Function wide_redc 

pub fn wide_redc<T>(t_lo: T, t_hi: T, modulus: T, n_prime: T) -> T
where
    T: Copy + Zero + One + PartialOrd + WideMul + OverflowingAdd + WrappingMul + WrappingSub,

REDC on a double-width input (t_lo, t_hi).

Computes (t_lo + t_hi * 2^W) * R^{-1} mod N.

Invariants:

• Inputs t_lo, t_hi represent a value T < N * R (product of two values < N)
• modulus is odd and non-zero
• n_prime = -N^{-1} mod 2^W