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

[Markus Trippelsdorf <markus at trippelsdorf dot de>]

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.

(I couldn't test --enable-build-poststage1-with-cxx, because it doesn't
seem to work with this configuration. Maybe the patch needs to be updated
to also cover LTO or PGO builds?)

Configured with: ../gcc/configure --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.0
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.0/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.0
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.0/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.0/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.0/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-ppl --without-cloog --enable-lto
--enable-nls --without-included-gettext --with-system-zlib
--disable-werror --with-gold --enable-secureplt --disable-multilib
--enable-libmudflap --disable-libssp --enable-libgomp --enable-cld
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.7.0/python
--enable-checking=release --disable-libgcj --enable-languages=c,c++
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --with-build-config=bootstrap-lto

And built with:
make -j4 BOOT_CFLAGS="-march=native -O2 -pipe"
STAGE1_CFLAGS="-march=native -O2 -pipe" CFLAGS_FOR_TARGET="-march=native
-O2 -pipe" profiledbootstrap

-- 
Markus