[llvm] [Intrinsics] Add @llvm.dereferenceable intrinsic. (PR #120755)

[Florian Hahn via llvm-commits]

fhahn wrote:

Ah sorry, another advantage of using an intrinsic is that it is easier to find a dominating `@llvm.dereferenceable`; with an assume bundle, it would be more complicated (iterating over all users of the pointer and checking if any is an assume that dominates the point we want to get deref info for

https://github.com/llvm/llvm-project/pull/120755