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

[Thomas Schwinge]

Hi!

On Sat, 16 Jul 2011 11:27:46 -0400, Diego Novillo <dnovillo@google.com> wrote:
> On Sat, Jul 16, 2011 at 02:52, Ian Lance Taylor <iant@google.com> wrote:
> 
> > 2011-07-15  Ian Lance Taylor  <iant@google.com>
> >
> >        * configure.ac: Add --enable-build-poststage1-with-cxx.  If set,
> >        make C++ a boot_language.  Set and substitute
> >        POSTSTAGE1_CONFIGURE_FLAGS.
> >        * Makefile.tpl (POSTSTAGE1_CONFIGURE_FLAGS): New variable.
> >        (STAGE[+id+]_CONFIGURE_FLAGS): Add $(POSTSTAGE1_CONFIGURE_FLAGS).
> >        * configure, Makefile.in: Rebuild.
> 
> I agree with this change.  For reference, have you measured the
> difference in bootstrap time?  Clearly, it will be slower, but how
> much?

I can provide some data from my GNU/Hurd regression and comparing to
GNU/Linux testing.

This is GCC Git master branch, going from
7c9f953a01d23c6b6885dc908d5b1dba8009efd4 (2011-07-18; ``before'') to
18540031a8b2070a56f5b7e94d6b24e8bd335c57 (2011-07-20; ``after''); which
is shortly before and after the switch to using g++.  For GNU/Hurd, I
have applied a few patches that are minor to this experiment.

kepler is a Xen domU on a AMD Athlon II X2 215 with 2700 MHz, the domU
has 1 GiB of RAM, and is running Debian GNU/Linux testing x86.

coulomb is a AMD Athlon XP with 1466 MHz, has 1 GiB of RAM, and is
running Debian GNU/Hurd unstable x86.

        kepler      coulomb
before  2 h 35 min  10 h 50 min
after   3 h 00 min  13 h 00 min

The ``after'' data is averaged from two iterations only, ``before'' data
has seen many more iterations, and has (roughly) been constant over a
long period of time.  Both systems have been idle apart from the GCC
build.  The build was essentially a native ``configure && make''.

So, yes, bootstrap is slower now.  The bootstrap time now is 16 % to 20 %
longer, roughly.


Grüße,
 Thomas
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