text: //===- llvm/CodeGen/AsmPrinter.h - AsmPrinter Framework ---------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file contains a class to be used as the base class for target specific
  // asm writers.  This class primarily handles common functionality used by
  // all asm writers.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CODEGEN_ASMPRINTER_H
  #define LLVM_CODEGEN_ASMPRINTER_H
  
  #include "llvm/ADT/MapVector.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/BinaryFormat/Dwarf.h"
  #include "llvm/CodeGen/AsmPrinterHandler.h"
  #include "llvm/CodeGen/DwarfStringPoolEntry.h"
  #include "llvm/CodeGen/MachineFunctionPass.h"
  #include "llvm/IR/InlineAsm.h"
  #include "llvm/IR/LLVMContext.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/SourceMgr.h"
  #include <cstdint>
  #include <memory>
  #include <utility>
  #include <vector>
  
  namespace llvm {
  
  class BasicBlock;
  class BlockAddress;
  class Constant;
  class ConstantArray;
  class DataLayout;
  class DIE;
  class DIEAbbrev;
  class DwarfDebug;
  class GCMetadataPrinter;
  class GCStrategy;
  class GlobalObject;
  class GlobalValue;
  class GlobalVariable;
  class MachineBasicBlock;
  class MachineConstantPoolValue;
  class MachineDominatorTree;
  class MachineFunction;
  class MachineInstr;
  class MachineJumpTableInfo;
  class MachineLoopInfo;
  class MachineModuleInfo;
  class MachineOptimizationRemarkEmitter;
  class MCAsmInfo;
  class MCCFIInstruction;
  class MCContext;
  class MCExpr;
  class MCInst;
  class MCSection;
  class MCStreamer;
  class MCSubtargetInfo;
  class MCSymbol;
  class MCTargetOptions;
  class MDNode;
  class Module;
  class PseudoProbeHandler;
  class raw_ostream;
  class StackMaps;
  class StringRef;
  class TargetLoweringObjectFile;
  class TargetMachine;
  class Twine;
  
  class GlobalPtrAuthInfo;
  
  namespace remarks {
  class RemarkStreamer;
  }
  
  /// This class is intended to be used as a driving class for all asm writers.
  class AsmPrinter : public MachineFunctionPass {
  public:
    /// Target machine description.
    TargetMachine &TM;
  
    /// Target Asm Printer information.
    const MCAsmInfo *MAI;
  
    /// This is the context for the output file that we are streaming. This owns
    /// all of the global MC-related objects for the generated translation unit.
    MCContext &OutContext;
  
    /// This is the MCStreamer object for the file we are generating. This
    /// contains the transient state for the current translation unit that we are
    /// generating (such as the current section etc).
    std::unique_ptr<MCStreamer> OutStreamer;
  
    /// The current machine function.
    MachineFunction *MF = nullptr;
  
    /// This is a pointer to the current MachineModuleInfo.
    MachineModuleInfo *MMI = nullptr;
  
    /// This is a pointer to the current MachineDominatorTree.
    MachineDominatorTree *MDT = nullptr;
  
    /// This is a pointer to the current MachineLoopInfo.
    MachineLoopInfo *MLI = nullptr;
  
    /// Optimization remark emitter.
    MachineOptimizationRemarkEmitter *ORE;
  
    /// The symbol for the entry in __patchable_function_entires.
    MCSymbol *CurrentPatchableFunctionEntrySym = nullptr;
  
    /// The symbol for the current function. This is recalculated at the beginning
    /// of each call to runOnMachineFunction().
    MCSymbol *CurrentFnSym = nullptr;
  
    /// The symbol for the current function descriptor on AIX. This is created
    /// at the beginning of each call to SetupMachineFunction().
    MCSymbol *CurrentFnDescSym = nullptr;
  
    /// The symbol used to represent the start of the current function for the
    /// purpose of calculating its size (e.g. using the .size directive). By
    /// default, this is equal to CurrentFnSym.
    MCSymbol *CurrentFnSymForSize = nullptr;
  
    /// Map a basic block section ID to the begin and end symbols of that section
    ///  which determine the section's range.
    struct MBBSectionRange {
      MCSymbol *BeginLabel, *EndLabel;
    };
  
    MapVector<unsigned, MBBSectionRange> MBBSectionRanges;
  
    /// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
    /// its number of uses by other globals.
    using GOTEquivUsePair = std::pair<const GlobalVariable *, unsigned>;
    MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
  
    /// struct HandlerInfo and Handlers permit users or target extended
    /// AsmPrinter to add their own handlers.
    struct HandlerInfo {
      std::unique_ptr<AsmPrinterHandler> Handler;
      StringRef TimerName;
      StringRef TimerDescription;
      StringRef TimerGroupName;
      StringRef TimerGroupDescription;
  
      HandlerInfo(std::unique_ptr<AsmPrinterHandler> Handler, StringRef TimerName,
                  StringRef TimerDescription, StringRef TimerGroupName,
                  StringRef TimerGroupDescription)
          : Handler(std::move(Handler)), TimerName(TimerName),
            TimerDescription(TimerDescription), TimerGroupName(TimerGroupName),
            TimerGroupDescription(TimerGroupDescription) {}
    };
  
    // Flags representing which CFI section is required for a function/module.
    enum class CFISection : unsigned {
      None = 0, ///< Do not emit either .eh_frame or .debug_frame
      EH = 1,   ///< Emit .eh_frame
      Debug = 2 ///< Emit .debug_frame
    };
  
  private:
    MCSymbol *CurrentFnEnd = nullptr;
  
    /// Map a basic block section ID to the exception symbol associated with that
    /// section. Map entries are assigned and looked up via
    /// AsmPrinter::getMBBExceptionSym.
    DenseMap<unsigned, MCSymbol *> MBBSectionExceptionSyms;
  
    // The symbol used to represent the start of the current BB section of the
    // function. This is used to calculate the size of the BB section.
    MCSymbol *CurrentSectionBeginSym = nullptr;
  
    // The garbage collection metadata printer table.
    void *GCMetadataPrinters = nullptr; // Really a DenseMap.
  
    /// Emit comments in assembly output if this is true.
    bool VerboseAsm;
  
    /// Output stream for the stack usage file (i.e., .su file).
    std::unique_ptr<raw_fd_ostream> StackUsageStream;
  
    static char ID;
  
  protected:
    MCSymbol *CurrentFnBegin = nullptr;
  
    /// A vector of all debug/EH info emitters we should use. This vector
    /// maintains ownership of the emitters.
    std::vector<HandlerInfo> Handlers;
    size_t NumUserHandlers = 0;
  
  private:
    /// If generated on the fly this own the instance.
    std::unique_ptr<MachineDominatorTree> OwnedMDT;
  
    /// If generated on the fly this own the instance.
    std::unique_ptr<MachineLoopInfo> OwnedMLI;
  
    /// If the target supports dwarf debug info, this pointer is non-null.
    DwarfDebug *DD = nullptr;
  
    /// A handler that supports pseudo probe emission with embedded inline
    /// context.
    PseudoProbeHandler *PP = nullptr;
  
    /// CFISection type the module needs i.e. either .eh_frame or .debug_frame.
    CFISection ModuleCFISection = CFISection::None;
  
  protected:
    explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
  
  public:
    ~AsmPrinter() override;
  
    DwarfDebug *getDwarfDebug() { return DD; }
    DwarfDebug *getDwarfDebug() const { return DD; }
  
    uint16_t getDwarfVersion() const;
    void setDwarfVersion(uint16_t Version);
  
    bool isDwarf64() const;
  
    /// Returns 4 for DWARF32 and 8 for DWARF64.
    unsigned int getDwarfOffsetByteSize() const;
  
    /// Returns 4 for DWARF32 and 12 for DWARF64.
    unsigned int getUnitLengthFieldByteSize() const;
  
    /// Returns information about the byte size of DW_FORM values.
    dwarf::FormParams getDwarfFormParams() const;
  
    bool isPositionIndependent() const;
  
    /// Return true if assembly output should contain comments.
    bool isVerbose() const { return VerboseAsm; }
  
    /// Return a unique ID for the current function.
    unsigned getFunctionNumber() const;
  
    /// Return symbol for the function pseudo stack if the stack frame is not a
    /// register based.
    virtual const MCSymbol *getFunctionFrameSymbol() const { return nullptr; }
  
    MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
    MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
  
    // Return the exception symbol associated with the MBB section containing a
    // given basic block.
    MCSymbol *getMBBExceptionSym(const MachineBasicBlock &MBB);
  
    /// Return information about object file lowering.
    const TargetLoweringObjectFile &getObjFileLowering() const;
  
    /// Return information about data layout.
    const DataLayout &getDataLayout() const;
  
    /// Return the pointer size from the TargetMachine
    unsigned getPointerSize() const;
  
    /// Return information about subtarget.
    const MCSubtargetInfo &getSubtargetInfo() const;
  
    void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
  
    /// Emits inital debug location directive.
    void emitInitialRawDwarfLocDirective(const MachineFunction &MF);
  
    /// Return the current section we are emitting to.
    const MCSection *getCurrentSection() const;
  
    void getNameWithPrefix(SmallVectorImpl<char> &Name,
                           const GlobalValue *GV) const;
  
    MCSymbol *getSymbol(const GlobalValue *GV) const;
  
    /// Similar to getSymbol() but preferred for references. On ELF, this uses a
    /// local symbol if a reference to GV is guaranteed to be resolved to the
    /// definition in the same module.
    MCSymbol *getSymbolPreferLocal(const GlobalValue &GV) const;
  
    //===------------------------------------------------------------------===//
    // XRay instrumentation implementation.
    //===------------------------------------------------------------------===//
  public:
    // This describes the kind of sled we're storing in the XRay table.
    enum class SledKind : uint8_t {
      FUNCTION_ENTER = 0,
      FUNCTION_EXIT = 1,
      TAIL_CALL = 2,
      LOG_ARGS_ENTER = 3,
      CUSTOM_EVENT = 4,
      TYPED_EVENT = 5,
    };
  
    // The table will contain these structs that point to the sled, the function
    // containing the sled, and what kind of sled (and whether they should always
    // be instrumented). We also use a version identifier that the runtime can use
    // to decide what to do with the sled, depending on the version of the sled.
    struct XRayFunctionEntry {
      const MCSymbol *Sled;
      const MCSymbol *Function;
      SledKind Kind;
      bool AlwaysInstrument;
      const class Function *Fn;
      uint8_t Version;
  
      void emit(int, MCStreamer *) const;
    };
  
    // All the sleds to be emitted.
    SmallVector<XRayFunctionEntry, 4> Sleds;
  
    // Helper function to record a given XRay sled.
    void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind,
                    uint8_t Version = 0);
  
    /// Emit a table with all XRay instrumentation points.
    void emitXRayTable();
  
    void emitPatchableFunctionEntries();
  
    //===------------------------------------------------------------------===//
    // MachineFunctionPass Implementation.
    //===------------------------------------------------------------------===//
  
    /// Record analysis usage.
    void getAnalysisUsage(AnalysisUsage &AU) const override;
  
    /// Set up the AsmPrinter when we are working on a new module. If your pass
    /// overrides this, it must make sure to explicitly call this implementation.
    bool doInitialization(Module &M) override;
  
    /// Shut down the asmprinter. If you override this in your pass, you must make
    /// sure to call it explicitly.
    bool doFinalization(Module &M) override;
  
    /// Emit the specified function out to the OutStreamer.
    bool runOnMachineFunction(MachineFunction &MF) override {
      SetupMachineFunction(MF);
      emitFunctionBody();
      return false;
    }
  
    //===------------------------------------------------------------------===//
    // Coarse grained IR lowering routines.
    //===------------------------------------------------------------------===//
  
    /// This should be called when a new MachineFunction is being processed from
    /// runOnMachineFunction.
    virtual void SetupMachineFunction(MachineFunction &MF);
  
    /// This method emits the body and trailer for a function.
    void emitFunctionBody();
  
    void emitCFIInstruction(const MachineInstr &MI);
  
    void emitFrameAlloc(const MachineInstr &MI);
  
    void emitStackSizeSection(const MachineFunction &MF);
  
    void emitStackUsage(const MachineFunction &MF);
  
    void emitBBAddrMapSection(const MachineFunction &MF);
  
    void emitPseudoProbe(const MachineInstr &MI);
  
    void emitRemarksSection(remarks::RemarkStreamer &RS);
  
    /// Get the CFISection type for a function.
    CFISection getFunctionCFISectionType(const Function &F) const;
  
    /// Get the CFISection type for a function.
    CFISection getFunctionCFISectionType(const MachineFunction &MF) const;
  
    /// Get the CFISection type for the module.
    CFISection getModuleCFISectionType() const { return ModuleCFISection; }
  
    bool needsSEHMoves();
  
    /// Since emitting CFI unwind information is entangled with supporting the
    /// exceptions, this returns true for platforms which use CFI unwind
    /// information for debugging purpose when
    /// `MCAsmInfo::ExceptionsType == ExceptionHandling::None`.
    bool needsCFIForDebug() const;
  
    /// Print to the current output stream assembly representations of the
    /// constants in the constant pool MCP. This is used to print out constants
    /// which have been "spilled to memory" by the code generator.
    virtual void emitConstantPool();
  
    /// Print assembly representations of the jump tables used by the current
    /// function to the current output stream.
    virtual void emitJumpTableInfo();
  
    /// Emit the specified global variable to the .s file.
    virtual void emitGlobalVariable(const GlobalVariable *GV);
  
    /// Check to see if the specified global is a special global used by LLVM. If
    /// so, emit it and return true, otherwise do nothing and return false.
    bool emitSpecialLLVMGlobal(const GlobalVariable *GV);
  
    /// `llvm.global_ctors` and `llvm.global_dtors` are arrays of Structor
    /// structs.
    ///
    /// Priority - init priority
    /// Func - global initialization or global clean-up function
    /// ComdatKey - associated data
    struct Structor {
      int Priority = 0;
      Constant *Func = nullptr;
      GlobalValue *ComdatKey = nullptr;
  
      Structor() = default;
    };
  
    /// This method gathers an array of Structors and then sorts them out by
    /// Priority.
    /// @param List The initializer of `llvm.global_ctors` or `llvm.global_dtors`
    /// array.
    /// @param[out] Structors Sorted Structor structs by Priority.
    void preprocessXXStructorList(const DataLayout &DL, const Constant *List,
                                  SmallVector<Structor, 8> &Structors);
  
    /// This method emits `llvm.global_ctors` or `llvm.global_dtors` list.
    virtual void emitXXStructorList(const DataLayout &DL, const Constant *List,
                                    bool IsCtor);
  
    /// Emit an alignment directive to the specified power of two boundary. If a
    /// global value is specified, and if that global has an explicit alignment
    /// requested, it will override the alignment request if required for
    /// correctness.
    void emitAlignment(Align Alignment, const GlobalObject *GV = nullptr,
                       unsigned MaxBytesToEmit = 0) const;
  
    /// Lower the specified LLVM Constant to an MCExpr.
    virtual const MCExpr *lowerConstant(const Constant *CV);
  
    /// Print a general LLVM constant to the .s file.
    void emitGlobalConstant(const DataLayout &DL, const Constant *CV);
  
    /// Unnamed constant global variables solely contaning a pointer to
    /// another globals variable act like a global variable "proxy", or GOT
    /// equivalents, i.e., it's only used to hold the address of the latter. One
    /// optimization is to replace accesses to these proxies by using the GOT
    /// entry for the final global instead. Hence, we select GOT equivalent
    /// candidates among all the module global variables, avoid emitting them
    /// unnecessarily and finally replace references to them by pc relative
    /// accesses to GOT entries.
    void computeGlobalGOTEquivs(Module &M);
  
    /// Constant expressions using GOT equivalent globals may not be
    /// eligible for PC relative GOT entry conversion, in such cases we need to
    /// emit the proxies we previously omitted in EmitGlobalVariable.
    void emitGlobalGOTEquivs();
  
    /// Emit the stack maps.
    void emitStackMaps(StackMaps &SM);
  
    //===------------------------------------------------------------------===//
    // Overridable Hooks
    //===------------------------------------------------------------------===//
  
    void addAsmPrinterHandler(HandlerInfo Handler) {
      Handlers.insert(Handlers.begin(), std::move(Handler));
      NumUserHandlers++;
    }
  
    // Targets can, or in the case of EmitInstruction, must implement these to
    // customize output.
  
    /// This virtual method can be overridden by targets that want to emit
    /// something at the start of their file.
    virtual void emitStartOfAsmFile(Module &) {}
  
    /// This virtual method can be overridden by targets that want to emit
    /// something at the end of their file.
    virtual void emitEndOfAsmFile(Module &) {}
  
    /// Targets can override this to emit stuff before the first basic block in
    /// the function.
    virtual void emitFunctionBodyStart() {}
  
    /// Targets can override this to emit stuff after the last basic block in the
    /// function.
    virtual void emitFunctionBodyEnd() {}
  
    /// Targets can override this to emit stuff at the start of a basic block.
    /// By default, this method prints the label for the specified
    /// MachineBasicBlock, an alignment (if present) and a comment describing it
    /// if appropriate.
    virtual void emitBasicBlockStart(const MachineBasicBlock &MBB);
  
    /// Targets can override this to emit stuff at the end of a basic block.
    virtual void emitBasicBlockEnd(const MachineBasicBlock &MBB);
  
    /// Targets should implement this to emit instructions.
    virtual void emitInstruction(const MachineInstr *) {
      llvm_unreachable("EmitInstruction not implemented");
    }
  
    /// Return the symbol for the specified constant pool entry.
    virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
  
    virtual void emitFunctionEntryLabel();
  
    virtual void emitFunctionDescriptor() {
      llvm_unreachable("Function descriptor is target-specific.");
    }
  
    virtual void emitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
  
    /// Targets can override this to change how global constants that are part of
    /// a C++ static/global constructor list are emitted.
    virtual void emitXXStructor(const DataLayout &DL, const Constant *CV) {
      emitGlobalConstant(DL, CV);
    }
  
    /// Return true if the basic block has exactly one predecessor and the control
    /// transfer mechanism between the predecessor and this block is a
    /// fall-through.
    virtual bool
    isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
  
    /// Targets can override this to customize the output of IMPLICIT_DEF
    /// instructions in verbose mode.
    virtual void emitImplicitDef(const MachineInstr *MI) const;
  
    /// Lower the specified "llvm.ptrauth" GlobalVariable to an MCExpr.
    virtual const MCExpr *
    lowerPtrAuthGlobalConstant(const GlobalPtrAuthInfo &PAI) {
      report_fatal_error("llvm.ptrauth global lowering not implemented");
    }
  
    /// Lower the specified "llvm.ptrauth" GlobalVariable to an MCExpr.
    virtual const MCExpr *
    lowerBlockAddressConstant(const BlockAddress *BA);
  
    /// Emit N NOP instructions.
    void emitNops(unsigned N);
  
    //===------------------------------------------------------------------===//
    // Symbol Lowering Routines.
    //===------------------------------------------------------------------===//
  
    MCSymbol *createTempSymbol(const Twine &Name) const;
  
    /// Return the MCSymbol for a private symbol with global value name as its
    /// base, with the specified suffix.
    MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
                                           StringRef Suffix) const;
  
    /// Return the MCSymbol for the specified ExternalSymbol.
    MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
  
    /// Return the symbol for the specified jump table entry.
    MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
  
    /// Return the symbol for the specified jump table .set
    /// FIXME: privatize to AsmPrinter.
    MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
  
    /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
    /// basic block.
    MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
    MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
  
    //===------------------------------------------------------------------===//
    // Emission Helper Routines.
    //===------------------------------------------------------------------===//
  
    /// This is just convenient handler for printing offsets.
    void printOffset(int64_t Offset, raw_ostream &OS) const;
  
    /// Emit a byte directive and value.
    void emitInt8(int Value) const;
  
    /// Emit a short directive and value.
    void emitInt16(int Value) const;
  
    /// Emit a long directive and value.
    void emitInt32(int Value) const;
  
    /// Emit a long long directive and value.
    void emitInt64(uint64_t Value) const;
  
    /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
    /// is specified by Size and Hi/Lo specify the labels.  This implicitly uses
    /// .set if it is available.
    void emitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
                             unsigned Size) const;
  
    /// Emit something like ".uleb128 Hi-Lo".
    void emitLabelDifferenceAsULEB128(const MCSymbol *Hi,
                                      const MCSymbol *Lo) const;
  
    /// Emit something like ".long Label+Offset" where the size in bytes of the
    /// directive is specified by Size and Label specifies the label.  This
    /// implicitly uses .set if it is available.
    void emitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
                             unsigned Size, bool IsSectionRelative = false) const;
  
    /// Emit something like ".long Label" where the size in bytes of the directive
    /// is specified by Size and Label specifies the label.
    void emitLabelReference(const MCSymbol *Label, unsigned Size,
                            bool IsSectionRelative = false) const {
      emitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
    }
  
    //===------------------------------------------------------------------===//
    // Dwarf Emission Helper Routines
    //===------------------------------------------------------------------===//
  
    /// Emit the specified signed leb128 value.
    void emitSLEB128(int64_t Value, const char *Desc = nullptr) const;
  
    /// Emit the specified unsigned leb128 value.
    void emitULEB128(uint64_t Value, const char *Desc = nullptr,
                     unsigned PadTo = 0) const;
  
    /// Emit a .byte 42 directive that corresponds to an encoding.  If verbose
    /// assembly output is enabled, we output comments describing the encoding.
    /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
    void emitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
  
    /// Return the size of the encoding in bytes.
    unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
  
    /// Emit reference to a ttype global with a specified encoding.
    virtual void emitTTypeReference(const GlobalValue *GV, unsigned Encoding);
  
    /// Emit a reference to a symbol for use in dwarf. Different object formats
    /// represent this in different ways. Some use a relocation others encode
    /// the label offset in its section.
    void emitDwarfSymbolReference(const MCSymbol *Label,
                                  bool ForceOffset = false) const;
  
    /// Emit the 4- or 8-byte offset of a string from the start of its section.
    ///
    /// When possible, emit a DwarfStringPool section offset without any
    /// relocations, and without using the symbol.  Otherwise, defers to \a
    /// emitDwarfSymbolReference().
    ///
    /// The length of the emitted value depends on the DWARF format.
    void emitDwarfStringOffset(DwarfStringPoolEntry S) const;
  
    /// Emit the 4-or 8-byte offset of a string from the start of its section.
    void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const {
      emitDwarfStringOffset(S.getEntry());
    }
  
    /// Emit something like ".long Label + Offset" or ".quad Label + Offset"
    /// depending on the DWARF format.
    void emitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const;
  
    /// Emit 32- or 64-bit value depending on the DWARF format.
    void emitDwarfLengthOrOffset(uint64_t Value) const;
  
    /// Emit a unit length field. The actual format, DWARF32 or DWARF64, is chosen
    /// according to the settings.
    void emitDwarfUnitLength(uint64_t Length, const Twine &Comment) const;
  
    /// Emit a unit length field. The actual format, DWARF32 or DWARF64, is chosen
    /// according to the settings.
    /// Return the end symbol generated inside, the caller needs to emit it.
    MCSymbol *emitDwarfUnitLength(const Twine &Prefix,
                                  const Twine &Comment) const;
  
    /// Emit reference to a call site with a specified encoding
    void emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
                            unsigned Encoding) const;
    /// Emit an integer value corresponding to the call site encoding
    void emitCallSiteValue(uint64_t Value, unsigned Encoding) const;
  
    /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
    virtual unsigned getISAEncoding() { return 0; }
  
    /// Emit the directive and value for debug thread local expression
    ///
    /// \p Value - The value to emit.
    /// \p Size - The size of the integer (in bytes) to emit.
    virtual void emitDebugValue(const MCExpr *Value, unsigned Size) const;
  
    //===------------------------------------------------------------------===//
    // Dwarf Lowering Routines
    //===------------------------------------------------------------------===//
  
    /// Emit frame instruction to describe the layout of the frame.
    void emitCFIInstruction(const MCCFIInstruction &Inst) const;
  
    /// Emit Dwarf abbreviation table.
    template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
      // For each abbreviation.
      for (const auto &Abbrev : Abbrevs)
        emitDwarfAbbrev(*Abbrev);
  
      // Mark end of abbreviations.
      emitULEB128(0, "EOM(3)");
    }
  
    void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
  
    /// Recursively emit Dwarf DIE tree.
    void emitDwarfDIE(const DIE &Die) const;
  
    //===------------------------------------------------------------------===//
    // Inline Asm Support
    //===------------------------------------------------------------------===//
  
    // These are hooks that targets can override to implement inline asm
    // support.  These should probably be moved out of AsmPrinter someday.
  
    /// Print information related to the specified machine instr that is
    /// independent of the operand, and may be independent of the instr itself.
    /// This can be useful for portably encoding the comment character or other
    /// bits of target-specific knowledge into the asmstrings.  The syntax used is
    /// ${:comment}.  Targets can override this to add support for their own
    /// strange codes.
    virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
                              StringRef Code) const;
  
    /// Print the MachineOperand as a symbol. Targets with complex handling of
    /// symbol references should override the base implementation.
    virtual void PrintSymbolOperand(const MachineOperand &MO, raw_ostream &OS);
  
    /// Print the specified operand of MI, an INLINEASM instruction, using the
    /// specified assembler variant.  Targets should override this to format as
    /// appropriate.  This method can return true if the operand is erroneous.
    virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                                 const char *ExtraCode, raw_ostream &OS);
  
    /// Print the specified operand of MI, an INLINEASM instruction, using the
    /// specified assembler variant as an address. Targets should override this to
    /// format as appropriate.  This method can return true if the operand is
    /// erroneous.
    virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                       const char *ExtraCode, raw_ostream &OS);
  
    /// Let the target do anything it needs to do before emitting inlineasm.
    /// \p StartInfo - the subtarget info before parsing inline asm
    virtual void emitInlineAsmStart() const;
  
    /// Let the target do anything it needs to do after emitting inlineasm.
    /// This callback can be used restore the original mode in case the
    /// inlineasm contains directives to switch modes.
    /// \p StartInfo - the original subtarget info before inline asm
    /// \p EndInfo   - the final subtarget info after parsing the inline asm,
    ///                or NULL if the value is unknown.
    virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                  const MCSubtargetInfo *EndInfo) const;
  
    /// This emits visibility information about symbol, if this is supported by
    /// the target.
    void emitVisibility(MCSymbol *Sym, unsigned Visibility,
                        bool IsDefinition = true) const;
  
    /// This emits linkage information about \p GVSym based on \p GV, if this is
    /// supported by the target.
    virtual void emitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
  
    /// Return the alignment for the specified \p GV.
    static Align getGVAlignment(const GlobalObject *GV, const DataLayout &DL,
                                Align InAlign = Align(1));
  
  private:
    /// Private state for PrintSpecial()
    // Assign a unique ID to this machine instruction.
    mutable const MachineInstr *LastMI = nullptr;
    mutable unsigned LastFn = 0;
    mutable unsigned Counter = ~0U;
  
    /// This method emits the header for the current function.
    virtual void emitFunctionHeader();
  
    /// This method emits a comment next to header for the current function.
    virtual void emitFunctionHeaderComment();
  
    /// Emit a blob of inline asm to the output streamer.
    void
    emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
                  const MCTargetOptions &MCOptions,
                  const MDNode *LocMDNode = nullptr,
                  InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
  
    /// This method formats and emits the specified machine instruction that is an
    /// inline asm.
    void emitInlineAsm(const MachineInstr *MI) const;
  
    /// Add inline assembly info to the diagnostics machinery, so we can
    /// emit file and position info. Returns SrcMgr memory buffer position.
    unsigned addInlineAsmDiagBuffer(StringRef AsmStr,
                                    const MDNode *LocMDNode) const;
  
    //===------------------------------------------------------------------===//
    // Internal Implementation Details
    //===------------------------------------------------------------------===//
  
    void emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
                            const MachineBasicBlock *MBB, unsigned uid) const;
    void emitLLVMUsedList(const ConstantArray *InitList);
    /// Emit llvm.ident metadata in an '.ident' directive.
    void emitModuleIdents(Module &M);
    /// Emit bytes for llvm.commandline metadata.
    void emitModuleCommandLines(Module &M);
  
    GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &S);
    void emitGlobalAlias(Module &M, const GlobalAlias &GA);
    void emitGlobalIFunc(Module &M, const GlobalIFunc &GI);
  
    /// This method decides whether the specified basic block requires a label.
    bool shouldEmitLabelForBasicBlock(const MachineBasicBlock &MBB) const;
  
  protected:
    virtual bool shouldEmitWeakSwiftAsyncExtendedFramePointerFlags() const {
      return false;
    }
  };
  
  } // end namespace llvm
  
  #endif // LLVM_CODEGEN_ASMPRINTER_H
  