[llvm] [polly] [SCEV] Introduce SDiv expressions (PR #216862)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Significant compile-time improvement: https://llvm-compile-time-tracker.com/compare.php?from=4e00d18cdc93e2a56941aaa583d1c227527580c4&to=910469a4787fe09ea365f8de56d09bbdfc4e8f62&stat=instructions:u.

https://github.com/llvm/llvm-project/pull/216862