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[InstCombine][AVX-512] When turning intrinsics with masking into native IR, don't emit a select if the mask is known to be all ones.

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This saves InstCombine the burden of having to optimize the select later.

llvm-svn: 290774
This commit is contained in:
Craig Topper 2016-12-30 23:06:28 +00:00
parent 7ad03af461
commit 037f3207df
1 changed files with 20 additions and 9 deletions
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29
lib/Transforms/InstCombine/InstCombineCalls.cpp
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@ -1038,13 +1038,20 @@ static Value *simplifyX86vpcom(const IntrinsicInst &II,
// masked intrinsics.
static Value *emitX86MaskSelect(Value *Mask, Value *Op0, Value *Op1,
InstCombiner::BuilderTy &Builder) {
unsigned VWidth = Op0->getType()->getVectorNumElements();
// If the mask is all ones we don't need the select. But we need to check
// only the bit thats will be used in case VWidth is less than 8.
if (auto *C = dyn_cast<ConstantInt>(Mask))
if (C->getValue().zextOrTrunc(VWidth).isAllOnesValue())
return Op0;
auto *MaskTy = VectorType::get(Builder.getInt1Ty(),
cast<IntegerType>(Mask->getType())->getBitWidth());
Mask = Builder.CreateBitCast(Mask, MaskTy);
// If we have less than 8 elements, then the starting mask was an i8 and
// we need to extract down to the right number of elements.
unsigned VWidth = Op0->getType()->getVectorNumElements();
if (VWidth < 8) {
uint32_t Indices[4];
for (unsigned i = 0; i != VWidth; ++i)
@ -1873,16 +1880,20 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
}
// Handle the masking aspect of the intrinsic.
// Cast the mask to an i1 vector and then extract the lowest element.
Value *Mask = II->getArgOperand(3);
auto *MaskTy = VectorType::get(Builder->getInt1Ty(),
auto *C = dyn_cast<ConstantInt>(Mask);
// We don't need a select if we know the mask bit is a 1.
if (!C || !C->getValue()[0]) {
// Cast the mask to an i1 vector and then extract the lowest element.
auto *MaskTy = VectorType::get(Builder->getInt1Ty(),
cast<IntegerType>(Mask->getType())->getBitWidth());
Mask = Builder->CreateBitCast(Mask, MaskTy);
Mask = Builder->CreateExtractElement(Mask, (uint64_t)0);
// Extract the lowest element from the passthru operand.
Value *Passthru = Builder->CreateExtractElement(II->getArgOperand(2),
(uint64_t)0);
V = Builder->CreateSelect(Mask, V, Passthru);
Mask = Builder->CreateBitCast(Mask, MaskTy);
Mask = Builder->CreateExtractElement(Mask, (uint64_t)0);
// Extract the lowest element from the passthru operand.
Value *Passthru = Builder->CreateExtractElement(II->getArgOperand(2),
(uint64_t)0);
V = Builder->CreateSelect(Mask, V, Passthru);
}
// Insert the result back into the original argument 0.
V = Builder->CreateInsertElement(Arg0, V, (uint64_t)0);