The interrupt keyword is used to declare a routine which will be used as an interrupt handler. On entry to this routine, all the registers will be saved and on exit, all registers will be restored and an interrupt or trap return will be executed (instead of the normal return from subroutine instruction).
On platforms where a return from interrupt does not exist, the normal exit code of routines will be done instead. For more information on the generated code, consult the Programmer’s Guide.