[lld] [PAC][ThinLTO] Fix auth key for GOT entries of function symbols (PR #131467)

[Daniil Kovalev via llvm-commits]

kovdan01 wrote:

> `elfSym.getName(obj->getStringTable())` is wasteful - as we could zip `obj->template getGlobalELFSyms<ELFT>()` with `obj->getGlobalSymbols()`.

@MaskRay Do I get your intention correct - you suggest to change this:

```
    for (typename ELFT::Sym elfSym : obj->template getGlobalELFSyms<ELFT>()) {
      StringRef elfSymName = check(elfSym.getName(obj->getStringTable()));
      if (Symbol *sym = ctx.symtab->find(elfSymName))
        if (sym->type == STT_NOTYPE)
          sym->type = elfSym.getType();
    }
```

to smth like this:

```
    for (const Symbol *globSym : obj->getGlobalSymbols())
      if (Symbol *sym = ctx.symtab->find(globSym->getName()))
        if (sym->type == STT_NOTYPE)
          sym->type = globSym->type;
```

If so, this does not look correct - function symbols from `obj->getGlobalSymbols()` will have `STT_NOTYPE` type, while corresponding ELF symbols will have `STT_FUNC` type. We want the latter behavior in order to change symbol type in symtab.

Please let me know if I misunderstood you.

https://github.com/llvm/llvm-project/pull/131467