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[TBAA] Extract logic to use TBAA tag for field of !tbaa.struct (NFC). #81284

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Merged
merged 2 commits into from
Feb 12, 2024
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[TBAA] Extract logic to use TBAA tag for field of !tbaa.struct (NFC). #81284

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e6de9f2
[TBAA] Extract logic to use TBAA tag for field of !tbaa.struct (NFC).
fhahn Feb 9, 2024
96a983c
!fixup fix formatting.
fhahn Feb 12, 2024
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5 changes: 5 additions & 0 deletions llvm/include/llvm/IR/Metadata.h
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Expand Up @@ -844,6 +844,11 @@ struct AAMDNodes {
/// together. Different from `merge`, where different locations should
/// overlap each other, `concat` puts non-overlapping locations together.
AAMDNodes concat(const AAMDNodes &Other) const;

/// Create a new AAMDNode for accessing \p AccessSize bytes of this AAMDNode.
/// If his AAMDNode has !tbaa.struct and \p AccessSize matches the size of the
/// field at offset 0, get the TBAA tag describing the accessed field.
AAMDNodes adjustForAccess(unsigned AccessSize);
};

// Specialize DenseMapInfo for AAMDNodes.
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14 changes: 14 additions & 0 deletions llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
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Expand Up @@ -817,3 +817,17 @@ MDNode *AAMDNodes::extendToTBAA(MDNode *MD, ssize_t Len) {
ConstantAsMetadata::get(ConstantInt::get(PreviousSize->getType(), Len));
return MDNode::get(MD->getContext(), NextNodes);
}

AAMDNodes AAMDNodes::adjustForAccess(unsigned AccessSize) {
AAMDNodes New = *this;
MDNode *M = New.TBAAStruct;
New.TBAAStruct = nullptr;
if (M && M->getNumOperands() == 3 && M->getOperand(0) &&
mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
mdconst::extract<ConstantInt>(M->getOperand(0))->isZero() &&
M->getOperand(1) && mdconst::hasa<ConstantInt>(M->getOperand(1)) &&
mdconst::extract<ConstantInt>(M->getOperand(1))->getValue() == AccessSize &&
M->getOperand(2) && isa<MDNode>(M->getOperand(2)))
New.TBAA = cast<MDNode>(M->getOperand(2));
return New;
}
15 changes: 1 addition & 14 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Expand Up @@ -172,20 +172,7 @@ Instruction *InstCombinerImpl::SimplifyAnyMemTransfer(AnyMemTransferInst *MI) {

// If the memcpy has metadata describing the members, see if we can get the
// TBAA tag describing our copy.
AAMDNodes AACopyMD = MI->getAAMetadata();

if (MDNode *M = AACopyMD.TBAAStruct) {
AACopyMD.TBAAStruct = nullptr;
if (M->getNumOperands() == 3 && M->getOperand(0) &&
mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
mdconst::extract<ConstantInt>(M->getOperand(0))->isZero() &&
M->getOperand(1) &&
mdconst::hasa<ConstantInt>(M->getOperand(1)) &&
mdconst::extract<ConstantInt>(M->getOperand(1))->getValue() ==
Size &&
M->getOperand(2) && isa<MDNode>(M->getOperand(2)))
AACopyMD.TBAA = cast<MDNode>(M->getOperand(2));
}
AAMDNodes AACopyMD = MI->getAAMetadata().adjustForAccess(Size);

Value *Src = MI->getArgOperand(1);
Value *Dest = MI->getArgOperand(0);
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