[lld] r257023 - [ELF] Add AMDGPU support

[Rafael Espíndola via llvm-commits]

> +
> +    // Symbol offsets for AMDGPU need to be the offset in bytes of the symbol
> +    // from the beginning of the section.
> +    if (Config->EMachine == EM_AMDGPU)
> +      return SC->getOffset(DR.Sym);
>      if (DR.Sym.getType() == STT_TLS)
>        return SC->OutSec->getVA() + SC->getOffset(DR.Sym) -
>               Out<ELFT>::TlsPhdr->p_vaddr;
> @@ -1325,7 +1330,11 @@ void SymbolTableSection<ELFT>::writeLoca
>            continue;
>          const OutputSectionBase<ELFT> *OutSec = Section->OutSec;
>          ESym->st_shndx = OutSec->SectionIndex;
> -        VA += OutSec->getVA() + Section->getOffset(Sym);
> +        VA = Section->getOffset(Sym);
> +        // Symbol offsets for AMDGPU need to be the offset in bytes of the
> +        // symbol from the beginning of the section.
> +        if (Config->EMachine != EM_AMDGPU)
> +          VA += OutSec->getVA();
>        }


This is a horrible design error. The ELF spec is very explicit:

In executable and shared object files, st_value holds a virtual address.

Is there any hope of fixing this? AMDGPU using ELF is relatively new,
so I hope so. Some options

* User -r.
* Change the consumer.

But please do something. The fact that symbols and relocations use
offsets in .o and addresses in .so and executables is central to ELF.

Cheers,
Rafael