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92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
//
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// Instruction.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 16/02/2024.
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// Copyright © 2024 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "Decoder.hpp"
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#include "Model.hpp"
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#include "Operation.hpp"
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namespace InstructionSet::ARM {
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enum class ShiftType {
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LogicalLeft = 0b00,
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LogicalRight = 0b01,
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ArithmeticRight = 0b10,
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RotateRight = 0b11,
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};
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template <Model model>
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class Instruction {
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public:
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constexpr Instruction(uint32_t opcode) noexcept : opcode_(opcode) {}
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Condition condition() const { return Condition(opcode_ >> 28); }
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Operation operation() const {
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return InstructionSet::ARM::operation<model>(opcode_);
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}
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//
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// B and BL.
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//
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/// Provides a 26-bit offset to add to the program counter for B and BL.
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uint32_t b_offset() const { return (opcode_ & 0xff'ffff) << 2; }
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//
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// Data processing (i.e. AND to MVN).
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//
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/// @returns @c true if this operation should set condition codes; @c false otherwise.
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/// @note Valid for data processing and multiply/multiply-accumulate.
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bool set_condition_codes() const { return opcode_ & (1 << 20); }
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// TODO: could build this into the Operation?
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/// The destination register index.
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int destination() const { return (opcode_ >> 12) & 0xf; }
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/// The operand 1 register index.
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int operand1() const { return (opcode_ >> 16) & 0xf; }
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/// @returns @c true if operand 2 is defined by the @c rotate() and @c immediate() fields;
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/// @c false if it is defined by the @c shift_*() and @c operand2() fields.
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bool operand2_is_immediate() const { return opcode_ & (1 << 25); }
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//
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// Register values for operand 2.
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//
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/// The operand 2 register index if @c operand2_is_immediate() is @c false; meaningless otherwise.
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int operand2() const { return opcode_ & 0xf; }
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/// The type of shift to apply to operand 2 if @c operand2_is_immediate() is @c false; meaningless otherwise.
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ShiftType shift_type() const { return ShiftType((opcode_ >> 5) & 3); }
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/// @returns @c true if the amount to shift by should be taken from a register; @c false if it is an immediate value.
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bool shift_count_is_register() const { return opcode_ & (1 << 4); }
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/// The shift amount register index if @c shift_count_is_register() is @c true; meaningless otherwise.
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int shift_register() const { return (opcode_ >> 8) & 0xf; }
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/// The amount to shift by if @c shift_count_is_register() is @c false; meaningless otherwise.
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int shift_amount() const { return (opcode_ >> 7) & 0x1f; }
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//
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// Immediate values for operand 2.
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//
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/// An 8-bit value to rotate right @c rotate() places if @c operand2_is_immediate() is @c true; meaningless otherwise.
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int immediate() const { return opcode_ & 0xff; }
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/// The number of bits to rotate @c immediate() by if @c operand2_is_immediate() is @c true; meaningless otherwise.
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int rotate() const { return (opcode_ >> 7) & 0x1e; }
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private:
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uint32_t opcode_;
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};
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// TODO: do MUL and MLA really transpose Rd and Rn as per the data sheet?
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// ARM: Assembly Language Programming by Cockerell thinks not.
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}
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