dependencies.hpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 2005, 2006, 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//** Dependencies represent assertions (approximate invariants) within 26// the class hierarchy. An example is an assertion that a given 27// method is not overridden; another example is that a type has only 28// one concrete subtype. Compiled code which relies on such 29// assertions must be discarded if they are overturned by changes in 30// the class hierarchy. We can think of these assertions as 31// approximate invariants, because we expect them to be overturned 32// very infrequently. We are willing to perform expensive recovery 33// operations when they are overturned. The benefit, of course, is 34// performing optimistic optimizations (!) on the object code. 35// 36// Changes in the class hierarchy due to dynamic linking or 37// class evolution can violate dependencies. There is enough 38// indexing between classes and nmethods to make dependency 39// checking reasonably efficient. 40 41class ciEnv; 42class nmethod; 43class OopRecorder; 44class xmlStream; 45class CompileLog; 46class DepChange; 47class No_Safepoint_Verifier; 48 49class Dependencies: public ResourceObj { 50 public: 51 // Note: In the comments on dependency types, most uses of the terms 52 // subtype and supertype are used in a "non-strict" or "inclusive" 53 // sense, and are starred to remind the reader of this fact. 54 // Strict uses of the terms use the word "proper". 55 // 56 // Specifically, every class is its own subtype* and supertype*. 57 // (This trick is easier than continually saying things like "Y is a 58 // subtype of X or X itself".) 59 // 60 // Sometimes we write X > Y to mean X is a proper supertype of Y. 61 // The notation X > {Y, Z} means X has proper subtypes Y, Z. 62 // The notation X.m > Y means that Y inherits m from X, while 63 // X.m > Y.m means Y overrides X.m. A star denotes abstractness, 64 // as *I > A, meaning (abstract) interface I is a super type of A, 65 // or A.*m > B.m, meaning B.m implements abstract method A.m. 66 // 67 // In this module, the terms "subtype" and "supertype" refer to 68 // Java-level reference type conversions, as detected by 69 // "instanceof" and performed by "checkcast" operations. The method 70 // Klass::is_subtype_of tests these relations. Note that "subtype" 71 // is richer than "subclass" (as tested by Klass::is_subclass_of), 72 // since it takes account of relations involving interface and array 73 // types. 74 // 75 // To avoid needless complexity, dependencies involving array types 76 // are not accepted. If you need to make an assertion about an 77 // array type, make the assertion about its corresponding element 78 // types. Any assertion that might change about an array type can 79 // be converted to an assertion about its element type. 80 // 81 // Most dependencies are evaluated over a "context type" CX, which 82 // stands for the set Subtypes(CX) of every Java type that is a subtype* 83 // of CX. When the system loads a new class or interface N, it is 84 // responsible for re-evaluating changed dependencies whose context 85 // type now includes N, that is, all super types of N. 86 // 87 enum DepType { 88 end_marker = 0, 89 90 // An 'evol' dependency simply notes that the contents of the 91 // method were used. If it evolves (is replaced), the nmethod 92 // must be recompiled. No other dependencies are implied. 93 evol_method, 94 FIRST_TYPE = evol_method, 95 96 // A context type CX is a leaf it if has no proper subtype. 97 leaf_type, 98 99 // An abstract class CX has exactly one concrete subtype CC. 100 abstract_with_unique_concrete_subtype, 101 102 // The type CX is purely abstract, with no concrete subtype* at all. 103 abstract_with_no_concrete_subtype, 104 105 // The concrete CX is free of concrete proper subtypes. 106 concrete_with_no_concrete_subtype, 107 108 // Given a method M1 and a context class CX, the set MM(CX, M1) of 109 // "concrete matching methods" in CX of M1 is the set of every 110 // concrete M2 for which it is possible to create an invokevirtual 111 // or invokeinterface call site that can reach either M1 or M2. 112 // That is, M1 and M2 share a name, signature, and vtable index. 113 // We wish to notice when the set MM(CX, M1) is just {M1}, or 114 // perhaps a set of two {M1,M2}, and issue dependencies on this. 115 116 // The set MM(CX, M1) can be computed by starting with any matching 117 // concrete M2 that is inherited into CX, and then walking the 118 // subtypes* of CX looking for concrete definitions. 119 120 // The parameters to this dependency are the method M1 and the 121 // context class CX. M1 must be either inherited in CX or defined 122 // in a subtype* of CX. It asserts that MM(CX, M1) is no greater 123 // than {M1}. 124 unique_concrete_method, // one unique concrete method under CX 125 126 // An "exclusive" assertion concerns two methods or subtypes, and 127 // declares that there are at most two (or perhaps later N>2) 128 // specific items that jointly satisfy the restriction. 129 // We list all items explicitly rather than just giving their 130 // count, for robustness in the face of complex schema changes. 131 132 // A context class CX (which may be either abstract or concrete) 133 // has two exclusive concrete subtypes* C1, C2 if every concrete 134 // subtype* of CX is either C1 or C2. Note that if neither C1 or C2 135 // are equal to CX, then CX itself must be abstract. But it is 136 // also possible (for example) that C1 is CX (a concrete class) 137 // and C2 is a proper subtype of C1. 138 abstract_with_exclusive_concrete_subtypes_2, 139 140 // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}. 141 exclusive_concrete_methods_2, 142 143 // This dependency asserts that no instances of class or it's 144 // subclasses require finalization registration. 145 no_finalizable_subclasses, 146 147 TYPE_LIMIT 148 }; 149 enum { 150 LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT)) 151 152 // handy categorizations of dependency types: 153 all_types = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE), 154 non_ctxk_types = (1<<evol_method), 155 ctxk_types = all_types & ~non_ctxk_types, 156 157 max_arg_count = 3, // current maximum number of arguments (incl. ctxk) 158 159 // A "context type" is a class or interface that 160 // provides context for evaluating a dependency. 161 // When present, it is one of the arguments (dep_context_arg). 162 // 163 // If a dependency does not have a context type, there is a 164 // default context, depending on the type of the dependency. 165 // This bit signals that a default context has been compressed away. 166 default_context_type_bit = (1<<LG2_TYPE_LIMIT) 167 }; 168 169 static const char* dep_name(DepType dept); 170 static int dep_args(DepType dept); 171 static int dep_context_arg(DepType dept) { 172 return dept_in_mask(dept, ctxk_types)? 0: -1; 173 } 174 175 private: 176 // State for writing a new set of dependencies: 177 GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept)) 178 GrowableArray<ciObject*>* _deps[TYPE_LIMIT]; 179 180 static const char* _dep_name[TYPE_LIMIT]; 181 static int _dep_args[TYPE_LIMIT]; 182 183 static bool dept_in_mask(DepType dept, int mask) { 184 return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0; 185 } 186 187 bool note_dep_seen(int dept, ciObject* x) { 188 assert(dept < BitsPerInt, "oob"); 189 int x_id = x->ident(); 190 assert(_dep_seen != NULL, "deps must be writable"); 191 int seen = _dep_seen->at_grow(x_id, 0); 192 _dep_seen->at_put(x_id, seen | (1<<dept)); 193 // return true if we've already seen dept/x 194 return (seen & (1<<dept)) != 0; 195 } 196 197 bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps, 198 int ctxk_i, ciKlass* ctxk); 199 200 void sort_all_deps(); 201 size_t estimate_size_in_bytes(); 202 203 // Initialize _deps, etc. 204 void initialize(ciEnv* env); 205 206 // State for making a new set of dependencies: 207 OopRecorder* _oop_recorder; 208 209 // Logging support 210 CompileLog* _log; 211 212 address _content_bytes; // everything but the oop references, encoded 213 size_t _size_in_bytes; 214 215 public: 216 // Make a new empty dependencies set. 217 Dependencies(ciEnv* env) { 218 initialize(env); 219 } 220 221 private: 222 // Check for a valid context type. 223 // Enforce the restriction against array types. 224 static void check_ctxk(ciKlass* ctxk) { 225 assert(ctxk->is_instance_klass(), "java types only"); 226 } 227 static void check_ctxk_concrete(ciKlass* ctxk) { 228 assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete"); 229 } 230 static void check_ctxk_abstract(ciKlass* ctxk) { 231 check_ctxk(ctxk); 232 assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract"); 233 } 234 235 void assert_common_1(DepType dept, ciObject* x); 236 void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x); 237 void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2); 238 239 public: 240 // Adding assertions to a new dependency set at compile time: 241 void assert_evol_method(ciMethod* m); 242 void assert_leaf_type(ciKlass* ctxk); 243 void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck); 244 void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk); 245 void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk); 246 void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm); 247 void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2); 248 void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2); 249 void assert_has_no_finalizable_subclasses(ciKlass* ctxk); 250 251 // Define whether a given method or type is concrete. 252 // These methods define the term "concrete" as used in this module. 253 // For this module, an "abstract" class is one which is non-concrete. 254 // 255 // Future optimizations may allow some classes to remain 256 // non-concrete until their first instantiation, and allow some 257 // methods to remain non-concrete until their first invocation. 258 // In that case, there would be a middle ground between concrete 259 // and abstract (as defined by the Java language and VM). 260 static bool is_concrete_klass(klassOop k); // k is instantiable 261 static bool is_concrete_method(methodOop m); // m is invocable 262 static Klass* find_finalizable_subclass(Klass* k); 263 264 // These versions of the concreteness queries work through the CI. 265 // The CI versions are allowed to skew sometimes from the VM 266 // (oop-based) versions. The cost of such a difference is a 267 // (safely) aborted compilation, or a deoptimization, or a missed 268 // optimization opportunity. 269 // 270 // In order to prevent spurious assertions, query results must 271 // remain stable within any single ciEnv instance. (I.e., they must 272 // not go back into the VM to get their value; they must cache the 273 // bit in the CI, either eagerly or lazily.) 274 static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable 275 static bool is_concrete_method(ciMethod* m); // m appears invocable 276 static bool has_finalizable_subclass(ciInstanceKlass* k); 277 278 // As a general rule, it is OK to compile under the assumption that 279 // a given type or method is concrete, even if it at some future 280 // point becomes abstract. So dependency checking is one-sided, in 281 // that it permits supposedly concrete classes or methods to turn up 282 // as really abstract. (This shouldn't happen, except during class 283 // evolution, but that's the logic of the checking.) However, if a 284 // supposedly abstract class or method suddenly becomes concrete, a 285 // dependency on it must fail. 286 287 // Checking old assertions at run-time (in the VM only): 288 static klassOop check_evol_method(methodOop m); 289 static klassOop check_leaf_type(klassOop ctxk); 290 static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck, 291 DepChange* changes = NULL); 292 static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk, 293 DepChange* changes = NULL); 294 static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk, 295 DepChange* changes = NULL); 296 static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm, 297 DepChange* changes = NULL); 298 static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2, 299 DepChange* changes = NULL); 300 static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2, 301 DepChange* changes = NULL); 302 static klassOop check_has_no_finalizable_subclasses(klassOop ctxk, 303 DepChange* changes = NULL); 304 // A returned klassOop is NULL if the dependency assertion is still 305 // valid. A non-NULL klassOop is a 'witness' to the assertion 306 // failure, a point in the class hierarchy where the assertion has 307 // been proven false. For example, if check_leaf_type returns 308 // non-NULL, the value is a subtype of the supposed leaf type. This 309 // witness value may be useful for logging the dependency failure. 310 // Note that, when a dependency fails, there may be several possible 311 // witnesses to the failure. The value returned from the check_foo 312 // method is chosen arbitrarily. 313 314 // The 'changes' value, if non-null, requests a limited spot-check 315 // near the indicated recent changes in the class hierarchy. 316 // It is used by DepStream::spot_check_dependency_at. 317 318 // Detecting possible new assertions: 319 static klassOop find_unique_concrete_subtype(klassOop ctxk); 320 static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m); 321 static int find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]); 322 static int find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]); 323 324 // Create the encoding which will be stored in an nmethod. 325 void encode_content_bytes(); 326 327 address content_bytes() { 328 assert(_content_bytes != NULL, "encode it first"); 329 return _content_bytes; 330 } 331 size_t size_in_bytes() { 332 assert(_content_bytes != NULL, "encode it first"); 333 return _size_in_bytes; 334 } 335 336 OopRecorder* oop_recorder() { return _oop_recorder; } 337 CompileLog* log() { return _log; } 338 339 void copy_to(nmethod* nm); 340 341 void log_all_dependencies(); 342 void log_dependency(DepType dept, int nargs, ciObject* args[]) { 343 write_dependency_to(log(), dept, nargs, args); 344 } 345 void log_dependency(DepType dept, 346 ciObject* x0, 347 ciObject* x1 = NULL, 348 ciObject* x2 = NULL) { 349 if (log() == NULL) return; 350 ciObject* args[max_arg_count]; 351 args[0] = x0; 352 args[1] = x1; 353 args[2] = x2; 354 assert(2 < max_arg_count, ""); 355 log_dependency(dept, dep_args(dept), args); 356 } 357 358 static void write_dependency_to(CompileLog* log, 359 DepType dept, 360 int nargs, ciObject* args[], 361 klassOop witness = NULL); 362 static void write_dependency_to(CompileLog* log, 363 DepType dept, 364 int nargs, oop args[], 365 klassOop witness = NULL); 366 static void write_dependency_to(xmlStream* xtty, 367 DepType dept, 368 int nargs, oop args[], 369 klassOop witness = NULL); 370 static void print_dependency(DepType dept, 371 int nargs, oop args[], 372 klassOop witness = NULL); 373 374 private: 375 // helper for encoding common context types as zero: 376 static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x); 377 378 static klassOop ctxk_encoded_as_null(DepType dept, oop x); 379 380 public: 381 // Use this to iterate over an nmethod's dependency set. 382 // Works on new and old dependency sets. 383 // Usage: 384 // 385 // ; 386 // Dependencies::DepType dept; 387 // for (Dependencies::DepStream deps(nm); deps.next(); ) { 388 // ... 389 // } 390 // 391 // The caller must be in the VM, since oops are not wrapped in handles. 392 class DepStream { 393 private: 394 nmethod* _code; // null if in a compiler thread 395 Dependencies* _deps; // null if not in a compiler thread 396 CompressedReadStream _bytes; 397#ifdef ASSERT 398 size_t _byte_limit; 399#endif 400 401 // iteration variables: 402 DepType _type; 403 int _xi[max_arg_count+1]; 404 405 void initial_asserts(size_t byte_limit) NOT_DEBUG({}); 406 407 inline oop recorded_oop_at(int i); 408 // => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i) 409 410 klassOop check_dependency_impl(DepChange* changes); 411 412 public: 413 DepStream(Dependencies* deps) 414 : _deps(deps), 415 _code(NULL), 416 _bytes(deps->content_bytes()) 417 { 418 initial_asserts(deps->size_in_bytes()); 419 } 420 DepStream(nmethod* code) 421 : _deps(NULL), 422 _code(code), 423 _bytes(code->dependencies_begin()) 424 { 425 initial_asserts(code->dependencies_size()); 426 } 427 428 bool next(); 429 430 DepType type() { return _type; } 431 int argument_count() { return dep_args(type()); } 432 int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob"); 433 return _xi[i]; } 434 oop argument(int i); // => recorded_oop_at(argument_index(i)) 435 klassOop context_type(); 436 437 methodOop method_argument(int i) { 438 oop x = argument(i); 439 assert(x->is_method(), "type"); 440 return (methodOop) x; 441 } 442 klassOop type_argument(int i) { 443 oop x = argument(i); 444 assert(x->is_klass(), "type"); 445 return (klassOop) x; 446 } 447 448 // The point of the whole exercise: Is this dep is still OK? 449 klassOop check_dependency() { 450 return check_dependency_impl(NULL); 451 } 452 // A lighter version: Checks only around recent changes in a class 453 // hierarchy. (See Universe::flush_dependents_on.) 454 klassOop spot_check_dependency_at(DepChange& changes); 455 456 // Log the current dependency to xtty or compilation log. 457 void log_dependency(klassOop witness = NULL); 458 459 // Print the current dependency to tty. 460 void print_dependency(klassOop witness = NULL, bool verbose = false); 461 }; 462 friend class Dependencies::DepStream; 463 464 static void print_statistics() PRODUCT_RETURN; 465}; 466 467// A class hierarchy change coming through the VM (under the Compile_lock). 468// The change is structured as a single new type with any number of supers 469// and implemented interface types. Other than the new type, any of the 470// super types can be context types for a relevant dependency, which the 471// new type could invalidate. 472class DepChange : public StackObj { 473 public: 474 enum ChangeType { 475 NO_CHANGE = 0, // an uninvolved klass 476 Change_new_type, // a newly loaded type 477 Change_new_sub, // a super with a new subtype 478 Change_new_impl, // an interface with a new implementation 479 CHANGE_LIMIT, 480 Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream 481 }; 482 483 private: 484 // each change set is rooted in exactly one new type (at present): 485 KlassHandle _new_type; 486 487 void initialize(); 488 489 public: 490 // notes the new type, marks it and all its super-types 491 DepChange(KlassHandle new_type) 492 : _new_type(new_type) 493 { 494 initialize(); 495 } 496 497 // cleans up the marks 498 ~DepChange(); 499 500 klassOop new_type() { return _new_type(); } 501 502 // involves_context(k) is true if k is new_type or any of the super types 503 bool involves_context(klassOop k); 504 505 // Usage: 506 // for (DepChange::ContextStream str(changes); str.next(); ) { 507 // klassOop k = str.klass(); 508 // switch (str.change_type()) { 509 // ... 510 // } 511 // } 512 class ContextStream : public StackObj { 513 private: 514 DepChange& _changes; 515 friend class DepChange; 516 517 // iteration variables: 518 ChangeType _change_type; 519 klassOop _klass; 520 objArrayOop _ti_base; // i.e., transitive_interfaces 521 int _ti_index; 522 int _ti_limit; 523 524 // start at the beginning: 525 void start() { 526 klassOop new_type = _changes.new_type(); 527 _change_type = (new_type == NULL ? NO_CHANGE: Start_Klass); 528 _klass = new_type; 529 _ti_base = NULL; 530 _ti_index = 0; 531 _ti_limit = 0; 532 } 533 534 public: 535 ContextStream(DepChange& changes) 536 : _changes(changes) 537 { start(); } 538 539 ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv) 540 : _changes(changes) 541 // the nsv argument makes it safe to hold oops like _klass 542 { start(); } 543 544 bool next(); 545 546 ChangeType change_type() { return _change_type; } 547 klassOop klass() { return _klass; } 548 }; 549 friend class DepChange::ContextStream; 550 551 void print(); 552}; 553