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

[Florian Hahn via llvm-commits]

fhahn wrote:

> > The semantics match the meaning of the dereferenceable function argument attribute.
> 
> Which semantics? In tree assumes two different ones, see the old old globally_dereferancably discussion/patch.
> 
> I assume this is dereferanceable "here", not "globally", right?

Yep, at the assume call; but I think that should match the assume bundle? I put up https://github.com/llvm/llvm-project/pull/121789 to expose the functionality via a builtin in clang, for now just with constant sizes.

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