[clang] [libclc] [llvm] [openmp] [Clang] `__attribute__((assume))` refactor (PR #84934)

[Anastasia Stulova via cfe-commits]

AnastasiaStulova wrote:

> From what I can tell, no-one except libclc is actually using this attribute? At least on github, the only matches I’ve found for __attribute__((assume("omp are in LLVM and various forks thereof. Given that it’s not particularly widely used, I don’t think removal without deprecation would be that big of a deal in this case, though if you think that that’s a non-option, then I’d instead suggest deprecating it and removing it in a later version of Clang.

This might be reasonable but I am not familiar enough with libclc to confirm. I imagine if someone volunteers to update it to use a new attribute this should be good enough or is there anything else needed? @svenvh or @efriedma-quic do you have an opinion or know anyone who could help answering this? 

https://github.com/llvm/llvm-project/pull/84934