src/v8/src/heap/slot-set.cc

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/heap/slot-set.h"

namespace v8 {
namespace internal {

TypedSlots::~TypedSlots() {
  Chunk* chunk = head_;
  while (chunk != nullptr) {
    Chunk* next = chunk->next;
    delete[] chunk->buffer;
    delete chunk;
    chunk = next;
  }
  head_ = nullptr;
  tail_ = nullptr;
}

void TypedSlots::Insert(SlotType type, uint32_t offset) {
  TypedSlot slot = {TypeField::encode(type) | OffsetField::encode(offset)};
  Chunk* chunk = EnsureChunk();
  DCHECK_LT(chunk->count, chunk->capacity);
  chunk->buffer[chunk->count] = slot;
  ++chunk->count;
}

void TypedSlots::Merge(TypedSlots* other) {
  if (other->head_ == nullptr) {
    return;
  }
  if (head_ == nullptr) {
    head_ = other->head_;
    tail_ = other->tail_;
  } else {
    tail_->next = other->head_;
    tail_ = other->tail_;
  }
  other->head_ = nullptr;
  other->tail_ = nullptr;
}

TypedSlots::Chunk* TypedSlots::EnsureChunk() {
  if (!head_) {
    head_ = tail_ = NewChunk(nullptr, kInitialBufferSize);
  }
  if (head_->count == head_->capacity) {
    head_ = NewChunk(head_, NextCapacity(head_->capacity));
  }
  return head_;
}

TypedSlots::Chunk* TypedSlots::NewChunk(Chunk* next, int capacity) {
  Chunk* chunk = new Chunk;
  chunk->next = next;
  chunk->buffer = new TypedSlot[capacity];
  chunk->capacity = capacity;
  chunk->count = 0;
  return chunk;
}

TypedSlotSet::~TypedSlotSet() { FreeToBeFreedChunks(); }

void TypedSlotSet::FreeToBeFreedChunks() {
  base::MutexGuard guard(&to_be_freed_chunks_mutex_);
  std::stack<std::unique_ptr<Chunk>> empty;
  to_be_freed_chunks_.swap(empty);
}

void TypedSlotSet::ClearInvalidSlots(
    const std::map<uint32_t, uint32_t>& invalid_ranges) {
  Chunk* chunk = LoadHead();
  while (chunk != nullptr) {
    TypedSlot* buffer = chunk->buffer;
    int count = chunk->count;
    for (int i = 0; i < count; i++) {
      TypedSlot slot = LoadTypedSlot(buffer + i);
      SlotType type = TypeField::decode(slot.type_and_offset);
      if (type == CLEARED_SLOT) continue;
      uint32_t offset = OffsetField::decode(slot.type_and_offset);
      std::map<uint32_t, uint32_t>::const_iterator upper_bound =
          invalid_ranges.upper_bound(offset);
      if (upper_bound == invalid_ranges.begin()) continue;
      // upper_bounds points to the invalid range after the given slot. Hence,
      // we have to go to the previous element.
      upper_bound--;
      DCHECK_LE(upper_bound->first, offset);
      if (upper_bound->second > offset) {
        ClearTypedSlot(buffer + i);
      }
    }
    chunk = LoadNext(chunk);
  }
}

}  // namespace internal
}  // namespace v8