From bd39263796fdf4f1c747a4a8449a0a484fdb3026 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sat, 28 Dec 2013 10:30:31 +0100
Subject: [PATCH] Improved $_MUX_ handling in opt_const

---
 passes/opt/opt_const.cc | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/passes/opt/opt_const.cc b/passes/opt/opt_const.cc
index 84285567e..0ead97b4e 100644
--- a/passes/opt/opt_const.cc
+++ b/passes/opt/opt_const.cc
@@ -17,8 +17,6 @@
  *
  */
 
-#undef MUX_UNDEF_SEL_TO_UNDEF_RESULTS
-
 #include "opt_status.h"
 #include "kernel/register.h"
 #include "kernel/sigtools.h"
@@ -133,15 +131,16 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				ACTION_DO("\\Y", input.extract(2, 1));
 			if (input.match("  0")) ACTION_DO("\\Y", input.extract(2, 1));
 			if (input.match("  1")) ACTION_DO("\\Y", input.extract(1, 1));
-#ifdef MUX_UNDEF_SEL_TO_UNDEF_RESULTS
 			if (input.match("01 ")) ACTION_DO("\\Y", input.extract(0, 1));
-			// TODO: "10 " -> replace with "!S" gate
-			// TODO: "0  " -> replace with "B AND S" gate
-			// TODO: " 1 " -> replace with "A OR S" gate
-			// TODO: "1  " -> replace with "B OR !S" gate (?)
-			// TODO: " 0 " -> replace with "A AND !S" gate (?)
-			if (input.match("  *")) ACTION_DO_Y(x);
-#endif
+			if (input.match("10 ")) {
+				cell->type = "$_INV_";
+				cell->connections["\\A"] = input.extract(0, 1);
+				cell->connections.erase("\\B");
+				cell->connections.erase("\\S");
+				goto next_cell;
+			}
+			if (input.match("01*")) ACTION_DO_Y(x);
+			if (input.match("10*")) ACTION_DO_Y(x);
 		}
 
 		if (cell->type == "$eq" || cell->type == "$ne" || cell->type == "$eqx" || cell->type == "$nex")
-- 
2.30.2