source: trunk/libs/newlib/src/libgloss/spu/crt0.S @ 453

/* (C) Copyright IBM Corp. 2005, 2006
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*/

/* crt0.S - entry function for C Runtime.
 *
 * With _STD_MAIN switch, the crt0.S will be compiled to crt2.o.
 * The crt2.o sets up a C99-style interface for the SPU application's
 * main() function, including a local copy of argv strings.
 * 
 * The number of argument strings is passed in R3.  The size and EA 
 * location of the argument vector region is passed in R4.  Once the
 * argv region is copied to the highest range of LS, and $SP is set 
 * just below it.
 *
 * Without _STD_MAIN, the crt0.S is compiled to crt1.o. 
 * The crt1.o prepares the entry for an SPU module. The main() function
 * is called with different parameter list: spu_id, param and env 
 * are passed by R3, R4 and R5 respectively.
 */

#ifdef _STD_MAIN
#define MFC_TAG_UPDATE_ALL      2
#define MFC_GET_CMD             0x40
#define TAGID                   0
#define TAGMASK                 1
#endif

.comm __ea_local_store,16,16

.text
.global _start
.type _start, @function
        
_start:
        /* Save the local store base from $6.  */
        stqr $6, __ea_local_store

#ifdef _STD_MAIN
        /* 
         * Copy the argument vector region from EA to LS.  The DMA
         * parameters are passed in R4:
         *
         *        +-------+-------+-------+-------+
         *     R4 |   LS  | EA-HI | EA-LO | SIZE  |
         *        +-------+-------+-------+-------+
         *  word     0       1       2       3
         *
         * By the end of this sequence, the prefered slot (word 0) of
         * R4 will contain the LS offset of argv region, which also
         * serves as the base offset for $SP.
         */
        wrch    $MFC_LSA, $4
        rotqbyi $4, $4, 4
        wrch    $MFC_EAH, $4
        rotqbyi $4, $4, 4
        wrch    $MFC_EAL, $4
        rotqbyi $4, $4, 4
        wrch    $MFC_Size, $4
        rotqbyi $4, $4, 4
        il      $LR, TAGID
        wrch    $MFC_TagID, $LR

        /* Issue MFC_GET_CMD, then wait for transfer of argument
         * vector region to complete.
         */
        il      $LR, MFC_GET_CMD
        wrch    $MFC_Cmd, $LR
        il      $LR, TAGMASK
        wrch    $MFC_WrTagMask, $LR
        il      $LR, MFC_TAG_UPDATE_ALL
        wrch    $MFC_WrTagUpdate, $LR
        rdch    $LR, $MFC_RdTagStat
#endif

        /* Save parameter list of main function to the non-volatile
         * registers. spu_thread module has three parameters, while
         * spulet only has two.
         */
        ori     $80, $3, 0
        ori     $81, $4, 0
#ifndef _STD_MAIN
        ori     $82, $5, 0
#endif

        /* The Link Register is initialized to NULL.
         */
        il      $LR, 0

#ifdef _STD_MAIN        
        /* For spulet, initialize stack pointer just below the argv region.
         */
        ai      $SP,$4,-16
#else
        /* For spe_thread module, the stack pointer is initialized 
         * below the area where __stack points to.
         */
        ila     $SP,__stack
#endif
        /* Initialize back chain to NULL.
         */
        stqd    $LR,0($SP)

        /* Allocate 2 slots for stack frame.
         */
        stqd    $SP,-32($SP)
        ai      $SP,$SP,-32

        /* Save the Link Register in Link Register Save Area.
         */
        stqd    $LR,16($SP)

        /* Calculate stack size.
         */
        ila     $3,_end
        sf      $3,$3,$SP
        rotqbyi $3,$3,12

        /* The BE Linux ABI passes the stack size in $2, or use
         * the default if $2 == 0.
         */
        rotqbyi $4,$2,12
        ceqi    $5,$4,0
        selb    $3,$4,$3,$5
        fsmbi   $4,3840
        selb    $SP,$SP,$3,$4

        /* Call the _init function.
         */
        brsl    $LR, _init
        
        /* Call the _fini function at exit time.
         */
        ila     $3, _fini
        brsl    $LR, atexit

#ifdef _PROFILE
        /* Call monstartup if profiling is enabled
         */
#ifdef _STD_MAIN
        ila     $3,0
#else
        ori     $3,$80,0
#endif
        brsl    $LR, __monstartup
#endif
        ori     $3,$80,0
        ori     $4,$81,0        
#ifndef _STD_MAIN
        ori     $5,$82,0
#endif

        /* Call the programs main.
         */
        brsl    $LR, main
        
        /* Call exit.
         */
        brsl    $LR, exit