[llvm] [SimplifyCFG] Fold the contiguous wrapping cases into ICmp. (PR #161000)

[via llvm-commits]

dianqk wrote:

> Maybe limit this to \>2 cases to start to avoid regressions?

This is still needed, some 2 cases have not been transformed: [[llvm.godbolt.org/z/Y71EovY4M](https://llvm.godbolt.org/z/Y71EovY4M)](https://llvm.godbolt.org/z/Y71EovY4M).

I think it's fine because it runs later in the passes pipeline.

https://github.com/llvm/llvm-project/pull/161000