1 /*
2 * Copyright (c) 1999, 2010, 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_VM_CI_CIFIELD_HPP
26 #define SHARE_VM_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
33 // ciField
34 //
35 // This class represents the result of a field lookup in the VM.
36 // The lookup may not succeed, in which case the information in
37 // the ciField will be incomplete.
38 class ciField : public ResourceObj {
39 CI_PACKAGE_ACCESS
40 friend class ciEnv;
41 friend class ciInstanceKlass;
42
43 private:
44 ciFlags _flags;
45 ciInstanceKlass* _holder;
46 ciSymbol* _name;
47 ciSymbol* _signature;
48 ciType* _type;
49 int _offset;
50 bool _is_constant;
51 ciInstanceKlass* _known_to_link_with;
52 ciConstant _constant_value;
53
54 // Used for will_link
55 int _cp_index;
56
57 ciType* compute_type();
58 ciType* compute_type_impl();
59
60 ciField(ciInstanceKlass* klass, int index);
61 ciField(fieldDescriptor* fd);
62
63 // shared constructor code
64 void initialize_from(fieldDescriptor* fd);
65
66 // The implementation of the print method.
67 void print_impl(outputStream* st);
68
69 public:
70 ciFlags flags() { 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() { return _holder; }
98
99 // Name of this field?
100 ciSymbol* name() { return _name; }
101
102 // Signature of this field?
103 ciSymbol* signature() { return _signature; }
104
105 // Of what type is this field?
106 ciType* type() { return (_type == NULL) ? compute_type() : _type; }
107
108 // How is this field actually stored in memory?
109 BasicType layout_type() { return type2field[(_type == NULL) ? 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?
115 int offset() {
116 assert(_offset >= 1, "illegal call to offset()");
117 return _offset;
118 }
119
120 // Same question, explicit units. (Fields are aligned to the byte level.)
121 int offset_in_bytes() {
122 return offset();
123 }
124
125 // // Is this field shared?
126 // bool is_shared() {
127 // // non-static fields of shared holders are cached
128 // return _holder->is_shared() && !is_static();
129 // }
130
131 // Is this field a constant?
132 //
133 // Clarification: A field is considered constant if:
134 // 1. The field is both static and final
135 // 2. The canonical holder of the field has undergone
136 // static initialization.
137 // 3. If the field is an object or array, then the oop
138 // in question is allocated in perm space.
139 // 4. The field is not one of the special static/final
140 // non-constant fields. These are java.lang.System.in
141 // and java.lang.System.out. Abomination.
142 //
143 // Note: the check for case 4 is not yet implemented.
144 bool is_constant() { return _is_constant; }
145
146 // Get the constant value of this field.
147 ciConstant constant_value() {
148 assert(is_static() && is_constant(), "illegal call to constant_value()");
149 return _constant_value;
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 assert(!is_static() && is_constant(), "only if field is non-static constant");
156 assert(object->is_instance(), "must be instance");
157 return object->as_instance()->field_value(this);
158 }
159
160 // Check for link time errors. Accessing a field from a
161 // certain class via a certain bytecode may or may not be legal.
162 // This call checks to see if an exception may be raised by
163 // an access of this field.
164 //
165 // Usage note: if the same field is accessed multiple times
166 // in the same compilation, will_link will need to be checked
167 // at each point of access.
168 bool will_link(ciInstanceKlass* accessing_klass,
169 Bytecodes::Code bc);
170
171 // Java access flags
172 bool is_public () { return flags().is_public(); }
173 bool is_private () { return flags().is_private(); }
174 bool is_protected () { return flags().is_protected(); }
175 bool is_static () { return flags().is_static(); }
176 bool is_final () { return flags().is_final(); }
177 bool is_volatile () { return flags().is_volatile(); }
178 bool is_transient () { return flags().is_transient(); }
179
180 // Debugging output
181 void print();
182 void print_name_on(outputStream* st);
183 };
184
185 #endif // SHARE_VM_CI_CIFIELD_HPP