On Thu, Aug 04, 2011 at 08:51:41PM +0200, Jan Hubicka wrote:
> > +Mark who has done size optimization tuning with FDO.
> >
> > On Thu, Aug 4, 2011 at 7:05 AM, Mike Hommey <mhom...@mozilla.com> wrote:
> > > Hi,
> > >
> > > We (Mozilla) are trying to get the best of the ARM toolchain for our
> > > Android build. I recently built an Android Native-code Development Kit
> > > with GCC 4.6.1 and binutils 2.21.53, instead of GCC 4.4.3 and binutils
> > > 2.19 that come with the default NDK.
> > >
> > > LTO doesn't work at all, I'm getting an ICE that looks like the one from
> > > bug 41159.
> > >
> > > FDO however, works, but sadly, the resulting build is not only quite
> > > bigger,
> >
> > Is this true for both 4.6 and 4.4 gcc? There is a bug in 4.6 that
> > prevents cold functions from be optimized for size with FDO. The bug
> > was fixed in trunk recently.
>
> You can also backport the patch to 4.6 tree. If the bug exists there, consider
> the patch preaproved.
Do you have a link to the bug or the patch?
> With FDO, -O2 and -O3 is not really that significandly different (i.e. -O2
> gets all the extra inlining, but it does not get vectorization that is
> probably
> not big deal for you). -Os is however different storry.
> > >
> > > Has there been significant changes to the ARM backend that would justify
> > > that I try some more with current GCC HEAD? Should I maybe try some more
> > > with the linaro GCC branch? Are there things we can do to help getting
> > > better ARM performance?
> >
> > It does not hurt to try it :)
>
> One thing that is really changed is inliner heuristics. If would be very
> happy
> to have some feedback on this early, since we plan to do re-tunning of it
> (LTO changes many things and there are also fortran benchmarks that shows a
> lot
> of problems. Mozilla may chime in and make my life even harder with hopefully
> some positive results on it).
>
> As discused earlier, I think it would be very good idea to start trakcing
> perfomrance of Mozilla built with mainline GCC like we track other benchmarks.
> We don't really monitor anything of this size and thus we are quite likely
> to find new interesting issues by doing so.
I unfortunately hit several problems with gcc 4.7 (latest snapshot).
One is bug 50022 that I filed today.
Another is the following error in stlport headers:
error: invalid use of incomplete type 'std::string {aka struct
std::basic_string<char, std::char_traits<char>, std::allocator<char> >}'
I also tried GNU libstdc++ instead of stlport but I hit some other
errors that boil down to the following:
error: 'std::wstring' has not been declared
Mike
