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Re: [PATCH] Don't use SSE4_2 instructions on Intel Silvermont Micro Architecture.
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Dmitrieva Liubov <liubov dot dmitrieva at gmail dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Mon, 17 Jun 2013 18:37:29 +0200
- Subject: Re: [PATCH] Don't use SSE4_2 instructions on Intel Silvermont Micro Architecture.
- References: <CAHjhQ93=uegeZg9iTqoJ+PFuUrvn8e2mA8tZ96Jy4CaV6aPbWg at mail dot gmail dot com>
On Mon, Jun 17, 2013 at 07:14:31PM +0400, Dmitrieva Liubov wrote:
> The second patch for Silvermont we hope to have in 2.18.
>
> SSE4_2 instructions can be executed on Silvermont, so some string
> functions like strchr where sse4_2 version is available were switched
> to sse4_2 versions. But it produces huge regressions.
>
> It would be good to switch SSE4_2 bit off.
>
> Tested on my machine.
> Ok to commit?
>
Not yet.
There are strspn/strcspn/strpbrk which where SSE4_2 gives big boost.
If they also have regression then I am ok with this patch. Otherwise I
would look how change ifunc of strspn et al.