85 lines
3.5 KiB
C++
85 lines
3.5 KiB
C++
/*
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* Copyright (c) 2017, 2018, 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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*/
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#ifndef SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
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#define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
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#include "gc/shared/collectedHeap.hpp"
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#include "memory/universe.hpp"
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#include "oops/oop.hpp"
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// Functions for encoding and decoding compressed oops.
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// If the oops are compressed, the type passed to these overloaded functions
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// is narrowOop. All functions are overloaded so they can be called by
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// template functions without conditionals (the compiler instantiates via
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// the right type and inlines the appropriate code).
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// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
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// offset from the heap base. Saving the check for null can save instructions
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// in inner GC loops so these are separated.
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namespace CompressedOops {
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inline bool is_null(oop obj) { return obj == NULL; }
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inline bool is_null(narrowOop obj) { return obj == 0; }
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inline oop decode_not_null(narrowOop v) {
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assert(!is_null(v), "narrow oop value can never be zero");
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address base = Universe::narrow_oop_base();
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int shift = Universe::narrow_oop_shift();
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oop result = (oop)(void*)((uintptr_t)base + ((uintptr_t)v << shift));
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assert(check_obj_alignment(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));
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return result;
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}
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inline oop decode(narrowOop v) {
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return is_null(v) ? (oop)NULL : decode_not_null(v);
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}
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inline narrowOop encode_not_null(oop v) {
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assert(!is_null(v), "oop value can never be zero");
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assert(check_obj_alignment(v), "Address not aligned");
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assert(Universe::heap()->is_in_reserved(v), "Address not in heap");
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address base = Universe::narrow_oop_base();
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int shift = Universe::narrow_oop_shift();
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uint64_t pd = (uint64_t)(pointer_delta((void*)v, (void*)base, 1));
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assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
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uint64_t result = pd >> shift;
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assert((result & CONST64(0xffffffff00000000)) == 0, "narrow oop overflow");
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assert(oopDesc::equals_raw(decode(result), v), "reversibility");
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return (narrowOop)result;
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}
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inline narrowOop encode(oop v) {
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return is_null(v) ? (narrowOop)0 : encode_not_null(v);
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}
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// No conversions needed for these overloads
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inline oop decode_not_null(oop v) { return v; }
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inline oop decode(oop v) { return v; }
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inline narrowOop encode_not_null(narrowOop v) { return v; }
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inline narrowOop encode(narrowOop v) { return v; }
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}
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#endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
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