1 /* 2 * Copyright (c) 1997, 2023, 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_OOP_HPP 26 #define SHARE_OOPS_OOP_HPP 27 28 #include "memory/iterator.hpp" 29 #include "memory/memRegion.hpp" 30 #include "oops/compressedKlass.hpp" 31 #include "oops/accessDecorators.hpp" 32 #include "oops/markWord.hpp" 33 #include "oops/metadata.hpp" 34 #include "runtime/atomic.hpp" 35 #include "utilities/globalDefinitions.hpp" 36 #include "utilities/macros.hpp" 37 #include <type_traits> 38 39 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe 40 // the format of Java objects so the fields can be accessed from C++. 41 // oopDesc is abstract. 42 // (see oopHierarchy for complete oop class hierarchy) 43 // 44 // no virtual functions allowed 45 46 // Forward declarations. 47 class OopClosure; 48 class PSPromotionManager; 49 class ParCompactionManager; 50 51 class oopDesc { 52 friend class VMStructs; 53 friend class JVMCIVMStructs; 54 private: 55 volatile markWord _mark; 56 union _metadata { 57 Klass* _klass; 58 narrowKlass _compressed_klass; 59 } _metadata; 60 61 // There may be ordering constraints on the initialization of fields that 62 // make use of the C++ copy/assign incorrect. 63 NONCOPYABLE(oopDesc); 64 65 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order); 66 67 public: 68 // Must be trivial; see verifying static assert after the class. 69 oopDesc() = default; 70 71 inline markWord mark() const; 72 inline markWord mark_acquire() const; 73 inline markWord* mark_addr() const; 74 75 inline void set_mark(markWord m); 76 static inline void set_mark(HeapWord* mem, markWord m); 77 static inline void release_set_mark(HeapWord* mem, markWord m); 78 79 inline void release_set_mark(markWord m); 80 inline markWord cas_set_mark(markWord new_mark, markWord old_mark); 81 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order); 82 83 inline markWord resolve_mark() const; 84 85 // Returns the prototype mark that should be used for this object. 86 inline markWord prototype_mark() const; 87 88 // Used only to re-initialize the mark word (e.g., of promoted 89 // objects during a GC) -- requires a valid klass pointer 90 inline void init_mark(); 91 92 inline Klass* klass() const; 93 inline Klass* klass_or_null() const; 94 inline Klass* klass_or_null_acquire() const; 95 // Get the klass without running any asserts. 96 inline Klass* klass_without_asserts() const; 97 98 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN; 99 inline void set_klass(Klass* k); 100 static inline void release_set_klass(HeapWord* mem, Klass* k); 101 102 // For klass field compression 103 static inline void set_klass_gap(HeapWord* mem, int z); 104 105 // size of object header, aligned to platform wordSize 106 static int header_size() { 107 if (UseCompactObjectHeaders) { 108 return sizeof(markWord) / HeapWordSize; 109 } else { 110 return sizeof(oopDesc)/HeapWordSize; 111 } 112 } 113 114 // Returns whether this is an instance of k or an instance of a subclass of k 115 inline bool is_a(Klass* k) const; 116 117 // Returns the actual oop size of the object in machine words 118 inline size_t size(); 119 120 // Sometimes (for complicated concurrency-related reasons), it is useful 121 // to be able to figure out the size of an object knowing its klass. 122 inline size_t size_given_klass(Klass* klass); 123 124 // The following set of methods is used to access the mark-word and related 125 // properties when the object may be forwarded. Be careful where and when 126 // using this method. It assumes that the forwardee is installed in 127 // the header as a plain pointer (or self-forwarded). In particular, 128 // those methods can not deal with the sliding-forwarding that is used 129 // in Serial, G1 and Shenandoah full-GCs. 130 private: 131 inline Klass* forward_safe_klass_impl(markWord m) const; 132 public: 133 inline Klass* forward_safe_klass() const; 134 inline Klass* forward_safe_klass(markWord m) const; 135 inline size_t forward_safe_size(); 136 inline void forward_safe_init_mark(); 137 138 // type test operations (inlined in oop.inline.hpp) 139 inline bool is_instance() const; 140 inline bool is_instanceRef() const; 141 inline bool is_stackChunk() const; 142 inline bool is_array() const; 143 inline bool is_objArray() const; 144 inline bool is_typeArray() const; 145 146 // type test operations that don't require inclusion of oop.inline.hpp. 147 bool is_instance_noinline() const; 148 bool is_instanceRef_noinline() const; 149 bool is_stackChunk_noinline() const; 150 bool is_array_noinline() const; 151 bool is_objArray_noinline() const; 152 bool is_typeArray_noinline() const; 153 154 protected: 155 inline oop as_oop() const { return const_cast<oopDesc*>(this); } 156 157 public: 158 template<typename T> 159 inline T* field_addr(int offset) const; 160 161 template <typename T> inline size_t field_offset(T* p) const; 162 163 // Standard compare function returns negative value if o1 < o2 164 // 0 if o1 == o2 165 // positive value if o1 > o2 166 inline static int compare(oop o1, oop o2) { 167 void* o1_addr = (void*)o1; 168 void* o2_addr = (void*)o2; 169 if (o1_addr < o2_addr) { 170 return -1; 171 } else if (o1_addr > o2_addr) { 172 return 1; 173 } else { 174 return 0; 175 } 176 } 177 178 // Access to fields in a instanceOop through these methods. 179 template<DecoratorSet decorators> 180 oop obj_field_access(int offset) const; 181 oop obj_field(int offset) const; 182 183 void obj_field_put(int offset, oop value); 184 void obj_field_put_raw(int offset, oop value); 185 void obj_field_put_volatile(int offset, oop value); 186 template<DecoratorSet decorators> 187 void obj_field_put_access(int offset, oop value); 188 189 Metadata* metadata_field(int offset) const; 190 void metadata_field_put(int offset, Metadata* value); 191 192 Metadata* metadata_field_acquire(int offset) const; 193 void release_metadata_field_put(int offset, Metadata* value); 194 195 jbyte byte_field(int offset) const; 196 void byte_field_put(int offset, jbyte contents); 197 198 jchar char_field(int offset) const; 199 void char_field_put(int offset, jchar contents); 200 201 jboolean bool_field(int offset) const; 202 void bool_field_put(int offset, jboolean contents); 203 jboolean bool_field_volatile(int offset) const; 204 void bool_field_put_volatile(int offset, jboolean contents); 205 206 jint int_field(int offset) const; 207 void int_field_put(int offset, jint contents); 208 209 jshort short_field(int offset) const; 210 void short_field_put(int offset, jshort contents); 211 212 jlong long_field(int offset) const; 213 void long_field_put(int offset, jlong contents); 214 215 jfloat float_field(int offset) const; 216 void float_field_put(int offset, jfloat contents); 217 218 jdouble double_field(int offset) const; 219 void double_field_put(int offset, jdouble contents); 220 221 address address_field(int offset) const; 222 void address_field_put(int offset, address contents); 223 224 oop obj_field_acquire(int offset) const; 225 void release_obj_field_put(int offset, oop value); 226 227 jbyte byte_field_acquire(int offset) const; 228 void release_byte_field_put(int offset, jbyte contents); 229 230 jchar char_field_acquire(int offset) const; 231 void release_char_field_put(int offset, jchar contents); 232 233 jboolean bool_field_acquire(int offset) const; 234 void release_bool_field_put(int offset, jboolean contents); 235 236 jint int_field_acquire(int offset) const; 237 void release_int_field_put(int offset, jint contents); 238 239 jshort short_field_acquire(int offset) const; 240 void release_short_field_put(int offset, jshort contents); 241 242 jlong long_field_acquire(int offset) const; 243 void release_long_field_put(int offset, jlong contents); 244 245 jfloat float_field_acquire(int offset) const; 246 void release_float_field_put(int offset, jfloat contents); 247 248 jdouble double_field_acquire(int offset) const; 249 void release_double_field_put(int offset, jdouble contents); 250 251 address address_field_acquire(int offset) const; 252 void release_address_field_put(int offset, address contents); 253 254 // printing functions for VM debugging 255 void print_on(outputStream* st) const; // First level print 256 void print_value_on(outputStream* st) const; // Second level print. 257 void print_address_on(outputStream* st) const; // Address printing 258 void print_name_on(outputStream* st) const; // External name printing. 259 260 // printing on default output stream 261 void print(); 262 void print_value(); 263 void print_address(); 264 265 // return the print strings 266 char* print_string(); 267 char* print_value_string(); 268 269 // verification operations 270 static void verify_on(outputStream* st, oopDesc* oop_desc); 271 static void verify(oopDesc* oopDesc); 272 273 // locking operations 274 inline bool is_locked() const; 275 inline bool is_unlocked() const; 276 277 // asserts and guarantees 278 static bool is_oop(oop obj, bool ignore_mark_word = false); 279 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false); 280 281 // garbage collection 282 inline bool is_gc_marked() const; 283 284 // Forward pointer operations for scavenge 285 inline bool is_forwarded() const; 286 inline bool is_self_forwarded() const; 287 288 inline void forward_to(oop p); 289 inline void forward_to_self(); 290 291 // Like "forward_to", but inserts the forwarding pointer atomically. 292 // Exactly one thread succeeds in inserting the forwarding pointer, and 293 // this call returns null for that thread; any other thread has the 294 // value of the forwarding pointer returned and does not modify "this". 295 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative); 296 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative); 297 298 inline oop forwardee() const; 299 inline oop forwardee(markWord header) const; 300 301 inline void unset_self_forwarded(); 302 303 // Age of object during scavenge 304 inline uint age() const; 305 inline void incr_age(); 306 307 template <typename OopClosureType> 308 inline void oop_iterate(OopClosureType* cl); 309 310 template <typename OopClosureType> 311 inline void oop_iterate(OopClosureType* cl, MemRegion mr); 312 313 template <typename OopClosureType> 314 inline size_t oop_iterate_size(OopClosureType* cl); 315 316 template <typename OopClosureType> 317 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr); 318 319 template <typename OopClosureType> 320 inline void oop_iterate_backwards(OopClosureType* cl); 321 322 template <typename OopClosureType> 323 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass); 324 325 inline static bool is_instanceof_or_null(oop obj, Klass* klass); 326 327 // identity hash; returns the identity hash key (computes it if necessary) 328 inline intptr_t identity_hash(); 329 intptr_t slow_identity_hash(); 330 inline bool fast_no_hash_check(); 331 332 // marks are forwarded to stack when object is locked 333 inline bool has_displaced_mark() const; 334 inline markWord displaced_mark() const; 335 inline void set_displaced_mark(markWord m); 336 337 // Checks if the mark word needs to be preserved 338 inline bool mark_must_be_preserved() const; 339 inline bool mark_must_be_preserved(markWord m) const; 340 341 static bool has_klass_gap(); 342 343 // for code generation 344 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); } 345 static int klass_offset_in_bytes() { 346 #ifdef _LP64 347 if (UseCompactObjectHeaders) { 348 constexpr int load_shift = markWord::klass_load_shift; 349 STATIC_ASSERT(load_shift % 8 == 0); 350 return mark_offset_in_bytes() + load_shift / 8; 351 } else 352 #endif 353 { 354 return (int)offset_of(oopDesc, _metadata._klass); 355 } 356 } 357 static int klass_gap_offset_in_bytes() { 358 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 359 assert(!UseCompactObjectHeaders, "don't use klass_offset_in_bytes() with compact headers"); 360 return klass_offset_in_bytes() + sizeof(narrowKlass); 361 } 362 363 static int base_offset_in_bytes() { 364 #ifdef _LP64 365 if (UseCompactObjectHeaders) { 366 // With compact headers, the Klass* field is not used for the Klass* 367 // and is used for the object fields instead. 368 STATIC_ASSERT(sizeof(markWord) == 8); 369 return sizeof(markWord); 370 } else if (UseCompressedClassPointers) { 371 return sizeof(markWord) + sizeof(narrowKlass); 372 } else 373 #endif 374 { 375 return sizeof(oopDesc); 376 } 377 } 378 379 // for error reporting 380 static void* load_oop_raw(oop obj, int offset); 381 382 DEBUG_ONLY(bool size_might_change();) 383 }; 384 385 // An oopDesc is not initialized via a constructor. Space is allocated in 386 // the Java heap, and static functions provided here on HeapWord* are used 387 // to fill in certain parts of that memory. The allocated memory is then 388 // treated as referring to an oopDesc. For that to be valid, the oopDesc 389 // class must have a trivial default constructor (C++14 3.8/1). 390 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 391 392 #endif // SHARE_OOPS_OOP_HPP