improve pre-processing

src/smt/smt_context.cpp

@@ -4612,9 +4612,15 @@ namespace smt {
         }
     }
 
-    expr_ref_vector context::get_trail() {        
+    expr_ref_vector context::get_trail(unsigned max_level) {        
         expr_ref_vector result(get_manager());
-        get_assignments(result);
+        for (literal lit : m_assigned_literals) {
+            if (get_assign_level(lit) > max_level + m_base_lvl)
+                continue;
+            expr_ref e(m);
+            literal2expr(lit, e);
+            result.push_back(std::move(e));
+        }
         return result;
     }
 
@@ -4622,15 +4628,10 @@ namespace smt {
         expr_mark visited;
         for (expr* fml : result)
             visited.mark(fml);
-        for (literal lit : m_assigned_literals) {
-            if (get_assign_level(lit) > m_base_lvl)
-                break;
-            expr_ref e(m);
-            literal2expr(lit, e);
-            if (visited.is_marked(e))
-                continue;
-            result.push_back(std::move(e));
-        }
+        expr_ref_vector trail = get_trail(0);
+        for (expr* t : trail) 
+            if (!visited.is_marked(t))
+                result.push_back(t);
     }
 
 

src/smt/smt_context.h

@@ -1667,7 +1667,7 @@ namespace smt {
 
         void get_levels(ptr_vector<expr> const& vars, unsigned_vector& depth);
 
-        expr_ref_vector get_trail();
+        expr_ref_vector get_trail(unsigned max_level);
 
         void get_model(model_ref & m);
 

src/smt/smt_kernel.cpp

@@ -248,8 +248,8 @@ namespace smt {
         m_imp->m_kernel.get_levels(vars, depth);
     }
 
-    expr_ref_vector kernel::get_trail() {
-        return m_imp->m_kernel.get_trail();
+    expr_ref_vector kernel::get_trail(unsigned max_level) {
+        return m_imp->m_kernel.get_trail(max_level);
     }
 
     void kernel::user_propagate_init(

src/smt/smt_kernel.h

@@ -248,7 +248,7 @@ namespace smt {
         /**
            \brief retrieve trail of assignment stack.
         */
-        expr_ref_vector get_trail();
+        expr_ref_vector get_trail(unsigned max_level);
 
         /**
            \brief (For debubbing purposes) Prints the state of the kernel

src/smt/smt_solver.cpp

@@ -208,8 +208,8 @@ namespace {
             m_context.get_levels(vars, depth);
         }
 
-        expr_ref_vector get_trail() override {
-            return m_context.get_trail();
+        expr_ref_vector get_trail(unsigned max_level) override {
+            return m_context.get_trail(max_level);
         }
 
         void user_propagate_init(