[llvm] [IR] Add nowrap flags for trunc instruction (PR #85592)

[via llvm-commits]

elhewaty wrote:

@antoniofrighetto 
> @nikic, I'm taking a look at point 3. Not super familiar w/ IV widening, but I guess whenever the uses are truncated, we want to preserve the information that previously got lost? I'm mainly referring to `widenIVUse`/`truncateIVUse` and variants thereof (e.g., `widenWithVariantUse`) (cc/ @dtcxzyw).

I am taking a look too, I am not familiar with w/ IV widening, So I think it's a good chance for me to work on it. I will look at the functions you mentioned too.
Thanks



https://github.com/llvm/llvm-project/pull/85592