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[VectorCombine] New folding pattern for extract/binop/shuffle chains #145232

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[VectorCombine] New folding pattern for extract/binop/shuffle chains #145232

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169 changes: 169 additions & 0 deletions llvm/lib/Transforms/Vectorize/VectorCombine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,7 @@ class VectorCombine {
bool foldShuffleOfIntrinsics(Instruction &I);
bool foldShuffleToIdentity(Instruction &I);
bool foldShuffleFromReductions(Instruction &I);
bool foldShuffleChainsToReduce(Instruction &I);
bool foldCastFromReductions(Instruction &I);
bool foldSelectShuffle(Instruction &I, bool FromReduction = false);
bool foldInterleaveIntrinsics(Instruction &I);
Expand Down Expand Up @@ -2910,6 +2911,171 @@ bool VectorCombine::foldShuffleFromReductions(Instruction &I) {
return foldSelectShuffle(*Shuffle, true);
}

bool VectorCombine::foldShuffleChainsToReduce(Instruction &I) {
auto *EEI = dyn_cast<ExtractElementInst>(&I);
if (!EEI)
return false;

std::queue<Value *> InstWorklist;
Value *InitEEV = nullptr;
Intrinsic::ID CommonOp = 0;

bool IsFirstEEInst = true, IsFirstCallInst = true;
bool ShouldBeCallInst = true;

SmallVector<Value *, 3> PrevVecV(3, nullptr);
int64_t ShuffleMaskHalf = -1, ExpectedShuffleMaskHalf = 1;
int64_t VecSize = -1;

InstWorklist.push(EEI);

while (!InstWorklist.empty()) {
Value *V = InstWorklist.front();
InstWorklist.pop();

auto *CI = dyn_cast<Instruction>(V);
if (!CI)
return false;

if (auto *EEInst = dyn_cast<ExtractElementInst>(CI)) {
if (!IsFirstEEInst)
return false;
IsFirstEEInst = false;

auto *VecOp = EEInst->getVectorOperand();
if (!VecOp)
return false;

auto *FVT = dyn_cast<FixedVectorType>(VecOp->getType());
if (!FVT)
return false;

VecSize = FVT->getNumElements();
if (VecSize < 2 || VecSize % 2 != 0)
return false;

auto *IndexOp = EEInst->getIndexOperand();
if (!IndexOp)
return false;

auto *ConstIndex = dyn_cast<ConstantInt>(IndexOp);
if (ConstIndex->getValue() != 0)
return false;

ShuffleMaskHalf = 1;
PrevVecV[2] = VecOp;
InitEEV = EEInst;
InstWorklist.push(PrevVecV[2]);
} else if (auto *CallI = dyn_cast<CallInst>(CI)) {
if (IsFirstEEInst || !ShouldBeCallInst || !PrevVecV[2])
return false;

if (!IsFirstCallInst &&
any_of(PrevVecV, [](Value *VecV) { return VecV == nullptr; }))
return false;

if (CallI != (IsFirstCallInst ? PrevVecV[2] : PrevVecV[0]))
return false;
IsFirstCallInst = false;

auto *II = dyn_cast<IntrinsicInst>(CallI);
if (!II)
return false;

if (!CommonOp)
CommonOp = II->getIntrinsicID();
if (II->getIntrinsicID() != CommonOp)
return false;

switch (II->getIntrinsicID()) {
case Intrinsic::umin:
case Intrinsic::umax:
case Intrinsic::smin:
case Intrinsic::smax: {
auto *Op0 = CallI->getOperand(0);
auto *Op1 = CallI->getOperand(1);
PrevVecV[0] = Op0;
PrevVecV[1] = Op1;
break;
}
default:
return false;
}
ShouldBeCallInst ^= 1;

if (!isa<ShuffleVectorInst>(PrevVecV[1]))
std::swap(PrevVecV[0], PrevVecV[1]);
InstWorklist.push(PrevVecV[1]);
InstWorklist.push(PrevVecV[0]);
} else if (auto *SVInst = dyn_cast<ShuffleVectorInst>(CI)) {
if (IsFirstEEInst || ShouldBeCallInst ||
any_of(PrevVecV, [](Value *VecV) { return VecV == nullptr; }))
return false;

if (SVInst != PrevVecV[1])
return false;

auto *ShuffleVec = SVInst->getOperand(0);
if (!ShuffleVec || ShuffleVec != PrevVecV[0])
return false;

SmallVector<int> CurMask;
SVInst->getShuffleMask(CurMask);

if (ShuffleMaskHalf != ExpectedShuffleMaskHalf)
return false;
ExpectedShuffleMaskHalf *= 2;

for (int Mask = 0, MaskSize = CurMask.size(); Mask != MaskSize; ++Mask) {
if (Mask < ShuffleMaskHalf && CurMask[Mask] != ShuffleMaskHalf + Mask)
return false;
if (Mask >= ShuffleMaskHalf && CurMask[Mask] != -1)
return false;
}
ShuffleMaskHalf *= 2;
if (ExpectedShuffleMaskHalf == VecSize)
break;
ShouldBeCallInst ^= 1;
} else {
return false;
}
}

if (IsFirstEEInst || ShouldBeCallInst)
return false;

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You need to compare costs - for VectorCombine its expected that a fold only occurs if there is a cost benefit.

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Yeah, will do this.

assert(VecSize != -1 && ExpectedShuffleMaskHalf == VecSize &&
"Expected Match for Vector Size and Mask Half");

Value *FinalVecV = PrevVecV[0];
if (!InitEEV || !FinalVecV)
return false;

Intrinsic::ID ReducedOp = 0;
switch (CommonOp) {
case Intrinsic::umin:
ReducedOp = Intrinsic::vector_reduce_umin;
break;
case Intrinsic::umax:
ReducedOp = Intrinsic::vector_reduce_umax;
break;
case Intrinsic::smin:
ReducedOp = Intrinsic::vector_reduce_smin;
break;
case Intrinsic::smax:
ReducedOp = Intrinsic::vector_reduce_smax;
break;
default:
return false;
}

auto *ReducedResult =
Builder.CreateIntrinsic(ReducedOp, {FinalVecV->getType()}, {FinalVecV});
replaceValue(*InitEEV, *ReducedResult);

return true;
}

/// Determine if its more efficient to fold:
/// reduce(trunc(x)) -> trunc(reduce(x)).
/// reduce(sext(x)) -> sext(reduce(x)).
Expand Down Expand Up @@ -3621,6 +3787,9 @@ bool VectorCombine::run() {
MadeChange |= foldShuffleFromReductions(I);
MadeChange |= foldCastFromReductions(I);
break;
case Instruction::ExtractElement:
MadeChange |= foldShuffleChainsToReduce(I);
break;
case Instruction::ICmp:
case Instruction::FCmp:
MadeChange |= foldExtractExtract(I);
Expand Down
18 changes: 18 additions & 0 deletions llvm/test/Transforms/VectorCombine/fold-shuffle-chains-to-reduce.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -passes=vector-combine -S | FileCheck %s

define i16 @test_reduce_v8i16(<8 x i16> %a0) local_unnamed_addr #0 {
; CHECK-LABEL: define i16 @test_reduce_v8i16(
; CHECK-SAME: <8 x i16> [[A0:%.*]]) local_unnamed_addr {
; CHECK-NEXT: [[TMP1:%.*]] = call i16 @llvm.vector.reduce.umin.v8i16(<8 x i16> [[A0]])
; CHECK-NEXT: ret i16 [[TMP1]]
;
%1 = shufflevector <8 x i16> %a0, <8 x i16> poison, <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 poison, i32 poison, i32 poison, i32 poison>
%2 = tail call <8 x i16> @llvm.umin.v8i16(<8 x i16> %a0, <8 x i16> %1)
%3 = shufflevector <8 x i16> %2, <8 x i16> poison, <8 x i32> <i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
%4 = tail call <8 x i16> @llvm.umin.v8i16(<8 x i16> %2, <8 x i16> %3)
%5 = shufflevector <8 x i16> %4, <8 x i16> poison, <8 x i32> <i32 1, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
%6 = tail call <8 x i16> @llvm.umin.v8i16(<8 x i16> %4, <8 x i16> %5)
%7 = extractelement <8 x i16> %6, i64 0
ret i16 %7
}
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