[llvm-dev] FireFox-46.0.1 build with interprocedural register allocation enabled

Mehdi Amini via llvm-dev llvm-dev at lists.llvm.org
Mon Jun 20 20:28:50 PDT 2016

> On Jun 20, 2016, at 3:00 PM, vivek pandya via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> On Mon, Jun 20, 2016 at 10:05 PM, Sanjoy Das <sanjoy at playingwithpointers.com <mailto:sanjoy at playingwithpointers.com>> wrote:
> Hi Vivek,
> vivek pandya wrote:
> > For Octane and Kraken I have run them 4 times and above result is
> > geometric mean. For Octane standard deviation (SD) is
> > 918.54 (NO_IPRA) and 597.82 (With_IPRA). For Kraken unfortunately I
> > don't have readings any more but there was very
> > minor change in each run. JetStream it self runs the test for 3
> > times reports the result. From next time onwards I will
> > run test at least for 10 times
> Oh, no, I used "10 times" as an anecdotal number.  Geomean of 4 times
> is enough.  Of course, if it does not take extra effort, running them
> for more iterations is better, but don't bother if it will e.g. take
> more than a trivial amount of manual work.
> >     It'd also be great to have a precise, non-measurement oriented view of
> >     the benchmarks.
> >
> > I don't understand this point actually all these benchmarks are
> > suggested by firefox-devs and they wanted the results back.
> I was talking about the `-stats` bit there ^.
> >     Is it possible to collect some statistics on how much
> >     you've improved the register allocation in these workloads?
> >
> > Actually while testing single source test case with debug build I
> > used to compare results of -stats with regalloc
> > keyword but while building such a huge software I prefer release
> > build of llvm. And also I don't know if there is any
> > way in llvm to generate stats for the whole build.
> Can you do something quick and dirty, like just have some local
> changes that dumps out some information on outs() ?
> Yes that should not take too much of time. 
> >     Perhaps
> >     you could count the instances where you preserved a register over a
> >     call site that wouldn't have been possible without IPRA?
> >
> > Yes this seems a good idea and I think this is implementable, after
> > calculating new regmask when inserting data into
> > immutable pass two regmasks can be compared to calculate
> > improvements. I will work on this and let you know the progress.
> Just to be clear: you don't *have* to do this (specifically, check
> with your mentor before sinking too much time into this).  But if we
> can come up with easy to "confirm your kill" (i.e. ensure what you
> think should happen is what is actually happening) then I think we
> should do it.
> I will try if this can be done in a simple way. I am sure mentors will welcome it.

Yes having more stats seems a nice thing to have.


> -Vivek 
> Thanks, and best of luck!
> -- Sanjoy
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