[runtime] Avoid @@isConcatSpreadable lookup for fast path Array.prototype.concat

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 2889 matching lines @@
   // Allocate the empty script.
   Handle<Script> script = factory->NewScript(factory->empty_string());
   script->set_type(Script::TYPE_NATIVE);
   set_empty_script(*script);
 
   Handle<PropertyCell> cell = factory->NewPropertyCell();
   cell->set_value(Smi::FromInt(Isolate::kArrayProtectorValid));
   set_array_protector(*cell);
 
   cell = factory->NewPropertyCell();
+  cell->set_value(
+      Smi::FromInt(Isolate::kArrayIsConcatSpreadableProtectorValid));
+  set_array_is_concat_spreadable_protector(*cell);

[Toon Verwaest, 2016/03/31 08:09:46]

Unless you want to be able to add dependencies to the cell in optimized code,
there's no need to use a PropertyCell rather than a Cell. The same is probably
true for species_cell below.

[Camillo Bruni, 2016/04/06 13:14:32]

ok.

+
+  cell = factory->NewPropertyCell();
   cell->set_value(the_hole_value());
   set_empty_property_cell(*cell);
 
   Handle<PropertyCell> species_cell = factory->NewPropertyCell();
   species_cell->set_value(Smi::FromInt(Isolate::kArrayProtectorValid));
   set_species_protector(*species_cell);
 
   set_weak_stack_trace_list(Smi::FromInt(0));
 
   set_noscript_shared_function_infos(Smi::FromInt(0));
@@ skipping 3553 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8