constant_time_select_64
r[i] = constant_time_select_64(mask, a[i], b[i]);
x[0].limb[i] = constant_time_select_64(is_z, z[0].limb[i],
static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a,
uint64_t selected = constant_time_select_64(CONSTTIME_TRUE_64, a, b);
selected = constant_time_select_64(CONSTTIME_FALSE_64, a, b);