Replace slots buffer with remembered set.

src/heap/slots-buffer.cc

-// Copyright 2015 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/slots-buffer.h"
-
-#include "src/assembler.h"
-#include "src/heap/heap.h"
-#include "src/objects-inl.h"
-
-namespace v8 {
-namespace internal {
-
-bool SlotsBuffer::IsTypedSlot(ObjectSlot slot) {
-  return reinterpret_cast<uintptr_t>(slot) < NUMBER_OF_SLOT_TYPES;
-}
-
-
-bool SlotsBuffer::AddTo(SlotsBufferAllocator* allocator,
-                        SlotsBuffer** buffer_address, SlotType type,
-                        Address addr, AdditionMode mode) {
-  SlotsBuffer* buffer = *buffer_address;
-  if (buffer == NULL || !buffer->HasSpaceForTypedSlot()) {
-    if (mode == FAIL_ON_OVERFLOW && ChainLengthThresholdReached(buffer)) {
-      allocator->DeallocateChain(buffer_address);
-      return false;
-    }
-    buffer = allocator->AllocateBuffer(buffer);
-    *buffer_address = buffer;
-  }
-  DCHECK(buffer->HasSpaceForTypedSlot());
-  buffer->Add(reinterpret_cast<ObjectSlot>(type));
-  buffer->Add(reinterpret_cast<ObjectSlot>(addr));
-  return true;
-}
-
-
-void SlotsBuffer::RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer) {
-  // Remove entries by replacing them with an old-space slot containing a smi
-  // that is located in an unmovable page.
-  const ObjectSlot kRemovedEntry = HeapObject::RawField(
-      heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
-  DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
-             ->NeverEvacuate());
-
-  while (buffer != NULL) {
-    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
-    intptr_t slots_count = buffer->idx_;
-
-    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
-      ObjectSlot slot = slots[slot_idx];
-      if (!IsTypedSlot(slot)) {
-        Object* object = *slot;
-        // Slots are invalid when they currently:
-        // - do not point to a heap object (SMI)
-        // - point to a heap object in new space
-        // - are not within a live heap object on a valid pointer slot
-        // - point to a heap object not on an evacuation candidate
-        // TODO(mlippautz): Move InNewSpace check above IsSlotInLiveObject once
-        //   we filter out unboxed double slots eagerly.
-        if (!object->IsHeapObject() ||
-            !heap->mark_compact_collector()->IsSlotInLiveObject(
-                reinterpret_cast<Address>(slot)) ||
-            heap->InNewSpace(object) ||
-            !Page::FromAddress(reinterpret_cast<Address>(object))
-                 ->IsEvacuationCandidate()) {
-          // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
-          // could shrink the slots buffer in-place.
-          slots[slot_idx] = kRemovedEntry;
-        }
-      } else {
-        ++slot_idx;
-        DCHECK(slot_idx < slots_count);
-      }
-    }
-    buffer = buffer->next();
-  }
-}
-
-
-void SlotsBuffer::RemoveObjectSlots(Heap* heap, SlotsBuffer* buffer,
-                                    Address start_slot, Address end_slot) {
-  // Remove entries by replacing them with an old-space slot containing a smi
-  // that is located in an unmovable page.
-  const ObjectSlot kRemovedEntry = HeapObject::RawField(
-      heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
-  DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
-             ->NeverEvacuate());
-
-  while (buffer != NULL) {
-    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
-    intptr_t slots_count = buffer->idx_;
-    bool is_typed_slot = false;
-
-    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
-      ObjectSlot slot = slots[slot_idx];
-      if (!IsTypedSlot(slot)) {
-        Address slot_address = reinterpret_cast<Address>(slot);
-        if (slot_address >= start_slot && slot_address < end_slot) {
-          // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
-          // could shrink the slots buffer in-place.
-          slots[slot_idx] = kRemovedEntry;
-          if (is_typed_slot) {
-            slots[slot_idx - 1] = kRemovedEntry;
-          }
-        }
-        is_typed_slot = false;
-      } else {
-        is_typed_slot = true;
-        DCHECK(slot_idx < slots_count);
-      }
-    }
-    buffer = buffer->next();
-  }
-}
-
-
-void SlotsBuffer::VerifySlots(Heap* heap, SlotsBuffer* buffer) {
-  while (buffer != NULL) {
-    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
-    intptr_t slots_count = buffer->idx_;
-
-    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
-      ObjectSlot slot = slots[slot_idx];
-      if (!IsTypedSlot(slot)) {
-        Object* object = *slot;
-        if (object->IsHeapObject()) {
-          HeapObject* heap_object = HeapObject::cast(object);
-          CHECK(!heap->InNewSpace(object));
-          heap->mark_compact_collector()->VerifyIsSlotInLiveObject(
-              reinterpret_cast<Address>(slot), heap_object);
-        }
-      } else {
-        ++slot_idx;
-        DCHECK(slot_idx < slots_count);
-      }
-    }
-    buffer = buffer->next();
-  }
-}
-
-
-SlotsBuffer* SlotsBufferAllocator::AllocateBuffer(SlotsBuffer* next_buffer) {
-  return new SlotsBuffer(next_buffer);
-}
-
-
-void SlotsBufferAllocator::DeallocateBuffer(SlotsBuffer* buffer) {
-  delete buffer;
-}
-
-
-void SlotsBufferAllocator::DeallocateChain(SlotsBuffer** buffer_address) {
-  SlotsBuffer* buffer = *buffer_address;
-  while (buffer != NULL) {
-    SlotsBuffer* next_buffer = buffer->next();
-    DeallocateBuffer(buffer);
-    buffer = next_buffer;
-  }
-  *buffer_address = NULL;
-}
-
-}  // namespace internal
-}  // namespace v8