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

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

Good to know that other targets have that sort of "how many work groups will be launched" information. Having that be a min/max (either per dimension or in total or both) may be the right approach here, and this could be a good excuse for the unification being talked about.

(This isn't anything I, as the initial proposer of the idea, am needing super urgently - this was spawned from "hey, I'm up here in MLIR generating kernels that always have N workgroups in the grid, can I be cleverer than just sticking `!range` metadata on the intrinsics?")

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