[llvm] [AMDGPU] Add post-RA peephole to fuse v_lshlrev_b32 + v_or_b32 into v_lshl_or_b32 (PR #202585)

[Barbara Mitic via llvm-commits]

barbara-amd wrote:

Hi @LU-JOHN @jayfoad  @arsenm  — you've worked on SIShrinkInstructions (the matchSwap peephole). This adds a similar post-RA peephole fusing v_lshlrev_b32 + v_or_b32 into v_lshl_or_b32. Could you review, or suggest reviewers? I can't add them myself. Thanks!

https://github.com/llvm/llvm-project/pull/202585