x86_64, 4.4 regression on optimization

[Richard Guenther]

On Mon, Jun 30, 2008 at 5:47 PM, Daniel Franke <franke.daniel@gmail.com> wrote:
>
> Hi all.
>
> Is anybody aware of regressions in the optimizer on x86_64?
>
> With latest SVN, my code runs nicely up to -O1, but goes haywire on -O2. This
> is not the case for 4.3.2 (both checkouts from 20080629).
>
> Any pointers to PRs or how to (easily) track down the offending option and
> code are be highly welcome. I think I did not go for optimizer problems
> before ...

Instead of searching for the optimization flag causing this I would suggest
to run the code through a profiler to spot the point in the source
that regresses
in performance.  It should then be not too difficult to compare the
optimized tree-dumps or the assembly of the regressed part - which is
also way more useful than a bugreport stating that option -ffoo makes things
worse.

Thanks,
Richard.