1 /*
2 * Copyright 1999-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // ciField
26 //
27 // This class represents the result of a field lookup in the VM.
28 // The lookup may not succeed, in which case the information in
29 // the ciField will be incomplete.
30 class ciField : public ResourceObj {
31 CI_PACKAGE_ACCESS
32 friend class ciEnv;
33 friend class ciInstanceKlass;
34 friend class NonStaticFieldFiller;
35
36 private:
37 ciFlags _flags;
38 ciInstanceKlass* _holder;
39 ciSymbol* _name;
40 ciSymbol* _signature;
41 ciType* _type;
42 int _offset;
43 bool _is_constant;
44 ciInstanceKlass* _known_to_link_with;
45 ciConstant _constant_value;
46
47 // Used for will_link
48 int _cp_index;
49
50 ciType* compute_type();
51 ciType* compute_type_impl();
52
53 ciField(ciInstanceKlass* klass, int index);
54 ciField(fieldDescriptor* fd);
55
56 // shared constructor code
57 void initialize_from(fieldDescriptor* fd);
58
59 // The implementation of the print method.
60 void print_impl(outputStream* st);
61
62 public:
63 ciFlags flags() { return _flags; }
64
65 // Of which klass is this field a member?
66 //
67 // Usage note: the declared holder of a field is the class
68 // referenced by name in the bytecodes. The canonical holder
69 // is the most general class which holds the field. This
70 // method returns the canonical holder. The declared holder
71 // can be accessed via a method in ciBytecodeStream.
72 //
73 // Ex.
74 // class A {
75 // public int f = 7;
76 // }
77 // class B extends A {
78 // public void test() {
79 // System.out.println(f);
80 // }
81 // }
82 //
83 // A java compiler is permitted to compile the access to
84 // field f as:
85 //
86 // getfield B.f
87 //
88 // In that case the declared holder of f would be B and
89 // the canonical holder of f would be A.
90 ciInstanceKlass* holder() { return _holder; }
91
92 // Name of this field?
93 ciSymbol* name() { return _name; }
94
95 // Signature of this field?
96 ciSymbol* signature() { return _signature; }
97
98 // Of what type is this field?
99 ciType* type() { return (_type == NULL) ? compute_type() : _type; }
100
101 // How is this field actually stored in memory?
102 BasicType layout_type() { return type2field[(_type == NULL) ? T_OBJECT : _type->basic_type()]; }
103
104 // How big is this field in memory?
105 int size_in_bytes() { return type2aelembytes(layout_type()); }
106
107 // What is the offset of this field?
108 int offset() {
109 assert(_offset >= 1, "illegal call to offset()");
110 return _offset;
111 }
112
113 // Same question, explicit units. (Fields are aligned to the byte level.)
114 int offset_in_bytes() {
115 return offset();
116 }
117
118 // Is this field shared?
119 bool is_shared() {
120 // non-static fields of shared holders are cached
121 return _holder->is_shared() && !is_static();
122 }
123
124 // Is this field a constant?
125 //
126 // Clarification: A field is considered constant if:
127 // 1. The field is both static and final
128 // 2. The canonical holder of the field has undergone
129 // static initialization.
130 // 3. If the field is an object or array, then the oop
131 // in question is allocated in perm space.
132 // 4. The field is not one of the special static/final
133 // non-constant fields. These are java.lang.System.in
134 // and java.lang.System.out. Abomination.
135 //
136 // Note: the check for case 4 is not yet implemented.
137 bool is_constant() { return _is_constant; }
138
139 // Get the constant value of this field.
140 ciConstant constant_value() {
141 assert(is_static() && is_constant(), "illegal call to constant_value()");
142 return _constant_value;
143 }
144
145 // Get the constant value of non-static final field in the given
146 // object.
147 ciConstant constant_value_of(ciObject* object) {
148 assert(!is_static() && is_constant(), "only if field is non-static constant");
149 assert(object->is_instance(), "must be instance");
150 return object->as_instance()->field_value(this);
151 }
152
153 // Check for link time errors. Accessing a field from a
154 // certain class via a certain bytecode may or may not be legal.
155 // This call checks to see if an exception may be raised by
156 // an access of this field.
157 //
158 // Usage note: if the same field is accessed multiple times
159 // in the same compilation, will_link will need to be checked
160 // at each point of access.
161 bool will_link(ciInstanceKlass* accessing_klass,
162 Bytecodes::Code bc);
163
164 // Java access flags
165 bool is_public () { return flags().is_public(); }
166 bool is_private () { return flags().is_private(); }
167 bool is_protected () { return flags().is_protected(); }
168 bool is_static () { return flags().is_static(); }
169 bool is_final () { return flags().is_final(); }
170 bool is_volatile () { return flags().is_volatile(); }
171 bool is_transient () { return flags().is_transient(); }
172
173 // Debugging output
174 void print();
175 void print_name_on(outputStream* st);
176 };