Replace cone-of-influence filter with generalized dataflow-engine

Signed-off-by: Henning Guenther <t-hennig@microsoft.com>

src/muz/dataflow/reachability.h

@@ -0,0 +1,82 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    reachability.h
+
+Abstract:
+
+    Abstract domain for tracking rule reachability.
+
+Author:
+    Henning Guenther (t-hennig)
+
+--*/
+
+#ifndef REACHABILITY_H_
+#define REACHABILITY_H_
+
+#include "dataflow.h"
+
+namespace datalog {
+    class reachability_info {
+        bool m_reachable;
+        reachability_info(bool r) : m_reachable(r) {}
+    public:
+        typedef ast_manager ctx_t;
+        static const reachability_info null_fact;
+        reachability_info() : m_reachable(false) {}
+
+        void init_down(const ctx_t& m, const rule* r) {
+            m_reachable = true;
+        }
+
+        bool init_up(const ctx_t& m, const rule* r) {
+            if (m_reachable) 
+                return false;
+            else {
+                m_reachable = true;
+                return true;
+            }
+        }
+
+        void propagate_down(const ctx_t& manager, const rule* r, fact_writer<reachability_info>& tail_facts) const {
+            SASSERT(m_reachable);
+            for (unsigned i = 0; i < r->get_uninterpreted_tail_size(); ++i) {
+                reachability_info& tail_fact = tail_facts.get(i);
+                if (!tail_fact.m_reachable) {
+                    tail_fact.m_reachable = true;
+                    tail_facts.set_changed(i);
+                }
+            }
+        }
+
+        bool propagate_up(const ctx_t& manager, const rule* r, const fact_reader<reachability_info>& tail_facts) {
+            if (m_reachable)
+                return false;
+
+            for (unsigned i = 0; i < r->get_positive_tail_size(); ++i) {
+                if (!tail_facts.get(i).m_reachable) {
+                    return false;
+                }
+            }
+            m_reachable = true;
+            return true;
+        }
+
+        void join(const ctx_t& manager, const reachability_info& oth) {
+            m_reachable |= oth.m_reachable;
+        }
+
+        void dump(const ctx_t& manager, std::ostream& outp) const {
+            outp << (m_reachable ? "reachable" : "unreachable");
+        }
+
+        bool is_reachable() const { return m_reachable; }
+    };
+
+    typedef dataflow_engine<reachability_info> reachability;
+}
+
+#endif