jdk-24/src/hotspot/share/gc/z/zForwardingTableEntry.hpp
2018-12-03 14:52:49 +01:00

98 lines
3.0 KiB
C++

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