[llvm] [SCEV] Strengthen nuw/nsw on add/mul with CR (PR #217638)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

This is the best I can do in terms of compile-time: https://llvm-compile-time-tracker.com/compare.php?from=e4ab7d421b5beb2f11594953b811e366485175fb&to=8fba25247658ab469fc54a43864b6531c453f01d&stat=instructions:u. I've restricted it to non-SCEVUnknown LHS. Computing the ranges don't have as big a role to play in the compile time, as LLVM optimizing with the new flags -- as a result, I think that maybe this is acceptable for the benefit?

https://github.com/llvm/llvm-project/pull/217638