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 static bool trust_final_non_static_fields(ciInstanceKlass* holder) { 202 if (holder == NULL) 203 return false; 204 if (holder->name() == ciSymbol::java_lang_System()) 205 // Never trust strangely unstable finals: System.out, etc. 206 return false; 207 // Even if general trusting is disabled, trust system-built closures in these packages. 208 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke")) 209 return true; 210 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized, 211 // so there is no hacking of finals going on with them. 212 if (holder->is_anonymous()) 213 return true; 214 // Trust final fields in all boxed classes 215 if (holder->is_box_klass()) 216 return true; 217 // Trust final fields in String 218 if (holder->name() == ciSymbol::java_lang_String()) 219 return true; 220 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one 221 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483. 222 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() || 223 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() || 224 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() || 225 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) { 226 return true; 227 } 228 return TrustFinalNonStaticFields; 229 } 230 231 void ciField::initialize_from(fieldDescriptor* fd) { 232 // Get the flags, offset, and canonical holder of the field. 233 _flags = ciFlags(fd->access_flags()); 234 _offset = fd->offset(); 235 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder()); 236 237 // Check to see if the field is constant. 238 Klass* k = _holder->get_Klass(); 239 bool is_stable_field = FoldStableValues && is_stable(); 240 if (is_final() || is_stable_field) { 241 if (is_static()) { 242 // This field just may be constant. The only case where it will 243 // not be constant is when the field is a *special* static & final field 244 // whose value may change. The three examples are java.lang.System.in, 245 // java.lang.System.out, and java.lang.System.err. 246 assert(SystemDictionary::System_klass() != NULL, "Check once per vm"); 247 if (k == SystemDictionary::System_klass()) { 248 // Check offsets for case 2: System.in, System.out, or System.err 249 if( _offset == java_lang_System::in_offset_in_bytes() || 250 _offset == java_lang_System::out_offset_in_bytes() || 251 _offset == java_lang_System::err_offset_in_bytes() ) { 252 _is_constant = false; 253 return; 254 } 255 } 256 _is_constant = true; 257 } else { 258 // An instance field can be constant if it's a final static field or if 259 // it's a final non-static field of a trusted class (classes in 260 // java.lang.invoke and sun.invoke packages and subpackages). 261 _is_constant = is_stable_field || trust_final_non_static_fields(_holder); 262 } 263 } else { 264 // For CallSite objects treat the target field as a compile time constant. 265 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized"); 266 if (k == SystemDictionary::CallSite_klass() && 267 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) { 268 _is_constant = true; 269 } else { 270 // Non-final & non-stable fields are not constants. 271 _is_constant = false; 272 } 273 } 274 } 275 276 // ------------------------------------------------------------------ 277 // ciField::constant_value 278 // Get the constant value of a this static field. 279 ciConstant ciField::constant_value() { 280 assert(is_static() && is_constant(), "illegal call to constant_value()"); 281 if (!_holder->is_initialized()) { 282 return ciConstant(); // Not initialized yet 283 } 284 if (_constant_value.basic_type() == T_ILLEGAL) { 285 // Static fields are placed in mirror objects. 286 VM_ENTRY_MARK; 287 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror()); 288 _constant_value = mirror->field_value_impl(type()->basic_type(), offset()); 289 } 290 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) { 291 return ciConstant(); 292 } 293 return _constant_value; 294 } 295 296 // ------------------------------------------------------------------ 297 // ciField::constant_value_of 298 // Get the constant value of non-static final field in the given object. 299 ciConstant ciField::constant_value_of(ciObject* object) { 300 assert(!is_static() && is_constant(), "only if field is non-static constant"); 301 assert(object->is_instance(), "must be instance"); 302 ciConstant field_value = object->as_instance()->field_value(this); 303 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) { 304 return ciConstant(); 305 } 306 return field_value; 307 } 308 309 // ------------------------------------------------------------------ 310 // ciField::compute_type 311 // 312 // Lazily compute the type, if it is an instance klass. 313 ciType* ciField::compute_type() { 314 GUARDED_VM_ENTRY(return compute_type_impl();) 315 } 316 317 ciType* ciField::compute_type_impl() { 318 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false); 319 if (!type->is_primitive_type() && is_shared()) { 320 // We must not cache a pointer to an unshared type, in a shared field. 321 bool type_is_also_shared = false; 322 if (type->is_type_array_klass()) { 323 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped 324 } else if (type->is_instance_klass()) { 325 type_is_also_shared = type->as_instance_klass()->is_shared(); 326 } else { 327 // Currently there is no 'shared' query for array types. 328 type_is_also_shared = !ciObjectFactory::is_initialized(); 329 } 330 if (!type_is_also_shared) 331 return type; // Bummer. 332 } 333 _type = type; 334 return type; 335 } 336 337 338 // ------------------------------------------------------------------ 339 // ciField::will_link 340 // 341 // Can a specific access to this field be made without causing 342 // link errors? 343 bool ciField::will_link(ciInstanceKlass* accessing_klass, 344 Bytecodes::Code bc) { 345 VM_ENTRY_MARK; 346 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic || 347 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield, 348 "unexpected bytecode"); 349 350 if (_offset == -1) { 351 // at creation we couldn't link to our holder so we need to 352 // maintain that stance, otherwise there's no safe way to use this 353 // ciField. 354 return false; 355 } 356 357 // Check for static/nonstatic mismatch 358 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic); 359 if (is_static != this->is_static()) { 360 return false; 361 } 362 363 // Get and put can have different accessibility rules 364 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic); 365 if (is_put) { 366 if (_known_to_link_with_put == accessing_klass) { 367 return true; 368 } 369 } else { 370 if (_known_to_link_with_get == accessing_klass) { 371 return true; 372 } 373 } 374 375 LinkInfo link_info(_holder->get_instanceKlass(), 376 _name->get_symbol(), _signature->get_symbol(), 377 accessing_klass->get_Klass()); 378 fieldDescriptor result; 379 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false)); 380 381 // update the hit-cache, unless there is a problem with memory scoping: 382 if (accessing_klass->is_shared() || !is_shared()) { 383 if (is_put) { 384 _known_to_link_with_put = accessing_klass; 385 } else { 386 _known_to_link_with_get = accessing_klass; 387 } 388 } 389 390 return true; 391 } 392 393 // ------------------------------------------------------------------ 394 // ciField::print 395 void ciField::print() { 396 tty->print("<ciField name="); 397 _holder->print_name(); 398 tty->print("."); 399 _name->print_symbol(); 400 tty->print(" signature="); 401 _signature->print_symbol(); 402 tty->print(" offset=%d type=", _offset); 403 if (_type != NULL) 404 _type->print_name(); 405 else 406 tty->print("(reference)"); 407 tty->print(" flags=%04x", flags().as_int()); 408 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 409 if (_is_constant && is_static()) { 410 tty->print(" constant_value="); 411 _constant_value.print(); 412 } 413 tty->print(">"); 414 } 415 416 // ------------------------------------------------------------------ 417 // ciField::print_name_on 418 // 419 // Print the name of this field 420 void ciField::print_name_on(outputStream* st) { 421 name()->print_symbol_on(st); 422 }