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InstructionSimplify: Simplify a shuffle with a undef mask to undef

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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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301764 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zvi Rackover 2017-04-30 06:06:26 +00:00
parent 258bb897bd
commit 778f5177f0
2 changed files with 11 additions and 0 deletions
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3
lib/Analysis/InstructionSimplify.cpp
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@ -4049,6 +4049,9 @@ static Value *foldIdentityShuffles(int DestElt, Value *Op0, Value *Op1,
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();

8
test/Transforms/InstSimplify/shufflevector.ll
View File

@ -118,6 +118,14 @@ define <4 x i32> @undef_mask(<4 x i32> %x) {
ret <4 x i32> %shuf
}
define <4 x i32> @undef_mask_1(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @undef_mask_1(
; CHECK-NEXT: ret <4 x i32> undef
;
%shuf = shufflevector <4 x i32> %x, <4 x i32> %y, <4 x i32> undef
ret <4 x i32> %shuf
}
define <4 x i32> @identity_mask_0(<4 x i32> %x) {
; CHECK-LABEL: @identity_mask_0(
; CHECK-NEXT: ret <4 x i32> [[X:%.*]]