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 void Klass::keep_alive() const { 41 // Resolving the holder (a WeakHandle) will keep the klass alive until the next safepoint. 42 // Making the klass's CLD handle oops (e.g. the java_mirror), safe to store in the object 43 // graph and its roots (e.g. Handles). 44 static_cast<void>(klass_holder()); 45 } 46 47 inline bool Klass::is_non_strong_hidden() const { 48 return is_hidden() && class_loader_data()->has_class_mirror_holder(); 49 } 50 51 // Iff the class loader (or mirror for non-strong hidden classes) is alive the 52 // Klass is considered alive. This is safe to call before the CLD is marked as 53 // unloading, and hence during concurrent class unloading. 54 // This returns false if the Klass is unloaded, or about to be unloaded because the holder of 55 // the CLD is no longer strongly reachable. 56 // The return value of this function may change from true to false after a safepoint. So the caller 57 // of this function must ensure that a safepoint doesn't happen while interpreting the return value. 58 inline bool Klass::is_loader_alive() const { 59 return class_loader_data()->is_alive(); 60 } 61 62 inline bool Klass::is_loader_present_and_alive() const { 63 ClassLoaderData* cld = class_loader_data(); 64 return (cld != nullptr) ? cld->is_alive() : false; 65 } 66 67 inline markWord Klass::prototype_header() const { 68 assert(UseCompactObjectHeaders, "only use with compact object headers"); 69 #ifdef _LP64 70 // You only need prototypes for allocating objects. If the class is not instantiable, it won't live in 71 // class space and have no narrow Klass ID. But in that case we should not need the prototype. 72 assert(_prototype_header.narrow_klass() > 0, "Klass " PTR_FORMAT ": invalid prototype (" PTR_FORMAT ")", 73 p2i(this), _prototype_header.value()); 74 #endif 75 return _prototype_header; 76 } 77 78 // This is only used when dumping the archive. In other cases, 79 // the _prototype_header is already initialized to the right thing. 80 inline void Klass::set_prototype_header(markWord header) { 81 assert(UseCompactObjectHeaders, "only with compact headers"); 82 _prototype_header = header; 83 } 84 85 // Loading the java_mirror does not keep its holder alive. See Klass::keep_alive(). 86 inline oop Klass::java_mirror() const { 87 return _java_mirror.resolve(); 88 } 89 90 inline oop Klass::java_mirror_no_keepalive() const { 91 return _java_mirror.peek(); 92 } 93 94 inline klassVtable Klass::vtable() const { 95 return klassVtable(const_cast<Klass*>(this), start_of_vtable(), vtable_length() / vtableEntry::size()); 96 } 97 98 inline oop Klass::class_loader() const { 99 return class_loader_data()->class_loader(); 100 } 101 102 inline vtableEntry* Klass::start_of_vtable() const { 103 return (vtableEntry*) ((address)this + in_bytes(vtable_start_offset())); 104 } 105 106 inline ByteSize Klass::vtable_start_offset() { 107 return in_ByteSize(InstanceKlass::header_size() * wordSize); 108 } 109 110 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it 111 inline bool Klass::is_subtype_of(Klass* k) const { 112 assert(secondary_supers() != nullptr, "must be"); 113 const juint off = k->super_check_offset(); 114 const juint secondary_offset = in_bytes(secondary_super_cache_offset()); 115 if (off == secondary_offset) { 116 return search_secondary_supers(k); 117 } else { 118 Klass* sup = *(Klass**)( (address)this + off ); 119 return (sup == k); 120 } 121 } 122 123 // Hashed search for secondary super k. 124 inline bool Klass::lookup_secondary_supers_table(Klass* k) const { 125 uintx bitmap = _secondary_supers_bitmap; 126 127 constexpr int highest_bit_number = SECONDARY_SUPERS_TABLE_SIZE - 1; 128 uint8_t slot = k->_hash_slot; 129 uintx shifted_bitmap = bitmap << (highest_bit_number - slot); 130 131 precond((int)population_count(bitmap) <= secondary_supers()->length()); 132 133 // First check the bitmap to see if super_klass might be present. If 134 // the bit is zero, we are certain that super_klass is not one of 135 // the secondary supers. 136 if (((shifted_bitmap >> highest_bit_number) & 1) == 0) { 137 return false; 138 } 139 140 // Calculate the initial hash probe 141 int index = population_count(shifted_bitmap) - 1; 142 if (secondary_supers()->at(index) == k) { 143 // Yes! It worked the first time. 144 return true; 145 } 146 147 // Is there another entry to check? Consult the bitmap. If Bit 1, 148 // the next bit to test, is zero, we are certain that super_klass is 149 // not one of the secondary supers. 150 bitmap = rotate_right(bitmap, slot); 151 if ((bitmap & 2) == 0) { 152 return false; 153 } 154 155 // Continue probing the hash table 156 return fallback_search_secondary_supers(k, index, bitmap); 157 } 158 159 inline bool Klass::search_secondary_supers(Klass *k) const { 160 // This is necessary because I am never in my own secondary_super list. 161 if (this == k) 162 return true; 163 164 bool result = lookup_secondary_supers_table(k); 165 166 #ifndef PRODUCT 167 if (VerifySecondarySupers) { 168 bool linear_result = linear_search_secondary_supers(k); 169 if (linear_result != result) { 170 on_secondary_supers_verification_failure((Klass*)this, k, linear_result, result, "mismatch"); 171 } 172 } 173 #endif // PRODUCT 174 175 return result; 176 } 177 178 // Returns true if this Klass needs to be addressable via narrow Klass ID. 179 inline bool Klass::needs_narrow_id() const { 180 // Classes that are never instantiated need no narrow Klass Id, since the 181 // only point of having a narrow id is to put it into an object header. Keeping 182 // never instantiated classes out of class space lessens the class space pressure. 183 // For more details, see JDK-8338526. 184 // Note: don't call this function before access flags are initialized. 185 return !is_abstract() && !is_interface(); 186 } 187 188 inline size_t Klass::oop_size(oop obj) const { 189 return oop_size(obj, obj->mark()); 190 } 191 192 #endif // SHARE_OOPS_KLASS_INLINE_HPP