Collects unused maps that are only kept alive by map transitions....

src/runtime.cc

 // Copyright 2006-2008 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 302 matching lines @@
   ASSERT(args.length() == 1);
   Object* arg = args[0];
   bool result = arg->IsObjectTemplateInfo() || arg->IsFunctionTemplateInfo();
   return Heap::ToBoolean(result);
 }
 
 
 static Object* Runtime_GetTemplateField(Arguments args) {
   ASSERT(args.length() == 2);
   CONVERT_CHECKED(HeapObject, templ, args[0]);
-  RUNTIME_ASSERT(templ->IsStruct());
   CONVERT_CHECKED(Smi, field, args[1]);
-  return HeapObject::GetHeapObjectField(templ, field->value());
+  int index = field->value();
+  int offset = index * kPointerSize + HeapObject::kHeaderSize;
+  InstanceType type = templ->map()->instance_type();
+  RUNTIME_ASSERT(type ==  FUNCTION_TEMPLATE_INFO_TYPE ||
+                 type ==  OBJECT_TEMPLATE_INFO_TYPE);
+  RUNTIME_ASSERT(offset > 0);
+  RUNTIME_ASSERT(offset < ((type ==  FUNCTION_TEMPLATE_INFO_TYPE) ?
+      FunctionTemplateInfo::kSize : ObjectTemplateInfo::kSize));
+  return HeapObject::RawField(templ, offset);
 }
 
 
 static Object* ThrowRedeclarationError(const char* type, Handle<String> name) {
   HandleScope scope;
   Handle<Object> type_handle = Factory::NewStringFromAscii(CStrVector(type));
   Handle<Object> args[2] = { type_handle, name };
   Handle<Object> error =
       Factory::NewTypeError("redeclaration", HandleVector(args, 2));
   return Top::Throw(*error);
@@ skipping 5187 matching lines @@
 
 void Runtime::PerformGC(Object* result) {
   Failure* failure = Failure::cast(result);
   // Try to do a garbage collection; ignore it if it fails. The C
   // entry stub will throw an out-of-memory exception in that case.
   Heap::CollectGarbage(failure->requested(), failure->allocation_space());
 }
 
 
 } }  // namespace v8::internal