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,
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/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 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 // Some flags created by the JVM, not in the class file itself,
128 // are in _misc_flags below.
129 KlassFlags _misc_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 markWord _prototype_header; // Used to initialize objects' header
166
167 // Bitmap and hash code used by hashed secondary supers.
168 uintx _secondary_supers_bitmap;
169 uint8_t _hash_slot;
170
171 private:
172 // This is an index into AOTClassLocationConfig::class_locations(), to
173 // indicate the AOTClassLocation where this class is loaded from during
174 // dump time. If a class is not loaded from the AOT cache, this field is
175 // -1.
176 s2 _shared_class_path_index;
177
178 #if INCLUDE_CDS
179 // Various attributes for shared classes. Should be zero for a non-shared class.
180 u2 _aot_class_flags;
181 enum {
182 _in_aot_cache = 1 << 0,
183 _archived_lambda_proxy_is_available = 1 << 1,
184 _has_value_based_class_annotation = 1 << 2,
185 _verified_at_dump_time = 1 << 3,
186 _has_archived_enum_objs = 1 << 4,
187 _is_aot_generated_class = 1 << 5, // this class was not loaded from a classfile in the module image
188 // or classpath, but was generated during AOT cache assembly.
189 _has_aot_initialized_mirror = 1 << 6, // archived mirror already initialized by AOT cache assembly.
190 // no further need to call <clinit>
191 _has_aot_safe_initializer = 1 << 7, // has @AOTSafeClassInitializer annotation
192 _is_runtime_setup_required = 1 << 8, // has a runtimeSetup method to be called when
193 // this class is loaded from AOT cache
194 };
195 #endif
196
197 int _vtable_len; // vtable length. This field may be read very often when we
198 // have lots of itable dispatches (e.g., lambdas and streams).
199 // Keep it away from the beginning of a Klass to avoid cacheline
200 // contention that may happen when a nearby object is modified.
201
202 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
203
204 public:
205
206 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
207
208 protected:
209
210 Klass(KlassKind kind, markWord prototype_header = markWord::prototype());
211 Klass();
212
213 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
214
215 public:
216 int kind() { return _kind; }
217
218 enum class DefaultsLookupMode { find, skip };
219 enum class OverpassLookupMode { find, skip };
220 enum class StaticLookupMode { find, skip };
221 enum class PrivateLookupMode { find, skip };
222
223 bool is_klass() const override { return true; }
224
225 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
226 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
227 // If this is not what your code expects, you're probably looking for:
228 // - Klass::java_super() - if you have a Klass*
229 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
230 Klass* super() const { return _super; }
231 void set_super(Klass* k) { _super = k; }
232
233 // initializes _super link, _primary_supers & _secondary_supers arrays
234 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
235
236 // klass-specific helper for initializing _secondary_supers
237 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
238 Array<InstanceKlass*>* transitive_interfaces);
239
240 // java_super is the Java-level super type as specified by Class.getSuperClass.
241 virtual InstanceKlass* java_super() const { return nullptr; }
242
243 juint super_check_offset() const { return _super_check_offset; }
244 void set_super_check_offset(juint o) { _super_check_offset = o; }
245
246 Klass* secondary_super_cache() const { return _secondary_super_cache; }
247 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
248
249 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
250 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
251
252 uint8_t hash_slot() const { return _hash_slot; }
253
254 // Return the element of the _super chain of the given depth.
255 // If there is no such element, return either null or this.
256 Klass* primary_super_of_depth(juint i) const {
257 assert(i < primary_super_limit(), "oob");
258 Klass* super = _primary_supers[i];
259 assert(super == nullptr || super->super_depth() == i, "correct display");
260 return super;
261 }
262
263 // Can this klass be a primary super? False for interfaces and arrays of
264 // interfaces. False also for arrays or classes with long super chains.
265 bool can_be_primary_super() const {
266 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
267 return super_check_offset() != secondary_offset;
268 }
269 virtual bool can_be_primary_super_slow() const;
270
271 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
272 juint super_depth() const {
273 if (!can_be_primary_super()) {
274 return primary_super_limit();
275 } else {
276 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
277 assert(d < primary_super_limit(), "oob");
278 assert(_primary_supers[d] == this, "proper init");
279 return d;
280 }
281 }
282
283 // java mirror
284 oop java_mirror() const;
285 oop java_mirror_no_keepalive() const;
286 void set_java_mirror(Handle m);
287
288 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
289
290 // Temporary mirror switch used by RedefineClasses
291 OopHandle java_mirror_handle() const { return _java_mirror; }
292 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
293
294 // Set java mirror OopHandle to null for CDS
295 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
296 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
297
298 // size helper
299 int layout_helper() const { return _layout_helper; }
300 void set_layout_helper(int lh) { _layout_helper = lh; }
301
302 // Note: for instances layout_helper() may include padding.
303 // Use InstanceKlass::contains_field_offset to classify field offsets.
304
305 // sub/superklass links
306 Klass* subklass() const;
307 Klass* next_sibling(bool log = false) const;
308
309 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
310
311 void set_next_link(Klass* k) { _next_link = k; }
312 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
313 Klass** next_link_addr() { return &_next_link; }
314
315 // class loader data
316 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
317 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
318
319 s2 shared_classpath_index() const {
320 return _shared_class_path_index;
321 };
322
323 void set_shared_classpath_index(s2 index) {
324 _shared_class_path_index = index;
325 };
326
327 bool has_archived_mirror_index() const {
328 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
329 NOT_CDS_JAVA_HEAP(return false);
330 }
331
332 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
333
334 void set_lambda_proxy_is_available() {
335 CDS_ONLY(_aot_class_flags |= _archived_lambda_proxy_is_available;)
336 }
337 void clear_lambda_proxy_is_available() {
338 CDS_ONLY(_aot_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
339 }
340 bool lambda_proxy_is_available() const {
341 CDS_ONLY(return (_aot_class_flags & _archived_lambda_proxy_is_available) != 0;)
342 NOT_CDS(return false;)
343 }
344
345 void set_has_value_based_class_annotation() {
346 CDS_ONLY(_aot_class_flags |= _has_value_based_class_annotation;)
347 }
348 void clear_has_value_based_class_annotation() {
349 CDS_ONLY(_aot_class_flags &= (u2)(~_has_value_based_class_annotation);)
350 }
351 bool has_value_based_class_annotation() const {
352 CDS_ONLY(return (_aot_class_flags & _has_value_based_class_annotation) != 0;)
353 NOT_CDS(return false;)
354 }
355
356 void set_verified_at_dump_time() {
357 CDS_ONLY(_aot_class_flags |= _verified_at_dump_time;)
358 }
359 bool verified_at_dump_time() const {
360 CDS_ONLY(return (_aot_class_flags & _verified_at_dump_time) != 0;)
361 NOT_CDS(return false;)
362 }
363
364 void set_has_archived_enum_objs() {
365 CDS_ONLY(_aot_class_flags |= _has_archived_enum_objs;)
366 }
367 bool has_archived_enum_objs() const {
368 CDS_ONLY(return (_aot_class_flags & _has_archived_enum_objs) != 0;)
369 NOT_CDS(return false;)
370 }
371
372 void set_is_aot_generated_class() {
373 CDS_ONLY(_aot_class_flags |= _is_aot_generated_class;)
374 }
375 bool is_aot_generated_class() const {
376 CDS_ONLY(return (_aot_class_flags & _is_aot_generated_class) != 0;)
377 NOT_CDS(return false;)
378 }
379
380 void set_has_aot_initialized_mirror() {
381 CDS_ONLY(_aot_class_flags |= _has_aot_initialized_mirror;)
382 }
383 bool has_aot_initialized_mirror() const {
384 CDS_ONLY(return (_aot_class_flags & _has_aot_initialized_mirror) != 0;)
385 NOT_CDS(return false;)
386 }
387
388 // Indicates presence of @AOTSafeClassInitializer. Also see AOTClassInitializer for more details.
389 void set_has_aot_safe_initializer() {
390 CDS_ONLY(_aot_class_flags |= _has_aot_safe_initializer;)
391 }
392 bool has_aot_safe_initializer() const {
393 CDS_ONLY(return (_aot_class_flags & _has_aot_safe_initializer) != 0;)
394 NOT_CDS(return false;)
395 }
396
397 // Indicates @AOTRuntimeSetup private static void runtimeSetup() presence.
398 void set_is_runtime_setup_required() {
399 CDS_ONLY(_aot_class_flags |= _is_runtime_setup_required;)
400 }
401 bool is_runtime_setup_required() const {
402 CDS_ONLY(return (_aot_class_flags & _is_runtime_setup_required) != 0;)
403 NOT_CDS(return false;)
404 }
405
406 bool in_aot_cache() const { // shadows MetaspaceObj::in_aot_cache)()
407 CDS_ONLY(return (_aot_class_flags & _in_aot_cache) != 0;)
408 NOT_CDS(return false;)
409 }
410
411 void set_in_aot_cache() {
412 CDS_ONLY(_aot_class_flags |= _in_aot_cache;)
413 }
414
415 // Obtain the module or package for this class
416 virtual ModuleEntry* module() const = 0;
417 virtual PackageEntry* package() const = 0;
418
419 void set_next_sibling(Klass* s);
420 protected: // internal accessors
421 void set_subklass(Klass* s);
422
423 private:
424 static uint8_t compute_hash_slot(Symbol* s);
425 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
426 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
427
428 bool search_secondary_supers(Klass* k) const;
429 bool lookup_secondary_supers_table(Klass *k) const;
430 bool linear_search_secondary_supers(const Klass* k) const;
431 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
432
433 public:
434 // Secondary supers table support
435 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
436 GrowableArray<Klass*>* primaries,
437 GrowableArray<Klass*>* secondaries,
438 uintx& bitmap,
439 TRAPS);
440
441 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
442 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
443
444 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
445 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
446
447 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
448 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
449
450 // Compiler support
451 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
452 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
453 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
454 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
455 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
456 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
457 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
458 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
459 #if INCLUDE_JVMCI
460 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
461 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
462 #endif
463 static ByteSize secondary_supers_bitmap_offset()
464 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
465 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
466 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
467
468 // Unpacking layout_helper:
469 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
470 static const int _lh_instance_slow_path_bit = 0x01;
471 static const int _lh_log2_element_size_shift = BitsPerByte*0;
472 static const int _lh_log2_element_size_mask = BitsPerLong-1;
473 static const int _lh_element_type_shift = BitsPerByte*1;
474 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
475 static const int _lh_header_size_shift = BitsPerByte*2;
476 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
477 static const int _lh_array_tag_bits = 4;
478 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
479
480 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
481 static const unsigned int _lh_array_tag_flat_value = 0Xfffffffa;
482 static const unsigned int _lh_array_tag_ref_value = 0Xfffffff8;
483
484 // null-free array flag bit under the array tag bits, shift one more to get array tag value
485 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
486 static const int _lh_null_free_mask = 1;
487
488 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << (_lh_array_tag_shift + 1));
489
490 static int layout_helper_size_in_bytes(jint lh) {
491 assert(lh > (jint)_lh_neutral_value, "must be instance");
492 return (int) lh & ~_lh_instance_slow_path_bit;
493 }
494 static bool layout_helper_needs_slow_path(jint lh) {
495 assert(lh > (jint)_lh_neutral_value, "must be instance");
496 return (lh & _lh_instance_slow_path_bit) != 0;
497 }
498 static bool layout_helper_is_instance(jint lh) {
499 return (jint)lh > (jint)_lh_neutral_value;
500 }
501 static bool layout_helper_is_array(jint lh) {
502 return (jint)lh < (jint)_lh_neutral_value;
503 }
504 static bool layout_helper_is_typeArray(jint lh) {
505 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
506 }
507 static bool layout_helper_is_refArray(jint lh) {
508 return (juint)_lh_array_tag_ref_value == (juint)(lh >> _lh_array_tag_shift);
509 }
510 static bool layout_helper_is_flatArray(jint lh) {
511 return (juint)_lh_array_tag_flat_value == (juint)(lh >> _lh_array_tag_shift);
512 }
513 static bool layout_helper_is_null_free(jint lh) {
514 assert(layout_helper_is_flatArray(lh) || layout_helper_is_refArray(lh), "must be array of inline types");
515 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
516 }
517 static jint layout_helper_set_null_free(jint lh) {
518 lh |= (_lh_null_free_mask << _lh_null_free_shift);
519 assert(layout_helper_is_null_free(lh), "Bad encoding");
520 return lh;
521 }
522 static int layout_helper_header_size(jint lh) {
523 assert(lh < (jint)_lh_neutral_value, "must be array");
524 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
525 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
526 return hsize;
527 }
528 static BasicType layout_helper_element_type(jint lh) {
529 assert(lh < (jint)_lh_neutral_value, "must be array");
530 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
531 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
532 return (BasicType) btvalue;
533 }
534
535 // Return a value containing a single set bit that is in the bitset difference between the
536 // layout helpers for array-of-boolean and array-of-byte.
537 static int layout_helper_boolean_diffbit() {
538 uint zlh = static_cast<uint>(array_layout_helper(T_BOOLEAN));
539 uint blh = static_cast<uint>(array_layout_helper(T_BYTE));
540 // get all the bits that are set in zlh and clear in blh
541 uint candidates = (zlh & ~blh);
542 assert(candidates != 0, "must be"); // must be some if there is a solution.
543 // Use well known bit hack to isolate the low bit of candidates.
544 uint result = candidates & (-candidates);
545 assert(is_power_of_2(result), "must be power of 2");
546 assert((result & zlh) != 0, "must be set in alh of T_BOOLEAN");
547 assert((result & blh) == 0, "must be clear in alh of T_BYTE");
548 return static_cast<int>(result);
549 }
550
551 static int layout_helper_log2_element_size(jint lh) {
552 assert(lh < (jint)_lh_neutral_value, "must be array");
553 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
554 assert(layout_helper_element_type(lh) == T_FLAT_ELEMENT || l2esz <= LogBytesPerLong,
555 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
556 return l2esz;
557 }
558 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
559 return (tag << _lh_array_tag_shift)
560 | ((null_free ? 1 : 0) << _lh_null_free_shift)
561 | (hsize << _lh_header_size_shift)
562 | ((int)etype << _lh_element_type_shift)
563 | (log2_esize << _lh_log2_element_size_shift);
564 }
565 static jint instance_layout_helper(jint size, bool slow_path_flag) {
566 return (size << LogBytesPerWord)
567 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
568 }
569 static int layout_helper_to_size_helper(jint lh) {
570 assert(lh > (jint)_lh_neutral_value, "must be instance");
571 // Note that the following expression discards _lh_instance_slow_path_bit.
572 return lh >> LogBytesPerWord;
573 }
574 // Out-of-line version computes everything based on the etype:
575 static jint array_layout_helper(BasicType etype);
576
577 // What is the maximum number of primary superclasses any klass can have?
578 static juint primary_super_limit() { return _primary_super_limit; }
579
580 // vtables
581 klassVtable vtable() const;
582 int vtable_length() const { return _vtable_len; }
583
584 // subclass check
585 bool is_subclass_of(const Klass* k) const;
586
587 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
588 bool is_subtype_of(Klass* k) const;
589
590 public:
591 // Find LCA in class hierarchy
592 Klass *LCA( Klass *k );
593
594 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
595 // if not, throw either an Error or an Exception.
596 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
597
598 // array copying
599 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
600
601 // tells if the class should be initialized
602 virtual bool should_be_initialized() const { return false; }
603 // initializes the klass
604 virtual void initialize(TRAPS);
605 virtual void initialize_preemptable(TRAPS);
606 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
607 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
608 OverpassLookupMode overpass_mode,
609 PrivateLookupMode = PrivateLookupMode::find) const;
610 public:
611 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
612 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
613 }
614
615 // array class with specific rank
616 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
617
618 // array class with this klass as element type
619 virtual ArrayKlass* array_klass(TRAPS) = 0;
620
621 // These will return null instead of allocating on the heap:
622 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
623 virtual ArrayKlass* array_klass_or_null() = 0;
624
625 virtual oop protection_domain() const = 0;
626
627 oop class_loader() const;
628
629 inline oop klass_holder() const;
630
631 inline void keep_alive() const;
632
633 protected:
634
635 // Error handling when length > max_length or length < 0
636 static void check_array_allocation_length(int length, int max_length, TRAPS);
637
638 void set_vtable_length(int len) { _vtable_len= len; }
639
640 vtableEntry* start_of_vtable() const;
641 #if INCLUDE_CDS
642 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
643 #endif
644 public:
645 Method* method_at_vtable(int index);
646
647 static ByteSize vtable_start_offset();
648 static ByteSize vtable_length_offset() {
649 return byte_offset_of(Klass, _vtable_len);
650 }
651
652 #if INCLUDE_CDS
653 // CDS support - remove and restore oops from metadata. Oops are not shared.
654 virtual void remove_unshareable_info();
655 virtual void remove_java_mirror();
656
657 bool is_unshareable_info_restored() const {
658 assert(in_aot_cache(), "use this for shared classes only");
659 if (has_archived_mirror_index()) {
660 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
661 return false;
662 } else if (_java_mirror.is_empty()) {
663 return false;
664 } else {
665 return true;
666 }
667 }
668 #endif // INCLUDE_CDS
669
670 public:
671 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
672 // These functions describe behavior for the oop not the KLASS.
673
674 // actual oop size of obj in memory in word size.
675 virtual size_t oop_size(oop obj) const = 0;
676
677 // Returns the Java name for a class (Resource allocated)
678 // For arrays, this returns the name of the element with a leading '['.
679 // For classes, this returns the name with the package separators
680 // turned into '.'s.
681 const char* external_name() const;
682 // Returns the name for a class (Resource allocated) as the class
683 // would appear in a signature.
684 // For arrays, this returns the name of the element with a leading '['.
685 // For classes, this returns the name with a leading 'L' and a trailing ';'
686 // and the package separators as '/'.
687 virtual const char* signature_name() const;
688
689 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
690 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
691
692 // Returns "interface", "abstract class" or "class".
693 const char* external_kind() const;
694
695 // type testing operations
696 #ifdef ASSERT
697 protected:
698 virtual bool is_instance_klass_slow() const { return false; }
699 virtual bool is_array_klass_slow() const { return false; }
700 virtual bool is_objArray_klass_slow() const { return false; }
701 virtual bool is_refArray_klass_slow() const { return false; }
702 virtual bool is_typeArray_klass_slow() const { return false; }
703 virtual bool is_flatArray_klass_slow() const { return false; }
704 #endif // ASSERT
705 // current implementation uses this method even in non debug builds
706 virtual bool is_inline_klass_slow() const { return false; }
707 public:
708
709 // Fast non-virtual versions
710 #ifndef ASSERT
711 #define assert_same_query(xval, xcheck) xval
712 #else
713 private:
714 static bool assert_same_query(bool xval, bool xslow) {
715 assert(xval == xslow, "slow and fast queries agree");
716 return xval;
717 }
718 public:
719 #endif
720
721 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
722 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
723 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
724 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
725 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
726 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
727 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
728 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
729 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind || _kind == RefArrayKlassKind || _kind == FlatArrayKlassKind, is_objArray_klass_slow()); }
730 bool is_refArray_klass() const { return assert_same_query( _kind == RefArrayKlassKind, is_refArray_klass_slow()); }
731 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
732 bool is_refined_objArray_klass() const { return is_refArray_klass() || is_flatArray_klass(); }
733 #undef assert_same_query
734
735 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
736
737
738 virtual bool is_interface() const { return false; }
739 virtual bool is_abstract() const { return false; }
740 virtual bool is_identity_class() const { return false; }
741
742 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
743 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
744 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
745 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
746 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
747 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
748
749 klass_flags_t misc_flags() const { return _misc_flags.value(); }
750
751 inline bool is_non_strong_hidden() const;
752
753 bool is_cloneable() const;
754 void set_is_cloneable_fast() { _misc_flags.set_is_cloneable_fast(true); }
755
756 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
757 inline markWord prototype_header() const;
758 inline void set_prototype_header(markWord header);
759 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
760 inline void set_prototype_header_klass(narrowKlass klass);
761
762 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
763
764 void metaspace_pointers_do(MetaspaceClosure* iter) override;
765 MetaspaceObj::Type type() const override { return ClassType; }
766
767 inline bool is_loader_alive() const;
768 inline bool is_loader_present_and_alive() const;
769
770 Klass* clean_subklass(bool log = false);
771
772 // Clean out unnecessary weak klass links from the whole klass hierarchy.
773 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
774 // Clean out unnecessary weak klass links from the given InstanceKlass.
775 static void clean_weak_instanceklass_links(InstanceKlass* ik);
776
777 // Return self, except for abstract classes with exactly 1
778 // implementor. Then return the 1 concrete implementation.
779 Klass *up_cast_abstract();
780
781 // klass name
782 Symbol* name() const { return _name; }
783 void set_name(Symbol* n);
784
785 virtual void release_C_heap_structures(bool release_constant_pool = true);
786
787 public:
788 // Get modifier flags from Java mirror cache.
789 int modifier_flags() const;
790
791 // Compute modifier flags from the original data. This also allows
792 // accessing flags when Java mirror is already dead, e.g. during class
793 // unloading.
794 virtual u2 compute_modifier_flags() const = 0;
795
796 // JVMTI support
797 virtual jint jvmti_class_status() const;
798
799 // Printing
800 void print_on(outputStream* st) const override;
801
802 virtual void oop_print_value_on(oop obj, outputStream* st);
803 virtual void oop_print_on (oop obj, outputStream* st);
804
805 void print_secondary_supers_on(outputStream* st) const;
806
807 // Verification
808 virtual void verify_on(outputStream* st);
809 void verify() { verify_on(tty); }
810
811 #ifndef PRODUCT
812 bool verify_vtable_index(int index);
813 #endif
814
815 virtual void oop_verify_on(oop obj, outputStream* st);
816
817 void validate_array_description(const ArrayDescription& ad) NOT_DEBUG_RETURN;
818
819 // for error reporting
820 static bool is_valid(Klass* k);
821
822 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
823 };
824
825 #endif // SHARE_OOPS_KLASS_HPP