1 /*
2 * Copyright (c) 1997, 2025, 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 *
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
24
25 #ifndef SHARE_OOPS_KLASS_HPP
26 #define SHARE_OOPS_KLASS_HPP
27
28 #include "oops/klassFlags.hpp"
29 #include "oops/markWord.hpp"
30 #include "oops/metadata.hpp"
31 #include "oops/oop.hpp"
32 #include "oops/oopHandle.hpp"
33 #include "utilities/accessFlags.hpp"
34 #include "utilities/macros.hpp"
35 #if INCLUDE_JFR
36 #include "jfr/support/jfrTraceIdExtension.hpp"
37 #endif
38
39 //
40 // A Klass provides:
41 // 1: language level class object (method dictionary etc.)
42 // 2: provide vm dispatch behavior for the object
43 // Both functions are combined into one C++ class.
44
45 // One reason for the oop/klass dichotomy in the implementation is
46 // that we don't want a C++ vtbl pointer in every object. Thus,
47 // normal oops don't have any virtual functions. Instead, they
48 // forward all "virtual" functions to their klass, which does have
49 // a vtbl and does the C++ dispatch depending on the object's
50 // actual type. (See oop.inline.hpp for some of the forwarding code.)
51 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
52
53 // Forward declarations.
54 template <class T> class Array;
55 template <class T> class GrowableArray;
56 class ClassLoaderData;
57 class fieldDescriptor;
58 class klassVtable;
59 class ModuleEntry;
60 class PackageEntry;
61 class vtableEntry;
62
63 class Klass : public Metadata {
64
65 friend class VMStructs;
66 friend class JVMCIVMStructs;
67 public:
68 // Klass Kinds for all subclasses of Klass
69 enum KlassKind : u2
70 {
71 InstanceKlassKind,
72 InlineKlassKind,
73 InstanceRefKlassKind,
74 InstanceMirrorKlassKind,
75 InstanceClassLoaderKlassKind,
76 InstanceStackChunkKlassKind,
77 TypeArrayKlassKind,
78 ObjArrayKlassKind,
79 RefArrayKlassKind,
80 FlatArrayKlassKind,
81 UnknownKlassKind
82 };
83
84 static const uint KLASS_KIND_COUNT = FlatArrayKlassKind + 1;
85 protected:
86
87 // If you add a new field that points to any metaspace object, you
88 // must add this field to Klass::metaspace_pointers_do().
89
90 // note: put frequently-used fields together at start of klass structure
91 // for better cache behavior (may not make much of a difference but sure won't hurt)
92 enum { _primary_super_limit = 8 };
93
94 // The "layout helper" is a combined descriptor of object layout.
95 // For klasses which are neither instance nor array, the value is zero.
96 //
97 // For instances, layout helper is a positive number, the instance size.
98 // This size is already passed through align_object_size and scaled to bytes.
99 // The low order bit is set if instances of this class cannot be
100 // allocated using the fastpath.
101 //
102 // For arrays, layout helper is a negative number, containing four
103 // distinct bytes, as follows:
104 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
105 // where:
106 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
107 // hsz is array header size in bytes (i.e., offset of first element)
108 // ebt is the BasicType of the elements
109 // esz is the element size in bytes
110 // This packed word is arranged so as to be quickly unpacked by the
111 // various fast paths that use the various subfields.
112 //
113 // The esz bits can be used directly by a SLL instruction, without masking.
114 //
115 // Note that the array-kind tag looks like 0x00 for instance klasses,
116 // since their length in bytes is always less than 24Mb.
117 //
118 // Final note: This comes first, immediately after C++ vtable,
119 // because it is frequently queried.
120 jint _layout_helper;
121
122 // Klass kind used to resolve the runtime type of the instance.
123 // - Used to implement devirtualized oop closure dispatching.
124 // - Various type checking in the JVM
125 const KlassKind _kind;
126
127 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
128 // Some flags created by the JVM, not in the class file itself,
129 // are in _misc_flags below.
130 KlassFlags _misc_flags;
131
132 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
133 // and _primary_supers all help make fast subtype checks. See big discussion
134 // in doc/server_compiler/checktype.txt
135 //
136 // Where to look to observe a supertype (it is &_secondary_super_cache for
137 // secondary supers, else is &_primary_supers[depth()].
138 juint _super_check_offset;
139
140 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
141 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
142 Symbol* _name;
143
144 // Cache of last observed secondary supertype
145 Klass* _secondary_super_cache;
146 // Array of all secondary supertypes
147 Array<Klass*>* _secondary_supers;
148 // Ordered list of all primary supertypes
149 Klass* _primary_supers[_primary_super_limit];
150 // java/lang/Class instance mirroring this class
151 OopHandle _java_mirror;
152 // Superclass
153 Klass* _super;
154 // First subclass (null if none); _subklass->next_sibling() is next one
155 Klass* volatile _subklass;
156 // Sibling link (or null); links all subklasses of a klass
157 Klass* volatile _next_sibling;
158
159 // All klasses loaded by a class loader are chained through these links
160 Klass* _next_link;
161
162 // The VM's representation of the ClassLoader used to load this class.
163 // Provide access the corresponding instance java.lang.ClassLoader.
164 ClassLoaderData* _class_loader_data;
165
166 markWord _prototype_header; // Used to initialize objects' header
167
168 // Bitmap and hash code used by hashed secondary supers.
169 uintx _secondary_supers_bitmap;
170 uint8_t _hash_slot;
171
172 private:
173 // This is an index into AOTClassLocationConfig::class_locations(), to
174 // indicate the AOTClassLocation where this class is loaded from during
175 // dump time. If a class is not loaded from the AOT cache, this field is
176 // -1.
177 s2 _shared_class_path_index;
178
179 #if INCLUDE_CDS
180 // Various attributes for shared classes. Should be zero for a non-shared class.
181 u2 _shared_class_flags;
182 enum CDSSharedClassFlags {
183 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
184 _archived_lambda_proxy_is_available = 1 << 1,
185 _has_value_based_class_annotation = 1 << 2,
186 _verified_at_dump_time = 1 << 3,
187 _has_archived_enum_objs = 1 << 4,
188 // This class was not loaded from a classfile in the module image
189 // or classpath.
190 _is_generated_shared_class = 1 << 5,
191 // archived mirror already initialized by AOT-cache assembly: no further need to call <clinit>
192 _has_aot_initialized_mirror = 1 << 6,
193 };
194 #endif
195
196 int _vtable_len; // vtable length. This field may be read very often when we
197 // have lots of itable dispatches (e.g., lambdas and streams).
198 // Keep it away from the beginning of a Klass to avoid cacheline
199 // contention that may happen when a nearby object is modified.
200
201 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
202
203 public:
204
205 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
206
207 protected:
208
209 Klass(KlassKind kind, markWord prototype_header = markWord::prototype());
210 Klass();
211
212 public:
213 int kind() { return _kind; }
214
215 enum class DefaultsLookupMode { find, skip };
216 enum class OverpassLookupMode { find, skip };
217 enum class StaticLookupMode { find, skip };
218 enum class PrivateLookupMode { find, skip };
219
220 virtual bool is_klass() const { return true; }
221
222 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
223 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
224 // If this is not what your code expects, you're probably looking for Klass::java_super().
225 Klass* super() const { return _super; }
226 void set_super(Klass* k) { _super = k; }
227
228 // initializes _super link, _primary_supers & _secondary_supers arrays
229 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
230
231 // klass-specific helper for initializing _secondary_supers
232 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
233 Array<InstanceKlass*>* transitive_interfaces);
234
235 // java_super is the Java-level super type as specified by Class.getSuperClass.
236 virtual InstanceKlass* java_super() const { return nullptr; }
237
238 juint super_check_offset() const { return _super_check_offset; }
239 void set_super_check_offset(juint o) { _super_check_offset = o; }
240
241 Klass* secondary_super_cache() const { return _secondary_super_cache; }
242 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
243
244 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
245 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
246
247 uint8_t hash_slot() const { return _hash_slot; }
248
249 // Return the element of the _super chain of the given depth.
250 // If there is no such element, return either null or this.
251 Klass* primary_super_of_depth(juint i) const {
252 assert(i < primary_super_limit(), "oob");
253 Klass* super = _primary_supers[i];
254 assert(super == nullptr || super->super_depth() == i, "correct display");
255 return super;
256 }
257
258 // Can this klass be a primary super? False for interfaces and arrays of
259 // interfaces. False also for arrays or classes with long super chains.
260 bool can_be_primary_super() const {
261 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
262 return super_check_offset() != secondary_offset;
263 }
264 virtual bool can_be_primary_super_slow() const;
265
266 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
267 juint super_depth() const {
268 if (!can_be_primary_super()) {
269 return primary_super_limit();
270 } else {
271 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
272 assert(d < primary_super_limit(), "oob");
273 assert(_primary_supers[d] == this, "proper init");
274 return d;
275 }
276 }
277
278 // java mirror
279 oop java_mirror() const;
280 oop java_mirror_no_keepalive() const;
281 void set_java_mirror(Handle m);
282
283 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
284
285 // Temporary mirror switch used by RedefineClasses
286 OopHandle java_mirror_handle() const { return _java_mirror; }
287 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
288
289 // Set java mirror OopHandle to null for CDS
290 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
291 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
292
293 // size helper
294 int layout_helper() const { return _layout_helper; }
295 void set_layout_helper(int lh) { _layout_helper = lh; }
296
297 // Note: for instances layout_helper() may include padding.
298 // Use InstanceKlass::contains_field_offset to classify field offsets.
299
300 // sub/superklass links
301 Klass* subklass(bool log = false) const;
302 Klass* next_sibling(bool log = false) const;
303
304 InstanceKlass* superklass() const;
305 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
306
307 void set_next_link(Klass* k) { _next_link = k; }
308 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
309 Klass** next_link_addr() { return &_next_link; }
310
311 // class loader data
312 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
313 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
314
315 s2 shared_classpath_index() const {
316 return _shared_class_path_index;
317 };
318
319 void set_shared_classpath_index(s2 index) {
320 _shared_class_path_index = index;
321 };
322
323 bool has_archived_mirror_index() const {
324 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
325 NOT_CDS_JAVA_HEAP(return false);
326 }
327
328 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
329
330 void set_lambda_proxy_is_available() {
331 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
332 }
333 void clear_lambda_proxy_is_available() {
334 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
335 }
336 bool lambda_proxy_is_available() const {
337 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
338 NOT_CDS(return false;)
339 }
340
341 void set_has_value_based_class_annotation() {
342 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
343 }
344 void clear_has_value_based_class_annotation() {
345 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
346 }
347 bool has_value_based_class_annotation() const {
348 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
349 NOT_CDS(return false;)
350 }
351
352 void set_verified_at_dump_time() {
353 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
354 }
355 bool verified_at_dump_time() const {
356 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
357 NOT_CDS(return false;)
358 }
359
360 void set_has_archived_enum_objs() {
361 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
362 }
363 bool has_archived_enum_objs() const {
364 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
365 NOT_CDS(return false;)
366 }
367
368 void set_is_generated_shared_class() {
369 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
370 }
371 bool is_generated_shared_class() const {
372 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
373 NOT_CDS(return false;)
374 }
375
376 void set_has_aot_initialized_mirror() {
377 CDS_ONLY(_shared_class_flags |= _has_aot_initialized_mirror;)
378 }
379 bool has_aot_initialized_mirror() const {
380 CDS_ONLY(return (_shared_class_flags & _has_aot_initialized_mirror) != 0;)
381 NOT_CDS(return false;)
382 }
383
384 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
385 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
386 NOT_CDS(return false;)
387 }
388
389 void set_is_shared() {
390 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
391 }
392
393 // Obtain the module or package for this class
394 virtual ModuleEntry* module() const = 0;
395 virtual PackageEntry* package() const = 0;
396
397 protected: // internal accessors
398 void set_subklass(Klass* s);
399 void set_next_sibling(Klass* s);
400
401 private:
402 static uint8_t compute_hash_slot(Symbol* s);
403 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
404 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
405
406 bool search_secondary_supers(Klass* k) const;
407 bool lookup_secondary_supers_table(Klass *k) const;
408 bool linear_search_secondary_supers(const Klass* k) const;
409 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
410
411 public:
412 // Secondary supers table support
413 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
414 GrowableArray<Klass*>* primaries,
415 GrowableArray<Klass*>* secondaries,
416 uintx& bitmap,
417 TRAPS);
418
419 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
420 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
421
422 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
423 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
424
425 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
426 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
427
428 // Compiler support
429 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
430 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
431 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
432 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
433 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
434 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
435 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
436 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
437 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
438 #if INCLUDE_JVMCI
439 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
440 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
441 #endif
442 static ByteSize secondary_supers_bitmap_offset()
443 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
444 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
445 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
446
447 // Unpacking layout_helper:
448 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
449 static const int _lh_instance_slow_path_bit = 0x01;
450 static const int _lh_log2_element_size_shift = BitsPerByte*0;
451 static const int _lh_log2_element_size_mask = BitsPerLong-1;
452 static const int _lh_element_type_shift = BitsPerByte*1;
453 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
454 static const int _lh_header_size_shift = BitsPerByte*2;
455 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
456 static const int _lh_array_tag_bits = 4;
457 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
458
459 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
460 static const unsigned int _lh_array_tag_flat_value = 0Xfffffffa;
461 static const unsigned int _lh_array_tag_ref_value = 0Xfffffff8;
462
463 // null-free array flag bit under the array tag bits, shift one more to get array tag value
464 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
465 static const int _lh_null_free_mask = 1;
466
467 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << (_lh_array_tag_shift + 1));
468
469 static int layout_helper_size_in_bytes(jint lh) {
470 assert(lh > (jint)_lh_neutral_value, "must be instance");
471 return (int) lh & ~_lh_instance_slow_path_bit;
472 }
473 static bool layout_helper_needs_slow_path(jint lh) {
474 assert(lh > (jint)_lh_neutral_value, "must be instance");
475 return (lh & _lh_instance_slow_path_bit) != 0;
476 }
477 static bool layout_helper_is_instance(jint lh) {
478 return (jint)lh > (jint)_lh_neutral_value;
479 }
480 static bool layout_helper_is_array(jint lh) {
481 return (jint)lh < (jint)_lh_neutral_value;
482 }
483 static bool layout_helper_is_typeArray(jint lh) {
484 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
485 }
486 static bool layout_helper_is_refArray(jint lh) {
487 return (juint)_lh_array_tag_ref_value == (juint)(lh >> _lh_array_tag_shift);
488 }
489 static bool layout_helper_is_flatArray(jint lh) {
490 return (juint)_lh_array_tag_flat_value == (juint)(lh >> _lh_array_tag_shift);
491 }
492 static bool layout_helper_is_null_free(jint lh) {
493 assert(layout_helper_is_flatArray(lh) || layout_helper_is_refArray(lh), "must be array of inline types");
494 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
495 }
496 static jint layout_helper_set_null_free(jint lh) {
497 lh |= (_lh_null_free_mask << _lh_null_free_shift);
498 assert(layout_helper_is_null_free(lh), "Bad encoding");
499 return lh;
500 }
501 static int layout_helper_header_size(jint lh) {
502 assert(lh < (jint)_lh_neutral_value, "must be array");
503 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
504 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
505 return hsize;
506 }
507 static BasicType layout_helper_element_type(jint lh) {
508 assert(lh < (jint)_lh_neutral_value, "must be array");
509 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
510 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
511 return (BasicType) btvalue;
512 }
513
514 // Want a pattern to quickly diff against layout header in register
515 // find something less clever!
516 static int layout_helper_boolean_diffbit() {
517 jint zlh = array_layout_helper(T_BOOLEAN);
518 jint blh = array_layout_helper(T_BYTE);
519 assert(zlh != blh, "array layout helpers must differ");
520 int diffbit = 1;
521 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
522 diffbit <<= 1;
523 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
524 }
525 return diffbit;
526 }
527
528 static int layout_helper_log2_element_size(jint lh) {
529 assert(lh < (jint)_lh_neutral_value, "must be array");
530 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
531 assert(layout_helper_element_type(lh) == T_FLAT_ELEMENT || l2esz <= LogBytesPerLong,
532 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
533 return l2esz;
534 }
535 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
536 return (tag << _lh_array_tag_shift)
537 | ((null_free ? 1 : 0) << _lh_null_free_shift)
538 | (hsize << _lh_header_size_shift)
539 | ((int)etype << _lh_element_type_shift)
540 | (log2_esize << _lh_log2_element_size_shift);
541 }
542 static jint instance_layout_helper(jint size, bool slow_path_flag) {
543 return (size << LogBytesPerWord)
544 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
545 }
546 static int layout_helper_to_size_helper(jint lh) {
547 assert(lh > (jint)_lh_neutral_value, "must be instance");
548 // Note that the following expression discards _lh_instance_slow_path_bit.
549 return lh >> LogBytesPerWord;
550 }
551 // Out-of-line version computes everything based on the etype:
552 static jint array_layout_helper(BasicType etype);
553
554 // What is the maximum number of primary superclasses any klass can have?
555 static juint primary_super_limit() { return _primary_super_limit; }
556
557 // vtables
558 klassVtable vtable() const;
559 int vtable_length() const { return _vtable_len; }
560
561 // subclass check
562 bool is_subclass_of(const Klass* k) const;
563
564 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
565 bool is_subtype_of(Klass* k) const;
566
567 public:
568 // Find LCA in class hierarchy
569 Klass *LCA( Klass *k );
570
571 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
572 // if not, throw either an Error or an Exception.
573 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
574
575 // array copying
576 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
577
578 // tells if the class should be initialized
579 virtual bool should_be_initialized() const { return false; }
580 // initializes the klass
581 virtual void initialize(TRAPS);
582 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
583 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
584 OverpassLookupMode overpass_mode,
585 PrivateLookupMode = PrivateLookupMode::find) const;
586 public:
587 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
588 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
589 }
590
591 // array class with specific rank
592 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
593
594 // array class with this klass as element type
595 virtual ArrayKlass* array_klass(TRAPS) = 0;
596
597 // These will return null instead of allocating on the heap:
598 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
599 virtual ArrayKlass* array_klass_or_null() = 0;
600
601 virtual oop protection_domain() const = 0;
602
603 oop class_loader() const;
604
605 inline oop klass_holder() const;
606
607 inline void keep_alive() const;
608
609 protected:
610
611 // Error handling when length > max_length or length < 0
612 static void check_array_allocation_length(int length, int max_length, TRAPS);
613
614 void set_vtable_length(int len) { _vtable_len= len; }
615
616 vtableEntry* start_of_vtable() const;
617 #if INCLUDE_CDS
618 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
619 #endif
620 public:
621 Method* method_at_vtable(int index);
622
623 static ByteSize vtable_start_offset();
624 static ByteSize vtable_length_offset() {
625 return byte_offset_of(Klass, _vtable_len);
626 }
627
628 #if INCLUDE_CDS
629 // CDS support - remove and restore oops from metadata. Oops are not shared.
630 virtual void remove_unshareable_info();
631 virtual void remove_java_mirror();
632
633 bool is_unshareable_info_restored() const {
634 assert(is_shared(), "use this for shared classes only");
635 if (has_archived_mirror_index()) {
636 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
637 return false;
638 } else if (_java_mirror.is_empty()) {
639 return false;
640 } else {
641 return true;
642 }
643 }
644 #endif // INCLUDE_CDS
645
646 public:
647 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
648 // These functions describe behavior for the oop not the KLASS.
649
650 // actual oop size of obj in memory in word size.
651 virtual size_t oop_size(oop obj) const = 0;
652
653 // Size of klass in word size.
654 virtual int size() const = 0;
655
656 // Returns the Java name for a class (Resource allocated)
657 // For arrays, this returns the name of the element with a leading '['.
658 // For classes, this returns the name with the package separators
659 // turned into '.'s.
660 const char* external_name() const;
661 // Returns the name for a class (Resource allocated) as the class
662 // would appear in a signature.
663 // For arrays, this returns the name of the element with a leading '['.
664 // For classes, this returns the name with a leading 'L' and a trailing ';'
665 // and the package separators as '/'.
666 virtual const char* signature_name() const;
667
668 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
669 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
670
671 // Returns "interface", "abstract class" or "class".
672 const char* external_kind() const;
673
674 // type testing operations
675 #ifdef ASSERT
676 protected:
677 virtual bool is_instance_klass_slow() const { return false; }
678 virtual bool is_array_klass_slow() const { return false; }
679 virtual bool is_objArray_klass_slow() const { return false; }
680 virtual bool is_refArray_klass_slow() const { return false; }
681 virtual bool is_typeArray_klass_slow() const { return false; }
682 virtual bool is_flatArray_klass_slow() const { return false; }
683 #endif // ASSERT
684 // current implementation uses this method even in non debug builds
685 virtual bool is_inline_klass_slow() const { return false; }
686 public:
687
688 // Fast non-virtual versions
689 #ifndef ASSERT
690 #define assert_same_query(xval, xcheck) xval
691 #else
692 private:
693 static bool assert_same_query(bool xval, bool xslow) {
694 assert(xval == xslow, "slow and fast queries agree");
695 return xval;
696 }
697 public:
698 #endif
699
700 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
701 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
702 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
703 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
704 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
705 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
706 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
707 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
708 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind || _kind == RefArrayKlassKind || _kind == FlatArrayKlassKind, is_objArray_klass_slow()); }
709 bool is_refArray_klass() const { return assert_same_query( _kind == RefArrayKlassKind, is_refArray_klass_slow()); }
710 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
711 bool is_refined_objArray_klass() const { return is_refArray_klass() || is_flatArray_klass(); }
712 #undef assert_same_query
713
714 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
715
716 // Access flags
717 AccessFlags access_flags() const { return _access_flags; }
718 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
719
720 bool is_public() const { return _access_flags.is_public(); }
721 bool is_final() const { return _access_flags.is_final(); }
722 bool is_interface() const { return _access_flags.is_interface(); }
723 bool is_abstract() const { return _access_flags.is_abstract(); }
724 bool is_synthetic() const { return _access_flags.is_synthetic(); }
725 bool is_identity_class() const { assert(is_instance_klass(), "only for instanceKlass"); return _access_flags.is_identity_class(); }
726 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
727 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
728 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
729 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
730 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
731 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
732 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
733
734 klass_flags_t misc_flags() const { return _misc_flags.value(); }
735
736 inline bool is_non_strong_hidden() const;
737
738 bool is_cloneable() const;
739 void set_is_cloneable();
740
741 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
742 inline markWord prototype_header() const;
743 inline void set_prototype_header(markWord header);
744 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
745 inline void set_prototype_header_klass(narrowKlass klass);
746
747 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
748
749 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
750 virtual MetaspaceObj::Type type() const { return ClassType; }
751
752 inline bool is_loader_alive() const;
753 inline bool is_loader_present_and_alive() const;
754
755 void clean_subklass();
756
757 // Clean out unnecessary weak klass links from the whole klass hierarchy.
758 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
759 // Clean out unnecessary weak klass links from the given InstanceKlass.
760 static void clean_weak_instanceklass_links(InstanceKlass* ik);
761
762 // Return self, except for abstract classes with exactly 1
763 // implementor. Then return the 1 concrete implementation.
764 Klass *up_cast_abstract();
765
766 // klass name
767 Symbol* name() const { return _name; }
768 void set_name(Symbol* n);
769
770 virtual void release_C_heap_structures(bool release_constant_pool = true);
771
772 public:
773 // Get modifier flags from Java mirror cache.
774 int modifier_flags() const;
775
776 // Compute modifier flags from the original data. This also allows
777 // accessing flags when Java mirror is already dead, e.g. during class
778 // unloading.
779 virtual u2 compute_modifier_flags() const = 0;
780
781 // JVMTI support
782 virtual jint jvmti_class_status() const;
783
784 // Printing
785 virtual void print_on(outputStream* st) const;
786
787 virtual void oop_print_value_on(oop obj, outputStream* st);
788 virtual void oop_print_on (oop obj, outputStream* st);
789
790 void print_secondary_supers_on(outputStream* st) const;
791
792 virtual const char* internal_name() const = 0;
793
794 // Verification
795 virtual void verify_on(outputStream* st);
796 void verify() { verify_on(tty); }
797
798 #ifndef PRODUCT
799 bool verify_vtable_index(int index);
800 #endif
801
802 virtual void oop_verify_on(oop obj, outputStream* st);
803
804 // for error reporting
805 static bool is_valid(Klass* k);
806
807 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
808
809 // Returns true if this Klass needs to be addressable via narrow Klass ID.
810 inline bool needs_narrow_id() const;
811
812 };
813
814 #endif // SHARE_OOPS_KLASS_HPP