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Re: i686 ---> i586, i386 ---> i586, x86_64 stays the same



Jan Pazdziora wrote:
On Sun, Apr 05, 2009 at 08:05:41PM -0400, Will Woods wrote:
Building for i686 gives *no* real performance benefit[1], but breaks
support for i586 machines - Via C7-based netbooks, AMD Geode (e.g. the
OLPC XO-1), and so on.

-w

[1] except on in-order CPUs like Atom and the original Pentium

Does this mean that for Atom-based machines we are taking the risk of
introducing some slowdown?

I compiled scimark using march=i686/i586 (both with tune=i686) and on an atom notebook the scores were 166+/-1 for both versions. Any change in performance is in the noise region. There are code changes but according to objdump the 586 compiled version did not use any CMOVs.


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