[clang] [llvm] [openmp] [OpenMP] Use generic IR for the OpenMP DeviceRTL (PR #119091)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > This probably should retain separate wave32/wave64 builds. Additionally, should have extension points for subtarget specific implementations
> 
> That's what Shilei was talking about since we have `__nvvm_reflect` for that for NVPTX.

First I will always consider NVVM reflect a giant hack. NVVM reflect cannot actually deal with the full range of wavesize issues. It is an incompatible ABI and the code should never be intermixed 

https://github.com/llvm/llvm-project/pull/119091