1/*
2 * Copyright (c) 2017, 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#include "precompiled.hpp"
26#include "classfile/javaClasses.inline.hpp"
27#include "gc/shared/accessBarrierSupport.inline.hpp"
28#include "oops/access.hpp"
29
30DecoratorSet AccessBarrierSupport::resolve_unknown_oop_ref_strength(DecoratorSet decorators, oop base, ptrdiff_t offset) {
31 // Note that the referent in a FinalReference is technically not strong.
32 // However, it always behaves like one in practice. The two cases are:
33 // 1) A mutator calls Reference.get(). However, a mutator can only ever
34 // see inactive FinalReferences, whose referents really are strong.
35 // 2) A GC heap walking operation. In this case the GC can see active
36 // FinalReferences, but the GC always wants to follow the referent
37 // as if it was strong.
38 DecoratorSet ds = decorators & ~ON_UNKNOWN_OOP_REF;
39 if (!java_lang_ref_Reference::is_referent_field(base, offset) ||
40 java_lang_ref_Reference::is_final(base)) {
41 ds |= ON_STRONG_OOP_REF;
42 } else if (java_lang_ref_Reference::is_phantom(base)) {
43 ds |= ON_PHANTOM_OOP_REF;
44 } else {
45 ds |= ON_WEAK_OOP_REF;
46 }
47 return ds;
48}
49