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Reland "Lazily register prototype users..."

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...when handing out validity cells to handlers; because invalidating said cells is
the only time we'll need the user registrations.
Along the way, fix a corner case in WeakFixedArray, which can now be empty after
the recently introduced compaction support.

This reverts commit 968715c653.

Original review: https://codereview.chromium.org/1104813004/

Review URL: https://codereview.chromium.org/1110513002

Cr-Commit-Position: refs/heads/master@{#28076}
This commit is contained in:
jkummerow 2015-04-27 05:59:55 -07:00 committed by Commit bot
parent 232b09825c
commit f6187fb3b5
4 changed files with 206 additions and 81 deletions
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165
src/objects.cc
View File

@ -1911,6 +1911,22 @@ void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
// prototype chains involving it.
InvalidatePrototypeChains(object->map());
Handle<Map> old_map(object->map());
// If the map was registered with its prototype before, ensure that it
// registers with its new prototype now. This preserves the invariant that
// when a map on a prototype chain is registered with its prototype, then
// all prototypes further up the chain are also registered with their
// respective prototypes.
Object* maybe_old_prototype = old_map->prototype();
if (maybe_old_prototype->IsJSObject()) {
Handle<JSObject> old_prototype(JSObject::cast(maybe_old_prototype));
bool was_registered =
JSObject::UnregisterPrototypeUser(old_prototype, old_map);
if (was_registered) {
JSObject::LazyRegisterPrototypeUser(new_map, new_map->GetIsolate());
}
}
if (object->HasFastProperties()) {
if (!new_map->is_dictionary_map()) {
MigrateFastToFast(object, new_map);
@ -1936,7 +1952,15 @@ void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
// Slow-to-slow migration is trivial.
object->set_map(*new_map);
}
if (old_map->is_prototype_map()) {
// Careful: Don't allocate here!
// For some callers of this method, |object| might be in an inconsistent
// state now: the new map might have a new elements_kind, but the object's
// elements pointer hasn't been updated yet. Callers will fix this, but in
// the meantime, (indirectly) calling JSObjectVerify() must be avoided.
DisallowHeapAllocation no_object_verification;
if (old_map->is_prototype_map() && FLAG_track_prototype_users) {
DCHECK(new_map->is_prototype_map());
DCHECK(object->map() == *new_map);
new_map->set_prototype_info(old_map->prototype_info());
@ -7088,12 +7112,6 @@ void Map::ConnectTransition(Handle<Map> parent, Handle<Map> child,
#endif
} else {
TransitionArray::Insert(parent, name, child, flag);
if (child->prototype()->IsJSObject()) {
Handle<JSObject> proto(JSObject::cast(child->prototype()));
if (!ShouldRegisterAsPrototypeUser(child, proto)) {
JSObject::UnregisterPrototypeUser(proto, child);
}
}
#if TRACE_MAPS
Map::TraceTransition("Transition", *parent, *child, *name);
#endif
@ -8258,15 +8276,18 @@ void WeakFixedArray::Set(Handle<WeakFixedArray> array, int index,
// static
Handle<WeakFixedArray> WeakFixedArray::Add(
Handle<Object> maybe_array, Handle<HeapObject> value,
SearchForDuplicates search_for_duplicates) {
SearchForDuplicates search_for_duplicates, bool* was_present) {
Handle<WeakFixedArray> array =
(maybe_array.is_null() || !maybe_array->IsWeakFixedArray())
? Allocate(value->GetIsolate(), 1, Handle<WeakFixedArray>::null())
: Handle<WeakFixedArray>::cast(maybe_array);
if (was_present != NULL) *was_present = false;
if (search_for_duplicates == kAddIfNotFound) {
for (int i = 0; i < array->Length(); ++i) {
if (array->Get(i) == *value) return array;
if (array->Get(i) == *value) {
if (was_present != NULL) *was_present = true;
return array;
}
}
#if 0 // Enable this if you want to check your search_for_duplicates flags.
} else {
@ -8279,6 +8300,7 @@ Handle<WeakFixedArray> WeakFixedArray::Add(
// Try to store the new entry if there's room. Optimize for consecutive
// accesses.
int first_index = array->last_used_index();
if (array->Length() > 0) {
for (int i = first_index;;) {
if (array->IsEmptySlot((i))) {
WeakFixedArray::Set(array, i, value);
@ -8290,9 +8312,11 @@ Handle<WeakFixedArray> WeakFixedArray::Add(
i = (i + 1) % array->Length();
if (i == first_index) break;
}
}
// No usable slot found, grow the array.
int new_length = array->Length() + (array->Length() >> 1) + 4;
int new_length =
array->Length() == 0 ? 1 : array->Length() + (array->Length() >> 1) + 4;
Handle<WeakFixedArray> new_array =
Allocate(array->GetIsolate(), new_length, array);
if (FLAG_trace_weak_arrays) {
@ -8317,7 +8341,8 @@ void WeakFixedArray::Compact() {
}
void WeakFixedArray::Remove(Handle<HeapObject> value) {
bool WeakFixedArray::Remove(Handle<HeapObject> value) {
if (Length() == 0) return false;
// Optimize for the most recently added element to be removed again.
int first_index = last_used_index();
for (int i = first_index;;) {
@ -8325,11 +8350,12 @@ void WeakFixedArray::Remove(Handle<HeapObject> value) {
clear(i);
// Users of WeakFixedArray should make sure that there are no duplicates,
// they can use Add(..., kAddIfNotFound) if necessary.
return;
return true;
}
i = (i + 1) % Length();
if (i == first_index) break;
if (i == first_index) return false;
}
UNREACHABLE();
}
@ -10062,36 +10088,55 @@ void JSObject::ReoptimizeIfPrototype(Handle<JSObject> object) {
// static
void JSObject::RegisterPrototypeUser(Handle<JSObject> prototype,
Handle<HeapObject> user) {
void JSObject::LazyRegisterPrototypeUser(Handle<Map> user, Isolate* isolate) {
DCHECK(FLAG_track_prototype_users);
Isolate* isolate = prototype->GetIsolate();
if (prototype->IsJSGlobalProxy()) {
PrototypeIterator iter(isolate, prototype);
prototype = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
// Contract: In line with InvalidatePrototypeChains()'s requirements,
// leaf maps don't need to register as users, only prototypes do.
DCHECK(user->is_prototype_map());
Handle<Map> current_user = user;
for (PrototypeIterator iter(user); !iter.IsAtEnd(); iter.Advance()) {
Handle<Object> maybe_proto = PrototypeIterator::GetCurrent(iter);
if (maybe_proto->IsJSGlobalProxy()) continue;
// Proxies on the prototype chain are not supported.
if (maybe_proto->IsJSProxy()) return;
Handle<JSObject> proto = Handle<JSObject>::cast(maybe_proto);
bool just_registered =
RegisterPrototypeUserIfNotRegistered(proto, current_user, isolate);
// Walk up the prototype chain as far as links haven't been registered yet.
if (!just_registered) break;
current_user = handle(proto->map(), isolate);
}
Handle<PrototypeInfo> proto_info;
Object* maybe_proto_info = prototype->map()->prototype_info();
if (maybe_proto_info->IsPrototypeInfo()) {
proto_info = handle(PrototypeInfo::cast(maybe_proto_info), isolate);
} else {
proto_info = isolate->factory()->NewPrototypeInfo();
prototype->map()->set_prototype_info(*proto_info);
}
// Returns true if the user was not yet registered.
// static
bool JSObject::RegisterPrototypeUserIfNotRegistered(Handle<JSObject> prototype,
Handle<HeapObject> user,
Isolate* isolate) {
Handle<PrototypeInfo> proto_info =
Map::GetOrCreatePrototypeInfo(prototype, isolate);
Handle<Object> maybe_registry(proto_info->prototype_users(), isolate);
Handle<WeakFixedArray> new_array = WeakFixedArray::Add(maybe_registry, user);
bool was_present = false;
Handle<WeakFixedArray> new_array = WeakFixedArray::Add(
maybe_registry, user, WeakFixedArray::kAddIfNotFound, &was_present);
if (!maybe_registry.is_identical_to(new_array)) {
proto_info->set_prototype_users(*new_array);
}
if (FLAG_trace_prototype_users) {
PrintF("Registering %p as a user of prototype %p.\n",
reinterpret_cast<void*>(*user), reinterpret_cast<void*>(*prototype));
if (FLAG_trace_prototype_users && !was_present) {
PrintF("Registering %p as a user of prototype %p (map=%p).\n",
reinterpret_cast<void*>(*user), reinterpret_cast<void*>(*prototype),
reinterpret_cast<void*>(prototype->map()));
}
return !was_present;
}
// Can be called regardless of whether |user| was actually registered with
// |prototype|. Returns true when there was a registration.
// static
void JSObject::UnregisterPrototypeUser(Handle<JSObject> prototype,
bool JSObject::UnregisterPrototypeUser(Handle<JSObject> prototype,
Handle<HeapObject> user) {
Isolate* isolate = prototype->GetIsolate();
if (prototype->IsJSGlobalProxy()) {
@ -10100,21 +10145,26 @@ void JSObject::UnregisterPrototypeUser(Handle<JSObject> prototype,
}
DCHECK(prototype->map()->is_prototype_map());
Object* maybe_proto_info = prototype->map()->prototype_info();
if (!maybe_proto_info->IsPrototypeInfo()) return;
if (!maybe_proto_info->IsPrototypeInfo()) return false;
Handle<PrototypeInfo> proto_info(PrototypeInfo::cast(maybe_proto_info),
isolate);
Object* maybe_registry = proto_info->prototype_users();
if (!maybe_registry->IsWeakFixedArray()) return;
WeakFixedArray::cast(maybe_registry)->Remove(user);
if (FLAG_trace_prototype_users) {
if (!maybe_registry->IsWeakFixedArray()) return false;
bool result = WeakFixedArray::cast(maybe_registry)->Remove(user);
if (FLAG_trace_prototype_users && result) {
PrintF("Unregistering %p as a user of prototype %p.\n",
reinterpret_cast<void*>(*user), reinterpret_cast<void*>(*prototype));
}
return result;
}
static void InvalidatePrototypeChainsInternal(Map* map) {
if (!map->is_prototype_map()) return;
if (FLAG_trace_prototype_users) {
PrintF("Invalidating prototype map %p 's cell\n",
reinterpret_cast<void*>(map));
}
Object* maybe_proto_info = map->prototype_info();
if (!maybe_proto_info->IsPrototypeInfo()) return;
PrototypeInfo* proto_info = PrototypeInfo::cast(maybe_proto_info);
@ -10153,6 +10203,19 @@ void JSObject::InvalidatePrototypeChains(Map* map) {
}
// static
Handle<PrototypeInfo> Map::GetOrCreatePrototypeInfo(Handle<JSObject> prototype,
Isolate* isolate) {
Object* maybe_proto_info = prototype->map()->prototype_info();
if (maybe_proto_info->IsPrototypeInfo()) {
return handle(PrototypeInfo::cast(maybe_proto_info), isolate);
}
Handle<PrototypeInfo> proto_info = isolate->factory()->NewPrototypeInfo();
prototype->map()->set_prototype_info(*proto_info);
return proto_info;
}
// static
Handle<Cell> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
Isolate* isolate) {
@ -10163,14 +10226,18 @@ Handle<Cell> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
PrototypeIterator iter(isolate, prototype);
prototype = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
}
Handle<PrototypeInfo> proto_info(
PrototypeInfo::cast(prototype->map()->prototype_info()), isolate);
// Ensure the prototype is registered with its own prototypes so its cell
// will be invalidated when necessary.
JSObject::LazyRegisterPrototypeUser(handle(prototype->map(), isolate),
isolate);
Handle<PrototypeInfo> proto_info =
GetOrCreatePrototypeInfo(prototype, isolate);
Object* maybe_cell = proto_info->validity_cell();
// Return existing cell if it's still valid.
if (maybe_cell->IsCell()) {
Handle<Cell> cell(Cell::cast(maybe_cell), isolate);
if (cell->value() == Smi::FromInt(Map::kPrototypeChainValid)) {
return handle(Cell::cast(maybe_cell), isolate);
return cell;
}
}
// Otherwise create a new cell.
@ -10181,18 +10248,12 @@ Handle<Cell> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
}
// static
void Map::SetPrototype(Handle<Map> map, Handle<Object> prototype,
PrototypeOptimizationMode proto_mode) {
if (map->prototype()->IsJSObject() && FLAG_track_prototype_users) {
Handle<JSObject> old_prototype(JSObject::cast(map->prototype()));
JSObject::UnregisterPrototypeUser(old_prototype, map);
}
if (prototype->IsJSObject()) {
Handle<JSObject> prototype_jsobj = Handle<JSObject>::cast(prototype);
JSObject::OptimizeAsPrototype(prototype_jsobj, proto_mode);
if (ShouldRegisterAsPrototypeUser(map, prototype_jsobj)) {
JSObject::RegisterPrototypeUser(prototype_jsobj, map);
}
}
WriteBarrierMode wb_mode =
prototype->IsNull() ? SKIP_WRITE_BARRIER : UPDATE_WRITE_BARRIER;
@ -10200,18 +10261,6 @@ void Map::SetPrototype(Handle<Map> map, Handle<Object> prototype,
}
// static
bool Map::ShouldRegisterAsPrototypeUser(Handle<Map> map,
Handle<JSObject> prototype) {
if (!FLAG_track_prototype_users) return false;
if (map->is_prototype_map()) return true;
Object* back = map->GetBackPointer();
if (!back->IsMap()) return true;
if (Map::cast(back)->prototype() != *prototype) return true;
return false;
}
Handle<Object> CacheInitialJSArrayMaps(
Handle<Context> native_context, Handle<Map> initial_map) {
// Replace all of the cached initial array maps in the native context with

24
src/objects.h
View File

@ -1841,9 +1841,11 @@ class JSObject: public JSReceiver {
static void OptimizeAsPrototype(Handle<JSObject> object,
PrototypeOptimizationMode mode);
static void ReoptimizeIfPrototype(Handle<JSObject> object);
static void RegisterPrototypeUser(Handle<JSObject> prototype,
Handle<HeapObject> user);
static void UnregisterPrototypeUser(Handle<JSObject> prototype,
static void LazyRegisterPrototypeUser(Handle<Map> user, Isolate* isolate);
static bool RegisterPrototypeUserIfNotRegistered(Handle<JSObject> prototype,
Handle<HeapObject> user,
Isolate* isolate);
static bool UnregisterPrototypeUser(Handle<JSObject> prototype,
Handle<HeapObject> user);
static void InvalidatePrototypeChains(Map* map);
@ -2621,9 +2623,11 @@ class WeakFixedArray : public FixedArray {
// If |maybe_array| is not a WeakFixedArray, a fresh one will be allocated.
static Handle<WeakFixedArray> Add(
Handle<Object> maybe_array, Handle<HeapObject> value,
SearchForDuplicates search_for_duplicates = kAlwaysAdd);
SearchForDuplicates search_for_duplicates = kAlwaysAdd,
bool* was_present = NULL);
void Remove(Handle<HeapObject> value);
// Returns true if an entry was found and removed.
bool Remove(Handle<HeapObject> value);
void Compact();
@ -5844,6 +5848,9 @@ class DependentCode: public FixedArray {
};
class PrototypeInfo;
// All heap objects have a Map that describes their structure.
// A Map contains information about:
// - Size information about the object
@ -6051,6 +6058,10 @@ class Map: public HeapObject {
// [prototype_info]: Per-prototype metadata. Aliased with transitions
// (which prototype maps don't have).
DECL_ACCESSORS(prototype_info, Object)
// PrototypeInfo is created lazily using this helper (which installs it on
// the given prototype's map).
static Handle<PrototypeInfo> GetOrCreatePrototypeInfo(
Handle<JSObject> prototype, Isolate* isolate);
// [prototype chain validity cell]: Associated with a prototype object,
// stored in that object's map's PrototypeInfo, indicates that prototype
@ -6123,9 +6134,6 @@ class Map: public HeapObject {
static void SetPrototype(
Handle<Map> map, Handle<Object> prototype,
PrototypeOptimizationMode proto_mode = FAST_PROTOTYPE);
static bool ShouldRegisterAsPrototypeUser(Handle<Map> map,
Handle<JSObject> prototype);
bool CanUseOptimizationsBasedOnPrototypeRegistry();
// [constructor]: points back to the function responsible for this map.
// The field overlaps with the back pointer. All maps in a transition tree

12
test/cctest/test-heap.cc
View File

@ -5367,3 +5367,15 @@ TEST(Regress472513) {
TestRightTrimFixedTypedArray(i::kExternalUint16Array, 8 - 1, 3);
TestRightTrimFixedTypedArray(i::kExternalUint32Array, 4, 3);
}
TEST(WeakFixedArray) {
CcTest::InitializeVM();
v8::HandleScope scope(CcTest::isolate());
Handle<HeapNumber> number = CcTest::i_isolate()->factory()->NewHeapNumber(1);
Handle<WeakFixedArray> array = WeakFixedArray::Add(Handle<Object>(), number);
array->Remove(number);
array->Compact();
WeakFixedArray::Add(array, number);
}

56
test/mjsunit/prototype-changes.js vendored Normal file
View File

@ -0,0 +1,56 @@
// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Flags: --allow-natives-syntax
function A() {
this.a = "a";
}
var a = new A();
function B() {
this.b = "b";
}
B.prototype = a;
function C() {
this.c = "c";
}
C.prototype = new B();
var c = new C();
function f(expected) {
var result = c.z;
assertEquals(expected, result);
}
f(undefined);
f(undefined);
%OptimizeFunctionOnNextCall(f);
f(undefined);
a.z = "z";
f("z");
f("z");
// Test updating .__proto__ pointers.
var p1 = {foo: 1.5};
var p2 = {}; p2.__proto__ = p1;
var p3 = {}; p3.__proto__ = p2;
var o = {}; o.__proto__ = p3;
for (var i = 0; i < 2; i++) o.foo; // Force registration.
var p1a = {foo: 1.7};
p2.__proto__ = p1a;
function g(o, expected) {
var result = o.foo;
assertEquals(expected, result);
}
g(o, 1.7);
g(o, 1.7);
g(o, 1.7);
Object.defineProperty(p1a, "foo", {get: function() { return "foo"}});
g(o, "foo");