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[LVI][SCCP] Avoid copying ValueLatticeElement #163901

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Merged
merged 3 commits into from
Oct 18, 2025
Merged

[LVI][SCCP] Avoid copying ValueLatticeElement #163901

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6a67889
[LVI][SCCP] Avoid copying ValueLatticeElement
dtcxzyw Oct 17, 2025
6b08eeb
[SCCP] Avoid implicit reallocation
dtcxzyw Oct 17, 2025
4ea449b
[SCCP] Address review comments
dtcxzyw Oct 18, 2025
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43 changes: 20 additions & 23 deletions llvm/lib/Transforms/Utils/SCCPSolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -638,14 +638,6 @@ class SCCPInstVisitor : public InstVisitor<SCCPInstVisitor> {
ValueLatticeElement::MergeOptions Opts = {
/*MayIncludeUndef=*/false, /*CheckWiden=*/false});

bool mergeInValue(Value *V, const ValueLatticeElement &MergeWithV,
ValueLatticeElement::MergeOptions Opts = {
/*MayIncludeUndef=*/false, /*CheckWiden=*/false}) {
assert(!V->getType()->isStructTy() &&
"non-structs should use markConstant");
return mergeInValue(ValueState[V], V, MergeWithV, Opts);
}

/// getValueState - Return the ValueLatticeElement object that corresponds to
/// the value. This function handles the case when the value hasn't been seen
/// yet by properly seeding constants etc.
Expand Down Expand Up @@ -987,7 +979,7 @@ class SCCPInstVisitor : public InstVisitor<SCCPInstVisitor> {
void trackValueOfArgument(Argument *A) {
if (A->getType()->isStructTy())
return (void)markOverdefined(A);
mergeInValue(A, getArgAttributeVL(A));
mergeInValue(ValueState[A], A, getArgAttributeVL(A));
}

bool isStructLatticeConstant(Function *F, StructType *STy);
Expand Down Expand Up @@ -1419,10 +1411,10 @@ void SCCPInstVisitor::visitPHINode(PHINode &PN) {
// extensions to match the number of active incoming values. This helps to
// limit multiple extensions caused by the same incoming value, if other
// incoming values are equal.
mergeInValue(&PN, PhiState,
ValueLatticeElement &PhiStateRef = ValueState[&PN];
mergeInValue(PhiStateRef, &PN, PhiState,
ValueLatticeElement::MergeOptions().setMaxWidenSteps(
NumActiveIncoming + 1));
ValueLatticeElement &PhiStateRef = getValueState(&PN);
PhiStateRef.setNumRangeExtensions(
std::max(NumActiveIncoming, PhiStateRef.getNumRangeExtensions()));
}
Expand Down Expand Up @@ -1532,7 +1524,7 @@ void SCCPInstVisitor::handleExtractOfWithOverflow(ExtractValueInst &EVI,
ConstantRange RR = R.asConstantRange(Ty, /*UndefAllowed=*/false);
if (Idx == 0) {
ConstantRange Res = LR.binaryOp(WO->getBinaryOp(), RR);
mergeInValue(&EVI, ValueLatticeElement::getRange(Res));
mergeInValue(ValueState[&EVI], &EVI, ValueLatticeElement::getRange(Res));
} else {
assert(Idx == 1 && "Index can only be 0 or 1");
ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
Expand Down Expand Up @@ -1564,7 +1556,7 @@ void SCCPInstVisitor::visitExtractValueInst(ExtractValueInst &EVI) {
if (auto *WO = dyn_cast<WithOverflowInst>(AggVal))
return handleExtractOfWithOverflow(EVI, WO, i);
ValueLatticeElement EltVal = getStructValueState(AggVal, i);
mergeInValue(getValueState(&EVI), &EVI, EltVal);
mergeInValue(ValueState[&EVI], &EVI, EltVal);
} else {
// Otherwise, must be extracting from an array.
return (void)markOverdefined(&EVI);
Expand Down Expand Up @@ -1627,7 +1619,10 @@ void SCCPInstVisitor::visitSelectInst(SelectInst &I) {
if (ConstantInt *CondCB =
getConstantInt(CondValue, I.getCondition()->getType())) {
Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
mergeInValue(&I, getValueState(OpVal));
const ValueLatticeElement &OpValState = getValueState(OpVal);
// Safety: ValueState[&I] doesn't invalidate OpValState since it is already
// in the map.
mergeInValue(ValueState[&I], &I, OpValState);
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@nikic nikic Oct 17, 2025

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It's unfortunate that ValueState.at(&I) returns a const reference, otherwise we could use that to assert existence.

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@dtcxzyw dtcxzyw Oct 18, 2025

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I added an assertion here.

return;
}

Expand Down Expand Up @@ -1725,7 +1720,7 @@ void SCCPInstVisitor::visitBinaryOperator(Instruction &I) {
// being a special floating value.
ValueLatticeElement NewV;
NewV.markConstant(C, /*MayIncludeUndef=*/true);
return (void)mergeInValue(&I, NewV);
return (void)mergeInValue(ValueState[&I], &I, NewV);
}
}

Expand All @@ -1745,7 +1740,7 @@ void SCCPInstVisitor::visitBinaryOperator(Instruction &I) {
R = A.overflowingBinaryOp(BO->getOpcode(), B, OBO->getNoWrapKind());
else
R = A.binaryOp(BO->getOpcode(), B);
mergeInValue(&I, ValueLatticeElement::getRange(R));
mergeInValue(ValueState[&I], &I, ValueLatticeElement::getRange(R));

// TODO: Currently we do not exploit special values that produce something
// better than overdefined with an overdefined operand for vector or floating
Expand All @@ -1771,7 +1766,7 @@ void SCCPInstVisitor::visitCmpInst(CmpInst &I) {
if (C) {
ValueLatticeElement CV;
CV.markConstant(C);
mergeInValue(&I, CV);
mergeInValue(ValueState[&I], &I, CV);
return;
}

Expand Down Expand Up @@ -1919,7 +1914,7 @@ void SCCPInstVisitor::visitLoadInst(LoadInst &I) {
}

// Fall back to metadata.
mergeInValue(&I, getValueFromMetadata(&I));
mergeInValue(ValueState[&I], &I, getValueFromMetadata(&I));
}

void SCCPInstVisitor::visitCallBase(CallBase &CB) {
Expand Down Expand Up @@ -1967,7 +1962,7 @@ void SCCPInstVisitor::handleCallOverdefined(CallBase &CB) {
}

// Fall back to metadata.
mergeInValue(&CB, getValueFromMetadata(&CB));
mergeInValue(ValueState[&CB], &CB, getValueFromMetadata(&CB));
}

void SCCPInstVisitor::handleCallArguments(CallBase &CB) {
Expand Down Expand Up @@ -1996,7 +1991,7 @@ void SCCPInstVisitor::handleCallArguments(CallBase &CB) {
getMaxWidenStepsOpts());
}
} else
mergeInValue(&*AI,
mergeInValue(ValueState[&*AI], &*AI,
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@nikic nikic Oct 17, 2025

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This looks potentially unsafe, is ValueState[&*AI] guaranteed to already exist?

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@dtcxzyw dtcxzyw Oct 18, 2025

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Fixed.

getValueState(*CAI).intersect(getArgAttributeVL(&*AI)),
getMaxWidenStepsOpts());
}
Expand Down Expand Up @@ -2079,7 +2074,8 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {
if (II->getIntrinsicID() == Intrinsic::vscale) {
unsigned BitWidth = CB.getType()->getScalarSizeInBits();
const ConstantRange Result = getVScaleRange(II->getFunction(), BitWidth);
return (void)mergeInValue(II, ValueLatticeElement::getRange(Result));
return (void)mergeInValue(ValueState[II], II,
ValueLatticeElement::getRange(Result));
}

if (ConstantRange::isIntrinsicSupported(II->getIntrinsicID())) {
Expand All @@ -2097,7 +2093,8 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {

ConstantRange Result =
ConstantRange::intrinsic(II->getIntrinsicID(), OpRanges);
return (void)mergeInValue(II, ValueLatticeElement::getRange(Result));
return (void)mergeInValue(ValueState[II], II,
ValueLatticeElement::getRange(Result));
}
}

Expand All @@ -2124,7 +2121,7 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {
return handleCallOverdefined(CB); // Not tracking this callee.

// If so, propagate the return value of the callee into this call result.
mergeInValue(&CB, TFRVI->second, getMaxWidenStepsOpts());
mergeInValue(ValueState[&CB], &CB, TFRVI->second, getMaxWidenStepsOpts());
}
}

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