1 /*
2 * Copyright (c) 2021 SAP SE. All rights reserved.
3 * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
4 *
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #include "precompiled.hpp"
28 #include "oops/compressedKlass.hpp"
29 #include "utilities/ostream.hpp"
30 #include "utilities/debug.hpp"
31 #include "runtime/globals.hpp"
32
33 address CompressedKlassPointers::_base = NULL;
34 int CompressedKlassPointers::_shift_copy = 0;
35
36 // Given an address range [addr, addr+len) which the encoding is supposed to
37 // cover, choose base, shift and range.
38 // The address range is the expected range of uncompressed Klass pointers we
39 // will encounter (and the implicit promise that there will be no Klass
40 // structures outside this range).
41 void CompressedKlassPointers::initialize(address addr, size_t len) {
42 #ifdef _LP64
43 assert(UseCompressedClassPointers, "Sanity");
44
45 assert(len <= (size_t)KlassEncodingMetaspaceMax, "Range " SIZE_FORMAT " too large "
46 "- cannot be contained fully in narrow Klass pointer encoding range.", len);
47
48 if (UseSharedSpaces || DumpSharedSpaces) {
49
50 // Special requirements if CDS is active:
51 // Encoding base and shift must be the same between dump and run time.
52 // CDS takes care that the SharedBaseAddress and CompressedClassSpaceSize
53 // are the same. Archive size will be probably different at runtime, but
54 // it can only be smaller than at, never larger, since archives get
55 // shrunk at the end of the dump process.
56 // From that it follows that the range [addr, len) we are handed in at
57 // runtime will start at the same address then at dumptime, and its len
58 // may be smaller at runtime then it was at dump time.
59 //
60 // To be very careful here, we avoid any optimizations and just keep using
61 // the same address and shift value. Specifically we avoid using zero-based
62 // encoding. We also set the expected value range to 4G (encoding range
63 // cannot be larger than that).
64
65 _base = addr;
66
67 } else {
68
69 // (Note that this case is almost not worth optimizing for. CDS is typically on.)
70 if ((addr + len) <= (address)KlassEncodingMetaspaceMax) {
71 _base = 0;
72 } else {
73 _base = addr;
74 }
75 }
76
77 assert(is_valid_base(_base), "Address " PTR_FORMAT " was chosen as encoding base for range ["
78 PTR_FORMAT ", " PTR_FORMAT ") but is not a valid encoding base",
79 p2i(_base), p2i(addr), p2i(addr + len));
80
81 // For SA
82 _shift_copy = LogKlassAlignmentInBytes;
83
84 #else
85 ShouldNotReachHere(); // 64-bit only
86 #endif
87 }
88
89 // 64-bit platforms define these functions on a per-platform base. They are not needed for
90 // 32-bit (in fact, the whole setup is not needed and could be excluded from compilation,
91 // but that is a question for another RFE).
92 #ifndef _LP64
93 // Given an address p, return true if p can be used as an encoding base.
94 // (Some platforms have restrictions of what constitutes a valid base address).
95 bool CompressedKlassPointers::is_valid_base(address p) {
96 ShouldNotReachHere(); // 64-bit only
97 return false;
98 }
99
100 void CompressedKlassPointers::print_mode(outputStream* st) {
101 }
102 #endif
103