Check for element-wise equality at construction and simplify zero/one…

… checks later (#3785)

src/ngraph/graph_util.cpp

@@ -327,17 +327,8 @@ bool ngraph::is_equal_to_const_value(std::string const_value, const Output<Node>
 {
     if (auto rc = dynamic_pointer_cast<ngraph::op::Constant>(reduce_constant.get_node_shared_ptr()))
     {
-        auto cshape = rc->get_shape();
-        size_t n = shape_size(cshape);
-        // way to construct a constant of a given type, shape, value
-        std::vector<std::string> vector_zero{n, const_value};
-        auto constant_val_op =
-            std::make_shared<ngraph::op::Constant>(rc->get_element_type(), cshape, vector_zero);
-
-        // way to compare elements to const_value
-        size_t n_bytes = n * rc->get_element_type().size();
-        NGRAPH_DEBUG << "Comparing " << n_bytes << " bytes";
-        return !memcmp(constant_val_op->get_data_ptr(), rc->get_data_ptr(), n_bytes);
+        return (rc->get_all_data_elements_bitwise_identical() &&
+                rc->convert_value_to_string(0) == const_value);
     }
     else
     {

src/ngraph/op/constant.hpp

@@ -70,6 +70,7 @@ namespace ngraph
                     write_values(values);
                 }
                 constructor_validate_and_infer_types();
+                m_all_elements_bitwise_identical = are_all_data_elements_bitwise_identical();
             }
 
             /// \brief Constructs a tensor constant
@@ -128,6 +129,7 @@ namespace ngraph
                     }
                 }
                 constructor_validate_and_infer_types();
+                m_all_elements_bitwise_identical = are_all_data_elements_bitwise_identical();
             }
 
             /// \brief Constructs a tensor constant with the same initialization value copied across
@@ -146,6 +148,7 @@ namespace ngraph
                                                         host_alignment()));
                 std::memcpy(m_data->get_ptr(), data, size);
                 constructor_validate_and_infer_types();
+                m_all_elements_bitwise_identical = are_all_data_elements_bitwise_identical();
             }
 
             virtual ~Constant() override;
@@ -246,6 +249,10 @@ namespace ngraph
 
             bool is_constant() const override { return true; }
             bool are_all_data_elements_bitwise_identical() const;
+            bool get_all_data_elements_bitwise_identical() const
+            {
+                return m_all_elements_bitwise_identical;
+            }
             std::string convert_value_to_string(size_t index) const;
 
         protected:
@@ -343,6 +350,7 @@ namespace ngraph
             element::Type m_element_type;
             Shape m_shape{};
             std::unique_ptr<runtime::AlignedBuffer> m_data;
+            bool m_all_elements_bitwise_identical;
             Constant(const Constant&) = delete;
             Constant operator=(const Constant&) = delete;
         };