[clang] [llvm] [Clang] Add __builtin_assume_dereferenceable to encode deref assumption. (PR #121789)

[Johannes Doerfert via llvm-commits]

jdoerfert wrote:

> I'm concerned about the soundness of our current implementation for these assumptions, see my comment at [#120962 (comment)](https://github.com/llvm/llvm-project/pull/120962#issuecomment-2582864870). Not sure we should be exposing the current implementation from clang.

Let's wait here and move the discussion into the other issue I guess. I replied there too.

https://github.com/llvm/llvm-project/pull/121789