[clang] [llvm] [AMDGPU] Implement AsyncMark Stages (PR #220442)

[Sameer Sahasrabuddhe via cfe-commits]

https://github.com/ssahasra commented:

The PR description needs to be updated. I am still reviewing SIInsertWaitcnts.cpp, but @Pierre-vh should definitely take a look at it.

https://github.com/llvm/llvm-project/pull/220442