deps/v8/src/elements.cc

   1 // Copyright 2012 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "src/v8.h"
   6
   7 #include "src/arguments.h"
   8 #include "src/conversions.h"
   9 #include "src/elements.h"
  10 #include "src/objects.h"
  11 #include "src/utils.h"
  12
  13 // Each concrete ElementsAccessor can handle exactly one ElementsKind,
  14 // several abstract ElementsAccessor classes are used to allow sharing
  15 // common code.
  16 //
  17 // Inheritance hierarchy:
  18 // - ElementsAccessorBase                        (abstract)
  19 //   - FastElementsAccessor                      (abstract)
  20 //     - FastSmiOrObjectElementsAccessor
  21 //       - FastPackedSmiElementsAccessor
  22 //       - FastHoleySmiElementsAccessor
  23 //       - FastPackedObjectElementsAccessor
  24 //       - FastHoleyObjectElementsAccessor
  25 //     - FastDoubleElementsAccessor
  26 //       - FastPackedDoubleElementsAccessor
  27 //       - FastHoleyDoubleElementsAccessor
  28 //   - TypedElementsAccessor: template, with instantiations:
  29 //     - ExternalInt8ElementsAccessor
  30 //     - ExternalUint8ElementsAccessor
  31 //     - ExternalInt16ElementsAccessor
  32 //     - ExternalUint16ElementsAccessor
  33 //     - ExternalInt32ElementsAccessor
  34 //     - ExternalUint32ElementsAccessor
  35 //     - ExternalFloat32ElementsAccessor
  36 //     - ExternalFloat64ElementsAccessor
  37 //     - ExternalUint8ClampedElementsAccessor
  38 //     - FixedUint8ElementsAccessor
  39 //     - FixedInt8ElementsAccessor
  40 //     - FixedUint16ElementsAccessor
  41 //     - FixedInt16ElementsAccessor
  42 //     - FixedUint32ElementsAccessor
  43 //     - FixedInt32ElementsAccessor
  44 //     - FixedFloat32ElementsAccessor
  45 //     - FixedFloat64ElementsAccessor
  46 //     - FixedUint8ClampedElementsAccessor
  47 //   - DictionaryElementsAccessor
  48 //   - SloppyArgumentsElementsAccessor
  49
  50
  51 namespace v8 {
  52 namespace internal {
  53
  54
  55 static const int kPackedSizeNotKnown = -1;
  56
  57
  58 // First argument in list is the accessor class, the second argument is the
  59 // accessor ElementsKind, and the third is the backing store class.  Use the
  60 // fast element handler for smi-only arrays.  The implementation is currently
  61 // identical.  Note that the order must match that of the ElementsKind enum for
  62 // the |accessor_array[]| below to work.
  63 #define ELEMENTS_LIST(V)                                                \
  64   V(FastPackedSmiElementsAccessor, FAST_SMI_ELEMENTS, FixedArray)       \
  65   V(FastHoleySmiElementsAccessor, FAST_HOLEY_SMI_ELEMENTS,              \
  66     FixedArray)                                                         \
  67   V(FastPackedObjectElementsAccessor, FAST_ELEMENTS, FixedArray)        \
  68   V(FastHoleyObjectElementsAccessor, FAST_HOLEY_ELEMENTS, FixedArray)   \
  69   V(FastPackedDoubleElementsAccessor, FAST_DOUBLE_ELEMENTS,             \
  70     FixedDoubleArray)                                                   \
  71   V(FastHoleyDoubleElementsAccessor, FAST_HOLEY_DOUBLE_ELEMENTS,        \
  72     FixedDoubleArray)                                                   \
  73   V(DictionaryElementsAccessor, DICTIONARY_ELEMENTS,                    \
  74     SeededNumberDictionary)                                             \
  75   V(SloppyArgumentsElementsAccessor, SLOPPY_ARGUMENTS_ELEMENTS,         \
  76     FixedArray)                                                         \
  77   V(ExternalInt8ElementsAccessor, EXTERNAL_INT8_ELEMENTS,               \
  78     ExternalInt8Array)                                                  \
  79   V(ExternalUint8ElementsAccessor,                                      \
  80     EXTERNAL_UINT8_ELEMENTS, ExternalUint8Array)                        \
  81   V(ExternalInt16ElementsAccessor, EXTERNAL_INT16_ELEMENTS,             \
  82     ExternalInt16Array)                                                 \
  83   V(ExternalUint16ElementsAccessor,                                     \
  84     EXTERNAL_UINT16_ELEMENTS, ExternalUint16Array)                      \
  85   V(ExternalInt32ElementsAccessor, EXTERNAL_INT32_ELEMENTS,             \
  86     ExternalInt32Array)                                                 \
  87   V(ExternalUint32ElementsAccessor,                                     \
  88     EXTERNAL_UINT32_ELEMENTS, ExternalUint32Array)                      \
  89   V(ExternalFloat32ElementsAccessor,                                    \
  90     EXTERNAL_FLOAT32_ELEMENTS, ExternalFloat32Array)                    \
  91   V(ExternalFloat64ElementsAccessor,                                    \
  92     EXTERNAL_FLOAT64_ELEMENTS, ExternalFloat64Array)                    \
  93   V(ExternalUint8ClampedElementsAccessor,                               \
  94     EXTERNAL_UINT8_CLAMPED_ELEMENTS,                                    \
  95     ExternalUint8ClampedArray)                                          \
  96   V(FixedUint8ElementsAccessor, UINT8_ELEMENTS, FixedUint8Array)        \
  97   V(FixedInt8ElementsAccessor, INT8_ELEMENTS, FixedInt8Array)           \
  98   V(FixedUint16ElementsAccessor, UINT16_ELEMENTS, FixedUint16Array)     \
  99   V(FixedInt16ElementsAccessor, INT16_ELEMENTS, FixedInt16Array)        \
 100   V(FixedUint32ElementsAccessor, UINT32_ELEMENTS, FixedUint32Array)     \
 101   V(FixedInt32ElementsAccessor, INT32_ELEMENTS, FixedInt32Array)        \
 102   V(FixedFloat32ElementsAccessor, FLOAT32_ELEMENTS, FixedFloat32Array)  \
 103   V(FixedFloat64ElementsAccessor, FLOAT64_ELEMENTS, FixedFloat64Array)  \
 104   V(FixedUint8ClampedElementsAccessor, UINT8_CLAMPED_ELEMENTS,          \
 105     FixedUint8ClampedArray)
 106
 107
 108 template<ElementsKind Kind> class ElementsKindTraits {
 109  public:
 110   typedef FixedArrayBase BackingStore;
 111 };
 112
 113 #define ELEMENTS_TRAITS(Class, KindParam, Store)               \
 114 template<> class ElementsKindTraits<KindParam> {               \
 115  public:   /* NOLINT */                                        \
 116   static const ElementsKind Kind = KindParam;                  \
 117   typedef Store BackingStore;                                  \
 118 };
 119 ELEMENTS_LIST(ELEMENTS_TRAITS)
 120 #undef ELEMENTS_TRAITS
 121
 122
 123 ElementsAccessor** ElementsAccessor::elements_accessors_ = NULL;
 124
 125
 126 static bool HasKey(Handle<FixedArray> array, Handle<Object> key_handle) {
 127   DisallowHeapAllocation no_gc;
 128   Object* key = *key_handle;
 129   int len0 = array->length();
 130   for (int i = 0; i < len0; i++) {
 131     Object* element = array->get(i);
 132     if (element->IsSmi() && element == key) return true;
 133     if (element->IsString() &&
 134         key->IsString() && String::cast(element)->Equals(String::cast(key))) {
 135       return true;
 136     }
 137   }
 138   return false;
 139 }
 140
 141
 142 MUST_USE_RESULT
 143 static MaybeHandle<Object> ThrowArrayLengthRangeError(Isolate* isolate) {
 144   THROW_NEW_ERROR(isolate, NewRangeError("invalid_array_length",
 145                                          HandleVector<Object>(NULL, 0)),
 146                   Object);
 147 }
 148
 149
 150 static void CopyObjectToObjectElements(FixedArrayBase* from_base,
 151                                        ElementsKind from_kind,
 152                                        uint32_t from_start,
 153                                        FixedArrayBase* to_base,
 154                                        ElementsKind to_kind, uint32_t to_start,
 155                                        int raw_copy_size) {
 156   DCHECK(to_base->map() !=
 157       from_base->GetIsolate()->heap()->fixed_cow_array_map());
 158   DisallowHeapAllocation no_allocation;
 159   int copy_size = raw_copy_size;
 160   if (raw_copy_size < 0) {
 161     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 162            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 163     copy_size = Min(from_base->length() - from_start,
 164                     to_base->length() - to_start);
 165     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 166       int start = to_start + copy_size;
 167       int length = to_base->length() - start;
 168       if (length > 0) {
 169         Heap* heap = from_base->GetHeap();
 170         MemsetPointer(FixedArray::cast(to_base)->data_start() + start,
 171                       heap->the_hole_value(), length);
 172       }
 173     }
 174   }
 175   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 176          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 177   if (copy_size == 0) return;
 178   FixedArray* from = FixedArray::cast(from_base);
 179   FixedArray* to = FixedArray::cast(to_base);
 180   DCHECK(IsFastSmiOrObjectElementsKind(from_kind));
 181   DCHECK(IsFastSmiOrObjectElementsKind(to_kind));
 182   Address to_address = to->address() + FixedArray::kHeaderSize;
 183   Address from_address = from->address() + FixedArray::kHeaderSize;
 184   CopyWords(reinterpret_cast<Object**>(to_address) + to_start,
 185             reinterpret_cast<Object**>(from_address) + from_start,
 186             static_cast<size_t>(copy_size));
 187   if (IsFastObjectElementsKind(from_kind) &&
 188       IsFastObjectElementsKind(to_kind)) {
 189     Heap* heap = from->GetHeap();
 190     if (!heap->InNewSpace(to)) {
 191       heap->RecordWrites(to->address(),
 192                          to->OffsetOfElementAt(to_start),
 193                          copy_size);
 194     }
 195     heap->incremental_marking()->RecordWrites(to);
 196   }
 197 }
 198
 199
 200 static void CopyDictionaryToObjectElements(
 201     FixedArrayBase* from_base, uint32_t from_start, FixedArrayBase* to_base,
 202     ElementsKind to_kind, uint32_t to_start, int raw_copy_size) {
 203   DisallowHeapAllocation no_allocation;
 204   SeededNumberDictionary* from = SeededNumberDictionary::cast(from_base);
 205   int copy_size = raw_copy_size;
 206   Heap* heap = from->GetHeap();
 207   if (raw_copy_size < 0) {
 208     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 209            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 210     copy_size = from->max_number_key() + 1 - from_start;
 211     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 212       int start = to_start + copy_size;
 213       int length = to_base->length() - start;
 214       if (length > 0) {
 215         Heap* heap = from->GetHeap();
 216         MemsetPointer(FixedArray::cast(to_base)->data_start() + start,
 217                       heap->the_hole_value(), length);
 218       }
 219     }
 220   }
 221   DCHECK(to_base != from_base);
 222   DCHECK(IsFastSmiOrObjectElementsKind(to_kind));
 223   if (copy_size == 0) return;
 224   FixedArray* to = FixedArray::cast(to_base);
 225   uint32_t to_length = to->length();
 226   if (to_start + copy_size > to_length) {
 227     copy_size = to_length - to_start;
 228   }
 229   for (int i = 0; i < copy_size; i++) {
 230     int entry = from->FindEntry(i + from_start);
 231     if (entry != SeededNumberDictionary::kNotFound) {
 232       Object* value = from->ValueAt(entry);
 233       DCHECK(!value->IsTheHole());
 234       to->set(i + to_start, value, SKIP_WRITE_BARRIER);
 235     } else {
 236       to->set_the_hole(i + to_start);
 237     }
 238   }
 239   if (IsFastObjectElementsKind(to_kind)) {
 240     if (!heap->InNewSpace(to)) {
 241       heap->RecordWrites(to->address(),
 242                          to->OffsetOfElementAt(to_start),
 243                          copy_size);
 244     }
 245     heap->incremental_marking()->RecordWrites(to);
 246   }
 247 }
 248
 249
 250 // NOTE: this method violates the handlified function signature convention:
 251 // raw pointer parameters in the function that allocates.
 252 // See ElementsAccessorBase::CopyElements() for details.
 253 static void CopyDoubleToObjectElements(FixedArrayBase* from_base,
 254                                        uint32_t from_start,
 255                                        FixedArrayBase* to_base,
 256                                        ElementsKind to_kind, uint32_t to_start,
 257                                        int raw_copy_size) {
 258   DCHECK(IsFastSmiOrObjectElementsKind(to_kind));
 259   int copy_size = raw_copy_size;
 260   if (raw_copy_size < 0) {
 261     DisallowHeapAllocation no_allocation;
 262     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 263            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 264     copy_size = Min(from_base->length() - from_start,
 265                     to_base->length() - to_start);
 266     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 267       // Also initialize the area that will be copied over since HeapNumber
 268       // allocation below can cause an incremental marking step, requiring all
 269       // existing heap objects to be propertly initialized.
 270       int start = to_start;
 271       int length = to_base->length() - start;
 272       if (length > 0) {
 273         Heap* heap = from_base->GetHeap();
 274         MemsetPointer(FixedArray::cast(to_base)->data_start() + start,
 275                       heap->the_hole_value(), length);
 276       }
 277     }
 278   }
 279   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 280          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 281   if (copy_size == 0) return;
 282
 283   // From here on, the code below could actually allocate. Therefore the raw
 284   // values are wrapped into handles.
 285   Isolate* isolate = from_base->GetIsolate();
 286   Handle<FixedDoubleArray> from(FixedDoubleArray::cast(from_base), isolate);
 287   Handle<FixedArray> to(FixedArray::cast(to_base), isolate);
 288   for (int i = 0; i < copy_size; ++i) {
 289     HandleScope scope(isolate);
 290     if (IsFastSmiElementsKind(to_kind)) {
 291       UNIMPLEMENTED();
 292     } else {
 293       DCHECK(IsFastObjectElementsKind(to_kind));
 294       Handle<Object> value = FixedDoubleArray::get(from, i + from_start);
 295       to->set(i + to_start, *value, UPDATE_WRITE_BARRIER);
 296     }
 297   }
 298 }
 299
 300
 301 static void CopyDoubleToDoubleElements(FixedArrayBase* from_base,
 302                                        uint32_t from_start,
 303                                        FixedArrayBase* to_base,
 304                                        uint32_t to_start, int raw_copy_size) {
 305   DisallowHeapAllocation no_allocation;
 306   int copy_size = raw_copy_size;
 307   if (raw_copy_size < 0) {
 308     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 309            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 310     copy_size = Min(from_base->length() - from_start,
 311                     to_base->length() - to_start);
 312     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 313       for (int i = to_start + copy_size; i < to_base->length(); ++i) {
 314         FixedDoubleArray::cast(to_base)->set_the_hole(i);
 315       }
 316     }
 317   }
 318   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 319          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 320   if (copy_size == 0) return;
 321   FixedDoubleArray* from = FixedDoubleArray::cast(from_base);
 322   FixedDoubleArray* to = FixedDoubleArray::cast(to_base);
 323   Address to_address = to->address() + FixedDoubleArray::kHeaderSize;
 324   Address from_address = from->address() + FixedDoubleArray::kHeaderSize;
 325   to_address += kDoubleSize * to_start;
 326   from_address += kDoubleSize * from_start;
 327   int words_per_double = (kDoubleSize / kPointerSize);
 328   CopyWords(reinterpret_cast<Object**>(to_address),
 329             reinterpret_cast<Object**>(from_address),
 330             static_cast<size_t>(words_per_double * copy_size));
 331 }
 332
 333
 334 static void CopySmiToDoubleElements(FixedArrayBase* from_base,
 335                                     uint32_t from_start,
 336                                     FixedArrayBase* to_base, uint32_t to_start,
 337                                     int raw_copy_size) {
 338   DisallowHeapAllocation no_allocation;
 339   int copy_size = raw_copy_size;
 340   if (raw_copy_size < 0) {
 341     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 342            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 343     copy_size = from_base->length() - from_start;
 344     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 345       for (int i = to_start + copy_size; i < to_base->length(); ++i) {
 346         FixedDoubleArray::cast(to_base)->set_the_hole(i);
 347       }
 348     }
 349   }
 350   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 351          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 352   if (copy_size == 0) return;
 353   FixedArray* from = FixedArray::cast(from_base);
 354   FixedDoubleArray* to = FixedDoubleArray::cast(to_base);
 355   Object* the_hole = from->GetHeap()->the_hole_value();
 356   for (uint32_t from_end = from_start + static_cast<uint32_t>(copy_size);
 357        from_start < from_end; from_start++, to_start++) {
 358     Object* hole_or_smi = from->get(from_start);
 359     if (hole_or_smi == the_hole) {
 360       to->set_the_hole(to_start);
 361     } else {
 362       to->set(to_start, Smi::cast(hole_or_smi)->value());
 363     }
 364   }
 365 }
 366
 367
 368 static void CopyPackedSmiToDoubleElements(FixedArrayBase* from_base,
 369                                           uint32_t from_start,
 370                                           FixedArrayBase* to_base,
 371                                           uint32_t to_start, int packed_size,
 372                                           int raw_copy_size) {
 373   DisallowHeapAllocation no_allocation;
 374   int copy_size = raw_copy_size;
 375   uint32_t to_end;
 376   if (raw_copy_size < 0) {
 377     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 378            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 379     copy_size = packed_size - from_start;
 380     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 381       to_end = to_base->length();
 382       for (uint32_t i = to_start + copy_size; i < to_end; ++i) {
 383         FixedDoubleArray::cast(to_base)->set_the_hole(i);
 384       }
 385     } else {
 386       to_end = to_start + static_cast<uint32_t>(copy_size);
 387     }
 388   } else {
 389     to_end = to_start + static_cast<uint32_t>(copy_size);
 390   }
 391   DCHECK(static_cast<int>(to_end) <= to_base->length());
 392   DCHECK(packed_size >= 0 && packed_size <= copy_size);
 393   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 394          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 395   if (copy_size == 0) return;
 396   FixedArray* from = FixedArray::cast(from_base);
 397   FixedDoubleArray* to = FixedDoubleArray::cast(to_base);
 398   for (uint32_t from_end = from_start + static_cast<uint32_t>(packed_size);
 399        from_start < from_end; from_start++, to_start++) {
 400     Object* smi = from->get(from_start);
 401     DCHECK(!smi->IsTheHole());
 402     to->set(to_start, Smi::cast(smi)->value());
 403   }
 404 }
 405
 406
 407 static void CopyObjectToDoubleElements(FixedArrayBase* from_base,
 408                                        uint32_t from_start,
 409                                        FixedArrayBase* to_base,
 410                                        uint32_t to_start, int raw_copy_size) {
 411   DisallowHeapAllocation no_allocation;
 412   int copy_size = raw_copy_size;
 413   if (raw_copy_size < 0) {
 414     DCHECK(raw_copy_size == ElementsAccessor::kCopyToEnd ||
 415            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 416     copy_size = from_base->length() - from_start;
 417     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 418       for (int i = to_start + copy_size; i < to_base->length(); ++i) {
 419         FixedDoubleArray::cast(to_base)->set_the_hole(i);
 420       }
 421     }
 422   }
 423   DCHECK((copy_size + static_cast<int>(to_start)) <= to_base->length() &&
 424          (copy_size + static_cast<int>(from_start)) <= from_base->length());
 425   if (copy_size == 0) return;
 426   FixedArray* from = FixedArray::cast(from_base);
 427   FixedDoubleArray* to = FixedDoubleArray::cast(to_base);
 428   Object* the_hole = from->GetHeap()->the_hole_value();
 429   for (uint32_t from_end = from_start + copy_size;
 430        from_start < from_end; from_start++, to_start++) {
 431     Object* hole_or_object = from->get(from_start);
 432     if (hole_or_object == the_hole) {
 433       to->set_the_hole(to_start);
 434     } else {
 435       to->set(to_start, hole_or_object->Number());
 436     }
 437   }
 438 }
 439
 440
 441 static void CopyDictionaryToDoubleElements(FixedArrayBase* from_base,
 442                                            uint32_t from_start,
 443                                            FixedArrayBase* to_base,
 444                                            uint32_t to_start,
 445                                            int raw_copy_size) {
 446   DisallowHeapAllocation no_allocation;
 447   SeededNumberDictionary* from = SeededNumberDictionary::cast(from_base);
 448   int copy_size = raw_copy_size;
 449   if (copy_size < 0) {
 450     DCHECK(copy_size == ElementsAccessor::kCopyToEnd ||
 451            copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
 452     copy_size = from->max_number_key() + 1 - from_start;
 453     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
 454       for (int i = to_start + copy_size; i < to_base->length(); ++i) {
 455         FixedDoubleArray::cast(to_base)->set_the_hole(i);
 456       }
 457     }
 458   }
 459   if (copy_size == 0) return;
 460   FixedDoubleArray* to = FixedDoubleArray::cast(to_base);
 461   uint32_t to_length = to->length();
 462   if (to_start + copy_size > to_length) {
 463     copy_size = to_length - to_start;
 464   }
 465   for (int i = 0; i < copy_size; i++) {
 466     int entry = from->FindEntry(i + from_start);
 467     if (entry != SeededNumberDictionary::kNotFound) {
 468       to->set(i + to_start, from->ValueAt(entry)->Number());
 469     } else {
 470       to->set_the_hole(i + to_start);
 471     }
 472   }
 473 }
 474
 475
 476 static void TraceTopFrame(Isolate* isolate) {
 477   StackFrameIterator it(isolate);
 478   if (it.done()) {
 479     PrintF("unknown location (no JavaScript frames present)");
 480     return;
 481   }
 482   StackFrame* raw_frame = it.frame();
 483   if (raw_frame->is_internal()) {
 484     Code* apply_builtin = isolate->builtins()->builtin(
 485         Builtins::kFunctionApply);
 486     if (raw_frame->unchecked_code() == apply_builtin) {
 487       PrintF("apply from ");
 488       it.Advance();
 489       raw_frame = it.frame();
 490     }
 491   }
 492   JavaScriptFrame::PrintTop(isolate, stdout, false, true);
 493 }
 494
 495
 496 void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t key,
 497                      bool allow_appending) {
 498   DisallowHeapAllocation no_allocation;
 499   Object* raw_length = NULL;
 500   const char* elements_type = "array";
 501   if (obj->IsJSArray()) {
 502     JSArray* array = JSArray::cast(*obj);
 503     raw_length = array->length();
 504   } else {
 505     raw_length = Smi::FromInt(obj->elements()->length());
 506     elements_type = "object";
 507   }
 508
 509   if (raw_length->IsNumber()) {
 510     double n = raw_length->Number();
 511     if (FastI2D(FastD2UI(n)) == n) {
 512       int32_t int32_length = DoubleToInt32(n);
 513       uint32_t compare_length = static_cast<uint32_t>(int32_length);
 514       if (allow_appending) compare_length++;
 515       if (key >= compare_length) {
 516         PrintF("[OOB %s %s (%s length = %d, element accessed = %d) in ",
 517                elements_type, op, elements_type,
 518                static_cast<int>(int32_length),
 519                static_cast<int>(key));
 520         TraceTopFrame(obj->GetIsolate());
 521         PrintF("]\n");
 522       }
 523     } else {
 524       PrintF("[%s elements length not integer value in ", elements_type);
 525       TraceTopFrame(obj->GetIsolate());
 526       PrintF("]\n");
 527     }
 528   } else {
 529     PrintF("[%s elements length not a number in ", elements_type);
 530     TraceTopFrame(obj->GetIsolate());
 531     PrintF("]\n");
 532   }
 533 }
 534
 535
 536 // Base class for element handler implementations. Contains the
 537 // the common logic for objects with different ElementsKinds.
 538 // Subclasses must specialize method for which the element
 539 // implementation differs from the base class implementation.
 540 //
 541 // This class is intended to be used in the following way:
 542 //
 543 //   class SomeElementsAccessor :
 544 //       public ElementsAccessorBase<SomeElementsAccessor,
 545 //                                   BackingStoreClass> {
 546 //     ...
 547 //   }
 548 //
 549 // This is an example of the Curiously Recurring Template Pattern (see
 550 // http://en.wikipedia.org/wiki/Curiously_recurring_template_pattern).  We use
 551 // CRTP to guarantee aggressive compile time optimizations (i.e.  inlining and
 552 // specialization of SomeElementsAccessor methods).
 553 template <typename ElementsAccessorSubclass,
 554           typename ElementsTraitsParam>
 555 class ElementsAccessorBase : public ElementsAccessor {
 556  protected:
 557   explicit ElementsAccessorBase(const char* name)
 558       : ElementsAccessor(name) { }
 559
 560   typedef ElementsTraitsParam ElementsTraits;
 561   typedef typename ElementsTraitsParam::BackingStore BackingStore;
 562
 563   ElementsKind kind() const FINAL { return ElementsTraits::Kind; }
 564
 565   static void ValidateContents(Handle<JSObject> holder, int length) {
 566   }
 567
 568   static void ValidateImpl(Handle<JSObject> holder) {
 569     Handle<FixedArrayBase> fixed_array_base(holder->elements());
 570     if (!fixed_array_base->IsHeapObject()) return;
 571     // Arrays that have been shifted in place can't be verified.
 572     if (fixed_array_base->IsFiller()) return;
 573     int length = 0;
 574     if (holder->IsJSArray()) {
 575       Object* length_obj = Handle<JSArray>::cast(holder)->length();
 576       if (length_obj->IsSmi()) {
 577         length = Smi::cast(length_obj)->value();
 578       }
 579     } else {
 580       length = fixed_array_base->length();
 581     }
 582     ElementsAccessorSubclass::ValidateContents(holder, length);
 583   }
 584
 585   void Validate(Handle<JSObject> holder) FINAL {
 586     DisallowHeapAllocation no_gc;
 587     ElementsAccessorSubclass::ValidateImpl(holder);
 588   }
 589
 590   static bool HasElementImpl(Handle<JSObject> holder, uint32_t key,
 591                              Handle<FixedArrayBase> backing_store) {
 592     return ElementsAccessorSubclass::GetAttributesImpl(holder, key,
 593                                                        backing_store) != ABSENT;
 594   }
 595
 596   virtual bool HasElement(Handle<JSObject> holder, uint32_t key,
 597                           Handle<FixedArrayBase> backing_store) FINAL {
 598     return ElementsAccessorSubclass::HasElementImpl(holder, key, backing_store);
 599   }
 600
 601   MUST_USE_RESULT virtual MaybeHandle<Object> Get(
 602       Handle<Object> receiver, Handle<JSObject> holder, uint32_t key,
 603       Handle<FixedArrayBase> backing_store) FINAL {
 604     if (!IsExternalArrayElementsKind(ElementsTraits::Kind) &&
 605         FLAG_trace_js_array_abuse) {
 606       CheckArrayAbuse(holder, "elements read", key);
 607     }
 608
 609     if (IsExternalArrayElementsKind(ElementsTraits::Kind) &&
 610         FLAG_trace_external_array_abuse) {
 611       CheckArrayAbuse(holder, "external elements read", key);
 612     }
 613
 614     return ElementsAccessorSubclass::GetImpl(
 615         receiver, holder, key, backing_store);
 616   }
 617
 618   MUST_USE_RESULT static MaybeHandle<Object> GetImpl(
 619       Handle<Object> receiver,
 620       Handle<JSObject> obj,
 621       uint32_t key,
 622       Handle<FixedArrayBase> backing_store) {
 623     if (key < ElementsAccessorSubclass::GetCapacityImpl(backing_store)) {
 624       return BackingStore::get(Handle<BackingStore>::cast(backing_store), key);
 625     } else {
 626       return backing_store->GetIsolate()->factory()->the_hole_value();
 627     }
 628   }
 629
 630   MUST_USE_RESULT virtual PropertyAttributes GetAttributes(
 631       Handle<JSObject> holder, uint32_t key,
 632       Handle<FixedArrayBase> backing_store) FINAL {
 633     return ElementsAccessorSubclass::GetAttributesImpl(holder, key,
 634                                                        backing_store);
 635   }
 636
 637   MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
 638         Handle<JSObject> obj,
 639         uint32_t key,
 640         Handle<FixedArrayBase> backing_store) {
 641     if (key >= ElementsAccessorSubclass::GetCapacityImpl(backing_store)) {
 642       return ABSENT;
 643     }
 644     return
 645         Handle<BackingStore>::cast(backing_store)->is_the_hole(key)
 646           ? ABSENT : NONE;
 647   }
 648
 649   MUST_USE_RESULT virtual MaybeHandle<AccessorPair> GetAccessorPair(
 650       Handle<JSObject> holder, uint32_t key,
 651       Handle<FixedArrayBase> backing_store) FINAL {
 652     return ElementsAccessorSubclass::GetAccessorPairImpl(holder, key,
 653                                                          backing_store);
 654   }
 655
 656   MUST_USE_RESULT static MaybeHandle<AccessorPair> GetAccessorPairImpl(
 657       Handle<JSObject> obj,
 658       uint32_t key,
 659       Handle<FixedArrayBase> backing_store) {
 660     return MaybeHandle<AccessorPair>();
 661   }
 662
 663   MUST_USE_RESULT virtual MaybeHandle<Object> SetLength(
 664       Handle<JSArray> array, Handle<Object> length) FINAL {
 665     return ElementsAccessorSubclass::SetLengthImpl(
 666         array, length, handle(array->elements()));
 667   }
 668
 669   MUST_USE_RESULT static MaybeHandle<Object> SetLengthImpl(
 670       Handle<JSObject> obj,
 671       Handle<Object> length,
 672       Handle<FixedArrayBase> backing_store);
 673
 674   virtual void SetCapacityAndLength(Handle<JSArray> array, int capacity,
 675                                     int length) FINAL {
 676     ElementsAccessorSubclass::
 677         SetFastElementsCapacityAndLength(array, capacity, length);
 678   }
 679
 680   static void SetFastElementsCapacityAndLength(
 681       Handle<JSObject> obj,
 682       int capacity,
 683       int length) {
 684     UNIMPLEMENTED();
 685   }
 686
 687   MUST_USE_RESULT virtual MaybeHandle<Object> Delete(
 688       Handle<JSObject> obj, uint32_t key,
 689       LanguageMode language_mode) OVERRIDE = 0;
 690
 691   static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
 692                                FixedArrayBase* to, ElementsKind from_kind,
 693                                uint32_t to_start, int packed_size,
 694                                int copy_size) {
 695     UNREACHABLE();
 696   }
 697
 698   virtual void CopyElements(Handle<FixedArrayBase> from, uint32_t from_start,
 699                             ElementsKind from_kind, Handle<FixedArrayBase> to,
 700                             uint32_t to_start, int copy_size) FINAL {
 701     DCHECK(!from.is_null());
 702     // NOTE: the ElementsAccessorSubclass::CopyElementsImpl() methods
 703     // violate the handlified function signature convention:
 704     // raw pointer parameters in the function that allocates. This is done
 705     // intentionally to avoid ArrayConcat() builtin performance degradation.
 706     // See the comment in another ElementsAccessorBase::CopyElements() for
 707     // details.
 708     ElementsAccessorSubclass::CopyElementsImpl(*from, from_start, *to,
 709                                                from_kind, to_start,
 710                                                kPackedSizeNotKnown, copy_size);
 711   }
 712
 713   virtual void CopyElements(JSObject* from_holder, uint32_t from_start,
 714                             ElementsKind from_kind, Handle<FixedArrayBase> to,
 715                             uint32_t to_start, int copy_size) FINAL {
 716     int packed_size = kPackedSizeNotKnown;
 717     bool is_packed = IsFastPackedElementsKind(from_kind) &&
 718         from_holder->IsJSArray();
 719     if (is_packed) {
 720       packed_size =
 721           Smi::cast(JSArray::cast(from_holder)->length())->value();
 722       if (copy_size >= 0 && packed_size > copy_size) {
 723         packed_size = copy_size;
 724       }
 725     }
 726     FixedArrayBase* from = from_holder->elements();
 727     // NOTE: the ElementsAccessorSubclass::CopyElementsImpl() methods
 728     // violate the handlified function signature convention:
 729     // raw pointer parameters in the function that allocates. This is done
 730     // intentionally to avoid ArrayConcat() builtin performance degradation.
 731     //
 732     // Details: The idea is that allocations actually happen only in case of
 733     // copying from object with fast double elements to object with object
 734     // elements. In all the other cases there are no allocations performed and
 735     // handle creation causes noticeable performance degradation of the builtin.
 736     ElementsAccessorSubclass::CopyElementsImpl(
 737         from, from_start, *to, from_kind, to_start, packed_size, copy_size);
 738   }
 739
 740   virtual MaybeHandle<FixedArray> AddElementsToFixedArray(
 741       Handle<Object> receiver, Handle<JSObject> holder, Handle<FixedArray> to,
 742       Handle<FixedArrayBase> from, FixedArray::KeyFilter filter) FINAL {
 743     int len0 = to->length();
 744 #ifdef ENABLE_SLOW_DCHECKS
 745     if (FLAG_enable_slow_asserts) {
 746       for (int i = 0; i < len0; i++) {
 747         DCHECK(!to->get(i)->IsTheHole());
 748       }
 749     }
 750 #endif
 751
 752     // Optimize if 'other' is empty.
 753     // We cannot optimize if 'this' is empty, as other may have holes.
 754     uint32_t len1 = ElementsAccessorSubclass::GetCapacityImpl(from);
 755     if (len1 == 0) return to;
 756
 757     Isolate* isolate = from->GetIsolate();
 758
 759     // Compute how many elements are not in other.
 760     uint32_t extra = 0;
 761     for (uint32_t y = 0; y < len1; y++) {
 762       uint32_t key = ElementsAccessorSubclass::GetKeyForIndexImpl(from, y);
 763       if (ElementsAccessorSubclass::HasElementImpl(holder, key, from)) {
 764         Handle<Object> value;
 765         ASSIGN_RETURN_ON_EXCEPTION(
 766             isolate, value,
 767             ElementsAccessorSubclass::GetImpl(receiver, holder, key, from),
 768             FixedArray);
 769
 770         DCHECK(!value->IsTheHole());
 771         if (filter == FixedArray::NON_SYMBOL_KEYS && value->IsSymbol()) {
 772           continue;
 773         }
 774         if (!HasKey(to, value)) {
 775           extra++;
 776         }
 777       }
 778     }
 779
 780     if (extra == 0) return to;
 781
 782     // Allocate the result
 783     Handle<FixedArray> result = isolate->factory()->NewFixedArray(len0 + extra);
 784
 785     // Fill in the content
 786     {
 787       DisallowHeapAllocation no_gc;
 788       WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
 789       for (int i = 0; i < len0; i++) {
 790         Object* e = to->get(i);
 791         DCHECK(e->IsString() || e->IsNumber());
 792         result->set(i, e, mode);
 793       }
 794     }
 795     // Fill in the extra values.
 796     uint32_t index = 0;
 797     for (uint32_t y = 0; y < len1; y++) {
 798       uint32_t key =
 799           ElementsAccessorSubclass::GetKeyForIndexImpl(from, y);
 800       if (ElementsAccessorSubclass::HasElementImpl(holder, key, from)) {
 801         Handle<Object> value;
 802         ASSIGN_RETURN_ON_EXCEPTION(
 803             isolate, value,
 804             ElementsAccessorSubclass::GetImpl(receiver, holder, key, from),
 805             FixedArray);
 806         if (filter == FixedArray::NON_SYMBOL_KEYS && value->IsSymbol()) {
 807           continue;
 808         }
 809         if (!value->IsTheHole() && !HasKey(to, value)) {
 810           result->set(len0 + index, *value);
 811           index++;
 812         }
 813       }
 814     }
 815     DCHECK(extra == index);
 816     return result;
 817   }
 818
 819  protected:
 820   static uint32_t GetCapacityImpl(Handle<FixedArrayBase> backing_store) {
 821     return backing_store->length();
 822   }
 823
 824   uint32_t GetCapacity(Handle<FixedArrayBase> backing_store) FINAL {
 825     return ElementsAccessorSubclass::GetCapacityImpl(backing_store);
 826   }
 827
 828   static uint32_t GetKeyForIndexImpl(Handle<FixedArrayBase> backing_store,
 829                                      uint32_t index) {
 830     return index;
 831   }
 832
 833   virtual uint32_t GetKeyForIndex(Handle<FixedArrayBase> backing_store,
 834                                   uint32_t index) FINAL {
 835     return ElementsAccessorSubclass::GetKeyForIndexImpl(backing_store, index);
 836   }
 837
 838  private:
 839   DISALLOW_COPY_AND_ASSIGN(ElementsAccessorBase);
 840 };
 841
 842
 843 // Super class for all fast element arrays.
 844 template<typename FastElementsAccessorSubclass,
 845          typename KindTraits>
 846 class FastElementsAccessor
 847     : public ElementsAccessorBase<FastElementsAccessorSubclass, KindTraits> {
 848  public:
 849   explicit FastElementsAccessor(const char* name)
 850       : ElementsAccessorBase<FastElementsAccessorSubclass,
 851                              KindTraits>(name) {}
 852  protected:
 853   friend class ElementsAccessorBase<FastElementsAccessorSubclass, KindTraits>;
 854   friend class SloppyArgumentsElementsAccessor;
 855
 856   typedef typename KindTraits::BackingStore BackingStore;
 857
 858   // Adjusts the length of the fast backing store.
 859   static Handle<Object> SetLengthWithoutNormalize(
 860       Handle<FixedArrayBase> backing_store,
 861       Handle<JSArray> array,
 862       Handle<Object> length_object,
 863       uint32_t length) {
 864     Isolate* isolate = array->GetIsolate();
 865     uint32_t old_capacity = backing_store->length();
 866     Handle<Object> old_length(array->length(), isolate);
 867     bool same_or_smaller_size = old_length->IsSmi() &&
 868         static_cast<uint32_t>(Handle<Smi>::cast(old_length)->value()) >= length;
 869     ElementsKind kind = array->GetElementsKind();
 870
 871     if (!same_or_smaller_size && IsFastElementsKind(kind) &&
 872         !IsFastHoleyElementsKind(kind)) {
 873       kind = GetHoleyElementsKind(kind);
 874       JSObject::TransitionElementsKind(array, kind);
 875     }
 876
 877     // Check whether the backing store should be shrunk.
 878     if (length <= old_capacity) {
 879       if (array->HasFastSmiOrObjectElements()) {
 880         backing_store = JSObject::EnsureWritableFastElements(array);
 881       }
 882       if (2 * length <= old_capacity) {
 883         // If more than half the elements won't be used, trim the array.
 884         if (length == 0) {
 885           array->initialize_elements();
 886         } else {
 887           isolate->heap()->RightTrimFixedArray<Heap::FROM_MUTATOR>(
 888               *backing_store, old_capacity - length);
 889         }
 890       } else {
 891         // Otherwise, fill the unused tail with holes.
 892         int old_length = FastD2IChecked(array->length()->Number());
 893         for (int i = length; i < old_length; i++) {
 894           Handle<BackingStore>::cast(backing_store)->set_the_hole(i);
 895         }
 896       }
 897       return length_object;
 898     }
 899
 900     // Check whether the backing store should be expanded.
 901     uint32_t min = JSObject::NewElementsCapacity(old_capacity);
 902     uint32_t new_capacity = length > min ? length : min;
 903     FastElementsAccessorSubclass::SetFastElementsCapacityAndLength(
 904         array, new_capacity, length);
 905     JSObject::ValidateElements(array);
 906     return length_object;
 907   }
 908
 909   static Handle<Object> DeleteCommon(Handle<JSObject> obj, uint32_t key,
 910                                      LanguageMode language_mode) {
 911     DCHECK(obj->HasFastSmiOrObjectElements() ||
 912            obj->HasFastDoubleElements() ||
 913            obj->HasFastArgumentsElements());
 914     Isolate* isolate = obj->GetIsolate();
 915     Heap* heap = obj->GetHeap();
 916     Handle<FixedArrayBase> elements(obj->elements());
 917     if (*elements == heap->empty_fixed_array()) {
 918       return isolate->factory()->true_value();
 919     }
 920     Handle<BackingStore> backing_store = Handle<BackingStore>::cast(elements);
 921     bool is_sloppy_arguments_elements_map =
 922         backing_store->map() == heap->sloppy_arguments_elements_map();
 923     if (is_sloppy_arguments_elements_map) {
 924       backing_store = handle(
 925           BackingStore::cast(Handle<FixedArray>::cast(backing_store)->get(1)),
 926           isolate);
 927     }
 928     uint32_t length = static_cast<uint32_t>(
 929         obj->IsJSArray()
 930         ? Smi::cast(Handle<JSArray>::cast(obj)->length())->value()
 931         : backing_store->length());
 932     if (key < length) {
 933       if (!is_sloppy_arguments_elements_map) {
 934         ElementsKind kind = KindTraits::Kind;
 935         if (IsFastPackedElementsKind(kind)) {
 936           JSObject::TransitionElementsKind(obj, GetHoleyElementsKind(kind));
 937         }
 938         if (IsFastSmiOrObjectElementsKind(KindTraits::Kind)) {
 939           Handle<Object> writable = JSObject::EnsureWritableFastElements(obj);
 940           backing_store = Handle<BackingStore>::cast(writable);
 941         }
 942       }
 943       backing_store->set_the_hole(key);
 944       // If an old space backing store is larger than a certain size and
 945       // has too few used values, normalize it.
 946       // To avoid doing the check on every delete we require at least
 947       // one adjacent hole to the value being deleted.
 948       const int kMinLengthForSparsenessCheck = 64;
 949       if (backing_store->length() >= kMinLengthForSparsenessCheck &&
 950           !heap->InNewSpace(*backing_store) &&
 951           ((key > 0 && backing_store->is_the_hole(key - 1)) ||
 952            (key + 1 < length && backing_store->is_the_hole(key + 1)))) {
 953         int num_used = 0;
 954         for (int i = 0; i < backing_store->length(); ++i) {
 955           if (!backing_store->is_the_hole(i)) ++num_used;
 956           // Bail out early if more than 1/4 is used.
 957           if (4 * num_used > backing_store->length()) break;
 958         }
 959         if (4 * num_used <= backing_store->length()) {
 960           JSObject::NormalizeElements(obj);
 961         }
 962       }
 963     }
 964     return isolate->factory()->true_value();
 965   }
 966
 967   virtual MaybeHandle<Object> Delete(Handle<JSObject> obj, uint32_t key,
 968                                      LanguageMode language_mode) FINAL {
 969     return DeleteCommon(obj, key, language_mode);
 970   }
 971
 972   static bool HasElementImpl(
 973       Handle<JSObject> holder,
 974       uint32_t key,
 975       Handle<FixedArrayBase> backing_store) {
 976     if (key >= static_cast<uint32_t>(backing_store->length())) {
 977       return false;
 978     }
 979     return !Handle<BackingStore>::cast(backing_store)->is_the_hole(key);
 980   }
 981
 982   static void ValidateContents(Handle<JSObject> holder, int length) {
 983 #if DEBUG
 984     Isolate* isolate = holder->GetIsolate();
 985     HandleScope scope(isolate);
 986     Handle<FixedArrayBase> elements(holder->elements(), isolate);
 987     Map* map = elements->map();
 988     DCHECK((IsFastSmiOrObjectElementsKind(KindTraits::Kind) &&
 989             (map == isolate->heap()->fixed_array_map() ||
 990              map == isolate->heap()->fixed_cow_array_map())) ||
 991            (IsFastDoubleElementsKind(KindTraits::Kind) ==
 992             ((map == isolate->heap()->fixed_array_map() && length == 0) ||
 993              map == isolate->heap()->fixed_double_array_map())));
 994     DisallowHeapAllocation no_gc;
 995     for (int i = 0; i < length; i++) {
 996       HandleScope scope(isolate);
 997       Handle<BackingStore> backing_store = Handle<BackingStore>::cast(elements);
 998       DCHECK((!IsFastSmiElementsKind(KindTraits::Kind) ||
 999               BackingStore::get(backing_store, i)->IsSmi()) ||
1000              (IsFastHoleyElementsKind(KindTraits::Kind) ==
1001               backing_store->is_the_hole(i)));
1002     }
1003 #endif
1004   }
1005 };
1006
1007
1008 static inline ElementsKind ElementsKindForArray(FixedArrayBase* array) {
1009   switch (array->map()->instance_type()) {
1010     case FIXED_ARRAY_TYPE:
1011       if (array->IsDictionary()) {
1012         return DICTIONARY_ELEMENTS;
1013       } else {
1014         return FAST_HOLEY_ELEMENTS;
1015       }
1016     case FIXED_DOUBLE_ARRAY_TYPE:
1017       return FAST_HOLEY_DOUBLE_ELEMENTS;
1018
1019 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
1020     case EXTERNAL_##TYPE##_ARRAY_TYPE:                                        \
1021       return EXTERNAL_##TYPE##_ELEMENTS;                                      \
1022     case FIXED_##TYPE##_ARRAY_TYPE:                                           \
1023       return TYPE##_ELEMENTS;
1024
1025     TYPED_ARRAYS(TYPED_ARRAY_CASE)
1026 #undef TYPED_ARRAY_CASE
1027
1028     default:
1029       UNREACHABLE();
1030   }
1031   return FAST_HOLEY_ELEMENTS;
1032 }
1033
1034
1035 template<typename FastElementsAccessorSubclass,
1036          typename KindTraits>
1037 class FastSmiOrObjectElementsAccessor
1038     : public FastElementsAccessor<FastElementsAccessorSubclass, KindTraits> {
1039  public:
1040   explicit FastSmiOrObjectElementsAccessor(const char* name)
1041       : FastElementsAccessor<FastElementsAccessorSubclass,
1042                              KindTraits>(name) {}
1043
1044   // NOTE: this method violates the handlified function signature convention:
1045   // raw pointer parameters in the function that allocates.
1046   // See ElementsAccessor::CopyElements() for details.
1047   // This method could actually allocate if copying from double elements to
1048   // object elements.
1049   static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
1050                                FixedArrayBase* to, ElementsKind from_kind,
1051                                uint32_t to_start, int packed_size,
1052                                int copy_size) {
1053     DisallowHeapAllocation no_gc;
1054     ElementsKind to_kind = KindTraits::Kind;
1055     switch (from_kind) {
1056       case FAST_SMI_ELEMENTS:
1057       case FAST_HOLEY_SMI_ELEMENTS:
1058       case FAST_ELEMENTS:
1059       case FAST_HOLEY_ELEMENTS:
1060         CopyObjectToObjectElements(from, from_kind, from_start, to, to_kind,
1061                                    to_start, copy_size);
1062         break;
1063       case FAST_DOUBLE_ELEMENTS:
1064       case FAST_HOLEY_DOUBLE_ELEMENTS: {
1065         AllowHeapAllocation allow_allocation;
1066         CopyDoubleToObjectElements(
1067             from, from_start, to, to_kind, to_start, copy_size);
1068         break;
1069       }
1070       case DICTIONARY_ELEMENTS:
1071         CopyDictionaryToObjectElements(from, from_start, to, to_kind, to_start,
1072                                        copy_size);
1073         break;
1074       case SLOPPY_ARGUMENTS_ELEMENTS: {
1075         // TODO(verwaest): This is a temporary hack to support extending
1076         // SLOPPY_ARGUMENTS_ELEMENTS in SetFastElementsCapacityAndLength.
1077         // This case should be UNREACHABLE().
1078         FixedArray* parameter_map = FixedArray::cast(from);
1079         FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
1080         ElementsKind from_kind = ElementsKindForArray(arguments);
1081         CopyElementsImpl(arguments, from_start, to, from_kind,
1082                          to_start, packed_size, copy_size);
1083         break;
1084       }
1085 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
1086       case EXTERNAL_##TYPE##_ELEMENTS:                                        \
1087       case TYPE##_ELEMENTS:                                                   \
1088         UNREACHABLE();
1089       TYPED_ARRAYS(TYPED_ARRAY_CASE)
1090 #undef TYPED_ARRAY_CASE
1091     }
1092   }
1093
1094
1095   static void SetFastElementsCapacityAndLength(
1096       Handle<JSObject> obj,
1097       uint32_t capacity,
1098       uint32_t length) {
1099     JSObject::SetFastElementsCapacitySmiMode set_capacity_mode =
1100         obj->HasFastSmiElements()
1101             ? JSObject::kAllowSmiElements
1102             : JSObject::kDontAllowSmiElements;
1103     JSObject::SetFastElementsCapacityAndLength(
1104         obj, capacity, length, set_capacity_mode);
1105   }
1106 };
1107
1108
1109 class FastPackedSmiElementsAccessor
1110     : public FastSmiOrObjectElementsAccessor<
1111         FastPackedSmiElementsAccessor,
1112         ElementsKindTraits<FAST_SMI_ELEMENTS> > {
1113  public:
1114   explicit FastPackedSmiElementsAccessor(const char* name)
1115       : FastSmiOrObjectElementsAccessor<
1116           FastPackedSmiElementsAccessor,
1117           ElementsKindTraits<FAST_SMI_ELEMENTS> >(name) {}
1118 };
1119
1120
1121 class FastHoleySmiElementsAccessor
1122     : public FastSmiOrObjectElementsAccessor<
1123         FastHoleySmiElementsAccessor,
1124         ElementsKindTraits<FAST_HOLEY_SMI_ELEMENTS> > {
1125  public:
1126   explicit FastHoleySmiElementsAccessor(const char* name)
1127       : FastSmiOrObjectElementsAccessor<
1128           FastHoleySmiElementsAccessor,
1129           ElementsKindTraits<FAST_HOLEY_SMI_ELEMENTS> >(name) {}
1130 };
1131
1132
1133 class FastPackedObjectElementsAccessor
1134     : public FastSmiOrObjectElementsAccessor<
1135         FastPackedObjectElementsAccessor,
1136         ElementsKindTraits<FAST_ELEMENTS> > {
1137  public:
1138   explicit FastPackedObjectElementsAccessor(const char* name)
1139       : FastSmiOrObjectElementsAccessor<
1140           FastPackedObjectElementsAccessor,
1141           ElementsKindTraits<FAST_ELEMENTS> >(name) {}
1142 };
1143
1144
1145 class FastHoleyObjectElementsAccessor
1146     : public FastSmiOrObjectElementsAccessor<
1147         FastHoleyObjectElementsAccessor,
1148         ElementsKindTraits<FAST_HOLEY_ELEMENTS> > {
1149  public:
1150   explicit FastHoleyObjectElementsAccessor(const char* name)
1151       : FastSmiOrObjectElementsAccessor<
1152           FastHoleyObjectElementsAccessor,
1153           ElementsKindTraits<FAST_HOLEY_ELEMENTS> >(name) {}
1154 };
1155
1156
1157 template<typename FastElementsAccessorSubclass,
1158          typename KindTraits>
1159 class FastDoubleElementsAccessor
1160     : public FastElementsAccessor<FastElementsAccessorSubclass, KindTraits> {
1161  public:
1162   explicit FastDoubleElementsAccessor(const char* name)
1163       : FastElementsAccessor<FastElementsAccessorSubclass,
1164                              KindTraits>(name) {}
1165
1166   static void SetFastElementsCapacityAndLength(Handle<JSObject> obj,
1167                                                uint32_t capacity,
1168                                                uint32_t length) {
1169     JSObject::SetFastDoubleElementsCapacityAndLength(obj, capacity, length);
1170   }
1171
1172  protected:
1173   static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
1174                                FixedArrayBase* to, ElementsKind from_kind,
1175                                uint32_t to_start, int packed_size,
1176                                int copy_size) {
1177     DisallowHeapAllocation no_allocation;
1178     switch (from_kind) {
1179       case FAST_SMI_ELEMENTS:
1180         CopyPackedSmiToDoubleElements(from, from_start, to, to_start,
1181                                       packed_size, copy_size);
1182         break;
1183       case FAST_HOLEY_SMI_ELEMENTS:
1184         CopySmiToDoubleElements(from, from_start, to, to_start, copy_size);
1185         break;
1186       case FAST_DOUBLE_ELEMENTS:
1187       case FAST_HOLEY_DOUBLE_ELEMENTS:
1188         CopyDoubleToDoubleElements(from, from_start, to, to_start, copy_size);
1189         break;
1190       case FAST_ELEMENTS:
1191       case FAST_HOLEY_ELEMENTS:
1192         CopyObjectToDoubleElements(from, from_start, to, to_start, copy_size);
1193         break;
1194       case DICTIONARY_ELEMENTS:
1195         CopyDictionaryToDoubleElements(from, from_start, to, to_start,
1196                                        copy_size);
1197         break;
1198       case SLOPPY_ARGUMENTS_ELEMENTS:
1199         UNREACHABLE();
1200
1201 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
1202       case EXTERNAL_##TYPE##_ELEMENTS:                                        \
1203       case TYPE##_ELEMENTS:                                                   \
1204         UNREACHABLE();
1205       TYPED_ARRAYS(TYPED_ARRAY_CASE)
1206 #undef TYPED_ARRAY_CASE
1207     }
1208   }
1209 };
1210
1211
1212 class FastPackedDoubleElementsAccessor
1213     : public FastDoubleElementsAccessor<
1214         FastPackedDoubleElementsAccessor,
1215         ElementsKindTraits<FAST_DOUBLE_ELEMENTS> > {
1216  public:
1217   friend class ElementsAccessorBase<FastPackedDoubleElementsAccessor,
1218                                     ElementsKindTraits<FAST_DOUBLE_ELEMENTS> >;
1219   explicit FastPackedDoubleElementsAccessor(const char* name)
1220       : FastDoubleElementsAccessor<
1221           FastPackedDoubleElementsAccessor,
1222           ElementsKindTraits<FAST_DOUBLE_ELEMENTS> >(name) {}
1223 };
1224
1225
1226 class FastHoleyDoubleElementsAccessor
1227     : public FastDoubleElementsAccessor<
1228         FastHoleyDoubleElementsAccessor,
1229         ElementsKindTraits<FAST_HOLEY_DOUBLE_ELEMENTS> > {
1230  public:
1231   friend class ElementsAccessorBase<
1232     FastHoleyDoubleElementsAccessor,
1233     ElementsKindTraits<FAST_HOLEY_DOUBLE_ELEMENTS> >;
1234   explicit FastHoleyDoubleElementsAccessor(const char* name)
1235       : FastDoubleElementsAccessor<
1236           FastHoleyDoubleElementsAccessor,
1237           ElementsKindTraits<FAST_HOLEY_DOUBLE_ELEMENTS> >(name) {}
1238 };
1239
1240
1241 // Super class for all external element arrays.
1242 template<ElementsKind Kind>
1243 class TypedElementsAccessor
1244     : public ElementsAccessorBase<TypedElementsAccessor<Kind>,
1245                                   ElementsKindTraits<Kind> > {
1246  public:
1247   explicit TypedElementsAccessor(const char* name)
1248       : ElementsAccessorBase<AccessorClass,
1249                              ElementsKindTraits<Kind> >(name) {}
1250
1251  protected:
1252   typedef typename ElementsKindTraits<Kind>::BackingStore BackingStore;
1253   typedef TypedElementsAccessor<Kind> AccessorClass;
1254
1255   friend class ElementsAccessorBase<AccessorClass,
1256                                     ElementsKindTraits<Kind> >;
1257
1258   MUST_USE_RESULT static MaybeHandle<Object> GetImpl(
1259       Handle<Object> receiver,
1260       Handle<JSObject> obj,
1261       uint32_t key,
1262       Handle<FixedArrayBase> backing_store) {
1263     if (key < AccessorClass::GetCapacityImpl(backing_store)) {
1264       return BackingStore::get(Handle<BackingStore>::cast(backing_store), key);
1265     } else {
1266       return backing_store->GetIsolate()->factory()->undefined_value();
1267     }
1268   }
1269
1270   MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
1271       Handle<JSObject> obj,
1272       uint32_t key,
1273       Handle<FixedArrayBase> backing_store) {
1274     return
1275         key < AccessorClass::GetCapacityImpl(backing_store)
1276           ? NONE : ABSENT;
1277   }
1278
1279   MUST_USE_RESULT static MaybeHandle<Object> SetLengthImpl(
1280       Handle<JSObject> obj,
1281       Handle<Object> length,
1282       Handle<FixedArrayBase> backing_store) {
1283     // External arrays do not support changing their length.
1284     UNREACHABLE();
1285     return obj;
1286   }
1287
1288   MUST_USE_RESULT virtual MaybeHandle<Object> Delete(
1289       Handle<JSObject> obj, uint32_t key, LanguageMode language_mode) FINAL {
1290     // External arrays always ignore deletes.
1291     return obj->GetIsolate()->factory()->true_value();
1292   }
1293
1294   static bool HasElementImpl(Handle<JSObject> holder, uint32_t key,
1295                              Handle<FixedArrayBase> backing_store) {
1296     uint32_t capacity =
1297         AccessorClass::GetCapacityImpl(backing_store);
1298     return key < capacity;
1299   }
1300 };
1301
1302
1303
1304 #define EXTERNAL_ELEMENTS_ACCESSOR(Type, type, TYPE, ctype, size)    \
1305   typedef TypedElementsAccessor<EXTERNAL_##TYPE##_ELEMENTS>          \
1306       External##Type##ElementsAccessor;
1307
1308 TYPED_ARRAYS(EXTERNAL_ELEMENTS_ACCESSOR)
1309 #undef EXTERNAL_ELEMENTS_ACCESSOR
1310
1311 #define FIXED_ELEMENTS_ACCESSOR(Type, type, TYPE, ctype, size)       \
1312   typedef TypedElementsAccessor<TYPE##_ELEMENTS >                    \
1313       Fixed##Type##ElementsAccessor;
1314
1315 TYPED_ARRAYS(FIXED_ELEMENTS_ACCESSOR)
1316 #undef FIXED_ELEMENTS_ACCESSOR
1317
1318
1319
1320 class DictionaryElementsAccessor
1321     : public ElementsAccessorBase<DictionaryElementsAccessor,
1322                                   ElementsKindTraits<DICTIONARY_ELEMENTS> > {
1323  public:
1324   explicit DictionaryElementsAccessor(const char* name)
1325       : ElementsAccessorBase<DictionaryElementsAccessor,
1326                              ElementsKindTraits<DICTIONARY_ELEMENTS> >(name) {}
1327
1328   // Adjusts the length of the dictionary backing store and returns the new
1329   // length according to ES5 section 15.4.5.2 behavior.
1330   static Handle<Object> SetLengthWithoutNormalize(
1331       Handle<FixedArrayBase> store,
1332       Handle<JSArray> array,
1333       Handle<Object> length_object,
1334       uint32_t length) {
1335     Handle<SeededNumberDictionary> dict =
1336         Handle<SeededNumberDictionary>::cast(store);
1337     Isolate* isolate = array->GetIsolate();
1338     int capacity = dict->Capacity();
1339     uint32_t new_length = length;
1340     uint32_t old_length = static_cast<uint32_t>(array->length()->Number());
1341     if (new_length < old_length) {
1342       // Find last non-deletable element in range of elements to be
1343       // deleted and adjust range accordingly.
1344       for (int i = 0; i < capacity; i++) {
1345         DisallowHeapAllocation no_gc;
1346         Object* key = dict->KeyAt(i);
1347         if (key->IsNumber()) {
1348           uint32_t number = static_cast<uint32_t>(key->Number());
1349           if (new_length <= number && number < old_length) {
1350             PropertyDetails details = dict->DetailsAt(i);
1351             if (!details.IsConfigurable()) new_length = number + 1;
1352           }
1353         }
1354       }
1355       if (new_length != length) {
1356         length_object = isolate->factory()->NewNumberFromUint(new_length);
1357       }
1358     }
1359
1360     if (new_length == 0) {
1361       // Flush the backing store.
1362       JSObject::ResetElements(array);
1363     } else {
1364       DisallowHeapAllocation no_gc;
1365       // Remove elements that should be deleted.
1366       int removed_entries = 0;
1367       Handle<Object> the_hole_value = isolate->factory()->the_hole_value();
1368       for (int i = 0; i < capacity; i++) {
1369         Object* key = dict->KeyAt(i);
1370         if (key->IsNumber()) {
1371           uint32_t number = static_cast<uint32_t>(key->Number());
1372           if (new_length <= number && number < old_length) {
1373             dict->SetEntry(i, the_hole_value, the_hole_value);
1374             removed_entries++;
1375           }
1376         }
1377       }
1378
1379       // Update the number of elements.
1380       dict->ElementsRemoved(removed_entries);
1381     }
1382     return length_object;
1383   }
1384
1385   MUST_USE_RESULT static MaybeHandle<Object> DeleteCommon(
1386       Handle<JSObject> obj, uint32_t key, LanguageMode language_mode) {
1387     Isolate* isolate = obj->GetIsolate();
1388     Handle<FixedArray> backing_store(FixedArray::cast(obj->elements()),
1389                                      isolate);
1390     bool is_arguments =
1391         (obj->GetElementsKind() == SLOPPY_ARGUMENTS_ELEMENTS);
1392     if (is_arguments) {
1393       backing_store = handle(FixedArray::cast(backing_store->get(1)), isolate);
1394     }
1395     Handle<SeededNumberDictionary> dictionary =
1396         Handle<SeededNumberDictionary>::cast(backing_store);
1397     int entry = dictionary->FindEntry(key);
1398     if (entry != SeededNumberDictionary::kNotFound) {
1399       Handle<Object> result =
1400           SeededNumberDictionary::DeleteProperty(dictionary, entry);
1401       if (*result == *isolate->factory()->false_value()) {
1402         if (is_strict(language_mode)) {
1403           // Deleting a non-configurable property in strict mode.
1404           Handle<Object> name = isolate->factory()->NewNumberFromUint(key);
1405           Handle<Object> args[2] = { name, obj };
1406           THROW_NEW_ERROR(isolate, NewTypeError("strict_delete_property",
1407                                                 HandleVector(args, 2)),
1408                           Object);
1409         }
1410         return isolate->factory()->false_value();
1411       }
1412       Handle<FixedArray> new_elements =
1413           SeededNumberDictionary::Shrink(dictionary, key);
1414
1415       if (is_arguments) {
1416         FixedArray::cast(obj->elements())->set(1, *new_elements);
1417       } else {
1418         obj->set_elements(*new_elements);
1419       }
1420     }
1421     return isolate->factory()->true_value();
1422   }
1423
1424   static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
1425                                FixedArrayBase* to, ElementsKind from_kind,
1426                                uint32_t to_start, int packed_size,
1427                                int copy_size) {
1428     UNREACHABLE();
1429   }
1430
1431
1432  protected:
1433   friend class ElementsAccessorBase<DictionaryElementsAccessor,
1434                                     ElementsKindTraits<DICTIONARY_ELEMENTS> >;
1435
1436   MUST_USE_RESULT virtual MaybeHandle<Object> Delete(
1437       Handle<JSObject> obj, uint32_t key, LanguageMode language_mode) FINAL {
1438     return DeleteCommon(obj, key, language_mode);
1439   }
1440
1441   MUST_USE_RESULT static MaybeHandle<Object> GetImpl(
1442       Handle<Object> receiver,
1443       Handle<JSObject> obj,
1444       uint32_t key,
1445       Handle<FixedArrayBase> store) {
1446     Handle<SeededNumberDictionary> backing_store =
1447         Handle<SeededNumberDictionary>::cast(store);
1448     Isolate* isolate = backing_store->GetIsolate();
1449     int entry = backing_store->FindEntry(key);
1450     if (entry != SeededNumberDictionary::kNotFound) {
1451       Handle<Object> element(backing_store->ValueAt(entry), isolate);
1452       PropertyDetails details = backing_store->DetailsAt(entry);
1453       if (details.type() == ACCESSOR_CONSTANT) {
1454         return JSObject::GetElementWithCallback(
1455             obj, receiver, element, key, obj);
1456       } else {
1457         return element;
1458       }
1459     }
1460     return isolate->factory()->the_hole_value();
1461   }
1462
1463   MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
1464       Handle<JSObject> obj,
1465       uint32_t key,
1466       Handle<FixedArrayBase> backing_store) {
1467     Handle<SeededNumberDictionary> dictionary =
1468         Handle<SeededNumberDictionary>::cast(backing_store);
1469     int entry = dictionary->FindEntry(key);
1470     if (entry != SeededNumberDictionary::kNotFound) {
1471       return dictionary->DetailsAt(entry).attributes();
1472     }
1473     return ABSENT;
1474   }
1475
1476   MUST_USE_RESULT static MaybeHandle<AccessorPair> GetAccessorPairImpl(
1477       Handle<JSObject> obj,
1478       uint32_t key,
1479       Handle<FixedArrayBase> store) {
1480     Handle<SeededNumberDictionary> backing_store =
1481         Handle<SeededNumberDictionary>::cast(store);
1482     int entry = backing_store->FindEntry(key);
1483     if (entry != SeededNumberDictionary::kNotFound &&
1484         backing_store->DetailsAt(entry).type() == ACCESSOR_CONSTANT &&
1485         backing_store->ValueAt(entry)->IsAccessorPair()) {
1486       return handle(AccessorPair::cast(backing_store->ValueAt(entry)));
1487     }
1488     return MaybeHandle<AccessorPair>();
1489   }
1490
1491   static bool HasElementImpl(Handle<JSObject> holder, uint32_t key,
1492                              Handle<FixedArrayBase> store) {
1493     Handle<SeededNumberDictionary> backing_store =
1494         Handle<SeededNumberDictionary>::cast(store);
1495     return backing_store->FindEntry(key) != SeededNumberDictionary::kNotFound;
1496   }
1497
1498   static uint32_t GetKeyForIndexImpl(Handle<FixedArrayBase> store,
1499                                      uint32_t index) {
1500     DisallowHeapAllocation no_gc;
1501     Handle<SeededNumberDictionary> dict =
1502         Handle<SeededNumberDictionary>::cast(store);
1503     Object* key = dict->KeyAt(index);
1504     return Smi::cast(key)->value();
1505   }
1506 };
1507
1508
1509 class SloppyArgumentsElementsAccessor : public ElementsAccessorBase<
1510     SloppyArgumentsElementsAccessor,
1511     ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> > {
1512  public:
1513   explicit SloppyArgumentsElementsAccessor(const char* name)
1514       : ElementsAccessorBase<
1515           SloppyArgumentsElementsAccessor,
1516           ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> >(name) {}
1517  protected:
1518   friend class ElementsAccessorBase<
1519       SloppyArgumentsElementsAccessor,
1520       ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> >;
1521
1522   MUST_USE_RESULT static MaybeHandle<Object> GetImpl(
1523       Handle<Object> receiver,
1524       Handle<JSObject> obj,
1525       uint32_t key,
1526       Handle<FixedArrayBase> parameters) {
1527     Isolate* isolate = obj->GetIsolate();
1528     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(parameters);
1529     Handle<Object> probe = GetParameterMapArg(obj, parameter_map, key);
1530     if (!probe->IsTheHole()) {
1531       DisallowHeapAllocation no_gc;
1532       Context* context = Context::cast(parameter_map->get(0));
1533       int context_index = Handle<Smi>::cast(probe)->value();
1534       DCHECK(!context->get(context_index)->IsTheHole());
1535       return handle(context->get(context_index), isolate);
1536     } else {
1537       // Object is not mapped, defer to the arguments.
1538       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)),
1539                                    isolate);
1540       Handle<Object> result;
1541       ASSIGN_RETURN_ON_EXCEPTION(
1542           isolate, result,
1543           ElementsAccessor::ForArray(arguments)->Get(
1544               receiver, obj, key, arguments),
1545           Object);
1546       // Elements of the arguments object in slow mode might be slow aliases.
1547       if (result->IsAliasedArgumentsEntry()) {
1548         DisallowHeapAllocation no_gc;
1549         AliasedArgumentsEntry* entry = AliasedArgumentsEntry::cast(*result);
1550         Context* context = Context::cast(parameter_map->get(0));
1551         int context_index = entry->aliased_context_slot();
1552         DCHECK(!context->get(context_index)->IsTheHole());
1553         return handle(context->get(context_index), isolate);
1554       } else {
1555         return result;
1556       }
1557     }
1558   }
1559
1560   MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
1561       Handle<JSObject> obj,
1562       uint32_t key,
1563       Handle<FixedArrayBase> backing_store) {
1564     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(backing_store);
1565     Handle<Object> probe = GetParameterMapArg(obj, parameter_map, key);
1566     if (!probe->IsTheHole()) {
1567       return NONE;
1568     } else {
1569       // If not aliased, check the arguments.
1570       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)));
1571       return ElementsAccessor::ForArray(arguments)
1572           ->GetAttributes(obj, key, arguments);
1573     }
1574   }
1575
1576   MUST_USE_RESULT static MaybeHandle<AccessorPair> GetAccessorPairImpl(
1577       Handle<JSObject> obj,
1578       uint32_t key,
1579       Handle<FixedArrayBase> parameters) {
1580     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(parameters);
1581     Handle<Object> probe = GetParameterMapArg(obj, parameter_map, key);
1582     if (!probe->IsTheHole()) {
1583       return MaybeHandle<AccessorPair>();
1584     } else {
1585       // If not aliased, check the arguments.
1586       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)));
1587       return ElementsAccessor::ForArray(arguments)
1588           ->GetAccessorPair(obj, key, arguments);
1589     }
1590   }
1591
1592   MUST_USE_RESULT static MaybeHandle<Object> SetLengthImpl(
1593       Handle<JSObject> obj,
1594       Handle<Object> length,
1595       Handle<FixedArrayBase> parameter_map) {
1596     // TODO(mstarzinger): This was never implemented but will be used once we
1597     // correctly implement [[DefineOwnProperty]] on arrays.
1598     UNIMPLEMENTED();
1599     return obj;
1600   }
1601
1602   MUST_USE_RESULT virtual MaybeHandle<Object> Delete(
1603       Handle<JSObject> obj, uint32_t key, LanguageMode language_mode) FINAL {
1604     Isolate* isolate = obj->GetIsolate();
1605     Handle<FixedArray> parameter_map(FixedArray::cast(obj->elements()));
1606     Handle<Object> probe = GetParameterMapArg(obj, parameter_map, key);
1607     if (!probe->IsTheHole()) {
1608       // TODO(kmillikin): We could check if this was the last aliased
1609       // parameter, and revert to normal elements in that case.  That
1610       // would enable GC of the context.
1611       parameter_map->set_the_hole(key + 2);
1612     } else {
1613       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)));
1614       if (arguments->IsDictionary()) {
1615         return DictionaryElementsAccessor::DeleteCommon(obj, key,
1616                                                         language_mode);
1617       } else {
1618         // It's difficult to access the version of DeleteCommon that is declared
1619         // in the templatized super class, call the concrete implementation in
1620         // the class for the most generalized ElementsKind subclass.
1621         return FastHoleyObjectElementsAccessor::DeleteCommon(obj, key,
1622                                                              language_mode);
1623       }
1624     }
1625     return isolate->factory()->true_value();
1626   }
1627
1628   static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
1629                                FixedArrayBase* to, ElementsKind from_kind,
1630                                uint32_t to_start, int packed_size,
1631                                int copy_size) {
1632     UNREACHABLE();
1633   }
1634
1635   static uint32_t GetCapacityImpl(Handle<FixedArrayBase> backing_store) {
1636     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(backing_store);
1637     Handle<FixedArrayBase> arguments(
1638         FixedArrayBase::cast(parameter_map->get(1)));
1639     return Max(static_cast<uint32_t>(parameter_map->length() - 2),
1640                ForArray(arguments)->GetCapacity(arguments));
1641   }
1642
1643   static uint32_t GetKeyForIndexImpl(Handle<FixedArrayBase> dict,
1644                                      uint32_t index) {
1645     return index;
1646   }
1647
1648  private:
1649   static Handle<Object> GetParameterMapArg(Handle<JSObject> holder,
1650                                            Handle<FixedArray> parameter_map,
1651                                            uint32_t key) {
1652     Isolate* isolate = holder->GetIsolate();
1653     uint32_t length = holder->IsJSArray()
1654         ? Smi::cast(Handle<JSArray>::cast(holder)->length())->value()
1655         : parameter_map->length();
1656     return key < (length - 2)
1657         ? handle(parameter_map->get(key + 2), isolate)
1658         : Handle<Object>::cast(isolate->factory()->the_hole_value());
1659   }
1660 };
1661
1662
1663 ElementsAccessor* ElementsAccessor::ForArray(Handle<FixedArrayBase> array) {
1664   return elements_accessors_[ElementsKindForArray(*array)];
1665 }
1666
1667
1668 void ElementsAccessor::InitializeOncePerProcess() {
1669   static ElementsAccessor* accessor_array[] = {
1670 #define ACCESSOR_ARRAY(Class, Kind, Store) new Class(#Kind),
1671     ELEMENTS_LIST(ACCESSOR_ARRAY)
1672 #undef ACCESSOR_ARRAY
1673   };
1674
1675   STATIC_ASSERT((sizeof(accessor_array) / sizeof(*accessor_array)) ==
1676                 kElementsKindCount);
1677
1678   elements_accessors_ = accessor_array;
1679 }
1680
1681
1682 void ElementsAccessor::TearDown() {
1683   if (elements_accessors_ == NULL) return;
1684 #define ACCESSOR_DELETE(Class, Kind, Store) delete elements_accessors_[Kind];
1685   ELEMENTS_LIST(ACCESSOR_DELETE)
1686 #undef ACCESSOR_DELETE
1687   elements_accessors_ = NULL;
1688 }
1689
1690
1691 template <typename ElementsAccessorSubclass, typename ElementsKindTraits>
1692 MUST_USE_RESULT
1693 MaybeHandle<Object> ElementsAccessorBase<ElementsAccessorSubclass,
1694                                          ElementsKindTraits>::
1695     SetLengthImpl(Handle<JSObject> obj,
1696                   Handle<Object> length,
1697                   Handle<FixedArrayBase> backing_store) {
1698   Isolate* isolate = obj->GetIsolate();
1699   Handle<JSArray> array = Handle<JSArray>::cast(obj);
1700
1701   // Fast case: The new length fits into a Smi.
1702   Handle<Object> smi_length;
1703
1704   if (Object::ToSmi(isolate, length).ToHandle(&smi_length) &&
1705       smi_length->IsSmi()) {
1706     const int value = Handle<Smi>::cast(smi_length)->value();
1707     if (value >= 0) {
1708       Handle<Object> new_length = ElementsAccessorSubclass::
1709           SetLengthWithoutNormalize(backing_store, array, smi_length, value);
1710       DCHECK(!new_length.is_null());
1711
1712       // even though the proposed length was a smi, new_length could
1713       // still be a heap number because SetLengthWithoutNormalize doesn't
1714       // allow the array length property to drop below the index of
1715       // non-deletable elements.
1716       DCHECK(new_length->IsSmi() || new_length->IsHeapNumber() ||
1717              new_length->IsUndefined());
1718       if (new_length->IsSmi()) {
1719         array->set_length(*Handle<Smi>::cast(new_length));
1720         return array;
1721       } else if (new_length->IsHeapNumber()) {
1722         array->set_length(*new_length);
1723         return array;
1724       }
1725     } else {
1726       return ThrowArrayLengthRangeError(isolate);
1727     }
1728   }
1729
1730   // Slow case: The new length does not fit into a Smi or conversion
1731   // to slow elements is needed for other reasons.
1732   if (length->IsNumber()) {
1733     uint32_t value;
1734     if (length->ToArrayIndex(&value)) {
1735       Handle<SeededNumberDictionary> dictionary =
1736           JSObject::NormalizeElements(array);
1737       DCHECK(!dictionary.is_null());
1738
1739       Handle<Object> new_length = DictionaryElementsAccessor::
1740           SetLengthWithoutNormalize(dictionary, array, length, value);
1741       DCHECK(!new_length.is_null());
1742
1743       DCHECK(new_length->IsNumber());
1744       array->set_length(*new_length);
1745       return array;
1746     } else {
1747       return ThrowArrayLengthRangeError(isolate);
1748     }
1749   }
1750
1751   // Fall-back case: The new length is not a number so make the array
1752   // size one and set only element to length.
1753   Handle<FixedArray> new_backing_store = isolate->factory()->NewFixedArray(1);
1754   new_backing_store->set(0, *length);
1755   JSArray::SetContent(array, new_backing_store);
1756   return array;
1757 }
1758
1759
1760 MaybeHandle<Object> ArrayConstructInitializeElements(Handle<JSArray> array,
1761                                                      Arguments* args) {
1762   // Optimize the case where there is one argument and the argument is a
1763   // small smi.
1764   if (args->length() == 1) {
1765     Handle<Object> obj = args->at<Object>(0);
1766     if (obj->IsSmi()) {
1767       int len = Handle<Smi>::cast(obj)->value();
1768       if (len > 0 && len < JSObject::kInitialMaxFastElementArray) {
1769         ElementsKind elements_kind = array->GetElementsKind();
1770         JSArray::Initialize(array, len, len);
1771
1772         if (!IsFastHoleyElementsKind(elements_kind)) {
1773           elements_kind = GetHoleyElementsKind(elements_kind);
1774           JSObject::TransitionElementsKind(array, elements_kind);
1775         }
1776         return array;
1777       } else if (len == 0) {
1778         JSArray::Initialize(array, JSArray::kPreallocatedArrayElements);
1779         return array;
1780       }
1781     }
1782
1783     // Take the argument as the length.
1784     JSArray::Initialize(array, 0);
1785
1786     return JSArray::SetElementsLength(array, obj);
1787   }
1788
1789   // Optimize the case where there are no parameters passed.
1790   if (args->length() == 0) {
1791     JSArray::Initialize(array, JSArray::kPreallocatedArrayElements);
1792     return array;
1793   }
1794
1795   Factory* factory = array->GetIsolate()->factory();
1796
1797   // Set length and elements on the array.
1798   int number_of_elements = args->length();
1799   JSObject::EnsureCanContainElements(
1800       array, args, 0, number_of_elements, ALLOW_CONVERTED_DOUBLE_ELEMENTS);
1801
1802   // Allocate an appropriately typed elements array.
1803   ElementsKind elements_kind = array->GetElementsKind();
1804   Handle<FixedArrayBase> elms;
1805   if (IsFastDoubleElementsKind(elements_kind)) {
1806     elms = Handle<FixedArrayBase>::cast(
1807         factory->NewFixedDoubleArray(number_of_elements));
1808   } else {
1809     elms = Handle<FixedArrayBase>::cast(
1810         factory->NewFixedArrayWithHoles(number_of_elements));
1811   }
1812
1813   // Fill in the content
1814   switch (array->GetElementsKind()) {
1815     case FAST_HOLEY_SMI_ELEMENTS:
1816     case FAST_SMI_ELEMENTS: {
1817       Handle<FixedArray> smi_elms = Handle<FixedArray>::cast(elms);
1818       for (int index = 0; index < number_of_elements; index++) {
1819         smi_elms->set(index, (*args)[index], SKIP_WRITE_BARRIER);
1820       }
1821       break;
1822     }
1823     case FAST_HOLEY_ELEMENTS:
1824     case FAST_ELEMENTS: {
1825       DisallowHeapAllocation no_gc;
1826       WriteBarrierMode mode = elms->GetWriteBarrierMode(no_gc);
1827       Handle<FixedArray> object_elms = Handle<FixedArray>::cast(elms);
1828       for (int index = 0; index < number_of_elements; index++) {
1829         object_elms->set(index, (*args)[index], mode);
1830       }
1831       break;
1832     }
1833     case FAST_HOLEY_DOUBLE_ELEMENTS:
1834     case FAST_DOUBLE_ELEMENTS: {
1835       Handle<FixedDoubleArray> double_elms =
1836           Handle<FixedDoubleArray>::cast(elms);
1837       for (int index = 0; index < number_of_elements; index++) {
1838         double_elms->set(index, (*args)[index]->Number());
1839       }
1840       break;
1841     }
1842     default:
1843       UNREACHABLE();
1844       break;
1845   }
1846
1847   array->set_elements(*elms);
1848   array->set_length(Smi::FromInt(number_of_elements));
1849   return array;
1850 }
1851
1852 } }  // namespace v8::internal