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/*
* linux/arch/arm/lib/memzero.S
*
* Copyright (C) 1995-2000 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
.text
.align 5
.word 0
/*
* Align the pointer in r0. r3 contains the number of bytes that we are
* mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
* don't bother; we use byte stores instead.
*/
1: subs r1, r1, #4 @ 1 do we have enough
blt 5f @ 1 bytes to align with?
cmp r3, #2 @ 1
strltb r2, [r0], #1 @ 1
strleb r2, [r0], #1 @ 1
strb r2, [r0], #1 @ 1
add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
/*
* The pointer is now aligned and the length is adjusted. Try doing the
* memzero again.
*/
ENTRY(__memzero)
mov r2, #0 @ 1
ands r3, r0, #3 @ 1 unaligned?
bne 1b @ 1
/*
* r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
*/
cmp r1, #16 @ 1 we can skip this chunk if we
blt 4f @ 1 have < 16 bytes
#if ! CALGN(1)+0
/*
* We need an extra register for this loop - save the return address and
* use the LR
*/
str lr, [sp, #-4]! @ 1
mov ip, r2 @ 1
mov lr, r2 @ 1
3: subs r1, r1, #64 @ 1 write 32 bytes out per loop
stmgeia r0!, {r2, r3, ip, lr} @ 4
stmgeia r0!, {r2, r3, ip, lr} @ 4
stmgeia r0!, {r2, r3, ip, lr} @ 4
stmgeia r0!, {r2, r3, ip, lr} @ 4
bgt 3b @ 1
ldmeqfd sp!, {pc} @ 1/2 quick exit
/*
* No need to correct the count; we're only testing bits from now on
*/
tst r1, #32 @ 1
stmneia r0!, {r2, r3, ip, lr} @ 4
stmneia r0!, {r2, r3, ip, lr} @ 4
tst r1, #16 @ 1 16 bytes or more?
stmneia r0!, {r2, r3, ip, lr} @ 4
ldr lr, [sp], #4 @ 1
#else
/*
* This version aligns the destination pointer in order to write
* whole cache lines at once.
*/
stmfd sp!, {r4-r7, lr}
mov r4, r2
mov r5, r2
mov r6, r2
mov r7, r2
mov ip, r2
mov lr, r2
cmp r1, #96
andgts ip, r0, #31
ble 3f
rsb ip, ip, #32
sub r1, r1, ip
movs ip, ip, lsl #(32 - 4)
stmcsia r0!, {r4, r5, r6, r7}
stmmiia r0!, {r4, r5}
movs ip, ip, lsl #2
strcs r2, [r0], #4
3: subs r1, r1, #64
stmgeia r0!, {r2-r7, ip, lr}
stmgeia r0!, {r2-r7, ip, lr}
bgt 3b
ldmeqfd sp!, {r4-r7, pc}
tst r1, #32
stmneia r0!, {r2-r7, ip, lr}
tst r1, #16
stmneia r0!, {r4-r7}
ldmfd sp!, {r4-r7, lr}
#endif
4: tst r1, #8 @ 1 8 bytes or more?
stmneia r0!, {r2, r3} @ 2
tst r1, #4 @ 1 4 bytes or more?
strne r2, [r0], #4 @ 1
/*
* When we get here, we've got less than 4 bytes to zero. We
* may have an unaligned pointer as well.
*/
5: tst r1, #2 @ 1 2 bytes or more?
strneb r2, [r0], #1 @ 1
strneb r2, [r0], #1 @ 1
tst r1, #1 @ 1 a byte left over
strneb r2, [r0], #1 @ 1
mov pc, lr @ 1
ENDPROC(__memzero)
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