[llvm] [DAG] Fold trunc(srl(extract_elt(vec,c1),c2)) -> extract_elt(bitcast(vec),c3) (PR #107987)

[David Green via llvm-commits]

https://github.com/davemgreen approved this pull request.

I believe this BE calculation looks correct. LGTM

https://github.com/llvm/llvm-project/pull/107987