http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55135
--- Comment #29 from rguenther at suse dot de <rguenther at suse dot de> 2013-03-06 12:23:21 UTC --- On Wed, 6 Mar 2013, steven at gcc dot gnu.org wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55135 > > --- Comment #28 from Steven Bosscher <steven at gcc dot gnu.org> 2013-03-06 > 12:18:01 UTC --- > (In reply to comment #22) > > Posted for discussion here: > > http://gcc.gnu.org/ml/gcc-patches/2013-03/msg00193.html > > OT: Another trivial speed-up for bitmaps used as regsets (and probably > in general) is to look at head->first if head->current is not the element > containing the sought bit, and *not* update head->current if head->first > is the right element. This speeds up regsets because a common access > pattern is to look at sets containing both pseudos and hardregs, and on > most targets all hardregs are in head->first. Not updating head->current > preserves a pointer to the latest accessed pseudos. > > I'll implement this idea and come back with some timings. Indeed a nice idea ;) I suppose ->current should only be updated if its new distance to head->first is bigger than <magic number> (and zero is of course an obvious one)
