On Tue, Apr 10, 2012 at 5:40 PM, Michael Matz <m...@suse.de> wrote: > Hi, > > On Tue, 10 Apr 2012, Steven Bosscher wrote: > >> This is OK. > > r186283. > >> Do you think it would be worthwhile to do this transformation in the >> middle end too, based on profile information for values? > > I'd think so, but it probably requires a new profiler that counts for how > often 0 <= A <= B for every "A % B". Just profiling the range of values > might be misleading (because A <= N and B <= M and N <= M doesn't imply > that A <= B often holds). > > But it would possibly be an interesting experiment already to do such > transformation generally (without profiling) and see what it gives on some > benchmarks. Just to get a feel what's on the plate.
The question is, of course, why on earth is a modulo operation in the loop setup so expensive that avoiding it improves the performance of the overall routine so much ... did you expect the code-gen difference of your patch? Richard. >> IIRC value-prof >> handles constant divmod but not ranges for modulo operations. > > Ciao, > Michael.
