1 /*
2 * Copyright (c) 1999, 2018, 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.inline.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc/shared/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/fieldDescriptor.inline.hpp"
35 #include "runtime/handles.inline.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) :
71 _is_flattened(false), _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
72 ASSERT_IN_VM;
73 CompilerThread *THREAD = CompilerThread::current();
74
75 assert(ciObjectFactory::is_initialized(), "not a shared field");
76
77 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
78
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 || field_type == T_VALUETYPE) {
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
112 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
113 holder_is_accessible,
114 klass);
115
116 if (generic_declared_holder->is_array_klass()) {
117 // If the declared holder of the field is an array class, assume that
118 // the canonical holder of that field is java.lang.Object. Arrays
119 // do not have fields; java.lang.Object is the only supertype of an
120 // array type that can declare fields and is therefore the canonical
121 // holder of the array type.
122 //
123 // Furthermore, the compilers assume that java.lang.Object does not
124 // have any fields. Therefore, the field is not looked up. Instead,
125 // the method returns partial information that will trigger special
126 // handling in ciField::will_link and will result in a
127 // java.lang.NoSuchFieldError exception being thrown by the compiled
128 // code (the expected behavior in this case).
129 _holder = ciEnv::current(THREAD)->Object_klass();
130 _offset = -1;
131 _is_constant = false;
132 return;
133 }
134
135 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
136
137 // The declared holder of this field may not have been loaded.
138 // Bail out with partial field information.
139 if (!holder_is_accessible) {
140 // _type has already been set.
141 // The default values for _flags and _constant_value will suffice.
142 // We need values for _holder, _offset, and _is_constant,
143 _holder = declared_holder;
144 _offset = -1;
145 _is_constant = false;
146 return;
147 }
148
149 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
150
151 // Perform the field lookup.
152 fieldDescriptor field_desc;
153 Klass* canonical_holder =
154 loaded_decl_holder->find_field(name, signature, &field_desc);
155 if (canonical_holder == NULL) {
156 // Field lookup failed. Will be detected by will_link.
157 _holder = declared_holder;
158 _offset = -1;
159 _is_constant = false;
160 return;
161 }
162
163 // Access check based on declared_holder. canonical_holder should not be used
164 // to check access because it can erroneously succeed. If this check fails,
165 // propagate the declared holder to will_link() which in turn will bail out
166 // compilation for this field access.
167 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
168 declared_holder->get_Klass(),
169 canonical_holder,
170 field_desc.access_flags(),
171 true, false, THREAD);
172 if (!can_access) {
173 _holder = declared_holder;
174 _offset = -1;
175 _is_constant = false;
176 // It's possible the access check failed due to a nestmate access check
177 // encountering an exception. We can't propagate the exception from here
178 // so we have to clear it. If the access check happens again in a different
179 // context then the exception will be thrown there.
180 if (HAS_PENDING_EXCEPTION) {
181 CLEAR_PENDING_EXCEPTION;
182 }
183 return;
184 }
185
186 assert(canonical_holder == field_desc.field_holder(), "just checking");
187 initialize_from(&field_desc);
188 }
189
190 ciField::ciField(fieldDescriptor *fd) :
191 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
192 ASSERT_IN_VM;
193
194 // Get the field's name, signature, and type.
195 ciEnv* env = CURRENT_ENV;
196 _name = env->get_symbol(fd->name());
197 _signature = env->get_symbol(fd->signature());
198
199 BasicType field_type = fd->field_type();
200
201 // If the field is a pointer type, get the klass of the
202 // field.
203 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) {
204 _type = NULL; // must call compute_type on first access
205 } else {
206 _type = ciType::make(field_type);
207 }
208
209 initialize_from(fd);
210
211 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
212 assert(is_shared() || ciObjectFactory::is_initialized(),
213 "bootstrap classes must not create & cache unshared fields");
214 }
215
216 // Special copy constructor used to flatten value type fields by
217 // copying the fields of the value type to a new holder klass.
218 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
219 assert(field->holder()->is_valuetype(), "should only be used for value type field flattening");
220 // Set the is_final flag
221 jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
222 AccessFlags flags(field->flags().as_int() & final);
223 _flags = ciFlags(flags);
224 _holder = holder;
225 _offset = offset;
226 // Copy remaining fields
227 _name = field->_name;
228 _signature = field->_signature;
229 _type = field->_type;
230 _is_constant = field->_is_constant;
231 _known_to_link_with_put = field->_known_to_link_with_put;
232 _known_to_link_with_get = field->_known_to_link_with_get;
233 _constant_value = field->_constant_value;
234 assert(!field->is_flattened(), "field must not be flattened");
235 assert(!field->is_flattenable(), "field must not be flattenable");
236 _is_flattened = false;
237 _is_flattenable = false;
238 }
239
240 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
241 if (holder == NULL)
242 return false;
243 if (holder->name() == ciSymbol::java_lang_System())
244 // Never trust strangely unstable finals: System.out, etc.
245 return false;
246 // Even if general trusting is disabled, trust system-built closures in these packages.
247 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
248 return true;
249 // Trust VM unsafe anonymous classes. They are private API (jdk.internal.misc.Unsafe)
250 // and can't be serialized, so there is no hacking of finals going on with them.
251 if (holder->is_unsafe_anonymous())
252 return true;
253 // Trust final fields in all boxed classes
254 if (holder->is_box_klass())
255 return true;
256 // Trust final fields in String
257 if (holder->name() == ciSymbol::java_lang_String())
258 return true;
259 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
260 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
261 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
262 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
263 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
264 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
265 return true;
266 }
267 return TrustFinalNonStaticFields;
268 }
269
270 void ciField::initialize_from(fieldDescriptor* fd) {
271 // Get the flags, offset, and canonical holder of the field.
272 _flags = ciFlags(fd->access_flags());
273 _offset = fd->offset();
274 Klass* field_holder = fd->field_holder();
275 assert(field_holder != NULL, "null field_holder");
276 _holder = CURRENT_ENV->get_instance_klass(field_holder);
277 _is_flattened = fd->is_flattened();
278 _is_flattenable = fd->is_flattenable();
279
280 // Check to see if the field is constant.
281 Klass* k = _holder->get_Klass();
282 bool is_stable_field = FoldStableValues && is_stable();
283 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
284 if (is_static()) {
285 // This field just may be constant. The only case where it will
286 // not be constant is when the field is a *special* static & final field
287 // whose value may change. The three examples are java.lang.System.in,
288 // java.lang.System.out, and java.lang.System.err.
289 assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
290 if (k == SystemDictionary::System_klass()) {
291 // Check offsets for case 2: System.in, System.out, or System.err
292 if( _offset == java_lang_System::in_offset_in_bytes() ||
293 _offset == java_lang_System::out_offset_in_bytes() ||
294 _offset == java_lang_System::err_offset_in_bytes() ) {
295 _is_constant = false;
296 return;
297 }
298 }
299 _is_constant = true;
300 } else {
301 // An instance field can be constant if it's a final static field or if
302 // it's a final non-static field of a trusted class (classes in
303 // java.lang.invoke and sun.invoke packages and subpackages).
304 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
305 }
306 } else {
307 // For CallSite objects treat the target field as a compile time constant.
308 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
309 if (k == SystemDictionary::CallSite_klass() &&
310 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
311 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
312 _is_constant = true;
313 } else {
314 // Non-final & non-stable fields are not constants.
315 _is_constant = false;
316 }
317 }
318 }
319
320 // ------------------------------------------------------------------
321 // ciField::constant_value
322 // Get the constant value of a this static field.
323 ciConstant ciField::constant_value() {
324 assert(is_static() && is_constant(), "illegal call to constant_value()");
325 if (!_holder->is_initialized()) {
326 return ciConstant(); // Not initialized yet
327 }
328 if (_constant_value.basic_type() == T_ILLEGAL) {
329 // Static fields are placed in mirror objects.
330 VM_ENTRY_MARK;
331 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
332 _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
333 }
334 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
335 return ciConstant();
336 }
337 return _constant_value;
338 }
339
340 // ------------------------------------------------------------------
341 // ciField::constant_value_of
342 // Get the constant value of non-static final field in the given object.
343 ciConstant ciField::constant_value_of(ciObject* object) {
344 assert(!is_static() && is_constant(), "only if field is non-static constant");
345 assert(object->is_instance(), "must be instance");
346 ciConstant field_value = object->as_instance()->field_value(this);
347 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
348 return ciConstant();
349 }
350 return field_value;
351 }
352
353 // ------------------------------------------------------------------
354 // ciField::compute_type
355 //
356 // Lazily compute the type, if it is an instance klass.
357 ciType* ciField::compute_type() {
358 GUARDED_VM_ENTRY(return compute_type_impl();)
359 }
360
361 ciType* ciField::compute_type_impl() {
362 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
363 if (!type->is_primitive_type() && is_shared()) {
364 // We must not cache a pointer to an unshared type, in a shared field.
365 bool type_is_also_shared = false;
366 if (type->is_type_array_klass()) {
367 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
368 } else if (type->is_instance_klass()) {
369 type_is_also_shared = type->as_instance_klass()->is_shared();
370 } else {
371 // Currently there is no 'shared' query for array types.
372 type_is_also_shared = !ciObjectFactory::is_initialized();
373 }
374 if (!type_is_also_shared)
375 return type; // Bummer.
376 }
377 _type = type;
378 return type;
379 }
380
381
382 // ------------------------------------------------------------------
383 // ciField::will_link
384 //
385 // Can a specific access to this field be made without causing
386 // link errors?
387 bool ciField::will_link(ciMethod* accessing_method,
388 Bytecodes::Code bc) {
389 VM_ENTRY_MARK;
390 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
391 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield ||
392 bc == Bytecodes::_withfield, "unexpected bytecode");
393
394 if (_offset == -1) {
395 // at creation we couldn't link to our holder so we need to
396 // maintain that stance, otherwise there's no safe way to use this
397 // ciField.
398 return false;
399 }
400
401 // Check for static/nonstatic mismatch
402 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
403 if (is_static != this->is_static()) {
404 return false;
405 }
406
407 // Get and put can have different accessibility rules
408 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
409 if (is_put) {
410 if (_known_to_link_with_put == accessing_method) {
411 return true;
412 }
413 } else {
414 if (_known_to_link_with_get == accessing_method->holder()) {
415 return true;
416 }
417 }
418
419 LinkInfo link_info(_holder->get_instanceKlass(),
420 _name->get_symbol(), _signature->get_symbol(),
421 accessing_method->get_Method());
422 fieldDescriptor result;
423 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
424
425 // update the hit-cache, unless there is a problem with memory scoping:
426 if (accessing_method->holder()->is_shared() || !is_shared()) {
427 if (is_put) {
428 _known_to_link_with_put = accessing_method;
429 } else {
430 _known_to_link_with_get = accessing_method->holder();
431 }
432 }
433
434 return true;
435 }
436
437 // ------------------------------------------------------------------
438 // ciField::print
439 void ciField::print() {
440 tty->print("<ciField name=");
441 _holder->print_name();
442 tty->print(".");
443 _name->print_symbol();
444 tty->print(" signature=");
445 _signature->print_symbol();
446 tty->print(" offset=%d type=", _offset);
447 if (_type != NULL)
448 _type->print_name();
449 else
450 tty->print("(reference)");
451 tty->print(" flags=%04x", flags().as_int());
452 tty->print(" is_constant=%s", bool_to_str(_is_constant));
453 if (_is_constant && is_static()) {
454 tty->print(" constant_value=");
455 _constant_value.print();
456 }
457 tty->print(">");
458 }
459
460 // ------------------------------------------------------------------
461 // ciField::print_name_on
462 //
463 // Print the name of this field
464 void ciField::print_name_on(outputStream* st) {
465 name()->print_symbol_on(st);
466 }