From d2106a3d3ac49d6aa914a7f6afa78c3ac5ecc009 Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Fri, 23 May 2008 10:29:44 -0700
Subject: [PATCH] Fix botched processing of MUX with constant select.

If the select input was constant, the code then tried to look at the
constant data input. Just plain wrong.
---
 compiler.h | 1 +
 cprop.cc   | 8 +++++++-
 main.cc    | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/compiler.h b/compiler.h
index 6b654e6e2..2b38802be 100644
--- a/compiler.h
+++ b/compiler.h
@@ -86,6 +86,7 @@ extern bool debug_scopes;
 extern bool debug_eval_tree;
 extern bool debug_elaborate;
 extern bool debug_synth2;
+extern bool debug_optimizer;
 
 /* Path to a directory useful for finding subcomponents. */
 extern const char*basedir;
diff --git a/cprop.cc b/cprop.cc
index d216d5d25..9345b9ea8 100644
--- a/cprop.cc
+++ b/cprop.cc
@@ -23,6 +23,7 @@
 # include  "netlist.h"
 # include  "netmisc.h"
 # include  "functor.h"
+# include  "compiler.h"
 # include  "ivl_assert.h"
 
 
@@ -831,11 +832,16 @@ void cprop_functor::lpm_mux(Design*des, NetMux*obj)
 
 	/* If the select input is constant, then replace with a BUFZ */
       flag = obj->pin_Sel().nexus()->drivers_constant();
-      verinum::V sel_val = flag? obj->pin_Data(1).nexus()->driven_value() : verinum::Vx;
+      verinum::V sel_val = flag? obj->pin_Sel().nexus()->driven_value() : verinum::Vx;
       if ((sel_val != verinum::Vz) && (sel_val != verinum::Vx)) {
 	    NetBUFZ*tmp = new NetBUFZ(obj->scope(), obj->name(), obj->width());
 	    tmp->set_line(*obj);
 
+	    if (debug_optimizer)
+		  cerr << obj->get_fileline() << ": debug: "
+		       << "Replace binary MUX with constant select=" << sel_val
+		       << " with a BUFZ to the selected input." << endl;
+
 	    tmp->rise_time(obj->rise_time());
 	    tmp->fall_time(obj->fall_time());
 	    tmp->decay_time(obj->decay_time());
diff --git a/main.cc b/main.cc
index 679e321dc..640fcf4d3 100644
--- a/main.cc
+++ b/main.cc
@@ -124,6 +124,8 @@ bool debug_scopes = false;
 bool debug_eval_tree = false;
 bool debug_elaborate = false;
 bool debug_synth2 = false;
+bool debug_optimizer = false;
+
 /*
  * Verbose messages enabled.
  */
@@ -391,6 +393,9 @@ static void read_iconfig_file(const char*ipath)
 		  } else if (strcmp(cp,"synth2") == 0) {
 			debug_synth2 = true;
 			cerr << "debug: Enable synth2 debug" << endl;
+		  } else if (strcmp(cp,"optimizer") == 0) {
+			debug_optimizer = true;
+			cerr << "debug: Enable optimizer debug" << endl;
 		  } else {
 		  }