fuse onnx gather after shufflechannel into split

tools/onnx/onnx2ncnn.cpp

@@ -432,6 +432,84 @@ static void fuse_shufflechannel(onnx::GraphProto* mutable_graph, std::map<std::s
     }
 }
 
+static void fuse_shufflechannel_split(onnx::GraphProto* mutable_graph, std::map<std::string, onnx::TensorProto>& weights, std::map<std::string, onnx::TensorProto>& binaryop_weights, std::map<std::string, int>& node_reference, std::set<std::string>& blob_names, int& reduced_node_count, std::vector<std::string>& reduced_binaryop_weights)
+{
+    int node_count = mutable_graph->node_size();
+    for (int i = 0; i < node_count; i++)
+    {
+        onnx::NodeProto* node = mutable_graph->mutable_node(i);
+
+        // Split <= ShuffleChannel(reverse type) - Gather(0) - Gather(1)
+        if (node->op_type() == "ShuffleChannel")
+        {
+            // reverse = 1
+            int reverse = get_node_attr_i(*node, "reverse");
+            if (reverse != 1)
+                continue;
+
+            if (i + 2 >= node_count)
+                continue;
+
+            onnx::NodeProto* node2 = mutable_graph->mutable_node(i + 1);
+            onnx::NodeProto* node3 = mutable_graph->mutable_node(i + 2);
+
+            if (node2->op_type() != "Gather" || node3->op_type() != "Gather")
+                continue;
+
+            if (node2->input(0) != node->output(0) || node3->input(0) != node->output(0))
+                continue;
+
+            // axis = 0
+            int gather2_axis = get_node_attr_i(*node2, "axis");
+            if (gather2_axis != 0)
+                continue;
+
+            // indices = 0
+            if (weights.find(node2->input(1)) == weights.end())
+                continue;
+
+            std::vector<int> gather2_indices = get_node_attr_from_input_ai(weights[node2->input(1)]);
+            if (gather2_indices.size() != 1 || gather2_indices[0] != 0)
+                continue;
+
+            // axis = 0
+            int gather3_axis = get_node_attr_i(*node3, "axis");
+            if (gather3_axis != 0)
+                continue;
+
+            // indices = 1
+            if (weights.find(node3->input(1)) == weights.end())
+                continue;
+
+            std::vector<int> gather3_indices = get_node_attr_from_input_ai(weights[node3->input(1)]);
+            if (gather3_indices.size() != 1 || gather3_indices[0] != 1)
+                continue;
+
+            // reduce
+            node2->set_op_type("noop_reducedncnn");
+
+            node_reference[node->output(0)] -= 1;
+
+            node_reference.erase(node_reference.find(node2->output(0)));
+            blob_names.erase(node2->output(0));
+
+            node3->set_op_type("Split");
+            node3->clear_input();
+            node3->add_input(node->output(0));
+            node3->add_output(node3->output(0));
+            node3->set_output(0, node2->output(0));
+
+            node3->clear_attribute();
+            onnx::AttributeProto* attr_axis = node3->add_attribute();
+            attr_axis->set_name("axis");
+            attr_axis->set_i(1);
+
+            reduced_node_count += 1;
+            i += 1;
+        }
+    }
+}
+
 static void fuse_hardswish(onnx::GraphProto* mutable_graph, std::map<std::string, onnx::TensorProto>& weights, std::map<std::string, onnx::TensorProto>& binaryop_weights, std::map<std::string, int>& node_reference, std::set<std::string>& blob_names, int& reduced_node_count, std::vector<std::string>& reduced_binaryop_weights)
 {
     int node_count = mutable_graph->node_size();
@@ -1383,6 +1461,7 @@ int main(int argc, char** argv)
     std::vector<std::string> reduced_binaryop_weights;
     fuse_matmul(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);
     fuse_shufflechannel(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);
+    fuse_shufflechannel_split(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);
     fuse_hardsigmoid(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);
     fuse_hardswish(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);
     fuse_swish(mutable_graph, weights, binaryop_weights, node_reference, blob_names, reduced_node_count, reduced_binaryop_weights);