// Compile with -C opt-level=3 -C target-cpu=native to see autovectorization
// assumes input's length is a multiple of 64
pub fn sum_array(input: &[i32]) -> i32 {
    if input.len() & 63 != 0 {
        unsafe { std::hint::unreachable_unchecked() }
    }

    input.iter().sum()
}