RE: 15 Sept notes from GCC improvement for Itanium conference call

["Mark K. Smith" <mksmith at gelato dot org>]

Another correction:

Shin-ming Liu (HP) attended the meeting. In fact, he led the call :-) 

> -----Original Message-----
> From: gcc-owner@gcc.gnu.org [mailto:gcc-owner@gcc.gnu.org] On Behalf
> Of Mark K. Smith
> Sent: Monday, September 19, 2005 4:00 PM
> To: Gelato-GCC; GCC
> Subject: 15 Sept notes from GCC improvement for Itanium conference
> call
> 
> ON THE CALL: Bob Kidd (UIUC), Vladimir Makarov (Red Hat), Mark Smith
> (Gelato), Wenguang Chen (Tsinghua), Mark Davis (Intel), Diego
> Novillo
> (Red Hat), Andrey Belevantsev (RAS), Dan Berlin (dberlin.org), Wen-
> mei
> Hwu (UIUC)
> 
> The call covered:
> - current status / updates on the 3 improvement areas
> - brain storming how to help out Dan with the alias analysis
>       improvement TODO list
> - GCC session at Brazil Gelato meeting
>     - planned presentations (tentative schedule):
>            - Diego Novillo (Monday 10/3, 7:30 to 8pm)
>            - Shin-ming Liu (Monday 10/3, 8 to 8:30pm)
>            - Bob Kidd (Monday 10/3, 8:30 to 9pm
>            - Canqun Yang (Tuesday 10/4, 10 to 10:30am)
>     - general discussion (Tuesday 10/4, 10:30 to 11:30am)
>            - next steps, action items
>            - continue discussion on alias analysis improvements
>              and determine concrete ways to help
>            - review and update IA-64 project list
>            - a discussion on corporate IP needed for GCC --
>              can companies donate IP to GCC?
>     - planned attendance (from those on the call)
>            - Bob Kidd
>            - Shin-ming Liu
>            - Mark Davis
>            - Wenguang Chen
>            - Diego Novillo
>            - Mark Smith
> 
> Additional detail can be found below.
> 
> NEXT MEETING: At Gelato Meeting in Porto Alegre, Brazil, October
2-5,
> 2005.
> 
> Bob Kidd:
> ---------
> The patch to move superblock formation is ready to go and tested on
> x86, x86_64, and ia64.  I'll post it to gcc-patches and post a
> message to the gcc mailing list with details shortly.
> 
> Dan Berlin:
> -----------
> The current status of the aliasing work is that work is proceeding
> on
> both intraprocedural and interprocedural call clobbering.  Most of
> the
> infrasturcture to get it to be able to be start work on the actual
> improved algorithms and use the results is done, or will be done by
> next week.
> 
> The main task that it would be helpful to have other people work on
> would be the "Aliasing Oracle" (pairwise query system for
> statements)
> implementation for tree-ssa.  The backend already uses a query
> system
> exclusively (because it's aliasing is almost exclusively type
based).
> This is an alternate way of representing and accessing the aliasing
> results that can provide better information (though more expensive
> to
> query) than the current representation provides.  Our current
> analyses
> can actually provide better information that we represent.  The
> eventual plan is to have a hybrid where optimizations use the
> current
> "virtual ssa" form to discover what appear to be things that alias,
> then query the "Aliasing Oracle" to see if it can disambiguate the
> aliases further if necessary (IE it decides it wants to try to sink
> a
> store past that point, or whatever).
> 
> The implementation can start out simple, (IE even something that
> simply looked at base + offset of pointers in the two statements,
> and
> gave answers, would be a good start)  and I'm more than happy to
> help
> mentor/introduce anyone to how to work with GCC's tree-ssa form to
> make this work, if they want to help implement it.  Seriously.  I'm
> really more than happy to spend hours teaching someone how to work
> with this stuff.  IBM Research is also more than happy to let me do
> so.  I already help Ken Zadeck a lot with understanding how to get
> things done in GCC, and he has become quite adept at working with
> GCC
> in a short time (< 6 months).  If somebody has the resources to
> provide someone competent to work on aliasing, I'm glad to put them
> to
> work for you being productive on GCC :).
> 
> Vladimir Makarov:
> -----------------
> Zdenek Dvorak submitted a patch implementing prefetching on tree-ssa
> recently.  It would be interesting to look how it will work for
> Itanium.
> 
> HP and Intel are interesting in gcc performance improvement.  If HP
> and Intel guys know for sure that gcc uses their patents or some
> their
> patents could be used for gcc performance improvement, it would be
> good to give FSF a permission to use the patents in gcc.  On the
> other
> hand, investigating what patents gcc uses might be a dangerous thing
> because any compiler most probably uses algorithms patented by other
> companies.
> 
> Diego Novillo:
> --------------
> I spoke briefly about GCC's development process:
> 
>   * Legal issues need to be resolved early.  Assign personal and
>     corporate copyright to the FSF.
>   * It's important to participate in the main development lists (gcc
>     and gcc-patches).  IRC is a good meeting place, too.
>   * GCC works in three main stages:
>         o Stage 1: Everything goes.
>         o Stage 2: Stabilization.
>         o Stage 3: Bug fixes only.
>   * Work that spans multiple GCC stages is done on CVS branches in
> the
>     main FSF repository.
>   * I will present at the next Gelato conference.  I'll describe
> GCC's
>     internals, its development process, what is going on and what
>     needs to be done.