1 /*
2 * Copyright (c) 1999, 2026, Oracle and/or its affiliates. All rights reserved.
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/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/layoutKind.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/fieldDescriptor.inline.hpp"
41 #include "runtime/handles.inline.hpp"
42 #include "runtime/reflection.hpp"
43 #include "utilities/globalDefinitions.hpp"
44
45 // ciField
46 //
47 // This class represents the result of a field lookup in the VM.
48 // The lookup may not succeed, in which case the information in
49 // the ciField will be incomplete.
50
51 // The ciObjectFactory cannot create circular data structures in one query.
52 // To avoid vicious circularities, we initialize ciField::_type to null
53 // for reference types and derive it lazily from the ciField::_signature.
54 // Primitive types are eagerly initialized, and basic layout queries
55 // can succeed without initialization, using only the BasicType of the field.
56
57 // Notes on bootstrapping and shared CI objects: A field is shared if and
58 // only if it is (a) non-static and (b) declared by a shared instance klass.
59 // This allows non-static field lists to be cached on shared types.
60 // Because the _type field is lazily initialized, however, there is a
61 // special restriction that a shared field cannot cache an unshared type.
62 // This puts a small performance penalty on shared fields with unshared
63 // types, such as StackTraceElement[] Throwable.stackTrace.
64 // (Throwable is shared because ClassCastException is shared, but
65 // StackTraceElement is not presently shared.)
66
67 // It is not a vicious circularity for a ciField to recursively create
68 // the ciSymbols necessary to represent its name and signature.
69 // Therefore, these items are created eagerly, and the name and signature
70 // of a shared field are themselves shared symbols. This somewhat
71 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
72 // with all of the additional 43 being uninteresting shared ciSymbols.
73 // This adds at most one step to the binary search, an amount which
74 // decreases for complex compilation tasks.
75
76 // ------------------------------------------------------------------
77 // ciField::ciField
78 ciField::ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc) :
79 _original_holder(nullptr), _is_flat(false), _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
80 ASSERT_IN_VM;
81 CompilerThread *THREAD = CompilerThread::current();
82
83 assert(ciObjectFactory::is_initialized(), "not a shared field");
84
85 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
86
87 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
88
89 // Get the field's name, signature, and type.
90 Symbol* name = cpool->name_ref_at(index, bc);
91 _name = ciEnv::current(THREAD)->get_symbol(name);
92
93 int nt_index = cpool->name_and_type_ref_index_at(index, bc);
94 int sig_index = cpool->signature_ref_index_at(nt_index);
95 Symbol* signature = cpool->symbol_at(sig_index);
96 _signature = ciEnv::current(THREAD)->get_symbol(signature);
97
98 BasicType field_type = Signature::basic_type(signature);
99
100 // If the field is a pointer type, get the klass of the
101 // field.
102 if (is_reference_type(field_type)) {
103 bool ignore;
104 // This is not really a class reference; the index always refers to the
105 // field's type signature, as a symbol. Linkage checks do not apply.
106 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
107 } else {
108 _type = ciType::make(field_type);
109 }
110
111 _is_null_free = false;
112 _null_marker_offset = -1;
113
114 // Get the field's declared holder.
115 //
116 // Note: we actually create a ciInstanceKlass for this klass,
117 // even though we may not need to.
118 int holder_index = cpool->klass_ref_index_at(index, bc);
119 bool holder_is_accessible;
120
121 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
122 holder_is_accessible,
123 klass);
124
125 if (generic_declared_holder->is_array_klass()) {
126 // If the declared holder of the field is an array class, assume that
127 // the canonical holder of that field is java.lang.Object. Arrays
128 // do not have fields; java.lang.Object is the only supertype of an
129 // array type that can declare fields and is therefore the canonical
130 // holder of the array type.
131 //
132 // Furthermore, the compilers assume that java.lang.Object does not
133 // have any fields. Therefore, the field is not looked up. Instead,
134 // the method returns partial information that will trigger special
135 // handling in ciField::will_link and will result in a
136 // java.lang.NoSuchFieldError exception being thrown by the compiled
137 // code (the expected behavior in this case).
138 _holder = ciEnv::current(THREAD)->Object_klass();
139 _offset = -1;
140 _is_constant = false;
141 return;
142 }
143
144 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
145
146 // The declared holder of this field may not have been loaded.
147 // Bail out with partial field information.
148 if (!holder_is_accessible) {
149 // _type has already been set.
150 // The default values for _flags and _constant_value will suffice.
151 // We need values for _holder, _offset, and _is_constant,
152 _holder = declared_holder;
153 _offset = -1;
154 _is_constant = false;
155 return;
156 }
157
158 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
159
160 // Perform the field lookup.
161 fieldDescriptor field_desc;
162 Klass* canonical_holder =
163 loaded_decl_holder->find_field(name, signature, &field_desc);
164 if (canonical_holder == nullptr) {
165 // Field lookup failed. Will be detected by will_link.
166 _holder = declared_holder;
167 _offset = -1;
168 _is_constant = false;
169 return;
170 }
171
172 // Access check based on declared_holder. canonical_holder should not be used
173 // to check access because it can erroneously succeed. If this check fails,
174 // propagate the declared holder to will_link() which in turn will bail out
175 // compilation for this field access.
176 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
177 declared_holder->get_Klass(),
178 canonical_holder,
179 field_desc.access_flags(),
180 true, false, THREAD);
181 if (!can_access) {
182 _holder = declared_holder;
183 _offset = -1;
184 _is_constant = false;
185 // It's possible the access check failed due to a nestmate access check
186 // encountering an exception. We can't propagate the exception from here
187 // so we have to clear it. If the access check happens again in a different
188 // context then the exception will be thrown there.
189 if (HAS_PENDING_EXCEPTION) {
190 CLEAR_PENDING_EXCEPTION;
191 }
192 return;
193 }
194
195 assert(canonical_holder == field_desc.field_holder(), "just checking");
196 initialize_from(&field_desc);
197 }
198
199 ciField::ciField(fieldDescriptor *fd) :
200 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
201 ASSERT_IN_VM;
202
203 // Get the field's name, signature, and type.
204 ciEnv* env = CURRENT_ENV;
205 _name = env->get_symbol(fd->name());
206 _signature = env->get_symbol(fd->signature());
207
208 BasicType field_type = fd->field_type();
209
210 // If the field is a pointer type, get the klass of the
211 // field.
212 if (is_reference_type(field_type)) {
213 _type = nullptr; // must call compute_type on first access
214 } else {
215 _type = ciType::make(field_type);
216 }
217
218 initialize_from(fd);
219
220 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
221 assert(is_shared() || ciObjectFactory::is_initialized(),
222 "bootstrap classes must not create & cache unshared fields");
223 }
224
225 // Special copy constructor used to flatten inline type fields by
226 // copying the fields of the inline type to a new holder klass.
227 ciField::ciField(ciField* declared_field, ciField* subfield) {
228 assert(subfield->holder()->is_inlinetype() || subfield->holder()->is_abstract(), "should only be used for inline type field flattening");
229 assert(!subfield->is_flat(), "subfield must not be flat");
230 assert(declared_field->is_flat(), "declared field must be flat");
231
232 _flags = declared_field->flags();
233 _holder = declared_field->holder();
234 _offset = declared_field->offset_in_bytes() + (subfield->offset_in_bytes() - declared_field->type()->as_inline_klass()->payload_offset());
235
236 char buffer[256];
237 jio_snprintf(buffer, sizeof(buffer), "%s.%s", declared_field->name()->as_utf8(), subfield->name()->as_utf8());
238 _name = ciSymbol::make(buffer);
239
240 _signature = subfield->_signature;
241 _type = subfield->_type;
242 _is_constant = (declared_field->is_strict() && declared_field->is_final()) || declared_field->is_constant();
243 _known_to_link_with_put = subfield->_known_to_link_with_put;
244 _known_to_link_with_get = subfield->_known_to_link_with_get;
245 _constant_value = ciConstant();
246
247 _is_flat = false;
248 _is_null_free = false;
249 _null_marker_offset = -1;
250 _original_holder = (subfield->_original_holder != nullptr) ? subfield->_original_holder : subfield->_holder;
251 _layout_kind = LayoutKind::UNKNOWN;
252 }
253
254 // Constructor for the ciField of a null marker
255 ciField::ciField(ciField* declared_field) {
256 assert(declared_field->is_flat(), "declared field must be flat");
257 assert(!declared_field->is_null_free(), "must have a null marker");
258
259 _flags = declared_field->flags();
260 _holder = declared_field->holder();
261 _offset = declared_field->null_marker_offset();
262
263 char buffer[256];
264 jio_snprintf(buffer, sizeof(buffer), "%s.$nullMarker$", declared_field->name()->as_utf8());
265 _name = ciSymbol::make(buffer);
266
267 _signature = ciSymbols::bool_signature();
268 _type = ciType::make(T_BOOLEAN);
269
270 _is_constant = (declared_field->is_strict() && declared_field->is_final()) || declared_field->is_constant();
271 _known_to_link_with_put = nullptr;
272 _known_to_link_with_get = nullptr;
273 _constant_value = ciConstant();
274
275 _is_flat = false;
276 _is_null_free = false;
277 _null_marker_offset = -1;
278 _original_holder = nullptr;
279 _layout_kind = LayoutKind::UNKNOWN;
280 }
281
282 static bool trust_final_nonstatic_fields(ciInstanceKlass* holder) {
283 if (holder == nullptr)
284 return false;
285 if (holder->trust_final_fields()) {
286 // Explicit opt-in from system classes
287 return true;
288 }
289 // Even if general trusting is disabled, trust system-built closures in these packages.
290 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
291 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
292 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
293 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
294 holder->is_in_package("java/lang"))
295 return true;
296 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
297 // can't be serialized, so there is no hacking of finals going on with them.
298 if (holder->is_hidden())
299 return true;
300 // Trust final fields in inline type buffers
301 if (holder->is_inlinetype())
302 return true;
303 // Trust final fields in records
304 if (holder->is_record())
305 return true;
306 return TrustFinalNonStaticFields;
307 }
308
309 void ciField::initialize_from(fieldDescriptor* fd) {
310 // Get the flags, offset, and canonical holder of the field.
311 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
312 _offset = fd->offset();
313 InstanceKlass* field_holder = fd->field_holder();
314 assert(field_holder != nullptr, "null field_holder");
315 _holder = CURRENT_ENV->get_instance_klass(field_holder);
316 _is_flat = fd->is_flat();
317 _is_null_free = fd->is_null_free_inline_type();
318 if (fd->has_null_marker()) {
319 InlineLayoutInfo* li = field_holder->inline_layout_info_adr(fd->index());
320 _null_marker_offset = li->null_marker_offset();
321 } else {
322 _null_marker_offset = -1;
323 }
324 _original_holder = nullptr;
325 _layout_kind = fd->is_flat() ? fd->layout_kind() : LayoutKind::UNKNOWN;
326
327 // Check to see if the field is constant.
328 Klass* k = _holder->get_Klass();
329 bool is_stable_field = FoldStableValues && is_stable();
330 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
331 if (is_static()) {
332 // This field just may be constant. The only case where it will
333 // not be constant is when the field is a *special* static & final field
334 // whose value may change. The three examples are java.lang.System.in,
335 // java.lang.System.out, and java.lang.System.err.
336 _is_constant = !fd->is_mutable_static_final();
337 } else {
338 // An instance field can be constant if it's a final static field or if
339 // it's a final non-static field of a trusted class (classes in
340 // java.lang.invoke and sun.invoke packages and subpackages).
341 _is_constant = is_stable_field || trust_final_nonstatic_fields(_holder);
342 }
343 } else {
344 // For CallSite objects treat the target field as a compile time constant.
345 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
346 if (k == vmClasses::CallSite_klass() &&
347 _offset == java_lang_invoke_CallSite::target_offset()) {
348 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
349 _is_constant = true;
350 } else {
351 // Non-final & non-stable fields are not constants.
352 _is_constant = false;
353 }
354 }
355 }
356
357 // ------------------------------------------------------------------
358 // ciField::constant_value
359 // Get the constant value of a this static field.
360 ciConstant ciField::constant_value() {
361 assert(is_static() && is_constant(), "illegal call to constant_value()");
362 if (!_holder->is_initialized()) {
363 return ciConstant(); // Not initialized yet
364 }
365 if (_constant_value.basic_type() == T_ILLEGAL) {
366 // Static fields are placed in mirror objects.
367 ciInstance* mirror = _holder->java_mirror();
368 _constant_value = mirror->field_value_impl(this);
369 }
370 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
371 return ciConstant();
372 }
373 return _constant_value;
374 }
375
376 // ------------------------------------------------------------------
377 // ciField::constant_value_of
378 // Get the constant value of non-static final field in the given object.
379 ciConstant ciField::constant_value_of(ciObject* object) {
380 assert(!is_static() && is_constant(), "only if field is non-static constant");
381 assert(object->is_instance(), "must be instance");
382 ciConstant field_value = object->as_instance()->field_value(this);
383 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
384 return ciConstant();
385 }
386 return field_value;
387 }
388
389 // ------------------------------------------------------------------
390 // ciField::compute_type
391 //
392 // Lazily compute the type, if it is an instance klass.
393 ciType* ciField::compute_type() {
394 GUARDED_VM_ENTRY(return compute_type_impl();)
395 }
396
397 ciType* ciField::compute_type_impl() {
398 // Use original holder for fields that came in through flattening
399 ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
400 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
401 if (!type->is_primitive_type() && is_shared()) {
402 // We must not cache a pointer to an unshared type, in a shared field.
403 bool type_is_also_shared = false;
404 if (type->is_type_array_klass()) {
405 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
406 } else if (type->is_instance_klass()) {
407 type_is_also_shared = type->as_instance_klass()->is_shared();
408 } else {
409 // Currently there is no 'shared' query for array types.
410 type_is_also_shared = !ciObjectFactory::is_initialized();
411 }
412 if (!type_is_also_shared)
413 return type; // Bummer.
414 }
415 _type = type;
416 return type;
417 }
418
419 bool ciField::is_atomic() {
420 assert(is_flat(), "should not ask this property for non-flat field %s.%s", holder()->name()->as_utf8(), name()->as_utf8());
421 return LayoutKindHelper::is_atomic_flat(_layout_kind) && !type()->as_inline_klass()->is_naturally_atomic(is_null_free());
422 }
423
424 // ------------------------------------------------------------------
425 // ciField::will_link
426 //
427 // Can a specific access to this field be made without causing
428 // link errors?
429 bool ciField::will_link(ciMethod* accessing_method,
430 Bytecodes::Code bc) {
431 VM_ENTRY_MARK;
432 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
433 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
434 "unexpected bytecode");
435
436 if (_offset == -1) {
437 // at creation we couldn't link to our holder so we need to
438 // maintain that stance, otherwise there's no safe way to use this
439 // ciField.
440 return false;
441 }
442
443 // Check for static/nonstatic mismatch
444 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
445 if (is_static != this->is_static()) {
446 return false;
447 }
448
449 // Get and put can have different accessibility rules
450 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
451 if (is_put) {
452 if (_known_to_link_with_put == accessing_method) {
453 return true;
454 }
455 } else {
456 if (_known_to_link_with_get == accessing_method->holder()) {
457 return true;
458 }
459 }
460
461 LinkInfo link_info(_holder->get_instanceKlass(),
462 _name->get_symbol(), _signature->get_symbol(),
463 methodHandle(THREAD, accessing_method->get_Method()));
464 fieldDescriptor result;
465 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(false));
466
467 // Strict statics may require tracking if their class is not fully initialized.
468 // For now we can bail out of the compiler and let the interpreter handle it.
469 if (is_static && result.is_strict_static_unset()) {
470 // If we left out this logic, we would get (a) spurious <clinit>
471 // failures for C2 code because compiled putstatic would not write
472 // the "unset" bits, and (b) missed failures for too-early reads,
473 // since the compiled getstatic would not check the "unset" bits.
474 // Test C1 on <clinit> with "-XX:TieredStopAtLevel=2 -Xcomp -Xbatch".
475 // Test C2 on <clinit> with "-XX:-TieredCompilation -Xcomp -Xbatch".
476 return false;
477 }
478
479 // update the hit-cache, unless there is a problem with memory scoping:
480 if (accessing_method->holder()->is_shared() || !is_shared()) {
481 if (is_put) {
482 _known_to_link_with_put = accessing_method;
483 } else {
484 _known_to_link_with_get = accessing_method->holder();
485 }
486 }
487
488 return true;
489 }
490
491 bool ciField::is_call_site_target() {
492 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
493 if (callsite_klass == nullptr)
494 return false;
495 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
496 }
497
498 bool ciField::is_autobox_cache() {
499 ciSymbol* klass_name = holder()->name();
500 return (name() == ciSymbols::cache_field_name() &&
501 holder()->uses_default_loader() &&
502 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
503 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
504 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
505 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
506 klass_name == ciSymbols::java_lang_Long_LongCache()));
507 }
508
509 // ------------------------------------------------------------------
510 // ciField::print
511 void ciField::print() const {
512 tty->print("<ciField name=");
513 _holder->print_name();
514 tty->print(".");
515 _name->print_symbol();
516 tty->print(" signature=");
517 _signature->print_symbol();
518 tty->print(" offset=%d type=", _offset);
519 if (_type != nullptr)
520 _type->print_name();
521 else
522 tty->print("(reference)");
523 tty->print(" flags=%04x", flags().as_int());
524 tty->print(" is_constant=%s", bool_to_str(_is_constant));
525 if (_is_constant && is_static()) {
526 tty->print(" constant_value=");
527 _constant_value.print();
528 }
529 tty->print(" is_flat=%s", bool_to_str(_is_flat));
530 tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
531 tty->print(" null_marker_offset=%d", _null_marker_offset);
532 tty->print(">");
533 }
534
535 // ------------------------------------------------------------------
536 // ciField::print_name_on
537 //
538 // Print the name of this field
539 void ciField::print_name_on(outputStream* st) {
540 name()->print_symbol_on(st);
541 }