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/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   union _metadata {
 59     Klass*      _klass;
 60     narrowKlass _compressed_klass;
 61   } _metadata;
 62 
 63   // There may be ordering constraints on the initialization of fields that
 64   // make use of the C++ copy/assign incorrect.
 65   NONCOPYABLE(oopDesc);
 66 
 67  public:
 68   // Must be trivial; see verifying static assert after the class.
 69   oopDesc() = default;
 70 
 71   inline markWord  mark()          const;
 72   inline markWord  mark_acquire()  const;
 73   inline markWord* mark_addr() const;
 74 
 75   inline void set_mark(markWord m);
 76   static inline void set_mark(HeapWord* mem, markWord m);
 77 
 78   inline void release_set_mark(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   narrowKlass narrow_klass_legacy() const { return _metadata._compressed_klass; }
 91   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
 92   inline void set_klass(Klass* k);
 93   static inline void release_set_klass(HeapWord* mem, Klass* k);
 94 
 95   // For klass field compression
 96   inline int klass_gap() const;
 97   inline void set_klass_gap(int z);
 98   static inline void set_klass_gap(HeapWord* mem, int z);
 99 
100   // size of object header, aligned to platform wordSize
101   static int header_size() { return sizeof(oopDesc)/HeapWordSize; }
102 
103   // Returns whether this is an instance of k or an instance of a subclass of k
104   inline bool is_a(Klass* k) const;
105 
106   // Returns the actual oop size of the object
107   inline size_t size();
108 
109   // Sometimes (for complicated concurrency-related reasons), it is useful
110   // to be able to figure out the size of an object knowing its klass.
111   inline size_t size_given_klass(Klass* klass);
112 
113   // type test operations (inlined in oop.inline.hpp)
114   inline bool is_instance()            const;
115   inline bool is_array()               const;
116   inline bool is_objArray()            const;
117   inline bool is_typeArray()           const;
118 
119   // type test operations that don't require inclusion of oop.inline.hpp.
120   bool is_instance_noinline()          const;
121   bool is_array_noinline()             const;
122   bool is_objArray_noinline()          const;
123   bool is_typeArray_noinline()         const;
124 
125  protected:
126   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
127 
128  public:
129   template<typename T>
130   inline T* field_addr(int offset) const;
131 
132   template <typename T> inline size_t field_offset(T* p) const;
133 
134   // Standard compare function returns negative value if o1 < o2
135   //                                   0              if o1 == o2
136   //                                   positive value if o1 > o2
137   inline static int  compare(oop o1, oop o2) {
138     void* o1_addr = (void*)o1;
139     void* o2_addr = (void*)o2;
140     if (o1_addr < o2_addr) {
141       return -1;
142     } else if (o1_addr > o2_addr) {
143       return 1;
144     } else {
145       return 0;
146     }
147   }
148 
149   // Access to fields in a instanceOop through these methods.
150   template <DecoratorSet decorator>
151   oop obj_field_access(int offset) const;
152   oop obj_field(int offset) const;
153   void obj_field_put(int offset, oop value);
154   void obj_field_put_raw(int offset, oop value);
155   void obj_field_put_volatile(int offset, oop value);
156 
157   Metadata* metadata_field(int offset) const;
158   void metadata_field_put(int offset, Metadata* value);
159 
160   Metadata* metadata_field_acquire(int offset) const;
161   void release_metadata_field_put(int offset, Metadata* value);
162 
163   jbyte byte_field(int offset) const;
164   void byte_field_put(int offset, jbyte contents);
165 
166   jchar char_field(int offset) const;
167   void char_field_put(int offset, jchar contents);
168 
169   jboolean bool_field(int offset) const;
170   void bool_field_put(int offset, jboolean contents);
171   jboolean bool_field_volatile(int offset) const;
172   void bool_field_put_volatile(int offset, jboolean contents);
173 
174   jint int_field(int offset) const;
175   void int_field_put(int offset, jint contents);
176 
177   jshort short_field(int offset) const;
178   void short_field_put(int offset, jshort contents);
179 
180   jlong long_field(int offset) const;
181   void long_field_put(int offset, jlong contents);
182 
183   jfloat float_field(int offset) const;
184   void float_field_put(int offset, jfloat contents);
185 
186   jdouble double_field(int offset) const;
187   void double_field_put(int offset, jdouble contents);
188 
189   address address_field(int offset) const;
190   void address_field_put(int offset, address contents);
191 
192   oop obj_field_acquire(int offset) const;
193   void release_obj_field_put(int offset, oop value);
194 
195   jbyte byte_field_acquire(int offset) const;
196   void release_byte_field_put(int offset, jbyte contents);
197 
198   jchar char_field_acquire(int offset) const;
199   void release_char_field_put(int offset, jchar contents);
200 
201   jboolean bool_field_acquire(int offset) const;
202   void release_bool_field_put(int offset, jboolean contents);
203 
204   jint int_field_acquire(int offset) const;
205   void release_int_field_put(int offset, jint contents);
206 
207   jshort short_field_acquire(int offset) const;
208   void release_short_field_put(int offset, jshort contents);
209 
210   jlong long_field_acquire(int offset) const;
211   void release_long_field_put(int offset, jlong contents);
212 
213   jfloat float_field_acquire(int offset) const;
214   void release_float_field_put(int offset, jfloat contents);
215 
216   jdouble double_field_acquire(int offset) const;
217   void release_double_field_put(int offset, jdouble contents);
218 
219   address address_field_acquire(int offset) const;
220   void release_address_field_put(int offset, address contents);
221 
222   // printing functions for VM debugging
223   void print_on(outputStream* st) const;        // First level print
224   void print_value_on(outputStream* st) const;  // Second level print.
225   void print_address_on(outputStream* st) const; // Address printing
226 
227   // printing on default output stream
228   void print();
229   void print_value();
230   void print_address();
231 
232   // return the print strings
233   char* print_string();
234   char* print_value_string();
235 
236   // verification operations
237   static void verify_on(outputStream* st, oopDesc* oop_desc);
238   static void verify(oopDesc* oopDesc);
239 
240   // locking operations
241   inline bool is_locked()   const;
242   inline bool is_unlocked() const;
243 
244   // asserts and guarantees
245   static bool is_oop(oop obj, bool ignore_mark_word = false);
246   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
247 
248   // garbage collection
249   inline bool is_gc_marked() const;
250 
251   // Forward pointer operations for scavenge
252   inline bool is_forwarded() const;
253 
254   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
255 
256   inline void forward_to(oop p);
257   inline void forward_to_self();
258 
259   // Like "forward_to", but inserts the forwarding pointer atomically.
260   // Exactly one thread succeeds in inserting the forwarding pointer, and
261   // this call returns "NULL" for that thread; any other thread has the
262   // value of the forwarding pointer returned and does not modify "this".
263   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
264   inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
265 
266   inline oop forwardee() const;
267   inline oop forwardee(markWord header) 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   // Runtime entry
321   static Klass* load_klass_runtime(oopDesc* o);
322 
323   // Avoid include gc_globals.hpp in oop.inline.hpp
324   DEBUG_ONLY(bool get_UseParallelGC();)
325   DEBUG_ONLY(bool get_UseG1GC();)
326 };
327 
328 // An oopDesc is not initialized via a constructor.  Space is allocated in
329 // the Java heap, and static functions provided here on HeapWord* are used
330 // to fill in certain parts of that memory.  The allocated memory is then
331 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
332 // class must have a trivial default constructor (C++14 3.8/1).
333 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
334 
335 #endif // SHARE_OOPS_OOP_HPP
--- EOF ---