1 /* 2 * Copyright (c) 2017, 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 #ifndef SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP 25 #define SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP 26 27 #include "gc/z/zBitField.hpp" 28 #include "memory/allocation.hpp" 29 #include "metaprogramming/primitiveConversions.hpp" 30 31 // 32 // Forwarding table entry layout 33 // ----------------------------- 34 // 35 // 6 4 4 0 36 // 3 2 1 0 37 // +------------------------+-----------------------------------------------+ 38 // |11111111 11111111 111111|11 11111111 11111111 11111111 11111111 11111111| 39 // +------------------------+-----------------------------------------------+ 40 // | | 41 // | * 41-0 To Object Offset (42-bits) 42 // | 43 // * 63-42 From Object Index (22-bits) 44 // 45 46 class ZForwardingTableEntry { 47 friend struct PrimitiveConversions; 48 49 private: 50 typedef ZBitField<uint64_t, size_t, 0, 42> field_to_offset; 51 typedef ZBitField<uint64_t, size_t, 42, 22> field_from_index; 52 53 uint64_t _entry; 54 55 public: 56 ZForwardingTableEntry() : 57 _entry(empty()) {} 58 59 ZForwardingTableEntry(size_t from_index, size_t to_offset) : 60 _entry(field_from_index::encode(from_index) | 61 field_to_offset::encode(to_offset)) {} 62 63 static uintptr_t empty() { 64 return (uintptr_t)-1; 65 } 66 67 bool is_empty() const { 68 return _entry == empty(); 69 } 70 71 size_t to_offset() const { 72 return field_to_offset::decode(_entry); 73 } 74 75 size_t from_index() const { 76 return field_from_index::decode(_entry); 77 } 78 }; 79 80 // Needed to allow atomic operations on ZForwardingTableEntry 81 template <> 82 struct PrimitiveConversions::Translate<ZForwardingTableEntry> : public TrueType { 83 typedef ZForwardingTableEntry Value; 84 typedef uint64_t Decayed; 85 86 static Decayed decay(Value v) { 87 return v._entry; 88 } 89 90 static Value recover(Decayed d) { 91 ZForwardingTableEntry entry; 92 entry._entry = d; 93 return entry; 94 } 95 }; 96 97 #endif // SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP