Enable map transitions for accessor properties.

To avoid a performance regression for context creation with snapshots, we avoid
creating a useless long map chain for regular expressions, keeping the snapshot
size almost the same as before.

Review URL: https://chromiumcodereview.appspot.com/10440045

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11664 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -397,8 +397,6 @@ DEFINE_int(random_seed, 0,
 
 // objects.cc
 DEFINE_bool(use_verbose_printer, true, "allows verbose printing")
-DEFINE_bool(fast_accessor_properties, false,
-            "use map transitions for JavaScript accessors")
 
 // parser.cc
 DEFINE_bool(allow_natives_syntax, false, "allow natives syntax")

src/objects.cc

@@ -4456,8 +4456,7 @@ MaybeObject* JSObject::DefinePropertyAccessor(String* name,
   // to do a lookup, which seems to be a bit of overkill.
   Heap* heap = GetHeap();
   bool only_attribute_changes = getter->IsNull() && setter->IsNull();
-  if (FLAG_fast_accessor_properties &&
-      HasFastProperties() && !only_attribute_changes) {
+  if (HasFastProperties() && !only_attribute_changes) {
     MaybeObject* getterOk = heap->undefined_value();
     if (!getter->IsNull()) {
       getterOk = DefineFastAccessor(name, ACCESSOR_GETTER, getter, attributes);

src/regexp.js

@@ -427,6 +427,7 @@ function SetUpRegExp() {
     LAST_INPUT(lastMatchInfo) = ToString(string);
   };
 
+  %OptimizeObjectForAddingMultipleProperties($RegExp, 22);
   %DefineOrRedefineAccessorProperty($RegExp, 'input', RegExpGetInput,
                                     RegExpSetInput, DONT_DELETE);
   %DefineOrRedefineAccessorProperty($RegExp, '$_', RegExpGetInput,
@@ -481,6 +482,7 @@ function SetUpRegExp() {
                                       RegExpMakeCaptureGetter(i), NoOpSetter,
                                       DONT_DELETE);
   }
+  %ToFastProperties($RegExp);
 }
 
 SetUpRegExp();