[graphite] Weekly phone call notes

[Tobias Grosser <grosser at fim dot uni-passau dot de>]

Hi gcc developers, hi graphities

here are some notes from our weekly phone call. Unfortunately I missed
to send out the notes from the last two phone calls, but I hope to get
them out more regulary. Believe in me! ;-)

http://gcc.gnu.org/wiki/Graphite_Phone_Call/2009_04_29

Attendees: Li, Jan, Konrad, Sebastian, Tobias, David, Christophe 

      * Reductions: Diego OK with going out of SSA. 
              * Patch not yet ready. The higher code coverage exposes an
                IVSTACK bug. 
      * IVStack: Sebastian is working on removing it 
      * Data dependence analysis: Committed to graphite branch. 
              * Not yet enabled, as the data reference still does not
                bootstrap. The lexicographic smaller than constraint is
                not yet added. This is not wrong but very conservative.
                Dependence test should be enabled with
                -fgraphite-identity. 
      * Loop transformations: We need some simple transformations to
        check data dependency analysis. 
              * Pranav? We did not hear anything yet. 
      * Data reference: Last bugs have to be fixed. 
              * Not yet enabled. Blocks data dependence analysis. 
      * PCP: 
              * Jan Implemented simplification/canonicalization for
                expressions. This will allow a systematic translation of
                expressions to constraints. Jan will work on a reduced
                polyhedral interface that is used in PCP. First PCP
                integration in gcc - later extended by reductions. 
                
                No good representation for reductions for the general
                case. Like conditions and PHI nodes (Sebastian) Maybe
                for a subset of the reductions we can add commutativaty
                of operations. 
                
      * Autopar: Li prepared some patches to trigger autopar by
        graphite. 
              * Autopar failed in the graphite branch even without
                graphite enabled. It seems we introduced a bug while
                using some code of it for graphite. The breakage happens
                in the reductions part. 
      * Merge from trunk: 
              * Sebastian wants to work on this Changes in vectorizer
                Last merge 4 months ago Tried mid march but was
                difficult. So stopped because of ENOTIME. 
      * Parts of graphite working well?: The polyhedral part of the
        graphite architecture will be described 
              * in the Tobias' paper at the summit and the PCP part by
                Jan. 
      * Worldwide interest: Cristianno Martins from Brazil showed some
        interest 
              * http://gcc.gnu.org/ml/gcc/2009-04/msg00711.html 
                
              * We already have people from the US, Europe and China
                contributing.