell->getPort("\\Y")), log_signal(cell->getPort("\\A")));
 		module->remove(cell);
 	}
@@ -551,6 +551,7 @@ struct CleanPass : public Pass {
 			rmunused_module(module, purge_mode, false, false);
 		}
 
+		log_suppressed();
 		if (count_rm_cells > 0 || count_rm_wires > 0)
 			log("Removed %d unused cells and %d unused wires.\n", count_rm_cells, count_rm_wires);
 
diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index a05db2a4f..af6d352af 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -67,7 +67,7 @@ void replace_undriven(RTLIL::Design *design, RTLIL::Module *module)
 		if (sig.size() == 0)
 			continue;
 
-		log("Setting undriven signal in %s to undef: %s\n", RTLIL::id2cstr(module->name), log_signal(c));
+		log_debug("Setting undriven signal in %s to undef: %s\n", RTLIL::id2cstr(module->name), log_signal(c));
 		module->connect(RTLIL::SigSig(c, RTLIL::SigSpec(RTLIL::State::Sx, c.width)));
 		did_something = true;
 	}
@@ -78,7 +78,7 @@ void replace_cell(SigMap &assign_map, RTLIL::Module *module, RTLIL::Cell *cell,
 	RTLIL::SigSpec Y = cell->getPort(out_port);
 	out_val.extend_u0(Y.size(), false);
 
-	log("Replacing %s cell `%s' (%s) in module `%s' with constant driver `%s = %s'.\n",
+	log_debug("Replacing %s cell `%s' (%s) in module `%s' with constant driver `%s = %s'.\n",
 			cell->type.c_str(), cell->name.c_str(), info.c_str(),
 			module->name.c_str(), log_signal(Y), log_signal(out_val));
 	// log_cell(cell);
@@ -134,7 +134,7 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
 		if (GetSize(grouped_bits[i]) == GetSize(bits_y))
 			return false;
 
-	log("Replacing %s cell `%s' in module `%s' with cells using grouped bits:\n",
+	log_debug("Replacing %s cell `%s' in module `%s' with cells using grouped bits:\n",
 			log_id(cell->type), log_id(cell), log_id(module));
 
 	for (int i = 0; i < GRP_N; i++)
@@ -156,7 +156,7 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
 		}
 
 		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));
+			log_debug("  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;
@@ -180,10 +180,10 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
 
 		module->connect(new_conn);
 
-		log("  New cell `%s': A=%s", log_id(c), log_signal(new_a));
+		log_debug("  New cell `%s': A=%s", log_id(c), log_signal(new_a));
 		if (b_name == "\\B")
-			log(", B=%s", log_signal(new_b));
-		log("\n");
+			log_debug(", B=%s", log_signal(new_b));
+		log_debug("\n");
 	}
 
 	cover_list("opt.opt_expr.fine.group", "$not", "$pos", "$and", "$or", "$xor", "$xnor", cell->type.str());
@@ -197,7 +197,7 @@ void handle_polarity_inv(Cell *cell, IdString port, IdString param, const SigMap
 {
 	SigSpec sig = assign_map(cell->getPort(port));
 	if (invert_map.count(sig)) {
-		log("Inverting %s of %s cell `%s' in module `%s': %s -> %s\n",
+		log_debug("Inverting %s of %s cell `%s' in module `%s': %s -> %s\n",
 				log_id(port), log_id(cell->type), log_id(cell), log_id(cell->module),
 				log_signal(sig), log_signal(invert_map.at(sig)));
 		cell->setPort(port, (invert_map.at(sig)));
@@ -226,7 +226,7 @@ void handle_clkpol_celltype_swap(Cell *cell, string type1, string type2, IdStrin
 	if (cell->type.in(type1, type2)) {
 		SigSpec sig = assign_map(cell->getPort(port));
 		if (invert_map.count(sig)) {
-			log("Inverting %s of %s cell `%s' in module `%s': %s -> %s\n",
+			log_debug("Inverting %s of %s cell `%s' in module `%s': %s -> %s\n",
 					log_id(port), log_id(cell->type), log_id(cell), log_id(cell->module),
 					log_signal(sig), log_signal(invert_map.at(sig)));
 			cell->setPort(port, (invert_map.at(sig)));
@@ -455,9 +455,10 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 		{
 			if (cell->type == "$reduce_xnor") {
 				cover("opt.opt_expr.reduce_xnor_not");
-				log("Replacing %s cell `%s' in module `%s' with $not cell.\n",
+				log_debug("Replacing %s cell `%s' in module `%s' with $not cell.\n",
 						log_id(cell->type), log_id(cell->name), log_id(module));
 				cell->type = "$not";
+				did_something = true;
 			} else {
 				cover("opt.opt_expr.unary_buffer");
 				replace_cell(assign_map, module, cell, "unary_buffer", "\\Y", cell->getPort("\\A"));
@@ -488,7 +489,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (GetSize(new_sig_a) < GetSize(sig_a)) {
 					cover_list("opt.opt_expr.fine.neutral_A", "$logic_not", "$logic_and", "$logic_or", "$reduce_or", "$reduce_and", "$reduce_bool", cell->type.str());
-					log("Replacing port A of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
+					log_debug("Replacing port A of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
 							cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_a), log_signal(new_sig_a));
 					cell->setPort("\\A", new_sig_a);
 					cell->parameters.at("\\A_WIDTH") = GetSize(new_sig_a);
@@ -511,7 +512,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (GetSize(new_sig_b) < GetSize(sig_b)) {
 					cover_list("opt.opt_expr.fine.neutral_B", "$logic_and", "$logic_or", cell->type.str());
-					log("Replacing port B of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
+					log_debug("Replacing port B of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
 							cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_b), log_signal(new_sig_b));
 					cell->setPort("\\B", new_sig_b);
 					cell->parameters.at("\\B_WIDTH") = GetSize(new_sig_b);
@@ -537,7 +538,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (new_a != RTLIL::State::Sm && RTLIL::SigSpec(new_a) != sig_a) {
 					cover("opt.opt_expr.fine.$reduce_and");
-					log("Replacing port A of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
+					log_debug("Replacing port A of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
 							cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_a), log_signal(new_a));
 					cell->setPort("\\A", sig_a = new_a);
 					cell->parameters.at("\\A_WIDTH") = 1;
@@ -563,7 +564,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (new_a != RTLIL::State::Sm && RTLIL::SigSpec(new_a) != sig_a) {
 					cover_list("opt.opt_expr.fine.A", "$logic_not", "$logic_and", "$logic_or", "$reduce_or", "$reduce_bool", cell->type.str());
-					log("Replacing port A of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
+					log_debug("Replacing port A of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
 							cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_a), log_signal(new_a));
 					cell->setPort("\\A", sig_a = new_a);
 					cell->parameters.at("\\A_WIDTH") = 1;
@@ -589,7 +590,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (new_b != RTLIL::State::Sm && RTLIL::SigSpec(new_b) != sig_b) {
 					cover_list("opt.opt_expr.fine.B", "$logic_and", "$logic_or", cell->type.str());
-					log("Replacing port B of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
+					log_debug("Replacing port B of %s cell `%s' in module `%s' with constant driver: %s -> %s\n",
 							cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_b), log_signal(new_b));
 					cell->setPort("\\B", sig_b = new_b);
 					cell->parameters.at("\\B_WIDTH") = 1;
@@ -640,7 +641,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 		if ((cell->type == "$_MUX_" || cell->type == "$mux") && invert_map.count(assign_map(cell->getPort("\\S"))) != 0) {
 			cover_list("opt.opt_expr.invert.muxsel", "$_MUX_", "$mux", cell->type.str());
-			log("Optimizing away select inverter for %s cell `%s' in module `%s'.\n", log_id(cell->type), log_id(cell), log_id(module));
+			log_debug("Optimizing away select inverter for %s cell `%s' in module `%s'.\n", log_id(cell->type), log_id(cell), log_id(module));
 			RTLIL::SigSpec tmp = cell->getPort("\\A");
 			cell->setPort("\\A", cell->getPort("\\B"));
 			cell->setPort("\\B", tmp);
@@ -750,7 +751,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				ACTION_DO("\\Y", cell->getPort("\\A"));
 			if (input == State::S0 && !a.is_fully_undef()) {
 				cover("opt.opt_expr.action_" S__LINE__);
-				log("Replacing data input of %s cell `%s' in module `%s' with constant undef.\n",
+				log_debug("Replacing data input of %s cell `%s' in module `%s' with constant undef.\n",
 					cell->type.c_str(), cell->name.c_str(), module->name.c_str());
 				cell->setPort("\\A", SigSpec(State::Sx, GetSize(a)));
 				did_something = true;
@@ -822,7 +823,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 					ACTION_DO("\\Y", cell->getPort("\\A"));
 				} else {
 					cover_list("opt.opt_expr.eqneq.isnot", "$eq", "$ne", cell->type.str());
-					log("Replacing %s cell `%s' in module `%s' with inverter.\n", log_id(cell->type), log_id(cell), log_id(module));
+					log_debug("Replacing %s cell `%s' in module `%s' with inverter.\n", log_id(cell->type), log_id(cell), log_id(module));
 					cell->type = "$not";
 					cell->parameters.erase("\\B_WIDTH");
 					cell->parameters.erase("\\B_SIGNED");
@@ -837,7 +838,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				(assign_map(cell->getPort("\\A")).is_fully_zero() || assign_map(cell->getPort("\\B")).is_fully_zero()))
 		{
 			cover_list("opt.opt_expr.eqneq.cmpzero", "$eq", "$ne", cell->type.str());
-			log("Replacing %s cell `%s' in module `%s' with %s.\n", log_id(cell->type), log_id(cell),
+			log_debug("Replacing %s cell `%s' in module `%s' with %s.\n", log_id(cell->type), log_id(cell),
 					log_id(module), "$eq" ? "$logic_not" : "$reduce_bool");
 			cell->type = cell->type == "$eq" ? "$logic_not" : "$reduce_bool";
 			if (assign_map(cell->getPort("\\A")).is_fully_zero()) {
@@ -876,7 +877,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 			cover_list("opt.opt_expr.constshift", "$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx", cell->type.str());
 
-			log("Replacing %s cell `%s' (B=%s, SHR=%d) in module `%s' with fixed wiring: %s\n",
+			log_debug("Replacing %s cell `%s' (B=%s, SHR=%d) in module `%s' with fixed wiring: %s\n",
 					log_id(cell->type), log_id(cell), log_signal(assign_map(cell->getPort("\\B"))), shift_bits, log_id(module), log_signal(sig_y));
 
 			module->connect(cell->getPort("\\Y"), sig_y);
@@ -939,7 +940,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				if (identity_wrt_b)
 					cover_list("opt.opt_expr.identwrt.b", "$add", "$sub", "$or", "$xor", "$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx", "$mul", "$div", cell->type.str());
 
-				log("Replacing %s cell `%s' in module `%s' with identity for port %c.\n",
+				log_debug("Replacing %s cell `%s' in module `%s' with identity for port %c.\n",
 					cell->type.c_str(), cell->name.c_str(), module->name.c_str(), identity_wrt_a ? 'A' : 'B');
 
 				if (!identity_wrt_a) {
@@ -969,7 +970,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 		if (mux_bool && (cell->type == "$mux" || cell->type == "$_MUX_") &&
 				cell->getPort("\\A") == RTLIL::SigSpec(1, 1) && cell->getPort("\\B") == RTLIL::SigSpec(0, 1)) {
 			cover_list("opt.opt_expr.mux_invert", "$mux", "$_MUX_", cell->type.str());
-			log("Replacing %s cell `%s' in module `%s' with inverter.\n", log_id(cell->type), log_id(cell), log_id(module));
+			log_debug("Replacing %s cell `%s' in module `%s' with inverter.\n", log_id(cell->type), log_id(cell), log_id(module));
 			cell->setPort("\\A", cell->getPort("\\S"));
 			cell->unsetPort("\\B");
 			cell->unsetPort("\\S");
@@ -988,7 +989,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 		if (consume_x && mux_bool && (cell->type == "$mux" || cell->type == "$_MUX_") && cell->getPort("\\A") == RTLIL::SigSpec(0, 1)) {
 			cover_list("opt.opt_expr.mux_and", "$mux", "$_MUX_", cell->type.str());
-			log("Replacing %s cell `%s' in module `%s' with and-gate.\n", log_id(cell->type), log_id(cell), log_id(module));
+			log_debug("Replacing %s cell `%s' in module `%s' with and-gate.\n", log_id(cell->type), log_id(cell), log_id(module));
 			cell->setPort("\\A", cell->getPort("\\S"));
 			cell->unsetPort("\\S");
 			if (cell->type == "$mux") {
@@ -1008,7 +1009,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 		if (consume_x && mux_bool && (cell->type == "$mux" || cell->type == "$_MUX_") && cell->getPort("\\B") == RTLIL::SigSpec(1, 1)) {
 			cover_list("opt.opt_expr.mux_or", "$mux", "$_MUX_", cell->type.str());
-			log("Replacing %s cell `%s' in module `%s' with or-gate.\n", log_id(cell->type), log_id(cell), log_id(module));
+			log_debug("Replacing %s cell `%s' in module `%s' with or-gate.\n", log_id(cell->type), log_id(cell), log_id(module));
 			cell->setPort("\\B", cell->getPort("\\S"));
 			cell->unsetPort("\\S");
 			if (cell->type == "$mux") {
@@ -1061,7 +1062,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 			}
 			if (cell->getPort("\\S").size() != new_s.size()) {
 				cover_list("opt.opt_expr.mux_reduce", "$mux", "$pmux", cell->type.str());
-				log("Optimized away %d select inputs of %s cell `%s' in module `%s'.\n",
+				log_debug("Optimized away %d select inputs of %s cell `%s' in module `%s'.\n",
 						GetSize(cell->getPort("\\S")) - GetSize(new_s), log_id(cell->type), log_id(cell), log_id(module));
 				cell->setPort("\\A", new_a);
 				cell->setPort("\\B", new_b);
@@ -1179,7 +1180,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				{
 					cover("opt.opt_expr.mul_shift.zero");
 
-					log("Replacing multiply-by-zero cell `%s' in module `%s' with zero-driver.\n",
+					log_debug("Replacing multiply-by-zero cell `%s' in module `%s' with zero-driver.\n",
 							cell->name.c_str(), module->name.c_str());
 
 					module->connect(RTLIL::SigSig(sig_y, RTLIL::SigSpec(0, sig_y.size())));
@@ -1197,7 +1198,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 						else
 							cover("opt.opt_expr.mul_shift.unswapped");
 
-						log("Replacing multiply-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
+						log_debug("Replacing multiply-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
 								a_val, cell->name.c_str(), module->name.c_str(), i);
 
 						if (!swapped_ab) {
@@ -1237,7 +1238,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				{
 					cover("opt.opt_expr.divmod_zero");
 
-					log("Replacing divide-by-zero cell `%s' in module `%s' with undef-driver.\n",
+					log_debug("Replacing divide-by-zero cell `%s' in module `%s' with undef-driver.\n",
 							cell->name.c_str(), module->name.c_str());
 
 					module->connect(RTLIL::SigSig(sig_y, RTLIL::SigSpec(State::Sx, sig_y.size())));
@@ -1254,7 +1255,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 						{
 							cover("opt.opt_expr.div_shift");
 
-							log("Replacing divide-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
+							log_debug("Replacing divide-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
 									b_val, cell->name.c_str(), module->name.c_str(), i);
 
 							std::vector<RTLIL::SigBit> new_b = RTLIL::SigSpec(i, 6);
@@ -1272,7 +1273,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 						{
 							cover("opt.opt_expr.mod_mask");
 
-							log("Replacing modulo-by-%d cell `%s' in module `%s' with bitmask.\n",
+							log_debug("Replacing modulo-by-%d cell `%s' in module `%s' with bitmask.\n",
 									b_val, cell->name.c_str(), module->name.c_str());
 
 							std::vector<RTLIL::SigBit> new_b = RTLIL::SigSpec(State::S1, i);
@@ -1342,7 +1343,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				SigSpec y_sig = cell->getPort("\\Y");
 				Const y_value(cell->type.in("$eq", "$eqx") ? 0 : 1, GetSize(y_sig));
 
-				log("Replacing cell `%s' in module `%s' with constant driver %s.\n",
+				log_debug("Replacing cell `%s' in module `%s' with constant driver %s.\n",
 					log_id(cell), log_id(module), log_signal(y_value));
 
 				module->connect(y_sig, y_value);
@@ -1354,7 +1355,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 			if (redundant_bits)
 			{
-				log("Removed %d redundant input bits from %s cell `%s' in module `%s'.\n",
+				log_debug("Removed %d redundant input bits from %s cell `%s' in module `%s'.\n",
 						redundant_bits, log_id(cell->type), log_id(cell), log_id(module));
 
 				cell->setPort("\\A", sig_a);
@@ -1493,7 +1494,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 				if (replace || remove)
 				{
-					log("Replacing %s cell `%s' (implementing %s) with %s.\n",
+					log_debug("Replacing %s cell `%s' (implementing %s) with %s.\n",
 							log_id(cell->type), log_id(cell), condition.c_str(), replacement.c_str());
 					if (replace)
 						module->connect(cell->getPort("\\Y"), replace_sig);
@@ -1599,8 +1600,14 @@ struct OptExprPass : public Pass {
 
 		for (auto module : design->selected_modules())
 		{
-			if (undriven)
+			log("Optimizing module %s.\n", log_id(module));
+
+			if (undriven) {
+				did_something = false;
 				replace_undriven(design, module);
+				if (did_something)
+					design->scratchpad_set_bool("opt.did_something", true);
+			}
 
 			do {
 				do {
@@ -1610,7 +1617,11 @@ struct OptExprPass : public Pass {
 						design->scratchpad_set_bool("opt.did_something", true);
 				} while (did_something);
 				replace_const_cells(design, module, true, mux_undef, mux_bool, do_fine, keepdc, clkinv);
+				if (did_something)
+					design->scratchpad_set_bool("opt.did_something", true);
 			} while (did_something);
+
+			log_suppressed();
 		}
 
 		log_pop();
diff --git a/passes/opt/opt_merge.cc b/passes/opt/opt_merge.cc
index eedf88904..7567d4657 100644
--- a/passes/opt/opt_merge.cc
+++ b/passes/opt/opt_merge.cc
@@ -315,17 +315,17 @@ struct OptMergeWorker
 			{
 				if (sharemap.count(cell) > 0) {
 					did_something = true;
-					log("  Cell `%s' is identical to cell `%s'.\n", cell->name.c_str(), sharemap[cell]->name.c_str());
+					log_debug("  Cell `%s' is identical to cell `%s'.\n", cell->name.c_str(), sharemap[cell]->name.c_str());
 					for (auto &it : cell->connections()) {
 						if (cell->output(it.first)) {
 							RTLIL::SigSpec other_sig = sharemap[cell]->getPort(it.first);
-							log("    Redirecting output %s: %s = %s\n", it.first.c_str(),
+							log_debug("    Redirecting output %s: %s = %s\n", it.first.c_str(),
 									log_signal(it.second), log_signal(other_sig));
 							module->connect(RTLIL::SigSig(it.second, other_sig));
 							assign_map.add(it.second, other_sig);
 						}
 					}
-					log("    Removing %s cell `%s' from module `%s'.\n", cell->type.c_str(), cell->name.c_str(), module->name.c_str());
+					log_debug("    Removing %s cell `%s' from module `%s'.\n", cell->type.c_str(), cell->name.c_str(), module->name.c_str());
 #ifdef USE_CELL_HASH_CACHE
 					cell_hash_cache.erase(cell);
 #endif
@@ -336,6 +336,8 @@ struct OptMergeWorker
 				}
 			}
 		}
+
+		log_suppressed();
 	}
 };
 
diff --git a/passes/opt/opt_muxtree.cc b/passes/opt/opt_muxtree.cc
index 375697dc8..dbebf21e0 100644
--- a/passes/opt/opt_muxtree.cc
+++ b/passes/opt/opt_muxtree.cc
@@ -181,14 +181,14 @@ struct OptMuxtreeWorker
 
 		for (int mux_idx = 0; mux_idx < GetSize(root_muxes); mux_idx++)
 			if (root_muxes.at(mux_idx)) {
-				log("    Root of a mux tree: %s%s\n", log_id(mux2info[mux_idx].cell), root_enable_muxes.at(mux_idx) ? " (pure)" : "");
+				log_debug("    Root of a mux tree: %s%s\n", log_id(mux2info[mux_idx].cell), root_enable_muxes.at(mux_idx) ? " (pure)" : "");
 				root_mux_rerun.erase(mux_idx);
 				eval_root_mux(mux_idx);
 			}
 
 		while (!root_mux_rerun.empty()) {
 			int mux_idx = *root_mux_rerun.begin();
-			log("    Root of a mux tree: %s (rerun as non-pure)\n", log_id(mux2info[mux_idx].cell));
+			log_debug("    Root of a mux tree: %s (rerun as non-pure)\n", log_id(mux2info[mux_idx].cell));
 			log_assert(root_enable_muxes.at(mux_idx));
 			root_mux_rerun.erase(mux_idx);
 			eval_root_mux(mux_idx);
@@ -326,7 +326,7 @@ struct OptMuxtreeWorker
 				if (abort_count == 0) {
 					root_mux_rerun.insert(m);
 					root_enable_muxes.at(m) = true;
-					log("      Removing pure flag from root mux %s.\n", log_id(mux2info[m].cell));
+					log_debug("      Removing pure flag from root mux %s.\n", log_id(mux2info[m].cell));
 				} else
 					eval_mux(knowledge, m, false, do_enable_ports, abort_count - 1);
 			} else
diff --git a/passes/opt/pmux2shiftx.cc b/passes/opt/pmux2shiftx.cc
index 5f897b131..29870f510 100644
--- a/passes/opt/pmux2shiftx.cc
+++ b/passes/opt/pmux2shiftx.cc
@@ -369,6 +369,7 @@ struct Pmux2ShiftxPass : public Pass {
 
 				dict<SigSpec, pool<int>> seldb;
 
+				SigSpec A = cell->getPort("\\A");
 				SigSpec B = cell->getPort("\\B");
 				SigSpec S = sigmap(cell->getPort("\\S"));
 				for (int i = 0; i < GetSize(S); i++)
@@ -419,6 +420,8 @@ struct Pmux2ShiftxPass : public Pass {
 						choices[val] = i;
 					}
 
+					bool full_pmux = GetSize(choices) == GetSize(S);
+
 					// TBD: also find choices that are using signals that are subsets of the bits in "sig"
 
 					if (!verbose)
@@ -634,7 +637,21 @@ struct Pmux2ShiftxPass : public Pass {
 					log("    range density: %d%%\n", range_density);
 					log("    absolute density: %d%%\n", absolute_density);
 
-					bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (max_choice+1 == GetSize(choices));
+					if (full_pmux) {
+						int full_density = 100*GetSize(choices) / (1 << GetSize(sig));
+						log("    full density: %d%%\n", full_density);
+						if (full_density < min_density) {
+							full_pmux = false;
+						} else {
+							min_choice = 0;
+							max_choice = (1 << GetSize(sig))-1;
+							log("    update to full case.\n");
+							log("    new min choice: %d\n", min_choice);
+							log("    new max choice: %d\n", max_choice);
+						}
+					}
+
+					bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (full_pmux || max_choice+1 == GetSize(choices));
 					log("    full case: %s\n", full_case ? "true" : "false");
 
 					// check density percentages
@@ -677,6 +694,10 @@ struct Pmux2ShiftxPass : public Pass {
 
 					// create data signal
 					SigSpec data(State::Sx, (max_choice+1)*extwidth);
+					if (full_pmux) {
+						for (int i = 0; i <= max_choice; i++)
+							data.replace(i*extwidth, A);
+					}
 					for (auto &it : perm_choices) {
 						int position = it.first.as_int()*extwidth;
 						int data_index = it.second;
diff --git a/passes/techmap/abc9.cc b/passes/techmap/abc9.cc
index b14eef485..3cee5a586 100644
--- a/passes/techmap/abc9.cc
+++ b/passes/techmap/abc9.cc
@@ -25,7 +25,8 @@
 #define ABC_COMMAND_LIB "strash; ifraig; scorr; dc2; dretime; strash; &get -n; &dch -f; &nf {D}; &put"
 #define ABC_COMMAND_CTR "strash; ifraig; scorr; dc2; dretime; strash; &get -n; &dch -f; &nf {D}; &put; buffer; upsize {D}; dnsize {D}; stime -p"
 //#define ABC_COMMAND_LUT "strash; ifraig; scorr; dc2; dretime; strash; dch -f; if; mfs2"
-#define ABC_COMMAND_LUT "&st; &fraig; &scorr; &dc2; &retime; &dch -f; &if; &mfs"
+//#define ABC_COMMAND_LUT "&st; &sweep; &scorr; &dc2; &retime; &dch -f; &if; &mfs; &ps"
+#define ABC_COMMAND_LUT "&st; &scorr; &dc2; &retime; &dch -f; &if; &ps -l -m"
 #define ABC_COMMAND_SOP "strash; ifraig; scorr; dc2; dretime; strash; dch -f; cover {I} {P}"
 #define ABC_COMMAND_DFL "strash; ifraig; scorr; dc2; dretime; strash; &get -n; &dch -f; &nf {D}; &put"
 
@@ -343,7 +344,7 @@ void abc9_module(RTLIL::Design *design, RTLIL::Module *current_module, std::stri
 	else
 		abc_script += stringf("read_library %s/stdcells.genlib; ", tempdir_name.c_str());
 
-	abc_script += stringf("&read %s/input.xaig; &ps ", tempdir_name.c_str());
+	abc_script += stringf("&read %s/input.xaig; &ps; ", tempdir_name.c_str());
 
 	if (!script_file.empty()) {
 		if (script_file[0] == '+') {
@@ -1401,6 +1402,9 @@ struct Abc9Pass : public Pass {
 
 		for (auto mod : design->selected_modules())
 		{
+			if (mod->attributes.count("\\abc_box_id"))
+				continue;
+
 			if (mod->processes.size() > 0) {
 				log("Skipping module %s as it contains processes.\n", log_id(mod));
 				continue;
diff --git a/passes/techmap/techmap.cc b/passes/techmap/techmap.cc
index 1a4318460..ab0bd3b54 100644
--- a/passes/techmap/techmap.cc
+++ b/passes/techmap/techmap.cc
@@ -72,6 +72,8 @@ struct TechmapWorker
 	pool<IdString> flatten_done_list;
 	pool<Cell*> flatten_keep_list;
 
+	pool<string> log_msg_cache;
+
 	struct TechmapWireData {
 		RTLIL::Wire *wire;
 		RTLIL::SigSpec value;
@@ -390,6 +392,7 @@ struct TechmapWorker
 
 		bool log_continue = false;
 		bool did_something = false;
+		LogMakeDebugHdl mkdebug;
 
 		SigMap sigmap(module);
 
@@ -547,6 +550,7 @@ struct TechmapWorker
 								if (extmapper_name == "wrap") {
 									std::string cmd_string = tpl->attributes.at("\\techmap_wrap").decode_string();
 									log("Running \"%s\" on wrapper %s.\n", cmd_string.c_str(), log_id(extmapper_module));
+									mkdebug.on();
 									Pass::call_on_module(extmapper_design, extmapper_module, cmd_string);
 									log_continue = true;
 								}
@@ -560,11 +564,21 @@ struct TechmapWorker
 								goto use_wrapper_tpl;
 							}
 
-							log("%s %s.%s (%s) to %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(cell->type), log_id(extmapper_module));
+							auto msg = stringf("Using extmapper %s for cells of type %s.", log_id(extmapper_module), log_id(cell->type));
+							if (!log_msg_cache.count(msg)) {
+								log_msg_cache.insert(msg);
+								log("%s\n", msg.c_str());
+							}
+							log_debug("%s %s.%s (%s) to %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(cell->type), log_id(extmapper_module));
 						}
 						else
 						{
-							log("%s %s.%s (%s) with %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(cell->type), extmapper_name.c_str());
+							auto msg = stringf("Using extmapper %s for cells of type %s.", extmapper_name.c_str(), log_id(cell->type));
+							if (!log_msg_cache.count(msg)) {
+								log_msg_cache.insert(msg);
+								log("%s\n", msg.c_str());
+							}
+							log_debug("%s %s.%s (%s) with %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(cell->type), extmapper_name.c_str());
 
 							if (extmapper_name == "simplemap") {
 								if (simplemap_mappers.count(cell->type) == 0)
@@ -662,6 +676,7 @@ struct TechmapWorker
 						tpl = techmap_cache[key];
 					} else {
 						if (parameters.size() != 0) {
+							mkdebug.on();
 							derived_name = tpl->derive(map, dict<RTLIL::IdString, RTLIL::Const>(parameters.begin(), parameters.end()));
 							tpl = map->module(derived_name);
 							log_continue = true;
@@ -831,6 +846,7 @@ struct TechmapWorker
 						if (log_continue) {
 							log_header(design, "Continuing TECHMAP pass.\n");
 							log_continue = false;
+							mkdebug.off();
 						}
 						while (techmap_module(map, tpl, map, handled_cells, celltypeMap, true)) { }
 					}
@@ -842,6 +858,7 @@ struct TechmapWorker
 				if (log_continue) {
 					log_header(design, "Continuing TECHMAP pass.\n");
 					log_continue = false;
+					mkdebug.off();
 				}
 
 				if (extern_mode && !in_recursion)
@@ -861,13 +878,18 @@ struct TechmapWorker
 						module_queue.insert(m);
 					}
 
-					log("%s %s.%s to imported %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(m_name));
+					log_debug("%s %s.%s to imported %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(m_name));
 					cell->type = m_name;
 					cell->parameters.clear();
 				}
 				else
 				{
-					log("%s %s.%s using %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(tpl));
+					auto msg = stringf("Using template %s for cells of type %s.", log_id(tpl), log_id(cell->type));
+					if (!log_msg_cache.count(msg)) {
+						log_msg_cache.insert(msg);
+						log("%s\n", msg.c_str());
+					}
+					log_debug("%s %s.%s (%s) using %s.\n", mapmsg_prefix.c_str(), log_id(module), log_id(cell), log_id(cell->type), log_id(tpl));
 					techmap_module_worker(design, module, cell, tpl);
 					cell = NULL;
 				}
@@ -885,6 +907,7 @@ struct TechmapWorker
 		if (log_continue) {
 			log_header(design, "Continuing TECHMAP pass.\n");
 			log_continue = false;
+			mkdebug.off();
 		}
 
 		return did_something;
@@ -1085,7 +1108,7 @@ struct TechmapPass : public Pass {
 		if (map_files.empty()) {
 			std::istringstream f(stdcells_code);
 			Frontend::frontend_call(map, &f, "<techmap.v>", verilog_frontend);
-		} else
+		} else {
 			for (auto &fn : map_files)
 				if (fn.substr(0, 1) == "%") {
 					if (!saved_designs.count(fn.substr(1))) {
@@ -1104,6 +1127,9 @@ struct TechmapPass : public Pass {
 						log_cmd_error("Can't open map file `%s'\n", fn.c_str());
 					Frontend::frontend_call(map, &f, fn, (fn.size() > 3 && fn.substr(fn.size()-3) == ".il") ? "ilang" : verilog_frontend);
 				}
+		}
+
+		log_header(design, "Continuing TECHMAP pass.\n");
 
 		std::map<RTLIL::IdString, std::set<RTLIL::IdString, RTLIL::sort_by_id_str>> celltypeMap;
 		for (auto &it : map->modules_) {
@@ -1211,6 +1237,7 @@ struct FlattenPass : public Pass {
 			}
 		}
 
+		log_suppressed();
 		log("No more expansions possible.\n");
 
 		if (top_mod != NULL)
diff --git a/techlibs/ice40/Makefile.inc b/techlibs/ice40/Makefile.inc
index 723b59d6f..d258d5a5d 100644
--- a/techlibs/ice40/Makefile.inc
+++ b/techlibs/ice40/Makefile.inc
@@ -28,6 +28,12 @@ $(eval $(call add_share_file,share/ice40,techlibs/ice40/cells_sim.v))
 $(eval $(call add_share_file,share/ice40,techlibs/ice40/latches_map.v))
 $(eval $(call add_share_file,share/ice40,techlibs/ice40/brams.txt))
 $(eval $(call add_share_file,share/ice40,techlibs/ice40/brams_map.v))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_hx.box))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_hx.lut))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_lp.box))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_lp.lut))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_u.box))
+$(eval $(call add_share_file,share/ice40,techlibs/ice40/abc_u.lut))
 
 $(eval $(call add_gen_share_file,share/ice40,techlibs/ice40/brams_init1.vh))
 $(eval $(call add_gen_share_file,share/ice40,techlibs/ice40/brams_init2.vh))
diff --git a/techlibs/ice40/abc_hx.box b/techlibs/ice40/abc_hx.box
new file mode 100644
index 000000000..994f3091d
--- /dev/null
+++ b/techlibs/ice40/abc_hx.box
@@ -0,0 +1,113 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_hx8k.txt
+
+# NB: Inputs/Outputs must be ordered alphabetically
+
+# Inputs: C D
+# Outputs: Q
+SB_DFF 1 1 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFE 2 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFSR 3 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFR 4 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFSS 5 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFS 6 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFESR 7 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFER 8 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFESS 9 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFES 10 0 4 1
+- - - -
+
+# Inputs: C D
+# Outputs: Q
+SB_DFFN 11 0 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFNE 12 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNSR 13 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNR 14 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNSS 15 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNS 16 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNESR 17 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNER 18 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNESS 19 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNES 20 0 4 1
+- - - -
+
+# Inputs: CI I0 I1
+# Outputs: CO
+SB_CARRY 21 1 3 1
+126 259 231
+
+# Inputs: I0 I1 I2 I3
+# Outputs: O
+SB_LUT4 22 0 4 1
+449 400 379 316
diff --git a/techlibs/ice40/abc_hx.lut b/techlibs/ice40/abc_hx.lut
new file mode 100644
index 000000000..3b3bb11e2
--- /dev/null
+++ b/techlibs/ice40/abc_hx.lut
@@ -0,0 +1,6 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_hx8k.txt
+#       I3  I2  I1  I0
+1   1   316
+2   1   316 379
+3   1   316 379 400
+4   1   316 379 400 449
diff --git a/techlibs/ice40/abc_lp.box b/techlibs/ice40/abc_lp.box
new file mode 100644
index 000000000..002b7bba4
--- /dev/null
+++ b/techlibs/ice40/abc_lp.box
@@ -0,0 +1,113 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_lp8k.txt
+
+# NB: Inputs/Outputs must be ordered alphabetically
+
+# Inputs: C D
+# Outputs: Q
+SB_DFF 1 1 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFE 2 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFSR 3 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFR 4 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFSS 5 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFS 6 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFESR 7 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFER 8 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFESS 9 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFES 10 0 4 1
+- - - -
+
+# Inputs: C D
+# Outputs: Q
+SB_DFFN 11 0 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFNE 12 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNSR 13 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNR 14 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNSS 15 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNS 16 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNESR 17 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNER 18 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNESS 19 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNES 20 0 4 1
+- - - -
+
+# Inputs: CI I0 I1
+# Outputs: CO
+SB_CARRY 21 1 3 1
+186 675 609
+
+# Inputs: I0 I1 I2 I3
+# Outputs: O
+SB_LUT4 22 0 4 1
+465 558 589 661
diff --git a/techlibs/ice40/abc_lp.lut b/techlibs/ice40/abc_lp.lut
new file mode 100644
index 000000000..e72f760a2
--- /dev/null
+++ b/techlibs/ice40/abc_lp.lut
@@ -0,0 +1,6 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_lp8k.txt
+#       I3  I2  I1  I0
+1   1   465
+2   1   465 558
+3   1   465 558 589
+4   1   465 558 589 661
diff --git a/techlibs/ice40/abc_u.box b/techlibs/ice40/abc_u.box
new file mode 100644
index 000000000..cb336181c
--- /dev/null
+++ b/techlibs/ice40/abc_u.box
@@ -0,0 +1,113 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_up5k.txt
+
+# NB: Inputs/Outputs must be ordered alphabetically
+
+# Inputs: C D
+# Outputs: Q
+SB_DFF 1 1 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFE 2 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFSR 3 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFR 4 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFSS 5 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFS 6 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFESR 7 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFER 8 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFESS 9 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFES 10 0 4 1
+- - - -
+
+# Inputs: C D
+# Outputs: Q
+SB_DFFN 11 0 2 1
+- -
+
+# Inputs: C D E
+# Outputs: Q
+SB_DFFNE 12 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNSR 13 0 3 1
+- - -
+
+# Inputs: C D R
+# Outputs: Q
+SB_DFFNR 14 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNSS 15 0 3 1
+- - -
+
+# Inputs: C D S
+# Outputs: Q
+SB_DFFNS 16 0 3 1
+- - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNESR 17 0 4 1
+- - - -
+
+# Inputs: C D E R
+# Outputs: Q
+SB_DFFNER 18 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNESS 19 0 4 1
+- - - -
+
+# Inputs: C D E S
+# Outputs: Q
+SB_DFFNES 20 0 4 1
+- - - -
+
+# Inputs: CI I0 I1
+# Outputs: CO
+SB_CARRY 21 1 3 1
+278 675 609
+
+# Inputs: I0 I1 I2 I3
+# Outputs: O
+SB_LUT4 22 0 4 1
+1285 1231 1205 874
diff --git a/techlibs/ice40/abc_u.lut b/techlibs/ice40/abc_u.lut
new file mode 100644
index 000000000..1e4fcadb6
--- /dev/null
+++ b/techlibs/ice40/abc_u.lut
@@ -0,0 +1,6 @@
+# From https://github.com/cliffordwolf/icestorm/blob/be0bca0/icefuzz/timings_up5k.txt
+#       I3  I2  I1  I0
+1   1   874
+2   1   874 1205
+3   1   874 1205 1231
+4   1   874 1205 1231 1285
diff --git a/techlibs/ice40/cells_map.v b/techlibs/ice40/cells_map.v
index d0ddfd02e..287c48b11 100644
--- a/techlibs/ice40/cells_map.v
+++ b/techlibs/ice40/cells_map.v
@@ -37,20 +37,24 @@ module \$lut (A, Y);
 
   generate
     if (WIDTH == 1) begin
-      SB_LUT4 #(.LUT_INIT(LUT)) _TECHMAP_REPLACE_ (.O(Y),
-        .I0(A[0]), .I1(1'b0), .I2(1'b0), .I3(1'b0));
+      localparam [15:0] INIT = {{8{LUT[1]}}, {8{LUT[0]}}};
+      SB_LUT4 #(.LUT_INIT(INIT)) _TECHMAP_REPLACE_ (.O(Y),
+        .I0(1'b0), .I1(1'b0), .I2(1'b0), .I3(A[0]));
     end else
     if (WIDTH == 2) begin
-      SB_LUT4 #(.LUT_INIT(LUT)) _TECHMAP_REPLACE_ (.O(Y),
-        .I0(A[0]), .I1(A[1]), .I2(1'b0), .I3(1'b0));
+      localparam [15:0] INIT = {{4{LUT[3]}}, {4{LUT[1]}}, {4{LUT[2]}}, {4{LUT[0]}}};
+      SB_LUT4 #(.LUT_INIT(INIT)) _TECHMAP_REPLACE_ (.O(Y),
+        .I0(1'b0), .I1(1'b0), .I2(A[1]), .I3(A[0]));
     end else
     if (WIDTH == 3) begin
-      SB_LUT4 #(.LUT_INIT(LUT)) _TECHMAP_REPLACE_ (.O(Y),
-        .I0(A[0]), .I1(A[1]), .I2(A[2]), .I3(1'b0));
+      localparam [15:0] INIT = {{2{LUT[7]}}, {2{LUT[3]}}, {2{LUT[5]}}, {2{LUT[1]}}, {2{LUT[6]}}, {2{LUT[2]}}, {2{LUT[4]}}, {2{LUT[0]}}};
+      SB_LUT4 #(.LUT_INIT(INIT)) _TECHMAP_REPLACE_ (.O(Y),
+        .I0(1'b0), .I1(A[2]), .I2(A[1]), .I3(A[0]));
     end else
     if (WIDTH == 4) begin
+      localparam [15:0] INIT = {LUT[15], LUT[7], LUT[11], LUT[3], LUT[13], LUT[5], LUT[9], LUT[1], LUT[14], LUT[6], LUT[10], LUT[2], LUT[12], LUT[4], LUT[8], LUT[0]};
       SB_LUT4 #(.LUT_INIT(LUT)) _TECHMAP_REPLACE_ (.O(Y),
-        .I0(A[0]), .I1(A[1]), .I2(A[2]), .I3(A[3]));
+        .I0(A[3]), .I1(A[2]), .I2(A[1]), .I3(A[0]));
     end else begin
       wire _TECHMAP_FAIL_ = 1;
     end
diff --git a/techlibs/ice40/cells_sim.v b/techlibs/ice40/cells_sim.v
index 00843b97c..40e54f9f0 100644
--- a/techlibs/ice40/cells_sim.v
+++ b/techlibs/ice40/cells_sim.v
@@ -127,6 +127,7 @@ endmodule
 
 // SiliconBlue Logic Cells
 
+(* abc_box_id = 22 *)
 module SB_LUT4 (output O, input I0, I1, I2, I3);
 	parameter [15:0] LUT_INIT = 0;
 	wire [7:0] s3 = I3 ? LUT_INIT[15:8] : LUT_INIT[7:0];
@@ -135,24 +136,32 @@ module SB_LUT4 (output O, input I0, I1, I2, I3);
 	assign O = I0 ? s1[1] : s1[0];
 endmodule
 
+(* abc_box_id = 21, lib_whitebox *)
 module SB_CARRY (output CO, input I0, I1, CI);
 	assign CO = (I0 && I1) || ((I0 || I1) && CI);
 endmodule
 
 // Positive Edge SiliconBlue FF Cells
 
-module SB_DFF (output `SB_DFF_REG, input C, D);
+(* abc_box_id = 1, abc_flop, lib_whitebox *)
+module SB_DFF ((* abc_flop_q *) output `SB_DFF_REG, input C, (* abc_flop_d *) input D);
+`ifndef ABC_MODEL
 	always @(posedge C)
 		Q <= D;
+`else
+    always @* Q = D;
+`endif
 endmodule
 
-module SB_DFFE (output `SB_DFF_REG, input C, E, D);
+//(* abc_box_id = 2, abc_flop *)
+module SB_DFFE ((* abc_flop_q *) output `SB_DFF_REG, input C, E, (* abc_flop_d *) input D);
 	always @(posedge C)
 		if (E)
 			Q <= D;
 endmodule
 
-module SB_DFFSR (output `SB_DFF_REG, input C, R, D);
+//(* abc_box_id = 3, abc_flop *)
+module SB_DFFSR ((* abc_flop_q *) output `SB_DFF_REG, input C, R, (* abc_flop_d *) input D);
 	always @(posedge C)
 		if (R)
 			Q <= 0;
@@ -160,7 +169,8 @@ module SB_DFFSR (output `SB_DFF_REG, input C, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFR (output `SB_DFF_REG, input C, R, D);
+//(* abc_box_id = 4, abc_flop *)
+module SB_DFFR ((* abc_flop_q *) output `SB_DFF_REG, input C, R, (* abc_flop_d *) input D);
 	always @(posedge C, posedge R)
 		if (R)
 			Q <= 0;
@@ -168,7 +178,8 @@ module SB_DFFR (output `SB_DFF_REG, input C, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFSS (output `SB_DFF_REG, input C, S, D);
+//(* abc_box_id = 5, abc_flop *)
+module SB_DFFSS ((* abc_flop_q *) output `SB_DFF_REG, input C, S, (* abc_flop_d *) input D);
 	always @(posedge C)
 		if (S)
 			Q <= 1;
@@ -176,7 +187,8 @@ module SB_DFFSS (output `SB_DFF_REG, input C, S, D);
 			Q <= D;
 endmodule
 
-module SB_DFFS (output `SB_DFF_REG, input C, S, D);
+//(* abc_box_id = 6, abc_flop *)
+module SB_DFFS ((* abc_flop_q *) output `SB_DFF_REG, input C, S, (* abc_flop_d *) input D);
 	always @(posedge C, posedge S)
 		if (S)
 			Q <= 1;
@@ -184,7 +196,8 @@ module SB_DFFS (output `SB_DFF_REG, input C, S, D);
 			Q <= D;
 endmodule
 
-module SB_DFFESR (output `SB_DFF_REG, input C, E, R, D);
+//(* abc_box_id = 7, abc_flop *)
+module SB_DFFESR ((* abc_flop_q *) output `SB_DFF_REG, input C, E, R, (* abc_flop_d *) input D);
 	always @(posedge C)
 		if (E) begin
 			if (R)
@@ -194,7 +207,8 @@ module SB_DFFESR (output `SB_DFF_REG, input C, E, R, D);
 		end
 endmodule
 
-module SB_DFFER (output `SB_DFF_REG, input C, E, R, D);
+//(* abc_box_id = 8, abc_flop *)
+module SB_DFFER ((* abc_flop_q *) output `SB_DFF_REG, input C, E, R, (* abc_flop_d *) input D);
 	always @(posedge C, posedge R)
 		if (R)
 			Q <= 0;
@@ -202,7 +216,8 @@ module SB_DFFER (output `SB_DFF_REG, input C, E, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFESS (output `SB_DFF_REG, input C, E, S, D);
+//(* abc_box_id = 9, abc_flop *)
+module SB_DFFESS ((* abc_flop_q *) output `SB_DFF_REG, input C, E, S, (* abc_flop_d *) input D);
 	always @(posedge C)
 		if (E) begin
 			if (S)
@@ -212,7 +227,8 @@ module SB_DFFESS (output `SB_DFF_REG, input C, E, S, D);
 		end
 endmodule
 
-module SB_DFFES (output `SB_DFF_REG, input C, E, S, D);
+//(* abc_box_id = 10, abc_flop *)
+module SB_DFFES ((* abc_flop_q *) output `SB_DFF_REG, input C, E, S, (* abc_flop_d *) input D);
 	always @(posedge C, posedge S)
 		if (S)
 			Q <= 1;
@@ -222,18 +238,21 @@ endmodule
 
 // Negative Edge SiliconBlue FF Cells
 
-module SB_DFFN (output `SB_DFF_REG, input C, D);
+//(* abc_box_id = 11, abc_flop *)
+module SB_DFFN ((* abc_flop_q *) output `SB_DFF_REG, input C, (* abc_flop_d *) input D);
 	always @(negedge C)
 		Q <= D;
 endmodule
 
-module SB_DFFNE (output `SB_DFF_REG, input C, E, D);
+//(* abc_box_id = 12, abc_flop *)
+module SB_DFFNE ((* abc_flop_q *) output `SB_DFF_REG, input C, E, (* abc_flop_d *) input D);
 	always @(negedge C)
 		if (E)
 			Q <= D;
 endmodule
 
-module SB_DFFNSR (output `SB_DFF_REG, input C, R, D);
+//(* abc_box_id = 13, abc_flop *)
+module SB_DFFNSR ((* abc_flop_q *) output `SB_DFF_REG, input C, R, (* abc_flop_d *) input D);
 	always @(negedge C)
 		if (R)
 			Q <= 0;
@@ -241,7 +260,8 @@ module SB_DFFNSR (output `SB_DFF_REG, input C, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFNR (output `SB_DFF_REG, input C, R, D);
+//(* abc_box_id = 14, abc_flop *)
+module SB_DFFNR ((* abc_flop_q *) output `SB_DFF_REG, input C, R, (* abc_flop_d *) input D);
 	always @(negedge C, posedge R)
 		if (R)
 			Q <= 0;
@@ -249,7 +269,8 @@ module SB_DFFNR (output `SB_DFF_REG, input C, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFNSS (output `SB_DFF_REG, input C, S, D);
+//(* abc_box_id = 15, abc_flop *)
+module SB_DFFNSS ((* abc_flop_q *) output `SB_DFF_REG, input C, S, (* abc_flop_d *) input D);
 	always @(negedge C)
 		if (S)
 			Q <= 1;
@@ -257,7 +278,8 @@ module SB_DFFNSS (output `SB_DFF_REG, input C, S, D);
 			Q <= D;
 endmodule
 
-module SB_DFFNS (output `SB_DFF_REG, input C, S, D);
+//(* abc_box_id = 16, abc_flop *)
+module SB_DFFNS ((* abc_flop_q *) output `SB_DFF_REG, input C, S, (* abc_flop_d *) input D);
 	always @(negedge C, posedge S)
 		if (S)
 			Q <= 1;
@@ -265,7 +287,8 @@ module SB_DFFNS (output `SB_DFF_REG, input C, S, D);
 			Q <= D;
 endmodule
 
-module SB_DFFNESR (output `SB_DFF_REG, input C, E, R, D);
+//(* abc_box_id = 17, abc_flop *)
+module SB_DFFNESR ((* abc_flop_q *) output `SB_DFF_REG, input C, E, R, (* abc_flop_d *) input D);
 	always @(negedge C)
 		if (E) begin
 			if (R)
@@ -275,7 +298,8 @@ module SB_DFFNESR (output `SB_DFF_REG, input C, E, R, D);
 		end
 endmodule
 
-module SB_DFFNER (output `SB_DFF_REG, input C, E, R, D);
+//(* abc_box_id = 18, abc_flop *)
+module SB_DFFNER ((* abc_flop_q *) output `SB_DFF_REG, input C, E, R, (* abc_flop_d *) input D);
 	always @(negedge C, posedge R)
 		if (R)
 			Q <= 0;
@@ -283,7 +307,8 @@ module SB_DFFNER (output `SB_DFF_REG, input C, E, R, D);
 			Q <= D;
 endmodule
 
-module SB_DFFNESS (output `SB_DFF_REG, input C, E, S, D);
+//(* abc_box_id = 19, abc_flop *)
+module SB_DFFNESS ((* abc_flop_q *) output `SB_DFF_REG, input C, E, S, (* abc_flop_d *) input D);
 	always @(negedge C)
 		if (E) begin
 			if (S)
@@ -293,7 +318,8 @@ module SB_DFFNESS (output `SB_DFF_REG, input C, E, S, D);
 		end
 endmodule
 
-module SB_DFFNES (output `SB_DFF_REG, input C, E, S, D);
+//(* abc_box_id = 20, abc_flop *)
+module SB_DFFNES ((* abc_flop_q *) output `SB_DFF_REG, input C, E, S, (* abc_flop_d *) input D);
 	always @(negedge C, posedge S)
 		if (S)
 			Q <= 1;
@@ -304,7 +330,7 @@ endmodule
 // SiliconBlue RAM Cells
 
 module SB_RAM40_4K (
-	output [15:0] RDATA,
+	(* abc_flop_q *) output [15:0] RDATA,
 	input         RCLK, RCLKE, RE,
 	input  [10:0] RADDR,
 	input         WCLK, WCLKE, WE,
@@ -472,7 +498,7 @@ module SB_RAM40_4K (
 endmodule
 
 module SB_RAM40_4KNR (
-	output [15:0] RDATA,
+	(* abc_flop_q *) output [15:0] RDATA,
 	input         RCLKN, RCLKE, RE,
 	input  [10:0] RADDR,
 	input         WCLK, WCLKE, WE,
@@ -537,7 +563,7 @@ module SB_RAM40_4KNR (
 endmodule
 
 module SB_RAM40_4KNW (
-	output [15:0] RDATA,
+	(* abc_flop_q *) output [15:0] RDATA,
 	input         RCLK, RCLKE, RE,
 	input  [10:0] RADDR,
 	input         WCLKN, WCLKE, WE,
@@ -602,7 +628,7 @@ module SB_RAM40_4KNW (
 endmodule
 
 module SB_RAM40_4KNRNW (
-	output [15:0] RDATA,
+	(* abc_flop_q *) output [15:0] RDATA,
 	input         RCLKN, RCLKE, RE,
 	input  [10:0] RADDR,
 	input         WCLKN, WCLKE, WE,
@@ -890,12 +916,13 @@ module SB_WARMBOOT (
 );
 endmodule
 
+(* nomem2reg *)
 module SB_SPRAM256KA (
 	input [13:0] ADDRESS,
 	input [15:0] DATAIN,
 	input [3:0] MASKWREN,
 	input WREN, CHIPSELECT, CLOCK, STANDBY, SLEEP, POWEROFF,
-	output reg [15:0] DATAOUT
+	(* abc_flop_q *) output reg [15:0] DATAOUT
 );
 `ifndef BLACKBOX
 `ifndef EQUIV
diff --git a/techlibs/ice40/synth_ice40.cc b/techlibs/ice40/synth_ice40.cc
index 6c77e5482..718f9d9e0 100644
--- a/techlibs/ice40/synth_ice40.cc
+++ b/techlibs/ice40/synth_ice40.cc
@@ -37,6 +37,10 @@ struct SynthIce40Pass : public ScriptPass
 		log("\n");
 		log("This command runs synthesis for iCE40 FPGAs.\n");
 		log("\n");
+		log("    -device < hx | lp | u >\n");
+		log("        optimise the synthesis netlist for the specified device.\n");
+		log("        HX is the default target if no device argument specified.\n");
+		log("\n");
 		log("    -top <module>\n");
 		log("        use the specified module as top module\n");
 		log("\n");
@@ -102,7 +106,7 @@ struct SynthIce40Pass : public ScriptPass
 	}
 
 
-	string top_opt, blif_file, edif_file, json_file, abc;
+	string top_opt, blif_file, edif_file, json_file, abc, device_opt;
 	bool nocarry, nodffe, nobram, dsp, flatten, retime, relut, noabc, abc2, vpr;
 	int min_ce_use;
 
@@ -124,6 +128,7 @@ struct SynthIce40Pass : public ScriptPass
 		abc2 = false;
 		vpr = false;
 		abc = "abc";
+		device_opt = "hx";
 	}
 
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
@@ -210,12 +215,18 @@ struct SynthIce40Pass : public ScriptPass
 				abc = "abc9";
 				continue;
 			}
+			if (args[argidx] == "-device" && argidx+1 < args.size()) {
+				device_opt = args[++argidx];
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
 
 		if (!design->full_selection())
 			log_cmd_error("This command only operates on fully selected designs!\n");
+		if (device_opt != "hx" && device_opt != "lp" && device_opt !="u")
+			log_cmd_error("Invalid or no device specified: '%s'\n", device_opt.c_str());
 
 		log_header(design, "Executing SYNTH_ICE40 pass.\n");
 		log_push();
@@ -229,7 +240,7 @@ struct SynthIce40Pass : public ScriptPass
 	{
 		if (check_label("begin"))
 		{
-			run("read_verilog -lib +/ice40/cells_sim.v");
+			run("read_verilog -lib -D ABC_MODEL +/ice40/cells_sim.v");
 			run(stringf("hierarchy -check %s", help_mode ? "-top <top>" : top_opt.c_str()));
 			run("proc");
 		}
@@ -282,7 +293,7 @@ struct SynthIce40Pass : public ScriptPass
 				run("techmap");
 			else
 				run("techmap -map +/techmap.v -map +/ice40/arith_map.v");
-			if (retime || help_mode)
+			if ((retime || help_mode) && abc != "abc9")
 				run(abc + " -dff", "(only if -retime)");
 			run("ice40_opt");
 		}
@@ -316,7 +327,10 @@ struct SynthIce40Pass : public ScriptPass
 				run("techmap -map +/gate2lut.v -D LUT_WIDTH=4", "(only if -noabc)");
 			}
 			if (!noabc) {
-				run(abc + " -dress -lut 4", "(skip if -noabc)");
+				if (abc == "abc9")
+					run(abc + stringf(" -dress -lut +/ice40/abc_%s.lut -box +/ice40/abc_%s.box", device_opt.c_str(), device_opt.c_str()), "(skip if -noabc)");
+				else
+					run(abc + " -lut 4", "(skip if -noabc)");
 			}
 			run("clean");
 			if (relut || help_mode) {
diff --git a/techlibs/intel/synth_intel.cc b/techlibs/intel/synth_intel.cc
index 0f1d7a7b5..d2291b8d4 100644
--- a/techlibs/intel/synth_intel.cc
+++ b/techlibs/intel/synth_intel.cc
@@ -38,7 +38,7 @@ struct SynthIntelPass : public ScriptPass {
     log("\n");
     log("    -family < max10 | a10gx | cyclone10 | cyclonev | cycloneiv | cycloneive>\n");
     log("        generate the synthesis netlist for the specified family.\n");
-    log("        MAX10 is the default target if not family argument specified.\n");
+    log("        MAX10 is the default target if no family argument specified.\n");
     log("        For Cyclone GX devices, use cycloneiv argument; For Cyclone E, use cycloneive.\n");
     log("        Cyclone V and Arria 10 GX devices are experimental, use it with a10gx argument.\n");
     log("\n");
@@ -146,7 +146,7 @@ struct SynthIntelPass : public ScriptPass {
     if (!design->full_selection())
       log_cmd_error("This command only operates on fully selected designs!\n");
     if (family_opt != "max10" && family_opt !="a10gx" && family_opt != "cyclonev" && family_opt !="cycloneiv" && family_opt !="cycloneive" && family_opt != "cyclone10")
-      log_cmd_error("Invalid or not family specified: '%s'\n", family_opt.c_str());
+      log_cmd_error("Invalid or no family specified: '%s'\n", family_opt.c_str());
 
     log_header(design, "Executing SYNTH_INTEL pass.\n");
     log_push();
diff --git a/tests/simple_abc9/run-test.sh b/tests/simple_abc9/run-test.sh
index af003d52e..97f284378 100755
--- a/tests/simple_abc9/run-test.sh
+++ b/tests/simple_abc9/run-test.sh
@@ -19,4 +19,4 @@ fi
 
 cp ../simple/*.v .
 DOLLAR='?'
-exec ${MAKE:-make} -f ../tools/autotest.mk $seed *.v EXTRA_FLAGS="-p 'hierarchy; synth -run coarse; techmap; opt -full; abc9 -lut 4; stat; check -assert; select -assert-none t:${DOLLAR}_NOT_ t:${DOLLAR}_AND_'"
+exec ${MAKE:-make} -f ../tools/autotest.mk $seed *.v EXTRA_FLAGS="-p 'hierarchy; synth -run coarse; techmap; opt -full; abc9 -lut 4; stat; check -assert; select -assert-none t:${DOLLAR}_NOT_ t:${DOLLAR}_AND_ %%'"
diff --git a/tests/various/pmux2shiftx.ys b/tests/various/pmux2shiftx.ys
index 6bb9626eb..deb134083 100644
--- a/tests/various/pmux2shiftx.ys
+++ b/tests/various/pmux2shiftx.ys
@@ -9,8 +9,8 @@ opt
 stat
 # show -width
 select -assert-count 1 t:$sub
-select -assert-count 2 t:$mux
-select -assert-count 2 t:$shift
+select -assert-count 1 t:$mux
+select -assert-count 1 t:$shift
 select -assert-count 3 t:$shiftx
 
 design -stash gate