1 /*
2 * Copyright (c) 2017, 2018, 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 #ifndef SHARE_OOPS_ACCESS_HPP
26 #define SHARE_OOPS_ACCESS_HPP
27
28 #include "memory/allocation.hpp"
29 #include "oops/accessBackend.hpp"
30 #include "oops/accessDecorators.hpp"
31 #include "oops/oopsHierarchy.hpp"
32 #include "utilities/debug.hpp"
33 #include "utilities/globalDefinitions.hpp"
34
35
36 // = GENERAL =
37 // Access is an API for performing accesses with declarative semantics. Each access can have a number of "decorators".
38 // A decorator is an attribute or property that affects the way a memory access is performed in some way.
39 // There are different groups of decorators. Some have to do with memory ordering, others to do with,
40 // e.g. strength of references, strength of GC barriers, or whether compression should be applied or not.
41 // Some decorators are set at buildtime, such as whether primitives require GC barriers or not, others
42 // at callsites such as whether an access is in the heap or not, and others are resolved at runtime
43 // such as GC-specific barriers and encoding/decoding compressed oops. For more information about what
44 // decorators are available, cf. oops/accessDecorators.hpp.
45 // By pipelining handling of these decorators, the design of the Access API allows separation of concern
46 // over the different orthogonal concerns of decorators, while providing a powerful way of
47 // expressing these orthogonal semantic properties in a unified way.
48 //
49 // == OPERATIONS ==
50 // * load: Load a value from an address.
51 // * load_at: Load a value from an internal pointer relative to a base object.
52 // * store: Store a value at an address.
53 // * store_at: Store a value in an internal pointer relative to a base object.
54 // * atomic_cmpxchg: Atomically compare-and-swap a new value at an address if previous value matched the compared value.
55 // * atomic_cmpxchg_at: Atomically compare-and-swap a new value at an internal pointer address if previous value matched the compared value.
56 // * atomic_xchg: Atomically swap a new value at an address if previous value matched the compared value.
57 // * atomic_xchg_at: Atomically swap a new value at an internal pointer address if previous value matched the compared value.
58 // * arraycopy: Copy data from one heap array to another heap array.
59 // * clone: Clone the contents of an object to a newly allocated object.
60 // * resolve: Resolve a stable to-space invariant oop that is guaranteed not to relocate its payload until a subsequent thread transition.
61 // * equals: Object equality, e.g. when different copies of the same objects are in use (from-space vs. to-space)
62 //
63 // == IMPLEMENTATION ==
64 // Each access goes through the following steps in a template pipeline.
65 // There are essentially 5 steps for each access:
66 // * Step 1: Set default decorators and decay types. This step gets rid of CV qualifiers
67 // and sets default decorators to sensible values.
68 // * Step 2: Reduce types. This step makes sure there is only a single T type and not
69 // multiple types. The P type of the address and T type of the value must
70 // match.
71 // * Step 3: Pre-runtime dispatch. This step checks whether a runtime call can be
72 // avoided, and in that case avoids it (calling raw accesses or
73 // primitive accesses in a build that does not require primitive GC barriers)
74 // * Step 4: Runtime-dispatch. This step performs a runtime dispatch to the corresponding
75 // BarrierSet::AccessBarrier accessor that attaches GC-required barriers
76 // to the access.
77 // * Step 5.a: Barrier resolution. This step is invoked the first time a runtime-dispatch
78 // happens for an access. The appropriate BarrierSet::AccessBarrier accessor
79 // is resolved, then the function pointer is updated to that accessor for
80 // future invocations.
81 // * Step 5.b: Post-runtime dispatch. This step now casts previously unknown types such
82 // as the address type of an oop on the heap (is it oop* or narrowOop*) to
83 // the appropriate type. It also splits sufficiently orthogonal accesses into
84 // different functions, such as whether the access involves oops or primitives
85 // and whether the access is performed on the heap or outside. Then the
86 // appropriate BarrierSet::AccessBarrier is called to perform the access.
87 //
88 // The implementation of step 1-4 resides in in accessBackend.hpp, to allow selected
89 // accesses to be accessible from only access.hpp, as opposed to access.inline.hpp.
90 // Steps 5.a and 5.b require knowledge about the GC backends, and therefore needs to
91 // include the various GC backend .inline.hpp headers. Their implementation resides in
92 // access.inline.hpp. The accesses that are allowed through the access.hpp file
93 // must be instantiated in access.cpp using the INSTANTIATE_HPP_ACCESS macro.
94
95 template <DecoratorSet decorators = INTERNAL_EMPTY>
96 class Access: public AllStatic {
97 // This function asserts that if an access gets passed in a decorator outside
98 // of the expected_decorators, then something is wrong. It additionally checks
99 // the consistency of the decorators so that supposedly disjoint decorators are indeed
100 // disjoint. For example, an access can not be both in heap and on root at the
101 // same time.
102 template <DecoratorSet expected_decorators>
103 static void verify_decorators();
104
105 template <DecoratorSet expected_mo_decorators>
106 static void verify_primitive_decorators() {
107 const DecoratorSet primitive_decorators = (AS_DECORATOR_MASK ^ AS_NO_KEEPALIVE ^ AS_DEST_NOT_INITIALIZED) |
108 IN_HEAP | IN_HEAP_ARRAY;
109 verify_decorators<expected_mo_decorators | primitive_decorators>();
110 }
111
112 template <DecoratorSet expected_mo_decorators>
113 static void verify_oop_decorators() {
114 const DecoratorSet oop_decorators = AS_DECORATOR_MASK | IN_DECORATOR_MASK |
115 (ON_DECORATOR_MASK ^ ON_UNKNOWN_OOP_REF) | // no unknown oop refs outside of the heap
116 OOP_DECORATOR_MASK;
117 verify_decorators<expected_mo_decorators | oop_decorators>();
118 }
119
120 template <DecoratorSet expected_mo_decorators>
121 static void verify_heap_oop_decorators() {
122 const DecoratorSet heap_oop_decorators = AS_DECORATOR_MASK | ON_DECORATOR_MASK |
123 OOP_DECORATOR_MASK | (IN_DECORATOR_MASK ^
124 (IN_ROOT | IN_CONCURRENT_ROOT)); // no root accesses in the heap
125 verify_decorators<expected_mo_decorators | heap_oop_decorators>();
126 }
127
128 static const DecoratorSet load_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_ACQUIRE | MO_SEQ_CST;
129 static const DecoratorSet store_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_RELEASE | MO_SEQ_CST;
130 static const DecoratorSet atomic_xchg_mo_decorators = MO_SEQ_CST;
131 static const DecoratorSet atomic_cmpxchg_mo_decorators = MO_RELAXED | MO_SEQ_CST;
132
133 public:
134 // Primitive heap accesses
135 static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) {
136 verify_primitive_decorators<load_mo_decorators>();
137 return AccessInternal::LoadAtProxy<decorators>(base, offset);
138 }
139
140 template <typename T>
141 static inline void store_at(oop base, ptrdiff_t offset, T value) {
142 verify_primitive_decorators<store_mo_decorators>();
143 AccessInternal::store_at<decorators>(base, offset, value);
144 }
145
146 template <typename T>
147 static inline T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
148 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
149 return AccessInternal::atomic_cmpxchg_at<decorators>(new_value, base, offset, compare_value);
150 }
151
152 template <typename T>
153 static inline T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
154 verify_primitive_decorators<atomic_xchg_mo_decorators>();
155 return AccessInternal::atomic_xchg_at<decorators>(new_value, base, offset);
156 }
157
158 template <typename T>
159 static inline void arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
160 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP |
161 AS_DECORATOR_MASK>();
162 AccessInternal::arraycopy<decorators>(src_obj, dst_obj, src, dst, length);
163 }
164
165 // Oop heap accesses
166 static inline AccessInternal::OopLoadAtProxy<decorators> oop_load_at(oop base, ptrdiff_t offset) {
167 verify_heap_oop_decorators<load_mo_decorators>();
168 return AccessInternal::OopLoadAtProxy<decorators>(base, offset);
169 }
170
171 template <typename T>
172 static inline void oop_store_at(oop base, ptrdiff_t offset, T value) {
173 verify_heap_oop_decorators<store_mo_decorators>();
174 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
175 OopType oop_value = value;
176 AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value);
177 }
178
179 template <typename T>
180 static inline T oop_atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
181 verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>();
182 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
183 OopType new_oop_value = new_value;
184 OopType compare_oop_value = compare_value;
185 return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset, compare_oop_value);
186 }
187
188 template <typename T>
189 static inline T oop_atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
190 verify_heap_oop_decorators<atomic_xchg_mo_decorators>();
191 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
192 OopType new_oop_value = new_value;
193 return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset);
194 }
195
196 template <typename T>
197 static inline bool oop_arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
198 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | AS_DECORATOR_MASK>();
199 return AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, dst_obj, src, dst, length);
200 }
201
202 // Clone an object from src to dst
203 static inline void clone(oop src, oop dst, size_t size) {
204 verify_decorators<IN_HEAP>();
205 AccessInternal::clone<decorators>(src, dst, size);
206 }
207
208 // Primitive accesses
209 template <typename P>
210 static inline P load(P* addr) {
211 verify_primitive_decorators<load_mo_decorators>();
212 return AccessInternal::load<decorators, P, P>(addr);
213 }
214
215 template <typename P, typename T>
216 static inline void store(P* addr, T value) {
217 verify_primitive_decorators<store_mo_decorators>();
218 AccessInternal::store<decorators>(addr, value);
219 }
220
221 template <typename P, typename T>
222 static inline T atomic_cmpxchg(T new_value, P* addr, T compare_value) {
223 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
224 return AccessInternal::atomic_cmpxchg<decorators>(new_value, addr, compare_value);
225 }
226
227 template <typename P, typename T>
228 static inline T atomic_xchg(T new_value, P* addr) {
229 verify_primitive_decorators<atomic_xchg_mo_decorators>();
230 return AccessInternal::atomic_xchg<decorators>(new_value, addr);
231 }
232
233 // Oop accesses
234 template <typename P>
235 static inline AccessInternal::OopLoadProxy<P, decorators> oop_load(P* addr) {
236 verify_oop_decorators<load_mo_decorators>();
237 return AccessInternal::OopLoadProxy<P, decorators>(addr);
238 }
239
240 template <typename P, typename T>
241 static inline void oop_store(P* addr, T value) {
242 verify_oop_decorators<store_mo_decorators>();
243 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
244 OopType oop_value = value;
245 AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value);
246 }
247
248 template <typename P, typename T>
249 static inline T oop_atomic_cmpxchg(T new_value, P* addr, T compare_value) {
250 verify_oop_decorators<atomic_cmpxchg_mo_decorators>();
251 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
252 OopType new_oop_value = new_value;
253 OopType compare_oop_value = compare_value;
254 return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr, compare_oop_value);
255 }
256
257 template <typename P, typename T>
258 static inline T oop_atomic_xchg(T new_value, P* addr) {
259 verify_oop_decorators<atomic_xchg_mo_decorators>();
260 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
261 OopType new_oop_value = new_value;
262 return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr);
263 }
264
265 static oop resolve(oop obj) {
266 verify_decorators<INTERNAL_EMPTY>();
267 return AccessInternal::resolve<decorators>(obj);
268 }
269
270 static bool equals(oop o1, oop o2) {
271 verify_decorators<INTERNAL_EMPTY>();
272 return AccessInternal::equals<decorators>(o1, o2);
273 }
274 };
275
276 // Helper for performing raw accesses (knows only of memory ordering
277 // atomicity decorators as well as compressed oops)
278 template <DecoratorSet decorators = INTERNAL_EMPTY>
279 class RawAccess: public Access<AS_RAW | decorators> {};
280
281 // Helper for performing normal accesses on the heap. These accesses
282 // may resolve an accessor on a GC barrier set
283 template <DecoratorSet decorators = INTERNAL_EMPTY>
284 class HeapAccess: public Access<IN_HEAP | decorators> {};
285
286 // Helper for performing normal accesses in roots. These accesses
287 // may resolve an accessor on a GC barrier set
288 template <DecoratorSet decorators = INTERNAL_EMPTY>
289 class RootAccess: public Access<IN_ROOT | decorators> {};
290
291 template <DecoratorSet decorators>
292 template <DecoratorSet expected_decorators>
293 void Access<decorators>::verify_decorators() {
294 STATIC_ASSERT((~expected_decorators & decorators) == 0); // unexpected decorator used
295 const DecoratorSet barrier_strength_decorators = decorators & AS_DECORATOR_MASK;
296 STATIC_ASSERT(barrier_strength_decorators == 0 || ( // make sure barrier strength decorators are disjoint if set
297 (barrier_strength_decorators ^ AS_NO_KEEPALIVE) == 0 ||
298 (barrier_strength_decorators ^ AS_DEST_NOT_INITIALIZED) == 0 ||
299 (barrier_strength_decorators ^ AS_RAW) == 0 ||
300 (barrier_strength_decorators ^ AS_NORMAL) == 0
301 ));
302 const DecoratorSet ref_strength_decorators = decorators & ON_DECORATOR_MASK;
303 STATIC_ASSERT(ref_strength_decorators == 0 || ( // make sure ref strength decorators are disjoint if set
304 (ref_strength_decorators ^ ON_STRONG_OOP_REF) == 0 ||
305 (ref_strength_decorators ^ ON_WEAK_OOP_REF) == 0 ||
306 (ref_strength_decorators ^ ON_PHANTOM_OOP_REF) == 0 ||
307 (ref_strength_decorators ^ ON_UNKNOWN_OOP_REF) == 0
308 ));
309 const DecoratorSet memory_ordering_decorators = decorators & MO_DECORATOR_MASK;
310 STATIC_ASSERT(memory_ordering_decorators == 0 || ( // make sure memory ordering decorators are disjoint if set
311 (memory_ordering_decorators ^ MO_UNORDERED) == 0 ||
312 (memory_ordering_decorators ^ MO_VOLATILE) == 0 ||
313 (memory_ordering_decorators ^ MO_RELAXED) == 0 ||
314 (memory_ordering_decorators ^ MO_ACQUIRE) == 0 ||
315 (memory_ordering_decorators ^ MO_RELEASE) == 0 ||
316 (memory_ordering_decorators ^ MO_SEQ_CST) == 0
317 ));
318 const DecoratorSet location_decorators = decorators & IN_DECORATOR_MASK;
319 STATIC_ASSERT(location_decorators == 0 || ( // make sure location decorators are disjoint if set
320 (location_decorators ^ IN_ROOT) == 0 ||
321 (location_decorators ^ IN_HEAP) == 0 ||
322 (location_decorators ^ (IN_HEAP | IN_HEAP_ARRAY)) == 0 ||
323 (location_decorators ^ (IN_ROOT | IN_CONCURRENT_ROOT)) == 0 ||
324 (location_decorators ^ (IN_ROOT | IN_ARCHIVE_ROOT)) == 0
325 ));
326 }
327
328 #endif // SHARE_OOPS_ACCESS_HPP