1 /*
2 * Copyright (c) 2000, 2010, 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,
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25 #ifndef SHARE_VM_MEMORY_BARRIERSET_HPP
26 #define SHARE_VM_MEMORY_BARRIERSET_HPP
27
28 #include "memory/memRegion.hpp"
29 #include "oops/oopsHierarchy.hpp"
30
31 // This class provides the interface between a barrier implementation and
32 // the rest of the system.
33
34 class BarrierSet: public CHeapObj {
35 friend class VMStructs;
36 public:
37 enum Name {
38 ModRef,
39 CardTableModRef,
40 CardTableExtension,
41 G1SATBCT,
42 G1SATBCTLogging,
43 Other,
44 Uninit
45 };
46
47 protected:
48 int _max_covered_regions;
49 Name _kind;
50
51 public:
52
53 BarrierSet() { _kind = Uninit; }
54 // To get around prohibition on RTTI.
55 BarrierSet::Name kind() { return _kind; }
56 virtual bool is_a(BarrierSet::Name bsn) = 0;
57
58 // These operations indicate what kind of barriers the BarrierSet has.
59 virtual bool has_read_ref_barrier() = 0;
60 virtual bool has_read_prim_barrier() = 0;
61 virtual bool has_write_ref_barrier() = 0;
62 virtual bool has_write_ref_pre_barrier() = 0;
63 virtual bool has_write_prim_barrier() = 0;
64
65 // These functions indicate whether a particular access of the given
66 // kinds requires a barrier.
67 virtual bool read_ref_needs_barrier(void* field) = 0;
68 virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
69 virtual bool write_ref_needs_barrier(void* field, oop new_val) = 0;
70 virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
71 juint val1, juint val2) = 0;
72
73 // The first four operations provide a direct implementation of the
74 // barrier set. An interpreter loop, for example, could call these
75 // directly, as appropriate.
76
77 // Invoke the barrier, if any, necessary when reading the given ref field.
78 virtual void read_ref_field(void* field) = 0;
79
80 // Invoke the barrier, if any, necessary when reading the given primitive
81 // "field" of "bytes" bytes in "obj".
82 virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
83
84 // Invoke the barrier, if any, necessary when writing "new_val" into the
85 // ref field at "offset" in "obj".
86 // (For efficiency reasons, this operation is specialized for certain
87 // barrier types. Semantically, it should be thought of as a call to the
88 // virtual "_work" function below, which must implement the barrier.)
89 // First the pre-write versions...
90 template <class T> inline void write_ref_field_pre(T* field, oop new_val);
91 private:
92 // Keep this private so as to catch violations at build time.
93 virtual void write_ref_field_pre_work( void* field, oop new_val) { guarantee(false, "Not needed"); };
94 protected:
95 virtual void write_ref_field_pre_work( oop* field, oop new_val) {};
96 virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
97 public:
98
99 // ...then the post-write version.
100 inline void write_ref_field(void* field, oop new_val);
101 protected:
102 virtual void write_ref_field_work(void* field, oop new_val) = 0;
103 public:
104
105 // Invoke the barrier, if any, necessary when writing the "bytes"-byte
106 // value(s) "val1" (and "val2") into the primitive "field".
107 virtual void write_prim_field(HeapWord* field, size_t bytes,
108 juint val1, juint val2) = 0;
109
110 // Operations on arrays, or general regions (e.g., for "clone") may be
111 // optimized by some barriers.
112
113 // The first six operations tell whether such an optimization exists for
114 // the particular barrier.
115 virtual bool has_read_ref_array_opt() = 0;
116 virtual bool has_read_prim_array_opt() = 0;
117 virtual bool has_write_ref_array_pre_opt() { return true; }
118 virtual bool has_write_ref_array_opt() = 0;
119 virtual bool has_write_prim_array_opt() = 0;
120
121 virtual bool has_read_region_opt() = 0;
122 virtual bool has_write_region_opt() = 0;
123
124 // These operations should assert false unless the correponding operation
125 // above returns true. Otherwise, they should perform an appropriate
126 // barrier for an array whose elements are all in the given memory region.
127 virtual void read_ref_array(MemRegion mr) = 0;
128 virtual void read_prim_array(MemRegion mr) = 0;
129
130 // Below length is the # array elements being written
131 virtual void write_ref_array_pre( oop* dst, int length) {}
132 virtual void write_ref_array_pre(narrowOop* dst, int length) {}
133 // Below count is the # array elements being written, starting
134 // at the address "start", which may not necessarily be HeapWord-aligned
135 inline void write_ref_array(HeapWord* start, size_t count);
136
137 // Static versions, suitable for calling from generated code;
138 // count is # array elements being written, starting with "start",
139 // which may not necessarily be HeapWord-aligned.
140 static void static_write_ref_array_pre(HeapWord* start, size_t count);
141 static void static_write_ref_array_post(HeapWord* start, size_t count);
142
143 protected:
144 virtual void write_ref_array_work(MemRegion mr) = 0;
145 public:
146 virtual void write_prim_array(MemRegion mr) = 0;
147
148 virtual void read_region(MemRegion mr) = 0;
149
150 // (For efficiency reasons, this operation is specialized for certain
151 // barrier types. Semantically, it should be thought of as a call to the
152 // virtual "_work" function below, which must implement the barrier.)
153 inline void write_region(MemRegion mr);
154 protected:
155 virtual void write_region_work(MemRegion mr) = 0;
156 public:
157
158 // Some barrier sets create tables whose elements correspond to parts of
159 // the heap; the CardTableModRefBS is an example. Such barrier sets will
160 // normally reserve space for such tables, and commit parts of the table
161 // "covering" parts of the heap that are committed. The constructor is
162 // passed the maximum number of independently committable subregions to
163 // be covered, and the "resize_covoered_region" function allows the
164 // sub-parts of the heap to inform the barrier set of changes of their
165 // sizes.
166 BarrierSet(int max_covered_regions) :
167 _max_covered_regions(max_covered_regions) {}
168
169 // Inform the BarrierSet that the the covered heap region that starts
170 // with "base" has been changed to have the given size (possibly from 0,
171 // for initialization.)
172 virtual void resize_covered_region(MemRegion new_region) = 0;
173
174 // If the barrier set imposes any alignment restrictions on boundaries
175 // within the heap, this function tells whether they are met.
176 virtual bool is_aligned(HeapWord* addr) = 0;
177
178 };
179
180 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP