DwarfDebug.h

//===- 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 "AddressPool.h"
#include "DbgValueHistoryCalculator.h"
#include "DebugHandlerBase.h"
#include "DebugLocStream.h"
#include "DwarfAccelTable.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/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 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 {
  const DILocalVariable *Var;                /// Variable Descriptor.
  const DILocation *IA;                      /// Inlined at location.
  DIE *TheDIE = nullptr;                     /// Variable DIE.
  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.

public:
  /// 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)
      : Var(V), IA(IA) {}

  /// 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(Var == DbgValue->getDebugVariable() && "Wrong variable");
    assert(IA == 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 Var; }
  const DILocation *getInlinedAt() const { return IA; }

  const DIExpression *getSingleExpression() const {
    assert(MInsn && FrameIndexExprs.size() <= 1);
    return FrameIndexExprs.size() ? FrameIndexExprs[0].Expr : nullptr;
  }

  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; }
  /// 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 (Var->isParameter())
      return dwarf::DW_TAG_formal_parameter;

    return dwarf::DW_TAG_variable;
  }

  /// 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 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;

private:
  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;
};

/// 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.
  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.
  SetVector<const DISubprogram *, SmallVector<const DISubprogram *, 16>,
            SmallPtrSet<const DISubprogram *, 16>>
      ProcessedSPNodes;

  /// 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;

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

  /// 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;

  /// DWARF5 Experimental Options
  /// @{
  bool HasDwarfAccelTables;
  bool HasAppleExtensionAttributes;
  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;

  AddressPool AddrPool;

  DwarfAccelTable AccelNames;
  DwarfAccelTable AccelObjC;
  DwarfAccelTable AccelNamespace;
  DwarfAccelTable 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 InlinedVariable = DbgValueHistoryMap::InlinedVariable;

  void ensureAbstractVariableIsCreated(DwarfCompileUnit &CU, InlinedVariable Var,
                                       const MDNode *Scope);
  void ensureAbstractVariableIsCreatedIfScoped(DwarfCompileUnit &CU, InlinedVariable Var,
                                               const MDNode *Scope);

  DbgVariable *createConcreteVariable(DwarfCompileUnit &TheCU,
                                      LexicalScope &Scope, InlinedVariable IV);

  /// Construct a DIE for this abstract scope.
  void constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU, LexicalScope *Scope);

  void finishVariableDefinitions();

  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 a specified accelerator table.
  void emitAccel(DwarfAccelTable &Accel, MCSection *Section,
                 StringRef TableName);

  /// 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();

  /// 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.
  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 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(DwarfCompileUnit &U, DIE &D) const;

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

  /// 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 collectVariableInfo(DwarfCompileUnit &TheCU, const DISubprogram *SP,
                           DenseSet<InlinedVariable> &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<InlinedVariable> &P);

protected:
  /// 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;

public:
  //===--------------------------------------------------------------------===//
  // 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; }

  // Experimental DWARF5 features.

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

  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; }

  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 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);

  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); }

  /// \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; }
  /// @}
};

} // end namespace llvm

#endif // LLVM_LIB_CODEGEN_ASMPRINTER_DWARFDEBUG_H