Macro gen_checked 

macro_rules! gen_checked {
    (@read $name:ident $ty:ty => $reg_constraint:tt $reg_modifier:tt) => { ... };
    (@write $name:ident $ty:ty => $reg_constraint:tt $reg_modifier:tt) => { ... };
}

Available on (x86 or x86-64) and crate feature full only.