[llvm] [AMDGPU] Constrain register class during COPY elimination based on their uses (PR #181909)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

This is a heavy hammer and should not be necessary. You should not need to integrate a use scan in this function. If you need a copy, you should just emit a copy 

https://github.com/llvm/llvm-project/pull/181909