1 /*
   2  * Copyright (c) 1999, 2013, 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_interface/collectedHeap.inline.hpp"
  31 #include "interpreter/linkResolver.hpp"
  32 #include "memory/universe.inline.hpp"
  33 #include "oops/oop.inline.hpp"
  34 #include "oops/oop.inline2.hpp"
  35 #include "runtime/fieldDescriptor.hpp"
  36 
  37 // ciField
  38 //
  39 // This class represents the result of a field lookup in the VM.
  40 // The lookup may not succeed, in which case the information in
  41 // the ciField will be incomplete.
  42 
  43 // The ciObjectFactory cannot create circular data structures in one query.
  44 // To avoid vicious circularities, we initialize ciField::_type to NULL
  45 // for reference types and derive it lazily from the ciField::_signature.
  46 // Primitive types are eagerly initialized, and basic layout queries
  47 // can succeed without initialization, using only the BasicType of the field.
  48 
  49 // Notes on bootstrapping and shared CI objects:  A field is shared if and
  50 // only if it is (a) non-static and (b) declared by a shared instance klass.
  51 // This allows non-static field lists to be cached on shared types.
  52 // Because the _type field is lazily initialized, however, there is a
  53 // special restriction that a shared field cannot cache an unshared type.
  54 // This puts a small performance penalty on shared fields with unshared
  55 // types, such as StackTraceElement[] Throwable.stackTrace.
  56 // (Throwable is shared because ClassCastException is shared, but
  57 // StackTraceElement is not presently shared.)
  58 
  59 // It is not a vicious circularity for a ciField to recursively create
  60 // the ciSymbols necessary to represent its name and signature.
  61 // Therefore, these items are created eagerly, and the name and signature
  62 // of a shared field are themselves shared symbols.  This somewhat
  63 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,
  64 // with all of the additional 43 being uninteresting shared ciSymbols.
  65 // This adds at most one step to the binary search, an amount which
  66 // decreases for complex compilation tasks.
  67 
  68 // ------------------------------------------------------------------
  69 // ciField::ciField
  70 ciField::ciField(ciInstanceKlass* klass, int index): _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 constan-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 (field_type == T_OBJECT || field_type == T_ARRAY) {
  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   ciInstanceKlass* declared_holder =
 111     ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
 112                                                holder_is_accessible,
 113                                                klass)->as_instance_klass();
 114 
 115   // The declared holder of this field may not have been loaded.
 116   // Bail out with partial field information.
 117   if (!holder_is_accessible) {
 118     // _type has already been set.
 119     // The default values for _flags and _constant_value will suffice.
 120     // We need values for _holder, _offset,  and _is_constant,
 121     _holder = declared_holder;
 122     _offset = -1;
 123     _is_constant = false;
 124     return;
 125   }
 126 
 127   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 128 
 129   // Perform the field lookup.
 130   fieldDescriptor field_desc;
 131   Klass* canonical_holder =
 132     loaded_decl_holder->find_field(name, signature, &field_desc);
 133   if (canonical_holder == NULL) {
 134     // Field lookup failed.  Will be detected by will_link.
 135     _holder = declared_holder;
 136     _offset = -1;
 137     _is_constant = false;
 138     return;
 139   }
 140 
 141   // Access check based on declared_holder. canonical_holder should not be used
 142   // to check access because it can erroneously succeed. If this check fails,
 143   // propagate the declared holder to will_link() which in turn will bail out
 144   // compilation for this field access.
 145   if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
 146     _holder = declared_holder;
 147     _offset = -1;
 148     _is_constant = false;
 149     return;
 150   }
 151 
 152   assert(canonical_holder == field_desc.field_holder(), "just checking");
 153   initialize_from(&field_desc);
 154 }
 155 
 156 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 157   ASSERT_IN_VM;
 158 
 159   // Get the field's name, signature, and type.
 160   ciEnv* env = CURRENT_ENV;
 161   _name = env->get_symbol(fd->name());
 162   _signature = env->get_symbol(fd->signature());
 163 
 164   BasicType field_type = fd->field_type();
 165 
 166   // If the field is a pointer type, get the klass of the
 167   // field.
 168   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 169     _type = NULL;  // must call compute_type on first access
 170   } else {
 171     _type = ciType::make(field_type);
 172   }
 173 
 174   initialize_from(fd);
 175 
 176   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 177   assert(is_shared() || ciObjectFactory::is_initialized(),
 178          "bootstrap classes must not create & cache unshared fields");
 179 }
 180 
 181 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 182   if (holder == NULL)
 183     return false;
 184   if (holder->name() == ciSymbol::java_lang_System())
 185     // Never trust strangely unstable finals:  System.out, etc.
 186     return false;
 187   // Even if general trusting is disabled, trust system-built closures in these packages.
 188   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 189     return true;
 190   return TrustFinalNonStaticFields;
 191 }
 192 
 193 void ciField::initialize_from(fieldDescriptor* fd) {
 194   // Get the flags, offset, and canonical holder of the field.
 195   _flags = ciFlags(fd->access_flags());
 196   _offset = fd->offset();
 197   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 198 
 199   // Check to see if the field is constant.
 200   bool is_final = this->is_final();
 201   bool is_stable = FoldStableValues && this->is_stable();
 202   if (_holder->is_initialized() && (is_final || is_stable)) {
 203     if (!this->is_static()) {
 204       // A field can be constant if it's a final static field or if
 205       // it's a final non-static field of a trusted class (classes in
 206       // java.lang.invoke and sun.invoke packages and subpackages).
 207       if (is_stable || trust_final_non_static_fields(_holder)) {
 208         _is_constant = true;
 209         return;
 210       }
 211       _is_constant = false;
 212       return;
 213     }
 214 
 215     // This field just may be constant.  The only case where it will
 216     // not be constant is when the field is a *special* static&final field
 217     // whose value may change.  The three examples are java.lang.System.in,
 218     // java.lang.System.out, and java.lang.System.err.
 219 
 220     KlassHandle k = _holder->get_Klass();
 221     assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
 222     if( k() == SystemDictionary::System_klass() ) {
 223       // Check offsets for case 2: System.in, System.out, or System.err
 224       if( _offset == java_lang_System::in_offset_in_bytes()  ||
 225           _offset == java_lang_System::out_offset_in_bytes() ||
 226           _offset == java_lang_System::err_offset_in_bytes() ) {
 227         _is_constant = false;
 228         return;
 229       }
 230     }
 231 
 232     Handle mirror = k->java_mirror();
 233 
 234     switch(type()->basic_type()) {
 235     case T_BYTE:
 236       _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
 237       break;
 238     case T_CHAR:
 239       _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
 240       break;
 241     case T_SHORT:
 242       _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
 243       break;
 244     case T_BOOLEAN:
 245       _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
 246       break;
 247     case T_INT:
 248       _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
 249       break;
 250     case T_FLOAT:
 251       _constant_value = ciConstant(mirror->float_field(_offset));
 252       break;
 253     case T_DOUBLE:
 254       _constant_value = ciConstant(mirror->double_field(_offset));
 255       break;
 256     case T_LONG:
 257       _constant_value = ciConstant(mirror->long_field(_offset));
 258       break;
 259     case T_OBJECT:
 260     case T_ARRAY:
 261       {
 262         oop o = mirror->obj_field(_offset);
 263 
 264         // A field will be "constant" if it is known always to be
 265         // a non-null reference to an instance of a particular class,
 266         // or to a particular array.  This can happen even if the instance
 267         // or array is not perm.  In such a case, an "unloaded" ciArray
 268         // or ciInstance is created.  The compiler may be able to use
 269         // information about the object's class (which is exact) or length.
 270 
 271         if (o == NULL) {
 272           _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
 273         } else {
 274           _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
 275           assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
 276         }
 277       }
 278     }
 279     if (is_stable && _constant_value.is_null_or_zero()) {
 280       // It is not a constant after all; treat it as uninitialized.
 281       _is_constant = false;
 282     } else {
 283       _is_constant = true;
 284     }
 285   } else {
 286     _is_constant = false;
 287   }
 288 }
 289 
 290 // ------------------------------------------------------------------
 291 // ciField::compute_type
 292 //
 293 // Lazily compute the type, if it is an instance klass.
 294 ciType* ciField::compute_type() {
 295   GUARDED_VM_ENTRY(return compute_type_impl();)
 296 }
 297 
 298 ciType* ciField::compute_type_impl() {
 299   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 300   if (!type->is_primitive_type() && is_shared()) {
 301     // We must not cache a pointer to an unshared type, in a shared field.
 302     bool type_is_also_shared = false;
 303     if (type->is_type_array_klass()) {
 304       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 305     } else if (type->is_instance_klass()) {
 306       type_is_also_shared = type->as_instance_klass()->is_shared();
 307     } else {
 308       // Currently there is no 'shared' query for array types.
 309       type_is_also_shared = !ciObjectFactory::is_initialized();
 310     }
 311     if (!type_is_also_shared)
 312       return type;              // Bummer.
 313   }
 314   _type = type;
 315   return type;
 316 }
 317 
 318 
 319 // ------------------------------------------------------------------
 320 // ciField::will_link
 321 //
 322 // Can a specific access to this field be made without causing
 323 // link errors?
 324 bool ciField::will_link(ciInstanceKlass* accessing_klass,
 325                         Bytecodes::Code bc) {
 326   VM_ENTRY_MARK;
 327   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 328          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 329          "unexpected bytecode");
 330 
 331   if (_offset == -1) {
 332     // at creation we couldn't link to our holder so we need to
 333     // maintain that stance, otherwise there's no safe way to use this
 334     // ciField.
 335     return false;
 336   }
 337 
 338   // Check for static/nonstatic mismatch
 339   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 340   if (is_static != this->is_static()) {
 341     return false;
 342   }
 343 
 344   // Get and put can have different accessibility rules
 345   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 346   if (is_put) {
 347     if (_known_to_link_with_put == accessing_klass) {
 348       return true;
 349     }
 350   } else {
 351     if (_known_to_link_with_get == accessing_klass) {
 352       return true;
 353     }
 354   }
 355 
 356   fieldDescriptor result;
 357   LinkResolver::resolve_field(result, _holder->get_instanceKlass(),
 358                               _name->get_symbol(), _signature->get_symbol(),
 359                               accessing_klass->get_Klass(), bc, true, false,
 360                               KILL_COMPILE_ON_FATAL_(false));
 361 
 362   // update the hit-cache, unless there is a problem with memory scoping:
 363   if (accessing_klass->is_shared() || !is_shared()) {
 364     if (is_put) {
 365       _known_to_link_with_put = accessing_klass;
 366     } else {
 367       _known_to_link_with_get = accessing_klass;
 368     }
 369   }
 370 
 371   return true;
 372 }
 373 
 374 // ------------------------------------------------------------------
 375 // ciField::print
 376 void ciField::print() {
 377   tty->print("<ciField name=");
 378   _holder->print_name();
 379   tty->print(".");
 380   _name->print_symbol();
 381   tty->print(" signature=");
 382   _signature->print_symbol();
 383   tty->print(" offset=%d type=", _offset);
 384   if (_type != NULL)
 385     _type->print_name();
 386   else
 387     tty->print("(reference)");
 388   tty->print(" flags=%04x", flags().as_int());
 389   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 390   if (_is_constant && is_static()) {
 391     tty->print(" constant_value=");
 392     _constant_value.print();
 393   }
 394   tty->print(">");
 395 }
 396 
 397 // ------------------------------------------------------------------
 398 // ciField::print_name_on
 399 //
 400 // Print the name of this field
 401 void ciField::print_name_on(outputStream* st) {
 402   name()->print_symbol_on(st);
 403 }