[llvm] Simplify `(a % b) lt/ge (b-1)` into `(a % b) eq/ne (b-1)` (PR #72504)

[Nikita Popov via llvm-commits]

nikic wrote:

@elhewaty It looks like we have to implement this fold first: https://alive2.llvm.org/ce/z/pqfbT7 It looks like this already happens when the comparison is with a positive number, so wherever that happens needs support for negative numbers as well.

https://github.com/llvm/llvm-project/pull/72504