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 *
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.
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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 _in_aot_cache = 1 << 0,
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:
225 // - Klass::java_super() - if you have a Klass*
226 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
227 Klass* super() const { return _super; }
228 void set_super(Klass* k) { _super = k; }
229
230 // initializes _super link, _primary_supers & _secondary_supers arrays
231 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
232
233 // klass-specific helper for initializing _secondary_supers
234 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
235 Array<InstanceKlass*>* transitive_interfaces);
236
237 // java_super is the Java-level super type as specified by Class.getSuperClass.
238 virtual InstanceKlass* java_super() const { return nullptr; }
239
240 juint super_check_offset() const { return _super_check_offset; }
241 void set_super_check_offset(juint o) { _super_check_offset = o; }
242
243 Klass* secondary_super_cache() const { return _secondary_super_cache; }
244 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
245
246 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
247 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
248
249 uint8_t hash_slot() const { return _hash_slot; }
250
251 // Return the element of the _super chain of the given depth.
252 // If there is no such element, return either null or this.
253 Klass* primary_super_of_depth(juint i) const {
254 assert(i < primary_super_limit(), "oob");
255 Klass* super = _primary_supers[i];
256 assert(super == nullptr || super->super_depth() == i, "correct display");
257 return super;
258 }
259
260 // Can this klass be a primary super? False for interfaces and arrays of
261 // interfaces. False also for arrays or classes with long super chains.
262 bool can_be_primary_super() const {
263 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
264 return super_check_offset() != secondary_offset;
265 }
266 virtual bool can_be_primary_super_slow() const;
267
268 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
269 juint super_depth() const {
270 if (!can_be_primary_super()) {
271 return primary_super_limit();
272 } else {
273 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
274 assert(d < primary_super_limit(), "oob");
275 assert(_primary_supers[d] == this, "proper init");
276 return d;
277 }
278 }
279
280 // java mirror
281 oop java_mirror() const;
282 oop java_mirror_no_keepalive() const;
283 void set_java_mirror(Handle m);
284
285 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
286
287 // Temporary mirror switch used by RedefineClasses
288 OopHandle java_mirror_handle() const { return _java_mirror; }
289 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
290
291 // Set java mirror OopHandle to null for CDS
292 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
293 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
294
295 // size helper
296 int layout_helper() const { return _layout_helper; }
297 void set_layout_helper(int lh) { _layout_helper = lh; }
298
299 // Note: for instances layout_helper() may include padding.
300 // Use InstanceKlass::contains_field_offset to classify field offsets.
301
302 // sub/superklass links
303 Klass* subklass(bool log = false) const;
304 Klass* next_sibling(bool log = false) const;
305
306 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
307
308 void set_next_link(Klass* k) { _next_link = k; }
309 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
310 Klass** next_link_addr() { return &_next_link; }
311
312 // class loader data
313 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
314 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
315
316 s2 shared_classpath_index() const {
317 return _shared_class_path_index;
318 };
319
320 void set_shared_classpath_index(s2 index) {
321 _shared_class_path_index = index;
322 };
323
324 bool has_archived_mirror_index() const {
325 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
326 NOT_CDS_JAVA_HEAP(return false);
327 }
328
329 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
330
331 void set_lambda_proxy_is_available() {
332 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
333 }
334 void clear_lambda_proxy_is_available() {
335 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
336 }
337 bool lambda_proxy_is_available() const {
338 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
339 NOT_CDS(return false;)
340 }
341
342 void set_has_value_based_class_annotation() {
343 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
344 }
345 void clear_has_value_based_class_annotation() {
346 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
347 }
348 bool has_value_based_class_annotation() const {
349 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
350 NOT_CDS(return false;)
351 }
352
353 void set_verified_at_dump_time() {
354 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
355 }
356 bool verified_at_dump_time() const {
357 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
358 NOT_CDS(return false;)
359 }
360
361 void set_has_archived_enum_objs() {
362 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
363 }
364 bool has_archived_enum_objs() const {
365 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
366 NOT_CDS(return false;)
367 }
368
369 void set_is_generated_shared_class() {
370 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
371 }
372 bool is_generated_shared_class() const {
373 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
374 NOT_CDS(return false;)
375 }
376
377 void set_has_aot_initialized_mirror() {
378 CDS_ONLY(_shared_class_flags |= _has_aot_initialized_mirror;)
379 }
380 bool has_aot_initialized_mirror() const {
381 CDS_ONLY(return (_shared_class_flags & _has_aot_initialized_mirror) != 0;)
382 NOT_CDS(return false;)
383 }
384
385 bool in_aot_cache() const { // shadows MetaspaceObj::in_aot_cache)()
386 CDS_ONLY(return (_shared_class_flags & _in_aot_cache) != 0;)
387 NOT_CDS(return false;)
388 }
389
390 void set_in_aot_cache() {
391 CDS_ONLY(_shared_class_flags |= _in_aot_cache;)
392 }
393
394 // Obtain the module or package for this class
395 virtual ModuleEntry* module() const = 0;
396 virtual PackageEntry* package() const = 0;
397
398 protected: // internal accessors
399 void set_subklass(Klass* s);
400 void set_next_sibling(Klass* s);
401
402 private:
403 static uint8_t compute_hash_slot(Symbol* s);
404 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
405 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
406
407 bool search_secondary_supers(Klass* k) const;
408 bool lookup_secondary_supers_table(Klass *k) const;
409 bool linear_search_secondary_supers(const Klass* k) const;
410 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
411
412 public:
413 // Secondary supers table support
414 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
415 GrowableArray<Klass*>* primaries,
416 GrowableArray<Klass*>* secondaries,
417 uintx& bitmap,
418 TRAPS);
419
420 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
421 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
422
423 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
424 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
425
426 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
427 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
428
429 // Compiler support
430 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
431 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
432 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
433 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
434 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
435 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
436 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
437 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
438 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
439 #if INCLUDE_JVMCI
440 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
441 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
442 #endif
443 static ByteSize secondary_supers_bitmap_offset()
444 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
445 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
446 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
447
448 // Unpacking layout_helper:
449 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
450 static const int _lh_instance_slow_path_bit = 0x01;
451 static const int _lh_log2_element_size_shift = BitsPerByte*0;
452 static const int _lh_log2_element_size_mask = BitsPerLong-1;
453 static const int _lh_element_type_shift = BitsPerByte*1;
454 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
455 static const int _lh_header_size_shift = BitsPerByte*2;
456 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
457 static const int _lh_array_tag_bits = 4;
458 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
459
460 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
461 static const unsigned int _lh_array_tag_flat_value = 0Xfffffffa;
462 static const unsigned int _lh_array_tag_ref_value = 0Xfffffff8;
463
464 // null-free array flag bit under the array tag bits, shift one more to get array tag value
465 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
466 static const int _lh_null_free_mask = 1;
467
468 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << (_lh_array_tag_shift + 1));
469
470 static int layout_helper_size_in_bytes(jint lh) {
471 assert(lh > (jint)_lh_neutral_value, "must be instance");
472 return (int) lh & ~_lh_instance_slow_path_bit;
473 }
474 static bool layout_helper_needs_slow_path(jint lh) {
475 assert(lh > (jint)_lh_neutral_value, "must be instance");
476 return (lh & _lh_instance_slow_path_bit) != 0;
477 }
478 static bool layout_helper_is_instance(jint lh) {
479 return (jint)lh > (jint)_lh_neutral_value;
480 }
481 static bool layout_helper_is_array(jint lh) {
482 return (jint)lh < (jint)_lh_neutral_value;
483 }
484 static bool layout_helper_is_typeArray(jint lh) {
485 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
486 }
487 static bool layout_helper_is_refArray(jint lh) {
488 return (juint)_lh_array_tag_ref_value == (juint)(lh >> _lh_array_tag_shift);
489 }
490 static bool layout_helper_is_flatArray(jint lh) {
491 return (juint)_lh_array_tag_flat_value == (juint)(lh >> _lh_array_tag_shift);
492 }
493 static bool layout_helper_is_null_free(jint lh) {
494 assert(layout_helper_is_flatArray(lh) || layout_helper_is_refArray(lh), "must be array of inline types");
495 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
496 }
497 static jint layout_helper_set_null_free(jint lh) {
498 lh |= (_lh_null_free_mask << _lh_null_free_shift);
499 assert(layout_helper_is_null_free(lh), "Bad encoding");
500 return lh;
501 }
502 static int layout_helper_header_size(jint lh) {
503 assert(lh < (jint)_lh_neutral_value, "must be array");
504 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
505 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
506 return hsize;
507 }
508 static BasicType layout_helper_element_type(jint lh) {
509 assert(lh < (jint)_lh_neutral_value, "must be array");
510 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
511 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
512 return (BasicType) btvalue;
513 }
514
515 // Want a pattern to quickly diff against layout header in register
516 // find something less clever!
517 static int layout_helper_boolean_diffbit() {
518 jint zlh = array_layout_helper(T_BOOLEAN);
519 jint blh = array_layout_helper(T_BYTE);
520 assert(zlh != blh, "array layout helpers must differ");
521 int diffbit = 1;
522 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
523 diffbit <<= 1;
524 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
525 }
526 return diffbit;
527 }
528
529 static int layout_helper_log2_element_size(jint lh) {
530 assert(lh < (jint)_lh_neutral_value, "must be array");
531 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
532 assert(layout_helper_element_type(lh) == T_FLAT_ELEMENT || l2esz <= LogBytesPerLong,
533 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
534 return l2esz;
535 }
536 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
537 return (tag << _lh_array_tag_shift)
538 | ((null_free ? 1 : 0) << _lh_null_free_shift)
539 | (hsize << _lh_header_size_shift)
540 | ((int)etype << _lh_element_type_shift)
541 | (log2_esize << _lh_log2_element_size_shift);
542 }
543 static jint instance_layout_helper(jint size, bool slow_path_flag) {
544 return (size << LogBytesPerWord)
545 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
546 }
547 static int layout_helper_to_size_helper(jint lh) {
548 assert(lh > (jint)_lh_neutral_value, "must be instance");
549 // Note that the following expression discards _lh_instance_slow_path_bit.
550 return lh >> LogBytesPerWord;
551 }
552 // Out-of-line version computes everything based on the etype:
553 static jint array_layout_helper(BasicType etype);
554
555 // What is the maximum number of primary superclasses any klass can have?
556 static juint primary_super_limit() { return _primary_super_limit; }
557
558 // vtables
559 klassVtable vtable() const;
560 int vtable_length() const { return _vtable_len; }
561
562 // subclass check
563 bool is_subclass_of(const Klass* k) const;
564
565 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
566 bool is_subtype_of(Klass* k) const;
567
568 public:
569 // Find LCA in class hierarchy
570 Klass *LCA( Klass *k );
571
572 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
573 // if not, throw either an Error or an Exception.
574 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
575
576 // array copying
577 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
578
579 // tells if the class should be initialized
580 virtual bool should_be_initialized() const { return false; }
581 // initializes the klass
582 virtual void initialize(TRAPS);
583 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
584 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
585 OverpassLookupMode overpass_mode,
586 PrivateLookupMode = PrivateLookupMode::find) const;
587 public:
588 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
589 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
590 }
591
592 // array class with specific rank
593 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
594
595 // array class with this klass as element type
596 virtual ArrayKlass* array_klass(TRAPS) = 0;
597
598 // These will return null instead of allocating on the heap:
599 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
600 virtual ArrayKlass* array_klass_or_null() = 0;
601
602 virtual oop protection_domain() const = 0;
603
604 oop class_loader() const;
605
606 inline oop klass_holder() const;
607
608 inline void keep_alive() const;
609
610 protected:
611
612 // Error handling when length > max_length or length < 0
613 static void check_array_allocation_length(int length, int max_length, TRAPS);
614
615 void set_vtable_length(int len) { _vtable_len= len; }
616
617 vtableEntry* start_of_vtable() const;
618 #if INCLUDE_CDS
619 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
620 #endif
621 public:
622 Method* method_at_vtable(int index);
623
624 static ByteSize vtable_start_offset();
625 static ByteSize vtable_length_offset() {
626 return byte_offset_of(Klass, _vtable_len);
627 }
628
629 #if INCLUDE_CDS
630 // CDS support - remove and restore oops from metadata. Oops are not shared.
631 virtual void remove_unshareable_info();
632 virtual void remove_java_mirror();
633
634 bool is_unshareable_info_restored() const {
635 assert(in_aot_cache(), "use this for shared classes only");
636 if (has_archived_mirror_index()) {
637 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
638 return false;
639 } else if (_java_mirror.is_empty()) {
640 return false;
641 } else {
642 return true;
643 }
644 }
645 #endif // INCLUDE_CDS
646
647 public:
648 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
649 // These functions describe behavior for the oop not the KLASS.
650
651 // actual oop size of obj in memory in word size.
652 virtual size_t oop_size(oop obj) const = 0;
653
654 // Size of klass in word size.
655 virtual int size() const = 0;
656
657 // Returns the Java name for a class (Resource allocated)
658 // For arrays, this returns the name of the element with a leading '['.
659 // For classes, this returns the name with the package separators
660 // turned into '.'s.
661 const char* external_name() const;
662 // Returns the name for a class (Resource allocated) as the class
663 // would appear in a signature.
664 // For arrays, this returns the name of the element with a leading '['.
665 // For classes, this returns the name with a leading 'L' and a trailing ';'
666 // and the package separators as '/'.
667 virtual const char* signature_name() const;
668
669 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
670 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
671
672 // Returns "interface", "abstract class" or "class".
673 const char* external_kind() const;
674
675 // type testing operations
676 #ifdef ASSERT
677 protected:
678 virtual bool is_instance_klass_slow() const { return false; }
679 virtual bool is_array_klass_slow() const { return false; }
680 virtual bool is_objArray_klass_slow() const { return false; }
681 virtual bool is_refArray_klass_slow() const { return false; }
682 virtual bool is_typeArray_klass_slow() const { return false; }
683 virtual bool is_flatArray_klass_slow() const { return false; }
684 #endif // ASSERT
685 // current implementation uses this method even in non debug builds
686 virtual bool is_inline_klass_slow() const { return false; }
687 public:
688
689 // Fast non-virtual versions
690 #ifndef ASSERT
691 #define assert_same_query(xval, xcheck) xval
692 #else
693 private:
694 static bool assert_same_query(bool xval, bool xslow) {
695 assert(xval == xslow, "slow and fast queries agree");
696 return xval;
697 }
698 public:
699 #endif
700
701 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
702 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
703 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
704 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
705 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
706 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
707 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
708 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
709 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind || _kind == RefArrayKlassKind || _kind == FlatArrayKlassKind, is_objArray_klass_slow()); }
710 bool is_refArray_klass() const { return assert_same_query( _kind == RefArrayKlassKind, is_refArray_klass_slow()); }
711 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
712 bool is_refined_objArray_klass() const { return is_refArray_klass() || is_flatArray_klass(); }
713 #undef assert_same_query
714
715 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
716
717 // Access flags
718 AccessFlags access_flags() const { return _access_flags; }
719 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
720
721 bool is_public() const { return _access_flags.is_public(); }
722 bool is_final() const { return _access_flags.is_final(); }
723 bool is_interface() const { return _access_flags.is_interface(); }
724 bool is_abstract() const { return _access_flags.is_abstract(); }
725 bool is_synthetic() const { return _access_flags.is_synthetic(); }
726 bool is_identity_class() const { assert(is_instance_klass(), "only for instanceKlass"); return _access_flags.is_identity_class(); }
727 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
728 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
729 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
730 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
731 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
732 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
733 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
734
735 klass_flags_t misc_flags() const { return _misc_flags.value(); }
736
737 inline bool is_non_strong_hidden() const;
738
739 bool is_cloneable() const;
740 void set_is_cloneable();
741
742 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
743 inline markWord prototype_header() const;
744 inline void set_prototype_header(markWord header);
745 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
746 inline void set_prototype_header_klass(narrowKlass klass);
747
748 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
749
750 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
751 virtual MetaspaceObj::Type type() const { return ClassType; }
752
753 inline bool is_loader_alive() const;
754 inline bool is_loader_present_and_alive() const;
755
756 void clean_subklass();
757
758 // Clean out unnecessary weak klass links from the whole klass hierarchy.
759 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
760 // Clean out unnecessary weak klass links from the given InstanceKlass.
761 static void clean_weak_instanceklass_links(InstanceKlass* ik);
762
763 // Return self, except for abstract classes with exactly 1
764 // implementor. Then return the 1 concrete implementation.
765 Klass *up_cast_abstract();
766
767 // klass name
768 Symbol* name() const { return _name; }
769 void set_name(Symbol* n);
770
771 virtual void release_C_heap_structures(bool release_constant_pool = true);
772
773 public:
774 // Get modifier flags from Java mirror cache.
775 int modifier_flags() const;
776
777 // Compute modifier flags from the original data. This also allows
778 // accessing flags when Java mirror is already dead, e.g. during class
779 // unloading.
780 virtual u2 compute_modifier_flags() const = 0;
781
782 // JVMTI support
783 virtual jint jvmti_class_status() const;
784
785 // Printing
786 virtual void print_on(outputStream* st) const;
787
788 virtual void oop_print_value_on(oop obj, outputStream* st);
789 virtual void oop_print_on (oop obj, outputStream* st);
790
791 void print_secondary_supers_on(outputStream* st) const;
792
793 virtual const char* internal_name() const = 0;
794
795 // Verification
796 virtual void verify_on(outputStream* st);
797 void verify() { verify_on(tty); }
798
799 #ifndef PRODUCT
800 bool verify_vtable_index(int index);
801 #endif
802
803 virtual void oop_verify_on(oop obj, outputStream* st);
804
805 // for error reporting
806 static bool is_valid(Klass* k);
807
808 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
809
810 // Returns true if this Klass needs to be addressable via narrow Klass ID.
811 inline bool needs_narrow_id() const;
812
813 };
814
815 #endif // SHARE_OOPS_KLASS_HPP