1 /*
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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
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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23 */
24
25 #include "ci/ciField.hpp"
26 #include "ci/ciInstanceKlass.hpp"
27 #include "ci/ciSymbols.hpp"
28 #include "ci/ciUtilities.inline.hpp"
29 #include "classfile/javaClasses.hpp"
30 #include "classfile/vmClasses.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "interpreter/linkResolver.hpp"
33 #include "oops/klass.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/fieldDescriptor.inline.hpp"
36 #include "runtime/handles.inline.hpp"
37 #include "runtime/reflection.hpp"
38
39 // ciField
40 //
41 // This class represents the result of a field lookup in the VM.
42 // The lookup may not succeed, in which case the information in
43 // the ciField will be incomplete.
44
45 // The ciObjectFactory cannot create circular data structures in one query.
46 // To avoid vicious circularities, we initialize ciField::_type to null
47 // for reference types and derive it lazily from the ciField::_signature.
48 // Primitive types are eagerly initialized, and basic layout queries
49 // can succeed without initialization, using only the BasicType of the field.
50
51 // Notes on bootstrapping and shared CI objects: A field is shared if and
52 // only if it is (a) non-static and (b) declared by a shared instance klass.
53 // This allows non-static field lists to be cached on shared types.
54 // Because the _type field is lazily initialized, however, there is a
55 // special restriction that a shared field cannot cache an unshared type.
56 // This puts a small performance penalty on shared fields with unshared
57 // types, such as StackTraceElement[] Throwable.stackTrace.
58 // (Throwable is shared because ClassCastException is shared, but
59 // StackTraceElement is not presently shared.)
60
61 // It is not a vicious circularity for a ciField to recursively create
62 // the ciSymbols necessary to represent its name and signature.
63 // Therefore, these items are created eagerly, and the name and signature
64 // of a shared field are themselves shared symbols. This somewhat
65 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
66 // with all of the additional 43 being uninteresting shared ciSymbols.
67 // This adds at most one step to the binary search, an amount which
68 // decreases for complex compilation tasks.
69
70 // ------------------------------------------------------------------
71 // ciField::ciField
72 ciField::ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc) :
73 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
74 ASSERT_IN_VM;
75 CompilerThread *THREAD = CompilerThread::current();
76
77 assert(ciObjectFactory::is_initialized(), "not a shared field");
78
79 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
80
81 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
82
83 // Get the field's name, signature, and type.
84 Symbol* name = cpool->name_ref_at(index, bc);
85 _name = ciEnv::current(THREAD)->get_symbol(name);
86
87 int nt_index = cpool->name_and_type_ref_index_at(index, bc);
88 int sig_index = cpool->signature_ref_index_at(nt_index);
89 Symbol* signature = cpool->symbol_at(sig_index);
90 _signature = ciEnv::current(THREAD)->get_symbol(signature);
91
92 BasicType field_type = Signature::basic_type(signature);
93
94 // If the field is a pointer type, get the klass of the
95 // field.
96 if (is_reference_type(field_type)) {
97 bool ignore;
98 // This is not really a class reference; the index always refers to the
99 // field's type signature, as a symbol. Linkage checks do not apply.
100 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
101 } else {
102 _type = ciType::make(field_type);
103 }
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, bc);
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 == nullptr) {
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(nullptr), _known_to_link_with_get(nullptr) {
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 (is_reference_type(field_type)) {
204 _type = nullptr; // 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 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
217 if (holder == nullptr)
218 return false;
219 // Even if general trusting is disabled, trust system-built closures in these packages.
220 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
221 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
222 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
223 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
224 holder->is_in_package("java/lang"))
225 return true;
226 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
227 // can't be serialized, so there is no hacking of finals going on with them.
228 if (holder->is_hidden())
229 return true;
230 // Trust final fields in records
231 if (holder->is_record())
232 return true;
233 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
234 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
235 if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
236 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
237 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
238 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
239 return true;
240 }
241 return TrustFinalNonStaticFields;
242 }
243
244 void ciField::initialize_from(fieldDescriptor* fd) {
245 // Get the flags, offset, and canonical holder of the field.
246 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
247 _offset = fd->offset();
248 Klass* field_holder = fd->field_holder();
249 assert(field_holder != nullptr, "null field_holder");
250 _holder = CURRENT_ENV->get_instance_klass(field_holder);
251
252 // Check to see if the field is constant.
253 Klass* k = _holder->get_Klass();
254 bool is_stable_field = FoldStableValues && is_stable();
255 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
256 if (is_static()) {
257 // This field just may be constant. The only case where it will
258 // not be constant is when the field is a *special* static & final field
259 // whose value may change. The three examples are java.lang.System.in,
260 // java.lang.System.out, and java.lang.System.err.
261 _is_constant = !fd->is_mutable_static_final();
262 } else {
263 // An instance field can be constant if it's a final static field or if
264 // it's a final non-static field of a trusted class (classes in
265 // java.lang.invoke and sun.invoke packages and subpackages).
266 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
267 }
268 } else {
269 // For CallSite objects treat the target field as a compile time constant.
270 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
271 if (k == vmClasses::CallSite_klass() &&
272 _offset == java_lang_invoke_CallSite::target_offset()) {
273 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
274 _is_constant = true;
275 } else {
276 // Non-final & non-stable fields are not constants.
277 _is_constant = false;
278 }
279 }
280 }
281
282 // ------------------------------------------------------------------
283 // ciField::constant_value
284 // Get the constant value of a this static field.
285 ciConstant ciField::constant_value() {
286 assert(is_static() && is_constant(), "illegal call to constant_value()");
287 if (!_holder->is_initialized()) {
288 return ciConstant(); // Not initialized yet
289 }
290 if (_constant_value.basic_type() == T_ILLEGAL) {
291 // Static fields are placed in mirror objects.
292 ciInstance* mirror = _holder->java_mirror();
293 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
294 }
295 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
296 return ciConstant();
297 }
298 return _constant_value;
299 }
300
301 // ------------------------------------------------------------------
302 // ciField::constant_value_of
303 // Get the constant value of non-static final field in the given object.
304 ciConstant ciField::constant_value_of(ciObject* object) {
305 assert(!is_static() && is_constant(), "only if field is non-static constant");
306 assert(object->is_instance(), "must be instance");
307 ciConstant field_value = object->as_instance()->field_value(this);
308 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
309 return ciConstant();
310 }
311 return field_value;
312 }
313
314 // ------------------------------------------------------------------
315 // ciField::compute_type
316 //
317 // Lazily compute the type, if it is an instance klass.
318 ciType* ciField::compute_type() {
319 GUARDED_VM_ENTRY(return compute_type_impl();)
320 }
321
322 ciType* ciField::compute_type_impl() {
323 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
324 if (!type->is_primitive_type() && is_shared()) {
325 // We must not cache a pointer to an unshared type, in a shared field.
326 bool type_is_also_shared = false;
327 if (type->is_type_array_klass()) {
328 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
329 } else if (type->is_instance_klass()) {
330 type_is_also_shared = type->as_instance_klass()->is_shared();
331 } else {
332 // Currently there is no 'shared' query for array types.
333 type_is_also_shared = !ciObjectFactory::is_initialized();
334 }
335 if (!type_is_also_shared)
336 return type; // Bummer.
337 }
338 _type = type;
339 return type;
340 }
341
342
343 // ------------------------------------------------------------------
344 // ciField::will_link
345 //
346 // Can a specific access to this field be made without causing
347 // link errors?
348 bool ciField::will_link(ciMethod* accessing_method,
349 Bytecodes::Code bc) {
350 VM_ENTRY_MARK;
351 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
352 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
353 "unexpected bytecode");
354
355 if (_offset == -1) {
356 // at creation we couldn't link to our holder so we need to
357 // maintain that stance, otherwise there's no safe way to use this
358 // ciField.
359 return false;
360 }
361
362 // Check for static/nonstatic mismatch
363 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
364 if (is_static != this->is_static()) {
365 return false;
366 }
367
368 // Get and put can have different accessibility rules
369 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
370 if (is_put) {
371 if (_known_to_link_with_put == accessing_method) {
372 return true;
373 }
374 } else {
375 if (_known_to_link_with_get == accessing_method->holder()) {
376 return true;
377 }
378 }
379
380 LinkInfo link_info(_holder->get_instanceKlass(),
381 _name->get_symbol(), _signature->get_symbol(),
382 methodHandle(THREAD, accessing_method->get_Method()));
383 fieldDescriptor result;
384 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(false));
385
386 // update the hit-cache, unless there is a problem with memory scoping:
387 if (accessing_method->holder()->is_shared() || !is_shared()) {
388 if (is_put) {
389 _known_to_link_with_put = accessing_method;
390 } else {
391 _known_to_link_with_get = accessing_method->holder();
392 }
393 }
394
395 return true;
396 }
397
398 bool ciField::is_call_site_target() {
399 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
400 if (callsite_klass == nullptr)
401 return false;
402 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
403 }
404
405 bool ciField::is_autobox_cache() {
406 ciSymbol* klass_name = holder()->name();
407 return (name() == ciSymbols::cache_field_name() &&
408 holder()->uses_default_loader() &&
409 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
410 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
411 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
412 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
413 klass_name == ciSymbols::java_lang_Long_LongCache()));
414 }
415
416 // ------------------------------------------------------------------
417 // ciField::print
418 void ciField::print() {
419 tty->print("<ciField name=");
420 _holder->print_name();
421 tty->print(".");
422 _name->print_symbol();
423 tty->print(" signature=");
424 _signature->print_symbol();
425 tty->print(" offset=%d type=", _offset);
426 if (_type != nullptr)
427 _type->print_name();
428 else
429 tty->print("(reference)");
430 tty->print(" flags=%04x", flags().as_int());
431 tty->print(" is_constant=%s", bool_to_str(_is_constant));
432 if (_is_constant && is_static()) {
433 tty->print(" constant_value=");
434 _constant_value.print();
435 }
436 tty->print(">");
437 }
438
439 // ------------------------------------------------------------------
440 // ciField::print_name_on
441 //
442 // Print the name of this field
443 void ciField::print_name_on(outputStream* st) {
444 name()->print_symbol_on(st);
445 }