[PATCH 3/2] Use strspn/strcspn/strpbrk ifunc in internal calls.

[H.J. Lu]

On Thu, Mar 5, 2015 at 6:03 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> On 18 Mar 2014 11:01, Ondřej Bílka wrote:
>> To make a strtok faster and improve performance in general we need to do one
>> additional change.
>>
>> A comment:
>>
>> /* It doesn't make sense to send libc-internal strcspn calls through a PLT.
>>    The speedup we get from using SSE4.2 instruction is likely eaten away
>>    by the indirect call in the PLT.  */
>>
>> Does not make sense at all because nobody bothered to check it. Gap
>> between these implementations is quite big, when haystack is empty a
>> sse2 is around 40 cycles slower because it needs to populate a lookup
>> table and difference only increases with size. That is much bigger than
>> plt slowdown which is few cycles.
>>
>> Even benchtest show a gap which also may be reverse by branch
>> misprediction but my internal benchmark shown.
>>
>>  simple_strspn stupid_strspn __strspn_sse42  __strspn_sse2
>> Length    0, alignment  0, acc len  6:  18.6562 35.2344 17.0469 61.6719
>> Length    6, alignment  0, acc len  6:  59.5469 72.5781 16.4219 73.625
>>
>> This patch also handles strpbrk which is implemented by including a
>> x86_64/multiarch/strcspn.S file.
>>
>>       * sysdeps/x86_64/multiarch/strspn.S: Remove plt indirection.
>>       * sysdeps/x86_64/multiarch/strcspn.S: Likewise.
>
> since H.J. wrote the code, he probably should be the one approving this change
> -mike

Looks good to me.  Please commit.  Sorry for the long delay.

Thanks.


-- 
H.J.