[clang] [llvm] [AMDGPU] Adding the amdgpu-num-work-groups function attribute (PR #79035)

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

Do we want to also get `min-num-work-groups` and `max-num-work-groups` versions?

https://github.com/llvm/llvm-project/pull/79035