https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80916
--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> --- It has internal linkage because one of its template arguments is a local class, and it isn't instantiated because it isn't ever used. It's added to cgraph as a possible devirtualization target. I think the last of these is the place to attack this issue, since it's also the source of the regression.
