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d3496c9f4f
Improve strcspn performance using a much faster algorithm. It is kept simple so it works well on most targets. It is generally at least 10 times faster than the existing implementation on bench-strcspn on a few AArch64 implementations, and for some tests 100 times as fast (repeatedly calling strchr on a small string is extremely slow...). In fact the string/bits/string2.h inlines make no longer sense, as GCC already uses strlen if reject is an empty string, strchrnul is 5 times as fast as __strcspn_c1, while __strcspn_c2 and __strcspn_c3 are slower than the strcspn main loop for large strings (though reject length 2-4 could be special cased in the future to gain even more performance). Tested on x86_64, i686, and aarch64. * string/Version (libc): Add GLIBC_2.24. * string/strcspn.c (strcspn): Rewrite function. * string/bits/string2.h (strcspn): Use __builtin_strcspn. (__strcspn_c1): Remove inline function. (__strcspn_c2): Likewise. (__strcspn_c3): Likewise. * string/string-inline.c [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strcspn_c1): Add compatibility symbol. [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strcspn_c2): Likewise. [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strcspn_c3): Likewise. * sysdeps/i386/string-inlines.c: Include generic string-inlines.c.
72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
/* Copyright (C) 1991-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <string.h>
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#include <stdint.h>
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#undef strcspn
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#ifndef STRCSPN
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# define STRCSPN strcspn
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#endif
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/* Return the length of the maximum initial segment of S
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which contains no characters from REJECT. */
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size_t
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STRCSPN (const char *str, const char *reject)
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{
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if (__glibc_unlikely (reject[0] == '\0') ||
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__glibc_unlikely (reject[1] == '\0'))
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return __strchrnul (str, reject [0]) - str;
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/* Use multiple small memsets to enable inlining on most targets. */
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unsigned char table[256];
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unsigned char *p = memset (table, 0, 64);
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memset (p + 64, 0, 64);
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memset (p + 128, 0, 64);
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memset (p + 192, 0, 64);
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unsigned char *s = (unsigned char*) reject;
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unsigned char tmp;
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do
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p[tmp = *s++] = 1;
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while (tmp);
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s = (unsigned char*) str;
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if (p[s[0]]) return 0;
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if (p[s[1]]) return 1;
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if (p[s[2]]) return 2;
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if (p[s[3]]) return 3;
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s = (unsigned char *) ((uintptr_t)(s) & ~3);
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unsigned int c0, c1, c2, c3;
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do
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{
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s += 4;
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c0 = p[s[0]];
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c1 = p[s[1]];
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c2 = p[s[2]];
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c3 = p[s[3]];
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}
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while ((c0 | c1 | c2 | c3) == 0);
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size_t count = s - (unsigned char *) str;
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return (c0 | c1) != 0 ? count - c0 + 1 : count - c2 + 3;
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}
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libc_hidden_builtin_def (strcspn)
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