[llvm] [MergeFunc] Preserve observable function pointer identity (PR #213604)

[Ralf Jung via llvm-commits]

RalfJung wrote:

> git diff --check: passed

Do you know what this command does? If you don't, then why are you using it? If you do, then you know that it does nothing of use, so why are you using it?
It is impolite to blindly forward LLM output to other people without their consent, so please refrain from doing that. It is not helpful to submit PRs that you cannot explain yourself in your own words.

https://github.com/llvm/llvm-project/pull/213604