1 /* 2 * Copyright (c) 2019, 2021, 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 25 #ifndef SHARE_OOPS_COMPRESSEDOOPS_HPP 26 #define SHARE_OOPS_COMPRESSEDOOPS_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/memRegion.hpp" 30 #include "oops/oopsHierarchy.hpp" 31 #include "utilities/globalDefinitions.hpp" 32 #include <type_traits> 33 34 class outputStream; 35 class ReservedHeapSpace; 36 37 struct NarrowPtrStruct { 38 // Base address for oop-within-java-object materialization. 39 // NULL if using wide oops or zero based narrow oops. 40 address _base; 41 // Number of shift bits for encoding/decoding narrow ptrs. 42 // 0 if using wide ptrs or zero based unscaled narrow ptrs, 43 // LogMinObjAlignmentInBytes/LogKlassAlignmentInBytes otherwise. 44 int _shift; 45 // Generate code with implicit null checks for narrow ptrs. 46 bool _use_implicit_null_checks; 47 }; 48 49 class CompressedOops : public AllStatic { 50 friend class VMStructs; 51 52 // For UseCompressedOops. 53 static NarrowPtrStruct _narrow_oop; 54 55 // The address range of the heap 56 static MemRegion _heap_address_range; 57 58 public: 59 // For UseCompressedOops 60 // Narrow Oop encoding mode: 61 // 0 - Use 32-bits oops without encoding when 62 // NarrowOopHeapBaseMin + heap_size < 4Gb 63 // 1 - Use zero based compressed oops with encoding when 64 // NarrowOopHeapBaseMin + heap_size < 32Gb 65 // 2 - Use compressed oops with disjoint heap base if 66 // base is 32G-aligned and base > 0. This allows certain 67 // optimizations in encoding/decoding. 68 // Disjoint: Bits used in base are disjoint from bits used 69 // for oops ==> oop = (cOop << 3) | base. One can disjoint 70 // the bits of an oop into base and compressed oop. 71 // 3 - Use compressed oops with heap base + encoding. 72 enum Mode { 73 UnscaledNarrowOop = 0, 74 ZeroBasedNarrowOop = 1, 75 DisjointBaseNarrowOop = 2, 76 HeapBasedNarrowOop = 3, 77 AnyNarrowOopMode = 4 78 }; 79 80 // The representation type for narrowOop is assumed to be uint32_t. 81 static_assert(std::is_same<uint32_t, std::underlying_type_t<narrowOop>>::value, 82 "narrowOop has unexpected representation type"); 83 84 static void initialize(const ReservedHeapSpace& heap_space); 85 86 static void set_base(address base); 87 static void set_shift(int shift); 88 static void set_use_implicit_null_checks(bool use); 89 base()90 static address base() { return _narrow_oop._base; } begin()91 static address begin() { return (address)_heap_address_range.start(); } end()92 static address end() { return (address)_heap_address_range.end(); } is_base(void * addr)93 static bool is_base(void* addr) { return (base() == (address)addr); } shift()94 static int shift() { return _narrow_oop._shift; } use_implicit_null_checks()95 static bool use_implicit_null_checks() { return _narrow_oop._use_implicit_null_checks; } 96 ptrs_base_addr()97 static address* ptrs_base_addr() { return &_narrow_oop._base; } ptrs_base()98 static address ptrs_base() { return _narrow_oop._base; } 99 100 static bool is_in(void* addr); 101 static bool is_in(MemRegion mr); 102 103 static Mode mode(); 104 static const char* mode_to_string(Mode mode); 105 106 // Test whether bits of addr and possible offsets into the heap overlap. 107 static bool is_disjoint_heap_base_address(address addr); 108 109 // Check for disjoint base compressed oops. 110 static bool base_disjoint(); 111 112 // Check for real heapbased compressed oops. 113 // We must subtract the base as the bits overlap. 114 // If we negate above function, we also get unscaled and zerobased. 115 static bool base_overlaps(); 116 117 static void print_mode(outputStream* st); 118 is_null(oop v)119 static bool is_null(oop v) { return v == NULL; } is_null(narrowOop v)120 static bool is_null(narrowOop v) { return v == narrowOop::null; } 121 122 static inline oop decode_raw_not_null(narrowOop v); 123 static inline oop decode_raw(narrowOop v); 124 static inline oop decode_not_null(narrowOop v); 125 static inline oop decode(narrowOop v); 126 static inline narrowOop encode_not_null(oop v); 127 static inline narrowOop encode(oop v); 128 129 // No conversions needed for these overloads 130 static inline oop decode_not_null(oop v); 131 static inline oop decode(oop v); 132 static inline narrowOop encode_not_null(narrowOop v); 133 static inline narrowOop encode(narrowOop v); 134 135 static inline uint32_t narrow_oop_value(oop o); 136 static inline uint32_t narrow_oop_value(narrowOop o); 137 138 template<typename T> 139 static inline narrowOop narrow_oop_cast(T i); 140 }; 141 142 // For UseCompressedClassPointers. 143 class CompressedKlassPointers : public AllStatic { 144 friend class VMStructs; 145 146 static NarrowPtrStruct _narrow_klass; 147 148 // Together with base, this defines the address range within which Klass 149 // structures will be located: [base, base+range). While the maximal 150 // possible encoding range is 4|32G for shift 0|3, if we know beforehand 151 // the expected range of Klass* pointers will be smaller, a platform 152 // could use this info to optimize encoding. 153 static size_t _range; 154 155 static void set_base(address base); 156 static void set_range(size_t range); 157 158 public: 159 160 static void set_shift(int shift); 161 162 163 // Given an address p, return true if p can be used as an encoding base. 164 // (Some platforms have restrictions of what constitutes a valid base 165 // address). 166 static bool is_valid_base(address p); 167 168 // Given an address range [addr, addr+len) which the encoding is supposed to 169 // cover, choose base, shift and range. 170 // The address range is the expected range of uncompressed Klass pointers we 171 // will encounter (and the implicit promise that there will be no Klass 172 // structures outside this range). 173 static void initialize(address addr, size_t len); 174 175 static void print_mode(outputStream* st); 176 base()177 static address base() { return _narrow_klass._base; } range()178 static size_t range() { return _range; } shift()179 static int shift() { return _narrow_klass._shift; } 180 is_null(Klass * v)181 static bool is_null(Klass* v) { return v == NULL; } is_null(narrowKlass v)182 static bool is_null(narrowKlass v) { return v == 0; } 183 184 static inline Klass* decode_raw(narrowKlass v, address base); 185 static inline Klass* decode_raw(narrowKlass v); 186 static inline Klass* decode_not_null(narrowKlass v); 187 static inline Klass* decode_not_null(narrowKlass v, address base); 188 static inline Klass* decode(narrowKlass v); 189 static inline narrowKlass encode_not_null(Klass* v); 190 static inline narrowKlass encode_not_null(Klass* v, address base); 191 static inline narrowKlass encode(Klass* v); 192 193 }; 194 195 #endif // SHARE_OOPS_COMPRESSEDOOPS_HPP 196