[llvm] [SCEV] BECount to zero if `((-1 + (1 smax %x))<nsw> /u %x)` holds (PR #104580)

[Nikita Popov via llvm-commits]

nikic wrote:

> Looks like this generalizes to any positive constant: https://alive2.llvm.org/ce/z/aS3SUe

We don't need nsw as a precondition either, it's implied: https://alive2.llvm.org/ce/z/_dLm8C

https://github.com/llvm/llvm-project/pull/104580