Remove more superfluous write barriers.

src/runtime.cc

 // Copyright 2011 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
@@ skipping 1776 matching lines @@
 
   Object* multiline = args[4];
   if (!multiline->IsTrue()) multiline = isolate->heap()->false_value();
 
   Map* map = regexp->map();
   Object* constructor = map->constructor();
   if (constructor->IsJSFunction() &&
       JSFunction::cast(constructor)->initial_map() == map) {
     // If we still have the original map, set in-object properties directly.
     regexp->InObjectPropertyAtPut(JSRegExp::kSourceFieldIndex, source);
-    // TODO(lrn): Consider skipping write barrier on booleans as well.
-    // Both true and false should be in oldspace at all times.
-    regexp->InObjectPropertyAtPut(JSRegExp::kGlobalFieldIndex, global);
-    regexp->InObjectPropertyAtPut(JSRegExp::kIgnoreCaseFieldIndex, ignoreCase);
-    regexp->InObjectPropertyAtPut(JSRegExp::kMultilineFieldIndex, multiline);
+    // Both true and false are immovable immortal objects so no need for write
+    // barrier.
+    regexp->InObjectPropertyAtPut(
+        JSRegExp::kGlobalFieldIndex, global, SKIP_WRITE_BARRIER);
+    regexp->InObjectPropertyAtPut(
+        JSRegExp::kIgnoreCaseFieldIndex, ignoreCase, SKIP_WRITE_BARRIER);
+    regexp->InObjectPropertyAtPut(
+        JSRegExp::kMultilineFieldIndex, multiline, SKIP_WRITE_BARRIER);
     regexp->InObjectPropertyAtPut(JSRegExp::kLastIndexFieldIndex,
                                   Smi::FromInt(0),
                                   SKIP_WRITE_BARRIER);  // It's a Smi.
     return regexp;
   }
 
   // Map has changed, so use generic, but slower, method.
   PropertyAttributes final =
       static_cast<PropertyAttributes>(READ_ONLY | DONT_ENUM | DONT_DELETE);
   PropertyAttributes writable =
@@ skipping 11725 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags);
   }
 }
 
 
 } }  // namespace v8::internal