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Improve strtok and strtok_r performance. Instead of calling strpbrk which

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calls strcspn, call strcspn directly so we get the end of the token without
an extra call to rawmemchr.  Also avoid an unnecessary call to strcspn after
the last token by adding an early exit for an empty string.  Change strtok
to tailcall strtok_r to avoid unnecessary code duplication.

Remove the special header optimization for strtok_r of a 1-character
constant string - both strspn and strcspn contain optimizations for this
case.  Benchmarking this showed similar performance in the worst case,
but up to 5.5x better performance in the "found" case for large inputs.

	* benchtests/bench-strtok.c (oldstrtok): Add old implementation.
	* string/strtok.c (strtok): Change to tailcall __strtok_r.
	* string/strtok_r.c (__strtok_r): Optimize for performance.
	* string/string-inlines.c (__old_strtok_r_1c): New function.
	* string/bits/string2.h (__strtok_r): Move to string-inlines.c.
This commit is contained in:
Wilco Dijkstra
2016-12-14 15:12:18 +00:00
parent 14348aaeff
commit d58ab810a6
6 changed files with 88 additions and 92 deletions
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30
string/string-inlines.c
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@ -35,6 +35,36 @@
#include "shlib-compat.h"
#if SHLIB_COMPAT (libc, GLIBC_2_1_1, GLIBC_2_25)
/* The inline functions are not used from GLIBC 2.25 and forward, however
they are required to provide the symbols through string-inlines.c
(if inlining is not possible for compatibility reasons). */
char *
__old_strtok_r_1c (char *__s, char __sep, char **__nextp)
{
char *__result;
if (__s == NULL)
__s = *__nextp;
while (*__s == __sep)
++__s;
__result = NULL;
if (*__s != '\0')
{
__result = __s++;
while (*__s != '\0')
if (*__s++ == __sep)
{
__s[-1] = '\0';
break;
}
}
*__nextp = __s;
return __result;
}
compat_symbol (libc, __old_strtok_r_1c, __strtok_r_1c, GLIBC_2_1_1);
#endif
#if SHLIB_COMPAT (libc, GLIBC_2_1_1, GLIBC_2_24)
/* The inline functions are not used from GLIBC 2.24 and forward, however
they are required to provide the symbols through string-inlines.c