From: Clifford Wolf <clifford@clifford.at>
Date: Mon, 28 May 2018 15:16:15 +0000 (+0200)
Subject: Disable memory_dff for initialized FFs
X-Git-Tag: yosys-0.8~83
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=cee4b1e6bc11fff1d2d97985a96e6990afc57950;p=yosys.git

Disable memory_dff for initialized FFs

Signed-off-by: Clifford Wolf <clifford@clifford.at>
---

diff --git a/passes/memory/memory_dff.cc b/passes/memory/memory_dff.cc
index 40691d160..6e036397d 100644
--- a/passes/memory/memory_dff.cc
+++ b/passes/memory/memory_dff.cc
@@ -33,8 +33,20 @@ struct MemoryDffWorker
 	dict<SigBit, int> sigbit_users_count;
 	dict<SigSpec, Cell*> mux_cells_a, mux_cells_b;
 	pool<Cell*> forward_merged_dffs, candidate_dffs;
+	pool<SigBit> init_bits;
 
-	MemoryDffWorker(Module *module) : module(module), sigmap(module) { }
+	MemoryDffWorker(Module *module) : module(module), sigmap(module)
+	{
+		for (auto wire : module->wires()) {
+			if (wire->attributes.count("\\init") == 0)
+				continue;
+			SigSpec sig = sigmap(wire);
+			Const initval = wire->attributes.count("\\init");
+			for (int i = 0; i < GetSize(sig) && i < GetSize(initval); i++)
+				if (initval[i] == State::S0 || initval[i] == State::S1)
+					init_bits.insert(sig[i]);
+		}
+	}
 
 	bool find_sig_before_dff(RTLIL::SigSpec &sig, RTLIL::SigSpec &clk, bool &clk_polarity, bool after = false)
 	{
@@ -45,6 +57,9 @@ struct MemoryDffWorker
 			if (bit.wire == NULL)
 				continue;
 
+			if (!after && init_bits.count(sigmap(bit)))
+				return false;
+
 			for (auto cell : dff_cells)
 			{
 				if (after && forward_merged_dffs.count(cell))
@@ -72,6 +87,9 @@ struct MemoryDffWorker
 				if (d.size() != 1)
 					continue;
 
+				if (after && init_bits.count(d))
+					return false;
+
 				bit = d;
 				clk = this_clk;
 				clk_polarity = this_clk_polarity;