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