1 | /* Copyright (c) 2017 SiFive Inc. All rights reserved. |
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2 | |
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3 | This copyrighted material is made available to anyone wishing to use, |
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4 | modify, copy, or redistribute it subject to the terms and conditions |
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5 | of the FreeBSD License. This program is distributed in the hope that |
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6 | it will be useful, but WITHOUT ANY WARRANTY expressed or implied, |
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7 | including the implied warranties of MERCHANTABILITY or FITNESS FOR |
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8 | A PARTICULAR PURPOSE. A copy of this license is available at |
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9 | http://www.opensource.org/licenses. |
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10 | */ |
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11 | |
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12 | #include <string.h> |
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13 | #include <stdint.h> |
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14 | |
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15 | size_t strlen(const char *str) |
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16 | { |
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17 | const char *start = str; |
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18 | |
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19 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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20 | while (*str++) |
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21 | ; |
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22 | return str - start - 1; |
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23 | #else |
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24 | if (__builtin_expect ((uintptr_t)str & (sizeof (long) - 1), 0)) do |
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25 | { |
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26 | char ch = *str; |
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27 | str++; |
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28 | if (!ch) |
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29 | return str - start - 1; |
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30 | } while ((uintptr_t)str & (sizeof (long) - 1)); |
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31 | |
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32 | unsigned long *ls = (unsigned long *)str; |
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33 | while (!__libc_detect_null (*ls++)) |
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34 | ; |
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35 | asm volatile ("" : "+r"(ls)); /* prevent "optimization" */ |
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36 | |
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37 | str = (const char *)ls; |
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38 | size_t ret = str - start, sl = sizeof (long); |
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39 | |
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40 | char c0 = str[0 - sl], c1 = str[1 - sl], c2 = str[2 - sl], c3 = str[3 - sl]; |
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41 | if (c0 == 0) return ret + 0 - sl; |
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42 | if (c1 == 0) return ret + 1 - sl; |
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43 | if (c2 == 0) return ret + 2 - sl; |
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44 | if (sl == 4 || c3 == 0) return ret + 3 - sl; |
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45 | |
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46 | c0 = str[4 - sl], c1 = str[5 - sl], c2 = str[6 - sl], c3 = str[7 - sl]; |
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47 | if (c0 == 0) return ret + 4 - sl; |
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48 | if (c1 == 0) return ret + 5 - sl; |
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49 | if (c2 == 0) return ret + 6 - sl; |
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50 | |
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51 | return ret + 7 - sl; |
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52 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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53 | } |
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