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 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, fieldDescriptor* fd) {
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 if (UseImplicitStableValues &&
187 holder->name() == ciSymbol::java_lang_String() && fd->is_final())
188 // All final fields in String are implicitly stable.
189 return true;
190 // Even if general trusting is disabled, trust system-built closures in these packages.
191 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
192 return true;
193 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
194 // so there is no hacking of finals going on with them.
195 if (holder->is_anonymous())
196 return true;
197 return TrustFinalNonStaticFields;
198 }
199
200 void ciField::initialize_from(fieldDescriptor* fd) {
201 // Get the flags, offset, and canonical holder of the field.
202 _flags = ciFlags(fd->access_flags());
203 _offset = fd->offset();
204 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
205
206 // Check to see if the field is constant.
207 bool is_final = this->is_final();
208 bool is_stable = FoldStableValues && this->is_stable();
209 if (_holder->is_initialized() && (is_final || is_stable)) {
210 if (!this->is_static()) {
211 // A field can be constant if it's a final static field or if
212 // it's a final non-static field of a trusted class (classes in
213 // java.lang.invoke and sun.invoke packages and subpackages).
214 if (is_stable || trust_final_non_static_fields(_holder, fd)) {
215 _is_constant = true;
216 return;
217 }
218 _is_constant = false;
219 return;
220 }
221
222 // This field just may be constant. The only case where it will
223 // not be constant is when the field is a *special* static&final field
224 // whose value may change. The three examples are java.lang.System.in,
225 // java.lang.System.out, and java.lang.System.err.
226
227 KlassHandle k = _holder->get_Klass();
228 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
229 if( k() == SystemDictionary::System_klass() ) {
230 // Check offsets for case 2: System.in, System.out, or System.err
231 if( _offset == java_lang_System::in_offset_in_bytes() ||
232 _offset == java_lang_System::out_offset_in_bytes() ||
233 _offset == java_lang_System::err_offset_in_bytes() ) {
234 _is_constant = false;
235 return;
236 }
237 }
238
239 Handle mirror = k->java_mirror();
240
241 switch(type()->basic_type()) {
242 case T_BYTE:
243 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
244 break;
245 case T_CHAR:
246 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
247 break;
248 case T_SHORT:
249 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
250 break;
251 case T_BOOLEAN:
252 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
253 break;
254 case T_INT:
255 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
256 break;
257 case T_FLOAT:
258 _constant_value = ciConstant(mirror->float_field(_offset));
259 break;
260 case T_DOUBLE:
261 _constant_value = ciConstant(mirror->double_field(_offset));
262 break;
263 case T_LONG:
264 _constant_value = ciConstant(mirror->long_field(_offset));
265 break;
266 case T_OBJECT:
267 case T_ARRAY:
268 {
269 oop o = mirror->obj_field(_offset);
270
271 // A field will be "constant" if it is known always to be
272 // a non-null reference to an instance of a particular class,
273 // or to a particular array. This can happen even if the instance
274 // or array is not perm. In such a case, an "unloaded" ciArray
275 // or ciInstance is created. The compiler may be able to use
276 // information about the object's class (which is exact) or length.
277
278 if (o == NULL) {
279 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
280 } else {
281 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
282 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
283 }
284 }
285 }
286 if (is_stable && _constant_value.is_null_or_zero()) {
287 // It is not a constant after all; treat it as uninitialized.
288 _is_constant = false;
289 } else {
290 _is_constant = true;
291 }
292 } else {
293 _is_constant = false;
294 }
295 }
296
297 // ------------------------------------------------------------------
298 // ciField::compute_type
299 //
300 // Lazily compute the type, if it is an instance klass.
301 ciType* ciField::compute_type() {
302 GUARDED_VM_ENTRY(return compute_type_impl();)
303 }
304
305 ciType* ciField::compute_type_impl() {
306 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
307 if (!type->is_primitive_type() && is_shared()) {
308 // We must not cache a pointer to an unshared type, in a shared field.
309 bool type_is_also_shared = false;
310 if (type->is_type_array_klass()) {
311 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
312 } else if (type->is_instance_klass()) {
313 type_is_also_shared = type->as_instance_klass()->is_shared();
314 } else {
315 // Currently there is no 'shared' query for array types.
316 type_is_also_shared = !ciObjectFactory::is_initialized();
317 }
318 if (!type_is_also_shared)
319 return type; // Bummer.
320 }
321 _type = type;
322 return type;
323 }
324
325
326 // ------------------------------------------------------------------
327 // ciField::will_link
328 //
329 // Can a specific access to this field be made without causing
330 // link errors?
331 bool ciField::will_link(ciInstanceKlass* accessing_klass,
332 Bytecodes::Code bc) {
333 VM_ENTRY_MARK;
334 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
335 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
336 "unexpected bytecode");
337
338 if (_offset == -1) {
339 // at creation we couldn't link to our holder so we need to
340 // maintain that stance, otherwise there's no safe way to use this
341 // ciField.
342 return false;
343 }
344
345 // Check for static/nonstatic mismatch
346 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
347 if (is_static != this->is_static()) {
348 return false;
349 }
350
351 // Get and put can have different accessibility rules
352 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
353 if (is_put) {
354 if (_known_to_link_with_put == accessing_klass) {
355 return true;
356 }
357 } else {
358 if (_known_to_link_with_get == accessing_klass) {
359 return true;
360 }
361 }
362
363 LinkInfo link_info(_holder->get_instanceKlass(),
364 _name->get_symbol(), _signature->get_symbol(),
365 accessing_klass->get_Klass());
366 fieldDescriptor result;
367 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
368
369 // update the hit-cache, unless there is a problem with memory scoping:
370 if (accessing_klass->is_shared() || !is_shared()) {
371 if (is_put) {
372 _known_to_link_with_put = accessing_klass;
373 } else {
374 _known_to_link_with_get = accessing_klass;
375 }
376 }
377
378 return true;
379 }
380
381 // ------------------------------------------------------------------
382 // ciField::print
383 void ciField::print() {
384 tty->print("<ciField name=");
385 _holder->print_name();
386 tty->print(".");
387 _name->print_symbol();
388 tty->print(" signature=");
389 _signature->print_symbol();
390 tty->print(" offset=%d type=", _offset);
391 if (_type != NULL)
392 _type->print_name();
393 else
394 tty->print("(reference)");
395 tty->print(" flags=%04x", flags().as_int());
396 tty->print(" is_constant=%s", bool_to_str(_is_constant));
397 if (_is_constant && is_static()) {
398 tty->print(" constant_value=");
399 _constant_value.print();
400 }
401 tty->print(">");
402 }
403
404 // ------------------------------------------------------------------
405 // ciField::print_name_on
406 //
407 // Print the name of this field
408 void ciField::print_name_on(outputStream* st) {
409 name()->print_symbol_on(st);
410 }