tensorflow/lite/micro/kernels/kelvin/reshape.cc

/*
 * Copyright 2024 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "tensorflow/lite/c/common.h"
#include "tensorflow/lite/kernels/kernel_util.h"
#include "tensorflow/lite/micro/kernels/kernel_util.h"
#include "tensorflow/lite/micro/memory_helpers.h"
#include "tensorflow/lite/micro/micro_utils.h"
#include "tflm/opt/opt.h"

namespace tflite {
namespace {

constexpr int kInputTensor = 0;
constexpr int kOutputTensor = 0;

TfLiteStatus ReshapeOutput(TfLiteContext* context, TfLiteNode* node) {
  MicroContext* micro_context = GetMicroContext(context);

  TfLiteTensor* input =
      micro_context->AllocateTempInputTensor(node, kInputTensor);
  TF_LITE_ENSURE(context, input != nullptr);
  TfLiteTensor* output =
      micro_context->AllocateTempOutputTensor(node, kOutputTensor);
  TF_LITE_ENSURE(context, output != nullptr);
  // Tensorflow's Reshape allows one of the shape components to have the
  // special -1 value, meaning it will be calculated automatically based on the
  // input. Here we calculate what that dimension should be so that the number
  // of output elements in the same as the number of input elements.
  int num_input_elements = NumElements(input);
  TfLiteIntArray* output_shape = output->dims;

  if (NumInputs(node) == 1 &&  // Legacy scalar supported with params.
      output_shape->size == 1 && output_shape->data[0] == 0) {
    // Legacy tflite models use a shape parameter of [0] to indicate scalars,
    // so adjust accordingly. TODO(b/111614235): Allow zero-sized buffers during
    // toco conversion.
    output_shape->size = 0;
  }

  int num_output_elements = 1;
  int stretch_dim = -1;
  for (int i = 0; i < output_shape->size; ++i) {
    int value = output_shape->data[i];
    if (value == -1) {
      TF_LITE_ENSURE_EQ(context, stretch_dim, -1);
      stretch_dim = i;
    } else {
      num_output_elements *= value;
    }
  }
  if (stretch_dim != -1) {
    TfLiteEvalTensor* output_eval =
        tflite::micro::GetEvalOutput(context, node, kOutputTensor);
    TF_LITE_ENSURE_STATUS(tflite::micro::CreateWritableTensorDimsWithCopy(
        context, output, output_eval));
    output_shape = output->dims;  // output tensor dims were moved
    output_shape->data[stretch_dim] = num_input_elements / num_output_elements;
    num_output_elements *= output_shape->data[stretch_dim];
  }

  TF_LITE_ENSURE_TYPES_EQ(context, input->type, output->type);
  TF_LITE_ENSURE_EQ(context, num_input_elements, num_output_elements);

  micro_context->DeallocateTempTfLiteTensor(input);
  micro_context->DeallocateTempTfLiteTensor(output);
  return kTfLiteOk;
}

TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {
  TF_LITE_ENSURE(context, NumInputs(node) == 1 || NumInputs(node) == 2);
  TF_LITE_ENSURE_EQ(context, NumOutputs(node), 1);
  TF_LITE_ENSURE_EQ(context, ReshapeOutput(context, node), kTfLiteOk);
  return kTfLiteOk;
}

TfLiteStatus Eval(TfLiteContext* context, TfLiteNode* node) {
  const TfLiteEvalTensor* input =
      tflite::micro::GetEvalInput(context, node, kInputTensor);
  TfLiteEvalTensor* output =
      tflite::micro::GetEvalOutput(context, node, kOutputTensor);

  // TODO(b/162522304): storing input bytes in OpData increases some models
  // significantly, possibly due to alignment issues.
  size_t input_bytes;
  TF_LITE_ENSURE_STATUS(TfLiteTypeSizeOf(input->type, &input_bytes));
  input_bytes *= ElementCount(*input->dims);

  // Do nothing for in-place reshape.
  if (input->data.raw != output->data.raw) {
    // Otherwise perform reshape with copy.
    kelvin::opt::Memcpy(output->data.raw, input->data.raw, input_bytes);
  }
  return kTfLiteOk;
}

}  // namespace

TFLMRegistration Register_RESHAPE() {
  return tflite::micro::RegisterOp(nullptr, Prepare, Eval);
}

}  // namespace tflite