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.
   8  *
   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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
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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
  21  * questions.
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  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciField.hpp"
  27 #include "ci/ciInstanceKlass.hpp"
  28 #include "ci/ciUtilities.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "interpreter/linkResolver.hpp"
  32 #include "memory/universe.inline.hpp"
  33 #include "oops/oop.inline.hpp"
  34 #include "runtime/fieldDescriptor.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): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
  70   ASSERT_IN_VM;
  71   CompilerThread *thread = CompilerThread::current();
  72 
  73   assert(ciObjectFactory::is_initialized(), "not a shared field");
  74 
  75   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
  76 
  77   constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
  78 
  79   // Get the field's name, signature, and type.
  80   Symbol* name  = cpool->name_ref_at(index);
  81   _name = ciEnv::current(thread)->get_symbol(name);
  82 
  83   int nt_index = cpool->name_and_type_ref_index_at(index);
  84   int sig_index = cpool->signature_ref_index_at(nt_index);
  85   Symbol* signature = cpool->symbol_at(sig_index);
  86   _signature = ciEnv::current(thread)->get_symbol(signature);
  87 
  88   BasicType field_type = FieldType::basic_type(signature);
  89 
  90   // If the field is a pointer type, get the klass of the
  91   // field.
  92   if (field_type == T_OBJECT || field_type == T_ARRAY) {
  93     bool ignore;
  94     // This is not really a class reference; the index always refers to the
  95     // field's type signature, as a symbol.  Linkage checks do not apply.
  96     _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
  97   } else {
  98     _type = ciType::make(field_type);
  99   }
 100 
 101   _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
 102 
 103   // Get the field's declared holder.
 104   //
 105   // Note: we actually create a ciInstanceKlass for this klass,
 106   // even though we may not need to.
 107   int holder_index = cpool->klass_ref_index_at(index);
 108   bool holder_is_accessible;
 109 
 110   ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
 111                                                                                 holder_is_accessible,
 112                                                                                 klass);
 113 
 114   if (generic_declared_holder->is_array_klass()) {
 115     // If the declared holder of the field is an array class, assume that
 116     // the canonical holder of that field is java.lang.Object. Arrays
 117     // do not have fields; java.lang.Object is the only supertype of an
 118     // array type that can declare fields and is therefore the canonical
 119     // holder of the array type.
 120     //
 121     // Furthermore, the compilers assume that java.lang.Object does not
 122     // have any fields. Therefore, the field is not looked up. Instead,
 123     // the method returns partial information that will trigger special
 124     // handling in ciField::will_link and will result in a
 125     // java.lang.NoSuchFieldError exception being thrown by the compiled
 126     // code (the expected behavior in this case).
 127     _holder = ciEnv::current(thread)->Object_klass();
 128     _offset = -1;
 129     _is_constant = false;
 130     return;
 131   }
 132 
 133   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
 134 
 135   // The declared holder of this field may not have been loaded.
 136   // Bail out with partial field information.
 137   if (!holder_is_accessible) {
 138     // _type has already been set.
 139     // The default values for _flags and _constant_value will suffice.
 140     // We need values for _holder, _offset,  and _is_constant,
 141     _holder = declared_holder;
 142     _offset = -1;
 143     _is_constant = false;
 144     return;
 145   }
 146 
 147   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 148 
 149   // Perform the field lookup.
 150   fieldDescriptor field_desc;
 151   Klass* canonical_holder =
 152     loaded_decl_holder->find_field(name, signature, &field_desc);
 153   if (canonical_holder == NULL) {
 154     // Field lookup failed.  Will be detected by will_link.
 155     _holder = declared_holder;
 156     _offset = -1;
 157     _is_constant = false;
 158     return;
 159   }
 160 
 161   // Access check based on declared_holder. canonical_holder should not be used
 162   // to check access because it can erroneously succeed. If this check fails,
 163   // propagate the declared holder to will_link() which in turn will bail out
 164   // compilation for this field access.
 165   if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
 166     _holder = declared_holder;
 167     _offset = -1;
 168     _is_constant = false;
 169     return;
 170   }
 171 
 172   assert(canonical_holder == field_desc.field_holder(), "just checking");
 173   initialize_from(&field_desc);
 174 }
 175 
 176 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 177   ASSERT_IN_VM;
 178 
 179   // Get the field's name, signature, and type.
 180   ciEnv* env = CURRENT_ENV;
 181   _name = env->get_symbol(fd->name());
 182   _signature = env->get_symbol(fd->signature());
 183 
 184   BasicType field_type = fd->field_type();
 185 
 186   // If the field is a pointer type, get the klass of the
 187   // field.
 188   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 189     _type = NULL;  // must call compute_type on first access
 190   } else {
 191     _type = ciType::make(field_type);
 192   }
 193 
 194   initialize_from(fd);
 195 
 196   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 197   assert(is_shared() || ciObjectFactory::is_initialized(),
 198          "bootstrap classes must not create & cache unshared fields");
 199 }
 200 
 201 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 202   if (holder == NULL)
 203     return false;
 204   if (holder->name() == ciSymbol::java_lang_System())
 205     // Never trust strangely unstable finals:  System.out, etc.
 206     return false;
 207   // Even if general trusting is disabled, trust system-built closures in these packages.
 208   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 209     return true;
 210   // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
 211   // so there is no hacking of finals going on with them.
 212   if (holder->is_anonymous())
 213     return true;
 214   // Trust final fields in all boxed classes
 215   if (holder->is_box_klass())
 216     return true;
 217   // Trust final fields in String
 218   if (holder->name() == ciSymbol::java_lang_String())
 219     return true;
 220   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
 221   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
 222   if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
 223       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
 224       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
 225       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
 226     return true;
 227   }
 228   return TrustFinalNonStaticFields;
 229 }
 230 
 231 void ciField::initialize_from(fieldDescriptor* fd) {
 232   // Get the flags, offset, and canonical holder of the field.
 233   _flags = ciFlags(fd->access_flags());
 234   _offset = fd->offset();
 235   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 236 
 237   // Check to see if the field is constant.
 238   Klass* k = _holder->get_Klass();
 239   bool is_stable_field = FoldStableValues && is_stable();
 240   if (is_final() || is_stable_field) {
 241     if (is_static()) {
 242       // This field just may be constant.  The only case where it will
 243       // not be constant is when the field is a *special* static & final field
 244       // whose value may change.  The three examples are java.lang.System.in,
 245       // java.lang.System.out, and java.lang.System.err.
 246       assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
 247       if (k == SystemDictionary::System_klass()) {
 248         // Check offsets for case 2: System.in, System.out, or System.err
 249         if( _offset == java_lang_System::in_offset_in_bytes()  ||
 250             _offset == java_lang_System::out_offset_in_bytes() ||
 251             _offset == java_lang_System::err_offset_in_bytes() ) {
 252           _is_constant = false;
 253           return;
 254         }
 255       }
 256       _is_constant = true;
 257     } else {
 258       // An instance field can be constant if it's a final static field or if
 259       // it's a final non-static field of a trusted class (classes in
 260       // java.lang.invoke and sun.invoke packages and subpackages).
 261       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
 262     }
 263   } else {
 264     // For CallSite objects treat the target field as a compile time constant.
 265     assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
 266     if (k == SystemDictionary::CallSite_klass() &&
 267         _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {

 268       _is_constant = true;
 269     } else {
 270       // Non-final & non-stable fields are not constants.
 271       _is_constant = false;
 272     }
 273   }
 274 }
 275 
 276 // ------------------------------------------------------------------
 277 // ciField::constant_value
 278 // Get the constant value of a this static field.
 279 ciConstant ciField::constant_value() {
 280   assert(is_static() && is_constant(), "illegal call to constant_value()");
 281   if (!_holder->is_initialized()) {
 282     return ciConstant(); // Not initialized yet
 283   }
 284   if (_constant_value.basic_type() == T_ILLEGAL) {
 285     // Static fields are placed in mirror objects.
 286     VM_ENTRY_MARK;
 287     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
 288     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
 289   }
 290   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
 291     return ciConstant();
 292   }
 293   return _constant_value;
 294 }
 295 
 296 // ------------------------------------------------------------------
 297 // ciField::constant_value_of
 298 // Get the constant value of non-static final field in the given object.
 299 ciConstant ciField::constant_value_of(ciObject* object) {
 300   assert(!is_static() && is_constant(), "only if field is non-static constant");
 301   assert(object->is_instance(), "must be instance");
 302   ciConstant field_value = object->as_instance()->field_value(this);
 303   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
 304     return ciConstant();
 305   }
 306   return field_value;
 307 }
 308 
 309 // ------------------------------------------------------------------
 310 // ciField::compute_type
 311 //
 312 // Lazily compute the type, if it is an instance klass.
 313 ciType* ciField::compute_type() {
 314   GUARDED_VM_ENTRY(return compute_type_impl();)
 315 }
 316 
 317 ciType* ciField::compute_type_impl() {
 318   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 319   if (!type->is_primitive_type() && is_shared()) {
 320     // We must not cache a pointer to an unshared type, in a shared field.
 321     bool type_is_also_shared = false;
 322     if (type->is_type_array_klass()) {
 323       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 324     } else if (type->is_instance_klass()) {
 325       type_is_also_shared = type->as_instance_klass()->is_shared();
 326     } else {
 327       // Currently there is no 'shared' query for array types.
 328       type_is_also_shared = !ciObjectFactory::is_initialized();
 329     }
 330     if (!type_is_also_shared)
 331       return type;              // Bummer.
 332   }
 333   _type = type;
 334   return type;
 335 }
 336 
 337 
 338 // ------------------------------------------------------------------
 339 // ciField::will_link
 340 //
 341 // Can a specific access to this field be made without causing
 342 // link errors?
 343 bool ciField::will_link(ciInstanceKlass* accessing_klass,

 344                         Bytecodes::Code bc) {
 345   VM_ENTRY_MARK;
 346   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 347          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 348          "unexpected bytecode");
 349 
 350   if (_offset == -1) {
 351     // at creation we couldn't link to our holder so we need to
 352     // maintain that stance, otherwise there's no safe way to use this
 353     // ciField.
 354     return false;
 355   }
 356 
 357   // Check for static/nonstatic mismatch
 358   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 359   if (is_static != this->is_static()) {
 360     return false;
 361   }
 362 
 363   // Get and put can have different accessibility rules
 364   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 365   if (is_put) {
 366     if (_known_to_link_with_put == accessing_klass) {
 367       return true;
 368     }
 369   } else {
 370     if (_known_to_link_with_get == accessing_klass) {
 371       return true;
 372     }
 373   }
 374 
 375   LinkInfo link_info(_holder->get_instanceKlass(),
 376                      _name->get_symbol(), _signature->get_symbol(),
 377                      accessing_klass->get_Klass());
 378   fieldDescriptor result;
 379   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 380 
 381   // update the hit-cache, unless there is a problem with memory scoping:
 382   if (accessing_klass->is_shared() || !is_shared()) {
 383     if (is_put) {
 384       _known_to_link_with_put = accessing_klass;
 385     } else {
 386       _known_to_link_with_get = accessing_klass;
 387     }
 388   }
 389 
 390   return true;
 391 }
 392 
 393 // ------------------------------------------------------------------
 394 // ciField::print
 395 void ciField::print() {
 396   tty->print("<ciField name=");
 397   _holder->print_name();
 398   tty->print(".");
 399   _name->print_symbol();
 400   tty->print(" signature=");
 401   _signature->print_symbol();
 402   tty->print(" offset=%d type=", _offset);
 403   if (_type != NULL)
 404     _type->print_name();
 405   else
 406     tty->print("(reference)");
 407   tty->print(" flags=%04x", flags().as_int());
 408   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 409   if (_is_constant && is_static()) {
 410     tty->print(" constant_value=");
 411     _constant_value.print();
 412   }
 413   tty->print(">");
 414 }
 415 
 416 // ------------------------------------------------------------------
 417 // ciField::print_name_on
 418 //
 419 // Print the name of this field
 420 void ciField::print_name_on(outputStream* st) {
 421   name()->print_symbol_on(st);
 422 }
--- EOF ---