[Sugar-devel] Planning for the future (Samuel Greenfeld)

[James Cameron]

On Wed, Feb 25, 2015 at 04:20:02PM -0600, Jerry Vonau wrote:
> > On February 25, 2015 at 3:09 PM James Cameron <quozl at laptop.org> wrote:
> > On Wed, Feb 25, 2015 at 01:20:19PM -0600, Jerry Vonau wrote:
> > > I know this is not a sugar issue directly, more of an OLPC issue
> > > but since Fedora F12 the entire i686 platform's userland is
> > > being compiled with -mtune=atom which would use sse. This causes
> > > problems for some parts of sugar now that java is being used
> > > more and the XO-1 lacks sse.  Fixing one package that uses sse
> > > might fix one issue but this is really a distro wide setting and
> > > other issues may float to the top in other areas.
> >
> > Thanks, wasn't aware -mtune=atom was being used upstream.  It
> > explains a lot.  First build after Fedora 11 was 11.2.0 (os874)
> > using Fedora 14.  So if we rebuild everything there may be an
> > improvement?  That's probably something that can be set running as
> > a test.
> >
> 
> Wouldn't all the rpms used need to be recompiled to ensure mtune is
> set to match throughout the distro?

Don't think so.  Check my logic:

The GCC documentation you referenced described -mtune as "Tune to
cpu-type everything applicable about the generated code, except for
the ABI and the set of available instructions. "

-march is more significant, as "Generate instructions for the machine
type cpu-type. The choices for cpu-type are the same as for
-mtune. Moreover, specifying -march=cpu-type implies
-mtune=cpu-type. "

If the ABI were different between i586 and i686 arch, that would be
very interesting.

> Tall order IMHO, good luck

;-)

For the moment, I'm doing a mock --rebuild of webkitgtk3 with
--arch=i586, and the logs so far show "-march=i586 -mtune=generic"
instead of "-march=i686 -mtune=atom":

$ grep mtune build.log | grep i586 | wc --lines
8564
$ grep mtune build.log | grep atom | wc --lines
0
$ 

> Jerry

-- 
James Cameron
http://quozl.linux.org.au/