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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/arch/arm/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
Nicolas Pitref91a8dc2008-04-11 21:04:28 -040042
43#if ! CALGN(1)+0
44
Linus Torvalds1da177e2005-04-16 15:20:36 -070045/*
46 * We need an extra register for this loop - save the return address and
47 * use the LR
48 */
49 str lr, [sp, #-4]! @ 1
50 mov ip, r2 @ 1
51 mov lr, r2 @ 1
52
533: subs r1, r1, #64 @ 1 write 32 bytes out per loop
54 stmgeia r0!, {r2, r3, ip, lr} @ 4
55 stmgeia r0!, {r2, r3, ip, lr} @ 4
56 stmgeia r0!, {r2, r3, ip, lr} @ 4
57 stmgeia r0!, {r2, r3, ip, lr} @ 4
58 bgt 3b @ 1
Russell King1b93a712006-06-25 11:23:45 +010059 ldmeqfd sp!, {pc} @ 1/2 quick exit
Linus Torvalds1da177e2005-04-16 15:20:36 -070060/*
61 * No need to correct the count; we're only testing bits from now on
62 */
63 tst r1, #32 @ 1
64 stmneia r0!, {r2, r3, ip, lr} @ 4
65 stmneia r0!, {r2, r3, ip, lr} @ 4
66 tst r1, #16 @ 1 16 bytes or more?
67 stmneia r0!, {r2, r3, ip, lr} @ 4
68 ldr lr, [sp], #4 @ 1
69
Nicolas Pitref91a8dc2008-04-11 21:04:28 -040070#else
71
72/*
73 * This version aligns the destination pointer in order to write
74 * whole cache lines at once.
75 */
76
77 stmfd sp!, {r4-r7, lr}
78 mov r4, r2
79 mov r5, r2
80 mov r6, r2
81 mov r7, r2
82 mov ip, r2
83 mov lr, r2
84
85 cmp r1, #96
86 andgts ip, r0, #31
87 ble 3f
88
89 rsb ip, ip, #32
90 sub r1, r1, ip
91 movs ip, ip, lsl #(32 - 4)
92 stmcsia r0!, {r4, r5, r6, r7}
93 stmmiia r0!, {r4, r5}
94 movs ip, ip, lsl #2
95 strcs r2, [r0], #4
96
973: subs r1, r1, #64
98 stmgeia r0!, {r2-r7, ip, lr}
99 stmgeia r0!, {r2-r7, ip, lr}
100 bgt 3b
101 ldmeqfd sp!, {r4-r7, pc}
102
103 tst r1, #32
104 stmneia r0!, {r2-r7, ip, lr}
105 tst r1, #16
106 stmneia r0!, {r4-r7}
107 ldmfd sp!, {r4-r7, lr}
108
109#endif
110
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114: tst r1, #8 @ 1 8 bytes or more?
112 stmneia r0!, {r2, r3} @ 2
113 tst r1, #4 @ 1 4 bytes or more?
114 strne r2, [r0], #4 @ 1
115/*
116 * When we get here, we've got less than 4 bytes to zero. We
117 * may have an unaligned pointer as well.
118 */
1195: tst r1, #2 @ 1 2 bytes or more?
120 strneb r2, [r0], #1 @ 1
121 strneb r2, [r0], #1 @ 1
122 tst r1, #1 @ 1 a byte left over
123 strneb r2, [r0], #1 @ 1
Russell King7999d8d2006-06-25 11:17:23 +0100124 mov pc, lr @ 1
Catalin Marinas93ed3972008-08-28 11:22:32 +0100125ENDPROC(__memzero)