1 /*
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   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
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciField.hpp"
  27 #include "ci/ciInstanceKlass.hpp"
  28 #include "ci/ciUtilities.inline.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "interpreter/linkResolver.hpp"
  32 #include "oops/oop.inline.hpp"
  33 #include "runtime/fieldDescriptor.inline.hpp"
  34 #include "runtime/handles.inline.hpp"
  35 
  36 // ciField
  37 //
  38 // This class represents the result of a field lookup in the VM.
  39 // The lookup may not succeed, in which case the information in
  40 // the ciField will be incomplete.
  41 
  42 // The ciObjectFactory cannot create circular data structures in one query.
  43 // To avoid vicious circularities, we initialize ciField::_type to NULL
  44 // for reference types and derive it lazily from the ciField::_signature.
  45 // Primitive types are eagerly initialized, and basic layout queries
  46 // can succeed without initialization, using only the BasicType of the field.
  47 
  48 // Notes on bootstrapping and shared CI objects:  A field is shared if and
  49 // only if it is (a) non-static and (b) declared by a shared instance klass.
  50 // This allows non-static field lists to be cached on shared types.
  51 // Because the _type field is lazily initialized, however, there is a
  52 // special restriction that a shared field cannot cache an unshared type.
  53 // This puts a small performance penalty on shared fields with unshared
  54 // types, such as StackTraceElement[] Throwable.stackTrace.
  55 // (Throwable is shared because ClassCastException is shared, but
  56 // StackTraceElement is not presently shared.)
  57 
  58 // It is not a vicious circularity for a ciField to recursively create
  59 // the ciSymbols necessary to represent its name and signature.
  60 // Therefore, these items are created eagerly, and the name and signature
  61 // of a shared field are themselves shared symbols.  This somewhat
  62 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,
  63 // with all of the additional 43 being uninteresting shared ciSymbols.
  64 // This adds at most one step to the binary search, an amount which
  65 // decreases for complex compilation tasks.
  66 
  67 // ------------------------------------------------------------------
  68 // ciField::ciField
  69 ciField::ciField(ciInstanceKlass* klass, int index) :
  70     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
  71   ASSERT_IN_VM;
  72   CompilerThread *THREAD = CompilerThread::current();
  73 
  74   assert(ciObjectFactory::is_initialized(), "not a shared field");
  75 
  76   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
  77 
  78   constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
  79 
  80   // Get the field's name, signature, and type.
  81   Symbol* name  = cpool->name_ref_at(index);
  82   _name = ciEnv::current(THREAD)->get_symbol(name);
  83 
  84   int nt_index = cpool->name_and_type_ref_index_at(index);
  85   int sig_index = cpool->signature_ref_index_at(nt_index);
  86   Symbol* signature = cpool->symbol_at(sig_index);
  87   _signature = ciEnv::current(THREAD)->get_symbol(signature);
  88 
  89   BasicType field_type = FieldType::basic_type(signature);
  90 
  91   // If the field is a pointer type, get the klass of the
  92   // field.
  93   if (is_reference_type(field_type)) {
  94     bool ignore;
  95     // This is not really a class reference; the index always refers to the
  96     // field's type signature, as a symbol.  Linkage checks do not apply.
  97     _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
  98   } else {
  99     _type = ciType::make(field_type);
 100   }
 101 
 102   _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
 103 
 104   // Get the field's declared holder.
 105   //
 106   // Note: we actually create a ciInstanceKlass for this klass,
 107   // even though we may not need to.
 108   int holder_index = cpool->klass_ref_index_at(index);
 109   bool holder_is_accessible;
 110 
 111   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
 112                                                                                 holder_is_accessible,
 113                                                                                 klass);
 114 
 115   if (generic_declared_holder->is_array_klass()) {
 116     // If the declared holder of the field is an array class, assume that
 117     // the canonical holder of that field is java.lang.Object. Arrays
 118     // do not have fields; java.lang.Object is the only supertype of an
 119     // array type that can declare fields and is therefore the canonical
 120     // holder of the array type.
 121     //
 122     // Furthermore, the compilers assume that java.lang.Object does not
 123     // have any fields. Therefore, the field is not looked up. Instead,
 124     // the method returns partial information that will trigger special
 125     // handling in ciField::will_link and will result in a
 126     // java.lang.NoSuchFieldError exception being thrown by the compiled
 127     // code (the expected behavior in this case).
 128     _holder = ciEnv::current(THREAD)->Object_klass();
 129     _offset = -1;
 130     _is_constant = false;
 131     return;
 132   }
 133 
 134   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
 135 
 136   // The declared holder of this field may not have been loaded.
 137   // Bail out with partial field information.
 138   if (!holder_is_accessible) {
 139     // _type has already been set.
 140     // The default values for _flags and _constant_value will suffice.
 141     // We need values for _holder, _offset,  and _is_constant,
 142     _holder = declared_holder;
 143     _offset = -1;
 144     _is_constant = false;
 145     return;
 146   }
 147 
 148   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 149 
 150   // Perform the field lookup.
 151   fieldDescriptor field_desc;
 152   Klass* canonical_holder =
 153     loaded_decl_holder->find_field(name, signature, &field_desc);
 154   if (canonical_holder == NULL) {
 155     // Field lookup failed.  Will be detected by will_link.
 156     _holder = declared_holder;
 157     _offset = -1;
 158     _is_constant = false;
 159     return;
 160   }
 161 
 162   // Access check based on declared_holder. canonical_holder should not be used
 163   // to check access because it can erroneously succeed. If this check fails,
 164   // propagate the declared holder to will_link() which in turn will bail out
 165   // compilation for this field access.
 166   bool can_access = Reflection::verify_member_access(klass->get_Klass(),
 167                                                      declared_holder->get_Klass(),
 168                                                      canonical_holder,
 169                                                      field_desc.access_flags(),
 170                                                      true, false, THREAD);
 171   if (!can_access) {
 172     _holder = declared_holder;
 173     _offset = -1;
 174     _is_constant = false;
 175     // It's possible the access check failed due to a nestmate access check
 176     // encountering an exception. We can't propagate the exception from here
 177     // so we have to clear it. If the access check happens again in a different
 178     // context then the exception will be thrown there.
 179     if (HAS_PENDING_EXCEPTION) {
 180       CLEAR_PENDING_EXCEPTION;
 181     }
 182     return;
 183   }
 184 
 185   assert(canonical_holder == field_desc.field_holder(), "just checking");
 186   initialize_from(&field_desc);
 187 }
 188 
 189 ciField::ciField(fieldDescriptor *fd) :
 190     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 191   ASSERT_IN_VM;
 192 
 193   // Get the field's name, signature, and type.
 194   ciEnv* env = CURRENT_ENV;
 195   _name = env->get_symbol(fd->name());
 196   _signature = env->get_symbol(fd->signature());
 197 
 198   BasicType field_type = fd->field_type();
 199 
 200   // If the field is a pointer type, get the klass of the
 201   // field.
 202   if (is_reference_type(field_type)) {
 203     _type = NULL;  // must call compute_type on first access
 204   } else {
 205     _type = ciType::make(field_type);
 206   }
 207 
 208   initialize_from(fd);
 209 
 210   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 211   assert(is_shared() || ciObjectFactory::is_initialized(),
 212          "bootstrap classes must not create & cache unshared fields");
 213 }
 214 
 215 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 216   if (holder == NULL)
 217     return false;
 218   if (holder->name() == ciSymbol::java_lang_System())
 219     // Never trust strangely unstable finals:  System.out, etc.
 220     return false;
 221   // Even if general trusting is disabled, trust system-built closures in these packages.
 222   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 223     return true;
 224   // Trust VM unsafe anonymous classes. They are private API (jdk.internal.misc.Unsafe)
 225   // and can't be serialized, so there is no hacking of finals going on with them.
 226   if (holder->is_unsafe_anonymous())
 227     return true;
 228   // Trust final fields in all boxed classes
 229   if (holder->is_box_klass())
 230     return true;
 231   // Trust final fields in String
 232   if (holder->name() == ciSymbol::java_lang_String())
 233     return true;
 234   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
 235   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
 236   if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
 237       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
 238       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
 239       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
 240     return true;
 241   }
 242   return TrustFinalNonStaticFields;
 243 }
 244 
 245 void ciField::initialize_from(fieldDescriptor* fd) {
 246   // Get the flags, offset, and canonical holder of the field.
 247   _flags = ciFlags(fd->access_flags());
 248   _offset = fd->offset();
 249   Klass* field_holder = fd->field_holder();
 250   assert(field_holder != NULL, "null field_holder");
 251   _holder = CURRENT_ENV->get_instance_klass(field_holder);
 252 
 253   // Check to see if the field is constant.
 254   Klass* k = _holder->get_Klass();
 255   bool is_stable_field = FoldStableValues && is_stable();
 256   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
 257     if (is_static()) {
 258       // This field just may be constant.  The only case where it will
 259       // not be constant is when the field is a *special* static & final field
 260       // whose value may change.  The three examples are java.lang.System.in,
 261       // java.lang.System.out, and java.lang.System.err.
 262       assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
 263       if (k == SystemDictionary::System_klass()) {
 264         // Check offsets for case 2: System.in, System.out, or System.err
 265         if( _offset == java_lang_System::in_offset_in_bytes()  ||
 266             _offset == java_lang_System::out_offset_in_bytes() ||
 267             _offset == java_lang_System::err_offset_in_bytes() ) {
 268           _is_constant = false;
 269           return;
 270         }
 271       }
 272       _is_constant = true;
 273     } else {
 274       // An instance field can be constant if it's a final static field or if
 275       // it's a final non-static field of a trusted class (classes in
 276       // java.lang.invoke and sun.invoke packages and subpackages).
 277       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
 278     }
 279   } else {
 280     // For CallSite objects treat the target field as a compile time constant.
 281     assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
 282     if (k == SystemDictionary::CallSite_klass() &&
 283         _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
 284       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
 285       _is_constant = true;
 286     } else {
 287       // Non-final & non-stable fields are not constants.
 288       _is_constant = false;
 289     }
 290   }
 291 }
 292 
 293 // ------------------------------------------------------------------
 294 // ciField::constant_value
 295 // Get the constant value of a this static field.
 296 ciConstant ciField::constant_value() {
 297   assert(is_static() && is_constant(), "illegal call to constant_value()");
 298   if (!_holder->is_initialized()) {
 299     return ciConstant(); // Not initialized yet
 300   }
 301   if (_constant_value.basic_type() == T_ILLEGAL) {
 302     // Static fields are placed in mirror objects.
 303     VM_ENTRY_MARK;
 304     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
 305     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
 306   }
 307   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
 308     return ciConstant();
 309   }
 310   return _constant_value;
 311 }
 312 
 313 // ------------------------------------------------------------------
 314 // ciField::constant_value_of
 315 // Get the constant value of non-static final field in the given object.
 316 ciConstant ciField::constant_value_of(ciObject* object) {
 317   assert(!is_static() && is_constant(), "only if field is non-static constant");
 318   assert(object->is_instance(), "must be instance");
 319   ciConstant field_value = object->as_instance()->field_value(this);
 320   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
 321     return ciConstant();
 322   }
 323   return field_value;
 324 }
 325 
 326 // ------------------------------------------------------------------
 327 // ciField::compute_type
 328 //
 329 // Lazily compute the type, if it is an instance klass.
 330 ciType* ciField::compute_type() {
 331   GUARDED_VM_ENTRY(return compute_type_impl();)
 332 }
 333 
 334 ciType* ciField::compute_type_impl() {
 335   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 336   if (!type->is_primitive_type() && is_shared()) {
 337     // We must not cache a pointer to an unshared type, in a shared field.
 338     bool type_is_also_shared = false;
 339     if (type->is_type_array_klass()) {
 340       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 341     } else if (type->is_instance_klass()) {
 342       type_is_also_shared = type->as_instance_klass()->is_shared();
 343     } else {
 344       // Currently there is no 'shared' query for array types.
 345       type_is_also_shared = !ciObjectFactory::is_initialized();
 346     }
 347     if (!type_is_also_shared)
 348       return type;              // Bummer.
 349   }
 350   _type = type;
 351   return type;
 352 }
 353 
 354 
 355 // ------------------------------------------------------------------
 356 // ciField::will_link
 357 //
 358 // Can a specific access to this field be made without causing
 359 // link errors?
 360 bool ciField::will_link(ciMethod* accessing_method,
 361                         Bytecodes::Code bc) {
 362   VM_ENTRY_MARK;
 363   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 364          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 365          "unexpected bytecode");
 366 
 367   if (_offset == -1) {
 368     // at creation we couldn't link to our holder so we need to
 369     // maintain that stance, otherwise there's no safe way to use this
 370     // ciField.
 371     return false;
 372   }
 373 
 374   // Check for static/nonstatic mismatch
 375   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 376   if (is_static != this->is_static()) {
 377     return false;
 378   }
 379 
 380   // Get and put can have different accessibility rules
 381   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 382   if (is_put) {
 383     if (_known_to_link_with_put == accessing_method) {
 384       return true;
 385     }
 386   } else {
 387     if (_known_to_link_with_get == accessing_method->holder()) {
 388       return true;
 389     }
 390   }
 391 
 392   LinkInfo link_info(_holder->get_instanceKlass(),
 393                      _name->get_symbol(), _signature->get_symbol(),
 394                      methodHandle(THREAD, accessing_method->get_Method()));
 395   fieldDescriptor result;
 396   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 397 
 398   // update the hit-cache, unless there is a problem with memory scoping:
 399   if (accessing_method->holder()->is_shared() || !is_shared()) {
 400     if (is_put) {
 401       _known_to_link_with_put = accessing_method;
 402     } else {
 403       _known_to_link_with_get = accessing_method->holder();
 404     }
 405   }
 406 
 407   return true;
 408 }
 409 
 410 // ------------------------------------------------------------------
 411 // ciField::print
 412 void ciField::print() {
 413   tty->print("<ciField name=");
 414   _holder->print_name();
 415   tty->print(".");
 416   _name->print_symbol();
 417   tty->print(" signature=");
 418   _signature->print_symbol();
 419   tty->print(" offset=%d type=", _offset);
 420   if (_type != NULL)
 421     _type->print_name();
 422   else
 423     tty->print("(reference)");
 424   tty->print(" flags=%04x", flags().as_int());
 425   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 426   if (_is_constant && is_static()) {
 427     tty->print(" constant_value=");
 428     _constant_value.print();
 429   }
 430   tty->print(">");
 431 }
 432 
 433 // ------------------------------------------------------------------
 434 // ciField::print_name_on
 435 //
 436 // Print the name of this field
 437 void ciField::print_name_on(outputStream* st) {
 438   name()->print_symbol_on(st);
 439 }