Hi,
On 07 Feb 2007, at 15:22, Diego Novillo wrote:
Kenneth Hoste wrote on 02/07/07 08:56:
[1] Almagor et al., Finding effective compilation sequences (LCES'04)
[2] Cooper et al., Optimizing for Reduced Code Space using
Genetic Algorithms (LCTES'99)
[3] Almagor et al., Compilation Order Matters: Exploring the
Structure of the Space of Compilation Sequences Using Randomized
Search Algorithms (Tech.Report)
[3] Acovea: Using Natural Selection to Investigate Software
Complexities (http://www.coyotegulch.com/products/acovea/)
You should also contact Ben Elliston (CC'd) and Grigori Fursin
(sorry, no email).
Ben worked on dynamic reordering of passes, his thesis will have
more information about it.
Grigori is working on an API for iterative an adaptive
optimization, implemented in GCC. He presented at the last HiPEAC
2007 GCC workshop. Their presentation should be
available at http://www.hipeac.net/node/746
I actually talked to Grigori about the -Ox flags, I was at the HiPEAC
conference too ;-) I didn't include references to his work, because
my aim wouldn't be at reordering of passes, but just selecting them.
I understand that reordering is of great importance while optimizing,
but I think this project is big enough as is.
Some other questions:
* I'm planning to do this work on an x86 platform (i.e.
Pentium4), but richi told me that's probably not a good idea,
because of the low number of registers available on x86. Comments?
When deriving ideal flag combinations for -Ox, we will probably
want common sets for the more popular architectures, so I would
definitely include x86.
OK. I think richi's comment on x86 was the fact that evaluating the
technique we are thinking about might produce results which are hard
to 'port' to a different architecture. But then again, we won't be
stating we have found _the_ best set of flags for a given goal...
Thank you for your comment.
* Since we have done quite some analysis on the SPEC2k
benchmarks, we'll also be using them for this work. Other
suggestions are highly appreciated.
We have a collection of tests from several user communities that we
use as performance benchmarks (DLV, TRAMP3D, MICO). There should
be links to the testers somewhere in http://gcc.gnu.org/
OK, sounds interesting, I'll look into it. In which way are these
benchmarks used? Just to test the general performance of GCC? Have
they been compared to say, SPEC CPU, or other 'research/industrial'
benchmark suites (such as MiBench, MediaBench, EEMBC, ...) ?
* Since there has been some previous work on this, I wonder why
none of it has made it into GCC development. Were the methods
proposed unfeasible for some reason? What would be needed to make
an approach to automatically find suitable flags for -Ox
interesting enough to incorporate it into GCC? Any references to
this previous work?
It's one of the things I would like to see implemented in GCC in
the near future. I've been chatting with Ben and Grigori about
their work and it would be a great idea if we could discuss this at
the next GCC Summit. I'm hoping someone will propose a BoF about it.
I'm hoping my ideas will lead to significant results, because I think
this is an important issue.
greetings,
Kenneth
--
Statistics are like a bikini. What they reveal is suggestive, but
what they conceal is vital (Aaron Levenstein)
Kenneth Hoste
ELIS - Ghent University
[EMAIL PROTECTED]
http://www.elis.ugent.be/~kehoste
