On Thu, 19 May 2011 09:52:11 -0500 Sebastian Pop <seb...@gmail.com> wrote:
> On Thu, May 19, 2011 at 09:21, Basile Starynkevitch > <bas...@starynkevitch.net> wrote: [...] > > How should I find the induction variable? > > What is your definition of induction variable? The one which is used by graphite. > My definitions are: > - every variable defined in a loop is an induction variable, > - an induction variable has a phi node with one of the > arguments defined in the loop. I am not sure to understand what exactly you call an argument defined in the loop and how to find one. > > If you take one of these definitions your pattern matching is easy. > > > I could loop at the internal name > > of the variable, and check if it starts with graphite_IV. > > I think this is a *very* bad idea, and unfortunately the graphite-opencl > code uses this strcmp technique to detect reductions, and that's why > the graphite-opencl code is broken right now. I definitely agree that comparing string naming internal generated variables is really aweful, and I would like to avoid it. I believe that the cleanest way to avoid that would be to have graphite invoke a plugin hook to signal the creation of that induction variable. For instance, we could add, in the function graphite_create_new_loop file gcc/graphite-clast-to-gimple.c (rev 172785 of the trunk), just after the call (near line 783) add_referenced_var (ivvar); a invoke_plugin_callbacks (PLUGIN_GRAPHITE_NEW_INDUCTION_VARIABLE, ivvar); I really think that several plugins could profit of such a hook. What do you think of such an idea? More generally, I believe that graphite is lacking of several plugin hooks (and by discussing with some INRIA people, I understood -perhaps wrongly- that they would also want them). Do graphite folks want to add plugin hooks inside graphite before 4.7? Regards. -- Basile STARYNKEVITCH http://starynkevitch.net/Basile/ email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359 8, rue de la Faiencerie, 92340 Bourg La Reine, France *** opinions {are only mine, sont seulement les miennes} ***
