[llvm] [Attributor] Pack out arguments into a struct (PR #119267)

[via llvm-commits]

elhewaty wrote:

> > ```
> >     AllocaInst *Alloca = EntryBuilder.CreateAlloca(  // this is AttributorAttributes.cpp:13069:21
> >         PtrToType[&OldArg], nullptr, OldArg.getName());
> > ```
> 
> You're not using the correct address space for the alloca. Regardless of that, I think the crash is probably because PtrToType[&OldArg] is nullptr

@arsenm  I tried to loop over `PtrToType` and assert to check if it has nullptr values but it doesn't. I think maybe the address space that causes the problem, any hint?

https://github.com/llvm/llvm-project/pull/119267