[PATCH] Don't use SSE4_2 instructions on Intel Silvermont Micro Architecture.

[Ondřej Bílka]

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.