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.
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23 */
24
25 #ifndef SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
26 #define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
27
28 #include "oops/compressedOops.hpp"
29
30 #include "memory/universe.hpp"
31 #include "oops/oop.hpp"
32 #include "utilities/align.hpp"
33 #include "utilities/globalDefinitions.hpp"
34
35 // Functions for encoding and decoding compressed oops.
36 // If the oops are compressed, the type passed to these overloaded functions
37 // is narrowOop. All functions are overloaded so they can be called by
38 // template functions without conditionals (the compiler instantiates via
39 // the right type and inlines the appropriate code).
40
41 // Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
42 // offset from the heap base. Saving the check for null can save instructions
43 // in inner GC loops so these are separated.
44
45 inline oop CompressedOops::decode_raw_not_null(narrowOop v) {
46 assert(!is_null(v), "narrow oop value can never be zero");
47 return decode_raw(v);
48 }
49
50 inline oop CompressedOops::decode_raw(narrowOop v) {
51 return cast_to_oop((uintptr_t)base() + ((uintptr_t)v << shift()));
52 }
53
54 inline oop CompressedOops::decode_not_null(narrowOop v) {
55 assert(!is_null(v), "narrow oop value can never be zero");
56 oop result = decode_raw(v);
57 assert(is_object_aligned(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));
58 assert(Universe::is_in_heap(result), "object not in heap " PTR_FORMAT, p2i((void*) result));
59 return result;
60 }
61
62 inline oop CompressedOops::decode(narrowOop v) {
63 return is_null(v) ? (oop)NULL : decode_not_null(v);
64 }
65
66 inline narrowOop CompressedOops::encode_not_null(oop v) {
67 assert(!is_null(v), "oop value can never be zero");
68 assert(is_object_aligned(v), "address not aligned: " PTR_FORMAT, p2i((void*)v));
69 assert(is_in(v), "address not in heap range: " PTR_FORMAT, p2i((void*)v));
70 uint64_t pd = (uint64_t)(pointer_delta((void*)v, (void*)base(), 1));
71 assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
72 narrowOop result = narrow_oop_cast(pd >> shift());
73 assert(decode_raw(result) == v, "reversibility");
74 return result;
75 }
76
77 inline narrowOop CompressedOops::encode(oop v) {
78 return is_null(v) ? narrowOop::null : encode_not_null(v);
79 }
80
81 inline oop CompressedOops::decode_not_null(oop v) {
82 assert(Universe::is_in_heap(v), "object not in heap " PTR_FORMAT, p2i((void*) v));
83 return v;
84 }
85
86 inline oop CompressedOops::decode(oop v) {
87 assert(Universe::is_in_heap_or_null(v), "object not in heap " PTR_FORMAT, p2i((void*) v));
88 return v;
89 }
90
91 inline narrowOop CompressedOops::encode_not_null(narrowOop v) {
92 return v;
93 }
94
95 inline narrowOop CompressedOops::encode(narrowOop v) {
96 return v;
97 }
98
99 inline uint32_t CompressedOops::narrow_oop_value(oop o) {
100 return narrow_oop_value(encode(o));
101 }
102
103 inline uint32_t CompressedOops::narrow_oop_value(narrowOop o) {
104 return static_cast<uint32_t>(o);
105 }
106
107 template<typename T>
108 inline narrowOop CompressedOops::narrow_oop_cast(T i) {
109 static_assert(std::is_integral<T>::value, "precondition");
110 uint32_t narrow_value = static_cast<uint32_t>(i);
111 // Ensure no bits lost in conversion to uint32_t.
112 assert(i == static_cast<T>(narrow_value), "narrowOop overflow");
113 return static_cast<narrowOop>(narrow_value);
114 }
115
116 #endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP