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MemCpyOpt: clarify logic in processStoreOfLoad (NFC) #108400

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Sep 12, 2024
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MemCpyOpt: clarify logic in processStoreOfLoad (NFC) #108400

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13 changes: 3 additions & 10 deletions llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -661,18 +661,11 @@ bool MemCpyOptPass::processStoreOfLoad(StoreInst *SI, LoadInst *LI,
}
}

// We found an instruction that may write to the loaded memory.
// We can try to promote at this position instead of the store
// If we found an instruction that may write to the loaded memory,
// we can try to promote at this position instead of the store
// position if nothing aliases the store memory after this and the store
// destination is not in the range.
if (P && P != SI) {
if (!moveUp(SI, P, LI))
P = nullptr;
}

// If a valid insertion position is found, then we can promote
// the load/store pair to a memcpy.
if (P) {
if (P == SI || moveUp(SI, P, LI)) {
// If we load from memory that may alias the memory we store to,
// memmove must be used to preserve semantic. If not, memcpy can
// be used. Also, if we load from constant memory, memcpy can be used
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