[llvm] AMDGPU] ISel & PEI for whole wave functions (PR #131334)

[Carl Ritson via llvm-commits]

https://github.com/perlfu commented:

Had a quick look.
This seems pretty clean as is.
However, I had assumed this would introduce a new calling convention, and WWM functions would use that calling convention?
Then there is no SubtargetFeature, etc

https://github.com/llvm/llvm-project/pull/131334