[llvm] [SelectionDAG]: Deduce KnownNeverZero from SMIN and SMAX (PR #85722)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

You need better vector tests - the vector CTTZ expansion won't be making use of is never known zero

https://github.com/llvm/llvm-project/pull/85722