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Improve generic strspn performance

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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.
This commit is contained in:
Adhemerval Zanella
2016-03-26 19:09:07 +00:00
parent d3496c9f4f
commit 91f3b75f47
4 changed files with 97 additions and 86 deletions
Download Patch File Download Diff File Expand all files Collapse all files

74
string/bits/string2.h
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@ -914,78 +914,10 @@ __stpcpy_small (char *__dest,
/* Return the length of the initial segment of S which
consists entirely of characters in ACCEPT. */
#if !defined _HAVE_STRING_ARCH_strspn || defined _FORCE_INLINES
# ifndef _HAVE_STRING_ARCH_strspn
# if __GNUC_PREREQ (3, 2)
# define strspn(s, accept) \
__extension__ \
({ char __a0, __a1, __a2; \
(__builtin_constant_p (accept) && __string2_1bptr_p (accept) \
? ((__builtin_constant_p (s) && __string2_1bptr_p (s)) \
? __builtin_strspn (s, accept) \
: ((__a0 = ((const char *) (accept))[0], __a0 == '\0') \
? ((void) (s), (size_t) 0) \
: ((__a1 = ((const char *) (accept))[1], __a1 == '\0') \
? __strspn_c1 (s, __a0) \
: ((__a2 = ((const char *) (accept))[2], __a2 == '\0') \
? __strspn_c2 (s, __a0, __a1) \
: (((const char *) (accept))[3] == '\0' \
? __strspn_c3 (s, __a0, __a1, __a2) \
: __builtin_strspn (s, accept)))))) \
: __builtin_strspn (s, accept)); })
# else
# define strspn(s, accept) \
__extension__ \
({ char __a0, __a1, __a2; \
(__builtin_constant_p (accept) && __string2_1bptr_p (accept) \
? ((__a0 = ((const char *) (accept))[0], __a0 == '\0') \
? ((void) (s), (size_t) 0) \
: ((__a1 = ((const char *) (accept))[1], __a1 == '\0') \
? __strspn_c1 (s, __a0) \
: ((__a2 = ((const char *) (accept))[2], __a2 == '\0') \
? __strspn_c2 (s, __a0, __a1) \
: (((const char *) (accept))[3] == '\0' \
? __strspn_c3 (s, __a0, __a1, __a2) \
: strspn (s, accept))))) \
: strspn (s, accept)); })
# endif
#ifndef _HAVE_STRING_ARCH_strspn
# if __GNUC_PREREQ (3, 2)
# define strspn(s, accept) __builtin_strspn (s, accept)
# endif
__STRING_INLINE size_t __strspn_c1 (const char *__s, int __accept);
__STRING_INLINE size_t
__strspn_c1 (const char *__s, int __accept)
{
size_t __result = 0;
/* Please note that __accept never can be '\0'. */
while (__s[__result] == __accept)
++__result;
return __result;
}
__STRING_INLINE size_t __strspn_c2 (const char *__s, int __accept1,
int __accept2);
__STRING_INLINE size_t
__strspn_c2 (const char *__s, int __accept1, int __accept2)
{
size_t __result = 0;
/* Please note that __accept1 and __accept2 never can be '\0'. */
while (__s[__result] == __accept1 || __s[__result] == __accept2)
++__result;
return __result;
}
__STRING_INLINE size_t __strspn_c3 (const char *__s, int __accept1,
int __accept2, int __accept3);
__STRING_INLINE size_t
__strspn_c3 (const char *__s, int __accept1, int __accept2, int __accept3)
{
size_t __result = 0;
/* Please note that __accept1 to __accept3 never can be '\0'. */
while (__s[__result] == __accept1 || __s[__result] == __accept2
|| __s[__result] == __accept3)
++__result;
return __result;
}
#endif