1 /*
2 * Copyright (c) 2005, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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.
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23 */
24
25 #ifndef SHARE_OOPS_KLASS_INLINE_HPP
26 #define SHARE_OOPS_KLASS_INLINE_HPP
27
28 #include "oops/klass.hpp"
29
30 #include "classfile/classLoaderData.inline.hpp"
31 #include "oops/klassVtable.hpp"
32 #include "oops/markWord.hpp"
33 #include "utilities/rotate_bits.hpp"
34
35 // This loads and keeps the klass's loader alive.
36 inline oop Klass::klass_holder() const {
37 return class_loader_data()->holder();
38 }
39
40 inline bool Klass::is_non_strong_hidden() const {
41 return is_hidden() && class_loader_data()->has_class_mirror_holder();
42 }
43
44 // Iff the class loader (or mirror for non-strong hidden classes) is alive the
45 // Klass is considered alive. This is safe to call before the CLD is marked as
46 // unloading, and hence during concurrent class unloading.
47 // This returns false if the Klass is unloaded, or about to be unloaded because the holder of
48 // the CLD is no longer strongly reachable.
49 // The return value of this function may change from true to false after a safepoint. So the caller
50 // of this function must ensure that a safepoint doesn't happen while interpreting the return value.
51 inline bool Klass::is_loader_alive() const {
52 return class_loader_data()->is_alive();
53 }
54
55 inline oop Klass::java_mirror() const {
56 return _java_mirror.resolve();
57 }
58
59 inline oop Klass::java_mirror_no_keepalive() const {
60 return _java_mirror.peek();
61 }
62
63 inline klassVtable Klass::vtable() const {
64 return klassVtable(const_cast<Klass*>(this), start_of_vtable(), vtable_length() / vtableEntry::size());
65 }
66
67 inline oop Klass::class_loader() const {
68 return class_loader_data()->class_loader();
69 }
70
71 inline vtableEntry* Klass::start_of_vtable() const {
72 return (vtableEntry*) ((address)this + in_bytes(vtable_start_offset()));
73 }
74
75 inline ByteSize Klass::vtable_start_offset() {
76 return in_ByteSize(InstanceKlass::header_size() * wordSize);
77 }
78
79 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
80 inline bool Klass::is_subtype_of(Klass* k) const {
81 assert(secondary_supers() != nullptr, "must be");
82 const juint off = k->super_check_offset();
83 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
84 if (off == secondary_offset) {
85 return search_secondary_supers(k);
86 } else {
87 Klass* sup = *(Klass**)( (address)this + off );
88 return (sup == k);
89 }
90 }
91
92 // Hashed search for secondary super k.
93 inline bool Klass::lookup_secondary_supers_table(Klass* k) const {
94 uintx bitmap = _secondary_supers_bitmap;
95
96 constexpr int highest_bit_number = SECONDARY_SUPERS_TABLE_SIZE - 1;
97 uint8_t slot = k->_hash_slot;
98 uintx shifted_bitmap = bitmap << (highest_bit_number - slot);
99
100 precond((int)population_count(bitmap) <= secondary_supers()->length());
101
102 // First check the bitmap to see if super_klass might be present. If
103 // the bit is zero, we are certain that super_klass is not one of
104 // the secondary supers.
105 if (((shifted_bitmap >> highest_bit_number) & 1) == 0) {
106 return false;
107 }
108
109 // Calculate the initial hash probe
110 int index = population_count(shifted_bitmap) - 1;
111 if (secondary_supers()->at(index) == k) {
112 // Yes! It worked the first time.
113 return true;
114 }
115
116 // Is there another entry to check? Consult the bitmap. If Bit 1,
117 // the next bit to test, is zero, we are certain that super_klass is
118 // not one of the secondary supers.
119 bitmap = rotate_right(bitmap, slot);
120 if ((bitmap & 2) == 0) {
121 return false;
122 }
123
124 // Continue probing the hash table
125 return fallback_search_secondary_supers(k, index, bitmap);
126 }
127
128 inline bool Klass::search_secondary_supers(Klass *k) const {
129 // This is necessary because I am never in my own secondary_super list.
130 if (this == k)
131 return true;
132
133 bool result = lookup_secondary_supers_table(k);
134
135 #ifndef PRODUCT
136 if (VerifySecondarySupers) {
137 bool linear_result = linear_search_secondary_supers(k);
138 if (linear_result != result) {
139 on_secondary_supers_verification_failure((Klass*)this, k, linear_result, result, "mismatch");
140 }
141 }
142 #endif // PRODUCT
143
144 return result;
145 }
146
147 #endif // SHARE_OOPS_KLASS_INLINE_HPP