InstructionSimplify: Simplify a shuffle with a undef mask to undef
Summary:
Following the discussion in pr32486, adding the simplification:
shuffle %x, %y, undef -> undef
Reviewers: spatel, RKSimon, andreadb, davide
Reviewed By: spatel
Subscribers: jroelofs, davide, llvm-commits
Differential Revision: https://reviews.llvm.org/D32293
llvm-svn: 301764
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8003820..d753c47 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4049,6 +4049,9 @@
static Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
Type *RetTy, const SimplifyQuery &Q,
unsigned MaxRecurse) {
+ if (isa<UndefValue>(Mask))
+ return UndefValue::get(RetTy);
+
Type *InVecTy = Op0->getType();
unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
unsigned InVecNumElts = InVecTy->getVectorNumElements();