{"ast_node_type":"other","tokens":[{"end":240,"kind":"keyword","start":0,"text":"|"}]}
| MIPS         | `$ra`                                   | Return address cannot be used as inputs or outputs.                                                                                                                                 |
| MIPS         | `$28`/`$gp`                             | Global pointer cannot be used as inputs or outputs.                                                                                                                                 |
| Hexagon      | `lr`                                    | This is the link register which cannot be used as an input or output.                                                                                                               |