summaryrefslogtreecommitdiffstats
path: root/js/src/vm/ObjectGroup.cpp
blob: 95fcada94667281cfbd6307fe58496a3b622b8eb (plain)
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
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "vm/ObjectGroup.h"

#include "jsexn.h"
#include "jshashutil.h"
#include "jsobj.h"

#include "gc/Marking.h"
#include "gc/Policy.h"
#include "gc/StoreBuffer.h"
#include "gc/Zone.h"
#include "js/CharacterEncoding.h"
#include "vm/ArrayObject.h"
#include "vm/Shape.h"
#include "vm/TaggedProto.h"
#include "vm/UnboxedObject.h"

#include "jsobjinlines.h"

#include "vm/UnboxedObject-inl.h"

using namespace js;

using mozilla::DebugOnly;
using mozilla::PodZero;

/////////////////////////////////////////////////////////////////////
// ObjectGroup
/////////////////////////////////////////////////////////////////////

ObjectGroup::ObjectGroup(const Class* clasp, TaggedProto proto, JSCompartment* comp,
                         ObjectGroupFlags initialFlags)
{
    PodZero(this);

    /* Windows may not appear on prototype chains. */
    MOZ_ASSERT_IF(proto.isObject(), !IsWindow(proto.toObject()));
    MOZ_ASSERT(JS::StringIsASCII(clasp->name));

    this->clasp_ = clasp;
    this->proto_ = proto;
    this->compartment_ = comp;
    this->flags_ = initialFlags;

    setGeneration(zone()->types.generation);
}

void
ObjectGroup::finalize(FreeOp* fop)
{
    if (newScriptDontCheckGeneration())
        newScriptDontCheckGeneration()->clear();
    fop->delete_(newScriptDontCheckGeneration());
    fop->delete_(maybeUnboxedLayoutDontCheckGeneration());
    if (maybePreliminaryObjectsDontCheckGeneration())
        maybePreliminaryObjectsDontCheckGeneration()->clear();
    fop->delete_(maybePreliminaryObjectsDontCheckGeneration());
}

void
ObjectGroup::setProtoUnchecked(TaggedProto proto)
{
    proto_ = proto;
    MOZ_ASSERT_IF(proto_.isObject() && proto_.toObject()->isNative(),
                  proto_.toObject()->isDelegate());
}

void
ObjectGroup::setProto(TaggedProto proto)
{
    MOZ_ASSERT(singleton());
    setProtoUnchecked(proto);
}

size_t
ObjectGroup::sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = 0;
    if (TypeNewScript* newScript = newScriptDontCheckGeneration())
        n += newScript->sizeOfIncludingThis(mallocSizeOf);
    if (UnboxedLayout* layout = maybeUnboxedLayoutDontCheckGeneration())
        n += layout->sizeOfIncludingThis(mallocSizeOf);
    return n;
}

void
ObjectGroup::setAddendum(AddendumKind kind, void* addendum, bool writeBarrier /* = true */)
{
    MOZ_ASSERT(!needsSweep());
    MOZ_ASSERT(kind <= (OBJECT_FLAG_ADDENDUM_MASK >> OBJECT_FLAG_ADDENDUM_SHIFT));

    if (writeBarrier) {
        // Manually trigger barriers if we are clearing new script or
        // preliminary object information. Other addendums are immutable.
        switch (addendumKind()) {
          case Addendum_PreliminaryObjects:
            PreliminaryObjectArrayWithTemplate::writeBarrierPre(maybePreliminaryObjects());
            break;
          case Addendum_NewScript:
            TypeNewScript::writeBarrierPre(newScript());
            break;
          case Addendum_None:
            break;
          default:
            MOZ_ASSERT(addendumKind() == kind);
        }
    }

    flags_ &= ~OBJECT_FLAG_ADDENDUM_MASK;
    flags_ |= kind << OBJECT_FLAG_ADDENDUM_SHIFT;
    addendum_ = addendum;
}

/* static */ bool
ObjectGroup::useSingletonForClone(JSFunction* fun)
{
    if (!fun->isInterpreted())
        return false;

    if (fun->isArrow())
        return false;

    if (fun->isSingleton())
        return false;

    /*
     * When a function is being used as a wrapper for another function, it
     * improves precision greatly to distinguish between different instances of
     * the wrapper; otherwise we will conflate much of the information about
     * the wrapped functions.
     *
     * An important example is the Class.create function at the core of the
     * Prototype.js library, which looks like:
     *
     * var Class = {
     *   create: function() {
     *     return function() {
     *       this.initialize.apply(this, arguments);
     *     }
     *   }
     * };
     *
     * Each instance of the innermost function will have a different wrapped
     * initialize method. We capture this, along with similar cases, by looking
     * for short scripts which use both .apply and arguments. For such scripts,
     * whenever creating a new instance of the function we both give that
     * instance a singleton type and clone the underlying script.
     */

    uint32_t begin, end;
    if (fun->hasScript()) {
        if (!fun->nonLazyScript()->isLikelyConstructorWrapper())
            return false;
        begin = fun->nonLazyScript()->sourceStart();
        end = fun->nonLazyScript()->sourceEnd();
    } else {
        if (!fun->lazyScript()->isLikelyConstructorWrapper())
            return false;
        begin = fun->lazyScript()->begin();
        end = fun->lazyScript()->end();
    }

    return end - begin <= 100;
}

/* static */ bool
ObjectGroup::useSingletonForNewObject(JSContext* cx, JSScript* script, jsbytecode* pc)
{
    /*
     * Make a heuristic guess at a use of JSOP_NEW that the constructed object
     * should have a fresh group. We do this when the NEW is immediately
     * followed by a simple assignment to an object's .prototype field.
     * This is designed to catch common patterns for subclassing in JS:
     *
     * function Super() { ... }
     * function Sub1() { ... }
     * function Sub2() { ... }
     *
     * Sub1.prototype = new Super();
     * Sub2.prototype = new Super();
     *
     * Using distinct groups for the particular prototypes of Sub1 and
     * Sub2 lets us continue to distinguish the two subclasses and any extra
     * properties added to those prototype objects.
     */
    if (script->isStarGenerator() || script->isLegacyGenerator() || script->isAsync())
        return false;
    if (JSOp(*pc) != JSOP_NEW)
        return false;
    pc += JSOP_NEW_LENGTH;
    if (JSOp(*pc) == JSOP_SETPROP) {
        if (script->getName(pc) == cx->names().prototype)
            return true;
    }
    return false;
}

/* static */ bool
ObjectGroup::useSingletonForAllocationSite(JSScript* script, jsbytecode* pc, JSProtoKey key)
{
    // The return value of this method can either be tested like a boolean or
    // passed to a NewObject method.
    JS_STATIC_ASSERT(GenericObject == 0);

    /*
     * Objects created outside loops in global and eval scripts should have
     * singleton types. For now this is only done for plain objects, but not
     * typed arrays or normal arrays.
     */

    if (script->functionNonDelazifying() && !script->treatAsRunOnce())
        return GenericObject;

    if (key != JSProto_Object)
        return GenericObject;

    // All loops in the script will have a try note indicating their boundary.

    if (!script->hasTrynotes())
        return SingletonObject;

    unsigned offset = script->pcToOffset(pc);

    JSTryNote* tn = script->trynotes()->vector;
    JSTryNote* tnlimit = tn + script->trynotes()->length;
    for (; tn < tnlimit; tn++) {
        if (tn->kind != JSTRY_FOR_IN && tn->kind != JSTRY_FOR_OF && tn->kind != JSTRY_LOOP)
            continue;

        unsigned startOffset = script->mainOffset() + tn->start;
        unsigned endOffset = startOffset + tn->length;

        if (offset >= startOffset && offset < endOffset)
            return GenericObject;
    }

    return SingletonObject;
}

/* static */ bool
ObjectGroup::useSingletonForAllocationSite(JSScript* script, jsbytecode* pc, const Class* clasp)
{
    return useSingletonForAllocationSite(script, pc, JSCLASS_CACHED_PROTO_KEY(clasp));
}

/////////////////////////////////////////////////////////////////////
// JSObject
/////////////////////////////////////////////////////////////////////

bool
JSObject::shouldSplicePrototype()
{
    /*
     * During bootstrapping, if inference is enabled we need to make sure not
     * to splice a new prototype in for Function.prototype or the global
     * object if their __proto__ had previously been set to null, as this
     * will change the prototype for all other objects with the same type.
     */
    if (staticPrototype() != nullptr)
        return false;
    return isSingleton();
}

/* static */ bool
JSObject::splicePrototype(JSContext* cx, HandleObject obj, const Class* clasp,
                          Handle<TaggedProto> proto)
{
    MOZ_ASSERT(cx->compartment() == obj->compartment());

    /*
     * For singleton groups representing only a single JSObject, the proto
     * can be rearranged as needed without destroying type information for
     * the old or new types.
     */
    MOZ_ASSERT(obj->isSingleton());

    // Windows may not appear on prototype chains.
    MOZ_ASSERT_IF(proto.isObject(), !IsWindow(proto.toObject()));

    if (proto.isObject()) {
        RootedObject protoObj(cx, proto.toObject());
        if (!JSObject::setDelegate(cx, protoObj))
            return false;
    }

    // Force type instantiation when splicing lazy group.
    RootedObjectGroup group(cx, JSObject::getGroup(cx, obj));
    if (!group)
        return false;
    RootedObjectGroup protoGroup(cx, nullptr);
    if (proto.isObject()) {
        RootedObject protoObj(cx, proto.toObject());
        protoGroup = JSObject::getGroup(cx, protoObj);
        if (!protoGroup)
            return false;
    }

    group->setClasp(clasp);
    group->setProto(proto);
    return true;
}

/* static */ ObjectGroup*
JSObject::makeLazyGroup(JSContext* cx, HandleObject obj)
{
    MOZ_ASSERT(obj->hasLazyGroup());
    MOZ_ASSERT(cx->compartment() == obj->compartment());

    /* De-lazification of functions can GC, so we need to do it up here. */
    if (obj->is<JSFunction>() && obj->as<JSFunction>().isInterpretedLazy()) {
        RootedFunction fun(cx, &obj->as<JSFunction>());
        if (!JSFunction::getOrCreateScript(cx, fun))
            return nullptr;
    }

    // Find flags which need to be specified immediately on the object.
    // Don't track whether singletons are packed.
    ObjectGroupFlags initialFlags = OBJECT_FLAG_SINGLETON | OBJECT_FLAG_NON_PACKED;

    if (obj->isIteratedSingleton())
        initialFlags |= OBJECT_FLAG_ITERATED;

    if (obj->isIndexed())
        initialFlags |= OBJECT_FLAG_SPARSE_INDEXES;

    if (obj->is<ArrayObject>() && obj->as<ArrayObject>().length() > INT32_MAX)
        initialFlags |= OBJECT_FLAG_LENGTH_OVERFLOW;

    Rooted<TaggedProto> proto(cx, obj->taggedProto());
    ObjectGroup* group = ObjectGroupCompartment::makeGroup(cx, obj->getClass(), proto,
                                                           initialFlags);
    if (!group)
        return nullptr;

    AutoEnterAnalysis enter(cx);

    /* Fill in the type according to the state of this object. */

    if (obj->is<JSFunction>() && obj->as<JSFunction>().isInterpreted())
        group->setInterpretedFunction(&obj->as<JSFunction>());

    obj->group_ = group;

    return group;
}

/* static */ bool
JSObject::setNewGroupUnknown(JSContext* cx, const js::Class* clasp, JS::HandleObject obj)
{
    ObjectGroup::setDefaultNewGroupUnknown(cx, clasp, obj);
    return JSObject::setFlags(cx, obj, BaseShape::NEW_GROUP_UNKNOWN);
}

/////////////////////////////////////////////////////////////////////
// ObjectGroupCompartment NewTable
/////////////////////////////////////////////////////////////////////

/*
 * Entries for the per-compartment set of groups which are the default
 * types to use for some prototype. An optional associated object is used which
 * allows multiple groups to be created with the same prototype. The
 * associated object may be a function (for types constructed with 'new') or a
 * type descriptor (for typed objects). These entries are also used for the set
 * of lazy groups in the compartment, which use a null associated object
 * (though there are only a few of these per compartment).
 */
struct ObjectGroupCompartment::NewEntry
{
    ReadBarrieredObjectGroup group;

    // Note: This pointer is only used for equality and does not need a read barrier.
    JSObject* associated;

    NewEntry(ObjectGroup* group, JSObject* associated)
      : group(group), associated(associated)
    {}

    struct Lookup {
        const Class* clasp;
        TaggedProto proto;
        JSObject* associated;

        Lookup(const Class* clasp, TaggedProto proto, JSObject* associated)
          : clasp(clasp), proto(proto), associated(associated)
        {}

        bool hasAssocId() const {
            return !associated || associated->zone()->hasUniqueId(associated);
        }

        bool ensureAssocId() const {
            uint64_t unusedId;
            return !associated ||
                   associated->zoneFromAnyThread()->getUniqueId(associated, &unusedId);
        }

        uint64_t getAssocId() const {
            return associated ? associated->zone()->getUniqueIdInfallible(associated) : 0;
        }
    };

    static bool hasHash(const Lookup& l) {
        return l.proto.hasUniqueId() && l.hasAssocId();
    }

    static bool ensureHash(const Lookup& l) {
        return l.proto.ensureUniqueId() && l.ensureAssocId();
    }

    static inline HashNumber hash(const Lookup& lookup) {
        MOZ_ASSERT(lookup.proto.hasUniqueId());
        MOZ_ASSERT(lookup.hasAssocId());
        HashNumber hash = uintptr_t(lookup.clasp);
        hash = mozilla::RotateLeft(hash, 4) ^ Zone::UniqueIdToHash(lookup.proto.uniqueId());
        hash = mozilla::RotateLeft(hash, 4) ^ Zone::UniqueIdToHash(lookup.getAssocId());
        return hash;
    }

    static inline bool match(const ObjectGroupCompartment::NewEntry& key, const Lookup& lookup) {
        TaggedProto proto = key.group.unbarrieredGet()->proto().unbarrieredGet();
        JSObject* assoc = key.associated;
        MOZ_ASSERT(proto.hasUniqueId());
        MOZ_ASSERT_IF(assoc, assoc->zone()->hasUniqueId(assoc));
        MOZ_ASSERT(lookup.proto.hasUniqueId());
        MOZ_ASSERT(lookup.hasAssocId());

        if (lookup.clasp && key.group.unbarrieredGet()->clasp() != lookup.clasp)
            return false;
        if (proto.uniqueId() != lookup.proto.uniqueId())
            return false;
        return !assoc || assoc->zone()->getUniqueIdInfallible(assoc) == lookup.getAssocId();
    }

    static void rekey(NewEntry& k, const NewEntry& newKey) { k = newKey; }

    bool needsSweep() {
        return (IsAboutToBeFinalized(&group) ||
                (associated && IsAboutToBeFinalizedUnbarriered(&associated)));
    }
};

namespace js {
template <>
struct FallibleHashMethods<ObjectGroupCompartment::NewEntry>
{
    template <typename Lookup> static bool hasHash(Lookup&& l) {
        return ObjectGroupCompartment::NewEntry::hasHash(mozilla::Forward<Lookup>(l));
    }
    template <typename Lookup> static bool ensureHash(Lookup&& l) {
        return ObjectGroupCompartment::NewEntry::ensureHash(mozilla::Forward<Lookup>(l));
    }
};
} // namespace js

class ObjectGroupCompartment::NewTable : public JS::WeakCache<js::GCHashSet<NewEntry, NewEntry,
                                                                            SystemAllocPolicy>>
{
    using Table = js::GCHashSet<NewEntry, NewEntry, SystemAllocPolicy>;
    using Base = JS::WeakCache<Table>;

  public:
    explicit NewTable(Zone* zone) : Base(zone, Table()) {}
};

/* static */ ObjectGroup*
ObjectGroup::defaultNewGroup(ExclusiveContext* cx, const Class* clasp,
                             TaggedProto proto, JSObject* associated)
{
    MOZ_ASSERT_IF(associated, proto.isObject());
    MOZ_ASSERT_IF(proto.isObject(), cx->isInsideCurrentCompartment(proto.toObject()));

    // A null lookup clasp is used for 'new' groups with an associated
    // function. The group starts out as a plain object but might mutate into an
    // unboxed plain object.
    MOZ_ASSERT_IF(!clasp, !!associated);

    AutoEnterAnalysis enter(cx);

    ObjectGroupCompartment::NewTable*& table = cx->compartment()->objectGroups.defaultNewTable;

    if (!table) {
        table = cx->new_<ObjectGroupCompartment::NewTable>(cx->zone());
        if (!table || !table->init()) {
            js_delete(table);
            table = nullptr;
            ReportOutOfMemory(cx);
            return nullptr;
        }
    }

    if (associated && !associated->is<TypeDescr>()) {
        MOZ_ASSERT(!clasp);
        if (associated->is<JSFunction>()) {

            // Canonicalize new functions to use the original one associated with its script.
            associated = associated->as<JSFunction>().maybeCanonicalFunction();

            // If we have previously cleared the 'new' script information for this
            // function, don't try to construct another one.
            if (associated && associated->wasNewScriptCleared())
                associated = nullptr;

        } else {
            associated = nullptr;
        }

        if (!associated)
            clasp = &PlainObject::class_;
    }

    if (proto.isObject() && !proto.toObject()->isDelegate()) {
        RootedObject protoObj(cx, proto.toObject());
        if (!JSObject::setDelegate(cx, protoObj))
            return nullptr;

        // Objects which are prototypes of one another should be singletons, so
        // that their type information can be tracked more precisely. Limit
        // this group change to plain objects, to avoid issues with other types
        // of singletons like typed arrays.
        if (protoObj->is<PlainObject>() && !protoObj->isSingleton()) {
            if (!JSObject::changeToSingleton(cx->asJSContext(), protoObj))
                return nullptr;
        }
    }

    ObjectGroupCompartment::NewTable::AddPtr p =
        table->lookupForAdd(ObjectGroupCompartment::NewEntry::Lookup(clasp, proto, associated));
    if (p) {
        ObjectGroup* group = p->group;
        MOZ_ASSERT_IF(clasp, group->clasp() == clasp);
        MOZ_ASSERT_IF(!clasp, group->clasp() == &PlainObject::class_ ||
                              group->clasp() == &UnboxedPlainObject::class_);
        MOZ_ASSERT(group->proto() == proto);
        return group;
    }

    ObjectGroupFlags initialFlags = 0;
    if (proto.isDynamic() || (proto.isObject() && proto.toObject()->isNewGroupUnknown()))
        initialFlags = OBJECT_FLAG_DYNAMIC_MASK;

    Rooted<TaggedProto> protoRoot(cx, proto);
    ObjectGroup* group = ObjectGroupCompartment::makeGroup(cx, clasp ? clasp : &PlainObject::class_,
                                                           protoRoot, initialFlags);
    if (!group)
        return nullptr;

    if (!table->add(p, ObjectGroupCompartment::NewEntry(group, associated))) {
        ReportOutOfMemory(cx);
        return nullptr;
    }

    if (associated) {
        if (associated->is<JSFunction>()) {
            if (!TypeNewScript::make(cx->asJSContext(), group, &associated->as<JSFunction>()))
                return nullptr;
        } else {
            group->setTypeDescr(&associated->as<TypeDescr>());
        }
    }

    /*
     * Some builtin objects have slotful native properties baked in at
     * creation via the Shape::{insert,get}initialShape mechanism. Since
     * these properties are never explicitly defined on new objects, update
     * the type information for them here.
     */

    const JSAtomState& names = cx->names();

    if (clasp == &RegExpObject::class_) {
        AddTypePropertyId(cx, group, nullptr, NameToId(names.lastIndex), TypeSet::Int32Type());
    } else if (clasp == &StringObject::class_) {
        AddTypePropertyId(cx, group, nullptr, NameToId(names.length), TypeSet::Int32Type());
    } else if (ErrorObject::isErrorClass(clasp)) {
        AddTypePropertyId(cx, group, nullptr, NameToId(names.fileName), TypeSet::StringType());
        AddTypePropertyId(cx, group, nullptr, NameToId(names.lineNumber), TypeSet::Int32Type());
        AddTypePropertyId(cx, group, nullptr, NameToId(names.columnNumber), TypeSet::Int32Type());
    }

    return group;
}

/* static */ ObjectGroup*
ObjectGroup::lazySingletonGroup(ExclusiveContext* cx, const Class* clasp, TaggedProto proto)
{
    MOZ_ASSERT_IF(proto.isObject(), cx->compartment() == proto.toObject()->compartment());

    ObjectGroupCompartment::NewTable*& table = cx->compartment()->objectGroups.lazyTable;

    if (!table) {
        table = cx->new_<ObjectGroupCompartment::NewTable>(cx->zone());
        if (!table || !table->init()) {
            ReportOutOfMemory(cx);
            js_delete(table);
            table = nullptr;
            return nullptr;
        }
    }

    ObjectGroupCompartment::NewTable::AddPtr p =
        table->lookupForAdd(ObjectGroupCompartment::NewEntry::Lookup(clasp, proto, nullptr));
    if (p) {
        ObjectGroup* group = p->group;
        MOZ_ASSERT(group->lazy());

        return group;
    }

    AutoEnterAnalysis enter(cx);

    Rooted<TaggedProto> protoRoot(cx, proto);
    ObjectGroup* group =
        ObjectGroupCompartment::makeGroup(cx, clasp, protoRoot,
                                          OBJECT_FLAG_SINGLETON | OBJECT_FLAG_LAZY_SINGLETON);
    if (!group)
        return nullptr;

    if (!table->add(p, ObjectGroupCompartment::NewEntry(group, nullptr))) {
        ReportOutOfMemory(cx);
        return nullptr;
    }

    return group;
}

/* static */ void
ObjectGroup::setDefaultNewGroupUnknown(JSContext* cx, const Class* clasp, HandleObject obj)
{
    // If the object already has a new group, mark that group as unknown.
    ObjectGroupCompartment::NewTable* table = cx->compartment()->objectGroups.defaultNewTable;
    if (table) {
        Rooted<TaggedProto> taggedProto(cx, TaggedProto(obj));
        auto lookup = ObjectGroupCompartment::NewEntry::Lookup(clasp, taggedProto, nullptr);
        auto p = table->lookup(lookup);
        if (p)
            MarkObjectGroupUnknownProperties(cx, p->group);
    }
}

#ifdef DEBUG
/* static */ bool
ObjectGroup::hasDefaultNewGroup(JSObject* proto, const Class* clasp, ObjectGroup* group)
{
    ObjectGroupCompartment::NewTable* table = proto->compartment()->objectGroups.defaultNewTable;

    if (table) {
        auto lookup = ObjectGroupCompartment::NewEntry::Lookup(clasp, TaggedProto(proto), nullptr);
        auto p = table->lookup(lookup);
        return p && p->group == group;
    }
    return false;
}
#endif /* DEBUG */

inline const Class*
GetClassForProtoKey(JSProtoKey key)
{
    switch (key) {
      case JSProto_Null:
      case JSProto_Object:
        return &PlainObject::class_;
      case JSProto_Array:
        return &ArrayObject::class_;

      case JSProto_Number:
        return &NumberObject::class_;
      case JSProto_Boolean:
        return &BooleanObject::class_;
      case JSProto_String:
        return &StringObject::class_;
      case JSProto_Symbol:
        return &SymbolObject::class_;
      case JSProto_RegExp:
        return &RegExpObject::class_;

      case JSProto_Int8Array:
      case JSProto_Uint8Array:
      case JSProto_Int16Array:
      case JSProto_Uint16Array:
      case JSProto_Int32Array:
      case JSProto_Uint32Array:
      case JSProto_Float32Array:
      case JSProto_Float64Array:
      case JSProto_Uint8ClampedArray:
        return &TypedArrayObject::classes[key - JSProto_Int8Array];

      case JSProto_ArrayBuffer:
        return &ArrayBufferObject::class_;

      case JSProto_SharedArrayBuffer:
        return &SharedArrayBufferObject::class_;

      case JSProto_DataView:
        return &DataViewObject::class_;

      default:
        MOZ_CRASH("Bad proto key");
    }
}

/* static */ ObjectGroup*
ObjectGroup::defaultNewGroup(JSContext* cx, JSProtoKey key)
{
    RootedObject proto(cx);
    if (key != JSProto_Null && !GetBuiltinPrototype(cx, key, &proto))
        return nullptr;
    return defaultNewGroup(cx, GetClassForProtoKey(key), TaggedProto(proto.get()));
}

/////////////////////////////////////////////////////////////////////
// ObjectGroupCompartment ArrayObjectTable
/////////////////////////////////////////////////////////////////////

struct ObjectGroupCompartment::ArrayObjectKey : public DefaultHasher<ArrayObjectKey>
{
    TypeSet::Type type;

    ArrayObjectKey()
      : type(TypeSet::UndefinedType())
    {}

    explicit ArrayObjectKey(TypeSet::Type type)
      : type(type)
    {}

    static inline uint32_t hash(const ArrayObjectKey& v) {
        return v.type.raw();
    }

    static inline bool match(const ArrayObjectKey& v1, const ArrayObjectKey& v2) {
        return v1.type == v2.type;
    }

    bool operator==(const ArrayObjectKey& other) {
        return type == other.type;
    }

    bool operator!=(const ArrayObjectKey& other) {
        return !(*this == other);
    }

    bool needsSweep() {
        MOZ_ASSERT(type.isUnknown() || !type.isSingleton());
        if (!type.isUnknown() && type.isGroup()) {
            ObjectGroup* group = type.groupNoBarrier();
            if (IsAboutToBeFinalizedUnbarriered(&group))
                return true;
            if (group != type.groupNoBarrier())
                type = TypeSet::ObjectType(group);
        }
        return false;
    }
};

static inline bool
NumberTypes(TypeSet::Type a, TypeSet::Type b)
{
    return (a.isPrimitive(JSVAL_TYPE_INT32) || a.isPrimitive(JSVAL_TYPE_DOUBLE))
        && (b.isPrimitive(JSVAL_TYPE_INT32) || b.isPrimitive(JSVAL_TYPE_DOUBLE));
}

/*
 * As for GetValueType, but requires object types to be non-singletons with
 * their default prototype. These are the only values that should appear in
 * arrays and objects whose type can be fixed.
 */
static inline TypeSet::Type
GetValueTypeForTable(const Value& v)
{
    TypeSet::Type type = TypeSet::GetValueType(v);
    MOZ_ASSERT(!type.isSingleton());
    return type;
}

/* static */ ArrayObject*
ObjectGroup::newArrayObject(ExclusiveContext* cx,
                            const Value* vp, size_t length,
                            NewObjectKind newKind, NewArrayKind arrayKind)
{
    MOZ_ASSERT(newKind != SingletonObject);

    // If we are making a copy on write array, don't try to adjust the group as
    // getOrFixupCopyOnWriteObject will do this before any objects are copied
    // from this one.
    if (arrayKind == NewArrayKind::CopyOnWrite) {
        ArrayObject* obj = NewDenseCopiedArray(cx, length, vp, nullptr, newKind);
        if (!obj || !ObjectElements::MakeElementsCopyOnWrite(cx, obj))
            return nullptr;
        return obj;
    }

    // Get a type which captures all the elements in the array to be created.
    Rooted<TypeSet::Type> elementType(cx, TypeSet::UnknownType());
    if (arrayKind != NewArrayKind::UnknownIndex && length != 0) {
        elementType = GetValueTypeForTable(vp[0]);
        for (unsigned i = 1; i < length; i++) {
            TypeSet::Type ntype = GetValueTypeForTable(vp[i]);
            if (ntype != elementType) {
                if (NumberTypes(elementType, ntype)) {
                    elementType = TypeSet::DoubleType();
                } else {
                    elementType = TypeSet::UnknownType();
                    break;
                }
            }
        }
    }

    ObjectGroupCompartment::ArrayObjectTable*& table =
        cx->compartment()->objectGroups.arrayObjectTable;

    if (!table) {
        table = cx->new_<ObjectGroupCompartment::ArrayObjectTable>();
        if (!table || !table->init()) {
            ReportOutOfMemory(cx);
            js_delete(table);
            table = nullptr;
            return nullptr;
        }
    }

    ObjectGroupCompartment::ArrayObjectKey key(elementType);
    DependentAddPtr<ObjectGroupCompartment::ArrayObjectTable> p(cx, *table, key);

    RootedObjectGroup group(cx);
    if (p) {
        group = p->value();
    } else {
        RootedObject proto(cx);
        if (!GetBuiltinPrototype(cx, JSProto_Array, &proto))
            return nullptr;
        Rooted<TaggedProto> taggedProto(cx, TaggedProto(proto));
        group = ObjectGroupCompartment::makeGroup(cx, &ArrayObject::class_, taggedProto);
        if (!group)
            return nullptr;

        AddTypePropertyId(cx, group, nullptr, JSID_VOID, elementType);

        if (!p.add(cx, *table, ObjectGroupCompartment::ArrayObjectKey(elementType), group))
            return nullptr;
    }

    // The type of the elements being added will already be reflected in type
    // information.
    ShouldUpdateTypes updateTypes = ShouldUpdateTypes::DontUpdate;
    return NewCopiedArrayTryUseGroup(cx, group, vp, length, newKind, updateTypes);
}

// Try to change the group of |source| to match that of |target|.
static bool
GiveObjectGroup(ExclusiveContext* cx, JSObject* source, JSObject* target)
{
    MOZ_ASSERT(source->group() != target->group());

    if (!target->is<ArrayObject>() || !source->is<ArrayObject>()) {
        return true;
    }

    source->setGroup(target->group());

    for (size_t i = 0; i < source->as<ArrayObject>().getDenseInitializedLength(); i++) {
        Value v = source->as<ArrayObject>().getDenseElement(i);
        AddTypePropertyId(cx, source->group(), source, JSID_VOID, v);
    }

    return true;
}

static bool
SameGroup(JSObject* first, JSObject* second)
{
    return first->group() == second->group();
}

// When generating a multidimensional array of literals, such as
// [[1,2],[3,4],[5.5,6.5]], try to ensure that each element of the array has
// the same group. This is mainly important when the elements might have
// different native vs. unboxed layouts, or different unboxed layouts, and
// accessing the heterogenous layouts from JIT code will be much slower than
// if they were homogenous.
//
// To do this, with each new array element we compare it with one of the
// previous ones, and try to mutate the group of the new element to fit that
// of the old element. If this isn't possible, the groups for all old elements
// are mutated to fit that of the new element.
bool
js::CombineArrayElementTypes(ExclusiveContext* cx, JSObject* newObj,
                             const Value* compare, size_t ncompare)
{
    if (!ncompare || !compare[0].isObject())
        return true;

    JSObject* oldObj = &compare[0].toObject();
    if (SameGroup(oldObj, newObj))
        return true;

    if (!GiveObjectGroup(cx, newObj, oldObj))
        return false;

    if (SameGroup(oldObj, newObj))
        return true;

    if (!GiveObjectGroup(cx, oldObj, newObj))
        return false;

    if (SameGroup(oldObj, newObj)) {
        for (size_t i = 1; i < ncompare; i++) {
            if (compare[i].isObject() && !SameGroup(&compare[i].toObject(), newObj)) {
                if (!GiveObjectGroup(cx, &compare[i].toObject(), newObj))
                    return false;
            }
        }
    }

    return true;
}

// Similarly to CombineArrayElementTypes, if we are generating an array of
// plain objects with a consistent property layout, such as
// [{p:[1,2]},{p:[3,4]},{p:[5.5,6.5]}], where those plain objects in
// turn have arrays as their own properties, try to ensure that a consistent
// group is given to each array held by the same property of the plain objects.
bool
js::CombinePlainObjectPropertyTypes(ExclusiveContext* cx, JSObject* newObj,
                                    const Value* compare, size_t ncompare)
{
    if (!ncompare || !compare[0].isObject())
        return true;

    JSObject* oldObj = &compare[0].toObject();
    if (!SameGroup(oldObj, newObj))
        return true;

    if (newObj->is<PlainObject>()) {
        if (newObj->as<PlainObject>().lastProperty() != oldObj->as<PlainObject>().lastProperty())
            return true;

        for (size_t slot = 0; slot < newObj->as<PlainObject>().slotSpan(); slot++) {
            Value newValue = newObj->as<PlainObject>().getSlot(slot);
            Value oldValue = oldObj->as<PlainObject>().getSlot(slot);

            if (!newValue.isObject() || !oldValue.isObject())
                continue;

            JSObject* newInnerObj = &newValue.toObject();
            JSObject* oldInnerObj = &oldValue.toObject();

            if (SameGroup(oldInnerObj, newInnerObj))
                continue;

            if (!GiveObjectGroup(cx, newInnerObj, oldInnerObj))
                return false;

            if (SameGroup(oldInnerObj, newInnerObj))
                continue;

            if (!GiveObjectGroup(cx, oldInnerObj, newInnerObj))
                return false;

            if (SameGroup(oldInnerObj, newInnerObj)) {
                for (size_t i = 1; i < ncompare; i++) {
                    if (compare[i].isObject() && SameGroup(&compare[i].toObject(), newObj)) {
                        Value otherValue = compare[i].toObject().as<PlainObject>().getSlot(slot);
                        if (otherValue.isObject() && !SameGroup(&otherValue.toObject(), newInnerObj)) {
                            if (!GiveObjectGroup(cx, &otherValue.toObject(), newInnerObj))
                                return false;
                        }
                    }
                }
            }
        }
    } else if (newObj->is<UnboxedPlainObject>()) {
        const UnboxedLayout& layout = newObj->as<UnboxedPlainObject>().layout();
        const int32_t* traceList = layout.traceList();
        if (!traceList)
            return true;

        uint8_t* newData = newObj->as<UnboxedPlainObject>().data();
        uint8_t* oldData = oldObj->as<UnboxedPlainObject>().data();

        for (; *traceList != -1; traceList++) {}
        traceList++;
        for (; *traceList != -1; traceList++) {
            JSObject* newInnerObj = *reinterpret_cast<JSObject**>(newData + *traceList);
            JSObject* oldInnerObj = *reinterpret_cast<JSObject**>(oldData + *traceList);

            if (!newInnerObj || !oldInnerObj || SameGroup(oldInnerObj, newInnerObj))
                continue;

            if (!GiveObjectGroup(cx, newInnerObj, oldInnerObj))
                return false;

            if (SameGroup(oldInnerObj, newInnerObj))
                continue;

            if (!GiveObjectGroup(cx, oldInnerObj, newInnerObj))
                return false;

            if (SameGroup(oldInnerObj, newInnerObj)) {
                for (size_t i = 1; i < ncompare; i++) {
                    if (compare[i].isObject() && SameGroup(&compare[i].toObject(), newObj)) {
                        uint8_t* otherData = compare[i].toObject().as<UnboxedPlainObject>().data();
                        JSObject* otherInnerObj = *reinterpret_cast<JSObject**>(otherData + *traceList);
                        if (otherInnerObj && !SameGroup(otherInnerObj, newInnerObj)) {
                            if (!GiveObjectGroup(cx, otherInnerObj, newInnerObj))
                                return false;
                        }
                    }
                }
            }
        }
    }

    return true;
}

/////////////////////////////////////////////////////////////////////
// ObjectGroupCompartment PlainObjectTable
/////////////////////////////////////////////////////////////////////

struct ObjectGroupCompartment::PlainObjectKey
{
    jsid* properties;
    uint32_t nproperties;

    struct Lookup {
        IdValuePair* properties;
        uint32_t nproperties;

        Lookup(IdValuePair* properties, uint32_t nproperties)
          : properties(properties), nproperties(nproperties)
        {}
    };

    static inline HashNumber hash(const Lookup& lookup) {
        return (HashNumber) (HashId(lookup.properties[lookup.nproperties - 1].id) ^
                             lookup.nproperties);
    }

    static inline bool match(const PlainObjectKey& v, const Lookup& lookup) {
        if (lookup.nproperties != v.nproperties)
            return false;
        for (size_t i = 0; i < lookup.nproperties; i++) {
            if (lookup.properties[i].id != v.properties[i])
                return false;
        }
        return true;
    }

    bool needsSweep() {
        for (unsigned i = 0; i < nproperties; i++) {
            if (gc::IsAboutToBeFinalizedUnbarriered(&properties[i]))
                return true;
        }
        return false;
    }
};

struct ObjectGroupCompartment::PlainObjectEntry
{
    ReadBarrieredObjectGroup group;
    ReadBarrieredShape shape;
    TypeSet::Type* types;

    bool needsSweep(unsigned nproperties) {
        if (IsAboutToBeFinalized(&group))
            return true;
        if (IsAboutToBeFinalized(&shape))
            return true;
        for (unsigned i = 0; i < nproperties; i++) {
            MOZ_ASSERT(!types[i].isSingleton());
            if (types[i].isGroup()) {
                ObjectGroup* group = types[i].groupNoBarrier();
                if (IsAboutToBeFinalizedUnbarriered(&group))
                    return true;
                if (group != types[i].groupNoBarrier())
                    types[i] = TypeSet::ObjectType(group);
            }
        }
        return false;
    }
};

static bool
CanShareObjectGroup(IdValuePair* properties, size_t nproperties)
{
    // Don't reuse groups for objects containing indexed properties, which
    // might end up as dense elements.
    for (size_t i = 0; i < nproperties; i++) {
        uint32_t index;
        if (IdIsIndex(properties[i].id, &index))
            return false;
    }
    return true;
}

static bool
AddPlainObjectProperties(ExclusiveContext* cx, HandlePlainObject obj,
                         IdValuePair* properties, size_t nproperties)
{
    RootedId propid(cx);
    RootedValue value(cx);

    for (size_t i = 0; i < nproperties; i++) {
        propid = properties[i].id;
        value = properties[i].value;
        if (!NativeDefineProperty(cx, obj, propid, value, nullptr, nullptr, JSPROP_ENUMERATE))
            return false;
    }

    return true;
}

PlainObject*
js::NewPlainObjectWithProperties(ExclusiveContext* cx, IdValuePair* properties, size_t nproperties,
                                 NewObjectKind newKind)
{
    gc::AllocKind allocKind = gc::GetGCObjectKind(nproperties);
    RootedPlainObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx, allocKind, newKind));
    if (!obj || !AddPlainObjectProperties(cx, obj, properties, nproperties))
        return nullptr;
    return obj;
}

/* static */ JSObject*
ObjectGroup::newPlainObject(ExclusiveContext* cx, IdValuePair* properties, size_t nproperties,
                            NewObjectKind newKind)
{
    // Watch for simple cases where we don't try to reuse plain object groups.
    if (newKind == SingletonObject || nproperties == 0 || nproperties >= PropertyTree::MAX_HEIGHT)
        return NewPlainObjectWithProperties(cx, properties, nproperties, newKind);

    ObjectGroupCompartment::PlainObjectTable*& table =
        cx->compartment()->objectGroups.plainObjectTable;

    if (!table) {
        table = cx->new_<ObjectGroupCompartment::PlainObjectTable>();
        if (!table || !table->init()) {
            ReportOutOfMemory(cx);
            js_delete(table);
            table = nullptr;
            return nullptr;
        }
    }

    ObjectGroupCompartment::PlainObjectKey::Lookup lookup(properties, nproperties);
    ObjectGroupCompartment::PlainObjectTable::Ptr p = table->lookup(lookup);

    if (!p) {
        if (!CanShareObjectGroup(properties, nproperties))
            return NewPlainObjectWithProperties(cx, properties, nproperties, newKind);

        RootedObject proto(cx);
        if (!GetBuiltinPrototype(cx, JSProto_Object, &proto))
            return nullptr;

        Rooted<TaggedProto> tagged(cx, TaggedProto(proto));
        RootedObjectGroup group(cx, ObjectGroupCompartment::makeGroup(cx, &PlainObject::class_,
                                                                      tagged));
        if (!group)
            return nullptr;

        gc::AllocKind allocKind = gc::GetGCObjectKind(nproperties);
        RootedPlainObject obj(cx, NewObjectWithGroup<PlainObject>(cx, group,
                                                                  allocKind, TenuredObject));
        if (!obj || !AddPlainObjectProperties(cx, obj, properties, nproperties))
            return nullptr;

        // Don't make entries with duplicate property names, which will show up
        // here as objects with fewer properties than we thought we were
        // adding to the object. In this case, reset the object's group to the
        // default (which will have unknown properties) so that the group we
        // just created will be collected by the GC.
        if (obj->slotSpan() != nproperties) {
            ObjectGroup* group = defaultNewGroup(cx, obj->getClass(), obj->taggedProto());
            if (!group)
                return nullptr;
            obj->setGroup(group);
            return obj;
        }

        // Keep track of the initial objects we create with this type.
        // If the initial ones have a consistent shape and property types, we
        // will try to use an unboxed layout for the group.
        PreliminaryObjectArrayWithTemplate* preliminaryObjects =
            cx->new_<PreliminaryObjectArrayWithTemplate>(obj->lastProperty());
        if (!preliminaryObjects)
            return nullptr;
        group->setPreliminaryObjects(preliminaryObjects);
        preliminaryObjects->registerNewObject(obj);

        ScopedJSFreePtr<jsid> ids(group->zone()->pod_calloc<jsid>(nproperties));
        if (!ids) {
            ReportOutOfMemory(cx);
            return nullptr;
        }

        ScopedJSFreePtr<TypeSet::Type> types(
            group->zone()->pod_calloc<TypeSet::Type>(nproperties));
        if (!types) {
            ReportOutOfMemory(cx);
            return nullptr;
        }

        for (size_t i = 0; i < nproperties; i++) {
            ids[i] = properties[i].id;
            types[i] = GetValueTypeForTable(obj->getSlot(i));
            AddTypePropertyId(cx, group, nullptr, IdToTypeId(ids[i]), types[i]);
        }

        ObjectGroupCompartment::PlainObjectKey key;
        key.properties = ids;
        key.nproperties = nproperties;
        MOZ_ASSERT(ObjectGroupCompartment::PlainObjectKey::match(key, lookup));

        ObjectGroupCompartment::PlainObjectEntry entry;
        entry.group.set(group);
        entry.shape.set(obj->lastProperty());
        entry.types = types;

        ObjectGroupCompartment::PlainObjectTable::AddPtr np = table->lookupForAdd(lookup);
        if (!table->add(np, key, entry)) {
            ReportOutOfMemory(cx);
            return nullptr;
        }

        ids.forget();
        types.forget();

        return obj;
    }

    RootedObjectGroup group(cx, p->value().group);

    // Watch for existing groups which now use an unboxed layout.
    if (group->maybeUnboxedLayout()) {
        MOZ_ASSERT(group->unboxedLayout().properties().length() == nproperties);
        return UnboxedPlainObject::createWithProperties(cx, group, newKind, properties);
    }

    // Update property types according to the properties we are about to add.
    // Do this before we do anything which can GC, which might move or remove
    // this table entry.
    if (!group->unknownProperties()) {
        for (size_t i = 0; i < nproperties; i++) {
            TypeSet::Type type = p->value().types[i];
            TypeSet::Type ntype = GetValueTypeForTable(properties[i].value);
            if (ntype == type)
                continue;
            if (ntype.isPrimitive(JSVAL_TYPE_INT32) &&
                type.isPrimitive(JSVAL_TYPE_DOUBLE))
            {
                // The property types already reflect 'int32'.
            } else {
                if (ntype.isPrimitive(JSVAL_TYPE_DOUBLE) &&
                    type.isPrimitive(JSVAL_TYPE_INT32))
                {
                    // Include 'double' in the property types to avoid the update below later.
                    p->value().types[i] = TypeSet::DoubleType();
                }
                AddTypePropertyId(cx, group, nullptr, IdToTypeId(properties[i].id), ntype);
            }
        }
    }

    RootedShape shape(cx, p->value().shape);

    if (group->maybePreliminaryObjects())
        newKind = TenuredObject;

    gc::AllocKind allocKind = gc::GetGCObjectKind(nproperties);
    RootedPlainObject obj(cx, NewObjectWithGroup<PlainObject>(cx, group, allocKind,
                                                              newKind));

    if (!obj || !obj->setLastProperty(cx, shape))
        return nullptr;

    for (size_t i = 0; i < nproperties; i++)
        obj->setSlot(i, properties[i].value);

    if (group->maybePreliminaryObjects()) {
        group->maybePreliminaryObjects()->registerNewObject(obj);
        group->maybePreliminaryObjects()->maybeAnalyze(cx, group);
    }

    return obj;
}

/////////////////////////////////////////////////////////////////////
// ObjectGroupCompartment AllocationSiteTable
/////////////////////////////////////////////////////////////////////

struct ObjectGroupCompartment::AllocationSiteKey : public DefaultHasher<AllocationSiteKey> {
    ReadBarrieredScript script;

    uint32_t offset : 24;
    JSProtoKey kind : 8;

    ReadBarrieredObject proto;

    static const uint32_t OFFSET_LIMIT = (1 << 23);

    AllocationSiteKey(JSScript* script_, uint32_t offset_, JSProtoKey kind_, JSObject* proto_)
      : script(script_), offset(offset_), kind(kind_), proto(proto_)
    {
        MOZ_ASSERT(offset_ < OFFSET_LIMIT);
    }

    AllocationSiteKey(const AllocationSiteKey& key)
      : script(key.script),
        offset(key.offset),
        kind(key.kind),
        proto(key.proto)
    { }

    AllocationSiteKey(AllocationSiteKey&& key)
      : script(mozilla::Move(key.script)),
        offset(key.offset),
        kind(key.kind),
        proto(mozilla::Move(key.proto))
    { }

    void operator=(AllocationSiteKey&& key) {
        script = mozilla::Move(key.script);
        offset = key.offset;
        kind = key.kind;
        proto = mozilla::Move(key.proto);
    }

    static inline uint32_t hash(AllocationSiteKey key) {
        return uint32_t(size_t(key.script->offsetToPC(key.offset)) ^ key.kind ^
               MovableCellHasher<JSObject*>::hash(key.proto));
    }

    static inline bool match(const AllocationSiteKey& a, const AllocationSiteKey& b) {
        return DefaultHasher<JSScript*>::match(a.script, b.script) &&
               a.offset == b.offset &&
               a.kind == b.kind &&
               MovableCellHasher<JSObject*>::match(a.proto, b.proto);
    }

    void trace(JSTracer* trc) {
        TraceRoot(trc, &script, "AllocationSiteKey script");
        TraceNullableRoot(trc, &proto, "AllocationSiteKey proto");
    }

    bool needsSweep() {
        return IsAboutToBeFinalizedUnbarriered(script.unsafeGet()) ||
            (proto && IsAboutToBeFinalizedUnbarriered(proto.unsafeGet()));
    }
};

class ObjectGroupCompartment::AllocationSiteTable
  : public JS::WeakCache<js::GCHashMap<AllocationSiteKey, ReadBarrieredObjectGroup,
                                       AllocationSiteKey, SystemAllocPolicy>>
{
    using Table = js::GCHashMap<AllocationSiteKey, ReadBarrieredObjectGroup,
                                AllocationSiteKey, SystemAllocPolicy>;
    using Base = JS::WeakCache<Table>;

  public:
    explicit AllocationSiteTable(Zone* zone) : Base(zone, Table()) {}
};

/* static */ ObjectGroup*
ObjectGroup::allocationSiteGroup(JSContext* cx, JSScript* scriptArg, jsbytecode* pc,
                                 JSProtoKey kind, HandleObject protoArg /* = nullptr */)
{
    MOZ_ASSERT(!useSingletonForAllocationSite(scriptArg, pc, kind));
    MOZ_ASSERT_IF(protoArg, kind == JSProto_Array);

    uint32_t offset = scriptArg->pcToOffset(pc);

    if (offset >= ObjectGroupCompartment::AllocationSiteKey::OFFSET_LIMIT) {
        if (protoArg)
            return defaultNewGroup(cx, GetClassForProtoKey(kind), TaggedProto(protoArg));
        return defaultNewGroup(cx, kind);
    }

    ObjectGroupCompartment::AllocationSiteTable*& table =
        cx->compartment()->objectGroups.allocationSiteTable;

    if (!table) {
        table = cx->new_<ObjectGroupCompartment::AllocationSiteTable>(cx->zone());
        if (!table || !table->init()) {
            ReportOutOfMemory(cx);
            js_delete(table);
            table = nullptr;
            return nullptr;
        }
    }

    RootedScript script(cx, scriptArg);
    RootedObject proto(cx, protoArg);
    if (!proto && kind != JSProto_Null && !GetBuiltinPrototype(cx, kind, &proto))
        return nullptr;

    Rooted<ObjectGroupCompartment::AllocationSiteKey> key(cx,
        ObjectGroupCompartment::AllocationSiteKey(script, offset, kind, proto));

    ObjectGroupCompartment::AllocationSiteTable::AddPtr p = table->lookupForAdd(key);
    if (p)
        return p->value();

    AutoEnterAnalysis enter(cx);

    Rooted<TaggedProto> tagged(cx, TaggedProto(proto));
    ObjectGroup* res = ObjectGroupCompartment::makeGroup(cx, GetClassForProtoKey(kind), tagged,
                                                         OBJECT_FLAG_FROM_ALLOCATION_SITE);
    if (!res)
        return nullptr;

    if (JSOp(*pc) == JSOP_NEWOBJECT) {
        // Keep track of the preliminary objects with this group, so we can try
        // to use an unboxed layout for the object once some are allocated.
        Shape* shape = script->getObject(pc)->as<PlainObject>().lastProperty();
        if (!shape->isEmptyShape()) {
            PreliminaryObjectArrayWithTemplate* preliminaryObjects =
                cx->new_<PreliminaryObjectArrayWithTemplate>(shape);
            if (preliminaryObjects)
                res->setPreliminaryObjects(preliminaryObjects);
            else
                cx->recoverFromOutOfMemory();
        }
    }

    if (!table->add(p, key, res)) {
        ReportOutOfMemory(cx);
        return nullptr;
    }

    return res;
}

void
ObjectGroupCompartment::replaceAllocationSiteGroup(JSScript* script, jsbytecode* pc,
                                                   JSProtoKey kind, ObjectGroup* group)
{
    AllocationSiteKey key(script, script->pcToOffset(pc), kind, group->proto().toObjectOrNull());

    AllocationSiteTable::Ptr p = allocationSiteTable->lookup(key);
    MOZ_RELEASE_ASSERT(p);
    allocationSiteTable->get().remove(p);
    {
        AutoEnterOOMUnsafeRegion oomUnsafe;
        if (!allocationSiteTable->putNew(key, group))
            oomUnsafe.crash("Inconsistent object table");
    }
}

/* static */ ObjectGroup*
ObjectGroup::callingAllocationSiteGroup(JSContext* cx, JSProtoKey key, HandleObject proto)
{
    MOZ_ASSERT_IF(proto, key == JSProto_Array);

    jsbytecode* pc;
    RootedScript script(cx, cx->currentScript(&pc));
    if (script)
        return allocationSiteGroup(cx, script, pc, key, proto);
    if (proto)
        return defaultNewGroup(cx, GetClassForProtoKey(key), TaggedProto(proto));
    return defaultNewGroup(cx, key);
}

/* static */ bool
ObjectGroup::setAllocationSiteObjectGroup(JSContext* cx,
                                          HandleScript script, jsbytecode* pc,
                                          HandleObject obj, bool singleton)
{
    JSProtoKey key = JSCLASS_CACHED_PROTO_KEY(obj->getClass());
    MOZ_ASSERT(key != JSProto_Null);
    MOZ_ASSERT(singleton == useSingletonForAllocationSite(script, pc, key));

    if (singleton) {
        MOZ_ASSERT(obj->isSingleton());

        /*
         * Inference does not account for types of run-once initializer
         * objects, as these may not be created until after the script
         * has been analyzed.
         */
        TypeScript::Monitor(cx, script, pc, ObjectValue(*obj));
    } else {
        ObjectGroup* group = allocationSiteGroup(cx, script, pc, key);
        if (!group)
            return false;
        obj->setGroup(group);
    }

    return true;
}

/* static */ ArrayObject*
ObjectGroup::getOrFixupCopyOnWriteObject(JSContext* cx, HandleScript script, jsbytecode* pc)
{
    // Make sure that the template object for script/pc has a type indicating
    // that the object and its copies have copy on write elements.
    RootedArrayObject obj(cx, &script->getObject(GET_UINT32_INDEX(pc))->as<ArrayObject>());
    MOZ_ASSERT(obj->denseElementsAreCopyOnWrite());

    if (obj->group()->fromAllocationSite()) {
        MOZ_ASSERT(obj->group()->hasAnyFlags(OBJECT_FLAG_COPY_ON_WRITE));
        return obj;
    }

    RootedObjectGroup group(cx, allocationSiteGroup(cx, script, pc, JSProto_Array));
    if (!group)
        return nullptr;

    group->addFlags(OBJECT_FLAG_COPY_ON_WRITE);

    // Update type information in the initializer object group.
    MOZ_ASSERT(obj->slotSpan() == 0);
    for (size_t i = 0; i < obj->getDenseInitializedLength(); i++) {
        const Value& v = obj->getDenseElement(i);
        AddTypePropertyId(cx, group, nullptr, JSID_VOID, v);
    }

    obj->setGroup(group);
    return obj;
}

/* static */ ArrayObject*
ObjectGroup::getCopyOnWriteObject(JSScript* script, jsbytecode* pc)
{
    // getOrFixupCopyOnWriteObject should already have been called for
    // script/pc, ensuring that the template object has a group with the
    // COPY_ON_WRITE flag. We don't assert this here, due to a corner case
    // where this property doesn't hold. See jsop_newarray_copyonwrite in
    // IonBuilder.
    ArrayObject* obj = &script->getObject(GET_UINT32_INDEX(pc))->as<ArrayObject>();
    MOZ_ASSERT(obj->denseElementsAreCopyOnWrite());

    return obj;
}

/* static */ bool
ObjectGroup::findAllocationSite(JSContext* cx, ObjectGroup* group,
                                JSScript** script, uint32_t* offset)
{
    *script = nullptr;
    *offset = 0;

    const ObjectGroupCompartment::AllocationSiteTable* table =
        cx->compartment()->objectGroups.allocationSiteTable;

    if (!table)
        return false;

    for (ObjectGroupCompartment::AllocationSiteTable::Range r = table->all();
         !r.empty();
         r.popFront())
    {
        if (group == r.front().value()) {
            *script = r.front().key().script;
            *offset = r.front().key().offset;
            return true;
        }
    }

    return false;
}

/////////////////////////////////////////////////////////////////////
// ObjectGroupCompartment
/////////////////////////////////////////////////////////////////////

ObjectGroupCompartment::ObjectGroupCompartment()
{
    PodZero(this);
}

ObjectGroupCompartment::~ObjectGroupCompartment()
{
    js_delete(defaultNewTable);
    js_delete(lazyTable);
    js_delete(arrayObjectTable);
    js_delete(plainObjectTable);
    js_delete(allocationSiteTable);
}

void
ObjectGroupCompartment::removeDefaultNewGroup(const Class* clasp, TaggedProto proto,
                                              JSObject* associated)
{
    auto p = defaultNewTable->lookup(NewEntry::Lookup(clasp, proto, associated));
    MOZ_RELEASE_ASSERT(p);

    defaultNewTable->get().remove(p);
}

void
ObjectGroupCompartment::replaceDefaultNewGroup(const Class* clasp, TaggedProto proto,
                                               JSObject* associated, ObjectGroup* group)
{
    NewEntry::Lookup lookup(clasp, proto, associated);

    auto p = defaultNewTable->lookup(lookup);
    MOZ_RELEASE_ASSERT(p);
    defaultNewTable->get().remove(p);
    {
        AutoEnterOOMUnsafeRegion oomUnsafe;
        if (!defaultNewTable->putNew(lookup, NewEntry(group, associated)))
            oomUnsafe.crash("Inconsistent object table");
    }
}

/* static */
ObjectGroup*
ObjectGroupCompartment::makeGroup(ExclusiveContext* cx, const Class* clasp,
                                  Handle<TaggedProto> proto,
                                  ObjectGroupFlags initialFlags /* = 0 */)
{
    MOZ_ASSERT_IF(proto.isObject(), cx->isInsideCurrentCompartment(proto.toObject()));

    ObjectGroup* group = Allocate<ObjectGroup>(cx);
    if (!group)
        return nullptr;
    new(group) ObjectGroup(clasp, proto, cx->compartment(), initialFlags);

    return group;
}

void
ObjectGroupCompartment::addSizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf,
                                               size_t* allocationSiteTables,
                                               size_t* arrayObjectGroupTables,
                                               size_t* plainObjectGroupTables,
                                               size_t* compartmentTables)
{
    if (allocationSiteTable)
        *allocationSiteTables += allocationSiteTable->sizeOfIncludingThis(mallocSizeOf);

    if (arrayObjectTable)
        *arrayObjectGroupTables += arrayObjectTable->sizeOfIncludingThis(mallocSizeOf);

    if (plainObjectTable) {
        *plainObjectGroupTables += plainObjectTable->sizeOfIncludingThis(mallocSizeOf);

        for (PlainObjectTable::Enum e(*plainObjectTable);
             !e.empty();
             e.popFront())
        {
            const PlainObjectKey& key = e.front().key();
            const PlainObjectEntry& value = e.front().value();

            /* key.ids and values.types have the same length. */
            *plainObjectGroupTables += mallocSizeOf(key.properties) + mallocSizeOf(value.types);
        }
    }

    if (defaultNewTable)
        *compartmentTables += defaultNewTable->sizeOfIncludingThis(mallocSizeOf);

    if (lazyTable)
        *compartmentTables += lazyTable->sizeOfIncludingThis(mallocSizeOf);
}

void
ObjectGroupCompartment::clearTables()
{
    if (allocationSiteTable && allocationSiteTable->initialized())
        allocationSiteTable->clear();
    if (arrayObjectTable && arrayObjectTable->initialized())
        arrayObjectTable->clear();
    if (plainObjectTable && plainObjectTable->initialized()) {
        for (PlainObjectTable::Enum e(*plainObjectTable); !e.empty(); e.popFront()) {
            const PlainObjectKey& key = e.front().key();
            PlainObjectEntry& entry = e.front().value();
            js_free(key.properties);
            js_free(entry.types);
        }
        plainObjectTable->clear();
    }
    if (defaultNewTable && defaultNewTable->initialized())
        defaultNewTable->clear();
    if (lazyTable && lazyTable->initialized())
        lazyTable->clear();
}

/* static */ bool
ObjectGroupCompartment::PlainObjectTableSweepPolicy::needsSweep(PlainObjectKey* key,
                                                                PlainObjectEntry* entry)
{
    if (!(JS::GCPolicy<PlainObjectKey>::needsSweep(key) || entry->needsSweep(key->nproperties)))
        return false;
    js_free(key->properties);
    js_free(entry->types);
    return true;
}

void
ObjectGroupCompartment::sweep(FreeOp* fop)
{
    /*
     * Iterate through the array/object group tables and remove all entries
     * referencing collected data. These tables only hold weak references.
     */

    if (arrayObjectTable)
        arrayObjectTable->sweep();
    if (plainObjectTable)
        plainObjectTable->sweep();
}

void
ObjectGroupCompartment::fixupNewTableAfterMovingGC(NewTable* table)
{
    /*
     * Each entry's hash depends on the object's prototype and we can't tell
     * whether that has been moved or not in sweepNewObjectGroupTable().
     */
    if (table && table->initialized()) {
        for (NewTable::Enum e(*table); !e.empty(); e.popFront()) {
            NewEntry& entry = e.mutableFront();

            ObjectGroup* group = entry.group.unbarrieredGet();
            if (IsForwarded(group)) {
                group = Forwarded(group);
                entry.group.set(group);
            }
            TaggedProto proto = group->proto();
            if (proto.isObject() && IsForwarded(proto.toObject())) {
                proto = TaggedProto(Forwarded(proto.toObject()));
                // Update the group's proto here so that we are able to lookup
                // entries in this table before all object pointers are updated.
                group->proto() = proto;
            }
            if (entry.associated && IsForwarded(entry.associated))
                entry.associated = Forwarded(entry.associated);
        }
    }
}

#ifdef JSGC_HASH_TABLE_CHECKS

void
ObjectGroupCompartment::checkNewTableAfterMovingGC(NewTable* table)
{
    /*
     * Assert that nothing points into the nursery or needs to be relocated, and
     * that the hash table entries are discoverable.
     */
    if (!table || !table->initialized())
        return;

    for (NewTable::Enum e(*table); !e.empty(); e.popFront()) {
        NewEntry entry = e.front();
        CheckGCThingAfterMovingGC(entry.group.unbarrieredGet());
        TaggedProto proto = entry.group.unbarrieredGet()->proto();
        if (proto.isObject())
            CheckGCThingAfterMovingGC(proto.toObject());
        CheckGCThingAfterMovingGC(entry.associated);

        const Class* clasp = entry.group.unbarrieredGet()->clasp();
        if (entry.associated && entry.associated->is<JSFunction>())
            clasp = nullptr;

        NewEntry::Lookup lookup(clasp, proto, entry.associated);
        auto ptr = table->lookup(lookup);
        MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &e.front());
    }
}

#endif // JSGC_HASH_TABLE_CHECKS