Optimizations

DJ Lucas dj_me at swbell.net
Wed Nov 27 23:55:52 PST 2002


Steve Crosby wrote:

> adrians at aska.com.pl (Adrian Smarzewski) wrote in
> news:20021127221451.56fe39cc.adrians at aska.com.pl:
>
>
> >>http://hints.us.linuxfromscratch.org/hints/crosscompiling-x86.txt
> >>
> >
> >There is no answer for that questions there. For example:
> >
> >1) Does configure script detect my machine and let gcc optimize the
> >code for my processor type? (i686 for example)
>
>
> Yes.  And as a result, will use instructions that *will not run* on lower
> class machines (i.e. Pentium).  You must pass the host/target/build
> parameters to the applicaitons configure script in order to have it 
> compile
> instructions that will run on Pentium and above machines.  The hint
> mentioned gives detailed instructions on how to accomplish this.


Okay.... Where does glibc and gcc's configure script get this info? 
 From proc?  From the currently running glibc?  From the static gcc? 
 From the currently running kernel?  Reason I'm asking...

COMPLETE SPECULATION:  if configure gets the arch info from the 
currently running kernel, then make your build environment's kernel for 
the lower arch..and problem solved.  Right?  Or if it gets it from 
/static/bin/gcc then it needs be done in the build there. etc.  I know 
nothing of this, just a guess.  But finding out where configure gets the 
arch info is a start so maybe you don't have to remember the extra 
switches for each package if you are building for multiple archs (lower 
than the one building on).  Maybe somebody who knows more would be able 
to put an educated comment on the way I'm thinkin here (or just tell me 
I dont' know what the hell I'm talkin about). ;-)

DJ

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