macro_rules! define_instruction_fn {
($name:ident, fuel_check = omit, $contents:expr) => { ... };
($name:ident, fuel_check = flat($opcode:expr), $contents:expr) => { ... };
($name: ident, fuel_check = flat_fc($opcode: expr), $contents:expr) => { ... };
($name: ident, fuel_check = flat_fd($opcode: expr), $contents:expr) => { ... };
}