Re: Good optimize idea! (Re: ramblings about old hardware, gzip, bz2, and pentium opts)
On 7 Dec 1999, Goswin Brederlow wrote:
> Onno <Onno@Willem.Alexanderschool.nl> writes:
>
> > At 03:04 PM 12/6/99 +0100, Tomasz Wegrzanowski wrote:
> > [snip]
> > >Didnt mean : use 486-or-better-only instructions
> > >Mean : use optimalizations for 486 using only 386-or-better instructions
> > >Is this ok ?
> > >486 is much more similar to modern hardware than 386 was.
> >
> > This sounds reasonable.
> >
> > The old i386 stuff can still run it, but the binaries are
> > optimized for somewhat modern hardsware.
> >
> > Great idea indeed!
>
> gcc will ALWAYS produce code that runs on a i386, as I was
> told. Exceptions of cause are direct asm instructions in the code
> (like MMX optimizations).
There are two different kinds of flags you can pass. One simply optimises
timings etc, whilst only using the i386+FPU instruction set. The other
actually uses the new instructions introduced on the pentium and later.
Since these instructions aren't that important, it doesn't make much
difference for most applications (MMX being one obvious exception) and so
the latter flag simply isn't passed.
In any case, it's not worth it :)
Jules
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