------- Comment #6 from rguenther at suse dot de 2009-06-20 17:12 ------- Subject: Re: long time needed in tree canonical iv
On Sat, 20 Jun 2009, rakdver at gcc dot gnu dot org wrote: > ------- Comment #5 from rakdver at gcc dot gnu dot org 2009-06-20 17:08 > ------- > (In reply to comment #4) > > With MAX_DOMINATORS_TO_WALK zero and find_loop_niter_by_eval completely > > disabled > > (checking enabled compiler, built with -O0): > > > > tree iv optimization : 11.12 ( 6%) usr 0.07 ( 5%) sys 12.02 ( 6%) > > wall > > 59123 kB (20%) ggc > > > > With just find_loop_niter_by_eval disabled: > > > > tree iv optimization : 10.81 ( 6%) usr 0.05 ( 3%) sys 11.44 ( 6%) > > wall > > 59123 kB (20%) ggc > > > > so that's it. > > I assume you were really looking at tree canonical iv counter, not on the tree > iv optimization one, otherwise I don't see how you got to this conclusion. Ah, yes. tree canonical iv is at 0% in all cases ... > > Zdenek - if for one exit we cannot determine the number of executions, > > shouldn't we return chrec_dont_know here instead of just examining the > > other exits? > > Why should we? The fact that we cannot determine number of iterations before > a > particular exit is taken does not tell you anything about the rest of the > exits. wouldn't that possibly overestimate the number of iterations? Ah, I see - the function searches for the exit with the least known number of iterations. Richard. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38729
