Re: Why not 03 ?
On Thu, May 29, 2014 at 12:21:06PM -0700, Russ Allbery wrote:
> Xavier Roche <xavier@debian.org> writes:
>
> > I have a rather silly question: most (all ?) packages are built by
> > default with -02 - something which is inherited from autotool's '-g -O2'
> > default flagsd, I presume.
>
> > Is -O3 considered too dangerous ? (AFAICS, potential issues are mainly
> > present in O2) Or is it considered worthless because the performance
> > gain would be really low ?
>
> Historically, -O3 has usually been slower than -O2 for a lot of software
> because the aggressive loop unrolling increases code size and interferes
> with processor caching strategies. I don't know if that's now been fixed
> in GCC, but that's probably much of the historical reason.
That's still true.
Mike
Reply to: