Re: [gentoo-user] gcc-4.3.x and Core 2 Duo, safe way

[Robert Bridge]

On Mon, 09 Jun 2008 06:43:41 +0100
Graham Murray <graham@×××××××××××.uk> wrote:

> Andrew Gaydenko <a@××××××××.com> writes:
>
> > gcc-4.3.1 is umasked now. I'm on ~amd64 with Core 2 Duo CPU. Is it
> > sufficient just to set
> >
> > CFLAGS="-O2 -march=core2 -mtune=core2 -pipe"
> >
> > instead of
> >
> > CFLAGS="-O2 -march=native -mtune=native -pipe"
> >
> > which I have in make.conf now? Are there any other things to do?
>
> Should the two not be equivalent? On a core2 processor, should
> -march=native not generate code for the core2?

If we are going to get picky about this, it should be noted the -march
implies -mtune, at least according to the gcc man pages, and I will
trust them to know. 

I can't remember which will actually be implemented if both are
specified, but march is a essentially a stronger version of mtune which
breaks compatibility with other CPUs within the same ARCH type. (i.e.
march=pentium4 may not run on a pentium3, but should run faster than
mtune on a pentium4)

RobbieAB
-- 
gentoo-user@l.g.o mailing list