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688903eb | 1 | /* Copyright (C) 1998-2018 Free Software Foundation, Inc. |
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2 | This file is part of the GNU C Library. |
3 | Code contributed by Matthew Wilcox <willy@odie.barnet.ac.uk> | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
3214b89b AJ |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
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9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
3214b89b | 13 | Lesser General Public License for more details. |
42d5b281 | 14 | |
3214b89b | 15 | You should have received a copy of the GNU Lesser General Public |
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16 | License along with the GNU C Library. If not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
42d5b281 | 18 | |
365261c3 RH |
19 | /* Thumb requires excessive IT insns here. */ |
20 | #define NO_THUMB | |
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21 | #include <sysdep.h> |
22 | ||
23 | /* size_t strlen(const char *S) | |
24 | * entry: r0 -> string | |
25 | * exit: r0 = len | |
26 | */ | |
27 | ||
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28 | .syntax unified |
29 | .text | |
30 | ||
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31 | ENTRY(strlen) |
32 | bic r1, r0, $3 @ addr of word containing first byte | |
81cb7a0b | 33 | ldr r2, [r1], $4 @ get the first word |
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34 | ands r3, r0, $3 @ how many bytes are duff? |
35 | rsb r0, r3, $0 @ get - that number into counter. | |
36 | beq Laligned @ skip into main check routine if no | |
37 | @ more | |
69069c4a | 38 | #ifdef __ARMEB__ |
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39 | orr r2, r2, $0xff000000 @ set this byte to non-zero |
40 | subs r3, r3, $1 @ any more to do? | |
41 | orrgt r2, r2, $0x00ff0000 @ if so, set this byte | |
42 | subs r3, r3, $1 @ more? | |
43 | orrgt r2, r2, $0x0000ff00 @ then set. | |
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44 | #else |
45 | orr r2, r2, $0x000000ff @ set this byte to non-zero | |
46 | subs r3, r3, $1 @ any more to do? | |
47 | orrgt r2, r2, $0x0000ff00 @ if so, set this byte | |
48 | subs r3, r3, $1 @ more? | |
49 | orrgt r2, r2, $0x00ff0000 @ then set. | |
50 | #endif | |
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51 | Laligned: @ here, we have a word in r2. Does it |
52 | tst r2, $0x000000ff @ contain any zeroes? | |
53 | tstne r2, $0x0000ff00 @ | |
54 | tstne r2, $0x00ff0000 @ | |
55 | tstne r2, $0xff000000 @ | |
56 | addne r0, r0, $4 @ if not, the string is 4 bytes longer | |
81cb7a0b | 57 | ldrne r2, [r1], $4 @ and we continue to the next word |
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58 | bne Laligned @ |
59 | Llastword: @ drop through to here once we find a | |
482f8700 RM |
60 | #ifdef __ARMEB__ |
61 | tst r2, $0xff000000 @ word that has a zero byte in it | |
62 | addne r0, r0, $1 @ | |
63 | tstne r2, $0x00ff0000 @ and add up to 3 bytes on to it | |
64 | addne r0, r0, $1 @ | |
65 | tstne r2, $0x0000ff00 @ (if first three all non-zero, 4th | |
66 | addne r0, r0, $1 @ must be zero) | |
67 | #else | |
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68 | tst r2, $0x000000ff @ word that has a zero byte in it |
69 | addne r0, r0, $1 @ | |
70 | tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it | |
71 | addne r0, r0, $1 @ | |
72 | tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th | |
73 | addne r0, r0, $1 @ must be zero) | |
482f8700 | 74 | #endif |
47f0752a | 75 | DO_RET(lr) |
42d5b281 | 76 | END(strlen) |
79b7c863 | 77 | libc_hidden_builtin_def (strlen) |