COMPMID-550: Adds support for branches.

Change-Id: I778007c9221ce3156400284c4039b90245eb2b7f
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/90043
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
diff --git a/src/graph/nodes/BranchLayer.cpp b/src/graph/nodes/BranchLayer.cpp
new file mode 100644
index 0000000..28f58c6
--- /dev/null
+++ b/src/graph/nodes/BranchLayer.cpp
@@ -0,0 +1,176 @@
+/*
+ * Copyright (c) 2017 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "arm_compute/graph/nodes/BranchLayer.h"
+
+#include "arm_compute/graph/Graph.h"
+#include "arm_compute/graph/SubGraph.h"
+#include "arm_compute/graph/Tensor.h"
+#include "arm_compute/runtime/IFunction.h"
+#include "support/ToolchainSupport.h"
+#include "utils/TypePrinter.h"
+
+#include <memory>
+#include <tuple>
+#include <vector>
+
+using namespace arm_compute::graph;
+
+namespace
+{
+void depth_concatenate_output_info(ITensorInfo *info, ITensorInfo *sub_tensor_info)
+{
+    ARM_COMPUTE_ERROR_ON(info == nullptr);
+    ARM_COMPUTE_ERROR_ON(sub_tensor_info == nullptr);
+
+    TensorShape        info_shape            = info->tensor_shape();
+    const TensorShape &sub_tensor_info_shape = sub_tensor_info->tensor_shape();
+
+    // Update parent info and valid region
+    if(info_shape.total_size() == 0)
+    {
+        arm_compute::auto_init_if_empty(*info,
+                                        sub_tensor_info->tensor_shape(),
+                                        sub_tensor_info->num_channels(),
+                                        sub_tensor_info->data_type(), sub_tensor_info->fixed_point_position());
+        info->set_valid_region(sub_tensor_info->valid_region());
+    }
+    else
+    {
+        ARM_COMPUTE_ERROR_ON(info->num_channels() != sub_tensor_info->num_channels());
+        ARM_COMPUTE_ERROR_ON(info->data_type() != sub_tensor_info->data_type());
+        ARM_COMPUTE_ERROR_ON(info->fixed_point_position() != sub_tensor_info->fixed_point_position());
+
+        // Concatenate depth
+        ARM_COMPUTE_ERROR_ON(info_shape.x() != sub_tensor_info_shape.x());
+        ARM_COMPUTE_ERROR_ON(info_shape.y() != sub_tensor_info_shape.y());
+        info_shape.set(2, info_shape.z() + sub_tensor_info_shape.z());
+        info->set_tensor_shape(info_shape);
+
+        // Update valid region
+        arm_compute::ValidRegion info_valid_region = info->valid_region();
+        info_valid_region.shape.set(2, info_shape.z());
+        arm_compute::ValidRegion updated_region = arm_compute::intersect_valid_regions(info_valid_region, sub_tensor_info->valid_region());
+        info->set_valid_region(updated_region);
+    }
+}
+} // namespace
+
+/** Branch function */
+class BranchFunction final : public arm_compute::IFunction
+{
+public:
+    /** Default Constructor */
+    BranchFunction()
+        : _graphs()
+    {
+    }
+    /** Registers graph to be executed by the branch function
+     *
+     * @param[in] graph Graph to register
+     */
+    void register_graph(std::unique_ptr<Graph> graph)
+    {
+        _graphs.push_back(std::move(graph));
+    }
+    // Inherited methods overriden:
+    void run() override
+    {
+        for(auto &g : _graphs)
+        {
+            ARM_COMPUTE_ERROR_ON(g.get() == nullptr);
+            g->run();
+        }
+    }
+
+private:
+    std::vector<std::unique_ptr<Graph>> _graphs;
+};
+
+std::unique_ptr<arm_compute::IFunction> BranchLayer::instantiate_node(GraphContext &ctx, ITensorObject *input, ITensorObject *output)
+{
+    ARM_COMPUTE_ERROR_ON(_branch_merge_method != BranchMergeMethod::DEPTH_CONCATENATE);
+    ARM_COMPUTE_UNUSED(_branch_merge_method);
+    ARM_COMPUTE_ERROR_ON(input == nullptr || input->tensor() == nullptr);
+    ARM_COMPUTE_ERROR_ON(output == nullptr || output->tensor() == nullptr);
+
+    // Create branch function
+    auto func = arm_compute::support::cpp14::make_unique<BranchFunction>();
+
+    // Track output SubTensorInfo and depth
+    TensorInfo out_info;
+    int        depth = 0;
+
+    // Constuct all sub-graphs given the input/output
+    for(auto &sg : _sub_graphs)
+    {
+        ARM_COMPUTE_ERROR_ON(sg.get() == nullptr);
+
+        // IO buffers
+        std::unique_ptr<ITensorObject> in;
+        std::unique_ptr<ITensorObject> out;
+        SubTensor                     *out_sub_tensor = nullptr;
+
+        // Create input sub-tensor
+        if(!sg->has_input())
+        {
+            ARM_COMPUTE_ERROR_ON(dynamic_cast<Tensor *>(input) == nullptr);
+            in = arm_compute::support::cpp14::make_unique<SubTensor>(*dynamic_cast<Tensor *>(input),
+                                                                     input->tensor()->info()->tensor_shape(),
+                                                                     Coordinates());
+        }
+
+        // Create output sub-tensor
+        if(!sg->has_output())
+        {
+            ARM_COMPUTE_ERROR_ON(dynamic_cast<Tensor *>(output) == nullptr);
+            out = arm_compute::support::cpp14::make_unique<SubTensor>(*dynamic_cast<Tensor *>(output),
+                                                                      output->tensor()->info()->tensor_shape(),
+                                                                      Coordinates(0, 0, depth));
+            out_sub_tensor = dynamic_cast<SubTensor *>(out.get());
+        }
+
+        // Construct sub_graph
+        auto g = sg->construct(ctx.hints().target_hint(), std::move(in), std::move(out));
+
+        // Register graph to function
+        func->register_graph(std::move(g));
+
+        // Update and track depth
+        if(out_sub_tensor != nullptr)
+        {
+            ARM_COMPUTE_ERROR_ON(out_sub_tensor->tensor() == nullptr);
+            depth += out_sub_tensor->tensor()->info()->tensor_shape()[2];
+            depth_concatenate_output_info(&out_info, out_sub_tensor->tensor()->info());
+        }
+    }
+
+    // Auto-init output
+    arm_compute::auto_init_if_empty(*output->tensor()->info(),
+                                    out_info.tensor_shape(),
+                                    out_info.num_channels(),
+                                    out_info.data_type(),
+                                    out_info.fixed_point_position());
+
+    return std::move(func);
+}
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