8069016: Add BarrierSet downcast support
authorkbarrett
Fri, 27 Feb 2015 19:52:48 -0500
changeset 29325 0e86e64c66e5
parent 29324 8672c9d7ae94
child 29326 ebaa169c6dc3
child 29327 b539902e30f8
8069016: Add BarrierSet downcast support Summary: Add FakeRttiSupport utility and use to provide barrier_set_cast. Reviewed-by: jmasa, sangheki
hotspot/src/cpu/ppc/vm/macroAssembler_ppc.cpp
hotspot/src/cpu/ppc/vm/stubGenerator_ppc.cpp
hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp
hotspot/src/cpu/sparc/vm/macroAssembler_sparc.cpp
hotspot/src/cpu/sparc/vm/stubGenerator_sparc.cpp
hotspot/src/cpu/x86/vm/c1_Runtime1_x86.cpp
hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp
hotspot/src/cpu/x86/vm/stubGenerator_x86_32.cpp
hotspot/src/cpu/x86/vm/stubGenerator_x86_64.cpp
hotspot/src/share/vm/c1/c1_LIRGenerator.cpp
hotspot/src/share/vm/compiler/disassembler.cpp
hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp
hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp
hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.hpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/psOldGen.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp
hotspot/src/share/vm/gc_implementation/parallelScavenge/psTasks.cpp
hotspot/src/share/vm/memory/barrierSet.hpp
hotspot/src/share/vm/memory/barrierSet.inline.hpp
hotspot/src/share/vm/memory/cardTableModRefBS.cpp
hotspot/src/share/vm/memory/cardTableModRefBS.hpp
hotspot/src/share/vm/memory/modRefBarrierSet.hpp
hotspot/src/share/vm/opto/graphKit.cpp
hotspot/src/share/vm/runtime/vmStructs.cpp
hotspot/src/share/vm/shark/sharkBuilder.cpp
hotspot/src/share/vm/utilities/fakeRttiSupport.hpp
--- a/hotspot/src/cpu/ppc/vm/macroAssembler_ppc.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/ppc/vm/macroAssembler_ppc.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2012, 2014 SAP AG. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -2204,7 +2204,8 @@
 
 // Write the card table byte if needed.
 void MacroAssembler::card_write_barrier_post(Register Rstore_addr, Register Rnew_val, Register Rtmp) {
-  CardTableModRefBS* bs = (CardTableModRefBS*) Universe::heap()->barrier_set();
+  CardTableModRefBS* bs =
+    barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
   assert(bs->kind() == BarrierSet::CardTableModRef ||
          bs->kind() == BarrierSet::CardTableExtension, "wrong barrier");
 #ifdef ASSERT
@@ -2310,9 +2311,8 @@
   Label& filtered = (filtered_ext != NULL) ? *filtered_ext : filtered_int;
   assert_different_registers(Rstore_addr, Rnew_val, Rtmp1, Rtmp2);
 
-  G1SATBCardTableModRefBS* bs = (G1SATBCardTableModRefBS*) Universe::heap()->barrier_set();
-  assert(bs->kind() == BarrierSet::G1SATBCT ||
-         bs->kind() == BarrierSet::G1SATBCTLogging, "wrong barrier");
+  G1SATBCardTableLoggingModRefBS* bs =
+    barrier_set_cast<G1SATBCardTableLoggingModRefBS>(Universe::heap()->barrier_set());
 
   // Does store cross heap regions?
   if (G1RSBarrierRegionFilter) {
--- a/hotspot/src/cpu/ppc/vm/stubGenerator_ppc.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/ppc/vm/stubGenerator_ppc.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -694,7 +694,7 @@
             __ release();
           }
 
-          CardTableModRefBS* const ct = (CardTableModRefBS*)bs;
+          CardTableModRefBS* const ct = barrier_set_cast<CardTableModRefBS>(bs);
           assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
           assert_different_registers(addr, count, tmp);
 
--- a/hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2015, 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
@@ -916,7 +916,7 @@
         Register cardtable = G5;
         Register tmp  = G1_scratch;
         Register tmp2 = G3_scratch;
-        jbyte* byte_map_base = ((CardTableModRefBS*)bs)->byte_map_base;
+        jbyte* byte_map_base = barrier_set_cast<CardTableModRefBS>(bs)->byte_map_base;
 
         Label not_already_dirty, restart, refill, young_card;
 
--- a/hotspot/src/cpu/sparc/vm/macroAssembler_sparc.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/sparc/vm/macroAssembler_sparc.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -3858,9 +3858,8 @@
 
   if (new_val == G0) return;
 
-  G1SATBCardTableModRefBS* bs = (G1SATBCardTableModRefBS*) Universe::heap()->barrier_set();
-  assert(bs->kind() == BarrierSet::G1SATBCT ||
-         bs->kind() == BarrierSet::G1SATBCTLogging, "wrong barrier");
+  G1SATBCardTableLoggingModRefBS* bs =
+    barrier_set_cast<G1SATBCardTableLoggingModRefBS>(Universe::heap()->barrier_set());
 
   if (G1RSBarrierRegionFilter) {
     xor3(store_addr, new_val, tmp);
@@ -3904,7 +3903,8 @@
 void MacroAssembler::card_write_barrier_post(Register store_addr, Register new_val, Register tmp) {
   // If we're writing constant NULL, we can skip the write barrier.
   if (new_val == G0) return;
-  CardTableModRefBS* bs = (CardTableModRefBS*) Universe::heap()->barrier_set();
+  CardTableModRefBS* bs =
+    barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
   assert(bs->kind() == BarrierSet::CardTableModRef ||
          bs->kind() == BarrierSet::CardTableExtension, "wrong barrier");
   card_table_write(bs->byte_map_base, tmp, store_addr);
--- a/hotspot/src/cpu/sparc/vm/stubGenerator_sparc.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/sparc/vm/stubGenerator_sparc.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, 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
@@ -1019,7 +1019,7 @@
       case BarrierSet::CardTableModRef:
       case BarrierSet::CardTableExtension:
         {
-          CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+          CardTableModRefBS* ct = barrier_set_cast<CardTableModRefBS>(bs);
           assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
           assert_different_registers(addr, count, tmp);
 
--- a/hotspot/src/cpu/x86/vm/c1_Runtime1_x86.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/x86/vm/c1_Runtime1_x86.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2015, 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
@@ -1718,8 +1718,8 @@
         // arg0: store_address
         Address store_addr(rbp, 2*BytesPerWord);
 
-        BarrierSet* bs = Universe::heap()->barrier_set();
-        CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+        CardTableModRefBS* ct =
+          barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
         assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
 
         Label done;
--- a/hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/x86/vm/macroAssembler_x86.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -4204,8 +4204,8 @@
   Address buffer(thread, in_bytes(JavaThread::dirty_card_queue_offset() +
                                        PtrQueue::byte_offset_of_buf()));
 
-  BarrierSet* bs = Universe::heap()->barrier_set();
-  CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+  CardTableModRefBS* ct =
+    barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
   assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
 
   Label done;
@@ -4305,7 +4305,7 @@
 void MacroAssembler::store_check_part_2(Register obj) {
   BarrierSet* bs = Universe::heap()->barrier_set();
   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
-  CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+  CardTableModRefBS* ct = barrier_set_cast<CardTableModRefBS>(bs);
   assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
 
   // The calculation for byte_map_base is as follows:
--- a/hotspot/src/cpu/x86/vm/stubGenerator_x86_32.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/x86/vm/stubGenerator_x86_32.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2015, 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
@@ -752,7 +752,7 @@
       case BarrierSet::CardTableModRef:
       case BarrierSet::CardTableExtension:
         {
-          CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+          CardTableModRefBS* ct = barrier_set_cast<CardTableModRefBS>(bs);
           assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
 
           Label L_loop;
--- a/hotspot/src/cpu/x86/vm/stubGenerator_x86_64.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/cpu/x86/vm/stubGenerator_x86_64.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2015, 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
@@ -1272,7 +1272,7 @@
       case BarrierSet::CardTableModRef:
       case BarrierSet::CardTableExtension:
         {
-          CardTableModRefBS* ct = (CardTableModRefBS*)bs;
+          CardTableModRefBS* ct = barrier_set_cast<CardTableModRefBS>(bs);
           assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
 
           Label L_loop;
--- a/hotspot/src/share/vm/c1/c1_LIRGenerator.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/c1/c1_LIRGenerator.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1582,9 +1582,9 @@
 ////////////////////////////////////////////////////////////////////////
 
 void LIRGenerator::CardTableModRef_post_barrier(LIR_OprDesc* addr, LIR_OprDesc* new_val) {
-
-  assert(sizeof(*((CardTableModRefBS*)_bs)->byte_map_base) == sizeof(jbyte), "adjust this code");
-  LIR_Const* card_table_base = new LIR_Const(((CardTableModRefBS*)_bs)->byte_map_base);
+  CardTableModRefBS* ct = barrier_set_cast<CardTableModRefBS>(_bs);
+  assert(sizeof(*(ct->byte_map_base)) == sizeof(jbyte), "adjust this code");
+  LIR_Const* card_table_base = new LIR_Const(ct->byte_map_base);
   if (addr->is_address()) {
     LIR_Address* address = addr->as_address_ptr();
     // ptr cannot be an object because we use this barrier for array card marks
@@ -1609,7 +1609,6 @@
     __ move(new LIR_Address(FrameMap::Rthread_opr, in_bytes(JavaThread::card_table_base_offset()), T_ADDRESS), tmp);
   }
 
-  CardTableModRefBS* ct = (CardTableModRefBS*)_bs;
   LIR_Address *card_addr = new LIR_Address(tmp, addr, (LIR_Address::Scale) -CardTableModRefBS::card_shift, 0, T_BYTE);
   if(((int)ct->byte_map_base & 0xff) == 0) {
     __ move(tmp, card_addr);
--- a/hotspot/src/share/vm/compiler/disassembler.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/compiler/disassembler.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -340,8 +340,8 @@
     }
 
     BarrierSet* bs = Universe::heap()->barrier_set();
-    if (bs->kind() == BarrierSet::CardTableModRef &&
-        adr == (address)((CardTableModRefBS*)(bs))->byte_map_base) {
+    if (bs->is_a(BarrierSet::CardTableModRef) &&
+        adr == (address)(barrier_set_cast<CardTableModRefBS>(bs)->byte_map_base)) {
       st->print("word_map_base");
       if (WizardMode) st->print(" " INTPTR_FORMAT, (intptr_t)adr);
       return;
--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, 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
@@ -1440,7 +1440,7 @@
   CMCountDataClosureBase(G1CollectedHeap* g1h,
                          BitMap* region_bm, BitMap* card_bm):
     _g1h(g1h), _cm(g1h->concurrent_mark()),
-    _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
+    _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
     _region_bm(region_bm), _card_bm(card_bm) { }
 };
 
@@ -3111,7 +3111,7 @@
                               BitMap* cm_card_bm,
                               uint max_worker_id) :
     _g1h(g1h), _cm(g1h->concurrent_mark()),
-    _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
+    _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
     _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
 
   bool doHeapRegion(HeapRegion* hr) {
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1274,7 +1274,7 @@
   virtual bool is_in_closed_subset(const void* p) const;
 
   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
-    return (G1SATBCardTableLoggingModRefBS*) barrier_set();
+    return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
   }
 
   // This resets the card table to all zeros.  It is used after
--- a/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -33,8 +33,11 @@
 #include "runtime/orderAccess.inline.hpp"
 #include "runtime/thread.inline.hpp"
 
-G1SATBCardTableModRefBS::G1SATBCardTableModRefBS(MemRegion whole_heap, BarrierSet::Name kind) :
-  CardTableModRefBS(whole_heap, kind) { }
+G1SATBCardTableModRefBS::G1SATBCardTableModRefBS(
+  MemRegion whole_heap,
+  const BarrierSet::FakeRtti& fake_rtti) :
+  CardTableModRefBS(whole_heap, fake_rtti.add_tag(BarrierSet::G1SATBCT))
+{ }
 
 void G1SATBCardTableModRefBS::enqueue(oop pre_val) {
   // Nulls should have been already filtered.
@@ -130,7 +133,7 @@
 
 G1SATBCardTableLoggingModRefBS::
 G1SATBCardTableLoggingModRefBS(MemRegion whole_heap) :
-  G1SATBCardTableModRefBS(whole_heap, BarrierSet::G1SATBCTLogging),
+  G1SATBCardTableModRefBS(whole_heap, BarrierSet::FakeRtti(G1SATBCTLogging)),
   _dcqs(JavaThread::dirty_card_queue_set()),
   _listener()
 {
@@ -203,7 +206,7 @@
   if (new_val == NULL) return;
   // Otherwise, log it.
   G1SATBCardTableLoggingModRefBS* g1_bs =
-    (G1SATBCardTableLoggingModRefBS*)Universe::heap()->barrier_set();
+    barrier_set_cast<G1SATBCardTableLoggingModRefBS>(Universe::heap()->barrier_set());
   g1_bs->write_ref_field_work(field, new_val);
 }
 
--- a/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -43,7 +43,7 @@
     g1_young_gen = CT_MR_BS_last_reserved << 1
   };
 
-  G1SATBCardTableModRefBS(MemRegion whole_heap, BarrierSet::Name kind);
+  G1SATBCardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti);
   ~G1SATBCardTableModRefBS() { }
 
 public:
@@ -53,10 +53,6 @@
   // pre-marking object graph.
   static void enqueue(oop pre_val);
 
-  bool is_a(BarrierSet::Name bsn) {
-    return bsn == BarrierSet::G1SATBCT || CardTableModRefBS::is_a(bsn);
-  }
-
   virtual bool has_write_ref_pre_barrier() { return true; }
 
   // This notes that we don't need to access any BarrierSet data
@@ -128,6 +124,11 @@
   }
 };
 
+template<>
+struct BarrierSet::GetName<G1SATBCardTableModRefBS> {
+  static const BarrierSet::Name value = BarrierSet::G1SATBCT;
+};
+
 class G1SATBCardTableLoggingModRefBSChangedListener : public G1MappingChangedListener {
  private:
   G1SATBCardTableLoggingModRefBS* _card_table;
@@ -159,11 +160,6 @@
 
   virtual void resize_covered_region(MemRegion new_region) { ShouldNotReachHere(); }
 
-  bool is_a(BarrierSet::Name bsn) {
-    return bsn == BarrierSet::G1SATBCTLogging ||
-      G1SATBCardTableModRefBS::is_a(bsn);
-  }
-
   void write_ref_field_work(void* field, oop new_val, bool release = false);
 
   // Can be called from static contexts.
@@ -177,4 +173,9 @@
   void write_ref_array_work(MemRegion mr) { invalidate(mr); }
 };
 
+template<>
+struct BarrierSet::GetName<G1SATBCardTableLoggingModRefBS> {
+  static const BarrierSet::Name value = BarrierSet::G1SATBCTLogging;
+};
+
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1SATBCARDTABLEMODREFBS_HPP
--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -193,7 +193,7 @@
   HeapRegionRemSet* hrrs = rem_set();
   hrrs->clear();
   CardTableModRefBS* ct_bs =
-                   (CardTableModRefBS*)G1CollectedHeap::heap()->barrier_set();
+    barrier_set_cast<CardTableModRefBS>(G1CollectedHeap::heap()->barrier_set());
   ct_bs->clear(MemRegion(bottom(), end()));
 }
 
@@ -643,13 +643,9 @@
   // _vo == UseNextMarking -> use "next" marking information,
   // _vo == UseMarkWord    -> use mark word from object header.
   VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
-    _g1h(g1h), _bs(NULL), _containing_obj(NULL),
-    _failures(false), _n_failures(0), _vo(vo)
-  {
-    BarrierSet* bs = _g1h->barrier_set();
-    if (bs->is_a(BarrierSet::CardTableModRef))
-      _bs = (CardTableModRefBS*)bs;
-  }
+    _g1h(g1h), _bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
+    _containing_obj(NULL), _failures(false), _n_failures(0), _vo(vo)
+  { }
 
   void set_containing_obj(oop obj) {
     _containing_obj = obj;
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, 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
@@ -81,7 +81,7 @@
     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 
     _young_gen = heap->young_gen();
-    _card_table = (CardTableExtension*)heap->barrier_set();
+    _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
     // No point in asserting barrier set type here. Need to make CardTableExtension
     // a unique barrier set type.
   }
@@ -341,7 +341,9 @@
 
   PSOldGen* old_gen = heap->old_gen();
 
-  CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set());
+  CheckForPreciseMarks check(
+    heap->young_gen(),
+    barrier_set_cast<CardTableExtension>(heap->barrier_set()));
 
   old_gen->oop_iterate_no_header(&check);
 
@@ -349,8 +351,8 @@
 }
 
 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) {
-  CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set();
-  // FIX ME ASSERT HERE
+  CardTableExtension* card_table =
+    barrier_set_cast<CardTableExtension>(Universe::heap()->barrier_set());
 
   jbyte* bot = card_table->byte_for(mr.start());
   jbyte* top = card_table->byte_for(mr.end());
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -54,10 +54,16 @@
   };
 
   CardTableExtension(MemRegion whole_heap) :
-    CardTableModRefBS(whole_heap, BarrierSet::CardTableModRef) { }
-
-  // Too risky for the 4/10/02 putback
-  // BarrierSet::Name kind() { return BarrierSet::CardTableExtension; }
+    CardTableModRefBS(
+      whole_heap,
+      // Concrete tag should be BarrierSet::CardTableExtension.
+      // That will presently break things in a bunch of places though.
+      // The concrete tag is used as a dispatch key in many places, and
+      // CardTableExtension does not correctly dispatch in some of those
+      // uses. This will be addressed as part of a reorganization of the
+      // BarrierSet hierarchy.
+      BarrierSet::FakeRtti(BarrierSet::CardTableModRef, 0).add_tag(BarrierSet::CardTableExtension))
+    { }
 
   // Scavenge support
   void scavenge_contents_parallel(ObjectStartArray* start_array,
@@ -110,4 +116,9 @@
 #endif // ASSERT
 };
 
+template<>
+struct BarrierSet::GetName<CardTableExtension> {
+  static const BarrierSet::Name value = BarrierSet::CardTableExtension;
+};
+
 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_CARDTABLEEXTENSION_HPP
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,6 +1,5 @@
-
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, 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
@@ -233,15 +232,12 @@
                       young_gen->to_space()->is_empty();
     young_gen_empty = eden_empty && survivors_empty;
 
-    BarrierSet* bs = heap->barrier_set();
-    if (bs->is_a(BarrierSet::ModRef)) {
-      ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
-      MemRegion old_mr = heap->old_gen()->reserved();
-      if (young_gen_empty) {
-        modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
-      } else {
-        modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
-      }
+    ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
+    MemRegion old_mr = heap->old_gen()->reserved();
+    if (young_gen_empty) {
+      modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
+    } else {
+      modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
     }
 
     // Delete metaspaces for unloaded class loaders and clean up loader_data graph
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psOldGen.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psOldGen.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, 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
@@ -111,8 +111,8 @@
 
   Universe::heap()->barrier_set()->resize_covered_region(cmr);
 
-  CardTableModRefBS* _ct = (CardTableModRefBS*)Universe::heap()->barrier_set();
-  assert (_ct->kind() == BarrierSet::CardTableModRef, "Sanity");
+  CardTableModRefBS* _ct =
+    barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
 
   // Verify that the start and end of this generation is the start of a card.
   // If this wasn't true, a single card could span more than one generation,
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2015, 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
@@ -1050,16 +1050,12 @@
   bool young_gen_empty = eden_empty && from_space->is_empty() &&
     to_space->is_empty();
 
-  BarrierSet* bs = heap->barrier_set();
-  if (bs->is_a(BarrierSet::ModRef)) {
-    ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
-    MemRegion old_mr = heap->old_gen()->reserved();
-
-    if (young_gen_empty) {
-      modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
-    } else {
-      modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
-    }
+  ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
+  MemRegion old_mr = heap->old_gen()->reserved();
+  if (young_gen_empty) {
+    modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
+  } else {
+    modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
   }
 
   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,6 +1,5 @@
-
 /*
- * Copyright (c) 2002, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2015, 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
@@ -866,9 +865,7 @@
                            NULL);                      // header provides liveness info
 
   // Cache the cardtable
-  BarrierSet* bs = Universe::heap()->barrier_set();
-  assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
-  _card_table = (CardTableExtension*)bs;
+  _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
 
   _counters = new CollectorCounters("PSScavenge", 0);
 }
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psTasks.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psTasks.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2015, 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
@@ -183,8 +183,8 @@
     PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(which);
 
     assert(Universe::heap()->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
-    CardTableExtension* card_table = (CardTableExtension *)Universe::heap()->barrier_set();
-    // FIX ME! Assert that card_table is the type we believe it to be.
+    CardTableExtension* card_table =
+      barrier_set_cast<CardTableExtension>(Universe::heap()->barrier_set());
 
     card_table->scavenge_contents_parallel(_gen->start_array(),
                                            _gen->object_space(),
--- a/hotspot/src/share/vm/memory/barrierSet.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/memory/barrierSet.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -27,6 +27,7 @@
 
 #include "memory/memRegion.hpp"
 #include "oops/oopsHierarchy.hpp"
+#include "utilities/fakeRttiSupport.hpp"
 
 // This class provides the interface between a barrier implementation and
 // the rest of the system.
@@ -34,18 +35,61 @@
 class BarrierSet: public CHeapObj<mtGC> {
   friend class VMStructs;
 public:
-  enum Name {
-    ModRef,
-    CardTableModRef,
-    CardTableExtension,
-    G1SATBCT,
-    G1SATBCTLogging
+  // Fake RTTI support.  For a derived class T to participate
+  // - T must have a corresponding Name entry.
+  // - GetName<T> must be specialized to return the corresponding Name
+  //   entry.
+  // - If T is a base class, the constructor must have a FakeRtti
+  //   parameter and pass it up to its base class, with the tag set
+  //   augmented with the corresponding Name entry.
+  // - If T is a concrete class, the constructor must create a
+  //   FakeRtti object whose tag set includes the corresponding Name
+  //   entry, and pass it up to its base class.
+
+  enum Name {                   // associated class
+    ModRef,                     // ModRefBarrierSet
+    CardTableModRef,            // CardTableModRefBS
+    CardTableForRS,             // CardTableModRefBSForCTRS
+    CardTableExtension,         // CardTableExtension
+    G1SATBCT,                   // G1SATBCardTableModRefBS
+    G1SATBCTLogging             // G1SATBCardTableLoggingModRefBS
   };
 
+protected:
+  typedef FakeRttiSupport<BarrierSet, Name> FakeRtti;
+
+private:
+  FakeRtti _fake_rtti;
+
+  // Metafunction mapping a class derived from BarrierSet to the
+  // corresponding Name enum tag.
+  template<typename T> struct GetName;
+
+  // Downcast argument to a derived barrier set type.
+  // The cast is checked in a debug build.
+  // T must have a specialization for BarrierSet::GetName<T>.
+  template<typename T>
+  friend T* barrier_set_cast(BarrierSet* bs) {
+    assert(bs->is_a(BarrierSet::GetName<T>::value), "wrong type of barrier set");
+    return static_cast<T*>(bs);
+  }
+
+public:
+  // Note: This is not presently the Name corresponding to the
+  // concrete class of this object.
+  BarrierSet::Name kind() const { return _fake_rtti.concrete_tag(); }
+
+  // Test whether this object is of the type corresponding to bsn.
+  bool is_a(BarrierSet::Name bsn) const { return _fake_rtti.has_tag(bsn); }
+
+  // End of fake RTTI support.
+
+public:
   enum Flags {
     None                = 0,
     TargetUninitialized = 1
   };
+
 protected:
   // Some barrier sets create tables whose elements correspond to parts of
   // the heap; the CardTableModRefBS is an example.  Such barrier sets will
@@ -53,17 +97,12 @@
   // "covering" parts of the heap that are committed. At most one covered
   // region per generation is needed.
   static const int _max_covered_regions = 2;
-  Name _kind;
 
-  BarrierSet(Name kind) : _kind(kind) { }
+  BarrierSet(const FakeRtti& fake_rtti) : _fake_rtti(fake_rtti) { }
   ~BarrierSet() { }
 
 public:
 
-  // To get around prohibition on RTTI.
-  BarrierSet::Name kind() { return _kind; }
-  virtual bool is_a(BarrierSet::Name bsn) = 0;
-
   // These operations indicate what kind of barriers the BarrierSet has.
   virtual bool has_read_ref_barrier() = 0;
   virtual bool has_read_prim_barrier() = 0;
--- a/hotspot/src/share/vm/memory/barrierSet.inline.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/memory/barrierSet.inline.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -34,7 +34,7 @@
 
 template <class T> void BarrierSet::write_ref_field_pre(T* field, oop new_val) {
   if (kind() == CardTableModRef) {
-    ((CardTableModRefBS*)this)->inline_write_ref_field_pre(field, new_val);
+    barrier_set_cast<CardTableModRefBS>(this)->inline_write_ref_field_pre(field, new_val);
   } else {
     write_ref_field_pre_work(field, new_val);
   }
@@ -42,7 +42,7 @@
 
 void BarrierSet::write_ref_field(void* field, oop new_val, bool release) {
   if (kind() == CardTableModRef) {
-    ((CardTableModRefBS*)this)->inline_write_ref_field(field, new_val, release);
+    barrier_set_cast<CardTableModRefBS>(this)->inline_write_ref_field(field, new_val, release);
   } else {
     write_ref_field_work(field, new_val, release);
   }
@@ -78,7 +78,7 @@
 
 inline void BarrierSet::write_region(MemRegion mr) {
   if (kind() == CardTableModRef) {
-    ((CardTableModRefBS*)this)->inline_write_region(mr);
+    barrier_set_cast<CardTableModRefBS>(this)->inline_write_region(mr);
   } else {
     write_region_work(mr);
   }
--- a/hotspot/src/share/vm/memory/cardTableModRefBS.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/memory/cardTableModRefBS.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -53,8 +53,10 @@
   return align_size_up(_guard_index + 1, MAX2(_page_size, granularity));
 }
 
-CardTableModRefBS::CardTableModRefBS(MemRegion whole_heap, BarrierSet::Name kind) :
-  ModRefBarrierSet(kind),
+CardTableModRefBS::CardTableModRefBS(
+  MemRegion whole_heap,
+  const BarrierSet::FakeRtti& fake_rtti) :
+  ModRefBarrierSet(fake_rtti.add_tag(BarrierSet::CardTableModRef)),
   _whole_heap(whole_heap),
   _guard_index(0),
   _guard_region(),
--- a/hotspot/src/share/vm/memory/cardTableModRefBS.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/memory/cardTableModRefBS.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -279,11 +279,6 @@
   static int precleaned_card_val() { return precleaned_card; }
   static int deferred_card_val()   { return deferred_card; }
 
-  // For RTTI simulation.
-  bool is_a(BarrierSet::Name bsn) {
-    return bsn == BarrierSet::CardTableModRef || ModRefBarrierSet::is_a(bsn);
-  }
-
   virtual void initialize();
 
   // *** Barrier set functions.
@@ -292,7 +287,7 @@
 
 protected:
 
-  CardTableModRefBS(MemRegion whole_heap, BarrierSet::Name kind);
+  CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti);
   ~CardTableModRefBS();
 
   // Record a reference update. Note that these versions are precise!
@@ -462,6 +457,11 @@
   void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
 };
 
+template<>
+struct BarrierSet::GetName<CardTableModRefBS> {
+  static const BarrierSet::Name value = BarrierSet::CardTableModRef;
+};
+
 class CardTableRS;
 
 // A specialization for the CardTableRS gen rem set.
@@ -472,10 +472,24 @@
   bool card_may_have_been_dirty(jbyte cv);
 public:
   CardTableModRefBSForCTRS(MemRegion whole_heap) :
-    CardTableModRefBS(whole_heap, BarrierSet::CardTableModRef) {}
+    CardTableModRefBS(
+      whole_heap,
+      // Concrete tag should be BarrierSet::CardTableForRS.
+      // That will presently break things in a bunch of places though.
+      // The concrete tag is used as a dispatch key in many places, and
+      // CardTableForRS does not correctly dispatch in some of those
+      // uses. This will be addressed as part of a reorganization of the
+      // BarrierSet hierarchy.
+      BarrierSet::FakeRtti(BarrierSet::CardTableModRef, 0).add_tag(BarrierSet::CardTableForRS))
+    {}
 
   void set_CTRS(CardTableRS* rs) { _rs = rs; }
 };
 
+template<>
+struct BarrierSet::GetName<CardTableModRefBSForCTRS> {
+  static const BarrierSet::Name value = BarrierSet::CardTableForRS;
+};
+
 
 #endif // SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
--- a/hotspot/src/share/vm/memory/modRefBarrierSet.hpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/memory/modRefBarrierSet.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -37,10 +37,6 @@
 class ModRefBarrierSet: public BarrierSet {
 public:
 
-  bool is_a(BarrierSet::Name bsn) {
-    return bsn == BarrierSet::ModRef;
-  }
-
   // Barriers only on ref writes.
   bool has_read_ref_barrier() { return false; }
   bool has_read_prim_barrier() { return false; }
@@ -60,7 +56,8 @@
 
 protected:
 
-  ModRefBarrierSet(BarrierSet::Name kind) : BarrierSet(kind) { }
+  ModRefBarrierSet(const BarrierSet::FakeRtti& fake_rtti)
+    : BarrierSet(fake_rtti.add_tag(BarrierSet::ModRef)) { }
   ~ModRefBarrierSet() { }
 
   virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
@@ -100,4 +97,9 @@
   virtual void clear(MemRegion mr) = 0;
 };
 
+template<>
+struct BarrierSet::GetName<ModRefBarrierSet> {
+  static const BarrierSet::Name value = BarrierSet::ModRef;
+};
+
 #endif // SHARE_VM_MEMORY_MODREFBARRIERSET_HPP
--- a/hotspot/src/share/vm/opto/graphKit.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/opto/graphKit.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -3759,7 +3759,8 @@
 
 Node* GraphKit::byte_map_base_node() {
   // Get base of card map
-  CardTableModRefBS* ct = (CardTableModRefBS*)(Universe::heap()->barrier_set());
+  CardTableModRefBS* ct =
+    barrier_set_cast<CardTableModRefBS>(Universe::heap()->barrier_set());
   assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust users of this code");
   if (ct->byte_map_base != NULL) {
     return makecon(TypeRawPtr::make((address)ct->byte_map_base));
--- a/hotspot/src/share/vm/runtime/vmStructs.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/runtime/vmStructs.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -481,7 +481,6 @@
                                                                                                                                      \
   unchecked_nonstatic_field(ageTable,          sizes,                                         sizeof(ageTable::sizes))               \
                                                                                                                                      \
-  nonstatic_field(BarrierSet,                  _kind,                                         BarrierSet::Name)                      \
   nonstatic_field(BlockOffsetTable,            _bottom,                                       HeapWord*)                             \
   nonstatic_field(BlockOffsetTable,            _end,                                          HeapWord*)                             \
                                                                                                                                      \
--- a/hotspot/src/share/vm/shark/sharkBuilder.cpp	Thu Feb 26 21:00:03 2015 +0100
+++ b/hotspot/src/share/vm/shark/sharkBuilder.cpp	Fri Feb 27 19:52:48 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2015, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2008, 2009, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -446,7 +446,7 @@
     CreateIntToPtr(
       CreateAdd(
         LLVMValue::intptr_constant(
-          (intptr_t) ((CardTableModRefBS *) bs)->byte_map_base),
+          (intptr_t) (barrier_set_cast<CardTableModRefBS>(bs)->byte_map_base)),
         CreateLShr(
           CreatePtrToInt(field, SharkType::intptr_type()),
           LLVMValue::intptr_constant(CardTableModRefBS::card_shift))),
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/utilities/fakeRttiSupport.hpp	Fri Feb 27 19:52:48 2015 -0500
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2015, 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_UTILITIES_FAKERTTISUPPORT_HPP
+#define SHARE_VM_UTILITIES_FAKERTTISUPPORT_HPP
+
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/debug.hpp"
+
+// Provides support for checked downcasts in a hierarchy of classes.
+// The base class provides a member of this type, specialized on that
+// base class and an associated tag type.  Tags are small non-negative
+// integer values uniquely associated with distinct classes in the
+// hierarchy.  A tag type is often an enum type.
+//
+// The concrete class specifies the concrete tag.
+//
+// The tag set specifies the set of classes in the derivation
+// sequence.  Classes in the derivation sequence add their associated
+// tag during construction.  Given the tag associated with a class, an
+// object is an instance of that class if the tag is included in the
+// object's set of recorded tags.
+//
+// A tag T is present in a tag set if the T'th bit of the tag set is
+// one.
+//
+// Note: The representation of a tag set being uintx sets an upper
+// bound on the size of a class hierarchy this utility can be used
+// with.
+template<typename T, typename TagType>
+class FakeRttiSupport VALUE_OBJ_CLASS_SPEC {
+public:
+  // Construct with the indicated concrete tag, and include the
+  // concrete tag in the associated tag set.
+  explicit FakeRttiSupport(TagType concrete_tag) :
+    _tag_set(tag_bit(concrete_tag)), _concrete_tag(concrete_tag) { }
+
+  // Construct with the indicated concrete tag and tag set.
+  // Note: This constructor is public only to allow clients to set up
+  // "unusual" (or perhaps buggy) fake RTTI configurations.
+  FakeRttiSupport(TagType concrete_tag, uintx tag_set) :
+    _tag_set(tag_set), _concrete_tag(validate_tag(concrete_tag)) { }
+
+  // Get the concrete tag.
+  TagType concrete_tag() const { return _concrete_tag; }
+
+  // Test whether tag is in the tag set.
+  bool has_tag(TagType tag) const {
+    return (_tag_set & tag_bit(tag)) != 0;
+  }
+
+  // Return a new support object which is the same as this, except tag
+  // has been added to the tag set.  The tag must not already be
+  // present in the tag set.
+  FakeRttiSupport add_tag(TagType tag) const {
+    uintx tbit = tag_bit(tag);
+    assert((_tag_set & tbit) == 0,
+           err_msg("Tag " UINTX_FORMAT " is already present in tag set: " UINTX_FORMAT,
+                   (uintx)tag, _tag_set));
+    return FakeRttiSupport(_concrete_tag, _tag_set | tbit);
+  }
+
+private:
+  uintx _tag_set;
+  TagType _concrete_tag;
+
+  static uintx tag_bit(TagType tag) {
+    return ((uintx)1) << validate_tag(tag);
+  }
+
+  static TagType validate_tag(uintx tag) {
+    // Type of tag is not TagType to dodge useless MacOSX compiler warning.
+    assert(tag < (sizeof(uintx) * BitsPerByte),
+           err_msg("Tag " UINTX_FORMAT " is too large", tag));
+    return static_cast<TagType>(tag);
+  }
+};
+
+#endif // include guard