-march=pentium2 + -mtune=pentium4 faster then -march=pentium4?

[Nikolas Britton]

On 3/27/06, Kris Kennaway <kris at obsecurity.org> wrote:
> On Mon, Mar 27, 2006 at 01:05:13PM -0600, Nikolas Britton wrote:
> > Why does GCC produce faster code using "-march=pentium2
> > -mtune=pentium4" on a Pentium 4 chip versus plain -march=pentium4?
> >
> > Try it...
> >
> > CPUTYPE=pentium2
> > CFLAGS+= -mtune=pentium4
> > COPTFLAGS+= -mtune=pentium4
>
> Talk to the gcc developers (and provide benchmarks).
>

What would be an adequate, proof, benchmark? I've already run several
tests with nbench, testing all of the possible configurations of
-march and -mtune.


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