nn_cnd_swap
ATTRIBUTE_WARN_UNUSED_RET int nn_cnd_swap(int cnd, nn_t in1, nn_t in2);
ret = nn_cnd_swap(!mbit, &(out->X.fp_val), &(dbl.X.fp_val)); EG(ret, err2);
ret = nn_cnd_swap(!mbit, &(out->Y.fp_val), &(dbl.Y.fp_val)); EG(ret, err2);
ret = nn_cnd_swap(!mbit, &(out->Z.fp_val), &(dbl.Z.fp_val)); EG(ret, err2);
ret = nn_cnd_swap((oldexplen == 0), out, &T[1 - rbit]);
ret = nn_cnd_swap((oldexplen == 1), out, &T[2]);
ret = nn_cnd_swap(((oldexplen != 0) && (oldexplen != 1)), out, &T[rbit]);
ret = nn_cnd_swap(swap, &a, &b); EG(ret, err);
ret = nn_cnd_swap(swap, &u, uu); EG(ret, err);