DwarfDebug.h   [plain text]

//===-- 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.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFDEBUG_H
#define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFDEBUG_H

#include "AsmPrinterHandler.h"
#include "DbgValueHistoryCalculator.h"
#include "DebugLocStream.h"
#include "DwarfAccelTable.h"
#include "DwarfFile.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/Support/Allocator.h"
#include <memory>

namespace llvm {

class AsmPrinter;
class ByteStreamer;
class ConstantInt;
class ConstantFP;
class DebugLocEntry;
class DwarfCompileUnit;
class DwarfDebug;
class DwarfTypeUnit;
class DwarfUnit;
class MachineModuleInfo;

//===----------------------------------------------------------------------===//
/// \brief This class is used to record source line correspondence.
class SrcLineInfo {
  unsigned Line;     // Source line number.
  unsigned Column;   // Source column.
  unsigned SourceID; // Source ID number.
  MCSymbol *Label;   // Label in code ID number.
public:
  SrcLineInfo(unsigned L, unsigned C, unsigned S, MCSymbol *label)
      : Line(L), Column(C), SourceID(S), Label(label) {}

  // Accessors
  unsigned getLine() const { return Line; }
  unsigned getColumn() const { return Column; }
  unsigned getSourceID() const { return SourceID; }
  MCSymbol *getLabel() const { return Label; }
};

//===----------------------------------------------------------------------===//
/// \brief This class is used to track local variable information.
///
/// - Variables whose location changes over time have a DebugLocListIndex and
///   the other fields are not used.
///
/// - Variables that are described by multiple MMI table entries have multiple
///   expressions and frame indices.
class DbgVariable {
  const DILocalVariable *Var; /// Variable Descriptor.
  const DILocation *IA;       /// Inlined at location.
  SmallVector<const DIExpression *, 1>
      Expr;                          /// Complex address location expression.
  DIE *TheDIE;                /// Variable DIE.
  unsigned DebugLocListIndex;        /// Offset in DebugLocs.
  const MachineInstr *MInsn;  /// DBG_VALUE instruction of the variable.
  SmallVector<int, 1> FrameIndex; /// Frame index of the variable.
  DwarfDebug *DD;

public:
  /// Construct a DbgVariable from a variable.
  DbgVariable(const DILocalVariable *V, const DILocation *IA,
              const DIExpression *E, DwarfDebug *DD, int FI = ~0)
      : Var(V), IA(IA), Expr(1, E), TheDIE(nullptr), DebugLocListIndex(~0U),
        MInsn(nullptr), DD(DD) {
    FrameIndex.push_back(FI);
    assert(!E || E->isValid());
  }

  /// Construct a DbgVariable from a DEBUG_VALUE.
  /// AbstractVar may be NULL.
  DbgVariable(const MachineInstr *DbgValue, DwarfDebug *DD)
      : Var(DbgValue->getDebugVariable()),
        IA(DbgValue->getDebugLoc()->getInlinedAt()),
        Expr(1, DbgValue->getDebugExpression()), TheDIE(nullptr),
        DebugLocListIndex(~0U), MInsn(DbgValue), DD(DD) {
    FrameIndex.push_back(~0);
  }

  // Accessors.
  const DILocalVariable *getVariable() const { return Var; }
  const DILocation *getInlinedAt() const { return IA; }
  const ArrayRef<const DIExpression *> getExpression() const { return Expr; }
  void setDIE(DIE &D) { TheDIE = &D; }
  DIE *getDIE() const { return TheDIE; }
  void setDebugLocListIndex(unsigned O) { DebugLocListIndex = O; }
  unsigned getDebugLocListIndex() const { return DebugLocListIndex; }
  StringRef getName() const { return Var->getName(); }
  const MachineInstr *getMInsn() const { return MInsn; }
  const ArrayRef<int> getFrameIndex() const { return FrameIndex; }

  void addMMIEntry(const DbgVariable &V) {
    assert(DebugLocListIndex == ~0U && !MInsn && "not an MMI entry");
    assert(V.DebugLocListIndex == ~0U && !V.MInsn && "not an MMI entry");
    assert(V.Var == Var && "conflicting variable");
    assert(V.IA == IA && "conflicting inlined-at location");

    if (V.getFrameIndex().back() != ~0) {
      auto E = V.getExpression();
      auto FI = V.getFrameIndex();
      Expr.append(E.begin(), E.end());
      FrameIndex.append(FI.begin(), FI.end());
    }
    assert(Expr.size() > 1 ? std::all_of(Expr.begin(), Expr.end(),
                                         [](const DIExpression *E) {
                                           return E->isBitPiece();
                                         })
                           : (true && "conflicting locations for variable"));
  }

  // Translate tag to proper Dwarf tag.
  dwarf::Tag getTag() const {
    if (Var->getTag() == dwarf::DW_TAG_arg_variable)
      return dwarf::DW_TAG_formal_parameter;

    return dwarf::DW_TAG_variable;
  }
  /// \brief Return true if DbgVariable is artificial.
  bool isArtificial() const {
    if (Var->isArtificial())
      return true;
    if (getType()->isArtificial())
      return true;
    return false;
  }

  bool isObjectPointer() const {
    if (Var->isObjectPointer())
      return true;
    if (getType()->isObjectPointer())
      return true;
    return false;
  }

  bool variableHasComplexAddress() const {
    assert(Var && "Invalid complex DbgVariable!");
    assert(Expr.size() == 1 &&
           "variableHasComplexAddress() invoked on multi-FI variable");
    return Expr.back()->getNumElements() > 0;
  }
  bool isBlockByrefVariable() const;
  const DIType *getType() const;

private:
  /// resolve - Look in the DwarfDebug map for the MDNode that
  /// corresponds to the reference.
  template <typename T> T *resolve(TypedDINodeRef<T> Ref) const;
};


/// \brief 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;
};

/// \brief Collects and handles dwarf debug information.
class DwarfDebug : public AsmPrinterHandler {
  // Target of Dwarf emission.
  AsmPrinter *Asm;

  // Collected machine module information.
  MachineModuleInfo *MMI;

  // All DIEValues are allocated through this allocator.
  BumpPtrAllocator DIEValueAllocator;

  // Maps MDNode with its corresponding DwarfCompileUnit.
  MapVector<const MDNode *, DwarfCompileUnit *> CUMap;

  // Maps subprogram MDNode with its corresponding DwarfCompileUnit.
  MapVector<const MDNode *, DwarfCompileUnit *> SPMap;

  // 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;

  LexicalScopes LScopes;

  // Collection of abstract variables.
  DenseMap<const MDNode *, std::unique_ptr<DbgVariable>> AbstractVariables;
  SmallVector<std::unique_ptr<DbgVariable>, 64> ConcreteVariables;

  // 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.
  SmallPtrSet<const MDNode *, 16> ProcessedSPNodes;

  // Maps instruction with label emitted before instruction.
  DenseMap<const MachineInstr *, MCSymbol *> LabelsBeforeInsn;

  // Maps instruction with label emitted after instruction.
  DenseMap<const MachineInstr *, MCSymbol *> LabelsAfterInsn;

  // History of DBG_VALUE and clobber instructions for each user variable.
  // Variables are listed in order of appearance.
  DbgValueHistoryMap DbgValues;

  // Previous instruction's location information. This is used to determine
  // label location to indicate scope boundries in dwarf debug info.
  DebugLoc PrevInstLoc;
  MCSymbol *PrevLabel;

  // This location indicates end of function prologue and beginning of function
  // body.
  DebugLoc PrologEndLoc;

  // If nonnull, stores the current machine function we're processing.
  const MachineFunction *CurFn;

  // If nonnull, stores the current machine instruction we're processing.
  const MachineInstr *CurMI;

  // 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;

  // Counter for assigning globally unique IDs for ranges.
  unsigned GlobalRangeCount;

  // 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.

  // Holder for imported entities.
  typedef SmallVector<std::pair<const MDNode *, const MDNode *>, 32>
  ImportedEntityMap;
  ImportedEntityMap ScopesWithImportedEntities;

  // Map from MDNodes for user-defined types to the type units that describe
  // them.
  DenseMap<const MDNode *, const DwarfTypeUnit *> DwarfTypeUnits;

  SmallVector<
      std::pair<std::unique_ptr<DwarfTypeUnit>, const DICompositeType *>, 1>
      TypeUnitsUnderConstruction;

  // Whether to emit the pubnames/pubtypes sections.
  bool HasDwarfPubSections;

  // Whether or not to use AT_ranges for compilation units.
  bool HasCURanges;

  // Whether we emitted a function into a section other than the default
  // text.
  bool UsedNonDefaultText;

  // Whether to use the GNU TLS opcode (instead of the standard opcode).
  bool UseGNUTLSOpcode;

  // Version of dwarf we're emitting.
  unsigned DwarfVersion;

  // Maps from a type identifier to the actual MDNode.
  DITypeIdentifierMap TypeIdentifierMap;

  // DWARF5 Experimental Options
  bool HasDwarfAccelTables;
  bool HasSplitDwarf;

  // 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;
  bool IsPS4;

  AddressPool AddrPool;

  DwarfAccelTable AccelNames;
  DwarfAccelTable AccelObjC;
  DwarfAccelTable AccelNamespace;
  DwarfAccelTable AccelTypes;
  DwarfAccelTable AccelExternalTypes;

  DenseMap<const Function *, DISubprogram *> FunctionDIs;

  MCDwarfDwoLineTable *getDwoLineTable(const DwarfCompileUnit &);

  const SmallVectorImpl<std::unique_ptr<DwarfUnit>> &getUnits() {
    return InfoHolder.getUnits();
  }

  typedef DbgValueHistoryMap::InlinedVariable InlinedVariable;

  /// \brief Find abstract variable associated with Var.
  DbgVariable *getExistingAbstractVariable(InlinedVariable IV,
                                           const DILocalVariable *&Cleansed);
  DbgVariable *getExistingAbstractVariable(InlinedVariable IV);
  void createAbstractVariable(const DILocalVariable *DV, LexicalScope *Scope);
  void ensureAbstractVariableIsCreated(InlinedVariable Var,
                                       const MDNode *Scope);
  void ensureAbstractVariableIsCreatedIfScoped(InlinedVariable Var,
                                               const MDNode *Scope);

  /// \brief Construct a DIE for this abstract scope.
  void constructAbstractSubprogramScopeDIE(LexicalScope *Scope);

  /// \brief Emit initial Dwarf sections with a label at the start of each one.
  void emitSectionLabels();

  /// \brief Compute the size and offset of a DIE given an incoming Offset.
  unsigned computeSizeAndOffset(DIE *Die, unsigned Offset);

  /// \brief Compute the size and offset of all the DIEs.
  void computeSizeAndOffsets();

  /// \brief Collect info for variables that were optimized out.
  void collectDeadVariables();

  void finishVariableDefinitions();

  void finishSubprogramDefinitions();

  /// \brief Finish off debug information after all functions have been
  /// processed.
  void finalizeModuleInfo();

  /// \brief Emit the debug info section.
  void emitDebugInfo();

  /// \brief Emit the abbreviation section.
  void emitAbbreviations();

  /// \brief Emit the last address of the section and the end of
  /// the line matrix.
  void emitEndOfLineMatrix(unsigned SectionEnd);

  /// \brief Emit a specified accelerator table.
  void emitAccel(DwarfAccelTable &Accel, const MCSection *Section,
                 StringRef TableName, StringRef SymName);

  /// \brief Emit visible names into a hashed accelerator table section.
  void emitAccelNames();

  /// \brief Emit objective C classes and categories into a hashed
  /// accelerator table section.
  void emitAccelObjC();

  /// \brief Emit namespace dies into a hashed accelerator table.
  void emitAccelNamespaces();

  /// \brief Emit type dies into a hashed accelerator table.
  void emitAccelTypes();

  void emitAccelExternalTypes();

  /// \brief Emit visible names into a debug pubnames section.
  /// \param GnuStyle determines whether or not we want to emit
  /// additional information into the table ala newer gcc for gdb
  /// index.
  void emitDebugPubNames(bool GnuStyle = false);

  /// \brief Emit visible types into a debug pubtypes section.
  /// \param GnuStyle determines whether or not we want to emit
  /// additional information into the table ala newer gcc for gdb
  /// index.
  void emitDebugPubTypes(bool GnuStyle = false);

  void emitDebugPubSection(
      bool GnuStyle, const MCSection *PSec, StringRef Name,
      const StringMap<const DIE *> &(DwarfCompileUnit::*Accessor)() const);

  /// \brief Emit visible names into a debug str section.
  void emitDebugStr();

  /// \brief Emit visible names into a debug loc section.
  void emitDebugLoc();

  /// \brief Emit visible names into a debug loc dwo section.
  void emitDebugLocDWO();

  /// \brief Emit visible names into a debug aranges section.
  void emitDebugARanges();

  /// \brief Emit visible names into a debug ranges section.
  void emitDebugRanges();

  /// \brief Emit inline info using custom format.
  void emitDebugInlineInfo();

  /// DWARF 5 Experimental Split Dwarf Emitters

  /// \brief Initialize common features of skeleton units.
  void initSkeletonUnit(const DwarfUnit &U, DIE &Die,
                        std::unique_ptr<DwarfUnit> NewU);

  /// \brief Construct the split debug info compile unit for the debug info
  /// section.
  DwarfCompileUnit &constructSkeletonCU(const DwarfCompileUnit &CU);

  /// \brief Construct the split debug info compile unit for the debug info
  /// section.
  DwarfTypeUnit &constructSkeletonTU(DwarfTypeUnit &TU);

  /// \brief Emit the debug info dwo section.
  void emitDebugInfoDWO();

  /// \brief Emit the debug abbrev dwo section.
  void emitDebugAbbrevDWO();

  /// \brief Emit the debug line dwo section.
  void emitDebugLineDWO();

  /// \brief Emit the debug str dwo section.
  void emitDebugStrDWO();

  /// 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(DwarfUnit &U, DIE &D) const;

  /// \brief Create new DwarfCompileUnit for the given metadata node with tag
  /// DW_TAG_compile_unit.
  DwarfCompileUnit &constructDwarfCompileUnit(const DICompileUnit *DIUnit);

  /// \brief Construct imported_module or imported_declaration DIE.
  void constructAndAddImportedEntityDIE(DwarfCompileUnit &TheCU,
                                        const DIImportedEntity *N);

  /// \brief 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);

  /// \brief Indentify instructions that are marking the beginning of or
  /// ending of a scope.
  void identifyScopeMarkers();

  /// \brief Populate LexicalScope entries with variables' info.
  void collectVariableInfo(DwarfCompileUnit &TheCU, const DISubprogram *SP,
                           DenseSet<InlinedVariable> &ProcessedVars);

  /// \brief 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);

  /// \brief Collect variable information from the side table maintained
  /// by MMI.
  void collectVariableInfoFromMMITable(DenseSet<InlinedVariable> &P);

  /// \brief Ensure that a label will be emitted before MI.
  void requestLabelBeforeInsn(const MachineInstr *MI) {
    LabelsBeforeInsn.insert(std::make_pair(MI, nullptr));
  }

  /// \brief Ensure that a label will be emitted after MI.
  void requestLabelAfterInsn(const MachineInstr *MI) {
    LabelsAfterInsn.insert(std::make_pair(MI, nullptr));
  }

public:
  //===--------------------------------------------------------------------===//
  // Main entry points.
  //
  DwarfDebug(AsmPrinter *A, Module *M);

  ~DwarfDebug() override;

  /// \brief Emit all Dwarf sections that should come prior to the
  /// content.
  void beginModule();

  /// \brief Emit all Dwarf sections that should come after the content.
  void endModule() override;

  /// \brief Gather pre-function debug information.
  void beginFunction(const MachineFunction *MF) override;

  /// \brief Gather and emit post-function debug information.
  void endFunction(const MachineFunction *MF) override;

  /// \brief Process beginning of an instruction.
  void beginInstruction(const MachineInstr *MI) override;

  /// \brief Process end of an instruction.
  void endInstruction() override;

  /// \brief 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);

  /// \brief Add a label so that arange data can be generated for it.
  void addArangeLabel(SymbolCU SCU) { ArangeLabels.push_back(SCU); }

  /// \brief 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;
  }

  /// \brief 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; }

  // Experimental DWARF5 features.

  /// \brief Returns whether or not to emit tables that dwarf consumers can
  /// use to accelerate lookup.
  bool useDwarfAccelTables() const { return HasDwarfAccelTables; }

  /// \brief Returns whether or not to change the current debug info for the
  /// split dwarf proposal support.
  bool useSplitDwarf() const { return HasSplitDwarf; }

  /// Returns the Dwarf Version.
  unsigned getDwarfVersion() const { return DwarfVersion; }

  /// 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; }

  /// \brief 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(TypeIdentifierMap);
  }

  /// \brief Return the TypeIdentifierMap.
  const DITypeIdentifierMap &getTypeIdentifierMap() const {
    return TypeIdentifierMap;
  }

  /// Find the DwarfCompileUnit for the given CU Die.
  DwarfCompileUnit *lookupUnit(const DIE *CU) const {
    return CUDieMap.lookup(CU);
  }
  /// isSubprogramContext - Return true if Context is either a subprogram
  /// or another context nested inside a subprogram.
  bool isSubprogramContext(const MDNode *Context);

  void addSubprogramNames(const DISubprogram *SP, DIE &Die);

  AddressPool &getAddressPool() { return AddrPool; }

  void addAccelName(StringRef Name, const DIE &Die);

  void addAccelObjC(StringRef Name, const DIE &Die);

  void addAccelNamespace(StringRef Name, const DIE &Die);

  void addAccelType(StringRef Name, const DIE &Die, char Flags);
  void addAccelExternalType(StringRef UID, StringRef Module);

  const MachineFunction *getCurrentFunction() const { return CurFn; }

  iterator_range<ImportedEntityMap::const_iterator>
  findImportedEntitiesForScope(const MDNode *Scope) const {
    return make_range(std::equal_range(
        ScopesWithImportedEntities.begin(), ScopesWithImportedEntities.end(),
        std::pair<const MDNode *, const MDNode *>(Scope, nullptr),
        less_first()));
  }

  /// \brief A helper function to check whether the DIE for a given Scope is
  /// going to be null.
  bool isLexicalScopeDIENull(LexicalScope *Scope);

  /// \brief Return Label preceding the instruction.
  MCSymbol *getLabelBeforeInsn(const MachineInstr *MI);

  /// \brief Return Label immediately following the instruction.
  MCSymbol *getLabelAfterInsn(const MachineInstr *MI);
  
  static uint64_t makeTypeSignature(StringRef Identifier);

  // FIXME: Consider rolling ranges up into DwarfDebug since we use a single
  // range_base anyway, so there's no need to keep them as separate per-CU range
  // lists. (though one day we might end up with a range.dwo section, in which
  // case it'd go to DwarfFile)
  unsigned getNextRangeNumber() { return GlobalRangeCount++; }

  // FIXME: Sink these functions down into DwarfFile/Dwarf*Unit.
  SmallPtrSet<const MDNode *, 16> &getProcessedSPNodes() {
    return ProcessedSPNodes;
  }
};
} // End of namespace llvm

#endif