/* Copyright 2024 The OpenXLA Authors.

 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 XLA_HLO_TRANSFORMS_HOST_OFFLOAD_LEGALIZE_H_
#define XLA_HLO_TRANSFORMS_HOST_OFFLOAD_LEGALIZE_H_

#include <cstdint>
#include <memory>
#include <vector>

#include "absl/container/flat_hash_set.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "xla/hlo/analysis/hlo_alias_analysis.h"
#include "xla/hlo/pass/hlo_pass_interface.h"

namespace xla {

class HloCostAnalysis;

// This pass legalizes the graph for the "host memory offloading" pass to
// correctly identified buffers that are meant to be move on the host. Any
// legalization that could block that is welcome into this pass.
class HostOffloadLegalize : public HloModulePass {
 public:
  HostOffloadLegalize() = default;
  ~HostOffloadLegalize() override = default;

  absl::string_view name() const override { return "host-offload-legalize"; }

 protected:
  absl::StatusOr<bool> RunImpl(
      HloModule* module,
      const absl::flat_hash_set<absl::string_view>& execution_threads) override;

 private:
  // For any memory offloaded to the host, return the instruction which is the
  // start of such and offload. These will either be "MoveToHost" annotations or
  // entry computation parameters.
  std::vector<HloInstruction*> FindStartingInstructionsOfHostMemoryOffload(
      HloModule* module,
      const absl::flat_hash_set<absl::string_view>& execution_threads) const;
};

}  // namespace xla

#endif  // XLA_HLO_TRANSFORMS_HOST_OFFLOAD_LEGALIZE_H_