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//===- DWARFAbbreviationDeclaration.h ---------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/Support/DataExtractor.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
namespace llvm {
class DWARFFormValue;
class DWARFUnit;
class raw_ostream;
class DWARFAbbreviationDeclaration {
struct AttributeSpec {
AttributeSpec(dwarf::Attribute A, dwarf::Form F, int64_t Value)
: Attr(A), Form(F), Value(Value) {
AttributeSpec(dwarf::Attribute A, dwarf::Form F, Optional<uint8_t> ByteSize)
: Attr(A), Form(F) {
this->ByteSize.HasByteSize = ByteSize.hasValue();
if (this->ByteSize.HasByteSize)
this->ByteSize.ByteSize = *ByteSize;
dwarf::Attribute Attr;
dwarf::Form Form;
/// The following field is used for ByteSize for non-implicit_const
/// attributes and as value for implicit_const ones, indicated by
/// Form == DW_FORM_implicit_const.
/// The following cases are distinguished:
/// * Form != DW_FORM_implicit_const and HasByteSize is true:
/// ByteSize contains the fixed size in bytes for the Form in this
/// object.
/// * Form != DW_FORM_implicit_const and HasByteSize is false:
/// byte size of Form either varies according to the DWARFUnit
/// that it is contained in or the value size varies and must be
/// decoded from the debug information in order to determine its size.
/// * Form == DW_FORM_implicit_const:
/// Value contains value for the implicit_const attribute.
struct ByteSizeStorage {
bool HasByteSize;
uint8_t ByteSize;
union {
ByteSizeStorage ByteSize;
int64_t Value;
bool isImplicitConst() const {
return Form == dwarf::DW_FORM_implicit_const;
int64_t getImplicitConstValue() const {
return Value;
/// Get the fixed byte size of this Form if possible. This function might
/// use the DWARFUnit to calculate the size of the Form, like for
/// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for
/// the ByteSize member.
Optional<int64_t> getByteSize(const DWARFUnit &U) const;
using AttributeSpecVector = SmallVector<AttributeSpec, 8>;
uint32_t getCode() const { return Code; }
uint8_t getCodeByteSize() const { return CodeByteSize; }
dwarf::Tag getTag() const { return Tag; }
bool hasChildren() const { return HasChildren; }
using attr_iterator_range =
attr_iterator_range attributes() const {
return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());
dwarf::Form getFormByIndex(uint32_t idx) const {
assert(idx < AttributeSpecs.size());
return AttributeSpecs[idx].Form;
size_t getNumAttributes() const {
return AttributeSpecs.size();
dwarf::Attribute getAttrByIndex(uint32_t idx) const {
assert(idx < AttributeSpecs.size());
return AttributeSpecs[idx].Attr;
/// Get the index of the specified attribute.
/// Searches the this abbreviation declaration for the index of the specified
/// attribute.
/// \param attr DWARF attribute to search for.
/// \returns Optional index of the attribute if found, None otherwise.
Optional<uint32_t> findAttributeIndex(dwarf::Attribute attr) const;
/// Extract a DWARF form value from a DIE specified by DIE offset.
/// Extract an attribute value for a DWARFUnit given the DIE offset and the
/// attribute.
/// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
/// code in the .debug_info data.
/// \param Attr DWARF attribute to search for.
/// \param U the DWARFUnit the contains the DIE.
/// \returns Optional DWARF form value if the attribute was extracted.
Optional<DWARFFormValue> getAttributeValue(const uint32_t DIEOffset,
const dwarf::Attribute Attr,
const DWARFUnit &U) const;
bool extract(DataExtractor Data, uint32_t* OffsetPtr);
void dump(raw_ostream &OS) const;
// Return an optional byte size of all attribute data in this abbreviation
// if a constant byte size can be calculated given a DWARFUnit. This allows
// DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.
Optional<size_t> getFixedAttributesByteSize(const DWARFUnit &U) const;
void clear();
/// A helper structure that can quickly determine the size in bytes of an
/// abbreviation declaration.
struct FixedSizeInfo {
/// The fixed byte size for fixed size forms.
uint16_t NumBytes = 0;
/// Number of DW_FORM_address forms in this abbrevation declaration.
uint8_t NumAddrs = 0;
/// Number of DW_FORM_ref_addr forms in this abbrevation declaration.
uint8_t NumRefAddrs = 0;
/// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.
uint8_t NumDwarfOffsets = 0;
FixedSizeInfo() = default;
/// Calculate the fixed size in bytes given a DWARFUnit.
/// \param U the DWARFUnit to use when determing the byte size.
/// \returns the size in bytes for all attribute data in this abbreviation.
/// The returned size does not include bytes for the ULEB128 abbreviation
/// code
size_t getByteSize(const DWARFUnit &U) const;
uint32_t Code;
dwarf::Tag Tag;
uint8_t CodeByteSize;
bool HasChildren;
AttributeSpecVector AttributeSpecs;
/// If this abbreviation has a fixed byte size then FixedAttributeSize member
/// variable below will have a value.
Optional<FixedSizeInfo> FixedAttributeSize;
} // end namespace llvm