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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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 _original_holder(nullptr), _is_flat(false), _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 _is_null_free = false;
106 _null_marker_offset = -1;
107
108 // Get the field's declared holder.
109 //
110 // Note: we actually create a ciInstanceKlass for this klass,
111 // even though we may not need to.
112 int holder_index = cpool->klass_ref_index_at(index, bc);
113 bool holder_is_accessible;
114
115 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
116 holder_is_accessible,
117 klass);
118
119 if (generic_declared_holder->is_array_klass()) {
120 // If the declared holder of the field is an array class, assume that
121 // the canonical holder of that field is java.lang.Object. Arrays
122 // do not have fields; java.lang.Object is the only supertype of an
123 // array type that can declare fields and is therefore the canonical
124 // holder of the array type.
125 //
126 // Furthermore, the compilers assume that java.lang.Object does not
127 // have any fields. Therefore, the field is not looked up. Instead,
128 // the method returns partial information that will trigger special
129 // handling in ciField::will_link and will result in a
130 // java.lang.NoSuchFieldError exception being thrown by the compiled
131 // code (the expected behavior in this case).
132 _holder = ciEnv::current(THREAD)->Object_klass();
133 _offset = -1;
134 _is_constant = false;
135 return;
136 }
137
138 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
139
140 // The declared holder of this field may not have been loaded.
141 // Bail out with partial field information.
142 if (!holder_is_accessible) {
143 // _type has already been set.
144 // The default values for _flags and _constant_value will suffice.
145 // We need values for _holder, _offset, and _is_constant,
146 _holder = declared_holder;
147 _offset = -1;
148 _is_constant = false;
149 return;
150 }
151
152 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
153
154 // Perform the field lookup.
155 fieldDescriptor field_desc;
156 Klass* canonical_holder =
157 loaded_decl_holder->find_field(name, signature, &field_desc);
158 if (canonical_holder == nullptr) {
159 // Field lookup failed. Will be detected by will_link.
160 _holder = declared_holder;
161 _offset = -1;
162 _is_constant = false;
163 return;
164 }
165
166 // Access check based on declared_holder. canonical_holder should not be used
167 // to check access because it can erroneously succeed. If this check fails,
168 // propagate the declared holder to will_link() which in turn will bail out
169 // compilation for this field access.
170 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
171 declared_holder->get_Klass(),
172 canonical_holder,
173 field_desc.access_flags(),
174 true, false, THREAD);
175 if (!can_access) {
176 _holder = declared_holder;
177 _offset = -1;
178 _is_constant = false;
179 // It's possible the access check failed due to a nestmate access check
180 // encountering an exception. We can't propagate the exception from here
181 // so we have to clear it. If the access check happens again in a different
182 // context then the exception will be thrown there.
183 if (HAS_PENDING_EXCEPTION) {
184 CLEAR_PENDING_EXCEPTION;
185 }
186 return;
187 }
188
189 assert(canonical_holder == field_desc.field_holder(), "just checking");
190 initialize_from(&field_desc);
191 }
192
193 ciField::ciField(fieldDescriptor *fd) :
194 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
195 ASSERT_IN_VM;
196
197 // Get the field's name, signature, and type.
198 ciEnv* env = CURRENT_ENV;
199 _name = env->get_symbol(fd->name());
200 _signature = env->get_symbol(fd->signature());
201
202 BasicType field_type = fd->field_type();
203
204 // If the field is a pointer type, get the klass of the
205 // field.
206 if (is_reference_type(field_type)) {
207 _type = nullptr; // must call compute_type on first access
208 } else {
209 _type = ciType::make(field_type);
210 }
211
212 initialize_from(fd);
213
214 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
215 assert(is_shared() || ciObjectFactory::is_initialized(),
216 "bootstrap classes must not create & cache unshared fields");
217 }
218
219 // Special copy constructor used to flatten inline type fields by
220 // copying the fields of the inline type to a new holder klass.
221 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
222 assert(field->holder()->is_inlinetype() || field->holder()->is_abstract(), "should only be used for inline type field flattening");
223 // Set the is_final flag
224 jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
225 AccessFlags flags(field->flags().as_int() & final);
226 _flags = ciFlags(flags);
227 _holder = holder;
228 _offset = offset;
229 // Copy remaining fields
230 _name = field->_name;
231 _signature = field->_signature;
232 _type = field->_type;
233 // Trust final flat fields
234 _is_constant = is_final;
235 _known_to_link_with_put = field->_known_to_link_with_put;
236 _known_to_link_with_get = field->_known_to_link_with_get;
237 _constant_value = field->_constant_value;
238 assert(!field->is_flat(), "field must not be flat");
239 _is_flat = false;
240 _is_null_free = field->_is_null_free;
241 _null_marker_offset = field->_null_marker_offset;
242 _original_holder = (field->_original_holder != nullptr) ? field->_original_holder : field->_holder;
243 }
244
245 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
246 if (holder == nullptr)
247 return false;
248 if (holder->name() == ciSymbols::java_lang_System())
249 // Never trust strangely unstable finals: System.out, etc.
250 return false;
251 // Even if general trusting is disabled, trust system-built closures in these packages.
252 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
253 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
254 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
255 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
256 holder->is_in_package("java/lang"))
257 return true;
258 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
259 // can't be serialized, so there is no hacking of finals going on with them.
260 if (holder->is_hidden())
261 return true;
262 // Trust final fields in inline type buffers
263 if (holder->is_inlinetype())
264 return true;
265 // Trust final fields in all boxed classes
266 if (holder->is_box_klass())
267 return true;
268 // Trust final fields in records
269 if (holder->is_record())
270 return true;
271 // Trust final fields in String
272 if (holder->name() == ciSymbols::java_lang_String())
273 return true;
274 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
275 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
276 if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
277 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
278 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
279 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
280 return true;
281 }
282 return TrustFinalNonStaticFields;
283 }
284
285 void ciField::initialize_from(fieldDescriptor* fd) {
286 // Get the flags, offset, and canonical holder of the field.
287 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
288 _offset = fd->offset();
289 InstanceKlass* field_holder = fd->field_holder();
290 assert(field_holder != nullptr, "null field_holder");
291 _holder = CURRENT_ENV->get_instance_klass(field_holder);
292 _is_flat = fd->is_flat();
293 _is_null_free = fd->is_null_free_inline_type();
294 if (fd->has_null_marker()) {
295 InlineLayoutInfo* li = field_holder->inline_layout_info_adr(fd->index());
296 _null_marker_offset = li->null_marker_offset();
297 } else {
298 _null_marker_offset = -1;
299 }
300 _original_holder = nullptr;
301
302 // Check to see if the field is constant.
303 Klass* k = _holder->get_Klass();
304 bool is_stable_field = FoldStableValues && is_stable();
305 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
306 if (is_static()) {
307 // This field just may be constant. The only case where it will
308 // not be constant is when the field is a *special* static & final field
309 // whose value may change. The three examples are java.lang.System.in,
310 // java.lang.System.out, and java.lang.System.err.
311 assert(vmClasses::System_klass() != nullptr, "Check once per vm");
312 if (k == vmClasses::System_klass()) {
313 // Check offsets for case 2: System.in, System.out, or System.err
314 if (_offset == java_lang_System::in_offset() ||
315 _offset == java_lang_System::out_offset() ||
316 _offset == java_lang_System::err_offset()) {
317 _is_constant = false;
318 return;
319 }
320 }
321 _is_constant = true;
322 } else {
323 // An instance field can be constant if it's a final static field or if
324 // it's a final non-static field of a trusted class (classes in
325 // java.lang.invoke and sun.invoke packages and subpackages).
326 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
327 }
328 } else {
329 // For CallSite objects treat the target field as a compile time constant.
330 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
331 if (k == vmClasses::CallSite_klass() &&
332 _offset == java_lang_invoke_CallSite::target_offset()) {
333 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
334 _is_constant = true;
335 } else {
336 // Non-final & non-stable fields are not constants.
337 _is_constant = false;
338 }
339 }
340 }
341
342 // ------------------------------------------------------------------
343 // ciField::constant_value
344 // Get the constant value of a this static field.
345 ciConstant ciField::constant_value() {
346 assert(is_static() && is_constant(), "illegal call to constant_value()");
347 if (!_holder->is_initialized()) {
348 return ciConstant(); // Not initialized yet
349 }
350 if (_constant_value.basic_type() == T_ILLEGAL) {
351 // Static fields are placed in mirror objects.
352 ciInstance* mirror = _holder->java_mirror();
353 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
354 }
355 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
356 return ciConstant();
357 }
358 return _constant_value;
359 }
360
361 // ------------------------------------------------------------------
362 // ciField::constant_value_of
363 // Get the constant value of non-static final field in the given object.
364 ciConstant ciField::constant_value_of(ciObject* object) {
365 assert(!is_static() && is_constant(), "only if field is non-static constant");
366 assert(object->is_instance(), "must be instance");
367 ciConstant field_value = object->as_instance()->field_value(this);
368 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
369 return ciConstant();
370 }
371 return field_value;
372 }
373
374 // ------------------------------------------------------------------
375 // ciField::compute_type
376 //
377 // Lazily compute the type, if it is an instance klass.
378 ciType* ciField::compute_type() {
379 GUARDED_VM_ENTRY(return compute_type_impl();)
380 }
381
382 ciType* ciField::compute_type_impl() {
383 // Use original holder for fields that came in through flattening
384 ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
385 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
386 if (!type->is_primitive_type() && is_shared()) {
387 // We must not cache a pointer to an unshared type, in a shared field.
388 bool type_is_also_shared = false;
389 if (type->is_type_array_klass()) {
390 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
391 } else if (type->is_instance_klass()) {
392 type_is_also_shared = type->as_instance_klass()->is_shared();
393 } else {
394 // Currently there is no 'shared' query for array types.
395 type_is_also_shared = !ciObjectFactory::is_initialized();
396 }
397 if (!type_is_also_shared)
398 return type; // Bummer.
399 }
400 _type = type;
401 return type;
402 }
403
404
405 // ------------------------------------------------------------------
406 // ciField::will_link
407 //
408 // Can a specific access to this field be made without causing
409 // link errors?
410 bool ciField::will_link(ciMethod* accessing_method,
411 Bytecodes::Code bc) {
412 VM_ENTRY_MARK;
413 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
414 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
415 "unexpected bytecode");
416
417 if (_offset == -1) {
418 // at creation we couldn't link to our holder so we need to
419 // maintain that stance, otherwise there's no safe way to use this
420 // ciField.
421 return false;
422 }
423
424 // Check for static/nonstatic mismatch
425 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
426 if (is_static != this->is_static()) {
427 return false;
428 }
429
430 // Get and put can have different accessibility rules
431 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
432 if (is_put) {
433 if (_known_to_link_with_put == accessing_method) {
434 return true;
435 }
436 } else {
437 if (_known_to_link_with_get == accessing_method->holder()) {
438 return true;
439 }
440 }
441
442 LinkInfo link_info(_holder->get_instanceKlass(),
443 _name->get_symbol(), _signature->get_symbol(),
444 methodHandle(THREAD, accessing_method->get_Method()));
445 fieldDescriptor result;
446 LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
447
448 // update the hit-cache, unless there is a problem with memory scoping:
449 if (accessing_method->holder()->is_shared() || !is_shared()) {
450 if (is_put) {
451 _known_to_link_with_put = accessing_method;
452 } else {
453 _known_to_link_with_get = accessing_method->holder();
454 }
455 }
456
457 return true;
458 }
459
460 bool ciField::is_call_site_target() {
461 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
462 if (callsite_klass == nullptr)
463 return false;
464 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
465 }
466
467 bool ciField::is_autobox_cache() {
468 ciSymbol* klass_name = holder()->name();
469 return (name() == ciSymbols::cache_field_name() &&
470 holder()->uses_default_loader() &&
471 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
472 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
473 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
474 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
475 klass_name == ciSymbols::java_lang_Long_LongCache()));
476 }
477
478 // ------------------------------------------------------------------
479 // ciField::print
480 void ciField::print() {
481 tty->print("<ciField name=");
482 _holder->print_name();
483 tty->print(".");
484 _name->print_symbol();
485 tty->print(" signature=");
486 _signature->print_symbol();
487 tty->print(" offset=%d type=", _offset);
488 if (_type != nullptr)
489 _type->print_name();
490 else
491 tty->print("(reference)");
492 tty->print(" flags=%04x", flags().as_int());
493 tty->print(" is_constant=%s", bool_to_str(_is_constant));
494 if (_is_constant && is_static()) {
495 tty->print(" constant_value=");
496 _constant_value.print();
497 }
498 tty->print(" is_flat=%s", bool_to_str(_is_flat));
499 tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
500 tty->print(" null_marker_offset=%d", _null_marker_offset);
501 tty->print(">");
502 }
503
504 // ------------------------------------------------------------------
505 // ciField::print_name_on
506 //
507 // Print the name of this field
508 void ciField::print_name_on(outputStream* st) {
509 name()->print_symbol_on(st);
510 }