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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 MCDISASSEMBLER_H
10 #define MCDISASSEMBLER_H
11 
12 #include "llvm/Support/DataTypes.h"
13 #include "llvm-c/Disassembler.h"
14 
15 namespace llvm {
16 
17 class MCInst;
18 class MCSubtargetInfo;
19 class MemoryObject;
20 class raw_ostream;
21 class MCContext;
22 
23 struct EDInstInfo;
24 
25 /// MCDisassembler - Superclass for all disassemblers.  Consumes a memory region
26 ///   and provides an 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   /// Constructor     - Performs initial setup for the disassembler.
MCDisassembler(const MCSubtargetInfo & STI)58   MCDisassembler(const MCSubtargetInfo &STI) : GetOpInfo(0), SymbolLookUp(0),
59                                                DisInfo(0), Ctx(0),
60                                                STI(STI), CommentStream(0) {}
61 
62   virtual ~MCDisassembler();
63 
64   /// getInstruction  - Returns the disassembly of a single instruction.
65   ///
66   /// @param instr    - An MCInst to populate with the contents of the
67   ///                   instruction.
68   /// @param size     - A value to populate with the size of the instruction, or
69   ///                   the number of bytes consumed while attempting to decode
70   ///                   an invalid instruction.
71   /// @param region   - The memory object to use as a source for machine code.
72   /// @param address  - The address, in the memory space of region, of the first
73   ///                   byte of the instruction.
74   /// @param vStream  - The stream to print warnings and diagnostic messages on.
75   /// @param cStream  - The stream to print comments and annotations on.
76   /// @return         - MCDisassembler::Success if the instruction is valid,
77   ///                   MCDisassembler::SoftFail if the instruction was
78   ///                                            disassemblable but invalid,
79   ///                   MCDisassembler::Fail if the instruction was invalid.
80   virtual DecodeStatus  getInstruction(MCInst& instr,
81                                        uint64_t& size,
82                                        const MemoryObject &region,
83                                        uint64_t address,
84                                        raw_ostream &vStream,
85                                        raw_ostream &cStream) const = 0;
86 
87   /// getEDInfo - Returns the enhanced instruction information corresponding to
88   ///   the disassembler.
89   ///
90   /// @return         - An array of instruction information, with one entry for
91   ///                   each MCInst opcode this disassembler returns.
92   ///                   NULL if there is no info for this target.
getEDInfo()93   virtual const EDInstInfo   *getEDInfo() const { return (EDInstInfo*)0; }
94 
95 private:
96   //
97   // Hooks for symbolic disassembly via the public 'C' interface.
98   //
99   // The function to get the symbolic information for operands.
100   LLVMOpInfoCallback GetOpInfo;
101   // The function to lookup a symbol name.
102   LLVMSymbolLookupCallback SymbolLookUp;
103   // The pointer to the block of symbolic information for above call back.
104   void *DisInfo;
105   // The assembly context for creating symbols and MCExprs in place of
106   // immediate operands when there is symbolic information.
107   MCContext *Ctx;
108 protected:
109   // Subtarget information, for instruction decoding predicates if required.
110   const MCSubtargetInfo &STI;
111 
112 public:
setupForSymbolicDisassembly(LLVMOpInfoCallback getOpInfo,LLVMSymbolLookupCallback symbolLookUp,void * disInfo,MCContext * ctx)113   void setupForSymbolicDisassembly(LLVMOpInfoCallback getOpInfo,
114                                    LLVMSymbolLookupCallback symbolLookUp,
115                                    void *disInfo,
116                                    MCContext *ctx) {
117     GetOpInfo = getOpInfo;
118     SymbolLookUp = symbolLookUp;
119     DisInfo = disInfo;
120     Ctx = ctx;
121   }
getLLVMOpInfoCallback()122   LLVMOpInfoCallback getLLVMOpInfoCallback() const { return GetOpInfo; }
getLLVMSymbolLookupCallback()123   LLVMSymbolLookupCallback getLLVMSymbolLookupCallback() const {
124     return SymbolLookUp;
125   }
getDisInfoBlock()126   void *getDisInfoBlock() const { return DisInfo; }
getMCContext()127   MCContext *getMCContext() const { return Ctx; }
128 
129   // Marked mutable because we cache it inside the disassembler, rather than
130   // having to pass it around as an argument through all the autogenerated code.
131   mutable raw_ostream *CommentStream;
132 };
133 
134 } // namespace llvm
135 
136 #endif
137