[llvm] [FunctionSpecializer] Keep the blocks in dead functions and remove the callsites of dead function properly. (PR #154668)

[Alexandros Lamprineas via llvm-commits]

https://github.com/labrinea commented:

Thanks for adding a test for addressTaken. One remark about the first test, otherwise the patch looks ok I think. I am wondering if we need another test to demonstrate the poisoning of users, and why does it now show in the first example.

https://github.com/llvm/llvm-project/pull/154668