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Re: dataflow branch merging plans.
- From: Mark Mitchell <mark at codesourcery dot com>
- To: Bernd Schmidt <bernds_cb1 at t-online dot de>
- Cc: Kenneth Zadeck <zadeck at naturalbridge dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>, Steven Bosscher <stevenb dot gcc at gmail dot com>, "Park, Seongbae" <seongbae dot park at gmail dot com>, "Bonzini, Paolo" <bonzini at gnu dot org>, Serge Belyshev <belyshev at depni dot sinp dot msu dot ru>, richard dot earnshaw at arm dot com, echristo at apple dot com, "Pinski, Andrew" <andrew_pinski at playstation dot sony dot com>, "Weigand, Ulrich" <Ulrich dot Weigand at de dot ibm dot com>, Ian Lance Taylor <iant at google dot com>, "Edelsohn, David" <dje at watson dot ibm dot com>, "Berlin, Daniel" <dberlin at dberlin dot org>
- Date: Mon, 28 May 2007 13:10:40 -0700
- Subject: Re: dataflow branch merging plans.
- References: <46543F49.8060104@naturalbridge.com> <46557380.9060105@t-online.de> <4655EF12.6060605@naturalbridge.com> <4656AFFD.1040605@t-online.de>
Bernd Schmidt wrote:
> Still, 6% compile time regression on several targets and typically a
> (very small) regression in SPEC scores - am I the only one who's not
> impressed? We don't normally accept patches with these kinds of
> results, and I don't see why we should make an exception here.
If Kenny commits to continuing to work on these issues, I think we
should trust him. We've been around on this issue before, and we all
need to bear in mind that the point of the dataflow branch is not to
have better code immediately, but to have infrastructure that helps us
get better code. So, as long as we're not significantly moving
backwards on generated code performance, I'm not worried about that
aspect.
As for compilation time, yes, that's a concern. However, I think it's
reasonable to move forward, as long as Kenny commits to continuing to
work on this. That might include, for example, converting more passes
to use the new machinery, so as to get more benefit from it.
Kenny, I think that what I would like to hear is that, roughly in order
of urgency:
(1) You will promptly address any regressions introduced by the merge
for all targets, provided you get a decent test-case.
(2) You will continue to work on integrating the new dataflow machinery
into the compiler, to help with the compile-time performance and to help
get better results out of the passes that roll their own dataflow stuff.
(3) You will promptly fix up coding standards issues that people point out.
That's what I understand you to be saying, and on that basis, I think
you should proceed with the merge. If there are objections from other
global write maintainers in the next 48 hours, then let's try to get
consensus before you go ahead. However, I would hope that we can all
agree to let Kenny move forward with this important piece of infrastructure.
Thanks,
--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713