/* Copyright 2022 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_SIMPLIFIERS_SIMPLIFY_FP_CONVERSIONS_H_
#define XLA_HLO_TRANSFORMS_SIMPLIFIERS_SIMPLIFY_FP_CONVERSIONS_H_

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

namespace xla {

// Simplifies chains of floating-point conversions.
//
// The algebraic simplifier will remove convert pairs of the form `X -> Y -> X`,
// only when they are a no-op, e.g. `bf16 -> f32 -> bf16` or
// `f32 -> bf16 -> f32`. Note that the latter optimization might lead to
// increased precision.
class SimplifyFPConversions : public HloModulePass {
 public:
  explicit SimplifyFPConversions() = default;

  absl::string_view name() const override { return "simplify-fp-conversions"; }

  using HloPassInterface::Run;
  absl::StatusOr<bool> Run(
      HloModule* module,
      const absl::flat_hash_set<absl::string_view>& execution_threads) override;
};

}  // namespace xla

#endif  // XLA_HLO_TRANSFORMS_SIMPLIFIERS_SIMPLIFY_FP_CONVERSIONS_H_