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