/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.

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.
==============================================================================*/

#ifndef TENSORFLOW_COMPILER_XLA_SERVICE_HLO_DCE_H_
#define TENSORFLOW_COMPILER_XLA_SERVICE_HLO_DCE_H_

#include "tensorflow/compiler/xla/service/hlo_computation.h"
#include "tensorflow/compiler/xla/service/hlo_instruction.h"
#include "tensorflow/compiler/xla/service/hlo_module.h"
#include "tensorflow/compiler/xla/service/hlo_pass_interface.h"
#include "tensorflow/compiler/xla/statusor.h"

namespace xla {

// HLO pass which removes all dead instructions from each computation in the
// module. An instruction is dead if it is not reachable from the root. This
// pass does not remove dead parameter instructions as parameter instructions
// cannot be deleted, nor does the pass remove dead computations.
class HloDCE : public HloPassInterface {
 public:
  ~HloDCE() override {}
  tensorflow::StringPiece name() const override { return "dce"; }

  // Run the pass on the given module. Returns whether the module was changed
  // (instructions were removed).
  StatusOr<bool> Run(HloModule* module) override;
};

}  // namespace xla

#endif  // TENSORFLOW_COMPILER_XLA_SERVICE_HLO_DCE_H_
