[llvm] [GlobalIsel] Combine G_ADD and G_SUB with constants (PR #97771)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

https://github.com/llvm/llvm-project/blob/8cae9dcd4a45ac78b22c05eff96b0fee3e1c5e55/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L3870
I would be surprised, if there are combines that make a huge impact. It is the sum of many small combines that will give us performance.

https://github.com/llvm/llvm-project/pull/97771