Frames src/hotspot/share/ci/ciField.cpp

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