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.
22 *
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 void Klass::set_prototype_header(markWord header) {
56 assert(!is_inline_klass() || header.is_inline_type(), "Unexpected prototype");
57 assert(_prototype_header.value() == 0 || _prototype_header == markWord::prototype(),
58 "Prototype already set");
59 #ifdef _LP64
60 assert(header == markWord::prototype() ||
61 header.is_inline_type() ||
62 header.is_flat_array() ||
63 header.is_null_free_array(),
64 "unknown prototype header");
65 #else
66 assert(header == markWord::prototype() ||
67 header.is_inline_type(),
68 "unknown prototype header");
69 #endif
70 _prototype_header = header;
71 }
72
73 inline oop Klass::java_mirror() const {
74 return _java_mirror.resolve();
75 }
76
77 inline oop Klass::java_mirror_no_keepalive() const {
78 return _java_mirror.peek();
79 }
80
81 inline klassVtable Klass::vtable() const {
82 return klassVtable(const_cast<Klass*>(this), start_of_vtable(), vtable_length() / vtableEntry::size());
83 }
84
85 inline oop Klass::class_loader() const {
86 return class_loader_data()->class_loader();
87 }
88
89 inline vtableEntry* Klass::start_of_vtable() const {
90 return (vtableEntry*) ((address)this + in_bytes(vtable_start_offset()));
91 }
92
93 inline ByteSize Klass::vtable_start_offset() {
94 return in_ByteSize(InstanceKlass::header_size() * wordSize);
95 }
96
97 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
98 inline bool Klass::is_subtype_of(Klass* k) const {
99 assert(secondary_supers() != nullptr, "must be");
100 const juint off = k->super_check_offset();
101 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
102 if (off == secondary_offset) {
103 return search_secondary_supers(k);
104 } else {
105 Klass* sup = *(Klass**)( (address)this + off );
106 return (sup == k);
107 }
108 }
109
110 // Hashed search for secondary super k.
111 inline bool Klass::lookup_secondary_supers_table(Klass* k) const {
112 uintx bitmap = _secondary_supers_bitmap;
113
114 constexpr int highest_bit_number = SECONDARY_SUPERS_TABLE_SIZE - 1;
115 uint8_t slot = k->_hash_slot;
116 uintx shifted_bitmap = bitmap << (highest_bit_number - slot);
117
118 precond((int)population_count(bitmap) <= secondary_supers()->length());
119
120 // First check the bitmap to see if super_klass might be present. If
121 // the bit is zero, we are certain that super_klass is not one of
122 // the secondary supers.
123 if (((shifted_bitmap >> highest_bit_number) & 1) == 0) {
124 return false;
125 }
126
127 // Calculate the initial hash probe
128 int index = population_count(shifted_bitmap) - 1;
129 if (secondary_supers()->at(index) == k) {
130 // Yes! It worked the first time.
131 return true;
132 }
133
134 // Is there another entry to check? Consult the bitmap. If Bit 1,
135 // the next bit to test, is zero, we are certain that super_klass is
136 // not one of the secondary supers.
137 bitmap = rotate_right(bitmap, slot);
138 if ((bitmap & 2) == 0) {
139 return false;
140 }
141
142 // Continue probing the hash table
143 return fallback_search_secondary_supers(k, index, bitmap);
144 }
145
146 inline bool Klass::search_secondary_supers(Klass *k) const {
147 // This is necessary because I am never in my own secondary_super list.
148 if (this == k)
149 return true;
150
151 bool result = lookup_secondary_supers_table(k);
152
153 #ifndef PRODUCT
154 if (VerifySecondarySupers) {
155 bool linear_result = linear_search_secondary_supers(k);
156 if (linear_result != result) {
157 on_secondary_supers_verification_failure((Klass*)this, k, linear_result, result, "mismatch");
158 }
159 }
160 #endif // PRODUCT
161
162 return result;
163 }
164
165 #endif // SHARE_OOPS_KLASS_INLINE_HPP