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