Correct value_set merge implementation.

Ensure bottom flag is cleared when returning a new object. Intervals and
constants can be merged into the a set.

Extend abstract_object_set to_interval to handle intervals in the set

Author: jezhiggins

src/analyses/variable-sensitivity/abstract_object.h

@@ -456,6 +456,10 @@ class abstract_objectt : public std::enable_shared_from_this<abstract_objectt>
     top = false;
     this->set_not_top_internal();
   }
+  void set_not_bottom()
+  {
+    bottom = false;
+  }
 };
 
 struct abstract_hashert

src/analyses/variable-sensitivity/abstract_object_set.cpp

@@ -41,13 +41,20 @@ constant_interval_exprt abstract_object_sett::to_interval() const
 {
   PRECONDITION(!values.empty());
 
-  exprt lower_expr = first()->to_constant();
-  exprt upper_expr = first()->to_constant();
+  const auto &initial =
+    std::dynamic_pointer_cast<const abstract_value_objectt>(first());
+
+  exprt lower_expr = initial->to_interval().get_lower();
+  exprt upper_expr = initial->to_interval().get_upper();
   for(const auto &value : values)
   {
-    const auto &value_expr = value->to_constant();
-    lower_expr = constant_interval_exprt::get_min(lower_expr, value_expr);
-    upper_expr = constant_interval_exprt::get_max(upper_expr, value_expr);
+    const auto &v =
+      std::dynamic_pointer_cast<const abstract_value_objectt>(value);
+    const auto &value_expr = v->to_interval();
+    lower_expr =
+      constant_interval_exprt::get_min(lower_expr, value_expr.get_lower());
+    upper_expr =
+      constant_interval_exprt::get_max(upper_expr, value_expr.get_upper());
   }
   return constant_interval_exprt(lower_expr, upper_expr);
 }

src/analyses/variable-sensitivity/value_set_abstract_object.cpp

@@ -229,19 +229,19 @@ abstract_object_pointert value_set_abstract_objectt::resolve_values(
 abstract_object_pointert
 value_set_abstract_objectt::merge(abstract_object_pointert other) const
 {
+  auto union_values = !is_bottom() ? values : abstract_object_sett{};
+
   auto other_value_set = std::dynamic_pointer_cast<const value_set_tag>(other);
   if(other_value_set)
   {
-    auto union_values = values;
     union_values.insert(other_value_set->get_values());
     return resolve_values(union_values);
   }
 
   auto other_value =
-    std::dynamic_pointer_cast<const constant_abstract_valuet>(other);
+    std::dynamic_pointer_cast<const abstract_value_objectt>(other);
   if(other_value)
   {
-    auto union_values = values;
     union_values.insert(other_value);
     return resolve_values(union_values);
   }
@@ -268,6 +268,7 @@ void value_set_abstract_objectt::set_values(
     set_not_top();
     values = other_values;
   }
+  set_not_bottom();
   verify();
 }
 

unit/analyses/variable-sensitivity/interval_abstract_value/merge.cpp

@@ -453,6 +453,32 @@ SCENARIO(
         EXPECT_MODIFIED(merged, val1, val4);
       }
     }
+    WHEN("merging [3, 4] with { [4, 6] }")
+    {
+      auto op1 = make_interval(val3, val4, environment, ns);
+      auto op2 =
+        make_value_set({constant_interval_exprt(val4, val6)}, environment, ns);
+
+      auto merged = merge(op1, op2);
+
+      THEN("result is modified [3, 6]")
+      {
+        EXPECT_MODIFIED(merged, val3, val6);
+      }
+    }
+    WHEN("merging [3, 4] with { 1, [3, 3] }")
+    {
+      auto op1 = make_interval(val3, val4, environment, ns);
+      auto op2 = make_value_set(
+        {val1, constant_interval_exprt(val3, val3)}, environment, ns);
+
+      auto merged = merge(op1, op2);
+
+      THEN("result is modified [1, 4]")
+      {
+        EXPECT_MODIFIED(merged, val1, val4);
+      }
+    }
     WHEN("merging BOTTOM with { 3 }")
     {
       auto op1 = make_bottom_interval();
@@ -478,4 +504,4 @@ SCENARIO(
       }
     }
   }
-}
+}

unit/analyses/variable-sensitivity/interval_abstract_value/module_dependencies.txt

@@ -1,3 +1,4 @@
 analyses
 testing-utils
+util
 

unit/analyses/variable-sensitivity/value_expression_evaluation/module_dependencies.txt

@@ -0,0 +1,3 @@
+analyses
+testing-utils
+util