1 /*
2 * Copyright (c) 1997, 2024, 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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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #ifndef SHARE_OOPS_KLASS_HPP
26 #define SHARE_OOPS_KLASS_HPP
27
28 #include "memory/iterator.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/klassFlags.hpp"
31 #include "oops/markWord.hpp"
32 #include "oops/metadata.hpp"
33 #include "oops/oop.hpp"
34 #include "oops/oopHandle.hpp"
35 #include "utilities/accessFlags.hpp"
36 #include "utilities/macros.hpp"
37 #if INCLUDE_JFR
38 #include "jfr/support/jfrTraceIdExtension.hpp"
39 #endif
40
41 //
42 // A Klass provides:
43 // 1: language level class object (method dictionary etc.)
44 // 2: provide vm dispatch behavior for the object
45 // Both functions are combined into one C++ class.
46
47 // One reason for the oop/klass dichotomy in the implementation is
48 // that we don't want a C++ vtbl pointer in every object. Thus,
49 // normal oops don't have any virtual functions. Instead, they
50 // forward all "virtual" functions to their klass, which does have
51 // a vtbl and does the C++ dispatch depending on the object's
52 // actual type. (See oop.inline.hpp for some of the forwarding code.)
53 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
54
55 // Forward declarations.
56 template <class T> class Array;
57 template <class T> class GrowableArray;
58 class ClassLoaderData;
59 class fieldDescriptor;
60 class klassVtable;
61 class ModuleEntry;
62 class PackageEntry;
63 class ParCompactionManager;
64 class PSPromotionManager;
65 class vtableEntry;
66
67 class Klass : public Metadata {
68 friend class VMStructs;
69 friend class JVMCIVMStructs;
70 public:
71 // Klass Kinds for all subclasses of Klass
72 enum KlassKind {
73 InstanceKlassKind,
74 InlineKlassKind,
75 InstanceRefKlassKind,
76 InstanceMirrorKlassKind,
77 InstanceClassLoaderKlassKind,
78 InstanceStackChunkKlassKind,
79 TypeArrayKlassKind,
80 FlatArrayKlassKind,
81 ObjArrayKlassKind,
82 UnknownKlassKind
83 };
84
85 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
86 protected:
87
88 // If you add a new field that points to any metaspace object, you
89 // must add this field to Klass::metaspace_pointers_do().
90
91 // note: put frequently-used fields together at start of klass structure
92 // for better cache behavior (may not make much of a difference but sure won't hurt)
93 enum { _primary_super_limit = 8 };
94
95 // The "layout helper" is a combined descriptor of object layout.
96 // For klasses which are neither instance nor array, the value is zero.
97 //
98 // For instances, layout helper is a positive number, the instance size.
99 // This size is already passed through align_object_size and scaled to bytes.
100 // The low order bit is set if instances of this class cannot be
101 // allocated using the fastpath.
102 //
103 // For arrays, layout helper is a negative number, containing four
104 // distinct bytes, as follows:
105 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
106 // where:
107 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
108 // hsz is array header size in bytes (i.e., offset of first element)
109 // ebt is the BasicType of the elements
110 // esz is the element size in bytes
111 // This packed word is arranged so as to be quickly unpacked by the
112 // various fast paths that use the various subfields.
113 //
114 // The esz bits can be used directly by a SLL instruction, without masking.
115 //
116 // Note that the array-kind tag looks like 0x00 for instance klasses,
117 // since their length in bytes is always less than 24Mb.
118 //
119 // Final note: This comes first, immediately after C++ vtable,
120 // because it is frequently queried.
121 jint _layout_helper;
122
123 // Klass kind used to resolve the runtime type of the instance.
124 // - Used to implement devirtualized oop closure dispatching.
125 // - Various type checking in the JVM
126 const KlassKind _kind;
127
128 // Processed access flags, for use by Class.getModifiers.
129 jint _modifier_flags;
130
131 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
132 // and _primary_supers all help make fast subtype checks. See big discussion
133 // in doc/server_compiler/checktype.txt
134 //
135 // Where to look to observe a supertype (it is &_secondary_super_cache for
136 // secondary supers, else is &_primary_supers[depth()].
137 juint _super_check_offset;
138
139 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
140 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
141 Symbol* _name;
142
143 // Cache of last observed secondary supertype
144 Klass* _secondary_super_cache;
145 // Array of all secondary supertypes
146 Array<Klass*>* _secondary_supers;
147 // Ordered list of all primary supertypes
148 Klass* _primary_supers[_primary_super_limit];
149 // java/lang/Class instance mirroring this class
150 OopHandle _java_mirror;
151 // Superclass
152 Klass* _super;
153 // First subclass (null if none); _subklass->next_sibling() is next one
154 Klass* volatile _subklass;
155 // Sibling link (or null); links all subklasses of a klass
156 Klass* volatile _next_sibling;
157
158 // All klasses loaded by a class loader are chained through these links
159 Klass* _next_link;
160
161 // The VM's representation of the ClassLoader used to load this class.
162 // Provide access the corresponding instance java.lang.ClassLoader.
163 ClassLoaderData* _class_loader_data;
164
165
166 int _vtable_len; // vtable length. This field may be read very often when we
167 // have lots of itable dispatches (e.g., lambdas and streams).
168 // Keep it away from the beginning of a Klass to avoid cacheline
169 // contention that may happen when a nearby object is modified.
170 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
171 // Some flags created by the JVM, not in the class file itself,
172 // are in _misc_flags below.
173
174 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
175
176 markWord _prototype_header; // inline type and inline array mark patterns
177 // Bitmap and hash code used by hashed secondary supers.
178 uintx _bitmap;
179 uint8_t _hash_slot;
180
181 private:
182 // This is an index into FileMapHeader::_shared_path_table[], to
183 // associate this class with the JAR file where it's loaded from during
184 // dump time. If a class is not loaded from the shared archive, this field is
185 // -1.
186 s2 _shared_class_path_index;
187
188 #if INCLUDE_CDS
189 // Various attributes for shared classes. Should be zero for a non-shared class.
190 u2 _shared_class_flags;
191 enum CDSSharedClassFlags {
192 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
193 _archived_lambda_proxy_is_available = 1 << 1,
194 _has_value_based_class_annotation = 1 << 2,
195 _verified_at_dump_time = 1 << 3,
196 _has_archived_enum_objs = 1 << 4,
197 // This class was not loaded from a classfile in the module image
198 // or classpath.
199 _is_generated_shared_class = 1 << 5
200 };
201 #endif
202
203 KlassFlags _misc_flags;
204
205 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
206
207 protected:
208
209 Klass(KlassKind kind);
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);
246 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
247
248 uint8_t hash_slot() const { return _hash_slot; }
249
250 // Return the element of the _super chain of the given depth.
251 // If there is no such element, return either null or this.
252 Klass* primary_super_of_depth(juint i) const {
253 assert(i < primary_super_limit(), "oob");
254 Klass* super = _primary_supers[i];
255 assert(super == nullptr || super->super_depth() == i, "correct display");
256 return super;
257 }
258
259 // Can this klass be a primary super? False for interfaces and arrays of
260 // interfaces. False also for arrays or classes with long super chains.
261 bool can_be_primary_super() const {
262 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
263 return super_check_offset() != secondary_offset;
264 }
265 virtual bool can_be_primary_super_slow() const;
266
267 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
268 juint super_depth() const {
269 if (!can_be_primary_super()) {
270 return primary_super_limit();
271 } else {
272 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
273 assert(d < primary_super_limit(), "oob");
274 assert(_primary_supers[d] == this, "proper init");
275 return d;
276 }
277 }
278
279 // java mirror
280 oop java_mirror() const;
281 oop java_mirror_no_keepalive() const;
282 void set_java_mirror(Handle m);
283
284 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
285 void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
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 // modifier flags
296 jint modifier_flags() const { return _modifier_flags; }
297 void set_modifier_flags(jint flags) { _modifier_flags = flags; }
298
299 // size helper
300 int layout_helper() const { return _layout_helper; }
301 void set_layout_helper(int lh) { _layout_helper = lh; }
302
303 // Note: for instances layout_helper() may include padding.
304 // Use InstanceKlass::contains_field_offset to classify field offsets.
305
306 // sub/superklass links
307 Klass* subklass(bool log = false) const;
308 Klass* next_sibling(bool log = false) const;
309
310 InstanceKlass* superklass() const;
311 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
312
313 void set_next_link(Klass* k) { _next_link = k; }
314 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
315 Klass** next_link_addr() { return &_next_link; }
316
317 // class loader data
318 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
319 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
320
321 s2 shared_classpath_index() const {
322 return _shared_class_path_index;
323 };
324
325 void set_shared_classpath_index(s2 index) {
326 _shared_class_path_index = index;
327 };
328
329 bool has_archived_mirror_index() const {
330 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
331 NOT_CDS_JAVA_HEAP(return false);
332 }
333
334 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
335
336 void set_lambda_proxy_is_available() {
337 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
338 }
339 void clear_lambda_proxy_is_available() {
340 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
341 }
342 bool lambda_proxy_is_available() const {
343 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
344 NOT_CDS(return false;)
345 }
346
347 void set_has_value_based_class_annotation() {
348 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
349 }
350 void clear_has_value_based_class_annotation() {
351 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
352 }
353 bool has_value_based_class_annotation() const {
354 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
355 NOT_CDS(return false;)
356 }
357
358 void set_verified_at_dump_time() {
359 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
360 }
361 bool verified_at_dump_time() const {
362 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
363 NOT_CDS(return false;)
364 }
365
366 void set_has_archived_enum_objs() {
367 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
368 }
369 bool has_archived_enum_objs() const {
370 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
371 NOT_CDS(return false;)
372 }
373
374 void set_is_generated_shared_class() {
375 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
376 }
377 bool is_generated_shared_class() const {
378 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
379 NOT_CDS(return false;)
380 }
381
382 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
383 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
384 NOT_CDS(return false;)
385 }
386
387 void set_is_shared() {
388 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
389 }
390
391 // Obtain the module or package for this class
392 virtual ModuleEntry* module() const = 0;
393 virtual PackageEntry* package() const = 0;
394
395 protected: // internal accessors
396 void set_subklass(Klass* s);
397 void set_next_sibling(Klass* s);
398
399 private:
400 static uint8_t compute_hash_slot(Symbol* s);
401 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
402 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
403
404 public:
405 // Secondary supers table support
406 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
407 GrowableArray<Klass*>* primaries,
408 GrowableArray<Klass*>* secondaries,
409 uintx& bitmap,
410 TRAPS);
411
412 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
413 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
414
415 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_bitmap) * 8;
416 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
417
418 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
419 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
420
421 // Compiler support
422 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
423 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
424 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
425 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
426 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
427 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
428 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
429 static ByteSize modifier_flags_offset() { return byte_offset_of(Klass, _modifier_flags); }
430 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
431 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
432 #if INCLUDE_JVMCI
433 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
434 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
435 #endif
436 static ByteSize bitmap_offset() { return byte_offset_of(Klass, _bitmap); }
437 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
438
439 // Unpacking layout_helper:
440 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
441 static const int _lh_instance_slow_path_bit = 0x01;
442 static const int _lh_log2_element_size_shift = BitsPerByte*0;
443 static const int _lh_log2_element_size_mask = BitsPerLong-1;
444 static const int _lh_element_type_shift = BitsPerByte*1;
445 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
446 static const int _lh_header_size_shift = BitsPerByte*2;
447 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
448 static const int _lh_array_tag_bits = 3;
449 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
450
451 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
452 static const unsigned int _lh_array_tag_vt_value = 0Xfffffffd;
453 static const unsigned int _lh_array_tag_obj_value = 0Xfffffffe;
454
455 // null-free array flag bit under the array tag bits, shift one more to get array tag value
456 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
457 static const int _lh_null_free_mask = 1;
458
459 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
460
461 static int layout_helper_size_in_bytes(jint lh) {
462 assert(lh > (jint)_lh_neutral_value, "must be instance");
463 return (int) lh & ~_lh_instance_slow_path_bit;
464 }
465 static bool layout_helper_needs_slow_path(jint lh) {
466 assert(lh > (jint)_lh_neutral_value, "must be instance");
467 return (lh & _lh_instance_slow_path_bit) != 0;
468 }
469 static bool layout_helper_is_instance(jint lh) {
470 return (jint)lh > (jint)_lh_neutral_value;
471 }
472 static bool layout_helper_is_array(jint lh) {
473 return (jint)lh < (jint)_lh_neutral_value;
474 }
475 static bool layout_helper_is_typeArray(jint lh) {
476 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
477 }
478 static bool layout_helper_is_objArray(jint lh) {
479 return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
480 }
481 static bool layout_helper_is_flatArray(jint lh) {
482 return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
483 }
484 static bool layout_helper_is_null_free(jint lh) {
485 assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
486 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
487 }
488 static jint layout_helper_set_null_free(jint lh) {
489 lh |= (_lh_null_free_mask << _lh_null_free_shift);
490 assert(layout_helper_is_null_free(lh), "Bad encoding");
491 return lh;
492 }
493 static int layout_helper_header_size(jint lh) {
494 assert(lh < (jint)_lh_neutral_value, "must be array");
495 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
496 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
497 return hsize;
498 }
499 static BasicType layout_helper_element_type(jint lh) {
500 assert(lh < (jint)_lh_neutral_value, "must be array");
501 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
502 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_PRIMITIVE_OBJECT, "sanity");
503 return (BasicType) btvalue;
504 }
505
506 // Want a pattern to quickly diff against layout header in register
507 // find something less clever!
508 static int layout_helper_boolean_diffbit() {
509 jint zlh = array_layout_helper(T_BOOLEAN);
510 jint blh = array_layout_helper(T_BYTE);
511 assert(zlh != blh, "array layout helpers must differ");
512 int diffbit = 1;
513 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
514 diffbit <<= 1;
515 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
516 }
517 return diffbit;
518 }
519
520 static int layout_helper_log2_element_size(jint lh) {
521 assert(lh < (jint)_lh_neutral_value, "must be array");
522 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
523 assert(layout_helper_element_type(lh) == T_PRIMITIVE_OBJECT || l2esz <= LogBytesPerLong,
524 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
525 return l2esz;
526 }
527 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
528 return (tag << _lh_array_tag_shift)
529 | ((null_free ? 1 : 0) << _lh_null_free_shift)
530 | (hsize << _lh_header_size_shift)
531 | ((int)etype << _lh_element_type_shift)
532 | (log2_esize << _lh_log2_element_size_shift);
533 }
534 static jint instance_layout_helper(jint size, bool slow_path_flag) {
535 return (size << LogBytesPerWord)
536 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
537 }
538 static int layout_helper_to_size_helper(jint lh) {
539 assert(lh > (jint)_lh_neutral_value, "must be instance");
540 // Note that the following expression discards _lh_instance_slow_path_bit.
541 return lh >> LogBytesPerWord;
542 }
543 // Out-of-line version computes everything based on the etype:
544 static jint array_layout_helper(BasicType etype);
545
546 // What is the maximum number of primary superclasses any klass can have?
547 static juint primary_super_limit() { return _primary_super_limit; }
548
549 // vtables
550 klassVtable vtable() const;
551 int vtable_length() const { return _vtable_len; }
552
553 // subclass check
554 bool is_subclass_of(const Klass* k) const;
555 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
556 bool is_subtype_of(Klass* k) const {
557 juint off = k->super_check_offset();
558 Klass* sup = *(Klass**)( (address)this + off );
559 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
560 if (sup == k) {
561 return true;
562 } else if (off != secondary_offset) {
563 return false;
564 } else {
565 return search_secondary_supers(k);
566 }
567 }
568
569 bool search_secondary_supers(Klass* k) const;
570
571 // Find LCA in class hierarchy
572 Klass *LCA( Klass *k );
573
574 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
575 // if not, throw either an Error or an Exception.
576 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
577
578 // array copying
579 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
580
581 // tells if the class should be initialized
582 virtual bool should_be_initialized() const { return false; }
583 // initializes the klass
584 virtual void initialize(TRAPS);
585 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
586 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
587 OverpassLookupMode overpass_mode,
588 PrivateLookupMode = PrivateLookupMode::find) const;
589 public:
590 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
591 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
592 }
593
594 // array class with specific rank
595 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
596
597 // array class with this klass as element type
598 virtual ArrayKlass* array_klass(TRAPS) = 0;
599
600 // These will return null instead of allocating on the heap:
601 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
602 virtual ArrayKlass* array_klass_or_null() = 0;
603
604 virtual oop protection_domain() const = 0;
605
606 oop class_loader() const;
607
608 inline oop klass_holder() 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(is_shared(), "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_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, is_objArray_klass_slow()); }
709 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
710 #undef assert_same_query
711
712 inline bool is_null_free_array_klass() const { return layout_helper_is_null_free(layout_helper()); }
713
714 // Access flags
715 AccessFlags access_flags() const { return _access_flags; }
716 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
717
718 bool is_public() const { return _access_flags.is_public(); }
719 bool is_final() const { return _access_flags.is_final(); }
720 bool is_interface() const { return _access_flags.is_interface(); }
721 bool is_abstract() const { return _access_flags.is_abstract(); }
722 bool is_synthetic() const { return _access_flags.is_synthetic(); }
723 bool is_identity_class() const { return _access_flags.is_identity_class(); }
724 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
725 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
726 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
727 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
728 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
729 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
730 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
731
732 klass_flags_t misc_flags() const { return _misc_flags.value(); }
733
734 inline bool is_non_strong_hidden() const;
735
736 bool is_cloneable() const;
737 void set_is_cloneable();
738
739 // inline types and inline type array patterns
740 markWord prototype_header() const {
741 return _prototype_header;
742 }
743 static inline markWord default_prototype_header(Klass* k) {
744 return (k == nullptr) ? markWord::prototype() : k->prototype_header();
745 }
746
747 inline void set_prototype_header(markWord header);
748 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
749
750 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
751
752 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
753 virtual MetaspaceObj::Type type() const { return ClassType; }
754
755 inline bool is_loader_alive() const;
756
757 void clean_subklass();
758
759 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
760 static void clean_subklass_tree() {
761 clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
762 }
763
764 // Return self, except for abstract classes with exactly 1
765 // implementor. Then return the 1 concrete implementation.
766 Klass *up_cast_abstract();
767
768 // klass name
769 Symbol* name() const { return _name; }
770 void set_name(Symbol* n);
771
772 virtual void release_C_heap_structures(bool release_constant_pool = true);
773
774 public:
775 virtual jint compute_modifier_flags() const = 0;
776
777 // JVMTI support
778 virtual jint jvmti_class_status() const;
779
780 // Printing
781 virtual void print_on(outputStream* st) const;
782
783 virtual void oop_print_value_on(oop obj, outputStream* st);
784 virtual void oop_print_on (oop obj, outputStream* st);
785
786 void print_secondary_supers_on(outputStream* st) const;
787
788 virtual const char* internal_name() const = 0;
789
790 // Verification
791 virtual void verify_on(outputStream* st);
792 void verify() { verify_on(tty); }
793
794 #ifndef PRODUCT
795 bool verify_vtable_index(int index);
796 #endif
797
798 virtual void oop_verify_on(oop obj, outputStream* st);
799
800 // for error reporting
801 static bool is_valid(Klass* k);
802
803 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
804 };
805
806 #endif // SHARE_OOPS_KLASS_HPP