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 23 namespace llvm { 24 25 namespace X86Disassembler { 26 27 /// ModRMFilter - Abstract base class for clases that recognize patterns in 28 /// ModR/M bytes. 29 class ModRMFilter { 30 virtual void anchor(); 31 public: 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. 52 class DumbFilter : public ModRMFilter { 53 virtual void anchor(); 54 public: 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. 67 class ModFilter : public ModRMFilter { 68 virtual void anchor(); 69 bool R; 70 public: 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. 94 class EscapeFilter : public ModRMFilter { 95 virtual void anchor(); 96 bool C0_FF; 97 uint8_t NNN_or_ModRM; 98 public: 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. 126 class AddRegEscapeFilter : public ModRMFilter { 127 virtual void anchor(); 128 uint8_t ModRM; 129 public: 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]. 147 class ExtendedFilter : public ModRMFilter { 148 virtual void anchor(); 149 bool R; 150 uint8_t NNN; 151 public: 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. 175 class ExactFilter : public ModRMFilter { 176 virtual void anchor(); 177 uint8_t ModRM; 178 public: 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
