Fix broadcast v1 reference (#3880)

* Added reproducer for issue with broadcast v1

* Make reference broadcast work with V1 broadcast

src/ngraph/runtime/reference/broadcast.hpp

@@ -34,13 +34,31 @@ namespace ngraph
                            const Shape& out_shape,
                            const AxisSet& broadcast_axes)
             {
-                CoordinateTransform input_transform(in_shape);
+                // Remove all broadcast axes from in_shape
+                Shape adjusted_in_shape;
+                for (auto length : in_shape)
+                {
+                    if (length != 1)
+                    {
+                        adjusted_in_shape.push_back(length);
+                    }
+                }
+                // Remove 1s from out_shape
+                AxisSet adjusted_axes(broadcast_axes);
+                for (uint64_t axis = 0; axis < out_shape.size(); ++axis)
+                {
+                    auto length = out_shape.at(axis);
+                    if (length == 1)
+                    {
+                        adjusted_axes.insert(axis);
+                    }
+                }
+                CoordinateTransform input_transform(adjusted_in_shape);
                 CoordinateTransform output_transform(out_shape);
 
                 for (const Coordinate& output_coord : output_transform)
                 {
-                    Coordinate input_coord = reduce(output_coord, broadcast_axes);
-
+                    Coordinate input_coord = reduce(output_coord, adjusted_axes);
                     out[output_transform.index(output_coord)] =
                         arg[input_transform.index(input_coord)];
                 }

test/constant_folding.cpp

@@ -206,6 +206,30 @@ TEST(constant_folding, constant_broadcast_v1)
     ASSERT_EQ(values_expected, values_out);
 }
 
+TEST(constant_folding, constant_broadcast_v1_with_target_shape)
+{
+    vector<int32_t> values_in{1};
+    auto constant_in = make_shared<op::Constant>(element::i32, Shape{1, 1, 1, 1}, values_in);
+    vector<int64_t> shape_in{1, 3, 1, 1};
+    auto target_shape = make_shared<op::Constant>(element::i64, Shape{4}, shape_in);
+    auto broadcast_v1 = make_shared<op::v1::Broadcast>(constant_in, target_shape);
+    auto f = make_shared<Function>(broadcast_v1, ParameterVector{});
+
+    pass::Manager pass_manager;
+    pass_manager.register_pass<pass::ConstantFolding>();
+    pass_manager.run_passes(f);
+
+    ASSERT_EQ(count_ops_of_type<op::v1::Broadcast>(f), 0);
+    ASSERT_EQ(count_ops_of_type<op::Constant>(f), 1);
+
+    auto new_const = as_type_ptr<op::Constant>(f->get_results().at(0)->get_argument(0));
+    ASSERT_TRUE(new_const);
+    auto values_out = new_const->get_vector<int32_t>();
+
+    vector<int32_t> values_expected{1, 1, 1};
+    ASSERT_EQ(values_expected, values_out);
+}
+
 TEST(constant_folding, constant_broadcast_v1_numpy)
 {
     vector<int32_t> values_in{0, 1};