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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/MapVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/StackMaps.h"
 #include "llvm/DebugInfo/CodeView/CodeView.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <cstdint>
 #include <memory>
 #include <utility>
 #include <vector>
 
 namespace llvm {
 
 class AddrLabelMap;
 class AsmPrinterHandler;
 class BasicBlock;
 class BlockAddress;
 class Constant;
 class ConstantArray;
 class ConstantPtrAuth;
 class DataLayout;
 class DebugHandlerBase;
 class DIE;
 class DIEAbbrev;
 class DwarfDebug;
 class EHStreamer;
 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 = nullptr;
 
   /// 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 = nullptr;
 
   /// 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<MBBSectionID, 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;
 
   // 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<MBBSectionID, 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 handle to the EH info emitter (if present).
   // Only for EHStreamer subtypes, but some C++ compilers will incorrectly warn
   // us if we declare that directly.
   SmallVector<std::unique_ptr<AsmPrinterHandler>, 1> EHHandlers;
 
   // A vector of all Debuginfo emitters we should use. Protected so that
   // targets can add their own. This vector maintains ownership of the
   // emitters.
   SmallVector<std::unique_ptr<AsmPrinterHandler>, 2> 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.
   std::unique_ptr<PseudoProbeHandler> PP;
 
   /// 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;
 
   /// True if debugging information is available in this module.
   bool DbgInfoAvailable = 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; }
 
   /// Returns true if valid debug info is present.
   bool hasDebugInfo() const { return DbgInfoAvailable; }
 
   bool needsSEHMoves();
 
   /// Since emitting CFI unwind information is entangled with supporting the
   /// exceptions, this returns true for platforms which use CFI unwind
   /// information for other purposes (debugging, sanitizers, ...) when
   /// `MCAsmInfo::ExceptionsType == ExceptionHandling::None`.
   bool usesCFIWithoutEH() 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(std::unique_ptr<AsmPrinterHandler> Handler);
 
   // 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);
   }
 
   virtual const MCExpr *lowerConstantPtrAuth(const ConstantPtrAuth &CPA) {
     report_fatal_error("ptrauth constant lowering not implemented");
   }
 
   /// Lower the specified BlockAddress to an MCExpr.
   virtual const MCExpr *lowerBlockAddressConstant(const BlockAddress &BA);
 
   /// 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;
 
   /// getSubtargetInfo() cannot be used where this is needed because we don't
   /// have a MachineFunction when we're lowering a GlobalIFunc, and
   /// getSubtargetInfo requires one. Override the implementation in targets
   /// that support the Mach-O IFunc lowering.
   virtual const MCSubtargetInfo *getIFuncMCSubtargetInfo() const {
     return nullptr;
   }
 
   virtual void emitMachOIFuncStubBody(Module &M, const GlobalIFunc &GI,
                                       MCSymbol *LazyPointer) {
     llvm_unreachable(
         "Mach-O IFunc lowering is not yet supported on this target");
   }
 
   virtual void emitMachOIFuncStubHelperBody(Module &M, const GlobalIFunc &GI,
                                             MCSymbol *LazyPointer) {
     llvm_unreachable(
         "Mach-O IFunc lowering is not yet supported on this target");
   }
 
   /// 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(Twine 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 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 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 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;
 
   //===------------------------------------------------------------------===//
   // CodeView Helper Routines
   //===------------------------------------------------------------------===//
 
   /// Gets information required to create a CodeView debug symbol for a jump
   /// table.
   /// Return value is <Base Address, Base Offset, Branch Address, Entry Size>
   virtual std::tuple<const MCSymbol *, uint64_t, const MCSymbol *,
                      codeview::JumpTableEntrySize>
   getCodeViewJumpTableInfo(int JTI, const MachineInstr *BranchInstr,
                            const MCSymbol *BranchLabel) 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();
 
   /// This method emits prefix-like data before the current function.
   void emitFunctionPrefix(ArrayRef<const Constant *> Prefix);
 
   /// 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 emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
                          ArrayRef<unsigned> JumpTableIndices,
                          bool JTInDiffSection);
   void emitJumpTableEntry(const MachineJumpTableInfo &MJTI,
                           const MachineBasicBlock *MBB, unsigned uid) const;
 
   void emitJumpTableSizesSection(const MachineJumpTableInfo &MJTI,
                                  const Function &F) const;
 
   void emitLLVMUsedList(const ConstantArray *InitList);
   /// Emit llvm.ident metadata in an '.ident' directive.
   void emitModuleIdents(Module &M);
   /// Emit bytes for llvm.commandline metadata.
   virtual void emitModuleCommandLines(Module &M);
 
   GCMetadataPrinter *getOrCreateGCPrinter(GCStrategy &S);
   void emitGlobalIFunc(Module &M, const GlobalIFunc &GI);
 
 private:
   /// This method decides whether the specified basic block requires a label.
   bool shouldEmitLabelForBasicBlock(const MachineBasicBlock &MBB) const;
 
 protected:
   virtual void emitGlobalAlias(const Module &M, const GlobalAlias &GA);
   virtual bool shouldEmitWeakSwiftAsyncExtendedFramePointerFlags() const {
     return false;
   }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_CODEGEN_ASMPRINTER_H

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