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[LAA] Hoist check for SCEV-uncomputable dist (NFC) #148841

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Merged
artagnon merged 2 commits into from
Jul 16, 2025
Merged

[LAA] Hoist check for SCEV-uncomputable dist (NFC) #148841

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703455c
[LAA] Hoist check for SCEV-uncomputable dist (NFC)
artagnon Jul 15, 2025
6fb910e
[LAA] Tweak dbg message
artagnon Jul 16, 2025
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13 changes: 6 additions & 7 deletions llvm/lib/Analysis/LoopAccessAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2085,6 +2085,12 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
if (!isa<SCEVConstant>(Dist))
FoundNonConstantDistanceDependence |= StrideAPtrInt == StrideBPtrInt;

// If distance is a SCEVCouldNotCompute, return Unknown immediately.
if (isa<SCEVCouldNotCompute>(Dist)) {
LLVM_DEBUG(dbgs() << "LAA: Uncomputable distance.\n");
return Dependence::Unknown;
}

return DepDistanceStrideAndSizeInfo(Dist, MaxStride, CommonStride,
TypeByteSize, AIsWrite, BIsWrite);
}
Expand Down Expand Up @@ -2122,13 +2128,6 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
std::get<DepDistanceStrideAndSizeInfo>(Res);
bool HasSameSize = TypeByteSize > 0;

if (isa<SCEVCouldNotCompute>(Dist)) {
if (CheckCompletelyBeforeOrAfter())
return Dependence::NoDep;
LLVM_DEBUG(dbgs() << "LAA: Dependence because of uncomputable distance.\n");
return Dependence::Unknown;
}

ScalarEvolution &SE = *PSE.getSE();
auto &DL = InnermostLoop->getHeader()->getDataLayout();

Expand Down