On Tue, Aug 16, 2022 at 1:38 PM Richard Biener <rguent...@suse.de> wrote: > > On Tue, 16 Aug 2022, Aldy Hernandez wrote: > > > On Mon, Aug 15, 2022 at 11:53 AM Richard Biener <rguent...@suse.de> wrote: > > > > > > The remaining issue I have with the path_range_query is that > > > we re-use the same instance in the back threader but the > > > class doesn't provide any way to "restart", aka give m_path > > > a lifetime. The "start a new path" API seems to essentially > > > be compute_ranges (), but there's no convenient way to end. > > > It might be more appropriate to re-instantiate the path_range_query, > > > though that comes at a cost. Or abstract an actual query, like > > > adding a > > > > Yes, compute_ranges() is the way to start a new path. It resets exit > > dependencies, the path, relations, etc. I think it would be clearer > > to name it set_path (or reset_path if we want to share nomenclature > > with the path_oracle). > > > > Instantiating a new path_range_query per path is fine, as long as you > > allocate the ranger it uses yourself, instead of letting > > path_range_query allocate it. Instantiating a new ranger does have a > > cost, and it's best to let path_range_query re-use a ranger from path > > to path. This is why path_range_query is (class) global in the > > backwards threader. Andrew mentioned last year making the ranger > > start-up 0-cost, but it still leaves the internal caching the ranger > > will do from path to path (well, the stuff outside the current path, > > cause the stuff inside the path is irrelevant since it'll get > > recalculated). > > > > However, why can't you use compute_ranges (or whatever we rename it to > > ;-))?? > > I've added > > auto_bb_flag m_on_path; > > to the path query and at set_path time set m_on_path on each BB so > the m_path->contains () linear walks go away. But I need to clear > the flag for which I would need something like finish_path (), > doing it just at the point we deallocate the path query object > or when we set the next path via compute_ranges doesn't look right > (and in fact it doesn't work out-of-the-box without adjusting the > lifetime of the path query object). > > So a more incremental thing would be to add such finish_path () > or to make the whole path query object single-shot, thus remove > compute_ranges and instead use the CTOR for this. > > Probably not too important (for short paths).
On a high level, I wonder if this matters since we don't allow long paths for other performance reasons you've already tackled. But OTOH, I've always been a little uncomfortable with contains_p linear search, so if you think this makes a difference, go right ahead :). I'm fine with either the finish_path() or the single-shot thing you speak of. Although making path query inmutable makes things cleaner in the long run. I like it! My guess is that the non-ranger instantiation penalty would be minimal. I'd even remove the default (auto-allocated) ranger from path_range_query, to make it obvious that you need to manage that yourself and avoid folks shooting themselves in the foot. Wanna have a go at it? If you'd rather not, I can work on it. Aldy
