Gather interval widening out into a little helper class of its own

Author: jezhiggins

src/analyses/Makefile

@@ -52,6 +52,7 @@ SRC = ai.cpp \
       variable-sensitivity/variable_sensitivity_dependence_graph.cpp \
       variable-sensitivity/variable_sensitivity_domain.cpp \
       variable-sensitivity/variable_sensitivity_object_factory.cpp \
+      variable-sensitivity/widened_range.cpp \
       variable-sensitivity/write_location_context.cpp \
       variable-sensitivity/write_stack.cpp \
       variable-sensitivity/write_stack_entry.cpp \

src/analyses/variable-sensitivity/interval_abstract_value.cpp

@@ -17,6 +17,7 @@
 #include "abstract_environment.h"
 #include "abstract_object_statistics.h"
 #include "interval_abstract_value.h"
+#include "widened_range.h"
 
 static index_range_implementation_ptrt make_interval_index_range(
   const constant_interval_exprt &interval,
@@ -346,83 +347,18 @@ void interval_abstract_valuet::output(
   }
 }
 
-exprt extend_lower_bound(
-  const exprt &lower_bound,
-  const exprt &range,
-  const namespacet &ns);
-exprt extend_upper_bound(
-  const exprt &upper_bound,
-  const exprt &range,
-  const namespacet &ns);
-
 abstract_object_pointert widening_merge(
   const constant_interval_exprt &lhs,
   const constant_interval_exprt &rhs)
 {
-  auto lower_bound =
-    constant_interval_exprt::get_min(lhs.get_lower(), rhs.get_lower());
-  auto upper_bound =
-    constant_interval_exprt::get_max(lhs.get_upper(), rhs.get_upper());
-
-  auto dummy_symbol_table = symbol_tablet{};
-  auto dummy_namespace = namespacet{dummy_symbol_table};
-
-  auto range = plus_exprt(
-    minus_exprt(upper_bound, lower_bound), from_integer(1, lhs.type()));
-
-  // should extend lower bound?
-  if(constant_interval_exprt::less_than(rhs.get_lower(), lhs.get_lower()))
-    lower_bound = extend_lower_bound(lower_bound, range, dummy_namespace);
-  // should extend upper bound?
-  if(constant_interval_exprt::less_than(lhs.get_upper(), rhs.get_upper()))
-    upper_bound = extend_upper_bound(upper_bound, range, dummy_namespace);
+  auto widened = widened_ranget(lhs, rhs);
 
   // new interval ...
-  auto new_interval = constant_interval_exprt(lower_bound, upper_bound);
+  auto new_interval =
+    constant_interval_exprt(widened.lower_bound, widened.upper_bound);
   return interval_abstract_valuet::make_interval(new_interval);
 }
 
-bool has_underflowed(const exprt &value)
-{
-  return constant_interval_exprt::greater_than(
-    value, from_integer(0, value.type()));
-}
-bool has_overflowed(const exprt &value)
-{
-  return constant_interval_exprt::less_than(
-    value, from_integer(0, value.type()));
-}
-
-exprt extend_lower_bound(
-  const exprt &lower_bound,
-  const exprt &range,
-  const namespacet &ns)
-{
-  auto new_lower_bound = simplify_expr(minus_exprt(lower_bound, range), ns);
-
-  if(
-    constant_interval_exprt::contains_extreme(new_lower_bound) ||
-    has_underflowed(new_lower_bound))
-    return min_exprt(lower_bound.type());
-
-  return new_lower_bound;
-}
-
-exprt extend_upper_bound(
-  const exprt &upper_bound,
-  const exprt &range,
-  const namespacet &ns)
-{
-  auto new_upper_bound = simplify_expr(plus_exprt(upper_bound, range), ns);
-
-  if(
-    constant_interval_exprt::contains_extreme(new_upper_bound) ||
-    has_overflowed(new_upper_bound))
-    return max_exprt(upper_bound.type());
-
-  return new_upper_bound;
-}
-
 abstract_object_pointert interval_abstract_valuet::merge_with_value(
   const abstract_value_pointert &other,
   const widen_modet &widen_mode) const

src/analyses/variable-sensitivity/widened_range.cpp

@@ -0,0 +1,51 @@
+/*******************************************************************\
+
+ Module: helper for extending intervals during widening merges
+
+ Author: Jez Higgins
+
+\*******************************************************************/
+
+#include "widened_range.h"
+#include <util/simplify_expr.h>
+
+static bool has_underflowed(const exprt &value)
+{
+  return constant_interval_exprt::greater_than(
+    value, from_integer(0, value.type()));
+}
+static bool has_overflowed(const exprt &value)
+{
+  return constant_interval_exprt::less_than(
+    value, from_integer(0, value.type()));
+}
+
+exprt widened_ranget::make_lower_bound() const
+{
+  if(!lower_extended)
+    return lower_;
+
+  auto new_lower_bound = simplify_expr(minus_exprt(lower_, range_), ns_);
+
+  if(
+    constant_interval_exprt::contains_extreme(new_lower_bound) ||
+    has_underflowed(new_lower_bound))
+    return min_exprt(lower_.type());
+
+  return new_lower_bound;
+}
+
+exprt widened_ranget::make_upper_bound() const
+{
+  if(!upper_extended)
+    return upper_;
+
+  auto new_upper_bound = simplify_expr(plus_exprt(upper_, range_), ns_);
+
+  if(
+    constant_interval_exprt::contains_extreme(new_upper_bound) ||
+    has_overflowed(new_upper_bound))
+    return max_exprt(upper_.type());
+
+  return new_upper_bound;
+}

src/analyses/variable-sensitivity/widened_range.h

@@ -0,0 +1,57 @@
+/*******************************************************************\
+
+ Module: helper for extending intervals during widening merges
+
+ Author: Jez Higgins
+
+\*******************************************************************/
+
+#ifndef CPROVER_ANALYSES_VARIABLE_SENSITIVITY_WIDENED_RANGE_H
+#define CPROVER_ANALYSES_VARIABLE_SENSITIVITY_WIDENED_RANGE_H
+
+#include <util/arith_tools.h>
+#include <util/interval.h>
+#include <util/namespace.h>
+#include <util/symbol_table.h>
+
+class widened_ranget
+{
+public:
+  widened_ranget(
+    const constant_interval_exprt &lhs,
+    const constant_interval_exprt &rhs)
+    : lower_extended(
+        constant_interval_exprt::less_than(rhs.get_lower(), lhs.get_lower())),
+      upper_extended(
+        constant_interval_exprt::less_than(lhs.get_upper(), rhs.get_upper())),
+      ns_(symbol_tablet{}),
+      lower_(
+        constant_interval_exprt::get_min(lhs.get_lower(), rhs.get_lower())),
+      upper_(
+        constant_interval_exprt::get_max(lhs.get_upper(), rhs.get_upper())),
+      range_(
+        plus_exprt(minus_exprt(upper_, lower_), from_integer(1, lhs.type()))),
+      lower_bound(make_lower_bound()),
+      upper_bound(make_upper_bound())
+  {
+  }
+
+  const bool lower_extended;
+  const bool upper_extended;
+
+private:
+  namespacet ns_;
+  exprt lower_;
+  exprt upper_;
+  exprt range_;
+
+public:
+  const exprt lower_bound;
+  const exprt upper_bound;
+
+private:
+  exprt make_lower_bound() const;
+  exprt make_upper_bound() const;
+};
+
+#endif // CPROVER_ANALYSES_VARIABLE_SENSITIVITY_WIDENED_RANGE_H