Allocate new AccessorPairs with holes instead of undefined.

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 1891 matching lines @@
   if (Map::kPadStart < Map::kSize) {
     memset(reinterpret_cast<byte*>(map) + Map::kPadStart - kHeapObjectTag,
            0,
            Map::kSize - Map::kPadStart);
   }
   return map;
 }
 
 
 MaybeObject* Heap::AllocateCodeCache() {
-  Object* result;
-  { MaybeObject* maybe_result = AllocateStruct(CODE_CACHE_TYPE);
-    if (!maybe_result->ToObject(&result)) return maybe_result;
+  CodeCache* code_cache;
+  { MaybeObject* maybe_code_cache = AllocateStruct(CODE_CACHE_TYPE);
+    if (!maybe_code_cache->To(&code_cache)) return maybe_code_cache;
   }
-  CodeCache* code_cache = CodeCache::cast(result);
   code_cache->set_default_cache(empty_fixed_array(), SKIP_WRITE_BARRIER);
   code_cache->set_normal_type_cache(undefined_value(), SKIP_WRITE_BARRIER);
   return code_cache;
 }
 
 
 MaybeObject* Heap::AllocatePolymorphicCodeCache() {
   return AllocateStruct(POLYMORPHIC_CODE_CACHE_TYPE);
 }
 
 
 MaybeObject* Heap::AllocateAccessorPair() {
-  Object* result;
-  { MaybeObject* maybe_result = AllocateStruct(ACCESSOR_PAIR_TYPE);
-    if (!maybe_result->ToObject(&result)) return maybe_result;
+  AccessorPair* accessors;
+  { MaybeObject* maybe_accessors = AllocateStruct(ACCESSOR_PAIR_TYPE);
+    if (!maybe_accessors->To(&accessors)) return maybe_accessors;
   }
-  AccessorPair* accessors = AccessorPair::cast(result);
-  // Later we will have to distinguish between undefined and the hole...
-  // accessors->set_getter(the_hole_value(), SKIP_WRITE_BARRIER);
-  // accessors->set_setter(the_hole_value(), SKIP_WRITE_BARRIER);
+  accessors->set_getter(the_hole_value(), SKIP_WRITE_BARRIER);
+  accessors->set_setter(the_hole_value(), SKIP_WRITE_BARRIER);

[Michael Starzinger, 2012/03/05 11:48:06]

It would be possible to add an AllocateStructWithFiller() that takes another
initial filler object (besides undefined). This would avoid two unnecessary
writes. But I suppose that's not worth the effort here. So I am fine with
leaving everything as it is.

   return accessors;
 }
 
 
 MaybeObject* Heap::AllocateTypeFeedbackInfo() {
   TypeFeedbackInfo* info;
-  { MaybeObject* maybe_result = AllocateStruct(TYPE_FEEDBACK_INFO_TYPE);
-    if (!maybe_result->To(&info)) return maybe_result;
+  { MaybeObject* maybe_info = AllocateStruct(TYPE_FEEDBACK_INFO_TYPE);
+    if (!maybe_info->To(&info)) return maybe_info;
   }
   info->set_ic_total_count(0);
   info->set_ic_with_typeinfo_count(0);
   info->set_type_feedback_cells(TypeFeedbackCells::cast(empty_fixed_array()),
                                 SKIP_WRITE_BARRIER);
   return info;
 }
 
 
 MaybeObject* Heap::AllocateAliasedArgumentsEntry(int aliased_context_slot) {
   AliasedArgumentsEntry* entry;
-  { MaybeObject* maybe_result = AllocateStruct(ALIASED_ARGUMENTS_ENTRY_TYPE);
-    if (!maybe_result->To(&entry)) return maybe_result;
+  { MaybeObject* maybe_entry = AllocateStruct(ALIASED_ARGUMENTS_ENTRY_TYPE);
+    if (!maybe_entry->To(&entry)) return maybe_entry;
   }
   entry->set_aliased_context_slot(aliased_context_slot);
   return entry;
 }
 
 
 const Heap::StringTypeTable Heap::string_type_table[] = {
 #define STRING_TYPE_ELEMENT(type, size, name, camel_name)                      \
   {type, size, k##camel_name##MapRootIndex},
   STRING_TYPE_LIST(STRING_TYPE_ELEMENT)
@@ skipping 4972 matching lines @@
   isolate_->heap()->store_buffer()->Compact();
   isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
     next = chunk->next_chunk();
     isolate_->memory_allocator()->Free(chunk);
   }
   chunks_queued_for_free_ = NULL;
 }
 
 } }  // namespace v8::internal