[wplug] what is optimized by -march in gcc?

[Vanco, Don]

Bill Moran [wmoran at potentialtech.com] wrote:
> Juan Zuluaga wrote:
>> I realized that many packages I compile by the "./configure;make;make
>> install" cycle use -march=i586 by default.
>> But, lucky me, I do have a Pentium MMX 266 in my machine :) .
>> So, I am tempted to type ./configure
>> CFLAGS="-march=pentium-mmx". Would that make the application foo run
>> faster,
> 
> Probably.  See:
> http://www.potentialtech.com/wmoran/source.php
	Interesting page - it might be kind of cool to take a distro
like Gentoo and install on a "like system" (of P4 class) twice, once
optimized for i386 and once optimized for i686 and compare things like
boot time, browser performance, OpenOffice run-times, etc.  I recall
when Mandrake made the leap from an i386 to an i586 base compile and the
overall performance increase was notable.
	It's also interesting to note that this flexibility (in open
source) has not been taken advantage of by Red Hat - for whatever reason
they've not made the leap to at least i586 on the Enterprise products -
even though the minimum hardware requirements exceed that i386 compile.
I have tried to re-compile the entire distro in the 2.1 days - but there
were not that many source packages that even had optimizations for
586/686.

Don