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 /*

  * Copyright (c) 1999, 2010, 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 "c1/c1_IR.hpp"

 #include "c1/c1_Instruction.hpp"

 #include "c1/c1_InstructionPrinter.hpp"

 #include "c1/c1_ValueStack.hpp"

 #include "ci/ciObjArrayKlass.hpp"

 #include "ci/ciTypeArrayKlass.hpp"

 // Implementation of Instruction

 Instruction::Condition Instruction::mirror(Condition cond) {

   switch (cond) {

     case eql: return eql;

     case neq: return neq;

     case lss: return gtr;

     case leq: return geq;

     case gtr: return lss;

     case geq: return leq;

   }

   ShouldNotReachHere();

   return eql;

 }

 Instruction::Condition Instruction::negate(Condition cond) {

   switch (cond) {

     case eql: return neq;

     case neq: return eql;

     case lss: return geq;

     case leq: return gtr;

     case gtr: return leq;

     case geq: return lss;

   }

   ShouldNotReachHere();

   return eql;

 }

 void Instruction::update_exception_state(ValueStack* state) {

   if (state != NULL && (state->kind() == ValueStack::EmptyExceptionState || state->kind() == ValueStack::ExceptionState)) {

     assert(state->kind() == ValueStack::EmptyExceptionState || Compilation::current()->env()->jvmti_can_access_local_variables(), "unexpected state kind");

     _exception_state = state;

   } else {

     _exception_state = NULL;

   }

 }

 Instruction* Instruction::prev(BlockBegin* block) {

   Instruction* p = NULL;

   Instruction* q = block;

   while (q != this) {

     assert(q != NULL, "this is not in the block's instruction list");

     p = q; q = q->next();

   }

   return p;

 }

 void Instruction::state_values_do(ValueVisitor* f) {

   if (state_before() != NULL) {

     state_before()->values_do(f);

   }

   if (exception_state() != NULL){

     exception_state()->values_do(f);

   }

 }

 #ifndef PRODUCT

 void Instruction::check_state(ValueStack* state) {

   if (state != NULL) {

     state->verify();

   }

 }

 void Instruction::print() {

   InstructionPrinter ip;

   print(ip);

 }

 void Instruction::print_line() {

   InstructionPrinter ip;

   ip.print_line(this);

 }

 void Instruction::print(InstructionPrinter& ip) {

   ip.print_head();

   ip.print_line(this);

   tty->cr();

 }

 #endif // PRODUCT

 // perform constant and interval tests on index value

 bool AccessIndexed::compute_needs_range_check() {

   Constant* clength = length()->as_Constant();

   Constant* cindex = index()->as_Constant();

   if (clength && cindex) {

     IntConstant* l = clength->type()->as_IntConstant();

     IntConstant* i = cindex->type()->as_IntConstant();

     if (l && i && i->value() < l->value() && i->value() >= 0) {

       return false;

     }

   }

   return true;

 }

 ciType* Local::exact_type() const {

   ciType* type = declared_type();

   // for primitive arrays, the declared type is the exact type

   if (type->is_type_array_klass()) {

     return type;

   } else if (type->is_instance_klass()) {

     ciInstanceKlass* ik = (ciInstanceKlass*)type;

     if (ik->is_loaded() && ik->is_final() && !ik->is_interface()) {

       return type;

     }

   } else if (type->is_obj_array_klass()) {

     ciObjArrayKlass* oak = (ciObjArrayKlass*)type;

     ciType* base = oak->base_element_type();

     if (base->is_instance_klass()) {

       ciInstanceKlass* ik = base->as_instance_klass();

       if (ik->is_loaded() && ik->is_final()) {

         return type;

       }

     } else if (base->is_primitive_type()) {

       return type;

     }

   }

   return NULL;

 }

 ciType* LoadIndexed::exact_type() const {

   ciType* array_type = array()->exact_type();

   if (array_type == NULL) {

     return NULL;

   }

   assert(array_type->is_array_klass(), "what else?");

   ciArrayKlass* ak = (ciArrayKlass*)array_type;

   if (ak->element_type()->is_instance_klass()) {

     ciInstanceKlass* ik = (ciInstanceKlass*)ak->element_type();

     if (ik->is_loaded() && ik->is_final()) {

       return ik;

     }

   }

   return NULL;

 }

 ciType* LoadIndexed::declared_type() const {

   ciType* array_type = array()->declared_type();

   if (array_type == NULL) {

     return NULL;

   }

   assert(array_type->is_array_klass(), "what else?");

   ciArrayKlass* ak = (ciArrayKlass*)array_type;

   return ak->element_type();

 }

 ciType* LoadField::declared_type() const {

   return field()->type();

 }

 ciType* LoadField::exact_type() const {

   ciType* type = declared_type();

   // for primitive arrays, the declared type is the exact type

   if (type->is_type_array_klass()) {

     return type;

   }

   if (type->is_instance_klass()) {

     ciInstanceKlass* ik = (ciInstanceKlass*)type;

     if (ik->is_loaded() && ik->is_final()) {

       return type;

     }

   }

   return NULL;

 }

 ciType* NewTypeArray::exact_type() const {

   return ciTypeArrayKlass::make(elt_type());

 }

 ciType* NewObjectArray::exact_type() const {

   return ciObjArrayKlass::make(klass());

 }

 ciType* NewArray::declared_type() const {

   return exact_type();

 }

 ciType* NewInstance::exact_type() const {

   return klass();

 }

 ciType* NewInstance::declared_type() const {

   return exact_type();

 }

 ciType* CheckCast::declared_type() const {

   return klass();

 }

 ciType* CheckCast::exact_type() const {

   if (klass()->is_instance_klass()) {

     ciInstanceKlass* ik = (ciInstanceKlass*)klass();

     if (ik->is_loaded() && ik->is_final()) {

       return ik;

     }

   }

   return NULL;

 }

 // Implementation of ArithmeticOp

 bool ArithmeticOp::is_commutative() const {

   switch (op()) {

     case Bytecodes::_iadd: // fall through

     case Bytecodes::_ladd: // fall through

     case Bytecodes::_fadd: // fall through

     case Bytecodes::_dadd: // fall through

     case Bytecodes::_imul: // fall through

     case Bytecodes::_lmul: // fall through

     case Bytecodes::_fmul: // fall through

     case Bytecodes::_dmul: return true;

   }

   return false;

 }

 bool ArithmeticOp::can_trap() const {

   switch (op()) {

     case Bytecodes::_idiv: // fall through

     case Bytecodes::_ldiv: // fall through

     case Bytecodes::_irem: // fall through

     case Bytecodes::_lrem: return true;

   }

   return false;

 }

 // Implementation of LogicOp

 bool LogicOp::is_commutative() const {

 #ifdef ASSERT

   switch (op()) {

     case Bytecodes::_iand: // fall through

     case Bytecodes::_land: // fall through

     case Bytecodes::_ior : // fall through

     case Bytecodes::_lor : // fall through

     case Bytecodes::_ixor: // fall through

     case Bytecodes::_lxor: break;

     default              : ShouldNotReachHere();

   }

 #endif

   // all LogicOps are commutative

   return true;

 }

 // Implementation of IfOp

 bool IfOp::is_commutative() const {

   return cond() == eql || cond() == neq;

 }

 // Implementation of StateSplit

 void StateSplit::substitute(BlockList& list, BlockBegin* old_block, BlockBegin* new_block) {

   NOT_PRODUCT(bool assigned = false;)

   for (int i = 0; i < list.length(); i++) {

     BlockBegin** b = list.adr_at(i);

     if (*b == old_block) {

       *b = new_block;

       NOT_PRODUCT(assigned = true;)

     }

   }

   assert(assigned == true, "should have assigned at least once");

 }

 IRScope* StateSplit::scope() const {

   return _state->scope();

 }

 void StateSplit::state_values_do(ValueVisitor* f) {

   Instruction::state_values_do(f);

   if (state() != NULL) state()->values_do(f);

 }

 void BlockBegin::state_values_do(ValueVisitor* f) {

   StateSplit::state_values_do(f);

   if (is_set(BlockBegin::exception_entry_flag)) {

     for (int i = 0; i < number_of_exception_states(); i++) {

       exception_state_at(i)->values_do(f);

     }

   }

 }

 // Implementation of Invoke

 Invoke::Invoke(Bytecodes::Code code, ValueType* result_type, Value recv, Values* args,

                int vtable_index, ciMethod* target, ValueStack* state_before)

   : StateSplit(result_type, state_before)

   , _code(code)

   , _recv(recv)

   , _args(args)

   , _vtable_index(vtable_index)

   , _target(target)

 {

   set_flag(TargetIsLoadedFlag,   target->is_loaded());

   set_flag(TargetIsFinalFlag,    target_is_loaded() && target->is_final_method());

   set_flag(TargetIsStrictfpFlag, target_is_loaded() && target->is_strict());

   assert(args != NULL, "args must exist");

 #ifdef ASSERT

   AssertValues assert_value;

   values_do(&assert_value);

 #endif

   // provide an initial guess of signature size.

   _signature = new BasicTypeList(number_of_arguments() + (has_receiver() ? 1 : 0));

   if (has_receiver()) {

     _signature->append(as_BasicType(receiver()->type()));

   } else if (is_invokedynamic()) {

     // Add the synthetic MethodHandle argument to the signature.

     _signature->append(T_OBJECT);

   }

   for (int i = 0; i < number_of_arguments(); i++) {

     ValueType* t = argument_at(i)->type();

     BasicType bt = as_BasicType(t);

     _signature->append(bt);

   }

 }

 void Invoke::state_values_do(ValueVisitor* f) {

   StateSplit::state_values_do(f);

   if (state_before() != NULL) state_before()->values_do(f);

   if (state()        != NULL) state()->values_do(f);

 }

 ciType* Invoke::declared_type() const {

   ciType *t = _target->signature()->return_type();

   assert(t->basic_type() != T_VOID, "need return value of void method?");

   return t;

 }

 // Implementation of Contant

 intx Constant::hash() const {

   if (state_before() == NULL) {

     switch (type()->tag()) {

     case intTag:

       return HASH2(name(), type()->as_IntConstant()->value());

     case longTag:

       {

         jlong temp = type()->as_LongConstant()->value();

         return HASH3(name(), high(temp), low(temp));

       }

     case floatTag:

       return HASH2(name(), jint_cast(type()->as_FloatConstant()->value()));

     case doubleTag:

       {

         jlong temp = jlong_cast(type()->as_DoubleConstant()->value());

         return HASH3(name(), high(temp), low(temp));

       }

     case objectTag:

       assert(type()->as_ObjectType()->is_loaded(), "can't handle unloaded values");

       return HASH2(name(), type()->as_ObjectType()->constant_value());

     }

   }

   return 0;

 }

 bool Constant::is_equal(Value v) const {

   if (v->as_Constant() == NULL) return false;

   switch (type()->tag()) {

     case intTag:

       {

         IntConstant* t1 =    type()->as_IntConstant();

         IntConstant* t2 = v->type()->as_IntConstant();

         return (t1 != NULL && t2 != NULL &&

                 t1->value() == t2->value());

       }

     case longTag:

       {

         LongConstant* t1 =    type()->as_LongConstant();

         LongConstant* t2 = v->type()->as_LongConstant();

         return (t1 != NULL && t2 != NULL &&

                 t1->value() == t2->value());

       }

     case floatTag:

       {

         FloatConstant* t1 =    type()->as_FloatConstant();

         FloatConstant* t2 = v->type()->as_FloatConstant();

         return (t1 != NULL && t2 != NULL &&

                 jint_cast(t1->value()) == jint_cast(t2->value()));

       }

     case doubleTag:

       {

         DoubleConstant* t1 =    type()->as_DoubleConstant();

         DoubleConstant* t2 = v->type()->as_DoubleConstant();

         return (t1 != NULL && t2 != NULL &&

                 jlong_cast(t1->value()) == jlong_cast(t2->value()));

       }

     case objectTag:

       {

         ObjectType* t1 =    type()->as_ObjectType();

         ObjectType* t2 = v->type()->as_ObjectType();

         return (t1 != NULL && t2 != NULL &&

                 t1->is_loaded() && t2->is_loaded() &&

                 t1->constant_value() == t2->constant_value());

       }

   }

   return false;

 }

 Constant::CompareResult Constant::compare(Instruction::Condition cond, Value right) const {

   Constant* rc = right->as_Constant();

   // other is not a constant

   if (rc == NULL) return not_comparable;

   ValueType* lt = type();

   ValueType* rt = rc->type();

   // different types

   if (lt->base() != rt->base()) return not_comparable;

   switch (lt->tag()) {

   case intTag: {

     int x = lt->as_IntConstant()->value();

     int y = rt->as_IntConstant()->value();

     switch (cond) {

     case If::eql: return x == y ? cond_true : cond_false;

     case If::neq: return x != y ? cond_true : cond_false;

     case If::lss: return x <  y ? cond_true : cond_false;

     case If::leq: return x <= y ? cond_true : cond_false;

     case If::gtr: return x >  y ? cond_true : cond_false;

     case If::geq: return x >= y ? cond_true : cond_false;

     }

     break;

   }

   case longTag: {

     jlong x = lt->as_LongConstant()->value();

     jlong y = rt->as_LongConstant()->value();

     switch (cond) {

     case If::eql: return x == y ? cond_true : cond_false;

     case If::neq: return x != y ? cond_true : cond_false;

     case If::lss: return x <  y ? cond_true : cond_false;

     case If::leq: return x <= y ? cond_true : cond_false;

     case If::gtr: return x >  y ? cond_true : cond_false;

     case If::geq: return x >= y ? cond_true : cond_false;

     }

     break;

   }

   case objectTag: {

     ciObject* xvalue = lt->as_ObjectType()->constant_value();

     ciObject* yvalue = rt->as_ObjectType()->constant_value();

     assert(xvalue != NULL && yvalue != NULL, "not constants");

     if (xvalue->is_loaded() && yvalue->is_loaded()) {

       switch (cond) {

       case If::eql: return xvalue == yvalue ? cond_true : cond_false;

       case If::neq: return xvalue != yvalue ? cond_true : cond_false;

       }

     }

     break;

   }

   }

   return not_comparable;

 }

 // Implementation of BlockBegin

 void BlockBegin::set_end(BlockEnd* end) {

   assert(end != NULL, "should not reset block end to NULL");

   if (end == _end) {

     return;

   }

   clear_end();

   // Set the new end

   _end = end;

   _successors.clear();

   // Now reset successors list based on BlockEnd

   for (int i = 0; i < end->number_of_sux(); i++) {

     BlockBegin* sux = end->sux_at(i);

     _successors.append(sux);

     sux->_predecessors.append(this);

   }

   _end->set_begin(this);

 }

 void BlockBegin::clear_end() {

   // Must make the predecessors/successors match up with the

   // BlockEnd's notion.

   if (_end != NULL) {

     // disconnect from the old end

     _end->set_begin(NULL);

     // disconnect this block from it's current successors

     for (int i = 0; i < _successors.length(); i++) {

       _successors.at(i)->remove_predecessor(this);

     }

     _end = NULL;

   }

 }

 void BlockBegin::disconnect_edge(BlockBegin* from, BlockBegin* to) {

   // disconnect any edges between from and to

 #ifndef PRODUCT

   if (PrintIR && Verbose) {

     tty->print_cr("Disconnected edge B%d -> B%d", from->block_id(), to->block_id());

   }

 #endif

   for (int s = 0; s < from->number_of_sux();) {

     BlockBegin* sux = from->sux_at(s);

     if (sux == to) {

       int index = sux->_predecessors.index_of(from);

       if (index >= 0) {

         sux->_predecessors.remove_at(index);

       }

       from->_successors.remove_at(s);

     } else {

       s++;

     }

   }

 }

 void BlockBegin::disconnect_from_graph() {

   // disconnect this block from all other blocks

   for (int p = 0; p < number_of_preds(); p++) {

     pred_at(p)->remove_successor(this);

   }

   for (int s = 0; s < number_of_sux(); s++) {

     sux_at(s)->remove_predecessor(this);

   }

 }

 void BlockBegin::substitute_sux(BlockBegin* old_sux, BlockBegin* new_sux) {

   // modify predecessors before substituting successors

   for (int i = 0; i < number_of_sux(); i++) {

     if (sux_at(i) == old_sux) {

       // remove old predecessor before adding new predecessor

       // otherwise there is a dead predecessor in the list

       new_sux->remove_predecessor(old_sux);

       new_sux->add_predecessor(this);

     }

   }

   old_sux->remove_predecessor(this);

   end()->substitute_sux(old_sux, new_sux);

 }

 // In general it is not possible to calculate a value for the field "depth_first_number"

 // of the inserted block, without recomputing the values of the other blocks

 // in the CFG. Therefore the value of "depth_first_number" in BlockBegin becomes meaningless.

 BlockBegin* BlockBegin::insert_block_between(BlockBegin* sux) {

   BlockBegin* new_sux = new BlockBegin(end()->state()->bci());

   // mark this block (special treatment when block order is computed)

   new_sux->set(critical_edge_split_flag);

   // This goto is not a safepoint.

   Goto* e = new Goto(sux, false);

   new_sux->set_next(e, end()->state()->bci());

   new_sux->set_end(e);

   // setup states

   ValueStack* s = end()->state();

   new_sux->set_state(s->copy());

   e->set_state(s->copy());

   assert(new_sux->state()->locals_size() == s->locals_size(), "local size mismatch!");

   assert(new_sux->state()->stack_size() == s->stack_size(), "stack size mismatch!");

   assert(new_sux->state()->locks_size() == s->locks_size(), "locks size mismatch!");

   // link predecessor to new block

   end()->substitute_sux(sux, new_sux);

   // The ordering needs to be the same, so remove the link that the

   // set_end call above added and substitute the new_sux for this

   // block.

   sux->remove_predecessor(new_sux);

   // the successor could be the target of a switch so it might have

   // multiple copies of this predecessor, so substitute the new_sux

   // for the first and delete the rest.

   bool assigned = false;

   BlockList& list = sux->_predecessors;

   for (int i = 0; i < list.length(); i++) {

     BlockBegin** b = list.adr_at(i);

     if (*b == this) {

       if (assigned) {

         list.remove_at(i);

         // reprocess this index

         i--;

       } else {

         assigned = true;

         *b = new_sux;

       }

       // link the new block back to it's predecessors.

       new_sux->add_predecessor(this);

     }

   }

   assert(assigned == true, "should have assigned at least once");

   return new_sux;

 }

 void BlockBegin::remove_successor(BlockBegin* pred) {

   int idx;

   while ((idx = _successors.index_of(pred)) >= 0) {

     _successors.remove_at(idx);

   }

 }

 void BlockBegin::add_predecessor(BlockBegin* pred) {

   _predecessors.append(pred);

 }

 void BlockBegin::remove_predecessor(BlockBegin* pred) {

   int idx;

   while ((idx = _predecessors.index_of(pred)) >= 0) {

     _predecessors.remove_at(idx);

   }

 }

 void BlockBegin::add_exception_handler(BlockBegin* b) {

   assert(b != NULL && (b->is_set(exception_entry_flag)), "exception handler must exist");

   // add only if not in the list already

   if (!_exception_handlers.contains(b)) _exception_handlers.append(b);

 }

 int BlockBegin::add_exception_state(ValueStack* state) {

   assert(is_set(exception_entry_flag), "only for xhandlers");

   if (_exception_states == NULL) {

     _exception_states = new ValueStackStack(4);

   }

   _exception_states->append(state);

   return _exception_states->length() - 1;

 }

 void BlockBegin::iterate_preorder(boolArray& mark, BlockClosure* closure) {

   if (!mark.at(block_id())) {

     mark.at_put(block_id(), true);

     closure->block_do(this);

     BlockEnd* e = end(); // must do this after block_do because block_do may change it!

     { for (int i = number_of_exception_handlers() - 1; i >= 0; i--) exception_handler_at(i)->iterate_preorder(mark, closure); }

     { for (int i = e->number_of_sux            () - 1; i >= 0; i--) e->sux_at           (i)->iterate_preorder(mark, closure); }

   }

 }

 void BlockBegin::iterate_postorder(boolArray& mark, BlockClosure* closure) {

   if (!mark.at(block_id())) {

     mark.at_put(block_id(), true);

     BlockEnd* e = end();

     { for (int i = number_of_exception_handlers() - 1; i >= 0; i--) exception_handler_at(i)->iterate_postorder(mark, closure); }

     { for (int i = e->number_of_sux            () - 1; i >= 0; i--) e->sux_at           (i)->iterate_postorder(mark, closure); }

     closure->block_do(this);

   }

 }

 void BlockBegin::iterate_preorder(BlockClosure* closure) {

   boolArray mark(number_of_blocks(), false);

   iterate_preorder(mark, closure);

 }

 void BlockBegin::iterate_postorder(BlockClosure* closure) {

   boolArray mark(number_of_blocks(), false);

   iterate_postorder(mark, closure);

 }

 void BlockBegin::block_values_do(ValueVisitor* f) {

   for (Instruction* n = this; n != NULL; n = n->next()) n->values_do(f);

 }

 #ifndef PRODUCT

    #define TRACE_PHI(code) if (PrintPhiFunctions) { code; }

 #else

    #define TRACE_PHI(coce)

 #endif

 bool BlockBegin::try_merge(ValueStack* new_state) {

   TRACE_PHI(tty->print_cr("********** try_merge for block B%d", block_id()));

   // local variables used for state iteration

   int index;

   Value new_value, existing_value;

   ValueStack* existing_state = state();

   if (existing_state == NULL) {

     TRACE_PHI(tty->print_cr("first call of try_merge for this block"));

     if (is_set(BlockBegin::was_visited_flag)) {

       // this actually happens for complicated jsr/ret structures

       return false; // BAILOUT in caller

     }

     // copy state because it is altered

     new_state = new_state->copy(ValueStack::BlockBeginState, bci());

     // Use method liveness to invalidate dead locals

     MethodLivenessResult liveness = new_state->scope()->method()->liveness_at_bci(bci());

     if (liveness.is_valid()) {

       assert((int)liveness.size() == new_state->locals_size(), "error in use of liveness");

       for_each_local_value(new_state, index, new_value) {

         if (!liveness.at(index) || new_value->type()->is_illegal()) {

           new_state->invalidate_local(index);

           TRACE_PHI(tty->print_cr("invalidating dead local %d", index));

         }

       }

     }

     if (is_set(BlockBegin::parser_loop_header_flag)) {

       TRACE_PHI(tty->print_cr("loop header block, initializing phi functions"));

       for_each_stack_value(new_state, index, new_value) {

         new_state->setup_phi_for_stack(this, index);

         TRACE_PHI(tty->print_cr("creating phi-function %c%d for stack %d", new_state->stack_at(index)->type()->tchar(), new_state->stack_at(index)->id(), index));

       }

       BitMap requires_phi_function = new_state->scope()->requires_phi_function();

       for_each_local_value(new_state, index, new_value) {

         bool requires_phi = requires_phi_function.at(index) || (new_value->type()->is_double_word() && requires_phi_function.at(index + 1));

         if (requires_phi || !SelectivePhiFunctions) {

           new_state->setup_phi_for_local(this, index);

           TRACE_PHI(tty->print_cr("creating phi-function %c%d for local %d", new_state->local_at(index)->type()->tchar(), new_state->local_at(index)->id(), index));

         }

       }

     }

     // initialize state of block

     set_state(new_state);

   } else if (existing_state->is_same(new_state)) {

     TRACE_PHI(tty->print_cr("exisiting state found"));

     assert(existing_state->scope() == new_state->scope(), "not matching");

     assert(existing_state->locals_size() == new_state->locals_size(), "not matching");

     assert(existing_state->stack_size() == new_state->stack_size(), "not matching");

     if (is_set(BlockBegin::was_visited_flag)) {

       TRACE_PHI(tty->print_cr("loop header block, phis must be present"));

       if (!is_set(BlockBegin::parser_loop_header_flag)) {

         // this actually happens for complicated jsr/ret structures

         return false; // BAILOUT in caller

       }

       for_each_local_value(existing_state, index, existing_value) {

         Value new_value = new_state->local_at(index);

         if (new_value == NULL || new_value->type()->tag() != existing_value->type()->tag()) {

           // The old code invalidated the phi function here

           // Because dead locals are replaced with NULL, this is a very rare case now, so simply bail out

           return false; // BAILOUT in caller

         }

       }

 #ifdef ASSERT

       // check that all necessary phi functions are present

       for_each_stack_value(existing_state, index, existing_value) {

         assert(existing_value->as_Phi() != NULL && existing_value->as_Phi()->block() == this, "phi function required");

       }

       for_each_local_value(existing_state, index, existing_value) {

         assert(existing_value == new_state->local_at(index) || (existing_value->as_Phi() != NULL && existing_value->as_Phi()->as_Phi()->block() == this), "phi function required");

       }

 #endif

     } else {

       TRACE_PHI(tty->print_cr("creating phi functions on demand"));

       // create necessary phi functions for stack

       for_each_stack_value(existing_state, index, existing_value) {

         Value new_value = new_state->stack_at(index);

         Phi* existing_phi = existing_value->as_Phi();

         if (new_value != existing_value && (existing_phi == NULL || existing_phi->block() != this)) {

           existing_state->setup_phi_for_stack(this, index);

           TRACE_PHI(tty->print_cr("creating phi-function %c%d for stack %d", existing_state->stack_at(index)->type()->tchar(), existing_state->stack_at(index)->id(), index));

         }

       }

       // create necessary phi functions for locals

       for_each_local_value(existing_state, index, existing_value) {

         Value new_value = new_state->local_at(index);

         Phi* existing_phi = existing_value->as_Phi();

         if (new_value == NULL || new_value->type()->tag() != existing_value->type()->tag()) {

           existing_state->invalidate_local(index);

           TRACE_PHI(tty->print_cr("invalidating local %d because of type mismatch", index));

         } else if (new_value != existing_value && (existing_phi == NULL || existing_phi->block() != this)) {

           existing_state->setup_phi_for_local(this, index);

           TRACE_PHI(tty->print_cr("creating phi-function %c%d for local %d", existing_state->local_at(index)->type()->tchar(), existing_state->local_at(index)->id(), index));

         }

       }

     }

     assert(existing_state->caller_state() == new_state->caller_state(), "caller states must be equal");

   } else {

     assert(false, "stack or locks not matching (invalid bytecodes)");

     return false;

   }

   TRACE_PHI(tty->print_cr("********** try_merge for block B%d successful", block_id()));

   return true;

 }

 #ifndef PRODUCT

 void BlockBegin::print_block() {

   InstructionPrinter ip;

   print_block(ip, false);

 }

 void BlockBegin::print_block(InstructionPrinter& ip, bool live_only) {

   ip.print_instr(this); tty->cr();

   ip.print_stack(this->state()); tty->cr();

   ip.print_inline_level(this);

   ip.print_head();

   for (Instruction* n = next(); n != NULL; n = n->next()) {

     if (!live_only || n->is_pinned() || n->use_count() > 0) {

       ip.print_line(n);

     }

   }

   tty->cr();

 }

 #endif // PRODUCT

 // Implementation of BlockList

 void BlockList::iterate_forward (BlockClosure* closure) {

   const int l = length();

   for (int i = 0; i < l; i++) closure->block_do(at(i));

 }

 void BlockList::iterate_backward(BlockClosure* closure) {

   for (int i = length() - 1; i >= 0; i--) closure->block_do(at(i));

 }

 void BlockList::blocks_do(void f(BlockBegin*)) {

   for (int i = length() - 1; i >= 0; i--) f(at(i));

 }

 void BlockList::values_do(ValueVisitor* f) {

   for (int i = length() - 1; i >= 0; i--) at(i)->block_values_do(f);

 }

 #ifndef PRODUCT

 void BlockList::print(bool cfg_only, bool live_only) {

   InstructionPrinter ip;

   for (int i = 0; i < length(); i++) {

     BlockBegin* block = at(i);

     if (cfg_only) {

       ip.print_instr(block); tty->cr();

     } else {

       block->print_block(ip, live_only);

     }

   }

 }

 #endif // PRODUCT

 // Implementation of BlockEnd

 void BlockEnd::set_begin(BlockBegin* begin) {

   BlockList* sux = NULL;

   if (begin != NULL) {

     sux = begin->successors();

   } else if (_begin != NULL) {

     // copy our sux list

     BlockList* sux = new BlockList(_begin->number_of_sux());

     for (int i = 0; i < _begin->number_of_sux(); i++) {

       sux->append(_begin->sux_at(i));

     }

   }

   _sux = sux;

   _begin = begin;

 }

 void BlockEnd::substitute_sux(BlockBegin* old_sux, BlockBegin* new_sux) {

   substitute(*_sux, old_sux, new_sux);

 }

 // Implementation of Phi

 // Normal phi functions take their operands from the last instruction of the

 // predecessor. Special handling is needed for xhanlder entries because there

 // the state of arbitrary instructions are needed.

 Value Phi::operand_at(int i) const {

   ValueStack* state;

   if (_block->is_set(BlockBegin::exception_entry_flag)) {

     state = _block->exception_state_at(i);

   } else {

     state = _block->pred_at(i)->end()->state();

   }

   assert(state != NULL, "");

   if (is_local()) {

     return state->local_at(local_index());

   } else {

     return state->stack_at(stack_index());

   }

 }

 int Phi::operand_count() const {

   if (_block->is_set(BlockBegin::exception_entry_flag)) {

     return _block->number_of_exception_states();

   } else {

     return _block->number_of_preds();

   }

 }

 void ProfileInvoke::state_values_do(ValueVisitor* f) {

   if (state() != NULL) state()->values_do(f);

 }