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Improve generic strcspn performance

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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.
This commit is contained in:
Wilco Dijkstra
2016-03-25 16:44:26 -03:00
committed by Adhemerval Zanella
parent d8a012c5c9
commit d3496c9f4f
6 changed files with 102 additions and 96 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
string/bits/string2.h
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@ -905,77 +905,10 @@ __stpcpy_small (char *__dest,
/* Return the length of the initial segment of S which
consists entirely of characters not in REJECT. */
#if !defined _HAVE_STRING_ARCH_strcspn || defined _FORCE_INLINES
# ifndef _HAVE_STRING_ARCH_strcspn
# if __GNUC_PREREQ (3, 2)
# define strcspn(s, reject) \
__extension__ \
({ char __r0, __r1, __r2; \
(__builtin_constant_p (reject) && __string2_1bptr_p (reject) \
? ((__builtin_constant_p (s) && __string2_1bptr_p (s)) \
? __builtin_strcspn (s, reject) \
: ((__r0 = ((const char *) (reject))[0], __r0 == '\0') \
? strlen (s) \
: ((__r1 = ((const char *) (reject))[1], __r1 == '\0') \
? __strcspn_c1 (s, __r0) \
: ((__r2 = ((const char *) (reject))[2], __r2 == '\0') \
? __strcspn_c2 (s, __r0, __r1) \
: (((const char *) (reject))[3] == '\0' \
? __strcspn_c3 (s, __r0, __r1, __r2) \
: __builtin_strcspn (s, reject)))))) \
: __builtin_strcspn (s, reject)); })
# else
# define strcspn(s, reject) \
__extension__ \
({ char __r0, __r1, __r2; \
(__builtin_constant_p (reject) && __string2_1bptr_p (reject) \
? ((__r0 = ((const char *) (reject))[0], __r0 == '\0') \
? strlen (s) \
: ((__r1 = ((const char *) (reject))[1], __r1 == '\0') \
? __strcspn_c1 (s, __r0) \
: ((__r2 = ((const char *) (reject))[2], __r2 == '\0') \
? __strcspn_c2 (s, __r0, __r1) \
: (((const char *) (reject))[3] == '\0' \
? __strcspn_c3 (s, __r0, __r1, __r2) \
: strcspn (s, reject))))) \
: strcspn (s, reject)); })
# endif
#ifndef _HAVE_STRING_ARCH_strcspn
# if __GNUC_PREREQ (3, 2)
# define strcspn(s, reject) __builtin_strcspn (s, reject)
# endif
__STRING_INLINE size_t __strcspn_c1 (const char *__s, int __reject);
__STRING_INLINE size_t
__strcspn_c1 (const char *__s, int __reject)
{
size_t __result = 0;
while (__s[__result] != '\0' && __s[__result] != __reject)
++__result;
return __result;
}
__STRING_INLINE size_t __strcspn_c2 (const char *__s, int __reject1,
int __reject2);
__STRING_INLINE size_t
__strcspn_c2 (const char *__s, int __reject1, int __reject2)
{
size_t __result = 0;
while (__s[__result] != '\0' && __s[__result] != __reject1
&& __s[__result] != __reject2)
++__result;
return __result;
}
__STRING_INLINE size_t __strcspn_c3 (const char *__s, int __reject1,
int __reject2, int __reject3);
__STRING_INLINE size_t
__strcspn_c3 (const char *__s, int __reject1, int __reject2,
int __reject3)
{
size_t __result = 0;
while (__s[__result] != '\0' && __s[__result] != __reject1
&& __s[__result] != __reject2 && __s[__result] != __reject3)
++__result;
return __result;
}
#endif