http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53646
--- Comment #10 from Michael Matz <matz at gcc dot gnu.org> 2012-06-12 16:02:28 UTC --- Yep, defaulting that ctor changes the ABI back to register passing. If we could change that in libstdc++, all the better, but I still think the issue is larger than just this specific case.
