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Re: What architecture are we?



Brian C White <bcwhite@verisim.com> writes:

> A better alternative, I think, would be to have the GCC maintainer tweak
> GCC just a bit so its default behavior conforms to the specifications
> laid down by our illustrious leader (hi, Bruce!).  I would suggest:
>
>  - optimize for i486 (maybe Pentium)
>  - use no instructions not available on the i386.

Code generated with -m386 code runs faster on Pentium machines than
code generated with -m486.  Hence, in the Linux kernel (in addition to
-O2 and such) these optimizations are used:

 i386:  -m386
 i486:  -m486
 i586:  -m486 -malign-loops=2 -malign-jumps=2 -malign-functions=2

The -malign options reduce the bloating of -m486 code and speed it up
on Pentiums.  I suggest that the GCC maintainer:

 - add a -m586 option that is equivalent to the above
 - make -m586 default if -m386, -m486, and -m586 are not specified
   and make this relatively easy to change for people running i486 or
   i386 machines

This may be more appropriate for the upstream GCC maintainer(s).

Dan

-- 
Daniel Quinlan                  http://www.pathname.com/~quinlan
quinlan@pathname.com            quinlan@transmeta.com (at work)

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