> On Sun, May 11, 2014 at 04:08:37PM -0400, James Cloos wrote:
> > >>>>> "RF" == Rich Felker <dalias@libc.org> writes:
> > 
> > RF> I've tested it on gcc.godbolt.org and others have tested with local
> > RF> gcc 4.8.2 and 4.9.0, probably distro-provided (I didn't ask).
> > 
> > I just tried debian-sid's 4.9.  That does show the bug.  As does their
> > gcc-snapshot version (a 4.10 pre).
> > 
> > Perhaps the distro(s) which have the bug with 4.8.2 backported the commit
> > where the bug first occurs?
> 
> Sounds plausible. Maybe that will help find the offending commit.
> 
> > RF> I wonder if the broken GCC is using isl/cloog
> > 
> > I use the graphite optimizer on my Gentoo box (which generated the
> > assembly I quoted).  The graphite code is only used when one or more
> > of -floop-interchange -floop-strip-mine -floop-block are specified.
> > 
> > Testing with those options doesn't change the results.
> 
> OK, ruled that out then.

FWIW, I *think* noticed that this problem only appeared in buildroot, without enabling c++ in the languages. Actually, when I decided to evaluate the C++ changes and therefore enabled C++ in buildroot (I am not sure what it does in addition to --enable-languages=c,c++). I cannot be certain and I have not had the time to retest this. 
Cheers
Thomo