Re: dataflow branch merging plans.

["Steven Bosscher" <stevenb.gcc@gmail.com>]

On 5/24/07, Bernd Schmidt <bernds_cb1@t-online.de> wrote:
> Kenneth Zadeck wrote:
> > I believe that the dataflow branch is now ready to merge into the
> > mainline.  We have fixed almost all of the performance problems
> > associated with it.  While there are still some left, we feel
> > confident that these can be addressed during the rest of stage I and
> > during stage II.
>
> Vlad's last benchmark run still showed up to 11% compile time
> regression, didn't it?

No, 8% in ia64, and somewhere between 5% and 6% on the other targets
Vlad's tested.  The 5-6% is mostly due to computing more accurate
liveness information and keeping the operands cache up to date. We'd
win a significant amount of time back if more passes would actually
use this information (esp. gcse's CPROP, and regmove, and combine).
The additional slowdown for ia64 is in the scheduler, which apparently
has more insns available to schedule. Note that the scheduler on ia64
is already dog slow even on the trunk. The DFA for Itanium is the
problem here.

Gr.
Steven