[InstCombine] fix undef propagation for vector urem transform (PR44186)
As described here:
https://bugs.llvm.org/show_bug.cgi?id=44186
The match() code safely allows undef values, but we can't safely
propagate a vector constant that contains an undef to the new
compare instruction.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 0b9128a..f7b39d9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1368,8 +1368,10 @@
}
// 1 urem X -> zext(X != 1)
- if (match(Op0, m_One()))
- return CastInst::CreateZExtOrBitCast(Builder.CreateICmpNE(Op1, Op0), Ty);
+ if (match(Op0, m_One())) {
+ Value *Cmp = Builder.CreateICmpNE(Op1, ConstantInt::get(Ty, 1));
+ return CastInst::CreateZExtOrBitCast(Cmp, Ty);
+ }
// X urem C -> X < C ? X : X - C, where C >= signbit.
if (match(Op1, m_Negative())) {