[PATCH] D88921: [MemCpyOpt] Fix thread-safety of call slot opimization

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added a comment.

> It turns out that this doesn't really change much: If the destination is captured, then the call itself needs to be argmemonly to not potentially modify the destination, and argmemonly currently (incorrectly...) implies willreturn. Thus the only requirement that actually gets added in practice is nounwind (even for alloca dest).

I did not get this :(

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If the caller is `nosync` there is no need for all this thread safety checking.

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The `isGuaranteedToTransferExecutionToSuccessor` loop is not necessary for `nounwind` + `willreturn` functions.

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I feel we probably need the same logic in different places and this might even deserve a helper.


Repository:
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  https://reviews.llvm.org/D88921/new/

https://reviews.llvm.org/D88921