COMPMID-1763 : NEON: Implement Gather

Change-Id: I9a3808315290bd395f5acce4530ab8daccddf8be
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/167195
Tested-by: bsgcomp <bsgcomp@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Reviewed-on: https://review.mlplatform.org/520
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Marquez <pablo.tello@arm.com>
diff --git a/src/core/NEON/kernels/NEGatherKernel.cpp b/src/core/NEON/kernels/NEGatherKernel.cpp
new file mode 100644
index 0000000..a05059d
--- /dev/null
+++ b/src/core/NEON/kernels/NEGatherKernel.cpp
@@ -0,0 +1,203 @@
+/*
+ * Copyright (c) 2019 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/core/NEON/kernels/NEGatherKernel.h"
+
+#include "arm_compute/core/Coordinates.h"
+#include "arm_compute/core/Error.h"
+#include "arm_compute/core/Helpers.h"
+#include "arm_compute/core/IAccessWindow.h"
+#include "arm_compute/core/TensorInfo.h"
+#include "arm_compute/core/Validate.h"
+#include "arm_compute/core/Window.h"
+#include "arm_compute/core/utils/misc/ShapeCalculator.h"
+
+namespace arm_compute
+{
+namespace
+{
+/** Validate the indices
+ *
+ * Validate that indices are not negative
+ *
+ * @param[in] indices Indices tensor info.
+ */
+template <typename U>
+void validate_indices(const ITensor *indices)
+{
+    for(size_t i = 0; i < indices->info()->tensor_shape()[0]; ++i)
+    {
+        ARM_COMPUTE_ERROR_ON(*(reinterpret_cast<U *>(indices->ptr_to_element(Coordinates(i)))) < 0);
+    }
+}
+
+} // namespace
+
+NEGatherKernel::NEGatherKernel()
+    : _input{}, _indices{}, _axis{}, _output{}, _func{}
+{
+}
+
+template <typename U>
+inline void NEGatherKernel::gather_0_axis(const Window &window, const ThreadInfo &info)
+{
+    ARM_COMPUTE_UNUSED(info);
+
+    // Validate that the indices are not negative
+    validate_indices<U>(_indices);
+
+    Iterator output_it(_output, window);
+    execute_window_loop(window, [&](const Coordinates & id)
+    {
+        Coordinates gather_id(id);
+
+        auto new_index = *(reinterpret_cast<U *>(_indices->ptr_to_element(Coordinates(id[0]))));
+        gather_id.set(0, new_index);
+
+        std::copy_n(_input->ptr_to_element(gather_id), _output->info()->element_size(), output_it.ptr());
+    },
+    output_it);
+}
+
+template <typename U>
+void NEGatherKernel::gather_n_axis(const Window &window, const ThreadInfo &info)
+{
+    ARM_COMPUTE_UNUSED(info);
+
+    // Validate that the indices are not negative
+    validate_indices<U>(_indices);
+
+    Window output_window{ window };
+    output_window.set(Window::DimX, Window::Dimension(0, 1, 1));
+
+    Iterator output_it(_output, output_window);
+    execute_window_loop(output_window, [&](const Coordinates & id)
+    {
+        Coordinates gather_id(id);
+
+        auto new_index = *(reinterpret_cast<U *>(_indices->ptr_to_element(Coordinates(id[_axis]))));
+        gather_id.set(_axis, new_index);
+
+        std::copy_n(_input->ptr_to_element(gather_id), _input->info()->dimension(0) * _output->info()->element_size(), output_it.ptr());
+    },
+    output_it);
+}
+
+void NEGatherKernel::configure(const ITensor *input, const ITensor *indices, ITensor *output, int axis)
+{
+    ARM_COMPUTE_ERROR_ON_NULLPTR(input, output, indices);
+    ARM_COMPUTE_ERROR_ON(indices->info()->num_dimensions() != 1);
+    ARM_COMPUTE_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(indices, 1, DataType::U32, DataType::S32);
+    ARM_COMPUTE_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(input, 1, DataType::U8, DataType::S8, DataType::QASYMM8, DataType::U16, DataType::S16, DataType::U32, DataType::S32, DataType::F16, DataType::F32);
+
+    _input   = input;
+    _indices = indices;
+    _output  = output;
+    _axis    = axis;
+
+    if(_axis < 0)
+    {
+        _axis += input->info()->num_dimensions();
+    }
+    ARM_COMPUTE_ERROR_ON(0 > _axis || _axis >= static_cast<int32_t>(input->info()->num_dimensions()));
+
+    if(0 == _axis)
+    {
+        switch(_indices->info()->data_type())
+        {
+            case DataType::U32:
+                _func = &NEGatherKernel::gather_0_axis<uint32_t>;
+                break;
+            case DataType::S32:
+                _func = &NEGatherKernel::gather_0_axis<int32_t>;
+                break;
+            default:
+                ARM_COMPUTE_ERROR("Not supported");
+                break;
+        }
+    }
+    else
+    {
+        switch(_indices->info()->data_type())
+        {
+            case DataType::U32:
+                _func = &NEGatherKernel::gather_n_axis<uint32_t>;
+                break;
+            case DataType::S32:
+                _func = &NEGatherKernel::gather_n_axis<int32_t>;
+                break;
+            default:
+                ARM_COMPUTE_ERROR("Not supported");
+                break;
+        }
+    }
+    // Output auto initialization if not yet initialized
+    TensorShape output_shape = arm_compute::misc::shape_calculator::compute_gather_shape(input->info()->tensor_shape(), indices->info()->tensor_shape(), _axis);
+    auto_init_if_empty(*output->info(), output_shape, 1, input->info()->data_type());
+
+    // Create window
+    Window win = calculate_max_window(*output->info(), Steps());
+    output->info()->set_valid_region(ValidRegion(Coordinates(), output->info()->tensor_shape()));
+
+    INEKernel::configure(win);
+}
+
+Status NEGatherKernel::validate(const ITensorInfo *input, const ITensorInfo *indices, const ITensorInfo *output, int axis)
+{
+    ARM_COMPUTE_RETURN_ERROR_ON_NULLPTR(input, indices, output);
+    ARM_COMPUTE_RETURN_ERROR_ON(indices->num_dimensions() > 1);
+    ARM_COMPUTE_RETURN_ERROR_ON(input->num_dimensions() > 4);
+
+    if(axis < 0)
+    {
+        axis += input->num_dimensions();
+    }
+
+    ARM_COMPUTE_RETURN_ERROR_ON(0 > axis || axis >= static_cast<int32_t>(input->num_dimensions()));
+    ARM_COMPUTE_RETURN_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(input, 1, DataType::U8, DataType::S8, DataType::QASYMM8,
+                                                         DataType::U16, DataType::S16,
+                                                         DataType::U32, DataType::S32, DataType::F16, DataType::F32);
+
+    if(output->total_size() != 0)
+    {
+        ARM_COMPUTE_RETURN_ERROR_ON_MISMATCHING_DATA_TYPES(input, output);
+        ARM_COMPUTE_RETURN_ERROR_ON_MISMATCHING_QUANTIZATION_INFO(input, output);
+        TensorShape output_shape = arm_compute::misc::shape_calculator::compute_gather_shape(input->tensor_shape(), indices->tensor_shape(), axis);
+        ARM_COMPUTE_RETURN_ERROR_ON(output_shape.total_size() != output->tensor_shape().total_size());
+    }
+
+    ARM_COMPUTE_RETURN_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(indices, 1, DataType::U32, DataType::S32);
+
+    return Status{};
+}
+
+void NEGatherKernel::run(const Window &window, const ThreadInfo &info)
+{
+    ARM_COMPUTE_UNUSED(info);
+    ARM_COMPUTE_ERROR_ON_UNCONFIGURED_KERNEL(this);
+    ARM_COMPUTE_ERROR_ON(_func == nullptr);
+
+    (this->*_func)(window, info);
+}
+
+} // namespace arm_compute