From ecdf1f5577dec6a02c944e68d1e923140e51f5bc Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Tue, 4 Feb 2014 12:02:47 +0100
Subject: [PATCH] Improved handling of reg init in opt_share and opt_rmdff

---
 passes/opt/opt_rmdff.cc | 36 +++++++++++++++++++++++++++++-------
 passes/opt/opt_share.cc | 19 +++++++++++++++++++
 2 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/passes/opt/opt_rmdff.cc b/passes/opt/opt_rmdff.cc
index a8e2c4121..02b7f77e7 100644
--- a/passes/opt/opt_rmdff.cc
+++ b/passes/opt/opt_rmdff.cc
@@ -24,7 +24,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 
-static SigMap assign_map;
+static SigMap assign_map, dff_init_map;
 static SigSet<RTLIL::Cell*> mux_drivers;
 
 static bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
@@ -73,6 +73,14 @@ static bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 	assign_map.apply(sig_c);
 	assign_map.apply(sig_r);
 
+	bool has_init;
+	RTLIL::Const val_init;
+	for (auto bit : dff_init_map(sig_q).to_sigbit_vector()) {
+		if (bit.wire == NULL)
+			has_init = true;
+		val_init.bits.push_back(bit.wire == NULL ? bit.data : RTLIL::State::Sx);
+	}
+
 	if (dff->type == "$dff" && mux_drivers.has(sig_d)) {
 		std::set<RTLIL::Cell*> muxes;
 		mux_drivers.find(sig_d, muxes);
@@ -92,31 +100,41 @@ static bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 		}
 	}
 
-	if (sig_c.is_fully_const()) {
+	if (sig_c.is_fully_const() && (!sig_r.width || !has_init)) {
 		if (val_rv.bits.size() == 0)
-			val_rv = RTLIL::Const(RTLIL::State::Sx, sig_q.width);
+			val_rv = val_init;
 		RTLIL::SigSig conn(sig_q, val_rv);
 		mod->connections.push_back(conn);
 		goto delete_dff;
 	}
 
-	if (sig_d.is_fully_undef() && sig_d.width == int(val_rv.bits.size())) {
+	if (sig_d.is_fully_undef() && sig_r.width && !has_init) {
 		RTLIL::SigSig conn(sig_q, val_rv);
 		mod->connections.push_back(conn);
 		goto delete_dff;
 	}
 
-	if (sig_d.is_fully_const() && sig_r.width == 0) {
+	if (sig_d.is_fully_undef() && !sig_r.width && has_init) {
+		RTLIL::SigSig conn(sig_q, val_init);
+		mod->connections.push_back(conn);
+		goto delete_dff;
+	}
+
+	if (sig_d.is_fully_const() && !sig_r.width && !has_init) {
 		RTLIL::SigSig conn(sig_q, sig_d);
 		mod->connections.push_back(conn);
 		goto delete_dff;
 	}
 
-	if (sig_d == sig_q) {
-		if (sig_r.width > 0) {
+	if (sig_d == sig_q && !(sig_r.width && has_init)) {
+		if (sig_r.width) {
 			RTLIL::SigSig conn(sig_q, val_rv);
 			mod->connections.push_back(conn);
 		}
+		if (has_init) {
+			RTLIL::SigSig conn(sig_q, val_init);
+			mod->connections.push_back(conn);
+		}
 		goto delete_dff;
 	}
 
@@ -155,6 +173,10 @@ struct OptRmdffPass : public Pass {
 				continue;
 
 			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)
+					dff_init_map.add(it.second, it.second->attributes.at("\\init"));
 			mux_drivers.clear();
 
 			std::vector<std::string> dff_list;
diff --git a/passes/opt/opt_share.cc b/passes/opt/opt_share.cc
index 43d1a57e1..eb639d8ab 100644
--- a/passes/opt/opt_share.cc
+++ b/passes/opt/opt_share.cc
@@ -35,6 +35,7 @@ struct OptShareWorker
 	RTLIL::Design *design;
 	RTLIL::Module *module;
 	SigMap assign_map;
+	SigMap dff_init_map;
 
 	CellTypes ct;
 	int total_count;
@@ -178,6 +179,16 @@ struct OptShareWorker
 			return true;
 		}
 
+		if (cell1->type.substr(0, 1) == "$" && conn1.count("\\Q") != 0) {
+			std::vector<RTLIL::SigBit> q1 = dff_init_map(cell1->connections.at("\\Q")).to_sigbit_vector();
+			std::vector<RTLIL::SigBit> q2 = dff_init_map(cell2->connections.at("\\Q")).to_sigbit_vector();
+			for (size_t i = 0; i < q1.size(); i++)
+				if ((q1.at(i).wire == NULL || q2.at(i).wire == NULL) && q1.at(i) != q2.at(i)) {
+					lt = q1.at(i) < q2.at(i);
+					return true;
+				}
+		}
+
 		return false;
 	}
 
@@ -189,6 +200,9 @@ struct OptShareWorker
 		if (!ct.cell_known(cell1->type))
 			return cell1 < cell2;
 
+		if (cell1->get_bool_attribute("\\keep") || cell2->get_bool_attribute("\\keep"))
+			return cell1 < cell2;
+
 		bool lt;
 		if (compare_cell_parameters_and_connections(cell1, cell2, lt))
 			return lt;
@@ -222,6 +236,11 @@ struct OptShareWorker
 		log("Finding identical cells in module `%s'.\n", module->name.c_str());
 		assign_map.set(module);
 
+		dff_init_map.set(module);
+		for (auto &it : module->wires)
+			if (it.second->attributes.count("\\init") != 0)
+				dff_init_map.add(it.second, it.second->attributes.at("\\init"));
+
 		bool did_something = true;
 		while (did_something)
 		{
-- 
2.30.2