commit ce5f93efd55285bf4ab1adcd9511973213e03982
author Duncan P. N. Exon Smith <dexonsmith@apple.com> Fri Dec 06 21:48:36 2013 +0000
committer Duncan P. N. Exon Smith <dexonsmith@apple.com> Fri Dec 06 21:48:36 2013 +0000
tree 27ef2044480087ce965429ab65daa93cbf40ea97
parent 3dedae12b5453757055857e83a1f2624bf08d914

Don't use isNullValue to evaluate ConstantExpr

ConstantExpr can evaluate to false even when isNullValue gives false.

Fixes PR18143.

llvm-svn: 196611

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 27f1a3eb..191a101 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -699,7 +699,10 @@
       Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB);
       Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB);
       Value *InV = 0;
-      if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
+      // Beware of ConstantExpr:  it may eventually evaluate to getNullValue,
+      // even if currently isNullValue gives false.
+      Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i));
+      if (InC && !isa<ConstantExpr>(InC))
         InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
       else
         InV = Builder->CreateSelect(PN->getIncomingValue(i),