[Pixman] add enable-cache-prefetch option

[Liu Xinyun]

OK. here is the work to clear all cache prefetch. Please review it. 3x



On Tue, Sep 21, 2010 at 11:36:30PM +0800, Soeren Sandmann wrote:
> Liu Xinyun <xinyun.liu at intel.com> writes:
> 
> >    This patch is to add a new configuration option: enable-cache-prefetch,
> > which is default yes.
> > 
> >    Here is a link which talks on cache issue.
> >    http://lists.freedesktop.org/archives/pixman/2010-June/000218.html
> > 
> >    When disable it on Atom CPU(configured with --enable-cache-prefetch=no),
> > it will have a little performance gain. Here is the patch.
> 
> I think the cache prefetch code should just be deleted outright. No
> benchmarks that I'm aware of show it to be an improvement.
> 
> 
> Thanks,
> Soren