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 //===- llvm/MC/MCDisassembler.h - Disassembler interface --------*- 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H
 #define LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/XCOFF.h"
 #include "llvm/MC/MCDisassembler/MCSymbolizer.h"
 #include "llvm/Support/Error.h"
 #include <cstdint>
 #include <memory>
 #include <vector>
 
 namespace llvm {
 
 struct XCOFFSymbolInfoTy {
   std::optional<XCOFF::StorageMappingClass> StorageMappingClass;
   std::optional<uint32_t> Index;
   bool IsLabel = false;
   bool operator<(const XCOFFSymbolInfoTy &SymInfo) const;
 };
 
 struct SymbolInfoTy {
   uint64_t Addr;
   StringRef Name;
   // XCOFF uses XCOFFSymInfo. Other targets use Type.
   XCOFFSymbolInfoTy XCOFFSymInfo;
   uint8_t Type;
   // Used by ELF to describe a mapping symbol that is usually not displayed.
   bool IsMappingSymbol;
 
 private:
   bool IsXCOFF;
   bool HasType;
 
 public:
   SymbolInfoTy(std::optional<XCOFF::StorageMappingClass> Smc, uint64_t Addr,
                StringRef Name, std::optional<uint32_t> Idx, bool Label)
       : Addr(Addr), Name(Name), XCOFFSymInfo{Smc, Idx, Label}, Type(0),
         IsMappingSymbol(false), IsXCOFF(true), HasType(false) {}
   SymbolInfoTy(uint64_t Addr, StringRef Name, uint8_t Type,
                bool IsMappingSymbol = false, bool IsXCOFF = false)
       : Addr(Addr), Name(Name), Type(Type), IsMappingSymbol(IsMappingSymbol),
         IsXCOFF(IsXCOFF), HasType(true) {}
   bool isXCOFF() const { return IsXCOFF; }
 
 private:
   friend bool operator<(const SymbolInfoTy &P1, const SymbolInfoTy &P2) {
     assert((P1.IsXCOFF == P2.IsXCOFF && P1.HasType == P2.HasType) &&
            "The value of IsXCOFF and HasType in P1 and P2 should be the same "
            "respectively.");
 
     if (P1.IsXCOFF && P1.HasType)
       return std::tie(P1.Addr, P1.Type, P1.Name) <
              std::tie(P2.Addr, P2.Type, P2.Name);
 
     if (P1.IsXCOFF)
       return std::tie(P1.Addr, P1.XCOFFSymInfo, P1.Name) <
              std::tie(P2.Addr, P2.XCOFFSymInfo, P2.Name);
 
     // With the same address, place mapping symbols first.
     bool MS1 = !P1.IsMappingSymbol, MS2 = !P2.IsMappingSymbol;
     return std::tie(P1.Addr, MS1, P1.Name, P1.Type) <
            std::tie(P2.Addr, MS2, P2.Name, P2.Type);
   }
 };
 
 using SectionSymbolsTy = std::vector<SymbolInfoTy>;
 
 template <typename T> class ArrayRef;
 class MCContext;
 class MCInst;
 class MCSubtargetInfo;
 class raw_ostream;
 
 /// Superclass for all disassemblers. Consumes a memory region and provides an
 /// array of assembly instructions.
 class MCDisassembler {
 public:
   /// Ternary decode status. Most backends will just use Fail and
   /// Success, however some have a concept of an instruction with
   /// understandable semantics but which is architecturally
   /// incorrect. An example of this is ARM UNPREDICTABLE instructions
   /// which are disassemblable but cause undefined behaviour.
   ///
   /// Because it makes sense to disassemble these instructions, there
   /// is a "soft fail" failure mode that indicates the MCInst& is
   /// valid but architecturally incorrect.
   ///
   /// The enum numbers are deliberately chosen such that reduction
   /// from Success->SoftFail ->Fail can be done with a simple
   /// bitwise-AND:
   ///
   ///   LEFT & TOP =  | Success       Unpredictable   Fail
   ///   --------------+-----------------------------------
   ///   Success       | Success       Unpredictable   Fail
   ///   Unpredictable | Unpredictable Unpredictable   Fail
   ///   Fail          | Fail          Fail            Fail
   ///
   /// An easy way of encoding this is as 0b11, 0b01, 0b00 for
   /// Success, SoftFail, Fail respectively.
   enum DecodeStatus {
     Fail = 0,
     SoftFail = 1,
     Success = 3
   };
 
   MCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
     : Ctx(Ctx), STI(STI) {}
 
   virtual ~MCDisassembler();
 
   /// Returns the disassembly of a single instruction.
   ///
   /// \param Instr    - An MCInst to populate with the contents of the
   ///                   instruction.
   /// \param Size     - A value to populate with the size of the instruction, or
   ///                   the number of bytes consumed while attempting to decode
   ///                   an invalid instruction.
   /// \param Address  - The address, in the memory space of region, of the first
   ///                   byte of the instruction.
   /// \param Bytes    - A reference to the actual bytes of the instruction.
   /// \param CStream  - The stream to print comments and annotations on.
   /// \return         - MCDisassembler::Success if the instruction is valid,
   ///                   MCDisassembler::SoftFail if the instruction was
   ///                                            disassemblable but invalid,
   ///                   MCDisassembler::Fail if the instruction was invalid.
   virtual DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
                                       ArrayRef<uint8_t> Bytes, uint64_t Address,
                                       raw_ostream &CStream) const = 0;
 
   /// Used to perform separate target specific disassembly for a particular
   /// symbol. May parse any prelude that precedes instructions after the
   /// start of a symbol, or the entire symbol.
   /// This is used for example by WebAssembly to decode preludes.
   ///
   /// Base implementation returns false. So all targets by default decline to
   /// treat symbols separately.
   ///
   /// \param Symbol   - The symbol.
   /// \param Size     - The number of bytes consumed.
   /// \param Address  - The address, in the memory space of region, of the first
   ///                   byte of the symbol.
   /// \param Bytes    - A reference to the actual bytes at the symbol location.
   /// \return         - True if this symbol triggered some target specific
   ///                   disassembly for this symbol. Size must be set with the
   ///                   number of bytes consumed.
   ///                 - Error if this symbol triggered some target specific
   ///                   disassembly for this symbol, but an error was found with
   ///                   it. Size must be set with the number of bytes consumed.
   ///                 - False if the target doesn't want to handle the symbol
   ///                   separately. The value of Size is ignored in this case,
   ///                   and Err must not be set.
   virtual Expected<bool> onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size,
                                        ArrayRef<uint8_t> Bytes,
                                        uint64_t Address) const;
   // TODO:
   // Implement similar hooks that can be used at other points during
   // disassembly. Something along the following lines:
   // - onBeforeInstructionDecode()
   // - onAfterInstructionDecode()
   // - onSymbolEnd()
   // It should help move much of the target specific code from llvm-objdump to
   // respective target disassemblers.
 
   /// Suggest a distance to skip in a buffer of data to find the next
   /// place to look for the start of an instruction. For example, if
   /// all instructions have a fixed alignment, this might advance to
   /// the next multiple of that alignment.
   ///
   /// If not overridden, the default is 1.
   ///
   /// \param Address  - The address, in the memory space of region, of the
   ///                   starting point (typically the first byte of something
   ///                   that did not decode as a valid instruction at all).
   /// \param Bytes    - A reference to the actual bytes at Address. May be
   ///                   needed in order to determine the width of an
   ///                   unrecognized instruction (e.g. in Thumb this is a simple
   ///                   consistent criterion that doesn't require knowing the
   ///                   specific instruction). The caller can pass as much data
   ///                   as they have available, and the function is required to
   ///                   make a reasonable default choice if not enough data is
   ///                   available to make a better one.
   /// \return         - A number of bytes to skip. Must always be greater than
   ///                   zero. May be greater than the size of Bytes.
   virtual uint64_t suggestBytesToSkip(ArrayRef<uint8_t> Bytes,
                                       uint64_t Address) const;
 
 private:
   MCContext &Ctx;
 
 protected:
   // Subtarget information, for instruction decoding predicates if required.
   const MCSubtargetInfo &STI;
   std::unique_ptr<MCSymbolizer> Symbolizer;
 
 public:
   // Helpers around MCSymbolizer
   bool tryAddingSymbolicOperand(MCInst &Inst, int64_t Value, uint64_t Address,
                                 bool IsBranch, uint64_t Offset, uint64_t OpSize,
                                 uint64_t InstSize) const;
 
   void tryAddingPcLoadReferenceComment(int64_t Value, uint64_t Address) const;
 
   /// Set \p Symzer as the current symbolizer.
   /// This takes ownership of \p Symzer, and deletes the previously set one.
   void setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer);
 
   MCContext& getContext() const { return Ctx; }
 
   const MCSubtargetInfo& getSubtargetInfo() const { return STI; }
 
   /// ELF-specific, set the ABI version from the object header.
   virtual void setABIVersion(unsigned Version) {}
 
   // Marked mutable because we cache it inside the disassembler, rather than
   // having to pass it around as an argument through all the autogenerated code.
   mutable raw_ostream *CommentStream = nullptr;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H

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