collatz.bril

# ARGS: 7

# Compute the Collatz sequence from *n*. This may not terminate for all *n*, but
# it is at least known to terminate for all *n* up to a large value.
# see https://en.wikipedia.org/wiki/Collatz_conjecture

@main(x: int) {
  one: int = const 1;
  two: int = const 2;
  three: int = const 3;
  jmp .print;
.cond:
  eq_one: bool = eq x one;
  br eq_one .end .loop;
.loop:
  # No modulus! x is even iff x/2 * 2 = x
  half: int = div x two;
  doublehalf: int = mul half two;
  even: bool = eq x doublehalf;
  br even .even .odd;
.even:
  x: int = div x two;
  jmp .print;
.odd:
  x: int = mul x three;
  x: int = add x one;
  # fallthrough
.print:
  print x;
  jmp .cond;
.end:
  ret;
}