[llvm] [InstCombine] Infer zext nneg flag directly (PR #71906)

[Nikita Popov via llvm-commits]

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

LGTM, though I'm not sure how much value there is in explicitly setting the flag in cases where it can be inferred anyway.

https://github.com/llvm/llvm-project/pull/71906