objects_must_conflict_p

[Richard Kenner]

    > Btw, why did you choose to always return 0 for scalar vs aggregate? In
    > this case, I think that alias_sets_conflict_p is the right criterion.

    ... if checked against each member of the aggregate of course.

No, I don't think so, since the subset mechanism should take care of it.
But, as I said, this whole routine is *very* confusing.  I wish there were
a better way of dealing with the problem other than crippling stack slot
sharing like this.