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// 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.
#ifndef V8_HEAP_HEAP_H_
#define V8_HEAP_HEAP_H_
#include <cmath>
#include "src/allocation.h"
#include "src/assert-scope.h"
#include "src/counters.h"
#include "src/globals.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/incremental-marking.h"
#include "src/heap/mark-compact.h"
#include "src/heap/objects-visiting.h"
#include "src/heap/spaces.h"
#include "src/heap/store-buffer.h"
#include "src/list.h"
#include "src/splay-tree-inl.h"
namespace v8 {
namespace internal {
// Defines all the roots in Heap.
V(Map, byte_array_map, ByteArrayMap) \
V(Map, free_space_map, FreeSpaceMap) \
V(Map, one_pointer_filler_map, OnePointerFillerMap) \
V(Map, two_pointer_filler_map, TwoPointerFillerMap) \
/* Cluster the most popular ones in a few cache lines here at the top. */ \
V(Smi, store_buffer_top, StoreBufferTop) \
V(Oddball, undefined_value, UndefinedValue) \
V(Oddball, the_hole_value, TheHoleValue) \
V(Oddball, null_value, NullValue) \
V(Oddball, true_value, TrueValue) \
V(Oddball, false_value, FalseValue) \
V(Oddball, uninitialized_value, UninitializedValue) \
V(Oddball, exception, Exception) \
V(Map, cell_map, CellMap) \
V(Map, global_property_cell_map, GlobalPropertyCellMap) \
V(Map, shared_function_info_map, SharedFunctionInfoMap) \
V(Map, meta_map, MetaMap) \
V(Map, heap_number_map, HeapNumberMap) \
V(Map, mutable_heap_number_map, MutableHeapNumberMap) \
V(Map, native_context_map, NativeContextMap) \
V(Map, fixed_array_map, FixedArrayMap) \
V(Map, code_map, CodeMap) \
V(Map, scope_info_map, ScopeInfoMap) \
V(Map, fixed_cow_array_map, FixedCOWArrayMap) \
V(Map, fixed_double_array_map, FixedDoubleArrayMap) \
V(Map, constant_pool_array_map, ConstantPoolArrayMap) \
V(Oddball, no_interceptor_result_sentinel, NoInterceptorResultSentinel) \
V(Map, hash_table_map, HashTableMap) \
V(Map, ordered_hash_table_map, OrderedHashTableMap) \
V(FixedArray, empty_fixed_array, EmptyFixedArray) \
V(ByteArray, empty_byte_array, EmptyByteArray) \
V(DescriptorArray, empty_descriptor_array, EmptyDescriptorArray) \
V(ConstantPoolArray, empty_constant_pool_array, EmptyConstantPoolArray) \
V(Oddball, arguments_marker, ArgumentsMarker) \
/* The roots above this line should be boring from a GC point of view. */ \
/* This means they are never in new space and never on a page that is */ \
/* being compacted. */ \
V(FixedArray, number_string_cache, NumberStringCache) \
V(Object, instanceof_cache_function, InstanceofCacheFunction) \
V(Object, instanceof_cache_map, InstanceofCacheMap) \
V(Object, instanceof_cache_answer, InstanceofCacheAnswer) \
V(FixedArray, single_character_string_cache, SingleCharacterStringCache) \
V(FixedArray, string_split_cache, StringSplitCache) \
V(FixedArray, regexp_multiple_cache, RegExpMultipleCache) \
V(Oddball, termination_exception, TerminationException) \
V(Smi, hash_seed, HashSeed) \
V(Map, symbol_map, SymbolMap) \
V(Map, string_map, StringMap) \
V(Map, ascii_string_map, AsciiStringMap) \
V(Map, cons_string_map, ConsStringMap) \
V(Map, cons_ascii_string_map, ConsAsciiStringMap) \
V(Map, sliced_string_map, SlicedStringMap) \
V(Map, sliced_ascii_string_map, SlicedAsciiStringMap) \
V(Map, external_string_map, ExternalStringMap) \
V(Map, external_string_with_one_byte_data_map, \
ExternalStringWithOneByteDataMap) \
V(Map, external_ascii_string_map, ExternalAsciiStringMap) \
V(Map, short_external_string_map, ShortExternalStringMap) \
V(Map, short_external_string_with_one_byte_data_map, \
ShortExternalStringWithOneByteDataMap) \
V(Map, internalized_string_map, InternalizedStringMap) \
V(Map, ascii_internalized_string_map, AsciiInternalizedStringMap) \
V(Map, external_internalized_string_map, ExternalInternalizedStringMap) \
V(Map, external_internalized_string_with_one_byte_data_map, \
ExternalInternalizedStringWithOneByteDataMap) \
V(Map, external_ascii_internalized_string_map, \
ExternalAsciiInternalizedStringMap) \
V(Map, short_external_internalized_string_map, \
ShortExternalInternalizedStringMap) \
V(Map, short_external_internalized_string_with_one_byte_data_map, \
ShortExternalInternalizedStringWithOneByteDataMap) \
V(Map, short_external_ascii_internalized_string_map, \
ShortExternalAsciiInternalizedStringMap) \
V(Map, short_external_ascii_string_map, ShortExternalAsciiStringMap) \
V(Map, undetectable_string_map, UndetectableStringMap) \
V(Map, undetectable_ascii_string_map, UndetectableAsciiStringMap) \
V(Map, external_int8_array_map, ExternalInt8ArrayMap) \
V(Map, external_uint8_array_map, ExternalUint8ArrayMap) \
V(Map, external_int16_array_map, ExternalInt16ArrayMap) \
V(Map, external_uint16_array_map, ExternalUint16ArrayMap) \
V(Map, external_int32_array_map, ExternalInt32ArrayMap) \
V(Map, external_uint32_array_map, ExternalUint32ArrayMap) \
V(Map, external_float32_array_map, ExternalFloat32ArrayMap) \
V(Map, external_float64_array_map, ExternalFloat64ArrayMap) \
V(Map, external_uint8_clamped_array_map, ExternalUint8ClampedArrayMap) \
V(ExternalArray, empty_external_int8_array, EmptyExternalInt8Array) \
V(ExternalArray, empty_external_uint8_array, EmptyExternalUint8Array) \
V(ExternalArray, empty_external_int16_array, EmptyExternalInt16Array) \
V(ExternalArray, empty_external_uint16_array, EmptyExternalUint16Array) \
V(ExternalArray, empty_external_int32_array, EmptyExternalInt32Array) \
V(ExternalArray, empty_external_uint32_array, EmptyExternalUint32Array) \
V(ExternalArray, empty_external_float32_array, EmptyExternalFloat32Array) \
V(ExternalArray, empty_external_float64_array, EmptyExternalFloat64Array) \
V(ExternalArray, empty_external_uint8_clamped_array, \
EmptyExternalUint8ClampedArray) \
V(Map, fixed_uint8_array_map, FixedUint8ArrayMap) \
V(Map, fixed_int8_array_map, FixedInt8ArrayMap) \
V(Map, fixed_uint16_array_map, FixedUint16ArrayMap) \
V(Map, fixed_int16_array_map, FixedInt16ArrayMap) \
V(Map, fixed_uint32_array_map, FixedUint32ArrayMap) \
V(Map, fixed_int32_array_map, FixedInt32ArrayMap) \
V(Map, fixed_float32_array_map, FixedFloat32ArrayMap) \
V(Map, fixed_float64_array_map, FixedFloat64ArrayMap) \
V(Map, fixed_uint8_clamped_array_map, FixedUint8ClampedArrayMap) \
V(FixedTypedArrayBase, empty_fixed_uint8_array, EmptyFixedUint8Array) \
V(FixedTypedArrayBase, empty_fixed_int8_array, EmptyFixedInt8Array) \
V(FixedTypedArrayBase, empty_fixed_uint16_array, EmptyFixedUint16Array) \
V(FixedTypedArrayBase, empty_fixed_int16_array, EmptyFixedInt16Array) \
V(FixedTypedArrayBase, empty_fixed_uint32_array, EmptyFixedUint32Array) \
V(FixedTypedArrayBase, empty_fixed_int32_array, EmptyFixedInt32Array) \
V(FixedTypedArrayBase, empty_fixed_float32_array, EmptyFixedFloat32Array) \
V(FixedTypedArrayBase, empty_fixed_float64_array, EmptyFixedFloat64Array) \
V(FixedTypedArrayBase, empty_fixed_uint8_clamped_array, \
EmptyFixedUint8ClampedArray) \
V(Map, sloppy_arguments_elements_map, SloppyArgumentsElementsMap) \
V(Map, function_context_map, FunctionContextMap) \
V(Map, catch_context_map, CatchContextMap) \
V(Map, with_context_map, WithContextMap) \
V(Map, block_context_map, BlockContextMap) \
V(Map, module_context_map, ModuleContextMap) \
V(Map, global_context_map, GlobalContextMap) \
V(Map, undefined_map, UndefinedMap) \
V(Map, the_hole_map, TheHoleMap) \
V(Map, null_map, NullMap) \
V(Map, boolean_map, BooleanMap) \
V(Map, uninitialized_map, UninitializedMap) \
V(Map, arguments_marker_map, ArgumentsMarkerMap) \
V(Map, no_interceptor_result_sentinel_map, NoInterceptorResultSentinelMap) \
V(Map, exception_map, ExceptionMap) \
V(Map, termination_exception_map, TerminationExceptionMap) \
V(Map, message_object_map, JSMessageObjectMap) \
V(Map, foreign_map, ForeignMap) \
V(HeapNumber, nan_value, NanValue) \
V(HeapNumber, infinity_value, InfinityValue) \
V(HeapNumber, minus_zero_value, MinusZeroValue) \
V(Map, neander_map, NeanderMap) \
V(JSObject, message_listeners, MessageListeners) \
V(UnseededNumberDictionary, code_stubs, CodeStubs) \
V(UnseededNumberDictionary, non_monomorphic_cache, NonMonomorphicCache) \
V(PolymorphicCodeCache, polymorphic_code_cache, PolymorphicCodeCache) \
V(Code, js_entry_code, JsEntryCode) \
V(Code, js_construct_entry_code, JsConstructEntryCode) \
V(FixedArray, natives_source_cache, NativesSourceCache) \
V(Script, empty_script, EmptyScript) \
V(NameDictionary, intrinsic_function_names, IntrinsicFunctionNames) \
V(Cell, undefined_cell, UndefineCell) \
V(JSObject, observation_state, ObservationState) \
V(Map, external_map, ExternalMap) \
V(Object, symbol_registry, SymbolRegistry) \
V(Symbol, frozen_symbol, FrozenSymbol) \
V(Symbol, nonexistent_symbol, NonExistentSymbol) \
V(Symbol, elements_transition_symbol, ElementsTransitionSymbol) \
V(SeededNumberDictionary, empty_slow_element_dictionary, \
EmptySlowElementDictionary) \
V(Symbol, observed_symbol, ObservedSymbol) \
V(Symbol, uninitialized_symbol, UninitializedSymbol) \
V(Symbol, megamorphic_symbol, MegamorphicSymbol) \
V(Symbol, stack_trace_symbol, StackTraceSymbol) \
V(Symbol, detailed_stack_trace_symbol, DetailedStackTraceSymbol) \
V(Symbol, normal_ic_symbol, NormalICSymbol) \
V(FixedArray, materialized_objects, MaterializedObjects) \
V(FixedArray, allocation_sites_scratchpad, AllocationSitesScratchpad) \
V(FixedArray, microtask_queue, MicrotaskQueue)
// Entries in this list are limited to Smis and are not visited during GC.
#define SMI_ROOT_LIST(V) \
V(Smi, stack_limit, StackLimit) \
V(Smi, real_stack_limit, RealStackLimit) \
V(Smi, last_script_id, LastScriptId) \
V(Smi, arguments_adaptor_deopt_pc_offset, ArgumentsAdaptorDeoptPCOffset) \
V(Smi, construct_stub_deopt_pc_offset, ConstructStubDeoptPCOffset) \
V(Smi, getter_stub_deopt_pc_offset, GetterStubDeoptPCOffset) \
V(Smi, setter_stub_deopt_pc_offset, SetterStubDeoptPCOffset)
#define ROOT_LIST(V) \
V(StringTable, string_table, StringTable)
// Heap roots that are known to be immortal immovable, for which we can safely
// skip write barriers.
V(byte_array_map) \
V(free_space_map) \
V(one_pointer_filler_map) \
V(two_pointer_filler_map) \
V(undefined_value) \
V(the_hole_value) \
V(null_value) \
V(true_value) \
V(false_value) \
V(uninitialized_value) \
V(cell_map) \
V(global_property_cell_map) \
V(shared_function_info_map) \
V(meta_map) \
V(heap_number_map) \
V(mutable_heap_number_map) \
V(native_context_map) \
V(fixed_array_map) \
V(code_map) \
V(scope_info_map) \
V(fixed_cow_array_map) \
V(fixed_double_array_map) \
V(constant_pool_array_map) \
V(no_interceptor_result_sentinel) \
V(hash_table_map) \
V(ordered_hash_table_map) \
V(empty_fixed_array) \
V(empty_byte_array) \
V(empty_descriptor_array) \
V(empty_constant_pool_array) \
V(arguments_marker) \
V(symbol_map) \
V(sloppy_arguments_elements_map) \
V(function_context_map) \
V(catch_context_map) \
V(with_context_map) \
V(block_context_map) \
V(module_context_map) \
V(global_context_map) \
V(undefined_map) \
V(the_hole_map) \
V(null_map) \
V(boolean_map) \
V(uninitialized_map) \
V(message_object_map) \
V(foreign_map) \
V(Array_string, "Array") \
V(Object_string, "Object") \
V(proto_string, "__proto__") \
V(arguments_string, "arguments") \
V(Arguments_string, "Arguments") \
V(call_string, "call") \
V(apply_string, "apply") \
V(caller_string, "caller") \
V(boolean_string, "boolean") \
V(Boolean_string, "Boolean") \
V(callee_string, "callee") \
V(constructor_string, "constructor") \
V(dot_result_string, ".result") \
V(dot_for_string, ".for.") \
V(eval_string, "eval") \
V(empty_string, "") \
V(function_string, "function") \
V(length_string, "length") \
V(name_string, "name") \
V(null_string, "null") \
V(number_string, "number") \
V(Number_string, "Number") \
V(nan_string, "NaN") \
V(RegExp_string, "RegExp") \
V(source_string, "source") \
V(source_url_string, "source_url") \
V(source_mapping_url_string, "source_mapping_url") \
V(global_string, "global") \
V(ignore_case_string, "ignoreCase") \
V(multiline_string, "multiline") \
V(input_string, "input") \
V(index_string, "index") \
V(last_index_string, "lastIndex") \
V(object_string, "object") \
V(literals_string, "literals") \
V(prototype_string, "prototype") \
V(string_string, "string") \
V(String_string, "String") \
V(symbol_string, "symbol") \
V(Symbol_string, "Symbol") \
V(for_string, "for") \
V(for_api_string, "for_api") \
V(for_intern_string, "for_intern") \
V(private_api_string, "private_api") \
V(private_intern_string, "private_intern") \
V(Date_string, "Date") \
V(to_string_string, "toString") \
V(char_at_string, "CharAt") \
V(undefined_string, "undefined") \
V(value_of_string, "valueOf") \
V(stack_string, "stack") \
V(toJSON_string, "toJSON") \
V(InitializeVarGlobal_string, "InitializeVarGlobal") \
V(InitializeConstGlobal_string, "InitializeConstGlobal") \
V(KeyedLoadMonomorphic_string, "KeyedLoadMonomorphic") \
V(KeyedStoreMonomorphic_string, "KeyedStoreMonomorphic") \
V(stack_overflow_string, "kStackOverflowBoilerplate") \
V(illegal_access_string, "illegal access") \
V(get_string, "get") \
V(set_string, "set") \
V(map_field_string, "%map") \
V(elements_field_string, "%elements") \
V(length_field_string, "%length") \
V(cell_value_string, "%cell_value") \
V(function_class_string, "Function") \
V(illegal_argument_string, "illegal argument") \
V(space_string, " ") \
V(exec_string, "exec") \
V(zero_string, "0") \
V(global_eval_string, "GlobalEval") \
V(identity_hash_string, "v8::IdentityHash") \
V(closure_string, "(closure)") \
V(dot_string, ".") \
V(compare_ic_string, "==") \
V(strict_compare_ic_string, "===") \
V(infinity_string, "Infinity") \
V(minus_infinity_string, "-Infinity") \
V(query_colon_string, "(?:)") \
V(Generator_string, "Generator") \
V(throw_string, "throw") \
V(done_string, "done") \
V(value_string, "value") \
V(next_string, "next") \
V(byte_length_string, "byteLength") \
V(byte_offset_string, "byteOffset") \
V(buffer_string, "buffer") \
V(intl_initialized_marker_string, "v8::intl_initialized_marker") \
V(intl_impl_object_string, "v8::intl_object")
// Forward declarations.
class HeapStats;
class Isolate;
class WeakObjectRetainer;
typedef String* (*ExternalStringTableUpdaterCallback)(Heap* heap,
Object** pointer);
class StoreBufferRebuilder {
explicit StoreBufferRebuilder(StoreBuffer* store_buffer)
: store_buffer_(store_buffer) {}
void Callback(MemoryChunk* page, StoreBufferEvent event);
StoreBuffer* store_buffer_;
// We record in this variable how full the store buffer was when we started
// iterating over the current page, finding pointers to new space. If the
// store buffer overflows again we can exempt the page from the store buffer
// by rewinding to this point instead of having to search the store buffer.
Object*** start_of_current_page_;
// The current page we are scanning in the store buffer iterator.
MemoryChunk* current_page_;
// A queue of objects promoted during scavenge. Each object is accompanied
// by it's size to avoid dereferencing a map pointer for scanning.
class PromotionQueue {
explicit PromotionQueue(Heap* heap)
: front_(NULL),
heap_(heap) {}
void Initialize();
void Destroy() {
delete emergency_stack_;
emergency_stack_ = NULL;
Page* GetHeadPage() {
return Page::FromAllocationTop(reinterpret_cast<Address>(rear_));
void SetNewLimit(Address limit) {
limit_ = reinterpret_cast<intptr_t*>(limit);
if (limit_ <= rear_) {
bool IsBelowPromotionQueue(Address to_space_top) {
// If the given to-space top pointer and the head of the promotion queue
// are not on the same page, then the to-space objects are below the
// promotion queue.
if (GetHeadPage() != Page::FromAddress(to_space_top)) {
return true;
// If the to space top pointer is smaller or equal than the promotion
// queue head, then the to-space objects are below the promotion queue.
return reinterpret_cast<intptr_t*>(to_space_top) <= rear_;
bool is_empty() {
return (front_ == rear_) &&
(emergency_stack_ == NULL || emergency_stack_->length() == 0);
inline void insert(HeapObject* target, int size);
void remove(HeapObject** target, int* size) {
if (front_ == rear_) {
Entry e = emergency_stack_->RemoveLast();
*target = e.obj_;
*size = e.size_;
if (NewSpacePage::IsAtStart(reinterpret_cast<Address>(front_))) {
NewSpacePage* front_page =
front_ = reinterpret_cast<intptr_t*>(front_page->prev_page()->area_end());
*target = reinterpret_cast<HeapObject*>(*(--front_));
*size = static_cast<int>(*(--front_));
// Assert no underflow.
// The front of the queue is higher in the memory page chain than the rear.
intptr_t* front_;
intptr_t* rear_;
intptr_t* limit_;
static const int kEntrySizeInWords = 2;
struct Entry {
Entry(HeapObject* obj, int size) : obj_(obj), size_(size) {}
HeapObject* obj_;
int size_;
List<Entry>* emergency_stack_;
Heap* heap_;
void RelocateQueueHead();
typedef void (*ScavengingCallback)(Map* map, HeapObject** slot,
HeapObject* object);
// External strings table is a place where all external strings are
// registered. We need to keep track of such strings to properly
// finalize them.
class ExternalStringTable {
// Registers an external string.
inline void AddString(String* string);
inline void Iterate(ObjectVisitor* v);
// Restores internal invariant and gets rid of collected strings.
// Must be called after each Iterate() that modified the strings.
void CleanUp();
// Destroys all allocated memory.
void TearDown();
explicit ExternalStringTable(Heap* heap) : heap_(heap) {}
friend class Heap;
inline void Verify();
inline void AddOldString(String* string);
// Notifies the table that only a prefix of the new list is valid.
inline void ShrinkNewStrings(int position);
// To speed up scavenge collections new space string are kept
// separate from old space strings.
List<Object*> new_space_strings_;
List<Object*> old_space_strings_;
Heap* heap_;
enum ArrayStorageAllocationMode {
class Heap {
// Configure heap size in MB before setup. Return false if the heap has been
// set up already.
bool ConfigureHeap(int max_semi_space_size, int max_old_space_size,
int max_executable_size, size_t code_range_size);
bool ConfigureHeapDefault();
// Prepares the heap, setting up memory areas that are needed in the isolate
// without actually creating any objects.
bool SetUp();
// Bootstraps the object heap with the core set of objects required to run.
// Returns whether it succeeded.
bool CreateHeapObjects();
// Destroys all memory allocated by the heap.
void TearDown();
// Set the stack limit in the roots_ array. Some architectures generate
// code that looks here, because it is faster than loading from the static
// jslimit_/real_jslimit_ variable in the StackGuard.
void SetStackLimits();
// Returns whether SetUp has been called.
bool HasBeenSetUp();
// Returns the maximum amount of memory reserved for the heap. For
// the young generation, we reserve 4 times the amount needed for a
// semi space. The young generation consists of two semi spaces and
// we reserve twice the amount needed for those in order to ensure
// that new space can be aligned to its size.
intptr_t MaxReserved() {
return 4 * reserved_semispace_size_ + max_old_generation_size_;
int MaxSemiSpaceSize() { return max_semi_space_size_; }
int ReservedSemiSpaceSize() { return reserved_semispace_size_; }
int InitialSemiSpaceSize() { return initial_semispace_size_; }
intptr_t MaxOldGenerationSize() { return max_old_generation_size_; }
intptr_t MaxExecutableSize() { return max_executable_size_; }
// Returns the capacity of the heap in bytes w/o growing. Heap grows when
// more spaces are needed until it reaches the limit.
intptr_t Capacity();
// Returns the amount of memory currently committed for the heap.
intptr_t CommittedMemory();
// Returns the amount of executable memory currently committed for the heap.
intptr_t CommittedMemoryExecutable();
// Returns the amount of phyical memory currently committed for the heap.
size_t CommittedPhysicalMemory();
// Returns the maximum amount of memory ever committed for the heap.
intptr_t MaximumCommittedMemory() { return maximum_committed_; }
// Updates the maximum committed memory for the heap. Should be called
// whenever a space grows.
void UpdateMaximumCommitted();
// Returns the available bytes in space w/o growing.
// Heap doesn't guarantee that it can allocate an object that requires
// all available bytes. Check MaxHeapObjectSize() instead.
intptr_t Available();
// Returns of size of all objects residing in the heap.
intptr_t SizeOfObjects();
// Return the starting address and a mask for the new space. And-masking an
// address with the mask will result in the start address of the new space
// for all addresses in either semispace.
Address NewSpaceStart() { return new_space_.start(); }
uintptr_t NewSpaceMask() { return new_space_.mask(); }
Address NewSpaceTop() { return; }
NewSpace* new_space() { return &new_space_; }
OldSpace* old_pointer_space() { return old_pointer_space_; }
OldSpace* old_data_space() { return old_data_space_; }
OldSpace* code_space() { return code_space_; }
MapSpace* map_space() { return map_space_; }
CellSpace* cell_space() { return cell_space_; }
PropertyCellSpace* property_cell_space() { return property_cell_space_; }
LargeObjectSpace* lo_space() { return lo_space_; }
PagedSpace* paged_space(int idx) {
switch (idx) {
return old_pointer_space();
return old_data_space();
return map_space();
return cell_space();
return property_cell_space();
return code_space();
case LO_SPACE:
return NULL;
bool always_allocate() { return always_allocate_scope_depth_ != 0; }
Address always_allocate_scope_depth_address() {
return reinterpret_cast<Address>(&always_allocate_scope_depth_);
Address* NewSpaceAllocationTopAddress() {
return new_space_.allocation_top_address();
Address* NewSpaceAllocationLimitAddress() {
return new_space_.allocation_limit_address();
Address* OldPointerSpaceAllocationTopAddress() {
return old_pointer_space_->allocation_top_address();
Address* OldPointerSpaceAllocationLimitAddress() {
return old_pointer_space_->allocation_limit_address();
Address* OldDataSpaceAllocationTopAddress() {
return old_data_space_->allocation_top_address();
Address* OldDataSpaceAllocationLimitAddress() {
return old_data_space_->allocation_limit_address();
// Returns a deep copy of the JavaScript object.
// Properties and elements are copied too.
// Optionally takes an AllocationSite to be appended in an AllocationMemento.
MUST_USE_RESULT AllocationResult
CopyJSObject(JSObject* source, AllocationSite* site = NULL);
// Clear the Instanceof cache (used when a prototype changes).
inline void ClearInstanceofCache();
// Iterates the whole code space to clear all ICs of the given kind.
void ClearAllICsByKind(Code::Kind kind);
// For use during bootup.
void RepairFreeListsAfterBoot();
template <typename T>
static inline bool IsOneByte(T t, int chars);
// Move len elements within a given array from src_index index to dst_index
// index.
void MoveElements(FixedArray* array, int dst_index, int src_index, int len);
// Sloppy mode arguments object size.
static const int kSloppyArgumentsObjectSize =
JSObject::kHeaderSize + 2 * kPointerSize;
// Strict mode arguments has no callee so it is smaller.
static const int kStrictArgumentsObjectSize =
JSObject::kHeaderSize + 1 * kPointerSize;
// Indicies for direct access into argument objects.
static const int kArgumentsLengthIndex = 0;
// callee is only valid in sloppy mode.
static const int kArgumentsCalleeIndex = 1;
// Finalizes an external string by deleting the associated external
// data and clearing the resource pointer.
inline void FinalizeExternalString(String* string);
// Initialize a filler object to keep the ability to iterate over the heap
// when introducing gaps within pages.
void CreateFillerObjectAt(Address addr, int size);
bool CanMoveObjectStart(HeapObject* object);
// Indicates whether live bytes adjustment is triggered from within the GC
// code or from mutator code.
enum InvocationMode { FROM_GC, FROM_MUTATOR };
// Maintain consistency of live bytes during incremental marking.
void AdjustLiveBytes(Address address, int by, InvocationMode mode);
// Trim the given array from the left. Note that this relocates the object
// start and hence is only valid if there is only a single reference to it.
FixedArrayBase* LeftTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
// Trim the given array from the right.
template<Heap::InvocationMode mode>
void RightTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
// Converts the given boolean condition to JavaScript boolean value.
inline Object* ToBoolean(bool condition);
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
inline bool CollectGarbage(
AllocationSpace space, const char* gc_reason = NULL,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
static const int kNoGCFlags = 0;
static const int kSweepPreciselyMask = 1;
static const int kReduceMemoryFootprintMask = 2;
static const int kAbortIncrementalMarkingMask = 4;
// Making the heap iterable requires us to sweep precisely and abort any
// incremental marking as well.
static const int kMakeHeapIterableMask =
kSweepPreciselyMask | kAbortIncrementalMarkingMask;
// Performs a full garbage collection. If (flags & kMakeHeapIterableMask) is
// non-zero, then the slower precise sweeper is used, which leaves the heap
// in a state where we can iterate over the heap visiting all objects.
void CollectAllGarbage(
int flags, const char* gc_reason = NULL,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Last hope GC, should try to squeeze as much as possible.
void CollectAllAvailableGarbage(const char* gc_reason = NULL);
// Check whether the heap is currently iterable.
bool IsHeapIterable();
// Notify the heap that a context has been disposed.
int NotifyContextDisposed();
inline void increment_scan_on_scavenge_pages() {
if (FLAG_gc_verbose) {
PrintF("Scan-on-scavenge pages: %d\n", scan_on_scavenge_pages_);
inline void decrement_scan_on_scavenge_pages() {
if (FLAG_gc_verbose) {
PrintF("Scan-on-scavenge pages: %d\n", scan_on_scavenge_pages_);
PromotionQueue* promotion_queue() { return &promotion_queue_; }
void AddGCPrologueCallback(v8::Isolate::GCPrologueCallback callback,
GCType gc_type_filter, bool pass_isolate = true);
void RemoveGCPrologueCallback(v8::Isolate::GCPrologueCallback callback);
void AddGCEpilogueCallback(v8::Isolate::GCEpilogueCallback callback,
GCType gc_type_filter, bool pass_isolate = true);
void RemoveGCEpilogueCallback(v8::Isolate::GCEpilogueCallback callback);
// Heap root getters. We have versions with and without type::cast() here.
// You can't use type::cast during GC because the assert fails.
// TODO(1490): Try removing the unchecked accessors, now that GC marking does
// not corrupt the map.
#define ROOT_ACCESSOR(type, name, camel_name) \
type* name() { return type::cast(roots_[k##camel_name##RootIndex]); } \
type* raw_unchecked_##name() { \
return reinterpret_cast<type*>(roots_[k##camel_name##RootIndex]); \
// Utility type maps
#define STRUCT_MAP_ACCESSOR(NAME, Name, name) \
Map* name##_map() { return Map::cast(roots_[k##Name##MapRootIndex]); }
#define STRING_ACCESSOR(name, str) \
String* name() { return String::cast(roots_[k##name##RootIndex]); }
// The hidden_string is special because it is the empty string, but does
// not match the empty string.
String* hidden_string() { return hidden_string_; }
void set_native_contexts_list(Object* object) {
native_contexts_list_ = object;
Object* native_contexts_list() const { return native_contexts_list_; }
void set_array_buffers_list(Object* object) { array_buffers_list_ = object; }
Object* array_buffers_list() const { return array_buffers_list_; }
void set_allocation_sites_list(Object* object) {
allocation_sites_list_ = object;
Object* allocation_sites_list() { return allocation_sites_list_; }
// Used in CreateAllocationSiteStub and the (de)serializer.
Object** allocation_sites_list_address() { return &allocation_sites_list_; }
Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
void set_encountered_weak_collections(Object* weak_collection) {
encountered_weak_collections_ = weak_collection;
Object* encountered_weak_collections() const {
return encountered_weak_collections_;
// Number of mark-sweeps.
unsigned int ms_count() { return ms_count_; }
// Iterates over all roots in the heap.
void IterateRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over all strong roots in the heap.
void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over entries in the smi roots list. Only interesting to the
// serializer/deserializer, since GC does not care about smis.
void IterateSmiRoots(ObjectVisitor* v);
// Iterates over all the other roots in the heap.
void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
// Iterate pointers to from semispace of new space found in memory interval
// from start to end.
void IterateAndMarkPointersToFromSpace(Address start, Address end,
ObjectSlotCallback callback);
// Returns whether the object resides in new space.
inline bool InNewSpace(Object* object);
inline bool InNewSpace(Address address);
inline bool InNewSpacePage(Address address);
inline bool InFromSpace(Object* object);
inline bool InToSpace(Object* object);
// Returns whether the object resides in old pointer space.
inline bool InOldPointerSpace(Address address);
inline bool InOldPointerSpace(Object* object);
// Returns whether the object resides in old data space.
inline bool InOldDataSpace(Address address);
inline bool InOldDataSpace(Object* object);
// Checks whether an address/object in the heap (including auxiliary
// area and unused area).
bool Contains(Address addr);
bool Contains(HeapObject* value);
// Checks whether an address/object in a space.
// Currently used by tests, serialization and heap verification only.
bool InSpace(Address addr, AllocationSpace space);
bool InSpace(HeapObject* value, AllocationSpace space);
// Finds out which space an object should get promoted to based on its type.
inline OldSpace* TargetSpace(HeapObject* object);
static inline AllocationSpace TargetSpaceId(InstanceType type);
// Checks whether the given object is allowed to be migrated from it's
// current space into the given destination space. Used for debugging.
inline bool AllowedToBeMigrated(HeapObject* object, AllocationSpace dest);
// Sets the stub_cache_ (only used when expanding the dictionary).
void public_set_code_stubs(UnseededNumberDictionary* value) {
roots_[kCodeStubsRootIndex] = value;
// Support for computing object sizes for old objects during GCs. Returns
// a function that is guaranteed to be safe for computing object sizes in
// the current GC phase.
HeapObjectCallback GcSafeSizeOfOldObjectFunction() {
return gc_safe_size_of_old_object_;
// Sets the non_monomorphic_cache_ (only used when expanding the dictionary).
void public_set_non_monomorphic_cache(UnseededNumberDictionary* value) {
roots_[kNonMonomorphicCacheRootIndex] = value;
void public_set_empty_script(Script* script) {
roots_[kEmptyScriptRootIndex] = script;
void public_set_store_buffer_top(Address* top) {
roots_[kStoreBufferTopRootIndex] = reinterpret_cast<Smi*>(top);
void public_set_materialized_objects(FixedArray* objects) {
roots_[kMaterializedObjectsRootIndex] = objects;
// Generated code can embed this address to get access to the roots.
Object** roots_array_start() { return roots_; }
Address* store_buffer_top_address() {
return reinterpret_cast<Address*>(&roots_[kStoreBufferTopRootIndex]);
// Verify the heap is in its normal state before or after a GC.
void Verify();
bool weak_embedded_objects_verification_enabled() {
return no_weak_object_verification_scope_depth_ == 0;
#ifdef DEBUG
void Print();
void PrintHandles();
void OldPointerSpaceCheckStoreBuffer();
void MapSpaceCheckStoreBuffer();
void LargeObjectSpaceCheckStoreBuffer();
// Report heap statistics.
void ReportHeapStatistics(const char* title);
void ReportCodeStatistics(const char* title);
// Zapping is needed for verify heap, and always done in debug builds.
static inline bool ShouldZapGarbage() {
#ifdef DEBUG
return true;
return FLAG_verify_heap;
return false;
// Number of "runtime allocations" done so far.
uint32_t allocations_count() { return allocations_count_; }
// Returns deterministic "time" value in ms. Works only with
// FLAG_verify_predictable.
double synthetic_time() { return allocations_count_ / 100.0; }
// Print short heap statistics.
void PrintShortHeapStatistics();
// Write barrier support for address[offset] = o.
INLINE(void RecordWrite(Address address, int offset));
// Write barrier support for address[start : start + len[ = o.
INLINE(void RecordWrites(Address address, int start, int len));
inline HeapState gc_state() { return gc_state_; }
inline bool IsInGCPostProcessing() { return gc_post_processing_depth_ > 0; }
#ifdef DEBUG
void set_allocation_timeout(int timeout) { allocation_timeout_ = timeout; }
void TracePathToObjectFrom(Object* target, Object* root);
void TracePathToObject(Object* target);
void TracePathToGlobal();
// Callback function passed to Heap::Iterate etc. Copies an object if
// necessary, the object might be promoted to an old space. The caller must
// ensure the precondition that the object is (a) a heap object and (b) in
// the heap's from space.
static inline void ScavengePointer(HeapObject** p);
static inline void ScavengeObject(HeapObject** p, HeapObject* object);
// If an object has an AllocationMemento trailing it, return it, otherwise
// return NULL;
inline AllocationMemento* FindAllocationMemento(HeapObject* object);
// An object may have an AllocationSite associated with it through a trailing
// AllocationMemento. Its feedback should be updated when objects are found
// in the heap.
static inline void UpdateAllocationSiteFeedback(HeapObject* object,
ScratchpadSlotMode mode);
// Support for partial snapshots. After calling this we have a linear
// space to write objects in each space.
void ReserveSpace(int* sizes, Address* addresses);
// Support for the API.
void CreateApiObjects();
inline intptr_t PromotedTotalSize() {
int64_t total = PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
if (total > kMaxInt) return static_cast<intptr_t>(kMaxInt);
if (total < 0) return 0;
return static_cast<intptr_t>(total);
inline intptr_t OldGenerationSpaceAvailable() {
return old_generation_allocation_limit_ - PromotedTotalSize();
inline intptr_t OldGenerationCapacityAvailable() {
return max_old_generation_size_ - PromotedTotalSize();
static const intptr_t kMinimumOldGenerationAllocationLimit =
8 * (Page::kPageSize > MB ? Page::kPageSize : MB);
static const int kPointerMultiplier = i::kPointerSize / 4;
// The new space size has to be a power of 2. Sizes are in MB.
static const int kMaxSemiSpaceSizeLowMemoryDevice = 1 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeMediumMemoryDevice = 4 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeHighMemoryDevice = 8 * kPointerMultiplier;
static const int kMaxSemiSpaceSizeHugeMemoryDevice = 8 * kPointerMultiplier;
// The old space size has to be a multiple of Page::kPageSize.
// Sizes are in MB.
static const int kMaxOldSpaceSizeLowMemoryDevice = 128 * kPointerMultiplier;
static const int kMaxOldSpaceSizeMediumMemoryDevice =
256 * kPointerMultiplier;
static const int kMaxOldSpaceSizeHighMemoryDevice = 512 * kPointerMultiplier;
static const int kMaxOldSpaceSizeHugeMemoryDevice = 700 * kPointerMultiplier;
// The executable size has to be a multiple of Page::kPageSize.
// Sizes are in MB.
static const int kMaxExecutableSizeLowMemoryDevice = 96 * kPointerMultiplier;
static const int kMaxExecutableSizeMediumMemoryDevice =
192 * kPointerMultiplier;
static const int kMaxExecutableSizeHighMemoryDevice =
256 * kPointerMultiplier;
static const int kMaxExecutableSizeHugeMemoryDevice =
256 * kPointerMultiplier;
intptr_t OldGenerationAllocationLimit(intptr_t old_gen_size,
int freed_global_handles);
// Indicates whether inline bump-pointer allocation has been disabled.
bool inline_allocation_disabled() { return inline_allocation_disabled_; }
// Switch whether inline bump-pointer allocation should be used.
void EnableInlineAllocation();
void DisableInlineAllocation();
// Implements the corresponding V8 API function.
bool IdleNotification(int hint);
// Declare all the root indices. This defines the root list order.
enum RootListIndex {
#define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
#define STRING_INDEX_DECLARATION(name, str) k##name##RootIndex,
// Utility type maps
#define DECLARE_STRUCT_MAP(NAME, Name, name) k##Name##MapRootIndex,
#define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
kStrongRootListLength = kStringTableRootIndex,
kSmiRootsStart = kStringTableRootIndex + 1
STATIC_ASSERT(kUndefinedValueRootIndex ==
STATIC_ASSERT(kNullValueRootIndex == Internals::kNullValueRootIndex);
STATIC_ASSERT(kTrueValueRootIndex == Internals::kTrueValueRootIndex);
STATIC_ASSERT(kFalseValueRootIndex == Internals::kFalseValueRootIndex);
STATIC_ASSERT(kempty_stringRootIndex == Internals::kEmptyStringRootIndex);
// Generated code can embed direct references to non-writable roots if
// they are in new space.
static bool RootCanBeWrittenAfterInitialization(RootListIndex root_index);
// Generated code can treat direct references to this root as constant.
bool RootCanBeTreatedAsConstant(RootListIndex root_index);
Map* MapForFixedTypedArray(ExternalArrayType array_type);
RootListIndex RootIndexForFixedTypedArray(ExternalArrayType array_type);
Map* MapForExternalArrayType(ExternalArrayType array_type);
RootListIndex RootIndexForExternalArrayType(ExternalArrayType array_type);
RootListIndex RootIndexForEmptyExternalArray(ElementsKind kind);
RootListIndex RootIndexForEmptyFixedTypedArray(ElementsKind kind);
ExternalArray* EmptyExternalArrayForMap(Map* map);
FixedTypedArrayBase* EmptyFixedTypedArrayForMap(Map* map);
void RecordStats(HeapStats* stats, bool take_snapshot = false);
// Copy block of memory from src to dst. Size of block should be aligned
// by pointer size.
static inline void CopyBlock(Address dst, Address src, int byte_size);
// Optimized version of memmove for blocks with pointer size aligned sizes and
// pointer size aligned addresses.
static inline void MoveBlock(Address dst, Address src, int byte_size);
// Check new space expansion criteria and expand semispaces if it was hit.
void CheckNewSpaceExpansionCriteria();
inline void IncrementPromotedObjectsSize(int object_size) {
DCHECK(object_size > 0);
promoted_objects_size_ += object_size;
inline void IncrementSemiSpaceCopiedObjectSize(int object_size) {
DCHECK(object_size > 0);
semi_space_copied_object_size_ += object_size;
inline void IncrementNodesDiedInNewSpace() { nodes_died_in_new_space_++; }
inline void IncrementNodesCopiedInNewSpace() { nodes_copied_in_new_space_++; }
inline void IncrementNodesPromoted() { nodes_promoted_++; }
inline void IncrementYoungSurvivorsCounter(int survived) {
DCHECK(survived >= 0);
survived_since_last_expansion_ += survived;
inline bool NextGCIsLikelyToBeFull() {
if (FLAG_gc_global) return true;
if (FLAG_stress_compaction && (gc_count_ & 1) != 0) return true;
intptr_t adjusted_allocation_limit =
old_generation_allocation_limit_ - new_space_.Capacity();
if (PromotedTotalSize() >= adjusted_allocation_limit) return true;
return false;
void UpdateNewSpaceReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func);
void UpdateReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func);
void ProcessWeakReferences(WeakObjectRetainer* retainer);
void VisitExternalResources(v8::ExternalResourceVisitor* visitor);
// An object should be promoted if the object has survived a
// scavenge operation.
inline bool ShouldBePromoted(Address old_address, int object_size);
void ClearJSFunctionResultCaches();
void ClearNormalizedMapCaches();
GCTracer* tracer() { return &tracer_; }
// Returns the size of objects residing in non new spaces.
intptr_t PromotedSpaceSizeOfObjects();
double total_regexp_code_generated() { return total_regexp_code_generated_; }
void IncreaseTotalRegexpCodeGenerated(int size) {
total_regexp_code_generated_ += size;
void IncrementCodeGeneratedBytes(bool is_crankshafted, int size) {
if (is_crankshafted) {
crankshaft_codegen_bytes_generated_ += size;
} else {
full_codegen_bytes_generated_ += size;
// Update GC statistics that are tracked on the Heap.
void UpdateCumulativeGCStatistics(double duration, double spent_in_mutator,
double marking_time);
// Returns maximum GC pause.
double get_max_gc_pause() { return max_gc_pause_; }
// Returns maximum size of objects alive after GC.
intptr_t get_max_alive_after_gc() { return max_alive_after_gc_; }
// Returns minimal interval between two subsequent collections.
double get_min_in_mutator() { return min_in_mutator_; }
MarkCompactCollector* mark_compact_collector() {
return &mark_compact_collector_;
StoreBuffer* store_buffer() { return &store_buffer_; }
Marking* marking() { return &marking_; }
IncrementalMarking* incremental_marking() { return &incremental_marking_; }
ExternalStringTable* external_string_table() {
return &external_string_table_;
// Returns the current sweep generation.
int sweep_generation() { return sweep_generation_; }
inline Isolate* isolate();
void CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags);
void CallGCEpilogueCallbacks(GCType gc_type, GCCallbackFlags flags);
inline bool OldGenerationAllocationLimitReached();
inline void DoScavengeObject(Map* map, HeapObject** slot, HeapObject* obj) {
scavenging_visitors_table_.GetVisitor(map)(map, slot, obj);
void QueueMemoryChunkForFree(MemoryChunk* chunk);
void FreeQueuedChunks();
int gc_count() const { return gc_count_; }
// Completely clear the Instanceof cache (to stop it keeping objects alive
// around a GC).
inline void CompletelyClearInstanceofCache();
// The roots that have an index less than this are always in old space.
static const int kOldSpaceRoots = 0x20;
uint32_t HashSeed() {
uint32_t seed = static_cast<uint32_t>(hash_seed()->value());
DCHECK(FLAG_randomize_hashes || seed == 0);
return seed;
void SetArgumentsAdaptorDeoptPCOffset(int pc_offset) {
DCHECK(arguments_adaptor_deopt_pc_offset() == Smi::FromInt(0));
void SetConstructStubDeoptPCOffset(int pc_offset) {
DCHECK(construct_stub_deopt_pc_offset() == Smi::FromInt(0));
void SetGetterStubDeoptPCOffset(int pc_offset) {
DCHECK(getter_stub_deopt_pc_offset() == Smi::FromInt(0));
void SetSetterStubDeoptPCOffset(int pc_offset) {
DCHECK(setter_stub_deopt_pc_offset() == Smi::FromInt(0));
// For post mortem debugging.
void RememberUnmappedPage(Address page, bool compacted);
// Global inline caching age: it is incremented on some GCs after context
// disposal. We use it to flush inline caches.
int global_ic_age() { return global_ic_age_; }
void AgeInlineCaches() {
global_ic_age_ = (global_ic_age_ + 1) & SharedFunctionInfo::ICAgeBits::kMax;
bool flush_monomorphic_ics() { return flush_monomorphic_ics_; }
int64_t amount_of_external_allocated_memory() {
return amount_of_external_allocated_memory_;
void DeoptMarkedAllocationSites();
bool MaximumSizeScavenge() { return maximum_size_scavenges_ > 0; }
bool DeoptMaybeTenuredAllocationSites() {
return new_space_.IsAtMaximumCapacity() && maximum_size_scavenges_ == 0;
// ObjectStats are kept in two arrays, counts and sizes. Related stats are
// stored in a contiguous linear buffer. Stats groups are stored one after
// another.
enum {
void RecordObjectStats(InstanceType type, size_t size) {
object_sizes_[type] += size;
void RecordCodeSubTypeStats(int code_sub_type, int code_age, size_t size) {
int code_sub_type_index = FIRST_CODE_KIND_SUB_TYPE + code_sub_type;
int code_age_index =
FIRST_CODE_AGE_SUB_TYPE + code_age - Code::kFirstCodeAge;
DCHECK(code_sub_type_index >= FIRST_CODE_KIND_SUB_TYPE &&
code_sub_type_index < FIRST_CODE_AGE_SUB_TYPE);
DCHECK(code_age_index >= FIRST_CODE_AGE_SUB_TYPE &&
code_age_index < OBJECT_STATS_COUNT);
object_sizes_[code_sub_type_index] += size;
object_sizes_[code_age_index] += size;
void RecordFixedArraySubTypeStats(int array_sub_type, size_t size) {
object_counts_[FIRST_FIXED_ARRAY_SUB_TYPE + array_sub_type]++;
object_sizes_[FIRST_FIXED_ARRAY_SUB_TYPE + array_sub_type] += size;
void CheckpointObjectStats();
// We don't use a LockGuard here since we want to lock the heap
// only when FLAG_concurrent_recompilation is true.
class RelocationLock {
explicit RelocationLock(Heap* heap) : heap_(heap) {
~RelocationLock() { heap_->relocation_mutex_.Unlock(); }
Heap* heap_;
void AddWeakObjectToCodeDependency(Handle<Object> obj,
Handle<DependentCode> dep);
DependentCode* LookupWeakObjectToCodeDependency(Handle<Object> obj);
void InitializeWeakObjectToCodeTable() {
void EnsureWeakObjectToCodeTable();
static void FatalProcessOutOfMemory(const char* location,
bool take_snapshot = false);
// This event is triggered after successful allocation of a new object made
// by runtime. Allocations of target space for object evacuation do not
// trigger the event. In order to track ALL allocations one must turn off
// FLAG_inline_new and FLAG_use_allocation_folding.
inline void OnAllocationEvent(HeapObject* object, int size_in_bytes);
// This event is triggered after object is moved to a new place.
inline void OnMoveEvent(HeapObject* target, HeapObject* source,
int size_in_bytes);
// Methods made available to tests.
// Allocates a JS Map in the heap.
MUST_USE_RESULT AllocationResult
AllocateMap(InstanceType instance_type, int instance_size,
ElementsKind elements_kind = TERMINAL_FAST_ELEMENTS_KIND);
// Allocates and initializes a new JavaScript object based on a
// constructor.
// If allocation_site is non-null, then a memento is emitted after the object
// that points to the site.
MUST_USE_RESULT AllocationResult
AllocateJSObject(JSFunction* constructor,
PretenureFlag pretenure = NOT_TENURED,
AllocationSite* allocation_site = NULL);
// Allocates and initializes a new JavaScript object based on a map.
// Passing an allocation site means that a memento will be created that
// points to the site.
MUST_USE_RESULT AllocationResult
AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure = NOT_TENURED,
bool alloc_props = true,
AllocationSite* allocation_site = NULL);
// Allocated a HeapNumber from value.
MUST_USE_RESULT AllocationResult
AllocateHeapNumber(double value, MutableMode mode = IMMUTABLE,
PretenureFlag pretenure = NOT_TENURED);
// Allocate a byte array of the specified length
MUST_USE_RESULT AllocationResult
AllocateByteArray(int length, PretenureFlag pretenure = NOT_TENURED);
// Copy the code and scope info part of the code object, but insert
// the provided data as the relocation information.
MUST_USE_RESULT AllocationResult
CopyCode(Code* code, Vector<byte> reloc_info);
MUST_USE_RESULT AllocationResult CopyCode(Code* code);
// Allocates a fixed array initialized with undefined values
MUST_USE_RESULT AllocationResult
AllocateFixedArray(int length, PretenureFlag pretenure = NOT_TENURED);
// The amount of external memory registered through the API kept alive
// by global handles
int64_t amount_of_external_allocated_memory_;
// Caches the amount of external memory registered at the last global gc.
int64_t amount_of_external_allocated_memory_at_last_global_gc_;
// This can be calculated directly from a pointer to the heap; however, it is
// more expedient to get at the isolate directly from within Heap methods.
Isolate* isolate_;
Object* roots_[kRootListLength];
size_t code_range_size_;
int reserved_semispace_size_;
int max_semi_space_size_;
int initial_semispace_size_;
intptr_t max_old_generation_size_;
intptr_t max_executable_size_;
intptr_t maximum_committed_;
// For keeping track of how much data has survived
// scavenge since last new space expansion.
int survived_since_last_expansion_;
// For keeping track on when to flush RegExp code.
int sweep_generation_;
int always_allocate_scope_depth_;
// For keeping track of context disposals.
int contexts_disposed_;
int global_ic_age_;
bool flush_monomorphic_ics_;
int scan_on_scavenge_pages_;
NewSpace new_space_;
OldSpace* old_pointer_space_;
OldSpace* old_data_space_;
OldSpace* code_space_;
MapSpace* map_space_;
CellSpace* cell_space_;
PropertyCellSpace* property_cell_space_;
LargeObjectSpace* lo_space_;
HeapState gc_state_;
int gc_post_processing_depth_;
Address new_space_top_after_last_gc_;
// Returns the amount of external memory registered since last global gc.
int64_t PromotedExternalMemorySize();
// How many "runtime allocations" happened.
uint32_t allocations_count_;
// Running hash over allocations performed.
uint32_t raw_allocations_hash_;
// Countdown counter, dumps allocation hash when 0.
uint32_t dump_allocations_hash_countdown_;
// How many mark-sweep collections happened.
unsigned int ms_count_;
// How many gc happened.
unsigned int gc_count_;
// For post mortem debugging.
static const int kRememberedUnmappedPages = 128;
int remembered_unmapped_pages_index_;
Address remembered_unmapped_pages_[kRememberedUnmappedPages];
// Total length of the strings we failed to flatten since the last GC.
int unflattened_strings_length_;
#define ROOT_ACCESSOR(type, name, camel_name) \
inline void set_##name(type* value) { \
/* The deserializer makes use of the fact that these common roots are */ \
/* never in new space and never on a page that is being compacted. */ \
DCHECK(k##camel_name##RootIndex >= kOldSpaceRoots || !InNewSpace(value)); \
roots_[k##camel_name##RootIndex] = value; \
#ifdef DEBUG
// If the --gc-interval flag is set to a positive value, this
// variable holds the value indicating the number of allocations
// remain until the next failure and garbage collection.
int allocation_timeout_;
#endif // DEBUG
// Limit that triggers a global GC on the next (normally caused) GC. This
// is checked when we have already decided to do a GC to help determine
// which collector to invoke, before expanding a paged space in the old
// generation and on every allocation in large object space.
intptr_t old_generation_allocation_limit_;
// Indicates that an allocation has failed in the old generation since the
// last GC.
bool old_gen_exhausted_;
// Indicates that inline bump-pointer allocation has been globally disabled
// for all spaces. This is used to disable allocations in generated code.
bool inline_allocation_disabled_;
// Weak list heads, threaded through the objects.
// List heads are initilized lazily and contain the undefined_value at start.
Object* native_contexts_list_;
Object* array_buffers_list_;
Object* allocation_sites_list_;
// WeakHashTable that maps objects embedded in optimized code to dependent
// code list. It is initilized lazily and contains the undefined_value at
// start.
Object* weak_object_to_code_table_;
// List of encountered weak collections (JSWeakMap and JSWeakSet) during
// marking. It is initialized during marking, destroyed after marking and
// contains Smi(0) while marking is not active.
Object* encountered_weak_collections_;
StoreBufferRebuilder store_buffer_rebuilder_;
struct StringTypeTable {
InstanceType type;
int size;
RootListIndex index;
struct ConstantStringTable {
const char* contents;
RootListIndex index;
struct StructTable {
InstanceType type;
int size;
RootListIndex index;
static const StringTypeTable string_type_table[];
static const ConstantStringTable constant_string_table[];
static const StructTable struct_table[];
// The special hidden string which is an empty string, but does not match
// any string when looked up in properties.
String* hidden_string_;
// GC callback function, called before and after mark-compact GC.
// Allocations in the callback function are disallowed.
struct GCPrologueCallbackPair {
GCPrologueCallbackPair(v8::Isolate::GCPrologueCallback callback,
GCType gc_type, bool pass_isolate)
: callback(callback), gc_type(gc_type), pass_isolate_(pass_isolate) {}
bool operator==(const GCPrologueCallbackPair& pair) const {
return pair.callback == callback;
v8::Isolate::GCPrologueCallback callback;
GCType gc_type;
// TODO(dcarney): remove variable
bool pass_isolate_;
List<GCPrologueCallbackPair> gc_prologue_callbacks_;
struct GCEpilogueCallbackPair {
GCEpilogueCallbackPair(v8::Isolate::GCPrologueCallback callback,
GCType gc_type, bool pass_isolate)
: callback(callback), gc_type(gc_type), pass_isolate_(pass_isolate) {}
bool operator==(const GCEpilogueCallbackPair& pair) const {
return pair.callback == callback;
v8::Isolate::GCPrologueCallback callback;
GCType gc_type;
// TODO(dcarney): remove variable
bool pass_isolate_;
List<GCEpilogueCallbackPair> gc_epilogue_callbacks_;
// Support for computing object sizes during GC.
HeapObjectCallback gc_safe_size_of_old_object_;
static int GcSafeSizeOfOldObject(HeapObject* object);
// Update the GC state. Called from the mark-compact collector.
void MarkMapPointersAsEncoded(bool encoded) {
gc_safe_size_of_old_object_ = &GcSafeSizeOfOldObject;
// Code that should be run before and after each GC. Includes some
// reporting/verification activities when compiled with DEBUG set.
void GarbageCollectionPrologue();
void GarbageCollectionEpilogue();
// Pretenuring decisions are made based on feedback collected during new
// space evacuation. Note that between feedback collection and calling this
// method object in old space must not move.
// Right now we only process pretenuring feedback in high promotion mode.
void ProcessPretenuringFeedback();
// Checks whether a global GC is necessary
GarbageCollector SelectGarbageCollector(AllocationSpace space,
const char** reason);
// Make sure there is a filler value behind the top of the new space
// so that the GC does not confuse some unintialized/stale memory
// with the allocation memento of the object at the top
void EnsureFillerObjectAtTop();
// Ensure that we have swept all spaces in such a way that we can iterate
// over all objects. May cause a GC.
void MakeHeapIterable();
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
bool CollectGarbage(
GarbageCollector collector, const char* gc_reason,
const char* collector_reason,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
// Performs garbage collection
// Returns whether there is a chance another major GC could
// collect more garbage.
bool PerformGarbageCollection(
GarbageCollector collector,
const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
inline void UpdateOldSpaceLimits();
// Selects the proper allocation space depending on the given object
// size, pretenuring decision, and preferred old-space.
static AllocationSpace SelectSpace(int object_size,
AllocationSpace preferred_old_space,
PretenureFlag pretenure) {
DCHECK(preferred_old_space == OLD_POINTER_SPACE ||
preferred_old_space == OLD_DATA_SPACE);
if (object_size > Page::kMaxRegularHeapObjectSize) return LO_SPACE;
return (pretenure == TENURED) ? preferred_old_space : NEW_SPACE;
// Allocate an uninitialized object. The memory is non-executable if the
// hardware and OS allow. This is the single choke-point for allocations
// performed by the runtime and should not be bypassed (to extend this to
// inlined allocations, use the Heap::DisableInlineAllocation() support).
MUST_USE_RESULT inline AllocationResult AllocateRaw(
int size_in_bytes, AllocationSpace space, AllocationSpace retry_space);
// Allocates a heap object based on the map.
MUST_USE_RESULT AllocationResult
Allocate(Map* map, AllocationSpace space,
AllocationSite* allocation_site = NULL);
// Allocates a partial map for bootstrapping.
MUST_USE_RESULT AllocationResult
AllocatePartialMap(InstanceType instance_type, int instance_size);
// Initializes a JSObject based on its map.
void InitializeJSObjectFromMap(JSObject* obj, FixedArray* properties,
Map* map);
void InitializeAllocationMemento(AllocationMemento* memento,
AllocationSite* allocation_site);
// Allocate a block of memory in the given space (filled with a filler).
// Used as a fall-back for generated code when the space is full.
MUST_USE_RESULT AllocationResult
AllocateFillerObject(int size, bool double_align, AllocationSpace space);
// Allocate an uninitialized fixed array.
MUST_USE_RESULT AllocationResult
AllocateRawFixedArray(int length, PretenureFlag pretenure);
// Allocate an uninitialized fixed double array.
MUST_USE_RESULT AllocationResult
AllocateRawFixedDoubleArray(int length, PretenureFlag pretenure);
// Allocate an initialized fixed array with the given filler value.
MUST_USE_RESULT AllocationResult
AllocateFixedArrayWithFiller(int length, PretenureFlag pretenure,
Object* filler);
// Allocate and partially initializes a String. There are two String
// encodings: ASCII and two byte. These functions allocate a string of the
// given length and set its map and length fields. The characters of the
// string are uninitialized.
MUST_USE_RESULT AllocationResult
AllocateRawOneByteString(int length, PretenureFlag pretenure);
MUST_USE_RESULT AllocationResult
AllocateRawTwoByteString(int length, PretenureFlag pretenure);
bool CreateInitialMaps();
void CreateInitialObjects();
// Allocates an internalized string in old space based on the character
// stream.
MUST_USE_RESULT inline AllocationResult AllocateInternalizedStringFromUtf8(
Vector<const char> str, int chars, uint32_t hash_field);
MUST_USE_RESULT inline AllocationResult AllocateOneByteInternalizedString(
Vector<const uint8_t> str, uint32_t hash_field);
MUST_USE_RESULT inline AllocationResult AllocateTwoByteInternalizedString(
Vector<const uc16> str, uint32_t hash_field);
template <bool is_one_byte, typename T>
MUST_USE_RESULT AllocationResult
AllocateInternalizedStringImpl(T t, int chars, uint32_t hash_field);
template <typename T>
MUST_USE_RESULT inline AllocationResult AllocateInternalizedStringImpl(
T t, int chars, uint32_t hash_field);
// Allocates an uninitialized fixed array. It must be filled by the caller.
MUST_USE_RESULT AllocationResult AllocateUninitializedFixedArray(int length);
// Make a copy of src and return it. Returns
// Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
MUST_USE_RESULT inline AllocationResult CopyFixedArray(FixedArray* src);
// Make a copy of src, set the map, and return the copy. Returns
// Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
MUST_USE_RESULT AllocationResult
CopyFixedArrayWithMap(FixedArray* src, Map* map);
// Make a copy of src and return it. Returns
// Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
MUST_USE_RESULT inline AllocationResult CopyFixedDoubleArray(
FixedDoubleArray* src);
// Make a copy of src and return it. Returns
// Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
MUST_USE_RESULT inline AllocationResult CopyConstantPoolArray(
ConstantPoolArray* src);
// Computes a single character string where the character has code.
// A cache is used for ASCII codes.
MUST_USE_RESULT AllocationResult
LookupSingleCharacterStringFromCode(uint16_t code);
// Allocate a symbol in old space.
MUST_USE_RESULT AllocationResult AllocateSymbol();
// Make a copy of src, set the map, and return the copy.
MUST_USE_RESULT AllocationResult
CopyConstantPoolArrayWithMap(ConstantPoolArray* src, Map* map);
MUST_USE_RESULT AllocationResult AllocateConstantPoolArray(
const ConstantPoolArray::NumberOfEntries& small);
MUST_USE_RESULT AllocationResult AllocateExtendedConstantPoolArray(
const ConstantPoolArray::NumberOfEntries& small,
const ConstantPoolArray::NumberOfEntries& extended);
// Allocates an external array of the specified length and type.
MUST_USE_RESULT AllocationResult
AllocateExternalArray(int length, ExternalArrayType array_type,
void* external_pointer, PretenureFlag pretenure);
// Allocates a fixed typed array of the specified length and type.
MUST_USE_RESULT AllocationResult
AllocateFixedTypedArray(int length, ExternalArrayType array_type,
PretenureFlag pretenure);
// Make a copy of src and return it.
MUST_USE_RESULT AllocationResult CopyAndTenureFixedCOWArray(FixedArray* src);
// Make a copy of src, set the map, and return the copy.
MUST_USE_RESULT AllocationResult
CopyFixedDoubleArrayWithMap(FixedDoubleArray* src, Map* map);
// Allocates a fixed double array with uninitialized values. Returns
MUST_USE_RESULT AllocationResult AllocateUninitializedFixedDoubleArray(
int length, PretenureFlag pretenure = NOT_TENURED);
// These five Create*EntryStub functions are here and forced to not be inlined
// because of a gcc-4.4 bug that assigns wrong vtable entries.
NO_INLINE(void CreateJSEntryStub());
NO_INLINE(void CreateJSConstructEntryStub());
void CreateFixedStubs();
// Allocate empty fixed array.
MUST_USE_RESULT AllocationResult AllocateEmptyFixedArray();
// Allocate empty external array of given type.
MUST_USE_RESULT AllocationResult
AllocateEmptyExternalArray(ExternalArrayType array_type);
// Allocate empty fixed typed array of given type.
MUST_USE_RESULT AllocationResult
AllocateEmptyFixedTypedArray(ExternalArrayType array_type);
// Allocate empty constant pool array.
MUST_USE_RESULT AllocationResult AllocateEmptyConstantPoolArray();
// Allocate a tenured simple cell.
MUST_USE_RESULT AllocationResult AllocateCell(Object* value);
// Allocate a tenured JS global property cell initialized with the hole.
MUST_USE_RESULT AllocationResult AllocatePropertyCell();
// Allocates a new utility object in the old generation.
MUST_USE_RESULT AllocationResult AllocateStruct(InstanceType type);
// Allocates a new foreign object.
MUST_USE_RESULT AllocationResult
AllocateForeign(Address address, PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT AllocationResult
AllocateCode(int object_size, bool immovable);
MUST_USE_RESULT AllocationResult InternalizeStringWithKey(HashTableKey* key);
MUST_USE_RESULT AllocationResult InternalizeString(String* str);
// Performs a minor collection in new generation.
void Scavenge();
// Commits from space if it is uncommitted.
void EnsureFromSpaceIsCommitted();
// Uncommit unused semi space.
bool UncommitFromSpace() { return new_space_.UncommitFromSpace(); }
// Fill in bogus values in from space
void ZapFromSpace();
static String* UpdateNewSpaceReferenceInExternalStringTableEntry(
Heap* heap, Object** pointer);
Address DoScavenge(ObjectVisitor* scavenge_visitor, Address new_space_front);
static void ScavengeStoreBufferCallback(Heap* heap, MemoryChunk* page,
StoreBufferEvent event);
// Performs a major collection in the whole heap.
void MarkCompact();
// Code to be run before and after mark-compact.
void MarkCompactPrologue();
void ProcessNativeContexts(WeakObjectRetainer* retainer);
void ProcessArrayBuffers(WeakObjectRetainer* retainer);
void ProcessAllocationSites(WeakObjectRetainer* retainer);
// Deopts all code that contains allocation instruction which are tenured or
// not tenured. Moreover it clears the pretenuring allocation site statistics.
void ResetAllAllocationSitesDependentCode(PretenureFlag flag);
// Evaluates local pretenuring for the old space and calls
// ResetAllTenuredAllocationSitesDependentCode if too many objects died in
// the old space.
void EvaluateOldSpaceLocalPretenuring(uint64_t size_of_objects_before_gc);
// Called on heap tear-down.
void TearDownArrayBuffers();
// Record statistics before and after garbage collection.
void ReportStatisticsBeforeGC();
void ReportStatisticsAfterGC();
// Slow part of scavenge object.
static void ScavengeObjectSlow(HeapObject** p, HeapObject* object);
// Total RegExp code ever generated
double total_regexp_code_generated_;
GCTracer tracer_;
// Creates and installs the full-sized number string cache.
int FullSizeNumberStringCacheLength();
// Flush the number to string cache.
void FlushNumberStringCache();
// Sets used allocation sites entries to undefined.
void FlushAllocationSitesScratchpad();
// Initializes the allocation sites scratchpad with undefined values.
void InitializeAllocationSitesScratchpad();
// Adds an allocation site to the scratchpad if there is space left.
void AddAllocationSiteToScratchpad(AllocationSite* site,
ScratchpadSlotMode mode);
void UpdateSurvivalStatistics(int start_new_space_size);
static const int kYoungSurvivalRateHighThreshold = 90;
static const int kYoungSurvivalRateAllowedDeviation = 15;
static const int kOldSurvivalRateLowThreshold = 10;
int high_survival_rate_period_length_;
intptr_t promoted_objects_size_;
double promotion_rate_;
intptr_t semi_space_copied_object_size_;
double semi_space_copied_rate_;
int nodes_died_in_new_space_;
int nodes_copied_in_new_space_;
int nodes_promoted_;
// This is the pretenuring trigger for allocation sites that are in maybe
// tenure state. When we switched to the maximum new space size we deoptimize
// the code that belongs to the allocation site and derive the lifetime
// of the allocation site.
unsigned int maximum_size_scavenges_;
// TODO(hpayer): Allocation site pretenuring may make this method obsolete.
// Re-visit incremental marking heuristics.
bool IsHighSurvivalRate() { return high_survival_rate_period_length_ > 0; }
void SelectScavengingVisitorsTable();
void StartIdleRound() { mark_sweeps_since_idle_round_started_ = 0; }
void FinishIdleRound() {
mark_sweeps_since_idle_round_started_ = kMaxMarkSweepsInIdleRound;
scavenges_since_last_idle_round_ = 0;
bool EnoughGarbageSinceLastIdleRound() {
return (scavenges_since_last_idle_round_ >= kIdleScavengeThreshold);
// Estimates how many milliseconds a Mark-Sweep would take to complete.
// In idle notification handler we assume that this function will return:
// - a number less than 10 for small heaps, which are less than 8Mb.
// - a number greater than 10 for large heaps, which are greater than 32Mb.
int TimeMarkSweepWouldTakeInMs() {
// Rough estimate of how many megabytes of heap can be processed in 1 ms.
static const int kMbPerMs = 2;
int heap_size_mb = static_cast<int>(SizeOfObjects() / MB);
return heap_size_mb / kMbPerMs;
void AdvanceIdleIncrementalMarking(intptr_t step_size);
void ClearObjectStats(bool clear_last_time_stats = false);
void set_weak_object_to_code_table(Object* value) {
weak_object_to_code_table_ = value;
Object** weak_object_to_code_table_address() {
return &weak_object_to_code_table_;
inline void UpdateAllocationsHash(HeapObject* object);
inline void UpdateAllocationsHash(uint32_t value);
inline void PrintAlloctionsHash();
static const int kInitialStringTableSize = 2048;
static const int kInitialEvalCacheSize = 64;
static const int kInitialNumberStringCacheSize = 256;
// Object counts and used memory by InstanceType
size_t object_counts_[OBJECT_STATS_COUNT];
size_t object_counts_last_time_[OBJECT_STATS_COUNT];
size_t object_sizes_[OBJECT_STATS_COUNT];
size_t object_sizes_last_time_[OBJECT_STATS_COUNT];
// Maximum GC pause.
double max_gc_pause_;
// Total time spent in GC.
double total_gc_time_ms_;
// Maximum size of objects alive after GC.
intptr_t max_alive_after_gc_;
// Minimal interval between two subsequent collections.
double min_in_mutator_;
// Cumulative GC time spent in marking
double marking_time_;
// Cumulative GC time spent in sweeping
double sweeping_time_;
MarkCompactCollector mark_compact_collector_;
StoreBuffer store_buffer_;
Marking marking_;
IncrementalMarking incremental_marking_;
int number_idle_notifications_;
unsigned int last_idle_notification_gc_count_;
bool last_idle_notification_gc_count_init_;
int mark_sweeps_since_idle_round_started_;
unsigned int gc_count_at_last_idle_gc_;
int scavenges_since_last_idle_round_;
// These two counters are monotomically increasing and never reset.
size_t full_codegen_bytes_generated_;
size_t crankshaft_codegen_bytes_generated_;
// If the --deopt_every_n_garbage_collections flag is set to a positive value,
// this variable holds the number of garbage collections since the last
// deoptimization triggered by garbage collection.
int gcs_since_last_deopt_;
int no_weak_object_verification_scope_depth_;
static const int kAllocationSiteScratchpadSize = 256;
int allocation_sites_scratchpad_length_;
static const int kMaxMarkSweepsInIdleRound = 7;
static const int kIdleScavengeThreshold = 5;
// Shared state read by the scavenge collector and set by ScavengeObject.
PromotionQueue promotion_queue_;
// Flag is set when the heap has been configured. The heap can be repeatedly
// configured through the API until it is set up.
bool configured_;
ExternalStringTable external_string_table_;
VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
MemoryChunk* chunks_queued_for_free_;
base::Mutex relocation_mutex_;
int gc_callbacks_depth_;
friend class AlwaysAllocateScope;
friend class Factory;
friend class GCCallbacksScope;
friend class GCTracer;
friend class HeapIterator;
friend class Isolate;
friend class MarkCompactCollector;
friend class MarkCompactMarkingVisitor;
friend class MapCompact;
friend class NoWeakObjectVerificationScope;
friend class Page;
class HeapStats {
static const int kStartMarker = 0xDECADE00;
static const int kEndMarker = 0xDECADE01;
int* start_marker; // 0
int* new_space_size; // 1
int* new_space_capacity; // 2
intptr_t* old_pointer_space_size; // 3
intptr_t* old_pointer_space_capacity; // 4
intptr_t* old_data_space_size; // 5
intptr_t* old_data_space_capacity; // 6
intptr_t* code_space_size; // 7
intptr_t* code_space_capacity; // 8
intptr_t* map_space_size; // 9
intptr_t* map_space_capacity; // 10
intptr_t* cell_space_size; // 11
intptr_t* cell_space_capacity; // 12
intptr_t* lo_space_size; // 13
int* global_handle_count; // 14
int* weak_global_handle_count; // 15
int* pending_global_handle_count; // 16
int* near_death_global_handle_count; // 17
int* free_global_handle_count; // 18
intptr_t* memory_allocator_size; // 19
intptr_t* memory_allocator_capacity; // 20
int* objects_per_type; // 21
int* size_per_type; // 22
int* os_error; // 23
int* end_marker; // 24
intptr_t* property_cell_space_size; // 25
intptr_t* property_cell_space_capacity; // 26
class AlwaysAllocateScope {
explicit inline AlwaysAllocateScope(Isolate* isolate);
inline ~AlwaysAllocateScope();
// Implicitly disable artificial allocation failures.
Heap* heap_;
DisallowAllocationFailure daf_;
class NoWeakObjectVerificationScope {
inline NoWeakObjectVerificationScope();
inline ~NoWeakObjectVerificationScope();
class GCCallbacksScope {
explicit inline GCCallbacksScope(Heap* heap);
inline ~GCCallbacksScope();
inline bool CheckReenter();
Heap* heap_;
// Visitor class to verify interior pointers in spaces that do not contain
// or care about intergenerational references. All heap object pointers have to
// point into the heap to a location that has a map pointer at its first word.
// Caveat: Heap::Contains is an approximation because it can return true for
// objects in a heap space but above the allocation pointer.
class VerifyPointersVisitor : public ObjectVisitor {
inline void VisitPointers(Object** start, Object** end);
// Verify that all objects are Smis.
class VerifySmisVisitor : public ObjectVisitor {
inline void VisitPointers(Object** start, Object** end);
// Space iterator for iterating over all spaces of the heap. Returns each space
// in turn, and null when it is done.
class AllSpaces BASE_EMBEDDED {
explicit AllSpaces(Heap* heap) : heap_(heap), counter_(FIRST_SPACE) {}
Space* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all old spaces of the heap: Old pointer
// space, old data space and code space. Returns each space in turn, and null
// when it is done.
class OldSpaces BASE_EMBEDDED {
explicit OldSpaces(Heap* heap) : heap_(heap), counter_(OLD_POINTER_SPACE) {}
OldSpace* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all the paged spaces of the heap: Map
// space, old pointer space, old data space, code space and cell space. Returns
// each space in turn, and null when it is done.
class PagedSpaces BASE_EMBEDDED {
explicit PagedSpaces(Heap* heap) : heap_(heap), counter_(OLD_POINTER_SPACE) {}
PagedSpace* next();
Heap* heap_;
int counter_;
// Space iterator for iterating over all spaces of the heap.
// For each space an object iterator is provided. The deallocation of the
// returned object iterators is handled by the space iterator.
class SpaceIterator : public Malloced {
explicit SpaceIterator(Heap* heap);
SpaceIterator(Heap* heap, HeapObjectCallback size_func);
virtual ~SpaceIterator();
bool has_next();
ObjectIterator* next();
ObjectIterator* CreateIterator();
Heap* heap_;
int current_space_; // from enum AllocationSpace.
ObjectIterator* iterator_; // object iterator for the current space.
HeapObjectCallback size_func_;
// A HeapIterator provides iteration over the whole heap. It
// aggregates the specific iterators for the different spaces as
// these can only iterate over one space only.
// HeapIterator ensures there is no allocation during its lifetime
// (using an embedded DisallowHeapAllocation instance).
// HeapIterator can skip free list nodes (that is, de-allocated heap
// objects that still remain in the heap). As implementation of free
// nodes filtering uses GC marks, it can't be used during MS/MC GC
// phases. Also, it is forbidden to interrupt iteration in this mode,
// as this will leave heap objects marked (and thus, unusable).
class HeapObjectsFilter;
class HeapIterator BASE_EMBEDDED {
enum HeapObjectsFiltering { kNoFiltering, kFilterUnreachable };
explicit HeapIterator(Heap* heap);
HeapIterator(Heap* heap, HeapObjectsFiltering filtering);
HeapObject* next();
void reset();
struct MakeHeapIterableHelper {
explicit MakeHeapIterableHelper(Heap* heap) { heap->MakeHeapIterable(); }
// Perform the initialization.
void Init();
// Perform all necessary shutdown (destruction) work.
void Shutdown();
HeapObject* NextObject();
MakeHeapIterableHelper make_heap_iterable_helper_;
DisallowHeapAllocation no_heap_allocation_;
Heap* heap_;
HeapObjectsFiltering filtering_;
HeapObjectsFilter* filter_;
// Space iterator for iterating all the spaces.
SpaceIterator* space_iterator_;
// Object iterator for the space currently being iterated.
ObjectIterator* object_iterator_;
// Cache for mapping (map, property name) into field offset.
// Cleared at startup and prior to mark sweep collection.
class KeyedLookupCache {
// Lookup field offset for (map, name). If absent, -1 is returned.
int Lookup(Handle<Map> map, Handle<Name> name);
// Update an element in the cache.
void Update(Handle<Map> map, Handle<Name> name, int field_offset);
// Clear the cache.
void Clear();
static const int kLength = 256;
static const int kCapacityMask = kLength - 1;
static const int kMapHashShift = 5;
static const int kHashMask = -4; // Zero the last two bits.
static const int kEntriesPerBucket = 4;
static const int kEntryLength = 2;
static const int kMapIndex = 0;
static const int kKeyIndex = 1;
static const int kNotFound = -1;
// kEntriesPerBucket should be a power of 2.
STATIC_ASSERT((kEntriesPerBucket & (kEntriesPerBucket - 1)) == 0);
STATIC_ASSERT(kEntriesPerBucket == -kHashMask);
KeyedLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].map = NULL;
keys_[i].name = NULL;
field_offsets_[i] = kNotFound;
static inline int Hash(Handle<Map> map, Handle<Name> name);
// Get the address of the keys and field_offsets arrays. Used in
// generated code to perform cache lookups.
Address keys_address() { return reinterpret_cast<Address>(&keys_); }
Address field_offsets_address() {
return reinterpret_cast<Address>(&field_offsets_);
struct Key {
Map* map;
Name* name;
Key keys_[kLength];
int field_offsets_[kLength];
friend class ExternalReference;
friend class Isolate;
// Cache for mapping (map, property name) into descriptor index.
// The cache contains both positive and negative results.
// Descriptor index equals kNotFound means the property is absent.
// Cleared at startup and prior to any gc.
class DescriptorLookupCache {
// Lookup descriptor index for (map, name).
// If absent, kAbsent is returned.
int Lookup(Map* source, Name* name) {
if (!name->IsUniqueName()) return kAbsent;
int index = Hash(source, name);
Key& key = keys_[index];
if ((key.source == source) && ( == name)) return results_[index];
return kAbsent;
// Update an element in the cache.
void Update(Map* source, Name* name, int result) {
DCHECK(result != kAbsent);
if (name->IsUniqueName()) {
int index = Hash(source, name);
Key& key = keys_[index];
key.source = source; = name;
results_[index] = result;
// Clear the cache.
void Clear();
static const int kAbsent = -2;
DescriptorLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].source = NULL;
keys_[i].name = NULL;
results_[i] = kAbsent;
static int Hash(Object* source, Name* name) {
// Uses only lower 32 bits if pointers are larger.
uint32_t source_hash =
static_cast<uint32_t>(reinterpret_cast<uintptr_t>(source)) >>
uint32_t name_hash =
static_cast<uint32_t>(reinterpret_cast<uintptr_t>(name)) >>
return (source_hash ^ name_hash) % kLength;
static const int kLength = 64;
struct Key {
Map* source;
Name* name;
Key keys_[kLength];
int results_[kLength];
friend class Isolate;
class RegExpResultsCache {
// Attempt to retrieve a cached result. On failure, 0 is returned as a Smi.
// On success, the returned result is guaranteed to be a COW-array.
static Object* Lookup(Heap* heap, String* key_string, Object* key_pattern,
ResultsCacheType type);
// Attempt to add value_array to the cache specified by type. On success,
// value_array is turned into a COW-array.
static void Enter(Isolate* isolate, Handle<String> key_string,
Handle<Object> key_pattern, Handle<FixedArray> value_array,
ResultsCacheType type);
static void Clear(FixedArray* cache);
static const int kRegExpResultsCacheSize = 0x100;
static const int kArrayEntriesPerCacheEntry = 4;
static const int kStringOffset = 0;
static const int kPatternOffset = 1;
static const int kArrayOffset = 2;
// Abstract base class for checking whether a weak object should be retained.
class WeakObjectRetainer {
virtual ~WeakObjectRetainer() {}
// Return whether this object should be retained. If NULL is returned the
// object has no references. Otherwise the address of the retained object
// should be returned as in some GC situations the object has been moved.
virtual Object* RetainAs(Object* object) = 0;
// Intrusive object marking uses least significant bit of
// heap object's map word to mark objects.
// Normally all map words have least significant bit set
// because they contain tagged map pointer.
// If the bit is not set object is marked.
// All objects should be unmarked before resuming
// JavaScript execution.
class IntrusiveMarking {
static bool IsMarked(HeapObject* object) {
return (object->map_word().ToRawValue() & kNotMarkedBit) == 0;
static void ClearMark(HeapObject* object) {
uintptr_t map_word = object->map_word().ToRawValue();
object->set_map_word(MapWord::FromRawValue(map_word | kNotMarkedBit));
static void SetMark(HeapObject* object) {
uintptr_t map_word = object->map_word().ToRawValue();
object->set_map_word(MapWord::FromRawValue(map_word & ~kNotMarkedBit));
static Map* MapOfMarkedObject(HeapObject* object) {
uintptr_t map_word = object->map_word().ToRawValue();
return MapWord::FromRawValue(map_word | kNotMarkedBit).ToMap();
static int SizeOfMarkedObject(HeapObject* object) {
return object->SizeFromMap(MapOfMarkedObject(object));
static const uintptr_t kNotMarkedBit = 0x1;
STATIC_ASSERT((kHeapObjectTag & kNotMarkedBit) != 0); // NOLINT
#ifdef DEBUG
// Helper class for tracing paths to a search target Object from all roots.
// The TracePathFrom() method can be used to trace paths from a specific
// object to the search target object.
class PathTracer : public ObjectVisitor {
enum WhatToFind {
FIND_ALL, // Will find all matches.
FIND_FIRST // Will stop the search after first match.
// Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
static const int kMarkTag = 2;
// For the WhatToFind arg, if FIND_FIRST is specified, tracing will stop
// after the first match. If FIND_ALL is specified, then tracing will be
// done for all matches.
PathTracer(Object* search_target, WhatToFind what_to_find,
VisitMode visit_mode)
: search_target_(search_target),
no_allocation() {}
virtual void VisitPointers(Object** start, Object** end);
void Reset();
void TracePathFrom(Object** root);
bool found() const { return found_target_; }
static Object* const kAnyGlobalObject;
class MarkVisitor;
class UnmarkVisitor;
void MarkRecursively(Object** p, MarkVisitor* mark_visitor);
void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);
virtual void ProcessResults();
Object* search_target_;
bool found_target_;
bool found_target_in_trace_;
WhatToFind what_to_find_;
VisitMode visit_mode_;
List<Object*> object_stack_;
DisallowHeapAllocation no_allocation; // i.e. no gc allowed.
#endif // DEBUG
} // namespace v8::internal
#endif // V8_HEAP_HEAP_H_