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src/hotspot/share/ci/ciField.cpp

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 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   _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
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,

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 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
220   if (holder == nullptr)
221     return false;
222   if (holder->name() == ciSymbols::java_lang_System())
223     // Never trust strangely unstable finals:  System.out, etc.
224     return false;
225   // Even if general trusting is disabled, trust system-built closures in these packages.
226   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
227       holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
228       holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
229       holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
230       holder->is_in_package("java/lang"))
231     return true;
232   // Trust hidden classes. They are created via Lookup.defineHiddenClass and
233   // can't be serialized, so there is no hacking of finals going on with them.
234   if (holder->is_hidden())
235     return true;



236   // Trust final fields in all boxed classes
237   if (holder->is_box_klass())
238     return true;
239   // Trust final fields in records
240   if (holder->is_record())
241     return true;
242   // Trust final fields in String
243   if (holder->name() == ciSymbols::java_lang_String())
244     return true;
245   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
246   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
247   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
248       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
249       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
250       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
251     return true;
252   }
253   return TrustFinalNonStaticFields;
254 }
255 
256 void ciField::initialize_from(fieldDescriptor* fd) {
257   // Get the flags, offset, and canonical holder of the field.
258   _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
259   _offset = fd->offset();
260   Klass* field_holder = fd->field_holder();
261   assert(field_holder != nullptr, "null field_holder");
262   _holder = CURRENT_ENV->get_instance_klass(field_holder);



263 
264   // Check to see if the field is constant.
265   Klass* k = _holder->get_Klass();
266   bool is_stable_field = FoldStableValues && is_stable();
267   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
268     if (is_static()) {
269       // This field just may be constant.  The only case where it will
270       // not be constant is when the field is a *special* static & final field
271       // whose value may change.  The three examples are java.lang.System.in,
272       // java.lang.System.out, and java.lang.System.err.
273       assert(vmClasses::System_klass() != nullptr, "Check once per vm");
274       if (k == vmClasses::System_klass()) {
275         // Check offsets for case 2: System.in, System.out, or System.err
276         if (_offset == java_lang_System::in_offset()  ||
277             _offset == java_lang_System::out_offset() ||
278             _offset == java_lang_System::err_offset()) {
279           _is_constant = false;
280           return;
281         }
282       }

325 // Get the constant value of non-static final field in the given object.
326 ciConstant ciField::constant_value_of(ciObject* object) {
327   assert(!is_static() && is_constant(), "only if field is non-static constant");
328   assert(object->is_instance(), "must be instance");
329   ciConstant field_value = object->as_instance()->field_value(this);
330   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
331     return ciConstant();
332   }
333   return field_value;
334 }
335 
336 // ------------------------------------------------------------------
337 // ciField::compute_type
338 //
339 // Lazily compute the type, if it is an instance klass.
340 ciType* ciField::compute_type() {
341   GUARDED_VM_ENTRY(return compute_type_impl();)
342 }
343 
344 ciType* ciField::compute_type_impl() {
345   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);


346   if (!type->is_primitive_type() && is_shared()) {
347     // We must not cache a pointer to an unshared type, in a shared field.
348     bool type_is_also_shared = false;
349     if (type->is_type_array_klass()) {
350       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
351     } else if (type->is_instance_klass()) {
352       type_is_also_shared = type->as_instance_klass()->is_shared();
353     } else {
354       // Currently there is no 'shared' query for array types.
355       type_is_also_shared = !ciObjectFactory::is_initialized();
356     }
357     if (!type_is_also_shared)
358       return type;              // Bummer.
359   }
360   _type = type;
361   return type;
362 }
363 
364 
365 // ------------------------------------------------------------------

438 // ------------------------------------------------------------------
439 // ciField::print
440 void ciField::print() {
441   tty->print("<ciField name=");
442   _holder->print_name();
443   tty->print(".");
444   _name->print_symbol();
445   tty->print(" signature=");
446   _signature->print_symbol();
447   tty->print(" offset=%d type=", _offset);
448   if (_type != nullptr)
449     _type->print_name();
450   else
451     tty->print("(reference)");
452   tty->print(" flags=%04x", flags().as_int());
453   tty->print(" is_constant=%s", bool_to_str(_is_constant));
454   if (_is_constant && is_static()) {
455     tty->print(" constant_value=");
456     _constant_value.print();
457   }


458   tty->print(">");
459 }
460 
461 // ------------------------------------------------------------------
462 // ciField::print_name_on
463 //
464 // Print the name of this field
465 void ciField::print_name_on(outputStream* st) {
466   name()->print_symbol_on(st);
467 }

 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   _original_holder(nullptr), _is_flat(false), _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   _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
107 
108   // this is needed if the field class is not yet loaded.
109   // _is_null_free = _signature->is_Q_signature();
110   _is_null_free = false; // JDK-8325660: null free-ness should be checked in FieldFlags instead of signature
111 
112   // Get the field's declared holder.
113   //
114   // Note: we actually create a ciInstanceKlass for this klass,
115   // even though we may not need to.
116   int holder_index = cpool->klass_ref_index_at(index, bc);
117   bool holder_is_accessible;
118 
119   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
120                                                                                 holder_is_accessible,
121                                                                                 klass);
122 
123   if (generic_declared_holder->is_array_klass()) {
124     // If the declared holder of the field is an array class, assume that
125     // the canonical holder of that field is java.lang.Object. Arrays
126     // do not have fields; java.lang.Object is the only supertype of an
127     // array type that can declare fields and is therefore the canonical
128     // holder of the array type.
129     //
130     // Furthermore, the compilers assume that java.lang.Object does not
131     // have any fields. Therefore, the field is not looked up. Instead,

203   _name = env->get_symbol(fd->name());
204   _signature = env->get_symbol(fd->signature());
205 
206   BasicType field_type = fd->field_type();
207 
208   // If the field is a pointer type, get the klass of the
209   // field.
210   if (is_reference_type(field_type)) {
211     _type = nullptr;  // must call compute_type on first access
212   } else {
213     _type = ciType::make(field_type);
214   }
215 
216   initialize_from(fd);
217 
218   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
219   assert(is_shared() || ciObjectFactory::is_initialized(),
220          "bootstrap classes must not create & cache unshared fields");
221 }
222 
223 // Special copy constructor used to flatten inline type fields by
224 // copying the fields of the inline type to a new holder klass.
225 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
226   assert(field->holder()->is_inlinetype(), "should only be used for inline type field flattening");
227   // Set the is_final flag
228   jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
229   AccessFlags flags(field->flags().as_int() & final);
230   _flags = ciFlags(flags);
231   _holder = holder;
232   _offset = offset;
233   // Copy remaining fields
234   _name = field->_name;
235   _signature = field->_signature;
236   _type = field->_type;
237   // Trust final flat fields
238   _is_constant = is_final;
239   _known_to_link_with_put = field->_known_to_link_with_put;
240   _known_to_link_with_get = field->_known_to_link_with_get;
241   _constant_value = field->_constant_value;
242   assert(!field->is_flat(), "field must not be flat");
243   _is_flat = false;
244   _is_null_free = field->_is_null_free;
245   _original_holder = (field->_original_holder != nullptr) ? field->_original_holder : field->_holder;
246 }
247 
248 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
249   if (holder == nullptr)
250     return false;
251   if (holder->name() == ciSymbols::java_lang_System())
252     // Never trust strangely unstable finals:  System.out, etc.
253     return false;
254   // Even if general trusting is disabled, trust system-built closures in these packages.
255   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
256       holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
257       holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
258       holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
259       holder->is_in_package("java/lang"))
260     return true;
261   // Trust hidden classes. They are created via Lookup.defineHiddenClass and
262   // can't be serialized, so there is no hacking of finals going on with them.
263   if (holder->is_hidden())
264     return true;
265   // Trust final fields in inline type buffers
266   if (holder->is_inlinetype())
267     return true;
268   // Trust final fields in all boxed classes
269   if (holder->is_box_klass())
270     return true;
271   // Trust final fields in records
272   if (holder->is_record())
273     return true;
274   // Trust final fields in String
275   if (holder->name() == ciSymbols::java_lang_String())
276     return true;
277   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
278   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
279   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
280       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
281       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
282       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
283     return true;
284   }
285   return TrustFinalNonStaticFields;
286 }
287 
288 void ciField::initialize_from(fieldDescriptor* fd) {
289   // Get the flags, offset, and canonical holder of the field.
290   _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
291   _offset = fd->offset();
292   Klass* field_holder = fd->field_holder();
293   assert(field_holder != nullptr, "null field_holder");
294   _holder = CURRENT_ENV->get_instance_klass(field_holder);
295   _is_flat = fd->is_flat();
296   _is_null_free = fd->is_null_free_inline_type();
297   _original_holder = nullptr;
298 
299   // Check to see if the field is constant.
300   Klass* k = _holder->get_Klass();
301   bool is_stable_field = FoldStableValues && is_stable();
302   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
303     if (is_static()) {
304       // This field just may be constant.  The only case where it will
305       // not be constant is when the field is a *special* static & final field
306       // whose value may change.  The three examples are java.lang.System.in,
307       // java.lang.System.out, and java.lang.System.err.
308       assert(vmClasses::System_klass() != nullptr, "Check once per vm");
309       if (k == vmClasses::System_klass()) {
310         // Check offsets for case 2: System.in, System.out, or System.err
311         if (_offset == java_lang_System::in_offset()  ||
312             _offset == java_lang_System::out_offset() ||
313             _offset == java_lang_System::err_offset()) {
314           _is_constant = false;
315           return;
316         }
317       }

360 // Get the constant value of non-static final field in the given object.
361 ciConstant ciField::constant_value_of(ciObject* object) {
362   assert(!is_static() && is_constant(), "only if field is non-static constant");
363   assert(object->is_instance(), "must be instance");
364   ciConstant field_value = object->as_instance()->field_value(this);
365   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
366     return ciConstant();
367   }
368   return field_value;
369 }
370 
371 // ------------------------------------------------------------------
372 // ciField::compute_type
373 //
374 // Lazily compute the type, if it is an instance klass.
375 ciType* ciField::compute_type() {
376   GUARDED_VM_ENTRY(return compute_type_impl();)
377 }
378 
379 ciType* ciField::compute_type_impl() {
380   // Use original holder for fields that came in through flattening
381   ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
382   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
383   if (!type->is_primitive_type() && is_shared()) {
384     // We must not cache a pointer to an unshared type, in a shared field.
385     bool type_is_also_shared = false;
386     if (type->is_type_array_klass()) {
387       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
388     } else if (type->is_instance_klass()) {
389       type_is_also_shared = type->as_instance_klass()->is_shared();
390     } else {
391       // Currently there is no 'shared' query for array types.
392       type_is_also_shared = !ciObjectFactory::is_initialized();
393     }
394     if (!type_is_also_shared)
395       return type;              // Bummer.
396   }
397   _type = type;
398   return type;
399 }
400 
401 
402 // ------------------------------------------------------------------

475 // ------------------------------------------------------------------
476 // ciField::print
477 void ciField::print() {
478   tty->print("<ciField name=");
479   _holder->print_name();
480   tty->print(".");
481   _name->print_symbol();
482   tty->print(" signature=");
483   _signature->print_symbol();
484   tty->print(" offset=%d type=", _offset);
485   if (_type != nullptr)
486     _type->print_name();
487   else
488     tty->print("(reference)");
489   tty->print(" flags=%04x", flags().as_int());
490   tty->print(" is_constant=%s", bool_to_str(_is_constant));
491   if (_is_constant && is_static()) {
492     tty->print(" constant_value=");
493     _constant_value.print();
494   }
495   tty->print(" is_flat=%s", bool_to_str(_is_flat));
496   tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
497   tty->print(">");
498 }
499 
500 // ------------------------------------------------------------------
501 // ciField::print_name_on
502 //
503 // Print the name of this field
504 void ciField::print_name_on(outputStream* st) {
505   name()->print_symbol_on(st);
506 }
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