From: Duncan Sands <baldrick@free.fr>
Date: Wed, 19 Sep 2007 10:16:17 +0000 (+0000)
Subject: Partial fix for PR1678: correct some parts of constant
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=780164433250ebc6f42671f5fdd259db14d71c0e;p=oota-llvm.git

Partial fix for PR1678: correct some parts of constant
fold that were missed in the fix for PR1646.  Probably
this null/not-null logic should be factorized somewhere.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42131 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 5c80a377ba7..a61dd06ff1f 100644
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -1124,7 +1124,8 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
   // icmp eq/ne(null,GV) -> false/true
   if (C1->isNullValue()) {
     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
-      if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
+      // Don't try to evaluate aliases.  External weak GV can be null.
+      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
         if (pred == ICmpInst::ICMP_EQ)
           return ConstantInt::getFalse();
         else if (pred == ICmpInst::ICMP_NE)
@@ -1132,7 +1133,8 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
   // icmp eq/ne(GV,null) -> false/true
   } else if (C2->isNullValue()) {
     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
-      if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
+      // Don't try to evaluate aliases.  External weak GV can be null.
+      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
         if (pred == ICmpInst::ICMP_EQ)
           return ConstantInt::getFalse();
         else if (pred == ICmpInst::ICMP_NE)