fix incorrect folding of icmp with undef, PR6481.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97659 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 1f8053a..8288e96 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -194,11 +194,10 @@
const Type *ITy = GetCompareTy(LHS);
// icmp X, X -> true/false
- if (LHS == RHS)
+ // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false
+ // because X could be 0.
+ if (LHS == RHS || isa<UndefValue>(RHS))
return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
-
- if (isa<UndefValue>(RHS)) // X icmp undef -> undef
- return UndefValue::get(ITy);
// icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
// addresses never equal each other! We already know that Op0 != Op1.