[Bug c++/58252] [4.9 Regression] ice in gimple_get_virt_method_for_binfo with -O2

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58252

--- Comment #11 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
I am still hoping for help from C++ FE maintainers, but I think the bits we are
missing is logic from 
tree
lookup_base (tree t, tree base, base_access access,
             base_kind *kind_ptr, tsubst_flags_t complain)

that seems to be the tool C++ FE looks up base and binfo of given subtype.  I
am trying to get through the (somewhat convoluted at first glance) logic of
this function.