1 /*
   2  * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
  26 // enumerate ref fields that have been modified (since the last
  27 // enumeration), using a card table.
  28 
  29 class OopClosure;
  30 class Generation;
  31 
  32 class ModRefBarrierSet: public BarrierSet {
  33 public:
  34 
  35   ModRefBarrierSet() { _kind = BarrierSet::ModRef; }
  36 
  37   bool is_a(BarrierSet::Name bsn) {
  38     return bsn == BarrierSet::ModRef;
  39   }
  40 
  41   // Barriers only on ref writes.
  42   bool has_read_ref_barrier() { return false; }
  43   bool has_read_prim_barrier() { return false; }
  44   bool has_write_ref_barrier() { return true; }
  45   bool has_write_prim_barrier() { return false; }
  46 
  47   bool read_ref_needs_barrier(void* field) { return false; }
  48   bool read_prim_needs_barrier(HeapWord* field, size_t bytes) { return false; }
  49   virtual bool write_ref_needs_barrier(void* field, oop new_val) = 0;
  50   bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
  51                                 juint val1, juint val2) { return false; }
  52 
  53   void write_prim_field(oop obj, size_t offset, size_t bytes,
  54                         juint val1, juint val2) {}
  55 
  56   void read_ref_field(void* field) {}
  57   void read_prim_field(HeapWord* field, size_t bytes) {}
  58 protected:
  59   virtual void write_ref_field_work(void* field, oop new_val) = 0;
  60 public:
  61   void write_prim_field(HeapWord* field, size_t bytes,
  62                         juint val1, juint val2) {}
  63 
  64   bool has_read_ref_array_opt() { return false; }
  65   bool has_read_prim_array_opt() { return false; }
  66   bool has_write_prim_array_opt() { return false; }
  67 
  68   bool has_read_region_opt() { return false; }
  69 
  70 
  71   // These operations should assert false unless the correponding operation
  72   // above returns true.
  73   void read_ref_array(MemRegion mr) {
  74     assert(false, "can't call");
  75   }
  76   void read_prim_array(MemRegion mr) {
  77     assert(false, "can't call");
  78   }
  79   void write_prim_array(MemRegion mr) {
  80     assert(false, "can't call");
  81   }
  82   void read_region(MemRegion mr) {
  83     assert(false, "can't call");
  84   }
  85 
  86   // Invoke "cl->do_oop" on (the address of) every possibly-modifed
  87   // reference field in objects in "sp".  If "clear" is "true", the oops
  88   // are no longer considered possibly modified after application of the
  89   // closure.  If' "before_save_marks" is true, oops in objects allocated
  90   // after the last call to "save_marks" on "sp" will not be considered.
  91   virtual void mod_oop_in_space_iterate(Space* sp, OopClosure* cl,
  92                                         bool clear = false,
  93                                         bool before_save_marks = false) = 0;
  94 
  95   // Causes all refs in "mr" to be assumed to be modified.  If "whole_heap"
  96   // is true, the caller asserts that the entire heap is being invalidated,
  97   // which may admit an optimized implementation for some barriers.
  98   virtual void invalidate(MemRegion mr, bool whole_heap = false) = 0;
  99 
 100   // The caller guarantees that "mr" contains no references.  (Perhaps it's
 101   // objects have been moved elsewhere.)
 102   virtual void clear(MemRegion mr) = 0;
 103 
 104   // Pass along the argument to the superclass.
 105   ModRefBarrierSet(int max_covered_regions) :
 106     BarrierSet(max_covered_regions) {}
 107 
 108 #ifndef PRODUCT
 109   // Verifies that the given region contains no modified references.
 110   virtual void verify_clean_region(MemRegion mr) = 0;
 111 #endif
 112 
 113 };