- unsigned using_irn_visited : 1; /**< set to 1 if we are currently using the visited flag */
- unsigned using_block_visited : 1; /**< set to 1 if we are currently using the block_visited flag */
- unsigned using_irn_link : 1; /**< set to 1 if we are currently using the irn_link fields */
- unsigned using_block_mark : 1; /**< set to 1 if we are currently using the block mark flags */