[llvm] MemCpyOpt: replace an AA query with MSSA query (NFC) (PR #108535)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

A disadvantage of using MSSA is that we'll scan for clobbers higher than the load instruction. This is a general problem with MSSA clobber walks though, it would be nice if they have an option to specify a "stop access" so we don't waste time scanning higher.

https://github.com/llvm/llvm-project/pull/108535