We don't need to track writes of

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 9191)
+++ src/hydrogen-instructions.h	(working copy)
@@ -2249,6 +2249,16 @@
 
   bool InOldSpace() const { return !HEAP->InNewSpace(*handle_); }
 
+  bool ImmortalImmovable() const {
+    Heap* heap = HEAP;
+    if (*handle_ == heap->undefined_value()) return true;
+    if (*handle_ == heap->null_value()) return true;
+    if (*handle_ == heap->true_value()) return true;
+    if (*handle_ == heap->false_value()) return true;
+    if (*handle_ == heap->the_hole_value()) return true;
+    return false;
+  }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::None();
   }
@@ -3333,7 +3343,9 @@
   // TODO(gc) On bleeding edge we omit write barrier when we are

[fschneider, 2011/09/08 19:57:43]

This TODO can be removed as well (or changed into a comment).

   // storing old space constant. We can't allow such an optimization
   // on GC branch.
-  return !value->type().IsSmi();
+  return !value->type().IsBoolean()
+      && !value->type().IsSmi()
+      && !(value->IsConstant() && HConstant::cast(value)->ImmortalImmovable());
 }