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/arch/arm26/lib/memzero.S

https://bitbucket.org/evzijst/gittest
Assembly | 80 lines | 78 code | 2 blank | 0 comment | 0 complexity | d40afc09ebfb255a0e84cf0b00e09ecd MD5 | raw file
 1/*
 2 *  linux/arch/arm26/lib/memzero.S
 3 *
 4 *  Copyright (C) 1995-2000 Russell King
 5 *
 6 * This program is free software; you can redistribute it and/or modify
 7 * it under the terms of the GNU General Public License version 2 as
 8 * published by the Free Software Foundation.
 9 */
10#include <linux/linkage.h>
11#include <asm/assembler.h>
12
13	.text
14	.align	5
15	.word	0
16/*
17 * Align the pointer in r0.  r3 contains the number of bytes that we are
18 * mis-aligned by, and r1 is the number of bytes.  If r1 < 4, then we
19 * don't bother; we use byte stores instead.
20 */
211:	subs	r1, r1, #4		@ 1 do we have enough
22	blt	5f			@ 1 bytes to align with?
23	cmp	r3, #2			@ 1
24	strltb	r2, [r0], #1		@ 1
25	strleb	r2, [r0], #1		@ 1
26	strb	r2, [r0], #1		@ 1
27	add	r1, r1, r3		@ 1 (r1 = r1 - (4 - r3))
28/*
29 * The pointer is now aligned and the length is adjusted.  Try doing the
30 * memzero again.
31 */
32
33ENTRY(__memzero)
34	mov	r2, #0			@ 1
35	ands	r3, r0, #3		@ 1 unaligned?
36	bne	1b			@ 1
37/*
38 * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
39 */
40	cmp	r1, #16			@ 1 we can skip this chunk if we
41	blt	4f			@ 1 have < 16 bytes
42/*
43 * We need an extra register for this loop - save the return address and
44 * use the LR
45 */
46	str	lr, [sp, #-4]!		@ 1
47	mov	ip, r2			@ 1
48	mov	lr, r2			@ 1
49
503:	subs	r1, r1, #64		@ 1 write 32 bytes out per loop
51	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
52	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
53	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
54	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
55	bgt	3b			@ 1
56	LOADREGS(eqfd, sp!, {pc})	@ 1/2 quick exit
57/*
58 * No need to correct the count; we're only testing bits from now on
59 */
60	tst	r1, #32			@ 1
61	stmneia	r0!, {r2, r3, ip, lr}	@ 4
62	stmneia	r0!, {r2, r3, ip, lr}	@ 4
63	tst	r1, #16			@ 1 16 bytes or more?
64	stmneia	r0!, {r2, r3, ip, lr}	@ 4
65	ldr	lr, [sp], #4		@ 1
66
674:	tst	r1, #8			@ 1 8 bytes or more?
68	stmneia	r0!, {r2, r3}		@ 2
69	tst	r1, #4			@ 1 4 bytes or more?
70	strne	r2, [r0], #4		@ 1
71/*
72 * When we get here, we've got less than 4 bytes to zero.  We
73 * may have an unaligned pointer as well.
74 */
755:	tst	r1, #2			@ 1 2 bytes or more?
76	strneb	r2, [r0], #1		@ 1
77	strneb	r2, [r0], #1		@ 1
78	tst	r1, #1			@ 1 a byte left over
79	strneb	r2, [r0], #1		@ 1
80	RETINSTR(mov,pc,lr)		@ 1