================
@@ -3382,6 +3418,17 @@ Instruction
*InstCombinerImpl::visitAllocSite(Instruction &MI) {
eraseInstFromFunction(*I);
Users[i] = nullptr; // Skip examining in the next loop.
}
+ if (auto *MTI = dyn_cast<MemTransferInst>(I)) {
+ if (KnowInitZero && getUnderlyingObject(MTI->getRawDest()) != &MI) {
+ IRBuilderBase::InsertPointGuard Guard(Builder);
+ Builder.SetInsertPoint(MTI);
+ auto *M = Builder.CreateMemSet(MTI->getRawDest(),
+ ConstantInt::get(Type::getInt8Ty(MI.getContext()), 0),
+ MTI->getLength(),
+ MTI->getDestAlign());
+ M->copyMetadata(*MTI, LLVMContext::MD_DIAssignID);
----------------
nikic wrote:
This depends a lot on the specific transform. Dropping or adjusting metadata is
often required when we're merging operations in some way (e.g. memcpy to memcpy
forwarding).
However, I believe that for this specific case where we're converting memcpy to
memset, preserving metadata should be fine. (We're only *removing* a read from
a location.)
https://github.com/llvm/llvm-project/pull/143958
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