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Re: Changing CFLAGS for i386 packages on x86_64



On Fri, 2006-07-14 at 10:06 +0200, dragoran wrote:
> Paul Howarth wrote:
> > On Fri, 2006-07-14 at 08:13 +0200, dragoran wrote:
> >   
> >> On i386 most of the packages are i386 and there are some i686 one like 
> >> kernel and glibc.
> >> On x86_64 there are some i386 packages installed by default too. Why are 
> >> they compiled with the same settings as on i386?
> >> On x86_64 it wont hurt enabling i686 (cmov) and see2 because all x86_64 
> >> cpus support this instructions.
> >>     
> >
> > Doing this would result in i386 packages in the x86_64 repo that are
> > different from the identically-named i386 packages in the i386 repo,
> > wouldn't it, since all Fedora arches are built from exactly the same
> > SRPMS?
> >
> > Paul.
> >
> >
> >   
> no it wont because they will be i686 builds and RPM_OPT_FLAGS would be 
> differnet so the same SRPM can be used.


but to what point?

I will actually here propose to stop doing i686 builds for most of the
things it's done now; cmov just isn't worth it, and if you want to use
SSE in 32 bit, that's not going to be cheap either (unlike 64 bit where
it's a standard part of the ABI); SSE in 32 bit is not "just used" by
gcc, only hand coded assembly uses it basically, and those can use .i386
just fine since generally they have a runtime detection mechanism.

And for optimization... even the i386 rpms are already optimized for
modern processors so there's no difference there either.


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