1/*
2 * Copyright (c) 1999, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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.
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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).
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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.
39class ciField : public ResourceObj {
40 CI_PACKAGE_ACCESS
41 friend class ciEnv;
42 friend class ciInstanceKlass;
43
44private:
45 ciFlags _flags;
46 ciInstanceKlass* _holder;
47 ciSymbol* _name;
48 ciSymbol* _signature;
49 ciType* _type;
50 int _offset;
51 bool _is_constant;
52 ciMethod* _known_to_link_with_put;
53 ciInstanceKlass* _known_to_link_with_get;
54 ciConstant _constant_value;
55
56 ciType* compute_type();
57 ciType* compute_type_impl();
58
59 ciField(ciInstanceKlass* klass, int index);
60 ciField(fieldDescriptor* fd);
61
62 // shared constructor code
63 void initialize_from(fieldDescriptor* fd);
64
65public:
66 ciFlags flags() const { return _flags; }
67
68 // Of which klass is this field a member?
69 //
70 // Usage note: the declared holder of a field is the class
71 // referenced by name in the bytecodes. The canonical holder
72 // is the most general class which holds the field. This
73 // method returns the canonical holder. The declared holder
74 // can be accessed via a method in ciBytecodeStream.
75 //
76 // Ex.
77 // class A {
78 // public int f = 7;
79 // }
80 // class B extends A {
81 // public void test() {
82 // System.out.println(f);
83 // }
84 // }
85 //
86 // A java compiler is permitted to compile the access to
87 // field f as:
88 //
89 // getfield B.f
90 //
91 // In that case the declared holder of f would be B and
92 // the canonical holder of f would be A.
93 ciInstanceKlass* holder() const { return _holder; }
94
95 // Name of this field?
96 ciSymbol* name() const { return _name; }
97
98 // Signature of this field?
99 ciSymbol* signature() const { return _signature; }
100
101 // Of what type is this field?
102 ciType* type() { return (_type == NULL) ? compute_type() : _type; }
103
104 // How is this field actually stored in memory?
105 BasicType layout_type() { return type2field[(_type == NULL) ? T_OBJECT : _type->basic_type()]; }
106
107 // How big is this field in memory?
108 int size_in_bytes() { return type2aelembytes(layout_type()); }
109
110 // What is the offset of this field?
111 int offset() const {
112 assert(_offset >= 1, "illegal call to offset()");
113 return _offset;
114 }
115
116 // Same question, explicit units. (Fields are aligned to the byte level.)
117 int offset_in_bytes() const {
118 return offset();
119 }
120
121 // Is this field shared?
122 bool is_shared() {
123 // non-static fields of shared holders are cached
124 return _holder->is_shared() && !is_static();
125 }
126
127 // Is this field a constant?
128 //
129 // Clarification: A field is considered constant if:
130 // 1. The field is both static and final
131 // 2. The field is not one of the special static/final
132 // non-constant fields. These are java.lang.System.in
133 // and java.lang.System.out. Abomination.
134 //
135 // A field is also considered constant if
136 // - it is marked @Stable and is non-null (or non-zero, if a primitive) or
137 // - it is trusted or
138 // - it is the target field of a CallSite object.
139 //
140 // See ciField::initialize_from() for more details.
141 //
142 // A user should also check the field value (constant_value().is_valid()), since
143 // constant fields of non-initialized classes don't have values yet.
144 bool is_constant() const { return _is_constant; }
145
146 // Get the constant value of the static field.
147 ciConstant constant_value();
148
149 bool is_static_constant() {
150 return is_static() && is_constant() && constant_value().is_valid();
151 }
152
153 // Get the constant value of non-static final field in the given
154 // object.
155 ciConstant constant_value_of(ciObject* object);
156
157 // Check for link time errors. Accessing a field from a
158 // certain method via a certain bytecode may or may not be legal.
159 // This call checks to see if an exception may be raised by
160 // an access of this field.
161 //
162 // Usage note: if the same field is accessed multiple times
163 // in the same compilation, will_link will need to be checked
164 // at each point of access.
165 bool will_link(ciMethod* accessing_method,
166 Bytecodes::Code bc);
167
168 // Java access flags
169 bool is_public () const { return flags().is_public(); }
170 bool is_private () const { return flags().is_private(); }
171 bool is_protected () const { return flags().is_protected(); }
172 bool is_static () const { return flags().is_static(); }
173 bool is_final () const { return flags().is_final(); }
174 bool is_stable () const { return flags().is_stable(); }
175 bool is_volatile () const { return flags().is_volatile(); }
176 bool is_transient () const { return flags().is_transient(); }
177 // The field is modified outside of instance initializer methods
178 // (or class/initializer methods if the field is static).
179 bool has_initialized_final_update() const { return flags().has_initialized_final_update(); }
180
181 bool is_call_site_target() {
182 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
183 if (callsite_klass == NULL)
184 return false;
185 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbol::target_name()));
186 }
187
188 bool is_autobox_cache() {
189 ciSymbol* klass_name = holder()->name();
190 return (name() == ciSymbol::cache_field_name() &&
191 holder()->uses_default_loader() &&
192 (klass_name == ciSymbol::java_lang_Character_CharacterCache() ||
193 klass_name == ciSymbol::java_lang_Byte_ByteCache() ||
194 klass_name == ciSymbol::java_lang_Short_ShortCache() ||
195 klass_name == ciSymbol::java_lang_Integer_IntegerCache() ||
196 klass_name == ciSymbol::java_lang_Long_LongCache()));
197 }
198
199 // Debugging output
200 void print();
201 void print_name_on(outputStream* st);
202};
203
204#endif // SHARE_CI_CIFIELD_HPP
205