[Mesa-dev] [PATCH V2] mesa: Permanently enable features supported by target CPU at compile time.

[Timothy Arceri]

On Sat, 2014-11-08 at 18:25 +0000, Emil Velikov wrote:
> On 08/11/14 08:35, Siavash Eliasi wrote:
> > This will remove the need for unnecessary runtime checks for CPU features if
> > already supported by target CPU, resulting in smaller and less branchy code.
> > 
> A comment I could not withheld based on your earlier post - "We require
> micro-benchmark for this code. It will take me hours to find why mesa is
> so slow now :P"

Hehe, you are technically correct, the best kind of correct.

>  
> Ideally mesa should have an infrastructure/farm that handles regressions
> - be that performance or otherwise. Pretty sure some companies have such
> features but those seem to be hidden behind locked doors :'(

I considered trying to work on a solution for this where anyone could
volunteer their machine to run such tests and send the results back to a
central server. But in the end its a pretty big project to get something
like this working correctly, and making it easy to setup thus
participate in.

I guess you could leverage something like the oibaf ppa to start with
rather than pulling down each commit and building. Anyway a much bigger
project than what I have time for at the moment.

> 
> But on a more mature note, currently only cpu_has_xmm
> (_tnl_generate_sse_emit) and cpu_has_sse4_1(vbo_get_minmax_index) are
> actually useful, with the former of questionable amount :P
> 
> Can you confirm that it does not cause issues with "interesting" setups
> such as https://bugs.freedesktop.org/show_bug.cgi?id=71547
> 

I think this patch should be find in this case as the solution there was
to wrap the code with #ifdef __SSE4_1__ which is what makes this patch
work. 

> 
> Thanks
> Emil
> 
> > V2:
> > - Removed the SSSE3 related part for the not yet merged patch.
> > - Avoiding redefinition of macros.
> > ---
> >  src/mesa/x86/common_x86_features.h | 26 ++++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> > 
> > diff --git a/src/mesa/x86/common_x86_features.h b/src/mesa/x86/common_x86_features.h
> > index 66f2cf6..65634aa 100644
> > --- a/src/mesa/x86/common_x86_features.h
> > +++ b/src/mesa/x86/common_x86_features.h
> > @@ -59,13 +59,39 @@
> >  #define X86_CPUEXT_3DNOW_EXT	(1<<30)
> >  #define X86_CPUEXT_3DNOW	(1<<31)
> >  
> > +#ifdef __MMX__
> > +#define cpu_has_mmx		1
> > +#else
> >  #define cpu_has_mmx		(_mesa_x86_cpu_features & X86_FEATURE_MMX)
> > +#endif
> > +
> >  #define cpu_has_mmxext		(_mesa_x86_cpu_features & X86_FEATURE_MMXEXT)
> > +
> > +#ifdef __SSE__
> > +#define cpu_has_xmm		1
> > +#else
> >  #define cpu_has_xmm		(_mesa_x86_cpu_features & X86_FEATURE_XMM)
> > +#endif
> > +
> > +#ifdef __SSE2__
> > +#define cpu_has_xmm2		1
> > +#else
> >  #define cpu_has_xmm2		(_mesa_x86_cpu_features & X86_FEATURE_XMM2)
> > +#endif
> > +
> > +#ifdef __3dNOW__
> > +#define cpu_has_3dnow		1
> > +#else
> >  #define cpu_has_3dnow		(_mesa_x86_cpu_features & X86_FEATURE_3DNOW)
> > +#endif
> > +
> >  #define cpu_has_3dnowext	(_mesa_x86_cpu_features & X86_FEATURE_3DNOWEXT)
> > +
> > +#ifdef __SSE4_1__
> > +#define cpu_has_sse4_1		1
> > +#else
> >  #define cpu_has_sse4_1		(_mesa_x86_cpu_features & X86_FEATURE_SSE4_1)
> > +#endif
> >  
> >  #endif
> >  
> > 
> 
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