From 2ef454c3f579a4b64abcddadf90d3746611d251d Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Fri, 14 Oct 2016 13:02:36 +0200
Subject: [PATCH] Added opt_rmdff support for $ff cells

---
 passes/opt/opt_rmdff.cc | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/passes/opt/opt_rmdff.cc b/passes/opt/opt_rmdff.cc
index 7e87d1adc..922f086f1 100644
--- a/passes/opt/opt_rmdff.cc
+++ b/passes/opt/opt_rmdff.cc
@@ -72,7 +72,11 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 	RTLIL::SigSpec sig_d, sig_q, sig_c, sig_r;
 	RTLIL::Const val_cp, val_rp, val_rv;
 
-	if (dff->type == "$_DFF_N_" || dff->type == "$_DFF_P_") {
+	if (dff->type == "$_FF_") {
+		sig_d = dff->getPort("\\D");
+		sig_q = dff->getPort("\\Q");
+	}
+	else if (dff->type == "$_DFF_N_" || dff->type == "$_DFF_P_") {
 		sig_d = dff->getPort("\\D");
 		sig_q = dff->getPort("\\Q");
 		sig_c = dff->getPort("\\C");
@@ -90,6 +94,10 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 		val_rp = RTLIL::Const(dff->type[7] == 'P', 1);
 		val_rv = RTLIL::Const(dff->type[8] == '1', 1);
 	}
+	else if (dff->type == "$ff") {
+		sig_d = dff->getPort("\\D");
+		sig_q = dff->getPort("\\Q");
+	}
 	else if (dff->type == "$dff") {
 		sig_d = dff->getPort("\\D");
 		sig_q = dff->getPort("\\Q");
@@ -121,7 +129,7 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 		val_init.bits.push_back(bit.wire == NULL ? bit.data : RTLIL::State::Sx);
 	}
 
-	if (dff->type == "$dff" && mux_drivers.has(sig_d)) {
+	if (dff->type.in("$ff", "$dff") && mux_drivers.has(sig_d)) {
 		std::set<RTLIL::Cell*> muxes;
 		mux_drivers.find(sig_d, muxes);
 		for (auto mux : muxes) {
@@ -138,7 +146,7 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
 		}
 	}
 
-	if (sig_c.is_fully_const() && (!sig_r.size() || !has_init || val_init == val_rv)) {
+	if (!sig_c.empty() && sig_c.is_fully_const() && (!sig_r.size() || !has_init || val_init == val_rv)) {
 		if (val_rv.bits.size() == 0)
 			val_rv = val_init;
 		mod->connect(sig_q, val_rv);
@@ -254,10 +262,10 @@ struct OptRmdffPass : public Pass {
 				if (!design->selected(module, cell))
 					continue;
 
-				if (cell->type.in("$_DFF_N_", "$_DFF_P_",
+				if (cell->type.in("$_FF_", "$_DFF_N_", "$_DFF_P_",
 						"$_DFF_NN0_", "$_DFF_NN1_", "$_DFF_NP0_", "$_DFF_NP1_",
 						"$_DFF_PN0_", "$_DFF_PN1_", "$_DFF_PP0_", "$_DFF_PP1_",
-						"$dff", "$adff"))
+						"$ff", "$dff", "$adff"))
 					dff_list.push_back(cell->name);
 
 				if (cell->type == "$dlatch")