[llvm] [Reassociate] Preserve NSW flags after expr tree rewriting (PR #93105)

[Nikita Popov via llvm-commits]

nikic wrote:

No compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=7d29718ff601c62f8c89be71e582358bfc18dd70&to=63794c145608f06c2883f680475f5f16522f4d4a&stat=instructions:u

https://github.com/llvm/llvm-project/pull/93105