Add control dependencies from function call to function entry point for old dependency graph

Author: danpoe

regression/goto-analyzer/dependence-graph13/main.c

@@ -0,0 +1,9 @@
+void func()
+{
+
+}
+
+void main(void)
+{
+  func();
+}

regression/goto-analyzer/dependence-graph13/test.desc

@@ -0,0 +1,12 @@
+CORE
+main.c
+--show --dependence-graph
+activate-multi-line-match
+^EXIT=0$
+^SIGNAL=0$
+Function: main\n.*\n.*\n.*\nControl dependencies: [0-9]+
+Function: func\n.*\n.*\n.*\nControl dependencies: [0-9]+
+Function: __CPROVER_initialize\n.*\n.*\n.*\nControl dependencies: [0-9]+
+--
+Function: __CPROVER__start\n.*\n.*\n.*\nControl dependencies: [0-9]+
+^warning: ignoring

src/analyses/dependence_graph.cpp

@@ -448,6 +448,25 @@ void dep_graph_domaint::transform(
   dependence_grapht *dep_graph=dynamic_cast<dependence_grapht*>(&ai);
   assert(dep_graph!=nullptr);
 
+  // We do not propagate control dependencies on function calls, i.e., only the
+  // entry point of a function should have a control dependency on the call
+  if(!control_deps.empty())
+  {
+    const goto_programt::const_targett &dep = control_deps.begin()->first;
+    if(dep->is_function_call())
+    {
+      INVARIANT(
+        std::all_of(
+          std::next(control_deps.begin()),
+          control_deps.end(),
+          [](const std::pair<const goto_programt::const_targett, tvt> &d)
+            { return d.first->is_function_call(); }),
+        "All entries must be function calls");
+
+      control_deps.clear();
+    }
+  }
+
   // propagate control dependencies across function calls
   if(from->is_function_call())
   {
@@ -477,6 +496,8 @@ void dep_graph_domaint::transform(
         s->has_changed=true;
 
       control_deps.clear();
+      control_deps.insert(std::make_pair(from, tvt::unknown()));
+
       control_dep_candidates.clear();
     }
   }