Use map transitions when defining accessor properties.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 3ec9428ab255d48da40b5537a8961cc559186906..395ea486589eecf09cd984b8ad69ec861abd2579 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -710,6 +710,7 @@ class FixedArrayBase;
 class ObjectVisitor;
 class StringStream;
 class Failure;
+class AccessorPair;

[Michael Starzinger, 2012/05/02 13:30:14]

Can we alpha-sort this?

[Sven Panne, 2012/05/03 09:39:02]

Done.

 
 struct ValueInfo : public Malloced {
   ValueInfo() : type(FIRST_TYPE), ptr(NULL), str(NULL), number(0) { }
@@ -1642,6 +1643,25 @@ class JSObject: public JSReceiver {
                                               Object* getter,
                                               Object* setter,
                                               PropertyAttributes attributes);
+  // Try to define a single accessor paying attention to map transitions.
+  // Returns a JavaScript null if this was not possible and we have to use the
+  // slow case. Note that we can fail due to allocations, too.
+  MUST_USE_RESULT MaybeObject* DefineFastAccessor(
+      String* name,
+      AccessorComponent component,
+      Object* accessor,
+      PropertyAttributes attributes);
+  MUST_USE_RESULT MaybeObject* CreateFreshAccessor(
+      String* name,
+      AccessorComponent component,
+      Object* accessor,
+      PropertyAttributes attributes);
+  MUST_USE_RESULT MaybeObject* NewCallbackTrans(
+      String* name,
+      AccessorComponent component,
+      Object* accessor,
+      PropertyAttributes attributes,
+      AccessorPair* accessors2);
   Object* LookupAccessor(String* name, AccessorComponent component);
 
   MUST_USE_RESULT MaybeObject* DefineAccessor(AccessorInfo* info);
@@ -8108,6 +8128,18 @@ class AccessorPair: public Struct {
 
   MUST_USE_RESULT MaybeObject* CopyWithoutTransitions();
 
+  Object* get(AccessorComponent component) {
+    return component == ACCESSOR_GETTER ? getter() : setter();
+  }
+
+  void set(AccessorComponent component, Object* value) {
+    if (component == ACCESSOR_GETTER) {
+      set_getter(value);
+    } else {
+      set_setter(value);
+    }
+  }
+
   // Note: Returns undefined instead in case of a hole.
   Object* GetComponent(AccessorComponent component);