From 2a0f577f839bc43a5045ddf5a2b580bba8cabeab Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sat, 24 Oct 2015 13:44:35 +0200
Subject: [PATCH] Fixed handling of driver-driver conflicts in wreduce

---
 kernel/modtools.h     | 23 ++++++++++++++++++++++-
 kernel/rtlil.cc       |  4 ++++
 passes/opt/wreduce.cc | 24 ++++++++++++++++--------
 3 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/kernel/modtools.h b/kernel/modtools.h
index 44c1bde12..1480ec71f 100644
--- a/kernel/modtools.h
+++ b/kernel/modtools.h
@@ -226,7 +226,7 @@ struct ModIndex : public RTLIL::Monitor
 		auto_reload_module = true;
 	}
 
-	ModIndex(RTLIL::Module *_m) : module(_m)
+	ModIndex(RTLIL::Module *_m) : sigmap(_m), module(_m)
 	{
 		auto_reload_counter = 0;
 		auto_reload_module = true;
@@ -274,6 +274,27 @@ struct ModIndex : public RTLIL::Monitor
 			return empty_result_set;
 		return info->ports;
 	}
+
+	void dump_db()
+	{
+		log("--- ModIndex Dump ---\n");
+
+		if (auto_reload_module) {
+			log("AUTO-RELOAD\n");
+			reload_module();
+		}
+
+		for (auto &it : database) {
+			log("BIT %s:\n", log_signal(it.first));
+			if (it.second.is_input)
+				log("  PRIMARY INPUT\n");
+			if (it.second.is_output)
+				log("  PRIMARY OUTPUT\n");
+			for (auto &port : it.second.ports)
+				log("  PORT: %s.%s[%d] (%s)\n", log_id(port.cell),
+						log_id(port.port), port.offset, log_id(port.cell->type));
+		}
+	}
 };
 
 struct ModWalker
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 7090fe913..8332219ae 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -1448,6 +1448,10 @@ void RTLIL::Module::connect(const RTLIL::SigSig &conn)
 		for (auto mon : design->monitors)
 			mon->notify_connect(this, conn);
 
+#ifndef NDEBUG
+	log_assert(!conn.first.has_const());
+#endif
+
 	if (yosys_xtrace) {
 		log("#X# Connect (SigSig) in %s: %s = %s (%d bits)\n", log_id(this), log_signal(conn.first), log_signal(conn.second), GetSize(conn.first));
 		log_backtrace("-X- ", yosys_xtrace-1);
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index c194d428d..e2d9a2c4f 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -66,6 +66,9 @@ struct WreduceWorker
 		SigSpec sig_y = mi.sigmap(cell->getPort("\\Y"));
 		std::vector<SigBit> bits_removed;
 
+		if (sig_y.has_const())
+			return;
+
 		for (int i = GetSize(sig_y)-1; i >= 0; i--)
 		{
 			auto info = mi.query(sig_y[i]);
@@ -173,6 +176,11 @@ struct WreduceWorker
 		if (cell->type.in("$mux", "$pmux"))
 			return run_cell_mux(cell);
 
+		SigSpec sig = mi.sigmap(cell->getPort("\\Y"));
+
+		if (sig.has_const())
+			return;
+
 
 		// Reduce size of ports A and B based on constant input bits and size of output port
 
@@ -180,8 +188,8 @@ struct WreduceWorker
 		int max_port_b_size = cell->hasPort("\\B") ? GetSize(cell->getPort("\\B")) : -1;
 
 		if (cell->type.in("$not", "$pos", "$neg", "$and", "$or", "$xor", "$add", "$sub")) {
-			max_port_a_size = std::min(max_port_a_size, GetSize(cell->getPort("\\Y")));
-			max_port_b_size = std::min(max_port_b_size, GetSize(cell->getPort("\\Y")));
+			max_port_a_size = std::min(max_port_a_size, GetSize(sig));
+			max_port_b_size = std::min(max_port_b_size, GetSize(sig));
 		}
 
 		bool port_a_signed = false;
@@ -196,8 +204,6 @@ struct WreduceWorker
 
 		// Reduce size of port Y based on sizes for A and B and unused bits in Y
 
-		SigSpec sig = mi.sigmap(cell->getPort("\\Y"));
-
 		int bits_removed = 0;
 		if (port_a_signed && cell->type == "$shr") {
 			// do not reduce size of output on $shr cells with signed A inputs
@@ -358,10 +364,12 @@ struct WreducePass : public Pass {
 						"$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt",
 						"$logic_not", "$logic_and", "$logic_or") && GetSize(c->getPort("\\Y")) > 1) {
 					SigSpec sig = c->getPort("\\Y");
-					c->setPort("\\Y", sig[0]);
-					c->setParam("\\Y_WIDTH", 1);
-					sig.remove(0);
-					module->connect(sig, Const(0, GetSize(sig)));
+					if (!sig.has_const()) {
+						c->setPort("\\Y", sig[0]);
+						c->setParam("\\Y_WIDTH", 1);
+						sig.remove(0);
+						module->connect(sig, Const(0, GetSize(sig)));
+					}
 				}
 
 			WreduceWorker worker(&config, module);
-- 
2.30.2