/* 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_SERVICE_LEGALIZE_SCHEDULING_ANNOTATIONS_H_
#define XLA_SERVICE_LEGALIZE_SCHEDULING_ANNOTATIONS_H_

#include <cstdint>
#include <string>
#include <utility>
#include <vector>

#include "absl/container/btree_map.h"
#include "absl/container/flat_hash_map.h"
#include "absl/container/flat_hash_set.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "xla/hlo/ir/hlo_computation.h"
#include "xla/hlo/ir/hlo_module.h"
#include "xla/hlo/pass/hlo_pass_interface.h"
#include "xla/service/scheduling_annotations_util.h"
#include "xla/util.h"

namespace xla {

// Legalizer pass for scheduling annotations (to be used in
//  LatencyHidingScheduler).
class LegalizeSchedulingAnnotations : public HloModulePass {
 public:
  struct Config {
    HloPredicate keep_sync_annotation = HloPredicateTrue;
    HloPredicate keep_trivial_sync_annotation = HloPredicateTrue;
    bool propagate_annotation = false;
    bool check_start_done_annotation_consistency = true;
    bool remove_loop_iteration_annotation_only = false;
    bool run_verification = false;
    bool keep_start_annotation = true;
    bool deannotate_unsupported_groups = false;
    bool check_gap_only = false;
    bool check_non_mitigatable_gap_only = false;
    bool skip_opt_barriers = false;
    std::string debug_str;
  };

  explicit LegalizeSchedulingAnnotations(Config config)
      : config_(std::move(config)) {}
  absl::string_view name() const override {
    return "legalize-scheduling-annotations";
  }

  // Propagates the annotation to fill the gaps between instructions with the
  // same annotation ID. If dry_run is true, it will only check if the
  // propagation is possible without actually annotating the instructions.
  static absl::StatusOr<bool> PropagateAnnotations(
      const HloComputation* computation,
      const absl::btree_map<Annotation, std::vector<HloInstruction*>>&
          annotation_to_instruction,
      bool dry_run = false);

  // Checks if there are gaps between annotated instructions that are along the
  // same path (for the same annotation ID). If a gap is found, returns an error
  // and prints the path from the annotated source instruction to the annotated
  // destination instruction. This function is configurable to skip over
  // optimization barriers and simple tuples, because they sometimes introduce
  // false positives.
  absl::Status CheckGapBetweenAnnotatedInstructions(
      const absl::flat_hash_map<
          Annotation,
          absl::flat_hash_map<HloComputation*, std::vector<HloInstruction*>>>&
          annotation_to_instruction,
      const absl::flat_hash_map<HloInstruction*, Annotation>&
          instruction_to_annotation);

  absl::Status Verify(HloModule* module);

  void LogConfig(int64_t level);

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

 private:
  bool KeepSchedulingAnnotation(HloInstruction* instr);
  bool RemoveTrivialGroups(
      const absl::flat_hash_map<
          Annotation,
          absl::flat_hash_map<HloComputation*, std::vector<HloInstruction*>>>&
          annotation_to_instruction);
  Config config_;
};

// This pass only checks that there are no direct data dependencies between
// instructions with scheduling annotations. If there are any indirect data
// dependencies(i.e. gaps), it will detected by the
// LegalizeSchedulingAnnotations pass.
class CheckNoDataDependencyInSchedulingAnnotations : public HloModulePass {
 public:
  absl::string_view name() const override {
    return "check-no-data-dependency-in-scheduling-annotations";
  }

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

}  // namespace xla

#endif  // XLA_SERVICE_LEGALIZE_SCHEDULING_ANNOTATIONS_H_