[Bug target/41989] Code optimized for AMD Geode is slower than generic

[ubizjak at gmail dot com]

------- Comment #22 from ubizjak at gmail dot com  2009-11-10 07:45 -------
(In reply to comment #20)
> Yes K6 is the best fallback for geode-lx, while pentium-mmx is the best one for
> geode.

BTW, recommended fallback is K6-2.

> I need to know if this new -march argument will be added so I edit the kernel
> patch.

Actually, according to gcc documentation, "-march=geode" is intended
specifically for geode-lx and switches on features and tuning options for
geode-lx.

If you want to play with tuning options, you can check differences between
m_PPRO and m_GEODE in i386.c, ix86_tune_features. By changing these settings,
you can narrow down which flag causes a regression. I would suggest to start
with flags that mention partial register stalls.

OTOH, you can also play with "-march=geode, -mtune=i686" to switch on various
tuning flags.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41989