Re: [PATCH] Use strlen when searching for a nul char

[pinskia at gmail dot com]

> On Oct 7, 2015, at 7:30 AM, Wilco Dijkstra <wdijkstr@arm.com> wrote:
> 
> Expand strchr (s, '\0') in C/C++ to use strlen. This is faster on most targets as strlen is a
> simpler function. Passes GLIBC tests. I'm planning to do the same for strrchr, strchrnul and
> rawmemchr in future patches as people frequently use all of these to find the end of a string.
> 
> OK for commit?

Shouldn't this also be an optimization inside gcc if not already?

Thanks,
Andrew

> 
> ChangeLog:
> 2015-10-07  Wilco Dijkstra  wdijkstr@arm.com
> 
>    * string/string.h (strchr): Use strlen when searching for nul char.
>    * string/bits/string.h (strchr): Remove define.
> 
> --
> string/bits/string2.h | 19 -------------------
> string/string.h       | 17 +++++++++++++++++
> 2 files changed, 17 insertions(+), 19 deletions(-)
> 
> diff --git a/string/bits/string2.h b/string/bits/string2.h
> index 7645176..db6457e 100644
> --- a/string/bits/string2.h
> +++ b/string/bits/string2.h
> @@ -387,25 +387,6 @@ __mempcpy_small (void *__dest, char __src1,
> # endif
> #endif
> 
> -
> -/* Return pointer to C in S.  */
> -#ifndef _HAVE_STRING_ARCH_strchr
> -extern void *__rawmemchr (const void *__s, int __c);
> -# if __GNUC_PREREQ (3, 2)
> -#  define strchr(s, c) \
> -  (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s)          \
> -          && (c) == '\0'                          \
> -          ? (char *) __rawmemchr (s, c)                      \
> -          : __builtin_strchr (s, c)))
> -# else
> -#  define strchr(s, c) \
> -  (__extension__ (__builtin_constant_p (c) && (c) == '\0'              \
> -          ? (char *) __rawmemchr (s, c)                      \
> -          : strchr (s, c)))
> -# endif
> -#endif
> -
> -
> /* Copy SRC to DEST.  */
> #if (!defined _HAVE_STRING_ARCH_strcpy && !__GNUC_PREREQ (3, 0)) \
>     || defined _FORCE_INLINES
> diff --git a/string/string.h b/string/string.h
> index 3ab7103..599f2db 100644
> --- a/string/string.h
> +++ b/string/string.h
> @@ -217,12 +217,16 @@ extern const char *strchr (const char *__s, int __c)
> __extern_always_inline char *
> strchr (char *__s, int __c) __THROW
> {
> +  if (__builtin_constant_p (__c) && __c == '\0')
> +    return __s + __builtin_strlen ((const char *) __s);
>   return __builtin_strchr (__s, __c);
> }
> 
> __extern_always_inline const char *
> strchr (const char *__s, int __c) __THROW
> {
> +  if (__builtin_constant_p (__c) && __c == '\0')
> +    return __s + __builtin_strlen (__s);
>   return __builtin_strchr (__s, __c);
> }
> # endif
> @@ -230,6 +234,19 @@ strchr (const char *__s, int __c) __THROW
> #else
> extern char *strchr (const char *__s, int __c)
>      __THROW __attribute_pure__ __nonnull ((1));
> +
> +# if defined __OPTIMIZE__ && defined __extern_always_inline \
> +    && __GNUC_PREREQ (3,2) && !defined _FORCE_INLINES        \
> +    && !defined _HAVE_STRING_ARCH_strchr
> +__extern_always_inline char *
> +strchr (const char *__s, int __c)
> +{
> +  if (__builtin_constant_p (__c) && __c == '\0')
> +    return (char *)__s + __builtin_strlen (__s);
> +  return __builtin_strchr (__s, __c);
> +}
> +#endif
> +
> #endif
> /* Find the last occurrence of C in S.  */
> #ifdef __CORRECT_ISO_CPP_STRING_H_PROTO
> -- 
> 1.9.1
> 
> 
>