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

[Charlie Brej]

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.