Changing CFLAGS for i386 packages on x86_64

[Arjan van de Ven]

On Fri, 2006-07-14 at 10:47 +0200, dragoran wrote:
> Arjan van de Ven wrote
> >> 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.
> >
> >   
> what do you mean by not used by gcc? there are flags to use it -msse2 ...
> many apps have runtime detection and use handcoded assembly but not all 
> of them

just because gcc has a flag for something doesn't mean that it will
magically start using it for applications and make those applications go
faster.... because it won't for -msse2.

Truely taking advantage of SSE means that the ABI needs to change (like
x86-64 did from the start); and the moment you do that you might as well
not bother; the entire purpose of i386-on-x86 is to use legacy binaries,
which have the fixed, non-SSE ABI.