
// Copyright 2015 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.

#include "src/compiler/access-info.h"

#include <optional>
#include <ostream>

#include "src/base/logging.h"
#include "src/builtins/accessors.h"
#include "src/common/globals.h"
#include "src/compiler/compilation-dependencies.h"
#include "src/compiler/heap-refs.h"
#include "src/compiler/js-heap-broker-inl.h"
#include "src/compiler/simplified-operator.h"
#include "src/compiler/type-cache.h"
#include "src/ic/call-optimization.h"
#include "src/ic/handler-configuration-inl.h"
#include "src/objects/cell-inl.h"
#include "src/objects/dictionary-inl.h"
#include "src/objects/elements-kind.h"
#include "src/objects/field-index-inl.h"
#include "src/objects/field-type.h"
#include "src/objects/instance-type-inl.h"
#include "src/objects/module-inl.h"
#include "src/objects/objects-inl.h"
#include "src/objects/property-details.h"
#include "src/objects/struct-inl.h"
#include "src/objects/swiss-name-dictionary.h"
#include "src/objects/templates.h"

#if V8_ENABLE_WEBASSEMBLY
#include "src/wasm/value-type.h"
#include "src/wasm/wasm-objects-inl.h"
#endif  // V8_ENABLE_WEBASSEMBLY

namespace v8 {
namespace internal {
namespace compiler {

namespace {

bool CanInlinePropertyAccess(MapRef map, AccessMode access_mode) {
  // We can inline property access to prototypes of all primitives, except
  // the special Oddball ones that have no wrapper counterparts (i.e. Null,
  // Undefined and TheHole).
  // We can only inline accesses to dictionary mode holders if the access is a
  // load and the holder is a prototype. The latter ensures a 1:1
  // relationship between the map and the object (and therefore the property
  // dictionary).
  static_assert(ODDBALL_TYPE == LAST_PRIMITIVE_HEAP_OBJECT_TYPE);
  if (IsBooleanMap(*map.object())) return true;
  if (map.instance_type() < LAST_PRIMITIVE_HEAP_OBJECT_TYPE) return true;
  if (IsJSObjectMap(*map.object())) {
    if (map.is_dictionary_map()) {
      if (!V8_DICT_PROPERTY_CONST_TRACKING_BOOL) return false;
      return access_mode == AccessMode::kLoad &&
             map.object()->is_prototype_map();
    }
    return !map.has_named_interceptor() &&
           // TODO(verwaest): Allowlist contexts to which we have access.
           !map.is_access_check_needed();
  }
#if V8_ENABLE_WEBASSEMBLY
  if (IsWasmObjectMap(*map.object())) {
    DCHECK(!map.has_named_interceptor());
    DCHECK(!map.is_access_check_needed());
    // Accesses to Wasm objects all go through the prototype chain, but
    // we can't express that in this helper function.
    return true;
  }
#endif  // V8_ENABLE_WEBASSEMBLY
  return false;
}

#ifdef DEBUG
bool HasFieldRepresentationDependenciesOnMap(
    ZoneVector<CompilationDependency const*>& dependencies,
    Handle<Map> const& field_owner_map) {
  for (auto dep : dependencies) {
    if (CompilationDependencies::IsFieldRepresentationDependencyOnMap(
            dep, field_owner_map)) {
      return true;
    }
  }
  return false;
}
#endif

}  // namespace

std::ostream& operator<<(std::ostream& os, AccessMode access_mode) {
  switch (access_mode) {
    case AccessMode::kLoad:
      return os << "Load";
    case AccessMode::kStore:
      return os << "Store";
    case AccessMode::kStoreInLiteral:
      return os << "StoreInLiteral";
    case AccessMode::kHas:
      return os << "Has";
    case AccessMode::kDefine:
      return os << "Define";
  }
  UNREACHABLE();
}

ElementAccessInfo::ElementAccessInfo(
    ZoneVector<MapRef>&& lookup_start_object_maps, ElementsKind elements_kind,
    Zone* zone)
    : elements_kind_(elements_kind),
      lookup_start_object_maps_(lookup_start_object_maps),
      transition_sources_(zone) {
  CHECK(!lookup_start_object_maps.empty());
}

ElementAccessInfo::ElementAccessInfo(MapRef map, ObjectRef accessor,
                                     ObjectRef target, bool string_keys,
                                     Zone* zone)
    : elements_kind_(map.elements_kind()),
      string_keys_(string_keys),
      lookup_start_object_maps_({map}, zone),
      transition_sources_(zone),
      accessor_(accessor),
      target_(target) {
  DCHECK(is_proxy_on_prototype());
}

// static
PropertyAccessInfo PropertyAccessInfo::Invalid(Zone* zone) {
  return PropertyAccessInfo(zone);
}

// static
PropertyAccessInfo PropertyAccessInfo::NotFound(Zone* zone, MapRef receiver_map,
                                                OptionalJSObjectRef holder) {
  return PropertyAccessInfo(zone, kNotFound, holder, {{receiver_map}, zone});
}

// static
PropertyAccessInfo PropertyAccessInfo::DataField(
    JSHeapBroker* broker, Zone* zone, MapRef receiver_map,
    ZoneVector<CompilationDependency const*>&& dependencies,
    FieldIndex field_index, Representation field_representation,
    Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
    OptionalJSObjectRef holder, OptionalMapRef transition_map) {
  DCHECK(!field_representation.IsNone());
  DCHECK_IMPLIES(
      field_representation.IsDouble(),
      HasFieldRepresentationDependenciesOnMap(
          dependencies, transition_map.has_value() ? transition_map->object()
                        : holder.has_value() ? holder->map(broker).object()
                                             : receiver_map.object()));
  return PropertyAccessInfo(kDataField, holder, transition_map, field_index,
                            field_representation, field_type, field_owner_map,
                            field_map, {{receiver_map}, zone},
                            std::move(dependencies));
}

// static
PropertyAccessInfo PropertyAccessInfo::FastDataConstant(
    Zone* zone, MapRef receiver_map,
    ZoneVector<CompilationDependency const*>&& dependencies,
    FieldIndex field_index, Representation field_representation,
    Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
    OptionalJSObjectRef holder, OptionalMapRef transition_map) {
  DCHECK(!field_representation.IsNone());
  return PropertyAccessInfo(kFastDataConstant, holder, transition_map,
                            field_index, field_representation, field_type,
                            field_owner_map, field_map, {{receiver_map}, zone},
                            std::move(dependencies));
}

// static
PropertyAccessInfo PropertyAccessInfo::FastAccessorConstant(
    Zone* zone, MapRef receiver_map, OptionalJSObjectRef holder,
    OptionalObjectRef constant, OptionalJSObjectRef api_holder) {
  return PropertyAccessInfo(zone, kFastAccessorConstant, holder, constant,
                            api_holder, {} /* name */, {{receiver_map}, zone});
}

// static
PropertyAccessInfo PropertyAccessInfo::ModuleExport(
    Zone* zone, MapRef receiver_map, CellRef cell, OptionalJSObjectRef holder) {
  return PropertyAccessInfo(zone, kModuleExport, holder, cell /* constant */,
                            {} /* api_holder */, {} /* name */,
                            {{receiver_map}, zone});
}

// static
PropertyAccessInfo PropertyAccessInfo::StringLength(Zone* zone,
                                                    MapRef receiver_map) {
  return PropertyAccessInfo(zone, kStringLength, {}, {{receiver_map}, zone});
}

// static
PropertyAccessInfo PropertyAccessInfo::StringWrapperLength(
    Zone* zone, MapRef receiver_map) {
  return PropertyAccessInfo(zone, kStringWrapperLength, {},
                            {{receiver_map}, zone});
}

// static
PropertyAccessInfo PropertyAccessInfo::TypedArrayLength(Zone* zone,
                                                        MapRef receiver_map) {
  PropertyAccessInfo result(zone, kTypedArrayLength, {},
                            {{receiver_map}, zone});
  result.set_elements_kind(receiver_map.elements_kind());
  return result;
}

// static
PropertyAccessInfo PropertyAccessInfo::DictionaryDataField(
    Zone* zone, MapRef receiver_map, OptionalJSObjectRef holder,
    InternalIndex dictionary_index, NameRef name) {
  return PropertyAccessInfo(zone, kDictionaryDataField, holder,
                            {{receiver_map}, zone}, dictionary_index, name);
}

// static
PropertyAccessInfo PropertyAccessInfo::DictionaryProtoDataConstant(
    Zone* zone, MapRef receiver_map, JSObjectRef holder,
    InternalIndex dictionary_index, NameRef name) {
  return PropertyAccessInfo(zone, kDictionaryProtoDataConstant, holder,
                            {{receiver_map}, zone}, dictionary_index, name);
}

// static
PropertyAccessInfo PropertyAccessInfo::DictionaryProtoAccessorConstant(
    Zone* zone, MapRef receiver_map, OptionalJSObjectRef holder,
    ObjectRef constant, OptionalJSObjectRef api_holder, NameRef property_name) {
  return PropertyAccessInfo(zone, kDictionaryProtoAccessorConstant, holder,
                            constant, api_holder, property_name,
                            {{receiver_map}, zone});
}

PropertyAccessInfo::PropertyAccessInfo(Zone* zone)
    : kind_(kInvalid),
      lookup_start_object_maps_(zone),
      unrecorded_dependencies_(zone),
      field_representation_(Representation::None()),
      field_type_(Type::None()),
      dictionary_index_(InternalIndex::NotFound()) {}

PropertyAccessInfo::PropertyAccessInfo(
    Zone* zone, Kind kind, OptionalJSObjectRef holder,
    ZoneVector<MapRef>&& lookup_start_object_maps)
    : kind_(kind),
      lookup_start_object_maps_(lookup_start_object_maps),
      holder_(holder),
      unrecorded_dependencies_(zone),
      field_representation_(Representation::None()),
      field_type_(Type::None()),
      dictionary_index_(InternalIndex::NotFound()) {}

PropertyAccessInfo::PropertyAccessInfo(
    Zone* zone, Kind kind, OptionalJSObjectRef holder,
    OptionalObjectRef constant, OptionalJSObjectRef api_holder,
    OptionalNameRef name, ZoneVector<MapRef>&& lookup_start_object_maps)
    : kind_(kind),
      lookup_start_object_maps_(lookup_start_object_maps),
      constant_(constant),
      holder_(holder),
      api_holder_(api_holder),
      unrecorded_dependencies_(zone),
      field_representation_(Representation::None()),
      field_type_(Type::Any()),
      dictionary_index_(InternalIndex::NotFound()),
      name_(name) {
  DCHECK_IMPLIES(kind == kDictionaryProtoAccessorConstant, name.has_value());
}

PropertyAccessInfo::PropertyAccessInfo(
    Kind kind, OptionalJSObjectRef holder, OptionalMapRef transition_map,
    FieldIndex field_index, Representation field_representation,
    Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
    ZoneVector<MapRef>&& lookup_start_object_maps,
    ZoneVector<CompilationDependency const*>&& unrecorded_dependencies)
    : kind_(kind),
      lookup_start_object_maps_(lookup_start_object_maps),
      holder_(holder),
      unrecorded_dependencies_(std::move(unrecorded_dependencies)),
      transition_map_(transition_map),
      field_index_(field_index),
      field_representation_(field_representation),
      field_type_(field_type),
      field_owner_map_(field_owner_map),
      field_map_(field_map),
      dictionary_index_(InternalIndex::NotFound()) {
  DCHECK_IMPLIES(transition_map.has_value(),
                 field_owner_map.equals(transition_map.value()));
}

PropertyAccessInfo::PropertyAccessInfo(
    Zone* zone, Kind kind, OptionalJSObjectRef holder,
    ZoneVector<MapRef>&& lookup_start_object_maps,
    InternalIndex dictionary_index, NameRef name)
    : kind_(kind),
      lookup_start_object_maps_(lookup_start_object_maps),
      holder_(holder),
      unrecorded_dependencies_(zone),
      field_representation_(Representation::None()),
      field_type_(Type::Any()),
      dictionary_index_(dictionary_index),
      name_{name} {}

namespace {

template <class RefT>
bool OptionalRefEquals(OptionalRef<RefT> lhs, OptionalRef<RefT> rhs) {
  if (!lhs.has_value()) return !rhs.has_value();
  if (!rhs.has_value()) return false;
  return lhs->equals(rhs.value());
}

template <class T>
void AppendVector(ZoneVector<T>* dst, const ZoneVector<T>& src) {
  dst->insert(dst->end(), src.begin(), src.end());
}

}  // namespace

bool PropertyAccessInfo::Merge(PropertyAccessInfo const* that,
                               AccessMode access_mode, Zone* zone) {
  if (kind_ != that->kind_) return false;
  if (!OptionalRefEquals(holder_, that->holder_)) return false;

  switch (kind_) {
    case kInvalid:
      DCHECK_EQ(that->kind_, kInvalid);
      return true;

    case kDataField:
    case kFastDataConstant: {
      // Check if we actually access the same field (we use the
      // GetFieldAccessStubKey method here just like the ICs do
      // since that way we only compare the relevant bits of the
      // field indices).
      if (field_index_.GetFieldAccessStubKey() !=
          that->field_index_.GetFieldAccessStubKey()) {
        return false;
      }

      switch (access_mode) {
        case AccessMode::kHas:
        case AccessMode::kLoad: {
          if (!field_representation_.Equals(that->field_representation_)) {
            if (field_representation_.IsDouble() ||
                that->field_representation_.IsDouble()) {
              return false;
            }
            field_representation_ = Representation::Tagged();
          }
          if (!OptionalRefEquals(field_map_, that->field_map_)) {
            field_map_ = {};
          }
          break;
        }
        case AccessMode::kStore:
        case AccessMode::kStoreInLiteral:
        case AccessMode::kDefine: {
          // For stores, the field map and field representation information
          // must match exactly, otherwise we cannot merge the stores. We
          // also need to make sure that in case of transitioning stores,
          // the transition targets match.
          if (!OptionalRefEquals(field_map_, that->field_map_) ||
              !field_representation_.Equals(that->field_representation_) ||
              !OptionalRefEquals(transition_map_, that->transition_map_)) {
            return false;
          }
          break;
        }
      }

      field_type_ = Type::Union(field_type_, that->field_type_, zone);
      AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
      AppendVector(&unrecorded_dependencies_, that->unrecorded_dependencies_);
      return true;
    }

    case kDictionaryProtoAccessorConstant:
    case kFastAccessorConstant: {
      // Check if we actually access the same constant.
      if (!OptionalRefEquals(constant_, that->constant_)) return false;

      DCHECK(unrecorded_dependencies_.empty());
      DCHECK(that->unrecorded_dependencies_.empty());
      AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
      return true;
    }

    case kDictionaryProtoDataConstant: {
      DCHECK_EQ(AccessMode::kLoad, access_mode);
      if (dictionary_index_ != that->dictionary_index_) return false;
      AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
      return true;
    }

    case kDictionaryDataField: {
      DCHECK_EQ(AccessMode::kLoad, access_mode);
      if (dictionary_index_ != that->dictionary_index_) return false;
      AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
      return true;
    }

    case kNotFound:
    case kStringLength:
    case kStringWrapperLength: {
      DCHECK(unrecorded_dependencies_.empty());
      DCHECK(that->unrecorded_dependencies_.empty());
      AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
      return true;
    }
    case kTypedArrayLength:
      DCHECK_EQ(lookup_start_object_maps_.size(), 1);
      DCHECK_EQ(that->lookup_start_object_maps_.size(), 1);
      return lookup_start_object_maps_[0] == that->lookup_start_object_maps_[0];
    case kModuleExport:
      return false;
  }
  UNREACHABLE();
}

ConstFieldInfo PropertyAccessInfo::GetConstFieldInfo() const {
  return IsFastDataConstant() ? ConstFieldInfo(*field_owner_map_)
                              : ConstFieldInfo::None();
}

AccessInfoFactory::AccessInfoFactory(JSHeapBroker* broker, Zone* zone)
    : broker_(broker), type_cache_(TypeCache::Get()), zone_(zone) {}

bool AccessInfoFactory::ObjectMayHaveElements(JSObjectRef obj,
                                              MapRef map) const {
  if (IsCustomElementsReceiverInstanceType(map.instance_type())) return true;
  // Ruled out by non-"custom elements" receiver type:
  DCHECK(!map.has_indexed_interceptor());
  if (map.is_extensible()) return true;
  // When the map is not extensible (as we just checked), an empty elements
  // array will always remain empty.
  OptionalFixedArrayBaseRef elements = obj.elements(broker(), kRelaxedLoad);
  if (!elements.has_value()) return true;
  return (elements.value() != broker()->empty_fixed_array() &&
          elements.value() != broker()->empty_slow_element_dictionary());
}

bool AccessInfoFactory::ObjectMayHaveOwnProperties(JSObjectRef obj,
                                                   MapRef map) const {
  if (IsSpecialReceiverInstanceType(map.instance_type())) return true;
  // Ruled out by non-"special" receiver type:
  DCHECK(!map.has_named_interceptor());
  if (map.is_extensible()) return true;
  // When the map is not extensible (as we just checked), an empty property
  // backing store will always remain empty.
  if (map.is_dictionary_map()) {
    if (V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL) {
      Tagged<SwissNameDictionary> dict =
          obj.object()->property_dictionary_swiss();
      return dict->NumberOfElements() > 0;
    } else {
      Tagged<NameDictionary> dict = obj.object()->property_dictionary();
      return dict->NumberOfElements() > 0;
    }
  } else {
    return map.NumberOfOwnDescriptors() > 0;
  }
}

// Determines whether the given {obj}, which is the "target" of a Proxy,
// meets the requirements for inlining the get/set traps of that Proxy.
// Specifically, consider steps 8 and 9 of
// https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver
//
//   8. Let targetDesc be ? target.[[GetOwnProperty]](P).
//   9. If targetDesc is not undefined and targetDesc.[[Configurable]] is
//      false, then...
//
// Since this is a fast path, we don't want to spend time on these checks or
// even emit code to perform them, so we require a target for which we can
// statically prove that *any* [[GetOwnProperty]] lookup will return undefined.
bool AccessInfoFactory::ObjectIsSuitableProxyTarget(KeyType key_type,
                                                    JSObjectRef obj) const {
  MapRef map = obj.map(broker());
  // If the object is empty and frozen, it is statically guaranteed to remain
  // that way, satisfying the fast path's requirements.
  if (!ObjectMayHaveElements(obj, map) &&
      (key_type == KeyType::kIndex || !ObjectMayHaveOwnProperties(obj, map))) {
    return true;
  }
  // Some use cases can't use frozen targets because that limits the flexibility
  // of other Proxy traps. So we also support objects where we can register
  // sufficient code dependencies to get a deopt if the object gains elements.
  //
  // For now, we support objects that are currently empty, have a stable map,
  // and have fast elements (which are always configurable and writable) by
  // installing a dependency on their map stability. Adding properties or
  // elements with non-default attributes would cause a map transition and
  // loss of stability.
  if (map.is_stable() && map.NumberOfOwnDescriptors() == 0 &&
      IsFastElementsKind(map.elements_kind())) {
    dependencies()->DependOnStableMap(map);
    return true;
  }

  // TODO(jkummerow): Instead of requiring "NumberOfOwnDescriptors() == 0" as
  // above, we could also allow stable maps where all fields are configurable.
  //
  // If there is a use case for it, we could also easily support the pristine
  // Array.prototype or Object.prototype when key_type == kIndex by depending
  // on the NoElementsProtector.

  // This target object is not (yet?) supported.
  return false;
}

std::optional<ElementAccessInfo> AccessInfoFactory::ComputeElementAccessInfo(
    MapRef map, AccessMode access_mode) const {
  if (map.CanInlineElementAccess()) {
    return ElementAccessInfo({{map}, zone()}, map.elements_kind(), zone());
  }
#if V8_ENABLE_WEBASSEMBLY
  if (map.IsWasmObjectMap() &&
      (access_mode == AccessMode::kLoad || access_mode == AccessMode::kStore)) {
    // See if there is a Proxy on the prototype chain that will handle
    // element accesses.
    HeapObjectRef prototype = map.prototype(broker());
    bool prototypes_may_have_properties = false;
    while (true) {
      if (prototype.IsNull()) return {};
      MapRef proto_map = prototype.map(broker());
      if (proto_map.is_access_check_needed()) return {};
      if (proto_map.IsJSObjectMap()) {
        // Any regular prototypes on the chain must be guaranteed not to have
        // or later acquire any elements. We need to require this for both
        // indexed and named mode.
        if (ObjectMayHaveElements(prototype.AsJSObject(), proto_map)) return {};
        // If the Proxy trap we'll find later (see reads of
        // {prototypes_may_have_properties}) supports named properties, we'll
        // need to know whether prototypes contained any named properties.
        prototypes_may_have_properties =
            prototypes_may_have_properties ||
            ObjectMayHaveOwnProperties(prototype.AsJSObject(), proto_map);
        // This prototype is okay. Continue walking the chain.
        prototype = proto_map.prototype(broker());
        continue;
      }
      if (proto_map.IsJSProxyMap()) {
        JSProxyRef proxy = prototype.AsJSProxy();
        if (proxy.is_revocable()) return {};

        // Check the "handler". We do this first because the specific trap
        // function we find determines what to require from the "target".
        OptionalObjectRef maybe_handler = proxy.GetHandler(broker());
        if (!maybe_handler.has_value()) return {};
        if (!maybe_handler->IsJSObject()) return {};
        JSObjectRef handler = maybe_handler.value().AsJSObject();
        MapRef handler_map = handler.map(broker());
        // We could implement support for dictionary-mode handlers, but it's
        // probably not worth it.
        if (handler_map.is_dictionary_map()) return {};
        NameRef trap_name = access_mode == AccessMode::kLoad
                                ? broker()->get_string()
                                : broker()->set_string();
        PropertyAccessInfo trap_info = broker()->GetPropertyAccessInfo(
            handler_map, trap_name, AccessMode::kLoad);
        if (!trap_info.IsFastDataConstant()) return {};
        Representation repr = trap_info.field_representation();
        if (!repr.IsHeapObject() && !repr.IsTagged()) return {};
        OptionalObjectRef trap = handler.GetOwnFastConstantDataProperty(
            broker(), repr, trap_info.field_index(), dependencies());
        if (!trap.has_value()) return {};
        ObjectRef trap_value = trap.value();

        // Check that the trap is a Wasm function. We require that for spec
        // compliance reasons: the JS-to-Wasm value conversion of parameters
        // hides the fact that we're not emitting toString conversion operations
        // for the property keys, which is in particular helpful when the
        // Wasm function wants integer indices anyway.
        if (!trap_value.IsHeapObject()) return {};
        // Support for other callables is not implemented.
        if (!trap_value.AsHeapObject().IsJSFunction()) return {};

        SharedFunctionInfoRef sfi = trap_value.AsJSFunction().shared(broker());
        Tagged<Union<Smi, TrustedObject>> trusted_data =
            sfi.object()->GetTrustedData(broker()->local_isolate_or_isolate());
        Tagged<WasmExportedFunctionData> wasm_data;
        if (!TryCast(trusted_data, &wasm_data)) return {};
        const wasm::CanonicalSig* wasm_signature = wasm_data->internal()->sig();
        if (wasm_signature->parameter_count() < 2) return {};
        wasm::CanonicalValueType key_type = wasm_signature->GetParam(1);

        // Check the "target".
        OptionalObjectRef maybe_target = proxy.GetTarget(broker());
        if (!maybe_target.has_value()) return {};
        if (!maybe_target->IsJSObject()) return {};
        JSObjectRef target = maybe_target.value().AsJSObject();
        if (key_type == wasm::kWasmExternRef) {
          // If the prototypes would handle some keys, we cannot take the fast
          // path, because it would let the trap handle all keys.
          if (prototypes_may_have_properties) return {};
          if (!ObjectIsSuitableProxyTarget(KeyType::kString, target)) return {};
        } else if (key_type == wasm::kWasmI32) {
          if (!ObjectIsSuitableProxyTarget(KeyType::kIndex, target)) return {};
        } else {
          return {};
        }

        // Finally: all good!
        bool string_keys = key_type == wasm::kWasmExternRef;
        return ElementAccessInfo(map, trap_value, target, string_keys, zone());
      }
      if (proto_map.IsWasmObjectMap()) {
        // Wasm objects are opaque and frozen, so we can safely skip over them.
        prototype = proto_map.prototype(broker());
        continue;
      }
      // Nothing else can occur on prototype chains.
      UNREACHABLE();
    }
  }
#endif  // V8_ENABLE_WEBASSEMBLY
  return {};
}

bool AccessInfoFactory::ComputeElementAccessInfos(
    ElementAccessFeedback const& feedback,
    ZoneVector<ElementAccessInfo>* access_infos) const {
  AccessMode access_mode = feedback.keyed_mode().access_mode();
  if (access_mode == AccessMode::kLoad || access_mode == AccessMode::kHas) {
    // For polymorphic loads of similar elements kinds (i.e. all tagged or all
    // double), always use the "worst case" code without a transition.  This is
    // much faster than transitioning the elements to the worst case, trading a
    // TransitionElementsKind for a CheckMaps, avoiding mutation of the array.
    std::optional<ElementAccessInfo> access_info =
        ConsolidateElementLoad(feedback);
    if (access_info.has_value()) {
      access_infos->push_back(*access_info);
      return true;
    }
  }

  for (auto const& group : feedback.transition_groups()) {
    DCHECK(!group.empty());
    OptionalMapRef target = group.front();
    std::optional<ElementAccessInfo> access_info =
        ComputeElementAccessInfo(target.value(), access_mode);
    if (!access_info.has_value()) return false;

    for (size_t i = 1; i < group.size(); ++i) {
      OptionalMapRef map_ref = group[i];
      if (!map_ref.has_value()) continue;
      access_info->AddTransitionSource(map_ref.value());
    }
    access_infos->push_back(*access_info);
  }
  return true;
}

PropertyAccessInfo AccessInfoFactory::ComputeDataFieldAccessInfo(
    MapRef receiver_map, MapRef map, NameRef name, OptionalJSObjectRef holder,
    InternalIndex descriptor, AccessMode access_mode) const {
  DCHECK(descriptor.is_found());
  // TODO(jgruber,v8:7790): Use DescriptorArrayRef instead.
  DirectHandle<DescriptorArray> descriptors =
      map.instance_descriptors(broker()).object();
  PropertyDetails const details = descriptors->GetDetails(descriptor);
  Representation details_representation = details.representation();
  if (details_representation.IsNone()) {
    // The ICs collect feedback in PREMONOMORPHIC state already,
    // but at this point the {receiver_map} might still contain
    // fields for which the representation has not yet been
    // determined by the runtime. So we need to catch this case
    // here and fall back to use the regular IC logic instead.
    return Invalid();
  }
  FieldIndex field_index = FieldIndex::ForDetails(*map.object(), details);
  // Private brands are used when loading private methods, which are stored in a
  // BlockContext, an internal object.
  Type field_type = name.object()->IsPrivateBrand() ? Type::OtherInternal()
                                                    : Type::NonInternal();
  OptionalMapRef field_map;

  ZoneVector<CompilationDependency const*> unrecorded_dependencies(zone());

  Handle<FieldType> descriptors_field_type =
      broker()->CanonicalPersistentHandle(
          descriptors->GetFieldType(descriptor));
  OptionalObjectRef descriptors_field_type_ref =
      TryMakeRef<Object>(broker(), descriptors_field_type);
  if (!descriptors_field_type_ref.has_value()) return Invalid();

  // Note: FindFieldOwner may be called multiple times throughout one
  // compilation. This is safe since its result is fixed for a given map and
  // descriptor.
  MapRef field_owner_map = map.FindFieldOwner(broker(), descriptor);

  if (details_representation.IsSmi()) {
    field_type = Type::SignedSmall();
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            map, field_owner_map, descriptor, details_representation));
  } else if (details_representation.IsDouble()) {
    field_type = type_cache_->kFloat64;
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            map, field_owner_map, descriptor, details_representation));
  } else if (details_representation.IsHeapObject()) {
    if (IsNone(*descriptors_field_type)) {
      // Cleared field-types are pre-monomorphic states. The field type was
      // garbge collected and we need to record an updated type.
      static_assert(FieldType::kFieldTypesCanBeClearedOnGC);
      switch (access_mode) {
        case AccessMode::kStore:
        case AccessMode::kStoreInLiteral:
        case AccessMode::kDefine:
          return Invalid();
        case AccessMode::kLoad:
        case AccessMode::kHas:
          break;
      }
    }
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            map, field_owner_map, descriptor, details_representation));
    if (IsClass(*descriptors_field_type)) {
      // Remember the field map, and try to infer a useful type.
      OptionalMapRef maybe_field_map =
          TryMakeRef(broker(), FieldType::AsClass(*descriptors_field_type));
      if (!maybe_field_map.has_value()) return Invalid();
      field_map = maybe_field_map;
      // field_type can only be inferred from field_map if it is stable and we
      // add a stability dependency. This happens on use in the access builder.
    }
  } else {
    CHECK(details_representation.IsTagged());
  }
  // TODO(turbofan): We may want to do this only depending on the use
  // of the access info.
  unrecorded_dependencies.push_back(
      dependencies()->FieldTypeDependencyOffTheRecord(
          map, field_owner_map, descriptor,
          descriptors_field_type_ref.value()));

  PropertyConstness constness =
      map.GetPropertyDetails(broker_, descriptor).constness();

  if (constness == PropertyConstness::kConst) {
    if (auto constness_dep =
            dependencies()->FieldConstnessDependencyOffTheRecord(
                map, field_owner_map, descriptor)) {
      unrecorded_dependencies.push_back(*constness_dep);
      return PropertyAccessInfo::FastDataConstant(
          zone(), receiver_map, std::move(unrecorded_dependencies), field_index,
          details_representation, field_type, field_owner_map, field_map,
          holder, {});
    }

    if (access_mode != AccessMode::kLoad && access_mode != AccessMode::kHas) {
      return PropertyAccessInfo::Invalid(zone());
    }
  }

  return PropertyAccessInfo::DataField(
      broker(), zone(), receiver_map, std::move(unrecorded_dependencies),
      field_index, details_representation, field_type, field_owner_map,
      field_map, holder, {});
}

namespace {

using AccessorsObjectGetter = std::function<Handle<Object>()>;

PropertyAccessInfo AccessorAccessInfoHelper(
    Isolate* isolate, Zone* zone, JSHeapBroker* broker,
    const AccessInfoFactory* ai_factory, MapRef receiver_map, NameRef name,
    MapRef holder_map, OptionalJSObjectRef holder, AccessMode access_mode,
    AccessorsObjectGetter get_accessors) {
  InstanceType holder_instance_type = holder_map.instance_type();
  if (holder_instance_type == JS_MODULE_NAMESPACE_TYPE ||
      holder_instance_type == JS_DEFERRED_MODULE_NAMESPACE_TYPE) {
    DCHECK(holder_map.object()->is_prototype_map());
    DirectHandle<PrototypeInfo> proto_info = broker->CanonicalPersistentHandle(
        Cast<PrototypeInfo>(holder_map.object()->prototype_info()));
    DirectHandle<JSModuleNamespace> module_namespace =
        broker->CanonicalPersistentHandle(
            Cast<JSModuleNamespace>(proto_info->module_namespace()));
    // A deferred module namespace triggers synchronous evaluation of its
    // module on the first non-symbol property access. We can only fold the
    // access into a direct cell load once that module is already evaluated;
    // before then, the load must go through the slow path that triggers
    // evaluation. The evaluated state is monotonic (a module never leaves
    // kEvaluated), so this remains valid for the lifetime of the optimized
    // code without an extra compilation dependency.
    if (holder_instance_type == JS_DEFERRED_MODULE_NAMESPACE_TYPE &&
        module_namespace->module()->status() != Module::kEvaluated) {
      return PropertyAccessInfo::Invalid(zone);
    }
    Handle<Cell> cell = broker->CanonicalPersistentHandle(
        Cast<Cell>(module_namespace->module()->exports()->Lookup(
            name.object(), Smi::ToInt(Object::GetHash(*name.object())))));
    if (IsAnyStore(access_mode)) {
      // https://tc39.es/ecma262/#sec-module-namespace-exotic-objects-set-p-v-receiver
      // https://tc39.es/ecma262/#sec-module-namespace-exotic-objects-defineownproperty-p-desc
      //
      // Storing to a module namespace object is always an error or a no-op in
      // JS.
      return PropertyAccessInfo::Invalid(zone);
    }
    if (IsTheHole(cell->value(kRelaxedLoad))) {
      // This module has not been fully initialized yet.
      return PropertyAccessInfo::Invalid(zone);
    }
    OptionalCellRef cell_ref = TryMakeRef(broker, cell);
    if (!cell_ref.has_value()) {
      return PropertyAccessInfo::Invalid(zone);
    }
    return PropertyAccessInfo::ModuleExport(zone, receiver_map,
                                            cell_ref.value(), holder);
  }
  if (access_mode == AccessMode::kHas) {
    // kHas is not supported for dictionary mode objects.
    DCHECK(!holder_map.is_dictionary_map());

    // HasProperty checks don't call getter/setters, existence is sufficient.
    return PropertyAccessInfo::FastAccessorConstant(zone, receiver_map, holder,
                                                    {}, {});
  }
  DirectHandle<Object> maybe_accessors = get_accessors();
  if (!IsAccessorPair(*maybe_accessors)) {
    return PropertyAccessInfo::Invalid(zone);
  }
  DirectHandle<AccessorPair> accessors = Cast<AccessorPair>(maybe_accessors);
  Handle<Object> accessor = broker->CanonicalPersistentHandle(
      access_mode == AccessMode::kLoad ? accessors->getter(kAcquireLoad)
                                       : accessors->setter(kAcquireLoad));

  OptionalObjectRef accessor_ref = TryMakeRef(broker, accessor);
  if (!accessor_ref.has_value()) return PropertyAccessInfo::Invalid(zone);

  OptionalJSObjectRef api_holder_ref;
  if (!IsJSFunction(*accessor)) {
    CallOptimization optimization(broker->local_isolate_or_isolate(), accessor);
    if (!optimization.is_simple_api_call() ||
        optimization.IsCrossContextLazyAccessorPair(
            *broker->target_native_context().object(), *holder_map.object())) {
      return PropertyAccessInfo::Invalid(zone);
    }
    if (DEBUG_BOOL && holder.has_value()) {
      std::optional<Tagged<NativeContext>> holder_creation_context =
          holder->object()->GetCreationContext();
      CHECK(holder_creation_context.has_value());
      CHECK_EQ(*broker->target_native_context().object(),
               holder_creation_context.value());
    }

    CallOptimization::HolderLookup holder_lookup;
    Handle<JSObject> api_holder = broker->CanonicalPersistentHandle(
        optimization.LookupHolderOfExpectedType(
            broker->local_isolate_or_isolate(), receiver_map.object(),
            &holder_lookup));
    if (holder_lookup == CallOptimization::kHolderNotFound) {
      return PropertyAccessInfo::Invalid(zone);
    }
    DCHECK_IMPLIES(holder_lookup == CallOptimization::kHolderIsReceiver,
                   api_holder.is_null());
    DCHECK_IMPLIES(holder_lookup == CallOptimization::kHolderFound,
                   !api_holder.is_null());

    if (!api_holder.is_null()) {
      api_holder_ref = TryMakeRef(broker, api_holder);
      if (!api_holder_ref.has_value()) return PropertyAccessInfo::Invalid(zone);
    }
  }
  if (access_mode == AccessMode::kLoad) {
    std::optional<Tagged<Name>> cached_property_name =
        FunctionTemplateInfo::TryGetCachedPropertyName(isolate, *accessor);
    if (cached_property_name.has_value()) {
      OptionalNameRef cached_property_name_ref =
          TryMakeRef(broker, cached_property_name.value());
      if (cached_property_name_ref.has_value()) {
        PropertyAccessInfo access_info = ai_factory->ComputePropertyAccessInfo(
            holder_map, cached_property_name_ref.value(), access_mode,
            std::nullopt);
        if (!access_info.IsInvalid()) return access_info;
      }
    }
  }

  if (holder_map.is_dictionary_map()) {
    CHECK(!api_holder_ref.has_value());
    return PropertyAccessInfo::DictionaryProtoAccessorConstant(
        zone, receiver_map, holder, accessor_ref.value(), api_holder_ref, name);
  } else {
    return PropertyAccessInfo::FastAccessorConstant(
        zone, receiver_map, holder, accessor_ref.value(), api_holder_ref);
  }
}

}  // namespace

PropertyAccessInfo AccessInfoFactory::ComputeAccessorDescriptorAccessInfo(
    MapRef receiver_map, NameRef name, MapRef holder_map,
    OptionalJSObjectRef holder, InternalIndex descriptor,
    AccessMode access_mode) const {
  DCHECK(descriptor.is_found());
  Handle<DescriptorArray> descriptors = broker()->CanonicalPersistentHandle(
      holder_map.object()->instance_descriptors(kAcquireLoad));
  SLOW_DCHECK(descriptor ==
              descriptors->Search(*name.object(), *holder_map.object(), true));

  auto get_accessors = [&]() {
    return broker()->CanonicalPersistentHandle(
        descriptors->GetStrongValue(descriptor));
  };
  return AccessorAccessInfoHelper(isolate(), zone(), broker(), this,
                                  receiver_map, name, holder_map, holder,
                                  access_mode, get_accessors);
}

PropertyAccessInfo AccessInfoFactory::ComputeDictionaryProtoAccessInfo(
    MapRef receiver_map, NameRef name, JSObjectRef holder,
    InternalIndex dictionary_index, AccessMode access_mode,
    PropertyDetails details) const {
  CHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
  DCHECK(holder.map(broker()).object()->is_prototype_map());
  DCHECK_EQ(access_mode, AccessMode::kLoad);

  // We can only inline accesses to constant properties.
  if (details.constness() != PropertyConstness::kConst) {
    return Invalid();
  }

  if (details.kind() == PropertyKind::kData) {
    return PropertyAccessInfo::DictionaryProtoDataConstant(
        zone(), receiver_map, holder, dictionary_index, name);
  }

  auto get_accessors = [&]() {
    return JSObject::DictionaryPropertyAt(isolate(), holder.object(),
                                          dictionary_index);
  };
  return AccessorAccessInfoHelper(isolate(), zone(), broker(), this,
                                  receiver_map, name, holder.map(broker()),
                                  holder, access_mode, get_accessors);
}

bool AccessInfoFactory::TryLoadPropertyDetails(
    MapRef map, OptionalJSObjectRef maybe_holder, NameRef name,
    InternalIndex* index_out, PropertyDetails* details_out) const {
  if (map.is_dictionary_map()) {
    DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
    DCHECK(map.object()->is_prototype_map());

    DisallowGarbageCollection no_gc;

    if (!maybe_holder.has_value()) {
      // TODO(v8:11457) In this situation, we have a dictionary mode prototype
      // as a receiver. Consider other means of obtaining the holder in this
      // situation.

      // Without the holder, we can't get the property details.
      return false;
    }

    DirectHandle<JSObject> holder = maybe_holder->object();
    if (V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL) {
      Tagged<SwissNameDictionary> dict = holder->property_dictionary_swiss();
      *index_out = dict->FindEntry(isolate(), name.object());
      if (index_out->is_found()) {
        *details_out = dict->DetailsAt(*index_out);
      }
    } else {
      Tagged<NameDictionary> dict = holder->property_dictionary();
      *index_out = dict->FindEntry(isolate(), name.object());
      if (index_out->is_found()) {
        *details_out = dict->DetailsAt(*index_out);
      }
    }
#if V8_ENABLE_WEBASSEMBLY
  } else if (InstanceTypeChecker::IsWasmObject(map.instance_type())) {
    DCHECK(index_out->is_not_found());
    return true;  // Skip to prototypes.
#endif            // V8_ENABLE_WEBASSEMBLY
  } else {
    Tagged<DescriptorArray> descriptors =
        *map.instance_descriptors(broker()).object();
    *index_out = descriptors->Search(*name.object(), *map.object(), true);
    if (index_out->is_found()) {
      *details_out = descriptors->GetDetails(*index_out);
    }
  }

  return true;
}

PropertyAccessInfo AccessInfoFactory::ComputePropertyAccessInfo(
    MapRef map, NameRef name, AccessMode access_mode,
    OptionalObjectRef handler) const {
  CHECK(name.IsUniqueName());

  // Dictionary property const tracking is unsupported with concurrent inlining.
  CHECK(!V8_DICT_PROPERTY_CONST_TRACKING_BOOL);

  JSHeapBroker::MapUpdaterGuardIfNeeded mumd_scope(broker());

  if (map.is_dictionary_map() && access_mode == AccessMode::kLoad &&
      handler.has_value() && handler->IsSmi()) {
    if constexpr (V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL) {
      return Invalid();
    }
    auto smi_handler = Cast<Smi>(*handler->object());
    if (LoadHandler::GetHandlerKind(smi_handler) ==
        LoadHandler::Kind::kNormal) {
      if (LoadHandler::IsDataPropertyBits::decode(smi_handler.value())) {
        uint32_t index =
            LoadHandler::DictionaryIndexBits::decode(smi_handler.value());
        if (index != LoadHandler::DictionaryIndexBits::kMax) {
          return PropertyAccessInfo::DictionaryDataField(
              zone(), map, OptionalJSObjectRef(), InternalIndex(index), name);
        }
      }
    }
  }

  if (access_mode == AccessMode::kHas && !IsJSReceiverMap(*map.object())) {
    return Invalid();
  }

  // Check if it is safe to inline property access for the {map}.
  if (!CanInlinePropertyAccess(map, access_mode)) {
    return Invalid();
  }

  // We support fast inline cases for certain JSObject getters.
  if (access_mode == AccessMode::kLoad || access_mode == AccessMode::kHas) {
    PropertyAccessInfo access_info = LookupSpecialFieldAccessor(map, name);
    if (!access_info.IsInvalid()) return access_info;
  }

  // Only relevant if V8_DICT_PROPERTY_CONST_TRACKING enabled.
  bool dictionary_prototype_on_chain = false;
  bool fast_mode_prototype_on_chain = false;

  // Remember the receiver map. We use {map} as loop variable.
  MapRef receiver_map = map;
  OptionalJSObjectRef holder;

  // Perform the implicit ToObject for primitives here.
  // Implemented according to ES6 section 7.3.2 GetV (V, P).
  // Note: Keep sync'd with
  // CompilationDependencies::DependOnStablePrototypeChains.
  if (receiver_map.IsPrimitiveMap()) {
    OptionalJSFunctionRef constructor =
        broker()->target_native_context().GetConstructorFunction(broker(),
                                                                 receiver_map);
    if (!constructor.has_value()) return Invalid();
    map = constructor->initial_map(broker());
    DCHECK(!map.IsPrimitiveMap());
  }

  while (true) {
    PropertyDetails details = PropertyDetails::Empty();
    InternalIndex index = InternalIndex::NotFound();
    if (!TryLoadPropertyDetails(map, holder, name, &index, &details)) {
      return Invalid();
    }

    if (index.is_found()) {
      if (IsAnyStore(access_mode)) {
        DCHECK(!map.is_dictionary_map());

        // Don't bother optimizing stores to read-only properties.
        if (details.IsReadOnly()) return Invalid();

        if (details.kind() == PropertyKind::kData && holder.has_value()) {
          // This is a store to a property not found on the receiver but on a
          // prototype. According to ES6 section 9.1.9 [[Set]], we need to
          // create a new data property on the receiver. We can still optimize
          // if such a transition already exists.
          return LookupTransition(receiver_map, name, holder, NONE);
        }
      }

      if (IsDefiningStore(access_mode)) {
        if (details.attributes() != PropertyAttributes::NONE ||
            details.kind() != PropertyKind::kData) {
          // We should store the property with WEC attributes, but that's not
          // the attributes of the property that we found. We just bail out and
          // let the runtime figure out what to do (which probably requires
          // changing the object's map).
          // Same for accessor case - we must reconfigure property to a data
          // property.
          return Invalid();
        }
      }

      if (map.is_dictionary_map()) {
        DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);

        if (fast_mode_prototype_on_chain) {
          // TODO(v8:11248) While the work on dictionary mode prototypes is in
          // progress, we may still see fast mode objects on the chain prior to
          // reaching a dictionary mode prototype holding the property . Due to
          // this only being an intermediate state, we don't stupport these kind
          // of heterogenous prototype chains.
          return Invalid();
        }

        // TryLoadPropertyDetails only succeeds if we know the holder.
        return ComputeDictionaryProtoAccessInfo(
            receiver_map, name, holder.value(), index, access_mode, details);
      }

      if (dictionary_prototype_on_chain) {
        // If V8_DICT_PROPERTY_CONST_TRACKING_BOOL was disabled, then a
        // dictionary prototype would have caused a bailout earlier.
        DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);

        // TODO(v8:11248) We have a fast mode holder, but there was a dictionary
        // mode prototype earlier on the chain. Note that seeing a fast mode
        // prototype even though V8_DICT_PROPERTY_CONST_TRACKING is enabled
        // should only be possible while the implementation of dictionary mode
        // prototypes is work in progress. Eventually, enabling
        // V8_DICT_PROPERTY_CONST_TRACKING will guarantee that all prototypes
        // are always in dictionary mode, making this case unreachable. However,
        // due to the complications of checking dictionary mode prototypes for
        // modification, we don't attempt to support dictionary mode prototypes
        // occuring before a fast mode holder on the chain.
        return Invalid();
      }

      if (access_mode == AccessMode::kLoad && holder.has_value()) {
        PropertyAccessInfo access_info = LookupSpecialFieldAccessorInHolder(
            receiver_map, name, *holder, details, index);
        if (!access_info.IsInvalid()) return access_info;
      }

      if (details.location() == PropertyLocation::kField) {
        if (details.kind() == PropertyKind::kData) {
          return ComputeDataFieldAccessInfo(receiver_map, map, name, holder,
                                            index, access_mode);
        } else {
          DCHECK_EQ(PropertyKind::kAccessor, details.kind());
          // TODO(turbofan): Add support for general accessors?
          return Invalid();
        }
      } else {
        DCHECK_EQ(PropertyLocation::kDescriptor, details.location());
        DCHECK_EQ(PropertyKind::kAccessor, details.kind());
        return ComputeAccessorDescriptorAccessInfo(receiver_map, name, map,
                                                   holder, index, access_mode);
      }

      UNREACHABLE();
    }

    // The property wasn't found on {map}. Look on the prototype if appropriate.
    DCHECK(!index.is_found());

    // Don't search on the prototype chain for special indices in case of
    // integer indexed exotic objects (see ES6 section 9.4.5).
    if (IsJSTypedArrayMap(*map.object()) && name.IsString()) {
      StringRef name_str = name.AsString();
      SharedStringAccessGuardIfNeeded access_guard(
          *name_str.object(), broker()->local_isolate_or_isolate());
      if (IsSpecialIndex(*name_str.object(), access_guard)) return Invalid();
    }

    // Don't search on the prototype when storing in literals, or performing a
    // Define operation
    if (access_mode == AccessMode::kStoreInLiteral ||
        access_mode == AccessMode::kDefine) {
      PropertyAttributes attrs = NONE;
      if (name.object()->IsAnyPrivate()) {
        // When PrivateNames are added to an object, they are by definition
        // non-enumerable.
        attrs = DONT_ENUM;
      }
      return LookupTransition(receiver_map, name, holder, attrs);
    }

    // Don't lookup private symbols on the prototype chain.
    if (name.object()->IsAnyPrivate()) {
      return Invalid();
    }

    if (V8_DICT_PROPERTY_CONST_TRACKING_BOOL && holder.has_value()) {
      // At this point, we are past the first loop iteration.
      DCHECK(holder->object()->map()->is_prototype_map());
      DCHECK(!holder->map(broker()).equals(receiver_map));

      fast_mode_prototype_on_chain =
          fast_mode_prototype_on_chain || !map.is_dictionary_map();
      dictionary_prototype_on_chain =
          dictionary_prototype_on_chain || map.is_dictionary_map();
    }

    // Walk up the prototype chain.
    // Load the map's prototype's map to guarantee that every time we use it,
    // we use the same Map.
    HeapObjectRef prototype = map.prototype(broker());

    MapRef map_prototype_map = prototype.map(broker());
    if (!IsJSObjectMap(*map_prototype_map.object())) {
      // Don't allow proxies on the prototype chain.
      if (!prototype.IsNull()) {
        DCHECK(IsJSProxy(*prototype.object()) ||
               IsWasmObject(*prototype.object()));
        return Invalid();
      }

      DCHECK(prototype.IsNull());

      if (dictionary_prototype_on_chain) {
        // TODO(v8:11248) See earlier comment about
        // dictionary_prototype_on_chain. We don't support absent properties
        // with dictionary mode prototypes on the chain, either. This is again
        // just due to how we currently deal with dependencies for dictionary
        // properties during finalization.
        return Invalid();
      }

      // Store to property not found on the receiver or any prototype, we need
      // to transition to a new data property.
      // Implemented according to ES6 section 9.1.9 [[Set]] (P, V, Receiver)
      if (access_mode == AccessMode::kStore) {
        return LookupTransition(receiver_map, name, holder, NONE);
      }

      // The property was not found (access returns undefined or throws
      // depending on the language mode of the load operation.
      // Implemented according to ES6 section 9.1.8 [[Get]] (P, Receiver)
      return PropertyAccessInfo::NotFound(zone(), receiver_map, holder);
    }

    CHECK(prototype.IsJSObject());
    holder = prototype.AsJSObject();
    map = map_prototype_map;

    if (!CanInlinePropertyAccess(map, access_mode)) {
      return Invalid();
    }

    // Successful lookup on prototype chain needs to guarantee that all the
    // prototypes up to the holder have stable maps, except for dictionary-mode
    // prototypes. We currently do this by taking a
    // DependOnStablePrototypeChains dependency in the caller.
    //
    // TODO(jgruber): This is brittle and easy to miss. Consider a refactor
    // that moves the responsibility of taking the dependency into
    // AccessInfoFactory.
  }
  UNREACHABLE();
}

PropertyAccessInfo AccessInfoFactory::FinalizePropertyAccessInfosAsOne(
    ZoneVector<PropertyAccessInfo> access_infos, AccessMode access_mode) const {
  ZoneVector<PropertyAccessInfo> merged_access_infos(zone());
  MergePropertyAccessInfos(access_infos, access_mode, &merged_access_infos);
  if (merged_access_infos.size() == 1) {
    PropertyAccessInfo& result = merged_access_infos.front();
    if (!result.IsInvalid()) {
      result.RecordDependencies(dependencies());
      return result;
    }
  }
  return Invalid();
}

void PropertyAccessInfo::RecordDependencies(
    CompilationDependencies* dependencies) {
  for (CompilationDependency const* d : unrecorded_dependencies_) {
    dependencies->RecordDependency(d);
  }
  unrecorded_dependencies_.clear();
}

bool AccessInfoFactory::FinalizePropertyAccessInfos(
    ZoneVector<PropertyAccessInfo> access_infos, AccessMode access_mode,
    ZoneVector<PropertyAccessInfo>* result) const {
  if (access_infos.empty()) return false;
  MergePropertyAccessInfos(access_infos, access_mode, result);
  for (PropertyAccessInfo const& info : *result) {
    if (info.IsInvalid()) return false;
  }
  for (PropertyAccessInfo& info : *result) {
    info.RecordDependencies(dependencies());
  }
  return true;
}

void AccessInfoFactory::MergePropertyAccessInfos(
    ZoneVector<PropertyAccessInfo> infos, AccessMode access_mode,
    ZoneVector<PropertyAccessInfo>* result) const {
  DCHECK(result->empty());
  for (auto it = infos.begin(), end = infos.end(); it != end; ++it) {
    bool merged = false;
    for (auto ot = it + 1; ot != end; ++ot) {
      if (ot->Merge(&(*it), access_mode, zone())) {
        merged = true;
        break;
      }
    }
    if (!merged) result->push_back(*it);
  }
  CHECK(!result->empty());
}

CompilationDependencies* AccessInfoFactory::dependencies() const {
  return broker()->dependencies();
}
Isolate* AccessInfoFactory::isolate() const { return broker()->isolate(); }

namespace {

Maybe<ElementsKind> GeneralizeElementsKind(ElementsKind this_kind,
                                           ElementsKind that_kind) {
  if (IsHoleyElementsKind(this_kind)) {
    that_kind = GetHoleyElementsKind(that_kind);
  } else if (IsHoleyElementsKind(that_kind)) {
    this_kind = GetHoleyElementsKind(this_kind);
  }
  if (this_kind == that_kind) return Just(this_kind);
  if (IsDoubleElementsKind(that_kind) == IsDoubleElementsKind(this_kind)) {
    if (IsMoreGeneralElementsKindTransition(that_kind, this_kind)) {
      return Just(this_kind);
    }
    if (IsMoreGeneralElementsKindTransition(this_kind, that_kind)) {
      return Just(that_kind);
    }
  }
  return Nothing<ElementsKind>();
}

}  // namespace

std::optional<ElementAccessInfo> AccessInfoFactory::ConsolidateElementLoad(
    ElementAccessFeedback const& feedback) const {
  if (feedback.transition_groups().empty()) return {};

  DCHECK(!feedback.transition_groups().front().empty());
  MapRef first_map = feedback.transition_groups().front().front();
  InstanceType instance_type = first_map.instance_type();
  ElementsKind elements_kind = first_map.elements_kind();

  ZoneVector<MapRef> maps(zone());
  for (auto const& group : feedback.transition_groups()) {
    for (MapRef map : group) {
      if (map.instance_type() != instance_type ||
          !map.CanInlineElementAccess()) {
        return {};
      }
      if (!GeneralizeElementsKind(elements_kind, map.elements_kind())
               .To(&elements_kind)) {
        return {};
      }
      maps.push_back(map);
    }
  }

  return ElementAccessInfo(std::move(maps), elements_kind, zone());
}

PropertyAccessInfo AccessInfoFactory::LookupSpecialFieldAccessor(
    MapRef map, NameRef name) const {
  // Check for String::length field accessor.
  if (IsStringMap(*map.object())) {
    if (Name::Equals(isolate(), name.object(),
                     isolate()->factory()->length_string())) {
      return PropertyAccessInfo::StringLength(zone(), map);
    }
    return Invalid();
  }
  if (IsJSPrimitiveWrapperMap(*map.object()) &&
      (map.elements_kind() == FAST_STRING_WRAPPER_ELEMENTS ||
       map.elements_kind() == SLOW_STRING_WRAPPER_ELEMENTS)) {
    if (Name::Equals(isolate(), name.object(),
                     isolate()->factory()->length_string())) {
      return PropertyAccessInfo::StringWrapperLength(zone(), map);
    }
  }
  // Check for special JSObject field accessors.
  FieldIndex field_index;
  if (Accessors::IsJSObjectFieldAccessor(isolate(), map.object(), name.object(),
                                         &field_index)) {
    Type field_type = Type::NonInternal();
    Representation field_representation = Representation::Tagged();
    if (IsJSArrayMap(*map.object())) {
      DCHECK(Name::Equals(isolate(), isolate()->factory()->length_string(),
                          name.object()));
      // The JSArray::length property is a smi in the range
      // [0, FixedDoubleArray::kMaxLength] in case of fast double
      // elements, a smi in the range [0, FixedArray::kMaxLength]
      // in case of other fast elements, and [0, kMaxUInt32] in
      // case of other arrays.
      if (IsDoubleElementsKind(map.elements_kind())) {
        field_type = type_cache_->kFixedDoubleArrayLengthType;
        field_representation = Representation::Smi();
      } else if (IsFastElementsKind(map.elements_kind())) {
        field_type = type_cache_->kFixedArrayLengthType;
        field_representation = Representation::Smi();
      } else {
        field_type = type_cache_->kJSArrayLengthType;
      }
    }
    // Special fields are always mutable.
    return PropertyAccessInfo::DataField(broker(), zone(), map, {{}, zone()},
                                         field_index, field_representation,
                                         field_type, map, {}, {}, {});
  }
  return Invalid();
}

PropertyAccessInfo AccessInfoFactory::LookupSpecialFieldAccessorInHolder(
    MapRef receiver_map, NameRef name, JSObjectRef holder,
    PropertyDetails details, InternalIndex index) const {
  // Check whether we're accessing the `length` property in a TypedArray
  // prototype.
  if (v8_flags.typed_array_length_loading &&
      IsJSTypedArrayMap(*receiver_map.object()) &&
      !IsJSDetachedTypedArrayMap(*receiver_map.object()) &&
      !IsRabGsabTypedArrayElementsKind(receiver_map.elements_kind()) &&
      Name::Equals(isolate(), name.object(),
                   isolate()->factory()->length_string()) &&
      details.location() == PropertyLocation::kDescriptor) {
    Tagged<DescriptorArray> descriptors =
        holder.map(broker_).object()->instance_descriptors(kAcquireLoad);
    SLOW_DCHECK(index == descriptors->Search(*name.object(),
                                             *holder.map(broker_).object(),
                                             true));
    Tagged<Object> maybe_accessors = descriptors->GetStrongValue(index);
    if (IsAccessorPair(maybe_accessors)) {
      Tagged<AccessorPair> accessors = Cast<AccessorPair>(maybe_accessors);
      Tagged<Object> maybe_getter = accessors->getter(kAcquireLoad);
      if (Tagged<JSFunction> getter;
          TryCast<JSFunction>(maybe_getter, &getter)) {
        if (getter->shared()->HasBuiltinId() &&
            getter->shared()->builtin_id() ==
                Builtin::kTypedArrayPrototypeLength) {
          if (v8_flags.turbolev ||
              broker_->dependencies()
                  ->DependOnArrayBufferDetachingProtector()) {
            // Maglev and Turbolev will add the ArrayBufferDetachingProtector
            // dependency themselves and handle the case where they cannot do
            // so. Turbofan doesn't.
            dependencies()->DependOnStablePrototypeChain(
                receiver_map, kStartAtPrototype, holder);
            return PropertyAccessInfo::TypedArrayLength(zone(), receiver_map);
          }
        }
      }
    }
  }

  return Invalid();
}

PropertyAccessInfo AccessInfoFactory::LookupTransition(
    MapRef map, NameRef name, OptionalJSObjectRef holder,
    PropertyAttributes attrs) const {
  // Check if the {map} has a data transition with the given {name}.
  Tagged<Map> transition =
      TransitionsAccessor(isolate(), *map.object(), true)
          .SearchTransition(*name.object(), PropertyKind::kData, attrs);
  if (transition.is_null()) return Invalid();
  OptionalMapRef maybe_transition_map = TryMakeRef(broker(), transition);
  if (!maybe_transition_map.has_value()) return Invalid();
  MapRef transition_map = maybe_transition_map.value();

  InternalIndex const number = transition_map.object()->LastAdded();
  DirectHandle<DescriptorArray> descriptors =
      transition_map.instance_descriptors(broker()).object();
  PropertyDetails const details = descriptors->GetDetails(number);

  // Don't bother optimizing stores to read-only properties.
  if (details.IsReadOnly()) return Invalid();

  // TODO(bmeurer): Handle transition to data constant?
  if (details.location() != PropertyLocation::kField) return Invalid();

  Representation details_representation = details.representation();
  if (details_representation.IsNone()) return Invalid();

  FieldIndex field_index =
      FieldIndex::ForDetails(*transition_map.object(), details);
  Type field_type = Type::NonInternal();
  OptionalMapRef field_map;

  DCHECK_EQ(transition_map, transition_map.FindFieldOwner(broker(), number));

  ZoneVector<CompilationDependency const*> unrecorded_dependencies(zone());
  if (details_representation.IsSmi()) {
    field_type = Type::SignedSmall();
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            transition_map, transition_map, number, details_representation));
  } else if (details_representation.IsDouble()) {
    field_type = type_cache_->kFloat64;
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            transition_map, transition_map, number, details_representation));
  } else if (details_representation.IsHeapObject()) {
    // Extract the field type from the property details (make sure its
    // representation is TaggedPointer to reflect the heap object case).
    // TODO(jgruber,v8:7790): Use DescriptorArrayRef instead.
    Handle<FieldType> descriptors_field_type =
        broker()->CanonicalPersistentHandle(descriptors->GetFieldType(number));
    OptionalObjectRef descriptors_field_type_ref =
        TryMakeRef<Object>(broker(), descriptors_field_type);
    if (!descriptors_field_type_ref.has_value()) return Invalid();

    if (IsNone(*descriptors_field_type)) {
      // Cleared field-types are pre-monomorphic states. The field type was
      // garbge collected and we need to record an updated type.
      static_assert(FieldType::kFieldTypesCanBeClearedOnGC);
      return Invalid();
    }
    unrecorded_dependencies.push_back(
        dependencies()->FieldRepresentationDependencyOffTheRecord(
            transition_map, transition_map, number, details_representation));
    if (IsClass(*descriptors_field_type)) {
      unrecorded_dependencies.push_back(
          dependencies()->FieldTypeDependencyOffTheRecord(
              transition_map, transition_map, number,
              *descriptors_field_type_ref));
      // Remember the field map, and try to infer a useful type.
      OptionalMapRef maybe_field_map =
          TryMakeRef(broker(), FieldType::AsClass(*descriptors_field_type));
      if (!maybe_field_map.has_value()) return Invalid();
      field_map = maybe_field_map;
      // field_type can only be inferred from field_map if it is stable and we
      // add a stability dependency. This happens on use in the access builder.
    }
  }

  unrecorded_dependencies.push_back(
      dependencies()->TransitionDependencyOffTheRecord(transition_map));
  // Transitioning stores *may* store to const fields. The resulting
  // DataConstant access infos can be distinguished from later, i.e. redundant,
  // stores to the same constant field by the presence of a transition map.

  PropertyConstness constness =
      transition_map.GetPropertyDetails(broker_, number).constness();
  switch (constness) {
    case PropertyConstness::kConst:
      if (auto constness_dep =
              dependencies()->FieldConstnessDependencyOffTheRecord(
                  transition_map, transition_map, number)) {
        unrecorded_dependencies.push_back(*constness_dep);
        return PropertyAccessInfo::FastDataConstant(
            zone(), map, std::move(unrecorded_dependencies), field_index,
            details_representation, field_type, transition_map, field_map,
            holder, transition_map);
      }
      return PropertyAccessInfo::Invalid(zone());
    case PropertyConstness::kMutable:
      return PropertyAccessInfo::DataField(
          broker(), zone(), map, std::move(unrecorded_dependencies),
          field_index, details_representation, field_type, transition_map,
          field_map, holder, transition_map);
  }
  UNREACHABLE();
}

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