Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 1997-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 // Portions of code courtesy of Clifford Click

 // Optimization - Graph Style

 #include "incls/_precompiled.incl"

 #include "incls/_cfgnode.cpp.incl"

 //=============================================================================

 //------------------------------Value------------------------------------------

 // Compute the type of the RegionNode.

 const Type *RegionNode::Value( PhaseTransform *phase ) const {

   for( uint i=1; i<req(); ++i ) {       // For all paths in

     Node *n = in(i);            // Get Control source

     if( !n ) continue;          // Missing inputs are TOP

     if( phase->type(n) == Type::CONTROL )

       return Type::CONTROL;

   }

   return Type::TOP;             // All paths dead?  Then so are we

 }

 //------------------------------Identity---------------------------------------

 // Check for Region being Identity.

 Node *RegionNode::Identity( PhaseTransform *phase ) {

   // Cannot have Region be an identity, even if it has only 1 input.

   // Phi users cannot have their Region input folded away for them,

   // since they need to select the proper data input

   return this;

 }

 //------------------------------merge_region-----------------------------------

 // If a Region flows into a Region, merge into one big happy merge.  This is

 // hard to do if there is stuff that has to happen

 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {

   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes

     return NULL;

   Node *progress = NULL;        // Progress flag

   PhaseIterGVN *igvn = phase->is_IterGVN();

   uint rreq = region->req();

   for( uint i = 1; i < rreq; i++ ) {

     Node *r = region->in(i);

     if( r && r->Opcode() == Op_Region && // Found a region?

         r->in(0) == r &&        // Not already collapsed?

         r != region &&          // Avoid stupid situations

         r->outcnt() == 2 ) {    // Self user and 'region' user only?

       assert(!r->as_Region()->has_phi(), "no phi users");

       if( !progress ) {         // No progress

         if (region->has_phi()) {

           return NULL;        // Only flatten if no Phi users

           // igvn->hash_delete( phi );

         }

         igvn->hash_delete( region );

         progress = region;      // Making progress

       }

       igvn->hash_delete( r );

       // Append inputs to 'r' onto 'region'

       for( uint j = 1; j < r->req(); j++ ) {

         // Move an input from 'r' to 'region'

         region->add_req(r->in(j));

         r->set_req(j, phase->C->top());

         // Update phis of 'region'

         //for( uint k = 0; k < max; k++ ) {

         //  Node *phi = region->out(k);

         //  if( phi->is_Phi() ) {

         //    phi->add_req(phi->in(i));

         //  }

         //}

         rreq++;                 // One more input to Region

       } // Found a region to merge into Region

       // Clobber pointer to the now dead 'r'

       region->set_req(i, phase->C->top());

     }

   }

   return progress;

 }

 //--------------------------------has_phi--------------------------------------

 // Helper function: Return any PhiNode that uses this region or NULL

 PhiNode* RegionNode::has_phi() const {

   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {

     Node* phi = fast_out(i);

     if (phi->is_Phi()) {   // Check for Phi users

       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");

       return phi->as_Phi();  // this one is good enough

     }

   }

   return NULL;

 }

 //-----------------------------has_unique_phi----------------------------------

 // Helper function: Return the only PhiNode that uses this region or NULL

 PhiNode* RegionNode::has_unique_phi() const {

   // Check that only one use is a Phi

   PhiNode* only_phi = NULL;

   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {

     Node* phi = fast_out(i);

     if (phi->is_Phi()) {   // Check for Phi users

       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");

       if (only_phi == NULL) {

         only_phi = phi->as_Phi();

       } else {

         return NULL;  // multiple phis

       }

     }

   }

   return only_phi;

 }

 //------------------------------check_phi_clipping-----------------------------

 // Helper function for RegionNode's identification of FP clipping

 // Check inputs to the Phi

 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {

   min     = NULL;

   max     = NULL;

   val     = NULL;

   min_idx = 0;

   max_idx = 0;

   val_idx = 0;

   uint  phi_max = phi->req();

   if( phi_max == 4 ) {

     for( uint j = 1; j < phi_max; ++j ) {

       Node *n = phi->in(j);

       int opcode = n->Opcode();

       switch( opcode ) {

       case Op_ConI:

         {

           if( min == NULL ) {

             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;

             min_idx = j;

           } else {

             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;

             max_idx = j;

             if( min->get_int() > max->get_int() ) {

               // Swap min and max

               ConNode *temp;

               uint     temp_idx;

               temp     = min;     min     = max;     max     = temp;

               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;

             }

           }

         }

         break;

       default:

         {

           val = n;

           val_idx = j;

         }

         break;

       }

     }

   }

   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );

 }

 //------------------------------check_if_clipping------------------------------

 // Helper function for RegionNode's identification of FP clipping

 // Check that inputs to Region come from two IfNodes,

 //

 //            If

 //      False    True

 //       If        |

 //  False  True    |

 //    |      |     |

 //  RegionNode_inputs

 //

 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {

   top_if = NULL;

   bot_if = NULL;

   // Check control structure above RegionNode for (if  ( if  ) )

   Node *in1 = region->in(1);

   Node *in2 = region->in(2);

   Node *in3 = region->in(3);

   // Check that all inputs are projections

   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {

     Node *in10 = in1->in(0);

     Node *in20 = in2->in(0);

     Node *in30 = in3->in(0);

     // Check that #1 and #2 are ifTrue and ifFalse from same If

     if( in10 != NULL && in10->is_If() &&

         in20 != NULL && in20->is_If() &&

         in30 != NULL && in30->is_If() && in10 == in20 &&

         (in1->Opcode() != in2->Opcode()) ) {

       Node  *in100 = in10->in(0);

       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;

       // Check that control for in10 comes from other branch of IF from in3

       if( in1000 != NULL && in1000->is_If() &&

           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {

         // Control pattern checks

         top_if = (IfNode*)in1000;

         bot_if = (IfNode*)in10;

       }

     }

   }

   return (top_if != NULL);

 }

 //------------------------------check_convf2i_clipping-------------------------

 // Helper function for RegionNode's identification of FP clipping

 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"

 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {

   convf2i = NULL;

   // Check for the RShiftNode

   Node *rshift = phi->in(idx);

   assert( rshift, "Previous checks ensure phi input is present");

   if( rshift->Opcode() != Op_RShiftI )  { return false; }

   // Check for the LShiftNode

   Node *lshift = rshift->in(1);

   assert( lshift, "Previous checks ensure phi input is present");

   if( lshift->Opcode() != Op_LShiftI )  { return false; }

   // Check for the ConvF2INode

   Node *conv = lshift->in(1);

   if( conv->Opcode() != Op_ConvF2I ) { return false; }

   // Check that shift amounts are only to get sign bits set after F2I

   jint max_cutoff     = max->get_int();

   jint min_cutoff     = min->get_int();

   jint left_shift     = lshift->in(2)->get_int();

   jint right_shift    = rshift->in(2)->get_int();

   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);

   if( left_shift != right_shift ||

       0 > left_shift || left_shift >= BitsPerJavaInteger ||

       max_post_shift < max_cutoff ||

       max_post_shift < -min_cutoff ) {

     // Shifts are necessary but current transformation eliminates them

     return false;

   }

   // OK to return the result of ConvF2I without shifting

   convf2i = (ConvF2INode*)conv;

   return true;

 }

 //------------------------------check_compare_clipping-------------------------

 // Helper function for RegionNode's identification of FP clipping

 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {

   Node *i1 = iff->in(1);

   if ( !i1->is_Bool() ) { return false; }

   BoolNode *bool1 = i1->as_Bool();

   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }

   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }

   const Node *cmpF = bool1->in(1);

   if( cmpF->Opcode() != Op_CmpF )      { return false; }

   // Test that the float value being compared against

   // is equivalent to the int value used as a limit

   Node *nodef = cmpF->in(2);

   if( nodef->Opcode() != Op_ConF ) { return false; }

   jfloat conf = nodef->getf();

   jint   coni = limit->get_int();

   if( ((int)conf) != coni )        { return false; }

   input = cmpF->in(1);

   return true;

 }

 //------------------------------is_unreachable_region--------------------------

 // Find if the Region node is reachable from the root.

 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {

   assert(req() == 2, "");

   // First, cut the simple case of fallthrough region when NONE of

   // region's phis references itself directly or through a data node.

   uint max = outcnt();

   uint i;

   for (i = 0; i < max; i++) {

     Node* phi = raw_out(i);

     if (phi != NULL && phi->is_Phi()) {

       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");

       if (phi->outcnt() == 0)

         continue; // Safe case - no loops

       if (phi->outcnt() == 1) {

         Node* u = phi->raw_out(0);

         // Skip if only one use is an other Phi or Call or Uncommon trap.

         // It is safe to consider this case as fallthrough.

         if (u != NULL && (u->is_Phi() || u->is_CFG()))

           continue;

       }

       // Check when phi references itself directly or through an other node.

       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)

         break; // Found possible unsafe data loop.

     }

   }

   if (i >= max)

     return false; // An unsafe case was NOT found - don't need graph walk.

   // Unsafe case - check if the Region node is reachable from root.

   ResourceMark rm;

   Arena *a = Thread::current()->resource_area();

   Node_List nstack(a);

   VectorSet visited(a);

   // Mark all control nodes reachable from root outputs

   Node *n = (Node*)phase->C->root();

   nstack.push(n);

   visited.set(n->_idx);

   while (nstack.size() != 0) {

     n = nstack.pop();

     uint max = n->outcnt();

     for (uint i = 0; i < max; i++) {

       Node* m = n->raw_out(i);

       if (m != NULL && m->is_CFG()) {

         if (phase->eqv(m, this)) {

           return false; // We reached the Region node - it is not dead.

         }

         if (!visited.test_set(m->_idx))

           nstack.push(m);

       }

     }

   }

   return true; // The Region node is unreachable - it is dead.

 }

 //------------------------------Ideal------------------------------------------

 // Return a node which is more "ideal" than the current node.  Must preserve

 // the CFG, but we can still strip out dead paths.

 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy

   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");

   // Check for RegionNode with no Phi users and both inputs come from either

   // arm of the same IF.  If found, then the control-flow split is useless.

   bool has_phis = false;

   if (can_reshape) {            // Need DU info to check for Phi users

     has_phis = (has_phi() != NULL);       // Cache result

     if (!has_phis) {            // No Phi users?  Nothing merging?

       for (uint i = 1; i < req()-1; i++) {

         Node *if1 = in(i);

         if( !if1 ) continue;

         Node *iff = if1->in(0);

         if( !iff || !iff->is_If() ) continue;

         for( uint j=i+1; j<req(); j++ ) {

           if( in(j) && in(j)->in(0) == iff &&

               if1->Opcode() != in(j)->Opcode() ) {

             // Add the IF Projections to the worklist. They (and the IF itself)

             // will be eliminated if dead.

             phase->is_IterGVN()->add_users_to_worklist(iff);

             set_req(i, iff->in(0));// Skip around the useless IF diamond

             set_req(j, NULL);

             return this;      // Record progress

           }

         }

       }

     }

   }

   // Remove TOP or NULL input paths. If only 1 input path remains, this Region

   // degrades to a copy.

   bool add_to_worklist = false;

   int cnt = 0;                  // Count of values merging

   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count

   int del_it = 0;               // The last input path we delete

   // For all inputs...

   for( uint i=1; i<req(); ++i ){// For all paths in

     Node *n = in(i);            // Get the input

     if( n != NULL ) {

       // Remove useless control copy inputs

       if( n->is_Region() && n->as_Region()->is_copy() ) {

         set_req(i, n->nonnull_req());

         i--;

         continue;

       }

       if( n->is_Proj() ) {      // Remove useless rethrows

         Node *call = n->in(0);

         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {

           set_req(i, call->in(0));

           i--;

           continue;

         }

       }

       if( phase->type(n) == Type::TOP ) {

         set_req(i, NULL);       // Ignore TOP inputs

         i--;

         continue;

       }

       cnt++;                    // One more value merging

     } else if (can_reshape) {   // Else found dead path with DU info

       PhaseIterGVN *igvn = phase->is_IterGVN();

       del_req(i);               // Yank path from self

       del_it = i;

       uint max = outcnt();

       DUIterator j;

       bool progress = true;

       while(progress) {         // Need to establish property over all users

         progress = false;

         for (j = outs(); has_out(j); j++) {

           Node *n = out(j);

           if( n->req() != req() && n->is_Phi() ) {

             assert( n->in(0) == this, "" );

             igvn->hash_delete(n); // Yank from hash before hacking edges

             n->set_req_X(i,NULL,igvn);// Correct DU info

             n->del_req(i);        // Yank path from Phis

             if( max != outcnt() ) {

               progress = true;

               j = refresh_out_pos(j);

               max = outcnt();

             }

           }

         }

       }

       add_to_worklist = true;

       i--;

     }

   }

   if (can_reshape && cnt == 1) {

     // Is it dead loop?

     // If it is LoopNopde it had 2 (+1 itself) inputs and

     // one of them was cut. The loop is dead if it was EntryContol.

     assert(!this->is_Loop() || cnt_orig == 3, "Loop node should have 3 inputs");

     if (this->is_Loop() && del_it == LoopNode::EntryControl ||

        !this->is_Loop() && has_phis && is_unreachable_region(phase)) {

       // Yes,  the region will be removed during the next step below.

       // Cut the backedge input and remove phis since no data paths left.

       // We don't cut outputs to other nodes here since we need to put them

       // on the worklist.

       del_req(1);

       cnt = 0;

       assert( req() == 1, "no more inputs expected" );

       uint max = outcnt();

       bool progress = true;

       Node *top = phase->C->top();

       PhaseIterGVN *igvn = phase->is_IterGVN();

       DUIterator j;

       while(progress) {

         progress = false;

         for (j = outs(); has_out(j); j++) {

           Node *n = out(j);

           if( n->is_Phi() ) {

             assert( igvn->eqv(n->in(0), this), "" );

             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );

             // Break dead loop data path.

             // Eagerly replace phis with top to avoid phis copies generation.

             igvn->add_users_to_worklist(n);

             igvn->hash_delete(n); // Yank from hash before hacking edges

             igvn->subsume_node(n, top);

             if( max != outcnt() ) {

               progress = true;

               j = refresh_out_pos(j);

               max = outcnt();

             }

           }

         }

       }

       add_to_worklist = true;

     }

   }

   if (add_to_worklist) {

     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis

   }

   if( cnt <= 1 ) {              // Only 1 path in?

     set_req(0, NULL);           // Null control input for region copy

     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.

       // No inputs or all inputs are NULL.

       return NULL;

     } else if (can_reshape) {   // Optimization phase - remove the node

       PhaseIterGVN *igvn = phase->is_IterGVN();

       Node *parent_ctrl;

       if( cnt == 0 ) {

         assert( req() == 1, "no inputs expected" );

         // During IGVN phase such region will be subsumed by TOP node

         // so region's phis will have TOP as control node.

         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.

         // Also set other user's input to top.

         parent_ctrl = phase->C->top();

       } else {

         // The fallthrough case since we already checked dead loops above.

         parent_ctrl = in(1);

         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");

         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");

       }

       if (!add_to_worklist)

         igvn->add_users_to_worklist(this); // Check for further allowed opts

       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {

         Node* n = last_out(i);

         igvn->hash_delete(n); // Remove from worklist before modifying edges

         if( n->is_Phi() ) {   // Collapse all Phis

           // Eagerly replace phis to avoid copies generation.

           igvn->add_users_to_worklist(n);

           igvn->hash_delete(n); // Yank from hash before hacking edges

           if( cnt == 0 ) {

             assert( n->req() == 1, "No data inputs expected" );

             igvn->subsume_node(n, parent_ctrl); // replaced by top

           } else {

             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );

             Node* in1 = n->in(1);               // replaced by unique input

             if( n->as_Phi()->is_unsafe_data_reference(in1) )

               in1 = phase->C->top();            // replaced by top

             igvn->subsume_node(n, in1);

           }

         }

         else if( n->is_Region() ) { // Update all incoming edges

           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");

           uint uses_found = 0;

           for( uint k=1; k < n->req(); k++ ) {

             if( n->in(k) == this ) {

               n->set_req(k, parent_ctrl);

               uses_found++;

             }

           }

           if( uses_found > 1 ) { // (--i) done at the end of the loop.

             i -= (uses_found - 1);

           }

         }

         else {

           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");

           n->set_req(0, parent_ctrl);

         }

 #ifdef ASSERT

         for( uint k=0; k < n->req(); k++ ) {

           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");

         }

 #endif

       }

       // Remove the RegionNode itself from DefUse info

       igvn->remove_dead_node(this);

       return NULL;

     }

     return this;                // Record progress

   }

   // If a Region flows into a Region, merge into one big happy merge.

   if (can_reshape) {

     Node *m = merge_region(this, phase);

     if (m != NULL)  return m;

   }

   // Check if this region is the root of a clipping idiom on floats

   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {

     // Check that only one use is a Phi and that it simplifies to two constants +

     PhiNode* phi = has_unique_phi();

     if (phi != NULL) {          // One Phi user

       // Check inputs to the Phi

       ConNode *min;

       ConNode *max;

       Node    *val;

       uint     min_idx;

       uint     max_idx;

       uint     val_idx;

       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {

         IfNode *top_if;

         IfNode *bot_if;

         if( check_if_clipping( this, bot_if, top_if ) ) {

           // Control pattern checks, now verify compares

           Node   *top_in = NULL;   // value being compared against

           Node   *bot_in = NULL;

           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&

               check_compare_clipping( false, top_if, max, top_in ) ) {

             if( bot_in == top_in ) {

               PhaseIterGVN *gvn = phase->is_IterGVN();

               assert( gvn != NULL, "Only had DefUse info in IterGVN");

               // Only remaining check is that bot_in == top_in == (Phi's val + mods)

               // Check for the ConvF2INode

               ConvF2INode *convf2i;

               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&

                 convf2i->in(1) == bot_in ) {

                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares

                 // max test

                 Node *cmp   = gvn->register_new_node_with_optimizer(new (phase->C, 3) CmpINode( convf2i, min ));

                 Node *boo   = gvn->register_new_node_with_optimizer(new (phase->C, 2) BoolNode( cmp, BoolTest::lt ));

                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C, 2) IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));

                 Node *if_min= gvn->register_new_node_with_optimizer(new (phase->C, 1) IfTrueNode (iff));

                 Node *ifF   = gvn->register_new_node_with_optimizer(new (phase->C, 1) IfFalseNode(iff));

                 // min test

                 cmp         = gvn->register_new_node_with_optimizer(new (phase->C, 3) CmpINode( convf2i, max ));

                 boo         = gvn->register_new_node_with_optimizer(new (phase->C, 2) BoolNode( cmp, BoolTest::gt ));

                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C, 2) IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));

                 Node *if_max= gvn->register_new_node_with_optimizer(new (phase->C, 1) IfTrueNode (iff));

                 ifF         = gvn->register_new_node_with_optimizer(new (phase->C, 1) IfFalseNode(iff));

                 // update input edges to region node

                 set_req_X( min_idx, if_min, gvn );

                 set_req_X( max_idx, if_max, gvn );

                 set_req_X( val_idx, ifF,    gvn );

                 // remove unnecessary 'LShiftI; RShiftI' idiom

                 gvn->hash_delete(phi);

                 phi->set_req_X( val_idx, convf2i, gvn );

                 gvn->hash_find_insert(phi);

                 // Return transformed region node

                 return this;

               }

             }

           }

         }

       }

     }

   }

   return NULL;

 }

 const RegMask &RegionNode::out_RegMask() const {

   return RegMask::Empty;

 }

 // Find the one non-null required input.  RegionNode only

 Node *Node::nonnull_req() const {

   assert( is_Region(), "" );

   for( uint i = 1; i < _cnt; i++ )

     if( in(i) )

       return in(i);

   ShouldNotReachHere();

   return NULL;

 }

 //=============================================================================

 // note that these functions assume that the _adr_type field is flattened

 uint PhiNode::hash() const {

   const Type* at = _adr_type;

   return TypeNode::hash() + (at ? at->hash() : 0);

 }

 uint PhiNode::cmp( const Node &n ) const {

   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;

 }

 static inline

 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {

   if (at == NULL || at == TypePtr::BOTTOM)  return at;

   return Compile::current()->alias_type(at)->adr_type();

 }

 //----------------------------make---------------------------------------------

 // create a new phi with edges matching r and set (initially) to x

 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {

   uint preds = r->req();   // Number of predecessor paths

   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");

   PhiNode* p = new (Compile::current(), preds) PhiNode(r, t, at);

   for (uint j = 1; j < preds; j++) {

     // Fill in all inputs, except those which the region does not yet have

     if (r->in(j) != NULL)

       p->init_req(j, x);

   }

   return p;

 }

 PhiNode* PhiNode::make(Node* r, Node* x) {

   const Type*    t  = x->bottom_type();

   const TypePtr* at = NULL;

   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());

   return make(r, x, t, at);

 }

 PhiNode* PhiNode::make_blank(Node* r, Node* x) {

   const Type*    t  = x->bottom_type();

   const TypePtr* at = NULL;

   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());

   return new (Compile::current(), r->req()) PhiNode(r, t, at);

 }

 //------------------------slice_memory-----------------------------------------

 // create a new phi with narrowed memory type

 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {

   PhiNode* mem = (PhiNode*) clone();

   *(const TypePtr**)&mem->_adr_type = adr_type;

   // convert self-loops, or else we get a bad graph

   for (uint i = 1; i < req(); i++) {

     if ((const Node*)in(i) == this)  mem->set_req(i, mem);

   }

   mem->verify_adr_type();

   return mem;

 }

 //------------------------split_out_instance-----------------------------------

 // Split out an instance type from a bottom phi.

 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {

   const TypeOopPtr *t_oop = at->isa_oopptr();

   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");

   const TypePtr *t = adr_type();

   assert(type() == Type::MEMORY &&

          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||

           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&

           t->is_oopptr()->cast_to_exactness(true)

            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())

            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),

          "bottom or raw memory required");

   // Check if an appropriate node already exists.

   Node *region = in(0);

   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {

     Node* use = region->fast_out(k);

     if( use->is_Phi()) {

       PhiNode *phi2 = use->as_Phi();

       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {

         return phi2;

       }

     }

   }

   Compile *C = igvn->C;

   Arena *a = Thread::current()->resource_area();

   Node_Array node_map = new Node_Array(a);

   Node_Stack stack(a, C->unique() >> 4);

   PhiNode *nphi = slice_memory(at);

   igvn->register_new_node_with_optimizer( nphi );

   node_map.map(_idx, nphi);

   stack.push((Node *)this, 1);

   while(!stack.is_empty()) {

     PhiNode *ophi = stack.node()->as_Phi();

     uint i = stack.index();

     assert(i >= 1, "not control edge");

     stack.pop();

     nphi = node_map[ophi->_idx]->as_Phi();

     for (; i < ophi->req(); i++) {

       Node *in = ophi->in(i);

       if (in == NULL || igvn->type(in) == Type::TOP)

         continue;

       Node *opt = MemNode::optimize_simple_memory_chain(in, at, igvn);

       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;

       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {

         opt = node_map[optphi->_idx];

         if (opt == NULL) {

           stack.push(ophi, i);

           nphi = optphi->slice_memory(at);

           igvn->register_new_node_with_optimizer( nphi );

           node_map.map(optphi->_idx, nphi);

           ophi = optphi;

           i = 0; // will get incremented at top of loop

           continue;

         }

       }

       nphi->set_req(i, opt);

     }

   }

   return nphi;

 }

 //------------------------verify_adr_type--------------------------------------

 #ifdef ASSERT

 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {

   if (visited.test_set(_idx))  return;  //already visited

   // recheck constructor invariants:

   verify_adr_type(false);

   // recheck local phi/phi consistency:

   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,

          "adr_type must be consistent across phi nest");

   // walk around

   for (uint i = 1; i < req(); i++) {

     Node* n = in(i);

     if (n == NULL)  continue;

     const Node* np = in(i);

     if (np->is_Phi()) {

       np->as_Phi()->verify_adr_type(visited, at);

     } else if (n->bottom_type() == Type::TOP

                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {

       // ignore top inputs

     } else {

       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());

       // recheck phi/non-phi consistency at leaves:

       assert((nat != NULL) == (at != NULL), "");

       assert(nat == at || nat == TypePtr::BOTTOM,

              "adr_type must be consistent at leaves of phi nest");

     }

   }

 }

 // Verify a whole nest of phis rooted at this one.

 void PhiNode::verify_adr_type(bool recursive) const {

   if (is_error_reported())  return;  // muzzle asserts when debugging an error

   if (Node::in_dump())      return;  // muzzle asserts when printing

   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");

   if (!VerifyAliases)       return;  // verify thoroughly only if requested

   assert(_adr_type == flatten_phi_adr_type(_adr_type),

          "Phi::adr_type must be pre-normalized");

   if (recursive) {

     VectorSet visited(Thread::current()->resource_area());

     verify_adr_type(visited, _adr_type);

   }

 }

 #endif

 //------------------------------Value------------------------------------------

 // Compute the type of the PhiNode

 const Type *PhiNode::Value( PhaseTransform *phase ) const {

   Node *r = in(0);              // RegionNode

   if( !r )                      // Copy or dead

     return in(1) ? phase->type(in(1)) : Type::TOP;

   // Note: During parsing, phis are often transformed before their regions.

   // This means we have to use type_or_null to defend against untyped regions.

   if( phase->type_or_null(r) == Type::TOP )  // Dead code?

     return Type::TOP;

   // Check for trip-counted loop.  If so, be smarter.

   CountedLoopNode *l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;

   if( l && l->can_be_counted_loop(phase) &&

       ((const Node*)l->phi() == this) ) { // Trip counted loop!

     // protect against init_trip() or limit() returning NULL

     const Node *init   = l->init_trip();

     const Node *limit  = l->limit();

     if( init != NULL && limit != NULL && l->stride_is_con() ) {

       const TypeInt *lo = init ->bottom_type()->isa_int();

       const TypeInt *hi = limit->bottom_type()->isa_int();

       if( lo && hi ) {            // Dying loops might have TOP here

         int stride = l->stride_con();

         if( stride < 0 ) {          // Down-counter loop

           const TypeInt *tmp = lo; lo = hi; hi = tmp;

           stride = -stride;

         }

         if( lo->_hi < hi->_lo )     // Reversed endpoints are well defined :-(

           return TypeInt::make(lo->_lo,hi->_hi,3);

       }

     }

   }

   // Until we have harmony between classes and interfaces in the type

   // lattice, we must tread carefully around phis which implicitly

   // convert the one to the other.

   const TypePtr* ttp = _type->make_ptr();

   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;

   bool is_intf = false;

   if (ttip != NULL) {

     ciKlass* k = ttip->klass();

     if (k->is_loaded() && k->is_interface())

       is_intf = true;

   }

   // Default case: merge all inputs

   const Type *t = Type::TOP;        // Merged type starting value

   for (uint i = 1; i < req(); ++i) {// For all paths in

     // Reachable control path?

     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {

       const Type* ti = phase->type(in(i));

       // We assume that each input of an interface-valued Phi is a true

       // subtype of that interface.  This might not be true of the meet

       // of all the input types.  The lattice is not distributive in

       // such cases.  Ward off asserts in type.cpp by refusing to do

       // meets between interfaces and proper classes.

       const TypePtr* tip = ti->make_ptr();

       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;

       if (tiip) {

         bool ti_is_intf = false;

         ciKlass* k = tiip->klass();

         if (k->is_loaded() && k->is_interface())

           ti_is_intf = true;

         if (is_intf != ti_is_intf)

           { t = _type; break; }

       }

       t = t->meet(ti);

     }

   }

   // The worst-case type (from ciTypeFlow) should be consistent with "t".

   // That is, we expect that "t->higher_equal(_type)" holds true.

   // There are various exceptions:

   // - Inputs which are phis might in fact be widened unnecessarily.

   //   For example, an input might be a widened int while the phi is a short.

   // - Inputs might be BotPtrs but this phi is dependent on a null check,

   //   and postCCP has removed the cast which encodes the result of the check.

   // - The type of this phi is an interface, and the inputs are classes.

   // - Value calls on inputs might produce fuzzy results.

   //   (Occurrences of this case suggest improvements to Value methods.)

   //

   // It is not possible to see Type::BOTTOM values as phi inputs,

   // because the ciTypeFlow pre-pass produces verifier-quality types.

   const Type* ft = t->filter(_type);  // Worst case type

 #ifdef ASSERT

   // The following logic has been moved into TypeOopPtr::filter.

   const Type* jt = t->join(_type);

   if( jt->empty() ) {           // Emptied out???

     // Check for evil case of 't' being a class and '_type' expecting an

     // interface.  This can happen because the bytecodes do not contain

     // enough type info to distinguish a Java-level interface variable

     // from a Java-level object variable.  If we meet 2 classes which

     // both implement interface I, but their meet is at 'j/l/O' which

     // doesn't implement I, we have no way to tell if the result should

     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows

     // into a Phi which "knows" it's an Interface type we'll have to

     // uplift the type.

     if( !t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface() )

       { assert(ft == _type, ""); } // Uplift to interface

     // Otherwise it's something stupid like non-overlapping int ranges

     // found on dying counted loops.

     else

       { assert(ft == Type::TOP, ""); } // Canonical empty value

   }

   else {

     // If we have an interface-typed Phi and we narrow to a class type, the join

     // should report back the class.  However, if we have a J/L/Object

     // class-typed Phi and an interface flows in, it's possible that the meet &

     // join report an interface back out.  This isn't possible but happens

     // because the type system doesn't interact well with interfaces.

     const TypePtr *jtp = jt->make_ptr();

     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;

     if( jtip && ttip ) {

       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&

           ttip->is_loaded() && !ttip->klass()->is_interface() ) {

         // Happens in a CTW of rt.jar, 320-341, no extra flags

         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||

                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");

         jt = ft;

       }

     }

     if (jt != ft && jt->base() == ft->base()) {

       if (jt->isa_int() &&

           jt->is_int()->_lo == ft->is_int()->_lo &&

           jt->is_int()->_hi == ft->is_int()->_hi)

         jt = ft;

       if (jt->isa_long() &&

           jt->is_long()->_lo == ft->is_long()->_lo &&

           jt->is_long()->_hi == ft->is_long()->_hi)

         jt = ft;

     }

     if (jt != ft) {

       tty->print("merge type:  "); t->dump(); tty->cr();

       tty->print("kill type:   "); _type->dump(); tty->cr();

       tty->print("join type:   "); jt->dump(); tty->cr();

       tty->print("filter type: "); ft->dump(); tty->cr();

     }

     assert(jt == ft, "");

   }

 #endif //ASSERT

   // Deal with conversion problems found in data loops.

   ft = phase->saturate(ft, phase->type_or_null(this), _type);

   return ft;

 }

 //------------------------------is_diamond_phi---------------------------------

 // Does this Phi represent a simple well-shaped diamond merge?  Return the

 // index of the true path or 0 otherwise.

 int PhiNode::is_diamond_phi() const {

   // Check for a 2-path merge

   Node *region = in(0);

   if( !region ) return 0;

   if( region->req() != 3 ) return 0;

   if(         req() != 3 ) return 0;

   // Check that both paths come from the same If

   Node *ifp1 = region->in(1);

   Node *ifp2 = region->in(2);

   if( !ifp1 || !ifp2 ) return 0;

   Node *iff = ifp1->in(0);

   if( !iff || !iff->is_If() ) return 0;

   if( iff != ifp2->in(0) ) return 0;

   // Check for a proper bool/cmp

   const Node *b = iff->in(1);

   if( !b->is_Bool() ) return 0;

   const Node *cmp = b->in(1);

   if( !cmp->is_Cmp() ) return 0;

   // Check for branching opposite expected

   if( ifp2->Opcode() == Op_IfTrue ) {

     assert( ifp1->Opcode() == Op_IfFalse, "" );

     return 2;

   } else {

     assert( ifp1->Opcode() == Op_IfTrue, "" );

     return 1;

   }

 }

 //----------------------------check_cmove_id-----------------------------------

 // Check for CMove'ing a constant after comparing against the constant.

 // Happens all the time now, since if we compare equality vs a constant in

 // the parser, we "know" the variable is constant on one path and we force

 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a

 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more

 // general in that we don't need constants.  Since CMove's are only inserted

 // in very special circumstances, we do it here on generic Phi's.

 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {

   assert(true_path !=0, "only diamond shape graph expected");

   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:

   // phi->region->if_proj->ifnode->bool->cmp

   Node*     region = in(0);

   Node*     iff    = region->in(1)->in(0);

   BoolNode* b      = iff->in(1)->as_Bool();

   Node*     cmp    = b->in(1);

   Node*     tval   = in(true_path);

   Node*     fval   = in(3-true_path);

   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);

   if (id == NULL)

     return NULL;

   // Either value might be a cast that depends on a branch of 'iff'.

   // Since the 'id' value will float free of the diamond, either

   // decast or return failure.

   Node* ctl = id->in(0);

   if (ctl != NULL && ctl->in(0) == iff) {

     if (id->is_ConstraintCast()) {

       return id->in(1);

     } else {

       // Don't know how to disentangle this value.

       return NULL;

     }

   }

   return id;

 }

 //------------------------------Identity---------------------------------------

 // Check for Region being Identity.

 Node *PhiNode::Identity( PhaseTransform *phase ) {

   // Check for no merging going on

   // (There used to be special-case code here when this->region->is_Loop.

   // It would check for a tributary phi on the backedge that the main phi

   // trivially, perhaps with a single cast.  The unique_input method

   // does all this and more, by reducing such tributaries to 'this'.)

   Node* uin = unique_input(phase);

   if (uin != NULL) {

     return uin;

   }

   int true_path = is_diamond_phi();

   if (true_path != 0) {

     Node* id = is_cmove_id(phase, true_path);

     if (id != NULL)  return id;

   }

   return this;                     // No identity

 }

 //-----------------------------unique_input------------------------------------

 // Find the unique value, discounting top, self-loops, and casts.

 // Return top if there are no inputs, and self if there are multiple.

 Node* PhiNode::unique_input(PhaseTransform* phase) {

   //  1) One unique direct input, or

   //  2) some of the inputs have an intervening ConstraintCast and

   //     the type of input is the same or sharper (more specific)

   //     than the phi's type.

   //  3) an input is a self loop

   //

   //  1) input   or   2) input     or   3) input __

   //     /   \           /   \               \  /  \

   //     \   /          |    cast             phi  cast

   //      phi            \   /               /  \  /

   //                      phi               /    --

   Node* r = in(0);                      // RegionNode

   if (r == NULL)  return in(1);         // Already degraded to a Copy

   Node* uncasted_input = NULL; // The unique uncasted input (ConstraintCasts removed)

   Node* direct_input   = NULL; // The unique direct input

   for (uint i = 1, cnt = req(); i < cnt; ++i) {

     Node* rc = r->in(i);

     if (rc == NULL || phase->type(rc) == Type::TOP)

       continue;                 // ignore unreachable control path

     Node* n = in(i);

     if (n == NULL)

       continue;

     Node* un = n->uncast();

     if (un == NULL || un == this || phase->type(un) == Type::TOP) {

       continue; // ignore if top, or in(i) and "this" are in a data cycle

     }

     // Check for a unique uncasted input

     if (uncasted_input == NULL) {

       uncasted_input = un;

     } else if (uncasted_input != un) {

       uncasted_input = NodeSentinel; // no unique uncasted input

     }

     // Check for a unique direct input

     if (direct_input == NULL) {

       direct_input = n;

     } else if (direct_input != n) {

       direct_input = NodeSentinel; // no unique direct input

     }

   }

   if (direct_input == NULL) {

     return phase->C->top();        // no inputs

   }

   assert(uncasted_input != NULL,"");

   if (direct_input != NodeSentinel) {

     return direct_input;           // one unique direct input

   }

   if (uncasted_input != NodeSentinel &&

       phase->type(uncasted_input)->higher_equal(type())) {

     return uncasted_input;         // one unique uncasted input

   }

   // Nothing.

   return NULL;

 }

 //------------------------------is_x2logic-------------------------------------

 // Check for simple convert-to-boolean pattern

 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)

 // Convert Phi to an ConvIB.

 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {

   assert(true_path !=0, "only diamond shape graph expected");

   // Convert the true/false index into an expected 0/1 return.

   // Map 2->0 and 1->1.

   int flipped = 2-true_path;

   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:

   // phi->region->if_proj->ifnode->bool->cmp

   Node *region = phi->in(0);

   Node *iff = region->in(1)->in(0);

   BoolNode *b = (BoolNode*)iff->in(1);

   const CmpNode *cmp = (CmpNode*)b->in(1);

   Node *zero = phi->in(1);

   Node *one  = phi->in(2);

   const Type *tzero = phase->type( zero );

   const Type *tone  = phase->type( one  );

   // Check for compare vs 0

   const Type *tcmp = phase->type(cmp->in(2));

   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {

     // Allow cmp-vs-1 if the other input is bounded by 0-1

     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )

       return NULL;

     flipped = 1-flipped;        // Test is vs 1 instead of 0!

   }

   // Check for setting zero/one opposite expected

   if( tzero == TypeInt::ZERO ) {

     if( tone == TypeInt::ONE ) {

     } else return NULL;

   } else if( tzero == TypeInt::ONE ) {

     if( tone == TypeInt::ZERO ) {

       flipped = 1-flipped;

     } else return NULL;

   } else return NULL;

   // Check for boolean test backwards

   if( b->_test._test == BoolTest::ne ) {

   } else if( b->_test._test == BoolTest::eq ) {

     flipped = 1-flipped;

   } else return NULL;

   // Build int->bool conversion

   Node *n = new (phase->C, 2) Conv2BNode( cmp->in(1) );

   if( flipped )

     n = new (phase->C, 3) XorINode( phase->transform(n), phase->intcon(1) );

   return n;

 }

 //------------------------------is_cond_add------------------------------------

 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"

 // To be profitable the control flow has to disappear; there can be no other

 // values merging here.  We replace the test-and-branch with:

 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by

 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.

 // Then convert Y to 0-or-Y and finally add.

 // This is a key transform for SpecJava _201_compress.

 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {

   assert(true_path !=0, "only diamond shape graph expected");

   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:

   // phi->region->if_proj->ifnode->bool->cmp

   RegionNode *region = (RegionNode*)phi->in(0);

   Node *iff = region->in(1)->in(0);

   BoolNode* b = iff->in(1)->as_Bool();

   const CmpNode *cmp = (CmpNode*)b->in(1);

   // Make sure only merging this one phi here

   if (region->has_unique_phi() != phi)  return NULL;

   // Make sure each arm of the diamond has exactly one output, which we assume

   // is the region.  Otherwise, the control flow won't disappear.

   if (region->in(1)->outcnt() != 1) return NULL;

   if (region->in(2)->outcnt() != 1) return NULL;

   // Check for "(P < Q)" of type signed int

   if (b->_test._test != BoolTest::lt)  return NULL;

   if (cmp->Opcode() != Op_CmpI)        return NULL;

   Node *p = cmp->in(1);

   Node *q = cmp->in(2);

   Node *n1 = phi->in(  true_path);

   Node *n2 = phi->in(3-true_path);

   int op = n1->Opcode();

   if( op != Op_AddI           // Need zero as additive identity

       /*&&op != Op_SubI &&

       op != Op_AddP &&

       op != Op_XorI &&

       op != Op_OrI*/ )

     return NULL;

   Node *x = n2;

   Node *y = n1->in(1);

   if( n2 == n1->in(1) ) {

     y = n1->in(2);

   } else if( n2 == n1->in(1) ) {

   } else return NULL;

   // Not so profitable if compare and add are constants

   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )

     return NULL;

   Node *cmplt = phase->transform( new (phase->C, 3) CmpLTMaskNode(p,q) );

   Node *j_and   = phase->transform( new (phase->C, 3) AndINode(cmplt,y) );

   return new (phase->C, 3) AddINode(j_and,x);

 }

 //------------------------------is_absolute------------------------------------

 // Check for absolute value.

 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {

   assert(true_path !=0, "only diamond shape graph expected");

   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero

   int  phi_x_idx = 0;           // Index of phi input where to find naked x

   // ABS ends with the merge of 2 control flow paths.

   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.

   int false_path = 3 - true_path;

   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:

   // phi->region->if_proj->ifnode->bool->cmp

   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();

   // Check bool sense

   switch( bol->_test._test ) {

   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;

   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;

   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;

   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;

   default:           return NULL;                              break;

   }

   // Test is next

   Node *cmp = bol->in(1);

   const Type *tzero = NULL;

   switch( cmp->Opcode() ) {

   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS

   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS

   default: return NULL;

   }

   // Find zero input of compare; the other input is being abs'd

   Node *x = NULL;

   bool flip = false;

   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {

     x = cmp->in(3 - cmp_zero_idx);

   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {

     // The test is inverted, we should invert the result...

     x = cmp->in(cmp_zero_idx);

     flip = true;

   } else {

     return NULL;

   }

   // Next get the 2 pieces being selected, one is the original value

   // and the other is the negated value.

   if( phi_root->in(phi_x_idx) != x ) return NULL;

   // Check other phi input for subtract node

   Node *sub = phi_root->in(3 - phi_x_idx);

   // Allow only Sub(0,X) and fail out for all others; Neg is not OK

   if( tzero == TypeF::ZERO ) {

     if( sub->Opcode() != Op_SubF ||

         sub->in(2) != x ||

         phase->type(sub->in(1)) != tzero ) return NULL;

     x = new (phase->C, 2) AbsFNode(x);

     if (flip) {

       x = new (phase->C, 3) SubFNode(sub->in(1), phase->transform(x));

     }

   } else {

     if( sub->Opcode() != Op_SubD ||

         sub->in(2) != x ||

         phase->type(sub->in(1)) != tzero ) return NULL;

     x = new (phase->C, 2) AbsDNode(x);

     if (flip) {

       x = new (phase->C, 3) SubDNode(sub->in(1), phase->transform(x));

     }

   }

   return x;

 }

 //------------------------------split_once-------------------------------------

 // Helper for split_flow_path

 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {

   igvn->hash_delete(n);         // Remove from hash before hacking edges

   uint j = 1;

   for( uint i = phi->req()-1; i > 0; i-- ) {

     if( phi->in(i) == val ) {   // Found a path with val?

       // Add to NEW Region/Phi, no DU info

       newn->set_req( j++, n->in(i) );

       // Remove from OLD Region/Phi

       n->del_req(i);

     }

   }

   // Register the new node but do not transform it.  Cannot transform until the

   // entire Region/Phi conglerate has been hacked as a single huge transform.

   igvn->register_new_node_with_optimizer( newn );

   // Now I can point to the new node.

   n->add_req(newn);

   igvn->_worklist.push(n);

 }

 //------------------------------split_flow_path--------------------------------

 // Check for merging identical values and split flow paths

 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {

   BasicType bt = phi->type()->basic_type();

   if( bt == T_ILLEGAL || type2size[bt] <= 0 )

     return NULL;                // Bail out on funny non-value stuff

   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a

     return NULL;                // third unequal input to be worth doing

   // Scan for a constant

   uint i;

   for( i = 1; i < phi->req()-1; i++ ) {

     Node *n = phi->in(i);

     if( !n ) return NULL;

     if( phase->type(n) == Type::TOP ) return NULL;

     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN )

       break;

   }

   if( i >= phi->req() )         // Only split for constants

     return NULL;

   Node *val = phi->in(i);       // Constant to split for

   uint hit = 0;                 // Number of times it occurs

   for( ; i < phi->req(); i++ ){ // Count occurances of constant

     Node *n = phi->in(i);

     if( !n ) return NULL;

     if( phase->type(n) == Type::TOP ) return NULL;

     if( phi->in(i) == val )

       hit++;

   }

   if( hit <= 1 ||               // Make sure we find 2 or more

       hit == phi->req()-1 )     // and not ALL the same value

     return NULL;

   // Now start splitting out the flow paths that merge the same value.

   // Split first the RegionNode.

   PhaseIterGVN *igvn = phase->is_IterGVN();

   Node *r = phi->region();

   RegionNode *newr = new (phase->C, hit+1) RegionNode(hit+1);

   split_once(igvn, phi, val, r, newr);

   // Now split all other Phis than this one

   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {

     Node* phi2 = r->fast_out(k);

     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {

       PhiNode *newphi = PhiNode::make_blank(newr, phi2);

       split_once(igvn, phi, val, phi2, newphi);

     }

   }

   // Clean up this guy

   igvn->hash_delete(phi);

   for( i = phi->req()-1; i > 0; i-- ) {

     if( phi->in(i) == val ) {

       phi->del_req(i);

     }

   }

   phi->add_req(val);

   return phi;

 }

 //=============================================================================

 //------------------------------simple_data_loop_check-------------------------

 //  Try to determing if the phi node in a simple safe/unsafe data loop.

 //  Returns:

 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };

 // Safe       - safe case when the phi and it's inputs reference only safe data

 //              nodes;

 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there

 //              is no reference back to the phi - need a graph walk

 //              to determine if it is in a loop;

 // UnsafeLoop - unsafe case when the phi references itself directly or through

 //              unsafe data node.

 //  Note: a safe data node is a node which could/never reference itself during

 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.

 //  I mark Phi nodes as safe node not only because they can reference itself

 //  but also to prevent mistaking the fallthrough case inside an outer loop

 //  as dead loop when the phi references itselfs through an other phi.

 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {

   // It is unsafe loop if the phi node references itself directly.

   if (in == (Node*)this)

     return UnsafeLoop; // Unsafe loop

   // Unsafe loop if the phi node references itself through an unsafe data node.

   // Exclude cases with null inputs or data nodes which could reference

   // itself (safe for dead loops).

   if (in != NULL && !in->is_dead_loop_safe()) {

     // Check inputs of phi's inputs also.

     // It is much less expensive then full graph walk.

     uint cnt = in->req();

     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;

     for (; i < cnt; ++i) {

       Node* m = in->in(i);

       if (m == (Node*)this)

         return UnsafeLoop; // Unsafe loop

       if (m != NULL && !m->is_dead_loop_safe()) {

         // Check the most common case (about 30% of all cases):

         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).

         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;

         if (m1 == (Node*)this)

           return UnsafeLoop; // Unsafe loop

         if (m1 != NULL && m1 == m->in(2) &&

             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {

           continue; // Safe case

         }

         // The phi references an unsafe node - need full analysis.

         return Unsafe;

       }

     }

   }

   return Safe; // Safe case - we can optimize the phi node.

 }

 //------------------------------is_unsafe_data_reference-----------------------

 // If phi can be reached through the data input - it is data loop.

 bool PhiNode::is_unsafe_data_reference(Node *in) const {

   assert(req() > 1, "");

   // First, check simple cases when phi references itself directly or

   // through an other node.

   LoopSafety safety = simple_data_loop_check(in);

   if (safety == UnsafeLoop)

     return true;  // phi references itself - unsafe loop

   else if (safety == Safe)

     return false; // Safe case - phi could be replaced with the unique input.

   // Unsafe case when we should go through data graph to determine

   // if the phi references itself.

   ResourceMark rm;

   Arena *a = Thread::current()->resource_area();

   Node_List nstack(a);

   VectorSet visited(a);

   nstack.push(in); // Start with unique input.

   visited.set(in->_idx);

   while (nstack.size() != 0) {

     Node* n = nstack.pop();

     uint cnt = n->req();

     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;

     for (; i < cnt; i++) {

       Node* m = n->in(i);

       if (m == (Node*)this) {

         return true;    // Data loop

       }

       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.

         if (!visited.test_set(m->_idx))

           nstack.push(m);

       }

     }

   }

   return false; // The phi is not reachable from its inputs

 }

 //------------------------------Ideal------------------------------------------

 // Return a node which is more "ideal" than the current node.  Must preserve

 // the CFG, but we can still strip out dead paths.

 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // The next should never happen after 6297035 fix.

   if( is_copy() )               // Already degraded to a Copy ?

     return NULL;                // No change

   Node *r = in(0);              // RegionNode

   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");

   // Note: During parsing, phis are often transformed before their regions.

   // This means we have to use type_or_null to defend against untyped regions.

   if( phase->type_or_null(r) == Type::TOP ) // Dead code?

     return NULL;                // No change

   Node *top = phase->C->top();

   // The are 2 situations when only one valid phi's input is left

   // (in addition to Region input).

   // One: region is not loop - replace phi with this input.

   // Two: region is loop - replace phi with top since this data path is dead

   //                       and we need to break the dead data loop.

   Node* progress = NULL;        // Record if any progress made

   for( uint j = 1; j < req(); ++j ){ // For all paths in

     // Check unreachable control paths

     Node* rc = r->in(j);

     Node* n = in(j);            // Get the input

     if (rc == NULL || phase->type(rc) == Type::TOP) {

       if (n != top) {           // Not already top?

         set_req(j, top);        // Nuke it down

         progress = this;        // Record progress

       }

     }

   }

   Node* uin = unique_input(phase);

   if (uin == top) {             // Simplest case: no alive inputs.

     if (can_reshape)            // IGVN transformation

       return top;

     else

       return NULL;              // Identity will return TOP

   } else if (uin != NULL) {

     // Only one not-NULL unique input path is left.

     // Determine if this input is backedge of a loop.

     // (Skip new phis which have no uses and dead regions).

     if( outcnt() > 0 && r->in(0) != NULL ) {

       // First, take the short cut when we know it is a loop and

       // the EntryControl data path is dead.

       assert(!r->is_Loop() || r->req() == 3, "Loop node should have 3 inputs");

       // Then, check if there is a data loop when phi references itself directly

       // or through other data nodes.

       if( r->is_Loop() && !phase->eqv_uncast(uin, in(LoopNode::EntryControl)) ||

          !r->is_Loop() && is_unsafe_data_reference(uin) ) {

         // Break this data loop to avoid creation of a dead loop.

         if (can_reshape) {

           return top;

         } else {

           // We can't return top if we are in Parse phase - cut inputs only

           // let Identity to handle the case.

           replace_edge(uin, top);

           return NULL;

         }

       }

     }

     // One unique input.

     debug_only(Node* ident = Identity(phase));

     // The unique input must eventually be detected by the Identity call.

 #ifdef ASSERT

     if (ident != uin && !ident->is_top()) {

       // print this output before failing assert

       r->dump(3);

       this->dump(3);

       ident->dump();

       uin->dump();

     }

 #endif

     assert(ident == uin || ident->is_top(), "Identity must clean this up");

     return NULL;

   }

   Node* opt = NULL;

   int true_path = is_diamond_phi();

   if( true_path != 0 ) {

     // Check for CMove'ing identity. If it would be unsafe,

     // handle it here. In the safe case, let Identity handle it.

     Node* unsafe_id = is_cmove_id(phase, true_path);

     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )

       opt = unsafe_id;

     // Check for simple convert-to-boolean pattern

     if( opt == NULL )

       opt = is_x2logic(phase, this, true_path);

     // Check for absolute value

     if( opt == NULL )

       opt = is_absolute(phase, this, true_path);

     // Check for conditional add

     if( opt == NULL && can_reshape )

       opt = is_cond_add(phase, this, true_path);

     // These 4 optimizations could subsume the phi:

     // have to check for a dead data loop creation.

     if( opt != NULL ) {

       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {

         // Found dead loop.

         if( can_reshape )

           return top;

         // We can't return top if we are in Parse phase - cut inputs only

         // to stop further optimizations for this phi. Identity will return TOP.

         assert(req() == 3, "only diamond merge phi here");

         set_req(1, top);

         set_req(2, top);

         return NULL;

       } else {

         return opt;

       }

     }

   }

   // Check for merging identical values and split flow paths

   if (can_reshape) {

     opt = split_flow_path(phase, this);

     // This optimization only modifies phi - don't need to check for dead loop.

     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");

     if (opt != NULL)  return opt;

   }

   // Split phis through memory merges, so that the memory merges will go away.

   // Piggy-back this transformation on the search for a unique input....

   // It will be as if the merged memory is the unique value of the phi.

   // (Do not attempt this optimization unless parsing is complete.

   // It would make the parser's memory-merge logic sick.)

   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)

   if (progress == NULL && can_reshape && type() == Type::MEMORY) {

     // see if this phi should be sliced

     uint merge_width = 0;

     bool saw_self = false;

     for( uint i=1; i<req(); ++i ) {// For all paths in

       Node *ii = in(i);

       if (ii->is_MergeMem()) {

         MergeMemNode* n = ii->as_MergeMem();

         merge_width = MAX2(merge_width, n->req());

         saw_self = saw_self || phase->eqv(n->base_memory(), this);

       }

     }

     // This restriction is temporarily necessary to ensure termination:

     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;

     if (merge_width > Compile::AliasIdxRaw) {

       // found at least one non-empty MergeMem

       const TypePtr* at = adr_type();

       if (at != TypePtr::BOTTOM) {

         // Patch the existing phi to select an input from the merge:

         // Phi:AT1(...MergeMem(m0, m1, m2)...) into

         //     Phi:AT1(...m1...)

         int alias_idx = phase->C->get_alias_index(at);

         for (uint i=1; i<req(); ++i) {

           Node *ii = in(i);

           if (ii->is_MergeMem()) {

             MergeMemNode* n = ii->as_MergeMem();

             // compress paths and change unreachable cycles to TOP

             // If not, we can update the input infinitely along a MergeMem cycle

             // Equivalent code is in MemNode::Ideal_common

             Node *m  = phase->transform(n);

             if (outcnt() == 0) {  // Above transform() may kill us!

               progress = phase->C->top();

               break;

             }

             // If tranformed to a MergeMem, get the desired slice

             // Otherwise the returned node represents memory for every slice

             Node *new_mem = (m->is_MergeMem()) ?

                              m->as_MergeMem()->memory_at(alias_idx) : m;

             // Update input if it is progress over what we have now

             if (new_mem != ii) {

               set_req(i, new_mem);

               progress = this;

             }

           }

         }

       } else {

         // We know that at least one MergeMem->base_memory() == this

         // (saw_self == true). If all other inputs also references this phi

         // (directly or through data nodes) - it is dead loop.

         bool saw_safe_input = false;

         for (uint j = 1; j < req(); ++j) {

           Node *n = in(j);

           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)

             continue;              // skip known cases

           if (!is_unsafe_data_reference(n)) {

             saw_safe_input = true; // found safe input

             break;

           }

         }

         if (!saw_safe_input)

           return top; // all inputs reference back to this phi - dead loop

         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into

         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))

         PhaseIterGVN *igvn = phase->is_IterGVN();

         Node* hook = new (phase->C, 1) Node(1);

         PhiNode* new_base = (PhiNode*) clone();

         // Must eagerly register phis, since they participate in loops.

         if (igvn) {

           igvn->register_new_node_with_optimizer(new_base);

           hook->add_req(new_base);

         }

         MergeMemNode* result = MergeMemNode::make(phase->C, new_base);

         for (uint i = 1; i < req(); ++i) {

           Node *ii = in(i);

           if (ii->is_MergeMem()) {

             MergeMemNode* n = ii->as_MergeMem();

             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {

               // If we have not seen this slice yet, make a phi for it.

               bool made_new_phi = false;

               if (mms.is_empty()) {

                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));

                 made_new_phi = true;

                 if (igvn) {

                   igvn->register_new_node_with_optimizer(new_phi);

                   hook->add_req(new_phi);

                 }

                 mms.set_memory(new_phi);

               }

               Node* phi = mms.memory();

               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");

               phi->set_req(i, mms.memory2());

             }

           }

         }

         // Distribute all self-loops.

         { // (Extra braces to hide mms.)

           for (MergeMemStream mms(result); mms.next_non_empty(); ) {

             Node* phi = mms.memory();

             for (uint i = 1; i < req(); ++i) {

               if (phi->in(i) == this)  phi->set_req(i, phi);

             }

           }

         }

         // now transform the new nodes, and return the mergemem

         for (MergeMemStream mms(result); mms.next_non_empty(); ) {

           Node* phi = mms.memory();

           mms.set_memory(phase->transform(phi));

         }

         if (igvn) { // Unhook.

           igvn->hash_delete(hook);

           for (uint i = 1; i < hook->req(); i++) {

             hook->set_req(i, NULL);

           }

         }

         // Replace self with the result.

         return result;

       }

     }

     //

     // Other optimizations on the memory chain

     //

     const TypePtr* at = adr_type();

     for( uint i=1; i<req(); ++i ) {// For all paths in

       Node *ii = in(i);

       Node *new_in = MemNode::optimize_memory_chain(ii, at, phase);

       if (ii != new_in ) {

         set_req(i, new_in);

         progress = this;

       }

     }

   }

 #ifdef _LP64

   // Push DecodeN down through phi.

   // The rest of phi graph will transform by split EncodeP node though phis up.

   if (UseCompressedOops && can_reshape && progress == NULL) {

     bool may_push = true;

     bool has_decodeN = false;

     Node* in_decodeN = NULL;

     for (uint i=1; i<req(); ++i) {// For all paths in

       Node *ii = in(i);

       if (ii->is_DecodeN() && ii->bottom_type() == bottom_type()) {

         has_decodeN = true;

         in_decodeN = ii->in(1);

       } else if (!ii->is_Phi()) {

         may_push = false;

       }

     }

     if (has_decodeN && may_push) {

       PhaseIterGVN *igvn = phase->is_IterGVN();

       // Note: in_decodeN is used only to define the type of new phi here.

       PhiNode *new_phi = PhiNode::make_blank(in(0), in_decodeN);

       uint orig_cnt = req();

       for (uint i=1; i<req(); ++i) {// For all paths in

         Node *ii = in(i);

         Node* new_ii = NULL;

         if (ii->is_DecodeN()) {

           assert(ii->bottom_type() == bottom_type(), "sanity");

           new_ii = ii->in(1);

         } else {

           assert(ii->is_Phi(), "sanity");

           if (ii->as_Phi() == this) {

             new_ii = new_phi;

           } else {

             new_ii = new (phase->C, 2) EncodePNode(ii, in_decodeN->bottom_type());

             igvn->register_new_node_with_optimizer(new_ii);

           }

         }

         new_phi->set_req(i, new_ii);

       }

       igvn->register_new_node_with_optimizer(new_phi, this);

       progress = new (phase->C, 2) DecodeNNode(new_phi, bottom_type());

     }

   }

 #endif

   return progress;              // Return any progress

 }

 //------------------------------is_tripcount-----------------------------------

 bool PhiNode::is_tripcount() const {

   return (in(0) != NULL && in(0)->is_CountedLoop() &&

           in(0)->as_CountedLoop()->phi() == this);

 }

 //------------------------------out_RegMask------------------------------------

 const RegMask &PhiNode::in_RegMask(uint i) const {

   return i ? out_RegMask() : RegMask::Empty;

 }

 const RegMask &PhiNode::out_RegMask() const {

   uint ideal_reg = Matcher::base2reg[_type->base()];

   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );

   if( ideal_reg == 0 ) return RegMask::Empty;

   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);

 }

 #ifndef PRODUCT

 void PhiNode::dump_spec(outputStream *st) const {

   TypeNode::dump_spec(st);

   if (is_tripcount()) {

     st->print(" #tripcount");

   }

 }

 #endif

 //=============================================================================

 const Type *GotoNode::Value( PhaseTransform *phase ) const {

   // If the input is reachable, then we are executed.

   // If the input is not reachable, then we are not executed.

   return phase->type(in(0));

 }

 Node *GotoNode::Identity( PhaseTransform *phase ) {

   return in(0);                // Simple copy of incoming control

 }

 const RegMask &GotoNode::out_RegMask() const {

   return RegMask::Empty;

 }

 //=============================================================================

 const RegMask &JumpNode::out_RegMask() const {

   return RegMask::Empty;

 }

 //=============================================================================

 const RegMask &JProjNode::out_RegMask() const {

   return RegMask::Empty;

 }

 //=============================================================================

 const RegMask &CProjNode::out_RegMask() const {

   return RegMask::Empty;

 }

 //=============================================================================

 uint PCTableNode::hash() const { return Node::hash() + _size; }

 uint PCTableNode::cmp( const Node &n ) const

 { return _size == ((PCTableNode&)n)._size; }

 const Type *PCTableNode::bottom_type() const {

   const Type** f = TypeTuple::fields(_size);

   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;

   return TypeTuple::make(_size, f);

 }

 //------------------------------Value------------------------------------------

 // Compute the type of the PCTableNode.  If reachable it is a tuple of

 // Control, otherwise the table targets are not reachable

 const Type *PCTableNode::Value( PhaseTransform *phase ) const {

   if( phase->type(in(0)) == Type::CONTROL )

     return bottom_type();

   return Type::TOP;             // All paths dead?  Then so are we

 }

 //------------------------------Ideal------------------------------------------

 // Return a node which is more "ideal" than the current node.  Strip out

 // control copies

 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   return remove_dead_region(phase, can_reshape) ? this : NULL;

 }

 //=============================================================================

 uint JumpProjNode::hash() const {

   return Node::hash() + _dest_bci;

 }

 uint JumpProjNode::cmp( const Node &n ) const {

   return ProjNode::cmp(n) &&

     _dest_bci == ((JumpProjNode&)n)._dest_bci;

 }

 #ifndef PRODUCT

 void JumpProjNode::dump_spec(outputStream *st) const {

   ProjNode::dump_spec(st);

    st->print("@bci %d ",_dest_bci);

 }

 #endif

 //=============================================================================

 //------------------------------Value------------------------------------------

 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot

 // have the default "fall_through_index" path.

 const Type *CatchNode::Value( PhaseTransform *phase ) const {

   // Unreachable?  Then so are all paths from here.

   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;

   // First assume all paths are reachable

   const Type** f = TypeTuple::fields(_size);

   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;

   // Identify cases that will always throw an exception

   // () rethrow call

   // () virtual or interface call with NULL receiver

   // () call is a check cast with incompatible arguments

   if( in(1)->is_Proj() ) {

     Node *i10 = in(1)->in(0);

     if( i10->is_Call() ) {

       CallNode *call = i10->as_Call();

       // Rethrows always throw exceptions, never return

       if (call->entry_point() == OptoRuntime::rethrow_stub()) {

         f[CatchProjNode::fall_through_index] = Type::TOP;

       } else if( call->req() > TypeFunc::Parms ) {

         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );

         // Check for null reciever to virtual or interface calls

         if( call->is_CallDynamicJava() &&

             arg0->higher_equal(TypePtr::NULL_PTR) ) {

           f[CatchProjNode::fall_through_index] = Type::TOP;

         }

       } // End of if not a runtime stub

     } // End of if have call above me

   } // End of slot 1 is not a projection

   return TypeTuple::make(_size, f);

 }

 //=============================================================================

 uint CatchProjNode::hash() const {

   return Node::hash() + _handler_bci;

 }

 uint CatchProjNode::cmp( const Node &n ) const {

   return ProjNode::cmp(n) &&

     _handler_bci == ((CatchProjNode&)n)._handler_bci;

 }

 //------------------------------Identity---------------------------------------

 // If only 1 target is possible, choose it if it is the main control

 Node *CatchProjNode::Identity( PhaseTransform *phase ) {

   // If my value is control and no other value is, then treat as ID

   const TypeTuple *t = phase->type(in(0))->is_tuple();

   if (t->field_at(_con) != Type::CONTROL)  return this;

   // If we remove the last CatchProj and elide the Catch/CatchProj, then we

   // also remove any exception table entry.  Thus we must know the call

   // feeding the Catch will not really throw an exception.  This is ok for

   // the main fall-thru control (happens when we know a call can never throw

   // an exception) or for "rethrow", because a further optimnization will

   // yank the rethrow (happens when we inline a function that can throw an

   // exception and the caller has no handler).  Not legal, e.g., for passing

   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.

   // These cases MUST throw an exception via the runtime system, so the VM

   // will be looking for a table entry.

   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode

   CallNode *call;

   if (_con != TypeFunc::Control && // Bail out if not the main control.

       !(proj->is_Proj() &&      // AND NOT a rethrow

         proj->in(0)->is_Call() &&

         (call = proj->in(0)->as_Call()) &&

         call->entry_point() == OptoRuntime::rethrow_stub()))

     return this;

   // Search for any other path being control

   for (uint i = 0; i < t->cnt(); i++) {

     if (i != _con && t->field_at(i) == Type::CONTROL)

       return this;

   }

   // Only my path is possible; I am identity on control to the jump

   return in(0)->in(0);

 }

 #ifndef PRODUCT

 void CatchProjNode::dump_spec(outputStream *st) const {

   ProjNode::dump_spec(st);

   st->print("@bci %d ",_handler_bci);

 }

 #endif

 //=============================================================================

 //------------------------------Identity---------------------------------------

 // Check for CreateEx being Identity.

 Node *CreateExNode::Identity( PhaseTransform *phase ) {

   if( phase->type(in(1)) == Type::TOP ) return in(1);

   if( phase->type(in(0)) == Type::TOP ) return in(0);

   // We only come from CatchProj, unless the CatchProj goes away.

   // If the CatchProj is optimized away, then we just carry the

   // exception oop through.

   CallNode *call = in(1)->in(0)->as_Call();

   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )

     ? this

     : call->in(TypeFunc::Parms);

 }

 //=============================================================================

 //------------------------------Value------------------------------------------

 // Check for being unreachable.

 const Type *NeverBranchNode::Value( PhaseTransform *phase ) const {

   if (!in(0) || in(0)->is_top()) return Type::TOP;

   return bottom_type();

 }

 //------------------------------Ideal------------------------------------------

 // Check for no longer being part of a loop

 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   if (can_reshape && !in(0)->is_Loop()) {

     // Dead code elimination can sometimes delete this projection so

     // if it's not there, there's nothing to do.

     Node* fallthru = proj_out(0);

     if (fallthru != NULL) {

       phase->is_IterGVN()->subsume_node(fallthru, in(0));

     }

     return phase->C->top();

   }

   return NULL;

 }

 #ifndef PRODUCT

 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {

   st->print("%s", Name());

 }

 #endif