[clang] [llvm] [AMDGPU] Adding the amdgpu-num-work-groups function attribute (PR #75647)

[Jun Wang via llvm-commits]

jwanggit86 wrote:

Two possible optimizations mentioned by the requester are, 
"1. This'll let the backend know the maximum size of the workgroup ID, and so we can do things like infer nsw or the ability to use a 16-bit add or so on

2. This could be used to optimize global sync stuff in the future
"

https://github.com/llvm/llvm-project/pull/75647