1 /*
2 * Copyright (c) 1999, 2015, 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
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/shared/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/fieldDescriptor.hpp"
35
36 // ciField
37 //
38 // This class represents the result of a field lookup in the VM.
39 // The lookup may not succeed, in which case the information in
40 // the ciField will be incomplete.
41
42 // The ciObjectFactory cannot create circular data structures in one query.
43 // To avoid vicious circularities, we initialize ciField::_type to NULL
44 // for reference types and derive it lazily from the ciField::_signature.
45 // Primitive types are eagerly initialized, and basic layout queries
46 // can succeed without initialization, using only the BasicType of the field.
47
48 // Notes on bootstrapping and shared CI objects: A field is shared if and
49 // only if it is (a) non-static and (b) declared by a shared instance klass.
50 // This allows non-static field lists to be cached on shared types.
51 // Because the _type field is lazily initialized, however, there is a
52 // special restriction that a shared field cannot cache an unshared type.
53 // This puts a small performance penalty on shared fields with unshared
54 // types, such as StackTraceElement[] Throwable.stackTrace.
55 // (Throwable is shared because ClassCastException is shared, but
56 // StackTraceElement is not presently shared.)
57
58 // It is not a vicious circularity for a ciField to recursively create
59 // the ciSymbols necessary to represent its name and signature.
60 // Therefore, these items are created eagerly, and the name and signature
61 // of a shared field are themselves shared symbols. This somewhat
62 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
63 // with all of the additional 43 being uninteresting shared ciSymbols.
64 // This adds at most one step to the binary search, an amount which
65 // decreases for complex compilation tasks.
66
67 // ------------------------------------------------------------------
68 // ciField::ciField
69 ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
70 ASSERT_IN_VM;
71 CompilerThread *thread = CompilerThread::current();
72
73 assert(ciObjectFactory::is_initialized(), "not a shared field");
74
75 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
76
77 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
78
79 // Get the field's name, signature, and type.
80 Symbol* name = cpool->name_ref_at(index);
81 _name = ciEnv::current(thread)->get_symbol(name);
82
83 int nt_index = cpool->name_and_type_ref_index_at(index);
84 int sig_index = cpool->signature_ref_index_at(nt_index);
85 Symbol* signature = cpool->symbol_at(sig_index);
86 _signature = ciEnv::current(thread)->get_symbol(signature);
87
88 BasicType field_type = FieldType::basic_type(signature);
89
90 // If the field is a pointer type, get the klass of the
91 // field.
92 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) {
93 bool ignore;
94 // This is not really a class reference; the index always refers to the
95 // field's type signature, as a symbol. Linkage checks do not apply.
96 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
97 } else {
98 _type = ciType::make(field_type);
99 }
100
101 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
102
103 // Get the field's declared holder.
104 //
105 // Note: we actually create a ciInstanceKlass for this klass,
106 // even though we may not need to.
107 int holder_index = cpool->klass_ref_index_at(index);
108 bool holder_is_accessible;
109
110 ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
111 holder_is_accessible,
112 klass);
113
114 if (generic_declared_holder->is_array_klass()) {
115 // If the declared holder of the field is an array class, assume that
116 // the canonical holder of that field is java.lang.Object. Arrays
117 // do not have fields; java.lang.Object is the only supertype of an
118 // array type that can declare fields and is therefore the canonical
119 // holder of the array type.
120 //
121 // Furthermore, the compilers assume that java.lang.Object does not
122 // have any fields. Therefore, the field is not looked up. Instead,
123 // the method returns partial information that will trigger special
124 // handling in ciField::will_link and will result in a
125 // java.lang.NoSuchFieldError exception being thrown by the compiled
126 // code (the expected behavior in this case).
127 _holder = ciEnv::current(thread)->Object_klass();
128 _offset = -1;
129 _is_constant = false;
130 return;
131 }
132
133 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
134
135 // The declared holder of this field may not have been loaded.
136 // Bail out with partial field information.
137 if (!holder_is_accessible) {
138 // _type has already been set.
139 // The default values for _flags and _constant_value will suffice.
140 // We need values for _holder, _offset, and _is_constant,
141 _holder = declared_holder;
142 _offset = -1;
143 _is_constant = false;
144 return;
145 }
146
147 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
148
149 // Perform the field lookup.
150 fieldDescriptor field_desc;
151 Klass* canonical_holder =
152 loaded_decl_holder->find_field(name, signature, &field_desc);
153 if (canonical_holder == NULL) {
154 // Field lookup failed. Will be detected by will_link.
155 _holder = declared_holder;
156 _offset = -1;
157 _is_constant = false;
158 return;
159 }
160
161 // Access check based on declared_holder. canonical_holder should not be used
162 // to check access because it can erroneously succeed. If this check fails,
163 // propagate the declared holder to will_link() which in turn will bail out
164 // compilation for this field access.
165 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
166 _holder = declared_holder;
167 _offset = -1;
168 _is_constant = false;
169 return;
170 }
171
172 assert(canonical_holder == field_desc.field_holder(), "just checking");
173 initialize_from(&field_desc);
174 }
175
176 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
177 ASSERT_IN_VM;
178
179 // Get the field's name, signature, and type.
180 ciEnv* env = CURRENT_ENV;
181 _name = env->get_symbol(fd->name());
182 _signature = env->get_symbol(fd->signature());
183
184 BasicType field_type = fd->field_type();
185
186 // If the field is a pointer type, get the klass of the
187 // field.
188 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) {
189 _type = NULL; // must call compute_type on first access
190 } else {
191 _type = ciType::make(field_type);
192 }
193
194 initialize_from(fd);
195
196 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
197 assert(is_shared() || ciObjectFactory::is_initialized(),
198 "bootstrap classes must not create & cache unshared fields");
199 }
200
201 // Special copy constructor used to flatten value type fields by
202 // copying the fields of the value type to a new holder klass.
203 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
204 assert(field->holder()->is_valuetype(), "should only be used for value type field flattening");
205 // Set the is_final flag
206 jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
207 AccessFlags flags(field->flags().as_int() & final);
208 _flags = ciFlags(flags);
209 _holder = holder;
210 _offset = offset;
211 // Copy remaining fields
212 _name = field->_name;
213 _signature = field->_signature;
214 _type = field->_type;
215 _is_constant = field->_is_constant;
216 _known_to_link_with_put = field->_known_to_link_with_put;
217 _known_to_link_with_get = field->_known_to_link_with_get;
218 _constant_value = field->_constant_value;
219 }
220
221 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
222 if (holder == NULL)
223 return false;
224 if (holder->name() == ciSymbol::java_lang_System())
225 // Never trust strangely unstable finals: System.out, etc.
226 return false;
227 // Even if general trusting is disabled, trust system-built closures in these packages.
228 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
229 return true;
230 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
231 // so there is no hacking of finals going on with them.
232 if (holder->is_anonymous())
233 return true;
234 // Trust final fields in all boxed classes
235 if (holder->is_box_klass())
236 return true;
237 // Trust final fields in String
238 if (holder->name() == ciSymbol::java_lang_String())
239 return true;
240 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
241 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
242 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
243 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
244 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
245 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
246 return true;
247 }
248 return TrustFinalNonStaticFields;
249 }
250
251 void ciField::initialize_from(fieldDescriptor* fd) {
252 // Get the flags, offset, and canonical holder of the field.
253 _flags = ciFlags(fd->access_flags());
254 _offset = fd->offset();
255 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
256
257 // Check to see if the field is constant.
258 bool is_final = this->is_final();
259 bool is_stable = FoldStableValues && this->is_stable();
260 if (_holder->is_initialized() && (is_final || is_stable)) {
261 if (!this->is_static()) {
262 // A field can be constant if it's a final static field or if
263 // it's a final non-static field of a trusted class (classes in
264 // java.lang.invoke and sun.invoke packages and subpackages).
265 if (is_stable || trust_final_non_static_fields(_holder)) {
266 _is_constant = true;
267 return;
268 }
269 _is_constant = false;
270 return;
271 }
272
273 // This field just may be constant. The only case where it will
274 // not be constant is when the field is a *special* static&final field
275 // whose value may change. The three examples are java.lang.System.in,
276 // java.lang.System.out, and java.lang.System.err.
277
278 KlassHandle k = _holder->get_Klass();
279 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
280 if( k() == SystemDictionary::System_klass() ) {
281 // Check offsets for case 2: System.in, System.out, or System.err
282 if( _offset == java_lang_System::in_offset_in_bytes() ||
283 _offset == java_lang_System::out_offset_in_bytes() ||
284 _offset == java_lang_System::err_offset_in_bytes() ) {
285 _is_constant = false;
286 return;
287 }
288 }
289
290 Handle mirror = k->java_mirror();
291
292 switch(type()->basic_type()) {
293 case T_BYTE:
294 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
295 break;
296 case T_CHAR:
297 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
298 break;
299 case T_SHORT:
300 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
301 break;
302 case T_BOOLEAN:
303 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
304 break;
305 case T_INT:
306 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
307 break;
308 case T_FLOAT:
309 _constant_value = ciConstant(mirror->float_field(_offset));
310 break;
311 case T_DOUBLE:
312 _constant_value = ciConstant(mirror->double_field(_offset));
313 break;
314 case T_LONG:
315 _constant_value = ciConstant(mirror->long_field(_offset));
316 break;
317 case T_OBJECT:
318 case T_ARRAY:
319 {
320 oop o = mirror->obj_field(_offset);
321
322 // A field will be "constant" if it is known always to be
323 // a non-null reference to an instance of a particular class,
324 // or to a particular array. This can happen even if the instance
325 // or array is not perm. In such a case, an "unloaded" ciArray
326 // or ciInstance is created. The compiler may be able to use
327 // information about the object's class (which is exact) or length.
328
329 if (o == NULL) {
330 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
331 } else {
332 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
333 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
334 }
335 }
336 }
337 if (is_stable && _constant_value.is_null_or_zero()) {
338 // It is not a constant after all; treat it as uninitialized.
339 _is_constant = false;
340 } else {
341 _is_constant = true;
342 }
343 } else {
344 _is_constant = false;
345 }
346 }
347
348 // ------------------------------------------------------------------
349 // ciField::compute_type
350 //
351 // Lazily compute the type, if it is an instance klass.
352 ciType* ciField::compute_type() {
353 GUARDED_VM_ENTRY(return compute_type_impl();)
354 }
355
356 ciType* ciField::compute_type_impl() {
357 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
358 if (!type->is_primitive_type() && is_shared()) {
359 // We must not cache a pointer to an unshared type, in a shared field.
360 bool type_is_also_shared = false;
361 if (type->is_type_array_klass()) {
362 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
363 } else if (type->is_instance_klass()) {
364 type_is_also_shared = type->as_instance_klass()->is_shared();
365 } else {
366 // Currently there is no 'shared' query for array types.
367 type_is_also_shared = !ciObjectFactory::is_initialized();
368 }
369 if (!type_is_also_shared)
370 return type; // Bummer.
371 }
372 _type = type;
373 return type;
374 }
375
376
377 // ------------------------------------------------------------------
378 // ciField::will_link
379 //
380 // Can a specific access to this field be made without causing
381 // link errors?
382 bool ciField::will_link(ciInstanceKlass* accessing_klass,
383 Bytecodes::Code bc) {
384 VM_ENTRY_MARK;
385 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
386 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield ||
387 bc == Bytecodes::_vgetfield, "unexpected bytecode");
388
389 if (_offset == -1) {
390 // at creation we couldn't link to our holder so we need to
391 // maintain that stance, otherwise there's no safe way to use this
392 // ciField.
393 return false;
394 }
395
396 // Check for static/nonstatic mismatch
397 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
398 if (is_static != this->is_static()) {
399 return false;
400 }
401
402 // Get and put can have different accessibility rules
403 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
404 if (is_put) {
405 if (_known_to_link_with_put == accessing_klass) {
406 return true;
407 }
408 } else {
409 if (_known_to_link_with_get == accessing_klass) {
410 return true;
411 }
412 }
413
414 LinkInfo link_info(_holder->get_instanceKlass(),
415 _name->get_symbol(), _signature->get_symbol(),
416 accessing_klass->get_Klass());
417 fieldDescriptor result;
418 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
419
420 // update the hit-cache, unless there is a problem with memory scoping:
421 if (accessing_klass->is_shared() || !is_shared()) {
422 if (is_put) {
423 _known_to_link_with_put = accessing_klass;
424 } else {
425 _known_to_link_with_get = accessing_klass;
426 }
427 }
428
429 return true;
430 }
431
432 // ------------------------------------------------------------------
433 // ciField::print
434 void ciField::print() {
435 tty->print("<ciField name=");
436 _holder->print_name();
437 tty->print(".");
438 _name->print_symbol();
439 tty->print(" signature=");
440 _signature->print_symbol();
441 tty->print(" offset=%d type=", _offset);
442 if (_type != NULL)
443 _type->print_name();
444 else
445 tty->print("(reference)");
446 tty->print(" flags=%04x", flags().as_int());
447 tty->print(" is_constant=%s", bool_to_str(_is_constant));
448 if (_is_constant && is_static()) {
449 tty->print(" constant_value=");
450 _constant_value.print();
451 }
452 tty->print(">");
453 }
454
455 // ------------------------------------------------------------------
456 // ciField::print_name_on
457 //
458 // Print the name of this field
459 void ciField::print_name_on(outputStream* st) {
460 name()->print_symbol_on(st);
461 }