[clang] [llvm] Remove __arm_atomic_store_with_stshh from llvm (PR #192419)

[David Green via cfe-commits]

davemgreen wrote:

> No you are right, this is a general issue with the calls. Nothing specific to the intrinsics. I just didn't worry about other calls. Basically there is no system in place for telling LLVM passes that there are memory ordering requirements imposed by the calls and they assume there aren't.

There is IntrNoSync, which should not be applying as the intrinsic is not using Default attributes. So I think it should work, but I'm not the biggest expert here. It is relatively rare, so could have bugs and it doesn't look like there is a way to be very precise with semantics.

But If you wanted to implement this instead using metadata on an atomic then that sounds like a fine idea to me, providing it works.

https://github.com/llvm/llvm-project/pull/192419