omputation to determine set of aliased parameter indices was very conservative,

omputation to determine set of aliased parameter indices was very conservative,
but correct, fortunately.  It used to list every parameter pair that could reach
a common node as aliased!  Yikes!  Actually, we want to see that parameters can
directly reference a common node, but further, they can only be aliased if the
edges to the shared node both have a common reachability state that is also on
the shared node.  Otherwise they cannot be referencing a common concrete object.