InstSimplify: A shuffle of a splat is always the splat itself
Summary:
Fold:
shuffle (splat-shuffle), undef, M --> splat-shuffle
Reviewers: spatel, RKSimon, craig.topper
Reviewed By: RKSimon
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D31527
llvm-svn: 299990
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 807bbd2..0e522cb 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4085,8 +4085,9 @@
static Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
Type *RetTy, const Query &Q,
unsigned MaxRecurse) {
+ Type *InVecTy = Op0->getType();
unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
- unsigned InVecNumElts = Op0->getType()->getVectorNumElements();
+ unsigned InVecNumElts = InVecTy->getVectorNumElements();
auto *Op0Const = dyn_cast<Constant>(Op0);
auto *Op1Const = dyn_cast<Constant>(Op1);
@@ -4108,11 +4109,22 @@
MaskSelects1 = true;
}
if (!MaskSelects0 && Op1Const)
- return ConstantFoldShuffleVectorInstruction(UndefValue::get(Op0->getType()),
+ return ConstantFoldShuffleVectorInstruction(UndefValue::get(InVecTy),
Op1Const, Mask);
if (!MaskSelects1 && Op0Const)
- return ConstantFoldShuffleVectorInstruction(
- Op0Const, UndefValue::get(Op0->getType()), Mask);
+ return ConstantFoldShuffleVectorInstruction(Op0Const,
+ UndefValue::get(InVecTy), Mask);
+
+ // A shuffle of a splat is always the splat itself. Legal if the shuffle's
+ // value type is same as the input vectors' type.
+ if (auto *OpShuf = dyn_cast<ShuffleVectorInst>(Op0))
+ if (!MaskSelects1 && RetTy == InVecTy &&
+ OpShuf->getMask()->getSplatValue())
+ return Op0;
+ if (auto *OpShuf = dyn_cast<ShuffleVectorInst>(Op1))
+ if (!MaskSelects0 && RetTy == InVecTy &&
+ OpShuf->getMask()->getSplatValue())
+ return Op1;
return nullptr;
}