Allow use of MKLDNN backprop when pointer to forward-prop op is missing (#523)

src/ngraph/runtime/cpu/cpu_emitter.cpp

@@ -2682,14 +2682,13 @@ namespace ngraph
             void CPU_Emitter::EMITTER_DECL(ngraph::op::MaxPoolBackprop)
             {
                 auto mpb = static_cast<const ngraph::op::MaxPoolBackprop*>(node);
-                auto max_pool_fprop_op = mpb->get_forward_op();
 
                 auto delta_shape = args[1].get_shape();
                 auto delta_rank = delta_shape.size();
                 auto out_shape = out[0].get_shape();
 
                 if (delta_rank == 4 && mpb->get_window_shape().size() == 2 &&
-                    args[0].get_element_type() == element::f32 && max_pool_fprop_op != nullptr)
+                    args[0].get_element_type() == element::f32)
                 {
                     const string& et =
                         get_mkldnn_data_type(args[1].get_element_type().c_type_string());
@@ -2725,10 +2724,10 @@ namespace ngraph
                               "pooling_forward::primitive_desc("
                            << "{prop_kind::forward, algorithm::pooling_max, "
                            << "max_pool_input_desc, max_pool_result_desc, {"
-                           << join(max_pool_fprop_op->get_window_movement_strides()) << "}, {"
-                           << join(max_pool_fprop_op->get_window_shape()) << "}, "
-                           << "{" << join(max_pool_fprop_op->get_padding_below()) << "}, "
-                           << "{" << join(max_pool_fprop_op->get_padding_above()) << "}, "
+                           << join(mpb->get_window_movement_strides()) << "}, {"
+                           << join(mpb->get_window_shape()) << "}, "
+                           << "{" << join(mpb->get_padding_below()) << "}, "
+                           << "{" << join(mpb->get_padding_above()) << "}, "
                            << "padding_kind::zero}, cpu_engine);\n";
 
                     // query the workspace from the forward primitive desc and allocates memory