include/llvm/MC/MCDisassembler/MCDisassembler.h

   1 //===- llvm/MC/MCDisassembler.h - Disassembler interface --------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H
  10 #define LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H
  11
  12 #include "llvm/MC/MCDisassembler/MCSymbolizer.h"
  13 #include <cstdint>
  14 #include <memory>
  15
  16 namespace llvm {
  17
  18 template <typename T> class ArrayRef;
  19 class StringRef;
  20 class MCContext;
  21 class MCInst;
  22 class MCSubtargetInfo;
  23 class raw_ostream;
  24
  25 /// Superclass for all disassemblers. Consumes a memory region and provides an
  26 /// array of assembly instructions.
  27 class MCDisassembler {
  28 public:
  29   /// Ternary decode status. Most backends will just use Fail and
  30   /// Success, however some have a concept of an instruction with
  31   /// understandable semantics but which is architecturally
  32   /// incorrect. An example of this is ARM UNPREDICTABLE instructions
  33   /// which are disassemblable but cause undefined behaviour.
  34   ///
  35   /// Because it makes sense to disassemble these instructions, there
  36   /// is a "soft fail" failure mode that indicates the MCInst& is
  37   /// valid but architecturally incorrect.
  38   ///
  39   /// The enum numbers are deliberately chosen such that reduction
  40   /// from Success->SoftFail ->Fail can be done with a simple
  41   /// bitwise-AND:
  42   ///
  43   ///   LEFT & TOP =  | Success       Unpredictable   Fail
  44   ///   --------------+-----------------------------------
  45   ///   Success       | Success       Unpredictable   Fail
  46   ///   Unpredictable | Unpredictable Unpredictable   Fail
  47   ///   Fail          | Fail          Fail            Fail
  48   ///
  49   /// An easy way of encoding this is as 0b11, 0b01, 0b00 for
  50   /// Success, SoftFail, Fail respectively.
  51   enum DecodeStatus {
  52     Fail = 0,
  53     SoftFail = 1,
  54     Success = 3
  55   };
  56
  57   MCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
  58     : Ctx(Ctx), STI(STI) {}
  59
  60   virtual ~MCDisassembler();
  61
  62   /// Returns the disassembly of a single instruction.
  63   ///
  64   /// \param Instr    - An MCInst to populate with the contents of the
  65   ///                   instruction.
  66   /// \param Size     - A value to populate with the size of the instruction, or
  67   ///                   the number of bytes consumed while attempting to decode
  68   ///                   an invalid instruction.
  69   /// \param Address  - The address, in the memory space of region, of the first
  70   ///                   byte of the instruction.
  71   /// \param Bytes    - A reference to the actual bytes of the instruction.
  72   /// \param VStream  - The stream to print warnings and diagnostic messages on.
  73   /// \param CStream  - The stream to print comments and annotations on.
  74   /// \return         - MCDisassembler::Success if the instruction is valid,
  75   ///                   MCDisassembler::SoftFail if the instruction was
  76   ///                                            disassemblable but invalid,
  77   ///                   MCDisassembler::Fail if the instruction was invalid.
  78   virtual DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
  79                                       ArrayRef<uint8_t> Bytes, uint64_t Address,
  80                                       raw_ostream &VStream,
  81                                       raw_ostream &CStream) const = 0;
  82
  83   /// May parse any prelude that precedes instructions after the start of a
  84   /// symbol. Needed for some targets, e.g. WebAssembly.
  85   ///
  86   /// \param Name     - The name of the symbol.
  87   /// \param Size     - The number of bytes consumed.
  88   /// \param Address  - The address, in the memory space of region, of the first
  89   ///                   byte of the symbol.
  90   /// \param Bytes    - A reference to the actual bytes at the symbol location.
  91   /// \param VStream  - The stream to print warnings and diagnostic messages on.
  92   /// \param CStream  - The stream to print comments and annotations on.
  93   /// \return         - MCDisassembler::Success if the bytes are valid,
  94   ///                   MCDisassembler::Fail if the bytes were invalid.
  95   virtual DecodeStatus onSymbolStart(StringRef Name, uint64_t &Size,
  96                                      ArrayRef<uint8_t> Bytes, uint64_t Address,
  97                                      raw_ostream &VStream,
  98                                      raw_ostream &CStream) const;
  99
 100 private:
 101   MCContext &Ctx;
 102
 103 protected:
 104   // Subtarget information, for instruction decoding predicates if required.
 105   const MCSubtargetInfo &STI;
 106   std::unique_ptr<MCSymbolizer> Symbolizer;
 107
 108 public:
 109   // Helpers around MCSymbolizer
 110   bool tryAddingSymbolicOperand(MCInst &Inst,
 111                                 int64_t Value,
 112                                 uint64_t Address, bool IsBranch,
 113                                 uint64_t Offset, uint64_t InstSize) const;
 114
 115   void tryAddingPcLoadReferenceComment(int64_t Value, uint64_t Address) const;
 116
 117   /// Set \p Symzer as the current symbolizer.
 118   /// This takes ownership of \p Symzer, and deletes the previously set one.
 119   void setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer);
 120
 121   MCContext& getContext() const { return Ctx; }
 122
 123   const MCSubtargetInfo& getSubtargetInfo() const { return STI; }
 124
 125   // Marked mutable because we cache it inside the disassembler, rather than
 126   // having to pass it around as an argument through all the autogenerated code.
 127   mutable raw_ostream *CommentStream = nullptr;
 128 };
 129
 130 } // end namespace llvm
 131
 132 #endif // LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H