1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
|
// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <ostream>
#include "src/compiler/access-info.h"
#include "src/accessors.h"
#include "src/compiler/compilation-dependencies.h"
#include "src/compiler/type-cache.h"
#include "src/field-index-inl.h"
#include "src/field-type.h"
#include "src/ic/call-optimization.h"
#include "src/objects-inl.h"
#include "src/objects/module-inl.h"
#include "src/objects/templates.h"
namespace v8 {
namespace internal {
namespace compiler {
namespace {
bool CanInlineElementAccess(Handle<Map> map) {
if (!map->IsJSObjectMap()) return false;
if (map->is_access_check_needed()) return false;
if (map->has_indexed_interceptor()) return false;
ElementsKind const elements_kind = map->elements_kind();
if (IsFastElementsKind(elements_kind)) return true;
if (IsFixedTypedArrayElementsKind(elements_kind) &&
elements_kind != BIGUINT64_ELEMENTS &&
elements_kind != BIGINT64_ELEMENTS) {
return true;
}
return false;
}
bool CanInlinePropertyAccess(Handle<Map> map) {
// We can inline property access to prototypes of all primitives, except
// the special Oddball ones that have no wrapper counterparts (i.e. Null,
// Undefined and TheHole).
STATIC_ASSERT(ODDBALL_TYPE == LAST_PRIMITIVE_TYPE);
if (map->IsBooleanMap()) return true;
if (map->instance_type() < LAST_PRIMITIVE_TYPE) return true;
return map->IsJSObjectMap() && !map->is_dictionary_map() &&
!map->has_named_interceptor() &&
// TODO(verwaest): Whitelist contexts to which we have access.
!map->is_access_check_needed();
}
} // namespace
std::ostream& operator<<(std::ostream& os, AccessMode access_mode) {
switch (access_mode) {
case AccessMode::kLoad:
return os << "Load";
case AccessMode::kStore:
return os << "Store";
case AccessMode::kStoreInLiteral:
return os << "StoreInLiteral";
}
UNREACHABLE();
}
ElementAccessInfo::ElementAccessInfo() {}
ElementAccessInfo::ElementAccessInfo(MapHandles const& receiver_maps,
ElementsKind elements_kind)
: elements_kind_(elements_kind), receiver_maps_(receiver_maps) {}
// static
PropertyAccessInfo PropertyAccessInfo::NotFound(MapHandles const& receiver_maps,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(holder, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::DataConstant(
MapHandles const& receiver_maps, Handle<Object> constant,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(kDataConstant, holder, constant, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::DataField(
PropertyConstness constness, MapHandles const& receiver_maps,
FieldIndex field_index, MachineRepresentation field_representation,
Type field_type, MaybeHandle<Map> field_map, MaybeHandle<JSObject> holder,
MaybeHandle<Map> transition_map) {
Kind kind =
constness == PropertyConstness::kConst ? kDataConstantField : kDataField;
return PropertyAccessInfo(kind, holder, transition_map, field_index,
field_representation, field_type, field_map,
receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::AccessorConstant(
MapHandles const& receiver_maps, Handle<Object> constant,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(kAccessorConstant, holder, constant, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::ModuleExport(
MapHandles const& receiver_maps, Handle<Cell> cell) {
return PropertyAccessInfo(kModuleExport, MaybeHandle<JSObject>(), cell,
receiver_maps);
}
PropertyAccessInfo::PropertyAccessInfo()
: kind_(kInvalid),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::None()) {}
PropertyAccessInfo::PropertyAccessInfo(MaybeHandle<JSObject> holder,
MapHandles const& receiver_maps)
: kind_(kNotFound),
receiver_maps_(receiver_maps),
holder_(holder),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::None()) {}
PropertyAccessInfo::PropertyAccessInfo(Kind kind, MaybeHandle<JSObject> holder,
Handle<Object> constant,
MapHandles const& receiver_maps)
: kind_(kind),
receiver_maps_(receiver_maps),
constant_(constant),
holder_(holder),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::Any()) {}
PropertyAccessInfo::PropertyAccessInfo(
Kind kind, MaybeHandle<JSObject> holder, MaybeHandle<Map> transition_map,
FieldIndex field_index, MachineRepresentation field_representation,
Type field_type, MaybeHandle<Map> field_map,
MapHandles const& receiver_maps)
: kind_(kind),
receiver_maps_(receiver_maps),
transition_map_(transition_map),
holder_(holder),
field_index_(field_index),
field_representation_(field_representation),
field_type_(field_type),
field_map_(field_map) {}
bool PropertyAccessInfo::Merge(PropertyAccessInfo const* that,
AccessMode access_mode, Zone* zone) {
if (this->kind_ != that->kind_) return false;
if (this->holder_.address() != that->holder_.address()) return false;
switch (this->kind_) {
case kInvalid:
break;
case kDataField:
case kDataConstantField: {
// Check if we actually access the same field (we use the
// GetFieldAccessStubKey method here just like the ICs do
// since that way we only compare the relevant bits of the
// field indices).
if (this->field_index_.GetFieldAccessStubKey() ==
that->field_index_.GetFieldAccessStubKey()) {
switch (access_mode) {
case AccessMode::kLoad: {
if (this->field_representation_ != that->field_representation_) {
if (!IsAnyTagged(this->field_representation_) ||
!IsAnyTagged(that->field_representation_)) {
return false;
}
this->field_representation_ = MachineRepresentation::kTagged;
}
if (this->field_map_.address() != that->field_map_.address()) {
this->field_map_ = MaybeHandle<Map>();
}
break;
}
case AccessMode::kStore:
case AccessMode::kStoreInLiteral: {
// For stores, the field map and field representation information
// must match exactly, otherwise we cannot merge the stores. We
// also need to make sure that in case of transitioning stores,
// the transition targets match.
if (this->field_map_.address() != that->field_map_.address() ||
this->field_representation_ != that->field_representation_ ||
this->transition_map_.address() !=
that->transition_map_.address()) {
return false;
}
break;
}
}
// Merge the field type.
this->field_type_ =
Type::Union(this->field_type_, that->field_type_, zone);
// Merge the receiver maps.
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
return false;
}
case kDataConstant:
case kAccessorConstant: {
// Check if we actually access the same constant.
if (this->constant_.address() == that->constant_.address()) {
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
return false;
}
case kNotFound: {
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
case kModuleExport: {
return false;
}
}
UNREACHABLE();
}
Handle<Cell> PropertyAccessInfo::export_cell() const {
DCHECK_EQ(kModuleExport, kind_);
return Handle<Cell>::cast(constant_);
}
AccessInfoFactory::AccessInfoFactory(JSHeapBroker* js_heap_broker,
CompilationDependencies* dependencies,
Handle<Context> native_context, Zone* zone)
: js_heap_broker_(js_heap_broker),
dependencies_(dependencies),
native_context_(native_context),
isolate_(native_context->GetIsolate()),
type_cache_(TypeCache::Get()),
zone_(zone) {
DCHECK(native_context->IsNativeContext());
}
bool AccessInfoFactory::ComputeElementAccessInfo(
Handle<Map> map, AccessMode access_mode, ElementAccessInfo* access_info) {
// Check if it is safe to inline element access for the {map}.
if (!CanInlineElementAccess(map)) return false;
ElementsKind const elements_kind = map->elements_kind();
*access_info = ElementAccessInfo(MapHandles{map}, elements_kind);
return true;
}
bool AccessInfoFactory::ComputeElementAccessInfos(
MapHandles const& maps, AccessMode access_mode,
ZoneVector<ElementAccessInfo>* access_infos) {
if (access_mode == AccessMode::kLoad) {
// For polymorphic loads of similar elements kinds (i.e. all tagged or all
// double), always use the "worst case" code without a transition. This is
// much faster than transitioning the elements to the worst case, trading a
// TransitionElementsKind for a CheckMaps, avoiding mutation of the array.
ElementAccessInfo access_info;
if (ConsolidateElementLoad(maps, &access_info)) {
access_infos->push_back(access_info);
return true;
}
}
// Collect possible transition targets.
MapHandles possible_transition_targets;
possible_transition_targets.reserve(maps.size());
for (Handle<Map> map : maps) {
if (Map::TryUpdate(isolate(), map).ToHandle(&map)) {
if (CanInlineElementAccess(map) &&
IsFastElementsKind(map->elements_kind()) &&
GetInitialFastElementsKind() != map->elements_kind()) {
possible_transition_targets.push_back(map);
}
}
}
// Separate the actual receiver maps and the possible transition sources.
MapHandles receiver_maps;
receiver_maps.reserve(maps.size());
MapTransitionList transitions(maps.size());
for (Handle<Map> map : maps) {
if (Map::TryUpdate(isolate(), map).ToHandle(&map)) {
// Don't generate elements kind transitions from stable maps.
Map* transition_target =
map->is_stable() ? nullptr
: map->FindElementsKindTransitionedMap(
isolate(), possible_transition_targets);
if (transition_target == nullptr) {
receiver_maps.push_back(map);
} else {
transitions.push_back(
std::make_pair(map, handle(transition_target, isolate())));
}
}
}
for (Handle<Map> receiver_map : receiver_maps) {
// Compute the element access information.
ElementAccessInfo access_info;
if (!ComputeElementAccessInfo(receiver_map, access_mode, &access_info)) {
return false;
}
// Collect the possible transitions for the {receiver_map}.
for (auto transition : transitions) {
if (transition.second.is_identical_to(receiver_map)) {
access_info.transitions().push_back(transition);
}
}
// Schedule the access information.
access_infos->push_back(access_info);
}
return true;
}
bool AccessInfoFactory::ComputePropertyAccessInfo(
Handle<Map> map, Handle<Name> name, AccessMode access_mode,
PropertyAccessInfo* access_info) {
// Check if it is safe to inline property access for the {map}.
if (!CanInlinePropertyAccess(map)) return false;
// Compute the receiver type.
Handle<Map> receiver_map = map;
// Property lookups require the name to be internalized.
name = isolate()->factory()->InternalizeName(name);
// We support fast inline cases for certain JSObject getters.
if (access_mode == AccessMode::kLoad &&
LookupSpecialFieldAccessor(map, name, access_info)) {
return true;
}
MaybeHandle<JSObject> holder;
do {
// Lookup the named property on the {map}.
Handle<DescriptorArray> descriptors(map->instance_descriptors(), isolate());
int const number = descriptors->Search(*name, *map);
if (number != DescriptorArray::kNotFound) {
PropertyDetails const details = descriptors->GetDetails(number);
if (access_mode == AccessMode::kStore ||
access_mode == AccessMode::kStoreInLiteral) {
// Don't bother optimizing stores to read-only properties.
if (details.IsReadOnly()) {
return false;
}
// Check for store to data property on a prototype.
if (details.kind() == kData && !holder.is_null()) {
// Store to property not found on the receiver but on a prototype, we
// need to transition to a new data property.
// Implemented according to ES6 section 9.1.9 [[Set]] (P, V, Receiver)
return LookupTransition(receiver_map, name, holder, access_info);
}
}
if (details.location() == kField) {
if (details.kind() == kData) {
int index = descriptors->GetFieldIndex(number);
Representation details_representation = details.representation();
FieldIndex field_index =
FieldIndex::ForPropertyIndex(*map, index, details_representation);
Type field_type = Type::NonInternal();
MachineRepresentation field_representation =
MachineRepresentation::kTagged;
MaybeHandle<Map> field_map;
if (details_representation.IsSmi()) {
field_type = Type::SignedSmall();
field_representation = MachineRepresentation::kTaggedSigned;
} else if (details_representation.IsDouble()) {
field_type = type_cache_.kFloat64;
field_representation = MachineRepresentation::kFloat64;
} else if (details_representation.IsHeapObject()) {
// Extract the field type from the property details (make sure its
// representation is TaggedPointer to reflect the heap object case).
field_representation = MachineRepresentation::kTaggedPointer;
Handle<FieldType> descriptors_field_type(
descriptors->GetFieldType(number), isolate());
if (descriptors_field_type->IsNone()) {
// Store is not safe if the field type was cleared.
if (access_mode == AccessMode::kStore) return false;
// The field type was cleared by the GC, so we don't know anything
// about the contents now.
} else if (descriptors_field_type->IsClass()) {
dependencies()->DependOnFieldType(MapRef(js_heap_broker(), map),
number);
// Remember the field map, and try to infer a useful type.
Handle<Map> map(descriptors_field_type->AsClass(), isolate());
field_type = Type::For(js_heap_broker(), map);
field_map = MaybeHandle<Map>(map);
}
}
*access_info = PropertyAccessInfo::DataField(
details.constness(), MapHandles{receiver_map}, field_index,
field_representation, field_type, field_map, holder);
return true;
} else {
DCHECK_EQ(kAccessor, details.kind());
// TODO(turbofan): Add support for general accessors?
return false;
}
} else {
DCHECK_EQ(kDescriptor, details.location());
if (details.kind() == kData) {
DCHECK(!FLAG_track_constant_fields);
*access_info = PropertyAccessInfo::DataConstant(
MapHandles{receiver_map},
handle(descriptors->GetStrongValue(number), isolate()), holder);
return true;
} else {
DCHECK_EQ(kAccessor, details.kind());
if (map->instance_type() == JS_MODULE_NAMESPACE_TYPE) {
DCHECK(map->is_prototype_map());
Handle<PrototypeInfo> proto_info =
Map::GetOrCreatePrototypeInfo(map, isolate());
Handle<JSModuleNamespace> module_namespace(
JSModuleNamespace::cast(proto_info->module_namespace()),
isolate());
Handle<Cell> cell(
Cell::cast(module_namespace->module()->exports()->Lookup(
ReadOnlyRoots(isolate()), name,
Smi::ToInt(name->GetHash()))),
isolate());
if (cell->value()->IsTheHole(isolate())) {
// This module has not been fully initialized yet.
return false;
}
*access_info = PropertyAccessInfo::ModuleExport(
MapHandles{receiver_map}, cell);
return true;
}
Handle<Object> accessors(descriptors->GetStrongValue(number),
isolate());
if (!accessors->IsAccessorPair()) return false;
Handle<Object> accessor(
access_mode == AccessMode::kLoad
? Handle<AccessorPair>::cast(accessors)->getter()
: Handle<AccessorPair>::cast(accessors)->setter(),
isolate());
if (!accessor->IsJSFunction()) {
CallOptimization optimization(isolate(), accessor);
if (!optimization.is_simple_api_call()) return false;
if (optimization.IsCrossContextLazyAccessorPair(*native_context_,
*map)) {
return false;
}
CallOptimization::HolderLookup lookup;
holder =
optimization.LookupHolderOfExpectedType(receiver_map, &lookup);
if (lookup == CallOptimization::kHolderNotFound) return false;
DCHECK_IMPLIES(lookup == CallOptimization::kHolderIsReceiver,
holder.is_null());
DCHECK_IMPLIES(lookup == CallOptimization::kHolderFound,
!holder.is_null());
if (V8_UNLIKELY(FLAG_runtime_stats)) return false;
}
if (access_mode == AccessMode::kLoad) {
Handle<Name> cached_property_name;
if (FunctionTemplateInfo::TryGetCachedPropertyName(isolate(),
accessor)
.ToHandle(&cached_property_name)) {
if (ComputePropertyAccessInfo(map, cached_property_name,
access_mode, access_info)) {
return true;
}
}
}
*access_info = PropertyAccessInfo::AccessorConstant(
MapHandles{receiver_map}, accessor, holder);
return true;
}
}
UNREACHABLE();
}
// Don't search on the prototype chain for special indices in case of
// integer indexed exotic objects (see ES6 section 9.4.5).
if (map->IsJSTypedArrayMap() && name->IsString() &&
IsSpecialIndex(isolate()->unicode_cache(), String::cast(*name))) {
return false;
}
// Don't search on the prototype when storing in literals
if (access_mode == AccessMode::kStoreInLiteral) {
return LookupTransition(receiver_map, name, holder, access_info);
}
// Don't lookup private symbols on the prototype chain.
if (name->IsPrivate()) return false;
// Walk up the prototype chain.
if (!map->prototype()->IsJSObject()) {
// Perform the implicit ToObject for primitives here.
// Implemented according to ES6 section 7.3.2 GetV (V, P).
Handle<JSFunction> constructor;
if (Map::GetConstructorFunction(map, native_context())
.ToHandle(&constructor)) {
map = handle(constructor->initial_map(), isolate());
DCHECK(map->prototype()->IsJSObject());
} else if (map->prototype()->IsNull(isolate())) {
// Store to property not found on the receiver or any prototype, we need
// to transition to a new data property.
// Implemented according to ES6 section 9.1.9 [[Set]] (P, V, Receiver)
if (access_mode == AccessMode::kStore) {
return LookupTransition(receiver_map, name, holder, access_info);
}
// The property was not found, return undefined or throw depending
// on the language mode of the load operation.
// Implemented according to ES6 section 9.1.8 [[Get]] (P, Receiver)
*access_info =
PropertyAccessInfo::NotFound(MapHandles{receiver_map}, holder);
return true;
} else {
return false;
}
}
Handle<JSObject> map_prototype(JSObject::cast(map->prototype()), isolate());
if (map_prototype->map()->is_deprecated()) {
// Try to migrate the prototype object so we don't embed the deprecated
// map into the optimized code.
JSObject::TryMigrateInstance(map_prototype);
}
map = handle(map_prototype->map(), isolate());
holder = map_prototype;
} while (CanInlinePropertyAccess(map));
return false;
}
bool AccessInfoFactory::ComputePropertyAccessInfo(
MapHandles const& maps, Handle<Name> name, AccessMode access_mode,
PropertyAccessInfo* access_info) {
ZoneVector<PropertyAccessInfo> access_infos(zone());
if (ComputePropertyAccessInfos(maps, name, access_mode, &access_infos) &&
access_infos.size() == 1) {
*access_info = access_infos.front();
return true;
}
return false;
}
bool AccessInfoFactory::ComputePropertyAccessInfos(
MapHandles const& maps, Handle<Name> name, AccessMode access_mode,
ZoneVector<PropertyAccessInfo>* access_infos) {
for (Handle<Map> map : maps) {
if (Map::TryUpdate(isolate(), map).ToHandle(&map)) {
PropertyAccessInfo access_info;
if (!ComputePropertyAccessInfo(map, name, access_mode, &access_info)) {
return false;
}
// Try to merge the {access_info} with an existing one.
bool merged = false;
for (PropertyAccessInfo& other_info : *access_infos) {
if (other_info.Merge(&access_info, access_mode, zone())) {
merged = true;
break;
}
}
if (!merged) access_infos->push_back(access_info);
}
}
return true;
}
namespace {
Maybe<ElementsKind> GeneralizeElementsKind(ElementsKind this_kind,
ElementsKind that_kind) {
if (IsHoleyElementsKind(this_kind)) {
that_kind = GetHoleyElementsKind(that_kind);
} else if (IsHoleyElementsKind(that_kind)) {
this_kind = GetHoleyElementsKind(this_kind);
}
if (this_kind == that_kind) return Just(this_kind);
if (IsDoubleElementsKind(that_kind) == IsDoubleElementsKind(this_kind)) {
if (IsMoreGeneralElementsKindTransition(that_kind, this_kind)) {
return Just(this_kind);
}
if (IsMoreGeneralElementsKindTransition(this_kind, that_kind)) {
return Just(that_kind);
}
}
return Nothing<ElementsKind>();
}
} // namespace
bool AccessInfoFactory::ConsolidateElementLoad(MapHandles const& maps,
ElementAccessInfo* access_info) {
if (maps.empty()) return false;
InstanceType instance_type = maps.front()->instance_type();
ElementsKind elements_kind = maps.front()->elements_kind();
for (Handle<Map> map : maps) {
if (!CanInlineElementAccess(map) || map->instance_type() != instance_type) {
return false;
}
if (!GeneralizeElementsKind(elements_kind, map->elements_kind())
.To(&elements_kind)) {
return false;
}
}
*access_info = ElementAccessInfo(maps, elements_kind);
return true;
}
bool AccessInfoFactory::LookupSpecialFieldAccessor(
Handle<Map> map, Handle<Name> name, PropertyAccessInfo* access_info) {
// Check for special JSObject field accessors.
FieldIndex field_index;
if (Accessors::IsJSObjectFieldAccessor(isolate(), map, name, &field_index)) {
Type field_type = Type::NonInternal();
MachineRepresentation field_representation = MachineRepresentation::kTagged;
if (map->IsStringMap()) {
DCHECK(Name::Equals(isolate(), factory()->length_string(), name));
// The String::length property is always a smi in the range
// [0, String::kMaxLength].
field_type = type_cache_.kStringLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else if (map->IsJSArrayMap()) {
DCHECK(Name::Equals(isolate(), factory()->length_string(), name));
// The JSArray::length property is a smi in the range
// [0, FixedDoubleArray::kMaxLength] in case of fast double
// elements, a smi in the range [0, FixedArray::kMaxLength]
// in case of other fast elements, and [0, kMaxUInt32] in
// case of other arrays.
if (IsDoubleElementsKind(map->elements_kind())) {
field_type = type_cache_.kFixedDoubleArrayLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else if (IsFastElementsKind(map->elements_kind())) {
field_type = type_cache_.kFixedArrayLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else {
field_type = type_cache_.kJSArrayLengthType;
}
}
// Special fields are always mutable.
*access_info = PropertyAccessInfo::DataField(
PropertyConstness::kMutable, MapHandles{map}, field_index,
field_representation, field_type);
return true;
}
return false;
}
bool AccessInfoFactory::LookupTransition(Handle<Map> map, Handle<Name> name,
MaybeHandle<JSObject> holder,
PropertyAccessInfo* access_info) {
// Check if the {map} has a data transition with the given {name}.
Map* transition =
TransitionsAccessor(isolate(), map).SearchTransition(*name, kData, NONE);
if (transition == nullptr) return false;
Handle<Map> transition_map(transition, isolate());
int const number = transition_map->LastAdded();
PropertyDetails const details =
transition_map->instance_descriptors()->GetDetails(number);
// Don't bother optimizing stores to read-only properties.
if (details.IsReadOnly()) return false;
// TODO(bmeurer): Handle transition to data constant?
if (details.location() != kField) return false;
int const index = details.field_index();
Representation details_representation = details.representation();
FieldIndex field_index = FieldIndex::ForPropertyIndex(*transition_map, index,
details_representation);
Type field_type = Type::NonInternal();
MaybeHandle<Map> field_map;
MachineRepresentation field_representation = MachineRepresentation::kTagged;
if (details_representation.IsSmi()) {
field_type = Type::SignedSmall();
field_representation = MachineRepresentation::kTaggedSigned;
} else if (details_representation.IsDouble()) {
field_type = type_cache_.kFloat64;
field_representation = MachineRepresentation::kFloat64;
} else if (details_representation.IsHeapObject()) {
// Extract the field type from the property details (make sure its
// representation is TaggedPointer to reflect the heap object case).
field_representation = MachineRepresentation::kTaggedPointer;
Handle<FieldType> descriptors_field_type(
transition_map->instance_descriptors()->GetFieldType(number),
isolate());
if (descriptors_field_type->IsNone()) {
// Store is not safe if the field type was cleared.
return false;
} else if (descriptors_field_type->IsClass()) {
dependencies()->DependOnFieldType(
MapRef(js_heap_broker(), transition_map), number);
// Remember the field map, and try to infer a useful type.
Handle<Map> map(descriptors_field_type->AsClass(), isolate());
field_type = Type::For(js_heap_broker(), map);
field_map = MaybeHandle<Map>(map);
}
}
dependencies()->DependOnTransition(MapRef(js_heap_broker(), transition_map));
// Transitioning stores are never stores to constant fields.
*access_info = PropertyAccessInfo::DataField(
PropertyConstness::kMutable, MapHandles{map}, field_index,
field_representation, field_type, field_map, holder, transition_map);
return true;
}
Factory* AccessInfoFactory::factory() const { return isolate()->factory(); }
} // namespace compiler
} // namespace internal
} // namespace v8
|