compiler/dex/dataflow_iterator-inl.h

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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 ART_COMPILER_DEX_DATAFLOW_ITERATOR_INL_H_
#define ART_COMPILER_DEX_DATAFLOW_ITERATOR_INL_H_

#include "dataflow_iterator.h"

namespace art {

// Single forward pass over the nodes.
inline BasicBlock* DataflowIterator::ForwardSingleNext() {
  BasicBlock* res = nullptr;

  // Are we not yet at the end?
  if (idx_ < end_idx_) {
    // Get the next index.
    BasicBlockId bb_id = (*block_id_list_)[idx_];
    res = mir_graph_->GetBasicBlock(bb_id);
    idx_++;
  }

  return res;
}

// Repeat full forward passes over all nodes until no change occurs during a complete pass.
inline BasicBlock* DataflowIterator::ForwardRepeatNext() {
  BasicBlock* res = nullptr;

  // Are we at the end and have we changed something?
  if ((idx_ >= end_idx_) && changed_ == true) {
    // Reset the index.
    idx_ = start_idx_;
    repeats_++;
    changed_ = false;
  }

  // Are we not yet at the end?
  if (idx_ < end_idx_) {
    // Get the BasicBlockId.
    BasicBlockId bb_id = (*block_id_list_)[idx_];
    res = mir_graph_->GetBasicBlock(bb_id);
    idx_++;
  }

  return res;
}

// Single reverse pass over the nodes.
inline BasicBlock* DataflowIterator::ReverseSingleNext() {
  BasicBlock* res = nullptr;

  // Are we not yet at the end?
  if (idx_ >= 0) {
    // Get the BasicBlockId.
    BasicBlockId bb_id = (*block_id_list_)[idx_];
    res = mir_graph_->GetBasicBlock(bb_id);
    idx_--;
  }

  return res;
}

// Repeat full backwards passes over all nodes until no change occurs during a complete pass.
inline BasicBlock* DataflowIterator::ReverseRepeatNext() {
  BasicBlock* res = nullptr;

  // Are we done and we changed something during the last iteration?
  if ((idx_ < 0) && changed_) {
    // Reset the index.
    idx_ = start_idx_;
    repeats_++;
    changed_ = false;
  }

  // Are we not yet done?
  if (idx_ >= 0) {
    // Get the BasicBlockId.
    BasicBlockId bb_id = (*block_id_list_)[idx_];
    res = mir_graph_->GetBasicBlock(bb_id);
    idx_--;
  }

  return res;
}

// AllNodes uses the existing block list, and should be considered unordered.
inline BasicBlock* AllNodesIterator::Next(bool had_change) {
  // Update changed: if had_changed is true, we remember it for the whole iteration.
  changed_ |= had_change;

  BasicBlock* res = nullptr;
  while (idx_ != end_idx_) {
    BasicBlock* bb = mir_graph_->GetBlockList()[idx_++];
    DCHECK(bb != nullptr);
    if (!bb->hidden) {
      res = bb;
      break;
    }
  }

  return res;
}

inline BasicBlock* TopologicalSortIterator::Next(bool had_change) {
  // Update changed: if had_changed is true, we remember it for the whole iteration.
  changed_ |= had_change;

  while (loop_head_stack_->size() != 0u &&
      (*loop_ends_)[loop_head_stack_->back().first] == idx_) {
    loop_head_stack_->pop_back();
  }

  if (idx_ == end_idx_) {
    return nullptr;
  }

  // Get next block and return it.
  BasicBlockId idx = idx_;
  idx_ += 1;
  BasicBlock* bb = mir_graph_->GetBasicBlock((*block_id_list_)[idx]);
  DCHECK(bb != nullptr);
  if ((*loop_ends_)[idx] != 0u) {
    loop_head_stack_->push_back(std::make_pair(idx, false));  // Not recalculating.
  }
  return bb;
}

inline BasicBlock* LoopRepeatingTopologicalSortIterator::Next(bool had_change) {
  if (idx_ != 0) {
    // Mark last processed block visited.
    BasicBlock* bb = mir_graph_->GetBasicBlock((*block_id_list_)[idx_ - 1]);
    bb->visited = true;
    if (had_change) {
      // If we had a change we need to revisit the children.
      ChildBlockIterator iter(bb, mir_graph_);
      for (BasicBlock* child_bb = iter.Next(); child_bb != nullptr; child_bb = iter.Next()) {
        child_bb->visited = false;
      }
    }
  }

  while (true) {
    // Pop loops we have left and check if we need to recalculate one of them.
    // NOTE: We need to do this even if idx_ == end_idx_.
    while (loop_head_stack_->size() != 0u &&
        (*loop_ends_)[loop_head_stack_->back().first] == idx_) {
      auto top = loop_head_stack_->back();
      uint16_t loop_head_idx = top.first;
      bool recalculated = top.second;
      loop_head_stack_->pop_back();
      BasicBlock* loop_head = mir_graph_->GetBasicBlock((*block_id_list_)[loop_head_idx]);
      DCHECK(loop_head != nullptr);
      if (!recalculated || !loop_head->visited) {
        // Recalculating this loop.
        loop_head_stack_->push_back(std::make_pair(loop_head_idx, true));
        idx_ = loop_head_idx + 1;
        return loop_head;
      }
    }

    if (idx_ == end_idx_) {
      return nullptr;
    }

    // Get next block and return it if unvisited.
    BasicBlockId idx = idx_;
    idx_ += 1;
    BasicBlock* bb = mir_graph_->GetBasicBlock((*block_id_list_)[idx]);
    DCHECK(bb != nullptr);
    if ((*loop_ends_)[idx] != 0u) {
      // If bb->visited is false, the loop needs to be processed from scratch.
      // Otherwise we mark it as recalculating; for a natural loop we will not
      // need to recalculate any block in the loop anyway, and for unnatural
      // loops we will recalculate the loop head only if one of its predecessors
      // actually changes.
      bool recalculating = bb->visited;
      loop_head_stack_->push_back(std::make_pair(idx, recalculating));
    }
    if (!bb->visited) {
      return bb;
    }
  }
}

}  // namespace art

#endif  // ART_COMPILER_DEX_DATAFLOW_ITERATOR_INL_H_