[llvm] Improved AMDGPU Lowering of abs(i16) and -abs(i16) (PR #165626)

[Juan Manuel Martinez Caamaño via llvm-commits]

https://github.com/jmmartinez commented:

To see better the improvement motivating this patch.

Could you squash the commits and split them in 2: one where you pre-commit the tests, and one where you solve the issue.

https://github.com/llvm/llvm-project/pull/165626