C++ DIE类代码示例

/// Climb up the parent chain to get the compile unit DIE to which this DIE
/// belongs.
DIE *DIE::getCompileUnit() {
  DIE *p = this;
  while (p) {
    if (p->getTag() == dwarf::DW_TAG_compile_unit)
      return p;
    p = p->getParent();
  }
  llvm_unreachable("We should not have orphaned DIEs.");
}

// Construct a DIE for this scope.
void DwarfCompileUnit::constructScopeDIE(
    LexicalScope *Scope, SmallVectorImpl<DIE *> &FinalChildren) {
  if (!Scope || !Scope->getScopeNode())
    return;

  auto *DS = Scope->getScopeNode();

  assert((Scope->getInlinedAt() || !isa<DISubprogram>(DS)) &&
         "Only handle inlined subprograms here, use "
         "constructSubprogramScopeDIE for non-inlined "
         "subprograms");

  SmallVector<DIE *, 8> Children;

  // We try to create the scope DIE first, then the children DIEs. This will
  // avoid creating un-used children then removing them later when we find out
  // the scope DIE is null.
  DIE *ScopeDIE;
  if (Scope->getParent() && isa<DISubprogram>(DS)) {
    ScopeDIE = constructInlinedScopeDIE(Scope);
    if (!ScopeDIE)
      return;
    // We create children when the scope DIE is not null.
    createScopeChildrenDIE(Scope, Children);
  } else {
    // Early exit when we know the scope DIE is going to be null.
    if (DD->isLexicalScopeDIENull(Scope))
      return;

    bool HasNonScopeChildren = false;

    // We create children here when we know the scope DIE is not going to be
    // null and the children will be added to the scope DIE.
    createScopeChildrenDIE(Scope, Children, &HasNonScopeChildren);

    // If there are only other scopes as children, put them directly in the
    // parent instead, as this scope would serve no purpose.
    if (!HasNonScopeChildren) {
      FinalChildren.insert(FinalChildren.end(),
                           std::make_move_iterator(Children.begin()),
                           std::make_move_iterator(Children.end()));
      return;
    }
    ScopeDIE = constructLexicalScopeDIE(Scope);
    assert(ScopeDIE && "Scope DIE should not be null.");
  }

  // Add children
  for (auto &I : Children)
    ScopeDIE->addChild(std::move(I));

  FinalChildren.push_back(std::move(ScopeDIE));
}

void DwarfCompileUnit::addLocalLabelAddress(DIE &Die,
                                            dwarf::Attribute Attribute,
                                            const MCSymbol *Label) {
  if (Label)
    DD->addArangeLabel(SymbolCU(this, Label));

  if (Label)
    Die.addValue(DIEValueAllocator, Attribute, dwarf::DW_FORM_addr,
                 DIELabel(Label));
  else
    Die.addValue(DIEValueAllocator, Attribute, dwarf::DW_FORM_addr,
                 DIEInteger(0));
}

/// addTemplateParams - Add template parameters in buffer.
void CompileUnit::addTemplateParams(DIE &Buffer, DIArray TParams) {
  // Add template parameters.
  for (unsigned i = 0, e = TParams.getNumElements(); i != e; ++i) {
    DIDescriptor Element = TParams.getElement(i);
    if (Element.isTemplateTypeParameter())
      Buffer.addChild(getOrCreateTemplateTypeParameterDIE(
                        DITemplateTypeParameter(Element)));
    else if (Element.isTemplateValueParameter())
      Buffer.addChild(getOrCreateTemplateValueParameterDIE(
                        DITemplateValueParameter(Element)));
  }

}

void CompileUnit::fixupForwardReferences() {
  for (const auto &Ref : ForwardDIEReferences) {
    DIE *RefDie;
    const CompileUnit *RefUnit;
    PatchLocation Attr;
    DeclContext *Ctxt;
    std::tie(RefDie, RefUnit, Ctxt, Attr) = Ref;
    if (Ctxt && Ctxt->getCanonicalDIEOffset())
      Attr.set(Ctxt->getCanonicalDIEOffset());
    else
      Attr.set(RefDie->getOffset() + RefUnit->getStartOffset());
  }
}

void test (DIE die, DIE *Die, DIE INT, DIE *FLOAT) {
  DIE.foo();  // expected-error {{cannot use dot operator on a type}}
  die.foo();

  DIE->foo();  // expected-error {{cannot use arrow operator on a type}}
  Die->foo();

  int.foo();  // expected-error {{cannot use dot operator on a type}}
  INT.foo();

  float->foo();  // expected-error {{cannot use arrow operator on a type}}
  FLOAT->foo();
}

void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
  // Emit the code (index) for the abbreviation.
  if (isVerbose())
    OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
                            Twine::utohexstr(Die.getOffset()) + ":0x" +
                            Twine::utohexstr(Die.getSize()) + " " +
                            dwarf::TagString(Die.getTag()));
  EmitULEB128(Die.getAbbrevNumber());

  // Emit the DIE attribute values.
  for (const auto &V : Die.values()) {
    dwarf::Attribute Attr = V.getAttribute();
    assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");

    if (isVerbose()) {
      OutStreamer->AddComment(dwarf::AttributeString(Attr));
      if (Attr == dwarf::DW_AT_accessibility)
        OutStreamer->AddComment(
            dwarf::AccessibilityString(V.getDIEInteger().getValue()));
    }

    // Emit an attribute using the defined form.
    V.EmitValue(this);
  }

  // Emit the DIE children if any.
  if (Die.hasChildren()) {
    for (auto &Child : Die.children())
      emitDwarfDIE(Child);

    OutStreamer->AddComment("End Of Children Mark");
    EmitInt8(0);
  }
}

/// constructTypeDIE - Construct derived type die from DIDerivedType.
void CompileUnit::constructTypeDIE(DIE &Buffer, DIDerivedType DTy) {
  // Get core information.
  StringRef Name = DTy.getName();
  uint64_t Size = DTy.getSizeInBits() >> 3;
  unsigned Tag = DTy.getTag();

  // FIXME - Workaround for templates.
  if (Tag == dwarf::DW_TAG_inheritance) Tag = dwarf::DW_TAG_reference_type;

  Buffer.setTag(Tag);

  // Map to main type, void will not have a type.
  DIType FromTy = DTy.getTypeDerivedFrom();
  addType(&Buffer, FromTy);

  // Add name if not anonymous or intermediate type.
  if (!Name.empty())
    addString(&Buffer, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);

  // Add size if non-zero (derived types might be zero-sized.)
  if (Size)
    addUInt(&Buffer, dwarf::DW_AT_byte_size, 0, Size);

  // Add source line info if available and TyDesc is not a forward declaration.
  if (!DTy.isForwardDecl())
    addSourceLine(&Buffer, DTy);
}

/// constructArrayTypeDIE - Construct array type DIE from DICompositeType.
void CompileUnit::constructArrayTypeDIE(DIE &Buffer,
                                        DICompositeType *CTy) {
  Buffer.setTag(dwarf::DW_TAG_array_type);
  if (CTy->getTag() == dwarf::DW_TAG_vector_type)
    addUInt(&Buffer, dwarf::DW_AT_GNU_vector, dwarf::DW_FORM_flag, 1);

  // Emit derived type.
  addType(&Buffer, CTy->getTypeDerivedFrom());
  DIArray Elements = CTy->getTypeArray();

  // Get an anonymous type for index type.
  DIE *IdxTy = getIndexTyDie();
  if (!IdxTy) {
    // Construct an anonymous type for index type.
    IdxTy = new DIE(dwarf::DW_TAG_base_type);
    addUInt(IdxTy, dwarf::DW_AT_byte_size, 0, sizeof(int32_t));
    addUInt(IdxTy, dwarf::DW_AT_encoding, dwarf::DW_FORM_data1,
            dwarf::DW_ATE_signed);
    addDie(IdxTy);
    setIndexTyDie(IdxTy);
  }

  // Add subranges to array type.
  for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
    DIDescriptor Element = Elements.getElement(i);
    if (Element.getTag() == dwarf::DW_TAG_subrange_type)
      constructSubrangeDIE(Buffer, DISubrange(Element), IdxTy);
  }
}

void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
  // Get the abbreviation for this DIE.
  const DIEAbbrev &Abbrev = Die.getAbbrev();

  // Emit the code (index) for the abbreviation.
  if (isVerbose())
    OutStreamer.AddComment("Abbrev [" + Twine(Abbrev.getNumber()) +
                           "] 0x" + Twine::utohexstr(Die.getOffset()) +
                           ":0x" + Twine::utohexstr(Die.getSize()) + " " +
                           dwarf::TagString(Abbrev.getTag()));
  EmitULEB128(Abbrev.getNumber());

  const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();

  // Emit the DIE attribute values.
  for (unsigned i = 0, N = Values.size(); i < N; ++i) {
    dwarf::Attribute Attr = AbbrevData[i].getAttribute();
    dwarf::Form Form = AbbrevData[i].getForm();
    assert(Form && "Too many attributes for DIE (check abbreviation)");

    if (isVerbose()) {
      OutStreamer.AddComment(dwarf::AttributeString(Attr));
      if (Attr == dwarf::DW_AT_accessibility)
        OutStreamer.AddComment(dwarf::AccessibilityString(
            cast<DIEInteger>(Values[i])->getValue()));
    }

    // Emit an attribute using the defined form.
    Values[i]->EmitValue(this, Form);
  }

  // Emit the DIE children if any.
  if (Abbrev.hasChildren()) {
    for (auto &Child : Die.getChildren())
      emitDwarfDIE(Child);

    OutStreamer.AddComment("End Of Children Mark");
    EmitInt8(0);
  }
}

/// constructSubrangeDIE - Construct subrange DIE from DISubrange.
void CompileUnit::constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy){
  DIE *DW_Subrange = new DIE(dwarf::DW_TAG_subrange_type);
  addDIEEntry(DW_Subrange, dwarf::DW_AT_type, dwarf::DW_FORM_ref4, IndexTy);
  int64_t L = SR.getLo();
  int64_t H = SR.getHi();

  // The L value defines the lower bounds which is typically zero for C/C++. The
  // H value is the upper bounds.  Values are 64 bit.  H - L + 1 is the size
  // of the array. If L > H then do not emit DW_AT_lower_bound and 
  // DW_AT_upper_bound attributes. If L is zero and H is also zero then the
  // array has one element and in such case do not emit lower bound.

  if (L > H) {
    Buffer.addChild(DW_Subrange);
    return;
  }
  if (L)
    addSInt(DW_Subrange, dwarf::DW_AT_lower_bound, 0, L);
  addSInt(DW_Subrange, dwarf::DW_AT_upper_bound, 0, H);
  Buffer.addChild(DW_Subrange);
}

void DwarfCompileUnit::constructAbstractSubprogramScopeDIE(
    LexicalScope *Scope) {
  DIE *&AbsDef = getAbstractSPDies()[Scope->getScopeNode()];
  if (AbsDef)
    return;

  auto *SP = cast<DISubprogram>(Scope->getScopeNode());

  DIE *ContextDIE;
  DwarfCompileUnit *ContextCU = this;

  if (includeMinimalInlineScopes())
    ContextDIE = &getUnitDie();
  // Some of this is duplicated from DwarfUnit::getOrCreateSubprogramDIE, with
  // the important distinction that the debug node is not associated with the
  // DIE (since the debug node will be associated with the concrete DIE, if
  // any). It could be refactored to some common utility function.
  else if (auto *SPDecl = SP->getDeclaration()) {
    ContextDIE = &getUnitDie();
    getOrCreateSubprogramDIE(SPDecl);
  } else {
    ContextDIE = getOrCreateContextDIE(resolve(SP->getScope()));
    // The scope may be shared with a subprogram that has already been
    // constructed in another CU, in which case we need to construct this
    // subprogram in the same CU.
    ContextCU = DD->lookupCU(ContextDIE->getUnitDie());
  }

  // Passing null as the associated node because the abstract definition
  // shouldn't be found by lookup.
  AbsDef = &ContextCU->createAndAddDIE(dwarf::DW_TAG_subprogram, *ContextDIE, nullptr);
  ContextCU->applySubprogramAttributesToDefinition(SP, *AbsDef);

  if (!ContextCU->includeMinimalInlineScopes())
    ContextCU->addUInt(*AbsDef, dwarf::DW_AT_inline, None, dwarf::DW_INL_inlined);
  if (DIE *ObjectPointer = ContextCU->createAndAddScopeChildren(Scope, *AbsDef))
    ContextCU->addDIEEntry(*AbsDef, dwarf::DW_AT_object_pointer, *ObjectPointer);
}

/// addLabelAddress - Add a dwarf label attribute data and value using
/// DW_FORM_addr or DW_FORM_GNU_addr_index.
void DwarfCompileUnit::addLabelAddress(DIE &Die, dwarf::Attribute Attribute,
                                       const MCSymbol *Label) {
  // Don't use the address pool in non-fission or in the skeleton unit itself.
  // FIXME: Once GDB supports this, it's probably worthwhile using the address
  // pool from the skeleton - maybe even in non-fission (possibly fewer
  // relocations by sharing them in the pool, but we have other ideas about how
  // to reduce the number of relocations as well/instead).
  if ((!DD->useSplitDwarf() || !Skeleton) && DD->getDwarfVersion() < 5)
    return addLocalLabelAddress(Die, Attribute, Label);

  if (Label)
    DD->addArangeLabel(SymbolCU(this, Label));

  unsigned idx = DD->getAddressPool().getIndex(Label);
  Die.addValue(DIEValueAllocator, Attribute,
               DD->getDwarfVersion() >= 5 ? dwarf::DW_FORM_addrx
                                          : dwarf::DW_FORM_GNU_addr_index,
               DIEInteger(idx));
}

/// addToContextOwner - Add Die into the list of its context owner's children.
void CompileUnit::addToContextOwner(DIE *Die, DIDescriptor Context) {
  if (Context.isType()) {
    DIE *ContextDIE = getOrCreateTypeDIE(DIType(Context));
    ContextDIE->addChild(Die);
  } else if (Context.isNameSpace()) {
    DIE *ContextDIE = getOrCreateNameSpace(DINameSpace(Context));
    ContextDIE->addChild(Die);
  } else if (Context.isSubprogram()) {
    DIE *ContextDIE = DD->createSubprogramDIE(DISubprogram(Context));
    ContextDIE->addChild(Die);
  } else if (DIE *ContextDIE = getDIE(Context))
    ContextDIE->addChild(Die);
  else
    addDie(Die);
}

// Compute the size and offset of a DIE. The offset is relative to start of the
// CU. It returns the offset after laying out the DIE.
unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
  // Record the abbreviation.
  assignAbbrevNumber(Die.getAbbrev());

  // Get the abbreviation for this DIE.
  const DIEAbbrev &Abbrev = Die.getAbbrev();

  // Set DIE offset
  Die.setOffset(Offset);

  // Start the size with the size of abbreviation code.
  Offset += getULEB128Size(Die.getAbbrevNumber());

  const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();

  // Size the DIE attribute values.
  for (unsigned i = 0, N = Values.size(); i < N; ++i)
    // Size attribute value.
    Offset += Values[i]->SizeOf(Asm, AbbrevData[i].getForm());

  // Get the children.
  const auto &Children = Die.getChildren();

  // Size the DIE children if any.
  if (!Children.empty()) {
    assert(Abbrev.hasChildren() && "Children flag not set");

    for (auto &Child : Children)
      Offset = computeSizeAndOffset(*Child, Offset);

    // End of children marker.
    Offset += sizeof(int8_t);
  }

  Die.setSize(Offset - Die.getOffset());
  return Offset;
}