1 /*
2 * Copyright (c) 1999, 2025, 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.
22 *
23 */
24
25 #include "ci/ciConstant.hpp"
26 #include "ci/ciField.hpp"
27 #include "ci/ciInlineKlass.hpp"
28 #include "ci/ciInstanceKlass.hpp"
29 #include "ci/ciSymbol.hpp"
30 #include "ci/ciSymbols.hpp"
31 #include "ci/ciUtilities.inline.hpp"
32 #include "classfile/javaClasses.hpp"
33 #include "classfile/vmClasses.hpp"
34 #include "gc/shared/collectedHeap.inline.hpp"
35 #include "interpreter/linkResolver.hpp"
36 #include "jvm_io.h"
37 #include "oops/klass.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "runtime/fieldDescriptor.inline.hpp"
40 #include "runtime/handles.inline.hpp"
41 #include "runtime/reflection.hpp"
42 #include "utilities/globalDefinitions.hpp"
43
44 // ciField
45 //
46 // This class represents the result of a field lookup in the VM.
47 // The lookup may not succeed, in which case the information in
48 // the ciField will be incomplete.
49
50 // The ciObjectFactory cannot create circular data structures in one query.
51 // To avoid vicious circularities, we initialize ciField::_type to null
52 // for reference types and derive it lazily from the ciField::_signature.
53 // Primitive types are eagerly initialized, and basic layout queries
54 // can succeed without initialization, using only the BasicType of the field.
55
56 // Notes on bootstrapping and shared CI objects: A field is shared if and
57 // only if it is (a) non-static and (b) declared by a shared instance klass.
58 // This allows non-static field lists to be cached on shared types.
59 // Because the _type field is lazily initialized, however, there is a
60 // special restriction that a shared field cannot cache an unshared type.
61 // This puts a small performance penalty on shared fields with unshared
62 // types, such as StackTraceElement[] Throwable.stackTrace.
63 // (Throwable is shared because ClassCastException is shared, but
64 // StackTraceElement is not presently shared.)
65
66 // It is not a vicious circularity for a ciField to recursively create
67 // the ciSymbols necessary to represent its name and signature.
68 // Therefore, these items are created eagerly, and the name and signature
69 // of a shared field are themselves shared symbols. This somewhat
70 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
71 // with all of the additional 43 being uninteresting shared ciSymbols.
72 // This adds at most one step to the binary search, an amount which
73 // decreases for complex compilation tasks.
74
75 // ------------------------------------------------------------------
76 // ciField::ciField
77 ciField::ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc) :
78 _original_holder(nullptr), _is_flat(false), _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
79 ASSERT_IN_VM;
80 CompilerThread *THREAD = CompilerThread::current();
81
82 assert(ciObjectFactory::is_initialized(), "not a shared field");
83
84 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
85
86 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
87
88 // Get the field's name, signature, and type.
89 Symbol* name = cpool->name_ref_at(index, bc);
90 _name = ciEnv::current(THREAD)->get_symbol(name);
91
92 int nt_index = cpool->name_and_type_ref_index_at(index, bc);
93 int sig_index = cpool->signature_ref_index_at(nt_index);
94 Symbol* signature = cpool->symbol_at(sig_index);
95 _signature = ciEnv::current(THREAD)->get_symbol(signature);
96
97 BasicType field_type = Signature::basic_type(signature);
98
99 // If the field is a pointer type, get the klass of the
100 // field.
101 if (is_reference_type(field_type)) {
102 bool ignore;
103 // This is not really a class reference; the index always refers to the
104 // field's type signature, as a symbol. Linkage checks do not apply.
105 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
106 } else {
107 _type = ciType::make(field_type);
108 }
109
110 _is_null_free = false;
111 _null_marker_offset = -1;
112
113 // Get the field's declared holder.
114 //
115 // Note: we actually create a ciInstanceKlass for this klass,
116 // even though we may not need to.
117 int holder_index = cpool->klass_ref_index_at(index, bc);
118 bool holder_is_accessible;
119
120 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
121 holder_is_accessible,
122 klass);
123
124 if (generic_declared_holder->is_array_klass()) {
125 // If the declared holder of the field is an array class, assume that
126 // the canonical holder of that field is java.lang.Object. Arrays
127 // do not have fields; java.lang.Object is the only supertype of an
128 // array type that can declare fields and is therefore the canonical
129 // holder of the array type.
130 //
131 // Furthermore, the compilers assume that java.lang.Object does not
132 // have any fields. Therefore, the field is not looked up. Instead,
133 // the method returns partial information that will trigger special
134 // handling in ciField::will_link and will result in a
135 // java.lang.NoSuchFieldError exception being thrown by the compiled
136 // code (the expected behavior in this case).
137 _holder = ciEnv::current(THREAD)->Object_klass();
138 _offset = -1;
139 _is_constant = false;
140 return;
141 }
142
143 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
144
145 // The declared holder of this field may not have been loaded.
146 // Bail out with partial field information.
147 if (!holder_is_accessible) {
148 // _type has already been set.
149 // The default values for _flags and _constant_value will suffice.
150 // We need values for _holder, _offset, and _is_constant,
151 _holder = declared_holder;
152 _offset = -1;
153 _is_constant = false;
154 return;
155 }
156
157 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
158
159 // Perform the field lookup.
160 fieldDescriptor field_desc;
161 Klass* canonical_holder =
162 loaded_decl_holder->find_field(name, signature, &field_desc);
163 if (canonical_holder == nullptr) {
164 // Field lookup failed. Will be detected by will_link.
165 _holder = declared_holder;
166 _offset = -1;
167 _is_constant = false;
168 return;
169 }
170
171 // Access check based on declared_holder. canonical_holder should not be used
172 // to check access because it can erroneously succeed. If this check fails,
173 // propagate the declared holder to will_link() which in turn will bail out
174 // compilation for this field access.
175 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
176 declared_holder->get_Klass(),
177 canonical_holder,
178 field_desc.access_flags(),
179 true, false, THREAD);
180 if (!can_access) {
181 _holder = declared_holder;
182 _offset = -1;
183 _is_constant = false;
184 // It's possible the access check failed due to a nestmate access check
185 // encountering an exception. We can't propagate the exception from here
186 // so we have to clear it. If the access check happens again in a different
187 // context then the exception will be thrown there.
188 if (HAS_PENDING_EXCEPTION) {
189 CLEAR_PENDING_EXCEPTION;
190 }
191 return;
192 }
193
194 assert(canonical_holder == field_desc.field_holder(), "just checking");
195 initialize_from(&field_desc);
196 }
197
198 ciField::ciField(fieldDescriptor *fd) :
199 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
200 ASSERT_IN_VM;
201
202 // Get the field's name, signature, and type.
203 ciEnv* env = CURRENT_ENV;
204 _name = env->get_symbol(fd->name());
205 _signature = env->get_symbol(fd->signature());
206
207 BasicType field_type = fd->field_type();
208
209 // If the field is a pointer type, get the klass of the
210 // field.
211 if (is_reference_type(field_type)) {
212 _type = nullptr; // must call compute_type on first access
213 } else {
214 _type = ciType::make(field_type);
215 }
216
217 initialize_from(fd);
218
219 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
220 assert(is_shared() || ciObjectFactory::is_initialized(),
221 "bootstrap classes must not create & cache unshared fields");
222 }
223
224 // Special copy constructor used to flatten inline type fields by
225 // copying the fields of the inline type to a new holder klass.
226 ciField::ciField(ciField* declared_field, ciField* subfield) {
227 assert(subfield->holder()->is_inlinetype() || subfield->holder()->is_abstract(), "should only be used for inline type field flattening");
228 assert(!subfield->is_flat(), "subfield must not be flat");
229 assert(declared_field->is_flat(), "declared field must be flat");
230
231 _flags = declared_field->flags();
232 _holder = declared_field->holder();
233 _offset = declared_field->offset_in_bytes() + (subfield->offset_in_bytes() - declared_field->type()->as_inline_klass()->payload_offset());
234
235 char buffer[256];
236 jio_snprintf(buffer, sizeof(buffer), "%s.%s", declared_field->name()->as_utf8(), subfield->name()->as_utf8());
237 _name = ciSymbol::make(buffer);
238
239 _signature = subfield->_signature;
240 _type = subfield->_type;
241 _is_constant = false;
242 _known_to_link_with_put = subfield->_known_to_link_with_put;
243 _known_to_link_with_get = subfield->_known_to_link_with_get;
244 _constant_value = ciConstant();
245
246 _is_flat = false;
247 _is_null_free = false;
248 _null_marker_offset = -1;
249 _original_holder = (subfield->_original_holder != nullptr) ? subfield->_original_holder : subfield->_holder;
250 }
251
252 // Constructor for the ciField of a null marker
253 ciField::ciField(ciField* declared_field) {
254 assert(declared_field->is_flat(), "declared field must be flat");
255 assert(!declared_field->is_null_free(), "must have a null marker");
256
257 _flags = declared_field->flags();
258 _holder = declared_field->holder();
259 _offset = declared_field->null_marker_offset();
260
261 char buffer[256];
262 jio_snprintf(buffer, sizeof(buffer), "%s.$nullMarker$", declared_field->name()->as_utf8());
263 _name = ciSymbol::make(buffer);
264
265 _signature = ciSymbols::bool_signature();
266 _type = ciType::make(T_BOOLEAN);
267
268 _is_constant = false;
269 _known_to_link_with_put = nullptr;
270 _known_to_link_with_get = nullptr;
271 _constant_value = ciConstant();
272
273 _is_flat = false;
274 _is_null_free = false;
275 _null_marker_offset = -1;
276 _original_holder = nullptr;
277 }
278
279 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
280 if (holder == nullptr)
281 return false;
282 if (holder->name() == ciSymbols::java_lang_System())
283 // Never trust strangely unstable finals: System.out, etc.
284 return false;
285 // Even if general trusting is disabled, trust system-built closures in these packages.
286 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
287 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
288 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
289 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
290 holder->is_in_package("java/lang"))
291 return true;
292 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
293 // can't be serialized, so there is no hacking of finals going on with them.
294 if (holder->is_hidden())
295 return true;
296 // Trust final fields in inline type buffers
297 if (holder->is_inlinetype())
298 return true;
299 // Trust final fields in all boxed classes
300 if (holder->is_box_klass())
301 return true;
302 // Trust final fields in records
303 if (holder->is_record())
304 return true;
305 // Trust final fields in String
306 if (holder->name() == ciSymbols::java_lang_String())
307 return true;
308 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
309 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
310 if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
311 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
312 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
313 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
314 return true;
315 }
316 return TrustFinalNonStaticFields;
317 }
318
319 void ciField::initialize_from(fieldDescriptor* fd) {
320 // Get the flags, offset, and canonical holder of the field.
321 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
322 _offset = fd->offset();
323 InstanceKlass* field_holder = fd->field_holder();
324 assert(field_holder != nullptr, "null field_holder");
325 _holder = CURRENT_ENV->get_instance_klass(field_holder);
326 _is_flat = fd->is_flat();
327 _is_null_free = fd->is_null_free_inline_type();
328 if (fd->has_null_marker()) {
329 InlineLayoutInfo* li = field_holder->inline_layout_info_adr(fd->index());
330 _null_marker_offset = li->null_marker_offset();
331 } else {
332 _null_marker_offset = -1;
333 }
334 _original_holder = nullptr;
335
336 // Check to see if the field is constant.
337 Klass* k = _holder->get_Klass();
338 bool is_stable_field = FoldStableValues && is_stable();
339 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
340 if (is_static()) {
341 // This field just may be constant. The only case where it will
342 // not be constant is when the field is a *special* static & final field
343 // whose value may change. The three examples are java.lang.System.in,
344 // java.lang.System.out, and java.lang.System.err.
345 assert(vmClasses::System_klass() != nullptr, "Check once per vm");
346 if (k == vmClasses::System_klass()) {
347 // Check offsets for case 2: System.in, System.out, or System.err
348 if (_offset == java_lang_System::in_offset() ||
349 _offset == java_lang_System::out_offset() ||
350 _offset == java_lang_System::err_offset()) {
351 _is_constant = false;
352 return;
353 }
354 }
355 _is_constant = true;
356 } else {
357 // An instance field can be constant if it's a final static field or if
358 // it's a final non-static field of a trusted class (classes in
359 // java.lang.invoke and sun.invoke packages and subpackages).
360 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
361 }
362 } else {
363 // For CallSite objects treat the target field as a compile time constant.
364 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
365 if (k == vmClasses::CallSite_klass() &&
366 _offset == java_lang_invoke_CallSite::target_offset()) {
367 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
368 _is_constant = true;
369 } else {
370 // Non-final & non-stable fields are not constants.
371 _is_constant = false;
372 }
373 }
374 }
375
376 // ------------------------------------------------------------------
377 // ciField::constant_value
378 // Get the constant value of a this static field.
379 ciConstant ciField::constant_value() {
380 assert(is_static() && is_constant(), "illegal call to constant_value()");
381 if (!_holder->is_initialized()) {
382 return ciConstant(); // Not initialized yet
383 }
384 if (_constant_value.basic_type() == T_ILLEGAL) {
385 // Static fields are placed in mirror objects.
386 ciInstance* mirror = _holder->java_mirror();
387 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
388 }
389 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
390 return ciConstant();
391 }
392 return _constant_value;
393 }
394
395 // ------------------------------------------------------------------
396 // ciField::constant_value_of
397 // Get the constant value of non-static final field in the given object.
398 ciConstant ciField::constant_value_of(ciObject* object) {
399 assert(!is_static() && is_constant(), "only if field is non-static constant");
400 assert(object->is_instance(), "must be instance");
401 ciConstant field_value = object->as_instance()->field_value(this);
402 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
403 return ciConstant();
404 }
405 return field_value;
406 }
407
408 // ------------------------------------------------------------------
409 // ciField::compute_type
410 //
411 // Lazily compute the type, if it is an instance klass.
412 ciType* ciField::compute_type() {
413 GUARDED_VM_ENTRY(return compute_type_impl();)
414 }
415
416 ciType* ciField::compute_type_impl() {
417 // Use original holder for fields that came in through flattening
418 ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
419 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
420 if (!type->is_primitive_type() && is_shared()) {
421 // We must not cache a pointer to an unshared type, in a shared field.
422 bool type_is_also_shared = false;
423 if (type->is_type_array_klass()) {
424 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
425 } else if (type->is_instance_klass()) {
426 type_is_also_shared = type->as_instance_klass()->is_shared();
427 } else {
428 // Currently there is no 'shared' query for array types.
429 type_is_also_shared = !ciObjectFactory::is_initialized();
430 }
431 if (!type_is_also_shared)
432 return type; // Bummer.
433 }
434 _type = type;
435 return type;
436 }
437
438
439 // ------------------------------------------------------------------
440 // ciField::will_link
441 //
442 // Can a specific access to this field be made without causing
443 // link errors?
444 bool ciField::will_link(ciMethod* accessing_method,
445 Bytecodes::Code bc) {
446 VM_ENTRY_MARK;
447 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
448 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
449 "unexpected bytecode");
450
451 if (_offset == -1) {
452 // at creation we couldn't link to our holder so we need to
453 // maintain that stance, otherwise there's no safe way to use this
454 // ciField.
455 return false;
456 }
457
458 // Check for static/nonstatic mismatch
459 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
460 if (is_static != this->is_static()) {
461 return false;
462 }
463
464 // Get and put can have different accessibility rules
465 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
466 if (is_put) {
467 if (_known_to_link_with_put == accessing_method) {
468 return true;
469 }
470 } else {
471 if (_known_to_link_with_get == accessing_method->holder()) {
472 return true;
473 }
474 }
475
476 LinkInfo link_info(_holder->get_instanceKlass(),
477 _name->get_symbol(), _signature->get_symbol(),
478 methodHandle(THREAD, accessing_method->get_Method()));
479 fieldDescriptor result;
480 LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
481
482 // update the hit-cache, unless there is a problem with memory scoping:
483 if (accessing_method->holder()->is_shared() || !is_shared()) {
484 if (is_put) {
485 _known_to_link_with_put = accessing_method;
486 } else {
487 _known_to_link_with_get = accessing_method->holder();
488 }
489 }
490
491 return true;
492 }
493
494 bool ciField::is_call_site_target() {
495 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
496 if (callsite_klass == nullptr)
497 return false;
498 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
499 }
500
501 bool ciField::is_autobox_cache() {
502 ciSymbol* klass_name = holder()->name();
503 return (name() == ciSymbols::cache_field_name() &&
504 holder()->uses_default_loader() &&
505 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
506 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
507 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
508 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
509 klass_name == ciSymbols::java_lang_Long_LongCache()));
510 }
511
512 // ------------------------------------------------------------------
513 // ciField::print
514 void ciField::print() {
515 tty->print("<ciField name=");
516 _holder->print_name();
517 tty->print(".");
518 _name->print_symbol();
519 tty->print(" signature=");
520 _signature->print_symbol();
521 tty->print(" offset=%d type=", _offset);
522 if (_type != nullptr)
523 _type->print_name();
524 else
525 tty->print("(reference)");
526 tty->print(" flags=%04x", flags().as_int());
527 tty->print(" is_constant=%s", bool_to_str(_is_constant));
528 if (_is_constant && is_static()) {
529 tty->print(" constant_value=");
530 _constant_value.print();
531 }
532 tty->print(" is_flat=%s", bool_to_str(_is_flat));
533 tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
534 tty->print(" null_marker_offset=%d", _null_marker_offset);
535 tty->print(">");
536 }
537
538 // ------------------------------------------------------------------
539 // ciField::print_name_on
540 //
541 // Print the name of this field
542 void ciField::print_name_on(outputStream* st) {
543 name()->print_symbol_on(st);
544 }