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.
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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 #include "precompiled.hpp"
26 #include "ci/ciField.hpp"
27 #include "ci/ciInstanceKlass.hpp"
28 #include "ci/ciUtilities.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc_interface/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "oops/oop.inline2.hpp"
35 #include "runtime/fieldDescriptor.hpp"
36
37 // ciField
38 //
39 // This class represents the result of a field lookup in the VM.
40 // The lookup may not succeed, in which case the information in
41 // the ciField will be incomplete.
42
43 // The ciObjectFactory cannot create circular data structures in one query.
44 // To avoid vicious circularities, we initialize ciField::_type to NULL
45 // for reference types and derive it lazily from the ciField::_signature.
46 // Primitive types are eagerly initialized, and basic layout queries
47 // can succeed without initialization, using only the BasicType of the field.
48
49 // Notes on bootstrapping and shared CI objects: A field is shared if and
50 // only if it is (a) non-static and (b) declared by a shared instance klass.
51 // This allows non-static field lists to be cached on shared types.
52 // Because the _type field is lazily initialized, however, there is a
53 // special restriction that a shared field cannot cache an unshared type.
54 // This puts a small performance penalty on shared fields with unshared
55 // types, such as StackTraceElement[] Throwable.stackTrace.
56 // (Throwable is shared because ClassCastException is shared, but
57 // StackTraceElement is not presently shared.)
58
59 // It is not a vicious circularity for a ciField to recursively create
60 // the ciSymbols necessary to represent its name and signature.
61 // Therefore, these items are created eagerly, and the name and signature
62 // of a shared field are themselves shared symbols. This somewhat
63 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
64 // with all of the additional 43 being uninteresting shared ciSymbols.
65 // This adds at most one step to the binary search, an amount which
66 // decreases for complex compilation tasks.
67
68 // ------------------------------------------------------------------
69 // ciField::ciField
70 ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with(NULL) {
71 ASSERT_IN_VM;
72 CompilerThread *thread = CompilerThread::current();
73
74 assert(ciObjectFactory::is_initialized(), "not a shared field");
75
76 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constan-pool");
77
78 _cp_index = index;
79 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
80
81 // Get the field's name, signature, and type.
82 Symbol* name = cpool->name_ref_at(index);
83 _name = ciEnv::current(thread)->get_symbol(name);
84
85 int nt_index = cpool->name_and_type_ref_index_at(index);
86 int sig_index = cpool->signature_ref_index_at(nt_index);
87 Symbol* signature = cpool->symbol_at(sig_index);
88 _signature = ciEnv::current(thread)->get_symbol(signature);
89
90 BasicType field_type = FieldType::basic_type(signature);
91
92 // If the field is a pointer type, get the klass of the
93 // field.
94 if (field_type == T_OBJECT || field_type == T_ARRAY) {
95 bool ignore;
96 // This is not really a class reference; the index always refers to the
97 // field's type signature, as a symbol. Linkage checks do not apply.
98 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
99 } else {
100 _type = ciType::make(field_type);
101 }
102
103 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
104
105 // Get the field's declared holder.
106 //
107 // Note: we actually create a ciInstanceKlass for this klass,
108 // even though we may not need to.
109 int holder_index = cpool->klass_ref_index_at(index);
110 bool holder_is_accessible;
111 ciInstanceKlass* declared_holder =
112 ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
113 holder_is_accessible,
114 klass)->as_instance_klass();
115
116 // The declared holder of this field may not have been loaded.
117 // Bail out with partial field information.
118 if (!holder_is_accessible) {
119 // _cp_index and _type have already been set.
120 // The default values for _flags and _constant_value will suffice.
121 // We need values for _holder, _offset, and _is_constant,
122 _holder = declared_holder;
123 _offset = -1;
124 _is_constant = false;
125 return;
126 }
127
128 instanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
129
130 // Perform the field lookup.
131 fieldDescriptor field_desc;
132 klassOop canonical_holder =
133 loaded_decl_holder->find_field(name, signature, &field_desc);
134 if (canonical_holder == NULL) {
135 // Field lookup failed. Will be detected by will_link.
136 _holder = declared_holder;
137 _offset = -1;
138 _is_constant = false;
139 return;
140 }
141
142 assert(canonical_holder == field_desc.field_holder(), "just checking");
143 initialize_from(&field_desc);
144 }
145
146 ciField::ciField(fieldDescriptor *fd): _known_to_link_with(NULL) {
147 ASSERT_IN_VM;
148
149 _cp_index = -1;
150
151 // Get the field's name, signature, and type.
152 ciEnv* env = CURRENT_ENV;
153 _name = env->get_symbol(fd->name());
154 _signature = env->get_symbol(fd->signature());
155
156 BasicType field_type = fd->field_type();
157
158 // If the field is a pointer type, get the klass of the
159 // field.
160 if (field_type == T_OBJECT || field_type == T_ARRAY) {
161 _type = NULL; // must call compute_type on first access
162 } else {
163 _type = ciType::make(field_type);
164 }
165
166 initialize_from(fd);
167
168 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
169 assert(is_shared() || ciObjectFactory::is_initialized(),
170 "bootstrap classes must not create & cache unshared fields");
171 }
172
173 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
174 if (holder == NULL)
175 return false;
176 if (holder->name() == ciSymbol::java_lang_System())
177 // Never trust strangely unstable finals: System.out, etc.
178 return false;
179 // Even if general trusting is disabled, trust system-built closures in these packages.
180 if (holder->is_in_package("java/dyn") || holder->is_in_package("sun/dyn"))
181 return true;
182 return TrustFinalNonStaticFields;
183 }
184
185 void ciField::initialize_from(fieldDescriptor* fd) {
186 // Get the flags, offset, and canonical holder of the field.
187 _flags = ciFlags(fd->access_flags());
188 _offset = fd->offset();
189 _holder = CURRENT_ENV->get_object(fd->field_holder())->as_instance_klass();
190
191 // Check to see if the field is constant.
192 if (_holder->is_initialized() && this->is_final()) {
193 if (!this->is_static()) {
194 // A field can be constant if it's a final static field or if it's
195 // a final non-static field of a trusted class ({java,sun}.dyn).
196 if (trust_final_non_static_fields(_holder)) {
197 _is_constant = true;
198 return;
199 }
200 _is_constant = false;
201 return;
202 }
203
204 // This field just may be constant. The only cases where it will
205 // not be constant are:
206 //
207 // 1. The field holds a non-perm-space oop. The field is, strictly
208 // speaking, constant but we cannot embed non-perm-space oops into
209 // generated code. For the time being we need to consider the
210 // field to be not constant.
211 // 2. The field is a *special* static&final field whose value
212 // may change. The three examples are java.lang.System.in,
213 // java.lang.System.out, and java.lang.System.err.
214
215 Handle k = _holder->get_klassOop();
216 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
217 if( k() == SystemDictionary::System_klass() ) {
218 // Check offsets for case 2: System.in, System.out, or System.err
219 if( _offset == java_lang_System::in_offset_in_bytes() ||
220 _offset == java_lang_System::out_offset_in_bytes() ||
221 _offset == java_lang_System::err_offset_in_bytes() ) {
222 _is_constant = false;
223 return;
224 }
225 }
226
227 _is_constant = true;
228 switch(type()->basic_type()) {
229 case T_BYTE:
230 _constant_value = ciConstant(type()->basic_type(), k->byte_field(_offset));
231 break;
232 case T_CHAR:
233 _constant_value = ciConstant(type()->basic_type(), k->char_field(_offset));
234 break;
235 case T_SHORT:
236 _constant_value = ciConstant(type()->basic_type(), k->short_field(_offset));
237 break;
238 case T_BOOLEAN:
239 _constant_value = ciConstant(type()->basic_type(), k->bool_field(_offset));
240 break;
241 case T_INT:
242 _constant_value = ciConstant(type()->basic_type(), k->int_field(_offset));
243 break;
244 case T_FLOAT:
245 _constant_value = ciConstant(k->float_field(_offset));
246 break;
247 case T_DOUBLE:
248 _constant_value = ciConstant(k->double_field(_offset));
249 break;
250 case T_LONG:
251 _constant_value = ciConstant(k->long_field(_offset));
252 break;
253 case T_OBJECT:
254 case T_ARRAY:
255 {
256 oop o = k->obj_field(_offset);
257
258 // A field will be "constant" if it is known always to be
259 // a non-null reference to an instance of a particular class,
260 // or to a particular array. This can happen even if the instance
261 // or array is not perm. In such a case, an "unloaded" ciArray
262 // or ciInstance is created. The compiler may be able to use
263 // information about the object's class (which is exact) or length.
264
265 if (o == NULL) {
266 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
267 } else {
268 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
269 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
270 }
271 }
272 }
273 } else {
274 _is_constant = false;
275 }
276 }
277
278 // ------------------------------------------------------------------
279 // ciField::compute_type
280 //
281 // Lazily compute the type, if it is an instance klass.
282 ciType* ciField::compute_type() {
283 GUARDED_VM_ENTRY(return compute_type_impl();)
284 }
285
286 ciType* ciField::compute_type_impl() {
287 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, _signature, false);
288 if (!type->is_primitive_type() && is_shared()) {
289 // We must not cache a pointer to an unshared type, in a shared field.
290 bool type_is_also_shared = false;
291 if (type->is_type_array_klass()) {
292 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
293 } else if (type->is_instance_klass()) {
294 type_is_also_shared = type->as_instance_klass()->is_shared();
295 } else {
296 // Currently there is no 'shared' query for array types.
297 type_is_also_shared = !ciObjectFactory::is_initialized();
298 }
299 if (!type_is_also_shared)
300 return type; // Bummer.
301 }
302 _type = type;
303 return type;
304 }
305
306
307 // ------------------------------------------------------------------
308 // ciField::will_link
309 //
310 // Can a specific access to this field be made without causing
311 // link errors?
312 bool ciField::will_link(ciInstanceKlass* accessing_klass,
313 Bytecodes::Code bc) {
314 VM_ENTRY_MARK;
315 if (_offset == -1) {
316 // at creation we couldn't link to our holder so we need to
317 // maintain that stance, otherwise there's no safe way to use this
318 // ciField.
319 return false;
320 }
321
322 if (_known_to_link_with == accessing_klass) {
323 return true;
324 }
325
326 FieldAccessInfo result;
327 constantPoolHandle c_pool(THREAD,
328 accessing_klass->get_instanceKlass()->constants());
329 LinkResolver::resolve_field(result, c_pool, _cp_index,
330 Bytecodes::java_code(bc),
331 true, false, KILL_COMPILE_ON_FATAL_(false));
332
333 // update the hit-cache, unless there is a problem with memory scoping:
334 if (accessing_klass->is_shared() || !is_shared())
335 _known_to_link_with = accessing_klass;
336
337 return true;
338 }
339
340 // ------------------------------------------------------------------
341 // ciField::print
342 void ciField::print() {
343 tty->print("<ciField ");
344 _holder->print_name();
345 tty->print(".");
346 _name->print_symbol();
347 tty->print(" offset=%d type=", _offset);
348 if (_type != NULL) _type->print_name();
349 else tty->print("(reference)");
350 tty->print(" is_constant=%s", bool_to_str(_is_constant));
351 if (_is_constant && is_static()) {
352 tty->print(" constant_value=");
353 _constant_value.print();
354 }
355 tty->print(">");
356 }
357
358 // ------------------------------------------------------------------
359 // ciField::print_name_on
360 //
361 // Print the name of this field
362 void ciField::print_name_on(outputStream* st) {
363 name()->print_symbol_on(st);
364 }