[lld] r261064 - Split SymbolTableSection::writeGlobalSymbols.

[Rafael Espíndola via llvm-commits]

Thanks!

On 16 February 2016 at 23:56, Rui Ueyama via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ruiu
> Date: Tue Feb 16 22:56:44 2016
> New Revision: 261064
>
> URL: http://llvm.org/viewvc/llvm-project?rev=261064&view=rev
> Log:
> Split SymbolTableSection::writeGlobalSymbols.
>
> Previously, we added garbage-collected symbols to the symbol table
> and filter them out when we were writing symbols to the file. In
> this patch, garbage-collected symbols are filtered out from beginning.
>
> Modified:
>     lld/trunk/ELF/OutputSections.cpp
>     lld/trunk/ELF/OutputSections.h
>     lld/trunk/ELF/Writer.cpp
>
> Modified: lld/trunk/ELF/OutputSections.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=261064&r1=261063&r2=261064&view=diff
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.cpp (original)
> +++ lld/trunk/ELF/OutputSections.cpp Tue Feb 16 22:56:44 2016
> @@ -1456,38 +1456,7 @@ void SymbolTableSection<ELFT>::writeGlob
>    auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
>    for (const std::pair<SymbolBody *, unsigned> &P : Symbols) {
>      SymbolBody *Body = P.first;
> -    const OutputSectionBase<ELFT> *OutSec = nullptr;
> -
> -    switch (Body->kind()) {
> -    case SymbolBody::DefinedSyntheticKind:
> -      OutSec = &cast<DefinedSynthetic<ELFT>>(Body)->Section;
> -      break;
> -    case SymbolBody::DefinedRegularKind: {
> -      auto *Sym = cast<DefinedRegular<ELFT>>(Body->repl());
> -      if (InputSectionBase<ELFT> *Sec = Sym->Section) {
> -        if (!Sec->isLive())
> -          continue;
> -        OutSec = Sec->OutSec;
> -      }
> -      break;
> -    }
> -    case SymbolBody::DefinedCommonKind:
> -      OutSec = Out<ELFT>::Bss;
> -      break;
> -    case SymbolBody::SharedKind: {
> -      if (cast<SharedSymbol<ELFT>>(Body)->needsCopy())
> -        OutSec = Out<ELFT>::Bss;
> -      break;
> -    }
> -    case SymbolBody::UndefinedElfKind:
> -    case SymbolBody::UndefinedKind:
> -    case SymbolBody::LazyKind:
> -      break;
> -    case SymbolBody::DefinedBitcodeKind:
> -      llvm_unreachable("Should have been replaced");
> -    }
> -
> -    ESym->st_name = P.second;
> +    unsigned SymIdx = P.second;
>
>      unsigned char Type = STT_NOTYPE;
>      uintX_t Size = 0;
> @@ -1501,19 +1470,47 @@ void SymbolTableSection<ELFT>::writeGlob
>
>      ESym->setBindingAndType(getSymbolBinding(Body), Type);
>      ESym->st_size = Size;
> +    ESym->st_name = SymIdx;
>      ESym->setVisibility(Body->getVisibility());
>      ESym->st_value = Body->getVA<ELFT>();
>
> -    if (OutSec)
> +    if (const OutputSectionBase<ELFT> *OutSec = getOutputSection(Body))
>        ESym->st_shndx = OutSec->SectionIndex;
>      else if (isa<DefinedRegular<ELFT>>(Body))
>        ESym->st_shndx = SHN_ABS;
> -
>      ++ESym;
>    }
>  }
>
>  template <class ELFT>
> +const OutputSectionBase<ELFT> *
> +SymbolTableSection<ELFT>::getOutputSection(SymbolBody *Sym) {
> +  switch (Sym->kind()) {
> +  case SymbolBody::DefinedSyntheticKind:
> +    return &cast<DefinedSynthetic<ELFT>>(Sym)->Section;
> +  case SymbolBody::DefinedRegularKind: {
> +    auto *D = cast<DefinedRegular<ELFT>>(Sym->repl());
> +    if (D->Section)
> +      return D->Section->OutSec;
> +    break;
> +  }
> +  case SymbolBody::DefinedCommonKind:
> +    return Out<ELFT>::Bss;
> +  case SymbolBody::SharedKind:
> +    if (cast<SharedSymbol<ELFT>>(Sym)->needsCopy())
> +      return Out<ELFT>::Bss;
> +    break;
> +  case SymbolBody::UndefinedElfKind:
> +  case SymbolBody::UndefinedKind:
> +  case SymbolBody::LazyKind:
> +    break;
> +  case SymbolBody::DefinedBitcodeKind:
> +    llvm_unreachable("Should have been replaced");
> +  }
> +  return nullptr;
> +}
> +
> +template <class ELFT>
>  uint8_t SymbolTableSection<ELFT>::getSymbolBinding(SymbolBody *Body) {
>    uint8_t Visibility = Body->getVisibility();
>    if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)
>
> Modified: lld/trunk/ELF/OutputSections.h
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=261064&r1=261063&r2=261064&view=diff
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.h (original)
> +++ lld/trunk/ELF/OutputSections.h Tue Feb 16 22:56:44 2016
> @@ -241,6 +241,7 @@ private:
>    void writeLocalSymbols(uint8_t *&Buf);
>    void writeGlobalSymbols(uint8_t *Buf);
>
> +  const OutputSectionBase<ELFT> *getOutputSection(SymbolBody *Sym);
>    static uint8_t getSymbolBinding(SymbolBody *Body);
>
>    SymbolTable<ELFT> &Table;
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=261064&r1=261063&r2=261064&view=diff
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Tue Feb 16 22:56:44 2016
> @@ -780,11 +780,14 @@ template <class ELFT> static bool includ
>    if (!B.isUsedInRegularObj())
>      return false;
>
> -  // Don't include synthetic symbols like __init_array_start in every output.
> -  if (auto *U = dyn_cast<DefinedRegular<ELFT>>(&B))
> -    if (&U->Sym == &ElfSym<ELFT>::Ignored)
> +  if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B)) {
> +    // Don't include synthetic symbols like __init_array_start in every output.
> +    if (&D->Sym == &ElfSym<ELFT>::Ignored)
>        return false;
> -
> +    // Exclude symbols pointing to garbage-collected sections.
> +    if (D->Section && !D->Section->isLive())
> +      return false;
> +  }
>    return true;
>  }
>
>
>
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