Port NEFlatten layer to a memory injecting interface

Resolves: COMPMID-4503

Signed-off-by: Georgios Pinitas <georgios.pinitas@arm.com>
Change-Id: Ic536f62a9561d709c16d5f9cca28784cb7f281b6
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5650
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michalis Spyrou <michalis.spyrou@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/runtime/NEON/functions/NEFlattenLayer.cpp b/src/runtime/NEON/functions/NEFlattenLayer.cpp
index c5aa162..4d1054a 100644
--- a/src/runtime/NEON/functions/NEFlattenLayer.cpp
+++ b/src/runtime/NEON/functions/NEFlattenLayer.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2020 Arm Limited.
+ * Copyright (c) 2017-2021 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -27,14 +27,34 @@
 #include "arm_compute/core/Validate.h"
 #include "arm_compute/core/utils/misc/ShapeCalculator.h"
 #include "src/core/helpers/AutoConfiguration.h"
+#include "src/runtime/cpu/operators/CpuFlatten.h"
 
 namespace arm_compute
 {
+struct NEFlattenLayer::Impl
+{
+    const ITensor                   *src{ nullptr };
+    ITensor                         *dst{ nullptr };
+    std::unique_ptr<cpu::CpuFlatten> op{ nullptr };
+};
+
+NEFlattenLayer::NEFlattenLayer()
+    : _impl(std::make_unique<Impl>())
+{
+}
+NEFlattenLayer::NEFlattenLayer(NEFlattenLayer &&) = default;
+NEFlattenLayer &NEFlattenLayer::operator=(NEFlattenLayer &&) = default;
+NEFlattenLayer::~NEFlattenLayer()                            = default;
+
 void NEFlattenLayer::configure(const ITensor *input, ITensor *output)
 {
     ARM_COMPUTE_ERROR_ON_NULLPTR(input, output);
+    _impl->src = input;
+    _impl->dst = output;
     auto_init_if_empty(*output->info(), input->info()->clone()->set_tensor_shape(misc::shape_calculator::compute_flatten_shape(input->info())));
-    _reshape.configure(input, output);
+
+    _impl->op = std::make_unique<cpu::CpuFlatten>();
+    _impl->op->configure(_impl->src->info(), _impl->dst->info());
 }
 
 Status NEFlattenLayer::validate(const ITensorInfo *input, const ITensorInfo *output)
@@ -45,10 +65,13 @@
         const TensorInfo tensor_info_output = input->clone()->set_tensor_shape(misc::shape_calculator::compute_flatten_shape(input));
         ARM_COMPUTE_RETURN_ERROR_ON_MISMATCHING_SHAPES(output, &tensor_info_output);
     }
-    return NEReshapeLayer::validate(input, output);
+    return cpu::CpuFlatten::validate(input, output);
 }
 void NEFlattenLayer::run()
 {
-    _reshape.run();
+    ITensorPack pack;
+    pack.add_tensor(TensorType::ACL_SRC, _impl->src);
+    pack.add_tensor(TensorType::ACL_DST, _impl->dst);
+    _impl->op->run(pack);
 }
 } // namespace arm_compute