xref: /openjdk10/hotspot/src/share/vm/ci/ciTypeFlow.cpp

/*
 * Copyright (c) 2000, 2009, 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 "incls/_precompiled.incl"
#include "incls/_ciTypeFlow.cpp.incl"

// ciTypeFlow::JsrSet
//
// A JsrSet represents some set of JsrRecords.  This class
// is used to record a set of all jsr routines which we permit
// execution to return (ret) from.
//
// During abstract interpretation, JsrSets are used to determine
// whether two paths which reach a given block are unique, and
// should be cloned apart, or are compatible, and should merge
// together.

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::JsrSet
ciTypeFlow::JsrSet::JsrSet(Arena* arena, int default_len) {
  if (arena != NULL) {
    // Allocate growable array in Arena.
    _set = new (arena) GrowableArray<JsrRecord*>(arena, default_len, 0, NULL);
  } else {
    // Allocate growable array in current ResourceArea.
    _set = new GrowableArray<JsrRecord*>(4, 0, NULL, false);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::copy_into
void ciTypeFlow::JsrSet::copy_into(JsrSet* jsrs) {
  int len = size();
  jsrs->_set->clear();
  for (int i = 0; i < len; i++) {
    jsrs->_set->append(_set->at(i));
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::is_compatible_with
//
// !!!! MISGIVINGS ABOUT THIS... disregard
//
// Is this JsrSet compatible with some other JsrSet?
//
// In set-theoretic terms, a JsrSet can be viewed as a partial function
// from entry addresses to return addresses.  Two JsrSets A and B are
// compatible iff
//
//   For any x,
//   A(x) defined and B(x) defined implies A(x) == B(x)
//
// Less formally, two JsrSets are compatible when they have identical
// return addresses for any entry addresses they share in common.
bool ciTypeFlow::JsrSet::is_compatible_with(JsrSet* other) {
  // Walk through both sets in parallel.  If the same entry address
  // appears in both sets, then the return address must match for
  // the sets to be compatible.
  int size1 = size();
  int size2 = other->size();

  // Special case.  If nothing is on the jsr stack, then there can
  // be no ret.
  if (size2 == 0) {
    return true;
  } else if (size1 != size2) {
    return false;
  } else {
    for (int i = 0; i < size1; i++) {
      JsrRecord* record1 = record_at(i);
      JsrRecord* record2 = other->record_at(i);
      if (record1->entry_address() != record2->entry_address() ||
          record1->return_address() != record2->return_address()) {
        return false;
      }
    }
    return true;
  }

#if 0
  int pos1 = 0;
  int pos2 = 0;
  int size1 = size();
  int size2 = other->size();
  while (pos1 < size1 && pos2 < size2) {
    JsrRecord* record1 = record_at(pos1);
    JsrRecord* record2 = other->record_at(pos2);
    int entry1 = record1->entry_address();
    int entry2 = record2->entry_address();
    if (entry1 < entry2) {
      pos1++;
    } else if (entry1 > entry2) {
      pos2++;
    } else {
      if (record1->return_address() == record2->return_address()) {
        pos1++;
        pos2++;
      } else {
        // These two JsrSets are incompatible.
        return false;
      }
    }
  }
  // The two JsrSets agree.
  return true;
#endif
}

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::insert_jsr_record
//
// Insert the given JsrRecord into the JsrSet, maintaining the order
// of the set and replacing any element with the same entry address.
void ciTypeFlow::JsrSet::insert_jsr_record(JsrRecord* record) {
  int len = size();
  int entry = record->entry_address();
  int pos = 0;
  for ( ; pos < len; pos++) {
    JsrRecord* current = record_at(pos);
    if (entry == current->entry_address()) {
      // Stomp over this entry.
      _set->at_put(pos, record);
      assert(size() == len, "must be same size");
      return;
    } else if (entry < current->entry_address()) {
      break;
    }
  }

  // Insert the record into the list.
  JsrRecord* swap = record;
  JsrRecord* temp = NULL;
  for ( ; pos < len; pos++) {
    temp = _set->at(pos);
    _set->at_put(pos, swap);
    swap = temp;
  }
  _set->append(swap);
  assert(size() == len+1, "must be larger");
}

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::remove_jsr_record
//
// Remove the JsrRecord with the given return address from the JsrSet.
void ciTypeFlow::JsrSet::remove_jsr_record(int return_address) {
  int len = size();
  for (int i = 0; i < len; i++) {
    if (record_at(i)->return_address() == return_address) {
      // We have found the proper entry.  Remove it from the
      // JsrSet and exit.
      for (int j = i+1; j < len ; j++) {
        _set->at_put(j-1, _set->at(j));
      }
      _set->trunc_to(len-1);
      assert(size() == len-1, "must be smaller");
      return;
    }
  }
  assert(false, "verify: returning from invalid subroutine");
}

// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::apply_control
//
// Apply the effect of a control-flow bytecode on the JsrSet.  The
// only bytecodes that modify the JsrSet are jsr and ret.
void ciTypeFlow::JsrSet::apply_control(ciTypeFlow* analyzer,
                                       ciBytecodeStream* str,
                                       ciTypeFlow::StateVector* state) {
  Bytecodes::Code code = str->cur_bc();
  if (code == Bytecodes::_jsr) {
    JsrRecord* record =
      analyzer->make_jsr_record(str->get_dest(), str->next_bci());
    insert_jsr_record(record);
  } else if (code == Bytecodes::_jsr_w) {
    JsrRecord* record =
      analyzer->make_jsr_record(str->get_far_dest(), str->next_bci());
    insert_jsr_record(record);
  } else if (code == Bytecodes::_ret) {
    Cell local = state->local(str->get_index());
    ciType* return_address = state->type_at(local);
    assert(return_address->is_return_address(), "verify: wrong type");
    if (size() == 0) {
      // Ret-state underflow:  Hit a ret w/o any previous jsrs.  Bail out.
      // This can happen when a loop is inside a finally clause (4614060).
      analyzer->record_failure("OSR in finally clause");
      return;
    }
    remove_jsr_record(return_address->as_return_address()->bci());
  }
}

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::JsrSet::print_on
void ciTypeFlow::JsrSet::print_on(outputStream* st) const {
  st->print("{ ");
  int num_elements = size();
  if (num_elements > 0) {
    int i = 0;
    for( ; i < num_elements - 1; i++) {
      _set->at(i)->print_on(st);
      st->print(", ");
    }
    _set->at(i)->print_on(st);
    st->print(" ");
  }
  st->print("}");
}
#endif

// ciTypeFlow::StateVector
//
// A StateVector summarizes the type information at some point in
// the program.

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::type_meet
//
// Meet two types.
//
// The semi-lattice of types use by this analysis are modeled on those
// of the verifier.  The lattice is as follows:
//
//        top_type() >= all non-extremal types >= bottom_type
//                             and
//   Every primitive type is comparable only with itself.  The meet of
//   reference types is determined by their kind: instance class,
//   interface, or array class.  The meet of two types of the same
//   kind is their least common ancestor.  The meet of two types of
//   different kinds is always java.lang.Object.
ciType* ciTypeFlow::StateVector::type_meet_internal(ciType* t1, ciType* t2, ciTypeFlow* analyzer) {
  assert(t1 != t2, "checked in caller");
  if (t1->equals(top_type())) {
    return t2;
  } else if (t2->equals(top_type())) {
    return t1;
  } else if (t1->is_primitive_type() || t2->is_primitive_type()) {
    // Special case null_type.  null_type meet any reference type T
    // is T.  null_type meet null_type is null_type.
    if (t1->equals(null_type())) {
      if (!t2->is_primitive_type() || t2->equals(null_type())) {
        return t2;
      }
    } else if (t2->equals(null_type())) {
      if (!t1->is_primitive_type()) {
        return t1;
      }
    }

    // At least one of the two types is a non-top primitive type.
    // The other type is not equal to it.  Fall to bottom.
    return bottom_type();
  } else {
    // Both types are non-top non-primitive types.  That is,
    // both types are either instanceKlasses or arrayKlasses.
    ciKlass* object_klass = analyzer->env()->Object_klass();
    ciKlass* k1 = t1->as_klass();
    ciKlass* k2 = t2->as_klass();
    if (k1->equals(object_klass) || k2->equals(object_klass)) {
      return object_klass;
    } else if (!k1->is_loaded() || !k2->is_loaded()) {
      // Unloaded classes fall to java.lang.Object at a merge.
      return object_klass;
    } else if (k1->is_interface() != k2->is_interface()) {
      // When an interface meets a non-interface, we get Object;
      // This is what the verifier does.
      return object_klass;
    } else if (k1->is_array_klass() || k2->is_array_klass()) {
      // When an array meets a non-array, we get Object.
      // When objArray meets typeArray, we also get Object.
      // And when typeArray meets different typeArray, we again get Object.
      // But when objArray meets objArray, we look carefully at element types.
      if (k1->is_obj_array_klass() && k2->is_obj_array_klass()) {
        // Meet the element types, then construct the corresponding array type.
        ciKlass* elem1 = k1->as_obj_array_klass()->element_klass();
        ciKlass* elem2 = k2->as_obj_array_klass()->element_klass();
        ciKlass* elem  = type_meet_internal(elem1, elem2, analyzer)->as_klass();
        // Do an easy shortcut if one type is a super of the other.
        if (elem == elem1) {
          assert(k1 == ciObjArrayKlass::make(elem), "shortcut is OK");
          return k1;
        } else if (elem == elem2) {
          assert(k2 == ciObjArrayKlass::make(elem), "shortcut is OK");
          return k2;
        } else {
          return ciObjArrayKlass::make(elem);
        }
      } else {
        return object_klass;
      }
    } else {
      // Must be two plain old instance klasses.
      assert(k1->is_instance_klass(), "previous cases handle non-instances");
      assert(k2->is_instance_klass(), "previous cases handle non-instances");
      return k1->least_common_ancestor(k2);
    }
  }
}


// ------------------------------------------------------------------
// ciTypeFlow::StateVector::StateVector
//
// Build a new state vector
ciTypeFlow::StateVector::StateVector(ciTypeFlow* analyzer) {
  _outer = analyzer;
  _stack_size = -1;
  _monitor_count = -1;
  // Allocate the _types array
  int max_cells = analyzer->max_cells();
  _types = (ciType**)analyzer->arena()->Amalloc(sizeof(ciType*) * max_cells);
  for (int i=0; i<max_cells; i++) {
    _types[i] = top_type();
  }
  _trap_bci = -1;
  _trap_index = 0;
  _def_locals.clear();
}


// ------------------------------------------------------------------
// ciTypeFlow::get_start_state
//
// Set this vector to the method entry state.
const ciTypeFlow::StateVector* ciTypeFlow::get_start_state() {
  StateVector* state = new StateVector(this);
  if (is_osr_flow()) {
    ciTypeFlow* non_osr_flow = method()->get_flow_analysis();
    if (non_osr_flow->failing()) {
      record_failure(non_osr_flow->failure_reason());
      return NULL;
    }
    JsrSet* jsrs = new JsrSet(NULL, 16);
    Block* non_osr_block = non_osr_flow->existing_block_at(start_bci(), jsrs);
    if (non_osr_block == NULL) {
      record_failure("cannot reach OSR point");
      return NULL;
    }
    // load up the non-OSR state at this point
    non_osr_block->copy_state_into(state);
    int non_osr_start = non_osr_block->start();
    if (non_osr_start != start_bci()) {
      // must flow forward from it
      if (CITraceTypeFlow) {
        tty->print_cr(">> Interpreting pre-OSR block %d:", non_osr_start);
      }
      Block* block = block_at(non_osr_start, jsrs);
      assert(block->limit() == start_bci(), "must flow forward to start");
      flow_block(block, state, jsrs);
    }
    return state;
    // Note:  The code below would be an incorrect for an OSR flow,
    // even if it were possible for an OSR entry point to be at bci zero.
  }
  // "Push" the method signature into the first few locals.
  state->set_stack_size(-max_locals());
  if (!method()->is_static()) {
    state->push(method()->holder());
    assert(state->tos() == state->local(0), "");
  }
  for (ciSignatureStream str(method()->signature());
       !str.at_return_type();
       str.next()) {
    state->push_translate(str.type());
  }
  // Set the rest of the locals to bottom.
  Cell cell = state->next_cell(state->tos());
  state->set_stack_size(0);
  int limit = state->limit_cell();
  for (; cell < limit; cell = state->next_cell(cell)) {
    state->set_type_at(cell, state->bottom_type());
  }
  // Lock an object, if necessary.
  state->set_monitor_count(method()->is_synchronized() ? 1 : 0);
  return state;
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::copy_into
//
// Copy our value into some other StateVector
void ciTypeFlow::StateVector::copy_into(ciTypeFlow::StateVector* copy)
const {
  copy->set_stack_size(stack_size());
  copy->set_monitor_count(monitor_count());
  Cell limit = limit_cell();
  for (Cell c = start_cell(); c < limit; c = next_cell(c)) {
    copy->set_type_at(c, type_at(c));
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::meet
//
// Meets this StateVector with another, destructively modifying this
// one.  Returns true if any modification takes place.
bool ciTypeFlow::StateVector::meet(const ciTypeFlow::StateVector* incoming) {
  if (monitor_count() == -1) {
    set_monitor_count(incoming->monitor_count());
  }
  assert(monitor_count() == incoming->monitor_count(), "monitors must match");

  if (stack_size() == -1) {
    set_stack_size(incoming->stack_size());
    Cell limit = limit_cell();
    #ifdef ASSERT
    { for (Cell c = start_cell(); c < limit; c = next_cell(c)) {
        assert(type_at(c) == top_type(), "");
    } }
    #endif
    // Make a simple copy of the incoming state.
    for (Cell c = start_cell(); c < limit; c = next_cell(c)) {
      set_type_at(c, incoming->type_at(c));
    }
    return true;  // it is always different the first time
  }
#ifdef ASSERT
  if (stack_size() != incoming->stack_size()) {
    _outer->method()->print_codes();
    tty->print_cr("!!!! Stack size conflict");
    tty->print_cr("Current state:");
    print_on(tty);
    tty->print_cr("Incoming state:");
    ((StateVector*)incoming)->print_on(tty);
  }
#endif
  assert(stack_size() == incoming->stack_size(), "sanity");

  bool different = false;
  Cell limit = limit_cell();
  for (Cell c = start_cell(); c < limit; c = next_cell(c)) {
    ciType* t1 = type_at(c);
    ciType* t2 = incoming->type_at(c);
    if (!t1->equals(t2)) {
      ciType* new_type = type_meet(t1, t2);
      if (!t1->equals(new_type)) {
        set_type_at(c, new_type);
        different = true;
      }
    }
  }
  return different;
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::meet_exception
//
// Meets this StateVector with another, destructively modifying this
// one.  The incoming state is coming via an exception.  Returns true
// if any modification takes place.
bool ciTypeFlow::StateVector::meet_exception(ciInstanceKlass* exc,
                                     const ciTypeFlow::StateVector* incoming) {
  if (monitor_count() == -1) {
    set_monitor_count(incoming->monitor_count());
  }
  assert(monitor_count() == incoming->monitor_count(), "monitors must match");

  if (stack_size() == -1) {
    set_stack_size(1);
  }

  assert(stack_size() ==  1, "must have one-element stack");

  bool different = false;

  // Meet locals from incoming array.
  Cell limit = local(_outer->max_locals()-1);
  for (Cell c = start_cell(); c <= limit; c = next_cell(c)) {
    ciType* t1 = type_at(c);
    ciType* t2 = incoming->type_at(c);
    if (!t1->equals(t2)) {
      ciType* new_type = type_meet(t1, t2);
      if (!t1->equals(new_type)) {
        set_type_at(c, new_type);
        different = true;
      }
    }
  }

  // Handle stack separately.  When an exception occurs, the
  // only stack entry is the exception instance.
  ciType* tos_type = type_at_tos();
  if (!tos_type->equals(exc)) {
    ciType* new_type = type_meet(tos_type, exc);
    if (!tos_type->equals(new_type)) {
      set_type_at_tos(new_type);
      different = true;
    }
  }

  return different;
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::push_translate
void ciTypeFlow::StateVector::push_translate(ciType* type) {
  BasicType basic_type = type->basic_type();
  if (basic_type == T_BOOLEAN || basic_type == T_CHAR ||
      basic_type == T_BYTE    || basic_type == T_SHORT) {
    push_int();
  } else {
    push(type);
    if (type->is_two_word()) {
      push(half_type(type));
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_aaload
void ciTypeFlow::StateVector::do_aaload(ciBytecodeStream* str) {
  pop_int();
  ciObjArrayKlass* array_klass = pop_objArray();
  if (array_klass == NULL) {
    // Did aaload on a null reference; push a null and ignore the exception.
    // This instruction will never continue normally.  All we have to do
    // is report a value that will meet correctly with any downstream
    // reference types on paths that will truly be executed.  This null type
    // meets with any reference type to yield that same reference type.
    // (The compiler will generate an unconditional exception here.)
    push(null_type());
    return;
  }
  if (!array_klass->is_loaded()) {
    // Only fails for some -Xcomp runs
    trap(str, array_klass,
         Deoptimization::make_trap_request
         (Deoptimization::Reason_unloaded,
          Deoptimization::Action_reinterpret));
    return;
  }
  ciKlass* element_klass = array_klass->element_klass();
  if (!element_klass->is_loaded() && element_klass->is_instance_klass()) {
    Untested("unloaded array element class in ciTypeFlow");
    trap(str, element_klass,
         Deoptimization::make_trap_request
         (Deoptimization::Reason_unloaded,
          Deoptimization::Action_reinterpret));
  } else {
    push_object(element_klass);
  }
}


// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_checkcast
void ciTypeFlow::StateVector::do_checkcast(ciBytecodeStream* str) {
  bool will_link;
  ciKlass* klass = str->get_klass(will_link);
  if (!will_link) {
    // VM's interpreter will not load 'klass' if object is NULL.
    // Type flow after this block may still be needed in two situations:
    // 1) C2 uses do_null_assert() and continues compilation for later blocks
    // 2) C2 does an OSR compile in a later block (see bug 4778368).
    pop_object();
    do_null_assert(klass);
  } else {
    pop_object();
    push_object(klass);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_getfield
void ciTypeFlow::StateVector::do_getfield(ciBytecodeStream* str) {
  // could add assert here for type of object.
  pop_object();
  do_getstatic(str);
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_getstatic
void ciTypeFlow::StateVector::do_getstatic(ciBytecodeStream* str) {
  bool will_link;
  ciField* field = str->get_field(will_link);
  if (!will_link) {
    trap(str, field->holder(), str->get_field_holder_index());
  } else {
    ciType* field_type = field->type();
    if (!field_type->is_loaded()) {
      // Normally, we need the field's type to be loaded if we are to
      // do anything interesting with its value.
      // We used to do this:  trap(str, str->get_field_signature_index());
      //
      // There is one good reason not to trap here.  Execution can
      // get past this "getfield" or "getstatic" if the value of
      // the field is null.  As long as the value is null, the class
      // does not need to be loaded!  The compiler must assume that
      // the value of the unloaded class reference is null; if the code
      // ever sees a non-null value, loading has occurred.
      //
      // This actually happens often enough to be annoying.  If the
      // compiler throws an uncommon trap at this bytecode, you can
      // get an endless loop of recompilations, when all the code
      // needs to do is load a series of null values.  Also, a trap
      // here can make an OSR entry point unreachable, triggering the
      // assert on non_osr_block in ciTypeFlow::get_start_state.
      // (See bug 4379915.)
      do_null_assert(field_type->as_klass());
    } else {
      push_translate(field_type);
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_invoke
void ciTypeFlow::StateVector::do_invoke(ciBytecodeStream* str,
                                        bool has_receiver) {
  bool will_link;
  ciMethod* method = str->get_method(will_link);
  if (!will_link) {
    // We weren't able to find the method.
    if (str->cur_bc() == Bytecodes::_invokedynamic) {
      trap(str, NULL,
           Deoptimization::make_trap_request
           (Deoptimization::Reason_uninitialized,
            Deoptimization::Action_reinterpret));
    } else {
      ciKlass* unloaded_holder = method->holder();
      trap(str, unloaded_holder, str->get_method_holder_index());
    }
  } else {
    ciSignature* signature = method->signature();
    ciSignatureStream sigstr(signature);
    int arg_size = signature->size();
    int stack_base = stack_size() - arg_size;
    int i = 0;
    for( ; !sigstr.at_return_type(); sigstr.next()) {
      ciType* type = sigstr.type();
      ciType* stack_type = type_at(stack(stack_base + i++));
      // Do I want to check this type?
      // assert(stack_type->is_subtype_of(type), "bad type for field value");
      if (type->is_two_word()) {
        ciType* stack_type2 = type_at(stack(stack_base + i++));
        assert(stack_type2->equals(half_type(type)), "must be 2nd half");
      }
    }
    assert(arg_size == i, "must match");
    for (int j = 0; j < arg_size; j++) {
      pop();
    }
    if (has_receiver) {
      // Check this?
      pop_object();
    }
    assert(!sigstr.is_done(), "must have return type");
    ciType* return_type = sigstr.type();
    if (!return_type->is_void()) {
      if (!return_type->is_loaded()) {
        // As in do_getstatic(), generally speaking, we need the return type to
        // be loaded if we are to do anything interesting with its value.
        // We used to do this:  trap(str, str->get_method_signature_index());
        //
        // We do not trap here since execution can get past this invoke if
        // the return value is null.  As long as the value is null, the class
        // does not need to be loaded!  The compiler must assume that
        // the value of the unloaded class reference is null; if the code
        // ever sees a non-null value, loading has occurred.
        //
        // See do_getstatic() for similar explanation, as well as bug 4684993.
        do_null_assert(return_type->as_klass());
      } else {
        push_translate(return_type);
      }
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_jsr
void ciTypeFlow::StateVector::do_jsr(ciBytecodeStream* str) {
  push(ciReturnAddress::make(str->next_bci()));
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_ldc
void ciTypeFlow::StateVector::do_ldc(ciBytecodeStream* str) {
  ciConstant con = str->get_constant();
  BasicType basic_type = con.basic_type();
  if (basic_type == T_ILLEGAL) {
    // OutOfMemoryError in the CI while loading constant
    push_null();
    outer()->record_failure("ldc did not link");
    return;
  }
  if (basic_type == T_OBJECT || basic_type == T_ARRAY) {
    ciObject* obj = con.as_object();
    if (obj->is_null_object()) {
      push_null();
    } else if (obj->is_klass()) {
      // The type of ldc <class> is java.lang.Class
      push_object(outer()->env()->Class_klass());
    } else {
      push_object(obj->klass());
    }
  } else {
    push_translate(ciType::make(basic_type));
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_multianewarray
void ciTypeFlow::StateVector::do_multianewarray(ciBytecodeStream* str) {
  int dimensions = str->get_dimensions();
  bool will_link;
  ciArrayKlass* array_klass = str->get_klass(will_link)->as_array_klass();
  if (!will_link) {
    trap(str, array_klass, str->get_klass_index());
  } else {
    for (int i = 0; i < dimensions; i++) {
      pop_int();
    }
    push_object(array_klass);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_new
void ciTypeFlow::StateVector::do_new(ciBytecodeStream* str) {
  bool will_link;
  ciKlass* klass = str->get_klass(will_link);
  if (!will_link || str->is_unresolved_klass()) {
    trap(str, klass, str->get_klass_index());
  } else {
    push_object(klass);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_newarray
void ciTypeFlow::StateVector::do_newarray(ciBytecodeStream* str) {
  pop_int();
  ciKlass* klass = ciTypeArrayKlass::make((BasicType)str->get_index());
  push_object(klass);
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_putfield
void ciTypeFlow::StateVector::do_putfield(ciBytecodeStream* str) {
  do_putstatic(str);
  if (_trap_bci != -1)  return;  // unloaded field holder, etc.
  // could add assert here for type of object.
  pop_object();
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_putstatic
void ciTypeFlow::StateVector::do_putstatic(ciBytecodeStream* str) {
  bool will_link;
  ciField* field = str->get_field(will_link);
  if (!will_link) {
    trap(str, field->holder(), str->get_field_holder_index());
  } else {
    ciType* field_type = field->type();
    ciType* type = pop_value();
    // Do I want to check this type?
    //      assert(type->is_subtype_of(field_type), "bad type for field value");
    if (field_type->is_two_word()) {
      ciType* type2 = pop_value();
      assert(type2->is_two_word(), "must be 2nd half");
      assert(type == half_type(type2), "must be 2nd half");
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_ret
void ciTypeFlow::StateVector::do_ret(ciBytecodeStream* str) {
  Cell index = local(str->get_index());

  ciType* address = type_at(index);
  assert(address->is_return_address(), "bad return address");
  set_type_at(index, bottom_type());
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::trap
//
// Stop interpretation of this path with a trap.
void ciTypeFlow::StateVector::trap(ciBytecodeStream* str, ciKlass* klass, int index) {
  _trap_bci = str->cur_bci();
  _trap_index = index;

  // Log information about this trap:
  CompileLog* log = outer()->env()->log();
  if (log != NULL) {
    int mid = log->identify(outer()->method());
    int kid = (klass == NULL)? -1: log->identify(klass);
    log->begin_elem("uncommon_trap method='%d' bci='%d'", mid, str->cur_bci());
    char buf[100];
    log->print(" %s", Deoptimization::format_trap_request(buf, sizeof(buf),
                                                          index));
    if (kid >= 0)
      log->print(" klass='%d'", kid);
    log->end_elem();
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::do_null_assert
// Corresponds to graphKit::do_null_assert.
void ciTypeFlow::StateVector::do_null_assert(ciKlass* unloaded_klass) {
  if (unloaded_klass->is_loaded()) {
    // We failed to link, but we can still compute with this class,
    // since it is loaded somewhere.  The compiler will uncommon_trap
    // if the object is not null, but the typeflow pass can not assume
    // that the object will be null, otherwise it may incorrectly tell
    // the parser that an object is known to be null. 4761344, 4807707
    push_object(unloaded_klass);
  } else {
    // The class is not loaded anywhere.  It is safe to model the
    // null in the typestates, because we can compile in a null check
    // which will deoptimize us if someone manages to load the
    // class later.
    push_null();
  }
}


// ------------------------------------------------------------------
// ciTypeFlow::StateVector::apply_one_bytecode
//
// Apply the effect of one bytecode to this StateVector
bool ciTypeFlow::StateVector::apply_one_bytecode(ciBytecodeStream* str) {
  _trap_bci = -1;
  _trap_index = 0;

  if (CITraceTypeFlow) {
    tty->print_cr(">> Interpreting bytecode %d:%s", str->cur_bci(),
                  Bytecodes::name(str->cur_bc()));
  }

  switch(str->cur_bc()) {
  case Bytecodes::_aaload: do_aaload(str);                       break;

  case Bytecodes::_aastore:
    {
      pop_object();
      pop_int();
      pop_objArray();
      break;
    }
  case Bytecodes::_aconst_null:
    {
      push_null();
      break;
    }
  case Bytecodes::_aload:   load_local_object(str->get_index());    break;
  case Bytecodes::_aload_0: load_local_object(0);                   break;
  case Bytecodes::_aload_1: load_local_object(1);                   break;
  case Bytecodes::_aload_2: load_local_object(2);                   break;
  case Bytecodes::_aload_3: load_local_object(3);                   break;

  case Bytecodes::_anewarray:
    {
      pop_int();
      bool will_link;
      ciKlass* element_klass = str->get_klass(will_link);
      if (!will_link) {
        trap(str, element_klass, str->get_klass_index());
      } else {
        push_object(ciObjArrayKlass::make(element_klass));
      }
      break;
    }
  case Bytecodes::_areturn:
  case Bytecodes::_ifnonnull:
  case Bytecodes::_ifnull:
    {
      pop_object();
      break;
    }
  case Bytecodes::_monitorenter:
    {
      pop_object();
      set_monitor_count(monitor_count() + 1);
      break;
    }
  case Bytecodes::_monitorexit:
    {
      pop_object();
      assert(monitor_count() > 0, "must be a monitor to exit from");
      set_monitor_count(monitor_count() - 1);
      break;
    }
  case Bytecodes::_arraylength:
    {
      pop_array();
      push_int();
      break;
    }
  case Bytecodes::_astore:   store_local_object(str->get_index());  break;
  case Bytecodes::_astore_0: store_local_object(0);                 break;
  case Bytecodes::_astore_1: store_local_object(1);                 break;
  case Bytecodes::_astore_2: store_local_object(2);                 break;
  case Bytecodes::_astore_3: store_local_object(3);                 break;

  case Bytecodes::_athrow:
    {
      NEEDS_CLEANUP;
      pop_object();
      break;
    }
  case Bytecodes::_baload:
  case Bytecodes::_caload:
  case Bytecodes::_iaload:
  case Bytecodes::_saload:
    {
      pop_int();
      ciTypeArrayKlass* array_klass = pop_typeArray();
      // Put assert here for right type?
      push_int();
      break;
    }
  case Bytecodes::_bastore:
  case Bytecodes::_castore:
  case Bytecodes::_iastore:
  case Bytecodes::_sastore:
    {
      pop_int();
      pop_int();
      pop_typeArray();
      // assert here?
      break;
    }
  case Bytecodes::_bipush:
  case Bytecodes::_iconst_m1:
  case Bytecodes::_iconst_0:
  case Bytecodes::_iconst_1:
  case Bytecodes::_iconst_2:
  case Bytecodes::_iconst_3:
  case Bytecodes::_iconst_4:
  case Bytecodes::_iconst_5:
  case Bytecodes::_sipush:
    {
      push_int();
      break;
    }
  case Bytecodes::_checkcast: do_checkcast(str);                  break;

  case Bytecodes::_d2f:
    {
      pop_double();
      push_float();
      break;
    }
  case Bytecodes::_d2i:
    {
      pop_double();
      push_int();
      break;
    }
  case Bytecodes::_d2l:
    {
      pop_double();
      push_long();
      break;
    }
  case Bytecodes::_dadd:
  case Bytecodes::_ddiv:
  case Bytecodes::_dmul:
  case Bytecodes::_drem:
  case Bytecodes::_dsub:
    {
      pop_double();
      pop_double();
      push_double();
      break;
    }
  case Bytecodes::_daload:
    {
      pop_int();
      ciTypeArrayKlass* array_klass = pop_typeArray();
      // Put assert here for right type?
      push_double();
      break;
    }
  case Bytecodes::_dastore:
    {
      pop_double();
      pop_int();
      pop_typeArray();
      // assert here?
      break;
    }
  case Bytecodes::_dcmpg:
  case Bytecodes::_dcmpl:
    {
      pop_double();
      pop_double();
      push_int();
      break;
    }
  case Bytecodes::_dconst_0:
  case Bytecodes::_dconst_1:
    {
      push_double();
      break;
    }
  case Bytecodes::_dload:   load_local_double(str->get_index());    break;
  case Bytecodes::_dload_0: load_local_double(0);                   break;
  case Bytecodes::_dload_1: load_local_double(1);                   break;
  case Bytecodes::_dload_2: load_local_double(2);                   break;
  case Bytecodes::_dload_3: load_local_double(3);                   break;

  case Bytecodes::_dneg:
    {
      pop_double();
      push_double();
      break;
    }
  case Bytecodes::_dreturn:
    {
      pop_double();
      break;
    }
  case Bytecodes::_dstore:   store_local_double(str->get_index());  break;
  case Bytecodes::_dstore_0: store_local_double(0);                 break;
  case Bytecodes::_dstore_1: store_local_double(1);                 break;
  case Bytecodes::_dstore_2: store_local_double(2);                 break;
  case Bytecodes::_dstore_3: store_local_double(3);                 break;

  case Bytecodes::_dup:
    {
      push(type_at_tos());
      break;
    }
  case Bytecodes::_dup_x1:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      push(value1);
      push(value2);
      push(value1);
      break;
    }
  case Bytecodes::_dup_x2:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      ciType* value3 = pop_value();
      push(value1);
      push(value3);
      push(value2);
      push(value1);
      break;
    }
  case Bytecodes::_dup2:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      push(value2);
      push(value1);
      push(value2);
      push(value1);
      break;
    }
  case Bytecodes::_dup2_x1:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      ciType* value3 = pop_value();
      push(value2);
      push(value1);
      push(value3);
      push(value2);
      push(value1);
      break;
    }
  case Bytecodes::_dup2_x2:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      ciType* value3 = pop_value();
      ciType* value4 = pop_value();
      push(value2);
      push(value1);
      push(value4);
      push(value3);
      push(value2);
      push(value1);
      break;
    }
  case Bytecodes::_f2d:
    {
      pop_float();
      push_double();
      break;
    }
  case Bytecodes::_f2i:
    {
      pop_float();
      push_int();
      break;
    }
  case Bytecodes::_f2l:
    {
      pop_float();
      push_long();
      break;
    }
  case Bytecodes::_fadd:
  case Bytecodes::_fdiv:
  case Bytecodes::_fmul:
  case Bytecodes::_frem:
  case Bytecodes::_fsub:
    {
      pop_float();
      pop_float();
      push_float();
      break;
    }
  case Bytecodes::_faload:
    {
      pop_int();
      ciTypeArrayKlass* array_klass = pop_typeArray();
      // Put assert here.
      push_float();
      break;
    }
  case Bytecodes::_fastore:
    {
      pop_float();
      pop_int();
      ciTypeArrayKlass* array_klass = pop_typeArray();
      // Put assert here.
      break;
    }
  case Bytecodes::_fcmpg:
  case Bytecodes::_fcmpl:
    {
      pop_float();
      pop_float();
      push_int();
      break;
    }
  case Bytecodes::_fconst_0:
  case Bytecodes::_fconst_1:
  case Bytecodes::_fconst_2:
    {
      push_float();
      break;
    }
  case Bytecodes::_fload:   load_local_float(str->get_index());     break;
  case Bytecodes::_fload_0: load_local_float(0);                    break;
  case Bytecodes::_fload_1: load_local_float(1);                    break;
  case Bytecodes::_fload_2: load_local_float(2);                    break;
  case Bytecodes::_fload_3: load_local_float(3);                    break;

  case Bytecodes::_fneg:
    {
      pop_float();
      push_float();
      break;
    }
  case Bytecodes::_freturn:
    {
      pop_float();
      break;
    }
  case Bytecodes::_fstore:    store_local_float(str->get_index());   break;
  case Bytecodes::_fstore_0:  store_local_float(0);                  break;
  case Bytecodes::_fstore_1:  store_local_float(1);                  break;
  case Bytecodes::_fstore_2:  store_local_float(2);                  break;
  case Bytecodes::_fstore_3:  store_local_float(3);                  break;

  case Bytecodes::_getfield:  do_getfield(str);                      break;
  case Bytecodes::_getstatic: do_getstatic(str);                     break;

  case Bytecodes::_goto:
  case Bytecodes::_goto_w:
  case Bytecodes::_nop:
  case Bytecodes::_return:
    {
      // do nothing.
      break;
    }
  case Bytecodes::_i2b:
  case Bytecodes::_i2c:
  case Bytecodes::_i2s:
  case Bytecodes::_ineg:
    {
      pop_int();
      push_int();
      break;
    }
  case Bytecodes::_i2d:
    {
      pop_int();
      push_double();
      break;
    }
  case Bytecodes::_i2f:
    {
      pop_int();
      push_float();
      break;
    }
  case Bytecodes::_i2l:
    {
      pop_int();
      push_long();
      break;
    }
  case Bytecodes::_iadd:
  case Bytecodes::_iand:
  case Bytecodes::_idiv:
  case Bytecodes::_imul:
  case Bytecodes::_ior:
  case Bytecodes::_irem:
  case Bytecodes::_ishl:
  case Bytecodes::_ishr:
  case Bytecodes::_isub:
  case Bytecodes::_iushr:
  case Bytecodes::_ixor:
    {
      pop_int();
      pop_int();
      push_int();
      break;
    }
  case Bytecodes::_if_acmpeq:
  case Bytecodes::_if_acmpne:
    {
      pop_object();
      pop_object();
      break;
    }
  case Bytecodes::_if_icmpeq:
  case Bytecodes::_if_icmpge:
  case Bytecodes::_if_icmpgt:
  case Bytecodes::_if_icmple:
  case Bytecodes::_if_icmplt:
  case Bytecodes::_if_icmpne:
    {
      pop_int();
      pop_int();
      break;
    }
  case Bytecodes::_ifeq:
  case Bytecodes::_ifle:
  case Bytecodes::_iflt:
  case Bytecodes::_ifge:
  case Bytecodes::_ifgt:
  case Bytecodes::_ifne:
  case Bytecodes::_ireturn:
  case Bytecodes::_lookupswitch:
  case Bytecodes::_tableswitch:
    {
      pop_int();
      break;
    }
  case Bytecodes::_iinc:
    {
      int lnum = str->get_index();
      check_int(local(lnum));
      store_to_local(lnum);
      break;
    }
  case Bytecodes::_iload:   load_local_int(str->get_index()); break;
  case Bytecodes::_iload_0: load_local_int(0);                      break;
  case Bytecodes::_iload_1: load_local_int(1);                      break;
  case Bytecodes::_iload_2: load_local_int(2);                      break;
  case Bytecodes::_iload_3: load_local_int(3);                      break;

  case Bytecodes::_instanceof:
    {
      // Check for uncommon trap:
      do_checkcast(str);
      pop_object();
      push_int();
      break;
    }
  case Bytecodes::_invokeinterface: do_invoke(str, true);           break;
  case Bytecodes::_invokespecial:   do_invoke(str, true);           break;
  case Bytecodes::_invokestatic:    do_invoke(str, false);          break;
  case Bytecodes::_invokevirtual:   do_invoke(str, true);           break;
  case Bytecodes::_invokedynamic:   do_invoke(str, false);          break;

  case Bytecodes::_istore:   store_local_int(str->get_index());     break;
  case Bytecodes::_istore_0: store_local_int(0);                    break;
  case Bytecodes::_istore_1: store_local_int(1);                    break;
  case Bytecodes::_istore_2: store_local_int(2);                    break;
  case Bytecodes::_istore_3: store_local_int(3);                    break;

  case Bytecodes::_jsr:
  case Bytecodes::_jsr_w: do_jsr(str);                              break;

  case Bytecodes::_l2d:
    {
      pop_long();
      push_double();
      break;
    }
  case Bytecodes::_l2f:
    {
      pop_long();
      push_float();
      break;
    }
  case Bytecodes::_l2i:
    {
      pop_long();
      push_int();
      break;
    }
  case Bytecodes::_ladd:
  case Bytecodes::_land:
  case Bytecodes::_ldiv:
  case Bytecodes::_lmul:
  case Bytecodes::_lor:
  case Bytecodes::_lrem:
  case Bytecodes::_lsub:
  case Bytecodes::_lxor:
    {
      pop_long();
      pop_long();
      push_long();
      break;
    }
  case Bytecodes::_laload:
    {
      pop_int();
      ciTypeArrayKlass* array_klass = pop_typeArray();
      // Put assert here for right type?
      push_long();
      break;
    }
  case Bytecodes::_lastore:
    {
      pop_long();
      pop_int();
      pop_typeArray();
      // assert here?
      break;
    }
  case Bytecodes::_lcmp:
    {
      pop_long();
      pop_long();
      push_int();
      break;
    }
  case Bytecodes::_lconst_0:
  case Bytecodes::_lconst_1:
    {
      push_long();
      break;
    }
  case Bytecodes::_ldc:
  case Bytecodes::_ldc_w:
  case Bytecodes::_ldc2_w:
    {
      do_ldc(str);
      break;
    }

  case Bytecodes::_lload:   load_local_long(str->get_index());      break;
  case Bytecodes::_lload_0: load_local_long(0);                     break;
  case Bytecodes::_lload_1: load_local_long(1);                     break;
  case Bytecodes::_lload_2: load_local_long(2);                     break;
  case Bytecodes::_lload_3: load_local_long(3);                     break;

  case Bytecodes::_lneg:
    {
      pop_long();
      push_long();
      break;
    }
  case Bytecodes::_lreturn:
    {
      pop_long();
      break;
    }
  case Bytecodes::_lshl:
  case Bytecodes::_lshr:
  case Bytecodes::_lushr:
    {
      pop_int();
      pop_long();
      push_long();
      break;
    }
  case Bytecodes::_lstore:   store_local_long(str->get_index());    break;
  case Bytecodes::_lstore_0: store_local_long(0);                   break;
  case Bytecodes::_lstore_1: store_local_long(1);                   break;
  case Bytecodes::_lstore_2: store_local_long(2);                   break;
  case Bytecodes::_lstore_3: store_local_long(3);                   break;

  case Bytecodes::_multianewarray: do_multianewarray(str);          break;

  case Bytecodes::_new:      do_new(str);                           break;

  case Bytecodes::_newarray: do_newarray(str);                      break;

  case Bytecodes::_pop:
    {
      pop();
      break;
    }
  case Bytecodes::_pop2:
    {
      pop();
      pop();
      break;
    }

  case Bytecodes::_putfield:       do_putfield(str);                 break;
  case Bytecodes::_putstatic:      do_putstatic(str);                break;

  case Bytecodes::_ret: do_ret(str);                                 break;

  case Bytecodes::_swap:
    {
      ciType* value1 = pop_value();
      ciType* value2 = pop_value();
      push(value1);
      push(value2);
      break;
    }
  case Bytecodes::_wide:
  default:
    {
      // The iterator should skip this.
      ShouldNotReachHere();
      break;
    }
  }

  if (CITraceTypeFlow) {
    print_on(tty);
  }

  return (_trap_bci != -1);
}

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::StateVector::print_cell_on
void ciTypeFlow::StateVector::print_cell_on(outputStream* st, Cell c) const {
  ciType* type = type_at(c);
  if (type == top_type()) {
    st->print("top");
  } else if (type == bottom_type()) {
    st->print("bottom");
  } else if (type == null_type()) {
    st->print("null");
  } else if (type == long2_type()) {
    st->print("long2");
  } else if (type == double2_type()) {
    st->print("double2");
  } else if (is_int(type)) {
    st->print("int");
  } else if (is_long(type)) {
    st->print("long");
  } else if (is_float(type)) {
    st->print("float");
  } else if (is_double(type)) {
    st->print("double");
  } else if (type->is_return_address()) {
    st->print("address(%d)", type->as_return_address()->bci());
  } else {
    if (type->is_klass()) {
      type->as_klass()->name()->print_symbol_on(st);
    } else {
      st->print("UNEXPECTED TYPE");
      type->print();
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::StateVector::print_on
void ciTypeFlow::StateVector::print_on(outputStream* st) const {
  int num_locals   = _outer->max_locals();
  int num_stack    = stack_size();
  int num_monitors = monitor_count();
  st->print_cr("  State : locals %d, stack %d, monitors %d", num_locals, num_stack, num_monitors);
  if (num_stack >= 0) {
    int i;
    for (i = 0; i < num_locals; i++) {
      st->print("    local %2d : ", i);
      print_cell_on(st, local(i));
      st->cr();
    }
    for (i = 0; i < num_stack; i++) {
      st->print("    stack %2d : ", i);
      print_cell_on(st, stack(i));
      st->cr();
    }
  }
}
#endif


// ------------------------------------------------------------------
// ciTypeFlow::SuccIter::next
//
void ciTypeFlow::SuccIter::next() {
  int succ_ct = _pred->successors()->length();
  int next = _index + 1;
  if (next < succ_ct) {
    _index = next;
    _succ = _pred->successors()->at(next);
    return;
  }
  for (int i = next - succ_ct; i < _pred->exceptions()->length(); i++) {
    // Do not compile any code for unloaded exception types.
    // Following compiler passes are responsible for doing this also.
    ciInstanceKlass* exception_klass = _pred->exc_klasses()->at(i);
    if (exception_klass->is_loaded()) {
      _index = next;
      _succ = _pred->exceptions()->at(i);
      return;
    }
    next++;
  }
  _index = -1;
  _succ = NULL;
}

// ------------------------------------------------------------------
// ciTypeFlow::SuccIter::set_succ
//
void ciTypeFlow::SuccIter::set_succ(Block* succ) {
  int succ_ct = _pred->successors()->length();
  if (_index < succ_ct) {
    _pred->successors()->at_put(_index, succ);
  } else {
    int idx = _index - succ_ct;
    _pred->exceptions()->at_put(idx, succ);
  }
}

// ciTypeFlow::Block
//
// A basic block.

// ------------------------------------------------------------------
// ciTypeFlow::Block::Block
ciTypeFlow::Block::Block(ciTypeFlow* outer,
                         ciBlock *ciblk,
                         ciTypeFlow::JsrSet* jsrs) {
  _ciblock = ciblk;
  _exceptions = NULL;
  _exc_klasses = NULL;
  _successors = NULL;
  _state = new (outer->arena()) StateVector(outer);
  JsrSet* new_jsrs =
    new (outer->arena()) JsrSet(outer->arena(), jsrs->size());
  jsrs->copy_into(new_jsrs);
  _jsrs = new_jsrs;
  _next = NULL;
  _on_work_list = false;
  _backedge_copy = false;
  _exception_entry = false;
  _trap_bci = -1;
  _trap_index = 0;
  df_init();

  if (CITraceTypeFlow) {
    tty->print_cr(">> Created new block");
    print_on(tty);
  }

  assert(this->outer() == outer, "outer link set up");
  assert(!outer->have_block_count(), "must not have mapped blocks yet");
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::df_init
void ciTypeFlow::Block::df_init() {
  _pre_order = -1; assert(!has_pre_order(), "");
  _post_order = -1; assert(!has_post_order(), "");
  _loop = NULL;
  _irreducible_entry = false;
  _rpo_next = NULL;
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::successors
//
// Get the successors for this Block.
GrowableArray<ciTypeFlow::Block*>*
ciTypeFlow::Block::successors(ciBytecodeStream* str,
                              ciTypeFlow::StateVector* state,
                              ciTypeFlow::JsrSet* jsrs) {
  if (_successors == NULL) {
    if (CITraceTypeFlow) {
      tty->print(">> Computing successors for block ");
      print_value_on(tty);
      tty->cr();
    }

    ciTypeFlow* analyzer = outer();
    Arena* arena = analyzer->arena();
    Block* block = NULL;
    bool has_successor = !has_trap() &&
                         (control() != ciBlock::fall_through_bci || limit() < analyzer->code_size());
    if (!has_successor) {
      _successors =
        new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);
      // No successors
    } else if (control() == ciBlock::fall_through_bci) {
      assert(str->cur_bci() == limit(), "bad block end");
      // This block simply falls through to the next.
      _successors =
        new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);

      Block* block = analyzer->block_at(limit(), _jsrs);
      assert(_successors->length() == FALL_THROUGH, "");
      _successors->append(block);
    } else {
      int current_bci = str->cur_bci();
      int next_bci = str->next_bci();
      int branch_bci = -1;
      Block* target = NULL;
      assert(str->next_bci() == limit(), "bad block end");
      // This block is not a simple fall-though.  Interpret
      // the current bytecode to find our successors.
      switch (str->cur_bc()) {
      case Bytecodes::_ifeq:         case Bytecodes::_ifne:
      case Bytecodes::_iflt:         case Bytecodes::_ifge:
      case Bytecodes::_ifgt:         case Bytecodes::_ifle:
      case Bytecodes::_if_icmpeq:    case Bytecodes::_if_icmpne:
      case Bytecodes::_if_icmplt:    case Bytecodes::_if_icmpge:
      case Bytecodes::_if_icmpgt:    case Bytecodes::_if_icmple:
      case Bytecodes::_if_acmpeq:    case Bytecodes::_if_acmpne:
      case Bytecodes::_ifnull:       case Bytecodes::_ifnonnull:
        // Our successors are the branch target and the next bci.
        branch_bci = str->get_dest();
        _successors =
          new (arena) GrowableArray<Block*>(arena, 2, 0, NULL);
        assert(_successors->length() == IF_NOT_TAKEN, "");
        _successors->append(analyzer->block_at(next_bci, jsrs));
        assert(_successors->length() == IF_TAKEN, "");
        _successors->append(analyzer->block_at(branch_bci, jsrs));
        break;

      case Bytecodes::_goto:
        branch_bci = str->get_dest();
        _successors =
          new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);
        assert(_successors->length() == GOTO_TARGET, "");
        _successors->append(analyzer->block_at(branch_bci, jsrs));
        break;

      case Bytecodes::_jsr:
        branch_bci = str->get_dest();
        _successors =
          new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);
        assert(_successors->length() == GOTO_TARGET, "");
        _successors->append(analyzer->block_at(branch_bci, jsrs));
        break;

      case Bytecodes::_goto_w:
      case Bytecodes::_jsr_w:
        _successors =
          new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);
        assert(_successors->length() == GOTO_TARGET, "");
        _successors->append(analyzer->block_at(str->get_far_dest(), jsrs));
        break;

      case Bytecodes::_tableswitch:  {
        Bytecode_tableswitch *tableswitch =
          Bytecode_tableswitch_at(str->cur_bcp());

        int len = tableswitch->length();
        _successors =
          new (arena) GrowableArray<Block*>(arena, len+1, 0, NULL);
        int bci = current_bci + tableswitch->default_offset();
        Block* block = analyzer->block_at(bci, jsrs);
        assert(_successors->length() == SWITCH_DEFAULT, "");
        _successors->append(block);
        while (--len >= 0) {
          int bci = current_bci + tableswitch->dest_offset_at(len);
          block = analyzer->block_at(bci, jsrs);
          assert(_successors->length() >= SWITCH_CASES, "");
          _successors->append_if_missing(block);
        }
        break;
      }

      case Bytecodes::_lookupswitch: {
        Bytecode_lookupswitch *lookupswitch =
          Bytecode_lookupswitch_at(str->cur_bcp());

        int npairs = lookupswitch->number_of_pairs();
        _successors =
          new (arena) GrowableArray<Block*>(arena, npairs+1, 0, NULL);
        int bci = current_bci + lookupswitch->default_offset();
        Block* block = analyzer->block_at(bci, jsrs);
        assert(_successors->length() == SWITCH_DEFAULT, "");
        _successors->append(block);
        while(--npairs >= 0) {
          LookupswitchPair *pair = lookupswitch->pair_at(npairs);
          int bci = current_bci + pair->offset();
          Block* block = analyzer->block_at(bci, jsrs);
          assert(_successors->length() >= SWITCH_CASES, "");
          _successors->append_if_missing(block);
        }
        break;
      }

      case Bytecodes::_athrow:     case Bytecodes::_ireturn:
      case Bytecodes::_lreturn:    case Bytecodes::_freturn:
      case Bytecodes::_dreturn:    case Bytecodes::_areturn:
      case Bytecodes::_return:
        _successors =
          new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);
        // No successors
        break;

      case Bytecodes::_ret: {
        _successors =
          new (arena) GrowableArray<Block*>(arena, 1, 0, NULL);

        Cell local = state->local(str->get_index());
        ciType* return_address = state->type_at(local);
        assert(return_address->is_return_address(), "verify: wrong type");
        int bci = return_address->as_return_address()->bci();
        assert(_successors->length() == GOTO_TARGET, "");
        _successors->append(analyzer->block_at(bci, jsrs));
        break;
      }

      case Bytecodes::_wide:
      default:
        ShouldNotReachHere();
        break;
      }
    }
  }
  return _successors;
}

// ------------------------------------------------------------------
// ciTypeFlow::Block:compute_exceptions
//
// Compute the exceptional successors and types for this Block.
void ciTypeFlow::Block::compute_exceptions() {
  assert(_exceptions == NULL && _exc_klasses == NULL, "repeat");

  if (CITraceTypeFlow) {
    tty->print(">> Computing exceptions for block ");
    print_value_on(tty);
    tty->cr();
  }

  ciTypeFlow* analyzer = outer();
  Arena* arena = analyzer->arena();

  // Any bci in the block will do.
  ciExceptionHandlerStream str(analyzer->method(), start());

  // Allocate our growable arrays.
  int exc_count = str.count();
  _exceptions = new (arena) GrowableArray<Block*>(arena, exc_count, 0, NULL);
  _exc_klasses = new (arena) GrowableArray<ciInstanceKlass*>(arena, exc_count,
                                                             0, NULL);

  for ( ; !str.is_done(); str.next()) {
    ciExceptionHandler* handler = str.handler();
    int bci = handler->handler_bci();
    ciInstanceKlass* klass = NULL;
    if (bci == -1) {
      // There is no catch all.  It is possible to exit the method.
      break;
    }
    if (handler->is_catch_all()) {
      klass = analyzer->env()->Throwable_klass();
    } else {
      klass = handler->catch_klass();
    }
    _exceptions->append(analyzer->block_at(bci, _jsrs));
    _exc_klasses->append(klass);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::set_backedge_copy
// Use this only to make a pre-existing public block into a backedge copy.
void ciTypeFlow::Block::set_backedge_copy(bool z) {
  assert(z || (z == is_backedge_copy()), "cannot make a backedge copy public");
  _backedge_copy = z;
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::is_clonable_exit
//
// At most 2 normal successors, one of which continues looping,
// and all exceptional successors must exit.
bool ciTypeFlow::Block::is_clonable_exit(ciTypeFlow::Loop* lp) {
  int normal_cnt  = 0;
  int in_loop_cnt = 0;
  for (SuccIter iter(this); !iter.done(); iter.next()) {
    Block* succ = iter.succ();
    if (iter.is_normal_ctrl()) {
      if (++normal_cnt > 2) return false;
      if (lp->contains(succ->loop())) {
        if (++in_loop_cnt > 1) return false;
      }
    } else {
      if (lp->contains(succ->loop())) return false;
    }
  }
  return in_loop_cnt == 1;
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::looping_succ
//
ciTypeFlow::Block* ciTypeFlow::Block::looping_succ(ciTypeFlow::Loop* lp) {
  assert(successors()->length() <= 2, "at most 2 normal successors");
  for (SuccIter iter(this); !iter.done(); iter.next()) {
    Block* succ = iter.succ();
    if (lp->contains(succ->loop())) {
      return succ;
    }
  }
  return NULL;
}

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::Block::print_value_on
void ciTypeFlow::Block::print_value_on(outputStream* st) const {
  if (has_pre_order()) st->print("#%-2d ", pre_order());
  if (has_rpo())       st->print("rpo#%-2d ", rpo());
  st->print("[%d - %d)", start(), limit());
  if (is_loop_head()) st->print(" lphd");
  if (is_irreducible_entry()) st->print(" irred");
  if (_jsrs->size() > 0) { st->print("/");  _jsrs->print_on(st); }
  if (is_backedge_copy())  st->print("/backedge_copy");
}

// ------------------------------------------------------------------
// ciTypeFlow::Block::print_on
void ciTypeFlow::Block::print_on(outputStream* st) const {
  if ((Verbose || WizardMode)) {
    outer()->method()->print_codes_on(start(), limit(), st);
  }
  st->print_cr("  ====================================================  ");
  st->print ("  ");
  print_value_on(st);
  st->print(" Stored locals: "); def_locals()->print_on(st, outer()->method()->max_locals()); tty->cr();
  if (loop() && loop()->parent() != NULL) {
    st->print(" loops:");
    Loop* lp = loop();
    do {
      st->print(" %d<-%d", lp->head()->pre_order(),lp->tail()->pre_order());
      if (lp->is_irreducible()) st->print("(ir)");
      lp = lp->parent();
    } while (lp->parent() != NULL);
  }
  st->cr();
  _state->print_on(st);
  if (_successors == NULL) {
    st->print_cr("  No successor information");
  } else {
    int num_successors = _successors->length();
    st->print_cr("  Successors : %d", num_successors);
    for (int i = 0; i < num_successors; i++) {
      Block* successor = _successors->at(i);
      st->print("    ");
      successor->print_value_on(st);
      st->cr();
    }
  }
  if (_exceptions == NULL) {
    st->print_cr("  No exception information");
  } else {
    int num_exceptions = _exceptions->length();
    st->print_cr("  Exceptions : %d", num_exceptions);
    for (int i = 0; i < num_exceptions; i++) {
      Block* exc_succ = _exceptions->at(i);
      ciInstanceKlass* exc_klass = _exc_klasses->at(i);
      st->print("    ");
      exc_succ->print_value_on(st);
      st->print(" -- ");
      exc_klass->name()->print_symbol_on(st);
      st->cr();
    }
  }
  if (has_trap()) {
    st->print_cr("  Traps on %d with trap index %d", trap_bci(), trap_index());
  }
  st->print_cr("  ====================================================  ");
}
#endif

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::LocalSet::print_on
void ciTypeFlow::LocalSet::print_on(outputStream* st, int limit) const {
  st->print("{");
  for (int i = 0; i < max; i++) {
    if (test(i)) st->print(" %d", i);
  }
  if (limit > max) {
    st->print(" %d..%d ", max, limit);
  }
  st->print(" }");
}
#endif

// ciTypeFlow
//
// This is a pass over the bytecodes which computes the following:
//   basic block structure
//   interpreter type-states (a la the verifier)

// ------------------------------------------------------------------
// ciTypeFlow::ciTypeFlow
ciTypeFlow::ciTypeFlow(ciEnv* env, ciMethod* method, int osr_bci) {
  _env = env;
  _method = method;
  _methodBlocks = method->get_method_blocks();
  _max_locals = method->max_locals();
  _max_stack = method->max_stack();
  _code_size = method->code_size();
  _has_irreducible_entry = false;
  _osr_bci = osr_bci;
  _failure_reason = NULL;
  assert(start_bci() >= 0 && start_bci() < code_size() , "correct osr_bci argument");
  _work_list = NULL;

  _ciblock_count = _methodBlocks->num_blocks();
  _idx_to_blocklist = NEW_ARENA_ARRAY(arena(), GrowableArray<Block*>*, _ciblock_count);
  for (int i = 0; i < _ciblock_count; i++) {
    _idx_to_blocklist[i] = NULL;
  }
  _block_map = NULL;  // until all blocks are seen
  _jsr_count = 0;
  _jsr_records = NULL;
}

// ------------------------------------------------------------------
// ciTypeFlow::work_list_next
//
// Get the next basic block from our work list.
ciTypeFlow::Block* ciTypeFlow::work_list_next() {
  assert(!work_list_empty(), "work list must not be empty");
  Block* next_block = _work_list;
  _work_list = next_block->next();
  next_block->set_next(NULL);
  next_block->set_on_work_list(false);
  return next_block;
}

// ------------------------------------------------------------------
// ciTypeFlow::add_to_work_list
//
// Add a basic block to our work list.
// List is sorted by decreasing postorder sort (same as increasing RPO)
void ciTypeFlow::add_to_work_list(ciTypeFlow::Block* block) {
  assert(!block->is_on_work_list(), "must not already be on work list");

  if (CITraceTypeFlow) {
    tty->print(">> Adding block ");
    block->print_value_on(tty);
    tty->print_cr(" to the work list : ");
  }

  block->set_on_work_list(true);

  // decreasing post order sort

  Block* prev = NULL;
  Block* current = _work_list;
  int po = block->post_order();
  while (current != NULL) {
    if (!current->has_post_order() || po > current->post_order())
      break;
    prev = current;
    current = current->next();
  }
  if (prev == NULL) {
    block->set_next(_work_list);
    _work_list = block;
  } else {
    block->set_next(current);
    prev->set_next(block);
  }

  if (CITraceTypeFlow) {
    tty->cr();
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::block_at
//
// Return the block beginning at bci which has a JsrSet compatible
// with jsrs.
ciTypeFlow::Block* ciTypeFlow::block_at(int bci, ciTypeFlow::JsrSet* jsrs, CreateOption option) {
  // First find the right ciBlock.
  if (CITraceTypeFlow) {
    tty->print(">> Requesting block for %d/", bci);
    jsrs->print_on(tty);
    tty->cr();
  }

  ciBlock* ciblk = _methodBlocks->block_containing(bci);
  assert(ciblk->start_bci() == bci, "bad ciBlock boundaries");
  Block* block = get_block_for(ciblk->index(), jsrs, option);

  assert(block == NULL? (option == no_create): block->is_backedge_copy() == (option == create_backedge_copy), "create option consistent with result");

  if (CITraceTypeFlow) {
    if (block != NULL) {
      tty->print(">> Found block ");
      block->print_value_on(tty);
      tty->cr();
    } else {
      tty->print_cr(">> No such block.");
    }
  }

  return block;
}

// ------------------------------------------------------------------
// ciTypeFlow::make_jsr_record
//
// Make a JsrRecord for a given (entry, return) pair, if such a record
// does not already exist.
ciTypeFlow::JsrRecord* ciTypeFlow::make_jsr_record(int entry_address,
                                                   int return_address) {
  if (_jsr_records == NULL) {
    _jsr_records = new (arena()) GrowableArray<JsrRecord*>(arena(),
                                                           _jsr_count,
                                                           0,
                                                           NULL);
  }
  JsrRecord* record = NULL;
  int len = _jsr_records->length();
  for (int i = 0; i < len; i++) {
    JsrRecord* record = _jsr_records->at(i);
    if (record->entry_address() == entry_address &&
        record->return_address() == return_address) {
      return record;
    }
  }

  record = new (arena()) JsrRecord(entry_address, return_address);
  _jsr_records->append(record);
  return record;
}

// ------------------------------------------------------------------
// ciTypeFlow::flow_exceptions
//
// Merge the current state into all exceptional successors at the
// current point in the code.
void ciTypeFlow::flow_exceptions(GrowableArray<ciTypeFlow::Block*>* exceptions,
                                 GrowableArray<ciInstanceKlass*>* exc_klasses,
                                 ciTypeFlow::StateVector* state) {
  int len = exceptions->length();
  assert(exc_klasses->length() == len, "must have same length");
  for (int i = 0; i < len; i++) {
    Block* block = exceptions->at(i);
    ciInstanceKlass* exception_klass = exc_klasses->at(i);

    if (!exception_klass->is_loaded()) {
      // Do not compile any code for unloaded exception types.
      // Following compiler passes are responsible for doing this also.
      continue;
    }

    if (block->meet_exception(exception_klass, state)) {
      // Block was modified and has PO.  Add it to the work list.
      if (block->has_post_order() &&
          !block->is_on_work_list()) {
        add_to_work_list(block);
      }
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::flow_successors
//
// Merge the current state into all successors at the current point
// in the code.
void ciTypeFlow::flow_successors(GrowableArray<ciTypeFlow::Block*>* successors,
                                 ciTypeFlow::StateVector* state) {
  int len = successors->length();
  for (int i = 0; i < len; i++) {
    Block* block = successors->at(i);
    if (block->meet(state)) {
      // Block was modified and has PO.  Add it to the work list.
      if (block->has_post_order() &&
          !block->is_on_work_list()) {
        add_to_work_list(block);
      }
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::can_trap
//
// Tells if a given instruction is able to generate an exception edge.
bool ciTypeFlow::can_trap(ciBytecodeStream& str) {
  // Cf. GenerateOopMap::do_exception_edge.
  if (!Bytecodes::can_trap(str.cur_bc()))  return false;

  switch (str.cur_bc()) {
    case Bytecodes::_ldc:
    case Bytecodes::_ldc_w:
    case Bytecodes::_ldc2_w:
    case Bytecodes::_aload_0:
      // These bytecodes can trap for rewriting.  We need to assume that
      // they do not throw exceptions to make the monitor analysis work.
      return false;

    case Bytecodes::_ireturn:
    case Bytecodes::_lreturn:
    case Bytecodes::_freturn:
    case Bytecodes::_dreturn:
    case Bytecodes::_areturn:
    case Bytecodes::_return:
      // We can assume the monitor stack is empty in this analysis.
      return false;

    case Bytecodes::_monitorexit:
      // We can assume monitors are matched in this analysis.
      return false;
  }

  return true;
}

// ------------------------------------------------------------------
// ciTypeFlow::clone_loop_heads
//
// Clone the loop heads
bool ciTypeFlow::clone_loop_heads(Loop* lp, StateVector* temp_vector, JsrSet* temp_set) {
  bool rslt = false;
  for (PreorderLoops iter(loop_tree_root()); !iter.done(); iter.next()) {
    lp = iter.current();
    Block* head = lp->head();
    if (lp == loop_tree_root() ||
        lp->is_irreducible() ||
        !head->is_clonable_exit(lp))
      continue;

    // check not already cloned
    if (head->backedge_copy_count() != 0)
      continue;

    // check _no_ shared head below us
    Loop* ch;
    for (ch = lp->child(); ch != NULL && ch->head() != head; ch = ch->sibling());
    if (ch != NULL)
      continue;

    // Clone head
    Block* new_head = head->looping_succ(lp);
    Block* clone = clone_loop_head(lp, temp_vector, temp_set);
    // Update lp's info
    clone->set_loop(lp);
    lp->set_head(new_head);
    lp->set_tail(clone);
    // And move original head into outer loop
    head->set_loop(lp->parent());

    rslt = true;
  }
  return rslt;
}

// ------------------------------------------------------------------
// ciTypeFlow::clone_loop_head
//
// Clone lp's head and replace tail's successors with clone.
//
//  |
//  v
// head <-> body
//  |
//  v
// exit
//
// new_head
//
//  |
//  v
// head ----------\
//  |             |
//  |             v
//  |  clone <-> body
//  |    |
//  | /--/
//  | |
//  v v
// exit
//
ciTypeFlow::Block* ciTypeFlow::clone_loop_head(Loop* lp, StateVector* temp_vector, JsrSet* temp_set) {
  Block* head = lp->head();
  Block* tail = lp->tail();
  if (CITraceTypeFlow) {
    tty->print(">> Requesting clone of loop head "); head->print_value_on(tty);
    tty->print("  for predecessor ");                tail->print_value_on(tty);
    tty->cr();
  }
  Block* clone = block_at(head->start(), head->jsrs(), create_backedge_copy);
  assert(clone->backedge_copy_count() == 1, "one backedge copy for all back edges");

  assert(!clone->has_pre_order(), "just created");
  clone->set_next_pre_order();

  // Insert clone after (orig) tail in reverse post order
  clone->set_rpo_next(tail->rpo_next());
  tail->set_rpo_next(clone);

  // tail->head becomes tail->clone
  for (SuccIter iter(tail); !iter.done(); iter.next()) {
    if (iter.succ() == head) {
      iter.set_succ(clone);
    }
  }
  flow_block(tail, temp_vector, temp_set);
  if (head == tail) {
    // For self-loops, clone->head becomes clone->clone
    flow_block(clone, temp_vector, temp_set);
    for (SuccIter iter(clone); !iter.done(); iter.next()) {
      if (iter.succ() == head) {
        iter.set_succ(clone);
        break;
      }
    }
  }
  flow_block(clone, temp_vector, temp_set);

  return clone;
}

// ------------------------------------------------------------------
// ciTypeFlow::flow_block
//
// Interpret the effects of the bytecodes on the incoming state
// vector of a basic block.  Push the changed state to succeeding
// basic blocks.
void ciTypeFlow::flow_block(ciTypeFlow::Block* block,
                            ciTypeFlow::StateVector* state,
                            ciTypeFlow::JsrSet* jsrs) {
  if (CITraceTypeFlow) {
    tty->print("\n>> ANALYZING BLOCK : ");
    tty->cr();
    block->print_on(tty);
  }
  assert(block->has_pre_order(), "pre-order is assigned before 1st flow");

  int start = block->start();
  int limit = block->limit();
  int control = block->control();
  if (control != ciBlock::fall_through_bci) {
    limit = control;
  }

  // Grab the state from the current block.
  block->copy_state_into(state);
  state->def_locals()->clear();

  GrowableArray<Block*>*           exceptions = block->exceptions();
  GrowableArray<ciInstanceKlass*>* exc_klasses = block->exc_klasses();
  bool has_exceptions = exceptions->length() > 0;

  bool exceptions_used = false;

  ciBytecodeStream str(method());
  str.reset_to_bci(start);
  Bytecodes::Code code;
  while ((code = str.next()) != ciBytecodeStream::EOBC() &&
         str.cur_bci() < limit) {
    // Check for exceptional control flow from this point.
    if (has_exceptions && can_trap(str)) {
      flow_exceptions(exceptions, exc_klasses, state);
      exceptions_used = true;
    }
    // Apply the effects of the current bytecode to our state.
    bool res = state->apply_one_bytecode(&str);

    // Watch for bailouts.
    if (failing())  return;

    if (res) {

      // We have encountered a trap.  Record it in this block.
      block->set_trap(state->trap_bci(), state->trap_index());

      if (CITraceTypeFlow) {
        tty->print_cr(">> Found trap");
        block->print_on(tty);
      }

      // Save set of locals defined in this block
      block->def_locals()->add(state->def_locals());

      // Record (no) successors.
      block->successors(&str, state, jsrs);

      assert(!has_exceptions || exceptions_used, "Not removing exceptions");

      // Discontinue interpretation of this Block.
      return;
    }
  }

  GrowableArray<Block*>* successors = NULL;
  if (control != ciBlock::fall_through_bci) {
    // Check for exceptional control flow from this point.
    if (has_exceptions && can_trap(str)) {
      flow_exceptions(exceptions, exc_klasses, state);
      exceptions_used = true;
    }

    // Fix the JsrSet to reflect effect of the bytecode.
    block->copy_jsrs_into(jsrs);
    jsrs->apply_control(this, &str, state);

    // Find successor edges based on old state and new JsrSet.
    successors = block->successors(&str, state, jsrs);

    // Apply the control changes to the state.
    state->apply_one_bytecode(&str);
  } else {
    // Fall through control
    successors = block->successors(&str, NULL, NULL);
  }

  // Save set of locals defined in this block
  block->def_locals()->add(state->def_locals());

  // Remove untaken exception paths
  if (!exceptions_used)
    exceptions->clear();

  // Pass our state to successors.
  flow_successors(successors, state);
}

// ------------------------------------------------------------------
// ciTypeFlow::PostOrderLoops::next
//
// Advance to next loop tree using a postorder, left-to-right traversal.
void ciTypeFlow::PostorderLoops::next() {
  assert(!done(), "must not be done.");
  if (_current->sibling() != NULL) {
    _current = _current->sibling();
    while (_current->child() != NULL) {
      _current = _current->child();
    }
  } else {
    _current = _current->parent();
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::PreOrderLoops::next
//
// Advance to next loop tree using a preorder, left-to-right traversal.
void ciTypeFlow::PreorderLoops::next() {
  assert(!done(), "must not be done.");
  if (_current->child() != NULL) {
    _current = _current->child();
  } else if (_current->sibling() != NULL) {
    _current = _current->sibling();
  } else {
    while (_current != _root && _current->sibling() == NULL) {
      _current = _current->parent();
    }
    if (_current == _root) {
      _current = NULL;
      assert(done(), "must be done.");
    } else {
      assert(_current->sibling() != NULL, "must be more to do");
      _current = _current->sibling();
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::Loop::sorted_merge
//
// Merge the branch lp into this branch, sorting on the loop head
// pre_orders. Returns the leaf of the merged branch.
// Child and sibling pointers will be setup later.
// Sort is (looking from leaf towards the root)
//  descending on primary key: loop head's pre_order, and
//  ascending  on secondary key: loop tail's pre_order.
ciTypeFlow::Loop* ciTypeFlow::Loop::sorted_merge(Loop* lp) {
  Loop* leaf = this;
  Loop* prev = NULL;
  Loop* current = leaf;
  while (lp != NULL) {
    int lp_pre_order = lp->head()->pre_order();
    // Find insertion point for "lp"
    while (current != NULL) {
      if (current == lp)
        return leaf; // Already in list
      if (current->head()->pre_order() < lp_pre_order)
        break;
      if (current->head()->pre_order() == lp_pre_order &&
          current->tail()->pre_order() > lp->tail()->pre_order()) {
        break;
      }
      prev = current;
      current = current->parent();
    }
    Loop* next_lp = lp->parent(); // Save future list of items to insert
    // Insert lp before current
    lp->set_parent(current);
    if (prev != NULL) {
      prev->set_parent(lp);
    } else {
      leaf = lp;
    }
    prev = lp;     // Inserted item is new prev[ious]
    lp = next_lp;  // Next item to insert
  }
  return leaf;
}

// ------------------------------------------------------------------
// ciTypeFlow::build_loop_tree
//
// Incrementally build loop tree.
void ciTypeFlow::build_loop_tree(Block* blk) {
  assert(!blk->is_post_visited(), "precondition");
  Loop* innermost = NULL; // merge of loop tree branches over all successors

  for (SuccIter iter(blk); !iter.done(); iter.next()) {
    Loop*  lp   = NULL;
    Block* succ = iter.succ();
    if (!succ->is_post_visited()) {
      // Found backedge since predecessor post visited, but successor is not
      assert(succ->pre_order() <= blk->pre_order(), "should be backedge");

      // Create a LoopNode to mark this loop.
      lp = new (arena()) Loop(succ, blk);
      if (succ->loop() == NULL)
        succ->set_loop(lp);
      // succ->loop will be updated to innermost loop on a later call, when blk==succ

    } else {  // Nested loop
      lp = succ->loop();

      // If succ is loop head, find outer loop.
      while (lp != NULL && lp->head() == succ) {
        lp = lp->parent();
      }
      if (lp == NULL) {
        // Infinite loop, it's parent is the root
        lp = loop_tree_root();
      }
    }

    // Check for irreducible loop.
    // Successor has already been visited. If the successor's loop head
    // has already been post-visited, then this is another entry into the loop.
    while (lp->head()->is_post_visited() && lp != loop_tree_root()) {
      _has_irreducible_entry = true;
      lp->set_irreducible(succ);
      if (!succ->is_on_work_list()) {
        // Assume irreducible entries need more data flow
        add_to_work_list(succ);
      }
      Loop* plp = lp->parent();
      if (plp == NULL) {
        // This only happens for some irreducible cases.  The parent
        // will be updated during a later pass.
        break;
      }
      lp = plp;
    }

    // Merge loop tree branch for all successors.
    innermost = innermost == NULL ? lp : innermost->sorted_merge(lp);

  } // end loop

  if (innermost == NULL) {
    assert(blk->successors()->length() == 0, "CFG exit");
    blk->set_loop(loop_tree_root());
  } else if (innermost->head() == blk) {
    // If loop header, complete the tree pointers
    if (blk->loop() != innermost) {
#if ASSERT
      assert(blk->loop()->head() == innermost->head(), "same head");
      Loop* dl;
      for (dl = innermost; dl != NULL && dl != blk->loop(); dl = dl->parent());
      assert(dl == blk->loop(), "blk->loop() already in innermost list");
#endif
      blk->set_loop(innermost);
    }
    innermost->def_locals()->add(blk->def_locals());
    Loop* l = innermost;
    Loop* p = l->parent();
    while (p && l->head() == blk) {
      l->set_sibling(p->child());  // Put self on parents 'next child'
      p->set_child(l);             // Make self the first child of parent
      p->def_locals()->add(l->def_locals());
      l = p;                       // Walk up the parent chain
      p = l->parent();
    }
  } else {
    blk->set_loop(innermost);
    innermost->def_locals()->add(blk->def_locals());
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::Loop::contains
//
// Returns true if lp is nested loop.
bool ciTypeFlow::Loop::contains(ciTypeFlow::Loop* lp) const {
  assert(lp != NULL, "");
  if (this == lp || head() == lp->head()) return true;
  int depth1 = depth();
  int depth2 = lp->depth();
  if (depth1 > depth2)
    return false;
  while (depth1 < depth2) {
    depth2--;
    lp = lp->parent();
  }
  return this == lp;
}

// ------------------------------------------------------------------
// ciTypeFlow::Loop::depth
//
// Loop depth
int ciTypeFlow::Loop::depth() const {
  int dp = 0;
  for (Loop* lp = this->parent(); lp != NULL; lp = lp->parent())
    dp++;
  return dp;
}

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::Loop::print
void ciTypeFlow::Loop::print(outputStream* st, int indent) const {
  for (int i = 0; i < indent; i++) st->print(" ");
  st->print("%d<-%d %s",
            is_root() ? 0 : this->head()->pre_order(),
            is_root() ? 0 : this->tail()->pre_order(),
            is_irreducible()?" irr":"");
  st->print(" defs: ");
  def_locals()->print_on(st, _head->outer()->method()->max_locals());
  st->cr();
  for (Loop* ch = child(); ch != NULL; ch = ch->sibling())
    ch->print(st, indent+2);
}
#endif

// ------------------------------------------------------------------
// ciTypeFlow::df_flow_types
//
// Perform the depth first type flow analysis. Helper for flow_types.
void ciTypeFlow::df_flow_types(Block* start,
                               bool do_flow,
                               StateVector* temp_vector,
                               JsrSet* temp_set) {
  int dft_len = 100;
  GrowableArray<Block*> stk(arena(), dft_len, 0, NULL);

  ciBlock* dummy = _methodBlocks->make_dummy_block();
  JsrSet* root_set = new JsrSet(NULL, 0);
  Block* root_head = new (arena()) Block(this, dummy, root_set);
  Block* root_tail = new (arena()) Block(this, dummy, root_set);
  root_head->set_pre_order(0);
  root_head->set_post_order(0);
  root_tail->set_pre_order(max_jint);
  root_tail->set_post_order(max_jint);
  set_loop_tree_root(new (arena()) Loop(root_head, root_tail));

  stk.push(start);

  _next_pre_order = 0;  // initialize pre_order counter
  _rpo_list = NULL;
  int next_po = 0;      // initialize post_order counter

  // Compute RPO and the control flow graph
  int size;
  while ((size = stk.length()) > 0) {
    Block* blk = stk.top(); // Leave node on stack
    if (!blk->is_visited()) {
      // forward arc in graph
      assert (!blk->has_pre_order(), "");
      blk->set_next_pre_order();

      if (_next_pre_order >= MaxNodeLimit / 2) {
        // Too many basic blocks.  Bail out.
        // This can happen when try/finally constructs are nested to depth N,
        // and there is O(2**N) cloning of jsr bodies.  See bug 4697245!
        // "MaxNodeLimit / 2" is used because probably the parser will
        // generate at least twice that many nodes and bail out.
        record_failure("too many basic blocks");
        return;
      }
      if (do_flow) {
        flow_block(blk, temp_vector, temp_set);
        if (failing()) return; // Watch for bailouts.
      }
    } else if (!blk->is_post_visited()) {
      // cross or back arc
      for (SuccIter iter(blk); !iter.done(); iter.next()) {
        Block* succ = iter.succ();
        if (!succ->is_visited()) {
          stk.push(succ);
        }
      }
      if (stk.length() == size) {
        // There were no additional children, post visit node now
        stk.pop(); // Remove node from stack

        build_loop_tree(blk);
        blk->set_post_order(next_po++);   // Assign post order
        prepend_to_rpo_list(blk);
        assert(blk->is_post_visited(), "");

        if (blk->is_loop_head() && !blk->is_on_work_list()) {
          // Assume loop heads need more data flow
          add_to_work_list(blk);
        }
      }
    } else {
      stk.pop(); // Remove post-visited node from stack
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::flow_types
//
// Perform the type flow analysis, creating and cloning Blocks as
// necessary.
void ciTypeFlow::flow_types() {
  ResourceMark rm;
  StateVector* temp_vector = new StateVector(this);
  JsrSet* temp_set = new JsrSet(NULL, 16);

  // Create the method entry block.
  Block* start = block_at(start_bci(), temp_set);

  // Load the initial state into it.
  const StateVector* start_state = get_start_state();
  if (failing())  return;
  start->meet(start_state);

  // Depth first visit
  df_flow_types(start, true /*do flow*/, temp_vector, temp_set);

  if (failing())  return;
  assert(_rpo_list == start, "must be start");

  // Any loops found?
  if (loop_tree_root()->child() != NULL &&
      env()->comp_level() >= CompLevel_full_optimization) {
      // Loop optimizations are not performed on Tier1 compiles.

    bool changed = clone_loop_heads(loop_tree_root(), temp_vector, temp_set);

    // If some loop heads were cloned, recompute postorder and loop tree
    if (changed) {
      loop_tree_root()->set_child(NULL);
      for (Block* blk = _rpo_list; blk != NULL;) {
        Block* next = blk->rpo_next();
        blk->df_init();
        blk = next;
      }
      df_flow_types(start, false /*no flow*/, temp_vector, temp_set);
    }
  }

  if (CITraceTypeFlow) {
    tty->print_cr("\nLoop tree");
    loop_tree_root()->print();
  }

  // Continue flow analysis until fixed point reached

  debug_only(int max_block = _next_pre_order;)

  while (!work_list_empty()) {
    Block* blk = work_list_next();
    assert (blk->has_post_order(), "post order assigned above");

    flow_block(blk, temp_vector, temp_set);

    assert (max_block == _next_pre_order, "no new blocks");
    assert (!failing(), "no more bailouts");
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::map_blocks
//
// Create the block map, which indexes blocks in reverse post-order.
void ciTypeFlow::map_blocks() {
  assert(_block_map == NULL, "single initialization");
  int block_ct = _next_pre_order;
  _block_map = NEW_ARENA_ARRAY(arena(), Block*, block_ct);
  assert(block_ct == block_count(), "");

  Block* blk = _rpo_list;
  for (int m = 0; m < block_ct; m++) {
    int rpo = blk->rpo();
    assert(rpo == m, "should be sequential");
    _block_map[rpo] = blk;
    blk = blk->rpo_next();
  }
  assert(blk == NULL, "should be done");

  for (int j = 0; j < block_ct; j++) {
    assert(_block_map[j] != NULL, "must not drop any blocks");
    Block* block = _block_map[j];
    // Remove dead blocks from successor lists:
    for (int e = 0; e <= 1; e++) {
      GrowableArray<Block*>* l = e? block->exceptions(): block->successors();
      for (int k = 0; k < l->length(); k++) {
        Block* s = l->at(k);
        if (!s->has_post_order()) {
          if (CITraceTypeFlow) {
            tty->print("Removing dead %s successor of #%d: ", (e? "exceptional":  "normal"), block->pre_order());
            s->print_value_on(tty);
            tty->cr();
          }
          l->remove(s);
          --k;
        }
      }
    }
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::get_block_for
//
// Find a block with this ciBlock which has a compatible JsrSet.
// If no such block exists, create it, unless the option is no_create.
// If the option is create_backedge_copy, always create a fresh backedge copy.
ciTypeFlow::Block* ciTypeFlow::get_block_for(int ciBlockIndex, ciTypeFlow::JsrSet* jsrs, CreateOption option) {
  Arena* a = arena();
  GrowableArray<Block*>* blocks = _idx_to_blocklist[ciBlockIndex];
  if (blocks == NULL) {
    // Query only?
    if (option == no_create)  return NULL;

    // Allocate the growable array.
    blocks = new (a) GrowableArray<Block*>(a, 4, 0, NULL);
    _idx_to_blocklist[ciBlockIndex] = blocks;
  }

  if (option != create_backedge_copy) {
    int len = blocks->length();
    for (int i = 0; i < len; i++) {
      Block* block = blocks->at(i);
      if (!block->is_backedge_copy() && block->is_compatible_with(jsrs)) {
        return block;
      }
    }
  }

  // Query only?
  if (option == no_create)  return NULL;

  // We did not find a compatible block.  Create one.
  Block* new_block = new (a) Block(this, _methodBlocks->block(ciBlockIndex), jsrs);
  if (option == create_backedge_copy)  new_block->set_backedge_copy(true);
  blocks->append(new_block);
  return new_block;
}

// ------------------------------------------------------------------
// ciTypeFlow::backedge_copy_count
//
int ciTypeFlow::backedge_copy_count(int ciBlockIndex, ciTypeFlow::JsrSet* jsrs) const {
  GrowableArray<Block*>* blocks = _idx_to_blocklist[ciBlockIndex];

  if (blocks == NULL) {
    return 0;
  }

  int count = 0;
  int len = blocks->length();
  for (int i = 0; i < len; i++) {
    Block* block = blocks->at(i);
    if (block->is_backedge_copy() && block->is_compatible_with(jsrs)) {
      count++;
    }
  }

  return count;
}

// ------------------------------------------------------------------
// ciTypeFlow::do_flow
//
// Perform type inference flow analysis.
void ciTypeFlow::do_flow() {
  if (CITraceTypeFlow) {
    tty->print_cr("\nPerforming flow analysis on method");
    method()->print();
    if (is_osr_flow())  tty->print(" at OSR bci %d", start_bci());
    tty->cr();
    method()->print_codes();
  }
  if (CITraceTypeFlow) {
    tty->print_cr("Initial CI Blocks");
    print_on(tty);
  }
  flow_types();
  // Watch for bailouts.
  if (failing()) {
    return;
  }

  map_blocks();

  if (CIPrintTypeFlow || CITraceTypeFlow) {
    rpo_print_on(tty);
  }
}

// ------------------------------------------------------------------
// ciTypeFlow::record_failure()
// The ciTypeFlow object keeps track of failure reasons separately from the ciEnv.
// This is required because there is not a 1-1 relation between the ciEnv and
// the TypeFlow passes within a compilation task.  For example, if the compiler
// is considering inlining a method, it will request a TypeFlow.  If that fails,
// the compilation as a whole may continue without the inlining.  Some TypeFlow
// requests are not optional; if they fail the requestor is responsible for
// copying the failure reason up to the ciEnv.  (See Parse::Parse.)
void ciTypeFlow::record_failure(const char* reason) {
  if (env()->log() != NULL) {
    env()->log()->elem("failure reason='%s' phase='typeflow'", reason);
  }
  if (_failure_reason == NULL) {
    // Record the first failure reason.
    _failure_reason = reason;
  }
}

#ifndef PRODUCT
// ------------------------------------------------------------------
// ciTypeFlow::print_on
void ciTypeFlow::print_on(outputStream* st) const {
  // Walk through CI blocks
  st->print_cr("********************************************************");
  st->print   ("TypeFlow for ");
  method()->name()->print_symbol_on(st);
  int limit_bci = code_size();
  st->print_cr("  %d bytes", limit_bci);
  ciMethodBlocks  *mblks = _methodBlocks;
  ciBlock* current = NULL;
  for (int bci = 0; bci < limit_bci; bci++) {
    ciBlock* blk = mblks->block_containing(bci);
    if (blk != NULL && blk != current) {
      current = blk;
      current->print_on(st);

      GrowableArray<Block*>* blocks = _idx_to_blocklist[blk->index()];
      int num_blocks = (blocks == NULL) ? 0 : blocks->length();

      if (num_blocks == 0) {
        st->print_cr("  No Blocks");
      } else {
        for (int i = 0; i < num_blocks; i++) {
          Block* block = blocks->at(i);
          block->print_on(st);
        }
      }
      st->print_cr("--------------------------------------------------------");
      st->cr();
    }
  }
  st->print_cr("********************************************************");
  st->cr();
}

void ciTypeFlow::rpo_print_on(outputStream* st) const {
  st->print_cr("********************************************************");
  st->print   ("TypeFlow for ");
  method()->name()->print_symbol_on(st);
  int limit_bci = code_size();
  st->print_cr("  %d bytes", limit_bci);
  for (Block* blk = _rpo_list; blk != NULL; blk = blk->rpo_next()) {
    blk->print_on(st);
    st->print_cr("--------------------------------------------------------");
    st->cr();
  }
  st->print_cr("********************************************************");
  st->cr();
}
#endif