de2-115-fpga-pong/software/Pong_Code_bsp/HAL/src/alt_exception_trap.S

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        /*
         * This is the trap exception handler for Nios2.
         */ 

        /*
         * Provide a label which can be used to pull this file in.
         */

        .section .exceptions.start
        .globl alt_exception_trap
alt_exception_trap:

        /*
         * Pull in the entry/exit code.
         */
        .globl alt_exception

        .section .exceptions.soft, "xa"

.Ltrap_handler:

        /*
         * Did a trap instruction cause the exception?
         *
         * The instruction which the exception occurred on has been loaded
         * into r2 by code in alt_exception_entry.S
         *
         */

#ifdef ALT_CPU_CPU_ARCH_NIOS2_R2
        movhi r3,0xb41d              /* upper half of trap opcode */
        ori   r3,r3,0x0020           /* lower half of trap opcode */
        beq   r2,r3,.Lis_trap
#ifdef NIOS2_CDX_PRESENT
        mov   r3,r2
        andhi r3,r3,0xffff
        ori   r3,r3,0xd009           /* trap.n opcode */
        beq   r2,r3,.Lis_trap
#endif
        br   .Lnot_trap
#else
        movhi r3,0x003b              /* upper half of trap opcode */
        ori   r3,r3,0x683a           /* lower half of trap opcode */
        bne   r2,r3,.Lnot_trap
#endif

.Lis_trap:
        /*
         *  There is no trap handler defined here, and so executing a trap
         *  instruction causes a software break.  If you provide a trap handler,
         *  then you must replace the break instruction below with your handler.
         *  Your handler must preserve ea and the usual callee saved registers.
         */

        break

        br   .Lexception_exit

.Lnot_trap:


        .section .exceptions.exit.label
.Lexception_exit: