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91f3b75f47
As for strcspn, this patch improves strspn performance using a much faster algorithm. It first constructs a 256-entry table based on the accept string and then uses it as a lookup table for the input string. As for strcspn optimization, it is generally at least 10 times faster than the existing implementation on bench-strspn on a few AArch64 implementations. Also the string/bits/string2.h inlines make no longer sense, as current implementation will already implement most of the optimizations. Tested on x86_64, i686, and aarch64. * string/strspn.c (strcspn): Rewrite function. * string/bits/string2.h (strspn): Use __builtin_strcspn. (__strspn_c1): Remove inline function. (__strspn_c2): Likewise. (__strspn_c3): Likewise. * string/string-inlines.c [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strspn_c1): Add compatibility symbol. [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strspn_c2): Likewise. [SHLIB_COMPAT(libc, GLIBC_2_1_1, GLIBC_2_24)] (__strspn_c3): Likewise.
75 lines
2.2 KiB
C
75 lines
2.2 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 strspn
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#ifndef STRSPN
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# define STRSPN strspn
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#endif
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/* Return the length of the maximum initial segment
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of S which contains only characters in ACCEPT. */
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size_t
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STRSPN (const char *str, const char *accept)
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{
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if (accept[0] == '\0')
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return 0;
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if (__glibc_unlikely (accept[1] == '\0'))
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{
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const char *a = str;
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for (; *str == *accept; str++);
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return str - a;
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}
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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*) accept;
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/* Different from strcspn it does not add the NULL on the table
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so can avoid check if str[i] is NULL, since table['\0'] will
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be 0 and thus stopping the loop check. */
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do
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p[*s++] = 1;
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while (*s);
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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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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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} 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 : count + c2 + 2;
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}
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libc_hidden_builtin_def (strspn)
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