[llvm] [SelectionDAG] Fold (icmp eq/ne (shift X, C), 0) -> (icmp eq/ne X, 0) (PR #88801)

[Björn Pettersson via llvm-commits]

bjope wrote:

> I kind of expect these flags to be present on the incoming IR, and combines need to do a better job of preserving them. Are there any examples where you need to recover the flags with value tracking late?

See yesterdays discussion with @goldsteinn here https://github.com/llvm/llvm-project/pull/88801/commits/f603024d54df8b87428e9eb3ddb6b44856c28b5a#r1591231882

https://github.com/llvm/llvm-project/pull/88801