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[VectorCombine] foldPermuteOfBinops - fold "shuffle (binop (shuffle, other)), undef" --> "binop (shuffle), (shuffle)". #122118

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Merged
merged 3 commits into from
Jan 14, 2025
Merged

[VectorCombine] foldPermuteOfBinops - fold "shuffle (binop (shuffle, other)), undef" --> "binop (shuffle), (shuffle)". #122118

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7d06d49
[VectorCombine] foldPermuteOfBinops - fold "shuffle (binop (shuffle, …
RKSimon Jan 8, 2025
069da73
Merge branch 'upstream' into vectorcombine-permute-binop-single-shuffle
RKSimon Jan 13, 2025
a91da15
Skip known identity shuffles
RKSimon Jan 13, 2025
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71 changes: 43 additions & 28 deletions llvm/lib/Transforms/Vectorize/VectorCombine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1592,17 +1592,21 @@ bool VectorCombine::foldPermuteOfBinops(Instruction &I) {
if (BinOp->isIntDivRem() && llvm::is_contained(OuterMask, PoisonMaskElem))
return false;

Value *Op00, *Op01;
ArrayRef<int> Mask0;
if (!match(BinOp->getOperand(0),
m_OneUse(m_Shuffle(m_Value(Op00), m_Value(Op01), m_Mask(Mask0)))))
Value *Op00, *Op01, *Op10, *Op11;
ArrayRef<int> Mask0, Mask1;
bool Match0 =
match(BinOp->getOperand(0),
m_OneUse(m_Shuffle(m_Value(Op00), m_Value(Op01), m_Mask(Mask0))));
bool Match1 =
match(BinOp->getOperand(1),
m_OneUse(m_Shuffle(m_Value(Op10), m_Value(Op11), m_Mask(Mask1))));
if (!Match0 && !Match1)
return false;

Value *Op10, *Op11;
ArrayRef<int> Mask1;
if (!match(BinOp->getOperand(1),
m_OneUse(m_Shuffle(m_Value(Op10), m_Value(Op11), m_Mask(Mask1)))))
return false;
Op00 = Match0 ? Op00 : BinOp->getOperand(0);
Op01 = Match0 ? Op01 : BinOp->getOperand(0);
Op10 = Match1 ? Op10 : BinOp->getOperand(1);
Op11 = Match1 ? Op11 : BinOp->getOperand(1);

Instruction::BinaryOps Opcode = BinOp->getOpcode();
auto *ShuffleDstTy = dyn_cast<FixedVectorType>(I.getType());
Expand All @@ -1620,37 +1624,46 @@ bool VectorCombine::foldPermuteOfBinops(Instruction &I) {
any_of(OuterMask, [NumSrcElts](int M) { return M >= (int)NumSrcElts; }))
return false;

// Merge outer / inner shuffles.
// Merge outer / inner (or identity if no match) shuffles.
SmallVector<int> NewMask0, NewMask1;
for (int M : OuterMask) {
if (M < 0 || M >= (int)NumSrcElts) {
NewMask0.push_back(PoisonMaskElem);
NewMask1.push_back(PoisonMaskElem);
} else {
NewMask0.push_back(Mask0[M]);
NewMask1.push_back(Mask1[M]);
NewMask0.push_back(Match0 ? Mask0[M] : M);
NewMask1.push_back(Match1 ? Mask1[M] : M);
}
}

unsigned NumOpElts = Op0Ty->getNumElements();
bool IsIdentity0 = ShuffleVectorInst::isIdentityMask(NewMask0, NumOpElts);
bool IsIdentity1 = ShuffleVectorInst::isIdentityMask(NewMask1, NumOpElts);

// Try to merge shuffles across the binop if the new shuffles are not costly.
InstructionCost OldCost =
TTI.getArithmeticInstrCost(Opcode, BinOpTy, CostKind) +
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteSingleSrc, BinOpTy,
OuterMask, CostKind, 0, nullptr, {BinOp}, &I) +
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op0Ty, Mask0,
CostKind, 0, nullptr, {Op00, Op01},
cast<Instruction>(BinOp->getOperand(0))) +
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op1Ty, Mask1,
CostKind, 0, nullptr, {Op10, Op11},
cast<Instruction>(BinOp->getOperand(1)));
OuterMask, CostKind, 0, nullptr, {BinOp}, &I);
if (Match0)
OldCost += TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op0Ty,
Mask0, CostKind, 0, nullptr, {Op00, Op01},
cast<Instruction>(BinOp->getOperand(0)));
if (Match1)
OldCost += TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op1Ty,
Mask1, CostKind, 0, nullptr, {Op10, Op11},
cast<Instruction>(BinOp->getOperand(1)));
Comment on lines +1649 to +1655
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Use getInstructionCost?

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getInstructionCost is still causing some regressions for some shuffle costs - I haven't been able to get to the bottom of them all yet - but the plan is to eventually move as much of the VectorCombine OldCost calculations over to getInstructionCost as possible.


InstructionCost NewCost =
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op0Ty, NewMask0,
CostKind, 0, nullptr, {Op00, Op01}) +
TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op1Ty, NewMask1,
CostKind, 0, nullptr, {Op10, Op11}) +
TTI.getArithmeticInstrCost(Opcode, ShuffleDstTy, CostKind);

if (!IsIdentity0)
NewCost += TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op0Ty,
NewMask0, CostKind, 0, nullptr, {Op00, Op01});
if (!IsIdentity1)
NewCost += TTI.getShuffleCost(TargetTransformInfo::SK_PermuteTwoSrc, Op1Ty,
NewMask1, CostKind, 0, nullptr, {Op10, Op11});

LLVM_DEBUG(dbgs() << "Found a shuffle feeding a shuffled binop: " << I
<< "\n OldCost: " << OldCost << " vs NewCost: " << NewCost
<< "\n");
Expand All @@ -1659,16 +1672,18 @@ bool VectorCombine::foldPermuteOfBinops(Instruction &I) {
if (NewCost > OldCost)
return false;

Value *Shuf0 = Builder.CreateShuffleVector(Op00, Op01, NewMask0);
Value *Shuf1 = Builder.CreateShuffleVector(Op10, Op11, NewMask1);
Value *NewBO = Builder.CreateBinOp(Opcode, Shuf0, Shuf1);
Value *LHS =
IsIdentity0 ? Op00 : Builder.CreateShuffleVector(Op00, Op01, NewMask0);
Value *RHS =
IsIdentity1 ? Op10 : Builder.CreateShuffleVector(Op10, Op11, NewMask1);
Value *NewBO = Builder.CreateBinOp(Opcode, LHS, RHS);

// Intersect flags from the old binops.
if (auto *NewInst = dyn_cast<Instruction>(NewBO))
NewInst->copyIRFlags(BinOp);

Worklist.pushValue(Shuf0);
Worklist.pushValue(Shuf1);
Worklist.pushValue(LHS);
Worklist.pushValue(RHS);
replaceValue(I, *NewBO);
return true;
}
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