u64_max
c.umin = a.umin / u64_max(b.umax, 1);
c.umax = a.umax / u64_max(b.umin, 1);
uint64_t max_abs_b = u64_max(s64_abs(b.smin), s64_abs(b.smax));
c.umax = u64_max(a.umax, b.umax);