Avoid repeated rewrites of global store to constant IC due to store of same value.

src/stub-cache.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 545 matching lines @@
   Isolate* isolate = cell->GetIsolate();
   Handle<Type> union_type(PropertyCell::UpdateType(cell, value), isolate);
   bool is_constant = union_type->IsConstant();
   StoreGlobalStub stub(strict_mode, is_constant);
 
   Handle<Code> code = FindIC(
       name, Handle<JSObject>::cast(receiver),
       Code::STORE_IC, Code::NORMAL, stub.GetExtraICState());
   if (!code.is_null()) return code;
 
-  if (is_constant) return stub.GetCode(isolate_);
-
   // Replace the placeholder cell and global object map with the actual global
   // cell and receiver map.
-  Handle<Map> cell_map(isolate_->heap()->global_property_cell_map());
   Handle<Map> meta_map(isolate_->heap()->meta_map());
   Handle<Object> receiver_map(receiver->map(), isolate_);
   code = stub.GetCodeCopyFromTemplate(isolate_);
   code->ReplaceNthObject(1, *meta_map, *receiver_map);
+  Handle<Map> cell_map(isolate_->heap()->global_property_cell_map());
   code->ReplaceNthObject(1, *cell_map, *cell);
+
   JSObject::UpdateMapCodeCache(receiver, name, code);
 
   return code;
 }
 
 
 Handle<Code> StubCache::ComputeStoreCallback(
     Handle<Name> name,
     Handle<JSObject> receiver,
     Handle<JSObject> holder,
@@ skipping 1616 matching lines @@
           Handle<FunctionTemplateInfo>(
               FunctionTemplateInfo::cast(signature->receiver()));
     }
   }
 
   is_simple_api_call_ = true;
 }
 
 
 } }  // namespace v8::internal