Replace ICStub for array.length with hydrogen stub

src/ic.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 837 matching lines @@
         if (FLAG_trace_ic) PrintF("[LoadIC : +#length /string]\n");
 #endif
       }
       // Get the string if we have a string wrapper object.
       Handle<Object> string = object->IsJSValue()
           ? Handle<Object>(Handle<JSValue>::cast(object)->value(), isolate())
           : object;
       return Smi::FromInt(String::cast(*string)->length());
     }
 
-    // Use specialized code for getting the length of arrays.
-    if (object->IsJSArray() &&
-        name->Equals(isolate()->heap()->length_string())) {
-      Handle<Code> stub;
-      if (state == UNINITIALIZED) {
-        stub = pre_monomorphic_stub();
-      } else if (state == PREMONOMORPHIC) {
-        ArrayLengthStub array_length_stub(kind());
-        stub = array_length_stub.GetCode(isolate());
-      } else if (state != MEGAMORPHIC) {
-        ASSERT(state != GENERIC);
-        stub = megamorphic_stub();
-      }
-      if (!stub.is_null()) {
-        set_target(*stub);
-#ifdef DEBUG
-        if (FLAG_trace_ic) PrintF("[LoadIC : +#length /array]\n");
-#endif
-      }
-      return JSArray::cast(*object)->length();
-    }
-
     // Use specialized code for getting prototype of functions.
     if (object->IsJSFunction() &&
         name->Equals(isolate()->heap()->prototype_string()) &&
         Handle<JSFunction>::cast(object)->should_have_prototype()) {
       Handle<Code> stub;
       if (state == UNINITIALIZED) {
         stub = pre_monomorphic_stub();
       } else if (state == PREMONOMORPHIC) {
         FunctionPrototypeStub function_prototype_stub(kind());
         stub = function_prototype_stub.GetCode(isolate());
@@ skipping 44 matching lines @@
         Object::GetProperty(object, object, &lookup, name, &attr);
     RETURN_IF_EMPTY_HANDLE(isolate(), result);
     // If the property is not present, check if we need to throw an
     // exception.
     if (attr == ABSENT && IsUndeclaredGlobal(object)) {
       return ReferenceError("not_defined", name);
     }
     return *result;
   }
 
+  if (object->IsJSArray() &&

[danno, 2013/03/12 11:16:16]

Doesn't GetProperty already handle this (it should)?

+        name->Equals(isolate()->heap()->length_string())) {
+    return JSArray::cast(*object)->length();
+  }
   // Get the property.
   return object->GetProperty(*object, &lookup, *name, &attr);
 }
 
 
 static bool AddOneReceiverMapIfMissing(MapHandleList* receiver_maps,
                                        Handle<Map> new_receiver_map) {
   ASSERT(!new_receiver_map.is_null());
   for (int current = 0; current < receiver_maps->length(); ++current) {
     if (!receiver_maps->at(current).is_null() &&
@@ skipping 262 matching lines @@
         return isolate()->stub_cache()->ComputeLoadCallback(
             name, receiver, holder, info);
       } else if (callback->IsAccessorPair()) {
         Handle<Object> getter(Handle<AccessorPair>::cast(callback)->getter(),
                               isolate());
         if (!getter->IsJSFunction()) break;
         if (holder->IsGlobalObject()) break;
         if (!holder->HasFastProperties()) break;
         return isolate()->stub_cache()->ComputeLoadViaGetter(
             name, receiver, holder, Handle<JSFunction>::cast(getter));
+      } else if (receiver->IsJSArray() &&
+          name->Equals(isolate()->heap()->length_string())) {
+        return isolate()->stub_cache()->ComputeLoadArrayLength(

[danno, 2013/03/12 11:16:16]

why not just:

Property index = 
  PropertyIndex::NewHeaderIndex(JSArray::kLengthOffset / kPointerSize);
return isolate()->stub_cache()->ComputeLoadField(
  name, receiver, holder, index);

That obviates the need for all the new code in stub-cache.cc

+            name, receiver, holder);
       }
       // TODO(dcarney): Handle correctly.
       if (callback->IsDeclaredAccessorInfo()) break;
       ASSERT(callback->IsForeign());
       // No IC support for old-style native accessors.
       break;
     }
     case INTERCEPTOR:
       ASSERT(HasInterceptorGetter(*holder));
       return isolate()->stub_cache()->ComputeLoadInterceptor(
@@ skipping 1501 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal