memset.s

MIPS下的boottloader yamon 的源代码

/************************************************************************
 *
 *  memset.S
 *
 *  Memory set
 *
 *
 * ######################################################################
 *
 * Copyright (c) 1999-2000 MIPS Technologies, Inc. All rights reserved. 
 * 
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 ************************************************************************/


/************************************************************************
 *  Include files
 ************************************************************************/

#include <mips.h>

/************************************************************************
 *  Definitions
 ************************************************************************/

/************************************************************************
 *  Public variables
 ************************************************************************/

/************************************************************************
 *  Static variables
 ************************************************************************/

/************************************************************************
 *  Implementation : Public functions
 ************************************************************************/

/* 
 * This routine could be optimized for MIPS64. The current code only
 * uses MIPS32 instructions.
 */	

#ifdef EB
#  define SWHI	swl		/* high part is left in big-endian	*/
#else
#  define SWHI	swr		/* high part is right in little-endian	*/
#endif

LEAF( memset )

	.set	noreorder
	.set	noat

	andi	a1, 0xff		# To avoid problems when extending
	slti	AT,a2,8
	bne	AT,zero,last8
	move	v0,a0
	beq	a1,zero,uneven
	subu	v1,zero,a0
	sll	t0,a1,8
	or	a1,a1,t0
	sll	t0,a1,16
	or	a1,a1,t0
uneven:	andi	v1,v1,0x3		# unaligned address?
	beq	v1,zero,chkw
	subu	a2,a2,v1
	SWHI	a1,0(a0)
	addu	a0,a0,v1
chkw:	andi	t0,a2,0x7
	beq	a2,t0,chkl
	subu	a3,a2,t0
	addu	a3,a3,a0
loopw:	addiu	a0,a0,8
	sw	a1,-8(a0)
	bne	a0,a3,loopw
	sw	a1,-4(a0)
	move	a2,t0
chkl:	andi	t0,a2,0x4
	beq	t0,zero,last8
	subu	a2,a2,t0
	sw	a1,0(a0)
	addiu	a0,a0,4
last8:	blez	a2,last8e
	addu	a3,a2,a0
last8l:	addiu	a0,a0,1
	bne	a0,a3,last8l
	sb	a1,-1(a0)
last8e:	j	ra
	nop

	.set	at
	.set	reorder

END( memset )


/************************************************************************
 *  Implementation : Static functions
 ************************************************************************/