1 /*
   2  * Copyright (c) 2005, 2018, 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/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 "memory/resourceArea.hpp"
  35 #include "utilities/growableArray.hpp"
  36 #include "utilities/hashtable.hpp"
  37 
  38 //** Dependencies represent assertions (approximate invariants) within
  39 // the runtime system, e.g. class hierarchy changes.  An example is an
  40 // assertion that a given method is not overridden; another example is
  41 // that a type has only one concrete subtype.  Compiled code which
  42 // relies on such assertions must be discarded if they are overturned
  43 // by changes in the runtime system.  We can think of these assertions
  44 // as approximate invariants, because we expect them to be overturned
  45 // very infrequently.  We are willing to perform expensive recovery
  46 // operations when they are overturned.  The benefit, of course, is
  47 // performing optimistic optimizations (!) on the object code.
  48 //
  49 // Changes in the class hierarchy due to dynamic linking or
  50 // class evolution can violate dependencies.  There is enough
  51 // indexing between classes and nmethods to make dependency
  52 // checking reasonably efficient.
  53 
  54 class ciEnv;
  55 class nmethod;
  56 class OopRecorder;
  57 class xmlStream;
  58 class CompileLog;
  59 class DepChange;
  60 class   KlassDepChange;
  61 class   CallSiteDepChange;
  62 class NoSafepointVerifier;
  63 
  64 class Dependencies: public ResourceObj {
  65  public:
  66   // Note: In the comments on dependency types, most uses of the terms
  67   // subtype and supertype are used in a "non-strict" or "inclusive"
  68   // sense, and are starred to remind the reader of this fact.
  69   // Strict uses of the terms use the word "proper".
  70   //
  71   // Specifically, every class is its own subtype* and supertype*.
  72   // (This trick is easier than continually saying things like "Y is a
  73   // subtype of X or X itself".)
  74   //
  75   // Sometimes we write X > Y to mean X is a proper supertype of Y.
  76   // The notation X > {Y, Z} means X has proper subtypes Y, Z.
  77   // The notation X.m > Y means that Y inherits m from X, while
  78   // X.m > Y.m means Y overrides X.m.  A star denotes abstractness,
  79   // as *I > A, meaning (abstract) interface I is a super type of A,
  80   // or A.*m > B.m, meaning B.m implements abstract method A.m.
  81   //
  82   // In this module, the terms "subtype" and "supertype" refer to
  83   // Java-level reference type conversions, as detected by
  84   // "instanceof" and performed by "checkcast" operations.  The method
  85   // Klass::is_subtype_of tests these relations.  Note that "subtype"
  86   // is richer than "subclass" (as tested by Klass::is_subclass_of),
  87   // since it takes account of relations involving interface and array
  88   // types.
  89   //
  90   // To avoid needless complexity, dependencies involving array types
  91   // are not accepted.  If you need to make an assertion about an
  92   // array type, make the assertion about its corresponding element
  93   // types.  Any assertion that might change about an array type can
  94   // be converted to an assertion about its element type.
  95   //
  96   // Most dependencies are evaluated over a "context type" CX, which
  97   // stands for the set Subtypes(CX) of every Java type that is a subtype*
  98   // of CX.  When the system loads a new class or interface N, it is
  99   // responsible for re-evaluating changed dependencies whose context
 100   // type now includes N, that is, all super types of N.
 101   //
 102   enum DepType {
 103     end_marker = 0,
 104 
 105     // An 'evol' dependency simply notes that the contents of the
 106     // method were used.  If it evolves (is replaced), the nmethod
 107     // must be recompiled.  No other dependencies are implied.
 108     evol_method,
 109     FIRST_TYPE = evol_method,
 110 
 111     // A context type CX is a leaf it if has no proper subtype.
 112     leaf_type,
 113 
 114     // An abstract class CX has exactly one concrete subtype CC.
 115     abstract_with_unique_concrete_subtype,
 116 
 117     // The type CX is purely abstract, with no concrete subtype* at all.
 118     abstract_with_no_concrete_subtype,
 119 
 120     // The concrete CX is free of concrete proper subtypes.
 121     concrete_with_no_concrete_subtype,
 122 
 123     // Given a method M1 and a context class CX, the set MM(CX, M1) of
 124     // "concrete matching methods" in CX of M1 is the set of every
 125     // concrete M2 for which it is possible to create an invokevirtual
 126     // or invokeinterface call site that can reach either M1 or M2.
 127     // That is, M1 and M2 share a name, signature, and vtable index.
 128     // We wish to notice when the set MM(CX, M1) is just {M1}, or
 129     // perhaps a set of two {M1,M2}, and issue dependencies on this.
 130 
 131     // The set MM(CX, M1) can be computed by starting with any matching
 132     // concrete M2 that is inherited into CX, and then walking the
 133     // subtypes* of CX looking for concrete definitions.
 134 
 135     // The parameters to this dependency are the method M1 and the
 136     // context class CX.  M1 must be either inherited in CX or defined
 137     // in a subtype* of CX.  It asserts that MM(CX, M1) is no greater
 138     // than {M1}.
 139     unique_concrete_method,       // one unique concrete method under CX
 140 
 141     // An "exclusive" assertion concerns two methods or subtypes, and
 142     // declares that there are at most two (or perhaps later N>2)
 143     // specific items that jointly satisfy the restriction.
 144     // We list all items explicitly rather than just giving their
 145     // count, for robustness in the face of complex schema changes.
 146 
 147     // A context class CX (which may be either abstract or concrete)
 148     // has two exclusive concrete subtypes* C1, C2 if every concrete
 149     // subtype* of CX is either C1 or C2.  Note that if neither C1 or C2
 150     // are equal to CX, then CX itself must be abstract.  But it is
 151     // also possible (for example) that C1 is CX (a concrete class)
 152     // and C2 is a proper subtype of C1.
 153     abstract_with_exclusive_concrete_subtypes_2,
 154 
 155     // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
 156     exclusive_concrete_methods_2,
 157 
 158     // This dependency asserts that no instances of class or it's
 159     // subclasses require finalization registration.
 160     no_finalizable_subclasses,
 161 
 162     // This dependency asserts when the CallSite.target value changed.
 163     call_site_target_value,
 164 
 165     TYPE_LIMIT
 166   };
 167   enum {
 168     LG2_TYPE_LIMIT = 4,  // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
 169 
 170     // handy categorizations of dependency types:
 171     all_types           = ((1 << TYPE_LIMIT) - 1) & ((~0u) << FIRST_TYPE),
 172 
 173     non_klass_types     = (1 << call_site_target_value),
 174     klass_types         = all_types & ~non_klass_types,
 175 
 176     non_ctxk_types      = (1 << evol_method) | (1 << call_site_target_value),
 177     implicit_ctxk_types = 0,
 178     explicit_ctxk_types = all_types & ~(non_ctxk_types | implicit_ctxk_types),
 179 
 180     max_arg_count = 3,   // current maximum number of arguments (incl. ctxk)
 181 
 182     // A "context type" is a class or interface that
 183     // provides context for evaluating a dependency.
 184     // When present, it is one of the arguments (dep_context_arg).
 185     //
 186     // If a dependency does not have a context type, there is a
 187     // default context, depending on the type of the dependency.
 188     // This bit signals that a default context has been compressed away.
 189     default_context_type_bit = (1<<LG2_TYPE_LIMIT)
 190   };
 191 
 192   static const char* dep_name(DepType dept);
 193   static int         dep_args(DepType dept);
 194 
 195   static bool is_klass_type(           DepType dept) { return dept_in_mask(dept, klass_types        ); }
 196 
 197   static bool has_explicit_context_arg(DepType dept) { return dept_in_mask(dept, explicit_ctxk_types); }
 198   static bool has_implicit_context_arg(DepType dept) { return dept_in_mask(dept, implicit_ctxk_types); }
 199 
 200   static int           dep_context_arg(DepType dept) { return has_explicit_context_arg(dept) ? 0 : -1; }
 201   static int  dep_implicit_context_arg(DepType dept) { return has_implicit_context_arg(dept) ? 0 : -1; }
 202 
 203   static void check_valid_dependency_type(DepType dept);
 204 
 205 #if INCLUDE_JVMCI
 206   // A Metadata* or object value recorded in an OopRecorder
 207   class DepValue {
 208    private:
 209     // Unique identifier of the value within the associated OopRecorder that
 210     // encodes both the category of the value (0: invalid, positive: metadata, negative: object)
 211     // and the index within a category specific array (metadata: index + 1, object: -(index + 1))
 212     int _id;
 213 
 214    public:
 215     DepValue() : _id(0) {}
 216     DepValue(OopRecorder* rec, Metadata* metadata, DepValue* candidate = NULL) {
 217       assert(candidate == NULL || candidate->is_metadata(), "oops");
 218       if (candidate != NULL && candidate->as_metadata(rec) == metadata) {
 219         _id = candidate->_id;
 220       } else {
 221         _id = rec->find_index(metadata) + 1;
 222       }
 223     }
 224     DepValue(OopRecorder* rec, jobject obj, DepValue* candidate = NULL) {
 225       assert(candidate == NULL || candidate->is_object(), "oops");
 226       if (candidate != NULL && candidate->as_object(rec) == obj) {
 227         _id = candidate->_id;
 228       } else {
 229         _id = -(rec->find_index(obj) + 1);
 230       }
 231     }
 232 
 233     // Used to sort values in ascending order of index() with metadata values preceding object values
 234     int sort_key() const { return -_id; }
 235 
 236     bool operator == (const DepValue& other) const   { return other._id == _id; }
 237 
 238     bool is_valid() const             { return _id != 0; }
 239     int  index() const                { assert(is_valid(), "oops"); return _id < 0 ? -(_id + 1) : _id - 1; }
 240     bool is_metadata() const          { assert(is_valid(), "oops"); return _id > 0; }
 241     bool is_object() const            { assert(is_valid(), "oops"); return _id < 0; }
 242 
 243     Metadata*  as_metadata(OopRecorder* rec) const    { assert(is_metadata(), "oops"); return rec->metadata_at(index()); }
 244     Klass*     as_klass(OopRecorder* rec) const {
 245       Metadata* m = as_metadata(rec);
 246       assert(m != NULL, "as_metadata returned NULL");
 247       assert(m->is_klass(), "oops");
 248       return (Klass*) m;
 249     }
 250     Method*    as_method(OopRecorder* rec) const {
 251       Metadata* m = as_metadata(rec);
 252       assert(m != NULL, "as_metadata returned NULL");
 253       assert(m->is_method(), "oops");
 254       return (Method*) m;
 255     }
 256     jobject    as_object(OopRecorder* rec) const      { assert(is_object(), "oops"); return rec->oop_at(index()); }
 257   };
 258 #endif // INCLUDE_JVMCI
 259 
 260  private:
 261   // State for writing a new set of dependencies:
 262   GrowableArray<int>*       _dep_seen;  // (seen[h->ident] & (1<<dept))
 263   GrowableArray<ciBaseObject*>*  _deps[TYPE_LIMIT];
 264 #if INCLUDE_JVMCI
 265   bool _using_dep_values;
 266   GrowableArray<DepValue>*  _dep_values[TYPE_LIMIT];
 267 #endif
 268 
 269   static const char* _dep_name[TYPE_LIMIT];
 270   static int         _dep_args[TYPE_LIMIT];
 271 
 272   static bool dept_in_mask(DepType dept, int mask) {
 273     return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
 274   }
 275 
 276   bool note_dep_seen(int dept, ciBaseObject* x) {
 277     assert(dept < BitsPerInt, "oob");
 278     int x_id = x->ident();
 279     assert(_dep_seen != NULL, "deps must be writable");
 280     int seen = _dep_seen->at_grow(x_id, 0);
 281     _dep_seen->at_put(x_id, seen | (1<<dept));
 282     // return true if we've already seen dept/x
 283     return (seen & (1<<dept)) != 0;
 284   }
 285 
 286 #if INCLUDE_JVMCI
 287   bool note_dep_seen(int dept, DepValue x) {
 288     assert(dept < BitsPerInt, "oops");
 289     // place metadata deps at even indexes, object deps at odd indexes
 290     int x_id = x.is_metadata() ? x.index() * 2 : (x.index() * 2) + 1;
 291     assert(_dep_seen != NULL, "deps must be writable");
 292     int seen = _dep_seen->at_grow(x_id, 0);
 293     _dep_seen->at_put(x_id, seen | (1<<dept));
 294     // return true if we've already seen dept/x
 295     return (seen & (1<<dept)) != 0;
 296   }
 297 #endif
 298 
 299   bool maybe_merge_ctxk(GrowableArray<ciBaseObject*>* deps,
 300                         int ctxk_i, ciKlass* ctxk);
 301 #if INCLUDE_JVMCI
 302   bool maybe_merge_ctxk(GrowableArray<DepValue>* deps,
 303                         int ctxk_i, DepValue ctxk);
 304 #endif
 305 
 306   void sort_all_deps();
 307   size_t estimate_size_in_bytes();
 308 
 309   // Initialize _deps, etc.
 310   void initialize(ciEnv* env);
 311 
 312   // State for making a new set of dependencies:
 313   OopRecorder* _oop_recorder;
 314 
 315   // Logging support
 316   CompileLog* _log;
 317 
 318   address  _content_bytes;  // everything but the oop references, encoded
 319   size_t   _size_in_bytes;
 320 
 321  public:
 322   // Make a new empty dependencies set.
 323   Dependencies(ciEnv* env) {
 324     initialize(env);
 325   }
 326 #if INCLUDE_JVMCI
 327   Dependencies(Arena* arena, OopRecorder* oop_recorder, CompileLog* log);
 328 #endif
 329 
 330  private:
 331   // Check for a valid context type.
 332   // Enforce the restriction against array types.
 333   static void check_ctxk(ciKlass* ctxk) {
 334     assert(ctxk->is_instance_klass(), "java types only");
 335   }
 336   static void check_ctxk_concrete(ciKlass* ctxk) {
 337     assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
 338   }
 339   static void check_ctxk_abstract(ciKlass* ctxk) {
 340     check_ctxk(ctxk);
 341     assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
 342   }
 343 
 344   void assert_common_1(DepType dept, ciBaseObject* x);
 345   void assert_common_2(DepType dept, ciBaseObject* x0, ciBaseObject* x1);
 346   void assert_common_3(DepType dept, ciKlass* ctxk, ciBaseObject* x1, ciBaseObject* x2);
 347 
 348  public:
 349   // Adding assertions to a new dependency set at compile time:
 350   void assert_evol_method(ciMethod* m);
 351   void assert_leaf_type(ciKlass* ctxk);
 352   void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
 353   void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
 354   void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
 355   void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
 356   void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
 357   void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
 358   void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
 359   void assert_call_site_target_value(ciCallSite* call_site, ciMethodHandle* method_handle);
 360 
 361 #if INCLUDE_JVMCI
 362  private:
 363   static void check_ctxk(Klass* ctxk) {
 364     assert(ctxk->is_instance_klass(), "java types only");
 365   }
 366   static void check_ctxk_abstract(Klass* ctxk) {
 367     check_ctxk(ctxk);
 368     assert(ctxk->is_abstract(), "must be abstract");
 369   }
 370   void assert_common_1(DepType dept, DepValue x);
 371   void assert_common_2(DepType dept, DepValue x0, DepValue x1);
 372 
 373  public:
 374   void assert_evol_method(Method* m);
 375   void assert_has_no_finalizable_subclasses(Klass* ctxk);
 376   void assert_leaf_type(Klass* ctxk);
 377   void assert_unique_concrete_method(Klass* ctxk, Method* uniqm);
 378   void assert_abstract_with_unique_concrete_subtype(Klass* ctxk, Klass* conck);
 379   void assert_call_site_target_value(oop callSite, oop methodHandle);
 380 #endif // INCLUDE_JVMCI
 381 
 382   // Define whether a given method or type is concrete.
 383   // These methods define the term "concrete" as used in this module.
 384   // For this module, an "abstract" class is one which is non-concrete.
 385   //
 386   // Future optimizations may allow some classes to remain
 387   // non-concrete until their first instantiation, and allow some
 388   // methods to remain non-concrete until their first invocation.
 389   // In that case, there would be a middle ground between concrete
 390   // and abstract (as defined by the Java language and VM).
 391   static bool is_concrete_klass(Klass* k);    // k is instantiable
 392   static bool is_concrete_method(Method* m, Klass* k);  // m is invocable
 393   static Klass* find_finalizable_subclass(Klass* k);
 394 
 395   // These versions of the concreteness queries work through the CI.
 396   // The CI versions are allowed to skew sometimes from the VM
 397   // (oop-based) versions.  The cost of such a difference is a
 398   // (safely) aborted compilation, or a deoptimization, or a missed
 399   // optimization opportunity.
 400   //
 401   // In order to prevent spurious assertions, query results must
 402   // remain stable within any single ciEnv instance.  (I.e., they must
 403   // not go back into the VM to get their value; they must cache the
 404   // bit in the CI, either eagerly or lazily.)
 405   static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
 406   static bool has_finalizable_subclass(ciInstanceKlass* k);
 407 
 408   // As a general rule, it is OK to compile under the assumption that
 409   // a given type or method is concrete, even if it at some future
 410   // point becomes abstract.  So dependency checking is one-sided, in
 411   // that it permits supposedly concrete classes or methods to turn up
 412   // as really abstract.  (This shouldn't happen, except during class
 413   // evolution, but that's the logic of the checking.)  However, if a
 414   // supposedly abstract class or method suddenly becomes concrete, a
 415   // dependency on it must fail.
 416 
 417   // Checking old assertions at run-time (in the VM only):
 418   static Klass* check_evol_method(Method* m);
 419   static Klass* check_leaf_type(Klass* ctxk);
 420   static Klass* check_abstract_with_unique_concrete_subtype(Klass* ctxk, Klass* conck,
 421                                                               KlassDepChange* changes = NULL);
 422   static Klass* check_abstract_with_no_concrete_subtype(Klass* ctxk,
 423                                                           KlassDepChange* changes = NULL);
 424   static Klass* check_concrete_with_no_concrete_subtype(Klass* ctxk,
 425                                                           KlassDepChange* changes = NULL);
 426   static Klass* check_unique_concrete_method(Klass* ctxk, Method* uniqm,
 427                                                KlassDepChange* changes = NULL);
 428   static Klass* check_abstract_with_exclusive_concrete_subtypes(Klass* ctxk, Klass* k1, Klass* k2,
 429                                                                   KlassDepChange* changes = NULL);
 430   static Klass* check_exclusive_concrete_methods(Klass* ctxk, Method* m1, Method* m2,
 431                                                    KlassDepChange* changes = NULL);
 432   static Klass* check_has_no_finalizable_subclasses(Klass* ctxk, KlassDepChange* changes = NULL);
 433   static Klass* check_call_site_target_value(oop call_site, oop method_handle, CallSiteDepChange* changes = NULL);
 434   // A returned Klass* is NULL if the dependency assertion is still
 435   // valid.  A non-NULL Klass* is a 'witness' to the assertion
 436   // failure, a point in the class hierarchy where the assertion has
 437   // been proven false.  For example, if check_leaf_type returns
 438   // non-NULL, the value is a subtype of the supposed leaf type.  This
 439   // witness value may be useful for logging the dependency failure.
 440   // Note that, when a dependency fails, there may be several possible
 441   // witnesses to the failure.  The value returned from the check_foo
 442   // method is chosen arbitrarily.
 443 
 444   // The 'changes' value, if non-null, requests a limited spot-check
 445   // near the indicated recent changes in the class hierarchy.
 446   // It is used by DepStream::spot_check_dependency_at.
 447 
 448   // Detecting possible new assertions:
 449   static Klass*    find_unique_concrete_subtype(Klass* ctxk);
 450   static Method*   find_unique_concrete_method(Klass* ctxk, Method* m);
 451   static int       find_exclusive_concrete_subtypes(Klass* ctxk, int klen, Klass* k[]);
 452 
 453   // Create the encoding which will be stored in an nmethod.
 454   void encode_content_bytes();
 455 
 456   address content_bytes() {
 457     assert(_content_bytes != NULL, "encode it first");
 458     return _content_bytes;
 459   }
 460   size_t size_in_bytes() {
 461     assert(_content_bytes != NULL, "encode it first");
 462     return _size_in_bytes;
 463   }
 464 
 465   OopRecorder* oop_recorder() { return _oop_recorder; }
 466   CompileLog*  log()          { return _log; }
 467 
 468   void copy_to(nmethod* nm);
 469 
 470   DepType validate_dependencies(CompileTask* task, bool counter_changed, char** failure_detail = NULL);
 471 
 472   void log_all_dependencies();
 473 
 474   void log_dependency(DepType dept, GrowableArray<ciBaseObject*>* args) {
 475     ResourceMark rm;
 476     int argslen = args->length();
 477     write_dependency_to(log(), dept, args);
 478     guarantee(argslen == args->length(),
 479               "args array cannot grow inside nested ResoureMark scope");
 480   }
 481 
 482   void log_dependency(DepType dept,
 483                       ciBaseObject* x0,
 484                       ciBaseObject* x1 = NULL,
 485                       ciBaseObject* x2 = NULL) {
 486     if (log() == NULL) {
 487       return;
 488     }
 489     ResourceMark rm;
 490     GrowableArray<ciBaseObject*>* ciargs =
 491                 new GrowableArray<ciBaseObject*>(dep_args(dept));
 492     assert (x0 != NULL, "no log x0");
 493     ciargs->push(x0);
 494 
 495     if (x1 != NULL) {
 496       ciargs->push(x1);
 497     }
 498     if (x2 != NULL) {
 499       ciargs->push(x2);
 500     }
 501     assert(ciargs->length() == dep_args(dept), "");
 502     log_dependency(dept, ciargs);
 503   }
 504 
 505   class DepArgument : public ResourceObj {
 506    private:
 507     bool  _is_oop;
 508     bool  _valid;
 509     void* _value;
 510    public:
 511     DepArgument() : _is_oop(false), _value(NULL), _valid(false) {}
 512     DepArgument(oop v): _is_oop(true), _value(v), _valid(true) {}
 513     DepArgument(Metadata* v): _is_oop(false), _value(v), _valid(true) {}
 514 
 515     bool is_null() const               { return _value == NULL; }
 516     bool is_oop() const                { return _is_oop; }
 517     bool is_metadata() const           { return !_is_oop; }
 518     bool is_klass() const              { return is_metadata() && metadata_value()->is_klass(); }
 519     bool is_method() const              { return is_metadata() && metadata_value()->is_method(); }
 520 
 521     oop oop_value() const              { assert(_is_oop && _valid, "must be"); return (oop) _value; }
 522     Metadata* metadata_value() const { assert(!_is_oop && _valid, "must be"); return (Metadata*) _value; }
 523   };
 524 
 525   static void print_dependency(DepType dept,
 526                                GrowableArray<DepArgument>* args,
 527                                Klass* witness = NULL, outputStream* st = tty);
 528 
 529  private:
 530   // helper for encoding common context types as zero:
 531   static ciKlass* ctxk_encoded_as_null(DepType dept, ciBaseObject* x);
 532 
 533   static Klass* ctxk_encoded_as_null(DepType dept, Metadata* x);
 534 
 535   static void write_dependency_to(CompileLog* log,
 536                                   DepType dept,
 537                                   GrowableArray<ciBaseObject*>* args,
 538                                   Klass* witness = NULL);
 539   static void write_dependency_to(CompileLog* log,
 540                                   DepType dept,
 541                                   GrowableArray<DepArgument>* args,
 542                                   Klass* witness = NULL);
 543   static void write_dependency_to(xmlStream* xtty,
 544                                   DepType dept,
 545                                   GrowableArray<DepArgument>* args,
 546                                   Klass* witness = NULL);
 547  public:
 548   // Use this to iterate over an nmethod's dependency set.
 549   // Works on new and old dependency sets.
 550   // Usage:
 551   //
 552   // ;
 553   // Dependencies::DepType dept;
 554   // for (Dependencies::DepStream deps(nm); deps.next(); ) {
 555   //   ...
 556   // }
 557   //
 558   // The caller must be in the VM, since oops are not wrapped in handles.
 559   class DepStream {
 560   private:
 561     nmethod*              _code;   // null if in a compiler thread
 562     Dependencies*         _deps;   // null if not in a compiler thread
 563     CompressedReadStream  _bytes;
 564 #ifdef ASSERT
 565     size_t                _byte_limit;
 566 #endif
 567 
 568     // iteration variables:
 569     DepType               _type;
 570     int                   _xi[max_arg_count+1];
 571 
 572     void initial_asserts(size_t byte_limit) NOT_DEBUG({});
 573 
 574     inline Metadata* recorded_metadata_at(int i);
 575     inline oop recorded_oop_at(int i);
 576 
 577     Klass* check_klass_dependency(KlassDepChange* changes);
 578     Klass* check_call_site_dependency(CallSiteDepChange* changes);
 579 
 580     void trace_and_log_witness(Klass* witness);
 581 
 582   public:
 583     DepStream(Dependencies* deps)
 584       : _deps(deps),
 585         _code(NULL),
 586         _bytes(deps->content_bytes())
 587     {
 588       initial_asserts(deps->size_in_bytes());
 589     }
 590     DepStream(nmethod* code)
 591       : _deps(NULL),
 592         _code(code),
 593         _bytes(code->dependencies_begin())
 594     {
 595       initial_asserts(code->dependencies_size());
 596     }
 597 
 598     bool next();
 599 
 600     DepType type()               { return _type; }
 601     bool is_oop_argument(int i)  { return type() == call_site_target_value; }
 602     uintptr_t get_identifier(int i);
 603 
 604     int argument_count()         { return dep_args(type()); }
 605     int argument_index(int i)    { assert(0 <= i && i < argument_count(), "oob");
 606                                    return _xi[i]; }
 607     Metadata* argument(int i);     // => recorded_oop_at(argument_index(i))
 608     oop argument_oop(int i);         // => recorded_oop_at(argument_index(i))
 609     Klass* context_type();
 610 
 611     bool is_klass_type()         { return Dependencies::is_klass_type(type()); }
 612 
 613     Method* method_argument(int i) {
 614       Metadata* x = argument(i);
 615       assert(x->is_method(), "type");
 616       return (Method*) x;
 617     }
 618     Klass* type_argument(int i) {
 619       Metadata* x = argument(i);
 620       assert(x->is_klass(), "type");
 621       return (Klass*) x;
 622     }
 623 
 624     // The point of the whole exercise:  Is this dep still OK?
 625     Klass* check_dependency() {
 626       Klass* result = check_klass_dependency(NULL);
 627       if (result != NULL)  return result;
 628       return check_call_site_dependency(NULL);
 629     }
 630 
 631     // A lighter version:  Checks only around recent changes in a class
 632     // hierarchy.  (See Universe::flush_dependents_on.)
 633     Klass* spot_check_dependency_at(DepChange& changes);
 634 
 635     // Log the current dependency to xtty or compilation log.
 636     void log_dependency(Klass* witness = NULL);
 637 
 638     // Print the current dependency to tty.
 639     void print_dependency(Klass* witness = NULL, bool verbose = false, outputStream* st = tty);
 640   };
 641   friend class Dependencies::DepStream;
 642 
 643   static void print_statistics() PRODUCT_RETURN;
 644 };
 645 
 646 
 647 class DependencySignature : public ResourceObj {
 648  private:
 649   int                   _args_count;
 650   uintptr_t             _argument_hash[Dependencies::max_arg_count];
 651   Dependencies::DepType _type;
 652 
 653  public:
 654   DependencySignature(Dependencies::DepStream& dep) {
 655     _args_count = dep.argument_count();
 656     _type = dep.type();
 657     for (int i = 0; i < _args_count; i++) {
 658       _argument_hash[i] = dep.get_identifier(i);
 659     }
 660   }
 661 
 662   static bool     equals(DependencySignature const& s1, DependencySignature const& s2);
 663   static unsigned hash  (DependencySignature const& s1) { return s1.arg(0) >> 2; }
 664 
 665   int args_count()             const { return _args_count; }
 666   uintptr_t arg(int idx)       const { return _argument_hash[idx]; }
 667   Dependencies::DepType type() const { return _type; }
 668 
 669 };
 670 
 671 
 672 // Every particular DepChange is a sub-class of this class.
 673 class DepChange : public StackObj {
 674  public:
 675   // What kind of DepChange is this?
 676   virtual bool is_klass_change()     const { return false; }
 677   virtual bool is_call_site_change() const { return false; }
 678 
 679   virtual void mark_for_deoptimization(nmethod* nm) = 0;
 680 
 681   // Subclass casting with assertions.
 682   KlassDepChange*    as_klass_change() {
 683     assert(is_klass_change(), "bad cast");
 684     return (KlassDepChange*) this;
 685   }
 686   CallSiteDepChange* as_call_site_change() {
 687     assert(is_call_site_change(), "bad cast");
 688     return (CallSiteDepChange*) this;
 689   }
 690 
 691   void print();
 692 
 693  public:
 694   enum ChangeType {
 695     NO_CHANGE = 0,              // an uninvolved klass
 696     Change_new_type,            // a newly loaded type
 697     Change_new_sub,             // a super with a new subtype
 698     Change_new_impl,            // an interface with a new implementation
 699     CHANGE_LIMIT,
 700     Start_Klass = CHANGE_LIMIT  // internal indicator for ContextStream
 701   };
 702 
 703   // Usage:
 704   // for (DepChange::ContextStream str(changes); str.next(); ) {
 705   //   Klass* k = str.klass();
 706   //   switch (str.change_type()) {
 707   //     ...
 708   //   }
 709   // }
 710   class ContextStream : public StackObj {
 711    private:
 712     DepChange&  _changes;
 713     friend class DepChange;
 714 
 715     // iteration variables:
 716     ChangeType  _change_type;
 717     Klass*      _klass;
 718     Array<Klass*>* _ti_base;    // i.e., transitive_interfaces
 719     int         _ti_index;
 720     int         _ti_limit;
 721 
 722     // start at the beginning:
 723     void start();
 724 
 725    public:
 726     ContextStream(DepChange& changes)
 727       : _changes(changes)
 728     { start(); }
 729 
 730     ContextStream(DepChange& changes, NoSafepointVerifier& nsv)
 731       : _changes(changes)
 732       // the nsv argument makes it safe to hold oops like _klass
 733     { start(); }
 734 
 735     bool next();
 736 
 737     ChangeType change_type()     { return _change_type; }
 738     Klass*     klass()           { return _klass; }
 739   };
 740   friend class DepChange::ContextStream;
 741 };
 742 
 743 
 744 // A class hierarchy change coming through the VM (under the Compile_lock).
 745 // The change is structured as a single new type with any number of supers
 746 // and implemented interface types.  Other than the new type, any of the
 747 // super types can be context types for a relevant dependency, which the
 748 // new type could invalidate.
 749 class KlassDepChange : public DepChange {
 750  private:
 751   // each change set is rooted in exactly one new type (at present):
 752   Klass* _new_type;
 753 
 754   void initialize();
 755 
 756  public:
 757   // notes the new type, marks it and all its super-types
 758   KlassDepChange(Klass* new_type)
 759     : _new_type(new_type)
 760   {
 761     initialize();
 762   }
 763 
 764   // cleans up the marks
 765   ~KlassDepChange();
 766 
 767   // What kind of DepChange is this?
 768   virtual bool is_klass_change() const { return true; }
 769 
 770   virtual void mark_for_deoptimization(nmethod* nm) {
 771     nm->mark_for_deoptimization(/*inc_recompile_counts=*/true);
 772   }
 773 
 774   Klass* new_type() { return _new_type; }
 775 
 776   // involves_context(k) is true if k is new_type or any of the super types
 777   bool involves_context(Klass* k);
 778 };
 779 
 780 
 781 // A CallSite has changed its target.
 782 class CallSiteDepChange : public DepChange {
 783  private:
 784   Handle _call_site;
 785   Handle _method_handle;
 786 
 787  public:
 788   CallSiteDepChange(Handle call_site, Handle method_handle);
 789 
 790   // What kind of DepChange is this?
 791   virtual bool is_call_site_change() const { return true; }
 792 
 793   virtual void mark_for_deoptimization(nmethod* nm) {
 794     nm->mark_for_deoptimization(/*inc_recompile_counts=*/false);
 795   }
 796 
 797   oop call_site()     const { return _call_site();     }
 798   oop method_handle() const { return _method_handle(); }
 799 };
 800 
 801 #endif // SHARE_VM_CODE_DEPENDENCIES_HPP