COMPMID-1461 SSD support: Create NEON PriorBox

Change-Id: I99e1c3939cfea4b9cb0ddfa313706f31b213ca89
diff --git a/arm_compute/core/NEON/kernels/NEPriorBoxLayerKernel.h b/arm_compute/core/NEON/kernels/NEPriorBoxLayerKernel.h
new file mode 100644
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+++ b/arm_compute/core/NEON/kernels/NEPriorBoxLayerKernel.h
@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2018 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.
+ */
+#ifndef __ARM_COMPUTE_NEPRIORBOXLAYERKERNEL_H__
+#define __ARM_COMPUTE_NEPRIORBOXLAYERKERNEL_H__
+
+#include "arm_compute/core/NEON/INEKernel.h"
+
+namespace arm_compute
+{
+class ITensor;
+
+/** Interface for the kernel to calculate prior boxes */
+class NEPriorBoxLayerKernel : public INEKernel
+{
+public:
+    const char *name() const override
+    {
+        return "NEPriorBoxLayerKernel";
+    }
+    /** Default constructor */
+    NEPriorBoxLayerKernel();
+    /** Prevent instances of this class from being copied (As this class contains pointers) */
+    NEPriorBoxLayerKernel(const NEPriorBoxLayerKernel &) = delete;
+    /** Prevent instances of this class from being copied (As this class contains pointers) */
+    NEPriorBoxLayerKernel &operator=(const NEPriorBoxLayerKernel &) = delete;
+    /** Allow instances of this class to be moved */
+    NEPriorBoxLayerKernel(NEPriorBoxLayerKernel &&) = default;
+    /** Allow instances of this class to be moved */
+    NEPriorBoxLayerKernel &operator=(NEPriorBoxLayerKernel &&) = default;
+    /** Set the input and output tensors.
+     *
+     * @param[in]  input1 First source tensor. Data types supported: F32. Data layouts supported: NCHW/NHWC.
+     * @param[in]  input2 Second source tensor. Data types and layouts supported: same as @p input1
+     * @param[out] output Destination tensor. Output dimensions are [W * H * num_priors * 4, 2]. Data type supported: same as @p input
+     * @param[in]  info   Prior box layer info.
+     */
+    void configure(const ITensor *input1, const ITensor *input2, ITensor *output, const PriorBoxLayerInfo &info);
+    /** Static function to check if given info will lead to a valid configuration of @ref NEPriorBoxLayerKernel
+     *
+     * @param[in] input1 First source tensor info. Data types supported: F32. Data layouts supported: NCHW/NHWC.
+     * @param[in] input2 Second source tensor info. Data types and layouts supported: same as @p input1
+     * @param[in] output Destination tensor info. Output dimensions are [W * H * num_priors * 4, 2]. Data type supported: same as @p input
+     * @param[in] info   Prior box layer info.
+     *
+     * @return a status
+     */
+    static Status validate(const ITensorInfo *input1, const ITensorInfo *input2, const ITensorInfo *output, const PriorBoxLayerInfo &info);
+
+    // Inherited methods overridden:
+    void run(const Window &window, const ThreadInfo &info) override;
+
+private:
+    /** Stores the coordinates of the calculated prior boxes.
+     *
+     * @param[out] out        Output pointer.
+     * @param[in]  offset     Output offset to write to.
+     * @param[in]  center_x   Center pixel value on x-axis.
+     * @param[in]  center_y   Center pixel value on y-axis.
+     * @param[in]  box_width  Prior box width.
+     * @param[in]  box_height Prior box height.
+     * @param[in]  width      Input width.
+     * @param[in]  height     Input height.
+     */
+    template <DataLayout DL>
+    void store_coordinates(float *out, const int offset, const float center_x, const float center_y, const float box_width, const float box_height, const int width, const int height);
+    /** Function to calculate prior boxes.
+     *
+     * @param[in] window Input region on which to execute the kernel.
+     */
+    template <DataLayout DL>
+    void calculate_prior_boxes(const Window &window);
+    /** Common signature for all the specialised PriorBox functions
+     *
+     * @param[in] window Input region on which to execute the kernel..
+     */
+    using PriorBoxFunction = void (NEPriorBoxLayerKernel::*)(const Window &window);
+    PriorBoxFunction  _func;
+    const ITensor    *_input1;
+    const ITensor    *_input2;
+    ITensor          *_output;
+    PriorBoxLayerInfo _info;
+};
+} // namespace arm_compute
+#endif /* __ARM_COMPUTE_NEPRIORBOXLAYERKERNEL_H__ */