[Mesa-dev] [PATCH v1 1/5] meson: compilation flags for sse

[Sergii Romantsov]

Thanks for a comments. I see the most of that patches have no sense,
probably, except one:

Yeah, I think we should land that if it fixes the build for 32bit x86.

Here is: https://patchwork.freedesktop.org/patch/259176/

On Mon, Oct 29, 2018 at 6:04 PM Dylan Baker <dylan at pnwbakers.com> wrote:

> Quoting Sergii Romantsov (2018-10-29 01:44:28)
> > Hello,
> >
> >     What problem are we solving?
> >
> >     That we don't get fast paths in rounding.h by default on i686, I
> think?
> >
> > Yes, it adds optimization for rounding.h. On x86_64 msse is enabled by
> default
> > (as example by gcc).
> > And additionally helps to fix autotools 32b build (missed linkage with
> m-lib if
> > no optimization).
> >
> >
> >     This will make the code non-portable from an SSE capable system to a
> >     non-sse
> >     capable system. That's a pretty old system at this point (Pentium
> III and
> >     Athlon
> >     XP)
> >
> > As i found in gcc-docs (https://gcc.gnu.org/onlinedocs/gcc-4.5.3/gcc/
> > i386-and-x86_002d64-Options.html) exactly mentioned systems are supports
> SSE.
> > But in the patch i'm checking if -msse supported by compiler.
> > If its incorrect than does it mean that compiler doesn't based on system
> > capabilities? And does it mean that adding option -msse4.1 is also
> enabled in
> > wrong way?
>
> Right, the compiler can support instructions the "build" machine (computer
> running the compiler) can't run. Even for builds of the same architecture.
>
> No, the -msee4.1 case in src/mesa is different. We have a runtime check in
> libmesa that detects sse4.1 features at run time and loads the sse4.1
> optimized
> functions if it can, or falls back to non-sse4.1 versions if it can't.
>
> > I'm cloning gcc to check how it supports 'sse' and if it based on system
> > capabilities. Also we may try to add some possibility to check
> cpu-capabilities
> > (around cpuid).
> > But if we don't need such optimization, than it will be nice at least to
> fix
> > autotools 32b build (https://patchwork.freedesktop.org/patch/258659/) -
> i will
> > update patch just by linking -lm with mesautil.
>
> Yeah, I think we should land that if it fixes the build for 32bit x86.
>
> Dylan
>


-- 
Sergii Romantsov
GlobalLogic Inc.
www.globallogic.com
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