51 // This allows non-static field lists to be cached on shared types.
52 // Because the _type field is lazily initialized, however, there is a
53 // special restriction that a shared field cannot cache an unshared type.
54 // This puts a small performance penalty on shared fields with unshared
55 // types, such as StackTraceElement[] Throwable.stackTrace.
56 // (Throwable is shared because ClassCastException is shared, but
57 // StackTraceElement is not presently shared.)
58
59 // It is not a vicious circularity for a ciField to recursively create
60 // the ciSymbols necessary to represent its name and signature.
61 // Therefore, these items are created eagerly, and the name and signature
62 // of a shared field are themselves shared symbols. This somewhat
63 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
64 // with all of the additional 43 being uninteresting shared ciSymbols.
65 // This adds at most one step to the binary search, an amount which
66 // decreases for complex compilation tasks.
67
68 // ------------------------------------------------------------------
69 // ciField::ciField
70 ciField::ciField(ciInstanceKlass* klass, int index) :
71 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
72 ASSERT_IN_VM;
73 CompilerThread *THREAD = CompilerThread::current();
74
75 assert(ciObjectFactory::is_initialized(), "not a shared field");
76
77 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
78
79 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
80
81 // Get the field's name, signature, and type.
82 Symbol* name = cpool->name_ref_at(index);
83 _name = ciEnv::current(THREAD)->get_symbol(name);
84
85 int nt_index = cpool->name_and_type_ref_index_at(index);
86 int sig_index = cpool->signature_ref_index_at(nt_index);
87 Symbol* signature = cpool->symbol_at(sig_index);
88 _signature = ciEnv::current(THREAD)->get_symbol(signature);
89
90 BasicType field_type = FieldType::basic_type(signature);
91
92 // If the field is a pointer type, get the klass of the
93 // field.
94 if (field_type == T_OBJECT || field_type == T_ARRAY) {
95 bool ignore;
96 // This is not really a class reference; the index always refers to the
97 // field's type signature, as a symbol. Linkage checks do not apply.
98 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
99 } else {
100 _type = ciType::make(field_type);
101 }
102
103 _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
104
105 // Get the field's declared holder.
106 //
107 // Note: we actually create a ciInstanceKlass for this klass,
108 // even though we may not need to.
109 int holder_index = cpool->klass_ref_index_at(index);
110 bool holder_is_accessible;
111
112 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
113 holder_is_accessible,
114 klass);
183 return;
184 }
185
186 assert(canonical_holder == field_desc.field_holder(), "just checking");
187 initialize_from(&field_desc);
188 }
189
190 ciField::ciField(fieldDescriptor *fd) :
191 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
192 ASSERT_IN_VM;
193
194 // Get the field's name, signature, and type.
195 ciEnv* env = CURRENT_ENV;
196 _name = env->get_symbol(fd->name());
197 _signature = env->get_symbol(fd->signature());
198
199 BasicType field_type = fd->field_type();
200
201 // If the field is a pointer type, get the klass of the
202 // field.
203 if (field_type == T_OBJECT || field_type == T_ARRAY) {
204 _type = NULL; // must call compute_type on first access
205 } else {
206 _type = ciType::make(field_type);
207 }
208
209 initialize_from(fd);
210
211 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
212 assert(is_shared() || ciObjectFactory::is_initialized(),
213 "bootstrap classes must not create & cache unshared fields");
214 }
215
216 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
217 if (holder == NULL)
218 return false;
219 if (holder->name() == ciSymbol::java_lang_System())
220 // Never trust strangely unstable finals: System.out, etc.
221 return false;
222 // Even if general trusting is disabled, trust system-built closures in these packages.
223 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
224 return true;
225 // Trust VM unsafe anonymous classes. They are private API (jdk.internal.misc.Unsafe)
226 // and can't be serialized, so there is no hacking of finals going on with them.
227 if (holder->is_unsafe_anonymous())
228 return true;
229 // Trust final fields in all boxed classes
230 if (holder->is_box_klass())
231 return true;
232 // Trust final fields in String
233 if (holder->name() == ciSymbol::java_lang_String())
234 return true;
235 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
236 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
237 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
238 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
239 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
240 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
241 return true;
242 }
243 return TrustFinalNonStaticFields;
244 }
245
246 void ciField::initialize_from(fieldDescriptor* fd) {
247 // Get the flags, offset, and canonical holder of the field.
248 _flags = ciFlags(fd->access_flags());
249 _offset = fd->offset();
250 Klass* field_holder = fd->field_holder();
251 assert(field_holder != NULL, "null field_holder");
252 _holder = CURRENT_ENV->get_instance_klass(field_holder);
253
254 // Check to see if the field is constant.
255 Klass* k = _holder->get_Klass();
256 bool is_stable_field = FoldStableValues && is_stable();
257 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
258 if (is_static()) {
259 // This field just may be constant. The only case where it will
260 // not be constant is when the field is a *special* static & final field
261 // whose value may change. The three examples are java.lang.System.in,
262 // java.lang.System.out, and java.lang.System.err.
263 assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
264 if (k == SystemDictionary::System_klass()) {
265 // Check offsets for case 2: System.in, System.out, or System.err
266 if( _offset == java_lang_System::in_offset_in_bytes() ||
267 _offset == java_lang_System::out_offset_in_bytes() ||
268 _offset == java_lang_System::err_offset_in_bytes() ) {
269 _is_constant = false;
270 return;
271 }
272 }
345 // Currently there is no 'shared' query for array types.
346 type_is_also_shared = !ciObjectFactory::is_initialized();
347 }
348 if (!type_is_also_shared)
349 return type; // Bummer.
350 }
351 _type = type;
352 return type;
353 }
354
355
356 // ------------------------------------------------------------------
357 // ciField::will_link
358 //
359 // Can a specific access to this field be made without causing
360 // link errors?
361 bool ciField::will_link(ciMethod* accessing_method,
362 Bytecodes::Code bc) {
363 VM_ENTRY_MARK;
364 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
365 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
366 "unexpected bytecode");
367
368 if (_offset == -1) {
369 // at creation we couldn't link to our holder so we need to
370 // maintain that stance, otherwise there's no safe way to use this
371 // ciField.
372 return false;
373 }
374
375 // Check for static/nonstatic mismatch
376 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
377 if (is_static != this->is_static()) {
378 return false;
379 }
380
381 // Get and put can have different accessibility rules
382 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
383 if (is_put) {
384 if (_known_to_link_with_put == accessing_method) {
385 return true;
386 }
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51 // This allows non-static field lists to be cached on shared types.
52 // Because the _type field is lazily initialized, however, there is a
53 // special restriction that a shared field cannot cache an unshared type.
54 // This puts a small performance penalty on shared fields with unshared
55 // types, such as StackTraceElement[] Throwable.stackTrace.
56 // (Throwable is shared because ClassCastException is shared, but
57 // StackTraceElement is not presently shared.)
58
59 // It is not a vicious circularity for a ciField to recursively create
60 // the ciSymbols necessary to represent its name and signature.
61 // Therefore, these items are created eagerly, and the name and signature
62 // of a shared field are themselves shared symbols. This somewhat
63 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
64 // with all of the additional 43 being uninteresting shared ciSymbols.
65 // This adds at most one step to the binary search, an amount which
66 // decreases for complex compilation tasks.
67
68 // ------------------------------------------------------------------
69 // ciField::ciField
70 ciField::ciField(ciInstanceKlass* klass, int index) :
71 _is_flattened(false), _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
72 ASSERT_IN_VM;
73 CompilerThread *THREAD = CompilerThread::current();
74
75 assert(ciObjectFactory::is_initialized(), "not a shared field");
76
77 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
78
79 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
80
81 // Get the field's name, signature, and type.
82 Symbol* name = cpool->name_ref_at(index);
83 _name = ciEnv::current(THREAD)->get_symbol(name);
84
85 int nt_index = cpool->name_and_type_ref_index_at(index);
86 int sig_index = cpool->signature_ref_index_at(nt_index);
87 Symbol* signature = cpool->symbol_at(sig_index);
88 _signature = ciEnv::current(THREAD)->get_symbol(signature);
89
90 BasicType field_type = FieldType::basic_type(signature);
91
92 // If the field is a pointer type, get the klass of the
93 // field.
94 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) {
95 bool ignore;
96 // This is not really a class reference; the index always refers to the
97 // field's type signature, as a symbol. Linkage checks do not apply.
98 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
99 } else {
100 _type = ciType::make(field_type);
101 }
102
103 _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
104
105 // Get the field's declared holder.
106 //
107 // Note: we actually create a ciInstanceKlass for this klass,
108 // even though we may not need to.
109 int holder_index = cpool->klass_ref_index_at(index);
110 bool holder_is_accessible;
111
112 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
113 holder_is_accessible,
114 klass);
183 return;
184 }
185
186 assert(canonical_holder == field_desc.field_holder(), "just checking");
187 initialize_from(&field_desc);
188 }
189
190 ciField::ciField(fieldDescriptor *fd) :
191 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
192 ASSERT_IN_VM;
193
194 // Get the field's name, signature, and type.
195 ciEnv* env = CURRENT_ENV;
196 _name = env->get_symbol(fd->name());
197 _signature = env->get_symbol(fd->signature());
198
199 BasicType field_type = fd->field_type();
200
201 // If the field is a pointer type, get the klass of the
202 // field.
203 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) {
204 _type = NULL; // must call compute_type on first access
205 } else {
206 _type = ciType::make(field_type);
207 }
208
209 initialize_from(fd);
210
211 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
212 assert(is_shared() || ciObjectFactory::is_initialized(),
213 "bootstrap classes must not create & cache unshared fields");
214 }
215
216 // Special copy constructor used to flatten value type fields by
217 // copying the fields of the value type to a new holder klass.
218 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
219 assert(field->holder()->is_valuetype(), "should only be used for value type field flattening");
220 // Set the is_final flag
221 jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
222 AccessFlags flags(field->flags().as_int() & final);
223 _flags = ciFlags(flags);
224 _holder = holder;
225 _offset = offset;
226 // Copy remaining fields
227 _name = field->_name;
228 _signature = field->_signature;
229 _type = field->_type;
230 _is_constant = field->_is_constant;
231 _known_to_link_with_put = field->_known_to_link_with_put;
232 _known_to_link_with_get = field->_known_to_link_with_get;
233 _constant_value = field->_constant_value;
234 assert(!field->is_flattened(), "field must not be flattened");
235 assert(!field->is_flattenable(), "field must not be flattenable");
236 _is_flattened = false;
237 _is_flattenable = false;
238 }
239
240 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
241 if (holder == NULL)
242 return false;
243 if (holder->name() == ciSymbol::java_lang_System())
244 // Never trust strangely unstable finals: System.out, etc.
245 return false;
246 // Even if general trusting is disabled, trust system-built closures in these packages.
247 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
248 return true;
249 // Trust VM unsafe anonymous classes. They are private API (jdk.internal.misc.Unsafe)
250 // and can't be serialized, so there is no hacking of finals going on with them.
251 if (holder->is_unsafe_anonymous())
252 return true;
253 // Trust final fields in all boxed classes
254 if (holder->is_box_klass())
255 return true;
256 // Trust final fields in String
257 if (holder->name() == ciSymbol::java_lang_String())
258 return true;
259 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
260 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
261 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
262 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
263 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
264 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
265 return true;
266 }
267 return TrustFinalNonStaticFields;
268 }
269
270 void ciField::initialize_from(fieldDescriptor* fd) {
271 // Get the flags, offset, and canonical holder of the field.
272 _flags = ciFlags(fd->access_flags());
273 _offset = fd->offset();
274 Klass* field_holder = fd->field_holder();
275 assert(field_holder != NULL, "null field_holder");
276 _holder = CURRENT_ENV->get_instance_klass(field_holder);
277 _is_flattened = fd->is_flattened();
278 _is_flattenable = fd->is_flattenable();
279
280 // Check to see if the field is constant.
281 Klass* k = _holder->get_Klass();
282 bool is_stable_field = FoldStableValues && is_stable();
283 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
284 if (is_static()) {
285 // This field just may be constant. The only case where it will
286 // not be constant is when the field is a *special* static & final field
287 // whose value may change. The three examples are java.lang.System.in,
288 // java.lang.System.out, and java.lang.System.err.
289 assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
290 if (k == SystemDictionary::System_klass()) {
291 // Check offsets for case 2: System.in, System.out, or System.err
292 if( _offset == java_lang_System::in_offset_in_bytes() ||
293 _offset == java_lang_System::out_offset_in_bytes() ||
294 _offset == java_lang_System::err_offset_in_bytes() ) {
295 _is_constant = false;
296 return;
297 }
298 }
371 // Currently there is no 'shared' query for array types.
372 type_is_also_shared = !ciObjectFactory::is_initialized();
373 }
374 if (!type_is_also_shared)
375 return type; // Bummer.
376 }
377 _type = type;
378 return type;
379 }
380
381
382 // ------------------------------------------------------------------
383 // ciField::will_link
384 //
385 // Can a specific access to this field be made without causing
386 // link errors?
387 bool ciField::will_link(ciMethod* accessing_method,
388 Bytecodes::Code bc) {
389 VM_ENTRY_MARK;
390 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
391 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield ||
392 bc == Bytecodes::_withfield, "unexpected bytecode");
393
394 if (_offset == -1) {
395 // at creation we couldn't link to our holder so we need to
396 // maintain that stance, otherwise there's no safe way to use this
397 // ciField.
398 return false;
399 }
400
401 // Check for static/nonstatic mismatch
402 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
403 if (is_static != this->is_static()) {
404 return false;
405 }
406
407 // Get and put can have different accessibility rules
408 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
409 if (is_put) {
410 if (_known_to_link_with_put == accessing_method) {
411 return true;
412 }
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