Basic support for tracking smi-only arrays on ia32.

src/bootstrapper.cc

 // Copyright 2011 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 1058 matching lines @@
     Handle<JSObject> result = factory->NewJSObjectFromMap(new_map);
     new_map->set_elements_kind(NON_STRICT_ARGUMENTS_ELEMENTS);
     // Set up a well-formed parameter map to make assertions happy.
     Handle<FixedArray> elements = factory->NewFixedArray(2);
     elements->set_map(heap->non_strict_arguments_elements_map());
     Handle<FixedArray> array;
     array = factory->NewFixedArray(0);
     elements->set(0, *array);
     array = factory->NewFixedArray(0);
     elements->set(1, *array);
+    Handle<Map> non_strict_arguments_elements_map =
+        factory->GetElementsTransitionMap(result,

[fschneider, 2011/10/18 10:30:20]

Is this call really necessary? It seems that this always return the same
(current) map because result->map() has already elements kind set to
NON_STRICT_ARGUMENTS_ELEMENTS.

+                                          NON_STRICT_ARGUMENTS_ELEMENTS);
+    result->set_map(*non_strict_arguments_elements_map);
+    ASSERT(result->HasNonStrictArgumentsElements());
     result->set_elements(*elements);
     global_context()->set_aliased_arguments_boilerplate(*result);
   }
 
   {  // --- strict mode arguments boilerplate
     const PropertyAttributes attributes =
       static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
 
     // Create the ThrowTypeError functions.
     Handle<FixedArray> callee = factory->NewFixedArray(2, TENURED);
@@ skipping 461 matching lines @@
                         Builtins::kArrayCode,
                         true);
     Handle<JSObject> prototype =
         factory()->NewJSObject(isolate()->object_function(), TENURED);
     SetPrototype(array_function, prototype);
 
     array_function->shared()->set_construct_stub(
         isolate()->builtins()->builtin(Builtins::kArrayConstructCode));
     array_function->shared()->DontAdaptArguments();
 
+    // InternalArrays should not use Smi-Only array optimizations. There are too
+    // many places in the C++ runtime code (e.g. RegEx) that assume that
+    // elements in InternalArrays can be set to non-Smi values without going
+    // through a common bottleneck that would make the SMI_ONLY -> FAST_ELEMENT
+    // transition easy to trap. Moreover, they rarely are smi-only.
+    MaybeObject* maybe_map =
+        array_function->initial_map()->CopyDropTransitions();
+    Map* new_map;
+    if (!maybe_map->To<Map>(&new_map)) return maybe_map;
+    new_map->set_elements_kind(FAST_ELEMENTS);
+    array_function->set_initial_map(new_map);
+
     // Make "length" magic on instances.
     Handle<DescriptorArray> array_descriptors =
         factory()->CopyAppendForeignDescriptor(
             factory()->empty_descriptor_array(),
             factory()->length_symbol(),
             factory()->NewForeign(&Accessors::ArrayLength),
             static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE));
 
     array_function->initial_map()->set_instance_descriptors(
         *array_descriptors);
@@ skipping 658 matching lines @@
   return from + sizeof(NestingCounterType);
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   ASSERT(!IsActive());
 }
 
 } }  // namespace v8::internal