[llvm] [InstCombine] Add fold for fabs(-x) -> fabs(x) (PR #94183)

[via llvm-commits]

goldsteinn wrote:

Thank you for the contribution.

You might want to see: https://llvm.org/docs/InstCombineContributorGuide.html

Particularly in the case of this PR, you are missing Alive2 Proofs and should Pre-Commit your tests.

https://github.com/llvm/llvm-project/pull/94183