Re: [PATCH 11/11] Make opt_pass and gcc::pipeline be GC-managed

[Richard Henderson <rth at redhat dot com>]

On 08/02/2013 09:08 AM, David Malcolm wrote:
> For opt_pass and pass_manager, something different is going on.

I'd wondered about that.

> For some reason gengtype doesn't generate the triad of gt_ggc_mx_FOO,
> gt_pch_nx_FOO, gt_pch_p_NFOO functions in gtype-desc.c, for types
> FOO=opt_pass and pass_manager.  Presumably this is because the types are
> only visited by code in context.c
> 
> So the global functions for opt_pass and pass_manager are a hand-written
> implementation of what gengtype would write; they are called *each time*
> the entity is reached during a traversal.  The member functions are
> called only the *first time* the entity is visited.

I wonder if we can reduce the amount of boiler-plate for this.  Perhaps,

-------------------------------------------------------------------
//
// These templates assume the presence of several member functions.
//

template<class T>
inline void gt_ggc_mx (T *p)
{
  if (ggc_test_and_set_mark (p))
    p->gt_ggc_mx ();
}

template<class T>
void gt_pch_nx_with_obj(void *this_obj, void *p,
                        gt_pointer_operator op, void *cookie)
{
  if (p == this_obj)
    {
      T *t = static_cast<T *>(p);
      t->gt_pch_nx_with_obj (op, cookie);
    }
}

template<class T>
inline void gt_pch_nx (T *p)
{
  if (gt_pch_note_object (p, p, gt_pch_nx_with_obj<T>))
    p->gt_pch_nx ();
}

---------------------------------------------------------------------

I had thought about an abstract base class instead of the templates, but
that would unnecessarily force the use of vtables in places that don't
need them.  In some cases this would be relatively harmless (e.g. the
very few pass_manager objects), but in others it might be a no-go.

The use of the template obviates that.  It ought only be instantiated when
necessary for gty user objects that don't have their own specialization.

Thoughts?


r~