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.
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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).
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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 constan-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) {
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 ciInstanceKlass* declared_holder =
110 ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
111 holder_is_accessible,
112 klass)->as_instance_klass();
113
114 // The declared holder of this field may not have been loaded.
115 // Bail out with partial field information.
116 if (!holder_is_accessible) {
117 // _type has already been set.
118 // The default values for _flags and _constant_value will suffice.
119 // We need values for _holder, _offset, and _is_constant,
120 _holder = declared_holder;
121 _offset = -1;
122 _is_constant = false;
123 return;
124 }
125
126 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
127
128 // Perform the field lookup.
129 fieldDescriptor field_desc;
130 Klass* canonical_holder =
131 loaded_decl_holder->find_field(name, signature, &field_desc);
132 if (canonical_holder == NULL) {
133 // Field lookup failed. Will be detected by will_link.
134 _holder = declared_holder;
135 _offset = -1;
136 _is_constant = false;
137 return;
138 }
139
140 // Access check based on declared_holder. canonical_holder should not be used
141 // to check access because it can erroneously succeed. If this check fails,
142 // propagate the declared holder to will_link() which in turn will bail out
143 // compilation for this field access.
144 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
145 _holder = declared_holder;
146 _offset = -1;
147 _is_constant = false;
148 return;
149 }
150
151 assert(canonical_holder == field_desc.field_holder(), "just checking");
152 initialize_from(&field_desc);
153 }
154
155 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
156 ASSERT_IN_VM;
157
158 // Get the field's name, signature, and type.
159 ciEnv* env = CURRENT_ENV;
160 _name = env->get_symbol(fd->name());
161 _signature = env->get_symbol(fd->signature());
162
163 BasicType field_type = fd->field_type();
164
165 // If the field is a pointer type, get the klass of the
166 // field.
167 if (field_type == T_OBJECT || field_type == T_ARRAY) {
168 _type = NULL; // must call compute_type on first access
169 } else {
170 _type = ciType::make(field_type);
171 }
172
173 initialize_from(fd);
174
175 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
176 assert(is_shared() || ciObjectFactory::is_initialized(),
177 "bootstrap classes must not create & cache unshared fields");
178 }
179
180 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
181 if (holder == NULL)
182 return false;
183 if (holder->name() == ciSymbol::java_lang_System())
184 // Never trust strangely unstable finals: System.out, etc.
185 return false;
186 // Even if general trusting is disabled, trust system-built closures in these packages.
187 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
188 return true;
189 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
190 // so there is no hacking of finals going on with them.
191 if (holder->is_anonymous())
192 return true;
193 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
194 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
195 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
196 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
197 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
198 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
199 return true;
200 }
201 return TrustFinalNonStaticFields;
202 }
203
204 void ciField::initialize_from(fieldDescriptor* fd) {
205 // Get the flags, offset, and canonical holder of the field.
206 _flags = ciFlags(fd->access_flags());
207 _offset = fd->offset();
208 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
209
210 // Check to see if the field is constant.
211 bool is_final = this->is_final();
212 bool is_stable = FoldStableValues && this->is_stable();
213 if (_holder->is_initialized() && (is_final || is_stable)) {
214 if (!this->is_static()) {
215 // A field can be constant if it's a final static field or if
216 // it's a final non-static field of a trusted class (classes in
217 // java.lang.invoke and sun.invoke packages and subpackages).
218 if (is_stable || trust_final_non_static_fields(_holder)) {
219 _is_constant = true;
220 return;
221 }
222 _is_constant = false;
223 return;
224 }
225
226 // This field just may be constant. The only case where it will
227 // not be constant is when the field is a *special* static&final field
228 // whose value may change. The three examples are java.lang.System.in,
229 // java.lang.System.out, and java.lang.System.err.
230
231 KlassHandle k = _holder->get_Klass();
232 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
233 if( k() == SystemDictionary::System_klass() ) {
234 // Check offsets for case 2: System.in, System.out, or System.err
235 if( _offset == java_lang_System::in_offset_in_bytes() ||
236 _offset == java_lang_System::out_offset_in_bytes() ||
237 _offset == java_lang_System::err_offset_in_bytes() ) {
238 _is_constant = false;
239 return;
240 }
241 }
242
243 Handle mirror = k->java_mirror();
244
245 switch(type()->basic_type()) {
246 case T_BYTE:
247 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
248 break;
249 case T_CHAR:
250 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
251 break;
252 case T_SHORT:
253 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
254 break;
255 case T_BOOLEAN:
256 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
257 break;
258 case T_INT:
259 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
260 break;
261 case T_FLOAT:
262 _constant_value = ciConstant(mirror->float_field(_offset));
263 break;
264 case T_DOUBLE:
265 _constant_value = ciConstant(mirror->double_field(_offset));
266 break;
267 case T_LONG:
268 _constant_value = ciConstant(mirror->long_field(_offset));
269 break;
270 case T_OBJECT:
271 case T_ARRAY:
272 {
273 oop o = mirror->obj_field(_offset);
274
275 // A field will be "constant" if it is known always to be
276 // a non-null reference to an instance of a particular class,
277 // or to a particular array. This can happen even if the instance
278 // or array is not perm. In such a case, an "unloaded" ciArray
279 // or ciInstance is created. The compiler may be able to use
280 // information about the object's class (which is exact) or length.
281
282 if (o == NULL) {
283 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
284 } else {
285 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
286 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
287 }
288 }
289 }
290 if (is_stable && _constant_value.is_null_or_zero()) {
291 // It is not a constant after all; treat it as uninitialized.
292 _is_constant = false;
293 } else {
294 _is_constant = true;
295 }
296 } else {
297 _is_constant = false;
298 }
299 }
300
301 // ------------------------------------------------------------------
302 // ciField::compute_type
303 //
304 // Lazily compute the type, if it is an instance klass.
305 ciType* ciField::compute_type() {
306 GUARDED_VM_ENTRY(return compute_type_impl();)
307 }
308
309 ciType* ciField::compute_type_impl() {
310 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
311 if (!type->is_primitive_type() && is_shared()) {
312 // We must not cache a pointer to an unshared type, in a shared field.
313 bool type_is_also_shared = false;
314 if (type->is_type_array_klass()) {
315 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
316 } else if (type->is_instance_klass()) {
317 type_is_also_shared = type->as_instance_klass()->is_shared();
318 } else {
319 // Currently there is no 'shared' query for array types.
320 type_is_also_shared = !ciObjectFactory::is_initialized();
321 }
322 if (!type_is_also_shared)
323 return type; // Bummer.
324 }
325 _type = type;
326 return type;
327 }
328
329
330 // ------------------------------------------------------------------
331 // ciField::will_link
332 //
333 // Can a specific access to this field be made without causing
334 // link errors?
335 bool ciField::will_link(ciInstanceKlass* accessing_klass,
336 Bytecodes::Code bc) {
337 VM_ENTRY_MARK;
338 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
339 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
340 "unexpected bytecode");
341
342 if (_offset == -1) {
343 // at creation we couldn't link to our holder so we need to
344 // maintain that stance, otherwise there's no safe way to use this
345 // ciField.
346 return false;
347 }
348
349 // Check for static/nonstatic mismatch
350 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
351 if (is_static != this->is_static()) {
352 return false;
353 }
354
355 // Get and put can have different accessibility rules
356 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
357 if (is_put) {
358 if (_known_to_link_with_put == accessing_klass) {
359 return true;
360 }
361 } else {
362 if (_known_to_link_with_get == accessing_klass) {
363 return true;
364 }
365 }
366
367 LinkInfo link_info(_holder->get_instanceKlass(),
368 _name->get_symbol(), _signature->get_symbol(),
369 accessing_klass->get_Klass());
370 fieldDescriptor result;
371 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
372
373 // update the hit-cache, unless there is a problem with memory scoping:
374 if (accessing_klass->is_shared() || !is_shared()) {
375 if (is_put) {
376 _known_to_link_with_put = accessing_klass;
377 } else {
378 _known_to_link_with_get = accessing_klass;
379 }
380 }
381
382 return true;
383 }
384
385 // ------------------------------------------------------------------
386 // ciField::print
387 void ciField::print() {
388 tty->print("<ciField name=");
389 _holder->print_name();
390 tty->print(".");
391 _name->print_symbol();
392 tty->print(" signature=");
393 _signature->print_symbol();
394 tty->print(" offset=%d type=", _offset);
395 if (_type != NULL)
396 _type->print_name();
397 else
398 tty->print("(reference)");
399 tty->print(" flags=%04x", flags().as_int());
400 tty->print(" is_constant=%s", bool_to_str(_is_constant));
401 if (_is_constant && is_static()) {
402 tty->print(" constant_value=");
403 _constant_value.print();
404 }
405 tty->print(">");
406 }
407
408 // ------------------------------------------------------------------
409 // ciField::print_name_on
410 //
411 // Print the name of this field
412 void ciField::print_name_on(outputStream* st) {
413 name()->print_symbol_on(st);
414 }