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//===- DWARFLinkerCompileUnit.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/AddressRanges.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
#include <optional>
namespace llvm {
class DeclContext;
/// Mapped value in the address map is the offset to apply to the
/// linked address.
using RangesTy = AddressRangesMap;
// This structure keeps patch for the attribute and, optionally,
// the value of relocation which should be applied. Currently,
// only location attribute needs to have relocation: either to the
// function ranges if location attribute is of type 'loclist',
// either to the operand of DW_OP_addr/DW_OP_addrx if location attribute
// is of type 'exprloc'.
// ASSUMPTION: Location attributes of 'loclist' type containing 'exprloc'
// with address expression operands are not supported yet.
struct PatchLocation {
DIE::value_iterator I;
int64_t RelocAdjustment = 0;
PatchLocation() = default;
PatchLocation(DIE::value_iterator I) : I(I) {}
PatchLocation(DIE::value_iterator I, int64_t Reloc)
: I(I), RelocAdjustment(Reloc) {}
void set(uint64_t New) const {
const auto &Old = *I;
assert(Old.getType() == DIEValue::isInteger);
*I = DIEValue(Old.getAttribute(), Old.getForm(), DIEInteger(New));
uint64_t get() const {
return I->getDIEInteger().getValue();
using RngListAttributesTy = SmallVector<PatchLocation>;
using LocListAttributesTy = SmallVector<PatchLocation>;
/// Stores all information relating to a compile unit, be it in its original
/// instance in the object file to its brand new cloned and generated DIE tree.
class CompileUnit {
/// Information gathered about a DIE in the object file.
struct DIEInfo {
/// Address offset to apply to the described entity.
int64_t AddrAdjust;
/// ODR Declaration context.
DeclContext *Ctxt;
/// Cloned version of that DIE.
DIE *Clone;
/// The index of this DIE's parent.
uint32_t ParentIdx;
/// Is the DIE part of the linked output?
bool Keep : 1;
/// Was this DIE's entity found in the map?
bool InDebugMap : 1;
/// Is this a pure forward declaration we can strip?
bool Prune : 1;
/// Does DIE transitively refer an incomplete decl?
bool Incomplete : 1;
/// Is DIE in the clang module scope?
bool InModuleScope : 1;
/// Is ODR marking done?
bool ODRMarkingDone : 1;
/// Is this a reference to a DIE that hasn't been cloned yet?
bool UnclonedReference : 1;
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump();
#endif // if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
CompileUnit(DWARFUnit &OrigUnit, unsigned ID, bool CanUseODR,
StringRef ClangModuleName)
: OrigUnit(OrigUnit), ID(ID), ClangModuleName(ClangModuleName) {
auto CUDie = OrigUnit.getUnitDIE(false);
if (!CUDie) {
HasODR = false;
if (auto Lang = dwarf::toUnsigned(CUDie.find(dwarf::DW_AT_language)))
HasODR = CanUseODR && (*Lang == dwarf::DW_LANG_C_plus_plus ||
*Lang == dwarf::DW_LANG_C_plus_plus_03 ||
*Lang == dwarf::DW_LANG_C_plus_plus_11 ||
*Lang == dwarf::DW_LANG_C_plus_plus_14 ||
*Lang == dwarf::DW_LANG_ObjC_plus_plus);
HasODR = false;
DWARFUnit &getOrigUnit() const { return OrigUnit; }
unsigned getUniqueID() const { return ID; }
void createOutputDIE() { NewUnit.emplace(OrigUnit.getUnitDIE().getTag()); }
DIE *getOutputUnitDIE() const {
if (NewUnit)
return &const_cast<BasicDIEUnit &>(*NewUnit).getUnitDie();
return nullptr;
bool hasODR() const { return HasODR; }
bool isClangModule() const { return !ClangModuleName.empty(); }
uint16_t getLanguage();
/// Return the DW_AT_LLVM_sysroot of the compile unit or an empty StringRef.
StringRef getSysRoot();
const std::string &getClangModuleName() const { return ClangModuleName; }
DIEInfo &getInfo(unsigned Idx) { return Info[Idx]; }
const DIEInfo &getInfo(unsigned Idx) const { return Info[Idx]; }
DIEInfo &getInfo(const DWARFDie &Die) {
unsigned Idx = getOrigUnit().getDIEIndex(Die);
return Info[Idx];
uint64_t getStartOffset() const { return StartOffset; }
uint64_t getNextUnitOffset() const { return NextUnitOffset; }
void setStartOffset(uint64_t DebugInfoSize) { StartOffset = DebugInfoSize; }
std::optional<uint64_t> getLowPc() const { return LowPc; }
uint64_t getHighPc() const { return HighPc; }
bool hasLabelAt(uint64_t Addr) const { return Labels.count(Addr); }
const RangesTy &getFunctionRanges() const { return Ranges; }
const RngListAttributesTy &getRangesAttributes() { return RangeAttributes; }
std::optional<PatchLocation> getUnitRangesAttribute() const {
return UnitRangeAttribute;
const LocListAttributesTy &getLocationAttributes() const {
return LocationAttributes;
/// Mark every DIE in this unit as kept. This function also
/// marks variables as InDebugMap so that they appear in the
/// reconstructed accelerator tables.
void markEverythingAsKept();
/// Compute the end offset for this unit. Must be called after the CU's DIEs
/// have been cloned. \returns the next unit offset (which is also the
/// current debug_info section size).
uint64_t computeNextUnitOffset(uint16_t DwarfVersion);
/// Keep track of a forward reference to DIE \p Die in \p RefUnit by \p
/// Attr. The attribute should be fixed up later to point to the absolute
/// offset of \p Die in the debug_info section or to the canonical offset of
/// \p Ctxt if it is non-null.
void noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
DeclContext *Ctxt, PatchLocation Attr);
/// Apply all fixups recorded by noteForwardReference().
void fixupForwardReferences();
/// Add the low_pc of a label that is relocated by applying
/// offset \p PCOffset.
void addLabelLowPc(uint64_t LabelLowPc, int64_t PcOffset);
/// Add a function range [\p LowPC, \p HighPC) that is relocated by applying
/// offset \p PCOffset.
void addFunctionRange(uint64_t LowPC, uint64_t HighPC, int64_t PCOffset);
/// Keep track of a DW_AT_range attribute that we will need to patch up later.
void noteRangeAttribute(const DIE &Die, PatchLocation Attr);
/// Keep track of a location attribute pointing to a location list in the
/// debug_loc section.
void noteLocationAttribute(PatchLocation Attr);
/// Add a name accelerator entry for \a Die with \a Name.
void addNamespaceAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name);
/// Add a name accelerator entry for \a Die with \a Name.
void addNameAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
bool SkipPubnamesSection = false);
/// Add various accelerator entries for \p Die with \p Name which is stored
/// in the string table at \p Offset. \p Name must be an Objective-C
/// selector.
void addObjCAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
bool SkipPubnamesSection = false);
/// Add a type accelerator entry for \p Die with \p Name which is stored in
/// the string table at \p Offset.
void addTypeAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
bool ObjcClassImplementation,
uint32_t QualifiedNameHash);
struct AccelInfo {
/// Name of the entry.
DwarfStringPoolEntryRef Name;
/// DIE this entry describes.
const DIE *Die;
/// Hash of the fully qualified name.
uint32_t QualifiedNameHash;
/// Emit this entry only in the apple_* sections.
bool SkipPubSection;
/// Is this an ObjC class implementation?
bool ObjcClassImplementation;
AccelInfo(DwarfStringPoolEntryRef Name, const DIE *Die,
bool SkipPubSection = false)
: Name(Name), Die(Die), SkipPubSection(SkipPubSection) {}
AccelInfo(DwarfStringPoolEntryRef Name, const DIE *Die,
uint32_t QualifiedNameHash, bool ObjCClassIsImplementation)
: Name(Name), Die(Die), QualifiedNameHash(QualifiedNameHash),
ObjcClassImplementation(ObjCClassIsImplementation) {}
const std::vector<AccelInfo> &getPubnames() const { return Pubnames; }
const std::vector<AccelInfo> &getPubtypes() const { return Pubtypes; }
const std::vector<AccelInfo> &getNamespaces() const { return Namespaces; }
const std::vector<AccelInfo> &getObjC() const { return ObjC; }
MCSymbol *getLabelBegin() { return LabelBegin; }
void setLabelBegin(MCSymbol *S) { LabelBegin = S; }
DWARFUnit &OrigUnit;
unsigned ID;
std::vector<DIEInfo> Info; ///< DIE info indexed by DIE index.
std::optional<BasicDIEUnit> NewUnit;
MCSymbol *LabelBegin = nullptr;
uint64_t StartOffset;
uint64_t NextUnitOffset;
std::optional<uint64_t> LowPc;
uint64_t HighPc = 0;
/// A list of attributes to fixup with the absolute offset of
/// a DIE in the debug_info section.
/// The offsets for the attributes in this array couldn't be set while
/// cloning because for cross-cu forward references the target DIE's offset
/// isn't known you emit the reference attribute.
std::tuple<DIE *, const CompileUnit *, DeclContext *, PatchLocation>>
/// The ranges in that map are the PC ranges for functions in this unit,
/// associated with the PC offset to apply to the addresses to get
/// the linked address.
RangesTy Ranges;
/// The DW_AT_low_pc of each DW_TAG_label.
SmallDenseMap<uint64_t, uint64_t, 1> Labels;
/// 'rnglist'(DW_AT_ranges, DW_AT_start_scope) attributes to patch after
/// we have gathered all the unit's function addresses.
/// @{
RngListAttributesTy RangeAttributes;
std::optional<PatchLocation> UnitRangeAttribute;
/// @}
/// Location attributes that need to be transferred from the
/// original debug_loc section to the linked one. They are stored
/// along with the PC offset that is to be applied to their
/// function's address or to be applied to address operands of
/// location expression.
LocListAttributesTy LocationAttributes;
/// Accelerator entries for the unit, both for the pub*
/// sections and the apple* ones.
/// @{
std::vector<AccelInfo> Pubnames;
std::vector<AccelInfo> Pubtypes;
std::vector<AccelInfo> Namespaces;
std::vector<AccelInfo> ObjC;
/// @}
/// Is this unit subject to the ODR rule?
bool HasODR;
/// The DW_AT_language of this unit.
uint16_t Language = 0;
/// The DW_AT_LLVM_sysroot of this unit.
std::string SysRoot;
/// If this is a Clang module, this holds the module's name.
std::string ClangModuleName;
} // end namespace llvm