[llvm] [AArch64] Use isKnownNonZero to optimize eligible compares to cmn (PR #96349)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

This is quite complex now, and the ccmn case is apparently still not happy. It would be useful to add more test cases for various conditions. or_neg looks good, but we should have test for all the cases that wouldn't be.

https://github.com/llvm/llvm-project/pull/96349