1 /*
2 * Copyright (c) 1999, 2013, 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.
18 *
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_interface/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "oops/oop.inline2.hpp"
35 #include "runtime/fieldDescriptor.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): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
71 ASSERT_IN_VM;
72 CompilerThread *thread = CompilerThread::current();
73
74 assert(ciObjectFactory::is_initialized(), "not a shared field");
75
76 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constan-pool");
77
78 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
79
80 // Get the field's name, signature, and type.
81 Symbol* name = cpool->name_ref_at(index);
82 _name = ciEnv::current(thread)->get_symbol(name);
83
84 int nt_index = cpool->name_and_type_ref_index_at(index);
85 int sig_index = cpool->signature_ref_index_at(nt_index);
86 Symbol* signature = cpool->symbol_at(sig_index);
87 _signature = ciEnv::current(thread)->get_symbol(signature);
88
89 BasicType field_type = FieldType::basic_type(signature);
90
91 // If the field is a pointer type, get the klass of the
92 // field.
93 if (field_type == T_OBJECT || field_type == T_ARRAY) {
94 bool ignore;
95 // This is not really a class reference; the index always refers to the
96 // field's type signature, as a symbol. Linkage checks do not apply.
97 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
98 } else {
99 _type = ciType::make(field_type);
100 }
101
102 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
103
104 // Get the field's declared holder.
105 //
106 // Note: we actually create a ciInstanceKlass for this klass,
107 // even though we may not need to.
108 int holder_index = cpool->klass_ref_index_at(index);
109 bool holder_is_accessible;
110 ciInstanceKlass* declared_holder =
111 ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
112 holder_is_accessible,
113 klass)->as_instance_klass();
114
115 // The declared holder of this field may not have been loaded.
116 // Bail out with partial field information.
117 if (!holder_is_accessible) {
118 // _type has already been set.
119 // The default values for _flags and _constant_value will suffice.
120 // We need values for _holder, _offset, and _is_constant,
121 _holder = declared_holder;
122 _offset = -1;
123 _is_constant = false;
124 return;
125 }
126
127 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
128
129 // Perform the field lookup.
130 fieldDescriptor field_desc;
131 Klass* canonical_holder =
132 loaded_decl_holder->find_field(name, signature, &field_desc);
133 if (canonical_holder == NULL) {
134 // Field lookup failed. Will be detected by will_link.
135 _holder = declared_holder;
136 _offset = -1;
137 _is_constant = false;
138 return;
139 }
140
141 // Access check based on declared_holder. canonical_holder should not be used
142 // to check access because it can erroneously succeed. If this check fails,
143 // propagate the declared holder to will_link() which in turn will bail out
144 // compilation for this field access.
145 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
146 _holder = declared_holder;
147 _offset = -1;
148 _is_constant = false;
149 return;
150 }
151
152 assert(canonical_holder == field_desc.field_holder(), "just checking");
153 initialize_from(&field_desc);
154 }
155
156 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
157 ASSERT_IN_VM;
158
159 // Get the field's name, signature, and type.
160 ciEnv* env = CURRENT_ENV;
161 _name = env->get_symbol(fd->name());
162 _signature = env->get_symbol(fd->signature());
163
164 BasicType field_type = fd->field_type();
165
166 // If the field is a pointer type, get the klass of the
167 // field.
168 if (field_type == T_OBJECT || field_type == T_ARRAY) {
169 _type = NULL; // must call compute_type on first access
170 } else {
171 _type = ciType::make(field_type);
172 }
173
174 initialize_from(fd);
175
176 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
177 assert(is_shared() || ciObjectFactory::is_initialized(),
178 "bootstrap classes must not create & cache unshared fields");
179 }
180
181 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
182 if (holder == NULL)
183 return false;
184 if (holder->name() == ciSymbol::java_lang_System())
185 // Never trust strangely unstable finals: System.out, etc.
186 return false;
187 // Even if general trusting is disabled, trust system-built closures in these packages.
188 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
189 return true;
190 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
191 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
192 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
193 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
194 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
195 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
196 return true;
197 }
198 return TrustFinalNonStaticFields;
199 }
200
201 void ciField::initialize_from(fieldDescriptor* fd) {
202 // Get the flags, offset, and canonical holder of the field.
203 _flags = ciFlags(fd->access_flags());
204 _offset = fd->offset();
205 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
206
207 // Check to see if the field is constant.
208 bool is_final = this->is_final();
209 bool is_stable = FoldStableValues && this->is_stable();
210 if (_holder->is_initialized() && ((is_final && !has_initialized_final_update()) || is_stable)) {
211 if (!this->is_static()) {
212 // A field can be constant if it's a final static field or if
213 // it's a final non-static field of a trusted class (classes in
214 // java.lang.invoke and sun.invoke packages and subpackages).
215 if (is_stable || trust_final_non_static_fields(_holder)) {
216 _is_constant = true;
217 return;
218 }
219 _is_constant = false;
220 return;
221 }
222
223 // This field just may be constant. The only cases where it will
224 // not be constant are:
225 //
226 // 1. The field holds a non-perm-space oop. The field is, strictly
227 // speaking, constant but we cannot embed non-perm-space oops into
228 // generated code. For the time being we need to consider the
229 // field to be not constant.
230 // 2. The field is a *special* static&final field whose value
231 // may change. The three examples are java.lang.System.in,
232 // java.lang.System.out, and java.lang.System.err.
233
234 KlassHandle k = _holder->get_Klass();
235 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
236 if( k() == SystemDictionary::System_klass() ) {
237 // Check offsets for case 2: System.in, System.out, or System.err
238 if( _offset == java_lang_System::in_offset_in_bytes() ||
239 _offset == java_lang_System::out_offset_in_bytes() ||
240 _offset == java_lang_System::err_offset_in_bytes() ) {
241 _is_constant = false;
242 return;
243 }
244 }
245
246 Handle mirror = k->java_mirror();
247
248 switch(type()->basic_type()) {
249 case T_BYTE:
250 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
251 break;
252 case T_CHAR:
253 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
254 break;
255 case T_SHORT:
256 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
257 break;
258 case T_BOOLEAN:
259 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
260 break;
261 case T_INT:
262 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
263 break;
264 case T_FLOAT:
265 _constant_value = ciConstant(mirror->float_field(_offset));
266 break;
267 case T_DOUBLE:
268 _constant_value = ciConstant(mirror->double_field(_offset));
269 break;
270 case T_LONG:
271 _constant_value = ciConstant(mirror->long_field(_offset));
272 break;
273 case T_OBJECT:
274 case T_ARRAY:
275 {
276 oop o = mirror->obj_field(_offset);
277
278 // A field will be "constant" if it is known always to be
279 // a non-null reference to an instance of a particular class,
280 // or to a particular array. This can happen even if the instance
281 // or array is not perm. In such a case, an "unloaded" ciArray
282 // or ciInstance is created. The compiler may be able to use
283 // information about the object's class (which is exact) or length.
284
285 if (o == NULL) {
286 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
287 } else {
288 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
289 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
290 }
291 }
292 }
293 if (is_stable && _constant_value.is_null_or_zero()) {
294 // It is not a constant after all; treat it as uninitialized.
295 _is_constant = false;
296 } else {
297 _is_constant = true;
298 }
299 } else {
300 _is_constant = false;
301 }
302 }
303
304 // ------------------------------------------------------------------
305 // ciField::compute_type
306 //
307 // Lazily compute the type, if it is an instance klass.
308 ciType* ciField::compute_type() {
309 GUARDED_VM_ENTRY(return compute_type_impl();)
310 }
311
312 ciType* ciField::compute_type_impl() {
313 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
314 if (!type->is_primitive_type() && is_shared()) {
315 // We must not cache a pointer to an unshared type, in a shared field.
316 bool type_is_also_shared = false;
317 if (type->is_type_array_klass()) {
318 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
319 } else if (type->is_instance_klass()) {
320 type_is_also_shared = type->as_instance_klass()->is_shared();
321 } else {
322 // Currently there is no 'shared' query for array types.
323 type_is_also_shared = !ciObjectFactory::is_initialized();
324 }
325 if (!type_is_also_shared)
326 return type; // Bummer.
327 }
328 _type = type;
329 return type;
330 }
331
332
333 // ------------------------------------------------------------------
334 // ciField::will_link
335 //
336 // Can a specific access to this field be made without causing
337 // link errors?
338 bool ciField::will_link(ciInstanceKlass* accessing_klass,
339 Bytecodes::Code bc) {
340 VM_ENTRY_MARK;
341 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
342 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
343 "unexpected bytecode");
344
345 if (_offset == -1) {
346 // at creation we couldn't link to our holder so we need to
347 // maintain that stance, otherwise there's no safe way to use this
348 // ciField.
349 return false;
350 }
351
352 // Check for static/nonstatic mismatch
353 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
354 if (is_static != this->is_static()) {
355 return false;
356 }
357
358 // Get and put can have different accessibility rules
359 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
360 if (is_put) {
361 if (_known_to_link_with_put == accessing_klass) {
362 return true;
363 }
364 } else {
365 if (_known_to_link_with_get == accessing_klass) {
366 return true;
367 }
368 }
369
370 fieldDescriptor result;
371 LinkResolver::resolve_field(result, _holder->get_instanceKlass(),
372 _name->get_symbol(), _signature->get_symbol(),
373 accessing_klass->get_Klass(), bc, true, false,
374 KILL_COMPILE_ON_FATAL_(false));
375
376 // update the hit-cache, unless there is a problem with memory scoping:
377 if (accessing_klass->is_shared() || !is_shared()) {
378 if (is_put) {
379 _known_to_link_with_put = accessing_klass;
380 } else {
381 _known_to_link_with_get = accessing_klass;
382 }
383 }
384
385 return true;
386 }
387
388 // ------------------------------------------------------------------
389 // ciField::print
390 void ciField::print() {
391 tty->print("<ciField name=");
392 _holder->print_name();
393 tty->print(".");
394 _name->print_symbol();
395 tty->print(" signature=");
396 _signature->print_symbol();
397 tty->print(" offset=%d type=", _offset);
398 if (_type != NULL)
399 _type->print_name();
400 else
401 tty->print("(reference)");
402 tty->print(" flags=%04x", flags().as_int());
403 tty->print(" is_constant=%s", bool_to_str(_is_constant));
404 if (_is_constant && is_static()) {
405 tty->print(" constant_value=");
406 _constant_value.print();
407 }
408 tty->print(">");
409 }
410
411 // ------------------------------------------------------------------
412 // ciField::print_name_on
413 //
414 // Print the name of this field
415 void ciField::print_name_on(outputStream* st) {
416 name()->print_symbol_on(st);
417 }