[llvm] [LangRef] asm clobber constrains: '~memory' allows reads and synchronization (PR #150191)

[Ralf Jung via llvm-commits]

RalfJung wrote:

> Maybe we should explicitly state this is a superset of "sideeffect", since synchronizing with other threads basically allows arbitrary effects.

Do you mean the `llvm.sideffect` intrinsic? That is `inaccessiblememonly` so it's way less than what we want here, seems potentially confusing to reference that.

> Do you anticipate any transforms need to be changed based on this?

This boils down to whether any transform considers asm blocks with this clobber to be `nosync`. I would hope that's not the case...

https://github.com/llvm/llvm-project/pull/150191