jdk8-mips64-public/hotspot: src/share/vm/code/dependencies.cpp@fdb992d83a87 (annotated)

src/share/vm/code/dependencies.cpp@fdb992d83a87 (annotated)

src/share/vm/code/dependencies.cpp

Tue, 16 Aug 2011 04:14:05 -0700

author: twisti
date: Tue, 16 Aug 2011 04:14:05 -0700
changeset 3050: fdb992d83a87
parent 2708: 1d1603768966
child 3094: b27c72d69fd1
permissions: -rw-r--r--

7071653: JSR 292: call site change notification should be pushed not pulled
Reviewed-by: kvn, never, bdelsart

 /*
  * Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "ci/ciArrayKlass.hpp"
 #include "ci/ciEnv.hpp"
 #include "ci/ciKlass.hpp"
 #include "ci/ciMethod.hpp"
 #include "code/dependencies.hpp"
 #include "compiler/compileLog.hpp"
 #include "oops/oop.inline.hpp"
 #include "runtime/handles.inline.hpp"
 #include "utilities/copy.hpp"
 #ifdef ASSERT
 static bool must_be_in_vm() {
   Thread* thread = Thread::current();
   if (thread->is_Java_thread())
     return ((JavaThread*)thread)->thread_state() == _thread_in_vm;
   else
     return true;  //something like this: thread->is_VM_thread();
 }
 #endif //ASSERT
 void Dependencies::initialize(ciEnv* env) {
   Arena* arena = env->arena();
   _oop_recorder = env->oop_recorder();
   _log = env->log();
   _dep_seen = new(arena) GrowableArray<int>(arena, 500, 0, 0);
   DEBUG_ONLY(_deps[end_marker] = NULL);
   for (int i = (int)FIRST_TYPE; i < (int)TYPE_LIMIT; i++) {
     _deps[i] = new(arena) GrowableArray<ciObject*>(arena, 10, 0, 0);
   }
   _content_bytes = NULL;
   _size_in_bytes = (size_t)-1;
   assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT), "sanity");
 }
 void Dependencies::assert_evol_method(ciMethod* m) {
   assert_common_1(evol_method, m);
 }
 void Dependencies::assert_leaf_type(ciKlass* ctxk) {
   if (ctxk->is_array_klass()) {
     // As a special case, support this assertion on an array type,
     // which reduces to an assertion on its element type.
     // Note that this cannot be done with assertions that
     // relate to concreteness or abstractness.
     ciType* elemt = ctxk->as_array_klass()->base_element_type();
     if (!elemt->is_instance_klass())  return;   // Ex:  int[][]
     ctxk = elemt->as_instance_klass();
     //if (ctxk->is_final())  return;            // Ex:  String[][]
   }
   check_ctxk(ctxk);
   assert_common_1(leaf_type, ctxk);
 }
 void Dependencies::assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck) {
   check_ctxk_abstract(ctxk);
   assert_common_2(abstract_with_unique_concrete_subtype, ctxk, conck);
 }
 void Dependencies::assert_abstract_with_no_concrete_subtype(ciKlass* ctxk) {
   check_ctxk_abstract(ctxk);
   assert_common_1(abstract_with_no_concrete_subtype, ctxk);
 }
 void Dependencies::assert_concrete_with_no_concrete_subtype(ciKlass* ctxk) {
   check_ctxk_concrete(ctxk);
   assert_common_1(concrete_with_no_concrete_subtype, ctxk);
 }
 void Dependencies::assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm) {
   check_ctxk(ctxk);
   assert_common_2(unique_concrete_method, ctxk, uniqm);
 }
 void Dependencies::assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2) {
   check_ctxk(ctxk);
   assert_common_3(abstract_with_exclusive_concrete_subtypes_2, ctxk, k1, k2);
 }
 void Dependencies::assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2) {
   check_ctxk(ctxk);
   assert_common_3(exclusive_concrete_methods_2, ctxk, m1, m2);
 }
 void Dependencies::assert_has_no_finalizable_subclasses(ciKlass* ctxk) {
   check_ctxk(ctxk);
   assert_common_1(no_finalizable_subclasses, ctxk);
 }
 void Dependencies::assert_call_site_target_value(ciKlass* ctxk, ciCallSite* call_site, ciMethodHandle* method_handle) {
   check_ctxk(ctxk);
   assert_common_3(call_site_target_value, ctxk, call_site, method_handle);
 }
 // Helper function.  If we are adding a new dep. under ctxk2,
 // try to find an old dep. under a broader* ctxk1.  If there is
 //
 bool Dependencies::maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
                                     int ctxk_i, ciKlass* ctxk2) {
   ciKlass* ctxk1 = deps->at(ctxk_i)->as_klass();
   if (ctxk2->is_subtype_of(ctxk1)) {
     return true;  // success, and no need to change
   } else if (ctxk1->is_subtype_of(ctxk2)) {
     // new context class fully subsumes previous one
     deps->at_put(ctxk_i, ctxk2);
     return true;
   } else {
     return false;
   }
 }
 void Dependencies::assert_common_1(Dependencies::DepType dept, ciObject* x) {
   assert(dep_args(dept) == 1, "sanity");
   log_dependency(dept, x);
   GrowableArray<ciObject*>* deps = _deps[dept];
   // see if the same (or a similar) dep is already recorded
   if (note_dep_seen(dept, x)) {
     assert(deps->find(x) >= 0, "sanity");
   } else {
     deps->append(x);
   }
 }
 void Dependencies::assert_common_2(Dependencies::DepType dept,
                                    ciKlass* ctxk, ciObject* x) {
   assert(dep_context_arg(dept) == 0, "sanity");
   assert(dep_args(dept) == 2, "sanity");
   log_dependency(dept, ctxk, x);
   GrowableArray<ciObject*>* deps = _deps[dept];
   // see if the same (or a similar) dep is already recorded
   if (note_dep_seen(dept, x)) {
     // look in this bucket for redundant assertions
     const int stride = 2;
     for (int i = deps->length(); (i -= stride) >= 0; ) {
       ciObject* x1 = deps->at(i+1);
       if (x == x1) {  // same subject; check the context
         if (maybe_merge_ctxk(deps, i+0, ctxk)) {
           return;
         }
       }
     }
   }
   // append the assertion in the correct bucket:
   deps->append(ctxk);
   deps->append(x);
 }
 void Dependencies::assert_common_3(Dependencies::DepType dept,
                                    ciKlass* ctxk, ciObject* x, ciObject* x2) {
   assert(dep_context_arg(dept) == 0, "sanity");
   assert(dep_args(dept) == 3, "sanity");
   log_dependency(dept, ctxk, x, x2);
   GrowableArray<ciObject*>* deps = _deps[dept];
   // try to normalize an unordered pair:
   bool swap = false;
   switch (dept) {
   case abstract_with_exclusive_concrete_subtypes_2:
     swap = (x->ident() > x2->ident() && x != ctxk);
     break;
   case exclusive_concrete_methods_2:
     swap = (x->ident() > x2->ident() && x->as_method()->holder() != ctxk);
     break;
   }
   if (swap) { ciObject* t = x; x = x2; x2 = t; }
   // see if the same (or a similar) dep is already recorded
   if (note_dep_seen(dept, x) && note_dep_seen(dept, x2)) {
     // look in this bucket for redundant assertions
     const int stride = 3;
     for (int i = deps->length(); (i -= stride) >= 0; ) {
       ciObject* y  = deps->at(i+1);
       ciObject* y2 = deps->at(i+2);
       if (x == y && x2 == y2) {  // same subjects; check the context
         if (maybe_merge_ctxk(deps, i+0, ctxk)) {
           return;
         }
       }
     }
   }
   // append the assertion in the correct bucket:
   deps->append(ctxk);
   deps->append(x);
   deps->append(x2);
 }
 /// Support for encoding dependencies into an nmethod:
 void Dependencies::copy_to(nmethod* nm) {
   address beg = nm->dependencies_begin();
   address end = nm->dependencies_end();
   guarantee(end - beg >= (ptrdiff_t) size_in_bytes(), "bad sizing");
   Copy::disjoint_words((HeapWord*) content_bytes(),
                        (HeapWord*) beg,
                        size_in_bytes() / sizeof(HeapWord));
   assert(size_in_bytes() % sizeof(HeapWord) == 0, "copy by words");
 }
 static int sort_dep(ciObject** p1, ciObject** p2, int narg) {
   for (int i = 0; i < narg; i++) {
     int diff = p1[i]->ident() - p2[i]->ident();
     if (diff != 0)  return diff;
   }
   return 0;
 }
 static int sort_dep_arg_1(ciObject** p1, ciObject** p2)
 { return sort_dep(p1, p2, 1); }
 static int sort_dep_arg_2(ciObject** p1, ciObject** p2)
 { return sort_dep(p1, p2, 2); }
 static int sort_dep_arg_3(ciObject** p1, ciObject** p2)
 { return sort_dep(p1, p2, 3); }
 void Dependencies::sort_all_deps() {
   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
     DepType dept = (DepType)deptv;
     GrowableArray<ciObject*>* deps = _deps[dept];
     if (deps->length() <= 1)  continue;
     switch (dep_args(dept)) {
     case 1: deps->sort(sort_dep_arg_1, 1); break;
     case 2: deps->sort(sort_dep_arg_2, 2); break;
     case 3: deps->sort(sort_dep_arg_3, 3); break;
     default: ShouldNotReachHere();
     }
   }
 }
 size_t Dependencies::estimate_size_in_bytes() {
   size_t est_size = 100;
   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
     DepType dept = (DepType)deptv;
     GrowableArray<ciObject*>* deps = _deps[dept];
     est_size += deps->length()*2;  // tags and argument(s)
   }
   return est_size;
 }
 ciKlass* Dependencies::ctxk_encoded_as_null(DepType dept, ciObject* x) {
   switch (dept) {
   case abstract_with_exclusive_concrete_subtypes_2:
     return x->as_klass();
   case unique_concrete_method:
   case exclusive_concrete_methods_2:
     return x->as_method()->holder();
   }
   return NULL;  // let NULL be NULL
 }
 klassOop Dependencies::ctxk_encoded_as_null(DepType dept, oop x) {
   assert(must_be_in_vm(), "raw oops here");
   switch (dept) {
   case abstract_with_exclusive_concrete_subtypes_2:
     assert(x->is_klass(), "sanity");
     return (klassOop) x;
   case unique_concrete_method:
   case exclusive_concrete_methods_2:
     assert(x->is_method(), "sanity");
     return ((methodOop)x)->method_holder();
   }
   return NULL;  // let NULL be NULL
 }
 void Dependencies::encode_content_bytes() {
   sort_all_deps();
   // cast is safe, no deps can overflow INT_MAX
   CompressedWriteStream bytes((int)estimate_size_in_bytes());
   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
     DepType dept = (DepType)deptv;
     GrowableArray<ciObject*>* deps = _deps[dept];
     if (deps->length() == 0)  continue;
     int stride = dep_args(dept);
     int ctxkj  = dep_context_arg(dept);  // -1 if no context arg
     assert(stride > 0, "sanity");
     for (int i = 0; i < deps->length(); i += stride) {
       jbyte code_byte = (jbyte)dept;
       int skipj = -1;
       if (ctxkj >= 0 && ctxkj+1 < stride) {
         ciKlass*  ctxk = deps->at(i+ctxkj+0)->as_klass();
         ciObject* x    = deps->at(i+ctxkj+1);  // following argument
         if (ctxk == ctxk_encoded_as_null(dept, x)) {
           skipj = ctxkj;  // we win:  maybe one less oop to keep track of
           code_byte |= default_context_type_bit;
         }
       }
       bytes.write_byte(code_byte);
       for (int j = 0; j < stride; j++) {
         if (j == skipj)  continue;
         bytes.write_int(_oop_recorder->find_index(deps->at(i+j)->constant_encoding()));
       }
     }
   }
   // write a sentinel byte to mark the end
   bytes.write_byte(end_marker);
   // round it out to a word boundary
   while (bytes.position() % sizeof(HeapWord) != 0) {
     bytes.write_byte(end_marker);
   }
   // check whether the dept byte encoding really works
   assert((jbyte)default_context_type_bit != 0, "byte overflow");
   _content_bytes = bytes.buffer();
   _size_in_bytes = bytes.position();
 }
 const char* Dependencies::_dep_name[TYPE_LIMIT] = {
   "end_marker",
   "evol_method",
   "leaf_type",
   "abstract_with_unique_concrete_subtype",
   "abstract_with_no_concrete_subtype",
   "concrete_with_no_concrete_subtype",
   "unique_concrete_method",
   "abstract_with_exclusive_concrete_subtypes_2",
   "exclusive_concrete_methods_2",
   "no_finalizable_subclasses",
   "call_site_target_value"
 };
 int Dependencies::_dep_args[TYPE_LIMIT] = {
   -1,// end_marker
 , // evol_method m
 , // leaf_type ctxk
 , // abstract_with_unique_concrete_subtype ctxk, k
 , // abstract_with_no_concrete_subtype ctxk
 , // concrete_with_no_concrete_subtype ctxk
 , // unique_concrete_method ctxk, m
 , // unique_concrete_subtypes_2 ctxk, k1, k2
 , // unique_concrete_methods_2 ctxk, m1, m2
 , // no_finalizable_subclasses ctxk
 // call_site_target_value ctxk, call_site, method_handle
 };
 const char* Dependencies::dep_name(Dependencies::DepType dept) {
   if (!dept_in_mask(dept, all_types))  return "?bad-dep?";
   return _dep_name[dept];
 }
 int Dependencies::dep_args(Dependencies::DepType dept) {
   if (!dept_in_mask(dept, all_types))  return -1;
   return _dep_args[dept];
 }
 void Dependencies::check_valid_dependency_type(DepType dept) {
   for (int deptv = (int) FIRST_TYPE; deptv < (int) TYPE_LIMIT; deptv++) {
     if (dept == ((DepType) deptv))  return;
   }
   ShouldNotReachHere();
 }
 // for the sake of the compiler log, print out current dependencies:
 void Dependencies::log_all_dependencies() {
   if (log() == NULL)  return;
   ciObject* args[max_arg_count];
   for (int deptv = (int)FIRST_TYPE; deptv < (int)TYPE_LIMIT; deptv++) {
     DepType dept = (DepType)deptv;
     GrowableArray<ciObject*>* deps = _deps[dept];
     if (deps->length() == 0)  continue;
     int stride = dep_args(dept);
     for (int i = 0; i < deps->length(); i += stride) {
       for (int j = 0; j < stride; j++) {
         // flush out the identities before printing
         args[j] = deps->at(i+j);
       }
       write_dependency_to(log(), dept, stride, args);
     }
   }
 }
 void Dependencies::write_dependency_to(CompileLog* log,
                                        DepType dept,
                                        int nargs, oop args[],
                                        klassOop witness) {
   if (log == NULL) {
     return;
   }
   ciEnv* env = ciEnv::current();
   ciObject* ciargs[max_arg_count];
   assert(nargs <= max_arg_count, "oob");
   for (int j = 0; j < nargs; j++) {
     ciargs[j] = env->get_object(args[j]);
   }
   Dependencies::write_dependency_to(log, dept, nargs, ciargs, witness);
 }
 void Dependencies::write_dependency_to(CompileLog* log,
                                        DepType dept,
                                        int nargs, ciObject* args[],
                                        klassOop witness) {
   if (log == NULL)  return;
   assert(nargs <= max_arg_count, "oob");
   int argids[max_arg_count];
   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
   int j;
   for (j = 0; j < nargs; j++) {
     argids[j] = log->identify(args[j]);
   }
   if (witness != NULL) {
     log->begin_elem("dependency_failed");
   } else {
     log->begin_elem("dependency");
   }
   log->print(" type='%s'", dep_name(dept));
   if (ctxkj >= 0) {
     log->print(" ctxk='%d'", argids[ctxkj]);
   }
   // write remaining arguments, if any.
   for (j = 0; j < nargs; j++) {
     if (j == ctxkj)  continue;  // already logged
     if (j == 1) {
       log->print(  " x='%d'",    argids[j]);
     } else {
       log->print(" x%d='%d'", j, argids[j]);
     }
   }
   if (witness != NULL) {
     log->object("witness", witness);
     log->stamp();
   }
   log->end_elem();
 }
 void Dependencies::write_dependency_to(xmlStream* xtty,
                                        DepType dept,
                                        int nargs, oop args[],
                                        klassOop witness) {
   if (xtty == NULL)  return;
   ttyLocker ttyl;
   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
   if (witness != NULL) {
     xtty->begin_elem("dependency_failed");
   } else {
     xtty->begin_elem("dependency");
   }
   xtty->print(" type='%s'", dep_name(dept));
   if (ctxkj >= 0) {
     xtty->object("ctxk", args[ctxkj]);
   }
   // write remaining arguments, if any.
   for (int j = 0; j < nargs; j++) {
     if (j == ctxkj)  continue;  // already logged
     if (j == 1) {
       xtty->object("x", args[j]);
     } else {
       char xn[10]; sprintf(xn, "x%d", j);
       xtty->object(xn, args[j]);
     }
   }
   if (witness != NULL) {
     xtty->object("witness", witness);
     xtty->stamp();
   }
   xtty->end_elem();
 }
 void Dependencies::print_dependency(DepType dept, int nargs, oop args[],
                                     klassOop witness) {
   ResourceMark rm;
   ttyLocker ttyl;   // keep the following output all in one block
   tty->print_cr("%s of type %s",
                 (witness == NULL)? "Dependency": "Failed dependency",
                 dep_name(dept));
   // print arguments
   int ctxkj = dep_context_arg(dept);  // -1 if no context arg
   for (int j = 0; j < nargs; j++) {
     oop arg = args[j];
     bool put_star = false;
     if (arg == NULL)  continue;
     const char* what;
     if (j == ctxkj) {
       what = "context";
       put_star = !Dependencies::is_concrete_klass((klassOop)arg);
     } else if (arg->is_method()) {
       what = "method ";
       put_star = !Dependencies::is_concrete_method((methodOop)arg);
     } else if (arg->is_klass()) {
       what = "class  ";
     } else {
       what = "object ";
     }
     tty->print("  %s = %s", what, (put_star? "*": ""));
     if (arg->is_klass())
       tty->print("%s", Klass::cast((klassOop)arg)->external_name());
     else
       arg->print_value();
     tty->cr();
   }
   if (witness != NULL) {
     bool put_star = !Dependencies::is_concrete_klass(witness);
     tty->print_cr("  witness = %s%s",
                   (put_star? "*": ""),
                   Klass::cast(witness)->external_name());
   }
 }
 void Dependencies::DepStream::log_dependency(klassOop witness) {
   if (_deps == NULL && xtty == NULL)  return;  // fast cutout for runtime
   int nargs = argument_count();
   oop args[max_arg_count];
   for (int j = 0; j < nargs; j++) {
     args[j] = argument(j);
   }
   if (_deps != NULL && _deps->log() != NULL) {
     Dependencies::write_dependency_to(_deps->log(),
                                       type(), nargs, args, witness);
   } else {
     Dependencies::write_dependency_to(xtty,
                                       type(), nargs, args, witness);
   }
 }
 void Dependencies::DepStream::print_dependency(klassOop witness, bool verbose) {
   int nargs = argument_count();
   oop args[max_arg_count];
   for (int j = 0; j < nargs; j++) {
     args[j] = argument(j);
   }
   Dependencies::print_dependency(type(), nargs, args, witness);
   if (verbose) {
     if (_code != NULL) {
       tty->print("  code: ");
       _code->print_value_on(tty);
       tty->cr();
     }
   }
 }
 /// Dependency stream support (decodes dependencies from an nmethod):
 #ifdef ASSERT
 void Dependencies::DepStream::initial_asserts(size_t byte_limit) {
   assert(must_be_in_vm(), "raw oops here");
   _byte_limit = byte_limit;
   _type       = (DepType)(end_marker-1);  // defeat "already at end" assert
   assert((_code!=NULL) + (_deps!=NULL) == 1, "one or t'other");
 }
 #endif //ASSERT
 bool Dependencies::DepStream::next() {
   assert(_type != end_marker, "already at end");
   if (_bytes.position() == 0 && _code != NULL
       && _code->dependencies_size() == 0) {
     // Method has no dependencies at all.
     return false;
   }
   int code_byte = (_bytes.read_byte() & 0xFF);
   if (code_byte == end_marker) {
     DEBUG_ONLY(_type = end_marker);
     return false;
   } else {
     int ctxk_bit = (code_byte & Dependencies::default_context_type_bit);
     code_byte -= ctxk_bit;
     DepType dept = (DepType)code_byte;
     _type = dept;
     guarantee((dept - FIRST_TYPE) < (TYPE_LIMIT - FIRST_TYPE),
               "bad dependency type tag");
     int stride = _dep_args[dept];
     assert(stride == dep_args(dept), "sanity");
     int skipj = -1;
     if (ctxk_bit != 0) {
       skipj = 0;  // currently the only context argument is at zero
       assert(skipj == dep_context_arg(dept), "zero arg always ctxk");
     }
     for (int j = 0; j < stride; j++) {
       _xi[j] = (j == skipj)? 0: _bytes.read_int();
     }
     DEBUG_ONLY(_xi[stride] = -1);   // help detect overruns
     return true;
   }
 }
 inline oop Dependencies::DepStream::recorded_oop_at(int i) {
   return (_code != NULL)
          ? _code->oop_at(i)
          : JNIHandles::resolve(_deps->oop_recorder()->handle_at(i));
 }
 oop Dependencies::DepStream::argument(int i) {
   return recorded_oop_at(argument_index(i));
 }
 klassOop Dependencies::DepStream::context_type() {
   assert(must_be_in_vm(), "raw oops here");
   int ctxkj = dep_context_arg(_type);  // -1 if no context arg
   if (ctxkj < 0) {
     return NULL;           // for example, evol_method
   } else {
     oop k = recorded_oop_at(_xi[ctxkj]);
     if (k != NULL) {       // context type was not compressed away
       assert(k->is_klass(), "type check");
       return (klassOop) k;
     } else {               // recompute "default" context type
       return ctxk_encoded_as_null(_type, recorded_oop_at(_xi[ctxkj+1]));
     }
   }
 }
 /// Checking dependencies:
 // This hierarchy walker inspects subtypes of a given type,
 // trying to find a "bad" class which breaks a dependency.
 // Such a class is called a "witness" to the broken dependency.
 // While searching around, we ignore "participants", which
 // are already known to the dependency.
 class ClassHierarchyWalker {
  public:
   enum { PARTICIPANT_LIMIT = 3 };
  private:
   // optional method descriptor to check for:
   Symbol* _name;
   Symbol* _signature;
   // special classes which are not allowed to be witnesses:
   klassOop  _participants[PARTICIPANT_LIMIT+1];
   int       _num_participants;
   // cache of method lookups
   methodOop _found_methods[PARTICIPANT_LIMIT+1];
   // if non-zero, tells how many witnesses to convert to participants
   int       _record_witnesses;
   void initialize(klassOop participant) {
     _record_witnesses = 0;
     _participants[0]  = participant;
     _found_methods[0] = NULL;
     _num_participants = 0;
     if (participant != NULL) {
       // Terminating NULL.
       _participants[1] = NULL;
       _found_methods[1] = NULL;
       _num_participants = 1;
     }
   }
   void initialize_from_method(methodOop m) {
     assert(m != NULL && m->is_method(), "sanity");
     _name      = m->name();
     _signature = m->signature();
   }
  public:
   // The walker is initialized to recognize certain methods and/or types
   // as friendly participants.
   ClassHierarchyWalker(klassOop participant, methodOop m) {
     initialize_from_method(m);
     initialize(participant);
   }
   ClassHierarchyWalker(methodOop m) {
     initialize_from_method(m);
     initialize(NULL);
   }
   ClassHierarchyWalker(klassOop participant = NULL) {
     _name      = NULL;
     _signature = NULL;
     initialize(participant);
   }
   // This is common code for two searches:  One for concrete subtypes,
   // the other for concrete method implementations and overrides.
   bool doing_subtype_search() {
     return _name == NULL;
   }
   int num_participants() { return _num_participants; }
   klassOop participant(int n) {
     assert((uint)n <= (uint)_num_participants, "oob");
     return _participants[n];
   }
   // Note:  If n==num_participants, returns NULL.
   methodOop found_method(int n) {
     assert((uint)n <= (uint)_num_participants, "oob");
     methodOop fm = _found_methods[n];
     assert(n == _num_participants || fm != NULL, "proper usage");
     assert(fm == NULL || fm->method_holder() == _participants[n], "sanity");
     return fm;
   }
 #ifdef ASSERT
   // Assert that m is inherited into ctxk, without intervening overrides.
   // (May return true even if this is not true, in corner cases where we punt.)
   bool check_method_context(klassOop ctxk, methodOop m) {
     if (m->method_holder() == ctxk)
       return true;  // Quick win.
     if (m->is_private())
       return false; // Quick lose.  Should not happen.
     if (!(m->is_public() || m->is_protected()))
       // The override story is complex when packages get involved.
       return true;  // Must punt the assertion to true.
     Klass* k = Klass::cast(ctxk);
     methodOop lm = k->lookup_method(m->name(), m->signature());
     if (lm == NULL && k->oop_is_instance()) {
       // It might be an abstract interface method, devoid of mirandas.
       lm = ((instanceKlass*)k)->lookup_method_in_all_interfaces(m->name(),
                                                                 m->signature());
     }
     if (lm == m)
       // Method m is inherited into ctxk.
       return true;
     if (lm != NULL) {
       if (!(lm->is_public() || lm->is_protected()))
         // Method is [package-]private, so the override story is complex.
         return true;  // Must punt the assertion to true.
       if (   !Dependencies::is_concrete_method(lm)
           && !Dependencies::is_concrete_method(m)
           && Klass::cast(lm->method_holder())->is_subtype_of(m->method_holder()))
         // Method m is overridden by lm, but both are non-concrete.
         return true;
     }
     ResourceMark rm;
     tty->print_cr("Dependency method not found in the associated context:");
     tty->print_cr("  context = %s", Klass::cast(ctxk)->external_name());
     tty->print(   "  method = "); m->print_short_name(tty); tty->cr();
     if (lm != NULL) {
       tty->print( "  found = "); lm->print_short_name(tty); tty->cr();
     }
     return false;
   }
 #endif
   void add_participant(klassOop participant) {
     assert(_num_participants + _record_witnesses < PARTICIPANT_LIMIT, "oob");
     int np = _num_participants++;
     _participants[np] = participant;
     _participants[np+1] = NULL;
     _found_methods[np+1] = NULL;
   }
   void record_witnesses(int add) {
     if (add > PARTICIPANT_LIMIT)  add = PARTICIPANT_LIMIT;
     assert(_num_participants + add < PARTICIPANT_LIMIT, "oob");
     _record_witnesses = add;
   }
   bool is_witness(klassOop k) {
     if (doing_subtype_search()) {
       return Dependencies::is_concrete_klass(k);
     } else {
       methodOop m = instanceKlass::cast(k)->find_method(_name, _signature);
       if (m == NULL || !Dependencies::is_concrete_method(m))  return false;
       _found_methods[_num_participants] = m;
       // Note:  If add_participant(k) is called,
       // the method m will already be memoized for it.
       return true;
     }
   }
   bool is_participant(klassOop k) {
     if (k == _participants[0]) {
       return true;
     } else if (_num_participants <= 1) {
       return false;
     } else {
       return in_list(k, &_participants[1]);
     }
   }
   bool ignore_witness(klassOop witness) {
     if (_record_witnesses == 0) {
       return false;
     } else {
       --_record_witnesses;
       add_participant(witness);
       return true;
     }
   }
   static bool in_list(klassOop x, klassOop* list) {
     for (int i = 0; ; i++) {
       klassOop y = list[i];
       if (y == NULL)  break;
       if (y == x)  return true;
     }
     return false;  // not in list
   }
  private:
   // the actual search method:
   klassOop find_witness_anywhere(klassOop context_type,
                                  bool participants_hide_witnesses,
                                  bool top_level_call = true);
   // the spot-checking version:
   klassOop find_witness_in(KlassDepChange& changes,
                            klassOop context_type,
                            bool participants_hide_witnesses);
  public:
   klassOop find_witness_subtype(klassOop context_type, KlassDepChange* changes = NULL) {
     assert(doing_subtype_search(), "must set up a subtype search");
     // When looking for unexpected concrete types,
     // do not look beneath expected ones.
     const bool participants_hide_witnesses = true;
     // CX > CC > C' is OK, even if C' is new.
     // CX > { CC,  C' } is not OK if C' is new, and C' is the witness.
     if (changes != NULL) {
       return find_witness_in(*changes, context_type, participants_hide_witnesses);
     } else {
       return find_witness_anywhere(context_type, participants_hide_witnesses);
     }
   }
   klassOop find_witness_definer(klassOop context_type, KlassDepChange* changes = NULL) {
     assert(!doing_subtype_search(), "must set up a method definer search");
     // When looking for unexpected concrete methods,
     // look beneath expected ones, to see if there are overrides.
     const bool participants_hide_witnesses = true;
     // CX.m > CC.m > C'.m is not OK, if C'.m is new, and C' is the witness.
     if (changes != NULL) {
       return find_witness_in(*changes, context_type, !participants_hide_witnesses);
     } else {
       return find_witness_anywhere(context_type, !participants_hide_witnesses);
     }
   }
 };
 #ifndef PRODUCT
 static int deps_find_witness_calls = 0;
 static int deps_find_witness_steps = 0;
 static int deps_find_witness_recursions = 0;
 static int deps_find_witness_singles = 0;
 static int deps_find_witness_print = 0; // set to -1 to force a final print
 static bool count_find_witness_calls() {
   if (TraceDependencies || LogCompilation) {
     int pcount = deps_find_witness_print + 1;
     bool final_stats      = (pcount == 0);
     bool initial_call     = (pcount == 1);
     bool occasional_print = ((pcount & ((1<<10) - 1)) == 0);
     if (pcount < 0)  pcount = 1; // crude overflow protection
     deps_find_witness_print = pcount;
     if (VerifyDependencies && initial_call) {
       tty->print_cr("Warning:  TraceDependencies results may be inflated by VerifyDependencies");
     }
     if (occasional_print || final_stats) {
       // Every now and then dump a little info about dependency searching.
       if (xtty != NULL) {
        ttyLocker ttyl;
        xtty->elem("deps_find_witness calls='%d' steps='%d' recursions='%d' singles='%d'",
                    deps_find_witness_calls,
                    deps_find_witness_steps,
                    deps_find_witness_recursions,
                    deps_find_witness_singles);
       }
       if (final_stats || (TraceDependencies && WizardMode)) {
         ttyLocker ttyl;
         tty->print_cr("Dependency check (find_witness) "
                       "calls=%d, steps=%d (avg=%.1f), recursions=%d, singles=%d",
                       deps_find_witness_calls,
                       deps_find_witness_steps,
                       (double)deps_find_witness_steps / deps_find_witness_calls,
                       deps_find_witness_recursions,
                       deps_find_witness_singles);
       }
     }
     return true;
   }
   return false;
 }
 #else
 #define count_find_witness_calls() (0)
 #endif //PRODUCT
 klassOop ClassHierarchyWalker::find_witness_in(KlassDepChange& changes,
                                                klassOop context_type,
                                                bool participants_hide_witnesses) {
   assert(changes.involves_context(context_type), "irrelevant dependency");
   klassOop new_type = changes.new_type();
   count_find_witness_calls();
   NOT_PRODUCT(deps_find_witness_singles++);
   // Current thread must be in VM (not native mode, as in CI):
   assert(must_be_in_vm(), "raw oops here");
   // Must not move the class hierarchy during this check:
   assert_locked_or_safepoint(Compile_lock);
   int nof_impls = instanceKlass::cast(context_type)->nof_implementors();
   if (nof_impls > 1) {
     // Avoid this case: *I.m > { A.m, C }; B.m > C
     // %%% Until this is fixed more systematically, bail out.
     // See corresponding comment in find_witness_anywhere.
     return context_type;
   }
   assert(!is_participant(new_type), "only old classes are participants");
   if (participants_hide_witnesses) {
     // If the new type is a subtype of a participant, we are done.
     for (int i = 0; i < num_participants(); i++) {
       klassOop part = participant(i);
       if (part == NULL)  continue;
       assert(changes.involves_context(part) == Klass::cast(new_type)->is_subtype_of(part),
              "correct marking of participants, b/c new_type is unique");
       if (changes.involves_context(part)) {
         // new guy is protected from this check by previous participant
         return NULL;
       }
     }
   }
   if (is_witness(new_type) &&
       !ignore_witness(new_type)) {
     return new_type;
   }
   return NULL;
 }
 // Walk hierarchy under a context type, looking for unexpected types.
 // Do not report participant types, and recursively walk beneath
 // them only if participants_hide_witnesses is false.
 // If top_level_call is false, skip testing the context type,
 // because the caller has already considered it.
 klassOop ClassHierarchyWalker::find_witness_anywhere(klassOop context_type,
                                                      bool participants_hide_witnesses,
                                                      bool top_level_call) {
   // Current thread must be in VM (not native mode, as in CI):
   assert(must_be_in_vm(), "raw oops here");
   // Must not move the class hierarchy during this check:
   assert_locked_or_safepoint(Compile_lock);
   bool do_counts = count_find_witness_calls();
   // Check the root of the sub-hierarchy first.
   if (top_level_call) {
     if (do_counts) {
       NOT_PRODUCT(deps_find_witness_calls++);
       NOT_PRODUCT(deps_find_witness_steps++);
     }
     if (is_participant(context_type)) {
       if (participants_hide_witnesses)  return NULL;
       // else fall through to search loop...
     } else if (is_witness(context_type) && !ignore_witness(context_type)) {
       // The context is an abstract class or interface, to start with.
       return context_type;
     }
   }
   // Now we must check each implementor and each subclass.
   // Use a short worklist to avoid blowing the stack.
   // Each worklist entry is a *chain* of subklass siblings to process.
   const int CHAINMAX = 100;  // >= 1 + instanceKlass::implementors_limit
   Klass* chains[CHAINMAX];
   int    chaini = 0;  // index into worklist
   Klass* chain;       // scratch variable
 #define ADD_SUBCLASS_CHAIN(k)                     {  \
     assert(chaini < CHAINMAX, "oob");                \
     chain = instanceKlass::cast(k)->subklass();      \
     if (chain != NULL)  chains[chaini++] = chain;    }
   // Look for non-abstract subclasses.
   // (Note:  Interfaces do not have subclasses.)
   ADD_SUBCLASS_CHAIN(context_type);
   // If it is an interface, search its direct implementors.
   // (Their subclasses are additional indirect implementors.
   // See instanceKlass::add_implementor.)
   // (Note:  nof_implementors is always zero for non-interfaces.)
   int nof_impls = instanceKlass::cast(context_type)->nof_implementors();
   if (nof_impls > 1) {
     // Avoid this case: *I.m > { A.m, C }; B.m > C
     // Here, I.m has 2 concrete implementations, but m appears unique
     // as A.m, because the search misses B.m when checking C.
     // The inherited method B.m was getting missed by the walker
     // when interface 'I' was the starting point.
     // %%% Until this is fixed more systematically, bail out.
     // (Old CHA had the same limitation.)
     return context_type;
   }
   for (int i = 0; i < nof_impls; i++) {
     klassOop impl = instanceKlass::cast(context_type)->implementor(i);
     if (impl == NULL) {
       // implementors array overflowed => no exact info.
       return context_type;  // report an inexact witness to this sad affair
     }
     if (do_counts)
       { NOT_PRODUCT(deps_find_witness_steps++); }
     if (is_participant(impl)) {
       if (participants_hide_witnesses)  continue;
       // else fall through to process this guy's subclasses
     } else if (is_witness(impl) && !ignore_witness(impl)) {
       return impl;
     }
     ADD_SUBCLASS_CHAIN(impl);
   }
   // Recursively process each non-trivial sibling chain.
   while (chaini > 0) {
     Klass* chain = chains[--chaini];
     for (Klass* subk = chain; subk != NULL; subk = subk->next_sibling()) {
       klassOop sub = subk->as_klassOop();
       if (do_counts) { NOT_PRODUCT(deps_find_witness_steps++); }
       if (is_participant(sub)) {
         if (participants_hide_witnesses)  continue;
         // else fall through to process this guy's subclasses
       } else if (is_witness(sub) && !ignore_witness(sub)) {
         return sub;
       }
       if (chaini < (VerifyDependencies? 2: CHAINMAX)) {
         // Fast path.  (Partially disabled if VerifyDependencies.)
         ADD_SUBCLASS_CHAIN(sub);
       } else {
         // Worklist overflow.  Do a recursive call.  Should be rare.
         // The recursive call will have its own worklist, of course.
         // (Note that sub has already been tested, so that there is
         // no need for the recursive call to re-test.  That's handy,
         // since the recursive call sees sub as the context_type.)
         if (do_counts) { NOT_PRODUCT(deps_find_witness_recursions++); }
         klassOop witness = find_witness_anywhere(sub,
                                                  participants_hide_witnesses,
                                                  /*top_level_call=*/ false);
         if (witness != NULL)  return witness;
       }
     }
   }
   // No witness found.  The dependency remains unbroken.
   return NULL;
 #undef ADD_SUBCLASS_CHAIN
 }
 bool Dependencies::is_concrete_klass(klassOop k) {
   if (Klass::cast(k)->is_abstract())  return false;
   // %%% We could treat classes which are concrete but
   // have not yet been instantiated as virtually abstract.
   // This would require a deoptimization barrier on first instantiation.
   //if (k->is_not_instantiated())  return false;
   return true;
 }
 bool Dependencies::is_concrete_method(methodOop m) {
   if (m->is_abstract())  return false;
   // %%% We could treat unexecuted methods as virtually abstract also.
   // This would require a deoptimization barrier on first execution.
   return !m->is_abstract();
 }
 Klass* Dependencies::find_finalizable_subclass(Klass* k) {
   if (k->is_interface())  return NULL;
   if (k->has_finalizer()) return k;
   k = k->subklass();
   while (k != NULL) {
     Klass* result = find_finalizable_subclass(k);
     if (result != NULL) return result;
     k = k->next_sibling();
   }
   return NULL;
 }
 bool Dependencies::is_concrete_klass(ciInstanceKlass* k) {
   if (k->is_abstract())  return false;
   // We could return also false if k does not yet appear to be
   // instantiated, if the VM version supports this distinction also.
   //if (k->is_not_instantiated())  return false;
   return true;
 }
 bool Dependencies::is_concrete_method(ciMethod* m) {
   // Statics are irrelevant to virtual call sites.
   if (m->is_static())  return false;
   // We could return also false if m does not yet appear to be
   // executed, if the VM version supports this distinction also.
   return !m->is_abstract();
 }
 bool Dependencies::has_finalizable_subclass(ciInstanceKlass* k) {
   return k->has_finalizable_subclass();
 }
 // Any use of the contents (bytecodes) of a method must be
 // marked by an "evol_method" dependency, if those contents
 // can change.  (Note: A method is always dependent on itself.)
 klassOop Dependencies::check_evol_method(methodOop m) {
   assert(must_be_in_vm(), "raw oops here");
   // Did somebody do a JVMTI RedefineClasses while our backs were turned?
   // Or is there a now a breakpoint?
   // (Assumes compiled code cannot handle bkpts; change if UseFastBreakpoints.)
   if (m->is_old()
       || m->number_of_breakpoints() > 0) {
     return m->method_holder();
   } else {
     return NULL;
   }
 }
 // This is a strong assertion:  It is that the given type
 // has no subtypes whatever.  It is most useful for
 // optimizing checks on reflected types or on array types.
 // (Checks on types which are derived from real instances
 // can be optimized more strongly than this, because we
 // know that the checked type comes from a concrete type,
 // and therefore we can disregard abstract types.)
 klassOop Dependencies::check_leaf_type(klassOop ctxk) {
   assert(must_be_in_vm(), "raw oops here");
   assert_locked_or_safepoint(Compile_lock);
   instanceKlass* ctx = instanceKlass::cast(ctxk);
   Klass* sub = ctx->subklass();
   if (sub != NULL) {
     return sub->as_klassOop();
   } else if (ctx->nof_implementors() != 0) {
     // if it is an interface, it must be unimplemented
     // (if it is not an interface, nof_implementors is always zero)
     klassOop impl = ctx->implementor(0);
     return (impl != NULL)? impl: ctxk;
   } else {
     return NULL;
   }
 }
 // Test the assertion that conck is the only concrete subtype* of ctxk.
 // The type conck itself is allowed to have have further concrete subtypes.
 // This allows the compiler to narrow occurrences of ctxk by conck,
 // when dealing with the types of actual instances.
 klassOop Dependencies::check_abstract_with_unique_concrete_subtype(klassOop ctxk,
                                                                    klassOop conck,
                                                                    KlassDepChange* changes) {
   ClassHierarchyWalker wf(conck);
   return wf.find_witness_subtype(ctxk, changes);
 }
 // If a non-concrete class has no concrete subtypes, it is not (yet)
 // instantiatable.  This can allow the compiler to make some paths go
 // dead, if they are gated by a test of the type.
 klassOop Dependencies::check_abstract_with_no_concrete_subtype(klassOop ctxk,
                                                                KlassDepChange* changes) {
   // Find any concrete subtype, with no participants:
   ClassHierarchyWalker wf;
   return wf.find_witness_subtype(ctxk, changes);
 }
 // If a concrete class has no concrete subtypes, it can always be
 // exactly typed.  This allows the use of a cheaper type test.
 klassOop Dependencies::check_concrete_with_no_concrete_subtype(klassOop ctxk,
                                                                KlassDepChange* changes) {
   // Find any concrete subtype, with only the ctxk as participant:
   ClassHierarchyWalker wf(ctxk);
   return wf.find_witness_subtype(ctxk, changes);
 }
 // Find the unique concrete proper subtype of ctxk, or NULL if there
 // is more than one concrete proper subtype.  If there are no concrete
 // proper subtypes, return ctxk itself, whether it is concrete or not.
 // The returned subtype is allowed to have have further concrete subtypes.
 // That is, return CC1 for CX > CC1 > CC2, but NULL for CX > { CC1, CC2 }.
 klassOop Dependencies::find_unique_concrete_subtype(klassOop ctxk) {
   ClassHierarchyWalker wf(ctxk);   // Ignore ctxk when walking.
   wf.record_witnesses(1);          // Record one other witness when walking.
   klassOop wit = wf.find_witness_subtype(ctxk);
   if (wit != NULL)  return NULL;   // Too many witnesses.
   klassOop conck = wf.participant(0);
   if (conck == NULL) {
 #ifndef PRODUCT
     // Make sure the dependency mechanism will pass this discovery:
     if (VerifyDependencies) {
       // Turn off dependency tracing while actually testing deps.
       FlagSetting fs(TraceDependencies, false);
       if (!Dependencies::is_concrete_klass(ctxk)) {
         guarantee(NULL ==
                   (void *)check_abstract_with_no_concrete_subtype(ctxk),
                   "verify dep.");
       } else {
         guarantee(NULL ==
                   (void *)check_concrete_with_no_concrete_subtype(ctxk),
                   "verify dep.");
       }
     }
 #endif //PRODUCT
     return ctxk;                   // Return ctxk as a flag for "no subtypes".
   } else {
 #ifndef PRODUCT
     // Make sure the dependency mechanism will pass this discovery:
     if (VerifyDependencies) {
       // Turn off dependency tracing while actually testing deps.
       FlagSetting fs(TraceDependencies, false);
       if (!Dependencies::is_concrete_klass(ctxk)) {
         guarantee(NULL == (void *)
                   check_abstract_with_unique_concrete_subtype(ctxk, conck),
                   "verify dep.");
       }
     }
 #endif //PRODUCT
     return conck;
   }
 }
 // Test the assertion that the k[12] are the only concrete subtypes of ctxk,
 // except possibly for further subtypes of k[12] themselves.
 // The context type must be abstract.  The types k1 and k2 are themselves
 // allowed to have further concrete subtypes.
 klassOop Dependencies::check_abstract_with_exclusive_concrete_subtypes(
                                                 klassOop ctxk,
                                                 klassOop k1,
                                                 klassOop k2,
                                                 KlassDepChange* changes) {
   ClassHierarchyWalker wf;
   wf.add_participant(k1);
   wf.add_participant(k2);
   return wf.find_witness_subtype(ctxk, changes);
 }
 // Search ctxk for concrete implementations.  If there are klen or fewer,
 // pack them into the given array and return the number.
 // Otherwise, return -1, meaning the given array would overflow.
 // (Note that a return of 0 means there are exactly no concrete subtypes.)
 // In this search, if ctxk is concrete, it will be reported alone.
 // For any type CC reported, no proper subtypes of CC will be reported.
 int Dependencies::find_exclusive_concrete_subtypes(klassOop ctxk,
                                                    int klen,
                                                    klassOop karray[]) {
   ClassHierarchyWalker wf;
   wf.record_witnesses(klen);
   klassOop wit = wf.find_witness_subtype(ctxk);
   if (wit != NULL)  return -1;  // Too many witnesses.
   int num = wf.num_participants();
   assert(num <= klen, "oob");
   // Pack the result array with the good news.
   for (int i = 0; i < num; i++)
     karray[i] = wf.participant(i);
 #ifndef PRODUCT
   // Make sure the dependency mechanism will pass this discovery:
   if (VerifyDependencies) {
     // Turn off dependency tracing while actually testing deps.
     FlagSetting fs(TraceDependencies, false);
     switch (Dependencies::is_concrete_klass(ctxk)? -1: num) {
     case -1: // ctxk was itself concrete
       guarantee(num == 1 && karray[0] == ctxk, "verify dep.");
       break;
     case 0:
       guarantee(NULL == (void *)check_abstract_with_no_concrete_subtype(ctxk),
                 "verify dep.");
       break;
     case 1:
       guarantee(NULL == (void *)
                 check_abstract_with_unique_concrete_subtype(ctxk, karray[0]),
                 "verify dep.");
       break;
     case 2:
       guarantee(NULL == (void *)
                 check_abstract_with_exclusive_concrete_subtypes(ctxk,
                                                                 karray[0],
                                                                 karray[1]),
                 "verify dep.");
       break;
     default:
       ShouldNotReachHere();  // klen > 2 yet supported
     }
   }
 #endif //PRODUCT
   return num;
 }
 // If a class (or interface) has a unique concrete method uniqm, return NULL.
 // Otherwise, return a class that contains an interfering method.
 klassOop Dependencies::check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
                                                     KlassDepChange* changes) {
   // Here is a missing optimization:  If uniqm->is_final(),
   // we don't really need to search beneath it for overrides.
   // This is probably not important, since we don't use dependencies
   // to track final methods.  (They can't be "definalized".)
   ClassHierarchyWalker wf(uniqm->method_holder(), uniqm);
   return wf.find_witness_definer(ctxk, changes);
 }
 // Find the set of all non-abstract methods under ctxk that match m.
 // (The method m must be defined or inherited in ctxk.)
 // Include m itself in the set, unless it is abstract.
 // If this set has exactly one element, return that element.
 methodOop Dependencies::find_unique_concrete_method(klassOop ctxk, methodOop m) {
   ClassHierarchyWalker wf(m);
   assert(wf.check_method_context(ctxk, m), "proper context");
   wf.record_witnesses(1);
   klassOop wit = wf.find_witness_definer(ctxk);
   if (wit != NULL)  return NULL;  // Too many witnesses.
   methodOop fm = wf.found_method(0);  // Will be NULL if num_parts == 0.
   if (Dependencies::is_concrete_method(m)) {
     if (fm == NULL) {
       // It turns out that m was always the only implementation.
       fm = m;
     } else if (fm != m) {
       // Two conflicting implementations after all.
       // (This can happen if m is inherited into ctxk and fm overrides it.)
       return NULL;
     }
   }
 #ifndef PRODUCT
   // Make sure the dependency mechanism will pass this discovery:
   if (VerifyDependencies && fm != NULL) {
     guarantee(NULL == (void *)check_unique_concrete_method(ctxk, fm),
               "verify dep.");
   }
 #endif //PRODUCT
   return fm;
 }
 klassOop Dependencies::check_exclusive_concrete_methods(klassOop ctxk,
                                                         methodOop m1,
                                                         methodOop m2,
                                                         KlassDepChange* changes) {
   ClassHierarchyWalker wf(m1);
   wf.add_participant(m1->method_holder());
   wf.add_participant(m2->method_holder());
   return wf.find_witness_definer(ctxk, changes);
 }
 // Find the set of all non-abstract methods under ctxk that match m[0].
 // (The method m[0] must be defined or inherited in ctxk.)
 // Include m itself in the set, unless it is abstract.
 // Fill the given array m[0..(mlen-1)] with this set, and return the length.
 // (The length may be zero if no concrete methods are found anywhere.)
 // If there are too many concrete methods to fit in marray, return -1.
 int Dependencies::find_exclusive_concrete_methods(klassOop ctxk,
                                                   int mlen,
                                                   methodOop marray[]) {
   methodOop m0 = marray[0];
   ClassHierarchyWalker wf(m0);
   assert(wf.check_method_context(ctxk, m0), "proper context");
   wf.record_witnesses(mlen);
   bool participants_hide_witnesses = true;
   klassOop wit = wf.find_witness_definer(ctxk);
   if (wit != NULL)  return -1;  // Too many witnesses.
   int num = wf.num_participants();
   assert(num <= mlen, "oob");
   // Keep track of whether m is also part of the result set.
   int mfill = 0;
   assert(marray[mfill] == m0, "sanity");
   if (Dependencies::is_concrete_method(m0))
     mfill++;  // keep m0 as marray[0], the first result
   for (int i = 0; i < num; i++) {
     methodOop fm = wf.found_method(i);
     if (fm == m0)  continue;  // Already put this guy in the list.
     if (mfill == mlen) {
       return -1;              // Oops.  Too many methods after all!
     }
     marray[mfill++] = fm;
   }
 #ifndef PRODUCT
   // Make sure the dependency mechanism will pass this discovery:
   if (VerifyDependencies) {
     // Turn off dependency tracing while actually testing deps.
     FlagSetting fs(TraceDependencies, false);
     switch (mfill) {
     case 1:
       guarantee(NULL == (void *)check_unique_concrete_method(ctxk, marray[0]),
                 "verify dep.");
       break;
     case 2:
       guarantee(NULL == (void *)
                 check_exclusive_concrete_methods(ctxk, marray[0], marray[1]),
                 "verify dep.");
       break;
     default:
       ShouldNotReachHere();  // mlen > 2 yet supported
     }
   }
 #endif //PRODUCT
   return mfill;
 }
 klassOop Dependencies::check_has_no_finalizable_subclasses(klassOop ctxk, KlassDepChange* changes) {
   Klass* search_at = ctxk->klass_part();
   if (changes != NULL)
     search_at = changes->new_type()->klass_part(); // just look at the new bit
   Klass* result = find_finalizable_subclass(search_at);
   if (result == NULL) {
     return NULL;
   }
   return result->as_klassOop();
 }
 klassOop Dependencies::check_call_site_target_value(klassOop ctxk, oop call_site, oop method_handle, CallSiteDepChange* changes) {
   assert(call_site    ->is_a(SystemDictionary::CallSite_klass()),     "sanity");
   assert(method_handle->is_a(SystemDictionary::MethodHandle_klass()), "sanity");
   if (changes == NULL) {
     // Validate all CallSites
     if (java_lang_invoke_CallSite::target(call_site) != method_handle)
       return ctxk;  // assertion failed
   } else {
     // Validate the given CallSite
     if (call_site == changes->call_site() && java_lang_invoke_CallSite::target(call_site) != changes->method_handle()) {
       assert(method_handle != changes->method_handle(), "must be");
       return ctxk;  // assertion failed
     }
   }
   assert(java_lang_invoke_CallSite::target(call_site) == method_handle, "should still be valid");
   return NULL;  // assertion still valid
 }
 void Dependencies::DepStream::trace_and_log_witness(klassOop witness) {
   if (witness != NULL) {
     if (TraceDependencies) {
       print_dependency(witness, /*verbose=*/ true);
     }
     // The following is a no-op unless logging is enabled:
     log_dependency(witness);
   }
 }
 klassOop Dependencies::DepStream::check_klass_dependency(KlassDepChange* changes) {
   assert_locked_or_safepoint(Compile_lock);
   Dependencies::check_valid_dependency_type(type());
   klassOop witness = NULL;
   switch (type()) {
   case evol_method:
     witness = check_evol_method(method_argument(0));
     break;
   case leaf_type:
     witness = check_leaf_type(context_type());
     break;
   case abstract_with_unique_concrete_subtype:
     witness = check_abstract_with_unique_concrete_subtype(context_type(), type_argument(1), changes);
     break;
   case abstract_with_no_concrete_subtype:
     witness = check_abstract_with_no_concrete_subtype(context_type(), changes);
     break;
   case concrete_with_no_concrete_subtype:
     witness = check_concrete_with_no_concrete_subtype(context_type(), changes);
     break;
   case unique_concrete_method:
     witness = check_unique_concrete_method(context_type(), method_argument(1), changes);
     break;
   case abstract_with_exclusive_concrete_subtypes_2:
     witness = check_abstract_with_exclusive_concrete_subtypes(context_type(), type_argument(1), type_argument(2), changes);
     break;
   case exclusive_concrete_methods_2:
     witness = check_exclusive_concrete_methods(context_type(), method_argument(1), method_argument(2), changes);
     break;
   case no_finalizable_subclasses:
     witness = check_has_no_finalizable_subclasses(context_type(), changes);
     break;
   default:
     witness = NULL;
     break;
   }
   trace_and_log_witness(witness);
   return witness;
 }
 klassOop Dependencies::DepStream::check_call_site_dependency(CallSiteDepChange* changes) {
   assert_locked_or_safepoint(Compile_lock);
   Dependencies::check_valid_dependency_type(type());
   klassOop witness = NULL;
   switch (type()) {
   case call_site_target_value:
     witness = check_call_site_target_value(context_type(), argument(1), argument(2), changes);
     break;
   default:
     witness = NULL;
     break;
   }
   trace_and_log_witness(witness);
   return witness;
 }
 klassOop Dependencies::DepStream::spot_check_dependency_at(DepChange& changes) {
   // Handle klass dependency
   if (changes.is_klass_change() && changes.as_klass_change()->involves_context(context_type()))
     return check_klass_dependency(changes.as_klass_change());
   // Handle CallSite dependency
   if (changes.is_call_site_change())
     return check_call_site_dependency(changes.as_call_site_change());
   // irrelevant dependency; skip it
   return NULL;
 }
 void DepChange::print() {
   int nsup = 0, nint = 0;
   for (ContextStream str(*this); str.next(); ) {
     klassOop k = str.klass();
     switch (str.change_type()) {
     case Change_new_type:
       tty->print_cr("  dependee = %s", instanceKlass::cast(k)->external_name());
       break;
     case Change_new_sub:
       if (!WizardMode) {
         ++nsup;
       } else {
         tty->print_cr("  context super = %s", instanceKlass::cast(k)->external_name());
       }
       break;
     case Change_new_impl:
       if (!WizardMode) {
         ++nint;
       } else {
         tty->print_cr("  context interface = %s", instanceKlass::cast(k)->external_name());
       }
       break;
     }
   }
   if (nsup + nint != 0) {
     tty->print_cr("  context supers = %d, interfaces = %d", nsup, nint);
   }
 }
 void DepChange::ContextStream::start() {
   klassOop new_type = _changes.is_klass_change() ? _changes.as_klass_change()->new_type() : (klassOop) NULL;
   _change_type = (new_type == NULL ? NO_CHANGE : Start_Klass);
   _klass = new_type;
   _ti_base = NULL;
   _ti_index = 0;
   _ti_limit = 0;
 }
 bool DepChange::ContextStream::next() {
   switch (_change_type) {
   case Start_Klass:             // initial state; _klass is the new type
     _ti_base = instanceKlass::cast(_klass)->transitive_interfaces();
     _ti_index = 0;
     _change_type = Change_new_type;
     return true;
   case Change_new_type:
     // fall through:
     _change_type = Change_new_sub;
   case Change_new_sub:
     // 6598190: brackets workaround Sun Studio C++ compiler bug 6629277
     {
       _klass = instanceKlass::cast(_klass)->super();
       if (_klass != NULL) {
         return true;
       }
     }
     // else set up _ti_limit and fall through:
     _ti_limit = (_ti_base == NULL) ? 0 : _ti_base->length();
     _change_type = Change_new_impl;
   case Change_new_impl:
     if (_ti_index < _ti_limit) {
       _klass = klassOop( _ti_base->obj_at(_ti_index++) );
       return true;
     }
     // fall through:
     _change_type = NO_CHANGE;  // iterator is exhausted
   case NO_CHANGE:
     break;
   default:
     ShouldNotReachHere();
   }
   return false;
 }
 void KlassDepChange::initialize() {
   // entire transaction must be under this lock:
   assert_lock_strong(Compile_lock);
   // Mark all dependee and all its superclasses
   // Mark transitive interfaces
   for (ContextStream str(*this); str.next(); ) {
     klassOop d = str.klass();
     assert(!instanceKlass::cast(d)->is_marked_dependent(), "checking");
     instanceKlass::cast(d)->set_is_marked_dependent(true);
   }
 }
 KlassDepChange::~KlassDepChange() {
   // Unmark all dependee and all its superclasses
   // Unmark transitive interfaces
   for (ContextStream str(*this); str.next(); ) {
     klassOop d = str.klass();
     instanceKlass::cast(d)->set_is_marked_dependent(false);
   }
 }
 bool KlassDepChange::involves_context(klassOop k) {
   if (k == NULL || !Klass::cast(k)->oop_is_instance()) {
     return false;
   }
   instanceKlass* ik = instanceKlass::cast(k);
   bool is_contained = ik->is_marked_dependent();
   assert(is_contained == Klass::cast(new_type())->is_subtype_of(k),
          "correct marking of potential context types");
   return is_contained;
 }
 #ifndef PRODUCT
 void Dependencies::print_statistics() {
   if (deps_find_witness_print != 0) {
     // Call one final time, to flush out the data.
     deps_find_witness_print = -1;
     count_find_witness_calls();
   }
 }
 #endif

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/code/dependencies.cpp@fdb992d83a87 (annotated)

src/share/vm/code/dependencies.cpp