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

[Thorsten Schütt via llvm-commits]

tschuett wrote:

CombinerHelper::matchCmpOfZero uses directly KB at most once per case in the switch statement of the icmp predicate, for reference: https://github.com/llvm/llvm-project/blob/ce9f9872950090eae9104ff49b77469e3dc0a3c5/llvm/lib/Analysis/InstructionSimplify.cpp#L2974

A different question is the isKnownNonZero analysis, but it is depth limited:
`bool isKnownNonZero(Register Reg, const MachineRegisterInfo &MRI,
                    GISelKnownBits *KB, unsigned Depth = 0);`

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