aoc-21-alt.js

const c1 = 15466939;
const c2 = 65899;
//const s = 5285447;15615244;

const nums = [];
const dupes = [];
let [r1, r2, r3, r4, r5] = [0, 0, 0, 0, 0];

let hits = 0;
L6: while(true) {
  r4 = 65536 | r5;
  r5 = c1;

  L8: while(true) {
    r3 = r4 & 0xff;
    r5 = (r5 + r3) & 0xffffff;
    r5 = (r5 * c2) & 0xffffff;

    if (256 > r4) {
      // custom
      ++hits;
      if (nums.includes(r5)) {
      } else {
        nums.push(r5);
        // for part 2, look at the last output of this
        console.log(hits, r5);
      }
      if (hits > 100000) {
        break L6;
      } else {
        continue L6;
      }
      // !custom
    } else {
      r3 = 0;

      while((r3 + 1) * 256 <= r4) {
        ++r3;
      }
      r4 = r3;
      continue L8;
    }
  }
}

console.log([r1, r2, r3, r4, r5]);

aoc-21.js

// C ← op(A, B)

let beforeIp;
let ip = 0;
let ipReg;
const regs = [0, 0, 0, 0, 0, 0];
const instructions = {
  setIp: (value, regs) => { beforeIp = regs[value]; ipReg = value; regs[value] = ip; },

  seti: ([a,b,c], r) => r[c] = a,
  setr: ([a,b,c], r) => r[c] = r[a],

  addi: ([a,b,c], r) => r[c] = r[a] + b,
  addr: ([a,b,c], r) => r[c] = r[a] + r[b],

  muli: ([a,b,c], r) => r[c] = r[a] * b,
  mulr: ([a,b,c], r) => r[c] = r[a] * r[b],

  bani: ([a,b,c], r) => r[c] = r[a] & b,
  banr: ([a,b,c], r) => r[c] = r[a] & r[b],

  bori: ([a,b,c], r) => r[c] = r[a] | b,
  borr: ([a,b,c], r) => r[c] = r[a] | r[b],

  gtir: ([a,b,c], r) => r[c] = Number(a > r[b]),
  gtri: ([a,b,c], r) => r[c] = Number(r[a] > b),
  gtrr: ([a,b,c], r) => r[c] = Number(r[a] > r[b]),

  eqir: ([a,b,c], r) => r[c] = Number(a === r[b]),
  eqri: ([a,b,c], r) => r[c] = Number(r[a] === b),
  eqrr: ([a,b,c], r) => r[c] = Number(r[a] === r[b]),
}

const program = require('fs').readFileSync('aoc-input-21', 'utf-8').trim()
  .split('\n')
  .map(line => {
    if (line.startsWith('#ip')) {
      return {
        action: instructions.setIp,
        value: Number(line.split(' ')[1]),
        line,
      }
    } else {
      const [inst, ...args] = line.split(' ');
      return {
        action: instructions[inst],
        value: args.map(Number),
        line,
      };
    }
  });

//apparently this instruction is not part of the program
const ipSetter = program.shift();
ipSetter.action(ipSetter.value, regs);

program.forEach((line, i) => {
  console.log(i.toString().padStart(2, '0'), line.line);
})

const initReg = 0;
regs[0] = initReg;
let gen = 0;
while(ip >= 0 && ip < program.length) {
  ++gen;
  const instr = program[ip];

  const pip = ip;

  instr.action(instr.value, regs);

  if (ip === 28) {
    console.log(regs[5]);
    break;
  }

  if (ipReg) {
    ++regs[ipReg];
    ip = regs[ipReg];
  } else {
    ++ip;
  }
}

aoc-input-21

#ip 2
seti 123 0 5
bani 5 456 5
eqri 5 72 5
addr 5 2 2
seti 0 0 2
seti 0 4 5
bori 5 65536 4
seti 15466939 9 5
bani 4 255 3
addr 5 3 5
bani 5 16777215 5
muli 5 65899 5
bani 5 16777215 5
gtir 256 4 3
addr 3 2 2
addi 2 1 2
seti 27 8 2
seti 0 7 3
addi 3 1 1
muli 1 256 1
gtrr 1 4 1
addr 1 2 2
addi 2 1 2
seti 25 2 2
addi 3 1 3
seti 17 7 2
setr 3 7 4
seti 7 3 2
eqrr 5 0 3
addr 3 2 2
seti 5 9 2