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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24
25 #ifndef SHARE_VM_GC_SHARED_BARRIERSET_HPP
26 #define SHARE_VM_GC_SHARED_BARRIERSET_HPP
27
28 #include "memory/memRegion.hpp"
29 #include "oops/oopsHierarchy.hpp"
30 #include "utilities/fakeRttiSupport.hpp"
31
32 // This class provides the interface between a barrier implementation and
33 // the rest of the system.
34
35 class BarrierSet: public CHeapObj<mtGC> {
36 friend class VMStructs;
37 public:
38 // Fake RTTI support. For a derived class T to participate
39 // - T must have a corresponding Name entry.
40 // - GetName<T> must be specialized to return the corresponding Name
41 // entry.
42 // - If T is a base class, the constructor must have a FakeRtti
43 // parameter and pass it up to its base class, with the tag set
44 // augmented with the corresponding Name entry.
45 // - If T is a concrete class, the constructor must create a
46 // FakeRtti object whose tag set includes the corresponding Name
47 // entry, and pass it up to its base class.
48
49 enum Name { // associated class
50 ModRef, // ModRefBarrierSet
51 CardTableModRef, // CardTableModRefBS
52 CardTableForRS, // CardTableModRefBSForCTRS
53 CardTableExtension, // CardTableExtension
54 G1SATBCT, // G1SATBCardTableModRefBS
55 G1SATBCTLogging, // G1SATBCardTableLoggingModRefBS
56 Epsilon, // EpsilonBarrierSet
57 };
58
59 protected:
60 typedef FakeRttiSupport<BarrierSet, Name> FakeRtti;
61
62 private:
63 FakeRtti _fake_rtti;
64
65 // Metafunction mapping a class derived from BarrierSet to the
66 // corresponding Name enum tag.
67 template<typename T> struct GetName;
68
69 // Downcast argument to a derived barrier set type.
70 // The cast is checked in a debug build.
71 // T must have a specialization for BarrierSet::GetName<T>.
72 template<typename T> friend T* barrier_set_cast(BarrierSet* bs);
73
74 public:
75 // Note: This is not presently the Name corresponding to the
76 // concrete class of this object.
77 BarrierSet::Name kind() const { return _fake_rtti.concrete_tag(); }
78
79 // Test whether this object is of the type corresponding to bsn.
80 bool is_a(BarrierSet::Name bsn) const { return _fake_rtti.has_tag(bsn); }
81
82 // End of fake RTTI support.
83
84 public:
85 enum Flags {
86 None = 0,
87 TargetUninitialized = 1
88 };
89
90 protected:
91 // Some barrier sets create tables whose elements correspond to parts of
92 // the heap; the CardTableModRefBS is an example. Such barrier sets will
93 // normally reserve space for such tables, and commit parts of the table
94 // "covering" parts of the heap that are committed. At most one covered
95 // region per generation is needed.
96 static const int _max_covered_regions = 2;
97
98 BarrierSet(const FakeRtti& fake_rtti) : _fake_rtti(fake_rtti) { }
99 ~BarrierSet() { }
100
101 public:
102
103 // These operations indicate what kind of barriers the BarrierSet has.
104 virtual bool has_read_ref_barrier() = 0;
105 virtual bool has_read_prim_barrier() = 0;
106 virtual bool has_write_ref_barrier() = 0;
107 virtual bool has_write_ref_pre_barrier() = 0;
108 virtual bool has_write_prim_barrier() = 0;
109
110 // These functions indicate whether a particular access of the given
111 // kinds requires a barrier.
112 virtual bool read_ref_needs_barrier(void* field) = 0;
113 virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
114 virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
115 juint val1, juint val2) = 0;
116
117 // The first four operations provide a direct implementation of the
118 // barrier set. An interpreter loop, for example, could call these
119 // directly, as appropriate.
120
121 // Invoke the barrier, if any, necessary when reading the given ref field.
122 virtual void read_ref_field(void* field) = 0;
123
124 // Invoke the barrier, if any, necessary when reading the given primitive
125 // "field" of "bytes" bytes in "obj".
126 virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
127
128 // Invoke the barrier, if any, necessary when writing "new_val" into the
129 // ref field at "offset" in "obj".
130 // (For efficiency reasons, this operation is specialized for certain
131 // barrier types. Semantically, it should be thought of as a call to the
132 // virtual "_work" function below, which must implement the barrier.)
133 // First the pre-write versions...
134 template <class T> inline void write_ref_field_pre(T* field, oop new_val);
135 private:
136 // Helper for write_ref_field_pre and friends, testing for specialized cases.
137 bool devirtualize_reference_writes() const;
138
139 // Keep this private so as to catch violations at build time.
140 virtual void write_ref_field_pre_work( void* field, oop new_val) { guarantee(false, "Not needed"); };
141 protected:
142 virtual void write_ref_field_pre_work( oop* field, oop new_val) {};
143 virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
144 public:
145
146 // ...then the post-write version.
147 inline void write_ref_field(void* field, oop new_val, bool release = false);
148 protected:
149 virtual void write_ref_field_work(void* field, oop new_val, bool release) = 0;
150 public:
151
152 // Invoke the barrier, if any, necessary when writing the "bytes"-byte
153 // value(s) "val1" (and "val2") into the primitive "field".
154 virtual void write_prim_field(HeapWord* field, size_t bytes,
155 juint val1, juint val2) = 0;
156
157 // Operations on arrays, or general regions (e.g., for "clone") may be
158 // optimized by some barriers.
159
160 // The first six operations tell whether such an optimization exists for
161 // the particular barrier.
162 virtual bool has_read_ref_array_opt() = 0;
163 virtual bool has_read_prim_array_opt() = 0;
164 virtual bool has_write_ref_array_pre_opt() { return true; }
165 virtual bool has_write_ref_array_opt() = 0;
166 virtual bool has_write_prim_array_opt() = 0;
167
168 virtual bool has_read_region_opt() = 0;
169 virtual bool has_write_region_opt() = 0;
170
171 // These operations should assert false unless the corresponding operation
172 // above returns true. Otherwise, they should perform an appropriate
173 // barrier for an array whose elements are all in the given memory region.
174 virtual void read_ref_array(MemRegion mr) = 0;
175 virtual void read_prim_array(MemRegion mr) = 0;
176
177 // Below length is the # array elements being written
178 virtual void write_ref_array_pre(oop* dst, int length,
179 bool dest_uninitialized = false) {}
180 virtual void write_ref_array_pre(narrowOop* dst, int length,
181 bool dest_uninitialized = false) {}
182 // Below count is the # array elements being written, starting
183 // at the address "start", which may not necessarily be HeapWord-aligned
184 inline void write_ref_array(HeapWord* start, size_t count);
185
186 // Static versions, suitable for calling from generated code;
187 // count is # array elements being written, starting with "start",
188 // which may not necessarily be HeapWord-aligned.
189 static void static_write_ref_array_pre(HeapWord* start, size_t count);
190 static void static_write_ref_array_post(HeapWord* start, size_t count);
191
192 virtual void write_ref_nmethod_pre(oop* dst, nmethod* nm) {}
193 virtual void write_ref_nmethod_post(oop* dst, nmethod* nm) {}
194
195 protected:
196 virtual void write_ref_array_work(MemRegion mr) = 0;
197 public:
198 virtual void write_prim_array(MemRegion mr) = 0;
199
200 virtual void read_region(MemRegion mr) = 0;
201
202 // (For efficiency reasons, this operation is specialized for certain
203 // barrier types. Semantically, it should be thought of as a call to the
204 // virtual "_work" function below, which must implement the barrier.)
205 void write_region(MemRegion mr);
206 protected:
207 virtual void write_region_work(MemRegion mr) = 0;
208 public:
209 // Inform the BarrierSet that the the covered heap region that starts
210 // with "base" has been changed to have the given size (possibly from 0,
211 // for initialization.)
212 virtual void resize_covered_region(MemRegion new_region) = 0;
213
214 // If the barrier set imposes any alignment restrictions on boundaries
215 // within the heap, this function tells whether they are met.
216 virtual bool is_aligned(HeapWord* addr) = 0;
217
218 // Print a description of the memory for the barrier set
219 virtual void print_on(outputStream* st) const = 0;
220 };
221
222 template<typename T>
223 inline T* barrier_set_cast(BarrierSet* bs) {
224 assert(bs->is_a(BarrierSet::GetName<T>::value), "wrong type of barrier set");
225 return static_cast<T*>(bs);
226 }
227
228 #endif // SHARE_VM_GC_SHARED_BARRIERSET_HPP