Merge arguments branch to bleeding edge (second try).

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 51ff5c0dea4d95adb72a9dfadfb047a6b4efdaba..dd58b2b70bfa70f454d123db1577182403c38029 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -876,7 +876,13 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_GetOwnProperty) {
           ASSERT(proto->IsJSGlobalObject());
           holder = Handle<JSObject>(JSObject::cast(proto));
         }
-        NumberDictionary* dictionary = holder->element_dictionary();
+        FixedArray* elements = FixedArray::cast(holder->elements());
+        NumberDictionary* dictionary = NULL;
+        if (elements->map() == heap->non_strict_arguments_elements_map()) {
+          dictionary = NumberDictionary::cast(elements->get(1));
+        } else {
+          dictionary = NumberDictionary::cast(elements);
+        }
         int entry = dictionary->FindEntry(index);
         ASSERT(entry != NumberDictionary::kNotFound);
         PropertyDetails details = dictionary->DetailsAt(entry);
@@ -4039,7 +4045,7 @@ MaybeObject* Runtime::SetObjectProperty(Isolate* isolate,
   Handle<String> name = Handle<String>::cast(converted);
 
   if (name->AsArrayIndex(&index)) {
-    return js_object->SetElement(index, *value, strict_mode);
+    return js_object->SetElement(index, *value, strict_mode, true);
   } else {
     return js_object->SetProperty(*name, *value, attr, strict_mode);
   }
@@ -4067,12 +4073,12 @@ MaybeObject* Runtime::ForceSetObjectProperty(Isolate* isolate,
       return *value;
     }
 
-    return js_object->SetElement(index, *value, kNonStrictMode);
+    return js_object->SetElement(index, *value, kNonStrictMode, true);
   }
 
   if (key->IsString()) {
     if (Handle<String>::cast(key)->AsArrayIndex(&index)) {
-      return js_object->SetElement(index, *value, kNonStrictMode);
+      return js_object->SetElement(index, *value, kNonStrictMode, true);
     } else {
       Handle<String> key_string = Handle<String>::cast(key);
       key_string->TryFlatten();
@@ -4089,7 +4095,7 @@ MaybeObject* Runtime::ForceSetObjectProperty(Isolate* isolate,
   Handle<String> name = Handle<String>::cast(converted);
 
   if (name->AsArrayIndex(&index)) {
-    return js_object->SetElement(index, *value, kNonStrictMode);
+    return js_object->SetElement(index, *value, kNonStrictMode, true);
   } else {
     return js_object->SetLocalPropertyIgnoreAttributes(*name, *value, attr);
   }
@@ -7343,6 +7349,103 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_DateYMDFromTime) {
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_NewArgumentsFast) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 3);
+
+  Handle<JSFunction> callee = args.at<JSFunction>(0);
+  Object** parameters = reinterpret_cast<Object**>(args[1]);
+  const int argument_count = Smi::cast(args[2])->value();
+
+  Handle<JSObject> result =
+      isolate->factory()->NewArgumentsObject(callee, argument_count);
+  // Allocate the elements if needed.
+  int parameter_count = callee->shared()->formal_parameter_count();
+  if (argument_count > 0) {
+    if (parameter_count > 0) {
+      int mapped_count = Min(argument_count, parameter_count);
+      Handle<FixedArray> parameter_map =
+          isolate->factory()->NewFixedArray(mapped_count + 2, NOT_TENURED);
+      parameter_map->set_map(
+          isolate->heap()->non_strict_arguments_elements_map());
+
+      Handle<Map> old_map(result->map());
+      Handle<Map> new_map =
+          isolate->factory()->CopyMapDropTransitions(old_map);
+      new_map->set_elements_kind(JSObject::NON_STRICT_ARGUMENTS_ELEMENTS);
+
+      result->set_map(*new_map);
+      result->set_elements(*parameter_map);
+
+      // Store the context and the arguments array at the beginning of the
+      // parameter map.
+      Handle<Context> context(isolate->context());
+      Handle<FixedArray> arguments =
+          isolate->factory()->NewFixedArray(argument_count, NOT_TENURED);
+      parameter_map->set(0, *context);
+      parameter_map->set(1, *arguments);
+
+      // Loop over the actual parameters backwards.
+      int index = argument_count - 1;
+      while (index >= mapped_count) {
+        // These go directly in the arguments array and have no
+        // corresponding slot in the parameter map.
+        arguments->set(index, *(parameters - index - 1));
+        --index;
+      }
+
+      ScopeInfo<> scope_info(callee->shared()->scope_info());
+      while (index >= 0) {
+        // Detect duplicate names to the right in the parameter list.
+        Handle<String> name = scope_info.parameter_name(index);
+        int context_slot_count = scope_info.number_of_context_slots();
+        bool duplicate = false;
+        for (int j = index + 1; j < parameter_count; ++j) {
+          if (scope_info.parameter_name(j).is_identical_to(name)) {
+            duplicate = true;
+            break;
+          }
+        }
+
+        if (duplicate) {
+          // This goes directly in the arguments array with a hole in the
+          // parameter map.
+          arguments->set(index, *(parameters - index - 1));
+          parameter_map->set_the_hole(index + 2);
+        } else {
+          // The context index goes in the parameter map with a hole in the
+          // arguments array.
+          int context_index = -1;
+          for (int j = Context::MIN_CONTEXT_SLOTS;
+               j < context_slot_count;
+               ++j) {
+            if (scope_info.context_slot_name(j).is_identical_to(name)) {
+              context_index = j;
+              break;
+            }
+          }
+          ASSERT(context_index >= 0);
+          arguments->set_the_hole(index);
+          parameter_map->set(index + 2, Smi::FromInt(context_index));
+        }
+
+        --index;
+      }
+    } else {
+      // If there is no aliasing, the arguments object elements are not
+      // special in any way.
+      Handle<FixedArray> elements =
+          isolate->factory()->NewFixedArray(argument_count, NOT_TENURED);
+      result->set_elements(*elements);
+      for (int i = 0; i < argument_count; ++i) {
+        elements->set(i, *(parameters - i - 1));
+      }
+    }
+  }
+  return *result;
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_NewStrictArgumentsFast) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 3);
 
@@ -7784,7 +7887,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_CompileForOnStackReplacement) {
   CONVERT_ARG_CHECKED(JSFunction, function, 0);
 
   // We're not prepared to handle a function with arguments object.
-  ASSERT(!function->shared()->scope_info()->HasArgumentsShadow());
+  ASSERT(!function->shared()->uses_arguments());
 
   // We have hit a back edge in an unoptimized frame for a function that was
   // selected for on-stack replacement.  Find the unoptimized code object.
@@ -8749,8 +8852,8 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_PushIfAbsent) {
   }
   Object* obj;
   // Strict not needed. Used for cycle detection in Array join implementation.
-  { MaybeObject* maybe_obj = array->SetFastElement(length, element,
-                                                   kNonStrictMode);
+  { MaybeObject* maybe_obj =
+        array->SetFastElement(length, element, kNonStrictMode, true);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   return isolate->heap()->true_value();
@@ -10061,18 +10164,14 @@ static bool CopyContextLocalsToScopeObject(
     int context_index = serialized_scope_info->ContextSlotIndex(
         *scope_info.context_slot_name(i), NULL);
 
-    // Don't include the arguments shadow (.arguments) context variable.
-    if (*scope_info.context_slot_name(i) !=
-        isolate->heap()->arguments_shadow_symbol()) {
-      RETURN_IF_EMPTY_HANDLE_VALUE(
-          isolate,
-          SetProperty(scope_object,
-                      scope_info.context_slot_name(i),
-                      Handle<Object>(context->get(context_index), isolate),
-                      NONE,
-                      kNonStrictMode),
-          false);
-    }
+    RETURN_IF_EMPTY_HANDLE_VALUE(
+        isolate,
+        SetProperty(scope_object,
+                    scope_info.context_slot_name(i),
+                    Handle<Object>(context->get(context_index), isolate),
+                    NONE,
+                    kNonStrictMode),
+        false);
   }
 
   return true;
@@ -10167,29 +10266,6 @@ static Handle<JSObject> MaterializeClosure(Isolate* isolate,
   Handle<JSObject> closure_scope =
       isolate->factory()->NewJSObject(isolate->object_function());
 
-  // Check whether the arguments shadow object exists.
-  int arguments_shadow_index =
-      shared->scope_info()->ContextSlotIndex(
-          isolate->heap()->arguments_shadow_symbol(), NULL);
-  if (arguments_shadow_index >= 0) {
-    // In this case all the arguments are available in the arguments shadow
-    // object.
-    Handle<JSObject> arguments_shadow(
-        JSObject::cast(context->get(arguments_shadow_index)));
-    for (int i = 0; i < scope_info.number_of_parameters(); ++i) {
-      // We don't expect exception-throwing getters on the arguments shadow.
-      Object* element = arguments_shadow->GetElement(i)->ToObjectUnchecked();
-      RETURN_IF_EMPTY_HANDLE_VALUE(
-          isolate,
-          SetProperty(closure_scope,
-                      scope_info.parameter_name(i),
-                      Handle<Object>(element, isolate),
-                      NONE,
-                      kNonStrictMode),
-          Handle<JSObject>());
-    }
-  }
-
   // Fill all context locals to the context extension.
   if (!CopyContextLocalsToScopeObject(isolate,
                                       serialized_scope_info, scope_info,