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[ConstantFold][SVE] Fix constant folding for shufflevector.

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Don't try to fold away shuffles which can't be folded.  Fix creation of
shufflevector constant expressions.

Differential Revision: https://reviews.llvm.org/D71147
This commit is contained in:
Eli Friedman 2019-12-06 12:33:46 -08:00
parent abfb9e7ee2
commit 2cf4b388e8
4 changed files with 19 additions and 2 deletions
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6
lib/IR/ConstantFold.cpp
View File

@ -873,6 +873,12 @@ Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
// Don't break the bitcode reader hack.
if (isa<ConstantExpr>(Mask)) return nullptr;
// Do not iterate on scalable vector. The num of elements is unknown at
// compile-time.
VectorType *ValTy = cast<VectorType>(V1->getType());
if (ValTy->isScalable())
return nullptr;
unsigned SrcNumElts = V1->getType()->getVectorNumElements();
// Loop over the shuffle mask, evaluating each element.

2
lib/IR/Constants.cpp
View File

@ -2211,7 +2211,7 @@ Constant *ConstantExpr::getShuffleVector(Constant *V1, Constant *V2,
if (Constant *FC = ConstantFoldShuffleVectorInstruction(V1, V2, Mask))
return FC; // Fold a few common cases.
unsigned NElts = Mask->getType()->getVectorNumElements();
ElementCount NElts = Mask->getType()->getVectorElementCount();
Type *EltTy = V1->getType()->getVectorElementType();
Type *ShufTy = VectorType::get(EltTy, NElts);

2
lib/IR/ConstantsContext.h
View File

@ -149,7 +149,7 @@ public:
ShuffleVectorConstantExpr(Constant *C1, Constant *C2, Constant *C3)
: ConstantExpr(VectorType::get(
cast<VectorType>(C1->getType())->getElementType(),
cast<VectorType>(C3->getType())->getNumElements()),
cast<VectorType>(C3->getType())->getElementCount()),
Instruction::ShuffleVector,
&Op<0>(), 3) {
Op<0>() = C1;

11
test/Analysis/ConstantFolding/shufflevector.ll Normal file
View File

@ -0,0 +1,11 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -constprop -S | FileCheck %s
define <vscale x 4 x i32> @shufflevector_scalable_constant() {
; CHECK-LABEL: @shufflevector_scalable_constant(
; CHECK-NEXT: ret <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 1, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer)
;
%i = insertelement <vscale x 4 x i32> undef, i32 1, i32 0
%i2 = shufflevector <vscale x 4 x i32> %i, <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer
ret <vscale x 4 x i32> %i2
}