--- old/src/hotspot/share/gc/g1/g1InCSetState.hpp	2018-11-26 21:50:53.008473598 +0100
+++ new/src/hotspot/share/gc/g1/g1InCSetState.hpp	2018-11-26 21:50:52.580471475 +0100
@@ -56,7 +56,8 @@
     // makes getting the next generation fast by a simple increment. They are also
     // used to index into arrays.
     // The negative values are used for objects requiring various special cases,
-    // for example eager reclamation of humongous objects.
+    // for example eager reclamation of humongous objects or optional regions.
+    Optional     = -2,    // The region is optional
     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.
@@ -78,10 +79,11 @@
   bool is_humongous() const            { return _value == Humongous; }
   bool is_young() const                { return _value == Young; }
   bool is_old() const                  { return _value == Old; }
+  bool is_optional() const             { return _value == Optional; }
 
 #ifdef ASSERT
   bool is_default() const              { return _value == NotInCSet; }
-  bool is_valid() const                { return (_value >= Humongous) && (_value < Num); }
+  bool is_valid() const                { return (_value >= Optional) && (_value < Num); }
   bool is_valid_gen() const            { return (_value >= Young && _value <= Old); }
 #endif
 };
@@ -101,6 +103,12 @@
  protected:
   InCSetState default_value() const { return InCSetState::NotInCSet; }
  public:
+  void set_optional(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::Optional);
+  }
+
   void set_humongous(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());