1/*
2 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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24
25#ifndef SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
26#define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
27
28#include "gc/shared/collectedHeap.hpp"
29#include "memory/universe.hpp"
30#include "oops/compressedOops.hpp"
31#include "oops/oop.hpp"
32
33// Functions for encoding and decoding compressed oops.
34// If the oops are compressed, the type passed to these overloaded functions
35// is narrowOop. All functions are overloaded so they can be called by
36// template functions without conditionals (the compiler instantiates via
37// the right type and inlines the appropriate code).
38
39// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
40// offset from the heap base. Saving the check for null can save instructions
41// in inner GC loops so these are separated.
42
43inline oop CompressedOops::decode_raw(narrowOop v) {
44 return (oop)(void*)((uintptr_t)base() + ((uintptr_t)v << shift()));
45}
46
47inline oop CompressedOops::decode_not_null(narrowOop v) {
48 assert(!is_null(v), "narrow oop value can never be zero");
49 oop result = decode_raw(v);
50 assert(check_obj_alignment(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));
51 return result;
52}
53
54inline oop CompressedOops::decode(narrowOop v) {
55 return is_null(v) ? (oop)NULL : decode_not_null(v);
56}
57
58inline narrowOop CompressedOops::encode_not_null(oop v) {
59 assert(!is_null(v), "oop value can never be zero");
60 assert(check_obj_alignment(v), "Address not aligned");
61 assert(Universe::heap()->is_in_reserved(v), "Address not in heap");
62 uint64_t pd = (uint64_t)(pointer_delta((void*)v, (void*)base(), 1));
63 assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
64 uint64_t result = pd >> shift();
65 assert((result & CONST64(0xffffffff00000000)) == 0, "narrow oop overflow");
66 assert(oopDesc::equals_raw(decode(result), v), "reversibility");
67 return (narrowOop)result;
68}
69
70inline narrowOop CompressedOops::encode(oop v) {
71 return is_null(v) ? (narrowOop)0 : encode_not_null(v);
72}
73
74static inline bool check_alignment(Klass* v) {
75 return (intptr_t)v % KlassAlignmentInBytes == 0;
76}
77
78inline Klass* CompressedKlassPointers::decode_raw(narrowKlass v) {
79 return (Klass*)(void*)((uintptr_t)base() +((uintptr_t)v << shift()));
80 }
81
82inline Klass* CompressedKlassPointers::decode_not_null(narrowKlass v) {
83 assert(!is_null(v), "narrow klass value can never be zero");
84 Klass* result = decode_raw(v);
85 assert(check_alignment(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));
86 return result;
87}
88
89inline Klass* CompressedKlassPointers::decode(narrowKlass v) {
90 return is_null(v) ? (Klass*)NULL : decode_not_null(v);
91}
92
93inline narrowKlass CompressedKlassPointers::encode_not_null(Klass* v) {
94 assert(!is_null(v), "klass value can never be zero");
95 assert(check_alignment(v), "Address not aligned");
96 uint64_t pd = (uint64_t)(pointer_delta((void*)v, base(), 1));
97 assert(KlassEncodingMetaspaceMax > pd, "change encoding max if new encoding");
98 uint64_t result = pd >> shift();
99 assert((result & CONST64(0xffffffff00000000)) == 0, "narrow klass pointer overflow");
100 assert(decode(result) == v, "reversibility");
101 return (narrowKlass)result;
102}
103
104inline narrowKlass CompressedKlassPointers::encode(Klass* v) {
105 return is_null(v) ? (narrowKlass)0 : encode_not_null(v);
106}
107
108#endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
109