1 /*
   2  * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/shared/barrierSet.hpp"
  27 #include "gc/shared/c2/barrierSetC2.hpp"
  28 #include "memory/allocation.inline.hpp"
  29 #include "memory/resourceArea.hpp"
  30 #include "oops/objArrayKlass.hpp"
  31 #include "opto/addnode.hpp"
  32 #include "opto/castnode.hpp"
  33 #include "opto/cfgnode.hpp"
  34 #include "opto/connode.hpp"
  35 #include "opto/convertnode.hpp"
  36 #include "opto/loopnode.hpp"
  37 #include "opto/machnode.hpp"
  38 #include "opto/movenode.hpp"
  39 #include "opto/narrowptrnode.hpp"
  40 #include "opto/mulnode.hpp"
  41 #include "opto/phaseX.hpp"
  42 #include "opto/regmask.hpp"
  43 #include "opto/runtime.hpp"
  44 #include "opto/subnode.hpp"
  45 #include "opto/vectornode.hpp"
  46 #include "utilities/vmError.hpp"
  47 
  48 // Portions of code courtesy of Clifford Click
  49 
  50 // Optimization - Graph Style
  51 
  52 //=============================================================================
  53 //------------------------------Value------------------------------------------
  54 // Compute the type of the RegionNode.
  55 const Type* RegionNode::Value(PhaseGVN* phase) const {
  56   for( uint i=1; i<req(); ++i ) {       // For all paths in
  57     Node *n = in(i);            // Get Control source
  58     if( !n ) continue;          // Missing inputs are TOP
  59     if( phase->type(n) == Type::CONTROL )
  60       return Type::CONTROL;
  61   }
  62   return Type::TOP;             // All paths dead?  Then so are we
  63 }
  64 
  65 //------------------------------Identity---------------------------------------
  66 // Check for Region being Identity.
  67 Node* RegionNode::Identity(PhaseGVN* phase) {
  68   // Cannot have Region be an identity, even if it has only 1 input.
  69   // Phi users cannot have their Region input folded away for them,
  70   // since they need to select the proper data input
  71   return this;
  72 }
  73 
  74 //------------------------------merge_region-----------------------------------
  75 // If a Region flows into a Region, merge into one big happy merge.  This is
  76 // hard to do if there is stuff that has to happen
  77 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  78   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  79     return NULL;
  80   Node *progress = NULL;        // Progress flag
  81   PhaseIterGVN *igvn = phase->is_IterGVN();
  82 
  83   uint rreq = region->req();
  84   for( uint i = 1; i < rreq; i++ ) {
  85     Node *r = region->in(i);
  86     if( r && r->Opcode() == Op_Region && // Found a region?
  87         r->in(0) == r &&        // Not already collapsed?
  88         r != region &&          // Avoid stupid situations
  89         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  90       assert(!r->as_Region()->has_phi(), "no phi users");
  91       if( !progress ) {         // No progress
  92         if (region->has_phi()) {
  93           return NULL;        // Only flatten if no Phi users
  94           // igvn->hash_delete( phi );
  95         }
  96         igvn->hash_delete( region );
  97         progress = region;      // Making progress
  98       }
  99       igvn->hash_delete( r );
 100 
 101       // Append inputs to 'r' onto 'region'
 102       for( uint j = 1; j < r->req(); j++ ) {
 103         // Move an input from 'r' to 'region'
 104         region->add_req(r->in(j));
 105         r->set_req(j, phase->C->top());
 106         // Update phis of 'region'
 107         //for( uint k = 0; k < max; k++ ) {
 108         //  Node *phi = region->out(k);
 109         //  if( phi->is_Phi() ) {
 110         //    phi->add_req(phi->in(i));
 111         //  }
 112         //}
 113 
 114         rreq++;                 // One more input to Region
 115       } // Found a region to merge into Region
 116       igvn->_worklist.push(r);
 117       // Clobber pointer to the now dead 'r'
 118       region->set_req(i, phase->C->top());
 119     }
 120   }
 121 
 122   return progress;
 123 }
 124 
 125 
 126 
 127 //--------------------------------has_phi--------------------------------------
 128 // Helper function: Return any PhiNode that uses this region or NULL
 129 PhiNode* RegionNode::has_phi() const {
 130   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 131     Node* phi = fast_out(i);
 132     if (phi->is_Phi()) {   // Check for Phi users
 133       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 134       return phi->as_Phi();  // this one is good enough
 135     }
 136   }
 137 
 138   return NULL;
 139 }
 140 
 141 
 142 //-----------------------------has_unique_phi----------------------------------
 143 // Helper function: Return the only PhiNode that uses this region or NULL
 144 PhiNode* RegionNode::has_unique_phi() const {
 145   // Check that only one use is a Phi
 146   PhiNode* only_phi = NULL;
 147   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 148     Node* phi = fast_out(i);
 149     if (phi->is_Phi()) {   // Check for Phi users
 150       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 151       if (only_phi == NULL) {
 152         only_phi = phi->as_Phi();
 153       } else {
 154         return NULL;  // multiple phis
 155       }
 156     }
 157   }
 158 
 159   return only_phi;
 160 }
 161 
 162 
 163 //------------------------------check_phi_clipping-----------------------------
 164 // Helper function for RegionNode's identification of FP clipping
 165 // Check inputs to the Phi
 166 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 167   min     = NULL;
 168   max     = NULL;
 169   val     = NULL;
 170   min_idx = 0;
 171   max_idx = 0;
 172   val_idx = 0;
 173   uint  phi_max = phi->req();
 174   if( phi_max == 4 ) {
 175     for( uint j = 1; j < phi_max; ++j ) {
 176       Node *n = phi->in(j);
 177       int opcode = n->Opcode();
 178       switch( opcode ) {
 179       case Op_ConI:
 180         {
 181           if( min == NULL ) {
 182             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 183             min_idx = j;
 184           } else {
 185             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 186             max_idx = j;
 187             if( min->get_int() > max->get_int() ) {
 188               // Swap min and max
 189               ConNode *temp;
 190               uint     temp_idx;
 191               temp     = min;     min     = max;     max     = temp;
 192               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 193             }
 194           }
 195         }
 196         break;
 197       default:
 198         {
 199           val = n;
 200           val_idx = j;
 201         }
 202         break;
 203       }
 204     }
 205   }
 206   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 207 }
 208 
 209 
 210 //------------------------------check_if_clipping------------------------------
 211 // Helper function for RegionNode's identification of FP clipping
 212 // Check that inputs to Region come from two IfNodes,
 213 //
 214 //            If
 215 //      False    True
 216 //       If        |
 217 //  False  True    |
 218 //    |      |     |
 219 //  RegionNode_inputs
 220 //
 221 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 222   top_if = NULL;
 223   bot_if = NULL;
 224 
 225   // Check control structure above RegionNode for (if  ( if  ) )
 226   Node *in1 = region->in(1);
 227   Node *in2 = region->in(2);
 228   Node *in3 = region->in(3);
 229   // Check that all inputs are projections
 230   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 231     Node *in10 = in1->in(0);
 232     Node *in20 = in2->in(0);
 233     Node *in30 = in3->in(0);
 234     // Check that #1 and #2 are ifTrue and ifFalse from same If
 235     if( in10 != NULL && in10->is_If() &&
 236         in20 != NULL && in20->is_If() &&
 237         in30 != NULL && in30->is_If() && in10 == in20 &&
 238         (in1->Opcode() != in2->Opcode()) ) {
 239       Node  *in100 = in10->in(0);
 240       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 241       // Check that control for in10 comes from other branch of IF from in3
 242       if( in1000 != NULL && in1000->is_If() &&
 243           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 244         // Control pattern checks
 245         top_if = (IfNode*)in1000;
 246         bot_if = (IfNode*)in10;
 247       }
 248     }
 249   }
 250 
 251   return (top_if != NULL);
 252 }
 253 
 254 
 255 //------------------------------check_convf2i_clipping-------------------------
 256 // Helper function for RegionNode's identification of FP clipping
 257 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 258 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 259   convf2i = NULL;
 260 
 261   // Check for the RShiftNode
 262   Node *rshift = phi->in(idx);
 263   assert( rshift, "Previous checks ensure phi input is present");
 264   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 265 
 266   // Check for the LShiftNode
 267   Node *lshift = rshift->in(1);
 268   assert( lshift, "Previous checks ensure phi input is present");
 269   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 270 
 271   // Check for the ConvF2INode
 272   Node *conv = lshift->in(1);
 273   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 274 
 275   // Check that shift amounts are only to get sign bits set after F2I
 276   jint max_cutoff     = max->get_int();
 277   jint min_cutoff     = min->get_int();
 278   jint left_shift     = lshift->in(2)->get_int();
 279   jint right_shift    = rshift->in(2)->get_int();
 280   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 281   if( left_shift != right_shift ||
 282       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 283       max_post_shift < max_cutoff ||
 284       max_post_shift < -min_cutoff ) {
 285     // Shifts are necessary but current transformation eliminates them
 286     return false;
 287   }
 288 
 289   // OK to return the result of ConvF2I without shifting
 290   convf2i = (ConvF2INode*)conv;
 291   return true;
 292 }
 293 
 294 
 295 //------------------------------check_compare_clipping-------------------------
 296 // Helper function for RegionNode's identification of FP clipping
 297 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 298   Node *i1 = iff->in(1);
 299   if ( !i1->is_Bool() ) { return false; }
 300   BoolNode *bool1 = i1->as_Bool();
 301   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 302   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 303   const Node *cmpF = bool1->in(1);
 304   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 305   // Test that the float value being compared against
 306   // is equivalent to the int value used as a limit
 307   Node *nodef = cmpF->in(2);
 308   if( nodef->Opcode() != Op_ConF ) { return false; }
 309   jfloat conf = nodef->getf();
 310   jint   coni = limit->get_int();
 311   if( ((int)conf) != coni )        { return false; }
 312   input = cmpF->in(1);
 313   return true;
 314 }
 315 
 316 //------------------------------is_unreachable_region--------------------------
 317 // Find if the Region node is reachable from the root.
 318 bool RegionNode::is_unreachable_region(const PhaseGVN* phase) {
 319   Node* top = phase->C->top();
 320   assert(req() == 2 || (req() == 3 && in(1) != NULL && in(2) == top), "sanity check arguments");
 321   if (_is_unreachable_region) {
 322     // Return cached result from previous evaluation which should still be valid
 323     assert(is_unreachable_from_root(phase), "walk the graph again and check if its indeed unreachable");
 324     return true;
 325   }
 326 
 327   // First, cut the simple case of fallthrough region when NONE of
 328   // region's phis references itself directly or through a data node.
 329   if (is_possible_unsafe_loop(phase)) {
 330     // If we have a possible unsafe loop, check if the region node is actually unreachable from root.
 331     if (is_unreachable_from_root(phase)) {
 332       _is_unreachable_region = true;
 333       return true;
 334     }
 335   }
 336   return false;
 337 }
 338 
 339 bool RegionNode::is_possible_unsafe_loop(const PhaseGVN* phase) const {
 340   uint max = outcnt();
 341   uint i;
 342   for (i = 0; i < max; i++) {
 343     Node* n = raw_out(i);
 344     if (n != NULL && n->is_Phi()) {
 345       PhiNode* phi = n->as_Phi();
 346       assert(phi->in(0) == this, "sanity check phi");
 347       if (phi->outcnt() == 0) {
 348         continue; // Safe case - no loops
 349       }
 350       if (phi->outcnt() == 1) {
 351         Node* u = phi->raw_out(0);
 352         // Skip if only one use is an other Phi or Call or Uncommon trap.
 353         // It is safe to consider this case as fallthrough.
 354         if (u != NULL && (u->is_Phi() || u->is_CFG())) {
 355           continue;
 356         }
 357       }
 358       // Check when phi references itself directly or through an other node.
 359       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe) {
 360         break; // Found possible unsafe data loop.
 361       }
 362     }
 363   }
 364   if (i >= max) {
 365     return false; // An unsafe case was NOT found - don't need graph walk.
 366   }
 367   return true;
 368 }
 369 
 370 bool RegionNode::is_unreachable_from_root(const PhaseGVN* phase) const {
 371   ResourceMark rm;
 372   Node_List nstack;
 373   VectorSet visited;
 374 
 375   // Mark all control nodes reachable from root outputs
 376   Node *n = (Node*)phase->C->root();
 377   nstack.push(n);
 378   visited.set(n->_idx);
 379   while (nstack.size() != 0) {
 380     n = nstack.pop();
 381     uint max = n->outcnt();
 382     for (uint i = 0; i < max; i++) {
 383       Node* m = n->raw_out(i);
 384       if (m != NULL && m->is_CFG()) {
 385         if (m == this) {
 386           return false; // We reached the Region node - it is not dead.
 387         }
 388         if (!visited.test_set(m->_idx))
 389           nstack.push(m);
 390       }
 391     }
 392   }
 393   return true; // The Region node is unreachable - it is dead.
 394 }
 395 
 396 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 397   // Incremental inlining + PhaseStringOpts sometimes produce:
 398   //
 399   // cmpP with 1 top input
 400   //           |
 401   //          If
 402   //         /  \
 403   //   IfFalse  IfTrue  /- Some Node
 404   //         \  /      /    /
 405   //        Region    / /-MergeMem
 406   //             \---Phi
 407   //
 408   //
 409   // It's expected by PhaseStringOpts that the Region goes away and is
 410   // replaced by If's control input but because there's still a Phi,
 411   // the Region stays in the graph. The top input from the cmpP is
 412   // propagated forward and a subgraph that is useful goes away. The
 413   // code below replaces the Phi with the MergeMem so that the Region
 414   // is simplified.
 415 
 416   PhiNode* phi = has_unique_phi();
 417   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 418     MergeMemNode* m = NULL;
 419     assert(phi->req() == 3, "same as region");
 420     for (uint i = 1; i < 3; ++i) {
 421       Node *mem = phi->in(i);
 422       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 423         // Nothing is control-dependent on path #i except the region itself.
 424         m = mem->as_MergeMem();
 425         uint j = 3 - i;
 426         Node* other = phi->in(j);
 427         if (other && other == m->base_memory()) {
 428           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 429           // This will allow the diamond to collapse completely.
 430           phase->is_IterGVN()->replace_node(phi, m);
 431           return true;
 432         }
 433       }
 434     }
 435   }
 436   return false;
 437 }
 438 
 439 //------------------------------Ideal------------------------------------------
 440 // Return a node which is more "ideal" than the current node.  Must preserve
 441 // the CFG, but we can still strip out dead paths.
 442 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 443   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 444   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 445 
 446   // Check for RegionNode with no Phi users and both inputs come from either
 447   // arm of the same IF.  If found, then the control-flow split is useless.
 448   bool has_phis = false;
 449   if (can_reshape) {            // Need DU info to check for Phi users
 450     has_phis = (has_phi() != NULL);       // Cache result
 451     if (has_phis && try_clean_mem_phi(phase)) {
 452       has_phis = false;
 453     }
 454 
 455     if (!has_phis) {            // No Phi users?  Nothing merging?
 456       for (uint i = 1; i < req()-1; i++) {
 457         Node *if1 = in(i);
 458         if( !if1 ) continue;
 459         Node *iff = if1->in(0);
 460         if( !iff || !iff->is_If() ) continue;
 461         for( uint j=i+1; j<req(); j++ ) {
 462           if( in(j) && in(j)->in(0) == iff &&
 463               if1->Opcode() != in(j)->Opcode() ) {
 464             // Add the IF Projections to the worklist. They (and the IF itself)
 465             // will be eliminated if dead.
 466             phase->is_IterGVN()->add_users_to_worklist(iff);
 467             set_req(i, iff->in(0));// Skip around the useless IF diamond
 468             set_req(j, NULL);
 469             return this;      // Record progress
 470           }
 471         }
 472       }
 473     }
 474   }
 475 
 476   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 477   // degrades to a copy.
 478   bool add_to_worklist = false;
 479   bool modified = false;
 480   int cnt = 0;                  // Count of values merging
 481   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 482   int del_it = 0;               // The last input path we delete
 483   // For all inputs...
 484   for( uint i=1; i<req(); ++i ){// For all paths in
 485     Node *n = in(i);            // Get the input
 486     if( n != NULL ) {
 487       // Remove useless control copy inputs
 488       if( n->is_Region() && n->as_Region()->is_copy() ) {
 489         set_req(i, n->nonnull_req());
 490         modified = true;
 491         i--;
 492         continue;
 493       }
 494       if( n->is_Proj() ) {      // Remove useless rethrows
 495         Node *call = n->in(0);
 496         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 497           set_req(i, call->in(0));
 498           modified = true;
 499           i--;
 500           continue;
 501         }
 502       }
 503       if( phase->type(n) == Type::TOP ) {
 504         set_req(i, NULL);       // Ignore TOP inputs
 505         modified = true;
 506         i--;
 507         continue;
 508       }
 509       cnt++;                    // One more value merging
 510 
 511     } else if (can_reshape) {   // Else found dead path with DU info
 512       PhaseIterGVN *igvn = phase->is_IterGVN();
 513       del_req(i);               // Yank path from self
 514       del_it = i;
 515       uint max = outcnt();
 516       DUIterator j;
 517       bool progress = true;
 518       while(progress) {         // Need to establish property over all users
 519         progress = false;
 520         for (j = outs(); has_out(j); j++) {
 521           Node *n = out(j);
 522           if( n->req() != req() && n->is_Phi() ) {
 523             assert( n->in(0) == this, "" );
 524             igvn->hash_delete(n); // Yank from hash before hacking edges
 525             n->set_req_X(i,NULL,igvn);// Correct DU info
 526             n->del_req(i);        // Yank path from Phis
 527             if( max != outcnt() ) {
 528               progress = true;
 529               j = refresh_out_pos(j);
 530               max = outcnt();
 531             }
 532           }
 533         }
 534       }
 535       add_to_worklist = true;
 536       i--;
 537     }
 538   }
 539 
 540   if (can_reshape && cnt == 1) {
 541     // Is it dead loop?
 542     // If it is LoopNopde it had 2 (+1 itself) inputs and
 543     // one of them was cut. The loop is dead if it was EntryContol.
 544     // Loop node may have only one input because entry path
 545     // is removed in PhaseIdealLoop::Dominators().
 546     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 547     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 548                              (del_it == 0 && is_unreachable_region(phase)))) ||
 549         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 550       // Yes,  the region will be removed during the next step below.
 551       // Cut the backedge input and remove phis since no data paths left.
 552       // We don't cut outputs to other nodes here since we need to put them
 553       // on the worklist.
 554       PhaseIterGVN *igvn = phase->is_IterGVN();
 555       if (in(1)->outcnt() == 1) {
 556         igvn->_worklist.push(in(1));
 557       }
 558       del_req(1);
 559       cnt = 0;
 560       assert( req() == 1, "no more inputs expected" );
 561       uint max = outcnt();
 562       bool progress = true;
 563       Node *top = phase->C->top();
 564       DUIterator j;
 565       while(progress) {
 566         progress = false;
 567         for (j = outs(); has_out(j); j++) {
 568           Node *n = out(j);
 569           if( n->is_Phi() ) {
 570             assert(n->in(0) == this, "");
 571             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 572             // Break dead loop data path.
 573             // Eagerly replace phis with top to avoid regionless phis.
 574             igvn->replace_node(n, top);
 575             if( max != outcnt() ) {
 576               progress = true;
 577               j = refresh_out_pos(j);
 578               max = outcnt();
 579             }
 580           }
 581         }
 582       }
 583       add_to_worklist = true;
 584     }
 585   }
 586   if (add_to_worklist) {
 587     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 588   }
 589 
 590   if( cnt <= 1 ) {              // Only 1 path in?
 591     set_req(0, NULL);           // Null control input for region copy
 592     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 593       // No inputs or all inputs are NULL.
 594       return NULL;
 595     } else if (can_reshape) {   // Optimization phase - remove the node
 596       PhaseIterGVN *igvn = phase->is_IterGVN();
 597       // Strip mined (inner) loop is going away, remove outer loop.
 598       if (is_CountedLoop() &&
 599           as_Loop()->is_strip_mined()) {
 600         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 601         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 602         if (outer_sfpt != NULL && outer_out != NULL) {
 603           Node* in = outer_sfpt->in(0);
 604           igvn->replace_node(outer_out, in);
 605           LoopNode* outer = as_CountedLoop()->outer_loop();
 606           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 607         }
 608       }
 609       if (is_CountedLoop()) {
 610         Node* opaq = as_CountedLoop()->is_canonical_loop_entry();
 611         if (opaq != NULL) {
 612           // This is not a loop anymore. No need to keep the Opaque1 node on the test that guards the loop as it won't be
 613           // subject to further loop opts.
 614           assert(opaq->Opcode() == Op_Opaque1, "");
 615           igvn->replace_node(opaq, opaq->in(1));
 616         }
 617       }
 618       Node *parent_ctrl;
 619       if( cnt == 0 ) {
 620         assert( req() == 1, "no inputs expected" );
 621         // During IGVN phase such region will be subsumed by TOP node
 622         // so region's phis will have TOP as control node.
 623         // Kill phis here to avoid it.
 624         // Also set other user's input to top.
 625         parent_ctrl = phase->C->top();
 626       } else {
 627         // The fallthrough case since we already checked dead loops above.
 628         parent_ctrl = in(1);
 629         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 630         assert(parent_ctrl != this, "Close dead loop");
 631       }
 632       if (!add_to_worklist)
 633         igvn->add_users_to_worklist(this); // Check for further allowed opts
 634       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 635         Node* n = last_out(i);
 636         igvn->hash_delete(n); // Remove from worklist before modifying edges
 637         if (n->outcnt() == 0) {
 638           int uses_found = n->replace_edge(this, phase->C->top(), igvn);
 639           if (uses_found > 1) { // (--i) done at the end of the loop.
 640             i -= (uses_found - 1);
 641           }
 642           continue;
 643         }
 644         if( n->is_Phi() ) {   // Collapse all Phis
 645           // Eagerly replace phis to avoid regionless phis.
 646           Node* in;
 647           if( cnt == 0 ) {
 648             assert( n->req() == 1, "No data inputs expected" );
 649             in = parent_ctrl; // replaced by top
 650           } else {
 651             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 652             in = n->in(1);               // replaced by unique input
 653             if( n->as_Phi()->is_unsafe_data_reference(in) )
 654               in = phase->C->top();      // replaced by top
 655           }
 656           igvn->replace_node(n, in);
 657         }
 658         else if( n->is_Region() ) { // Update all incoming edges
 659           assert(n != this, "Must be removed from DefUse edges");
 660           int uses_found = n->replace_edge(this, parent_ctrl, igvn);
 661           if (uses_found > 1) { // (--i) done at the end of the loop.
 662             i -= (uses_found - 1);
 663           }
 664         }
 665         else {
 666           assert(n->in(0) == this, "Expect RegionNode to be control parent");
 667           n->set_req(0, parent_ctrl);
 668         }
 669 #ifdef ASSERT
 670         for( uint k=0; k < n->req(); k++ ) {
 671           assert(n->in(k) != this, "All uses of RegionNode should be gone");
 672         }
 673 #endif
 674       }
 675       // Remove the RegionNode itself from DefUse info
 676       igvn->remove_dead_node(this);
 677       return NULL;
 678     }
 679     return this;                // Record progress
 680   }
 681 
 682 
 683   // If a Region flows into a Region, merge into one big happy merge.
 684   if (can_reshape) {
 685     Node *m = merge_region(this, phase);
 686     if (m != NULL)  return m;
 687   }
 688 
 689   // Check if this region is the root of a clipping idiom on floats
 690   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 691     // Check that only one use is a Phi and that it simplifies to two constants +
 692     PhiNode* phi = has_unique_phi();
 693     if (phi != NULL) {          // One Phi user
 694       // Check inputs to the Phi
 695       ConNode *min;
 696       ConNode *max;
 697       Node    *val;
 698       uint     min_idx;
 699       uint     max_idx;
 700       uint     val_idx;
 701       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 702         IfNode *top_if;
 703         IfNode *bot_if;
 704         if( check_if_clipping( this, bot_if, top_if ) ) {
 705           // Control pattern checks, now verify compares
 706           Node   *top_in = NULL;   // value being compared against
 707           Node   *bot_in = NULL;
 708           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 709               check_compare_clipping( false, top_if, max, top_in ) ) {
 710             if( bot_in == top_in ) {
 711               PhaseIterGVN *gvn = phase->is_IterGVN();
 712               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 713               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 714 
 715               // Check for the ConvF2INode
 716               ConvF2INode *convf2i;
 717               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 718                 convf2i->in(1) == bot_in ) {
 719                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 720                 // max test
 721                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 722                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 723                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 724                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 725                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 726                 // min test
 727                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 728                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 729                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 730                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 731                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 732                 // update input edges to region node
 733                 set_req_X( min_idx, if_min, gvn );
 734                 set_req_X( max_idx, if_max, gvn );
 735                 set_req_X( val_idx, ifF,    gvn );
 736                 // remove unnecessary 'LShiftI; RShiftI' idiom
 737                 gvn->hash_delete(phi);
 738                 phi->set_req_X( val_idx, convf2i, gvn );
 739                 gvn->hash_find_insert(phi);
 740                 // Return transformed region node
 741                 return this;
 742               }
 743             }
 744           }
 745         }
 746       }
 747     }
 748   }
 749 
 750   if (can_reshape) {
 751     modified |= optimize_trichotomy(phase->is_IterGVN());
 752   }
 753 
 754   return modified ? this : NULL;
 755 }
 756 
 757 //------------------------------optimize_trichotomy--------------------------
 758 // Optimize nested comparisons of the following kind:
 759 //
 760 // int compare(int a, int b) {
 761 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 762 // }
 763 //
 764 // Shape 1:
 765 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 766 //
 767 // Shape 2:
 768 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 769 //
 770 // Above code leads to the following IR shapes where both Ifs compare the
 771 // same value and two out of three region inputs idx1 and idx2 map to
 772 // the same value and control flow.
 773 //
 774 // (1)   If                 (2)   If
 775 //      /  \                     /  \
 776 //   Proj  Proj               Proj  Proj
 777 //     |      \                |      \
 778 //     |       If              |      If                      If
 779 //     |      /  \             |     /  \                    /  \
 780 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 781 //     |   /      /            \    |    /                  |    /
 782 //    Region     /              \   |   /                   |   /
 783 //         \    /                \  |  /                    |  /
 784 //         Region                Region                    Region
 785 //
 786 // The method returns true if 'this' is modified and false otherwise.
 787 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 788   int idx1 = 1, idx2 = 2;
 789   Node* region = NULL;
 790   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 791     // Shape 1: Check if one of the inputs is a region that merges two control
 792     // inputs and has no other users (especially no Phi users).
 793     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 794     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 795       return false; // No suitable region input found
 796     }
 797   } else if (req() == 4) {
 798     // Shape 2: Check if two control inputs map to the same value of the unique phi
 799     // user and treat these as if they would come from another region (shape (1)).
 800     PhiNode* phi = has_unique_phi();
 801     if (phi == NULL) {
 802       return false; // No unique phi user
 803     }
 804     if (phi->in(idx1) != phi->in(idx2)) {
 805       idx2 = 3;
 806       if (phi->in(idx1) != phi->in(idx2)) {
 807         idx1 = 2;
 808         if (phi->in(idx1) != phi->in(idx2)) {
 809           return false; // No equal phi inputs found
 810         }
 811       }
 812     }
 813     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 814     region = this;
 815   }
 816   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 817     return false; // Region does not merge two control inputs
 818   }
 819   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 820   // value and control flow. Now search for ifs that feed into these region inputs.
 821   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 822   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 823   if (proj1 == NULL || proj1->outcnt() != 1 ||
 824       proj2 == NULL || proj2->outcnt() != 1) {
 825     return false; // No projection inputs with region as unique user found
 826   }
 827   assert(proj1 != proj2, "should be different projections");
 828   IfNode* iff1 = proj1->in(0)->isa_If();
 829   IfNode* iff2 = proj2->in(0)->isa_If();
 830   if (iff1 == NULL || iff1->outcnt() != 2 ||
 831       iff2 == NULL || iff2->outcnt() != 2) {
 832     return false; // No ifs found
 833   }
 834   if (iff1 == iff2) {
 835     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 836     igvn->replace_input_of(region, idx1, iff1->in(0));
 837     igvn->replace_input_of(region, idx2, igvn->C->top());
 838     return (region == this); // Remove useless if (both projections map to the same control/value)
 839   }
 840   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 841   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 842   if (bol1 == NULL || bol2 == NULL) {
 843     return false; // No bool inputs found
 844   }
 845   Node* cmp1 = bol1->in(1);
 846   Node* cmp2 = bol2->in(1);
 847   bool commute = false;
 848   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 849     return false; // No comparison
 850   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 851              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 852              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 853              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN ||
 854              cmp1->is_SubTypeCheck() || cmp2->is_SubTypeCheck()) {
 855     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 856     // SubTypeCheck is not commutative
 857     return false;
 858   } else if (cmp1 != cmp2) {
 859     if (cmp1->in(1) == cmp2->in(2) &&
 860         cmp1->in(2) == cmp2->in(1)) {
 861       commute = true; // Same but swapped inputs, commute the test
 862     } else {
 863       return false; // Ifs are not comparing the same values
 864     }
 865   }
 866   proj1 = proj1->other_if_proj();
 867   proj2 = proj2->other_if_proj();
 868   if (!((proj1->unique_ctrl_out() == iff2 &&
 869          proj2->unique_ctrl_out() == this) ||
 870         (proj2->unique_ctrl_out() == iff1 &&
 871          proj1->unique_ctrl_out() == this))) {
 872     return false; // Ifs are not connected through other projs
 873   }
 874   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 875   // through 'region' and map to the same value. Merge the boolean tests and replace
 876   // the ifs by a single comparison.
 877   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 878   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 879   test1 = commute ? test1.commute() : test1;
 880   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 881   BoolTest::mask res = test1.merge(test2);
 882   if (res == BoolTest::illegal) {
 883     return false; // Unable to merge tests
 884   }
 885   // Adjust iff1 to always pass (only iff2 will remain)
 886   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 887   if (res == BoolTest::never) {
 888     // Merged test is always false, adjust iff2 to always fail
 889     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 890   } else {
 891     // Replace bool input of iff2 with merged test
 892     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 893     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 894     if (new_bol->outcnt() == 0) {
 895       igvn->remove_dead_node(new_bol);
 896     }
 897   }
 898   return false;
 899 }
 900 
 901 const RegMask &RegionNode::out_RegMask() const {
 902   return RegMask::Empty;
 903 }
 904 
 905 // Find the one non-null required input.  RegionNode only
 906 Node *Node::nonnull_req() const {
 907   assert( is_Region(), "" );
 908   for( uint i = 1; i < _cnt; i++ )
 909     if( in(i) )
 910       return in(i);
 911   ShouldNotReachHere();
 912   return NULL;
 913 }
 914 
 915 
 916 //=============================================================================
 917 // note that these functions assume that the _adr_type field is flattened
 918 uint PhiNode::hash() const {
 919   const Type* at = _adr_type;
 920   return TypeNode::hash() + (at ? at->hash() : 0);
 921 }
 922 bool PhiNode::cmp( const Node &n ) const {
 923   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 924 }
 925 static inline
 926 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 927   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 928   return Compile::current()->alias_type(at)->adr_type();
 929 }
 930 
 931 //----------------------------make---------------------------------------------
 932 // create a new phi with edges matching r and set (initially) to x
 933 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 934   uint preds = r->req();   // Number of predecessor paths
 935   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 936   PhiNode* p = new PhiNode(r, t, at);
 937   for (uint j = 1; j < preds; j++) {
 938     // Fill in all inputs, except those which the region does not yet have
 939     if (r->in(j) != NULL)
 940       p->init_req(j, x);
 941   }
 942   return p;
 943 }
 944 PhiNode* PhiNode::make(Node* r, Node* x) {
 945   const Type*    t  = x->bottom_type();
 946   const TypePtr* at = NULL;
 947   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 948   return make(r, x, t, at);
 949 }
 950 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 951   const Type*    t  = x->bottom_type();
 952   const TypePtr* at = NULL;
 953   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 954   return new PhiNode(r, t, at);
 955 }
 956 
 957 
 958 //------------------------slice_memory-----------------------------------------
 959 // create a new phi with narrowed memory type
 960 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 961   PhiNode* mem = (PhiNode*) clone();
 962   *(const TypePtr**)&mem->_adr_type = adr_type;
 963   // convert self-loops, or else we get a bad graph
 964   for (uint i = 1; i < req(); i++) {
 965     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 966   }
 967   mem->verify_adr_type();
 968   return mem;
 969 }
 970 
 971 //------------------------split_out_instance-----------------------------------
 972 // Split out an instance type from a bottom phi.
 973 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 974   const TypeOopPtr *t_oop = at->isa_oopptr();
 975   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 976   const TypePtr *t = adr_type();
 977   assert(type() == Type::MEMORY &&
 978          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 979           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 980           t->is_oopptr()->cast_to_exactness(true)
 981            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 982            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 983          "bottom or raw memory required");
 984 
 985   // Check if an appropriate node already exists.
 986   Node *region = in(0);
 987   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 988     Node* use = region->fast_out(k);
 989     if( use->is_Phi()) {
 990       PhiNode *phi2 = use->as_Phi();
 991       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 992         return phi2;
 993       }
 994     }
 995   }
 996   Compile *C = igvn->C;
 997   Arena *a = Thread::current()->resource_area();
 998   Node_Array node_map = new Node_Array(a);
 999   Node_Stack stack(a, C->live_nodes() >> 4);
1000   PhiNode *nphi = slice_memory(at);
1001   igvn->register_new_node_with_optimizer( nphi );
1002   node_map.map(_idx, nphi);
1003   stack.push((Node *)this, 1);
1004   while(!stack.is_empty()) {
1005     PhiNode *ophi = stack.node()->as_Phi();
1006     uint i = stack.index();
1007     assert(i >= 1, "not control edge");
1008     stack.pop();
1009     nphi = node_map[ophi->_idx]->as_Phi();
1010     for (; i < ophi->req(); i++) {
1011       Node *in = ophi->in(i);
1012       if (in == NULL || igvn->type(in) == Type::TOP)
1013         continue;
1014       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
1015       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
1016       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
1017         opt = node_map[optphi->_idx];
1018         if (opt == NULL) {
1019           stack.push(ophi, i);
1020           nphi = optphi->slice_memory(at);
1021           igvn->register_new_node_with_optimizer( nphi );
1022           node_map.map(optphi->_idx, nphi);
1023           ophi = optphi;
1024           i = 0; // will get incremented at top of loop
1025           continue;
1026         }
1027       }
1028       nphi->set_req(i, opt);
1029     }
1030   }
1031   return nphi;
1032 }
1033 
1034 //------------------------verify_adr_type--------------------------------------
1035 #ifdef ASSERT
1036 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1037   if (visited.test_set(_idx))  return;  //already visited
1038 
1039   // recheck constructor invariants:
1040   verify_adr_type(false);
1041 
1042   // recheck local phi/phi consistency:
1043   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1044          "adr_type must be consistent across phi nest");
1045 
1046   // walk around
1047   for (uint i = 1; i < req(); i++) {
1048     Node* n = in(i);
1049     if (n == NULL)  continue;
1050     const Node* np = in(i);
1051     if (np->is_Phi()) {
1052       np->as_Phi()->verify_adr_type(visited, at);
1053     } else if (n->bottom_type() == Type::TOP
1054                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1055       // ignore top inputs
1056     } else {
1057       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1058       // recheck phi/non-phi consistency at leaves:
1059       assert((nat != NULL) == (at != NULL), "");
1060       assert(nat == at || nat == TypePtr::BOTTOM,
1061              "adr_type must be consistent at leaves of phi nest");
1062     }
1063   }
1064 }
1065 
1066 // Verify a whole nest of phis rooted at this one.
1067 void PhiNode::verify_adr_type(bool recursive) const {
1068   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1069   if (Node::in_dump())               return;  // muzzle asserts when printing
1070 
1071   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1072 
1073   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1074 
1075   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1076          "Phi::adr_type must be pre-normalized");
1077 
1078   if (recursive) {
1079     VectorSet visited;
1080     verify_adr_type(visited, _adr_type);
1081   }
1082 }
1083 #endif
1084 
1085 
1086 //------------------------------Value------------------------------------------
1087 // Compute the type of the PhiNode
1088 const Type* PhiNode::Value(PhaseGVN* phase) const {
1089   Node *r = in(0);              // RegionNode
1090   if( !r )                      // Copy or dead
1091     return in(1) ? phase->type(in(1)) : Type::TOP;
1092 
1093   // Note: During parsing, phis are often transformed before their regions.
1094   // This means we have to use type_or_null to defend against untyped regions.
1095   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1096     return Type::TOP;
1097 
1098   // Check for trip-counted loop.  If so, be smarter.
1099   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : NULL;
1100   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1101     // protect against init_trip() or limit() returning NULL
1102     if (l->can_be_counted_loop(phase)) {
1103       const Node* init = l->init_trip();
1104       const Node* limit = l->limit();
1105       const Node* stride = l->stride();
1106       if (init != NULL && limit != NULL && stride != NULL) {
1107         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1108         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1109         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1110         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1111           assert(stride_t->hi_as_long() >= stride_t->lo_as_long(), "bad stride type");
1112           BoolTest::mask bt = l->loopexit()->test_trip();
1113           // If the loop exit condition is "not equal", the condition
1114           // would not trigger if init > limit (if stride > 0) or if
1115           // init < limit if (stride > 0) so we can't deduce bounds
1116           // for the iv from the exit condition.
1117           if (bt != BoolTest::ne) {
1118             if (stride_t->hi_as_long() < 0) {          // Down-counter loop
1119               swap(lo, hi);
1120               return TypeInteger::make(MIN2(lo->lo_as_long(), hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1121             } else if (stride_t->lo_as_long() >= 0) {
1122               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), hi->hi_as_long()), 3, l->bt())->filter_speculative(_type);
1123             }
1124           }
1125         }
1126       }
1127     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1128                in(LoopNode::EntryControl) != NULL &&
1129                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1130       // During CCP, if we saturate the type of a counted loop's Phi
1131       // before the special code for counted loop above has a chance
1132       // to run (that is as long as the type of the backedge's control
1133       // is top), we might end up with non monotonic types
1134       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1135     }
1136   }
1137 
1138   // Until we have harmony between classes and interfaces in the type
1139   // lattice, we must tread carefully around phis which implicitly
1140   // convert the one to the other.
1141   const TypePtr* ttp = _type->make_ptr();
1142   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1143   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_instklassptr() : NULL;
1144   bool is_intf = false;
1145   if (ttip != NULL) {
1146     ciKlass* k = ttip->klass();
1147     if (k->is_loaded() && k->is_interface())
1148       is_intf = true;
1149   }
1150   if (ttkp != NULL) {
1151     ciKlass* k = ttkp->klass();
1152     if (k->is_loaded() && k->is_interface())
1153       is_intf = true;
1154   }
1155 
1156   // Default case: merge all inputs
1157   const Type *t = Type::TOP;        // Merged type starting value
1158   for (uint i = 1; i < req(); ++i) {// For all paths in
1159     // Reachable control path?
1160     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1161       const Type* ti = phase->type(in(i));
1162       // We assume that each input of an interface-valued Phi is a true
1163       // subtype of that interface.  This might not be true of the meet
1164       // of all the input types.  The lattice is not distributive in
1165       // such cases.  Ward off asserts in type.cpp by refusing to do
1166       // meets between interfaces and proper classes.
1167       const TypePtr* tip = ti->make_ptr();
1168       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1169       if (tiip) {
1170         bool ti_is_intf = false;
1171         ciKlass* k = tiip->klass();
1172         if (k->is_loaded() && k->is_interface())
1173           ti_is_intf = true;
1174         if (is_intf != ti_is_intf)
1175           { t = _type; break; }
1176       }
1177       t = t->meet_speculative(ti);
1178     }
1179   }
1180 
1181   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1182   // That is, we expect that "t->higher_equal(_type)" holds true.
1183   // There are various exceptions:
1184   // - Inputs which are phis might in fact be widened unnecessarily.
1185   //   For example, an input might be a widened int while the phi is a short.
1186   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1187   //   and postCCP has removed the cast which encodes the result of the check.
1188   // - The type of this phi is an interface, and the inputs are classes.
1189   // - Value calls on inputs might produce fuzzy results.
1190   //   (Occurrences of this case suggest improvements to Value methods.)
1191   //
1192   // It is not possible to see Type::BOTTOM values as phi inputs,
1193   // because the ciTypeFlow pre-pass produces verifier-quality types.
1194   const Type* ft = t->filter_speculative(_type);  // Worst case type
1195 
1196 #ifdef ASSERT
1197   // The following logic has been moved into TypeOopPtr::filter.
1198   const Type* jt = t->join_speculative(_type);
1199   if (jt->empty()) {           // Emptied out???
1200 
1201     // Check for evil case of 't' being a class and '_type' expecting an
1202     // interface.  This can happen because the bytecodes do not contain
1203     // enough type info to distinguish a Java-level interface variable
1204     // from a Java-level object variable.  If we meet 2 classes which
1205     // both implement interface I, but their meet is at 'j/l/O' which
1206     // doesn't implement I, we have no way to tell if the result should
1207     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1208     // into a Phi which "knows" it's an Interface type we'll have to
1209     // uplift the type.
1210     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1211       assert(ft == _type, ""); // Uplift to interface
1212     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1213       assert(ft == _type, ""); // Uplift to interface
1214     } else {
1215       // We also have to handle 'evil cases' of interface- vs. class-arrays
1216       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1217       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1218           assert(ft == _type, "");   // Uplift to array of interface
1219       } else {
1220         // Otherwise it's something stupid like non-overlapping int ranges
1221         // found on dying counted loops.
1222         assert(ft == Type::TOP, ""); // Canonical empty value
1223       }
1224     }
1225   }
1226 
1227   else {
1228 
1229     // If we have an interface-typed Phi and we narrow to a class type, the join
1230     // should report back the class.  However, if we have a J/L/Object
1231     // class-typed Phi and an interface flows in, it's possible that the meet &
1232     // join report an interface back out.  This isn't possible but happens
1233     // because the type system doesn't interact well with interfaces.
1234     const TypePtr *jtp = jt->make_ptr();
1235     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1236     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_instklassptr() : NULL;
1237     if( jtip && ttip ) {
1238       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1239           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1240         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1241                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1242         jt = ft;
1243       }
1244     }
1245     if( jtkp && ttkp ) {
1246       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1247           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1248           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1249         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1250                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1251         jt = ft;
1252       }
1253     }
1254     if (jt != ft && jt->base() == ft->base()) {
1255       if (jt->isa_int() &&
1256           jt->is_int()->_lo == ft->is_int()->_lo &&
1257           jt->is_int()->_hi == ft->is_int()->_hi)
1258         jt = ft;
1259       if (jt->isa_long() &&
1260           jt->is_long()->_lo == ft->is_long()->_lo &&
1261           jt->is_long()->_hi == ft->is_long()->_hi)
1262         jt = ft;
1263     }
1264     if (jt != ft) {
1265       tty->print("merge type:  "); t->dump(); tty->cr();
1266       tty->print("kill type:   "); _type->dump(); tty->cr();
1267       tty->print("join type:   "); jt->dump(); tty->cr();
1268       tty->print("filter type: "); ft->dump(); tty->cr();
1269     }
1270     assert(jt == ft, "");
1271   }
1272 #endif //ASSERT
1273 
1274   // Deal with conversion problems found in data loops.
1275   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1276 
1277   return ft;
1278 }
1279 
1280 
1281 //------------------------------is_diamond_phi---------------------------------
1282 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1283 // index of the true path or 0 otherwise.
1284 // If check_control_only is true, do not inspect the If node at the
1285 // top, and return -1 (not an edge number) on success.
1286 int PhiNode::is_diamond_phi(bool check_control_only) const {
1287   // Check for a 2-path merge
1288   Node *region = in(0);
1289   if( !region ) return 0;
1290   if( region->req() != 3 ) return 0;
1291   if(         req() != 3 ) return 0;
1292   // Check that both paths come from the same If
1293   Node *ifp1 = region->in(1);
1294   Node *ifp2 = region->in(2);
1295   if( !ifp1 || !ifp2 ) return 0;
1296   Node *iff = ifp1->in(0);
1297   if( !iff || !iff->is_If() ) return 0;
1298   if( iff != ifp2->in(0) ) return 0;
1299   if (check_control_only)  return -1;
1300   // Check for a proper bool/cmp
1301   const Node *b = iff->in(1);
1302   if( !b->is_Bool() ) return 0;
1303   const Node *cmp = b->in(1);
1304   if( !cmp->is_Cmp() ) return 0;
1305 
1306   // Check for branching opposite expected
1307   if( ifp2->Opcode() == Op_IfTrue ) {
1308     assert( ifp1->Opcode() == Op_IfFalse, "" );
1309     return 2;
1310   } else {
1311     assert( ifp1->Opcode() == Op_IfTrue, "" );
1312     return 1;
1313   }
1314 }
1315 
1316 //----------------------------check_cmove_id-----------------------------------
1317 // Check for CMove'ing a constant after comparing against the constant.
1318 // Happens all the time now, since if we compare equality vs a constant in
1319 // the parser, we "know" the variable is constant on one path and we force
1320 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1321 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1322 // general in that we don't need constants.  Since CMove's are only inserted
1323 // in very special circumstances, we do it here on generic Phi's.
1324 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1325   assert(true_path !=0, "only diamond shape graph expected");
1326 
1327   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1328   // phi->region->if_proj->ifnode->bool->cmp
1329   Node*     region = in(0);
1330   Node*     iff    = region->in(1)->in(0);
1331   BoolNode* b      = iff->in(1)->as_Bool();
1332   Node*     cmp    = b->in(1);
1333   Node*     tval   = in(true_path);
1334   Node*     fval   = in(3-true_path);
1335   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1336   if (id == NULL)
1337     return NULL;
1338 
1339   // Either value might be a cast that depends on a branch of 'iff'.
1340   // Since the 'id' value will float free of the diamond, either
1341   // decast or return failure.
1342   Node* ctl = id->in(0);
1343   if (ctl != NULL && ctl->in(0) == iff) {
1344     if (id->is_ConstraintCast()) {
1345       return id->in(1);
1346     } else {
1347       // Don't know how to disentangle this value.
1348       return NULL;
1349     }
1350   }
1351 
1352   return id;
1353 }
1354 
1355 //------------------------------Identity---------------------------------------
1356 // Check for Region being Identity.
1357 Node* PhiNode::Identity(PhaseGVN* phase) {
1358   // Check for no merging going on
1359   // (There used to be special-case code here when this->region->is_Loop.
1360   // It would check for a tributary phi on the backedge that the main phi
1361   // trivially, perhaps with a single cast.  The unique_input method
1362   // does all this and more, by reducing such tributaries to 'this'.)
1363   Node* uin = unique_input(phase, false);
1364   if (uin != NULL) {
1365     return uin;
1366   }
1367 
1368   int true_path = is_diamond_phi();
1369   if (true_path != 0) {
1370     Node* id = is_cmove_id(phase, true_path);
1371     if (id != NULL)  return id;
1372   }
1373 
1374   // Looking for phis with identical inputs.  If we find one that has
1375   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1376   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1377       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1378     uint phi_len = req();
1379     Node* phi_reg = region();
1380     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1381       Node* u = phi_reg->fast_out(i);
1382       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1383           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1384           u->req() == phi_len) {
1385         for (uint j = 1; j < phi_len; j++) {
1386           if (in(j) != u->in(j)) {
1387             u = NULL;
1388             break;
1389           }
1390         }
1391         if (u != NULL) {
1392           return u;
1393         }
1394       }
1395     }
1396   }
1397 
1398   return this;                     // No identity
1399 }
1400 
1401 //-----------------------------unique_input------------------------------------
1402 // Find the unique value, discounting top, self-loops, and casts.
1403 // Return top if there are no inputs, and self if there are multiple.
1404 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1405   //  1) One unique direct input,
1406   // or if uncast is true:
1407   //  2) some of the inputs have an intervening ConstraintCast
1408   //  3) an input is a self loop
1409   //
1410   //  1) input   or   2) input     or   3) input __
1411   //     /   \           /   \               \  /  \
1412   //     \   /          |    cast             phi  cast
1413   //      phi            \   /               /  \  /
1414   //                      phi               /    --
1415 
1416   Node* r = in(0);                      // RegionNode
1417   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1418 
1419   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1420     Node* rc = r->in(i);
1421     if (rc == NULL || phase->type(rc) == Type::TOP)
1422       continue;                 // ignore unreachable control path
1423     Node* n = in(i);
1424     if (n == NULL)
1425       continue;
1426     Node* un = n;
1427     if (uncast) {
1428 #ifdef ASSERT
1429       Node* m = un->uncast();
1430 #endif
1431       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1432         Node* next = un->in(1);
1433         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1434           // risk exposing raw ptr at safepoint
1435           break;
1436         }
1437         un = next;
1438       }
1439       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1440     }
1441     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1442       continue; // ignore if top, or in(i) and "this" are in a data cycle
1443     }
1444     // Check for a unique input (maybe uncasted)
1445     if (input == NULL) {
1446       input = un;
1447     } else if (input != un) {
1448       input = NodeSentinel; // no unique input
1449     }
1450   }
1451   if (input == NULL) {
1452     return phase->C->top();        // no inputs
1453   }
1454 
1455   if (input != NodeSentinel) {
1456     return input;           // one unique direct input
1457   }
1458 
1459   // Nothing.
1460   return NULL;
1461 }
1462 
1463 //------------------------------is_x2logic-------------------------------------
1464 // Check for simple convert-to-boolean pattern
1465 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1466 // Convert Phi to an ConvIB.
1467 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1468   assert(true_path !=0, "only diamond shape graph expected");
1469   // Convert the true/false index into an expected 0/1 return.
1470   // Map 2->0 and 1->1.
1471   int flipped = 2-true_path;
1472 
1473   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1474   // phi->region->if_proj->ifnode->bool->cmp
1475   Node *region = phi->in(0);
1476   Node *iff = region->in(1)->in(0);
1477   BoolNode *b = (BoolNode*)iff->in(1);
1478   const CmpNode *cmp = (CmpNode*)b->in(1);
1479 
1480   Node *zero = phi->in(1);
1481   Node *one  = phi->in(2);
1482   const Type *tzero = phase->type( zero );
1483   const Type *tone  = phase->type( one  );
1484 
1485   // Check for compare vs 0
1486   const Type *tcmp = phase->type(cmp->in(2));
1487   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1488     // Allow cmp-vs-1 if the other input is bounded by 0-1
1489     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1490       return NULL;
1491     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1492   }
1493 
1494   // Check for setting zero/one opposite expected
1495   if( tzero == TypeInt::ZERO ) {
1496     if( tone == TypeInt::ONE ) {
1497     } else return NULL;
1498   } else if( tzero == TypeInt::ONE ) {
1499     if( tone == TypeInt::ZERO ) {
1500       flipped = 1-flipped;
1501     } else return NULL;
1502   } else return NULL;
1503 
1504   // Check for boolean test backwards
1505   if( b->_test._test == BoolTest::ne ) {
1506   } else if( b->_test._test == BoolTest::eq ) {
1507     flipped = 1-flipped;
1508   } else return NULL;
1509 
1510   // Build int->bool conversion
1511   Node *n = new Conv2BNode(cmp->in(1));
1512   if( flipped )
1513     n = new XorINode( phase->transform(n), phase->intcon(1) );
1514 
1515   return n;
1516 }
1517 
1518 //------------------------------is_cond_add------------------------------------
1519 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1520 // To be profitable the control flow has to disappear; there can be no other
1521 // values merging here.  We replace the test-and-branch with:
1522 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1523 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1524 // Then convert Y to 0-or-Y and finally add.
1525 // This is a key transform for SpecJava _201_compress.
1526 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1527   assert(true_path !=0, "only diamond shape graph expected");
1528 
1529   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1530   // phi->region->if_proj->ifnode->bool->cmp
1531   RegionNode *region = (RegionNode*)phi->in(0);
1532   Node *iff = region->in(1)->in(0);
1533   BoolNode* b = iff->in(1)->as_Bool();
1534   const CmpNode *cmp = (CmpNode*)b->in(1);
1535 
1536   // Make sure only merging this one phi here
1537   if (region->has_unique_phi() != phi)  return NULL;
1538 
1539   // Make sure each arm of the diamond has exactly one output, which we assume
1540   // is the region.  Otherwise, the control flow won't disappear.
1541   if (region->in(1)->outcnt() != 1) return NULL;
1542   if (region->in(2)->outcnt() != 1) return NULL;
1543 
1544   // Check for "(P < Q)" of type signed int
1545   if (b->_test._test != BoolTest::lt)  return NULL;
1546   if (cmp->Opcode() != Op_CmpI)        return NULL;
1547 
1548   Node *p = cmp->in(1);
1549   Node *q = cmp->in(2);
1550   Node *n1 = phi->in(  true_path);
1551   Node *n2 = phi->in(3-true_path);
1552 
1553   int op = n1->Opcode();
1554   if( op != Op_AddI           // Need zero as additive identity
1555       /*&&op != Op_SubI &&
1556       op != Op_AddP &&
1557       op != Op_XorI &&
1558       op != Op_OrI*/ )
1559     return NULL;
1560 
1561   Node *x = n2;
1562   Node *y = NULL;
1563   if( x == n1->in(1) ) {
1564     y = n1->in(2);
1565   } else if( x == n1->in(2) ) {
1566     y = n1->in(1);
1567   } else return NULL;
1568 
1569   // Not so profitable if compare and add are constants
1570   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1571     return NULL;
1572 
1573   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1574   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1575   return new AddINode(j_and,x);
1576 }
1577 
1578 //------------------------------is_absolute------------------------------------
1579 // Check for absolute value.
1580 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1581   assert(true_path !=0, "only diamond shape graph expected");
1582 
1583   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1584   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1585 
1586   // ABS ends with the merge of 2 control flow paths.
1587   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1588   int false_path = 3 - true_path;
1589 
1590   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1591   // phi->region->if_proj->ifnode->bool->cmp
1592   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1593   Node *cmp = bol->in(1);
1594 
1595   // Check bool sense
1596   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1597     switch (bol->_test._test) {
1598     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1599     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1600     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1601     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1602     default:           return NULL;                              break;
1603     }
1604   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1605     switch (bol->_test._test) {
1606     case BoolTest::lt:
1607     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1608     case BoolTest::gt:
1609     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1610     default:           return NULL;                              break;
1611     }
1612   }
1613 
1614   // Test is next
1615   const Type *tzero = NULL;
1616   switch (cmp->Opcode()) {
1617   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1618   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1619   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1620   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1621   default: return NULL;
1622   }
1623 
1624   // Find zero input of compare; the other input is being abs'd
1625   Node *x = NULL;
1626   bool flip = false;
1627   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1628     x = cmp->in(3 - cmp_zero_idx);
1629   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1630     // The test is inverted, we should invert the result...
1631     x = cmp->in(cmp_zero_idx);
1632     flip = true;
1633   } else {
1634     return NULL;
1635   }
1636 
1637   // Next get the 2 pieces being selected, one is the original value
1638   // and the other is the negated value.
1639   if( phi_root->in(phi_x_idx) != x ) return NULL;
1640 
1641   // Check other phi input for subtract node
1642   Node *sub = phi_root->in(3 - phi_x_idx);
1643 
1644   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1645                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1646 
1647   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1648   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return NULL;
1649 
1650   if (tzero == TypeF::ZERO) {
1651     x = new AbsFNode(x);
1652     if (flip) {
1653       x = new SubFNode(sub->in(1), phase->transform(x));
1654     }
1655   } else if (tzero == TypeD::ZERO) {
1656     x = new AbsDNode(x);
1657     if (flip) {
1658       x = new SubDNode(sub->in(1), phase->transform(x));
1659     }
1660   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1661     x = new AbsINode(x);
1662     if (flip) {
1663       x = new SubINode(sub->in(1), phase->transform(x));
1664     }
1665   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1666     x = new AbsLNode(x);
1667     if (flip) {
1668       x = new SubLNode(sub->in(1), phase->transform(x));
1669     }
1670   } else return NULL;
1671 
1672   return x;
1673 }
1674 
1675 //------------------------------split_once-------------------------------------
1676 // Helper for split_flow_path
1677 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1678   igvn->hash_delete(n);         // Remove from hash before hacking edges
1679 
1680   uint j = 1;
1681   for (uint i = phi->req()-1; i > 0; i--) {
1682     if (phi->in(i) == val) {   // Found a path with val?
1683       // Add to NEW Region/Phi, no DU info
1684       newn->set_req( j++, n->in(i) );
1685       // Remove from OLD Region/Phi
1686       n->del_req(i);
1687     }
1688   }
1689 
1690   // Register the new node but do not transform it.  Cannot transform until the
1691   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1692   igvn->register_new_node_with_optimizer( newn );
1693 
1694   // Now I can point to the new node.
1695   n->add_req(newn);
1696   igvn->_worklist.push(n);
1697 }
1698 
1699 //------------------------------split_flow_path--------------------------------
1700 // Check for merging identical values and split flow paths
1701 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1702   BasicType bt = phi->type()->basic_type();
1703   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1704     return NULL;                // Bail out on funny non-value stuff
1705   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1706     return NULL;                // third unequal input to be worth doing
1707 
1708   // Scan for a constant
1709   uint i;
1710   for( i = 1; i < phi->req()-1; i++ ) {
1711     Node *n = phi->in(i);
1712     if( !n ) return NULL;
1713     if( phase->type(n) == Type::TOP ) return NULL;
1714     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1715       break;
1716   }
1717   if( i >= phi->req() )         // Only split for constants
1718     return NULL;
1719 
1720   Node *val = phi->in(i);       // Constant to split for
1721   uint hit = 0;                 // Number of times it occurs
1722   Node *r = phi->region();
1723 
1724   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1725     Node *n = phi->in(i);
1726     if( !n ) return NULL;
1727     if( phase->type(n) == Type::TOP ) return NULL;
1728     if( phi->in(i) == val ) {
1729       hit++;
1730       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1731         return NULL;            // don't split loop entry path
1732       }
1733     }
1734   }
1735 
1736   if( hit <= 1 ||               // Make sure we find 2 or more
1737       hit == phi->req()-1 )     // and not ALL the same value
1738     return NULL;
1739 
1740   // Now start splitting out the flow paths that merge the same value.
1741   // Split first the RegionNode.
1742   PhaseIterGVN *igvn = phase->is_IterGVN();
1743   RegionNode *newr = new RegionNode(hit+1);
1744   split_once(igvn, phi, val, r, newr);
1745 
1746   // Now split all other Phis than this one
1747   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1748     Node* phi2 = r->fast_out(k);
1749     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1750       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1751       split_once(igvn, phi, val, phi2, newphi);
1752     }
1753   }
1754 
1755   // Clean up this guy
1756   igvn->hash_delete(phi);
1757   for( i = phi->req()-1; i > 0; i-- ) {
1758     if( phi->in(i) == val ) {
1759       phi->del_req(i);
1760     }
1761   }
1762   phi->add_req(val);
1763 
1764   return phi;
1765 }
1766 
1767 //=============================================================================
1768 //------------------------------simple_data_loop_check-------------------------
1769 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1770 //  Returns:
1771 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1772 // Safe       - safe case when the phi and it's inputs reference only safe data
1773 //              nodes;
1774 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1775 //              is no reference back to the phi - need a graph walk
1776 //              to determine if it is in a loop;
1777 // UnsafeLoop - unsafe case when the phi references itself directly or through
1778 //              unsafe data node.
1779 //  Note: a safe data node is a node which could/never reference itself during
1780 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1781 //  I mark Phi nodes as safe node not only because they can reference itself
1782 //  but also to prevent mistaking the fallthrough case inside an outer loop
1783 //  as dead loop when the phi references itselfs through an other phi.
1784 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1785   // It is unsafe loop if the phi node references itself directly.
1786   if (in == (Node*)this)
1787     return UnsafeLoop; // Unsafe loop
1788   // Unsafe loop if the phi node references itself through an unsafe data node.
1789   // Exclude cases with null inputs or data nodes which could reference
1790   // itself (safe for dead loops).
1791   if (in != NULL && !in->is_dead_loop_safe()) {
1792     // Check inputs of phi's inputs also.
1793     // It is much less expensive then full graph walk.
1794     uint cnt = in->req();
1795     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1796     for (; i < cnt; ++i) {
1797       Node* m = in->in(i);
1798       if (m == (Node*)this)
1799         return UnsafeLoop; // Unsafe loop
1800       if (m != NULL && !m->is_dead_loop_safe()) {
1801         // Check the most common case (about 30% of all cases):
1802         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1803         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1804         if (m1 == (Node*)this)
1805           return UnsafeLoop; // Unsafe loop
1806         if (m1 != NULL && m1 == m->in(2) &&
1807             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1808           continue; // Safe case
1809         }
1810         // The phi references an unsafe node - need full analysis.
1811         return Unsafe;
1812       }
1813     }
1814   }
1815   return Safe; // Safe case - we can optimize the phi node.
1816 }
1817 
1818 //------------------------------is_unsafe_data_reference-----------------------
1819 // If phi can be reached through the data input - it is data loop.
1820 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1821   assert(req() > 1, "");
1822   // First, check simple cases when phi references itself directly or
1823   // through an other node.
1824   LoopSafety safety = simple_data_loop_check(in);
1825   if (safety == UnsafeLoop)
1826     return true;  // phi references itself - unsafe loop
1827   else if (safety == Safe)
1828     return false; // Safe case - phi could be replaced with the unique input.
1829 
1830   // Unsafe case when we should go through data graph to determine
1831   // if the phi references itself.
1832 
1833   ResourceMark rm;
1834 
1835   Node_List nstack;
1836   VectorSet visited;
1837 
1838   nstack.push(in); // Start with unique input.
1839   visited.set(in->_idx);
1840   while (nstack.size() != 0) {
1841     Node* n = nstack.pop();
1842     uint cnt = n->req();
1843     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1844     for (; i < cnt; i++) {
1845       Node* m = n->in(i);
1846       if (m == (Node*)this) {
1847         return true;    // Data loop
1848       }
1849       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1850         if (!visited.test_set(m->_idx))
1851           nstack.push(m);
1852       }
1853     }
1854   }
1855   return false; // The phi is not reachable from its inputs
1856 }
1857 
1858 // Is this Phi's region or some inputs to the region enqueued for IGVN
1859 // and so could cause the region to be optimized out?
1860 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1861   PhaseIterGVN* igvn = phase->is_IterGVN();
1862   Unique_Node_List& worklist = igvn->_worklist;
1863   bool delay = false;
1864   Node* r = in(0);
1865   for (uint j = 1; j < req(); j++) {
1866     Node* rc = r->in(j);
1867     Node* n = in(j);
1868     if (rc != NULL &&
1869         rc->is_Proj()) {
1870       if (worklist.member(rc)) {
1871         delay = true;
1872       } else if (rc->in(0) != NULL &&
1873                  rc->in(0)->is_If()) {
1874         if (worklist.member(rc->in(0))) {
1875           delay = true;
1876         } else if (rc->in(0)->in(1) != NULL &&
1877                    rc->in(0)->in(1)->is_Bool()) {
1878           if (worklist.member(rc->in(0)->in(1))) {
1879             delay = true;
1880           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1881                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1882             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1883               delay = true;
1884             }
1885           }
1886         }
1887       }
1888     }
1889   }
1890   if (delay) {
1891     worklist.push(this);
1892   }
1893   return delay;
1894 }
1895 
1896 //------------------------------Ideal------------------------------------------
1897 // Return a node which is more "ideal" than the current node.  Must preserve
1898 // the CFG, but we can still strip out dead paths.
1899 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1900   Node *r = in(0);              // RegionNode
1901   assert(r != NULL && r->is_Region(), "this phi must have a region");
1902   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1903 
1904   // Note: During parsing, phis are often transformed before their regions.
1905   // This means we have to use type_or_null to defend against untyped regions.
1906   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1907     return NULL;                // No change
1908 
1909   Node *top = phase->C->top();
1910   bool new_phi = (outcnt() == 0); // transforming new Phi
1911   // No change for igvn if new phi is not hooked
1912   if (new_phi && can_reshape)
1913     return NULL;
1914 
1915   // The are 2 situations when only one valid phi's input is left
1916   // (in addition to Region input).
1917   // One: region is not loop - replace phi with this input.
1918   // Two: region is loop - replace phi with top since this data path is dead
1919   //                       and we need to break the dead data loop.
1920   Node* progress = NULL;        // Record if any progress made
1921   for( uint j = 1; j < req(); ++j ){ // For all paths in
1922     // Check unreachable control paths
1923     Node* rc = r->in(j);
1924     Node* n = in(j);            // Get the input
1925     if (rc == NULL || phase->type(rc) == Type::TOP) {
1926       if (n != top) {           // Not already top?
1927         PhaseIterGVN *igvn = phase->is_IterGVN();
1928         if (can_reshape && igvn != NULL) {
1929           igvn->_worklist.push(r);
1930         }
1931         // Nuke it down
1932         set_req_X(j, top, phase);
1933         progress = this;        // Record progress
1934       }
1935     }
1936   }
1937 
1938   if (can_reshape && outcnt() == 0) {
1939     // set_req() above may kill outputs if Phi is referenced
1940     // only by itself on the dead (top) control path.
1941     return top;
1942   }
1943 
1944   bool uncasted = false;
1945   Node* uin = unique_input(phase, false);
1946   if (uin == NULL && can_reshape &&
1947       // If there is a chance that the region can be optimized out do
1948       // not add a cast node that we can't remove yet.
1949       !wait_for_region_igvn(phase)) {
1950     uncasted = true;
1951     uin = unique_input(phase, true);
1952   }
1953   if (uin == top) {             // Simplest case: no alive inputs.
1954     if (can_reshape)            // IGVN transformation
1955       return top;
1956     else
1957       return NULL;              // Identity will return TOP
1958   } else if (uin != NULL) {
1959     // Only one not-NULL unique input path is left.
1960     // Determine if this input is backedge of a loop.
1961     // (Skip new phis which have no uses and dead regions).
1962     if (outcnt() > 0 && r->in(0) != NULL) {
1963       if (is_data_loop(r->as_Region(), uin, phase)) {
1964         // Break this data loop to avoid creation of a dead loop.
1965         if (can_reshape) {
1966           return top;
1967         } else {
1968           // We can't return top if we are in Parse phase - cut inputs only
1969           // let Identity to handle the case.
1970           replace_edge(uin, top, phase);
1971           return NULL;
1972         }
1973       }
1974     }
1975 
1976     if (uncasted) {
1977       // Add cast nodes between the phi to be removed and its unique input.
1978       // Wait until after parsing for the type information to propagate from the casts.
1979       assert(can_reshape, "Invalid during parsing");
1980       const Type* phi_type = bottom_type();
1981       // Add casts to carry the control dependency of the Phi that is
1982       // going away
1983       Node* cast = NULL;
1984       if (phi_type->isa_ptr()) {
1985         const Type* uin_type = phase->type(uin);
1986         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1987           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
1988         } else {
1989           // Use a CastPP for a cast to not null and a CheckCastPP for
1990           // a cast to a new klass (and both if both null-ness and
1991           // klass change).
1992 
1993           // If the type of phi is not null but the type of uin may be
1994           // null, uin's type must be casted to not null
1995           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1996               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1997             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency);
1998           }
1999 
2000           // If the type of phi and uin, both casted to not null,
2001           // differ the klass of uin must be (check)cast'ed to match
2002           // that of phi
2003           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2004             Node* n = uin;
2005             if (cast != NULL) {
2006               cast = phase->transform(cast);
2007               n = cast;
2008             }
2009             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, ConstraintCastNode::StrongDependency);
2010           }
2011           if (cast == NULL) {
2012             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2013           }
2014         }
2015       } else {
2016         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency);
2017       }
2018       assert(cast != NULL, "cast should be set");
2019       cast = phase->transform(cast);
2020       // set all inputs to the new cast(s) so the Phi is removed by Identity
2021       PhaseIterGVN* igvn = phase->is_IterGVN();
2022       for (uint i = 1; i < req(); i++) {
2023         set_req_X(i, cast, igvn);
2024       }
2025       uin = cast;
2026     }
2027 
2028     // One unique input.
2029     debug_only(Node* ident = Identity(phase));
2030     // The unique input must eventually be detected by the Identity call.
2031 #ifdef ASSERT
2032     if (ident != uin && !ident->is_top()) {
2033       // print this output before failing assert
2034       r->dump(3);
2035       this->dump(3);
2036       ident->dump();
2037       uin->dump();
2038     }
2039 #endif
2040     assert(ident == uin || ident->is_top(), "Identity must clean this up");
2041     return NULL;
2042   }
2043 
2044   Node* opt = NULL;
2045   int true_path = is_diamond_phi();
2046   if (true_path != 0 &&
2047       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2048       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2049       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2050       !(can_reshape && wait_for_region_igvn(phase))) {
2051     // Check for CMove'ing identity. If it would be unsafe,
2052     // handle it here. In the safe case, let Identity handle it.
2053     Node* unsafe_id = is_cmove_id(phase, true_path);
2054     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
2055       opt = unsafe_id;
2056 
2057     // Check for simple convert-to-boolean pattern
2058     if( opt == NULL )
2059       opt = is_x2logic(phase, this, true_path);
2060 
2061     // Check for absolute value
2062     if( opt == NULL )
2063       opt = is_absolute(phase, this, true_path);
2064 
2065     // Check for conditional add
2066     if( opt == NULL && can_reshape )
2067       opt = is_cond_add(phase, this, true_path);
2068 
2069     // These 4 optimizations could subsume the phi:
2070     // have to check for a dead data loop creation.
2071     if( opt != NULL ) {
2072       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2073         // Found dead loop.
2074         if( can_reshape )
2075           return top;
2076         // We can't return top if we are in Parse phase - cut inputs only
2077         // to stop further optimizations for this phi. Identity will return TOP.
2078         assert(req() == 3, "only diamond merge phi here");
2079         set_req(1, top);
2080         set_req(2, top);
2081         return NULL;
2082       } else {
2083         return opt;
2084       }
2085     }
2086   }
2087 
2088   // Check for merging identical values and split flow paths
2089   if (can_reshape) {
2090     opt = split_flow_path(phase, this);
2091     // This optimization only modifies phi - don't need to check for dead loop.
2092     assert(opt == NULL || opt == this, "do not elide phi");
2093     if (opt != NULL)  return opt;
2094   }
2095 
2096   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2097     // Try to undo Phi of AddP:
2098     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2099     // becomes:
2100     // newbase := (Phi base base2)
2101     // newaddress := (Phi address address2)
2102     // newoffset := (Phi offset offset2)
2103     // (AddP newbase newaddress newoffset)
2104     //
2105     // This occurs as a result of unsuccessful split_thru_phi and
2106     // interferes with taking advantage of addressing modes. See the
2107     // clone_shift_expressions code in matcher.cpp
2108     Node* addp = in(1);
2109     Node* base = addp->in(AddPNode::Base);
2110     Node* address = addp->in(AddPNode::Address);
2111     Node* offset = addp->in(AddPNode::Offset);
2112     if (base != NULL && address != NULL && offset != NULL &&
2113         !base->is_top() && !address->is_top() && !offset->is_top()) {
2114       const Type* base_type = base->bottom_type();
2115       const Type* address_type = address->bottom_type();
2116       // make sure that all the inputs are similar to the first one,
2117       // i.e. AddP with base == address and same offset as first AddP
2118       bool doit = true;
2119       for (uint i = 2; i < req(); i++) {
2120         if (in(i) == NULL ||
2121             in(i)->Opcode() != Op_AddP ||
2122             in(i)->in(AddPNode::Base) == NULL ||
2123             in(i)->in(AddPNode::Address) == NULL ||
2124             in(i)->in(AddPNode::Offset) == NULL ||
2125             in(i)->in(AddPNode::Base)->is_top() ||
2126             in(i)->in(AddPNode::Address)->is_top() ||
2127             in(i)->in(AddPNode::Offset)->is_top()) {
2128           doit = false;
2129           break;
2130         }
2131         if (in(i)->in(AddPNode::Offset) != base) {
2132           base = NULL;
2133         }
2134         if (in(i)->in(AddPNode::Offset) != offset) {
2135           offset = NULL;
2136         }
2137         if (in(i)->in(AddPNode::Address) != address) {
2138           address = NULL;
2139         }
2140         // Accumulate type for resulting Phi
2141         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2142         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2143       }
2144       if (doit && base == NULL) {
2145         // Check for neighboring AddP nodes in a tree.
2146         // If they have a base, use that it.
2147         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2148           Node* u = this->fast_out(k);
2149           if (u->is_AddP()) {
2150             Node* base2 = u->in(AddPNode::Base);
2151             if (base2 != NULL && !base2->is_top()) {
2152               if (base == NULL)
2153                 base = base2;
2154               else if (base != base2)
2155                 { doit = false; break; }
2156             }
2157           }
2158         }
2159       }
2160       if (doit) {
2161         if (base == NULL) {
2162           base = new PhiNode(in(0), base_type, NULL);
2163           for (uint i = 1; i < req(); i++) {
2164             base->init_req(i, in(i)->in(AddPNode::Base));
2165           }
2166           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2167         }
2168         if (address == NULL) {
2169           address = new PhiNode(in(0), address_type, NULL);
2170           for (uint i = 1; i < req(); i++) {
2171             address->init_req(i, in(i)->in(AddPNode::Address));
2172           }
2173           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2174         }
2175         if (offset == NULL) {
2176           offset = new PhiNode(in(0), TypeX_X, NULL);
2177           for (uint i = 1; i < req(); i++) {
2178             offset->init_req(i, in(i)->in(AddPNode::Offset));
2179           }
2180           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2181         }
2182         return new AddPNode(base, address, offset);
2183       }
2184     }
2185   }
2186 
2187   // Split phis through memory merges, so that the memory merges will go away.
2188   // Piggy-back this transformation on the search for a unique input....
2189   // It will be as if the merged memory is the unique value of the phi.
2190   // (Do not attempt this optimization unless parsing is complete.
2191   // It would make the parser's memory-merge logic sick.)
2192   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2193   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2194     // see if this phi should be sliced
2195     uint merge_width = 0;
2196     bool saw_self = false;
2197     for( uint i=1; i<req(); ++i ) {// For all paths in
2198       Node *ii = in(i);
2199       // TOP inputs should not be counted as safe inputs because if the
2200       // Phi references itself through all other inputs then splitting the
2201       // Phi through memory merges would create dead loop at later stage.
2202       if (ii == top) {
2203         return NULL; // Delay optimization until graph is cleaned.
2204       }
2205       if (ii->is_MergeMem()) {
2206         MergeMemNode* n = ii->as_MergeMem();
2207         merge_width = MAX2(merge_width, n->req());
2208         saw_self = saw_self || (n->base_memory() == this);
2209       }
2210     }
2211 
2212     // This restriction is temporarily necessary to ensure termination:
2213     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2214 
2215     if (merge_width > Compile::AliasIdxRaw) {
2216       // found at least one non-empty MergeMem
2217       const TypePtr* at = adr_type();
2218       if (at != TypePtr::BOTTOM) {
2219         // Patch the existing phi to select an input from the merge:
2220         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2221         //     Phi:AT1(...m1...)
2222         int alias_idx = phase->C->get_alias_index(at);
2223         for (uint i=1; i<req(); ++i) {
2224           Node *ii = in(i);
2225           if (ii->is_MergeMem()) {
2226             MergeMemNode* n = ii->as_MergeMem();
2227             // compress paths and change unreachable cycles to TOP
2228             // If not, we can update the input infinitely along a MergeMem cycle
2229             // Equivalent code is in MemNode::Ideal_common
2230             Node *m  = phase->transform(n);
2231             if (outcnt() == 0) {  // Above transform() may kill us!
2232               return top;
2233             }
2234             // If transformed to a MergeMem, get the desired slice
2235             // Otherwise the returned node represents memory for every slice
2236             Node *new_mem = (m->is_MergeMem()) ?
2237                              m->as_MergeMem()->memory_at(alias_idx) : m;
2238             // Update input if it is progress over what we have now
2239             if (new_mem != ii) {
2240               set_req_X(i, new_mem, phase->is_IterGVN());
2241               progress = this;
2242             }
2243           }
2244         }
2245       } else {
2246         // We know that at least one MergeMem->base_memory() == this
2247         // (saw_self == true). If all other inputs also references this phi
2248         // (directly or through data nodes) - it is a dead loop.
2249         bool saw_safe_input = false;
2250         for (uint j = 1; j < req(); ++j) {
2251           Node* n = in(j);
2252           if (n->is_MergeMem()) {
2253             MergeMemNode* mm = n->as_MergeMem();
2254             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2255               // Skip this input if it references back to this phi or if the memory path is dead
2256               continue;
2257             }
2258           }
2259           if (!is_unsafe_data_reference(n)) {
2260             saw_safe_input = true; // found safe input
2261             break;
2262           }
2263         }
2264         if (!saw_safe_input) {
2265           // There is a dead loop: All inputs are either dead or reference back to this phi
2266           return top;
2267         }
2268 
2269         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2270         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2271         PhaseIterGVN* igvn = phase->is_IterGVN();
2272         Node* hook = new Node(1);
2273         PhiNode* new_base = (PhiNode*) clone();
2274         // Must eagerly register phis, since they participate in loops.
2275         if (igvn) {
2276           igvn->register_new_node_with_optimizer(new_base);
2277           hook->add_req(new_base);
2278         }
2279         MergeMemNode* result = MergeMemNode::make(new_base);
2280         for (uint i = 1; i < req(); ++i) {
2281           Node *ii = in(i);
2282           if (ii->is_MergeMem()) {
2283             MergeMemNode* n = ii->as_MergeMem();
2284             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2285               // If we have not seen this slice yet, make a phi for it.
2286               bool made_new_phi = false;
2287               if (mms.is_empty()) {
2288                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2289                 made_new_phi = true;
2290                 if (igvn) {
2291                   igvn->register_new_node_with_optimizer(new_phi);
2292                   hook->add_req(new_phi);
2293                 }
2294                 mms.set_memory(new_phi);
2295               }
2296               Node* phi = mms.memory();
2297               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2298               phi->set_req(i, mms.memory2());
2299             }
2300           }
2301         }
2302         // Distribute all self-loops.
2303         { // (Extra braces to hide mms.)
2304           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2305             Node* phi = mms.memory();
2306             for (uint i = 1; i < req(); ++i) {
2307               if (phi->in(i) == this)  phi->set_req(i, phi);
2308             }
2309           }
2310         }
2311         // now transform the new nodes, and return the mergemem
2312         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2313           Node* phi = mms.memory();
2314           mms.set_memory(phase->transform(phi));
2315         }
2316         hook->destruct(igvn);
2317         // Replace self with the result.
2318         return result;
2319       }
2320     }
2321     //
2322     // Other optimizations on the memory chain
2323     //
2324     const TypePtr* at = adr_type();
2325     for( uint i=1; i<req(); ++i ) {// For all paths in
2326       Node *ii = in(i);
2327       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2328       if (ii != new_in ) {
2329         set_req(i, new_in);
2330         progress = this;
2331       }
2332     }
2333   }
2334 
2335 #ifdef _LP64
2336   // Push DecodeN/DecodeNKlass down through phi.
2337   // The rest of phi graph will transform by split EncodeP node though phis up.
2338   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2339     bool may_push = true;
2340     bool has_decodeN = false;
2341     bool is_decodeN = false;
2342     for (uint i=1; i<req(); ++i) {// For all paths in
2343       Node *ii = in(i);
2344       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2345         // Do optimization if a non dead path exist.
2346         if (ii->in(1)->bottom_type() != Type::TOP) {
2347           has_decodeN = true;
2348           is_decodeN = ii->is_DecodeN();
2349         }
2350       } else if (!ii->is_Phi()) {
2351         may_push = false;
2352       }
2353     }
2354 
2355     if (has_decodeN && may_push) {
2356       PhaseIterGVN *igvn = phase->is_IterGVN();
2357       // Make narrow type for new phi.
2358       const Type* narrow_t;
2359       if (is_decodeN) {
2360         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2361       } else {
2362         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2363       }
2364       PhiNode* new_phi = new PhiNode(r, narrow_t);
2365       uint orig_cnt = req();
2366       for (uint i=1; i<req(); ++i) {// For all paths in
2367         Node *ii = in(i);
2368         Node* new_ii = NULL;
2369         if (ii->is_DecodeNarrowPtr()) {
2370           assert(ii->bottom_type() == bottom_type(), "sanity");
2371           new_ii = ii->in(1);
2372         } else {
2373           assert(ii->is_Phi(), "sanity");
2374           if (ii->as_Phi() == this) {
2375             new_ii = new_phi;
2376           } else {
2377             if (is_decodeN) {
2378               new_ii = new EncodePNode(ii, narrow_t);
2379             } else {
2380               new_ii = new EncodePKlassNode(ii, narrow_t);
2381             }
2382             igvn->register_new_node_with_optimizer(new_ii);
2383           }
2384         }
2385         new_phi->set_req(i, new_ii);
2386       }
2387       igvn->register_new_node_with_optimizer(new_phi, this);
2388       if (is_decodeN) {
2389         progress = new DecodeNNode(new_phi, bottom_type());
2390       } else {
2391         progress = new DecodeNKlassNode(new_phi, bottom_type());
2392       }
2393     }
2394   }
2395 #endif
2396 
2397   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2398   if (EnableVectorReboxing && can_reshape && progress == NULL && type()->isa_oopptr()) {
2399     progress = merge_through_phi(this, phase->is_IterGVN());
2400   }
2401 
2402   return progress;              // Return any progress
2403 }
2404 
2405 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2406   Node_Stack stack(1);
2407   VectorSet  visited;
2408   Node_List  node_map;
2409 
2410   stack.push(root_phi, 1); // ignore control
2411   visited.set(root_phi->_idx);
2412 
2413   Node* new_phi = new PhiNode(root_phi->in(0), t);
2414   node_map.map(root_phi->_idx, new_phi);
2415 
2416   while (stack.is_nonempty()) {
2417     Node* n   = stack.node();
2418     uint  idx = stack.index();
2419     assert(n->is_Phi(), "not a phi");
2420     if (idx < n->req()) {
2421       stack.set_index(idx + 1);
2422       Node* def = n->in(idx);
2423       if (def == NULL) {
2424         continue; // ignore dead path
2425       } else if (def->is_Phi()) { // inner node
2426         Node* new_phi = node_map[n->_idx];
2427         if (!visited.test_set(def->_idx)) { // not visited yet
2428           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2429           stack.push(def, 1); // ignore control
2430         }
2431         Node* new_in = node_map[def->_idx];
2432         new_phi->set_req(idx, new_in);
2433       } else if (def->Opcode() == Op_VectorBox) { // leaf
2434         assert(n->is_Phi(), "not a phi");
2435         Node* new_phi = node_map[n->_idx];
2436         new_phi->set_req(idx, def->in(c));
2437       } else {
2438         assert(false, "not optimizeable");
2439         return NULL;
2440       }
2441     } else {
2442       Node* new_phi = node_map[n->_idx];
2443       igvn->register_new_node_with_optimizer(new_phi, n);
2444       stack.pop();
2445     }
2446   }
2447   return new_phi;
2448 }
2449 
2450 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
2451   Node_Stack stack(1);
2452   VectorSet  visited;
2453 
2454   stack.push(root_phi, 1); // ignore control
2455   visited.set(root_phi->_idx);
2456 
2457   VectorBoxNode* cached_vbox = NULL;
2458   while (stack.is_nonempty()) {
2459     Node* n   = stack.node();
2460     uint  idx = stack.index();
2461     if (idx < n->req()) {
2462       stack.set_index(idx + 1);
2463       Node* in = n->in(idx);
2464       if (in == NULL) {
2465         continue; // ignore dead path
2466       } else if (in->isa_Phi()) {
2467         if (!visited.test_set(in->_idx)) {
2468           stack.push(in, 1); // ignore control
2469         }
2470       } else if (in->Opcode() == Op_VectorBox) {
2471         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
2472         if (cached_vbox == NULL) {
2473           cached_vbox = vbox;
2474         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
2475           // TODO: vector type mismatch can be handled with additional reinterpret casts
2476           assert(Type::cmp(vbox->vec_type(), cached_vbox->vec_type()) != 0, "inconsistent");
2477           return NULL; // not optimizable: vector type mismatch
2478         } else if (vbox->box_type() != cached_vbox->box_type()) {
2479           assert(Type::cmp(vbox->box_type(), cached_vbox->box_type()) != 0, "inconsistent");
2480           return NULL; // not optimizable: box type mismatch
2481         }
2482       } else {
2483         return NULL; // not optimizable: neither Phi nor VectorBox
2484       }
2485     } else {
2486       stack.pop();
2487     }
2488   }
2489   assert(cached_vbox != NULL, "sanity");
2490   const TypeInstPtr* btype = cached_vbox->box_type();
2491   const TypeVect*    vtype = cached_vbox->vec_type();
2492   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
2493   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
2494   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
2495 }
2496 
2497 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
2498   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
2499   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
2500   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
2501   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
2502   const bool is_loop = (r->is_Loop() && r->req() == 3);
2503   const Node* top = phase->C->top();
2504   if (is_loop) {
2505     return !uin->eqv_uncast(in(LoopNode::EntryControl));
2506   } else {
2507     // We have a data loop either with an unsafe data reference or if a region is unreachable.
2508     return is_unsafe_data_reference(uin)
2509            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
2510   }
2511 }
2512 
2513 //------------------------------is_tripcount-----------------------------------
2514 bool PhiNode::is_tripcount(BasicType bt) const {
2515   return (in(0) != NULL && in(0)->is_BaseCountedLoop() &&
2516           in(0)->as_BaseCountedLoop()->operates_on(bt, true) &&
2517           in(0)->as_BaseCountedLoop()->phi() == this);
2518 }
2519 
2520 //------------------------------out_RegMask------------------------------------
2521 const RegMask &PhiNode::in_RegMask(uint i) const {
2522   return i ? out_RegMask() : RegMask::Empty;
2523 }
2524 
2525 const RegMask &PhiNode::out_RegMask() const {
2526   uint ideal_reg = _type->ideal_reg();
2527   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2528   if( ideal_reg == 0 ) return RegMask::Empty;
2529   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2530   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2531 }
2532 
2533 #ifndef PRODUCT
2534 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2535   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2536   // and all outputs till level 1. In compact mode, inputs till level 1 are
2537   // collected.
2538   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2539   this->collect_nodes(out_rel, -1, false, false);
2540 }
2541 
2542 void PhiNode::dump_spec(outputStream *st) const {
2543   TypeNode::dump_spec(st);
2544   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
2545     st->print(" #tripcount");
2546   }
2547 }
2548 #endif
2549 
2550 
2551 //=============================================================================
2552 const Type* GotoNode::Value(PhaseGVN* phase) const {
2553   // If the input is reachable, then we are executed.
2554   // If the input is not reachable, then we are not executed.
2555   return phase->type(in(0));
2556 }
2557 
2558 Node* GotoNode::Identity(PhaseGVN* phase) {
2559   return in(0);                // Simple copy of incoming control
2560 }
2561 
2562 const RegMask &GotoNode::out_RegMask() const {
2563   return RegMask::Empty;
2564 }
2565 
2566 #ifndef PRODUCT
2567 //-----------------------------related-----------------------------------------
2568 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2569 // outputs at level 1. This is regardless of compact mode.
2570 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2571   this->collect_nodes(in_rel, 1, false, false);
2572   this->collect_nodes(out_rel, -1, false, false);
2573 }
2574 #endif
2575 
2576 
2577 //=============================================================================
2578 const RegMask &JumpNode::out_RegMask() const {
2579   return RegMask::Empty;
2580 }
2581 
2582 #ifndef PRODUCT
2583 //-----------------------------related-----------------------------------------
2584 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2585 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2586 // This is regardless of compact mode.
2587 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2588   this->collect_nodes(in_rel, 1, false, false);
2589   this->collect_nodes(out_rel, -2, false, false);
2590 }
2591 #endif
2592 
2593 //=============================================================================
2594 const RegMask &JProjNode::out_RegMask() const {
2595   return RegMask::Empty;
2596 }
2597 
2598 //=============================================================================
2599 const RegMask &CProjNode::out_RegMask() const {
2600   return RegMask::Empty;
2601 }
2602 
2603 
2604 
2605 //=============================================================================
2606 
2607 uint PCTableNode::hash() const { return Node::hash() + _size; }
2608 bool PCTableNode::cmp( const Node &n ) const
2609 { return _size == ((PCTableNode&)n)._size; }
2610 
2611 const Type *PCTableNode::bottom_type() const {
2612   const Type** f = TypeTuple::fields(_size);
2613   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2614   return TypeTuple::make(_size, f);
2615 }
2616 
2617 //------------------------------Value------------------------------------------
2618 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2619 // Control, otherwise the table targets are not reachable
2620 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2621   if( phase->type(in(0)) == Type::CONTROL )
2622     return bottom_type();
2623   return Type::TOP;             // All paths dead?  Then so are we
2624 }
2625 
2626 //------------------------------Ideal------------------------------------------
2627 // Return a node which is more "ideal" than the current node.  Strip out
2628 // control copies
2629 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2630   return remove_dead_region(phase, can_reshape) ? this : NULL;
2631 }
2632 
2633 //=============================================================================
2634 uint JumpProjNode::hash() const {
2635   return Node::hash() + _dest_bci;
2636 }
2637 
2638 bool JumpProjNode::cmp( const Node &n ) const {
2639   return ProjNode::cmp(n) &&
2640     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2641 }
2642 
2643 #ifndef PRODUCT
2644 void JumpProjNode::dump_spec(outputStream *st) const {
2645   ProjNode::dump_spec(st);
2646   st->print("@bci %d ",_dest_bci);
2647 }
2648 
2649 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2650   ProjNode::dump_compact_spec(st);
2651   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2652 }
2653 
2654 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2655   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2656   this->collect_nodes(in_rel, 1, false, false);
2657   this->collect_nodes(out_rel, -1, false, false);
2658 }
2659 #endif
2660 
2661 //=============================================================================
2662 //------------------------------Value------------------------------------------
2663 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2664 // have the default "fall_through_index" path.
2665 const Type* CatchNode::Value(PhaseGVN* phase) const {
2666   // Unreachable?  Then so are all paths from here.
2667   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2668   // First assume all paths are reachable
2669   const Type** f = TypeTuple::fields(_size);
2670   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2671   // Identify cases that will always throw an exception
2672   // () rethrow call
2673   // () virtual or interface call with NULL receiver
2674   // () call is a check cast with incompatible arguments
2675   if( in(1)->is_Proj() ) {
2676     Node *i10 = in(1)->in(0);
2677     if( i10->is_Call() ) {
2678       CallNode *call = i10->as_Call();
2679       // Rethrows always throw exceptions, never return
2680       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2681         f[CatchProjNode::fall_through_index] = Type::TOP;
2682       } else if( call->req() > TypeFunc::Parms ) {
2683         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2684         // Check for null receiver to virtual or interface calls
2685         if( call->is_CallDynamicJava() &&
2686             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2687           f[CatchProjNode::fall_through_index] = Type::TOP;
2688         }
2689       } // End of if not a runtime stub
2690     } // End of if have call above me
2691   } // End of slot 1 is not a projection
2692   return TypeTuple::make(_size, f);
2693 }
2694 
2695 //=============================================================================
2696 uint CatchProjNode::hash() const {
2697   return Node::hash() + _handler_bci;
2698 }
2699 
2700 
2701 bool CatchProjNode::cmp( const Node &n ) const {
2702   return ProjNode::cmp(n) &&
2703     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2704 }
2705 
2706 
2707 //------------------------------Identity---------------------------------------
2708 // If only 1 target is possible, choose it if it is the main control
2709 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2710   // If my value is control and no other value is, then treat as ID
2711   const TypeTuple *t = phase->type(in(0))->is_tuple();
2712   if (t->field_at(_con) != Type::CONTROL)  return this;
2713   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2714   // also remove any exception table entry.  Thus we must know the call
2715   // feeding the Catch will not really throw an exception.  This is ok for
2716   // the main fall-thru control (happens when we know a call can never throw
2717   // an exception) or for "rethrow", because a further optimization will
2718   // yank the rethrow (happens when we inline a function that can throw an
2719   // exception and the caller has no handler).  Not legal, e.g., for passing
2720   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2721   // These cases MUST throw an exception via the runtime system, so the VM
2722   // will be looking for a table entry.
2723   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2724   CallNode *call;
2725   if (_con != TypeFunc::Control && // Bail out if not the main control.
2726       !(proj->is_Proj() &&      // AND NOT a rethrow
2727         proj->in(0)->is_Call() &&
2728         (call = proj->in(0)->as_Call()) &&
2729         call->entry_point() == OptoRuntime::rethrow_stub()))
2730     return this;
2731 
2732   // Search for any other path being control
2733   for (uint i = 0; i < t->cnt(); i++) {
2734     if (i != _con && t->field_at(i) == Type::CONTROL)
2735       return this;
2736   }
2737   // Only my path is possible; I am identity on control to the jump
2738   return in(0)->in(0);
2739 }
2740 
2741 
2742 #ifndef PRODUCT
2743 void CatchProjNode::dump_spec(outputStream *st) const {
2744   ProjNode::dump_spec(st);
2745   st->print("@bci %d ",_handler_bci);
2746 }
2747 #endif
2748 
2749 //=============================================================================
2750 //------------------------------Identity---------------------------------------
2751 // Check for CreateEx being Identity.
2752 Node* CreateExNode::Identity(PhaseGVN* phase) {
2753   if( phase->type(in(1)) == Type::TOP ) return in(1);
2754   if( phase->type(in(0)) == Type::TOP ) return in(0);
2755   // We only come from CatchProj, unless the CatchProj goes away.
2756   // If the CatchProj is optimized away, then we just carry the
2757   // exception oop through.
2758   CallNode *call = in(1)->in(0)->as_Call();
2759 
2760   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2761     ? this
2762     : call->in(TypeFunc::Parms);
2763 }
2764 
2765 //=============================================================================
2766 //------------------------------Value------------------------------------------
2767 // Check for being unreachable.
2768 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2769   if (!in(0) || in(0)->is_top()) return Type::TOP;
2770   return bottom_type();
2771 }
2772 
2773 //------------------------------Ideal------------------------------------------
2774 // Check for no longer being part of a loop
2775 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2776   if (can_reshape && !in(0)->is_Region()) {
2777     // Dead code elimination can sometimes delete this projection so
2778     // if it's not there, there's nothing to do.
2779     Node* fallthru = proj_out_or_null(0);
2780     if (fallthru != NULL) {
2781       phase->is_IterGVN()->replace_node(fallthru, in(0));
2782     }
2783     return phase->C->top();
2784   }
2785   return NULL;
2786 }
2787 
2788 #ifndef PRODUCT
2789 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2790   st->print("%s", Name());
2791 }
2792 #endif