1 /*
   2  * Copyright (c) 2005, 2015, 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   ConstantFieldDepChange;
  63 class No_Safepoint_Verifier;
  64 
  65 class Dependencies: public ResourceObj {
  66  public:
  67   // Note: In the comments on dependency types, most uses of the terms
  68   // subtype and supertype are used in a "non-strict" or "inclusive"
  69   // sense, and are starred to remind the reader of this fact.
  70   // Strict uses of the terms use the word "proper".
  71   //
  72   // Specifically, every class is its own subtype* and supertype*.
  73   // (This trick is easier than continually saying things like "Y is a
  74   // subtype of X or X itself".)
  75   //
  76   // Sometimes we write X > Y to mean X is a proper supertype of Y.
  77   // The notation X > {Y, Z} means X has proper subtypes Y, Z.
  78   // The notation X.m > Y means that Y inherits m from X, while
  79   // X.m > Y.m means Y overrides X.m.  A star denotes abstractness,
  80   // as *I > A, meaning (abstract) interface I is a super type of A,
  81   // or A.*m > B.m, meaning B.m implements abstract method A.m.
  82   //
  83   // In this module, the terms "subtype" and "supertype" refer to
  84   // Java-level reference type conversions, as detected by
  85   // "instanceof" and performed by "checkcast" operations.  The method
  86   // Klass::is_subtype_of tests these relations.  Note that "subtype"
  87   // is richer than "subclass" (as tested by Klass::is_subclass_of),
  88   // since it takes account of relations involving interface and array
  89   // types.
  90   //
  91   // To avoid needless complexity, dependencies involving array types
  92   // are not accepted.  If you need to make an assertion about an
  93   // array type, make the assertion about its corresponding element
  94   // types.  Any assertion that might change about an array type can
  95   // be converted to an assertion about its element type.
  96   //
  97   // Most dependencies are evaluated over a "context type" CX, which
  98   // stands for the set Subtypes(CX) of every Java type that is a subtype*
  99   // of CX.  When the system loads a new class or interface N, it is
 100   // responsible for re-evaluating changed dependencies whose context
 101   // type now includes N, that is, all super types of N.
 102   //
 103   enum DepType {
 104     end_marker = 0,
 105 
 106     // An 'evol' dependency simply notes that the contents of the
 107     // method were used.  If it evolves (is replaced), the nmethod
 108     // must be recompiled.  No other dependencies are implied.
 109     evol_method,
 110     FIRST_TYPE = evol_method,
 111 
 112     // A context type CX is a leaf it if has no proper subtype.
 113     leaf_type,
 114 
 115     // An abstract class CX has exactly one concrete subtype CC.
 116     abstract_with_unique_concrete_subtype,
 117 
 118     // The type CX is purely abstract, with no concrete subtype* at all.
 119     abstract_with_no_concrete_subtype,
 120 
 121     // The concrete CX is free of concrete proper subtypes.
 122     concrete_with_no_concrete_subtype,
 123 
 124     // Given a method M1 and a context class CX, the set MM(CX, M1) of
 125     // "concrete matching methods" in CX of M1 is the set of every
 126     // concrete M2 for which it is possible to create an invokevirtual
 127     // or invokeinterface call site that can reach either M1 or M2.
 128     // That is, M1 and M2 share a name, signature, and vtable index.
 129     // We wish to notice when the set MM(CX, M1) is just {M1}, or
 130     // perhaps a set of two {M1,M2}, and issue dependencies on this.
 131 
 132     // The set MM(CX, M1) can be computed by starting with any matching
 133     // concrete M2 that is inherited into CX, and then walking the
 134     // subtypes* of CX looking for concrete definitions.
 135 
 136     // The parameters to this dependency are the method M1 and the
 137     // context class CX.  M1 must be either inherited in CX or defined
 138     // in a subtype* of CX.  It asserts that MM(CX, M1) is no greater
 139     // than {M1}.
 140     unique_concrete_method,       // one unique concrete method under CX
 141 
 142     // An "exclusive" assertion concerns two methods or subtypes, and
 143     // declares that there are at most two (or perhaps later N>2)
 144     // specific items that jointly satisfy the restriction.
 145     // We list all items explicitly rather than just giving their
 146     // count, for robustness in the face of complex schema changes.
 147 
 148     // A context class CX (which may be either abstract or concrete)
 149     // has two exclusive concrete subtypes* C1, C2 if every concrete
 150     // subtype* of CX is either C1 or C2.  Note that if neither C1 or C2
 151     // are equal to CX, then CX itself must be abstract.  But it is
 152     // also possible (for example) that C1 is CX (a concrete class)
 153     // and C2 is a proper subtype of C1.
 154     abstract_with_exclusive_concrete_subtypes_2,
 155 
 156     // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
 157     exclusive_concrete_methods_2,
 158 
 159     // This dependency asserts that no instances of class or it's
 160     // subclasses require finalization registration.
 161     no_finalizable_subclasses,
 162 
 163     // This dependency asserts when the CallSite.target value changed.
 164     call_site_target_value,
 165 
 166     constant_field_value_instance,
 167     constant_field_value_klass,
 168 
 169     TYPE_LIMIT
 170   };
 171   enum {
 172     LG2_TYPE_LIMIT = 4,  // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
 173 
 174     // handy categorizations of dependency types:
 175     all_types           = ((1 << TYPE_LIMIT) - 1) & ((-1) << FIRST_TYPE),
 176 
 177     non_klass_types     = (1 << call_site_target_value),
 178     klass_types         = all_types & ~non_klass_types,
 179 
 180     non_ctxk_types      = (1 << evol_method) | (1 << call_site_target_value),
 181     implicit_ctxk_types = 0,
 182     explicit_ctxk_types = all_types & ~(non_ctxk_types | implicit_ctxk_types),
 183 
 184     max_arg_count = 3,   // current maximum number of arguments (incl. ctxk)
 185 
 186     // A "context type" is a class or interface that
 187     // provides context for evaluating a dependency.
 188     // When present, it is one of the arguments (dep_context_arg).
 189     //
 190     // If a dependency does not have a context type, there is a
 191     // default context, depending on the type of the dependency.
 192     // This bit signals that a default context has been compressed away.
 193     default_context_type_bit = (1<<LG2_TYPE_LIMIT)
 194   };
 195 
 196   static const char* dep_name(DepType dept);
 197   static int         dep_args(DepType dept);
 198 
 199   static bool is_klass_type(           DepType dept) { return dept_in_mask(dept, klass_types        ); }
 200 
 201   static bool has_explicit_context_arg(DepType dept) { return dept_in_mask(dept, explicit_ctxk_types); }
 202   static bool has_implicit_context_arg(DepType dept) { return dept_in_mask(dept, implicit_ctxk_types); }
 203 
 204   static int           dep_context_arg(DepType dept) { return has_explicit_context_arg(dept) ? 0 : -1; }
 205   static int  dep_implicit_context_arg(DepType dept) { return has_implicit_context_arg(dept) ? 0 : -1; }
 206 
 207   static void check_valid_dependency_type(DepType dept);
 208 
 209  private:
 210   // State for writing a new set of dependencies:
 211   GrowableArray<int>*       _dep_seen;  // (seen[h->ident] & (1<<dept))
 212   GrowableArray<ciBaseObject*>*  _deps[TYPE_LIMIT];
 213 
 214   static const char* _dep_name[TYPE_LIMIT];
 215   static int         _dep_args[TYPE_LIMIT];
 216 
 217   static bool dept_in_mask(DepType dept, int mask) {
 218     return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
 219   }
 220 
 221   bool note_dep_seen(int dept, ciBaseObject* x) {
 222     assert(dept < BitsPerInt, "oob");
 223     int x_id = x->ident();
 224     assert(_dep_seen != NULL, "deps must be writable");
 225     int seen = _dep_seen->at_grow(x_id, 0);
 226     _dep_seen->at_put(x_id, seen | (1<<dept));
 227     // return true if we've already seen dept/x
 228     return (seen & (1<<dept)) != 0;
 229   }
 230 
 231   bool maybe_merge_ctxk(GrowableArray<ciBaseObject*>* deps,
 232                         int ctxk_i, ciKlass* ctxk);
 233 
 234   void sort_all_deps();
 235   size_t estimate_size_in_bytes();
 236 
 237   // Initialize _deps, etc.
 238   void initialize(ciEnv* env);
 239 
 240   // State for making a new set of dependencies:
 241   OopRecorder* _oop_recorder;
 242 
 243   // Logging support
 244   CompileLog* _log;
 245 
 246   address  _content_bytes;  // everything but the oop references, encoded
 247   size_t   _size_in_bytes;
 248 
 249  public:
 250   // Make a new empty dependencies set.
 251   Dependencies(ciEnv* env) {
 252     initialize(env);
 253   }
 254 
 255  private:
 256   // Check for a valid context type.
 257   // Enforce the restriction against array types.
 258   static void check_ctxk(ciKlass* ctxk) {
 259     assert(ctxk->is_instance_klass(), "java types only");
 260   }
 261   static void check_ctxk_concrete(ciKlass* ctxk) {
 262     assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
 263   }
 264   static void check_ctxk_abstract(ciKlass* ctxk) {
 265     check_ctxk(ctxk);
 266     assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
 267   }
 268 
 269   void assert_common_1(DepType dept, ciBaseObject* x);
 270   void assert_common_2(DepType dept, ciBaseObject* x0, ciBaseObject* x1);
 271   void assert_common_3(DepType dept, ciKlass* ctxk, ciBaseObject* x1, ciBaseObject* x2);
 272 
 273  public:
 274   // Adding assertions to a new dependency set at compile time:
 275   void assert_evol_method(ciMethod* m);
 276   void assert_leaf_type(ciKlass* ctxk);
 277   void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
 278   void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
 279   void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
 280   void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
 281   void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
 282   void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
 283   void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
 284   void assert_call_site_target_value(ciCallSite* call_site, ciMethodHandle* method_handle);
 285 
 286   void assert_constant_field_value_klass(ciField* field, ciKlass* ctxk);
 287   void assert_constant_field_value_instance(ciField* field, ciObject* obj);
 288 
 289   // Define whether a given method or type is concrete.
 290   // These methods define the term "concrete" as used in this module.
 291   // For this module, an "abstract" class is one which is non-concrete.
 292   //
 293   // Future optimizations may allow some classes to remain
 294   // non-concrete until their first instantiation, and allow some
 295   // methods to remain non-concrete until their first invocation.
 296   // In that case, there would be a middle ground between concrete
 297   // and abstract (as defined by the Java language and VM).
 298   static bool is_concrete_klass(Klass* k);    // k is instantiable
 299   static bool is_concrete_method(Method* m, Klass* k);  // m is invocable
 300   static Klass* find_finalizable_subclass(Klass* k);
 301 
 302   // These versions of the concreteness queries work through the CI.
 303   // The CI versions are allowed to skew sometimes from the VM
 304   // (oop-based) versions.  The cost of such a difference is a
 305   // (safely) aborted compilation, or a deoptimization, or a missed
 306   // optimization opportunity.
 307   //
 308   // In order to prevent spurious assertions, query results must
 309   // remain stable within any single ciEnv instance.  (I.e., they must
 310   // not go back into the VM to get their value; they must cache the
 311   // bit in the CI, either eagerly or lazily.)
 312   static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
 313   static bool has_finalizable_subclass(ciInstanceKlass* k);
 314 
 315   // As a general rule, it is OK to compile under the assumption that
 316   // a given type or method is concrete, even if it at some future
 317   // point becomes abstract.  So dependency checking is one-sided, in
 318   // that it permits supposedly concrete classes or methods to turn up
 319   // as really abstract.  (This shouldn't happen, except during class
 320   // evolution, but that's the logic of the checking.)  However, if a
 321   // supposedly abstract class or method suddenly becomes concrete, a
 322   // dependency on it must fail.
 323 
 324   // Checking old assertions at run-time (in the VM only):
 325   static Klass* check_evol_method(Method* m);
 326   static Klass* check_leaf_type(Klass* ctxk);
 327   static Klass* check_abstract_with_unique_concrete_subtype(Klass* ctxk, Klass* conck,
 328                                                               KlassDepChange* changes = NULL);
 329   static Klass* check_abstract_with_no_concrete_subtype(Klass* ctxk,
 330                                                           KlassDepChange* changes = NULL);
 331   static Klass* check_concrete_with_no_concrete_subtype(Klass* ctxk,
 332                                                           KlassDepChange* changes = NULL);
 333   static Klass* check_unique_concrete_method(Klass* ctxk, Method* uniqm,
 334                                                KlassDepChange* changes = NULL);
 335   static Klass* check_abstract_with_exclusive_concrete_subtypes(Klass* ctxk, Klass* k1, Klass* k2,
 336                                                                   KlassDepChange* changes = NULL);
 337   static Klass* check_exclusive_concrete_methods(Klass* ctxk, Method* m1, Method* m2,
 338                                                    KlassDepChange* changes = NULL);
 339   static Klass* check_has_no_finalizable_subclasses(Klass* ctxk, KlassDepChange* changes = NULL);
 340   static Klass* check_call_site_target_value(oop call_site, oop method_handle, CallSiteDepChange* changes = NULL);
 341   // A returned Klass* is NULL if the dependency assertion is still
 342   // valid.  A non-NULL Klass* is a 'witness' to the assertion
 343   // failure, a point in the class hierarchy where the assertion has
 344   // been proven false.  For example, if check_leaf_type returns
 345   // non-NULL, the value is a subtype of the supposed leaf type.  This
 346   // witness value may be useful for logging the dependency failure.
 347   // Note that, when a dependency fails, there may be several possible
 348   // witnesses to the failure.  The value returned from the check_foo
 349   // method is chosen arbitrarily.
 350 
 351   // The 'changes' value, if non-null, requests a limited spot-check
 352   // near the indicated recent changes in the class hierarchy.
 353   // It is used by DepStream::spot_check_dependency_at.
 354 
 355   // Detecting possible new assertions:
 356   static Klass*    find_unique_concrete_subtype(Klass* ctxk);
 357   static Method*   find_unique_concrete_method(Klass* ctxk, Method* m);
 358   static int       find_exclusive_concrete_subtypes(Klass* ctxk, int klen, Klass* k[]);
 359 
 360   static void invalidate_dependent_nmethods(instanceKlassHandle ctxk, DepChange& changes, TRAPS);
 361 
 362   // Create the encoding which will be stored in an nmethod.
 363   void encode_content_bytes();
 364 
 365   address content_bytes() {
 366     assert(_content_bytes != NULL, "encode it first");
 367     return _content_bytes;
 368   }
 369   size_t size_in_bytes() {
 370     assert(_content_bytes != NULL, "encode it first");
 371     return _size_in_bytes;
 372   }
 373 
 374   OopRecorder* oop_recorder() { return _oop_recorder; }
 375   CompileLog*  log()          { return _log; }
 376 
 377   void copy_to(nmethod* nm);
 378 
 379   void log_all_dependencies();
 380 
 381   void log_dependency(DepType dept, GrowableArray<ciBaseObject*>* args) {
 382     ResourceMark rm;
 383     int argslen = args->length();
 384     write_dependency_to(log(), dept, args);
 385     guarantee(argslen == args->length(),
 386               "args array cannot grow inside nested ResoureMark scope");
 387   }
 388 
 389   void log_dependency(DepType dept,
 390                       ciBaseObject* x0,
 391                       ciBaseObject* x1 = NULL,
 392                       ciBaseObject* x2 = NULL) {
 393     if (log() == NULL) {
 394       return;
 395     }
 396     ResourceMark rm;
 397     GrowableArray<ciBaseObject*>* ciargs =
 398                 new GrowableArray<ciBaseObject*>(dep_args(dept));
 399     assert (x0 != NULL, "no log x0");
 400     ciargs->push(x0);
 401 
 402     if (x1 != NULL) {
 403       ciargs->push(x1);
 404     }
 405     if (x2 != NULL) {
 406       ciargs->push(x2);
 407     }
 408     assert(ciargs->length() == dep_args(dept), "");
 409     log_dependency(dept, ciargs);
 410   }
 411 
 412   static PerfCounter* _perf_dependency_checking_time;
 413   static PerfCounter* _perf_dependencies_checked_count;
 414   static PerfCounter* _perf_dependencies_context_traversals;
 415   static PerfCounter* _perf_dependencies_invalidated;
 416   static PerfCounter* _perf_dependencies_total_count;
 417 
 418   class DepArgument : public ResourceObj {
 419    private:
 420     bool  _is_oop;
 421     bool  _valid;
 422     void* _value;
 423    public:
 424     DepArgument() : _is_oop(false), _value(NULL), _valid(false) {}
 425     DepArgument(oop v): _is_oop(true), _value(v), _valid(true) {}
 426     DepArgument(Metadata* v): _is_oop(false), _value(v), _valid(true) {}
 427 
 428     bool is_null() const               { return _value == NULL; }
 429     bool is_oop() const                { return _is_oop; }
 430     bool is_metadata() const           { return !_is_oop; }
 431     bool is_klass() const              { return is_metadata() && metadata_value()->is_klass(); }
 432     bool is_method() const              { return is_metadata() && metadata_value()->is_method(); }
 433 
 434     oop oop_value() const              { assert(_is_oop && _valid, "must be"); return (oop) _value; }
 435     Metadata* metadata_value() const { assert(!_is_oop && _valid, "must be"); return (Metadata*) _value; }
 436   };
 437 
 438   static void print_dependency(DepType dept,
 439                                GrowableArray<DepArgument>* args,
 440                                Klass* witness = NULL);
 441 
 442  private:
 443   // helper for encoding common context types as zero:
 444   static ciKlass* ctxk_encoded_as_null(DepType dept, ciBaseObject* x);
 445 
 446   static Klass* ctxk_encoded_as_null(DepType dept, Metadata* x);
 447 
 448   static void write_dependency_to(CompileLog* log,
 449                                   DepType dept,
 450                                   GrowableArray<ciBaseObject*>* args,
 451                                   Klass* witness = NULL);
 452   static void write_dependency_to(CompileLog* log,
 453                                   DepType dept,
 454                                   GrowableArray<DepArgument>* args,
 455                                   Klass* witness = NULL);
 456   static void write_dependency_to(xmlStream* xtty,
 457                                   DepType dept,
 458                                   GrowableArray<DepArgument>* args,
 459                                   Klass* witness = NULL);
 460  public:
 461   // Use this to iterate over an nmethod's dependency set.
 462   // Works on new and old dependency sets.
 463   // Usage:
 464   //
 465   // ;
 466   // Dependencies::DepType dept;
 467   // for (Dependencies::DepStream deps(nm); deps.next(); ) {
 468   //   ...
 469   // }
 470   //
 471   // The caller must be in the VM, since oops are not wrapped in handles.
 472   class DepStream {
 473   private:
 474     nmethod*              _code;   // null if in a compiler thread
 475     Dependencies*         _deps;   // null if not in a compiler thread
 476     CompressedReadStream  _bytes;
 477 #ifdef ASSERT
 478     size_t                _byte_limit;
 479 #endif
 480 
 481     // iteration variables:
 482     DepType               _type;
 483     int                   _xi[max_arg_count+1];
 484 
 485     void initial_asserts(size_t byte_limit) NOT_DEBUG({});
 486 
 487     inline Metadata* recorded_metadata_at(int i);
 488     inline oop recorded_oop_at(int i);
 489 
 490     Klass* check_klass_dependency(KlassDepChange* changes);
 491     Klass* check_call_site_dependency(CallSiteDepChange* changes);
 492 
 493     void trace_and_log_witness(Klass* witness);
 494 
 495   public:
 496     DepStream(Dependencies* deps)
 497       : _deps(deps),
 498         _code(NULL),
 499         _bytes(deps->content_bytes())
 500     {
 501       initial_asserts(deps->size_in_bytes());
 502     }
 503     DepStream(nmethod* code)
 504       : _deps(NULL),
 505         _code(code),
 506         _bytes(code->dependencies_begin())
 507     {
 508       initial_asserts(code->dependencies_size());
 509     }
 510 
 511     bool next();
 512 
 513     DepType type()               { return _type; }
 514     bool is_oop_argument(int i)  {
 515       assert(0 <= i && i < argument_count(), "oob");
 516       switch (type()) {
 517         case call_site_target_value:        return true;
 518         case constant_field_value_instance: return (i == 1);
 519         default:                            return false;
 520       }
 521     }
 522     bool is_int_argument(int i) {
 523       assert(0 <= i && i < argument_count(), "oob");
 524       switch (type()) {
 525         case constant_field_value_instance: return (i == 2);
 526         case constant_field_value_klass:    return (i == 1);
 527         default:                            return false;
 528       }
 529     }
 530     uintptr_t get_identifier(int i);
 531 
 532     int argument_count()         { return dep_args(type()); }
 533     int argument_index(int i)    { assert(0 <= i && i < argument_count(), "oob");
 534                                    return _xi[i]; }
 535     Metadata* argument(int i);     // => recorded_oop_at(argument_index(i))
 536     oop argument_oop(int i);       // => recorded_oop_at(argument_index(i))
 537     int argument_int(int i)      { return argument_index(i); }
 538     Klass* context_type();
 539 
 540     bool is_klass_type()         { return Dependencies::is_klass_type(type()); }
 541 
 542     Method* method_argument(int i) {
 543       Metadata* x = argument(i);
 544       assert(x->is_method(), "type");
 545       return (Method*) x;
 546     }
 547     Klass* type_argument(int i) {
 548       Metadata* x = argument(i);
 549       assert(x->is_klass(), "type");
 550       return (Klass*) x;
 551     }
 552 
 553     // The point of the whole exercise:  Is this dep still OK?
 554     Klass* check_dependency() {
 555       Klass* result = check_klass_dependency(NULL);
 556       if (result != NULL)  return result;
 557       return check_call_site_dependency(NULL);
 558     }
 559 
 560     // A lighter version:  Checks only around recent changes in a class
 561     // hierarchy.  (See Universe::flush_dependents_on.)
 562     Klass* spot_check_dependency_at(DepChange& changes);
 563 
 564     // Log the current dependency to xtty or compilation log.
 565     void log_dependency(Klass* witness = NULL);
 566 
 567     // Print the current dependency to tty.
 568     void print_dependency(Klass* witness = NULL, bool verbose = false);
 569   };
 570   friend class Dependencies::DepStream;
 571 
 572   static void print_statistics() PRODUCT_RETURN;
 573 };
 574 
 575 
 576 class DependencySignature : public ResourceObj {
 577  private:
 578   int                   _args_count;
 579   uintptr_t             _argument_hash[Dependencies::max_arg_count];
 580   Dependencies::DepType _type;
 581 
 582  public:
 583   DependencySignature(Dependencies::DepStream& dep) {
 584     _args_count = dep.argument_count();
 585     _type = dep.type();
 586     for (int i = 0; i < _args_count; i++) {
 587       _argument_hash[i] = dep.get_identifier(i);
 588     }
 589   }
 590 
 591   static bool     equals(DependencySignature const& s1, DependencySignature const& s2);
 592   static unsigned hash  (DependencySignature const& s1) { return s1.arg(0) >> 2; }
 593 
 594   int args_count()             const { return _args_count; }
 595   uintptr_t arg(int idx)       const { return _argument_hash[idx]; }
 596   Dependencies::DepType type() const { return _type; }
 597 
 598 };
 599 
 600 
 601 // Every particular DepChange is a sub-class of this class.
 602 class DepChange : public StackObj {
 603  public:
 604   // What kind of DepChange is this?
 605   virtual bool is_klass_change()     const { return false; }
 606   virtual bool is_call_site_change() const { return false; }
 607   virtual bool is_constant_field_change() const { return false; }
 608 
 609   // Subclass casting with assertions.
 610   KlassDepChange*    as_klass_change() {
 611     assert(is_klass_change(), "bad cast");
 612     return (KlassDepChange*) this;
 613   }
 614   CallSiteDepChange* as_call_site_change() {
 615     assert(is_call_site_change(), "bad cast");
 616     return (CallSiteDepChange*) this;
 617   }
 618   ConstantFieldDepChange* as_constant_field_change() {
 619     assert(is_constant_field_change(), "bad cast");
 620     return (ConstantFieldDepChange*) this;
 621   }
 622 
 623   void print();
 624 
 625  public:
 626   enum ChangeType {
 627     NO_CHANGE = 0,              // an uninvolved klass
 628     Change_new_type,            // a newly loaded type
 629     Change_new_sub,             // a super with a new subtype
 630     Change_new_impl,            // an interface with a new implementation
 631     CHANGE_LIMIT,
 632     Start_Klass = CHANGE_LIMIT  // internal indicator for ContextStream
 633   };
 634 
 635   // Usage:
 636   // for (DepChange::ContextStream str(changes); str.next(); ) {
 637   //   Klass* k = str.klass();
 638   //   switch (str.change_type()) {
 639   //     ...
 640   //   }
 641   // }
 642   class ContextStream : public StackObj {
 643    private:
 644     DepChange&  _changes;
 645     friend class DepChange;
 646 
 647     // iteration variables:
 648     ChangeType  _change_type;
 649     Klass*      _klass;
 650     Array<Klass*>* _ti_base;    // i.e., transitive_interfaces
 651     int         _ti_index;
 652     int         _ti_limit;
 653 
 654     // start at the beginning:
 655     void start();
 656 
 657    public:
 658     ContextStream(DepChange& changes)
 659       : _changes(changes)
 660     { start(); }
 661 
 662     ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
 663       : _changes(changes)
 664       // the nsv argument makes it safe to hold oops like _klass
 665     { start(); }
 666 
 667     bool next();
 668 
 669     ChangeType change_type()     { return _change_type; }
 670     Klass*     klass()           { return _klass; }
 671   };
 672   friend class DepChange::ContextStream;
 673 };
 674 
 675 
 676 // A class hierarchy change coming through the VM (under the Compile_lock).
 677 // The change is structured as a single new type with any number of supers
 678 // and implemented interface types.  Other than the new type, any of the
 679 // super types can be context types for a relevant dependency, which the
 680 // new type could invalidate.
 681 class KlassDepChange : public DepChange {
 682  private:
 683   // each change set is rooted in exactly one new type (at present):
 684   KlassHandle _new_type;
 685 
 686   void initialize();
 687 
 688  public:
 689   // notes the new type, marks it and all its super-types
 690   KlassDepChange(KlassHandle new_type)
 691     : _new_type(new_type)
 692   {
 693     initialize();
 694   }
 695 
 696   // cleans up the marks
 697   ~KlassDepChange();
 698 
 699   // What kind of DepChange is this?
 700   virtual bool is_klass_change() const { return true; }
 701 
 702   Klass* new_type() { return _new_type(); }
 703 
 704   // involves_context(k) is true if k is new_type or any of the super types
 705   bool involves_context(Klass* k);
 706 };
 707 
 708 
 709 // A CallSite has changed its target.
 710 class CallSiteDepChange : public DepChange {
 711  private:
 712   Handle _call_site;
 713   Handle _method_handle;
 714 
 715  public:
 716   CallSiteDepChange(Handle call_site, Handle method_handle)
 717     : _call_site(call_site),
 718       _method_handle(method_handle)
 719   {
 720     assert(_call_site()    ->is_a(SystemDictionary::CallSite_klass()),     "must be");
 721     assert(_method_handle.is_null() || _method_handle()->is_a(SystemDictionary::MethodHandle_klass()), "must be");
 722   }
 723 
 724   // What kind of DepChange is this?
 725   virtual bool is_call_site_change() const { return true; }
 726 
 727   oop call_site()     const { return _call_site();     }
 728   oop method_handle() const { return _method_handle(); }
 729 };
 730 
 731 class ConstantFieldDepChange : public DepChange {
 732  private:
 733   Handle _holder;
 734   int _offset;
 735 
 736  public:
 737   ConstantFieldDepChange(Handle holder, int offset) : _holder(holder), _offset(offset) {}
 738 
 739   // What kind of DepChange is this?
 740   virtual bool is_constant_field_change() const { return true; }
 741 
 742   oop holder() const { return _holder(); }
 743   int offset() const { return _offset;   }
 744 };
 745 
 746 
 747 #endif // SHARE_VM_CODE_DEPENDENCIES_HPP
--- EOF ---