[llvm] [AMDGPU] Optimize rotate instruction selection patterns (PR #143551)

[Jay Foad via llvm-commits]

jayfoad wrote:

> I do have some stashed changes for this third approach, though the implementation isn’t fully finished yet. If you believe this direction is acceptable, I can continue and complete the patch.

I can't be 100% sure but I think it is worth trying.

https://github.com/llvm/llvm-project/pull/143551