text: //===- MCStreamer.h - High-level Streaming Machine Code Output --*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file declares the MCStreamer class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_MC_MCSTREAMER_H
  #define LLVM_MC_MCSTREAMER_H
  
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/MC/MCDirectives.h"
  #include "llvm/MC/MCDwarf.h"
  #include "llvm/MC/MCLinkerOptimizationHint.h"
  #include "llvm/MC/MCSymbol.h"
  #include "llvm/MC/MCWinEH.h"
  #include "llvm/Support/SMLoc.h"
  #include "llvm/Support/TargetParser.h"
  #include <cassert>
  #include <cstdint>
  #include <memory>
  #include <string>
  #include <utility>
  #include <vector>
  
  namespace llvm {
  
  class AssemblerConstantPools;
  class formatted_raw_ostream;
  class MCAsmBackend;
  class MCCodeEmitter;
  struct MCCodePaddingContext;
  class MCContext;
  class MCExpr;
  class MCInst;
  class MCInstPrinter;
  class MCSection;
  class MCStreamer;
  class MCSymbolRefExpr;
  class MCSubtargetInfo;
  class raw_ostream;
  class Twine;
  
  using MCSectionSubPair = std::pair<MCSection *, const MCExpr *>;
  
  /// Target specific streamer interface. This is used so that targets can
  /// implement support for target specific assembly directives.
  ///
  /// If target foo wants to use this, it should implement 3 classes:
  /// * FooTargetStreamer : public MCTargetStreamer
  /// * FooTargetAsmStreamer : public FooTargetStreamer
  /// * FooTargetELFStreamer : public FooTargetStreamer
  ///
  /// FooTargetStreamer should have a pure virtual method for each directive. For
  /// example, for a ".bar symbol_name" directive, it should have
  /// virtual emitBar(const MCSymbol &Symbol) = 0;
  ///
  /// The FooTargetAsmStreamer and FooTargetELFStreamer classes implement the
  /// method. The assembly streamer just prints ".bar symbol_name". The object
  /// streamer does whatever is needed to implement .bar in the object file.
  ///
  /// In the assembly printer and parser the target streamer can be used by
  /// calling getTargetStreamer and casting it to FooTargetStreamer:
  ///
  /// MCTargetStreamer &TS = OutStreamer.getTargetStreamer();
  /// FooTargetStreamer &ATS = static_cast<FooTargetStreamer &>(TS);
  ///
  /// The base classes FooTargetAsmStreamer and FooTargetELFStreamer should
  /// *never* be treated differently. Callers should always talk to a
  /// FooTargetStreamer.
  class MCTargetStreamer {
  protected:
    MCStreamer &Streamer;
  
  public:
    MCTargetStreamer(MCStreamer &S);
    virtual ~MCTargetStreamer();
  
    MCStreamer &getStreamer() { return Streamer; }
  
    // Allow a target to add behavior to the EmitLabel of MCStreamer.
    virtual void emitLabel(MCSymbol *Symbol);
    // Allow a target to add behavior to the emitAssignment of MCStreamer.
    virtual void emitAssignment(MCSymbol *Symbol, const MCExpr *Value);
  
    virtual void prettyPrintAsm(MCInstPrinter &InstPrinter, raw_ostream &OS,
                                const MCInst &Inst, const MCSubtargetInfo &STI);
  
    virtual void emitDwarfFileDirective(StringRef Directive);
  
    /// Update streamer for a new active section.
    ///
    /// This is called by PopSection and SwitchSection, if the current
    /// section changes.
    virtual void changeSection(const MCSection *CurSection, MCSection *Section,
                               const MCExpr *SubSection, raw_ostream &OS);
  
    virtual void emitValue(const MCExpr *Value);
  
    virtual void finish();
  };
  
  // FIXME: declared here because it is used from
  // lib/CodeGen/AsmPrinter/ARMException.cpp.
  class ARMTargetStreamer : public MCTargetStreamer {
  public:
    ARMTargetStreamer(MCStreamer &S);
    ~ARMTargetStreamer() override;
  
    virtual void emitFnStart();
    virtual void emitFnEnd();
    virtual void emitCantUnwind();
    virtual void emitPersonality(const MCSymbol *Personality);
    virtual void emitPersonalityIndex(unsigned Index);
    virtual void emitHandlerData();
    virtual void emitSetFP(unsigned FpReg, unsigned SpReg,
                           int64_t Offset = 0);
    virtual void emitMovSP(unsigned Reg, int64_t Offset = 0);
    virtual void emitPad(int64_t Offset);
    virtual void emitRegSave(const SmallVectorImpl<unsigned> &RegList,
                             bool isVector);
    virtual void emitUnwindRaw(int64_t StackOffset,
                               const SmallVectorImpl<uint8_t> &Opcodes);
  
    virtual void switchVendor(StringRef Vendor);
    virtual void emitAttribute(unsigned Attribute, unsigned Value);
    virtual void emitTextAttribute(unsigned Attribute, StringRef String);
    virtual void emitIntTextAttribute(unsigned Attribute, unsigned IntValue,
                                      StringRef StringValue = "");
    virtual void emitFPU(unsigned FPU);
    virtual void emitArch(ARM::ArchKind Arch);
    virtual void emitArchExtension(unsigned ArchExt);
    virtual void emitObjectArch(ARM::ArchKind Arch);
    void emitTargetAttributes(const MCSubtargetInfo &STI);
    virtual void finishAttributeSection();
    virtual void emitInst(uint32_t Inst, char Suffix = '\0');
  
    virtual void AnnotateTLSDescriptorSequence(const MCSymbolRefExpr *SRE);
  
    virtual void emitThumbSet(MCSymbol *Symbol, const MCExpr *Value);
  
    void finish() override;
  
    /// Reset any state between object emissions, i.e. the equivalent of
    /// MCStreamer's reset method.
    virtual void reset();
  
    /// Callback used to implement the ldr= pseudo.
    /// Add a new entry to the constant pool for the current section and return an
    /// MCExpr that can be used to refer to the constant pool location.
    const MCExpr *addConstantPoolEntry(const MCExpr *, SMLoc Loc);
  
    /// Callback used to implemnt the .ltorg directive.
    /// Emit contents of constant pool for the current section.
    void emitCurrentConstantPool();
  
  private:
    std::unique_ptr<AssemblerConstantPools> ConstantPools;
  };
  
  /// \brief Streaming machine code generation interface.
  ///
  /// This interface is intended to provide a programatic interface that is very
  /// similar to the level that an assembler .s file provides.  It has callbacks
  /// to emit bytes, handle directives, etc.  The implementation of this interface
  /// retains state to know what the current section is etc.
  ///
  /// There are multiple implementations of this interface: one for writing out
  /// a .s file, and implementations that write out .o files of various formats.
  ///
  class MCStreamer {
    MCContext &Context;
    std::unique_ptr<MCTargetStreamer> TargetStreamer;
  
    std::vector<MCDwarfFrameInfo> DwarfFrameInfos;
    MCDwarfFrameInfo *getCurrentDwarfFrameInfo();
  
    /// Similar to DwarfFrameInfos, but for SEH unwind info. Chained frames may
    /// refer to each other, so use std::unique_ptr to provide pointer stability.
    std::vector<std::unique_ptr<WinEH::FrameInfo>> WinFrameInfos;
  
    WinEH::FrameInfo *CurrentWinFrameInfo;
  
    /// Retreive the current frame info if one is available and it is not yet
    /// closed. Otherwise, issue an error and return null.
    WinEH::FrameInfo *EnsureValidWinFrameInfo(SMLoc Loc);
  
    /// \brief Tracks an index to represent the order a symbol was emitted in.
    /// Zero means we did not emit that symbol.
    DenseMap<const MCSymbol *, unsigned> SymbolOrdering;
  
    /// \brief This is stack of current and previous section values saved by
    /// PushSection.
    SmallVector<std::pair<MCSectionSubPair, MCSectionSubPair>, 4> SectionStack;
  
    /// The next unique ID to use when creating a WinCFI-related section (.pdata
    /// or .xdata). This ID ensures that we have a one-to-one mapping from
    /// code section to unwind info section, which MSVC's incremental linker
    /// requires.
    unsigned NextWinCFIID = 0;
  
  protected:
    MCStreamer(MCContext &Ctx);
  
    virtual void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame);
    virtual void EmitCFIEndProcImpl(MCDwarfFrameInfo &CurFrame);
  
    /// When emitting an object file, create and emit a real label. When emitting
    /// textual assembly, this should do nothing to avoid polluting our output.
    virtual MCSymbol *EmitCFILabel();
  
    WinEH::FrameInfo *getCurrentWinFrameInfo() {
      return CurrentWinFrameInfo;
    }
  
    virtual void EmitWindowsUnwindTables();
  
    virtual void EmitRawTextImpl(StringRef String);
  
  public:
    MCStreamer(const MCStreamer &) = delete;
    MCStreamer &operator=(const MCStreamer &) = delete;
    virtual ~MCStreamer();
  
    void visitUsedExpr(const MCExpr &Expr);
    virtual void visitUsedSymbol(const MCSymbol &Sym);
  
    void setTargetStreamer(MCTargetStreamer *TS) {
      TargetStreamer.reset(TS);
    }
  
    /// State management
    ///
    virtual void reset();
  
    MCContext &getContext() const { return Context; }
  
    MCTargetStreamer *getTargetStreamer() {
      return TargetStreamer.get();
    }
  
    unsigned getNumFrameInfos() { return DwarfFrameInfos.size(); }
    ArrayRef<MCDwarfFrameInfo> getDwarfFrameInfos() const {
      return DwarfFrameInfos;
    }
  
    bool hasUnfinishedDwarfFrameInfo();
  
    unsigned getNumWinFrameInfos() { return WinFrameInfos.size(); }
    ArrayRef<std::unique_ptr<WinEH::FrameInfo>> getWinFrameInfos() const {
      return WinFrameInfos;
    }
  
    void generateCompactUnwindEncodings(MCAsmBackend *MAB);
  
    /// \name Assembly File Formatting.
    /// @{
  
    /// \brief Return true if this streamer supports verbose assembly and if it is
    /// enabled.
    virtual bool isVerboseAsm() const { return false; }
  
    /// \brief Return true if this asm streamer supports emitting unformatted text
    /// to the .s file with EmitRawText.
    virtual bool hasRawTextSupport() const { return false; }
  
    /// \brief Is the integrated assembler required for this streamer to function
    /// correctly?
    virtual bool isIntegratedAssemblerRequired() const { return false; }
  
    /// \brief Add a textual comment.
    ///
    /// Typically for comments that can be emitted to the generated .s
    /// file if applicable as a QoI issue to make the output of the compiler
    /// more readable.  This only affects the MCAsmStreamer, and only when
    /// verbose assembly output is enabled.
    ///
    /// If the comment includes embedded \n's, they will each get the comment
    /// prefix as appropriate.  The added comment should not end with a \n.
    /// By default, each comment is terminated with an end of line, i.e. the
    /// EOL param is set to true by default. If one prefers not to end the 
    /// comment with a new line then the EOL param should be passed 
    /// with a false value.
    virtual void AddComment(const Twine &T, bool EOL = true) {}
  
    /// \brief Return a raw_ostream that comments can be written to. Unlike
    /// AddComment, you are required to terminate comments with \n if you use this
    /// method.
    virtual raw_ostream &GetCommentOS();
  
    /// \brief Print T and prefix it with the comment string (normally #) and
    /// optionally a tab. This prints the comment immediately, not at the end of
    /// the current line. It is basically a safe version of EmitRawText: since it
    /// only prints comments, the object streamer ignores it instead of asserting.
    virtual void emitRawComment(const Twine &T, bool TabPrefix = true);
  
    /// \brief Add explicit comment T. T is required to be a valid
    /// comment in the output and does not need to be escaped.
    virtual void addExplicitComment(const Twine &T);
  
    /// \brief Emit added explicit comments.
    virtual void emitExplicitComments();
  
    /// AddBlankLine - Emit a blank line to a .s file to pretty it up.
    virtual void AddBlankLine() {}
  
    /// @}
  
    /// \name Symbol & Section Management
    /// @{
  
    /// \brief Return the current section that the streamer is emitting code to.
    MCSectionSubPair getCurrentSection() const {
      if (!SectionStack.empty())
        return SectionStack.back().first;
      return MCSectionSubPair();
    }
    MCSection *getCurrentSectionOnly() const { return getCurrentSection().first; }
  
    /// \brief Return the previous section that the streamer is emitting code to.
    MCSectionSubPair getPreviousSection() const {
      if (!SectionStack.empty())
        return SectionStack.back().second;
      return MCSectionSubPair();
    }
  
    /// \brief Returns an index to represent the order a symbol was emitted in.
    /// (zero if we did not emit that symbol)
    unsigned GetSymbolOrder(const MCSymbol *Sym) const {
      return SymbolOrdering.lookup(Sym);
    }
  
    /// \brief Update streamer for a new active section.
    ///
    /// This is called by PopSection and SwitchSection, if the current
    /// section changes.
    virtual void ChangeSection(MCSection *, const MCExpr *);
  
    /// \brief Save the current and previous section on the section stack.
    void PushSection() {
      SectionStack.push_back(
          std::make_pair(getCurrentSection(), getPreviousSection()));
    }
  
    /// \brief Restore the current and previous section from the section stack.
    /// Calls ChangeSection as needed.
    ///
    /// Returns false if the stack was empty.
    bool PopSection() {
      if (SectionStack.size() <= 1)
        return false;
      auto I = SectionStack.end();
      --I;
      MCSectionSubPair OldSection = I->first;
      --I;
      MCSectionSubPair NewSection = I->first;
  
      if (OldSection != NewSection)
        ChangeSection(NewSection.first, NewSection.second);
      SectionStack.pop_back();
      return true;
    }
  
    bool SubSection(const MCExpr *Subsection) {
      if (SectionStack.empty())
        return false;
  
      SwitchSection(SectionStack.back().first.first, Subsection);
      return true;
    }
  
    /// Set the current section where code is being emitted to \p Section.  This
    /// is required to update CurSection.
    ///
    /// This corresponds to assembler directives like .section, .text, etc.
    virtual void SwitchSection(MCSection *Section,
                               const MCExpr *Subsection = nullptr);
  
    /// \brief Set the current section where code is being emitted to \p Section.
    /// This is required to update CurSection. This version does not call
    /// ChangeSection.
    void SwitchSectionNoChange(MCSection *Section,
                               const MCExpr *Subsection = nullptr) {
      assert(Section && "Cannot switch to a null section!");
      MCSectionSubPair curSection = SectionStack.back().first;
      SectionStack.back().second = curSection;
      if (MCSectionSubPair(Section, Subsection) != curSection)
        SectionStack.back().first = MCSectionSubPair(Section, Subsection);
    }
  
    /// \brief Create the default sections and set the initial one.
    virtual void InitSections(bool NoExecStack);
  
    MCSymbol *endSection(MCSection *Section);
  
    /// \brief Sets the symbol's section.
    ///
    /// Each emitted symbol will be tracked in the ordering table,
    /// so we can sort on them later.
    void AssignFragment(MCSymbol *Symbol, MCFragment *Fragment);
  
    /// \brief Emit a label for \p Symbol into the current section.
    ///
    /// This corresponds to an assembler statement such as:
    ///   foo:
    ///
    /// \param Symbol - The symbol to emit. A given symbol should only be
    /// emitted as a label once, and symbols emitted as a label should never be
    /// used in an assignment.
    // FIXME: These emission are non-const because we mutate the symbol to
    // add the section we're emitting it to later.
    virtual void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc());
  
    virtual void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol);
  
    /// \brief Note in the output the specified \p Flag.
    virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
  
    /// \brief Emit the given list \p Options of strings as linker
    /// options into the output.
    virtual void EmitLinkerOptions(ArrayRef<std::string> Kind) {}
  
    /// \brief Note in the output the specified region \p Kind.
    virtual void EmitDataRegion(MCDataRegionType Kind) {}
  
    /// \brief Specify the Mach-O minimum deployment target version.
    virtual void EmitVersionMin(MCVersionMinType Type, unsigned Major,
                                unsigned Minor, unsigned Update) {}
  
    /// Emit/Specify Mach-O build version command.
    /// \p Platform should be one of MachO::PlatformType.
    virtual void EmitBuildVersion(unsigned Platform, unsigned Major,
                                  unsigned Minor, unsigned Update) {}
  
    void EmitVersionForTarget(const Triple &Target);
  
    /// \brief Note in the output that the specified \p Func is a Thumb mode
    /// function (ARM target only).
    virtual void EmitThumbFunc(MCSymbol *Func);
  
    /// \brief Emit an assignment of \p Value to \p Symbol.
    ///
    /// This corresponds to an assembler statement such as:
    ///  symbol = value
    ///
    /// The assignment generates no code, but has the side effect of binding the
    /// value in the current context. For the assembly streamer, this prints the
    /// binding into the .s file.
    ///
    /// \param Symbol - The symbol being assigned to.
    /// \param Value - The value for the symbol.
    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
  
    /// \brief Emit an weak reference from \p Alias to \p Symbol.
    ///
    /// This corresponds to an assembler statement such as:
    ///  .weakref alias, symbol
    ///
    /// \param Alias - The alias that is being created.
    /// \param Symbol - The symbol being aliased.
    virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol);
  
    /// \brief Add the given \p Attribute to \p Symbol.
    virtual bool EmitSymbolAttribute(MCSymbol *Symbol,
                                     MCSymbolAttr Attribute) = 0;
  
    /// \brief Set the \p DescValue for the \p Symbol.
    ///
    /// \param Symbol - The symbol to have its n_desc field set.
    /// \param DescValue - The value to set into the n_desc field.
    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
  
    /// \brief Start emitting COFF symbol definition
    ///
    /// \param Symbol - The symbol to have its External & Type fields set.
    virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol);
  
    /// \brief Emit the storage class of the symbol.
    ///
    /// \param StorageClass - The storage class the symbol should have.
    virtual void EmitCOFFSymbolStorageClass(int StorageClass);
  
    /// \brief Emit the type of the symbol.
    ///
    /// \param Type - A COFF type identifier (see COFF::SymbolType in X86COFF.h)
    virtual void EmitCOFFSymbolType(int Type);
  
    /// \brief Marks the end of the symbol definition.
    virtual void EndCOFFSymbolDef();
  
    virtual void EmitCOFFSafeSEH(MCSymbol const *Symbol);
  
    /// \brief Emits a COFF section index.
    ///
    /// \param Symbol - Symbol the section number relocation should point to.
    virtual void EmitCOFFSectionIndex(MCSymbol const *Symbol);
  
    /// \brief Emits a COFF section relative relocation.
    ///
    /// \param Symbol - Symbol the section relative relocation should point to.
    virtual void EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset);
  
    /// \brief Emit an ELF .size directive.
    ///
    /// This corresponds to an assembler statement such as:
    ///  .size symbol, expression
    virtual void emitELFSize(MCSymbol *Symbol, const MCExpr *Value);
  
    /// \brief Emit an ELF .symver directive.
    ///
    /// This corresponds to an assembler statement such as:
    ///  .symver _start, foo@@SOME_VERSION
    /// \param Alias - The versioned alias (i.e. "foo@@SOME_VERSION")
    /// \param Aliasee - The aliased symbol (i.e. "_start")
    virtual void emitELFSymverDirective(MCSymbol *Alias, const MCSymbol *Aliasee);
  
    /// \brief Emit a Linker Optimization Hint (LOH) directive.
    /// \param Args - Arguments of the LOH.
    virtual void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) {}
  
    /// \brief Emit a common symbol.
    ///
    /// \param Symbol - The common symbol to emit.
    /// \param Size - The size of the common symbol.
    /// \param ByteAlignment - The alignment of the symbol if
    /// non-zero. This must be a power of 2.
    virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                  unsigned ByteAlignment) = 0;
  
    /// \brief Emit a local common (.lcomm) symbol.
    ///
    /// \param Symbol - The common symbol to emit.
    /// \param Size - The size of the common symbol.
    /// \param ByteAlignment - The alignment of the common symbol in bytes.
    virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment);
  
    /// \brief Emit the zerofill section and an optional symbol.
    ///
    /// \param Section - The zerofill section to create and or to put the symbol
    /// \param Symbol - The zerofill symbol to emit, if non-NULL.
    /// \param Size - The size of the zerofill symbol.
    /// \param ByteAlignment - The alignment of the zerofill symbol if
    /// non-zero. This must be a power of 2 on some targets.
    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
                              uint64_t Size = 0, unsigned ByteAlignment = 0) = 0;
  
    /// \brief Emit a thread local bss (.tbss) symbol.
    ///
    /// \param Section - The thread local common section.
    /// \param Symbol - The thread local common symbol to emit.
    /// \param Size - The size of the symbol.
    /// \param ByteAlignment - The alignment of the thread local common symbol
    /// if non-zero.  This must be a power of 2 on some targets.
    virtual void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
                                uint64_t Size, unsigned ByteAlignment = 0);
  
    /// @}
    /// \name Generating Data
    /// @{
  
    /// \brief Emit the bytes in \p Data into the output.
    ///
    /// This is used to implement assembler directives such as .byte, .ascii,
    /// etc.
    virtual void EmitBytes(StringRef Data);
  
    /// Functionally identical to EmitBytes. When emitting textual assembly, this
    /// method uses .byte directives instead of .ascii or .asciz for readability.
    virtual void EmitBinaryData(StringRef Data);
  
    /// \brief Emit the expression \p Value into the output as a native
    /// integer of the given \p Size bytes.
    ///
    /// This is used to implement assembler directives such as .word, .quad,
    /// etc.
    ///
    /// \param Value - The value to emit.
    /// \param Size - The size of the integer (in bytes) to emit. This must
    /// match a native machine width.
    /// \param Loc - The location of the expression for error reporting.
    virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
                               SMLoc Loc = SMLoc());
  
    void EmitValue(const MCExpr *Value, unsigned Size, SMLoc Loc = SMLoc());
  
    /// \brief Special case of EmitValue that avoids the client having
    /// to pass in a MCExpr for constant integers.
    virtual void EmitIntValue(uint64_t Value, unsigned Size);
  
    virtual void EmitULEB128Value(const MCExpr *Value);
  
    virtual void EmitSLEB128Value(const MCExpr *Value);
  
    /// \brief Special case of EmitULEB128Value that avoids the client having to
    /// pass in a MCExpr for constant integers.
    void EmitULEB128IntValue(uint64_t Value);
  
    /// \brief Like EmitULEB128Value but pads the output to specific number of
    /// bytes.
    void EmitPaddedULEB128IntValue(uint64_t Value, unsigned PadTo);
  
    /// \brief Special case of EmitSLEB128Value that avoids the client having to
    /// pass in a MCExpr for constant integers.
    void EmitSLEB128IntValue(int64_t Value);
  
    /// \brief Special case of EmitValue that avoids the client having to pass in
    /// a MCExpr for MCSymbols.
    void EmitSymbolValue(const MCSymbol *Sym, unsigned Size,
                         bool IsSectionRelative = false);
  
    /// \brief Emit the expression \p Value into the output as a dtprel
    /// (64-bit DTP relative) value.
    ///
    /// This is used to implement assembler directives such as .dtpreldword on
    /// targets that support them.
    virtual void EmitDTPRel64Value(const MCExpr *Value);
  
    /// \brief Emit the expression \p Value into the output as a dtprel
    /// (32-bit DTP relative) value.
    ///
    /// This is used to implement assembler directives such as .dtprelword on
    /// targets that support them.
    virtual void EmitDTPRel32Value(const MCExpr *Value);
  
    /// \brief Emit the expression \p Value into the output as a tprel
    /// (64-bit TP relative) value.
    ///
    /// This is used to implement assembler directives such as .tpreldword on
    /// targets that support them.
    virtual void EmitTPRel64Value(const MCExpr *Value);
  
    /// \brief Emit the expression \p Value into the output as a tprel
    /// (32-bit TP relative) value.
    ///
    /// This is used to implement assembler directives such as .tprelword on
    /// targets that support them.
    virtual void EmitTPRel32Value(const MCExpr *Value);
  
    /// \brief Emit the expression \p Value into the output as a gprel64 (64-bit
    /// GP relative) value.
    ///
    /// This is used to implement assembler directives such as .gpdword on
    /// targets that support them.
    virtual void EmitGPRel64Value(const MCExpr *Value);
  
    /// \brief Emit the expression \p Value into the output as a gprel32 (32-bit
    /// GP relative) value.
    ///
    /// This is used to implement assembler directives such as .gprel32 on
    /// targets that support them.
    virtual void EmitGPRel32Value(const MCExpr *Value);
  
    /// \brief Emit NumBytes bytes worth of the value specified by FillValue.
    /// This implements directives such as '.space'.
    virtual void emitFill(uint64_t NumBytes, uint8_t FillValue);
  
    /// \brief Emit \p Size bytes worth of the value specified by \p FillValue.
    ///
    /// This is used to implement assembler directives such as .space or .skip.
    ///
    /// \param NumBytes - The number of bytes to emit.
    /// \param FillValue - The value to use when filling bytes.
    /// \param Loc - The location of the expression for error reporting.
    virtual void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
                          SMLoc Loc = SMLoc());
  
    /// \brief Emit \p NumValues copies of \p Size bytes. Each \p Size bytes is
    /// taken from the lowest order 4 bytes of \p Expr expression.
    ///
    /// This is used to implement assembler directives such as .fill.
    ///
    /// \param NumValues - The number of copies of \p Size bytes to emit.
    /// \param Size - The size (in bytes) of each repeated value.
    /// \param Expr - The expression from which \p Size bytes are used.
    virtual void emitFill(uint64_t NumValues, int64_t Size, int64_t Expr);
    virtual void emitFill(const MCExpr &NumValues, int64_t Size, int64_t Expr,
                          SMLoc Loc = SMLoc());
  
    /// \brief Emit NumBytes worth of zeros.
    /// This function properly handles data in virtual sections.
    void EmitZeros(uint64_t NumBytes);
  
    /// \brief Emit some number of copies of \p Value until the byte alignment \p
    /// ByteAlignment is reached.
    ///
    /// If the number of bytes need to emit for the alignment is not a multiple
    /// of \p ValueSize, then the contents of the emitted fill bytes is
    /// undefined.
    ///
    /// This used to implement the .align assembler directive.
    ///
    /// \param ByteAlignment - The alignment to reach. This must be a power of
    /// two on some targets.
    /// \param Value - The value to use when filling bytes.
    /// \param ValueSize - The size of the integer (in bytes) to emit for
    /// \p Value. This must match a native machine width.
    /// \param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
    /// the alignment cannot be reached in this many bytes, no bytes are
    /// emitted.
    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
                                      unsigned ValueSize = 1,
                                      unsigned MaxBytesToEmit = 0);
  
    /// \brief Emit nops until the byte alignment \p ByteAlignment is reached.
    ///
    /// This used to align code where the alignment bytes may be executed.  This
    /// can emit different bytes for different sizes to optimize execution.
    ///
    /// \param ByteAlignment - The alignment to reach. This must be a power of
    /// two on some targets.
    /// \param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
    /// the alignment cannot be reached in this many bytes, no bytes are
    /// emitted.
    virtual void EmitCodeAlignment(unsigned ByteAlignment,
                                   unsigned MaxBytesToEmit = 0);
  
    /// \brief Emit some number of copies of \p Value until the byte offset \p
    /// Offset is reached.
    ///
    /// This is used to implement assembler directives such as .org.
    ///
    /// \param Offset - The offset to reach. This may be an expression, but the
    /// expression must be associated with the current section.
    /// \param Value - The value to use when filling bytes.
    virtual void emitValueToOffset(const MCExpr *Offset, unsigned char Value,
                                   SMLoc Loc);
  
    virtual void
    EmitCodePaddingBasicBlockStart(const MCCodePaddingContext &Context) {}
  
    virtual void
    EmitCodePaddingBasicBlockEnd(const MCCodePaddingContext &Context) {}
  
    /// @}
  
    /// \brief Switch to a new logical file.  This is used to implement the '.file
    /// "foo.c"' assembler directive.
    virtual void EmitFileDirective(StringRef Filename);
  
    /// \brief Emit the "identifiers" directive.  This implements the
    /// '.ident "version foo"' assembler directive.
    virtual void EmitIdent(StringRef IdentString) {}
  
    /// \brief Associate a filename with a specified logical file number.  This
    /// implements the DWARF2 '.file 4 "foo.c"' assembler directive.
    virtual unsigned EmitDwarfFileDirective(unsigned FileNo, StringRef Directory,
                                            StringRef Filename,
                                            unsigned CUID = 0);
  
    /// \brief This implements the DWARF2 '.loc fileno lineno ...' assembler
    /// directive.
    virtual void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                       unsigned Column, unsigned Flags,
                                       unsigned Isa, unsigned Discriminator,
                                       StringRef FileName);
  
    /// Associate a filename with a specified logical file number, and also
    /// specify that file's checksum information.  This implements the '.cv_file 4
    /// "foo.c"' assembler directive. Returns true on success.
    virtual bool EmitCVFileDirective(unsigned FileNo, StringRef Filename,
                                     ArrayRef<uint8_t> Checksum,
                                     unsigned ChecksumKind);
  
    /// \brief Introduces a function id for use with .cv_loc.
    virtual bool EmitCVFuncIdDirective(unsigned FunctionId);
  
    /// \brief Introduces an inline call site id for use with .cv_loc. Includes
    /// extra information for inline line table generation.
    virtual bool EmitCVInlineSiteIdDirective(unsigned FunctionId, unsigned IAFunc,
                                             unsigned IAFile, unsigned IALine,
                                             unsigned IACol, SMLoc Loc);
  
    /// \brief This implements the CodeView '.cv_loc' assembler directive.
    virtual void EmitCVLocDirective(unsigned FunctionId, unsigned FileNo,
                                    unsigned Line, unsigned Column,
                                    bool PrologueEnd, bool IsStmt,
                                    StringRef FileName, SMLoc Loc);
  
    /// \brief This implements the CodeView '.cv_linetable' assembler directive.
    virtual void EmitCVLinetableDirective(unsigned FunctionId,
                                          const MCSymbol *FnStart,
                                          const MCSymbol *FnEnd);
  
    /// \brief This implements the CodeView '.cv_inline_linetable' assembler
    /// directive.
    virtual void EmitCVInlineLinetableDirective(unsigned PrimaryFunctionId,
                                                unsigned SourceFileId,
                                                unsigned SourceLineNum,
                                                const MCSymbol *FnStartSym,
                                                const MCSymbol *FnEndSym);
  
    /// \brief This implements the CodeView '.cv_def_range' assembler
    /// directive.
    virtual void EmitCVDefRangeDirective(
        ArrayRef<std::pair<const MCSymbol *, const MCSymbol *>> Ranges,
        StringRef FixedSizePortion);
  
    /// \brief This implements the CodeView '.cv_stringtable' assembler directive.
    virtual void EmitCVStringTableDirective() {}
  
    /// \brief This implements the CodeView '.cv_filechecksums' assembler directive.
    virtual void EmitCVFileChecksumsDirective() {}
  
    /// This implements the CodeView '.cv_filechecksumoffset' assembler
    /// directive.
    virtual void EmitCVFileChecksumOffsetDirective(unsigned FileNo) {}
  
    /// This implements the CodeView '.cv_fpo_data' assembler directive.
    virtual void EmitCVFPOData(const MCSymbol *ProcSym, SMLoc Loc = {}) {}
  
    /// Emit the absolute difference between two symbols.
    ///
    /// \pre Offset of \c Hi is greater than the offset \c Lo.
    virtual void emitAbsoluteSymbolDiff(const MCSymbol *Hi, const MCSymbol *Lo,
                                        unsigned Size);
  
    virtual MCSymbol *getDwarfLineTableSymbol(unsigned CUID);
    virtual void EmitCFISections(bool EH, bool Debug);
    void EmitCFIStartProc(bool IsSimple);
    void EmitCFIEndProc();
    virtual void EmitCFIDefCfa(int64_t Register, int64_t Offset);
    virtual void EmitCFIDefCfaOffset(int64_t Offset);
    virtual void EmitCFIDefCfaRegister(int64_t Register);
    virtual void EmitCFIOffset(int64_t Register, int64_t Offset);
    virtual void EmitCFIPersonality(const MCSymbol *Sym, unsigned Encoding);
    virtual void EmitCFILsda(const MCSymbol *Sym, unsigned Encoding);
    virtual void EmitCFIRememberState();
    virtual void EmitCFIRestoreState();
    virtual void EmitCFISameValue(int64_t Register);
    virtual void EmitCFIRestore(int64_t Register);
    virtual void EmitCFIRelOffset(int64_t Register, int64_t Offset);
    virtual void EmitCFIAdjustCfaOffset(int64_t Adjustment);
    virtual void EmitCFIEscape(StringRef Values);
    virtual void EmitCFIReturnColumn(int64_t Register);
    virtual void EmitCFIGnuArgsSize(int64_t Size);
    virtual void EmitCFISignalFrame();
    virtual void EmitCFIUndefined(int64_t Register);
    virtual void EmitCFIRegister(int64_t Register1, int64_t Register2);
    virtual void EmitCFIWindowSave();
  
    virtual void EmitWinCFIStartProc(const MCSymbol *Symbol, SMLoc Loc = SMLoc());
    virtual void EmitWinCFIEndProc(SMLoc Loc = SMLoc());
    virtual void EmitWinCFIStartChained(SMLoc Loc = SMLoc());
    virtual void EmitWinCFIEndChained(SMLoc Loc = SMLoc());
    virtual void EmitWinCFIPushReg(unsigned Register, SMLoc Loc = SMLoc());
    virtual void EmitWinCFISetFrame(unsigned Register, unsigned Offset,
                                    SMLoc Loc = SMLoc());
    virtual void EmitWinCFIAllocStack(unsigned Size, SMLoc Loc = SMLoc());
    virtual void EmitWinCFISaveReg(unsigned Register, unsigned Offset,
                                   SMLoc Loc = SMLoc());
    virtual void EmitWinCFISaveXMM(unsigned Register, unsigned Offset,
                                   SMLoc Loc = SMLoc());
    virtual void EmitWinCFIPushFrame(bool Code, SMLoc Loc = SMLoc());
    virtual void EmitWinCFIEndProlog(SMLoc Loc = SMLoc());
    virtual void EmitWinEHHandler(const MCSymbol *Sym, bool Unwind, bool Except,
                                  SMLoc Loc = SMLoc());
    virtual void EmitWinEHHandlerData(SMLoc Loc = SMLoc());
  
    /// Get the .pdata section used for the given section. Typically the given
    /// section is either the main .text section or some other COMDAT .text
    /// section, but it may be any section containing code.
    MCSection *getAssociatedPDataSection(const MCSection *TextSec);
  
    /// Get the .xdata section used for the given section.
    MCSection *getAssociatedXDataSection(const MCSection *TextSec);
  
    virtual void EmitSyntaxDirective();
  
    /// \brief Emit a .reloc directive.
    /// Returns true if the relocation could not be emitted because Name is not
    /// known.
    virtual bool EmitRelocDirective(const MCExpr &Offset, StringRef Name,
                                    const MCExpr *Expr, SMLoc Loc) {
      return true;
    }
  
    /// \brief Emit the given \p Instruction into the current section.
    /// PrintSchedInfo == true then schedul comment should be added to output
    virtual void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
                                 bool PrintSchedInfo = false);
  
    /// \brief Set the bundle alignment mode from now on in the section.
    /// The argument is the power of 2 to which the alignment is set. The
    /// value 0 means turn the bundle alignment off.
    virtual void EmitBundleAlignMode(unsigned AlignPow2);
  
    /// \brief The following instructions are a bundle-locked group.
    ///
    /// \param AlignToEnd - If true, the bundle-locked group will be aligned to
    ///                     the end of a bundle.
    virtual void EmitBundleLock(bool AlignToEnd);
  
    /// \brief Ends a bundle-locked group.
    virtual void EmitBundleUnlock();
  
    /// \brief If this file is backed by a assembly streamer, this dumps the
    /// specified string in the output .s file.  This capability is indicated by
    /// the hasRawTextSupport() predicate.  By default this aborts.
    void EmitRawText(const Twine &String);
  
    /// \brief Streamer specific finalization.
    virtual void FinishImpl();
    /// \brief Finish emission of machine code.
    void Finish();
  
    virtual bool mayHaveInstructions(MCSection &Sec) const { return true; }
  };
  
  /// Create a dummy machine code streamer, which does nothing. This is useful for
  /// timing the assembler front end.
  MCStreamer *createNullStreamer(MCContext &Ctx);
  
  /// Create a machine code streamer which will print out assembly for the native
  /// target, suitable for compiling with a native assembler.
  ///
  /// \param InstPrint - If given, the instruction printer to use. If not given
  /// the MCInst representation will be printed.  This method takes ownership of
  /// InstPrint.
  ///
  /// \param CE - If given, a code emitter to use to show the instruction
  /// encoding inline with the assembly. This method takes ownership of \p CE.
  ///
  /// \param TAB - If given, a target asm backend to use to show the fixup
  /// information in conjunction with encoding information. This method takes
  /// ownership of \p TAB.
  ///
  /// \param ShowInst - Whether to show the MCInst representation inline with
  /// the assembly.
  MCStreamer *createAsmStreamer(MCContext &Ctx,
                                std::unique_ptr<formatted_raw_ostream> OS,
                                bool isVerboseAsm, bool useDwarfDirectory,
                                MCInstPrinter *InstPrint, MCCodeEmitter *CE,
                                MCAsmBackend *TAB, bool ShowInst);
  
  } // end namespace llvm
  
  #endif // LLVM_MC_MCSTREAMER_H
  