1 /*

     2  * Copyright 2000-2002 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any 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   // Barriers only on ref writes.

    35   bool has_read_ref_barrier() { return false; }

    36   bool has_read_prim_barrier() { return false; }

    37   bool has_write_ref_barrier() { return true; }

    38   bool has_write_prim_barrier() { return false; }

    39 

    40   bool read_ref_needs_barrier(oop* field) { return false; }

    41   bool read_prim_needs_barrier(HeapWord* field, size_t bytes) { return false; }

    42   virtual bool write_ref_needs_barrier(oop* field, oop new_val) = 0;

    43   bool write_prim_needs_barrier(HeapWord* field, size_t bytes,

    44                                 juint val1, juint val2) { return false; }

    45 

    46   void write_prim_field(oop obj, size_t offset, size_t bytes,

    47                         juint val1, juint val2) {}

    48 

    49   void read_ref_field(oop* field) {}

    50   void read_prim_field(HeapWord* field, size_t bytes) {}

    51 protected:

    52   virtual void write_ref_field_work(oop* field, oop new_val) = 0;

    53 public:

    54   void write_prim_field(HeapWord* field, size_t bytes,

    55                         juint val1, juint val2) {}

    56 

    57   bool has_read_ref_array_opt() { return false; }

    58   bool has_read_prim_array_opt() { return false; }

    59   bool has_write_prim_array_opt() { return false; }

    60 

    61   bool has_read_region_opt() { return false; }

    62 

    63 

    64   // These operations should assert false unless the correponding operation

    65   // above returns true.

    66   void read_ref_array(MemRegion mr) {

    67     assert(false, "can't call");

    68   }

    69   void read_prim_array(MemRegion mr) {

    70     assert(false, "can't call");

    71   }

    72   void write_prim_array(MemRegion mr) {

    73     assert(false, "can't call");

    74   }

    75   void read_region(MemRegion mr) {

    76     assert(false, "can't call");

    77   }

    78 

    79   // Invoke "cl->do_oop" on (the address of) every possibly-modifed

    80   // reference field in objects in "sp".  If "clear" is "true", the oops

    81   // are no longer considered possibly modified after application of the

    82   // closure.  If' "before_save_marks" is true, oops in objects allocated

    83   // after the last call to "save_marks" on "sp" will not be considered.

    84   virtual void mod_oop_in_space_iterate(Space* sp, OopClosure* cl,

    85                                         bool clear = false,

    86                                         bool before_save_marks = false) = 0;

    87 

    88   // Causes all refs in "mr" to be assumed to be modified.

    89   virtual void invalidate(MemRegion mr) = 0;

    90 

    91   // The caller guarantees that "mr" contains no references.  (Perhaps it's

    92   // objects have been moved elsewhere.)

    93   virtual void clear(MemRegion mr) = 0;

    94 

    95   // Pass along the argument to the superclass.

    96   ModRefBarrierSet(int max_covered_regions) :

    97     BarrierSet(max_covered_regions) {}

    98 

    99 #ifndef PRODUCT

   100   // Verifies that the given region contains no modified references.

   101   virtual void verify_clean_region(MemRegion mr) = 0;

   102 #endif

   103 

   104 };