llvm-3.9-dev 1:3.9.1-19ubuntu1 / usr / include / llvm-3.9 / llvm / MC / MCContext.h

//===- MCContext.h - Machine Code Context -----------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_MC_MCCONTEXT_H
#define LLVM_MC_MCCONTEXT_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCCodeView.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h"
#include <map>
#include <tuple>
#include <vector> // FIXME: Shouldn't be needed.

namespace llvm {
  class MCAsmInfo;
  class MCExpr;
  class MCSection;
  class MCSymbol;
  class MCSymbolELF;
  class MCLabel;
  struct MCDwarfFile;
  class MCDwarfLoc;
  class MCObjectFileInfo;
  class MCRegisterInfo;
  class MCLineSection;
  class SMLoc;
  class MCSectionMachO;
  class MCSectionELF;
  class MCSectionCOFF;
  class CodeViewContext;

  /// Context object for machine code objects.  This class owns all of the
  /// sections that it creates.
  ///
  class MCContext {
    MCContext(const MCContext &) = delete;
    MCContext &operator=(const MCContext &) = delete;

  public:
    typedef StringMap<MCSymbol *, BumpPtrAllocator &> SymbolTable;

  private:
    /// The SourceMgr for this object, if any.
    const SourceMgr *SrcMgr;

    /// The MCAsmInfo for this target.
    const MCAsmInfo *MAI;

    /// The MCRegisterInfo for this target.
    const MCRegisterInfo *MRI;

    /// The MCObjectFileInfo for this target.
    const MCObjectFileInfo *MOFI;

    std::unique_ptr<CodeViewContext> CVContext;

    /// Allocator object used for creating machine code objects.
    ///
    /// We use a bump pointer allocator to avoid the need to track all allocated
    /// objects.
    BumpPtrAllocator Allocator;

    SpecificBumpPtrAllocator<MCSectionCOFF> COFFAllocator;
    SpecificBumpPtrAllocator<MCSectionELF> ELFAllocator;
    SpecificBumpPtrAllocator<MCSectionMachO> MachOAllocator;

    /// Bindings of names to symbols.
    SymbolTable Symbols;

    /// ELF sections can have a corresponding symbol. This maps one to the
    /// other.
    DenseMap<const MCSectionELF *, MCSymbolELF *> SectionSymbols;

    /// A mapping from a local label number and an instance count to a symbol.
    /// For example, in the assembly
    ///     1:
    ///     2:
    ///     1:
    /// We have three labels represented by the pairs (1, 0), (2, 0) and (1, 1)
    DenseMap<std::pair<unsigned, unsigned>, MCSymbol *> LocalSymbols;

    /// Keeps tracks of names that were used both for used declared and
    /// artificial symbols. The value is "true" if the name has been used for a
    /// non-section symbol (there can be at most one of those, plus an unlimited
    /// number of section symbols with the same name).
    StringMap<bool, BumpPtrAllocator &> UsedNames;

    /// The next ID to dole out to an unnamed assembler temporary symbol with
    /// a given prefix.
    StringMap<unsigned> NextID;

    /// Instances of directional local labels.
    DenseMap<unsigned, MCLabel *> Instances;
    /// NextInstance() creates the next instance of the directional local label
    /// for the LocalLabelVal and adds it to the map if needed.
    unsigned NextInstance(unsigned LocalLabelVal);
    /// GetInstance() gets the current instance of the directional local label
    /// for the LocalLabelVal and adds it to the map if needed.
    unsigned GetInstance(unsigned LocalLabelVal);

    /// The file name of the log file from the environment variable
    /// AS_SECURE_LOG_FILE.  Which must be set before the .secure_log_unique
    /// directive is used or it is an error.
    char *SecureLogFile;
    /// The stream that gets written to for the .secure_log_unique directive.
    std::unique_ptr<raw_fd_ostream> SecureLog;
    /// Boolean toggled when .secure_log_unique / .secure_log_reset is seen to
    /// catch errors if .secure_log_unique appears twice without
    /// .secure_log_reset appearing between them.
    bool SecureLogUsed;

    /// The compilation directory to use for DW_AT_comp_dir.
    SmallString<128> CompilationDir;

    /// The main file name if passed in explicitly.
    std::string MainFileName;

    /// The dwarf file and directory tables from the dwarf .file directive.
    /// We now emit a line table for each compile unit. To reduce the prologue
    /// size of each line table, the files and directories used by each compile
    /// unit are separated.
    std::map<unsigned, MCDwarfLineTable> MCDwarfLineTablesCUMap;

    /// The current dwarf line information from the last dwarf .loc directive.
    MCDwarfLoc CurrentDwarfLoc;
    bool DwarfLocSeen;

    /// The current CodeView line information from the last .cv_loc directive.
    MCCVLoc CurrentCVLoc = MCCVLoc(0, 0, 0, 0, false, true);
    bool CVLocSeen = false;

    /// Generate dwarf debugging info for assembly source files.
    bool GenDwarfForAssembly;

    /// The current dwarf file number when generate dwarf debugging info for
    /// assembly source files.
    unsigned GenDwarfFileNumber;

    /// Sections for generating the .debug_ranges and .debug_aranges sections.
    SetVector<MCSection *> SectionsForRanges;

    /// The information gathered from labels that will have dwarf label
    /// entries when generating dwarf assembly source files.
    std::vector<MCGenDwarfLabelEntry> MCGenDwarfLabelEntries;

    /// The string to embed in the debug information for the compile unit, if
    /// non-empty.
    StringRef DwarfDebugFlags;

    /// The string to embed in as the dwarf AT_producer for the compile unit, if
    /// non-empty.
    StringRef DwarfDebugProducer;

    /// The maximum version of dwarf that we should emit.
    uint16_t DwarfVersion;

    /// Honor temporary labels, this is useful for debugging semantic
    /// differences between temporary and non-temporary labels (primarily on
    /// Darwin).
    bool AllowTemporaryLabels;
    bool UseNamesOnTempLabels = true;

    /// The Compile Unit ID that we are currently processing.
    unsigned DwarfCompileUnitID;

    struct ELFSectionKey {
      std::string SectionName;
      StringRef GroupName;
      unsigned UniqueID;
      ELFSectionKey(StringRef SectionName, StringRef GroupName,
                    unsigned UniqueID)
          : SectionName(SectionName), GroupName(GroupName), UniqueID(UniqueID) {
      }
      bool operator<(const ELFSectionKey &Other) const {
        if (SectionName != Other.SectionName)
          return SectionName < Other.SectionName;
        if (GroupName != Other.GroupName)
          return GroupName < Other.GroupName;
        return UniqueID < Other.UniqueID;
      }
    };

    struct COFFSectionKey {
      std::string SectionName;
      StringRef GroupName;
      int SelectionKey;
      unsigned UniqueID;
      COFFSectionKey(StringRef SectionName, StringRef GroupName,
                     int SelectionKey, unsigned UniqueID)
          : SectionName(SectionName), GroupName(GroupName),
            SelectionKey(SelectionKey), UniqueID(UniqueID) {}
      bool operator<(const COFFSectionKey &Other) const {
        if (SectionName != Other.SectionName)
          return SectionName < Other.SectionName;
        if (GroupName != Other.GroupName)
          return GroupName < Other.GroupName;
        if (SelectionKey != Other.SelectionKey)
          return SelectionKey < Other.SelectionKey;
        return UniqueID < Other.UniqueID;
      }
    };

    StringMap<MCSectionMachO *> MachOUniquingMap;
    std::map<ELFSectionKey, MCSectionELF *> ELFUniquingMap;
    std::map<COFFSectionKey, MCSectionCOFF *> COFFUniquingMap;
    StringMap<bool> ELFRelSecNames;

    SpecificBumpPtrAllocator<MCSubtargetInfo> MCSubtargetAllocator;

    /// Do automatic reset in destructor
    bool AutoReset;

    bool HadError;

    MCSymbol *createSymbolImpl(const StringMapEntry<bool> *Name,
                               bool CanBeUnnamed);
    MCSymbol *createSymbol(StringRef Name, bool AlwaysAddSuffix,
                           bool IsTemporary);

    MCSymbol *getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
                                                unsigned Instance);

  public:
    explicit MCContext(const MCAsmInfo *MAI, const MCRegisterInfo *MRI,
                       const MCObjectFileInfo *MOFI,
                       const SourceMgr *Mgr = nullptr, bool DoAutoReset = true);
    ~MCContext();

    const SourceMgr *getSourceManager() const { return SrcMgr; }

    const MCAsmInfo *getAsmInfo() const { return MAI; }

    const MCRegisterInfo *getRegisterInfo() const { return MRI; }

    const MCObjectFileInfo *getObjectFileInfo() const { return MOFI; }

    CodeViewContext &getCVContext();

    void setAllowTemporaryLabels(bool Value) { AllowTemporaryLabels = Value; }
    void setUseNamesOnTempLabels(bool Value) { UseNamesOnTempLabels = Value; }

    /// \name Module Lifetime Management
    /// @{

    /// reset - return object to right after construction state to prepare
    /// to process a new module
    void reset();

    /// @}

    /// \name Symbol Management
    /// @{

    /// Create and return a new linker temporary symbol with a unique but
    /// unspecified name.
    MCSymbol *createLinkerPrivateTempSymbol();

    /// Create and return a new assembler temporary symbol with a unique but
    /// unspecified name.
    MCSymbol *createTempSymbol(bool CanBeUnnamed = true);

    MCSymbol *createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
                               bool CanBeUnnamed = true);

    /// Create the definition of a directional local symbol for numbered label
    /// (used for "1:" definitions).
    MCSymbol *createDirectionalLocalSymbol(unsigned LocalLabelVal);

    /// Create and return a directional local symbol for numbered label (used
    /// for "1b" or 1f" references).
    MCSymbol *getDirectionalLocalSymbol(unsigned LocalLabelVal, bool Before);

    /// Lookup the symbol inside with the specified \p Name.  If it exists,
    /// return it.  If not, create a forward reference and return it.
    ///
    /// \param Name - The symbol name, which must be unique across all symbols.
    MCSymbol *getOrCreateSymbol(const Twine &Name);

    MCSymbolELF *getOrCreateSectionSymbol(const MCSectionELF &Section);

    /// Gets a symbol that will be defined to the final stack offset of a local
    /// variable after codegen.
    ///
    /// \param Idx - The index of a local variable passed to @llvm.localescape.
    MCSymbol *getOrCreateFrameAllocSymbol(StringRef FuncName, unsigned Idx);

    MCSymbol *getOrCreateParentFrameOffsetSymbol(StringRef FuncName);

    MCSymbol *getOrCreateLSDASymbol(StringRef FuncName);

    /// Get the symbol for \p Name, or null.
    MCSymbol *lookupSymbol(const Twine &Name) const;

    /// getSymbols - Get a reference for the symbol table for clients that
    /// want to, for example, iterate over all symbols. 'const' because we
    /// still want any modifications to the table itself to use the MCContext
    /// APIs.
    const SymbolTable &getSymbols() const { return Symbols; }

    /// @}

    /// \name Section Management
    /// @{

    enum : unsigned {
      /// Pass this value as the UniqueID during section creation to get the
      /// generic section with the given name and characteristics. The usual
      /// sections such as .text use this ID.
      GenericSectionID = ~0U
    };

    /// Return the MCSection for the specified mach-o section.  This requires
    /// the operands to be valid.
    MCSectionMachO *getMachOSection(StringRef Segment, StringRef Section,
                                    unsigned TypeAndAttributes,
                                    unsigned Reserved2, SectionKind K,
                                    const char *BeginSymName = nullptr);

    MCSectionMachO *getMachOSection(StringRef Segment, StringRef Section,
                                    unsigned TypeAndAttributes, SectionKind K,
                                    const char *BeginSymName = nullptr) {
      return getMachOSection(Segment, Section, TypeAndAttributes, 0, K,
                             BeginSymName);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags) {
      return getELFSection(Section, Type, Flags, nullptr);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, const char *BeginSymName) {
      return getELFSection(Section, Type, Flags, 0, "", BeginSymName);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, unsigned EntrySize,
                                const Twine &Group) {
      return getELFSection(Section, Type, Flags, EntrySize, Group, nullptr);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, unsigned EntrySize,
                                const Twine &Group, const char *BeginSymName) {
      return getELFSection(Section, Type, Flags, EntrySize, Group, ~0,
                           BeginSymName);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, unsigned EntrySize,
                                const Twine &Group, unsigned UniqueID) {
      return getELFSection(Section, Type, Flags, EntrySize, Group, UniqueID,
                           nullptr);
    }

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, unsigned EntrySize,
                                const Twine &Group, unsigned UniqueID,
                                const char *BeginSymName);

    MCSectionELF *getELFSection(const Twine &Section, unsigned Type,
                                unsigned Flags, unsigned EntrySize,
                                const MCSymbolELF *Group, unsigned UniqueID,
                                const char *BeginSymName,
                                const MCSectionELF *Associated);

    /// Get a section with the provided group identifier. This section is
    /// named by concatenating \p Prefix with '.' then \p Suffix. The \p Type
    /// describes the type of the section and \p Flags are used to further
    /// configure this named section.
    MCSectionELF *getELFNamedSection(const Twine &Prefix, const Twine &Suffix,
                                     unsigned Type, unsigned Flags,
                                     unsigned EntrySize = 0);

    MCSectionELF *createELFRelSection(const Twine &Name, unsigned Type,
                                      unsigned Flags, unsigned EntrySize,
                                      const MCSymbolELF *Group,
                                      const MCSectionELF *Associated);

    void renameELFSection(MCSectionELF *Section, StringRef Name);

    MCSectionELF *createELFGroupSection(const MCSymbolELF *Group);

    MCSectionCOFF *getCOFFSection(StringRef Section, unsigned Characteristics,
                                  SectionKind Kind, StringRef COMDATSymName,
                                  int Selection,
                                  unsigned UniqueID = GenericSectionID,
                                  const char *BeginSymName = nullptr);

    MCSectionCOFF *getCOFFSection(StringRef Section, unsigned Characteristics,
                                  SectionKind Kind,
                                  const char *BeginSymName = nullptr);

    MCSectionCOFF *getCOFFSection(StringRef Section);

    /// Gets or creates a section equivalent to Sec that is associated with the
    /// section containing KeySym. For example, to create a debug info section
    /// associated with an inline function, pass the normal debug info section
    /// as Sec and the function symbol as KeySym.
    MCSectionCOFF *
    getAssociativeCOFFSection(MCSectionCOFF *Sec, const MCSymbol *KeySym,
                              unsigned UniqueID = GenericSectionID);

    // Create and save a copy of STI and return a reference to the copy.
    MCSubtargetInfo &getSubtargetCopy(const MCSubtargetInfo &STI);

    /// @}

    /// \name Dwarf Management
    /// @{

    /// \brief Get the compilation directory for DW_AT_comp_dir
    /// The compilation directory should be set with \c setCompilationDir before
    /// calling this function. If it is unset, an empty string will be returned.
    StringRef getCompilationDir() const { return CompilationDir; }

    /// \brief Set the compilation directory for DW_AT_comp_dir
    void setCompilationDir(StringRef S) { CompilationDir = S.str(); }

    /// \brief Get the main file name for use in error messages and debug
    /// info. This can be set to ensure we've got the correct file name
    /// after preprocessing or for -save-temps.
    const std::string &getMainFileName() const { return MainFileName; }

    /// \brief Set the main file name and override the default.
    void setMainFileName(StringRef S) { MainFileName = S; }

    /// Creates an entry in the dwarf file and directory tables.
    unsigned getDwarfFile(StringRef Directory, StringRef FileName,
                          unsigned FileNumber, unsigned CUID);

    bool isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID = 0);

    const std::map<unsigned, MCDwarfLineTable> &getMCDwarfLineTables() const {
      return MCDwarfLineTablesCUMap;
    }

    MCDwarfLineTable &getMCDwarfLineTable(unsigned CUID) {
      return MCDwarfLineTablesCUMap[CUID];
    }

    const MCDwarfLineTable &getMCDwarfLineTable(unsigned CUID) const {
      auto I = MCDwarfLineTablesCUMap.find(CUID);
      assert(I != MCDwarfLineTablesCUMap.end());
      return I->second;
    }

    const SmallVectorImpl<MCDwarfFile> &getMCDwarfFiles(unsigned CUID = 0) {
      return getMCDwarfLineTable(CUID).getMCDwarfFiles();
    }
    const SmallVectorImpl<std::string> &getMCDwarfDirs(unsigned CUID = 0) {
      return getMCDwarfLineTable(CUID).getMCDwarfDirs();
    }

    bool hasMCLineSections() const {
      for (const auto &Table : MCDwarfLineTablesCUMap)
        if (!Table.second.getMCDwarfFiles().empty() || Table.second.getLabel())
          return true;
      return false;
    }
    unsigned getDwarfCompileUnitID() { return DwarfCompileUnitID; }
    void setDwarfCompileUnitID(unsigned CUIndex) {
      DwarfCompileUnitID = CUIndex;
    }
    void setMCLineTableCompilationDir(unsigned CUID, StringRef CompilationDir) {
      getMCDwarfLineTable(CUID).setCompilationDir(CompilationDir);
    }

    /// Saves the information from the currently parsed dwarf .loc directive
    /// and sets DwarfLocSeen.  When the next instruction is assembled an entry
    /// in the line number table with this information and the address of the
    /// instruction will be created.
    void setCurrentDwarfLoc(unsigned FileNum, unsigned Line, unsigned Column,
                            unsigned Flags, unsigned Isa,
                            unsigned Discriminator) {
      CurrentDwarfLoc.setFileNum(FileNum);
      CurrentDwarfLoc.setLine(Line);
      CurrentDwarfLoc.setColumn(Column);
      CurrentDwarfLoc.setFlags(Flags);
      CurrentDwarfLoc.setIsa(Isa);
      CurrentDwarfLoc.setDiscriminator(Discriminator);
      DwarfLocSeen = true;
    }
    void clearDwarfLocSeen() { DwarfLocSeen = false; }

    bool getDwarfLocSeen() { return DwarfLocSeen; }
    const MCDwarfLoc &getCurrentDwarfLoc() { return CurrentDwarfLoc; }

    bool getGenDwarfForAssembly() { return GenDwarfForAssembly; }
    void setGenDwarfForAssembly(bool Value) { GenDwarfForAssembly = Value; }
    unsigned getGenDwarfFileNumber() { return GenDwarfFileNumber; }
    void setGenDwarfFileNumber(unsigned FileNumber) {
      GenDwarfFileNumber = FileNumber;
    }
    const SetVector<MCSection *> &getGenDwarfSectionSyms() {
      return SectionsForRanges;
    }
    bool addGenDwarfSection(MCSection *Sec) {
      return SectionsForRanges.insert(Sec);
    }

    void finalizeDwarfSections(MCStreamer &MCOS);
    const std::vector<MCGenDwarfLabelEntry> &getMCGenDwarfLabelEntries() const {
      return MCGenDwarfLabelEntries;
    }
    void addMCGenDwarfLabelEntry(const MCGenDwarfLabelEntry &E) {
      MCGenDwarfLabelEntries.push_back(E);
    }

    void setDwarfDebugFlags(StringRef S) { DwarfDebugFlags = S; }
    StringRef getDwarfDebugFlags() { return DwarfDebugFlags; }

    void setDwarfDebugProducer(StringRef S) { DwarfDebugProducer = S; }
    StringRef getDwarfDebugProducer() { return DwarfDebugProducer; }

    void setDwarfVersion(uint16_t v) { DwarfVersion = v; }
    uint16_t getDwarfVersion() const { return DwarfVersion; }

    /// @}


    /// \name CodeView Management
    /// @{

    /// Creates an entry in the cv file table.
    unsigned getCVFile(StringRef FileName, unsigned FileNumber);

    /// Saves the information from the currently parsed .cv_loc directive
    /// and sets CVLocSeen.  When the next instruction is assembled an entry
    /// in the line number table with this information and the address of the
    /// instruction will be created.
    void setCurrentCVLoc(unsigned FunctionId, unsigned FileNo, unsigned Line,
                         unsigned Column, bool PrologueEnd, bool IsStmt) {
      CurrentCVLoc.setFunctionId(FunctionId);
      CurrentCVLoc.setFileNum(FileNo);
      CurrentCVLoc.setLine(Line);
      CurrentCVLoc.setColumn(Column);
      CurrentCVLoc.setPrologueEnd(PrologueEnd);
      CurrentCVLoc.setIsStmt(IsStmt);
      CVLocSeen = true;
    }
    void clearCVLocSeen() { CVLocSeen = false; }

    bool getCVLocSeen() { return CVLocSeen; }
    const MCCVLoc &getCurrentCVLoc() { return CurrentCVLoc; }

    bool isValidCVFileNumber(unsigned FileNumber);
    /// @}

    char *getSecureLogFile() { return SecureLogFile; }
    raw_fd_ostream *getSecureLog() { return SecureLog.get(); }
    bool getSecureLogUsed() { return SecureLogUsed; }
    void setSecureLog(std::unique_ptr<raw_fd_ostream> Value) {
      SecureLog = std::move(Value);
    }
    void setSecureLogUsed(bool Value) { SecureLogUsed = Value; }

    void *allocate(unsigned Size, unsigned Align = 8) {
      return Allocator.Allocate(Size, Align);
    }
    void deallocate(void *Ptr) {}

    bool hadError() { return HadError; }
    void reportError(SMLoc L, const Twine &Msg);
    // Unrecoverable error has occurred. Display the best diagnostic we can
    // and bail via exit(1). For now, most MC backend errors are unrecoverable.
    // FIXME: We should really do something about that.
    LLVM_ATTRIBUTE_NORETURN void reportFatalError(SMLoc L,
                                                  const Twine &Msg);
  };

} // end namespace llvm

// operator new and delete aren't allowed inside namespaces.
// The throw specifications are mandated by the standard.
/// \brief Placement new for using the MCContext's allocator.
///
/// This placement form of operator new uses the MCContext's allocator for
/// obtaining memory. It is a non-throwing new, which means that it returns
/// null on error. (If that is what the allocator does. The current does, so if
/// this ever changes, this operator will have to be changed, too.)
/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
/// \code
/// // Default alignment (8)
/// IntegerLiteral *Ex = new (Context) IntegerLiteral(arguments);
/// // Specific alignment
/// IntegerLiteral *Ex2 = new (Context, 4) IntegerLiteral(arguments);
/// \endcode
/// Please note that you cannot use delete on the pointer; it must be
/// deallocated using an explicit destructor call followed by
/// \c Context.Deallocate(Ptr).
///
/// \param Bytes The number of bytes to allocate. Calculated by the compiler.
/// \param C The MCContext that provides the allocator.
/// \param Alignment The alignment of the allocated memory (if the underlying
///                  allocator supports it).
/// \return The allocated memory. Could be NULL.
inline void *operator new(size_t Bytes, llvm::MCContext &C,
                          size_t Alignment = 8) LLVM_NOEXCEPT {
  return C.allocate(Bytes, Alignment);
}
/// \brief Placement delete companion to the new above.
///
/// This operator is just a companion to the new above. There is no way of
/// invoking it directly; see the new operator for more details. This operator
/// is called implicitly by the compiler if a placement new expression using
/// the MCContext throws in the object constructor.
inline void operator delete(void *Ptr, llvm::MCContext &C,
                            size_t) LLVM_NOEXCEPT {
  C.deallocate(Ptr);
}

/// This placement form of operator new[] uses the MCContext's allocator for
/// obtaining memory. It is a non-throwing new[], which means that it returns
/// null on error.
/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
/// \code
/// // Default alignment (8)
/// char *data = new (Context) char[10];
/// // Specific alignment
/// char *data = new (Context, 4) char[10];
/// \endcode
/// Please note that you cannot use delete on the pointer; it must be
/// deallocated using an explicit destructor call followed by
/// \c Context.Deallocate(Ptr).
///
/// \param Bytes The number of bytes to allocate. Calculated by the compiler.
/// \param C The MCContext that provides the allocator.
/// \param Alignment The alignment of the allocated memory (if the underlying
///                  allocator supports it).
/// \return The allocated memory. Could be NULL.
inline void *operator new[](size_t Bytes, llvm::MCContext &C,
                            size_t Alignment = 8) LLVM_NOEXCEPT {
  return C.allocate(Bytes, Alignment);
}

/// \brief Placement delete[] companion to the new[] above.
///
/// This operator is just a companion to the new[] above. There is no way of
/// invoking it directly; see the new[] operator for more details. This operator
/// is called implicitly by the compiler if a placement new[] expression using
/// the MCContext throws in the object constructor.
inline void operator delete[](void *Ptr, llvm::MCContext &C) LLVM_NOEXCEPT {
  C.deallocate(Ptr);
}

#endif