1 /*
   2  * Copyright (c) 1997, 2018, 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_VM_OOPS_KLASS_HPP
  26 #define SHARE_VM_OOPS_KLASS_HPP
  27 
  28 #include "memory/genOopClosures.hpp"
  29 #include "memory/iterator.hpp"
  30 #include "memory/memRegion.hpp"
  31 #include "memory/specialized_oop_closures.hpp"
  32 #include "oops/klassPS.hpp"
  33 #include "oops/metadata.hpp"
  34 #include "oops/oop.hpp"
  35 #include "trace/traceMacros.hpp"
  36 #include "utilities/accessFlags.hpp"
  37 #include "utilities/macros.hpp"
  38 #if INCLUDE_ALL_GCS
  39 #include "gc_implementation/concurrentMarkSweep/cmsOopClosures.hpp"
  40 #include "gc_implementation/g1/g1OopClosures.hpp"
  41 #include "gc_implementation/parNew/parOopClosures.hpp"
  42 #endif // INCLUDE_ALL_GCS
  43 
  44 //
  45 // A Klass provides:
  46 //  1: language level class object (method dictionary etc.)
  47 //  2: provide vm dispatch behavior for the object
  48 // Both functions are combined into one C++ class.
  49 
  50 // One reason for the oop/klass dichotomy in the implementation is
  51 // that we don't want a C++ vtbl pointer in every object.  Thus,
  52 // normal oops don't have any virtual functions.  Instead, they
  53 // forward all "virtual" functions to their klass, which does have
  54 // a vtbl and does the C++ dispatch depending on the object's
  55 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
  56 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
  57 
  58 //  Klass layout:
  59 //    [C++ vtbl ptr  ] (contained in Metadata)
  60 //    [layout_helper ]
  61 //    [super_check_offset   ] for fast subtype checks
  62 //    [name          ]
  63 //    [secondary_super_cache] for fast subtype checks
  64 //    [secondary_supers     ] array of 2ndary supertypes
  65 //    [primary_supers 0]
  66 //    [primary_supers 1]
  67 //    [primary_supers 2]
  68 //    ...
  69 //    [primary_supers 7]
  70 //    [java_mirror   ]
  71 //    [super         ]
  72 //    [subklass      ] first subclass
  73 //    [next_sibling  ] link to chain additional subklasses
  74 //    [next_link     ]
  75 //    [class_loader_data]
  76 //    [modifier_flags]
  77 //    [access_flags  ]
  78 //    [last_biased_lock_bulk_revocation_time] (64 bits)
  79 //    [prototype_header]
  80 //    [biased_lock_revocation_count]
  81 //    [_modified_oops]
  82 //    [_accumulated_modified_oops]
  83 //    [trace_id]
  84 
  85 
  86 // Forward declarations.
  87 template <class T> class Array;
  88 template <class T> class GrowableArray;
  89 class ClassLoaderData;
  90 class klassVtable;
  91 class ParCompactionManager;
  92 class KlassSizeStats;
  93 class fieldDescriptor;
  94 
  95 class Klass : public Metadata {
  96   friend class VMStructs;
  97  protected:
  98   // note: put frequently-used fields together at start of klass structure
  99   // for better cache behavior (may not make much of a difference but sure won't hurt)
 100   enum { _primary_super_limit = 8 };
 101 
 102   // The "layout helper" is a combined descriptor of object layout.
 103   // For klasses which are neither instance nor array, the value is zero.
 104   //
 105   // For instances, layout helper is a positive number, the instance size.
 106   // This size is already passed through align_object_size and scaled to bytes.
 107   // The low order bit is set if instances of this class cannot be
 108   // allocated using the fastpath.
 109   //
 110   // For arrays, layout helper is a negative number, containing four
 111   // distinct bytes, as follows:
 112   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
 113   // where:
 114   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
 115   //    hsz is array header size in bytes (i.e., offset of first element)
 116   //    ebt is the BasicType of the elements
 117   //    esz is the element size in bytes
 118   // This packed word is arranged so as to be quickly unpacked by the
 119   // various fast paths that use the various subfields.
 120   //
 121   // The esz bits can be used directly by a SLL instruction, without masking.
 122   //
 123   // Note that the array-kind tag looks like 0x00 for instance klasses,
 124   // since their length in bytes is always less than 24Mb.
 125   //
 126   // Final note:  This comes first, immediately after C++ vtable,
 127   // because it is frequently queried.
 128   jint        _layout_helper;
 129 
 130   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
 131   // and _primary_supers all help make fast subtype checks.  See big discussion
 132   // in doc/server_compiler/checktype.txt
 133   //
 134   // Where to look to observe a supertype (it is &_secondary_super_cache for
 135   // secondary supers, else is &_primary_supers[depth()].
 136   juint       _super_check_offset;
 137 
 138   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
 139   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
 140   Symbol*     _name;
 141 
 142   // Cache of last observed secondary supertype
 143   Klass*      _secondary_super_cache;
 144   // Array of all secondary supertypes
 145   Array<Klass*>* _secondary_supers;
 146   // Ordered list of all primary supertypes
 147   Klass*      _primary_supers[_primary_super_limit];
 148   // java/lang/Class instance mirroring this class
 149   oop       _java_mirror;
 150   // Superclass
 151   Klass*      _super;
 152   // First subclass (NULL if none); _subklass->next_sibling() is next one
 153   Klass*      _subklass;
 154   // Sibling link (or NULL); links all subklasses of a klass
 155   Klass*      _next_sibling;
 156 
 157   // All klasses loaded by a class loader are chained through these links
 158   Klass*      _next_link;
 159 
 160   // The VM's representation of the ClassLoader used to load this class.
 161   // Provide access the corresponding instance java.lang.ClassLoader.
 162   ClassLoaderData* _class_loader_data;
 163 
 164   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
 165   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
 166 
 167   // Biased locking implementation and statistics
 168   // (the 64-bit chunk goes first, to avoid some fragmentation)
 169   jlong    _last_biased_lock_bulk_revocation_time;
 170   markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type
 171   jint     _biased_lock_revocation_count;
 172 
 173   TRACE_DEFINE_KLASS_TRACE_ID;
 174 
 175   // Remembered sets support for the oops in the klasses.
 176   jbyte _modified_oops;             // Card Table Equivalent (YC/CMS support)
 177   jbyte _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
 178 
 179 private:
 180   // This is an index into FileMapHeader::_classpath_entry_table[], to
 181   // associate this class with the JAR file where it's loaded from during
 182   // dump time. If a class is not loaded from the shared archive, this field is
 183   // -1.
 184   jshort _shared_class_path_index;
 185 
 186   friend class SharedClassUtil;
 187 protected:
 188 
 189   // Constructor
 190   Klass();
 191 
 192   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
 193 
 194  public:
 195   enum DefaultsLookupMode { find_defaults, skip_defaults };
 196   enum OverpassLookupMode { find_overpass, skip_overpass };
 197   enum StaticLookupMode   { find_static,   skip_static };
 198   enum PrivateLookupMode  { find_private,  skip_private };
 199 
 200   bool is_klass() const volatile { return true; }
 201 
 202   // super
 203   Klass* super() const               { return _super; }
 204   void set_super(Klass* k)           { _super = k; }
 205 
 206   // initializes _super link, _primary_supers & _secondary_supers arrays
 207   void initialize_supers(Klass* k, TRAPS);
 208   void initialize_supers_impl1(Klass* k);
 209   void initialize_supers_impl2(Klass* k);
 210 
 211   // klass-specific helper for initializing _secondary_supers
 212   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots);
 213 
 214   // java_super is the Java-level super type as specified by Class.getSuperClass.
 215   virtual Klass* java_super() const  { return NULL; }
 216 
 217   juint    super_check_offset() const  { return _super_check_offset; }
 218   void set_super_check_offset(juint o) { _super_check_offset = o; }
 219 
 220   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
 221   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
 222 
 223   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
 224   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
 225 
 226   // Return the element of the _super chain of the given depth.
 227   // If there is no such element, return either NULL or this.
 228   Klass* primary_super_of_depth(juint i) const {
 229     assert(i < primary_super_limit(), "oob");
 230     Klass* super = _primary_supers[i];
 231     assert(super == NULL || super->super_depth() == i, "correct display");
 232     return super;
 233   }
 234 
 235   // Can this klass be a primary super?  False for interfaces and arrays of
 236   // interfaces.  False also for arrays or classes with long super chains.
 237   bool can_be_primary_super() const {
 238     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 239     return super_check_offset() != secondary_offset;
 240   }
 241   virtual bool can_be_primary_super_slow() const;
 242 
 243   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
 244   juint super_depth() const {
 245     if (!can_be_primary_super()) {
 246       return primary_super_limit();
 247     } else {
 248       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
 249       assert(d < primary_super_limit(), "oob");
 250       assert(_primary_supers[d] == this, "proper init");
 251       return d;
 252     }
 253   }
 254 
 255   // store an oop into a field of a Klass
 256   void klass_oop_store(oop* p, oop v);
 257   void klass_oop_store(volatile oop* p, oop v);
 258 
 259   // java mirror
 260   oop java_mirror() const              { return _java_mirror; }
 261   void set_java_mirror(oop m) { klass_oop_store(&_java_mirror, m); }
 262 
 263   // modifier flags
 264   jint modifier_flags() const          { return _modifier_flags; }
 265   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
 266 
 267   // size helper
 268   int layout_helper() const            { return _layout_helper; }
 269   void set_layout_helper(int lh)       { _layout_helper = lh; }
 270 
 271   // Note: for instances layout_helper() may include padding.
 272   // Use InstanceKlass::contains_field_offset to classify field offsets.
 273 
 274   // sub/superklass links
 275   InstanceKlass* superklass() const;
 276   Klass* subklass() const;
 277   Klass* next_sibling() const;
 278   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
 279 
 280   void set_next_link(Klass* k) { _next_link = k; }
 281   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
 282 
 283   // class loader data
 284   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
 285   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
 286 
 287   // The Klasses are not placed in the Heap, so the Card Table or
 288   // the Mod Union Table can't be used to mark when klasses have modified oops.
 289   // The CT and MUT bits saves this information for the individual Klasses.
 290   void record_modified_oops()            { _modified_oops = 1; }
 291   void clear_modified_oops()             { _modified_oops = 0; }
 292   bool has_modified_oops()               { return _modified_oops == 1; }
 293 
 294   void accumulate_modified_oops()        { if (has_modified_oops()) _accumulated_modified_oops = 1; }
 295   void clear_accumulated_modified_oops() { _accumulated_modified_oops = 0; }
 296   bool has_accumulated_modified_oops()   { return _accumulated_modified_oops == 1; }
 297 
 298   int shared_classpath_index() const   {
 299     return _shared_class_path_index;
 300   };
 301 
 302   void set_shared_classpath_index(int index) {
 303     _shared_class_path_index = index;
 304   };
 305 
 306 
 307  protected:                                // internal accessors
 308   Klass* subklass_oop() const            { return _subklass; }
 309   Klass* next_sibling_oop() const        { return _next_sibling; }
 310   void     set_subklass(Klass* s);
 311   void     set_next_sibling(Klass* s);
 312 
 313  public:
 314 
 315   // Compiler support
 316   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
 317   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
 318   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
 319   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
 320   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
 321   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
 322   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
 323   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
 324   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
 325 
 326   // Unpacking layout_helper:
 327   enum {
 328     _lh_neutral_value           = 0,  // neutral non-array non-instance value
 329     _lh_instance_slow_path_bit  = 0x01,
 330     _lh_log2_element_size_shift = BitsPerByte*0,
 331     _lh_log2_element_size_mask  = BitsPerLong-1,
 332     _lh_element_type_shift      = BitsPerByte*1,
 333     _lh_element_type_mask       = right_n_bits(BitsPerByte),  // shifted mask
 334     _lh_header_size_shift       = BitsPerByte*2,
 335     _lh_header_size_mask        = right_n_bits(BitsPerByte),  // shifted mask
 336     _lh_array_tag_bits          = 2,
 337     _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits,
 338     _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 30
 339   };
 340 
 341   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
 342 
 343   static int layout_helper_size_in_bytes(jint lh) {
 344     assert(lh > (jint)_lh_neutral_value, "must be instance");
 345     return (int) lh & ~_lh_instance_slow_path_bit;
 346   }
 347   static bool layout_helper_needs_slow_path(jint lh) {
 348     assert(lh > (jint)_lh_neutral_value, "must be instance");
 349     return (lh & _lh_instance_slow_path_bit) != 0;
 350   }
 351   static bool layout_helper_is_instance(jint lh) {
 352     return (jint)lh > (jint)_lh_neutral_value;
 353   }
 354   static bool layout_helper_is_array(jint lh) {
 355     return (jint)lh < (jint)_lh_neutral_value;
 356   }
 357   static bool layout_helper_is_typeArray(jint lh) {
 358     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
 359     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 360   }
 361   static bool layout_helper_is_objArray(jint lh) {
 362     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
 363     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 364   }
 365   static int layout_helper_header_size(jint lh) {
 366     assert(lh < (jint)_lh_neutral_value, "must be array");
 367     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
 368     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
 369     return hsize;
 370   }
 371   static BasicType layout_helper_element_type(jint lh) {
 372     assert(lh < (jint)_lh_neutral_value, "must be array");
 373     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
 374     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
 375     return (BasicType) btvalue;
 376   }
 377 
 378   // Want a pattern to quickly diff against layout header in register
 379   // find something less clever!
 380   static int layout_helper_boolean_diffbit() {
 381     jint zlh = array_layout_helper(T_BOOLEAN);
 382     jint blh = array_layout_helper(T_BYTE);
 383     assert(zlh != blh, "array layout helpers must differ");
 384     int diffbit = 1;
 385     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
 386       diffbit <<= 1;
 387       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
 388     }
 389     return diffbit;
 390   }
 391 
 392   static int layout_helper_log2_element_size(jint lh) {
 393     assert(lh < (jint)_lh_neutral_value, "must be array");
 394     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
 395     assert(l2esz <= LogBitsPerLong,
 396         err_msg("sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh));
 397     return l2esz;
 398   }
 399   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
 400     return (tag        << _lh_array_tag_shift)
 401       |    (hsize      << _lh_header_size_shift)
 402       |    ((int)etype << _lh_element_type_shift)
 403       |    (log2_esize << _lh_log2_element_size_shift);
 404   }
 405   static jint instance_layout_helper(jint size, bool slow_path_flag) {
 406     return (size << LogHeapWordSize)
 407       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
 408   }
 409   static int layout_helper_to_size_helper(jint lh) {
 410     assert(lh > (jint)_lh_neutral_value, "must be instance");
 411     // Note that the following expression discards _lh_instance_slow_path_bit.
 412     return lh >> LogHeapWordSize;
 413   }
 414   // Out-of-line version computes everything based on the etype:
 415   static jint array_layout_helper(BasicType etype);
 416 
 417   // What is the maximum number of primary superclasses any klass can have?
 418 #ifdef PRODUCT
 419   static juint primary_super_limit()         { return _primary_super_limit; }
 420 #else
 421   static juint primary_super_limit() {
 422     assert(FastSuperclassLimit <= _primary_super_limit, "parameter oob");
 423     return FastSuperclassLimit;
 424   }
 425 #endif
 426 
 427   // vtables
 428   virtual klassVtable* vtable() const        { return NULL; }
 429   virtual int vtable_length() const          { return 0; }
 430 
 431   // subclass check
 432   bool is_subclass_of(const Klass* k) const;
 433   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
 434   bool is_subtype_of(Klass* k) const {
 435     juint    off = k->super_check_offset();
 436     Klass* sup = *(Klass**)( (address)this + off );
 437     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 438     if (sup == k) {
 439       return true;
 440     } else if (off != secondary_offset) {
 441       return false;
 442     } else {
 443       return search_secondary_supers(k);
 444     }
 445   }
 446   bool search_secondary_supers(Klass* k) const;
 447 
 448   // Find LCA in class hierarchy
 449   Klass *LCA( Klass *k );
 450 
 451   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
 452   // if not, throw either an Error or an Exception.
 453   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
 454 
 455   // array copying
 456   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
 457 
 458   // tells if the class should be initialized
 459   virtual bool should_be_initialized() const    { return false; }
 460   // initializes the klass
 461   virtual void initialize(TRAPS);
 462   // lookup operation for MethodLookupCache
 463   friend class MethodLookupCache;
 464   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
 465   virtual Method* uncached_lookup_method(Symbol* name, Symbol* signature, OverpassLookupMode overpass_mode) const;
 466  public:
 467   Method* lookup_method(Symbol* name, Symbol* signature) const {
 468     return uncached_lookup_method(name, signature, find_overpass);
 469   }
 470 
 471   // array class with specific rank
 472   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }
 473 
 474   // array class with this klass as element type
 475   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }
 476 
 477   // These will return NULL instead of allocating on the heap:
 478   // NB: these can block for a mutex, like other functions with TRAPS arg.
 479   Klass* array_klass_or_null(int rank);
 480   Klass* array_klass_or_null();
 481 
 482   virtual oop protection_domain() const = 0;
 483 
 484   oop class_loader() const;
 485 
 486   virtual oop klass_holder() const      { return class_loader(); }
 487 
 488  protected:
 489   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
 490   virtual Klass* array_klass_impl(bool or_null, TRAPS);
 491 
 492  public:
 493   // CDS support - remove and restore oops from metadata. Oops are not shared.
 494   virtual void remove_unshareable_info();
 495   virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
 496 
 497  protected:
 498   // computes the subtype relationship
 499   virtual bool compute_is_subtype_of(Klass* k);
 500  public:
 501   // subclass accessor (here for convenience; undefined for non-klass objects)
 502   virtual bool is_leaf_class() const { fatal("not a class"); return false; }
 503  public:
 504   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
 505   // These functions describe behavior for the oop not the KLASS.
 506 
 507   // actual oop size of obj in memory
 508   virtual int oop_size(oop obj) const = 0;
 509 
 510   // Size of klass in word size.
 511   virtual int size() const = 0;
 512 #if INCLUDE_SERVICES
 513   virtual void collect_statistics(KlassSizeStats *sz) const;
 514 #endif
 515 
 516   // Returns the Java name for a class (Resource allocated)
 517   // For arrays, this returns the name of the element with a leading '['.
 518   // For classes, this returns the name with the package separators
 519   //     turned into '.'s.
 520   const char* external_name() const;
 521   // Returns the name for a class (Resource allocated) as the class
 522   // would appear in a signature.
 523   // For arrays, this returns the name of the element with a leading '['.
 524   // For classes, this returns the name with a leading 'L' and a trailing ';'
 525   //     and the package separators as '/'.
 526   virtual const char* signature_name() const;
 527 
 528   // garbage collection support
 529   virtual void oop_follow_contents(oop obj) = 0;
 530   virtual int  oop_adjust_pointers(oop obj) = 0;
 531 
 532   // Parallel Scavenge and Parallel Old
 533   PARALLEL_GC_DECLS_PV
 534 
 535   // type testing operations
 536  protected:
 537   virtual bool oop_is_instance_slow()       const { return false; }
 538   virtual bool oop_is_array_slow()          const { return false; }
 539   virtual bool oop_is_objArray_slow()       const { return false; }
 540   virtual bool oop_is_typeArray_slow()      const { return false; }
 541  public:
 542   virtual bool oop_is_instanceClassLoader() const { return false; }
 543   virtual bool oop_is_instanceMirror()      const { return false; }
 544   virtual bool oop_is_instanceRef()         const { return false; }
 545 
 546   // Fast non-virtual versions
 547   #ifndef ASSERT
 548   #define assert_same_query(xval, xcheck) xval
 549   #else
 550  private:
 551   static bool assert_same_query(bool xval, bool xslow) {
 552     assert(xval == xslow, "slow and fast queries agree");
 553     return xval;
 554   }
 555  public:
 556   #endif
 557   inline  bool oop_is_instance()            const { return assert_same_query(
 558                                                     layout_helper_is_instance(layout_helper()),
 559                                                     oop_is_instance_slow()); }
 560   inline  bool oop_is_array()               const { return assert_same_query(
 561                                                     layout_helper_is_array(layout_helper()),
 562                                                     oop_is_array_slow()); }
 563   inline  bool oop_is_objArray()            const { return assert_same_query(
 564                                                     layout_helper_is_objArray(layout_helper()),
 565                                                     oop_is_objArray_slow()); }
 566   inline  bool oop_is_typeArray()           const { return assert_same_query(
 567                                                     layout_helper_is_typeArray(layout_helper()),
 568                                                     oop_is_typeArray_slow()); }
 569   #undef assert_same_query
 570 
 571   // Access flags
 572   AccessFlags access_flags() const         { return _access_flags;  }
 573   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
 574 
 575   bool is_public() const                { return _access_flags.is_public(); }
 576   bool is_final() const                 { return _access_flags.is_final(); }
 577   bool is_interface() const             { return _access_flags.is_interface(); }
 578   bool is_abstract() const              { return _access_flags.is_abstract(); }
 579   bool is_super() const                 { return _access_flags.is_super(); }
 580   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
 581   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
 582   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
 583   bool has_final_method() const         { return _access_flags.has_final_method(); }
 584   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
 585   void set_has_final_method()           { _access_flags.set_has_final_method(); }
 586   bool is_cloneable() const;
 587   void set_is_cloneable();
 588   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
 589   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
 590   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
 591   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
 592 
 593   // Biased locking support
 594   // Note: the prototype header is always set up to be at least the
 595   // prototype markOop. If biased locking is enabled it may further be
 596   // biasable and have an epoch.
 597   markOop prototype_header() const      { return _prototype_header; }
 598   // NOTE: once instances of this klass are floating around in the
 599   // system, this header must only be updated at a safepoint.
 600   // NOTE 2: currently we only ever set the prototype header to the
 601   // biasable prototype for instanceKlasses. There is no technical
 602   // reason why it could not be done for arrayKlasses aside from
 603   // wanting to reduce the initial scope of this optimization. There
 604   // are potential problems in setting the bias pattern for
 605   // JVM-internal oops.
 606   inline void set_prototype_header(markOop header);
 607   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
 608 
 609   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }
 610   // Atomically increments biased_lock_revocation_count and returns updated value
 611   int atomic_incr_biased_lock_revocation_count();
 612   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }
 613   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }
 614   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }
 615 
 616   TRACE_DEFINE_KLASS_METHODS;
 617 
 618   // garbage collection support
 619   virtual void oops_do(OopClosure* cl);
 620 
 621   // Iff the class loader (or mirror for anonymous classes) is alive the
 622   // Klass is considered alive.
 623   // The is_alive closure passed in depends on the Garbage Collector used.
 624   bool is_loader_alive(BoolObjectClosure* is_alive);
 625 
 626   static void clean_weak_klass_links(BoolObjectClosure* is_alive, bool clean_alive_klasses = true);
 627   static void clean_subklass_tree(BoolObjectClosure* is_alive) {
 628     clean_weak_klass_links(is_alive, false /* clean_alive_klasses */);
 629   }
 630 
 631   // iterators
 632   virtual int oop_oop_iterate(oop obj, ExtendedOopClosure* blk) = 0;
 633   virtual int oop_oop_iterate_v(oop obj, ExtendedOopClosure* blk) {
 634     return oop_oop_iterate(obj, blk);
 635   }
 636 
 637 #if INCLUDE_ALL_GCS
 638   // In case we don't have a specialized backward scanner use forward
 639   // iteration.
 640   virtual int oop_oop_iterate_backwards_v(oop obj, ExtendedOopClosure* blk) {
 641     return oop_oop_iterate_v(obj, blk);
 642   }
 643 #endif // INCLUDE_ALL_GCS
 644 
 645   // Iterates "blk" over all the oops in "obj" (of type "this") within "mr".
 646   // (I don't see why the _m should be required, but without it the Solaris
 647   // C++ gives warning messages about overridings of the "oop_oop_iterate"
 648   // defined above "hiding" this virtual function.  (DLD, 6/20/00)) */
 649   virtual int oop_oop_iterate_m(oop obj, ExtendedOopClosure* blk, MemRegion mr) = 0;
 650   virtual int oop_oop_iterate_v_m(oop obj, ExtendedOopClosure* blk, MemRegion mr) {
 651     return oop_oop_iterate_m(obj, blk, mr);
 652   }
 653 
 654   // Versions of the above iterators specialized to particular subtypes
 655   // of OopClosure, to avoid closure virtual calls.
 656 #define Klass_OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)                \
 657   virtual int oop_oop_iterate##nv_suffix(oop obj, OopClosureType* blk) {     \
 658     /* Default implementation reverts to general version. */                 \
 659     return oop_oop_iterate(obj, blk);                                        \
 660   }                                                                          \
 661                                                                              \
 662   /* Iterates "blk" over all the oops in "obj" (of type "this") within "mr". \
 663      (I don't see why the _m should be required, but without it the Solaris  \
 664      C++ gives warning messages about overridings of the "oop_oop_iterate"   \
 665      defined above "hiding" this virtual function.  (DLD, 6/20/00)) */       \
 666   virtual int oop_oop_iterate##nv_suffix##_m(oop obj,                        \
 667                                              OopClosureType* blk,            \
 668                                              MemRegion mr) {                 \
 669     return oop_oop_iterate_m(obj, blk, mr);                                  \
 670   }
 671 
 672   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_DECL)
 673   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_DECL)
 674 
 675 #if INCLUDE_ALL_GCS
 676 #define Klass_OOP_OOP_ITERATE_BACKWARDS_DECL(OopClosureType, nv_suffix)      \
 677   virtual int oop_oop_iterate_backwards##nv_suffix(oop obj,                  \
 678                                                    OopClosureType* blk) {    \
 679     /* Default implementation reverts to general version. */                 \
 680     return oop_oop_iterate_backwards_v(obj, blk);                            \
 681   }
 682 
 683   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_BACKWARDS_DECL)
 684   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_BACKWARDS_DECL)
 685 #endif // INCLUDE_ALL_GCS
 686 
 687   virtual void array_klasses_do(void f(Klass* k)) {}
 688 
 689   // Return self, except for abstract classes with exactly 1
 690   // implementor.  Then return the 1 concrete implementation.
 691   Klass *up_cast_abstract();
 692 
 693   // klass name
 694   Symbol* name() const                   { return _name; }
 695   void set_name(Symbol* n);
 696 
 697  public:
 698   // jvm support
 699   virtual jint compute_modifier_flags(TRAPS) const;
 700 
 701   // JVMTI support
 702   virtual jint jvmti_class_status() const;
 703 
 704   // Printing
 705   virtual void print_on(outputStream* st) const;
 706 
 707   virtual void oop_print_value_on(oop obj, outputStream* st);
 708   virtual void oop_print_on      (oop obj, outputStream* st);
 709 
 710   virtual const char* internal_name() const = 0;
 711 
 712   // Verification
 713   virtual void verify_on(outputStream* st);
 714   void verify() { verify_on(tty); }
 715 
 716 #ifndef PRODUCT
 717   bool verify_vtable_index(int index);
 718   bool verify_itable_index(int index);
 719 #endif
 720 
 721   virtual void oop_verify_on(oop obj, outputStream* st);
 722 
 723   static bool is_null(narrowKlass obj);
 724   static bool is_null(Klass* obj);
 725 
 726   // klass encoding for klass pointer in objects.
 727   static narrowKlass encode_klass_not_null(Klass* v);
 728   static narrowKlass encode_klass(Klass* v);
 729 
 730   static Klass* decode_klass_not_null(narrowKlass v);
 731   static Klass* decode_klass(narrowKlass v);
 732 
 733  private:
 734   // barriers used by klass_oop_store
 735   void klass_update_barrier_set(oop v);
 736   void klass_update_barrier_set_pre(oop* p, oop v);
 737 };
 738 
 739 #endif // SHARE_VM_OOPS_KLASS_HPP