[Bug target/63874] vtable address generation goes through memory

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63874

--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
Sounds like this might be confusion between weak definitions and weak
references.  If we have a weak reference to the object, we cannot convert it
into a pc-relative expression, since that would mean we couldn't detect NULL. 
However, if we have a non-weak reference to a weak object we can replace that
with a pc-relative addressing mode, _provided_ that we can guarantee that the
definition will appear in the same link unit (ie it's not part of building a
DSO).