Tidy up the code that handles function return edges

Author: martin

src/pointer-analysis/value_set_domain.h

@@ -99,19 +99,6 @@ class value_set_domain_templatet : public ai_domain_baset
     value_set.get_reference_set(expr, dest, ns);
   }
 
-  exprt get_return_lhs(locationt to) const
-  {
-    // get predecessor of "to"
-    to--;
-
-    if(to->is_end_function())
-      return static_cast<const exprt &>(get_nil_irep());
-
-    INVARIANT(to->is_function_call(), "must be the function call");
-
-    return to->call_lhs();
-  }
-
   xmlt output_xml(const ai_baset &ai, const namespacet &ns) const override
   {
     return value_set.output_xml();
@@ -143,7 +130,9 @@ void value_set_domain_templatet<VST>::transform(
 
   case END_FUNCTION:
   {
-    value_set.do_end_function(get_return_lhs(to_l), ns);
+    locationt caller{to_l};
+    --caller; // Unsafe in general but ai_baset should guarantee safety
+    value_set.do_end_function(caller->call_lhs(), ns);
     break;
   }