modRefBarrierSet.hpp revision 8413:92457dfb91bd 
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24
25#ifndef SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP
26#define SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP
27
28#include "gc/shared/barrierSet.hpp"
29
30// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
31// enumerate ref fields that have been modified (since the last
32// enumeration), using a card table.
33
34class OopClosure;
35class Generation;
36
37class ModRefBarrierSet: public BarrierSet {
38public:
39
40  // Barriers only on ref writes.
41  bool has_read_ref_barrier() { return false; }
42  bool has_read_prim_barrier() { return false; }
43  bool has_write_ref_barrier() { return true; }
44  bool has_write_prim_barrier() { return false; }
45
46  bool read_ref_needs_barrier(void* field) { return false; }
47  bool read_prim_needs_barrier(HeapWord* field, size_t bytes) { return false; }
48  bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
49                                juint val1, juint val2) { return false; }
50
51  void write_prim_field(oop obj, size_t offset, size_t bytes,
52                        juint val1, juint val2) {}
53
54  void read_ref_field(void* field) {}
55  void read_prim_field(HeapWord* field, size_t bytes) {}
56
57protected:
58
59  ModRefBarrierSet(const BarrierSet::FakeRtti& fake_rtti)
60    : BarrierSet(fake_rtti.add_tag(BarrierSet::ModRef)) { }
61  ~ModRefBarrierSet() { }
62
63  virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
64public:
65  void write_prim_field(HeapWord* field, size_t bytes,
66                        juint val1, juint val2) {}
67
68  bool has_read_ref_array_opt() { return false; }
69  bool has_read_prim_array_opt() { return false; }
70  bool has_write_prim_array_opt() { return false; }
71
72  bool has_read_region_opt() { return false; }
73
74
75  // These operations should assert false unless the corresponding operation
76  // above returns true.
77  void read_ref_array(MemRegion mr) {
78    assert(false, "can't call");
79  }
80  void read_prim_array(MemRegion mr) {
81    assert(false, "can't call");
82  }
83  void write_prim_array(MemRegion mr) {
84    assert(false, "can't call");
85  }
86  void read_region(MemRegion mr) {
87    assert(false, "can't call");
88  }
89
90  // Causes all refs in "mr" to be assumed to be modified.  If "whole_heap"
91  // is true, the caller asserts that the entire heap is being invalidated,
92  // which may admit an optimized implementation for some barriers.
93  virtual void invalidate(MemRegion mr, bool whole_heap = false) = 0;
94
95  // The caller guarantees that "mr" contains no references.  (Perhaps it's
96  // objects have been moved elsewhere.)
97  virtual void clear(MemRegion mr) = 0;
98};
99
100template<>
101struct BarrierSet::GetName<ModRefBarrierSet> {
102  static const BarrierSet::Name value = BarrierSet::ModRef;
103};
104
105#endif // SHARE_VM_GC_SHARED_MODREFBARRIERSET_HPP
106