Upgrade to 3.29
Update V8 to 3.29.88.17 and update makefiles to support building on
all the relevant platforms.
Bug: 17370214
Change-Id: Ia3407c157fd8d72a93e23d8318ccaf6ecf77fa4e
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
new file mode 100644
index 0000000..9f9a658
--- /dev/null
+++ b/src/heap/mark-compact.cc
@@ -0,0 +1,4562 @@
+// Copyright 2012 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/v8.h"
+
+#include "src/base/atomicops.h"
+#include "src/base/bits.h"
+#include "src/code-stubs.h"
+#include "src/compilation-cache.h"
+#include "src/cpu-profiler.h"
+#include "src/deoptimizer.h"
+#include "src/execution.h"
+#include "src/gdb-jit.h"
+#include "src/global-handles.h"
+#include "src/heap/incremental-marking.h"
+#include "src/heap/mark-compact.h"
+#include "src/heap/objects-visiting.h"
+#include "src/heap/objects-visiting-inl.h"
+#include "src/heap/spaces-inl.h"
+#include "src/heap/sweeper-thread.h"
+#include "src/heap-profiler.h"
+#include "src/ic/ic.h"
+#include "src/ic/stub-cache.h"
+
+namespace v8 {
+namespace internal {
+
+
+const char* Marking::kWhiteBitPattern = "00";
+const char* Marking::kBlackBitPattern = "10";
+const char* Marking::kGreyBitPattern = "11";
+const char* Marking::kImpossibleBitPattern = "01";
+
+
+// -------------------------------------------------------------------------
+// MarkCompactCollector
+
+MarkCompactCollector::MarkCompactCollector(Heap* heap)
+ : // NOLINT
+#ifdef DEBUG
+ state_(IDLE),
+#endif
+ reduce_memory_footprint_(false),
+ abort_incremental_marking_(false),
+ marking_parity_(ODD_MARKING_PARITY),
+ compacting_(false),
+ was_marked_incrementally_(false),
+ sweeping_in_progress_(false),
+ pending_sweeper_jobs_semaphore_(0),
+ sequential_sweeping_(false),
+ migration_slots_buffer_(NULL),
+ heap_(heap),
+ code_flusher_(NULL),
+ have_code_to_deoptimize_(false) {
+}
+
+#ifdef VERIFY_HEAP
+class VerifyMarkingVisitor : public ObjectVisitor {
+ public:
+ explicit VerifyMarkingVisitor(Heap* heap) : heap_(heap) {}
+
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** current = start; current < end; current++) {
+ if ((*current)->IsHeapObject()) {
+ HeapObject* object = HeapObject::cast(*current);
+ CHECK(heap_->mark_compact_collector()->IsMarked(object));
+ }
+ }
+ }
+
+ void VisitEmbeddedPointer(RelocInfo* rinfo) {
+ DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
+ if (!rinfo->host()->IsWeakObject(rinfo->target_object())) {
+ Object* p = rinfo->target_object();
+ VisitPointer(&p);
+ }
+ }
+
+ void VisitCell(RelocInfo* rinfo) {
+ Code* code = rinfo->host();
+ DCHECK(rinfo->rmode() == RelocInfo::CELL);
+ if (!code->IsWeakObject(rinfo->target_cell())) {
+ ObjectVisitor::VisitCell(rinfo);
+ }
+ }
+
+ private:
+ Heap* heap_;
+};
+
+
+static void VerifyMarking(Heap* heap, Address bottom, Address top) {
+ VerifyMarkingVisitor visitor(heap);
+ HeapObject* object;
+ Address next_object_must_be_here_or_later = bottom;
+
+ for (Address current = bottom; current < top; current += kPointerSize) {
+ object = HeapObject::FromAddress(current);
+ if (MarkCompactCollector::IsMarked(object)) {
+ CHECK(current >= next_object_must_be_here_or_later);
+ object->Iterate(&visitor);
+ next_object_must_be_here_or_later = current + object->Size();
+ }
+ }
+}
+
+
+static void VerifyMarking(NewSpace* space) {
+ Address end = space->top();
+ NewSpacePageIterator it(space->bottom(), end);
+ // The bottom position is at the start of its page. Allows us to use
+ // page->area_start() as start of range on all pages.
+ CHECK_EQ(space->bottom(),
+ NewSpacePage::FromAddress(space->bottom())->area_start());
+ while (it.has_next()) {
+ NewSpacePage* page = it.next();
+ Address limit = it.has_next() ? page->area_end() : end;
+ CHECK(limit == end || !page->Contains(end));
+ VerifyMarking(space->heap(), page->area_start(), limit);
+ }
+}
+
+
+static void VerifyMarking(PagedSpace* space) {
+ PageIterator it(space);
+
+ while (it.has_next()) {
+ Page* p = it.next();
+ VerifyMarking(space->heap(), p->area_start(), p->area_end());
+ }
+}
+
+
+static void VerifyMarking(Heap* heap) {
+ VerifyMarking(heap->old_pointer_space());
+ VerifyMarking(heap->old_data_space());
+ VerifyMarking(heap->code_space());
+ VerifyMarking(heap->cell_space());
+ VerifyMarking(heap->property_cell_space());
+ VerifyMarking(heap->map_space());
+ VerifyMarking(heap->new_space());
+
+ VerifyMarkingVisitor visitor(heap);
+
+ LargeObjectIterator it(heap->lo_space());
+ for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
+ if (MarkCompactCollector::IsMarked(obj)) {
+ obj->Iterate(&visitor);
+ }
+ }
+
+ heap->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
+}
+
+
+class VerifyEvacuationVisitor : public ObjectVisitor {
+ public:
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** current = start; current < end; current++) {
+ if ((*current)->IsHeapObject()) {
+ HeapObject* object = HeapObject::cast(*current);
+ CHECK(!MarkCompactCollector::IsOnEvacuationCandidate(object));
+ }
+ }
+ }
+};
+
+
+static void VerifyEvacuation(Page* page) {
+ VerifyEvacuationVisitor visitor;
+ HeapObjectIterator iterator(page, NULL);
+ for (HeapObject* heap_object = iterator.Next(); heap_object != NULL;
+ heap_object = iterator.Next()) {
+ // We skip free space objects.
+ if (!heap_object->IsFiller()) {
+ heap_object->Iterate(&visitor);
+ }
+ }
+}
+
+
+static void VerifyEvacuation(NewSpace* space) {
+ NewSpacePageIterator it(space->bottom(), space->top());
+ VerifyEvacuationVisitor visitor;
+
+ while (it.has_next()) {
+ NewSpacePage* page = it.next();
+ Address current = page->area_start();
+ Address limit = it.has_next() ? page->area_end() : space->top();
+ CHECK(limit == space->top() || !page->Contains(space->top()));
+ while (current < limit) {
+ HeapObject* object = HeapObject::FromAddress(current);
+ object->Iterate(&visitor);
+ current += object->Size();
+ }
+ }
+}
+
+
+static void VerifyEvacuation(Heap* heap, PagedSpace* space) {
+ if (FLAG_use_allocation_folding &&
+ (space == heap->old_pointer_space() || space == heap->old_data_space())) {
+ return;
+ }
+ PageIterator it(space);
+
+ while (it.has_next()) {
+ Page* p = it.next();
+ if (p->IsEvacuationCandidate()) continue;
+ VerifyEvacuation(p);
+ }
+}
+
+
+static void VerifyEvacuation(Heap* heap) {
+ VerifyEvacuation(heap, heap->old_pointer_space());
+ VerifyEvacuation(heap, heap->old_data_space());
+ VerifyEvacuation(heap, heap->code_space());
+ VerifyEvacuation(heap, heap->cell_space());
+ VerifyEvacuation(heap, heap->property_cell_space());
+ VerifyEvacuation(heap, heap->map_space());
+ VerifyEvacuation(heap->new_space());
+
+ VerifyEvacuationVisitor visitor;
+ heap->IterateStrongRoots(&visitor, VISIT_ALL);
+}
+#endif // VERIFY_HEAP
+
+
+#ifdef DEBUG
+class VerifyNativeContextSeparationVisitor : public ObjectVisitor {
+ public:
+ VerifyNativeContextSeparationVisitor() : current_native_context_(NULL) {}
+
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** current = start; current < end; current++) {
+ if ((*current)->IsHeapObject()) {
+ HeapObject* object = HeapObject::cast(*current);
+ if (object->IsString()) continue;
+ switch (object->map()->instance_type()) {
+ case JS_FUNCTION_TYPE:
+ CheckContext(JSFunction::cast(object)->context());
+ break;
+ case JS_GLOBAL_PROXY_TYPE:
+ CheckContext(JSGlobalProxy::cast(object)->native_context());
+ break;
+ case JS_GLOBAL_OBJECT_TYPE:
+ case JS_BUILTINS_OBJECT_TYPE:
+ CheckContext(GlobalObject::cast(object)->native_context());
+ break;
+ case JS_ARRAY_TYPE:
+ case JS_DATE_TYPE:
+ case JS_OBJECT_TYPE:
+ case JS_REGEXP_TYPE:
+ VisitPointer(HeapObject::RawField(object, JSObject::kMapOffset));
+ break;
+ case MAP_TYPE:
+ VisitPointer(HeapObject::RawField(object, Map::kPrototypeOffset));
+ VisitPointer(HeapObject::RawField(object, Map::kConstructorOffset));
+ break;
+ case FIXED_ARRAY_TYPE:
+ if (object->IsContext()) {
+ CheckContext(object);
+ } else {
+ FixedArray* array = FixedArray::cast(object);
+ int length = array->length();
+ // Set array length to zero to prevent cycles while iterating
+ // over array bodies, this is easier than intrusive marking.
+ array->set_length(0);
+ array->IterateBody(FIXED_ARRAY_TYPE, FixedArray::SizeFor(length),
+ this);
+ array->set_length(length);
+ }
+ break;
+ case CELL_TYPE:
+ case JS_PROXY_TYPE:
+ case JS_VALUE_TYPE:
+ case TYPE_FEEDBACK_INFO_TYPE:
+ object->Iterate(this);
+ break;
+ case DECLARED_ACCESSOR_INFO_TYPE:
+ case EXECUTABLE_ACCESSOR_INFO_TYPE:
+ case BYTE_ARRAY_TYPE:
+ case CALL_HANDLER_INFO_TYPE:
+ case CODE_TYPE:
+ case FIXED_DOUBLE_ARRAY_TYPE:
+ case HEAP_NUMBER_TYPE:
+ case MUTABLE_HEAP_NUMBER_TYPE:
+ case INTERCEPTOR_INFO_TYPE:
+ case ODDBALL_TYPE:
+ case SCRIPT_TYPE:
+ case SHARED_FUNCTION_INFO_TYPE:
+ break;
+ default:
+ UNREACHABLE();
+ }
+ }
+ }
+ }
+
+ private:
+ void CheckContext(Object* context) {
+ if (!context->IsContext()) return;
+ Context* native_context = Context::cast(context)->native_context();
+ if (current_native_context_ == NULL) {
+ current_native_context_ = native_context;
+ } else {
+ CHECK_EQ(current_native_context_, native_context);
+ }
+ }
+
+ Context* current_native_context_;
+};
+
+
+static void VerifyNativeContextSeparation(Heap* heap) {
+ HeapObjectIterator it(heap->code_space());
+
+ for (Object* object = it.Next(); object != NULL; object = it.Next()) {
+ VerifyNativeContextSeparationVisitor visitor;
+ Code::cast(object)->CodeIterateBody(&visitor);
+ }
+}
+#endif
+
+
+void MarkCompactCollector::SetUp() {
+ free_list_old_data_space_.Reset(new FreeList(heap_->old_data_space()));
+ free_list_old_pointer_space_.Reset(new FreeList(heap_->old_pointer_space()));
+}
+
+
+void MarkCompactCollector::TearDown() { AbortCompaction(); }
+
+
+void MarkCompactCollector::AddEvacuationCandidate(Page* p) {
+ p->MarkEvacuationCandidate();
+ evacuation_candidates_.Add(p);
+}
+
+
+static void TraceFragmentation(PagedSpace* space) {
+ int number_of_pages = space->CountTotalPages();
+ intptr_t reserved = (number_of_pages * space->AreaSize());
+ intptr_t free = reserved - space->SizeOfObjects();
+ PrintF("[%s]: %d pages, %d (%.1f%%) free\n",
+ AllocationSpaceName(space->identity()), number_of_pages,
+ static_cast<int>(free), static_cast<double>(free) * 100 / reserved);
+}
+
+
+bool MarkCompactCollector::StartCompaction(CompactionMode mode) {
+ if (!compacting_) {
+ DCHECK(evacuation_candidates_.length() == 0);
+
+#ifdef ENABLE_GDB_JIT_INTERFACE
+ // If GDBJIT interface is active disable compaction.
+ if (FLAG_gdbjit) return false;
+#endif
+
+ CollectEvacuationCandidates(heap()->old_pointer_space());
+ CollectEvacuationCandidates(heap()->old_data_space());
+
+ if (FLAG_compact_code_space && (mode == NON_INCREMENTAL_COMPACTION ||
+ FLAG_incremental_code_compaction)) {
+ CollectEvacuationCandidates(heap()->code_space());
+ } else if (FLAG_trace_fragmentation) {
+ TraceFragmentation(heap()->code_space());
+ }
+
+ if (FLAG_trace_fragmentation) {
+ TraceFragmentation(heap()->map_space());
+ TraceFragmentation(heap()->cell_space());
+ TraceFragmentation(heap()->property_cell_space());
+ }
+
+ heap()->old_pointer_space()->EvictEvacuationCandidatesFromFreeLists();
+ heap()->old_data_space()->EvictEvacuationCandidatesFromFreeLists();
+ heap()->code_space()->EvictEvacuationCandidatesFromFreeLists();
+
+ compacting_ = evacuation_candidates_.length() > 0;
+ }
+
+ return compacting_;
+}
+
+
+void MarkCompactCollector::CollectGarbage() {
+ // Make sure that Prepare() has been called. The individual steps below will
+ // update the state as they proceed.
+ DCHECK(state_ == PREPARE_GC);
+
+ MarkLiveObjects();
+ DCHECK(heap_->incremental_marking()->IsStopped());
+
+ if (FLAG_collect_maps) ClearNonLiveReferences();
+
+ ClearWeakCollections();
+
+#ifdef VERIFY_HEAP
+ if (FLAG_verify_heap) {
+ VerifyMarking(heap_);
+ }
+#endif
+
+ SweepSpaces();
+
+#ifdef DEBUG
+ if (FLAG_verify_native_context_separation) {
+ VerifyNativeContextSeparation(heap_);
+ }
+#endif
+
+#ifdef VERIFY_HEAP
+ if (heap()->weak_embedded_objects_verification_enabled()) {
+ VerifyWeakEmbeddedObjectsInCode();
+ }
+ if (FLAG_collect_maps && FLAG_omit_map_checks_for_leaf_maps) {
+ VerifyOmittedMapChecks();
+ }
+#endif
+
+ Finish();
+
+ if (marking_parity_ == EVEN_MARKING_PARITY) {
+ marking_parity_ = ODD_MARKING_PARITY;
+ } else {
+ DCHECK(marking_parity_ == ODD_MARKING_PARITY);
+ marking_parity_ = EVEN_MARKING_PARITY;
+ }
+}
+
+
+#ifdef VERIFY_HEAP
+void MarkCompactCollector::VerifyMarkbitsAreClean(PagedSpace* space) {
+ PageIterator it(space);
+
+ while (it.has_next()) {
+ Page* p = it.next();
+ CHECK(p->markbits()->IsClean());
+ CHECK_EQ(0, p->LiveBytes());
+ }
+}
+
+
+void MarkCompactCollector::VerifyMarkbitsAreClean(NewSpace* space) {
+ NewSpacePageIterator it(space->bottom(), space->top());
+
+ while (it.has_next()) {
+ NewSpacePage* p = it.next();
+ CHECK(p->markbits()->IsClean());
+ CHECK_EQ(0, p->LiveBytes());
+ }
+}
+
+
+void MarkCompactCollector::VerifyMarkbitsAreClean() {
+ VerifyMarkbitsAreClean(heap_->old_pointer_space());
+ VerifyMarkbitsAreClean(heap_->old_data_space());
+ VerifyMarkbitsAreClean(heap_->code_space());
+ VerifyMarkbitsAreClean(heap_->cell_space());
+ VerifyMarkbitsAreClean(heap_->property_cell_space());
+ VerifyMarkbitsAreClean(heap_->map_space());
+ VerifyMarkbitsAreClean(heap_->new_space());
+
+ LargeObjectIterator it(heap_->lo_space());
+ for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
+ MarkBit mark_bit = Marking::MarkBitFrom(obj);
+ CHECK(Marking::IsWhite(mark_bit));
+ CHECK_EQ(0, Page::FromAddress(obj->address())->LiveBytes());
+ }
+}
+
+
+void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() {
+ HeapObjectIterator code_iterator(heap()->code_space());
+ for (HeapObject* obj = code_iterator.Next(); obj != NULL;
+ obj = code_iterator.Next()) {
+ Code* code = Code::cast(obj);
+ if (!code->is_optimized_code() && !code->is_weak_stub()) continue;
+ if (WillBeDeoptimized(code)) continue;
+ code->VerifyEmbeddedObjectsDependency();
+ }
+}
+
+
+void MarkCompactCollector::VerifyOmittedMapChecks() {
+ HeapObjectIterator iterator(heap()->map_space());
+ for (HeapObject* obj = iterator.Next(); obj != NULL; obj = iterator.Next()) {
+ Map* map = Map::cast(obj);
+ map->VerifyOmittedMapChecks();
+ }
+}
+#endif // VERIFY_HEAP
+
+
+static void ClearMarkbitsInPagedSpace(PagedSpace* space) {
+ PageIterator it(space);
+
+ while (it.has_next()) {
+ Bitmap::Clear(it.next());
+ }
+}
+
+
+static void ClearMarkbitsInNewSpace(NewSpace* space) {
+ NewSpacePageIterator it(space->ToSpaceStart(), space->ToSpaceEnd());
+
+ while (it.has_next()) {
+ Bitmap::Clear(it.next());
+ }
+}
+
+
+void MarkCompactCollector::ClearMarkbits() {
+ ClearMarkbitsInPagedSpace(heap_->code_space());
+ ClearMarkbitsInPagedSpace(heap_->map_space());
+ ClearMarkbitsInPagedSpace(heap_->old_pointer_space());
+ ClearMarkbitsInPagedSpace(heap_->old_data_space());
+ ClearMarkbitsInPagedSpace(heap_->cell_space());
+ ClearMarkbitsInPagedSpace(heap_->property_cell_space());
+ ClearMarkbitsInNewSpace(heap_->new_space());
+
+ LargeObjectIterator it(heap_->lo_space());
+ for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
+ MarkBit mark_bit = Marking::MarkBitFrom(obj);
+ mark_bit.Clear();
+ mark_bit.Next().Clear();
+ Page::FromAddress(obj->address())->ResetProgressBar();
+ Page::FromAddress(obj->address())->ResetLiveBytes();
+ }
+}
+
+
+class MarkCompactCollector::SweeperTask : public v8::Task {
+ public:
+ SweeperTask(Heap* heap, PagedSpace* space) : heap_(heap), space_(space) {}
+
+ virtual ~SweeperTask() {}
+
+ private:
+ // v8::Task overrides.
+ virtual void Run() OVERRIDE {
+ heap_->mark_compact_collector()->SweepInParallel(space_, 0);
+ heap_->mark_compact_collector()->pending_sweeper_jobs_semaphore_.Signal();
+ }
+
+ Heap* heap_;
+ PagedSpace* space_;
+
+ DISALLOW_COPY_AND_ASSIGN(SweeperTask);
+};
+
+
+void MarkCompactCollector::StartSweeperThreads() {
+ DCHECK(free_list_old_pointer_space_.get()->IsEmpty());
+ DCHECK(free_list_old_data_space_.get()->IsEmpty());
+ sweeping_in_progress_ = true;
+ for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
+ isolate()->sweeper_threads()[i]->StartSweeping();
+ }
+ if (FLAG_job_based_sweeping) {
+ V8::GetCurrentPlatform()->CallOnBackgroundThread(
+ new SweeperTask(heap(), heap()->old_data_space()),
+ v8::Platform::kShortRunningTask);
+ V8::GetCurrentPlatform()->CallOnBackgroundThread(
+ new SweeperTask(heap(), heap()->old_pointer_space()),
+ v8::Platform::kShortRunningTask);
+ }
+}
+
+
+void MarkCompactCollector::EnsureSweepingCompleted() {
+ DCHECK(sweeping_in_progress_ == true);
+
+ // If sweeping is not completed, we try to complete it here. If we do not
+ // have sweeper threads we have to complete since we do not have a good
+ // indicator for a swept space in that case.
+ if (!AreSweeperThreadsActivated() || !IsSweepingCompleted()) {
+ SweepInParallel(heap()->paged_space(OLD_DATA_SPACE), 0);
+ SweepInParallel(heap()->paged_space(OLD_POINTER_SPACE), 0);
+ }
+
+ for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
+ isolate()->sweeper_threads()[i]->WaitForSweeperThread();
+ }
+ if (FLAG_job_based_sweeping) {
+ // Wait twice for both jobs.
+ pending_sweeper_jobs_semaphore_.Wait();
+ pending_sweeper_jobs_semaphore_.Wait();
+ }
+ ParallelSweepSpacesComplete();
+ sweeping_in_progress_ = false;
+ RefillFreeList(heap()->paged_space(OLD_DATA_SPACE));
+ RefillFreeList(heap()->paged_space(OLD_POINTER_SPACE));
+ heap()->paged_space(OLD_DATA_SPACE)->ResetUnsweptFreeBytes();
+ heap()->paged_space(OLD_POINTER_SPACE)->ResetUnsweptFreeBytes();
+
+#ifdef VERIFY_HEAP
+ if (FLAG_verify_heap) {
+ VerifyEvacuation(heap_);
+ }
+#endif
+}
+
+
+bool MarkCompactCollector::IsSweepingCompleted() {
+ for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
+ if (!isolate()->sweeper_threads()[i]->SweepingCompleted()) {
+ return false;
+ }
+ }
+
+ if (FLAG_job_based_sweeping) {
+ if (!pending_sweeper_jobs_semaphore_.WaitFor(
+ base::TimeDelta::FromSeconds(0))) {
+ return false;
+ }
+ pending_sweeper_jobs_semaphore_.Signal();
+ }
+
+ return true;
+}
+
+
+void MarkCompactCollector::RefillFreeList(PagedSpace* space) {
+ FreeList* free_list;
+
+ if (space == heap()->old_pointer_space()) {
+ free_list = free_list_old_pointer_space_.get();
+ } else if (space == heap()->old_data_space()) {
+ free_list = free_list_old_data_space_.get();
+ } else {
+ // Any PagedSpace might invoke RefillFreeLists, so we need to make sure
+ // to only refill them for old data and pointer spaces.
+ return;
+ }
+
+ intptr_t freed_bytes = space->free_list()->Concatenate(free_list);
+ space->AddToAccountingStats(freed_bytes);
+ space->DecrementUnsweptFreeBytes(freed_bytes);
+}
+
+
+bool MarkCompactCollector::AreSweeperThreadsActivated() {
+ return isolate()->sweeper_threads() != NULL || FLAG_job_based_sweeping;
+}
+
+
+void Marking::TransferMark(Address old_start, Address new_start) {
+ // This is only used when resizing an object.
+ DCHECK(MemoryChunk::FromAddress(old_start) ==
+ MemoryChunk::FromAddress(new_start));
+
+ if (!heap_->incremental_marking()->IsMarking()) return;
+
+ // If the mark doesn't move, we don't check the color of the object.
+ // It doesn't matter whether the object is black, since it hasn't changed
+ // size, so the adjustment to the live data count will be zero anyway.
+ if (old_start == new_start) return;
+
+ MarkBit new_mark_bit = MarkBitFrom(new_start);
+ MarkBit old_mark_bit = MarkBitFrom(old_start);
+
+#ifdef DEBUG
+ ObjectColor old_color = Color(old_mark_bit);
+#endif
+
+ if (Marking::IsBlack(old_mark_bit)) {
+ old_mark_bit.Clear();
+ DCHECK(IsWhite(old_mark_bit));
+ Marking::MarkBlack(new_mark_bit);
+ return;
+ } else if (Marking::IsGrey(old_mark_bit)) {
+ old_mark_bit.Clear();
+ old_mark_bit.Next().Clear();
+ DCHECK(IsWhite(old_mark_bit));
+ heap_->incremental_marking()->WhiteToGreyAndPush(
+ HeapObject::FromAddress(new_start), new_mark_bit);
+ heap_->incremental_marking()->RestartIfNotMarking();
+ }
+
+#ifdef DEBUG
+ ObjectColor new_color = Color(new_mark_bit);
+ DCHECK(new_color == old_color);
+#endif
+}
+
+
+const char* AllocationSpaceName(AllocationSpace space) {
+ switch (space) {
+ case NEW_SPACE:
+ return "NEW_SPACE";
+ case OLD_POINTER_SPACE:
+ return "OLD_POINTER_SPACE";
+ case OLD_DATA_SPACE:
+ return "OLD_DATA_SPACE";
+ case CODE_SPACE:
+ return "CODE_SPACE";
+ case MAP_SPACE:
+ return "MAP_SPACE";
+ case CELL_SPACE:
+ return "CELL_SPACE";
+ case PROPERTY_CELL_SPACE:
+ return "PROPERTY_CELL_SPACE";
+ case LO_SPACE:
+ return "LO_SPACE";
+ default:
+ UNREACHABLE();
+ }
+
+ return NULL;
+}
+
+
+// Returns zero for pages that have so little fragmentation that it is not
+// worth defragmenting them. Otherwise a positive integer that gives an
+// estimate of fragmentation on an arbitrary scale.
+static int FreeListFragmentation(PagedSpace* space, Page* p) {
+ // If page was not swept then there are no free list items on it.
+ if (!p->WasSwept()) {
+ if (FLAG_trace_fragmentation) {
+ PrintF("%p [%s]: %d bytes live (unswept)\n", reinterpret_cast<void*>(p),
+ AllocationSpaceName(space->identity()), p->LiveBytes());
+ }
+ return 0;
+ }
+
+ PagedSpace::SizeStats sizes;
+ space->ObtainFreeListStatistics(p, &sizes);
+
+ intptr_t ratio;
+ intptr_t ratio_threshold;
+ intptr_t area_size = space->AreaSize();
+ if (space->identity() == CODE_SPACE) {
+ ratio = (sizes.medium_size_ * 10 + sizes.large_size_ * 2) * 100 / area_size;
+ ratio_threshold = 10;
+ } else {
+ ratio = (sizes.small_size_ * 5 + sizes.medium_size_) * 100 / area_size;
+ ratio_threshold = 15;
+ }
+
+ if (FLAG_trace_fragmentation) {
+ PrintF("%p [%s]: %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %s\n",
+ reinterpret_cast<void*>(p), AllocationSpaceName(space->identity()),
+ static_cast<int>(sizes.small_size_),
+ static_cast<double>(sizes.small_size_ * 100) / area_size,
+ static_cast<int>(sizes.medium_size_),
+ static_cast<double>(sizes.medium_size_ * 100) / area_size,
+ static_cast<int>(sizes.large_size_),
+ static_cast<double>(sizes.large_size_ * 100) / area_size,
+ static_cast<int>(sizes.huge_size_),
+ static_cast<double>(sizes.huge_size_ * 100) / area_size,
+ (ratio > ratio_threshold) ? "[fragmented]" : "");
+ }
+
+ if (FLAG_always_compact && sizes.Total() != area_size) {
+ return 1;
+ }
+
+ if (ratio <= ratio_threshold) return 0; // Not fragmented.
+
+ return static_cast<int>(ratio - ratio_threshold);
+}
+
+
+void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) {
+ DCHECK(space->identity() == OLD_POINTER_SPACE ||
+ space->identity() == OLD_DATA_SPACE ||
+ space->identity() == CODE_SPACE);
+
+ static const int kMaxMaxEvacuationCandidates = 1000;
+ int number_of_pages = space->CountTotalPages();
+ int max_evacuation_candidates =
+ static_cast<int>(std::sqrt(number_of_pages / 2.0) + 1);
+
+ if (FLAG_stress_compaction || FLAG_always_compact) {
+ max_evacuation_candidates = kMaxMaxEvacuationCandidates;
+ }
+
+ class Candidate {
+ public:
+ Candidate() : fragmentation_(0), page_(NULL) {}
+ Candidate(int f, Page* p) : fragmentation_(f), page_(p) {}
+
+ int fragmentation() { return fragmentation_; }
+ Page* page() { return page_; }
+
+ private:
+ int fragmentation_;
+ Page* page_;
+ };
+
+ enum CompactionMode { COMPACT_FREE_LISTS, REDUCE_MEMORY_FOOTPRINT };
+
+ CompactionMode mode = COMPACT_FREE_LISTS;
+
+ intptr_t reserved = number_of_pages * space->AreaSize();
+ intptr_t over_reserved = reserved - space->SizeOfObjects();
+ static const intptr_t kFreenessThreshold = 50;
+
+ if (reduce_memory_footprint_ && over_reserved >= space->AreaSize()) {
+ // If reduction of memory footprint was requested, we are aggressive
+ // about choosing pages to free. We expect that half-empty pages
+ // are easier to compact so slightly bump the limit.
+ mode = REDUCE_MEMORY_FOOTPRINT;
+ max_evacuation_candidates += 2;
+ }
+
+
+ if (over_reserved > reserved / 3 && over_reserved >= 2 * space->AreaSize()) {
+ // If over-usage is very high (more than a third of the space), we
+ // try to free all mostly empty pages. We expect that almost empty
+ // pages are even easier to compact so bump the limit even more.
+ mode = REDUCE_MEMORY_FOOTPRINT;
+ max_evacuation_candidates *= 2;
+ }
+
+ if (FLAG_trace_fragmentation && mode == REDUCE_MEMORY_FOOTPRINT) {
+ PrintF(
+ "Estimated over reserved memory: %.1f / %.1f MB (threshold %d), "
+ "evacuation candidate limit: %d\n",
+ static_cast<double>(over_reserved) / MB,
+ static_cast<double>(reserved) / MB,
+ static_cast<int>(kFreenessThreshold), max_evacuation_candidates);
+ }
+
+ intptr_t estimated_release = 0;
+
+ Candidate candidates[kMaxMaxEvacuationCandidates];
+
+ max_evacuation_candidates =
+ Min(kMaxMaxEvacuationCandidates, max_evacuation_candidates);
+
+ int count = 0;
+ int fragmentation = 0;
+ Candidate* least = NULL;
+
+ PageIterator it(space);
+ if (it.has_next()) it.next(); // Never compact the first page.
+
+ while (it.has_next()) {
+ Page* p = it.next();
+ p->ClearEvacuationCandidate();
+
+ if (FLAG_stress_compaction) {
+ unsigned int counter = space->heap()->ms_count();
+ uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits;
+ if ((counter & 1) == (page_number & 1)) fragmentation = 1;
+ } else if (mode == REDUCE_MEMORY_FOOTPRINT) {
+ // Don't try to release too many pages.
+ if (estimated_release >= over_reserved) {
+ continue;
+ }
+
+ intptr_t free_bytes = 0;
+
+ if (!p->WasSwept()) {
+ free_bytes = (p->area_size() - p->LiveBytes());
+ } else {
+ PagedSpace::SizeStats sizes;
+ space->ObtainFreeListStatistics(p, &sizes);
+ free_bytes = sizes.Total();
+ }
+
+ int free_pct = static_cast<int>(free_bytes * 100) / p->area_size();
+
+ if (free_pct >= kFreenessThreshold) {
+ estimated_release += free_bytes;
+ fragmentation = free_pct;
+ } else {
+ fragmentation = 0;
+ }
+
+ if (FLAG_trace_fragmentation) {
+ PrintF("%p [%s]: %d (%.2f%%) free %s\n", reinterpret_cast<void*>(p),
+ AllocationSpaceName(space->identity()),
+ static_cast<int>(free_bytes),
+ static_cast<double>(free_bytes * 100) / p->area_size(),
+ (fragmentation > 0) ? "[fragmented]" : "");
+ }
+ } else {
+ fragmentation = FreeListFragmentation(space, p);
+ }
+
+ if (fragmentation != 0) {
+ if (count < max_evacuation_candidates) {
+ candidates[count++] = Candidate(fragmentation, p);
+ } else {
+ if (least == NULL) {
+ for (int i = 0; i < max_evacuation_candidates; i++) {
+ if (least == NULL ||
+ candidates[i].fragmentation() < least->fragmentation()) {
+ least = candidates + i;
+ }
+ }
+ }
+ if (least->fragmentation() < fragmentation) {
+ *least = Candidate(fragmentation, p);
+ least = NULL;
+ }
+ }
+ }
+ }
+
+ for (int i = 0; i < count; i++) {
+ AddEvacuationCandidate(candidates[i].page());
+ }
+
+ if (count > 0 && FLAG_trace_fragmentation) {
+ PrintF("Collected %d evacuation candidates for space %s\n", count,
+ AllocationSpaceName(space->identity()));
+ }
+}
+
+
+void MarkCompactCollector::AbortCompaction() {
+ if (compacting_) {
+ int npages = evacuation_candidates_.length();
+ for (int i = 0; i < npages; i++) {
+ Page* p = evacuation_candidates_[i];
+ slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address());
+ p->ClearEvacuationCandidate();
+ p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION);
+ }
+ compacting_ = false;
+ evacuation_candidates_.Rewind(0);
+ invalidated_code_.Rewind(0);
+ }
+ DCHECK_EQ(0, evacuation_candidates_.length());
+}
+
+
+void MarkCompactCollector::Prepare() {
+ was_marked_incrementally_ = heap()->incremental_marking()->IsMarking();
+
+#ifdef DEBUG
+ DCHECK(state_ == IDLE);
+ state_ = PREPARE_GC;
+#endif
+
+ DCHECK(!FLAG_never_compact || !FLAG_always_compact);
+
+ if (sweeping_in_progress()) {
+ // Instead of waiting we could also abort the sweeper threads here.
+ EnsureSweepingCompleted();
+ }
+
+ // Clear marking bits if incremental marking is aborted.
+ if (was_marked_incrementally_ && abort_incremental_marking_) {
+ heap()->incremental_marking()->Abort();
+ ClearMarkbits();
+ AbortWeakCollections();
+ AbortCompaction();
+ was_marked_incrementally_ = false;
+ }
+
+ // Don't start compaction if we are in the middle of incremental
+ // marking cycle. We did not collect any slots.
+ if (!FLAG_never_compact && !was_marked_incrementally_) {
+ StartCompaction(NON_INCREMENTAL_COMPACTION);
+ }
+
+ PagedSpaces spaces(heap());
+ for (PagedSpace* space = spaces.next(); space != NULL;
+ space = spaces.next()) {
+ space->PrepareForMarkCompact();
+ }
+
+#ifdef VERIFY_HEAP
+ if (!was_marked_incrementally_ && FLAG_verify_heap) {
+ VerifyMarkbitsAreClean();
+ }
+#endif
+}
+
+
+void MarkCompactCollector::Finish() {
+#ifdef DEBUG
+ DCHECK(state_ == SWEEP_SPACES || state_ == RELOCATE_OBJECTS);
+ state_ = IDLE;
+#endif
+ // The stub cache is not traversed during GC; clear the cache to
+ // force lazy re-initialization of it. This must be done after the
+ // GC, because it relies on the new address of certain old space
+ // objects (empty string, illegal builtin).
+ isolate()->stub_cache()->Clear();
+
+ if (have_code_to_deoptimize_) {
+ // Some code objects were marked for deoptimization during the GC.
+ Deoptimizer::DeoptimizeMarkedCode(isolate());
+ have_code_to_deoptimize_ = false;
+ }
+}
+
+
+// -------------------------------------------------------------------------
+// Phase 1: tracing and marking live objects.
+// before: all objects are in normal state.
+// after: a live object's map pointer is marked as '00'.
+
+// Marking all live objects in the heap as part of mark-sweep or mark-compact
+// collection. Before marking, all objects are in their normal state. After
+// marking, live objects' map pointers are marked indicating that the object
+// has been found reachable.
+//
+// The marking algorithm is a (mostly) depth-first (because of possible stack
+// overflow) traversal of the graph of objects reachable from the roots. It
+// uses an explicit stack of pointers rather than recursion. The young
+// generation's inactive ('from') space is used as a marking stack. The
+// objects in the marking stack are the ones that have been reached and marked
+// but their children have not yet been visited.
+//
+// The marking stack can overflow during traversal. In that case, we set an
+// overflow flag. When the overflow flag is set, we continue marking objects
+// reachable from the objects on the marking stack, but no longer push them on
+// the marking stack. Instead, we mark them as both marked and overflowed.
+// When the stack is in the overflowed state, objects marked as overflowed
+// have been reached and marked but their children have not been visited yet.
+// After emptying the marking stack, we clear the overflow flag and traverse
+// the heap looking for objects marked as overflowed, push them on the stack,
+// and continue with marking. This process repeats until all reachable
+// objects have been marked.
+
+void CodeFlusher::ProcessJSFunctionCandidates() {
+ Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
+ Object* undefined = isolate_->heap()->undefined_value();
+
+ JSFunction* candidate = jsfunction_candidates_head_;
+ JSFunction* next_candidate;
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+ ClearNextCandidate(candidate, undefined);
+
+ SharedFunctionInfo* shared = candidate->shared();
+
+ Code* code = shared->code();
+ MarkBit code_mark = Marking::MarkBitFrom(code);
+ if (!code_mark.Get()) {
+ if (FLAG_trace_code_flushing && shared->is_compiled()) {
+ PrintF("[code-flushing clears: ");
+ shared->ShortPrint();
+ PrintF(" - age: %d]\n", code->GetAge());
+ }
+ shared->set_code(lazy_compile);
+ candidate->set_code(lazy_compile);
+ } else {
+ candidate->set_code(code);
+ }
+
+ // We are in the middle of a GC cycle so the write barrier in the code
+ // setter did not record the slot update and we have to do that manually.
+ Address slot = candidate->address() + JSFunction::kCodeEntryOffset;
+ Code* target = Code::cast(Code::GetObjectFromEntryAddress(slot));
+ isolate_->heap()->mark_compact_collector()->RecordCodeEntrySlot(slot,
+ target);
+
+ Object** shared_code_slot =
+ HeapObject::RawField(shared, SharedFunctionInfo::kCodeOffset);
+ isolate_->heap()->mark_compact_collector()->RecordSlot(
+ shared_code_slot, shared_code_slot, *shared_code_slot);
+
+ candidate = next_candidate;
+ }
+
+ jsfunction_candidates_head_ = NULL;
+}
+
+
+void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
+ Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
+
+ SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
+ SharedFunctionInfo* next_candidate;
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+ ClearNextCandidate(candidate);
+
+ Code* code = candidate->code();
+ MarkBit code_mark = Marking::MarkBitFrom(code);
+ if (!code_mark.Get()) {
+ if (FLAG_trace_code_flushing && candidate->is_compiled()) {
+ PrintF("[code-flushing clears: ");
+ candidate->ShortPrint();
+ PrintF(" - age: %d]\n", code->GetAge());
+ }
+ candidate->set_code(lazy_compile);
+ }
+
+ Object** code_slot =
+ HeapObject::RawField(candidate, SharedFunctionInfo::kCodeOffset);
+ isolate_->heap()->mark_compact_collector()->RecordSlot(code_slot, code_slot,
+ *code_slot);
+
+ candidate = next_candidate;
+ }
+
+ shared_function_info_candidates_head_ = NULL;
+}
+
+
+void CodeFlusher::ProcessOptimizedCodeMaps() {
+ STATIC_ASSERT(SharedFunctionInfo::kEntryLength == 4);
+
+ SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+ SharedFunctionInfo* next_holder;
+
+ while (holder != NULL) {
+ next_holder = GetNextCodeMap(holder);
+ ClearNextCodeMap(holder);
+
+ FixedArray* code_map = FixedArray::cast(holder->optimized_code_map());
+ int new_length = SharedFunctionInfo::kEntriesStart;
+ int old_length = code_map->length();
+ for (int i = SharedFunctionInfo::kEntriesStart; i < old_length;
+ i += SharedFunctionInfo::kEntryLength) {
+ Code* code =
+ Code::cast(code_map->get(i + SharedFunctionInfo::kCachedCodeOffset));
+ if (!Marking::MarkBitFrom(code).Get()) continue;
+
+ // Move every slot in the entry.
+ for (int j = 0; j < SharedFunctionInfo::kEntryLength; j++) {
+ int dst_index = new_length++;
+ Object** slot = code_map->RawFieldOfElementAt(dst_index);
+ Object* object = code_map->get(i + j);
+ code_map->set(dst_index, object);
+ if (j == SharedFunctionInfo::kOsrAstIdOffset) {
+ DCHECK(object->IsSmi());
+ } else {
+ DCHECK(
+ Marking::IsBlack(Marking::MarkBitFrom(HeapObject::cast(*slot))));
+ isolate_->heap()->mark_compact_collector()->RecordSlot(slot, slot,
+ *slot);
+ }
+ }
+ }
+
+ // Trim the optimized code map if entries have been removed.
+ if (new_length < old_length) {
+ holder->TrimOptimizedCodeMap(old_length - new_length);
+ }
+
+ holder = next_holder;
+ }
+
+ optimized_code_map_holder_head_ = NULL;
+}
+
+
+void CodeFlusher::EvictCandidate(SharedFunctionInfo* shared_info) {
+ // Make sure previous flushing decisions are revisited.
+ isolate_->heap()->incremental_marking()->RecordWrites(shared_info);
+
+ if (FLAG_trace_code_flushing) {
+ PrintF("[code-flushing abandons function-info: ");
+ shared_info->ShortPrint();
+ PrintF("]\n");
+ }
+
+ SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
+ SharedFunctionInfo* next_candidate;
+ if (candidate == shared_info) {
+ next_candidate = GetNextCandidate(shared_info);
+ shared_function_info_candidates_head_ = next_candidate;
+ ClearNextCandidate(shared_info);
+ } else {
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+
+ if (next_candidate == shared_info) {
+ next_candidate = GetNextCandidate(shared_info);
+ SetNextCandidate(candidate, next_candidate);
+ ClearNextCandidate(shared_info);
+ break;
+ }
+
+ candidate = next_candidate;
+ }
+ }
+}
+
+
+void CodeFlusher::EvictCandidate(JSFunction* function) {
+ DCHECK(!function->next_function_link()->IsUndefined());
+ Object* undefined = isolate_->heap()->undefined_value();
+
+ // Make sure previous flushing decisions are revisited.
+ isolate_->heap()->incremental_marking()->RecordWrites(function);
+ isolate_->heap()->incremental_marking()->RecordWrites(function->shared());
+
+ if (FLAG_trace_code_flushing) {
+ PrintF("[code-flushing abandons closure: ");
+ function->shared()->ShortPrint();
+ PrintF("]\n");
+ }
+
+ JSFunction* candidate = jsfunction_candidates_head_;
+ JSFunction* next_candidate;
+ if (candidate == function) {
+ next_candidate = GetNextCandidate(function);
+ jsfunction_candidates_head_ = next_candidate;
+ ClearNextCandidate(function, undefined);
+ } else {
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+
+ if (next_candidate == function) {
+ next_candidate = GetNextCandidate(function);
+ SetNextCandidate(candidate, next_candidate);
+ ClearNextCandidate(function, undefined);
+ break;
+ }
+
+ candidate = next_candidate;
+ }
+ }
+}
+
+
+void CodeFlusher::EvictOptimizedCodeMap(SharedFunctionInfo* code_map_holder) {
+ DCHECK(!FixedArray::cast(code_map_holder->optimized_code_map())
+ ->get(SharedFunctionInfo::kNextMapIndex)
+ ->IsUndefined());
+
+ // Make sure previous flushing decisions are revisited.
+ isolate_->heap()->incremental_marking()->RecordWrites(code_map_holder);
+
+ if (FLAG_trace_code_flushing) {
+ PrintF("[code-flushing abandons code-map: ");
+ code_map_holder->ShortPrint();
+ PrintF("]\n");
+ }
+
+ SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+ SharedFunctionInfo* next_holder;
+ if (holder == code_map_holder) {
+ next_holder = GetNextCodeMap(code_map_holder);
+ optimized_code_map_holder_head_ = next_holder;
+ ClearNextCodeMap(code_map_holder);
+ } else {
+ while (holder != NULL) {
+ next_holder = GetNextCodeMap(holder);
+
+ if (next_holder == code_map_holder) {
+ next_holder = GetNextCodeMap(code_map_holder);
+ SetNextCodeMap(holder, next_holder);
+ ClearNextCodeMap(code_map_holder);
+ break;
+ }
+
+ holder = next_holder;
+ }
+ }
+}
+
+
+void CodeFlusher::EvictJSFunctionCandidates() {
+ JSFunction* candidate = jsfunction_candidates_head_;
+ JSFunction* next_candidate;
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+ EvictCandidate(candidate);
+ candidate = next_candidate;
+ }
+ DCHECK(jsfunction_candidates_head_ == NULL);
+}
+
+
+void CodeFlusher::EvictSharedFunctionInfoCandidates() {
+ SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
+ SharedFunctionInfo* next_candidate;
+ while (candidate != NULL) {
+ next_candidate = GetNextCandidate(candidate);
+ EvictCandidate(candidate);
+ candidate = next_candidate;
+ }
+ DCHECK(shared_function_info_candidates_head_ == NULL);
+}
+
+
+void CodeFlusher::EvictOptimizedCodeMaps() {
+ SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+ SharedFunctionInfo* next_holder;
+ while (holder != NULL) {
+ next_holder = GetNextCodeMap(holder);
+ EvictOptimizedCodeMap(holder);
+ holder = next_holder;
+ }
+ DCHECK(optimized_code_map_holder_head_ == NULL);
+}
+
+
+void CodeFlusher::IteratePointersToFromSpace(ObjectVisitor* v) {
+ Heap* heap = isolate_->heap();
+
+ JSFunction** slot = &jsfunction_candidates_head_;
+ JSFunction* candidate = jsfunction_candidates_head_;
+ while (candidate != NULL) {
+ if (heap->InFromSpace(candidate)) {
+ v->VisitPointer(reinterpret_cast<Object**>(slot));
+ }
+ candidate = GetNextCandidate(*slot);
+ slot = GetNextCandidateSlot(*slot);
+ }
+}
+
+
+MarkCompactCollector::~MarkCompactCollector() {
+ if (code_flusher_ != NULL) {
+ delete code_flusher_;
+ code_flusher_ = NULL;
+ }
+}
+
+
+static inline HeapObject* ShortCircuitConsString(Object** p) {
+ // Optimization: If the heap object pointed to by p is a non-internalized
+ // cons string whose right substring is HEAP->empty_string, update
+ // it in place to its left substring. Return the updated value.
+ //
+ // Here we assume that if we change *p, we replace it with a heap object
+ // (i.e., the left substring of a cons string is always a heap object).
+ //
+ // The check performed is:
+ // object->IsConsString() && !object->IsInternalizedString() &&
+ // (ConsString::cast(object)->second() == HEAP->empty_string())
+ // except the maps for the object and its possible substrings might be
+ // marked.
+ HeapObject* object = HeapObject::cast(*p);
+ if (!FLAG_clever_optimizations) return object;
+ Map* map = object->map();
+ InstanceType type = map->instance_type();
+ if (!IsShortcutCandidate(type)) return object;
+
+ Object* second = reinterpret_cast<ConsString*>(object)->second();
+ Heap* heap = map->GetHeap();
+ if (second != heap->empty_string()) {
+ return object;
+ }
+
+ // Since we don't have the object's start, it is impossible to update the
+ // page dirty marks. Therefore, we only replace the string with its left
+ // substring when page dirty marks do not change.
+ Object* first = reinterpret_cast<ConsString*>(object)->first();
+ if (!heap->InNewSpace(object) && heap->InNewSpace(first)) return object;
+
+ *p = first;
+ return HeapObject::cast(first);
+}
+
+
+class MarkCompactMarkingVisitor
+ : public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
+ public:
+ static void ObjectStatsVisitBase(StaticVisitorBase::VisitorId id, Map* map,
+ HeapObject* obj);
+
+ static void ObjectStatsCountFixedArray(
+ FixedArrayBase* fixed_array, FixedArraySubInstanceType fast_type,
+ FixedArraySubInstanceType dictionary_type);
+
+ template <MarkCompactMarkingVisitor::VisitorId id>
+ class ObjectStatsTracker {
+ public:
+ static inline void Visit(Map* map, HeapObject* obj);
+ };
+
+ static void Initialize();
+
+ INLINE(static void VisitPointer(Heap* heap, Object** p)) {
+ MarkObjectByPointer(heap->mark_compact_collector(), p, p);
+ }
+
+ INLINE(static void VisitPointers(Heap* heap, Object** start, Object** end)) {
+ // Mark all objects pointed to in [start, end).
+ const int kMinRangeForMarkingRecursion = 64;
+ if (end - start >= kMinRangeForMarkingRecursion) {
+ if (VisitUnmarkedObjects(heap, start, end)) return;
+ // We are close to a stack overflow, so just mark the objects.
+ }
+ MarkCompactCollector* collector = heap->mark_compact_collector();
+ for (Object** p = start; p < end; p++) {
+ MarkObjectByPointer(collector, start, p);
+ }
+ }
+
+ // Marks the object black and pushes it on the marking stack.
+ INLINE(static void MarkObject(Heap* heap, HeapObject* object)) {
+ MarkBit mark = Marking::MarkBitFrom(object);
+ heap->mark_compact_collector()->MarkObject(object, mark);
+ }
+
+ // Marks the object black without pushing it on the marking stack.
+ // Returns true if object needed marking and false otherwise.
+ INLINE(static bool MarkObjectWithoutPush(Heap* heap, HeapObject* object)) {
+ MarkBit mark_bit = Marking::MarkBitFrom(object);
+ if (!mark_bit.Get()) {
+ heap->mark_compact_collector()->SetMark(object, mark_bit);
+ return true;
+ }
+ return false;
+ }
+
+ // Mark object pointed to by p.
+ INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector,
+ Object** anchor_slot, Object** p)) {
+ if (!(*p)->IsHeapObject()) return;
+ HeapObject* object = ShortCircuitConsString(p);
+ collector->RecordSlot(anchor_slot, p, object);
+ MarkBit mark = Marking::MarkBitFrom(object);
+ collector->MarkObject(object, mark);
+ }
+
+
+ // Visit an unmarked object.
+ INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector,
+ HeapObject* obj)) {
+#ifdef DEBUG
+ DCHECK(collector->heap()->Contains(obj));
+ DCHECK(!collector->heap()->mark_compact_collector()->IsMarked(obj));
+#endif
+ Map* map = obj->map();
+ Heap* heap = obj->GetHeap();
+ MarkBit mark = Marking::MarkBitFrom(obj);
+ heap->mark_compact_collector()->SetMark(obj, mark);
+ // Mark the map pointer and the body.
+ MarkBit map_mark = Marking::MarkBitFrom(map);
+ heap->mark_compact_collector()->MarkObject(map, map_mark);
+ IterateBody(map, obj);
+ }
+
+ // Visit all unmarked objects pointed to by [start, end).
+ // Returns false if the operation fails (lack of stack space).
+ INLINE(static bool VisitUnmarkedObjects(Heap* heap, Object** start,
+ Object** end)) {
+ // Return false is we are close to the stack limit.
+ StackLimitCheck check(heap->isolate());
+ if (check.HasOverflowed()) return false;
+
+ MarkCompactCollector* collector = heap->mark_compact_collector();
+ // Visit the unmarked objects.
+ for (Object** p = start; p < end; p++) {
+ Object* o = *p;
+ if (!o->IsHeapObject()) continue;
+ collector->RecordSlot(start, p, o);
+ HeapObject* obj = HeapObject::cast(o);
+ MarkBit mark = Marking::MarkBitFrom(obj);
+ if (mark.Get()) continue;
+ VisitUnmarkedObject(collector, obj);
+ }
+ return true;
+ }
+
+ private:
+ template <int id>
+ static inline void TrackObjectStatsAndVisit(Map* map, HeapObject* obj);
+
+ // Code flushing support.
+
+ static const int kRegExpCodeThreshold = 5;
+
+ static void UpdateRegExpCodeAgeAndFlush(Heap* heap, JSRegExp* re,
+ bool is_one_byte) {
+ // Make sure that the fixed array is in fact initialized on the RegExp.
+ // We could potentially trigger a GC when initializing the RegExp.
+ if (HeapObject::cast(re->data())->map()->instance_type() !=
+ FIXED_ARRAY_TYPE)
+ return;
+
+ // Make sure this is a RegExp that actually contains code.
+ if (re->TypeTag() != JSRegExp::IRREGEXP) return;
+
+ Object* code = re->DataAt(JSRegExp::code_index(is_one_byte));
+ if (!code->IsSmi() &&
+ HeapObject::cast(code)->map()->instance_type() == CODE_TYPE) {
+ // Save a copy that can be reinstated if we need the code again.
+ re->SetDataAt(JSRegExp::saved_code_index(is_one_byte), code);
+
+ // Saving a copy might create a pointer into compaction candidate
+ // that was not observed by marker. This might happen if JSRegExp data
+ // was marked through the compilation cache before marker reached JSRegExp
+ // object.
+ FixedArray* data = FixedArray::cast(re->data());
+ Object** slot =
+ data->data_start() + JSRegExp::saved_code_index(is_one_byte);
+ heap->mark_compact_collector()->RecordSlot(slot, slot, code);
+
+ // Set a number in the 0-255 range to guarantee no smi overflow.
+ re->SetDataAt(JSRegExp::code_index(is_one_byte),
+ Smi::FromInt(heap->sweep_generation() & 0xff));
+ } else if (code->IsSmi()) {
+ int value = Smi::cast(code)->value();
+ // The regexp has not been compiled yet or there was a compilation error.
+ if (value == JSRegExp::kUninitializedValue ||
+ value == JSRegExp::kCompilationErrorValue) {
+ return;
+ }
+
+ // Check if we should flush now.
+ if (value == ((heap->sweep_generation() - kRegExpCodeThreshold) & 0xff)) {
+ re->SetDataAt(JSRegExp::code_index(is_one_byte),
+ Smi::FromInt(JSRegExp::kUninitializedValue));
+ re->SetDataAt(JSRegExp::saved_code_index(is_one_byte),
+ Smi::FromInt(JSRegExp::kUninitializedValue));
+ }
+ }
+ }
+
+
+ // Works by setting the current sweep_generation (as a smi) in the
+ // code object place in the data array of the RegExp and keeps a copy
+ // around that can be reinstated if we reuse the RegExp before flushing.
+ // If we did not use the code for kRegExpCodeThreshold mark sweep GCs
+ // we flush the code.
+ static void VisitRegExpAndFlushCode(Map* map, HeapObject* object) {
+ Heap* heap = map->GetHeap();
+ MarkCompactCollector* collector = heap->mark_compact_collector();
+ if (!collector->is_code_flushing_enabled()) {
+ VisitJSRegExp(map, object);
+ return;
+ }
+ JSRegExp* re = reinterpret_cast<JSRegExp*>(object);
+ // Flush code or set age on both one byte and two byte code.
+ UpdateRegExpCodeAgeAndFlush(heap, re, true);
+ UpdateRegExpCodeAgeAndFlush(heap, re, false);
+ // Visit the fields of the RegExp, including the updated FixedArray.
+ VisitJSRegExp(map, object);
+ }
+
+ static VisitorDispatchTable<Callback> non_count_table_;
+};
+
+
+void MarkCompactMarkingVisitor::ObjectStatsCountFixedArray(
+ FixedArrayBase* fixed_array, FixedArraySubInstanceType fast_type,
+ FixedArraySubInstanceType dictionary_type) {
+ Heap* heap = fixed_array->map()->GetHeap();
+ if (fixed_array->map() != heap->fixed_cow_array_map() &&
+ fixed_array->map() != heap->fixed_double_array_map() &&
+ fixed_array != heap->empty_fixed_array()) {
+ if (fixed_array->IsDictionary()) {
+ heap->RecordFixedArraySubTypeStats(dictionary_type, fixed_array->Size());
+ } else {
+ heap->RecordFixedArraySubTypeStats(fast_type, fixed_array->Size());
+ }
+ }
+}
+
+
+void MarkCompactMarkingVisitor::ObjectStatsVisitBase(
+ MarkCompactMarkingVisitor::VisitorId id, Map* map, HeapObject* obj) {
+ Heap* heap = map->GetHeap();
+ int object_size = obj->Size();
+ heap->RecordObjectStats(map->instance_type(), object_size);
+ non_count_table_.GetVisitorById(id)(map, obj);
+ if (obj->IsJSObject()) {
+ JSObject* object = JSObject::cast(obj);
+ ObjectStatsCountFixedArray(object->elements(), DICTIONARY_ELEMENTS_SUB_TYPE,
+ FAST_ELEMENTS_SUB_TYPE);
+ ObjectStatsCountFixedArray(object->properties(),
+ DICTIONARY_PROPERTIES_SUB_TYPE,
+ FAST_PROPERTIES_SUB_TYPE);
+ }
+}
+
+
+template <MarkCompactMarkingVisitor::VisitorId id>
+void MarkCompactMarkingVisitor::ObjectStatsTracker<id>::Visit(Map* map,
+ HeapObject* obj) {
+ ObjectStatsVisitBase(id, map, obj);
+}
+
+
+template <>
+class MarkCompactMarkingVisitor::ObjectStatsTracker<
+ MarkCompactMarkingVisitor::kVisitMap> {
+ public:
+ static inline void Visit(Map* map, HeapObject* obj) {
+ Heap* heap = map->GetHeap();
+ Map* map_obj = Map::cast(obj);
+ DCHECK(map->instance_type() == MAP_TYPE);
+ DescriptorArray* array = map_obj->instance_descriptors();
+ if (map_obj->owns_descriptors() &&
+ array != heap->empty_descriptor_array()) {
+ int fixed_array_size = array->Size();
+ heap->RecordFixedArraySubTypeStats(DESCRIPTOR_ARRAY_SUB_TYPE,
+ fixed_array_size);
+ }
+ if (map_obj->HasTransitionArray()) {
+ int fixed_array_size = map_obj->transitions()->Size();
+ heap->RecordFixedArraySubTypeStats(TRANSITION_ARRAY_SUB_TYPE,
+ fixed_array_size);
+ }
+ if (map_obj->has_code_cache()) {
+ CodeCache* cache = CodeCache::cast(map_obj->code_cache());
+ heap->RecordFixedArraySubTypeStats(MAP_CODE_CACHE_SUB_TYPE,
+ cache->default_cache()->Size());
+ if (!cache->normal_type_cache()->IsUndefined()) {
+ heap->RecordFixedArraySubTypeStats(
+ MAP_CODE_CACHE_SUB_TYPE,
+ FixedArray::cast(cache->normal_type_cache())->Size());
+ }
+ }
+ ObjectStatsVisitBase(kVisitMap, map, obj);
+ }
+};
+
+
+template <>
+class MarkCompactMarkingVisitor::ObjectStatsTracker<
+ MarkCompactMarkingVisitor::kVisitCode> {
+ public:
+ static inline void Visit(Map* map, HeapObject* obj) {
+ Heap* heap = map->GetHeap();
+ int object_size = obj->Size();
+ DCHECK(map->instance_type() == CODE_TYPE);
+ Code* code_obj = Code::cast(obj);
+ heap->RecordCodeSubTypeStats(code_obj->kind(), code_obj->GetRawAge(),
+ object_size);
+ ObjectStatsVisitBase(kVisitCode, map, obj);
+ }
+};
+
+
+template <>
+class MarkCompactMarkingVisitor::ObjectStatsTracker<
+ MarkCompactMarkingVisitor::kVisitSharedFunctionInfo> {
+ public:
+ static inline void Visit(Map* map, HeapObject* obj) {
+ Heap* heap = map->GetHeap();
+ SharedFunctionInfo* sfi = SharedFunctionInfo::cast(obj);
+ if (sfi->scope_info() != heap->empty_fixed_array()) {
+ heap->RecordFixedArraySubTypeStats(
+ SCOPE_INFO_SUB_TYPE, FixedArray::cast(sfi->scope_info())->Size());
+ }
+ ObjectStatsVisitBase(kVisitSharedFunctionInfo, map, obj);
+ }
+};
+
+
+template <>
+class MarkCompactMarkingVisitor::ObjectStatsTracker<
+ MarkCompactMarkingVisitor::kVisitFixedArray> {
+ public:
+ static inline void Visit(Map* map, HeapObject* obj) {
+ Heap* heap = map->GetHeap();
+ FixedArray* fixed_array = FixedArray::cast(obj);
+ if (fixed_array == heap->string_table()) {
+ heap->RecordFixedArraySubTypeStats(STRING_TABLE_SUB_TYPE,
+ fixed_array->Size());
+ }
+ ObjectStatsVisitBase(kVisitFixedArray, map, obj);
+ }
+};
+
+
+void MarkCompactMarkingVisitor::Initialize() {
+ StaticMarkingVisitor<MarkCompactMarkingVisitor>::Initialize();
+
+ table_.Register(kVisitJSRegExp, &VisitRegExpAndFlushCode);
+
+ if (FLAG_track_gc_object_stats) {
+ // Copy the visitor table to make call-through possible.
+ non_count_table_.CopyFrom(&table_);
+#define VISITOR_ID_COUNT_FUNCTION(id) \
+ table_.Register(kVisit##id, ObjectStatsTracker<kVisit##id>::Visit);
+ VISITOR_ID_LIST(VISITOR_ID_COUNT_FUNCTION)
+#undef VISITOR_ID_COUNT_FUNCTION
+ }
+}
+
+
+VisitorDispatchTable<MarkCompactMarkingVisitor::Callback>
+ MarkCompactMarkingVisitor::non_count_table_;
+
+
+class CodeMarkingVisitor : public ThreadVisitor {
+ public:
+ explicit CodeMarkingVisitor(MarkCompactCollector* collector)
+ : collector_(collector) {}
+
+ void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
+ collector_->PrepareThreadForCodeFlushing(isolate, top);
+ }
+
+ private:
+ MarkCompactCollector* collector_;
+};
+
+
+class SharedFunctionInfoMarkingVisitor : public ObjectVisitor {
+ public:
+ explicit SharedFunctionInfoMarkingVisitor(MarkCompactCollector* collector)
+ : collector_(collector) {}
+
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** p = start; p < end; p++) VisitPointer(p);
+ }
+
+ void VisitPointer(Object** slot) {
+ Object* obj = *slot;
+ if (obj->IsSharedFunctionInfo()) {
+ SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(obj);
+ MarkBit shared_mark = Marking::MarkBitFrom(shared);
+ MarkBit code_mark = Marking::MarkBitFrom(shared->code());
+ collector_->MarkObject(shared->code(), code_mark);
+ collector_->MarkObject(shared, shared_mark);
+ }
+ }
+
+ private:
+ MarkCompactCollector* collector_;
+};
+
+
+void MarkCompactCollector::PrepareThreadForCodeFlushing(Isolate* isolate,
+ ThreadLocalTop* top) {
+ for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) {
+ // Note: for the frame that has a pending lazy deoptimization
+ // StackFrame::unchecked_code will return a non-optimized code object for
+ // the outermost function and StackFrame::LookupCode will return
+ // actual optimized code object.
+ StackFrame* frame = it.frame();
+ Code* code = frame->unchecked_code();
+ MarkBit code_mark = Marking::MarkBitFrom(code);
+ MarkObject(code, code_mark);
+ if (frame->is_optimized()) {
+ MarkCompactMarkingVisitor::MarkInlinedFunctionsCode(heap(),
+ frame->LookupCode());
+ }
+ }
+}
+
+
+void MarkCompactCollector::PrepareForCodeFlushing() {
+ // Enable code flushing for non-incremental cycles.
+ if (FLAG_flush_code && !FLAG_flush_code_incrementally) {
+ EnableCodeFlushing(!was_marked_incrementally_);
+ }
+
+ // If code flushing is disabled, there is no need to prepare for it.
+ if (!is_code_flushing_enabled()) return;
+
+ // Ensure that empty descriptor array is marked. Method MarkDescriptorArray
+ // relies on it being marked before any other descriptor array.
+ HeapObject* descriptor_array = heap()->empty_descriptor_array();
+ MarkBit descriptor_array_mark = Marking::MarkBitFrom(descriptor_array);
+ MarkObject(descriptor_array, descriptor_array_mark);
+
+ // Make sure we are not referencing the code from the stack.
+ DCHECK(this == heap()->mark_compact_collector());
+ PrepareThreadForCodeFlushing(heap()->isolate(),
+ heap()->isolate()->thread_local_top());
+
+ // Iterate the archived stacks in all threads to check if
+ // the code is referenced.
+ CodeMarkingVisitor code_marking_visitor(this);
+ heap()->isolate()->thread_manager()->IterateArchivedThreads(
+ &code_marking_visitor);
+
+ SharedFunctionInfoMarkingVisitor visitor(this);
+ heap()->isolate()->compilation_cache()->IterateFunctions(&visitor);
+ heap()->isolate()->handle_scope_implementer()->Iterate(&visitor);
+
+ ProcessMarkingDeque();
+}
+
+
+// Visitor class for marking heap roots.
+class RootMarkingVisitor : public ObjectVisitor {
+ public:
+ explicit RootMarkingVisitor(Heap* heap)
+ : collector_(heap->mark_compact_collector()) {}
+
+ void VisitPointer(Object** p) { MarkObjectByPointer(p); }
+
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
+ }
+
+ // Skip the weak next code link in a code object, which is visited in
+ // ProcessTopOptimizedFrame.
+ void VisitNextCodeLink(Object** p) {}
+
+ private:
+ void MarkObjectByPointer(Object** p) {
+ if (!(*p)->IsHeapObject()) return;
+
+ // Replace flat cons strings in place.
+ HeapObject* object = ShortCircuitConsString(p);
+ MarkBit mark_bit = Marking::MarkBitFrom(object);
+ if (mark_bit.Get()) return;
+
+ Map* map = object->map();
+ // Mark the object.
+ collector_->SetMark(object, mark_bit);
+
+ // Mark the map pointer and body, and push them on the marking stack.
+ MarkBit map_mark = Marking::MarkBitFrom(map);
+ collector_->MarkObject(map, map_mark);
+ MarkCompactMarkingVisitor::IterateBody(map, object);
+
+ // Mark all the objects reachable from the map and body. May leave
+ // overflowed objects in the heap.
+ collector_->EmptyMarkingDeque();
+ }
+
+ MarkCompactCollector* collector_;
+};
+
+
+// Helper class for pruning the string table.
+template <bool finalize_external_strings>
+class StringTableCleaner : public ObjectVisitor {
+ public:
+ explicit StringTableCleaner(Heap* heap) : heap_(heap), pointers_removed_(0) {}
+
+ virtual void VisitPointers(Object** start, Object** end) {
+ // Visit all HeapObject pointers in [start, end).
+ for (Object** p = start; p < end; p++) {
+ Object* o = *p;
+ if (o->IsHeapObject() &&
+ !Marking::MarkBitFrom(HeapObject::cast(o)).Get()) {
+ if (finalize_external_strings) {
+ DCHECK(o->IsExternalString());
+ heap_->FinalizeExternalString(String::cast(*p));
+ } else {
+ pointers_removed_++;
+ }
+ // Set the entry to the_hole_value (as deleted).
+ *p = heap_->the_hole_value();
+ }
+ }
+ }
+
+ int PointersRemoved() {
+ DCHECK(!finalize_external_strings);
+ return pointers_removed_;
+ }
+
+ private:
+ Heap* heap_;
+ int pointers_removed_;
+};
+
+
+typedef StringTableCleaner<false> InternalizedStringTableCleaner;
+typedef StringTableCleaner<true> ExternalStringTableCleaner;
+
+
+// Implementation of WeakObjectRetainer for mark compact GCs. All marked objects
+// are retained.
+class MarkCompactWeakObjectRetainer : public WeakObjectRetainer {
+ public:
+ virtual Object* RetainAs(Object* object) {
+ if (Marking::MarkBitFrom(HeapObject::cast(object)).Get()) {
+ return object;
+ } else if (object->IsAllocationSite() &&
+ !(AllocationSite::cast(object)->IsZombie())) {
+ // "dead" AllocationSites need to live long enough for a traversal of new
+ // space. These sites get a one-time reprieve.
+ AllocationSite* site = AllocationSite::cast(object);
+ site->MarkZombie();
+ site->GetHeap()->mark_compact_collector()->MarkAllocationSite(site);
+ return object;
+ } else {
+ return NULL;
+ }
+ }
+};
+
+
+// Fill the marking stack with overflowed objects returned by the given
+// iterator. Stop when the marking stack is filled or the end of the space
+// is reached, whichever comes first.
+template <class T>
+static void DiscoverGreyObjectsWithIterator(Heap* heap,
+ MarkingDeque* marking_deque,
+ T* it) {
+ // The caller should ensure that the marking stack is initially not full,
+ // so that we don't waste effort pointlessly scanning for objects.
+ DCHECK(!marking_deque->IsFull());
+
+ Map* filler_map = heap->one_pointer_filler_map();
+ for (HeapObject* object = it->Next(); object != NULL; object = it->Next()) {
+ MarkBit markbit = Marking::MarkBitFrom(object);
+ if ((object->map() != filler_map) && Marking::IsGrey(markbit)) {
+ Marking::GreyToBlack(markbit);
+ MemoryChunk::IncrementLiveBytesFromGC(object->address(), object->Size());
+ marking_deque->PushBlack(object);
+ if (marking_deque->IsFull()) return;
+ }
+ }
+}
+
+
+static inline int MarkWordToObjectStarts(uint32_t mark_bits, int* starts);
+
+
+static void DiscoverGreyObjectsOnPage(MarkingDeque* marking_deque,
+ MemoryChunk* p) {
+ DCHECK(!marking_deque->IsFull());
+ DCHECK(strcmp(Marking::kWhiteBitPattern, "00") == 0);
+ DCHECK(strcmp(Marking::kBlackBitPattern, "10") == 0);
+ DCHECK(strcmp(Marking::kGreyBitPattern, "11") == 0);
+ DCHECK(strcmp(Marking::kImpossibleBitPattern, "01") == 0);
+
+ for (MarkBitCellIterator it(p); !it.Done(); it.Advance()) {
+ Address cell_base = it.CurrentCellBase();
+ MarkBit::CellType* cell = it.CurrentCell();
+
+ const MarkBit::CellType current_cell = *cell;
+ if (current_cell == 0) continue;
+
+ MarkBit::CellType grey_objects;
+ if (it.HasNext()) {
+ const MarkBit::CellType next_cell = *(cell + 1);
+ grey_objects = current_cell & ((current_cell >> 1) |
+ (next_cell << (Bitmap::kBitsPerCell - 1)));
+ } else {
+ grey_objects = current_cell & (current_cell >> 1);
+ }
+
+ int offset = 0;
+ while (grey_objects != 0) {
+ int trailing_zeros = base::bits::CountTrailingZeros32(grey_objects);
+ grey_objects >>= trailing_zeros;
+ offset += trailing_zeros;
+ MarkBit markbit(cell, 1 << offset, false);
+ DCHECK(Marking::IsGrey(markbit));
+ Marking::GreyToBlack(markbit);
+ Address addr = cell_base + offset * kPointerSize;
+ HeapObject* object = HeapObject::FromAddress(addr);
+ MemoryChunk::IncrementLiveBytesFromGC(object->address(), object->Size());
+ marking_deque->PushBlack(object);
+ if (marking_deque->IsFull()) return;
+ offset += 2;
+ grey_objects >>= 2;
+ }
+
+ grey_objects >>= (Bitmap::kBitsPerCell - 1);
+ }
+}
+
+
+int MarkCompactCollector::DiscoverAndEvacuateBlackObjectsOnPage(
+ NewSpace* new_space, NewSpacePage* p) {
+ DCHECK(strcmp(Marking::kWhiteBitPattern, "00") == 0);
+ DCHECK(strcmp(Marking::kBlackBitPattern, "10") == 0);
+ DCHECK(strcmp(Marking::kGreyBitPattern, "11") == 0);
+ DCHECK(strcmp(Marking::kImpossibleBitPattern, "01") == 0);
+
+ MarkBit::CellType* cells = p->markbits()->cells();
+ int survivors_size = 0;
+
+ for (MarkBitCellIterator it(p); !it.Done(); it.Advance()) {
+ Address cell_base = it.CurrentCellBase();
+ MarkBit::CellType* cell = it.CurrentCell();
+
+ MarkBit::CellType current_cell = *cell;
+ if (current_cell == 0) continue;
+
+ int offset = 0;
+ while (current_cell != 0) {
+ int trailing_zeros = base::bits::CountTrailingZeros32(current_cell);
+ current_cell >>= trailing_zeros;
+ offset += trailing_zeros;
+ Address address = cell_base + offset * kPointerSize;
+ HeapObject* object = HeapObject::FromAddress(address);
+
+ int size = object->Size();
+ survivors_size += size;
+
+ Heap::UpdateAllocationSiteFeedback(object, Heap::RECORD_SCRATCHPAD_SLOT);
+
+ offset++;
+ current_cell >>= 1;
+
+ // TODO(hpayer): Refactor EvacuateObject and call this function instead.
+ if (heap()->ShouldBePromoted(object->address(), size) &&
+ TryPromoteObject(object, size)) {
+ continue;
+ }
+
+ AllocationResult allocation = new_space->AllocateRaw(size);
+ if (allocation.IsRetry()) {
+ if (!new_space->AddFreshPage()) {
+ // Shouldn't happen. We are sweeping linearly, and to-space
+ // has the same number of pages as from-space, so there is
+ // always room.
+ UNREACHABLE();
+ }
+ allocation = new_space->AllocateRaw(size);
+ DCHECK(!allocation.IsRetry());
+ }
+ Object* target = allocation.ToObjectChecked();
+
+ MigrateObject(HeapObject::cast(target), object, size, NEW_SPACE);
+ heap()->IncrementSemiSpaceCopiedObjectSize(size);
+ }
+ *cells = 0;
+ }
+ return survivors_size;
+}
+
+
+static void DiscoverGreyObjectsInSpace(Heap* heap, MarkingDeque* marking_deque,
+ PagedSpace* space) {
+ PageIterator it(space);
+ while (it.has_next()) {
+ Page* p = it.next();
+ DiscoverGreyObjectsOnPage(marking_deque, p);
+ if (marking_deque->IsFull()) return;
+ }
+}
+
+
+static void DiscoverGreyObjectsInNewSpace(Heap* heap,
+ MarkingDeque* marking_deque) {
+ NewSpace* space = heap->new_space();
+ NewSpacePageIterator it(space->bottom(), space->top());
+ while (it.has_next()) {
+ NewSpacePage* page = it.next();
+ DiscoverGreyObjectsOnPage(marking_deque, page);
+ if (marking_deque->IsFull()) return;
+ }
+}
+
+
+bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) {
+ Object* o = *p;
+ if (!o->IsHeapObject()) return false;
+ HeapObject* heap_object = HeapObject::cast(o);
+ MarkBit mark = Marking::MarkBitFrom(heap_object);
+ return !mark.Get();
+}
+
+
+bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
+ Object** p) {
+ Object* o = *p;
+ DCHECK(o->IsHeapObject());
+ HeapObject* heap_object = HeapObject::cast(o);
+ MarkBit mark = Marking::MarkBitFrom(heap_object);
+ return !mark.Get();
+}
+
+
+void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) {
+ StringTable* string_table = heap()->string_table();
+ // Mark the string table itself.
+ MarkBit string_table_mark = Marking::MarkBitFrom(string_table);
+ if (!string_table_mark.Get()) {
+ // String table could have already been marked by visiting the handles list.
+ SetMark(string_table, string_table_mark);
+ }
+ // Explicitly mark the prefix.
+ string_table->IteratePrefix(visitor);
+ ProcessMarkingDeque();
+}
+
+
+void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
+ MarkBit mark_bit = Marking::MarkBitFrom(site);
+ SetMark(site, mark_bit);
+}
+
+
+void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
+ // Mark the heap roots including global variables, stack variables,
+ // etc., and all objects reachable from them.
+ heap()->IterateStrongRoots(visitor, VISIT_ONLY_STRONG);
+
+ // Handle the string table specially.
+ MarkStringTable(visitor);
+
+ MarkWeakObjectToCodeTable();
+
+ // There may be overflowed objects in the heap. Visit them now.
+ while (marking_deque_.overflowed()) {
+ RefillMarkingDeque();
+ EmptyMarkingDeque();
+ }
+}
+
+
+void MarkCompactCollector::MarkImplicitRefGroups() {
+ List<ImplicitRefGroup*>* ref_groups =
+ isolate()->global_handles()->implicit_ref_groups();
+
+ int last = 0;
+ for (int i = 0; i < ref_groups->length(); i++) {
+ ImplicitRefGroup* entry = ref_groups->at(i);
+ DCHECK(entry != NULL);
+
+ if (!IsMarked(*entry->parent)) {
+ (*ref_groups)[last++] = entry;
+ continue;
+ }
+
+ Object*** children = entry->children;
+ // A parent object is marked, so mark all child heap objects.
+ for (size_t j = 0; j < entry->length; ++j) {
+ if ((*children[j])->IsHeapObject()) {
+ HeapObject* child = HeapObject::cast(*children[j]);
+ MarkBit mark = Marking::MarkBitFrom(child);
+ MarkObject(child, mark);
+ }
+ }
+
+ // Once the entire group has been marked, dispose it because it's
+ // not needed anymore.
+ delete entry;
+ }
+ ref_groups->Rewind(last);
+}
+
+
+void MarkCompactCollector::MarkWeakObjectToCodeTable() {
+ HeapObject* weak_object_to_code_table =
+ HeapObject::cast(heap()->weak_object_to_code_table());
+ if (!IsMarked(weak_object_to_code_table)) {
+ MarkBit mark = Marking::MarkBitFrom(weak_object_to_code_table);
+ SetMark(weak_object_to_code_table, mark);
+ }
+}
+
+
+// Mark all objects reachable from the objects on the marking stack.
+// Before: the marking stack contains zero or more heap object pointers.
+// After: the marking stack is empty, and all objects reachable from the
+// marking stack have been marked, or are overflowed in the heap.
+void MarkCompactCollector::EmptyMarkingDeque() {
+ while (!marking_deque_.IsEmpty()) {
+ HeapObject* object = marking_deque_.Pop();
+ DCHECK(object->IsHeapObject());
+ DCHECK(heap()->Contains(object));
+ DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+
+ Map* map = object->map();
+ MarkBit map_mark = Marking::MarkBitFrom(map);
+ MarkObject(map, map_mark);
+
+ MarkCompactMarkingVisitor::IterateBody(map, object);
+ }
+}
+
+
+// Sweep the heap for overflowed objects, clear their overflow bits, and
+// push them on the marking stack. Stop early if the marking stack fills
+// before sweeping completes. If sweeping completes, there are no remaining
+// overflowed objects in the heap so the overflow flag on the markings stack
+// is cleared.
+void MarkCompactCollector::RefillMarkingDeque() {
+ DCHECK(marking_deque_.overflowed());
+
+ DiscoverGreyObjectsInNewSpace(heap(), &marking_deque_);
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_,
+ heap()->old_pointer_space());
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_, heap()->old_data_space());
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_, heap()->code_space());
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_, heap()->map_space());
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_, heap()->cell_space());
+ if (marking_deque_.IsFull()) return;
+
+ DiscoverGreyObjectsInSpace(heap(), &marking_deque_,
+ heap()->property_cell_space());
+ if (marking_deque_.IsFull()) return;
+
+ LargeObjectIterator lo_it(heap()->lo_space());
+ DiscoverGreyObjectsWithIterator(heap(), &marking_deque_, &lo_it);
+ if (marking_deque_.IsFull()) return;
+
+ marking_deque_.ClearOverflowed();
+}
+
+
+// Mark all objects reachable (transitively) from objects on the marking
+// stack. Before: the marking stack contains zero or more heap object
+// pointers. After: the marking stack is empty and there are no overflowed
+// objects in the heap.
+void MarkCompactCollector::ProcessMarkingDeque() {
+ EmptyMarkingDeque();
+ while (marking_deque_.overflowed()) {
+ RefillMarkingDeque();
+ EmptyMarkingDeque();
+ }
+}
+
+
+// Mark all objects reachable (transitively) from objects on the marking
+// stack including references only considered in the atomic marking pause.
+void MarkCompactCollector::ProcessEphemeralMarking(ObjectVisitor* visitor) {
+ bool work_to_do = true;
+ DCHECK(marking_deque_.IsEmpty());
+ while (work_to_do) {
+ isolate()->global_handles()->IterateObjectGroups(
+ visitor, &IsUnmarkedHeapObjectWithHeap);
+ MarkImplicitRefGroups();
+ ProcessWeakCollections();
+ work_to_do = !marking_deque_.IsEmpty();
+ ProcessMarkingDeque();
+ }
+}
+
+
+void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
+ for (StackFrameIterator it(isolate(), isolate()->thread_local_top());
+ !it.done(); it.Advance()) {
+ if (it.frame()->type() == StackFrame::JAVA_SCRIPT) {
+ return;
+ }
+ if (it.frame()->type() == StackFrame::OPTIMIZED) {
+ Code* code = it.frame()->LookupCode();
+ if (!code->CanDeoptAt(it.frame()->pc())) {
+ code->CodeIterateBody(visitor);
+ }
+ ProcessMarkingDeque();
+ return;
+ }
+ }
+}
+
+
+void MarkCompactCollector::MarkLiveObjects() {
+ GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_MARK);
+ double start_time = 0.0;
+ if (FLAG_print_cumulative_gc_stat) {
+ start_time = base::OS::TimeCurrentMillis();
+ }
+ // The recursive GC marker detects when it is nearing stack overflow,
+ // and switches to a different marking system. JS interrupts interfere
+ // with the C stack limit check.
+ PostponeInterruptsScope postpone(isolate());
+
+ bool incremental_marking_overflowed = false;
+ IncrementalMarking* incremental_marking = heap_->incremental_marking();
+ if (was_marked_incrementally_) {
+ // Finalize the incremental marking and check whether we had an overflow.
+ // Both markers use grey color to mark overflowed objects so
+ // non-incremental marker can deal with them as if overflow
+ // occured during normal marking.
+ // But incremental marker uses a separate marking deque
+ // so we have to explicitly copy its overflow state.
+ incremental_marking->Finalize();
+ incremental_marking_overflowed =
+ incremental_marking->marking_deque()->overflowed();
+ incremental_marking->marking_deque()->ClearOverflowed();
+ } else {
+ // Abort any pending incremental activities e.g. incremental sweeping.
+ incremental_marking->Abort();
+ }
+
+#ifdef DEBUG
+ DCHECK(state_ == PREPARE_GC);
+ state_ = MARK_LIVE_OBJECTS;
+#endif
+ // The to space contains live objects, a page in from space is used as a
+ // marking stack.
+ Address marking_deque_start = heap()->new_space()->FromSpacePageLow();
+ Address marking_deque_end = heap()->new_space()->FromSpacePageHigh();
+ if (FLAG_force_marking_deque_overflows) {
+ marking_deque_end = marking_deque_start + 64 * kPointerSize;
+ }
+ marking_deque_.Initialize(marking_deque_start, marking_deque_end);
+ DCHECK(!marking_deque_.overflowed());
+
+ if (incremental_marking_overflowed) {
+ // There are overflowed objects left in the heap after incremental marking.
+ marking_deque_.SetOverflowed();
+ }
+
+ PrepareForCodeFlushing();
+
+ if (was_marked_incrementally_) {
+ // There is no write barrier on cells so we have to scan them now at the end
+ // of the incremental marking.
+ {
+ HeapObjectIterator cell_iterator(heap()->cell_space());
+ HeapObject* cell;
+ while ((cell = cell_iterator.Next()) != NULL) {
+ DCHECK(cell->IsCell());
+ if (IsMarked(cell)) {
+ int offset = Cell::kValueOffset;
+ MarkCompactMarkingVisitor::VisitPointer(
+ heap(), reinterpret_cast<Object**>(cell->address() + offset));
+ }
+ }
+ }
+ {
+ HeapObjectIterator js_global_property_cell_iterator(
+ heap()->property_cell_space());
+ HeapObject* cell;
+ while ((cell = js_global_property_cell_iterator.Next()) != NULL) {
+ DCHECK(cell->IsPropertyCell());
+ if (IsMarked(cell)) {
+ MarkCompactMarkingVisitor::VisitPropertyCell(cell->map(), cell);
+ }
+ }
+ }
+ }
+
+ RootMarkingVisitor root_visitor(heap());
+ MarkRoots(&root_visitor);
+
+ ProcessTopOptimizedFrame(&root_visitor);
+
+ // The objects reachable from the roots are marked, yet unreachable
+ // objects are unmarked. Mark objects reachable due to host
+ // application specific logic or through Harmony weak maps.
+ ProcessEphemeralMarking(&root_visitor);
+
+ // The objects reachable from the roots, weak maps or object groups
+ // are marked, yet unreachable objects are unmarked. Mark objects
+ // reachable only from weak global handles.
+ //
+ // First we identify nonlive weak handles and mark them as pending
+ // destruction.
+ heap()->isolate()->global_handles()->IdentifyWeakHandles(
+ &IsUnmarkedHeapObject);
+ // Then we mark the objects and process the transitive closure.
+ heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor);
+ while (marking_deque_.overflowed()) {
+ RefillMarkingDeque();
+ EmptyMarkingDeque();
+ }
+
+ // Repeat host application specific and Harmony weak maps marking to
+ // mark unmarked objects reachable from the weak roots.
+ ProcessEphemeralMarking(&root_visitor);
+
+ AfterMarking();
+
+ if (FLAG_print_cumulative_gc_stat) {
+ heap_->tracer()->AddMarkingTime(base::OS::TimeCurrentMillis() - start_time);
+ }
+}
+
+
+void MarkCompactCollector::AfterMarking() {
+ // Object literal map caches reference strings (cache keys) and maps
+ // (cache values). At this point still useful maps have already been
+ // marked. Mark the keys for the alive values before we process the
+ // string table.
+ ProcessMapCaches();
+
+ // Prune the string table removing all strings only pointed to by the
+ // string table. Cannot use string_table() here because the string
+ // table is marked.
+ StringTable* string_table = heap()->string_table();
+ InternalizedStringTableCleaner internalized_visitor(heap());
+ string_table->IterateElements(&internalized_visitor);
+ string_table->ElementsRemoved(internalized_visitor.PointersRemoved());
+
+ ExternalStringTableCleaner external_visitor(heap());
+ heap()->external_string_table_.Iterate(&external_visitor);
+ heap()->external_string_table_.CleanUp();
+
+ // Process the weak references.
+ MarkCompactWeakObjectRetainer mark_compact_object_retainer;
+ heap()->ProcessWeakReferences(&mark_compact_object_retainer);
+
+ // Remove object groups after marking phase.
+ heap()->isolate()->global_handles()->RemoveObjectGroups();
+ heap()->isolate()->global_handles()->RemoveImplicitRefGroups();
+
+ // Flush code from collected candidates.
+ if (is_code_flushing_enabled()) {
+ code_flusher_->ProcessCandidates();
+ // If incremental marker does not support code flushing, we need to
+ // disable it before incremental marking steps for next cycle.
+ if (FLAG_flush_code && !FLAG_flush_code_incrementally) {
+ EnableCodeFlushing(false);
+ }
+ }
+
+ if (FLAG_track_gc_object_stats) {
+ heap()->CheckpointObjectStats();
+ }
+}
+
+
+void MarkCompactCollector::ProcessMapCaches() {
+ Object* raw_context = heap()->native_contexts_list();
+ while (raw_context != heap()->undefined_value()) {
+ Context* context = reinterpret_cast<Context*>(raw_context);
+ if (IsMarked(context)) {
+ HeapObject* raw_map_cache =
+ HeapObject::cast(context->get(Context::MAP_CACHE_INDEX));
+ // A map cache may be reachable from the stack. In this case
+ // it's already transitively marked and it's too late to clean
+ // up its parts.
+ if (!IsMarked(raw_map_cache) &&
+ raw_map_cache != heap()->undefined_value()) {
+ MapCache* map_cache = reinterpret_cast<MapCache*>(raw_map_cache);
+ int existing_elements = map_cache->NumberOfElements();
+ int used_elements = 0;
+ for (int i = MapCache::kElementsStartIndex; i < map_cache->length();
+ i += MapCache::kEntrySize) {
+ Object* raw_key = map_cache->get(i);
+ if (raw_key == heap()->undefined_value() ||
+ raw_key == heap()->the_hole_value())
+ continue;
+ STATIC_ASSERT(MapCache::kEntrySize == 2);
+ Object* raw_map = map_cache->get(i + 1);
+ if (raw_map->IsHeapObject() && IsMarked(raw_map)) {
+ ++used_elements;
+ } else {
+ // Delete useless entries with unmarked maps.
+ DCHECK(raw_map->IsMap());
+ map_cache->set_the_hole(i);
+ map_cache->set_the_hole(i + 1);
+ }
+ }
+ if (used_elements == 0) {
+ context->set(Context::MAP_CACHE_INDEX, heap()->undefined_value());
+ } else {
+ // Note: we don't actually shrink the cache here to avoid
+ // extra complexity during GC. We rely on subsequent cache
+ // usages (EnsureCapacity) to do this.
+ map_cache->ElementsRemoved(existing_elements - used_elements);
+ MarkBit map_cache_markbit = Marking::MarkBitFrom(map_cache);
+ MarkObject(map_cache, map_cache_markbit);
+ }
+ }
+ }
+ // Move to next element in the list.
+ raw_context = context->get(Context::NEXT_CONTEXT_LINK);
+ }
+ ProcessMarkingDeque();
+}
+
+
+void MarkCompactCollector::ClearNonLiveReferences() {
+ // Iterate over the map space, setting map transitions that go from
+ // a marked map to an unmarked map to null transitions. This action
+ // is carried out only on maps of JSObjects and related subtypes.
+ HeapObjectIterator map_iterator(heap()->map_space());
+ for (HeapObject* obj = map_iterator.Next(); obj != NULL;
+ obj = map_iterator.Next()) {
+ Map* map = Map::cast(obj);
+
+ if (!map->CanTransition()) continue;
+
+ MarkBit map_mark = Marking::MarkBitFrom(map);
+ ClearNonLivePrototypeTransitions(map);
+ ClearNonLiveMapTransitions(map, map_mark);
+
+ if (map_mark.Get()) {
+ ClearNonLiveDependentCode(map->dependent_code());
+ } else {
+ ClearDependentCode(map->dependent_code());
+ map->set_dependent_code(DependentCode::cast(heap()->empty_fixed_array()));
+ }
+ }
+
+ // Iterate over property cell space, removing dependent code that is not
+ // otherwise kept alive by strong references.
+ HeapObjectIterator cell_iterator(heap_->property_cell_space());
+ for (HeapObject* cell = cell_iterator.Next(); cell != NULL;
+ cell = cell_iterator.Next()) {
+ if (IsMarked(cell)) {
+ ClearNonLiveDependentCode(PropertyCell::cast(cell)->dependent_code());
+ }
+ }
+
+ // Iterate over allocation sites, removing dependent code that is not
+ // otherwise kept alive by strong references.
+ Object* undefined = heap()->undefined_value();
+ for (Object* site = heap()->allocation_sites_list(); site != undefined;
+ site = AllocationSite::cast(site)->weak_next()) {
+ if (IsMarked(site)) {
+ ClearNonLiveDependentCode(AllocationSite::cast(site)->dependent_code());
+ }
+ }
+
+ if (heap_->weak_object_to_code_table()->IsHashTable()) {
+ WeakHashTable* table =
+ WeakHashTable::cast(heap_->weak_object_to_code_table());
+ uint32_t capacity = table->Capacity();
+ for (uint32_t i = 0; i < capacity; i++) {
+ uint32_t key_index = table->EntryToIndex(i);
+ Object* key = table->get(key_index);
+ if (!table->IsKey(key)) continue;
+ uint32_t value_index = table->EntryToValueIndex(i);
+ Object* value = table->get(value_index);
+ if (key->IsCell() && !IsMarked(key)) {
+ Cell* cell = Cell::cast(key);
+ Object* object = cell->value();
+ if (IsMarked(object)) {
+ MarkBit mark = Marking::MarkBitFrom(cell);
+ SetMark(cell, mark);
+ Object** value_slot = HeapObject::RawField(cell, Cell::kValueOffset);
+ RecordSlot(value_slot, value_slot, *value_slot);
+ }
+ }
+ if (IsMarked(key)) {
+ if (!IsMarked(value)) {
+ HeapObject* obj = HeapObject::cast(value);
+ MarkBit mark = Marking::MarkBitFrom(obj);
+ SetMark(obj, mark);
+ }
+ ClearNonLiveDependentCode(DependentCode::cast(value));
+ } else {
+ ClearDependentCode(DependentCode::cast(value));
+ table->set(key_index, heap_->the_hole_value());
+ table->set(value_index, heap_->the_hole_value());
+ table->ElementRemoved();
+ }
+ }
+ }
+}
+
+
+void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
+ int number_of_transitions = map->NumberOfProtoTransitions();
+ FixedArray* prototype_transitions = map->GetPrototypeTransitions();
+
+ int new_number_of_transitions = 0;
+ const int header = Map::kProtoTransitionHeaderSize;
+ const int proto_offset = header + Map::kProtoTransitionPrototypeOffset;
+ const int map_offset = header + Map::kProtoTransitionMapOffset;
+ const int step = Map::kProtoTransitionElementsPerEntry;
+ for (int i = 0; i < number_of_transitions; i++) {
+ Object* prototype = prototype_transitions->get(proto_offset + i * step);
+ Object* cached_map = prototype_transitions->get(map_offset + i * step);
+ if (IsMarked(prototype) && IsMarked(cached_map)) {
+ DCHECK(!prototype->IsUndefined());
+ int proto_index = proto_offset + new_number_of_transitions * step;
+ int map_index = map_offset + new_number_of_transitions * step;
+ if (new_number_of_transitions != i) {
+ prototype_transitions->set(proto_index, prototype,
+ UPDATE_WRITE_BARRIER);
+ prototype_transitions->set(map_index, cached_map, SKIP_WRITE_BARRIER);
+ }
+ Object** slot = prototype_transitions->RawFieldOfElementAt(proto_index);
+ RecordSlot(slot, slot, prototype);
+ new_number_of_transitions++;
+ }
+ }
+
+ if (new_number_of_transitions != number_of_transitions) {
+ map->SetNumberOfProtoTransitions(new_number_of_transitions);
+ }
+
+ // Fill slots that became free with undefined value.
+ for (int i = new_number_of_transitions * step;
+ i < number_of_transitions * step; i++) {
+ prototype_transitions->set_undefined(header + i);
+ }
+}
+
+
+void MarkCompactCollector::ClearNonLiveMapTransitions(Map* map,
+ MarkBit map_mark) {
+ Object* potential_parent = map->GetBackPointer();
+ if (!potential_parent->IsMap()) return;
+ Map* parent = Map::cast(potential_parent);
+
+ // Follow back pointer, check whether we are dealing with a map transition
+ // from a live map to a dead path and in case clear transitions of parent.
+ bool current_is_alive = map_mark.Get();
+ bool parent_is_alive = Marking::MarkBitFrom(parent).Get();
+ if (!current_is_alive && parent_is_alive) {
+ ClearMapTransitions(parent);
+ }
+}
+
+
+// Clear a possible back pointer in case the transition leads to a dead map.
+// Return true in case a back pointer has been cleared and false otherwise.
+bool MarkCompactCollector::ClearMapBackPointer(Map* target) {
+ if (Marking::MarkBitFrom(target).Get()) return false;
+ target->SetBackPointer(heap_->undefined_value(), SKIP_WRITE_BARRIER);
+ return true;
+}
+
+
+void MarkCompactCollector::ClearMapTransitions(Map* map) {
+ // If there are no transitions to be cleared, return.
+ // TODO(verwaest) Should be an assert, otherwise back pointers are not
+ // properly cleared.
+ if (!map->HasTransitionArray()) return;
+
+ TransitionArray* t = map->transitions();
+
+ int transition_index = 0;
+
+ DescriptorArray* descriptors = map->instance_descriptors();
+ bool descriptors_owner_died = false;
+
+ // Compact all live descriptors to the left.
+ for (int i = 0; i < t->number_of_transitions(); ++i) {
+ Map* target = t->GetTarget(i);
+ if (ClearMapBackPointer(target)) {
+ if (target->instance_descriptors() == descriptors) {
+ descriptors_owner_died = true;
+ }
+ } else {
+ if (i != transition_index) {
+ Name* key = t->GetKey(i);
+ t->SetKey(transition_index, key);
+ Object** key_slot = t->GetKeySlot(transition_index);
+ RecordSlot(key_slot, key_slot, key);
+ // Target slots do not need to be recorded since maps are not compacted.
+ t->SetTarget(transition_index, t->GetTarget(i));
+ }
+ transition_index++;
+ }
+ }
+
+ // If there are no transitions to be cleared, return.
+ // TODO(verwaest) Should be an assert, otherwise back pointers are not
+ // properly cleared.
+ if (transition_index == t->number_of_transitions()) return;
+
+ int number_of_own_descriptors = map->NumberOfOwnDescriptors();
+
+ if (descriptors_owner_died) {
+ if (number_of_own_descriptors > 0) {
+ TrimDescriptorArray(map, descriptors, number_of_own_descriptors);
+ DCHECK(descriptors->number_of_descriptors() == number_of_own_descriptors);
+ map->set_owns_descriptors(true);
+ } else {
+ DCHECK(descriptors == heap_->empty_descriptor_array());
+ }
+ }
+
+ // Note that we never eliminate a transition array, though we might right-trim
+ // such that number_of_transitions() == 0. If this assumption changes,
+ // TransitionArray::CopyInsert() will need to deal with the case that a
+ // transition array disappeared during GC.
+ int trim = t->number_of_transitions() - transition_index;
+ if (trim > 0) {
+ heap_->RightTrimFixedArray<Heap::FROM_GC>(
+ t, t->IsSimpleTransition() ? trim
+ : trim * TransitionArray::kTransitionSize);
+ }
+ DCHECK(map->HasTransitionArray());
+}
+
+
+void MarkCompactCollector::TrimDescriptorArray(Map* map,
+ DescriptorArray* descriptors,
+ int number_of_own_descriptors) {
+ int number_of_descriptors = descriptors->number_of_descriptors_storage();
+ int to_trim = number_of_descriptors - number_of_own_descriptors;
+ if (to_trim == 0) return;
+
+ heap_->RightTrimFixedArray<Heap::FROM_GC>(
+ descriptors, to_trim * DescriptorArray::kDescriptorSize);
+ descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
+
+ if (descriptors->HasEnumCache()) TrimEnumCache(map, descriptors);
+ descriptors->Sort();
+}
+
+
+void MarkCompactCollector::TrimEnumCache(Map* map,
+ DescriptorArray* descriptors) {
+ int live_enum = map->EnumLength();
+ if (live_enum == kInvalidEnumCacheSentinel) {
+ live_enum = map->NumberOfDescribedProperties(OWN_DESCRIPTORS, DONT_ENUM);
+ }
+ if (live_enum == 0) return descriptors->ClearEnumCache();
+
+ FixedArray* enum_cache = descriptors->GetEnumCache();
+
+ int to_trim = enum_cache->length() - live_enum;
+ if (to_trim <= 0) return;
+ heap_->RightTrimFixedArray<Heap::FROM_GC>(descriptors->GetEnumCache(),
+ to_trim);
+
+ if (!descriptors->HasEnumIndicesCache()) return;
+ FixedArray* enum_indices_cache = descriptors->GetEnumIndicesCache();
+ heap_->RightTrimFixedArray<Heap::FROM_GC>(enum_indices_cache, to_trim);
+}
+
+
+void MarkCompactCollector::ClearDependentICList(Object* head) {
+ Object* current = head;
+ Object* undefined = heap()->undefined_value();
+ while (current != undefined) {
+ Code* code = Code::cast(current);
+ if (IsMarked(code)) {
+ DCHECK(code->is_weak_stub());
+ IC::InvalidateMaps(code);
+ }
+ current = code->next_code_link();
+ code->set_next_code_link(undefined);
+ }
+}
+
+
+void MarkCompactCollector::ClearDependentCode(DependentCode* entries) {
+ DisallowHeapAllocation no_allocation;
+ DependentCode::GroupStartIndexes starts(entries);
+ int number_of_entries = starts.number_of_entries();
+ if (number_of_entries == 0) return;
+ int g = DependentCode::kWeakICGroup;
+ if (starts.at(g) != starts.at(g + 1)) {
+ int i = starts.at(g);
+ DCHECK(i + 1 == starts.at(g + 1));
+ Object* head = entries->object_at(i);
+ ClearDependentICList(head);
+ }
+ g = DependentCode::kWeakCodeGroup;
+ for (int i = starts.at(g); i < starts.at(g + 1); i++) {
+ // If the entry is compilation info then the map must be alive,
+ // and ClearDependentCode shouldn't be called.
+ DCHECK(entries->is_code_at(i));
+ Code* code = entries->code_at(i);
+ if (IsMarked(code) && !code->marked_for_deoptimization()) {
+ DependentCode::SetMarkedForDeoptimization(
+ code, static_cast<DependentCode::DependencyGroup>(g));
+ code->InvalidateEmbeddedObjects();
+ have_code_to_deoptimize_ = true;
+ }
+ }
+ for (int i = 0; i < number_of_entries; i++) {
+ entries->clear_at(i);
+ }
+}
+
+
+int MarkCompactCollector::ClearNonLiveDependentCodeInGroup(
+ DependentCode* entries, int group, int start, int end, int new_start) {
+ int survived = 0;
+ if (group == DependentCode::kWeakICGroup) {
+ // Dependent weak IC stubs form a linked list and only the head is stored
+ // in the dependent code array.
+ if (start != end) {
+ DCHECK(start + 1 == end);
+ Object* old_head = entries->object_at(start);
+ MarkCompactWeakObjectRetainer retainer;
+ Object* head = VisitWeakList<Code>(heap(), old_head, &retainer);
+ entries->set_object_at(new_start, head);
+ Object** slot = entries->slot_at(new_start);
+ RecordSlot(slot, slot, head);
+ // We do not compact this group even if the head is undefined,
+ // more dependent ICs are likely to be added later.
+ survived = 1;
+ }
+ } else {
+ for (int i = start; i < end; i++) {
+ Object* obj = entries->object_at(i);
+ DCHECK(obj->IsCode() || IsMarked(obj));
+ if (IsMarked(obj) &&
+ (!obj->IsCode() || !WillBeDeoptimized(Code::cast(obj)))) {
+ if (new_start + survived != i) {
+ entries->set_object_at(new_start + survived, obj);
+ }
+ Object** slot = entries->slot_at(new_start + survived);
+ RecordSlot(slot, slot, obj);
+ survived++;
+ }
+ }
+ }
+ entries->set_number_of_entries(
+ static_cast<DependentCode::DependencyGroup>(group), survived);
+ return survived;
+}
+
+
+void MarkCompactCollector::ClearNonLiveDependentCode(DependentCode* entries) {
+ DisallowHeapAllocation no_allocation;
+ DependentCode::GroupStartIndexes starts(entries);
+ int number_of_entries = starts.number_of_entries();
+ if (number_of_entries == 0) return;
+ int new_number_of_entries = 0;
+ // Go through all groups, remove dead codes and compact.
+ for (int g = 0; g < DependentCode::kGroupCount; g++) {
+ int survived = ClearNonLiveDependentCodeInGroup(
+ entries, g, starts.at(g), starts.at(g + 1), new_number_of_entries);
+ new_number_of_entries += survived;
+ }
+ for (int i = new_number_of_entries; i < number_of_entries; i++) {
+ entries->clear_at(i);
+ }
+}
+
+
+void MarkCompactCollector::ProcessWeakCollections() {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_WEAKCOLLECTION_PROCESS);
+ Object* weak_collection_obj = heap()->encountered_weak_collections();
+ while (weak_collection_obj != Smi::FromInt(0)) {
+ JSWeakCollection* weak_collection =
+ reinterpret_cast<JSWeakCollection*>(weak_collection_obj);
+ DCHECK(MarkCompactCollector::IsMarked(weak_collection));
+ if (weak_collection->table()->IsHashTable()) {
+ ObjectHashTable* table = ObjectHashTable::cast(weak_collection->table());
+ Object** anchor = reinterpret_cast<Object**>(table->address());
+ for (int i = 0; i < table->Capacity(); i++) {
+ if (MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) {
+ Object** key_slot =
+ table->RawFieldOfElementAt(ObjectHashTable::EntryToIndex(i));
+ RecordSlot(anchor, key_slot, *key_slot);
+ Object** value_slot =
+ table->RawFieldOfElementAt(ObjectHashTable::EntryToValueIndex(i));
+ MarkCompactMarkingVisitor::MarkObjectByPointer(this, anchor,
+ value_slot);
+ }
+ }
+ }
+ weak_collection_obj = weak_collection->next();
+ }
+}
+
+
+void MarkCompactCollector::ClearWeakCollections() {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_WEAKCOLLECTION_CLEAR);
+ Object* weak_collection_obj = heap()->encountered_weak_collections();
+ while (weak_collection_obj != Smi::FromInt(0)) {
+ JSWeakCollection* weak_collection =
+ reinterpret_cast<JSWeakCollection*>(weak_collection_obj);
+ DCHECK(MarkCompactCollector::IsMarked(weak_collection));
+ if (weak_collection->table()->IsHashTable()) {
+ ObjectHashTable* table = ObjectHashTable::cast(weak_collection->table());
+ for (int i = 0; i < table->Capacity(); i++) {
+ HeapObject* key = HeapObject::cast(table->KeyAt(i));
+ if (!MarkCompactCollector::IsMarked(key)) {
+ table->RemoveEntry(i);
+ }
+ }
+ }
+ weak_collection_obj = weak_collection->next();
+ weak_collection->set_next(heap()->undefined_value());
+ }
+ heap()->set_encountered_weak_collections(Smi::FromInt(0));
+}
+
+
+void MarkCompactCollector::AbortWeakCollections() {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_WEAKCOLLECTION_ABORT);
+ Object* weak_collection_obj = heap()->encountered_weak_collections();
+ while (weak_collection_obj != Smi::FromInt(0)) {
+ JSWeakCollection* weak_collection =
+ reinterpret_cast<JSWeakCollection*>(weak_collection_obj);
+ weak_collection_obj = weak_collection->next();
+ weak_collection->set_next(heap()->undefined_value());
+ }
+ heap()->set_encountered_weak_collections(Smi::FromInt(0));
+}
+
+
+void MarkCompactCollector::RecordMigratedSlot(Object* value, Address slot) {
+ if (heap_->InNewSpace(value)) {
+ heap_->store_buffer()->Mark(slot);
+ } else if (value->IsHeapObject() && IsOnEvacuationCandidate(value)) {
+ SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
+ reinterpret_cast<Object**>(slot),
+ SlotsBuffer::IGNORE_OVERFLOW);
+ }
+}
+
+
+// We scavange new space simultaneously with sweeping. This is done in two
+// passes.
+//
+// The first pass migrates all alive objects from one semispace to another or
+// promotes them to old space. Forwarding address is written directly into
+// first word of object without any encoding. If object is dead we write
+// NULL as a forwarding address.
+//
+// The second pass updates pointers to new space in all spaces. It is possible
+// to encounter pointers to dead new space objects during traversal of pointers
+// to new space. We should clear them to avoid encountering them during next
+// pointer iteration. This is an issue if the store buffer overflows and we
+// have to scan the entire old space, including dead objects, looking for
+// pointers to new space.
+void MarkCompactCollector::MigrateObject(HeapObject* dst, HeapObject* src,
+ int size, AllocationSpace dest) {
+ Address dst_addr = dst->address();
+ Address src_addr = src->address();
+ DCHECK(heap()->AllowedToBeMigrated(src, dest));
+ DCHECK(dest != LO_SPACE && size <= Page::kMaxRegularHeapObjectSize);
+ if (dest == OLD_POINTER_SPACE) {
+ Address src_slot = src_addr;
+ Address dst_slot = dst_addr;
+ DCHECK(IsAligned(size, kPointerSize));
+
+ for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
+ Object* value = Memory::Object_at(src_slot);
+
+ Memory::Object_at(dst_slot) = value;
+
+ if (!src->MayContainRawValues()) {
+ RecordMigratedSlot(value, dst_slot);
+ }
+
+ src_slot += kPointerSize;
+ dst_slot += kPointerSize;
+ }
+
+ if (compacting_ && dst->IsJSFunction()) {
+ Address code_entry_slot = dst_addr + JSFunction::kCodeEntryOffset;
+ Address code_entry = Memory::Address_at(code_entry_slot);
+
+ if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) {
+ SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
+ SlotsBuffer::CODE_ENTRY_SLOT, code_entry_slot,
+ SlotsBuffer::IGNORE_OVERFLOW);
+ }
+ } else if (dst->IsConstantPoolArray()) {
+ // We special case ConstantPoolArrays since they could contain integers
+ // value entries which look like tagged pointers.
+ // TODO(mstarzinger): restructure this code to avoid this special-casing.
+ ConstantPoolArray* array = ConstantPoolArray::cast(dst);
+ ConstantPoolArray::Iterator code_iter(array, ConstantPoolArray::CODE_PTR);
+ while (!code_iter.is_finished()) {
+ Address code_entry_slot =
+ dst_addr + array->OffsetOfElementAt(code_iter.next_index());
+ Address code_entry = Memory::Address_at(code_entry_slot);
+
+ if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) {
+ SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
+ SlotsBuffer::CODE_ENTRY_SLOT, code_entry_slot,
+ SlotsBuffer::IGNORE_OVERFLOW);
+ }
+ }
+ ConstantPoolArray::Iterator heap_iter(array, ConstantPoolArray::HEAP_PTR);
+ while (!heap_iter.is_finished()) {
+ Address heap_slot =
+ dst_addr + array->OffsetOfElementAt(heap_iter.next_index());
+ Object* value = Memory::Object_at(heap_slot);
+ RecordMigratedSlot(value, heap_slot);
+ }
+ }
+ } else if (dest == CODE_SPACE) {
+ PROFILE(isolate(), CodeMoveEvent(src_addr, dst_addr));
+ heap()->MoveBlock(dst_addr, src_addr, size);
+ SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
+ SlotsBuffer::RELOCATED_CODE_OBJECT, dst_addr,
+ SlotsBuffer::IGNORE_OVERFLOW);
+ Code::cast(dst)->Relocate(dst_addr - src_addr);
+ } else {
+ DCHECK(dest == OLD_DATA_SPACE || dest == NEW_SPACE);
+ heap()->MoveBlock(dst_addr, src_addr, size);
+ }
+ heap()->OnMoveEvent(dst, src, size);
+ Memory::Address_at(src_addr) = dst_addr;
+}
+
+
+// Visitor for updating pointers from live objects in old spaces to new space.
+// It does not expect to encounter pointers to dead objects.
+class PointersUpdatingVisitor : public ObjectVisitor {
+ public:
+ explicit PointersUpdatingVisitor(Heap* heap) : heap_(heap) {}
+
+ void VisitPointer(Object** p) { UpdatePointer(p); }
+
+ void VisitPointers(Object** start, Object** end) {
+ for (Object** p = start; p < end; p++) UpdatePointer(p);
+ }
+
+ void VisitEmbeddedPointer(RelocInfo* rinfo) {
+ DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
+ Object* target = rinfo->target_object();
+ Object* old_target = target;
+ VisitPointer(&target);
+ // Avoid unnecessary changes that might unnecessary flush the instruction
+ // cache.
+ if (target != old_target) {
+ rinfo->set_target_object(target);
+ }
+ }
+
+ void VisitCodeTarget(RelocInfo* rinfo) {
+ DCHECK(RelocInfo::IsCodeTarget(rinfo->rmode()));
+ Object* target = Code::GetCodeFromTargetAddress(rinfo->target_address());
+ Object* old_target = target;
+ VisitPointer(&target);
+ if (target != old_target) {
+ rinfo->set_target_address(Code::cast(target)->instruction_start());
+ }
+ }
+
+ void VisitCodeAgeSequence(RelocInfo* rinfo) {
+ DCHECK(RelocInfo::IsCodeAgeSequence(rinfo->rmode()));
+ Object* stub = rinfo->code_age_stub();
+ DCHECK(stub != NULL);
+ VisitPointer(&stub);
+ if (stub != rinfo->code_age_stub()) {
+ rinfo->set_code_age_stub(Code::cast(stub));
+ }
+ }
+
+ void VisitDebugTarget(RelocInfo* rinfo) {
+ DCHECK((RelocInfo::IsJSReturn(rinfo->rmode()) &&
+ rinfo->IsPatchedReturnSequence()) ||
+ (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) &&
+ rinfo->IsPatchedDebugBreakSlotSequence()));
+ Object* target = Code::GetCodeFromTargetAddress(rinfo->call_address());
+ VisitPointer(&target);
+ rinfo->set_call_address(Code::cast(target)->instruction_start());
+ }
+
+ static inline void UpdateSlot(Heap* heap, Object** slot) {
+ Object* obj = *slot;
+
+ if (!obj->IsHeapObject()) return;
+
+ HeapObject* heap_obj = HeapObject::cast(obj);
+
+ MapWord map_word = heap_obj->map_word();
+ if (map_word.IsForwardingAddress()) {
+ DCHECK(heap->InFromSpace(heap_obj) ||
+ MarkCompactCollector::IsOnEvacuationCandidate(heap_obj));
+ HeapObject* target = map_word.ToForwardingAddress();
+ *slot = target;
+ DCHECK(!heap->InFromSpace(target) &&
+ !MarkCompactCollector::IsOnEvacuationCandidate(target));
+ }
+ }
+
+ private:
+ inline void UpdatePointer(Object** p) { UpdateSlot(heap_, p); }
+
+ Heap* heap_;
+};
+
+
+static void UpdatePointer(HeapObject** address, HeapObject* object) {
+ Address new_addr = Memory::Address_at(object->address());
+
+ // The new space sweep will overwrite the map word of dead objects
+ // with NULL. In this case we do not need to transfer this entry to
+ // the store buffer which we are rebuilding.
+ // We perform the pointer update with a no barrier compare-and-swap. The
+ // compare and swap may fail in the case where the pointer update tries to
+ // update garbage memory which was concurrently accessed by the sweeper.
+ if (new_addr != NULL) {
+ base::NoBarrier_CompareAndSwap(
+ reinterpret_cast<base::AtomicWord*>(address),
+ reinterpret_cast<base::AtomicWord>(object),
+ reinterpret_cast<base::AtomicWord>(HeapObject::FromAddress(new_addr)));
+ }
+}
+
+
+static String* UpdateReferenceInExternalStringTableEntry(Heap* heap,
+ Object** p) {
+ MapWord map_word = HeapObject::cast(*p)->map_word();
+
+ if (map_word.IsForwardingAddress()) {
+ return String::cast(map_word.ToForwardingAddress());
+ }
+
+ return String::cast(*p);
+}
+
+
+bool MarkCompactCollector::TryPromoteObject(HeapObject* object,
+ int object_size) {
+ DCHECK(object_size <= Page::kMaxRegularHeapObjectSize);
+
+ OldSpace* target_space = heap()->TargetSpace(object);
+
+ DCHECK(target_space == heap()->old_pointer_space() ||
+ target_space == heap()->old_data_space());
+ HeapObject* target;
+ AllocationResult allocation = target_space->AllocateRaw(object_size);
+ if (allocation.To(&target)) {
+ MigrateObject(target, object, object_size, target_space->identity());
+ heap()->IncrementPromotedObjectsSize(object_size);
+ return true;
+ }
+
+ return false;
+}
+
+
+void MarkCompactCollector::EvacuateNewSpace() {
+ // There are soft limits in the allocation code, designed trigger a mark
+ // sweep collection by failing allocations. But since we are already in
+ // a mark-sweep allocation, there is no sense in trying to trigger one.
+ AlwaysAllocateScope scope(isolate());
+
+ NewSpace* new_space = heap()->new_space();
+
+ // Store allocation range before flipping semispaces.
+ Address from_bottom = new_space->bottom();
+ Address from_top = new_space->top();
+
+ // Flip the semispaces. After flipping, to space is empty, from space has
+ // live objects.
+ new_space->Flip();
+ new_space->ResetAllocationInfo();
+
+ int survivors_size = 0;
+
+ // First pass: traverse all objects in inactive semispace, remove marks,
+ // migrate live objects and write forwarding addresses. This stage puts
+ // new entries in the store buffer and may cause some pages to be marked
+ // scan-on-scavenge.
+ NewSpacePageIterator it(from_bottom, from_top);
+ while (it.has_next()) {
+ NewSpacePage* p = it.next();
+ survivors_size += DiscoverAndEvacuateBlackObjectsOnPage(new_space, p);
+ }
+
+ heap_->IncrementYoungSurvivorsCounter(survivors_size);
+ new_space->set_age_mark(new_space->top());
+}
+
+
+void MarkCompactCollector::EvacuateLiveObjectsFromPage(Page* p) {
+ AlwaysAllocateScope always_allocate(isolate());
+ PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+ DCHECK(p->IsEvacuationCandidate() && !p->WasSwept());
+ p->SetWasSwept();
+
+ int offsets[16];
+
+ for (MarkBitCellIterator it(p); !it.Done(); it.Advance()) {
+ Address cell_base = it.CurrentCellBase();
+ MarkBit::CellType* cell = it.CurrentCell();
+
+ if (*cell == 0) continue;
+
+ int live_objects = MarkWordToObjectStarts(*cell, offsets);
+ for (int i = 0; i < live_objects; i++) {
+ Address object_addr = cell_base + offsets[i] * kPointerSize;
+ HeapObject* object = HeapObject::FromAddress(object_addr);
+ DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
+
+ int size = object->Size();
+
+ HeapObject* target_object;
+ AllocationResult allocation = space->AllocateRaw(size);
+ if (!allocation.To(&target_object)) {
+ // If allocation failed, use emergency memory and re-try allocation.
+ CHECK(space->HasEmergencyMemory());
+ space->UseEmergencyMemory();
+ allocation = space->AllocateRaw(size);
+ }
+ if (!allocation.To(&target_object)) {
+ // OS refused to give us memory.
+ V8::FatalProcessOutOfMemory("Evacuation");
+ return;
+ }
+
+ MigrateObject(target_object, object, size, space->identity());
+ DCHECK(object->map_word().IsForwardingAddress());
+ }
+
+ // Clear marking bits for current cell.
+ *cell = 0;
+ }
+ p->ResetLiveBytes();
+}
+
+
+void MarkCompactCollector::EvacuatePages() {
+ int npages = evacuation_candidates_.length();
+ for (int i = 0; i < npages; i++) {
+ Page* p = evacuation_candidates_[i];
+ DCHECK(p->IsEvacuationCandidate() ||
+ p->IsFlagSet(Page::RESCAN_ON_EVACUATION));
+ DCHECK(static_cast<int>(p->parallel_sweeping()) ==
+ MemoryChunk::SWEEPING_DONE);
+ PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+ // Allocate emergency memory for the case when compaction fails due to out
+ // of memory.
+ if (!space->HasEmergencyMemory()) {
+ space->CreateEmergencyMemory();
+ }
+ if (p->IsEvacuationCandidate()) {
+ // During compaction we might have to request a new page. Check that we
+ // have an emergency page and the space still has room for that.
+ if (space->HasEmergencyMemory() && space->CanExpand()) {
+ EvacuateLiveObjectsFromPage(p);
+ } else {
+ // Without room for expansion evacuation is not guaranteed to succeed.
+ // Pessimistically abandon unevacuated pages.
+ for (int j = i; j < npages; j++) {
+ Page* page = evacuation_candidates_[j];
+ slots_buffer_allocator_.DeallocateChain(page->slots_buffer_address());
+ page->ClearEvacuationCandidate();
+ page->SetFlag(Page::RESCAN_ON_EVACUATION);
+ }
+ break;
+ }
+ }
+ }
+ if (npages > 0) {
+ // Release emergency memory.
+ PagedSpaces spaces(heap());
+ for (PagedSpace* space = spaces.next(); space != NULL;
+ space = spaces.next()) {
+ if (space->HasEmergencyMemory()) {
+ space->FreeEmergencyMemory();
+ }
+ }
+ }
+}
+
+
+class EvacuationWeakObjectRetainer : public WeakObjectRetainer {
+ public:
+ virtual Object* RetainAs(Object* object) {
+ if (object->IsHeapObject()) {
+ HeapObject* heap_object = HeapObject::cast(object);
+ MapWord map_word = heap_object->map_word();
+ if (map_word.IsForwardingAddress()) {
+ return map_word.ToForwardingAddress();
+ }
+ }
+ return object;
+ }
+};
+
+
+static inline void UpdateSlot(Isolate* isolate, ObjectVisitor* v,
+ SlotsBuffer::SlotType slot_type, Address addr) {
+ switch (slot_type) {
+ case SlotsBuffer::CODE_TARGET_SLOT: {
+ RelocInfo rinfo(addr, RelocInfo::CODE_TARGET, 0, NULL);
+ rinfo.Visit(isolate, v);
+ break;
+ }
+ case SlotsBuffer::CODE_ENTRY_SLOT: {
+ v->VisitCodeEntry(addr);
+ break;
+ }
+ case SlotsBuffer::RELOCATED_CODE_OBJECT: {
+ HeapObject* obj = HeapObject::FromAddress(addr);
+ Code::cast(obj)->CodeIterateBody(v);
+ break;
+ }
+ case SlotsBuffer::DEBUG_TARGET_SLOT: {
+ RelocInfo rinfo(addr, RelocInfo::DEBUG_BREAK_SLOT, 0, NULL);
+ if (rinfo.IsPatchedDebugBreakSlotSequence()) rinfo.Visit(isolate, v);
+ break;
+ }
+ case SlotsBuffer::JS_RETURN_SLOT: {
+ RelocInfo rinfo(addr, RelocInfo::JS_RETURN, 0, NULL);
+ if (rinfo.IsPatchedReturnSequence()) rinfo.Visit(isolate, v);
+ break;
+ }
+ case SlotsBuffer::EMBEDDED_OBJECT_SLOT: {
+ RelocInfo rinfo(addr, RelocInfo::EMBEDDED_OBJECT, 0, NULL);
+ rinfo.Visit(isolate, v);
+ break;
+ }
+ default:
+ UNREACHABLE();
+ break;
+ }
+}
+
+
+enum SweepingMode { SWEEP_ONLY, SWEEP_AND_VISIT_LIVE_OBJECTS };
+
+
+enum SkipListRebuildingMode { REBUILD_SKIP_LIST, IGNORE_SKIP_LIST };
+
+
+enum FreeSpaceTreatmentMode { IGNORE_FREE_SPACE, ZAP_FREE_SPACE };
+
+
+template <MarkCompactCollector::SweepingParallelism mode>
+static intptr_t Free(PagedSpace* space, FreeList* free_list, Address start,
+ int size) {
+ if (mode == MarkCompactCollector::SWEEP_ON_MAIN_THREAD) {
+ DCHECK(free_list == NULL);
+ return space->Free(start, size);
+ } else {
+ // TODO(hpayer): account for wasted bytes in concurrent sweeping too.
+ return size - free_list->Free(start, size);
+ }
+}
+
+
+// Sweeps a page. After sweeping the page can be iterated.
+// Slots in live objects pointing into evacuation candidates are updated
+// if requested.
+// Returns the size of the biggest continuous freed memory chunk in bytes.
+template <SweepingMode sweeping_mode,
+ MarkCompactCollector::SweepingParallelism parallelism,
+ SkipListRebuildingMode skip_list_mode,
+ FreeSpaceTreatmentMode free_space_mode>
+static int Sweep(PagedSpace* space, FreeList* free_list, Page* p,
+ ObjectVisitor* v) {
+ DCHECK(!p->IsEvacuationCandidate() && !p->WasSwept());
+ DCHECK_EQ(skip_list_mode == REBUILD_SKIP_LIST,
+ space->identity() == CODE_SPACE);
+ DCHECK((p->skip_list() == NULL) || (skip_list_mode == REBUILD_SKIP_LIST));
+ DCHECK(parallelism == MarkCompactCollector::SWEEP_ON_MAIN_THREAD ||
+ sweeping_mode == SWEEP_ONLY);
+
+ Address free_start = p->area_start();
+ DCHECK(reinterpret_cast<intptr_t>(free_start) % (32 * kPointerSize) == 0);
+ int offsets[16];
+
+ SkipList* skip_list = p->skip_list();
+ int curr_region = -1;
+ if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list) {
+ skip_list->Clear();
+ }
+
+ intptr_t freed_bytes = 0;
+ intptr_t max_freed_bytes = 0;
+
+ for (MarkBitCellIterator it(p); !it.Done(); it.Advance()) {
+ Address cell_base = it.CurrentCellBase();
+ MarkBit::CellType* cell = it.CurrentCell();
+ int live_objects = MarkWordToObjectStarts(*cell, offsets);
+ int live_index = 0;
+ for (; live_objects != 0; live_objects--) {
+ Address free_end = cell_base + offsets[live_index++] * kPointerSize;
+ if (free_end != free_start) {
+ int size = static_cast<int>(free_end - free_start);
+ if (free_space_mode == ZAP_FREE_SPACE) {
+ memset(free_start, 0xcc, size);
+ }
+ freed_bytes = Free<parallelism>(space, free_list, free_start, size);
+ max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+#ifdef ENABLE_GDB_JIT_INTERFACE
+ if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
+ GDBJITInterface::RemoveCodeRange(free_start, free_end);
+ }
+#endif
+ }
+ HeapObject* live_object = HeapObject::FromAddress(free_end);
+ DCHECK(Marking::IsBlack(Marking::MarkBitFrom(live_object)));
+ Map* map = live_object->map();
+ int size = live_object->SizeFromMap(map);
+ if (sweeping_mode == SWEEP_AND_VISIT_LIVE_OBJECTS) {
+ live_object->IterateBody(map->instance_type(), size, v);
+ }
+ if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list != NULL) {
+ int new_region_start = SkipList::RegionNumber(free_end);
+ int new_region_end =
+ SkipList::RegionNumber(free_end + size - kPointerSize);
+ if (new_region_start != curr_region || new_region_end != curr_region) {
+ skip_list->AddObject(free_end, size);
+ curr_region = new_region_end;
+ }
+ }
+ free_start = free_end + size;
+ }
+ // Clear marking bits for current cell.
+ *cell = 0;
+ }
+ if (free_start != p->area_end()) {
+ int size = static_cast<int>(p->area_end() - free_start);
+ if (free_space_mode == ZAP_FREE_SPACE) {
+ memset(free_start, 0xcc, size);
+ }
+ freed_bytes = Free<parallelism>(space, free_list, free_start, size);
+ max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+#ifdef ENABLE_GDB_JIT_INTERFACE
+ if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
+ GDBJITInterface::RemoveCodeRange(free_start, p->area_end());
+ }
+#endif
+ }
+ p->ResetLiveBytes();
+
+ if (parallelism == MarkCompactCollector::SWEEP_IN_PARALLEL) {
+ // When concurrent sweeping is active, the page will be marked after
+ // sweeping by the main thread.
+ p->set_parallel_sweeping(MemoryChunk::SWEEPING_FINALIZE);
+ } else {
+ p->SetWasSwept();
+ }
+ return FreeList::GuaranteedAllocatable(static_cast<int>(max_freed_bytes));
+}
+
+
+static bool SetMarkBitsUnderInvalidatedCode(Code* code, bool value) {
+ Page* p = Page::FromAddress(code->address());
+
+ if (p->IsEvacuationCandidate() || p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
+ return false;
+ }
+
+ Address code_start = code->address();
+ Address code_end = code_start + code->Size();
+
+ uint32_t start_index = MemoryChunk::FastAddressToMarkbitIndex(code_start);
+ uint32_t end_index =
+ MemoryChunk::FastAddressToMarkbitIndex(code_end - kPointerSize);
+
+ Bitmap* b = p->markbits();
+
+ MarkBit start_mark_bit = b->MarkBitFromIndex(start_index);
+ MarkBit end_mark_bit = b->MarkBitFromIndex(end_index);
+
+ MarkBit::CellType* start_cell = start_mark_bit.cell();
+ MarkBit::CellType* end_cell = end_mark_bit.cell();
+
+ if (value) {
+ MarkBit::CellType start_mask = ~(start_mark_bit.mask() - 1);
+ MarkBit::CellType end_mask = (end_mark_bit.mask() << 1) - 1;
+
+ if (start_cell == end_cell) {
+ *start_cell |= start_mask & end_mask;
+ } else {
+ *start_cell |= start_mask;
+ for (MarkBit::CellType* cell = start_cell + 1; cell < end_cell; cell++) {
+ *cell = ~0;
+ }
+ *end_cell |= end_mask;
+ }
+ } else {
+ for (MarkBit::CellType* cell = start_cell; cell <= end_cell; cell++) {
+ *cell = 0;
+ }
+ }
+
+ return true;
+}
+
+
+static bool IsOnInvalidatedCodeObject(Address addr) {
+ // We did not record any slots in large objects thus
+ // we can safely go to the page from the slot address.
+ Page* p = Page::FromAddress(addr);
+
+ // First check owner's identity because old pointer and old data spaces
+ // are swept lazily and might still have non-zero mark-bits on some
+ // pages.
+ if (p->owner()->identity() != CODE_SPACE) return false;
+
+ // In code space only bits on evacuation candidates (but we don't record
+ // any slots on them) and under invalidated code objects are non-zero.
+ MarkBit mark_bit =
+ p->markbits()->MarkBitFromIndex(Page::FastAddressToMarkbitIndex(addr));
+
+ return mark_bit.Get();
+}
+
+
+void MarkCompactCollector::InvalidateCode(Code* code) {
+ if (heap_->incremental_marking()->IsCompacting() &&
+ !ShouldSkipEvacuationSlotRecording(code)) {
+ DCHECK(compacting_);
+
+ // If the object is white than no slots were recorded on it yet.
+ MarkBit mark_bit = Marking::MarkBitFrom(code);
+ if (Marking::IsWhite(mark_bit)) return;
+
+ invalidated_code_.Add(code);
+ }
+}
+
+
+// Return true if the given code is deoptimized or will be deoptimized.
+bool MarkCompactCollector::WillBeDeoptimized(Code* code) {
+ return code->is_optimized_code() && code->marked_for_deoptimization();
+}
+
+
+bool MarkCompactCollector::MarkInvalidatedCode() {
+ bool code_marked = false;
+
+ int length = invalidated_code_.length();
+ for (int i = 0; i < length; i++) {
+ Code* code = invalidated_code_[i];
+
+ if (SetMarkBitsUnderInvalidatedCode(code, true)) {
+ code_marked = true;
+ }
+ }
+
+ return code_marked;
+}
+
+
+void MarkCompactCollector::RemoveDeadInvalidatedCode() {
+ int length = invalidated_code_.length();
+ for (int i = 0; i < length; i++) {
+ if (!IsMarked(invalidated_code_[i])) invalidated_code_[i] = NULL;
+ }
+}
+
+
+void MarkCompactCollector::ProcessInvalidatedCode(ObjectVisitor* visitor) {
+ int length = invalidated_code_.length();
+ for (int i = 0; i < length; i++) {
+ Code* code = invalidated_code_[i];
+ if (code != NULL) {
+ code->Iterate(visitor);
+ SetMarkBitsUnderInvalidatedCode(code, false);
+ }
+ }
+ invalidated_code_.Rewind(0);
+}
+
+
+void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
+ Heap::RelocationLock relocation_lock(heap());
+
+ bool code_slots_filtering_required;
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_SWEEP_NEWSPACE);
+ code_slots_filtering_required = MarkInvalidatedCode();
+ EvacuateNewSpace();
+ }
+
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_EVACUATE_PAGES);
+ EvacuatePages();
+ }
+
+ // Second pass: find pointers to new space and update them.
+ PointersUpdatingVisitor updating_visitor(heap());
+
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_NEW_TO_NEW_POINTERS);
+ // Update pointers in to space.
+ SemiSpaceIterator to_it(heap()->new_space()->bottom(),
+ heap()->new_space()->top());
+ for (HeapObject* object = to_it.Next(); object != NULL;
+ object = to_it.Next()) {
+ Map* map = object->map();
+ object->IterateBody(map->instance_type(), object->SizeFromMap(map),
+ &updating_visitor);
+ }
+ }
+
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_ROOT_TO_NEW_POINTERS);
+ // Update roots.
+ heap_->IterateRoots(&updating_visitor, VISIT_ALL_IN_SWEEP_NEWSPACE);
+ }
+
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_OLD_TO_NEW_POINTERS);
+ StoreBufferRebuildScope scope(heap_, heap_->store_buffer(),
+ &Heap::ScavengeStoreBufferCallback);
+ heap_->store_buffer()->IteratePointersToNewSpaceAndClearMaps(
+ &UpdatePointer);
+ }
+
+ {
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_POINTERS_TO_EVACUATED);
+ SlotsBuffer::UpdateSlotsRecordedIn(heap_, migration_slots_buffer_,
+ code_slots_filtering_required);
+ if (FLAG_trace_fragmentation) {
+ PrintF(" migration slots buffer: %d\n",
+ SlotsBuffer::SizeOfChain(migration_slots_buffer_));
+ }
+
+ if (compacting_ && was_marked_incrementally_) {
+ // It's difficult to filter out slots recorded for large objects.
+ LargeObjectIterator it(heap_->lo_space());
+ for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
+ // LargeObjectSpace is not swept yet thus we have to skip
+ // dead objects explicitly.
+ if (!IsMarked(obj)) continue;
+
+ Page* p = Page::FromAddress(obj->address());
+ if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
+ obj->Iterate(&updating_visitor);
+ p->ClearFlag(Page::RESCAN_ON_EVACUATION);
+ }
+ }
+ }
+ }
+
+ int npages = evacuation_candidates_.length();
+ {
+ GCTracer::Scope gc_scope(
+ heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_POINTERS_BETWEEN_EVACUATED);
+ for (int i = 0; i < npages; i++) {
+ Page* p = evacuation_candidates_[i];
+ DCHECK(p->IsEvacuationCandidate() ||
+ p->IsFlagSet(Page::RESCAN_ON_EVACUATION));
+
+ if (p->IsEvacuationCandidate()) {
+ SlotsBuffer::UpdateSlotsRecordedIn(heap_, p->slots_buffer(),
+ code_slots_filtering_required);
+ if (FLAG_trace_fragmentation) {
+ PrintF(" page %p slots buffer: %d\n", reinterpret_cast<void*>(p),
+ SlotsBuffer::SizeOfChain(p->slots_buffer()));
+ }
+
+ // Important: skip list should be cleared only after roots were updated
+ // because root iteration traverses the stack and might have to find
+ // code objects from non-updated pc pointing into evacuation candidate.
+ SkipList* list = p->skip_list();
+ if (list != NULL) list->Clear();
+ } else {
+ if (FLAG_gc_verbose) {
+ PrintF("Sweeping 0x%" V8PRIxPTR " during evacuation.\n",
+ reinterpret_cast<intptr_t>(p));
+ }
+ PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+ p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION);
+
+ switch (space->identity()) {
+ case OLD_DATA_SPACE:
+ Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD,
+ IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(space, NULL, p,
+ &updating_visitor);
+ break;
+ case OLD_POINTER_SPACE:
+ Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD,
+ IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(space, NULL, p,
+ &updating_visitor);
+ break;
+ case CODE_SPACE:
+ if (FLAG_zap_code_space) {
+ Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD,
+ REBUILD_SKIP_LIST, ZAP_FREE_SPACE>(space, NULL, p,
+ &updating_visitor);
+ } else {
+ Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD,
+ REBUILD_SKIP_LIST, IGNORE_FREE_SPACE>(space, NULL, p,
+ &updating_visitor);
+ }
+ break;
+ default:
+ UNREACHABLE();
+ break;
+ }
+ }
+ }
+ }
+
+ GCTracer::Scope gc_scope(heap()->tracer(),
+ GCTracer::Scope::MC_UPDATE_MISC_POINTERS);
+
+ // Update pointers from cells.
+ HeapObjectIterator cell_iterator(heap_->cell_space());
+ for (HeapObject* cell = cell_iterator.Next(); cell != NULL;
+ cell = cell_iterator.Next()) {
+ if (cell->IsCell()) {
+ Cell::BodyDescriptor::IterateBody(cell, &updating_visitor);
+ }
+ }
+
+ HeapObjectIterator js_global_property_cell_iterator(
+ heap_->property_cell_space());
+ for (HeapObject* cell = js_global_property_cell_iterator.Next(); cell != NULL;
+ cell = js_global_property_cell_iterator.Next()) {
+ if (cell->IsPropertyCell()) {
+ PropertyCell::BodyDescriptor::IterateBody(cell, &updating_visitor);
+ }
+ }
+
+ heap_->string_table()->Iterate(&updating_visitor);
+ updating_visitor.VisitPointer(heap_->weak_object_to_code_table_address());
+ if (heap_->weak_object_to_code_table()->IsHashTable()) {
+ WeakHashTable* table =
+ WeakHashTable::cast(heap_->weak_object_to_code_table());
+ table->Iterate(&updating_visitor);
+ table->Rehash(heap_->isolate()->factory()->undefined_value());
+ }
+
+ // Update pointers from external string table.
+ heap_->UpdateReferencesInExternalStringTable(
+ &UpdateReferenceInExternalStringTableEntry);
+
+ EvacuationWeakObjectRetainer evacuation_object_retainer;
+ heap()->ProcessWeakReferences(&evacuation_object_retainer);
+
+ // Visit invalidated code (we ignored all slots on it) and clear mark-bits
+ // under it.
+ ProcessInvalidatedCode(&updating_visitor);
+
+ heap_->isolate()->inner_pointer_to_code_cache()->Flush();
+
+ slots_buffer_allocator_.DeallocateChain(&migration_slots_buffer_);
+ DCHECK(migration_slots_buffer_ == NULL);
+}
+
+
+void MarkCompactCollector::MoveEvacuationCandidatesToEndOfPagesList() {
+ int npages = evacuation_candidates_.length();
+ for (int i = 0; i < npages; i++) {
+ Page* p = evacuation_candidates_[i];
+ if (!p->IsEvacuationCandidate()) continue;
+ p->Unlink();
+ PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+ p->InsertAfter(space->LastPage());
+ }
+}
+
+
+void MarkCompactCollector::ReleaseEvacuationCandidates() {
+ int npages = evacuation_candidates_.length();
+ for (int i = 0; i < npages; i++) {
+ Page* p = evacuation_candidates_[i];
+ if (!p->IsEvacuationCandidate()) continue;
+ PagedSpace* space = static_cast<PagedSpace*>(p->owner());
+ space->Free(p->area_start(), p->area_size());
+ p->set_scan_on_scavenge(false);
+ slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address());
+ p->ResetLiveBytes();
+ space->ReleasePage(p);
+ }
+ evacuation_candidates_.Rewind(0);
+ compacting_ = false;
+ heap()->FreeQueuedChunks();
+}
+
+
+static const int kStartTableEntriesPerLine = 5;
+static const int kStartTableLines = 171;
+static const int kStartTableInvalidLine = 127;
+static const int kStartTableUnusedEntry = 126;
+
+#define _ kStartTableUnusedEntry
+#define X kStartTableInvalidLine
+// Mark-bit to object start offset table.
+//
+// The line is indexed by the mark bits in a byte. The first number on
+// the line describes the number of live object starts for the line and the
+// other numbers on the line describe the offsets (in words) of the object
+// starts.
+//
+// Since objects are at least 2 words large we don't have entries for two
+// consecutive 1 bits. All entries after 170 have at least 2 consecutive bits.
+char kStartTable[kStartTableLines * kStartTableEntriesPerLine] = {
+ 0, _, _,
+ _, _, // 0
+ 1, 0, _,
+ _, _, // 1
+ 1, 1, _,
+ _, _, // 2
+ X, _, _,
+ _, _, // 3
+ 1, 2, _,
+ _, _, // 4
+ 2, 0, 2,
+ _, _, // 5
+ X, _, _,
+ _, _, // 6
+ X, _, _,
+ _, _, // 7
+ 1, 3, _,
+ _, _, // 8
+ 2, 0, 3,
+ _, _, // 9
+ 2, 1, 3,
+ _, _, // 10
+ X, _, _,
+ _, _, // 11
+ X, _, _,
+ _, _, // 12
+ X, _, _,
+ _, _, // 13
+ X, _, _,
+ _, _, // 14
+ X, _, _,
+ _, _, // 15
+ 1, 4, _,
+ _, _, // 16
+ 2, 0, 4,
+ _, _, // 17
+ 2, 1, 4,
+ _, _, // 18
+ X, _, _,
+ _, _, // 19
+ 2, 2, 4,
+ _, _, // 20
+ 3, 0, 2,
+ 4, _, // 21
+ X, _, _,
+ _, _, // 22
+ X, _, _,
+ _, _, // 23
+ X, _, _,
+ _, _, // 24
+ X, _, _,
+ _, _, // 25
+ X, _, _,
+ _, _, // 26
+ X, _, _,
+ _, _, // 27
+ X, _, _,
+ _, _, // 28
+ X, _, _,
+ _, _, // 29
+ X, _, _,
+ _, _, // 30
+ X, _, _,
+ _, _, // 31
+ 1, 5, _,
+ _, _, // 32
+ 2, 0, 5,
+ _, _, // 33
+ 2, 1, 5,
+ _, _, // 34
+ X, _, _,
+ _, _, // 35
+ 2, 2, 5,
+ _, _, // 36
+ 3, 0, 2,
+ 5, _, // 37
+ X, _, _,
+ _, _, // 38
+ X, _, _,
+ _, _, // 39
+ 2, 3, 5,
+ _, _, // 40
+ 3, 0, 3,
+ 5, _, // 41
+ 3, 1, 3,
+ 5, _, // 42
+ X, _, _,
+ _, _, // 43
+ X, _, _,
+ _, _, // 44
+ X, _, _,
+ _, _, // 45
+ X, _, _,
+ _, _, // 46
+ X, _, _,
+ _, _, // 47
+ X, _, _,
+ _, _, // 48
+ X, _, _,
+ _, _, // 49
+ X, _, _,
+ _, _, // 50
+ X, _, _,
+ _, _, // 51
+ X, _, _,
+ _, _, // 52
+ X, _, _,
+ _, _, // 53
+ X, _, _,
+ _, _, // 54
+ X, _, _,
+ _, _, // 55
+ X, _, _,
+ _, _, // 56
+ X, _, _,
+ _, _, // 57
+ X, _, _,
+ _, _, // 58
+ X, _, _,
+ _, _, // 59
+ X, _, _,
+ _, _, // 60
+ X, _, _,
+ _, _, // 61
+ X, _, _,
+ _, _, // 62
+ X, _, _,
+ _, _, // 63
+ 1, 6, _,
+ _, _, // 64
+ 2, 0, 6,
+ _, _, // 65
+ 2, 1, 6,
+ _, _, // 66
+ X, _, _,
+ _, _, // 67
+ 2, 2, 6,
+ _, _, // 68
+ 3, 0, 2,
+ 6, _, // 69
+ X, _, _,
+ _, _, // 70
+ X, _, _,
+ _, _, // 71
+ 2, 3, 6,
+ _, _, // 72
+ 3, 0, 3,
+ 6, _, // 73
+ 3, 1, 3,
+ 6, _, // 74
+ X, _, _,
+ _, _, // 75
+ X, _, _,
+ _, _, // 76
+ X, _, _,
+ _, _, // 77
+ X, _, _,
+ _, _, // 78
+ X, _, _,
+ _, _, // 79
+ 2, 4, 6,
+ _, _, // 80
+ 3, 0, 4,
+ 6, _, // 81
+ 3, 1, 4,
+ 6, _, // 82
+ X, _, _,
+ _, _, // 83
+ 3, 2, 4,
+ 6, _, // 84
+ 4, 0, 2,
+ 4, 6, // 85
+ X, _, _,
+ _, _, // 86
+ X, _, _,
+ _, _, // 87
+ X, _, _,
+ _, _, // 88
+ X, _, _,
+ _, _, // 89
+ X, _, _,
+ _, _, // 90
+ X, _, _,
+ _, _, // 91
+ X, _, _,
+ _, _, // 92
+ X, _, _,
+ _, _, // 93
+ X, _, _,
+ _, _, // 94
+ X, _, _,
+ _, _, // 95
+ X, _, _,
+ _, _, // 96
+ X, _, _,
+ _, _, // 97
+ X, _, _,
+ _, _, // 98
+ X, _, _,
+ _, _, // 99
+ X, _, _,
+ _, _, // 100
+ X, _, _,
+ _, _, // 101
+ X, _, _,
+ _, _, // 102
+ X, _, _,
+ _, _, // 103
+ X, _, _,
+ _, _, // 104
+ X, _, _,
+ _, _, // 105
+ X, _, _,
+ _, _, // 106
+ X, _, _,
+ _, _, // 107
+ X, _, _,
+ _, _, // 108
+ X, _, _,
+ _, _, // 109
+ X, _, _,
+ _, _, // 110
+ X, _, _,
+ _, _, // 111
+ X, _, _,
+ _, _, // 112
+ X, _, _,
+ _, _, // 113
+ X, _, _,
+ _, _, // 114
+ X, _, _,
+ _, _, // 115
+ X, _, _,
+ _, _, // 116
+ X, _, _,
+ _, _, // 117
+ X, _, _,
+ _, _, // 118
+ X, _, _,
+ _, _, // 119
+ X, _, _,
+ _, _, // 120
+ X, _, _,
+ _, _, // 121
+ X, _, _,
+ _, _, // 122
+ X, _, _,
+ _, _, // 123
+ X, _, _,
+ _, _, // 124
+ X, _, _,
+ _, _, // 125
+ X, _, _,
+ _, _, // 126
+ X, _, _,
+ _, _, // 127
+ 1, 7, _,
+ _, _, // 128
+ 2, 0, 7,
+ _, _, // 129
+ 2, 1, 7,
+ _, _, // 130
+ X, _, _,
+ _, _, // 131
+ 2, 2, 7,
+ _, _, // 132
+ 3, 0, 2,
+ 7, _, // 133
+ X, _, _,
+ _, _, // 134
+ X, _, _,
+ _, _, // 135
+ 2, 3, 7,
+ _, _, // 136
+ 3, 0, 3,
+ 7, _, // 137
+ 3, 1, 3,
+ 7, _, // 138
+ X, _, _,
+ _, _, // 139
+ X, _, _,
+ _, _, // 140
+ X, _, _,
+ _, _, // 141
+ X, _, _,
+ _, _, // 142
+ X, _, _,
+ _, _, // 143
+ 2, 4, 7,
+ _, _, // 144
+ 3, 0, 4,
+ 7, _, // 145
+ 3, 1, 4,
+ 7, _, // 146
+ X, _, _,
+ _, _, // 147
+ 3, 2, 4,
+ 7, _, // 148
+ 4, 0, 2,
+ 4, 7, // 149
+ X, _, _,
+ _, _, // 150
+ X, _, _,
+ _, _, // 151
+ X, _, _,
+ _, _, // 152
+ X, _, _,
+ _, _, // 153
+ X, _, _,
+ _, _, // 154
+ X, _, _,
+ _, _, // 155
+ X, _, _,
+ _, _, // 156
+ X, _, _,
+ _, _, // 157
+ X, _, _,
+ _, _, // 158
+ X, _, _,
+ _, _, // 159
+ 2, 5, 7,
+ _, _, // 160
+ 3, 0, 5,
+ 7, _, // 161
+ 3, 1, 5,
+ 7, _, // 162
+ X, _, _,
+ _, _, // 163
+ 3, 2, 5,
+ 7, _, // 164
+ 4, 0, 2,
+ 5, 7, // 165
+ X, _, _,
+ _, _, // 166
+ X, _, _,
+ _, _, // 167
+ 3, 3, 5,
+ 7, _, // 168
+ 4, 0, 3,
+ 5, 7, // 169
+ 4, 1, 3,
+ 5, 7 // 170
+};
+#undef _
+#undef X
+
+
+// Takes a word of mark bits. Returns the number of objects that start in the
+// range. Puts the offsets of the words in the supplied array.
+static inline int MarkWordToObjectStarts(uint32_t mark_bits, int* starts) {
+ int objects = 0;
+ int offset = 0;
+
+ // No consecutive 1 bits.
+ DCHECK((mark_bits & 0x180) != 0x180);
+ DCHECK((mark_bits & 0x18000) != 0x18000);
+ DCHECK((mark_bits & 0x1800000) != 0x1800000);
+
+ while (mark_bits != 0) {
+ int byte = (mark_bits & 0xff);
+ mark_bits >>= 8;
+ if (byte != 0) {
+ DCHECK(byte < kStartTableLines); // No consecutive 1 bits.
+ char* table = kStartTable + byte * kStartTableEntriesPerLine;
+ int objects_in_these_8_words = table[0];
+ DCHECK(objects_in_these_8_words != kStartTableInvalidLine);
+ DCHECK(objects_in_these_8_words < kStartTableEntriesPerLine);
+ for (int i = 0; i < objects_in_these_8_words; i++) {
+ starts[objects++] = offset + table[1 + i];
+ }
+ }
+ offset += 8;
+ }
+ return objects;
+}
+
+
+int MarkCompactCollector::SweepInParallel(PagedSpace* space,
+ int required_freed_bytes) {
+ int max_freed = 0;
+ int max_freed_overall = 0;
+ PageIterator it(space);
+ while (it.has_next()) {
+ Page* p = it.next();
+ max_freed = SweepInParallel(p, space);
+ DCHECK(max_freed >= 0);
+ if (required_freed_bytes > 0 && max_freed >= required_freed_bytes) {
+ return max_freed;
+ }
+ max_freed_overall = Max(max_freed, max_freed_overall);
+ if (p == space->end_of_unswept_pages()) break;
+ }
+ return max_freed_overall;
+}
+
+
+int MarkCompactCollector::SweepInParallel(Page* page, PagedSpace* space) {
+ int max_freed = 0;
+ if (page->TryParallelSweeping()) {
+ FreeList* free_list = space == heap()->old_pointer_space()
+ ? free_list_old_pointer_space_.get()
+ : free_list_old_data_space_.get();
+ FreeList private_free_list(space);
+ max_freed = Sweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST,
+ IGNORE_FREE_SPACE>(space, &private_free_list, page, NULL);
+ free_list->Concatenate(&private_free_list);
+ }
+ return max_freed;
+}
+
+
+void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
+ space->ClearStats();
+
+ // We defensively initialize end_of_unswept_pages_ here with the first page
+ // of the pages list.
+ space->set_end_of_unswept_pages(space->FirstPage());
+
+ PageIterator it(space);
+
+ int pages_swept = 0;
+ bool unused_page_present = false;
+ bool parallel_sweeping_active = false;
+
+ while (it.has_next()) {
+ Page* p = it.next();
+ DCHECK(p->parallel_sweeping() == MemoryChunk::SWEEPING_DONE);
+
+ // Clear sweeping flags indicating that marking bits are still intact.
+ p->ClearWasSwept();
+
+ if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION) ||
+ p->IsEvacuationCandidate()) {
+ // Will be processed in EvacuateNewSpaceAndCandidates.
+ DCHECK(evacuation_candidates_.length() > 0);
+ continue;
+ }
+
+ // One unused page is kept, all further are released before sweeping them.
+ if (p->LiveBytes() == 0) {
+ if (unused_page_present) {
+ if (FLAG_gc_verbose) {
+ PrintF("Sweeping 0x%" V8PRIxPTR " released page.\n",
+ reinterpret_cast<intptr_t>(p));
+ }
+ // Adjust unswept free bytes because releasing a page expects said
+ // counter to be accurate for unswept pages.
+ space->IncreaseUnsweptFreeBytes(p);
+ space->ReleasePage(p);
+ continue;
+ }
+ unused_page_present = true;
+ }
+
+ switch (sweeper) {
+ case CONCURRENT_SWEEPING:
+ case PARALLEL_SWEEPING:
+ if (!parallel_sweeping_active) {
+ if (FLAG_gc_verbose) {
+ PrintF("Sweeping 0x%" V8PRIxPTR ".\n",
+ reinterpret_cast<intptr_t>(p));
+ }
+ Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, IGNORE_SKIP_LIST,
+ IGNORE_FREE_SPACE>(space, NULL, p, NULL);
+ pages_swept++;
+ parallel_sweeping_active = true;
+ } else {
+ if (FLAG_gc_verbose) {
+ PrintF("Sweeping 0x%" V8PRIxPTR " in parallel.\n",
+ reinterpret_cast<intptr_t>(p));
+ }
+ p->set_parallel_sweeping(MemoryChunk::SWEEPING_PENDING);
+ space->IncreaseUnsweptFreeBytes(p);
+ }
+ space->set_end_of_unswept_pages(p);
+ break;
+ case SEQUENTIAL_SWEEPING: {
+ if (FLAG_gc_verbose) {
+ PrintF("Sweeping 0x%" V8PRIxPTR ".\n", reinterpret_cast<intptr_t>(p));
+ }
+ if (space->identity() == CODE_SPACE && FLAG_zap_code_space) {
+ Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, REBUILD_SKIP_LIST,
+ ZAP_FREE_SPACE>(space, NULL, p, NULL);
+ } else if (space->identity() == CODE_SPACE) {
+ Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, REBUILD_SKIP_LIST,
+ IGNORE_FREE_SPACE>(space, NULL, p, NULL);
+ } else {
+ Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, IGNORE_SKIP_LIST,
+ IGNORE_FREE_SPACE>(space, NULL, p, NULL);
+ }
+ pages_swept++;
+ break;
+ }
+ default: { UNREACHABLE(); }
+ }
+ }
+
+ if (FLAG_gc_verbose) {
+ PrintF("SweepSpace: %s (%d pages swept)\n",
+ AllocationSpaceName(space->identity()), pages_swept);
+ }
+
+ // Give pages that are queued to be freed back to the OS.
+ heap()->FreeQueuedChunks();
+}
+
+
+static bool ShouldStartSweeperThreads(MarkCompactCollector::SweeperType type) {
+ return type == MarkCompactCollector::PARALLEL_SWEEPING ||
+ type == MarkCompactCollector::CONCURRENT_SWEEPING;
+}
+
+
+static bool ShouldWaitForSweeperThreads(
+ MarkCompactCollector::SweeperType type) {
+ return type == MarkCompactCollector::PARALLEL_SWEEPING;
+}
+
+
+void MarkCompactCollector::SweepSpaces() {
+ GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_SWEEP);
+ double start_time = 0.0;
+ if (FLAG_print_cumulative_gc_stat) {
+ start_time = base::OS::TimeCurrentMillis();
+ }
+
+#ifdef DEBUG
+ state_ = SWEEP_SPACES;
+#endif
+ SweeperType how_to_sweep = CONCURRENT_SWEEPING;
+ if (FLAG_parallel_sweeping) how_to_sweep = PARALLEL_SWEEPING;
+ if (FLAG_concurrent_sweeping) how_to_sweep = CONCURRENT_SWEEPING;
+
+ MoveEvacuationCandidatesToEndOfPagesList();
+
+ // Noncompacting collections simply sweep the spaces to clear the mark
+ // bits and free the nonlive blocks (for old and map spaces). We sweep
+ // the map space last because freeing non-live maps overwrites them and
+ // the other spaces rely on possibly non-live maps to get the sizes for
+ // non-live objects.
+ {
+ GCTracer::Scope sweep_scope(heap()->tracer(),
+ GCTracer::Scope::MC_SWEEP_OLDSPACE);
+ {
+ SequentialSweepingScope scope(this);
+ SweepSpace(heap()->old_pointer_space(), how_to_sweep);
+ SweepSpace(heap()->old_data_space(), how_to_sweep);
+ }
+
+ if (ShouldStartSweeperThreads(how_to_sweep)) {
+ StartSweeperThreads();
+ }
+
+ if (ShouldWaitForSweeperThreads(how_to_sweep)) {
+ EnsureSweepingCompleted();
+ }
+ }
+ RemoveDeadInvalidatedCode();
+
+ {
+ GCTracer::Scope sweep_scope(heap()->tracer(),
+ GCTracer::Scope::MC_SWEEP_CODE);
+ SweepSpace(heap()->code_space(), SEQUENTIAL_SWEEPING);
+ }
+
+ {
+ GCTracer::Scope sweep_scope(heap()->tracer(),
+ GCTracer::Scope::MC_SWEEP_CELL);
+ SweepSpace(heap()->cell_space(), SEQUENTIAL_SWEEPING);
+ SweepSpace(heap()->property_cell_space(), SEQUENTIAL_SWEEPING);
+ }
+
+ EvacuateNewSpaceAndCandidates();
+
+ // ClearNonLiveTransitions depends on precise sweeping of map space to
+ // detect whether unmarked map became dead in this collection or in one
+ // of the previous ones.
+ {
+ GCTracer::Scope sweep_scope(heap()->tracer(),
+ GCTracer::Scope::MC_SWEEP_MAP);
+ SweepSpace(heap()->map_space(), SEQUENTIAL_SWEEPING);
+ }
+
+ // Deallocate unmarked objects and clear marked bits for marked objects.
+ heap_->lo_space()->FreeUnmarkedObjects();
+
+ // Deallocate evacuated candidate pages.
+ ReleaseEvacuationCandidates();
+
+ if (FLAG_print_cumulative_gc_stat) {
+ heap_->tracer()->AddSweepingTime(base::OS::TimeCurrentMillis() -
+ start_time);
+ }
+}
+
+
+void MarkCompactCollector::ParallelSweepSpaceComplete(PagedSpace* space) {
+ PageIterator it(space);
+ while (it.has_next()) {
+ Page* p = it.next();
+ if (p->parallel_sweeping() == MemoryChunk::SWEEPING_FINALIZE) {
+ p->set_parallel_sweeping(MemoryChunk::SWEEPING_DONE);
+ p->SetWasSwept();
+ }
+ DCHECK(p->parallel_sweeping() == MemoryChunk::SWEEPING_DONE);
+ }
+}
+
+
+void MarkCompactCollector::ParallelSweepSpacesComplete() {
+ ParallelSweepSpaceComplete(heap()->old_pointer_space());
+ ParallelSweepSpaceComplete(heap()->old_data_space());
+}
+
+
+void MarkCompactCollector::EnableCodeFlushing(bool enable) {
+ if (isolate()->debug()->is_loaded() ||
+ isolate()->debug()->has_break_points()) {
+ enable = false;
+ }
+
+ if (enable) {
+ if (code_flusher_ != NULL) return;
+ code_flusher_ = new CodeFlusher(isolate());
+ } else {
+ if (code_flusher_ == NULL) return;
+ code_flusher_->EvictAllCandidates();
+ delete code_flusher_;
+ code_flusher_ = NULL;
+ }
+
+ if (FLAG_trace_code_flushing) {
+ PrintF("[code-flushing is now %s]\n", enable ? "on" : "off");
+ }
+}
+
+
+// TODO(1466) ReportDeleteIfNeeded is not called currently.
+// Our profiling tools do not expect intersections between
+// code objects. We should either reenable it or change our tools.
+void MarkCompactCollector::ReportDeleteIfNeeded(HeapObject* obj,
+ Isolate* isolate) {
+ if (obj->IsCode()) {
+ PROFILE(isolate, CodeDeleteEvent(obj->address()));
+ }
+}
+
+
+Isolate* MarkCompactCollector::isolate() const { return heap_->isolate(); }
+
+
+void MarkCompactCollector::Initialize() {
+ MarkCompactMarkingVisitor::Initialize();
+ IncrementalMarking::Initialize();
+}
+
+
+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;
+}
+
+
+static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) {
+ if (RelocInfo::IsCodeTarget(rmode)) {
+ return SlotsBuffer::CODE_TARGET_SLOT;
+ } else if (RelocInfo::IsEmbeddedObject(rmode)) {
+ return SlotsBuffer::EMBEDDED_OBJECT_SLOT;
+ } else if (RelocInfo::IsDebugBreakSlot(rmode)) {
+ return SlotsBuffer::DEBUG_TARGET_SLOT;
+ } else if (RelocInfo::IsJSReturn(rmode)) {
+ return SlotsBuffer::JS_RETURN_SLOT;
+ }
+ UNREACHABLE();
+ return SlotsBuffer::NUMBER_OF_SLOT_TYPES;
+}
+
+
+void MarkCompactCollector::RecordRelocSlot(RelocInfo* rinfo, Object* target) {
+ Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target));
+ RelocInfo::Mode rmode = rinfo->rmode();
+ if (target_page->IsEvacuationCandidate() &&
+ (rinfo->host() == NULL ||
+ !ShouldSkipEvacuationSlotRecording(rinfo->host()))) {
+ bool success;
+ if (RelocInfo::IsEmbeddedObject(rmode) && rinfo->IsInConstantPool()) {
+ // This doesn't need to be typed since it is just a normal heap pointer.
+ Object** target_pointer =
+ reinterpret_cast<Object**>(rinfo->constant_pool_entry_address());
+ success = SlotsBuffer::AddTo(
+ &slots_buffer_allocator_, target_page->slots_buffer_address(),
+ target_pointer, SlotsBuffer::FAIL_ON_OVERFLOW);
+ } else if (RelocInfo::IsCodeTarget(rmode) && rinfo->IsInConstantPool()) {
+ success = SlotsBuffer::AddTo(
+ &slots_buffer_allocator_, target_page->slots_buffer_address(),
+ SlotsBuffer::CODE_ENTRY_SLOT, rinfo->constant_pool_entry_address(),
+ SlotsBuffer::FAIL_ON_OVERFLOW);
+ } else {
+ success = SlotsBuffer::AddTo(
+ &slots_buffer_allocator_, target_page->slots_buffer_address(),
+ SlotTypeForRMode(rmode), rinfo->pc(), SlotsBuffer::FAIL_ON_OVERFLOW);
+ }
+ if (!success) {
+ EvictEvacuationCandidate(target_page);
+ }
+ }
+}
+
+
+void MarkCompactCollector::RecordCodeEntrySlot(Address slot, Code* target) {
+ Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target));
+ if (target_page->IsEvacuationCandidate() &&
+ !ShouldSkipEvacuationSlotRecording(reinterpret_cast<Object**>(slot))) {
+ if (!SlotsBuffer::AddTo(&slots_buffer_allocator_,
+ target_page->slots_buffer_address(),
+ SlotsBuffer::CODE_ENTRY_SLOT, slot,
+ SlotsBuffer::FAIL_ON_OVERFLOW)) {
+ EvictEvacuationCandidate(target_page);
+ }
+ }
+}
+
+
+void MarkCompactCollector::RecordCodeTargetPatch(Address pc, Code* target) {
+ DCHECK(heap()->gc_state() == Heap::MARK_COMPACT);
+ if (is_compacting()) {
+ Code* host =
+ isolate()->inner_pointer_to_code_cache()->GcSafeFindCodeForInnerPointer(
+ pc);
+ MarkBit mark_bit = Marking::MarkBitFrom(host);
+ if (Marking::IsBlack(mark_bit)) {
+ RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
+ RecordRelocSlot(&rinfo, target);
+ }
+ }
+}
+
+
+static inline SlotsBuffer::SlotType DecodeSlotType(
+ SlotsBuffer::ObjectSlot slot) {
+ return static_cast<SlotsBuffer::SlotType>(reinterpret_cast<intptr_t>(slot));
+}
+
+
+void SlotsBuffer::UpdateSlots(Heap* heap) {
+ PointersUpdatingVisitor v(heap);
+
+ for (int slot_idx = 0; slot_idx < idx_; ++slot_idx) {
+ ObjectSlot slot = slots_[slot_idx];
+ if (!IsTypedSlot(slot)) {
+ PointersUpdatingVisitor::UpdateSlot(heap, slot);
+ } else {
+ ++slot_idx;
+ DCHECK(slot_idx < idx_);
+ UpdateSlot(heap->isolate(), &v, DecodeSlotType(slot),
+ reinterpret_cast<Address>(slots_[slot_idx]));
+ }
+ }
+}
+
+
+void SlotsBuffer::UpdateSlotsWithFilter(Heap* heap) {
+ PointersUpdatingVisitor v(heap);
+
+ for (int slot_idx = 0; slot_idx < idx_; ++slot_idx) {
+ ObjectSlot slot = slots_[slot_idx];
+ if (!IsTypedSlot(slot)) {
+ if (!IsOnInvalidatedCodeObject(reinterpret_cast<Address>(slot))) {
+ PointersUpdatingVisitor::UpdateSlot(heap, slot);
+ }
+ } else {
+ ++slot_idx;
+ DCHECK(slot_idx < idx_);
+ Address pc = reinterpret_cast<Address>(slots_[slot_idx]);
+ if (!IsOnInvalidatedCodeObject(pc)) {
+ UpdateSlot(heap->isolate(), &v, DecodeSlotType(slot),
+ reinterpret_cast<Address>(slots_[slot_idx]));
+ }
+ }
+ }
+}
+
+
+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 v8::internal