From: Chris Lattner <sabre@nondot.org>
Date: Fri, 17 Jun 2005 01:45:53 +0000 (+0000)
Subject: Don't crash on:  X = phi (X, X).
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=0289929c6212229980c9057853860ccfd3f81678;p=oota-llvm.git

Don't crash on:  X = phi (X, X).

This fixes PR584 and Transforms/SimplifyCFG/2005-06-16-PHICrash.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22232 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index ad78506ad42..6a3b803cbdb 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1461,12 +1461,15 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
         BasicBlock::iterator AfterPHIIt = BB->begin();
         while (isa<PHINode>(AfterPHIIt)) {
           PHINode *PN = cast<PHINode>(AfterPHIIt++);
-          if (PN->getIncomingValue(0) == PN->getIncomingValue(1))
-            PN->replaceAllUsesWith(PN->getIncomingValue(0));
-          else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
-                                        &AggressiveInsts) ||
-                   !DominatesMergePoint(PN->getIncomingValue(1), BB,
-                                        &AggressiveInsts)) {
+          if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
+            if (PN->getIncomingValue(0) != PN)
+              PN->replaceAllUsesWith(PN->getIncomingValue(0));
+            else
+              PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+          } else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
+                                          &AggressiveInsts) ||
+                     !DominatesMergePoint(PN->getIncomingValue(1), BB,
+                                          &AggressiveInsts)) {
             CanPromote = false;
             break;
           }