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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) :
 74     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 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);
 86   _name = ciEnv::current(THREAD)->get_symbol(name);
 87 
 88   int nt_index = cpool->name_and_type_ref_index_at(index);
 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);
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 = NULL;  // 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 == NULL)
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("jdk/internal/foreign") || holder->is_in_package("jdk/incubator/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 all boxed classes
236   if (holder->is_box_klass())
237     return true;
238   // Trust final fields in records
239   if (holder->is_record())
240     return true;
241   // Trust final fields in String
242   if (holder->name() == ciSymbols::java_lang_String())
243     return true;
244   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
245   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
246   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
247       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
248       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
249       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
250     return true;
251   }
252   return TrustFinalNonStaticFields;
253 }
254 
255 void ciField::initialize_from(fieldDescriptor* fd) {
256   // Get the flags, offset, and canonical holder of the field.
257   _flags = ciFlags(fd->access_flags());
258   _offset = fd->offset();
259   Klass* field_holder = fd->field_holder();
260   assert(field_holder != NULL, "null field_holder");
261   _holder = CURRENT_ENV->get_instance_klass(field_holder);


262 
263   // Check to see if the field is constant.
264   Klass* k = _holder->get_Klass();
265   bool is_stable_field = FoldStableValues && is_stable();
266   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
267     if (is_static()) {
268       // This field just may be constant.  The only case where it will
269       // not be constant is when the field is a *special* static & final field
270       // whose value may change.  The three examples are java.lang.System.in,
271       // java.lang.System.out, and java.lang.System.err.
272       assert(vmClasses::System_klass() != NULL, "Check once per vm");
273       if (k == vmClasses::System_klass()) {
274         // Check offsets for case 2: System.in, System.out, or System.err
275         if (_offset == java_lang_System::in_offset()  ||
276             _offset == java_lang_System::out_offset() ||
277             _offset == java_lang_System::err_offset()) {
278           _is_constant = false;
279           return;
280         }
281       }

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 // ------------------------------------------------------------------
366 // ciField::will_link
367 //
368 // Can a specific access to this field be made without causing
369 // link errors?
370 bool ciField::will_link(ciMethod* accessing_method,
371                         Bytecodes::Code bc) {
372   VM_ENTRY_MARK;
373   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
374          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
375          "unexpected bytecode");
376 
377   if (_offset == -1) {
378     // at creation we couldn't link to our holder so we need to
379     // maintain that stance, otherwise there's no safe way to use this
380     // ciField.
381     return false;
382   }
383 
384   // Check for static/nonstatic mismatch
385   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
386   if (is_static != this->is_static()) {
387     return false;
388   }
389 
390   // Get and put can have different accessibility rules
391   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
392   if (is_put) {
393     if (_known_to_link_with_put == accessing_method) {
394       return true;
395     }

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 != NULL)
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) :
 74   _is_flattened(false), _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 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);
 86   _name = ciEnv::current(THREAD)->get_symbol(name);
 87 
 88   int nt_index = cpool->name_and_type_ref_index_at(index);
 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 
111   // Get the field's declared holder.
112   //
113   // Note: we actually create a ciInstanceKlass for this klass,
114   // even though we may not need to.
115   int holder_index = cpool->klass_ref_index_at(index);
116   bool holder_is_accessible;
117 
118   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
119                                                                                 holder_is_accessible,
120                                                                                 klass);
121 
122   if (generic_declared_holder->is_array_klass()) {
123     // If the declared holder of the field is an array class, assume that
124     // the canonical holder of that field is java.lang.Object. Arrays
125     // do not have fields; java.lang.Object is the only supertype of an
126     // array type that can declare fields and is therefore the canonical
127     // holder of the array type.
128     //
129     // Furthermore, the compilers assume that java.lang.Object does not
130     // have any fields. Therefore, the field is not looked up. Instead,

202   _name = env->get_symbol(fd->name());
203   _signature = env->get_symbol(fd->signature());
204 
205   BasicType field_type = fd->field_type();
206 
207   // If the field is a pointer type, get the klass of the
208   // field.
209   if (is_reference_type(field_type)) {
210     _type = NULL;  // must call compute_type on first access
211   } else {
212     _type = ciType::make(field_type);
213   }
214 
215   initialize_from(fd);
216 
217   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
218   assert(is_shared() || ciObjectFactory::is_initialized(),
219          "bootstrap classes must not create & cache unshared fields");
220 }
221 
222 // Special copy constructor used to flatten inline type fields by
223 // copying the fields of the inline type to a new holder klass.
224 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
225   assert(field->holder()->is_inlinetype(), "should only be used for inline type field flattening");
226   // Set the is_final flag
227   jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
228   AccessFlags flags(field->flags().as_int() & final);
229   _flags = ciFlags(flags);
230   _holder = holder;
231   _offset = offset;
232   // Copy remaining fields
233   _name = field->_name;
234   _signature = field->_signature;
235   _type = field->_type;
236   // Trust final flattened fields
237   _is_constant = is_final;
238   _known_to_link_with_put = field->_known_to_link_with_put;
239   _known_to_link_with_get = field->_known_to_link_with_get;
240   _constant_value = field->_constant_value;
241   assert(!field->is_flattened(), "field must not be flattened");
242   _is_flattened = false;
243   _is_null_free = field->is_null_free();
244 }
245 
246 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
247   if (holder == NULL)
248     return false;
249   if (holder->name() == ciSymbols::java_lang_System())
250     // Never trust strangely unstable finals:  System.out, etc.
251     return false;
252   // Even if general trusting is disabled, trust system-built closures in these packages.
253   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
254       holder->is_in_package("jdk/internal/foreign") || holder->is_in_package("jdk/incubator/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());
288   _offset = fd->offset();
289   Klass* field_holder = fd->field_holder();
290   assert(field_holder != NULL, "null field_holder");
291   _holder = CURRENT_ENV->get_instance_klass(field_holder);
292   _is_flattened = fd->is_inlined();
293   _is_null_free = fd->signature()->is_Q_signature();
294 
295   // Check to see if the field is constant.
296   Klass* k = _holder->get_Klass();
297   bool is_stable_field = FoldStableValues && is_stable();
298   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
299     if (is_static()) {
300       // This field just may be constant.  The only case where it will
301       // not be constant is when the field is a *special* static & final field
302       // whose value may change.  The three examples are java.lang.System.in,
303       // java.lang.System.out, and java.lang.System.err.
304       assert(vmClasses::System_klass() != NULL, "Check once per vm");
305       if (k == vmClasses::System_klass()) {
306         // Check offsets for case 2: System.in, System.out, or System.err
307         if (_offset == java_lang_System::in_offset()  ||
308             _offset == java_lang_System::out_offset() ||
309             _offset == java_lang_System::err_offset()) {
310           _is_constant = false;
311           return;
312         }
313       }

386       // Currently there is no 'shared' query for array types.
387       type_is_also_shared = !ciObjectFactory::is_initialized();
388     }
389     if (!type_is_also_shared)
390       return type;              // Bummer.
391   }
392   _type = type;
393   return type;
394 }
395 
396 
397 // ------------------------------------------------------------------
398 // ciField::will_link
399 //
400 // Can a specific access to this field be made without causing
401 // link errors?
402 bool ciField::will_link(ciMethod* accessing_method,
403                         Bytecodes::Code bc) {
404   VM_ENTRY_MARK;
405   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
406          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield  ||
407          bc == Bytecodes::_withfield, "unexpected bytecode");
408 
409   if (_offset == -1) {
410     // at creation we couldn't link to our holder so we need to
411     // maintain that stance, otherwise there's no safe way to use this
412     // ciField.
413     return false;
414   }
415 
416   // Check for static/nonstatic mismatch
417   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
418   if (is_static != this->is_static()) {
419     return false;
420   }
421 
422   // Get and put can have different accessibility rules
423   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
424   if (is_put) {
425     if (_known_to_link_with_put == accessing_method) {
426       return true;
427     }

470 // ------------------------------------------------------------------
471 // ciField::print
472 void ciField::print() {
473   tty->print("<ciField name=");
474   _holder->print_name();
475   tty->print(".");
476   _name->print_symbol();
477   tty->print(" signature=");
478   _signature->print_symbol();
479   tty->print(" offset=%d type=", _offset);
480   if (_type != NULL)
481     _type->print_name();
482   else
483     tty->print("(reference)");
484   tty->print(" flags=%04x", flags().as_int());
485   tty->print(" is_constant=%s", bool_to_str(_is_constant));
486   if (_is_constant && is_static()) {
487     tty->print(" constant_value=");
488     _constant_value.print();
489   }
490   tty->print(" is_flattened=%s", bool_to_str(_is_flattened));
491   tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
492   tty->print(">");
493 }
494 
495 // ------------------------------------------------------------------
496 // ciField::print_name_on
497 //
498 // Print the name of this field
499 void ciField::print_name_on(outputStream* st) {
500   name()->print_symbol_on(st);
501 }
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