1 /*
   2  * Copyright (c) 1997, 2022, 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 // Check if the RegionNode is part of an unsafe loop and unreachable from 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 = true;
 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_X(i, NULL, phase); // 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 = false;
 536       phase->is_IterGVN()->add_users_to_worklist(this);
 537       i--;
 538     }
 539   }
 540 
 541   if (can_reshape && cnt == 1) {
 542     // Is it dead loop?
 543     // If it is LoopNopde it had 2 (+1 itself) inputs and
 544     // one of them was cut. The loop is dead if it was EntryContol.
 545     // Loop node may have only one input because entry path
 546     // is removed in PhaseIdealLoop::Dominators().
 547     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 548     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 549                              (del_it == 0 && is_unreachable_region(phase)))) ||
 550         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 551       // This region and therefore all nodes on the input control path(s) are unreachable
 552       // from root. To avoid incomplete removal of unreachable subgraphs, walk up the CFG
 553       // and aggressively replace all nodes by top.
 554       PhaseIterGVN* igvn = phase->is_IterGVN();
 555       Node* top = phase->C->top();
 556       ResourceMark rm;
 557       Node_List nstack;
 558       VectorSet visited;
 559       nstack.push(this);
 560       visited.set(_idx);
 561       while (nstack.size() != 0) {
 562         Node* n = nstack.pop();
 563         for (uint i = 0; i < n->req(); ++i) {
 564           Node* m = n->in(i);
 565           assert(m != (Node*)phase->C->root(), "Should be unreachable from root");
 566           if (m != NULL && m->is_CFG() && !visited.test_set(m->_idx)) {
 567             nstack.push(m);
 568           }
 569         }
 570         if (n->is_Region()) {
 571           // Eagerly replace phis with top to avoid regionless phis.
 572           n->set_req(0, NULL);
 573           bool progress = true;
 574           uint max = n->outcnt();
 575           DUIterator j;
 576           while (progress) {
 577             progress = false;
 578             for (j = n->outs(); n->has_out(j); j++) {
 579               Node* u = n->out(j);
 580               if (u->is_Phi()) {
 581                 igvn->replace_node(u, top);
 582                 if (max != n->outcnt()) {
 583                   progress = true;
 584                   j = n->refresh_out_pos(j);
 585                   max = n->outcnt();
 586                 }
 587               }
 588             }
 589           }
 590         }
 591         igvn->replace_node(n, top);
 592       }
 593       return NULL;
 594     }
 595   }
 596 
 597   if( cnt <= 1 ) {              // Only 1 path in?
 598     set_req(0, NULL);           // Null control input for region copy
 599     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 600       // No inputs or all inputs are NULL.
 601       return NULL;
 602     } else if (can_reshape) {   // Optimization phase - remove the node
 603       PhaseIterGVN *igvn = phase->is_IterGVN();
 604       // Strip mined (inner) loop is going away, remove outer loop.
 605       if (is_CountedLoop() &&
 606           as_Loop()->is_strip_mined()) {
 607         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 608         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 609         if (outer_sfpt != NULL && outer_out != NULL) {
 610           Node* in = outer_sfpt->in(0);
 611           igvn->replace_node(outer_out, in);
 612           LoopNode* outer = as_CountedLoop()->outer_loop();
 613           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 614         }
 615       }
 616       if (is_CountedLoop()) {
 617         Node* opaq = as_CountedLoop()->is_canonical_loop_entry();
 618         if (opaq != NULL) {
 619           // 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
 620           // subject to further loop opts.
 621           assert(opaq->Opcode() == Op_Opaque1, "");
 622           igvn->replace_node(opaq, opaq->in(1));
 623         }
 624       }
 625       Node *parent_ctrl;
 626       if( cnt == 0 ) {
 627         assert( req() == 1, "no inputs expected" );
 628         // During IGVN phase such region will be subsumed by TOP node
 629         // so region's phis will have TOP as control node.
 630         // Kill phis here to avoid it.
 631         // Also set other user's input to top.
 632         parent_ctrl = phase->C->top();
 633       } else {
 634         // The fallthrough case since we already checked dead loops above.
 635         parent_ctrl = in(1);
 636         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 637         assert(parent_ctrl != this, "Close dead loop");
 638       }
 639       if (add_to_worklist) {
 640         igvn->add_users_to_worklist(this); // Check for further allowed opts
 641       }
 642       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 643         Node* n = last_out(i);
 644         igvn->hash_delete(n); // Remove from worklist before modifying edges
 645         if (n->outcnt() == 0) {
 646           int uses_found = n->replace_edge(this, phase->C->top(), igvn);
 647           if (uses_found > 1) { // (--i) done at the end of the loop.
 648             i -= (uses_found - 1);
 649           }
 650           continue;
 651         }
 652         if( n->is_Phi() ) {   // Collapse all Phis
 653           // Eagerly replace phis to avoid regionless phis.
 654           Node* in;
 655           if( cnt == 0 ) {
 656             assert( n->req() == 1, "No data inputs expected" );
 657             in = parent_ctrl; // replaced by top
 658           } else {
 659             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 660             in = n->in(1);               // replaced by unique input
 661             if( n->as_Phi()->is_unsafe_data_reference(in) )
 662               in = phase->C->top();      // replaced by top
 663           }
 664           igvn->replace_node(n, in);
 665         }
 666         else if( n->is_Region() ) { // Update all incoming edges
 667           assert(n != this, "Must be removed from DefUse edges");
 668           int uses_found = n->replace_edge(this, parent_ctrl, igvn);
 669           if (uses_found > 1) { // (--i) done at the end of the loop.
 670             i -= (uses_found - 1);
 671           }
 672         }
 673         else {
 674           assert(n->in(0) == this, "Expect RegionNode to be control parent");
 675           n->set_req(0, parent_ctrl);
 676         }
 677 #ifdef ASSERT
 678         for( uint k=0; k < n->req(); k++ ) {
 679           assert(n->in(k) != this, "All uses of RegionNode should be gone");
 680         }
 681 #endif
 682       }
 683       // Remove the RegionNode itself from DefUse info
 684       igvn->remove_dead_node(this);
 685       return NULL;
 686     }
 687     return this;                // Record progress
 688   }
 689 
 690 
 691   // If a Region flows into a Region, merge into one big happy merge.
 692   if (can_reshape) {
 693     Node *m = merge_region(this, phase);
 694     if (m != NULL)  return m;
 695   }
 696 
 697   // Check if this region is the root of a clipping idiom on floats
 698   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 699     // Check that only one use is a Phi and that it simplifies to two constants +
 700     PhiNode* phi = has_unique_phi();
 701     if (phi != NULL) {          // One Phi user
 702       // Check inputs to the Phi
 703       ConNode *min;
 704       ConNode *max;
 705       Node    *val;
 706       uint     min_idx;
 707       uint     max_idx;
 708       uint     val_idx;
 709       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 710         IfNode *top_if;
 711         IfNode *bot_if;
 712         if( check_if_clipping( this, bot_if, top_if ) ) {
 713           // Control pattern checks, now verify compares
 714           Node   *top_in = NULL;   // value being compared against
 715           Node   *bot_in = NULL;
 716           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 717               check_compare_clipping( false, top_if, max, top_in ) ) {
 718             if( bot_in == top_in ) {
 719               PhaseIterGVN *gvn = phase->is_IterGVN();
 720               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 721               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 722 
 723               // Check for the ConvF2INode
 724               ConvF2INode *convf2i;
 725               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 726                 convf2i->in(1) == bot_in ) {
 727                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 728                 // max test
 729                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 730                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 731                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 732                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 733                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 734                 // min test
 735                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 736                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 737                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 738                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 739                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 740                 // update input edges to region node
 741                 set_req_X( min_idx, if_min, gvn );
 742                 set_req_X( max_idx, if_max, gvn );
 743                 set_req_X( val_idx, ifF,    gvn );
 744                 // remove unnecessary 'LShiftI; RShiftI' idiom
 745                 gvn->hash_delete(phi);
 746                 phi->set_req_X( val_idx, convf2i, gvn );
 747                 gvn->hash_find_insert(phi);
 748                 // Return transformed region node
 749                 return this;
 750               }
 751             }
 752           }
 753         }
 754       }
 755     }
 756   }
 757 
 758   if (can_reshape) {
 759     modified |= optimize_trichotomy(phase->is_IterGVN());
 760   }
 761 
 762   return modified ? this : NULL;
 763 }
 764 
 765 //------------------------------optimize_trichotomy--------------------------
 766 // Optimize nested comparisons of the following kind:
 767 //
 768 // int compare(int a, int b) {
 769 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 770 // }
 771 //
 772 // Shape 1:
 773 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 774 //
 775 // Shape 2:
 776 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 777 //
 778 // Above code leads to the following IR shapes where both Ifs compare the
 779 // same value and two out of three region inputs idx1 and idx2 map to
 780 // the same value and control flow.
 781 //
 782 // (1)   If                 (2)   If
 783 //      /  \                     /  \
 784 //   Proj  Proj               Proj  Proj
 785 //     |      \                |      \
 786 //     |       If              |      If                      If
 787 //     |      /  \             |     /  \                    /  \
 788 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 789 //     |   /      /            \    |    /                  |    /
 790 //    Region     /              \   |   /                   |   /
 791 //         \    /                \  |  /                    |  /
 792 //         Region                Region                    Region
 793 //
 794 // The method returns true if 'this' is modified and false otherwise.
 795 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 796   int idx1 = 1, idx2 = 2;
 797   Node* region = NULL;
 798   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 799     // Shape 1: Check if one of the inputs is a region that merges two control
 800     // inputs and has no other users (especially no Phi users).
 801     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 802     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 803       return false; // No suitable region input found
 804     }
 805   } else if (req() == 4) {
 806     // Shape 2: Check if two control inputs map to the same value of the unique phi
 807     // user and treat these as if they would come from another region (shape (1)).
 808     PhiNode* phi = has_unique_phi();
 809     if (phi == NULL) {
 810       return false; // No unique phi user
 811     }
 812     if (phi->in(idx1) != phi->in(idx2)) {
 813       idx2 = 3;
 814       if (phi->in(idx1) != phi->in(idx2)) {
 815         idx1 = 2;
 816         if (phi->in(idx1) != phi->in(idx2)) {
 817           return false; // No equal phi inputs found
 818         }
 819       }
 820     }
 821     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 822     region = this;
 823   }
 824   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 825     return false; // Region does not merge two control inputs
 826   }
 827   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 828   // value and control flow. Now search for ifs that feed into these region inputs.
 829   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 830   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 831   if (proj1 == NULL || proj1->outcnt() != 1 ||
 832       proj2 == NULL || proj2->outcnt() != 1) {
 833     return false; // No projection inputs with region as unique user found
 834   }
 835   assert(proj1 != proj2, "should be different projections");
 836   IfNode* iff1 = proj1->in(0)->isa_If();
 837   IfNode* iff2 = proj2->in(0)->isa_If();
 838   if (iff1 == NULL || iff1->outcnt() != 2 ||
 839       iff2 == NULL || iff2->outcnt() != 2) {
 840     return false; // No ifs found
 841   }
 842   if (iff1 == iff2) {
 843     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 844     igvn->replace_input_of(region, idx1, iff1->in(0));
 845     igvn->replace_input_of(region, idx2, igvn->C->top());
 846     return (region == this); // Remove useless if (both projections map to the same control/value)
 847   }
 848   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 849   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 850   if (bol1 == NULL || bol2 == NULL) {
 851     return false; // No bool inputs found
 852   }
 853   Node* cmp1 = bol1->in(1);
 854   Node* cmp2 = bol2->in(1);
 855   bool commute = false;
 856   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 857     return false; // No comparison
 858   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 859              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 860              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 861              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN ||
 862              cmp1->is_SubTypeCheck() || cmp2->is_SubTypeCheck()) {
 863     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 864     // SubTypeCheck is not commutative
 865     return false;
 866   } else if (cmp1 != cmp2) {
 867     if (cmp1->in(1) == cmp2->in(2) &&
 868         cmp1->in(2) == cmp2->in(1)) {
 869       commute = true; // Same but swapped inputs, commute the test
 870     } else {
 871       return false; // Ifs are not comparing the same values
 872     }
 873   }
 874   proj1 = proj1->other_if_proj();
 875   proj2 = proj2->other_if_proj();
 876   if (!((proj1->unique_ctrl_out_or_null() == iff2 &&
 877          proj2->unique_ctrl_out_or_null() == this) ||
 878         (proj2->unique_ctrl_out_or_null() == iff1 &&
 879          proj1->unique_ctrl_out_or_null() == this))) {
 880     return false; // Ifs are not connected through other projs
 881   }
 882   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 883   // through 'region' and map to the same value. Merge the boolean tests and replace
 884   // the ifs by a single comparison.
 885   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 886   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 887   test1 = commute ? test1.commute() : test1;
 888   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 889   BoolTest::mask res = test1.merge(test2);
 890   if (res == BoolTest::illegal) {
 891     return false; // Unable to merge tests
 892   }
 893   // Adjust iff1 to always pass (only iff2 will remain)
 894   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 895   if (res == BoolTest::never) {
 896     // Merged test is always false, adjust iff2 to always fail
 897     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 898   } else {
 899     // Replace bool input of iff2 with merged test
 900     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 901     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 902     if (new_bol->outcnt() == 0) {
 903       igvn->remove_dead_node(new_bol);
 904     }
 905   }
 906   return false;
 907 }
 908 
 909 const RegMask &RegionNode::out_RegMask() const {
 910   return RegMask::Empty;
 911 }
 912 
 913 // Find the one non-null required input.  RegionNode only
 914 Node *Node::nonnull_req() const {
 915   assert( is_Region(), "" );
 916   for( uint i = 1; i < _cnt; i++ )
 917     if( in(i) )
 918       return in(i);
 919   ShouldNotReachHere();
 920   return NULL;
 921 }
 922 
 923 
 924 //=============================================================================
 925 // note that these functions assume that the _adr_type field is flattened
 926 uint PhiNode::hash() const {
 927   const Type* at = _adr_type;
 928   return TypeNode::hash() + (at ? at->hash() : 0);
 929 }
 930 bool PhiNode::cmp( const Node &n ) const {
 931   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 932 }
 933 static inline
 934 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 935   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 936   return Compile::current()->alias_type(at)->adr_type();
 937 }
 938 
 939 //----------------------------make---------------------------------------------
 940 // create a new phi with edges matching r and set (initially) to x
 941 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 942   uint preds = r->req();   // Number of predecessor paths
 943   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 944   PhiNode* p = new PhiNode(r, t, at);
 945   for (uint j = 1; j < preds; j++) {
 946     // Fill in all inputs, except those which the region does not yet have
 947     if (r->in(j) != NULL)
 948       p->init_req(j, x);
 949   }
 950   return p;
 951 }
 952 PhiNode* PhiNode::make(Node* r, Node* x) {
 953   const Type*    t  = x->bottom_type();
 954   const TypePtr* at = NULL;
 955   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 956   return make(r, x, t, at);
 957 }
 958 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 959   const Type*    t  = x->bottom_type();
 960   const TypePtr* at = NULL;
 961   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 962   return new PhiNode(r, t, at);
 963 }
 964 
 965 
 966 //------------------------slice_memory-----------------------------------------
 967 // create a new phi with narrowed memory type
 968 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 969   PhiNode* mem = (PhiNode*) clone();
 970   *(const TypePtr**)&mem->_adr_type = adr_type;
 971   // convert self-loops, or else we get a bad graph
 972   for (uint i = 1; i < req(); i++) {
 973     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 974   }
 975   mem->verify_adr_type();
 976   return mem;
 977 }
 978 
 979 //------------------------split_out_instance-----------------------------------
 980 // Split out an instance type from a bottom phi.
 981 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 982   const TypeOopPtr *t_oop = at->isa_oopptr();
 983   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 984   const TypePtr *t = adr_type();
 985   assert(type() == Type::MEMORY &&
 986          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 987           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 988           t->is_oopptr()->cast_to_exactness(true)
 989            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 990            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 991          "bottom or raw memory required");
 992 
 993   // Check if an appropriate node already exists.
 994   Node *region = in(0);
 995   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 996     Node* use = region->fast_out(k);
 997     if( use->is_Phi()) {
 998       PhiNode *phi2 = use->as_Phi();
 999       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
1000         return phi2;
1001       }
1002     }
1003   }
1004   Compile *C = igvn->C;
1005   Arena *a = Thread::current()->resource_area();
1006   Node_Array node_map = new Node_Array(a);
1007   Node_Stack stack(a, C->live_nodes() >> 4);
1008   PhiNode *nphi = slice_memory(at);
1009   igvn->register_new_node_with_optimizer( nphi );
1010   node_map.map(_idx, nphi);
1011   stack.push((Node *)this, 1);
1012   while(!stack.is_empty()) {
1013     PhiNode *ophi = stack.node()->as_Phi();
1014     uint i = stack.index();
1015     assert(i >= 1, "not control edge");
1016     stack.pop();
1017     nphi = node_map[ophi->_idx]->as_Phi();
1018     for (; i < ophi->req(); i++) {
1019       Node *in = ophi->in(i);
1020       if (in == NULL || igvn->type(in) == Type::TOP)
1021         continue;
1022       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
1023       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
1024       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
1025         opt = node_map[optphi->_idx];
1026         if (opt == NULL) {
1027           stack.push(ophi, i);
1028           nphi = optphi->slice_memory(at);
1029           igvn->register_new_node_with_optimizer( nphi );
1030           node_map.map(optphi->_idx, nphi);
1031           ophi = optphi;
1032           i = 0; // will get incremented at top of loop
1033           continue;
1034         }
1035       }
1036       nphi->set_req(i, opt);
1037     }
1038   }
1039   return nphi;
1040 }
1041 
1042 //------------------------verify_adr_type--------------------------------------
1043 #ifdef ASSERT
1044 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1045   if (visited.test_set(_idx))  return;  //already visited
1046 
1047   // recheck constructor invariants:
1048   verify_adr_type(false);
1049 
1050   // recheck local phi/phi consistency:
1051   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1052          "adr_type must be consistent across phi nest");
1053 
1054   // walk around
1055   for (uint i = 1; i < req(); i++) {
1056     Node* n = in(i);
1057     if (n == NULL)  continue;
1058     const Node* np = in(i);
1059     if (np->is_Phi()) {
1060       np->as_Phi()->verify_adr_type(visited, at);
1061     } else if (n->bottom_type() == Type::TOP
1062                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1063       // ignore top inputs
1064     } else {
1065       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1066       // recheck phi/non-phi consistency at leaves:
1067       assert((nat != NULL) == (at != NULL), "");
1068       assert(nat == at || nat == TypePtr::BOTTOM,
1069              "adr_type must be consistent at leaves of phi nest");
1070     }
1071   }
1072 }
1073 
1074 // Verify a whole nest of phis rooted at this one.
1075 void PhiNode::verify_adr_type(bool recursive) const {
1076   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1077   if (Node::in_dump())               return;  // muzzle asserts when printing
1078 
1079   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1080 
1081   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1082 
1083   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1084          "Phi::adr_type must be pre-normalized");
1085 
1086   if (recursive) {
1087     VectorSet visited;
1088     verify_adr_type(visited, _adr_type);
1089   }
1090 }
1091 #endif
1092 
1093 
1094 //------------------------------Value------------------------------------------
1095 // Compute the type of the PhiNode
1096 const Type* PhiNode::Value(PhaseGVN* phase) const {
1097   Node *r = in(0);              // RegionNode
1098   if( !r )                      // Copy or dead
1099     return in(1) ? phase->type(in(1)) : Type::TOP;
1100 
1101   // Note: During parsing, phis are often transformed before their regions.
1102   // This means we have to use type_or_null to defend against untyped regions.
1103   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1104     return Type::TOP;
1105 
1106   // Check for trip-counted loop.  If so, be smarter.
1107   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : NULL;
1108   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1109     // protect against init_trip() or limit() returning NULL
1110     if (l->can_be_counted_loop(phase)) {
1111       const Node* init = l->init_trip();
1112       const Node* limit = l->limit();
1113       const Node* stride = l->stride();
1114       if (init != NULL && limit != NULL && stride != NULL) {
1115         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1116         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1117         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1118         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1119           assert(stride_t->is_con(), "bad stride type");
1120           BoolTest::mask bt = l->loopexit()->test_trip();
1121           // If the loop exit condition is "not equal", the condition
1122           // would not trigger if init > limit (if stride > 0) or if
1123           // init < limit if (stride > 0) so we can't deduce bounds
1124           // for the iv from the exit condition.
1125           if (bt != BoolTest::ne) {
1126             jlong stride_con = stride_t->get_con_as_long(l->bt());
1127             if (stride_con < 0) {          // Down-counter loop
1128               swap(lo, hi);
1129               jlong iv_range_lower_limit = lo->lo_as_long();
1130               // Prevent overflow when adding one below
1131               if (iv_range_lower_limit < max_signed_integer(l->bt())) {
1132                 // The loop exit condition is: iv + stride > limit (iv is this Phi). So the loop iterates until
1133                 // iv + stride <= limit
1134                 // We know that: limit >= lo->lo_as_long() and stride <= -1
1135                 // So when the loop exits, iv has to be at most lo->lo_as_long() + 1
1136                 iv_range_lower_limit += 1; // lo is after decrement
1137                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1138                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != -1) {
1139                   julong uhi = static_cast<julong>(hi->lo_as_long());
1140                   julong ulo = static_cast<julong>(lo->hi_as_long());
1141                   julong diff = ((uhi - ulo - 1) / (-stride_con)) * (-stride_con);
1142                   julong ufirst = hi->lo_as_long() - diff;
1143                   iv_range_lower_limit = reinterpret_cast<jlong &>(ufirst);
1144                   assert(iv_range_lower_limit >= lo->lo_as_long() + 1, "should end up with narrower range");
1145                 }
1146               }
1147               return TypeInteger::make(MIN2(iv_range_lower_limit, hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1148             } else if (stride_con >= 0) {
1149               jlong iv_range_upper_limit = hi->hi_as_long();
1150               // Prevent overflow when subtracting one below
1151               if (iv_range_upper_limit > min_signed_integer(l->bt())) {
1152                 // The loop exit condition is: iv + stride < limit (iv is this Phi). So the loop iterates until
1153                 // iv + stride >= limit
1154                 // We know that: limit <= hi->hi_as_long() and stride >= 1
1155                 // So when the loop exits, iv has to be at most hi->hi_as_long() - 1
1156                 iv_range_upper_limit -= 1;
1157                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1158                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != 1) {
1159                   julong uhi = static_cast<julong>(hi->lo_as_long());
1160                   julong ulo = static_cast<julong>(lo->hi_as_long());
1161                   julong diff = ((uhi - ulo - 1) / stride_con) * stride_con;
1162                   julong ulast = lo->hi_as_long() + diff;
1163                   iv_range_upper_limit = reinterpret_cast<jlong &>(ulast);
1164                   assert(iv_range_upper_limit <= hi->hi_as_long() - 1, "should end up with narrower range");
1165                 }
1166               }
1167               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), iv_range_upper_limit), 3, l->bt())->filter_speculative(_type);
1168             }
1169           }
1170         }
1171       }
1172     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1173                in(LoopNode::EntryControl) != NULL &&
1174                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1175       // During CCP, if we saturate the type of a counted loop's Phi
1176       // before the special code for counted loop above has a chance
1177       // to run (that is as long as the type of the backedge's control
1178       // is top), we might end up with non monotonic types
1179       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1180     }
1181   }
1182 
1183   // Until we have harmony between classes and interfaces in the type
1184   // lattice, we must tread carefully around phis which implicitly
1185   // convert the one to the other.
1186   const TypePtr* ttp = _type->make_ptr();
1187   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1188   const TypeInstKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_instklassptr() : NULL;
1189   bool is_intf = false;
1190   if (ttip != NULL) {
1191     if (ttip->is_interface())
1192       is_intf = true;
1193   }
1194   if (ttkp != NULL) {
1195     if (ttkp->is_interface())
1196       is_intf = true;
1197   }
1198 
1199   // Default case: merge all inputs
1200   const Type *t = Type::TOP;        // Merged type starting value
1201   for (uint i = 1; i < req(); ++i) {// For all paths in
1202     // Reachable control path?
1203     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1204       const Type* ti = phase->type(in(i));
1205       // We assume that each input of an interface-valued Phi is a true
1206       // subtype of that interface.  This might not be true of the meet
1207       // of all the input types.  The lattice is not distributive in
1208       // such cases.  Ward off asserts in type.cpp by refusing to do
1209       // meets between interfaces and proper classes.
1210       const TypePtr* tip = ti->make_ptr();
1211       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1212       if (tiip) {
1213         bool ti_is_intf = false;
1214         if (tiip->is_interface())
1215           ti_is_intf = true;
1216         if (is_intf != ti_is_intf)
1217           { t = _type; break; }
1218       }
1219       t = t->meet_speculative(ti);
1220     }
1221   }
1222 
1223   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1224   // That is, we expect that "t->higher_equal(_type)" holds true.
1225   // There are various exceptions:
1226   // - Inputs which are phis might in fact be widened unnecessarily.
1227   //   For example, an input might be a widened int while the phi is a short.
1228   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1229   //   and postCCP has removed the cast which encodes the result of the check.
1230   // - The type of this phi is an interface, and the inputs are classes.
1231   // - Value calls on inputs might produce fuzzy results.
1232   //   (Occurrences of this case suggest improvements to Value methods.)
1233   //
1234   // It is not possible to see Type::BOTTOM values as phi inputs,
1235   // because the ciTypeFlow pre-pass produces verifier-quality types.
1236   const Type* ft = t->filter_speculative(_type);  // Worst case type
1237 
1238 #ifdef ASSERT
1239   // The following logic has been moved into TypeOopPtr::filter.
1240   const Type* jt = t->join_speculative(_type);
1241   if (jt->empty()) {           // Emptied out???
1242 
1243     // Check for evil case of 't' being a class and '_type' expecting an
1244     // interface.  This can happen because the bytecodes do not contain
1245     // enough type info to distinguish a Java-level interface variable
1246     // from a Java-level object variable.  If we meet 2 classes which
1247     // both implement interface I, but their meet is at 'j/l/O' which
1248     // doesn't implement I, we have no way to tell if the result should
1249     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1250     // into a Phi which "knows" it's an Interface type we'll have to
1251     // uplift the type.
1252     if (!t->empty() && ttip && ttip->is_interface()) {
1253       assert(ft == _type, ""); // Uplift to interface
1254     } else if (!t->empty() && ttkp && ttkp->is_interface()) {
1255       assert(ft == _type, ""); // Uplift to interface
1256     } else {
1257       // We also have to handle 'evil cases' of interface- vs. class-arrays
1258       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1259       if (!t->empty() && ttip != NULL && ttip->is_interface()) {
1260           assert(ft == _type, "");   // Uplift to array of interface
1261       } else {
1262         // Otherwise it's something stupid like non-overlapping int ranges
1263         // found on dying counted loops.
1264         assert(ft == Type::TOP, ""); // Canonical empty value
1265       }
1266     }
1267   }
1268 
1269   else {
1270 
1271     // If we have an interface-typed Phi and we narrow to a class type, the join
1272     // should report back the class.  However, if we have a J/L/Object
1273     // class-typed Phi and an interface flows in, it's possible that the meet &
1274     // join report an interface back out.  This isn't possible but happens
1275     // because the type system doesn't interact well with interfaces.
1276     const TypePtr *jtp = jt->make_ptr();
1277     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1278     const TypeInstKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_instklassptr() : NULL;
1279     if (jtip && ttip) {
1280       if (jtip->is_interface() &&
1281           !ttip->is_interface()) {
1282         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1283                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1284         jt = ft;
1285       }
1286     }
1287     if (jtkp && ttkp) {
1288       if (jtkp->is_interface() &&
1289           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1290           ttkp->is_loaded() && !ttkp->is_interface()) {
1291         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1292                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1293         jt = ft;
1294       }
1295     }
1296     if (jt != ft && jt->base() == ft->base()) {
1297       if (jt->isa_int() &&
1298           jt->is_int()->_lo == ft->is_int()->_lo &&
1299           jt->is_int()->_hi == ft->is_int()->_hi)
1300         jt = ft;
1301       if (jt->isa_long() &&
1302           jt->is_long()->_lo == ft->is_long()->_lo &&
1303           jt->is_long()->_hi == ft->is_long()->_hi)
1304         jt = ft;
1305     }
1306     if (jt != ft) {
1307       tty->print("merge type:  "); t->dump(); tty->cr();
1308       tty->print("kill type:   "); _type->dump(); tty->cr();
1309       tty->print("join type:   "); jt->dump(); tty->cr();
1310       tty->print("filter type: "); ft->dump(); tty->cr();
1311     }
1312     assert(jt == ft, "");
1313   }
1314 #endif //ASSERT
1315 
1316   // Deal with conversion problems found in data loops.
1317   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1318 
1319   return ft;
1320 }
1321 
1322 
1323 //------------------------------is_diamond_phi---------------------------------
1324 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1325 // index of the true path or 0 otherwise.
1326 // If check_control_only is true, do not inspect the If node at the
1327 // top, and return -1 (not an edge number) on success.
1328 int PhiNode::is_diamond_phi(bool check_control_only) const {
1329   // Check for a 2-path merge
1330   Node *region = in(0);
1331   if( !region ) return 0;
1332   if( region->req() != 3 ) return 0;
1333   if(         req() != 3 ) return 0;
1334   // Check that both paths come from the same If
1335   Node *ifp1 = region->in(1);
1336   Node *ifp2 = region->in(2);
1337   if( !ifp1 || !ifp2 ) return 0;
1338   Node *iff = ifp1->in(0);
1339   if( !iff || !iff->is_If() ) return 0;
1340   if( iff != ifp2->in(0) ) return 0;
1341   if (check_control_only)  return -1;
1342   // Check for a proper bool/cmp
1343   const Node *b = iff->in(1);
1344   if( !b->is_Bool() ) return 0;
1345   const Node *cmp = b->in(1);
1346   if( !cmp->is_Cmp() ) return 0;
1347 
1348   // Check for branching opposite expected
1349   if( ifp2->Opcode() == Op_IfTrue ) {
1350     assert( ifp1->Opcode() == Op_IfFalse, "" );
1351     return 2;
1352   } else {
1353     assert( ifp1->Opcode() == Op_IfTrue, "" );
1354     return 1;
1355   }
1356 }
1357 
1358 //----------------------------check_cmove_id-----------------------------------
1359 // Check for CMove'ing a constant after comparing against the constant.
1360 // Happens all the time now, since if we compare equality vs a constant in
1361 // the parser, we "know" the variable is constant on one path and we force
1362 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1363 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1364 // general in that we don't need constants.  Since CMove's are only inserted
1365 // in very special circumstances, we do it here on generic Phi's.
1366 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1367   assert(true_path !=0, "only diamond shape graph expected");
1368 
1369   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1370   // phi->region->if_proj->ifnode->bool->cmp
1371   Node*     region = in(0);
1372   Node*     iff    = region->in(1)->in(0);
1373   BoolNode* b      = iff->in(1)->as_Bool();
1374   Node*     cmp    = b->in(1);
1375   Node*     tval   = in(true_path);
1376   Node*     fval   = in(3-true_path);
1377   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1378   if (id == NULL)
1379     return NULL;
1380 
1381   // Either value might be a cast that depends on a branch of 'iff'.
1382   // Since the 'id' value will float free of the diamond, either
1383   // decast or return failure.
1384   Node* ctl = id->in(0);
1385   if (ctl != NULL && ctl->in(0) == iff) {
1386     if (id->is_ConstraintCast()) {
1387       return id->in(1);
1388     } else {
1389       // Don't know how to disentangle this value.
1390       return NULL;
1391     }
1392   }
1393 
1394   return id;
1395 }
1396 
1397 //------------------------------Identity---------------------------------------
1398 // Check for Region being Identity.
1399 Node* PhiNode::Identity(PhaseGVN* phase) {
1400   // Check for no merging going on
1401   // (There used to be special-case code here when this->region->is_Loop.
1402   // It would check for a tributary phi on the backedge that the main phi
1403   // trivially, perhaps with a single cast.  The unique_input method
1404   // does all this and more, by reducing such tributaries to 'this'.)
1405   Node* uin = unique_input(phase, false);
1406   if (uin != NULL) {
1407     return uin;
1408   }
1409 
1410   int true_path = is_diamond_phi();
1411   // Delay CMove'ing identity if Ideal has not had the chance to handle unsafe cases, yet.
1412   if (true_path != 0 && !(phase->is_IterGVN() && wait_for_region_igvn(phase))) {
1413     Node* id = is_cmove_id(phase, true_path);
1414     if (id != NULL) {
1415       return id;
1416     }
1417   }
1418 
1419   // Looking for phis with identical inputs.  If we find one that has
1420   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1421   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1422       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1423     uint phi_len = req();
1424     Node* phi_reg = region();
1425     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1426       Node* u = phi_reg->fast_out(i);
1427       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1428           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1429           u->req() == phi_len) {
1430         for (uint j = 1; j < phi_len; j++) {
1431           if (in(j) != u->in(j)) {
1432             u = NULL;
1433             break;
1434           }
1435         }
1436         if (u != NULL) {
1437           return u;
1438         }
1439       }
1440     }
1441   }
1442 
1443   return this;                     // No identity
1444 }
1445 
1446 //-----------------------------unique_input------------------------------------
1447 // Find the unique value, discounting top, self-loops, and casts.
1448 // Return top if there are no inputs, and self if there are multiple.
1449 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1450   //  1) One unique direct input,
1451   // or if uncast is true:
1452   //  2) some of the inputs have an intervening ConstraintCast
1453   //  3) an input is a self loop
1454   //
1455   //  1) input   or   2) input     or   3) input __
1456   //     /   \           /   \               \  /  \
1457   //     \   /          |    cast             phi  cast
1458   //      phi            \   /               /  \  /
1459   //                      phi               /    --
1460 
1461   Node* r = in(0);                      // RegionNode
1462   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1463 
1464   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1465     Node* rc = r->in(i);
1466     if (rc == NULL || phase->type(rc) == Type::TOP)
1467       continue;                 // ignore unreachable control path
1468     Node* n = in(i);
1469     if (n == NULL)
1470       continue;
1471     Node* un = n;
1472     if (uncast) {
1473 #ifdef ASSERT
1474       Node* m = un->uncast();
1475 #endif
1476       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1477         Node* next = un->in(1);
1478         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1479           // risk exposing raw ptr at safepoint
1480           break;
1481         }
1482         un = next;
1483       }
1484       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1485     }
1486     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1487       continue; // ignore if top, or in(i) and "this" are in a data cycle
1488     }
1489     // Check for a unique input (maybe uncasted)
1490     if (input == NULL) {
1491       input = un;
1492     } else if (input != un) {
1493       input = NodeSentinel; // no unique input
1494     }
1495   }
1496   if (input == NULL) {
1497     return phase->C->top();        // no inputs
1498   }
1499 
1500   if (input != NodeSentinel) {
1501     return input;           // one unique direct input
1502   }
1503 
1504   // Nothing.
1505   return NULL;
1506 }
1507 
1508 //------------------------------is_x2logic-------------------------------------
1509 // Check for simple convert-to-boolean pattern
1510 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1511 // Convert Phi to an ConvIB.
1512 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1513   assert(true_path !=0, "only diamond shape graph expected");
1514   // Convert the true/false index into an expected 0/1 return.
1515   // Map 2->0 and 1->1.
1516   int flipped = 2-true_path;
1517 
1518   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1519   // phi->region->if_proj->ifnode->bool->cmp
1520   Node *region = phi->in(0);
1521   Node *iff = region->in(1)->in(0);
1522   BoolNode *b = (BoolNode*)iff->in(1);
1523   const CmpNode *cmp = (CmpNode*)b->in(1);
1524 
1525   Node *zero = phi->in(1);
1526   Node *one  = phi->in(2);
1527   const Type *tzero = phase->type( zero );
1528   const Type *tone  = phase->type( one  );
1529 
1530   // Check for compare vs 0
1531   const Type *tcmp = phase->type(cmp->in(2));
1532   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1533     // Allow cmp-vs-1 if the other input is bounded by 0-1
1534     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1535       return NULL;
1536     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1537   }
1538 
1539   // Check for setting zero/one opposite expected
1540   if( tzero == TypeInt::ZERO ) {
1541     if( tone == TypeInt::ONE ) {
1542     } else return NULL;
1543   } else if( tzero == TypeInt::ONE ) {
1544     if( tone == TypeInt::ZERO ) {
1545       flipped = 1-flipped;
1546     } else return NULL;
1547   } else return NULL;
1548 
1549   // Check for boolean test backwards
1550   if( b->_test._test == BoolTest::ne ) {
1551   } else if( b->_test._test == BoolTest::eq ) {
1552     flipped = 1-flipped;
1553   } else return NULL;
1554 
1555   // Build int->bool conversion
1556   Node *n = new Conv2BNode(cmp->in(1));
1557   if( flipped )
1558     n = new XorINode( phase->transform(n), phase->intcon(1) );
1559 
1560   return n;
1561 }
1562 
1563 //------------------------------is_cond_add------------------------------------
1564 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1565 // To be profitable the control flow has to disappear; there can be no other
1566 // values merging here.  We replace the test-and-branch with:
1567 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1568 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1569 // Then convert Y to 0-or-Y and finally add.
1570 // This is a key transform for SpecJava _201_compress.
1571 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1572   assert(true_path !=0, "only diamond shape graph expected");
1573 
1574   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1575   // phi->region->if_proj->ifnode->bool->cmp
1576   RegionNode *region = (RegionNode*)phi->in(0);
1577   Node *iff = region->in(1)->in(0);
1578   BoolNode* b = iff->in(1)->as_Bool();
1579   const CmpNode *cmp = (CmpNode*)b->in(1);
1580 
1581   // Make sure only merging this one phi here
1582   if (region->has_unique_phi() != phi)  return NULL;
1583 
1584   // Make sure each arm of the diamond has exactly one output, which we assume
1585   // is the region.  Otherwise, the control flow won't disappear.
1586   if (region->in(1)->outcnt() != 1) return NULL;
1587   if (region->in(2)->outcnt() != 1) return NULL;
1588 
1589   // Check for "(P < Q)" of type signed int
1590   if (b->_test._test != BoolTest::lt)  return NULL;
1591   if (cmp->Opcode() != Op_CmpI)        return NULL;
1592 
1593   Node *p = cmp->in(1);
1594   Node *q = cmp->in(2);
1595   Node *n1 = phi->in(  true_path);
1596   Node *n2 = phi->in(3-true_path);
1597 
1598   int op = n1->Opcode();
1599   if( op != Op_AddI           // Need zero as additive identity
1600       /*&&op != Op_SubI &&
1601       op != Op_AddP &&
1602       op != Op_XorI &&
1603       op != Op_OrI*/ )
1604     return NULL;
1605 
1606   Node *x = n2;
1607   Node *y = NULL;
1608   if( x == n1->in(1) ) {
1609     y = n1->in(2);
1610   } else if( x == n1->in(2) ) {
1611     y = n1->in(1);
1612   } else return NULL;
1613 
1614   // Not so profitable if compare and add are constants
1615   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1616     return NULL;
1617 
1618   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1619   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1620   return new AddINode(j_and,x);
1621 }
1622 
1623 //------------------------------is_absolute------------------------------------
1624 // Check for absolute value.
1625 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1626   assert(true_path !=0, "only diamond shape graph expected");
1627 
1628   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1629   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1630 
1631   // ABS ends with the merge of 2 control flow paths.
1632   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1633   int false_path = 3 - true_path;
1634 
1635   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1636   // phi->region->if_proj->ifnode->bool->cmp
1637   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1638   Node *cmp = bol->in(1);
1639 
1640   // Check bool sense
1641   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1642     switch (bol->_test._test) {
1643     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1644     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1645     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1646     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1647     default:           return NULL;                              break;
1648     }
1649   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1650     switch (bol->_test._test) {
1651     case BoolTest::lt:
1652     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1653     case BoolTest::gt:
1654     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1655     default:           return NULL;                              break;
1656     }
1657   }
1658 
1659   // Test is next
1660   const Type *tzero = NULL;
1661   switch (cmp->Opcode()) {
1662   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1663   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1664   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1665   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1666   default: return NULL;
1667   }
1668 
1669   // Find zero input of compare; the other input is being abs'd
1670   Node *x = NULL;
1671   bool flip = false;
1672   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1673     x = cmp->in(3 - cmp_zero_idx);
1674   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1675     // The test is inverted, we should invert the result...
1676     x = cmp->in(cmp_zero_idx);
1677     flip = true;
1678   } else {
1679     return NULL;
1680   }
1681 
1682   // Next get the 2 pieces being selected, one is the original value
1683   // and the other is the negated value.
1684   if( phi_root->in(phi_x_idx) != x ) return NULL;
1685 
1686   // Check other phi input for subtract node
1687   Node *sub = phi_root->in(3 - phi_x_idx);
1688 
1689   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1690                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1691 
1692   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1693   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return NULL;
1694 
1695   if (tzero == TypeF::ZERO) {
1696     x = new AbsFNode(x);
1697     if (flip) {
1698       x = new SubFNode(sub->in(1), phase->transform(x));
1699     }
1700   } else if (tzero == TypeD::ZERO) {
1701     x = new AbsDNode(x);
1702     if (flip) {
1703       x = new SubDNode(sub->in(1), phase->transform(x));
1704     }
1705   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1706     x = new AbsINode(x);
1707     if (flip) {
1708       x = new SubINode(sub->in(1), phase->transform(x));
1709     }
1710   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1711     x = new AbsLNode(x);
1712     if (flip) {
1713       x = new SubLNode(sub->in(1), phase->transform(x));
1714     }
1715   } else return NULL;
1716 
1717   return x;
1718 }
1719 
1720 //------------------------------split_once-------------------------------------
1721 // Helper for split_flow_path
1722 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1723   igvn->hash_delete(n);         // Remove from hash before hacking edges
1724 
1725   uint j = 1;
1726   for (uint i = phi->req()-1; i > 0; i--) {
1727     if (phi->in(i) == val) {   // Found a path with val?
1728       // Add to NEW Region/Phi, no DU info
1729       newn->set_req( j++, n->in(i) );
1730       // Remove from OLD Region/Phi
1731       n->del_req(i);
1732     }
1733   }
1734 
1735   // Register the new node but do not transform it.  Cannot transform until the
1736   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1737   igvn->register_new_node_with_optimizer( newn );
1738 
1739   // Now I can point to the new node.
1740   n->add_req(newn);
1741   igvn->_worklist.push(n);
1742 }
1743 
1744 //------------------------------split_flow_path--------------------------------
1745 // Check for merging identical values and split flow paths
1746 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1747   BasicType bt = phi->type()->basic_type();
1748   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1749     return NULL;                // Bail out on funny non-value stuff
1750   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1751     return NULL;                // third unequal input to be worth doing
1752 
1753   // Scan for a constant
1754   uint i;
1755   for( i = 1; i < phi->req()-1; i++ ) {
1756     Node *n = phi->in(i);
1757     if( !n ) return NULL;
1758     if( phase->type(n) == Type::TOP ) return NULL;
1759     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1760       break;
1761   }
1762   if( i >= phi->req() )         // Only split for constants
1763     return NULL;
1764 
1765   Node *val = phi->in(i);       // Constant to split for
1766   uint hit = 0;                 // Number of times it occurs
1767   Node *r = phi->region();
1768 
1769   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1770     Node *n = phi->in(i);
1771     if( !n ) return NULL;
1772     if( phase->type(n) == Type::TOP ) return NULL;
1773     if( phi->in(i) == val ) {
1774       hit++;
1775       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1776         return NULL;            // don't split loop entry path
1777       }
1778     }
1779   }
1780 
1781   if( hit <= 1 ||               // Make sure we find 2 or more
1782       hit == phi->req()-1 )     // and not ALL the same value
1783     return NULL;
1784 
1785   // Now start splitting out the flow paths that merge the same value.
1786   // Split first the RegionNode.
1787   PhaseIterGVN *igvn = phase->is_IterGVN();
1788   RegionNode *newr = new RegionNode(hit+1);
1789   split_once(igvn, phi, val, r, newr);
1790 
1791   // Now split all other Phis than this one
1792   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1793     Node* phi2 = r->fast_out(k);
1794     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1795       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1796       split_once(igvn, phi, val, phi2, newphi);
1797     }
1798   }
1799 
1800   // Clean up this guy
1801   igvn->hash_delete(phi);
1802   for( i = phi->req()-1; i > 0; i-- ) {
1803     if( phi->in(i) == val ) {
1804       phi->del_req(i);
1805     }
1806   }
1807   phi->add_req(val);
1808 
1809   return phi;
1810 }
1811 
1812 //=============================================================================
1813 //------------------------------simple_data_loop_check-------------------------
1814 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1815 //  Returns:
1816 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1817 // Safe       - safe case when the phi and it's inputs reference only safe data
1818 //              nodes;
1819 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1820 //              is no reference back to the phi - need a graph walk
1821 //              to determine if it is in a loop;
1822 // UnsafeLoop - unsafe case when the phi references itself directly or through
1823 //              unsafe data node.
1824 //  Note: a safe data node is a node which could/never reference itself during
1825 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1826 //  I mark Phi nodes as safe node not only because they can reference itself
1827 //  but also to prevent mistaking the fallthrough case inside an outer loop
1828 //  as dead loop when the phi references itself through an other phi.
1829 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1830   // It is unsafe loop if the phi node references itself directly.
1831   if (in == (Node*)this)
1832     return UnsafeLoop; // Unsafe loop
1833   // Unsafe loop if the phi node references itself through an unsafe data node.
1834   // Exclude cases with null inputs or data nodes which could reference
1835   // itself (safe for dead loops).
1836   if (in != NULL && !in->is_dead_loop_safe()) {
1837     // Check inputs of phi's inputs also.
1838     // It is much less expensive then full graph walk.
1839     uint cnt = in->req();
1840     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1841     for (; i < cnt; ++i) {
1842       Node* m = in->in(i);
1843       if (m == (Node*)this)
1844         return UnsafeLoop; // Unsafe loop
1845       if (m != NULL && !m->is_dead_loop_safe()) {
1846         // Check the most common case (about 30% of all cases):
1847         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1848         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1849         if (m1 == (Node*)this)
1850           return UnsafeLoop; // Unsafe loop
1851         if (m1 != NULL && m1 == m->in(2) &&
1852             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1853           continue; // Safe case
1854         }
1855         // The phi references an unsafe node - need full analysis.
1856         return Unsafe;
1857       }
1858     }
1859   }
1860   return Safe; // Safe case - we can optimize the phi node.
1861 }
1862 
1863 //------------------------------is_unsafe_data_reference-----------------------
1864 // If phi can be reached through the data input - it is data loop.
1865 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1866   assert(req() > 1, "");
1867   // First, check simple cases when phi references itself directly or
1868   // through an other node.
1869   LoopSafety safety = simple_data_loop_check(in);
1870   if (safety == UnsafeLoop)
1871     return true;  // phi references itself - unsafe loop
1872   else if (safety == Safe)
1873     return false; // Safe case - phi could be replaced with the unique input.
1874 
1875   // Unsafe case when we should go through data graph to determine
1876   // if the phi references itself.
1877 
1878   ResourceMark rm;
1879 
1880   Node_List nstack;
1881   VectorSet visited;
1882 
1883   nstack.push(in); // Start with unique input.
1884   visited.set(in->_idx);
1885   while (nstack.size() != 0) {
1886     Node* n = nstack.pop();
1887     uint cnt = n->req();
1888     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1889     for (; i < cnt; i++) {
1890       Node* m = n->in(i);
1891       if (m == (Node*)this) {
1892         return true;    // Data loop
1893       }
1894       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1895         if (!visited.test_set(m->_idx))
1896           nstack.push(m);
1897       }
1898     }
1899   }
1900   return false; // The phi is not reachable from its inputs
1901 }
1902 
1903 // Is this Phi's region or some inputs to the region enqueued for IGVN
1904 // and so could cause the region to be optimized out?
1905 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1906   PhaseIterGVN* igvn = phase->is_IterGVN();
1907   Unique_Node_List& worklist = igvn->_worklist;
1908   bool delay = false;
1909   Node* r = in(0);
1910   for (uint j = 1; j < req(); j++) {
1911     Node* rc = r->in(j);
1912     Node* n = in(j);
1913     if (rc != NULL &&
1914         rc->is_Proj()) {
1915       if (worklist.member(rc)) {
1916         delay = true;
1917       } else if (rc->in(0) != NULL &&
1918                  rc->in(0)->is_If()) {
1919         if (worklist.member(rc->in(0))) {
1920           delay = true;
1921         } else if (rc->in(0)->in(1) != NULL &&
1922                    rc->in(0)->in(1)->is_Bool()) {
1923           if (worklist.member(rc->in(0)->in(1))) {
1924             delay = true;
1925           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1926                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1927             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1928               delay = true;
1929             }
1930           }
1931         }
1932       }
1933     }
1934   }
1935   if (delay) {
1936     worklist.push(this);
1937   }
1938   return delay;
1939 }
1940 
1941 //------------------------------Ideal------------------------------------------
1942 // Return a node which is more "ideal" than the current node.  Must preserve
1943 // the CFG, but we can still strip out dead paths.
1944 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1945   Node *r = in(0);              // RegionNode
1946   assert(r != NULL && r->is_Region(), "this phi must have a region");
1947   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1948 
1949   // Note: During parsing, phis are often transformed before their regions.
1950   // This means we have to use type_or_null to defend against untyped regions.
1951   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1952     return NULL;                // No change
1953 
1954   Node *top = phase->C->top();
1955   bool new_phi = (outcnt() == 0); // transforming new Phi
1956   // No change for igvn if new phi is not hooked
1957   if (new_phi && can_reshape)
1958     return NULL;
1959 
1960   // The are 2 situations when only one valid phi's input is left
1961   // (in addition to Region input).
1962   // One: region is not loop - replace phi with this input.
1963   // Two: region is loop - replace phi with top since this data path is dead
1964   //                       and we need to break the dead data loop.
1965   Node* progress = NULL;        // Record if any progress made
1966   for( uint j = 1; j < req(); ++j ){ // For all paths in
1967     // Check unreachable control paths
1968     Node* rc = r->in(j);
1969     Node* n = in(j);            // Get the input
1970     if (rc == NULL || phase->type(rc) == Type::TOP) {
1971       if (n != top) {           // Not already top?
1972         PhaseIterGVN *igvn = phase->is_IterGVN();
1973         if (can_reshape && igvn != NULL) {
1974           igvn->_worklist.push(r);
1975         }
1976         // Nuke it down
1977         set_req_X(j, top, phase);
1978         progress = this;        // Record progress
1979       }
1980     }
1981   }
1982 
1983   if (can_reshape && outcnt() == 0) {
1984     // set_req() above may kill outputs if Phi is referenced
1985     // only by itself on the dead (top) control path.
1986     return top;
1987   }
1988 
1989   bool uncasted = false;
1990   Node* uin = unique_input(phase, false);
1991   if (uin == NULL && can_reshape &&
1992       // If there is a chance that the region can be optimized out do
1993       // not add a cast node that we can't remove yet.
1994       !wait_for_region_igvn(phase)) {
1995     uncasted = true;
1996     uin = unique_input(phase, true);
1997   }
1998   if (uin == top) {             // Simplest case: no alive inputs.
1999     if (can_reshape)            // IGVN transformation
2000       return top;
2001     else
2002       return NULL;              // Identity will return TOP
2003   } else if (uin != NULL) {
2004     // Only one not-NULL unique input path is left.
2005     // Determine if this input is backedge of a loop.
2006     // (Skip new phis which have no uses and dead regions).
2007     if (outcnt() > 0 && r->in(0) != NULL) {
2008       if (is_data_loop(r->as_Region(), uin, phase)) {
2009         // Break this data loop to avoid creation of a dead loop.
2010         if (can_reshape) {
2011           return top;
2012         } else {
2013           // We can't return top if we are in Parse phase - cut inputs only
2014           // let Identity to handle the case.
2015           replace_edge(uin, top, phase);
2016           return NULL;
2017         }
2018       }
2019     }
2020 
2021     if (uncasted) {
2022       // Add cast nodes between the phi to be removed and its unique input.
2023       // Wait until after parsing for the type information to propagate from the casts.
2024       assert(can_reshape, "Invalid during parsing");
2025       const Type* phi_type = bottom_type();
2026       // Add casts to carry the control dependency of the Phi that is
2027       // going away
2028       Node* cast = NULL;
2029       if (phi_type->isa_ptr()) {
2030         const Type* uin_type = phase->type(uin);
2031         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
2032           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2033         } else {
2034           // Use a CastPP for a cast to not null and a CheckCastPP for
2035           // a cast to a new klass (and both if both null-ness and
2036           // klass change).
2037 
2038           // If the type of phi is not null but the type of uin may be
2039           // null, uin's type must be casted to not null
2040           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
2041               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
2042             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency);
2043           }
2044 
2045           // If the type of phi and uin, both casted to not null,
2046           // differ the klass of uin must be (check)cast'ed to match
2047           // that of phi
2048           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2049             Node* n = uin;
2050             if (cast != NULL) {
2051               cast = phase->transform(cast);
2052               n = cast;
2053             }
2054             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, ConstraintCastNode::StrongDependency);
2055           }
2056           if (cast == NULL) {
2057             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2058           }
2059         }
2060       } else {
2061         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency);
2062       }
2063       assert(cast != NULL, "cast should be set");
2064       cast = phase->transform(cast);
2065       // set all inputs to the new cast(s) so the Phi is removed by Identity
2066       PhaseIterGVN* igvn = phase->is_IterGVN();
2067       for (uint i = 1; i < req(); i++) {
2068         set_req_X(i, cast, igvn);
2069       }
2070       uin = cast;
2071     }
2072 
2073     // One unique input.
2074     debug_only(Node* ident = Identity(phase));
2075     // The unique input must eventually be detected by the Identity call.
2076 #ifdef ASSERT
2077     if (ident != uin && !ident->is_top()) {
2078       // print this output before failing assert
2079       r->dump(3);
2080       this->dump(3);
2081       ident->dump();
2082       uin->dump();
2083     }
2084 #endif
2085     assert(ident == uin || ident->is_top(), "Identity must clean this up");
2086     return NULL;
2087   }
2088 
2089   Node* opt = NULL;
2090   int true_path = is_diamond_phi();
2091   if (true_path != 0 &&
2092       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2093       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2094       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2095       !(can_reshape && wait_for_region_igvn(phase))) {
2096     // Check for CMove'ing identity. If it would be unsafe,
2097     // handle it here. In the safe case, let Identity handle it.
2098     Node* unsafe_id = is_cmove_id(phase, true_path);
2099     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
2100       opt = unsafe_id;
2101 
2102     // Check for simple convert-to-boolean pattern
2103     if( opt == NULL )
2104       opt = is_x2logic(phase, this, true_path);
2105 
2106     // Check for absolute value
2107     if( opt == NULL )
2108       opt = is_absolute(phase, this, true_path);
2109 
2110     // Check for conditional add
2111     if( opt == NULL && can_reshape )
2112       opt = is_cond_add(phase, this, true_path);
2113 
2114     // These 4 optimizations could subsume the phi:
2115     // have to check for a dead data loop creation.
2116     if( opt != NULL ) {
2117       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2118         // Found dead loop.
2119         if( can_reshape )
2120           return top;
2121         // We can't return top if we are in Parse phase - cut inputs only
2122         // to stop further optimizations for this phi. Identity will return TOP.
2123         assert(req() == 3, "only diamond merge phi here");
2124         set_req(1, top);
2125         set_req(2, top);
2126         return NULL;
2127       } else {
2128         return opt;
2129       }
2130     }
2131   }
2132 
2133   // Check for merging identical values and split flow paths
2134   if (can_reshape) {
2135     opt = split_flow_path(phase, this);
2136     // This optimization only modifies phi - don't need to check for dead loop.
2137     assert(opt == NULL || opt == this, "do not elide phi");
2138     if (opt != NULL)  return opt;
2139   }
2140 
2141   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2142     // Try to undo Phi of AddP:
2143     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2144     // becomes:
2145     // newbase := (Phi base base2)
2146     // newaddress := (Phi address address2)
2147     // newoffset := (Phi offset offset2)
2148     // (AddP newbase newaddress newoffset)
2149     //
2150     // This occurs as a result of unsuccessful split_thru_phi and
2151     // interferes with taking advantage of addressing modes. See the
2152     // clone_shift_expressions code in matcher.cpp
2153     Node* addp = in(1);
2154     Node* base = addp->in(AddPNode::Base);
2155     Node* address = addp->in(AddPNode::Address);
2156     Node* offset = addp->in(AddPNode::Offset);
2157     if (base != NULL && address != NULL && offset != NULL &&
2158         !base->is_top() && !address->is_top() && !offset->is_top()) {
2159       const Type* base_type = base->bottom_type();
2160       const Type* address_type = address->bottom_type();
2161       // make sure that all the inputs are similar to the first one,
2162       // i.e. AddP with base == address and same offset as first AddP
2163       bool doit = true;
2164       for (uint i = 2; i < req(); i++) {
2165         if (in(i) == NULL ||
2166             in(i)->Opcode() != Op_AddP ||
2167             in(i)->in(AddPNode::Base) == NULL ||
2168             in(i)->in(AddPNode::Address) == NULL ||
2169             in(i)->in(AddPNode::Offset) == NULL ||
2170             in(i)->in(AddPNode::Base)->is_top() ||
2171             in(i)->in(AddPNode::Address)->is_top() ||
2172             in(i)->in(AddPNode::Offset)->is_top()) {
2173           doit = false;
2174           break;
2175         }
2176         if (in(i)->in(AddPNode::Base) != base) {
2177           base = NULL;
2178         }
2179         if (in(i)->in(AddPNode::Offset) != offset) {
2180           offset = NULL;
2181         }
2182         if (in(i)->in(AddPNode::Address) != address) {
2183           address = NULL;
2184         }
2185         // Accumulate type for resulting Phi
2186         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2187         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2188       }
2189       if (doit && base == NULL) {
2190         // Check for neighboring AddP nodes in a tree.
2191         // If they have a base, use that it.
2192         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2193           Node* u = this->fast_out(k);
2194           if (u->is_AddP()) {
2195             Node* base2 = u->in(AddPNode::Base);
2196             if (base2 != NULL && !base2->is_top()) {
2197               if (base == NULL)
2198                 base = base2;
2199               else if (base != base2)
2200                 { doit = false; break; }
2201             }
2202           }
2203         }
2204       }
2205       if (doit) {
2206         if (base == NULL) {
2207           base = new PhiNode(in(0), base_type, NULL);
2208           for (uint i = 1; i < req(); i++) {
2209             base->init_req(i, in(i)->in(AddPNode::Base));
2210           }
2211           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2212         }
2213         if (address == NULL) {
2214           address = new PhiNode(in(0), address_type, NULL);
2215           for (uint i = 1; i < req(); i++) {
2216             address->init_req(i, in(i)->in(AddPNode::Address));
2217           }
2218           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2219         }
2220         if (offset == NULL) {
2221           offset = new PhiNode(in(0), TypeX_X, NULL);
2222           for (uint i = 1; i < req(); i++) {
2223             offset->init_req(i, in(i)->in(AddPNode::Offset));
2224           }
2225           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2226         }
2227         return new AddPNode(base, address, offset);
2228       }
2229     }
2230   }
2231 
2232   // Split phis through memory merges, so that the memory merges will go away.
2233   // Piggy-back this transformation on the search for a unique input....
2234   // It will be as if the merged memory is the unique value of the phi.
2235   // (Do not attempt this optimization unless parsing is complete.
2236   // It would make the parser's memory-merge logic sick.)
2237   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2238   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2239     // see if this phi should be sliced
2240     uint merge_width = 0;
2241     bool saw_self = false;
2242     for( uint i=1; i<req(); ++i ) {// For all paths in
2243       Node *ii = in(i);
2244       // TOP inputs should not be counted as safe inputs because if the
2245       // Phi references itself through all other inputs then splitting the
2246       // Phi through memory merges would create dead loop at later stage.
2247       if (ii == top) {
2248         return NULL; // Delay optimization until graph is cleaned.
2249       }
2250       if (ii->is_MergeMem()) {
2251         MergeMemNode* n = ii->as_MergeMem();
2252         merge_width = MAX2(merge_width, n->req());
2253         saw_self = saw_self || (n->base_memory() == this);
2254       }
2255     }
2256 
2257     // This restriction is temporarily necessary to ensure termination:
2258     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2259 
2260     if (merge_width > Compile::AliasIdxRaw) {
2261       // found at least one non-empty MergeMem
2262       const TypePtr* at = adr_type();
2263       if (at != TypePtr::BOTTOM) {
2264         // Patch the existing phi to select an input from the merge:
2265         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2266         //     Phi:AT1(...m1...)
2267         int alias_idx = phase->C->get_alias_index(at);
2268         for (uint i=1; i<req(); ++i) {
2269           Node *ii = in(i);
2270           if (ii->is_MergeMem()) {
2271             MergeMemNode* n = ii->as_MergeMem();
2272             // compress paths and change unreachable cycles to TOP
2273             // If not, we can update the input infinitely along a MergeMem cycle
2274             // Equivalent code is in MemNode::Ideal_common
2275             Node *m  = phase->transform(n);
2276             if (outcnt() == 0) {  // Above transform() may kill us!
2277               return top;
2278             }
2279             // If transformed to a MergeMem, get the desired slice
2280             // Otherwise the returned node represents memory for every slice
2281             Node *new_mem = (m->is_MergeMem()) ?
2282                              m->as_MergeMem()->memory_at(alias_idx) : m;
2283             // Update input if it is progress over what we have now
2284             if (new_mem != ii) {
2285               set_req_X(i, new_mem, phase->is_IterGVN());
2286               progress = this;
2287             }
2288           }
2289         }
2290       } else {
2291         // We know that at least one MergeMem->base_memory() == this
2292         // (saw_self == true). If all other inputs also references this phi
2293         // (directly or through data nodes) - it is a dead loop.
2294         bool saw_safe_input = false;
2295         for (uint j = 1; j < req(); ++j) {
2296           Node* n = in(j);
2297           if (n->is_MergeMem()) {
2298             MergeMemNode* mm = n->as_MergeMem();
2299             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2300               // Skip this input if it references back to this phi or if the memory path is dead
2301               continue;
2302             }
2303           }
2304           if (!is_unsafe_data_reference(n)) {
2305             saw_safe_input = true; // found safe input
2306             break;
2307           }
2308         }
2309         if (!saw_safe_input) {
2310           // There is a dead loop: All inputs are either dead or reference back to this phi
2311           return top;
2312         }
2313 
2314         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2315         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2316         PhaseIterGVN* igvn = phase->is_IterGVN();
2317         assert(igvn != NULL, "sanity check");
2318         Node* hook = new Node(1);
2319         PhiNode* new_base = (PhiNode*) clone();
2320         // Must eagerly register phis, since they participate in loops.
2321         igvn->register_new_node_with_optimizer(new_base);
2322         hook->add_req(new_base);
2323 
2324         MergeMemNode* result = MergeMemNode::make(new_base);
2325         for (uint i = 1; i < req(); ++i) {
2326           Node *ii = in(i);
2327           if (ii->is_MergeMem()) {
2328             MergeMemNode* n = ii->as_MergeMem();
2329             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2330               // If we have not seen this slice yet, make a phi for it.
2331               bool made_new_phi = false;
2332               if (mms.is_empty()) {
2333                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2334                 made_new_phi = true;
2335                 igvn->register_new_node_with_optimizer(new_phi);
2336                 hook->add_req(new_phi);
2337                 mms.set_memory(new_phi);
2338               }
2339               Node* phi = mms.memory();
2340               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2341               phi->set_req(i, mms.memory2());
2342             }
2343           }
2344         }
2345         // Distribute all self-loops.
2346         { // (Extra braces to hide mms.)
2347           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2348             Node* phi = mms.memory();
2349             for (uint i = 1; i < req(); ++i) {
2350               if (phi->in(i) == this)  phi->set_req(i, phi);
2351             }
2352           }
2353         }
2354         // Already replace this phi node to cut it off from the graph to not interfere in dead loop checks during the
2355         // transformations of the new phi nodes below. Otherwise, we could wrongly conclude that there is no dead loop
2356         // because we are finding this phi node again. Also set the type of the new MergeMem node in case we are also
2357         // visiting it in the transformations below.
2358         igvn->replace_node(this, result);
2359         igvn->set_type(result, result->bottom_type());
2360 
2361         // now transform the new nodes, and return the mergemem
2362         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2363           Node* phi = mms.memory();
2364           mms.set_memory(phase->transform(phi));
2365         }
2366         hook->destruct(igvn);
2367         // Replace self with the result.
2368         return result;
2369       }
2370     }
2371     //
2372     // Other optimizations on the memory chain
2373     //
2374     const TypePtr* at = adr_type();
2375     for( uint i=1; i<req(); ++i ) {// For all paths in
2376       Node *ii = in(i);
2377       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2378       if (ii != new_in ) {
2379         set_req(i, new_in);
2380         progress = this;
2381       }
2382     }
2383   }
2384 
2385 #ifdef _LP64
2386   // Push DecodeN/DecodeNKlass down through phi.
2387   // The rest of phi graph will transform by split EncodeP node though phis up.
2388   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2389     bool may_push = true;
2390     bool has_decodeN = false;
2391     bool is_decodeN = false;
2392     for (uint i=1; i<req(); ++i) {// For all paths in
2393       Node *ii = in(i);
2394       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2395         // Do optimization if a non dead path exist.
2396         if (ii->in(1)->bottom_type() != Type::TOP) {
2397           has_decodeN = true;
2398           is_decodeN = ii->is_DecodeN();
2399         }
2400       } else if (!ii->is_Phi()) {
2401         may_push = false;
2402       }
2403     }
2404 
2405     if (has_decodeN && may_push) {
2406       PhaseIterGVN *igvn = phase->is_IterGVN();
2407       // Make narrow type for new phi.
2408       const Type* narrow_t;
2409       if (is_decodeN) {
2410         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2411       } else {
2412         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2413       }
2414       PhiNode* new_phi = new PhiNode(r, narrow_t);
2415       uint orig_cnt = req();
2416       for (uint i=1; i<req(); ++i) {// For all paths in
2417         Node *ii = in(i);
2418         Node* new_ii = NULL;
2419         if (ii->is_DecodeNarrowPtr()) {
2420           assert(ii->bottom_type() == bottom_type(), "sanity");
2421           new_ii = ii->in(1);
2422         } else {
2423           assert(ii->is_Phi(), "sanity");
2424           if (ii->as_Phi() == this) {
2425             new_ii = new_phi;
2426           } else {
2427             if (is_decodeN) {
2428               new_ii = new EncodePNode(ii, narrow_t);
2429             } else {
2430               new_ii = new EncodePKlassNode(ii, narrow_t);
2431             }
2432             igvn->register_new_node_with_optimizer(new_ii);
2433           }
2434         }
2435         new_phi->set_req(i, new_ii);
2436       }
2437       igvn->register_new_node_with_optimizer(new_phi, this);
2438       if (is_decodeN) {
2439         progress = new DecodeNNode(new_phi, bottom_type());
2440       } else {
2441         progress = new DecodeNKlassNode(new_phi, bottom_type());
2442       }
2443     }
2444   }
2445 #endif
2446 
2447   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2448   if (EnableVectorReboxing && can_reshape && progress == NULL && type()->isa_oopptr()) {
2449     progress = merge_through_phi(this, phase->is_IterGVN());
2450   }
2451 
2452   return progress;              // Return any progress
2453 }
2454 
2455 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2456   Node_Stack stack(1);
2457   VectorSet  visited;
2458   Node_List  node_map;
2459 
2460   stack.push(root_phi, 1); // ignore control
2461   visited.set(root_phi->_idx);
2462 
2463   Node* new_phi = new PhiNode(root_phi->in(0), t);
2464   node_map.map(root_phi->_idx, new_phi);
2465 
2466   while (stack.is_nonempty()) {
2467     Node* n   = stack.node();
2468     uint  idx = stack.index();
2469     assert(n->is_Phi(), "not a phi");
2470     if (idx < n->req()) {
2471       stack.set_index(idx + 1);
2472       Node* def = n->in(idx);
2473       if (def == NULL) {
2474         continue; // ignore dead path
2475       } else if (def->is_Phi()) { // inner node
2476         Node* new_phi = node_map[n->_idx];
2477         if (!visited.test_set(def->_idx)) { // not visited yet
2478           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2479           stack.push(def, 1); // ignore control
2480         }
2481         Node* new_in = node_map[def->_idx];
2482         new_phi->set_req(idx, new_in);
2483       } else if (def->Opcode() == Op_VectorBox) { // leaf
2484         assert(n->is_Phi(), "not a phi");
2485         Node* new_phi = node_map[n->_idx];
2486         new_phi->set_req(idx, def->in(c));
2487       } else {
2488         assert(false, "not optimizeable");
2489         return NULL;
2490       }
2491     } else {
2492       Node* new_phi = node_map[n->_idx];
2493       igvn->register_new_node_with_optimizer(new_phi, n);
2494       stack.pop();
2495     }
2496   }
2497   return new_phi;
2498 }
2499 
2500 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
2501   Node_Stack stack(1);
2502   VectorSet  visited;
2503 
2504   stack.push(root_phi, 1); // ignore control
2505   visited.set(root_phi->_idx);
2506 
2507   VectorBoxNode* cached_vbox = NULL;
2508   while (stack.is_nonempty()) {
2509     Node* n   = stack.node();
2510     uint  idx = stack.index();
2511     if (idx < n->req()) {
2512       stack.set_index(idx + 1);
2513       Node* in = n->in(idx);
2514       if (in == NULL) {
2515         continue; // ignore dead path
2516       } else if (in->isa_Phi()) {
2517         if (!visited.test_set(in->_idx)) {
2518           stack.push(in, 1); // ignore control
2519         }
2520       } else if (in->Opcode() == Op_VectorBox) {
2521         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
2522         if (cached_vbox == NULL) {
2523           cached_vbox = vbox;
2524         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
2525           // TODO: vector type mismatch can be handled with additional reinterpret casts
2526           assert(Type::cmp(vbox->vec_type(), cached_vbox->vec_type()) != 0, "inconsistent");
2527           return NULL; // not optimizable: vector type mismatch
2528         } else if (vbox->box_type() != cached_vbox->box_type()) {
2529           assert(Type::cmp(vbox->box_type(), cached_vbox->box_type()) != 0, "inconsistent");
2530           return NULL; // not optimizable: box type mismatch
2531         }
2532       } else {
2533         return NULL; // not optimizable: neither Phi nor VectorBox
2534       }
2535     } else {
2536       stack.pop();
2537     }
2538   }
2539   assert(cached_vbox != NULL, "sanity");
2540   const TypeInstPtr* btype = cached_vbox->box_type();
2541   const TypeVect*    vtype = cached_vbox->vec_type();
2542   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
2543   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
2544   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
2545 }
2546 
2547 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
2548   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
2549   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
2550   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
2551   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
2552   const bool is_loop = (r->is_Loop() && r->req() == 3);
2553   const Node* top = phase->C->top();
2554   if (is_loop) {
2555     return !uin->eqv_uncast(in(LoopNode::EntryControl));
2556   } else {
2557     // We have a data loop either with an unsafe data reference or if a region is unreachable.
2558     return is_unsafe_data_reference(uin)
2559            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
2560   }
2561 }
2562 
2563 //------------------------------is_tripcount-----------------------------------
2564 bool PhiNode::is_tripcount(BasicType bt) const {
2565   return (in(0) != NULL && in(0)->is_BaseCountedLoop() &&
2566           in(0)->as_BaseCountedLoop()->bt() == bt &&
2567           in(0)->as_BaseCountedLoop()->phi() == this);
2568 }
2569 
2570 //------------------------------out_RegMask------------------------------------
2571 const RegMask &PhiNode::in_RegMask(uint i) const {
2572   return i ? out_RegMask() : RegMask::Empty;
2573 }
2574 
2575 const RegMask &PhiNode::out_RegMask() const {
2576   uint ideal_reg = _type->ideal_reg();
2577   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2578   if( ideal_reg == 0 ) return RegMask::Empty;
2579   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2580   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2581 }
2582 
2583 #ifndef PRODUCT
2584 void PhiNode::dump_spec(outputStream *st) const {
2585   TypeNode::dump_spec(st);
2586   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
2587     st->print(" #tripcount");
2588   }
2589 }
2590 #endif
2591 
2592 
2593 //=============================================================================
2594 const Type* GotoNode::Value(PhaseGVN* phase) const {
2595   // If the input is reachable, then we are executed.
2596   // If the input is not reachable, then we are not executed.
2597   return phase->type(in(0));
2598 }
2599 
2600 Node* GotoNode::Identity(PhaseGVN* phase) {
2601   return in(0);                // Simple copy of incoming control
2602 }
2603 
2604 const RegMask &GotoNode::out_RegMask() const {
2605   return RegMask::Empty;
2606 }
2607 
2608 //=============================================================================
2609 const RegMask &JumpNode::out_RegMask() const {
2610   return RegMask::Empty;
2611 }
2612 
2613 //=============================================================================
2614 const RegMask &JProjNode::out_RegMask() const {
2615   return RegMask::Empty;
2616 }
2617 
2618 //=============================================================================
2619 const RegMask &CProjNode::out_RegMask() const {
2620   return RegMask::Empty;
2621 }
2622 
2623 
2624 
2625 //=============================================================================
2626 
2627 uint PCTableNode::hash() const { return Node::hash() + _size; }
2628 bool PCTableNode::cmp( const Node &n ) const
2629 { return _size == ((PCTableNode&)n)._size; }
2630 
2631 const Type *PCTableNode::bottom_type() const {
2632   const Type** f = TypeTuple::fields(_size);
2633   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2634   return TypeTuple::make(_size, f);
2635 }
2636 
2637 //------------------------------Value------------------------------------------
2638 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2639 // Control, otherwise the table targets are not reachable
2640 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2641   if( phase->type(in(0)) == Type::CONTROL )
2642     return bottom_type();
2643   return Type::TOP;             // All paths dead?  Then so are we
2644 }
2645 
2646 //------------------------------Ideal------------------------------------------
2647 // Return a node which is more "ideal" than the current node.  Strip out
2648 // control copies
2649 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2650   return remove_dead_region(phase, can_reshape) ? this : NULL;
2651 }
2652 
2653 //=============================================================================
2654 uint JumpProjNode::hash() const {
2655   return Node::hash() + _dest_bci;
2656 }
2657 
2658 bool JumpProjNode::cmp( const Node &n ) const {
2659   return ProjNode::cmp(n) &&
2660     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2661 }
2662 
2663 #ifndef PRODUCT
2664 void JumpProjNode::dump_spec(outputStream *st) const {
2665   ProjNode::dump_spec(st);
2666   st->print("@bci %d ",_dest_bci);
2667 }
2668 
2669 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2670   ProjNode::dump_compact_spec(st);
2671   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2672 }
2673 #endif
2674 
2675 //=============================================================================
2676 //------------------------------Value------------------------------------------
2677 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2678 // have the default "fall_through_index" path.
2679 const Type* CatchNode::Value(PhaseGVN* phase) const {
2680   // Unreachable?  Then so are all paths from here.
2681   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2682   // First assume all paths are reachable
2683   const Type** f = TypeTuple::fields(_size);
2684   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2685   // Identify cases that will always throw an exception
2686   // () rethrow call
2687   // () virtual or interface call with NULL receiver
2688   // () call is a check cast with incompatible arguments
2689   if( in(1)->is_Proj() ) {
2690     Node *i10 = in(1)->in(0);
2691     if( i10->is_Call() ) {
2692       CallNode *call = i10->as_Call();
2693       // Rethrows always throw exceptions, never return
2694       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2695         f[CatchProjNode::fall_through_index] = Type::TOP;
2696       } else if (call->is_AllocateArray()) {
2697         Node* klass_node = call->in(AllocateNode::KlassNode);
2698         Node* length = call->in(AllocateNode::ALength);
2699         const Type* length_type = phase->type(length);
2700         const Type* klass_type = phase->type(klass_node);
2701         Node* valid_length_test = call->in(AllocateNode::ValidLengthTest);
2702         const Type* valid_length_test_t = phase->type(valid_length_test);
2703         if (length_type == Type::TOP || klass_type == Type::TOP || valid_length_test_t == Type::TOP ||
2704             valid_length_test_t->is_int()->is_con(0)) {
2705           f[CatchProjNode::fall_through_index] = Type::TOP;
2706         }
2707       } else if( call->req() > TypeFunc::Parms ) {
2708         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2709         // Check for null receiver to virtual or interface calls
2710         if( call->is_CallDynamicJava() &&
2711             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2712           f[CatchProjNode::fall_through_index] = Type::TOP;
2713         }
2714       } // End of if not a runtime stub
2715     } // End of if have call above me
2716   } // End of slot 1 is not a projection
2717   return TypeTuple::make(_size, f);
2718 }
2719 
2720 //=============================================================================
2721 uint CatchProjNode::hash() const {
2722   return Node::hash() + _handler_bci;
2723 }
2724 
2725 
2726 bool CatchProjNode::cmp( const Node &n ) const {
2727   return ProjNode::cmp(n) &&
2728     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2729 }
2730 
2731 
2732 //------------------------------Identity---------------------------------------
2733 // If only 1 target is possible, choose it if it is the main control
2734 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2735   // If my value is control and no other value is, then treat as ID
2736   const TypeTuple *t = phase->type(in(0))->is_tuple();
2737   if (t->field_at(_con) != Type::CONTROL)  return this;
2738   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2739   // also remove any exception table entry.  Thus we must know the call
2740   // feeding the Catch will not really throw an exception.  This is ok for
2741   // the main fall-thru control (happens when we know a call can never throw
2742   // an exception) or for "rethrow", because a further optimization will
2743   // yank the rethrow (happens when we inline a function that can throw an
2744   // exception and the caller has no handler).  Not legal, e.g., for passing
2745   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2746   // These cases MUST throw an exception via the runtime system, so the VM
2747   // will be looking for a table entry.
2748   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2749   CallNode *call;
2750   if (_con != TypeFunc::Control && // Bail out if not the main control.
2751       !(proj->is_Proj() &&      // AND NOT a rethrow
2752         proj->in(0)->is_Call() &&
2753         (call = proj->in(0)->as_Call()) &&
2754         call->entry_point() == OptoRuntime::rethrow_stub()))
2755     return this;
2756 
2757   // Search for any other path being control
2758   for (uint i = 0; i < t->cnt(); i++) {
2759     if (i != _con && t->field_at(i) == Type::CONTROL)
2760       return this;
2761   }
2762   // Only my path is possible; I am identity on control to the jump
2763   return in(0)->in(0);
2764 }
2765 
2766 
2767 #ifndef PRODUCT
2768 void CatchProjNode::dump_spec(outputStream *st) const {
2769   ProjNode::dump_spec(st);
2770   st->print("@bci %d ",_handler_bci);
2771 }
2772 #endif
2773 
2774 //=============================================================================
2775 //------------------------------Identity---------------------------------------
2776 // Check for CreateEx being Identity.
2777 Node* CreateExNode::Identity(PhaseGVN* phase) {
2778   if( phase->type(in(1)) == Type::TOP ) return in(1);
2779   if( phase->type(in(0)) == Type::TOP ) return in(0);
2780   // We only come from CatchProj, unless the CatchProj goes away.
2781   // If the CatchProj is optimized away, then we just carry the
2782   // exception oop through.
2783   CallNode *call = in(1)->in(0)->as_Call();
2784 
2785   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2786     ? this
2787     : call->in(TypeFunc::Parms);
2788 }
2789 
2790 //=============================================================================
2791 //------------------------------Value------------------------------------------
2792 // Check for being unreachable.
2793 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2794   if (!in(0) || in(0)->is_top()) return Type::TOP;
2795   return bottom_type();
2796 }
2797 
2798 //------------------------------Ideal------------------------------------------
2799 // Check for no longer being part of a loop
2800 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2801   if (can_reshape && !in(0)->is_Region()) {
2802     // Dead code elimination can sometimes delete this projection so
2803     // if it's not there, there's nothing to do.
2804     Node* fallthru = proj_out_or_null(0);
2805     if (fallthru != NULL) {
2806       phase->is_IterGVN()->replace_node(fallthru, in(0));
2807     }
2808     return phase->C->top();
2809   }
2810   return NULL;
2811 }
2812 
2813 #ifndef PRODUCT
2814 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2815   st->print("%s", Name());
2816 }
2817 #endif