// SmallVector<Values, 4> new_values;
// for (int i = 0; i < num_iterations; ++i) {
//   body_fn(old_values, &new_values, ...);
//   old_values = new_values;
// }
// ```
//
// Under the hood an induction variable is prepended to values to control the
// number of iterations, but that is transparent to `body_fn`, which does not
// need to care about that.
static void CreateWhile32(Location loc, int num_iterations,