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 InstanceKlassKind,
71 InlineKlassKind,
72 InstanceRefKlassKind,
73 InstanceMirrorKlassKind,
74 InstanceClassLoaderKlassKind,
75 InstanceStackChunkKlassKind,
76 TypeArrayKlassKind,
77 FlatArrayKlassKind,
78 ObjArrayKlassKind,
79 UnknownKlassKind
80 };
81
82 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
83 protected:
84
85 // If you add a new field that points to any metaspace object, you
86 // must add this field to Klass::metaspace_pointers_do().
87
88 // note: put frequently-used fields together at start of klass structure
89 // for better cache behavior (may not make much of a difference but sure won't hurt)
90 enum { _primary_super_limit = 8 };
91
92 // The "layout helper" is a combined descriptor of object layout.
93 // For klasses which are neither instance nor array, the value is zero.
94 //
95 // For instances, layout helper is a positive number, the instance size.
96 // This size is already passed through align_object_size and scaled to bytes.
97 // The low order bit is set if instances of this class cannot be
98 // allocated using the fastpath.
99 //
100 // For arrays, layout helper is a negative number, containing four
101 // distinct bytes, as follows:
102 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
103 // where:
104 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
105 // hsz is array header size in bytes (i.e., offset of first element)
106 // ebt is the BasicType of the elements
107 // esz is the element size in bytes
108 // This packed word is arranged so as to be quickly unpacked by the
109 // various fast paths that use the various subfields.
110 //
111 // The esz bits can be used directly by a SLL instruction, without masking.
112 //
113 // Note that the array-kind tag looks like 0x00 for instance klasses,
114 // since their length in bytes is always less than 24Mb.
115 //
116 // Final note: This comes first, immediately after C++ vtable,
117 // because it is frequently queried.
118 jint _layout_helper;
119
120 // Klass kind used to resolve the runtime type of the instance.
121 // - Used to implement devirtualized oop closure dispatching.
122 // - Various type checking in the JVM
123 const KlassKind _kind;
124
125 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
126 // Some flags created by the JVM, not in the class file itself,
127 // are in _misc_flags below.
128 KlassFlags _misc_flags;
129
130 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
131 // and _primary_supers all help make fast subtype checks. See big discussion
132 // in doc/server_compiler/checktype.txt
133 //
134 // Where to look to observe a supertype (it is &_secondary_super_cache for
135 // secondary supers, else is &_primary_supers[depth()].
136 juint _super_check_offset;
137
138 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
139 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
140 Symbol* _name;
141
142 // Cache of last observed secondary supertype
143 Klass* _secondary_super_cache;
144 // Array of all secondary supertypes
145 Array<Klass*>* _secondary_supers;
146 // Ordered list of all primary supertypes
147 Klass* _primary_supers[_primary_super_limit];
148 // java/lang/Class instance mirroring this class
149 OopHandle _java_mirror;
150 // Superclass
151 Klass* _super;
152 // First subclass (null if none); _subklass->next_sibling() is next one
153 Klass* volatile _subklass;
154 // Sibling link (or null); links all subklasses of a klass
155 Klass* volatile _next_sibling;
156
157 // All klasses loaded by a class loader are chained through these links
158 Klass* _next_link;
159
160 // The VM's representation of the ClassLoader used to load this class.
161 // Provide access the corresponding instance java.lang.ClassLoader.
162 ClassLoaderData* _class_loader_data;
163
164 markWord _prototype_header; // Used to initialize objects' header
165
166 // Bitmap and hash code used by hashed secondary supers.
167 uintx _secondary_supers_bitmap;
168 uint8_t _hash_slot;
169
170 private:
171 // This is an index into AOTClassLocationConfig::class_locations(), to
172 // indicate the AOTClassLocation where this class is loaded from during
173 // dump time. If a class is not loaded from the AOT cache, this field is
174 // -1.
175 s2 _shared_class_path_index;
176
177 #if INCLUDE_CDS
178 // Various attributes for shared classes. Should be zero for a non-shared class.
179 u2 _shared_class_flags;
180 enum CDSSharedClassFlags {
181 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
182 _archived_lambda_proxy_is_available = 1 << 1,
183 _has_value_based_class_annotation = 1 << 2,
184 _verified_at_dump_time = 1 << 3,
185 _has_archived_enum_objs = 1 << 4,
186 // This class was not loaded from a classfile in the module image
187 // or classpath.
188 _is_generated_shared_class = 1 << 5,
189 // archived mirror already initialized by AOT-cache assembly: no further need to call <clinit>
190 _has_aot_initialized_mirror = 1 << 6,
191 // If this class has been aot-inititalized, do we need to call its runtimeSetup()
192 // method during the production run?
193 _is_runtime_setup_required = 1 << 7,
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 public:
214 int kind() { return _kind; }
215
216 enum class DefaultsLookupMode { find, skip };
217 enum class OverpassLookupMode { find, skip };
218 enum class StaticLookupMode { find, skip };
219 enum class PrivateLookupMode { find, skip };
220
221 virtual bool is_klass() const { return true; }
222
223 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
224 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
225 // If this is not what your code expects, you're probably looking for Klass::java_super().
226 Klass* super() const { return _super; }
227 void set_super(Klass* k) { _super = k; }
228
229 // initializes _super link, _primary_supers & _secondary_supers arrays
230 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
231
232 // klass-specific helper for initializing _secondary_supers
233 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
234 Array<InstanceKlass*>* transitive_interfaces);
235
236 // java_super is the Java-level super type as specified by Class.getSuperClass.
237 virtual InstanceKlass* java_super() const { return nullptr; }
238
239 juint super_check_offset() const { return _super_check_offset; }
240 void set_super_check_offset(juint o) { _super_check_offset = o; }
241
242 Klass* secondary_super_cache() const { return _secondary_super_cache; }
243 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
244
245 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
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
286 // Temporary mirror switch used by RedefineClasses
287 OopHandle java_mirror_handle() const { return _java_mirror; }
288 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
289
290 // Set java mirror OopHandle to null for CDS
291 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
292 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
293
294 // size helper
295 int layout_helper() const { return _layout_helper; }
296 void set_layout_helper(int lh) { _layout_helper = lh; }
297
298 // Note: for instances layout_helper() may include padding.
299 // Use InstanceKlass::contains_field_offset to classify field offsets.
300
301 // sub/superklass links
302 Klass* subklass(bool log = false) const;
303 Klass* next_sibling(bool log = false) const;
304
305 InstanceKlass* superklass() const;
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 void set_is_runtime_setup_required() {
386 assert(has_aot_initialized_mirror(), "sanity");
387 CDS_ONLY(_shared_class_flags |= _is_runtime_setup_required;)
388 }
389 bool is_runtime_setup_required() const {
390 CDS_ONLY(return (_shared_class_flags & _is_runtime_setup_required) != 0;)
391 NOT_CDS(return false;)
392 }
393
394 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
395 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
396 NOT_CDS(return false;)
397 }
398
399 void set_is_shared() {
400 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
401 }
402
403 // Obtain the module or package for this class
404 virtual ModuleEntry* module() const = 0;
405 virtual PackageEntry* package() const = 0;
406
407 protected: // internal accessors
408 void set_subklass(Klass* s);
409 void set_next_sibling(Klass* s);
410
411 private:
412 static uint8_t compute_hash_slot(Symbol* s);
413 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
414 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
415
416 bool search_secondary_supers(Klass* k) const;
417 bool lookup_secondary_supers_table(Klass *k) const;
418 bool linear_search_secondary_supers(const Klass* k) const;
419 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
420
421 public:
422 // Secondary supers table support
423 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
424 GrowableArray<Klass*>* primaries,
425 GrowableArray<Klass*>* secondaries,
426 uintx& bitmap,
427 TRAPS);
428
429 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
430 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
431
432 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
433 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
434
435 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
436 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
437
438 // Compiler support
439 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
440 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
441 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
442 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
443 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
444 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
445 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
446 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
447 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
448 #if INCLUDE_JVMCI
449 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
450 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
451 #endif
452 static ByteSize secondary_supers_bitmap_offset()
453 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
454 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
455 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
456
457 // Unpacking layout_helper:
458 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
459 static const int _lh_instance_slow_path_bit = 0x01;
460 static const int _lh_log2_element_size_shift = BitsPerByte*0;
461 static const int _lh_log2_element_size_mask = BitsPerLong-1;
462 static const int _lh_element_type_shift = BitsPerByte*1;
463 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
464 static const int _lh_header_size_shift = BitsPerByte*2;
465 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
466 static const int _lh_array_tag_bits = 3;
467 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
468
469 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
470 static const unsigned int _lh_array_tag_vt_value = 0Xfffffffd;
471 static const unsigned int _lh_array_tag_obj_value = 0Xfffffffe;
472
473 // null-free array flag bit under the array tag bits, shift one more to get array tag value
474 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
475 static const int _lh_null_free_mask = 1;
476
477 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
478
479 static int layout_helper_size_in_bytes(jint lh) {
480 assert(lh > (jint)_lh_neutral_value, "must be instance");
481 return (int) lh & ~_lh_instance_slow_path_bit;
482 }
483 static bool layout_helper_needs_slow_path(jint lh) {
484 assert(lh > (jint)_lh_neutral_value, "must be instance");
485 return (lh & _lh_instance_slow_path_bit) != 0;
486 }
487 static bool layout_helper_is_instance(jint lh) {
488 return (jint)lh > (jint)_lh_neutral_value;
489 }
490 static bool layout_helper_is_array(jint lh) {
491 return (jint)lh < (jint)_lh_neutral_value;
492 }
493 static bool layout_helper_is_typeArray(jint lh) {
494 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
495 }
496 static bool layout_helper_is_objArray(jint lh) {
497 return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
498 }
499 static bool layout_helper_is_flatArray(jint lh) {
500 return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
501 }
502 static bool layout_helper_is_null_free(jint lh) {
503 assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
504 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
505 }
506 static jint layout_helper_set_null_free(jint lh) {
507 lh |= (_lh_null_free_mask << _lh_null_free_shift);
508 assert(layout_helper_is_null_free(lh), "Bad encoding");
509 return lh;
510 }
511 static int layout_helper_header_size(jint lh) {
512 assert(lh < (jint)_lh_neutral_value, "must be array");
513 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
514 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
515 return hsize;
516 }
517 static BasicType layout_helper_element_type(jint lh) {
518 assert(lh < (jint)_lh_neutral_value, "must be array");
519 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
520 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
521 return (BasicType) btvalue;
522 }
523
524 // Want a pattern to quickly diff against layout header in register
525 // find something less clever!
526 static int layout_helper_boolean_diffbit() {
527 jint zlh = array_layout_helper(T_BOOLEAN);
528 jint blh = array_layout_helper(T_BYTE);
529 assert(zlh != blh, "array layout helpers must differ");
530 int diffbit = 1;
531 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
532 diffbit <<= 1;
533 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
534 }
535 return diffbit;
536 }
537
538 static int layout_helper_log2_element_size(jint lh) {
539 assert(lh < (jint)_lh_neutral_value, "must be array");
540 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
541 assert(layout_helper_element_type(lh) == T_FLAT_ELEMENT || l2esz <= LogBytesPerLong,
542 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
543 return l2esz;
544 }
545 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
546 return (tag << _lh_array_tag_shift)
547 | ((null_free ? 1 : 0) << _lh_null_free_shift)
548 | (hsize << _lh_header_size_shift)
549 | ((int)etype << _lh_element_type_shift)
550 | (log2_esize << _lh_log2_element_size_shift);
551 }
552 static jint instance_layout_helper(jint size, bool slow_path_flag) {
553 return (size << LogBytesPerWord)
554 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
555 }
556 static int layout_helper_to_size_helper(jint lh) {
557 assert(lh > (jint)_lh_neutral_value, "must be instance");
558 // Note that the following expression discards _lh_instance_slow_path_bit.
559 return lh >> LogBytesPerWord;
560 }
561 // Out-of-line version computes everything based on the etype:
562 static jint array_layout_helper(BasicType etype);
563
564 // What is the maximum number of primary superclasses any klass can have?
565 static juint primary_super_limit() { return _primary_super_limit; }
566
567 // vtables
568 klassVtable vtable() const;
569 int vtable_length() const { return _vtable_len; }
570
571 // subclass check
572 bool is_subclass_of(const Klass* k) const;
573
574 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
575 bool is_subtype_of(Klass* k) const;
576
577 public:
578 // Find LCA in class hierarchy
579 Klass *LCA( Klass *k );
580
581 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
582 // if not, throw either an Error or an Exception.
583 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
584
585 // array copying
586 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
587
588 // tells if the class should be initialized
589 virtual bool should_be_initialized() const { return false; }
590 // initializes the klass
591 virtual void initialize(TRAPS);
592 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
593 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
594 OverpassLookupMode overpass_mode,
595 PrivateLookupMode = PrivateLookupMode::find) const;
596 public:
597 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
598 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
599 }
600
601 // array class with specific rank
602 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
603
604 // array class with this klass as element type
605 virtual ArrayKlass* array_klass(TRAPS) = 0;
606
607 // These will return null instead of allocating on the heap:
608 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
609 virtual ArrayKlass* array_klass_or_null() = 0;
610
611 virtual oop protection_domain() const = 0;
612
613 oop class_loader() const;
614
615 inline oop klass_holder() const;
616
617 inline void keep_alive() const;
618
619 protected:
620
621 // Error handling when length > max_length or length < 0
622 static void check_array_allocation_length(int length, int max_length, TRAPS);
623
624 void set_vtable_length(int len) { _vtable_len= len; }
625
626 vtableEntry* start_of_vtable() const;
627 #if INCLUDE_CDS
628 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
629 #endif
630 public:
631 Method* method_at_vtable(int index);
632
633 static ByteSize vtable_start_offset();
634 static ByteSize vtable_length_offset() {
635 return byte_offset_of(Klass, _vtable_len);
636 }
637
638 #if INCLUDE_CDS
639 // CDS support - remove and restore oops from metadata. Oops are not shared.
640 virtual void remove_unshareable_info();
641 virtual void remove_java_mirror();
642
643 bool is_unshareable_info_restored() const {
644 assert(is_shared(), "use this for shared classes only");
645 if (has_archived_mirror_index()) {
646 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
647 return false;
648 } else if (_java_mirror.is_empty()) {
649 return false;
650 } else {
651 return true;
652 }
653 }
654 #endif // INCLUDE_CDS
655
656 public:
657 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
658 // These functions describe behavior for the oop not the KLASS.
659
660 // actual oop size of obj in memory in word size.
661 virtual size_t oop_size(oop obj) const = 0;
662
663 // Size of klass in word size.
664 virtual int size() const = 0;
665
666 // Returns the Java name for a class (Resource allocated)
667 // For arrays, this returns the name of the element with a leading '['.
668 // For classes, this returns the name with the package separators
669 // turned into '.'s.
670 const char* external_name() const;
671 // Returns the name for a class (Resource allocated) as the class
672 // would appear in a signature.
673 // For arrays, this returns the name of the element with a leading '['.
674 // For classes, this returns the name with a leading 'L' and a trailing ';'
675 // and the package separators as '/'.
676 virtual const char* signature_name() const;
677
678 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
679 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
680
681 // Returns "interface", "abstract class" or "class".
682 const char* external_kind() const;
683
684 // type testing operations
685 #ifdef ASSERT
686 protected:
687 virtual bool is_instance_klass_slow() const { return false; }
688 virtual bool is_array_klass_slow() const { return false; }
689 virtual bool is_objArray_klass_slow() const { return false; }
690 virtual bool is_typeArray_klass_slow() const { return false; }
691 virtual bool is_flatArray_klass_slow() const { return false; }
692 #endif // ASSERT
693 // current implementation uses this method even in non debug builds
694 virtual bool is_inline_klass_slow() const { return false; }
695 public:
696
697 // Fast non-virtual versions
698 #ifndef ASSERT
699 #define assert_same_query(xval, xcheck) xval
700 #else
701 private:
702 static bool assert_same_query(bool xval, bool xslow) {
703 assert(xval == xslow, "slow and fast queries agree");
704 return xval;
705 }
706 public:
707 #endif
708
709 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
710 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
711 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
712 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
713 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
714 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
715 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
716 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
717 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
718 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
719 #undef assert_same_query
720
721 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
722
723 // Access flags
724 AccessFlags access_flags() const { return _access_flags; }
725 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
726
727 bool is_public() const { return _access_flags.is_public(); }
728 bool is_final() const { return _access_flags.is_final(); }
729 bool is_interface() const { return _access_flags.is_interface(); }
730 bool is_abstract() const { return _access_flags.is_abstract(); }
731 bool is_synthetic() const { return _access_flags.is_synthetic(); }
732 bool is_identity_class() const { return _access_flags.is_identity_class(); }
733 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
734 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
735 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
736 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
737 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
738 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
739 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
740
741 klass_flags_t misc_flags() const { return _misc_flags.value(); }
742
743 inline bool is_non_strong_hidden() const;
744
745 bool is_cloneable() const;
746 void set_is_cloneable();
747
748 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
749 inline markWord prototype_header() const;
750 inline void set_prototype_header(markWord header);
751 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
752 static inline markWord default_prototype_header(Klass* k);
753
754 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
755
756 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
757 virtual MetaspaceObj::Type type() const { return ClassType; }
758
759 inline bool is_loader_alive() const;
760
761 void clean_subklass();
762
763 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
764 static void clean_subklass_tree() {
765 clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
766 }
767
768 // Return self, except for abstract classes with exactly 1
769 // implementor. Then return the 1 concrete implementation.
770 Klass *up_cast_abstract();
771
772 // klass name
773 Symbol* name() const { return _name; }
774 void set_name(Symbol* n);
775
776 virtual void release_C_heap_structures(bool release_constant_pool = true);
777
778 public:
779 // Get modifier flags from Java mirror cache.
780 int modifier_flags() const;
781
782 // Compute modifier flags from the original data. This also allows
783 // accessing flags when Java mirror is already dead, e.g. during class
784 // unloading.
785 virtual u2 compute_modifier_flags() const = 0;
786
787 // JVMTI support
788 virtual jint jvmti_class_status() const;
789
790 // Printing
791 virtual void print_on(outputStream* st) const;
792
793 virtual void oop_print_value_on(oop obj, outputStream* st);
794 virtual void oop_print_on (oop obj, outputStream* st);
795
796 void print_secondary_supers_on(outputStream* st) const;
797
798 virtual const char* internal_name() const = 0;
799
800 // Verification
801 virtual void verify_on(outputStream* st);
802 void verify() { verify_on(tty); }
803
804 #ifndef PRODUCT
805 bool verify_vtable_index(int index);
806 #endif
807
808 virtual void oop_verify_on(oop obj, outputStream* st);
809
810 // for error reporting
811 static bool is_valid(Klass* k);
812
813 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
814
815 // Returns true if this Klass needs to be addressable via narrow Klass ID.
816 inline bool needs_narrow_id() const;
817
818 };
819
820 #endif // SHARE_OOPS_KLASS_HPP