Call graph: add constructors that only include reachable functions

These start from a nominated node and walk outwards, rather than build
the entire call-graph as usual.

Author: smowton

src/analyses/call_graph.cpp

@@ -35,9 +35,9 @@ call_grapht::call_grapht(
   }
 }
 
-void call_grapht::add(
-  const irep_idt &function,
-  const goto_programt &body)
+static void forall_callsites(
+  const goto_programt &body,
+  std::function<void(goto_programt::const_targett, const irep_idt &)> call_task)
 {
   forall_goto_program_instructions(i_it, body)
   {
@@ -47,14 +47,73 @@ void call_grapht::add(
       if(function_expr.id()==ID_symbol)
       {
         const irep_idt &callee=to_symbol_expr(function_expr).get_identifier();
-        add(function, callee);
-        if(collect_callsites)
-          callsites[{function, callee}].insert(i_it);
+        call_task(i_it, callee);
       }
     }
   }
 }
 
+/// Create call graph restricted to functions reachable from `root`
+/// \param functions: functions to search for callsites
+/// \param root: function to start exploring the graph
+/// \param collect_callsites: if true, then each added graph edge will have
+///   the calling instruction recorded in `callsites` map.
+call_grapht::call_grapht(
+  const goto_functionst &goto_functions,
+  const irep_idt &root,
+  bool collect_callsites)
+{
+  std::stack<irep_idt, std::vector<irep_idt>> pending_stack;
+  pending_stack.push(root);
+
+  while(!pending_stack.empty())
+  {
+    irep_idt function=pending_stack.top();
+    pending_stack.pop();
+    const goto_programt &goto_program=
+      goto_functions.function_map.at(function).body;
+
+    forall_callsites(
+      goto_program,
+      [&](goto_programt::const_targett i_it, const irep_idt &callee)
+      {
+        add(function, callee, i_it);
+        if(graph.find(callee)==graph.end())
+          pending_stack.push(callee);
+      }
+    ); // NOLINT
+  }
+}
+
+/// Create call graph restricted to functions reachable from `root`
+/// \param goto_model: model to search for callsites
+/// \param root: function to start exploring the graph
+/// \param collect_callsites: if true, then each added graph edge will have
+///   the calling instruction recorded in `callsites` map.
+call_grapht::call_grapht(
+  const goto_modelt &goto_model,
+  const irep_idt &root,
+  bool collect_callsites):
+  call_grapht(goto_model.goto_functions, root, collect_callsites)
+{
+}
+
+void call_grapht::add(
+  const irep_idt &function,
+  const goto_programt &body)
+{
+  forall_callsites(
+    body,
+    [&](goto_programt::const_targett i_it, const irep_idt &callee)
+    {
+      add(function, callee, i_it);
+    }
+  ); // NOLINT
+}
+
+/// Add edge
+/// \param caller: caller function
+/// \param callee: callee function
 void call_grapht::add(
   const irep_idt &caller,
   const irep_idt &callee)

src/analyses/call_graph.h

@@ -25,6 +25,17 @@ class call_grapht
   explicit call_grapht(const goto_modelt &, bool collect_callsites=false);
   explicit call_grapht(const goto_functionst &, bool collect_callsites=false);
 
+  // These two constructors build a call graph restricted to functions
+  // reachable from the given root.
+  call_grapht(
+    const goto_modelt &model,
+    const irep_idt &root,
+    bool collect_callsites);
+  call_grapht(
+    const goto_functionst &functions,
+    const irep_idt &root,
+    bool collect_callsites);
+
   void output_dot(std::ostream &out) const;
   void output(std::ostream &out) const;
   void output_xml(std::ostream &out) const;