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

[Rafael Avila de Espindola via llvm-commits]

> +  applySynthetic<ELFT>(Synthetics,
> +                       [](SyntheticSection<ELFT> *SS) { SS->finalize(); });

For the names, how about:

* startLayout
* updateAllocSize
* endLayout

A more precise set of names would be atLayoutStart, updateAllocSize and
atLayoutEnd, but not sure if it is actually better.

>  }
>  
>  template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
> Index: ELF/SyntheticSections.h
> ===================================================================
> --- ELF/SyntheticSections.h
> +++ ELF/SyntheticSections.h
> @@ -47,6 +47,12 @@
>    virtual ~SyntheticSection() = default;
>    virtual void writeTo(uint8_t *Buf) = 0;
>    virtual size_t getSize() const = 0;
> +  // Finalize is split up into 3 parts to accommodate Thunks, early finalize
> +  // should do as much as possible including finalizing the section size

"finalizing" is a bit strong since we have updateAllocSize. It should
compute as good a lower bound as possible.


> +  // If the size calculation needs to be updated during Thunk creation

incomplete sentence.

> +  virtual void updateAllocSize() {}
> +  // Runs after all content has been added, must not alter section
> size

and all addresses are know?


> +template <class ELFT> void DynamicSection<ELFT>::earlyFinalize() {
>    if (In<ELFT>::RelaDyn->OutSec->Size > 0) {
>      bool IsRela = Config->Rela;
>      add({IsRela ? DT_RELA : DT_REL, In<ELFT>::RelaDyn});
> @@ -941,13 +941,17 @@
>        add({DT_MIPS_RLD_MAP, In<ELFT>::MipsRldMap});
>    }
>  
> -  this->OutSec->Entsize = this->Entsize;
> -  this->OutSec->Link = this->Link;

Why does setting the link has to be delayed too?

> +template <class ELFT> void SymbolTableSection<ELFT>::finalize() {
> +  this->OutSec->Link = this->Link = StrTabSec.OutSec->SectionIndex;
> +  this->OutSec->Entsize = this->Entsize;
> +
> +  if (StrTabSec.isDynamic()) {
> +    this->OutSec->Info = this->Info = 1;

This can be set early, no?

Cheers,
Rafael