Function emit_optimized_chain 

fn emit_optimized_chain(
    out: &mut Vec<u8>,
    func: &Function,
    cfg: &FunctionCfg,
    chain: &[usize],
    callee_args: &BTreeMap<u32, u8>,
    used_s: &mut BTreeSet<usize>,
    non_volatile_count: u16,
    volatile_count: u16,
    indent: &str,
)