--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/cardTableBarrierSet.hpp	Mon Mar 19 07:38:18 2018 +0100
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2000, 2018, 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_SHARED_CARDTABLEBARRIERSET_HPP
+#define SHARE_VM_GC_SHARED_CARDTABLEBARRIERSET_HPP
+
+#include "gc/shared/modRefBarrierSet.hpp"
+#include "utilities/align.hpp"
+
+class CardTable;
+
+// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
+// enumerate ref fields that have been modified (since the last
+// enumeration.)
+
+// As it currently stands, this barrier is *imprecise*: when a ref field in
+// an object "o" is modified, the card table entry for the card containing
+// the head of "o" is dirtied, not necessarily the card containing the
+// modified field itself.  For object arrays, however, the barrier *is*
+// precise; only the card containing the modified element is dirtied.
+// Closures used to scan dirty cards should take these
+// considerations into account.
+
+class CardTableBarrierSet: public ModRefBarrierSet {
+  // Some classes get to look at some private stuff.
+  friend class VMStructs;
+ protected:
+
+  // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
+  // or INCLUDE_JVMCI is being used
+  bool       _defer_initial_card_mark;
+  CardTable* _card_table;
+
+  CardTableBarrierSet(CardTable* card_table, const BarrierSet::FakeRtti& fake_rtti);
+
+ public:
+  CardTableBarrierSet(CardTable* card_table);
+  ~CardTableBarrierSet();
+
+  CardTable* card_table() const { return _card_table; }
+
+  virtual void initialize();
+
+  void write_region(MemRegion mr) {
+    invalidate(mr);
+  }
+
+ protected:
+  void write_ref_array_work(MemRegion mr);
+
+ public:
+  // Record a reference update. Note that these versions are precise!
+  // The scanning code has to handle the fact that the write barrier may be
+  // either precise or imprecise. We make non-virtual inline variants of
+  // these functions here for performance.
+  template <DecoratorSet decorators, typename T>
+  void write_ref_field_post(T* field, oop newVal);
+
+  virtual void invalidate(MemRegion mr);
+
+  // ReduceInitialCardMarks
+  void initialize_deferred_card_mark_barriers();
+
+  // If the CollectedHeap was asked to defer a store barrier above,
+  // this informs it to flush such a deferred store barrier to the
+  // remembered set.
+  void flush_deferred_card_mark_barrier(JavaThread* thread);
+
+  // Can a compiler initialize a new object without store barriers?
+  // This permission only extends from the creation of a new object
+  // via a TLAB up to the first subsequent safepoint. If such permission
+  // is granted for this heap type, the compiler promises to call
+  // defer_store_barrier() below on any slow path allocation of
+  // a new object for which such initializing store barriers will
+  // have been elided. G1, like CMS, allows this, but should be
+  // ready to provide a compensating write barrier as necessary
+  // if that storage came out of a non-young region. The efficiency
+  // of this implementation depends crucially on being able to
+  // answer very efficiently in constant time whether a piece of
+  // storage in the heap comes from a young region or not.
+  // See ReduceInitialCardMarks.
+  virtual bool can_elide_tlab_store_barriers() const {
+    return true;
+  }
+
+  // If a compiler is eliding store barriers for TLAB-allocated objects,
+  // we will be informed of a slow-path allocation by a call
+  // to on_slowpath_allocation_exit() below. Such a call precedes the
+  // initialization of the object itself, and no post-store-barriers will
+  // be issued. Some heap types require that the barrier strictly follows
+  // the initializing stores. (This is currently implemented by deferring the
+  // barrier until the next slow-path allocation or gc-related safepoint.)
+  // This interface answers whether a particular barrier type needs the card
+  // mark to be thus strictly sequenced after the stores.
+  virtual bool card_mark_must_follow_store() const;
+
+  virtual void on_slowpath_allocation_exit(JavaThread* thread, oop new_obj);
+  virtual void on_thread_detach(JavaThread* thread);
+
+  virtual void make_parsable(JavaThread* thread) { flush_deferred_card_mark_barrier(thread); }
+
+  virtual void print_on(outputStream* st) const;
+
+  template <DecoratorSet decorators, typename BarrierSetT = CardTableBarrierSet>
+  class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> {};
+};
+
+template<>
+struct BarrierSet::GetName<CardTableBarrierSet> {
+  static const BarrierSet::Name value = BarrierSet::CardTableBarrierSet;
+};
+
+template<>
+struct BarrierSet::GetType<BarrierSet::CardTableBarrierSet> {
+  typedef ::CardTableBarrierSet type;
+};
+
+#endif // SHARE_VM_GC_SHARED_CARDTABLEBARRIERSET_HPP