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.
18 *
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.
22 *
23 */
24
25 #ifndef SHARE_OOPS_KLASS_HPP
26 #define SHARE_OOPS_KLASS_HPP
27
28 #include "oops/klassFlags.hpp"
29 #include "oops/markWord.hpp"
30 #include "oops/metadata.hpp"
31 #include "oops/oop.hpp"
32 #include "oops/oopHandle.hpp"
33 #include "utilities/accessFlags.hpp"
34 #include "utilities/macros.hpp"
35 #if INCLUDE_JFR
36 #include "jfr/support/jfrTraceIdExtension.hpp"
37 #endif
38
39 //
40 // A Klass provides:
41 // 1: language level class object (method dictionary etc.)
42 // 2: provide vm dispatch behavior for the object
43 // Both functions are combined into one C++ class.
44
45 // One reason for the oop/klass dichotomy in the implementation is
46 // that we don't want a C++ vtbl pointer in every object. Thus,
47 // normal oops don't have any virtual functions. Instead, they
48 // forward all "virtual" functions to their klass, which does have
49 // a vtbl and does the C++ dispatch depending on the object's
50 // actual type. (See oop.inline.hpp for some of the forwarding code.)
51 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
52
53 // Forward declarations.
54 template <class T> class Array;
55 template <class T> class GrowableArray;
56 class ClassLoaderData;
57 class fieldDescriptor;
58 class klassVtable;
59 class ModuleEntry;
60 class PackageEntry;
61 class vtableEntry;
62
63 class Klass : public Metadata {
64
65 friend class VMStructs;
66 friend class JVMCIVMStructs;
67 public:
68 // Klass Kinds for all subclasses of Klass
69 enum KlassKind : u2
70 {
71 InstanceKlassKind,
72 InlineKlassKind,
73 InstanceRefKlassKind,
74 InstanceMirrorKlassKind,
75 InstanceClassLoaderKlassKind,
76 InstanceStackChunkKlassKind,
77 TypeArrayKlassKind,
78 ObjArrayKlassKind,
79 RefArrayKlassKind,
80 FlatArrayKlassKind,
81 UnknownKlassKind
82 };
83
84 static const uint KLASS_KIND_COUNT = FlatArrayKlassKind + 1;
85 protected:
86
87 // If you add a new field that points to any metaspace object, you
88 // must add this field to Klass::metaspace_pointers_do().
89
90 // note: put frequently-used fields together at start of klass structure
91 // for better cache behavior (may not make much of a difference but sure won't hurt)
92 enum { _primary_super_limit = 8 };
93
94 // The "layout helper" is a combined descriptor of object layout.
95 // For klasses which are neither instance nor array, the value is zero.
96 //
97 // For instances, layout helper is a positive number, the instance size.
98 // This size is already passed through align_object_size and scaled to bytes.
99 // The low order bit is set if instances of this class cannot be
100 // allocated using the fastpath.
101 //
102 // For arrays, layout helper is a negative number, containing four
103 // distinct bytes, as follows:
104 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
105 // where:
106 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
107 // hsz is array header size in bytes (i.e., offset of first element)
108 // ebt is the BasicType of the elements
109 // esz is the element size in bytes
110 // This packed word is arranged so as to be quickly unpacked by the
111 // various fast paths that use the various subfields.
112 //
113 // The esz bits can be used directly by a SLL instruction, without masking.
114 //
115 // Note that the array-kind tag looks like 0x00 for instance klasses,
116 // since their length in bytes is always less than 24Mb.
117 //
118 // Final note: This comes first, immediately after C++ vtable,
119 // because it is frequently queried.
120 jint _layout_helper;
121
122 // Klass kind used to resolve the runtime type of the instance.
123 // - Used to implement devirtualized oop closure dispatching.
124 // - Various type checking in the JVM
125 const KlassKind _kind;
126
127 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
128 // Some flags created by the JVM, not in the class file itself,
129 // are in _misc_flags below.
130 KlassFlags _misc_flags;
131
132 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
133 // and _primary_supers all help make fast subtype checks. See big discussion
134 // in doc/server_compiler/checktype.txt
135 //
136 // Where to look to observe a supertype (it is &_secondary_super_cache for
137 // secondary supers, else is &_primary_supers[depth()].
138 juint _super_check_offset;
139
140 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
141 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
142 Symbol* _name;
143
144 // Cache of last observed secondary supertype
145 Klass* _secondary_super_cache;
146 // Array of all secondary supertypes
147 Array<Klass*>* _secondary_supers;
148 // Ordered list of all primary supertypes
149 Klass* _primary_supers[_primary_super_limit];
150 // java/lang/Class instance mirroring this class
151 OopHandle _java_mirror;
152 // Superclass
153 Klass* _super;
154 // First subclass (null if none); _subklass->next_sibling() is next one
155 Klass* volatile _subklass;
156 // Sibling link (or null); links all subklasses of a klass
157 Klass* volatile _next_sibling;
158
159 // All klasses loaded by a class loader are chained through these links
160 Klass* _next_link;
161
162 // The VM's representation of the ClassLoader used to load this class.
163 // Provide access the corresponding instance java.lang.ClassLoader.
164 ClassLoaderData* _class_loader_data;
165
166 markWord _prototype_header; // Used to initialize objects' header
167
168 // Bitmap and hash code used by hashed secondary supers.
169 uintx _secondary_supers_bitmap;
170 uint8_t _hash_slot;
171
172 private:
173 // This is an index into AOTClassLocationConfig::class_locations(), to
174 // indicate the AOTClassLocation where this class is loaded from during
175 // dump time. If a class is not loaded from the AOT cache, this field is
176 // -1.
177 s2 _shared_class_path_index;
178
179 #if INCLUDE_CDS
180 // Various attributes for shared classes. Should be zero for a non-shared class.
181 u2 _aot_class_flags;
182 enum {
183 _in_aot_cache = 1 << 0,
184 _archived_lambda_proxy_is_available = 1 << 1,
185 _has_value_based_class_annotation = 1 << 2,
186 _verified_at_dump_time = 1 << 3,
187 _has_archived_enum_objs = 1 << 4,
188 _is_aot_generated_class = 1 << 5, // this class was not loaded from a classfile in the module image
189 // or classpath, but was generated during AOT cache assembly.
190 _has_aot_initialized_mirror = 1 << 6, // archived mirror already initialized by AOT cache assembly.
191 // no further need to call <clinit>
192 _has_aot_safe_initializer = 1 << 7, // has @AOTSafeClassInitializer annotation
193 _is_runtime_setup_required = 1 << 8, // has a runtimeSetup method to be called when
194 // this class is loaded from AOT cache
195 };
196 #endif
197
198 int _vtable_len; // vtable length. This field may be read very often when we
199 // have lots of itable dispatches (e.g., lambdas and streams).
200 // Keep it away from the beginning of a Klass to avoid cacheline
201 // contention that may happen when a nearby object is modified.
202
203 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
204
205 public:
206
207 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
208
209 protected:
210
211 Klass(KlassKind kind, markWord prototype_header = markWord::prototype());
212 Klass();
213
214 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
215
216 public:
217 int kind() { return _kind; }
218
219 enum class DefaultsLookupMode { find, skip };
220 enum class OverpassLookupMode { find, skip };
221 enum class StaticLookupMode { find, skip };
222 enum class PrivateLookupMode { find, skip };
223
224 virtual bool is_klass() const { return true; }
225
226 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
227 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
228 // If this is not what your code expects, you're probably looking for:
229 // - Klass::java_super() - if you have a Klass*
230 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
231 Klass* super() const { return _super; }
232 void set_super(Klass* k) { _super = k; }
233
234 // initializes _super link, _primary_supers & _secondary_supers arrays
235 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
236
237 // klass-specific helper for initializing _secondary_supers
238 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
239 Array<InstanceKlass*>* transitive_interfaces);
240
241 // java_super is the Java-level super type as specified by Class.getSuperClass.
242 virtual InstanceKlass* java_super() const { return nullptr; }
243
244 juint super_check_offset() const { return _super_check_offset; }
245 void set_super_check_offset(juint o) { _super_check_offset = o; }
246
247 Klass* secondary_super_cache() const { return _secondary_super_cache; }
248 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
249
250 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
251 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
252
253 uint8_t hash_slot() const { return _hash_slot; }
254
255 // Return the element of the _super chain of the given depth.
256 // If there is no such element, return either null or this.
257 Klass* primary_super_of_depth(juint i) const {
258 assert(i < primary_super_limit(), "oob");
259 Klass* super = _primary_supers[i];
260 assert(super == nullptr || super->super_depth() == i, "correct display");
261 return super;
262 }
263
264 // Can this klass be a primary super? False for interfaces and arrays of
265 // interfaces. False also for arrays or classes with long super chains.
266 bool can_be_primary_super() const {
267 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
268 return super_check_offset() != secondary_offset;
269 }
270 virtual bool can_be_primary_super_slow() const;
271
272 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
273 juint super_depth() const {
274 if (!can_be_primary_super()) {
275 return primary_super_limit();
276 } else {
277 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
278 assert(d < primary_super_limit(), "oob");
279 assert(_primary_supers[d] == this, "proper init");
280 return d;
281 }
282 }
283
284 // java mirror
285 oop java_mirror() const;
286 oop java_mirror_no_keepalive() const;
287 void set_java_mirror(Handle m);
288
289 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
290
291 // Temporary mirror switch used by RedefineClasses
292 OopHandle java_mirror_handle() const { return _java_mirror; }
293 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
294
295 // Set java mirror OopHandle to null for CDS
296 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
297 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
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() const;
308 Klass* next_sibling(bool log = false) const;
309
310 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
311
312 void set_next_link(Klass* k) { _next_link = k; }
313 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
314 Klass** next_link_addr() { return &_next_link; }
315
316 // class loader data
317 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
318 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
319
320 s2 shared_classpath_index() const {
321 return _shared_class_path_index;
322 };
323
324 void set_shared_classpath_index(s2 index) {
325 _shared_class_path_index = index;
326 };
327
328 bool has_archived_mirror_index() const {
329 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
330 NOT_CDS_JAVA_HEAP(return false);
331 }
332
333 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
334
335 void set_lambda_proxy_is_available() {
336 CDS_ONLY(_aot_class_flags |= _archived_lambda_proxy_is_available;)
337 }
338 void clear_lambda_proxy_is_available() {
339 CDS_ONLY(_aot_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
340 }
341 bool lambda_proxy_is_available() const {
342 CDS_ONLY(return (_aot_class_flags & _archived_lambda_proxy_is_available) != 0;)
343 NOT_CDS(return false;)
344 }
345
346 void set_has_value_based_class_annotation() {
347 CDS_ONLY(_aot_class_flags |= _has_value_based_class_annotation;)
348 }
349 void clear_has_value_based_class_annotation() {
350 CDS_ONLY(_aot_class_flags &= (u2)(~_has_value_based_class_annotation);)
351 }
352 bool has_value_based_class_annotation() const {
353 CDS_ONLY(return (_aot_class_flags & _has_value_based_class_annotation) != 0;)
354 NOT_CDS(return false;)
355 }
356
357 void set_verified_at_dump_time() {
358 CDS_ONLY(_aot_class_flags |= _verified_at_dump_time;)
359 }
360 bool verified_at_dump_time() const {
361 CDS_ONLY(return (_aot_class_flags & _verified_at_dump_time) != 0;)
362 NOT_CDS(return false;)
363 }
364
365 void set_has_archived_enum_objs() {
366 CDS_ONLY(_aot_class_flags |= _has_archived_enum_objs;)
367 }
368 bool has_archived_enum_objs() const {
369 CDS_ONLY(return (_aot_class_flags & _has_archived_enum_objs) != 0;)
370 NOT_CDS(return false;)
371 }
372
373 void set_is_aot_generated_class() {
374 CDS_ONLY(_aot_class_flags |= _is_aot_generated_class;)
375 }
376 bool is_aot_generated_class() const {
377 CDS_ONLY(return (_aot_class_flags & _is_aot_generated_class) != 0;)
378 NOT_CDS(return false;)
379 }
380
381 void set_has_aot_initialized_mirror() {
382 CDS_ONLY(_aot_class_flags |= _has_aot_initialized_mirror;)
383 }
384 bool has_aot_initialized_mirror() const {
385 CDS_ONLY(return (_aot_class_flags & _has_aot_initialized_mirror) != 0;)
386 NOT_CDS(return false;)
387 }
388
389 // Indicates presence of @AOTSafeClassInitializer. Also see AOTClassInitializer for more details.
390 void set_has_aot_safe_initializer() {
391 CDS_ONLY(_aot_class_flags |= _has_aot_safe_initializer;)
392 }
393 bool has_aot_safe_initializer() const {
394 CDS_ONLY(return (_aot_class_flags & _has_aot_safe_initializer) != 0;)
395 NOT_CDS(return false;)
396 }
397
398 // Indicates @AOTRuntimeSetup private static void runtimeSetup() presence.
399 void set_is_runtime_setup_required() {
400 CDS_ONLY(_aot_class_flags |= _is_runtime_setup_required;)
401 }
402 bool is_runtime_setup_required() const {
403 CDS_ONLY(return (_aot_class_flags & _is_runtime_setup_required) != 0;)
404 NOT_CDS(return false;)
405 }
406
407 bool in_aot_cache() const { // shadows MetaspaceObj::in_aot_cache)()
408 CDS_ONLY(return (_aot_class_flags & _in_aot_cache) != 0;)
409 NOT_CDS(return false;)
410 }
411
412 void set_in_aot_cache() {
413 CDS_ONLY(_aot_class_flags |= _in_aot_cache;)
414 }
415
416 // Obtain the module or package for this class
417 virtual ModuleEntry* module() const = 0;
418 virtual PackageEntry* package() const = 0;
419
420 void set_next_sibling(Klass* s);
421 protected: // internal accessors
422 void set_subklass(Klass* s);
423
424 private:
425 static uint8_t compute_hash_slot(Symbol* s);
426 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
427 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
428
429 bool search_secondary_supers(Klass* k) const;
430 bool lookup_secondary_supers_table(Klass *k) const;
431 bool linear_search_secondary_supers(const Klass* k) const;
432 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
433
434 public:
435 // Secondary supers table support
436 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
437 GrowableArray<Klass*>* primaries,
438 GrowableArray<Klass*>* secondaries,
439 uintx& bitmap,
440 TRAPS);
441
442 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
443 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
444
445 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
446 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
447
448 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
449 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
450
451 // Compiler support
452 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
453 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
454 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
455 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
456 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
457 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
458 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
459 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
460 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
461 #if INCLUDE_JVMCI
462 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
463 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
464 #endif
465 static ByteSize secondary_supers_bitmap_offset()
466 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
467 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
468 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
469
470 // Unpacking layout_helper:
471 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
472 static const int _lh_instance_slow_path_bit = 0x01;
473 static const int _lh_log2_element_size_shift = BitsPerByte*0;
474 static const int _lh_log2_element_size_mask = BitsPerLong-1;
475 static const int _lh_element_type_shift = BitsPerByte*1;
476 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
477 static const int _lh_header_size_shift = BitsPerByte*2;
478 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
479 static const int _lh_array_tag_bits = 4;
480 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
481
482 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
483 static const unsigned int _lh_array_tag_flat_value = 0Xfffffffa;
484 static const unsigned int _lh_array_tag_ref_value = 0Xfffffff8;
485
486 // null-free array flag bit under the array tag bits, shift one more to get array tag value
487 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
488 static const int _lh_null_free_mask = 1;
489
490 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << (_lh_array_tag_shift + 1));
491
492 static int layout_helper_size_in_bytes(jint lh) {
493 assert(lh > (jint)_lh_neutral_value, "must be instance");
494 return (int) lh & ~_lh_instance_slow_path_bit;
495 }
496 static bool layout_helper_needs_slow_path(jint lh) {
497 assert(lh > (jint)_lh_neutral_value, "must be instance");
498 return (lh & _lh_instance_slow_path_bit) != 0;
499 }
500 static bool layout_helper_is_instance(jint lh) {
501 return (jint)lh > (jint)_lh_neutral_value;
502 }
503 static bool layout_helper_is_array(jint lh) {
504 return (jint)lh < (jint)_lh_neutral_value;
505 }
506 static bool layout_helper_is_typeArray(jint lh) {
507 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
508 }
509 static bool layout_helper_is_refArray(jint lh) {
510 return (juint)_lh_array_tag_ref_value == (juint)(lh >> _lh_array_tag_shift);
511 }
512 static bool layout_helper_is_flatArray(jint lh) {
513 return (juint)_lh_array_tag_flat_value == (juint)(lh >> _lh_array_tag_shift);
514 }
515 static bool layout_helper_is_null_free(jint lh) {
516 assert(layout_helper_is_flatArray(lh) || layout_helper_is_refArray(lh), "must be array of inline types");
517 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
518 }
519 static jint layout_helper_set_null_free(jint lh) {
520 lh |= (_lh_null_free_mask << _lh_null_free_shift);
521 assert(layout_helper_is_null_free(lh), "Bad encoding");
522 return lh;
523 }
524 static int layout_helper_header_size(jint lh) {
525 assert(lh < (jint)_lh_neutral_value, "must be array");
526 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
527 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
528 return hsize;
529 }
530 static BasicType layout_helper_element_type(jint lh) {
531 assert(lh < (jint)_lh_neutral_value, "must be array");
532 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
533 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_FLAT_ELEMENT, "sanity");
534 return (BasicType) btvalue;
535 }
536
537 // Want a pattern to quickly diff against layout header in register
538 // find something less clever!
539 static int layout_helper_boolean_diffbit() {
540 jint zlh = array_layout_helper(T_BOOLEAN);
541 jint blh = array_layout_helper(T_BYTE);
542 assert(zlh != blh, "array layout helpers must differ");
543 int diffbit = 1;
544 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
545 diffbit <<= 1;
546 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
547 }
548 return diffbit;
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 Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
606 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
607 OverpassLookupMode overpass_mode,
608 PrivateLookupMode = PrivateLookupMode::find) const;
609 public:
610 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
611 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
612 }
613
614 // array class with specific rank
615 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
616
617 // array class with this klass as element type
618 virtual ArrayKlass* array_klass(TRAPS) = 0;
619
620 // These will return null instead of allocating on the heap:
621 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
622 virtual ArrayKlass* array_klass_or_null() = 0;
623
624 virtual oop protection_domain() const = 0;
625
626 oop class_loader() const;
627
628 inline oop klass_holder() const;
629
630 inline void keep_alive() const;
631
632 protected:
633
634 // Error handling when length > max_length or length < 0
635 static void check_array_allocation_length(int length, int max_length, TRAPS);
636
637 void set_vtable_length(int len) { _vtable_len= len; }
638
639 vtableEntry* start_of_vtable() const;
640 #if INCLUDE_CDS
641 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
642 #endif
643 public:
644 Method* method_at_vtable(int index);
645
646 static ByteSize vtable_start_offset();
647 static ByteSize vtable_length_offset() {
648 return byte_offset_of(Klass, _vtable_len);
649 }
650
651 #if INCLUDE_CDS
652 // CDS support - remove and restore oops from metadata. Oops are not shared.
653 virtual void remove_unshareable_info();
654 virtual void remove_java_mirror();
655
656 bool is_unshareable_info_restored() const {
657 assert(in_aot_cache(), "use this for shared classes only");
658 if (has_archived_mirror_index()) {
659 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
660 return false;
661 } else if (_java_mirror.is_empty()) {
662 return false;
663 } else {
664 return true;
665 }
666 }
667 #endif // INCLUDE_CDS
668
669 public:
670 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
671 // These functions describe behavior for the oop not the KLASS.
672
673 // actual oop size of obj in memory in word size.
674 virtual size_t oop_size(oop obj) const = 0;
675
676 // Size of klass in word size.
677 virtual int size() const = 0;
678
679 // Returns the Java name for a class (Resource allocated)
680 // For arrays, this returns the name of the element with a leading '['.
681 // For classes, this returns the name with the package separators
682 // turned into '.'s.
683 const char* external_name() const;
684 // Returns the name for a class (Resource allocated) as the class
685 // would appear in a signature.
686 // For arrays, this returns the name of the element with a leading '['.
687 // For classes, this returns the name with a leading 'L' and a trailing ';'
688 // and the package separators as '/'.
689 virtual const char* signature_name() const;
690
691 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
692 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
693
694 // Returns "interface", "abstract class" or "class".
695 const char* external_kind() const;
696
697 // type testing operations
698 #ifdef ASSERT
699 protected:
700 virtual bool is_instance_klass_slow() const { return false; }
701 virtual bool is_array_klass_slow() const { return false; }
702 virtual bool is_objArray_klass_slow() const { return false; }
703 virtual bool is_refArray_klass_slow() const { return false; }
704 virtual bool is_typeArray_klass_slow() const { return false; }
705 virtual bool is_flatArray_klass_slow() const { return false; }
706 #endif // ASSERT
707 // current implementation uses this method even in non debug builds
708 virtual bool is_inline_klass_slow() const { return false; }
709 public:
710
711 // Fast non-virtual versions
712 #ifndef ASSERT
713 #define assert_same_query(xval, xcheck) xval
714 #else
715 private:
716 static bool assert_same_query(bool xval, bool xslow) {
717 assert(xval == xslow, "slow and fast queries agree");
718 return xval;
719 }
720 public:
721 #endif
722
723 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
724 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
725 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
726 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
727 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
728 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
729 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
730 bool is_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
731 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind || _kind == RefArrayKlassKind || _kind == FlatArrayKlassKind, is_objArray_klass_slow()); }
732 bool is_refArray_klass() const { return assert_same_query( _kind == RefArrayKlassKind, is_refArray_klass_slow()); }
733 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
734 bool is_refined_objArray_klass() const { return is_refArray_klass() || is_flatArray_klass(); }
735 #undef assert_same_query
736
737 inline bool is_null_free_array_klass() const { return !is_typeArray_klass() && layout_helper_is_null_free(layout_helper()); }
738
739 // Access flags
740 AccessFlags access_flags() const { return _access_flags; }
741 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
742
743 bool is_public() const { return _access_flags.is_public(); }
744 bool is_final() const { return _access_flags.is_final(); }
745 bool is_interface() const { return _access_flags.is_interface(); }
746 bool is_abstract() const { return _access_flags.is_abstract(); }
747 bool is_synthetic() const { return _access_flags.is_synthetic(); }
748 bool is_identity_class() const { assert(is_instance_klass(), "only for instanceKlass"); return _access_flags.is_identity_class(); }
749 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
750 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
751 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
752 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
753 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
754 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
755 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
756
757 klass_flags_t misc_flags() const { return _misc_flags.value(); }
758
759 inline bool is_non_strong_hidden() const;
760
761 bool is_cloneable() const;
762 void set_is_cloneable();
763
764 static inline markWord make_prototype_header(const Klass* kls, markWord prototype = markWord::prototype());
765 inline markWord prototype_header() const;
766 inline void set_prototype_header(markWord header);
767 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
768 inline void set_prototype_header_klass(narrowKlass klass);
769
770 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
771
772 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
773 virtual MetaspaceObj::Type type() const { return ClassType; }
774
775 inline bool is_loader_alive() const;
776 inline bool is_loader_present_and_alive() const;
777
778 Klass* clean_subklass(bool log = false);
779
780 // Clean out unnecessary weak klass links from the whole klass hierarchy.
781 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
782 // Clean out unnecessary weak klass links from the given InstanceKlass.
783 static void clean_weak_instanceklass_links(InstanceKlass* ik);
784
785 // Return self, except for abstract classes with exactly 1
786 // implementor. Then return the 1 concrete implementation.
787 Klass *up_cast_abstract();
788
789 // klass name
790 Symbol* name() const { return _name; }
791 void set_name(Symbol* n);
792
793 virtual void release_C_heap_structures(bool release_constant_pool = true);
794
795 public:
796 // Get modifier flags from Java mirror cache.
797 int modifier_flags() const;
798
799 // Compute modifier flags from the original data. This also allows
800 // accessing flags when Java mirror is already dead, e.g. during class
801 // unloading.
802 virtual u2 compute_modifier_flags() const = 0;
803
804 // JVMTI support
805 virtual jint jvmti_class_status() const;
806
807 // Printing
808 virtual void print_on(outputStream* st) const;
809
810 virtual void oop_print_value_on(oop obj, outputStream* st);
811 virtual void oop_print_on (oop obj, outputStream* st);
812
813 void print_secondary_supers_on(outputStream* st) const;
814
815 virtual const char* internal_name() const = 0;
816
817 // Verification
818 virtual void verify_on(outputStream* st);
819 void verify() { verify_on(tty); }
820
821 #ifndef PRODUCT
822 bool verify_vtable_index(int index);
823 #endif
824
825 virtual void oop_verify_on(oop obj, outputStream* st);
826
827 // for error reporting
828 static bool is_valid(Klass* k);
829
830 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
831 };
832
833 #endif // SHARE_OOPS_KLASS_HPP