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[X86] getX86MaskVec - replace mask limit from NumElts < 8 with NumElts <= 4 

As noted on PR46885, the number of mask elements should always be a power of 2, so to fix the static analyzer warning we are better off replacing the condition to <= 4, and I've added a pow2 assertion as well.
This commit is contained in:
Simon Pilgrim 2020-08-06 11:46:19 +01:00
parent 87c5437afd
commit 807467009d
1 changed files with 6 additions and 6 deletions
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12
llvm/lib/IR/AutoUpgrade.cpp
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@ -966,19 +966,19 @@ static Value *UpgradeX86PSRLDQIntrinsics(IRBuilder<> &Builder, Value *Op,
static Value *getX86MaskVec(IRBuilder<> &Builder, Value *Mask, static Value *getX86MaskVec(IRBuilder<> &Builder, Value *Mask,
unsigned NumElts) { unsigned NumElts) {
assert(isPowerOf2_32(NumElts) && "Expected power-of-2 mask elements");
llvm::VectorType *MaskTy = FixedVectorType::get( llvm::VectorType *MaskTy = FixedVectorType::get(
Builder.getInt1Ty(), cast<IntegerType>(Mask->getType())->getBitWidth()); Builder.getInt1Ty(), cast<IntegerType>(Mask->getType())->getBitWidth());
Mask = Builder.CreateBitCast(Mask, MaskTy); Mask = Builder.CreateBitCast(Mask, MaskTy);
// If we have less than 8 elements, then the starting mask was an i8 and // If we have less than 8 elements (1, 2 or 4), then the starting mask was an
// we need to extract down to the right number of elements. // i8 and we need to extract down to the right number of elements.
if (NumElts < 8) { if (NumElts <= 4) {
int Indices[4]; int Indices[4];
for (unsigned i = 0; i != NumElts; ++i) for (unsigned i = 0; i != NumElts; ++i)
Indices[i] = i; Indices[i] = i;
Mask = Builder.CreateShuffleVector(Mask, Mask, Mask = Builder.CreateShuffleVector(
makeArrayRef(Indices, NumElts), Mask, Mask, makeArrayRef(Indices, NumElts), "extract");
"extract");
} }
return Mask; return Mask;