This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: PATCH RFA: Build stages 2 and 3 with C++


On 2011.07.17 at 18:54 +0200, Markus Trippelsdorf wrote:
> On 2011.07.17 at 18:30 +0200, Richard Guenther wrote:
> > On Sun, Jul 17, 2011 at 1:30 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> > >> I have measured it at some point and IIRC it was about 10% slower
> > >> (comparing C bootstrap with C++ in stag1 languages with C++ bootstrap,
> > >> not sure if that included bootstrapping libstdc++ for the former).
> > >
> > > IMO acceptable now that the build time of libjava has been halved.
> > 
> > Actually the penalty for using C++ was only 1.5%, that of bootstrapping C++ and
> > libstdc++ was 15%.  For reference:
> 
> I've tested the difference today on an average 4 CPU machine with 8GB
> RAM. This is the result of otherwise identical LTO+PGO builds:
> 
> --enable-build-with-cxx  make -j4 profiledbootstrap  3384.20s user 177.02s system 291% cpu 20:23.12 total
> <default>                make -j4 profiledbootstrap  3011.03s user 144.30s system 297% cpu 17:41.59 total
> 
> That's a ~15% increase in build time.

And I guess that most of it comes from building libstdc++ to train the
instrumented compiler. This doesn't happen in the default case AFAICS.

-- 
Markus


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]