Add implementation of (signed) division operator (bvsdiv).

In addition, modify the tests and the implementation of the conversion function
to account for signed/unsigned input.

Author: NlightNFotis

src/solvers/smt2_incremental/convert_expr_to_smt.cpp

@@ -366,10 +366,22 @@ static smt_termt convert_expr_to_smt(const div_exprt &divide)
     can_cast_type<integer_bitvector_typet>(divide.lhs().type()) &&
     can_cast_type<integer_bitvector_typet>(divide.rhs().type());
 
+  const bool both_operands_unsigned =
+    can_cast_type<unsignedbv_typet>(divide.lhs().type()) &&
+    can_cast_type<unsignedbv_typet>(divide.rhs().type());
+
   if(both_operands_bitvector)
   {
-    return smt_bit_vector_theoryt::unsigned_divide(
-      convert_expr_to_smt(divide.lhs()), convert_expr_to_smt(divide.rhs()));
+    if(both_operands_unsigned)
+    {
+      return smt_bit_vector_theoryt::unsigned_divide(
+        convert_expr_to_smt(divide.lhs()), convert_expr_to_smt(divide.rhs()));
+    }
+    else
+    {
+      return smt_bit_vector_theoryt::signed_divide(
+        convert_expr_to_smt(divide.lhs()), convert_expr_to_smt(divide.rhs()));
+    }
   }
   else
   {

src/solvers/smt2_incremental/smt_bit_vector_theory.cpp

@@ -296,3 +296,26 @@ void smt_bit_vector_theoryt::unsigned_dividet::validate(
 const smt_function_application_termt::factoryt<
   smt_bit_vector_theoryt::unsigned_dividet>
   smt_bit_vector_theoryt::unsigned_divide{};
+
+const char *smt_bit_vector_theoryt::signed_dividet::identifier()
+{
+  return "bvsdiv";
+}
+
+smt_sortt smt_bit_vector_theoryt::signed_dividet::return_sort(
+  const smt_termt &lhs,
+  const smt_termt &rhs)
+{
+  return lhs.get_sort();
+}
+
+void smt_bit_vector_theoryt::signed_dividet::validate(
+  const smt_termt &lhs,
+  const smt_termt &rhs)
+{
+  validate_bit_vector_predicate_arguments(lhs, rhs);
+}
+
+const smt_function_application_termt::factoryt<
+  smt_bit_vector_theoryt::signed_dividet>
+  smt_bit_vector_theoryt::signed_divide{};

src/solvers/smt2_incremental/smt_bit_vector_theory.h

@@ -117,6 +117,15 @@ class smt_bit_vector_theoryt
   };
   static const smt_function_application_termt::factoryt<unsigned_dividet>
     unsigned_divide;
+
+  struct signed_dividet final
+  {
+    static const char *identifier();
+    static smt_sortt return_sort(const smt_termt &lhs, const smt_termt &rhs);
+    static void validate(const smt_termt &lhs, const smt_termt &rhs);
+  };
+  static const smt_function_application_termt::factoryt<signed_dividet>
+    signed_divide;
 };
 
 #endif // CPROVER_SOLVERS_SMT2_INCREMENTAL_SMT_BIT_VECTOR_THEORY_H

unit/solvers/smt2_incremental/convert_expr_to_smt.cpp

@@ -350,11 +350,19 @@ TEST_CASE(
   // truncates over zero)
   SECTION("Division of two constant size bit-vectors")
   {
+    // Check of division expression with unsigned operands
     const auto constructed_term =
       convert_expr_to_smt(div_exprt{one_bvint_unsigned, two_bvint_unsigned});
     const auto expected_term =
       smt_bit_vector_theoryt::unsigned_divide(smt_term_one, smt_term_two);
     CHECK(constructed_term == expected_term);
+
+    // Check of division expression with signed operands
+    const auto constructed_term_signed =
+      convert_expr_to_smt(div_exprt{one_bvint, two_bvint});
+    const auto expected_term_signed =
+      smt_bit_vector_theoryt::signed_divide(smt_term_one, smt_term_two);
+    CHECK(constructed_term_signed == expected_term_signed);
   }
 
   SECTION(

unit/solvers/smt2_incremental/smt_bit_vector_theory.cpp

@@ -250,4 +250,23 @@ TEST_CASE(
     // A division of a bool and a bitvector should hit an invariant violation.
     REQUIRE_THROWS(smt_bit_vector_theoryt::unsigned_divide(true_val, three));
   }
+
+  SECTION("Signed Division")
+  {
+    const auto function_application =
+      smt_bit_vector_theoryt::signed_divide(two, three);
+    REQUIRE(
+      function_application.function_identifier() ==
+      smt_identifier_termt("bvsdiv", smt_bit_vector_sortt{8}));
+    REQUIRE(function_application.get_sort() == smt_bit_vector_sortt{8});
+    REQUIRE(function_application.arguments().size() == 2);
+    REQUIRE(function_application.arguments()[0].get() == two);
+    REQUIRE(function_application.arguments()[1].get() == three);
+
+    cbmc_invariants_should_throwt invariants_throw;
+    // Bit-vectors of mismatched sorts are going to hit an invariant violation.
+    REQUIRE_THROWS(smt_bit_vector_theoryt::signed_divide(three, four));
+    // A division of a bool and a bitvector should hit an invariant violation.
+    REQUIRE_THROWS(smt_bit_vector_theoryt::signed_divide(true_val, three));
+  }
 }