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135 lines
4.0 KiB
C++
135 lines
4.0 KiB
C++
//===- X86ModRMFilters.h - Disassembler ModR/M filterss ---------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is part of the X86 Disassembler Emitter.
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// It contains ModR/M filters that determine which values of the ModR/M byte
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// are valid for a partiuclar instruction.
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// Documentation for the disassembler emitter in general can be found in
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// X86DisassemblerEmitter.h.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_UTILS_TABLEGEN_X86MODRMFILTERS_H
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#define LLVM_UTILS_TABLEGEN_X86MODRMFILTERS_H
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#include "llvm/Support/DataTypes.h"
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namespace llvm {
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namespace X86Disassembler {
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/// ModRMFilter - Abstract base class for clases that recognize patterns in
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/// ModR/M bytes.
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class ModRMFilter {
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virtual void anchor();
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public:
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/// Destructor - Override as necessary.
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virtual ~ModRMFilter() { }
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/// isDumb - Indicates whether this filter returns the same value for
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/// any value of the ModR/M byte.
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///
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/// @result - True if the filter returns the same value for any ModR/M
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/// byte; false if not.
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virtual bool isDumb() const { return false; }
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/// accepts - Indicates whether the filter accepts a particular ModR/M
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/// byte value.
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///
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/// @result - True if the filter accepts the ModR/M byte; false if not.
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virtual bool accepts(uint8_t modRM) const = 0;
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};
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/// DumbFilter - Accepts any ModR/M byte. Used for instructions that do not
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/// require a ModR/M byte or instructions where the entire ModR/M byte is used
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/// for operands.
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class DumbFilter : public ModRMFilter {
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void anchor() override;
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public:
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bool isDumb() const override {
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return true;
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}
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bool accepts(uint8_t modRM) const override {
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return true;
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}
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};
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/// ModFilter - Filters based on the mod bits [bits 7-6] of the ModR/M byte.
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/// Some instructions are classified based on whether they are 11 or anything
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/// else. This filter performs that classification.
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class ModFilter : public ModRMFilter {
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void anchor() override;
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bool R;
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public:
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/// Constructor
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///
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/// \param r True if the mod bits of the ModR/M byte must be 11; false
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/// otherwise. The name r derives from the fact that the mod
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/// bits indicate whether the R/M bits [bits 2-0] signify a
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/// register or a memory operand.
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ModFilter(bool r) :
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ModRMFilter(),
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R(r) {
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}
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bool accepts(uint8_t modRM) const override {
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return (R == ((modRM & 0xc0) == 0xc0));
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}
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};
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/// ExtendedFilter - Extended opcodes are classified based on the value of the
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/// mod field [bits 7-6] and the value of the nnn field [bits 5-3].
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class ExtendedFilter : public ModRMFilter {
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void anchor() override;
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bool R;
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uint8_t NNN;
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public:
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/// Constructor
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///
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/// \param r True if the mod field must be set to 11; false otherwise.
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/// The name is explained at ModFilter.
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/// \param nnn The required value of the nnn field.
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ExtendedFilter(bool r, uint8_t nnn) :
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ModRMFilter(),
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R(r),
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NNN(nnn) {
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}
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bool accepts(uint8_t modRM) const override {
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return (((R && ((modRM & 0xc0) == 0xc0)) ||
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(!R && ((modRM & 0xc0) != 0xc0))) &&
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(((modRM & 0x38) >> 3) == NNN));
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}
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};
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/// ExactFilter - The occasional extended opcode (such as VMCALL or MONITOR)
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/// requires the ModR/M byte to have a specific value.
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class ExactFilter : public ModRMFilter {
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void anchor() override;
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uint8_t ModRM;
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public:
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/// Constructor
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///
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/// \param modRM The required value of the full ModR/M byte.
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ExactFilter(uint8_t modRM) :
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ModRMFilter(),
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ModRM(modRM) {
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}
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bool accepts(uint8_t modRM) const override {
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return (ModRM == modRM);
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}
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};
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} // namespace X86Disassembler
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} // namespace llvm
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#endif
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