path: root/deps/v8/src/compiler/js-heap-broker.h

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_COMPILER_JS_HEAP_BROKER_H_
#define V8_COMPILER_JS_HEAP_BROKER_H_

#include "src/base/compiler-specific.h"
#include "src/base/optional.h"
#include "src/common/globals.h"
#include "src/compiler/refs-map.h"
#include "src/handles/handles.h"
#include "src/objects/feedback-vector.h"
#include "src/objects/function-kind.h"
#include "src/objects/instance-type.h"
#include "src/objects/objects.h"
#include "src/utils/ostreams.h"
#include "src/zone/zone-containers.h"

namespace v8 {
namespace internal {

class BytecodeArray;
class CallHandlerInfo;
class FixedDoubleArray;
class FunctionTemplateInfo;
class HeapNumber;
class InternalizedString;
class JSBoundFunction;
class JSDataView;
class JSGlobalProxy;
class JSRegExp;
class JSTypedArray;
class NativeContext;
class ScriptContextTable;
class VectorSlotPair;

namespace compiler {

// Whether we are loading a property or storing to a property.
// For a store during literal creation, do not walk up the prototype chain.
enum class AccessMode { kLoad, kStore, kStoreInLiteral, kHas };

enum class OddballType : uint8_t {
  kNone,     // Not an Oddball.
  kBoolean,  // True or False.
  kUndefined,
  kNull,
  kHole,
  kUninitialized,
  kOther  // Oddball, but none of the above.
};

// This list is sorted such that subtypes appear before their supertypes.
// DO NOT VIOLATE THIS PROPERTY!
#define HEAP_BROKER_OBJECT_LIST(V) \
  /* Subtypes of JSObject */       \
  V(JSArray)                       \
  V(JSBoundFunction)               \
  V(JSDataView)                    \
  V(JSFunction)                    \
  V(JSGlobalProxy)                 \
  V(JSRegExp)                      \
  V(JSTypedArray)                  \
  /* Subtypes of Context */        \
  V(NativeContext)                 \
  /* Subtypes of FixedArray */     \
  V(Context)                       \
  V(ScopeInfo)                     \
  V(ScriptContextTable)            \
  /* Subtypes of FixedArrayBase */ \
  V(BytecodeArray)                 \
  V(FixedArray)                    \
  V(FixedDoubleArray)              \
  /* Subtypes of Name */           \
  V(InternalizedString)            \
  V(String)                        \
  V(Symbol)                        \
  /* Subtypes of HeapObject */     \
  V(AllocationSite)                \
  V(CallHandlerInfo)               \
  V(Cell)                          \
  V(Code)                          \
  V(DescriptorArray)               \
  V(FeedbackCell)                  \
  V(FeedbackVector)                \
  V(FixedArrayBase)                \
  V(FunctionTemplateInfo)          \
  V(HeapNumber)                    \
  V(JSObject)                      \
  V(Map)                           \
  V(Module)                        \
  V(MutableHeapNumber)             \
  V(Name)                          \
  V(PropertyCell)                  \
  V(SharedFunctionInfo)            \
  /* Subtypes of Object */         \
  V(HeapObject)

class CompilationDependencies;
class JSHeapBroker;
class ObjectData;
class PerIsolateCompilerCache;
class PropertyAccessInfo;
#define FORWARD_DECL(Name) class Name##Ref;
HEAP_BROKER_OBJECT_LIST(FORWARD_DECL)
#undef FORWARD_DECL

class V8_EXPORT_PRIVATE ObjectRef {
 public:
  ObjectRef(JSHeapBroker* broker, Handle<Object> object);
  ObjectRef(JSHeapBroker* broker, ObjectData* data)
      : data_(data), broker_(broker) {
    CHECK_NOT_NULL(data_);
  }

  Handle<Object> object() const;

  bool equals(const ObjectRef& other) const;

  bool IsSmi() const;
  int AsSmi() const;

#define HEAP_IS_METHOD_DECL(Name) bool Is##Name() const;
  HEAP_BROKER_OBJECT_LIST(HEAP_IS_METHOD_DECL)
#undef HEAP_IS_METHOD_DECL

#define HEAP_AS_METHOD_DECL(Name) Name##Ref As##Name() const;
  HEAP_BROKER_OBJECT_LIST(HEAP_AS_METHOD_DECL)
#undef HEAP_AS_METHOD_DECL

  bool IsNullOrUndefined() const;

  bool BooleanValue() const;
  Maybe<double> OddballToNumber() const;

  // Return the element at key {index} if {index} is known to be an own data
  // property of the object that is non-writable and non-configurable.
  base::Optional<ObjectRef> GetOwnConstantElement(uint32_t index,
                                                  bool serialize = false) const;

  Isolate* isolate() const;

 protected:
  JSHeapBroker* broker() const;
  ObjectData* data() const;
  ObjectData* data_;  // Should be used only by object() getters.

 private:
  friend class JSArrayData;
  friend class JSGlobalProxyRef;
  friend class JSGlobalProxyData;
  friend class JSObjectData;
  friend class StringData;

  friend std::ostream& operator<<(std::ostream& os, const ObjectRef& ref);

  JSHeapBroker* broker_;
};

std::ostream& operator<<(std::ostream& os, const ObjectRef& ref);

// Temporary class that carries information from a Map. We'd like to remove
// this class and use MapRef instead, but we can't as long as we support the
// kDisabled broker mode. That's because obtaining the MapRef via
// HeapObjectRef::map() requires a HandleScope when the broker is disabled.
// During OptimizeGraph we generally don't have a HandleScope, however. There
// are two places where we therefore use GetHeapObjectType() instead. Both that
// function and this class should eventually be removed.
class HeapObjectType {
 public:
  enum Flag : uint8_t { kUndetectable = 1 << 0, kCallable = 1 << 1 };

  using Flags = base::Flags<Flag>;

  HeapObjectType(InstanceType instance_type, Flags flags,
                 OddballType oddball_type)
      : instance_type_(instance_type),
        oddball_type_(oddball_type),
        flags_(flags) {
    DCHECK_EQ(instance_type == ODDBALL_TYPE,
              oddball_type != OddballType::kNone);
  }

  OddballType oddball_type() const { return oddball_type_; }
  InstanceType instance_type() const { return instance_type_; }
  Flags flags() const { return flags_; }

  bool is_callable() const { return flags_ & kCallable; }
  bool is_undetectable() const { return flags_ & kUndetectable; }

 private:
  InstanceType const instance_type_;
  OddballType const oddball_type_;
  Flags const flags_;
};

class HeapObjectRef : public ObjectRef {
 public:
  using ObjectRef::ObjectRef;
  Handle<HeapObject> object() const;

  MapRef map() const;

  // See the comment on the HeapObjectType class.
  HeapObjectType GetHeapObjectType() const;
};

class PropertyCellRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<PropertyCell> object() const;

  PropertyDetails property_details() const;

  void Serialize();
  ObjectRef value() const;
};

class JSObjectRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<JSObject> object() const;

  uint64_t RawFastDoublePropertyAsBitsAt(FieldIndex index) const;
  double RawFastDoublePropertyAt(FieldIndex index) const;
  ObjectRef RawFastPropertyAt(FieldIndex index) const;

  FixedArrayBaseRef elements() const;
  void EnsureElementsTenured();
  ElementsKind GetElementsKind() const;

  void SerializeObjectCreateMap();
  base::Optional<MapRef> GetObjectCreateMap() const;
};

class JSDataViewRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSDataView> object() const;

  size_t byte_length() const;
  size_t byte_offset() const;
};

class JSBoundFunctionRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSBoundFunction> object() const;

  void Serialize();

  // The following are available only after calling Serialize().
  ObjectRef bound_target_function() const;
  ObjectRef bound_this() const;
  FixedArrayRef bound_arguments() const;
};

class V8_EXPORT_PRIVATE JSFunctionRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSFunction> object() const;

  bool has_feedback_vector() const;
  bool has_initial_map() const;
  bool has_prototype() const;
  bool PrototypeRequiresRuntimeLookup() const;

  void Serialize();
  bool serialized() const;

  // The following are available only after calling Serialize().
  ObjectRef prototype() const;
  MapRef initial_map() const;
  ContextRef context() const;
  NativeContextRef native_context() const;
  SharedFunctionInfoRef shared() const;
  FeedbackVectorRef feedback_vector() const;
  int InitialMapInstanceSizeWithMinSlack() const;

  bool IsSerializedForCompilation() const;
};

class JSRegExpRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSRegExp> object() const;

  ObjectRef raw_properties_or_hash() const;
  ObjectRef data() const;
  ObjectRef source() const;
  ObjectRef flags() const;
  ObjectRef last_index() const;
};

class HeapNumberRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<HeapNumber> object() const;

  double value() const;
};

class MutableHeapNumberRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<MutableHeapNumber> object() const;

  double value() const;
};

class ContextRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Context> object() const;

  void SerializeContextChain();
  ContextRef previous() const;

  void SerializeSlot(int index);
  ObjectRef get(int index) const;
};

#define BROKER_COMPULSORY_NATIVE_CONTEXT_FIELDS(V)                    \
  V(JSFunction, array_function)                                       \
  V(JSFunction, boolean_function)                                     \
  V(JSFunction, bigint_function)                                      \
  V(JSFunction, number_function)                                      \
  V(JSFunction, object_function)                                      \
  V(JSFunction, promise_function)                                     \
  V(JSFunction, promise_then)                                         \
  V(JSFunction, string_function)                                      \
  V(JSFunction, symbol_function)                                      \
  V(JSGlobalProxy, global_proxy_object)                               \
  V(JSObject, promise_prototype)                                      \
  V(Map, bound_function_with_constructor_map)                         \
  V(Map, bound_function_without_constructor_map)                      \
  V(Map, fast_aliased_arguments_map)                                  \
  V(Map, initial_array_iterator_map)                                  \
  V(Map, initial_string_iterator_map)                                 \
  V(Map, iterator_result_map)                                         \
  V(Map, js_array_holey_double_elements_map)                          \
  V(Map, js_array_holey_elements_map)                                 \
  V(Map, js_array_holey_smi_elements_map)                             \
  V(Map, js_array_packed_double_elements_map)                         \
  V(Map, js_array_packed_elements_map)                                \
  V(Map, js_array_packed_smi_elements_map)                            \
  V(Map, sloppy_arguments_map)                                        \
  V(Map, slow_object_with_null_prototype_map)                         \
  V(Map, strict_arguments_map)                                        \
  V(ScriptContextTable, script_context_table)                         \
  V(SharedFunctionInfo, promise_capability_default_reject_shared_fun) \
  V(SharedFunctionInfo, promise_catch_finally_shared_fun)             \
  V(SharedFunctionInfo, promise_then_finally_shared_fun)              \
  V(SharedFunctionInfo, promise_capability_default_resolve_shared_fun)

// Those are set by Bootstrapper::ExportFromRuntime, which may not yet have
// happened when Turbofan is invoked via --always-opt.
#define BROKER_OPTIONAL_NATIVE_CONTEXT_FIELDS(V) \
  V(Map, async_function_object_map)              \
  V(Map, map_key_iterator_map)                   \
  V(Map, map_key_value_iterator_map)             \
  V(Map, map_value_iterator_map)                 \
  V(Map, set_key_value_iterator_map)             \
  V(Map, set_value_iterator_map)

#define BROKER_NATIVE_CONTEXT_FIELDS(V)      \
  BROKER_COMPULSORY_NATIVE_CONTEXT_FIELDS(V) \
  BROKER_OPTIONAL_NATIVE_CONTEXT_FIELDS(V)

class NativeContextRef : public ContextRef {
 public:
  using ContextRef::ContextRef;
  Handle<NativeContext> object() const;

  void Serialize();

#define DECL_ACCESSOR(type, name) type##Ref name() const;
  BROKER_NATIVE_CONTEXT_FIELDS(DECL_ACCESSOR)
#undef DECL_ACCESSOR

  MapRef GetFunctionMapFromIndex(int index) const;
  MapRef GetInitialJSArrayMap(ElementsKind kind) const;
  base::Optional<JSFunctionRef> GetConstructorFunction(const MapRef& map) const;
};

class NameRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Name> object() const;

  bool IsUniqueName() const;
};

class ScriptContextTableRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<ScriptContextTable> object() const;

  struct LookupResult {
    ContextRef context;
    bool immutable;
    int index;
  };

  base::Optional<LookupResult> lookup(const NameRef& name) const;
};

class DescriptorArrayRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<DescriptorArray> object() const;
};

class FeedbackCellRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<FeedbackCell> object() const;

  HeapObjectRef value() const;
};

class FeedbackVectorRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<FeedbackVector> object() const;

  ObjectRef get(FeedbackSlot slot) const;

  void SerializeSlots();
};

class FunctionTemplateInfoRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<FunctionTemplateInfo> object() const;

  void Serialize();
  ObjectRef call_code() const;
};

class CallHandlerInfoRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<CallHandlerInfo> object() const;

  Address callback() const;

  void Serialize();
  ObjectRef data() const;
};

class AllocationSiteRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<AllocationSite> object() const;

  bool PointsToLiteral() const;
  AllocationType GetAllocationType() const;
  ObjectRef nested_site() const;

  // {IsFastLiteral} determines whether the given array or object literal
  // boilerplate satisfies all limits to be considered for fast deep-copying
  // and computes the total size of all objects that are part of the graph.
  //
  // If PointsToLiteral() is false, then IsFastLiteral() is also false.
  bool IsFastLiteral() const;
  // We only serialize boilerplate if IsFastLiteral is true.
  base::Optional<JSObjectRef> boilerplate() const;

  ElementsKind GetElementsKind() const;
  bool CanInlineCall() const;
};

class V8_EXPORT_PRIVATE MapRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Map> object() const;

  int instance_size() const;
  InstanceType instance_type() const;
  int GetInObjectProperties() const;
  int GetInObjectPropertiesStartInWords() const;
  int NumberOfOwnDescriptors() const;
  int GetInObjectPropertyOffset(int index) const;
  int constructor_function_index() const;
  int NextFreePropertyIndex() const;
  int UnusedPropertyFields() const;
  ElementsKind elements_kind() const;
  bool is_stable() const;
  bool is_extensible() const;
  bool is_constructor() const;
  bool has_prototype_slot() const;
  bool is_access_check_needed() const;
  bool is_deprecated() const;
  bool CanBeDeprecated() const;
  bool CanTransition() const;
  bool IsInobjectSlackTrackingInProgress() const;
  bool is_dictionary_map() const;
  bool IsFixedCowArrayMap() const;
  bool IsPrimitiveMap() const;
  bool is_undetectable() const;
  bool is_callable() const;
  bool has_indexed_interceptor() const;
  bool has_hidden_prototype() const;
  bool is_migration_target() const;
  bool supports_fast_array_iteration() const;
  bool supports_fast_array_resize() const;
  bool IsMapOfCurrentGlobalProxy() const;

  OddballType oddball_type() const;

#define DEF_TESTER(Type, ...) bool Is##Type##Map() const;
  INSTANCE_TYPE_CHECKERS(DEF_TESTER)
#undef DEF_TESTER

  void SerializeBackPointer();
  HeapObjectRef GetBackPointer() const;

  void SerializePrototype();
  bool serialized_prototype() const;
  HeapObjectRef prototype() const;

  void SerializeForElementLoad();

  void SerializeForElementStore();
  bool HasOnlyStablePrototypesWithFastElements(
      ZoneVector<MapRef>* prototype_maps);

  // Concerning the underlying instance_descriptors:
  void SerializeOwnDescriptors();
  void SerializeOwnDescriptor(int descriptor_index);
  MapRef FindFieldOwner(int descriptor_index) const;
  PropertyDetails GetPropertyDetails(int descriptor_index) const;
  NameRef GetPropertyKey(int descriptor_index) const;
  FieldIndex GetFieldIndexFor(int descriptor_index) const;
  ObjectRef GetFieldType(int descriptor_index) const;
  bool IsUnboxedDoubleField(int descriptor_index) const;

  // Available after calling JSFunctionRef::Serialize on a function that has
  // this map as initial map.
  ObjectRef GetConstructor() const;
  base::Optional<MapRef> AsElementsKind(ElementsKind kind) const;
};

class FixedArrayBaseRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<FixedArrayBase> object() const;

  int length() const;
};

class FixedArrayRef : public FixedArrayBaseRef {
 public:
  using FixedArrayBaseRef::FixedArrayBaseRef;
  Handle<FixedArray> object() const;

  ObjectRef get(int i) const;
};

class FixedDoubleArrayRef : public FixedArrayBaseRef {
 public:
  using FixedArrayBaseRef::FixedArrayBaseRef;
  Handle<FixedDoubleArray> object() const;

  double get_scalar(int i) const;
  bool is_the_hole(int i) const;
};

class BytecodeArrayRef : public FixedArrayBaseRef {
 public:
  using FixedArrayBaseRef::FixedArrayBaseRef;
  Handle<BytecodeArray> object() const;

  int register_count() const;
  int parameter_count() const;
  interpreter::Register incoming_new_target_or_generator_register() const;
};

class JSArrayRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSArray> object() const;

  ObjectRef length() const;

  // Return the element at key {index} if the array has a copy-on-write elements
  // storage and {index} is known to be an own data property.
  base::Optional<ObjectRef> GetOwnCowElement(uint32_t index,
                                             bool serialize = false) const;
};

class ScopeInfoRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<ScopeInfo> object() const;

  int ContextLength() const;
};

#define BROKER_SFI_FIELDS(V)                 \
  V(int, internal_formal_parameter_count)    \
  V(bool, has_duplicate_parameters)          \
  V(int, function_map_index)                 \
  V(FunctionKind, kind)                      \
  V(LanguageMode, language_mode)             \
  V(bool, native)                            \
  V(bool, HasBreakInfo)                      \
  V(bool, HasBuiltinId)                      \
  V(bool, construct_as_builtin)              \
  V(bool, HasBytecodeArray)                  \
  V(bool, is_safe_to_skip_arguments_adaptor) \
  V(bool, IsInlineable)                      \
  V(bool, is_compiled)

class V8_EXPORT_PRIVATE SharedFunctionInfoRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<SharedFunctionInfo> object() const;

  int builtin_id() const;
  BytecodeArrayRef GetBytecodeArray() const;

#define DECL_ACCESSOR(type, name) type name() const;
  BROKER_SFI_FIELDS(DECL_ACCESSOR)
#undef DECL_ACCESSOR

  bool IsSerializedForCompilation(FeedbackVectorRef feedback) const;
  void SetSerializedForCompilation(FeedbackVectorRef feedback);
};

class StringRef : public NameRef {
 public:
  using NameRef::NameRef;
  Handle<String> object() const;

  int length() const;
  uint16_t GetFirstChar();
  base::Optional<double> ToNumber();
  bool IsSeqString() const;
  bool IsExternalString() const;
};

class SymbolRef : public NameRef {
 public:
  using NameRef::NameRef;
  Handle<Symbol> object() const;
};

class JSTypedArrayRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSTypedArray> object() const;

  bool is_on_heap() const;
  size_t length() const;
  void* external_pointer() const;

  void Serialize();
  bool serialized() const;

  HeapObjectRef buffer() const;
};

class ModuleRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Module> object() const;

  void Serialize();

  CellRef GetCell(int cell_index) const;
};

class CellRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Cell> object() const;

  ObjectRef value() const;
};

class JSGlobalProxyRef : public JSObjectRef {
 public:
  using JSObjectRef::JSObjectRef;
  Handle<JSGlobalProxy> object() const;

  // If {serialize} is false:
  //   If the property is known to exist as a property cell (on the global
  //   object), return that property cell. Otherwise (not known to exist as a
  //   property cell or known not to exist as a property cell) return nothing.
  // If {serialize} is true:
  //   Like above but potentially access the heap and serialize the necessary
  //   information.
  base::Optional<PropertyCellRef> GetPropertyCell(NameRef const& name,
                                                  bool serialize = false) const;
};

class CodeRef : public HeapObjectRef {
 public:
  using HeapObjectRef::HeapObjectRef;
  Handle<Code> object() const;
};

class InternalizedStringRef : public StringRef {
 public:
  using StringRef::StringRef;
  Handle<InternalizedString> object() const;
};

class ElementAccessFeedback;
class NamedAccessFeedback;

class ProcessedFeedback : public ZoneObject {
 public:
  enum Kind { kInsufficient, kGlobalAccess, kNamedAccess, kElementAccess };
  Kind kind() const { return kind_; }

  ElementAccessFeedback const* AsElementAccess() const;
  NamedAccessFeedback const* AsNamedAccess() const;

 protected:
  explicit ProcessedFeedback(Kind kind) : kind_(kind) {}

 private:
  Kind const kind_;
};

class InsufficientFeedback final : public ProcessedFeedback {
 public:
  InsufficientFeedback();
};

class GlobalAccessFeedback : public ProcessedFeedback {
 public:
  explicit GlobalAccessFeedback(PropertyCellRef cell);
  GlobalAccessFeedback(ContextRef script_context, int slot_index,
                       bool immutable);

  bool IsPropertyCell() const;
  PropertyCellRef property_cell() const;

  bool IsScriptContextSlot() const { return !IsPropertyCell(); }
  ContextRef script_context() const;
  int slot_index() const;
  bool immutable() const;

  base::Optional<ObjectRef> GetConstantHint() const;

 private:
  ObjectRef const cell_or_context_;
  int const index_and_immutable_;
};

class ElementAccessFeedback : public ProcessedFeedback {
 public:
  explicit ElementAccessFeedback(Zone* zone);

  // No transition sources appear in {receiver_maps}.
  // All transition targets appear in {receiver_maps}.
  ZoneVector<Handle<Map>> receiver_maps;
  ZoneVector<std::pair<Handle<Map>, Handle<Map>>> transitions;

  class MapIterator {
   public:
    bool done() const;
    void advance();
    MapRef current() const;

   private:
    friend class ElementAccessFeedback;

    explicit MapIterator(ElementAccessFeedback const& processed,
                         JSHeapBroker* broker);

    ElementAccessFeedback const& processed_;
    JSHeapBroker* const broker_;
    size_t index_ = 0;
  };

  // Iterator over all maps: first {receiver_maps}, then transition sources.
  MapIterator all_maps(JSHeapBroker* broker) const;
};

class NamedAccessFeedback : public ProcessedFeedback {
 public:
  NamedAccessFeedback(NameRef const& name,
                      ZoneVector<PropertyAccessInfo> const& access_infos);

  NameRef const& name() const { return name_; }
  ZoneVector<PropertyAccessInfo> const& access_infos() const {
    return access_infos_;
  }

 private:
  NameRef const name_;
  ZoneVector<PropertyAccessInfo> const access_infos_;
};

struct FeedbackSource {
  FeedbackSource(Handle<FeedbackVector> vector_, FeedbackSlot slot_)
      : vector(vector_), slot(slot_) {}
  explicit FeedbackSource(FeedbackNexus const& nexus);
  explicit FeedbackSource(VectorSlotPair const& pair);

  Handle<FeedbackVector> const vector;
  FeedbackSlot const slot;

  struct Hash {
    size_t operator()(FeedbackSource const& source) const {
      return base::hash_combine(source.vector.address(), source.slot);
    }
  };

  struct Equal {
    bool operator()(FeedbackSource const& lhs,
                    FeedbackSource const& rhs) const {
      return lhs.vector.equals(rhs.vector) && lhs.slot == rhs.slot;
    }
  };
};

#define TRACE_BROKER(broker, x)                                       \
  do {                                                                \
    if (FLAG_trace_heap_broker_verbose) broker->Trace() << x << '\n'; \
  } while (false)

#define TRACE_BROKER_MISSING(broker, x)                             \
  do {                                                              \
    if (FLAG_trace_heap_broker)                                     \
      broker->Trace() << __FUNCTION__ << ": missing " << x << '\n'; \
  } while (false)

class V8_EXPORT_PRIVATE JSHeapBroker {
 public:
  JSHeapBroker(Isolate* isolate, Zone* broker_zone);

  void SetNativeContextRef();
  void SerializeStandardObjects();

  Isolate* isolate() const { return isolate_; }
  Zone* zone() const { return current_zone_; }
  NativeContextRef native_context() const { return native_context_.value(); }
  PerIsolateCompilerCache* compiler_cache() const { return compiler_cache_; }

  enum BrokerMode { kDisabled, kSerializing, kSerialized, kRetired };
  BrokerMode mode() const { return mode_; }
  void StartSerializing();
  void StopSerializing();
  void Retire();
  bool SerializingAllowed() const;

  // Returns nullptr iff handle unknown.
  ObjectData* GetData(Handle<Object>) const;
  // Never returns nullptr.
  ObjectData* GetOrCreateData(Handle<Object>);
  // Like the previous but wraps argument in handle first (for convenience).
  ObjectData* GetOrCreateData(Object);

  // Check if {object} is any native context's %ArrayPrototype% or
  // %ObjectPrototype%.
  bool IsArrayOrObjectPrototype(const JSObjectRef& object) const;

  bool HasFeedback(FeedbackSource const& source) const;
  // The processed {feedback} can be {nullptr}, indicating that the original
  // feedback didn't contain information relevant for Turbofan.
  void SetFeedback(FeedbackSource const& source,
                   ProcessedFeedback const* feedback);
  ProcessedFeedback const* GetFeedback(FeedbackSource const& source) const;

  // Convenience wrappers around GetFeedback.
  GlobalAccessFeedback const* GetGlobalAccessFeedback(
      FeedbackSource const& source) const;

  // TODO(neis): Move these into serializer when we're always in the background.
  ElementAccessFeedback const* ProcessFeedbackMapsForElementAccess(
      MapHandles const& maps);
  GlobalAccessFeedback const* ProcessFeedbackForGlobalAccess(
      FeedbackSource const& source);

  base::Optional<NameRef> GetNameFeedback(FeedbackNexus const& nexus);

  std::ostream& Trace();
  void IncrementTracingIndentation();
  void DecrementTracingIndentation();

 private:
  friend class HeapObjectRef;
  friend class ObjectRef;
  friend class ObjectData;

  void SerializeShareableObjects();
  void CollectArrayAndObjectPrototypes();

  Isolate* const isolate_;
  Zone* const broker_zone_;
  Zone* current_zone_;
  base::Optional<NativeContextRef> native_context_;
  RefsMap* refs_;
  ZoneUnorderedSet<Handle<JSObject>, Handle<JSObject>::hash,
                   Handle<JSObject>::equal_to>
      array_and_object_prototypes_;
  BrokerMode mode_ = kDisabled;
  StdoutStream trace_out_;
  unsigned trace_indentation_ = 0;
  PerIsolateCompilerCache* compiler_cache_;
  ZoneUnorderedMap<FeedbackSource, ProcessedFeedback const*,
                   FeedbackSource::Hash, FeedbackSource::Equal>
      feedback_;

  static const size_t kMinimalRefsBucketCount = 8;     // must be power of 2
  static const size_t kInitialRefsBucketCount = 1024;  // must be power of 2
};

class TraceScope {
 public:
  TraceScope(JSHeapBroker* broker, const char* label)
      : TraceScope(broker, static_cast<void*>(broker), label) {}

  TraceScope(JSHeapBroker* broker, ObjectData* data, const char* label)
      : TraceScope(broker, static_cast<void*>(data), label) {}

  TraceScope(JSHeapBroker* broker, void* subject, const char* label)
      : broker_(broker) {
    TRACE_BROKER(broker_, "Running " << label << " on " << subject);
    broker_->IncrementTracingIndentation();
  }

  ~TraceScope() { broker_->DecrementTracingIndentation(); }

 private:
  JSHeapBroker* const broker_;
};

#define ASSIGN_RETURN_NO_CHANGE_IF_DATA_MISSING(something_var,             \
                                                optionally_something)      \
  auto optionally_something_ = optionally_something;                       \
  if (!optionally_something_)                                              \
    return NoChangeBecauseOfMissingData(broker(), __FUNCTION__, __LINE__); \
  something_var = *optionally_something_;

class Reduction;
Reduction NoChangeBecauseOfMissingData(JSHeapBroker* broker,
                                       const char* function, int line);

// Miscellaneous definitions that should be moved elsewhere once concurrent
// compilation is finished.
bool CanInlineElementAccess(MapRef const& map);

}  // namespace compiler
}  // namespace internal
}  // namespace v8

#endif  // V8_COMPILER_JS_HEAP_BROKER_H_