Remove vtable_method field in cgraph_node

[Jan Hubicka]

> Ah, no.  We _did_ that in CCP but now we only adjust the OBJ_TYPE_REF
> expr in CCP and defer to fold_stmt to eventually "devirtualize" it.
> See PR45878.  Then rev.165435 was necessary, as we dropped OBJ_TYPE_REF
> for the non-devirtualized call as well.  As both cases were because

Hmm, sounds slipperly.
In any case OBJ_TYPE_REF of constant argument should be banned, or
we would need to extend gimple_call_fndecl to return contained fndecl.
Devirtualization without enabling an inlining is essentially useless transform
and it is precisely what we do now on this testcase...
> of type conversion issues this should be fixed with separating the
> call function type as we do now.
> 
> I'll look into handling copyprop and FRE similarly.

Thanks,  I would not even mind having some automatic check that the constant
OBJ_TYPE_REFs don't leak at cgraph edge construction time...
Honza
> 
> Richard.