Replace ICStub for array.length with hydrogen stub

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 8499b9925eaee3523628d2352cfdfc5ad2c626b6..ca728be0c70564523c132697d698e18450eb42c7 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1050,6 +1050,11 @@ HInstruction* HGraphBuilder::BuildUncheckedMonomorphicElementAccess(
                                 elements_kind, is_store);
 }
 
+HInstruction* HGraphBuilder::BuildFastArrayLengthLoad(HValue* object) {
+  Zone* zone = this->zone();
+  return new (zone) HJSArrayLength(object, NULL, HType::Smi());
+}
+
 
 HValue* HGraphBuilder::BuildAllocateElements(HContext* context,
                                              ElementsKind kind,
@@ -6734,6 +6739,15 @@ HInstruction* HOptimizedGraphBuilder::BuildLoadNamedMonomorphic(
     Handle<Map> map) {
   // Handle a load from a known field.
   ASSERT(!map->is_dictionary_map());
+
+  // Handle access to various length properties
+  if (name->Equals(isolate()->heap()->length_string())) {
+    if (map->instance_type() == JS_ARRAY_TYPE) {
+      AddCheckMapsWithTransitions(object, map);

[danno, 2013/03/13 11:49:48]

I think with your changes, you may not need WithTransitions here, because we
will already have calculated the set of maps that we need to handle, including
those with transitions.

[Dmitry Lomov (no reviews), 2013/03/13 16:14:31]

Done.

+      return BuildFastArrayLengthLoad(object);
+    }
+  }
+
   LookupResult lookup(isolate());
   map->LookupDescriptor(NULL, *name, &lookup);
   if (lookup.IsField()) {
@@ -7220,13 +7234,7 @@ void HOptimizedGraphBuilder::VisitProperty(Property* expr) {
   CHECK_ALIVE(VisitForValue(expr->obj()));
 
   HInstruction* instr = NULL;
-  if (expr->AsProperty()->IsArrayLength()) {
-    HValue* array = Pop();
-    AddInstruction(new(zone()) HCheckNonSmi(array));
-    HInstruction* mapcheck =
-        AddInstruction(HCheckInstanceType::NewIsJSArray(array, zone()));
-    instr = new(zone()) HJSArrayLength(array, mapcheck);
-  } else if (expr->IsStringLength()) {
+  if (expr->IsStringLength()) {
     HValue* string = Pop();
     AddInstruction(new(zone()) HCheckNonSmi(string));
     AddInstruction(HCheckInstanceType::NewIsString(string, zone()));