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/* $OpenBSD: memset.S,v 1.2 2000/03/03 00:54:46 todd Exp $ */
/* $NetBSD: memset.S,v 1.1 1996/01/31 23:16:35 mark Exp $ */
/*
* Copyright (c) 1995 Mark Brinicombe.
* Copyright (c) 1995 Brini.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Mark Brinicombe.
* 4. The name of the company nor the name of the author may be used to
* endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* RiscBSD kernel project
*
* memset.S
*
* optimized memset function
*
* Created : 16/05/95
* Last updated : 16/05/95
*
*/
sp .req r13
lr .req r14
pc .req r15
.text
.global _memset
/* Sets a block of memory to the specified value
*
* r0 - address
* r1 - byte to write
* r2 - number of bytes to write
*/
_memset:
and r1, r1, #0x000000ff /* We write bytes */
cmp r2, #0x00000004 /* Do we have less than 4 bytes */
blt memset_lessthanfour
/* Ok first we will word align the address */
ands r3, r0, #0x00000003 /* Get the bottom two bits */
beq memset_addraligned /* The address is word aligned */
rsb r3, r3, #0x00000004
sub r2, r2, r3
cmp r3, #0x00000002
strb r1, [r0], #0x0001 /* Set 1 byte */
strgeb r1, [r0], #0x0001 /* Set another byte */
strgtb r1, [r0], #0x0001 /* and a third */
cmp r2, #0x00000004
blt memset_lessthanfour
/* Now we must be word aligned */
memset_addraligned:
orr r3, r1, r1, lsl #8 /* Repeat the byte into a word */
orr r3, r3, r3, lsl #16
/* We know we have at least 4 bytes ... */
cmp r2, #0x00000020 /* If less than 32 then use words */
blt memset_lessthan32
/* We have at least 32 so lets use quad words */
stmfd sp!, {r4-r6} /* Store registers */
mov r4, r3 /* Duplicate data */
mov r5, r3
mov r6, r3
memset_loop16:
stmia r0!, {r3-r6} /* Store 16 bytes */
sub r2, r2, #0x00000010 /* Adjust count */
cmp r2, #0x00000010 /* Still got at least 16 bytes ? */
bgt memset_loop16
ldmfd sp!, {r4-r6} /* Restore registers */
/* Do we need to set some words as well ? */
cmp r2, #0x00000004
blt memset_lessthanfour
/* Have either less than 16 or less than 32 depending on route taken */
memset_lessthan32:
/* We have at least 4 bytes so copy as words */
memset_loop4:
str r3, [r0], #0x0004
sub r2, r2, #0x0004
cmp r2, #0x00000004
bge memset_loop4
memset_lessthanfour:
cmp r2, #0x00000000
moveq pc, lr /* Zero length so exit */
cmp r2, #0x00000002
strb r1, [r0], #0x0001 /* Set 1 byte */
strgeb r1, [r0], #0x0001 /* Set another byte */
strgtb r1, [r0], #0x0001 /* and a third */
mov pc, lr /* Exit */
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