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//===- llvm/CodeGen/DwarfDebug.h - Dwarf Debug Framework --------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file contains support for writing dwarf debug info into asm files.
#include "AddressPool.h"
#include "DebugLocStream.h"
#include "DwarfFile.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AccelTable.h"
#include "llvm/CodeGen/DbgEntityHistoryCalculator.h"
#include "llvm/CodeGen/DebugHandlerBase.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Metadata.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Target/TargetOptions.h"
#include <cassert>
#include <cstdint>
#include <limits>
#include <memory>
#include <utility>
#include <vector>
namespace llvm {
class AsmPrinter;
class ByteStreamer;
class DebugLocEntry;
class DIE;
class DwarfCompileUnit;
class DwarfTypeUnit;
class DwarfUnit;
class LexicalScope;
class MachineFunction;
class MCSection;
class MCSymbol;
class MDNode;
class Module;
/// This class is defined as the common parent of DbgVariable and DbgLabel
/// such that it could levarage polymorphism to extract common code for
/// DbgVariable and DbgLabel.
class DbgEntity {
const DINode *Entity;
const DILocation *InlinedAt;
DIE *TheDIE = nullptr;
unsigned SubclassID;
enum DbgEntityKind {
DbgEntity(const DINode *N, const DILocation *IA, unsigned ID)
: Entity(N), InlinedAt(IA), SubclassID(ID) {}
virtual ~DbgEntity() {}
/// Accessors.
/// @{
const DINode *getEntity() const { return Entity; }
const DILocation *getInlinedAt() const { return InlinedAt; }
DIE *getDIE() const { return TheDIE; }
unsigned getDbgEntityID() const { return SubclassID; }
/// @}
void setDIE(DIE &D) { TheDIE = &D; }
static bool classof(const DbgEntity *N) {
switch (N->getDbgEntityID()) {
return false;
case DbgVariableKind:
case DbgLabelKind:
return true;
/// This class is used to track local variable information.
/// Variables can be created from allocas, in which case they're generated from
/// the MMI table. Such variables can have multiple expressions and frame
/// indices.
/// Variables can be created from \c DBG_VALUE instructions. Those whose
/// location changes over time use \a DebugLocListIndex, while those with a
/// single instruction use \a MInsn and (optionally) a single entry of \a Expr.
/// Variables that have been optimized out use none of these fields.
class DbgVariable : public DbgEntity {
unsigned DebugLocListIndex = ~0u; /// Offset in DebugLocs.
const MachineInstr *MInsn = nullptr; /// DBG_VALUE instruction.
struct FrameIndexExpr {
int FI;
const DIExpression *Expr;
mutable SmallVector<FrameIndexExpr, 1>
FrameIndexExprs; /// Frame index + expression.
/// Construct a DbgVariable.
/// Creates a variable without any DW_AT_location. Call \a initializeMMI()
/// for MMI entries, or \a initializeDbgValue() for DBG_VALUE instructions.
DbgVariable(const DILocalVariable *V, const DILocation *IA)
: DbgEntity(V, IA, DbgVariableKind) {}
/// Initialize from the MMI table.
void initializeMMI(const DIExpression *E, int FI) {
assert(FrameIndexExprs.empty() && "Already initialized?");
assert(!MInsn && "Already initialized?");
assert((!E || E->isValid()) && "Expected valid expression");
assert(FI != std::numeric_limits<int>::max() && "Expected valid index");
FrameIndexExprs.push_back({FI, E});
/// Initialize from a DBG_VALUE instruction.
void initializeDbgValue(const MachineInstr *DbgValue) {
assert(FrameIndexExprs.empty() && "Already initialized?");
assert(!MInsn && "Already initialized?");
assert(getVariable() == DbgValue->getDebugVariable() && "Wrong variable");
assert(getInlinedAt() == DbgValue->getDebugLoc()->getInlinedAt() &&
"Wrong inlined-at");
MInsn = DbgValue;
if (auto *E = DbgValue->getDebugExpression())
if (E->getNumElements())
FrameIndexExprs.push_back({0, E});
// Accessors.
const DILocalVariable *getVariable() const {
return cast<DILocalVariable>(getEntity());
const DIExpression *getSingleExpression() const {
assert(MInsn && FrameIndexExprs.size() <= 1);
return FrameIndexExprs.size() ? FrameIndexExprs[0].Expr : nullptr;
void setDebugLocListIndex(unsigned O) { DebugLocListIndex = O; }
unsigned getDebugLocListIndex() const { return DebugLocListIndex; }
StringRef getName() const { return getVariable()->getName(); }
const MachineInstr *getMInsn() const { return MInsn; }
/// Get the FI entries, sorted by fragment offset.
ArrayRef<FrameIndexExpr> getFrameIndexExprs() const;
bool hasFrameIndexExprs() const { return !FrameIndexExprs.empty(); }
void addMMIEntry(const DbgVariable &V);
// Translate tag to proper Dwarf tag.
dwarf::Tag getTag() const {
// FIXME: Why don't we just infer this tag and store it all along?
if (getVariable()->isParameter())
return dwarf::DW_TAG_formal_parameter;
return dwarf::DW_TAG_variable;
/// Return true if DbgVariable is artificial.
bool isArtificial() const {
if (getVariable()->isArtificial())
return true;
if (getType()->isArtificial())
return true;
return false;
bool isObjectPointer() const {
if (getVariable()->isObjectPointer())
return true;
if (getType()->isObjectPointer())
return true;
return false;
bool hasComplexAddress() const {
assert(MInsn && "Expected DBG_VALUE, not MMI variable");
assert((FrameIndexExprs.empty() ||
(FrameIndexExprs.size() == 1 &&
FrameIndexExprs[0].Expr->getNumElements())) &&
"Invalid Expr for DBG_VALUE");
return !FrameIndexExprs.empty();
bool isBlockByrefVariable() const;
const DIType *getType() const;
static bool classof(const DbgEntity *N) {
return N->getDbgEntityID() == DbgVariableKind;
template <typename T> T *resolve(TypedDINodeRef<T> Ref) const {
return Ref.resolve();
/// This class is used to track label information.
/// Labels are collected from \c DBG_LABEL instructions.
class DbgLabel : public DbgEntity {
const MCSymbol *Sym; /// Symbol before DBG_LABEL instruction.
/// We need MCSymbol information to generate DW_AT_low_pc.
DbgLabel(const DILabel *L, const DILocation *IA, const MCSymbol *Sym = nullptr)
: DbgEntity(L, IA, DbgLabelKind), Sym(Sym) {}
/// Accessors.
/// @{
const DILabel *getLabel() const { return cast<DILabel>(getEntity()); }
const MCSymbol *getSymbol() const { return Sym; }
StringRef getName() const { return getLabel()->getName(); }
/// @}
/// Translate tag to proper Dwarf tag.
dwarf::Tag getTag() const {
return dwarf::DW_TAG_label;
static bool classof(const DbgEntity *N) {
return N->getDbgEntityID() == DbgLabelKind;
template <typename T> T *resolve(TypedDINodeRef<T> Ref) const {
return Ref.resolve();
/// Helper used to pair up a symbol and its DWARF compile unit.
struct SymbolCU {
SymbolCU(DwarfCompileUnit *CU, const MCSymbol *Sym) : Sym(Sym), CU(CU) {}
const MCSymbol *Sym;
DwarfCompileUnit *CU;
/// The kind of accelerator tables we should emit.
enum class AccelTableKind {
Default, ///< Platform default.
None, ///< None.
Apple, ///< .apple_names, .apple_namespaces, .apple_types, .apple_objc.
Dwarf, ///< DWARF v5 .debug_names.
/// Collects and handles dwarf debug information.
class DwarfDebug : public DebugHandlerBase {
/// All DIEValues are allocated through this allocator.
BumpPtrAllocator DIEValueAllocator;
/// Maps MDNode with its corresponding DwarfCompileUnit.
MapVector<const MDNode *, DwarfCompileUnit *> CUMap;
/// Maps a CU DIE with its corresponding DwarfCompileUnit.
DenseMap<const DIE *, DwarfCompileUnit *> CUDieMap;
/// List of all labels used in aranges generation.
std::vector<SymbolCU> ArangeLabels;
/// Size of each symbol emitted (for those symbols that have a specific size).
DenseMap<const MCSymbol *, uint64_t> SymSize;
/// Collection of abstract variables/labels.
SmallVector<std::unique_ptr<DbgEntity>, 64> ConcreteEntities;
/// Collection of DebugLocEntry. Stored in a linked list so that DIELocLists
/// can refer to them in spite of insertions into this list.
DebugLocStream DebugLocs;
/// This is a collection of subprogram MDNodes that are processed to
/// create DIEs.
SetVector<const DISubprogram *, SmallVector<const DISubprogram *, 16>,
SmallPtrSet<const DISubprogram *, 16>>
/// If nonnull, stores the current machine function we're processing.
const MachineFunction *CurFn = nullptr;
/// If nonnull, stores the CU in which the previous subprogram was contained.
const DwarfCompileUnit *PrevCU;
/// As an optimization, there is no need to emit an entry in the directory
/// table for the same directory as DW_AT_comp_dir.
StringRef CompilationDir;
/// Holder for the file specific debug information.
DwarfFile InfoHolder;
/// Holders for the various debug information flags that we might need to
/// have exposed. See accessor functions below for description.
/// Map from MDNodes for user-defined types to their type signatures. Also
/// used to keep track of which types we have emitted type units for.
DenseMap<const MDNode *, uint64_t> TypeSignatures;
DenseMap<const MCSection *, const MCSymbol *> SectionLabels;
std::pair<std::unique_ptr<DwarfTypeUnit>, const DICompositeType *>, 1>
/// Whether to use the GNU TLS opcode (instead of the standard opcode).
bool UseGNUTLSOpcode;
/// Whether to use DWARF 2 bitfields (instead of the DWARF 4 format).
bool UseDWARF2Bitfields;
/// Whether to emit all linkage names, or just abstract subprograms.
bool UseAllLinkageNames;
/// Use inlined strings.
bool UseInlineStrings = false;
/// Allow emission of .debug_ranges section.
bool UseRangesSection = true;
/// True if the sections itself must be used as references and don't create
/// temp symbols inside DWARF sections.
bool UseSectionsAsReferences = false;
///Allow emission of the .debug_loc section.
bool UseLocSection = true;
/// Generate DWARF v4 type units.
bool GenerateTypeUnits;
/// DWARF5 Experimental Options
/// @{
AccelTableKind TheAccelTableKind;
bool HasAppleExtensionAttributes;
bool HasSplitDwarf;
/// Whether to generate the DWARF v5 string offsets table.
/// It consists of a series of contributions, each preceded by a header.
/// The pre-DWARF v5 string offsets table for split dwarf is, in contrast,
/// a monolithic sequence of string offsets.
bool UseSegmentedStringOffsetsTable;
/// Separated Dwarf Variables
/// In general these will all be for bits that are left in the
/// original object file, rather than things that are meant
/// to be in the .dwo sections.
/// Holder for the skeleton information.
DwarfFile SkeletonHolder;
/// Store file names for type units under fission in a line table
/// header that will be emitted into debug_line.dwo.
// FIXME: replace this with a map from comp_dir to table so that we
// can emit multiple tables during LTO each of which uses directory
// 0, referencing the comp_dir of all the type units that use it.
MCDwarfDwoLineTable SplitTypeUnitFileTable;
/// @}
/// True iff there are multiple CUs in this module.
bool SingleCU;
bool IsDarwin;
AddressPool AddrPool;
/// Accelerator tables.
AccelTable<DWARF5AccelTableData> AccelDebugNames;
AccelTable<AppleAccelTableOffsetData> AccelNames;
AccelTable<AppleAccelTableOffsetData> AccelObjC;
AccelTable<AppleAccelTableOffsetData> AccelNamespace;
AccelTable<AppleAccelTableTypeData> AccelTypes;
// Identify a debugger for "tuning" the debug info.
DebuggerKind DebuggerTuning = DebuggerKind::Default;
MCDwarfDwoLineTable *getDwoLineTable(const DwarfCompileUnit &);
const SmallVectorImpl<std::unique_ptr<DwarfCompileUnit>> &getUnits() {
return InfoHolder.getUnits();
using InlinedEntity = DbgValueHistoryMap::InlinedEntity;
void ensureAbstractEntityIsCreated(DwarfCompileUnit &CU,
const DINode *Node,
const MDNode *Scope);
void ensureAbstractEntityIsCreatedIfScoped(DwarfCompileUnit &CU,
const DINode *Node,
const MDNode *Scope);
DbgEntity *createConcreteEntity(DwarfCompileUnit &TheCU,
LexicalScope &Scope,
const DINode *Node,
const DILocation *Location,
const MCSymbol *Sym = nullptr);
/// Construct a DIE for this abstract scope.
void constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU, LexicalScope *Scope);
/// Construct DIEs for call site entries describing the calls in \p MF.
void constructCallSiteEntryDIEs(const DISubprogram &SP, DwarfCompileUnit &CU,
DIE &ScopeDIE, const MachineFunction &MF);
template <typename DataT>
void addAccelNameImpl(const DICompileUnit &CU, AccelTable<DataT> &AppleAccel,
StringRef Name, const DIE &Die);
void finishEntityDefinitions();
void finishSubprogramDefinitions();
/// Finish off debug information after all functions have been
/// processed.
void finalizeModuleInfo();
/// Emit the debug info section.
void emitDebugInfo();
/// Emit the abbreviation section.
void emitAbbreviations();
/// Emit the string offsets table header.
void emitStringOffsetsTableHeader();
/// Emit a specified accelerator table.
template <typename AccelTableT>
void emitAccel(AccelTableT &Accel, MCSection *Section, StringRef TableName);
/// Emit DWARF v5 accelerator table.
void emitAccelDebugNames();
/// Emit visible names into a hashed accelerator table section.
void emitAccelNames();
/// Emit objective C classes and categories into a hashed
/// accelerator table section.
void emitAccelObjC();
/// Emit namespace dies into a hashed accelerator table.
void emitAccelNamespaces();
/// Emit type dies into a hashed accelerator table.
void emitAccelTypes();
/// Emit visible names and types into debug pubnames and pubtypes sections.
void emitDebugPubSections();
void emitDebugPubSection(bool GnuStyle, StringRef Name,
DwarfCompileUnit *TheU,
const StringMap<const DIE *> &Globals);
/// Emit null-terminated strings into a debug str section.
void emitDebugStr();
/// Emit variable locations into a debug loc section.
void emitDebugLoc();
/// Emit variable locations into a debug loc dwo section.
void emitDebugLocDWO();
/// Emit address ranges into a debug aranges section.
void emitDebugARanges();
/// Emit address ranges into a debug ranges section.
void emitDebugRanges();
void emitDebugRangesDWO();
/// Emit macros into a debug macinfo section.
void emitDebugMacinfo();
void emitMacro(DIMacro &M);
void emitMacroFile(DIMacroFile &F, DwarfCompileUnit &U);
void handleMacroNodes(DIMacroNodeArray Nodes, DwarfCompileUnit &U);
/// DWARF 5 Experimental Split Dwarf Emitters
/// Initialize common features of skeleton units.
void initSkeletonUnit(const DwarfUnit &U, DIE &Die,
std::unique_ptr<DwarfCompileUnit> NewU);
/// Construct the split debug info compile unit for the debug info section.
/// In DWARF v5, the skeleton unit DIE may have the following attributes:
/// DW_AT_addr_base, DW_AT_comp_dir, DW_AT_dwo_name, DW_AT_high_pc,
/// DW_AT_low_pc, DW_AT_ranges, DW_AT_stmt_list, and DW_AT_str_offsets_base.
/// Prior to DWARF v5 it may also have DW_AT_GNU_dwo_id. DW_AT_GNU_dwo_name
/// is used instead of DW_AT_dwo_name, Dw_AT_GNU_addr_base instead of
/// DW_AT_addr_base, and DW_AT_GNU_ranges_base instead of DW_AT_rnglists_base.
DwarfCompileUnit &constructSkeletonCU(const DwarfCompileUnit &CU);
/// Emit the debug info dwo section.
void emitDebugInfoDWO();
/// Emit the debug abbrev dwo section.
void emitDebugAbbrevDWO();
/// Emit the debug line dwo section.
void emitDebugLineDWO();
/// Emit the dwo stringoffsets table header.
void emitStringOffsetsTableHeaderDWO();
/// Emit the debug str dwo section.
void emitDebugStrDWO();
/// Emit DWO addresses.
void emitDebugAddr();
/// Flags to let the linker know we have emitted new style pubnames. Only
/// emit it here if we don't have a skeleton CU for split dwarf.
void addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const;
/// Create new DwarfCompileUnit for the given metadata node with tag
/// DW_TAG_compile_unit.
DwarfCompileUnit &getOrCreateDwarfCompileUnit(const DICompileUnit *DIUnit);
void finishUnitAttributes(const DICompileUnit *DIUnit,
DwarfCompileUnit &NewCU);
/// Construct imported_module or imported_declaration DIE.
void constructAndAddImportedEntityDIE(DwarfCompileUnit &TheCU,
const DIImportedEntity *N);
/// Register a source line with debug info. Returns the unique
/// label that was emitted and which provides correspondence to the
/// source line list.
void recordSourceLine(unsigned Line, unsigned Col, const MDNode *Scope,
unsigned Flags);
/// Populate LexicalScope entries with variables' info.
void collectEntityInfo(DwarfCompileUnit &TheCU, const DISubprogram *SP,
DenseSet<InlinedEntity> &ProcessedVars);
/// Build the location list for all DBG_VALUEs in the
/// function that describe the same variable.
void buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc,
const DbgValueHistoryMap::InstrRanges &Ranges);
/// Collect variable information from the side table maintained by MF.
void collectVariableInfoFromMFTable(DwarfCompileUnit &TheCU,
DenseSet<InlinedEntity> &P);
/// Emit the reference to the section.
void emitSectionReference(const DwarfCompileUnit &CU);
/// Gather pre-function debug information.
void beginFunctionImpl(const MachineFunction *MF) override;
/// Gather and emit post-function debug information.
void endFunctionImpl(const MachineFunction *MF) override;
void skippedNonDebugFunction() override;
// Main entry points.
DwarfDebug(AsmPrinter *A, Module *M);
~DwarfDebug() override;
/// Emit all Dwarf sections that should come prior to the
/// content.
void beginModule();
/// Emit all Dwarf sections that should come after the content.
void endModule() override;
/// Process beginning of an instruction.
void beginInstruction(const MachineInstr *MI) override;
/// Perform an MD5 checksum of \p Identifier and return the lower 64 bits.
static uint64_t makeTypeSignature(StringRef Identifier);
/// Add a DIE to the set of types that we're going to pull into
/// type units.
void addDwarfTypeUnitType(DwarfCompileUnit &CU, StringRef Identifier,
DIE &Die, const DICompositeType *CTy);
/// Add a label so that arange data can be generated for it.
void addArangeLabel(SymbolCU SCU) { ArangeLabels.push_back(SCU); }
/// For symbols that have a size designated (e.g. common symbols),
/// this tracks that size.
void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {
SymSize[Sym] = Size;
/// Returns whether we should emit all DW_AT_[MIPS_]linkage_name.
/// If not, we still might emit certain cases.
bool useAllLinkageNames() const { return UseAllLinkageNames; }
/// Returns whether to use DW_OP_GNU_push_tls_address, instead of the
/// standard DW_OP_form_tls_address opcode
bool useGNUTLSOpcode() const { return UseGNUTLSOpcode; }
/// Returns whether to use the DWARF2 format for bitfields instyead of the
/// DWARF4 format.
bool useDWARF2Bitfields() const { return UseDWARF2Bitfields; }
/// Returns whether to use inline strings.
bool useInlineStrings() const { return UseInlineStrings; }
/// Returns whether ranges section should be emitted.
bool useRangesSection() const { return UseRangesSection; }
/// Returns whether to use sections as labels rather than temp symbols.
bool useSectionsAsReferences() const {
return UseSectionsAsReferences;
/// Returns whether .debug_loc section should be emitted.
bool useLocSection() const { return UseLocSection; }
/// Returns whether to generate DWARF v4 type units.
bool generateTypeUnits() const { return GenerateTypeUnits; }
// Experimental DWARF5 features.
/// Returns what kind (if any) of accelerator tables to emit.
AccelTableKind getAccelTableKind() const { return TheAccelTableKind; }
bool useAppleExtensionAttributes() const {
return HasAppleExtensionAttributes;
/// Returns whether or not to change the current debug info for the
/// split dwarf proposal support.
bool useSplitDwarf() const { return HasSplitDwarf; }
/// Returns whether to generate a string offsets table with (possibly shared)
/// contributions from each CU and type unit. This implies the use of
/// DW_FORM_strx* indirect references with DWARF v5 and beyond. Note that
/// DW_FORM_GNU_str_index is also an indirect reference, but it is used with
/// a pre-DWARF v5 implementation of split DWARF sections, which uses a
/// monolithic string offsets table.
bool useSegmentedStringOffsetsTable() const {
return UseSegmentedStringOffsetsTable;
bool shareAcrossDWOCUs() const;
/// Returns the Dwarf Version.
uint16_t getDwarfVersion() const;
/// Returns the previous CU that was being updated
const DwarfCompileUnit *getPrevCU() const { return PrevCU; }
void setPrevCU(const DwarfCompileUnit *PrevCU) { this->PrevCU = PrevCU; }
/// Returns the entries for the .debug_loc section.
const DebugLocStream &getDebugLocs() const { return DebugLocs; }
/// Emit an entry for the debug loc section. This can be used to
/// handle an entry that's going to be emitted into the debug loc section.
void emitDebugLocEntry(ByteStreamer &Streamer,
const DebugLocStream::Entry &Entry);
/// Emit the location for a debug loc entry, including the size header.
void emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry);
/// Find the MDNode for the given reference.
template <typename T> T *resolve(TypedDINodeRef<T> Ref) const {
return Ref.resolve();
void addSubprogramNames(const DICompileUnit &CU, const DISubprogram *SP,
DIE &Die);
AddressPool &getAddressPool() { return AddrPool; }
void addAccelName(const DICompileUnit &CU, StringRef Name, const DIE &Die);
void addAccelObjC(const DICompileUnit &CU, StringRef Name, const DIE &Die);
void addAccelNamespace(const DICompileUnit &CU, StringRef Name,
const DIE &Die);
void addAccelType(const DICompileUnit &CU, StringRef Name, const DIE &Die,
char Flags);
const MachineFunction *getCurrentFunction() const { return CurFn; }
/// A helper function to check whether the DIE for a given Scope is
/// going to be null.
bool isLexicalScopeDIENull(LexicalScope *Scope);
/// Find the matching DwarfCompileUnit for the given CU DIE.
DwarfCompileUnit *lookupCU(const DIE *Die) { return CUDieMap.lookup(Die); }
const DwarfCompileUnit *lookupCU(const DIE *Die) const {
return CUDieMap.lookup(Die);
/// \defgroup DebuggerTuning Predicates to tune DWARF for a given debugger.
/// Returns whether we are "tuning" for a given debugger.
/// @{
bool tuneForGDB() const { return DebuggerTuning == DebuggerKind::GDB; }
bool tuneForLLDB() const { return DebuggerTuning == DebuggerKind::LLDB; }
bool tuneForSCE() const { return DebuggerTuning == DebuggerKind::SCE; }
/// @}
void addSectionLabel(const MCSymbol *Sym);
const MCSymbol *getSectionLabel(const MCSection *S);
} // end namespace llvm