1  /*
  2   * Copyright (C) 2012-2020 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   * 1. Redistributions of source code must retain the above copyright
  8   *    notice, this list of conditions and the following disclaimer.
  9   * 2. Redistributions in binary form must reproduce the above copyright
 10   *    notice, this list of conditions and the following disclaimer in the
 11   *    documentation and/or other materials provided with the distribution.
 12   *
 13   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 14   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 15   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 16   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 17   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 18   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 19   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 20   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 21   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 22   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 23   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 24   */
 25  
 26  #include "config.h"
 27  #include "GetByStatus.h"
 28  
 29  #include "BytecodeStructs.h"
 30  #include "CacheableIdentifierInlines.h"
 31  #include "CodeBlock.h"
 32  #include "ComplexGetStatus.h"
 33  #include "GetterSetterAccessCase.h"
 34  #include "ICStatusUtils.h"
 35  #include "IntrinsicGetterAccessCase.h"
 36  #include "ModuleNamespaceAccessCase.h"
 37  #include "PolymorphicAccess.h"
 38  #include "StructureStubInfo.h"
 39  #include <wtf/ListDump.h>
 40  
 41  namespace JSC {
 42  
 43  bool GetByStatus::appendVariant(const GetByIdVariant& variant)
 44  {
 45      return appendICStatusVariant(m_variants, variant);
 46  }
 47  
 48  GetByStatus GetByStatus::computeFromLLInt(CodeBlock* profiledBlock, BytecodeIndex bytecodeIndex)
 49  {
 50      VM& vm = profiledBlock->vm();
 51      
 52      auto instruction = profiledBlock->instructions().at(bytecodeIndex.offset());
 53  
 54      StructureID structureID;
 55      const Identifier* identifier = nullptr;
 56      switch (instruction->opcodeID()) {
 57      case op_get_by_id: {
 58          auto& metadata = instruction->as<OpGetById>().metadata(profiledBlock);
 59          // FIXME: We should not just bail if we see a get_by_id_proto_load.
 60          // https://bugs.webkit.org/show_bug.cgi?id=158039
 61          if (metadata.m_modeMetadata.mode != GetByIdMode::Default)
 62              return GetByStatus(NoInformation, false);
 63          structureID = metadata.m_modeMetadata.defaultMode.structureID;
 64  
 65          identifier = &(profiledBlock->identifier(instruction->as<OpGetById>().m_property));
 66          break;
 67      }
 68      case op_get_by_id_direct:
 69          structureID = instruction->as<OpGetByIdDirect>().metadata(profiledBlock).m_structureID;
 70          identifier = &(profiledBlock->identifier(instruction->as<OpGetByIdDirect>().m_property));
 71          break;
 72      case op_try_get_by_id: {
 73          // FIXME: We should not just bail if we see a try_get_by_id.
 74          // https://bugs.webkit.org/show_bug.cgi?id=158039
 75          return GetByStatus(NoInformation, false);
 76      }
 77  
 78      case op_get_by_val:
 79          return GetByStatus(NoInformation, false);
 80  
 81      case op_iterator_open: {
 82          ASSERT(bytecodeIndex.checkpoint() == OpIteratorOpen::getNext);
 83          auto& metadata = instruction->as<OpIteratorOpen>().metadata(profiledBlock);
 84  
 85          // FIXME: We should not just bail if we see a get_by_id_proto_load.
 86          // https://bugs.webkit.org/show_bug.cgi?id=158039
 87          if (metadata.m_modeMetadata.mode != GetByIdMode::Default)
 88              return GetByStatus(NoInformation, false);
 89          structureID = metadata.m_modeMetadata.defaultMode.structureID;
 90          identifier = &vm.propertyNames->next;
 91          break;
 92      }
 93  
 94      case op_iterator_next: {
 95          auto& metadata = instruction->as<OpIteratorNext>().metadata(profiledBlock);
 96          if (bytecodeIndex.checkpoint() == OpIteratorNext::getDone) {
 97              if (metadata.m_doneModeMetadata.mode != GetByIdMode::Default)
 98                  return GetByStatus(NoInformation, false);
 99              structureID = metadata.m_doneModeMetadata.defaultMode.structureID;
100              identifier = &vm.propertyNames->done;
101          } else {
102              ASSERT(bytecodeIndex.checkpoint() == OpIteratorNext::getValue);
103              if (metadata.m_valueModeMetadata.mode != GetByIdMode::Default)
104                  return GetByStatus(NoInformation, false);
105              structureID = metadata.m_valueModeMetadata.defaultMode.structureID;
106              identifier = &vm.propertyNames->value;
107          }
108          break;
109      }
110  
111      case op_get_private_name:
112          // FIXME: Consider using LLInt caches or IC information to populate GetByStatus
113          // https://bugs.webkit.org/show_bug.cgi?id=217245
114          return GetByStatus(NoInformation, false);
115  
116      default: {
117          ASSERT_NOT_REACHED();
118          return GetByStatus(NoInformation, false);
119      }
120      }
121  
122      if (!structureID)
123          return GetByStatus(NoInformation, false);
124  
125      Structure* structure = vm.heap.structureIDTable().get(structureID);
126  
127      if (structure->takesSlowPathInDFGForImpureProperty())
128          return GetByStatus(NoInformation, false);
129  
130      unsigned attributes;
131      PropertyOffset offset = structure->getConcurrently(identifier->impl(), attributes);
132      if (!isValidOffset(offset))
133          return GetByStatus(NoInformation, false);
134      if (attributes & PropertyAttribute::CustomAccessorOrValue)
135          return GetByStatus(NoInformation, false);
136  
137      GetByStatus result(Simple, false);
138      result.appendVariant(GetByIdVariant(nullptr, StructureSet(structure), offset));
139      return result;
140  }
141  
142  GetByStatus GetByStatus::computeFor(CodeBlock* profiledBlock, ICStatusMap& map, BytecodeIndex bytecodeIndex, ExitFlag didExit, CallLinkStatus::ExitSiteData callExitSiteData)
143  {
144      ConcurrentJSLocker locker(profiledBlock->m_lock);
145  
146      GetByStatus result;
147  
148  #if ENABLE(DFG_JIT)
149      result = computeForStubInfoWithoutExitSiteFeedback(
150          locker, profiledBlock, map.get(CodeOrigin(bytecodeIndex)).stubInfo, callExitSiteData);
151      
152      if (didExit)
153          return result.slowVersion();
154  #else
155      UNUSED_PARAM(map);
156      UNUSED_PARAM(didExit);
157      UNUSED_PARAM(callExitSiteData);
158  #endif
159  
160      if (!result)
161          return computeFromLLInt(profiledBlock, bytecodeIndex);
162      
163      return result;
164  }
165  
166  #if ENABLE(JIT)
167  GetByStatus::GetByStatus(StubInfoSummary summary, StructureStubInfo& stubInfo)
168      : m_wasSeenInJIT(true)
169  {
170      switch (summary) {
171      case StubInfoSummary::NoInformation:
172          m_state = NoInformation;
173          return;
174      case StubInfoSummary::Simple:
175      case StubInfoSummary::MakesCalls:
176          RELEASE_ASSERT_NOT_REACHED();
177          return;
178      case StubInfoSummary::TakesSlowPath:
179          m_state = stubInfo.tookSlowPath ? ObservedTakesSlowPath : LikelyTakesSlowPath;
180          return;
181      case StubInfoSummary::TakesSlowPathAndMakesCalls:
182          m_state = stubInfo.tookSlowPath ? ObservedSlowPathAndMakesCalls : MakesCalls;
183          return;
184      }
185      RELEASE_ASSERT_NOT_REACHED();
186  }
187  
188  GetByStatus::GetByStatus(const ModuleNamespaceAccessCase& accessCase)
189      : m_moduleNamespaceData(Box<ModuleNamespaceData>::create(ModuleNamespaceData { accessCase.moduleNamespaceObject(), accessCase.moduleEnvironment(), accessCase.scopeOffset(), accessCase.identifier() }))
190      , m_state(ModuleNamespace)
191      , m_wasSeenInJIT(true)
192  {
193  }
194  
195  GetByStatus GetByStatus::computeForStubInfoWithoutExitSiteFeedback(
196      const ConcurrentJSLocker& locker, CodeBlock* profiledBlock, StructureStubInfo* stubInfo, CallLinkStatus::ExitSiteData callExitSiteData)
197  {
198      StubInfoSummary summary = StructureStubInfo::summary(profiledBlock->vm(), stubInfo);
199      if (!isInlineable(summary))
200          return GetByStatus(summary, *stubInfo);
201      
202      // Finally figure out if we can derive an access strategy.
203      GetByStatus result;
204      result.m_state = Simple;
205      result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
206      switch (stubInfo->cacheType()) {
207      case CacheType::Unset:
208          return GetByStatus(NoInformation);
209          
210      case CacheType::GetByIdSelf: {
211          Structure* structure = stubInfo->u.byIdSelf.baseObjectStructure.get();
212          if (structure->takesSlowPathInDFGForImpureProperty())
213              return GetByStatus(JSC::slowVersion(summary), *stubInfo);
214          CacheableIdentifier identifier = stubInfo->identifier();
215          UniquedStringImpl* uid = identifier.uid();
216          RELEASE_ASSERT(uid);
217          GetByIdVariant variant(WTFMove(identifier));
218          unsigned attributes;
219          variant.m_offset = structure->getConcurrently(uid, attributes);
220          if (!isValidOffset(variant.m_offset))
221              return GetByStatus(JSC::slowVersion(summary), *stubInfo);
222          if (attributes & PropertyAttribute::CustomAccessorOrValue)
223              return GetByStatus(JSC::slowVersion(summary), *stubInfo);
224          
225          variant.m_structureSet.add(structure);
226          bool didAppend = result.appendVariant(variant);
227          ASSERT_UNUSED(didAppend, didAppend);
228          return result;
229      }
230          
231      case CacheType::Stub: {
232          PolymorphicAccess* list = stubInfo->u.stub;
233          if (list->size() == 1) {
234              const AccessCase& access = list->at(0);
235              switch (access.type()) {
236              case AccessCase::ModuleNamespaceLoad:
237                  return GetByStatus(access.as<ModuleNamespaceAccessCase>());
238              default:
239                  break;
240              }
241          }
242  
243          for (unsigned listIndex = 0; listIndex < list->size(); ++listIndex) {
244              const AccessCase& access = list->at(listIndex);
245              if (access.viaProxy())
246                  return GetByStatus(JSC::slowVersion(summary), *stubInfo);
247  
248              if (access.usesPolyProto())
249                  return GetByStatus(JSC::slowVersion(summary), *stubInfo);
250  
251              if (!access.requiresIdentifierNameMatch()) {
252                  // FIXME: We could use this for indexed loads in the future. This is pretty solid profiling
253                  // information, and probably better than ArrayProfile when it's available.
254                  // https://bugs.webkit.org/show_bug.cgi?id=204215
255                  return GetByStatus(JSC::slowVersion(summary), *stubInfo);
256              }
257              
258              Structure* structure = access.structure();
259              if (!structure) {
260                  // The null structure cases arise due to array.length and string.length. We have no way
261                  // of creating a GetByIdVariant for those, and we don't really have to since the DFG
262                  // handles those cases in FixupPhase using value profiling. That's a bit awkward - we
263                  // shouldn't have to use value profiling to discover something that the AccessCase
264                  // could have told us. But, it works well enough. So, our only concern here is to not
265                  // crash on null structure.
266                  return GetByStatus(JSC::slowVersion(summary), *stubInfo);
267              }
268              
269              ComplexGetStatus complexGetStatus = ComplexGetStatus::computeFor(
270                  structure, access.conditionSet(), access.uid());
271               
272              switch (complexGetStatus.kind()) {
273              case ComplexGetStatus::ShouldSkip:
274                  continue;
275                   
276              case ComplexGetStatus::TakesSlowPath:
277                  return GetByStatus(JSC::slowVersion(summary), *stubInfo);
278                   
279              case ComplexGetStatus::Inlineable: {
280                  std::unique_ptr<CallLinkStatus> callLinkStatus;
281                  JSFunction* intrinsicFunction = nullptr;
282                  FunctionPtr<CustomAccessorPtrTag> customAccessorGetter;
283                  std::unique_ptr<DOMAttributeAnnotation> domAttribute;
284                  bool haveDOMAttribute = false;
285  
286                  switch (access.type()) {
287                  case AccessCase::Load:
288                  case AccessCase::GetGetter:
289                  case AccessCase::Miss: {
290                      break;
291                  }
292                  case AccessCase::IntrinsicGetter: {
293                      intrinsicFunction = access.as<IntrinsicGetterAccessCase>().intrinsicFunction();
294                      break;
295                  }
296                  case AccessCase::Getter: {
297                      callLinkStatus = makeUnique<CallLinkStatus>();
298                      if (CallLinkInfo* callLinkInfo = access.as<GetterSetterAccessCase>().callLinkInfo()) {
299                          *callLinkStatus = CallLinkStatus::computeFor(
300                              locker, profiledBlock, *callLinkInfo, callExitSiteData);
301                      }
302                      break;
303                  }
304                  case AccessCase::CustomAccessorGetter: {
305                      customAccessorGetter = access.as<GetterSetterAccessCase>().customAccessor();
306                      if (!access.as<GetterSetterAccessCase>().domAttribute())
307                          return GetByStatus(JSC::slowVersion(summary), *stubInfo);
308                      domAttribute = WTF::makeUnique<DOMAttributeAnnotation>(*access.as<GetterSetterAccessCase>().domAttribute());
309                      haveDOMAttribute = true;
310                      result.m_state = Custom;
311                      break;
312                  }
313                  default: {
314                      // FIXME: It would be totally sweet to support more of these at some point in the
315                      // future. https://bugs.webkit.org/show_bug.cgi?id=133052
316                      return GetByStatus(JSC::slowVersion(summary), *stubInfo);
317                  } }
318  
319                  ASSERT((AccessCase::Miss == access.type() || access.isCustom()) == (access.offset() == invalidOffset));
320                  GetByIdVariant variant(access.identifier(), StructureSet(structure), complexGetStatus.offset(),
321                      complexGetStatus.conditionSet(), WTFMove(callLinkStatus),
322                      intrinsicFunction,
323                      customAccessorGetter,
324                      WTFMove(domAttribute));
325  
326                  if (!result.appendVariant(variant))
327                      return GetByStatus(JSC::slowVersion(summary), *stubInfo);
328  
329                  if (haveDOMAttribute) {
330                      // Give up when custom accesses are not merged into one.
331                      if (result.numVariants() != 1)
332                          return GetByStatus(JSC::slowVersion(summary), *stubInfo);
333                  } else {
334                      // Give up when custom access and simple access are mixed.
335                      if (result.m_state == Custom)
336                          return GetByStatus(JSC::slowVersion(summary), *stubInfo);
337                  }
338                  break;
339              } }
340          }
341          
342          return result;
343      }
344          
345      default:
346          return GetByStatus(JSC::slowVersion(summary), *stubInfo);
347      }
348      
349      RELEASE_ASSERT_NOT_REACHED();
350      return GetByStatus();
351  }
352  
353  GetByStatus GetByStatus::computeFor(
354      CodeBlock* profiledBlock, ICStatusMap& baselineMap,
355      ICStatusContextStack& icContextStack, CodeOrigin codeOrigin)
356  {
357      BytecodeIndex bytecodeIndex = codeOrigin.bytecodeIndex();
358      CallLinkStatus::ExitSiteData callExitSiteData = CallLinkStatus::computeExitSiteData(profiledBlock, bytecodeIndex);
359      ExitFlag didExit = hasBadCacheExitSite(profiledBlock, bytecodeIndex);
360  
361      for (ICStatusContext* context : icContextStack) {
362          ICStatus status = context->get(codeOrigin);
363          
364          auto bless = [&] (const GetByStatus& result) -> GetByStatus {
365              if (!context->isInlined(codeOrigin)) {
366                  // Merge with baseline result, which also happens to contain exit data for both
367                  // inlined and not-inlined.
368                  GetByStatus baselineResult = computeFor(
369                      profiledBlock, baselineMap, bytecodeIndex, didExit,
370                      callExitSiteData);
371                  baselineResult.merge(result);
372                  return baselineResult;
373              }
374              if (didExit.isSet(ExitFromInlined))
375                  return result.slowVersion();
376              return result;
377          };
378          
379          if (status.stubInfo) {
380              GetByStatus result;
381              {
382                  ConcurrentJSLocker locker(context->optimizedCodeBlock->m_lock);
383                  result = computeForStubInfoWithoutExitSiteFeedback(
384                      locker, context->optimizedCodeBlock, status.stubInfo, callExitSiteData);
385              }
386              if (result.isSet())
387                  return bless(result);
388          }
389          
390          if (status.getStatus)
391              return bless(*status.getStatus);
392      }
393      
394      return computeFor(profiledBlock, baselineMap, bytecodeIndex, didExit, callExitSiteData);
395  }
396  
397  GetByStatus GetByStatus::computeFor(const StructureSet& set, UniquedStringImpl* uid)
398  {
399      // For now we only handle the super simple self access case. We could handle the
400      // prototype case in the future.
401      //
402      // Note that this code is also used for GetByIdDirect since this function only looks
403      // into direct properties. When supporting prototype chains, we should split this for
404      // GetById and GetByIdDirect.
405      
406      if (set.isEmpty())
407          return GetByStatus();
408  
409      if (parseIndex(*uid))
410          return GetByStatus(LikelyTakesSlowPath);
411      
412      GetByStatus result;
413      result.m_state = Simple;
414      result.m_wasSeenInJIT = false;
415      for (unsigned i = 0; i < set.size(); ++i) {
416          Structure* structure = set[i];
417          if (structure->typeInfo().overridesGetOwnPropertySlot() && structure->typeInfo().type() != GlobalObjectType)
418              return GetByStatus(LikelyTakesSlowPath);
419          
420          if (!structure->propertyAccessesAreCacheable())
421              return GetByStatus(LikelyTakesSlowPath);
422          
423          unsigned attributes;
424          PropertyOffset offset = structure->getConcurrently(uid, attributes);
425          if (!isValidOffset(offset))
426              return GetByStatus(LikelyTakesSlowPath); // It's probably a prototype lookup. Give up on life for now, even though we could totally be way smarter about it.
427          if (attributes & PropertyAttribute::Accessor)
428              return GetByStatus(MakesCalls); // We could be smarter here, like strength-reducing this to a Call.
429          if (attributes & PropertyAttribute::CustomAccessorOrValue)
430              return GetByStatus(LikelyTakesSlowPath);
431          
432          if (!result.appendVariant(GetByIdVariant(nullptr, structure, offset)))
433              return GetByStatus(LikelyTakesSlowPath);
434      }
435      
436      return result;
437  }
438  #endif // ENABLE(JIT)
439  
440  bool GetByStatus::makesCalls() const
441  {
442      switch (m_state) {
443      case NoInformation:
444      case LikelyTakesSlowPath:
445      case ObservedTakesSlowPath:
446      case Custom:
447      case ModuleNamespace:
448          return false;
449      case Simple:
450          for (unsigned i = m_variants.size(); i--;) {
451              if (m_variants[i].callLinkStatus())
452                  return true;
453          }
454          return false;
455      case MakesCalls:
456      case ObservedSlowPathAndMakesCalls:
457          return true;
458      }
459      RELEASE_ASSERT_NOT_REACHED();
460  
461      return false;
462  }
463  
464  GetByStatus GetByStatus::slowVersion() const
465  {
466      if (observedStructureStubInfoSlowPath())
467          return GetByStatus(makesCalls() ? ObservedSlowPathAndMakesCalls : ObservedTakesSlowPath, wasSeenInJIT());
468      return GetByStatus(makesCalls() ? MakesCalls : LikelyTakesSlowPath, wasSeenInJIT());
469  }
470  
471  void GetByStatus::merge(const GetByStatus& other)
472  {
473      if (other.m_state == NoInformation)
474          return;
475      
476      auto mergeSlow = [&] () {
477          if (observedStructureStubInfoSlowPath() || other.observedStructureStubInfoSlowPath())
478              *this = GetByStatus((makesCalls() || other.makesCalls()) ? ObservedSlowPathAndMakesCalls : ObservedTakesSlowPath);
479          else
480              *this = GetByStatus((makesCalls() || other.makesCalls()) ? MakesCalls : LikelyTakesSlowPath);
481      };
482      
483      switch (m_state) {
484      case NoInformation:
485          *this = other;
486          return;
487          
488      case Simple:
489      case Custom:
490          if (m_state != other.m_state)
491              return mergeSlow();
492          
493          for (const GetByIdVariant& otherVariant : other.m_variants) {
494              if (!appendVariant(otherVariant))
495                  return mergeSlow();
496          }
497          return;
498          
499      case ModuleNamespace:
500          if (other.m_state != ModuleNamespace)
501              return mergeSlow();
502          
503          if (m_moduleNamespaceData->m_moduleNamespaceObject != other.m_moduleNamespaceData->m_moduleNamespaceObject)
504              return mergeSlow();
505          
506          if (m_moduleNamespaceData->m_moduleEnvironment != other.m_moduleNamespaceData->m_moduleEnvironment)
507              return mergeSlow();
508          
509          if (m_moduleNamespaceData->m_scopeOffset != other.m_moduleNamespaceData->m_scopeOffset)
510              return mergeSlow();
511          
512          return;
513          
514      case LikelyTakesSlowPath:
515      case ObservedTakesSlowPath:
516      case MakesCalls:
517      case ObservedSlowPathAndMakesCalls:
518          return mergeSlow();
519      }
520      
521      RELEASE_ASSERT_NOT_REACHED();
522  }
523  
524  void GetByStatus::filter(const StructureSet& set)
525  {
526      if (m_state != Simple)
527          return;
528      filterICStatusVariants(m_variants, set);
529      if (m_variants.isEmpty())
530          m_state = NoInformation;
531  }
532  
533  void GetByStatus::visitAggregate(SlotVisitor& visitor)
534  {
535      if (isModuleNamespace())
536          m_moduleNamespaceData->m_identifier.visitAggregate(visitor);
537      for (GetByIdVariant& variant : m_variants)
538          variant.visitAggregate(visitor);
539  }
540  
541  void GetByStatus::markIfCheap(SlotVisitor& visitor)
542  {
543      for (GetByIdVariant& variant : m_variants)
544          variant.markIfCheap(visitor);
545  }
546  
547  bool GetByStatus::finalize(VM& vm)
548  {
549      for (GetByIdVariant& variant : m_variants) {
550          if (!variant.finalize(vm))
551              return false;
552      }
553      if (isModuleNamespace()) {
554          if (m_moduleNamespaceData->m_moduleNamespaceObject && !vm.heap.isMarked(m_moduleNamespaceData->m_moduleNamespaceObject))
555              return false;
556          if (m_moduleNamespaceData->m_moduleEnvironment && !vm.heap.isMarked(m_moduleNamespaceData->m_moduleEnvironment))
557              return false;
558      }
559      return true;
560  }
561  
562  CacheableIdentifier GetByStatus::singleIdentifier() const
563  {
564      if (isModuleNamespace())
565          return m_moduleNamespaceData->m_identifier;
566  
567      if (m_variants.isEmpty())
568          return nullptr;
569  
570      CacheableIdentifier result = m_variants.first().identifier();
571      if (!result)
572          return nullptr;
573      for (size_t i = 1; i < m_variants.size(); ++i) {
574          CacheableIdentifier identifier = m_variants[i].identifier();
575          if (!identifier)
576              return nullptr;
577          if (identifier != result)
578              return nullptr;
579      }
580      return result;
581  }
582  
583  void GetByStatus::dump(PrintStream& out) const
584  {
585      out.print("(");
586      switch (m_state) {
587      case NoInformation:
588          out.print("NoInformation");
589          break;
590      case Simple:
591          out.print("Simple");
592          break;
593      case Custom:
594          out.print("Custom");
595          break;
596      case ModuleNamespace:
597          out.print("ModuleNamespace");
598          break;
599      case LikelyTakesSlowPath:
600          out.print("LikelyTakesSlowPath");
601          break;
602      case ObservedTakesSlowPath:
603          out.print("ObservedTakesSlowPath");
604          break;
605      case MakesCalls:
606          out.print("MakesCalls");
607          break;
608      case ObservedSlowPathAndMakesCalls:
609          out.print("ObservedSlowPathAndMakesCalls");
610          break;
611      }
612      out.print(", ", listDump(m_variants), ", seenInJIT = ", m_wasSeenInJIT, ")");
613  }
614  
615  } // namespace JSC
616