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[VectorCombine] refactor - make helper function for extract to shuffle logic; NFC

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Preliminary for D82474
This commit is contained in:
Sanjay Patel 2020-06-29 09:47:13 -04:00
parent 876df18aec
commit 3b95d8346d
1 changed files with 45 additions and 18 deletions
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63
llvm/lib/Transforms/Vectorize/VectorCombine.cpp
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@ -63,6 +63,9 @@ private:
const TargetTransformInfo &TTI;
const DominatorTree &DT;
ExtractElementInst *getShuffleExtract(ExtractElementInst *Ext0,
ExtractElementInst *Ext1,
unsigned PreferredExtractIndex) const;
bool isExtractExtractCheap(ExtractElementInst *Ext0, ExtractElementInst *Ext1,
unsigned Opcode,
ExtractElementInst *&ConvertToShuffle,
@ -81,6 +84,46 @@ static void replaceValue(Value &Old, Value &New) {
New.takeName(&Old);
}
/// Determine which, if any, of the inputs should be replaced by a shuffle
/// followed by extract from a different index.
ExtractElementInst *VectorCombine::getShuffleExtract(
ExtractElementInst *Ext0, ExtractElementInst *Ext1,
unsigned PreferredExtractIndex = InvalidIndex) const {
assert(isa<ConstantInt>(Ext0->getIndexOperand()) &&
isa<ConstantInt>(Ext1->getIndexOperand()) &&
"Expected constant extract indexes");
unsigned Index0 = cast<ConstantInt>(Ext0->getIndexOperand())->getZExtValue();
unsigned Index1 = cast<ConstantInt>(Ext1->getIndexOperand())->getZExtValue();
// If the extract indexes are identical, no shuffle is needed.
if (Index0 == Index1)
return nullptr;
Type *VecTy = Ext0->getVectorOperand()->getType();
assert(VecTy == Ext1->getVectorOperand()->getType() && "Need matching types");
int Cost0 = TTI.getVectorInstrCost(Ext0->getOpcode(), VecTy, Index0);
int Cost1 = TTI.getVectorInstrCost(Ext1->getOpcode(), VecTy, Index1);
// We are extracting from 2 different indexes, so one operand must be shuffled
// before performing a vector operation and/or extract. The more expensive
// extract will be replaced by a shuffle.
if (Cost0 > Cost1)
return Ext0;
if (Cost1 > Cost0)
return Ext1;
// If the costs are equal and there is a preferred extract index, shuffle the
// opposite operand.
if (PreferredExtractIndex == Index0)
return Ext1;
if (PreferredExtractIndex == Index1)
return Ext0;
// Otherwise, replace the extract with the higher index.
return Index0 > Index1 ? Ext0 : Ext1;
}
/// Compare the relative costs of 2 extracts followed by scalar operation vs.
/// vector operation(s) followed by extract. Return true if the existing
/// instructions are cheaper than a vector alternative. Otherwise, return false
@ -152,10 +195,8 @@ bool VectorCombine::isExtractExtractCheap(ExtractElementInst *Ext0,
!Ext1->hasOneUse() * Extract1Cost;
}
if (Ext0Index == Ext1Index) {
// If the extract indexes are identical, no shuffle is needed.
ConvertToShuffle = nullptr;
} else {
ConvertToShuffle = getShuffleExtract(Ext0, Ext1, PreferredExtractIndex);
if (ConvertToShuffle) {
if (IsBinOp && DisableBinopExtractShuffle)
return true;
@ -168,20 +209,6 @@ bool VectorCombine::isExtractExtractCheap(ExtractElementInst *Ext0,
// (splat-from-element-0), but no option for a more general splat.
NewCost +=
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteSingleSrc, VecTy);
// The more expensive extract will be replaced by a shuffle. If the costs
// are equal and there is a preferred extract index, shuffle the opposite
// operand. Otherwise, replace the extract with the higher index.
if (Extract0Cost > Extract1Cost)
ConvertToShuffle = Ext0;
else if (Extract1Cost > Extract0Cost)
ConvertToShuffle = Ext1;
else if (PreferredExtractIndex == Ext0Index)
ConvertToShuffle = Ext1;
else if (PreferredExtractIndex == Ext1Index)
ConvertToShuffle = Ext0;
else
ConvertToShuffle = Ext0Index > Ext1Index ? Ext0 : Ext1;
}
// Aggressively form a vector op if the cost is equal because the transform