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Re: Linux doesn't follow x86/x86-64 ABI wrt direction flag
On Thu, Mar 6, 2008 at 11:06 PM, Andi Kleen <email@example.com> wrote:
> On Thu, Mar 06, 2008 at 12:56:16PM -0800, H. Peter Anvin wrote:
> > Richard Guenther wrote:
> > >
> > >A patched GCC IMHO makes only sense if it is always-on, yet another option
> > >won't help in corner cases. And corner cases is exactly what people seem
> > >to care about. For this reason that we have this single release, 4.3.0,
> > >that
> > >behaves "bad" is already a problem.
> > >
> > The option will help embedded vendors who can guarantee that it's not a
> > problem.
> For very very low values of "help".
> To be realistic it is very unlikely anybody will measure a difference
> from a few more or a few less clds in a program. It's not that they're
> expensive instructions and they normally don't happen in inner loops either.
> "If you enable this option you will get an optimization that you cannot
> measure" @)
Which is probably true for most of GCCs options. Oh wait - you can measure
the effect on compile-time and compile-time memory usage! :)