1 /*
 2  * Copyright (c) 2019, 2021, Red Hat, Inc. 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_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_INLINE_HPP
27 
28 #include "gc/shenandoah/shenandoahStringDedup.hpp"
29 
30 #include "classfile/javaClasses.inline.hpp"
31 
32 bool ShenandoahStringDedup::is_string_candidate(oop obj) {
33   assert(Thread::current()->is_Worker_thread(),
34         "Only from a GC worker thread");
35   return java_lang_String::is_instance(obj) &&
36          java_lang_String::value(obj) != nullptr;
37 }
38 
39 bool ShenandoahStringDedup::dedup_requested(oop obj) {
40   return java_lang_String::test_and_set_deduplication_requested(obj);
41 }
42 
43 bool ShenandoahStringDedup::is_candidate(oop obj) {
44   if (!is_string_candidate(obj)) {
45     return false;
46   }
47 
48   if (StringDedup::is_below_threshold_age(obj->age())) {
49     const markWord mark = obj->mark();
50     // Having/had displaced header, too risk to deal with them, skip
51     if (mark == markWord::INFLATING() || mark.has_displaced_mark_helper()) {
52       return false;
53     }
54 
55     // Increase string age and enqueue it when it rearches age threshold
56     markWord new_mark = mark.incr_age();
57     if (mark == obj->cas_set_mark(new_mark, mark)) {
58       return StringDedup::is_threshold_age(new_mark.age()) &&
59              !dedup_requested(obj);
60     }
61   }
62   return false;
63 }
64 
65 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_INLINE_HPP