Re: [PATCH v2] Faster strchr implementation.

[Liubov Dmitrieva <liubov dot dmitrieva at gmail dot com>]

Can you please attach the patch itself to review including style issues.


--
Liubov Dmitrieva

On Fri, Aug 16, 2013 at 1:59 PM, OndÅej BÃlka <neleai@seznam.cz> wrote:
> On Thu, Aug 08, 2013 at 10:22:36PM +0400, Liubov Dmitrieva wrote:
> A strchr will need to rerun tests.
>
> Hi, I tuned my implementation do decrease loop overhead. It decreases
> loop overhead by significant constant factor over previous
> implementation.
>
> There are architectures that I do not cover,
> haswell - an avx2 implementation that I posted is better and it is
>           better posted separately.
>
> atom - An loop caused big overhead for sizes around 64 bytes and we need
>        work on more effective header, we keep no-bsf implementation for now.
>
> silvermont - similar issues as atom but we need separate IFUNC casing to
>              choose no-bsf variant
>
> athlon,athlon x2 - Same situation an we also need flag to choose other variant.
>
> I updated results of my profiler.
> In my random test strchr would always find terminating zero. This does
> not happen in practice so now strchr will find character with 50%
> probability.
>
> http://kam.mff.cuni.cz/~ondra/benchmark_string/strchr_profile.html
> http://kam.mff.cuni.cz/~ondra/benchmark_string/strchr_profile160813.tar.bz2
>
>
> OK to commit this iteration?
>
>         * sysdeps/x86_64/multiarch/ifunc-impl-list.c
>         (__libc_ifunc_impl_list): Remove: __strchr_sse42.
>         * sysdeps/x86_64/multiarch/strchr.S (__strchr_sse42): Remove.
>         (strchr): Remove __strchr_sse42 ifunc selection.
>         * sysdeps/x86_64/strchr.S (strchr): Use optimized implementation.
>         * sysdeps/x86_64/strchrnul.S: Include sysdeps/x86_64/strchr.S.
>
>
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 28d3579..8486294 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c