[clang] [llvm] [AMDGPU] Introduce asyncmark/wait intrinsics (PR #173259)

[Sameer Sahasrabuddhe via cfe-commits]

ssahasra wrote:

> Functionally good, maybe we could note some TODOs here in regards to marking what regs are part of an async operation and how that interplays with waitcnts generated/deemed necessary for synchronous operations.

Right most of those TODOs are port of the next piece of work. For now, I have added a comment saying that LOAD_CNT is not the only counter, and other counters will get involved with future work.

https://github.com/llvm/llvm-project/pull/173259