[llvm] [LoopUtils] prevent negative estimated trip count result (PR #195610)

[Nikita Popov via llvm-commits]

nikic wrote:

> > I'm also wondering if we should reject negative estimated loop trip counts in the verifier.
> 
> That makes sense to me.

I don't think we should reject "negative" trip counts -- the trip count is unsigned, the negative number is just a display artifact.

(This code should also treat it as unsigned, not int...)

https://github.com/llvm/llvm-project/pull/195610