Function jump_step 

const fn jump_step(
    f: i64,
    g: i64,
    delta: i64,
    t: [[i64; 2]; 2],
) -> (i64, i64, i64, [[i64; 2]; 2])

Perform one step of the gcd reduction in constant time. This follows the half-delta variant of safegcd-bounds which reduces the round count. https://github.com/sipa/safegcd-bounds