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//===- X86ModRMFilters.h - Disassembler ModR/M filterss ---------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is part of the X86 Disassembler Emitter.
// It contains ModR/M filters that determine which values of the ModR/M byte
// are valid for a partiuclar instruction.
// Documentation for the disassembler emitter in general can be found in
// X86DisasemblerEmitter.h.
//
//===----------------------------------------------------------------------===//
#ifndef X86MODRMFILTERS_H
#define X86MODRMFILTERS_H
#include "llvm/Support/DataTypes.h"
namespace llvm {
namespace X86Disassembler {
/// ModRMFilter - Abstract base class for clases that recognize patterns in
/// ModR/M bytes.
class ModRMFilter {
public:
/// Destructor - Override as necessary.
virtual ~ModRMFilter() { }
/// isDumb - Indicates whether this filter returns the same value for
/// any value of the ModR/M byte.
///
/// @result - True if the filter returns the same value for any ModR/M
/// byte; false if not.
virtual bool isDumb() const { return false; }
/// accepts - Indicates whether the filter accepts a particular ModR/M
/// byte value.
///
/// @result - True if the filter accepts the ModR/M byte; false if not.
virtual bool accepts(uint8_t modRM) const = 0;
};
/// DumbFilter - Accepts any ModR/M byte. Used for instructions that do not
/// require a ModR/M byte or instructions where the entire ModR/M byte is used
/// for operands.
class DumbFilter : public ModRMFilter {
public:
bool isDumb() const {
return true;
}
bool accepts(uint8_t modRM) const {
return true;
}
};
/// ModFilter - Filters based on the mod bits [bits 7-6] of the ModR/M byte.
/// Some instructions are classified based on whether they are 11 or anything
/// else. This filter performs that classification.
class ModFilter : public ModRMFilter {
private:
bool R;
public:
/// Constructor
///
/// @r - True if the mod bits of the ModR/M byte must be 11; false
/// otherwise. The name r derives from the fact that the mod
/// bits indicate whether the R/M bits [bits 2-0] signify a
/// register or a memory operand.
ModFilter(bool r) :
ModRMFilter(),
R(r) {
}
bool accepts(uint8_t modRM) const {
if (R == ((modRM & 0xc0) == 0xc0))
return true;
else
return false;
}
};
/// EscapeFilter - Filters escape opcodes, which are classified in two ways. If
/// the ModR/M byte is between 0xc0 and 0xff, then there is one slot for each
/// possible value. Otherwise, there is one instruction for each value of the
/// nnn field [bits 5-3], known elsewhere as the reg field.
class EscapeFilter : public ModRMFilter {
private:
bool C0_FF;
uint8_t NNN_or_ModRM;
public:
/// Constructor
///
/// @c0_ff - True if the ModR/M byte must fall between 0xc0 and 0xff;
/// false otherwise.
/// @nnn_or_modRM - If c0_ff is true, the required value of the entire ModR/M
/// byte. If c0_ff is false, the required value of the nnn
/// field.
EscapeFilter(bool c0_ff, uint8_t nnn_or_modRM) :
ModRMFilter(),
C0_FF(c0_ff),
NNN_or_ModRM(nnn_or_modRM) {
}
bool accepts(uint8_t modRM) const {
if ((C0_FF && modRM >= 0xc0 && (modRM == NNN_or_ModRM)) ||
(!C0_FF && modRM < 0xc0 && ((modRM & 0x38) >> 3) == NNN_or_ModRM))
return true;
else
return false;
}
};
/// AddRegEscapeFilter - Some escape opcodes have one of the register operands
/// added to the ModR/M byte, meaning that a range of eight ModR/M values
/// maps to a single instruction. Such instructions require the ModR/M byte
/// to fall between 0xc0 and 0xff.
class AddRegEscapeFilter : public ModRMFilter {
private:
uint8_t ModRM;
public:
/// Constructor
///
/// @modRM - The value of the ModR/M byte when the register operand
/// refers to the first register in the register set.
AddRegEscapeFilter(uint8_t modRM) : ModRM(modRM) {
}
bool accepts(uint8_t modRM) const {
if (modRM >= ModRM && modRM < ModRM + 8)
return true;
else
return false;
}
};
/// ExtendedFilter - Extended opcodes are classified based on the value of the
/// mod field [bits 7-6] and the value of the nnn field [bits 5-3].
class ExtendedFilter : public ModRMFilter {
private:
bool R;
uint8_t NNN;
public:
/// Constructor
///
/// @r - True if the mod field must be set to 11; false otherwise.
/// The name is explained at ModFilter.
/// @nnn - The required value of the nnn field.
ExtendedFilter(bool r, uint8_t nnn) :
ModRMFilter(),
R(r),
NNN(nnn) {
}
bool accepts(uint8_t modRM) const {
if (((R && ((modRM & 0xc0) == 0xc0)) ||
(!R && ((modRM & 0xc0) != 0xc0))) &&
(((modRM & 0x38) >> 3) == NNN))
return true;
else
return false;
}
};
/// ExactFilter - The occasional extended opcode (such as VMCALL or MONITOR)
/// requires the ModR/M byte to have a specific value.
class ExactFilter : public ModRMFilter
{
private:
uint8_t ModRM;
public:
/// Constructor
///
/// @modRM - The required value of the full ModR/M byte.
ExactFilter(uint8_t modRM) :
ModRMFilter(),
ModRM(modRM) {
}
bool accepts(uint8_t modRM) const {
if (ModRM == modRM)
return true;
else
return false;
}
};
} // namespace X86Disassembler
} // namespace llvm
#endif
|
