1 /*
2 * Copyright (c) 2005, 2011, 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
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23 */
24
25 #ifndef SHARE_VM_CODE_DEPENDENCIES_HPP
26 #define SHARE_VM_CODE_DEPENDENCIES_HPP
27
28 #include "ci/ciCallSite.hpp"
29 #include "ci/ciKlass.hpp"
30 #include "ci/ciMethodHandle.hpp"
31 #include "classfile/systemDictionary.hpp"
32 #include "code/compressedStream.hpp"
33 #include "code/nmethod.hpp"
34 #include "utilities/growableArray.hpp"
35
36 //** Dependencies represent assertions (approximate invariants) within
37 // the runtime system, e.g. class hierarchy changes. An example is an
38 // assertion that a given method is not overridden; another example is
39 // that a type has only one concrete subtype. Compiled code which
40 // relies on such assertions must be discarded if they are overturned
41 // by changes in the runtime system. We can think of these assertions
42 // as approximate invariants, because we expect them to be overturned
43 // very infrequently. We are willing to perform expensive recovery
44 // operations when they are overturned. The benefit, of course, is
45 // performing optimistic optimizations (!) on the object code.
46 //
47 // Changes in the class hierarchy due to dynamic linking or
48 // class evolution can violate dependencies. There is enough
49 // indexing between classes and nmethods to make dependency
50 // checking reasonably efficient.
51
52 class ciEnv;
53 class nmethod;
54 class OopRecorder;
55 class xmlStream;
56 class CompileLog;
57 class DepChange;
58 class KlassDepChange;
59 class CallSiteDepChange;
60 class No_Safepoint_Verifier;
61
62 class Dependencies: public ResourceObj {
63 public:
64 // Note: In the comments on dependency types, most uses of the terms
65 // subtype and supertype are used in a "non-strict" or "inclusive"
66 // sense, and are starred to remind the reader of this fact.
67 // Strict uses of the terms use the word "proper".
68 //
69 // Specifically, every class is its own subtype* and supertype*.
70 // (This trick is easier than continually saying things like "Y is a
71 // subtype of X or X itself".)
72 //
73 // Sometimes we write X > Y to mean X is a proper supertype of Y.
74 // The notation X > {Y, Z} means X has proper subtypes Y, Z.
75 // The notation X.m > Y means that Y inherits m from X, while
76 // X.m > Y.m means Y overrides X.m. A star denotes abstractness,
77 // as *I > A, meaning (abstract) interface I is a super type of A,
78 // or A.*m > B.m, meaning B.m implements abstract method A.m.
79 //
80 // In this module, the terms "subtype" and "supertype" refer to
81 // Java-level reference type conversions, as detected by
82 // "instanceof" and performed by "checkcast" operations. The method
83 // Klass::is_subtype_of tests these relations. Note that "subtype"
84 // is richer than "subclass" (as tested by Klass::is_subclass_of),
85 // since it takes account of relations involving interface and array
86 // types.
87 //
88 // To avoid needless complexity, dependencies involving array types
89 // are not accepted. If you need to make an assertion about an
90 // array type, make the assertion about its corresponding element
91 // types. Any assertion that might change about an array type can
92 // be converted to an assertion about its element type.
93 //
94 // Most dependencies are evaluated over a "context type" CX, which
95 // stands for the set Subtypes(CX) of every Java type that is a subtype*
96 // of CX. When the system loads a new class or interface N, it is
97 // responsible for re-evaluating changed dependencies whose context
98 // type now includes N, that is, all super types of N.
99 //
100 enum DepType {
101 end_marker = 0,
102
103 // An 'evol' dependency simply notes that the contents of the
104 // method were used. If it evolves (is replaced), the nmethod
105 // must be recompiled. No other dependencies are implied.
106 evol_method,
107 FIRST_TYPE = evol_method,
108
109 // A context type CX is a leaf it if has no proper subtype.
110 leaf_type,
111
112 // An abstract class CX has exactly one concrete subtype CC.
113 abstract_with_unique_concrete_subtype,
114
115 // The type CX is purely abstract, with no concrete subtype* at all.
116 abstract_with_no_concrete_subtype,
117
118 // The concrete CX is free of concrete proper subtypes.
119 concrete_with_no_concrete_subtype,
120
121 // Given a method M1 and a context class CX, the set MM(CX, M1) of
122 // "concrete matching methods" in CX of M1 is the set of every
123 // concrete M2 for which it is possible to create an invokevirtual
124 // or invokeinterface call site that can reach either M1 or M2.
125 // That is, M1 and M2 share a name, signature, and vtable index.
126 // We wish to notice when the set MM(CX, M1) is just {M1}, or
127 // perhaps a set of two {M1,M2}, and issue dependencies on this.
128
129 // The set MM(CX, M1) can be computed by starting with any matching
130 // concrete M2 that is inherited into CX, and then walking the
131 // subtypes* of CX looking for concrete definitions.
132
133 // The parameters to this dependency are the method M1 and the
134 // context class CX. M1 must be either inherited in CX or defined
135 // in a subtype* of CX. It asserts that MM(CX, M1) is no greater
136 // than {M1}.
137 unique_concrete_method, // one unique concrete method under CX
138
139 // An "exclusive" assertion concerns two methods or subtypes, and
140 // declares that there are at most two (or perhaps later N>2)
141 // specific items that jointly satisfy the restriction.
142 // We list all items explicitly rather than just giving their
143 // count, for robustness in the face of complex schema changes.
144
145 // A context class CX (which may be either abstract or concrete)
146 // has two exclusive concrete subtypes* C1, C2 if every concrete
147 // subtype* of CX is either C1 or C2. Note that if neither C1 or C2
148 // are equal to CX, then CX itself must be abstract. But it is
149 // also possible (for example) that C1 is CX (a concrete class)
150 // and C2 is a proper subtype of C1.
151 abstract_with_exclusive_concrete_subtypes_2,
152
153 // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
154 exclusive_concrete_methods_2,
155
156 // This dependency asserts that no instances of class or it's
157 // subclasses require finalization registration.
158 no_finalizable_subclasses,
159
160 // This dependency asserts when the CallSite.target value changed.
161 call_site_target_value,
162
163 TYPE_LIMIT
164 };
165 enum {
166 LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
167
168 // handy categorizations of dependency types:
169 all_types = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE),
170 non_ctxk_types = (1<<evol_method),
171 ctxk_types = all_types & ~non_ctxk_types,
172
173 max_arg_count = 3, // current maximum number of arguments (incl. ctxk)
174
175 // A "context type" is a class or interface that
176 // provides context for evaluating a dependency.
177 // When present, it is one of the arguments (dep_context_arg).
178 //
179 // If a dependency does not have a context type, there is a
180 // default context, depending on the type of the dependency.
181 // This bit signals that a default context has been compressed away.
182 default_context_type_bit = (1<<LG2_TYPE_LIMIT)
183 };
184
185 static const char* dep_name(DepType dept);
186 static int dep_args(DepType dept);
187 static int dep_context_arg(DepType dept) {
188 return dept_in_mask(dept, ctxk_types)? 0: -1;
189 }
190 static void check_valid_dependency_type(DepType dept);
191
192 private:
193 // State for writing a new set of dependencies:
194 GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept))
195 GrowableArray<ciObject*>* _deps[TYPE_LIMIT];
196
197 static const char* _dep_name[TYPE_LIMIT];
198 static int _dep_args[TYPE_LIMIT];
199
200 static bool dept_in_mask(DepType dept, int mask) {
201 return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
202 }
203
204 bool note_dep_seen(int dept, ciObject* x) {
205 assert(dept < BitsPerInt, "oob");
206 int x_id = x->ident();
207 assert(_dep_seen != NULL, "deps must be writable");
208 int seen = _dep_seen->at_grow(x_id, 0);
209 _dep_seen->at_put(x_id, seen | (1<<dept));
210 // return true if we've already seen dept/x
211 return (seen & (1<<dept)) != 0;
212 }
213
214 bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
215 int ctxk_i, ciKlass* ctxk);
216
217 void sort_all_deps();
218 size_t estimate_size_in_bytes();
219
220 // Initialize _deps, etc.
221 void initialize(ciEnv* env);
222
223 // State for making a new set of dependencies:
224 OopRecorder* _oop_recorder;
225
226 // Logging support
227 CompileLog* _log;
228
229 address _content_bytes; // everything but the oop references, encoded
230 size_t _size_in_bytes;
231
232 public:
233 // Make a new empty dependencies set.
234 Dependencies(ciEnv* env) {
235 initialize(env);
236 }
237
238 private:
239 // Check for a valid context type.
240 // Enforce the restriction against array types.
241 static void check_ctxk(ciKlass* ctxk) {
242 assert(ctxk->is_instance_klass(), "java types only");
243 }
244 static void check_ctxk_concrete(ciKlass* ctxk) {
245 assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
246 }
247 static void check_ctxk_abstract(ciKlass* ctxk) {
248 check_ctxk(ctxk);
249 assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
250 }
251
252 void assert_common_1(DepType dept, ciObject* x);
253 void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x);
254 void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2);
255
256 public:
257 // Adding assertions to a new dependency set at compile time:
258 void assert_evol_method(ciMethod* m);
259 void assert_leaf_type(ciKlass* ctxk);
260 void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
261 void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
262 void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
263 void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
264 void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
265 void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
266 void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
267 void assert_call_site_target_value(ciKlass* ctxk, ciCallSite* call_site, ciMethodHandle* method_handle);
268
269 // Define whether a given method or type is concrete.
270 // These methods define the term "concrete" as used in this module.
271 // For this module, an "abstract" class is one which is non-concrete.
272 //
273 // Future optimizations may allow some classes to remain
274 // non-concrete until their first instantiation, and allow some
275 // methods to remain non-concrete until their first invocation.
276 // In that case, there would be a middle ground between concrete
277 // and abstract (as defined by the Java language and VM).
278 static bool is_concrete_klass(klassOop k); // k is instantiable
279 static bool is_concrete_method(methodOop m); // m is invocable
280 static Klass* find_finalizable_subclass(Klass* k);
281
282 // These versions of the concreteness queries work through the CI.
283 // The CI versions are allowed to skew sometimes from the VM
284 // (oop-based) versions. The cost of such a difference is a
285 // (safely) aborted compilation, or a deoptimization, or a missed
286 // optimization opportunity.
287 //
288 // In order to prevent spurious assertions, query results must
289 // remain stable within any single ciEnv instance. (I.e., they must
290 // not go back into the VM to get their value; they must cache the
291 // bit in the CI, either eagerly or lazily.)
292 static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
293 static bool is_concrete_method(ciMethod* m); // m appears invocable
294 static bool has_finalizable_subclass(ciInstanceKlass* k);
295
296 // As a general rule, it is OK to compile under the assumption that
297 // a given type or method is concrete, even if it at some future
298 // point becomes abstract. So dependency checking is one-sided, in
299 // that it permits supposedly concrete classes or methods to turn up
300 // as really abstract. (This shouldn't happen, except during class
301 // evolution, but that's the logic of the checking.) However, if a
302 // supposedly abstract class or method suddenly becomes concrete, a
303 // dependency on it must fail.
304
305 // Checking old assertions at run-time (in the VM only):
306 static klassOop check_evol_method(methodOop m);
307 static klassOop check_leaf_type(klassOop ctxk);
308 static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck,
309 KlassDepChange* changes = NULL);
310 static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk,
311 KlassDepChange* changes = NULL);
312 static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk,
313 KlassDepChange* changes = NULL);
314 static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
315 KlassDepChange* changes = NULL);
316 static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2,
317 KlassDepChange* changes = NULL);
318 static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2,
319 KlassDepChange* changes = NULL);
320 static klassOop check_has_no_finalizable_subclasses(klassOop ctxk, KlassDepChange* changes = NULL);
321 static klassOop check_call_site_target_value(klassOop ctxk, oop call_site, oop method_handle, CallSiteDepChange* changes = NULL);
322 // A returned klassOop is NULL if the dependency assertion is still
323 // valid. A non-NULL klassOop is a 'witness' to the assertion
324 // failure, a point in the class hierarchy where the assertion has
325 // been proven false. For example, if check_leaf_type returns
326 // non-NULL, the value is a subtype of the supposed leaf type. This
327 // witness value may be useful for logging the dependency failure.
328 // Note that, when a dependency fails, there may be several possible
329 // witnesses to the failure. The value returned from the check_foo
330 // method is chosen arbitrarily.
331
332 // The 'changes' value, if non-null, requests a limited spot-check
333 // near the indicated recent changes in the class hierarchy.
334 // It is used by DepStream::spot_check_dependency_at.
335
336 // Detecting possible new assertions:
337 static klassOop find_unique_concrete_subtype(klassOop ctxk);
338 static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m);
339 static int find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]);
340 static int find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]);
341
342 // Create the encoding which will be stored in an nmethod.
343 void encode_content_bytes();
344
345 address content_bytes() {
346 assert(_content_bytes != NULL, "encode it first");
347 return _content_bytes;
348 }
349 size_t size_in_bytes() {
350 assert(_content_bytes != NULL, "encode it first");
351 return _size_in_bytes;
352 }
353
354 OopRecorder* oop_recorder() { return _oop_recorder; }
355 CompileLog* log() { return _log; }
356
357 void copy_to(nmethod* nm);
358
359 void log_all_dependencies();
360 void log_dependency(DepType dept, int nargs, ciObject* args[]) {
361 write_dependency_to(log(), dept, nargs, args);
362 }
363 void log_dependency(DepType dept,
364 ciObject* x0,
365 ciObject* x1 = NULL,
366 ciObject* x2 = NULL) {
367 if (log() == NULL) return;
368 ciObject* args[max_arg_count];
369 args[0] = x0;
370 args[1] = x1;
371 args[2] = x2;
372 assert(2 < max_arg_count, "");
373 log_dependency(dept, dep_args(dept), args);
374 }
375
376 static void write_dependency_to(CompileLog* log,
377 DepType dept,
378 int nargs, ciObject* args[],
379 klassOop witness = NULL);
380 static void write_dependency_to(CompileLog* log,
381 DepType dept,
382 int nargs, oop args[],
383 klassOop witness = NULL);
384 static void write_dependency_to(xmlStream* xtty,
385 DepType dept,
386 int nargs, oop args[],
387 klassOop witness = NULL);
388 static void print_dependency(DepType dept,
389 int nargs, oop args[],
390 klassOop witness = NULL);
391
392 private:
393 // helper for encoding common context types as zero:
394 static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x);
395
396 static klassOop ctxk_encoded_as_null(DepType dept, oop x);
397
398 public:
399 // Use this to iterate over an nmethod's dependency set.
400 // Works on new and old dependency sets.
401 // Usage:
402 //
403 // ;
404 // Dependencies::DepType dept;
405 // for (Dependencies::DepStream deps(nm); deps.next(); ) {
406 // ...
407 // }
408 //
409 // The caller must be in the VM, since oops are not wrapped in handles.
410 class DepStream {
411 private:
412 nmethod* _code; // null if in a compiler thread
413 Dependencies* _deps; // null if not in a compiler thread
414 CompressedReadStream _bytes;
415 #ifdef ASSERT
416 size_t _byte_limit;
417 #endif
418
419 // iteration variables:
420 DepType _type;
421 int _xi[max_arg_count+1];
422
423 void initial_asserts(size_t byte_limit) NOT_DEBUG({});
424
425 inline oop recorded_oop_at(int i);
426 // => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i)
427
428 klassOop check_klass_dependency(KlassDepChange* changes);
429 klassOop check_call_site_dependency(CallSiteDepChange* changes);
430
431 void trace_and_log_witness(klassOop witness);
432
433 public:
434 DepStream(Dependencies* deps)
435 : _deps(deps),
436 _code(NULL),
437 _bytes(deps->content_bytes())
438 {
439 initial_asserts(deps->size_in_bytes());
440 }
441 DepStream(nmethod* code)
442 : _deps(NULL),
443 _code(code),
444 _bytes(code->dependencies_begin())
445 {
446 initial_asserts(code->dependencies_size());
447 }
448
449 bool next();
450
451 DepType type() { return _type; }
452 int argument_count() { return dep_args(type()); }
453 int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob");
454 return _xi[i]; }
455 oop argument(int i); // => recorded_oop_at(argument_index(i))
456 klassOop context_type();
457
458 methodOop method_argument(int i) {
459 oop x = argument(i);
460 assert(x->is_method(), "type");
461 return (methodOop) x;
462 }
463 klassOop type_argument(int i) {
464 oop x = argument(i);
465 assert(x->is_klass(), "type");
466 return (klassOop) x;
467 }
468
469 // The point of the whole exercise: Is this dep still OK?
470 klassOop check_dependency() {
471 klassOop result = check_klass_dependency(NULL);
472 if (result != NULL) return result;
473 return check_call_site_dependency(NULL);
474 }
475
476 // A lighter version: Checks only around recent changes in a class
477 // hierarchy. (See Universe::flush_dependents_on.)
478 klassOop spot_check_dependency_at(DepChange& changes);
479
480 // Log the current dependency to xtty or compilation log.
481 void log_dependency(klassOop witness = NULL);
482
483 // Print the current dependency to tty.
484 void print_dependency(klassOop witness = NULL, bool verbose = false);
485 };
486 friend class Dependencies::DepStream;
487
488 static void print_statistics() PRODUCT_RETURN;
489 };
490
491
492 // Every particular DepChange is a sub-class of this class.
493 class DepChange : public StackObj {
494 public:
495 // What kind of DepChange is this?
496 virtual bool is_klass_change() const { return false; }
497 virtual bool is_call_site_change() const { return false; }
498
499 // Subclass casting with assertions.
500 KlassDepChange* as_klass_change() {
501 assert(is_klass_change(), "bad cast");
502 return (KlassDepChange*) this;
503 }
504 CallSiteDepChange* as_call_site_change() {
505 assert(is_call_site_change(), "bad cast");
506 return (CallSiteDepChange*) this;
507 }
508
509 void print();
510
511 public:
512 enum ChangeType {
513 NO_CHANGE = 0, // an uninvolved klass
514 Change_new_type, // a newly loaded type
515 Change_new_sub, // a super with a new subtype
516 Change_new_impl, // an interface with a new implementation
517 CHANGE_LIMIT,
518 Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream
519 };
520
521 // Usage:
522 // for (DepChange::ContextStream str(changes); str.next(); ) {
523 // klassOop k = str.klass();
524 // switch (str.change_type()) {
525 // ...
526 // }
527 // }
528 class ContextStream : public StackObj {
529 private:
530 DepChange& _changes;
531 friend class DepChange;
532
533 // iteration variables:
534 ChangeType _change_type;
535 klassOop _klass;
536 objArrayOop _ti_base; // i.e., transitive_interfaces
537 int _ti_index;
538 int _ti_limit;
539
540 // start at the beginning:
541 void start();
542
543 public:
544 ContextStream(DepChange& changes)
545 : _changes(changes)
546 { start(); }
547
548 ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
549 : _changes(changes)
550 // the nsv argument makes it safe to hold oops like _klass
551 { start(); }
552
553 bool next();
554
555 ChangeType change_type() { return _change_type; }
556 klassOop klass() { return _klass; }
557 };
558 friend class DepChange::ContextStream;
559 };
560
561
562 // A class hierarchy change coming through the VM (under the Compile_lock).
563 // The change is structured as a single new type with any number of supers
564 // and implemented interface types. Other than the new type, any of the
565 // super types can be context types for a relevant dependency, which the
566 // new type could invalidate.
567 class KlassDepChange : public DepChange {
568 private:
569 // each change set is rooted in exactly one new type (at present):
570 KlassHandle _new_type;
571
572 void initialize();
573
574 public:
575 // notes the new type, marks it and all its super-types
576 KlassDepChange(KlassHandle new_type)
577 : _new_type(new_type)
578 {
579 initialize();
580 }
581
582 // cleans up the marks
583 ~KlassDepChange();
584
585 // What kind of DepChange is this?
586 virtual bool is_klass_change() const { return true; }
587
588 klassOop new_type() { return _new_type(); }
589
590 // involves_context(k) is true if k is new_type or any of the super types
591 bool involves_context(klassOop k);
592 };
593
594
595 // A CallSite has changed its target.
596 class CallSiteDepChange : public DepChange {
597 private:
598 Handle _call_site;
599 Handle _method_handle;
600
601 public:
602 CallSiteDepChange(Handle call_site, Handle method_handle)
603 : _call_site(call_site),
604 _method_handle(method_handle)
605 {
606 assert(_call_site() ->is_a(SystemDictionary::CallSite_klass()), "must be");
607 assert(_method_handle()->is_a(SystemDictionary::MethodHandle_klass()), "must be");
608 }
609
610 // What kind of DepChange is this?
611 virtual bool is_call_site_change() const { return true; }
612
613 oop call_site() const { return _call_site(); }
614 oop method_handle() const { return _method_handle(); }
615 };
616
617 #endif // SHARE_VM_CODE_DEPENDENCIES_HPP