[runtime] Replace hidden_string with a 0-hash-code private symbol

src/heap/heap.cc

 // 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.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 2649 matching lines @@
   set_exception(*factory->NewOddball(factory->exception_map(), "exception",
                                      handle(Smi::FromInt(-5), isolate()),
                                      "undefined", Oddball::kException));
 
   for (unsigned i = 0; i < arraysize(constant_string_table); i++) {
     Handle<String> str =
         factory->InternalizeUtf8String(constant_string_table[i].contents);
     roots_[constant_string_table[i].index] = *str;
   }
 
-  // The {hidden_string} is special because it is an empty string, but does not
-  // match any string (even the {empty_string}) when looked up in properties.
-  // Allocate the hidden string which is used to identify the hidden properties
-  // in JSObjects. The hash code has a special value so that it will not match
-  // the empty string when searching for the property. It cannot be part of the
-  // loop above because it needs to be allocated manually with the special
-  // hash code in place. The hash code for the hidden_string is zero to ensure
-  // that it will always be at the first entry in property descriptors.
-  set_hidden_string(*factory->NewOneByteInternalizedString(
-      OneByteVector("", 0), String::kEmptyStringHash));
-
   // Create the code_stubs dictionary. The initial size is set to avoid
   // expanding the dictionary during bootstrapping.
   set_code_stubs(*UnseededNumberDictionary::New(isolate(), 128));
 
   // Create the non_monomorphic_cache used in stub-cache.cc. The initial size
   // is set to avoid expanding the dictionary during bootstrapping.
   set_non_monomorphic_cache(*UnseededNumberDictionary::New(isolate(), 64));
 
   set_polymorphic_code_cache(PolymorphicCodeCache::cast(
       *factory->NewStruct(POLYMORPHIC_CODE_CACHE_TYPE)));
 
   set_instanceof_cache_function(Smi::FromInt(0));
   set_instanceof_cache_map(Smi::FromInt(0));
   set_instanceof_cache_answer(Smi::FromInt(0));
 
   {
     HandleScope scope(isolate());
 #define SYMBOL_INIT(name)                                              \
   {                                                                    \
     Handle<String> name##d = factory->NewStringFromStaticChars(#name); \
     Handle<Symbol> symbol(isolate()->factory()->NewPrivateSymbol());   \
     symbol->set_name(*name##d);                                        \
     roots_[k##name##RootIndex] = *symbol;                              \
   }
     PRIVATE_SYMBOL_LIST(SYMBOL_INIT)
 #undef SYMBOL_INIT
   }
 
+  // The {hidden_properties_symbol} is special because it is the only name with
+  // hash code zero. This ensures that it will always be the first entry as
+  // sorted by hash code in descriptor arrays. It is used to identify the hidden
+  // properties in JSObjects.
+  // kIsNotArrayIndexMask is a computed hash with value zero.
+  Symbol::cast(roots_[khidden_properties_symbolRootIndex])
+      ->set_hash_field(Name::kIsNotArrayIndexMask);

[ulan, 2016/02/17 10:45:22]

Oh well

+
   {
     HandleScope scope(isolate());
 #define SYMBOL_INIT(name, description)                                      \
   Handle<Symbol> name = factory->NewSymbol();                               \
   Handle<String> name##d = factory->NewStringFromStaticChars(#description); \
   name->set_name(*name##d);                                                 \
   roots_[k##name##RootIndex] = *name;
     PUBLIC_SYMBOL_LIST(SYMBOL_INIT)
 #undef SYMBOL_INIT
 
@@ skipping 3546 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8