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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).


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

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