1 /*
 2  * Copyright (c) 2017, 2021, 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 #include "precompiled.hpp"
25 #include "gc/shared/preservedMarks.inline.hpp"
26 #include "gc/shared/slidingForwarding.inline.hpp"
27 #include "oops/oop.inline.hpp"
28 #include "unittest.hpp"
29 
30 static markWord originalMark() { return markWord(markWord::lock_mask_in_place); }
31 static markWord changedMark()  { return markWord(0x4711); }
32 
33 #define ASSERT_MARK_WORD_EQ(a, b) ASSERT_EQ((a).value(), (b).value())
34 
35 TEST_VM(PreservedMarks, iterate_and_restore) {
36   PreservedMarks pm;
37 
38   HeapWord fakeheap[32] = { nullptr };
39   HeapWord* heap = align_up(fakeheap, 8 * sizeof(HeapWord));
40   SlidingForwarding::initialize(MemRegion(&heap[0], &heap[16]), 8);
41 
42   oop o1 = cast_to_oop(&heap[0]); o1->set_mark(originalMark());
43   oop o2 = cast_to_oop(&heap[2]); o2->set_mark(originalMark());
44   oop o3 = cast_to_oop(&heap[4]); o3->set_mark(originalMark());
45   oop o4 = cast_to_oop(&heap[6]); o4->set_mark(originalMark());
46 
47   // Make sure initial marks are correct.
48   ASSERT_MARK_WORD_EQ(o1->mark(), originalMark());
49   ASSERT_MARK_WORD_EQ(o2->mark(), originalMark());
50   ASSERT_MARK_WORD_EQ(o3->mark(), originalMark());
51   ASSERT_MARK_WORD_EQ(o4->mark(), originalMark());
52 
53   // Change the marks and verify change.
54   o1->set_mark(changedMark());
55   o2->set_mark(changedMark());
56   ASSERT_MARK_WORD_EQ(o1->mark(), changedMark());
57   ASSERT_MARK_WORD_EQ(o2->mark(), changedMark());
58 
59   SlidingForwarding::begin();
60 
61   // Push o1 and o2 to have their marks preserved.
62   pm.push_if_necessary(o1, o1->mark());
63   pm.push_if_necessary(o2, o2->mark());
64 
65   // Fake a move from o1->o3 and o2->o4.
66   SlidingForwarding::forward_to(o1, o3);
67   SlidingForwarding::forward_to(o2, o4);
68   ASSERT_EQ(SlidingForwarding::forwardee(o1), o3);
69   ASSERT_EQ(SlidingForwarding::forwardee(o2), o4);
70   // Adjust will update the PreservedMarks stack to
71   // make sure the mark is updated at the new location.
72   pm.adjust_during_full_gc();
73 
74   // Restore all preserved and verify that the changed
75   // mark is now present at o3 and o4.
76   pm.restore();
77   ASSERT_MARK_WORD_EQ(o3->mark(), changedMark());
78   ASSERT_MARK_WORD_EQ(o4->mark(), changedMark());
79   SlidingForwarding::end();
80 }