1 /*
   2  * Copyright (c) 1997, 2018, 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 "classfile/systemDictionary.hpp"
  27 #include "gc/shared/barrierSet.hpp"
  28 #include "gc/shared/c2/barrierSetC2.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "oops/objArrayKlass.hpp"
  32 #include "opto/addnode.hpp"
  33 #include "opto/castnode.hpp"
  34 #include "opto/cfgnode.hpp"
  35 #include "opto/connode.hpp"
  36 #include "opto/convertnode.hpp"
  37 #include "opto/loopnode.hpp"
  38 #include "opto/machnode.hpp"
  39 #include "opto/movenode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/mulnode.hpp"
  42 #include "opto/phaseX.hpp"
  43 #include "opto/regmask.hpp"
  44 #include "opto/runtime.hpp"
  45 #include "opto/subnode.hpp"
  46 #include "utilities/vmError.hpp"
  47 
  48 // Portions of code courtesy of Clifford Click
  49 
  50 // Optimization - Graph Style
  51 
  52 //=============================================================================
  53 //------------------------------Value------------------------------------------
  54 // Compute the type of the RegionNode.
  55 const Type* RegionNode::Value(PhaseGVN* phase) const {
  56   for( uint i=1; i<req(); ++i ) {       // For all paths in
  57     Node *n = in(i);            // Get Control source
  58     if( !n ) continue;          // Missing inputs are TOP
  59     if( phase->type(n) == Type::CONTROL )
  60       return Type::CONTROL;
  61   }
  62   return Type::TOP;             // All paths dead?  Then so are we
  63 }
  64 
  65 //------------------------------Identity---------------------------------------
  66 // Check for Region being Identity.
  67 Node* RegionNode::Identity(PhaseGVN* phase) {
  68   // Cannot have Region be an identity, even if it has only 1 input.
  69   // Phi users cannot have their Region input folded away for them,
  70   // since they need to select the proper data input
  71   return this;
  72 }
  73 
  74 //------------------------------merge_region-----------------------------------
  75 // If a Region flows into a Region, merge into one big happy merge.  This is
  76 // hard to do if there is stuff that has to happen
  77 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  78   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  79     return NULL;
  80   Node *progress = NULL;        // Progress flag
  81   PhaseIterGVN *igvn = phase->is_IterGVN();
  82 
  83   uint rreq = region->req();
  84   for( uint i = 1; i < rreq; i++ ) {
  85     Node *r = region->in(i);
  86     if( r && r->Opcode() == Op_Region && // Found a region?
  87         r->in(0) == r &&        // Not already collapsed?
  88         r != region &&          // Avoid stupid situations
  89         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  90       assert(!r->as_Region()->has_phi(), "no phi users");
  91       if( !progress ) {         // No progress
  92         if (region->has_phi()) {
  93           return NULL;        // Only flatten if no Phi users
  94           // igvn->hash_delete( phi );
  95         }
  96         igvn->hash_delete( region );
  97         progress = region;      // Making progress
  98       }
  99       igvn->hash_delete( r );
 100 
 101       // Append inputs to 'r' onto 'region'
 102       for( uint j = 1; j < r->req(); j++ ) {
 103         // Move an input from 'r' to 'region'
 104         region->add_req(r->in(j));
 105         r->set_req(j, phase->C->top());
 106         // Update phis of 'region'
 107         //for( uint k = 0; k < max; k++ ) {
 108         //  Node *phi = region->out(k);
 109         //  if( phi->is_Phi() ) {
 110         //    phi->add_req(phi->in(i));
 111         //  }
 112         //}
 113 
 114         rreq++;                 // One more input to Region
 115       } // Found a region to merge into Region
 116       igvn->_worklist.push(r);
 117       // Clobber pointer to the now dead 'r'
 118       region->set_req(i, phase->C->top());
 119     }
 120   }
 121 
 122   return progress;
 123 }
 124 
 125 
 126 
 127 //--------------------------------has_phi--------------------------------------
 128 // Helper function: Return any PhiNode that uses this region or NULL
 129 PhiNode* RegionNode::has_phi() const {
 130   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 131     Node* phi = fast_out(i);
 132     if (phi->is_Phi()) {   // Check for Phi users
 133       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 134       return phi->as_Phi();  // this one is good enough
 135     }
 136   }
 137 
 138   return NULL;
 139 }
 140 
 141 
 142 //-----------------------------has_unique_phi----------------------------------
 143 // Helper function: Return the only PhiNode that uses this region or NULL
 144 PhiNode* RegionNode::has_unique_phi() const {
 145   // Check that only one use is a Phi
 146   PhiNode* only_phi = NULL;
 147   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 148     Node* phi = fast_out(i);
 149     if (phi->is_Phi()) {   // Check for Phi users
 150       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 151       if (only_phi == NULL) {
 152         only_phi = phi->as_Phi();
 153       } else {
 154         return NULL;  // multiple phis
 155       }
 156     }
 157   }
 158 
 159   return only_phi;
 160 }
 161 
 162 
 163 //------------------------------check_phi_clipping-----------------------------
 164 // Helper function for RegionNode's identification of FP clipping
 165 // Check inputs to the Phi
 166 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 167   min     = NULL;
 168   max     = NULL;
 169   val     = NULL;
 170   min_idx = 0;
 171   max_idx = 0;
 172   val_idx = 0;
 173   uint  phi_max = phi->req();
 174   if( phi_max == 4 ) {
 175     for( uint j = 1; j < phi_max; ++j ) {
 176       Node *n = phi->in(j);
 177       int opcode = n->Opcode();
 178       switch( opcode ) {
 179       case Op_ConI:
 180         {
 181           if( min == NULL ) {
 182             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 183             min_idx = j;
 184           } else {
 185             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 186             max_idx = j;
 187             if( min->get_int() > max->get_int() ) {
 188               // Swap min and max
 189               ConNode *temp;
 190               uint     temp_idx;
 191               temp     = min;     min     = max;     max     = temp;
 192               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 193             }
 194           }
 195         }
 196         break;
 197       default:
 198         {
 199           val = n;
 200           val_idx = j;
 201         }
 202         break;
 203       }
 204     }
 205   }
 206   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 207 }
 208 
 209 
 210 //------------------------------check_if_clipping------------------------------
 211 // Helper function for RegionNode's identification of FP clipping
 212 // Check that inputs to Region come from two IfNodes,
 213 //
 214 //            If
 215 //      False    True
 216 //       If        |
 217 //  False  True    |
 218 //    |      |     |
 219 //  RegionNode_inputs
 220 //
 221 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 222   top_if = NULL;
 223   bot_if = NULL;
 224 
 225   // Check control structure above RegionNode for (if  ( if  ) )
 226   Node *in1 = region->in(1);
 227   Node *in2 = region->in(2);
 228   Node *in3 = region->in(3);
 229   // Check that all inputs are projections
 230   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 231     Node *in10 = in1->in(0);
 232     Node *in20 = in2->in(0);
 233     Node *in30 = in3->in(0);
 234     // Check that #1 and #2 are ifTrue and ifFalse from same If
 235     if( in10 != NULL && in10->is_If() &&
 236         in20 != NULL && in20->is_If() &&
 237         in30 != NULL && in30->is_If() && in10 == in20 &&
 238         (in1->Opcode() != in2->Opcode()) ) {
 239       Node  *in100 = in10->in(0);
 240       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 241       // Check that control for in10 comes from other branch of IF from in3
 242       if( in1000 != NULL && in1000->is_If() &&
 243           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 244         // Control pattern checks
 245         top_if = (IfNode*)in1000;
 246         bot_if = (IfNode*)in10;
 247       }
 248     }
 249   }
 250 
 251   return (top_if != NULL);
 252 }
 253 
 254 
 255 //------------------------------check_convf2i_clipping-------------------------
 256 // Helper function for RegionNode's identification of FP clipping
 257 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 258 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 259   convf2i = NULL;
 260 
 261   // Check for the RShiftNode
 262   Node *rshift = phi->in(idx);
 263   assert( rshift, "Previous checks ensure phi input is present");
 264   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 265 
 266   // Check for the LShiftNode
 267   Node *lshift = rshift->in(1);
 268   assert( lshift, "Previous checks ensure phi input is present");
 269   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 270 
 271   // Check for the ConvF2INode
 272   Node *conv = lshift->in(1);
 273   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 274 
 275   // Check that shift amounts are only to get sign bits set after F2I
 276   jint max_cutoff     = max->get_int();
 277   jint min_cutoff     = min->get_int();
 278   jint left_shift     = lshift->in(2)->get_int();
 279   jint right_shift    = rshift->in(2)->get_int();
 280   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 281   if( left_shift != right_shift ||
 282       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 283       max_post_shift < max_cutoff ||
 284       max_post_shift < -min_cutoff ) {
 285     // Shifts are necessary but current transformation eliminates them
 286     return false;
 287   }
 288 
 289   // OK to return the result of ConvF2I without shifting
 290   convf2i = (ConvF2INode*)conv;
 291   return true;
 292 }
 293 
 294 
 295 //------------------------------check_compare_clipping-------------------------
 296 // Helper function for RegionNode's identification of FP clipping
 297 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 298   Node *i1 = iff->in(1);
 299   if ( !i1->is_Bool() ) { return false; }
 300   BoolNode *bool1 = i1->as_Bool();
 301   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 302   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 303   const Node *cmpF = bool1->in(1);
 304   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 305   // Test that the float value being compared against
 306   // is equivalent to the int value used as a limit
 307   Node *nodef = cmpF->in(2);
 308   if( nodef->Opcode() != Op_ConF ) { return false; }
 309   jfloat conf = nodef->getf();
 310   jint   coni = limit->get_int();
 311   if( ((int)conf) != coni )        { return false; }
 312   input = cmpF->in(1);
 313   return true;
 314 }
 315 
 316 //------------------------------is_unreachable_region--------------------------
 317 // Find if the Region node is reachable from the root.
 318 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
 319   assert(req() == 2, "");
 320 
 321   // First, cut the simple case of fallthrough region when NONE of
 322   // region's phis references itself directly or through a data node.
 323   uint max = outcnt();
 324   uint i;
 325   for (i = 0; i < max; i++) {
 326     Node* phi = raw_out(i);
 327     if (phi != NULL && phi->is_Phi()) {
 328       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
 329       if (phi->outcnt() == 0)
 330         continue; // Safe case - no loops
 331       if (phi->outcnt() == 1) {
 332         Node* u = phi->raw_out(0);
 333         // Skip if only one use is an other Phi or Call or Uncommon trap.
 334         // It is safe to consider this case as fallthrough.
 335         if (u != NULL && (u->is_Phi() || u->is_CFG()))
 336           continue;
 337       }
 338       // Check when phi references itself directly or through an other node.
 339       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
 340         break; // Found possible unsafe data loop.
 341     }
 342   }
 343   if (i >= max)
 344     return false; // An unsafe case was NOT found - don't need graph walk.
 345 
 346   // Unsafe case - check if the Region node is reachable from root.
 347   ResourceMark rm;
 348 
 349   Arena *a = Thread::current()->resource_area();
 350   Node_List nstack(a);
 351   VectorSet visited(a);
 352 
 353   // Mark all control nodes reachable from root outputs
 354   Node *n = (Node*)phase->C->root();
 355   nstack.push(n);
 356   visited.set(n->_idx);
 357   while (nstack.size() != 0) {
 358     n = nstack.pop();
 359     uint max = n->outcnt();
 360     for (uint i = 0; i < max; i++) {
 361       Node* m = n->raw_out(i);
 362       if (m != NULL && m->is_CFG()) {
 363         if (phase->eqv(m, this)) {
 364           return false; // We reached the Region node - it is not dead.
 365         }
 366         if (!visited.test_set(m->_idx))
 367           nstack.push(m);
 368       }
 369     }
 370   }
 371 
 372   return true; // The Region node is unreachable - it is dead.
 373 }
 374 
 375 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 376   // Incremental inlining + PhaseStringOpts sometimes produce:
 377   //
 378   // cmpP with 1 top input
 379   //           |
 380   //          If
 381   //         /  \
 382   //   IfFalse  IfTrue  /- Some Node
 383   //         \  /      /    /
 384   //        Region    / /-MergeMem
 385   //             \---Phi
 386   //
 387   //
 388   // It's expected by PhaseStringOpts that the Region goes away and is
 389   // replaced by If's control input but because there's still a Phi,
 390   // the Region stays in the graph. The top input from the cmpP is
 391   // propagated forward and a subgraph that is useful goes away. The
 392   // code below replaces the Phi with the MergeMem so that the Region
 393   // is simplified.
 394 
 395   PhiNode* phi = has_unique_phi();
 396   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 397     MergeMemNode* m = NULL;
 398     assert(phi->req() == 3, "same as region");
 399     for (uint i = 1; i < 3; ++i) {
 400       Node *mem = phi->in(i);
 401       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 402         // Nothing is control-dependent on path #i except the region itself.
 403         m = mem->as_MergeMem();
 404         uint j = 3 - i;
 405         Node* other = phi->in(j);
 406         if (other && other == m->base_memory()) {
 407           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 408           // This will allow the diamond to collapse completely.
 409           phase->is_IterGVN()->replace_node(phi, m);
 410           return true;
 411         }
 412       }
 413     }
 414   }
 415   return false;
 416 }
 417 
 418 //------------------------------Ideal------------------------------------------
 419 // Return a node which is more "ideal" than the current node.  Must preserve
 420 // the CFG, but we can still strip out dead paths.
 421 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 422   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 423   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 424 
 425   // Check for RegionNode with no Phi users and both inputs come from either
 426   // arm of the same IF.  If found, then the control-flow split is useless.
 427   bool has_phis = false;
 428   if (can_reshape) {            // Need DU info to check for Phi users
 429     has_phis = (has_phi() != NULL);       // Cache result
 430     if (has_phis && try_clean_mem_phi(phase)) {
 431       has_phis = false;
 432     }
 433 
 434     if (!has_phis) {            // No Phi users?  Nothing merging?
 435       for (uint i = 1; i < req()-1; i++) {
 436         Node *if1 = in(i);
 437         if( !if1 ) continue;
 438         Node *iff = if1->in(0);
 439         if( !iff || !iff->is_If() ) continue;
 440         for( uint j=i+1; j<req(); j++ ) {
 441           if( in(j) && in(j)->in(0) == iff &&
 442               if1->Opcode() != in(j)->Opcode() ) {
 443             // Add the IF Projections to the worklist. They (and the IF itself)
 444             // will be eliminated if dead.
 445             phase->is_IterGVN()->add_users_to_worklist(iff);
 446             set_req(i, iff->in(0));// Skip around the useless IF diamond
 447             set_req(j, NULL);
 448             return this;      // Record progress
 449           }
 450         }
 451       }
 452     }
 453   }
 454 
 455   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 456   // degrades to a copy.
 457   bool add_to_worklist = false;
 458   bool modified = false;
 459   int cnt = 0;                  // Count of values merging
 460   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 461   int del_it = 0;               // The last input path we delete
 462   // For all inputs...
 463   for( uint i=1; i<req(); ++i ){// For all paths in
 464     Node *n = in(i);            // Get the input
 465     if( n != NULL ) {
 466       // Remove useless control copy inputs
 467       if( n->is_Region() && n->as_Region()->is_copy() ) {
 468         set_req(i, n->nonnull_req());
 469         modified = true;
 470         i--;
 471         continue;
 472       }
 473       if( n->is_Proj() ) {      // Remove useless rethrows
 474         Node *call = n->in(0);
 475         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 476           set_req(i, call->in(0));
 477           modified = true;
 478           i--;
 479           continue;
 480         }
 481       }
 482       if( phase->type(n) == Type::TOP ) {
 483         set_req(i, NULL);       // Ignore TOP inputs
 484         modified = true;
 485         i--;
 486         continue;
 487       }
 488       cnt++;                    // One more value merging
 489 
 490     } else if (can_reshape) {   // Else found dead path with DU info
 491       PhaseIterGVN *igvn = phase->is_IterGVN();
 492       del_req(i);               // Yank path from self
 493       del_it = i;
 494       uint max = outcnt();
 495       DUIterator j;
 496       bool progress = true;
 497       while(progress) {         // Need to establish property over all users
 498         progress = false;
 499         for (j = outs(); has_out(j); j++) {
 500           Node *n = out(j);
 501           if( n->req() != req() && n->is_Phi() ) {
 502             assert( n->in(0) == this, "" );
 503             igvn->hash_delete(n); // Yank from hash before hacking edges
 504             n->set_req_X(i,NULL,igvn);// Correct DU info
 505             n->del_req(i);        // Yank path from Phis
 506             if( max != outcnt() ) {
 507               progress = true;
 508               j = refresh_out_pos(j);
 509               max = outcnt();
 510             }
 511           }
 512         }
 513       }
 514       add_to_worklist = true;
 515       i--;
 516     }
 517   }
 518 
 519   if (can_reshape && cnt == 1) {
 520     // Is it dead loop?
 521     // If it is LoopNopde it had 2 (+1 itself) inputs and
 522     // one of them was cut. The loop is dead if it was EntryContol.
 523     // Loop node may have only one input because entry path
 524     // is removed in PhaseIdealLoop::Dominators().
 525     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 526     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 527                              (del_it == 0 && is_unreachable_region(phase)))) ||
 528         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 529       // Yes,  the region will be removed during the next step below.
 530       // Cut the backedge input and remove phis since no data paths left.
 531       // We don't cut outputs to other nodes here since we need to put them
 532       // on the worklist.
 533       PhaseIterGVN *igvn = phase->is_IterGVN();
 534       if (in(1)->outcnt() == 1) {
 535         igvn->_worklist.push(in(1));
 536       }
 537       del_req(1);
 538       cnt = 0;
 539       assert( req() == 1, "no more inputs expected" );
 540       uint max = outcnt();
 541       bool progress = true;
 542       Node *top = phase->C->top();
 543       DUIterator j;
 544       while(progress) {
 545         progress = false;
 546         for (j = outs(); has_out(j); j++) {
 547           Node *n = out(j);
 548           if( n->is_Phi() ) {
 549             assert( igvn->eqv(n->in(0), this), "" );
 550             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 551             // Break dead loop data path.
 552             // Eagerly replace phis with top to avoid phis copies generation.
 553             igvn->replace_node(n, top);
 554             if( max != outcnt() ) {
 555               progress = true;
 556               j = refresh_out_pos(j);
 557               max = outcnt();
 558             }
 559           }
 560         }
 561       }
 562       add_to_worklist = true;
 563     }
 564   }
 565   if (add_to_worklist) {
 566     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 567   }
 568 
 569   if( cnt <= 1 ) {              // Only 1 path in?
 570     set_req(0, NULL);           // Null control input for region copy
 571     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 572       // No inputs or all inputs are NULL.
 573       return NULL;
 574     } else if (can_reshape) {   // Optimization phase - remove the node
 575       PhaseIterGVN *igvn = phase->is_IterGVN();
 576       // Strip mined (inner) loop is going away, remove outer loop.
 577       if (is_CountedLoop() &&
 578           as_Loop()->is_strip_mined()) {
 579         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 580         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 581         if (outer_sfpt != NULL && outer_out != NULL) {
 582           Node* in = outer_sfpt->in(0);
 583           igvn->replace_node(outer_out, in);
 584           LoopNode* outer = as_CountedLoop()->outer_loop();
 585           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 586         }
 587       }
 588       Node *parent_ctrl;
 589       if( cnt == 0 ) {
 590         assert( req() == 1, "no inputs expected" );
 591         // During IGVN phase such region will be subsumed by TOP node
 592         // so region's phis will have TOP as control node.
 593         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 594         // Also set other user's input to top.
 595         parent_ctrl = phase->C->top();
 596       } else {
 597         // The fallthrough case since we already checked dead loops above.
 598         parent_ctrl = in(1);
 599         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 600         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 601       }
 602       if (!add_to_worklist)
 603         igvn->add_users_to_worklist(this); // Check for further allowed opts
 604       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 605         Node* n = last_out(i);
 606         igvn->hash_delete(n); // Remove from worklist before modifying edges
 607         if( n->is_Phi() ) {   // Collapse all Phis
 608           // Eagerly replace phis to avoid copies generation.
 609           Node* in;
 610           if( cnt == 0 ) {
 611             assert( n->req() == 1, "No data inputs expected" );
 612             in = parent_ctrl; // replaced by top
 613           } else {
 614             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 615             in = n->in(1);               // replaced by unique input
 616             if( n->as_Phi()->is_unsafe_data_reference(in) )
 617               in = phase->C->top();      // replaced by top
 618           }
 619           igvn->replace_node(n, in);
 620         }
 621         else if( n->is_Region() ) { // Update all incoming edges
 622           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 623           uint uses_found = 0;
 624           for( uint k=1; k < n->req(); k++ ) {
 625             if( n->in(k) == this ) {
 626               n->set_req(k, parent_ctrl);
 627               uses_found++;
 628             }
 629           }
 630           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 631             i -= (uses_found - 1);
 632           }
 633         }
 634         else {
 635           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 636           n->set_req(0, parent_ctrl);
 637         }
 638 #ifdef ASSERT
 639         for( uint k=0; k < n->req(); k++ ) {
 640           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 641         }
 642 #endif
 643       }
 644       // Remove the RegionNode itself from DefUse info
 645       igvn->remove_dead_node(this);
 646       return NULL;
 647     }
 648     return this;                // Record progress
 649   }
 650 
 651 
 652   // If a Region flows into a Region, merge into one big happy merge.
 653   if (can_reshape) {
 654     Node *m = merge_region(this, phase);
 655     if (m != NULL)  return m;
 656   }
 657 
 658   // Check if this region is the root of a clipping idiom on floats
 659   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 660     // Check that only one use is a Phi and that it simplifies to two constants +
 661     PhiNode* phi = has_unique_phi();
 662     if (phi != NULL) {          // One Phi user
 663       // Check inputs to the Phi
 664       ConNode *min;
 665       ConNode *max;
 666       Node    *val;
 667       uint     min_idx;
 668       uint     max_idx;
 669       uint     val_idx;
 670       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 671         IfNode *top_if;
 672         IfNode *bot_if;
 673         if( check_if_clipping( this, bot_if, top_if ) ) {
 674           // Control pattern checks, now verify compares
 675           Node   *top_in = NULL;   // value being compared against
 676           Node   *bot_in = NULL;
 677           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 678               check_compare_clipping( false, top_if, max, top_in ) ) {
 679             if( bot_in == top_in ) {
 680               PhaseIterGVN *gvn = phase->is_IterGVN();
 681               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 682               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 683 
 684               // Check for the ConvF2INode
 685               ConvF2INode *convf2i;
 686               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 687                 convf2i->in(1) == bot_in ) {
 688                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 689                 // max test
 690                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 691                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 692                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 693                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 694                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 695                 // min test
 696                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 697                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 698                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 699                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 700                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 701                 // update input edges to region node
 702                 set_req_X( min_idx, if_min, gvn );
 703                 set_req_X( max_idx, if_max, gvn );
 704                 set_req_X( val_idx, ifF,    gvn );
 705                 // remove unnecessary 'LShiftI; RShiftI' idiom
 706                 gvn->hash_delete(phi);
 707                 phi->set_req_X( val_idx, convf2i, gvn );
 708                 gvn->hash_find_insert(phi);
 709                 // Return transformed region node
 710                 return this;
 711               }
 712             }
 713           }
 714         }
 715       }
 716     }
 717   }
 718 
 719   if (can_reshape) {
 720     modified |= optimize_trichotomy(phase->is_IterGVN());
 721   }
 722 
 723   return modified ? this : NULL;
 724 }
 725 
 726 //------------------------------optimize_trichotomy--------------------------
 727 // Optimize nested comparisons of the following kind:
 728 //
 729 // int compare(int a, int b) {
 730 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 731 // }
 732 //
 733 // Shape 1:
 734 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 735 //
 736 // Shape 2:
 737 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 738 //
 739 // Above code leads to the following IR shapes where both Ifs compare the
 740 // same value and two out of three region inputs idx1 and idx2 map to
 741 // the same value and control flow.
 742 //
 743 // (1)   If                 (2)   If
 744 //      /  \                     /  \
 745 //   Proj  Proj               Proj  Proj
 746 //     |      \                |      \
 747 //     |       If              |      If                      If
 748 //     |      /  \             |     /  \                    /  \
 749 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 750 //     |   /      /            \    |    /                  |    /
 751 //    Region     /              \   |   /                   |   /
 752 //         \    /                \  |  /                    |  /
 753 //         Region                Region                    Region
 754 //
 755 // The method returns true if 'this' is modified and false otherwise.
 756 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 757   int idx1 = 1, idx2 = 2;
 758   Node* region = NULL;
 759   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 760     // Shape 1: Check if one of the inputs is a region that merges two control
 761     // inputs and has no other users (especially no Phi users).
 762     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 763     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 764       return false; // No suitable region input found
 765     }
 766   } else if (req() == 4) {
 767     // Shape 2: Check if two control inputs map to the same value of the unique phi
 768     // user and treat these as if they would come from another region (shape (1)).
 769     PhiNode* phi = has_unique_phi();
 770     if (phi == NULL) {
 771       return false; // No unique phi user
 772     }
 773     if (phi->in(idx1) != phi->in(idx2)) {
 774       idx2 = 3;
 775       if (phi->in(idx1) != phi->in(idx2)) {
 776         idx1 = 2;
 777         if (phi->in(idx1) != phi->in(idx2)) {
 778           return false; // No equal phi inputs found
 779         }
 780       }
 781     }
 782     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 783     region = this;
 784   }
 785   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 786     return false; // Region does not merge two control inputs
 787   }
 788   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 789   // value and control flow. Now search for ifs that feed into these region inputs.
 790   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 791   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 792   if (proj1 == NULL || proj1->outcnt() != 1 ||
 793       proj2 == NULL || proj2->outcnt() != 1) {
 794     return false; // No projection inputs with region as unique user found
 795   }
 796   assert(proj1 != proj2, "should be different projections");
 797   IfNode* iff1 = proj1->in(0)->isa_If();
 798   IfNode* iff2 = proj2->in(0)->isa_If();
 799   if (iff1 == NULL || iff1->outcnt() != 2 ||
 800       iff2 == NULL || iff2->outcnt() != 2) {
 801     return false; // No ifs found
 802   }
 803   if (iff1 == iff2) {
 804     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 805     igvn->replace_input_of(region, idx1, iff1->in(0));
 806     igvn->replace_input_of(region, idx2, igvn->C->top());
 807     return (region == this); // Remove useless if (both projections map to the same control/value)
 808   }
 809   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 810   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 811   if (bol1 == NULL || bol2 == NULL) {
 812     return false; // No bool inputs found
 813   }
 814   Node* cmp1 = bol1->in(1);
 815   Node* cmp2 = bol2->in(1);
 816   bool commute = false;
 817   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 818     return false; // No comparison
 819   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 820              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 821              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 822              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN) {
 823     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 824     return false;
 825   } else if (cmp1 != cmp2) {
 826     if (cmp1->in(1) == cmp2->in(2) &&
 827         cmp1->in(2) == cmp2->in(1)) {
 828       commute = true; // Same but swapped inputs, commute the test
 829     } else {
 830       return false; // Ifs are not comparing the same values
 831     }
 832   }
 833   proj1 = proj1->other_if_proj();
 834   proj2 = proj2->other_if_proj();
 835   if (!((proj1->unique_ctrl_out() == iff2 &&
 836          proj2->unique_ctrl_out() == this) ||
 837         (proj2->unique_ctrl_out() == iff1 &&
 838          proj1->unique_ctrl_out() == this))) {
 839     return false; // Ifs are not connected through other projs
 840   }
 841   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 842   // through 'region' and map to the same value. Merge the boolean tests and replace
 843   // the ifs by a single comparison.
 844   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 845   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 846   test1 = commute ? test1.commute() : test1;
 847   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 848   BoolTest::mask res = test1.merge(test2);
 849   if (res == BoolTest::illegal) {
 850     return false; // Unable to merge tests
 851   }
 852   // Adjust iff1 to always pass (only iff2 will remain)
 853   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 854   if (res == BoolTest::never) {
 855     // Merged test is always false, adjust iff2 to always fail
 856     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 857   } else {
 858     // Replace bool input of iff2 with merged test
 859     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 860     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 861   }
 862   return false;
 863 }
 864 
 865 const RegMask &RegionNode::out_RegMask() const {
 866   return RegMask::Empty;
 867 }
 868 
 869 // Find the one non-null required input.  RegionNode only
 870 Node *Node::nonnull_req() const {
 871   assert( is_Region(), "" );
 872   for( uint i = 1; i < _cnt; i++ )
 873     if( in(i) )
 874       return in(i);
 875   ShouldNotReachHere();
 876   return NULL;
 877 }
 878 
 879 
 880 //=============================================================================
 881 // note that these functions assume that the _adr_type field is flattened
 882 uint PhiNode::hash() const {
 883   const Type* at = _adr_type;
 884   return TypeNode::hash() + (at ? at->hash() : 0);
 885 }
 886 bool PhiNode::cmp( const Node &n ) const {
 887   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 888 }
 889 static inline
 890 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 891   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 892   return Compile::current()->alias_type(at)->adr_type();
 893 }
 894 
 895 //----------------------------make---------------------------------------------
 896 // create a new phi with edges matching r and set (initially) to x
 897 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 898   uint preds = r->req();   // Number of predecessor paths
 899   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 900   PhiNode* p = new PhiNode(r, t, at);
 901   for (uint j = 1; j < preds; j++) {
 902     // Fill in all inputs, except those which the region does not yet have
 903     if (r->in(j) != NULL)
 904       p->init_req(j, x);
 905   }
 906   return p;
 907 }
 908 PhiNode* PhiNode::make(Node* r, Node* x) {
 909   const Type*    t  = x->bottom_type();
 910   const TypePtr* at = NULL;
 911   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 912   return make(r, x, t, at);
 913 }
 914 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 915   const Type*    t  = x->bottom_type();
 916   const TypePtr* at = NULL;
 917   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 918   return new PhiNode(r, t, at);
 919 }
 920 
 921 
 922 //------------------------slice_memory-----------------------------------------
 923 // create a new phi with narrowed memory type
 924 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 925   PhiNode* mem = (PhiNode*) clone();
 926   *(const TypePtr**)&mem->_adr_type = adr_type;
 927   // convert self-loops, or else we get a bad graph
 928   for (uint i = 1; i < req(); i++) {
 929     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 930   }
 931   mem->verify_adr_type();
 932   return mem;
 933 }
 934 
 935 //------------------------split_out_instance-----------------------------------
 936 // Split out an instance type from a bottom phi.
 937 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 938   const TypeOopPtr *t_oop = at->isa_oopptr();
 939   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 940   const TypePtr *t = adr_type();
 941   assert(type() == Type::MEMORY &&
 942          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 943           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 944           t->is_oopptr()->cast_to_exactness(true)
 945            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 946            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 947          "bottom or raw memory required");
 948 
 949   // Check if an appropriate node already exists.
 950   Node *region = in(0);
 951   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 952     Node* use = region->fast_out(k);
 953     if( use->is_Phi()) {
 954       PhiNode *phi2 = use->as_Phi();
 955       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 956         return phi2;
 957       }
 958     }
 959   }
 960   Compile *C = igvn->C;
 961   Arena *a = Thread::current()->resource_area();
 962   Node_Array node_map = new Node_Array(a);
 963   Node_Stack stack(a, C->live_nodes() >> 4);
 964   PhiNode *nphi = slice_memory(at);
 965   igvn->register_new_node_with_optimizer( nphi );
 966   node_map.map(_idx, nphi);
 967   stack.push((Node *)this, 1);
 968   while(!stack.is_empty()) {
 969     PhiNode *ophi = stack.node()->as_Phi();
 970     uint i = stack.index();
 971     assert(i >= 1, "not control edge");
 972     stack.pop();
 973     nphi = node_map[ophi->_idx]->as_Phi();
 974     for (; i < ophi->req(); i++) {
 975       Node *in = ophi->in(i);
 976       if (in == NULL || igvn->type(in) == Type::TOP)
 977         continue;
 978       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
 979       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 980       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 981         opt = node_map[optphi->_idx];
 982         if (opt == NULL) {
 983           stack.push(ophi, i);
 984           nphi = optphi->slice_memory(at);
 985           igvn->register_new_node_with_optimizer( nphi );
 986           node_map.map(optphi->_idx, nphi);
 987           ophi = optphi;
 988           i = 0; // will get incremented at top of loop
 989           continue;
 990         }
 991       }
 992       nphi->set_req(i, opt);
 993     }
 994   }
 995   return nphi;
 996 }
 997 
 998 //------------------------verify_adr_type--------------------------------------
 999 #ifdef ASSERT
1000 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1001   if (visited.test_set(_idx))  return;  //already visited
1002 
1003   // recheck constructor invariants:
1004   verify_adr_type(false);
1005 
1006   // recheck local phi/phi consistency:
1007   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1008          "adr_type must be consistent across phi nest");
1009 
1010   // walk around
1011   for (uint i = 1; i < req(); i++) {
1012     Node* n = in(i);
1013     if (n == NULL)  continue;
1014     const Node* np = in(i);
1015     if (np->is_Phi()) {
1016       np->as_Phi()->verify_adr_type(visited, at);
1017     } else if (n->bottom_type() == Type::TOP
1018                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1019       // ignore top inputs
1020     } else {
1021       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1022       // recheck phi/non-phi consistency at leaves:
1023       assert((nat != NULL) == (at != NULL), "");
1024       assert(nat == at || nat == TypePtr::BOTTOM,
1025              "adr_type must be consistent at leaves of phi nest");
1026     }
1027   }
1028 }
1029 
1030 // Verify a whole nest of phis rooted at this one.
1031 void PhiNode::verify_adr_type(bool recursive) const {
1032   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1033   if (Node::in_dump())               return;  // muzzle asserts when printing
1034 
1035   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1036 
1037   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1038 
1039   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1040          "Phi::adr_type must be pre-normalized");
1041 
1042   if (recursive) {
1043     VectorSet visited(Thread::current()->resource_area());
1044     verify_adr_type(visited, _adr_type);
1045   }
1046 }
1047 #endif
1048 
1049 
1050 //------------------------------Value------------------------------------------
1051 // Compute the type of the PhiNode
1052 const Type* PhiNode::Value(PhaseGVN* phase) const {
1053   Node *r = in(0);              // RegionNode
1054   if( !r )                      // Copy or dead
1055     return in(1) ? phase->type(in(1)) : Type::TOP;
1056 
1057   // Note: During parsing, phis are often transformed before their regions.
1058   // This means we have to use type_or_null to defend against untyped regions.
1059   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1060     return Type::TOP;
1061 
1062   // Check for trip-counted loop.  If so, be smarter.
1063   CountedLoopNode* l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
1064   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1065     // protect against init_trip() or limit() returning NULL
1066     if (l->can_be_counted_loop(phase)) {
1067       const Node *init   = l->init_trip();
1068       const Node *limit  = l->limit();
1069       const Node* stride = l->stride();
1070       if (init != NULL && limit != NULL && stride != NULL) {
1071         const TypeInt* lo = phase->type(init)->isa_int();
1072         const TypeInt* hi = phase->type(limit)->isa_int();
1073         const TypeInt* stride_t = phase->type(stride)->isa_int();
1074         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1075           assert(stride_t->_hi >= stride_t->_lo, "bad stride type");
1076           BoolTest::mask bt = l->loopexit()->test_trip();
1077           // If the loop exit condition is "not equal", the condition
1078           // would not trigger if init > limit (if stride > 0) or if
1079           // init < limit if (stride > 0) so we can't deduce bounds
1080           // for the iv from the exit condition.
1081           if (bt != BoolTest::ne) {
1082             if (stride_t->_hi < 0) {          // Down-counter loop
1083               swap(lo, hi);
1084               return TypeInt::make(MIN2(lo->_lo, hi->_lo) , hi->_hi, 3);
1085             } else if (stride_t->_lo >= 0) {
1086               return TypeInt::make(lo->_lo, MAX2(lo->_hi, hi->_hi), 3);
1087             }
1088           }
1089         }
1090       }
1091     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1092                in(LoopNode::EntryControl) != NULL &&
1093                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1094       // During CCP, if we saturate the type of a counted loop's Phi
1095       // before the special code for counted loop above has a chance
1096       // to run (that is as long as the type of the backedge's control
1097       // is top), we might end up with non monotonic types
1098       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1099     }
1100   }
1101 
1102   // Until we have harmony between classes and interfaces in the type
1103   // lattice, we must tread carefully around phis which implicitly
1104   // convert the one to the other.
1105   const TypePtr* ttp = _type->make_ptr();
1106   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1107   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
1108   bool is_intf = false;
1109   if (ttip != NULL) {
1110     ciKlass* k = ttip->klass();
1111     if (k->is_loaded() && k->is_interface())
1112       is_intf = true;
1113   }
1114   if (ttkp != NULL) {
1115     ciKlass* k = ttkp->klass();
1116     if (k->is_loaded() && k->is_interface())
1117       is_intf = true;
1118   }
1119 
1120   // Default case: merge all inputs
1121   const Type *t = Type::TOP;        // Merged type starting value
1122   for (uint i = 1; i < req(); ++i) {// For all paths in
1123     // Reachable control path?
1124     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1125       const Type* ti = phase->type(in(i));
1126       // We assume that each input of an interface-valued Phi is a true
1127       // subtype of that interface.  This might not be true of the meet
1128       // of all the input types.  The lattice is not distributive in
1129       // such cases.  Ward off asserts in type.cpp by refusing to do
1130       // meets between interfaces and proper classes.
1131       const TypePtr* tip = ti->make_ptr();
1132       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1133       if (tiip) {
1134         bool ti_is_intf = false;
1135         ciKlass* k = tiip->klass();
1136         if (k->is_loaded() && k->is_interface())
1137           ti_is_intf = true;
1138         if (is_intf != ti_is_intf)
1139           { t = _type; break; }
1140       }
1141       t = t->meet_speculative(ti);
1142     }
1143   }
1144 
1145   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1146   // That is, we expect that "t->higher_equal(_type)" holds true.
1147   // There are various exceptions:
1148   // - Inputs which are phis might in fact be widened unnecessarily.
1149   //   For example, an input might be a widened int while the phi is a short.
1150   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1151   //   and postCCP has removed the cast which encodes the result of the check.
1152   // - The type of this phi is an interface, and the inputs are classes.
1153   // - Value calls on inputs might produce fuzzy results.
1154   //   (Occurrences of this case suggest improvements to Value methods.)
1155   //
1156   // It is not possible to see Type::BOTTOM values as phi inputs,
1157   // because the ciTypeFlow pre-pass produces verifier-quality types.
1158   const Type* ft = t->filter_speculative(_type);  // Worst case type
1159 
1160 #ifdef ASSERT
1161   // The following logic has been moved into TypeOopPtr::filter.
1162   const Type* jt = t->join_speculative(_type);
1163   if (jt->empty()) {           // Emptied out???
1164 
1165     // Check for evil case of 't' being a class and '_type' expecting an
1166     // interface.  This can happen because the bytecodes do not contain
1167     // enough type info to distinguish a Java-level interface variable
1168     // from a Java-level object variable.  If we meet 2 classes which
1169     // both implement interface I, but their meet is at 'j/l/O' which
1170     // doesn't implement I, we have no way to tell if the result should
1171     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1172     // into a Phi which "knows" it's an Interface type we'll have to
1173     // uplift the type.
1174     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1175       assert(ft == _type, ""); // Uplift to interface
1176     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1177       assert(ft == _type, ""); // Uplift to interface
1178     } else {
1179       // We also have to handle 'evil cases' of interface- vs. class-arrays
1180       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1181       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1182           assert(ft == _type, "");   // Uplift to array of interface
1183       } else {
1184         // Otherwise it's something stupid like non-overlapping int ranges
1185         // found on dying counted loops.
1186         assert(ft == Type::TOP, ""); // Canonical empty value
1187       }
1188     }
1189   }
1190 
1191   else {
1192 
1193     // If we have an interface-typed Phi and we narrow to a class type, the join
1194     // should report back the class.  However, if we have a J/L/Object
1195     // class-typed Phi and an interface flows in, it's possible that the meet &
1196     // join report an interface back out.  This isn't possible but happens
1197     // because the type system doesn't interact well with interfaces.
1198     const TypePtr *jtp = jt->make_ptr();
1199     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1200     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
1201     if( jtip && ttip ) {
1202       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1203           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1204         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1205                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1206         jt = ft;
1207       }
1208     }
1209     if( jtkp && ttkp ) {
1210       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1211           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1212           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1213         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1214                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1215         jt = ft;
1216       }
1217     }
1218     if (jt != ft && jt->base() == ft->base()) {
1219       if (jt->isa_int() &&
1220           jt->is_int()->_lo == ft->is_int()->_lo &&
1221           jt->is_int()->_hi == ft->is_int()->_hi)
1222         jt = ft;
1223       if (jt->isa_long() &&
1224           jt->is_long()->_lo == ft->is_long()->_lo &&
1225           jt->is_long()->_hi == ft->is_long()->_hi)
1226         jt = ft;
1227     }
1228     if (jt != ft) {
1229       tty->print("merge type:  "); t->dump(); tty->cr();
1230       tty->print("kill type:   "); _type->dump(); tty->cr();
1231       tty->print("join type:   "); jt->dump(); tty->cr();
1232       tty->print("filter type: "); ft->dump(); tty->cr();
1233     }
1234     assert(jt == ft, "");
1235   }
1236 #endif //ASSERT
1237 
1238   // Deal with conversion problems found in data loops.
1239   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1240 
1241   return ft;
1242 }
1243 
1244 
1245 //------------------------------is_diamond_phi---------------------------------
1246 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1247 // index of the true path or 0 otherwise.
1248 // If check_control_only is true, do not inspect the If node at the
1249 // top, and return -1 (not an edge number) on success.
1250 int PhiNode::is_diamond_phi(bool check_control_only) const {
1251   // Check for a 2-path merge
1252   Node *region = in(0);
1253   if( !region ) return 0;
1254   if( region->req() != 3 ) return 0;
1255   if(         req() != 3 ) return 0;
1256   // Check that both paths come from the same If
1257   Node *ifp1 = region->in(1);
1258   Node *ifp2 = region->in(2);
1259   if( !ifp1 || !ifp2 ) return 0;
1260   Node *iff = ifp1->in(0);
1261   if( !iff || !iff->is_If() ) return 0;
1262   if( iff != ifp2->in(0) ) return 0;
1263   if (check_control_only)  return -1;
1264   // Check for a proper bool/cmp
1265   const Node *b = iff->in(1);
1266   if( !b->is_Bool() ) return 0;
1267   const Node *cmp = b->in(1);
1268   if( !cmp->is_Cmp() ) return 0;
1269 
1270   // Check for branching opposite expected
1271   if( ifp2->Opcode() == Op_IfTrue ) {
1272     assert( ifp1->Opcode() == Op_IfFalse, "" );
1273     return 2;
1274   } else {
1275     assert( ifp1->Opcode() == Op_IfTrue, "" );
1276     return 1;
1277   }
1278 }
1279 
1280 //----------------------------check_cmove_id-----------------------------------
1281 // Check for CMove'ing a constant after comparing against the constant.
1282 // Happens all the time now, since if we compare equality vs a constant in
1283 // the parser, we "know" the variable is constant on one path and we force
1284 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1285 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1286 // general in that we don't need constants.  Since CMove's are only inserted
1287 // in very special circumstances, we do it here on generic Phi's.
1288 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1289   assert(true_path !=0, "only diamond shape graph expected");
1290 
1291   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1292   // phi->region->if_proj->ifnode->bool->cmp
1293   Node*     region = in(0);
1294   Node*     iff    = region->in(1)->in(0);
1295   BoolNode* b      = iff->in(1)->as_Bool();
1296   Node*     cmp    = b->in(1);
1297   Node*     tval   = in(true_path);
1298   Node*     fval   = in(3-true_path);
1299   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1300   if (id == NULL)
1301     return NULL;
1302 
1303   // Either value might be a cast that depends on a branch of 'iff'.
1304   // Since the 'id' value will float free of the diamond, either
1305   // decast or return failure.
1306   Node* ctl = id->in(0);
1307   if (ctl != NULL && ctl->in(0) == iff) {
1308     if (id->is_ConstraintCast()) {
1309       return id->in(1);
1310     } else {
1311       // Don't know how to disentangle this value.
1312       return NULL;
1313     }
1314   }
1315 
1316   return id;
1317 }
1318 
1319 //------------------------------Identity---------------------------------------
1320 // Check for Region being Identity.
1321 Node* PhiNode::Identity(PhaseGVN* phase) {
1322   // Check for no merging going on
1323   // (There used to be special-case code here when this->region->is_Loop.
1324   // It would check for a tributary phi on the backedge that the main phi
1325   // trivially, perhaps with a single cast.  The unique_input method
1326   // does all this and more, by reducing such tributaries to 'this'.)
1327   Node* uin = unique_input(phase, false);
1328   if (uin != NULL) {
1329     return uin;
1330   }
1331 
1332   int true_path = is_diamond_phi();
1333   if (true_path != 0) {
1334     Node* id = is_cmove_id(phase, true_path);
1335     if (id != NULL)  return id;
1336   }
1337 
1338   return this;                     // No identity
1339 }
1340 
1341 //-----------------------------unique_input------------------------------------
1342 // Find the unique value, discounting top, self-loops, and casts.
1343 // Return top if there are no inputs, and self if there are multiple.
1344 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1345   //  1) One unique direct input,
1346   // or if uncast is true:
1347   //  2) some of the inputs have an intervening ConstraintCast
1348   //  3) an input is a self loop
1349   //
1350   //  1) input   or   2) input     or   3) input __
1351   //     /   \           /   \               \  /  \
1352   //     \   /          |    cast             phi  cast
1353   //      phi            \   /               /  \  /
1354   //                      phi               /    --
1355 
1356   Node* r = in(0);                      // RegionNode
1357   if (r == NULL)  return in(1);         // Already degraded to a Copy
1358   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1359 
1360   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1361     Node* rc = r->in(i);
1362     if (rc == NULL || phase->type(rc) == Type::TOP)
1363       continue;                 // ignore unreachable control path
1364     Node* n = in(i);
1365     if (n == NULL)
1366       continue;
1367     Node* un = n;
1368     if (uncast) {
1369 #ifdef ASSERT
1370       Node* m = un->uncast();
1371 #endif
1372       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1373         Node* next = un->in(1);
1374         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1375           // risk exposing raw ptr at safepoint
1376           break;
1377         }
1378         un = next;
1379       }
1380       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1381     }
1382     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1383       continue; // ignore if top, or in(i) and "this" are in a data cycle
1384     }
1385     // Check for a unique input (maybe uncasted)
1386     if (input == NULL) {
1387       input = un;
1388     } else if (input != un) {
1389       input = NodeSentinel; // no unique input
1390     }
1391   }
1392   if (input == NULL) {
1393     return phase->C->top();        // no inputs
1394   }
1395 
1396   if (input != NodeSentinel) {
1397     return input;           // one unique direct input
1398   }
1399 
1400   // Nothing.
1401   return NULL;
1402 }
1403 
1404 //------------------------------is_x2logic-------------------------------------
1405 // Check for simple convert-to-boolean pattern
1406 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1407 // Convert Phi to an ConvIB.
1408 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1409   assert(true_path !=0, "only diamond shape graph expected");
1410   // Convert the true/false index into an expected 0/1 return.
1411   // Map 2->0 and 1->1.
1412   int flipped = 2-true_path;
1413 
1414   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1415   // phi->region->if_proj->ifnode->bool->cmp
1416   Node *region = phi->in(0);
1417   Node *iff = region->in(1)->in(0);
1418   BoolNode *b = (BoolNode*)iff->in(1);
1419   const CmpNode *cmp = (CmpNode*)b->in(1);
1420 
1421   Node *zero = phi->in(1);
1422   Node *one  = phi->in(2);
1423   const Type *tzero = phase->type( zero );
1424   const Type *tone  = phase->type( one  );
1425 
1426   // Check for compare vs 0
1427   const Type *tcmp = phase->type(cmp->in(2));
1428   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1429     // Allow cmp-vs-1 if the other input is bounded by 0-1
1430     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1431       return NULL;
1432     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1433   }
1434 
1435   // Check for setting zero/one opposite expected
1436   if( tzero == TypeInt::ZERO ) {
1437     if( tone == TypeInt::ONE ) {
1438     } else return NULL;
1439   } else if( tzero == TypeInt::ONE ) {
1440     if( tone == TypeInt::ZERO ) {
1441       flipped = 1-flipped;
1442     } else return NULL;
1443   } else return NULL;
1444 
1445   // Check for boolean test backwards
1446   if( b->_test._test == BoolTest::ne ) {
1447   } else if( b->_test._test == BoolTest::eq ) {
1448     flipped = 1-flipped;
1449   } else return NULL;
1450 
1451   // Build int->bool conversion
1452   Node *n = new Conv2BNode(cmp->in(1));
1453   if( flipped )
1454     n = new XorINode( phase->transform(n), phase->intcon(1) );
1455 
1456   return n;
1457 }
1458 
1459 //------------------------------is_cond_add------------------------------------
1460 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1461 // To be profitable the control flow has to disappear; there can be no other
1462 // values merging here.  We replace the test-and-branch with:
1463 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1464 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1465 // Then convert Y to 0-or-Y and finally add.
1466 // This is a key transform for SpecJava _201_compress.
1467 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1468   assert(true_path !=0, "only diamond shape graph expected");
1469 
1470   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1471   // phi->region->if_proj->ifnode->bool->cmp
1472   RegionNode *region = (RegionNode*)phi->in(0);
1473   Node *iff = region->in(1)->in(0);
1474   BoolNode* b = iff->in(1)->as_Bool();
1475   const CmpNode *cmp = (CmpNode*)b->in(1);
1476 
1477   // Make sure only merging this one phi here
1478   if (region->has_unique_phi() != phi)  return NULL;
1479 
1480   // Make sure each arm of the diamond has exactly one output, which we assume
1481   // is the region.  Otherwise, the control flow won't disappear.
1482   if (region->in(1)->outcnt() != 1) return NULL;
1483   if (region->in(2)->outcnt() != 1) return NULL;
1484 
1485   // Check for "(P < Q)" of type signed int
1486   if (b->_test._test != BoolTest::lt)  return NULL;
1487   if (cmp->Opcode() != Op_CmpI)        return NULL;
1488 
1489   Node *p = cmp->in(1);
1490   Node *q = cmp->in(2);
1491   Node *n1 = phi->in(  true_path);
1492   Node *n2 = phi->in(3-true_path);
1493 
1494   int op = n1->Opcode();
1495   if( op != Op_AddI           // Need zero as additive identity
1496       /*&&op != Op_SubI &&
1497       op != Op_AddP &&
1498       op != Op_XorI &&
1499       op != Op_OrI*/ )
1500     return NULL;
1501 
1502   Node *x = n2;
1503   Node *y = NULL;
1504   if( x == n1->in(1) ) {
1505     y = n1->in(2);
1506   } else if( x == n1->in(2) ) {
1507     y = n1->in(1);
1508   } else return NULL;
1509 
1510   // Not so profitable if compare and add are constants
1511   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1512     return NULL;
1513 
1514   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1515   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1516   return new AddINode(j_and,x);
1517 }
1518 
1519 //------------------------------is_absolute------------------------------------
1520 // Check for absolute value.
1521 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1522   assert(true_path !=0, "only diamond shape graph expected");
1523 
1524   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1525   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1526 
1527   // ABS ends with the merge of 2 control flow paths.
1528   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1529   int false_path = 3 - true_path;
1530 
1531   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1532   // phi->region->if_proj->ifnode->bool->cmp
1533   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1534 
1535   // Check bool sense
1536   switch( bol->_test._test ) {
1537   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1538   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1539   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1540   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1541   default:           return NULL;                              break;
1542   }
1543 
1544   // Test is next
1545   Node *cmp = bol->in(1);
1546   const Type *tzero = NULL;
1547   switch( cmp->Opcode() ) {
1548   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1549   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1550   default: return NULL;
1551   }
1552 
1553   // Find zero input of compare; the other input is being abs'd
1554   Node *x = NULL;
1555   bool flip = false;
1556   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1557     x = cmp->in(3 - cmp_zero_idx);
1558   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1559     // The test is inverted, we should invert the result...
1560     x = cmp->in(cmp_zero_idx);
1561     flip = true;
1562   } else {
1563     return NULL;
1564   }
1565 
1566   // Next get the 2 pieces being selected, one is the original value
1567   // and the other is the negated value.
1568   if( phi_root->in(phi_x_idx) != x ) return NULL;
1569 
1570   // Check other phi input for subtract node
1571   Node *sub = phi_root->in(3 - phi_x_idx);
1572 
1573   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1574   if( tzero == TypeF::ZERO ) {
1575     if( sub->Opcode() != Op_SubF ||
1576         sub->in(2) != x ||
1577         phase->type(sub->in(1)) != tzero ) return NULL;
1578     x = new AbsFNode(x);
1579     if (flip) {
1580       x = new SubFNode(sub->in(1), phase->transform(x));
1581     }
1582   } else {
1583     if( sub->Opcode() != Op_SubD ||
1584         sub->in(2) != x ||
1585         phase->type(sub->in(1)) != tzero ) return NULL;
1586     x = new AbsDNode(x);
1587     if (flip) {
1588       x = new SubDNode(sub->in(1), phase->transform(x));
1589     }
1590   }
1591 
1592   return x;
1593 }
1594 
1595 //------------------------------split_once-------------------------------------
1596 // Helper for split_flow_path
1597 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1598   igvn->hash_delete(n);         // Remove from hash before hacking edges
1599 
1600   uint j = 1;
1601   for (uint i = phi->req()-1; i > 0; i--) {
1602     if (phi->in(i) == val) {   // Found a path with val?
1603       // Add to NEW Region/Phi, no DU info
1604       newn->set_req( j++, n->in(i) );
1605       // Remove from OLD Region/Phi
1606       n->del_req(i);
1607     }
1608   }
1609 
1610   // Register the new node but do not transform it.  Cannot transform until the
1611   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1612   igvn->register_new_node_with_optimizer( newn );
1613 
1614   // Now I can point to the new node.
1615   n->add_req(newn);
1616   igvn->_worklist.push(n);
1617 }
1618 
1619 //------------------------------split_flow_path--------------------------------
1620 // Check for merging identical values and split flow paths
1621 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1622   BasicType bt = phi->type()->basic_type();
1623   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1624     return NULL;                // Bail out on funny non-value stuff
1625   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1626     return NULL;                // third unequal input to be worth doing
1627 
1628   // Scan for a constant
1629   uint i;
1630   for( i = 1; i < phi->req()-1; i++ ) {
1631     Node *n = phi->in(i);
1632     if( !n ) return NULL;
1633     if( phase->type(n) == Type::TOP ) return NULL;
1634     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1635       break;
1636   }
1637   if( i >= phi->req() )         // Only split for constants
1638     return NULL;
1639 
1640   Node *val = phi->in(i);       // Constant to split for
1641   uint hit = 0;                 // Number of times it occurs
1642   Node *r = phi->region();
1643 
1644   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1645     Node *n = phi->in(i);
1646     if( !n ) return NULL;
1647     if( phase->type(n) == Type::TOP ) return NULL;
1648     if( phi->in(i) == val ) {
1649       hit++;
1650       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1651         return NULL;            // don't split loop entry path
1652       }
1653     }
1654   }
1655 
1656   if( hit <= 1 ||               // Make sure we find 2 or more
1657       hit == phi->req()-1 )     // and not ALL the same value
1658     return NULL;
1659 
1660   // Now start splitting out the flow paths that merge the same value.
1661   // Split first the RegionNode.
1662   PhaseIterGVN *igvn = phase->is_IterGVN();
1663   RegionNode *newr = new RegionNode(hit+1);
1664   split_once(igvn, phi, val, r, newr);
1665 
1666   // Now split all other Phis than this one
1667   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1668     Node* phi2 = r->fast_out(k);
1669     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1670       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1671       split_once(igvn, phi, val, phi2, newphi);
1672     }
1673   }
1674 
1675   // Clean up this guy
1676   igvn->hash_delete(phi);
1677   for( i = phi->req()-1; i > 0; i-- ) {
1678     if( phi->in(i) == val ) {
1679       phi->del_req(i);
1680     }
1681   }
1682   phi->add_req(val);
1683 
1684   return phi;
1685 }
1686 
1687 //=============================================================================
1688 //------------------------------simple_data_loop_check-------------------------
1689 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1690 //  Returns:
1691 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1692 // Safe       - safe case when the phi and it's inputs reference only safe data
1693 //              nodes;
1694 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1695 //              is no reference back to the phi - need a graph walk
1696 //              to determine if it is in a loop;
1697 // UnsafeLoop - unsafe case when the phi references itself directly or through
1698 //              unsafe data node.
1699 //  Note: a safe data node is a node which could/never reference itself during
1700 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1701 //  I mark Phi nodes as safe node not only because they can reference itself
1702 //  but also to prevent mistaking the fallthrough case inside an outer loop
1703 //  as dead loop when the phi references itselfs through an other phi.
1704 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1705   // It is unsafe loop if the phi node references itself directly.
1706   if (in == (Node*)this)
1707     return UnsafeLoop; // Unsafe loop
1708   // Unsafe loop if the phi node references itself through an unsafe data node.
1709   // Exclude cases with null inputs or data nodes which could reference
1710   // itself (safe for dead loops).
1711   if (in != NULL && !in->is_dead_loop_safe()) {
1712     // Check inputs of phi's inputs also.
1713     // It is much less expensive then full graph walk.
1714     uint cnt = in->req();
1715     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1716     for (; i < cnt; ++i) {
1717       Node* m = in->in(i);
1718       if (m == (Node*)this)
1719         return UnsafeLoop; // Unsafe loop
1720       if (m != NULL && !m->is_dead_loop_safe()) {
1721         // Check the most common case (about 30% of all cases):
1722         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1723         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1724         if (m1 == (Node*)this)
1725           return UnsafeLoop; // Unsafe loop
1726         if (m1 != NULL && m1 == m->in(2) &&
1727             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1728           continue; // Safe case
1729         }
1730         // The phi references an unsafe node - need full analysis.
1731         return Unsafe;
1732       }
1733     }
1734   }
1735   return Safe; // Safe case - we can optimize the phi node.
1736 }
1737 
1738 //------------------------------is_unsafe_data_reference-----------------------
1739 // If phi can be reached through the data input - it is data loop.
1740 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1741   assert(req() > 1, "");
1742   // First, check simple cases when phi references itself directly or
1743   // through an other node.
1744   LoopSafety safety = simple_data_loop_check(in);
1745   if (safety == UnsafeLoop)
1746     return true;  // phi references itself - unsafe loop
1747   else if (safety == Safe)
1748     return false; // Safe case - phi could be replaced with the unique input.
1749 
1750   // Unsafe case when we should go through data graph to determine
1751   // if the phi references itself.
1752 
1753   ResourceMark rm;
1754 
1755   Arena *a = Thread::current()->resource_area();
1756   Node_List nstack(a);
1757   VectorSet visited(a);
1758 
1759   nstack.push(in); // Start with unique input.
1760   visited.set(in->_idx);
1761   while (nstack.size() != 0) {
1762     Node* n = nstack.pop();
1763     uint cnt = n->req();
1764     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1765     for (; i < cnt; i++) {
1766       Node* m = n->in(i);
1767       if (m == (Node*)this) {
1768         return true;    // Data loop
1769       }
1770       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1771         if (!visited.test_set(m->_idx))
1772           nstack.push(m);
1773       }
1774     }
1775   }
1776   return false; // The phi is not reachable from its inputs
1777 }
1778 
1779 // Is this Phi's region or some inputs to the region enqueued for IGVN
1780 // and so could cause the region to be optimized out?
1781 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1782   PhaseIterGVN* igvn = phase->is_IterGVN();
1783   Unique_Node_List& worklist = igvn->_worklist;
1784   bool delay = false;
1785   Node* r = in(0);
1786   for (uint j = 1; j < req(); j++) {
1787     Node* rc = r->in(j);
1788     Node* n = in(j);
1789     if (rc != NULL &&
1790         rc->is_Proj()) {
1791       if (worklist.member(rc)) {
1792         delay = true;
1793       } else if (rc->in(0) != NULL &&
1794                  rc->in(0)->is_If()) {
1795         if (worklist.member(rc->in(0))) {
1796           delay = true;
1797         } else if (rc->in(0)->in(1) != NULL &&
1798                    rc->in(0)->in(1)->is_Bool()) {
1799           if (worklist.member(rc->in(0)->in(1))) {
1800             delay = true;
1801           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1802                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1803             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1804               delay = true;
1805             }
1806           }
1807         }
1808       }
1809     }
1810   }
1811   if (delay) {
1812     worklist.push(this);
1813   }
1814   return delay;
1815 }
1816 
1817 //------------------------------Ideal------------------------------------------
1818 // Return a node which is more "ideal" than the current node.  Must preserve
1819 // the CFG, but we can still strip out dead paths.
1820 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1821   // The next should never happen after 6297035 fix.
1822   if( is_copy() )               // Already degraded to a Copy ?
1823     return NULL;                // No change
1824 
1825   Node *r = in(0);              // RegionNode
1826   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1827 
1828   // Note: During parsing, phis are often transformed before their regions.
1829   // This means we have to use type_or_null to defend against untyped regions.
1830   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1831     return NULL;                // No change
1832 
1833   Node *top = phase->C->top();
1834   bool new_phi = (outcnt() == 0); // transforming new Phi
1835   // No change for igvn if new phi is not hooked
1836   if (new_phi && can_reshape)
1837     return NULL;
1838 
1839   // The are 2 situations when only one valid phi's input is left
1840   // (in addition to Region input).
1841   // One: region is not loop - replace phi with this input.
1842   // Two: region is loop - replace phi with top since this data path is dead
1843   //                       and we need to break the dead data loop.
1844   Node* progress = NULL;        // Record if any progress made
1845   for( uint j = 1; j < req(); ++j ){ // For all paths in
1846     // Check unreachable control paths
1847     Node* rc = r->in(j);
1848     Node* n = in(j);            // Get the input
1849     if (rc == NULL || phase->type(rc) == Type::TOP) {
1850       if (n != top) {           // Not already top?
1851         PhaseIterGVN *igvn = phase->is_IterGVN();
1852         if (can_reshape && igvn != NULL) {
1853           igvn->_worklist.push(r);
1854         }
1855         // Nuke it down
1856         if (can_reshape) {
1857           set_req_X(j, top, igvn);
1858         } else {
1859           set_req(j, top);
1860         }
1861         progress = this;        // Record progress
1862       }
1863     }
1864   }
1865 
1866   if (can_reshape && outcnt() == 0) {
1867     // set_req() above may kill outputs if Phi is referenced
1868     // only by itself on the dead (top) control path.
1869     return top;
1870   }
1871 
1872   bool uncasted = false;
1873   Node* uin = unique_input(phase, false);
1874   if (uin == NULL && can_reshape &&
1875       // If there is a chance that the region can be optimized out do
1876       // not add a cast node that we can't remove yet.
1877       !wait_for_region_igvn(phase)) {
1878     uncasted = true;
1879     uin = unique_input(phase, true);
1880   }
1881   if (uin == top) {             // Simplest case: no alive inputs.
1882     if (can_reshape)            // IGVN transformation
1883       return top;
1884     else
1885       return NULL;              // Identity will return TOP
1886   } else if (uin != NULL) {
1887     // Only one not-NULL unique input path is left.
1888     // Determine if this input is backedge of a loop.
1889     // (Skip new phis which have no uses and dead regions).
1890     if (outcnt() > 0 && r->in(0) != NULL) {
1891       // First, take the short cut when we know it is a loop and
1892       // the EntryControl data path is dead.
1893       // Loop node may have only one input because entry path
1894       // is removed in PhaseIdealLoop::Dominators().
1895       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1896       bool is_loop = (r->is_Loop() && r->req() == 3);
1897       // Then, check if there is a data loop when phi references itself directly
1898       // or through other data nodes.
1899       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1900           (!is_loop && is_unsafe_data_reference(uin))) {
1901         // Break this data loop to avoid creation of a dead loop.
1902         if (can_reshape) {
1903           return top;
1904         } else {
1905           // We can't return top if we are in Parse phase - cut inputs only
1906           // let Identity to handle the case.
1907           replace_edge(uin, top);
1908           return NULL;
1909         }
1910       }
1911     }
1912 
1913     if (uncasted) {
1914       // Add cast nodes between the phi to be removed and its unique input.
1915       // Wait until after parsing for the type information to propagate from the casts.
1916       assert(can_reshape, "Invalid during parsing");
1917       const Type* phi_type = bottom_type();
1918       assert(phi_type->isa_int() || phi_type->isa_long() || phi_type->isa_ptr(), "bad phi type");
1919       // Add casts to carry the control dependency of the Phi that is going away
1920       Node* cast = NULL;
1921       if (phi_type->isa_int()) {
1922         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1923       } else if (phi_type->isa_long()) {
1924         cast = ConstraintCastNode::make_cast(Op_CastLL, r, uin, phi_type, true);
1925       } else {
1926         const Type* uin_type = phase->type(uin);
1927         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1928           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1929         } else {
1930           // Use a CastPP for a cast to not null and a CheckCastPP for
1931           // a cast to a new klass (and both if both null-ness and
1932           // klass change).
1933 
1934           // If the type of phi is not null but the type of uin may be
1935           // null, uin's type must be casted to not null
1936           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1937               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1938             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1939           }
1940 
1941           // If the type of phi and uin, both casted to not null,
1942           // differ the klass of uin must be (check)cast'ed to match
1943           // that of phi
1944           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1945             Node* n = uin;
1946             if (cast != NULL) {
1947               cast = phase->transform(cast);
1948               n = cast;
1949             }
1950             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
1951           }
1952           if (cast == NULL) {
1953             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1954           }
1955         }
1956       }
1957       assert(cast != NULL, "cast should be set");
1958       cast = phase->transform(cast);
1959       // set all inputs to the new cast(s) so the Phi is removed by Identity
1960       PhaseIterGVN* igvn = phase->is_IterGVN();
1961       for (uint i = 1; i < req(); i++) {
1962         set_req_X(i, cast, igvn);
1963       }
1964       uin = cast;
1965     }
1966 
1967     // One unique input.
1968     debug_only(Node* ident = Identity(phase));
1969     // The unique input must eventually be detected by the Identity call.
1970 #ifdef ASSERT
1971     if (ident != uin && !ident->is_top()) {
1972       // print this output before failing assert
1973       r->dump(3);
1974       this->dump(3);
1975       ident->dump();
1976       uin->dump();
1977     }
1978 #endif
1979     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1980     return NULL;
1981   }
1982 
1983   Node* opt = NULL;
1984   int true_path = is_diamond_phi();
1985   if( true_path != 0 ) {
1986     // Check for CMove'ing identity. If it would be unsafe,
1987     // handle it here. In the safe case, let Identity handle it.
1988     Node* unsafe_id = is_cmove_id(phase, true_path);
1989     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1990       opt = unsafe_id;
1991 
1992     // Check for simple convert-to-boolean pattern
1993     if( opt == NULL )
1994       opt = is_x2logic(phase, this, true_path);
1995 
1996     // Check for absolute value
1997     if( opt == NULL )
1998       opt = is_absolute(phase, this, true_path);
1999 
2000     // Check for conditional add
2001     if( opt == NULL && can_reshape )
2002       opt = is_cond_add(phase, this, true_path);
2003 
2004     // These 4 optimizations could subsume the phi:
2005     // have to check for a dead data loop creation.
2006     if( opt != NULL ) {
2007       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2008         // Found dead loop.
2009         if( can_reshape )
2010           return top;
2011         // We can't return top if we are in Parse phase - cut inputs only
2012         // to stop further optimizations for this phi. Identity will return TOP.
2013         assert(req() == 3, "only diamond merge phi here");
2014         set_req(1, top);
2015         set_req(2, top);
2016         return NULL;
2017       } else {
2018         return opt;
2019       }
2020     }
2021   }
2022 
2023   // Check for merging identical values and split flow paths
2024   if (can_reshape) {
2025     opt = split_flow_path(phase, this);
2026     // This optimization only modifies phi - don't need to check for dead loop.
2027     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
2028     if (opt != NULL)  return opt;
2029   }
2030 
2031   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2032     // Try to undo Phi of AddP:
2033     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2034     // becomes:
2035     // newbase := (Phi base base2)
2036     // newaddress := (Phi address address2)
2037     // newoffset := (Phi offset offset2)
2038     // (AddP newbase newaddress newoffset)
2039     //
2040     // This occurs as a result of unsuccessful split_thru_phi and
2041     // interferes with taking advantage of addressing modes. See the
2042     // clone_shift_expressions code in matcher.cpp
2043     Node* addp = in(1);
2044     Node* base = addp->in(AddPNode::Base);
2045     Node* address = addp->in(AddPNode::Address);
2046     Node* offset = addp->in(AddPNode::Offset);
2047     if (base != NULL && address != NULL && offset != NULL &&
2048         !base->is_top() && !address->is_top() && !offset->is_top()) {
2049       const Type* base_type = base->bottom_type();
2050       const Type* address_type = address->bottom_type();
2051       // make sure that all the inputs are similar to the first one,
2052       // i.e. AddP with base == address and same offset as first AddP
2053       bool doit = true;
2054       for (uint i = 2; i < req(); i++) {
2055         if (in(i) == NULL ||
2056             in(i)->Opcode() != Op_AddP ||
2057             in(i)->in(AddPNode::Base) == NULL ||
2058             in(i)->in(AddPNode::Address) == NULL ||
2059             in(i)->in(AddPNode::Offset) == NULL ||
2060             in(i)->in(AddPNode::Base)->is_top() ||
2061             in(i)->in(AddPNode::Address)->is_top() ||
2062             in(i)->in(AddPNode::Offset)->is_top()) {
2063           doit = false;
2064           break;
2065         }
2066         if (in(i)->in(AddPNode::Offset) != base) {
2067           base = NULL;
2068         }
2069         if (in(i)->in(AddPNode::Offset) != offset) {
2070           offset = NULL;
2071         }
2072         if (in(i)->in(AddPNode::Address) != address) {
2073           address = NULL;
2074         }
2075         // Accumulate type for resulting Phi
2076         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2077         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2078       }
2079       if (doit && base == NULL) {
2080         // Check for neighboring AddP nodes in a tree.
2081         // If they have a base, use that it.
2082         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2083           Node* u = this->fast_out(k);
2084           if (u->is_AddP()) {
2085             Node* base2 = u->in(AddPNode::Base);
2086             if (base2 != NULL && !base2->is_top()) {
2087               if (base == NULL)
2088                 base = base2;
2089               else if (base != base2)
2090                 { doit = false; break; }
2091             }
2092           }
2093         }
2094       }
2095       if (doit) {
2096         if (base == NULL) {
2097           base = new PhiNode(in(0), base_type, NULL);
2098           for (uint i = 1; i < req(); i++) {
2099             base->init_req(i, in(i)->in(AddPNode::Base));
2100           }
2101           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2102         }
2103         if (address == NULL) {
2104           address = new PhiNode(in(0), address_type, NULL);
2105           for (uint i = 1; i < req(); i++) {
2106             address->init_req(i, in(i)->in(AddPNode::Address));
2107           }
2108           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2109         }
2110         if (offset == NULL) {
2111           offset = new PhiNode(in(0), TypeX_X, NULL);
2112           for (uint i = 1; i < req(); i++) {
2113             offset->init_req(i, in(i)->in(AddPNode::Offset));
2114           }
2115           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2116         }
2117         return new AddPNode(base, address, offset);
2118       }
2119     }
2120   }
2121 
2122   // Split phis through memory merges, so that the memory merges will go away.
2123   // Piggy-back this transformation on the search for a unique input....
2124   // It will be as if the merged memory is the unique value of the phi.
2125   // (Do not attempt this optimization unless parsing is complete.
2126   // It would make the parser's memory-merge logic sick.)
2127   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2128   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2129     // see if this phi should be sliced
2130     uint merge_width = 0;
2131     bool saw_self = false;
2132     for( uint i=1; i<req(); ++i ) {// For all paths in
2133       Node *ii = in(i);
2134       // TOP inputs should not be counted as safe inputs because if the
2135       // Phi references itself through all other inputs then splitting the
2136       // Phi through memory merges would create dead loop at later stage.
2137       if (ii == top) {
2138         return NULL; // Delay optimization until graph is cleaned.
2139       }
2140       if (ii->is_MergeMem()) {
2141         MergeMemNode* n = ii->as_MergeMem();
2142         merge_width = MAX2(merge_width, n->req());
2143         saw_self = saw_self || phase->eqv(n->base_memory(), this);
2144       }
2145     }
2146 
2147     // This restriction is temporarily necessary to ensure termination:
2148     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2149 
2150     if (merge_width > Compile::AliasIdxRaw) {
2151       // found at least one non-empty MergeMem
2152       const TypePtr* at = adr_type();
2153       if (at != TypePtr::BOTTOM) {
2154         // Patch the existing phi to select an input from the merge:
2155         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2156         //     Phi:AT1(...m1...)
2157         int alias_idx = phase->C->get_alias_index(at);
2158         for (uint i=1; i<req(); ++i) {
2159           Node *ii = in(i);
2160           if (ii->is_MergeMem()) {
2161             MergeMemNode* n = ii->as_MergeMem();
2162             // compress paths and change unreachable cycles to TOP
2163             // If not, we can update the input infinitely along a MergeMem cycle
2164             // Equivalent code is in MemNode::Ideal_common
2165             Node *m  = phase->transform(n);
2166             if (outcnt() == 0) {  // Above transform() may kill us!
2167               return top;
2168             }
2169             // If transformed to a MergeMem, get the desired slice
2170             // Otherwise the returned node represents memory for every slice
2171             Node *new_mem = (m->is_MergeMem()) ?
2172                              m->as_MergeMem()->memory_at(alias_idx) : m;
2173             // Update input if it is progress over what we have now
2174             if (new_mem != ii) {
2175               set_req(i, new_mem);
2176               progress = this;
2177             }
2178           }
2179         }
2180       } else {
2181         // We know that at least one MergeMem->base_memory() == this
2182         // (saw_self == true). If all other inputs also references this phi
2183         // (directly or through data nodes) - it is dead loop.
2184         bool saw_safe_input = false;
2185         for (uint j = 1; j < req(); ++j) {
2186           Node *n = in(j);
2187           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
2188             continue;              // skip known cases
2189           if (!is_unsafe_data_reference(n)) {
2190             saw_safe_input = true; // found safe input
2191             break;
2192           }
2193         }
2194         if (!saw_safe_input)
2195           return top; // all inputs reference back to this phi - dead loop
2196 
2197         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2198         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2199         PhaseIterGVN *igvn = phase->is_IterGVN();
2200         Node* hook = new Node(1);
2201         PhiNode* new_base = (PhiNode*) clone();
2202         // Must eagerly register phis, since they participate in loops.
2203         if (igvn) {
2204           igvn->register_new_node_with_optimizer(new_base);
2205           hook->add_req(new_base);
2206         }
2207         MergeMemNode* result = MergeMemNode::make(new_base);
2208         for (uint i = 1; i < req(); ++i) {
2209           Node *ii = in(i);
2210           if (ii->is_MergeMem()) {
2211             MergeMemNode* n = ii->as_MergeMem();
2212             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2213               // If we have not seen this slice yet, make a phi for it.
2214               bool made_new_phi = false;
2215               if (mms.is_empty()) {
2216                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2217                 made_new_phi = true;
2218                 if (igvn) {
2219                   igvn->register_new_node_with_optimizer(new_phi);
2220                   hook->add_req(new_phi);
2221                 }
2222                 mms.set_memory(new_phi);
2223               }
2224               Node* phi = mms.memory();
2225               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2226               phi->set_req(i, mms.memory2());
2227             }
2228           }
2229         }
2230         // Distribute all self-loops.
2231         { // (Extra braces to hide mms.)
2232           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2233             Node* phi = mms.memory();
2234             for (uint i = 1; i < req(); ++i) {
2235               if (phi->in(i) == this)  phi->set_req(i, phi);
2236             }
2237           }
2238         }
2239         // now transform the new nodes, and return the mergemem
2240         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2241           Node* phi = mms.memory();
2242           mms.set_memory(phase->transform(phi));
2243         }
2244         if (igvn) { // Unhook.
2245           igvn->hash_delete(hook);
2246           for (uint i = 1; i < hook->req(); i++) {
2247             hook->set_req(i, NULL);
2248           }
2249         }
2250         // Replace self with the result.
2251         return result;
2252       }
2253     }
2254     //
2255     // Other optimizations on the memory chain
2256     //
2257     const TypePtr* at = adr_type();
2258     for( uint i=1; i<req(); ++i ) {// For all paths in
2259       Node *ii = in(i);
2260       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2261       if (ii != new_in ) {
2262         set_req(i, new_in);
2263         progress = this;
2264       }
2265     }
2266   }
2267 
2268 #ifdef _LP64
2269   // Push DecodeN/DecodeNKlass down through phi.
2270   // The rest of phi graph will transform by split EncodeP node though phis up.
2271   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2272     bool may_push = true;
2273     bool has_decodeN = false;
2274     bool is_decodeN = false;
2275     for (uint i=1; i<req(); ++i) {// For all paths in
2276       Node *ii = in(i);
2277       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2278         // Do optimization if a non dead path exist.
2279         if (ii->in(1)->bottom_type() != Type::TOP) {
2280           has_decodeN = true;
2281           is_decodeN = ii->is_DecodeN();
2282         }
2283       } else if (!ii->is_Phi()) {
2284         may_push = false;
2285       }
2286     }
2287 
2288     if (has_decodeN && may_push) {
2289       PhaseIterGVN *igvn = phase->is_IterGVN();
2290       // Make narrow type for new phi.
2291       const Type* narrow_t;
2292       if (is_decodeN) {
2293         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2294       } else {
2295         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2296       }
2297       PhiNode* new_phi = new PhiNode(r, narrow_t);
2298       uint orig_cnt = req();
2299       for (uint i=1; i<req(); ++i) {// For all paths in
2300         Node *ii = in(i);
2301         Node* new_ii = NULL;
2302         if (ii->is_DecodeNarrowPtr()) {
2303           assert(ii->bottom_type() == bottom_type(), "sanity");
2304           new_ii = ii->in(1);
2305         } else {
2306           assert(ii->is_Phi(), "sanity");
2307           if (ii->as_Phi() == this) {
2308             new_ii = new_phi;
2309           } else {
2310             if (is_decodeN) {
2311               new_ii = new EncodePNode(ii, narrow_t);
2312             } else {
2313               new_ii = new EncodePKlassNode(ii, narrow_t);
2314             }
2315             igvn->register_new_node_with_optimizer(new_ii);
2316           }
2317         }
2318         new_phi->set_req(i, new_ii);
2319       }
2320       igvn->register_new_node_with_optimizer(new_phi, this);
2321       if (is_decodeN) {
2322         progress = new DecodeNNode(new_phi, bottom_type());
2323       } else {
2324         progress = new DecodeNKlassNode(new_phi, bottom_type());
2325       }
2326     }
2327   }
2328 #endif
2329 
2330   return progress;              // Return any progress
2331 }
2332 
2333 //------------------------------is_tripcount-----------------------------------
2334 bool PhiNode::is_tripcount() const {
2335   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2336           in(0)->as_CountedLoop()->phi() == this);
2337 }
2338 
2339 //------------------------------out_RegMask------------------------------------
2340 const RegMask &PhiNode::in_RegMask(uint i) const {
2341   return i ? out_RegMask() : RegMask::Empty;
2342 }
2343 
2344 const RegMask &PhiNode::out_RegMask() const {
2345   uint ideal_reg = _type->ideal_reg();
2346   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2347   if( ideal_reg == 0 ) return RegMask::Empty;
2348   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2349   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2350 }
2351 
2352 #ifndef PRODUCT
2353 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2354   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2355   // and all outputs till level 1. In compact mode, inputs till level 1 are
2356   // collected.
2357   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2358   this->collect_nodes(out_rel, -1, false, false);
2359 }
2360 
2361 void PhiNode::dump_spec(outputStream *st) const {
2362   TypeNode::dump_spec(st);
2363   if (is_tripcount()) {
2364     st->print(" #tripcount");
2365   }
2366 }
2367 #endif
2368 
2369 
2370 //=============================================================================
2371 const Type* GotoNode::Value(PhaseGVN* phase) const {
2372   // If the input is reachable, then we are executed.
2373   // If the input is not reachable, then we are not executed.
2374   return phase->type(in(0));
2375 }
2376 
2377 Node* GotoNode::Identity(PhaseGVN* phase) {
2378   return in(0);                // Simple copy of incoming control
2379 }
2380 
2381 const RegMask &GotoNode::out_RegMask() const {
2382   return RegMask::Empty;
2383 }
2384 
2385 #ifndef PRODUCT
2386 //-----------------------------related-----------------------------------------
2387 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2388 // outputs at level 1. This is regardless of compact mode.
2389 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2390   this->collect_nodes(in_rel, 1, false, false);
2391   this->collect_nodes(out_rel, -1, false, false);
2392 }
2393 #endif
2394 
2395 
2396 //=============================================================================
2397 const RegMask &JumpNode::out_RegMask() const {
2398   return RegMask::Empty;
2399 }
2400 
2401 #ifndef PRODUCT
2402 //-----------------------------related-----------------------------------------
2403 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2404 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2405 // This is regardless of compact mode.
2406 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2407   this->collect_nodes(in_rel, 1, false, false);
2408   this->collect_nodes(out_rel, -2, false, false);
2409 }
2410 #endif
2411 
2412 //=============================================================================
2413 const RegMask &JProjNode::out_RegMask() const {
2414   return RegMask::Empty;
2415 }
2416 
2417 //=============================================================================
2418 const RegMask &CProjNode::out_RegMask() const {
2419   return RegMask::Empty;
2420 }
2421 
2422 
2423 
2424 //=============================================================================
2425 
2426 uint PCTableNode::hash() const { return Node::hash() + _size; }
2427 bool PCTableNode::cmp( const Node &n ) const
2428 { return _size == ((PCTableNode&)n)._size; }
2429 
2430 const Type *PCTableNode::bottom_type() const {
2431   const Type** f = TypeTuple::fields(_size);
2432   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2433   return TypeTuple::make(_size, f);
2434 }
2435 
2436 //------------------------------Value------------------------------------------
2437 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2438 // Control, otherwise the table targets are not reachable
2439 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2440   if( phase->type(in(0)) == Type::CONTROL )
2441     return bottom_type();
2442   return Type::TOP;             // All paths dead?  Then so are we
2443 }
2444 
2445 //------------------------------Ideal------------------------------------------
2446 // Return a node which is more "ideal" than the current node.  Strip out
2447 // control copies
2448 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2449   return remove_dead_region(phase, can_reshape) ? this : NULL;
2450 }
2451 
2452 //=============================================================================
2453 uint JumpProjNode::hash() const {
2454   return Node::hash() + _dest_bci;
2455 }
2456 
2457 bool JumpProjNode::cmp( const Node &n ) const {
2458   return ProjNode::cmp(n) &&
2459     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2460 }
2461 
2462 #ifndef PRODUCT
2463 void JumpProjNode::dump_spec(outputStream *st) const {
2464   ProjNode::dump_spec(st);
2465   st->print("@bci %d ",_dest_bci);
2466 }
2467 
2468 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2469   ProjNode::dump_compact_spec(st);
2470   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2471 }
2472 
2473 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2474   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2475   this->collect_nodes(in_rel, 1, false, false);
2476   this->collect_nodes(out_rel, -1, false, false);
2477 }
2478 #endif
2479 
2480 //=============================================================================
2481 //------------------------------Value------------------------------------------
2482 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2483 // have the default "fall_through_index" path.
2484 const Type* CatchNode::Value(PhaseGVN* phase) const {
2485   // Unreachable?  Then so are all paths from here.
2486   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2487   // First assume all paths are reachable
2488   const Type** f = TypeTuple::fields(_size);
2489   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2490   // Identify cases that will always throw an exception
2491   // () rethrow call
2492   // () virtual or interface call with NULL receiver
2493   // () call is a check cast with incompatible arguments
2494   if( in(1)->is_Proj() ) {
2495     Node *i10 = in(1)->in(0);
2496     if( i10->is_Call() ) {
2497       CallNode *call = i10->as_Call();
2498       // Rethrows always throw exceptions, never return
2499       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2500         f[CatchProjNode::fall_through_index] = Type::TOP;
2501       } else if( call->req() > TypeFunc::Parms ) {
2502         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2503         // Check for null receiver to virtual or interface calls
2504         if( call->is_CallDynamicJava() &&
2505             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2506           f[CatchProjNode::fall_through_index] = Type::TOP;
2507         }
2508       } // End of if not a runtime stub
2509     } // End of if have call above me
2510   } // End of slot 1 is not a projection
2511   return TypeTuple::make(_size, f);
2512 }
2513 
2514 //=============================================================================
2515 uint CatchProjNode::hash() const {
2516   return Node::hash() + _handler_bci;
2517 }
2518 
2519 
2520 bool CatchProjNode::cmp( const Node &n ) const {
2521   return ProjNode::cmp(n) &&
2522     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2523 }
2524 
2525 
2526 //------------------------------Identity---------------------------------------
2527 // If only 1 target is possible, choose it if it is the main control
2528 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2529   // If my value is control and no other value is, then treat as ID
2530   const TypeTuple *t = phase->type(in(0))->is_tuple();
2531   if (t->field_at(_con) != Type::CONTROL)  return this;
2532   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2533   // also remove any exception table entry.  Thus we must know the call
2534   // feeding the Catch will not really throw an exception.  This is ok for
2535   // the main fall-thru control (happens when we know a call can never throw
2536   // an exception) or for "rethrow", because a further optimization will
2537   // yank the rethrow (happens when we inline a function that can throw an
2538   // exception and the caller has no handler).  Not legal, e.g., for passing
2539   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2540   // These cases MUST throw an exception via the runtime system, so the VM
2541   // will be looking for a table entry.
2542   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2543   CallNode *call;
2544   if (_con != TypeFunc::Control && // Bail out if not the main control.
2545       !(proj->is_Proj() &&      // AND NOT a rethrow
2546         proj->in(0)->is_Call() &&
2547         (call = proj->in(0)->as_Call()) &&
2548         call->entry_point() == OptoRuntime::rethrow_stub()))
2549     return this;
2550 
2551   // Search for any other path being control
2552   for (uint i = 0; i < t->cnt(); i++) {
2553     if (i != _con && t->field_at(i) == Type::CONTROL)
2554       return this;
2555   }
2556   // Only my path is possible; I am identity on control to the jump
2557   return in(0)->in(0);
2558 }
2559 
2560 
2561 #ifndef PRODUCT
2562 void CatchProjNode::dump_spec(outputStream *st) const {
2563   ProjNode::dump_spec(st);
2564   st->print("@bci %d ",_handler_bci);
2565 }
2566 #endif
2567 
2568 //=============================================================================
2569 //------------------------------Identity---------------------------------------
2570 // Check for CreateEx being Identity.
2571 Node* CreateExNode::Identity(PhaseGVN* phase) {
2572   if( phase->type(in(1)) == Type::TOP ) return in(1);
2573   if( phase->type(in(0)) == Type::TOP ) return in(0);
2574   // We only come from CatchProj, unless the CatchProj goes away.
2575   // If the CatchProj is optimized away, then we just carry the
2576   // exception oop through.
2577   CallNode *call = in(1)->in(0)->as_Call();
2578 
2579   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2580     ? this
2581     : call->in(TypeFunc::Parms);
2582 }
2583 
2584 //=============================================================================
2585 //------------------------------Value------------------------------------------
2586 // Check for being unreachable.
2587 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2588   if (!in(0) || in(0)->is_top()) return Type::TOP;
2589   return bottom_type();
2590 }
2591 
2592 //------------------------------Ideal------------------------------------------
2593 // Check for no longer being part of a loop
2594 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2595   if (can_reshape && !in(0)->is_Loop()) {
2596     // Dead code elimination can sometimes delete this projection so
2597     // if it's not there, there's nothing to do.
2598     Node* fallthru = proj_out_or_null(0);
2599     if (fallthru != NULL) {
2600       phase->is_IterGVN()->replace_node(fallthru, in(0));
2601     }
2602     return phase->C->top();
2603   }
2604   return NULL;
2605 }
2606 
2607 #ifndef PRODUCT
2608 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2609   st->print("%s", Name());
2610 }
2611 #endif