Avoid one repeated property lookup when computing store ICs.

src/lookup.h

 // Copyright 2014 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.
 
 #ifndef V8_LOOKUP_H_
 #define V8_LOOKUP_H_
 
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects.h"
@@ skipping 19 matching lines @@
     CHECK_DERIVED = CHECK_DERIVED_SKIP_INTERCEPTOR | CHECK_INTERCEPTOR,
     CHECK_HIDDEN = CHECK_HIDDEN_SKIP_INTERCEPTOR | CHECK_INTERCEPTOR
   };
 
   enum State {
     ACCESS_CHECK,
     INTERCEPTOR,
     JSPROXY,
     NOT_FOUND,
     PROPERTY,
+    TRANSITION,
     // Set state_ to BEFORE_PROPERTY to ensure that the next lookup will be a
     // PROPERTY lookup.
     BEFORE_PROPERTY = INTERCEPTOR
   };
 
   enum PropertyKind {
     DATA,
     ACCESSOR
   };
 
@@ skipping 57 matching lines @@
   void NotFound() {
     has_property_ = false;
     state_ = NOT_FOUND;
   }
 
   Heap* heap() const { return isolate_->heap(); }
   Factory* factory() const { return isolate_->factory(); }
   Handle<Object> GetReceiver() const {
     return maybe_receiver_.ToHandleChecked();
   }
+  Handle<JSObject> GetPropertyTarget() const;

[Toon Verwaest, 2014/08/21 15:07:06]

GetStoreTarget() ?

[Jakob Kummerow, 2014/08/21 16:14:53]

Done.

   Handle<Map> holder_map() const { return holder_map_; }
+  Handle<Map> transition_map() const {
+    DCHECK_EQ(TRANSITION, state_);
+    return transition_map_;
+  }
   template <class T>
   Handle<T> GetHolder() const {
     DCHECK(IsFound());
     return Handle<T>::cast(maybe_holder_.ToHandleChecked());
   }
   Handle<JSReceiver> GetRoot() const;
   bool HolderIsReceiverOrHiddenPrototype() const;
   bool HolderIsNonGlobalHiddenPrototype() const;
 
   /* ACCESS_CHECK */
   bool HasAccess(v8::AccessType access_type) const;
 
   /* PROPERTY */
   // HasProperty needs to be called before any of the other PROPERTY methods
   // below can be used. It ensures that we are able to provide a definite
   // answer, and loads extra information about the property.
   bool HasProperty();
+  // has_property returns the cached result from the last HasProperty call.
+  bool has_property() const { return has_property_; }

[Toon Verwaest, 2014/08/21 15:07:06]

This shouldn't be necessary

[Jakob Kummerow, 2014/08/21 16:14:53]

Done.

   void PrepareForDataProperty(Handle<Object> value);
-  void TransitionToDataProperty(Handle<Object> value,
-                                PropertyAttributes attributes,
-                                Object::StoreFromKeyed store_mode);
+  void PrepareTransitionToDataProperty(Handle<Object> value,
+                                       PropertyAttributes attributes,
+                                       Object::StoreFromKeyed store_mode);
+  bool IsCacheableTransition() {
+    bool cacheable =
+        state_ == TRANSITION && transition_map()->GetBackPointer()->IsMap();
+    if (cacheable) {
+      property_details_ = transition_map_->GetLastDescriptorDetails();
+      LoadPropertyKind();
+      has_property_ = true;
+    }
+    return cacheable;
+  }
+  void ApplyTransitionToDataProperty();
   void ReconfigureDataProperty(Handle<Object> value,
                                PropertyAttributes attributes);
   void TransitionToAccessorProperty(AccessorComponent component,
                                     Handle<Object> accessor,
                                     PropertyAttributes attributes);
   PropertyKind property_kind() const {
     DCHECK(has_property_);
     return property_kind_;
   }
   PropertyEncoding property_encoding() const {
     DCHECK(has_property_);
     return property_encoding_;
   }
   PropertyDetails property_details() const {
     DCHECK(has_property_);
     return property_details_;
   }
   bool IsConfigurable() const { return property_details().IsConfigurable(); }
   bool IsReadOnly() const { return property_details().IsReadOnly(); }
   Representation representation() const {
     return property_details().representation();
   }
   FieldIndex GetFieldIndex() const;
+  Handle<HeapType> GetFieldType() const;
   int GetConstantIndex() const;
   Handle<PropertyCell> GetPropertyCell() const;
   Handle<Object> GetAccessors() const;
   Handle<Object> GetDataValue() const;
   void WriteDataValue(Handle<Object> value);
 
   void InternalizeName();
 
  private:
   Handle<Map> GetReceiverMap() const;
 
   MUST_USE_RESULT inline JSReceiver* NextHolder(Map* map);
   inline State LookupInHolder(Map* map);
   Handle<Object> FetchValue() const;
   void ReloadPropertyInformation();
+  void LoadPropertyKind();
 
   bool IsBootstrapping() const;
 
   // Methods that fetch data from the holder ensure they always have a holder.
   // This means the receiver needs to be present as opposed to just the receiver
   // map. Other objects in the prototype chain are transitively guaranteed to be
   // present via the receiver map.
   bool is_guaranteed_to_have_holder() const {
     return !maybe_receiver_.is_null();
   }
@@ skipping 33 matching lines @@
   // HolderIsReceiverOrHiddenPrototype.
   Configuration configuration_;
   State state_;
   bool has_property_;
   PropertyKind property_kind_;
   PropertyEncoding property_encoding_;
   PropertyDetails property_details_;
   Isolate* isolate_;
   Handle<Name> name_;
   Handle<Map> holder_map_;
+  Handle<Map> transition_map_;
   MaybeHandle<Object> maybe_receiver_;
   MaybeHandle<JSReceiver> maybe_holder_;
 
   int number_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOOKUP_H_