[clang] [llvm] OpenMP offload 'simd' directive (PR #91261)

[Johannes Doerfert via cfe-commits]

https://github.com/jdoerfert commented:

There is too much unrelated stuff, printfs, commented code, etc. too review it properly.

I left high-level comments, including why there is a hardcoded simdlen of 1 and globalization for all allocas.

https://github.com/llvm/llvm-project/pull/91261