1//===-- llvm/MC/MCDisassembler.h - Disassembler interface -------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9#ifndef LLVM_MC_MCDISASSEMBLER_H
10#define LLVM_MC_MCDISASSEMBLER_H
11
12#include "llvm-c/Disassembler.h"
13#include "llvm/MC/MCRelocationInfo.h"
14#include "llvm/MC/MCSymbolizer.h"
15#include "llvm/Support/DataTypes.h"
16
17namespace llvm {
18
19class MCInst;
20class MCSubtargetInfo;
21class MemoryObject;
22class raw_ostream;
23class MCContext;
24
25/// MCDisassembler - Superclass for all disassemblers.  Consumes a memory region
26///   and provides an array of assembly instructions.
27class MCDisassembler {
28public:
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  /// Constructor     - Performs initial setup for the disassembler.
58  MCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
59    : Ctx(Ctx), STI(STI), Symbolizer(), CommentStream(nullptr) {}
60
61  virtual ~MCDisassembler();
62
63  /// getInstruction  - Returns the disassembly of a single instruction.
64  ///
65  /// @param instr    - An MCInst to populate with the contents of the
66  ///                   instruction.
67  /// @param size     - A value to populate with the size of the instruction, or
68  ///                   the number of bytes consumed while attempting to decode
69  ///                   an invalid instruction.
70  /// @param region   - The memory object to use as a source for machine code.
71  /// @param address  - The address, in the memory space of region, of the first
72  ///                   byte of the instruction.
73  /// @param vStream  - The stream to print warnings and diagnostic messages on.
74  /// @param cStream  - The stream to print comments and annotations on.
75  /// @return         - MCDisassembler::Success if the instruction is valid,
76  ///                   MCDisassembler::SoftFail if the instruction was
77  ///                                            disassemblable but invalid,
78  ///                   MCDisassembler::Fail if the instruction was invalid.
79  virtual DecodeStatus  getInstruction(MCInst& instr,
80                                       uint64_t& size,
81                                       const MemoryObject &region,
82                                       uint64_t address,
83                                       raw_ostream &vStream,
84                                       raw_ostream &cStream) const = 0;
85private:
86  MCContext &Ctx;
87
88protected:
89  // Subtarget information, for instruction decoding predicates if required.
90  const MCSubtargetInfo &STI;
91  std::unique_ptr<MCSymbolizer> Symbolizer;
92
93public:
94  // Helpers around MCSymbolizer
95  bool tryAddingSymbolicOperand(MCInst &Inst,
96                                int64_t Value,
97                                uint64_t Address, bool IsBranch,
98                                uint64_t Offset, uint64_t InstSize) const;
99
100  void tryAddingPcLoadReferenceComment(int64_t Value, uint64_t Address) const;
101
102  /// Set \p Symzer as the current symbolizer.
103  /// This takes ownership of \p Symzer, and deletes the previously set one.
104  void setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer);
105
106  MCContext& getContext() const { return Ctx; }
107
108  const MCSubtargetInfo& getSubtargetInfo() const { return STI; }
109
110  // Marked mutable because we cache it inside the disassembler, rather than
111  // having to pass it around as an argument through all the autogenerated code.
112  mutable raw_ostream *CommentStream;
113};
114
115} // namespace llvm
116
117#endif
118