From dd9771cbcdc14366c6acc501833c6050c39251de Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Mon, 8 Jul 2019 19:14:54 -0700
Subject: [PATCH] Add synth -keepdc option

---
 techlibs/common/synth.cc | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/techlibs/common/synth.cc b/techlibs/common/synth.cc
index 555de9fba..af70cc498 100644
--- a/techlibs/common/synth.cc
+++ b/techlibs/common/synth.cc
@@ -78,6 +78,9 @@ struct SynthPass : public ScriptPass
 		log("    -abc9\n");
 		log("        use new ABC9 flow (EXPERIMENTAL)\n");
 		log("\n");
+		log("    -keepdc\n");
+		log("        do not optimize explicit don't-care values on $mux cells.\n");
+		log("\n");
 		log("\n");
 		log("The following commands are executed by this synthesis command:\n");
 		help_script();
@@ -85,7 +88,7 @@ struct SynthPass : public ScriptPass
 	}
 
 	string top_module, fsm_opts, memory_opts, abc;
-	bool autotop, flatten, noalumacc, nofsm, noabc, noshare;
+	bool autotop, flatten, noalumacc, nofsm, noabc, noshare, keepdc;
 	int lut;
 
 	void clear_flags() YS_OVERRIDE
@@ -102,6 +105,7 @@ struct SynthPass : public ScriptPass
 		noabc = false;
 		noshare = false;
 		abc = "abc";
+		keepdc = false;
 	}
 
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
@@ -167,6 +171,10 @@ struct SynthPass : public ScriptPass
 				abc = "abc9";
 				continue;
 			}
+			if (args[argidx] == "-keepdc") {
+				keepdc = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
@@ -211,7 +219,10 @@ struct SynthPass : public ScriptPass
 			run("opt_clean");
 			run("check");
 			run("opt");
-			run("wreduce");
+			if (help_mode)
+				run("wreduce [-keepdc]");
+			else
+				run("wreduce" + std::string(keepdc ? " -keepdc" : ""));
 			run("peepopt");
 			run("opt_clean");
 			if (help_mode)
-- 
2.30.2