[llvm] [AA] No synchronization effects for never-escaping identified local (PR #193939)

[Antonio Frighetto via llvm-commits]

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antoniofrighetto wrote:

I think this comment may be dropped now? (Also not sure if it could make sense to add another check_aa_is_sane test w/o noalias on %b (showing that the cmpxchg atomic is still a Def for the load))

https://github.com/llvm/llvm-project/pull/193939