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 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 void ciField::initialize_from(fieldDescriptor* fd) {
 202   // Get the flags, offset, and canonical holder of the field.
 203   _flags = ciFlags(fd->access_flags());
 204   _offset = fd->offset();
 205   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
 206 
 207   // Check to see if the field is constant.
 208   Klass* k = _holder->get_Klass();
 209   bool is_stable_field = FoldStableValues && is_stable();

























 210   assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
 211   if (is_stable_field ||
 212       (k == SystemDictionary::CallSite_klass() &&
 213        _offset == java_lang_invoke_CallSite::target_offset_in_bytes())) {
 214     _is_constant = true;
 215   } else {

 216     _is_constant = false;
 217   }

 218 }
 219 
 220 // ------------------------------------------------------------------
 221 // ciField::constant_value
 222 // Get the constant value of a this static field.
 223 ciConstant ciField::constant_value() {
 224   assert(is_static() && is_constant(), "illegal call to constant_value()");
 225   if (!_holder->is_initialized()) {
 226     return ciConstant(); // Not initialized yet
 227   }
 228   if (_constant_value.basic_type() == T_ILLEGAL) {
 229     // Static fields are placed in mirror objects.
 230     VM_ENTRY_MARK;
 231     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
 232     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
 233   }
 234   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
 235     return ciConstant();
 236   }
 237   return _constant_value;
 238 }
 239 
 240 // ------------------------------------------------------------------
 241 // ciField::constant_value_of
 242 // Get the constant value of non-static final field in the given object.
 243 ciConstant ciField::constant_value_of(ciObject* object) {
 244   assert(!is_static() && is_constant(), "only if field is non-static constant");
 245   assert(object->is_instance(), "must be instance");
 246   ciConstant field_value = object->as_instance()->field_value(this);
 247   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
 248     return ciConstant();
 249   }
 250   return field_value;
 251 }
 252 
 253 // ------------------------------------------------------------------
 254 // ciField::compute_type
 255 //
 256 // Lazily compute the type, if it is an instance klass.
 257 ciType* ciField::compute_type() {
 258   GUARDED_VM_ENTRY(return compute_type_impl();)
 259 }
 260 
 261 ciType* ciField::compute_type_impl() {
 262   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 263   if (!type->is_primitive_type() && is_shared()) {
 264     // We must not cache a pointer to an unshared type, in a shared field.
 265     bool type_is_also_shared = false;
 266     if (type->is_type_array_klass()) {
 267       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 268     } else if (type->is_instance_klass()) {
 269       type_is_also_shared = type->as_instance_klass()->is_shared();
 270     } else {
 271       // Currently there is no 'shared' query for array types.
 272       type_is_also_shared = !ciObjectFactory::is_initialized();
 273     }
 274     if (!type_is_also_shared)
 275       return type;              // Bummer.
 276   }
 277   _type = type;
 278   return type;
 279 }
 280 
 281 
 282 // ------------------------------------------------------------------
 283 // ciField::will_link
 284 //
 285 // Can a specific access to this field be made without causing
 286 // link errors?
 287 bool ciField::will_link(ciInstanceKlass* accessing_klass,
 288                         ciMethod* accessing_method,
 289                         Bytecodes::Code bc) {
 290   VM_ENTRY_MARK;
 291   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 292          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 293          "unexpected bytecode");
 294 
 295   if (_offset == -1) {
 296     // at creation we couldn't link to our holder so we need to
 297     // maintain that stance, otherwise there's no safe way to use this
 298     // ciField.
 299     return false;
 300   }
 301 
 302   // Check for static/nonstatic mismatch
 303   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 304   if (is_static != this->is_static()) {
 305     return false;
 306   }
 307 
 308   // Get and put can have different accessibility rules
 309   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 310   if (is_put) {
 311     if (_known_to_link_with_put == accessing_klass) {
 312       return true;
 313     }
 314   } else {
 315     if (_known_to_link_with_get == accessing_klass) {
 316       return true;
 317     }
 318   }
 319 
 320   LinkInfo link_info(_holder->get_instanceKlass(),
 321                      _name->get_symbol(), _signature->get_symbol(),
 322                      accessing_klass->get_Klass(), accessing_method->get_Method());
 323   fieldDescriptor result;
 324   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 325 
 326   // update the hit-cache, unless there is a problem with memory scoping:
 327   if (accessing_klass->is_shared() || !is_shared()) {
 328     if (is_put) {
 329       _known_to_link_with_put = accessing_klass;
 330     } else {
 331       _known_to_link_with_get = accessing_klass;
 332     }
 333   }
 334 
 335   return true;
 336 }
 337 
 338 // ------------------------------------------------------------------
 339 // ciField::print
 340 void ciField::print() {
 341   tty->print("<ciField name=");
 342   _holder->print_name();
 343   tty->print(".");
 344   _name->print_symbol();
 345   tty->print(" signature=");
 346   _signature->print_symbol();
 347   tty->print(" offset=%d type=", _offset);
 348   if (_type != NULL)
 349     _type->print_name();
 350   else
 351     tty->print("(reference)");
 352   tty->print(" flags=%04x", flags().as_int());
 353   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 354   if (_is_constant && is_static()) {
 355     tty->print(" constant_value=");
 356     _constant_value.print();
 357   }
 358   tty->print(">");
 359 }
 360 
 361 // ------------------------------------------------------------------
 362 // ciField::print_name_on
 363 //
 364 // Print the name of this field
 365 void ciField::print_name_on(outputStream* st) {
 366   name()->print_symbol_on(st);
 367 }
--- EOF ---