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[SLP][NFC]Simplify analysis of the scalars, NFC. #170382

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Merged
alexey-bataev merged 2 commits into from
Dec 4, 2025
Merged

[SLP][NFC]Simplify analysis of the scalars, NFC. #170382

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d9cd54a
[𝘀𝗽𝗿] initial version
alexey-bataev Dec 2, 2025
82158d6
Add assertion
alexey-bataev Dec 2, 2025
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192 changes: 92 additions & 100 deletions llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11315,44 +11315,90 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
VL, *this, TryCopyableElementsVectorization,
/*WithProfitabilityCheck=*/true, TryCopyableElementsVectorization);

bool AreScatterAllGEPSameBlock = false;
if (!S) {
SmallVector<unsigned> SortedIndices;
BasicBlock *BB = nullptr;
bool IsScatterVectorizeUserTE =
UserTreeIdx.UserTE &&
UserTreeIdx.UserTE->State == TreeEntry::ScatterVectorize;
AreScatterAllGEPSameBlock =
(IsScatterVectorizeUserTE && VL.front()->getType()->isPointerTy() &&
VL.size() > 2 &&
all_of(VL,
[&BB](Value *V) {
auto *I = dyn_cast<GetElementPtrInst>(V);
if (!I)
return doesNotNeedToBeScheduled(V);
if (!BB)
BB = I->getParent();
return BB == I->getParent() && I->getNumOperands() == 2;
}) &&
BB &&
sortPtrAccesses(VL, UserTreeIdx.UserTE->getMainOp()->getType(), *DL,
*SE, SortedIndices));
if (!AreScatterAllGEPSameBlock) {
LLVM_DEBUG(dbgs() << "SLP: Try split and if failed, gathering due to "
"C,S,B,O, small shuffle. \n";
dbgs() << "[";
interleaveComma(VL, dbgs(), [&](Value *V) { dbgs() << *V; });
dbgs() << "]\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false,
/*TryToFindDuplicates=*/true,
/*TrySplitVectorize=*/true);
}
// Reset S to make it GetElementPtr kind of node.
const auto *It = find_if(VL, IsaPred<GetElementPtrInst>);
assert(It != VL.end() && "Expected at least one GEP.");
S = getSameOpcode(*It, *TLI);
}

// Don't handle vectors.
if (!SLPReVec && getValueType(VL.front())->isVectorTy()) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to vector type.\n");
// Do not try to pack to avoid extra instructions here.
return ScalarsVectorizationLegality(S, /*IsLegal=*/false,
/*TryToFindDuplicates=*/false);
}

// Check that all of the users of the scalars that we want to vectorize are
// schedulable.
BasicBlock *BB = S.getMainOp()->getParent();

if (BB->isEHPad() || isa_and_nonnull<UnreachableInst>(BB->getTerminator()) ||
!DT->isReachableFromEntry(BB)) {
// Don't go into unreachable blocks. They may contain instructions with
// dependency cycles which confuse the final scheduling.
// Do not vectorize EH and non-returning blocks, not profitable in most
// cases.
LLVM_DEBUG(dbgs() << "SLP: bundle in unreachable block.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}

// Don't go into catchswitch blocks, which can happen with PHIs.
// Such blocks can only have PHIs and the catchswitch. There is no
// place to insert a shuffle if we need to, so just avoid that issue.
if (S && isa<CatchSwitchInst>(S.getMainOp()->getParent()->getTerminator())) {
if (isa<CatchSwitchInst>(BB->getTerminator())) {
LLVM_DEBUG(dbgs() << "SLP: bundle in catchswitch block.\n");
// Do not try to pack to avoid extra instructions here.
return ScalarsVectorizationLegality(S, /*IsLegal=*/false,
/*TryToFindDuplicates=*/false);
}

// Check if this is a duplicate of another entry.
if (S) {
LLVM_DEBUG(dbgs() << "SLP: \tChecking bundle: " << *S.getMainOp() << ".\n");
for (TreeEntry *E : getTreeEntries(S.getMainOp())) {
if (E->isSame(VL)) {
LLVM_DEBUG(dbgs() << "SLP: Perfect diamond merge at " << *S.getMainOp()
<< ".\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}
SmallPtrSet<Value *, 8> Values(llvm::from_range, E->Scalars);
if (all_of(VL, [&](Value *V) {
return isa<PoisonValue>(V) || Values.contains(V) ||
(S.getOpcode() == Instruction::PHI && isa<PHINode>(V) &&
LI->getLoopFor(S.getMainOp()->getParent()) &&
isVectorized(V));
})) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to full overlap.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}
}
// Don't handle scalable vectors
if (S.getOpcode() == Instruction::ExtractElement &&
isa<ScalableVectorType>(
cast<ExtractElementInst>(S.getMainOp())->getVectorOperandType())) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to scalable vector type.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}

// Gather if we hit the RecursionMaxDepth, unless this is a load (or z/sext of
// a load), in which case peek through to include it in the tree, without
// ballooning over-budget.
if (Depth >= RecursionMaxDepth &&
!(S && !S.isAltShuffle() && VL.size() >= 4 &&
(match(S.getMainOp(), m_Load(m_Value())) ||
(S.isAltShuffle() || VL.size() < 4 ||
!(match(S.getMainOp(), m_Load(m_Value())) ||
all_of(VL, [&S](const Value *I) {
return match(I,
m_OneUse(m_ZExtOrSExt(m_OneUse(m_Load(m_Value()))))) &&
Expand All @@ -11362,20 +11408,24 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}

// Don't handle scalable vectors
if (S && S.getOpcode() == Instruction::ExtractElement &&
isa<ScalableVectorType>(
cast<ExtractElementInst>(S.getMainOp())->getVectorOperandType())) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to scalable vector type.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}

// Don't handle vectors.
if (!SLPReVec && getValueType(VL.front())->isVectorTy()) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to vector type.\n");
// Do not try to pack to avoid extra instructions here.
return ScalarsVectorizationLegality(S, /*IsLegal=*/false,
/*TryToFindDuplicates=*/false);
// Check if this is a duplicate of another entry.
LLVM_DEBUG(dbgs() << "SLP: \tChecking bundle: " << *S.getMainOp() << ".\n");
for (TreeEntry *E : getTreeEntries(S.getMainOp())) {
if (E->isSame(VL)) {
LLVM_DEBUG(dbgs() << "SLP: Perfect diamond merge at " << *S.getMainOp()
<< ".\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}
SmallPtrSet<Value *, 8> Values(llvm::from_range, E->Scalars);
if (all_of(VL, [&](Value *V) {
return isa<PoisonValue>(V) || Values.contains(V) ||
(S.getOpcode() == Instruction::PHI && isa<PHINode>(V) &&
LI->getLoopFor(S.getMainOp()->getParent()) &&
isVectorized(V));
})) {
LLVM_DEBUG(dbgs() << "SLP: Gathering due to full overlap.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}
}

// If all of the operands are identical or constant we have a simple solution.
Expand Down Expand Up @@ -11434,44 +11484,13 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
}
return true;
};
SmallVector<unsigned> SortedIndices;
BasicBlock *BB = nullptr;
bool IsScatterVectorizeUserTE =
UserTreeIdx.UserTE &&
UserTreeIdx.UserTE->State == TreeEntry::ScatterVectorize;
bool AreAllSameBlock = S.valid();
bool AreScatterAllGEPSameBlock =
(IsScatterVectorizeUserTE && VL.front()->getType()->isPointerTy() &&
VL.size() > 2 &&
all_of(VL,
[&BB](Value *V) {
auto *I = dyn_cast<GetElementPtrInst>(V);
if (!I)
return doesNotNeedToBeScheduled(V);
if (!BB)
BB = I->getParent();
return BB == I->getParent() && I->getNumOperands() == 2;
}) &&
BB &&
sortPtrAccesses(VL, UserTreeIdx.UserTE->getMainOp()->getType(), *DL, *SE,
SortedIndices));
bool AreAllSameBlock = !AreScatterAllGEPSameBlock;
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Copilot AI Dec 2, 2025

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The variable AreAllSameBlock is now unconditionally set to !AreScatterAllGEPSameBlock, which differs from the original logic where it was set to S.valid(). This appears to be a logic change rather than just a refactoring. If this is intentional, the variable name may be misleading since it no longer represents whether all values are in the same block, but rather whether scatter GEP analysis was not performed.

Suggested change
bool AreAllSameBlock = !AreScatterAllGEPSameBlock;
bool AreAllSameBlock = S.valid();

Copilot uses AI. Check for mistakes.
bool AreAllSameInsts = AreAllSameBlock || AreScatterAllGEPSameBlock;
if (!AreAllSameInsts || (!S && allConstant(VL)) || isSplat(VL) ||
(S &&
isa<InsertElementInst, ExtractValueInst, ExtractElementInst>(
if (!AreAllSameInsts || isSplat(VL) ||
(isa<InsertElementInst, ExtractValueInst, ExtractElementInst>(
S.getMainOp()) &&
!all_of(VL, isVectorLikeInstWithConstOps)) ||
NotProfitableForVectorization(VL)) {
Comment on lines 11490 to 11494
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Copilot AI Dec 2, 2025

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The removal of the allConstant(VL) check and the !S guard before the isa<...> check could lead to a null pointer dereference if S.getMainOp() is null when S is invalid. The original code only performed this check when S was valid.

Copilot uses AI. Check for mistakes.
if (!S) {
LLVM_DEBUG(dbgs() << "SLP: Try split and if failed, gathering due to "
"C,S,B,O, small shuffle. \n";
dbgs() << "[";
interleaveComma(VL, dbgs(), [&](Value *V) { dbgs() << *V; });
dbgs() << "]\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false,
/*TryToFindDuplicates=*/true,
/*TrySplitVectorize=*/true);
}
LLVM_DEBUG(dbgs() << "SLP: Gathering due to C,S,B,O, small shuffle. \n";
dbgs() << "[";
interleaveComma(VL, dbgs(), [&](Value *V) { dbgs() << *V; });
Expand All @@ -11480,7 +11499,7 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
}

// Don't vectorize ephemeral values.
if (S && !EphValues.empty()) {
if (!EphValues.empty()) {
for (Value *V : VL) {
if (EphValues.count(V)) {
LLVM_DEBUG(dbgs() << "SLP: The instruction (" << *V
Expand All @@ -11498,7 +11517,7 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
// Check that none of the instructions in the bundle are already in the tree
// and the node may be not profitable for the vectorization as the small
// alternate node.
if (S && S.isAltShuffle()) {
if (S.isAltShuffle()) {
auto GetNumVectorizedExtracted = [&]() {
APInt Extracted = APInt::getZero(VL.size());
APInt Vectorized = APInt::getAllOnes(VL.size());
Expand Down Expand Up @@ -11550,33 +11569,6 @@ BoUpSLP::ScalarsVectorizationLegality BoUpSLP::getScalarsVectorizationLegality(
}
}

// Special processing for sorted pointers for ScatterVectorize node with
// constant indeces only.
if (!AreAllSameBlock && AreScatterAllGEPSameBlock) {
assert(VL.front()->getType()->isPointerTy() &&
count_if(VL, IsaPred<GetElementPtrInst>) >= 2 &&
"Expected pointers only.");
// Reset S to make it GetElementPtr kind of node.
const auto *It = find_if(VL, IsaPred<GetElementPtrInst>);
assert(It != VL.end() && "Expected at least one GEP.");
S = getSameOpcode(*It, *TLI);
}

// Check that all of the users of the scalars that we want to vectorize are
// schedulable.
Instruction *VL0 = S.getMainOp();
BB = VL0->getParent();

if (S &&
(BB->isEHPad() || isa_and_nonnull<UnreachableInst>(BB->getTerminator()) ||
!DT->isReachableFromEntry(BB))) {
// Don't go into unreachable blocks. They may contain instructions with
// dependency cycles which confuse the final scheduling.
// Do not vectorize EH and non-returning blocks, not profitable in most
// cases.
LLVM_DEBUG(dbgs() << "SLP: bundle in unreachable block.\n");
return ScalarsVectorizationLegality(S, /*IsLegal=*/false);
}
return ScalarsVectorizationLegality(S, /*IsLegal=*/true);
}

Expand Down