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