Add implementation of (unsigned) division operator bvudiv.

Along with tests of its conversion and the function application factory integrity.

Author: NlightNFotis

src/solvers/smt2_incremental/convert_expr_to_smt.cpp

@@ -361,8 +361,20 @@ static smt_termt convert_expr_to_smt(const minus_exprt &minus)
 
 static smt_termt convert_expr_to_smt(const div_exprt &divide)
 {
-  UNIMPLEMENTED_FEATURE(
-    "Generation of SMT formula for divide expression: " + divide.pretty());
+  const bool both_operands_bitvector =
+    can_cast_type<integer_bitvector_typet>(divide.lhs().type()) &&
+    can_cast_type<integer_bitvector_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()));
+  }
+  else
+  {
+    UNIMPLEMENTED_FEATURE(
+      "Generation of SMT formula for divide expression: " + divide.pretty());
+  }
 }
 
 static smt_termt convert_expr_to_smt(const ieee_float_op_exprt &float_operation)

src/solvers/smt2_incremental/smt_bit_vector_theory.cpp

@@ -273,3 +273,26 @@ void smt_bit_vector_theoryt::multiplyt::validate(
 const smt_function_application_termt::factoryt<
   smt_bit_vector_theoryt::multiplyt>
   smt_bit_vector_theoryt::multiply{};
+
+const char *smt_bit_vector_theoryt::unsigned_dividet::identifier()
+{
+  return "bvudiv";
+}
+
+smt_sortt smt_bit_vector_theoryt::unsigned_dividet::return_sort(
+  const smt_termt &lhs,
+  const smt_termt &rhs)
+{
+  return lhs.get_sort();
+}
+
+void smt_bit_vector_theoryt::unsigned_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::unsigned_dividet>
+  smt_bit_vector_theoryt::unsigned_divide{};

src/solvers/smt2_incremental/smt_bit_vector_theory.h

@@ -108,6 +108,15 @@ class smt_bit_vector_theoryt
     static void validate(const smt_termt &lhs, const smt_termt &rhs);
   };
   static const smt_function_application_termt::factoryt<multiplyt> multiply;
+
+  struct unsigned_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<unsigned_dividet>
+    unsigned_divide;
 };
 
 #endif // CPROVER_SOLVERS_SMT2_INCREMENTAL_SMT_BIT_VECTOR_THEORY_H

unit/solvers/smt2_incremental/convert_expr_to_smt.cpp

@@ -345,4 +345,23 @@ TEST_CASE(
     const cbmc_invariants_should_throwt invariants_throw;
     REQUIRE_THROWS(convert_expr_to_smt(mult_exprt{one_bvint, false_exprt{}}));
   }
+
+  // Division is defined over unsigned numbers only (theory notes say it
+  // truncates over zero)
+  SECTION("Division of two constant size bit-vectors")
+  {
+    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);
+  }
+
+  SECTION(
+    "Ensure that division node conversion fails if the operands are not "
+    "bit-vector based")
+  {
+    const cbmc_invariants_should_throwt invariants_throw;
+    REQUIRE_THROWS(convert_expr_to_smt(div_exprt{one_bvint, false_exprt{}}));
+  }
 }

unit/solvers/smt2_incremental/smt_bit_vector_theory.cpp

@@ -233,4 +233,23 @@ TEST_CASE(
     // invariant violation.
     REQUIRE_THROWS(smt_bit_vector_theoryt::multiply(true_val, three));
   }
+
+  SECTION("Unsigned Division")
+  {
+    const auto function_application =
+      smt_bit_vector_theoryt::unsigned_divide(two, three);
+    REQUIRE(
+      function_application.function_identifier() ==
+      smt_identifier_termt("bvudiv", 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::unsigned_divide(three, four));
+    // A division of a bool and a bitvector should hit an invariant violation.
+    REQUIRE_THROWS(smt_bit_vector_theoryt::unsigned_divide(true_val, three));
+  }
 }