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// 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
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