1 /*
2 * Copyright (c) 2023, 2026, 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.
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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
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23 */
24
25 #ifndef SHARE_OOPS_RESOLVEDFIELDENTRY_HPP
26 #define SHARE_OOPS_RESOLVEDFIELDENTRY_HPP
27
28 #include "interpreter/bytecodes.hpp"
29 #include "runtime/atomicAccess.hpp"
30 #include "utilities/checkedCast.hpp"
31 #include "utilities/sizes.hpp"
32
33 // ResolvedFieldEntry contains the resolution information for field related bytecodes like
34 // like getfield, putfield, getstatic, and putstatic. A member of this class can be initialized
35 // with the constant pool index associated with the bytecode before any resolution is done, where
36 // "resolution" refers to populating the getcode and putcode fields and other relevant information.
37 // The field's type (TOS), offset, holder klass, and index within that class can all be acquired
38 // together and are used to populate this structure. These entries are contained
39 // within the ConstantPoolCache and are accessed with indices added to the bytecode after
40 // rewriting.
41
42 // Field bytecodes start with a constant pool index as their operand, which is then rewritten to
43 // a "field index", which is an index into the array of ResolvedFieldEntry.
44
45 // The explicit paddings are necessary for generating deterministic CDS archives. They prevent
46 // the C++ compiler from potentially inserting random values in unused gaps.
47
48 class InstanceKlass;
49
50 class ResolvedFieldEntry {
51 friend class VMStructs;
52
53 InstanceKlass* _field_holder; // Field holder klass
54 int _field_offset; // Field offset in bytes
55 u2 _field_index; // Index into field information in holder InstanceKlass
56 u2 _cpool_index; // Constant pool index
57 u1 _tos_state; // TOS state
58 u1 _flags; // Flags: [000|has_null_marker|is_null_free_inline_type|is_flat|is_final|is_volatile]
59 u1 _get_code, _put_code; // Get and Put bytecodes of the field
60 #ifdef _LP64
61 u4 _padding;
62 #endif
63
64 public:
65 ResolvedFieldEntry(u2 cpi) :
66 _field_holder(nullptr),
67 _field_offset(0),
68 _field_index(0),
69 _cpool_index(cpi),
70 _tos_state(0),
71 _flags(0),
72 _get_code(0),
73 _put_code(0)
74 #ifdef _LP64
75 , _padding(0)
76 #endif
77 {}
78
79 ResolvedFieldEntry() :
80 ResolvedFieldEntry(0) {}
81
82 // Bit shift to get flags
83 enum {
84 is_volatile_shift = 0,
85 is_final_shift = 1, // unused
86 is_flat_shift = 2,
87 is_null_free_inline_type_shift = 3,
88 has_null_marker_shift = 4,
89 max_flag_shift = has_null_marker_shift
90 };
91
92 // Getters
93 InstanceKlass* field_holder() const { return _field_holder; }
94 int field_offset() const { return _field_offset; }
95 u2 field_index() const { return _field_index; }
96 u2 constant_pool_index() const { return _cpool_index; }
97 u1 tos_state() const { return _tos_state; }
98 u1 get_code() const { return AtomicAccess::load_acquire(&_get_code); }
99 u1 put_code() const { return AtomicAccess::load_acquire(&_put_code); }
100 bool is_volatile () const { return (_flags & (1 << is_volatile_shift)) != 0; }
101 bool is_final() const { return (_flags & (1 << is_final_shift)) != 0; }
102 bool is_flat() const { return (_flags & (1 << is_flat_shift)) != 0; }
103 bool is_null_free_inline_type() const { return (_flags & (1 << is_null_free_inline_type_shift)) != 0; }
104 bool has_null_marker() const { return (_flags & (1 << has_null_marker_shift)) != 0; }
105 bool is_resolved(Bytecodes::Code code) const {
106 switch(code) {
107 case Bytecodes::_getstatic:
108 case Bytecodes::_getfield:
109 return (get_code() == code);
110 case Bytecodes::_putstatic:
111 case Bytecodes::_putfield:
112 return (put_code() == code);
113 default:
114 ShouldNotReachHere();
115 return false;
116 }
117 }
118
119 // Printing
120 void print_on(outputStream* st) const;
121
122 private:
123 void set_flags(bool is_volatile_flag,
124 bool is_final_flag,
125 bool is_flat_flag,
126 bool is_null_free_inline_type_flag,
127 bool has_null_marker_flag) {
128 int new_flags =
129 ((is_volatile_flag ? 1 : 0) << is_volatile_shift) |
130 ((is_final_flag ? 1 : 0) << is_final_shift) |
131 ((is_flat_flag ? 1 : 0) << is_flat_shift) |
132 ((is_null_free_inline_type_flag ? 1 : 0) << is_null_free_inline_type_shift) |
133 ((has_null_marker_flag ? 1 : 0) << has_null_marker_shift);
134 _flags = checked_cast<u1>(new_flags);
135 assert(is_volatile() == is_volatile_flag, "Must be");
136 assert(is_final() == is_final_flag, "Must be");
137 assert(is_flat() == is_flat_flag, "Must be");
138 assert(is_null_free_inline_type() == is_null_free_inline_type_flag, "Must be");
139 assert(has_null_marker() == has_null_marker_flag, "Must be");
140 }
141
142 inline void set_bytecode(u1* code, u1 new_code) {
143 #ifdef ASSERT
144 // Read once.
145 volatile Bytecodes::Code c = (Bytecodes::Code)*code;
146 assert(c == 0 || c == new_code || new_code == 0, "update must be consistent");
147 #endif
148 AtomicAccess::release_store(code, new_code);
149 }
150
151 // Debug help
152 void assert_is_valid() const NOT_DEBUG_RETURN;
153
154 public:
155 // Populate the strucutre with resolution information
156 void fill_in(const fieldDescriptor& info, u1 tos_state, u1 get_code, u1 put_code);
157
158 // CDS
159 #if INCLUDE_CDS
160 void remove_unshareable_info();
161 void mark_and_relocate();
162 #endif
163
164 // Offsets
165 static ByteSize field_holder_offset() { return byte_offset_of(ResolvedFieldEntry, _field_holder); }
166 static ByteSize field_offset_offset() { return byte_offset_of(ResolvedFieldEntry, _field_offset); }
167 static ByteSize field_index_offset() { return byte_offset_of(ResolvedFieldEntry, _field_index); }
168 static ByteSize get_code_offset() { return byte_offset_of(ResolvedFieldEntry, _get_code); }
169 static ByteSize put_code_offset() { return byte_offset_of(ResolvedFieldEntry, _put_code); }
170 static ByteSize type_offset() { return byte_offset_of(ResolvedFieldEntry, _tos_state); }
171 static ByteSize flags_offset() { return byte_offset_of(ResolvedFieldEntry, _flags); }
172 };
173
174 #endif //SHARE_OOPS_RESOLVEDFIELDENTRY_HPP