diff -r 00448aa81791 -r c02ec279b062 src/share/vm/gc_implementation/g1/heapRegionType.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/heapRegionType.hpp	Tue Sep 16 14:27:40 2014 +0200
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONTYPE_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONTYPE_HPP
+
+#include "memory/allocation.hpp"
+
+#define hrt_assert_is_valid(tag) \
+  assert(is_valid((tag)), err_msg("invalid HR type: %u", (uint) (tag)))
+
+class HeapRegionType VALUE_OBJ_CLASS_SPEC {
+private:
+  // We encode the value of the heap region type so the generation can be
+  // determined quickly. The tag is split into two parts:
+  //
+  //   major type (young, humongous)                         : top N-1 bits
+  //   minor type (eden / survivor, starts / cont hum, etc.) : bottom 1 bit
+  //
+  // If there's need to increase the number of minor types in the
+  // future, we'll have to increase the size of the latter and hence
+  // decrease the size of the former.
+  //
+  // 0000 0 [ 0] Free
+  //
+  // 0001 0      Young Mask
+  // 0001 0 [ 2] Eden
+  // 0001 1 [ 3] Survivor
+  //
+  // 0010 0      Humongous Mask
+  // 0010 0 [ 4] Humongous Starts
+  // 0010 1 [ 5] Humongous Continues
+  //
+  // 01000 [ 8] Old
+  typedef enum {
+    FreeTag       = 0,
+
+    YoungMask     = 2,
+    EdenTag       = YoungMask,
+    SurvTag       = YoungMask + 1,
+
+    HumMask       = 4,
+    HumStartsTag  = HumMask,
+    HumContTag    = HumMask + 1,
+
+    OldTag        = 8
+  } Tag;
+
+  volatile Tag _tag;
+
+  static bool is_valid(Tag tag);
+
+  Tag get() const {
+    hrt_assert_is_valid(_tag);
+    return _tag;
+  }
+
+  // Sets the type to 'tag'.
+  void set(Tag tag) {
+    hrt_assert_is_valid(tag);
+    hrt_assert_is_valid(_tag);
+    _tag = tag;
+  }
+
+  // Sets the type to 'tag', expecting the type to be 'before'. This
+  // is available for when we want to add sanity checking to the type
+  // transition.
+  void set_from(Tag tag, Tag before) {
+    hrt_assert_is_valid(tag);
+    hrt_assert_is_valid(before);
+    hrt_assert_is_valid(_tag);
+    assert(_tag == before,
+           err_msg("HR tag: %u, expected: %u new tag; %u", _tag, before, tag));
+    _tag = tag;
+  }
+
+public:
+  // Queries
+
+  bool is_free() const { return get() == FreeTag; }
+
+  bool is_young()    const { return (get() & YoungMask) != 0; }
+  bool is_eden()     const { return get() == EdenTag;  }
+  bool is_survivor() const { return get() == SurvTag;  }
+
+  bool is_humongous()           const { return (get() & HumMask) != 0; }
+  bool is_starts_humongous()    const { return get() == HumStartsTag;  }
+  bool is_continues_humongous() const { return get() == HumContTag;    }
+
+  bool is_old() const { return get() == OldTag; }
+
+  // Setters
+
+  void set_free() { set(FreeTag); }
+
+  void set_eden()        { set_from(EdenTag, FreeTag); }
+  void set_eden_pre_gc() { set_from(EdenTag, SurvTag); }
+  void set_survivor()    { set_from(SurvTag, FreeTag); }
+
+  void set_starts_humongous()    { set_from(HumStartsTag, FreeTag); }
+  void set_continues_humongous() { set_from(HumContTag,   FreeTag); }
+
+  void set_old() { set(OldTag); }
+
+  // Misc
+
+  const char* get_str() const;
+  const char* get_short_str() const;
+
+  HeapRegionType() : _tag(FreeTag) { hrt_assert_is_valid(_tag); }
+};
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONTYPE_HPP