1 /*
   2  * Copyright (c) 1999, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   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
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  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.
  22  *
  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 static 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   return TrustFinalNonStaticFields;
 190 }
 191 
 192 void ciField::initialize_from(fieldDescriptor* fd) {
 193   // Get the flags, offset, and canonical holder of the field.
 194   _flags = ciFlags(fd->access_flags());
 195   _offset = fd->offset();
 196   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 197 
 198   // Check to see if the field is constant.
 199   bool is_final = this->is_final();
 200   bool is_stable = FoldStableValues && this->is_stable();
 201   if (_holder->is_initialized() && (is_final || is_stable)) {
 202     if (!this->is_static()) {
 203       // A field can be constant if it's a final static field or if
 204       // it's a final non-static field of a trusted class (classes in
 205       // java.lang.invoke and sun.invoke packages and subpackages).
 206       if (is_stable || trust_final_non_static_fields(_holder)) {
 207         _is_constant = true;
 208         return;
 209       }
 210       _is_constant = false;
 211       return;
 212     }
 213 
 214     // This field just may be constant.  The only case where it will
 215     // not be constant is when the field is a *special* static&final field
 216     // whose value may change.  The three examples are java.lang.System.in,
 217     // java.lang.System.out, and java.lang.System.err.
 218 
 219     KlassHandle k = _holder->get_Klass();
 220     assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
 221     if( k() == SystemDictionary::System_klass() ) {
 222       // Check offsets for case 2: System.in, System.out, or System.err
 223       if( _offset == java_lang_System::in_offset_in_bytes()  ||
 224           _offset == java_lang_System::out_offset_in_bytes() ||
 225           _offset == java_lang_System::err_offset_in_bytes() ) {
 226         _is_constant = false;
 227         return;
 228       }
 229     }
 230 
 231     Handle mirror = k->java_mirror();
 232 
 233     switch(type()->basic_type()) {
 234     case T_BYTE:
 235       _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
 236       break;
 237     case T_CHAR:
 238       _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
 239       break;
 240     case T_SHORT:
 241       _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
 242       break;
 243     case T_BOOLEAN:
 244       _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
 245       break;
 246     case T_INT:
 247       _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
 248       break;
 249     case T_FLOAT:
 250       _constant_value = ciConstant(mirror->float_field(_offset));
 251       break;
 252     case T_DOUBLE:
 253       _constant_value = ciConstant(mirror->double_field(_offset));
 254       break;
 255     case T_LONG:
 256       _constant_value = ciConstant(mirror->long_field(_offset));
 257       break;
 258     case T_OBJECT:
 259     case T_ARRAY:
 260       {
 261         oop o = mirror->obj_field(_offset);
 262 
 263         // A field will be "constant" if it is known always to be
 264         // a non-null reference to an instance of a particular class,
 265         // or to a particular array.  This can happen even if the instance
 266         // or array is not perm.  In such a case, an "unloaded" ciArray
 267         // or ciInstance is created.  The compiler may be able to use
 268         // information about the object's class (which is exact) or length.
 269 
 270         if (o == NULL) {
 271           _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
 272         } else {
 273           _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
 274           assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
 275         }
 276       }
 277     }
 278     if (is_stable && _constant_value.is_null_or_zero()) {
 279       // It is not a constant after all; treat it as uninitialized.
 280       _is_constant = false;
 281     } else {
 282       _is_constant = true;
 283     }
 284   } else {
 285     _is_constant = false;
 286   }
 287 }
 288 
 289 // ------------------------------------------------------------------
 290 // ciField::compute_type
 291 //
 292 // Lazily compute the type, if it is an instance klass.
 293 ciType* ciField::compute_type() {
 294   GUARDED_VM_ENTRY(return compute_type_impl();)
 295 }
 296 
 297 ciType* ciField::compute_type_impl() {
 298   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 299   if (!type->is_primitive_type() && is_shared()) {
 300     // We must not cache a pointer to an unshared type, in a shared field.
 301     bool type_is_also_shared = false;
 302     if (type->is_type_array_klass()) {
 303       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 304     } else if (type->is_instance_klass()) {
 305       type_is_also_shared = type->as_instance_klass()->is_shared();
 306     } else {
 307       // Currently there is no 'shared' query for array types.
 308       type_is_also_shared = !ciObjectFactory::is_initialized();
 309     }
 310     if (!type_is_also_shared)
 311       return type;              // Bummer.
 312   }
 313   _type = type;
 314   return type;
 315 }
 316 
 317 
 318 // ------------------------------------------------------------------
 319 // ciField::will_link
 320 //
 321 // Can a specific access to this field be made without causing
 322 // link errors?
 323 bool ciField::will_link(ciInstanceKlass* accessing_klass,
 324                         Bytecodes::Code bc) {
 325   VM_ENTRY_MARK;
 326   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 327          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 328          "unexpected bytecode");
 329 
 330   if (_offset == -1) {
 331     // at creation we couldn't link to our holder so we need to
 332     // maintain that stance, otherwise there's no safe way to use this
 333     // ciField.
 334     return false;
 335   }
 336 
 337   // Check for static/nonstatic mismatch
 338   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 339   if (is_static != this->is_static()) {
 340     return false;
 341   }
 342 
 343   // Get and put can have different accessibility rules
 344   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 345   if (is_put) {
 346     if (_known_to_link_with_put == accessing_klass) {
 347       return true;
 348     }
 349   } else {
 350     if (_known_to_link_with_get == accessing_klass) {
 351       return true;
 352     }
 353   }
 354 
 355   LinkInfo link_info(_holder->get_instanceKlass(),
 356                      _name->get_symbol(), _signature->get_symbol(),
 357                      accessing_klass->get_Klass());
 358   fieldDescriptor result;
 359   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 360 
 361   // update the hit-cache, unless there is a problem with memory scoping:
 362   if (accessing_klass->is_shared() || !is_shared()) {
 363     if (is_put) {
 364       _known_to_link_with_put = accessing_klass;
 365     } else {
 366       _known_to_link_with_get = accessing_klass;
 367     }
 368   }
 369 
 370   return true;
 371 }
 372 
 373 // ------------------------------------------------------------------
 374 // ciField::print
 375 void ciField::print() {
 376   tty->print("<ciField name=");
 377   _holder->print_name();
 378   tty->print(".");
 379   _name->print_symbol();
 380   tty->print(" signature=");
 381   _signature->print_symbol();
 382   tty->print(" offset=%d type=", _offset);
 383   if (_type != NULL)
 384     _type->print_name();
 385   else
 386     tty->print("(reference)");
 387   tty->print(" flags=%04x", flags().as_int());
 388   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 389   if (_is_constant && is_static()) {
 390     tty->print(" constant_value=");
 391     _constant_value.print();
 392   }
 393   tty->print(">");
 394 }
 395 
 396 // ------------------------------------------------------------------
 397 // ciField::print_name_on
 398 //
 399 // Print the name of this field
 400 void ciField::print_name_on(outputStream* st) {
 401   name()->print_symbol_on(st);
 402 }
--- EOF ---