Reland ^4 "[builtins] Port getting property from Proxy to CSA"

This is a reland of edc4ae14

With fixes for crbug.com/752846, crbug.com/752712, crbug.com/752850

Previously landed as: 47a97aa5 / 47113
Previously landed as: 15ef03cb / 47159
Previously landed as: e86c066b / 47235
Previously landed as: edc4ae14 / 47245

TBR=jkummerow@chromium.org, franzih@chromium.org, bmeurer@chromium.org,
jgruber@chromium.org, mstarzinger@chromium.org

Bug: v8:6559, v8:6557
Change-Id: I956486e90aab36ba95676bd4ec2febebed509fc1
Reviewed-on: https://chromium-review.googlesource.com/609781Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Franziska Hinkelmann <franzih@chromium.org>
Commit-Queue: Maya Lekova <mslekova@google.com>
Cr-Commit-Position: refs/heads/master@{#47299}

BUILD.gn

@@ -994,6 +994,8 @@ v8_source_set("v8_builtins_generators") {
     "src/builtins/builtins-promise-gen.cc",
     "src/builtins/builtins-promise-gen.h",
     "src/builtins/builtins-proxy-gen.cc",
+    "src/builtins/builtins-proxy-helpers-gen.cc",
+    "src/builtins/builtins-proxy-helpers-gen.h",
     "src/builtins/builtins-regexp-gen.cc",
     "src/builtins/builtins-regexp-gen.h",
     "src/builtins/builtins-sharedarraybuffer-gen.cc",

src/builtins/builtins-definitions.h

@@ -802,6 +802,7 @@ namespace internal {
   TFJ(ProxyConstructor, 0)                                                     \
   TFJ(ProxyConstructor_ConstructStub,                                          \
       SharedFunctionInfo::kDontAdaptArgumentsSentinel)                         \
+  TFS(ProxyGetProperty, kProxy, kName, kReceiverValue)                         \
                                                                                \
   /* Reflect */                                                                \
   ASM(ReflectApply)                                                            \

src/builtins/builtins-proxy-helpers-gen.cc

+// Copyright 2017 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/builtins/builtins-proxy-helpers-gen.h"
+#include "src/builtins/builtins-utils-gen.h"
+
+namespace v8 {
+namespace internal {
+TF_BUILTIN(ProxyGetProperty, ProxyAssembler) {
+  Node* context = Parameter(Descriptor::kContext);
+  Node* proxy = Parameter(Descriptor::kProxy);
+  Node* name = Parameter(Descriptor::kName);
+  Node* receiver = Parameter(Descriptor::kReceiverValue);
+
+  CSA_ASSERT(this, IsJSProxy(proxy));
+
+  // 1. Assert: IsPropertyKey(P) is true.
+  CSA_ASSERT(this, IsName(name));
+
+  Label throw_proxy_handler_revoked(this, Label::kDeferred),
+      trap_undefined(this), no_target_desc(this, Label::kDeferred),
+      trap_not_callable(this, Label::kDeferred);
+
+  // 2. Let handler be O.[[ProxyHandler]].
+  Node* handler = LoadObjectField(proxy, JSProxy::kHandlerOffset);
+
+  // 3. If handler is null, throw a TypeError exception.
+  GotoIf(IsNull(handler), &throw_proxy_handler_revoked);
+
+  // 4. Assert: Type(handler) is Object.
+  CSA_ASSERT(this, IsJSReceiver(handler));
+
+  // 5. Let target be O.[[ProxyTarget]].
+  Node* target = LoadObjectField(proxy, JSProxy::kTargetOffset);
+
+  // 6. Let trap be ? GetMethod(handler, "get").
+  // 7. If trap is undefined, then (see 7.a below).
+  Handle<Name> trap_name = factory()->get_string();
+  Node* trap = GetMethod(context, handler, trap_name, &trap_undefined);
+
+  GotoIf(TaggedIsSmi(trap), &trap_not_callable);
+  GotoIfNot(IsCallable(trap), &trap_not_callable);
+
+  // 8. Let trapResult be ? Call(trap, handler, « target, P, Receiver »).
+  Node* trap_result = CallJS(CodeFactory::Call(isolate()), context, trap,
+                             handler, target, name, receiver);
+  // 9. Let targetDesc be ? target.[[GetOwnProperty]](P).
+  Label return_result(this);
+  CheckGetTrapResult(context, target, proxy, name, trap_result, &return_result,
+                     &no_target_desc);
+
+  BIND(&return_result);
+  {
+    // 11. Return trapResult.
+    Return(trap_result);
+  }
+
+  BIND(&no_target_desc);
+  {
+    CSA_ASSERT(this, IsJSReceiver(target));
+    CallRuntime(Runtime::kCheckProxyGetTrapResult, context, name, target,
+                trap_result);
+    Return(trap_result);
+  }
+
+  BIND(&trap_undefined);
+  {
+    // 7.a. Return ? target.[[Get]](P, Receiver).
+    Return(CallRuntime(Runtime::kGetPropertyWithReceiver, context, target, name,
+                       receiver));
+  }
+
+  BIND(&throw_proxy_handler_revoked);
+  { ThrowTypeError(context, MessageTemplate::kProxyRevoked, "get"); }
+
+  BIND(&trap_not_callable);
+  {
+    ThrowTypeError(context, MessageTemplate::kPropertyNotFunction, trap,
+                   StringConstant("get"), receiver);
+  }
+}
+
+void ProxyAssembler::CheckGetTrapResult(Node* context, Node* target,
+                                        Node* proxy, Node* name,
+                                        Node* trap_result, Label* check_passed,
+                                        Label* if_bailout) {
+  Node* map = LoadMap(target);
+  VARIABLE(var_value, MachineRepresentation::kTagged);
+  VARIABLE(var_details, MachineRepresentation::kWord32);
+  VARIABLE(var_raw_value, MachineRepresentation::kTagged);
+
+  Label if_found_value(this, Label::kDeferred);
+
+  Node* instance_type = LoadInstanceType(target);
+  TryGetOwnProperty(context, proxy, target, map, instance_type, name,
+                    &if_found_value, &var_value, &var_details, &var_raw_value,
+                    check_passed, if_bailout);
+
+  BIND(&if_found_value);
+  {
+    Label throw_non_configurable_data(this, Label::kDeferred),
+        throw_non_configurable_accessor(this, Label::kDeferred),
+        check_accessor(this), check_data(this);
+
+    // 10. If targetDesc is not undefined and targetDesc.[[Configurable]] is
+    // false, then:
+    GotoIfNot(IsSetWord32(var_details.value(),
+                          PropertyDetails::kAttributesDontDeleteMask),
+              check_passed);
+
+    // 10.a. If IsDataDescriptor(targetDesc) is true and
+    // targetDesc.[[Writable]] is false, then:
+    BranchIfAccessorPair(var_raw_value.value(), &check_accessor, &check_data);
+
+    BIND(&check_data);
+    {
+      Node* read_only = IsSetWord32(var_details.value(),
+                                    PropertyDetails::kAttributesReadOnlyMask);
+      GotoIfNot(read_only, check_passed);
+
+      // 10.a.i. If SameValue(trapResult, targetDesc.[[Value]]) is false,
+      // throw a TypeError exception.
+      GotoIfNot(SameValue(trap_result, var_value.value()),
+                &throw_non_configurable_data);
+      Goto(check_passed);
+    }
+
+    BIND(&check_accessor);
+    {
+      // 10.b. If IsAccessorDescriptor(targetDesc) is true and
+      // targetDesc.[[Get]] is undefined, then:
+      Node* accessor_pair = var_raw_value.value();
+      Node* getter =
+          LoadObjectField(accessor_pair, AccessorPair::kGetterOffset);
+
+      // Here we check for null as well because if the getter was never
+      // defined it's set as null.
+      GotoIfNot(Word32Or(IsUndefined(getter), IsNull(getter)), check_passed);
+
+      // 10.b.i. If trapResult is not undefined, throw a TypeError exception.
+      GotoIfNot(IsUndefined(trap_result), &throw_non_configurable_accessor);
+      Goto(check_passed);
+    }
+
+    BIND(&throw_non_configurable_data);
+    {
+      ThrowTypeError(context, MessageTemplate::kProxyGetNonConfigurableData,
+                     name, var_value.value(), trap_result);
+    }
+
+    BIND(&throw_non_configurable_accessor);
+    {
+      ThrowTypeError(context, MessageTemplate::kProxyGetNonConfigurableAccessor,
+                     name, trap_result);
+    }
+  }
+}
+}  // namespace internal
+}  // namespace v8

src/builtins/builtins-proxy-helpers-gen.h

+// Copyright 2017 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_BUILTINS_BUILTINS_PROXY_HELPERS_GEN_H_
+#define V8_BUILTINS_BUILTINS_PROXY_HELPERS_GEN_H_
+
+#include "src/code-stub-assembler.h"
+
+namespace v8 {
+namespace internal {
+using compiler::Node;
+
+class ProxyAssembler : public CodeStubAssembler {
+ public:
+  explicit ProxyAssembler(compiler::CodeAssemblerState* state)
+      : CodeStubAssembler(state) {}
+
+  void BranchIfAccessorPair(Node* value, Label* if_accessor_pair,
+                            Label* if_not_accessor_pair) {
+    GotoIf(TaggedIsSmi(value), if_not_accessor_pair);
+    Branch(IsAccessorPair(value), if_accessor_pair, if_not_accessor_pair);
+  }
+
+  // ES6 section 9.5.8 [[Get]] ( P, Receiver )
+  Node* ProxyGetProperty(Node* context, Node* proxy, Node* name,
+                         Node* receiver);
+
+ protected:
+  void CheckGetTrapResult(Node* context, Node* target, Node* proxy, Node* name,
+                          Node* trap_result, Label* if_not_found,
+                          Label* if_bailout);
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_BUILTINS_BUILTINS_PROXY_HELPERS_GEN_H_

src/code-stub-assembler.cc

@@ -6036,6 +6036,16 @@ void CodeStubAssembler::TryGetOwnProperty(
     Node* context, Node* receiver, Node* object, Node* map, Node* instance_type,
     Node* unique_name, Label* if_found_value, Variable* var_value,
     Label* if_not_found, Label* if_bailout) {
+  TryGetOwnProperty(context, receiver, object, map, instance_type, unique_name,
+                    if_found_value, var_value, nullptr, nullptr, if_not_found,
+                    if_bailout);
+}
+
+void CodeStubAssembler::TryGetOwnProperty(
+    Node* context, Node* receiver, Node* object, Node* map, Node* instance_type,
+    Node* unique_name, Label* if_found_value, Variable* var_value,
+    Variable* var_details, Variable* var_raw_value, Label* if_not_found,
+    Label* if_bailout) {
   DCHECK_EQ(MachineRepresentation::kTagged, var_value->rep());
   Comment("TryGetOwnProperty");
 
@@ -6044,8 +6054,11 @@ void CodeStubAssembler::TryGetOwnProperty(
 
   Label if_found_fast(this), if_found_dict(this), if_found_global(this);
 
-  VARIABLE(var_details, MachineRepresentation::kWord32);
-  Variable* vars[] = {var_value, &var_details};
+  VARIABLE(local_var_details, MachineRepresentation::kWord32);
+  if (!var_details) {
+    var_details = &local_var_details;
+  }
+  Variable* vars[] = {var_value, var_details};
   Label if_found(this, 2, vars);
 
   TryLookupProperty(object, map, instance_type, unique_name, &if_found_fast,
@@ -6057,14 +6070,14 @@ void CodeStubAssembler::TryGetOwnProperty(
     Node* name_index = var_entry.value();
 
     LoadPropertyFromFastObject(object, map, descriptors, name_index,
-                               &var_details, var_value);
+                               var_details, var_value);
     Goto(&if_found);
   }
   BIND(&if_found_dict);
   {
     Node* dictionary = var_meta_storage.value();
     Node* entry = var_entry.value();
-    LoadPropertyFromNameDictionary(dictionary, entry, &var_details, var_value);
+    LoadPropertyFromNameDictionary(dictionary, entry, var_details, var_value);
     Goto(&if_found);
   }
   BIND(&if_found_global);
@@ -6072,14 +6085,17 @@ void CodeStubAssembler::TryGetOwnProperty(
     Node* dictionary = var_meta_storage.value();
     Node* entry = var_entry.value();
 
-    LoadPropertyFromGlobalDictionary(dictionary, entry, &var_details, var_value,
+    LoadPropertyFromGlobalDictionary(dictionary, entry, var_details, var_value,
                                      if_not_found);
     Goto(&if_found);
   }
   // Here we have details and value which could be an accessor.
   BIND(&if_found);
   {
-    Node* value = CallGetterIfAccessor(var_value->value(), var_details.value(),
+    if (var_raw_value) {
+      var_raw_value->Bind(var_value->value());
+    }
+    Node* value = CallGetterIfAccessor(var_value->value(), var_details->value(),
                                        context, receiver, if_bailout);
     var_value->Bind(value);
     Goto(if_found_value);

src/code-stub-assembler.h

@@ -1304,6 +1304,11 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
                          Node* instance_type, Node* unique_name,
                          Label* if_found, Variable* var_value,
                          Label* if_not_found, Label* if_bailout);
+  void TryGetOwnProperty(Node* context, Node* receiver, Node* object, Node* map,
+                         Node* instance_type, Node* unique_name,
+                         Label* if_found, Variable* var_value,
+                         Variable* var_details, Variable* var_raw_value,
+                         Label* if_not_found, Label* if_bailout);
 
   Node* GetProperty(Node* context, Node* receiver, Handle<Name> name) {
     return GetProperty(context, receiver, HeapConstant(name));

src/ic/accessor-assembler.cc

@@ -261,7 +261,8 @@ void AccessorAssembler::HandleLoadICSmiHandlerCase(
 
   Label constant(this), field(this), normal(this, Label::kDeferred),
       interceptor(this, Label::kDeferred), nonexistent(this),
-      accessor(this, Label::kDeferred), global(this, Label::kDeferred);
+      accessor(this, Label::kDeferred), proxy(this, Label::kDeferred),
+      global(this, Label::kDeferred);
   GotoIf(WordEqual(handler_kind, IntPtrConstant(LoadHandler::kField)), &field);
 
   GotoIf(WordEqual(handler_kind, IntPtrConstant(LoadHandler::kConstant)),
@@ -276,6 +277,8 @@ void AccessorAssembler::HandleLoadICSmiHandlerCase(
   GotoIf(WordEqual(handler_kind, IntPtrConstant(LoadHandler::kAccessor)),
          &accessor);
 
+  GotoIf(WordEqual(handler_kind, IntPtrConstant(LoadHandler::kProxy)), &proxy);
+
   Branch(WordEqual(handler_kind, IntPtrConstant(LoadHandler::kGlobal)), &global,
          &interceptor);
 
@@ -362,6 +365,13 @@ void AccessorAssembler::HandleLoadICSmiHandlerCase(
     exit_point->Return(CallJS(callable, p->context, getter, p->receiver));
   }
 
+  BIND(&proxy);
+  {
+    exit_point->ReturnCallStub(
+        Builtins::CallableFor(isolate(), Builtins::kProxyGetProperty),
+        p->context, holder, p->name, p->receiver);
+  }
+
   BIND(&global);
   {
     CSA_ASSERT(this, IsPropertyCell(holder));
@@ -1471,15 +1481,15 @@ void AccessorAssembler::GenericPropertyLoad(Node* receiver, Node* receiver_map,
 
   Comment("key is unique name");
   Label if_found_on_receiver(this), if_property_dictionary(this),
-      lookup_prototype_chain(this);
+      lookup_prototype_chain(this), special_receiver(this);
   VARIABLE(var_details, MachineRepresentation::kWord32);
   VARIABLE(var_value, MachineRepresentation::kTagged);
 
   // Receivers requiring non-standard accesses (interceptors, access
-  // checks, strings and string wrappers, proxies) are handled in the runtime.
+  // checks, strings and string wrappers) are handled in the runtime.
   GotoIf(Int32LessThanOrEqual(instance_type,
                               Int32Constant(LAST_SPECIAL_RECEIVER_TYPE)),
-         slow);
+         &special_receiver);
 
   // Check if the receiver has fast or slow properties.
   Node* bitfield3 = LoadMapBitField3(receiver_map);
@@ -1600,6 +1610,16 @@ void AccessorAssembler::GenericPropertyLoad(Node* receiver, Node* receiver_map,
     BIND(&return_undefined);
     Return(UndefinedConstant());
   }
+
+  BIND(&special_receiver);
+  {
+    GotoIfNot(Word32Equal(instance_type, Int32Constant(JS_PROXY_TYPE)), slow);
+
+    direct_exit.ReturnCallStub(
+        Builtins::CallableFor(isolate(), Builtins::kProxyGetProperty),
+        p->context, receiver /*holder is the same as receiver*/, p->name,
+        receiver);
+  }
 }
 
 //////////////////// Stub cache access helpers.

src/ic/handler-configuration-inl.h

@@ -53,6 +53,11 @@ Handle<Smi> LoadHandler::LoadAccessor(Isolate* isolate, int descriptor) {
   return handle(Smi::FromInt(config), isolate);
 }
 
+Handle<Smi> LoadHandler::LoadProxy(Isolate* isolate) {
+  int config = KindBits::encode(kProxy);
+  return handle(Smi::FromInt(config), isolate);
+}
+
 Handle<Smi> LoadHandler::LoadApiGetter(Isolate* isolate, int descriptor) {
   int config = KindBits::encode(kConstant) | IsAccessorInfoBits::encode(true) |
                DescriptorBits::encode(descriptor);

src/ic/handler-configuration.h

@@ -25,9 +25,10 @@ class LoadHandler {
     kConstant,
     kAccessor,
     kInterceptor,
+    kProxy,
     kNonExistent
   };
-  class KindBits : public BitField<Kind, 0, 3> {};
+  class KindBits : public BitField<Kind, 0, 4> {};
 
   // Defines whether access rights check should be done on receiver object.
   // Applicable to named property kinds only when loading value from prototype
@@ -113,6 +114,9 @@ class LoadHandler {
   // Creates a Smi-handler for calling a getter on a fast object.
   static inline Handle<Smi> LoadAccessor(Isolate* isolate, int descriptor);
 
+  // Creates a Smi-handler for calling a getter on a proxy.
+  static inline Handle<Smi> LoadProxy(Isolate* isolate);
+
   // Creates a Smi-handler for loading an Api getter property from fast object.
   static inline Handle<Smi> LoadApiGetter(Isolate* isolate, int descriptor);
 

src/ic/ic.cc

@@ -773,7 +773,7 @@ namespace {
 
 template <bool fill_array = true>
 int InitPrototypeChecks(Isolate* isolate, Handle<Map> receiver_map,
-                        Handle<JSObject> holder, Handle<Name> name,
+                        Handle<JSReceiver> holder, Handle<Name> name,
                         Handle<FixedArray> array, int first_index) {
   if (!holder.is_null() && holder->map() == *receiver_map) return 0;
 
@@ -814,7 +814,8 @@ int InitPrototypeChecks(Isolate* isolate, Handle<Map> receiver_map,
                                           : PrototypeIterator::END_AT_NULL;
   for (PrototypeIterator iter(receiver_map, end); !iter.IsAtEnd();
        iter.Advance()) {
-    Handle<JSObject> current = PrototypeIterator::GetCurrent<JSObject>(iter);
+    Handle<JSReceiver> current =
+        PrototypeIterator::GetCurrent<JSReceiver>(iter);
     if (holder.is_identical_to(current)) break;
     Handle<Map> current_map(current->map(), isolate);
 
@@ -851,7 +852,7 @@ int InitPrototypeChecks(Isolate* isolate, Handle<Map> receiver_map,
 // Returns -1 if the handler has to be compiled or the number of prototype
 // checks otherwise.
 int GetPrototypeCheckCount(Isolate* isolate, Handle<Map> receiver_map,
-                           Handle<JSObject> holder, Handle<Name> name) {
+                           Handle<JSReceiver> holder, Handle<Name> name) {
   return InitPrototypeChecks<false>(isolate, receiver_map, holder, name,
                                     Handle<FixedArray>(), 0);
 }
@@ -861,7 +862,7 @@ enum class HolderCellRequest {
   kHolder,
 };
 
-Handle<WeakCell> HolderCell(Isolate* isolate, Handle<JSObject> holder,
+Handle<WeakCell> HolderCell(Isolate* isolate, Handle<JSReceiver> holder,
                             Handle<Name> name, HolderCellRequest request) {
   if (request == HolderCellRequest::kGlobalPropertyCell) {
     DCHECK(holder->IsJSGlobalObject());
@@ -878,7 +879,7 @@ Handle<WeakCell> HolderCell(Isolate* isolate, Handle<JSObject> holder,
 }  // namespace
 
 Handle<Object> LoadIC::LoadFromPrototype(Handle<Map> receiver_map,
-                                         Handle<JSObject> holder,
+                                         Handle<JSReceiver> holder,
                                          Handle<Name> name,
                                          Handle<Smi> smi_handler) {
   int checks_count =
@@ -926,7 +927,7 @@ Handle<Object> LoadIC::LoadFromPrototype(Handle<Map> receiver_map,
 Handle<Object> LoadIC::LoadFullChain(Handle<Map> receiver_map,
                                      Handle<Object> holder, Handle<Name> name,
                                      Handle<Smi> smi_handler) {
-  Handle<JSObject> end;  // null handle
+  Handle<JSReceiver> end;  // null handle
   int checks_count = GetPrototypeCheckCount(isolate(), receiver_map, end, name);
   DCHECK_LE(0, checks_count);
 
@@ -977,8 +978,7 @@ void LoadIC::UpdateCaches(LookupIterator* lookup) {
   }
 
   Handle<Object> code;
-  if (lookup->state() == LookupIterator::JSPROXY ||
-      lookup->state() == LookupIterator::ACCESS_CHECK) {
+  if (lookup->state() == LookupIterator::ACCESS_CHECK) {
     code = slow_stub();
   } else if (!lookup->IsFound()) {
     TRACE_HANDLER_STATS(isolate(), LoadIC_LoadNonexistentDH);
@@ -1102,8 +1102,13 @@ Handle<Object> LoadIC::GetMapIndependentHandler(LookupIterator* lookup) {
   }
 
   Handle<Map> map = receiver_map();
-  Handle<JSObject> holder = lookup->GetHolder<JSObject>();
-  bool receiver_is_holder = receiver.is_identical_to(holder);
+  Handle<JSObject> holder;
+  bool receiver_is_holder;
+  if (lookup->state() != LookupIterator::JSPROXY) {
+    holder = lookup->GetHolder<JSObject>();
+    receiver_is_holder = receiver.is_identical_to(holder);
+  }
+
   switch (lookup->state()) {
     case LookupIterator::INTERCEPTOR: {
       Handle<Smi> smi_handler = LoadHandler::LoadInterceptor(isolate());
@@ -1264,8 +1269,16 @@ Handle<Object> LoadIC::GetMapIndependentHandler(LookupIterator* lookup) {
     case LookupIterator::INTEGER_INDEXED_EXOTIC:
       TRACE_HANDLER_STATS(isolate(), LoadIC_LoadIntegerIndexedExoticDH);
       return LoadHandler::LoadNonExistent(isolate());
+    case LookupIterator::JSPROXY: {
+      Handle<JSProxy> holder_proxy = lookup->GetHolder<JSProxy>();
+      bool receiver_is_holder_proxy = receiver.is_identical_to(holder_proxy);
+      Handle<Smi> smi_handler = LoadHandler::LoadProxy(isolate());
+      if (receiver_is_holder_proxy) {
+        return smi_handler;
+      }
+      return LoadFromPrototype(map, holder_proxy, lookup->name(), smi_handler);
+    }
     case LookupIterator::ACCESS_CHECK:
-    case LookupIterator::JSPROXY:
     case LookupIterator::NOT_FOUND:
     case LookupIterator::TRANSITION:
       UNREACHABLE();
@@ -1722,6 +1735,7 @@ Handle<Object> StoreIC::StoreTransition(Handle<Map> receiver_map,
 
   int checks_count =
       GetPrototypeCheckCount(isolate(), receiver_map, holder, name);
+
   DCHECK_LE(0, checks_count);
   DCHECK(!receiver_map->IsJSGlobalObjectMap());
 

src/ic/ic.h

@@ -283,7 +283,7 @@ class LoadIC : public IC {
   // by given Smi-handler that encoded a load from the holder.
   // Can be used only if GetPrototypeCheckCount() returns non negative value.
   Handle<Object> LoadFromPrototype(Handle<Map> receiver_map,
-                                   Handle<JSObject> holder, Handle<Name> name,
+                                   Handle<JSReceiver> holder, Handle<Name> name,
                                    Handle<Smi> smi_handler);
 
   // Creates a data handler that represents a load of a non-existent property.

src/objects.cc

@@ -1105,6 +1105,22 @@ MaybeHandle<Object> JSProxy::GetProperty(Isolate* isolate,
   ASSIGN_RETURN_ON_EXCEPTION(
       isolate, trap_result,
       Execution::Call(isolate, trap, handler, arraysize(args), args), Object);
+
+  MaybeHandle<Object> result =
+      JSProxy::CheckGetTrapResult(isolate, name, target, trap_result);
+  if (result.is_null()) {
+    return result;
+  }
+
+  // 11. Return trap_result
+  return trap_result;
+}
+
+// static
+MaybeHandle<Object> JSProxy::CheckGetTrapResult(Isolate* isolate,
+                                                Handle<Name> name,
+                                                Handle<JSReceiver> target,
+                                                Handle<Object> trap_result) {
   // 9. Let targetDesc be ? target.[[GetOwnProperty]](P).
   PropertyDescriptor target_desc;
   Maybe<bool> target_found =
@@ -1141,8 +1157,7 @@ MaybeHandle<Object> JSProxy::GetProperty(Isolate* isolate,
           Object);
     }
   }
-  // 11. Return trap_result
-  return trap_result;
+  return isolate->factory()->undefined_value();
 }
 
 
@@ -12605,7 +12620,12 @@ Handle<Cell> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
   } else {
     maybe_prototype =
         handle(map->GetPrototypeChainRootMap(isolate)->prototype(), isolate);
-    if (!maybe_prototype->IsJSObject()) return Handle<Cell>::null();
+    if (!maybe_prototype->IsJSReceiver()) return Handle<Cell>::null();
+  }
+  if (maybe_prototype->IsJSProxy()) {
+    Handle<Cell> cell = isolate->factory()->NewCell(
+        handle(Smi::FromInt(Map::kPrototypeChainValid), isolate));
+    return cell;
   }
   Handle<JSObject> prototype = Handle<JSObject>::cast(maybe_prototype);
   // Ensure the prototype is registered with its own prototypes so its cell
@@ -12630,11 +12650,16 @@ Handle<Cell> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
 }
 
 // static
-Handle<WeakCell> Map::GetOrCreatePrototypeWeakCell(Handle<JSObject> prototype,
+Handle<WeakCell> Map::GetOrCreatePrototypeWeakCell(Handle<JSReceiver> prototype,
                                                    Isolate* isolate) {
   DCHECK(!prototype.is_null());
+  if (prototype->IsJSProxy()) {
+    Handle<WeakCell> cell = isolate->factory()->NewWeakCell(prototype);
+    return cell;
+  }
+
   Handle<PrototypeInfo> proto_info =
-      GetOrCreatePrototypeInfo(prototype, isolate);
+      GetOrCreatePrototypeInfo(Handle<JSObject>::cast(prototype), isolate);
   Object* maybe_cell = proto_info->weak_cell();
   // Return existing cell if it's already created.
   if (maybe_cell->IsWeakCell()) {

src/objects.h

@@ -6295,6 +6295,11 @@ class JSProxy: public JSReceiver {
       Isolate* isolate, Handle<JSProxy> proxy, Handle<Name> name,
       Handle<Object> receiver, bool* was_found);
 
+  static MaybeHandle<Object> CheckGetTrapResult(Isolate* isolate,
+                                                Handle<Name> name,
+                                                Handle<JSReceiver> target,
+                                                Handle<Object> trap_result);
+
   // ES6 9.5.9
   MUST_USE_RESULT static Maybe<bool> SetProperty(Handle<JSProxy> proxy,
                                                  Handle<Name> name,

src/objects/map.h

@@ -320,7 +320,7 @@ class Map : public HeapObject {
   // Returns a WeakCell object containing given prototype. The cell is cached
   // in PrototypeInfo which is created lazily.
   static Handle<WeakCell> GetOrCreatePrototypeWeakCell(
-      Handle<JSObject> prototype, Isolate* isolate);
+      Handle<JSReceiver> prototype, Isolate* isolate);
 
   Map* FindRootMap() const;
   Map* FindFieldOwner(int descriptor) const;

src/runtime/runtime-proxy.cc

@@ -46,5 +46,30 @@ RUNTIME_FUNCTION(Runtime_JSProxyRevoke) {
   return isolate->heap()->undefined_value();
 }
 
+RUNTIME_FUNCTION(Runtime_GetPropertyWithReceiver) {
+  HandleScope scope(isolate);
+
+  DCHECK_EQ(3, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, holder, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 2);
+
+  LookupIterator it =
+      LookupIterator::PropertyOrElement(isolate, receiver, name, holder);
+  RETURN_RESULT_OR_FAILURE(isolate, Object::GetProperty(&it));
+}
+
+RUNTIME_FUNCTION(Runtime_CheckProxyGetTrapResult) {
+  HandleScope scope(isolate);
+
+  DCHECK_EQ(3, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 0);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, target, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, trap_result, 2);
+
+  RETURN_RESULT_OR_FAILURE(
+      isolate, JSProxy::CheckGetTrapResult(isolate, name, target, trap_result));
+}
+
 }  // namespace internal
 }  // namespace v8

src/runtime/runtime.h

@@ -461,11 +461,13 @@ namespace internal {
   F(PromiseStatus, 1, 1)                    \
   F(ReportPromiseReject, 2, 1)
 
-#define FOR_EACH_INTRINSIC_PROXY(F)     \
-  F(IsJSProxy, 1, 1)                    \
-  F(JSProxyGetTarget, 1, 1)             \
-  F(JSProxyGetHandler, 1, 1)            \
-  F(JSProxyRevoke, 1, 1)
+#define FOR_EACH_INTRINSIC_PROXY(F) \
+  F(IsJSProxy, 1, 1)                \
+  F(JSProxyGetTarget, 1, 1)         \
+  F(JSProxyGetHandler, 1, 1)        \
+  F(JSProxyRevoke, 1, 1)            \
+  F(GetPropertyWithReceiver, 2, 1)  \
+  F(CheckProxyGetTrapResult, 2, 1)
 
 #define FOR_EACH_INTRINSIC_REGEXP(F)                \
   F(IsRegExp, 1, 1)                                 \

src/v8.gyp

@@ -207,6 +207,8 @@
         'builtins/builtins-promise-gen.cc',
         'builtins/builtins-promise-gen.h',
         'builtins/builtins-proxy-gen.cc',
+        'builtins/builtins-proxy-helpers-gen.cc',
+        'builtins/builtins-proxy-helpers-gen.h',
         'builtins/builtins-regexp-gen.cc',
         'builtins/builtins-regexp-gen.h',
         'builtins/builtins-sharedarraybuffer-gen.cc',

test/mjsunit/es6/proxies-get.js

@@ -35,6 +35,12 @@
   assertThrows("proxy.property", Error);
 })();
 
+(function testThrowOnTrapNotCallable() {
+  var handler = new Proxy({}, {get: 'not_callable' });
+  var proxy = new Proxy({}, handler);
+  assertThrows("proxy.property", Error);
+})();
+
 (function testFallback() {
   var target = {property:"value"};
   var proxy = new Proxy(target, {});
@@ -125,3 +131,83 @@
     "[[Get]](iterator, next)"
   ], log);
 })();
+
+(function testGetterWithSideEffect() {
+  var obj = {
+    key: 0
+  }
+  assertEquals(obj.key, 0);
+  var p = new Proxy(obj, {});
+  var q = new Proxy(p, {
+    get(target, name) {
+      if (name != 'key') return Reflect.get(target, name);
+      target.key++;
+      return target.key;
+    }
+  });
+
+  assertEquals(0, p.key);
+  // Assert the trap is not called twice.
+  assertEquals(1, q.key);
+})();
+
+(function testReceiverWithTrap() {
+  var obj = {};
+  var p = new Proxy(obj, {
+    get(target, name, receiver) {
+      if (name != 'key') return Reflect.get(target, name);
+
+      assertSame(target, obj);
+      assertSame(receiver, p);
+      return 42;
+    }
+  });
+  assertEquals(42, p.key);
+})();
+
+(function testReceiverWithoutTrap() {
+  var obj = {
+    get prop() {
+      assertSame(this, p);
+      return 42;
+    }
+  };
+  var p = new Proxy(obj, {});
+  assertEquals(42, p.prop);
+})();
+
+(function testGetPropertyDetailsBailout() {
+  var obj = {
+  }
+  var p = new Proxy(obj, {
+    getOwnPropertyDescriptor() {
+      throw new Error('Error from proxy getOwnPropertyDescriptor trap');
+    }
+  });
+  var q = new Proxy(p, {
+    get(target, name) {
+      return 42;
+    }
+  });
+  assertThrows(function(){ q.prop }, Error,
+    'Error from proxy getOwnPropertyDescriptor trap');
+})();
+
+
+(function testGetPropertyDetailsBailout2() {
+  var obj = {};
+  Object.defineProperty(obj, 'prop', {
+    value: 53,
+    configurable: false
+  });
+  var p = new Proxy(obj, {});
+  var q = new Proxy(p, {
+    get(target, name) {
+      return 42;
+    }
+  });
+  assertThrows(function(){ q.prop }, TypeError,
+    "'get' on proxy: property 'prop' is a read-only and non-configurable data" +
+    " property on the proxy target but the proxy did not return its actual" +
+    " value (expected '53' but got '42')");
+})();

test/mjsunit/regress/regress-crbug-752712.js

+// Copyright 2017 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.
+
+// Flags: --allow-natives-syntax
+
+// Proxy get trap doesn't fail when the value returned by it
+// is a number.
+
+var number = 1;
+
+(function testFailingInvariant() {
+  var obj = {};
+  var handler = {
+    get: function() {}
+  };
+  var proxy = new Proxy(obj, handler);
+  Object.defineProperty(handler, 'get', {
+    get: function() {
+      return number;
+    }
+  });
+  assertThrows(function(){ proxy.property; }, TypeError);
+})();

test/mjsunit/regress/regress-crbug-752846.js

+// Copyright 2017 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.
+
+// Flags: --allow-natives-syntax
+
+// Check that the receiver of Runtime_GetPropertyWithReceiver can be
+// a plain JS value.
+
+var values = [
+  10,
+  false,
+  "test"
+];
+
+for (let val of values) {
+  var proto = Object.getPrototypeOf(val);
+
+  var proxy = new Proxy({}, {});
+  Object.setPrototypeOf(proto, proxy);
+}