1/*
2 * Copyright (c) 2019, 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.
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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
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23 */
24
25#ifndef SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP
26#define SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP
27
28#include "memory/allocation.hpp"
29#include "utilities/globalDefinitions.hpp"
30
31class nmethod;
32
33class ScavengableNMethodsData : public CHeapObj<mtGC> {
34 // State bits put into the two lower alignment bits.
35 static const uintptr_t state_bits = 2;
36 static const uintptr_t state_mask = (1 << state_bits) - 1;
37 static const uintptr_t state_on_list = 0x1;
38 static const uintptr_t state_marked = 0x2;
39
40 // nmethod containing the GC data.
41 nmethod* const _nm;
42
43 // The data is stored as a bit pattern in a void* inside the nmethod.
44 uintptr_t data() const { return reinterpret_cast<uintptr_t>(_nm->gc_data<void>()); }
45 void set_data(uintptr_t data) const { _nm->set_gc_data(reinterpret_cast<void*>(data)); }
46
47 jbyte state() const { return data() & state_mask; }
48 void set_state(jbyte state) const { set_data((data() & ~state_mask) | state); }
49
50 uintptr_t from_nmethod(nmethod* nm) const { return reinterpret_cast<uintptr_t>(nm); }
51 nmethod* to_nmethod(uintptr_t data) const { return reinterpret_cast<nmethod*>(data); }
52
53public:
54 ScavengableNMethodsData(nmethod* nm) : _nm(nm) {
55 assert(is_aligned(nm, 4), "Must be aligned to fit state bits");
56 }
57
58 // Scavengable oop support
59 bool on_list() const { return (state() & state_on_list) != 0; }
60 void set_on_list() { set_state(state_on_list); }
61 void clear_on_list() { set_state(0); }
62
63#ifndef PRODUCT
64 void set_marked() { set_state(state() | state_marked); }
65 void clear_marked() { set_state(state() & ~state_marked); }
66 bool not_marked() { return (state() & ~state_on_list) == 0; }
67 // N.B. there is no positive marked query, and we only use the not_marked query for asserts.
68#endif //PRODUCT
69
70 nmethod* next() const { return to_nmethod(data() & ~state_mask); }
71 void set_next(nmethod *n) { set_data(from_nmethod(n) | state()); }
72};
73
74#endif // SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP
75