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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 <andi@firstfloor.org> 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! :)

... *runs*


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