[llvm] [InstSimplify][InstCombine] Handle nsz in fabs(fneg x) (llvm#151303) (PR #187994)

[Yunbo Ni via llvm-commits]

cardigan1008 wrote:

> All the other tests are actually an effect of not simplifying the instruction with nsz flag. So I belive they do not change if changing the code in ValueTracking.

The change in ValueTracking would influence them as well. For example, @fabs_sqrt_nnan_nsz cannot be folded with -0.0. Same with the sqrt + copysign test. 

https://github.com/llvm/llvm-project/pull/187994