[llvm] [AArch64] Enable CmpBcc fusion for Neoverse-v2 (PR #90608)

[Elvina Yakubova via llvm-commits]

ElvinaYakubova wrote:

> I actually suggested that we remove this from some cores recently, as when I've tried it in the past (a long time ago now) the performance hasn't looked great. Perhaps things have changed since then. It's certainly true that the cores can do this fusion, my suspicion was that the implementation was a little too aggressive in llvm and led to worse codegen in places from knock-on effects.
> 
> Can you give more details on the "benchmark that improves significantly"? Do you happen to know why it improves?

The benchmark is Eigen, and we've seen 15% improvement. There are plenty of 
```
cmp	
str
b.cc/b.eq/b.lt
```
code sequences there


https://github.com/llvm/llvm-project/pull/90608