1 /*
   2  * Copyright (c) 2005, 2013, 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 #include "precompiled.hpp"
  26 #include "ci/ciArrayKlass.hpp"
  27 #include "ci/ciEnv.hpp"
  28 #include "ci/ciKlass.hpp"
  29 #include "ci/ciMethod.hpp"
  30 #include "code/dependencies.hpp"
  31 #include "compiler/compileLog.hpp"
  32 #include "oops/oop.inline.hpp"
  33 #include "runtime/handles.hpp"
  34 #include "runtime/handles.inline.hpp"
  35 #include "runtime/thread.inline.hpp"
  36 #include "utilities/copy.hpp"
  37 
  38 
  39 #ifdef ASSERT
  40 static bool must_be_in_vm() {
  41   Thread* thread = Thread::current();
  42   if (thread->is_Java_thread())
  43     return ((JavaThread*)thread)->thread_state() == _thread_in_vm;
  44   else
  45     return true;  //something like this: thread->is_VM_thread();
  46 }
  47 #endif //ASSERT
  48 
  49 void Dependencies::initialize(ciEnv* env) {
  50   Arena* arena = env->arena();
  51   _oop_recorder = env->oop_recorder();
  52   _log = env->log();
  53   _dep_seen = new(arena) GrowableArray<int>(arena, 500, 0, 0);
  54   DEBUG_ONLY(_deps[end_marker] = NULL);
  55   for (int i = (int)FIRST_TYPE; i < (int)TYPE_LIMIT; i++) {
  56     _deps[i] = new(arena) GrowableArray<ciBaseObject*>(arena, 10, 0, 0);
  57   }
  58   _content_bytes = NULL;
  59   _size_in_bytes = (size_t)-1;
  60 
  61   assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT), "sanity");
  62 }
  63 
  64 void Dependencies::assert_evol_method(ciMethod* m) {
  65   assert_common_1(evol_method, m);
  66 }
  67 
  68 void Dependencies::assert_leaf_type(ciKlass* ctxk) {
  69   if (ctxk->is_array_klass()) {
  70     // As a special case, support this assertion on an array type,
  71     // which reduces to an assertion on its element type.
  72     // Note that this cannot be done with assertions that
  73     // relate to concreteness or abstractness.
  74     ciType* elemt = ctxk->as_array_klass()->base_element_type();
  75     if (!elemt->is_instance_klass())  return;   // Ex:  int[][]
  76     ctxk = elemt->as_instance_klass();
  77     //if (ctxk->is_final())  return;            // Ex:  String[][]
  78   }
  79   check_ctxk(ctxk);
  80   assert_common_1(leaf_type, ctxk);
  81 }
  82 
  83 void Dependencies::assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck) {
  84   check_ctxk_abstract(ctxk);
  85   assert_common_2(abstract_with_unique_concrete_subtype, ctxk, conck);
  86 }
  87 
  88 void Dependencies::assert_abstract_with_no_concrete_subtype(ciKlass* ctxk) {
  89   check_ctxk_abstract(ctxk);
  90   assert_common_1(abstract_with_no_concrete_subtype, ctxk);
  91 }
  92 
  93 void Dependencies::assert_concrete_with_no_concrete_subtype(ciKlass* ctxk) {
  94   check_ctxk_concrete(ctxk);
  95   assert_common_1(concrete_with_no_concrete_subtype, ctxk);
  96 }
  97 
  98 void Dependencies::assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm) {
  99   check_ctxk(ctxk);
 100   assert_common_2(unique_concrete_method, ctxk, uniqm);
 101 }
 102 
 103 void Dependencies::assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2) {
 104   check_ctxk(ctxk);
 105   assert_common_3(abstract_with_exclusive_concrete_subtypes_2, ctxk, k1, k2);
 106 }
 107 
 108 void Dependencies::assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2) {
 109   check_ctxk(ctxk);
 110   assert_common_3(exclusive_concrete_methods_2, ctxk, m1, m2);
 111 }
 112 
 113 void Dependencies::assert_has_no_finalizable_subclasses(ciKlass* ctxk) {
 114   check_ctxk(ctxk);
 115   assert_common_1(no_finalizable_subclasses, ctxk);
 116 }
 117 
 118 void Dependencies::assert_call_site_target_value(ciCallSite* call_site, ciMethodHandle* method_handle) {
 119   check_ctxk(call_site->klass());
 120   assert_common_2(call_site_target_value, call_site, method_handle);
 121 }
 122 
 123 // Helper function.  If we are adding a new dep. under ctxk2,
 124 // try to find an old dep. under a broader* ctxk1.  If there is
 125 //
 126 bool Dependencies::maybe_merge_ctxk(GrowableArray<ciBaseObject*>* deps,
 127                                     int ctxk_i, ciKlass* ctxk2) {
 128   ciKlass* ctxk1 = deps->at(ctxk_i)->as_metadata()->as_klass();
 129   if (ctxk2->is_subtype_of(ctxk1)) {
 130     return true;  // success, and no need to change
 131   } else if (ctxk1->is_subtype_of(ctxk2)) {
 132     // new context class fully subsumes previous one
 133     deps->at_put(ctxk_i, ctxk2);
 134     return true;
 135   } else {
 136     return false;
 137   }
 138 }
 139 
 140 void Dependencies::assert_common_1(DepType dept, ciBaseObject* x) {
 141   assert(dep_args(dept) == 1, "sanity");
 142   log_dependency(dept, x);
 143   GrowableArray<ciBaseObject*>* deps = _deps[dept];
 144 
 145   // see if the same (or a similar) dep is already recorded
 146   if (note_dep_seen(dept, x)) {
 147     assert(deps->find(x) >= 0, "sanity");
 148   } else {
 149     deps->append(x);
 150   }
 151 }
 152 
 153 void Dependencies::assert_common_2(DepType dept,
 154                                    ciBaseObject* x0, ciBaseObject* x1) {
 155   assert(dep_args(dept) == 2, "sanity");
 156   log_dependency(dept, x0, x1);
 157   GrowableArray<ciBaseObject*>* deps = _deps[dept];
 158 
 159   // see if the same (or a similar) dep is already recorded
 160   bool has_ctxk = has_explicit_context_arg(dept);
 161   if (has_ctxk) {
 162     assert(dep_context_arg(dept) == 0, "sanity");
 163     if (note_dep_seen(dept, x1)) {
 164       // look in this bucket for redundant assertions
 165       const int stride = 2;
 166       for (int i = deps->length(); (i -= stride) >= 0; ) {
 167         ciBaseObject* y1 = deps->at(i+1);
 168         if (x1 == y1) {  // same subject; check the context
 169           if (maybe_merge_ctxk(deps, i+0, x0->as_metadata()->as_klass())) {
 170             return;
 171           }
 172         }
 173       }
 174     }
 175   } else {
 176     assert(dep_implicit_context_arg(dept) == 0, "sanity");
 177     if (note_dep_seen(dept, x0) && note_dep_seen(dept, x1)) {
 178       // look in this bucket for redundant assertions
 179       const int stride = 2;
 180       for (int i = deps->length(); (i -= stride) >= 0; ) {
 181         ciBaseObject* y0 = deps->at(i+0);
 182         ciBaseObject* y1 = deps->at(i+1);
 183         if (x0 == y0 && x1 == y1) {
 184           return;
 185         }
 186       }
 187     }
 188   }
 189 
 190   // append the assertion in the correct bucket:
 191   deps->append(x0);
 192   deps->append(x1);
 193 }
 194 
 195 void Dependencies::assert_common_3(DepType dept,
 196                                    ciKlass* ctxk, ciBaseObject* x, ciBaseObject* x2) {
 197   assert(dep_context_arg(dept) == 0, "sanity");
 198   assert(dep_args(dept) == 3, "sanity");
 199   log_dependency(dept, ctxk, x, x2);
 200   GrowableArray<ciBaseObject*>* deps = _deps[dept];
 201 
 202   // try to normalize an unordered pair:
 203   bool swap = false;
 204   switch (dept) {
 205   case abstract_with_exclusive_concrete_subtypes_2:
 206     swap = (x->ident() > x2->ident() && x->as_metadata()->as_klass() != ctxk);
 207     break;
 208   case exclusive_concrete_methods_2:
 209     swap = (x->ident() > x2->ident() && x->as_metadata()->as_method()->holder() != ctxk);
 210     break;
 211   }
 212   if (swap) { ciBaseObject* t = x; x = x2; x2 = t; }
 213 
 214   // see if the same (or a similar) dep is already recorded
 215   if (note_dep_seen(dept, x) && note_dep_seen(dept, x2)) {
 216     // look in this bucket for redundant assertions
 217     const int stride = 3;
 218     for (int i = deps->length(); (i -= stride) >= 0; ) {
 219       ciBaseObject* y  = deps->at(i+1);
 220       ciBaseObject* y2 = deps->at(i+2);
 221       if (x == y && x2 == y2) {  // same subjects; check the context
 222         if (maybe_merge_ctxk(deps, i+0, ctxk)) {
 223           return;
 224         }
 225       }
 226     }
 227   }
 228   // append the assertion in the correct bucket:
 229   deps->append(ctxk);
 230   deps->append(x);
 231   deps->append(x2);
 232 }
 233 
 234 /// Support for encoding dependencies into an nmethod:
 235 
 236 void Dependencies::copy_to(nmethod* nm) {
 237   address beg = nm->dependencies_begin();
 238   address end = nm->dependencies_end();
 239   guarantee(end - beg >= (ptrdiff_t) size_in_bytes(), "bad sizing");
 240   Copy::disjoint_words((HeapWord*) content_bytes(),
 241                        (HeapWord*) beg,
 242                        size_in_bytes() / sizeof(HeapWord));
 243   assert(size_in_bytes() % sizeof(HeapWord) == 0, "copy by words");
 244 }
 245 
 246 static int sort_dep(ciBaseObject** p1, ciBaseObject** p2, int narg) {
 247   for (int i = 0; i < narg; i++) {
 248     int diff = p1[i]->ident() - p2[i]->ident();
 249     if (diff != 0)  return diff;
 250   }
 251   return 0;
 252 }
 253 static int sort_dep_arg_1(ciBaseObject** p1, ciBaseObject** p2)
 254 { return sort_dep(p1, p2, 1); }
 255 static int sort_dep_arg_2(ciBaseObject** p1, ciBaseObject** p2)
 256 { return sort_dep(p1, p2, 2); }
 257 static int sort_dep_arg_3(ciBaseObject** p1, ciBaseObject** p2)
 258 { return sort_dep(p1, p2, 3); }
 259 
 260 void Dependencies::sort_all_deps() {
 261   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 262     DepType dept = (DepType)deptv;
 263     GrowableArray<ciBaseObject*>* deps = _deps[dept];
 264     if (deps->length() <= 1)  continue;
 265     switch (dep_args(dept)) {
 266     case 1: deps->sort(sort_dep_arg_1, 1); break;
 267     case 2: deps->sort(sort_dep_arg_2, 2); break;
 268     case 3: deps->sort(sort_dep_arg_3, 3); break;
 269     default: ShouldNotReachHere();
 270     }
 271   }
 272 }
 273 
 274 size_t Dependencies::estimate_size_in_bytes() {
 275   size_t est_size = 100;
 276   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 277     DepType dept = (DepType)deptv;
 278     GrowableArray<ciBaseObject*>* deps = _deps[dept];
 279     est_size += deps->length()*2;  // tags and argument(s)
 280   }
 281   return est_size;
 282 }
 283 
 284 ciKlass* Dependencies::ctxk_encoded_as_null(DepType dept, ciBaseObject* x) {
 285   switch (dept) {
 286   case abstract_with_exclusive_concrete_subtypes_2:
 287     return x->as_metadata()->as_klass();
 288   case unique_concrete_method:
 289   case exclusive_concrete_methods_2:
 290     return x->as_metadata()->as_method()->holder();
 291   }
 292   return NULL;  // let NULL be NULL
 293 }
 294 
 295 Klass* Dependencies::ctxk_encoded_as_null(DepType dept, Metadata* x) {
 296   assert(must_be_in_vm(), "raw oops here");
 297   switch (dept) {
 298   case abstract_with_exclusive_concrete_subtypes_2:
 299     assert(x->is_klass(), "sanity");
 300     return (Klass*) x;
 301   case unique_concrete_method:
 302   case exclusive_concrete_methods_2:
 303     assert(x->is_method(), "sanity");
 304     return ((Method*)x)->method_holder();
 305   }
 306   return NULL;  // let NULL be NULL
 307 }
 308 
 309 void Dependencies::encode_content_bytes() {
 310   sort_all_deps();
 311 
 312   // cast is safe, no deps can overflow INT_MAX
 313   CompressedWriteStream bytes((int)estimate_size_in_bytes());
 314 
 315   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 316     DepType dept = (DepType)deptv;
 317     GrowableArray<ciBaseObject*>* deps = _deps[dept];
 318     if (deps->length() == 0)  continue;
 319     int stride = dep_args(dept);
 320     int ctxkj  = dep_context_arg(dept);  // -1 if no context arg
 321     assert(stride > 0, "sanity");
 322     for (int i = 0; i < deps->length(); i += stride) {
 323       jbyte code_byte = (jbyte)dept;
 324       int skipj = -1;
 325       if (ctxkj >= 0 && ctxkj+1 < stride) {
 326         ciKlass*  ctxk = deps->at(i+ctxkj+0)->as_metadata()->as_klass();
 327         ciBaseObject* x     = deps->at(i+ctxkj+1);  // following argument
 328         if (ctxk == ctxk_encoded_as_null(dept, x)) {
 329           skipj = ctxkj;  // we win:  maybe one less oop to keep track of
 330           code_byte |= default_context_type_bit;
 331         }
 332       }
 333       bytes.write_byte(code_byte);
 334       for (int j = 0; j < stride; j++) {
 335         if (j == skipj)  continue;
 336         ciBaseObject* v = deps->at(i+j);
 337         int idx;
 338         if (v->is_object()) {
 339           idx = _oop_recorder->find_index(v->as_object()->constant_encoding());
 340         } else {
 341           ciMetadata* meta = v->as_metadata();
 342           idx = _oop_recorder->find_index(meta->constant_encoding());
 343         }
 344         bytes.write_int(idx);
 345       }
 346     }
 347   }
 348 
 349   // write a sentinel byte to mark the end
 350   bytes.write_byte(end_marker);
 351 
 352   // round it out to a word boundary
 353   while (bytes.position() % sizeof(HeapWord) != 0) {
 354     bytes.write_byte(end_marker);
 355   }
 356 
 357   // check whether the dept byte encoding really works
 358   assert((jbyte)default_context_type_bit != 0, "byte overflow");
 359 
 360   _content_bytes = bytes.buffer();
 361   _size_in_bytes = bytes.position();
 362 }
 363 
 364 
 365 const char* Dependencies::_dep_name[TYPE_LIMIT] = {
 366   "end_marker",
 367   "evol_method",
 368   "leaf_type",
 369   "abstract_with_unique_concrete_subtype",
 370   "abstract_with_no_concrete_subtype",
 371   "concrete_with_no_concrete_subtype",
 372   "unique_concrete_method",
 373   "abstract_with_exclusive_concrete_subtypes_2",
 374   "exclusive_concrete_methods_2",
 375   "no_finalizable_subclasses",
 376   "call_site_target_value"
 377 };
 378 
 379 int Dependencies::_dep_args[TYPE_LIMIT] = {
 380   -1,// end_marker
 381   1, // evol_method m
 382   1, // leaf_type ctxk
 383   2, // abstract_with_unique_concrete_subtype ctxk, k
 384   1, // abstract_with_no_concrete_subtype ctxk
 385   1, // concrete_with_no_concrete_subtype ctxk
 386   2, // unique_concrete_method ctxk, m
 387   3, // unique_concrete_subtypes_2 ctxk, k1, k2
 388   3, // unique_concrete_methods_2 ctxk, m1, m2
 389   1, // no_finalizable_subclasses ctxk
 390   2  // call_site_target_value call_site, method_handle
 391 };
 392 
 393 const char* Dependencies::dep_name(Dependencies::DepType dept) {
 394   if (!dept_in_mask(dept, all_types))  return "?bad-dep?";
 395   return _dep_name[dept];
 396 }
 397 
 398 int Dependencies::dep_args(Dependencies::DepType dept) {
 399   if (!dept_in_mask(dept, all_types))  return -1;
 400   return _dep_args[dept];
 401 }
 402 
 403 void Dependencies::check_valid_dependency_type(DepType dept) {
 404   guarantee(FIRST_TYPE <= dept && dept < TYPE_LIMIT, err_msg("invalid dependency type: %d", (int) dept));
 405 }
 406 
 407 // for the sake of the compiler log, print out current dependencies:
 408 void Dependencies::log_all_dependencies() {
 409   if (log() == NULL)  return;
 410   ResourceMark rm;
 411   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 412     DepType dept = (DepType)deptv;
 413     GrowableArray<ciBaseObject*>* deps = _deps[dept];
 414     int deplen = deps->length();
 415     if (deplen == 0) {
 416       continue;
 417     }
 418     int stride = dep_args(dept);
 419     GrowableArray<ciBaseObject*>* ciargs = new GrowableArray<ciBaseObject*>(stride);
 420     for (int i = 0; i < deps->length(); i += stride) {
 421       for (int j = 0; j < stride; j++) {
 422         // flush out the identities before printing
 423         ciargs->push(deps->at(i+j));
 424       }
 425       write_dependency_to(log(), dept, ciargs);
 426       ciargs->clear();
 427     }
 428     guarantee(deplen == deps->length(), "deps array cannot grow inside nested ResoureMark scope");
 429   }
 430 }
 431 
 432 void Dependencies::write_dependency_to(CompileLog* log,
 433                                        DepType dept,
 434                                        GrowableArray<DepArgument>* args,
 435                                        Klass* witness) {
 436   if (log == NULL) {
 437     return;
 438   }
 439   ResourceMark rm;
 440   ciEnv* env = ciEnv::current();
 441   GrowableArray<ciBaseObject*>* ciargs = new GrowableArray<ciBaseObject*>(args->length());
 442   for (GrowableArrayIterator<DepArgument> it = args->begin(); it != args->end(); ++it) {
 443     DepArgument arg = *it;
 444     if (arg.is_oop()) {
 445       ciargs->push(env->get_object(arg.oop_value()));
 446     } else {
 447       ciargs->push(env->get_metadata(arg.metadata_value()));
 448     }
 449   }
 450   int argslen = ciargs->length();
 451   Dependencies::write_dependency_to(log, dept, ciargs, witness);
 452   guarantee(argslen == ciargs->length(), "ciargs array cannot grow inside nested ResoureMark scope");
 453 }
 454 
 455 void Dependencies::write_dependency_to(CompileLog* log,
 456                                        DepType dept,
 457                                        GrowableArray<ciBaseObject*>* args,
 458                                        Klass* witness) {
 459   if (log == NULL) {
 460     return;
 461   }
 462   ResourceMark rm;
 463   GrowableArray<int>* argids = new GrowableArray<int>(args->length());
 464   for (GrowableArrayIterator<ciBaseObject*> it = args->begin(); it != args->end(); ++it) {
 465     ciBaseObject* obj = *it;
 466     if (obj->is_object()) {
 467       argids->push(log->identify(obj->as_object()));
 468     } else {
 469       argids->push(log->identify(obj->as_metadata()));
 470     }
 471   }
 472   if (witness != NULL) {
 473     log->begin_elem("dependency_failed");
 474   } else {
 475     log->begin_elem("dependency");
 476   }
 477   log->print(" type='%s'", dep_name(dept));
 478   const int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 479   if (ctxkj >= 0 && ctxkj < argids->length()) {
 480     log->print(" ctxk='%d'", argids->at(ctxkj));
 481   }
 482   // write remaining arguments, if any.
 483   for (int j = 0; j < argids->length(); j++) {
 484     if (j == ctxkj)  continue;  // already logged
 485     if (j == 1) {
 486       log->print(  " x='%d'",    argids->at(j));
 487     } else {
 488       log->print(" x%d='%d'", j, argids->at(j));
 489     }
 490   }
 491   if (witness != NULL) {
 492     log->object("witness", witness);
 493     log->stamp();
 494   }
 495   log->end_elem();
 496 }
 497 
 498 void Dependencies::write_dependency_to(xmlStream* xtty,
 499                                        DepType dept,
 500                                        GrowableArray<DepArgument>* args,
 501                                        Klass* witness) {
 502   if (xtty == NULL) {
 503     return;
 504   }
 505   ResourceMark rm;
 506   ttyLocker ttyl;
 507   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 508   if (witness != NULL) {
 509     xtty->begin_elem("dependency_failed");
 510   } else {
 511     xtty->begin_elem("dependency");
 512   }
 513   xtty->print(" type='%s'", dep_name(dept));
 514   if (ctxkj >= 0) {
 515     xtty->object("ctxk", args->at(ctxkj).metadata_value());
 516   }
 517   // write remaining arguments, if any.
 518   for (int j = 0; j < args->length(); j++) {
 519     if (j == ctxkj)  continue;  // already logged
 520     DepArgument arg = args->at(j);
 521     if (j == 1) {
 522       if (arg.is_oop()) {
 523         xtty->object("x", arg.oop_value());
 524       } else {
 525         xtty->object("x", arg.metadata_value());
 526       }
 527     } else {
 528       char xn[10]; sprintf(xn, "x%d", j);
 529       if (arg.is_oop()) {
 530         xtty->object(xn, arg.oop_value());
 531       } else {
 532         xtty->object(xn, arg.metadata_value());
 533       }
 534     }
 535   }
 536   if (witness != NULL) {
 537     xtty->object("witness", witness);
 538     xtty->stamp();
 539   }
 540   xtty->end_elem();
 541 }
 542 
 543 void Dependencies::print_dependency(DepType dept, GrowableArray<DepArgument>* args,
 544                                     Klass* witness) {
 545   ResourceMark rm;
 546   ttyLocker ttyl;   // keep the following output all in one block
 547   tty->print_cr("%s of type %s",
 548                 (witness == NULL)? "Dependency": "Failed dependency",
 549                 dep_name(dept));
 550   // print arguments
 551   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 552   for (int j = 0; j < args->length(); j++) {
 553     DepArgument arg = args->at(j);
 554     bool put_star = false;
 555     if (arg.is_null())  continue;
 556     const char* what;
 557     if (j == ctxkj) {
 558       assert(arg.is_metadata(), "must be");
 559       what = "context";
 560       put_star = !Dependencies::is_concrete_klass((Klass*)arg.metadata_value());
 561     } else if (arg.is_method()) {
 562       what = "method ";
 563       put_star = !Dependencies::is_concrete_method((Method*)arg.metadata_value());
 564     } else if (arg.is_klass()) {
 565       what = "class  ";
 566     } else {
 567       what = "object ";
 568     }
 569     tty->print("  %s = %s", what, (put_star? "*": ""));
 570     if (arg.is_klass())
 571       tty->print("%s", ((Klass*)arg.metadata_value())->external_name());
 572     else if (arg.is_method())
 573       ((Method*)arg.metadata_value())->print_value();
 574     else
 575       ShouldNotReachHere(); // Provide impl for this type.
 576     tty->cr();
 577   }
 578   if (witness != NULL) {
 579     bool put_star = !Dependencies::is_concrete_klass(witness);
 580     tty->print_cr("  witness = %s%s",
 581                   (put_star? "*": ""),
 582                   witness->external_name());
 583   }
 584 }
 585 
 586 void Dependencies::DepStream::log_dependency(Klass* witness) {
 587   if (_deps == NULL && xtty == NULL)  return;  // fast cutout for runtime
 588   ResourceMark rm;
 589   const int nargs = argument_count();
 590   GrowableArray<DepArgument>* args = new GrowableArray<DepArgument>(nargs);
 591   for (int j = 0; j < nargs; j++) {
 592     if (type() == call_site_target_value) {
 593       args->push(argument_oop(j));
 594     } else {
 595       args->push(argument(j));
 596     }
 597   }
 598   int argslen = args->length();
 599   if (_deps != NULL && _deps->log() != NULL) {
 600     Dependencies::write_dependency_to(_deps->log(), type(), args, witness);
 601   } else {
 602     Dependencies::write_dependency_to(xtty, type(), args, witness);
 603   }
 604   guarantee(argslen == args->length(), "args array cannot grow inside nested ResoureMark scope");
 605 }
 606 
 607 void Dependencies::DepStream::print_dependency(Klass* witness, bool verbose) {
 608   ResourceMark rm;
 609   int nargs = argument_count();
 610   GrowableArray<DepArgument>* args = new GrowableArray<DepArgument>(nargs);
 611   for (int j = 0; j < nargs; j++) {
 612     args->push(argument(j));
 613   }
 614   int argslen = args->length();
 615   Dependencies::print_dependency(type(), args, witness);
 616   if (verbose) {
 617     if (_code != NULL) {
 618       tty->print("  code: ");
 619       _code->print_value_on(tty);
 620       tty->cr();
 621     }
 622   }
 623   guarantee(argslen == args->length(), "args array cannot grow inside nested ResoureMark scope");
 624 }
 625 
 626 
 627 /// Dependency stream support (decodes dependencies from an nmethod):
 628 
 629 #ifdef ASSERT
 630 void Dependencies::DepStream::initial_asserts(size_t byte_limit) {
 631   assert(must_be_in_vm(), "raw oops here");
 632   _byte_limit = byte_limit;
 633   _type       = (DepType)(end_marker-1);  // defeat "already at end" assert
 634   assert((_code!=NULL) + (_deps!=NULL) == 1, "one or t'other");
 635 }
 636 #endif //ASSERT
 637 
 638 bool Dependencies::DepStream::next() {
 639   assert(_type != end_marker, "already at end");
 640   if (_bytes.position() == 0 && _code != NULL
 641       && _code->dependencies_size() == 0) {
 642     // Method has no dependencies at all.
 643     return false;
 644   }
 645   int code_byte = (_bytes.read_byte() & 0xFF);
 646   if (code_byte == end_marker) {
 647     DEBUG_ONLY(_type = end_marker);
 648     return false;
 649   } else {
 650     int ctxk_bit = (code_byte & Dependencies::default_context_type_bit);
 651     code_byte -= ctxk_bit;
 652     DepType dept = (DepType)code_byte;
 653     _type = dept;
 654     Dependencies::check_valid_dependency_type(dept);
 655     int stride = _dep_args[dept];
 656     assert(stride == dep_args(dept), "sanity");
 657     int skipj = -1;
 658     if (ctxk_bit != 0) {
 659       skipj = 0;  // currently the only context argument is at zero
 660       assert(skipj == dep_context_arg(dept), "zero arg always ctxk");
 661     }
 662     for (int j = 0; j < stride; j++) {
 663       _xi[j] = (j == skipj)? 0: _bytes.read_int();
 664     }
 665     DEBUG_ONLY(_xi[stride] = -1);   // help detect overruns
 666     return true;
 667   }
 668 }
 669 
 670 inline Metadata* Dependencies::DepStream::recorded_metadata_at(int i) {
 671   Metadata* o = NULL;
 672   if (_code != NULL) {
 673     o = _code->metadata_at(i);
 674   } else {
 675     o = _deps->oop_recorder()->metadata_at(i);
 676   }
 677   return o;
 678 }
 679 
 680 inline oop Dependencies::DepStream::recorded_oop_at(int i) {
 681   return (_code != NULL)
 682          ? _code->oop_at(i)
 683     : JNIHandles::resolve(_deps->oop_recorder()->oop_at(i));
 684 }
 685 
 686 Metadata* Dependencies::DepStream::argument(int i) {
 687   Metadata* result = recorded_metadata_at(argument_index(i));
 688 
 689   if (result == NULL) { // Explicit context argument can be compressed
 690     int ctxkj = dep_context_arg(type());  // -1 if no explicit context arg
 691     if (ctxkj >= 0 && i == ctxkj && ctxkj+1 < argument_count()) {
 692       result = ctxk_encoded_as_null(type(), argument(ctxkj+1));
 693     }
 694   }
 695 
 696   assert(result == NULL || result->is_klass() || result->is_method(), "must be");
 697   return result;
 698 }
 699 
 700 /**
 701  * Returns a unique identifier for each dependency argument.
 702  */
 703 uintptr_t Dependencies::DepStream::get_identifier(int i) {
 704   if (has_oop_argument()) {
 705     return (uintptr_t)(oopDesc*)argument_oop(i);
 706   } else {
 707     return (uintptr_t)argument(i);
 708   }
 709 }
 710 
 711 oop Dependencies::DepStream::argument_oop(int i) {
 712   oop result = recorded_oop_at(argument_index(i));
 713   assert(result == NULL || result->is_oop(), "must be");
 714   return result;
 715 }
 716 
 717 Klass* Dependencies::DepStream::context_type() {
 718   assert(must_be_in_vm(), "raw oops here");
 719 
 720   // Most dependencies have an explicit context type argument.
 721   {
 722     int ctxkj = dep_context_arg(type());  // -1 if no explicit context arg
 723     if (ctxkj >= 0) {
 724       Metadata* k = argument(ctxkj);
 725       assert(k != NULL && k->is_klass(), "type check");
 726       return (Klass*)k;
 727     }
 728   }
 729 
 730   // Some dependencies are using the klass of the first object
 731   // argument as implicit context type (e.g. call_site_target_value).
 732   {
 733     int ctxkj = dep_implicit_context_arg(type());
 734     if (ctxkj >= 0) {
 735       Klass* k = argument_oop(ctxkj)->klass();
 736       assert(k != NULL && k->is_klass(), "type check");
 737       return (Klass*) k;
 738     }
 739   }
 740 
 741   // And some dependencies don't have a context type at all,
 742   // e.g. evol_method.
 743   return NULL;
 744 }
 745 
 746 // ----------------- DependencySignature --------------------------------------
 747 bool DependencySignature::equals(DependencySignature const& s1, DependencySignature const& s2) {
 748   if ((s1.type() != s2.type()) || (s1.args_count() != s2.args_count())) {
 749     return false;
 750   }
 751 
 752   for (int i = 0; i < s1.args_count(); i++) {
 753     if (s1.arg(i) != s2.arg(i)) {
 754       return false;
 755     }
 756   }
 757   return true;
 758 }
 759 
 760 /// Checking dependencies:
 761 
 762 // This hierarchy walker inspects subtypes of a given type,
 763 // trying to find a "bad" class which breaks a dependency.
 764 // Such a class is called a "witness" to the broken dependency.
 765 // While searching around, we ignore "participants", which
 766 // are already known to the dependency.
 767 class ClassHierarchyWalker {
 768  public:
 769   enum { PARTICIPANT_LIMIT = 3 };
 770 
 771  private:
 772   // optional method descriptor to check for:
 773   Symbol* _name;
 774   Symbol* _signature;
 775 
 776   // special classes which are not allowed to be witnesses:
 777   Klass*    _participants[PARTICIPANT_LIMIT+1];
 778   int       _num_participants;
 779 
 780   // cache of method lookups
 781   Method* _found_methods[PARTICIPANT_LIMIT+1];
 782 
 783   // if non-zero, tells how many witnesses to convert to participants
 784   int       _record_witnesses;
 785 
 786   void initialize(Klass* participant) {
 787     _record_witnesses = 0;
 788     _participants[0]  = participant;
 789     _found_methods[0] = NULL;
 790     _num_participants = 0;
 791     if (participant != NULL) {
 792       // Terminating NULL.
 793       _participants[1] = NULL;
 794       _found_methods[1] = NULL;
 795       _num_participants = 1;
 796     }
 797   }
 798 
 799   void initialize_from_method(Method* m) {
 800     assert(m != NULL && m->is_method(), "sanity");
 801     _name      = m->name();
 802     _signature = m->signature();
 803   }
 804 
 805  public:
 806   // The walker is initialized to recognize certain methods and/or types
 807   // as friendly participants.
 808   ClassHierarchyWalker(Klass* participant, Method* m) {
 809     initialize_from_method(m);
 810     initialize(participant);
 811   }
 812   ClassHierarchyWalker(Method* m) {
 813     initialize_from_method(m);
 814     initialize(NULL);
 815   }
 816   ClassHierarchyWalker(Klass* participant = NULL) {
 817     _name      = NULL;
 818     _signature = NULL;
 819     initialize(participant);
 820   }
 821 
 822   // This is common code for two searches:  One for concrete subtypes,
 823   // the other for concrete method implementations and overrides.
 824   bool doing_subtype_search() {
 825     return _name == NULL;
 826   }
 827 
 828   int num_participants() { return _num_participants; }
 829   Klass* participant(int n) {
 830     assert((uint)n <= (uint)_num_participants, "oob");
 831     return _participants[n];
 832   }
 833 
 834   // Note:  If n==num_participants, returns NULL.
 835   Method* found_method(int n) {
 836     assert((uint)n <= (uint)_num_participants, "oob");
 837     Method* fm = _found_methods[n];
 838     assert(n == _num_participants || fm != NULL, "proper usage");
 839     assert(fm == NULL || fm->method_holder() == _participants[n], "sanity");
 840     return fm;
 841   }
 842 
 843 #ifdef ASSERT
 844   // Assert that m is inherited into ctxk, without intervening overrides.
 845   // (May return true even if this is not true, in corner cases where we punt.)
 846   bool check_method_context(Klass* ctxk, Method* m) {
 847     if (m->method_holder() == ctxk)
 848       return true;  // Quick win.
 849     if (m->is_private())
 850       return false; // Quick lose.  Should not happen.
 851     if (!(m->is_public() || m->is_protected()))
 852       // The override story is complex when packages get involved.
 853       return true;  // Must punt the assertion to true.
 854     Klass* k = ctxk;
 855     Method* lm = k->lookup_method(m->name(), m->signature());
 856     if (lm == NULL && k->oop_is_instance()) {
 857       // It might be an interface method
 858         lm = ((InstanceKlass*)k)->lookup_method_in_ordered_interfaces(m->name(),
 859                                                                 m->signature());
 860     }
 861     if (lm == m)
 862       // Method m is inherited into ctxk.
 863       return true;
 864     if (lm != NULL) {
 865       if (!(lm->is_public() || lm->is_protected())) {
 866         // Method is [package-]private, so the override story is complex.
 867         return true;  // Must punt the assertion to true.
 868       }
 869       if (lm->is_static()) {
 870         // Static methods don't override non-static so punt
 871         return true;
 872       }
 873       if (   !Dependencies::is_concrete_method(lm)
 874           && !Dependencies::is_concrete_method(m)
 875           && lm->method_holder()->is_subtype_of(m->method_holder()))
 876         // Method m is overridden by lm, but both are non-concrete.
 877         return true;
 878     }
 879     ResourceMark rm;
 880     tty->print_cr("Dependency method not found in the associated context:");
 881     tty->print_cr("  context = %s", ctxk->external_name());
 882     tty->print(   "  method = "); m->print_short_name(tty); tty->cr();
 883     if (lm != NULL) {
 884       tty->print( "  found = "); lm->print_short_name(tty); tty->cr();
 885     }
 886     return false;
 887   }
 888 #endif
 889 
 890   void add_participant(Klass* participant) {
 891     assert(_num_participants + _record_witnesses < PARTICIPANT_LIMIT, "oob");
 892     int np = _num_participants++;
 893     _participants[np] = participant;
 894     _participants[np+1] = NULL;
 895     _found_methods[np+1] = NULL;
 896   }
 897 
 898   void record_witnesses(int add) {
 899     if (add > PARTICIPANT_LIMIT)  add = PARTICIPANT_LIMIT;
 900     assert(_num_participants + add < PARTICIPANT_LIMIT, "oob");
 901     _record_witnesses = add;
 902   }
 903 
 904   bool is_witness(Klass* k) {
 905     if (doing_subtype_search()) {
 906       return Dependencies::is_concrete_klass(k);
 907     } else {
 908       Method* m = InstanceKlass::cast(k)->find_method(_name, _signature);
 909       if (m == NULL || !Dependencies::is_concrete_method(m))  return false;
 910       _found_methods[_num_participants] = m;
 911       // Note:  If add_participant(k) is called,
 912       // the method m will already be memoized for it.
 913       return true;
 914     }
 915   }
 916 
 917   bool is_participant(Klass* k) {
 918     if (k == _participants[0]) {
 919       return true;
 920     } else if (_num_participants <= 1) {
 921       return false;
 922     } else {
 923       return in_list(k, &_participants[1]);
 924     }
 925   }
 926   bool ignore_witness(Klass* witness) {
 927     if (_record_witnesses == 0) {
 928       return false;
 929     } else {
 930       --_record_witnesses;
 931       add_participant(witness);
 932       return true;
 933     }
 934   }
 935   static bool in_list(Klass* x, Klass** list) {
 936     for (int i = 0; ; i++) {
 937       Klass* y = list[i];
 938       if (y == NULL)  break;
 939       if (y == x)  return true;
 940     }
 941     return false;  // not in list
 942   }
 943 
 944  private:
 945   // the actual search method:
 946   Klass* find_witness_anywhere(Klass* context_type,
 947                                  bool participants_hide_witnesses,
 948                                  bool top_level_call = true);
 949   // the spot-checking version:
 950   Klass* find_witness_in(KlassDepChange& changes,
 951                          Klass* context_type,
 952                            bool participants_hide_witnesses);
 953  public:
 954   Klass* find_witness_subtype(Klass* context_type, KlassDepChange* changes = NULL) {
 955     assert(doing_subtype_search(), "must set up a subtype search");
 956     // When looking for unexpected concrete types,
 957     // do not look beneath expected ones.
 958     const bool participants_hide_witnesses = true;
 959     // CX > CC > C' is OK, even if C' is new.
 960     // CX > { CC,  C' } is not OK if C' is new, and C' is the witness.
 961     if (changes != NULL) {
 962       return find_witness_in(*changes, context_type, participants_hide_witnesses);
 963     } else {
 964       return find_witness_anywhere(context_type, participants_hide_witnesses);
 965     }
 966   }
 967   Klass* find_witness_definer(Klass* context_type, KlassDepChange* changes = NULL) {
 968     assert(!doing_subtype_search(), "must set up a method definer search");
 969     // When looking for unexpected concrete methods,
 970     // look beneath expected ones, to see if there are overrides.
 971     const bool participants_hide_witnesses = true;
 972     // CX.m > CC.m > C'.m is not OK, if C'.m is new, and C' is the witness.
 973     if (changes != NULL) {
 974       return find_witness_in(*changes, context_type, !participants_hide_witnesses);
 975     } else {
 976       return find_witness_anywhere(context_type, !participants_hide_witnesses);
 977     }
 978   }
 979 };
 980 
 981 #ifndef PRODUCT
 982 static int deps_find_witness_calls = 0;
 983 static int deps_find_witness_steps = 0;
 984 static int deps_find_witness_recursions = 0;
 985 static int deps_find_witness_singles = 0;
 986 static int deps_find_witness_print = 0; // set to -1 to force a final print
 987 static bool count_find_witness_calls() {
 988   if (TraceDependencies || LogCompilation) {
 989     int pcount = deps_find_witness_print + 1;
 990     bool final_stats      = (pcount == 0);
 991     bool initial_call     = (pcount == 1);
 992     bool occasional_print = ((pcount & ((1<<10) - 1)) == 0);
 993     if (pcount < 0)  pcount = 1; // crude overflow protection
 994     deps_find_witness_print = pcount;
 995     if (VerifyDependencies && initial_call) {
 996       tty->print_cr("Warning:  TraceDependencies results may be inflated by VerifyDependencies");
 997     }
 998     if (occasional_print || final_stats) {
 999       // Every now and then dump a little info about dependency searching.
1000       if (xtty != NULL) {
1001        ttyLocker ttyl;
1002        xtty->elem("deps_find_witness calls='%d' steps='%d' recursions='%d' singles='%d'",
1003                    deps_find_witness_calls,
1004                    deps_find_witness_steps,
1005                    deps_find_witness_recursions,
1006                    deps_find_witness_singles);
1007       }
1008       if (final_stats || (TraceDependencies && WizardMode)) {
1009         ttyLocker ttyl;
1010         tty->print_cr("Dependency check (find_witness) "
1011                       "calls=%d, steps=%d (avg=%.1f), recursions=%d, singles=%d",
1012                       deps_find_witness_calls,
1013                       deps_find_witness_steps,
1014                       (double)deps_find_witness_steps / deps_find_witness_calls,
1015                       deps_find_witness_recursions,
1016                       deps_find_witness_singles);
1017       }
1018     }
1019     return true;
1020   }
1021   return false;
1022 }
1023 #else
1024 #define count_find_witness_calls() (0)
1025 #endif //PRODUCT
1026 
1027 
1028 Klass* ClassHierarchyWalker::find_witness_in(KlassDepChange& changes,
1029                                                Klass* context_type,
1030                                                bool participants_hide_witnesses) {
1031   assert(changes.involves_context(context_type), "irrelevant dependency");
1032   Klass* new_type = changes.new_type();
1033 
1034   (void)count_find_witness_calls();
1035   NOT_PRODUCT(deps_find_witness_singles++);
1036 
1037   // Current thread must be in VM (not native mode, as in CI):
1038   assert(must_be_in_vm(), "raw oops here");
1039   // Must not move the class hierarchy during this check:
1040   assert_locked_or_safepoint(Compile_lock);
1041 
1042   int nof_impls = InstanceKlass::cast(context_type)->nof_implementors();
1043   if (nof_impls > 1) {
1044     // Avoid this case: *I.m > { A.m, C }; B.m > C
1045     // %%% Until this is fixed more systematically, bail out.
1046     // See corresponding comment in find_witness_anywhere.
1047     return context_type;
1048   }
1049 
1050   assert(!is_participant(new_type), "only old classes are participants");
1051   if (participants_hide_witnesses) {
1052     // If the new type is a subtype of a participant, we are done.
1053     for (int i = 0; i < num_participants(); i++) {
1054       Klass* part = participant(i);
1055       if (part == NULL)  continue;
1056       assert(changes.involves_context(part) == new_type->is_subtype_of(part),
1057              "correct marking of participants, b/c new_type is unique");
1058       if (changes.involves_context(part)) {
1059         // new guy is protected from this check by previous participant
1060         return NULL;
1061       }
1062     }
1063   }
1064 
1065   if (is_witness(new_type) &&
1066       !ignore_witness(new_type)) {
1067     return new_type;
1068   }
1069 
1070   return NULL;
1071 }
1072 
1073 
1074 // Walk hierarchy under a context type, looking for unexpected types.
1075 // Do not report participant types, and recursively walk beneath
1076 // them only if participants_hide_witnesses is false.
1077 // If top_level_call is false, skip testing the context type,
1078 // because the caller has already considered it.
1079 Klass* ClassHierarchyWalker::find_witness_anywhere(Klass* context_type,
1080                                                      bool participants_hide_witnesses,
1081                                                      bool top_level_call) {
1082   // Current thread must be in VM (not native mode, as in CI):
1083   assert(must_be_in_vm(), "raw oops here");
1084   // Must not move the class hierarchy during this check:
1085   assert_locked_or_safepoint(Compile_lock);
1086 
1087   bool do_counts = count_find_witness_calls();
1088 
1089   // Check the root of the sub-hierarchy first.
1090   if (top_level_call) {
1091     if (do_counts) {
1092       NOT_PRODUCT(deps_find_witness_calls++);
1093       NOT_PRODUCT(deps_find_witness_steps++);
1094     }
1095     if (is_participant(context_type)) {
1096       if (participants_hide_witnesses)  return NULL;
1097       // else fall through to search loop...
1098     } else if (is_witness(context_type) && !ignore_witness(context_type)) {
1099       // The context is an abstract class or interface, to start with.
1100       return context_type;
1101     }
1102   }
1103 
1104   // Now we must check each implementor and each subclass.
1105   // Use a short worklist to avoid blowing the stack.
1106   // Each worklist entry is a *chain* of subklass siblings to process.
1107   const int CHAINMAX = 100;  // >= 1 + InstanceKlass::implementors_limit
1108   Klass* chains[CHAINMAX];
1109   int    chaini = 0;  // index into worklist
1110   Klass* chain;       // scratch variable
1111 #define ADD_SUBCLASS_CHAIN(k)                     {  \
1112     assert(chaini < CHAINMAX, "oob");                \
1113     chain = InstanceKlass::cast(k)->subklass();      \
1114     if (chain != NULL)  chains[chaini++] = chain;    }
1115 
1116   // Look for non-abstract subclasses.
1117   // (Note:  Interfaces do not have subclasses.)
1118   ADD_SUBCLASS_CHAIN(context_type);
1119 
1120   // If it is an interface, search its direct implementors.
1121   // (Their subclasses are additional indirect implementors.
1122   // See InstanceKlass::add_implementor.)
1123   // (Note:  nof_implementors is always zero for non-interfaces.)
1124   int nof_impls = InstanceKlass::cast(context_type)->nof_implementors();
1125   if (nof_impls > 1) {
1126     // Avoid this case: *I.m > { A.m, C }; B.m > C
1127     // Here, I.m has 2 concrete implementations, but m appears unique
1128     // as A.m, because the search misses B.m when checking C.
1129     // The inherited method B.m was getting missed by the walker
1130     // when interface 'I' was the starting point.
1131     // %%% Until this is fixed more systematically, bail out.
1132     // (Old CHA had the same limitation.)
1133     return context_type;
1134   }
1135   if (nof_impls > 0) {
1136     Klass* impl = InstanceKlass::cast(context_type)->implementor();
1137     assert(impl != NULL, "just checking");
1138     // If impl is the same as the context_type, then more than one
1139     // implementor has seen. No exact info in this case.
1140     if (impl == context_type) {
1141       return context_type;  // report an inexact witness to this sad affair
1142     }
1143     if (do_counts)
1144       { NOT_PRODUCT(deps_find_witness_steps++); }
1145     if (is_participant(impl)) {
1146       if (!participants_hide_witnesses) {
1147         ADD_SUBCLASS_CHAIN(impl);
1148       }
1149     } else if (is_witness(impl) && !ignore_witness(impl)) {
1150       return impl;
1151     } else {
1152       ADD_SUBCLASS_CHAIN(impl);
1153     }
1154   }
1155 
1156   // Recursively process each non-trivial sibling chain.
1157   while (chaini > 0) {
1158     Klass* chain = chains[--chaini];
1159     for (Klass* sub = chain; sub != NULL; sub = sub->next_sibling()) {
1160       if (do_counts) { NOT_PRODUCT(deps_find_witness_steps++); }
1161       if (is_participant(sub)) {
1162         if (participants_hide_witnesses)  continue;
1163         // else fall through to process this guy's subclasses
1164       } else if (is_witness(sub) && !ignore_witness(sub)) {
1165         return sub;
1166       }
1167       if (chaini < (VerifyDependencies? 2: CHAINMAX)) {
1168         // Fast path.  (Partially disabled if VerifyDependencies.)
1169         ADD_SUBCLASS_CHAIN(sub);
1170       } else {
1171         // Worklist overflow.  Do a recursive call.  Should be rare.
1172         // The recursive call will have its own worklist, of course.
1173         // (Note that sub has already been tested, so that there is
1174         // no need for the recursive call to re-test.  That's handy,
1175         // since the recursive call sees sub as the context_type.)
1176         if (do_counts) { NOT_PRODUCT(deps_find_witness_recursions++); }
1177         Klass* witness = find_witness_anywhere(sub,
1178                                                  participants_hide_witnesses,
1179                                                  /*top_level_call=*/ false);
1180         if (witness != NULL)  return witness;
1181       }
1182     }
1183   }
1184 
1185   // No witness found.  The dependency remains unbroken.
1186   return NULL;
1187 #undef ADD_SUBCLASS_CHAIN
1188 }
1189 
1190 
1191 bool Dependencies::is_concrete_klass(Klass* k) {
1192   if (k->is_abstract())  return false;
1193   // %%% We could treat classes which are concrete but
1194   // have not yet been instantiated as virtually abstract.
1195   // This would require a deoptimization barrier on first instantiation.
1196   //if (k->is_not_instantiated())  return false;
1197   return true;
1198 }
1199 
1200 bool Dependencies::is_concrete_method(Method* m) {
1201   // Statics are irrelevant to virtual call sites.
1202   if (m->is_static())  return false;
1203 
1204   // We could also return false if m does not yet appear to be
1205   // executed, if the VM version supports this distinction also.
1206   // Default methods are considered "concrete" as well.
1207   return !m->is_abstract() &&
1208          !m->is_overpass(); // error functions aren't concrete
1209 }
1210 
1211 
1212 Klass* Dependencies::find_finalizable_subclass(Klass* k) {
1213   if (k->is_interface())  return NULL;
1214   if (k->has_finalizer()) return k;
1215   k = k->subklass();
1216   while (k != NULL) {
1217     Klass* result = find_finalizable_subclass(k);
1218     if (result != NULL) return result;
1219     k = k->next_sibling();
1220   }
1221   return NULL;
1222 }
1223 
1224 
1225 bool Dependencies::is_concrete_klass(ciInstanceKlass* k) {
1226   if (k->is_abstract())  return false;
1227   // We could also return false if k does not yet appear to be
1228   // instantiated, if the VM version supports this distinction also.
1229   //if (k->is_not_instantiated())  return false;
1230   return true;
1231 }
1232 
1233 bool Dependencies::is_concrete_method(ciMethod* m) {
1234   // Statics are irrelevant to virtual call sites.
1235   if (m->is_static())  return false;
1236 
1237   // We could also return false if m does not yet appear to be
1238   // executed, if the VM version supports this distinction also.
1239   return !m->is_abstract();
1240 }
1241 
1242 
1243 bool Dependencies::has_finalizable_subclass(ciInstanceKlass* k) {
1244   return k->has_finalizable_subclass();
1245 }
1246 
1247 
1248 // Any use of the contents (bytecodes) of a method must be
1249 // marked by an "evol_method" dependency, if those contents
1250 // can change.  (Note: A method is always dependent on itself.)
1251 Klass* Dependencies::check_evol_method(Method* m) {
1252   assert(must_be_in_vm(), "raw oops here");
1253   // Did somebody do a JVMTI RedefineClasses while our backs were turned?
1254   // Or is there a now a breakpoint?
1255   // (Assumes compiled code cannot handle bkpts; change if UseFastBreakpoints.)
1256   if (m->is_old()
1257       || m->number_of_breakpoints() > 0) {
1258     return m->method_holder();
1259   } else {
1260     return NULL;
1261   }
1262 }
1263 
1264 // This is a strong assertion:  It is that the given type
1265 // has no subtypes whatever.  It is most useful for
1266 // optimizing checks on reflected types or on array types.
1267 // (Checks on types which are derived from real instances
1268 // can be optimized more strongly than this, because we
1269 // know that the checked type comes from a concrete type,
1270 // and therefore we can disregard abstract types.)
1271 Klass* Dependencies::check_leaf_type(Klass* ctxk) {
1272   assert(must_be_in_vm(), "raw oops here");
1273   assert_locked_or_safepoint(Compile_lock);
1274   InstanceKlass* ctx = InstanceKlass::cast(ctxk);
1275   Klass* sub = ctx->subklass();
1276   if (sub != NULL) {
1277     return sub;
1278   } else if (ctx->nof_implementors() != 0) {
1279     // if it is an interface, it must be unimplemented
1280     // (if it is not an interface, nof_implementors is always zero)
1281     Klass* impl = ctx->implementor();
1282     assert(impl != NULL, "must be set");
1283     return impl;
1284   } else {
1285     return NULL;
1286   }
1287 }
1288 
1289 // Test the assertion that conck is the only concrete subtype* of ctxk.
1290 // The type conck itself is allowed to have have further concrete subtypes.
1291 // This allows the compiler to narrow occurrences of ctxk by conck,
1292 // when dealing with the types of actual instances.
1293 Klass* Dependencies::check_abstract_with_unique_concrete_subtype(Klass* ctxk,
1294                                                                    Klass* conck,
1295                                                                    KlassDepChange* changes) {
1296   ClassHierarchyWalker wf(conck);
1297   return wf.find_witness_subtype(ctxk, changes);
1298 }
1299 
1300 // If a non-concrete class has no concrete subtypes, it is not (yet)
1301 // instantiatable.  This can allow the compiler to make some paths go
1302 // dead, if they are gated by a test of the type.
1303 Klass* Dependencies::check_abstract_with_no_concrete_subtype(Klass* ctxk,
1304                                                                KlassDepChange* changes) {
1305   // Find any concrete subtype, with no participants:
1306   ClassHierarchyWalker wf;
1307   return wf.find_witness_subtype(ctxk, changes);
1308 }
1309 
1310 
1311 // If a concrete class has no concrete subtypes, it can always be
1312 // exactly typed.  This allows the use of a cheaper type test.
1313 Klass* Dependencies::check_concrete_with_no_concrete_subtype(Klass* ctxk,
1314                                                                KlassDepChange* changes) {
1315   // Find any concrete subtype, with only the ctxk as participant:
1316   ClassHierarchyWalker wf(ctxk);
1317   return wf.find_witness_subtype(ctxk, changes);
1318 }
1319 
1320 
1321 // Find the unique concrete proper subtype of ctxk, or NULL if there
1322 // is more than one concrete proper subtype.  If there are no concrete
1323 // proper subtypes, return ctxk itself, whether it is concrete or not.
1324 // The returned subtype is allowed to have have further concrete subtypes.
1325 // That is, return CC1 for CX > CC1 > CC2, but NULL for CX > { CC1, CC2 }.
1326 Klass* Dependencies::find_unique_concrete_subtype(Klass* ctxk) {
1327   ClassHierarchyWalker wf(ctxk);   // Ignore ctxk when walking.
1328   wf.record_witnesses(1);          // Record one other witness when walking.
1329   Klass* wit = wf.find_witness_subtype(ctxk);
1330   if (wit != NULL)  return NULL;   // Too many witnesses.
1331   Klass* conck = wf.participant(0);
1332   if (conck == NULL) {
1333 #ifndef PRODUCT
1334     // Make sure the dependency mechanism will pass this discovery:
1335     if (VerifyDependencies) {
1336       // Turn off dependency tracing while actually testing deps.
1337       FlagSetting fs(TraceDependencies, false);
1338       if (!Dependencies::is_concrete_klass(ctxk)) {
1339         guarantee(NULL ==
1340                   (void *)check_abstract_with_no_concrete_subtype(ctxk),
1341                   "verify dep.");
1342       } else {
1343         guarantee(NULL ==
1344                   (void *)check_concrete_with_no_concrete_subtype(ctxk),
1345                   "verify dep.");
1346       }
1347     }
1348 #endif //PRODUCT
1349     return ctxk;                   // Return ctxk as a flag for "no subtypes".
1350   } else {
1351 #ifndef PRODUCT
1352     // Make sure the dependency mechanism will pass this discovery:
1353     if (VerifyDependencies) {
1354       // Turn off dependency tracing while actually testing deps.
1355       FlagSetting fs(TraceDependencies, false);
1356       if (!Dependencies::is_concrete_klass(ctxk)) {
1357         guarantee(NULL == (void *)
1358                   check_abstract_with_unique_concrete_subtype(ctxk, conck),
1359                   "verify dep.");
1360       }
1361     }
1362 #endif //PRODUCT
1363     return conck;
1364   }
1365 }
1366 
1367 // Test the assertion that the k[12] are the only concrete subtypes of ctxk,
1368 // except possibly for further subtypes of k[12] themselves.
1369 // The context type must be abstract.  The types k1 and k2 are themselves
1370 // allowed to have further concrete subtypes.
1371 Klass* Dependencies::check_abstract_with_exclusive_concrete_subtypes(
1372                                                 Klass* ctxk,
1373                                                 Klass* k1,
1374                                                 Klass* k2,
1375                                                 KlassDepChange* changes) {
1376   ClassHierarchyWalker wf;
1377   wf.add_participant(k1);
1378   wf.add_participant(k2);
1379   return wf.find_witness_subtype(ctxk, changes);
1380 }
1381 
1382 // Search ctxk for concrete implementations.  If there are klen or fewer,
1383 // pack them into the given array and return the number.
1384 // Otherwise, return -1, meaning the given array would overflow.
1385 // (Note that a return of 0 means there are exactly no concrete subtypes.)
1386 // In this search, if ctxk is concrete, it will be reported alone.
1387 // For any type CC reported, no proper subtypes of CC will be reported.
1388 int Dependencies::find_exclusive_concrete_subtypes(Klass* ctxk,
1389                                                    int klen,
1390                                                    Klass* karray[]) {
1391   ClassHierarchyWalker wf;
1392   wf.record_witnesses(klen);
1393   Klass* wit = wf.find_witness_subtype(ctxk);
1394   if (wit != NULL)  return -1;  // Too many witnesses.
1395   int num = wf.num_participants();
1396   assert(num <= klen, "oob");
1397   // Pack the result array with the good news.
1398   for (int i = 0; i < num; i++)
1399     karray[i] = wf.participant(i);
1400 #ifndef PRODUCT
1401   // Make sure the dependency mechanism will pass this discovery:
1402   if (VerifyDependencies) {
1403     // Turn off dependency tracing while actually testing deps.
1404     FlagSetting fs(TraceDependencies, false);
1405     switch (Dependencies::is_concrete_klass(ctxk)? -1: num) {
1406     case -1: // ctxk was itself concrete
1407       guarantee(num == 1 && karray[0] == ctxk, "verify dep.");
1408       break;
1409     case 0:
1410       guarantee(NULL == (void *)check_abstract_with_no_concrete_subtype(ctxk),
1411                 "verify dep.");
1412       break;
1413     case 1:
1414       guarantee(NULL == (void *)
1415                 check_abstract_with_unique_concrete_subtype(ctxk, karray[0]),
1416                 "verify dep.");
1417       break;
1418     case 2:
1419       guarantee(NULL == (void *)
1420                 check_abstract_with_exclusive_concrete_subtypes(ctxk,
1421                                                                 karray[0],
1422                                                                 karray[1]),
1423                 "verify dep.");
1424       break;
1425     default:
1426       ShouldNotReachHere();  // klen > 2 yet supported
1427     }
1428   }
1429 #endif //PRODUCT
1430   return num;
1431 }
1432 
1433 // If a class (or interface) has a unique concrete method uniqm, return NULL.
1434 // Otherwise, return a class that contains an interfering method.
1435 Klass* Dependencies::check_unique_concrete_method(Klass* ctxk, Method* uniqm,
1436                                                     KlassDepChange* changes) {
1437   // Here is a missing optimization:  If uniqm->is_final(),
1438   // we don't really need to search beneath it for overrides.
1439   // This is probably not important, since we don't use dependencies
1440   // to track final methods.  (They can't be "definalized".)
1441   ClassHierarchyWalker wf(uniqm->method_holder(), uniqm);
1442   return wf.find_witness_definer(ctxk, changes);
1443 }
1444 
1445 // Find the set of all non-abstract methods under ctxk that match m.
1446 // (The method m must be defined or inherited in ctxk.)
1447 // Include m itself in the set, unless it is abstract.
1448 // If this set has exactly one element, return that element.
1449 Method* Dependencies::find_unique_concrete_method(Klass* ctxk, Method* m) {
1450   // Return NULL if m is marked old; must have been a redefined method.
1451   if (m->is_old()) {
1452     return NULL;
1453   }
1454   ClassHierarchyWalker wf(m);
1455   assert(wf.check_method_context(ctxk, m), "proper context");
1456   wf.record_witnesses(1);
1457   Klass* wit = wf.find_witness_definer(ctxk);
1458   if (wit != NULL)  return NULL;  // Too many witnesses.
1459   Method* fm = wf.found_method(0);  // Will be NULL if num_parts == 0.
1460   if (Dependencies::is_concrete_method(m)) {
1461     if (fm == NULL) {
1462       // It turns out that m was always the only implementation.
1463       fm = m;
1464     } else if (fm != m) {
1465       // Two conflicting implementations after all.
1466       // (This can happen if m is inherited into ctxk and fm overrides it.)
1467       return NULL;
1468     }
1469   }
1470 #ifndef PRODUCT
1471   // Make sure the dependency mechanism will pass this discovery:
1472   if (VerifyDependencies && fm != NULL) {
1473     guarantee(NULL == (void *)check_unique_concrete_method(ctxk, fm),
1474               "verify dep.");
1475   }
1476 #endif //PRODUCT
1477   return fm;
1478 }
1479 
1480 Klass* Dependencies::check_exclusive_concrete_methods(Klass* ctxk,
1481                                                         Method* m1,
1482                                                         Method* m2,
1483                                                         KlassDepChange* changes) {
1484   ClassHierarchyWalker wf(m1);
1485   wf.add_participant(m1->method_holder());
1486   wf.add_participant(m2->method_holder());
1487   return wf.find_witness_definer(ctxk, changes);
1488 }
1489 
1490 // Find the set of all non-abstract methods under ctxk that match m[0].
1491 // (The method m[0] must be defined or inherited in ctxk.)
1492 // Include m itself in the set, unless it is abstract.
1493 // Fill the given array m[0..(mlen-1)] with this set, and return the length.
1494 // (The length may be zero if no concrete methods are found anywhere.)
1495 // If there are too many concrete methods to fit in marray, return -1.
1496 int Dependencies::find_exclusive_concrete_methods(Klass* ctxk,
1497                                                   int mlen,
1498                                                   Method* marray[]) {
1499   Method* m0 = marray[0];
1500   ClassHierarchyWalker wf(m0);
1501   assert(wf.check_method_context(ctxk, m0), "proper context");
1502   wf.record_witnesses(mlen);
1503   bool participants_hide_witnesses = true;
1504   Klass* wit = wf.find_witness_definer(ctxk);
1505   if (wit != NULL)  return -1;  // Too many witnesses.
1506   int num = wf.num_participants();
1507   assert(num <= mlen, "oob");
1508   // Keep track of whether m is also part of the result set.
1509   int mfill = 0;
1510   assert(marray[mfill] == m0, "sanity");
1511   if (Dependencies::is_concrete_method(m0))
1512     mfill++;  // keep m0 as marray[0], the first result
1513   for (int i = 0; i < num; i++) {
1514     Method* fm = wf.found_method(i);
1515     if (fm == m0)  continue;  // Already put this guy in the list.
1516     if (mfill == mlen) {
1517       return -1;              // Oops.  Too many methods after all!
1518     }
1519     marray[mfill++] = fm;
1520   }
1521 #ifndef PRODUCT
1522   // Make sure the dependency mechanism will pass this discovery:
1523   if (VerifyDependencies) {
1524     // Turn off dependency tracing while actually testing deps.
1525     FlagSetting fs(TraceDependencies, false);
1526     switch (mfill) {
1527     case 1:
1528       guarantee(NULL == (void *)check_unique_concrete_method(ctxk, marray[0]),
1529                 "verify dep.");
1530       break;
1531     case 2:
1532       guarantee(NULL == (void *)
1533                 check_exclusive_concrete_methods(ctxk, marray[0], marray[1]),
1534                 "verify dep.");
1535       break;
1536     default:
1537       ShouldNotReachHere();  // mlen > 2 yet supported
1538     }
1539   }
1540 #endif //PRODUCT
1541   return mfill;
1542 }
1543 
1544 
1545 Klass* Dependencies::check_has_no_finalizable_subclasses(Klass* ctxk, KlassDepChange* changes) {
1546   Klass* search_at = ctxk;
1547   if (changes != NULL)
1548     search_at = changes->new_type(); // just look at the new bit
1549   return find_finalizable_subclass(search_at);
1550 }
1551 
1552 
1553 Klass* Dependencies::check_call_site_target_value(oop call_site, oop method_handle, CallSiteDepChange* changes) {
1554   assert(call_site    ->is_a(SystemDictionary::CallSite_klass()),     "sanity");
1555   assert(method_handle->is_a(SystemDictionary::MethodHandle_klass()), "sanity");
1556   if (changes == NULL) {
1557     // Validate all CallSites
1558     if (java_lang_invoke_CallSite::target(call_site) != method_handle)
1559       return call_site->klass();  // assertion failed
1560   } else {
1561     // Validate the given CallSite
1562     if (call_site == changes->call_site() && java_lang_invoke_CallSite::target(call_site) != changes->method_handle()) {
1563       assert(method_handle != changes->method_handle(), "must be");
1564       return call_site->klass();  // assertion failed
1565     }
1566   }
1567   return NULL;  // assertion still valid
1568 }
1569 
1570 
1571 void Dependencies::DepStream::trace_and_log_witness(Klass* witness) {
1572   if (witness != NULL) {
1573     if (TraceDependencies) {
1574       print_dependency(witness, /*verbose=*/ true);
1575     }
1576     // The following is a no-op unless logging is enabled:
1577     log_dependency(witness);
1578   }
1579 }
1580 
1581 
1582 Klass* Dependencies::DepStream::check_klass_dependency(KlassDepChange* changes) {
1583   assert_locked_or_safepoint(Compile_lock);
1584   Dependencies::check_valid_dependency_type(type());
1585 
1586   Klass* witness = NULL;
1587   switch (type()) {
1588   case evol_method:
1589     witness = check_evol_method(method_argument(0));
1590     break;
1591   case leaf_type:
1592     witness = check_leaf_type(context_type());
1593     break;
1594   case abstract_with_unique_concrete_subtype:
1595     witness = check_abstract_with_unique_concrete_subtype(context_type(), type_argument(1), changes);
1596     break;
1597   case abstract_with_no_concrete_subtype:
1598     witness = check_abstract_with_no_concrete_subtype(context_type(), changes);
1599     break;
1600   case concrete_with_no_concrete_subtype:
1601     witness = check_concrete_with_no_concrete_subtype(context_type(), changes);
1602     break;
1603   case unique_concrete_method:
1604     witness = check_unique_concrete_method(context_type(), method_argument(1), changes);
1605     break;
1606   case abstract_with_exclusive_concrete_subtypes_2:
1607     witness = check_abstract_with_exclusive_concrete_subtypes(context_type(), type_argument(1), type_argument(2), changes);
1608     break;
1609   case exclusive_concrete_methods_2:
1610     witness = check_exclusive_concrete_methods(context_type(), method_argument(1), method_argument(2), changes);
1611     break;
1612   case no_finalizable_subclasses:
1613     witness = check_has_no_finalizable_subclasses(context_type(), changes);
1614     break;
1615   default:
1616     witness = NULL;
1617     break;
1618   }
1619   trace_and_log_witness(witness);
1620   return witness;
1621 }
1622 
1623 
1624 Klass* Dependencies::DepStream::check_call_site_dependency(CallSiteDepChange* changes) {
1625   assert_locked_or_safepoint(Compile_lock);
1626   Dependencies::check_valid_dependency_type(type());
1627 
1628   Klass* witness = NULL;
1629   switch (type()) {
1630   case call_site_target_value:
1631     witness = check_call_site_target_value(argument_oop(0), argument_oop(1), changes);
1632     break;
1633   default:
1634     witness = NULL;
1635     break;
1636   }
1637   trace_and_log_witness(witness);
1638   return witness;
1639 }
1640 
1641 
1642 Klass* Dependencies::DepStream::spot_check_dependency_at(DepChange& changes) {
1643   // Handle klass dependency
1644   if (changes.is_klass_change() && changes.as_klass_change()->involves_context(context_type()))
1645     return check_klass_dependency(changes.as_klass_change());
1646 
1647   // Handle CallSite dependency
1648   if (changes.is_call_site_change())
1649     return check_call_site_dependency(changes.as_call_site_change());
1650 
1651   // irrelevant dependency; skip it
1652   return NULL;
1653 }
1654 
1655 
1656 void DepChange::print() {
1657   int nsup = 0, nint = 0;
1658   for (ContextStream str(*this); str.next(); ) {
1659     Klass* k = str.klass();
1660     switch (str.change_type()) {
1661     case Change_new_type:
1662       tty->print_cr("  dependee = %s", InstanceKlass::cast(k)->external_name());
1663       break;
1664     case Change_new_sub:
1665       if (!WizardMode) {
1666         ++nsup;
1667       } else {
1668         tty->print_cr("  context super = %s", InstanceKlass::cast(k)->external_name());
1669       }
1670       break;
1671     case Change_new_impl:
1672       if (!WizardMode) {
1673         ++nint;
1674       } else {
1675         tty->print_cr("  context interface = %s", InstanceKlass::cast(k)->external_name());
1676       }
1677       break;
1678     }
1679   }
1680   if (nsup + nint != 0) {
1681     tty->print_cr("  context supers = %d, interfaces = %d", nsup, nint);
1682   }
1683 }
1684 
1685 void DepChange::ContextStream::start() {
1686   Klass* new_type = _changes.is_klass_change() ? _changes.as_klass_change()->new_type() : (Klass*) NULL;
1687   _change_type = (new_type == NULL ? NO_CHANGE : Start_Klass);
1688   _klass = new_type;
1689   _ti_base = NULL;
1690   _ti_index = 0;
1691   _ti_limit = 0;
1692 }
1693 
1694 bool DepChange::ContextStream::next() {
1695   switch (_change_type) {
1696   case Start_Klass:             // initial state; _klass is the new type
1697     _ti_base = InstanceKlass::cast(_klass)->transitive_interfaces();
1698     _ti_index = 0;
1699     _change_type = Change_new_type;
1700     return true;
1701   case Change_new_type:
1702     // fall through:
1703     _change_type = Change_new_sub;
1704   case Change_new_sub:
1705     // 6598190: brackets workaround Sun Studio C++ compiler bug 6629277
1706     {
1707       _klass = InstanceKlass::cast(_klass)->super();
1708       if (_klass != NULL) {
1709         return true;
1710       }
1711     }
1712     // else set up _ti_limit and fall through:
1713     _ti_limit = (_ti_base == NULL) ? 0 : _ti_base->length();
1714     _change_type = Change_new_impl;
1715   case Change_new_impl:
1716     if (_ti_index < _ti_limit) {
1717       _klass = _ti_base->at(_ti_index++);
1718       return true;
1719     }
1720     // fall through:
1721     _change_type = NO_CHANGE;  // iterator is exhausted
1722   case NO_CHANGE:
1723     break;
1724   default:
1725     ShouldNotReachHere();
1726   }
1727   return false;
1728 }
1729 
1730 void KlassDepChange::initialize() {
1731   // entire transaction must be under this lock:
1732   assert_lock_strong(Compile_lock);
1733 
1734   // Mark all dependee and all its superclasses
1735   // Mark transitive interfaces
1736   for (ContextStream str(*this); str.next(); ) {
1737     Klass* d = str.klass();
1738     assert(!InstanceKlass::cast(d)->is_marked_dependent(), "checking");
1739     InstanceKlass::cast(d)->set_is_marked_dependent(true);
1740   }
1741 }
1742 
1743 KlassDepChange::~KlassDepChange() {
1744   // Unmark all dependee and all its superclasses
1745   // Unmark transitive interfaces
1746   for (ContextStream str(*this); str.next(); ) {
1747     Klass* d = str.klass();
1748     InstanceKlass::cast(d)->set_is_marked_dependent(false);
1749   }
1750 }
1751 
1752 bool KlassDepChange::involves_context(Klass* k) {
1753   if (k == NULL || !k->oop_is_instance()) {
1754     return false;
1755   }
1756   InstanceKlass* ik = InstanceKlass::cast(k);
1757   bool is_contained = ik->is_marked_dependent();
1758   assert(is_contained == new_type()->is_subtype_of(k),
1759          "correct marking of potential context types");
1760   return is_contained;
1761 }
1762 
1763 #ifndef PRODUCT
1764 void Dependencies::print_statistics() {
1765   if (deps_find_witness_print != 0) {
1766     // Call one final time, to flush out the data.
1767     deps_find_witness_print = -1;
1768     count_find_witness_calls();
1769   }
1770 }
1771 #endif