98 lines
3.0 KiB
C++
98 lines
3.0 KiB
C++
/*
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* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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#ifndef SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP
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#define SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP
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#include "gc/z/zBitField.hpp"
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#include "memory/allocation.hpp"
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#include "metaprogramming/primitiveConversions.hpp"
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//
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// Forwarding table entry layout
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// -----------------------------
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//
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// 6 4 4 0
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// 3 2 1 0
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// +------------------------+-----------------------------------------------+
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// |11111111 11111111 111111|11 11111111 11111111 11111111 11111111 11111111|
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// +------------------------+-----------------------------------------------+
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// | |
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// | * 41-0 To Object Offset (42-bits)
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// |
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// * 63-42 From Object Index (22-bits)
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//
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class ZForwardingTableEntry {
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friend struct PrimitiveConversions;
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private:
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typedef ZBitField<uint64_t, size_t, 0, 42> field_to_offset;
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typedef ZBitField<uint64_t, size_t, 42, 22> field_from_index;
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uint64_t _entry;
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static uintptr_t empty() {
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return (uintptr_t)-1;
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}
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public:
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ZForwardingTableEntry() :
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_entry(empty()) {}
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ZForwardingTableEntry(size_t from_index, size_t to_offset) :
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_entry(field_from_index::encode(from_index) |
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field_to_offset::encode(to_offset)) {}
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bool is_empty() const {
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return _entry == empty();
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}
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size_t to_offset() const {
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return field_to_offset::decode(_entry);
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}
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size_t from_index() const {
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return field_from_index::decode(_entry);
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}
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};
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// Needed to allow atomic operations on ZForwardingTableEntry
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template <>
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struct PrimitiveConversions::Translate<ZForwardingTableEntry> : public TrueType {
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typedef ZForwardingTableEntry Value;
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typedef uint64_t Decayed;
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static Decayed decay(Value v) {
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return v._entry;
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}
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static Value recover(Decayed d) {
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ZForwardingTableEntry entry;
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entry._entry = d;
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return entry;
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}
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};
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#endif // SHARE_GC_Z_ZFORWARDINGTABLEENTRY_HPP
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