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//===- X86ModRMFilters.h - Disassembler ModR/M filterss ---------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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
// X86DisassemblerEmitter.h.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_UTILS_TABLEGEN_X86MODRMFILTERS_H
#define LLVM_UTILS_TABLEGEN_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 {
virtual void anchor();
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 {
void anchor() override;
public:
bool isDumb() const override {
return true;
}
bool accepts(uint8_t modRM) const override {
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 {
void anchor() override;
bool R;
public:
/// Constructor
///
/// \param 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) : R(r) {}
bool accepts(uint8_t modRM) const override {
return (R == ((modRM & 0xc0) == 0xc0));
}
};
/// 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 {
void anchor() override;
bool R;
uint8_t NNN;
public:
/// Constructor
///
/// \param r True if the mod field must be set to 11; false otherwise.
/// The name is explained at ModFilter.
/// \param nnn The required value of the nnn field.
ExtendedFilter(bool r, uint8_t nnn) : R(r), NNN(nnn) {}
bool accepts(uint8_t modRM) const override {
return (((R && ((modRM & 0xc0) == 0xc0)) ||
(!R && ((modRM & 0xc0) != 0xc0))) &&
(((modRM & 0x38) >> 3) == NNN));
}
};
/// ExtendedRMFilter - Extended opcodes are classified based on the value of the
/// mod field [bits 7-6] and the value of the nnn field [bits 2-0].
class ExtendedRMFilter : public ModRMFilter {
void anchor() override;
bool R;
uint8_t NNN;
public:
/// Constructor
///
/// \param r True if the mod field must be set to 11; false otherwise.
/// The name is explained at ModFilter.
/// \param nnn The required value of the nnn field.
ExtendedRMFilter(bool r, uint8_t nnn) : R(r), NNN(nnn) {}
bool accepts(uint8_t modRM) const override {
return ((R && ((modRM & 0xc0) == 0xc0)) &&
((modRM & 0x7) == NNN));
}
};
/// ExactFilter - The occasional extended opcode (such as VMCALL or MONITOR)
/// requires the ModR/M byte to have a specific value.
class ExactFilter : public ModRMFilter {
void anchor() override;
uint8_t ModRM;
public:
/// Constructor
///
/// \param modRM The required value of the full ModR/M byte.
ExactFilter(uint8_t modRM) : ModRM(modRM) {}
bool accepts(uint8_t modRM) const override {
return (ModRM == modRM);
}
};
} // namespace X86Disassembler
} // namespace llvm
#endif
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