[Bug middle-end/92059] Crash on tr2::dynamic_bitset::operator=() with optimization

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92059

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to John Harris from comment #2)
> I figured this out.  The assignment operator doesn't have a return statement.
> Why that matters, I don't know.  But adding return *this fixes it.

Because if you fallthrough to the end without a return, it is undefined.  Newer
GCC's changed the behavior there.