.....
alt_exception_unknown:
#ifdef NIOS2_HAS_DEBUG_STUB
       /*
        *  Either tell the user now (if there is a debugger attached) or go into
        *  the debug monitor which will loop until a debugger is attached.
        */
        break
#else /* NIOS2_HAS_DEBUG_STUB disabled */
       /*
        *  If there is no debug stub, an infinite loop is more useful.
        */
        br   alt_exception_unknown
#endif /* NIOS2_HAS_DEBUG_STUB */
#endif /* ALT_INCLUDE_INSTRUCTION_RELATED_EXCEPTION_API */

        .section .exceptions.exit.label
.Lexception_exit:

        .section .exceptions.exit, "xa"

        /*
         * Restore the saved registers, so that all general purpose registers
         * have been restored to their state at the time the interrupt occured.
         */

        ldw   r5,  68(sp)
        ldw   ea,  72(sp)  /* This becomes the PC once eret is executed */
        ldw   ra,   0(sp)

        wrctl estatus, r5

        ldw   r1,   8(sp)
        ldw   r2,  12(sp)
        ldw   r3,  16(sp)
        ldw   r4,  20(sp)
        ldw   r5,  24(sp)
        ldw   r6,  28(sp)
        ldw   r7,  32(sp)
......