Reland: track global accesses to constant types

src/objects.cc

 // Copyright 2013 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 <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 1768 matching lines @@
 }
 
 
 void JSObject::AddSlowProperty(Handle<JSObject> object,
                                Handle<Name> name,
                                Handle<Object> value,
                                PropertyAttributes attributes) {
   DCHECK(!object->HasFastProperties());
   Isolate* isolate = object->GetIsolate();
   Handle<NameDictionary> dict(object->property_dictionary());
-  PropertyDetails details(attributes, DATA, 0, PropertyCellType::kInvalid);
+  PropertyDetails details(attributes, DATA, 0, PropertyCellType::kNoCell);
   if (object->IsGlobalObject()) {
     int entry = dict->FindEntry(name);
     // If there's a cell there, just invalidate and set the property.
     if (entry != NameDictionary::kNotFound) {
       PropertyCell::UpdateCell(dict, entry, value, details);
       // TODO(dcarney): move this to UpdateCell.
       // Need to adjust the details.
       int index = dict->NextEnumerationIndex();
       dict->SetNextEnumerationIndex(index + 1);
       details = dict->DetailsAt(entry).set_index(index);
@@ skipping 2787 matching lines @@
       NameDictionary::New(isolate, property_count);
 
   Handle<DescriptorArray> descs(map->instance_descriptors());
   for (int i = 0; i < real_size; i++) {
     PropertyDetails details = descs->GetDetails(i);
     Handle<Name> key(descs->GetKey(i));
     switch (details.type()) {
       case DATA_CONSTANT: {
         Handle<Object> value(descs->GetConstant(i), isolate);
         PropertyDetails d(details.attributes(), DATA, i + 1,
-                          PropertyCellType::kInvalid);
+                          PropertyCellType::kNoCell);
         dictionary = NameDictionary::Add(dictionary, key, value, d);
         break;
       }
       case DATA: {
         FieldIndex index = FieldIndex::ForDescriptor(*map, i);
         Handle<Object> value;
         if (object->IsUnboxedDoubleField(index)) {
           double old_value = object->RawFastDoublePropertyAt(index);
           value = isolate->factory()->NewHeapNumber(old_value);
         } else {
           value = handle(object->RawFastPropertyAt(index), isolate);
           if (details.representation().IsDouble()) {
             DCHECK(value->IsMutableHeapNumber());
             Handle<HeapNumber> old = Handle<HeapNumber>::cast(value);
             value = isolate->factory()->NewHeapNumber(old->value());
           }
         }
         PropertyDetails d(details.attributes(), DATA, i + 1,
-                          PropertyCellType::kInvalid);
+                          PropertyCellType::kNoCell);
         dictionary = NameDictionary::Add(dictionary, key, value, d);
         break;
       }
       case ACCESSOR: {
         FieldIndex index = FieldIndex::ForDescriptor(*map, i);
         Handle<Object> value(object->RawFastPropertyAt(index), isolate);
         PropertyDetails d(details.attributes(), ACCESSOR_CONSTANT, i + 1,
-                          PropertyCellType::kInvalid);
+                          PropertyCellType::kNoCell);
         dictionary = NameDictionary::Add(dictionary, key, value, d);
         break;
       }
       case ACCESSOR_CONSTANT: {
         Handle<Object> value(descs->GetCallbacksObject(i), isolate);
         PropertyDetails d(details.attributes(), ACCESSOR_CONSTANT, i + 1,
-                          PropertyCellType::kInvalid);
+                          PropertyCellType::kNoCell);
         dictionary = NameDictionary::Add(dictionary, key, value, d);
         break;
       }
     }
   }
 
   // Copy the next enumeration index from instance descriptor.
   dictionary->SetNextEnumerationIndex(real_size + 1);
 
   // From here on we cannot fail and we shouldn't GC anymore.
@@ skipping 709 matching lines @@
   Handle<NameDictionary> dictionary(object->property_dictionary());
   int entry = dictionary->FindEntry(name);
   DCHECK_NE(NameDictionary::kNotFound, entry);
 
   // If we have a global object, invalidate the cell and swap in a new one.
   if (object->IsGlobalObject()) {
     auto cell = PropertyCell::InvalidateEntry(dictionary, entry);
     cell->set_value(isolate->heap()->the_hole_value());
     // TODO(dcarney): InvalidateForDelete
     dictionary->DetailsAtPut(entry, dictionary->DetailsAt(entry).set_cell_type(
-                                        PropertyCellType::kDeleted));
+                                        PropertyCellType::kInvalidated));
     return;
   }
 
   NameDictionary::DeleteProperty(dictionary, entry);
   Handle<NameDictionary> new_properties =
       NameDictionary::Shrink(dictionary, name);
   object->set_properties(*new_properties);
 }
 
 
@@ skipping 1054 matching lines @@
     PropertyAttributes attributes) {
   int entry = dictionary->FindEntry(index);
   if (entry != SeededNumberDictionary::kNotFound) {
     Object* result = dictionary->ValueAt(entry);
     PropertyDetails details = dictionary->DetailsAt(entry);
     if (details.type() == ACCESSOR_CONSTANT && result->IsAccessorPair()) {
       DCHECK(details.IsConfigurable());
       if (details.attributes() != attributes) {
         dictionary->DetailsAtPut(
             entry, PropertyDetails(attributes, ACCESSOR_CONSTANT, index,
-                                   PropertyCellType::kInvalid));
+                                   PropertyCellType::kNoCell));
       }
       AccessorPair::cast(result)->SetComponents(getter, setter);
       return true;
     }
   }
   return false;
 }
 
 
 void JSObject::DefineElementAccessor(Handle<JSObject> object,
@@ skipping 82 matching lines @@
   return false;
 }
 
 
 void JSObject::SetElementCallback(Handle<JSObject> object,
                                   uint32_t index,
                                   Handle<Object> structure,
                                   PropertyAttributes attributes) {
   Heap* heap = object->GetHeap();
   PropertyDetails details = PropertyDetails(attributes, ACCESSOR_CONSTANT, 0,
-                                            PropertyCellType::kInvalid);
+                                            PropertyCellType::kNoCell);
 
   // Normalize elements to make this operation simple.
   bool had_dictionary_elements = object->HasDictionaryElements();
   Handle<SeededNumberDictionary> dictionary = NormalizeElements(object);
   DCHECK(object->HasDictionaryElements() ||
          object->HasDictionaryArgumentsElements());
   // Update the dictionary with the new ACCESSOR_CONSTANT property.
   dictionary = SeededNumberDictionary::Set(dictionary, index, structure,
                                            details);
   dictionary->set_requires_slow_elements();
@@ skipping 6368 matching lines @@
       // is read-only (a declared const that has not been initialized).
       return WriteToReadOnlyProperty(
           isolate, object, isolate->factory()->NewNumberFromUint(index),
           isolate->factory()->undefined_value(), language_mode);
     } else {
       DCHECK(details.IsConfigurable() || !details.IsReadOnly() ||
              element->IsTheHole());
       dictionary->UpdateMaxNumberKey(index);
       if (set_mode == DEFINE_PROPERTY) {
         details = PropertyDetails(attributes, DATA, details.dictionary_index(),
-                                  PropertyCellType::kInvalid);
+                                  PropertyCellType::kNoCell);
         dictionary->DetailsAtPut(entry, details);
       }
 
       // Elements of the arguments object in slow mode might be slow aliases.
       if (is_arguments && element->IsAliasedArgumentsEntry()) {
         Handle<AliasedArgumentsEntry> entry =
             Handle<AliasedArgumentsEntry>::cast(element);
         Handle<Context> context(Context::cast(elements->get(0)));
         int context_index = entry->aliased_context_slot();
         DCHECK(!context->get(context_index)->IsTheHole());
@@ skipping 22 matching lines @@
         Handle<Object> number = isolate->factory()->NewNumberFromUint(index);
         Handle<String> name = isolate->factory()->NumberToString(number);
         Handle<Object> args[] = {name};
         THROW_NEW_ERROR(isolate,
                         NewTypeError("object_not_extensible",
                                      HandleVector(args, arraysize(args))),
                         Object);
       }
     }
 
-    PropertyDetails details(attributes, DATA, 0, PropertyCellType::kInvalid);
+    PropertyDetails details(attributes, DATA, 0, PropertyCellType::kNoCell);
     Handle<SeededNumberDictionary> new_dictionary =
         SeededNumberDictionary::AddNumberEntry(dictionary, index, value,
                                                details);
     if (*dictionary != *new_dictionary) {
       if (is_arguments) {
         elements->set(1, *new_dictionary);
       } else {
         object->set_elements(*new_dictionary);
       }
       dictionary = new_dictionary;
@@ skipping 2426 matching lines @@
     Handle<GlobalObject> global, Handle<Name> name) {
   DCHECK(!global->HasFastProperties());
   auto dictionary = handle(global->property_dictionary());
   int entry = dictionary->FindEntry(name);
   Handle<PropertyCell> cell;
   if (entry != NameDictionary::kNotFound) {
     // This call should be idempotent.
     DCHECK(dictionary->DetailsAt(entry).cell_type() ==
                PropertyCellType::kUninitialized ||
            dictionary->DetailsAt(entry).cell_type() ==
-               PropertyCellType::kDeleted);
+               PropertyCellType::kInvalidated);
     DCHECK(dictionary->ValueAt(entry)->IsPropertyCell());
     cell = handle(PropertyCell::cast(dictionary->ValueAt(entry)));
     DCHECK(cell->value()->IsTheHole());
     return cell;
   }
   Isolate* isolate = global->GetIsolate();
   cell = isolate->factory()->NewPropertyCell();
   PropertyDetails details(NONE, DATA, 0, PropertyCellType::kUninitialized);
   dictionary = NameDictionary::Add(dictionary, name, cell, details);
   global->set_properties(*dictionary);
@@ skipping 1587 matching lines @@
   Isolate* isolate = dictionary->GetIsolate();
   // Swap with a copy.
   DCHECK(dictionary->ValueAt(entry)->IsPropertyCell());
   Handle<PropertyCell> cell(PropertyCell::cast(dictionary->ValueAt(entry)));
   auto new_cell = isolate->factory()->NewPropertyCell();
   new_cell->set_value(cell->value());
   dictionary->ValueAtPut(entry, *new_cell);
   bool is_the_hole = cell->value()->IsTheHole();
   // Cell is officially mutable henceforth.
   auto details = dictionary->DetailsAt(entry);
-  details = details.set_cell_type(is_the_hole ? PropertyCellType::kDeleted
+  details = details.set_cell_type(is_the_hole ? PropertyCellType::kInvalidated
                                               : PropertyCellType::kMutable);
   dictionary->DetailsAtPut(entry, details);
   // Old cell is ready for invalidation.
   if (is_the_hole) {
     cell->set_value(isolate->heap()->undefined_value());
   } else {
     cell->set_value(isolate->heap()->the_hole_value());
   }
   cell->dependent_code()->DeoptimizeDependentCodeGroup(
       isolate, DependentCode::kPropertyCellChangedGroup);
   return new_cell;
 }
 
 
+PropertyCellConstantType PropertyCell::GetConstantType() {
+  if (value()->IsSmi()) return PropertyCellConstantType::kSmi;
+  return PropertyCellConstantType::kStableMap;
+}
+
+
+static bool RemainsConstantType(Handle<PropertyCell> cell,
+                                Handle<Object> value) {
+  // TODO(dcarney): double->smi and smi->double transition from kConstant
+  if (cell->value()->IsSmi() && value->IsSmi()) {
+    return true;
+  } else if (cell->value()->IsHeapObject() && value->IsHeapObject()) {
+    return HeapObject::cast(cell->value())->map() ==
+               HeapObject::cast(*value)->map() &&
+           HeapObject::cast(*value)->map()->is_stable();
+  }
+  return false;
+}
+
+
 PropertyCellType PropertyCell::UpdatedType(Handle<PropertyCell> cell,
                                            Handle<Object> value,
                                            PropertyDetails details) {
   PropertyCellType type = details.cell_type();
   DCHECK(!value->IsTheHole());
-  DCHECK_IMPLIES(cell->value()->IsTheHole(),
-                 type == PropertyCellType::kUninitialized ||
-                     type == PropertyCellType::kDeleted);
+  if (cell->value()->IsTheHole()) {
+    switch (type) {
+      // Only allow a cell to transition once into constant state.
+      case PropertyCellType::kUninitialized:
+        if (value->IsUndefined()) return PropertyCellType::kUndefined;
+        return PropertyCellType::kConstant;
+      case PropertyCellType::kInvalidated:
+        return PropertyCellType::kMutable;
+      default:
+        UNREACHABLE();
+        return PropertyCellType::kMutable;
+    }
+  }
   switch (type) {
-    // Only allow a cell to transition once into constant state.
-    case PropertyCellType::kUninitialized:
-      if (value->IsUndefined()) return PropertyCellType::kUndefined;
-      return PropertyCellType::kConstant;
     case PropertyCellType::kUndefined:
       return PropertyCellType::kConstant;
     case PropertyCellType::kConstant:
-      // No transition.
       if (*value == cell->value()) return PropertyCellType::kConstant;
     // Fall through.
+    case PropertyCellType::kConstantType:
+      if (RemainsConstantType(cell, value)) {
+        return PropertyCellType::kConstantType;
+      }
+    // Fall through.
     case PropertyCellType::kMutable:
       return PropertyCellType::kMutable;
   }
   UNREACHABLE();
   return PropertyCellType::kMutable;
 }
 
 
 Handle<Object> PropertyCell::UpdateCell(Handle<NameDictionary> dictionary,
                                         int entry, Handle<Object> value,
@@ skipping 32 matching lines @@
 
   auto new_type = UpdatedType(cell, value, original_details);
   if (invalidate) cell = PropertyCell::InvalidateEntry(dictionary, entry);
 
   // Install new property details and cell value.
   details = details.set_cell_type(new_type);
   dictionary->DetailsAtPut(entry, details);
   cell->set_value(*value);
 
   // Deopt when transitioning from a constant type.
-  if (!invalidate && old_type == PropertyCellType::kConstant &&
-      new_type != PropertyCellType::kConstant) {
+  if (!invalidate && (old_type != new_type)) {
     auto isolate = dictionary->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
   return value;
 }
 
 
 // static
 void PropertyCell::SetValueWithInvalidation(Handle<PropertyCell> cell,
                                             Handle<Object> new_value) {
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 } }  // namespace v8::internal