1 /*
2 * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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).
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15 * You should have received a copy of the GNU General Public License version
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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 };
45
46 enum Flags {
47 None = 0,
48 TargetUninitialized = 1
49 };
50 protected:
51 // Some barrier sets create tables whose elements correspond to parts of
52 // the heap; the CardTableModRefBS is an example. Such barrier sets will
53 // normally reserve space for such tables, and commit parts of the table
54 // "covering" parts of the heap that are committed. At most one covered
55 // region per generation is needed.
56 static const int _max_covered_regions = 2;
57 Name _kind;
58
59 BarrierSet(Name kind) : _kind(kind) { }
60 ~BarrierSet() { }
61
62 public:
63
64 // To get around prohibition on RTTI.
65 BarrierSet::Name kind() { return _kind; }
66 virtual bool is_a(BarrierSet::Name bsn) = 0;
67
68 // These operations indicate what kind of barriers the BarrierSet has.
69 virtual bool has_read_ref_barrier() = 0;
70 virtual bool has_read_prim_barrier() = 0;
71 virtual bool has_write_ref_barrier() = 0;
72 virtual bool has_write_ref_pre_barrier() = 0;
73 virtual bool has_write_prim_barrier() = 0;
74
75 // These functions indicate whether a particular access of the given
76 // kinds requires a barrier.
77 virtual bool read_ref_needs_barrier(void* field) = 0;
78 virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
79 virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
80 juint val1, juint val2) = 0;
81
82 // The first four operations provide a direct implementation of the
83 // barrier set. An interpreter loop, for example, could call these
84 // directly, as appropriate.
85
86 // Invoke the barrier, if any, necessary when reading the given ref field.
87 virtual void read_ref_field(void* field) = 0;
88
89 // Invoke the barrier, if any, necessary when reading the given primitive
90 // "field" of "bytes" bytes in "obj".
91 virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
92
93 // Invoke the barrier, if any, necessary when writing "new_val" into the
94 // ref field at "offset" in "obj".
95 // (For efficiency reasons, this operation is specialized for certain
96 // barrier types. Semantically, it should be thought of as a call to the
97 // virtual "_work" function below, which must implement the barrier.)
98 // First the pre-write versions...
99 template <class T> inline void write_ref_field_pre(T* field, oop new_val);
100 private:
101 // Keep this private so as to catch violations at build time.
102 virtual void write_ref_field_pre_work( void* field, oop new_val) { guarantee(false, "Not needed"); };
103 protected:
104 virtual void write_ref_field_pre_work( oop* field, oop new_val) {};
105 virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
106 public:
107
108 // ...then the post-write version.
109 inline void write_ref_field(void* field, oop new_val, bool release = false);
110 protected:
111 virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
112 public:
113
114 // Invoke the barrier, if any, necessary when writing the "bytes"-byte
115 // value(s) "val1" (and "val2") into the primitive "field".
116 virtual void write_prim_field(HeapWord* field, size_t bytes,
117 juint val1, juint val2) = 0;
118
119 // Operations on arrays, or general regions (e.g., for "clone") may be
120 // optimized by some barriers.
121
122 // The first six operations tell whether such an optimization exists for
123 // the particular barrier.
124 virtual bool has_read_ref_array_opt() = 0;
125 virtual bool has_read_prim_array_opt() = 0;
126 virtual bool has_write_ref_array_pre_opt() { return true; }
127 virtual bool has_write_ref_array_opt() = 0;
128 virtual bool has_write_prim_array_opt() = 0;
129
130 virtual bool has_read_region_opt() = 0;
131 virtual bool has_write_region_opt() = 0;
132
133 // These operations should assert false unless the corresponding operation
134 // above returns true. Otherwise, they should perform an appropriate
135 // barrier for an array whose elements are all in the given memory region.
136 virtual void read_ref_array(MemRegion mr) = 0;
137 virtual void read_prim_array(MemRegion mr) = 0;
138
139 // Below length is the # array elements being written
140 virtual void write_ref_array_pre(oop* dst, int length,
141 bool dest_uninitialized = false) {}
142 virtual void write_ref_array_pre(narrowOop* dst, int length,
143 bool dest_uninitialized = false) {}
144 // Below count is the # array elements being written, starting
145 // at the address "start", which may not necessarily be HeapWord-aligned
146 inline void write_ref_array(HeapWord* start, size_t count);
147
148 // Static versions, suitable for calling from generated code;
149 // count is # array elements being written, starting with "start",
150 // which may not necessarily be HeapWord-aligned.
151 static void static_write_ref_array_pre(HeapWord* start, size_t count);
152 static void static_write_ref_array_post(HeapWord* start, size_t count);
153
154 protected:
155 virtual void write_ref_array_work(MemRegion mr) = 0;
156 public:
157 virtual void write_prim_array(MemRegion mr) = 0;
158
159 virtual void read_region(MemRegion mr) = 0;
160
161 // (For efficiency reasons, this operation is specialized for certain
162 // barrier types. Semantically, it should be thought of as a call to the
163 // virtual "_work" function below, which must implement the barrier.)
164 inline void write_region(MemRegion mr);
165 protected:
166 virtual void write_region_work(MemRegion mr) = 0;
167 public:
168 // Inform the BarrierSet that the the covered heap region that starts
169 // with "base" has been changed to have the given size (possibly from 0,
170 // for initialization.)
171 virtual void resize_covered_region(MemRegion new_region) = 0;
172
173 // If the barrier set imposes any alignment restrictions on boundaries
174 // within the heap, this function tells whether they are met.
175 virtual bool is_aligned(HeapWord* addr) = 0;
176
177 // Print a description of the memory for the barrier set
178 virtual void print_on(outputStream* st) const = 0;
179 };
180
181 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP