1 /*
 2  * Copyright Amazon.com Inc. 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 
25 #include "oops/markWord.hpp"
26 #include "oops/objLayout.hpp"
27 #include "runtime/globals.hpp"
28 #include "utilities/debug.hpp"
29 
30 ObjLayout::Mode ObjLayout::_klass_mode = ObjLayout::Undefined;
31 int ObjLayout::_oop_base_offset_in_bytes = 0;
32 bool ObjLayout::_oop_has_klass_gap = false;
33 
34 void ObjLayout::initialize() {
35 #ifdef _LP64
36   assert(_klass_mode == Undefined, "ObjLayout initialized twice");
37   if (UseCompactObjectHeaders) {
38     _klass_mode = Compact;
39     _oop_base_offset_in_bytes = sizeof(markWord);
40     _oop_has_klass_gap = false;
41   } else if (UseCompressedClassPointers) {
42     _klass_mode = Compressed;
43     _oop_base_offset_in_bytes = sizeof(markWord) + sizeof(narrowKlass);
44     _oop_has_klass_gap = true;
45   } else {
46     _klass_mode = Uncompressed;
47     _oop_base_offset_in_bytes = sizeof(markWord) + sizeof(Klass*);
48     _oop_has_klass_gap = false;
49   }
50 #else
51   assert(_klass_mode == Undefined, "ObjLayout initialized twice");
52   assert(!UseCompactObjectHeaders, "COH unsupported on 32-bit");
53   // We support +-UseCompressedClassPointers on 32-bit, but the layout
54   // is exactly the same as it was with uncompressed klass pointers
55   _klass_mode = UseCompressedClassPointers ? Compressed : Uncompressed;
56   _oop_base_offset_in_bytes = sizeof(markWord) + sizeof(Klass*);
57   _oop_has_klass_gap = false;
58 #endif
59 }