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 *in1 = cmp->in(1);
1453   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1454   in1 = bs->step_over_gc_barrier(in1);
1455   Node *n = new Conv2BNode(in1);
1456   if( flipped )
1457     n = new XorINode( phase->transform(n), phase->intcon(1) );
1458 
1459   return n;
1460 }
1461 
1462 //------------------------------is_cond_add------------------------------------
1463 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1464 // To be profitable the control flow has to disappear; there can be no other
1465 // values merging here.  We replace the test-and-branch with:
1466 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1467 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1468 // Then convert Y to 0-or-Y and finally add.
1469 // This is a key transform for SpecJava _201_compress.
1470 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1471   assert(true_path !=0, "only diamond shape graph expected");
1472 
1473   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1474   // phi->region->if_proj->ifnode->bool->cmp
1475   RegionNode *region = (RegionNode*)phi->in(0);
1476   Node *iff = region->in(1)->in(0);
1477   BoolNode* b = iff->in(1)->as_Bool();
1478   const CmpNode *cmp = (CmpNode*)b->in(1);
1479 
1480   // Make sure only merging this one phi here
1481   if (region->has_unique_phi() != phi)  return NULL;
1482 
1483   // Make sure each arm of the diamond has exactly one output, which we assume
1484   // is the region.  Otherwise, the control flow won't disappear.
1485   if (region->in(1)->outcnt() != 1) return NULL;
1486   if (region->in(2)->outcnt() != 1) return NULL;
1487 
1488   // Check for "(P < Q)" of type signed int
1489   if (b->_test._test != BoolTest::lt)  return NULL;
1490   if (cmp->Opcode() != Op_CmpI)        return NULL;
1491 
1492   Node *p = cmp->in(1);
1493   Node *q = cmp->in(2);
1494   Node *n1 = phi->in(  true_path);
1495   Node *n2 = phi->in(3-true_path);
1496 
1497   int op = n1->Opcode();
1498   if( op != Op_AddI           // Need zero as additive identity
1499       /*&&op != Op_SubI &&
1500       op != Op_AddP &&
1501       op != Op_XorI &&
1502       op != Op_OrI*/ )
1503     return NULL;
1504 
1505   Node *x = n2;
1506   Node *y = NULL;
1507   if( x == n1->in(1) ) {
1508     y = n1->in(2);
1509   } else if( x == n1->in(2) ) {
1510     y = n1->in(1);
1511   } else return NULL;
1512 
1513   // Not so profitable if compare and add are constants
1514   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1515     return NULL;
1516 
1517   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1518   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1519   return new AddINode(j_and,x);
1520 }
1521 
1522 //------------------------------is_absolute------------------------------------
1523 // Check for absolute value.
1524 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1525   assert(true_path !=0, "only diamond shape graph expected");
1526 
1527   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1528   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1529 
1530   // ABS ends with the merge of 2 control flow paths.
1531   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1532   int false_path = 3 - true_path;
1533 
1534   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1535   // phi->region->if_proj->ifnode->bool->cmp
1536   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1537 
1538   // Check bool sense
1539   switch( bol->_test._test ) {
1540   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1541   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1542   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1543   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1544   default:           return NULL;                              break;
1545   }
1546 
1547   // Test is next
1548   Node *cmp = bol->in(1);
1549   const Type *tzero = NULL;
1550   switch( cmp->Opcode() ) {
1551   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1552   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1553   default: return NULL;
1554   }
1555 
1556   // Find zero input of compare; the other input is being abs'd
1557   Node *x = NULL;
1558   bool flip = false;
1559   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1560     x = cmp->in(3 - cmp_zero_idx);
1561   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1562     // The test is inverted, we should invert the result...
1563     x = cmp->in(cmp_zero_idx);
1564     flip = true;
1565   } else {
1566     return NULL;
1567   }
1568 
1569   // Next get the 2 pieces being selected, one is the original value
1570   // and the other is the negated value.
1571   if( phi_root->in(phi_x_idx) != x ) return NULL;
1572 
1573   // Check other phi input for subtract node
1574   Node *sub = phi_root->in(3 - phi_x_idx);
1575 
1576   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1577   if( tzero == TypeF::ZERO ) {
1578     if( sub->Opcode() != Op_SubF ||
1579         sub->in(2) != x ||
1580         phase->type(sub->in(1)) != tzero ) return NULL;
1581     x = new AbsFNode(x);
1582     if (flip) {
1583       x = new SubFNode(sub->in(1), phase->transform(x));
1584     }
1585   } else {
1586     if( sub->Opcode() != Op_SubD ||
1587         sub->in(2) != x ||
1588         phase->type(sub->in(1)) != tzero ) return NULL;
1589     x = new AbsDNode(x);
1590     if (flip) {
1591       x = new SubDNode(sub->in(1), phase->transform(x));
1592     }
1593   }
1594 
1595   return x;
1596 }
1597 
1598 //------------------------------split_once-------------------------------------
1599 // Helper for split_flow_path
1600 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1601   igvn->hash_delete(n);         // Remove from hash before hacking edges
1602 
1603   uint j = 1;
1604   for (uint i = phi->req()-1; i > 0; i--) {
1605     if (phi->in(i) == val) {   // Found a path with val?
1606       // Add to NEW Region/Phi, no DU info
1607       newn->set_req( j++, n->in(i) );
1608       // Remove from OLD Region/Phi
1609       n->del_req(i);
1610     }
1611   }
1612 
1613   // Register the new node but do not transform it.  Cannot transform until the
1614   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1615   igvn->register_new_node_with_optimizer( newn );
1616 
1617   // Now I can point to the new node.
1618   n->add_req(newn);
1619   igvn->_worklist.push(n);
1620 }
1621 
1622 //------------------------------split_flow_path--------------------------------
1623 // Check for merging identical values and split flow paths
1624 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1625   BasicType bt = phi->type()->basic_type();
1626   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1627     return NULL;                // Bail out on funny non-value stuff
1628   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1629     return NULL;                // third unequal input to be worth doing
1630 
1631   // Scan for a constant
1632   uint i;
1633   for( i = 1; i < phi->req()-1; i++ ) {
1634     Node *n = phi->in(i);
1635     if( !n ) return NULL;
1636     if( phase->type(n) == Type::TOP ) return NULL;
1637     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1638       break;
1639   }
1640   if( i >= phi->req() )         // Only split for constants
1641     return NULL;
1642 
1643   Node *val = phi->in(i);       // Constant to split for
1644   uint hit = 0;                 // Number of times it occurs
1645   Node *r = phi->region();
1646 
1647   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1648     Node *n = phi->in(i);
1649     if( !n ) return NULL;
1650     if( phase->type(n) == Type::TOP ) return NULL;
1651     if( phi->in(i) == val ) {
1652       hit++;
1653       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1654         return NULL;            // don't split loop entry path
1655       }
1656     }
1657   }
1658 
1659   if( hit <= 1 ||               // Make sure we find 2 or more
1660       hit == phi->req()-1 )     // and not ALL the same value
1661     return NULL;
1662 
1663   // Now start splitting out the flow paths that merge the same value.
1664   // Split first the RegionNode.
1665   PhaseIterGVN *igvn = phase->is_IterGVN();
1666   RegionNode *newr = new RegionNode(hit+1);
1667   split_once(igvn, phi, val, r, newr);
1668 
1669   // Now split all other Phis than this one
1670   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1671     Node* phi2 = r->fast_out(k);
1672     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1673       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1674       split_once(igvn, phi, val, phi2, newphi);
1675     }
1676   }
1677 
1678   // Clean up this guy
1679   igvn->hash_delete(phi);
1680   for( i = phi->req()-1; i > 0; i-- ) {
1681     if( phi->in(i) == val ) {
1682       phi->del_req(i);
1683     }
1684   }
1685   phi->add_req(val);
1686 
1687   return phi;
1688 }
1689 
1690 //=============================================================================
1691 //------------------------------simple_data_loop_check-------------------------
1692 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1693 //  Returns:
1694 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1695 // Safe       - safe case when the phi and it's inputs reference only safe data
1696 //              nodes;
1697 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1698 //              is no reference back to the phi - need a graph walk
1699 //              to determine if it is in a loop;
1700 // UnsafeLoop - unsafe case when the phi references itself directly or through
1701 //              unsafe data node.
1702 //  Note: a safe data node is a node which could/never reference itself during
1703 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1704 //  I mark Phi nodes as safe node not only because they can reference itself
1705 //  but also to prevent mistaking the fallthrough case inside an outer loop
1706 //  as dead loop when the phi references itselfs through an other phi.
1707 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1708   // It is unsafe loop if the phi node references itself directly.
1709   if (in == (Node*)this)
1710     return UnsafeLoop; // Unsafe loop
1711   // Unsafe loop if the phi node references itself through an unsafe data node.
1712   // Exclude cases with null inputs or data nodes which could reference
1713   // itself (safe for dead loops).
1714   if (in != NULL && !in->is_dead_loop_safe()) {
1715     // Check inputs of phi's inputs also.
1716     // It is much less expensive then full graph walk.
1717     uint cnt = in->req();
1718     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1719     for (; i < cnt; ++i) {
1720       Node* m = in->in(i);
1721       if (m == (Node*)this)
1722         return UnsafeLoop; // Unsafe loop
1723       if (m != NULL && !m->is_dead_loop_safe()) {
1724         // Check the most common case (about 30% of all cases):
1725         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1726         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1727         if (m1 == (Node*)this)
1728           return UnsafeLoop; // Unsafe loop
1729         if (m1 != NULL && m1 == m->in(2) &&
1730             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1731           continue; // Safe case
1732         }
1733         // The phi references an unsafe node - need full analysis.
1734         return Unsafe;
1735       }
1736     }
1737   }
1738   return Safe; // Safe case - we can optimize the phi node.
1739 }
1740 
1741 //------------------------------is_unsafe_data_reference-----------------------
1742 // If phi can be reached through the data input - it is data loop.
1743 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1744   assert(req() > 1, "");
1745   // First, check simple cases when phi references itself directly or
1746   // through an other node.
1747   LoopSafety safety = simple_data_loop_check(in);
1748   if (safety == UnsafeLoop)
1749     return true;  // phi references itself - unsafe loop
1750   else if (safety == Safe)
1751     return false; // Safe case - phi could be replaced with the unique input.
1752 
1753   // Unsafe case when we should go through data graph to determine
1754   // if the phi references itself.
1755 
1756   ResourceMark rm;
1757 
1758   Arena *a = Thread::current()->resource_area();
1759   Node_List nstack(a);
1760   VectorSet visited(a);
1761 
1762   nstack.push(in); // Start with unique input.
1763   visited.set(in->_idx);
1764   while (nstack.size() != 0) {
1765     Node* n = nstack.pop();
1766     uint cnt = n->req();
1767     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1768     for (; i < cnt; i++) {
1769       Node* m = n->in(i);
1770       if (m == (Node*)this) {
1771         return true;    // Data loop
1772       }
1773       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1774         if (!visited.test_set(m->_idx))
1775           nstack.push(m);
1776       }
1777     }
1778   }
1779   return false; // The phi is not reachable from its inputs
1780 }
1781 
1782 
1783 //------------------------------Ideal------------------------------------------
1784 // Return a node which is more "ideal" than the current node.  Must preserve
1785 // the CFG, but we can still strip out dead paths.
1786 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1787   // The next should never happen after 6297035 fix.
1788   if( is_copy() )               // Already degraded to a Copy ?
1789     return NULL;                // No change
1790 
1791   Node *r = in(0);              // RegionNode
1792   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1793 
1794   // Note: During parsing, phis are often transformed before their regions.
1795   // This means we have to use type_or_null to defend against untyped regions.
1796   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1797     return NULL;                // No change
1798 
1799   Node *top = phase->C->top();
1800   bool new_phi = (outcnt() == 0); // transforming new Phi
1801   // No change for igvn if new phi is not hooked
1802   if (new_phi && can_reshape)
1803     return NULL;
1804 
1805   // The are 2 situations when only one valid phi's input is left
1806   // (in addition to Region input).
1807   // One: region is not loop - replace phi with this input.
1808   // Two: region is loop - replace phi with top since this data path is dead
1809   //                       and we need to break the dead data loop.
1810   Node* progress = NULL;        // Record if any progress made
1811   for( uint j = 1; j < req(); ++j ){ // For all paths in
1812     // Check unreachable control paths
1813     Node* rc = r->in(j);
1814     Node* n = in(j);            // Get the input
1815     if (rc == NULL || phase->type(rc) == Type::TOP) {
1816       if (n != top) {           // Not already top?
1817         PhaseIterGVN *igvn = phase->is_IterGVN();
1818         if (can_reshape && igvn != NULL) {
1819           igvn->_worklist.push(r);
1820         }
1821         // Nuke it down
1822         if (can_reshape) {
1823           set_req_X(j, top, igvn);
1824         } else {
1825           set_req(j, top);
1826         }
1827         progress = this;        // Record progress
1828       }
1829     }
1830   }
1831 
1832   if (can_reshape && outcnt() == 0) {
1833     // set_req() above may kill outputs if Phi is referenced
1834     // only by itself on the dead (top) control path.
1835     return top;
1836   }
1837 
1838   bool uncasted = false;
1839   Node* uin = unique_input(phase, false);
1840   if (uin == NULL && can_reshape) {
1841     uncasted = true;
1842     uin = unique_input(phase, true);
1843   }
1844   if (uin == top) {             // Simplest case: no alive inputs.
1845     if (can_reshape)            // IGVN transformation
1846       return top;
1847     else
1848       return NULL;              // Identity will return TOP
1849   } else if (uin != NULL) {
1850     // Only one not-NULL unique input path is left.
1851     // Determine if this input is backedge of a loop.
1852     // (Skip new phis which have no uses and dead regions).
1853     if (outcnt() > 0 && r->in(0) != NULL) {
1854       // First, take the short cut when we know it is a loop and
1855       // the EntryControl data path is dead.
1856       // Loop node may have only one input because entry path
1857       // is removed in PhaseIdealLoop::Dominators().
1858       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1859       bool is_loop = (r->is_Loop() && r->req() == 3);
1860       // Then, check if there is a data loop when phi references itself directly
1861       // or through other data nodes.
1862       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1863           (!is_loop && is_unsafe_data_reference(uin))) {
1864         // Break this data loop to avoid creation of a dead loop.
1865         if (can_reshape) {
1866           return top;
1867         } else {
1868           // We can't return top if we are in Parse phase - cut inputs only
1869           // let Identity to handle the case.
1870           replace_edge(uin, top);
1871           return NULL;
1872         }
1873       }
1874     }
1875 
1876     if (uncasted) {
1877       // Add cast nodes between the phi to be removed and its unique input.
1878       // Wait until after parsing for the type information to propagate from the casts.
1879       assert(can_reshape, "Invalid during parsing");
1880       const Type* phi_type = bottom_type();
1881       assert(phi_type->isa_int() || phi_type->isa_ptr(), "bad phi type");
1882       // Add casts to carry the control dependency of the Phi that is
1883       // going away
1884       Node* cast = NULL;
1885       if (phi_type->isa_int()) {
1886         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1887       } else {
1888         const Type* uin_type = phase->type(uin);
1889         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1890           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1891         } else {
1892           // Use a CastPP for a cast to not null and a CheckCastPP for
1893           // a cast to a new klass (and both if both null-ness and
1894           // klass change).
1895 
1896           // If the type of phi is not null but the type of uin may be
1897           // null, uin's type must be casted to not null
1898           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1899               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1900             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1901           }
1902 
1903           // If the type of phi and uin, both casted to not null,
1904           // differ the klass of uin must be (check)cast'ed to match
1905           // that of phi
1906           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1907             Node* n = uin;
1908             if (cast != NULL) {
1909               cast = phase->transform(cast);
1910               n = cast;
1911             }
1912             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
1913           }
1914           if (cast == NULL) {
1915             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1916           }
1917         }
1918       }
1919       assert(cast != NULL, "cast should be set");
1920       cast = phase->transform(cast);
1921       // set all inputs to the new cast(s) so the Phi is removed by Identity
1922       PhaseIterGVN* igvn = phase->is_IterGVN();
1923       for (uint i = 1; i < req(); i++) {
1924         set_req_X(i, cast, igvn);
1925       }
1926       uin = cast;
1927     }
1928 
1929     // One unique input.
1930     debug_only(Node* ident = Identity(phase));
1931     // The unique input must eventually be detected by the Identity call.
1932 #ifdef ASSERT
1933     if (ident != uin && !ident->is_top()) {
1934       // print this output before failing assert
1935       r->dump(3);
1936       this->dump(3);
1937       ident->dump();
1938       uin->dump();
1939     }
1940 #endif
1941     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1942     return NULL;
1943   }
1944 
1945   Node* opt = NULL;
1946   int true_path = is_diamond_phi();
1947   if( true_path != 0 ) {
1948     // Check for CMove'ing identity. If it would be unsafe,
1949     // handle it here. In the safe case, let Identity handle it.
1950     Node* unsafe_id = is_cmove_id(phase, true_path);
1951     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1952       opt = unsafe_id;
1953 
1954     // Check for simple convert-to-boolean pattern
1955     if( opt == NULL )
1956       opt = is_x2logic(phase, this, true_path);
1957 
1958     // Check for absolute value
1959     if( opt == NULL )
1960       opt = is_absolute(phase, this, true_path);
1961 
1962     // Check for conditional add
1963     if( opt == NULL && can_reshape )
1964       opt = is_cond_add(phase, this, true_path);
1965 
1966     // These 4 optimizations could subsume the phi:
1967     // have to check for a dead data loop creation.
1968     if( opt != NULL ) {
1969       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
1970         // Found dead loop.
1971         if( can_reshape )
1972           return top;
1973         // We can't return top if we are in Parse phase - cut inputs only
1974         // to stop further optimizations for this phi. Identity will return TOP.
1975         assert(req() == 3, "only diamond merge phi here");
1976         set_req(1, top);
1977         set_req(2, top);
1978         return NULL;
1979       } else {
1980         return opt;
1981       }
1982     }
1983   }
1984 
1985   // Check for merging identical values and split flow paths
1986   if (can_reshape) {
1987     opt = split_flow_path(phase, this);
1988     // This optimization only modifies phi - don't need to check for dead loop.
1989     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
1990     if (opt != NULL)  return opt;
1991   }
1992 
1993   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
1994     // Try to undo Phi of AddP:
1995     // (Phi (AddP base base y) (AddP base2 base2 y))
1996     // becomes:
1997     // newbase := (Phi base base2)
1998     // (AddP newbase newbase y)
1999     //
2000     // This occurs as a result of unsuccessful split_thru_phi and
2001     // interferes with taking advantage of addressing modes. See the
2002     // clone_shift_expressions code in matcher.cpp
2003     Node* addp = in(1);
2004     const Type* type = addp->in(AddPNode::Base)->bottom_type();
2005     Node* y = addp->in(AddPNode::Offset);
2006     if (y != NULL && addp->in(AddPNode::Base) == addp->in(AddPNode::Address)) {
2007       // make sure that all the inputs are similar to the first one,
2008       // i.e. AddP with base == address and same offset as first AddP
2009       bool doit = true;
2010       for (uint i = 2; i < req(); i++) {
2011         if (in(i) == NULL ||
2012             in(i)->Opcode() != Op_AddP ||
2013             in(i)->in(AddPNode::Base) != in(i)->in(AddPNode::Address) ||
2014             in(i)->in(AddPNode::Offset) != y) {
2015           doit = false;
2016           break;
2017         }
2018         // Accumulate type for resulting Phi
2019         type = type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2020       }
2021       Node* base = NULL;
2022       if (doit) {
2023         // Check for neighboring AddP nodes in a tree.
2024         // If they have a base, use that it.
2025         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2026           Node* u = this->fast_out(k);
2027           if (u->is_AddP()) {
2028             Node* base2 = u->in(AddPNode::Base);
2029             if (base2 != NULL && !base2->is_top()) {
2030               if (base == NULL)
2031                 base = base2;
2032               else if (base != base2)
2033                 { doit = false; break; }
2034             }
2035           }
2036         }
2037       }
2038       if (doit) {
2039         if (base == NULL) {
2040           base = new PhiNode(in(0), type, NULL);
2041           for (uint i = 1; i < req(); i++) {
2042             base->init_req(i, in(i)->in(AddPNode::Base));
2043           }
2044           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2045         }
2046         return new AddPNode(base, base, y);
2047       }
2048     }
2049   }
2050 
2051   // Split phis through memory merges, so that the memory merges will go away.
2052   // Piggy-back this transformation on the search for a unique input....
2053   // It will be as if the merged memory is the unique value of the phi.
2054   // (Do not attempt this optimization unless parsing is complete.
2055   // It would make the parser's memory-merge logic sick.)
2056   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2057   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2058     // see if this phi should be sliced
2059     uint merge_width = 0;
2060     bool saw_self = false;
2061     for( uint i=1; i<req(); ++i ) {// For all paths in
2062       Node *ii = in(i);
2063       // TOP inputs should not be counted as safe inputs because if the
2064       // Phi references itself through all other inputs then splitting the
2065       // Phi through memory merges would create dead loop at later stage.
2066       if (ii == top) {
2067         return NULL; // Delay optimization until graph is cleaned.
2068       }
2069       if (ii->is_MergeMem()) {
2070         MergeMemNode* n = ii->as_MergeMem();
2071         merge_width = MAX2(merge_width, n->req());
2072         saw_self = saw_self || phase->eqv(n->base_memory(), this);
2073       }
2074     }
2075 
2076     // This restriction is temporarily necessary to ensure termination:
2077     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2078 
2079     if (merge_width > Compile::AliasIdxRaw) {
2080       // found at least one non-empty MergeMem
2081       const TypePtr* at = adr_type();
2082       if (at != TypePtr::BOTTOM) {
2083         // Patch the existing phi to select an input from the merge:
2084         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2085         //     Phi:AT1(...m1...)
2086         int alias_idx = phase->C->get_alias_index(at);
2087         for (uint i=1; i<req(); ++i) {
2088           Node *ii = in(i);
2089           if (ii->is_MergeMem()) {
2090             MergeMemNode* n = ii->as_MergeMem();
2091             // compress paths and change unreachable cycles to TOP
2092             // If not, we can update the input infinitely along a MergeMem cycle
2093             // Equivalent code is in MemNode::Ideal_common
2094             Node *m  = phase->transform(n);
2095             if (outcnt() == 0) {  // Above transform() may kill us!
2096               return top;
2097             }
2098             // If transformed to a MergeMem, get the desired slice
2099             // Otherwise the returned node represents memory for every slice
2100             Node *new_mem = (m->is_MergeMem()) ?
2101                              m->as_MergeMem()->memory_at(alias_idx) : m;
2102             // Update input if it is progress over what we have now
2103             if (new_mem != ii) {
2104               set_req(i, new_mem);
2105               progress = this;
2106             }
2107           }
2108         }
2109       } else {
2110         // We know that at least one MergeMem->base_memory() == this
2111         // (saw_self == true). If all other inputs also references this phi
2112         // (directly or through data nodes) - it is dead loop.
2113         bool saw_safe_input = false;
2114         for (uint j = 1; j < req(); ++j) {
2115           Node *n = in(j);
2116           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
2117             continue;              // skip known cases
2118           if (!is_unsafe_data_reference(n)) {
2119             saw_safe_input = true; // found safe input
2120             break;
2121           }
2122         }
2123         if (!saw_safe_input)
2124           return top; // all inputs reference back to this phi - dead loop
2125 
2126         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2127         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2128         PhaseIterGVN *igvn = phase->is_IterGVN();
2129         Node* hook = new Node(1);
2130         PhiNode* new_base = (PhiNode*) clone();
2131         // Must eagerly register phis, since they participate in loops.
2132         if (igvn) {
2133           igvn->register_new_node_with_optimizer(new_base);
2134           hook->add_req(new_base);
2135         }
2136         MergeMemNode* result = MergeMemNode::make(new_base);
2137         for (uint i = 1; i < req(); ++i) {
2138           Node *ii = in(i);
2139           if (ii->is_MergeMem()) {
2140             MergeMemNode* n = ii->as_MergeMem();
2141             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2142               // If we have not seen this slice yet, make a phi for it.
2143               bool made_new_phi = false;
2144               if (mms.is_empty()) {
2145                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2146                 made_new_phi = true;
2147                 if (igvn) {
2148                   igvn->register_new_node_with_optimizer(new_phi);
2149                   hook->add_req(new_phi);
2150                 }
2151                 mms.set_memory(new_phi);
2152               }
2153               Node* phi = mms.memory();
2154               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2155               phi->set_req(i, mms.memory2());
2156             }
2157           }
2158         }
2159         // Distribute all self-loops.
2160         { // (Extra braces to hide mms.)
2161           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2162             Node* phi = mms.memory();
2163             for (uint i = 1; i < req(); ++i) {
2164               if (phi->in(i) == this)  phi->set_req(i, phi);
2165             }
2166           }
2167         }
2168         // now transform the new nodes, and return the mergemem
2169         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2170           Node* phi = mms.memory();
2171           mms.set_memory(phase->transform(phi));
2172         }
2173         if (igvn) { // Unhook.
2174           igvn->hash_delete(hook);
2175           for (uint i = 1; i < hook->req(); i++) {
2176             hook->set_req(i, NULL);
2177           }
2178         }
2179         // Replace self with the result.
2180         return result;
2181       }
2182     }
2183     //
2184     // Other optimizations on the memory chain
2185     //
2186     const TypePtr* at = adr_type();
2187     for( uint i=1; i<req(); ++i ) {// For all paths in
2188       Node *ii = in(i);
2189       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2190       if (ii != new_in ) {
2191         set_req(i, new_in);
2192         progress = this;
2193       }
2194     }
2195   }
2196 
2197 #ifdef _LP64
2198   // Push DecodeN/DecodeNKlass down through phi.
2199   // The rest of phi graph will transform by split EncodeP node though phis up.
2200   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2201     bool may_push = true;
2202     bool has_decodeN = false;
2203     bool is_decodeN = false;
2204     for (uint i=1; i<req(); ++i) {// For all paths in
2205       Node *ii = in(i);
2206       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2207         // Do optimization if a non dead path exist.
2208         if (ii->in(1)->bottom_type() != Type::TOP) {
2209           has_decodeN = true;
2210           is_decodeN = ii->is_DecodeN();
2211         }
2212       } else if (!ii->is_Phi()) {
2213         may_push = false;
2214       }
2215     }
2216 
2217     if (has_decodeN && may_push) {
2218       PhaseIterGVN *igvn = phase->is_IterGVN();
2219       // Make narrow type for new phi.
2220       const Type* narrow_t;
2221       if (is_decodeN) {
2222         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2223       } else {
2224         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2225       }
2226       PhiNode* new_phi = new PhiNode(r, narrow_t);
2227       uint orig_cnt = req();
2228       for (uint i=1; i<req(); ++i) {// For all paths in
2229         Node *ii = in(i);
2230         Node* new_ii = NULL;
2231         if (ii->is_DecodeNarrowPtr()) {
2232           assert(ii->bottom_type() == bottom_type(), "sanity");
2233           new_ii = ii->in(1);
2234         } else {
2235           assert(ii->is_Phi(), "sanity");
2236           if (ii->as_Phi() == this) {
2237             new_ii = new_phi;
2238           } else {
2239             if (is_decodeN) {
2240               new_ii = new EncodePNode(ii, narrow_t);
2241             } else {
2242               new_ii = new EncodePKlassNode(ii, narrow_t);
2243             }
2244             igvn->register_new_node_with_optimizer(new_ii);
2245           }
2246         }
2247         new_phi->set_req(i, new_ii);
2248       }
2249       igvn->register_new_node_with_optimizer(new_phi, this);
2250       if (is_decodeN) {
2251         progress = new DecodeNNode(new_phi, bottom_type());
2252       } else {
2253         progress = new DecodeNKlassNode(new_phi, bottom_type());
2254       }
2255     }
2256   }
2257 #endif
2258 
2259   return progress;              // Return any progress
2260 }
2261 
2262 //------------------------------is_tripcount-----------------------------------
2263 bool PhiNode::is_tripcount() const {
2264   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2265           in(0)->as_CountedLoop()->phi() == this);
2266 }
2267 
2268 //------------------------------out_RegMask------------------------------------
2269 const RegMask &PhiNode::in_RegMask(uint i) const {
2270   return i ? out_RegMask() : RegMask::Empty;
2271 }
2272 
2273 const RegMask &PhiNode::out_RegMask() const {
2274   uint ideal_reg = _type->ideal_reg();
2275   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2276   if( ideal_reg == 0 ) return RegMask::Empty;
2277   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2278   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2279 }
2280 
2281 #ifndef PRODUCT
2282 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2283   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2284   // and all outputs till level 1. In compact mode, inputs till level 1 are
2285   // collected.
2286   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2287   this->collect_nodes(out_rel, -1, false, false);
2288 }
2289 
2290 void PhiNode::dump_spec(outputStream *st) const {
2291   TypeNode::dump_spec(st);
2292   if (is_tripcount()) {
2293     st->print(" #tripcount");
2294   }
2295 }
2296 #endif
2297 
2298 
2299 //=============================================================================
2300 const Type* GotoNode::Value(PhaseGVN* phase) const {
2301   // If the input is reachable, then we are executed.
2302   // If the input is not reachable, then we are not executed.
2303   return phase->type(in(0));
2304 }
2305 
2306 Node* GotoNode::Identity(PhaseGVN* phase) {
2307   return in(0);                // Simple copy of incoming control
2308 }
2309 
2310 const RegMask &GotoNode::out_RegMask() const {
2311   return RegMask::Empty;
2312 }
2313 
2314 #ifndef PRODUCT
2315 //-----------------------------related-----------------------------------------
2316 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2317 // outputs at level 1. This is regardless of compact mode.
2318 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2319   this->collect_nodes(in_rel, 1, false, false);
2320   this->collect_nodes(out_rel, -1, false, false);
2321 }
2322 #endif
2323 
2324 
2325 //=============================================================================
2326 const RegMask &JumpNode::out_RegMask() const {
2327   return RegMask::Empty;
2328 }
2329 
2330 #ifndef PRODUCT
2331 //-----------------------------related-----------------------------------------
2332 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2333 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2334 // This is regardless of compact mode.
2335 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2336   this->collect_nodes(in_rel, 1, false, false);
2337   this->collect_nodes(out_rel, -2, false, false);
2338 }
2339 #endif
2340 
2341 //=============================================================================
2342 const RegMask &JProjNode::out_RegMask() const {
2343   return RegMask::Empty;
2344 }
2345 
2346 //=============================================================================
2347 const RegMask &CProjNode::out_RegMask() const {
2348   return RegMask::Empty;
2349 }
2350 
2351 
2352 
2353 //=============================================================================
2354 
2355 uint PCTableNode::hash() const { return Node::hash() + _size; }
2356 bool PCTableNode::cmp( const Node &n ) const
2357 { return _size == ((PCTableNode&)n)._size; }
2358 
2359 const Type *PCTableNode::bottom_type() const {
2360   const Type** f = TypeTuple::fields(_size);
2361   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2362   return TypeTuple::make(_size, f);
2363 }
2364 
2365 //------------------------------Value------------------------------------------
2366 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2367 // Control, otherwise the table targets are not reachable
2368 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2369   if( phase->type(in(0)) == Type::CONTROL )
2370     return bottom_type();
2371   return Type::TOP;             // All paths dead?  Then so are we
2372 }
2373 
2374 //------------------------------Ideal------------------------------------------
2375 // Return a node which is more "ideal" than the current node.  Strip out
2376 // control copies
2377 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2378   return remove_dead_region(phase, can_reshape) ? this : NULL;
2379 }
2380 
2381 //=============================================================================
2382 uint JumpProjNode::hash() const {
2383   return Node::hash() + _dest_bci;
2384 }
2385 
2386 bool JumpProjNode::cmp( const Node &n ) const {
2387   return ProjNode::cmp(n) &&
2388     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2389 }
2390 
2391 #ifndef PRODUCT
2392 void JumpProjNode::dump_spec(outputStream *st) const {
2393   ProjNode::dump_spec(st);
2394   st->print("@bci %d ",_dest_bci);
2395 }
2396 
2397 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2398   ProjNode::dump_compact_spec(st);
2399   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2400 }
2401 
2402 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2403   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2404   this->collect_nodes(in_rel, 1, false, false);
2405   this->collect_nodes(out_rel, -1, false, false);
2406 }
2407 #endif
2408 
2409 //=============================================================================
2410 //------------------------------Value------------------------------------------
2411 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2412 // have the default "fall_through_index" path.
2413 const Type* CatchNode::Value(PhaseGVN* phase) const {
2414   // Unreachable?  Then so are all paths from here.
2415   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2416   // First assume all paths are reachable
2417   const Type** f = TypeTuple::fields(_size);
2418   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2419   // Identify cases that will always throw an exception
2420   // () rethrow call
2421   // () virtual or interface call with NULL receiver
2422   // () call is a check cast with incompatible arguments
2423   if( in(1)->is_Proj() ) {
2424     Node *i10 = in(1)->in(0);
2425     if( i10->is_Call() ) {
2426       CallNode *call = i10->as_Call();
2427       // Rethrows always throw exceptions, never return
2428       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2429         f[CatchProjNode::fall_through_index] = Type::TOP;
2430       } else if( call->req() > TypeFunc::Parms ) {
2431         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2432         // Check for null receiver to virtual or interface calls
2433         if( call->is_CallDynamicJava() &&
2434             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2435           f[CatchProjNode::fall_through_index] = Type::TOP;
2436         }
2437       } // End of if not a runtime stub
2438     } // End of if have call above me
2439   } // End of slot 1 is not a projection
2440   return TypeTuple::make(_size, f);
2441 }
2442 
2443 //=============================================================================
2444 uint CatchProjNode::hash() const {
2445   return Node::hash() + _handler_bci;
2446 }
2447 
2448 
2449 bool CatchProjNode::cmp( const Node &n ) const {
2450   return ProjNode::cmp(n) &&
2451     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2452 }
2453 
2454 
2455 //------------------------------Identity---------------------------------------
2456 // If only 1 target is possible, choose it if it is the main control
2457 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2458   // If my value is control and no other value is, then treat as ID
2459   const TypeTuple *t = phase->type(in(0))->is_tuple();
2460   if (t->field_at(_con) != Type::CONTROL)  return this;
2461   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2462   // also remove any exception table entry.  Thus we must know the call
2463   // feeding the Catch will not really throw an exception.  This is ok for
2464   // the main fall-thru control (happens when we know a call can never throw
2465   // an exception) or for "rethrow", because a further optimization will
2466   // yank the rethrow (happens when we inline a function that can throw an
2467   // exception and the caller has no handler).  Not legal, e.g., for passing
2468   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2469   // These cases MUST throw an exception via the runtime system, so the VM
2470   // will be looking for a table entry.
2471   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2472   CallNode *call;
2473   if (_con != TypeFunc::Control && // Bail out if not the main control.
2474       !(proj->is_Proj() &&      // AND NOT a rethrow
2475         proj->in(0)->is_Call() &&
2476         (call = proj->in(0)->as_Call()) &&
2477         call->entry_point() == OptoRuntime::rethrow_stub()))
2478     return this;
2479 
2480   // Search for any other path being control
2481   for (uint i = 0; i < t->cnt(); i++) {
2482     if (i != _con && t->field_at(i) == Type::CONTROL)
2483       return this;
2484   }
2485   // Only my path is possible; I am identity on control to the jump
2486   return in(0)->in(0);
2487 }
2488 
2489 
2490 #ifndef PRODUCT
2491 void CatchProjNode::dump_spec(outputStream *st) const {
2492   ProjNode::dump_spec(st);
2493   st->print("@bci %d ",_handler_bci);
2494 }
2495 #endif
2496 
2497 //=============================================================================
2498 //------------------------------Identity---------------------------------------
2499 // Check for CreateEx being Identity.
2500 Node* CreateExNode::Identity(PhaseGVN* phase) {
2501   if( phase->type(in(1)) == Type::TOP ) return in(1);
2502   if( phase->type(in(0)) == Type::TOP ) return in(0);
2503   // We only come from CatchProj, unless the CatchProj goes away.
2504   // If the CatchProj is optimized away, then we just carry the
2505   // exception oop through.
2506   CallNode *call = in(1)->in(0)->as_Call();
2507 
2508   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2509     ? this
2510     : call->in(TypeFunc::Parms);
2511 }
2512 
2513 //=============================================================================
2514 //------------------------------Value------------------------------------------
2515 // Check for being unreachable.
2516 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2517   if (!in(0) || in(0)->is_top()) return Type::TOP;
2518   return bottom_type();
2519 }
2520 
2521 //------------------------------Ideal------------------------------------------
2522 // Check for no longer being part of a loop
2523 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2524   if (can_reshape && !in(0)->is_Loop()) {
2525     // Dead code elimination can sometimes delete this projection so
2526     // if it's not there, there's nothing to do.
2527     Node* fallthru = proj_out_or_null(0);
2528     if (fallthru != NULL) {
2529       phase->is_IterGVN()->replace_node(fallthru, in(0));
2530     }
2531     return phase->C->top();
2532   }
2533   return NULL;
2534 }
2535 
2536 #ifndef PRODUCT
2537 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2538   st->print("%s", Name());
2539 }
2540 #endif