[llvm] [GlobalISel] Add G_ABDS and G_ABDU instructions (PR #118122)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

The DAG combine:
https://github.com/llvm/llvm-project/blob/be75a14207ab0dac6ad9f9097957f14a918ac611/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L11081

https://github.com/llvm/llvm-project/pull/118122