1 /*
2 * Copyright (c) 1999, 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
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.
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23 */
24
25 #ifndef SHARE_CI_CIFIELD_HPP
26 #define SHARE_CI_CIFIELD_HPP
27
28 #include "ci/ciClassList.hpp"
29 #include "ci/ciConstant.hpp"
30 #include "ci/ciFlags.hpp"
31 #include "ci/ciInstance.hpp"
32 #include "ci/ciUtilities.hpp"
33
34 // ciField
35 //
36 // This class represents the result of a field lookup in the VM.
37 // The lookup may not succeed, in which case the information in
38 // the ciField will be incomplete.
39 class ciField : public ArenaObj {
40 CI_PACKAGE_ACCESS
41 friend class ciEnv;
42 friend class ciInstanceKlass;
43
44 private:
45 ciFlags _flags;
46 ciInstanceKlass* _holder;
47 ciInstanceKlass* _original_holder; // For fields nested in flat fields
48 ciSymbol* _name;
49 ciSymbol* _signature;
50 ciType* _type;
51 int _offset;
52 bool _is_constant;
53 bool _is_flat;
54 bool _is_null_free;
55 ciMethod* _known_to_link_with_put;
56 ciInstanceKlass* _known_to_link_with_get;
57 ciConstant _constant_value;
58
59 ciType* compute_type();
60 ciType* compute_type_impl();
61
62 ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc);
63 ciField(fieldDescriptor* fd);
64 ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final);
65
66 // shared constructor code
67 void initialize_from(fieldDescriptor* fd);
68
69 public:
70 ciFlags flags() const { return _flags; }
71
72 // Of which klass is this field a member?
73 //
74 // Usage note: the declared holder of a field is the class
75 // referenced by name in the bytecodes. The canonical holder
76 // is the most general class which holds the field. This
77 // method returns the canonical holder. The declared holder
78 // can be accessed via a method in ciBytecodeStream.
79 //
80 // Ex.
81 // class A {
82 // public int f = 7;
83 // }
84 // class B extends A {
85 // public void test() {
86 // System.out.println(f);
87 // }
88 // }
89 //
90 // A java compiler is permitted to compile the access to
91 // field f as:
92 //
93 // getfield B.f
94 //
95 // In that case the declared holder of f would be B and
96 // the canonical holder of f would be A.
97 ciInstanceKlass* holder() const { return _holder; }
98
99 // Name of this field?
100 ciSymbol* name() const { return _name; }
101
102 // Signature of this field?
103 ciSymbol* signature() const { return _signature; }
104
105 // Of what type is this field?
106 ciType* type() { return (_type == nullptr) ? compute_type() : _type; }
107
108 // How is this field actually stored in memory?
109 BasicType layout_type() { return type2field[(_type == nullptr) ? T_OBJECT : _type->basic_type()]; }
110
111 // How big is this field in memory?
112 int size_in_bytes() { return type2aelembytes(layout_type()); }
113
114 // What is the offset of this field? (Fields are aligned to the byte level.)
115 int offset_in_bytes() const {
116 assert(_offset >= 1, "illegal call to offset()");
117 return _offset;
118 }
119
120 // Is this field shared?
121 bool is_shared() {
122 // non-static fields of shared holders are cached
123 return _holder->is_shared() && !is_static();
124 }
125
126 // Is this field a constant?
127 //
128 // Clarification: A field is considered constant if:
129 // 1. The field is both static and final
130 // 2. The field is not one of the special static/final
131 // non-constant fields. These are java.lang.System.in
132 // and java.lang.System.out. Abomination.
133 //
134 // A field is also considered constant if
135 // - it is marked @Stable and is non-null (or non-zero, if a primitive) or
136 // - it is trusted or
137 // - it is the target field of a CallSite object.
138 //
139 // See ciField::initialize_from() for more details.
140 //
141 // A user should also check the field value (constant_value().is_valid()), since
142 // constant fields of non-initialized classes don't have values yet.
143 bool is_constant() const { return _is_constant; }
144
145 // Get the constant value of the static field.
146 ciConstant constant_value();
147
148 bool is_static_constant() {
149 return is_static() && is_constant() && constant_value().is_valid();
150 }
151
152 // Get the constant value of non-static final field in the given
153 // object.
154 ciConstant constant_value_of(ciObject* object);
155
156 // Check for link time errors. Accessing a field from a
157 // certain method via a certain bytecode may or may not be legal.
158 // This call checks to see if an exception may be raised by
159 // an access of this field.
160 //
161 // Usage note: if the same field is accessed multiple times
162 // in the same compilation, will_link will need to be checked
163 // at each point of access.
164 bool will_link(ciMethod* accessing_method,
165 Bytecodes::Code bc);
166
167 // Java access flags
168 bool is_public () const { return flags().is_public(); }
169 bool is_private () const { return flags().is_private(); }
170 bool is_protected () const { return flags().is_protected(); }
171 bool is_static () const { return flags().is_static(); }
172 bool is_final () const { return flags().is_final(); }
173 bool is_stable () const { return flags().is_stable(); }
174 bool is_volatile () const { return flags().is_volatile(); }
175 bool is_transient () const { return flags().is_transient(); }
176 bool is_flat () const { return _is_flat; }
177 bool is_null_free () const { return _is_null_free; }
178
179 // The field is modified outside of instance initializer methods
180 // (or class/initializer methods if the field is static).
181 bool has_initialized_final_update() const { return flags().has_initialized_final_update(); }
182
183 bool is_call_site_target();
184
185 bool is_autobox_cache();
186
187 // Debugging output
188 void print();
189 void print_name_on(outputStream* st);
190 };
191
192 #endif // SHARE_CI_CIFIELD_HPP