1 /*
   2  * Copyright (c) 1997, 2020, 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_KLASS_HPP
  26 #define SHARE_OOPS_KLASS_HPP
  27 
  28 #include "classfile/classLoaderData.hpp"
  29 #include "memory/iterator.hpp"
  30 #include "memory/memRegion.hpp"
  31 #include "oops/markWord.hpp"
  32 #include "oops/metadata.hpp"
  33 #include "oops/oop.hpp"
  34 #include "oops/oopHandle.hpp"
  35 #include "utilities/accessFlags.hpp"
  36 #include "utilities/macros.hpp"
  37 #if INCLUDE_JFR
  38 #include "jfr/support/jfrTraceIdExtension.hpp"
  39 #endif
  40 
  41 // Klass IDs for all subclasses of Klass
  42 enum KlassID {
  43   InstanceKlassID,
  44   InstanceRefKlassID,
  45   InstanceMirrorKlassID,
  46   InstanceClassLoaderKlassID,
  47   TypeArrayKlassID,
  48   ObjArrayKlassID
  49 };
  50 
  51 const uint KLASS_ID_COUNT = 6;
  52 
  53 //
  54 // A Klass provides:
  55 //  1: language level class object (method dictionary etc.)
  56 //  2: provide vm dispatch behavior for the object
  57 // Both functions are combined into one C++ class.
  58 
  59 // One reason for the oop/klass dichotomy in the implementation is
  60 // that we don't want a C++ vtbl pointer in every object.  Thus,
  61 // normal oops don't have any virtual functions.  Instead, they
  62 // forward all "virtual" functions to their klass, which does have
  63 // a vtbl and does the C++ dispatch depending on the object's
  64 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
  65 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
  66 
  67 // Forward declarations.
  68 template <class T> class Array;
  69 template <class T> class GrowableArray;
  70 class fieldDescriptor;
  71 class klassVtable;
  72 class ModuleEntry;
  73 class PackageEntry;
  74 class ParCompactionManager;
  75 class PSPromotionManager;
  76 class vtableEntry;
  77 
  78 class Klass : public Metadata {
  79   friend class VMStructs;
  80   friend class JVMCIVMStructs;
  81  protected:
  82   // If you add a new field that points to any metaspace object, you
  83   // must add this field to Klass::metaspace_pointers_do().
  84 
  85   // note: put frequently-used fields together at start of klass structure
  86   // for better cache behavior (may not make much of a difference but sure won't hurt)
  87   enum { _primary_super_limit = 8 };
  88 
  89   // The "layout helper" is a combined descriptor of object layout.
  90   // For klasses which are neither instance nor array, the value is zero.
  91   //
  92   // For instances, layout helper is a positive number, the instance size.
  93   // This size is already passed through align_object_size and scaled to bytes.
  94   // The low order bit is set if instances of this class cannot be
  95   // allocated using the fastpath.
  96   //
  97   // For arrays, layout helper is a negative number, containing four
  98   // distinct bytes, as follows:
  99   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
 100   // where:
 101   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
 102   //    hsz is array header size in bytes (i.e., offset of first element)
 103   //    ebt is the BasicType of the elements
 104   //    esz is the element size in bytes
 105   // This packed word is arranged so as to be quickly unpacked by the
 106   // various fast paths that use the various subfields.
 107   //
 108   // The esz bits can be used directly by a SLL instruction, without masking.
 109   //
 110   // Note that the array-kind tag looks like 0x00 for instance klasses,
 111   // since their length in bytes is always less than 24Mb.
 112   //
 113   // Final note:  This comes first, immediately after C++ vtable,
 114   // because it is frequently queried.
 115   jint        _layout_helper;
 116 
 117   // Klass identifier used to implement devirtualized oop closure dispatching.
 118   const KlassID _id;
 119 
 120   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
 121   // and _primary_supers all help make fast subtype checks.  See big discussion
 122   // in doc/server_compiler/checktype.txt
 123   //
 124   // Where to look to observe a supertype (it is &_secondary_super_cache for
 125   // secondary supers, else is &_primary_supers[depth()].
 126   juint       _super_check_offset;
 127 
 128   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
 129   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
 130   Symbol*     _name;
 131 
 132   // Cache of last observed secondary supertype
 133   Klass*      _secondary_super_cache;
 134   // Array of all secondary supertypes
 135   Array<Klass*>* _secondary_supers;
 136   // Ordered list of all primary supertypes
 137   Klass*      _primary_supers[_primary_super_limit];
 138   // java/lang/Class instance mirroring this class
 139   OopHandle _java_mirror;
 140   // Superclass
 141   Klass*      _super;
 142   // First subclass (NULL if none); _subklass->next_sibling() is next one
 143   Klass* volatile _subklass;
 144   // Sibling link (or NULL); links all subklasses of a klass
 145   Klass* volatile _next_sibling;
 146 
 147   // All klasses loaded by a class loader are chained through these links
 148   Klass*      _next_link;
 149 
 150   // The VM's representation of the ClassLoader used to load this class.
 151   // Provide access the corresponding instance java.lang.ClassLoader.
 152   ClassLoaderData* _class_loader_data;
 153 
 154   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
 155   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
 156 
 157   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
 158 
 159   // Biased locking implementation and statistics
 160   // (the 64-bit chunk goes first, to avoid some fragmentation)
 161   jlong    _last_biased_lock_bulk_revocation_time;
 162   markWord _prototype_header;   // Used when biased locking is both enabled and disabled for this type
 163   jint     _biased_lock_revocation_count;
 164 
 165   // vtable length
 166   int _vtable_len;
 167 
 168 private:
 169   // This is an index into FileMapHeader::_shared_path_table[], to
 170   // associate this class with the JAR file where it's loaded from during
 171   // dump time. If a class is not loaded from the shared archive, this field is
 172   // -1.
 173   jshort _shared_class_path_index;
 174 
 175 #if INCLUDE_CDS
 176   // Flags of the current shared class.
 177   u2     _shared_class_flags;
 178   enum {
 179     _has_raw_archived_mirror = 1
 180   };
 181 #endif
 182   // The _archived_mirror is set at CDS dump time pointing to the cached mirror
 183   // in the open archive heap region when archiving java object is supported.
 184   CDS_JAVA_HEAP_ONLY(narrowOop _archived_mirror;)
 185 
 186 protected:
 187 
 188   // Constructor
 189   Klass(KlassID id);
 190   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
 191 
 192   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
 193 
 194  public:
 195   int id() { return _id; }
 196 
 197   enum DefaultsLookupMode { find_defaults, skip_defaults };
 198   enum OverpassLookupMode { find_overpass, skip_overpass };
 199   enum StaticLookupMode   { find_static,   skip_static };
 200   enum PrivateLookupMode  { find_private,  skip_private };
 201 
 202   bool is_klass() const volatile { return true; }
 203 
 204   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
 205   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
 206   // If this is not what your code expects, you're probably looking for Klass::java_super().
 207   Klass* super() const               { return _super; }
 208   void set_super(Klass* k)           { _super = k; }
 209 
 210   // initializes _super link, _primary_supers & _secondary_supers arrays
 211   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
 212 
 213   // klass-specific helper for initializing _secondary_supers
 214   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
 215                                                           Array<InstanceKlass*>* transitive_interfaces);
 216 
 217   // java_super is the Java-level super type as specified by Class.getSuperClass.
 218   virtual InstanceKlass* java_super() const  { return NULL; }
 219 
 220   juint    super_check_offset() const  { return _super_check_offset; }
 221   void set_super_check_offset(juint o) { _super_check_offset = o; }
 222 
 223   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
 224   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
 225 
 226   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
 227   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
 228 
 229   // Return the element of the _super chain of the given depth.
 230   // If there is no such element, return either NULL or this.
 231   Klass* primary_super_of_depth(juint i) const {
 232     assert(i < primary_super_limit(), "oob");
 233     Klass* super = _primary_supers[i];
 234     assert(super == NULL || super->super_depth() == i, "correct display");
 235     return super;
 236   }
 237 
 238   // Can this klass be a primary super?  False for interfaces and arrays of
 239   // interfaces.  False also for arrays or classes with long super chains.
 240   bool can_be_primary_super() const {
 241     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 242     return super_check_offset() != secondary_offset;
 243   }
 244   virtual bool can_be_primary_super_slow() const;
 245 
 246   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
 247   juint super_depth() const {
 248     if (!can_be_primary_super()) {
 249       return primary_super_limit();
 250     } else {
 251       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
 252       assert(d < primary_super_limit(), "oob");
 253       assert(_primary_supers[d] == this, "proper init");
 254       return d;
 255     }
 256   }
 257 
 258   // java mirror
 259   oop java_mirror() const;
 260   oop java_mirror_no_keepalive() const;
 261   void set_java_mirror(Handle m);
 262 
 263   oop archived_java_mirror_raw() NOT_CDS_JAVA_HEAP_RETURN_(NULL); // no GC barrier
 264   narrowOop archived_java_mirror_raw_narrow() NOT_CDS_JAVA_HEAP_RETURN_(0); // no GC barrier
 265   void set_archived_java_mirror_raw(oop m) NOT_CDS_JAVA_HEAP_RETURN; // no GC barrier
 266 
 267   // Temporary mirror switch used by RedefineClasses
 268   // Both mirrors are on the ClassLoaderData::_handles list already so no
 269   // barriers are needed.
 270   void set_java_mirror_handle(OopHandle mirror) { _java_mirror = mirror; }
 271   OopHandle java_mirror_handle() const          {
 272     return _java_mirror;
 273   }
 274 
 275   // modifier flags
 276   jint modifier_flags() const          { return _modifier_flags; }
 277   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
 278 
 279   // size helper
 280   int layout_helper() const            { return _layout_helper; }
 281   void set_layout_helper(int lh)       { _layout_helper = lh; }
 282 
 283   // Note: for instances layout_helper() may include padding.
 284   // Use InstanceKlass::contains_field_offset to classify field offsets.
 285 
 286   // sub/superklass links
 287   Klass* subklass(bool log = false) const;
 288   Klass* next_sibling(bool log = false) const;
 289 
 290   InstanceKlass* superklass() const;
 291   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
 292 
 293   void set_next_link(Klass* k) { _next_link = k; }
 294   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
 295 
 296   // class loader data
 297   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
 298   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
 299 
 300   int shared_classpath_index() const   {
 301     return _shared_class_path_index;
 302   };
 303 
 304   void set_shared_classpath_index(int index) {
 305     _shared_class_path_index = index;
 306   };
 307 
 308   void set_has_raw_archived_mirror() {
 309     CDS_ONLY(_shared_class_flags |= _has_raw_archived_mirror;)
 310   }
 311   void clear_has_raw_archived_mirror() {
 312     CDS_ONLY(_shared_class_flags &= ~_has_raw_archived_mirror;)
 313   }
 314   bool has_raw_archived_mirror() const {
 315     CDS_ONLY(return (_shared_class_flags & _has_raw_archived_mirror) != 0;)
 316     NOT_CDS(return false;)
 317   }
 318 
 319   // Obtain the module or package for this class
 320   virtual ModuleEntry* module() const = 0;
 321   virtual PackageEntry* package() const = 0;
 322 
 323  protected:                                // internal accessors
 324   void     set_subklass(Klass* s);
 325   void     set_next_sibling(Klass* s);
 326 
 327  public:
 328 
 329   // Compiler support
 330   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
 331   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
 332   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
 333   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
 334   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
 335   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
 336   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
 337   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
 338   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
 339   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
 340 
 341   // Unpacking layout_helper:
 342   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
 343   static const int _lh_instance_slow_path_bit  = 0x01;
 344   static const int _lh_log2_element_size_shift = BitsPerByte*0;
 345   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
 346   static const int _lh_element_type_shift      = BitsPerByte*1;
 347   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
 348   static const int _lh_header_size_shift       = BitsPerByte*2;
 349   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
 350   static const int _lh_array_tag_bits          = 2;
 351   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
 352   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
 353 
 354   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
 355 
 356   static int layout_helper_size_in_bytes(jint lh) {
 357     assert(lh > (jint)_lh_neutral_value, "must be instance");
 358     return (int) lh & ~_lh_instance_slow_path_bit;
 359   }
 360   static bool layout_helper_needs_slow_path(jint lh) {
 361     assert(lh > (jint)_lh_neutral_value, "must be instance");
 362     return (lh & _lh_instance_slow_path_bit) != 0;
 363   }
 364   static bool layout_helper_is_instance(jint lh) {
 365     return (jint)lh > (jint)_lh_neutral_value;
 366   }
 367   static bool layout_helper_is_array(jint lh) {
 368     return (jint)lh < (jint)_lh_neutral_value;
 369   }
 370   static bool layout_helper_is_typeArray(jint lh) {
 371     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
 372     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 373   }
 374   static bool layout_helper_is_objArray(jint lh) {
 375     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
 376     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 377   }
 378   static int layout_helper_header_size(jint lh) {
 379     assert(lh < (jint)_lh_neutral_value, "must be array");
 380     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
 381     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
 382     return hsize;
 383   }
 384   static BasicType layout_helper_element_type(jint lh) {
 385     assert(lh < (jint)_lh_neutral_value, "must be array");
 386     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
 387     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
 388     return (BasicType) btvalue;
 389   }
 390 
 391   // Want a pattern to quickly diff against layout header in register
 392   // find something less clever!
 393   static int layout_helper_boolean_diffbit() {
 394     jint zlh = array_layout_helper(T_BOOLEAN);
 395     jint blh = array_layout_helper(T_BYTE);
 396     assert(zlh != blh, "array layout helpers must differ");
 397     int diffbit = 1;
 398     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
 399       diffbit <<= 1;
 400       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
 401     }
 402     return diffbit;
 403   }
 404 
 405   static int layout_helper_log2_element_size(jint lh) {
 406     assert(lh < (jint)_lh_neutral_value, "must be array");
 407     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
 408     assert(l2esz <= LogBytesPerLong,
 409            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
 410     return l2esz;
 411   }
 412   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
 413     return (tag        << _lh_array_tag_shift)
 414       |    (hsize      << _lh_header_size_shift)
 415       |    ((int)etype << _lh_element_type_shift)
 416       |    (log2_esize << _lh_log2_element_size_shift);
 417   }
 418   static jint instance_layout_helper(jint size, bool slow_path_flag) {
 419     return (size << LogBytesPerWord)
 420       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
 421   }
 422   static int layout_helper_to_size_helper(jint lh) {
 423     assert(lh > (jint)_lh_neutral_value, "must be instance");
 424     // Note that the following expression discards _lh_instance_slow_path_bit.
 425     return lh >> LogBytesPerWord;
 426   }
 427   // Out-of-line version computes everything based on the etype:
 428   static jint array_layout_helper(BasicType etype);
 429 
 430   // What is the maximum number of primary superclasses any klass can have?
 431   static juint primary_super_limit()         { return _primary_super_limit; }
 432 
 433   // vtables
 434   klassVtable vtable() const;
 435   int vtable_length() const { return _vtable_len; }
 436 
 437   // subclass check
 438   bool is_subclass_of(const Klass* k) const;
 439   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
 440   bool is_subtype_of(Klass* k) const {
 441     juint    off = k->super_check_offset();
 442     Klass* sup = *(Klass**)( (address)this + off );
 443     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 444     if (sup == k) {
 445       return true;
 446     } else if (off != secondary_offset) {
 447       return false;
 448     } else {
 449       return search_secondary_supers(k);
 450     }
 451   }
 452 
 453   bool search_secondary_supers(Klass* k) const;
 454 
 455   // Find LCA in class hierarchy
 456   Klass *LCA( Klass *k );
 457 
 458   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
 459   // if not, throw either an Error or an Exception.
 460   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
 461 
 462   // array copying
 463   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
 464 
 465   // tells if the class should be initialized
 466   virtual bool should_be_initialized() const    { return false; }
 467   // initializes the klass
 468   virtual void initialize(TRAPS);
 469   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
 470   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
 471                                          OverpassLookupMode overpass_mode,
 472                                          PrivateLookupMode = find_private) const;
 473  public:
 474   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
 475     return uncached_lookup_method(name, signature, find_overpass);
 476   }
 477 
 478   // array class with specific rank
 479   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }
 480 
 481   // array class with this klass as element type
 482   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }
 483 
 484   // These will return NULL instead of allocating on the heap:
 485   // NB: these can block for a mutex, like other functions with TRAPS arg.
 486   Klass* array_klass_or_null(int rank);
 487   Klass* array_klass_or_null();
 488 
 489   virtual oop protection_domain() const = 0;
 490 
 491   oop class_loader() const;
 492 
 493   // This loads the klass's holder as a phantom. This is useful when a weak Klass
 494   // pointer has been "peeked" and then must be kept alive before it may
 495   // be used safely.  All uses of klass_holder need to apply the appropriate barriers,
 496   // except during GC.
 497   oop klass_holder() const { return class_loader_data()->holder_phantom(); }
 498 
 499  protected:
 500   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
 501   virtual Klass* array_klass_impl(bool or_null, TRAPS);
 502 
 503   // Error handling when length > max_length or length < 0
 504   static void check_array_allocation_length(int length, int max_length, TRAPS);
 505 
 506   void set_vtable_length(int len) { _vtable_len= len; }
 507 
 508   vtableEntry* start_of_vtable() const;
 509  public:
 510   Method* method_at_vtable(int index);
 511 
 512   static ByteSize vtable_start_offset();
 513   static ByteSize vtable_length_offset() {
 514     return byte_offset_of(Klass, _vtable_len);
 515   }
 516 
 517   // CDS support - remove and restore oops from metadata. Oops are not shared.
 518   virtual void remove_unshareable_info();
 519   virtual void remove_java_mirror();
 520   virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
 521 
 522   bool is_unshareable_info_restored() const {
 523     assert(is_shared(), "use this for shared classes only");
 524     if (has_raw_archived_mirror()) {
 525       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
 526       return false;
 527     } else if (_java_mirror.ptr_raw() == NULL) {
 528       return false;
 529     } else {
 530       return true;
 531     }
 532   }
 533 
 534  public:
 535   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
 536   // These functions describe behavior for the oop not the KLASS.
 537 
 538   // actual oop size of obj in memory
 539   virtual int oop_size(oop obj) const = 0;
 540 
 541   // Size of klass in word size.
 542   virtual int size() const = 0;
 543 
 544   // Returns the Java name for a class (Resource allocated)
 545   // For arrays, this returns the name of the element with a leading '['.
 546   // For classes, this returns the name with the package separators
 547   //     turned into '.'s.
 548   const char* external_name() const;
 549   // Returns the name for a class (Resource allocated) as the class
 550   // would appear in a signature.
 551   // For arrays, this returns the name of the element with a leading '['.
 552   // For classes, this returns the name with a leading 'L' and a trailing ';'
 553   //     and the package separators as '/'.
 554   virtual const char* signature_name() const;
 555 
 556   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
 557   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
 558 
 559   // Returns "interface", "abstract class" or "class".
 560   const char* external_kind() const;
 561 
 562   // type testing operations
 563 #ifdef ASSERT
 564  protected:
 565   virtual bool is_instance_klass_slow()     const { return false; }
 566   virtual bool is_array_klass_slow()        const { return false; }
 567   virtual bool is_objArray_klass_slow()     const { return false; }
 568   virtual bool is_typeArray_klass_slow()    const { return false; }
 569 #endif // ASSERT
 570  public:
 571 
 572   // Fast non-virtual versions
 573   #ifndef ASSERT
 574   #define assert_same_query(xval, xcheck) xval
 575   #else
 576  private:
 577   static bool assert_same_query(bool xval, bool xslow) {
 578     assert(xval == xslow, "slow and fast queries agree");
 579     return xval;
 580   }
 581  public:
 582   #endif
 583   inline  bool is_instance_klass()            const { return assert_same_query(
 584                                                       layout_helper_is_instance(layout_helper()),
 585                                                       is_instance_klass_slow()); }
 586   inline  bool is_array_klass()               const { return assert_same_query(
 587                                                     layout_helper_is_array(layout_helper()),
 588                                                     is_array_klass_slow()); }
 589   inline  bool is_objArray_klass()            const { return assert_same_query(
 590                                                     layout_helper_is_objArray(layout_helper()),
 591                                                     is_objArray_klass_slow()); }
 592   inline  bool is_typeArray_klass()           const { return assert_same_query(
 593                                                     layout_helper_is_typeArray(layout_helper()),
 594                                                     is_typeArray_klass_slow()); }
 595   #undef assert_same_query
 596 
 597   // Access flags
 598   AccessFlags access_flags() const         { return _access_flags;  }
 599   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
 600 
 601   bool is_public() const                { return _access_flags.is_public(); }
 602   bool is_final() const                 { return _access_flags.is_final(); }
 603   bool is_interface() const             { return _access_flags.is_interface(); }
 604   bool is_abstract() const              { return _access_flags.is_abstract(); }
 605   bool is_super() const                 { return _access_flags.is_super(); }
 606   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
 607   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
 608   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
 609   bool has_final_method() const         { return _access_flags.has_final_method(); }
 610   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
 611   void set_has_final_method()           { _access_flags.set_has_final_method(); }
 612   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
 613   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
 614   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
 615   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
 616   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
 617   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
 618   bool is_hidden() const                { return access_flags().is_hidden_class(); }
 619   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
 620   bool is_non_strong_hidden() const     { return access_flags().is_hidden_class() &&
 621                                           class_loader_data()->has_class_mirror_holder(); }
 622 
 623   bool is_cloneable() const;
 624   void set_is_cloneable();
 625 
 626   // Biased locking support
 627   // Note: the prototype header is always set up to be at least the
 628   // prototype markWord. If biased locking is enabled it may further be
 629   // biasable and have an epoch.
 630   markWord prototype_header() const      { return _prototype_header; }
 631   // NOTE: once instances of this klass are floating around in the
 632   // system, this header must only be updated at a safepoint.
 633   // NOTE 2: currently we only ever set the prototype header to the
 634   // biasable prototype for instanceKlasses. There is no technical
 635   // reason why it could not be done for arrayKlasses aside from
 636   // wanting to reduce the initial scope of this optimization. There
 637   // are potential problems in setting the bias pattern for
 638   // JVM-internal oops.
 639   inline void set_prototype_header(markWord header);
 640   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
 641 
 642   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }
 643   // Atomically increments biased_lock_revocation_count and returns updated value
 644   int atomic_incr_biased_lock_revocation_count();
 645   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }
 646   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }
 647   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }
 648 
 649   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
 650 
 651   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
 652   virtual MetaspaceObj::Type type() const { return ClassType; }
 653 
 654   // Iff the class loader (or mirror for unsafe anonymous classes) is alive the
 655   // Klass is considered alive. This is safe to call before the CLD is marked as
 656   // unloading, and hence during concurrent class unloading.
 657   bool is_loader_alive() const { return class_loader_data()->is_alive(); }
 658 
 659   void clean_subklass();
 660 
 661   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
 662   static void clean_subklass_tree() {
 663     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
 664   }
 665 
 666   virtual void array_klasses_do(void f(Klass* k)) {}
 667 
 668   // Return self, except for abstract classes with exactly 1
 669   // implementor.  Then return the 1 concrete implementation.
 670   Klass *up_cast_abstract();
 671 
 672   // klass name
 673   Symbol* name() const                   { return _name; }
 674   void set_name(Symbol* n);
 675 
 676  public:
 677   // jvm support
 678   virtual jint compute_modifier_flags(TRAPS) const;
 679 
 680   // JVMTI support
 681   virtual jint jvmti_class_status() const;
 682 
 683   // Printing
 684   virtual void print_on(outputStream* st) const;
 685 
 686   virtual void oop_print_value_on(oop obj, outputStream* st);
 687   virtual void oop_print_on      (oop obj, outputStream* st);
 688 
 689   virtual const char* internal_name() const = 0;
 690 
 691   // Verification
 692   virtual void verify_on(outputStream* st);
 693   void verify() { verify_on(tty); }
 694 
 695 #ifndef PRODUCT
 696   bool verify_vtable_index(int index);
 697 #endif
 698 
 699   virtual void oop_verify_on(oop obj, outputStream* st);
 700 
 701   // for error reporting
 702   static bool is_valid(Klass* k);
 703 };
 704 
 705 #endif // SHARE_OOPS_KLASS_HPP