[llvm] [SimplifyCFG] handle monotonic wrapped case for D150943 (PR #65882)

[Nikita Popov via llvm-commits]

nikic wrote:

Can you please update the PR description with more details about what the problematic case is an how this fixes it?

My understanding is that in this case we are mapping (after index adjustment) the indices (0, 1, 2, 3) to (-4, -2, 0, 2) so we have a monotonic sequence, but this is done by doing a multiply first, so we go through (0, 2, -4, -2) first, which wraps.

https://github.com/llvm/llvm-project/pull/65882