1 /*
   2  * Copyright (c) 1999, 2012, 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   _cp_index = index;
  79   constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
  80 
  81   // Get the field's name, signature, and type.
  82   Symbol* name  = cpool->name_ref_at(index);
  83   _name = ciEnv::current(thread)->get_symbol(name);
  84 
  85   int nt_index = cpool->name_and_type_ref_index_at(index);
  86   int sig_index = cpool->signature_ref_index_at(nt_index);
  87   Symbol* signature = cpool->symbol_at(sig_index);
  88   _signature = ciEnv::current(thread)->get_symbol(signature);
  89 
  90   BasicType field_type = FieldType::basic_type(signature);
  91 
  92   // If the field is a pointer type, get the klass of the
  93   // field.
  94   if (field_type == T_OBJECT || field_type == T_ARRAY) {
  95     bool ignore;
  96     // This is not really a class reference; the index always refers to the
  97     // field's type signature, as a symbol.  Linkage checks do not apply.
  98     _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
  99   } else {
 100     _type = ciType::make(field_type);
 101   }
 102 
 103   _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
 104 
 105   // Get the field's declared holder.
 106   //
 107   // Note: we actually create a ciInstanceKlass for this klass,
 108   // even though we may not need to.
 109   int holder_index = cpool->klass_ref_index_at(index);
 110   bool holder_is_accessible;
 111   ciInstanceKlass* declared_holder =
 112     ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
 113                                                holder_is_accessible,
 114                                                klass)->as_instance_klass();
 115 
 116   // The declared holder of this field may not have been loaded.
 117   // Bail out with partial field information.
 118   if (!holder_is_accessible) {
 119     // _cp_index and _type have already been set.
 120     // The default values for _flags and _constant_value will suffice.
 121     // We need values for _holder, _offset,  and _is_constant,
 122     _holder = declared_holder;
 123     _offset = -1;
 124     _is_constant = false;
 125     return;
 126   }
 127 
 128   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 129 
 130   // Perform the field lookup.
 131   fieldDescriptor field_desc;
 132   Klass* canonical_holder =
 133     loaded_decl_holder->find_field(name, signature, &field_desc);
 134   if (canonical_holder == NULL) {
 135     // Field lookup failed.  Will be detected by will_link.
 136     _holder = declared_holder;
 137     _offset = -1;
 138     _is_constant = false;
 139     return;
 140   }
 141 
 142   assert(canonical_holder == field_desc.field_holder(), "just checking");
 143   initialize_from(&field_desc);
 144 }
 145 
 146 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 147   ASSERT_IN_VM;
 148 
 149   _cp_index = -1;
 150 
 151   // Get the field's name, signature, and type.
 152   ciEnv* env = CURRENT_ENV;
 153   _name = env->get_symbol(fd->name());
 154   _signature = env->get_symbol(fd->signature());
 155 
 156   BasicType field_type = fd->field_type();
 157 
 158   // If the field is a pointer type, get the klass of the
 159   // field.
 160   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 161     _type = NULL;  // must call compute_type on first access
 162   } else {
 163     _type = ciType::make(field_type);
 164   }
 165 
 166   initialize_from(fd);
 167 
 168   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 169   assert(is_shared() || ciObjectFactory::is_initialized(),
 170          "bootstrap classes must not create & cache unshared fields");
 171 }
 172 
 173 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 174   if (holder == NULL)
 175     return false;
 176   if (holder->name() == ciSymbol::java_lang_System())
 177     // Never trust strangely unstable finals:  System.out, etc.
 178     return false;
 179   // Even if general trusting is disabled, trust system-built closures in these packages.
 180   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 181     return true;
 182   return TrustFinalNonStaticFields;
 183 }
 184 
 185 void ciField::initialize_from(fieldDescriptor* fd) {
 186   // Get the flags, offset, and canonical holder of the field.
 187   _flags = ciFlags(fd->access_flags());
 188   _offset = fd->offset();
 189   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 190 
 191   // Check to see if the field is constant.
 192   if (_holder->is_initialized() && this->is_final()) {
 193     if (!this->is_static()) {
 194       // A field can be constant if it's a final static field or if
 195       // it's a final non-static field of a trusted class (classes in
 196       // java.lang.invoke and sun.invoke packages and subpackages).
 197       if (trust_final_non_static_fields(_holder)) {
 198         _is_constant = true;
 199         return;
 200       }
 201       _is_constant = false;
 202       return;
 203     }
 204 
 205     // This field just may be constant.  The only cases where it will
 206     // not be constant are:
 207     //
 208     // 1. The field holds a non-perm-space oop.  The field is, strictly
 209     //    speaking, constant but we cannot embed non-perm-space oops into
 210     //    generated code.  For the time being we need to consider the
 211     //    field to be not constant.
 212     // 2. The field is a *special* static&final field whose value
 213     //    may change.  The three examples are java.lang.System.in,
 214     //    java.lang.System.out, and java.lang.System.err.
 215 
 216     KlassHandle k = _holder->get_Klass();
 217     assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
 218     if( k() == SystemDictionary::System_klass() ) {
 219       // Check offsets for case 2: System.in, System.out, or System.err
 220       if( _offset == java_lang_System::in_offset_in_bytes()  ||
 221           _offset == java_lang_System::out_offset_in_bytes() ||
 222           _offset == java_lang_System::err_offset_in_bytes() ) {
 223         _is_constant = false;
 224         return;
 225       }
 226     }
 227 
 228     Handle mirror = k->java_mirror();
 229 
 230     _is_constant = true;
 231     switch(type()->basic_type()) {
 232     case T_BYTE:
 233       _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
 234       break;
 235     case T_CHAR:
 236       _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
 237       break;
 238     case T_SHORT:
 239       _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
 240       break;
 241     case T_BOOLEAN:
 242       _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
 243       break;
 244     case T_INT:
 245       _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
 246       break;
 247     case T_FLOAT:
 248       _constant_value = ciConstant(mirror->float_field(_offset));
 249       break;
 250     case T_DOUBLE:
 251       _constant_value = ciConstant(mirror->double_field(_offset));
 252       break;
 253     case T_LONG:
 254       _constant_value = ciConstant(mirror->long_field(_offset));
 255       break;
 256     case T_OBJECT:
 257     case T_ARRAY:
 258       {
 259         oop o = mirror->obj_field(_offset);
 260 
 261         // A field will be "constant" if it is known always to be
 262         // a non-null reference to an instance of a particular class,
 263         // or to a particular array.  This can happen even if the instance
 264         // or array is not perm.  In such a case, an "unloaded" ciArray
 265         // or ciInstance is created.  The compiler may be able to use
 266         // information about the object's class (which is exact) or length.
 267 
 268         if (o == NULL) {
 269           _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
 270         } else {
 271           _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
 272           assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
 273         }
 274       }
 275     }
 276   } else {
 277     _is_constant = false;
 278   }
 279 }
 280 
 281 // ------------------------------------------------------------------
 282 // ciField::compute_type
 283 //
 284 // Lazily compute the type, if it is an instance klass.
 285 ciType* ciField::compute_type() {
 286   GUARDED_VM_ENTRY(return compute_type_impl();)
 287 }
 288 
 289 ciType* ciField::compute_type_impl() {
 290   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 291   if (!type->is_primitive_type() && is_shared()) {
 292     // We must not cache a pointer to an unshared type, in a shared field.
 293     bool type_is_also_shared = false;
 294     if (type->is_type_array_klass()) {
 295       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 296     } else if (type->is_instance_klass()) {
 297       type_is_also_shared = type->as_instance_klass()->is_shared();
 298     } else {
 299       // Currently there is no 'shared' query for array types.
 300       type_is_also_shared = !ciObjectFactory::is_initialized();
 301     }
 302     if (!type_is_also_shared)
 303       return type;              // Bummer.
 304   }
 305   _type = type;
 306   return type;
 307 }
 308 
 309 
 310 // ------------------------------------------------------------------
 311 // ciField::will_link
 312 //
 313 // Can a specific access to this field be made without causing
 314 // link errors?
 315 bool ciField::will_link(ciInstanceKlass* accessing_klass,
 316                         Bytecodes::Code bc) {
 317   VM_ENTRY_MARK;
 318   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 319          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 320          "unexpected bytecode");
 321 
 322   if (_offset == -1) {
 323     // at creation we couldn't link to our holder so we need to
 324     // maintain that stance, otherwise there's no safe way to use this
 325     // ciField.
 326     return false;
 327   }
 328 
 329   // Check for static/nonstatic mismatch
 330   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 331   if (is_static != this->is_static()) {
 332     return false;
 333   }
 334 
 335   // Get and put can have different accessibility rules
 336   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 337   if (is_put) {
 338     if (_known_to_link_with_put == accessing_klass) {
 339       return true;
 340     }
 341   } else {
 342     if (_known_to_link_with_get == accessing_klass) {
 343       return true;
 344     }
 345   }
 346 
 347   FieldAccessInfo result;
 348   constantPoolHandle c_pool(THREAD,
 349                          accessing_klass->get_instanceKlass()->constants());
 350   LinkResolver::resolve_field(result, c_pool, _cp_index,
 351                               Bytecodes::java_code(bc),
 352                               true, false, KILL_COMPILE_ON_FATAL_(false));
 353 
 354   // update the hit-cache, unless there is a problem with memory scoping:
 355   if (accessing_klass->is_shared() || !is_shared()) {
 356     if (is_put) {
 357       _known_to_link_with_put = accessing_klass;
 358     } else {
 359       _known_to_link_with_get = accessing_klass;
 360     }
 361   }
 362 
 363   return true;
 364 }
 365 
 366 // ------------------------------------------------------------------
 367 // ciField::print
 368 void ciField::print() {
 369   tty->print("<ciField ");
 370   _holder->print_name();
 371   tty->print(".");
 372   _name->print_symbol();
 373   tty->print(" offset=%d type=", _offset);
 374   if (_type != NULL) _type->print_name();
 375   else               tty->print("(reference)");
 376   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 377   if (_is_constant && is_static()) {
 378     tty->print(" constant_value=");
 379     _constant_value.print();
 380   }
 381   tty->print(">");
 382 }
 383 
 384 // ------------------------------------------------------------------
 385 // ciField::print_name_on
 386 //
 387 // Print the name of this field
 388 void ciField::print_name_on(outputStream* st) {
 389   name()->print_symbol_on(st);
 390 }