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src/hotspot/share/oops/oop.hpp

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 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 // Forward declarations.
 46 class OopClosure;
 47 class FilteringClosure;
 48 
 49 class PSPromotionManager;
 50 class ParCompactionManager;
 51 
 52 class oopDesc {
 53   friend class VMStructs;
 54   friend class JVMCIVMStructs;
 55  private:
 56   volatile markWord _mark;
 57   union _metadata {
 58     Klass*      _klass;
 59     narrowKlass _compressed_klass;
 60   } _metadata;
 61 
 62   // There may be ordering constraints on the initialization of fields that
 63   // make use of the C++ copy/assign incorrect.
 64   NONCOPYABLE(oopDesc);
 65 
 66  public:
 67   // Must be trivial; see verifying static assert after the class.
 68   oopDesc() = default;
 69 
 70   inline markWord  mark()          const;
 71   inline markWord  mark_acquire()  const;
 72   inline markWord* mark_addr() const;
 73 
 74   inline void set_mark(markWord m);
 75   static inline void set_mark(HeapWord* mem, markWord m);
 76 
 77   inline void release_set_mark(markWord m);

 78   inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
 79   inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
 80 
 81   // Used only to re-initialize the mark word (e.g., of promoted
 82   // objects during a GC) -- requires a valid klass pointer
 83   inline void init_mark();
 84 
 85   inline Klass* klass() const;
 86   inline Klass* klass_or_null() const;
 87   inline Klass* klass_or_null_acquire() const;
 88 
 89   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
 90   inline void set_klass(Klass* k);
 91   static inline void release_set_klass(HeapWord* mem, Klass* k);
 92 
 93   // For klass field compression
 94   static inline void set_klass_gap(HeapWord* mem, int z);
 95 
 96   // size of object header, aligned to platform wordSize
 97   static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
 98 
 99   // Returns whether this is an instance of k or an instance of a subclass of k
100   inline bool is_a(Klass* k) const;
101 
102   // Returns the actual oop size of the object in machine words
103   inline size_t size();
104 
105   // Sometimes (for complicated concurrency-related reasons), it is useful
106   // to be able to figure out the size of an object knowing its klass.
107   inline size_t size_given_klass(Klass* klass);
108 
109   // type test operations (inlined in oop.inline.hpp)
110   inline bool is_instance()    const;
111   inline bool is_instanceRef() const;
112   inline bool is_stackChunk()  const;
113   inline bool is_array()       const;
114   inline bool is_objArray()    const;

240   static void verify_on(outputStream* st, oopDesc* oop_desc);
241   static void verify(oopDesc* oopDesc);
242 
243   // locking operations
244   inline bool is_locked()   const;
245   inline bool is_unlocked() const;
246 
247   // asserts and guarantees
248   static bool is_oop(oop obj, bool ignore_mark_word = false);
249   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
250 
251   // garbage collection
252   inline bool is_gc_marked() const;
253 
254   // Forward pointer operations for scavenge
255   inline bool is_forwarded() const;
256 
257   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
258 
259   inline void forward_to(oop p);

260 
261   // Like "forward_to", but inserts the forwarding pointer atomically.
262   // Exactly one thread succeeds in inserting the forwarding pointer, and
263   // this call returns "NULL" for that thread; any other thread has the
264   // value of the forwarding pointer returned and does not modify "this".
265   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);

266 
267   inline oop forwardee() const;

268 
269   // Age of object during scavenge
270   inline uint age() const;
271   inline void incr_age();
272 
273   template <typename OopClosureType>
274   inline void oop_iterate(OopClosureType* cl);
275 
276   template <typename OopClosureType>
277   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
278 
279   template <typename OopClosureType>
280   inline size_t oop_iterate_size(OopClosureType* cl);
281 
282   template <typename OopClosureType>
283   inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
284 
285   template <typename OopClosureType>
286   inline void oop_iterate_backwards(OopClosureType* cl);
287 
288   template <typename OopClosureType>
289   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
290 
291   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
292 
293   // identity hash; returns the identity hash key (computes it if necessary)
294   inline intptr_t identity_hash();
295   intptr_t slow_identity_hash();
296 
297   // marks are forwarded to stack when object is locked
298   inline bool     has_displaced_mark() const;
299   inline markWord displaced_mark() const;
300   inline void     set_displaced_mark(markWord m);
301 
302   // Checks if the mark word needs to be preserved
303   inline bool mark_must_be_preserved() const;
304   inline bool mark_must_be_preserved(markWord m) const;
305 
306   static bool has_klass_gap();
307 
308   // for code generation
309   static int mark_offset_in_bytes()      { return offset_of(oopDesc, _mark); }
310   static int klass_offset_in_bytes()     { return offset_of(oopDesc, _metadata._klass); }
311   static int klass_gap_offset_in_bytes() {
312     assert(has_klass_gap(), "only applicable to compressed klass pointers");
313     return klass_offset_in_bytes() + sizeof(narrowKlass);



314   }
315 
316   // for error reporting
317   static void* load_klass_raw(oop obj);
318   static void* load_oop_raw(oop obj, int offset);
319 





320   DEBUG_ONLY(bool size_might_change();)
321 };
322 
323 // An oopDesc is not initialized via a constructor.  Space is allocated in
324 // the Java heap, and static functions provided here on HeapWord* are used
325 // to fill in certain parts of that memory.  The allocated memory is then
326 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
327 // class must have a trivial default constructor (C++14 3.8/1).
328 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
329 
330 #endif // SHARE_OOPS_OOP_HPP

 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/compressedKlass.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 FilteringClosure;
 49 
 50 class PSPromotionManager;
 51 class ParCompactionManager;
 52 
 53 class oopDesc {
 54   friend class VMStructs;
 55   friend class JVMCIVMStructs;
 56  private:
 57   volatile markWord _mark;
 58 #ifndef _LP64
 59   Klass*            _klass;
 60 #endif

 61 
 62   // There may be ordering constraints on the initialization of fields that
 63   // make use of the C++ copy/assign incorrect.
 64   NONCOPYABLE(oopDesc);
 65 
 66  public:
 67   // Must be trivial; see verifying static assert after the class.
 68   oopDesc() = default;
 69 
 70   inline markWord  mark()          const;
 71   inline markWord  mark_acquire()  const;
 72   inline markWord* mark_addr() const;
 73 
 74   inline void set_mark(markWord m);
 75   static inline void set_mark(HeapWord* mem, markWord m);
 76 
 77   inline void release_set_mark(markWord m);
 78   static inline void release_set_mark(HeapWord* mem, markWord m);
 79   inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
 80   inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
 81 
 82   // Used only to re-initialize the mark word (e.g., of promoted
 83   // objects during a GC) -- requires a valid klass pointer
 84   inline void init_mark();
 85 
 86   inline Klass* klass() const;
 87   inline Klass* klass_or_null() const;
 88   inline Klass* klass_or_null_acquire() const;
 89 
 90 #ifndef _LP64
 91   inline void set_klass(Klass* k);
 92   static inline void release_set_klass(HeapWord* mem, Klass* k);
 93 #endif


 94 
 95   // size of object header, aligned to platform wordSize
 96   static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
 97 
 98   // Returns whether this is an instance of k or an instance of a subclass of k
 99   inline bool is_a(Klass* k) const;
100 
101   // Returns the actual oop size of the object in machine words
102   inline size_t size();
103 
104   // Sometimes (for complicated concurrency-related reasons), it is useful
105   // to be able to figure out the size of an object knowing its klass.
106   inline size_t size_given_klass(Klass* klass);
107 
108   // type test operations (inlined in oop.inline.hpp)
109   inline bool is_instance()    const;
110   inline bool is_instanceRef() const;
111   inline bool is_stackChunk()  const;
112   inline bool is_array()       const;
113   inline bool is_objArray()    const;

239   static void verify_on(outputStream* st, oopDesc* oop_desc);
240   static void verify(oopDesc* oopDesc);
241 
242   // locking operations
243   inline bool is_locked()   const;
244   inline bool is_unlocked() const;
245 
246   // asserts and guarantees
247   static bool is_oop(oop obj, bool ignore_mark_word = false);
248   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
249 
250   // garbage collection
251   inline bool is_gc_marked() const;
252 
253   // Forward pointer operations for scavenge
254   inline bool is_forwarded() const;
255 
256   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
257 
258   inline void forward_to(oop p);
259   inline void forward_to_self();
260 
261   // Like "forward_to", but inserts the forwarding pointer atomically.
262   // Exactly one thread succeeds in inserting the forwarding pointer, and
263   // this call returns "NULL" for that thread; any other thread has the
264   // value of the forwarding pointer returned and does not modify "this".
265   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
266   inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
267 
268   inline oop forwardee() const;
269   inline oop forwardee(markWord header) const;
270 
271   // Age of object during scavenge
272   inline uint age() const;
273   inline void incr_age();
274 
275   template <typename OopClosureType>
276   inline void oop_iterate(OopClosureType* cl);
277 
278   template <typename OopClosureType>
279   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
280 
281   template <typename OopClosureType>
282   inline size_t oop_iterate_size(OopClosureType* cl);
283 
284   template <typename OopClosureType>
285   inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
286 
287   template <typename OopClosureType>
288   inline void oop_iterate_backwards(OopClosureType* cl);
289 
290   template <typename OopClosureType>
291   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
292 
293   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
294 
295   // identity hash; returns the identity hash key (computes it if necessary)
296   inline intptr_t identity_hash();
297   intptr_t slow_identity_hash();
298 
299   // marks are forwarded to stack when object is locked
300   inline bool     has_displaced_mark() const;
301   inline markWord displaced_mark() const;
302   inline void     set_displaced_mark(markWord m);
303 
304   // Checks if the mark word needs to be preserved
305   inline bool mark_must_be_preserved() const;
306   inline bool mark_must_be_preserved(markWord m) const;
307 


308   // for code generation
309   static int mark_offset_in_bytes()      { return offset_of(oopDesc, _mark); }
310   static int klass_offset_in_bytes()     {
311 #ifdef _LP64
312     STATIC_ASSERT(markWord::klass_shift % 8 == 0);
313     return mark_offset_in_bytes() + markWord::klass_shift / 8;
314 #else
315     return offset_of(oopDesc, _klass);
316 #endif
317   }
318 
319   // for error reporting
320   static void* load_klass_raw(oop obj);
321   static void* load_oop_raw(oop obj, int offset);
322 
323   // Runtime entry
324 #ifdef _LP64
325   static narrowKlass load_nklass_runtime(oopDesc* o);
326 #endif
327 
328   DEBUG_ONLY(bool size_might_change();)
329 };
330 
331 // An oopDesc is not initialized via a constructor.  Space is allocated in
332 // the Java heap, and static functions provided here on HeapWord* are used
333 // to fill in certain parts of that memory.  The allocated memory is then
334 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
335 // class must have a trivial default constructor (C++14 3.8/1).
336 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
337 
338 #endif // SHARE_OOPS_OOP_HPP
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