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Re: PATH: removing quadratic complexity strstr, strcasestr and strcasestr-nonascii

From: Mike Frysinger <vapier at gentoo dot org>
To: libc-alpha at sourceware dot org
Cc: Maxim Kuvyrkov <maxim at codesourcery dot com>,Dmitrieva Liubov <liubov dot dmitrieva at gmail dot com>
Date: Tue, 3 Jul 2012 16:34:31 -0400
Subject: Re: PATH: removing quadratic complexity strstr, strcasestr and strcasestr-nonascii
References: <CAHjhQ92pjrpesn+ai7N71V4Cqs_Ty5nO+dqtCCSzevyrDNmqfA@mail.gmail.com> <C3F6DE13-790C-441C-B1AD-D7504A11E759@codesourcery.com>

On Monday 02 July 2012 15:07:54 Maxim Kuvyrkov wrote:
> On 30/06/2012, at 3:31 AM, Dmitrieva Liubov wrote:
> > This patch removes SSE42 strstr, strcasestr and strcasestr-nonascii
> > because these SSE42 algorithms have quadratic complexity.
> > 
> > The patch was checked on x86_64 and x86_32.
> > 
> > ChangeLog:
> > 
> > 2012-06-29  Liubov Dmitrieva  <liubov.dmitrieva@gmail.com>
> > 
> >       * sysdeps/i386/i686/multiarch/Makefile: Update
> >       Remove strstr, strcasesrt, strcasestr-nonascii
> >       SSE42 optimizations since algos have quadratic complexity
> >       * sysdeps/i386/i686/multiarch/strcasestr-c.c: Delete
> >       * sysdeps/i386/i686/multiarch/strcasestr-nonascii.c: Delete
> >       * sysdeps/i386/i686/multiarch/strstr-c.c: Delete
> >       * sysdeps/i386/i686/multiarch/strstr.c: Delete
> >       
> >       * sysdeps/x86_64/multiarch/Makefile: Update
> >       Remove strstr, strcasesrt, strcasestr-nonascii
> >       SSE42 optimizations since algos have quadratic complexity
> >       * sysdeps/x86_64/multiarch/strcasestr-c.c: Delete
> >       * sysdeps/x86_64/multiarch/strcasestr-nonascii.c: Delete
> >       * sysdeps/x86_64/multiarch/strstr-c.c: Delete
> >       * sysdeps/x86_64/multiarch/strstr.c: Delete
> 
> While I don't have strong opinion about this patch, it doesn't seem right
> to throw away a perfectly good SSE42 implementation that outperforms the
> generic one by a factor of 2 on small needles.

+1
-mike

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References:
- Re: PATH: removing quadratic complexity strstr, strcasestr and strcasestr-nonascii
  - From: Maxim Kuvyrkov

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