[PATCH] D29983: [LLD][ELF] Calculate sizes of SHF_ALLOC Synthetic Sections early

[Rafael Avila de Espindola via llvm-commits]

> +  if (In<ELFT>::GnuHashTab && In<ELFT>::DynSymTab)
> +    In<ELFT>::DynSymTab->addSymbolsToGnuHashTab();

Having the gnu hash implies that we also have a dynamic symbol table,
no?

>    // Dynamic section must be the last one in this list and dynamic
>    // symbol table section (DynSymTab) must be the first one.

This comment should stay with the definition of the Synthetics array.

> +// Add remaining entries to complete .dynamic contents.
> +template <class ELFT> void DynamicSection<ELFT>::updateAllocSize() {
> +  std::vector<Entry> LateEntries = addLateEntries();
> +  // +1 for DT_NULL
> +  this->Size = (Entries.size() + LateEntries.size() + 1) * this->Entsize;
> +}
> +
> +// Add remaining entries to complete .dynamic contents.
> +template <class ELFT> void DynamicSection<ELFT>::finalize() {
> +  this->Link = In<ELFT>::DynStrTab->OutSec->SectionIndex;
> +  std::vector<Entry> LateEntries = addLateEntries();
> +  Entries.insert(Entries.end(), LateEntries.begin(), LateEntries.end());
>    this->OutSec->Entsize = this->Entsize;
>    this->OutSec->Link = this->Link;
> -
>    // +1 for DT_NULL
>    this->Size = (Entries.size() + 1) * this->Entsize;

Can you call updateAllocSize instead? Why do you need to split
addLateEntries btw? The actual number of entries doesn't change when
adding thunks, right? I looks like it should be sufficient to just
populate Entries earlier.

> -template <class ELFT> void GnuHashTableSection<ELFT>::finalize() {
> +template <class ELFT> void GnuHashTableSection<ELFT>::updateAllocSize() {
>    unsigned NumHashed = Symbols.size();
>    NBuckets = calcNBuckets(NumHashed);
>    MaskWords = calcMaskWords(NumHashed);

Do you need to do this in every updateAllocSize?

If I understand it correctly, this patch is in an odd middle ground. I
think I would prefer to either call the full finalize multiple times if
thunks are added or split finalize is 3 methods:

* One that is called early and only once. It would do most of the work
  that finalize currently does.
* updateAllocSize, which is empty for most sections and just updates
  whatever can change the size in response to other sections changing
  size.
* A real finalize method, that is called only once and can set values
  that depend on the final address of the sections.

Cheers,
Rafael