add rewriting option to simplify store equalities

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

src/ast/rewriter/array_rewriter.cpp

@@ -25,6 +25,7 @@ void array_rewriter::updt_params(params_ref const & _p) {
     array_rewriter_params p(_p);
     m_sort_store = p.sort_store();
     m_expand_select_store = p.expand_select_store();
+    m_expand_store_eq = p.expand_store_eq();
 }
 
 void array_rewriter::get_param_descrs(param_descrs & r) {
@@ -365,3 +366,40 @@ br_status array_rewriter::mk_set_subset(expr * arg1, expr * arg2, expr_ref & res
     return BR_REWRITE3;
 }
 
+br_status array_rewriter::mk_eq_core(expr * lhs, expr * rhs, expr_ref & result) {
+    if (!m_expand_store_eq) {
+        return BR_FAILED;
+    }
+    expr* lhs1 = lhs;
+    while (m_util.is_store(lhs1)) {
+        lhs1 = to_app(lhs1)->get_arg(0);
+    }
+    expr* rhs1 = rhs;
+    while (m_util.is_store(rhs1)) {
+        rhs1 = to_app(rhs1)->get_arg(0);
+    }
+    if (lhs1 != rhs1) {
+        return BR_FAILED;
+    }
+    ptr_buffer<expr> fmls, args;
+    expr* e;
+    expr_ref tmp1(m()), tmp2(m());
+#define MK_EQ()                                                         \
+    while (m_util.is_store(e)) {                                        \
+        args.push_back(lhs);                                            \
+        args.append(to_app(e)->get_num_args()-2,to_app(e)->get_args()+1); \
+        mk_select(args.size(), args.c_ptr(), tmp1);                     \
+        args[0] = rhs;                                                  \
+        mk_select(args.size(), args.c_ptr(), tmp2);                     \
+        fmls.push_back(m().mk_eq(tmp1, tmp2));                          \
+        e = to_app(e)->get_arg(0);                                      \
+        args.reset();                                                   \
+    }                                                \
+    
+    e = lhs;
+    MK_EQ();
+    e = rhs;
+    MK_EQ();
+    result = m().mk_and(fmls.size(), fmls.c_ptr());
+    return BR_REWRITE_FULL;
+}

src/ast/rewriter/array_rewriter.h

@@ -31,12 +31,14 @@ class array_rewriter {
     array_util    m_util;
     bool          m_sort_store;
     bool          m_expand_select_store;
+    bool          m_expand_store_eq;
     template<bool CHECK_DISEQ>
     lbool compare_args(unsigned num_args, expr * const * args1, expr * const * args2);
 public:    
     array_rewriter(ast_manager & m, params_ref const & p = params_ref()):
         m_util(m) {
         updt_params(p);
+
     }
     ast_manager & m() const { return m_util.get_manager(); }
     family_id get_fid() const { return m_util.get_family_id(); }
@@ -60,6 +62,7 @@ public:
     br_status mk_set_complement(expr * arg, expr_ref & result);
     br_status mk_set_difference(expr * arg1, expr * arg2, expr_ref & result);
     br_status mk_set_subset(expr * arg1, expr * arg2, expr_ref & result);
+    br_status mk_eq_core(expr * lhs, expr * rhs, expr_ref & result);
 };
 
 #endif

src/ast/rewriter/array_rewriter_params.pyg

@@ -2,4 +2,5 @@ def_module_params(module_name='rewriter',
                   class_name='array_rewriter_params',
                   export=True,
                   params=(("expand_select_store", BOOL, False, "replace a (select (store ...) ...) term by an if-then-else term"),
+			  ("expand_store_eq", BOOL, False, "reduce (store ...) = (store ...) with a common base into selects"),
                           ("sort_store", BOOL, False, "sort nested stores when the indices are known to be different")))

src/ast/rewriter/mk_simplified_app.cpp

@@ -62,6 +62,8 @@ struct mk_simplified_app::imp {
                     st = m_dt_rw.mk_eq_core(args[0], args[1], result);
                 else if (s_fid == m_f_rw.get_fid())
                     st = m_f_rw.mk_eq_core(args[0], args[1], result);
+                else if (s_fid == m_ar_rw.get_fid())
+                    st = m_ar_rw.mk_eq_core(args[0], args[1], result);
                 
                 if (st != BR_FAILED)
                     return st;

src/ast/rewriter/th_rewriter.cpp

@@ -169,7 +169,9 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
                     st = m_dt_rw.mk_eq_core(args[0], args[1], result);
                 else if (s_fid == m_f_rw.get_fid())
                     st = m_f_rw.mk_eq_core(args[0], args[1], result);
-
+                else if (s_fid == m_ar_rw.get_fid())
+                    st = m_ar_rw.mk_eq_core(args[0], args[1], result);
+                
                 if (st != BR_FAILED)
                     return st;
             }