6502-cpp/src/main.cpp

#include <iostream>
#include <vector>
#include <set>
#include <string>
#include <regex>
#include <cassert>
#include <map>
#include <cctype>
#include <fstream>

struct ASMLine
{
  enum class Type {
    Label,
    Instruction,
    Directive
  };

  ASMLine(Type t, std::string te) : type(t), text(std::move(te)) {}

  Type type;
  std::string text;
};

int parse_8bit_literal(const std::string &s)
{
  return std::stoi(std::string(std::next(std::begin(s)), std::end(s)));
}


std::string strip_lo_hi(const std::string &s)
{
  if ((s.starts_with("lo8(") || s.starts_with("hi8("))
      && s.ends_with(")")) {
    return s.substr(4, s.size() - 5);
  }

  return s;
}

std::string fixup_8bit_literal(const std::string &s)
{
  if (s[0] == '$') {
    return "#" + std::to_string(static_cast<uint8_t>(parse_8bit_literal(s)));
  }

  if (s.starts_with("0x")) {
    return "#$" + s.substr(2);
  }

  if (s.starts_with("lo8(") && s.ends_with(")")) {
    return "#<" + strip_lo_hi(s);
  }
  if (s.starts_with("hi8(") && s.ends_with(")")) {
    return "#>" + strip_lo_hi(s);
  }

  const auto is_num = std::all_of(begin(s), end(s), [](const auto c) { return (c >= '0' && c <= '9') || c == '-'; });

  if (is_num) {
    return "#<" + s;
  }

  return s;
}

struct Operand
{
  enum class Type {
    empty,
    literal,
    reg /*ister*/
  };

  Type type = Type::empty;
  int reg_num = 0;
  std::string value;

  Operand() = default;

  bool operator==(const Operand &other) const
  {
    return type == other.type && reg_num == other.reg_num && value == other.value;
  }

  Operand(const Type t, std::string v)
    : type(t), value(std::move(v))
  {

    assert(type == Type::literal);
  }

  Operand(const Type t, const int num)
    : type(t), reg_num(num)
  {
    assert(type == Type::reg);
  }
};

struct mos6502 : ASMLine
{
  enum class OpCode {
    unknown,
    lda,
    asl,
    rol,
    ldy,
    tay,
    tya,
    tax,
    txa,
    cpy,
    eor,
    sta,
    sty,
    pha,
    pla,
    php,
    plp,
    lsr,
    ror,
    AND,
    inc,
    dec,
    ORA,
    cmp,
    bne,
    beq,
    bmi,
    bpl,
    jmp,
    adc,
    sbc,
    rts,
    clc,
    sec,
    bit,
    jsr,
    bcc,
    bcs
  };

  static bool get_is_branch(const OpCode o)
  {
    switch (o) {
    case OpCode::beq:
    case OpCode::bne:
    case OpCode::bmi:
    case OpCode::bpl:
    case OpCode::bcc:
    case OpCode::bcs:
      return true;
    case OpCode::lda:
    case OpCode::ldy:
    case OpCode::tay:
    case OpCode::tya:
    case OpCode::tax:
    case OpCode::txa:
    case OpCode::cpy:
    case OpCode::eor:
    case OpCode::sta:
    case OpCode::sty:
    case OpCode::pha:
    case OpCode::pla:
    case OpCode::php:
    case OpCode::plp:
    case OpCode::lsr:
    case OpCode::ror:
    case OpCode::AND:
    case OpCode::inc:
    case OpCode::dec:
    case OpCode::ORA:
    case OpCode::cmp:
    case OpCode::jmp:
    case OpCode::jsr:
    case OpCode::adc:
    case OpCode::sbc:
    case OpCode::rts:
    case OpCode::clc:
    case OpCode::sec:
    case OpCode::bit:
    case OpCode::asl:
    case OpCode::rol:
    case OpCode::unknown:
      break;
    }
    return false;
  }

  static bool get_is_comparison(const OpCode o)
  {
    switch (o) {
    case OpCode::cmp:
    case OpCode::cpy:
    case OpCode::bit:
      return true;
    case OpCode::lda:
    case OpCode::ldy:
    case OpCode::tay:
    case OpCode::tya:
    case OpCode::tax:
    case OpCode::txa:
    case OpCode::eor:
    case OpCode::sta:
    case OpCode::sty:
    case OpCode::pha:
    case OpCode::pla:
    case OpCode::php:
    case OpCode::plp:
    case OpCode::lsr:
    case OpCode::ror:
    case OpCode::AND:
    case OpCode::inc:
    case OpCode::dec:
    case OpCode::ORA:
    case OpCode::jmp:
    case OpCode::jsr:
    case OpCode::bne:
    case OpCode::bmi:
    case OpCode::beq:
    case OpCode::adc:
    case OpCode::sbc:
    case OpCode::rts:
    case OpCode::clc:
    case OpCode::sec:
    case OpCode::rol:
    case OpCode::asl:
    case OpCode::unknown:
      break;
    }
    return false;
  }


  explicit mos6502(const OpCode o)
    : ASMLine(Type::Instruction, to_string(o)), opcode(o), is_branch(get_is_branch(o)), is_comparison(get_is_comparison(o))
  {
  }

  mos6502(const Type t, std::string s)
    : ASMLine(t, std::move(s))
  {
  }

  mos6502(const OpCode o, Operand t_o)
    : ASMLine(Type::Instruction, to_string(o)), opcode(o), op(std::move(t_o)), is_branch(get_is_branch(o)), is_comparison(get_is_comparison(o))
  {
  }

  static std::string to_string(const OpCode o)
  {
    switch (o) {
    case OpCode::lda:
      return "lda";
    case OpCode::asl:
      return "asl";
    case OpCode::rol:
      return "rol";
    case OpCode::ldy:
      return "ldy";
    case OpCode::tay:
      return "tay";
    case OpCode::tya:
      return "tya";
    case OpCode::tax:
      return "tax";
    case OpCode::txa:
      return "txa";
    case OpCode::cpy:
      return "cpy";
    case OpCode::eor:
      return "eor";
    case OpCode::sta:
      return "sta";
    case OpCode::sty:
      return "sty";
    case OpCode::pha:
      return "pha";
    case OpCode::pla:
      return "pla";
    case OpCode::php:
      return "php";
    case OpCode::plp:
      return "plp";
    case OpCode::lsr:
      return "lsr";
    case OpCode::ror:
      return "ror";
    case OpCode::AND:
      return "and";
    case OpCode::inc:
      return "inc";
    case OpCode::dec:
      return "dec";
    case OpCode::ORA:
      return "ora";
    case OpCode::cmp:
      return "cmp";
    case OpCode::bne:
      return "bne";
    case OpCode::bmi:
      return "bmi";
    case OpCode::beq:
      return "beq";
    case OpCode::jmp:
      return "jmp";
    case OpCode::adc:
      return "adc";
    case OpCode::sbc:
      return "sbc";
    case OpCode::rts:
      return "rts";
    case OpCode::clc:
      return "clc";
    case OpCode::sec:
      return "sec";
    case OpCode::bit:
      return "bit";
    case OpCode::jsr:
      return "jsr";
    case OpCode::bpl:
      return "bpl";
    case OpCode::bcc:
      return "bcc";
    case OpCode::bcs:
      return "bcs";
    case OpCode::unknown:
      return "";
    };

    return "";
  }

  std::string to_string() const
  {
    switch (type) {
    case ASMLine::Type::Label:
      return text;// + ':';
    case ASMLine::Type::Directive:
    case ASMLine::Type::Instruction: {
      const std::string line = '\t' + text + ' ' + op.value;
      return line + std::string(static_cast<size_t>(std::max(15 - static_cast<int>(line.size()), 1)), ' ') + "; " + comment;
    }
    };
    throw std::runtime_error("Unable to render: " + text);
  }


  OpCode opcode = OpCode::unknown;
  Operand op;
  std::string comment;
  bool is_branch = false;
  bool is_comparison = false;
};

struct i386 : ASMLine
{
  enum class OpCode {
    unknown,
    movzbl,
    movzwl,
    shrb,
    shrl,
    xorl,
    andl,
    andb,
    addb,
    ret,
    movb,
    cmpb,
    movl,
    jmp,
    jne,
    je,
    js,
    testb,
    incl,
    incb,
    decl,
    decb,
    sarl,
    addl,
    subl,
    subb,
    sall,
    orl,
    orb,
    rep,
    pushl,
    sbbb,
    negb,
    notb,
    retl,
    call
  };

  static Operand get_register(const int reg_num, const int offset = 0)
  {
    switch (reg_num) {
    //  http://sta.c64.org/cbm64mem.html
    case 0x00:
      return Operand(Operand::Type::literal, "$03");// unused, fp->int routine pointer
    case 0x01:
      return Operand(Operand::Type::literal, "$04");
    case 0x02:
      return Operand(Operand::Type::literal, "$05");// unused, int->fp routine pointer
    case 0x03:
      return Operand(Operand::Type::literal, "$06");
    case 0x04:
      return Operand(Operand::Type::literal, "$fb");// unused
    case 0x05:
      return Operand(Operand::Type::literal, "$fc");// unused
    case 0x06:
      return Operand(Operand::Type::literal, "$fd");// unused
    case 0x07:
      return Operand(Operand::Type::literal, "$fe");// unused
    case 0x08:
      return Operand(Operand::Type::literal, "$22");// unused
    case 0x09:
      return Operand(Operand::Type::literal, "$23");// unused
    case 0x0A:
      return Operand(Operand::Type::literal, "$39");// Current BASIC line number
    case 0x0B:
      return Operand(Operand::Type::literal, "$3a");// Current BASIC line number
    case 0x10:
      return get_register(0x00 + offset);
    case 0x11:
      return get_register(0x02 + offset);
    case 0x12:
      return get_register(0x04 + offset);
    case 0x13:
      return get_register(0x06 + offset);
    case 0x14:
      return get_register(0x08 + offset);
    case 0x15:
      return get_register(0x0A + offset);
    };
    throw std::runtime_error("Unhandled register number: " + std::to_string(reg_num));
  }


  static OpCode parse_opcode(Type t, const std::string &o)
  {
    switch (t) {
    case Type::Label:
      return OpCode::unknown;
    case Type::Directive:
      return OpCode::unknown;
    case Type::Instruction: {
      if (o == "movzwl") return OpCode::movzwl;
      if (o == "movzbl") return OpCode::movzbl;
      if (o == "shrb") return OpCode::shrb;
      if (o == "shrl") return OpCode::shrl;
      if (o == "xorl") return OpCode::xorl;
      if (o == "andl") return OpCode::andl;
      if (o == "ret") return OpCode::ret;
      if (o == "movb") return OpCode::movb;
      if (o == "cmpb") return OpCode::cmpb;
      if (o == "movl") return OpCode::movl;
      if (o == "jmp") return OpCode::jmp;
      if (o == "testb") return OpCode::testb;
      if (o == "incl") return OpCode::incl;
      if (o == "sarl") return OpCode::sarl;
      if (o == "decl") return OpCode::decl;
      if (o == "jne") return OpCode::jne;
      if (o == "je") return OpCode::je;
      if (o == "js") return OpCode::js;
      if (o == "subl") return OpCode::subl;
      if (o == "subb") return OpCode::subb;
      if (o == "addl") return OpCode::addl;
      if (o == "addb") return OpCode::addb;
      if (o == "sall") return OpCode::sall;
      if (o == "orl") return OpCode::orl;
      if (o == "andb") return OpCode::andb;
      if (o == "orb") return OpCode::orb;
      if (o == "decb") return OpCode::decb;
      if (o == "incb") return OpCode::incb;
      if (o == "rep") return OpCode::rep;
      if (o == "notb") return OpCode::notb;
      if (o == "negb") return OpCode::negb;
      if (o == "sbbb") return OpCode::sbbb;
      if (o == "pushl") return OpCode::pushl;
      if (o == "retl") return OpCode::retl;
      if (o == "call") return OpCode::call;
      if (o == "calll") return OpCode::call;
    }
    }
    throw std::runtime_error("Unknown opcode: " + o);
  }

  static Operand parse_operand(std::string o)
  {
    if (o.empty()) {
      return Operand();
    }

    if (o[0] == '%') {
      if (o == "%al") {
        return Operand(Operand::Type::reg, 0x00);
      } else if (o == "%ah") {
        return Operand(Operand::Type::reg, 0x01);
      } else if (o == "%bl") {
        return Operand(Operand::Type::reg, 0x02);
      } else if (o == "%bh") {
        return Operand(Operand::Type::reg, 0x03);
      } else if (o == "%cl") {
        return Operand(Operand::Type::reg, 0x04);
      } else if (o == "%ch") {
        return Operand(Operand::Type::reg, 0x05);
      } else if (o == "%dl") {
        return Operand(Operand::Type::reg, 0x06);
      } else if (o == "%dh") {
        return Operand(Operand::Type::reg, 0x07);
      } else if (o == "%sil") {
        return Operand(Operand::Type::reg, 0x08);
      } else if (o == "%dil") {
        return Operand(Operand::Type::reg, 0x0A);
      } else if (o == "%ax" || o == "%eax") {
        return Operand(Operand::Type::reg, 0x10);
      } else if (o == "%bx" || o == "%ebx") {
        return Operand(Operand::Type::reg, 0x11);
      } else if (o == "%cx" || o == "%ecx") {
        return Operand(Operand::Type::reg, 0x12);
      } else if (o == "%dx" || o == "%edx") {
        return Operand(Operand::Type::reg, 0x13);
      } else if (o == "%si" || o == "%esi") {
        return Operand(Operand::Type::reg, 0x14);
      } else if (o == "%di" || o == "%edi") {
        return Operand(Operand::Type::reg, 0x15);
      } else {
        throw std::runtime_error("Unknown register operand: '" + o + "'");
      }
    } else {
      return Operand(Operand::Type::literal, std::move(o));
    }
  }

  i386(const int t_line_num, std::string t_line_text, Type t, std::string t_opcode, std::string o1 = "", std::string o2 = "")
    : ASMLine(t, t_opcode), line_num(t_line_num), line_text(std::move(t_line_text)),
      opcode(parse_opcode(t, t_opcode)), operand1(parse_operand(o1)), operand2(parse_operand(o2))
  {
  }

  int line_num;
  std::string line_text;
  OpCode opcode;
  Operand operand1;
  Operand operand2;
};


struct AVR : ASMLine
{
  enum class OpCode {
    unknown,
    ldi,
    sts,
    ret,
    mov,
    lsl,
    rol,
    rcall,
    ld,
    subi,
    sbci,
    st,
    lds,
    lsr,
    andi,
    eor,
    sbrc,
    sbrs,
    brne,
    rjmp,
    dec,
    sbiw,
    push,
    pop,
    com,
    swap,
    clr,
    cpse,
    cpi,
    brlo,
    add,
    adc,
    cpc,
    brsh,
    breq
  };

  static OpCode parse_opcode(Type t, const std::string &o)
  {
    switch (t) {
    case Type::Label:
    case Type::Directive:
      return OpCode::unknown;
    case Type::Instruction: {
      if (o == "ldi") return OpCode::ldi;
      if (o == "sts") return OpCode::sts;
      if (o == "ret") return OpCode::ret;
      if (o == "mov") return OpCode::mov;
      if (o == "lsl") return OpCode::lsl;
      if (o == "rol") return OpCode::rol;
      if (o == "rcall") return OpCode::rcall;
      if (o == "ld") return OpCode::ld;
      if (o == "subi") return OpCode::subi;
      if (o == "sbci") return OpCode::sbci;
      if (o == "st") return OpCode::st;
      if (o == "lds") return OpCode::lds;
      if (o == "lsr") return OpCode::lsr;
      if (o == "andi") return OpCode::andi;
      if (o == "eor") return OpCode::eor;
      if (o == "sbrc") return OpCode::sbrc;
      if (o == "rjmp") return OpCode::rjmp;
      if (o == "sbrs") return OpCode::sbrs;
      if (o == "brne") return OpCode::brne;
      if (o == "dec") return OpCode::dec;
      if (o == "sbiw") return OpCode::sbiw;
      if (o == "push") return OpCode::push;
      if (o == "pop") return OpCode::pop;
      if (o == "com") return OpCode::com;
      if (o == "swap") return OpCode::swap;
      if (o == "clr") return OpCode::clr;
      if (o == "cpse") return OpCode::cpse;
      if (o == "cpi") return OpCode::cpi;
      if (o == "brlo") return OpCode::brlo;
      if (o == "add") return OpCode::add;
      if (o == "adc") return OpCode::adc;
      if (o == "cpc") return OpCode::cpc;
      if (o == "brsh") return OpCode::brsh;
      if (o == "breq") return OpCode::breq;
    }
    }
    throw std::runtime_error("Unknown opcode: " + o);
  }

  static int get_register_number(const char reg_name)
  {
    if (reg_name == 'X') {
      return 26;
    }
    if (reg_name == 'Y') {
      return 28;
    }
    if (reg_name == 'Z') {
      return 30;
    }

    throw std::runtime_error("Unknown register name");
  }

  static Operand get_register(const char reg_name, const int byte = 0)
  {
    return get_register(get_register_number(reg_name), byte);
  }

  static Operand get_register(const int reg_num, [[maybe_unused]] const int offset = 0)
  {
    switch (reg_num) {
    //  http://sta.c64.org/cbm64mem.html
    case 0:
      return Operand(Operand::Type::literal, "$a7");// bit buffer for rs232
    case 1:
      return Operand(Operand::Type::literal, "$a8");// counter for rs232
    case 2:
      return Operand(Operand::Type::literal, "$05");// unused, int->fp routine pointer
    case 3:
      return Operand(Operand::Type::literal, "$06");
    case 4:
      return Operand(Operand::Type::literal, "$fb");// unused
    case 5:
      return Operand(Operand::Type::literal, "$fc");// unused
    case 6:
      return Operand(Operand::Type::literal, "$fd");// unused
    case 7:
      return Operand(Operand::Type::literal, "$fe");// unused
    case 8:
      return Operand(Operand::Type::literal, "$22");// unused
    case 9:
      return Operand(Operand::Type::literal, "$23");// unused
    case 10:
      return Operand(Operand::Type::literal, "$39");// Current BASIC line number
    case 11:
      return Operand(Operand::Type::literal, "$3a");// Current BASIC line number
    case 12:
      return Operand(Operand::Type::literal, "$61");// arithmetic register #1
    case 13:
      return Operand(Operand::Type::literal, "$62");
    case 14:
      return Operand(Operand::Type::literal, "$63");
    case 15:
      return Operand(Operand::Type::literal, "$64");
    case 16:
      return Operand(Operand::Type::literal, "$65");
    case 17:
      return Operand(Operand::Type::literal, "$69");// arithmetic register #2
    case 18:
      return Operand(Operand::Type::literal, "$6a");
    case 19:
      return Operand(Operand::Type::literal, "$6b");
    case 20:
      return Operand(Operand::Type::literal, "$6c");
    case 21:
      return Operand(Operand::Type::literal, "$6d");
    case 22:
      return Operand(Operand::Type::literal, "$57");// arithmetic register #3
    case 23:
      return Operand(Operand::Type::literal, "$58");
    case 24:
      return Operand(Operand::Type::literal, "$59");
    case 25:
      return Operand(Operand::Type::literal, "$5a");
    case 26:
      return Operand(Operand::Type::literal, "$5b");
    case 27:
      return Operand(Operand::Type::literal, "$5c");// arithmetic register #4
    case 28:
      return Operand(Operand::Type::literal, "$5d");
    case 29:
      return Operand(Operand::Type::literal, "$5e");
    case 30:
      return Operand(Operand::Type::literal, "$5f");
    case 31:
      return Operand(Operand::Type::literal, "$60");
    }
    throw std::runtime_error("Unhandled register number: " + std::to_string(reg_num));
  }


  static Operand parse_operand(std::string o)
  {
    if (o.empty()) {
      return Operand();
    }

    if (o[0] == 'r' && o.size() > 1) {
      return Operand(Operand::Type::reg, atoi(&o[1]));
    } else {
      return Operand(Operand::Type::literal, std::move(o));
    }
  }

  AVR(const int t_line_num, std::string t_line_text, Type t, std::string t_opcode, std::string o1 = "", std::string o2 = "")
    : ASMLine(t, t_opcode), line_num(t_line_num), line_text(std::move(t_line_text)),
      opcode(parse_opcode(t, t_opcode)), operand1(parse_operand(o1)), operand2(parse_operand(o2))
  {
  }

  int line_num;
  std::string line_text;
  OpCode opcode;
  Operand operand1;
  Operand operand2;
};

void indirect_load(std::vector<mos6502> &instructions, const std::string &from_address_low_byte, const std::string &to_address)
{
  instructions.emplace_back(mos6502::OpCode::ldy, Operand(Operand::Type::literal, "#0"));
  instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "(" + from_address_low_byte + "), Y"));
  instructions.emplace_back(mos6502::OpCode::sta, Operand(Operand::Type::literal, to_address));
}

void indirect_store(std::vector<mos6502> &instructions, const std::string &from_address, const std::string &to_address_low_byte)
{
  instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, from_address));
  instructions.emplace_back(mos6502::OpCode::ldy, Operand(Operand::Type::literal, "#0"));
  instructions.emplace_back(mos6502::OpCode::sta, Operand(Operand::Type::literal, "(" + to_address_low_byte + "), Y"));
}

void fixup_16_bit_N_Z_flags(std::vector<mos6502> &instructions)
{

  // need to get both Z and N set appropriately
  // assuming A contains higher order byte and Y contains lower order byte
  instructions.emplace_back(ASMLine::Type::Directive, "; BEGIN remove if next is lda");
  instructions.emplace_back(ASMLine::Type::Directive, "; set CPU flags assuming A holds the higher order byte already");
  std::string set_flag_label = "flags_set_after_16_bit_op_" + std::to_string(instructions.size());
  // if high order is negative, we know it's not 0 and it is negative
  instructions.emplace_back(mos6502::OpCode::bmi, Operand(Operand::Type::literal, set_flag_label));
  // if it's not 0, then branch down, we know the result is not 0 and not negative
  instructions.emplace_back(mos6502::OpCode::bne, Operand(Operand::Type::literal, set_flag_label));
  // if the higher order byte is 0, test the lower order byte, which was saved for us in Y
  instructions.emplace_back(mos6502::OpCode::txa);
  // if low order is not negative, we know it's 0 or not 0
  instructions.emplace_back(mos6502::OpCode::bpl, Operand(Operand::Type::literal, set_flag_label));
  // if low order byte is negative, shift right by one bit, then we'll get the proper Z/N flags
  instructions.emplace_back(mos6502::OpCode::lsr);
  instructions.emplace_back(ASMLine::Type::Label, set_flag_label);
  instructions.emplace_back(ASMLine::Type::Directive, "; END remove if next is lda");
}


void subtract_16_bit(std::vector<mos6502> &instructions, int reg, const std::uint16_t value)
{
  //instructions.emplace_back(mos6502::OpCode::sta, Operand(Operand::Type::literal, address_low_byte));
  instructions.emplace_back(mos6502::OpCode::sec);
  instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(reg));
  instructions.emplace_back(mos6502::OpCode::sbc, Operand(Operand::Type::literal, "#" + std::to_string(value & 0xFF)));
  instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(reg));
  instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(reg + 1));
  instructions.emplace_back(mos6502::OpCode::sbc, Operand(Operand::Type::literal, "#" + std::to_string((value >> 8) & 0xFF)));
  instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(reg + 1));
  instructions.emplace_back(mos6502::OpCode::tax);
  fixup_16_bit_N_Z_flags(instructions);
}

void increment_16_bit(std::vector<mos6502> &instructions, int reg)
{
  //instructions.emplace_back(mos6502::OpCode::sta, Operand(Operand::Type::literal, address_low_byte));
  instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(reg));
  instructions.emplace_back(mos6502::OpCode::clc);
  instructions.emplace_back(mos6502::OpCode::adc, Operand(Operand::Type::literal, "#1"));
  instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(reg));
  instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(reg + 1));
  instructions.emplace_back(mos6502::OpCode::adc, Operand(Operand::Type::literal, "#0"));
  instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(reg + 1));
}

void translate_instruction(std::vector<mos6502> &instructions, const AVR::OpCode op, const Operand &o1, const Operand &o2)
{
  const auto translate_register_number = [](const Operand &reg) {
    if (reg.value == "__zero_reg__") {
      return 1;
    } else if (reg.value == "__temp_reg__") {
      return 0;
    } else {
      return reg.reg_num;
    }
  };

  const auto o1_reg_num = translate_register_number(o1);
  const auto o2_reg_num = translate_register_number(o2);

  switch (op) {
  case AVR::OpCode::dec:
    instructions.emplace_back(mos6502::OpCode::dec, AVR::get_register(o1_reg_num));
    return;
  case AVR::OpCode::ldi:
    instructions.emplace_back(mos6502::OpCode::lda, Operand(o2.type, fixup_8bit_literal(o2.value)));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  case AVR::OpCode::sts:
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o2_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, Operand(o1.type, o1.value));
    return;
  case AVR::OpCode::ret:
    instructions.emplace_back(mos6502::OpCode::rts);
    return;
  case AVR::OpCode::mov:
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o2_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  case AVR::OpCode::lsl:
    instructions.emplace_back(mos6502::OpCode::asl, AVR::get_register(o1_reg_num));
    return;
  case AVR::OpCode::rol:
    instructions.emplace_back(mos6502::OpCode::rol, AVR::get_register(o1_reg_num));
    return;
  case AVR::OpCode::rcall:
    instructions.emplace_back(mos6502::OpCode::jsr, o1);
    return;
  case AVR::OpCode::ld: {
    if (o2.value == "Z" || o2.value == "X" || o2.value == "Y") {
      indirect_load(instructions, AVR::get_register(o2.value[0]).value, AVR::get_register(o1_reg_num).value);
      return;
    }
    if (o2.value == "Z+" || o2.value == "X+" || o2.value == "Y+") {
      indirect_load(instructions, AVR::get_register(o2.value[0]).value, AVR::get_register(o1_reg_num).value);
      increment_16_bit(instructions, AVR::get_register_number(o2.value[0]));
      return;
    }
    throw std::runtime_error("Unhandled ld to non-Z");
  }
  case AVR::OpCode::sbci: {
    // we want to utilize the carry flag, however it was set previously
    // (it's really a borrow flag on the 6502)
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::sbc, Operand(o2.type, fixup_8bit_literal(o2.value)));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    fixup_16_bit_N_Z_flags(instructions);
    return;
  }
  case AVR::OpCode::subi: {
    // to do: deal with Carry bit (and other flags) nonsense from AVR
    // if |x| < |y| -> x-y +carry
    // for these special cases with -(1) and -(-(1))
    if (o2.value == "lo8(-(-1))") {
      instructions.emplace_back(mos6502::OpCode::dec, AVR::get_register(o1_reg_num));
      return;
    }
    if (o2.value == "lo8(-(1))") {
      instructions.emplace_back(mos6502::OpCode::inc, AVR::get_register(o1_reg_num));
      return;
    }

    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    // have to set carry flag, since it gets inverted by sbc
    instructions.emplace_back(mos6502::OpCode::sec);
    instructions.emplace_back(mos6502::OpCode::sbc, Operand(o2.type, fixup_8bit_literal(o2.value)));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    // temporarily store lower order (not carried substraction) byte into Y for checking
    // later if this is a two byte subtraction operation
    instructions.emplace_back(mos6502::OpCode::tax);
    return;
  }
  case AVR::OpCode::st: {
    if (o1.value == "Z" || o1.value == "Y" || o1.value == "X") {
      indirect_store(instructions, AVR::get_register(o2_reg_num).value, AVR::get_register(o1.value[0]).value);
      return;
    }
    if (o1.value == "Z+" || o1.value == "Y+" || o1.value == "X+") {
      indirect_store(instructions, AVR::get_register(o2_reg_num).value, AVR::get_register(o1.value[0]).value);
      increment_16_bit(instructions, AVR::get_register_number(o1.value[0]));
      return;
    }
    throw std::runtime_error("Unhandled st");
  }
  case AVR::OpCode::lds: {
    instructions.emplace_back(mos6502::OpCode::lda, o2);
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::lsr: {
    instructions.emplace_back(mos6502::OpCode::lsr, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::andi: {
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::AND, Operand(o2.type, fixup_8bit_literal(o2.value)));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::eor: {
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::eor, AVR::get_register(o2_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::cpse: {
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::bit, AVR::get_register(o2_reg_num));
    std::string new_label_name = "skip_next_instruction_" + std::to_string(instructions.size());
    instructions.emplace_back(mos6502::OpCode::beq, Operand(Operand::Type::literal, new_label_name));
    instructions.emplace_back(ASMLine::Type::Directive, new_label_name);
    return;
  }
  case AVR::OpCode::sbrc: {
    instructions.emplace_back(mos6502::OpCode::lda, Operand(o2.type, fixup_8bit_literal("$" + std::to_string(1 << (atoi(o2.value.c_str()))))));
    instructions.emplace_back(mos6502::OpCode::bit, AVR::get_register(o1_reg_num));
    std::string new_label_name = "skip_next_instruction_" + std::to_string(instructions.size());
    instructions.emplace_back(mos6502::OpCode::beq, Operand(Operand::Type::literal, new_label_name));
    instructions.emplace_back(ASMLine::Type::Directive, new_label_name);
    return;
  }
  case AVR::OpCode::sbrs: {
    instructions.emplace_back(mos6502::OpCode::lda, Operand(o2.type, fixup_8bit_literal("$" + std::to_string(1 << (atoi(o2.value.c_str()))))));
    instructions.emplace_back(mos6502::OpCode::bit, AVR::get_register(o1_reg_num));
    std::string new_label_name = "skip_next_instruction_" + std::to_string(instructions.size());
    instructions.emplace_back(mos6502::OpCode::bne, Operand(Operand::Type::literal, new_label_name));
    instructions.emplace_back(ASMLine::Type::Directive, new_label_name);
    return;
  }
  case AVR::OpCode::brne: {
    if (o1.value == "0b") {
      instructions.emplace_back(mos6502::OpCode::bne, Operand(Operand::Type::literal, "memcpy_0"));
    } else {
      instructions.emplace_back(mos6502::OpCode::bne, o1);
    }
    return;
  }

  case AVR::OpCode::rjmp: {
    instructions.emplace_back(mos6502::OpCode::jmp, o1);
    return;
  }

  case AVR::OpCode::sbiw: {
    subtract_16_bit(instructions, o1_reg_num, atoi(o2.value.c_str()));
    return;
  }

  case AVR::OpCode::push: {
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::pha);
    return;
  }
  case AVR::OpCode::pop: {
    instructions.emplace_back(mos6502::OpCode::pla);
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::com: {
    // We're doing this in the same way the AVR does it, to make sure the C flag is set properly
    instructions.emplace_back(mos6502::OpCode::clc);
    instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#$FF"));
    instructions.emplace_back(mos6502::OpCode::sbc, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::clr: {
    instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#$00"));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::cpi: {
    // note that this will leave the C flag in the 6502 borrow state, not normal carry state
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::cmp, Operand(o2.type, fixup_8bit_literal(o2.value)));
    return;
  }
  case AVR::OpCode::brlo: {

    if (o1.value == ".+2") {
      // assumes 6502 'borrow' for Carry flag instead of carry, so bcc instead of bcs
      std::string new_label_name = "skip_next_instruction_" + std::to_string(instructions.size());
      instructions.emplace_back(mos6502::OpCode::bcc, Operand(Operand::Type::literal, new_label_name));
      instructions.emplace_back(ASMLine::Type::Directive, new_label_name);
      return;
    } else {
      instructions.emplace_back(mos6502::OpCode::bcc, o1);
      return;
    }
  }
  case AVR::OpCode::swap: {
    // from http://www.6502.org/source/general/SWN.html
    // ASL  A
    // ADC  #$80
    // ROL  A
    // ASL  A
    // ADC  #$80
    // ROL  A

    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::asl);
    instructions.emplace_back(mos6502::OpCode::adc, Operand(Operand::Type::literal, "#$80"));
    instructions.emplace_back(mos6502::OpCode::rol);
    instructions.emplace_back(mos6502::OpCode::asl);
    instructions.emplace_back(mos6502::OpCode::adc, Operand(Operand::Type::literal, "#$80"));
    instructions.emplace_back(mos6502::OpCode::rol);
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));

    return;
  }
  case AVR::OpCode::add: {
    instructions.emplace_back(mos6502::OpCode::clc);
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::adc, AVR::get_register(o2_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::adc: {
    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::adc, AVR::get_register(o2_reg_num));
    instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(o1_reg_num));
    return;
  }
  case AVR::OpCode::cpc: {
    // this instruction seems to need to be used in the case after a sbc operation, where the
    // carry flag is set to the appropriate borrow state, so I'm going to not invert
    // the carry flag here, and assume that it's set how the 6502 wants it to be
    // set from the previous operation

    instructions.emplace_back(mos6502::OpCode::lda, AVR::get_register(o1_reg_num));
    instructions.emplace_back(mos6502::OpCode::sbc, AVR::get_register(o2_reg_num));
    return;
  }
  case AVR::OpCode::brsh: {
    if (o1.value == ".+2") {
      // assumes 6502 'borrow' for Carry flag instead of carry, so bcs instead of bcc
      std::string new_label_name = "skip_next_instruction_" + std::to_string(instructions.size());
      instructions.emplace_back(mos6502::OpCode::bcs, Operand(Operand::Type::literal, new_label_name));
      instructions.emplace_back(ASMLine::Type::Directive, new_label_name);
      return;
    } else {
      instructions.emplace_back(mos6502::OpCode::bcs, o1);
      return;
    }

  }

  case AVR::OpCode::breq: {
    instructions.emplace_back(mos6502::OpCode::beq, o1);
    return;
  }

  }

  throw std::runtime_error("Could not translate unhandled instruction");
}

void translate_instruction(std::vector<mos6502> &instructions, const i386::OpCode op, const Operand &o1, const Operand &o2)
{
  switch (op) {
  case i386::OpCode::ret:
    instructions.emplace_back(mos6502::OpCode::rts);
    break;
  case i386::OpCode::retl:
    /// \todo I don't know if this is completely correct for retl translation
    instructions.emplace_back(mos6502::OpCode::rts);
    break;
  case i386::OpCode::movl:
    if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num, 1));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num, 1));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, "#<" + o1.value));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, "#>" + o1.value));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num, 1));
    } else {
      throw std::runtime_error("Cannot translate movl instruction");
    }
    break;
  case i386::OpCode::xorl:
    if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg
        && o1.reg_num == o2.reg_num) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#$00"));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num, 1));
    } else {
      throw std::runtime_error("Cannot translate xorl instruction");
    }
    break;
  case i386::OpCode::movb:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else if (o1.type == Operand::Type::reg && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else {
      throw std::runtime_error("Cannot translate movb instruction");
    }
    break;
  case i386::OpCode::orb:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::ORA, o2);
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::ORA, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::ORA, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else {
      throw std::runtime_error("Cannot translate orb instruction");
    }
    break;

  case i386::OpCode::movzbl:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, o1);
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else {
      throw std::runtime_error("Cannot translate movzbl instruction");
    }
    break;
  case i386::OpCode::shrb:
    if (o1.type == Operand::Type::reg || o2.type == Operand::Type::reg) {
      const auto do_shift = [&instructions](const int reg_num) {
        instructions.emplace_back(mos6502::OpCode::lsr, i386::get_register(reg_num));
      };

      if (o1.type == Operand::Type::literal) {
        const auto count = parse_8bit_literal(o1.value);
        for (int i = 0; i < count; ++i) {
          do_shift(o2.reg_num);
        }
      } else {
        do_shift(o1.reg_num);
      }
    } else {
      throw std::runtime_error("Cannot translate shrb instruction");
    }
    break;
  case i386::OpCode::shrl:
    if (o1.type == Operand::Type::reg || o2.type == Operand::Type::reg) {
      const auto do_shift = [&instructions](const int reg_num) {
        instructions.emplace_back(mos6502::OpCode::lsr, i386::get_register(reg_num, 1));
        instructions.emplace_back(mos6502::OpCode::ror, i386::get_register(reg_num));
      };

      if (o1.type == Operand::Type::literal) {
        const auto count = parse_8bit_literal(o1.value);
        for (int i = 0; i < count; ++i) {
          do_shift(o2.reg_num);
        }
      } else {
        do_shift(o1.reg_num);
      }
    } else {
      throw std::runtime_error("Cannot translate shrl instruction");
    }
    break;
  case i386::OpCode::testb:
    if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg && o1.reg_num == o2.reg_num) {
      // this just tests the register for 0
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      //        instructions.emplace_back(mos6502::OpCode::bit, Operand(Operand::Type::literal, "#$00"));
    } else if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg) {
      // ands the values
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::bit, i386::get_register(o2.reg_num));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      // ands the values
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::bit, i386::get_register(o2.reg_num));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      // ands the values
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::bit, o2);
    } else {
      throw std::runtime_error("Cannot translate testb instruction");
    }
    break;
  case i386::OpCode::decb:
    if (o1.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::dec, i386::get_register(o1.reg_num));
    } else {
      instructions.emplace_back(mos6502::OpCode::dec, o1);
    }
    break;
  case i386::OpCode::incb:
    if (o1.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::inc, i386::get_register(o1.reg_num));
    } else {
      instructions.emplace_back(mos6502::OpCode::inc, o1);
    }
    break;
  case i386::OpCode::jne:
    instructions.emplace_back(mos6502::OpCode::bne, o1);
    break;
  case i386::OpCode::je:
    instructions.emplace_back(mos6502::OpCode::beq, o1);
    break;
  case i386::OpCode::js:
    instructions.emplace_back(mos6502::OpCode::bmi, o1);
    break;
  case i386::OpCode::jmp:
    instructions.emplace_back(mos6502::OpCode::jmp, o1);
    break;
  case i386::OpCode::addb:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::clc);
      instructions.emplace_back(mos6502::OpCode::adc, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::clc);
      instructions.emplace_back(mos6502::OpCode::adc, o2);
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else if (o1.type == Operand::Type::reg && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::clc);
      instructions.emplace_back(mos6502::OpCode::adc, o2);
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else {
      throw std::runtime_error("Cannot translate addb instruction");
    }
    break;
  case i386::OpCode::cmpb:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, o2);
      instructions.emplace_back(mos6502::OpCode::cmp, Operand(o1.type, fixup_8bit_literal(o1.value)));
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o2.reg_num));
      instructions.emplace_back(mos6502::OpCode::cmp, Operand(o1.type, fixup_8bit_literal(o1.value)));
    } else {
      throw std::runtime_error("Cannot translate cmpb instruction");
    }
    break;
  case i386::OpCode::andb:
    if (o1.type == Operand::Type::literal && o2.type == Operand::Type::reg) {
      const auto reg = i386::get_register(o2.reg_num);
      instructions.emplace_back(mos6502::OpCode::lda, reg);
      instructions.emplace_back(mos6502::OpCode::AND, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::sta, reg);
    } else if (o1.type == Operand::Type::literal && o2.type == Operand::Type::literal) {
      const auto reg = i386::get_register(o2.reg_num);
      instructions.emplace_back(mos6502::OpCode::lda, o2);
      instructions.emplace_back(mos6502::OpCode::AND, Operand(o1.type, fixup_8bit_literal(o1.value)));
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else {
      throw std::runtime_error("Cannot translate andb instruction");
    }
    break;
  case i386::OpCode::negb:
    if (o1.type == Operand::Type::reg) {
      // perform a two's complement of the register location
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::eor, Operand(Operand::Type::literal, "#$ff"));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::inc, i386::get_register(o1.reg_num));
    } else {
      throw std::runtime_error("Cannot translate negb instruction");
    }
    break;
  case i386::OpCode::notb:
    if (o1.type == Operand::Type::reg) {
      // exclusive or against 0xff to perform a logical not
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::eor, Operand(Operand::Type::literal, "#$ff"));
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o1.reg_num));
    } else {
      throw std::runtime_error("Cannot translate notb instruction");
    }
    break;
  case i386::OpCode::subb:
    // DEST <- DEST - SRC
    // o2 = o2 - o1
    // Ensure that we set the carry flag before performing the subtraction
    if (o1.type == Operand::Type::reg && o2.type == Operand::Type::literal) {
      instructions.emplace_back(mos6502::OpCode::lda, o2);
      instructions.emplace_back(mos6502::OpCode::sec);
      instructions.emplace_back(mos6502::OpCode::sbc, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::sta, o2);
    } else {
      throw std::runtime_error("Cannot translate subb instruction");
    }
    break;
  case i386::OpCode::pushl:
    if (o1.type == Operand::Type::reg) {
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num));
      instructions.emplace_back(mos6502::OpCode::pha);
      instructions.emplace_back(mos6502::OpCode::lda, i386::get_register(o1.reg_num, 1));
      instructions.emplace_back(mos6502::OpCode::pha);
    } else {
      throw std::runtime_error("Cannot translate pushl instruction");
    }
    break;

  case i386::OpCode::sbbb:
    // DEST <- (DEST – (SRC + CF))
    // o2 <- (o2 - (o1 + cf))
    // if o1 and o2 are the same we get
    // o2 <- (o2 - (o2 + cf))
    // o2 <- -cf
    if (o1.type == Operand::Type::reg && o2.type == Operand::Type::reg
        && o1.reg_num == o2.reg_num) {
      instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#$00"));// reset a
      instructions.emplace_back(mos6502::OpCode::sbc, Operand(Operand::Type::literal, "#$00"));// subtract out the carry flag
      instructions.emplace_back(mos6502::OpCode::eor, Operand(Operand::Type::literal, "#$ff"));// invert the bits
      instructions.emplace_back(mos6502::OpCode::sta, i386::get_register(o2.reg_num));// place the value
    } else {
      throw std::runtime_error("Cannot translate sbbb instruction");
    }
    break;

  case i386::OpCode::call:
    instructions.emplace_back(mos6502::OpCode::jsr, o1);
    break;

  default:
    throw std::runtime_error("Cannot translate unhandled instruction");
  }
}

enum class LogLevel {
  Warning,
  Error
};

std::string to_string(const LogLevel ll)
{
  switch (ll) {
  case LogLevel::Warning:
    return "warning";
  case LogLevel::Error:
    return "error";
  }
  return "unknown";
}


template<typename FromArch>
void log(LogLevel ll, const FromArch &i, const std::string &message)
{
  std::cerr << to_string(ll) << ": " << i.line_num << ": " << message << ": `" << i.line_text << "`\n";
}

void log(LogLevel ll, const int line_no, const std::string &line, const std::string &message)
{
  std::cerr << to_string(ll) << ": " << line_no << ": " << message << ": `" << line << "`\n";
}

template<typename FromArch>
void to_mos6502(const FromArch &i, std::vector<mos6502> &instructions)
{
  try {
    switch (i.type) {
    case ASMLine::Type::Label:
      if (i.text == "0") {
        instructions.emplace_back(i.type, "-memcpy_0");
      } else {
        instructions.emplace_back(i.type, i.text);
      }
      return;
    case ASMLine::Type::Directive:
      if (i.text.starts_with(".string")) {
        instructions.emplace_back(ASMLine::Type::Directive, ".asc " + i.text.substr(7));
      } else if (i.text.starts_with(".zero")) {
        const auto count = atoi(i.text.data() + 6);

        std::string zeros;
        for (int i = 0; i < count; ++i) {
          if ((i % 20) == 0) {
            if (!zeros.empty()) {
              instructions.emplace_back(ASMLine::Type::Directive, zeros);
              zeros.clear();
            }
            zeros += ".byt 0";
          } else {
            zeros += ",0";
          }
        }

        if (!zeros.empty()) {
          instructions.emplace_back(ASMLine::Type::Directive, zeros);
        }

      } else {
        instructions.emplace_back(ASMLine::Type::Directive, "; Unknown directive: " + i.text);
      }
      return;
    case ASMLine::Type::Instruction:
      const auto head = instructions.size();

      try {
        translate_instruction(instructions, i.opcode, i.operand1, i.operand2);
      } catch (const std::exception &e) {
        instructions.emplace_back(ASMLine::Type::Directive, "; Unhandled opcode: '" + i.text + "' " + e.what());
        log(LogLevel::Error, i, e.what());
      }

      auto text = i.line_text;
      if (text[0] == '\t') {
        text.erase(0, 1);
      }
      for_each(std::next(instructions.begin(), head), instructions.end(), [text](auto &ins) {
        ins.comment = text;
      });
      return;
    }
  } catch (const std::exception &e) {
    log(LogLevel::Error, i, e.what());
  }
}

bool optimize(std::vector<mos6502> &instructions)
{
  if (instructions.size() < 2) {
    return false;
  }

  const auto next_instruction = [&instructions](auto i) {
    do {
      ++i;
    } while (i < instructions.size() && instructions[i].type == ASMLine::Type::Directive);
    return i;
  };


  // remove unused flag-fix-up blocks
  // it might make sense in the future to only insert these if determined they are needed?
  for (size_t op = 10; op < instructions.size(); ++op) {
    if (instructions[op].opcode == mos6502::OpCode::lda) {
      if (instructions[op-1].text == "; END remove if next is lda")
      {
        for (size_t inner_op = op-1; inner_op > 1; --inner_op) {
          instructions[inner_op] = mos6502(ASMLine::Type::Directive,
            "; removed unused flag fix-up: " + instructions[inner_op].to_string());

          if (instructions[inner_op].text.find("; BEGIN") != std::string::npos) {
            return true;
          }
        }
      }
    }
  }


  // look for redundant load of lda after a tax
  for (size_t op = 0; op < instructions.size() - 3; ++op) {
    if (instructions[op].opcode == mos6502::OpCode::sta
        && instructions[op+1].opcode == mos6502::OpCode::tax
        && instructions[op+2].opcode == mos6502::OpCode::lda
        && instructions[op].op.value == instructions[op+2].op.value)
    {
      instructions[op+2] = mos6502(ASMLine::Type::Directive, "; removed redundant lda: " + instructions[op+2].to_string());
      return true;
    }
  }

  // look for redundant stores to 0-page registers with sta
  for (size_t op = 0; op < instructions.size(); ++op) {
    // todo, make sure this is in the register map
    if (instructions[op].opcode == mos6502::OpCode::sta
        && instructions[op].op.value.size() == 3)
    {
      for (size_t next_op = op + 1; next_op < instructions.size(); ++next_op) {
        if (instructions[next_op].opcode != mos6502::OpCode::sta && instructions[next_op].op.value == instructions[op].op.value) {
          // we just found a use of ourselves back, abort the search, there's probably something else going on
          break;
        }

        // abort at label
        if (instructions[next_op].type == ASMLine::Type::Label) {
          break;
        }

        if (instructions[next_op].opcode == mos6502::OpCode::sta
          && instructions[next_op].op.value == instructions[op].op.value) {
          // looks like we found a redundant store, remove the first one
          instructions[op] = mos6502(ASMLine::Type::Directive,
            "; removed redundant sta: " + instructions[op].to_string());
          return true;
        }
      }
    }

  }

  for (size_t op = 0; op < instructions.size() - 1; ++op) {
    // look for a transfer of Y -> A immediately followed by A -> Y
    if (instructions[op].opcode == mos6502::OpCode::tya) {
      next_instruction(op);
      if (instructions[op].opcode == mos6502::OpCode::tay) {
        instructions[op] = mos6502(ASMLine::Type::Directive,
          "; removed redundant tay: " + instructions[op].to_string());
        return true;
      }
    }
  }

  for (size_t op = 0; op < instructions.size() - 1; ++op) {
    // look for a store A -> loc immediately followed by loc -> A
    if (instructions[op].opcode == mos6502::OpCode::sta) {
      const auto next = next_instruction(op);
      if (instructions[next].opcode == mos6502::OpCode::lda
          && instructions[next].op == instructions[op].op) {
        instructions[next] = mos6502(ASMLine::Type::Directive,
          "; removed redundant lda: " + instructions[next].to_string());
        return true;
      }
    }
  }

  for (size_t op = 0; op < instructions.size() - 1; ++op) {
    if (instructions[op].opcode == mos6502::OpCode::ldy && instructions[op].op.type == Operand::Type::literal) {
      auto op2 = op + 1;

      while (op2 < instructions.size() && (instructions[op2].type != ASMLine::Type::Label)) {
        // while inside this label
        if (instructions[op2].opcode == mos6502::OpCode::ldy && instructions[op2].op.value == instructions[op].op.value) {
          instructions[op2] = mos6502(ASMLine::Type::Directive, "; removed redundant ldy: " + instructions[op2].to_string());
          return true;
        }
        ++op2;
      }
    }
  }

  for (size_t op = 0; op < instructions.size() - 1; ++op) {
    if (instructions[op].opcode == mos6502::OpCode::lda
        && instructions[op].op.type == Operand::Type::literal) {
      const auto operand = instructions[op].op;
      auto op2 = op + 1;
      // look for multiple stores of the same value
      while (op2 < instructions.size() && (instructions[op2].opcode == mos6502::OpCode::sta || instructions[op2].type == ASMLine::Type::Directive)) {
        ++op2;
      }
      if (instructions[op2].opcode == mos6502::OpCode::lda
          && operand == instructions[op2].op) {
        instructions[op2] = mos6502(ASMLine::Type::Directive,
          "; removed redundant lda: " + instructions[op2].to_string());
        return true;
      }
    }
  }

  return false;
}

bool fix_long_branches(std::vector<mos6502> &instructions, int &branch_patch_count)
{
  std::map<std::string, size_t> labels;
  for (size_t op = 0; op < instructions.size(); ++op) {
    if (instructions[op].type == ASMLine::Type::Label) {
      labels[instructions[op].text] = op;
    }
  }

  for (size_t op = 0; op < instructions.size(); ++op) {
    if (instructions[op].is_branch && std::abs(static_cast<int>(labels[instructions[op].op.value]) - static_cast<int>(op)) * 3 > 255) {
      ++branch_patch_count;
      const auto going_to = instructions[op].op.value;
      const auto new_pos = "patch_" + std::to_string(branch_patch_count);
      // uh-oh too long of a branch, have to convert this to a jump...
      if (instructions[op].opcode == mos6502::OpCode::bne) {
        const auto comment = instructions[op].comment;
        instructions[op] = mos6502(mos6502::OpCode::beq, Operand(Operand::Type::literal, new_pos));
        instructions.insert(std::next(std::begin(instructions), op + 1), mos6502(mos6502::OpCode::jmp, Operand(Operand::Type::literal, going_to)));
        instructions.insert(std::next(std::begin(instructions), op + 2), mos6502(ASMLine::Type::Label, new_pos));
        instructions[op].comment = instructions[op + 1].comment = instructions[op + 2].comment = comment;
        return true;
      } else if (instructions[op].opcode == mos6502::OpCode::beq) {
        const auto comment = instructions[op].comment;
        instructions[op] = mos6502(mos6502::OpCode::bne, Operand(Operand::Type::literal, new_pos));
        instructions.insert(std::next(std::begin(instructions), op + 1), mos6502(mos6502::OpCode::jmp, Operand(Operand::Type::literal, going_to)));
        instructions.insert(std::next(std::begin(instructions), op + 2), mos6502(ASMLine::Type::Label, new_pos));
        instructions[op].comment = instructions[op + 1].comment = instructions[op + 2].comment = comment;
        return true;
      } else if (instructions[op].opcode == mos6502::OpCode::bcc) {
        const auto comment = instructions[op].comment;
        instructions[op] = mos6502(mos6502::OpCode::bcs, Operand(Operand::Type::literal, new_pos));
        instructions.insert(std::next(std::begin(instructions), op + 1),
          mos6502(mos6502::OpCode::jmp, Operand(Operand::Type::literal, going_to)));
        instructions.insert(std::next(std::begin(instructions), op + 2), mos6502(ASMLine::Type::Label, new_pos));
        instructions[op].comment = instructions[op + 1].comment = instructions[op + 2].comment = comment;
        return true;
      } else if (instructions[op].opcode == mos6502::OpCode::bcs) {
        const auto comment = instructions[op].comment;
        instructions[op] = mos6502(mos6502::OpCode::bcc, Operand(Operand::Type::literal, new_pos));
        instructions.insert(std::next(std::begin(instructions), op + 1),
          mos6502(mos6502::OpCode::jmp, Operand(Operand::Type::literal, going_to)));
        instructions.insert(std::next(std::begin(instructions), op + 2), mos6502(ASMLine::Type::Label, new_pos));
        instructions[op].comment = instructions[op + 1].comment = instructions[op + 2].comment = comment;
        return true;
      } else {
        throw std::runtime_error("Don't know how to reorg this branch: " + instructions[op].to_string());
      }
    }
  }
  return false;
}


bool fix_overwritten_flags(std::vector<mos6502> &instructions)
{
  if (instructions.size() < 3) {
    return false;
  }

  for (size_t op = 0; op < instructions.size(); ++op) {
    if (instructions[op].is_comparison) {
      auto op2 = op + 1;
      while (op2 < instructions.size()
             && !instructions[op2].is_comparison
             && !instructions[op2].is_branch) {
        ++op2;
      }

      if (op2 < instructions.size()
          && (op2 - op) > 1
          && instructions[op2 - 1].opcode != mos6502::OpCode::plp) {
        if (instructions[op2].is_comparison) {
          continue;
        }

        if (instructions[op2].is_branch) {
          // insert a pull of processor status before the branch
          instructions.insert(std::next(std::begin(instructions), op2), mos6502(mos6502::OpCode::plp));
          // insert a push of processor status after the comparison
          instructions.insert(std::next(std::begin(instructions), op + 1), mos6502(mos6502::OpCode::php));

          return true;
        }
      }
    }
  }

  return false;
}

void setup_target_cpu_state([[maybe_unused]] const std::vector<AVR> &instructions, std::vector<mos6502> &new_instructions)
{
  // set __zero_reg__ (reg 1 on AVR) to 0
  new_instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#$00"));
  new_instructions.emplace_back(mos6502::OpCode::sta, AVR::get_register(1));
}


void setup_target_cpu_state([[maybe_unused]] const std::vector<i386> &instructions, [[maybe_unused]] std::vector<mos6502> &new_instructions)
{
}

template<typename Arch>
void run(std::istream &input)
{
  std::regex Comment(R"(\s*\#.*)");
  std::regex Label(R"(^\s*(\S+):.*)");
  std::regex Directive(R"(^\s*(\..+))");
  std::regex UnaryInstruction(R"(^\s+(\S+)\s+(\S+))");
  std::regex BinaryInstruction(R"(^\s+(\S+)\s+(\S+),\s*(\S+))");
  std::regex Instruction(R"(^\s+(\S+))");

  int lineno = 0;


  std::vector<Arch> instructions;

  while (input.good()) {
    std::string line;
    getline(input, line);
    try {
      std::smatch match;
      if (std::regex_match(line, match, Label)) {
        instructions.emplace_back(lineno, line, ASMLine::Type::Label, match[1]);
      } else if (std::regex_match(line, match, Comment)) {
        // don't care about comments
      } else if (std::regex_match(line, match, Directive)) {
        instructions.emplace_back(lineno, line, ASMLine::Type::Directive, match[1]);
      } else if (std::regex_match(line, match, BinaryInstruction)) {
        instructions.emplace_back(lineno, line, ASMLine::Type::Instruction, match[1], match[2], match[3]);
      } else if (std::regex_match(line, match, UnaryInstruction)) {
        instructions.emplace_back(lineno, line, ASMLine::Type::Instruction, match[1], match[2]);
      } else if (std::regex_match(line, match, Instruction)) {
        instructions.emplace_back(lineno, line, ASMLine::Type::Instruction, match[1]);
      } else if (line == "") {
      }
    } catch (const std::exception &e) {
      log(LogLevel::Error, lineno, line, e.what());
    }

    ++lineno;
  }

  std::set<std::string> labels;

  for (const auto &i : instructions) {
    if (i.type == ASMLine::Type::Label) {
      labels.insert(i.text);
    }
  }

  std::set<std::string> used_labels{ "main" };

  for (const auto &i : instructions) {
    if (i.type == ASMLine::Type::Instruction) {

      const auto check_label = [&](const auto &value) {
        if (labels.count(value) != 0) {
          used_labels.insert(value);
        }
      };

      check_label(i.operand1.value);
      check_label(i.operand2.value);
      check_label(strip_lo_hi(i.operand1.value));
      check_label(strip_lo_hi(i.operand2.value));
    }
  }

  const auto new_labels =
    [&used_labels]() {
      std::map<std::string, std::string> result;
      for (const auto &l : used_labels) {
        auto newl = l;
        std::transform(newl.begin(), newl.end(), newl.begin(), [](const auto c) { return std::tolower(c); });
        newl.erase(std::remove_if(newl.begin(), newl.end(), [](const auto c) { return !std::isalnum(c); }), std::end(newl));

        result.emplace(std::make_pair(l, newl));
      }
      return result;
    }();


  for (const auto &l : new_labels) {
    std::clog << "Label: '" << l.first << "': '" << l.second << "'\n";
  }

  for (auto &i : instructions) {
    if (i.type == ASMLine::Type::Label) {
      std::clog << "Looking up Label: '" << i.text << "'\n";
      if (i.text == "0") {
        i.text = "-memcpy_0";
      } else {
        i.text = new_labels.at(i.text);
      }
    }

    if (i.operand2.value.starts_with("lo8(") || i.operand2.value.starts_with("hi8(")) {
      const auto potential_label = strip_lo_hi(i.operand2.value);
      const auto itr1 = new_labels.find(potential_label);
      if (itr1 != new_labels.end()) {
        i.operand2.value.replace(4, potential_label.size(), itr1->second);
      }
    }

    const auto itr1 = new_labels.find(i.operand1.value);
    if (itr1 != new_labels.end()) {
      i.operand1.value = itr1->second;
    }

    const auto itr2 = new_labels.find(i.operand2.value);
    if (itr2 != new_labels.end()) {
      i.operand2.value = itr2->second;
    }
  }


  std::vector<mos6502> new_instructions;
  new_instructions.emplace_back(ASMLine::Type::Directive, ".word $1000");
  new_instructions.emplace_back(ASMLine::Type::Directive, "* = $1000");
  setup_target_cpu_state(instructions, new_instructions);
  new_instructions.emplace_back(mos6502::OpCode::jmp, Operand(Operand::Type::literal, "main"));


  int instructions_to_skip = 0;
  std::string next_label_name;
  for (const auto &i : instructions) {
    to_mos6502(i, new_instructions);

    // intentionally copy so we don't invalidate the reference
    const auto last_instruction = new_instructions.back();
    const auto last_instruction_loc = new_instructions.size() - 1;

    if (instructions_to_skip == 1) {
      new_instructions.emplace_back(ASMLine::Type::Label, next_label_name);
    }

    --instructions_to_skip;

    if (last_instruction.type == ASMLine::Type::Directive && last_instruction.text.starts_with("skip_next_instruction")) {
      instructions_to_skip = 1;
      next_label_name = last_instruction.text;
      new_instructions.erase(std::next(new_instructions.begin(), static_cast<std::ptrdiff_t>(last_instruction_loc)));
    }
    if (last_instruction.type == ASMLine::Type::Directive && last_instruction.text.starts_with("skip_next_2_instructions")) {
      instructions_to_skip = 2;
      next_label_name = last_instruction.text;
      new_instructions.erase(std::next(new_instructions.begin(), static_cast<std::ptrdiff_t>(last_instruction_loc)));
    }
  }

  while (fix_overwritten_flags(new_instructions)) {
    // do it however many times it takes
  }

  while (optimize(new_instructions)) {
    // do it however many times it takes
  }

  int branch_patch_count = 0;
  while (fix_long_branches(new_instructions, branch_patch_count)) {
    // do it however many times it takes
  }


  for (const auto i : new_instructions) {
    std::cout << i.to_string() << '\n';
  }
}

int main([[maybe_unused]] const int argc, const char *argv[])
{
  std::ifstream input_file;

  std::istream &input = [&]() -> std::istream & {
    if (argc > 1) {
      input_file.open(argv[1]);
      return input_file;
    } else {
      return std::cin;
    }
  }();

  const bool is_avr = [&]() {
    for (std::size_t index = 0; index < static_cast<std::size_t>(argc); ++index) {
      if (strstr(argv[index], "avr") != nullptr) {
        return true;
      }
    }
    return false;
  }();

  if (is_avr) {
    std::cout << "; AVR Mode\n";
    run<AVR>(input);
  } else {
    run<i386>(input);
  }
}