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
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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 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
202 if (holder == NULL)
203 return false;
204 if (holder->name() == ciSymbol::java_lang_System())
205 // Never trust strangely unstable finals: System.out, etc.
206 return false;
207 // Even if general trusting is disabled, trust system-built closures in these packages.
208 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
209 return true;
210 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
211 // so there is no hacking of finals going on with them.
212 if (holder->is_anonymous())
213 return true;
214 // Trust final fields in all boxed classes
215 if (holder->is_box_klass())
216 return true;
217 // Trust final fields in String
218 if (holder->name() == ciSymbol::java_lang_String())
219 return true;
220 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
221 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
222 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
223 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
224 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
225 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
226 return true;
227 }
228 return TrustFinalNonStaticFields;
229 }
230
231 void ciField::initialize_from(fieldDescriptor* fd) {
232 // Get the flags, offset, and canonical holder of the field.
233 _flags = ciFlags(fd->access_flags());
234 _offset = fd->offset();
235 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
236
237 // Check to see if the field is constant.
238 bool is_final = this->is_final();
239 bool is_stable = FoldStableValues && this->is_stable();
240 if (_holder->is_initialized() && (is_final || is_stable)) {
241 if (!this->is_static()) {
242 // A field can be constant if it's a final static field or if
243 // it's a final non-static field of a trusted class (classes in
244 // java.lang.invoke and sun.invoke packages and subpackages).
245 if (is_stable || trust_final_non_static_fields(_holder)) {
246 _is_constant = true;
247 return;
248 }
249 _is_constant = false;
250 return;
251 }
252
253 // This field just may be constant. The only case where it will
254 // not be constant is when the field is a *special* static&final field
255 // whose value may change. The three examples are java.lang.System.in,
256 // java.lang.System.out, and java.lang.System.err.
257
258 KlassHandle k = _holder->get_Klass();
259 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
260 if( k() == SystemDictionary::System_klass() ) {
261 // Check offsets for case 2: System.in, System.out, or System.err
262 if( _offset == java_lang_System::in_offset_in_bytes() ||
263 _offset == java_lang_System::out_offset_in_bytes() ||
264 _offset == java_lang_System::err_offset_in_bytes() ) {
265 _is_constant = false;
266 return;
267 }
268 }
269
270 Handle mirror = k->java_mirror();
271
272 switch(type()->basic_type()) {
273 case T_BYTE:
274 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
275 break;
276 case T_CHAR:
277 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
278 break;
279 case T_SHORT:
280 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
281 break;
282 case T_BOOLEAN:
283 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
284 break;
285 case T_INT:
286 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
287 break;
288 case T_FLOAT:
289 _constant_value = ciConstant(mirror->float_field(_offset));
290 break;
291 case T_DOUBLE:
292 _constant_value = ciConstant(mirror->double_field(_offset));
293 break;
294 case T_LONG:
295 _constant_value = ciConstant(mirror->long_field(_offset));
296 break;
297 case T_OBJECT:
298 case T_ARRAY:
299 {
300 oop o = mirror->obj_field(_offset);
301
302 // A field will be "constant" if it is known always to be
303 // a non-null reference to an instance of a particular class,
304 // or to a particular array. This can happen even if the instance
305 // or array is not perm. In such a case, an "unloaded" ciArray
306 // or ciInstance is created. The compiler may be able to use
307 // information about the object's class (which is exact) or length.
308
309 if (o == NULL) {
310 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
311 } else {
312 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
313 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
314 }
315 }
316 }
317 if (is_stable && _constant_value.is_null_or_zero()) {
318 // It is not a constant after all; treat it as uninitialized.
319 _is_constant = false;
320 } else {
321 _is_constant = true;
322 }
323 } else {
324 _is_constant = false;
325 }
326 }
327
328 // ------------------------------------------------------------------
329 // ciField::compute_type
330 //
331 // Lazily compute the type, if it is an instance klass.
332 ciType* ciField::compute_type() {
333 GUARDED_VM_ENTRY(return compute_type_impl();)
334 }
335
336 ciType* ciField::compute_type_impl() {
337 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
338 if (!type->is_primitive_type() && is_shared()) {
339 // We must not cache a pointer to an unshared type, in a shared field.
340 bool type_is_also_shared = false;
341 if (type->is_type_array_klass()) {
342 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
343 } else if (type->is_instance_klass()) {
344 type_is_also_shared = type->as_instance_klass()->is_shared();
345 } else {
346 // Currently there is no 'shared' query for array types.
347 type_is_also_shared = !ciObjectFactory::is_initialized();
348 }
349 if (!type_is_also_shared)
350 return type; // Bummer.
351 }
352 _type = type;
353 return type;
354 }
355
356
357 // ------------------------------------------------------------------
358 // ciField::will_link
359 //
360 // Can a specific access to this field be made without causing
361 // link errors?
362 bool ciField::will_link(ciInstanceKlass* accessing_klass,
363 Bytecodes::Code bc) {
364 VM_ENTRY_MARK;
365 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
366 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield ||
367 bc == Bytecodes::_vgetfield, "unexpected bytecode");
368
369 if (_offset == -1) {
370 // at creation we couldn't link to our holder so we need to
371 // maintain that stance, otherwise there's no safe way to use this
372 // ciField.
373 return false;
374 }
375
376 // Check for static/nonstatic mismatch
377 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
378 if (is_static != this->is_static()) {
379 return false;
380 }
381
382 // Get and put can have different accessibility rules
383 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
384 if (is_put) {
385 if (_known_to_link_with_put == accessing_klass) {
386 return true;
387 }
388 } else {
389 if (_known_to_link_with_get == accessing_klass) {
390 return true;
391 }
392 }
393
394 LinkInfo link_info(_holder->get_instanceKlass(),
395 _name->get_symbol(), _signature->get_symbol(),
396 accessing_klass->get_Klass());
397 fieldDescriptor result;
398 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
399
400 // update the hit-cache, unless there is a problem with memory scoping:
401 if (accessing_klass->is_shared() || !is_shared()) {
402 if (is_put) {
403 _known_to_link_with_put = accessing_klass;
404 } else {
405 _known_to_link_with_get = accessing_klass;
406 }
407 }
408
409 return true;
410 }
411
412 // ------------------------------------------------------------------
413 // ciField::print
414 void ciField::print() {
415 tty->print("<ciField name=");
416 _holder->print_name();
417 tty->print(".");
418 _name->print_symbol();
419 tty->print(" signature=");
420 _signature->print_symbol();
421 tty->print(" offset=%d type=", _offset);
422 if (_type != NULL)
423 _type->print_name();
424 else
425 tty->print("(reference)");
426 tty->print(" flags=%04x", flags().as_int());
427 tty->print(" is_constant=%s", bool_to_str(_is_constant));
428 if (_is_constant && is_static()) {
429 tty->print(" constant_value=");
430 _constant_value.print();
431 }
432 tty->print(">");
433 }
434
435 // ------------------------------------------------------------------
436 // ciField::print_name_on
437 //
438 // Print the name of this field
439 void ciField::print_name_on(outputStream* st) {
440 name()->print_symbol_on(st);
441 }