diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/gc/shared/cardTableModRefBS.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/cardTableModRefBS.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,338 @@
+/*
+ * Copyright (c) 2000, 2016, 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_CARDTABLEMODREFBS_HPP
+#define SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP
+
+#include "gc/shared/modRefBarrierSet.hpp"
+#include "oops/oop.hpp"
+#include "utilities/align.hpp"
+
+// 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 CardTableModRefBS: public ModRefBarrierSet {
+  // Some classes get to look at some private stuff.
+  friend class VMStructs;
+ protected:
+
+  enum CardValues {
+    clean_card                  = -1,
+    // The mask contains zeros in places for all other values.
+    clean_card_mask             = clean_card - 31,
+
+    dirty_card                  =  0,
+    precleaned_card             =  1,
+    claimed_card                =  2,
+    deferred_card               =  4,
+    last_card                   =  8,
+    CT_MR_BS_last_reserved      = 16
+  };
+
+  // a word's worth (row) of clean card values
+  static const intptr_t clean_card_row = (intptr_t)(-1);
+
+  // The declaration order of these const fields is important; see the
+  // constructor before changing.
+  const MemRegion _whole_heap;       // the region covered by the card table
+  size_t          _guard_index;      // index of very last element in the card
+                                     // table; it is set to a guard value
+                                     // (last_card) and should never be modified
+  size_t          _last_valid_index; // index of the last valid element
+  const size_t    _page_size;        // page size used when mapping _byte_map
+  size_t          _byte_map_size;    // in bytes
+  jbyte*          _byte_map;         // the card marking array
+
+  int _cur_covered_regions;
+  // The covered regions should be in address order.
+  MemRegion* _covered;
+  // The committed regions correspond one-to-one to the covered regions.
+  // They represent the card-table memory that has been committed to service
+  // the corresponding covered region.  It may be that committed region for
+  // one covered region corresponds to a larger region because of page-size
+  // roundings.  Thus, a committed region for one covered region may
+  // actually extend onto the card-table space for the next covered region.
+  MemRegion* _committed;
+
+  // The last card is a guard card, and we commit the page for it so
+  // we can use the card for verification purposes. We make sure we never
+  // uncommit the MemRegion for that page.
+  MemRegion _guard_region;
+
+ protected:
+  inline size_t compute_byte_map_size();
+
+  // Finds and return the index of the region, if any, to which the given
+  // region would be contiguous.  If none exists, assign a new region and
+  // returns its index.  Requires that no more than the maximum number of
+  // covered regions defined in the constructor are ever in use.
+  int find_covering_region_by_base(HeapWord* base);
+
+  // Same as above, but finds the region containing the given address
+  // instead of starting at a given base address.
+  int find_covering_region_containing(HeapWord* addr);
+
+  // Resize one of the regions covered by the remembered set.
+  virtual void resize_covered_region(MemRegion new_region);
+
+  // Returns the leftmost end of a committed region corresponding to a
+  // covered region before covered region "ind", or else "NULL" if "ind" is
+  // the first covered region.
+  HeapWord* largest_prev_committed_end(int ind) const;
+
+  // Returns the part of the region mr that doesn't intersect with
+  // any committed region other than self.  Used to prevent uncommitting
+  // regions that are also committed by other regions.  Also protects
+  // against uncommitting the guard region.
+  MemRegion committed_unique_to_self(int self, MemRegion mr) const;
+
+  // Mapping from address to card marking array entry
+  jbyte* byte_for(const void* p) const {
+    assert(_whole_heap.contains(p),
+           "Attempt to access p = " PTR_FORMAT " out of bounds of "
+           " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
+           p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
+    jbyte* result = &byte_map_base[uintptr_t(p) >> card_shift];
+    assert(result >= _byte_map && result < _byte_map + _byte_map_size,
+           "out of bounds accessor for card marking array");
+    return result;
+  }
+
+  // The card table byte one after the card marking array
+  // entry for argument address. Typically used for higher bounds
+  // for loops iterating through the card table.
+  jbyte* byte_after(const void* p) const {
+    return byte_for(p) + 1;
+  }
+
+ protected:
+  // Dirty the bytes corresponding to "mr" (not all of which must be
+  // covered.)
+  void dirty_MemRegion(MemRegion mr);
+
+  // Clear (to clean_card) the bytes entirely contained within "mr" (not
+  // all of which must be covered.)
+  void clear_MemRegion(MemRegion mr);
+
+public:
+  // Constants
+  enum SomePublicConstants {
+    card_shift                  = 9,
+    card_size                   = 1 << card_shift,
+    card_size_in_words          = card_size / sizeof(HeapWord)
+  };
+
+  static int clean_card_val()      { return clean_card; }
+  static int clean_card_mask_val() { return clean_card_mask; }
+  static int dirty_card_val()      { return dirty_card; }
+  static int claimed_card_val()    { return claimed_card; }
+  static int precleaned_card_val() { return precleaned_card; }
+  static int deferred_card_val()   { return deferred_card; }
+
+  virtual void initialize();
+
+  // *** Barrier set functions.
+
+  bool has_write_ref_pre_barrier() { return false; }
+
+  // Initialization utilities; covered_words is the size of the covered region
+  // in, um, words.
+  inline size_t cards_required(size_t covered_words) {
+    // Add one for a guard card, used to detect errors.
+    const size_t words = align_up(covered_words, card_size_in_words);
+    return words / card_size_in_words + 1;
+  }
+
+protected:
+
+  CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti);
+  ~CardTableModRefBS();
+
+  // 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.
+
+  void write_ref_field_work(oop obj, size_t offset, oop newVal);
+  virtual void write_ref_field_work(void* field, oop newVal, bool release);
+public:
+
+  bool has_write_ref_array_opt() { return true; }
+  bool has_write_region_opt() { return true; }
+
+  inline void inline_write_region(MemRegion mr) {
+    dirty_MemRegion(mr);
+  }
+protected:
+  void write_region_work(MemRegion mr) {
+    inline_write_region(mr);
+  }
+public:
+
+  inline void inline_write_ref_array(MemRegion mr) {
+    dirty_MemRegion(mr);
+  }
+protected:
+  void write_ref_array_work(MemRegion mr) {
+    inline_write_ref_array(mr);
+  }
+public:
+
+  bool is_aligned(HeapWord* addr) {
+    return is_card_aligned(addr);
+  }
+
+  // *** Card-table-barrier-specific things.
+
+  template <class T> inline void inline_write_ref_field_pre(T* field, oop newVal) {}
+
+  template <class T> inline void inline_write_ref_field(T* field, oop newVal, bool release);
+
+  // These are used by G1, when it uses the card table as a temporary data
+  // structure for card claiming.
+  bool is_card_dirty(size_t card_index) {
+    return _byte_map[card_index] == dirty_card_val();
+  }
+
+  void mark_card_dirty(size_t card_index) {
+    _byte_map[card_index] = dirty_card_val();
+  }
+
+  bool is_card_clean(size_t card_index) {
+    return _byte_map[card_index] == clean_card_val();
+  }
+
+  // Card marking array base (adjusted for heap low boundary)
+  // This would be the 0th element of _byte_map, if the heap started at 0x0.
+  // But since the heap starts at some higher address, this points to somewhere
+  // before the beginning of the actual _byte_map.
+  jbyte* byte_map_base;
+
+  // Return true if "p" is at the start of a card.
+  bool is_card_aligned(HeapWord* p) {
+    jbyte* pcard = byte_for(p);
+    return (addr_for(pcard) == p);
+  }
+
+  HeapWord* align_to_card_boundary(HeapWord* p) {
+    jbyte* pcard = byte_for(p + card_size_in_words - 1);
+    return addr_for(pcard);
+  }
+
+  // The kinds of precision a CardTableModRefBS may offer.
+  enum PrecisionStyle {
+    Precise,
+    ObjHeadPreciseArray
+  };
+
+  // Tells what style of precision this card table offers.
+  PrecisionStyle precision() {
+    return ObjHeadPreciseArray; // Only one supported for now.
+  }
+
+  // ModRefBS functions.
+  virtual void invalidate(MemRegion mr);
+  void clear(MemRegion mr);
+  void dirty(MemRegion mr);
+
+  // *** Card-table-RemSet-specific things.
+
+  static uintx ct_max_alignment_constraint();
+
+  // Apply closure "cl" to the dirty cards containing some part of
+  // MemRegion "mr".
+  void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);
+
+  // Return the MemRegion corresponding to the first maximal run
+  // of dirty cards lying completely within MemRegion mr.
+  // If reset is "true", then sets those card table entries to the given
+  // value.
+  MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
+                                         int reset_val);
+
+  // Provide read-only access to the card table array.
+  const jbyte* byte_for_const(const void* p) const {
+    return byte_for(p);
+  }
+  const jbyte* byte_after_const(const void* p) const {
+    return byte_after(p);
+  }
+
+  // Mapping from card marking array entry to address of first word
+  HeapWord* addr_for(const jbyte* p) const {
+    assert(p >= _byte_map && p < _byte_map + _byte_map_size,
+           "out of bounds access to card marking array. p: " PTR_FORMAT
+           " _byte_map: " PTR_FORMAT " _byte_map + _byte_map_size: " PTR_FORMAT,
+           p2i(p), p2i(_byte_map), p2i(_byte_map + _byte_map_size));
+    size_t delta = pointer_delta(p, byte_map_base, sizeof(jbyte));
+    HeapWord* result = (HeapWord*) (delta << card_shift);
+    assert(_whole_heap.contains(result),
+           "Returning result = " PTR_FORMAT " out of bounds of "
+           " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
+           p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
+    return result;
+  }
+
+  // Mapping from address to card marking array index.
+  size_t index_for(void* p) {
+    assert(_whole_heap.contains(p),
+           "Attempt to access p = " PTR_FORMAT " out of bounds of "
+           " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
+           p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
+    return byte_for(p) - _byte_map;
+  }
+
+  const jbyte* byte_for_index(const size_t card_index) const {
+    return _byte_map + card_index;
+  }
+
+  // Print a description of the memory for the barrier set
+  virtual void print_on(outputStream* st) const;
+
+  void verify();
+  void verify_guard();
+
+  // val_equals -> it will check that all cards covered by mr equal val
+  // !val_equals -> it will check that all cards covered by mr do not equal val
+  void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
+  void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
+  void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
+};
+
+template<>
+struct BarrierSet::GetName<CardTableModRefBS> {
+  static const BarrierSet::Name value = BarrierSet::CardTableModRef;
+};
+
+
+#endif // SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP