[graphite] Weekly phone call - Automatic parallelization

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

Hi,

to keep everybody updated what is happening in the GRAPHITE branch, I
would like to post the notes of our weekly phone call.

Attendees: Razya, Li, Konrad, Jan, Tobi, David, Sebastian, Christophe 

Discussed topics: 

      * Data dependencies: Tobias committed a patch filling the access
        polyhedrons 
              * Not yet enabled as there are some bootstrap bugs 
              * All arrays access the same alias set 
              * Reductions are not yet included in the access
                polyhedrons (Same as last week, but now really
                committed) 
      * Bug in building of scattering matrices fixed. 
      * Bug in condition detection on its way to be fixed. 
      * Automatic Parallelization: 
              * Li will start integrating graphite and code generation
                (If his summer of code proposal is accepted) 
              * Mark all loops parallel if new flag
                "-fgraphite-force-parallel" is set. 
              * How to connect auto par? 
                      * Directly in graphite code generation (clast to
                        gimple): We call the autopar backend after
                        generating a serial gimple loop. This is the
                        easiest approach. Also we still access to the
                        polyhedral information so we can use it to give
                        autopar more information. 
                      * By annotating loops: In the graphite pass we
                        annotate gimple loops as parallel . Later the
                        autopar pass is scheduled, which bypasses its
                        analysis if it sees a loop annotated parallel.
                        This allows to schedule scalar optimizations in
                        between graphite and autopar, but we loose the
                        polyhedral information. As we do not need the
                        additional information, but we definitely need
                        some scalar optimization like PRE the
                        "annotating loops" approach seems to be our
                        first try. 

The notes of all calls are available on the wiki:
http://gcc.gnu.org/wiki/Graphite_Phone_Call

More information about graphite at:
http://gcc.gnu.org/wiki/Graphite

Tobi