[llvm] [DAG] Fold bitreverse(shl/srl(bitreverse(x),y)) -> srl/shl(x,y) (PR #89897)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Can you also do the globalisel equivalent? 

https://github.com/llvm/llvm-project/pull/89897