[llvm] [SCEV] Don't use non-deterministic constant folding for trip counts (PR #90942)

[Nikita Popov via llvm-commits]

nikic wrote:

> Do we need to do something with fast-math flags?

I think so. I've disabled folding for nsz and reassoc/arcp/contract. I didn't try to come up with realistic examples for them, but I think they could all cause issues.

https://github.com/llvm/llvm-project/pull/90942