Cleanup: Remove unnecessary ContextExtension wrapper

Bug: v8:7066
Change-Id: Icfcb40b2048997c158fba5f3e250145bed4ca1e3
Reviewed-on: https://chromium-review.googlesource.com/1042386
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52981}

src/compiler/access-builder.cc

@@ -851,25 +851,6 @@ FieldAccess AccessBuilder::ForContextSlot(size_t index) {
   return access;
 }
 
-// static
-FieldAccess AccessBuilder::ForContextExtensionScopeInfo() {
-  FieldAccess access = {
-      kTaggedBase,           ContextExtension::kScopeInfoOffset,
-      Handle<Name>(),        MaybeHandle<Map>(),
-      Type::OtherInternal(), MachineType::AnyTagged(),
-      kFullWriteBarrier};
-  return access;
-}
-
-// static
-FieldAccess AccessBuilder::ForContextExtensionExtension() {
-  FieldAccess access = {kTaggedBase,      ContextExtension::kExtensionOffset,
-                        Handle<Name>(),   MaybeHandle<Map>(),
-                        Type::Any(),      MachineType::AnyTagged(),
-                        kFullWriteBarrier};
-  return access;
-}
-
 // static
 ElementAccess AccessBuilder::ForFixedArrayElement() {
   ElementAccess access = {kTaggedBase, FixedArray::kHeaderSize, Type::Any(),

src/compiler/access-builder.h

@@ -273,10 +273,6 @@ class V8_EXPORT_PRIVATE AccessBuilder final
   // Provides access to Context slots.
   static FieldAccess ForContextSlot(size_t index);
 
-  // Provides access to ContextExtension fields.
-  static FieldAccess ForContextExtensionScopeInfo();
-  static FieldAccess ForContextExtensionExtension();
-
   // Provides access to FixedArray elements.
   static ElementAccess ForFixedArrayElement();
   static ElementAccess ForFixedArrayElement(

src/compiler/js-create-lowering.cc

@@ -1330,19 +1330,12 @@ Reduction JSCreateLowering::ReduceJSCreateFunctionContext(Node* node) {
 Reduction JSCreateLowering::ReduceJSCreateWithContext(Node* node) {
   DCHECK_EQ(IrOpcode::kJSCreateWithContext, node->opcode());
   Handle<ScopeInfo> scope_info = ScopeInfoOf(node->op());
-  Node* object = NodeProperties::GetValueInput(node, 0);
+  Node* extension = NodeProperties::GetValueInput(node, 0);
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
   Node* context = NodeProperties::GetContextInput(node);
 
-  AllocationBuilder aa(jsgraph(), effect, control);
-  aa.Allocate(ContextExtension::kSize);
-  aa.Store(AccessBuilder::ForMap(), factory()->context_extension_map());
-  aa.Store(AccessBuilder::ForContextExtensionScopeInfo(), scope_info);
-  aa.Store(AccessBuilder::ForContextExtensionExtension(), object);
-  Node* extension = aa.Finish();
-
-  AllocationBuilder a(jsgraph(), extension, control);
+  AllocationBuilder a(jsgraph(), effect, control);
   STATIC_ASSERT(Context::MIN_CONTEXT_SLOTS == 4);  // Ensure fully covered.
   a.AllocateContext(Context::MIN_CONTEXT_SLOTS, factory()->with_context_map());
   a.Store(AccessBuilder::ForContextSlot(Context::SCOPE_INFO_INDEX), scope_info);
@@ -1360,27 +1353,19 @@ Reduction JSCreateLowering::ReduceJSCreateCatchContext(Node* node) {
   const CreateCatchContextParameters& parameters =
       CreateCatchContextParametersOf(node->op());
   Handle<ScopeInfo> scope_info = parameters.scope_info();
+  Handle<String> catch_name = parameters.catch_name();
   Node* exception = NodeProperties::GetValueInput(node, 0);
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
   Node* context = NodeProperties::GetContextInput(node);
 
-  AllocationBuilder aa(jsgraph(), effect, control);
-  aa.Allocate(ContextExtension::kSize);
-  aa.Store(AccessBuilder::ForMap(), factory()->context_extension_map());
-  aa.Store(AccessBuilder::ForContextExtensionScopeInfo(),
-           parameters.scope_info());
-  aa.Store(AccessBuilder::ForContextExtensionExtension(),
-           parameters.catch_name());
-  Node* extension = aa.Finish();
-
-  AllocationBuilder a(jsgraph(), extension, control);
+  AllocationBuilder a(jsgraph(), effect, control);
   STATIC_ASSERT(Context::MIN_CONTEXT_SLOTS == 4);  // Ensure fully covered.
   a.AllocateContext(Context::MIN_CONTEXT_SLOTS + 1,
                     factory()->catch_context_map());
   a.Store(AccessBuilder::ForContextSlot(Context::SCOPE_INFO_INDEX), scope_info);
   a.Store(AccessBuilder::ForContextSlot(Context::PREVIOUS_INDEX), context);
-  a.Store(AccessBuilder::ForContextSlot(Context::EXTENSION_INDEX), extension);
+  a.Store(AccessBuilder::ForContextSlot(Context::EXTENSION_INDEX), catch_name);
   a.Store(AccessBuilder::ForContextSlot(Context::NATIVE_CONTEXT_INDEX),
           jsgraph()->HeapConstant(native_context()));
   a.Store(AccessBuilder::ForContextSlot(Context::THROWN_OBJECT_INDEX),

src/compiler/types.cc

@@ -327,7 +327,6 @@ Type::bitset BitsetType::Lub(i::Map* map) {
     case WASM_SHARED_MODULE_DATA_TYPE:
     case LOAD_HANDLER_TYPE:
     case STORE_HANDLER_TYPE:
-    case CONTEXT_EXTENSION_TYPE:
     case ASYNC_GENERATOR_REQUEST_TYPE:
     case CODE_DATA_CONTAINER_TYPE:
     case CALLBACK_TASK_TYPE:

src/contexts.cc

@@ -93,10 +93,6 @@ JSObject* Context::extension_object() {
          IsEvalContext());
   HeapObject* object = extension();
   if (object->IsTheHole(GetIsolate())) return nullptr;
-  if (IsBlockContext()) {
-    if (!object->IsContextExtension()) return nullptr;
-    object = JSObject::cast(ContextExtension::cast(object)->extension());
-  }
   DCHECK(object->IsJSContextExtensionObject() ||
          (IsNativeContext() && object->IsJSGlobalObject()));
   return JSObject::cast(object);
@@ -105,9 +101,7 @@ JSObject* Context::extension_object() {
 JSReceiver* Context::extension_receiver() {
   DCHECK(IsNativeContext() || IsWithContext() || IsEvalContext() ||
          IsFunctionContext() || IsBlockContext());
-  return IsWithContext() ? JSReceiver::cast(
-                               ContextExtension::cast(extension())->extension())
-                         : extension_object();
+  return IsWithContext() ? JSReceiver::cast(extension()) : extension_object();
 }
 
 ScopeInfo* Context::scope_info() {
@@ -124,7 +118,7 @@ Module* Context::module() {
 
 String* Context::catch_name() {
   DCHECK(IsCatchContext());
-  return String::cast(ContextExtension::cast(extension())->extension());
+  return String::cast(extension());
 }
 
 
@@ -378,16 +372,13 @@ Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
     } else if (context->IsDebugEvaluateContext()) {
       // Check materialized locals.
       Object* ext = context->get(EXTENSION_INDEX);
-      if (ext->IsContextExtension()) {
-        Object* obj = ContextExtension::cast(ext)->extension();
-        if (obj->IsJSReceiver()) {
-          Handle<JSReceiver> extension(JSReceiver::cast(obj));
-          LookupIterator it(extension, name, extension);
-          Maybe<bool> found = JSReceiver::HasProperty(&it);
-          if (found.FromMaybe(false)) {
-            *attributes = NONE;
-            return extension;
-          }
+      if (ext->IsJSReceiver()) {
+        Handle<JSReceiver> extension(JSReceiver::cast(ext));
+        LookupIterator it(extension, name, extension);
+        Maybe<bool> found = JSReceiver::HasProperty(&it);
+        if (found.FromMaybe(false)) {
+          *attributes = NONE;
+          return extension;
         }
       }
       // Check the original context, but do not follow its context chain.

src/contexts.h

@@ -382,18 +382,15 @@ class ScriptContextTable : public FixedArray {
 //
 // [ extension      ]  Additional data.
 //
-//                     For catch contexts, it contains a ContextExtension object
-//                     consisting of the ScopeInfo and the name of the catch
+//                     For catch contexts, it contains the name of the catch
 //                     variable.
 //
 //                     For module contexts, it contains the module object.
 //
-//                     For block contexts, it may contain a ContextExtension
-//                     object consisting of the ScopeInfo and an "extension
-//                     object" (see below).
+//                     For block contexts, it may contain an "extension object"
+//                     (see below).
 //
-//                     For with contexts, it contains a ContextExtension object
-//                     consisting of the ScopeInfo and an "extension object".
+//                     For with contexts, it contains an "extension object".
 //
 //                     An "extension object" is used to dynamically extend a
 //                     context with additional variables, namely in the

src/deoptimizer.cc

@@ -3419,7 +3419,6 @@ void TranslatedState::InitializeCapturedObjectAt(
     case BOILERPLATE_DESCRIPTION_TYPE:
     case HASH_TABLE_TYPE:
     case PROPERTY_ARRAY_TYPE:
-    case CONTEXT_EXTENSION_TYPE:
       InitializeObjectWithTaggedFieldsAt(frame, &value_index, slot, map,
                                          no_allocation);
       break;
@@ -3586,14 +3585,6 @@ void TranslatedState::EnsureCapturedObjectAllocatedAt(
                                      &value_index, worklist);
     }
 
-    case CONTEXT_EXTENSION_TYPE: {
-      CHECK_EQ(map->instance_size(), slot->GetChildrenCount() * kPointerSize);
-      slot->set_storage(AllocateStorageFor(slot));
-      // Make sure all the remaining children (after the map) are allocated.
-      return EnsureChildrenAllocated(slot->GetChildrenCount() - 1, frame,
-                                     &value_index, worklist);
-    }
-
     default:
       CHECK(map->IsJSObjectMap());
       EnsureJSObjectAllocated(slot, map);

src/heap/factory.cc

@@ -155,15 +155,6 @@ Handle<Tuple3> Factory::NewTuple3(Handle<Object> value1, Handle<Object> value2,
   return result;
 }
 
-Handle<ContextExtension> Factory::NewContextExtension(
-    Handle<ScopeInfo> scope_info, Handle<Object> extension) {
-  Handle<ContextExtension> result = Handle<ContextExtension>::cast(
-      NewStruct(CONTEXT_EXTENSION_TYPE, TENURED));
-  result->set_scope_info(*scope_info);
-  result->set_extension(*extension);
-  return result;
-}
-
 Handle<ConstantElementsPair> Factory::NewConstantElementsPair(
     ElementsKind elements_kind, Handle<FixedArrayBase> constant_values) {
   Handle<ConstantElementsPair> result =
@@ -1343,12 +1334,11 @@ Handle<Context> Factory::NewCatchContext(Handle<Context> previous,
                                          Handle<String> name,
                                          Handle<Object> thrown_object) {
   STATIC_ASSERT(Context::MIN_CONTEXT_SLOTS == Context::THROWN_OBJECT_INDEX);
-  Handle<ContextExtension> extension = NewContextExtension(scope_info, name);
   Handle<Context> context = NewFixedArrayWithMap<Context>(
       Heap::kCatchContextMapRootIndex, Context::MIN_CONTEXT_SLOTS + 1);
   context->set_scope_info(*scope_info);
   context->set_previous(*previous);
-  context->set_extension(*extension);
+  context->set_extension(*name);
   context->set_native_context(previous->native_context());
   context->set(Context::THROWN_OBJECT_INDEX, *thrown_object);
   return context;
@@ -1361,15 +1351,15 @@ Handle<Context> Factory::NewDebugEvaluateContext(Handle<Context> previous,
                                                  Handle<StringSet> whitelist) {
   STATIC_ASSERT(Context::WHITE_LIST_INDEX == Context::MIN_CONTEXT_SLOTS + 1);
   DCHECK(scope_info->IsDebugEvaluateScope());
-  Handle<ContextExtension> context_extension = NewContextExtension(
-      scope_info, extension.is_null() ? Handle<Object>::cast(undefined_value())
-                                      : Handle<Object>::cast(extension));
+  Handle<HeapObject> ext = extension.is_null()
+                               ? Handle<HeapObject>::cast(the_hole_value())
+                               : Handle<HeapObject>::cast(extension);
   Handle<Context> c = NewFixedArrayWithMap<Context>(
       Heap::kDebugEvaluateContextMapRootIndex, Context::MIN_CONTEXT_SLOTS + 2);
   c->set_scope_info(*scope_info);
   c->set_previous(*previous);
   c->set_native_context(previous->native_context());
-  c->set_extension(*context_extension);
+  c->set_extension(*ext);
   if (!wrapped.is_null()) c->set(Context::WRAPPED_CONTEXT_INDEX, *wrapped);
   if (!whitelist.is_null()) c->set(Context::WHITE_LIST_INDEX, *whitelist);
   return c;
@@ -1378,13 +1368,11 @@ Handle<Context> Factory::NewDebugEvaluateContext(Handle<Context> previous,
 Handle<Context> Factory::NewWithContext(Handle<Context> previous,
                                         Handle<ScopeInfo> scope_info,
                                         Handle<JSReceiver> extension) {
-  Handle<ContextExtension> context_extension =
-      NewContextExtension(scope_info, extension);
   Handle<Context> context = NewFixedArrayWithMap<Context>(
       Heap::kWithContextMapRootIndex, Context::MIN_CONTEXT_SLOTS);
   context->set_scope_info(*scope_info);
   context->set_previous(*previous);
-  context->set_extension(*context_extension);
+  context->set_extension(*extension);
   context->set_native_context(previous->native_context());
   return context;
 }

src/heap/factory.h

@@ -186,10 +186,6 @@ class V8_EXPORT_PRIVATE Factory {
   Handle<Tuple3> NewTuple3(Handle<Object> value1, Handle<Object> value2,
                            Handle<Object> value3, PretenureFlag pretenure);
 
-  // Create a new ContextExtension struct.
-  Handle<ContextExtension> NewContextExtension(Handle<ScopeInfo> scope_info,
-                                               Handle<Object> extension);
-
   // Create a new ConstantElementsPair struct.
   Handle<ConstantElementsPair> NewConstantElementsPair(
       ElementsKind elements_kind, Handle<FixedArrayBase> constant_values);

src/heap/incremental-marking.cc

@@ -716,8 +716,7 @@ int IncrementalMarking::VisitObject(Map* map, HeapObject* obj) {
     //    unsafe layout change.
     // 4. The object is materizalized by the deoptimizer.
     DCHECK(obj->IsHashTable() || obj->IsPropertyArray() ||
-           obj->IsContextExtension() || obj->IsFixedArray() ||
-           obj->IsJSObject() || obj->IsString());
+           obj->IsFixedArray() || obj->IsJSObject() || obj->IsString());
   }
   DCHECK(marking_state()->IsBlack(obj));
   WhiteToGreyAndPush(map);

src/objects-debug.cc

@@ -1611,12 +1611,6 @@ void StoreHandler::StoreHandlerVerify() {
   // TODO(ishell): check handler integrity
 }
 
-void ContextExtension::ContextExtensionVerify() {
-  CHECK(IsContextExtension());
-  VerifyObjectField(kScopeInfoOffset);
-  VerifyObjectField(kExtensionOffset);
-}
-
 void AccessorInfo::AccessorInfoVerify() {
   CHECK(IsAccessorInfo());
   VerifyPointer(name());

src/objects-inl.h

@@ -571,7 +571,6 @@ CAST_ACCESSOR(BigInt)
 CAST_ACCESSOR(BoilerplateDescription)
 CAST_ACCESSOR(Cell)
 CAST_ACCESSOR(ConstantElementsPair)
-CAST_ACCESSOR(ContextExtension)
 CAST_ACCESSOR(DescriptorArray)
 CAST_ACCESSOR(EnumCache)
 CAST_ACCESSOR(FeedbackCell)
@@ -2324,9 +2323,6 @@ ACCESSORS(Tuple2, value1, Object, kValue1Offset)
 ACCESSORS(Tuple2, value2, Object, kValue2Offset)
 ACCESSORS(Tuple3, value3, Object, kValue3Offset)
 
-ACCESSORS(ContextExtension, scope_info, ScopeInfo, kScopeInfoOffset)
-ACCESSORS(ContextExtension, extension, Object, kExtensionOffset)
-
 SMI_ACCESSORS(ConstantElementsPair, elements_kind, kElementsKindOffset)
 ACCESSORS(ConstantElementsPair, constant_values, FixedArrayBase,
           kConstantValuesOffset)

src/objects-printer.cc

@@ -1645,13 +1645,6 @@ void StoreHandler::StoreHandlerPrint(std::ostream& os) {  // NOLINT
   os << "\n";
 }
 
-void ContextExtension::ContextExtensionPrint(std::ostream& os) {  // NOLINT
-  HeapObject::PrintHeader(os, "ContextExtension");
-  os << "\n - scope_info: " << Brief(scope_info());
-  os << "\n - extension: " << Brief(extension());
-  os << "\n";
-}
-
 void AccessorPair::AccessorPairPrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "AccessorPair");
   os << "\n - getter: " << Brief(getter());

src/objects.h

@@ -382,7 +382,6 @@ const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
   V(ALLOCATION_MEMENTO_TYPE)                                    \
   V(ALLOCATION_SITE_TYPE)                                       \
   V(ASYNC_GENERATOR_REQUEST_TYPE)                               \
-  V(CONTEXT_EXTENSION_TYPE)                                     \
   V(DEBUG_INFO_TYPE)                                            \
   V(FUNCTION_TEMPLATE_INFO_TYPE)                                \
   V(INTERCEPTOR_INFO_TYPE)                                      \
@@ -557,7 +556,6 @@ const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
   V(ALLOCATION_MEMENTO, AllocationMemento, allocation_memento)               \
   V(ALLOCATION_SITE, AllocationSite, allocation_site)                        \
   V(ASYNC_GENERATOR_REQUEST, AsyncGeneratorRequest, async_generator_request) \
-  V(CONTEXT_EXTENSION, ContextExtension, context_extension)                  \
   V(DEBUG_INFO, DebugInfo, debug_info)                                       \
   V(FUNCTION_TEMPLATE_INFO, FunctionTemplateInfo, function_template_info)    \
   V(INTERCEPTOR_INFO, InterceptorInfo, interceptor_info)                     \
@@ -752,7 +750,6 @@ enum InstanceType : uint16_t {
   ALLOCATION_MEMENTO_TYPE,
   ALLOCATION_SITE_TYPE,
   ASYNC_GENERATOR_REQUEST_TYPE,
-  CONTEXT_EXTENSION_TYPE,
   DEBUG_INFO_TYPE,
   FUNCTION_TEMPLATE_INFO_TYPE,
   INTERCEPTOR_INFO_TYPE,
@@ -2988,32 +2985,6 @@ class PrototypeInfo : public Struct {
   DISALLOW_IMPLICIT_CONSTRUCTORS(PrototypeInfo);
 };
 
-// Pair used to store both a ScopeInfo and an extension object in the extension
-// slot of a block, catch, or with context. Needed in the rare case where a
-// declaration block scope (a "varblock" as used to desugar parameter
-// destructuring) also contains a sloppy direct eval, or for with and catch
-// scopes. (In no other case both are needed at the same time.)
-class ContextExtension : public Struct {
- public:
-  // [scope_info]: Scope info.
-  DECL_ACCESSORS(scope_info, ScopeInfo)
-  // [extension]: Extension object.
-  DECL_ACCESSORS(extension, Object)
-
-  DECL_CAST(ContextExtension)
-
-  // Dispatched behavior.
-  DECL_PRINTER(ContextExtension)
-  DECL_VERIFIER(ContextExtension)
-
-  static const int kScopeInfoOffset = HeapObject::kHeaderSize;
-  static const int kExtensionOffset = kScopeInfoOffset + kPointerSize;
-  static const int kSize = kExtensionOffset + kPointerSize;
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(ContextExtension);
-};
-
 // List of builtin functions we want to identify to improve code
 // generation.
 //

src/runtime/runtime-scopes.cc

@@ -297,14 +297,7 @@ Object* DeclareEvalHelper(Isolate* isolate, Handle<String> name,
     object =
         isolate->factory()->NewJSObject(isolate->context_extension_function());
 
-    if (context->IsBlockContext()) {
-      Handle<ContextExtension> extension =
-          isolate->factory()->NewContextExtension(handle(context->scope_info()),
-                                                  object);
-      context->set_extension(*extension);
-    } else {
-      context->set_extension(*object);
-    }
+    context->set_extension(*object);
   }
 
   RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::SetOwnPropertyIgnoreAttributes(