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/regalloc.hpp"
  43 #include "opto/regmask.hpp"
  44 #include "opto/runtime.hpp"
  45 #include "opto/subnode.hpp"
  46 #include "opto/vectornode.hpp"
  47 #include "utilities/vmError.hpp"
  48 
  49 // Portions of code courtesy of Clifford Click
  50 
  51 // Optimization - Graph Style
  52 
  53 //=============================================================================
  54 //------------------------------Value------------------------------------------
  55 // Compute the type of the RegionNode.
  56 const Type* RegionNode::Value(PhaseGVN* phase) const {
  57   for( uint i=1; i<req(); ++i ) {       // For all paths in
  58     Node *n = in(i);            // Get Control source
  59     if( !n ) continue;          // Missing inputs are TOP
  60     if( phase->type(n) == Type::CONTROL )
  61       return Type::CONTROL;
  62   }
  63   return Type::TOP;             // All paths dead?  Then so are we
  64 }
  65 
  66 //------------------------------Identity---------------------------------------
  67 // Check for Region being Identity.
  68 Node* RegionNode::Identity(PhaseGVN* phase) {
  69   // Cannot have Region be an identity, even if it has only 1 input.
  70   // Phi users cannot have their Region input folded away for them,
  71   // since they need to select the proper data input
  72   return this;
  73 }
  74 
  75 //------------------------------merge_region-----------------------------------
  76 // If a Region flows into a Region, merge into one big happy merge.  This is
  77 // hard to do if there is stuff that has to happen
  78 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  79   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  80     return NULL;
  81   Node *progress = NULL;        // Progress flag
  82   PhaseIterGVN *igvn = phase->is_IterGVN();
  83 
  84   uint rreq = region->req();
  85   for( uint i = 1; i < rreq; i++ ) {
  86     Node *r = region->in(i);
  87     if( r && r->Opcode() == Op_Region && // Found a region?
  88         r->in(0) == r &&        // Not already collapsed?
  89         r != region &&          // Avoid stupid situations
  90         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  91       assert(!r->as_Region()->has_phi(), "no phi users");
  92       if( !progress ) {         // No progress
  93         if (region->has_phi()) {
  94           return NULL;        // Only flatten if no Phi users
  95           // igvn->hash_delete( phi );
  96         }
  97         igvn->hash_delete( region );
  98         progress = region;      // Making progress
  99       }
 100       igvn->hash_delete( r );
 101 
 102       // Append inputs to 'r' onto 'region'
 103       for( uint j = 1; j < r->req(); j++ ) {
 104         // Move an input from 'r' to 'region'
 105         region->add_req(r->in(j));
 106         r->set_req(j, phase->C->top());
 107         // Update phis of 'region'
 108         //for( uint k = 0; k < max; k++ ) {
 109         //  Node *phi = region->out(k);
 110         //  if( phi->is_Phi() ) {
 111         //    phi->add_req(phi->in(i));
 112         //  }
 113         //}
 114 
 115         rreq++;                 // One more input to Region
 116       } // Found a region to merge into Region
 117       igvn->_worklist.push(r);
 118       // Clobber pointer to the now dead 'r'
 119       region->set_req(i, phase->C->top());
 120     }
 121   }
 122 
 123   return progress;
 124 }
 125 
 126 
 127 
 128 //--------------------------------has_phi--------------------------------------
 129 // Helper function: Return any PhiNode that uses this region or NULL
 130 PhiNode* RegionNode::has_phi() const {
 131   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 132     Node* phi = fast_out(i);
 133     if (phi->is_Phi()) {   // Check for Phi users
 134       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 135       return phi->as_Phi();  // this one is good enough
 136     }
 137   }
 138 
 139   return NULL;
 140 }
 141 
 142 
 143 //-----------------------------has_unique_phi----------------------------------
 144 // Helper function: Return the only PhiNode that uses this region or NULL
 145 PhiNode* RegionNode::has_unique_phi() const {
 146   // Check that only one use is a Phi
 147   PhiNode* only_phi = NULL;
 148   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 149     Node* phi = fast_out(i);
 150     if (phi->is_Phi()) {   // Check for Phi users
 151       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 152       if (only_phi == NULL) {
 153         only_phi = phi->as_Phi();
 154       } else {
 155         return NULL;  // multiple phis
 156       }
 157     }
 158   }
 159 
 160   return only_phi;
 161 }
 162 
 163 
 164 //------------------------------check_phi_clipping-----------------------------
 165 // Helper function for RegionNode's identification of FP clipping
 166 // Check inputs to the Phi
 167 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 168   min     = NULL;
 169   max     = NULL;
 170   val     = NULL;
 171   min_idx = 0;
 172   max_idx = 0;
 173   val_idx = 0;
 174   uint  phi_max = phi->req();
 175   if( phi_max == 4 ) {
 176     for( uint j = 1; j < phi_max; ++j ) {
 177       Node *n = phi->in(j);
 178       int opcode = n->Opcode();
 179       switch( opcode ) {
 180       case Op_ConI:
 181         {
 182           if( min == NULL ) {
 183             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 184             min_idx = j;
 185           } else {
 186             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 187             max_idx = j;
 188             if( min->get_int() > max->get_int() ) {
 189               // Swap min and max
 190               ConNode *temp;
 191               uint     temp_idx;
 192               temp     = min;     min     = max;     max     = temp;
 193               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 194             }
 195           }
 196         }
 197         break;
 198       default:
 199         {
 200           val = n;
 201           val_idx = j;
 202         }
 203         break;
 204       }
 205     }
 206   }
 207   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 208 }
 209 
 210 
 211 //------------------------------check_if_clipping------------------------------
 212 // Helper function for RegionNode's identification of FP clipping
 213 // Check that inputs to Region come from two IfNodes,
 214 //
 215 //            If
 216 //      False    True
 217 //       If        |
 218 //  False  True    |
 219 //    |      |     |
 220 //  RegionNode_inputs
 221 //
 222 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 223   top_if = NULL;
 224   bot_if = NULL;
 225 
 226   // Check control structure above RegionNode for (if  ( if  ) )
 227   Node *in1 = region->in(1);
 228   Node *in2 = region->in(2);
 229   Node *in3 = region->in(3);
 230   // Check that all inputs are projections
 231   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 232     Node *in10 = in1->in(0);
 233     Node *in20 = in2->in(0);
 234     Node *in30 = in3->in(0);
 235     // Check that #1 and #2 are ifTrue and ifFalse from same If
 236     if( in10 != NULL && in10->is_If() &&
 237         in20 != NULL && in20->is_If() &&
 238         in30 != NULL && in30->is_If() && in10 == in20 &&
 239         (in1->Opcode() != in2->Opcode()) ) {
 240       Node  *in100 = in10->in(0);
 241       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 242       // Check that control for in10 comes from other branch of IF from in3
 243       if( in1000 != NULL && in1000->is_If() &&
 244           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 245         // Control pattern checks
 246         top_if = (IfNode*)in1000;
 247         bot_if = (IfNode*)in10;
 248       }
 249     }
 250   }
 251 
 252   return (top_if != NULL);
 253 }
 254 
 255 
 256 //------------------------------check_convf2i_clipping-------------------------
 257 // Helper function for RegionNode's identification of FP clipping
 258 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 259 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 260   convf2i = NULL;
 261 
 262   // Check for the RShiftNode
 263   Node *rshift = phi->in(idx);
 264   assert( rshift, "Previous checks ensure phi input is present");
 265   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 266 
 267   // Check for the LShiftNode
 268   Node *lshift = rshift->in(1);
 269   assert( lshift, "Previous checks ensure phi input is present");
 270   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 271 
 272   // Check for the ConvF2INode
 273   Node *conv = lshift->in(1);
 274   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 275 
 276   // Check that shift amounts are only to get sign bits set after F2I
 277   jint max_cutoff     = max->get_int();
 278   jint min_cutoff     = min->get_int();
 279   jint left_shift     = lshift->in(2)->get_int();
 280   jint right_shift    = rshift->in(2)->get_int();
 281   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 282   if( left_shift != right_shift ||
 283       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 284       max_post_shift < max_cutoff ||
 285       max_post_shift < -min_cutoff ) {
 286     // Shifts are necessary but current transformation eliminates them
 287     return false;
 288   }
 289 
 290   // OK to return the result of ConvF2I without shifting
 291   convf2i = (ConvF2INode*)conv;
 292   return true;
 293 }
 294 
 295 
 296 //------------------------------check_compare_clipping-------------------------
 297 // Helper function for RegionNode's identification of FP clipping
 298 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 299   Node *i1 = iff->in(1);
 300   if ( !i1->is_Bool() ) { return false; }
 301   BoolNode *bool1 = i1->as_Bool();
 302   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 303   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 304   const Node *cmpF = bool1->in(1);
 305   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 306   // Test that the float value being compared against
 307   // is equivalent to the int value used as a limit
 308   Node *nodef = cmpF->in(2);
 309   if( nodef->Opcode() != Op_ConF ) { return false; }
 310   jfloat conf = nodef->getf();
 311   jint   coni = limit->get_int();
 312   if( ((int)conf) != coni )        { return false; }
 313   input = cmpF->in(1);
 314   return true;
 315 }
 316 
 317 //------------------------------is_unreachable_region--------------------------
 318 // Check if the RegionNode is part of an unsafe loop and unreachable from root.
 319 bool RegionNode::is_unreachable_region(const PhaseGVN* phase) {
 320   Node* top = phase->C->top();
 321   assert(req() == 2 || (req() == 3 && in(1) != NULL && in(2) == top), "sanity check arguments");
 322   if (_is_unreachable_region) {
 323     // Return cached result from previous evaluation which should still be valid
 324     assert(is_unreachable_from_root(phase), "walk the graph again and check if its indeed unreachable");
 325     return true;
 326   }
 327 
 328   // First, cut the simple case of fallthrough region when NONE of
 329   // region's phis references itself directly or through a data node.
 330   if (is_possible_unsafe_loop(phase)) {
 331     // If we have a possible unsafe loop, check if the region node is actually unreachable from root.
 332     if (is_unreachable_from_root(phase)) {
 333       _is_unreachable_region = true;
 334       return true;
 335     }
 336   }
 337   return false;
 338 }
 339 
 340 bool RegionNode::is_possible_unsafe_loop(const PhaseGVN* phase) const {
 341   uint max = outcnt();
 342   uint i;
 343   for (i = 0; i < max; i++) {
 344     Node* n = raw_out(i);
 345     if (n != NULL && n->is_Phi()) {
 346       PhiNode* phi = n->as_Phi();
 347       assert(phi->in(0) == this, "sanity check phi");
 348       if (phi->outcnt() == 0) {
 349         continue; // Safe case - no loops
 350       }
 351       if (phi->outcnt() == 1) {
 352         Node* u = phi->raw_out(0);
 353         // Skip if only one use is an other Phi or Call or Uncommon trap.
 354         // It is safe to consider this case as fallthrough.
 355         if (u != NULL && (u->is_Phi() || u->is_CFG())) {
 356           continue;
 357         }
 358       }
 359       // Check when phi references itself directly or through an other node.
 360       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe) {
 361         break; // Found possible unsafe data loop.
 362       }
 363     }
 364   }
 365   if (i >= max) {
 366     return false; // An unsafe case was NOT found - don't need graph walk.
 367   }
 368   return true;
 369 }
 370 
 371 bool RegionNode::is_unreachable_from_root(const PhaseGVN* phase) const {
 372   ResourceMark rm;
 373   Node_List nstack;
 374   VectorSet visited;
 375 
 376   // Mark all control nodes reachable from root outputs
 377   Node* n = (Node*)phase->C->root();
 378   nstack.push(n);
 379   visited.set(n->_idx);
 380   while (nstack.size() != 0) {
 381     n = nstack.pop();
 382     uint max = n->outcnt();
 383     for (uint i = 0; i < max; i++) {
 384       Node* m = n->raw_out(i);
 385       if (m != NULL && m->is_CFG()) {
 386         if (m == this) {
 387           return false; // We reached the Region node - it is not dead.
 388         }
 389         if (!visited.test_set(m->_idx))
 390           nstack.push(m);
 391       }
 392     }
 393   }
 394   return true; // The Region node is unreachable - it is dead.
 395 }
 396 
 397 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 398   // Incremental inlining + PhaseStringOpts sometimes produce:
 399   //
 400   // cmpP with 1 top input
 401   //           |
 402   //          If
 403   //         /  \
 404   //   IfFalse  IfTrue  /- Some Node
 405   //         \  /      /    /
 406   //        Region    / /-MergeMem
 407   //             \---Phi
 408   //
 409   //
 410   // It's expected by PhaseStringOpts that the Region goes away and is
 411   // replaced by If's control input but because there's still a Phi,
 412   // the Region stays in the graph. The top input from the cmpP is
 413   // propagated forward and a subgraph that is useful goes away. The
 414   // code below replaces the Phi with the MergeMem so that the Region
 415   // is simplified.
 416 
 417   PhiNode* phi = has_unique_phi();
 418   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 419     MergeMemNode* m = NULL;
 420     assert(phi->req() == 3, "same as region");
 421     for (uint i = 1; i < 3; ++i) {
 422       Node *mem = phi->in(i);
 423       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 424         // Nothing is control-dependent on path #i except the region itself.
 425         m = mem->as_MergeMem();
 426         uint j = 3 - i;
 427         Node* other = phi->in(j);
 428         if (other && other == m->base_memory()) {
 429           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 430           // This will allow the diamond to collapse completely.
 431           phase->is_IterGVN()->replace_node(phi, m);
 432           return true;
 433         }
 434       }
 435     }
 436   }
 437   return false;
 438 }
 439 
 440 //------------------------------Ideal------------------------------------------
 441 // Return a node which is more "ideal" than the current node.  Must preserve
 442 // the CFG, but we can still strip out dead paths.
 443 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 444   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 445   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 446 
 447   // Check for RegionNode with no Phi users and both inputs come from either
 448   // arm of the same IF.  If found, then the control-flow split is useless.
 449   bool has_phis = false;
 450   if (can_reshape) {            // Need DU info to check for Phi users
 451     has_phis = (has_phi() != NULL);       // Cache result
 452     if (has_phis && try_clean_mem_phi(phase)) {
 453       has_phis = false;
 454     }
 455 
 456     if (!has_phis) {            // No Phi users?  Nothing merging?
 457       for (uint i = 1; i < req()-1; i++) {
 458         Node *if1 = in(i);
 459         if( !if1 ) continue;
 460         Node *iff = if1->in(0);
 461         if( !iff || !iff->is_If() ) continue;
 462         for( uint j=i+1; j<req(); j++ ) {
 463           if( in(j) && in(j)->in(0) == iff &&
 464               if1->Opcode() != in(j)->Opcode() ) {
 465             // Add the IF Projections to the worklist. They (and the IF itself)
 466             // will be eliminated if dead.
 467             phase->is_IterGVN()->add_users_to_worklist(iff);
 468             set_req(i, iff->in(0));// Skip around the useless IF diamond
 469             set_req(j, NULL);
 470             return this;      // Record progress
 471           }
 472         }
 473       }
 474     }
 475   }
 476 
 477   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 478   // degrades to a copy.
 479   bool add_to_worklist = true;
 480   bool modified = false;
 481   int cnt = 0;                  // Count of values merging
 482   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 483   int del_it = 0;               // The last input path we delete
 484   // For all inputs...
 485   for( uint i=1; i<req(); ++i ){// For all paths in
 486     Node *n = in(i);            // Get the input
 487     if( n != NULL ) {
 488       // Remove useless control copy inputs
 489       if( n->is_Region() && n->as_Region()->is_copy() ) {
 490         set_req(i, n->nonnull_req());
 491         modified = true;
 492         i--;
 493         continue;
 494       }
 495       if( n->is_Proj() ) {      // Remove useless rethrows
 496         Node *call = n->in(0);
 497         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 498           set_req(i, call->in(0));
 499           modified = true;
 500           i--;
 501           continue;
 502         }
 503       }
 504       if( phase->type(n) == Type::TOP ) {
 505         set_req_X(i, NULL, phase); // Ignore TOP inputs
 506         modified = true;
 507         i--;
 508         continue;
 509       }
 510       cnt++;                    // One more value merging
 511 
 512     } else if (can_reshape) {   // Else found dead path with DU info
 513       PhaseIterGVN *igvn = phase->is_IterGVN();
 514       del_req(i);               // Yank path from self
 515       del_it = i;
 516       uint max = outcnt();
 517       DUIterator j;
 518       bool progress = true;
 519       while(progress) {         // Need to establish property over all users
 520         progress = false;
 521         for (j = outs(); has_out(j); j++) {
 522           Node *n = out(j);
 523           if( n->req() != req() && n->is_Phi() ) {
 524             assert( n->in(0) == this, "" );
 525             igvn->hash_delete(n); // Yank from hash before hacking edges
 526             n->set_req_X(i,NULL,igvn);// Correct DU info
 527             n->del_req(i);        // Yank path from Phis
 528             if( max != outcnt() ) {
 529               progress = true;
 530               j = refresh_out_pos(j);
 531               max = outcnt();
 532             }
 533           }
 534         }
 535       }
 536       add_to_worklist = false;
 537       phase->is_IterGVN()->add_users_to_worklist(this);
 538       i--;
 539     }
 540   }
 541 
 542   if (can_reshape && cnt == 1) {
 543     // Is it dead loop?
 544     // If it is LoopNopde it had 2 (+1 itself) inputs and
 545     // one of them was cut. The loop is dead if it was EntryContol.
 546     // Loop node may have only one input because entry path
 547     // is removed in PhaseIdealLoop::Dominators().
 548     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 549     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 550                              (del_it == 0 && is_unreachable_region(phase)))) ||
 551         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 552       // This region and therefore all nodes on the input control path(s) are unreachable
 553       // from root. To avoid incomplete removal of unreachable subgraphs, walk up the CFG
 554       // and aggressively replace all nodes by top.
 555       PhaseIterGVN* igvn = phase->is_IterGVN();
 556       Node* top = phase->C->top();
 557       ResourceMark rm;
 558       Node_List nstack;
 559       VectorSet visited;
 560       nstack.push(this);
 561       visited.set(_idx);
 562       while (nstack.size() != 0) {
 563         Node* n = nstack.pop();
 564         for (uint i = 0; i < n->req(); ++i) {
 565           Node* m = n->in(i);
 566           assert(m != (Node*)phase->C->root(), "Should be unreachable from root");
 567           if (m != NULL && m->is_CFG() && !visited.test_set(m->_idx)) {
 568             nstack.push(m);
 569           }
 570         }
 571         if (n->is_Region()) {
 572           // Eagerly replace phis with top to avoid regionless phis.
 573           n->set_req(0, NULL);
 574           bool progress = true;
 575           uint max = n->outcnt();
 576           DUIterator j;
 577           while (progress) {
 578             progress = false;
 579             for (j = n->outs(); n->has_out(j); j++) {
 580               Node* u = n->out(j);
 581               if (u->is_Phi()) {
 582                 igvn->replace_node(u, top);
 583                 if (max != n->outcnt()) {
 584                   progress = true;
 585                   j = n->refresh_out_pos(j);
 586                   max = n->outcnt();
 587                 }
 588               }
 589             }
 590           }
 591         }
 592         igvn->replace_node(n, top);
 593       }
 594       return NULL;
 595     }
 596   }
 597 
 598   if( cnt <= 1 ) {              // Only 1 path in?
 599     set_req(0, NULL);           // Null control input for region copy
 600     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 601       // No inputs or all inputs are NULL.
 602       return NULL;
 603     } else if (can_reshape) {   // Optimization phase - remove the node
 604       PhaseIterGVN *igvn = phase->is_IterGVN();
 605       // Strip mined (inner) loop is going away, remove outer loop.
 606       if (is_CountedLoop() &&
 607           as_Loop()->is_strip_mined()) {
 608         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 609         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 610         if (outer_sfpt != NULL && outer_out != NULL) {
 611           Node* in = outer_sfpt->in(0);
 612           igvn->replace_node(outer_out, in);
 613           LoopNode* outer = as_CountedLoop()->outer_loop();
 614           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 615         }
 616       }
 617       if (is_CountedLoop()) {
 618         Node* opaq = as_CountedLoop()->is_canonical_loop_entry();
 619         if (opaq != NULL) {
 620           // 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
 621           // subject to further loop opts.
 622           assert(opaq->Opcode() == Op_Opaque1, "");
 623           igvn->replace_node(opaq, opaq->in(1));
 624         }
 625       }
 626       Node *parent_ctrl;
 627       if( cnt == 0 ) {
 628         assert( req() == 1, "no inputs expected" );
 629         // During IGVN phase such region will be subsumed by TOP node
 630         // so region's phis will have TOP as control node.
 631         // Kill phis here to avoid it.
 632         // Also set other user's input to top.
 633         parent_ctrl = phase->C->top();
 634       } else {
 635         // The fallthrough case since we already checked dead loops above.
 636         parent_ctrl = in(1);
 637         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 638         assert(parent_ctrl != this, "Close dead loop");
 639       }
 640       if (add_to_worklist) {
 641         igvn->add_users_to_worklist(this); // Check for further allowed opts
 642       }
 643       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 644         Node* n = last_out(i);
 645         igvn->hash_delete(n); // Remove from worklist before modifying edges
 646         if (n->outcnt() == 0) {
 647           int uses_found = n->replace_edge(this, phase->C->top(), igvn);
 648           if (uses_found > 1) { // (--i) done at the end of the loop.
 649             i -= (uses_found - 1);
 650           }
 651           continue;
 652         }
 653         if( n->is_Phi() ) {   // Collapse all Phis
 654           // Eagerly replace phis to avoid regionless phis.
 655           Node* in;
 656           if( cnt == 0 ) {
 657             assert( n->req() == 1, "No data inputs expected" );
 658             in = parent_ctrl; // replaced by top
 659           } else {
 660             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 661             in = n->in(1);               // replaced by unique input
 662             if( n->as_Phi()->is_unsafe_data_reference(in) )
 663               in = phase->C->top();      // replaced by top
 664           }
 665           igvn->replace_node(n, in);
 666         }
 667         else if( n->is_Region() ) { // Update all incoming edges
 668           assert(n != this, "Must be removed from DefUse edges");
 669           int uses_found = n->replace_edge(this, parent_ctrl, igvn);
 670           if (uses_found > 1) { // (--i) done at the end of the loop.
 671             i -= (uses_found - 1);
 672           }
 673         }
 674         else {
 675           assert(n->in(0) == this, "Expect RegionNode to be control parent");
 676           n->set_req(0, parent_ctrl);
 677         }
 678 #ifdef ASSERT
 679         for( uint k=0; k < n->req(); k++ ) {
 680           assert(n->in(k) != this, "All uses of RegionNode should be gone");
 681         }
 682 #endif
 683       }
 684       // Remove the RegionNode itself from DefUse info
 685       igvn->remove_dead_node(this);
 686       return NULL;
 687     }
 688     return this;                // Record progress
 689   }
 690 
 691 
 692   // If a Region flows into a Region, merge into one big happy merge.
 693   if (can_reshape) {
 694     Node *m = merge_region(this, phase);
 695     if (m != NULL)  return m;
 696   }
 697 
 698   // Check if this region is the root of a clipping idiom on floats
 699   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 700     // Check that only one use is a Phi and that it simplifies to two constants +
 701     PhiNode* phi = has_unique_phi();
 702     if (phi != NULL) {          // One Phi user
 703       // Check inputs to the Phi
 704       ConNode *min;
 705       ConNode *max;
 706       Node    *val;
 707       uint     min_idx;
 708       uint     max_idx;
 709       uint     val_idx;
 710       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 711         IfNode *top_if;
 712         IfNode *bot_if;
 713         if( check_if_clipping( this, bot_if, top_if ) ) {
 714           // Control pattern checks, now verify compares
 715           Node   *top_in = NULL;   // value being compared against
 716           Node   *bot_in = NULL;
 717           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 718               check_compare_clipping( false, top_if, max, top_in ) ) {
 719             if( bot_in == top_in ) {
 720               PhaseIterGVN *gvn = phase->is_IterGVN();
 721               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 722               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 723 
 724               // Check for the ConvF2INode
 725               ConvF2INode *convf2i;
 726               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 727                 convf2i->in(1) == bot_in ) {
 728                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 729                 // max test
 730                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 731                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 732                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 733                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 734                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 735                 // min test
 736                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 737                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 738                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 739                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 740                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 741                 // update input edges to region node
 742                 set_req_X( min_idx, if_min, gvn );
 743                 set_req_X( max_idx, if_max, gvn );
 744                 set_req_X( val_idx, ifF,    gvn );
 745                 // remove unnecessary 'LShiftI; RShiftI' idiom
 746                 gvn->hash_delete(phi);
 747                 phi->set_req_X( val_idx, convf2i, gvn );
 748                 gvn->hash_find_insert(phi);
 749                 // Return transformed region node
 750                 return this;
 751               }
 752             }
 753           }
 754         }
 755       }
 756     }
 757   }
 758 
 759   if (can_reshape) {
 760     modified |= optimize_trichotomy(phase->is_IterGVN());
 761   }
 762 
 763   return modified ? this : NULL;
 764 }
 765 
 766 //------------------------------optimize_trichotomy--------------------------
 767 // Optimize nested comparisons of the following kind:
 768 //
 769 // int compare(int a, int b) {
 770 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 771 // }
 772 //
 773 // Shape 1:
 774 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 775 //
 776 // Shape 2:
 777 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 778 //
 779 // Above code leads to the following IR shapes where both Ifs compare the
 780 // same value and two out of three region inputs idx1 and idx2 map to
 781 // the same value and control flow.
 782 //
 783 // (1)   If                 (2)   If
 784 //      /  \                     /  \
 785 //   Proj  Proj               Proj  Proj
 786 //     |      \                |      \
 787 //     |       If              |      If                      If
 788 //     |      /  \             |     /  \                    /  \
 789 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 790 //     |   /      /            \    |    /                  |    /
 791 //    Region     /              \   |   /                   |   /
 792 //         \    /                \  |  /                    |  /
 793 //         Region                Region                    Region
 794 //
 795 // The method returns true if 'this' is modified and false otherwise.
 796 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 797   int idx1 = 1, idx2 = 2;
 798   Node* region = NULL;
 799   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 800     // Shape 1: Check if one of the inputs is a region that merges two control
 801     // inputs and has no other users (especially no Phi users).
 802     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 803     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 804       return false; // No suitable region input found
 805     }
 806   } else if (req() == 4) {
 807     // Shape 2: Check if two control inputs map to the same value of the unique phi
 808     // user and treat these as if they would come from another region (shape (1)).
 809     PhiNode* phi = has_unique_phi();
 810     if (phi == NULL) {
 811       return false; // No unique phi user
 812     }
 813     if (phi->in(idx1) != phi->in(idx2)) {
 814       idx2 = 3;
 815       if (phi->in(idx1) != phi->in(idx2)) {
 816         idx1 = 2;
 817         if (phi->in(idx1) != phi->in(idx2)) {
 818           return false; // No equal phi inputs found
 819         }
 820       }
 821     }
 822     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 823     region = this;
 824   }
 825   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 826     return false; // Region does not merge two control inputs
 827   }
 828   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 829   // value and control flow. Now search for ifs that feed into these region inputs.
 830   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 831   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 832   if (proj1 == NULL || proj1->outcnt() != 1 ||
 833       proj2 == NULL || proj2->outcnt() != 1) {
 834     return false; // No projection inputs with region as unique user found
 835   }
 836   assert(proj1 != proj2, "should be different projections");
 837   IfNode* iff1 = proj1->in(0)->isa_If();
 838   IfNode* iff2 = proj2->in(0)->isa_If();
 839   if (iff1 == NULL || iff1->outcnt() != 2 ||
 840       iff2 == NULL || iff2->outcnt() != 2) {
 841     return false; // No ifs found
 842   }
 843   if (iff1 == iff2) {
 844     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 845     igvn->replace_input_of(region, idx1, iff1->in(0));
 846     igvn->replace_input_of(region, idx2, igvn->C->top());
 847     return (region == this); // Remove useless if (both projections map to the same control/value)
 848   }
 849   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 850   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 851   if (bol1 == NULL || bol2 == NULL) {
 852     return false; // No bool inputs found
 853   }
 854   Node* cmp1 = bol1->in(1);
 855   Node* cmp2 = bol2->in(1);
 856   bool commute = false;
 857   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 858     return false; // No comparison
 859   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 860              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 861              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 862              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN ||
 863              cmp1->is_SubTypeCheck() || cmp2->is_SubTypeCheck()) {
 864     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 865     // SubTypeCheck is not commutative
 866     return false;
 867   } else if (cmp1 != cmp2) {
 868     if (cmp1->in(1) == cmp2->in(2) &&
 869         cmp1->in(2) == cmp2->in(1)) {
 870       commute = true; // Same but swapped inputs, commute the test
 871     } else {
 872       return false; // Ifs are not comparing the same values
 873     }
 874   }
 875   proj1 = proj1->other_if_proj();
 876   proj2 = proj2->other_if_proj();
 877   if (!((proj1->unique_ctrl_out_or_null() == iff2 &&
 878          proj2->unique_ctrl_out_or_null() == this) ||
 879         (proj2->unique_ctrl_out_or_null() == iff1 &&
 880          proj1->unique_ctrl_out_or_null() == this))) {
 881     return false; // Ifs are not connected through other projs
 882   }
 883   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 884   // through 'region' and map to the same value. Merge the boolean tests and replace
 885   // the ifs by a single comparison.
 886   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 887   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 888   test1 = commute ? test1.commute() : test1;
 889   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 890   BoolTest::mask res = test1.merge(test2);
 891   if (res == BoolTest::illegal) {
 892     return false; // Unable to merge tests
 893   }
 894   // Adjust iff1 to always pass (only iff2 will remain)
 895   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 896   if (res == BoolTest::never) {
 897     // Merged test is always false, adjust iff2 to always fail
 898     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 899   } else {
 900     // Replace bool input of iff2 with merged test
 901     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 902     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 903     if (new_bol->outcnt() == 0) {
 904       igvn->remove_dead_node(new_bol);
 905     }
 906   }
 907   return false;
 908 }
 909 
 910 const RegMask &RegionNode::out_RegMask() const {
 911   return RegMask::Empty;
 912 }
 913 
 914 // Find the one non-null required input.  RegionNode only
 915 Node *Node::nonnull_req() const {
 916   assert( is_Region(), "" );
 917   for( uint i = 1; i < _cnt; i++ )
 918     if( in(i) )
 919       return in(i);
 920   ShouldNotReachHere();
 921   return NULL;
 922 }
 923 
 924 
 925 //=============================================================================
 926 // note that these functions assume that the _adr_type field is flattened
 927 uint PhiNode::hash() const {
 928   const Type* at = _adr_type;
 929   return TypeNode::hash() + (at ? at->hash() : 0);
 930 }
 931 bool PhiNode::cmp( const Node &n ) const {
 932   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 933 }
 934 static inline
 935 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 936   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 937   return Compile::current()->alias_type(at)->adr_type();
 938 }
 939 
 940 //----------------------------make---------------------------------------------
 941 // create a new phi with edges matching r and set (initially) to x
 942 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 943   uint preds = r->req();   // Number of predecessor paths
 944   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 945   PhiNode* p = new PhiNode(r, t, at);
 946   for (uint j = 1; j < preds; j++) {
 947     // Fill in all inputs, except those which the region does not yet have
 948     if (r->in(j) != NULL)
 949       p->init_req(j, x);
 950   }
 951   return p;
 952 }
 953 PhiNode* PhiNode::make(Node* r, Node* x) {
 954   const Type*    t  = x->bottom_type();
 955   const TypePtr* at = NULL;
 956   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 957   return make(r, x, t, at);
 958 }
 959 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 960   const Type*    t  = x->bottom_type();
 961   const TypePtr* at = NULL;
 962   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 963   return new PhiNode(r, t, at);
 964 }
 965 
 966 
 967 //------------------------slice_memory-----------------------------------------
 968 // create a new phi with narrowed memory type
 969 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 970   PhiNode* mem = (PhiNode*) clone();
 971   *(const TypePtr**)&mem->_adr_type = adr_type;
 972   // convert self-loops, or else we get a bad graph
 973   for (uint i = 1; i < req(); i++) {
 974     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 975   }
 976   mem->verify_adr_type();
 977   return mem;
 978 }
 979 
 980 //------------------------split_out_instance-----------------------------------
 981 // Split out an instance type from a bottom phi.
 982 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 983   const TypeOopPtr *t_oop = at->isa_oopptr();
 984   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 985   const TypePtr *t = adr_type();
 986   assert(type() == Type::MEMORY &&
 987          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 988           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 989           t->is_oopptr()->cast_to_exactness(true)
 990            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 991            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 992          "bottom or raw memory required");
 993 
 994   // Check if an appropriate node already exists.
 995   Node *region = in(0);
 996   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 997     Node* use = region->fast_out(k);
 998     if( use->is_Phi()) {
 999       PhiNode *phi2 = use->as_Phi();
1000       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
1001         return phi2;
1002       }
1003     }
1004   }
1005   Compile *C = igvn->C;
1006   Arena *a = Thread::current()->resource_area();
1007   Node_Array node_map = new Node_Array(a);
1008   Node_Stack stack(a, C->live_nodes() >> 4);
1009   PhiNode *nphi = slice_memory(at);
1010   igvn->register_new_node_with_optimizer( nphi );
1011   node_map.map(_idx, nphi);
1012   stack.push((Node *)this, 1);
1013   while(!stack.is_empty()) {
1014     PhiNode *ophi = stack.node()->as_Phi();
1015     uint i = stack.index();
1016     assert(i >= 1, "not control edge");
1017     stack.pop();
1018     nphi = node_map[ophi->_idx]->as_Phi();
1019     for (; i < ophi->req(); i++) {
1020       Node *in = ophi->in(i);
1021       if (in == NULL || igvn->type(in) == Type::TOP)
1022         continue;
1023       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
1024       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
1025       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
1026         opt = node_map[optphi->_idx];
1027         if (opt == NULL) {
1028           stack.push(ophi, i);
1029           nphi = optphi->slice_memory(at);
1030           igvn->register_new_node_with_optimizer( nphi );
1031           node_map.map(optphi->_idx, nphi);
1032           ophi = optphi;
1033           i = 0; // will get incremented at top of loop
1034           continue;
1035         }
1036       }
1037       nphi->set_req(i, opt);
1038     }
1039   }
1040   return nphi;
1041 }
1042 
1043 //------------------------verify_adr_type--------------------------------------
1044 #ifdef ASSERT
1045 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1046   if (visited.test_set(_idx))  return;  //already visited
1047 
1048   // recheck constructor invariants:
1049   verify_adr_type(false);
1050 
1051   // recheck local phi/phi consistency:
1052   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1053          "adr_type must be consistent across phi nest");
1054 
1055   // walk around
1056   for (uint i = 1; i < req(); i++) {
1057     Node* n = in(i);
1058     if (n == NULL)  continue;
1059     const Node* np = in(i);
1060     if (np->is_Phi()) {
1061       np->as_Phi()->verify_adr_type(visited, at);
1062     } else if (n->bottom_type() == Type::TOP
1063                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1064       // ignore top inputs
1065     } else {
1066       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1067       // recheck phi/non-phi consistency at leaves:
1068       assert((nat != NULL) == (at != NULL), "");
1069       assert(nat == at || nat == TypePtr::BOTTOM,
1070              "adr_type must be consistent at leaves of phi nest");
1071     }
1072   }
1073 }
1074 
1075 // Verify a whole nest of phis rooted at this one.
1076 void PhiNode::verify_adr_type(bool recursive) const {
1077   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1078   if (Node::in_dump())               return;  // muzzle asserts when printing
1079 
1080   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1081 
1082   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1083 
1084   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1085          "Phi::adr_type must be pre-normalized");
1086 
1087   if (recursive) {
1088     VectorSet visited;
1089     verify_adr_type(visited, _adr_type);
1090   }
1091 }
1092 #endif
1093 
1094 
1095 //------------------------------Value------------------------------------------
1096 // Compute the type of the PhiNode
1097 const Type* PhiNode::Value(PhaseGVN* phase) const {
1098   Node *r = in(0);              // RegionNode
1099   if( !r )                      // Copy or dead
1100     return in(1) ? phase->type(in(1)) : Type::TOP;
1101 
1102   // Note: During parsing, phis are often transformed before their regions.
1103   // This means we have to use type_or_null to defend against untyped regions.
1104   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1105     return Type::TOP;
1106 
1107   // Check for trip-counted loop.  If so, be smarter.
1108   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : NULL;
1109   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1110     // protect against init_trip() or limit() returning NULL
1111     if (l->can_be_counted_loop(phase)) {
1112       const Node* init = l->init_trip();
1113       const Node* limit = l->limit();
1114       const Node* stride = l->stride();
1115       if (init != NULL && limit != NULL && stride != NULL) {
1116         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1117         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1118         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1119         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1120           assert(stride_t->is_con(), "bad stride type");
1121           BoolTest::mask bt = l->loopexit()->test_trip();
1122           // If the loop exit condition is "not equal", the condition
1123           // would not trigger if init > limit (if stride > 0) or if
1124           // init < limit if (stride > 0) so we can't deduce bounds
1125           // for the iv from the exit condition.
1126           if (bt != BoolTest::ne) {
1127             jlong stride_con = stride_t->get_con_as_long(l->bt());
1128             if (stride_con < 0) {          // Down-counter loop
1129               swap(lo, hi);
1130               jlong iv_range_lower_limit = lo->lo_as_long();
1131               // Prevent overflow when adding one below
1132               if (iv_range_lower_limit < max_signed_integer(l->bt())) {
1133                 // The loop exit condition is: iv + stride > limit (iv is this Phi). So the loop iterates until
1134                 // iv + stride <= limit
1135                 // We know that: limit >= lo->lo_as_long() and stride <= -1
1136                 // So when the loop exits, iv has to be at most lo->lo_as_long() + 1
1137                 iv_range_lower_limit += 1; // lo is after decrement
1138                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1139                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != -1) {
1140                   julong uhi = static_cast<julong>(hi->lo_as_long());
1141                   julong ulo = static_cast<julong>(lo->hi_as_long());
1142                   julong diff = ((uhi - ulo - 1) / (-stride_con)) * (-stride_con);
1143                   julong ufirst = hi->lo_as_long() - diff;
1144                   iv_range_lower_limit = reinterpret_cast<jlong &>(ufirst);
1145                   assert(iv_range_lower_limit >= lo->lo_as_long() + 1, "should end up with narrower range");
1146                 }
1147               }
1148               return TypeInteger::make(MIN2(iv_range_lower_limit, hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1149             } else if (stride_con >= 0) {
1150               jlong iv_range_upper_limit = hi->hi_as_long();
1151               // Prevent overflow when subtracting one below
1152               if (iv_range_upper_limit > min_signed_integer(l->bt())) {
1153                 // The loop exit condition is: iv + stride < limit (iv is this Phi). So the loop iterates until
1154                 // iv + stride >= limit
1155                 // We know that: limit <= hi->hi_as_long() and stride >= 1
1156                 // So when the loop exits, iv has to be at most hi->hi_as_long() - 1
1157                 iv_range_upper_limit -= 1;
1158                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1159                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != 1) {
1160                   julong uhi = static_cast<julong>(hi->lo_as_long());
1161                   julong ulo = static_cast<julong>(lo->hi_as_long());
1162                   julong diff = ((uhi - ulo - 1) / stride_con) * stride_con;
1163                   julong ulast = lo->hi_as_long() + diff;
1164                   iv_range_upper_limit = reinterpret_cast<jlong &>(ulast);
1165                   assert(iv_range_upper_limit <= hi->hi_as_long() - 1, "should end up with narrower range");
1166                 }
1167               }
1168               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), iv_range_upper_limit), 3, l->bt())->filter_speculative(_type);
1169             }
1170           }
1171         }
1172       }
1173     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1174                in(LoopNode::EntryControl) != NULL &&
1175                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1176       // During CCP, if we saturate the type of a counted loop's Phi
1177       // before the special code for counted loop above has a chance
1178       // to run (that is as long as the type of the backedge's control
1179       // is top), we might end up with non monotonic types
1180       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1181     }
1182   }
1183 
1184   // Until we have harmony between classes and interfaces in the type
1185   // lattice, we must tread carefully around phis which implicitly
1186   // convert the one to the other.
1187   const TypePtr* ttp = _type->make_ptr();
1188   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1189   const TypeInstKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_instklassptr() : NULL;
1190   bool is_intf = false;
1191   if (ttip != NULL) {
1192     if (ttip->is_interface())
1193       is_intf = true;
1194   }
1195   if (ttkp != NULL) {
1196     if (ttkp->is_interface())
1197       is_intf = true;
1198   }
1199 
1200   // Default case: merge all inputs
1201   const Type *t = Type::TOP;        // Merged type starting value
1202   for (uint i = 1; i < req(); ++i) {// For all paths in
1203     // Reachable control path?
1204     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1205       const Type* ti = phase->type(in(i));
1206       // We assume that each input of an interface-valued Phi is a true
1207       // subtype of that interface.  This might not be true of the meet
1208       // of all the input types.  The lattice is not distributive in
1209       // such cases.  Ward off asserts in type.cpp by refusing to do
1210       // meets between interfaces and proper classes.
1211       const TypePtr* tip = ti->make_ptr();
1212       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1213       if (tiip) {
1214         bool ti_is_intf = false;
1215         if (tiip->is_interface())
1216           ti_is_intf = true;
1217         if (is_intf != ti_is_intf)
1218           { t = _type; break; }
1219       }
1220       t = t->meet_speculative(ti);
1221     }
1222   }
1223 
1224   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1225   // That is, we expect that "t->higher_equal(_type)" holds true.
1226   // There are various exceptions:
1227   // - Inputs which are phis might in fact be widened unnecessarily.
1228   //   For example, an input might be a widened int while the phi is a short.
1229   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1230   //   and postCCP has removed the cast which encodes the result of the check.
1231   // - The type of this phi is an interface, and the inputs are classes.
1232   // - Value calls on inputs might produce fuzzy results.
1233   //   (Occurrences of this case suggest improvements to Value methods.)
1234   //
1235   // It is not possible to see Type::BOTTOM values as phi inputs,
1236   // because the ciTypeFlow pre-pass produces verifier-quality types.
1237   const Type* ft = t->filter_speculative(_type);  // Worst case type
1238 
1239 #ifdef ASSERT
1240   // The following logic has been moved into TypeOopPtr::filter.
1241   const Type* jt = t->join_speculative(_type);
1242   if (jt->empty()) {           // Emptied out???
1243 
1244     // Check for evil case of 't' being a class and '_type' expecting an
1245     // interface.  This can happen because the bytecodes do not contain
1246     // enough type info to distinguish a Java-level interface variable
1247     // from a Java-level object variable.  If we meet 2 classes which
1248     // both implement interface I, but their meet is at 'j/l/O' which
1249     // doesn't implement I, we have no way to tell if the result should
1250     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1251     // into a Phi which "knows" it's an Interface type we'll have to
1252     // uplift the type.
1253     if (!t->empty() && ttip && ttip->is_interface()) {
1254       assert(ft == _type, ""); // Uplift to interface
1255     } else if (!t->empty() && ttkp && ttkp->is_interface()) {
1256       assert(ft == _type, ""); // Uplift to interface
1257     } else {
1258       // We also have to handle 'evil cases' of interface- vs. class-arrays
1259       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1260       if (!t->empty() && ttip != NULL && ttip->is_interface()) {
1261           assert(ft == _type, "");   // Uplift to array of interface
1262       } else {
1263         // Otherwise it's something stupid like non-overlapping int ranges
1264         // found on dying counted loops.
1265         assert(ft == Type::TOP, ""); // Canonical empty value
1266       }
1267     }
1268   }
1269 
1270   else {
1271 
1272     // If we have an interface-typed Phi and we narrow to a class type, the join
1273     // should report back the class.  However, if we have a J/L/Object
1274     // class-typed Phi and an interface flows in, it's possible that the meet &
1275     // join report an interface back out.  This isn't possible but happens
1276     // because the type system doesn't interact well with interfaces.
1277     const TypePtr *jtp = jt->make_ptr();
1278     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1279     const TypeInstKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_instklassptr() : NULL;
1280     if (jtip && ttip) {
1281       if (jtip->is_interface() &&
1282           !ttip->is_interface()) {
1283         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1284                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1285         jt = ft;
1286       }
1287     }
1288     if (jtkp && ttkp) {
1289       if (jtkp->is_interface() &&
1290           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1291           ttkp->is_loaded() && !ttkp->is_interface()) {
1292         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1293                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1294         jt = ft;
1295       }
1296     }
1297     if (jt != ft && jt->base() == ft->base()) {
1298       if (jt->isa_int() &&
1299           jt->is_int()->_lo == ft->is_int()->_lo &&
1300           jt->is_int()->_hi == ft->is_int()->_hi)
1301         jt = ft;
1302       if (jt->isa_long() &&
1303           jt->is_long()->_lo == ft->is_long()->_lo &&
1304           jt->is_long()->_hi == ft->is_long()->_hi)
1305         jt = ft;
1306     }
1307     if (jt != ft) {
1308       tty->print("merge type:  "); t->dump(); tty->cr();
1309       tty->print("kill type:   "); _type->dump(); tty->cr();
1310       tty->print("join type:   "); jt->dump(); tty->cr();
1311       tty->print("filter type: "); ft->dump(); tty->cr();
1312     }
1313     assert(jt == ft, "");
1314   }
1315 #endif //ASSERT
1316 
1317   // Deal with conversion problems found in data loops.
1318   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1319 
1320   return ft;
1321 }
1322 
1323 
1324 //------------------------------is_diamond_phi---------------------------------
1325 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1326 // index of the true path or 0 otherwise.
1327 // If check_control_only is true, do not inspect the If node at the
1328 // top, and return -1 (not an edge number) on success.
1329 int PhiNode::is_diamond_phi(bool check_control_only) const {
1330   // Check for a 2-path merge
1331   Node *region = in(0);
1332   if( !region ) return 0;
1333   if( region->req() != 3 ) return 0;
1334   if(         req() != 3 ) return 0;
1335   // Check that both paths come from the same If
1336   Node *ifp1 = region->in(1);
1337   Node *ifp2 = region->in(2);
1338   if( !ifp1 || !ifp2 ) return 0;
1339   Node *iff = ifp1->in(0);
1340   if( !iff || !iff->is_If() ) return 0;
1341   if( iff != ifp2->in(0) ) return 0;
1342   if (check_control_only)  return -1;
1343   // Check for a proper bool/cmp
1344   const Node *b = iff->in(1);
1345   if( !b->is_Bool() ) return 0;
1346   const Node *cmp = b->in(1);
1347   if( !cmp->is_Cmp() ) return 0;
1348 
1349   // Check for branching opposite expected
1350   if( ifp2->Opcode() == Op_IfTrue ) {
1351     assert( ifp1->Opcode() == Op_IfFalse, "" );
1352     return 2;
1353   } else {
1354     assert( ifp1->Opcode() == Op_IfTrue, "" );
1355     return 1;
1356   }
1357 }
1358 
1359 //----------------------------check_cmove_id-----------------------------------
1360 // Check for CMove'ing a constant after comparing against the constant.
1361 // Happens all the time now, since if we compare equality vs a constant in
1362 // the parser, we "know" the variable is constant on one path and we force
1363 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1364 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1365 // general in that we don't need constants.  Since CMove's are only inserted
1366 // in very special circumstances, we do it here on generic Phi's.
1367 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1368   assert(true_path !=0, "only diamond shape graph expected");
1369 
1370   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1371   // phi->region->if_proj->ifnode->bool->cmp
1372   Node*     region = in(0);
1373   Node*     iff    = region->in(1)->in(0);
1374   BoolNode* b      = iff->in(1)->as_Bool();
1375   Node*     cmp    = b->in(1);
1376   Node*     tval   = in(true_path);
1377   Node*     fval   = in(3-true_path);
1378   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1379   if (id == NULL)
1380     return NULL;
1381 
1382   // Either value might be a cast that depends on a branch of 'iff'.
1383   // Since the 'id' value will float free of the diamond, either
1384   // decast or return failure.
1385   Node* ctl = id->in(0);
1386   if (ctl != NULL && ctl->in(0) == iff) {
1387     if (id->is_ConstraintCast()) {
1388       return id->in(1);
1389     } else {
1390       // Don't know how to disentangle this value.
1391       return NULL;
1392     }
1393   }
1394 
1395   return id;
1396 }
1397 
1398 //------------------------------Identity---------------------------------------
1399 // Check for Region being Identity.
1400 Node* PhiNode::Identity(PhaseGVN* phase) {
1401   // Check for no merging going on
1402   // (There used to be special-case code here when this->region->is_Loop.
1403   // It would check for a tributary phi on the backedge that the main phi
1404   // trivially, perhaps with a single cast.  The unique_input method
1405   // does all this and more, by reducing such tributaries to 'this'.)
1406   Node* uin = unique_input(phase, false);
1407   if (uin != NULL) {
1408     return uin;
1409   }
1410 
1411   int true_path = is_diamond_phi();
1412   // Delay CMove'ing identity if Ideal has not had the chance to handle unsafe cases, yet.
1413   if (true_path != 0 && !(phase->is_IterGVN() && wait_for_region_igvn(phase))) {
1414     Node* id = is_cmove_id(phase, true_path);
1415     if (id != NULL) {
1416       return id;
1417     }
1418   }
1419 
1420   // Looking for phis with identical inputs.  If we find one that has
1421   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1422   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1423       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1424     uint phi_len = req();
1425     Node* phi_reg = region();
1426     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1427       Node* u = phi_reg->fast_out(i);
1428       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1429           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1430           u->req() == phi_len) {
1431         for (uint j = 1; j < phi_len; j++) {
1432           if (in(j) != u->in(j)) {
1433             u = NULL;
1434             break;
1435           }
1436         }
1437         if (u != NULL) {
1438           return u;
1439         }
1440       }
1441     }
1442   }
1443 
1444   return this;                     // No identity
1445 }
1446 
1447 //-----------------------------unique_input------------------------------------
1448 // Find the unique value, discounting top, self-loops, and casts.
1449 // Return top if there are no inputs, and self if there are multiple.
1450 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1451   //  1) One unique direct input,
1452   // or if uncast is true:
1453   //  2) some of the inputs have an intervening ConstraintCast
1454   //  3) an input is a self loop
1455   //
1456   //  1) input   or   2) input     or   3) input __
1457   //     /   \           /   \               \  /  \
1458   //     \   /          |    cast             phi  cast
1459   //      phi            \   /               /  \  /
1460   //                      phi               /    --
1461 
1462   Node* r = in(0);                      // RegionNode
1463   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1464 
1465   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1466     Node* rc = r->in(i);
1467     if (rc == NULL || phase->type(rc) == Type::TOP)
1468       continue;                 // ignore unreachable control path
1469     Node* n = in(i);
1470     if (n == NULL)
1471       continue;
1472     Node* un = n;
1473     if (uncast) {
1474 #ifdef ASSERT
1475       Node* m = un->uncast();
1476 #endif
1477       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1478         Node* next = un->in(1);
1479         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1480           // risk exposing raw ptr at safepoint
1481           break;
1482         }
1483         un = next;
1484       }
1485       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1486     }
1487     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1488       continue; // ignore if top, or in(i) and "this" are in a data cycle
1489     }
1490     // Check for a unique input (maybe uncasted)
1491     if (input == NULL) {
1492       input = un;
1493     } else if (input != un) {
1494       input = NodeSentinel; // no unique input
1495     }
1496   }
1497   if (input == NULL) {
1498     return phase->C->top();        // no inputs
1499   }
1500 
1501   if (input != NodeSentinel) {
1502     return input;           // one unique direct input
1503   }
1504 
1505   // Nothing.
1506   return NULL;
1507 }
1508 
1509 //------------------------------is_x2logic-------------------------------------
1510 // Check for simple convert-to-boolean pattern
1511 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1512 // Convert Phi to an ConvIB.
1513 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1514   assert(true_path !=0, "only diamond shape graph expected");
1515   // Convert the true/false index into an expected 0/1 return.
1516   // Map 2->0 and 1->1.
1517   int flipped = 2-true_path;
1518 
1519   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1520   // phi->region->if_proj->ifnode->bool->cmp
1521   Node *region = phi->in(0);
1522   Node *iff = region->in(1)->in(0);
1523   BoolNode *b = (BoolNode*)iff->in(1);
1524   const CmpNode *cmp = (CmpNode*)b->in(1);
1525 
1526   Node *zero = phi->in(1);
1527   Node *one  = phi->in(2);
1528   const Type *tzero = phase->type( zero );
1529   const Type *tone  = phase->type( one  );
1530 
1531   // Check for compare vs 0
1532   const Type *tcmp = phase->type(cmp->in(2));
1533   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1534     // Allow cmp-vs-1 if the other input is bounded by 0-1
1535     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1536       return NULL;
1537     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1538   }
1539 
1540   // Check for setting zero/one opposite expected
1541   if( tzero == TypeInt::ZERO ) {
1542     if( tone == TypeInt::ONE ) {
1543     } else return NULL;
1544   } else if( tzero == TypeInt::ONE ) {
1545     if( tone == TypeInt::ZERO ) {
1546       flipped = 1-flipped;
1547     } else return NULL;
1548   } else return NULL;
1549 
1550   // Check for boolean test backwards
1551   if( b->_test._test == BoolTest::ne ) {
1552   } else if( b->_test._test == BoolTest::eq ) {
1553     flipped = 1-flipped;
1554   } else return NULL;
1555 
1556   // Build int->bool conversion
1557   Node *n = new Conv2BNode(cmp->in(1));
1558   if( flipped )
1559     n = new XorINode( phase->transform(n), phase->intcon(1) );
1560 
1561   return n;
1562 }
1563 
1564 //------------------------------is_cond_add------------------------------------
1565 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1566 // To be profitable the control flow has to disappear; there can be no other
1567 // values merging here.  We replace the test-and-branch with:
1568 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1569 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1570 // Then convert Y to 0-or-Y and finally add.
1571 // This is a key transform for SpecJava _201_compress.
1572 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1573   assert(true_path !=0, "only diamond shape graph expected");
1574 
1575   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1576   // phi->region->if_proj->ifnode->bool->cmp
1577   RegionNode *region = (RegionNode*)phi->in(0);
1578   Node *iff = region->in(1)->in(0);
1579   BoolNode* b = iff->in(1)->as_Bool();
1580   const CmpNode *cmp = (CmpNode*)b->in(1);
1581 
1582   // Make sure only merging this one phi here
1583   if (region->has_unique_phi() != phi)  return NULL;
1584 
1585   // Make sure each arm of the diamond has exactly one output, which we assume
1586   // is the region.  Otherwise, the control flow won't disappear.
1587   if (region->in(1)->outcnt() != 1) return NULL;
1588   if (region->in(2)->outcnt() != 1) return NULL;
1589 
1590   // Check for "(P < Q)" of type signed int
1591   if (b->_test._test != BoolTest::lt)  return NULL;
1592   if (cmp->Opcode() != Op_CmpI)        return NULL;
1593 
1594   Node *p = cmp->in(1);
1595   Node *q = cmp->in(2);
1596   Node *n1 = phi->in(  true_path);
1597   Node *n2 = phi->in(3-true_path);
1598 
1599   int op = n1->Opcode();
1600   if( op != Op_AddI           // Need zero as additive identity
1601       /*&&op != Op_SubI &&
1602       op != Op_AddP &&
1603       op != Op_XorI &&
1604       op != Op_OrI*/ )
1605     return NULL;
1606 
1607   Node *x = n2;
1608   Node *y = NULL;
1609   if( x == n1->in(1) ) {
1610     y = n1->in(2);
1611   } else if( x == n1->in(2) ) {
1612     y = n1->in(1);
1613   } else return NULL;
1614 
1615   // Not so profitable if compare and add are constants
1616   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1617     return NULL;
1618 
1619   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1620   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1621   return new AddINode(j_and,x);
1622 }
1623 
1624 //------------------------------is_absolute------------------------------------
1625 // Check for absolute value.
1626 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1627   assert(true_path !=0, "only diamond shape graph expected");
1628 
1629   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1630   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1631 
1632   // ABS ends with the merge of 2 control flow paths.
1633   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1634   int false_path = 3 - true_path;
1635 
1636   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1637   // phi->region->if_proj->ifnode->bool->cmp
1638   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1639   Node *cmp = bol->in(1);
1640 
1641   // Check bool sense
1642   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1643     switch (bol->_test._test) {
1644     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1645     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1646     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1647     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1648     default:           return NULL;                              break;
1649     }
1650   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1651     switch (bol->_test._test) {
1652     case BoolTest::lt:
1653     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1654     case BoolTest::gt:
1655     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1656     default:           return NULL;                              break;
1657     }
1658   }
1659 
1660   // Test is next
1661   const Type *tzero = NULL;
1662   switch (cmp->Opcode()) {
1663   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1664   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1665   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1666   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1667   default: return NULL;
1668   }
1669 
1670   // Find zero input of compare; the other input is being abs'd
1671   Node *x = NULL;
1672   bool flip = false;
1673   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1674     x = cmp->in(3 - cmp_zero_idx);
1675   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1676     // The test is inverted, we should invert the result...
1677     x = cmp->in(cmp_zero_idx);
1678     flip = true;
1679   } else {
1680     return NULL;
1681   }
1682 
1683   // Next get the 2 pieces being selected, one is the original value
1684   // and the other is the negated value.
1685   if( phi_root->in(phi_x_idx) != x ) return NULL;
1686 
1687   // Check other phi input for subtract node
1688   Node *sub = phi_root->in(3 - phi_x_idx);
1689 
1690   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1691                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1692 
1693   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1694   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return NULL;
1695 
1696   if (tzero == TypeF::ZERO) {
1697     x = new AbsFNode(x);
1698     if (flip) {
1699       x = new SubFNode(sub->in(1), phase->transform(x));
1700     }
1701   } else if (tzero == TypeD::ZERO) {
1702     x = new AbsDNode(x);
1703     if (flip) {
1704       x = new SubDNode(sub->in(1), phase->transform(x));
1705     }
1706   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1707     x = new AbsINode(x);
1708     if (flip) {
1709       x = new SubINode(sub->in(1), phase->transform(x));
1710     }
1711   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1712     x = new AbsLNode(x);
1713     if (flip) {
1714       x = new SubLNode(sub->in(1), phase->transform(x));
1715     }
1716   } else return NULL;
1717 
1718   return x;
1719 }
1720 
1721 //------------------------------split_once-------------------------------------
1722 // Helper for split_flow_path
1723 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1724   igvn->hash_delete(n);         // Remove from hash before hacking edges
1725 
1726   uint j = 1;
1727   for (uint i = phi->req()-1; i > 0; i--) {
1728     if (phi->in(i) == val) {   // Found a path with val?
1729       // Add to NEW Region/Phi, no DU info
1730       newn->set_req( j++, n->in(i) );
1731       // Remove from OLD Region/Phi
1732       n->del_req(i);
1733     }
1734   }
1735 
1736   // Register the new node but do not transform it.  Cannot transform until the
1737   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1738   igvn->register_new_node_with_optimizer( newn );
1739 
1740   // Now I can point to the new node.
1741   n->add_req(newn);
1742   igvn->_worklist.push(n);
1743 }
1744 
1745 //------------------------------split_flow_path--------------------------------
1746 // Check for merging identical values and split flow paths
1747 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1748   BasicType bt = phi->type()->basic_type();
1749   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1750     return NULL;                // Bail out on funny non-value stuff
1751   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1752     return NULL;                // third unequal input to be worth doing
1753 
1754   // Scan for a constant
1755   uint i;
1756   for( i = 1; i < phi->req()-1; i++ ) {
1757     Node *n = phi->in(i);
1758     if( !n ) return NULL;
1759     if( phase->type(n) == Type::TOP ) return NULL;
1760     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1761       break;
1762   }
1763   if( i >= phi->req() )         // Only split for constants
1764     return NULL;
1765 
1766   Node *val = phi->in(i);       // Constant to split for
1767   uint hit = 0;                 // Number of times it occurs
1768   Node *r = phi->region();
1769 
1770   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1771     Node *n = phi->in(i);
1772     if( !n ) return NULL;
1773     if( phase->type(n) == Type::TOP ) return NULL;
1774     if( phi->in(i) == val ) {
1775       hit++;
1776       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1777         return NULL;            // don't split loop entry path
1778       }
1779     }
1780   }
1781 
1782   if( hit <= 1 ||               // Make sure we find 2 or more
1783       hit == phi->req()-1 )     // and not ALL the same value
1784     return NULL;
1785 
1786   // Now start splitting out the flow paths that merge the same value.
1787   // Split first the RegionNode.
1788   PhaseIterGVN *igvn = phase->is_IterGVN();
1789   RegionNode *newr = new RegionNode(hit+1);
1790   split_once(igvn, phi, val, r, newr);
1791 
1792   // Now split all other Phis than this one
1793   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1794     Node* phi2 = r->fast_out(k);
1795     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1796       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1797       split_once(igvn, phi, val, phi2, newphi);
1798     }
1799   }
1800 
1801   // Clean up this guy
1802   igvn->hash_delete(phi);
1803   for( i = phi->req()-1; i > 0; i-- ) {
1804     if( phi->in(i) == val ) {
1805       phi->del_req(i);
1806     }
1807   }
1808   phi->add_req(val);
1809 
1810   return phi;
1811 }
1812 
1813 //=============================================================================
1814 //------------------------------simple_data_loop_check-------------------------
1815 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1816 //  Returns:
1817 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1818 // Safe       - safe case when the phi and it's inputs reference only safe data
1819 //              nodes;
1820 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1821 //              is no reference back to the phi - need a graph walk
1822 //              to determine if it is in a loop;
1823 // UnsafeLoop - unsafe case when the phi references itself directly or through
1824 //              unsafe data node.
1825 //  Note: a safe data node is a node which could/never reference itself during
1826 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1827 //  I mark Phi nodes as safe node not only because they can reference itself
1828 //  but also to prevent mistaking the fallthrough case inside an outer loop
1829 //  as dead loop when the phi references itself through an other phi.
1830 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1831   // It is unsafe loop if the phi node references itself directly.
1832   if (in == (Node*)this)
1833     return UnsafeLoop; // Unsafe loop
1834   // Unsafe loop if the phi node references itself through an unsafe data node.
1835   // Exclude cases with null inputs or data nodes which could reference
1836   // itself (safe for dead loops).
1837   if (in != NULL && !in->is_dead_loop_safe()) {
1838     // Check inputs of phi's inputs also.
1839     // It is much less expensive then full graph walk.
1840     uint cnt = in->req();
1841     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1842     for (; i < cnt; ++i) {
1843       Node* m = in->in(i);
1844       if (m == (Node*)this)
1845         return UnsafeLoop; // Unsafe loop
1846       if (m != NULL && !m->is_dead_loop_safe()) {
1847         // Check the most common case (about 30% of all cases):
1848         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1849         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1850         if (m1 == (Node*)this)
1851           return UnsafeLoop; // Unsafe loop
1852         if (m1 != NULL && m1 == m->in(2) &&
1853             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1854           continue; // Safe case
1855         }
1856         // The phi references an unsafe node - need full analysis.
1857         return Unsafe;
1858       }
1859     }
1860   }
1861   return Safe; // Safe case - we can optimize the phi node.
1862 }
1863 
1864 //------------------------------is_unsafe_data_reference-----------------------
1865 // If phi can be reached through the data input - it is data loop.
1866 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1867   assert(req() > 1, "");
1868   // First, check simple cases when phi references itself directly or
1869   // through an other node.
1870   LoopSafety safety = simple_data_loop_check(in);
1871   if (safety == UnsafeLoop)
1872     return true;  // phi references itself - unsafe loop
1873   else if (safety == Safe)
1874     return false; // Safe case - phi could be replaced with the unique input.
1875 
1876   // Unsafe case when we should go through data graph to determine
1877   // if the phi references itself.
1878 
1879   ResourceMark rm;
1880 
1881   Node_List nstack;
1882   VectorSet visited;
1883 
1884   nstack.push(in); // Start with unique input.
1885   visited.set(in->_idx);
1886   while (nstack.size() != 0) {
1887     Node* n = nstack.pop();
1888     uint cnt = n->req();
1889     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1890     for (; i < cnt; i++) {
1891       Node* m = n->in(i);
1892       if (m == (Node*)this) {
1893         return true;    // Data loop
1894       }
1895       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1896         if (!visited.test_set(m->_idx))
1897           nstack.push(m);
1898       }
1899     }
1900   }
1901   return false; // The phi is not reachable from its inputs
1902 }
1903 
1904 // Is this Phi's region or some inputs to the region enqueued for IGVN
1905 // and so could cause the region to be optimized out?
1906 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1907   PhaseIterGVN* igvn = phase->is_IterGVN();
1908   Unique_Node_List& worklist = igvn->_worklist;
1909   bool delay = false;
1910   Node* r = in(0);
1911   for (uint j = 1; j < req(); j++) {
1912     Node* rc = r->in(j);
1913     Node* n = in(j);
1914     if (rc != NULL &&
1915         rc->is_Proj()) {
1916       if (worklist.member(rc)) {
1917         delay = true;
1918       } else if (rc->in(0) != NULL &&
1919                  rc->in(0)->is_If()) {
1920         if (worklist.member(rc->in(0))) {
1921           delay = true;
1922         } else if (rc->in(0)->in(1) != NULL &&
1923                    rc->in(0)->in(1)->is_Bool()) {
1924           if (worklist.member(rc->in(0)->in(1))) {
1925             delay = true;
1926           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1927                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1928             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1929               delay = true;
1930             }
1931           }
1932         }
1933       }
1934     }
1935   }
1936   if (delay) {
1937     worklist.push(this);
1938   }
1939   return delay;
1940 }
1941 
1942 //------------------------------Ideal------------------------------------------
1943 // Return a node which is more "ideal" than the current node.  Must preserve
1944 // the CFG, but we can still strip out dead paths.
1945 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1946   Node *r = in(0);              // RegionNode
1947   assert(r != NULL && r->is_Region(), "this phi must have a region");
1948   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1949 
1950   // Note: During parsing, phis are often transformed before their regions.
1951   // This means we have to use type_or_null to defend against untyped regions.
1952   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1953     return NULL;                // No change
1954 
1955   Node *top = phase->C->top();
1956   bool new_phi = (outcnt() == 0); // transforming new Phi
1957   // No change for igvn if new phi is not hooked
1958   if (new_phi && can_reshape)
1959     return NULL;
1960 
1961   // The are 2 situations when only one valid phi's input is left
1962   // (in addition to Region input).
1963   // One: region is not loop - replace phi with this input.
1964   // Two: region is loop - replace phi with top since this data path is dead
1965   //                       and we need to break the dead data loop.
1966   Node* progress = NULL;        // Record if any progress made
1967   for( uint j = 1; j < req(); ++j ){ // For all paths in
1968     // Check unreachable control paths
1969     Node* rc = r->in(j);
1970     Node* n = in(j);            // Get the input
1971     if (rc == NULL || phase->type(rc) == Type::TOP) {
1972       if (n != top) {           // Not already top?
1973         PhaseIterGVN *igvn = phase->is_IterGVN();
1974         if (can_reshape && igvn != NULL) {
1975           igvn->_worklist.push(r);
1976         }
1977         // Nuke it down
1978         set_req_X(j, top, phase);
1979         progress = this;        // Record progress
1980       }
1981     }
1982   }
1983 
1984   if (can_reshape && outcnt() == 0) {
1985     // set_req() above may kill outputs if Phi is referenced
1986     // only by itself on the dead (top) control path.
1987     return top;
1988   }
1989 
1990   bool uncasted = false;
1991   Node* uin = unique_input(phase, false);
1992   if (uin == NULL && can_reshape &&
1993       // If there is a chance that the region can be optimized out do
1994       // not add a cast node that we can't remove yet.
1995       !wait_for_region_igvn(phase)) {
1996     uncasted = true;
1997     uin = unique_input(phase, true);
1998   }
1999   if (uin == top) {             // Simplest case: no alive inputs.
2000     if (can_reshape)            // IGVN transformation
2001       return top;
2002     else
2003       return NULL;              // Identity will return TOP
2004   } else if (uin != NULL) {
2005     // Only one not-NULL unique input path is left.
2006     // Determine if this input is backedge of a loop.
2007     // (Skip new phis which have no uses and dead regions).
2008     if (outcnt() > 0 && r->in(0) != NULL) {
2009       if (is_data_loop(r->as_Region(), uin, phase)) {
2010         // Break this data loop to avoid creation of a dead loop.
2011         if (can_reshape) {
2012           return top;
2013         } else {
2014           // We can't return top if we are in Parse phase - cut inputs only
2015           // let Identity to handle the case.
2016           replace_edge(uin, top, phase);
2017           return NULL;
2018         }
2019       }
2020     }
2021 
2022     if (uncasted) {
2023       // Add cast nodes between the phi to be removed and its unique input.
2024       // Wait until after parsing for the type information to propagate from the casts.
2025       assert(can_reshape, "Invalid during parsing");
2026       const Type* phi_type = bottom_type();
2027       // Add casts to carry the control dependency of the Phi that is
2028       // going away
2029       Node* cast = NULL;
2030       if (phi_type->isa_ptr()) {
2031         const Type* uin_type = phase->type(uin);
2032         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
2033           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2034         } else {
2035           // Use a CastPP for a cast to not null and a CheckCastPP for
2036           // a cast to a new klass (and both if both null-ness and
2037           // klass change).
2038 
2039           // If the type of phi is not null but the type of uin may be
2040           // null, uin's type must be casted to not null
2041           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
2042               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
2043             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency);
2044           }
2045 
2046           // If the type of phi and uin, both casted to not null,
2047           // differ the klass of uin must be (check)cast'ed to match
2048           // that of phi
2049           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2050             Node* n = uin;
2051             if (cast != NULL) {
2052               cast = phase->transform(cast);
2053               n = cast;
2054             }
2055             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, ConstraintCastNode::StrongDependency);
2056           }
2057           if (cast == NULL) {
2058             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2059           }
2060         }
2061       } else {
2062         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency);
2063       }
2064       assert(cast != NULL, "cast should be set");
2065       cast = phase->transform(cast);
2066       // set all inputs to the new cast(s) so the Phi is removed by Identity
2067       PhaseIterGVN* igvn = phase->is_IterGVN();
2068       for (uint i = 1; i < req(); i++) {
2069         set_req_X(i, cast, igvn);
2070       }
2071       uin = cast;
2072     }
2073 
2074     // One unique input.
2075     debug_only(Node* ident = Identity(phase));
2076     // The unique input must eventually be detected by the Identity call.
2077 #ifdef ASSERT
2078     if (ident != uin && !ident->is_top()) {
2079       // print this output before failing assert
2080       r->dump(3);
2081       this->dump(3);
2082       ident->dump();
2083       uin->dump();
2084     }
2085 #endif
2086     assert(ident == uin || ident->is_top(), "Identity must clean this up");
2087     return NULL;
2088   }
2089 
2090   Node* opt = NULL;
2091   int true_path = is_diamond_phi();
2092   if (true_path != 0 &&
2093       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2094       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2095       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2096       !(can_reshape && wait_for_region_igvn(phase))) {
2097     // Check for CMove'ing identity. If it would be unsafe,
2098     // handle it here. In the safe case, let Identity handle it.
2099     Node* unsafe_id = is_cmove_id(phase, true_path);
2100     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
2101       opt = unsafe_id;
2102 
2103     // Check for simple convert-to-boolean pattern
2104     if( opt == NULL )
2105       opt = is_x2logic(phase, this, true_path);
2106 
2107     // Check for absolute value
2108     if( opt == NULL )
2109       opt = is_absolute(phase, this, true_path);
2110 
2111     // Check for conditional add
2112     if( opt == NULL && can_reshape )
2113       opt = is_cond_add(phase, this, true_path);
2114 
2115     // These 4 optimizations could subsume the phi:
2116     // have to check for a dead data loop creation.
2117     if( opt != NULL ) {
2118       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2119         // Found dead loop.
2120         if( can_reshape )
2121           return top;
2122         // We can't return top if we are in Parse phase - cut inputs only
2123         // to stop further optimizations for this phi. Identity will return TOP.
2124         assert(req() == 3, "only diamond merge phi here");
2125         set_req(1, top);
2126         set_req(2, top);
2127         return NULL;
2128       } else {
2129         return opt;
2130       }
2131     }
2132   }
2133 
2134   // Check for merging identical values and split flow paths
2135   if (can_reshape) {
2136     opt = split_flow_path(phase, this);
2137     // This optimization only modifies phi - don't need to check for dead loop.
2138     assert(opt == NULL || opt == this, "do not elide phi");
2139     if (opt != NULL)  return opt;
2140   }
2141 
2142   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2143     // Try to undo Phi of AddP:
2144     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2145     // becomes:
2146     // newbase := (Phi base base2)
2147     // newaddress := (Phi address address2)
2148     // newoffset := (Phi offset offset2)
2149     // (AddP newbase newaddress newoffset)
2150     //
2151     // This occurs as a result of unsuccessful split_thru_phi and
2152     // interferes with taking advantage of addressing modes. See the
2153     // clone_shift_expressions code in matcher.cpp
2154     Node* addp = in(1);
2155     Node* base = addp->in(AddPNode::Base);
2156     Node* address = addp->in(AddPNode::Address);
2157     Node* offset = addp->in(AddPNode::Offset);
2158     if (base != NULL && address != NULL && offset != NULL &&
2159         !base->is_top() && !address->is_top() && !offset->is_top()) {
2160       const Type* base_type = base->bottom_type();
2161       const Type* address_type = address->bottom_type();
2162       // make sure that all the inputs are similar to the first one,
2163       // i.e. AddP with base == address and same offset as first AddP
2164       bool doit = true;
2165       for (uint i = 2; i < req(); i++) {
2166         if (in(i) == NULL ||
2167             in(i)->Opcode() != Op_AddP ||
2168             in(i)->in(AddPNode::Base) == NULL ||
2169             in(i)->in(AddPNode::Address) == NULL ||
2170             in(i)->in(AddPNode::Offset) == NULL ||
2171             in(i)->in(AddPNode::Base)->is_top() ||
2172             in(i)->in(AddPNode::Address)->is_top() ||
2173             in(i)->in(AddPNode::Offset)->is_top()) {
2174           doit = false;
2175           break;
2176         }
2177         if (in(i)->in(AddPNode::Base) != base) {
2178           base = NULL;
2179         }
2180         if (in(i)->in(AddPNode::Offset) != offset) {
2181           offset = NULL;
2182         }
2183         if (in(i)->in(AddPNode::Address) != address) {
2184           address = NULL;
2185         }
2186         // Accumulate type for resulting Phi
2187         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2188         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2189       }
2190       if (doit && base == NULL) {
2191         // Check for neighboring AddP nodes in a tree.
2192         // If they have a base, use that it.
2193         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2194           Node* u = this->fast_out(k);
2195           if (u->is_AddP()) {
2196             Node* base2 = u->in(AddPNode::Base);
2197             if (base2 != NULL && !base2->is_top()) {
2198               if (base == NULL)
2199                 base = base2;
2200               else if (base != base2)
2201                 { doit = false; break; }
2202             }
2203           }
2204         }
2205       }
2206       if (doit) {
2207         if (base == NULL) {
2208           base = new PhiNode(in(0), base_type, NULL);
2209           for (uint i = 1; i < req(); i++) {
2210             base->init_req(i, in(i)->in(AddPNode::Base));
2211           }
2212           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2213         }
2214         if (address == NULL) {
2215           address = new PhiNode(in(0), address_type, NULL);
2216           for (uint i = 1; i < req(); i++) {
2217             address->init_req(i, in(i)->in(AddPNode::Address));
2218           }
2219           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2220         }
2221         if (offset == NULL) {
2222           offset = new PhiNode(in(0), TypeX_X, NULL);
2223           for (uint i = 1; i < req(); i++) {
2224             offset->init_req(i, in(i)->in(AddPNode::Offset));
2225           }
2226           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2227         }
2228         return new AddPNode(base, address, offset);
2229       }
2230     }
2231   }
2232 
2233   // Split phis through memory merges, so that the memory merges will go away.
2234   // Piggy-back this transformation on the search for a unique input....
2235   // It will be as if the merged memory is the unique value of the phi.
2236   // (Do not attempt this optimization unless parsing is complete.
2237   // It would make the parser's memory-merge logic sick.)
2238   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2239   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2240     // see if this phi should be sliced
2241     uint merge_width = 0;
2242     bool saw_self = false;
2243     for( uint i=1; i<req(); ++i ) {// For all paths in
2244       Node *ii = in(i);
2245       // TOP inputs should not be counted as safe inputs because if the
2246       // Phi references itself through all other inputs then splitting the
2247       // Phi through memory merges would create dead loop at later stage.
2248       if (ii == top) {
2249         return NULL; // Delay optimization until graph is cleaned.
2250       }
2251       if (ii->is_MergeMem()) {
2252         MergeMemNode* n = ii->as_MergeMem();
2253         merge_width = MAX2(merge_width, n->req());
2254         saw_self = saw_self || (n->base_memory() == this);
2255       }
2256     }
2257 
2258     // This restriction is temporarily necessary to ensure termination:
2259     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2260 
2261     if (merge_width > Compile::AliasIdxRaw) {
2262       // found at least one non-empty MergeMem
2263       const TypePtr* at = adr_type();
2264       if (at != TypePtr::BOTTOM) {
2265         // Patch the existing phi to select an input from the merge:
2266         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2267         //     Phi:AT1(...m1...)
2268         int alias_idx = phase->C->get_alias_index(at);
2269         for (uint i=1; i<req(); ++i) {
2270           Node *ii = in(i);
2271           if (ii->is_MergeMem()) {
2272             MergeMemNode* n = ii->as_MergeMem();
2273             // compress paths and change unreachable cycles to TOP
2274             // If not, we can update the input infinitely along a MergeMem cycle
2275             // Equivalent code is in MemNode::Ideal_common
2276             Node *m  = phase->transform(n);
2277             if (outcnt() == 0) {  // Above transform() may kill us!
2278               return top;
2279             }
2280             // If transformed to a MergeMem, get the desired slice
2281             // Otherwise the returned node represents memory for every slice
2282             Node *new_mem = (m->is_MergeMem()) ?
2283                              m->as_MergeMem()->memory_at(alias_idx) : m;
2284             // Update input if it is progress over what we have now
2285             if (new_mem != ii) {
2286               set_req_X(i, new_mem, phase->is_IterGVN());
2287               progress = this;
2288             }
2289           }
2290         }
2291       } else {
2292         // We know that at least one MergeMem->base_memory() == this
2293         // (saw_self == true). If all other inputs also references this phi
2294         // (directly or through data nodes) - it is a dead loop.
2295         bool saw_safe_input = false;
2296         for (uint j = 1; j < req(); ++j) {
2297           Node* n = in(j);
2298           if (n->is_MergeMem()) {
2299             MergeMemNode* mm = n->as_MergeMem();
2300             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2301               // Skip this input if it references back to this phi or if the memory path is dead
2302               continue;
2303             }
2304           }
2305           if (!is_unsafe_data_reference(n)) {
2306             saw_safe_input = true; // found safe input
2307             break;
2308           }
2309         }
2310         if (!saw_safe_input) {
2311           // There is a dead loop: All inputs are either dead or reference back to this phi
2312           return top;
2313         }
2314 
2315         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2316         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2317         PhaseIterGVN* igvn = phase->is_IterGVN();
2318         assert(igvn != NULL, "sanity check");
2319         Node* hook = new Node(1);
2320         PhiNode* new_base = (PhiNode*) clone();
2321         // Must eagerly register phis, since they participate in loops.
2322         igvn->register_new_node_with_optimizer(new_base);
2323         hook->add_req(new_base);
2324 
2325         MergeMemNode* result = MergeMemNode::make(new_base);
2326         for (uint i = 1; i < req(); ++i) {
2327           Node *ii = in(i);
2328           if (ii->is_MergeMem()) {
2329             MergeMemNode* n = ii->as_MergeMem();
2330             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2331               // If we have not seen this slice yet, make a phi for it.
2332               bool made_new_phi = false;
2333               if (mms.is_empty()) {
2334                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2335                 made_new_phi = true;
2336                 igvn->register_new_node_with_optimizer(new_phi);
2337                 hook->add_req(new_phi);
2338                 mms.set_memory(new_phi);
2339               }
2340               Node* phi = mms.memory();
2341               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2342               phi->set_req(i, mms.memory2());
2343             }
2344           }
2345         }
2346         // Distribute all self-loops.
2347         { // (Extra braces to hide mms.)
2348           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2349             Node* phi = mms.memory();
2350             for (uint i = 1; i < req(); ++i) {
2351               if (phi->in(i) == this)  phi->set_req(i, phi);
2352             }
2353           }
2354         }
2355         // Already replace this phi node to cut it off from the graph to not interfere in dead loop checks during the
2356         // transformations of the new phi nodes below. Otherwise, we could wrongly conclude that there is no dead loop
2357         // because we are finding this phi node again. Also set the type of the new MergeMem node in case we are also
2358         // visiting it in the transformations below.
2359         igvn->replace_node(this, result);
2360         igvn->set_type(result, result->bottom_type());
2361 
2362         // now transform the new nodes, and return the mergemem
2363         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2364           Node* phi = mms.memory();
2365           mms.set_memory(phase->transform(phi));
2366         }
2367         hook->destruct(igvn);
2368         // Replace self with the result.
2369         return result;
2370       }
2371     }
2372     //
2373     // Other optimizations on the memory chain
2374     //
2375     const TypePtr* at = adr_type();
2376     for( uint i=1; i<req(); ++i ) {// For all paths in
2377       Node *ii = in(i);
2378       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2379       if (ii != new_in ) {
2380         set_req(i, new_in);
2381         progress = this;
2382       }
2383     }
2384   }
2385 
2386 #ifdef _LP64
2387   // Push DecodeN/DecodeNKlass down through phi.
2388   // The rest of phi graph will transform by split EncodeP node though phis up.
2389   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2390     bool may_push = true;
2391     bool has_decodeN = false;
2392     bool is_decodeN = false;
2393     for (uint i=1; i<req(); ++i) {// For all paths in
2394       Node *ii = in(i);
2395       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2396         // Do optimization if a non dead path exist.
2397         if (ii->in(1)->bottom_type() != Type::TOP) {
2398           has_decodeN = true;
2399           is_decodeN = ii->is_DecodeN();
2400         }
2401       } else if (!ii->is_Phi()) {
2402         may_push = false;
2403       }
2404     }
2405 
2406     if (has_decodeN && may_push) {
2407       PhaseIterGVN *igvn = phase->is_IterGVN();
2408       // Make narrow type for new phi.
2409       const Type* narrow_t;
2410       if (is_decodeN) {
2411         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2412       } else {
2413         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2414       }
2415       PhiNode* new_phi = new PhiNode(r, narrow_t);
2416       uint orig_cnt = req();
2417       for (uint i=1; i<req(); ++i) {// For all paths in
2418         Node *ii = in(i);
2419         Node* new_ii = NULL;
2420         if (ii->is_DecodeNarrowPtr()) {
2421           assert(ii->bottom_type() == bottom_type(), "sanity");
2422           new_ii = ii->in(1);
2423         } else {
2424           assert(ii->is_Phi(), "sanity");
2425           if (ii->as_Phi() == this) {
2426             new_ii = new_phi;
2427           } else {
2428             if (is_decodeN) {
2429               new_ii = new EncodePNode(ii, narrow_t);
2430             } else {
2431               new_ii = new EncodePKlassNode(ii, narrow_t);
2432             }
2433             igvn->register_new_node_with_optimizer(new_ii);
2434           }
2435         }
2436         new_phi->set_req(i, new_ii);
2437       }
2438       igvn->register_new_node_with_optimizer(new_phi, this);
2439       if (is_decodeN) {
2440         progress = new DecodeNNode(new_phi, bottom_type());
2441       } else {
2442         progress = new DecodeNKlassNode(new_phi, bottom_type());
2443       }
2444     }
2445   }
2446 #endif
2447 
2448   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2449   if (EnableVectorReboxing && can_reshape && progress == NULL && type()->isa_oopptr()) {
2450     progress = merge_through_phi(this, phase->is_IterGVN());
2451   }
2452 
2453   return progress;              // Return any progress
2454 }
2455 
2456 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2457   Node_Stack stack(1);
2458   VectorSet  visited;
2459   Node_List  node_map;
2460 
2461   stack.push(root_phi, 1); // ignore control
2462   visited.set(root_phi->_idx);
2463 
2464   Node* new_phi = new PhiNode(root_phi->in(0), t);
2465   node_map.map(root_phi->_idx, new_phi);
2466 
2467   while (stack.is_nonempty()) {
2468     Node* n   = stack.node();
2469     uint  idx = stack.index();
2470     assert(n->is_Phi(), "not a phi");
2471     if (idx < n->req()) {
2472       stack.set_index(idx + 1);
2473       Node* def = n->in(idx);
2474       if (def == NULL) {
2475         continue; // ignore dead path
2476       } else if (def->is_Phi()) { // inner node
2477         Node* new_phi = node_map[n->_idx];
2478         if (!visited.test_set(def->_idx)) { // not visited yet
2479           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2480           stack.push(def, 1); // ignore control
2481         }
2482         Node* new_in = node_map[def->_idx];
2483         new_phi->set_req(idx, new_in);
2484       } else if (def->Opcode() == Op_VectorBox) { // leaf
2485         assert(n->is_Phi(), "not a phi");
2486         Node* new_phi = node_map[n->_idx];
2487         new_phi->set_req(idx, def->in(c));
2488       } else {
2489         assert(false, "not optimizeable");
2490         return NULL;
2491       }
2492     } else {
2493       Node* new_phi = node_map[n->_idx];
2494       igvn->register_new_node_with_optimizer(new_phi, n);
2495       stack.pop();
2496     }
2497   }
2498   return new_phi;
2499 }
2500 
2501 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
2502   Node_Stack stack(1);
2503   VectorSet  visited;
2504 
2505   stack.push(root_phi, 1); // ignore control
2506   visited.set(root_phi->_idx);
2507 
2508   VectorBoxNode* cached_vbox = NULL;
2509   while (stack.is_nonempty()) {
2510     Node* n   = stack.node();
2511     uint  idx = stack.index();
2512     if (idx < n->req()) {
2513       stack.set_index(idx + 1);
2514       Node* in = n->in(idx);
2515       if (in == NULL) {
2516         continue; // ignore dead path
2517       } else if (in->isa_Phi()) {
2518         if (!visited.test_set(in->_idx)) {
2519           stack.push(in, 1); // ignore control
2520         }
2521       } else if (in->Opcode() == Op_VectorBox) {
2522         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
2523         if (cached_vbox == NULL) {
2524           cached_vbox = vbox;
2525         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
2526           // TODO: vector type mismatch can be handled with additional reinterpret casts
2527           assert(Type::cmp(vbox->vec_type(), cached_vbox->vec_type()) != 0, "inconsistent");
2528           return NULL; // not optimizable: vector type mismatch
2529         } else if (vbox->box_type() != cached_vbox->box_type()) {
2530           assert(Type::cmp(vbox->box_type(), cached_vbox->box_type()) != 0, "inconsistent");
2531           return NULL; // not optimizable: box type mismatch
2532         }
2533       } else {
2534         return NULL; // not optimizable: neither Phi nor VectorBox
2535       }
2536     } else {
2537       stack.pop();
2538     }
2539   }
2540   assert(cached_vbox != NULL, "sanity");
2541   const TypeInstPtr* btype = cached_vbox->box_type();
2542   const TypeVect*    vtype = cached_vbox->vec_type();
2543   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
2544   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
2545   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
2546 }
2547 
2548 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
2549   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
2550   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
2551   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
2552   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
2553   const bool is_loop = (r->is_Loop() && r->req() == 3);
2554   const Node* top = phase->C->top();
2555   if (is_loop) {
2556     return !uin->eqv_uncast(in(LoopNode::EntryControl));
2557   } else {
2558     // We have a data loop either with an unsafe data reference or if a region is unreachable.
2559     return is_unsafe_data_reference(uin)
2560            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
2561   }
2562 }
2563 
2564 //------------------------------is_tripcount-----------------------------------
2565 bool PhiNode::is_tripcount(BasicType bt) const {
2566   return (in(0) != NULL && in(0)->is_BaseCountedLoop() &&
2567           in(0)->as_BaseCountedLoop()->bt() == bt &&
2568           in(0)->as_BaseCountedLoop()->phi() == this);
2569 }
2570 
2571 //------------------------------out_RegMask------------------------------------
2572 const RegMask &PhiNode::in_RegMask(uint i) const {
2573   return i ? out_RegMask() : RegMask::Empty;
2574 }
2575 
2576 const RegMask &PhiNode::out_RegMask() const {
2577   uint ideal_reg = _type->ideal_reg();
2578   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2579   if( ideal_reg == 0 ) return RegMask::Empty;
2580   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2581   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2582 }
2583 
2584 #ifndef PRODUCT
2585 void PhiNode::dump_spec(outputStream *st) const {
2586   TypeNode::dump_spec(st);
2587   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
2588     st->print(" #tripcount");
2589   }
2590 }
2591 #endif
2592 
2593 
2594 //=============================================================================
2595 const Type* GotoNode::Value(PhaseGVN* phase) const {
2596   // If the input is reachable, then we are executed.
2597   // If the input is not reachable, then we are not executed.
2598   return phase->type(in(0));
2599 }
2600 
2601 Node* GotoNode::Identity(PhaseGVN* phase) {
2602   return in(0);                // Simple copy of incoming control
2603 }
2604 
2605 const RegMask &GotoNode::out_RegMask() const {
2606   return RegMask::Empty;
2607 }
2608 
2609 //=============================================================================
2610 const RegMask &JumpNode::out_RegMask() const {
2611   return RegMask::Empty;
2612 }
2613 
2614 //=============================================================================
2615 const RegMask &JProjNode::out_RegMask() const {
2616   return RegMask::Empty;
2617 }
2618 
2619 //=============================================================================
2620 const RegMask &CProjNode::out_RegMask() const {
2621   return RegMask::Empty;
2622 }
2623 
2624 
2625 
2626 //=============================================================================
2627 
2628 uint PCTableNode::hash() const { return Node::hash() + _size; }
2629 bool PCTableNode::cmp( const Node &n ) const
2630 { return _size == ((PCTableNode&)n)._size; }
2631 
2632 const Type *PCTableNode::bottom_type() const {
2633   const Type** f = TypeTuple::fields(_size);
2634   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2635   return TypeTuple::make(_size, f);
2636 }
2637 
2638 //------------------------------Value------------------------------------------
2639 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2640 // Control, otherwise the table targets are not reachable
2641 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2642   if( phase->type(in(0)) == Type::CONTROL )
2643     return bottom_type();
2644   return Type::TOP;             // All paths dead?  Then so are we
2645 }
2646 
2647 //------------------------------Ideal------------------------------------------
2648 // Return a node which is more "ideal" than the current node.  Strip out
2649 // control copies
2650 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2651   return remove_dead_region(phase, can_reshape) ? this : NULL;
2652 }
2653 
2654 //=============================================================================
2655 uint JumpProjNode::hash() const {
2656   return Node::hash() + _dest_bci;
2657 }
2658 
2659 bool JumpProjNode::cmp( const Node &n ) const {
2660   return ProjNode::cmp(n) &&
2661     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2662 }
2663 
2664 #ifndef PRODUCT
2665 void JumpProjNode::dump_spec(outputStream *st) const {
2666   ProjNode::dump_spec(st);
2667   st->print("@bci %d ",_dest_bci);
2668 }
2669 
2670 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2671   ProjNode::dump_compact_spec(st);
2672   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2673 }
2674 #endif
2675 
2676 //=============================================================================
2677 //------------------------------Value------------------------------------------
2678 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2679 // have the default "fall_through_index" path.
2680 const Type* CatchNode::Value(PhaseGVN* phase) const {
2681   // Unreachable?  Then so are all paths from here.
2682   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2683   // First assume all paths are reachable
2684   const Type** f = TypeTuple::fields(_size);
2685   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2686   // Identify cases that will always throw an exception
2687   // () rethrow call
2688   // () virtual or interface call with NULL receiver
2689   // () call is a check cast with incompatible arguments
2690   if( in(1)->is_Proj() ) {
2691     Node *i10 = in(1)->in(0);
2692     if( i10->is_Call() ) {
2693       CallNode *call = i10->as_Call();
2694       // Rethrows always throw exceptions, never return
2695       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2696         f[CatchProjNode::fall_through_index] = Type::TOP;
2697       } else if (call->is_AllocateArray()) {
2698         Node* klass_node = call->in(AllocateNode::KlassNode);
2699         Node* length = call->in(AllocateNode::ALength);
2700         const Type* length_type = phase->type(length);
2701         const Type* klass_type = phase->type(klass_node);
2702         Node* valid_length_test = call->in(AllocateNode::ValidLengthTest);
2703         const Type* valid_length_test_t = phase->type(valid_length_test);
2704         if (length_type == Type::TOP || klass_type == Type::TOP || valid_length_test_t == Type::TOP ||
2705             valid_length_test_t->is_int()->is_con(0)) {
2706           f[CatchProjNode::fall_through_index] = Type::TOP;
2707         }
2708       } else if( call->req() > TypeFunc::Parms ) {
2709         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2710         // Check for null receiver to virtual or interface calls
2711         if( call->is_CallDynamicJava() &&
2712             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2713           f[CatchProjNode::fall_through_index] = Type::TOP;
2714         }
2715       } // End of if not a runtime stub
2716     } // End of if have call above me
2717   } // End of slot 1 is not a projection
2718   return TypeTuple::make(_size, f);
2719 }
2720 
2721 //=============================================================================
2722 uint CatchProjNode::hash() const {
2723   return Node::hash() + _handler_bci;
2724 }
2725 
2726 
2727 bool CatchProjNode::cmp( const Node &n ) const {
2728   return ProjNode::cmp(n) &&
2729     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2730 }
2731 
2732 
2733 //------------------------------Identity---------------------------------------
2734 // If only 1 target is possible, choose it if it is the main control
2735 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2736   // If my value is control and no other value is, then treat as ID
2737   const TypeTuple *t = phase->type(in(0))->is_tuple();
2738   if (t->field_at(_con) != Type::CONTROL)  return this;
2739   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2740   // also remove any exception table entry.  Thus we must know the call
2741   // feeding the Catch will not really throw an exception.  This is ok for
2742   // the main fall-thru control (happens when we know a call can never throw
2743   // an exception) or for "rethrow", because a further optimization will
2744   // yank the rethrow (happens when we inline a function that can throw an
2745   // exception and the caller has no handler).  Not legal, e.g., for passing
2746   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2747   // These cases MUST throw an exception via the runtime system, so the VM
2748   // will be looking for a table entry.
2749   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2750   CallNode *call;
2751   if (_con != TypeFunc::Control && // Bail out if not the main control.
2752       !(proj->is_Proj() &&      // AND NOT a rethrow
2753         proj->in(0)->is_Call() &&
2754         (call = proj->in(0)->as_Call()) &&
2755         call->entry_point() == OptoRuntime::rethrow_stub()))
2756     return this;
2757 
2758   // Search for any other path being control
2759   for (uint i = 0; i < t->cnt(); i++) {
2760     if (i != _con && t->field_at(i) == Type::CONTROL)
2761       return this;
2762   }
2763   // Only my path is possible; I am identity on control to the jump
2764   return in(0)->in(0);
2765 }
2766 
2767 
2768 #ifndef PRODUCT
2769 void CatchProjNode::dump_spec(outputStream *st) const {
2770   ProjNode::dump_spec(st);
2771   st->print("@bci %d ",_handler_bci);
2772 }
2773 #endif
2774 
2775 //=============================================================================
2776 //------------------------------Identity---------------------------------------
2777 // Check for CreateEx being Identity.
2778 Node* CreateExNode::Identity(PhaseGVN* phase) {
2779   if( phase->type(in(1)) == Type::TOP ) return in(1);
2780   if( phase->type(in(0)) == Type::TOP ) return in(0);
2781   // We only come from CatchProj, unless the CatchProj goes away.
2782   // If the CatchProj is optimized away, then we just carry the
2783   // exception oop through.
2784   CallNode *call = in(1)->in(0)->as_Call();
2785 
2786   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2787     ? this
2788     : call->in(TypeFunc::Parms);
2789 }
2790 
2791 //=============================================================================
2792 //------------------------------Value------------------------------------------
2793 // Check for being unreachable.
2794 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2795   if (!in(0) || in(0)->is_top()) return Type::TOP;
2796   return bottom_type();
2797 }
2798 
2799 //------------------------------Ideal------------------------------------------
2800 // Check for no longer being part of a loop
2801 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2802   if (can_reshape && !in(0)->is_Region()) {
2803     // Dead code elimination can sometimes delete this projection so
2804     // if it's not there, there's nothing to do.
2805     Node* fallthru = proj_out_or_null(0);
2806     if (fallthru != NULL) {
2807       phase->is_IterGVN()->replace_node(fallthru, in(0));
2808     }
2809     return phase->C->top();
2810   }
2811   return NULL;
2812 }
2813 
2814 #ifndef PRODUCT
2815 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2816   st->print("%s", Name());
2817 }
2818 #endif
2819 
2820 #ifndef PRODUCT
2821 void BlackholeNode::format(PhaseRegAlloc* ra, outputStream* st) const {
2822   st->print("blackhole ");
2823   bool first = true;
2824   for (uint i = 0; i < req(); i++) {
2825     Node* n = in(i);
2826     if (n != NULL && OptoReg::is_valid(ra->get_reg_first(n))) {
2827       if (first) {
2828         first = false;
2829       } else {
2830         st->print(", ");
2831       }
2832       char buf[128];
2833       ra->dump_register(n, buf);
2834       st->print("%s", buf);
2835     }
2836   }
2837   st->cr();
2838 }
2839 #endif
2840