Uint63Sourceint_min n m returns the minimum of n and m, m must be in 0, 2^30-1.
int_min n m returns the minimum of n and m, m must be in 0, 2^30-1.
div21 xh xl y returns q % 2^63, r s.t. xh * 2^63 + xl = q * y + r and r < y. When y is 0, returns 0, 0.