From 1be8f8023ab5d3685480e9e6e584e2e608458b45 Mon Sep 17 00:00:00 2001
From: "Emil J. Tywoniak" <emil@tywoniak.eu>
Date: Thu, 20 Jun 2024 23:41:09 +0200
Subject: [PATCH] add morphCell instead of type assignments, test_cell passes
 for all cells

---
 frontends/ast/genrtlil.cc               |  7 ++--
 frontends/liberty/liberty.cc            |  8 ++---
 frontends/rpc/rpc_frontend.cc           |  2 +-
 kernel/mem.cc                           |  8 ++---
 kernel/rtlil.cc                         | 27 +++++++++++++++-
 kernel/rtlil.h                          | 17 +++++++---
 passes/cmds/chformal.cc                 |  4 +--
 passes/cmds/chtype.cc                   |  4 +--
 passes/cmds/design.cc                   |  2 +-
 passes/cmds/dft_tag.cc                  |  2 +-
 passes/cmds/setattr.cc                  |  2 +-
 passes/hierarchy/hierarchy.cc           |  2 +-
 passes/hierarchy/uniquify.cc            |  2 +-
 passes/opt/muxpack.cc                   |  2 +-
 passes/opt/opt_demorgan.cc              |  4 +--
 passes/opt/opt_expr.cc                  | 43 ++++++++++---------------
 passes/opt/opt_lut_ins.cc               | 12 +++----
 passes/opt/opt_muxtree.cc               |  2 +-
 passes/opt/opt_reduce.cc                |  4 +--
 passes/pmgen/pmgen.py                   |  2 ++
 passes/proc/proc_dlatch.cc              |  4 +--
 passes/proc/proc_mux.cc                 |  2 +-
 passes/techmap/abc9_ops.cc              |  6 ++--
 passes/techmap/extract_counter.cc       |  2 +-
 passes/techmap/shregmap.cc              |  2 +-
 passes/techmap/techmap.cc               | 20 ++++++------
 passes/techmap/tribuf.cc                |  4 +--
 passes/tests/test_cell.cc               |  4 +--
 techlibs/coolrunner2/coolrunner2_sop.cc | 16 ++++-----
 techlibs/greenpak4/greenpak4_dffinv.cc  |  4 +--
 techlibs/ice40/ice40_opt.cc             |  4 +--
 techlibs/quicklogic/ql_bram_types.cc    |  2 +-
 techlibs/quicklogic/ql_dsp_io_regs.cc   |  2 +-
 33 files changed, 129 insertions(+), 99 deletions(-)

diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index 3d47bd3c0..a5578d75a 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -2093,9 +2093,10 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 			for (auto it = children.begin(); it != children.end(); it++) {
 				AstNode *child = *it;
 				if (child->type == AST_CELLTYPE) {
-					cell->type = child->str;
-					if (flag_icells && cell->type.begins_with("\\$"))
-						cell->type = cell->type.substr(1);
+					auto type = IdString(child->str);
+					if (flag_icells && type.begins_with("\\$"))
+						type = type.substr(1);
+					cell = cell->module->morphCell(type, cell);
 					continue;
 				}
 				if (child->type == AST_PARASET) {
diff --git a/frontends/liberty/liberty.cc b/frontends/liberty/liberty.cc
index cadbcaee6..a228cff0d 100644
--- a/frontends/liberty/liberty.cc
+++ b/frontends/liberty/liberty.cc
@@ -269,21 +269,21 @@ static void create_ff(RTLIL::Module *module, LibertyAst *node)
 	cell->setPort(ID::C, clk_sig);
 
 	if (clear_sig.size() == 0 && preset_sig.size() == 0) {
-		cell->type = stringf("$_DFF_%c_", clk_polarity ? 'P' : 'N');
+		cell = cell->module->morphCell(stringf("$_DFF_%c_", clk_polarity ? 'P' : 'N'), cell);
 	}
 
 	if (clear_sig.size() == 1 && preset_sig.size() == 0) {
-		cell->type = stringf("$_DFF_%c%c0_", clk_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N');
+		cell = cell->module->morphCell(stringf("$_DFF_%c%c0_", clk_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N'), cell);
 		cell->setPort(ID::R, clear_sig);
 	}
 
 	if (clear_sig.size() == 0 && preset_sig.size() == 1) {
-		cell->type = stringf("$_DFF_%c%c1_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N');
+		cell = cell->module->morphCell(stringf("$_DFF_%c%c1_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N'), cell);
 		cell->setPort(ID::R, preset_sig);
 	}
 
 	if (clear_sig.size() == 1 && preset_sig.size() == 1) {
-		cell->type = stringf("$_DFFSR_%c%c%c_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N');
+		cell = cell->module->morphCell(stringf("$_DFFSR_%c%c%c_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N'), cell);
 		cell->setPort(ID::S, preset_sig);
 		cell->setPort(ID::R, clear_sig);
 	}
diff --git a/frontends/rpc/rpc_frontend.cc b/frontends/rpc/rpc_frontend.cc
index ec3952661..73dad9c81 100644
--- a/frontends/rpc/rpc_frontend.cc
+++ b/frontends/rpc/rpc_frontend.cc
@@ -207,7 +207,7 @@ struct RpcModule : RTLIL::Module {
 			for (auto module : derived_design->modules())
 				for (auto cell : module->cells())
 					if (name_mangling.count(cell->type.str()))
-						cell->type = name_mangling[cell->type.str()];
+						cell = cell->module->morphCell(name_mangling[cell->type.str()], cell);
 
 			for (auto module : derived_design->modules_) {
 				std::string mangled_name = name_mangling[module.first.str()];
diff --git a/kernel/mem.cc b/kernel/mem.cc
index bd7910f0a..8bfbe7ed4 100644
--- a/kernel/mem.cc
+++ b/kernel/mem.cc
@@ -125,7 +125,7 @@ void Mem::emit() {
 				memid = NEW_ID;
 			cell = module->addCell(memid, ID($mem_v2));
 		}
-		cell->type = ID($mem_v2);
+		cell = cell->module->morphCell(ID($mem_v2), cell);
 		cell->attributes = attributes;
 		cell->parameters[ID::MEMID] = Const(memid.str());
 		cell->parameters[ID::WIDTH] = Const(width);
@@ -280,7 +280,7 @@ void Mem::emit() {
 		for (auto &port : rd_ports) {
 			if (!port.cell)
 				port.cell = module->addCell(NEW_ID, ID($memrd_v2));
-			port.cell->type = ID($memrd_v2);
+			port.cell = cell->module->morphCell(ID($memrd_v2), cell);
 			port.cell->attributes = port.attributes;
 			port.cell->parameters[ID::MEMID] = memid.str();
 			port.cell->parameters[ID::ABITS] = GetSize(port.addr);
@@ -305,7 +305,7 @@ void Mem::emit() {
 		for (auto &port : wr_ports) {
 			if (!port.cell)
 				port.cell = module->addCell(NEW_ID, ID($memwr_v2));
-			port.cell->type = ID($memwr_v2);
+			port.cell = cell->module->morphCell(ID($memwr_v2), cell);
 			port.cell->attributes = port.attributes;
 			if (port.cell->parameters.count(ID::PRIORITY))
 				port.cell->parameters.erase(ID::PRIORITY);
@@ -327,7 +327,7 @@ void Mem::emit() {
 			if (!init.cell)
 				init.cell = module->addCell(NEW_ID, v2 ? ID($meminit_v2) : ID($meminit));
 			else
-				init.cell->type = v2 ? ID($meminit_v2) : ID($meminit);
+				init.cell = cell->module->morphCell(v2 ? ID($meminit_v2) : ID($meminit), cell);
 			init.cell->attributes = init.attributes;
 			init.cell->parameters[ID::MEMID] = memid.str();
 			init.cell->parameters[ID::ABITS] = GetSize(init.addr);
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 67dd6a3db..7a7d1d655 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -2434,7 +2434,6 @@ RTLIL::Cell *RTLIL::Module::addCell(RTLIL::IdString name, RTLIL::IdString type)
 	cell->type = type;
 	if (RTLIL::Cell::is_legacy_type(type)) {
 		cell->legacy = new RTLIL::OldCell;
-		cell->legacy->name = name;
 		cell->legacy->type = type;
 		cell->legacy->module = this;
 		log_assert(this);
@@ -2466,6 +2465,32 @@ RTLIL::Cell *RTLIL::Module::addCell(RTLIL::IdString name, const RTLIL::Cell *oth
 	return cell;
 }
 
+// Swap cell for a new one with a different type, keeping everything else
+// Throws if their types don't allow it
+RTLIL::Cell *RTLIL::Module::morphCell(RTLIL::IdString type, RTLIL::Cell *old)
+{
+	// if (old->is_legacy() && Cell::is_legacy_type(type)) {
+	// 	old->type = type;
+	// 	return old;
+	// }
+	// TODO xtrace
+	if (yosys_xtrace) {
+		log("#X# Morphing %s.%s from type %s to %s\n", log_id(this), log_id(old), log_id(old->type), log_id(type));
+		log_backtrace("-X- ", yosys_xtrace-1);
+	}
+	log_assert(old);
+	cells_.erase(old->name);
+	RTLIL::Cell *new_cell = addCell(old->name, type);
+	new_cell->connections_ = old->connections_.as_dict();
+	new_cell->parameters = old->parameters.as_dict();
+	new_cell->attributes = old->attributes;
+	new_cell->name = old->name;
+	log_assert(refcount_cells_ == 0);
+	cells_[new_cell->name] = new_cell;
+	delete old;
+	return new_cell;
+}
+
 RTLIL::Memory *RTLIL::Module::addMemory(RTLIL::IdString name, const RTLIL::Memory *other)
 {
 	RTLIL::Memory *mem = new RTLIL::Memory;
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index 9ccf12fc1..cc9bed4fa 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -1276,6 +1276,8 @@ public:
 	RTLIL::Cell *addCell(RTLIL::IdString name, RTLIL::IdString type);
 	RTLIL::Cell *addCell(RTLIL::IdString name, const RTLIL::Cell *other);
 
+	RTLIL::Cell *morphCell(RTLIL::IdString type, RTLIL::Cell *old);
+
 	RTLIL::Memory *addMemory(RTLIL::IdString name, const RTLIL::Memory *other);
 
 	RTLIL::Process *addProcess(RTLIL::IdString name);
@@ -1559,6 +1561,7 @@ struct RTLIL::OldCell
 
 protected:
 	// use module->addCell() and module->remove() to create or destroy cells
+	// also see morphCell
 	friend struct RTLIL::Module;
 	friend struct RTLIL::Cell;
 	OldCell();
@@ -1711,8 +1714,10 @@ public:
 			return parent->getMutParam(name);
 		}
 		void operator=(dict<IdString, Const> from) {
-			if (parent->is_legacy())
+			if (parent->is_legacy()) {
 				parent->legacy->parameters = from;
+				return;
+			}
 
 			if (parent->type == ID($not)) {
 				parent->not_.params_from_dict(from);
@@ -1991,7 +1996,7 @@ public:
 				throw std::out_of_range("Cell::getParam()");
 			}
 		}
-		void operator=(const FakeConns& from) {
+		void operator=(const FakeConns& from) { // TODO check warning
 			log_assert(parent->type == from.parent->type);
 
 			if (parent->is_legacy()) {
@@ -2269,8 +2274,10 @@ public:
 	}
 	// TODO check
 	void unsetPort(const RTLIL::IdString& portname) {
-		if (is_legacy())
+		if (is_legacy()) {
 			legacy->unsetPort(portname);
+			return;
+		}
 		try {
 			setPort(portname, SigSpec());
 		} catch (const std::out_of_range& e) {}
@@ -2289,8 +2296,10 @@ public:
 	}
 	// TODO check
 	void unsetParam(const RTLIL::IdString& paramname) {
-		if (is_legacy())
+		if (is_legacy()) {
 			legacy->unsetParam(paramname);
+			return;
+		}
 		try {
 			setPort(paramname, Const());
 		} catch (const std::out_of_range& e) {}
diff --git a/passes/cmds/chformal.cc b/passes/cmds/chformal.cc
index 03187d014..6d61e25fe 100644
--- a/passes/cmds/chformal.cc
+++ b/passes/cmds/chformal.cc
@@ -46,7 +46,7 @@ static RTLIL::IdString formal_flavor(RTLIL::Cell *cell)
 static void set_formal_flavor(RTLIL::Cell *cell, RTLIL::IdString flavor)
 {
 	if (cell->type != ID($check)) {
-		cell->type = flavor;
+		cell = cell->module->morphCell(flavor, cell);
 		return;
 	}
 
@@ -423,7 +423,7 @@ struct ChformalPass : public Pass {
 					if (cell->getPort(ID::ARGS).empty()) {
 						module->remove(cell);
 					} else {
-						cell->type = ID($print);
+						cell = cell->module->morphCell(ID($print), cell);
 						cell->setPort(ID::EN, combined_en);
 						cell->unsetPort(ID::A);
 						cell->unsetParam(ID(FLAVOR));
diff --git a/passes/cmds/chtype.cc b/passes/cmds/chtype.cc
index dc8786dde..7ef64c4c5 100644
--- a/passes/cmds/chtype.cc
+++ b/passes/cmds/chtype.cc
@@ -70,12 +70,12 @@ struct ChtypePass : public Pass {
 			for (auto cell : module->selected_cells())
 			{
 				if (map_types.count(cell->type)) {
-					cell->type = map_types.at(cell->type);
+					cell = cell->module->morphCell(map_types.at(cell->type), cell);
 					continue;
 				}
 
 				if (set_type != IdString()) {
-					cell->type = set_type;
+					cell = cell->module->morphCell(set_type, cell);
 					continue;
 				}
 			}
diff --git a/passes/cmds/design.cc b/passes/cmds/design.cc
index c4f1bc161..212598381 100644
--- a/passes/cmds/design.cc
+++ b/passes/cmds/design.cc
@@ -318,7 +318,7 @@ struct DesignPass : public Pass {
 						done[cell->type] = trg_name;
 					}
 
-					cell->type = done.at(cell->type);
+					cell = cell->module->morphCell(done.at(cell->type), cell);
 				}
 			}
 		}
diff --git a/passes/cmds/dft_tag.cc b/passes/cmds/dft_tag.cc
index 5ea55de44..d4da5dcdc 100644
--- a/passes/cmds/dft_tag.cc
+++ b/passes/cmds/dft_tag.cc
@@ -109,7 +109,7 @@ struct DftTagWorker {
 			module->remove(cell);
 		}
 		for (auto cell : original_cells) {
-			cell->type = ID($get_tag);
+			cell = cell->module->morphCell(ID($get_tag), cell);
 		}
 
 		if (design_changed)
diff --git a/passes/cmds/setattr.cc b/passes/cmds/setattr.cc
index e4e4c3dd6..f5ad8c8e8 100644
--- a/passes/cmds/setattr.cc
+++ b/passes/cmds/setattr.cc
@@ -220,7 +220,7 @@ struct SetparamPass : public Pass {
 		{
 			for (auto cell : module->selected_cells()) {
 				if (!new_cell_type.empty())
-					cell->type = new_cell_type;
+					cell = cell->module->morphCell(new_cell_type, cell);
 				do_setunset(cell->parameters, setunset_list);
 			}
 		}
diff --git a/passes/hierarchy/hierarchy.cc b/passes/hierarchy/hierarchy.cc
index b54d75e84..cdbb16f0d 100644
--- a/passes/hierarchy/hierarchy.cc
+++ b/passes/hierarchy/hierarchy.cc
@@ -473,7 +473,7 @@ bool expand_module(RTLIL::Design *design, RTLIL::Module *module, bool flag_check
 			int idx = atoi(cell->type.substr(pos_idx + 1, pos_num).c_str());
 			int num = atoi(cell->type.substr(pos_num + 1, pos_type).c_str());
 			array_cells[cell] = std::pair<int, int>(idx, num);
-			cell->type = cell->type.substr(pos_type + 1);
+			cell = cell->module->morphCell(cell->type.substr(pos_type + 1), cell);
 		}
 
 		RTLIL::Module *mod = design->module(cell->type);
diff --git a/passes/hierarchy/uniquify.cc b/passes/hierarchy/uniquify.cc
index 94f2d9dfd..260c900c1 100644
--- a/passes/hierarchy/uniquify.cc
+++ b/passes/hierarchy/uniquify.cc
@@ -89,7 +89,7 @@ struct UniquifyPass : public Pass {
 
 					auto smod = tmod->clone();
 					smod->name = newname;
-					cell->type = newname;
+					cell = cell->module->morphCell(newname, cell);
 					smod->set_bool_attribute(ID::unique);
 					if (smod->attributes.count(ID::hdlname) == 0)
 						smod->attributes[ID::hdlname] = string(log_id(tmod->name));
diff --git a/passes/opt/muxpack.cc b/passes/opt/muxpack.cc
index fd40a2a9c..d7eb145a1 100644
--- a/passes/opt/muxpack.cc
+++ b/passes/opt/muxpack.cc
@@ -269,7 +269,7 @@ struct MuxpackWorker
 			mux_count += cases;
 			pmux_count += 1;
 
-			first_cell->type = ID($pmux);
+			first_cell = first_cell->module->morphCell(ID($pmux), first_cell);
 			SigSpec b_sig = first_cell->getPort(ID::B);
 			SigSpec s_sig = first_cell->getPort(ID::S);
 
diff --git a/passes/opt/opt_demorgan.cc b/passes/opt/opt_demorgan.cc
index a33b452db..7a8b400f7 100644
--- a/passes/opt/opt_demorgan.cc
+++ b/passes/opt/opt_demorgan.cc
@@ -155,9 +155,9 @@ void demorgan_worker(
 
 	//Change the cell type
 	if(cell->type == ID($reduce_and))
-		cell->type = ID($reduce_or);
+		cell = m->morphCell(ID($reduce_or), cell);
 	else if(cell->type == ID($reduce_or))
-		cell->type = ID($reduce_and);
+		cell = m->morphCell(ID($reduce_and), cell);
 	//don't change XOR
 
 	//Add an inverter to the output
diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index 364a0dd92..c7905bef1 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -125,7 +125,6 @@ void replace_cell(SigMap &assign_map, RTLIL::Module *module, RTLIL::Cell *cell,
 	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);
 	assign_map.add(Y, out_val);
 	module->connect(Y, out_val);
 	module->remove(cell);
@@ -341,7 +340,7 @@ void handle_clkpol_celltype_swap(Cell *cell, string type1, string type2, IdStrin
 					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)));
-			cell->type = cell->type == type1 ? type2 : type1;
+			cell = cell->module->morphCell(cell->type == type1 ? type2 : type1, cell);
 		}
 	}
 }
@@ -408,8 +407,6 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 
 	for (auto cell : module->cells())
 		if (design->selected(module, cell) && cell->type[0] == '$') {
-			log("%s\n", cell->name.c_str());
-			log_cell(cell, "inner ");
 			if (cell->type.in(ID($_NOT_), ID($not), ID($logic_not)) &&
 					GetSize(cell->getPort(ID::A)) == 1 && GetSize(cell->getPort(ID::Y)) == 1)
 				invert_map[assign_map(cell->getPort(ID::Y))] = assign_map(cell->getPort(ID::A));
@@ -642,7 +639,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				cover("opt.opt_expr.reduce_xnor_not");
 				log_debug("Replacing %s cell `%s' in module `%s' with $not cell.\n",
 						log_id(cell->type), log_id(cell->name), log_id(module));
-				cell->type = ID($not);
+				cell = cell->module->morphCell(ID($not), cell);
 				did_something = true;
 			} else {
 				cover("opt.opt_expr.unary_buffer");
@@ -1169,7 +1166,7 @@ skip_fine_alu:
 			if (input.match("01 ")) ACTION_DO(ID::Y, input.extract(0, 1));
 			if (input.match("10 ")) {
 				cover("opt.opt_expr.mux_to_inv");
-				cell->type = ID($_NOT_);
+				cell = cell->module->morphCell(ID($_NOT_), cell);
 				cell->setPort(ID::A, input.extract(0, 1));
 				cell->unsetPort(ID::B);
 				cell->unsetPort(ID::S);
@@ -1273,7 +1270,7 @@ skip_fine_alu:
 				} else {
 					cover_list("opt.opt_expr.eqneq.isnot", "$eq", "$ne", cell->type.str());
 					log_debug("Replacing %s cell `%s' in module `%s' with inverter.\n", log_id(cell->type), log_id(cell), log_id(module));
-					cell->type = ID($not);
+					cell = cell->module->morphCell(ID($not), cell);
 					cell->parameters.erase(ID::B_WIDTH);
 					cell->parameters.erase(ID::B_SIGNED);
 					cell->unsetPort(ID::B);
@@ -1289,7 +1286,7 @@ skip_fine_alu:
 			cover_list("opt.opt_expr.eqneq.cmpzero", "$eq", "$ne", cell->type.str());
 			log_debug("Replacing %s cell `%s' in module `%s' with %s.\n", log_id(cell->type), log_id(cell),
 					log_id(module), cell->type == ID($eq) ? "$logic_not" : "$reduce_bool");
-			cell->type = cell->type == ID($eq) ? ID($logic_not) : ID($reduce_bool);
+			cell = cell->module->morphCell(cell->type == ID($eq) ? ID($logic_not) : ID($reduce_bool), cell);
 			if (assign_map(cell->getPort(ID::A)).is_fully_zero()) {
 				cell->setPort(ID::A, cell->getPort(ID::B));
 				cell->setParam(ID::A_SIGNED, cell->getParam(ID::B_SIGNED));
@@ -1437,7 +1434,7 @@ skip_fine_alu:
 					cell->setParam(ID::A_SIGNED, cell->getParam(ID::B_SIGNED));
 				}
 
-				cell->type = arith_inverse ? ID($neg) : ID($pos);
+				cell = cell->module->morphCell(arith_inverse ? ID($neg) : ID($pos), cell);
 				cell->unsetPort(ID::B);
 				cell->parameters.erase(ID::B_WIDTH);
 				cell->parameters.erase(ID::B_SIGNED);
@@ -1469,9 +1466,9 @@ skip_identity:
 				cell->parameters[ID::Y_WIDTH] = width;
 				cell->parameters[ID::A_SIGNED] = 0;
 				cell->parameters.erase(ID::WIDTH);
-				cell->type = ID($not);
+				cell = cell->module->morphCell(ID($not), cell);
 			} else
-				cell->type = ID($_NOT_);
+				cell = cell->module->morphCell(ID($_NOT_), cell);
 			did_something = true;
 			goto next_cell;
 		}
@@ -1489,9 +1486,9 @@ skip_identity:
 				cell->parameters[ID::A_SIGNED] = 0;
 				cell->parameters[ID::B_SIGNED] = 0;
 				cell->parameters.erase(ID::WIDTH);
-				cell->type = ID($and);
+				cell = cell->module->morphCell(ID($and), cell);
 			} else
-				cell->type = ID($_AND_);
+				cell = cell->module->morphCell(ID($_AND_), cell);
 			did_something = true;
 			goto next_cell;
 		}
@@ -1509,9 +1506,9 @@ skip_identity:
 				cell->parameters[ID::A_SIGNED] = 0;
 				cell->parameters[ID::B_SIGNED] = 0;
 				cell->parameters.erase(ID::WIDTH);
-				cell->type = ID($or);
+				cell = cell->module->morphCell(ID($or), cell);
 			} else
-				cell->type = ID($_OR_);
+				cell = cell->module->morphCell(ID($_OR_), cell);
 			did_something = true;
 			goto next_cell;
 		}
@@ -1557,10 +1554,10 @@ skip_identity:
 				cell->setPort(ID::B, new_b);
 				cell->setPort(ID::S, new_s);
 				if (new_s.size() > 1) {
-					cell->type = ID($pmux);
+					cell = cell->module->morphCell(ID($pmux), cell);
 					cell->parameters[ID::S_WIDTH] = new_s.size();
 				} else {
-					cell->type = ID($mux);
+					cell = cell->module->morphCell(ID($mux), cell);
 					cell->parameters.erase(ID::S_WIDTH);
 				}
 				did_something = true;
@@ -1733,7 +1730,7 @@ skip_identity:
 
 					Const new_b = exp;
 
-					cell->type = ID($shl);
+					cell = cell->module->morphCell(ID($shl), cell);
 					cell->parameters[ID::B_WIDTH] = GetSize(new_b);
 					cell->parameters[ID::B_SIGNED] = false;
 					cell->setPort(ID::B, new_b);
@@ -1824,7 +1821,7 @@ skip_identity:
 
 						Const new_b = exp;
 
-						cell->type = ID($sshr);
+						cell = cell->module->morphCell(ID($sshr), cell);
 						cell->parameters[ID::B_WIDTH] = GetSize(new_b);
 						cell->parameters[ID::B_SIGNED] = false;
 						cell->setPort(ID::B, new_b);
@@ -1873,7 +1870,7 @@ skip_identity:
 							if (b_signed || exp == 0)
 								new_b.push_back(State::S0);
 
-							cell->type = ID($and);
+							cell = cell->module->morphCell(ID($and), cell);
 							cell->parameters[ID::B_WIDTH] = GetSize(new_b);
 							cell->setPort(ID::B, new_b);
 							cell->check();
@@ -2307,9 +2304,6 @@ struct OptExprPass : public Pass {
 		CellTypes ct(design);
 		for (auto module : design->selected_modules())
 		{
-			for (auto cell : module->cells()) {
-				log_cell(cell, "start ");
-			}
 			log("Optimizing module %s.\n", log_id(module));
 
 			if (undriven) {
@@ -2318,9 +2312,6 @@ struct OptExprPass : public Pass {
 				if (did_something)
 					design->scratchpad_set_bool("opt.did_something", true);
 			}
-			for (auto cell : module->cells()) {
-				log_cell(cell, "mid ");
-			}
 
 			do {
 				do {
diff --git a/passes/opt/opt_lut_ins.cc b/passes/opt/opt_lut_ins.cc
index 296fccb5a..e660aa036 100644
--- a/passes/opt/opt_lut_ins.cc
+++ b/passes/opt/opt_lut_ins.cc
@@ -244,17 +244,17 @@ struct OptLutInsPass : public Pass {
 						else
 							log_assert(GetSize(new_inputs) <= 4);
 						if (GetSize(new_inputs) == 1)
-							cell->type = ID(LUT1);
+							cell = cell->module->morphCell(ID(LUT1), cell);
 						else if (GetSize(new_inputs) == 2)
-							cell->type = ID(LUT2);
+							cell = cell->module->morphCell(ID(LUT2), cell);
 						else if (GetSize(new_inputs) == 3)
-							cell->type = ID(LUT3);
+							cell = cell->module->morphCell(ID(LUT3), cell);
 						else if (GetSize(new_inputs) == 4)
-							cell->type = ID(LUT4);
+							cell = cell->module->morphCell(ID(LUT4), cell);
 						else if (GetSize(new_inputs) == 5)
-							cell->type = ID(LUT5);
+							cell = cell->module->morphCell(ID(LUT5), cell);
 						else if (GetSize(new_inputs) == 6)
-							cell->type = ID(LUT6);
+							cell = cell->module->morphCell(ID(LUT6), cell);
 						else
 							log_assert(0);
 						cell->unsetPort(ID(I0));
diff --git a/passes/opt/opt_muxtree.cc b/passes/opt/opt_muxtree.cc
index faf448bc9..64016bd86 100644
--- a/passes/opt/opt_muxtree.cc
+++ b/passes/opt/opt_muxtree.cc
@@ -259,7 +259,7 @@ struct OptMuxtreeWorker
 				mi.cell->setPort(ID::B, new_sig_b);
 				mi.cell->setPort(ID::S, new_sig_s);
 				if (GetSize(new_sig_s) == 1) {
-					mi.cell->type = ID($mux);
+					mi.cell = mi.cell->module->morphCell(ID($mux), mi.cell);
 					mi.cell->parameters.erase(ID::S_WIDTH);
 				} else {
 					mi.cell->parameters[ID::S_WIDTH] = RTLIL::Const(GetSize(new_sig_s));
diff --git a/passes/opt/opt_reduce.cc b/passes/opt/opt_reduce.cc
index e3e77b6e3..fe90c28dc 100644
--- a/passes/opt/opt_reduce.cc
+++ b/passes/opt/opt_reduce.cc
@@ -160,7 +160,7 @@ struct OptReduceWorker
 			if (new_sig_s.size() > 1) {
 				cell->parameters[ID::S_WIDTH] = RTLIL::Const(new_sig_s.size());
 			} else {
-				cell->type = ID($mux);
+				cell = cell->module->morphCell(ID($mux), cell);
 				cell->parameters.erase(ID::S_WIDTH);
 			}
 		}
@@ -228,7 +228,7 @@ struct OptReduceWorker
 
 		if (new_sig_s.size() == 1)
 		{
-			cell->type = ID($mux);
+			cell = cell->module->morphCell(ID($mux), cell);
 			cell->setPort(ID::A, new_sig_a.extract(0, width));
 			cell->setPort(ID::B, new_sig_a.extract(width, width));
 			cell->setPort(ID::S, new_sig_s);
diff --git a/passes/pmgen/pmgen.py b/passes/pmgen/pmgen.py
index 6e2fabeeb..4a23cda4a 100644
--- a/passes/pmgen/pmgen.py
+++ b/passes/pmgen/pmgen.py
@@ -5,6 +5,8 @@ import sys
 import pprint
 import getopt
 
+# TODO there's an invalid cell type assignment here that should be turned into morphCell
+
 pp = pprint.PrettyPrinter(indent=4)
 
 prefix = None
diff --git a/passes/proc/proc_dlatch.cc b/passes/proc/proc_dlatch.cc
index b9b0414c9..0446a5cec 100644
--- a/passes/proc/proc_dlatch.cc
+++ b/passes/proc/proc_dlatch.cc
@@ -293,10 +293,10 @@ struct proc_dlatch_db_t
 			cell->setPort(ID::A, sig_any_valid_b);
 
 		if (GetSize(sig_new_s) == 1) {
-			cell->type = ID($mux);
+			cell = cell->module->morphCell(ID($mux), cell);
 			cell->unsetParam(ID::S_WIDTH);
 		} else {
-			cell->type = ID($pmux);
+			cell = cell->module->morphCell(ID($pmux), cell);
 			cell->setParam(ID::S_WIDTH, GetSize(sig_new_s));
 		}
 
diff --git a/passes/proc/proc_mux.cc b/passes/proc/proc_mux.cc
index c49f35b9b..412f45ea7 100644
--- a/passes/proc/proc_mux.cc
+++ b/passes/proc/proc_mux.cc
@@ -262,7 +262,7 @@ void append_pmux(RTLIL::Module *mod, const RTLIL::SigSpec &signal, const std::ve
 
 	RTLIL::SigSpec ctrl_sig = gen_cmp(mod, signal, compare, sw, cs, ifxmode);
 	log_assert(ctrl_sig.size() == 1);
-	last_mux_cell->type = ID($pmux);
+	last_mux_cell = last_mux_cell->module->morphCell(ID($pmux), last_mux_cell);
 
 	RTLIL::SigSpec new_s = last_mux_cell->getPort(ID::S);
 	new_s.append(ctrl_sig);
diff --git a/passes/techmap/abc9_ops.cc b/passes/techmap/abc9_ops.cc
index 7c6474dd6..57476c3aa 100644
--- a/passes/techmap/abc9_ops.cc
+++ b/passes/techmap/abc9_ops.cc
@@ -195,7 +195,7 @@ void prep_hier(RTLIL::Design *design, bool dff_mode)
 						// If derived_type is present in unmap_design, it means that it was processed previously, but found to be incompatible -- e.g. if
 						// it contained a non-zero initial state. In this case, continue to replace the cell type/parameters so that it has the same properties
 						// as a compatible type, yet will be safely unmapped later
-						cell->type = derived_type;
+						cell = cell->module->morphCell(derived_type, cell);
 						cell->parameters.clear();
 						unused_derived.erase(derived_type);
 					}
@@ -255,7 +255,7 @@ void prep_hier(RTLIL::Design *design, bool dff_mode)
 				}
 			}
 
-			cell->type = derived_type;
+			cell = cell->module->morphCell(derived_type, cell);
 			cell->parameters.clear();
 			unused_derived.erase(derived_type);
 		}
@@ -1344,7 +1344,7 @@ void reintegrate(RTLIL::Module *module, bool dff_mode)
 			RTLIL::Module* box_module = design->module(existing_cell->type);
 			log_assert(existing_cell->parameters.empty());
 			log_assert(mapped_cell->type == stringf("$__boxid%d", box_module->attributes.at(ID::abc9_box_id).as_int()));
-			mapped_cell->type = existing_cell->type;
+			mapped_cell = mapped_cell->module->morphCell(existing_cell->type, mapped_cell);
 
 			RTLIL::Cell *cell = module->addCell(remap_name(mapped_cell->name), mapped_cell->type);
 			cell->parameters = existing_cell->parameters;
diff --git a/passes/techmap/extract_counter.cc b/passes/techmap/extract_counter.cc
index 08dac523c..24bbbf61f 100644
--- a/passes/techmap/extract_counter.cc
+++ b/passes/techmap/extract_counter.cc
@@ -628,7 +628,7 @@ void counter_worker(
 	cell->unsetParam(ID::Y_WIDTH);
 
 	//Change the cell type
-	cell->type = ID($__COUNT_);
+	cell = cell->module->morphCell(ID($__COUNT_), cell);
 
 	//Hook up resets
 	if(extract.has_reset)
diff --git a/passes/techmap/shregmap.cc b/passes/techmap/shregmap.cc
index b50c20ad0..492e760af 100644
--- a/passes/techmap/shregmap.cc
+++ b/passes/techmap/shregmap.cc
@@ -332,7 +332,7 @@ struct ShregmapWorker
 				if (opts.ffe) first_cell->setParam(ID(ENPOL), param_enpol);
 			}
 
-			first_cell->type = shreg_cell_type_str;
+			first_cell = first_cell->module->morphCell(shreg_cell_type_str, first_cell);
 			first_cell->setPort(q_port, last_cell->getPort(q_port));
 			first_cell->setParam(ID::DEPTH, depth);
 
diff --git a/passes/techmap/techmap.cc b/passes/techmap/techmap.cc
index a33187954..139f89bc4 100644
--- a/passes/techmap/techmap.cc
+++ b/passes/techmap/techmap.cc
@@ -331,16 +331,18 @@ struct TechmapWorker
 			else
 				apply_prefix(cell->name, c_name);
 
+			auto type = tpl_cell->type;
 			RTLIL::Cell *c = module->addCell(c_name, tpl_cell);
 			design->select(module, c);
 
-			if (c->type.begins_with("\\$"))
-				c->type = c->type.substr(1);
-			
-			if (c->type == ID::_TECHMAP_PLACEHOLDER_ && tpl_cell->has_attribute(ID::techmap_chtype)) {
-				c->type = RTLIL::escape_id(tpl_cell->get_string_attribute(ID::techmap_chtype));
+			if (type.begins_with("\\$"))
+				type = type.substr(1);
+
+			if (type == ID::_TECHMAP_PLACEHOLDER_ && tpl_cell->has_attribute(ID::techmap_chtype)) {
+				type = RTLIL::escape_id(tpl_cell->get_string_attribute(ID::techmap_chtype));
 				c->attributes.erase(ID::techmap_chtype);
 			}
+			c = module->morphCell(type, c);
 
 			vector<IdString> autopurge_ports;
 
@@ -508,7 +510,7 @@ struct TechmapWorker
 
 				if (!extmapper_name.empty())
 				{
-					cell->type = cell_type;
+					cell = cell->module->morphCell(cell_type, cell);
 
 					if ((extern_mode && !in_recursion) || extmapper_name == "wrap")
 					{
@@ -570,7 +572,7 @@ struct TechmapWorker
 							}
 						}
 
-						cell->type = extmapper_module->name;
+						cell = cell->module->morphCell(extmapper_module->name, cell);
 						cell->parameters.clear();
 
 						if (!extern_mode || in_recursion) {
@@ -937,14 +939,14 @@ struct TechmapWorker
 
 						for (auto cell : m->cells()) {
 							if (cell->type.begins_with("\\$"))
-								cell->type = cell->type.substr(1);
+								cell = cell->module->morphCell(cell->type.substr(1), cell);
 						}
 
 						module_queue.insert(m);
 					}
 
 					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 = cell->module->morphCell(m_name, cell);
 					cell->parameters.clear();
 				}
 				else
diff --git a/passes/techmap/tribuf.cc b/passes/techmap/tribuf.cc
index 9f58727e4..d106712f5 100644
--- a/passes/techmap/tribuf.cc
+++ b/passes/techmap/tribuf.cc
@@ -86,7 +86,7 @@ struct TribufWorker {
 					cell->setPort(en_port, cell->getPort(ID::S));
 					cell->unsetPort(ID::B);
 					cell->unsetPort(ID::S);
-					cell->type = tri_type;
+					cell = cell->module->morphCell(tri_type, cell);
 					tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
 					module->design->scratchpad_set_bool("tribuf.added_something", true);
 					continue;
@@ -96,7 +96,7 @@ struct TribufWorker {
 					cell->setPort(en_port, module->Not(NEW_ID, cell->getPort(ID::S)));
 					cell->unsetPort(ID::B);
 					cell->unsetPort(ID::S);
-					cell->type = tri_type;
+					cell = cell->module->morphCell(tri_type, cell);
 					tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
 					module->design->scratchpad_set_bool("tribuf.added_something", true);
 					continue;
diff --git a/passes/tests/test_cell.cc b/passes/tests/test_cell.cc
index 79eb6b6ea..66f75e603 100644
--- a/passes/tests/test_cell.cc
+++ b/passes/tests/test_cell.cc
@@ -973,9 +973,9 @@ struct TestCellPass : public Pass {
 					Frontend::frontend_call(design, NULL, std::string(), "rtlil " + rtlil_file);
 				else
 					create_gold_module(design, cell_type, cell_types.at(cell_type), constmode, muxdiv);
-				if (!write_prefix.empty()) {
+				if (!write_prefix.empty())
 					Pass::call(design, stringf("write_rtlil %s_%s_%05d.il", write_prefix.c_str(), cell_type.c_str()+1, i));
-				} else if (edges) {
+				if (edges) {
 					Pass::call(design, "dump gold");
 					run_edges_test(design, verbose);
 				} else {
diff --git a/techlibs/coolrunner2/coolrunner2_sop.cc b/techlibs/coolrunner2/coolrunner2_sop.cc
index 17e0d8432..9ab7c5173 100644
--- a/techlibs/coolrunner2/coolrunner2_sop.cc
+++ b/techlibs/coolrunner2/coolrunner2_sop.cc
@@ -170,14 +170,14 @@ struct Coolrunner2SopPass : public Pass {
 								if (has_invert)
 								{
 									auto cell = std::get<0>(x);
-									if (cell->type == ID(FDCP)) cell->type = ID(FDCP_N);
-									else if (cell->type == ID(FDCP_N)) cell->type = ID(FDCP);
-									else if (cell->type == ID(FTCP)) cell->type = ID(FTCP_N);
-									else if (cell->type == ID(FTCP_N)) cell->type = ID(FTCP);
-									else if (cell->type == ID(FDCPE)) cell->type = ID(FDCPE_N);
-									else if (cell->type == ID(FDCPE_N)) cell->type = ID(FDCPE);
-									else if (cell->type == ID(LDCP)) cell->type = ID(LDCP_N);
-									else if (cell->type == ID(LDCP_N)) cell->type = ID(LDCP);
+									if (cell->type == ID(FDCP)) cell = cell->module->morphCell(ID(FDCP_N), cell);
+									else if (cell->type == ID(FDCP_N)) cell = cell->module->morphCell(ID(FDCP), cell);
+									else if (cell->type == ID(FTCP)) cell = cell->module->morphCell(ID(FTCP_N), cell);
+									else if (cell->type == ID(FTCP_N)) cell = cell->module->morphCell(ID(FTCP), cell);
+									else if (cell->type == ID(FDCPE)) cell = cell->module->morphCell(ID(FDCPE_N), cell);
+									else if (cell->type == ID(FDCPE_N)) cell = cell->module->morphCell(ID(FDCPE), cell);
+									else if (cell->type == ID(LDCP)) cell = cell->module->morphCell(ID(LDCP_N), cell);
+									else if (cell->type == ID(LDCP_N)) cell = cell->module->morphCell(ID(LDCP), cell);
 									else log_assert(!"Internal error! Bad cell type!");
 								}
 							}
diff --git a/techlibs/greenpak4/greenpak4_dffinv.cc b/techlibs/greenpak4/greenpak4_dffinv.cc
index a77711e01..c779c3f0d 100644
--- a/techlibs/greenpak4/greenpak4_dffinv.cc
+++ b/techlibs/greenpak4/greenpak4_dffinv.cc
@@ -81,9 +81,9 @@ void invert_gp_dff(Cell *cell, bool invert_input)
 	}
 
 	if(cell_type_latch)
-		cell->type = stringf("\\GP_DLATCH%s%s%s", cell_type_s ? "S" : "", cell_type_r ? "R" : "", cell_type_i ? "I" : "");
+		cell = cell->module->morphCell(stringf("\\GP_DLATCH%s%s%s", cell_type_s ? "S" : "", cell_type_r ? "R" : "", cell_type_i ? "I" : ""), cell);
 	else
-		cell->type = stringf("\\GP_DFF%s%s%s", cell_type_s ? "S" : "", cell_type_r ? "R" : "", cell_type_i ? "I" : "");
+		cell = cell->module->morphCell(stringf("\\GP_DFF%s%s%s", cell_type_s ? "S" : "", cell_type_r ? "R" : "", cell_type_i ? "I" : ""), cell);
 
 	log("Merged %s inverter into cell %s.%s: %s -> %s\n", invert_input ? "input" : "output",
 			log_id(cell->module), log_id(cell), cell_type.c_str()+1, log_id(cell->type));
diff --git a/techlibs/ice40/ice40_opt.cc b/techlibs/ice40/ice40_opt.cc
index b13d33018..ee5de195b 100644
--- a/techlibs/ice40/ice40_opt.cc
+++ b/techlibs/ice40/ice40_opt.cc
@@ -138,7 +138,7 @@ static void run_ice40_opts(Module *module)
 				module->design->scratchpad_set_bool("opt.did_something", true);
 				log("Optimized $__ICE40_CARRY_WRAPPER cell back to logic (without SB_CARRY) %s.%s: CO=%s\n",
 						log_id(module), log_id(cell), log_signal(replacement_output));
-				cell->type = ID($lut);
+				cell = cell->module->morphCell(ID($lut), cell);
 				auto I3 = get_bit_or_zero(cell->getPort(cell->getParam(ID(I3_IS_CI)).as_bool() ? ID::CI : ID(I3)));
 				cell->setPort(ID::A, { I3, inbit[1], inbit[0], get_bit_or_zero(cell->getPort(ID(I0))) });
 				cell->setPort(ID::Y, cell->getPort(ID::O));
@@ -177,7 +177,7 @@ static void run_ice40_opts(Module *module)
 		module->design->scratchpad_set_bool("opt.did_something", true);
 		log("Mapping SB_LUT4 cell %s.%s back to logic.\n", log_id(module), log_id(cell));
 
-		cell->type = ID($lut);
+		cell = cell->module->morphCell(ID($lut), cell);
 		cell->setParam(ID::WIDTH, 4);
 		cell->setParam(ID::LUT, cell->getParam(ID(LUT_INIT)));
 		cell->unsetParam(ID(LUT_INIT));
diff --git a/techlibs/quicklogic/ql_bram_types.cc b/techlibs/quicklogic/ql_bram_types.cc
index cf42703aa..393c668a5 100644
--- a/techlibs/quicklogic/ql_bram_types.cc
+++ b/techlibs/quicklogic/ql_bram_types.cc
@@ -154,7 +154,7 @@ struct QlBramTypesPass : public Pass {
 					type += "nonsplit";
 				}
 
-				cell->type = RTLIL::escape_id(type);
+				cell = cell->module->morphCell(RTLIL::escape_id(type), cell);
 				log_debug("Changed type of memory cell %s to %s\n", log_id(cell->name), log_id(cell->type));
 			}
 	}
diff --git a/techlibs/quicklogic/ql_dsp_io_regs.cc b/techlibs/quicklogic/ql_dsp_io_regs.cc
index ecf163dbf..986c59aea 100644
--- a/techlibs/quicklogic/ql_dsp_io_regs.cc
+++ b/techlibs/quicklogic/ql_dsp_io_regs.cc
@@ -127,7 +127,7 @@ struct QlDspIORegs : public Pass {
 			}
 
 			// Set new type name
-			cell->type = RTLIL::IdString(new_type);
+			cell = cell->module->morphCell(RTLIL::IdString(new_type), cell);
 
 			std::vector<std::string> ports2del;