runtime/SymbolTable.h

   1 /*
   2  * Copyright (C) 2007, 2008, 2012-2015 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef SymbolTable_h
  30 #define SymbolTable_h
  31
  32 #include "ConcurrentJITLock.h"
  33 #include "ConstantMode.h"
  34 #include "InferredValue.h"
  35 #include "JSObject.h"
  36 #include "ScopedArgumentsTable.h"
  37 #include "TypeLocation.h"
  38 #include "VarOffset.h"
  39 #include "Watchpoint.h"
  40 #include <memory>
  41 #include <wtf/HashTraits.h>
  42 #include <wtf/text/UniquedStringImpl.h>
  43
  44 namespace JSC {
  45
  46 class SymbolTable;
  47
  48 static ALWAYS_INLINE int missingSymbolMarker() { return std::numeric_limits<int>::max(); }
  49
  50 // The bit twiddling in this class assumes that every register index is a
  51 // reasonably small positive or negative number, and therefore has its high
  52 // four bits all set or all unset.
  53
  54 // In addition to implementing semantics-mandated variable attributes and
  55 // implementation-mandated variable indexing, this class also implements
  56 // watchpoints to be used for JIT optimizations. Because watchpoints are
  57 // meant to be relatively rare, this class optimizes heavily for the case
  58 // that they are not being used. To that end, this class uses the thin-fat
  59 // idiom: either it is thin, in which case it contains an in-place encoded
  60 // word that consists of attributes, the index, and a bit saying that it is
  61 // thin; or it is fat, in which case it contains a pointer to a malloc'd
  62 // data structure and a bit saying that it is fat. The malloc'd data
  63 // structure will be malloced a second time upon copy, to preserve the
  64 // property that in-place edits to SymbolTableEntry do not manifest in any
  65 // copies. However, the malloc'd FatEntry data structure contains a ref-
  66 // counted pointer to a shared WatchpointSet. Thus, in-place edits of the
  67 // WatchpointSet will manifest in all copies. Here's a picture:
  68 //
  69 // SymbolTableEntry --> FatEntry --> WatchpointSet
  70 //
  71 // If you make a copy of a SymbolTableEntry, you will have:
  72 //
  73 // original: SymbolTableEntry --> FatEntry --> WatchpointSet
  74 // copy:     SymbolTableEntry --> FatEntry -----^
  75
  76 struct SymbolTableEntry {
  77 private:
  78     static VarOffset varOffsetFromBits(intptr_t bits)
  79     {
  80         VarKind kind;
  81         intptr_t kindBits = bits & KindBitsMask;
  82         if (kindBits <= UnwatchableScopeKindBits)
  83             kind = VarKind::Scope;
  84         else if (kindBits == StackKindBits)
  85             kind = VarKind::Stack;
  86         else
  87             kind = VarKind::DirectArgument;
  88         return VarOffset::assemble(kind, static_cast<int>(bits >> FlagBits));
  89     }
  90
  91     static ScopeOffset scopeOffsetFromBits(intptr_t bits)
  92     {
  93         ASSERT((bits & KindBitsMask) <= UnwatchableScopeKindBits);
  94         return ScopeOffset(static_cast<int>(bits >> FlagBits));
  95     }
  96
  97 public:
  98
  99     // Use the SymbolTableEntry::Fast class, either via implicit cast or by calling
 100     // getFast(), when you (1) only care about isNull(), getIndex(), and isReadOnly(),
 101     // and (2) you are in a hot path where you need to minimize the number of times
 102     // that you branch on isFat() when getting the bits().
 103     class Fast {
 104     public:
 105         Fast()
 106             : m_bits(SlimFlag)
 107         {
 108         }
 109
 110         ALWAYS_INLINE Fast(const SymbolTableEntry& entry)
 111             : m_bits(entry.bits())
 112         {
 113         }
 114
 115         bool isNull() const
 116         {
 117             return !(m_bits & ~SlimFlag);
 118         }
 119
 120         VarOffset varOffset() const
 121         {
 122             return varOffsetFromBits(m_bits);
 123         }
 124
 125         // Asserts if the offset is anything but a scope offset. This structures the assertions
 126         // in a way that may result in better code, even in release, than doing
 127         // varOffset().scopeOffset().
 128         ScopeOffset scopeOffset() const
 129         {
 130             return scopeOffsetFromBits(m_bits);
 131         }
 132
 133         bool isReadOnly() const
 134         {
 135             return m_bits & ReadOnlyFlag;
 136         }
 137
 138         bool isDontEnum() const
 139         {
 140             return m_bits & DontEnumFlag;
 141         }
 142
 143         unsigned getAttributes() const
 144         {
 145             unsigned attributes = 0;
 146             if (isReadOnly())
 147                 attributes |= ReadOnly;
 148             if (isDontEnum())
 149                 attributes |= DontEnum;
 150             return attributes;
 151         }
 152
 153         bool isFat() const
 154         {
 155             return !(m_bits & SlimFlag);
 156         }
 157
 158     private:
 159         friend struct SymbolTableEntry;
 160         intptr_t m_bits;
 161     };
 162
 163     SymbolTableEntry()
 164         : m_bits(SlimFlag)
 165     {
 166     }
 167
 168     SymbolTableEntry(VarOffset offset)
 169         : m_bits(SlimFlag)
 170     {
 171         ASSERT(isValidVarOffset(offset));
 172         pack(offset, true, false, false);
 173     }
 174
 175     SymbolTableEntry(VarOffset offset, unsigned attributes)
 176         : m_bits(SlimFlag)
 177     {
 178         ASSERT(isValidVarOffset(offset));
 179         pack(offset, true, attributes & ReadOnly, attributes & DontEnum);
 180     }
 181
 182     ~SymbolTableEntry()
 183     {
 184         freeFatEntry();
 185     }
 186
 187     SymbolTableEntry(const SymbolTableEntry& other)
 188         : m_bits(SlimFlag)
 189     {
 190         *this = other;
 191     }
 192
 193     SymbolTableEntry& operator=(const SymbolTableEntry& other)
 194     {
 195         if (UNLIKELY(other.isFat()))
 196             return copySlow(other);
 197         freeFatEntry();
 198         m_bits = other.m_bits;
 199         return *this;
 200     }
 201
 202     bool isNull() const
 203     {
 204         return !(bits() & ~SlimFlag);
 205     }
 206
 207     VarOffset varOffset() const
 208     {
 209         return varOffsetFromBits(bits());
 210     }
 211
 212     bool isWatchable() const
 213     {
 214         return (m_bits & KindBitsMask) == ScopeKindBits;
 215     }
 216
 217     // Asserts if the offset is anything but a scope offset. This structures the assertions
 218     // in a way that may result in better code, even in release, than doing
 219     // varOffset().scopeOffset().
 220     ScopeOffset scopeOffset() const
 221     {
 222         return scopeOffsetFromBits(bits());
 223     }
 224
 225     ALWAYS_INLINE Fast getFast() const
 226     {
 227         return Fast(*this);
 228     }
 229
 230     ALWAYS_INLINE Fast getFast(bool& wasFat) const
 231     {
 232         Fast result;
 233         wasFat = isFat();
 234         if (wasFat)
 235             result.m_bits = fatEntry()->m_bits | SlimFlag;
 236         else
 237             result.m_bits = m_bits;
 238         return result;
 239     }
 240
 241     unsigned getAttributes() const
 242     {
 243         return getFast().getAttributes();
 244     }
 245
 246     void setAttributes(unsigned attributes)
 247     {
 248         pack(varOffset(), isWatchable(), attributes & ReadOnly, attributes & DontEnum);
 249     }
 250
 251     bool isReadOnly() const
 252     {
 253         return bits() & ReadOnlyFlag;
 254     }
 255
 256     ConstantMode constantMode() const
 257     {
 258         return modeForIsConstant(isReadOnly());
 259     }
 260
 261     bool isDontEnum() const
 262     {
 263         return bits() & DontEnumFlag;
 264     }
 265
 266     void disableWatching()
 267     {
 268         if (WatchpointSet* set = watchpointSet())
 269             set->invalidate("Disabling watching in symbol table");
 270         if (varOffset().isScope())
 271             pack(varOffset(), false, isReadOnly(), isDontEnum());
 272     }
 273
 274     void prepareToWatch();
 275
 276     void addWatchpoint(Watchpoint*);
 277
 278     // This watchpoint set is initialized clear, and goes through the following state transitions:
 279     //
 280     // First write to this var, in any scope that has this symbol table: Clear->IsWatched.
 281     //
 282     // Second write to this var, in any scope that has this symbol table: IsWatched->IsInvalidated.
 283     //
 284     // We ensure that we touch the set (i.e. trigger its state transition) after we do the write. This
 285     // means that if you're in the compiler thread, and you:
 286     //
 287     // 1) Observe that the set IsWatched and commit to adding your watchpoint.
 288     // 2) Load a value from any scope that has this watchpoint set.
 289     //
 290     // Then you can be sure that that value is either going to be the correct value for that var forever,
 291     // or the watchpoint set will invalidate and you'll get fired.
 292     //
 293     // It's possible to write a program that first creates multiple scopes with the same var, and then
 294     // initializes that var in just one of them. This means that a compilation could constant-fold to one
 295     // of the scopes that still has an undefined value for this variable. That's fine, because at that
 296     // point any write to any of the instances of that variable would fire the watchpoint.
 297     WatchpointSet* watchpointSet()
 298     {
 299         if (!isFat())
 300             return 0;
 301         return fatEntry()->m_watchpoints.get();
 302     }
 303
 304 private:
 305     static const intptr_t SlimFlag = 0x1;
 306     static const intptr_t ReadOnlyFlag = 0x2;
 307     static const intptr_t DontEnumFlag = 0x4;
 308     static const intptr_t NotNullFlag = 0x8;
 309     static const intptr_t KindBitsMask = 0x30;
 310     static const intptr_t ScopeKindBits = 0x00;
 311     static const intptr_t UnwatchableScopeKindBits = 0x10;
 312     static const intptr_t StackKindBits = 0x20;
 313     static const intptr_t DirectArgumentKindBits = 0x30;
 314     static const intptr_t FlagBits = 6;
 315
 316     class FatEntry {
 317         WTF_MAKE_FAST_ALLOCATED;
 318     public:
 319         FatEntry(intptr_t bits)
 320             : m_bits(bits & ~SlimFlag)
 321         {
 322         }
 323
 324         intptr_t m_bits; // always has FatFlag set and exactly matches what the bits would have been if this wasn't fat.
 325
 326         RefPtr<WatchpointSet> m_watchpoints;
 327     };
 328
 329     SymbolTableEntry& copySlow(const SymbolTableEntry&);
 330     JS_EXPORT_PRIVATE void notifyWriteSlow(VM&, JSValue, const FireDetail&);
 331
 332     bool isFat() const
 333     {
 334         return !(m_bits & SlimFlag);
 335     }
 336
 337     const FatEntry* fatEntry() const
 338     {
 339         ASSERT(isFat());
 340         return bitwise_cast<const FatEntry*>(m_bits);
 341     }
 342
 343     FatEntry* fatEntry()
 344     {
 345         ASSERT(isFat());
 346         return bitwise_cast<FatEntry*>(m_bits);
 347     }
 348
 349     FatEntry* inflate()
 350     {
 351         if (LIKELY(isFat()))
 352             return fatEntry();
 353         return inflateSlow();
 354     }
 355
 356     FatEntry* inflateSlow();
 357
 358     ALWAYS_INLINE intptr_t bits() const
 359     {
 360         if (isFat())
 361             return fatEntry()->m_bits;
 362         return m_bits;
 363     }
 364
 365     ALWAYS_INLINE intptr_t& bits()
 366     {
 367         if (isFat())
 368             return fatEntry()->m_bits;
 369         return m_bits;
 370     }
 371
 372     void freeFatEntry()
 373     {
 374         if (LIKELY(!isFat()))
 375             return;
 376         freeFatEntrySlow();
 377     }
 378
 379     JS_EXPORT_PRIVATE void freeFatEntrySlow();
 380
 381     void pack(VarOffset offset, bool isWatchable, bool readOnly, bool dontEnum)
 382     {
 383         ASSERT(!isFat());
 384         intptr_t& bitsRef = bits();
 385         bitsRef =
 386             (static_cast<intptr_t>(offset.rawOffset()) << FlagBits) | NotNullFlag | SlimFlag;
 387         if (readOnly)
 388             bitsRef |= ReadOnlyFlag;
 389         if (dontEnum)
 390             bitsRef |= DontEnumFlag;
 391         switch (offset.kind()) {
 392         case VarKind::Scope:
 393             if (isWatchable)
 394                 bitsRef |= ScopeKindBits;
 395             else
 396                 bitsRef |= UnwatchableScopeKindBits;
 397             break;
 398         case VarKind::Stack:
 399             bitsRef |= StackKindBits;
 400             break;
 401         case VarKind::DirectArgument:
 402             bitsRef |= DirectArgumentKindBits;
 403             break;
 404         default:
 405             RELEASE_ASSERT_NOT_REACHED();
 406             break;
 407         }
 408     }
 409
 410     static bool isValidVarOffset(VarOffset offset)
 411     {
 412         return ((static_cast<intptr_t>(offset.rawOffset()) << FlagBits) >> FlagBits) == static_cast<intptr_t>(offset.rawOffset());
 413     }
 414
 415     intptr_t m_bits;
 416 };
 417
 418 struct SymbolTableIndexHashTraits : HashTraits<SymbolTableEntry> {
 419     static const bool needsDestruction = true;
 420 };
 421
 422 class SymbolTable final : public JSCell {
 423 public:
 424     typedef JSCell Base;
 425     static const unsigned StructureFlags = Base::StructureFlags | StructureIsImmortal;
 426
 427     typedef HashMap<RefPtr<UniquedStringImpl>, SymbolTableEntry, IdentifierRepHash, HashTraits<RefPtr<UniquedStringImpl>>, SymbolTableIndexHashTraits> Map;
 428     typedef HashMap<RefPtr<UniquedStringImpl>, GlobalVariableID, IdentifierRepHash> UniqueIDMap;
 429     typedef HashMap<RefPtr<UniquedStringImpl>, RefPtr<TypeSet>, IdentifierRepHash> UniqueTypeSetMap;
 430     typedef HashMap<VarOffset, RefPtr<UniquedStringImpl>> OffsetToVariableMap;
 431     typedef Vector<SymbolTableEntry*> LocalToEntryVec;
 432
 433     static SymbolTable* create(VM& vm)
 434     {
 435         SymbolTable* symbolTable = new (NotNull, allocateCell<SymbolTable>(vm.heap)) SymbolTable(vm);
 436         symbolTable->finishCreation(vm);
 437         return symbolTable;
 438     }
 439
 440     static SymbolTable* createNameScopeTable(VM& vm, const Identifier& ident, unsigned attributes)
 441     {
 442         SymbolTable* result = create(vm);
 443         result->add(ident.impl(), SymbolTableEntry(VarOffset(ScopeOffset(0)), attributes));
 444         return result;
 445     }
 446
 447     static const bool needsDestruction = true;
 448     static void destroy(JSCell*);
 449
 450     static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)
 451     {
 452         return Structure::create(vm, globalObject, prototype, TypeInfo(CellType, StructureFlags), info());
 453     }
 454
 455     // You must hold the lock until after you're done with the iterator.
 456     Map::iterator find(const ConcurrentJITLocker&, UniquedStringImpl* key)
 457     {
 458         return m_map.find(key);
 459     }
 460
 461     Map::iterator find(const GCSafeConcurrentJITLocker&, UniquedStringImpl* key)
 462     {
 463         return m_map.find(key);
 464     }
 465
 466     SymbolTableEntry get(const ConcurrentJITLocker&, UniquedStringImpl* key)
 467     {
 468         return m_map.get(key);
 469     }
 470
 471     SymbolTableEntry get(UniquedStringImpl* key)
 472     {
 473         ConcurrentJITLocker locker(m_lock);
 474         return get(locker, key);
 475     }
 476
 477     SymbolTableEntry inlineGet(const ConcurrentJITLocker&, UniquedStringImpl* key)
 478     {
 479         return m_map.inlineGet(key);
 480     }
 481
 482     SymbolTableEntry inlineGet(UniquedStringImpl* key)
 483     {
 484         ConcurrentJITLocker locker(m_lock);
 485         return inlineGet(locker, key);
 486     }
 487
 488     Map::iterator begin(const ConcurrentJITLocker&)
 489     {
 490         return m_map.begin();
 491     }
 492
 493     Map::iterator end(const ConcurrentJITLocker&)
 494     {
 495         return m_map.end();
 496     }
 497
 498     Map::iterator end(const GCSafeConcurrentJITLocker&)
 499     {
 500         return m_map.end();
 501     }
 502
 503     size_t size(const ConcurrentJITLocker&) const
 504     {
 505         return m_map.size();
 506     }
 507
 508     size_t size() const
 509     {
 510         ConcurrentJITLocker locker(m_lock);
 511         return size(locker);
 512     }
 513
 514     ScopeOffset maxScopeOffset() const
 515     {
 516         return m_maxScopeOffset;
 517     }
 518
 519     void didUseScopeOffset(ScopeOffset offset)
 520     {
 521         if (!m_maxScopeOffset || m_maxScopeOffset < offset)
 522             m_maxScopeOffset = offset;
 523     }
 524
 525     void didUseVarOffset(VarOffset offset)
 526     {
 527         if (offset.isScope())
 528             didUseScopeOffset(offset.scopeOffset());
 529     }
 530
 531     unsigned scopeSize() const
 532     {
 533         ScopeOffset maxScopeOffset = this->maxScopeOffset();
 534
 535         // Do some calculation that relies on invalid scope offset plus one being zero.
 536         unsigned fastResult = maxScopeOffset.offsetUnchecked() + 1;
 537
 538         // Assert that this works.
 539         ASSERT(fastResult == (!maxScopeOffset ? 0 : maxScopeOffset.offset() + 1));
 540
 541         return fastResult;
 542     }
 543
 544     ScopeOffset nextScopeOffset() const
 545     {
 546         return ScopeOffset(scopeSize());
 547     }
 548
 549     ScopeOffset takeNextScopeOffset(const ConcurrentJITLocker&)
 550     {
 551         ScopeOffset result = nextScopeOffset();
 552         m_maxScopeOffset = result;
 553         return result;
 554     }
 555
 556     ScopeOffset takeNextScopeOffset()
 557     {
 558         ConcurrentJITLocker locker(m_lock);
 559         return takeNextScopeOffset(locker);
 560     }
 561
 562     void add(const ConcurrentJITLocker&, UniquedStringImpl* key, const SymbolTableEntry& entry)
 563     {
 564         RELEASE_ASSERT(!m_localToEntry);
 565         didUseVarOffset(entry.varOffset());
 566         Map::AddResult result = m_map.add(key, entry);
 567         ASSERT_UNUSED(result, result.isNewEntry);
 568     }
 569
 570     void add(UniquedStringImpl* key, const SymbolTableEntry& entry)
 571     {
 572         ConcurrentJITLocker locker(m_lock);
 573         add(locker, key, entry);
 574     }
 575
 576     void set(const ConcurrentJITLocker&, UniquedStringImpl* key, const SymbolTableEntry& entry)
 577     {
 578         RELEASE_ASSERT(!m_localToEntry);
 579         didUseVarOffset(entry.varOffset());
 580         m_map.set(key, entry);
 581     }
 582
 583     void set(UniquedStringImpl* key, const SymbolTableEntry& entry)
 584     {
 585         ConcurrentJITLocker locker(m_lock);
 586         set(locker, key, entry);
 587     }
 588
 589     bool contains(const ConcurrentJITLocker&, UniquedStringImpl* key)
 590     {
 591         return m_map.contains(key);
 592     }
 593
 594     bool contains(UniquedStringImpl* key)
 595     {
 596         ConcurrentJITLocker locker(m_lock);
 597         return contains(locker, key);
 598     }
 599
 600     // The principle behind ScopedArgumentsTable modifications is that we will create one and
 601     // leave it unlocked - thereby allowing in-place changes - until someone asks for a pointer to
 602     // the table. Then, we will lock it. Then both our future changes and their future changes
 603     // will first have to make a copy. This discipline means that usually when we create a
 604     // ScopedArguments object, we don't have to make a copy of the ScopedArgumentsTable - instead
 605     // we just take a reference to one that we already have.
 606
 607     uint32_t argumentsLength() const
 608     {
 609         if (!m_arguments)
 610             return 0;
 611         return m_arguments->length();
 612     }
 613
 614     void setArgumentsLength(VM& vm, uint32_t length)
 615     {
 616         if (UNLIKELY(!m_arguments))
 617             m_arguments.set(vm, this, ScopedArgumentsTable::create(vm));
 618         m_arguments.set(vm, this, m_arguments->setLength(vm, length));
 619     }
 620
 621     ScopeOffset argumentOffset(uint32_t i) const
 622     {
 623         ASSERT_WITH_SECURITY_IMPLICATION(m_arguments);
 624         return m_arguments->get(i);
 625     }
 626
 627     void setArgumentOffset(VM& vm, uint32_t i, ScopeOffset offset)
 628     {
 629         ASSERT_WITH_SECURITY_IMPLICATION(m_arguments);
 630         m_arguments.set(vm, this, m_arguments->set(vm, i, offset));
 631     }
 632
 633     ScopedArgumentsTable* arguments() const
 634     {
 635         if (!m_arguments)
 636             return nullptr;
 637         m_arguments->lock();
 638         return m_arguments.get();
 639     }
 640
 641     const LocalToEntryVec& localToEntry(const ConcurrentJITLocker&);
 642     SymbolTableEntry* entryFor(const ConcurrentJITLocker&, ScopeOffset);
 643
 644     GlobalVariableID uniqueIDForVariable(const ConcurrentJITLocker&, UniquedStringImpl* key, VM&);
 645     GlobalVariableID uniqueIDForOffset(const ConcurrentJITLocker&, VarOffset, VM&);
 646     RefPtr<TypeSet> globalTypeSetForOffset(const ConcurrentJITLocker&, VarOffset, VM&);
 647     RefPtr<TypeSet> globalTypeSetForVariable(const ConcurrentJITLocker&, UniquedStringImpl* key, VM&);
 648
 649     bool usesNonStrictEval() { return m_usesNonStrictEval; }
 650     void setUsesNonStrictEval(bool usesNonStrictEval) { m_usesNonStrictEval = usesNonStrictEval; }
 651
 652     SymbolTable* cloneScopePart(VM&);
 653
 654     void prepareForTypeProfiling(const ConcurrentJITLocker&);
 655
 656     InferredValue* singletonScope() { return m_singletonScope.get(); }
 657
 658     static void visitChildren(JSCell*, SlotVisitor&);
 659
 660     DECLARE_EXPORT_INFO;
 661
 662 private:
 663     JS_EXPORT_PRIVATE SymbolTable(VM&);
 664     ~SymbolTable();
 665
 666     JS_EXPORT_PRIVATE void finishCreation(VM&);
 667
 668     Map m_map;
 669     ScopeOffset m_maxScopeOffset;
 670
 671     struct TypeProfilingRareData {
 672         UniqueIDMap m_uniqueIDMap;
 673         OffsetToVariableMap m_offsetToVariableMap;
 674         UniqueTypeSetMap m_uniqueTypeSetMap;
 675     };
 676     std::unique_ptr<TypeProfilingRareData> m_typeProfilingRareData;
 677
 678     bool m_usesNonStrictEval;
 679
 680     WriteBarrier<ScopedArgumentsTable> m_arguments;
 681     WriteBarrier<InferredValue> m_singletonScope;
 682
 683     std::unique_ptr<LocalToEntryVec> m_localToEntry;
 684
 685 public:
 686     mutable ConcurrentJITLock m_lock;
 687 };
 688
 689 } // namespace JSC
 690
 691 #endif // SymbolTable_h