1 /*
2 * Copyright (c) 2019, 2023, 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
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7 * published by the Free Software Foundation.
8 *
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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.
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20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #ifndef SHARE_OOPS_COMPRESSEDOOPS_HPP
26 #define SHARE_OOPS_COMPRESSEDOOPS_HPP
27
28 #include "memory/allStatic.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
90 static address base() { return _narrow_oop._base; }
91 static address begin() { return (address)_heap_address_range.start(); }
92 static address end() { return (address)_heap_address_range.end(); }
93 static bool is_base(void* addr) { return (base() == (address)addr); }
94 static int shift() { return _narrow_oop._shift; }
95 static bool use_implicit_null_checks() { return _narrow_oop._use_implicit_null_checks; }
96
97 static address ptrs_base_addr() { return (address)&_narrow_oop._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
119 static bool is_null(oop v) { return v == nullptr; }
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_raw_not_null(oop v);
131 static inline oop decode_not_null(oop v);
132 static inline oop decode(oop v);
133 static inline narrowOop encode_not_null(narrowOop v);
134 static inline narrowOop encode(narrowOop v);
135
136 static inline uint32_t narrow_oop_value(oop o);
137 static inline uint32_t narrow_oop_value(narrowOop o);
138
139 template<typename T>
140 static inline narrowOop narrow_oop_cast(T i);
141 };
142
143 #endif // SHARE_OOPS_COMPRESSEDOOPS_HPP