From f43815054e9784d9e1a1b28b5ea2db8404c91d58 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Tue, 18 Aug 2015 13:50:15 +0200
Subject: [PATCH] Properly clean up unused "init" attributes

---
 passes/opt/opt_rmdff.cc   | 20 ++++++++++++++++++--
 passes/techmap/dffinit.cc | 22 ++++++++++++++++++----
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/passes/opt/opt_rmdff.cc b/passes/opt/opt_rmdff.cc
index 2ecbb31a8..e1b184af3 100644
--- a/passes/opt/opt_rmdff.cc
+++ b/passes/opt/opt_rmdff.cc
@@ -28,6 +28,15 @@ PRIVATE_NAMESPACE_BEGIN
 
 SigMap assign_map, dff_init_map;
 SigSet<RTLIL::Cell*> mux_drivers;
+dict<SigBit, pool<SigBit>> init_attributes;
+
+void remove_init_attr(SigSpec sig)
+{
+	for (auto bit : assign_map(sig))
+		if (init_attributes.count(bit))
+			for (auto wbit : init_attributes.at(bit))
+				wbit.wire->attributes.at("\\init")[wbit.offset] = State::Sx;
+}
 
 bool handle_dlatch(RTLIL::Module *mod, RTLIL::Cell *dlatch)
 {
@@ -52,6 +61,7 @@ bool handle_dlatch(RTLIL::Module *mod, RTLIL::Cell *dlatch)
 
 delete_dlatch:
 	log("Removing %s (%s) from module %s.\n", dlatch->name.c_str(), dlatch->type.c_str(), mod->name.c_str());
+	remove_init_attr(dlatch->getPort("\\Q"));
 	mod->remove(dlatch);
 	return true;
 }
@@ -145,7 +155,6 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 	}
 
 	if (sig_d.is_fully_const() && (!sig_r.size() || val_rv == sig_d.as_const()) && (!has_init || val_init == sig_d.as_const())) {
-		log_dump(sig_q, sig_d);
 		mod->connect(sig_q, sig_d);
 		goto delete_dff;
 	}
@@ -162,6 +171,7 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 
 delete_dff:
 	log("Removing %s (%s) from module %s.\n", dff->name.c_str(), dff->type.c_str(), mod->name.c_str());
+	remove_init_attr(dff->getPort("\\Q"));
 	mod->remove(dff);
 	return true;
 }
@@ -193,8 +203,14 @@ struct OptRmdffPass : public Pass {
 			assign_map.set(mod_it.second);
 			dff_init_map.set(mod_it.second);
 			for (auto &it : mod_it.second->wires_)
-				if (it.second->attributes.count("\\init") != 0)
+				if (it.second->attributes.count("\\init") != 0) {
 					dff_init_map.add(it.second, it.second->attributes.at("\\init"));
+					for (int i = 0; i < GetSize(it.second); i++) {
+						SigBit wire_bit(it.second, i), mapped_bit = assign_map(wire_bit);
+						if (mapped_bit.wire)
+							init_attributes[mapped_bit].insert(wire_bit);
+					}
+				}
 			mux_drivers.clear();
 
 			std::vector<RTLIL::IdString> dff_list;
diff --git a/passes/techmap/dffinit.cc b/passes/techmap/dffinit.cc
index 2215c18e5..84770ff3e 100644
--- a/passes/techmap/dffinit.cc
+++ b/passes/techmap/dffinit.cc
@@ -63,16 +63,26 @@ struct DffinitPass : public Pass {
 			SigMap sigmap(module);
 			dict<SigBit, State> init_bits;
 			pool<SigBit> cleanup_bits;
+			pool<SigBit> used_bits;
 
-			for (auto wire : module->selected_wires())
+			for (auto wire : module->selected_wires()) {
 				if (wire->attributes.count("\\init")) {
 					Const value = wire->attributes.at("\\init");
 					for (int i = 0; i < std::min(GetSize(value), GetSize(wire)); i++)
 						init_bits[sigmap(SigBit(wire, i))] = value[i];
 				}
+				if (wire->port_output)
+					for (auto bit : sigmap(wire))
+						used_bits.insert(bit);
+			}
 
 			for (auto cell : module->selected_cells())
 			{
+				for (auto it : cell->connections())
+					if (!cell->known() || cell->input(it.first))
+						for (auto bit : sigmap(it.second))
+							used_bits.insert(bit);
+
 				if (ff_types.count(cell->type) == 0)
 					continue;
 
@@ -104,11 +114,15 @@ struct DffinitPass : public Pass {
 
 			for (auto wire : module->selected_wires())
 				if (wire->attributes.count("\\init")) {
-					Const value = wire->attributes.at("\\init");
+					Const &value = wire->attributes.at("\\init");
 					bool do_cleanup = true;
-					for (int i = 0; i < std::min(GetSize(value), GetSize(wire)); i++)
-						if (cleanup_bits.count(sigmap(SigBit(wire, i))) == 0)
+					for (int i = 0; i < std::min(GetSize(value), GetSize(wire)); i++) {
+						SigBit bit = sigmap(SigBit(wire, i));
+						if (cleanup_bits.count(bit) || !used_bits.count(bit))
+							value[i] = State::Sx;
+						else if (value[i] != State::Sx)
 							do_cleanup = false;
+					}
 					if (do_cleanup) {
 						log("Removing init attribute from wire %s.%s.\n", log_id(module), log_id(wire));
 						wire->attributes.erase("\\init");