1 /* 2 * Copyright (c) 2017, 2022, 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/allStatic.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 // * value_copy: Copy the contents of a value type from one heap address to another 61 // 62 // == IMPLEMENTATION == 63 // Each access goes through the following steps in a template pipeline. 64 // There are essentially 5 steps for each access: 65 // * Step 1: Set default decorators and decay types. This step gets rid of CV qualifiers 66 // and sets default decorators to sensible values. 67 // * Step 2: Reduce types. This step makes sure there is only a single T type and not 68 // multiple types. The P type of the address and T type of the value must 69 // match. 70 // * Step 3: Pre-runtime dispatch. This step checks whether a runtime call can be 71 // avoided, and in that case avoids it (calling raw accesses or 72 // primitive accesses in a build that does not require primitive GC barriers) 73 // * Step 4: Runtime-dispatch. This step performs a runtime dispatch to the corresponding 74 // BarrierSet::AccessBarrier accessor that attaches GC-required barriers 75 // to the access. 76 // * Step 5.a: Barrier resolution. This step is invoked the first time a runtime-dispatch 77 // happens for an access. The appropriate BarrierSet::AccessBarrier accessor 78 // is resolved, then the function pointer is updated to that accessor for 79 // future invocations. 80 // * Step 5.b: Post-runtime dispatch. This step now casts previously unknown types such 81 // as the address type of an oop on the heap (is it oop* or narrowOop*) to 82 // the appropriate type. It also splits sufficiently orthogonal accesses into 83 // different functions, such as whether the access involves oops or primitives 84 // and whether the access is performed on the heap or outside. Then the 85 // appropriate BarrierSet::AccessBarrier is called to perform the access. 86 // 87 // The implementation of step 1-4 resides in in accessBackend.hpp, to allow selected 88 // accesses to be accessible from only access.hpp, as opposed to access.inline.hpp. 89 // Steps 5.a and 5.b require knowledge about the GC backends, and therefore needs to 90 // include the various GC backend .inline.hpp headers. Their implementation resides in 91 // access.inline.hpp. The accesses that are allowed through the access.hpp file 92 // must be instantiated in access.cpp using the INSTANTIATE_HPP_ACCESS macro. 93 94 class InlineKlass; 95 96 template <DecoratorSet decorators = DECORATORS_NONE> 97 class Access: public AllStatic { 98 // This function asserts that if an access gets passed in a decorator outside 99 // of the expected_decorators, then something is wrong. It additionally checks 100 // the consistency of the decorators so that supposedly disjoint decorators are indeed 101 // disjoint. For example, an access can not be both in heap and on root at the 102 // same time. 103 template <DecoratorSet expected_decorators> 104 static void verify_decorators(); 105 106 template <DecoratorSet expected_mo_decorators> 107 static void verify_primitive_decorators() { 108 const DecoratorSet primitive_decorators = (AS_DECORATOR_MASK ^ AS_NO_KEEPALIVE) | 109 IN_HEAP | IS_ARRAY; 110 verify_decorators<expected_mo_decorators | primitive_decorators>(); 111 } 112 113 template <DecoratorSet expected_mo_decorators> 114 static void verify_oop_decorators() { 115 const DecoratorSet oop_decorators = AS_DECORATOR_MASK | IN_DECORATOR_MASK | 116 (ON_DECORATOR_MASK ^ ON_UNKNOWN_OOP_REF) | // no unknown oop refs outside of the heap 117 IS_ARRAY | IS_NOT_NULL | IS_DEST_UNINITIALIZED; 118 verify_decorators<expected_mo_decorators | oop_decorators>(); 119 } 120 121 template <DecoratorSet expected_mo_decorators> 122 static void verify_heap_oop_decorators() { 123 const DecoratorSet heap_oop_decorators = AS_DECORATOR_MASK | ON_DECORATOR_MASK | 124 IN_HEAP | IS_ARRAY | IS_NOT_NULL | IS_DEST_UNINITIALIZED; 125 verify_decorators<expected_mo_decorators | heap_oop_decorators>(); 126 } 127 128 template <DecoratorSet expected_mo_decorators> 129 static void verify_heap_value_decorators() { 130 const DecoratorSet heap_value_decorators = IN_HEAP | IS_DEST_UNINITIALIZED; 131 verify_decorators<expected_mo_decorators | heap_value_decorators>(); 132 } 133 134 static const DecoratorSet load_mo_decorators = MO_UNORDERED | MO_RELAXED | MO_ACQUIRE | MO_SEQ_CST; 135 static const DecoratorSet store_mo_decorators = MO_UNORDERED | MO_RELAXED | MO_RELEASE | MO_SEQ_CST; 136 static const DecoratorSet atomic_xchg_mo_decorators = MO_SEQ_CST; 137 static const DecoratorSet atomic_cmpxchg_mo_decorators = MO_RELAXED | MO_SEQ_CST; 138 139 protected: 140 template <typename T> 141 static inline void oop_arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, const T* src_raw, 142 arrayOop dst_obj, size_t dst_offset_in_bytes, T* dst_raw, 143 size_t length) { 144 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | 145 AS_DECORATOR_MASK | IS_ARRAY | IS_DEST_UNINITIALIZED>(); 146 AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, src_offset_in_bytes, src_raw, 147 dst_obj, dst_offset_in_bytes, dst_raw, 148 length); 149 } 150 151 template <typename T> 152 static inline void arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, const T* src_raw, 153 arrayOop dst_obj, size_t dst_offset_in_bytes, T* dst_raw, 154 size_t length) { 155 verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | 156 AS_DECORATOR_MASK | IS_ARRAY>(); 157 AccessInternal::arraycopy<decorators>(src_obj, src_offset_in_bytes, src_raw, 158 dst_obj, dst_offset_in_bytes, dst_raw, 159 length); 160 } 161 162 public: 163 // Primitive heap accesses 164 static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) { 165 verify_primitive_decorators<load_mo_decorators>(); 166 return AccessInternal::LoadAtProxy<decorators>(base, offset); 167 } 168 169 template <typename T> 170 static inline void store_at(oop base, ptrdiff_t offset, T value) { 171 verify_primitive_decorators<store_mo_decorators>(); 172 AccessInternal::store_at<decorators>(base, offset, value); 173 } 174 175 template <typename T> 176 static inline T atomic_cmpxchg_at(oop base, ptrdiff_t offset, T compare_value, T new_value) { 177 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>(); 178 return AccessInternal::atomic_cmpxchg_at<decorators>(base, offset, compare_value, new_value); 179 } 180 181 template <typename T> 182 static inline T atomic_xchg_at(oop base, ptrdiff_t offset, T new_value) { 183 verify_primitive_decorators<atomic_xchg_mo_decorators>(); 184 return AccessInternal::atomic_xchg_at<decorators>(base, offset, new_value); 185 } 186 187 // Oop heap accesses 188 static inline AccessInternal::OopLoadAtProxy<decorators> oop_load_at(oop base, ptrdiff_t offset) { 189 verify_heap_oop_decorators<load_mo_decorators>(); 190 return AccessInternal::OopLoadAtProxy<decorators>(base, offset); 191 } 192 193 template <typename T> 194 static inline void oop_store_at(oop base, ptrdiff_t offset, T value) { 195 verify_heap_oop_decorators<store_mo_decorators>(); 196 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 197 OopType oop_value = value; 198 AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value); 199 } 200 201 template <typename T> 202 static inline T oop_atomic_cmpxchg_at(oop base, ptrdiff_t offset, T compare_value, T new_value) { 203 verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>(); 204 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 205 OopType new_oop_value = new_value; 206 OopType compare_oop_value = compare_value; 207 return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, compare_oop_value, new_oop_value); 208 } 209 210 template <typename T> 211 static inline T oop_atomic_xchg_at(oop base, ptrdiff_t offset, T new_value) { 212 verify_heap_oop_decorators<atomic_xchg_mo_decorators>(); 213 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 214 OopType new_oop_value = new_value; 215 return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, new_oop_value); 216 } 217 218 // Clone an object from src to dst 219 static inline void clone(oop src, oop dst, size_t size) { 220 verify_decorators<IN_HEAP>(); 221 AccessInternal::clone<decorators>(src, dst, size); 222 } 223 224 // inline type heap access (when inlined)... 225 226 // Copy value type data from src to dst 227 static inline void value_copy(void* src, void* dst, InlineKlass* md) { 228 verify_heap_value_decorators<IN_HEAP>(); 229 AccessInternal::value_copy<decorators>(src, dst, md); 230 } 231 232 // Primitive accesses 233 template <typename P> 234 static inline P load(P* addr) { 235 verify_primitive_decorators<load_mo_decorators>(); 236 return AccessInternal::load<decorators, P, P>(addr); 237 } 238 239 template <typename P, typename T> 240 static inline void store(P* addr, T value) { 241 verify_primitive_decorators<store_mo_decorators>(); 242 AccessInternal::store<decorators>(addr, value); 243 } 244 245 template <typename P, typename T> 246 static inline T atomic_cmpxchg(P* addr, T compare_value, T new_value) { 247 verify_primitive_decorators<atomic_cmpxchg_mo_decorators>(); 248 return AccessInternal::atomic_cmpxchg<decorators>(addr, compare_value, new_value); 249 } 250 251 template <typename P, typename T> 252 static inline T atomic_xchg(P* addr, T new_value) { 253 verify_primitive_decorators<atomic_xchg_mo_decorators>(); 254 return AccessInternal::atomic_xchg<decorators>(addr, new_value); 255 } 256 257 // Oop accesses 258 template <typename P> 259 static inline AccessInternal::OopLoadProxy<P, decorators> oop_load(P* addr) { 260 verify_oop_decorators<load_mo_decorators>(); 261 return AccessInternal::OopLoadProxy<P, decorators>(addr); 262 } 263 264 template <typename P, typename T> 265 static inline void oop_store(P* addr, T value) { 266 verify_oop_decorators<store_mo_decorators>(); 267 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 268 OopType oop_value = value; 269 AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value); 270 } 271 272 template <typename P, typename T> 273 static inline T oop_atomic_cmpxchg(P* addr, T compare_value, T new_value) { 274 verify_oop_decorators<atomic_cmpxchg_mo_decorators>(); 275 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 276 OopType new_oop_value = new_value; 277 OopType compare_oop_value = compare_value; 278 return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(addr, compare_oop_value, new_oop_value); 279 } 280 281 template <typename P, typename T> 282 static inline T oop_atomic_xchg(P* addr, T new_value) { 283 verify_oop_decorators<atomic_xchg_mo_decorators>(); 284 typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType; 285 OopType new_oop_value = new_value; 286 return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(addr, new_oop_value); 287 } 288 }; 289 290 // Helper for performing raw accesses (knows only of memory ordering 291 // atomicity decorators as well as compressed oops). 292 template <DecoratorSet decorators = DECORATORS_NONE> 293 class RawAccess: public Access<AS_RAW | decorators> {}; 294 295 // Helper for performing normal accesses on the heap. These accesses 296 // may resolve an accessor on a GC barrier set. 297 template <DecoratorSet decorators = DECORATORS_NONE> 298 class HeapAccess: public Access<IN_HEAP | decorators> {}; 299 300 // Helper for performing normal accesses in roots. These accesses 301 // may resolve an accessor on a GC barrier set. 302 template <DecoratorSet decorators = DECORATORS_NONE> 303 class NativeAccess: public Access<IN_NATIVE | decorators> {}; 304 305 // Helper for performing accesses in nmethods. These accesses 306 // may resolve an accessor on a GC barrier set. 307 template <DecoratorSet decorators = DECORATORS_NONE> 308 class NMethodAccess: public Access<IN_NMETHOD | decorators> {}; 309 310 // Helper for array access. 311 template <DecoratorSet decorators = DECORATORS_NONE> 312 class ArrayAccess: public HeapAccess<IS_ARRAY | decorators> { 313 typedef HeapAccess<IS_ARRAY | decorators> AccessT; 314 public: 315 template <typename T> 316 static inline void arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, 317 arrayOop dst_obj, size_t dst_offset_in_bytes, 318 size_t length) { 319 AccessT::arraycopy(src_obj, src_offset_in_bytes, static_cast<const T*>(nullptr), 320 dst_obj, dst_offset_in_bytes, static_cast<T*>(nullptr), 321 length); 322 } 323 324 template <typename T> 325 static inline void arraycopy_to_native(arrayOop src_obj, size_t src_offset_in_bytes, 326 T* dst, 327 size_t length) { 328 AccessT::arraycopy(src_obj, src_offset_in_bytes, static_cast<const T*>(nullptr), 329 NULL, 0, dst, 330 length); 331 } 332 333 template <typename T> 334 static inline void arraycopy_from_native(const T* src, 335 arrayOop dst_obj, size_t dst_offset_in_bytes, 336 size_t length) { 337 AccessT::arraycopy(NULL, 0, src, 338 dst_obj, dst_offset_in_bytes, static_cast<T*>(nullptr), 339 length); 340 } 341 342 static inline void oop_arraycopy(arrayOop src_obj, size_t src_offset_in_bytes, 343 arrayOop dst_obj, size_t dst_offset_in_bytes, 344 size_t length) { 345 AccessT::oop_arraycopy(src_obj, src_offset_in_bytes, static_cast<const HeapWord*>(nullptr), 346 dst_obj, dst_offset_in_bytes, static_cast<HeapWord*>(nullptr), 347 length); 348 } 349 350 template <typename T> 351 static inline void oop_arraycopy_raw(T* src, T* dst, size_t length) { 352 AccessT::oop_arraycopy(NULL, 0, src, 353 NULL, 0, dst, 354 length); 355 } 356 357 }; 358 359 template <DecoratorSet decorators> 360 template <DecoratorSet expected_decorators> 361 void Access<decorators>::verify_decorators() { 362 STATIC_ASSERT((~expected_decorators & decorators) == 0); // unexpected decorator used 363 const DecoratorSet barrier_strength_decorators = decorators & AS_DECORATOR_MASK; 364 STATIC_ASSERT(barrier_strength_decorators == 0 || ( // make sure barrier strength decorators are disjoint if set 365 (barrier_strength_decorators ^ AS_NO_KEEPALIVE) == 0 || 366 (barrier_strength_decorators ^ AS_RAW) == 0 || 367 (barrier_strength_decorators ^ AS_NORMAL) == 0 368 )); 369 const DecoratorSet ref_strength_decorators = decorators & ON_DECORATOR_MASK; 370 STATIC_ASSERT(ref_strength_decorators == 0 || ( // make sure ref strength decorators are disjoint if set 371 (ref_strength_decorators ^ ON_STRONG_OOP_REF) == 0 || 372 (ref_strength_decorators ^ ON_WEAK_OOP_REF) == 0 || 373 (ref_strength_decorators ^ ON_PHANTOM_OOP_REF) == 0 || 374 (ref_strength_decorators ^ ON_UNKNOWN_OOP_REF) == 0 375 )); 376 const DecoratorSet memory_ordering_decorators = decorators & MO_DECORATOR_MASK; 377 STATIC_ASSERT(memory_ordering_decorators == 0 || ( // make sure memory ordering decorators are disjoint if set 378 (memory_ordering_decorators ^ MO_UNORDERED) == 0 || 379 (memory_ordering_decorators ^ MO_RELAXED) == 0 || 380 (memory_ordering_decorators ^ MO_ACQUIRE) == 0 || 381 (memory_ordering_decorators ^ MO_RELEASE) == 0 || 382 (memory_ordering_decorators ^ MO_SEQ_CST) == 0 383 )); 384 const DecoratorSet location_decorators = decorators & IN_DECORATOR_MASK; 385 STATIC_ASSERT(location_decorators == 0 || ( // make sure location decorators are disjoint if set 386 (location_decorators ^ IN_NATIVE) == 0 || 387 (location_decorators ^ IN_NMETHOD) == 0 || 388 (location_decorators ^ IN_HEAP) == 0 389 )); 390 } 391 392 #endif // SHARE_OOPS_ACCESS_HPP