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Re: -O3 and new optimizations in 4.4.0
On Fri, Apr 24, 2009 at 01:34:37PM -0700, Andi Kleen wrote:
> Robert Dewar <dewar@adacore.com> writes:
>
> > Sebastian Pop wrote:
> >> On Fri, Apr 24, 2009 at 08:12, Robert Dewar <dewar@adacore.com> wrote:
> >>>> What would we have to do to make PPL and CLooG required to build GCC?
> >>> Why would that be desirable? Seems to me the current situation is
> >>> clearly preferable.
> >> To enable loop transforms in -O3.
> >
> > To me, you would have to show very clearly a significant performance
> > gain for typical applications to justify the impact of adding
> > PPL and CLooG. I don't see it. If you want these transformations
> > you can get them, why go to all this disruptive effort for the
> > default optimization case?
>
> I think his point was that they would be only widely used if they
> were part of -O3 because likely most users are not willing to
> set individual -f optimization flags.
Agreed. It might be a wise idea to include them in -O3 in 4.5,
provided that we are confident by then that they are a consistent win.
At that stage the libraries could be required.