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 constan-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   ciInstanceKlass* declared_holder =
 110     ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
 111                                                holder_is_accessible,
 112                                                klass)->as_instance_klass();
 113 
 114   // The declared holder of this field may not have been loaded.
 115   // Bail out with partial field information.
 116   if (!holder_is_accessible) {
 117     // _type has already been set.
 118     // The default values for _flags and _constant_value will suffice.
 119     // We need values for _holder, _offset,  and _is_constant,
 120     _holder = declared_holder;
 121     _offset = -1;
 122     _is_constant = false;
 123     return;
 124   }
 125 
 126   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 127 
 128   // Perform the field lookup.
 129   fieldDescriptor field_desc;
 130   Klass* canonical_holder =
 131     loaded_decl_holder->find_field(name, signature, &field_desc);
 132   if (canonical_holder == NULL) {
 133     // Field lookup failed.  Will be detected by will_link.
 134     _holder = declared_holder;
 135     _offset = -1;
 136     _is_constant = false;
 137     return;
 138   }
 139 
 140   // Access check based on declared_holder. canonical_holder should not be used
 141   // to check access because it can erroneously succeed. If this check fails,
 142   // propagate the declared holder to will_link() which in turn will bail out
 143   // compilation for this field access.
 144   if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
 145     _holder = declared_holder;
 146     _offset = -1;
 147     _is_constant = false;
 148     return;
 149   }
 150 
 151   assert(canonical_holder == field_desc.field_holder(), "just checking");
 152   initialize_from(&field_desc);
 153 }
 154 
 155 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 156   ASSERT_IN_VM;
 157 
 158   // Get the field's name, signature, and type.
 159   ciEnv* env = CURRENT_ENV;
 160   _name = env->get_symbol(fd->name());
 161   _signature = env->get_symbol(fd->signature());
 162 
 163   BasicType field_type = fd->field_type();
 164 
 165   // If the field is a pointer type, get the klass of the
 166   // field.
 167   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 168     _type = NULL;  // must call compute_type on first access
 169   } else {
 170     _type = ciType::make(field_type);
 171   }
 172 
 173   initialize_from(fd);
 174 
 175   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 176   assert(is_shared() || ciObjectFactory::is_initialized(),
 177          "bootstrap classes must not create & cache unshared fields");
 178 }
 179 
 180 bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 181   if (holder == NULL)
 182     return false;
 183   if (holder->name() == ciSymbol::java_lang_System())
 184     // Never trust strangely unstable finals:  System.out, etc.
 185     return false;
 186   // Even if general trusting is disabled, trust system-built closures in these packages.
 187   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 188     return true;
 189   // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
 190   // so there is no hacking of finals going on with them.
 191   if (holder->is_anonymous())
 192     return true;
 193   // Trust the non-serializable classes in java/util/concurrent/atomic
 194   if (UseNewCode && holder->is_in_package("java/util/concurrent/atomic")) {
 195     return !holder->is_subtype_of(CURRENT_ENV->Serializable_klass());
 196   }
 197   return TrustFinalNonStaticFields;
 198 }
 199 
 200 void ciField::initialize_from(fieldDescriptor* fd) {
 201   // Get the flags, offset, and canonical holder of the field.
 202   _flags = ciFlags(fd->access_flags());
 203   _offset = fd->offset();
 204   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 205 
 206   // Check to see if the field is constant.
 207   bool is_final = this->is_final();
 208   bool is_stable = FoldStableValues && this->is_stable();
 209   if (_holder->is_initialized() && (is_final || is_stable)) {
 210     if (!this->is_static()) {
 211       // A field can be constant if it's a final static field or if
 212       // it's a final non-static field of a trusted class (classes in
 213       // java.lang.invoke and sun.invoke packages and subpackages).
 214       if (is_stable || trust_final_non_static_fields(_holder)) {
 215         _is_constant = true;
 216         return;
 217       }
 218       _is_constant = false;
 219       return;
 220     }
 221 
 222     // This field just may be constant.  The only case where it will
 223     // not be constant is when the field is a *special* static&final field
 224     // whose value may change.  The three examples are java.lang.System.in,
 225     // java.lang.System.out, and java.lang.System.err.
 226 
 227     KlassHandle k = _holder->get_Klass();
 228     assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
 229     if( k() == SystemDictionary::System_klass() ) {
 230       // Check offsets for case 2: System.in, System.out, or System.err
 231       if( _offset == java_lang_System::in_offset_in_bytes()  ||
 232           _offset == java_lang_System::out_offset_in_bytes() ||
 233           _offset == java_lang_System::err_offset_in_bytes() ) {
 234         _is_constant = false;
 235         return;
 236       }
 237     }
 238 
 239     Handle mirror = k->java_mirror();
 240 
 241     switch(type()->basic_type()) {
 242     case T_BYTE:
 243       _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
 244       break;
 245     case T_CHAR:
 246       _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
 247       break;
 248     case T_SHORT:
 249       _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
 250       break;
 251     case T_BOOLEAN:
 252       _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
 253       break;
 254     case T_INT:
 255       _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
 256       break;
 257     case T_FLOAT:
 258       _constant_value = ciConstant(mirror->float_field(_offset));
 259       break;
 260     case T_DOUBLE:
 261       _constant_value = ciConstant(mirror->double_field(_offset));
 262       break;
 263     case T_LONG:
 264       _constant_value = ciConstant(mirror->long_field(_offset));
 265       break;
 266     case T_OBJECT:
 267     case T_ARRAY:
 268       {
 269         oop o = mirror->obj_field(_offset);
 270 
 271         // A field will be "constant" if it is known always to be
 272         // a non-null reference to an instance of a particular class,
 273         // or to a particular array.  This can happen even if the instance
 274         // or array is not perm.  In such a case, an "unloaded" ciArray
 275         // or ciInstance is created.  The compiler may be able to use
 276         // information about the object's class (which is exact) or length.
 277 
 278         if (o == NULL) {
 279           _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
 280         } else {
 281           _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
 282           assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
 283         }
 284       }
 285     }
 286     if (is_stable && _constant_value.is_null_or_zero()) {
 287       // It is not a constant after all; treat it as uninitialized.
 288       _is_constant = false;
 289     } else {
 290       _is_constant = true;
 291     }
 292   } else {
 293     _is_constant = false;
 294   }
 295 }
 296 
 297 // ------------------------------------------------------------------
 298 // ciField::compute_type
 299 //
 300 // Lazily compute the type, if it is an instance klass.
 301 ciType* ciField::compute_type() {
 302   GUARDED_VM_ENTRY(return compute_type_impl();)
 303 }
 304 
 305 ciType* ciField::compute_type_impl() {
 306   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 307   if (!type->is_primitive_type() && is_shared()) {
 308     // We must not cache a pointer to an unshared type, in a shared field.
 309     bool type_is_also_shared = false;
 310     if (type->is_type_array_klass()) {
 311       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 312     } else if (type->is_instance_klass()) {
 313       type_is_also_shared = type->as_instance_klass()->is_shared();
 314     } else {
 315       // Currently there is no 'shared' query for array types.
 316       type_is_also_shared = !ciObjectFactory::is_initialized();
 317     }
 318     if (!type_is_also_shared)
 319       return type;              // Bummer.
 320   }
 321   _type = type;
 322   return type;
 323 }
 324 
 325 
 326 // ------------------------------------------------------------------
 327 // ciField::will_link
 328 //
 329 // Can a specific access to this field be made without causing
 330 // link errors?
 331 bool ciField::will_link(ciInstanceKlass* accessing_klass,
 332                         Bytecodes::Code bc) {
 333   VM_ENTRY_MARK;
 334   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 335          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 336          "unexpected bytecode");
 337 
 338   if (_offset == -1) {
 339     // at creation we couldn't link to our holder so we need to
 340     // maintain that stance, otherwise there's no safe way to use this
 341     // ciField.
 342     return false;
 343   }
 344 
 345   // Check for static/nonstatic mismatch
 346   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 347   if (is_static != this->is_static()) {
 348     return false;
 349   }
 350 
 351   // Get and put can have different accessibility rules
 352   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 353   if (is_put) {
 354     if (_known_to_link_with_put == accessing_klass) {
 355       return true;
 356     }
 357   } else {
 358     if (_known_to_link_with_get == accessing_klass) {
 359       return true;
 360     }
 361   }
 362 
 363   LinkInfo link_info(_holder->get_instanceKlass(),
 364                      _name->get_symbol(), _signature->get_symbol(),
 365                      accessing_klass->get_Klass());
 366   fieldDescriptor result;
 367   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 368 
 369   // update the hit-cache, unless there is a problem with memory scoping:
 370   if (accessing_klass->is_shared() || !is_shared()) {
 371     if (is_put) {
 372       _known_to_link_with_put = accessing_klass;
 373     } else {
 374       _known_to_link_with_get = accessing_klass;
 375     }
 376   }
 377 
 378   return true;
 379 }
 380 
 381 // ------------------------------------------------------------------
 382 // ciField::print
 383 void ciField::print() {
 384   tty->print("<ciField name=");
 385   _holder->print_name();
 386   tty->print(".");
 387   _name->print_symbol();
 388   tty->print(" signature=");
 389   _signature->print_symbol();
 390   tty->print(" offset=%d type=", _offset);
 391   if (_type != NULL)
 392     _type->print_name();
 393   else
 394     tty->print("(reference)");
 395   tty->print(" flags=%04x", flags().as_int());
 396   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 397   if (_is_constant && is_static()) {
 398     tty->print(" constant_value=");
 399     _constant_value.print();
 400   }
 401   tty->print(">");
 402 }
 403 
 404 // ------------------------------------------------------------------
 405 // ciField::print_name_on
 406 //
 407 // Print the name of this field
 408 void ciField::print_name_on(outputStream* st) {
 409   name()->print_symbol_on(st);
 410 }