1 /* 2 * Copyright (c) 1997, 2021, 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/accessDecorators.hpp" 31 #include "oops/markWord.hpp" 32 #include "oops/metadata.hpp" 33 #include "runtime/atomic.hpp" 34 #include "utilities/globalDefinitions.hpp" 35 #include "utilities/macros.hpp" 36 #include <type_traits> 37 38 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe 39 // the format of Java objects so the fields can be accessed from C++. 40 // oopDesc is abstract. 41 // (see oopHierarchy for complete oop class hierarchy) 42 // 43 // no virtual functions allowed 44 // 45 // oopDesc::_mark - the "oop mark word" encoding to be found separately in markWord.hpp 46 // 47 // oopDesc::_metadata - encodes the object's klass pointer, as a raw pointer in "_klass" 48 // or compressed pointer in "_compressed_klass" 49 // 50 // The overall size of the _metadata field is dependent on "UseCompressedClassPointers", 51 // hence the terms "narrow" (32 bits) vs "wide" (64 bits). 52 // 53 54 55 // Forward declarations. 56 class OopClosure; 57 class FilteringClosure; 58 59 class PSPromotionManager; 60 class ParCompactionManager; 61 62 class oopDesc { 63 friend class VMStructs; 64 friend class JVMCIVMStructs; 65 private: 66 volatile markWord _mark; 67 union _metadata { 68 Klass* _klass; 69 narrowKlass _compressed_klass; 70 } _metadata; 71 72 // There may be ordering constraints on the initialization of fields that 73 // make use of the C++ copy/assign incorrect. 74 NONCOPYABLE(oopDesc); 75 76 public: 77 // Must be trivial; see verifying static assert after the class. 78 oopDesc() = default; 79 80 inline markWord mark() const; 81 inline markWord mark_acquire() const; 82 inline markWord* mark_addr() const; 83 84 inline void set_mark(markWord m); 85 static inline void 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 99 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN; 100 inline void set_klass(Klass* k); 101 static inline void release_set_klass(HeapWord* mem, Klass* k); 102 103 // For klass field compression 104 static inline void set_klass_gap(HeapWord* mem, int z); 105 106 // size of object header, aligned to platform wordSize 107 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; } 108 109 // Returns whether this is an instance of k or an instance of a subclass of k 110 inline bool is_a(Klass* k) const; 111 112 // Returns the actual oop size of the object 113 inline size_t size(); 114 115 // Sometimes (for complicated concurrency-related reasons), it is useful 116 // to be able to figure out the size of an object knowing its klass. 117 inline size_t size_given_klass(Klass* klass); 118 119 // type test operations (inlined in oop.inline.hpp) 120 inline bool is_instance() const; 121 inline bool is_array() const; 122 inline bool is_objArray() const; 123 inline bool is_typeArray() const; 124 inline bool is_inline_type() const; 125 inline bool is_flatArray() const; 126 inline bool is_null_free_array() const; 127 128 // type test operations that don't require inclusion of oop.inline.hpp. 129 bool is_instance_noinline() const; 130 bool is_array_noinline() const; 131 bool is_objArray_noinline() const; 132 bool is_typeArray_noinline() const; 133 bool is_flatArray_noinline() const; 134 bool is_null_free_array_noinline() const; 135 136 protected: 137 inline oop as_oop() const { return const_cast<oopDesc*>(this); } 138 139 public: 140 template<typename T> 141 inline T* field_addr(int offset) const; 142 143 template <typename T> inline size_t field_offset(T* p) const; 144 145 // Standard compare function returns negative value if o1 < o2 146 // 0 if o1 == o2 147 // positive value if o1 > o2 148 inline static int compare(oop o1, oop o2) { 149 void* o1_addr = (void*)o1; 150 void* o2_addr = (void*)o2; 151 if (o1_addr < o2_addr) { 152 return -1; 153 } else if (o1_addr > o2_addr) { 154 return 1; 155 } else { 156 return 0; 157 } 158 } 159 160 // Access to fields in a instanceOop through these methods. 161 template <DecoratorSet decorator> 162 oop obj_field_access(int offset) const; 163 oop obj_field(int offset) const; 164 void obj_field_put(int offset, oop value); 165 void obj_field_put_raw(int offset, oop value); 166 void obj_field_put_volatile(int offset, oop value); 167 168 Metadata* metadata_field(int offset) const; 169 void metadata_field_put(int offset, Metadata* value); 170 171 Metadata* metadata_field_acquire(int offset) const; 172 void release_metadata_field_put(int offset, Metadata* value); 173 174 jbyte byte_field(int offset) const; 175 void byte_field_put(int offset, jbyte contents); 176 177 jchar char_field(int offset) const; 178 void char_field_put(int offset, jchar contents); 179 180 jboolean bool_field(int offset) const; 181 void bool_field_put(int offset, jboolean contents); 182 jboolean bool_field_volatile(int offset) const; 183 void bool_field_put_volatile(int offset, jboolean contents); 184 185 jint int_field(int offset) const; 186 void int_field_put(int offset, jint contents); 187 188 jshort short_field(int offset) const; 189 void short_field_put(int offset, jshort contents); 190 191 jlong long_field(int offset) const; 192 void long_field_put(int offset, jlong contents); 193 194 jfloat float_field(int offset) const; 195 void float_field_put(int offset, jfloat contents); 196 197 jdouble double_field(int offset) const; 198 void double_field_put(int offset, jdouble contents); 199 200 address address_field(int offset) const; 201 void address_field_put(int offset, address contents); 202 203 oop obj_field_acquire(int offset) const; 204 void release_obj_field_put(int offset, oop value); 205 206 jbyte byte_field_acquire(int offset) const; 207 void release_byte_field_put(int offset, jbyte contents); 208 209 jchar char_field_acquire(int offset) const; 210 void release_char_field_put(int offset, jchar contents); 211 212 jboolean bool_field_acquire(int offset) const; 213 void release_bool_field_put(int offset, jboolean contents); 214 215 jint int_field_acquire(int offset) const; 216 void release_int_field_put(int offset, jint contents); 217 218 jshort short_field_acquire(int offset) const; 219 void release_short_field_put(int offset, jshort contents); 220 221 jlong long_field_acquire(int offset) const; 222 void release_long_field_put(int offset, jlong contents); 223 224 jfloat float_field_acquire(int offset) const; 225 void release_float_field_put(int offset, jfloat contents); 226 227 jdouble double_field_acquire(int offset) const; 228 void release_double_field_put(int offset, jdouble contents); 229 230 address address_field_acquire(int offset) const; 231 void release_address_field_put(int offset, address contents); 232 233 // printing functions for VM debugging 234 void print_on(outputStream* st) const; // First level print 235 void print_value_on(outputStream* st) const; // Second level print. 236 void print_address_on(outputStream* st) const; // Address printing 237 238 // printing on default output stream 239 void print(); 240 void print_value(); 241 void print_address(); 242 243 // return the print strings 244 char* print_string(); 245 char* print_value_string(); 246 247 // verification operations 248 static void verify_on(outputStream* st, oopDesc* oop_desc); 249 static void verify(oopDesc* oopDesc); 250 251 // locking operations 252 inline bool is_locked() const; 253 inline bool is_unlocked() const; 254 255 // asserts and guarantees 256 static bool is_oop(oop obj, bool ignore_mark_word = false); 257 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false); 258 259 // garbage collection 260 inline bool is_gc_marked() const; 261 262 // Forward pointer operations for scavenge 263 inline bool is_forwarded() const; 264 265 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN; 266 267 inline void forward_to(oop p); 268 269 // Like "forward_to", but inserts the forwarding pointer atomically. 270 // Exactly one thread succeeds in inserting the forwarding pointer, and 271 // this call returns "NULL" for that thread; any other thread has the 272 // value of the forwarding pointer returned and does not modify "this". 273 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative); 274 275 inline oop forwardee() const; 276 277 // Age of object during scavenge 278 inline uint age() const; 279 inline void incr_age(); 280 281 template <typename OopClosureType> 282 inline void oop_iterate(OopClosureType* cl); 283 284 template <typename OopClosureType> 285 inline void oop_iterate(OopClosureType* cl, MemRegion mr); 286 287 template <typename OopClosureType> 288 inline size_t oop_iterate_size(OopClosureType* cl); 289 290 template <typename OopClosureType> 291 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr); 292 293 template <typename OopClosureType> 294 inline void oop_iterate_backwards(OopClosureType* cl); 295 296 template <typename OopClosureType> 297 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass); 298 299 inline static bool is_instanceof_or_null(oop obj, Klass* klass); 300 301 // identity hash; returns the identity hash key (computes it if necessary) 302 inline intptr_t identity_hash(); 303 intptr_t slow_identity_hash(); 304 305 // marks are forwarded to stack when object is locked 306 inline bool has_displaced_mark() const; 307 inline markWord displaced_mark() const; 308 inline void set_displaced_mark(markWord m); 309 310 // Checks if the mark word needs to be preserved 311 inline bool mark_must_be_preserved() const; 312 inline bool mark_must_be_preserved(markWord m) const; 313 314 static bool has_klass_gap(); 315 316 // for code generation 317 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); } 318 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); } 319 static int klass_gap_offset_in_bytes() { 320 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 321 return klass_offset_in_bytes() + sizeof(narrowKlass); 322 } 323 324 // for error reporting 325 static void* load_klass_raw(oop obj); 326 static void* load_oop_raw(oop obj, int offset); 327 328 // Avoid include gc_globals.hpp in oop.inline.hpp 329 DEBUG_ONLY(bool get_UseParallelGC();) 330 DEBUG_ONLY(bool get_UseG1GC();) 331 }; 332 333 // An oopDesc is not initialized via a constructor. Space is allocated in 334 // the Java heap, and static functions provided here on HeapWord* are used 335 // to fill in certain parts of that memory. The allocated memory is then 336 // treated as referring to an oopDesc. For that to be valid, the oopDesc 337 // class must have a trivial default constructor (C++14 3.8/1). 338 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 339 340 #endif // SHARE_OOPS_OOP_HPP