1//===- X86ModRMFilters.h - Disassembler ModR/M filterss ---------*- 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//
10// This file is part of the X86 Disassembler Emitter.
11// It contains ModR/M filters that determine which values of the ModR/M byte
12//  are valid for a partiuclar instruction.
13// Documentation for the disassembler emitter in general can be found in
14//  X86DisasemblerEmitter.h.
15//
16//===----------------------------------------------------------------------===//
17
18#ifndef X86MODRMFILTERS_H
19#define X86MODRMFILTERS_H
20
21#include "llvm/Support/DataTypes.h"
22
23namespace llvm {
24
25namespace X86Disassembler {
26
27/// ModRMFilter - Abstract base class for clases that recognize patterns in
28///   ModR/M bytes.
29class ModRMFilter {
30  virtual void anchor();
31public:
32  /// Destructor    - Override as necessary.
33  virtual ~ModRMFilter() { }
34
35  /// isDumb        - Indicates whether this filter returns the same value for
36  ///                 any value of the ModR/M byte.
37  ///
38  /// @result       - True if the filter returns the same value for any ModR/M
39  ///                 byte; false if not.
40  virtual bool isDumb() const { return false; }
41
42  /// accepts       - Indicates whether the filter accepts a particular ModR/M
43  ///                 byte value.
44  ///
45  /// @result       - True if the filter accepts the ModR/M byte; false if not.
46  virtual bool accepts(uint8_t modRM) const = 0;
47};
48
49/// DumbFilter - Accepts any ModR/M byte.  Used for instructions that do not
50///   require a ModR/M byte or instructions where the entire ModR/M byte is used
51///   for operands.
52class DumbFilter : public ModRMFilter {
53  virtual void anchor();
54public:
55  bool isDumb() const {
56    return true;
57  }
58
59  bool accepts(uint8_t modRM) const {
60    return true;
61  }
62};
63
64/// ModFilter - Filters based on the mod bits [bits 7-6] of the ModR/M byte.
65///   Some instructions are classified based on whether they are 11 or anything
66///   else.  This filter performs that classification.
67class ModFilter : public ModRMFilter {
68  virtual void anchor();
69  bool R;
70public:
71  /// Constructor
72  ///
73  /// \param r        True if the mod bits of the ModR/M byte must be 11; false
74  ///                 otherwise.  The name r derives from the fact that the mod
75  ///                 bits indicate whether the R/M bits [bits 2-0] signify a
76  ///                 register or a memory operand.
77  ModFilter(bool r) :
78    ModRMFilter(),
79    R(r) {
80  }
81
82  bool accepts(uint8_t modRM) const {
83    if (R == ((modRM & 0xc0) == 0xc0))
84      return true;
85    else
86      return false;
87  }
88};
89
90/// EscapeFilter - Filters escape opcodes, which are classified in two ways.  If
91///   the ModR/M byte is between 0xc0 and 0xff, then there is one slot for each
92///   possible value.  Otherwise, there is one instruction for each value of the
93///   nnn field [bits 5-3], known elsewhere as the reg field.
94class EscapeFilter : public ModRMFilter {
95  virtual void anchor();
96  bool C0_FF;
97  uint8_t NNN_or_ModRM;
98public:
99  /// Constructor
100  ///
101  /// \param c0_ff True if the ModR/M byte must fall between 0xc0 and 0xff;
102  ///              false otherwise.
103  ///
104  /// \param nnn_or_modRM If c0_ff is true, the required value of the entire
105  ///                     ModR/M byte.  If c0_ff is false, the required value
106  ///                     of the nnn field.
107  EscapeFilter(bool c0_ff, uint8_t nnn_or_modRM) :
108    ModRMFilter(),
109    C0_FF(c0_ff),
110    NNN_or_ModRM(nnn_or_modRM) {
111  }
112
113  bool accepts(uint8_t modRM) const {
114    if ((C0_FF && modRM >= 0xc0 && (modRM == NNN_or_ModRM)) ||
115        (!C0_FF && modRM < 0xc0  && ((modRM & 0x38) >> 3) == NNN_or_ModRM))
116      return true;
117    else
118      return false;
119  }
120};
121
122/// AddRegEscapeFilter - Some escape opcodes have one of the register operands
123///   added to the ModR/M byte, meaning that a range of eight ModR/M values
124///   maps to a single instruction.  Such instructions require the ModR/M byte
125///   to fall between 0xc0 and 0xff.
126class AddRegEscapeFilter : public ModRMFilter {
127  virtual void anchor();
128  uint8_t ModRM;
129public:
130  /// Constructor
131  ///
132  /// \param modRM The value of the ModR/M byte when the register operand
133  ///              refers to the first register in the register set.
134  AddRegEscapeFilter(uint8_t modRM) : ModRM(modRM) {
135  }
136
137  bool accepts(uint8_t modRM) const {
138    if (modRM >= ModRM && modRM < ModRM + 8)
139      return true;
140    else
141      return false;
142  }
143};
144
145/// ExtendedFilter - Extended opcodes are classified based on the value of the
146///   mod field [bits 7-6] and the value of the nnn field [bits 5-3].
147class ExtendedFilter : public ModRMFilter {
148  virtual void anchor();
149  bool R;
150  uint8_t NNN;
151public:
152  /// Constructor
153  ///
154  /// \param r   True if the mod field must be set to 11; false otherwise.
155  ///            The name is explained at ModFilter.
156  /// \param nnn The required value of the nnn field.
157  ExtendedFilter(bool r, uint8_t nnn) :
158    ModRMFilter(),
159    R(r),
160    NNN(nnn) {
161  }
162
163  bool accepts(uint8_t modRM) const {
164    if (((R  && ((modRM & 0xc0) == 0xc0)) ||
165        (!R && ((modRM & 0xc0) != 0xc0))) &&
166        (((modRM & 0x38) >> 3) == NNN))
167      return true;
168    else
169      return false;
170  }
171};
172
173/// ExactFilter - The occasional extended opcode (such as VMCALL or MONITOR)
174///   requires the ModR/M byte to have a specific value.
175class ExactFilter : public ModRMFilter {
176  virtual void anchor();
177  uint8_t ModRM;
178public:
179  /// Constructor
180  ///
181  /// \param modRM The required value of the full ModR/M byte.
182  ExactFilter(uint8_t modRM) :
183    ModRMFilter(),
184    ModRM(modRM) {
185  }
186
187  bool accepts(uint8_t modRM) const {
188    if (ModRM == modRM)
189      return true;
190    else
191      return false;
192  }
193};
194
195} // namespace X86Disassembler
196
197} // namespace llvm
198
199#endif
200