add anf and aig simplifier modules, cut-set enumeration, aig_finder, hoist out xor_finder from ba_solver

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

src/sat/sat_aig_finder.h

@@ -0,0 +1,52 @@
+/*++
+  Copyright (c) 2020 Microsoft Corporation
+
+  Module Name:
+
+   sat_aig_finder.h
+
+  Abstract:
+   
+    extract AIG definitions from clauses.
+    An example AIG clause is:
+       head \/ l1 \/ l2
+    such that 
+       ~l1 /\ ~l2 => head
+       head => ~l1, head => ~l2
+
+  Author:
+
+    Nikolaj Bjorner 2020-01-02
+
+  Notes:
+  
+    AIG finder
+  --*/
+
+#pragma once;
+
+#include "util/params.h"
+#include "util/statistics.h"
+#include "sat/sat_clause.h"
+#include "sat/sat_types.h"
+#include "sat/sat_solver.h"
+#include "sat/sat_big.h"
+
+namespace sat {
+
+    class aig_finder {
+        solver& s;
+        big                     m_big;
+        literal_vector          m_ands; 
+        std::function<void (literal head, literal_vector const& ands, clause& orig)> m_aig_def;
+        bool implies(literal a, literal b);
+        bool find_aig(clause& c);
+        bool find_if(clause& c);
+
+    public:
+        aig_finder(solver& s) : s(s), m_big(s.rand()) {}
+        ~aig_finder() {}                
+        void set(std::function<void (literal head, literal_vector const& ands, clause& orig)>& f) { m_aig_def = f; }
+        void operator()(clause_vector const& clauses);
+    };
+}