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).
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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/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