1 /*
2 * Copyright (c) 1999, 2012, 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 #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_put(NULL), _known_to_link_with_get(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 Klass* 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_put(NULL), _known_to_link_with_get(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/lang/invoke") || holder->is_in_package("sun/invoke"))
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_instance_klass(fd->field_holder());
190
191 // Check to see if the field is constant.
192 bool is_final = this->is_final();
193 bool is_stable = FoldStableValues && this->is_stable();
194 if (_holder->is_initialized() && (is_final || is_stable)) {
195 if (!this->is_static()) {
196 // A field can be constant if it's a final static field or if
197 // it's a final non-static field of a trusted class (classes in
198 // java.lang.invoke and sun.invoke packages and subpackages).
199 if (is_stable || trust_final_non_static_fields(_holder)) {
200 _is_constant = true;
201 return;
202 }
203 _is_constant = false;
204 return;
205 }
206
207 // This field just may be constant. The only cases where it will
208 // not be constant are:
209 //
210 // 1. The field holds a non-perm-space oop. The field is, strictly
211 // speaking, constant but we cannot embed non-perm-space oops into
212 // generated code. For the time being we need to consider the
213 // field to be not constant.
214 // 2. The field is a *special* static&final field whose value
215 // may change. The three examples are java.lang.System.in,
216 // java.lang.System.out, and java.lang.System.err.
217
218 KlassHandle k = _holder->get_Klass();
219 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
220 if( k() == SystemDictionary::System_klass() ) {
221 // Check offsets for case 2: System.in, System.out, or System.err
222 if( _offset == java_lang_System::in_offset_in_bytes() ||
223 _offset == java_lang_System::out_offset_in_bytes() ||
224 _offset == java_lang_System::err_offset_in_bytes() ) {
225 _is_constant = false;
226 return;
227 }
228 }
229
230 Handle mirror = k->java_mirror();
231
232 switch(type()->basic_type()) {
233 case T_BYTE:
234 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
235 break;
236 case T_CHAR:
237 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
238 break;
239 case T_SHORT:
240 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
241 break;
242 case T_BOOLEAN:
243 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
244 break;
245 case T_INT:
246 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
247 break;
248 case T_FLOAT:
249 _constant_value = ciConstant(mirror->float_field(_offset));
250 break;
251 case T_DOUBLE:
252 _constant_value = ciConstant(mirror->double_field(_offset));
253 break;
254 case T_LONG:
255 _constant_value = ciConstant(mirror->long_field(_offset));
256 break;
257 case T_OBJECT:
258 case T_ARRAY:
259 {
260 oop o = mirror->obj_field(_offset);
261
262 // A field will be "constant" if it is known always to be
263 // a non-null reference to an instance of a particular class,
264 // or to a particular array. This can happen even if the instance
265 // or array is not perm. In such a case, an "unloaded" ciArray
266 // or ciInstance is created. The compiler may be able to use
267 // information about the object's class (which is exact) or length.
268
269 if (o == NULL) {
270 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
271 } else {
272 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
273 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
274 }
275 }
276 }
277 if (is_stable && _constant_value.is_null_or_zero()) {
278 // It is not a constant after all; treat it as uninitialized.
279 _is_constant = false;
280 } else {
281 _is_constant = true;
282 }
283 } else {
284 _is_constant = false;
285 }
286 }
287
288 // ------------------------------------------------------------------
289 // ciField::compute_type
290 //
291 // Lazily compute the type, if it is an instance klass.
292 ciType* ciField::compute_type() {
293 GUARDED_VM_ENTRY(return compute_type_impl();)
294 }
295
296 ciType* ciField::compute_type_impl() {
297 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
298 if (!type->is_primitive_type() && is_shared()) {
299 // We must not cache a pointer to an unshared type, in a shared field.
300 bool type_is_also_shared = false;
301 if (type->is_type_array_klass()) {
302 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
303 } else if (type->is_instance_klass()) {
304 type_is_also_shared = type->as_instance_klass()->is_shared();
305 } else {
306 // Currently there is no 'shared' query for array types.
307 type_is_also_shared = !ciObjectFactory::is_initialized();
308 }
309 if (!type_is_also_shared)
310 return type; // Bummer.
311 }
312 _type = type;
313 return type;
314 }
315
316
317 // ------------------------------------------------------------------
318 // ciField::will_link
319 //
320 // Can a specific access to this field be made without causing
321 // link errors?
322 bool ciField::will_link(ciInstanceKlass* accessing_klass,
323 Bytecodes::Code bc) {
324 VM_ENTRY_MARK;
325 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
326 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
327 "unexpected bytecode");
328
329 if (_offset == -1) {
330 // at creation we couldn't link to our holder so we need to
331 // maintain that stance, otherwise there's no safe way to use this
332 // ciField.
333 return false;
334 }
335
336 // Check for static/nonstatic mismatch
337 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
338 if (is_static != this->is_static()) {
339 return false;
340 }
341
342 // Get and put can have different accessibility rules
343 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
344 if (is_put) {
345 if (_known_to_link_with_put == accessing_klass) {
346 return true;
347 }
348 } else {
349 if (_known_to_link_with_get == accessing_klass) {
350 return true;
351 }
352 }
353
354 FieldAccessInfo result;
355 constantPoolHandle c_pool(THREAD,
356 accessing_klass->get_instanceKlass()->constants());
357 LinkResolver::resolve_field(result, c_pool, _cp_index,
358 Bytecodes::java_code(bc),
359 true, false, KILL_COMPILE_ON_FATAL_(false));
360
361 // update the hit-cache, unless there is a problem with memory scoping:
362 if (accessing_klass->is_shared() || !is_shared()) {
363 if (is_put) {
364 _known_to_link_with_put = accessing_klass;
365 } else {
366 _known_to_link_with_get = accessing_klass;
367 }
368 }
369
370 return true;
371 }
372
373 // ------------------------------------------------------------------
374 // ciField::print
375 void ciField::print() {
376 tty->print("<ciField name=");
377 _holder->print_name();
378 tty->print(".");
379 _name->print_symbol();
380 tty->print(" signature=");
381 _signature->print_symbol();
382 tty->print(" offset=%d type=", _offset);
383 if (_type != NULL)
384 _type->print_name();
385 else
386 tty->print("(reference)");
387 tty->print(" flags=%04x", flags().as_int());
388 tty->print(" is_constant=%s", bool_to_str(_is_constant));
389 if (_is_constant && is_static()) {
390 tty->print(" constant_value=");
391 _constant_value.print();
392 }
393 tty->print(">");
394 }
395
396 // ------------------------------------------------------------------
397 // ciField::print_name_on
398 //
399 // Print the name of this field
400 void ciField::print_name_on(outputStream* st) {
401 name()->print_symbol_on(st);
402 }