Dependence graph fix

- adds call to initialize() in parent class to initialize the states at all locations
- does not set node id in make_top/bottom/entry as get_state() is overridden to initialize the node id

regression/goto-instrument/dependence-graph1/main.c

@@ -0,0 +1,18 @@
+
+int x;
+
+void func()
+{
+  int r;
+
+  r = x;
+}
+
+int main()
+{
+  x = 1;
+  func();
+
+  return 0;
+}
+

regression/goto-instrument/dependence-graph1/test.desc

@@ -0,0 +1,7 @@
+CORE
+main.c
+--show-dependence-graph
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring

src/analyses/dependence_graph.h

@@ -94,14 +94,20 @@ class dep_graph_domaint:public ai_domain_baset
 
   void make_top() final override
   {
+    assert(node_id!=std::numeric_limits<node_indext>::max());
+
     has_values=tvt(true);
-    node_id=std::numeric_limits<node_indext>::max();
+    control_deps.clear();
+    data_deps.clear();
   }
 
   void make_bottom() final override
   {
+    assert(node_id!=std::numeric_limits<node_indext>::max());
+
     has_values=tvt(false);
-    node_id=std::numeric_limits<node_indext>::max();
+    control_deps.clear();
+    data_deps.clear();
   }
 
   void make_entry() final override
@@ -161,6 +167,7 @@ class dependence_grapht:
 
   void initialize(const goto_programt &goto_program)
   {
+    ait<dep_graph_domaint>::initialize(goto_program);
     post_dominators(goto_program);
   }