Free up 11 bits in fast-mode PropertyDetails by removing the enumeration-index.

src/property-details.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 131 matching lines @@
   int8_t kind_;
 };
 
 
 // PropertyDetails captures type and attributes for a property.
 // They are used both in property dictionaries and instance descriptors.
 class PropertyDetails BASE_EMBEDDED {
  public:
   PropertyDetails(PropertyAttributes attributes,
                   PropertyType type,
-                  Representation representation,
-                  int index = 0) {
+                  int index) {
     value_ = TypeField::encode(type)
         | AttributesField::encode(attributes)
-        | RepresentationField::encode(EncodeRepresentation(representation))
         | DictionaryStorageField::encode(index);
 
     ASSERT(type == this->type());
     ASSERT(attributes == this->attributes());
-    if (representation.IsNone()) {
-      ASSERT(index == this->dictionary_index());
-    } else {
-      ASSERT(index == this->descriptor_index());
-    }
+  }
+
+  PropertyDetails(PropertyAttributes attributes,
+                  PropertyType type,
+                  Representation representation) {
+    value_ = TypeField::encode(type)
+        | AttributesField::encode(attributes)
+        | RepresentationField::encode(EncodeRepresentation(representation));
   }
 
   int pointer() { return DescriptorPointer::decode(value_); }
 
   PropertyDetails set_pointer(int i) { return PropertyDetails(value_, i); }
 
   PropertyDetails CopyWithRepresentation(Representation representation) {
     return PropertyDetails(value_, representation);
   }
 
   // Conversion for storing details as Object*.
   explicit inline PropertyDetails(Smi* smi);
   inline Smi* AsSmi();
 
   static uint8_t EncodeRepresentation(Representation representation) {
-    ASSERT(representation.kind() <= Representation::kTagged);
-    if (representation.kind() < Representation::kInteger32) {
-      return representation.kind();
-    } else {
-      return representation.kind() - 1;
-    }
+    return representation.kind();
   }
 
   static Representation DecodeRepresentation(uint32_t bits) {
-    ASSERT(bits <= Representation::kTagged);
-    if (bits >= Representation::kInteger32) bits += 1;
     return Representation::FromKind(static_cast<Representation::Kind>(bits));
   }
 
   PropertyType type() { return TypeField::decode(value_); }
 
   PropertyAttributes attributes() const {
     return AttributesField::decode(value_);
   }
 
   int dictionary_index() {
     return DictionaryStorageField::decode(value_);
   }
 
-  int descriptor_index() {
-    return DescriptorStorageField::decode(value_);
-  }
-
   Representation representation() {
     return DecodeRepresentation(RepresentationField::decode(value_));
   }
 
   inline PropertyDetails AsDeleted();
 
   static bool IsValidIndex(int index) {
     return DictionaryStorageField::is_valid(index);
   }
 
   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
   bool IsDontDelete() const { return (attributes() & DONT_DELETE) != 0; }
   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
   bool IsDeleted() const { return DeletedField::decode(value_) != 0;}
 
   // Bit fields in value_ (type, shift, size). Must be public so the
   // constants can be embedded in generated code.
   class TypeField:                public BitField<PropertyType,       0,  3> {};
   class AttributesField:          public BitField<PropertyAttributes, 3,  3> {};
   class DeletedField:             public BitField<uint32_t,           6,  1> {};
   class DictionaryStorageField:   public BitField<uint32_t,           7, 24> {};
-  class DescriptorStorageField:   public BitField<uint32_t,           7, 11> {};
-  class DescriptorPointer:        public BitField<uint32_t,          18, 11> {};
-  class RepresentationField:      public BitField<uint32_t,          29,  2> {};
+  class DescriptorPointer:        public BitField<uint32_t,           7, 11> {};
+  class RepresentationField:      public BitField<uint32_t,          18,  3> {};
 
   static const int kInitialIndex = 1;
 
  private:
   PropertyDetails(int value, int pointer) {
     value_ = DescriptorPointer::update(value, pointer);
   }
   PropertyDetails(int value, Representation representation) {
     value_ = RepresentationField::update(
         value, EncodeRepresentation(representation));
   }
 
   uint32_t value_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_DETAILS_H_