Macro impl_shared 

macro_rules! impl_shared {
    (
        $ty:ident,
        $lane_ty:ident,
        $add_intrinsic:ident,
        $sub_intrinsic:ident,
        $shl_intrinsic:ident,
        $shr_intrinsic:ident,
        $extract_intrinsic:ident
    ) => { ... };
}