--- old/src/share/vm/gc/g1/g1InCSetState.hpp	2015-12-04 15:40:32.232407313 +0100
+++ new/src/share/vm/gc/g1/g1InCSetState.hpp	2015-12-04 15:40:32.140403504 +0100
@@ -55,6 +55,7 @@
     // this encoding allows us to use an > 0 check.
     // The other values are simply encoded in increasing generation order, which
     // makes getting the next generation fast by a simple increment.
+    Ext          = -2,    // Extension point
     Humongous    = -1,    // The region is humongous
     NotInCSet    =  0,    // The region is not in the collection set.
     Young        =  1,    // The region is in the collection set and a young region.
@@ -76,10 +77,11 @@
   bool is_humongous() const            { return _value == Humongous; }
   bool is_young() const                { return _value == Young; }
   bool is_old() const                  { return _value == Old; }
+  bool is_ext() const                  { return _value == Ext; }
 
 #ifdef ASSERT
-  bool is_default() const              { return !is_in_cset_or_humongous(); }
-  bool is_valid() const                { return (_value >= Humongous) && (_value < Num); }
+  bool is_default() const              { return _value == NotInCSet; }
+  bool is_valid() const                { return (_value >= Ext) && (_value < Num); }
   bool is_valid_gen() const            { return (_value >= Young && _value <= Old); }
 #endif
 };
@@ -105,6 +107,12 @@
     set_by_index(index, InCSetState::Humongous);
   }
 
+  void set_ext(uintptr_t index) {
+    assert(get_by_index(index).is_default(),
+           "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
+    set_by_index(index, InCSetState::Ext);
+  }
+
   void clear_humongous(uintptr_t index) {
     set_by_index(index, InCSetState::NotInCSet);
   }