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v8/src/heap.h
sgjesse@chromium.org b0fa94777e Refactored PathTracer in heap.cc. 
This is so that it can be reused by LOL code later.

Patch by Mark Lam from Hewlett-Packard Development Company, LP

Review URL: http://codereview.chromium.org/6541044


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6886 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
2011-02-22 10:05:30 +00:00

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// Copyright 2010 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_HEAP_H_
#define V8_HEAP_H_
#include <math.h>
#include "globals.h"
#include "list.h"
#include "spaces.h"
#include "splay-tree-inl.h"
#include "v8-counters.h"
namespace v8 {
namespace internal {
// Defines all the roots in Heap.
#define UNCONDITIONAL_STRONG_ROOT_LIST(V) \
/* Put the byte array map early. We need it to be in place by the time */ \
/* the deserializer hits the next page, since it wants to put a byte */ \
/* array in the unused space at the end of the page. */ \
V(Map, byte_array_map, ByteArrayMap) \
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, stack_limit, StackLimit) \
V(Object, undefined_value, UndefinedValue) \
V(Object, the_hole_value, TheHoleValue) \
V(Object, null_value, NullValue) \
V(Object, true_value, TrueValue) \
V(Object, false_value, FalseValue) \
V(Object, arguments_marker, ArgumentsMarker) \
V(Map, heap_number_map, HeapNumberMap) \
V(Map, global_context_map, GlobalContextMap) \
V(Map, fixed_array_map, FixedArrayMap) \
V(Map, fixed_cow_array_map, FixedCOWArrayMap) \
V(Object, no_interceptor_result_sentinel, NoInterceptorResultSentinel) \
V(Map, meta_map, MetaMap) \
V(Object, termination_exception, TerminationException) \
V(Map, hash_table_map, HashTableMap) \
V(FixedArray, empty_fixed_array, EmptyFixedArray) \
V(ByteArray, empty_byte_array, EmptyByteArray) \
V(Map, string_map, StringMap) \
V(Map, ascii_string_map, AsciiStringMap) \
V(Map, symbol_map, SymbolMap) \
V(Map, ascii_symbol_map, AsciiSymbolMap) \
V(Map, cons_symbol_map, ConsSymbolMap) \
V(Map, cons_ascii_symbol_map, ConsAsciiSymbolMap) \
V(Map, external_symbol_map, ExternalSymbolMap) \
V(Map, external_symbol_with_ascii_data_map, ExternalSymbolWithAsciiDataMap) \
V(Map, external_ascii_symbol_map, ExternalAsciiSymbolMap) \
V(Map, cons_string_map, ConsStringMap) \
V(Map, cons_ascii_string_map, ConsAsciiStringMap) \
V(Map, external_string_map, ExternalStringMap) \
V(Map, external_string_with_ascii_data_map, ExternalStringWithAsciiDataMap) \
V(Map, external_ascii_string_map, ExternalAsciiStringMap) \
V(Map, undetectable_string_map, UndetectableStringMap) \
V(Map, undetectable_ascii_string_map, UndetectableAsciiStringMap) \
V(Map, pixel_array_map, PixelArrayMap) \
V(Map, external_byte_array_map, ExternalByteArrayMap) \
V(Map, external_unsigned_byte_array_map, ExternalUnsignedByteArrayMap) \
V(Map, external_short_array_map, ExternalShortArrayMap) \
V(Map, external_unsigned_short_array_map, ExternalUnsignedShortArrayMap) \
V(Map, external_int_array_map, ExternalIntArrayMap) \
V(Map, external_unsigned_int_array_map, ExternalUnsignedIntArrayMap) \
V(Map, external_float_array_map, ExternalFloatArrayMap) \
V(Map, context_map, ContextMap) \
V(Map, catch_context_map, CatchContextMap) \
V(Map, code_map, CodeMap) \
V(Map, oddball_map, OddballMap) \
V(Map, global_property_cell_map, GlobalPropertyCellMap) \
V(Map, shared_function_info_map, SharedFunctionInfoMap) \
V(Map, message_object_map, JSMessageObjectMap) \
V(Map, proxy_map, ProxyMap) \
V(Object, nan_value, NanValue) \
V(Object, minus_zero_value, MinusZeroValue) \
V(Object, instanceof_cache_function, InstanceofCacheFunction) \
V(Object, instanceof_cache_map, InstanceofCacheMap) \
V(Object, instanceof_cache_answer, InstanceofCacheAnswer) \
V(String, empty_string, EmptyString) \
V(DescriptorArray, empty_descriptor_array, EmptyDescriptorArray) \
V(Map, neander_map, NeanderMap) \
V(JSObject, message_listeners, MessageListeners) \
V(Proxy, prototype_accessors, PrototypeAccessors) \
V(NumberDictionary, code_stubs, CodeStubs) \
V(NumberDictionary, non_monomorphic_cache, NonMonomorphicCache) \
V(Code, js_entry_code, JsEntryCode) \
V(Code, js_construct_entry_code, JsConstructEntryCode) \
V(Code, c_entry_code, CEntryCode) \
V(FixedArray, number_string_cache, NumberStringCache) \
V(FixedArray, single_character_string_cache, SingleCharacterStringCache) \
V(FixedArray, natives_source_cache, NativesSourceCache) \
V(Object, last_script_id, LastScriptId) \
V(Script, empty_script, EmptyScript) \
V(Smi, real_stack_limit, RealStackLimit) \
V(StringDictionary, intrinsic_function_names, IntrinsicFunctionNames) \
#if V8_TARGET_ARCH_ARM && !V8_INTERPRETED_REGEXP
#define STRONG_ROOT_LIST(V) \
UNCONDITIONAL_STRONG_ROOT_LIST(V) \
V(Code, re_c_entry_code, RegExpCEntryCode) \
V(Code, direct_c_entry_code, DirectCEntryCode)
#elif V8_TARGET_ARCH_ARM
#define STRONG_ROOT_LIST(V) \
UNCONDITIONAL_STRONG_ROOT_LIST(V) \
V(Code, direct_c_entry_code, DirectCEntryCode)
#else
#define STRONG_ROOT_LIST(V) UNCONDITIONAL_STRONG_ROOT_LIST(V)
#endif
#define ROOT_LIST(V) \
STRONG_ROOT_LIST(V) \
V(SymbolTable, symbol_table, SymbolTable)
#define SYMBOL_LIST(V) \
V(Array_symbol, "Array") \
V(Object_symbol, "Object") \
V(Proto_symbol, "__proto__") \
V(StringImpl_symbol, "StringImpl") \
V(arguments_symbol, "arguments") \
V(Arguments_symbol, "Arguments") \
V(arguments_shadow_symbol, ".arguments") \
V(call_symbol, "call") \
V(apply_symbol, "apply") \
V(caller_symbol, "caller") \
V(boolean_symbol, "boolean") \
V(Boolean_symbol, "Boolean") \
V(callee_symbol, "callee") \
V(constructor_symbol, "constructor") \
V(code_symbol, ".code") \
V(result_symbol, ".result") \
V(catch_var_symbol, ".catch-var") \
V(empty_symbol, "") \
V(eval_symbol, "eval") \
V(function_symbol, "function") \
V(length_symbol, "length") \
V(name_symbol, "name") \
V(number_symbol, "number") \
V(Number_symbol, "Number") \
V(RegExp_symbol, "RegExp") \
V(source_symbol, "source") \
V(global_symbol, "global") \
V(ignore_case_symbol, "ignoreCase") \
V(multiline_symbol, "multiline") \
V(input_symbol, "input") \
V(index_symbol, "index") \
V(last_index_symbol, "lastIndex") \
V(object_symbol, "object") \
V(prototype_symbol, "prototype") \
V(string_symbol, "string") \
V(String_symbol, "String") \
V(Date_symbol, "Date") \
V(this_symbol, "this") \
V(to_string_symbol, "toString") \
V(char_at_symbol, "CharAt") \
V(undefined_symbol, "undefined") \
V(value_of_symbol, "valueOf") \
V(InitializeVarGlobal_symbol, "InitializeVarGlobal") \
V(InitializeConstGlobal_symbol, "InitializeConstGlobal") \
V(KeyedLoadSpecialized_symbol, "KeyedLoadSpecialized") \
V(KeyedStoreSpecialized_symbol, "KeyedStoreSpecialized") \
V(KeyedLoadPixelArray_symbol, "KeyedLoadPixelArray") \
V(KeyedStorePixelArray_symbol, "KeyedStorePixelArray") \
V(stack_overflow_symbol, "kStackOverflowBoilerplate") \
V(illegal_access_symbol, "illegal access") \
V(out_of_memory_symbol, "out-of-memory") \
V(illegal_execution_state_symbol, "illegal execution state") \
V(get_symbol, "get") \
V(set_symbol, "set") \
V(function_class_symbol, "Function") \
V(illegal_argument_symbol, "illegal argument") \
V(MakeReferenceError_symbol, "MakeReferenceError") \
V(MakeSyntaxError_symbol, "MakeSyntaxError") \
V(MakeTypeError_symbol, "MakeTypeError") \
V(invalid_lhs_in_assignment_symbol, "invalid_lhs_in_assignment") \
V(invalid_lhs_in_for_in_symbol, "invalid_lhs_in_for_in") \
V(invalid_lhs_in_postfix_op_symbol, "invalid_lhs_in_postfix_op") \
V(invalid_lhs_in_prefix_op_symbol, "invalid_lhs_in_prefix_op") \
V(illegal_return_symbol, "illegal_return") \
V(illegal_break_symbol, "illegal_break") \
V(illegal_continue_symbol, "illegal_continue") \
V(unknown_label_symbol, "unknown_label") \
V(redeclaration_symbol, "redeclaration") \
V(failure_symbol, "<failure>") \
V(space_symbol, " ") \
V(exec_symbol, "exec") \
V(zero_symbol, "0") \
V(global_eval_symbol, "GlobalEval") \
V(identity_hash_symbol, "v8::IdentityHash") \
V(closure_symbol, "(closure)") \
V(use_strict, "use strict") \
V(KeyedLoadExternalArray_symbol, "KeyedLoadExternalArray") \
V(KeyedStoreExternalArray_symbol, "KeyedStoreExternalArray")
// Forward declarations.
class GCTracer;
class HeapStats;
class WeakObjectRetainer;
typedef String* (*ExternalStringTableUpdaterCallback)(Object** pointer);
typedef bool (*DirtyRegionCallback)(Address start,
Address end,
ObjectSlotCallback copy_object_func);
// The all static Heap captures the interface to the global object heap.
// All JavaScript contexts by this process share the same object heap.
class Heap : public AllStatic {
public:
// Configure heap size before setup. Return false if the heap has been
// setup already.
static bool ConfigureHeap(int max_semispace_size,
int max_old_gen_size,
int max_executable_size);
static bool ConfigureHeapDefault();
// Initializes the global object heap. If create_heap_objects is true,
// also creates the basic non-mutable objects.
// Returns whether it succeeded.
static bool Setup(bool create_heap_objects);
// Destroys all memory allocated by the heap.
static 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.
static void SetStackLimits();
// Returns whether Setup has been called.
static 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.
static intptr_t MaxReserved() {
return 4 * reserved_semispace_size_ + max_old_generation_size_;
}
static int MaxSemiSpaceSize() { return max_semispace_size_; }
static int ReservedSemiSpaceSize() { return reserved_semispace_size_; }
static int InitialSemiSpaceSize() { return initial_semispace_size_; }
static intptr_t MaxOldGenerationSize() { return max_old_generation_size_; }
static 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.
static intptr_t Capacity();
// Returns the amount of memory currently committed for the heap.
static intptr_t CommittedMemory();
// Returns the amount of executable memory currently committed for the heap.
static intptr_t CommittedMemoryExecutable();
// 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.
static intptr_t Available();
// Returns the maximum object size in paged space.
static inline int MaxObjectSizeInPagedSpace();
// Returns of size of all objects residing in the heap.
static 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.
static Address NewSpaceStart() { return new_space_.start(); }
static uintptr_t NewSpaceMask() { return new_space_.mask(); }
static Address NewSpaceTop() { return new_space_.top(); }
static NewSpace* new_space() { return &new_space_; }
static OldSpace* old_pointer_space() { return old_pointer_space_; }
static OldSpace* old_data_space() { return old_data_space_; }
static OldSpace* code_space() { return code_space_; }
static MapSpace* map_space() { return map_space_; }
static CellSpace* cell_space() { return cell_space_; }
static LargeObjectSpace* lo_space() { return lo_space_; }
static bool always_allocate() { return always_allocate_scope_depth_ != 0; }
static Address always_allocate_scope_depth_address() {
return reinterpret_cast<Address>(&always_allocate_scope_depth_);
}
static bool linear_allocation() {
return linear_allocation_scope_depth_ != 0;
}
static Address* NewSpaceAllocationTopAddress() {
return new_space_.allocation_top_address();
}
static Address* NewSpaceAllocationLimitAddress() {
return new_space_.allocation_limit_address();
}
// Uncommit unused semi space.
static bool UncommitFromSpace() { return new_space_.UncommitFromSpace(); }
#ifdef ENABLE_HEAP_PROTECTION
// Protect/unprotect the heap by marking all spaces read-only/writable.
static void Protect();
static void Unprotect();
#endif
// Allocates and initializes a new JavaScript object based on a
// constructor.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateJSObject(
JSFunction* constructor, PretenureFlag pretenure = NOT_TENURED);
// Allocates and initializes a new global object based on a constructor.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateGlobalObject(
JSFunction* constructor);
// Returns a deep copy of the JavaScript object.
// Properties and elements are copied too.
// Returns failure if allocation failed.
MUST_USE_RESULT static MaybeObject* CopyJSObject(JSObject* source);
// Allocates the function prototype.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateFunctionPrototype(
JSFunction* function);
// Reinitialize an JSGlobalProxy based on a constructor. The object
// must have the same size as objects allocated using the
// constructor. The object is reinitialized and behaves as an
// object that has been freshly allocated using the constructor.
MUST_USE_RESULT static MaybeObject* ReinitializeJSGlobalProxy(
JSFunction* constructor,
JSGlobalProxy* global);
// Allocates and initializes a new JavaScript object based on a map.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateJSObjectFromMap(
Map* map, PretenureFlag pretenure = NOT_TENURED);
// Allocates a heap object based on the map.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* Allocate(Map* map, AllocationSpace space);
// Allocates a JS Map in the heap.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateMap(InstanceType instance_type,
int instance_size);
// Allocates a partial map for bootstrapping.
MUST_USE_RESULT static MaybeObject* AllocatePartialMap(
InstanceType instance_type,
int instance_size);
// Allocate a map for the specified function
MUST_USE_RESULT static MaybeObject* AllocateInitialMap(JSFunction* fun);
// Allocates an empty code cache.
MUST_USE_RESULT static MaybeObject* AllocateCodeCache();
// Clear the Instanceof cache (used when a prototype changes).
static void ClearInstanceofCache() {
set_instanceof_cache_function(the_hole_value());
}
// Allocates and fully initializes a String. There are two String
// encodings: ASCII and two byte. One should choose between the three string
// allocation functions based on the encoding of the string buffer used to
// initialized the string.
// - ...FromAscii initializes the string from a buffer that is ASCII
// encoded (it does not check that the buffer is ASCII encoded) and the
// result will be ASCII encoded.
// - ...FromUTF8 initializes the string from a buffer that is UTF-8
// encoded. If the characters are all single-byte characters, the
// result will be ASCII encoded, otherwise it will converted to two
// byte.
// - ...FromTwoByte initializes the string from a buffer that is two-byte
// encoded. If the characters are all single-byte characters, the
// result will be converted to ASCII, otherwise it will be left as
// two-byte.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateStringFromAscii(
Vector<const char> str,
PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT static inline MaybeObject* AllocateStringFromUtf8(
Vector<const char> str,
PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT static MaybeObject* AllocateStringFromUtf8Slow(
Vector<const char> str,
PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT static MaybeObject* AllocateStringFromTwoByte(
Vector<const uc16> str,
PretenureFlag pretenure = NOT_TENURED);
// Allocates a symbol in old space based on the character stream.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* AllocateSymbol(
Vector<const char> str,
int chars,
uint32_t hash_field);
MUST_USE_RESULT static inline MaybeObject* AllocateAsciiSymbol(
Vector<const char> str,
uint32_t hash_field);
MUST_USE_RESULT static inline MaybeObject* AllocateTwoByteSymbol(
Vector<const uc16> str,
uint32_t hash_field);
MUST_USE_RESULT static MaybeObject* AllocateInternalSymbol(
unibrow::CharacterStream* buffer, int chars, uint32_t hash_field);
MUST_USE_RESULT static MaybeObject* AllocateExternalSymbol(
Vector<const char> str,
int chars);
// Allocates 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.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateRawAsciiString(
int length,
PretenureFlag pretenure = NOT_TENURED);
MUST_USE_RESULT static MaybeObject* AllocateRawTwoByteString(
int length,
PretenureFlag pretenure = NOT_TENURED);
// Computes a single character string where the character has code.
// A cache is used for ascii codes.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed. Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* LookupSingleCharacterStringFromCode(
uint16_t code);
// Allocate a byte array of the specified length
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateByteArray(int length,
PretenureFlag pretenure);
// Allocate a non-tenured byte array of the specified length
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateByteArray(int length);
// Allocate a pixel array of the specified length
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocatePixelArray(int length,
uint8_t* external_pointer,
PretenureFlag pretenure);
// Allocates an external array of the specified length and type.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateExternalArray(
int length,
ExternalArrayType array_type,
void* external_pointer,
PretenureFlag pretenure);
// Allocate a tenured JS global property cell.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateJSGlobalPropertyCell(
Object* value);
// Allocates a fixed array initialized with undefined values
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateFixedArray(
int length,
PretenureFlag pretenure);
// Allocates a fixed array initialized with undefined values
MUST_USE_RESULT static MaybeObject* AllocateFixedArray(int length);
// Allocates an uninitialized fixed array. It must be filled by the caller.
//
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateUninitializedFixedArray(
int length);
// Make a copy of src and return it. Returns
// Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
MUST_USE_RESULT static inline MaybeObject* 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 static MaybeObject* CopyFixedArrayWithMap(FixedArray* src,
Map* map);
// Allocates a fixed array initialized with the hole values.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateFixedArrayWithHoles(
int length,
PretenureFlag pretenure = NOT_TENURED);
// AllocateHashTable is identical to AllocateFixedArray except
// that the resulting object has hash_table_map as map.
MUST_USE_RESULT static MaybeObject* AllocateHashTable(
int length, PretenureFlag pretenure = NOT_TENURED);
// Allocate a global (but otherwise uninitialized) context.
MUST_USE_RESULT static MaybeObject* AllocateGlobalContext();
// Allocate a function context.
MUST_USE_RESULT static MaybeObject* AllocateFunctionContext(
int length,
JSFunction* closure);
// Allocate a 'with' context.
MUST_USE_RESULT static MaybeObject* AllocateWithContext(
Context* previous,
JSObject* extension,
bool is_catch_context);
// Allocates a new utility object in the old generation.
MUST_USE_RESULT static MaybeObject* AllocateStruct(InstanceType type);
// Allocates a function initialized with a shared part.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateFunction(
Map* function_map,
SharedFunctionInfo* shared,
Object* prototype,
PretenureFlag pretenure = TENURED);
// Indicies for direct access into argument objects.
static const int kArgumentsObjectSize =
JSObject::kHeaderSize + 2 * kPointerSize;
static const int arguments_callee_index = 0;
static const int arguments_length_index = 1;
// Allocates an arguments object - optionally with an elements array.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateArgumentsObject(Object* callee,
int length);
// Same as NewNumberFromDouble, but may return a preallocated/immutable
// number object (e.g., minus_zero_value_, nan_value_)
MUST_USE_RESULT static MaybeObject* NumberFromDouble(
double value, PretenureFlag pretenure = NOT_TENURED);
// Allocated a HeapNumber from value.
MUST_USE_RESULT static MaybeObject* AllocateHeapNumber(
double value,
PretenureFlag pretenure);
// pretenure = NOT_TENURED.
MUST_USE_RESULT static MaybeObject* AllocateHeapNumber(double value);
// Converts an int into either a Smi or a HeapNumber object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* NumberFromInt32(int32_t value);
// Converts an int into either a Smi or a HeapNumber object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* NumberFromUint32(uint32_t value);
// Allocates a new proxy object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateProxy(
Address proxy,
PretenureFlag pretenure = NOT_TENURED);
// Allocates a new SharedFunctionInfo object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateSharedFunctionInfo(Object* name);
// Allocates a new JSMessageObject object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note that this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateJSMessageObject(
String* type,
JSArray* arguments,
int start_position,
int end_position,
Object* script,
Object* stack_trace,
Object* stack_frames);
// Allocates a new cons string object.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateConsString(String* first,
String* second);
// Allocates a new sub string object which is a substring of an underlying
// string buffer stretching from the index start (inclusive) to the index
// end (exclusive).
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateSubString(
String* buffer,
int start,
int end,
PretenureFlag pretenure = NOT_TENURED);
// Allocate a new external string object, which is backed by a string
// resource that resides outside the V8 heap.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* AllocateExternalStringFromAscii(
ExternalAsciiString::Resource* resource);
MUST_USE_RESULT static MaybeObject* AllocateExternalStringFromTwoByte(
ExternalTwoByteString::Resource* resource);
// Finalizes an external string by deleting the associated external
// data and clearing the resource pointer.
static inline void FinalizeExternalString(String* string);
// Allocates an uninitialized object. The memory is non-executable if the
// hardware and OS allow.
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* AllocateRaw(
int size_in_bytes,
AllocationSpace space,
AllocationSpace retry_space);
// Initialize a filler object to keep the ability to iterate over the heap
// when shortening objects.
static void CreateFillerObjectAt(Address addr, int size);
// Makes a new native code object
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed. On success, the pointer to the Code object is stored in the
// self_reference. This allows generated code to reference its own Code
// object by containing this pointer.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* CreateCode(const CodeDesc& desc,
Code::Flags flags,
Handle<Object> self_reference);
MUST_USE_RESULT static MaybeObject* CopyCode(Code* code);
// Copy the code and scope info part of the code object, but insert
// the provided data as the relocation information.
MUST_USE_RESULT static MaybeObject* CopyCode(Code* code,
Vector<byte> reloc_info);
// Finds the symbol for string in the symbol table.
// If not found, a new symbol is added to the table and returned.
// Returns Failure::RetryAfterGC(requested_bytes, space) if allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* LookupSymbol(Vector<const char> str);
MUST_USE_RESULT static MaybeObject* LookupAsciiSymbol(Vector<const char> str);
MUST_USE_RESULT static MaybeObject* LookupTwoByteSymbol(
Vector<const uc16> str);
MUST_USE_RESULT static MaybeObject* LookupAsciiSymbol(const char* str) {
return LookupSymbol(CStrVector(str));
}
MUST_USE_RESULT static MaybeObject* LookupSymbol(String* str);
static bool LookupSymbolIfExists(String* str, String** symbol);
static bool LookupTwoCharsSymbolIfExists(String* str, String** symbol);
// Compute the matching symbol map for a string if possible.
// NULL is returned if string is in new space or not flattened.
static Map* SymbolMapForString(String* str);
// Tries to flatten a string before compare operation.
//
// Returns a failure in case it was decided that flattening was
// necessary and failed. Note, if flattening is not necessary the
// string might stay non-flat even when not a failure is returned.
//
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* PrepareForCompare(String* str);
// Converts the given boolean condition to JavaScript boolean value.
static Object* ToBoolean(bool condition) {
return condition ? true_value() : false_value();
}
// Code that should be run before and after each GC. Includes some
// reporting/verification activities when compiled with DEBUG set.
static void GarbageCollectionPrologue();
static void GarbageCollectionEpilogue();
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
static bool CollectGarbage(AllocationSpace space, GarbageCollector collector);
// Performs garbage collection operation.
// Returns whether there is a chance that another major GC could
// collect more garbage.
inline static bool CollectGarbage(AllocationSpace space);
// Performs a full garbage collection. Force compaction if the
// parameter is true.
static void CollectAllGarbage(bool force_compaction);
// Last hope GC, should try to squeeze as much as possible.
static void CollectAllAvailableGarbage();
// Notify the heap that a context has been disposed.
static int NotifyContextDisposed() { return ++contexts_disposed_; }
// Utility to invoke the scavenger. This is needed in test code to
// ensure correct callback for weak global handles.
static void PerformScavenge();
#ifdef DEBUG
// Utility used with flag gc-greedy.
static void GarbageCollectionGreedyCheck();
#endif
static void AddGCPrologueCallback(
GCEpilogueCallback callback, GCType gc_type_filter);
static void RemoveGCPrologueCallback(GCEpilogueCallback callback);
static void AddGCEpilogueCallback(
GCEpilogueCallback callback, GCType gc_type_filter);
static void RemoveGCEpilogueCallback(GCEpilogueCallback callback);
static void SetGlobalGCPrologueCallback(GCCallback callback) {
ASSERT((callback == NULL) ^ (global_gc_prologue_callback_ == NULL));
global_gc_prologue_callback_ = callback;
}
static void SetGlobalGCEpilogueCallback(GCCallback callback) {
ASSERT((callback == NULL) ^ (global_gc_epilogue_callback_ == NULL));
global_gc_epilogue_callback_ = 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.
#define ROOT_ACCESSOR(type, name, camel_name) \
static inline type* name() { \
return type::cast(roots_[k##camel_name##RootIndex]); \
} \
static inline type* raw_unchecked_##name() { \
return reinterpret_cast<type*>(roots_[k##camel_name##RootIndex]); \
}
ROOT_LIST(ROOT_ACCESSOR)
#undef ROOT_ACCESSOR
// Utility type maps
#define STRUCT_MAP_ACCESSOR(NAME, Name, name) \
static inline Map* name##_map() { \
return Map::cast(roots_[k##Name##MapRootIndex]); \
}
STRUCT_LIST(STRUCT_MAP_ACCESSOR)
#undef STRUCT_MAP_ACCESSOR
#define SYMBOL_ACCESSOR(name, str) static inline String* name() { \
return String::cast(roots_[k##name##RootIndex]); \
}
SYMBOL_LIST(SYMBOL_ACCESSOR)
#undef SYMBOL_ACCESSOR
// The hidden_symbol is special because it is the empty string, but does
// not match the empty string.
static String* hidden_symbol() { return hidden_symbol_; }
static void set_global_contexts_list(Object* object) {
global_contexts_list_ = object;
}
static Object* global_contexts_list() { return global_contexts_list_; }
// Iterates over all roots in the heap.
static void IterateRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over all strong roots in the heap.
static void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
// Iterates over all the other roots in the heap.
static void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
enum ExpectedPageWatermarkState {
WATERMARK_SHOULD_BE_VALID,
WATERMARK_CAN_BE_INVALID
};
// For each dirty region on a page in use from an old space call
// visit_dirty_region callback.
// If either visit_dirty_region or callback can cause an allocation
// in old space and changes in allocation watermark then
// can_preallocate_during_iteration should be set to true.
// All pages will be marked as having invalid watermark upon
// iteration completion.
static void IterateDirtyRegions(
PagedSpace* space,
DirtyRegionCallback visit_dirty_region,
ObjectSlotCallback callback,
ExpectedPageWatermarkState expected_page_watermark_state);
// Interpret marks as a bitvector of dirty marks for regions of size
// Page::kRegionSize aligned by Page::kRegionAlignmentMask and covering
// memory interval from start to top. For each dirty region call a
// visit_dirty_region callback. Return updated bitvector of dirty marks.
static uint32_t IterateDirtyRegions(uint32_t marks,
Address start,
Address end,
DirtyRegionCallback visit_dirty_region,
ObjectSlotCallback callback);
// Iterate pointers to from semispace of new space found in memory interval
// from start to end.
// Update dirty marks for page containing start address.
static void IterateAndMarkPointersToFromSpace(Address start,
Address end,
ObjectSlotCallback callback);
// Iterate pointers to new space found in memory interval from start to end.
// Return true if pointers to new space was found.
static bool IteratePointersInDirtyRegion(Address start,
Address end,
ObjectSlotCallback callback);
// Iterate pointers to new space found in memory interval from start to end.
// This interval is considered to belong to the map space.
// Return true if pointers to new space was found.
static bool IteratePointersInDirtyMapsRegion(Address start,
Address end,
ObjectSlotCallback callback);
// Returns whether the object resides in new space.
static inline bool InNewSpace(Object* object);
static inline bool InFromSpace(Object* object);
static inline bool InToSpace(Object* object);
// Checks whether an address/object in the heap (including auxiliary
// area and unused area).
static bool Contains(Address addr);
static bool Contains(HeapObject* value);
// Checks whether an address/object in a space.
// Currently used by tests, serialization and heap verification only.
static bool InSpace(Address addr, AllocationSpace space);
static bool InSpace(HeapObject* value, AllocationSpace space);
// Finds out which space an object should get promoted to based on its type.
static inline OldSpace* TargetSpace(HeapObject* object);
static inline AllocationSpace TargetSpaceId(InstanceType type);
// Sets the stub_cache_ (only used when expanding the dictionary).
static void public_set_code_stubs(NumberDictionary* 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.
static HeapObjectCallback GcSafeSizeOfOldObjectFunction() {
return gc_safe_size_of_old_object_;
}
// Sets the non_monomorphic_cache_ (only used when expanding the dictionary).
static void public_set_non_monomorphic_cache(NumberDictionary* value) {
roots_[kNonMonomorphicCacheRootIndex] = value;
}
static void public_set_empty_script(Script* script) {
roots_[kEmptyScriptRootIndex] = script;
}
// Update the next script id.
static inline void SetLastScriptId(Object* last_script_id);
// Generated code can embed this address to get access to the roots.
static Object** roots_address() { return roots_; }
// Get address of global contexts list for serialization support.
static Object** global_contexts_list_address() {
return &global_contexts_list_;
}
#ifdef DEBUG
static void Print();
static void PrintHandles();
// Verify the heap is in its normal state before or after a GC.
static void Verify();
// Report heap statistics.
static void ReportHeapStatistics(const char* title);
static void ReportCodeStatistics(const char* title);
// Fill in bogus values in from space
static void ZapFromSpace();
#endif
#if defined(ENABLE_LOGGING_AND_PROFILING)
// Print short heap statistics.
static void PrintShortHeapStatistics();
#endif
// Makes a new symbol object
// Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
// failed.
// Please note this function does not perform a garbage collection.
MUST_USE_RESULT static MaybeObject* CreateSymbol(const char* str,
int length,
int hash);
MUST_USE_RESULT static MaybeObject* CreateSymbol(String* str);
// Write barrier support for address[offset] = o.
static inline void RecordWrite(Address address, int offset);
// Write barrier support for address[start : start + len[ = o.
static inline void RecordWrites(Address address, int start, int len);
// Given an address occupied by a live code object, return that object.
static Object* FindCodeObject(Address a);
// Invoke Shrink on shrinkable spaces.
static void Shrink();
enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT };
static inline HeapState gc_state() { return gc_state_; }
#ifdef DEBUG
static bool IsAllocationAllowed() { return allocation_allowed_; }
static inline bool allow_allocation(bool enable);
static bool disallow_allocation_failure() {
return disallow_allocation_failure_;
}
static void TracePathToObject(Object* target);
static void TracePathToGlobal();
#endif
// 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 void ScavengePointer(HeapObject** p);
static inline void ScavengeObject(HeapObject** p, HeapObject* object);
// Commits from space if it is uncommitted.
static void EnsureFromSpaceIsCommitted();
// Support for partial snapshots. After calling this we can allocate a
// certain number of bytes using only linear allocation (with a
// LinearAllocationScope and an AlwaysAllocateScope) without using freelists
// or causing a GC. It returns true of space was reserved or false if a GC is
// needed. For paged spaces the space requested must include the space wasted
// at the end of each page when allocating linearly.
static void ReserveSpace(
int new_space_size,
int pointer_space_size,
int data_space_size,
int code_space_size,
int map_space_size,
int cell_space_size,
int large_object_size);
//
// Support for the API.
//
static bool CreateApiObjects();
// Attempt to find the number in a small cache. If we finds it, return
// the string representation of the number. Otherwise return undefined.
static Object* GetNumberStringCache(Object* number);
// Update the cache with a new number-string pair.
static void SetNumberStringCache(Object* number, String* str);
// Adjusts the amount of registered external memory.
// Returns the adjusted value.
static inline int AdjustAmountOfExternalAllocatedMemory(int change_in_bytes);
// Allocate uninitialized fixed array.
MUST_USE_RESULT static MaybeObject* AllocateRawFixedArray(int length);
MUST_USE_RESULT static MaybeObject* AllocateRawFixedArray(
int length,
PretenureFlag pretenure);
// True if we have reached the allocation limit in the old generation that
// should force the next GC (caused normally) to be a full one.
static bool OldGenerationPromotionLimitReached() {
return (PromotedSpaceSize() + PromotedExternalMemorySize())
> old_gen_promotion_limit_;
}
static intptr_t OldGenerationSpaceAvailable() {
return old_gen_allocation_limit_ -
(PromotedSpaceSize() + PromotedExternalMemorySize());
}
// True if we have reached the allocation limit in the old generation that
// should artificially cause a GC right now.
static bool OldGenerationAllocationLimitReached() {
return OldGenerationSpaceAvailable() < 0;
}
// Can be called when the embedding application is idle.
static bool IdleNotification();
// Declare all the root indices.
enum RootListIndex {
#define ROOT_INDEX_DECLARATION(type, name, camel_name) k##camel_name##RootIndex,
STRONG_ROOT_LIST(ROOT_INDEX_DECLARATION)
#undef ROOT_INDEX_DECLARATION
// Utility type maps
#define DECLARE_STRUCT_MAP(NAME, Name, name) k##Name##MapRootIndex,
STRUCT_LIST(DECLARE_STRUCT_MAP)
#undef DECLARE_STRUCT_MAP
#define SYMBOL_INDEX_DECLARATION(name, str) k##name##RootIndex,
SYMBOL_LIST(SYMBOL_INDEX_DECLARATION)
#undef SYMBOL_DECLARATION
kSymbolTableRootIndex,
kStrongRootListLength = kSymbolTableRootIndex,
kRootListLength
};
MUST_USE_RESULT static MaybeObject* NumberToString(
Object* number,
bool check_number_string_cache = true);
static Map* MapForExternalArrayType(ExternalArrayType array_type);
static RootListIndex RootIndexForExternalArrayType(
ExternalArrayType array_type);
static 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);
static inline void CopyBlockToOldSpaceAndUpdateRegionMarks(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);
static inline void MoveBlockToOldSpaceAndUpdateRegionMarks(Address dst,
Address src,
int byte_size);
// Check new space expansion criteria and expand semispaces if it was hit.
static void CheckNewSpaceExpansionCriteria();
static inline void IncrementYoungSurvivorsCounter(int survived) {
young_survivors_after_last_gc_ = survived;
survived_since_last_expansion_ += survived;
}
static void UpdateNewSpaceReferencesInExternalStringTable(
ExternalStringTableUpdaterCallback updater_func);
static void ProcessWeakReferences(WeakObjectRetainer* retainer);
// Helper function that governs the promotion policy from new space to
// old. If the object's old address lies below the new space's age
// mark or if we've already filled the bottom 1/16th of the to space,
// we try to promote this object.
static inline bool ShouldBePromoted(Address old_address, int object_size);
static int MaxObjectSizeInNewSpace() { return kMaxObjectSizeInNewSpace; }
static void ClearJSFunctionResultCaches();
static void ClearNormalizedMapCaches();
static GCTracer* tracer() { return tracer_; }
private:
static int reserved_semispace_size_;
static int max_semispace_size_;
static int initial_semispace_size_;
static intptr_t max_old_generation_size_;
static intptr_t max_executable_size_;
static intptr_t code_range_size_;
// For keeping track of how much data has survived
// scavenge since last new space expansion.
static int survived_since_last_expansion_;
static int always_allocate_scope_depth_;
static int linear_allocation_scope_depth_;
// For keeping track of context disposals.
static int contexts_disposed_;
#if defined(V8_TARGET_ARCH_X64)
static const int kMaxObjectSizeInNewSpace = 1024*KB;
#else
static const int kMaxObjectSizeInNewSpace = 512*KB;
#endif
static NewSpace new_space_;
static OldSpace* old_pointer_space_;
static OldSpace* old_data_space_;
static OldSpace* code_space_;
static MapSpace* map_space_;
static CellSpace* cell_space_;
static LargeObjectSpace* lo_space_;
static HeapState gc_state_;
// Returns the size of object residing in non new spaces.
static intptr_t PromotedSpaceSize();
// Returns the amount of external memory registered since last global gc.
static int PromotedExternalMemorySize();
static int mc_count_; // how many mark-compact collections happened
static int ms_count_; // how many mark-sweep collections happened
static unsigned int gc_count_; // how many gc happened
// Total length of the strings we failed to flatten since the last GC.
static int unflattened_strings_length_;
#define ROOT_ACCESSOR(type, name, camel_name) \
static inline void set_##name(type* value) { \
roots_[k##camel_name##RootIndex] = value; \
}
ROOT_LIST(ROOT_ACCESSOR)
#undef ROOT_ACCESSOR
#ifdef DEBUG
static bool allocation_allowed_;
// 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.
static int allocation_timeout_;
// Do we expect to be able to handle allocation failure at this
// time?
static bool disallow_allocation_failure_;
#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.
static intptr_t old_gen_promotion_limit_;
// Limit that triggers a global GC as soon as is reasonable. This is
// checked before expanding a paged space in the old generation and on
// every allocation in large object space.
static intptr_t old_gen_allocation_limit_;
// Limit on the amount of externally allocated memory allowed
// between global GCs. If reached a global GC is forced.
static intptr_t external_allocation_limit_;
// The amount of external memory registered through the API kept alive
// by global handles
static int amount_of_external_allocated_memory_;
// Caches the amount of external memory registered at the last global gc.
static int amount_of_external_allocated_memory_at_last_global_gc_;
// Indicates that an allocation has failed in the old generation since the
// last GC.
static int old_gen_exhausted_;
static Object* roots_[kRootListLength];
static Object* global_contexts_list_;
struct StringTypeTable {
InstanceType type;
int size;
RootListIndex index;
};
struct ConstantSymbolTable {
const char* contents;
RootListIndex index;
};
struct StructTable {
InstanceType type;
int size;
RootListIndex index;
};
static const StringTypeTable string_type_table[];
static const ConstantSymbolTable constant_symbol_table[];
static const StructTable struct_table[];
// The special hidden symbol which is an empty string, but does not match
// any string when looked up in properties.
static String* hidden_symbol_;
// GC callback function, called before and after mark-compact GC.
// Allocations in the callback function are disallowed.
struct GCPrologueCallbackPair {
GCPrologueCallbackPair(GCPrologueCallback callback, GCType gc_type)
: callback(callback), gc_type(gc_type) {
}
bool operator==(const GCPrologueCallbackPair& pair) const {
return pair.callback == callback;
}
GCPrologueCallback callback;
GCType gc_type;
};
static List<GCPrologueCallbackPair> gc_prologue_callbacks_;
struct GCEpilogueCallbackPair {
GCEpilogueCallbackPair(GCEpilogueCallback callback, GCType gc_type)
: callback(callback), gc_type(gc_type) {
}
bool operator==(const GCEpilogueCallbackPair& pair) const {
return pair.callback == callback;
}
GCEpilogueCallback callback;
GCType gc_type;
};
static List<GCEpilogueCallbackPair> gc_epilogue_callbacks_;
static GCCallback global_gc_prologue_callback_;
static GCCallback global_gc_epilogue_callback_;
// Support for computing object sizes during GC.
static HeapObjectCallback gc_safe_size_of_old_object_;
static int GcSafeSizeOfOldObject(HeapObject* object);
static int GcSafeSizeOfOldObjectWithEncodedMap(HeapObject* object);
// Update the GC state. Called from the mark-compact collector.
static void MarkMapPointersAsEncoded(bool encoded) {
gc_safe_size_of_old_object_ = encoded
? &GcSafeSizeOfOldObjectWithEncodedMap
: &GcSafeSizeOfOldObject;
}
// Checks whether a global GC is necessary
static GarbageCollector SelectGarbageCollector(AllocationSpace space);
// Performs garbage collection
// Returns whether there is a chance another major GC could
// collect more garbage.
static bool PerformGarbageCollection(GarbageCollector collector,
GCTracer* tracer);
// Allocate an uninitialized object in map space. The behavior is identical
// to Heap::AllocateRaw(size_in_bytes, MAP_SPACE), except that (a) it doesn't
// have to test the allocation space argument and (b) can reduce code size
// (since both AllocateRaw and AllocateRawMap are inlined).
MUST_USE_RESULT static inline MaybeObject* AllocateRawMap();
// Allocate an uninitialized object in the global property cell space.
MUST_USE_RESULT static inline MaybeObject* AllocateRawCell();
// Initializes a JSObject based on its map.
static void InitializeJSObjectFromMap(JSObject* obj,
FixedArray* properties,
Map* map);
static bool CreateInitialMaps();
static bool CreateInitialObjects();
// 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(static void CreateCEntryStub());
NO_INLINE(static void CreateJSEntryStub());
NO_INLINE(static void CreateJSConstructEntryStub());
NO_INLINE(static void CreateRegExpCEntryStub());
NO_INLINE(static void CreateDirectCEntryStub());
static void CreateFixedStubs();
MUST_USE_RESULT static MaybeObject* CreateOddball(const char* to_string,
Object* to_number);
// Allocate empty fixed array.
MUST_USE_RESULT static MaybeObject* AllocateEmptyFixedArray();
// Performs a minor collection in new generation.
static void Scavenge();
static String* UpdateNewSpaceReferenceInExternalStringTableEntry(
Object** pointer);
static Address DoScavenge(ObjectVisitor* scavenge_visitor,
Address new_space_front);
// Performs a major collection in the whole heap.
static void MarkCompact(GCTracer* tracer);
// Code to be run before and after mark-compact.
static void MarkCompactPrologue(bool is_compacting);
// Completely clear the Instanceof cache (to stop it keeping objects alive
// around a GC).
static void CompletelyClearInstanceofCache() {
set_instanceof_cache_map(the_hole_value());
set_instanceof_cache_function(the_hole_value());
}
#if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
// Record statistics before and after garbage collection.
static void ReportStatisticsBeforeGC();
static void ReportStatisticsAfterGC();
#endif
// Slow part of scavenge object.
static void ScavengeObjectSlow(HeapObject** p, HeapObject* object);
// Initializes a function with a shared part and prototype.
// Returns the function.
// Note: this code was factored out of AllocateFunction such that
// other parts of the VM could use it. Specifically, a function that creates
// instances of type JS_FUNCTION_TYPE benefit from the use of this function.
// Please note this does not perform a garbage collection.
MUST_USE_RESULT static inline MaybeObject* InitializeFunction(
JSFunction* function,
SharedFunctionInfo* shared,
Object* prototype);
static GCTracer* tracer_;
// Initializes the number to string cache based on the max semispace size.
MUST_USE_RESULT static MaybeObject* InitializeNumberStringCache();
// Flush the number to string cache.
static void FlushNumberStringCache();
static void UpdateSurvivalRateTrend(int start_new_space_size);
enum SurvivalRateTrend { INCREASING, STABLE, DECREASING, FLUCTUATING };
static const int kYoungSurvivalRateThreshold = 90;
static const int kYoungSurvivalRateAllowedDeviation = 15;
static int young_survivors_after_last_gc_;
static int high_survival_rate_period_length_;
static double survival_rate_;
static SurvivalRateTrend previous_survival_rate_trend_;
static SurvivalRateTrend survival_rate_trend_;
static void set_survival_rate_trend(SurvivalRateTrend survival_rate_trend) {
ASSERT(survival_rate_trend != FLUCTUATING);
previous_survival_rate_trend_ = survival_rate_trend_;
survival_rate_trend_ = survival_rate_trend;
}
static SurvivalRateTrend survival_rate_trend() {
if (survival_rate_trend_ == STABLE) {
return STABLE;
} else if (previous_survival_rate_trend_ == STABLE) {
return survival_rate_trend_;
} else if (survival_rate_trend_ != previous_survival_rate_trend_) {
return FLUCTUATING;
} else {
return survival_rate_trend_;
}
}
static bool IsStableOrIncreasingSurvivalTrend() {
switch (survival_rate_trend()) {
case STABLE:
case INCREASING:
return true;
default:
return false;
}
}
static bool IsIncreasingSurvivalTrend() {
return survival_rate_trend() == INCREASING;
}
static bool IsHighSurvivalRate() {
return high_survival_rate_period_length_ > 0;
}
static const int kInitialSymbolTableSize = 2048;
static const int kInitialEvalCacheSize = 64;
friend class Factory;
friend class DisallowAllocationFailure;
friend class AlwaysAllocateScope;
friend class LinearAllocationScope;
friend class MarkCompactCollector;
};
class HeapStats {
public:
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* destroyed_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
};
class AlwaysAllocateScope {
public:
AlwaysAllocateScope() {
// We shouldn't hit any nested scopes, because that requires
// non-handle code to call handle code. The code still works but
// performance will degrade, so we want to catch this situation
// in debug mode.
ASSERT(Heap::always_allocate_scope_depth_ == 0);
Heap::always_allocate_scope_depth_++;
}
~AlwaysAllocateScope() {
Heap::always_allocate_scope_depth_--;
ASSERT(Heap::always_allocate_scope_depth_ == 0);
}
};
class LinearAllocationScope {
public:
LinearAllocationScope() {
Heap::linear_allocation_scope_depth_++;
}
~LinearAllocationScope() {
Heap::linear_allocation_scope_depth_--;
ASSERT(Heap::linear_allocation_scope_depth_ >= 0);
}
};
#ifdef DEBUG
// 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 {
public:
void VisitPointers(Object** start, Object** end) {
for (Object** current = start; current < end; current++) {
if ((*current)->IsHeapObject()) {
HeapObject* object = HeapObject::cast(*current);
ASSERT(Heap::Contains(object));
ASSERT(object->map()->IsMap());
}
}
}
};
// Visitor class to verify interior pointers in spaces that use region marks
// to keep track of intergenerational references.
// As VerifyPointersVisitor but also checks that dirty marks are set
// for regions covering intergenerational references.
class VerifyPointersAndDirtyRegionsVisitor: public ObjectVisitor {
public:
void VisitPointers(Object** start, Object** end) {
for (Object** current = start; current < end; current++) {
if ((*current)->IsHeapObject()) {
HeapObject* object = HeapObject::cast(*current);
ASSERT(Heap::Contains(object));
ASSERT(object->map()->IsMap());
if (Heap::InNewSpace(object)) {
ASSERT(Heap::InToSpace(object));
Address addr = reinterpret_cast<Address>(current);
ASSERT(Page::FromAddress(addr)->IsRegionDirty(addr));
}
}
}
}
};
#endif
// 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 {
public:
Space* next();
AllSpaces() { counter_ = FIRST_SPACE; }
private:
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 {
public:
OldSpace* next();
OldSpaces() { counter_ = OLD_POINTER_SPACE; }
private:
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 {
public:
PagedSpace* next();
PagedSpaces() { counter_ = OLD_POINTER_SPACE; }
private:
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 {
public:
SpaceIterator();
explicit SpaceIterator(HeapObjectCallback size_func);
virtual ~SpaceIterator();
bool has_next();
ObjectIterator* next();
private:
ObjectIterator* CreateIterator();
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 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 {
public:
enum HeapObjectsFiltering {
kNoFiltering,
kFilterFreeListNodes,
kFilterUnreachable
};
HeapIterator();
explicit HeapIterator(HeapObjectsFiltering filtering);
~HeapIterator();
HeapObject* next();
void reset();
private:
// Perform the initialization.
void Init();
// Perform all necessary shutdown (destruction) work.
void Shutdown();
HeapObject* NextObject();
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 {
public:
// Lookup field offset for (map, name). If absent, -1 is returned.
static int Lookup(Map* map, String* name);
// Update an element in the cache.
static void Update(Map* map, String* name, int field_offset);
// Clear the cache.
static void Clear();
static const int kLength = 64;
static const int kCapacityMask = kLength - 1;
static const int kMapHashShift = 2;
private:
static inline int Hash(Map* map, String* name);
// Get the address of the keys and field_offsets arrays. Used in
// generated code to perform cache lookups.
static Address keys_address() {
return reinterpret_cast<Address>(&keys_);
}
static Address field_offsets_address() {
return reinterpret_cast<Address>(&field_offsets_);
}
struct Key {
Map* map;
String* name;
};
static Key keys_[kLength];
static int field_offsets_[kLength];
friend class ExternalReference;
};
// Cache for mapping (array, 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 {
public:
// Lookup descriptor index for (map, name).
// If absent, kAbsent is returned.
static int Lookup(DescriptorArray* array, String* name) {
if (!StringShape(name).IsSymbol()) return kAbsent;
int index = Hash(array, name);
Key& key = keys_[index];
if ((key.array == array) && (key.name == name)) return results_[index];
return kAbsent;
}
// Update an element in the cache.
static void Update(DescriptorArray* array, String* name, int result) {
ASSERT(result != kAbsent);
if (StringShape(name).IsSymbol()) {
int index = Hash(array, name);
Key& key = keys_[index];
key.array = array;
key.name = name;
results_[index] = result;
}
}
// Clear the cache.
static void Clear();
static const int kAbsent = -2;
private:
static int Hash(DescriptorArray* array, String* name) {
// Uses only lower 32 bits if pointers are larger.
uint32_t array_hash =
static_cast<uint32_t>(reinterpret_cast<uintptr_t>(array)) >> 2;
uint32_t name_hash =
static_cast<uint32_t>(reinterpret_cast<uintptr_t>(name)) >> 2;
return (array_hash ^ name_hash) % kLength;
}
static const int kLength = 64;
struct Key {
DescriptorArray* array;
String* name;
};
static Key keys_[kLength];
static int results_[kLength];
};
// ----------------------------------------------------------------------------
// Marking stack for tracing live objects.
class MarkingStack {
public:
void Initialize(Address low, Address high) {
top_ = low_ = reinterpret_cast<HeapObject**>(low);
high_ = reinterpret_cast<HeapObject**>(high);
overflowed_ = false;
}
bool is_full() { return top_ >= high_; }
bool is_empty() { return top_ <= low_; }
bool overflowed() { return overflowed_; }
void clear_overflowed() { overflowed_ = false; }
// Push the (marked) object on the marking stack if there is room,
// otherwise mark the object as overflowed and wait for a rescan of the
// heap.
void Push(HeapObject* object) {
CHECK(object->IsHeapObject());
if (is_full()) {
object->SetOverflow();
overflowed_ = true;
} else {
*(top_++) = object;
}
}
HeapObject* Pop() {
ASSERT(!is_empty());
HeapObject* object = *(--top_);
CHECK(object->IsHeapObject());
return object;
}
private:
HeapObject** low_;
HeapObject** top_;
HeapObject** high_;
bool overflowed_;
};
// A helper class to document/test C++ scopes where we do not
// expect a GC. Usage:
//
// /* Allocation not allowed: we cannot handle a GC in this scope. */
// { AssertNoAllocation nogc;
// ...
// }
#ifdef DEBUG
class DisallowAllocationFailure {
public:
DisallowAllocationFailure() {
old_state_ = Heap::disallow_allocation_failure_;
Heap::disallow_allocation_failure_ = true;
}
~DisallowAllocationFailure() {
Heap::disallow_allocation_failure_ = old_state_;
}
private:
bool old_state_;
};
class AssertNoAllocation {
public:
AssertNoAllocation() {
old_state_ = Heap::allow_allocation(false);
}
~AssertNoAllocation() {
Heap::allow_allocation(old_state_);
}
private:
bool old_state_;
};
class DisableAssertNoAllocation {
public:
DisableAssertNoAllocation() {
old_state_ = Heap::allow_allocation(true);
}
~DisableAssertNoAllocation() {
Heap::allow_allocation(old_state_);
}
private:
bool old_state_;
};
#else // ndef DEBUG
class AssertNoAllocation {
public:
AssertNoAllocation() { }
~AssertNoAllocation() { }
};
class DisableAssertNoAllocation {
public:
DisableAssertNoAllocation() { }
~DisableAssertNoAllocation() { }
};
#endif
// GCTracer collects and prints ONE line after each garbage collector
// invocation IFF --trace_gc is used.
class GCTracer BASE_EMBEDDED {
public:
class Scope BASE_EMBEDDED {
public:
enum ScopeId {
EXTERNAL,
MC_MARK,
MC_SWEEP,
MC_SWEEP_NEWSPACE,
MC_COMPACT,
MC_FLUSH_CODE,
kNumberOfScopes
};
Scope(GCTracer* tracer, ScopeId scope)
: tracer_(tracer),
scope_(scope) {
start_time_ = OS::TimeCurrentMillis();
}
~Scope() {
ASSERT(scope_ < kNumberOfScopes); // scope_ is unsigned.
tracer_->scopes_[scope_] += OS::TimeCurrentMillis() - start_time_;
}
private:
GCTracer* tracer_;
ScopeId scope_;
double start_time_;
};
GCTracer();
~GCTracer();
// Sets the collector.
void set_collector(GarbageCollector collector) { collector_ = collector; }
// Sets the GC count.
void set_gc_count(unsigned int count) { gc_count_ = count; }
// Sets the full GC count.
void set_full_gc_count(int count) { full_gc_count_ = count; }
// Sets the flag that this is a compacting full GC.
void set_is_compacting() { is_compacting_ = true; }
bool is_compacting() const { return is_compacting_; }
// Increment and decrement the count of marked objects.
void increment_marked_count() { ++marked_count_; }
void decrement_marked_count() { --marked_count_; }
int marked_count() { return marked_count_; }
void increment_promoted_objects_size(int object_size) {
promoted_objects_size_ += object_size;
}
// Returns maximum GC pause.
static int get_max_gc_pause() { return max_gc_pause_; }
// Returns maximum size of objects alive after GC.
static intptr_t get_max_alive_after_gc() { return max_alive_after_gc_; }
// Returns minimal interval between two subsequent collections.
static int get_min_in_mutator() { return min_in_mutator_; }
private:
// Returns a string matching the collector.
const char* CollectorString();
// Returns size of object in heap (in MB).
double SizeOfHeapObjects() {
return (static_cast<double>(Heap::SizeOfObjects())) / MB;
}
double start_time_; // Timestamp set in the constructor.
intptr_t start_size_; // Size of objects in heap set in constructor.
GarbageCollector collector_; // Type of collector.
// A count (including this one, eg, the first collection is 1) of the
// number of garbage collections.
unsigned int gc_count_;
// A count (including this one) of the number of full garbage collections.
int full_gc_count_;
// True if the current GC is a compacting full collection, false
// otherwise.
bool is_compacting_;
// True if the *previous* full GC cwas a compacting collection (will be
// false if there has not been a previous full GC).
bool previous_has_compacted_;
// On a full GC, a count of the number of marked objects. Incremented
// when an object is marked and decremented when an object's mark bit is
// cleared. Will be zero on a scavenge collection.
int marked_count_;
// The count from the end of the previous full GC. Will be zero if there
// was no previous full GC.
int previous_marked_count_;
// Amounts of time spent in different scopes during GC.
double scopes_[Scope::kNumberOfScopes];
// Total amount of space either wasted or contained in one of free lists
// before the current GC.
intptr_t in_free_list_or_wasted_before_gc_;
// Difference between space used in the heap at the beginning of the current
// collection and the end of the previous collection.
intptr_t allocated_since_last_gc_;
// Amount of time spent in mutator that is time elapsed between end of the
// previous collection and the beginning of the current one.
double spent_in_mutator_;
// Size of objects promoted during the current collection.
intptr_t promoted_objects_size_;
// Maximum GC pause.
static int max_gc_pause_;
// Maximum size of objects alive after GC.
static intptr_t max_alive_after_gc_;
// Minimal interval between two subsequent collections.
static int min_in_mutator_;
// Size of objects alive after last GC.
static intptr_t alive_after_last_gc_;
static double last_gc_end_timestamp_;
};
class TranscendentalCache {
public:
enum Type {ACOS, ASIN, ATAN, COS, EXP, LOG, SIN, TAN, kNumberOfCaches};
static const int kTranscendentalTypeBits = 3;
STATIC_ASSERT((1 << kTranscendentalTypeBits) >= kNumberOfCaches);
explicit TranscendentalCache(Type t);
// Returns a heap number with f(input), where f is a math function specified
// by the 'type' argument.
MUST_USE_RESULT static inline MaybeObject* Get(Type type, double input) {
TranscendentalCache* cache = caches_[type];
if (cache == NULL) {
caches_[type] = cache = new TranscendentalCache(type);
}
return cache->Get(input);
}
// The cache contains raw Object pointers. This method disposes of
// them before a garbage collection.
static void Clear();
private:
MUST_USE_RESULT inline MaybeObject* Get(double input) {
Converter c;
c.dbl = input;
int hash = Hash(c);
Element e = elements_[hash];
if (e.in[0] == c.integers[0] &&
e.in[1] == c.integers[1]) {
ASSERT(e.output != NULL);
Counters::transcendental_cache_hit.Increment();
return e.output;
}
double answer = Calculate(input);
Counters::transcendental_cache_miss.Increment();
Object* heap_number;
{ MaybeObject* maybe_heap_number = Heap::AllocateHeapNumber(answer);
if (!maybe_heap_number->ToObject(&heap_number)) return maybe_heap_number;
}
elements_[hash].in[0] = c.integers[0];
elements_[hash].in[1] = c.integers[1];
elements_[hash].output = heap_number;
return heap_number;
}
inline double Calculate(double input) {
switch (type_) {
case ACOS:
return acos(input);
case ASIN:
return asin(input);
case ATAN:
return atan(input);
case COS:
return cos(input);
case EXP:
return exp(input);
case LOG:
return log(input);
case SIN:
return sin(input);
case TAN:
return tan(input);
default:
return 0.0; // Never happens.
}
}
static const int kCacheSize = 512;
struct Element {
uint32_t in[2];
Object* output;
};
union Converter {
double dbl;
uint32_t integers[2];
};
inline static int Hash(const Converter& c) {
uint32_t hash = (c.integers[0] ^ c.integers[1]);
hash ^= static_cast<int32_t>(hash) >> 16;
hash ^= static_cast<int32_t>(hash) >> 8;
return (hash & (kCacheSize - 1));
}
static Address cache_array_address() {
// Used to create an external reference.
return reinterpret_cast<Address>(caches_);
}
// Allow access to the caches_ array as an ExternalReference.
friend class ExternalReference;
// Inline implementation of the cache.
friend class TranscendentalCacheStub;
static TranscendentalCache* caches_[kNumberOfCaches];
Element elements_[kCacheSize];
Type type_;
};
// 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 : public AllStatic {
public:
// Registers an external string.
inline static void AddString(String* string);
inline static void Iterate(ObjectVisitor* v);
// Restores internal invariant and gets rid of collected strings.
// Must be called after each Iterate() that modified the strings.
static void CleanUp();
// Destroys all allocated memory.
static void TearDown();
private:
friend class Heap;
inline static void Verify();
inline static void AddOldString(String* string);
// Notifies the table that only a prefix of the new list is valid.
inline static void ShrinkNewStrings(int position);
// To speed up scavenge collections new space string are kept
// separate from old space strings.
static List<Object*> new_space_strings_;
static List<Object*> old_space_strings_;
};
// Abstract base class for checking whether a weak object should be retained.
class WeakObjectRetainer {
public:
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;
};
#if defined(DEBUG) || defined(LIVE_OBJECT_LIST)
// 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 {
public:
enum WhatToFind {
FIND_ALL, // Will find all matches.
FIND_FIRST // Will stop the search after first match.
};
// 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),
found_target_(false),
found_target_in_trace_(false),
what_to_find_(what_to_find),
visit_mode_(visit_mode),
object_stack_(20),
no_alloc() {}
virtual void VisitPointers(Object** start, Object** end);
void Reset();
void TracePathFrom(Object** root);
bool found() const { return found_target_; }
static Object* const kAnyGlobalObject;
protected:
class MarkVisitor;
class UnmarkVisitor;
void MarkRecursively(Object** p, MarkVisitor* mark_visitor);
void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);
virtual void ProcessResults();
// Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
static const int kMarkTag = 2;
Object* search_target_;
bool found_target_;
bool found_target_in_trace_;
WhatToFind what_to_find_;
VisitMode visit_mode_;
List<Object*> object_stack_;
AssertNoAllocation no_alloc; // i.e. no gc allowed.
DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
};
#endif // DEBUG || LIVE_OBJECT_LIST
} } // namespace v8::internal
#endif // V8_HEAP_H_
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