[clang] [llvm] [Loads] Check context instruction for context-sensitive derefability (PR #109277)

[Danila Malyutin via cfe-commits]

danilaml wrote:

@nikic By the way, are there plans to support allocation functions other than alloca in this check? I don't see currently any llvm passes assigning dereferenceable(_or_null) attribute to something like `malloc(42)` , but I don't see why not and in that case this should also be something not reliant on the context.

https://github.com/llvm/llvm-project/pull/109277