From da04e4d3837e57f1bbab6a516a0d73b21176cae3 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 22 Jan 2004 16:31:08 +0000
Subject: [PATCH] Bug fix:  X.mergeWith(Y) was not updating Y if Y  was a null
 node handle!

llvm-svn: 10953
---
 lib/Analysis/DataStructure/DataStructure.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/Analysis/DataStructure/DataStructure.cpp b/lib/Analysis/DataStructure/DataStructure.cpp
index caabff8d19c..043579c72f5 100644
--- a/lib/Analysis/DataStructure/DataStructure.cpp
+++ b/lib/Analysis/DataStructure/DataStructure.cpp
@@ -679,13 +679,20 @@ void DSNode::MergeNodes(DSNodeHandle& CurNodeH, DSNodeHandle& NH) {
 // Offset indicates what offset the specified node is to be merged into the
 // current node.
 //
-// The specified node may be a null pointer (in which case, nothing happens).
+// The specified node may be a null pointer (in which case, we update it to
+// point to this node).
 //
 void DSNode::mergeWith(const DSNodeHandle &NH, unsigned Offset) {
   DSNode *N = NH.getNode();
-  if (N == 0 || (N == this && NH.getOffset() == Offset))
+  if (N == this && NH.getOffset() == Offset)
     return;  // Noop
 
+  // If the RHS is a null node, make it point to this node!
+  if (N == 0) {
+    NH.mergeWith(DSNodeHandle(this, Offset));
+    return;
+  }
+
   assert(!N->isDeadNode() && !isDeadNode());
   assert(!hasNoReferrers() && "Should not try to fold a useless node!");