1 /*
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 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
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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 // 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 FilteringClosure;
 59 
 60 class PSPromotionManager;
 61 class ParCompactionManager;
 62 
 63 class oopDesc {
 64   friend class VMStructs;
 65   friend class JVMCIVMStructs;
 66  private:
 67   volatile markWord _mark;
 68   union _metadata {
 69     Klass*      _klass;
 70     narrowKlass _compressed_klass;
 71   } _metadata;
 72 
 73   // There may be ordering constraints on the initialization of fields that
 74   // make use of the C++ copy/assign incorrect.
 75   NONCOPYABLE(oopDesc);
 76 
 77  public:
 78   // Must be trivial; see verifying static assert after the class.
 79   oopDesc() = default;
 80 
 81   inline markWord  mark()          const;
 82   inline markWord  mark_acquire()  const;
 83   inline markWord* mark_addr() const;
 84 
 85   inline void set_mark(markWord m);
 86   static inline void set_mark(HeapWord* mem, markWord m);
 87   static inline void release_set_mark(HeapWord* mem, markWord m);
 88 
 89   inline void release_set_mark(markWord m);
 90   inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
 91   inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
 92 
 93   // Used only to re-initialize the mark word (e.g., of promoted
 94   // objects during a GC) -- requires a valid klass pointer
 95   inline void init_mark();
 96 
 97   inline Klass* klass() const;
 98   inline Klass* klass_or_null() const;
 99   inline Klass* klass_or_null_acquire() const;
100   // Get the raw value without any checks.
101   inline Klass* klass_raw() const;
102 
103   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
104   inline void set_klass(Klass* k);
105   static inline void release_set_klass(HeapWord* mem, Klass* k);
106 
107   // For klass field compression
108   static inline void set_klass_gap(HeapWord* mem, int z);
109 
110   // size of object header, aligned to platform wordSize
111   static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
112 
113   // Returns whether this is an instance of k or an instance of a subclass of k
114   inline bool is_a(Klass* k) const;
115 
116   // Returns the actual oop size of the object in machine words
117   inline size_t size();
118 
119   // Sometimes (for complicated concurrency-related reasons), it is useful
120   // to be able to figure out the size of an object knowing its klass.
121   inline size_t size_given_klass(Klass* klass);
122 
123   // type test operations (inlined in oop.inline.hpp)
124   inline bool is_instance()         const;
125   inline bool is_inline_type()      const;
126   inline bool is_instanceRef()      const;
127   inline bool is_stackChunk()       const;
128   inline bool is_array()            const;
129   inline bool is_objArray()         const;
130   inline bool is_typeArray()        const;
131   inline bool is_flatArray()        const;
132   inline bool is_null_free_array()  const;
133 
134   // type test operations that don't require inclusion of oop.inline.hpp.
135   bool is_instance_noinline()         const;
136   bool is_instanceRef_noinline()      const;
137   bool is_stackChunk_noinline()       const;
138   bool is_array_noinline()            const;
139   bool is_objArray_noinline()         const;
140   bool is_typeArray_noinline()        const;
141   bool is_flatArray_noinline()        const;
142   bool is_null_free_array_noinline()  const;
143 
144  protected:
145   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
146 
147  public:
148   template<typename T>
149   inline T* field_addr(int offset) const;
150 
151   template <typename T> inline size_t field_offset(T* p) const;
152 
153   // Standard compare function returns negative value if o1 < o2
154   //                                   0              if o1 == o2
155   //                                   positive value if o1 > o2
156   inline static int  compare(oop o1, oop o2) {
157     void* o1_addr = (void*)o1;
158     void* o2_addr = (void*)o2;
159     if (o1_addr < o2_addr) {
160       return -1;
161     } else if (o1_addr > o2_addr) {
162       return 1;
163     } else {
164       return 0;
165     }
166   }
167 
168   // Access to fields in a instanceOop through these methods.
169   template<DecoratorSet decorators>
170   oop obj_field_access(int offset) const;
171   oop obj_field(int offset) const;
172 
173   void obj_field_put(int offset, oop value);
174   void obj_field_put_raw(int offset, oop value);
175   void obj_field_put_volatile(int offset, oop value);
176   template<DecoratorSet decorators>
177   void obj_field_put_access(int offset, oop value);
178 
179   Metadata* metadata_field(int offset) const;
180   void metadata_field_put(int offset, Metadata* value);
181 
182   Metadata* metadata_field_acquire(int offset) const;
183   void release_metadata_field_put(int offset, Metadata* value);
184 
185   jbyte byte_field(int offset) const;
186   void byte_field_put(int offset, jbyte contents);
187 
188   jchar char_field(int offset) const;
189   void char_field_put(int offset, jchar contents);
190 
191   jboolean bool_field(int offset) const;
192   void bool_field_put(int offset, jboolean contents);
193   jboolean bool_field_volatile(int offset) const;
194   void bool_field_put_volatile(int offset, jboolean contents);
195 
196   jint int_field(int offset) const;
197   void int_field_put(int offset, jint contents);
198 
199   jshort short_field(int offset) const;
200   void short_field_put(int offset, jshort contents);
201 
202   jlong long_field(int offset) const;
203   void long_field_put(int offset, jlong contents);
204 
205   jfloat float_field(int offset) const;
206   void float_field_put(int offset, jfloat contents);
207 
208   jdouble double_field(int offset) const;
209   void double_field_put(int offset, jdouble contents);
210 
211   address address_field(int offset) const;
212   void address_field_put(int offset, address contents);
213 
214   oop obj_field_acquire(int offset) const;
215   void release_obj_field_put(int offset, oop value);
216 
217   jbyte byte_field_acquire(int offset) const;
218   void release_byte_field_put(int offset, jbyte contents);
219 
220   jchar char_field_acquire(int offset) const;
221   void release_char_field_put(int offset, jchar contents);
222 
223   jboolean bool_field_acquire(int offset) const;
224   void release_bool_field_put(int offset, jboolean contents);
225 
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_klass_raw(oop obj);
337   static void* load_oop_raw(oop obj, int offset);
338 
339   DEBUG_ONLY(bool size_might_change();)
340 };
341 
342 // An oopDesc is not initialized via a constructor.  Space is allocated in
343 // the Java heap, and static functions provided here on HeapWord* are used
344 // to fill in certain parts of that memory.  The allocated memory is then
345 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
346 // class must have a trivial default constructor (C++14 3.8/1).
347 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
348 
349 #endif // SHARE_OOPS_OOP_HPP