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235 lines
5.8 KiB
235 lines
5.8 KiB
// SPDX-License-Identifier: MIT
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// Copyright Murad Karammaev, Nikita Kuzmin
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use ux::{u2, u3, u4};
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#[derive(Debug)]
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pub enum Register {
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R0,
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R1,
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}
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#[derive(Debug)]
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pub enum ShiftMode {
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Logical,
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Circular,
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}
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#[derive(Debug)]
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pub enum Instruction {
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Load {
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reg: Register,
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addr: u4,
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},
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Store {
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reg: Register,
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addr: u4,
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},
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LoadImmediate {
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low: bool,
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reg: Register,
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val: u4,
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},
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NearJumpBackward {
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use_carry: bool,
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offset: u2,
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},
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NearJumpForward {
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use_carry: bool,
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offset: u3,
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},
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FarJump {
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reg: Register,
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use_carry: bool,
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},
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CmpEqual,
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CmpGreater,
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CmpLess,
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Not,
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BitShift {
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right: bool,
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reg: Register,
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mode: ShiftMode,
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len: u3,
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},
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Inc {
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reg: Register,
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},
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Dec {
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reg: Register,
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},
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Add,
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Sub,
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And,
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Or,
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Xor,
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Xnor,
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Complement {
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reg: Register,
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},
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BitShiftVar {
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right: bool,
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mode: ShiftMode,
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},
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Copy {
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reg_from: Register,
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},
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Setc {
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carry: bool,
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},
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Nop,
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Halt,
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Cload {
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reg: Register,
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},
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Zero {
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reg: Register,
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},
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Div,
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Mul,
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Swap,
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PortReady,
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ReadPort,
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WritePort,
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}
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pub fn decode(insn: u8) -> Instruction {
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match insn {
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0b00000000..=0b00111111 => {
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let reg = if insn & 0b00010000 == 0 {
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Register::R0
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} else {
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Register::R1
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};
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let addr = u4::new(insn & 0b00001111);
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match insn & 0b00100000 {
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0 => Instruction::Load { reg, addr },
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_ => Instruction::Store { reg, addr },
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}
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}
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0b01000000..=0b01111111 => Instruction::LoadImmediate {
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low: insn & 0b00100000 == 0,
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reg: if insn & 0b00010000 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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val: u4::new(insn & 0b00001111),
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},
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0b10001000..=0b10001111 => Instruction::NearJumpBackward {
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use_carry: insn & 0b00000100 != 0,
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offset: u2::new(insn & 0b00000011),
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},
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0b10010000..=0b10011111 => Instruction::NearJumpForward {
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use_carry: insn & 0b00001000 != 0,
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offset: u3::new(insn & 0b00000111),
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},
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0b10000000..=0b10000011 => Instruction::FarJump {
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reg: if insn & 0b00000010 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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use_carry: insn & 0b00000001 != 0,
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},
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0b10000100 => Instruction::CmpEqual,
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0b10000101 => Instruction::CmpGreater,
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0b10000110 => Instruction::CmpLess,
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0b10000111 => Instruction::Not,
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0b10100000..=0b10111111 => Instruction::BitShift {
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right: true,
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reg: if insn & 0b00010000 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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mode: if insn & 0b00001000 == 0 {
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ShiftMode::Logical
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} else {
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ShiftMode::Circular
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},
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len: u3::new(insn & 0b00000111),
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},
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0b11000000..=0b11011111 => Instruction::BitShift {
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right: false,
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reg: if insn & 0b00010000 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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mode: if insn & 0b00001000 == 0 {
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ShiftMode::Logical
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} else {
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ShiftMode::Circular
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},
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len: u3::new(insn & 0b00000111),
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},
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0b11100000..=0b11100001 => Instruction::Inc {
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reg: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11100010..=0b11100011 => Instruction::Dec {
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reg: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11100100 => Instruction::Add,
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0b11100101 => Instruction::Sub,
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0b11100110 => Instruction::And,
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0b11100111 => Instruction::Or,
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0b11101000 => Instruction::Xor,
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0b11101001 => Instruction::Xnor,
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0b11101010..=0b11101011 => Instruction::Complement {
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reg: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11101100..=0b11101111 => Instruction::BitShiftVar {
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right: insn & 0b00000010 == 0,
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mode: if insn & 0b00000001 == 0 {
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ShiftMode::Logical
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} else {
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ShiftMode::Circular
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},
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},
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0b11110000..=0b11110001 => Instruction::Copy {
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reg_from: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11110010..=0b11110011 => Instruction::Setc {
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carry: insn & 0b00000001 != 0,
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},
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0b11110100 => Instruction::Nop,
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0b11110101 => Instruction::Halt,
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0b11110110..=0b11110111 => Instruction::Cload {
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reg: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11111000..=0b11111001 => Instruction::Zero {
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reg: if insn & 0b00000001 == 0 {
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Register::R0
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} else {
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Register::R1
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},
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},
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0b11111010 => Instruction::Div,
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0b11111011 => Instruction::Mul,
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0b11111100 => Instruction::Swap,
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0b11111101 => Instruction::PortReady,
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0b11111110 => Instruction::ReadPort,
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0b11111111 => Instruction::WritePort,
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}
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}
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