https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61515
--- Comment #13 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 17 Jun 2014, law at redhat dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61515 > > Jeffrey A. Law <law at redhat dot com> changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC| |law at redhat dot com > Assignee|unassigned at gcc dot gnu.org |law at redhat dot com > > --- Comment #12 from Jeffrey A. Law <law at redhat dot com> --- > Fundamentally we don't have a way to know what equivalences we need to > invalidate. > Invalidation is, umm, painful. The question in my mind is why are we getting > so many invalidations to start with. That's the first thing to look at. Well, it's easy to avoid the quadraticness - you can always create testcases that need a lot of invalidates. But the current algorithm really does not scale. > Honestly though, I really wonder if handling backedges is worth the effort, > even though it's important for one benchmark. Not sure about that, but trivial improvements to the scalability are possible here. Walking all SSA names is O(number of stmts) - if you do that O(number of stmts) time (as you do) that's clearly the bug.
