[PATCH] Do not transform strchr into rawmemchr

[Zack Weinberg]

On Wed, Nov 16, 2016 at 1:59 PM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
> GLIBC uses strchr (s, '\0') as an idiom to find the end of a string.
> This is transformed into rawmemchr by the bits/string2.h header.
> However this is generally slower than strlen on most targets, even when
> an optimized rawmemchr implementation exists.  Since GCC7 optimizes
> strchr (s, '\0') to strlen (s) + s, the GLIBC headers should not
> transform this to rawmemchr.

I endorse the removal of the non-optimization, but ...

>  #ifndef _HAVE_STRING_ARCH_strchr
> -extern void *__rawmemchr (const void *__s, int __c);
> -#  define strchr(s, c) \
> -  (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s)              \
> -                 && (c) == '\0'                                       \
> -                 ? (char *) __rawmemchr (s, c)                                \
> -                 : __builtin_strchr (s, c)))
> +# define strchr(s, c) __builtin_strchr (s, c)
>  #endif

... wouldn't it be just as effective to remove this block entirely?
That is, don't #define strchr at all.

zw