When following an accessor transition for an already existing accessor, don't...

When following an accessor transition for an already existing accessor, don't load the last added descriptor but the same descriptor as we already found previously.

BUG=137689
TEST=test/mjsunit/regress/regress-crbug-137689.js

Review URL: https://chromiumcodereview.appspot.com/10808005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12115 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -4424,19 +4424,19 @@ MaybeObject* JSObject::DefineAccessor(String* name,
 
 static MaybeObject* TryAccessorTransition(JSObject* self,
                                           Map* transitioned_map,
-                                          String* name,
+                                          int target_descriptor,
                                           AccessorComponent component,
                                           Object* accessor,
                                           PropertyAttributes attributes) {
   DescriptorArray* descs = transitioned_map->instance_descriptors();
-  int number = descs->LastAdded();
-  PropertyDetails details = descs->GetDetails(number);
+  PropertyDetails details = descs->GetDetails(target_descriptor);
 
   // If the transition target was not callbacks, fall back to the slow case.
   if (details.type() != CALLBACKS) return self->GetHeap()->null_value();
+  Object* descriptor = descs->GetCallbacksObject(target_descriptor);
+  if (!descriptor->IsAccessorPair()) return self->GetHeap()->null_value();
 
-  Object* target_accessor =
-      AccessorPair::cast(descs->GetCallbacksObject(number))->get(component);
+  Object* target_accessor = AccessorPair::cast(descriptor)->get(component);
   PropertyAttributes target_attributes = details.attributes();
 
   // Reuse transition if adding same accessor with same attributes.
@@ -4473,17 +4473,34 @@ MaybeObject* JSObject::DefineFastAccessor(String* name,
       if (entry == accessor && result.GetAttributes() == attributes) {
         return this;
       }
+    } else {
+      return GetHeap()->null_value();
     }
-  }
 
-  // If not, lookup a transition.
-  map()->LookupTransition(this, name, &result);
+    int descriptor_number = result.GetDescriptorIndex();
 
-  // If there is a transition, try to follow it.
-  if (result.IsFound()) {
-    Map* target = result.GetTransitionTarget();
-    return TryAccessorTransition(
-        this, target, name, component, accessor, attributes);
+    map()->LookupTransition(this, name, &result);
+
+    if (result.IsFound()) {
+      Map* target = result.GetTransitionTarget();
+      ASSERT(target->instance_descriptors()->number_of_descriptors() ==
+             map()->instance_descriptors()->number_of_descriptors());
+      ASSERT(target->instance_descriptors()->GetKey(descriptor_number) == name);
+      return TryAccessorTransition(
+          this, target, descriptor_number, component, accessor, attributes);
+    }
+  } else {
+    // If not, lookup a transition.
+    map()->LookupTransition(this, name, &result);
+
+    // If there is a transition, try to follow it.
+    if (result.IsFound()) {
+      Map* target = result.GetTransitionTarget();
+      int descriptor_number = target->instance_descriptors()->LastAdded();
+      ASSERT(target->instance_descriptors()->GetKey(descriptor_number) == name);
+      return TryAccessorTransition(
+          this, target, descriptor_number, component, accessor, attributes);
+    }
   }
 
   // If there is no transition yet, add a transition to the a new accessor pair

src/property.h

@@ -328,6 +328,11 @@ class LookupResult BASE_EMBEDDED {
     return number_;
   }
 
+  int GetDescriptorIndex() {
+    ASSERT(lookup_type_ == DESCRIPTOR_TYPE);
+    return number_;
+  }
+
   int GetFieldIndex() {
     ASSERT(lookup_type_ == DESCRIPTOR_TYPE);
     ASSERT(IsField());

test/mjsunit/regress/regress-crbug-137689.js

+// 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+function getter() { return 10; }
+function setter(v) { }
+function getter2() { return 20; }
+
+var o = {};
+var o2 = {};
+
+Object.defineProperty(o, "foo", { get: getter, configurable: true });
+Object.defineProperty(o2, "foo", { get: getter, configurable: true });
+assertTrue(%HaveSameMap(o, o2));
+
+Object.defineProperty(o, "bar", { get: getter2 });
+Object.defineProperty(o2, "bar", { get: getter2 });
+assertTrue(%HaveSameMap(o, o2));
+
+Object.defineProperty(o, "foo", { set: setter, configurable: true });
+Object.defineProperty(o2, "foo", { set: setter, configurable: true });
+assertTrue(%HaveSameMap(o, o2));