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 *
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 ClassLoaderData;
56 class fieldDescriptor;
57 class klassVtable;
58 class ModuleEntry;
59 class PackageEntry;
60 class vtableEntry;
61
62 class Klass : public Metadata {
63
64 friend class VMStructs;
65 friend class JVMCIVMStructs;
66 public:
67 // Klass Kinds for all subclasses of Klass
68 enum KlassKind : u2 {
69 InstanceKlassKind,
70 InstanceRefKlassKind,
71 InstanceMirrorKlassKind,
72 InstanceClassLoaderKlassKind,
73 InstanceStackChunkKlassKind,
74 TypeArrayKlassKind,
75 ObjArrayKlassKind,
76 UnknownKlassKind
77 };
78
79 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
80 protected:
81
82 // If you add a new field that points to any metaspace object, you
83 // must add this field to Klass::metaspace_pointers_do().
84
85 // note: put frequently-used fields together at start of klass structure
86 // for better cache behavior (may not make much of a difference but sure won't hurt)
87 enum { _primary_super_limit = 8 };
88
89 // The "layout helper" is a combined descriptor of object layout.
90 // For klasses which are neither instance nor array, the value is zero.
91 //
92 // For instances, layout helper is a positive number, the instance size.
93 // This size is already passed through align_object_size and scaled to bytes.
94 // The low order bit is set if instances of this class cannot be
95 // allocated using the fastpath.
96 //
97 // For arrays, layout helper is a negative number, containing four
98 // distinct bytes, as follows:
99 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
100 // where:
101 // tag is 0x80 if the elements are oops, 0xC0 if non-oops
102 // hsz is array header size in bytes (i.e., offset of first element)
103 // ebt is the BasicType of the elements
104 // esz is the element size in bytes
105 // This packed word is arranged so as to be quickly unpacked by the
106 // various fast paths that use the various subfields.
107 //
108 // The esz bits can be used directly by a SLL instruction, without masking.
109 //
110 // Note that the array-kind tag looks like 0x00 for instance klasses,
111 // since their length in bytes is always less than 24Mb.
112 //
113 // Final note: This comes first, immediately after C++ vtable,
114 // because it is frequently queried.
115 jint _layout_helper;
116
117 // Klass kind used to resolve the runtime type of the instance.
118 // - Used to implement devirtualized oop closure dispatching.
119 // - Various type checking in the JVM
120 const KlassKind _kind;
121
185 // no further need to call <clinit>
186 _has_aot_safe_initializer = 1 << 7, // has @AOTSafeClassInitializer annotation
187 _is_runtime_setup_required = 1 << 8, // has a runtimeSetup method to be called when
188 // this class is loaded from AOT cache
189 };
190 #endif
191
192 int _vtable_len; // vtable length. This field may be read very often when we
193 // have lots of itable dispatches (e.g., lambdas and streams).
194 // Keep it away from the beginning of a Klass to avoid cacheline
195 // contention that may happen when a nearby object is modified.
196
197 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
198
199 public:
200
201 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
202
203 protected:
204
205 Klass(KlassKind kind);
206 Klass();
207
208 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
209
210 public:
211 int kind() { return _kind; }
212
213 enum class DefaultsLookupMode { find, skip };
214 enum class OverpassLookupMode { find, skip };
215 enum class StaticLookupMode { find, skip };
216 enum class PrivateLookupMode { find, skip };
217
218 bool is_klass() const override { return true; }
219
220 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
221 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
222 // If this is not what your code expects, you're probably looking for:
223 // - Klass::java_super() - if you have a Klass*
224 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
225 Klass* super() const { return _super; }
452 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
453 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
454 #if INCLUDE_JVMCI
455 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
456 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
457 #endif
458 static ByteSize secondary_supers_bitmap_offset()
459 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
460 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
461 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
462
463 // Unpacking layout_helper:
464 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
465 static const int _lh_instance_slow_path_bit = 0x01;
466 static const int _lh_log2_element_size_shift = BitsPerByte*0;
467 static const int _lh_log2_element_size_mask = BitsPerLong-1;
468 static const int _lh_element_type_shift = BitsPerByte*1;
469 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
470 static const int _lh_header_size_shift = BitsPerByte*2;
471 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
472 static const int _lh_array_tag_bits = 2;
473 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
474 static const int _lh_array_tag_obj_value = ~0x01; // 0x80000000 >> 30
475
476 static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00, // 0xC0000000 >> 30
477
478 static int layout_helper_size_in_bytes(jint lh) {
479 assert(lh > (jint)_lh_neutral_value, "must be instance");
480 return (int) lh & ~_lh_instance_slow_path_bit;
481 }
482 static bool layout_helper_needs_slow_path(jint lh) {
483 assert(lh > (jint)_lh_neutral_value, "must be instance");
484 return (lh & _lh_instance_slow_path_bit) != 0;
485 }
486 static bool layout_helper_is_instance(jint lh) {
487 return (jint)lh > (jint)_lh_neutral_value;
488 }
489 static bool layout_helper_is_array(jint lh) {
490 return (jint)lh < (jint)_lh_neutral_value;
491 }
492 static bool layout_helper_is_typeArray(jint lh) {
493 // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
494 return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
495 }
496 static bool layout_helper_is_objArray(jint lh) {
497 // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
498 return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
499 }
500 static int layout_helper_header_size(jint lh) {
501 assert(lh < (jint)_lh_neutral_value, "must be array");
502 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
503 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
504 return hsize;
505 }
506 static BasicType layout_helper_element_type(jint lh) {
507 assert(lh < (jint)_lh_neutral_value, "must be array");
508 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
509 assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
510 return (BasicType) btvalue;
511 }
512
513 // Return a value containing a single set bit that is in the bitset difference between the
514 // layout helpers for array-of-boolean and array-of-byte.
515 static int layout_helper_boolean_diffbit() {
516 uint zlh = static_cast<uint>(array_layout_helper(T_BOOLEAN));
517 uint blh = static_cast<uint>(array_layout_helper(T_BYTE));
518 // get all the bits that are set in zlh and clear in blh
519 uint candidates = (zlh & ~blh);
520 assert(candidates != 0, "must be"); // must be some if there is a solution.
521 // Use well known bit hack to isolate the low bit of candidates.
522 uint result = candidates & (-candidates);
523 assert(is_power_of_2(result), "must be power of 2");
524 assert((result & zlh) != 0, "must be set in alh of T_BOOLEAN");
525 assert((result & blh) == 0, "must be clear in alh of T_BYTE");
526 return static_cast<int>(result);
527 }
528
529 static int layout_helper_log2_element_size(jint lh) {
530 assert(lh < (jint)_lh_neutral_value, "must be array");
531 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
532 assert(l2esz <= LogBytesPerLong,
533 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
534 return l2esz;
535 }
536 static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
537 return (tag << _lh_array_tag_shift)
538 | (hsize << _lh_header_size_shift)
539 | ((int)etype << _lh_element_type_shift)
540 | (log2_esize << _lh_log2_element_size_shift);
541 }
542 static jint instance_layout_helper(jint size, bool slow_path_flag) {
543 return (size << LogBytesPerWord)
544 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
545 }
546 static int layout_helper_to_size_helper(jint lh) {
547 assert(lh > (jint)_lh_neutral_value, "must be instance");
548 // Note that the following expression discards _lh_instance_slow_path_bit.
549 return lh >> LogBytesPerWord;
550 }
551 // Out-of-line version computes everything based on the etype:
552 static jint array_layout_helper(BasicType etype);
553
554 // What is the maximum number of primary superclasses any klass can have?
555 static juint primary_super_limit() { return _primary_super_limit; }
556
557 // vtables
658 const char* external_name() const;
659 // Returns the name for a class (Resource allocated) as the class
660 // would appear in a signature.
661 // For arrays, this returns the name of the element with a leading '['.
662 // For classes, this returns the name with a leading 'L' and a trailing ';'
663 // and the package separators as '/'.
664 virtual const char* signature_name() const;
665
666 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
667 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
668
669 // Returns "interface", "abstract class" or "class".
670 const char* external_kind() const;
671
672 // type testing operations
673 #ifdef ASSERT
674 protected:
675 virtual bool is_instance_klass_slow() const { return false; }
676 virtual bool is_array_klass_slow() const { return false; }
677 virtual bool is_objArray_klass_slow() const { return false; }
678 virtual bool is_typeArray_klass_slow() const { return false; }
679 #endif // ASSERT
680 public:
681
682 // Fast non-virtual versions
683 #ifndef ASSERT
684 #define assert_same_query(xval, xcheck) xval
685 #else
686 private:
687 static bool assert_same_query(bool xval, bool xslow) {
688 assert(xval == xslow, "slow and fast queries agree");
689 return xval;
690 }
691 public:
692 #endif
693
694 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
695 // Other is anything that is not one of the more specialized kinds of InstanceKlass.
696 bool is_other_instance_klass() const { return _kind == InstanceKlassKind; }
697 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
698 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
699 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
700 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
701 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
702 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
703 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
704 #undef assert_same_query
705
706
707 virtual bool is_interface() const { return false; }
708 virtual bool is_abstract() const { return false; }
709
710 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
711 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
712 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
713 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
714 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
715 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
716
717 klass_flags_t misc_flags() const { return _misc_flags.value(); }
718
719 inline bool is_non_strong_hidden() const;
720
721 bool is_cloneable() const;
722 void set_is_cloneable_fast() { _misc_flags.set_is_cloneable_fast(true); }
723
724 inline markWord prototype_header() const;
725 inline void set_prototype_header(markWord header);
726 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
727
728 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
729
730 void metaspace_pointers_do(MetaspaceClosure* iter) override;
731 MetaspaceObj::Type type() const override { return ClassType; }
732
733 inline bool is_loader_alive() const;
734 inline bool is_loader_present_and_alive() const;
735
736 Klass* clean_subklass(bool log = false);
737
738 // Clean out unnecessary weak klass links from the whole klass hierarchy.
739 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
740 // Clean out unnecessary weak klass links from the given InstanceKlass.
741 static void clean_weak_instanceklass_links(InstanceKlass* ik);
742
743 // Return self, except for abstract classes with exactly 1
744 // implementor. Then return the 1 concrete implementation.
745 Klass *up_cast_abstract();
746
763 virtual jint jvmti_class_status() const;
764
765 // Printing
766 void print_on(outputStream* st) const override;
767
768 virtual void oop_print_value_on(oop obj, outputStream* st);
769 virtual void oop_print_on (oop obj, outputStream* st);
770
771 void print_secondary_supers_on(outputStream* st) const;
772
773 // Verification
774 virtual void verify_on(outputStream* st);
775 void verify() { verify_on(tty); }
776
777 #ifndef PRODUCT
778 bool verify_vtable_index(int index);
779 #endif
780
781 virtual void oop_verify_on(oop obj, outputStream* st);
782
783 // for error reporting
784 static bool is_valid(Klass* k);
785
786 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
787 };
788
789 #endif // SHARE_OOPS_KLASS_HPP
|
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.
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 *
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
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; }
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
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
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
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