1 /* 2 * Copyright (c) 2005, 2010, 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 #ifndef SHARE_VM_CODE_DEPENDENCIES_HPP 26 #define SHARE_VM_CODE_DEPENDENCIES_HPP 27 28 #include "ci/ciKlass.hpp" 29 #include "code/compressedStream.hpp" 30 #include "code/nmethod.hpp" 31 #include "utilities/growableArray.hpp" 32 33 //** Dependencies represent assertions (approximate invariants) within 34 // the class hierarchy. An example is an assertion that a given 35 // method is not overridden; another example is that a type has only 36 // one concrete subtype. Compiled code which relies on such 37 // assertions must be discarded if they are overturned by changes in 38 // the class hierarchy. We can think of these assertions as 39 // approximate invariants, because we expect them to be overturned 40 // very infrequently. We are willing to perform expensive recovery 41 // operations when they are overturned. The benefit, of course, is 42 // performing optimistic optimizations (!) on the object code. 43 // 44 // Changes in the class hierarchy due to dynamic linking or 45 // class evolution can violate dependencies. There is enough 46 // indexing between classes and nmethods to make dependency 47 // checking reasonably efficient. 48 49 class ciEnv; 50 class nmethod; 51 class OopRecorder; 52 class xmlStream; 53 class CompileLog; 54 class DepChange; 55 class No_Safepoint_Verifier; 56 57 class Dependencies: public ResourceObj { 58 public: 59 // Note: In the comments on dependency types, most uses of the terms 60 // subtype and supertype are used in a "non-strict" or "inclusive" 61 // sense, and are starred to remind the reader of this fact. 62 // Strict uses of the terms use the word "proper". 63 // 64 // Specifically, every class is its own subtype* and supertype*. 65 // (This trick is easier than continually saying things like "Y is a 66 // subtype of X or X itself".) 67 // 68 // Sometimes we write X > Y to mean X is a proper supertype of Y. 69 // The notation X > {Y, Z} means X has proper subtypes Y, Z. 70 // The notation X.m > Y means that Y inherits m from X, while 71 // X.m > Y.m means Y overrides X.m. A star denotes abstractness, 72 // as *I > A, meaning (abstract) interface I is a super type of A, 73 // or A.*m > B.m, meaning B.m implements abstract method A.m. 74 // 75 // In this module, the terms "subtype" and "supertype" refer to 76 // Java-level reference type conversions, as detected by 77 // "instanceof" and performed by "checkcast" operations. The method 78 // Klass::is_subtype_of tests these relations. Note that "subtype" 79 // is richer than "subclass" (as tested by Klass::is_subclass_of), 80 // since it takes account of relations involving interface and array 81 // types. 82 // 83 // To avoid needless complexity, dependencies involving array types 84 // are not accepted. If you need to make an assertion about an 85 // array type, make the assertion about its corresponding element 86 // types. Any assertion that might change about an array type can 87 // be converted to an assertion about its element type. 88 // 89 // Most dependencies are evaluated over a "context type" CX, which 90 // stands for the set Subtypes(CX) of every Java type that is a subtype* 91 // of CX. When the system loads a new class or interface N, it is 92 // responsible for re-evaluating changed dependencies whose context 93 // type now includes N, that is, all super types of N. 94 // 95 enum DepType { 96 end_marker = 0, 97 98 // An 'evol' dependency simply notes that the contents of the 99 // method were used. If it evolves (is replaced), the nmethod 100 // must be recompiled. No other dependencies are implied. 101 evol_method, 102 FIRST_TYPE = evol_method, 103 104 // A context type CX is a leaf it if has no proper subtype. 105 leaf_type, 106 107 // An abstract class CX has exactly one concrete subtype CC. 108 abstract_with_unique_concrete_subtype, 109 110 // The type CX is purely abstract, with no concrete subtype* at all. 111 abstract_with_no_concrete_subtype, 112 113 // The concrete CX is free of concrete proper subtypes. 114 concrete_with_no_concrete_subtype, 115 116 // Given a method M1 and a context class CX, the set MM(CX, M1) of 117 // "concrete matching methods" in CX of M1 is the set of every 118 // concrete M2 for which it is possible to create an invokevirtual 119 // or invokeinterface call site that can reach either M1 or M2. 120 // That is, M1 and M2 share a name, signature, and vtable index. 121 // We wish to notice when the set MM(CX, M1) is just {M1}, or 122 // perhaps a set of two {M1,M2}, and issue dependencies on this. 123 124 // The set MM(CX, M1) can be computed by starting with any matching 125 // concrete M2 that is inherited into CX, and then walking the 126 // subtypes* of CX looking for concrete definitions. 127 128 // The parameters to this dependency are the method M1 and the 129 // context class CX. M1 must be either inherited in CX or defined 130 // in a subtype* of CX. It asserts that MM(CX, M1) is no greater 131 // than {M1}. 132 unique_concrete_method, // one unique concrete method under CX 133 134 // An "exclusive" assertion concerns two methods or subtypes, and 135 // declares that there are at most two (or perhaps later N>2) 136 // specific items that jointly satisfy the restriction. 137 // We list all items explicitly rather than just giving their 138 // count, for robustness in the face of complex schema changes. 139 140 // A context class CX (which may be either abstract or concrete) 141 // has two exclusive concrete subtypes* C1, C2 if every concrete 142 // subtype* of CX is either C1 or C2. Note that if neither C1 or C2 143 // are equal to CX, then CX itself must be abstract. But it is 144 // also possible (for example) that C1 is CX (a concrete class) 145 // and C2 is a proper subtype of C1. 146 abstract_with_exclusive_concrete_subtypes_2, 147 148 // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}. 149 exclusive_concrete_methods_2, 150 151 // This dependency asserts that no instances of class or it's 152 // subclasses require finalization registration. 153 no_finalizable_subclasses, 154 155 TYPE_LIMIT 156 }; 157 enum { 158 LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT)) 159 160 // handy categorizations of dependency types: 161 all_types = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE), 162 non_ctxk_types = (1<<evol_method), 163 ctxk_types = all_types & ~non_ctxk_types, 164 165 max_arg_count = 3, // current maximum number of arguments (incl. ctxk) 166 167 // A "context type" is a class or interface that 168 // provides context for evaluating a dependency. 169 // When present, it is one of the arguments (dep_context_arg). 170 // 171 // If a dependency does not have a context type, there is a 172 // default context, depending on the type of the dependency. 173 // This bit signals that a default context has been compressed away. 174 default_context_type_bit = (1<<LG2_TYPE_LIMIT) 175 }; 176 177 static const char* dep_name(DepType dept); 178 static int dep_args(DepType dept); 179 static int dep_context_arg(DepType dept) { 180 return dept_in_mask(dept, ctxk_types)? 0: -1; 181 } 182 183 private: 184 // State for writing a new set of dependencies: 185 GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept)) 186 GrowableArray<ciObject*>* _deps[TYPE_LIMIT]; 187 188 static const char* _dep_name[TYPE_LIMIT]; 189 static int _dep_args[TYPE_LIMIT]; 190 191 static bool dept_in_mask(DepType dept, int mask) { 192 return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0; 193 } 194 195 bool note_dep_seen(int dept, ciObject* x) { 196 assert(dept < BitsPerInt, "oob"); 197 int x_id = x->ident(); 198 assert(_dep_seen != NULL, "deps must be writable"); 199 int seen = _dep_seen->at_grow(x_id, 0); 200 _dep_seen->at_put(x_id, seen | (1<<dept)); 201 // return true if we've already seen dept/x 202 return (seen & (1<<dept)) != 0; 203 } 204 205 bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps, 206 int ctxk_i, ciKlass* ctxk); 207 208 void sort_all_deps(); 209 size_t estimate_size_in_bytes(); 210 211 // Initialize _deps, etc. 212 void initialize(ciEnv* env); 213 214 // State for making a new set of dependencies: 215 OopRecorder* _oop_recorder; 216 217 // Logging support 218 CompileLog* _log; 219 220 address _content_bytes; // everything but the oop references, encoded 221 size_t _size_in_bytes; 222 223 public: 224 // Make a new empty dependencies set. 225 Dependencies(ciEnv* env) { 226 initialize(env); 227 } 228 229 private: 230 // Check for a valid context type. 231 // Enforce the restriction against array types. 232 static void check_ctxk(ciKlass* ctxk) { 233 assert(ctxk->is_instance_klass(), "java types only"); 234 } 235 static void check_ctxk_concrete(ciKlass* ctxk) { 236 assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete"); 237 } 238 static void check_ctxk_abstract(ciKlass* ctxk) { 239 check_ctxk(ctxk); 240 assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract"); 241 } 242 243 void assert_common_1(DepType dept, ciObject* x); 244 void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x); 245 void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2); 246 247 public: 248 // Adding assertions to a new dependency set at compile time: 249 void assert_evol_method(ciMethod* m); 250 void assert_leaf_type(ciKlass* ctxk); 251 void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck); 252 void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk); 253 void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk); 254 void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm); 255 void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2); 256 void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2); 257 void assert_has_no_finalizable_subclasses(ciKlass* ctxk); 258 259 // Define whether a given method or type is concrete. 260 // These methods define the term "concrete" as used in this module. 261 // For this module, an "abstract" class is one which is non-concrete. 262 // 263 // Future optimizations may allow some classes to remain 264 // non-concrete until their first instantiation, and allow some 265 // methods to remain non-concrete until their first invocation. 266 // In that case, there would be a middle ground between concrete 267 // and abstract (as defined by the Java language and VM). 268 static bool is_concrete_klass(klassOop k); // k is instantiable 269 static bool is_concrete_method(methodOop m); // m is invocable 270 static Klass* find_finalizable_subclass(Klass* k); 271 272 // These versions of the concreteness queries work through the CI. 273 // The CI versions are allowed to skew sometimes from the VM 274 // (oop-based) versions. The cost of such a difference is a 275 // (safely) aborted compilation, or a deoptimization, or a missed 276 // optimization opportunity. 277 // 278 // In order to prevent spurious assertions, query results must 279 // remain stable within any single ciEnv instance. (I.e., they must 280 // not go back into the VM to get their value; they must cache the 281 // bit in the CI, either eagerly or lazily.) 282 static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable 283 static bool is_concrete_method(ciMethod* m); // m appears invocable 284 static bool has_finalizable_subclass(ciInstanceKlass* k); 285 286 // As a general rule, it is OK to compile under the assumption that 287 // a given type or method is concrete, even if it at some future 288 // point becomes abstract. So dependency checking is one-sided, in 289 // that it permits supposedly concrete classes or methods to turn up 290 // as really abstract. (This shouldn't happen, except during class 291 // evolution, but that's the logic of the checking.) However, if a 292 // supposedly abstract class or method suddenly becomes concrete, a 293 // dependency on it must fail. 294 295 // Checking old assertions at run-time (in the VM only): 296 static klassOop check_evol_method(methodOop m); 297 static klassOop check_leaf_type(klassOop ctxk); 298 static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck, 299 DepChange* changes = NULL); 300 static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk, 301 DepChange* changes = NULL); 302 static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk, 303 DepChange* changes = NULL); 304 static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm, 305 DepChange* changes = NULL); 306 static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2, 307 DepChange* changes = NULL); 308 static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2, 309 DepChange* changes = NULL); 310 static klassOop check_has_no_finalizable_subclasses(klassOop ctxk, 311 DepChange* changes = NULL); 312 // A returned klassOop is NULL if the dependency assertion is still 313 // valid. A non-NULL klassOop is a 'witness' to the assertion 314 // failure, a point in the class hierarchy where the assertion has 315 // been proven false. For example, if check_leaf_type returns 316 // non-NULL, the value is a subtype of the supposed leaf type. This 317 // witness value may be useful for logging the dependency failure. 318 // Note that, when a dependency fails, there may be several possible 319 // witnesses to the failure. The value returned from the check_foo 320 // method is chosen arbitrarily. 321 322 // The 'changes' value, if non-null, requests a limited spot-check 323 // near the indicated recent changes in the class hierarchy. 324 // It is used by DepStream::spot_check_dependency_at. 325 326 // Detecting possible new assertions: 327 static klassOop find_unique_concrete_subtype(klassOop ctxk); 328 static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m); 329 static int find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]); 330 static int find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]); 331 332 // Create the encoding which will be stored in an nmethod. 333 void encode_content_bytes(); 334 335 address content_bytes() { 336 assert(_content_bytes != NULL, "encode it first"); 337 return _content_bytes; 338 } 339 size_t size_in_bytes() { 340 assert(_content_bytes != NULL, "encode it first"); 341 return _size_in_bytes; 342 } 343 344 OopRecorder* oop_recorder() { return _oop_recorder; } 345 CompileLog* log() { return _log; } 346 347 void copy_to(nmethod* nm); 348 349 void log_all_dependencies(); 350 void log_dependency(DepType dept, int nargs, ciObject* args[]) { 351 write_dependency_to(log(), dept, nargs, args); 352 } 353 void log_dependency(DepType dept, 354 ciObject* x0, 355 ciObject* x1 = NULL, 356 ciObject* x2 = NULL) { 357 if (log() == NULL) return; 358 ciObject* args[max_arg_count]; 359 args[0] = x0; 360 args[1] = x1; 361 args[2] = x2; 362 assert(2 < max_arg_count, ""); 363 log_dependency(dept, dep_args(dept), args); 364 } 365 366 static void write_dependency_to(CompileLog* log, 367 DepType dept, 368 int nargs, ciObject* args[], 369 klassOop witness = NULL); 370 static void write_dependency_to(CompileLog* log, 371 DepType dept, 372 int nargs, oop args[], 373 klassOop witness = NULL); 374 static void write_dependency_to(xmlStream* xtty, 375 DepType dept, 376 int nargs, oop args[], 377 klassOop witness = NULL); 378 static void print_dependency(DepType dept, 379 int nargs, oop args[], 380 klassOop witness = NULL); 381 382 private: 383 // helper for encoding common context types as zero: 384 static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x); 385 386 static klassOop ctxk_encoded_as_null(DepType dept, oop x); 387 388 public: 389 // Use this to iterate over an nmethod's dependency set. 390 // Works on new and old dependency sets. 391 // Usage: 392 // 393 // ; 394 // Dependencies::DepType dept; 395 // for (Dependencies::DepStream deps(nm); deps.next(); ) { 396 // ... 397 // } 398 // 399 // The caller must be in the VM, since oops are not wrapped in handles. 400 class DepStream { 401 private: 402 nmethod* _code; // null if in a compiler thread 403 Dependencies* _deps; // null if not in a compiler thread 404 CompressedReadStream _bytes; 405 #ifdef ASSERT 406 size_t _byte_limit; 407 #endif 408 409 // iteration variables: 410 DepType _type; 411 int _xi[max_arg_count+1]; 412 413 void initial_asserts(size_t byte_limit) NOT_DEBUG({}); 414 415 inline oop recorded_oop_at(int i); 416 // => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i) 417 418 klassOop check_dependency_impl(DepChange* changes); 419 420 public: 421 DepStream(Dependencies* deps) 422 : _deps(deps), 423 _code(NULL), 424 _bytes(deps->content_bytes()) 425 { 426 initial_asserts(deps->size_in_bytes()); 427 } 428 DepStream(nmethod* code) 429 : _deps(NULL), 430 _code(code), 431 _bytes(code->dependencies_begin()) 432 { 433 initial_asserts(code->dependencies_size()); 434 } 435 436 bool next(); 437 438 DepType type() { return _type; } 439 int argument_count() { return dep_args(type()); } 440 int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob"); 441 return _xi[i]; } 442 oop argument(int i); // => recorded_oop_at(argument_index(i)) 443 klassOop context_type(); 444 445 methodOop method_argument(int i) { 446 oop x = argument(i); 447 assert(x->is_method(), "type"); 448 return (methodOop) x; 449 } 450 klassOop type_argument(int i) { 451 oop x = argument(i); 452 assert(x->is_klass(), "type"); 453 return (klassOop) x; 454 } 455 456 // The point of the whole exercise: Is this dep is still OK? 457 klassOop check_dependency() { 458 return check_dependency_impl(NULL); 459 } 460 // A lighter version: Checks only around recent changes in a class 461 // hierarchy. (See Universe::flush_dependents_on.) 462 klassOop spot_check_dependency_at(DepChange& changes); 463 464 // Log the current dependency to xtty or compilation log. 465 void log_dependency(klassOop witness = NULL); 466 467 // Print the current dependency to tty. 468 void print_dependency(klassOop witness = NULL, bool verbose = false); 469 }; 470 friend class Dependencies::DepStream; 471 472 static void print_statistics() PRODUCT_RETURN; 473 }; 474 475 // A class hierarchy change coming through the VM (under the Compile_lock). 476 // The change is structured as a single new type with any number of supers 477 // and implemented interface types. Other than the new type, any of the 478 // super types can be context types for a relevant dependency, which the 479 // new type could invalidate. 480 class DepChange : public StackObj { 481 public: 482 enum ChangeType { 483 NO_CHANGE = 0, // an uninvolved klass 484 Change_new_type, // a newly loaded type 485 Change_new_sub, // a super with a new subtype 486 Change_new_impl, // an interface with a new implementation 487 CHANGE_LIMIT, 488 Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream 489 }; 490 491 private: 492 // each change set is rooted in exactly one new type (at present): 493 KlassHandle _new_type; 494 495 void initialize(); 496 497 public: 498 // notes the new type, marks it and all its super-types 499 DepChange(KlassHandle new_type) 500 : _new_type(new_type) 501 { 502 initialize(); 503 } 504 505 // cleans up the marks 506 ~DepChange(); 507 508 klassOop new_type() { return _new_type(); } 509 510 // involves_context(k) is true if k is new_type or any of the super types 511 bool involves_context(klassOop k); 512 513 // Usage: 514 // for (DepChange::ContextStream str(changes); str.next(); ) { 515 // klassOop k = str.klass(); 516 // switch (str.change_type()) { 517 // ... 518 // } 519 // } 520 class ContextStream : public StackObj { 521 private: 522 DepChange& _changes; 523 friend class DepChange; 524 525 // iteration variables: 526 ChangeType _change_type; 527 klassOop _klass; 528 objArrayOop _ti_base; // i.e., transitive_interfaces 529 int _ti_index; 530 int _ti_limit; 531 532 // start at the beginning: 533 void start() { 534 klassOop new_type = _changes.new_type(); 535 _change_type = (new_type == NULL ? NO_CHANGE: Start_Klass); 536 _klass = new_type; 537 _ti_base = NULL; 538 _ti_index = 0; 539 _ti_limit = 0; 540 } 541 542 public: 543 ContextStream(DepChange& changes) 544 : _changes(changes) 545 { start(); } 546 547 ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv) 548 : _changes(changes) 549 // the nsv argument makes it safe to hold oops like _klass 550 { start(); } 551 552 bool next(); 553 554 ChangeType change_type() { return _change_type; } 555 klassOop klass() { return _klass; } 556 }; 557 friend class DepChange::ContextStream; 558 559 void print(); 560 }; 561 562 #endif // SHARE_VM_CODE_DEPENDENCIES_HPP