newlib/libgloss/spu/crt0.S

/* (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

.text
.global _start
.type _start, @function
	
_start:
#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

        /* 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

	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