1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 namespace AccessInternal {
96 template <DecoratorSet decorators, typename T>
97 void store_at(oop base, ptrdiff_t offset, T value);
98
99 template <DecoratorSet decorators, typename T>
100 T load_at(oop base, ptrdiff_t offset);
101
102 template <DecoratorSet decorators, typename T>
103 T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value);
104
105 template <DecoratorSet decorators, typename T>
106 T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset);
107
108 template <DecoratorSet decorators, typename P, typename T>
109 void store(P* addr, T value);
110
111 template <DecoratorSet decorators, typename P, typename T>
112 T load(P* addr);
113
114 template <DecoratorSet decorators, typename P, typename T>
115 T atomic_cmpxchg(T new_value, P* addr, T compare_value);
116
117 template <DecoratorSet decorators, typename P, typename T>
118 T atomic_xchg(T new_value, P* addr);
119
120 template <DecoratorSet decorators, typename T>
121 bool arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length);
122
123 template <DecoratorSet decorators>
124 void clone(oop src, oop dst, size_t size);
125
126 template <DecoratorSet decorators>
127 oop resolve(oop src);
128
129 template <DecoratorSet decorators>
130 bool equals(oop o1, oop o2);
131
132 // Infer the type that should be returned from a load.
133 template <typename P, DecoratorSet decorators>
134 class OopLoadProxy: public StackObj {
135 private:
136 P *const _addr;
137 public:
138 OopLoadProxy(P* addr) : _addr(addr) {}
139
140 inline operator oop() {
141 return load<decorators | INTERNAL_VALUE_IS_OOP, P, oop>(_addr);
142 }
143
144 inline operator narrowOop() {
145 return load<decorators | INTERNAL_VALUE_IS_OOP, P, narrowOop>(_addr);
146 }
147
148 template <typename T>
149 inline bool operator ==(const T& other) const {
150 return load<decorators | INTERNAL_VALUE_IS_OOP, P, T>(_addr) == other;
151 }
152
153 template <typename T>
154 inline bool operator !=(const T& other) const {
155 return load<decorators | INTERNAL_VALUE_IS_OOP, P, T>(_addr) != other;
156 }
157 };
158
159 // Infer the type that should be returned from a load_at.
160 template <DecoratorSet decorators>
161 class LoadAtProxy: public StackObj {
162 private:
163 const oop _base;
164 const ptrdiff_t _offset;
165 public:
166 LoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}
167
168 template <typename T>
169 inline operator T() const {
170 return load_at<decorators, T>(_base, _offset);
171 }
172
173 template <typename T>
174 inline bool operator ==(const T& other) const { return load_at<decorators, T>(_base, _offset) == other; }
175
176 template <typename T>
177 inline bool operator !=(const T& other) const { return load_at<decorators, T>(_base, _offset) != other; }
178 };
179
180 template <DecoratorSet decorators>
181 class OopLoadAtProxy: public StackObj {
182 private:
183 const oop _base;
184 const ptrdiff_t _offset;
185 public:
186 OopLoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}
187
188 inline operator oop() const {
189 return load_at<decorators | INTERNAL_VALUE_IS_OOP, oop>(_base, _offset);
190 }
191
192 inline operator narrowOop() const {
193 return load_at<decorators | INTERNAL_VALUE_IS_OOP, narrowOop>(_base, _offset);
194 }
195
196 template <typename T>
197 inline bool operator ==(const T& other) const {
198 return load_at<decorators | INTERNAL_VALUE_IS_OOP, T>(_base, _offset) == other;
199 }
200
201 template <typename T>
202 inline bool operator !=(const T& other) const {
203 return load_at<decorators | INTERNAL_VALUE_IS_OOP, T>(_base, _offset) != other;
204 }
205 };
206 }
207
208 template <DecoratorSet decorators = INTERNAL_EMPTY>
209 class Access: public AllStatic {
210 // This function asserts that if an access gets passed in a decorator outside
211 // of the expected_decorators, then something is wrong. It additionally checks
212 // the consistency of the decorators so that supposedly disjoint decorators are indeed
213 // disjoint. For example, an access can not be both in heap and on root at the
214 // same time.
215 template <DecoratorSet expected_decorators>
216 static void verify_decorators();
217
218 template <DecoratorSet expected_mo_decorators>
219 static void verify_primitive_decorators() {
220 const DecoratorSet primitive_decorators = (AS_DECORATOR_MASK ^ AS_NO_KEEPALIVE ^ AS_DEST_NOT_INITIALIZED) |
221 IN_HEAP | IN_HEAP_ARRAY;
222 verify_decorators<expected_mo_decorators | primitive_decorators>();
223 }
224
225 template <DecoratorSet expected_mo_decorators>
226 static void verify_oop_decorators() {
227 const DecoratorSet oop_decorators = AS_DECORATOR_MASK | IN_DECORATOR_MASK |
228 (ON_DECORATOR_MASK ^ ON_UNKNOWN_OOP_REF) | // no unknown oop refs outside of the heap
229 OOP_DECORATOR_MASK;
230 verify_decorators<expected_mo_decorators | oop_decorators>();
231 }
232
233 template <DecoratorSet expected_mo_decorators>
234 static void verify_heap_oop_decorators() {
235 const DecoratorSet heap_oop_decorators = AS_DECORATOR_MASK | ON_DECORATOR_MASK |
236 OOP_DECORATOR_MASK | (IN_DECORATOR_MASK ^
237 (IN_ROOT | IN_CONCURRENT_ROOT)); // no root accesses in the heap
238 verify_decorators<expected_mo_decorators | heap_oop_decorators>();
239 }
240
241 static const DecoratorSet load_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_ACQUIRE | MO_SEQ_CST;
242 static const DecoratorSet store_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_RELEASE | MO_SEQ_CST;
243 static const DecoratorSet atomic_xchg_mo_decorators = MO_SEQ_CST;
244 static const DecoratorSet atomic_cmpxchg_mo_decorators = MO_RELAXED | MO_SEQ_CST;
245
246 public:
247 // Primitive heap accesses
248 static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) {
249 verify_primitive_decorators<load_mo_decorators>();
250 return AccessInternal::LoadAtProxy<decorators>(base, offset);
251 }
252
253 template <typename T>
254 static inline void store_at(oop base, ptrdiff_t offset, T value) {
255 verify_primitive_decorators<store_mo_decorators>();
256 AccessInternal::store_at<decorators>(base, offset, value);
257 }
258
259 template <typename T>
260 static inline T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
261 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
262 return AccessInternal::atomic_cmpxchg_at<decorators>(new_value, base, offset, compare_value);
263 }
264
265 template <typename T>
266 static inline T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
267 verify_primitive_decorators<atomic_xchg_mo_decorators>();
268 return AccessInternal::atomic_xchg_at<decorators>(new_value, base, offset);
269 }
270
271 template <typename T>
272 static inline void arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
273 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP |
274 AS_DECORATOR_MASK>();
275 AccessInternal::arraycopy<decorators>(src_obj, dst_obj, src, dst, length);
276 }
277
278 // Oop heap accesses
279 static inline AccessInternal::OopLoadAtProxy<decorators> oop_load_at(oop base, ptrdiff_t offset) {
280 verify_heap_oop_decorators<load_mo_decorators>();
281 return AccessInternal::OopLoadAtProxy<decorators>(base, offset);
282 }
283
284 template <typename T>
285 static inline void oop_store_at(oop base, ptrdiff_t offset, T value) {
286 verify_heap_oop_decorators<store_mo_decorators>();
287 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
288 OopType oop_value = value;
289 AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value);
290 }
291
292 template <typename T>
293 static inline T oop_atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
294 verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>();
295 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
296 OopType new_oop_value = new_value;
297 OopType compare_oop_value = compare_value;
298 return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset, compare_oop_value);
299 }
300
301 template <typename T>
302 static inline T oop_atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
303 verify_heap_oop_decorators<atomic_xchg_mo_decorators>();
304 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
305 OopType new_oop_value = new_value;
306 return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset);
307 }
308
309 template <typename T>
310 static inline bool oop_arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
311 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | AS_DECORATOR_MASK>();
312 return AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, dst_obj, src, dst, length);
313 }
314
315 // Clone an object from src to dst
316 static inline void clone(oop src, oop dst, size_t size) {
317 verify_decorators<IN_HEAP>();
318 AccessInternal::clone<decorators>(src, dst, size);
319 }
320
321 // Primitive accesses
322 template <typename P>
323 static inline P load(P* addr) {
324 verify_primitive_decorators<load_mo_decorators>();
325 return AccessInternal::load<decorators, P, P>(addr);
326 }
327
328 template <typename P, typename T>
329 static inline void store(P* addr, T value) {
330 verify_primitive_decorators<store_mo_decorators>();
331 AccessInternal::store<decorators>(addr, value);
332 }
333
334 template <typename P, typename T>
335 static inline T atomic_cmpxchg(T new_value, P* addr, T compare_value) {
336 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
337 return AccessInternal::atomic_cmpxchg<decorators>(new_value, addr, compare_value);
338 }
339
340 template <typename P, typename T>
341 static inline T atomic_xchg(T new_value, P* addr) {
342 verify_primitive_decorators<atomic_xchg_mo_decorators>();
343 return AccessInternal::atomic_xchg<decorators>(new_value, addr);
344 }
345
346 // Oop accesses
347 template <typename P>
348 static inline AccessInternal::OopLoadProxy<P, decorators> oop_load(P* addr) {
349 verify_oop_decorators<load_mo_decorators>();
350 return AccessInternal::OopLoadProxy<P, decorators>(addr);
351 }
352
353 template <typename P, typename T>
354 static inline void oop_store(P* addr, T value) {
355 verify_oop_decorators<store_mo_decorators>();
356 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
357 OopType oop_value = value;
358 AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value);
359 }
360
361 template <typename P, typename T>
362 static inline T oop_atomic_cmpxchg(T new_value, P* addr, T compare_value) {
363 verify_oop_decorators<atomic_cmpxchg_mo_decorators>();
364 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
365 OopType new_oop_value = new_value;
366 OopType compare_oop_value = compare_value;
367 return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr, compare_oop_value);
368 }
369
370 template <typename P, typename T>
371 static inline T oop_atomic_xchg(T new_value, P* addr) {
372 verify_oop_decorators<atomic_xchg_mo_decorators>();
373 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
374 OopType new_oop_value = new_value;
375 return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr);
376 }
377
378 static oop resolve(oop obj) {
379 verify_decorators<INTERNAL_EMPTY>();
380 return AccessInternal::resolve<decorators>(obj);
381 }
382
383 static bool equals(oop o1, oop o2) {
384 verify_decorators<INTERNAL_EMPTY>();
385 return AccessInternal::equals<decorators>(o1, o2);
386 }
387 };
388
389 // Helper for performing raw accesses (knows only of memory ordering
390 // atomicity decorators as well as compressed oops)
391 template <DecoratorSet decorators = INTERNAL_EMPTY>
392 class RawAccess: public Access<AS_RAW | decorators> {};
393
394 // Helper for performing normal accesses on the heap. These accesses
395 // may resolve an accessor on a GC barrier set
396 template <DecoratorSet decorators = INTERNAL_EMPTY>
397 class HeapAccess: public Access<IN_HEAP | decorators> {};
398
399 // Helper for performing normal accesses in roots. These accesses
400 // may resolve an accessor on a GC barrier set
401 template <DecoratorSet decorators = INTERNAL_EMPTY>
402 class RootAccess: public Access<IN_ROOT | decorators> {};
403
404 template <DecoratorSet decorators>
405 template <DecoratorSet expected_decorators>
406 void Access<decorators>::verify_decorators() {
407 STATIC_ASSERT((~expected_decorators & decorators) == 0); // unexpected decorator used
408 const DecoratorSet barrier_strength_decorators = decorators & AS_DECORATOR_MASK;
409 STATIC_ASSERT(barrier_strength_decorators == 0 || ( // make sure barrier strength decorators are disjoint if set
410 (barrier_strength_decorators ^ AS_NO_KEEPALIVE) == 0 ||
411 (barrier_strength_decorators ^ AS_DEST_NOT_INITIALIZED) == 0 ||
412 (barrier_strength_decorators ^ AS_RAW) == 0 ||
413 (barrier_strength_decorators ^ AS_NORMAL) == 0
414 ));
415 const DecoratorSet ref_strength_decorators = decorators & ON_DECORATOR_MASK;
416 STATIC_ASSERT(ref_strength_decorators == 0 || ( // make sure ref strength decorators are disjoint if set
417 (ref_strength_decorators ^ ON_STRONG_OOP_REF) == 0 ||
418 (ref_strength_decorators ^ ON_WEAK_OOP_REF) == 0 ||
419 (ref_strength_decorators ^ ON_PHANTOM_OOP_REF) == 0 ||
420 (ref_strength_decorators ^ ON_UNKNOWN_OOP_REF) == 0
421 ));
422 const DecoratorSet memory_ordering_decorators = decorators & MO_DECORATOR_MASK;
423 STATIC_ASSERT(memory_ordering_decorators == 0 || ( // make sure memory ordering decorators are disjoint if set
424 (memory_ordering_decorators ^ MO_UNORDERED) == 0 ||
425 (memory_ordering_decorators ^ MO_VOLATILE) == 0 ||
426 (memory_ordering_decorators ^ MO_RELAXED) == 0 ||
427 (memory_ordering_decorators ^ MO_ACQUIRE) == 0 ||
428 (memory_ordering_decorators ^ MO_RELEASE) == 0 ||
429 (memory_ordering_decorators ^ MO_SEQ_CST) == 0
430 ));
431 const DecoratorSet location_decorators = decorators & IN_DECORATOR_MASK;
432 STATIC_ASSERT(location_decorators == 0 || ( // make sure location decorators are disjoint if set
433 (location_decorators ^ IN_ROOT) == 0 ||
434 (location_decorators ^ IN_HEAP) == 0 ||
435 (location_decorators ^ (IN_HEAP | IN_HEAP_ARRAY)) == 0 ||
436 (location_decorators ^ (IN_ROOT | IN_CONCURRENT_ROOT)) == 0 ||
437 (location_decorators ^ (IN_ROOT | IN_ARCHIVE_ROOT)) == 0
438 ));
439 }
440
441 #endif // SHARE_OOPS_ACCESS_HPP