[llvm] AtomicExpand: Preserve metadata when expanding partword RMW (PR #89769)

[James Y Knight via llvm-commits]

jyknight wrote:

Is it really a good idea to blindly preserve all unknown metadata?

ISTM we have no way of knowing if the metadata will be valid on the modified instruction or not. Maybe better to preserve only known-to-be-OK metadata?

https://github.com/llvm/llvm-project/pull/89769