--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -4737,7 +4737,7 @@
 }
 
 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
-  const char* type = "";
+  const char* type       = r->get_type_str();
   HeapWord* bottom       = r->bottom();
   HeapWord* end          = r->end();
   size_t capacity_bytes  = r->capacity();
@@ -4748,15 +4748,7 @@
   size_t remset_bytes    = r->rem_set()->mem_size();
   size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
 
-  if (r->used() == 0) {
-    type = "FREE";
-  } else if (r->is_survivor()) {
-    type = "SURV";
-  } else if (r->is_young()) {
-    type = "EDEN";
-  } else if (r->startsHumongous()) {
-    type = "HUMS";
-
+  if (r->startsHumongous()) {
     assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
            _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
            "they should have been zeroed after the last time we used them");
@@ -4769,12 +4761,9 @@
                   &prev_live_bytes, &next_live_bytes);
     end = bottom + HeapRegion::GrainWords;
   } else if (r->continuesHumongous()) {
-    type = "HUMC";
     get_hum_bytes(&used_bytes, &capacity_bytes,
                   &prev_live_bytes, &next_live_bytes);
     assert(end == bottom + HeapRegion::GrainWords, "invariant");
-  } else {
-    type = "OLD";
   }
 
   _total_used_bytes      += used_bytes;

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -211,7 +211,10 @@
     HeapRegion* next = list->get_next_young_region();
     list->set_next_young_region(NULL);
     list->uninstall_surv_rate_group();
-    list->set_not_young();
+    // This is called before a Full GC and all the non-empty /
+    // non-humongous regions at the end of the Full GC will end up as
+    // old anyway.
+    list->set_old();
     list = next;
   }
 }
@@ -370,7 +373,7 @@
     if (curr == NULL)
       gclog_or_tty->print_cr("  empty");
     while (curr != NULL) {
-      gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
+      gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
                              HR_FORMAT_PARAMS(curr),
                              curr->prev_top_at_mark_start(),
                              curr->next_top_at_mark_start(),
@@ -802,6 +805,7 @@
 #ifdef ASSERT
       for (uint i = first; i < first + obj_regions; ++i) {
         HeapRegion* hr = region_at(i);
+        assert(hr->is_free(), "sanity");
         assert(hr->is_empty(), "sanity");
         assert(is_on_master_free_list(hr), "sanity");
       }
@@ -1225,21 +1229,21 @@
 public:
   bool doHeapRegion(HeapRegion* hr) {
     assert(!hr->is_young(), "not expecting to find young regions");
-    // We only generate output for non-empty regions.
-    if (!hr->is_empty()) {
-      if (!hr->isHumongous()) {
-        _hr_printer->post_compaction(hr, G1HRPrinter::Old);
-      } else if (hr->startsHumongous()) {
-        if (hr->region_num() == 1) {
-          // single humongous region
-          _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
-        } else {
-          _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
-        }
+    if (hr->is_free()) {
+      // We only generate output for non-empty regions.
+    } else if (hr->startsHumongous()) {
+      if (hr->region_num() == 1) {
+        // single humongous region
+        _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
       } else {
-        assert(hr->continuesHumongous(), "only way to get here");
-        _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
+        _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
       }
+    } else if (hr->continuesHumongous()) {
+      _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
+    } else if (hr->is_old()) {
+      _hr_printer->post_compaction(hr, G1HRPrinter::Old);
+    } else {
+      ShouldNotReachHere();
     }
     return false;
   }
@@ -2121,8 +2125,8 @@
   // We'll re-use the same region whether the alloc region will
   // require BOT updates or not and, if it doesn't, then a non-young
   // region will complain that it cannot support allocations without
-  // BOT updates. So we'll tag the dummy region as young to avoid that.
-  dummy_region->set_young();
+  // BOT updates. So we'll tag the dummy region as eden to avoid that.
+  dummy_region->set_eden();
   // Make sure it's full.
   dummy_region->set_top(dummy_region->end());
   G1AllocRegion::setup(this, dummy_region);
@@ -4031,14 +4035,6 @@
         if (_hr_printer.is_active()) {
           HeapRegion* hr = g1_policy()->collection_set();
           while (hr != NULL) {
-            G1HRPrinter::RegionType type;
-            if (!hr->is_young()) {
-              type = G1HRPrinter::Old;
-            } else if (hr->is_survivor()) {
-              type = G1HRPrinter::Survivor;
-            } else {
-              type = G1HRPrinter::Eden;
-            }
             _hr_printer.cset(hr);
             hr = hr->next_in_collection_set();
           }
@@ -6063,7 +6059,7 @@
                                   FreeRegionList* free_list,
                                   bool par,
                                   bool locked) {
-  assert(!hr->isHumongous(), "this is only for non-humongous regions");
+  assert(!hr->is_free(), "the region should not be free");
   assert(!hr->is_empty(), "the region should not be empty");
   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
   assert(free_list != NULL, "pre-condition");
@@ -6093,14 +6089,14 @@
   // We need to read this before we make the region non-humongous,
   // otherwise the information will be gone.
   uint last_index = hr->last_hc_index();
-  hr->set_notHumongous();
+  hr->clear_humongous();
   free_region(hr, free_list, par);
 
   uint i = hr->hrm_index() + 1;
   while (i < last_index) {
     HeapRegion* curr_hr = region_at(i);
     assert(curr_hr->continuesHumongous(), "invariant");
-    curr_hr->set_notHumongous();
+    curr_hr->clear_humongous();
     free_region(curr_hr, free_list, par);
     i += 1;
   }
@@ -6408,9 +6404,9 @@
       if (cur->is_young()) {
         cur->set_young_index_in_cset(-1);
       }
-      cur->set_not_young();
       cur->set_evacuation_failed(false);
       // The region is now considered to be old.
+      cur->set_old();
       _old_set.add(cur);
       evacuation_info.increment_collectionset_used_after(cur->used());
     }
@@ -6697,16 +6693,15 @@
   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
 
   bool doHeapRegion(HeapRegion* r) {
-    if (r->is_empty()) {
-      // We ignore empty regions, we'll empty the free list afterwards
-    } else if (r->is_young()) {
-      // We ignore young regions, we'll empty the young list afterwards
-    } else if (r->isHumongous()) {
+    if (r->is_old()) {
+      _old_set->remove(r);
+    } else {
+      // We ignore free regions, we'll empty the free list afterwards.
+      // We ignore young regions, we'll empty the young list afterwards.
       // We ignore humongous regions, we're not tearing down the
-      // humongous region set
-    } else {
-      // The rest should be old
-      _old_set->remove(r);
+      // humongous regions set.
+      assert(r->is_free() || r->is_young() || r->isHumongous(),
+             "it cannot be another type");
     }
     return false;
   }
@@ -6756,6 +6751,7 @@
 
     if (r->is_empty()) {
       // Add free regions to the free list
+      r->set_free();
       _hrm->insert_into_free_list(r);
     } else if (!_free_list_only) {
       assert(!r->is_young(), "we should not come across young regions");
@@ -6763,7 +6759,11 @@
       if (r->isHumongous()) {
         // We ignore humongous regions, we left the humongous set unchanged
       } else {
-        // The rest should be old, add them to the old set
+        // Objects that were compacted would have ended up on regions
+        // that were previously old or free.
+        assert(r->is_free() || r->is_old(), "invariant");
+        // We now consider them old, so register as such.
+        r->set_old();
         _old_set->add(r);
       }
       _total_used += r->used();
@@ -6830,7 +6830,7 @@
 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
                                                   size_t allocated_bytes) {
   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
-  assert(alloc_region->is_young(), "all mutator alloc regions should be young");
+  assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
 
   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
   _summary_bytes_used += allocated_bytes;
@@ -6889,6 +6889,7 @@
         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
         check_bitmaps("Survivor Region Allocation", new_alloc_region);
       } else {
+        new_alloc_region->set_old();
         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
         check_bitmaps("Old Region Allocation", new_alloc_region);
       }
@@ -7000,9 +7001,11 @@
     } else if (hr->is_empty()) {
       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
       _free_count.increment(1u, hr->capacity());
-    } else {
+    } else if (hr->is_old()) {
       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
       _old_count.increment(1u, hr->capacity());
+    } else {
+      ShouldNotReachHere();
     }
     return false;
   }

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -1665,7 +1665,7 @@
 // Add the heap region at the head of the non-incremental collection set
 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
   assert(_inc_cset_build_state == Active, "Precondition");
-  assert(!hr->is_young(), "non-incremental add of young region");
+  assert(hr->is_old(), "the region should be old");
 
   assert(!hr->in_collection_set(), "should not already be in the CSet");
   hr->set_in_collection_set(true);
@@ -1811,7 +1811,7 @@
 // Add the region at the RHS of the incremental cset
 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
   // We should only ever be appending survivors at the end of a pause
-  assert( hr->is_survivor(), "Logic");
+  assert(hr->is_survivor(), "Logic");
 
   // Do the 'common' stuff
   add_region_to_incremental_cset_common(hr);
@@ -1829,7 +1829,7 @@
 // Add the region to the LHS of the incremental cset
 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
   // Survivors should be added to the RHS at the end of a pause
-  assert(!hr->is_survivor(), "Logic");
+  assert(hr->is_eden(), "Logic");
 
   // Do the 'common' stuff
   add_region_to_incremental_cset_common(hr);
@@ -1989,7 +1989,11 @@
   HeapRegion* hr = young_list->first_survivor_region();
   while (hr != NULL) {
     assert(hr->is_survivor(), "badly formed young list");
-    hr->set_young();
+    // There is a convention that all the young regions in the CSet
+    // are tagged as "eden", so we do this for the survivors here. We
+    // use the special set_eden_pre_gc() as it doesn't check that the
+    // region is free (which is not the case here).
+    hr->set_eden_pre_gc();
     hr = hr->get_next_young_region();
   }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Mon Sep 15 12:19:31 2014 +0200
@@ -299,13 +299,13 @@
   // Accessors
 
   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
-    hr->set_young();
+    hr->set_eden();
     hr->install_surv_rate_group(_short_lived_surv_rate_group);
     hr->set_young_index_in_cset(young_index_in_cset);
   }
 
   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
-    assert(hr->is_young() && hr->is_survivor(), "pre-condition");
+    assert(hr->is_survivor(), "pre-condition");
     hr->install_surv_rate_group(_survivor_surv_rate_group);
     hr->set_young_index_in_cset(young_index_in_cset);
   }

--- a/hotspot/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -27,7 +27,6 @@
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1HotCardCache.hpp"
 #include "gc_implementation/g1/g1RemSet.hpp"
-#include "gc_implementation/g1/heapRegion.hpp"
 #include "runtime/atomic.inline.hpp"
 
 G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):
@@ -136,7 +135,6 @@
 }
 
 void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
-  assert(!hr->isHumongous(), "Should have been cleared");
   _card_counts.clear_region(hr);
 }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -259,14 +259,16 @@
     size_t code_root_elems = hrrs->strong_code_roots_list_length();
 
     RegionTypeCounter* current = NULL;
-    if (r->is_young()) {
+    if (r->is_free()) {
+      current = &_free;
+    } else if (r->is_young()) {
       current = &_young;
     } else if (r->isHumongous()) {
       current = &_humonguous;
-    } else if (r->is_empty()) {
-      current = &_free;
+    } else if (r->is_old()) {
+      current = &_old;
     } else {
-      current = &_old;
+      ShouldNotReachHere();
     }
     current->add(rs_mem_sz, occupied_cards, code_root_mem_sz, code_root_elems);
     _all.add(rs_mem_sz, occupied_cards, code_root_mem_sz, code_root_elems);

--- a/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Mon Sep 15 12:19:31 2014 +0200
@@ -31,8 +31,6 @@
 #include "oops/oop.inline.hpp"
 #include "utilities/macros.hpp"
 
-#if INCLUDE_ALL_GCS
-
 class DirtyCardQueueSet;
 class G1SATBCardTableLoggingModRefBS;
 
@@ -180,7 +178,4 @@
   void write_ref_array_work(MemRegion mr) { invalidate(mr); }
 };
 
-
-#endif // INCLUDE_ALL_GCS
-
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1SATBCARDTABLEMODREFBS_HPP

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -211,8 +211,6 @@
 }
 
 void HeapRegion::hr_clear(bool par, bool clear_space, bool locked) {
-  assert(_humongous_type == NotHumongous,
-         "we should have already filtered out humongous regions");
   assert(_humongous_start_region == NULL,
          "we should have already filtered out humongous regions");
   assert(_end == _orig_end,
@@ -222,7 +220,7 @@
 
   set_young_index_in_cset(-1);
   uninstall_surv_rate_group();
-  set_young_type(NotYoung);
+  set_free();
   reset_pre_dummy_top();
 
   if (!par) {
@@ -273,7 +271,7 @@
   assert(top() == bottom(), "should be empty");
   assert(bottom() <= new_top && new_top <= new_end, "pre-condition");
 
-  _humongous_type = StartsHumongous;
+  _type.set_starts_humongous();
   _humongous_start_region = this;
 
   set_end(new_end);
@@ -287,11 +285,11 @@
   assert(top() == bottom(), "should be empty");
   assert(first_hr->startsHumongous(), "pre-condition");
 
-  _humongous_type = ContinuesHumongous;
+  _type.set_continues_humongous();
   _humongous_start_region = first_hr;
 }
 
-void HeapRegion::set_notHumongous() {
+void HeapRegion::clear_humongous() {
   assert(isHumongous(), "pre-condition");
 
   if (startsHumongous()) {
@@ -307,7 +305,6 @@
   }
 
   assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
-  _humongous_type = NotHumongous;
   _humongous_start_region = NULL;
 }
 
@@ -327,12 +324,12 @@
                        MemRegion mr) :
     G1OffsetTableContigSpace(sharedOffsetArray, mr),
     _hrm_index(hrm_index),
-    _humongous_type(NotHumongous), _humongous_start_region(NULL),
+    _humongous_start_region(NULL),
     _in_collection_set(false),
     _next_in_special_set(NULL), _orig_end(NULL),
     _claimed(InitialClaimValue), _evacuation_failed(false),
     _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
-    _young_type(NotYoung), _next_young_region(NULL),
+    _next_young_region(NULL),
     _next_dirty_cards_region(NULL), _next(NULL), _prev(NULL),
 #ifdef ASSERT
     _containing_set(NULL),
@@ -686,26 +683,11 @@
 
 void HeapRegion::print() const { print_on(gclog_or_tty); }
 void HeapRegion::print_on(outputStream* st) const {
-  if (isHumongous()) {
-    if (startsHumongous())
-      st->print(" HS");
-    else
-      st->print(" HC");
-  } else {
-    st->print("   ");
-  }
+  st->print(" %2s", get_short_type_str());
   if (in_collection_set())
     st->print(" CS");
   else
     st->print("   ");
-  if (is_young())
-    st->print(is_survivor() ? " SU" : " Y ");
-  else
-    st->print("   ");
-  if (is_empty())
-    st->print(" F");
-  else
-    st->print("  ");
   st->print(" TS %5d", _gc_time_stamp);
   st->print(" PTAMS "PTR_FORMAT" NTAMS "PTR_FORMAT,
             prev_top_at_mark_start(), next_top_at_mark_start());

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Mon Sep 15 12:19:31 2014 +0200
@@ -27,6 +27,7 @@
 
 #include "gc_implementation/g1/g1BlockOffsetTable.hpp"
 #include "gc_implementation/g1/g1_specialized_oop_closures.hpp"
+#include "gc_implementation/g1/heapRegionType.hpp"
 #include "gc_implementation/g1/survRateGroup.hpp"
 #include "gc_implementation/shared/ageTable.hpp"
 #include "gc_implementation/shared/spaceDecorator.hpp"
@@ -34,8 +35,6 @@
 #include "memory/watermark.hpp"
 #include "utilities/macros.hpp"
 
-#if INCLUDE_ALL_GCS
-
 // A HeapRegion is the smallest piece of a G1CollectedHeap that
 // can be collected independently.
 
@@ -55,10 +54,7 @@
 #define HR_FORMAT "%u:(%s)["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
 #define HR_FORMAT_PARAMS(_hr_) \
                 (_hr_)->hrm_index(), \
-                (_hr_)->is_survivor() ? "S" : (_hr_)->is_young() ? "E" : \
-                (_hr_)->startsHumongous() ? "HS" : \
-                (_hr_)->continuesHumongous() ? "HC" : \
-                !(_hr_)->is_empty() ? "O" : "F", \
+                (_hr_)->get_short_type_str(), \
                 p2i((_hr_)->bottom()), p2i((_hr_)->top()), p2i((_hr_)->end())
 
 // sentinel value for hrm_index
@@ -215,12 +211,6 @@
   friend class VMStructs;
  private:
 
-  enum HumongousType {
-    NotHumongous = 0,
-    StartsHumongous,
-    ContinuesHumongous
-  };
-
   // The remembered set for this region.
   // (Might want to make this "inline" later, to avoid some alloc failure
   // issues.)
@@ -232,7 +222,8 @@
   // The index of this region in the heap region sequence.
   uint  _hrm_index;
 
-  HumongousType _humongous_type;
+  HeapRegionType _type;
+
   // For a humongous region, region in which it starts.
   HeapRegion* _humongous_start_region;
   // For the start region of a humongous sequence, it's original end().
@@ -274,13 +265,6 @@
   // The calculated GC efficiency of the region.
   double _gc_efficiency;
 
-  enum YoungType {
-    NotYoung,                   // a region is not young
-    Young,                      // a region is young
-    Survivor                    // a region is young and it contains survivors
-  };
-
-  volatile YoungType _young_type;
   int  _young_index_in_cset;
   SurvRateGroup* _surv_rate_group;
   int  _age_index;
@@ -305,12 +289,6 @@
     _next_top_at_mark_start = bot;
   }
 
-  void set_young_type(YoungType new_type) {
-    //assert(_young_type != new_type, "setting the same type" );
-    // TODO: add more assertions here
-    _young_type = new_type;
-  }
-
   // Cached attributes used in the collection set policy information
 
   // The RSet length that was added to the total value
@@ -430,9 +408,21 @@
     _prev_marked_bytes = _next_marked_bytes = 0;
   }
 
-  bool isHumongous() const { return _humongous_type != NotHumongous; }
-  bool startsHumongous() const { return _humongous_type == StartsHumongous; }
-  bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }
+  const char* get_type_str() const { return _type.get_str(); }
+  const char* get_short_type_str() const { return _type.get_short_str(); }
+
+  bool is_free() const { return _type.is_free(); }
+
+  bool is_young()    const { return _type.is_young();    }
+  bool is_eden()     const { return _type.is_eden();     }
+  bool is_survivor() const { return _type.is_survivor(); }
+
+  bool isHumongous() const { return _type.is_humongous(); }
+  bool startsHumongous() const { return _type.is_starts_humongous(); }
+  bool continuesHumongous() const { return _type.is_continues_humongous();   }
+
+  bool is_old() const { return _type.is_old(); }
+
   // For a humongous region, region in which it starts.
   HeapRegion* humongous_start_region() const {
     return _humongous_start_region;
@@ -496,7 +486,7 @@
   void set_continuesHumongous(HeapRegion* first_hr);
 
   // Unsets the humongous-related fields on the region.
-  void set_notHumongous();
+  void clear_humongous();
 
   // If the region has a remembered set, return a pointer to it.
   HeapRegionRemSet* rem_set() const {
@@ -623,9 +613,6 @@
   void calc_gc_efficiency(void);
   double gc_efficiency() { return _gc_efficiency;}
 
-  bool is_young() const     { return _young_type != NotYoung; }
-  bool is_survivor() const  { return _young_type == Survivor; }
-
   int  young_index_in_cset() const { return _young_index_in_cset; }
   void set_young_index_in_cset(int index) {
     assert( (index == -1) || is_young(), "pre-condition" );
@@ -677,11 +664,13 @@
     }
   }
 
-  void set_young() { set_young_type(Young); }
+  void set_free() { _type.set_free(); }
 
-  void set_survivor() { set_young_type(Survivor); }
+  void set_eden()        { _type.set_eden();        }
+  void set_eden_pre_gc() { _type.set_eden_pre_gc(); }
+  void set_survivor()    { _type.set_survivor();    }
 
-  void set_not_young() { set_young_type(NotYoung); }
+  void set_old() { _type.set_old(); }
 
   // Determine if an object has been allocated since the last
   // mark performed by the collector. This returns true iff the object
@@ -809,6 +798,4 @@
   bool complete() { return _complete; }
 };
 
-#endif // INCLUDE_ALL_GCS
-
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.cpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -42,7 +42,9 @@
   assert(hr->containing_set() == this, err_msg("Inconsistent containing set for %u", hr->hrm_index()));
   assert(!hr->is_young(), err_msg("Adding young region %u", hr->hrm_index())); // currently we don't use these sets for young regions
   assert(hr->isHumongous() == regions_humongous(), err_msg("Wrong humongous state for region %u and set %s", hr->hrm_index(), name()));
-  assert(hr->is_empty() == regions_empty(), err_msg("Wrong empty state for region %u and set %s", hr->hrm_index(), name()));
+  assert(hr->is_free() == regions_free(), err_msg("Wrong free state for region %u and set %s", hr->hrm_index(), name()));
+  assert(!hr->is_free() || hr->is_empty(), err_msg("Free region %u is not empty for set %s", hr->hrm_index(), name()));
+  assert(!hr->is_empty() || hr->is_free(), err_msg("Empty region %u is not free for set %s", hr->hrm_index(), name()));
   assert(hr->rem_set()->verify_ready_for_par_iteration(), err_msg("Wrong iteration state %u", hr->hrm_index()));
 }
 #endif
@@ -85,16 +87,16 @@
   out->print_cr("Set: %s ("PTR_FORMAT")", name(), this);
   out->print_cr("  Region Assumptions");
   out->print_cr("    humongous         : %s", BOOL_TO_STR(regions_humongous()));
-  out->print_cr("    empty             : %s", BOOL_TO_STR(regions_empty()));
+  out->print_cr("    free              : %s", BOOL_TO_STR(regions_free()));
   out->print_cr("  Attributes");
   out->print_cr("    length            : %14u", length());
   out->print_cr("    total capacity    : "SIZE_FORMAT_W(14)" bytes",
                 total_capacity_bytes());
 }
 
-HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool empty, HRSMtSafeChecker* mt_safety_checker)
+HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool free, HRSMtSafeChecker* mt_safety_checker)
   : _name(name), _verify_in_progress(false),
-    _is_humongous(humongous), _is_empty(empty), _mt_safety_checker(mt_safety_checker),
+    _is_humongous(humongous), _is_free(free), _mt_safety_checker(mt_safety_checker),
     _count()
 { }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Thu Sep 11 14:21:24 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Mon Sep 15 12:19:31 2014 +0200
@@ -81,7 +81,7 @@
   friend class VMStructs;
 private:
   bool _is_humongous;
-  bool _is_empty;
+  bool _is_free;
   HRSMtSafeChecker* _mt_safety_checker;
 
 protected:
@@ -102,9 +102,9 @@
   // not. Only used during verification.
   bool regions_humongous() { return _is_humongous; }
 
-  // Indicates whether all regions in the set should be empty or
+  // Indicates whether all regions in the set should be free or
   // not. Only used during verification.
-  bool regions_empty() { return _is_empty; }
+  bool regions_free() { return _is_free; }
 
   void check_mt_safety() {
     if (_mt_safety_checker != NULL) {
@@ -114,7 +114,7 @@
 
   virtual void fill_in_ext_msg_extra(hrs_ext_msg* msg) { }
 
-  HeapRegionSetBase(const char* name, bool humongous, bool empty, HRSMtSafeChecker* mt_safety_checker);
+  HeapRegionSetBase(const char* name, bool humongous, bool free, HRSMtSafeChecker* mt_safety_checker);
 
 public:
   const char* name() { return _name; }
@@ -171,7 +171,7 @@
   do {                                                                        \
     assert(((_set1_)->regions_humongous() ==                                  \
                                             (_set2_)->regions_humongous()) && \
-           ((_set1_)->regions_empty() == (_set2_)->regions_empty()),          \
+           ((_set1_)->regions_free() == (_set2_)->regions_free()),            \
            hrs_err_msg("the contents of set %s and set %s should match",      \
                        (_set1_)->name(), (_set2_)->name()));                  \
   } while (0)
@@ -184,7 +184,7 @@
 class HeapRegionSet : public HeapRegionSetBase {
 public:
   HeapRegionSet(const char* name, bool humongous, HRSMtSafeChecker* mt_safety_checker):
-    HeapRegionSetBase(name, humongous, false /* empty */, mt_safety_checker) { }
+    HeapRegionSetBase(name, humongous, false /* free */, mt_safety_checker) { }
 
   void bulk_remove(const HeapRegionSetCount& removed) {
     _count.decrement(removed.length(), removed.capacity());

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionType.cpp	Mon Sep 15 12:19:31 2014 +0200
@@ -0,0 +1,69 @@
+/*
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc_implementation/g1/heapRegionType.hpp"
+
+bool HeapRegionType::is_valid(Tag tag) {
+  switch (tag) {
+    case FreeTag:
+    case EdenTag:
+    case SurvTag:
+    case HumStartsTag:
+    case HumContTag:
+    case OldTag:
+      return true;
+  }
+  return false;
+}
+
+const char* HeapRegionType::get_str() const {
+  hrt_assert_is_valid(_tag);
+  switch (_tag) {
+    case FreeTag:      return "FREE";
+    case EdenTag:      return "EDEN";
+    case SurvTag:      return "SURV";
+    case HumStartsTag: return "HUMS";
+    case HumContTag:   return "HUMC";
+    case OldTag:       return "OLD";
+  }
+  ShouldNotReachHere();
+  // keep some compilers happy
+  return NULL;
+}
+
+const char* HeapRegionType::get_short_str() const {
+  hrt_assert_is_valid(_tag);
+  switch (_tag) {
+    case FreeTag:      return "F";
+    case EdenTag:      return "E";
+    case SurvTag:      return "S";
+    case HumStartsTag: return "HS";
+    case HumContTag:   return "HC";
+    case OldTag:       return "O";
+  }
+  ShouldNotReachHere();
+  // keep some compilers happy
+  return NULL;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionType.hpp	Mon Sep 15 12:19:31 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