ES6 symbols: Introduce Symbol class, along with abstract Name class

src/heap.cc

 // 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 2369 matching lines @@
         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_scope_info_map(Map::cast(obj));
 
   { MaybeObject* maybe_obj = AllocateMap(HEAP_NUMBER_TYPE, HeapNumber::kSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_heap_number_map(Map::cast(obj));
 
+  { MaybeObject* maybe_obj = AllocateMap(SYMBOL_TYPE, Symbol::kSize);
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
+  set_symbol_map(Map::cast(obj));
+
   { MaybeObject* maybe_obj = AllocateMap(FOREIGN_TYPE, Foreign::kSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_foreign_map(Map::cast(obj));
 
   for (unsigned i = 0; i < ARRAY_SIZE(string_type_table); i++) {
     const StringTypeTable& entry = string_type_table[i];
     { MaybeObject* maybe_obj = AllocateMap(entry.type, entry.size);
       if (!maybe_obj->ToObject(&obj)) return false;
     }
@@ skipping 2763 matching lines @@
   { MaybeObject* maybe_result = AllocateFixedArray(length, pretenure);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   reinterpret_cast<HeapObject*>(result)->set_map_no_write_barrier(
       hash_table_map());
   ASSERT(result->IsHashTable());
   return result;
 }
 
 
+MaybeObject* Heap::AllocateSymbol(PretenureFlag pretenure) {
+  // Statically ensure that it is safe to allocate heap numbers in paged spaces.
+  STATIC_ASSERT(HeapNumber::kSize <= Page::kNonCodeObjectAreaSize);

[Michael Starzinger, 2013/02/12 10:03:53]

Both comment and assertion are out-dated and use the wrong size constant.

[rossberg, 2013/02/13 10:04:28]

Oops, done.

+  AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
+
+  Object* result;
+  MaybeObject* maybe = AllocateRaw(Symbol::kSize, space, OLD_DATA_SPACE);
+  if (!maybe->ToObject(&result)) return maybe;
+
+  HeapObject::cast(result)->set_map_no_write_barrier(symbol_map());
+
+  // Generate a random hash value.
+  int hash;
+  int attempts = 0;
+  do {
+    hash = V8::RandomPrivate(isolate()) & Name::kHashBitMask;
+    attempts++;
+  } while (hash == 0 && attempts < 30);
+  if (hash == 0) hash = 1;  // never return 0
+
+  Symbol::cast(result)->set_hash_field(
+      Name::kIsNotArrayIndexMask | (hash << Name::kHashShift));
+
+  ASSERT(result->IsSymbol());
+  return result;
+}
+
+
 MaybeObject* Heap::AllocateNativeContext() {
   Object* result;
   { MaybeObject* maybe_result =
         AllocateFixedArray(Context::NATIVE_CONTEXT_SLOTS);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   Context* context = reinterpret_cast<Context*>(result);
   context->set_map_no_write_barrier(native_context_map());
   context->set_js_array_maps(undefined_value());
   ASSERT(context->IsNativeContext());
@@ skipping 2345 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal