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

src/objects-inl.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 40 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 PropertyDetails::PropertyDetails(Smi* smi) {
   value_ = smi->value();
 }
 
 
 Smi* PropertyDetails::AsSmi() {
-  // Ensure the upper 2 bits have the same value by sign extending it. This is
-  // necessary to be able to use the 31st bit of the property details.
-  int value = value_ << 1;
-  return Smi::FromInt(value >> 1);
+  return Smi::FromInt(value_);
 }
 
 
 PropertyDetails PropertyDetails::AsDeleted() {
   Smi* smi = Smi::FromInt(value_ | DeletedField::encode(1));
   return PropertyDetails(smi);
 }
 
 
 #define TYPE_CHECKER(type, instancetype)                                \
@@ skipping 2265 matching lines @@
              GetValue(descriptor_number),
              GetDetails(descriptor_number));
 }
 
 
 void DescriptorArray::Set(int descriptor_number,
                           Descriptor* desc,
                           const WhitenessWitness&) {
   // Range check.
   ASSERT(descriptor_number < number_of_descriptors());
-  ASSERT(desc->GetDetails().descriptor_index() <=
-         number_of_descriptors());
-  ASSERT(desc->GetDetails().descriptor_index() > 0);
 
   ASSERT(!desc->GetDetails().representation().IsNone());
   NoIncrementalWriteBarrierSet(this,
                                ToKeyIndex(descriptor_number),
                                desc->GetKey());
   NoIncrementalWriteBarrierSet(this,
                                ToValueIndex(descriptor_number),
                                desc->GetValue());
   NoIncrementalWriteBarrierSet(this,
                                ToDetailsIndex(descriptor_number),
                                desc->GetDetails().AsSmi());
 }
 
 
 void DescriptorArray::Set(int descriptor_number, Descriptor* desc) {
   // Range check.
   ASSERT(descriptor_number < number_of_descriptors());
-  ASSERT(desc->GetDetails().descriptor_index() <=
-         number_of_descriptors());
-  ASSERT(desc->GetDetails().descriptor_index() > 0);
   ASSERT(!desc->GetDetails().representation().IsNone());
 
   set(ToKeyIndex(descriptor_number), desc->GetKey());
   set(ToValueIndex(descriptor_number), desc->GetValue());
   set(ToDetailsIndex(descriptor_number), desc->GetDetails().AsSmi());
 }
 
 
 void DescriptorArray::Append(Descriptor* desc,
                              const WhitenessWitness& witness) {
   int descriptor_number = number_of_descriptors();
-  int enumeration_index = descriptor_number + 1;
   SetNumberOfDescriptors(descriptor_number + 1);
-  desc->SetEnumerationIndex(enumeration_index);
   Set(descriptor_number, desc, witness);
 
   uint32_t hash = desc->GetKey()->Hash();
 
   int insertion;
 
   for (insertion = descriptor_number; insertion > 0; --insertion) {
     Name* key = GetSortedKey(insertion - 1);
     if (key->Hash() <= hash) break;
     SetSortedKey(insertion, GetSortedKeyIndex(insertion - 1));
   }
 
   SetSortedKey(insertion, descriptor_number);
 }
 
 
 void DescriptorArray::Append(Descriptor* desc) {
   int descriptor_number = number_of_descriptors();
-  int enumeration_index = descriptor_number + 1;
   SetNumberOfDescriptors(descriptor_number + 1);
-  desc->SetEnumerationIndex(enumeration_index);
   Set(descriptor_number, desc);
 
   uint32_t hash = desc->GetKey()->Hash();
 
   int insertion;
 
   for (insertion = descriptor_number; insertion > 0; --insertion) {
     Name* key = GetSortedKey(insertion - 1);
     if (key->Hash() <= hash) break;
     SetSortedKey(insertion, GetSortedKeyIndex(insertion - 1));
@@ skipping 1727 matching lines @@
   } else {
     return map;
   }
   map->set_transitions(transitions);
   return transitions;
 }
 
 
 void Map::InitializeDescriptors(DescriptorArray* descriptors) {
   int len = descriptors->number_of_descriptors();
-#ifdef DEBUG
-  ASSERT(len <= DescriptorArray::kMaxNumberOfDescriptors);
-
-  bool used_indices[DescriptorArray::kMaxNumberOfDescriptors];
-  for (int i = 0; i < len; ++i) used_indices[i] = false;
-
-  // Ensure that all enumeration indexes between 1 and length occur uniquely in
-  // the descriptor array.
-  for (int i = 0; i < len; ++i) {
-    int enum_index = descriptors->GetDetails(i).descriptor_index() -
-                     PropertyDetails::kInitialIndex;
-    ASSERT(0 <= enum_index && enum_index < len);
-    ASSERT(!used_indices[enum_index]);
-    used_indices[enum_index] = true;
-  }
-#endif
-
   set_instance_descriptors(descriptors);
   SetNumberOfOwnDescriptors(len);
 }
 
 
 ACCESSORS(Map, instance_descriptors, DescriptorArray, kDescriptorsOffset)
 SMI_ACCESSORS(Map, bit_field3, kBitField3Offset)
 
 
 void Map::ClearTransitions(Heap* heap, WriteBarrierMode mode) {
@@ skipping 2045 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_