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

[Danila Malyutin via cfe-commits]

danilaml wrote:

@nikic I mean not in theory but currently. I don't see those (except allocas) handled anywhere unless I'm missing something?

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