On 03/01/2014 03:52 AM, Jan Hubicka wrote:
a hidden function. We don't do that for user-defined virtual
functions because the user controls whether or not they are defined
in the header, and we don't devirtualize if no definition is
available, but implicitly-declared functions are different because
the user has no way to prevent the definition from being available.
This also isn't a problem for cprop devirtualization, because in
that situation we must have already referred to the vtable.
Is this always the case? For normal virtual method you can have something
like:
foo(class bla a)
{
a->bar();
}
Here we will devirutalize bar into bla's method without ever seeing the vtable.
I am not sure if I can construct a testcase for dtor w/o referencing the
vtable, since generally those are cases where dtor is generated autmatically.
But it is a bit fragile assumption to be made.
For pass-by-value we need to be able to call a constructor, which needs
to be able to reference the vtable, so I think it should be OK
typically. Sure, people can do all kinds of weird and broken things
with visibility; I'm just trying to make what seems to be a common and
understandable pattern work.
Jason
