[llvm] [WIP][AMDGPU] Improve the handling of `inreg` arguments (PR #133614)

[Shilei Tian via llvm-commits]

https://github.com/shiltian commented:

This PR now contains changes from all the three PRs because Graphite doesn't allow to retarget a PR.

https://github.com/llvm/llvm-project/pull/133614