From c1c4d8c86328fa378da5d8d306b2ec701768667a Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Fri, 11 Mar 2016 17:32:12 +0000
Subject: [PATCH] Fix bitmask merging in synthesis.

A conditional clause that doesn't drive any bits of a particular nexus
should not affect the bitmask generated for that nexus. The completely
undriven case is handled by the enable signal.
---
 synth2.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/synth2.cc b/synth2.cc
index b30b7576c..9dff45a0f 100644
--- a/synth2.cc
+++ b/synth2.cc
@@ -165,10 +165,10 @@ static void merge_sequential_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub
 
 static void merge_parallel_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub_mask)
 {
-      if (top_mask.size() == 0)
+      if (sub_mask.size() == 0)
 	    return;
 
-      if (sub_mask.size() == 0) {
+      if (top_mask.size() == 0) {
 	    top_mask = sub_mask;
 	    return;
       }