swim a special case of broadcast (#2034)

src/ngraph/runtime/cpu/pass/cpu_reshape_sinking.cpp

@@ -84,6 +84,25 @@ static void delete_reshape(std::shared_ptr<Node> reshape)
     }
 }
 
+static bool unique_dims(const Shape& shape)
+{
+    if (shape.size() == 0)
+    {
+        return true;
+    }
+
+    size_t n = shape.at(0);
+    for (size_t i = 1; i < shape.size(); i++)
+    {
+        if (n == shape.at(i))
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 static void mark_reshape_for_deletion(std::shared_ptr<Node> reshape,
                                       std::set<std::shared_ptr<Node>>& reshapes_to_delete)
 {
@@ -144,6 +163,23 @@ void swim(descriptor::Input* input, std::shared_ptr<op::Reshape> reshape)
             NGRAPH_DEBUG << "Propagating reshape " << describe_reshape(csw.reshape) << " for "
                          << n->get_name() << " to " << unary->get_argument(0);
         }
+        else if (std::dynamic_pointer_cast<op::Broadcast>(n) &&
+                 n->get_argument(0)->get_shape().size() == 1 && unique_dims(n->get_shape()))
+        {
+            auto old_broadcast = std::static_pointer_cast<op::Broadcast>(n);
+            ngraph::AxisSet as;
+            size_t channel = n->get_argument(0)->get_shape().at(0);
+            for (size_t i = 0; i < n->get_shape().size(); i++)
+            {
+                if (csw.reshape->get_shape().at(i) != channel)
+                {
+                    as.insert(i);
+                }
+            }
+            auto new_broadcast =
+                std::make_shared<op::Broadcast>(n->get_argument(0), csw.reshape->get_shape(), as);
+            csw.input->replace_output(new_broadcast->get_outputs().at(0));
+        }
         //TODO: Add cases to push through Reshape and BinaryElementwiseArithmetic
         else
         {