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//===- 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/DenseMap.h"

#include "llvm/ADT/DenseSet.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/CodeGen/StackMaps.h"

#include "llvm/IR/InlineAsm.h"

#include "llvm/Support/ErrorHandling.h"

#include <cstdint>

#include <memory>

#include <utility>

#include <vector>

namespace llvm {

class AddrLabelMap;

class BasicBlock;

class BlockAddress;

class Constant;

class ConstantArray;

class DataLayout;

class DIE;

class DIEAbbrev;

class DwarfDebug;

class GCMetadataPrinter;

class GCStrategy;

class GlobalAlias;

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 StringRef;

class TargetLoweringObjectFile;

class TargetMachine;

class Twine;

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;

  /// This map keeps track of which symbol is being used for the specified basic

  /// block's address of label.

  std::unique_ptr<AddrLabelMap> AddrLabelSymbols;

  /// The garbage collection metadata printer table.

  DenseMap<GCStrategy *, std::unique_ptr<GCMetadataPrinter>> GCMetadataPrinters;

  /// 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;

  /// List of symbols to be inserted into PC sections.

  DenseMap<const MDNode *, SmallVector<const MCSymbol *>> PCSectionsSymbols;

  static char ID;

protected:

  MCSymbol *CurrentFnBegin = nullptr;

  /// For dso_local functions, the current $local alias for the function.

  MCSymbol *CurrentFnBeginLocal = 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;

  StackMaps SM;

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;

  /// True if the module contains split-stack functions. This is used to

  /// emit .note.GNU-split-stack section as required by the linker for

  /// special handling split-stack function calling no-split-stack function.

  bool HasSplitStack = false;

  /// True if the module contains no-split-stack functions. This is used to emit

  /// .note.GNU-no-split-stack section when it also contains functions without a

  /// split stack prologue.

  bool HasNoSplitStack = false;

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 the symbol to be used for the specified basic block when its

  /// address is taken.  This cannot be its normal LBB label because the block

  /// may be accessed outside its containing function.

  MCSymbol *getAddrLabelSymbol(const BasicBlock *BB) {

    return getAddrLabelSymbolToEmit(BB).front();

  }

  /// Return the symbol to be used for the specified basic block when its

  /// address is taken.  If other blocks were RAUW'd to this one, we may have

  /// to emit them as well, return the whole set.

  ArrayRef<MCSymbol *> getAddrLabelSymbolToEmit(const BasicBlock *BB);

  /// If the specified function has had any references to address-taken blocks

  /// generated, but the block got deleted, return the symbol now so we can

  /// emit it.  This prevents emitting a reference to a symbol that has no

  /// definition.

  void takeDeletedSymbolsForFunction(const Function *F,

                                     std::vector<MCSymbol *> &Result);

  /// 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;

  bool doesDwarfUseRelocationsAcrossSections() const {

    return DwarfUsesRelocationsAcrossSections;

  }

  void setDwarfUsesRelocationsAcrossSections(bool Enable) {

    DwarfUsesRelocationsAcrossSections = Enable;

  }

  //===------------------------------------------------------------------===//

  // 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 emitKCFITrapEntry(const MachineFunction &MF, const MCSymbol *Symbol);

  virtual void emitKCFITypeId(const MachineFunction &MF);

  void emitPseudoProbe(const MachineInstr &MI);

  void emitRemarksSection(remarks::RemarkStreamer &RS);

  /// Emits a label as reference for PC sections.

  void emitPCSectionsLabel(const MachineFunction &MF, const MDNode &MD);

  /// Emits the PC sections collected from instructions.

  void emitPCSections(const MachineFunction &MF);

  /// 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.

  /// On AIX, when an alias refers to a sub-element of a global variable, the

  /// label of that alias needs to be emitted before the corresponding element.

  using AliasMapTy = DenseMap<uint64_t, SmallVector<const GlobalAlias *, 1>>;

  void emitGlobalConstant(const DataLayout &DL, const Constant *CV,

                          AliasMapTy *AliasList = nullptr);

  /// 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();

  //===------------------------------------------------------------------===//

  // 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;

  /// 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;

  bool DwarfUsesRelocationsAcrossSections = false;

  /// 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);