[clang] [llvm] [OpenMP][Clang] Add no-loop SPMD kernel promotion (PR #205325)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 commented:

I've forgotten about a lot of this stuff, but wasn't the issue that OpenMP thread counts can be changed via environment variables or something? OR something like saying you want `N` threads just means OpenMP gives you 'up to N' threads, I forget.

The problem with doing this in the frontend is that there's a very narrow definition for what SPMD is because the compiler has no concept of IPO. I'm wondering if instead we could attach these options as metadata to the generated kernel and handle it in OpenMPOpt.

https://github.com/llvm/llvm-project/pull/205325