1 /*
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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. The ArrayAccess class has convenience functions for this.
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_NATIVE | 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 protected:
134 template <typename T>
135 static inline bool oop_arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, const T* src_raw,
136 arrayOop dst_obj, size_t dst_offset_in_bytes, T* dst_raw,
137 size_t length) {
138 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | IN_HEAP_ARRAY |
139 AS_DECORATOR_MASK>();
140 return AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, src_offset_in_bytes, src_raw,
141 dst_obj, dst_offset_in_bytes, dst_raw,
142 length);
143 }
144
145 template <typename T>
146 static inline void arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, const T* src_raw,
147 arrayOop dst_obj, size_t dst_offset_in_bytes, T* dst_raw,
148 size_t length) {
149 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | IN_HEAP_ARRAY |
150 AS_DECORATOR_MASK>();
151 AccessInternal::arraycopy<decorators>(src_obj, src_offset_in_bytes, src_raw,
152 dst_obj, dst_offset_in_bytes, dst_raw,
153 length);
154 }
155
156 public:
157 // Primitive heap accesses
158 static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) {
159 verify_primitive_decorators<load_mo_decorators>();
160 return AccessInternal::LoadAtProxy<decorators>(base, offset);
161 }
162
163 template <typename T>
164 static inline void store_at(oop base, ptrdiff_t offset, T value) {
165 verify_primitive_decorators<store_mo_decorators>();
166 AccessInternal::store_at<decorators>(base, offset, value);
167 }
168
169 template <typename T>
170 static inline T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
171 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
172 return AccessInternal::atomic_cmpxchg_at<decorators>(new_value, base, offset, compare_value);
173 }
174
175 template <typename T>
176 static inline T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
177 verify_primitive_decorators<atomic_xchg_mo_decorators>();
178 return AccessInternal::atomic_xchg_at<decorators>(new_value, base, offset);
179 }
180
181 // Oop heap accesses
182 static inline AccessInternal::OopLoadAtProxy<decorators> oop_load_at(oop base, ptrdiff_t offset) {
183 verify_heap_oop_decorators<load_mo_decorators>();
184 return AccessInternal::OopLoadAtProxy<decorators>(base, offset);
185 }
186
187 template <typename T>
188 static inline void oop_store_at(oop base, ptrdiff_t offset, T value) {
189 verify_heap_oop_decorators<store_mo_decorators>();
190 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
191 OopType oop_value = value;
192 AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value);
193 }
194
195 template <typename T>
196 static inline T oop_atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
197 verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>();
198 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
199 OopType new_oop_value = new_value;
200 OopType compare_oop_value = compare_value;
201 return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset, compare_oop_value);
202 }
203
204 template <typename T>
205 static inline T oop_atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
206 verify_heap_oop_decorators<atomic_xchg_mo_decorators>();
207 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
208 OopType new_oop_value = new_value;
209 return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset);
210 }
211
212 // Clone an object from src to dst
213 static inline void clone(oop src, oop dst, size_t size) {
214 verify_decorators<IN_HEAP>();
215 AccessInternal::clone<decorators>(src, dst, size);
216 }
217
218 // Primitive accesses
219 template <typename P>
220 static inline P load(P* addr) {
221 verify_primitive_decorators<load_mo_decorators>();
222 return AccessInternal::load<decorators, P, P>(addr);
223 }
224
225 template <typename P, typename T>
226 static inline void store(P* addr, T value) {
227 verify_primitive_decorators<store_mo_decorators>();
228 AccessInternal::store<decorators>(addr, value);
229 }
230
231 template <typename P, typename T>
232 static inline T atomic_cmpxchg(T new_value, P* addr, T compare_value) {
233 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
234 return AccessInternal::atomic_cmpxchg<decorators>(new_value, addr, compare_value);
235 }
236
237 template <typename P, typename T>
238 static inline T atomic_xchg(T new_value, P* addr) {
239 verify_primitive_decorators<atomic_xchg_mo_decorators>();
240 return AccessInternal::atomic_xchg<decorators>(new_value, addr);
241 }
242
243 // Oop accesses
244 template <typename P>
245 static inline AccessInternal::OopLoadProxy<P, decorators> oop_load(P* addr) {
246 verify_oop_decorators<load_mo_decorators>();
247 return AccessInternal::OopLoadProxy<P, decorators>(addr);
248 }
249
250 template <typename P, typename T>
251 static inline void oop_store(P* addr, T value) {
252 verify_oop_decorators<store_mo_decorators>();
253 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
254 OopType oop_value = value;
255 AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value);
256 }
257
258 template <typename P, typename T>
259 static inline T oop_atomic_cmpxchg(T new_value, P* addr, T compare_value) {
260 verify_oop_decorators<atomic_cmpxchg_mo_decorators>();
261 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
262 OopType new_oop_value = new_value;
263 OopType compare_oop_value = compare_value;
264 return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr, compare_oop_value);
265 }
266
267 template <typename P, typename T>
268 static inline T oop_atomic_xchg(T new_value, P* addr) {
269 verify_oop_decorators<atomic_xchg_mo_decorators>();
270 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
271 OopType new_oop_value = new_value;
272 return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr);
273 }
274
275 static oop resolve(oop obj) {
276 verify_decorators<INTERNAL_EMPTY>();
277 return AccessInternal::resolve<decorators>(obj);
278 }
279
280 static bool equals(oop o1, oop o2) {
281 verify_decorators<INTERNAL_EMPTY>();
282 return AccessInternal::equals<decorators>(o1, o2);
283 }
284 };
285
286 // Helper for performing raw accesses (knows only of memory ordering
287 // atomicity decorators as well as compressed oops)
288 template <DecoratorSet decorators = INTERNAL_EMPTY>
289 class RawAccess: public Access<AS_RAW | decorators> {};
290
291 // Helper for performing normal accesses on the heap. These accesses
292 // may resolve an accessor on a GC barrier set
293 template <DecoratorSet decorators = INTERNAL_EMPTY>
294 class HeapAccess: public Access<IN_HEAP | decorators> {};
295
296 // Helper for performing normal accesses in roots. These accesses
297 // may resolve an accessor on a GC barrier set
298 template <DecoratorSet decorators = INTERNAL_EMPTY>
299 class NativeAccess: public Access<IN_NATIVE | decorators> {};
300
301 // Helper for array access.
302 template <DecoratorSet decorators = INTERNAL_EMPTY>
303 class ArrayAccess: public HeapAccess<IN_HEAP_ARRAY | decorators> {
304 typedef HeapAccess<IN_HEAP_ARRAY | decorators> AccessT;
305 public:
306 template <typename T>
307 static inline void arraycopy(arrayOop src_obj, size_t src_offset_in_bytes,
308 arrayOop dst_obj, size_t dst_offset_in_bytes,
309 size_t length) {
310 AccessT::arraycopy(src_obj, src_offset_in_bytes, reinterpret_cast<const T*>(NULL),
311 dst_obj, dst_offset_in_bytes, reinterpret_cast<T*>(NULL),
312 length);
313 }
314
315 template <typename T>
316 static inline void arraycopy_to_native(arrayOop src_obj, size_t src_offset_in_bytes,
317 T* dst,
318 size_t length) {
319 AccessT::arraycopy(src_obj, src_offset_in_bytes, reinterpret_cast<const T*>(NULL),
320 NULL, 0, dst,
321 length);
322 }
323
324 template <typename T>
325 static inline void arraycopy_from_native(const T* src,
326 arrayOop dst_obj, size_t dst_offset_in_bytes,
327 size_t length) {
328 AccessT::arraycopy(NULL, 0, src,
329 dst_obj, dst_offset_in_bytes, reinterpret_cast<T*>(NULL),
330 length);
331 }
332
333 static inline bool oop_arraycopy(arrayOop src_obj, size_t src_offset_in_bytes,
334 arrayOop dst_obj, size_t dst_offset_in_bytes,
335 size_t length) {
336 return AccessT::oop_arraycopy(src_obj, src_offset_in_bytes, reinterpret_cast<const HeapWord*>(NULL),
337 dst_obj, dst_offset_in_bytes, reinterpret_cast<HeapWord*>(NULL),
338 length);
339 }
340
341 template <typename T>
342 static inline bool oop_arraycopy_raw(T* src, T* dst, size_t length) {
343 return AccessT::oop_arraycopy(NULL, 0, src,
344 NULL, 0, dst,
345 length);
346 }
347
348 };
349
350 template <DecoratorSet decorators>
351 template <DecoratorSet expected_decorators>
352 void Access<decorators>::verify_decorators() {
353 STATIC_ASSERT((~expected_decorators & decorators) == 0); // unexpected decorator used
354 const DecoratorSet barrier_strength_decorators = decorators & AS_DECORATOR_MASK;
355 STATIC_ASSERT(barrier_strength_decorators == 0 || ( // make sure barrier strength decorators are disjoint if set
356 (barrier_strength_decorators ^ AS_NO_KEEPALIVE) == 0 ||
357 (barrier_strength_decorators ^ AS_DEST_NOT_INITIALIZED) == 0 ||
358 (barrier_strength_decorators ^ AS_RAW) == 0 ||
359 (barrier_strength_decorators ^ AS_NORMAL) == 0
360 ));
361 const DecoratorSet ref_strength_decorators = decorators & ON_DECORATOR_MASK;
362 STATIC_ASSERT(ref_strength_decorators == 0 || ( // make sure ref strength decorators are disjoint if set
363 (ref_strength_decorators ^ ON_STRONG_OOP_REF) == 0 ||
364 (ref_strength_decorators ^ ON_WEAK_OOP_REF) == 0 ||
365 (ref_strength_decorators ^ ON_PHANTOM_OOP_REF) == 0 ||
366 (ref_strength_decorators ^ ON_UNKNOWN_OOP_REF) == 0
367 ));
368 const DecoratorSet memory_ordering_decorators = decorators & MO_DECORATOR_MASK;
369 STATIC_ASSERT(memory_ordering_decorators == 0 || ( // make sure memory ordering decorators are disjoint if set
370 (memory_ordering_decorators ^ MO_UNORDERED) == 0 ||
371 (memory_ordering_decorators ^ MO_VOLATILE) == 0 ||
372 (memory_ordering_decorators ^ MO_RELAXED) == 0 ||
373 (memory_ordering_decorators ^ MO_ACQUIRE) == 0 ||
374 (memory_ordering_decorators ^ MO_RELEASE) == 0 ||
375 (memory_ordering_decorators ^ MO_SEQ_CST) == 0
376 ));
377 const DecoratorSet location_decorators = decorators & IN_DECORATOR_MASK;
378 STATIC_ASSERT(location_decorators == 0 || ( // make sure location decorators are disjoint if set
379 (location_decorators ^ IN_NATIVE) == 0 ||
380 (location_decorators ^ IN_HEAP) == 0 ||
381 (location_decorators ^ (IN_HEAP | IN_HEAP_ARRAY)) == 0 ||
382 (location_decorators ^ (IN_NATIVE | IN_CONCURRENT_ROOT)) == 0
383 ));
384 }
385
386 #endif // SHARE_OOPS_ACCESS_HPP