What is exactly in O2?

[Jean Francois Martinez]

I would like to learn how can I determine exactly  the set of compile flags who
are triggered by O2.  The doc is vague on this point: 'it says anything who
increases speed but does not increase size".  However some performanxce issues
lend me to think that the set of flags varies depending on what value you set
for processor and that some parm who increases size could be triggered behind
the scenes.

Concretely on Pentium IIs and IIIs I have found that siome code goes
significantly faster if you compile it with  cpu=i386 than with arch=i686.  But
I have found that on that code a certain alignment flag gave no effect with
cpu=i386 and a big speed bonus to arch=i686 placing it ahead.  This suggests
that selecting cpu=i386 had triggered it on the first place and that is not
true with arch=i686

A subsidiary question if this is the right place to ask this kind of questions.


								JF Martinez