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,
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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 int _max_covered_regions;
53 Name _kind;
54
55 public:
56
57 BarrierSet() { _kind = Uninit; }
58 // To get around prohibition on RTTI.
59 BarrierSet::Name kind() { return _kind; }
60 virtual bool is_a(BarrierSet::Name bsn) = 0;
61
62 // These operations indicate what kind of barriers the BarrierSet has.
63 virtual bool has_read_ref_barrier() = 0;
64 virtual bool has_read_prim_barrier() = 0;
65 virtual bool has_write_ref_barrier() = 0;
66 virtual bool has_write_ref_pre_barrier() = 0;
67 virtual bool has_write_prim_barrier() = 0;
68
69 // These functions indicate whether a particular access of the given
70 // kinds requires a barrier.
71 virtual bool read_ref_needs_barrier(void* field) = 0;
72 virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
73 virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
74 juint val1, juint val2) = 0;
75
76 // The first four operations provide a direct implementation of the
77 // barrier set. An interpreter loop, for example, could call these
78 // directly, as appropriate.
79
80 // Invoke the barrier, if any, necessary when reading the given ref field.
81 virtual void read_ref_field(void* field) = 0;
82
83 // Invoke the barrier, if any, necessary when reading the given primitive
84 // "field" of "bytes" bytes in "obj".
85 virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
86
87 // Invoke the barrier, if any, necessary when writing "new_val" into the
88 // ref field at "offset" in "obj".
89 // (For efficiency reasons, this operation is specialized for certain
90 // barrier types. Semantically, it should be thought of as a call to the
91 // virtual "_work" function below, which must implement the barrier.)
92 // First the pre-write versions...
93 template <class T> inline void write_ref_field_pre(T* field, oop new_val);
94 private:
95 // Keep this private so as to catch violations at build time.
96 virtual void write_ref_field_pre_work( void* field, oop new_val) { guarantee(false, "Not needed"); };
97 protected:
98 virtual void write_ref_field_pre_work( oop* field, oop new_val) {};
99 virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
100 public:
101
102 // ...then the post-write version.
103 inline void write_ref_field(void* field, oop new_val);
104 protected:
105 virtual void write_ref_field_work(void* field, oop new_val) = 0;
106 public:
107
108 // Invoke the barrier, if any, necessary when writing the "bytes"-byte
109 // value(s) "val1" (and "val2") into the primitive "field".
110 virtual void write_prim_field(HeapWord* field, size_t bytes,
111 juint val1, juint val2) = 0;
112
113 // Operations on arrays, or general regions (e.g., for "clone") may be
114 // optimized by some barriers.
115
116 // The first six operations tell whether such an optimization exists for
117 // the particular barrier.
118 virtual bool has_read_ref_array_opt() = 0;
119 virtual bool has_read_prim_array_opt() = 0;
120 virtual bool has_write_ref_array_pre_opt() { return true; }
121 virtual bool has_write_ref_array_opt() = 0;
122 virtual bool has_write_prim_array_opt() = 0;
123
124 virtual bool has_read_region_opt() = 0;
125 virtual bool has_write_region_opt() = 0;
126
127 // These operations should assert false unless the corresponding operation
128 // above returns true. Otherwise, they should perform an appropriate
129 // barrier for an array whose elements are all in the given memory region.
130 virtual void read_ref_array(MemRegion mr) = 0;
131 virtual void read_prim_array(MemRegion mr) = 0;
132
133 // Below length is the # array elements being written
134 virtual void write_ref_array_pre(oop* dst, int length,
135 bool dest_uninitialized = false) {}
136 virtual void write_ref_array_pre(narrowOop* dst, int length,
137 bool dest_uninitialized = false) {}
138 // Below count is the # array elements being written, starting
139 // at the address "start", which may not necessarily be HeapWord-aligned
140 inline void write_ref_array(HeapWord* start, size_t count);
141
142 // Static versions, suitable for calling from generated code;
143 // count is # array elements being written, starting with "start",
144 // which may not necessarily be HeapWord-aligned.
145 static void static_write_ref_array_pre(HeapWord* start, size_t count);
146 static void static_write_ref_array_post(HeapWord* start, size_t count);
147
148 protected:
149 virtual void write_ref_array_work(MemRegion mr) = 0;
150 public:
151 virtual void write_prim_array(MemRegion mr) = 0;
152
153 virtual void read_region(MemRegion mr) = 0;
154
155 // (For efficiency reasons, this operation is specialized for certain
156 // barrier types. Semantically, it should be thought of as a call to the
157 // virtual "_work" function below, which must implement the barrier.)
158 inline void write_region(MemRegion mr);
159 protected:
160 virtual void write_region_work(MemRegion mr) = 0;
161 public:
162
163 // Some barrier sets create tables whose elements correspond to parts of
164 // the heap; the CardTableModRefBS is an example. Such barrier sets will
165 // normally reserve space for such tables, and commit parts of the table
166 // "covering" parts of the heap that are committed. The constructor is
167 // passed the maximum number of independently committable subregions to
168 // be covered, and the "resize_covered_region" function allows the
169 // sub-parts of the heap to inform the barrier set of changes of their
170 // sizes.
171 BarrierSet(int max_covered_regions) :
172 _max_covered_regions(max_covered_regions) {}
173
174 // Inform the BarrierSet that the the covered heap region that starts
175 // with "base" has been changed to have the given size (possibly from 0,
176 // for initialization.)
177 virtual void resize_covered_region(MemRegion new_region) = 0;
178
179 // If the barrier set imposes any alignment restrictions on boundaries
180 // within the heap, this function tells whether they are met.
181 virtual bool is_aligned(HeapWord* addr) = 0;
182
183 // Print a description of the memory for the barrier set
184 virtual void print_on(outputStream* st) const = 0;
185 };
186
187 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP