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

[Nikita Popov via llvm-commits]

nikic wrote:

@akshayrdeodhar Is there a specific real-world motivation for the special case? If you're not aware of any, then no, having the special case is not a good idea.

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