[llvm] [DAGCombiner] Fold smax(X, -1) to or(X, ashr(X, BW-1)) for code size (PR #206242)

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Andarwinux wrote:

This should apply to O2+ not just Oz: https://godbolt.org/z/YGrcvqq4e

https://github.com/llvm/llvm-project/pull/206242