On 10/12/12, Richard Biener <richard.guent...@gmail.com> wrote: > On Oct 12, 2012 Diego Novillo <dnovi...@google.com> wrote: > > On 2012-10-12 04:26 , Richard Biener wrote: > > > What's the issue with always returning the changed status? > > > bitmap operations (even more so sbitmap operations) are > > > memory-bound, accumulating one more register isn't speed > > > critial. > > > > Not a big issue, but it was going to be a behaviour change, > > which we are trying to minimize. > > > > I have no problem in always returning a status change, if you > > are OK with that. > > I am ok with that.
There is some rationale for being concerned about performance, as the checking routines need to read memory locations that they otherwise would only write. As a consequence, we have reason to believe that there would be both an new latency waiting on the the additional read and increased pressure on the read bandwidth. I haven't done any performance measures, but I take as evidence that someone thought there was enough of a performance difference to make it worth the extra work of writing a second set of routines. I'm okay with always returning the status change, but we might get a significant performance change, and I don't want the blame if it shows up. :-) -- Lawrence Crowl
