[llvm] [KnownBits] Make abdu and abds optimal (PR #89081)

[Simon Pilgrim via llvm-commits]

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

LGTM - I'm not sure how we should start addressing the anti-conflict approach, it doesn't sound like something that can be easily fixed piece by piece....

https://github.com/llvm/llvm-project/pull/89081