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