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 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