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Re: [PATCH][BZ #12100] strstr with unaligned loads.
- From: Rich Felker <dalias at aerifal dot cx>
- To: OndÅej BÃlka <neleai at seznam dot cz>
- Cc: libc-alpha at sourceware dot org
- Date: Sun, 25 Aug 2013 11:54:06 -0400
- Subject: Re: [PATCH][BZ #12100] strstr with unaligned loads.
- References: <20130825090758 dot GA23686 at domone dot kolej dot mff dot cuni dot cz>
On Sun, Aug 25, 2013 at 11:07:58AM +0200, OndÅej BÃlka wrote:
> Hi,
>
> This patch continues to remove ineffective sse4.2 functions. Now we
> focus on strstr.
>
> I use a techique of doing vectorized search for first pair of characters
> which is fastest in practice.
What do you do after finding the first pair? As far as I can tell,
this approach is only useful at the start of the string. Once you've
gotten into two-way, searching for the next occurrence of the first
two characters is not a useful operation. Of course it looks to me
like the hideous quadratic-runtime SSE4.2 code is still present...
This just needs to be removed...
Rich