1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 "code/aotCodeCache.hpp"
32 #include "gc/shared/collectedHeap.inline.hpp"
33 #include "interpreter/linkResolver.hpp"
34 #include "oops/klass.inline.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/fieldDescriptor.inline.hpp"
37 #include "runtime/handles.inline.hpp"
38 #include "runtime/reflection.hpp"
39
40 // ciField
41 //
42 // This class represents the result of a field lookup in the VM.
43 // The lookup may not succeed, in which case the information in
44 // the ciField will be incomplete.
45
46 // The ciObjectFactory cannot create circular data structures in one query.
47 // To avoid vicious circularities, we initialize ciField::_type to null
48 // for reference types and derive it lazily from the ciField::_signature.
49 // Primitive types are eagerly initialized, and basic layout queries
50 // can succeed without initialization, using only the BasicType of the field.
51
52 // Notes on bootstrapping and shared CI objects: A field is shared if and
53 // only if it is (a) non-static and (b) declared by a shared instance klass.
54 // This allows non-static field lists to be cached on shared types.
55 // Because the _type field is lazily initialized, however, there is a
56 // special restriction that a shared field cannot cache an unshared type.
57 // This puts a small performance penalty on shared fields with unshared
58 // types, such as StackTraceElement[] Throwable.stackTrace.
59 // (Throwable is shared because ClassCastException is shared, but
60 // StackTraceElement is not presently shared.)
61
62 // It is not a vicious circularity for a ciField to recursively create
63 // the ciSymbols necessary to represent its name and signature.
64 // Therefore, these items are created eagerly, and the name and signature
65 // of a shared field are themselves shared symbols. This somewhat
66 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
67 // with all of the additional 43 being uninteresting shared ciSymbols.
68 // This adds at most one step to the binary search, an amount which
69 // decreases for complex compilation tasks.
70
71 // ------------------------------------------------------------------
72 // ciField::ciField
73 ciField::ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc) :
74 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
75 ASSERT_IN_VM;
76 CompilerThread *THREAD = CompilerThread::current();
77
78 assert(ciObjectFactory::is_initialized(), "not a shared field");
79
80 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
81
82 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
83
84 // Get the field's name, signature, and type.
85 Symbol* name = cpool->name_ref_at(index, bc);
86 _name = ciEnv::current(THREAD)->get_symbol(name);
87
88 int nt_index = cpool->name_and_type_ref_index_at(index, bc);
89 int sig_index = cpool->signature_ref_index_at(nt_index);
90 Symbol* signature = cpool->symbol_at(sig_index);
91 _signature = ciEnv::current(THREAD)->get_symbol(signature);
92
93 BasicType field_type = Signature::basic_type(signature);
94
95 // If the field is a pointer type, get the klass of the
96 // field.
97 if (is_reference_type(field_type)) {
98 bool ignore;
99 // This is not really a class reference; the index always refers to the
100 // field's type signature, as a symbol. Linkage checks do not apply.
101 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
102 } else {
103 _type = ciType::make(field_type);
104 }
105
106 // Get the field's declared holder.
107 //
108 // Note: we actually create a ciInstanceKlass for this klass,
109 // even though we may not need to.
110 int holder_index = cpool->klass_ref_index_at(index, bc);
111 bool holder_is_accessible;
112
113 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
114 holder_is_accessible,
115 klass);
116
117 if (generic_declared_holder->is_array_klass()) {
118 // If the declared holder of the field is an array class, assume that
119 // the canonical holder of that field is java.lang.Object. Arrays
120 // do not have fields; java.lang.Object is the only supertype of an
121 // array type that can declare fields and is therefore the canonical
122 // holder of the array type.
123 //
124 // Furthermore, the compilers assume that java.lang.Object does not
125 // have any fields. Therefore, the field is not looked up. Instead,
126 // the method returns partial information that will trigger special
127 // handling in ciField::will_link and will result in a
128 // java.lang.NoSuchFieldError exception being thrown by the compiled
129 // code (the expected behavior in this case).
130 _holder = ciEnv::current(THREAD)->Object_klass();
131 _offset = -1;
132 _is_constant = false;
133 return;
134 }
135
136 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
137
138 // The declared holder of this field may not have been loaded.
139 // Bail out with partial field information.
140 if (!holder_is_accessible) {
141 // _type has already been set.
142 // The default values for _flags and _constant_value will suffice.
143 // We need values for _holder, _offset, and _is_constant,
144 _holder = declared_holder;
145 _offset = -1;
146 _is_constant = false;
147 return;
148 }
149
150 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
151
152 // Perform the field lookup.
153 fieldDescriptor field_desc;
154 Klass* canonical_holder =
155 loaded_decl_holder->find_field(name, signature, &field_desc);
156 if (canonical_holder == nullptr) {
157 // Field lookup failed. Will be detected by will_link.
158 _holder = declared_holder;
159 _offset = -1;
160 _is_constant = false;
161 return;
162 }
163
164 // Access check based on declared_holder. canonical_holder should not be used
165 // to check access because it can erroneously succeed. If this check fails,
166 // propagate the declared holder to will_link() which in turn will bail out
167 // compilation for this field access.
168 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
169 declared_holder->get_Klass(),
170 canonical_holder,
171 field_desc.access_flags(),
172 true, false, THREAD);
173 if (!can_access) {
174 _holder = declared_holder;
175 _offset = -1;
176 _is_constant = false;
177 // It's possible the access check failed due to a nestmate access check
178 // encountering an exception. We can't propagate the exception from here
179 // so we have to clear it. If the access check happens again in a different
180 // context then the exception will be thrown there.
181 if (HAS_PENDING_EXCEPTION) {
182 CLEAR_PENDING_EXCEPTION;
183 }
184 return;
185 }
186
187 assert(canonical_holder == field_desc.field_holder(), "just checking");
188 initialize_from(&field_desc);
189 }
190
191 ciField::ciField(fieldDescriptor *fd) :
192 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
193 ASSERT_IN_VM;
194
195 // Get the field's name, signature, and type.
196 ciEnv* env = CURRENT_ENV;
197 _name = env->get_symbol(fd->name());
198 _signature = env->get_symbol(fd->signature());
199
200 BasicType field_type = fd->field_type();
201
202 // If the field is a pointer type, get the klass of the
203 // field.
204 if (is_reference_type(field_type)) {
205 _type = nullptr; // must call compute_type on first access
206 } else {
207 _type = ciType::make(field_type);
208 }
209
210 initialize_from(fd);
211
212 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
213 assert(is_shared() || ciObjectFactory::is_initialized(),
214 "bootstrap classes must not create & cache unshared fields");
215 }
216
217 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
218 if (holder == nullptr)
219 return false;
220 if (holder->trust_final_fields()) {
221 // Explicit opt-in from system classes
222 return true;
223 }
224 // Even if general trusting is disabled, trust system-built closures in these packages.
225 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
226 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
227 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
228 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
229 holder->is_in_package("java/lang"))
230 return true;
231 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
232 // can't be serialized, so there is no hacking of finals going on with them.
233 if (holder->is_hidden())
234 return true;
235 // Trust final fields in records
236 if (holder->is_record())
237 return true;
238 return TrustFinalNonStaticFields;
239 }
240
241 void ciField::initialize_from(fieldDescriptor* fd) {
242 // Get the flags, offset, and canonical holder of the field.
243 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
244 _offset = fd->offset();
245 Klass* field_holder = fd->field_holder();
246 assert(field_holder != nullptr, "null field_holder");
247 _holder = CURRENT_ENV->get_instance_klass(field_holder);
248
249 // Check to see if the field is constant.
250 Klass* k = _holder->get_Klass();
251 bool is_stable_field = FoldStableValues && is_stable();
252 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
253 if (is_static()) {
254 // This field just may be constant. The only case where it will
255 // not be constant is when the field is a *special* static & final field
256 // whose value may change. The three examples are java.lang.System.in,
257 // java.lang.System.out, and java.lang.System.err.
258 _is_constant = !fd->is_mutable_static_final();
259 } else {
260 // An instance field can be constant if it's a final static field or if
261 // it's a final non-static field of a trusted class (classes in
262 // java.lang.invoke and sun.invoke packages and subpackages).
263 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
264 }
265 } else {
266 // For CallSite objects treat the target field as a compile time constant.
267 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
268 if (k == vmClasses::CallSite_klass() &&
269 _offset == java_lang_invoke_CallSite::target_offset()) {
270 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
271 _is_constant = true;
272 } else {
273 // Non-final & non-stable fields are not constants.
274 _is_constant = false;
275 }
276 }
277 }
278
279 // ------------------------------------------------------------------
280 // ciField::constant_value
281 // Get the constant value of a this static field.
282 ciConstant ciField::constant_value() {
283 assert(is_static() && is_constant(), "illegal call to constant_value()");
284 if (!_holder->is_initialized()) {
285 return ciConstant(); // Not initialized yet
286 }
287 if (_constant_value.basic_type() == T_ILLEGAL) {
288 // Static fields are placed in mirror objects.
289 ciInstance* mirror = _holder->java_mirror();
290 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
291 }
292 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
293 return ciConstant();
294 }
295 if (!AOTCodeCache::allow_const_field(_constant_value)) {
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 if (!AOTCodeCache::allow_const_field(field_value)) {
312 return ciConstant();
313 }
314 return field_value;
315 }
316
317 // ------------------------------------------------------------------
318 // ciField::compute_type
319 //
320 // Lazily compute the type, if it is an instance klass.
321 ciType* ciField::compute_type() {
322 GUARDED_VM_ENTRY(return compute_type_impl();)
323 }
324
325 ciType* ciField::compute_type_impl() {
326 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
327 if (!type->is_primitive_type() && is_shared()) {
328 // We must not cache a pointer to an unshared type, in a shared field.
329 bool type_is_also_shared = false;
330 if (type->is_type_array_klass()) {
331 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
332 } else if (type->is_instance_klass()) {
333 type_is_also_shared = type->as_instance_klass()->is_shared();
334 } else {
335 // Currently there is no 'shared' query for array types.
336 type_is_also_shared = !ciObjectFactory::is_initialized();
337 }
338 if (!type_is_also_shared)
339 return type; // Bummer.
340 }
341 _type = type;
342 return type;
343 }
344
345
346 // ------------------------------------------------------------------
347 // ciField::will_link
348 //
349 // Can a specific access to this field be made without causing
350 // link errors?
351 bool ciField::will_link(ciMethod* accessing_method,
352 Bytecodes::Code bc) {
353 VM_ENTRY_MARK;
354 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
355 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
356 "unexpected bytecode");
357
358 if (_offset == -1) {
359 // at creation we couldn't link to our holder so we need to
360 // maintain that stance, otherwise there's no safe way to use this
361 // ciField.
362 return false;
363 }
364
365 // Check for static/nonstatic mismatch
366 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
367 if (is_static != this->is_static()) {
368 return false;
369 }
370
371 // Get and put can have different accessibility rules
372 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
373 if (is_put) {
374 if (_known_to_link_with_put == accessing_method) {
375 return true;
376 }
377 } else {
378 if (_known_to_link_with_get == accessing_method->holder()) {
379 return true;
380 }
381 }
382
383 LinkInfo link_info(_holder->get_instanceKlass(),
384 _name->get_symbol(), _signature->get_symbol(),
385 methodHandle(THREAD, accessing_method->get_Method()));
386 fieldDescriptor result;
387 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(false));
388
389 // update the hit-cache, unless there is a problem with memory scoping:
390 if (accessing_method->holder()->is_shared() || !is_shared()) {
391 if (is_put) {
392 _known_to_link_with_put = accessing_method;
393 } else {
394 _known_to_link_with_get = accessing_method->holder();
395 }
396 }
397
398 return true;
399 }
400
401 bool ciField::is_call_site_target() {
402 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
403 if (callsite_klass == nullptr)
404 return false;
405 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
406 }
407
408 bool ciField::is_autobox_cache() {
409 ciSymbol* klass_name = holder()->name();
410 return (name() == ciSymbols::cache_field_name() &&
411 holder()->uses_default_loader() &&
412 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
413 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
414 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
415 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
416 klass_name == ciSymbols::java_lang_Long_LongCache()));
417 }
418
419 // ------------------------------------------------------------------
420 // ciField::print
421 void ciField::print() {
422 tty->print("<ciField name=");
423 _holder->print_name();
424 tty->print(".");
425 _name->print_symbol();
426 tty->print(" signature=");
427 _signature->print_symbol();
428 tty->print(" offset=%d type=", _offset);
429 if (_type != nullptr)
430 _type->print_name();
431 else
432 tty->print("(reference)");
433 tty->print(" flags=%04x", flags().as_int());
434 tty->print(" is_constant=%s", bool_to_str(_is_constant));
435 if (_is_constant && is_static()) {
436 tty->print(" constant_value=");
437 _constant_value.print();
438 }
439 tty->print(">");
440 }
441
442 // ------------------------------------------------------------------
443 // ciField::print_name_on
444 //
445 // Print the name of this field
446 void ciField::print_name_on(outputStream* st) {
447 name()->print_symbol_on(st);
448 }