[runtime] Add PropertyConstness bit to PropertyDetails.

src/property-details.h

 // Copyright 2012 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_PROPERTY_DETAILS_H_
 #define V8_PROPERTY_DETAILS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/utils.h"
@@ skipping 54 matching lines @@
 class TypeInfo;
 
 // Order of kinds is significant.
 // Must fit in the BitField PropertyDetails::KindField.
 enum PropertyKind { kData = 0, kAccessor = 1 };
 
 // Order of modes is significant.
 // Must fit in the BitField PropertyDetails::LocationField.
 enum PropertyLocation { kField = 0, kDescriptor = 1 };
 
+// Order of modes is significant.
+// Must fit in the BitField PropertyDetails::ConstnessField.
+enum PropertyConstness { kMutable = 0, kConst = 1 };
+
 class Representation {
  public:
   enum Kind {
     kNone,
     kInteger8,
     kUInteger8,
     kInteger16,
     kUInteger16,
     kSmi,
     kInteger32,
@@ skipping 139 matching lines @@
   PropertyDetails(PropertyKind kind, PropertyAttributes attributes, int index,
                   PropertyCellType cell_type) {
     value_ = KindField::encode(kind) | LocationField::encode(kField) |
              AttributesField::encode(attributes) |
              DictionaryStorageField::encode(index) |
              PropertyCellTypeField::encode(cell_type);
   }
 
   // Property details for fast mode properties.
   PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
-                  PropertyLocation location, Representation representation,
-                  int field_index = 0) {
-    value_ = KindField::encode(kind) | LocationField::encode(location) |
-             AttributesField::encode(attributes) |
+                  PropertyLocation location, PropertyConstness constness,
+                  Representation representation, int field_index = 0) {
+    value_ = KindField::encode(kind) | AttributesField::encode(attributes) |
+             LocationField::encode(location) |
+             ConstnessField::encode(constness) |
              RepresentationField::encode(EncodeRepresentation(representation)) |
              FieldIndexField::encode(field_index);
   }
 
   static PropertyDetails Empty(
       PropertyCellType cell_type = PropertyCellType::kNoCell) {
     return PropertyDetails(kData, NONE, 0, cell_type);
   }
 
   int pointer() const { return DescriptorPointer::decode(value_); }
@@ skipping 30 matching lines @@
   static uint8_t EncodeRepresentation(Representation representation) {
     return representation.kind();
   }
 
   static Representation DecodeRepresentation(uint32_t bits) {
     return Representation::FromKind(static_cast<Representation::Kind>(bits));
   }
 
   PropertyKind kind() const { return KindField::decode(value_); }
   PropertyLocation location() const { return LocationField::decode(value_); }
+  PropertyConstness constness() const { return ConstnessField::decode(value_); }
 
   PropertyAttributes attributes() const {
     return AttributesField::decode(value_);
   }
 
   int dictionary_index() const {
     return DictionaryStorageField::decode(value_);
   }
 
   Representation representation() const {
@@ skipping 12 matching lines @@
   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
   bool IsEnumerable() const { return !IsDontEnum(); }
   PropertyCellType cell_type() const {
     return PropertyCellTypeField::decode(value_);
   }
 
   // Bit fields in value_ (type, shift, size). Must be public so the
   // constants can be embedded in generated code.
   class KindField : public BitField<PropertyKind, 0, 1> {};
-  class LocationField : public BitField<PropertyLocation, 1, 1> {};
-  class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
+  class LocationField : public BitField<PropertyLocation, KindField::kNext, 1> {
+  };
+  class ConstnessField
+      : public BitField<PropertyConstness, LocationField::kNext, 1> {};
+  class AttributesField
+      : public BitField<PropertyAttributes, ConstnessField::kNext, 3> {};
   static const int kAttributesReadOnlyMask =
       (READ_ONLY << AttributesField::kShift);
 
   // Bit fields for normalized objects.
-  class PropertyCellTypeField : public BitField<PropertyCellType, 5, 2> {};
-  class DictionaryStorageField : public BitField<uint32_t, 7, 24> {};
+  class PropertyCellTypeField
+      : public BitField<PropertyCellType, AttributesField::kNext, 2> {};
+  class DictionaryStorageField
+      : public BitField<uint32_t, PropertyCellTypeField::kNext, 23> {};
 
   // Bit fields for fast objects.
-  class RepresentationField : public BitField<uint32_t, 5, 4> {};
+  class RepresentationField
+      : public BitField<uint32_t, AttributesField::kNext, 4> {};
   class DescriptorPointer
-      : public BitField<uint32_t, 9, kDescriptorIndexBitCount> {};  // NOLINT
-  class FieldIndexField
-      : public BitField<uint32_t, 9 + kDescriptorIndexBitCount,
+      : public BitField<uint32_t, RepresentationField::kNext,
                         kDescriptorIndexBitCount> {};  // NOLINT
+  class FieldIndexField : public BitField<uint32_t, DescriptorPointer::kNext,
+                                          kDescriptorIndexBitCount> {
+  };  // NOLINT
 
   // All bits for both fast and slow objects must fit in a smi.
   STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
   STATIC_ASSERT(FieldIndexField::kNext <= 31);
 
   static const int kInitialIndex = 1;
 
 #ifdef OBJECT_PRINT
   // For our gdb macros, we should perhaps change these in the future.
   void Print(bool dictionary_mode);
@@ skipping 20 matching lines @@
     value_ = RepresentationField::update(
         value, EncodeRepresentation(representation));
   }
   PropertyDetails(int value, PropertyAttributes attributes) {
     value_ = AttributesField::update(value, attributes);
   }
 
   uint32_t value_;
 };
 
+// kField location is more general than kDescriptor, kDescriptor generalizes
+// only to itself.
+inline bool IsGeneralizableTo(PropertyLocation a, PropertyLocation b) {
+  return b == kField || a == kDescriptor;
+}
+
+// kMutable constness is more general than kConst, kConst generalizes only to
+// itself.
+inline bool IsGeneralizableTo(PropertyConstness a, PropertyConstness b) {
+  return b == kMutable || a == kConst;
+}
+
+inline PropertyConstness GeneralizeConstness(PropertyConstness a,
+                                             PropertyConstness b) {
+  return a == kMutable ? kMutable : b;
+}
 
 std::ostream& operator<<(std::ostream& os,
                          const PropertyAttributes& attributes);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PROPERTY_DETAILS_H_