Re: [gentoo-user] USE="mmx mmxext sse sse2 ssse3 3dnow 3dnowext"

[Daniel Iliev <daniel.iliev@gmail.com>]

On Tue, 26 May 2009 22:07:10 +0100
Stroller <stroller@stellar.eclipse.co.uk> wrote:

> 
> On 26 May 2009, at 15:31, Daniel Iliev wrote:
> >
> >> Looks like `echo media-video/mplayer mmx mmxext sse sse2 ssse3
> >> 3dnow 3dnowext >> /etc/portage/package.use` unless someone else is
> >> able to be more informative.
> >>
> >
> > Yes, just add "cpudetection" to those or put it in in make.conf.
> 
> Apparently not!
> 
> I rebuilt using that flag & received this message:
> 
>   * You've enabled the cpudetection flag.  This feature is
>   * included mainly for people who want to use the same
>   * binary on another system with a different CPU architecture.
>   * MPlayer will already detect your CPU settings by default at
>   * buildtime; this flag is used for runtime detection.
>   * You won't need this turned on if you are only building
>   * mplayer for this system.  Also, if your compile fails, try
>   * disabling this use flag.
> 
> I think this speaks for itself.
> 
> Stroller.
> 
>

I can't see any problems here?

The idea is to enable the "cpudetection" flag and all USE flags which
correspond to one or another extended instruction set (EIS)  and build
mplayer with support for all EIS plus extra code for "*run-time* cpu
detection". This way mplayer *could* use all EIS that are implemented
in its code, but *will* detect which EIS are supported by your CPU and
use only them. In other words the same binary will use different EIS on
different CPUs.

There could be problems if you had enabled all the EIS flags globally
(in make.conf) instead only for mplayer, because other programs don't
have the "run-time cpu detection" feature and will fail in their
attempts to use for example 3dnow! on an Intel CPU.

I hope I was clear enough, apologies for my Englush.

-- 
Best regards,
Daniel