Hi Luc, On 13 August 2017 at 15:25, Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> wrote: >> OTOH with -rc4, it takes only 0.05s ! >> >> The situation is really weird, it's an interaction between the patches: >> - remove single-store shortcut (first slowdown to 0.8s) >> - fix ptrlist corruption while killing unreachable BBs (second slowdown to 2.9s) >> - mark pseudo users as deleted instead of removing them (third slowdown to 5.5s) >> >> All three patches were expected to create *some* slowdown, >> the first one very obviously and much more than the others. >> >> It's interesting to note that without the 'remove single shortcut' patch, the >> two others ones don't seem to have a significative effect on the time. >> >> My guess here is that indeed, with this input, the single-store shortcut >> is a huge optimization and without it much much more code is created >> (phi-nodes, I suppose) and this impact very negatively the two other fixes. >> >> I'll see what can be done. > > It's also interesting to note that with the new SSA construction, there is no > slowdown (0.064s here but too small to be measured accurately). > This confirms me that the single-store shortcut was very much needed for > performance (not simply because it's faster than the general case but that > it creates much less intermediate code) but it created bad code ... > I wonder if it is worth doing these changes - instead we should probably look at your new SSA construction approach. Regards Dibyendu -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
