[llvm] [GlobalIsel] Visit ICmp (PR #105991)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

For G_PTR_ADD, we already a visit function, which ought to be MIR patterns: 
https://github.com/llvm/llvm-project/blob/dbd81ba2e85c2f244f22c983d96a106eae65c06a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp#L4750

The market share of combined G_BR_CONDs is probably not that hight, but I have no data.
```
G_CONSTANT $const, $imm,
G_BR_COND $root, $const, $x,
```

https://github.com/llvm/llvm-project/pull/105991