1 /*
   2  * Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   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.inline.hpp"
  34 #include "utilities/copy.hpp"
  35 
  36 
  37 #ifdef ASSERT
  38 static bool must_be_in_vm() {
  39   Thread* thread = Thread::current();
  40   if (thread->is_Java_thread())
  41     return ((JavaThread*)thread)->thread_state() == _thread_in_vm;
  42   else
  43     return true;  //something like this: thread->is_VM_thread();
  44 }
  45 #endif //ASSERT
  46 
  47 void Dependencies::initialize(ciEnv* env) {
  48   Arena* arena = env->arena();
  49   _oop_recorder = env->oop_recorder();
  50   _log = env->log();
  51   _dep_seen = new(arena) GrowableArray<int>(arena, 500, 0, 0);
  52   DEBUG_ONLY(_deps[end_marker] = NULL);
  53   for (int i = (int)FIRST_TYPE; i < (int)TYPE_LIMIT; i++) {
  54     _deps[i] = new(arena) GrowableArray<ciObject*>(arena, 10, 0, 0);
  55   }
  56   _content_bytes = NULL;
  57   _size_in_bytes = (size_t)-1;
  58 
  59   assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT), "sanity");
  60 }
  61 
  62 void Dependencies::assert_evol_method(ciMethod* m) {
  63   assert_common_1(evol_method, m);
  64 }
  65 
  66 void Dependencies::assert_leaf_type(ciKlass* ctxk) {
  67   if (ctxk->is_array_klass()) {
  68     // As a special case, support this assertion on an array type,
  69     // which reduces to an assertion on its element type.
  70     // Note that this cannot be done with assertions that
  71     // relate to concreteness or abstractness.
  72     ciType* elemt = ctxk->as_array_klass()->base_element_type();
  73     if (!elemt->is_instance_klass())  return;   // Ex:  int[][]
  74     ctxk = elemt->as_instance_klass();
  75     //if (ctxk->is_final())  return;            // Ex:  String[][]
  76   }
  77   check_ctxk(ctxk);
  78   assert_common_1(leaf_type, ctxk);
  79 }
  80 
  81 void Dependencies::assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck) {
  82   check_ctxk_abstract(ctxk);
  83   assert_common_2(abstract_with_unique_concrete_subtype, ctxk, conck);
  84 }
  85 
  86 void Dependencies::assert_abstract_with_no_concrete_subtype(ciKlass* ctxk) {
  87   check_ctxk_abstract(ctxk);
  88   assert_common_1(abstract_with_no_concrete_subtype, ctxk);
  89 }
  90 
  91 void Dependencies::assert_concrete_with_no_concrete_subtype(ciKlass* ctxk) {
  92   check_ctxk_concrete(ctxk);
  93   assert_common_1(concrete_with_no_concrete_subtype, ctxk);
  94 }
  95 
  96 void Dependencies::assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm) {
  97   check_ctxk(ctxk);
  98   assert_common_2(unique_concrete_method, ctxk, uniqm);
  99 }
 100 
 101 void Dependencies::assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2) {
 102   check_ctxk(ctxk);
 103   assert_common_3(abstract_with_exclusive_concrete_subtypes_2, ctxk, k1, k2);
 104 }
 105 
 106 void Dependencies::assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2) {
 107   check_ctxk(ctxk);
 108   assert_common_3(exclusive_concrete_methods_2, ctxk, m1, m2);
 109 }
 110 
 111 void Dependencies::assert_has_no_finalizable_subclasses(ciKlass* ctxk) {
 112   check_ctxk(ctxk);
 113   assert_common_1(no_finalizable_subclasses, ctxk);
 114 }
 115 
 116 void Dependencies::assert_call_site_target_value(ciCallSite* call_site, ciMethodHandle* method_handle) {
 117   check_ctxk(call_site->klass());
 118   assert_common_2(call_site_target_value, call_site, method_handle);
 119 }
 120 
 121 // Helper function.  If we are adding a new dep. under ctxk2,
 122 // try to find an old dep. under a broader* ctxk1.  If there is
 123 //
 124 bool Dependencies::maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
 125                                     int ctxk_i, ciKlass* ctxk2) {
 126   ciKlass* ctxk1 = deps->at(ctxk_i)->as_klass();
 127   if (ctxk2->is_subtype_of(ctxk1)) {
 128     return true;  // success, and no need to change
 129   } else if (ctxk1->is_subtype_of(ctxk2)) {
 130     // new context class fully subsumes previous one
 131     deps->at_put(ctxk_i, ctxk2);
 132     return true;
 133   } else {
 134     return false;
 135   }
 136 }
 137 
 138 void Dependencies::assert_common_1(DepType dept, ciObject* x) {
 139   assert(dep_args(dept) == 1, "sanity");
 140   log_dependency(dept, x);
 141   GrowableArray<ciObject*>* deps = _deps[dept];
 142 
 143   // see if the same (or a similar) dep is already recorded
 144   if (note_dep_seen(dept, x)) {
 145     assert(deps->find(x) >= 0, "sanity");
 146   } else {
 147     deps->append(x);
 148   }
 149 }
 150 
 151 void Dependencies::assert_common_2(DepType dept,
 152                                    ciObject* x0, ciObject* x1) {
 153   assert(dep_args(dept) == 2, "sanity");
 154   log_dependency(dept, x0, x1);
 155   GrowableArray<ciObject*>* deps = _deps[dept];
 156 
 157   // see if the same (or a similar) dep is already recorded
 158   bool has_ctxk = has_explicit_context_arg(dept);
 159   if (has_ctxk) {
 160     assert(dep_context_arg(dept) == 0, "sanity");
 161     if (note_dep_seen(dept, x1)) {
 162       // look in this bucket for redundant assertions
 163       const int stride = 2;
 164       for (int i = deps->length(); (i -= stride) >= 0; ) {
 165         ciObject* y1 = deps->at(i+1);
 166         if (x1 == y1) {  // same subject; check the context
 167           if (maybe_merge_ctxk(deps, i+0, x0->as_klass())) {
 168             return;
 169           }
 170         }
 171       }
 172     }
 173   } else {
 174     assert(dep_implicit_context_arg(dept) == 0, "sanity");
 175     if (note_dep_seen(dept, x0) && note_dep_seen(dept, x1)) {
 176       // look in this bucket for redundant assertions
 177       const int stride = 2;
 178       for (int i = deps->length(); (i -= stride) >= 0; ) {
 179         ciObject* y0 = deps->at(i+0);
 180         ciObject* y1 = deps->at(i+1);
 181         if (x0 == y0 && x1 == y1) {
 182           return;
 183         }
 184       }
 185     }
 186   }
 187 
 188   // append the assertion in the correct bucket:
 189   deps->append(x0);
 190   deps->append(x1);
 191 }
 192 
 193 void Dependencies::assert_common_3(DepType dept,
 194                                    ciKlass* ctxk, ciObject* x, ciObject* x2) {
 195   assert(dep_context_arg(dept) == 0, "sanity");
 196   assert(dep_args(dept) == 3, "sanity");
 197   log_dependency(dept, ctxk, x, x2);
 198   GrowableArray<ciObject*>* deps = _deps[dept];
 199 
 200   // try to normalize an unordered pair:
 201   bool swap = false;
 202   switch (dept) {
 203   case abstract_with_exclusive_concrete_subtypes_2:
 204     swap = (x->ident() > x2->ident() && x != ctxk);
 205     break;
 206   case exclusive_concrete_methods_2:
 207     swap = (x->ident() > x2->ident() && x->as_method()->holder() != ctxk);
 208     break;
 209   }
 210   if (swap) { ciObject* t = x; x = x2; x2 = t; }
 211 
 212   // see if the same (or a similar) dep is already recorded
 213   if (note_dep_seen(dept, x) && note_dep_seen(dept, x2)) {
 214     // look in this bucket for redundant assertions
 215     const int stride = 3;
 216     for (int i = deps->length(); (i -= stride) >= 0; ) {
 217       ciObject* y  = deps->at(i+1);
 218       ciObject* y2 = deps->at(i+2);
 219       if (x == y && x2 == y2) {  // same subjects; check the context
 220         if (maybe_merge_ctxk(deps, i+0, ctxk)) {
 221           return;
 222         }
 223       }
 224     }
 225   }
 226   // append the assertion in the correct bucket:
 227   deps->append(ctxk);
 228   deps->append(x);
 229   deps->append(x2);
 230 }
 231 
 232 /// Support for encoding dependencies into an nmethod:
 233 
 234 void Dependencies::copy_to(nmethod* nm) {
 235   address beg = nm->dependencies_begin();
 236   address end = nm->dependencies_end();
 237   guarantee(end - beg >= (ptrdiff_t) size_in_bytes(), "bad sizing");
 238   Copy::disjoint_words((HeapWord*) content_bytes(),
 239                        (HeapWord*) beg,
 240                        size_in_bytes() / sizeof(HeapWord));
 241   assert(size_in_bytes() % sizeof(HeapWord) == 0, "copy by words");
 242 }
 243 
 244 static int sort_dep(ciObject** p1, ciObject** p2, int narg) {
 245   for (int i = 0; i < narg; i++) {
 246     int diff = p1[i]->ident() - p2[i]->ident();
 247     if (diff != 0)  return diff;
 248   }
 249   return 0;
 250 }
 251 static int sort_dep_arg_1(ciObject** p1, ciObject** p2)
 252 { return sort_dep(p1, p2, 1); }
 253 static int sort_dep_arg_2(ciObject** p1, ciObject** p2)
 254 { return sort_dep(p1, p2, 2); }
 255 static int sort_dep_arg_3(ciObject** p1, ciObject** p2)
 256 { return sort_dep(p1, p2, 3); }
 257 
 258 void Dependencies::sort_all_deps() {
 259   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 260     DepType dept = (DepType)deptv;
 261     GrowableArray<ciObject*>* deps = _deps[dept];
 262     if (deps->length() <= 1)  continue;
 263     switch (dep_args(dept)) {
 264     case 1: deps->sort(sort_dep_arg_1, 1); break;
 265     case 2: deps->sort(sort_dep_arg_2, 2); break;
 266     case 3: deps->sort(sort_dep_arg_3, 3); break;
 267     default: ShouldNotReachHere();
 268     }
 269   }
 270 }
 271 
 272 size_t Dependencies::estimate_size_in_bytes() {
 273   size_t est_size = 100;
 274   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 275     DepType dept = (DepType)deptv;
 276     GrowableArray<ciObject*>* deps = _deps[dept];
 277     est_size += deps->length()*2;  // tags and argument(s)
 278   }
 279   return est_size;
 280 }
 281 
 282 ciKlass* Dependencies::ctxk_encoded_as_null(DepType dept, ciObject* x) {
 283   switch (dept) {
 284   case abstract_with_exclusive_concrete_subtypes_2:
 285     return x->as_klass();
 286   case unique_concrete_method:
 287   case exclusive_concrete_methods_2:
 288     return x->as_method()->holder();
 289   }
 290   return NULL;  // let NULL be NULL
 291 }
 292 
 293 klassOop Dependencies::ctxk_encoded_as_null(DepType dept, oop x) {
 294   assert(must_be_in_vm(), "raw oops here");
 295   switch (dept) {
 296   case abstract_with_exclusive_concrete_subtypes_2:
 297     assert(x->is_klass(), "sanity");
 298     return (klassOop) x;
 299   case unique_concrete_method:
 300   case exclusive_concrete_methods_2:
 301     assert(x->is_method(), "sanity");
 302     return ((methodOop)x)->method_holder();
 303   }
 304   return NULL;  // let NULL be NULL
 305 }
 306 
 307 void Dependencies::encode_content_bytes() {
 308   sort_all_deps();
 309 
 310   // cast is safe, no deps can overflow INT_MAX
 311   CompressedWriteStream bytes((int)estimate_size_in_bytes());
 312 
 313   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 314     DepType dept = (DepType)deptv;
 315     GrowableArray<ciObject*>* deps = _deps[dept];
 316     if (deps->length() == 0)  continue;
 317     int stride = dep_args(dept);
 318     int ctxkj  = dep_context_arg(dept);  // -1 if no context arg
 319     assert(stride > 0, "sanity");
 320     for (int i = 0; i < deps->length(); i += stride) {
 321       jbyte code_byte = (jbyte)dept;
 322       int skipj = -1;
 323       if (ctxkj >= 0 && ctxkj+1 < stride) {
 324         ciKlass*  ctxk = deps->at(i+ctxkj+0)->as_klass();
 325         ciObject* x    = deps->at(i+ctxkj+1);  // following argument
 326         if (ctxk == ctxk_encoded_as_null(dept, x)) {
 327           skipj = ctxkj;  // we win:  maybe one less oop to keep track of
 328           code_byte |= default_context_type_bit;
 329         }
 330       }
 331       bytes.write_byte(code_byte);
 332       for (int j = 0; j < stride; j++) {
 333         if (j == skipj)  continue;
 334         bytes.write_int(_oop_recorder->find_index(deps->at(i+j)->constant_encoding()));
 335       }
 336     }
 337   }
 338 
 339   // write a sentinel byte to mark the end
 340   bytes.write_byte(end_marker);
 341 
 342   // round it out to a word boundary
 343   while (bytes.position() % sizeof(HeapWord) != 0) {
 344     bytes.write_byte(end_marker);
 345   }
 346 
 347   // check whether the dept byte encoding really works
 348   assert((jbyte)default_context_type_bit != 0, "byte overflow");
 349 
 350   _content_bytes = bytes.buffer();
 351   _size_in_bytes = bytes.position();
 352 }
 353 
 354 
 355 const char* Dependencies::_dep_name[TYPE_LIMIT] = {
 356   "end_marker",
 357   "evol_method",
 358   "leaf_type",
 359   "abstract_with_unique_concrete_subtype",
 360   "abstract_with_no_concrete_subtype",
 361   "concrete_with_no_concrete_subtype",
 362   "unique_concrete_method",
 363   "abstract_with_exclusive_concrete_subtypes_2",
 364   "exclusive_concrete_methods_2",
 365   "no_finalizable_subclasses",
 366   "call_site_target_value"
 367 };
 368 
 369 int Dependencies::_dep_args[TYPE_LIMIT] = {
 370   -1,// end_marker
 371   1, // evol_method m
 372   1, // leaf_type ctxk
 373   2, // abstract_with_unique_concrete_subtype ctxk, k
 374   1, // abstract_with_no_concrete_subtype ctxk
 375   1, // concrete_with_no_concrete_subtype ctxk
 376   2, // unique_concrete_method ctxk, m
 377   3, // unique_concrete_subtypes_2 ctxk, k1, k2
 378   3, // unique_concrete_methods_2 ctxk, m1, m2
 379   1, // no_finalizable_subclasses ctxk
 380   2  // call_site_target_value call_site, method_handle
 381 };
 382 
 383 const char* Dependencies::dep_name(Dependencies::DepType dept) {
 384   if (!dept_in_mask(dept, all_types))  return "?bad-dep?";
 385   return _dep_name[dept];
 386 }
 387 
 388 int Dependencies::dep_args(Dependencies::DepType dept) {
 389   if (!dept_in_mask(dept, all_types))  return -1;
 390   return _dep_args[dept];
 391 }
 392 
 393 void Dependencies::check_valid_dependency_type(DepType dept) {
 394   guarantee(FIRST_TYPE <= dept && dept < TYPE_LIMIT, err_msg("invalid dependency type: %d", (int) dept));
 395 }
 396 
 397 // for the sake of the compiler log, print out current dependencies:
 398 void Dependencies::log_all_dependencies() {
 399   if (log() == NULL)  return;
 400   ciObject* args[max_arg_count];
 401   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
 402     DepType dept = (DepType)deptv;
 403     GrowableArray<ciObject*>* deps = _deps[dept];
 404     if (deps->length() == 0)  continue;
 405     int stride = dep_args(dept);
 406     for (int i = 0; i < deps->length(); i += stride) {
 407       for (int j = 0; j < stride; j++) {
 408         // flush out the identities before printing
 409         args[j] = deps->at(i+j);
 410       }
 411       write_dependency_to(log(), dept, stride, args);
 412     }
 413   }
 414 }
 415 
 416 void Dependencies::write_dependency_to(CompileLog* log,
 417                                        DepType dept,
 418                                        int nargs, oop args[],
 419                                        klassOop witness) {
 420   if (log == NULL) {
 421     return;
 422   }
 423   ciEnv* env = ciEnv::current();
 424   ciObject* ciargs[max_arg_count];
 425   assert(nargs <= max_arg_count, "oob");
 426   for (int j = 0; j < nargs; j++) {
 427     ciargs[j] = env->get_object(args[j]);
 428   }
 429   Dependencies::write_dependency_to(log, dept, nargs, ciargs, witness);
 430 }
 431 
 432 void Dependencies::write_dependency_to(CompileLog* log,
 433                                        DepType dept,
 434                                        int nargs, ciObject* args[],
 435                                        klassOop witness) {
 436   if (log == NULL)  return;
 437   assert(nargs <= max_arg_count, "oob");
 438   int argids[max_arg_count];
 439   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 440   int j;
 441   for (j = 0; j < nargs; j++) {
 442     argids[j] = log->identify(args[j]);
 443   }
 444   if (witness != NULL) {
 445     log->begin_elem("dependency_failed");
 446   } else {
 447     log->begin_elem("dependency");
 448   }
 449   log->print(" type='%s'", dep_name(dept));
 450   if (ctxkj >= 0) {
 451     log->print(" ctxk='%d'", argids[ctxkj]);
 452   }
 453   // write remaining arguments, if any.
 454   for (j = 0; j < nargs; j++) {
 455     if (j == ctxkj)  continue;  // already logged
 456     if (j == 1) {
 457       log->print(  " x='%d'",    argids[j]);
 458     } else {
 459       log->print(" x%d='%d'", j, argids[j]);
 460     }
 461   }
 462   if (witness != NULL) {
 463     log->object("witness", witness);
 464     log->stamp();
 465   }
 466   log->end_elem();
 467 }
 468 
 469 void Dependencies::write_dependency_to(xmlStream* xtty,
 470                                        DepType dept,
 471                                        int nargs, oop args[],
 472                                        klassOop witness) {
 473   if (xtty == NULL)  return;
 474   ttyLocker ttyl;
 475   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 476   if (witness != NULL) {
 477     xtty->begin_elem("dependency_failed");
 478   } else {
 479     xtty->begin_elem("dependency");
 480   }
 481   xtty->print(" type='%s'", dep_name(dept));
 482   if (ctxkj >= 0) {
 483     xtty->object("ctxk", args[ctxkj]);
 484   }
 485   // write remaining arguments, if any.
 486   for (int j = 0; j < nargs; j++) {
 487     if (j == ctxkj)  continue;  // already logged
 488     if (j == 1) {
 489       xtty->object("x", args[j]);
 490     } else {
 491       char xn[10]; sprintf(xn, "x%d", j);
 492       xtty->object(xn, args[j]);
 493     }
 494   }
 495   if (witness != NULL) {
 496     xtty->object("witness", witness);
 497     xtty->stamp();
 498   }
 499   xtty->end_elem();
 500 }
 501 
 502 void Dependencies::print_dependency(DepType dept, int nargs, oop args[],
 503                                     klassOop witness) {
 504   ResourceMark rm;
 505   ttyLocker ttyl;   // keep the following output all in one block
 506   tty->print_cr("%s of type %s",
 507                 (witness == NULL)? "Dependency": "Failed dependency",
 508                 dep_name(dept));
 509   // print arguments
 510   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
 511   for (int j = 0; j < nargs; j++) {
 512     oop arg = args[j];
 513     bool put_star = false;
 514     if (arg == NULL)  continue;
 515     const char* what;
 516     if (j == ctxkj) {
 517       what = "context";
 518       put_star = !Dependencies::is_concrete_klass((klassOop)arg);
 519     } else if (arg->is_method()) {
 520       what = "method ";
 521       put_star = !Dependencies::is_concrete_method((methodOop)arg);
 522     } else if (arg->is_klass()) {
 523       what = "class  ";
 524     } else {
 525       what = "object ";
 526     }
 527     tty->print("  %s = %s", what, (put_star? "*": ""));
 528     if (arg->is_klass())
 529       tty->print("%s", Klass::cast((klassOop)arg)->external_name());
 530     else
 531       arg->print_value();
 532     tty->cr();
 533   }
 534   if (witness != NULL) {
 535     bool put_star = !Dependencies::is_concrete_klass(witness);
 536     tty->print_cr("  witness = %s%s",
 537                   (put_star? "*": ""),
 538                   Klass::cast(witness)->external_name());
 539   }
 540 }
 541 
 542 void Dependencies::DepStream::log_dependency(klassOop witness) {
 543   if (_deps == NULL && xtty == NULL)  return;  // fast cutout for runtime
 544   int nargs = argument_count();
 545   oop args[max_arg_count];
 546   for (int j = 0; j < nargs; j++) {
 547     args[j] = argument(j);
 548   }
 549   if (_deps != NULL && _deps->log() != NULL) {
 550     Dependencies::write_dependency_to(_deps->log(),
 551                                       type(), nargs, args, witness);
 552   } else {
 553     Dependencies::write_dependency_to(xtty,
 554                                       type(), nargs, args, witness);
 555   }
 556 }
 557 
 558 void Dependencies::DepStream::print_dependency(klassOop witness, bool verbose) {
 559   int nargs = argument_count();
 560   oop args[max_arg_count];
 561   for (int j = 0; j < nargs; j++) {
 562     args[j] = argument(j);
 563   }
 564   Dependencies::print_dependency(type(), nargs, args, witness);
 565   if (verbose) {
 566     if (_code != NULL) {
 567       tty->print("  code: ");
 568       _code->print_value_on(tty);
 569       tty->cr();
 570     }
 571   }
 572 }
 573 
 574 
 575 /// Dependency stream support (decodes dependencies from an nmethod):
 576 
 577 #ifdef ASSERT
 578 void Dependencies::DepStream::initial_asserts(size_t byte_limit) {
 579   assert(must_be_in_vm(), "raw oops here");
 580   _byte_limit = byte_limit;
 581   _type       = (DepType)(end_marker-1);  // defeat "already at end" assert
 582   assert((_code!=NULL) + (_deps!=NULL) == 1, "one or t'other");
 583 }
 584 #endif //ASSERT
 585 
 586 bool Dependencies::DepStream::next() {
 587   assert(_type != end_marker, "already at end");
 588   if (_bytes.position() == 0 && _code != NULL
 589       && _code->dependencies_size() == 0) {
 590     // Method has no dependencies at all.
 591     return false;
 592   }
 593   int code_byte = (_bytes.read_byte() & 0xFF);
 594   if (code_byte == end_marker) {
 595     DEBUG_ONLY(_type = end_marker);
 596     return false;
 597   } else {
 598     int ctxk_bit = (code_byte & Dependencies::default_context_type_bit);
 599     code_byte -= ctxk_bit;
 600     DepType dept = (DepType)code_byte;
 601     _type = dept;
 602     Dependencies::check_valid_dependency_type(dept);
 603     int stride = _dep_args[dept];
 604     assert(stride == dep_args(dept), "sanity");
 605     int skipj = -1;
 606     if (ctxk_bit != 0) {
 607       skipj = 0;  // currently the only context argument is at zero
 608       assert(skipj == dep_context_arg(dept), "zero arg always ctxk");
 609     }
 610     for (int j = 0; j < stride; j++) {
 611       _xi[j] = (j == skipj)? 0: _bytes.read_int();
 612     }
 613     DEBUG_ONLY(_xi[stride] = -1);   // help detect overruns
 614     return true;
 615   }
 616 }
 617 
 618 inline oop Dependencies::DepStream::recorded_oop_at(int i) {
 619   return (_code != NULL)
 620          ? _code->oop_at(i)
 621          : JNIHandles::resolve(_deps->oop_recorder()->handle_at(i));
 622 }
 623 
 624 oop Dependencies::DepStream::argument(int i) {
 625   return recorded_oop_at(argument_index(i));
 626 }
 627 
 628 klassOop Dependencies::DepStream::context_type() {
 629   assert(must_be_in_vm(), "raw oops here");
 630 
 631   // Most dependencies have an explicit context type argument.
 632   {
 633     int ctxkj = dep_context_arg(_type);  // -1 if no explicit context arg
 634     if (ctxkj >= 0) {
 635       oop k = argument(ctxkj);
 636       if (k != NULL) {       // context type was not compressed away
 637         assert(k->is_klass(), "type check");
 638         return (klassOop) k;
 639       }
 640       // recompute "default" context type
 641       return ctxk_encoded_as_null(_type, argument(ctxkj+1));
 642     }
 643   }
 644 
 645   // Some dependencies are using the klass of the first object
 646   // argument as implicit context type (e.g. call_site_target_value).
 647   {
 648     int ctxkj = dep_implicit_context_arg(_type);
 649     if (ctxkj >= 0) {
 650       oop k = argument(ctxkj)->klass();
 651       assert(k->is_klass(), "type check");
 652       return (klassOop) k;
 653     }
 654   }
 655 
 656   // And some dependencies don't have a context type at all,
 657   // e.g. evol_method.
 658   return NULL;
 659 }
 660 
 661 /// Checking dependencies:
 662 
 663 // This hierarchy walker inspects subtypes of a given type,
 664 // trying to find a "bad" class which breaks a dependency.
 665 // Such a class is called a "witness" to the broken dependency.
 666 // While searching around, we ignore "participants", which
 667 // are already known to the dependency.
 668 class ClassHierarchyWalker {
 669  public:
 670   enum { PARTICIPANT_LIMIT = 3 };
 671 
 672  private:
 673   // optional method descriptor to check for:
 674   Symbol* _name;
 675   Symbol* _signature;
 676 
 677   // special classes which are not allowed to be witnesses:
 678   klassOop  _participants[PARTICIPANT_LIMIT+1];
 679   int       _num_participants;
 680 
 681   // cache of method lookups
 682   methodOop _found_methods[PARTICIPANT_LIMIT+1];
 683 
 684   // if non-zero, tells how many witnesses to convert to participants
 685   int       _record_witnesses;
 686 
 687   void initialize(klassOop participant) {
 688     _record_witnesses = 0;
 689     _participants[0]  = participant;
 690     _found_methods[0] = NULL;
 691     _num_participants = 0;
 692     if (participant != NULL) {
 693       // Terminating NULL.
 694       _participants[1] = NULL;
 695       _found_methods[1] = NULL;
 696       _num_participants = 1;
 697     }
 698   }
 699 
 700   void initialize_from_method(methodOop m) {
 701     assert(m != NULL && m->is_method(), "sanity");
 702     _name      = m->name();
 703     _signature = m->signature();
 704   }
 705 
 706  public:
 707   // The walker is initialized to recognize certain methods and/or types
 708   // as friendly participants.
 709   ClassHierarchyWalker(klassOop participant, methodOop m) {
 710     initialize_from_method(m);
 711     initialize(participant);
 712   }
 713   ClassHierarchyWalker(methodOop m) {
 714     initialize_from_method(m);
 715     initialize(NULL);
 716   }
 717   ClassHierarchyWalker(klassOop participant = NULL) {
 718     _name      = NULL;
 719     _signature = NULL;
 720     initialize(participant);
 721   }
 722 
 723   // This is common code for two searches:  One for concrete subtypes,
 724   // the other for concrete method implementations and overrides.
 725   bool doing_subtype_search() {
 726     return _name == NULL;
 727   }
 728 
 729   int num_participants() { return _num_participants; }
 730   klassOop participant(int n) {
 731     assert((uint)n <= (uint)_num_participants, "oob");
 732     return _participants[n];
 733   }
 734 
 735   // Note:  If n==num_participants, returns NULL.
 736   methodOop found_method(int n) {
 737     assert((uint)n <= (uint)_num_participants, "oob");
 738     methodOop fm = _found_methods[n];
 739     assert(n == _num_participants || fm != NULL, "proper usage");
 740     assert(fm == NULL || fm->method_holder() == _participants[n], "sanity");
 741     return fm;
 742   }
 743 
 744 #ifdef ASSERT
 745   // Assert that m is inherited into ctxk, without intervening overrides.
 746   // (May return true even if this is not true, in corner cases where we punt.)
 747   bool check_method_context(klassOop ctxk, methodOop m) {
 748     if (m->method_holder() == ctxk)
 749       return true;  // Quick win.
 750     if (m->is_private())
 751       return false; // Quick lose.  Should not happen.
 752     if (!(m->is_public() || m->is_protected()))
 753       // The override story is complex when packages get involved.
 754       return true;  // Must punt the assertion to true.
 755     Klass* k = Klass::cast(ctxk);
 756     methodOop lm = k->lookup_method(m->name(), m->signature());
 757     if (lm == NULL && k->oop_is_instance()) {
 758       // It might be an abstract interface method, devoid of mirandas.
 759       lm = ((instanceKlass*)k)->lookup_method_in_all_interfaces(m->name(),
 760                                                                 m->signature());
 761     }
 762     if (lm == m)
 763       // Method m is inherited into ctxk.
 764       return true;
 765     if (lm != NULL) {
 766       if (!(lm->is_public() || lm->is_protected()))
 767         // Method is [package-]private, so the override story is complex.
 768         return true;  // Must punt the assertion to true.
 769       if (lm->is_static()) {
 770         // Static methods don't override non-static so punt
 771         return true;
 772       }
 773       if (   !Dependencies::is_concrete_method(lm)
 774           && !Dependencies::is_concrete_method(m)
 775           && Klass::cast(lm->method_holder())->is_subtype_of(m->method_holder()))
 776         // Method m is overridden by lm, but both are non-concrete.
 777         return true;
 778     }
 779     ResourceMark rm;
 780     tty->print_cr("Dependency method not found in the associated context:");
 781     tty->print_cr("  context = %s", Klass::cast(ctxk)->external_name());
 782     tty->print(   "  method = "); m->print_short_name(tty); tty->cr();
 783     if (lm != NULL) {
 784       tty->print( "  found = "); lm->print_short_name(tty); tty->cr();
 785     }
 786     return false;
 787   }
 788 #endif
 789 
 790   void add_participant(klassOop participant) {
 791     assert(_num_participants + _record_witnesses < PARTICIPANT_LIMIT, "oob");
 792     int np = _num_participants++;
 793     _participants[np] = participant;
 794     _participants[np+1] = NULL;
 795     _found_methods[np+1] = NULL;
 796   }
 797 
 798   void record_witnesses(int add) {
 799     if (add > PARTICIPANT_LIMIT)  add = PARTICIPANT_LIMIT;
 800     assert(_num_participants + add < PARTICIPANT_LIMIT, "oob");
 801     _record_witnesses = add;
 802   }
 803 
 804   bool is_witness(klassOop k) {
 805     if (doing_subtype_search()) {
 806       return Dependencies::is_concrete_klass(k);
 807     } else {
 808       methodOop m = instanceKlass::cast(k)->find_method(_name, _signature);
 809       if (m == NULL || !Dependencies::is_concrete_method(m))  return false;
 810       _found_methods[_num_participants] = m;
 811       // Note:  If add_participant(k) is called,
 812       // the method m will already be memoized for it.
 813       return true;
 814     }
 815   }
 816 
 817   bool is_participant(klassOop k) {
 818     if (k == _participants[0]) {
 819       return true;
 820     } else if (_num_participants <= 1) {
 821       return false;
 822     } else {
 823       return in_list(k, &_participants[1]);
 824     }
 825   }
 826   bool ignore_witness(klassOop witness) {
 827     if (_record_witnesses == 0) {
 828       return false;
 829     } else {
 830       --_record_witnesses;
 831       add_participant(witness);
 832       return true;
 833     }
 834   }
 835   static bool in_list(klassOop x, klassOop* list) {
 836     for (int i = 0; ; i++) {
 837       klassOop y = list[i];
 838       if (y == NULL)  break;
 839       if (y == x)  return true;
 840     }
 841     return false;  // not in list
 842   }
 843 
 844  private:
 845   // the actual search method:
 846   klassOop find_witness_anywhere(klassOop context_type,
 847                                  bool participants_hide_witnesses,
 848                                  bool top_level_call = true);
 849   // the spot-checking version:
 850   klassOop find_witness_in(KlassDepChange& changes,
 851                            klassOop context_type,
 852                            bool participants_hide_witnesses);
 853  public:
 854   klassOop find_witness_subtype(klassOop context_type, KlassDepChange* changes = NULL) {
 855     assert(doing_subtype_search(), "must set up a subtype search");
 856     // When looking for unexpected concrete types,
 857     // do not look beneath expected ones.
 858     const bool participants_hide_witnesses = true;
 859     // CX > CC > C' is OK, even if C' is new.
 860     // CX > { CC,  C' } is not OK if C' is new, and C' is the witness.
 861     if (changes != NULL) {
 862       return find_witness_in(*changes, context_type, participants_hide_witnesses);
 863     } else {
 864       return find_witness_anywhere(context_type, participants_hide_witnesses);
 865     }
 866   }
 867   klassOop find_witness_definer(klassOop context_type, KlassDepChange* changes = NULL) {
 868     assert(!doing_subtype_search(), "must set up a method definer search");
 869     // When looking for unexpected concrete methods,
 870     // look beneath expected ones, to see if there are overrides.
 871     const bool participants_hide_witnesses = true;
 872     // CX.m > CC.m > C'.m is not OK, if C'.m is new, and C' is the witness.
 873     if (changes != NULL) {
 874       return find_witness_in(*changes, context_type, !participants_hide_witnesses);
 875     } else {
 876       return find_witness_anywhere(context_type, !participants_hide_witnesses);
 877     }
 878   }
 879 };
 880 
 881 #ifndef PRODUCT
 882 static int deps_find_witness_calls = 0;
 883 static int deps_find_witness_steps = 0;
 884 static int deps_find_witness_recursions = 0;
 885 static int deps_find_witness_singles = 0;
 886 static int deps_find_witness_print = 0; // set to -1 to force a final print
 887 static bool count_find_witness_calls() {
 888   if (TraceDependencies || LogCompilation) {
 889     int pcount = deps_find_witness_print + 1;
 890     bool final_stats      = (pcount == 0);
 891     bool initial_call     = (pcount == 1);
 892     bool occasional_print = ((pcount & ((1<<10) - 1)) == 0);
 893     if (pcount < 0)  pcount = 1; // crude overflow protection
 894     deps_find_witness_print = pcount;
 895     if (VerifyDependencies && initial_call) {
 896       tty->print_cr("Warning:  TraceDependencies results may be inflated by VerifyDependencies");
 897     }
 898     if (occasional_print || final_stats) {
 899       // Every now and then dump a little info about dependency searching.
 900       if (xtty != NULL) {
 901        ttyLocker ttyl;
 902        xtty->elem("deps_find_witness calls='%d' steps='%d' recursions='%d' singles='%d'",
 903                    deps_find_witness_calls,
 904                    deps_find_witness_steps,
 905                    deps_find_witness_recursions,
 906                    deps_find_witness_singles);
 907       }
 908       if (final_stats || (TraceDependencies && WizardMode)) {
 909         ttyLocker ttyl;
 910         tty->print_cr("Dependency check (find_witness) "
 911                       "calls=%d, steps=%d (avg=%.1f), recursions=%d, singles=%d",
 912                       deps_find_witness_calls,
 913                       deps_find_witness_steps,
 914                       (double)deps_find_witness_steps / deps_find_witness_calls,
 915                       deps_find_witness_recursions,
 916                       deps_find_witness_singles);
 917       }
 918     }
 919     return true;
 920   }
 921   return false;
 922 }
 923 #else
 924 #define count_find_witness_calls() (0)
 925 #endif //PRODUCT
 926 
 927 
 928 klassOop ClassHierarchyWalker::find_witness_in(KlassDepChange& changes,
 929                                                klassOop context_type,
 930                                                bool participants_hide_witnesses) {
 931   assert(changes.involves_context(context_type), "irrelevant dependency");
 932   klassOop new_type = changes.new_type();
 933 
 934   count_find_witness_calls();
 935   NOT_PRODUCT(deps_find_witness_singles++);
 936 
 937   // Current thread must be in VM (not native mode, as in CI):
 938   assert(must_be_in_vm(), "raw oops here");
 939   // Must not move the class hierarchy during this check:
 940   assert_locked_or_safepoint(Compile_lock);
 941 
 942   int nof_impls = instanceKlass::cast(context_type)->nof_implementors();
 943   if (nof_impls > 1) {
 944     // Avoid this case: *I.m > { A.m, C }; B.m > C
 945     // %%% Until this is fixed more systematically, bail out.
 946     // See corresponding comment in find_witness_anywhere.
 947     return context_type;
 948   }
 949 
 950   assert(!is_participant(new_type), "only old classes are participants");
 951   if (participants_hide_witnesses) {
 952     // If the new type is a subtype of a participant, we are done.
 953     for (int i = 0; i < num_participants(); i++) {
 954       klassOop part = participant(i);
 955       if (part == NULL)  continue;
 956       assert(changes.involves_context(part) == Klass::cast(new_type)->is_subtype_of(part),
 957              "correct marking of participants, b/c new_type is unique");
 958       if (changes.involves_context(part)) {
 959         // new guy is protected from this check by previous participant
 960         return NULL;
 961       }
 962     }
 963   }
 964 
 965   if (is_witness(new_type) &&
 966       !ignore_witness(new_type)) {
 967     return new_type;
 968   }
 969 
 970   return NULL;
 971 }
 972 
 973 
 974 // Walk hierarchy under a context type, looking for unexpected types.
 975 // Do not report participant types, and recursively walk beneath
 976 // them only if participants_hide_witnesses is false.
 977 // If top_level_call is false, skip testing the context type,
 978 // because the caller has already considered it.
 979 klassOop ClassHierarchyWalker::find_witness_anywhere(klassOop context_type,
 980                                                      bool participants_hide_witnesses,
 981                                                      bool top_level_call) {
 982   // Current thread must be in VM (not native mode, as in CI):
 983   assert(must_be_in_vm(), "raw oops here");
 984   // Must not move the class hierarchy during this check:
 985   assert_locked_or_safepoint(Compile_lock);
 986 
 987   bool do_counts = count_find_witness_calls();
 988 
 989   // Check the root of the sub-hierarchy first.
 990   if (top_level_call) {
 991     if (do_counts) {
 992       NOT_PRODUCT(deps_find_witness_calls++);
 993       NOT_PRODUCT(deps_find_witness_steps++);
 994     }
 995     if (is_participant(context_type)) {
 996       if (participants_hide_witnesses)  return NULL;
 997       // else fall through to search loop...
 998     } else if (is_witness(context_type) && !ignore_witness(context_type)) {
 999       // The context is an abstract class or interface, to start with.
1000       return context_type;
1001     }
1002   }
1003 
1004   // Now we must check each implementor and each subclass.
1005   // Use a short worklist to avoid blowing the stack.
1006   // Each worklist entry is a *chain* of subklass siblings to process.
1007   const int CHAINMAX = 100;  // >= 1 + instanceKlass::implementors_limit
1008   Klass* chains[CHAINMAX];
1009   int    chaini = 0;  // index into worklist
1010   Klass* chain;       // scratch variable
1011 #define ADD_SUBCLASS_CHAIN(k)                     {  \
1012     assert(chaini < CHAINMAX, "oob");                \
1013     chain = instanceKlass::cast(k)->subklass();      \
1014     if (chain != NULL)  chains[chaini++] = chain;    }
1015 
1016   // Look for non-abstract subclasses.
1017   // (Note:  Interfaces do not have subclasses.)
1018   ADD_SUBCLASS_CHAIN(context_type);
1019 
1020   // If it is an interface, search its direct implementors.
1021   // (Their subclasses are additional indirect implementors.
1022   // See instanceKlass::add_implementor.)
1023   // (Note:  nof_implementors is always zero for non-interfaces.)
1024   int nof_impls = instanceKlass::cast(context_type)->nof_implementors();
1025   if (nof_impls > 1) {
1026     // Avoid this case: *I.m > { A.m, C }; B.m > C
1027     // Here, I.m has 2 concrete implementations, but m appears unique
1028     // as A.m, because the search misses B.m when checking C.
1029     // The inherited method B.m was getting missed by the walker
1030     // when interface 'I' was the starting point.
1031     // %%% Until this is fixed more systematically, bail out.
1032     // (Old CHA had the same limitation.)
1033     return context_type;
1034   }
1035   for (int i = 0; i < nof_impls; i++) {
1036     klassOop impl = instanceKlass::cast(context_type)->implementor(i);
1037     if (impl == NULL) {
1038       // implementors array overflowed => no exact info.
1039       return context_type;  // report an inexact witness to this sad affair
1040     }
1041     if (do_counts)
1042       { NOT_PRODUCT(deps_find_witness_steps++); }
1043     if (is_participant(impl)) {
1044       if (participants_hide_witnesses)  continue;
1045       // else fall through to process this guy's subclasses
1046     } else if (is_witness(impl) && !ignore_witness(impl)) {
1047       return impl;
1048     }
1049     ADD_SUBCLASS_CHAIN(impl);
1050   }
1051 
1052   // Recursively process each non-trivial sibling chain.
1053   while (chaini > 0) {
1054     Klass* chain = chains[--chaini];
1055     for (Klass* subk = chain; subk != NULL; subk = subk->next_sibling()) {
1056       klassOop sub = subk->as_klassOop();
1057       if (do_counts) { NOT_PRODUCT(deps_find_witness_steps++); }
1058       if (is_participant(sub)) {
1059         if (participants_hide_witnesses)  continue;
1060         // else fall through to process this guy's subclasses
1061       } else if (is_witness(sub) && !ignore_witness(sub)) {
1062         return sub;
1063       }
1064       if (chaini < (VerifyDependencies? 2: CHAINMAX)) {
1065         // Fast path.  (Partially disabled if VerifyDependencies.)
1066         ADD_SUBCLASS_CHAIN(sub);
1067       } else {
1068         // Worklist overflow.  Do a recursive call.  Should be rare.
1069         // The recursive call will have its own worklist, of course.
1070         // (Note that sub has already been tested, so that there is
1071         // no need for the recursive call to re-test.  That's handy,
1072         // since the recursive call sees sub as the context_type.)
1073         if (do_counts) { NOT_PRODUCT(deps_find_witness_recursions++); }
1074         klassOop witness = find_witness_anywhere(sub,
1075                                                  participants_hide_witnesses,
1076                                                  /*top_level_call=*/ false);
1077         if (witness != NULL)  return witness;
1078       }
1079     }
1080   }
1081 
1082   // No witness found.  The dependency remains unbroken.
1083   return NULL;
1084 #undef ADD_SUBCLASS_CHAIN
1085 }
1086 
1087 
1088 bool Dependencies::is_concrete_klass(klassOop k) {
1089   if (Klass::cast(k)->is_abstract())  return false;
1090   // %%% We could treat classes which are concrete but
1091   // have not yet been instantiated as virtually abstract.
1092   // This would require a deoptimization barrier on first instantiation.
1093   //if (k->is_not_instantiated())  return false;
1094   return true;
1095 }
1096 
1097 bool Dependencies::is_concrete_method(methodOop m) {
1098   // Statics are irrelevant to virtual call sites.
1099   if (m->is_static())  return false;
1100 
1101   // We could also return false if m does not yet appear to be
1102   // executed, if the VM version supports this distinction also.
1103   return !m->is_abstract();
1104 }
1105 
1106 
1107 Klass* Dependencies::find_finalizable_subclass(Klass* k) {
1108   if (k->is_interface())  return NULL;
1109   if (k->has_finalizer()) return k;
1110   k = k->subklass();
1111   while (k != NULL) {
1112     Klass* result = find_finalizable_subclass(k);
1113     if (result != NULL) return result;
1114     k = k->next_sibling();
1115   }
1116   return NULL;
1117 }
1118 
1119 
1120 bool Dependencies::is_concrete_klass(ciInstanceKlass* k) {
1121   if (k->is_abstract())  return false;
1122   // We could also return false if k does not yet appear to be
1123   // instantiated, if the VM version supports this distinction also.
1124   //if (k->is_not_instantiated())  return false;
1125   return true;
1126 }
1127 
1128 bool Dependencies::is_concrete_method(ciMethod* m) {
1129   // Statics are irrelevant to virtual call sites.
1130   if (m->is_static())  return false;
1131 
1132   // We could also return false if m does not yet appear to be
1133   // executed, if the VM version supports this distinction also.
1134   return !m->is_abstract();
1135 }
1136 
1137 
1138 bool Dependencies::has_finalizable_subclass(ciInstanceKlass* k) {
1139   return k->has_finalizable_subclass();
1140 }
1141 
1142 
1143 // Any use of the contents (bytecodes) of a method must be
1144 // marked by an "evol_method" dependency, if those contents
1145 // can change.  (Note: A method is always dependent on itself.)
1146 klassOop Dependencies::check_evol_method(methodOop m) {
1147   assert(must_be_in_vm(), "raw oops here");
1148   // Did somebody do a JVMTI RedefineClasses while our backs were turned?
1149   // Or is there a now a breakpoint?
1150   // (Assumes compiled code cannot handle bkpts; change if UseFastBreakpoints.)
1151   if (m->is_old()
1152       || m->number_of_breakpoints() > 0) {
1153     return m->method_holder();
1154   } else {
1155     return NULL;
1156   }
1157 }
1158 
1159 // This is a strong assertion:  It is that the given type
1160 // has no subtypes whatever.  It is most useful for
1161 // optimizing checks on reflected types or on array types.
1162 // (Checks on types which are derived from real instances
1163 // can be optimized more strongly than this, because we
1164 // know that the checked type comes from a concrete type,
1165 // and therefore we can disregard abstract types.)
1166 klassOop Dependencies::check_leaf_type(klassOop ctxk) {
1167   assert(must_be_in_vm(), "raw oops here");
1168   assert_locked_or_safepoint(Compile_lock);
1169   instanceKlass* ctx = instanceKlass::cast(ctxk);
1170   Klass* sub = ctx->subklass();
1171   if (sub != NULL) {
1172     return sub->as_klassOop();
1173   } else if (ctx->nof_implementors() != 0) {
1174     // if it is an interface, it must be unimplemented
1175     // (if it is not an interface, nof_implementors is always zero)
1176     klassOop impl = ctx->implementor(0);
1177     return (impl != NULL)? impl: ctxk;
1178   } else {
1179     return NULL;
1180   }
1181 }
1182 
1183 // Test the assertion that conck is the only concrete subtype* of ctxk.
1184 // The type conck itself is allowed to have have further concrete subtypes.
1185 // This allows the compiler to narrow occurrences of ctxk by conck,
1186 // when dealing with the types of actual instances.
1187 klassOop Dependencies::check_abstract_with_unique_concrete_subtype(klassOop ctxk,
1188                                                                    klassOop conck,
1189                                                                    KlassDepChange* changes) {
1190   ClassHierarchyWalker wf(conck);
1191   return wf.find_witness_subtype(ctxk, changes);
1192 }
1193 
1194 // If a non-concrete class has no concrete subtypes, it is not (yet)
1195 // instantiatable.  This can allow the compiler to make some paths go
1196 // dead, if they are gated by a test of the type.
1197 klassOop Dependencies::check_abstract_with_no_concrete_subtype(klassOop ctxk,
1198                                                                KlassDepChange* changes) {
1199   // Find any concrete subtype, with no participants:
1200   ClassHierarchyWalker wf;
1201   return wf.find_witness_subtype(ctxk, changes);
1202 }
1203 
1204 
1205 // If a concrete class has no concrete subtypes, it can always be
1206 // exactly typed.  This allows the use of a cheaper type test.
1207 klassOop Dependencies::check_concrete_with_no_concrete_subtype(klassOop ctxk,
1208                                                                KlassDepChange* changes) {
1209   // Find any concrete subtype, with only the ctxk as participant:
1210   ClassHierarchyWalker wf(ctxk);
1211   return wf.find_witness_subtype(ctxk, changes);
1212 }
1213 
1214 
1215 // Find the unique concrete proper subtype of ctxk, or NULL if there
1216 // is more than one concrete proper subtype.  If there are no concrete
1217 // proper subtypes, return ctxk itself, whether it is concrete or not.
1218 // The returned subtype is allowed to have have further concrete subtypes.
1219 // That is, return CC1 for CX > CC1 > CC2, but NULL for CX > { CC1, CC2 }.
1220 klassOop Dependencies::find_unique_concrete_subtype(klassOop ctxk) {
1221   ClassHierarchyWalker wf(ctxk);   // Ignore ctxk when walking.
1222   wf.record_witnesses(1);          // Record one other witness when walking.
1223   klassOop wit = wf.find_witness_subtype(ctxk);
1224   if (wit != NULL)  return NULL;   // Too many witnesses.
1225   klassOop conck = wf.participant(0);
1226   if (conck == NULL) {
1227 #ifndef PRODUCT
1228     // Make sure the dependency mechanism will pass this discovery:
1229     if (VerifyDependencies) {
1230       // Turn off dependency tracing while actually testing deps.
1231       FlagSetting fs(TraceDependencies, false);
1232       if (!Dependencies::is_concrete_klass(ctxk)) {
1233         guarantee(NULL ==
1234                   (void *)check_abstract_with_no_concrete_subtype(ctxk),
1235                   "verify dep.");
1236       } else {
1237         guarantee(NULL ==
1238                   (void *)check_concrete_with_no_concrete_subtype(ctxk),
1239                   "verify dep.");
1240       }
1241     }
1242 #endif //PRODUCT
1243     return ctxk;                   // Return ctxk as a flag for "no subtypes".
1244   } else {
1245 #ifndef PRODUCT
1246     // Make sure the dependency mechanism will pass this discovery:
1247     if (VerifyDependencies) {
1248       // Turn off dependency tracing while actually testing deps.
1249       FlagSetting fs(TraceDependencies, false);
1250       if (!Dependencies::is_concrete_klass(ctxk)) {
1251         guarantee(NULL == (void *)
1252                   check_abstract_with_unique_concrete_subtype(ctxk, conck),
1253                   "verify dep.");
1254       }
1255     }
1256 #endif //PRODUCT
1257     return conck;
1258   }
1259 }
1260 
1261 // Test the assertion that the k[12] are the only concrete subtypes of ctxk,
1262 // except possibly for further subtypes of k[12] themselves.
1263 // The context type must be abstract.  The types k1 and k2 are themselves
1264 // allowed to have further concrete subtypes.
1265 klassOop Dependencies::check_abstract_with_exclusive_concrete_subtypes(
1266                                                 klassOop ctxk,
1267                                                 klassOop k1,
1268                                                 klassOop k2,
1269                                                 KlassDepChange* changes) {
1270   ClassHierarchyWalker wf;
1271   wf.add_participant(k1);
1272   wf.add_participant(k2);
1273   return wf.find_witness_subtype(ctxk, changes);
1274 }
1275 
1276 // Search ctxk for concrete implementations.  If there are klen or fewer,
1277 // pack them into the given array and return the number.
1278 // Otherwise, return -1, meaning the given array would overflow.
1279 // (Note that a return of 0 means there are exactly no concrete subtypes.)
1280 // In this search, if ctxk is concrete, it will be reported alone.
1281 // For any type CC reported, no proper subtypes of CC will be reported.
1282 int Dependencies::find_exclusive_concrete_subtypes(klassOop ctxk,
1283                                                    int klen,
1284                                                    klassOop karray[]) {
1285   ClassHierarchyWalker wf;
1286   wf.record_witnesses(klen);
1287   klassOop wit = wf.find_witness_subtype(ctxk);
1288   if (wit != NULL)  return -1;  // Too many witnesses.
1289   int num = wf.num_participants();
1290   assert(num <= klen, "oob");
1291   // Pack the result array with the good news.
1292   for (int i = 0; i < num; i++)
1293     karray[i] = wf.participant(i);
1294 #ifndef PRODUCT
1295   // Make sure the dependency mechanism will pass this discovery:
1296   if (VerifyDependencies) {
1297     // Turn off dependency tracing while actually testing deps.
1298     FlagSetting fs(TraceDependencies, false);
1299     switch (Dependencies::is_concrete_klass(ctxk)? -1: num) {
1300     case -1: // ctxk was itself concrete
1301       guarantee(num == 1 && karray[0] == ctxk, "verify dep.");
1302       break;
1303     case 0:
1304       guarantee(NULL == (void *)check_abstract_with_no_concrete_subtype(ctxk),
1305                 "verify dep.");
1306       break;
1307     case 1:
1308       guarantee(NULL == (void *)
1309                 check_abstract_with_unique_concrete_subtype(ctxk, karray[0]),
1310                 "verify dep.");
1311       break;
1312     case 2:
1313       guarantee(NULL == (void *)
1314                 check_abstract_with_exclusive_concrete_subtypes(ctxk,
1315                                                                 karray[0],
1316                                                                 karray[1]),
1317                 "verify dep.");
1318       break;
1319     default:
1320       ShouldNotReachHere();  // klen > 2 yet supported
1321     }
1322   }
1323 #endif //PRODUCT
1324   return num;
1325 }
1326 
1327 // If a class (or interface) has a unique concrete method uniqm, return NULL.
1328 // Otherwise, return a class that contains an interfering method.
1329 klassOop Dependencies::check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
1330                                                     KlassDepChange* changes) {
1331   // Here is a missing optimization:  If uniqm->is_final(),
1332   // we don't really need to search beneath it for overrides.
1333   // This is probably not important, since we don't use dependencies
1334   // to track final methods.  (They can't be "definalized".)
1335   ClassHierarchyWalker wf(uniqm->method_holder(), uniqm);
1336   return wf.find_witness_definer(ctxk, changes);
1337 }
1338 
1339 // Find the set of all non-abstract methods under ctxk that match m.
1340 // (The method m must be defined or inherited in ctxk.)
1341 // Include m itself in the set, unless it is abstract.
1342 // If this set has exactly one element, return that element.
1343 methodOop Dependencies::find_unique_concrete_method(klassOop ctxk, methodOop m) {
1344   ClassHierarchyWalker wf(m);
1345   assert(wf.check_method_context(ctxk, m), "proper context");
1346   wf.record_witnesses(1);
1347   klassOop wit = wf.find_witness_definer(ctxk);
1348   if (wit != NULL)  return NULL;  // Too many witnesses.
1349   methodOop fm = wf.found_method(0);  // Will be NULL if num_parts == 0.
1350   if (Dependencies::is_concrete_method(m)) {
1351     if (fm == NULL) {
1352       // It turns out that m was always the only implementation.
1353       fm = m;
1354     } else if (fm != m) {
1355       // Two conflicting implementations after all.
1356       // (This can happen if m is inherited into ctxk and fm overrides it.)
1357       return NULL;
1358     }
1359   }
1360 #ifndef PRODUCT
1361   // Make sure the dependency mechanism will pass this discovery:
1362   if (VerifyDependencies && fm != NULL) {
1363     guarantee(NULL == (void *)check_unique_concrete_method(ctxk, fm),
1364               "verify dep.");
1365   }
1366 #endif //PRODUCT
1367   return fm;
1368 }
1369 
1370 klassOop Dependencies::check_exclusive_concrete_methods(klassOop ctxk,
1371                                                         methodOop m1,
1372                                                         methodOop m2,
1373                                                         KlassDepChange* changes) {
1374   ClassHierarchyWalker wf(m1);
1375   wf.add_participant(m1->method_holder());
1376   wf.add_participant(m2->method_holder());
1377   return wf.find_witness_definer(ctxk, changes);
1378 }
1379 
1380 // Find the set of all non-abstract methods under ctxk that match m[0].
1381 // (The method m[0] must be defined or inherited in ctxk.)
1382 // Include m itself in the set, unless it is abstract.
1383 // Fill the given array m[0..(mlen-1)] with this set, and return the length.
1384 // (The length may be zero if no concrete methods are found anywhere.)
1385 // If there are too many concrete methods to fit in marray, return -1.
1386 int Dependencies::find_exclusive_concrete_methods(klassOop ctxk,
1387                                                   int mlen,
1388                                                   methodOop marray[]) {
1389   methodOop m0 = marray[0];
1390   ClassHierarchyWalker wf(m0);
1391   assert(wf.check_method_context(ctxk, m0), "proper context");
1392   wf.record_witnesses(mlen);
1393   bool participants_hide_witnesses = true;
1394   klassOop wit = wf.find_witness_definer(ctxk);
1395   if (wit != NULL)  return -1;  // Too many witnesses.
1396   int num = wf.num_participants();
1397   assert(num <= mlen, "oob");
1398   // Keep track of whether m is also part of the result set.
1399   int mfill = 0;
1400   assert(marray[mfill] == m0, "sanity");
1401   if (Dependencies::is_concrete_method(m0))
1402     mfill++;  // keep m0 as marray[0], the first result
1403   for (int i = 0; i < num; i++) {
1404     methodOop fm = wf.found_method(i);
1405     if (fm == m0)  continue;  // Already put this guy in the list.
1406     if (mfill == mlen) {
1407       return -1;              // Oops.  Too many methods after all!
1408     }
1409     marray[mfill++] = fm;
1410   }
1411 #ifndef PRODUCT
1412   // Make sure the dependency mechanism will pass this discovery:
1413   if (VerifyDependencies) {
1414     // Turn off dependency tracing while actually testing deps.
1415     FlagSetting fs(TraceDependencies, false);
1416     switch (mfill) {
1417     case 1:
1418       guarantee(NULL == (void *)check_unique_concrete_method(ctxk, marray[0]),
1419                 "verify dep.");
1420       break;
1421     case 2:
1422       guarantee(NULL == (void *)
1423                 check_exclusive_concrete_methods(ctxk, marray[0], marray[1]),
1424                 "verify dep.");
1425       break;
1426     default:
1427       ShouldNotReachHere();  // mlen > 2 yet supported
1428     }
1429   }
1430 #endif //PRODUCT
1431   return mfill;
1432 }
1433 
1434 
1435 klassOop Dependencies::check_has_no_finalizable_subclasses(klassOop ctxk, KlassDepChange* changes) {
1436   Klass* search_at = ctxk->klass_part();
1437   if (changes != NULL)
1438     search_at = changes->new_type()->klass_part(); // just look at the new bit
1439   Klass* result = find_finalizable_subclass(search_at);
1440   if (result == NULL) {
1441     return NULL;
1442   }
1443   return result->as_klassOop();
1444 }
1445 
1446 
1447 klassOop Dependencies::check_call_site_target_value(oop call_site, oop method_handle, CallSiteDepChange* changes) {
1448   assert(call_site    ->is_a(SystemDictionary::CallSite_klass()),     "sanity");
1449   assert(method_handle->is_a(SystemDictionary::MethodHandle_klass()), "sanity");
1450   if (changes == NULL) {
1451     // Validate all CallSites
1452     if (java_lang_invoke_CallSite::target(call_site) != method_handle)
1453       return call_site->klass();  // assertion failed
1454   } else {
1455     // Validate the given CallSite
1456     if (call_site == changes->call_site() && java_lang_invoke_CallSite::target(call_site) != changes->method_handle()) {
1457       assert(method_handle != changes->method_handle(), "must be");
1458       return call_site->klass();  // assertion failed
1459     }
1460   }
1461   return NULL;  // assertion still valid
1462 }
1463 
1464 
1465 void Dependencies::DepStream::trace_and_log_witness(klassOop witness) {
1466   if (witness != NULL) {
1467     if (TraceDependencies) {
1468       print_dependency(witness, /*verbose=*/ true);
1469     }
1470     // The following is a no-op unless logging is enabled:
1471     log_dependency(witness);
1472   }
1473 }
1474 
1475 
1476 klassOop Dependencies::DepStream::check_klass_dependency(KlassDepChange* changes) {
1477   assert_locked_or_safepoint(Compile_lock);
1478   Dependencies::check_valid_dependency_type(type());
1479 
1480   klassOop witness = NULL;
1481   switch (type()) {
1482   case evol_method:
1483     witness = check_evol_method(method_argument(0));
1484     break;
1485   case leaf_type:
1486     witness = check_leaf_type(context_type());
1487     break;
1488   case abstract_with_unique_concrete_subtype:
1489     witness = check_abstract_with_unique_concrete_subtype(context_type(), type_argument(1), changes);
1490     break;
1491   case abstract_with_no_concrete_subtype:
1492     witness = check_abstract_with_no_concrete_subtype(context_type(), changes);
1493     break;
1494   case concrete_with_no_concrete_subtype:
1495     witness = check_concrete_with_no_concrete_subtype(context_type(), changes);
1496     break;
1497   case unique_concrete_method:
1498     witness = check_unique_concrete_method(context_type(), method_argument(1), changes);
1499     break;
1500   case abstract_with_exclusive_concrete_subtypes_2:
1501     witness = check_abstract_with_exclusive_concrete_subtypes(context_type(), type_argument(1), type_argument(2), changes);
1502     break;
1503   case exclusive_concrete_methods_2:
1504     witness = check_exclusive_concrete_methods(context_type(), method_argument(1), method_argument(2), changes);
1505     break;
1506   case no_finalizable_subclasses:
1507     witness = check_has_no_finalizable_subclasses(context_type(), changes);
1508     break;
1509   default:
1510     witness = NULL;
1511     break;
1512   }
1513   trace_and_log_witness(witness);
1514   return witness;
1515 }
1516 
1517 
1518 klassOop Dependencies::DepStream::check_call_site_dependency(CallSiteDepChange* changes) {
1519   assert_locked_or_safepoint(Compile_lock);
1520   Dependencies::check_valid_dependency_type(type());
1521 
1522   klassOop witness = NULL;
1523   switch (type()) {
1524   case call_site_target_value:
1525     witness = check_call_site_target_value(argument(0), argument(1), changes);
1526     break;
1527   default:
1528     witness = NULL;
1529     break;
1530   }
1531   trace_and_log_witness(witness);
1532   return witness;
1533 }
1534 
1535 
1536 klassOop Dependencies::DepStream::spot_check_dependency_at(DepChange& changes) {
1537   // Handle klass dependency
1538   if (changes.is_klass_change() && changes.as_klass_change()->involves_context(context_type()))
1539     return check_klass_dependency(changes.as_klass_change());
1540 
1541   // Handle CallSite dependency
1542   if (changes.is_call_site_change())
1543     return check_call_site_dependency(changes.as_call_site_change());
1544 
1545   // irrelevant dependency; skip it
1546   return NULL;
1547 }
1548 
1549 
1550 void DepChange::print() {
1551   int nsup = 0, nint = 0;
1552   for (ContextStream str(*this); str.next(); ) {
1553     klassOop k = str.klass();
1554     switch (str.change_type()) {
1555     case Change_new_type:
1556       tty->print_cr("  dependee = %s", instanceKlass::cast(k)->external_name());
1557       break;
1558     case Change_new_sub:
1559       if (!WizardMode) {
1560         ++nsup;
1561       } else {
1562         tty->print_cr("  context super = %s", instanceKlass::cast(k)->external_name());
1563       }
1564       break;
1565     case Change_new_impl:
1566       if (!WizardMode) {
1567         ++nint;
1568       } else {
1569         tty->print_cr("  context interface = %s", instanceKlass::cast(k)->external_name());
1570       }
1571       break;
1572     }
1573   }
1574   if (nsup + nint != 0) {
1575     tty->print_cr("  context supers = %d, interfaces = %d", nsup, nint);
1576   }
1577 }
1578 
1579 void DepChange::ContextStream::start() {
1580   klassOop new_type = _changes.is_klass_change() ? _changes.as_klass_change()->new_type() : (klassOop) NULL;
1581   _change_type = (new_type == NULL ? NO_CHANGE : Start_Klass);
1582   _klass = new_type;
1583   _ti_base = NULL;
1584   _ti_index = 0;
1585   _ti_limit = 0;
1586 }
1587 
1588 bool DepChange::ContextStream::next() {
1589   switch (_change_type) {
1590   case Start_Klass:             // initial state; _klass is the new type
1591     _ti_base = instanceKlass::cast(_klass)->transitive_interfaces();
1592     _ti_index = 0;
1593     _change_type = Change_new_type;
1594     return true;
1595   case Change_new_type:
1596     // fall through:
1597     _change_type = Change_new_sub;
1598   case Change_new_sub:
1599     // 6598190: brackets workaround Sun Studio C++ compiler bug 6629277
1600     {
1601       _klass = instanceKlass::cast(_klass)->super();
1602       if (_klass != NULL) {
1603         return true;
1604       }
1605     }
1606     // else set up _ti_limit and fall through:
1607     _ti_limit = (_ti_base == NULL) ? 0 : _ti_base->length();
1608     _change_type = Change_new_impl;
1609   case Change_new_impl:
1610     if (_ti_index < _ti_limit) {
1611       _klass = klassOop( _ti_base->obj_at(_ti_index++) );
1612       return true;
1613     }
1614     // fall through:
1615     _change_type = NO_CHANGE;  // iterator is exhausted
1616   case NO_CHANGE:
1617     break;
1618   default:
1619     ShouldNotReachHere();
1620   }
1621   return false;
1622 }
1623 
1624 void KlassDepChange::initialize() {
1625   // entire transaction must be under this lock:
1626   assert_lock_strong(Compile_lock);
1627 
1628   // Mark all dependee and all its superclasses
1629   // Mark transitive interfaces
1630   for (ContextStream str(*this); str.next(); ) {
1631     klassOop d = str.klass();
1632     assert(!instanceKlass::cast(d)->is_marked_dependent(), "checking");
1633     instanceKlass::cast(d)->set_is_marked_dependent(true);
1634   }
1635 }
1636 
1637 KlassDepChange::~KlassDepChange() {
1638   // Unmark all dependee and all its superclasses
1639   // Unmark transitive interfaces
1640   for (ContextStream str(*this); str.next(); ) {
1641     klassOop d = str.klass();
1642     instanceKlass::cast(d)->set_is_marked_dependent(false);
1643   }
1644 }
1645 
1646 bool KlassDepChange::involves_context(klassOop k) {
1647   if (k == NULL || !Klass::cast(k)->oop_is_instance()) {
1648     return false;
1649   }
1650   instanceKlass* ik = instanceKlass::cast(k);
1651   bool is_contained = ik->is_marked_dependent();
1652   assert(is_contained == Klass::cast(new_type())->is_subtype_of(k),
1653          "correct marking of potential context types");
1654   return is_contained;
1655 }
1656 
1657 #ifndef PRODUCT
1658 void Dependencies::print_statistics() {
1659   if (deps_find_witness_print != 0) {
1660     // Call one final time, to flush out the data.
1661     deps_find_witness_print = -1;
1662     count_find_witness_calls();
1663   }
1664 }
1665 #endif