fix #1488

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/util/top_sort.h

@@ -0,0 +1,101 @@
+/*++
+Copyright (c) 2018 Microsoft Corporation
+
+Module Name:
+
+    top_sort.h
+
+Abstract:
+    Topological sort over objects
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2018-02-14
+
+Revision History:
+
+--*/
+
+#ifndef TOP_SORT_H_
+#define TOP_SORT_H_
+
+#include "util/obj_hashtable.h"
+#include "util/vector.h"
+#include<algorithm>
+#include<type_traits>
+#include<memory.h>
+#include "util/memory_manager.h"
+
+
+template<typename T>
+class top_sort {
+    typedef obj_hashtable<T> T_set;
+    obj_map<T, unsigned> m_partition_id;
+    obj_map<T, unsigned> m_dfs_num;
+    ptr_vector<T>        m_top_sorted;
+    ptr_vector<T>        m_stack_S;
+    ptr_vector<T>        m_stack_P;
+    unsigned             m_next_preorder;    
+    obj_map<T, T_set*>   m_deps;
+
+    void traverse(T* f) {
+        unsigned p_id = 0;
+        if (m_dfs_num.find(f, p_id)) {
+            if (!m_partition_id.contains(f)) {
+                while (!m_stack_P.empty() && m_partition_id[m_stack_P.back()] > p_id) {
+                    m_stack_P.pop_back();
+                }
+            }
+        }
+        else if (!m_deps.contains(f)) {
+            return;
+        }
+        else {
+            m_dfs_num.insert(f, m_next_preorder++);        
+            m_stack_S.push_back(f);
+            m_stack_P.push_back(f);  
+            for (T* g : *m_deps[f]) {
+                traverse(g);
+            }        
+            if (f == m_stack_P.back()) {
+                
+                p_id = m_top_sorted.size();            
+                T* s_f;
+                do {
+                    s_f = m_stack_S.back();
+                    m_stack_S.pop_back();
+                    m_top_sorted.push_back(s_f);
+                    m_partition_id.insert(s_f, p_id);
+                } 
+                while (s_f != f);
+                m_stack_P.pop_back();
+        }
+        }
+    }
+
+public:
+
+    ~top_sort() {
+        for (auto & kv : m_deps) dealloc(kv.m_value);
+    }
+
+    void topological_sort() {
+        m_next_preorder = 0;
+        m_partition_id.reset();
+        m_top_sorted.reset();
+        for (auto & kv : m_deps) {
+            traverse(kv.m_key);
+        }
+        SASSERT(m_stack_S.empty());
+        SASSERT(m_stack_P.empty());
+        m_dfs_num.reset();        
+    }
+
+    void insert(T* t, T_set* s) { 
+        m_deps.insert(t, s); 
+    }
+
+    ptr_vector<T> const& top_sorted() { return m_top_sorted; }    
+};
+
+#endif /* TOP_SORT_H_ */