Performence issue + wrapping_{add,sub}

[albttx]

Hello, first of all, i'm new with rust, so i could miss some concept...

i have a MerkleTree in rust, and i was using the ethnum library.
the library was missing the Serialize/Deserialize, and your library is more complete. so i decided to switched.

Just i was missing those function:

• wrapping_add
• wrapping_sub

which i implemented that way:

pub fn wrapping_add(lhs: U256, rhs: U256) -> U256 {
    match lhs.checked_add(rhs) {
        None => {
            if lhs > rhs {
                lhs - (U256::MAX - rhs) - 1
            } else {
                rhs - (U256::MAX - lhs) - 1
            }
        }
        Some(x) => x,
    }
}

pub fn wrapping_sub(lhs: U256, rhs: U256) -> U256 {
    match lhs.checked_sub(rhs) {
        None => {
            if lhs > rhs {
                U256::MAX - (rhs - lhs) + 1
            } else {
                U256::MAX - (rhs - lhs) + 1
            }
        }
        Some(x) => x,
    }
}

Maybe it's because of those functions... (or something else ?) but my MerkleTree(16 floors) creation + insert 1 leaf went from ~6s to 19s...

Do you have any tips or advice to reduce this time ?