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

[via llvm-commits]

AtariDreams wrote:

> OK - I was just being careful as we are so close to the release and some of the issues can be subtle. I gave it a more thorough test and everything seems OK.
> 
> 
> 
> By "tested this and found no issue", does that include running a bootstrap and the llvm-test-suite? If so and you add a some extra test coverage then this LGTM.

Yes I ran the entire test suite. 

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