1 /*
2 * Copyright (c) 2000, 2012, 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.
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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<mtGC> {
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 enum Flags {
48 None = 0,
49 TargetUninitialized = 1
50 };
51 protected:
52 // Some barrier sets create tables whose elements correspond to parts of
53 // the heap; the CardTableModRefBS is an example. Such barrier sets will
54 // normally reserve space for such tables, and commit parts of the table
55 // "covering" parts of the heap that are committed. At most one covered
56 // region per generation is needed.
57 static const int _max_covered_regions = 2;
58 Name _kind;
59
60 BarrierSet(Name kind) { _kind = kind; }
61 ~BarrierSet() { }
62
63 public:
64
65 // To get around prohibition on RTTI.
66 BarrierSet::Name kind() { return _kind; }
67 virtual bool is_a(BarrierSet::Name bsn) = 0;
68
69 // These operations indicate what kind of barriers the BarrierSet has.
70 virtual bool has_read_ref_barrier() = 0;
71 virtual bool has_read_prim_barrier() = 0;
72 virtual bool has_write_ref_barrier() = 0;
73 virtual bool has_write_ref_pre_barrier() = 0;
74 virtual bool has_write_prim_barrier() = 0;
75
76 // These functions indicate whether a particular access of the given
77 // kinds requires a barrier.
78 virtual bool read_ref_needs_barrier(void* field) = 0;
79 virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
80 virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
81 juint val1, juint val2) = 0;
82
83 // The first four operations provide a direct implementation of the
84 // barrier set. An interpreter loop, for example, could call these
85 // directly, as appropriate.
86
87 // Invoke the barrier, if any, necessary when reading the given ref field.
88 virtual void read_ref_field(void* field) = 0;
89
90 // Invoke the barrier, if any, necessary when reading the given primitive
91 // "field" of "bytes" bytes in "obj".
92 virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
93
94 // Invoke the barrier, if any, necessary when writing "new_val" into the
95 // ref field at "offset" in "obj".
96 // (For efficiency reasons, this operation is specialized for certain
97 // barrier types. Semantically, it should be thought of as a call to the
98 // virtual "_work" function below, which must implement the barrier.)
99 // First the pre-write versions...
100 template <class T> inline void write_ref_field_pre(T* field, oop new_val);
101 private:
102 // Keep this private so as to catch violations at build time.
103 virtual void write_ref_field_pre_work( void* field, oop new_val) { guarantee(false, "Not needed"); };
104 protected:
105 virtual void write_ref_field_pre_work( oop* field, oop new_val) {};
106 virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
107 public:
108
109 // ...then the post-write version.
110 inline void write_ref_field(void* field, oop new_val, bool release = false);
111 protected:
112 virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
113 public:
114
115 // Invoke the barrier, if any, necessary when writing the "bytes"-byte
116 // value(s) "val1" (and "val2") into the primitive "field".
117 virtual void write_prim_field(HeapWord* field, size_t bytes,
118 juint val1, juint val2) = 0;
119
120 // Operations on arrays, or general regions (e.g., for "clone") may be
121 // optimized by some barriers.
122
123 // The first six operations tell whether such an optimization exists for
124 // the particular barrier.
125 virtual bool has_read_ref_array_opt() = 0;
126 virtual bool has_read_prim_array_opt() = 0;
127 virtual bool has_write_ref_array_pre_opt() { return true; }
128 virtual bool has_write_ref_array_opt() = 0;
129 virtual bool has_write_prim_array_opt() = 0;
130
131 virtual bool has_read_region_opt() = 0;
132 virtual bool has_write_region_opt() = 0;
133
134 // These operations should assert false unless the corresponding operation
135 // above returns true. Otherwise, they should perform an appropriate
136 // barrier for an array whose elements are all in the given memory region.
137 virtual void read_ref_array(MemRegion mr) = 0;
138 virtual void read_prim_array(MemRegion mr) = 0;
139
140 // Below length is the # array elements being written
141 virtual void write_ref_array_pre(oop* dst, int length,
142 bool dest_uninitialized = false) {}
143 virtual void write_ref_array_pre(narrowOop* dst, int length,
144 bool dest_uninitialized = false) {}
145 // Below count is the # array elements being written, starting
146 // at the address "start", which may not necessarily be HeapWord-aligned
147 inline void write_ref_array(HeapWord* start, size_t count);
148
149 // Static versions, suitable for calling from generated code;
150 // count is # array elements being written, starting with "start",
151 // which may not necessarily be HeapWord-aligned.
152 static void static_write_ref_array_pre(HeapWord* start, size_t count);
153 static void static_write_ref_array_post(HeapWord* start, size_t count);
154
155 protected:
156 virtual void write_ref_array_work(MemRegion mr) = 0;
157 public:
158 virtual void write_prim_array(MemRegion mr) = 0;
159
160 virtual void read_region(MemRegion mr) = 0;
161
162 // (For efficiency reasons, this operation is specialized for certain
163 // barrier types. Semantically, it should be thought of as a call to the
164 // virtual "_work" function below, which must implement the barrier.)
165 inline void write_region(MemRegion mr);
166 protected:
167 virtual void write_region_work(MemRegion mr) = 0;
168 public:
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 // Print a description of the memory for the barrier set
179 virtual void print_on(outputStream* st) const = 0;
180 };
181
182 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP