1 /*
2 * Copyright (c) 2005, 2012, 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 *
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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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/ciMethod.hpp"
31 #include "ci/ciMethodHandle.hpp"
32 #include "classfile/systemDictionary.hpp"
33 #include "code/compressedStream.hpp"
34 #include "code/nmethod.hpp"
35 #include "utilities/growableArray.hpp"
36
37 //** Dependencies represent assertions (approximate invariants) within
38 // the runtime system, e.g. class hierarchy changes. An example is an
39 // assertion that a given method is not overridden; another example is
40 // that a type has only one concrete subtype. Compiled code which
41 // relies on such assertions must be discarded if they are overturned
42 // by changes in the runtime system. We can think of these assertions
43 // as approximate invariants, because we expect them to be overturned
44 // very infrequently. We are willing to perform expensive recovery
45 // operations when they are overturned. The benefit, of course, is
46 // performing optimistic optimizations (!) on the object code.
47 //
48 // Changes in the class hierarchy due to dynamic linking or
49 // class evolution can violate dependencies. There is enough
50 // indexing between classes and nmethods to make dependency
51 // checking reasonably efficient.
52
53 class ciEnv;
54 class nmethod;
55 class OopRecorder;
56 class xmlStream;
57 class CompileLog;
58 class DepChange;
59 class KlassDepChange;
60 class CallSiteDepChange;
61 class No_Safepoint_Verifier;
62
63 class Dependencies: public ResourceObj {
64 public:
65 // Note: In the comments on dependency types, most uses of the terms
66 // subtype and supertype are used in a "non-strict" or "inclusive"
67 // sense, and are starred to remind the reader of this fact.
68 // Strict uses of the terms use the word "proper".
69 //
70 // Specifically, every class is its own subtype* and supertype*.
71 // (This trick is easier than continually saying things like "Y is a
72 // subtype of X or X itself".)
73 //
74 // Sometimes we write X > Y to mean X is a proper supertype of Y.
75 // The notation X > {Y, Z} means X has proper subtypes Y, Z.
76 // The notation X.m > Y means that Y inherits m from X, while
77 // X.m > Y.m means Y overrides X.m. A star denotes abstractness,
78 // as *I > A, meaning (abstract) interface I is a super type of A,
79 // or A.*m > B.m, meaning B.m implements abstract method A.m.
80 //
81 // In this module, the terms "subtype" and "supertype" refer to
82 // Java-level reference type conversions, as detected by
83 // "instanceof" and performed by "checkcast" operations. The method
84 // Klass::is_subtype_of tests these relations. Note that "subtype"
85 // is richer than "subclass" (as tested by Klass::is_subclass_of),
86 // since it takes account of relations involving interface and array
87 // types.
88 //
89 // To avoid needless complexity, dependencies involving array types
90 // are not accepted. If you need to make an assertion about an
91 // array type, make the assertion about its corresponding element
92 // types. Any assertion that might change about an array type can
93 // be converted to an assertion about its element type.
94 //
95 // Most dependencies are evaluated over a "context type" CX, which
96 // stands for the set Subtypes(CX) of every Java type that is a subtype*
97 // of CX. When the system loads a new class or interface N, it is
98 // responsible for re-evaluating changed dependencies whose context
99 // type now includes N, that is, all super types of N.
100 //
101 enum DepType {
102 end_marker = 0,
103
104 // An 'evol' dependency simply notes that the contents of the
105 // method were used. If it evolves (is replaced), the nmethod
106 // must be recompiled. No other dependencies are implied.
107 evol_method,
108 FIRST_TYPE = evol_method,
109
110 // A context type CX is a leaf it if has no proper subtype.
111 leaf_type,
112
113 // An abstract class CX has exactly one concrete subtype CC.
114 abstract_with_unique_concrete_subtype,
115
116 // The type CX is purely abstract, with no concrete subtype* at all.
117 abstract_with_no_concrete_subtype,
118
119 // The concrete CX is free of concrete proper subtypes.
120 concrete_with_no_concrete_subtype,
121
122 // Given a method M1 and a context class CX, the set MM(CX, M1) of
123 // "concrete matching methods" in CX of M1 is the set of every
124 // concrete M2 for which it is possible to create an invokevirtual
125 // or invokeinterface call site that can reach either M1 or M2.
126 // That is, M1 and M2 share a name, signature, and vtable index.
127 // We wish to notice when the set MM(CX, M1) is just {M1}, or
128 // perhaps a set of two {M1,M2}, and issue dependencies on this.
129
130 // The set MM(CX, M1) can be computed by starting with any matching
131 // concrete M2 that is inherited into CX, and then walking the
132 // subtypes* of CX looking for concrete definitions.
133
134 // The parameters to this dependency are the method M1 and the
135 // context class CX. M1 must be either inherited in CX or defined
136 // in a subtype* of CX. It asserts that MM(CX, M1) is no greater
137 // than {M1}.
138 unique_concrete_method, // one unique concrete method under CX
139
140 // An "exclusive" assertion concerns two methods or subtypes, and
141 // declares that there are at most two (or perhaps later N>2)
142 // specific items that jointly satisfy the restriction.
143 // We list all items explicitly rather than just giving their
144 // count, for robustness in the face of complex schema changes.
145
146 // A context class CX (which may be either abstract or concrete)
147 // has two exclusive concrete subtypes* C1, C2 if every concrete
148 // subtype* of CX is either C1 or C2. Note that if neither C1 or C2
149 // are equal to CX, then CX itself must be abstract. But it is
150 // also possible (for example) that C1 is CX (a concrete class)
151 // and C2 is a proper subtype of C1.
152 abstract_with_exclusive_concrete_subtypes_2,
153
154 // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
155 exclusive_concrete_methods_2,
156
157 // This dependency asserts that no instances of class or it's
158 // subclasses require finalization registration.
159 no_finalizable_subclasses,
160
161 // This dependency asserts when the CallSite.target value changed.
162 call_site_target_value,
163
164 TYPE_LIMIT
165 };
166 enum {
167 LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
168
169 // handy categorizations of dependency types:
170 all_types = ((1 << TYPE_LIMIT) - 1) & ((-1) << FIRST_TYPE),
171
172 non_klass_types = (1 << call_site_target_value),
173 klass_types = all_types & ~non_klass_types,
174
175 non_ctxk_types = (1 << evol_method),
176 implicit_ctxk_types = (1 << call_site_target_value),
177 explicit_ctxk_types = all_types & ~(non_ctxk_types | implicit_ctxk_types),
178
179 max_arg_count = 3, // current maximum number of arguments (incl. ctxk)
180
181 // A "context type" is a class or interface that
182 // provides context for evaluating a dependency.
183 // When present, it is one of the arguments (dep_context_arg).
184 //
185 // If a dependency does not have a context type, there is a
186 // default context, depending on the type of the dependency.
187 // This bit signals that a default context has been compressed away.
188 default_context_type_bit = (1<<LG2_TYPE_LIMIT)
189 };
190
191 static const char* dep_name(DepType dept);
192 static int dep_args(DepType dept);
193
194 static bool is_klass_type( DepType dept) { return dept_in_mask(dept, klass_types ); }
195
196 static bool has_explicit_context_arg(DepType dept) { return dept_in_mask(dept, explicit_ctxk_types); }
197 static bool has_implicit_context_arg(DepType dept) { return dept_in_mask(dept, implicit_ctxk_types); }
198
199 static int dep_context_arg(DepType dept) { return has_explicit_context_arg(dept) ? 0 : -1; }
200 static int dep_implicit_context_arg(DepType dept) { return has_implicit_context_arg(dept) ? 0 : -1; }
201
202 static void check_valid_dependency_type(DepType dept);
203
204 // A Metadata* or object value recorded in an OopRecorder
205 class DepValue VALUE_OBJ_CLASS_SPEC {
206 private:
207 // Unique identifier of the value within the associated OopRecorder that
208 // encodes both the category of the value (0: invalid, positive: metadata, negative: object)
209 // and the index within a category specific array (metadata: index + 1, object: -(index + 1))
210 int _id;
211
212 public:
213 DepValue() : _id(0) {}
214 DepValue(OopRecorder* rec, Metadata* metadata, DepValue* candidate = NULL) {
215 assert(candidate == NULL || candidate->is_metadata(), "oops");
216 if (candidate != NULL && candidate->as_metadata(rec) == metadata) {
217 _id = candidate->_id;
218 } else {
219 _id = rec->find_index(metadata) + 1;
220 }
221 }
222 DepValue(OopRecorder* rec, jobject obj, DepValue* candidate = NULL) {
223 assert(candidate == NULL || candidate->is_object(), "oops");
224 if (candidate != NULL && candidate->as_object(rec) == obj) {
225 _id = candidate->_id;
226 } else {
227 _id = -(rec->find_index(obj) + 1);
228 }
229 }
230
231 // Used to sort values in ascending order of index() with metadata values preceding object values
232 int sort_key() const { return -_id; }
233
234 bool operator == (const DepValue& other) const { return other._id == _id; }
235
236 bool is_valid() const { return _id != 0; }
237 int index() const { assert(is_valid(), "oops"); return _id < 0 ? -(_id + 1) : _id - 1; }
238 bool is_metadata() const { assert(is_valid(), "oops"); return _id > 0; }
239 bool is_object() const { assert(is_valid(), "oops"); return _id < 0; }
240
241 Metadata* as_metadata(OopRecorder* rec) const { assert(is_metadata(), "oops"); return rec->metadata_at(index()); }
242 Klass* as_klass(OopRecorder* rec) const { assert(as_metadata(rec)->is_klass(), "oops"); return (Klass*) as_metadata(rec); }
243 Method* as_method(OopRecorder* rec) const { assert(as_metadata(rec)->is_method(), "oops"); return (Method*) as_metadata(rec); }
244 jobject as_object(OopRecorder* rec) const { assert(is_object(), "oops"); return rec->oop_at(index()); }
245 };
246
247 private:
248 // State for writing a new set of dependencies:
249 GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept))
250 GrowableArray<DepValue>* _deps[TYPE_LIMIT];
251
252 static const char* _dep_name[TYPE_LIMIT];
253 static int _dep_args[TYPE_LIMIT];
254
255 static bool dept_in_mask(DepType dept, int mask) {
256 return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
257 }
258
259 bool note_dep_seen(int dept, DepValue x) {
260 assert(dept < BitsPerInt, "oops");
261 // place metadata deps at even indexes, object deps at odd indexes
262 int x_id = x.is_metadata() ? x.index() * 2 : (x.index() * 2) + 1;
263 assert(_dep_seen != NULL, "deps must be writable");
264 int seen = _dep_seen->at_grow(x_id, 0);
265 _dep_seen->at_put(x_id, seen | (1<<dept));
266 // return true if we've already seen dept/x
267 return (seen & (1<<dept)) != 0;
268 }
269
270 bool maybe_merge_ctxk(GrowableArray<DepValue>* deps,
271 int ctxk_i, Klass* ctxk);
272
273 void sort_all_deps();
274 size_t estimate_size_in_bytes();
275
276 // Initialize _deps, etc.
277 void initialize(ciEnv* env);
278
279 // State for making a new set of dependencies:
280 OopRecorder* _oop_recorder;
281
282 // Logging support
283 CompileLog* _log;
284
285 address _content_bytes; // everything but the oop references, encoded
286 size_t _size_in_bytes;
287
288 public:
289 // Make a new empty dependencies set.
290 Dependencies(ciEnv* env) {
291 initialize(env);
292 }
293
294 private:
295 // Check for a valid context type.
296 // Enforce the restriction against array types.
297 static void check_ctxk(Klass* ctxk) {
298 assert(ctxk->oop_is_instance(), "java types only");
299 }
300 static void check_ctxk_concrete(Klass* ctxk) {
301 check_ctxk(ctxk);
302 assert(!ctxk->is_abstract(), "must be abstract");
303 }
304 static void check_ctxk_abstract(Klass* ctxk) {
305 check_ctxk(ctxk);
306 assert(ctxk->is_abstract(), "must be abstract");
307 }
308
309 void assert_common_1(DepType dept, DepValue x);
310 void assert_common_2(DepType dept, DepValue x0, DepValue x1);
311 void assert_common_3(DepType dept, Klass* ctxk, DepValue x1, DepValue x2);
312
313 public:
314 // Adding assertions to a new dependency set at compile time:
315 void assert_evol_method(Method* m);
316 void assert_leaf_type(Klass* ctxk);
317 void assert_abstract_with_unique_concrete_subtype(Klass* ctxk, Klass* conck);
318 void assert_abstract_with_no_concrete_subtype(Klass* ctxk);
319 void assert_concrete_with_no_concrete_subtype(Klass* ctxk);
320 void assert_unique_concrete_method(Klass* ctxk, Method* uniqm);
321 void assert_abstract_with_exclusive_concrete_subtypes(Klass* ctxk, Klass* k1, Klass* k2);
322 void assert_exclusive_concrete_methods(Klass* ctxk, Method* m1, Method* m2);
323 void assert_has_no_finalizable_subclasses(Klass* ctxk);
324 void assert_call_site_target_value(jobject call_site, jobject method_handle);
325
326 // Wrappers for the above in terms of ci classes:
327 void assert_evol_method(ciMethod* m) {
328 assert_evol_method(m->get_Method());
329 }
330 void assert_leaf_type(ciKlass* ctxk) {
331 assert_leaf_type(ctxk->get_Klass());
332 }
333 void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck) {
334 assert_abstract_with_unique_concrete_subtype(ctxk->get_Klass(), conck->get_Klass());
335 }
336 void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk) {
337 assert_abstract_with_no_concrete_subtype(ctxk->get_Klass());
338 }
339 void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk) {
340 assert_concrete_with_no_concrete_subtype(ctxk->get_Klass());
341 }
342 void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm) {
343 assert_unique_concrete_method(ctxk->get_Klass(), uniqm->get_Method());
344 }
345 void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2) {
346 assert_abstract_with_exclusive_concrete_subtypes(ctxk->get_Klass(), k1->get_Klass(), k2->get_Klass());
347 }
348 void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2) {
349 assert_exclusive_concrete_methods(ctxk->get_Klass(), m1->get_Method(), m2->get_Method());
350 }
351 void assert_has_no_finalizable_subclasses(ciKlass* ctxk) {
352 assert_has_no_finalizable_subclasses(ctxk->get_Klass());
353 }
354 void assert_call_site_target_value(ciCallSite* call_site, ciMethodHandle* method_handle) {
355 assert_call_site_target_value(call_site->constant_encoding(), method_handle->constant_encoding());
356 }
357
358 // Define whether a given method or type is concrete.
359 // These methods define the term "concrete" as used in this module.
360 // For this module, an "abstract" class is one which is non-concrete.
361 //
362 // Future optimizations may allow some classes to remain
363 // non-concrete until their first instantiation, and allow some
364 // methods to remain non-concrete until their first invocation.
365 // In that case, there would be a middle ground between concrete
366 // and abstract (as defined by the Java language and VM).
367 static bool is_concrete_klass(Klass* k); // k is instantiable
368 static bool is_concrete_method(Method* m); // m is invocable
369 static Klass* find_finalizable_subclass(Klass* k);
370
371 // These versions of the concreteness queries work through the CI.
372 // The CI versions are allowed to skew sometimes from the VM
373 // (oop-based) versions. The cost of such a difference is a
374 // (safely) aborted compilation, or a deoptimization, or a missed
375 // optimization opportunity.
376 //
377 // In order to prevent spurious assertions, query results must
378 // remain stable within any single ciEnv instance. (I.e., they must
379 // not go back into the VM to get their value; they must cache the
380 // bit in the CI, either eagerly or lazily.)
381 static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
382 static bool is_concrete_method(ciMethod* m); // m appears invocable
383 static bool has_finalizable_subclass(ciInstanceKlass* k);
384
385 // As a general rule, it is OK to compile under the assumption that
386 // a given type or method is concrete, even if it at some future
387 // point becomes abstract. So dependency checking is one-sided, in
388 // that it permits supposedly concrete classes or methods to turn up
389 // as really abstract. (This shouldn't happen, except during class
390 // evolution, but that's the logic of the checking.) However, if a
391 // supposedly abstract class or method suddenly becomes concrete, a
392 // dependency on it must fail.
393
394 // Checking old assertions at run-time (in the VM only):
395 static Klass* check_evol_method(Method* m);
396 static Klass* check_leaf_type(Klass* ctxk);
397 static Klass* check_abstract_with_unique_concrete_subtype(Klass* ctxk, Klass* conck,
398 KlassDepChange* changes = NULL);
399 static Klass* check_abstract_with_no_concrete_subtype(Klass* ctxk,
400 KlassDepChange* changes = NULL);
401 static Klass* check_concrete_with_no_concrete_subtype(Klass* ctxk,
402 KlassDepChange* changes = NULL);
403 static Klass* check_unique_concrete_method(Klass* ctxk, Method* uniqm,
404 KlassDepChange* changes = NULL);
405 static Klass* check_abstract_with_exclusive_concrete_subtypes(Klass* ctxk, Klass* k1, Klass* k2,
406 KlassDepChange* changes = NULL);
407 static Klass* check_exclusive_concrete_methods(Klass* ctxk, Method* m1, Method* m2,
408 KlassDepChange* changes = NULL);
409 static Klass* check_has_no_finalizable_subclasses(Klass* ctxk, KlassDepChange* changes = NULL);
410 static Klass* check_call_site_target_value(oop call_site, oop method_handle, CallSiteDepChange* changes = NULL);
411 // A returned Klass* is NULL if the dependency assertion is still
412 // valid. A non-NULL Klass* is a 'witness' to the assertion
413 // failure, a point in the class hierarchy where the assertion has
414 // been proven false. For example, if check_leaf_type returns
415 // non-NULL, the value is a subtype of the supposed leaf type. This
416 // witness value may be useful for logging the dependency failure.
417 // Note that, when a dependency fails, there may be several possible
418 // witnesses to the failure. The value returned from the check_foo
419 // method is chosen arbitrarily.
420
421 // The 'changes' value, if non-null, requests a limited spot-check
422 // near the indicated recent changes in the class hierarchy.
423 // It is used by DepStream::spot_check_dependency_at.
424
425 // Detecting possible new assertions:
426 static Klass* find_unique_concrete_subtype(Klass* ctxk);
427 static Method* find_unique_concrete_method(Klass* ctxk, Method* m);
428 static int find_exclusive_concrete_subtypes(Klass* ctxk, int klen, Klass* k[]);
429 static int find_exclusive_concrete_methods(Klass* ctxk, int mlen, Method* m[]);
430
431 // Create the encoding which will be stored in an nmethod.
432 void encode_content_bytes();
433
434 address content_bytes() {
435 assert(_content_bytes != NULL, "encode it first");
436 return _content_bytes;
437 }
438 size_t size_in_bytes() {
439 assert(_content_bytes != NULL, "encode it first");
440 return _size_in_bytes;
441 }
442
443 OopRecorder* oop_recorder() { return _oop_recorder; }
444 CompileLog* log() { return _log; }
445
446 void copy_to(nmethod* nm);
447
448 void log_all_dependencies();
449 void log_dependency(DepType dept, int nargs, DepValue args[]) {
450 write_dependency_to(log(), dept, nargs, args);
451 }
452 void log_dependency(DepType dept,
453 DepValue x0,
454 DepValue x1 = DepValue(),
455 DepValue x2 = DepValue()) {
456 if (log() == NULL) return;
457 DepValue args[max_arg_count];
458 args[0] = x0;
459 args[1] = x1;
460 args[2] = x2;
461 assert(2 < max_arg_count, "");
462 log_dependency(dept, dep_args(dept), args);
463 }
464
465 class DepArgument : public ResourceObj {
466 private:
467 bool _is_oop;
468 bool _valid;
469 void* _value;
470 public:
471 DepArgument() : _is_oop(false), _value(NULL), _valid(false) {}
472 DepArgument(oop v): _is_oop(true), _value(v), _valid(true) {}
473 DepArgument(Metadata* v): _is_oop(false), _value(v), _valid(true) {}
474
475 bool is_null() const { return _value == NULL; }
476 bool is_oop() const { return _is_oop; }
477 bool is_metadata() const { return !_is_oop; }
478 bool is_klass() const { return is_metadata() && metadata_value()->is_klass(); }
479 bool is_method() const { return is_metadata() && metadata_value()->is_method(); }
480
481 oop oop_value() const { assert(_is_oop && _valid, "must be"); return (oop) _value; }
482 Metadata* metadata_value() const { assert(!_is_oop && _valid, "must be"); return (Metadata*) _value; }
483 };
484
485 static void write_dependency_to(CompileLog* log,
486 DepType dept,
487 int nargs, ciBaseObject* args[],
488 Klass* witness = NULL);
489 static void write_dependency_to(CompileLog* log,
490 DepType dept,
491 int nargs, DepArgument args[],
492 Klass* witness = NULL);
493 void write_dependency_to(CompileLog* log,
494 DepType dept,
495 int nargs, DepValue args[],
496 Klass* witness = NULL);
497 static void write_dependency_to(xmlStream* xtty,
498 DepType dept,
499 int nargs, DepArgument args[],
500 Klass* witness = NULL);
501 static void print_dependency(DepType dept,
502 int nargs, DepArgument args[],
503 Klass* witness = NULL);
504
505 private:
506 // helper for encoding common context types as zero:
507 static Klass* ctxk_encoded_as_null(OopRecorder* oop_recorder, DepType dept, DepValue x);
508
509 static Klass* ctxk_encoded_as_null(DepType dept, Metadata* x);
510
511 public:
512 // Use this to iterate over an nmethod's dependency set.
513 // Works on new and old dependency sets.
514 // Usage:
515 //
516 // ;
517 // Dependencies::DepType dept;
518 // for (Dependencies::DepStream deps(nm); deps.next(); ) {
519 // ...
520 // }
521 //
522 // The caller must be in the VM, since oops are not wrapped in handles.
523 class DepStream {
524 private:
525 nmethod* _code; // null if in a compiler thread
526 Dependencies* _deps; // null if not in a compiler thread
527 CompressedReadStream _bytes;
528 #ifdef ASSERT
529 size_t _byte_limit;
530 #endif
531
532 // iteration variables:
533 DepType _type;
534 int _xi[max_arg_count+1];
535
536 void initial_asserts(size_t byte_limit) NOT_DEBUG({});
537
538 inline Metadata* recorded_metadata_at(int i);
539 inline oop recorded_oop_at(int i);
540
541 Klass* check_klass_dependency(KlassDepChange* changes);
542 Klass* check_call_site_dependency(CallSiteDepChange* changes);
543
544 void trace_and_log_witness(Klass* witness);
545
546 public:
547 DepStream(Dependencies* deps)
548 : _deps(deps),
549 _code(NULL),
550 _bytes(deps->content_bytes())
551 {
552 initial_asserts(deps->size_in_bytes());
553 }
554 DepStream(nmethod* code)
555 : _deps(NULL),
556 _code(code),
557 _bytes(code->dependencies_begin())
558 {
559 initial_asserts(code->dependencies_size());
560 }
561
562 bool next();
563
564 DepType type() { return _type; }
565 int argument_count() { return dep_args(type()); }
566 int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob");
567 return _xi[i]; }
568 Metadata* argument(int i); // => recorded_oop_at(argument_index(i))
569 oop argument_oop(int i); // => recorded_oop_at(argument_index(i))
570 Klass* context_type();
571
572 bool is_klass_type() { return Dependencies::is_klass_type(type()); }
573
574 Method* method_argument(int i) {
575 Metadata* x = argument(i);
576 assert(x->is_method(), "type");
577 return (Method*) x;
578 }
579 Klass* type_argument(int i) {
580 Metadata* x = argument(i);
581 assert(x->is_klass(), "type");
582 return (Klass*) x;
583 }
584
585 // The point of the whole exercise: Is this dep still OK?
586 Klass* check_dependency() {
587 Klass* result = check_klass_dependency(NULL);
588 if (result != NULL) return result;
589 return check_call_site_dependency(NULL);
590 }
591
592 // A lighter version: Checks only around recent changes in a class
593 // hierarchy. (See Universe::flush_dependents_on.)
594 Klass* spot_check_dependency_at(DepChange& changes);
595
596 // Log the current dependency to xtty or compilation log.
597 void log_dependency(Klass* witness = NULL);
598
599 // Print the current dependency to tty.
600 void print_dependency(Klass* witness = NULL, bool verbose = false);
601 };
602 friend class Dependencies::DepStream;
603
604 static void print_statistics() PRODUCT_RETURN;
605 };
606
607
608 // Every particular DepChange is a sub-class of this class.
609 class DepChange : public StackObj {
610 public:
611 // What kind of DepChange is this?
612 virtual bool is_klass_change() const { return false; }
613 virtual bool is_call_site_change() const { return false; }
614
615 // Subclass casting with assertions.
616 KlassDepChange* as_klass_change() {
617 assert(is_klass_change(), "bad cast");
618 return (KlassDepChange*) this;
619 }
620 CallSiteDepChange* as_call_site_change() {
621 assert(is_call_site_change(), "bad cast");
622 return (CallSiteDepChange*) this;
623 }
624
625 void print();
626
627 public:
628 enum ChangeType {
629 NO_CHANGE = 0, // an uninvolved klass
630 Change_new_type, // a newly loaded type
631 Change_new_sub, // a super with a new subtype
632 Change_new_impl, // an interface with a new implementation
633 CHANGE_LIMIT,
634 Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream
635 };
636
637 // Usage:
638 // for (DepChange::ContextStream str(changes); str.next(); ) {
639 // Klass* k = str.klass();
640 // switch (str.change_type()) {
641 // ...
642 // }
643 // }
644 class ContextStream : public StackObj {
645 private:
646 DepChange& _changes;
647 friend class DepChange;
648
649 // iteration variables:
650 ChangeType _change_type;
651 Klass* _klass;
652 Array<Klass*>* _ti_base; // i.e., transitive_interfaces
653 int _ti_index;
654 int _ti_limit;
655
656 // start at the beginning:
657 void start();
658
659 public:
660 ContextStream(DepChange& changes)
661 : _changes(changes)
662 { start(); }
663
664 ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
665 : _changes(changes)
666 // the nsv argument makes it safe to hold oops like _klass
667 { start(); }
668
669 bool next();
670
671 ChangeType change_type() { return _change_type; }
672 Klass* klass() { return _klass; }
673 };
674 friend class DepChange::ContextStream;
675 };
676
677
678 // A class hierarchy change coming through the VM (under the Compile_lock).
679 // The change is structured as a single new type with any number of supers
680 // and implemented interface types. Other than the new type, any of the
681 // super types can be context types for a relevant dependency, which the
682 // new type could invalidate.
683 class KlassDepChange : public DepChange {
684 private:
685 // each change set is rooted in exactly one new type (at present):
686 KlassHandle _new_type;
687
688 void initialize();
689
690 public:
691 // notes the new type, marks it and all its super-types
692 KlassDepChange(KlassHandle new_type)
693 : _new_type(new_type)
694 {
695 initialize();
696 }
697
698 // cleans up the marks
699 ~KlassDepChange();
700
701 // What kind of DepChange is this?
702 virtual bool is_klass_change() const { return true; }
703
704 Klass* new_type() { return _new_type(); }
705
706 // involves_context(k) is true if k is new_type or any of the super types
707 bool involves_context(Klass* k);
708 };
709
710
711 // A CallSite has changed its target.
712 class CallSiteDepChange : public DepChange {
713 private:
714 Handle _call_site;
715 Handle _method_handle;
716
717 public:
718 CallSiteDepChange(Handle call_site, Handle method_handle)
719 : _call_site(call_site),
720 _method_handle(method_handle)
721 {
722 assert(_call_site() ->is_a(SystemDictionary::CallSite_klass()), "must be");
723 assert(_method_handle()->is_a(SystemDictionary::MethodHandle_klass()), "must be");
724 }
725
726 // What kind of DepChange is this?
727 virtual bool is_call_site_change() const { return true; }
728
729 oop call_site() const { return _call_site(); }
730 oop method_handle() const { return _method_handle(); }
731 };
732
733 #endif // SHARE_VM_CODE_DEPENDENCIES_HPP