text: //===- GdbIndex.cpp -------------------------------------------------------===//
  //
  //                             The LLVM Linker
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // The -gdb-index option instructs the linker to emit a .gdb_index section.
  // The section contains information to make gdb startup faster.
  // The format of the section is described at
  // https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html.
  //
  //===----------------------------------------------------------------------===//
  
  #include "GdbIndex.h"
  #include "Symbols.h"
  #include "lld/Common/Memory.h"
  #include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h"
  #include "llvm/Object/ELFObjectFile.h"
  
  using namespace llvm;
  using namespace llvm::object;
  using namespace lld;
  using namespace lld::elf;
  
  template <class ELFT> LLDDwarfObj<ELFT>::LLDDwarfObj(ObjFile<ELFT> *Obj) {
    for (InputSectionBase *Sec : Obj->getSections()) {
      if (!Sec)
        continue;
      if (LLDDWARFSection *M = StringSwitch<LLDDWARFSection *>(Sec->Name)
                                   .Case(".debug_info", &InfoSection)
                                   .Case(".debug_ranges", &RangeSection)
                                   .Case(".debug_line", &LineSection)
                                   .Default(nullptr)) {
        Sec->maybeUncompress();
        M->Data = toStringRef(Sec->Data);
        M->Sec = Sec;
        continue;
      }
      if (Sec->Name == ".debug_abbrev")
        AbbrevSection = toStringRef(Sec->Data);
      else if (Sec->Name == ".debug_gnu_pubnames")
        GnuPubNamesSection = toStringRef(Sec->Data);
      else if (Sec->Name == ".debug_gnu_pubtypes")
        GnuPubTypesSection = toStringRef(Sec->Data);
      else if (Sec->Name == ".debug_str")
        StrSection = toStringRef(Sec->Data);
    }
  }
  
  // Find if there is a relocation at Pos in Sec.  The code is a bit
  // more complicated than usual because we need to pass a section index
  // to llvm since it has no idea about InputSection.
  template <class ELFT>
  template <class RelTy>
  Optional<RelocAddrEntry>
  LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos,
                             ArrayRef<RelTy> Rels) const {
    auto It = std::lower_bound(
        Rels.begin(), Rels.end(), Pos,
        [](const RelTy &A, uint64_t B) { return A.r_offset < B; });
    if (It == Rels.end() || It->r_offset != Pos)
      return None;
    const RelTy &Rel = *It;
  
    const ObjFile<ELFT> *File = Sec.getFile<ELFT>();
    uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL);
    const typename ELFT::Sym &Sym = File->getELFSyms()[SymIndex];
    uint32_t SecIndex = File->getSectionIndex(Sym);
  
    // Broken debug info can point to a non-Defined symbol.
    auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel));
    if (!DR) {
      error("unsupported relocation target while parsing debug info");
      return None;
    }
    uint64_t Val = DR->Value + getAddend<ELFT>(Rel);
  
    // FIXME: We should be consistent about always adding the file
    // offset or not.
    if (DR->Section->Flags & ELF::SHF_ALLOC)
      Val += cast<InputSection>(DR->Section)->getOffsetInFile();
  
    return RelocAddrEntry{SecIndex, Val};
  }
  
  template <class ELFT>
  Optional<RelocAddrEntry> LLDDwarfObj<ELFT>::find(const llvm::DWARFSection &S,
                                                   uint64_t Pos) const {
    auto &Sec = static_cast<const LLDDWARFSection &>(S);
    if (Sec.Sec->AreRelocsRela)
      return findAux(*Sec.Sec, Pos, Sec.Sec->template relas<ELFT>());
    return findAux(*Sec.Sec, Pos, Sec.Sec->template rels<ELFT>());
  }
  
  template class elf::LLDDwarfObj<ELF32LE>;
  template class elf::LLDDwarfObj<ELF32BE>;
  template class elf::LLDDwarfObj<ELF64LE>;
  template class elf::LLDDwarfObj<ELF64BE>;
  