From 9a94d557381177c0c7f9059d3189466bd6ec0608 Mon Sep 17 00:00:00 2001
From: Cary R <cygcary@yahoo.com>
Date: Sun, 21 Mar 2010 22:00:44 -0700
Subject: [PATCH] Ignore zero replication constants.

This patch enhances elaboration to drop/ignore zero replication
count constants. Not doing this was causing problems later in
the compiler. We still pass non-constant expressions since
both user and system functions must be run for their possible
side effects. Constants can never have a side effect so just
dropping them is acceptable.
---
 elab_expr.cc        | 25 ++++++++++++++++++++-----
 tgt-vvp/eval_expr.c |  2 +-
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/elab_expr.cc b/elab_expr.cc
index eee54849a..e277154f3 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -1686,11 +1686,9 @@ NetExpr* PEConcat::elaborate_expr(Design*des, NetScope*scope,
 	    repeat = rep;
       }
 
-	/* Make the empty concat expression. */
-      NetEConcat*tmp = new NetEConcat(parms_.count(), repeat);
-      tmp->set_line(*this);
-
       unsigned wid_sum = 0;
+      unsigned parm_cnt = 0;
+      svector<NetExpr*> parms(parms_.count());
 
 	/* Elaborate all the parameters and attach them to the concat node. */
       for (unsigned idx = 0 ;  idx < parms_.count() ;  idx += 1) {
@@ -1724,8 +1722,25 @@ NetExpr* PEConcat::elaborate_expr(Design*des, NetScope*scope,
 		  continue;
 	    }
 
+	      /* We are going to ignore zero width constants. */
+	    if ((ex->expr_width() == 0) && dynamic_cast<NetEConst*>(ex)) {
+		  parms[idx] = 0;
+	    } else {
+		  parms[idx] = ex;
+		  parm_cnt += 1;
+	    }
 	    wid_sum += ex->expr_width();
-	    tmp->set(idx, ex);
+      }
+
+	/* Make the empty concat expression. */
+      NetEConcat*tmp = new NetEConcat(parm_cnt, repeat);
+      tmp->set_line(*this);
+
+	/* Remove any zero width constants. */
+      unsigned off = 0;
+      for (unsigned idx = 0 ;  idx < parm_cnt ;  idx += 1) {
+	    while (parms[off+idx] == 0) off += 1;
+	    tmp->set(idx, parms[off+idx]);
       }
 
       tmp->set_width(wid_sum * tmp->repeat());
diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index 84449a883..b696c9d84 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -3134,7 +3134,7 @@ static void draw_eval_expr_dest(ivl_expr_t exp, struct vector_info dest,
 	    break;
       }
 
-	/* Fallback, is to draw the expression by width, and mov it to
+	/* Fallback, is to draw the expression by width, and move it to
 	   the required dest. */
       tmp = draw_eval_expr_wid(exp, dest.wid, stuff_ok_flag);
       assert(tmp.wid == dest.wid);