InstSimplify: If divisor element is undef simplify to undef
Summary:
If any vector divisor element is undef, we can arbitrarily choose it be
zero which would make the div/rem an undef value by definition.
Reviewers: spatel, reames
Reviewed By: spatel
Subscribers: magabari, llvm-commits
Differential Revision: https://reviews.llvm.org/D42485
llvm-svn: 323343
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 245133f..a258c4d 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -868,13 +868,14 @@
if (match(Op1, m_Zero()))
return UndefValue::get(Ty);
- // If any element of a constant divisor vector is zero, the whole op is undef.
+ // If any element of a constant divisor vector is zero or undef, the whole op
+ // is undef.
auto *Op1C = dyn_cast<Constant>(Op1);
if (Op1C && Ty->isVectorTy()) {
unsigned NumElts = Ty->getVectorNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *Elt = Op1C->getAggregateElement(i);
- if (Elt && Elt->isNullValue())
+ if (Elt && (Elt->isNullValue() || isa<UndefValue>(Elt)))
return UndefValue::get(Ty);
}
}