1 /*
2 * Copyright (c) 1997, 2026, 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,
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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/macros.hpp"
34 #if INCLUDE_JFR
35 #include "jfr/support/jfrTraceIdExtension.hpp"
36 #endif
37
38 //
39 // A Klass provides:
40 // 1: language level class object (method dictionary etc.)
41 // 2: provide vm dispatch behavior for the object
42 // Both functions are combined into one C++ class.
43
44 // One reason for the oop/klass dichotomy in the implementation is
45 // that we don't want a C++ vtbl pointer in every object. Thus,
46 // normal oops don't have any virtual functions. Instead, they
47 // forward all "virtual" functions to their klass, which does have
48 // a vtbl and does the C++ dispatch depending on the object's
49 // actual type. (See oop.inline.hpp for some of the forwarding code.)
50 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
51
52 // Forward declarations.
53 template <class T> class Array;
54 template <class T> class GrowableArray;
55 class ArrayDescription;
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 public:
67 // Klass Kinds for all subclasses of Klass
68 enum KlassKind : u2
69 {
70 InstanceKlassKind,
71 InlineKlassKind,
72 InstanceRefKlassKind,
73 InstanceMirrorKlassKind,
74 InstanceClassLoaderKlassKind,
75 InstanceStackChunkKlassKind,
76 TypeArrayKlassKind,
77 ObjArrayKlassKind,
78 RefArrayKlassKind,
79 FlatArrayKlassKind,
80 UnknownKlassKind
81 };
82
83 static const uint KLASS_KIND_COUNT = FlatArrayKlassKind + 1;
84 protected:
85
86 // If you add a new field that points to any metaspace object, you
87 // must add this field to Klass::metaspace_pointers_do().
88
89 // note: put frequently-used fields together at start of klass structure
90 // for better cache behavior (may not make much of a difference but sure won't hurt)
91 enum { _primary_super_limit = 8 };
92
93 // The "layout helper" is a combined descriptor of object layout.
94 // For klasses which are neither instance nor array, the value is zero.
95 //
96 // For instances, layout helper is a positive number, the instance size.
97 // This size is already passed through align_object_size and scaled to bytes.
98 // The low order bit is set if instances of this class cannot be
99 // allocated using the fastpath.
100 //
101 // For arrays, layout helper is a negative number, containing four
102 // distinct bytes, as follows:
103 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
104 // where:
105 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
106 // hsz is array header size in bytes (i.e., offset of first element)
107 // ebt is the BasicType of the elements
108 // esz is the element size in bytes
109 // This packed word is arranged so as to be quickly unpacked by the
110 // various fast paths that use the various subfields.
111 //
112 // The esz bits can be used directly by a SLL instruction, without masking.
113 //
114 // Note that the array-kind tag looks like 0x00 for instance klasses,
115 // since their length in bytes is always less than 24Mb.
116 //
117 // Final note: This comes first, immediately after C++ vtable,
118 // because it is frequently queried.
119 jint _layout_helper;
120
121 // Klass kind used to resolve the runtime type of the instance.
122 // - Used to implement devirtualized oop closure dispatching.
123 // - Various type checking in the JVM
124 const KlassKind _kind;
125
126 // Some flags created by the JVM, not in the class file itself,
127 // are in _misc_flags below.
128 KlassFlags _misc_flags;
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 OopHandle _java_mirror;
150 // Superclass
151 Klass* _super;
152 // First subclass (null if none); _subklass->next_sibling() is next one
153 Klass* volatile _subklass;
154 // Sibling link (or null); links all subklasses of a klass
155 Klass* volatile _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 markWord _prototype_header; // Used to initialize objects' header
165
166 // Bitmap and hash code used by hashed secondary supers.
167 uintx _secondary_supers_bitmap;
168 uint8_t _hash_slot;
169
170 private:
171 // This is an index into AOTClassLocationConfig::class_locations(), to
172 // indicate the AOTClassLocation where this class is loaded from during
173 // dump time. If a class is not loaded from the AOT cache, this field is
174 // -1.
175 s2 _shared_class_path_index;
176
177 #if INCLUDE_CDS
178 // Various attributes for shared classes. Should be zero for a non-shared class.
179 u2 _aot_class_flags;
180 enum {
181 _in_aot_cache = 1 << 0,
182 _archived_lambda_proxy_is_available = 1 << 1,
183 _has_value_based_class_annotation = 1 << 2,
184 _verified_at_dump_time = 1 << 3,
185 _has_archived_enum_objs = 1 << 4,
186 _is_aot_generated_class = 1 << 5, // this class was not loaded from a classfile in the module image
187 // or classpath, but was generated during AOT cache assembly.
188 _has_aot_initialized_mirror = 1 << 6, // archived mirror already initialized by AOT cache assembly.
189 // no further need to call <clinit>
190 _has_aot_safe_initializer = 1 << 7, // has @AOTSafeClassInitializer annotation
191 _is_runtime_setup_required = 1 << 8, // has a runtimeSetup method to be called when
192 // this class is loaded from AOT cache
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 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
213
214 public:
215 int kind() { return _kind; }
216
217 enum class DefaultsLookupMode { find, skip };
218 enum class OverpassLookupMode { find, skip };
219 enum class StaticLookupMode { find, skip };
220 enum class PrivateLookupMode { find, skip };
221
222 bool is_klass() const override { return true; }
223
224 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
225 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
226 // If this is not what your code expects, you're probably looking for:
227 // - Klass::java_super() - if you have a Klass*
228 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
229 Klass* super() const { return _super; }
230 void set_super(Klass* k) { _super = k; }
231
232 // initializes _super link, _primary_supers & _secondary_supers arrays
233 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
234
235 // klass-specific helper for initializing _secondary_supers
236 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
237 Array<InstanceKlass*>* transitive_interfaces);
238
239 // java_super is the Java-level super type as specified by Class.getSuperClass.
240 virtual InstanceKlass* java_super() const { return nullptr; }
241
242 juint super_check_offset() const { return _super_check_offset; }
243 void set_super_check_offset(juint o) { _super_check_offset = o; }
244
245 Klass* secondary_super_cache() const { return _secondary_super_cache; }
246 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
247
248 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
249 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
250
251 uint8_t hash_slot() const { return _hash_slot; }
252
253 // Return the element of the _super chain of the given depth.
254 // If there is no such element, return either null or this.
255 Klass* primary_super_of_depth(juint i) const {
256 assert(i < primary_super_limit(), "oob");
257 Klass* super = _primary_supers[i];
258 assert(super == nullptr || super->super_depth() == i, "correct display");
259 return super;
260 }
261
262 // Can this klass be a primary super? False for interfaces and arrays of
263 // interfaces. False also for arrays or classes with long super chains.
264 bool can_be_primary_super() const {
265 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
266 return super_check_offset() != secondary_offset;
267 }
268 virtual bool can_be_primary_super_slow() const;
269
270 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
271 juint super_depth() const {
272 if (!can_be_primary_super()) {
273 return primary_super_limit();
274 } else {
275 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
276 assert(d < primary_super_limit(), "oob");
277 assert(_primary_supers[d] == this, "proper init");
278 return d;
279 }
280 }
281
282 // java mirror
283 oop java_mirror() const;
284 oop java_mirror_no_keepalive() const;
285 void set_java_mirror(Handle m);
286
287 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
288
289 // Temporary mirror switch used by RedefineClasses
290 OopHandle java_mirror_handle() const { return _java_mirror; }
291 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
292
293 // Set java mirror OopHandle to null for CDS
294 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
295 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
296
297 // size helper
298 int layout_helper() const { return _layout_helper; }
299 void set_layout_helper(int lh) { _layout_helper = lh; }
300
301 // Note: for instances layout_helper() may include padding.
302 // Use InstanceKlass::contains_field_offset to classify field offsets.
303
304 // sub/superklass links
305 Klass* subklass() const;
306 Klass* next_sibling(bool log = false) const;
307
308 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
309
310 void set_next_link(Klass* k) { _next_link = k; }
311 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
312 Klass** next_link_addr() { return &_next_link; }
313
314 // class loader data
315 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
316 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
317
318 s2 shared_classpath_index() const {
319 return _shared_class_path_index;
320 };
321
322 void set_shared_classpath_index(s2 index) {
323 _shared_class_path_index = index;
324 };
325
326 bool has_archived_mirror_index() const {
327 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
328 NOT_CDS_JAVA_HEAP(return false);
329 }
330
331 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
332
333 void set_lambda_proxy_is_available() {
334 CDS_ONLY(_aot_class_flags |= _archived_lambda_proxy_is_available;)
335 }
336 void clear_lambda_proxy_is_available() {
337 CDS_ONLY(_aot_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
338 }
339 bool lambda_proxy_is_available() const {
340 CDS_ONLY(return (_aot_class_flags & _archived_lambda_proxy_is_available) != 0;)
341 NOT_CDS(return false;)
342 }
343
344 void set_has_value_based_class_annotation() {
345 CDS_ONLY(_aot_class_flags |= _has_value_based_class_annotation;)
346 }
347 void clear_has_value_based_class_annotation() {
348 CDS_ONLY(_aot_class_flags &= (u2)(~_has_value_based_class_annotation);)
349 }
350 bool has_value_based_class_annotation() const {
351 CDS_ONLY(return (_aot_class_flags & _has_value_based_class_annotation) != 0;)
352 NOT_CDS(return false;)
353 }
354
355 void set_verified_at_dump_time() {
356 CDS_ONLY(_aot_class_flags |= _verified_at_dump_time;)
357 }
358 bool verified_at_dump_time() const {
359 CDS_ONLY(return (_aot_class_flags & _verified_at_dump_time) != 0;)
360 NOT_CDS(return false;)
361 }
362
363 void set_has_archived_enum_objs() {
364 CDS_ONLY(_aot_class_flags |= _has_archived_enum_objs;)
365 }
366 bool has_archived_enum_objs() const {
367 CDS_ONLY(return (_aot_class_flags & _has_archived_enum_objs) != 0;)
368 NOT_CDS(return false;)
369 }
370
371 void set_is_aot_generated_class() {
372 CDS_ONLY(_aot_class_flags |= _is_aot_generated_class;)
373 }
374 bool is_aot_generated_class() const {
375 CDS_ONLY(return (_aot_class_flags & _is_aot_generated_class) != 0;)
376 NOT_CDS(return false;)
377 }
378
379 void set_has_aot_initialized_mirror() {
380 CDS_ONLY(_aot_class_flags |= _has_aot_initialized_mirror;)
381 }
382 bool has_aot_initialized_mirror() const {
383 CDS_ONLY(return (_aot_class_flags & _has_aot_initialized_mirror) != 0;)
384 NOT_CDS(return false;)
385 }
386
387 // Indicates presence of @AOTSafeClassInitializer. Also see AOTClassInitializer for more details.
388 void set_has_aot_safe_initializer() {
389 CDS_ONLY(_aot_class_flags |= _has_aot_safe_initializer;)
390 }
391 bool has_aot_safe_initializer() const {
392 CDS_ONLY(return (_aot_class_flags & _has_aot_safe_initializer) != 0;)
393 NOT_CDS(return false;)
394 }
395
396 // Indicates @AOTRuntimeSetup private static void runtimeSetup() presence.
397 void set_is_runtime_setup_required() {
398 CDS_ONLY(_aot_class_flags |= _is_runtime_setup_required;)
399 }
400 bool is_runtime_setup_required() const {
401 CDS_ONLY(return (_aot_class_flags & _is_runtime_setup_required) != 0;)
402 NOT_CDS(return false;)
403 }
404
405 bool in_aot_cache() const { // shadows MetaspaceObj::in_aot_cache)()
406 CDS_ONLY(return (_aot_class_flags & _in_aot_cache) != 0;)
407 NOT_CDS(return false;)
408 }
409
410 void set_in_aot_cache() {
411 CDS_ONLY(_aot_class_flags |= _in_aot_cache;)
412 }
413
414 // Obtain the module or package for this class
415 virtual ModuleEntry* module() const = 0;
416 virtual PackageEntry* package() const = 0;
417
418 void set_next_sibling(Klass* s);
419 protected: // internal accessors
420 void set_subklass(Klass* s);
421
422 private:
423 static uint8_t compute_hash_slot(Symbol* s);
424 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
425 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
426
427 bool search_secondary_supers(Klass* k) const;
428 bool lookup_secondary_supers_table(Klass *k) const;
429 bool linear_search_secondary_supers(const Klass* k) const;
430 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
431
432 public:
433 // Secondary supers table support
434 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
435 GrowableArray<Klass*>* primaries,
436 GrowableArray<Klass*>* secondaries,
437 uintx& bitmap,
438 TRAPS);
439
440 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
441 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
442
443 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
444 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
445
446 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
447 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
448
449 // Compiler support
450 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
451 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
452 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
453 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
454 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
455 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
456 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
457 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
458 static ByteSize secondary_supers_bitmap_offset()
459 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
460 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
461 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
462
463 // Unpacking layout_helper:
464 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
465 static const int _lh_instance_slow_path_bit = 0x01;
466 static const int _lh_log2_element_size_shift = BitsPerByte*0;
467 static const int _lh_log2_element_size_mask = BitsPerLong-1;
468 static const int _lh_element_type_shift = BitsPerByte*1;
469 static const int _lh_element_type_mask = right_n_bits<int>(BitsPerByte); // shifted mask
470 static const int _lh_header_size_shift = BitsPerByte*2;
471 static const int _lh_header_size_mask = right_n_bits<int>(BitsPerByte); // shifted mask
472 static const int _lh_array_tag_bits = 4;
473 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
474
475 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
476 static const unsigned int _lh_array_tag_flat_value = 0Xfffffffa;
477 static const unsigned int _lh_array_tag_ref_value = 0Xfffffff8;
478
479 // null-free array flag bit under the array tag bits, shift one more to get array tag value
480 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
481 static const int _lh_null_free_mask = 1;
482
483 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << (_lh_array_tag_shift + 1));
484
485 static int layout_helper_size_in_bytes(jint lh) {
486 assert(lh > (jint)_lh_neutral_value, "must be instance");
487 return (int) lh & ~_lh_instance_slow_path_bit;
488 }
489 static bool layout_helper_needs_slow_path(jint lh) {
490 assert(lh > (jint)_lh_neutral_value, "must be instance");
491 return (lh & _lh_instance_slow_path_bit) != 0;
492 }
493 static bool layout_helper_is_instance(jint lh) {
494 return (jint)lh > (jint)_lh_neutral_value;
495 }
496 static bool layout_helper_is_array(jint lh) {
497 return (jint)lh < (jint)_lh_neutral_value;
498 }
499 static bool layout_helper_is_typeArray(jint lh) {
500 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
501 }
502 static bool layout_helper_is_refArray(jint lh) {
503 return (juint)_lh_array_tag_ref_value == (juint)(lh >> _lh_array_tag_shift);
504 }
505 static bool layout_helper_is_flatArray(jint lh) {
506 return (juint)_lh_array_tag_flat_value == (juint)(lh >> _lh_array_tag_shift);
507 }
508 static bool layout_helper_is_null_free(jint lh) {
509 assert(layout_helper_is_flatArray(lh) || layout_helper_is_refArray(lh), "must be array of inline types");
510 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
511 }
512 static jint layout_helper_set_null_free(jint lh) {
513 lh |= (_lh_null_free_mask << _lh_null_free_shift);
514 assert(layout_helper_is_null_free(lh), "Bad encoding");
515 return lh;
516 }
517 static int layout_helper_header_size(jint lh) {
518 assert(lh < (jint)_lh_neutral_value, "must be array");
519 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
520 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
521 return hsize;
522 }
523 static BasicType layout_helper_element_type(jint lh) {
524 assert(lh < (jint)_lh_neutral_value, "must be array");
525 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
526 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
527 return (BasicType) btvalue;
528 }
529
530 // Return a value containing a single set bit that is in the bitset difference between the
531 // layout helpers for array-of-boolean and array-of-byte.
532 static int layout_helper_boolean_diffbit() {
533 uint zlh = static_cast<uint>(array_layout_helper(T_BOOLEAN));
534 uint blh = static_cast<uint>(array_layout_helper(T_BYTE));
535 // get all the bits that are set in zlh and clear in blh
536 uint candidates = (zlh & ~blh);
537 assert(candidates != 0, "must be"); // must be some if there is a solution.
538 // Use well known bit hack to isolate the low bit of candidates.
539 uint result = candidates & (-candidates);
540 assert(is_power_of_2(result), "must be power of 2");
541 assert((result & zlh) != 0, "must be set in alh of T_BOOLEAN");
542 assert((result & blh) == 0, "must be clear in alh of T_BYTE");
543 return static_cast<int>(result);
544 }
545
546 static int layout_helper_log2_element_size(jint lh) {
547 assert(lh < (jint)_lh_neutral_value, "must be array");
548 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
549 assert(layout_helper_element_type(lh) == T_FLAT_ELEMENT || l2esz <= LogBytesPerLong,
550 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
551 return l2esz;
552 }
553 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
554 return (tag << _lh_array_tag_shift)
555 | ((null_free ? 1 : 0) << _lh_null_free_shift)
556 | (hsize << _lh_header_size_shift)
557 | ((int)etype << _lh_element_type_shift)
558 | (log2_esize << _lh_log2_element_size_shift);
559 }
560 static jint instance_layout_helper(jint size, bool slow_path_flag) {
561 return (size << LogBytesPerWord)
562 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
563 }
564 static int layout_helper_to_size_helper(jint lh) {
565 assert(lh > (jint)_lh_neutral_value, "must be instance");
566 // Note that the following expression discards _lh_instance_slow_path_bit.
567 return lh >> LogBytesPerWord;
568 }
569 // Out-of-line version computes everything based on the etype:
570 static jint array_layout_helper(BasicType etype);
571
572 // What is the maximum number of primary superclasses any klass can have?
573 static juint primary_super_limit() { return _primary_super_limit; }
574
575 // vtables
576 klassVtable vtable() const;
577 int vtable_length() const { return _vtable_len; }
578
579 // subclass check
580 bool is_subclass_of(const Klass* k) const;
581
582 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
583 bool is_subtype_of(Klass* k) const;
584
585 public:
586 // Find LCA in class hierarchy
587 Klass *LCA( Klass *k );
588
589 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
590 // if not, throw either an Error or an Exception.
591 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
592
593 // array copying
594 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
595
596 // tells if the class should be initialized
597 virtual bool should_be_initialized() const { return false; }
598 // initializes the klass
599 virtual void initialize(TRAPS);
600 virtual void initialize_preemptable(TRAPS);
601 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
602 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
603 OverpassLookupMode overpass_mode,
604 PrivateLookupMode = PrivateLookupMode::find) const;
605 public:
606 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
607 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
608 }
609
610 // array class with specific rank
611 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
612
613 // array class with this klass as element type
614 virtual ArrayKlass* array_klass(TRAPS) = 0;
615
616 // These will return null instead of allocating on the heap:
617 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
618 virtual ArrayKlass* array_klass_or_null() = 0;
619
620 virtual oop protection_domain() const = 0;
621
622 oop class_loader() const;
623
624 inline oop klass_holder() const;
625
626 inline void keep_alive() const;
627
628 protected:
629
630 // Error handling when length > max_length or length < 0
631 static void check_array_allocation_length(int length, int max_length, TRAPS);
632
633 void set_vtable_length(int len) { _vtable_len= len; }
634
635 vtableEntry* start_of_vtable() const;
636 #if INCLUDE_CDS
637 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
638 #endif
639 public:
640 Method* method_at_vtable(int index);
641
642 static ByteSize vtable_start_offset();
643 static ByteSize vtable_length_offset() {
644 return byte_offset_of(Klass, _vtable_len);
645 }
646
647 #if INCLUDE_CDS
648 // CDS support - remove and restore oops from metadata. Oops are not shared.
649 virtual void remove_unshareable_info();
650 virtual void remove_java_mirror();
651
652 bool is_unshareable_info_restored() const {
653 assert(in_aot_cache(), "use this for shared classes only");
654 if (has_archived_mirror_index()) {
655 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
656 return false;
657 } else if (_java_mirror.is_empty()) {
658 return false;
659 } else {
660 return true;
661 }
662 }
663 #endif // INCLUDE_CDS
664
665 public:
666 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
667 // These functions describe behavior for the oop not the KLASS.
668
669 // actual oop size of obj in memory in word size.
670 virtual size_t oop_size(oop obj) const = 0;
671
672 // Returns the Java name for a class (Resource allocated)
673 // For arrays, this returns the name of the element with a leading '['.
674 // For classes, this returns the name with the package separators
675 // turned into '.'s.
676 const char* external_name() const;
677 // Returns the name for a class (Resource allocated) as the class
678 // would appear in a signature.
679 // For arrays, this returns the name of the element with a leading '['.
680 // For classes, this returns the name with a leading 'L' and a trailing ';'
681 // and the package separators as '/'.
682 virtual const char* signature_name() const;
683
684 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
685 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
686
687 // Returns "interface", "abstract class" or "class".
688 const char* external_kind() const;
689
690 // type testing operations
691 #ifdef ASSERT
692 protected:
693 virtual bool is_instance_klass_slow() const { return false; }
694 virtual bool is_array_klass_slow() const { return false; }
695 virtual bool is_objArray_klass_slow() const { return false; }
696 virtual bool is_refArray_klass_slow() const { return false; }
697 virtual bool is_typeArray_klass_slow() const { return false; }
698 virtual bool is_flatArray_klass_slow() const { return false; }
699 #endif // ASSERT
700 // current implementation uses this method even in non debug builds
701 virtual bool is_inline_klass_slow() const { return false; }
702 public:
703
704 // Fast non-virtual versions
705 #ifndef ASSERT
706 #define assert_same_query(xval, xcheck) xval
707 #else
708 private:
709 static bool assert_same_query(bool xval, bool xslow) {
710 assert(xval == xslow, "slow and fast queries agree");
711 return xval;
712 }
713 public:
714 #endif
715
716 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
717 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
718 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
719 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
720 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
721 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
722 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
723 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
724 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind || _kind == RefArrayKlassKind || _kind == FlatArrayKlassKind, is_objArray_klass_slow()); }
725 bool is_refArray_klass() const { return assert_same_query( _kind == RefArrayKlassKind, is_refArray_klass_slow()); }
726 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
727 bool is_refined_objArray_klass() const { return is_refArray_klass() || is_flatArray_klass(); }
728 bool is_unrefined_objArray_klass() const { return _kind == ObjArrayKlassKind; }
729 #undef assert_same_query
730
731 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
732
733 virtual bool is_interface() const { return false; }
734 virtual bool is_abstract() const { return false; }
735 virtual bool is_identity_class() const { return false; }
736
737 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
738 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
739 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
740 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
741 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
742 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
743
744 klass_flags_t misc_flags() const { return _misc_flags.value(); }
745
746 inline bool is_non_strong_hidden() const;
747
748 bool is_cloneable() const;
749 void set_is_cloneable_fast() { _misc_flags.set_is_cloneable_fast(true); }
750
751 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
752 inline markWord prototype_header() const;
753 inline void set_prototype_header(markWord header);
754 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
755 inline void set_prototype_header_klass(narrowKlass klass);
756
757 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
758
759 void metaspace_pointers_do(MetaspaceClosure* iter) override;
760 MetaspaceObj::Type type() const override { return ClassType; }
761
762 inline bool is_loader_alive() const;
763 inline bool is_loader_present_and_alive() const;
764
765 Klass* clean_subklass(bool log = false);
766
767 // Clean out unnecessary weak klass links from the whole klass hierarchy.
768 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
769 // Clean out unnecessary weak klass links from the given InstanceKlass.
770 static void clean_weak_instanceklass_links(InstanceKlass* ik);
771
772 // Return self, except for abstract classes with exactly 1
773 // implementor. Then return the 1 concrete implementation.
774 Klass *up_cast_abstract();
775
776 // klass name
777 Symbol* name() const { return _name; }
778 void set_name(Symbol* n);
779
780 virtual void release_C_heap_structures(bool release_constant_pool = true);
781
782 public:
783 // Get modifier flags from Java mirror cache.
784 int modifier_flags() const;
785
786 // Compute modifier flags from the original data. This also allows
787 // accessing flags when Java mirror is already dead, e.g. during class
788 // unloading.
789 virtual u2 compute_modifier_flags() const = 0;
790
791 // JVMTI support
792 virtual jint jvmti_class_status() const;
793
794 // Printing
795 void print_on(outputStream* st) const override;
796
797 virtual void oop_print_value_on(oop obj, outputStream* st);
798 virtual void oop_print_on (oop obj, outputStream* st);
799
800 void print_secondary_supers_on(outputStream* st) const;
801
802 // Verification
803 virtual void verify_on(outputStream* st);
804 void verify() { verify_on(tty); }
805
806 #ifndef PRODUCT
807 bool verify_vtable_index(int index);
808 #endif
809
810 virtual void oop_verify_on(oop obj, outputStream* st);
811
812 void validate_array_description(const ArrayDescription& ad) NOT_DEBUG_RETURN;
813
814 // for error reporting
815 static bool is_valid(Klass* k);
816
817 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
818 };
819
820 #endif // SHARE_OOPS_KLASS_HPP