C++ MCSymbolELF类代码示例

MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
                                              unsigned Flags, SectionKind K,
                                              unsigned EntrySize,
                                              const MCSymbolELF *Group,
                                              unsigned UniqueID,
                                              const MCSymbolELF *Associated) {
  MCSymbolELF *R;
  MCSymbol *&Sym = Symbols[Section];
  // A section symbol can not redefine regular symbols. There may be multiple
  // sections with the same name, in which case the first such section wins.
  if (Sym && Sym->isDefined() &&
      (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
    reportError(SMLoc(), "invalid symbol redefinition");
  if (Sym && Sym->isUndefined()) {
    R = cast<MCSymbolELF>(Sym);
  } else {
    auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
    R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
    if (!Sym)
      Sym = R;
  }
  R->setBinding(ELF::STB_LOCAL);
  R->setType(ELF::STT_SECTION);

  auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
      Section, Type, Flags, K, EntrySize, Group, UniqueID, R, Associated);

  auto *F = new MCDataFragment();
  Ret->getFragmentList().insert(Ret->begin(), F);
  F->setParent(Ret);
  R->setFragment(F);

  return Ret;
}

void AMDGPUTargetELFStreamer::EmitAMDGPUHsaProgramScopeGlobal(
    StringRef GlobalName) {

  MCSymbolELF *Symbol = cast<MCSymbolELF>(
      getStreamer().getContext().getOrCreateSymbol(GlobalName));
  Symbol->setType(ELF::STT_OBJECT);
  Symbol->setBinding(ELF::STB_GLOBAL);
}

bool ELFObjectWriter::isInSymtab(const MCAsmLayout &Layout,
                                 const MCSymbolELF &Symbol, bool Used,
                                 bool Renamed) {
  if (Symbol.isVariable()) {
    const MCExpr *Expr = Symbol.getVariableValue();
    if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
      if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
        return false;
    }
  }

  if (Used)
    return true;

  if (Renamed)
    return false;

  if (Symbol.isVariable() && Symbol.isUndefined()) {
    // FIXME: this is here just to diagnose the case of a var = commmon_sym.
    Layout.getBaseSymbol(Symbol);
    return false;
  }

  if (Symbol.isUndefined() && !Symbol.isBindingSet())
    return false;

  if (Symbol.isTemporary())
    return false;

  if (Symbol.getType() == ELF::STT_SECTION)
    return false;

  return true;
}

// True if the assembler knows nothing about the final value of the symbol.
// This doesn't cover the comdat issues, since in those cases the assembler
// can at least know that all symbols in the section will move together.
static bool isWeak(const MCSymbolELF &Sym) {
  if (Sym.getType() == ELF::STT_GNU_IFUNC)
    return true;

  switch (Sym.getBinding()) {
  default:
    llvm_unreachable("Unknown binding");
  case ELF::STB_LOCAL:
    return false;
  case ELF::STB_GLOBAL:
    return false;
  case ELF::STB_WEAK:
  case ELF::STB_GNU_UNIQUE:
    return true;
  }
}

void TargetLoweringObjectFileELF::emitPersonalityValue(
    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
  SmallString<64> NameData("DW.ref.");
  NameData += Sym->getName();
  MCSymbolELF *Label =
      cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
  Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
  Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
  MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
                                                   ELF::SHT_PROGBITS, Flags, 0);
  unsigned Size = DL.getPointerSize();
  Streamer.SwitchSection(Sec);
  Streamer.EmitValueToAlignment(DL.getPointerABIAlignment());
  Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
  const MCExpr *E = MCConstantExpr::create(Size, getContext());
  Streamer.emitELFSize(Label, E);
  Streamer.EmitLabel(Label);

  Streamer.EmitSymbolValue(Sym, Size);
}

void AMDGPUTargetELFStreamer::EmitAmdhsaKernelDescriptor(
    const MCSubtargetInfo &STI, StringRef KernelName,
    const amdhsa::kernel_descriptor_t &KernelDescriptor, uint64_t NextVGPR,
    uint64_t NextSGPR, bool ReserveVCC, bool ReserveFlatScr,
    bool ReserveXNACK) {
  auto &Streamer = getStreamer();
  auto &Context = Streamer.getContext();

  MCSymbolELF *KernelDescriptorSymbol = cast<MCSymbolELF>(
      Context.getOrCreateSymbol(Twine(KernelName) + Twine(".kd")));
  KernelDescriptorSymbol->setBinding(ELF::STB_GLOBAL);
  KernelDescriptorSymbol->setType(ELF::STT_OBJECT);
  KernelDescriptorSymbol->setSize(
      MCConstantExpr::create(sizeof(KernelDescriptor), Context));

  MCSymbolELF *KernelCodeSymbol = cast<MCSymbolELF>(
      Context.getOrCreateSymbol(Twine(KernelName)));
  KernelCodeSymbol->setBinding(ELF::STB_LOCAL);

  Streamer.EmitLabel(KernelDescriptorSymbol);
  Streamer.EmitBytes(StringRef(
      (const char*)&(KernelDescriptor),
      offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset)));
  // FIXME: Remove the use of VK_AMDGPU_REL64 in the expression below. The
  // expression being created is:
  //   (start of kernel code) - (start of kernel descriptor)
  // It implies R_AMDGPU_REL64, but ends up being R_AMDGPU_ABS64.
  Streamer.EmitValue(MCBinaryExpr::createSub(
      MCSymbolRefExpr::create(
          KernelCodeSymbol, MCSymbolRefExpr::VK_AMDGPU_REL64, Context),
      MCSymbolRefExpr::create(
          KernelDescriptorSymbol, MCSymbolRefExpr::VK_None, Context),
      Context),
      sizeof(KernelDescriptor.kernel_code_entry_byte_offset));
  Streamer.EmitBytes(StringRef(
      (const char*)&(KernelDescriptor) +
          offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset) +
          sizeof(KernelDescriptor.kernel_code_entry_byte_offset),
      sizeof(KernelDescriptor) -
          offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset) -
          sizeof(KernelDescriptor.kernel_code_entry_byte_offset)));
}

void AMDGPUTargetELFStreamer::EmitAmdhsaKernelDescriptor(
    const MCSubtargetInfo &STI, StringRef KernelName,
    const amdhsa::kernel_descriptor_t &KernelDescriptor, uint64_t NextVGPR,
    uint64_t NextSGPR, bool ReserveVCC, bool ReserveFlatScr,
    bool ReserveXNACK) {
  auto &Streamer = getStreamer();
  auto &Context = Streamer.getContext();

  MCSymbolELF *KernelCodeSymbol = cast<MCSymbolELF>(
      Context.getOrCreateSymbol(Twine(KernelName)));
  MCSymbolELF *KernelDescriptorSymbol = cast<MCSymbolELF>(
      Context.getOrCreateSymbol(Twine(KernelName) + Twine(".kd")));

  // Copy kernel descriptor symbol's binding, other and visibility from the
  // kernel code symbol.
  KernelDescriptorSymbol->setBinding(KernelCodeSymbol->getBinding());
  KernelDescriptorSymbol->setOther(KernelCodeSymbol->getOther());
  KernelDescriptorSymbol->setVisibility(KernelCodeSymbol->getVisibility());
  // Kernel descriptor symbol's type and size are fixed.
  KernelDescriptorSymbol->setType(ELF::STT_OBJECT);
  KernelDescriptorSymbol->setSize(
      MCConstantExpr::create(sizeof(KernelDescriptor), Context));

  // The visibility of the kernel code symbol must be protected or less to allow
  // static relocations from the kernel descriptor to be used.
  if (KernelCodeSymbol->getVisibility() == ELF::STV_DEFAULT)
    KernelCodeSymbol->setVisibility(ELF::STV_PROTECTED);

  Streamer.EmitLabel(KernelDescriptorSymbol);
  Streamer.EmitBytes(StringRef(
      (const char*)&(KernelDescriptor),
      offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset)));
  // FIXME: Remove the use of VK_AMDGPU_REL64 in the expression below. The
  // expression being created is:
  //   (start of kernel code) - (start of kernel descriptor)
  // It implies R_AMDGPU_REL64, but ends up being R_AMDGPU_ABS64.
  Streamer.EmitValue(MCBinaryExpr::createSub(
      MCSymbolRefExpr::create(
          KernelCodeSymbol, MCSymbolRefExpr::VK_AMDGPU_REL64, Context),
      MCSymbolRefExpr::create(
          KernelDescriptorSymbol, MCSymbolRefExpr::VK_None, Context),
      Context),
      sizeof(KernelDescriptor.kernel_code_entry_byte_offset));
  Streamer.EmitBytes(StringRef(
      (const char*)&(KernelDescriptor) +
          offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset) +
          sizeof(KernelDescriptor.kernel_code_entry_byte_offset),
      sizeof(KernelDescriptor) -
          offsetof(amdhsa::kernel_descriptor_t, kernel_code_entry_byte_offset) -
          sizeof(KernelDescriptor.kernel_code_entry_byte_offset)));
}

void AMDGPUTargetELFStreamer::EmitAMDGPUSymbolType(StringRef SymbolName,
                                                   unsigned Type) {
  MCSymbolELF *Symbol = cast<MCSymbolELF>(
      getStreamer().getContext().getOrCreateSymbol(SymbolName));
  Symbol->setType(Type);
}