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 "opto/vectornode.hpp"
  47 #include "utilities/vmError.hpp"
  48 
  49 // Portions of code courtesy of Clifford Click
  50 
  51 // Optimization - Graph Style
  52 
  53 //=============================================================================
  54 //------------------------------Value------------------------------------------
  55 // Compute the type of the RegionNode.
  56 const Type* RegionNode::Value(PhaseGVN* phase) const {
  57   for( uint i=1; i<req(); ++i ) {       // For all paths in
  58     Node *n = in(i);            // Get Control source
  59     if( !n ) continue;          // Missing inputs are TOP
  60     if( phase->type(n) == Type::CONTROL )
  61       return Type::CONTROL;
  62   }
  63   return Type::TOP;             // All paths dead?  Then so are we
  64 }
  65 
  66 //------------------------------Identity---------------------------------------
  67 // Check for Region being Identity.
  68 Node* RegionNode::Identity(PhaseGVN* phase) {
  69   // Cannot have Region be an identity, even if it has only 1 input.
  70   // Phi users cannot have their Region input folded away for them,
  71   // since they need to select the proper data input
  72   return this;
  73 }
  74 
  75 //------------------------------merge_region-----------------------------------
  76 // If a Region flows into a Region, merge into one big happy merge.  This is
  77 // hard to do if there is stuff that has to happen
  78 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  79   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  80     return NULL;
  81   Node *progress = NULL;        // Progress flag
  82   PhaseIterGVN *igvn = phase->is_IterGVN();
  83 
  84   uint rreq = region->req();
  85   for( uint i = 1; i < rreq; i++ ) {
  86     Node *r = region->in(i);
  87     if( r && r->Opcode() == Op_Region && // Found a region?
  88         r->in(0) == r &&        // Not already collapsed?
  89         r != region &&          // Avoid stupid situations
  90         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  91       assert(!r->as_Region()->has_phi(), "no phi users");
  92       if( !progress ) {         // No progress
  93         if (region->has_phi()) {
  94           return NULL;        // Only flatten if no Phi users
  95           // igvn->hash_delete( phi );
  96         }
  97         igvn->hash_delete( region );
  98         progress = region;      // Making progress
  99       }
 100       igvn->hash_delete( r );
 101 
 102       // Append inputs to 'r' onto 'region'
 103       for( uint j = 1; j < r->req(); j++ ) {
 104         // Move an input from 'r' to 'region'
 105         region->add_req(r->in(j));
 106         r->set_req(j, phase->C->top());
 107         // Update phis of 'region'
 108         //for( uint k = 0; k < max; k++ ) {
 109         //  Node *phi = region->out(k);
 110         //  if( phi->is_Phi() ) {
 111         //    phi->add_req(phi->in(i));
 112         //  }
 113         //}
 114 
 115         rreq++;                 // One more input to Region
 116       } // Found a region to merge into Region
 117       igvn->_worklist.push(r);
 118       // Clobber pointer to the now dead 'r'
 119       region->set_req(i, phase->C->top());
 120     }
 121   }
 122 
 123   return progress;
 124 }
 125 
 126 
 127 
 128 //--------------------------------has_phi--------------------------------------
 129 // Helper function: Return any PhiNode that uses this region or NULL
 130 PhiNode* RegionNode::has_phi() const {
 131   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 132     Node* phi = fast_out(i);
 133     if (phi->is_Phi()) {   // Check for Phi users
 134       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 135       return phi->as_Phi();  // this one is good enough
 136     }
 137   }
 138 
 139   return NULL;
 140 }
 141 
 142 
 143 //-----------------------------has_unique_phi----------------------------------
 144 // Helper function: Return the only PhiNode that uses this region or NULL
 145 PhiNode* RegionNode::has_unique_phi() const {
 146   // Check that only one use is a Phi
 147   PhiNode* only_phi = NULL;
 148   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 149     Node* phi = fast_out(i);
 150     if (phi->is_Phi()) {   // Check for Phi users
 151       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 152       if (only_phi == NULL) {
 153         only_phi = phi->as_Phi();
 154       } else {
 155         return NULL;  // multiple phis
 156       }
 157     }
 158   }
 159 
 160   return only_phi;
 161 }
 162 
 163 
 164 //------------------------------check_phi_clipping-----------------------------
 165 // Helper function for RegionNode's identification of FP clipping
 166 // Check inputs to the Phi
 167 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 168   min     = NULL;
 169   max     = NULL;
 170   val     = NULL;
 171   min_idx = 0;
 172   max_idx = 0;
 173   val_idx = 0;
 174   uint  phi_max = phi->req();
 175   if( phi_max == 4 ) {
 176     for( uint j = 1; j < phi_max; ++j ) {
 177       Node *n = phi->in(j);
 178       int opcode = n->Opcode();
 179       switch( opcode ) {
 180       case Op_ConI:
 181         {
 182           if( min == NULL ) {
 183             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 184             min_idx = j;
 185           } else {
 186             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 187             max_idx = j;
 188             if( min->get_int() > max->get_int() ) {
 189               // Swap min and max
 190               ConNode *temp;
 191               uint     temp_idx;
 192               temp     = min;     min     = max;     max     = temp;
 193               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 194             }
 195           }
 196         }
 197         break;
 198       default:
 199         {
 200           val = n;
 201           val_idx = j;
 202         }
 203         break;
 204       }
 205     }
 206   }
 207   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 208 }
 209 
 210 
 211 //------------------------------check_if_clipping------------------------------
 212 // Helper function for RegionNode's identification of FP clipping
 213 // Check that inputs to Region come from two IfNodes,
 214 //
 215 //            If
 216 //      False    True
 217 //       If        |
 218 //  False  True    |
 219 //    |      |     |
 220 //  RegionNode_inputs
 221 //
 222 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 223   top_if = NULL;
 224   bot_if = NULL;
 225 
 226   // Check control structure above RegionNode for (if  ( if  ) )
 227   Node *in1 = region->in(1);
 228   Node *in2 = region->in(2);
 229   Node *in3 = region->in(3);
 230   // Check that all inputs are projections
 231   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 232     Node *in10 = in1->in(0);
 233     Node *in20 = in2->in(0);
 234     Node *in30 = in3->in(0);
 235     // Check that #1 and #2 are ifTrue and ifFalse from same If
 236     if( in10 != NULL && in10->is_If() &&
 237         in20 != NULL && in20->is_If() &&
 238         in30 != NULL && in30->is_If() && in10 == in20 &&
 239         (in1->Opcode() != in2->Opcode()) ) {
 240       Node  *in100 = in10->in(0);
 241       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 242       // Check that control for in10 comes from other branch of IF from in3
 243       if( in1000 != NULL && in1000->is_If() &&
 244           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 245         // Control pattern checks
 246         top_if = (IfNode*)in1000;
 247         bot_if = (IfNode*)in10;
 248       }
 249     }
 250   }
 251 
 252   return (top_if != NULL);
 253 }
 254 
 255 
 256 //------------------------------check_convf2i_clipping-------------------------
 257 // Helper function for RegionNode's identification of FP clipping
 258 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 259 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 260   convf2i = NULL;
 261 
 262   // Check for the RShiftNode
 263   Node *rshift = phi->in(idx);
 264   assert( rshift, "Previous checks ensure phi input is present");
 265   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 266 
 267   // Check for the LShiftNode
 268   Node *lshift = rshift->in(1);
 269   assert( lshift, "Previous checks ensure phi input is present");
 270   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 271 
 272   // Check for the ConvF2INode
 273   Node *conv = lshift->in(1);
 274   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 275 
 276   // Check that shift amounts are only to get sign bits set after F2I
 277   jint max_cutoff     = max->get_int();
 278   jint min_cutoff     = min->get_int();
 279   jint left_shift     = lshift->in(2)->get_int();
 280   jint right_shift    = rshift->in(2)->get_int();
 281   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 282   if( left_shift != right_shift ||
 283       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 284       max_post_shift < max_cutoff ||
 285       max_post_shift < -min_cutoff ) {
 286     // Shifts are necessary but current transformation eliminates them
 287     return false;
 288   }
 289 
 290   // OK to return the result of ConvF2I without shifting
 291   convf2i = (ConvF2INode*)conv;
 292   return true;
 293 }
 294 
 295 
 296 //------------------------------check_compare_clipping-------------------------
 297 // Helper function for RegionNode's identification of FP clipping
 298 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 299   Node *i1 = iff->in(1);
 300   if ( !i1->is_Bool() ) { return false; }
 301   BoolNode *bool1 = i1->as_Bool();
 302   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 303   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 304   const Node *cmpF = bool1->in(1);
 305   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 306   // Test that the float value being compared against
 307   // is equivalent to the int value used as a limit
 308   Node *nodef = cmpF->in(2);
 309   if( nodef->Opcode() != Op_ConF ) { return false; }
 310   jfloat conf = nodef->getf();
 311   jint   coni = limit->get_int();
 312   if( ((int)conf) != coni )        { return false; }
 313   input = cmpF->in(1);
 314   return true;
 315 }
 316 
 317 //------------------------------is_unreachable_region--------------------------
 318 // Find if the Region node is reachable from the root.
 319 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
 320   assert(req() == 2, "");
 321 
 322   // First, cut the simple case of fallthrough region when NONE of
 323   // region's phis references itself directly or through a data node.
 324   uint max = outcnt();
 325   uint i;
 326   for (i = 0; i < max; i++) {
 327     Node* phi = raw_out(i);
 328     if (phi != NULL && phi->is_Phi()) {
 329       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
 330       if (phi->outcnt() == 0)
 331         continue; // Safe case - no loops
 332       if (phi->outcnt() == 1) {
 333         Node* u = phi->raw_out(0);
 334         // Skip if only one use is an other Phi or Call or Uncommon trap.
 335         // It is safe to consider this case as fallthrough.
 336         if (u != NULL && (u->is_Phi() || u->is_CFG()))
 337           continue;
 338       }
 339       // Check when phi references itself directly or through an other node.
 340       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
 341         break; // Found possible unsafe data loop.
 342     }
 343   }
 344   if (i >= max)
 345     return false; // An unsafe case was NOT found - don't need graph walk.
 346 
 347   // Unsafe case - check if the Region node is reachable from root.
 348   ResourceMark rm;
 349 
 350   Arena *a = Thread::current()->resource_area();
 351   Node_List nstack(a);
 352   VectorSet visited(a);
 353 
 354   // Mark all control nodes reachable from root outputs
 355   Node *n = (Node*)phase->C->root();
 356   nstack.push(n);
 357   visited.set(n->_idx);
 358   while (nstack.size() != 0) {
 359     n = nstack.pop();
 360     uint max = n->outcnt();
 361     for (uint i = 0; i < max; i++) {
 362       Node* m = n->raw_out(i);
 363       if (m != NULL && m->is_CFG()) {
 364         if (phase->eqv(m, this)) {
 365           return false; // We reached the Region node - it is not dead.
 366         }
 367         if (!visited.test_set(m->_idx))
 368           nstack.push(m);
 369       }
 370     }
 371   }
 372 
 373   return true; // The Region node is unreachable - it is dead.
 374 }
 375 
 376 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 377   // Incremental inlining + PhaseStringOpts sometimes produce:
 378   //
 379   // cmpP with 1 top input
 380   //           |
 381   //          If
 382   //         /  \
 383   //   IfFalse  IfTrue  /- Some Node
 384   //         \  /      /    /
 385   //        Region    / /-MergeMem
 386   //             \---Phi
 387   //
 388   //
 389   // It's expected by PhaseStringOpts that the Region goes away and is
 390   // replaced by If's control input but because there's still a Phi,
 391   // the Region stays in the graph. The top input from the cmpP is
 392   // propagated forward and a subgraph that is useful goes away. The
 393   // code below replaces the Phi with the MergeMem so that the Region
 394   // is simplified.
 395 
 396   PhiNode* phi = has_unique_phi();
 397   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 398     MergeMemNode* m = NULL;
 399     assert(phi->req() == 3, "same as region");
 400     for (uint i = 1; i < 3; ++i) {
 401       Node *mem = phi->in(i);
 402       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 403         // Nothing is control-dependent on path #i except the region itself.
 404         m = mem->as_MergeMem();
 405         uint j = 3 - i;
 406         Node* other = phi->in(j);
 407         if (other && other == m->base_memory()) {
 408           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 409           // This will allow the diamond to collapse completely.
 410           phase->is_IterGVN()->replace_node(phi, m);
 411           return true;
 412         }
 413       }
 414     }
 415   }
 416   return false;
 417 }
 418 
 419 //------------------------------Ideal------------------------------------------
 420 // Return a node which is more "ideal" than the current node.  Must preserve
 421 // the CFG, but we can still strip out dead paths.
 422 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 423   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 424   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 425 
 426   // Check for RegionNode with no Phi users and both inputs come from either
 427   // arm of the same IF.  If found, then the control-flow split is useless.
 428   bool has_phis = false;
 429   if (can_reshape) {            // Need DU info to check for Phi users
 430     has_phis = (has_phi() != NULL);       // Cache result
 431     if (has_phis && try_clean_mem_phi(phase)) {
 432       has_phis = false;
 433     }
 434 
 435     if (!has_phis) {            // No Phi users?  Nothing merging?
 436       for (uint i = 1; i < req()-1; i++) {
 437         Node *if1 = in(i);
 438         if( !if1 ) continue;
 439         Node *iff = if1->in(0);
 440         if( !iff || !iff->is_If() ) continue;
 441         for( uint j=i+1; j<req(); j++ ) {
 442           if( in(j) && in(j)->in(0) == iff &&
 443               if1->Opcode() != in(j)->Opcode() ) {
 444             // Add the IF Projections to the worklist. They (and the IF itself)
 445             // will be eliminated if dead.
 446             phase->is_IterGVN()->add_users_to_worklist(iff);
 447             set_req(i, iff->in(0));// Skip around the useless IF diamond
 448             set_req(j, NULL);
 449             return this;      // Record progress
 450           }
 451         }
 452       }
 453     }
 454   }
 455 
 456   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 457   // degrades to a copy.
 458   bool add_to_worklist = false;
 459   bool modified = false;
 460   int cnt = 0;                  // Count of values merging
 461   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 462   int del_it = 0;               // The last input path we delete
 463   // For all inputs...
 464   for( uint i=1; i<req(); ++i ){// For all paths in
 465     Node *n = in(i);            // Get the input
 466     if( n != NULL ) {
 467       // Remove useless control copy inputs
 468       if( n->is_Region() && n->as_Region()->is_copy() ) {
 469         set_req(i, n->nonnull_req());
 470         modified = true;
 471         i--;
 472         continue;
 473       }
 474       if( n->is_Proj() ) {      // Remove useless rethrows
 475         Node *call = n->in(0);
 476         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 477           set_req(i, call->in(0));
 478           modified = true;
 479           i--;
 480           continue;
 481         }
 482       }
 483       if( phase->type(n) == Type::TOP ) {
 484         set_req(i, NULL);       // Ignore TOP inputs
 485         modified = true;
 486         i--;
 487         continue;
 488       }
 489       cnt++;                    // One more value merging
 490 
 491     } else if (can_reshape) {   // Else found dead path with DU info
 492       PhaseIterGVN *igvn = phase->is_IterGVN();
 493       del_req(i);               // Yank path from self
 494       del_it = i;
 495       uint max = outcnt();
 496       DUIterator j;
 497       bool progress = true;
 498       while(progress) {         // Need to establish property over all users
 499         progress = false;
 500         for (j = outs(); has_out(j); j++) {
 501           Node *n = out(j);
 502           if( n->req() != req() && n->is_Phi() ) {
 503             assert( n->in(0) == this, "" );
 504             igvn->hash_delete(n); // Yank from hash before hacking edges
 505             n->set_req_X(i,NULL,igvn);// Correct DU info
 506             n->del_req(i);        // Yank path from Phis
 507             if( max != outcnt() ) {
 508               progress = true;
 509               j = refresh_out_pos(j);
 510               max = outcnt();
 511             }
 512           }
 513         }
 514       }
 515       add_to_worklist = true;
 516       i--;
 517     }
 518   }
 519 
 520   if (can_reshape && cnt == 1) {
 521     // Is it dead loop?
 522     // If it is LoopNopde it had 2 (+1 itself) inputs and
 523     // one of them was cut. The loop is dead if it was EntryContol.
 524     // Loop node may have only one input because entry path
 525     // is removed in PhaseIdealLoop::Dominators().
 526     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 527     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 528                              (del_it == 0 && is_unreachable_region(phase)))) ||
 529         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 530       // Yes,  the region will be removed during the next step below.
 531       // Cut the backedge input and remove phis since no data paths left.
 532       // We don't cut outputs to other nodes here since we need to put them
 533       // on the worklist.
 534       PhaseIterGVN *igvn = phase->is_IterGVN();
 535       if (in(1)->outcnt() == 1) {
 536         igvn->_worklist.push(in(1));
 537       }
 538       del_req(1);
 539       cnt = 0;
 540       assert( req() == 1, "no more inputs expected" );
 541       uint max = outcnt();
 542       bool progress = true;
 543       Node *top = phase->C->top();
 544       DUIterator j;
 545       while(progress) {
 546         progress = false;
 547         for (j = outs(); has_out(j); j++) {
 548           Node *n = out(j);
 549           if( n->is_Phi() ) {
 550             assert( igvn->eqv(n->in(0), this), "" );
 551             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 552             // Break dead loop data path.
 553             // Eagerly replace phis with top to avoid phis copies generation.
 554             igvn->replace_node(n, top);
 555             if( max != outcnt() ) {
 556               progress = true;
 557               j = refresh_out_pos(j);
 558               max = outcnt();
 559             }
 560           }
 561         }
 562       }
 563       add_to_worklist = true;
 564     }
 565   }
 566   if (add_to_worklist) {
 567     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 568   }
 569 
 570   if( cnt <= 1 ) {              // Only 1 path in?
 571     set_req(0, NULL);           // Null control input for region copy
 572     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 573       // No inputs or all inputs are NULL.
 574       return NULL;
 575     } else if (can_reshape) {   // Optimization phase - remove the node
 576       PhaseIterGVN *igvn = phase->is_IterGVN();
 577       // Strip mined (inner) loop is going away, remove outer loop.
 578       if (is_CountedLoop() &&
 579           as_Loop()->is_strip_mined()) {
 580         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 581         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 582         if (outer_sfpt != NULL && outer_out != NULL) {
 583           Node* in = outer_sfpt->in(0);
 584           igvn->replace_node(outer_out, in);
 585           LoopNode* outer = as_CountedLoop()->outer_loop();
 586           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 587         }
 588       }
 589       Node *parent_ctrl;
 590       if( cnt == 0 ) {
 591         assert( req() == 1, "no inputs expected" );
 592         // During IGVN phase such region will be subsumed by TOP node
 593         // so region's phis will have TOP as control node.
 594         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 595         // Also set other user's input to top.
 596         parent_ctrl = phase->C->top();
 597       } else {
 598         // The fallthrough case since we already checked dead loops above.
 599         parent_ctrl = in(1);
 600         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 601         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 602       }
 603       if (!add_to_worklist)
 604         igvn->add_users_to_worklist(this); // Check for further allowed opts
 605       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 606         Node* n = last_out(i);
 607         igvn->hash_delete(n); // Remove from worklist before modifying edges
 608         if( n->is_Phi() ) {   // Collapse all Phis
 609           // Eagerly replace phis to avoid copies generation.
 610           Node* in;
 611           if( cnt == 0 ) {
 612             assert( n->req() == 1, "No data inputs expected" );
 613             in = parent_ctrl; // replaced by top
 614           } else {
 615             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 616             in = n->in(1);               // replaced by unique input
 617             if( n->as_Phi()->is_unsafe_data_reference(in) )
 618               in = phase->C->top();      // replaced by top
 619           }
 620           igvn->replace_node(n, in);
 621         }
 622         else if( n->is_Region() ) { // Update all incoming edges
 623           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 624           uint uses_found = 0;
 625           for( uint k=1; k < n->req(); k++ ) {
 626             if( n->in(k) == this ) {
 627               n->set_req(k, parent_ctrl);
 628               uses_found++;
 629             }
 630           }
 631           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 632             i -= (uses_found - 1);
 633           }
 634         }
 635         else {
 636           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 637           n->set_req(0, parent_ctrl);
 638         }
 639 #ifdef ASSERT
 640         for( uint k=0; k < n->req(); k++ ) {
 641           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 642         }
 643 #endif
 644       }
 645       // Remove the RegionNode itself from DefUse info
 646       igvn->remove_dead_node(this);
 647       return NULL;
 648     }
 649     return this;                // Record progress
 650   }
 651 
 652 
 653   // If a Region flows into a Region, merge into one big happy merge.
 654   if (can_reshape) {
 655     Node *m = merge_region(this, phase);
 656     if (m != NULL)  return m;
 657   }
 658 
 659   // Check if this region is the root of a clipping idiom on floats
 660   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 661     // Check that only one use is a Phi and that it simplifies to two constants +
 662     PhiNode* phi = has_unique_phi();
 663     if (phi != NULL) {          // One Phi user
 664       // Check inputs to the Phi
 665       ConNode *min;
 666       ConNode *max;
 667       Node    *val;
 668       uint     min_idx;
 669       uint     max_idx;
 670       uint     val_idx;
 671       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 672         IfNode *top_if;
 673         IfNode *bot_if;
 674         if( check_if_clipping( this, bot_if, top_if ) ) {
 675           // Control pattern checks, now verify compares
 676           Node   *top_in = NULL;   // value being compared against
 677           Node   *bot_in = NULL;
 678           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 679               check_compare_clipping( false, top_if, max, top_in ) ) {
 680             if( bot_in == top_in ) {
 681               PhaseIterGVN *gvn = phase->is_IterGVN();
 682               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 683               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 684 
 685               // Check for the ConvF2INode
 686               ConvF2INode *convf2i;
 687               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 688                 convf2i->in(1) == bot_in ) {
 689                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 690                 // max test
 691                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 692                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 693                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 694                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 695                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 696                 // min test
 697                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 698                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 699                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 700                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 701                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 702                 // update input edges to region node
 703                 set_req_X( min_idx, if_min, gvn );
 704                 set_req_X( max_idx, if_max, gvn );
 705                 set_req_X( val_idx, ifF,    gvn );
 706                 // remove unnecessary 'LShiftI; RShiftI' idiom
 707                 gvn->hash_delete(phi);
 708                 phi->set_req_X( val_idx, convf2i, gvn );
 709                 gvn->hash_find_insert(phi);
 710                 // Return transformed region node
 711                 return this;
 712               }
 713             }
 714           }
 715         }
 716       }
 717     }
 718   }
 719 
 720   if (can_reshape) {
 721     modified |= optimize_trichotomy(phase->is_IterGVN());
 722   }
 723 
 724   return modified ? this : NULL;
 725 }
 726 
 727 //------------------------------optimize_trichotomy--------------------------
 728 // Optimize nested comparisons of the following kind:
 729 //
 730 // int compare(int a, int b) {
 731 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 732 // }
 733 //
 734 // Shape 1:
 735 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 736 //
 737 // Shape 2:
 738 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 739 //
 740 // Above code leads to the following IR shapes where both Ifs compare the
 741 // same value and two out of three region inputs idx1 and idx2 map to
 742 // the same value and control flow.
 743 //
 744 // (1)   If                 (2)   If
 745 //      /  \                     /  \
 746 //   Proj  Proj               Proj  Proj
 747 //     |      \                |      \
 748 //     |       If              |      If                      If
 749 //     |      /  \             |     /  \                    /  \
 750 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 751 //     |   /      /            \    |    /                  |    /
 752 //    Region     /              \   |   /                   |   /
 753 //         \    /                \  |  /                    |  /
 754 //         Region                Region                    Region
 755 //
 756 // The method returns true if 'this' is modified and false otherwise.
 757 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 758   int idx1 = 1, idx2 = 2;
 759   Node* region = NULL;
 760   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 761     // Shape 1: Check if one of the inputs is a region that merges two control
 762     // inputs and has no other users (especially no Phi users).
 763     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 764     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 765       return false; // No suitable region input found
 766     }
 767   } else if (req() == 4) {
 768     // Shape 2: Check if two control inputs map to the same value of the unique phi
 769     // user and treat these as if they would come from another region (shape (1)).
 770     PhiNode* phi = has_unique_phi();
 771     if (phi == NULL) {
 772       return false; // No unique phi user
 773     }
 774     if (phi->in(idx1) != phi->in(idx2)) {
 775       idx2 = 3;
 776       if (phi->in(idx1) != phi->in(idx2)) {
 777         idx1 = 2;
 778         if (phi->in(idx1) != phi->in(idx2)) {
 779           return false; // No equal phi inputs found
 780         }
 781       }
 782     }
 783     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 784     region = this;
 785   }
 786   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 787     return false; // Region does not merge two control inputs
 788   }
 789   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 790   // value and control flow. Now search for ifs that feed into these region inputs.
 791   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 792   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 793   if (proj1 == NULL || proj1->outcnt() != 1 ||
 794       proj2 == NULL || proj2->outcnt() != 1) {
 795     return false; // No projection inputs with region as unique user found
 796   }
 797   assert(proj1 != proj2, "should be different projections");
 798   IfNode* iff1 = proj1->in(0)->isa_If();
 799   IfNode* iff2 = proj2->in(0)->isa_If();
 800   if (iff1 == NULL || iff1->outcnt() != 2 ||
 801       iff2 == NULL || iff2->outcnt() != 2) {
 802     return false; // No ifs found
 803   }
 804   if (iff1 == iff2) {
 805     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 806     igvn->replace_input_of(region, idx1, iff1->in(0));
 807     igvn->replace_input_of(region, idx2, igvn->C->top());
 808     return (region == this); // Remove useless if (both projections map to the same control/value)
 809   }
 810   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 811   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 812   if (bol1 == NULL || bol2 == NULL) {
 813     return false; // No bool inputs found
 814   }
 815   Node* cmp1 = bol1->in(1);
 816   Node* cmp2 = bol2->in(1);
 817   bool commute = false;
 818   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 819     return false; // No comparison
 820   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 821              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 822              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 823              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN) {
 824     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 825     return false;
 826   } else if (cmp1 != cmp2) {
 827     if (cmp1->in(1) == cmp2->in(2) &&
 828         cmp1->in(2) == cmp2->in(1)) {
 829       commute = true; // Same but swapped inputs, commute the test
 830     } else {
 831       return false; // Ifs are not comparing the same values
 832     }
 833   }
 834   proj1 = proj1->other_if_proj();
 835   proj2 = proj2->other_if_proj();
 836   if (!((proj1->unique_ctrl_out() == iff2 &&
 837          proj2->unique_ctrl_out() == this) ||
 838         (proj2->unique_ctrl_out() == iff1 &&
 839          proj1->unique_ctrl_out() == this))) {
 840     return false; // Ifs are not connected through other projs
 841   }
 842   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 843   // through 'region' and map to the same value. Merge the boolean tests and replace
 844   // the ifs by a single comparison.
 845   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 846   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 847   test1 = commute ? test1.commute() : test1;
 848   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 849   BoolTest::mask res = test1.merge(test2);
 850   if (res == BoolTest::illegal) {
 851     return false; // Unable to merge tests
 852   }
 853   // Adjust iff1 to always pass (only iff2 will remain)
 854   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 855   if (res == BoolTest::never) {
 856     // Merged test is always false, adjust iff2 to always fail
 857     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 858   } else {
 859     // Replace bool input of iff2 with merged test
 860     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 861     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 862   }
 863   return false;
 864 }
 865 
 866 const RegMask &RegionNode::out_RegMask() const {
 867   return RegMask::Empty;
 868 }
 869 
 870 // Find the one non-null required input.  RegionNode only
 871 Node *Node::nonnull_req() const {
 872   assert( is_Region(), "" );
 873   for( uint i = 1; i < _cnt; i++ )
 874     if( in(i) )
 875       return in(i);
 876   ShouldNotReachHere();
 877   return NULL;
 878 }
 879 
 880 
 881 //=============================================================================
 882 // note that these functions assume that the _adr_type field is flattened
 883 uint PhiNode::hash() const {
 884   const Type* at = _adr_type;
 885   return TypeNode::hash() + (at ? at->hash() : 0);
 886 }
 887 bool PhiNode::cmp( const Node &n ) const {
 888   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 889 }
 890 static inline
 891 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 892   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 893   return Compile::current()->alias_type(at)->adr_type();
 894 }
 895 
 896 //----------------------------make---------------------------------------------
 897 // create a new phi with edges matching r and set (initially) to x
 898 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 899   uint preds = r->req();   // Number of predecessor paths
 900   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 901   PhiNode* p = new PhiNode(r, t, at);
 902   for (uint j = 1; j < preds; j++) {
 903     // Fill in all inputs, except those which the region does not yet have
 904     if (r->in(j) != NULL)
 905       p->init_req(j, x);
 906   }
 907   return p;
 908 }
 909 PhiNode* PhiNode::make(Node* r, Node* x) {
 910   const Type*    t  = x->bottom_type();
 911   const TypePtr* at = NULL;
 912   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 913   return make(r, x, t, at);
 914 }
 915 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 916   const Type*    t  = x->bottom_type();
 917   const TypePtr* at = NULL;
 918   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 919   return new PhiNode(r, t, at);
 920 }
 921 
 922 
 923 //------------------------slice_memory-----------------------------------------
 924 // create a new phi with narrowed memory type
 925 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 926   PhiNode* mem = (PhiNode*) clone();
 927   *(const TypePtr**)&mem->_adr_type = adr_type;
 928   // convert self-loops, or else we get a bad graph
 929   for (uint i = 1; i < req(); i++) {
 930     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 931   }
 932   mem->verify_adr_type();
 933   return mem;
 934 }
 935 
 936 //------------------------split_out_instance-----------------------------------
 937 // Split out an instance type from a bottom phi.
 938 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 939   const TypeOopPtr *t_oop = at->isa_oopptr();
 940   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 941   const TypePtr *t = adr_type();
 942   assert(type() == Type::MEMORY &&
 943          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 944           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 945           t->is_oopptr()->cast_to_exactness(true)
 946            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 947            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 948          "bottom or raw memory required");
 949 
 950   // Check if an appropriate node already exists.
 951   Node *region = in(0);
 952   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 953     Node* use = region->fast_out(k);
 954     if( use->is_Phi()) {
 955       PhiNode *phi2 = use->as_Phi();
 956       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 957         return phi2;
 958       }
 959     }
 960   }
 961   Compile *C = igvn->C;
 962   Arena *a = Thread::current()->resource_area();
 963   Node_Array node_map = new Node_Array(a);
 964   Node_Stack stack(a, C->live_nodes() >> 4);
 965   PhiNode *nphi = slice_memory(at);
 966   igvn->register_new_node_with_optimizer( nphi );
 967   node_map.map(_idx, nphi);
 968   stack.push((Node *)this, 1);
 969   while(!stack.is_empty()) {
 970     PhiNode *ophi = stack.node()->as_Phi();
 971     uint i = stack.index();
 972     assert(i >= 1, "not control edge");
 973     stack.pop();
 974     nphi = node_map[ophi->_idx]->as_Phi();
 975     for (; i < ophi->req(); i++) {
 976       Node *in = ophi->in(i);
 977       if (in == NULL || igvn->type(in) == Type::TOP)
 978         continue;
 979       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
 980       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 981       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 982         opt = node_map[optphi->_idx];
 983         if (opt == NULL) {
 984           stack.push(ophi, i);
 985           nphi = optphi->slice_memory(at);
 986           igvn->register_new_node_with_optimizer( nphi );
 987           node_map.map(optphi->_idx, nphi);
 988           ophi = optphi;
 989           i = 0; // will get incremented at top of loop
 990           continue;
 991         }
 992       }
 993       nphi->set_req(i, opt);
 994     }
 995   }
 996   return nphi;
 997 }
 998 
 999 //------------------------verify_adr_type--------------------------------------
1000 #ifdef ASSERT
1001 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1002   if (visited.test_set(_idx))  return;  //already visited
1003 
1004   // recheck constructor invariants:
1005   verify_adr_type(false);
1006 
1007   // recheck local phi/phi consistency:
1008   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1009          "adr_type must be consistent across phi nest");
1010 
1011   // walk around
1012   for (uint i = 1; i < req(); i++) {
1013     Node* n = in(i);
1014     if (n == NULL)  continue;
1015     const Node* np = in(i);
1016     if (np->is_Phi()) {
1017       np->as_Phi()->verify_adr_type(visited, at);
1018     } else if (n->bottom_type() == Type::TOP
1019                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1020       // ignore top inputs
1021     } else {
1022       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1023       // recheck phi/non-phi consistency at leaves:
1024       assert((nat != NULL) == (at != NULL), "");
1025       assert(nat == at || nat == TypePtr::BOTTOM,
1026              "adr_type must be consistent at leaves of phi nest");
1027     }
1028   }
1029 }
1030 
1031 // Verify a whole nest of phis rooted at this one.
1032 void PhiNode::verify_adr_type(bool recursive) const {
1033   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1034   if (Node::in_dump())               return;  // muzzle asserts when printing
1035 
1036   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1037 
1038   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1039 
1040   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1041          "Phi::adr_type must be pre-normalized");
1042 
1043   if (recursive) {
1044     VectorSet visited(Thread::current()->resource_area());
1045     verify_adr_type(visited, _adr_type);
1046   }
1047 }
1048 #endif
1049 
1050 
1051 //------------------------------Value------------------------------------------
1052 // Compute the type of the PhiNode
1053 const Type* PhiNode::Value(PhaseGVN* phase) const {
1054   Node *r = in(0);              // RegionNode
1055   if( !r )                      // Copy or dead
1056     return in(1) ? phase->type(in(1)) : Type::TOP;
1057 
1058   // Note: During parsing, phis are often transformed before their regions.
1059   // This means we have to use type_or_null to defend against untyped regions.
1060   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1061     return Type::TOP;
1062 
1063   // Check for trip-counted loop.  If so, be smarter.
1064   CountedLoopNode* l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
1065   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1066     // protect against init_trip() or limit() returning NULL
1067     if (l->can_be_counted_loop(phase)) {
1068       const Node *init   = l->init_trip();
1069       const Node *limit  = l->limit();
1070       const Node* stride = l->stride();
1071       if (init != NULL && limit != NULL && stride != NULL) {
1072         const TypeInt* lo = phase->type(init)->isa_int();
1073         const TypeInt* hi = phase->type(limit)->isa_int();
1074         const TypeInt* stride_t = phase->type(stride)->isa_int();
1075         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1076           assert(stride_t->_hi >= stride_t->_lo, "bad stride type");
1077           BoolTest::mask bt = l->loopexit()->test_trip();
1078           // If the loop exit condition is "not equal", the condition
1079           // would not trigger if init > limit (if stride > 0) or if
1080           // init < limit if (stride > 0) so we can't deduce bounds
1081           // for the iv from the exit condition.
1082           if (bt != BoolTest::ne) {
1083             if (stride_t->_hi < 0) {          // Down-counter loop
1084               swap(lo, hi);
1085               return TypeInt::make(MIN2(lo->_lo, hi->_lo) , hi->_hi, 3);
1086             } else if (stride_t->_lo >= 0) {
1087               return TypeInt::make(lo->_lo, MAX2(lo->_hi, hi->_hi), 3);
1088             }
1089           }
1090         }
1091       }
1092     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1093                in(LoopNode::EntryControl) != NULL &&
1094                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1095       // During CCP, if we saturate the type of a counted loop's Phi
1096       // before the special code for counted loop above has a chance
1097       // to run (that is as long as the type of the backedge's control
1098       // is top), we might end up with non monotonic types
1099       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1100     }
1101   }
1102 
1103   // Until we have harmony between classes and interfaces in the type
1104   // lattice, we must tread carefully around phis which implicitly
1105   // convert the one to the other.
1106   const TypePtr* ttp = _type->make_ptr();
1107   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1108   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
1109   bool is_intf = false;
1110   if (ttip != NULL) {
1111     ciKlass* k = ttip->klass();
1112     if (k->is_loaded() && k->is_interface())
1113       is_intf = true;
1114   }
1115   if (ttkp != NULL) {
1116     ciKlass* k = ttkp->klass();
1117     if (k->is_loaded() && k->is_interface())
1118       is_intf = true;
1119   }
1120 
1121   // Default case: merge all inputs
1122   const Type *t = Type::TOP;        // Merged type starting value
1123   for (uint i = 1; i < req(); ++i) {// For all paths in
1124     // Reachable control path?
1125     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1126       const Type* ti = phase->type(in(i));
1127       // We assume that each input of an interface-valued Phi is a true
1128       // subtype of that interface.  This might not be true of the meet
1129       // of all the input types.  The lattice is not distributive in
1130       // such cases.  Ward off asserts in type.cpp by refusing to do
1131       // meets between interfaces and proper classes.
1132       const TypePtr* tip = ti->make_ptr();
1133       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1134       if (tiip) {
1135         bool ti_is_intf = false;
1136         ciKlass* k = tiip->klass();
1137         if (k->is_loaded() && k->is_interface())
1138           ti_is_intf = true;
1139         if (is_intf != ti_is_intf)
1140           { t = _type; break; }
1141       }
1142       t = t->meet_speculative(ti);
1143     }
1144   }
1145 
1146   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1147   // That is, we expect that "t->higher_equal(_type)" holds true.
1148   // There are various exceptions:
1149   // - Inputs which are phis might in fact be widened unnecessarily.
1150   //   For example, an input might be a widened int while the phi is a short.
1151   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1152   //   and postCCP has removed the cast which encodes the result of the check.
1153   // - The type of this phi is an interface, and the inputs are classes.
1154   // - Value calls on inputs might produce fuzzy results.
1155   //   (Occurrences of this case suggest improvements to Value methods.)
1156   //
1157   // It is not possible to see Type::BOTTOM values as phi inputs,
1158   // because the ciTypeFlow pre-pass produces verifier-quality types.
1159   const Type* ft = t->filter_speculative(_type);  // Worst case type
1160 
1161 #ifdef ASSERT
1162   // The following logic has been moved into TypeOopPtr::filter.
1163   const Type* jt = t->join_speculative(_type);
1164   if (jt->empty()) {           // Emptied out???
1165 
1166     // Check for evil case of 't' being a class and '_type' expecting an
1167     // interface.  This can happen because the bytecodes do not contain
1168     // enough type info to distinguish a Java-level interface variable
1169     // from a Java-level object variable.  If we meet 2 classes which
1170     // both implement interface I, but their meet is at 'j/l/O' which
1171     // doesn't implement I, we have no way to tell if the result should
1172     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1173     // into a Phi which "knows" it's an Interface type we'll have to
1174     // uplift the type.
1175     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1176       assert(ft == _type, ""); // Uplift to interface
1177     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1178       assert(ft == _type, ""); // Uplift to interface
1179     } else {
1180       // We also have to handle 'evil cases' of interface- vs. class-arrays
1181       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1182       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1183           assert(ft == _type, "");   // Uplift to array of interface
1184       } else {
1185         // Otherwise it's something stupid like non-overlapping int ranges
1186         // found on dying counted loops.
1187         assert(ft == Type::TOP, ""); // Canonical empty value
1188       }
1189     }
1190   }
1191 
1192   else {
1193 
1194     // If we have an interface-typed Phi and we narrow to a class type, the join
1195     // should report back the class.  However, if we have a J/L/Object
1196     // class-typed Phi and an interface flows in, it's possible that the meet &
1197     // join report an interface back out.  This isn't possible but happens
1198     // because the type system doesn't interact well with interfaces.
1199     const TypePtr *jtp = jt->make_ptr();
1200     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1201     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
1202     if( jtip && ttip ) {
1203       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1204           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1205         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1206                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1207         jt = ft;
1208       }
1209     }
1210     if( jtkp && ttkp ) {
1211       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1212           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1213           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1214         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1215                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1216         jt = ft;
1217       }
1218     }
1219     if (jt != ft && jt->base() == ft->base()) {
1220       if (jt->isa_int() &&
1221           jt->is_int()->_lo == ft->is_int()->_lo &&
1222           jt->is_int()->_hi == ft->is_int()->_hi)
1223         jt = ft;
1224       if (jt->isa_long() &&
1225           jt->is_long()->_lo == ft->is_long()->_lo &&
1226           jt->is_long()->_hi == ft->is_long()->_hi)
1227         jt = ft;
1228     }
1229     if (jt != ft) {
1230       tty->print("merge type:  "); t->dump(); tty->cr();
1231       tty->print("kill type:   "); _type->dump(); tty->cr();
1232       tty->print("join type:   "); jt->dump(); tty->cr();
1233       tty->print("filter type: "); ft->dump(); tty->cr();
1234     }
1235     assert(jt == ft, "");
1236   }
1237 #endif //ASSERT
1238 
1239   // Deal with conversion problems found in data loops.
1240   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1241 
1242   return ft;
1243 }
1244 
1245 
1246 //------------------------------is_diamond_phi---------------------------------
1247 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1248 // index of the true path or 0 otherwise.
1249 // If check_control_only is true, do not inspect the If node at the
1250 // top, and return -1 (not an edge number) on success.
1251 int PhiNode::is_diamond_phi(bool check_control_only) const {
1252   // Check for a 2-path merge
1253   Node *region = in(0);
1254   if( !region ) return 0;
1255   if( region->req() != 3 ) return 0;
1256   if(         req() != 3 ) return 0;
1257   // Check that both paths come from the same If
1258   Node *ifp1 = region->in(1);
1259   Node *ifp2 = region->in(2);
1260   if( !ifp1 || !ifp2 ) return 0;
1261   Node *iff = ifp1->in(0);
1262   if( !iff || !iff->is_If() ) return 0;
1263   if( iff != ifp2->in(0) ) return 0;
1264   if (check_control_only)  return -1;
1265   // Check for a proper bool/cmp
1266   const Node *b = iff->in(1);
1267   if( !b->is_Bool() ) return 0;
1268   const Node *cmp = b->in(1);
1269   if( !cmp->is_Cmp() ) return 0;
1270 
1271   // Check for branching opposite expected
1272   if( ifp2->Opcode() == Op_IfTrue ) {
1273     assert( ifp1->Opcode() == Op_IfFalse, "" );
1274     return 2;
1275   } else {
1276     assert( ifp1->Opcode() == Op_IfTrue, "" );
1277     return 1;
1278   }
1279 }
1280 
1281 //----------------------------check_cmove_id-----------------------------------
1282 // Check for CMove'ing a constant after comparing against the constant.
1283 // Happens all the time now, since if we compare equality vs a constant in
1284 // the parser, we "know" the variable is constant on one path and we force
1285 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1286 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1287 // general in that we don't need constants.  Since CMove's are only inserted
1288 // in very special circumstances, we do it here on generic Phi's.
1289 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1290   assert(true_path !=0, "only diamond shape graph expected");
1291 
1292   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1293   // phi->region->if_proj->ifnode->bool->cmp
1294   Node*     region = in(0);
1295   Node*     iff    = region->in(1)->in(0);
1296   BoolNode* b      = iff->in(1)->as_Bool();
1297   Node*     cmp    = b->in(1);
1298   Node*     tval   = in(true_path);
1299   Node*     fval   = in(3-true_path);
1300   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1301   if (id == NULL)
1302     return NULL;
1303 
1304   // Either value might be a cast that depends on a branch of 'iff'.
1305   // Since the 'id' value will float free of the diamond, either
1306   // decast or return failure.
1307   Node* ctl = id->in(0);
1308   if (ctl != NULL && ctl->in(0) == iff) {
1309     if (id->is_ConstraintCast()) {
1310       return id->in(1);
1311     } else {
1312       // Don't know how to disentangle this value.
1313       return NULL;
1314     }
1315   }
1316 
1317   return id;
1318 }
1319 
1320 //------------------------------Identity---------------------------------------
1321 // Check for Region being Identity.
1322 Node* PhiNode::Identity(PhaseGVN* phase) {
1323   // Check for no merging going on
1324   // (There used to be special-case code here when this->region->is_Loop.
1325   // It would check for a tributary phi on the backedge that the main phi
1326   // trivially, perhaps with a single cast.  The unique_input method
1327   // does all this and more, by reducing such tributaries to 'this'.)
1328   Node* uin = unique_input(phase, false);
1329   if (uin != NULL) {
1330     return uin;
1331   }
1332 
1333   int true_path = is_diamond_phi();
1334   if (true_path != 0) {
1335     Node* id = is_cmove_id(phase, true_path);
1336     if (id != NULL)  return id;
1337   }
1338 
1339   return this;                     // No identity
1340 }
1341 
1342 //-----------------------------unique_input------------------------------------
1343 // Find the unique value, discounting top, self-loops, and casts.
1344 // Return top if there are no inputs, and self if there are multiple.
1345 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1346   //  1) One unique direct input,
1347   // or if uncast is true:
1348   //  2) some of the inputs have an intervening ConstraintCast
1349   //  3) an input is a self loop
1350   //
1351   //  1) input   or   2) input     or   3) input __
1352   //     /   \           /   \               \  /  \
1353   //     \   /          |    cast             phi  cast
1354   //      phi            \   /               /  \  /
1355   //                      phi               /    --
1356 
1357   Node* r = in(0);                      // RegionNode
1358   if (r == NULL)  return in(1);         // Already degraded to a Copy
1359   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1360 
1361   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1362     Node* rc = r->in(i);
1363     if (rc == NULL || phase->type(rc) == Type::TOP)
1364       continue;                 // ignore unreachable control path
1365     Node* n = in(i);
1366     if (n == NULL)
1367       continue;
1368     Node* un = n;
1369     if (uncast) {
1370 #ifdef ASSERT
1371       Node* m = un->uncast();
1372 #endif
1373       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1374         Node* next = un->in(1);
1375         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1376           // risk exposing raw ptr at safepoint
1377           break;
1378         }
1379         un = next;
1380       }
1381       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1382     }
1383     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1384       continue; // ignore if top, or in(i) and "this" are in a data cycle
1385     }
1386     // Check for a unique input (maybe uncasted)
1387     if (input == NULL) {
1388       input = un;
1389     } else if (input != un) {
1390       input = NodeSentinel; // no unique input
1391     }
1392   }
1393   if (input == NULL) {
1394     return phase->C->top();        // no inputs
1395   }
1396 
1397   if (input != NodeSentinel) {
1398     return input;           // one unique direct input
1399   }
1400 
1401   // Nothing.
1402   return NULL;
1403 }
1404 
1405 //------------------------------is_x2logic-------------------------------------
1406 // Check for simple convert-to-boolean pattern
1407 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1408 // Convert Phi to an ConvIB.
1409 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1410   assert(true_path !=0, "only diamond shape graph expected");
1411   // Convert the true/false index into an expected 0/1 return.
1412   // Map 2->0 and 1->1.
1413   int flipped = 2-true_path;
1414 
1415   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1416   // phi->region->if_proj->ifnode->bool->cmp
1417   Node *region = phi->in(0);
1418   Node *iff = region->in(1)->in(0);
1419   BoolNode *b = (BoolNode*)iff->in(1);
1420   const CmpNode *cmp = (CmpNode*)b->in(1);
1421 
1422   Node *zero = phi->in(1);
1423   Node *one  = phi->in(2);
1424   const Type *tzero = phase->type( zero );
1425   const Type *tone  = phase->type( one  );
1426 
1427   // Check for compare vs 0
1428   const Type *tcmp = phase->type(cmp->in(2));
1429   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1430     // Allow cmp-vs-1 if the other input is bounded by 0-1
1431     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1432       return NULL;
1433     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1434   }
1435 
1436   // Check for setting zero/one opposite expected
1437   if( tzero == TypeInt::ZERO ) {
1438     if( tone == TypeInt::ONE ) {
1439     } else return NULL;
1440   } else if( tzero == TypeInt::ONE ) {
1441     if( tone == TypeInt::ZERO ) {
1442       flipped = 1-flipped;
1443     } else return NULL;
1444   } else return NULL;
1445 
1446   // Check for boolean test backwards
1447   if( b->_test._test == BoolTest::ne ) {
1448   } else if( b->_test._test == BoolTest::eq ) {
1449     flipped = 1-flipped;
1450   } else return NULL;
1451 
1452   // Build int->bool conversion
1453   Node *n = new Conv2BNode(cmp->in(1));
1454   if( flipped )
1455     n = new XorINode( phase->transform(n), phase->intcon(1) );
1456 
1457   return n;
1458 }
1459 
1460 //------------------------------is_cond_add------------------------------------
1461 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1462 // To be profitable the control flow has to disappear; there can be no other
1463 // values merging here.  We replace the test-and-branch with:
1464 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1465 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1466 // Then convert Y to 0-or-Y and finally add.
1467 // This is a key transform for SpecJava _201_compress.
1468 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1469   assert(true_path !=0, "only diamond shape graph expected");
1470 
1471   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1472   // phi->region->if_proj->ifnode->bool->cmp
1473   RegionNode *region = (RegionNode*)phi->in(0);
1474   Node *iff = region->in(1)->in(0);
1475   BoolNode* b = iff->in(1)->as_Bool();
1476   const CmpNode *cmp = (CmpNode*)b->in(1);
1477 
1478   // Make sure only merging this one phi here
1479   if (region->has_unique_phi() != phi)  return NULL;
1480 
1481   // Make sure each arm of the diamond has exactly one output, which we assume
1482   // is the region.  Otherwise, the control flow won't disappear.
1483   if (region->in(1)->outcnt() != 1) return NULL;
1484   if (region->in(2)->outcnt() != 1) return NULL;
1485 
1486   // Check for "(P < Q)" of type signed int
1487   if (b->_test._test != BoolTest::lt)  return NULL;
1488   if (cmp->Opcode() != Op_CmpI)        return NULL;
1489 
1490   Node *p = cmp->in(1);
1491   Node *q = cmp->in(2);
1492   Node *n1 = phi->in(  true_path);
1493   Node *n2 = phi->in(3-true_path);
1494 
1495   int op = n1->Opcode();
1496   if( op != Op_AddI           // Need zero as additive identity
1497       /*&&op != Op_SubI &&
1498       op != Op_AddP &&
1499       op != Op_XorI &&
1500       op != Op_OrI*/ )
1501     return NULL;
1502 
1503   Node *x = n2;
1504   Node *y = NULL;
1505   if( x == n1->in(1) ) {
1506     y = n1->in(2);
1507   } else if( x == n1->in(2) ) {
1508     y = n1->in(1);
1509   } else return NULL;
1510 
1511   // Not so profitable if compare and add are constants
1512   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1513     return NULL;
1514 
1515   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1516   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1517   return new AddINode(j_and,x);
1518 }
1519 
1520 //------------------------------is_absolute------------------------------------
1521 // Check for absolute value.
1522 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1523   assert(true_path !=0, "only diamond shape graph expected");
1524 
1525   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1526   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1527 
1528   // ABS ends with the merge of 2 control flow paths.
1529   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1530   int false_path = 3 - true_path;
1531 
1532   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1533   // phi->region->if_proj->ifnode->bool->cmp
1534   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1535 
1536   // Check bool sense
1537   switch( bol->_test._test ) {
1538   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1539   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1540   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1541   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1542   default:           return NULL;                              break;
1543   }
1544 
1545   // Test is next
1546   Node *cmp = bol->in(1);
1547   const Type *tzero = NULL;
1548   switch( cmp->Opcode() ) {
1549   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1550   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1551   default: return NULL;
1552   }
1553 
1554   // Find zero input of compare; the other input is being abs'd
1555   Node *x = NULL;
1556   bool flip = false;
1557   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1558     x = cmp->in(3 - cmp_zero_idx);
1559   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1560     // The test is inverted, we should invert the result...
1561     x = cmp->in(cmp_zero_idx);
1562     flip = true;
1563   } else {
1564     return NULL;
1565   }
1566 
1567   // Next get the 2 pieces being selected, one is the original value
1568   // and the other is the negated value.
1569   if( phi_root->in(phi_x_idx) != x ) return NULL;
1570 
1571   // Check other phi input for subtract node
1572   Node *sub = phi_root->in(3 - phi_x_idx);
1573 
1574   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1575   if( tzero == TypeF::ZERO ) {
1576     if( sub->Opcode() != Op_SubF ||
1577         sub->in(2) != x ||
1578         phase->type(sub->in(1)) != tzero ) return NULL;
1579     x = new AbsFNode(x);
1580     if (flip) {
1581       x = new SubFNode(sub->in(1), phase->transform(x));
1582     }
1583   } else {
1584     if( sub->Opcode() != Op_SubD ||
1585         sub->in(2) != x ||
1586         phase->type(sub->in(1)) != tzero ) return NULL;
1587     x = new AbsDNode(x);
1588     if (flip) {
1589       x = new SubDNode(sub->in(1), phase->transform(x));
1590     }
1591   }
1592 
1593   return x;
1594 }
1595 
1596 //------------------------------split_once-------------------------------------
1597 // Helper for split_flow_path
1598 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1599   igvn->hash_delete(n);         // Remove from hash before hacking edges
1600 
1601   uint j = 1;
1602   for (uint i = phi->req()-1; i > 0; i--) {
1603     if (phi->in(i) == val) {   // Found a path with val?
1604       // Add to NEW Region/Phi, no DU info
1605       newn->set_req( j++, n->in(i) );
1606       // Remove from OLD Region/Phi
1607       n->del_req(i);
1608     }
1609   }
1610 
1611   // Register the new node but do not transform it.  Cannot transform until the
1612   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1613   igvn->register_new_node_with_optimizer( newn );
1614 
1615   // Now I can point to the new node.
1616   n->add_req(newn);
1617   igvn->_worklist.push(n);
1618 }
1619 
1620 //------------------------------split_flow_path--------------------------------
1621 // Check for merging identical values and split flow paths
1622 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1623   BasicType bt = phi->type()->basic_type();
1624   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1625     return NULL;                // Bail out on funny non-value stuff
1626   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1627     return NULL;                // third unequal input to be worth doing
1628 
1629   // Scan for a constant
1630   uint i;
1631   for( i = 1; i < phi->req()-1; i++ ) {
1632     Node *n = phi->in(i);
1633     if( !n ) return NULL;
1634     if( phase->type(n) == Type::TOP ) return NULL;
1635     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1636       break;
1637   }
1638   if( i >= phi->req() )         // Only split for constants
1639     return NULL;
1640 
1641   Node *val = phi->in(i);       // Constant to split for
1642   uint hit = 0;                 // Number of times it occurs
1643   Node *r = phi->region();
1644 
1645   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1646     Node *n = phi->in(i);
1647     if( !n ) return NULL;
1648     if( phase->type(n) == Type::TOP ) return NULL;
1649     if( phi->in(i) == val ) {
1650       hit++;
1651       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1652         return NULL;            // don't split loop entry path
1653       }
1654     }
1655   }
1656 
1657   if( hit <= 1 ||               // Make sure we find 2 or more
1658       hit == phi->req()-1 )     // and not ALL the same value
1659     return NULL;
1660 
1661   // Now start splitting out the flow paths that merge the same value.
1662   // Split first the RegionNode.
1663   PhaseIterGVN *igvn = phase->is_IterGVN();
1664   RegionNode *newr = new RegionNode(hit+1);
1665   split_once(igvn, phi, val, r, newr);
1666 
1667   // Now split all other Phis than this one
1668   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1669     Node* phi2 = r->fast_out(k);
1670     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1671       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1672       split_once(igvn, phi, val, phi2, newphi);
1673     }
1674   }
1675 
1676   // Clean up this guy
1677   igvn->hash_delete(phi);
1678   for( i = phi->req()-1; i > 0; i-- ) {
1679     if( phi->in(i) == val ) {
1680       phi->del_req(i);
1681     }
1682   }
1683   phi->add_req(val);
1684 
1685   return phi;
1686 }
1687 
1688 //=============================================================================
1689 //------------------------------simple_data_loop_check-------------------------
1690 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1691 //  Returns:
1692 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1693 // Safe       - safe case when the phi and it's inputs reference only safe data
1694 //              nodes;
1695 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1696 //              is no reference back to the phi - need a graph walk
1697 //              to determine if it is in a loop;
1698 // UnsafeLoop - unsafe case when the phi references itself directly or through
1699 //              unsafe data node.
1700 //  Note: a safe data node is a node which could/never reference itself during
1701 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1702 //  I mark Phi nodes as safe node not only because they can reference itself
1703 //  but also to prevent mistaking the fallthrough case inside an outer loop
1704 //  as dead loop when the phi references itselfs through an other phi.
1705 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1706   // It is unsafe loop if the phi node references itself directly.
1707   if (in == (Node*)this)
1708     return UnsafeLoop; // Unsafe loop
1709   // Unsafe loop if the phi node references itself through an unsafe data node.
1710   // Exclude cases with null inputs or data nodes which could reference
1711   // itself (safe for dead loops).
1712   if (in != NULL && !in->is_dead_loop_safe()) {
1713     // Check inputs of phi's inputs also.
1714     // It is much less expensive then full graph walk.
1715     uint cnt = in->req();
1716     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1717     for (; i < cnt; ++i) {
1718       Node* m = in->in(i);
1719       if (m == (Node*)this)
1720         return UnsafeLoop; // Unsafe loop
1721       if (m != NULL && !m->is_dead_loop_safe()) {
1722         // Check the most common case (about 30% of all cases):
1723         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1724         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1725         if (m1 == (Node*)this)
1726           return UnsafeLoop; // Unsafe loop
1727         if (m1 != NULL && m1 == m->in(2) &&
1728             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1729           continue; // Safe case
1730         }
1731         // The phi references an unsafe node - need full analysis.
1732         return Unsafe;
1733       }
1734     }
1735   }
1736   return Safe; // Safe case - we can optimize the phi node.
1737 }
1738 
1739 //------------------------------is_unsafe_data_reference-----------------------
1740 // If phi can be reached through the data input - it is data loop.
1741 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1742   assert(req() > 1, "");
1743   // First, check simple cases when phi references itself directly or
1744   // through an other node.
1745   LoopSafety safety = simple_data_loop_check(in);
1746   if (safety == UnsafeLoop)
1747     return true;  // phi references itself - unsafe loop
1748   else if (safety == Safe)
1749     return false; // Safe case - phi could be replaced with the unique input.
1750 
1751   // Unsafe case when we should go through data graph to determine
1752   // if the phi references itself.
1753 
1754   ResourceMark rm;
1755 
1756   Arena *a = Thread::current()->resource_area();
1757   Node_List nstack(a);
1758   VectorSet visited(a);
1759 
1760   nstack.push(in); // Start with unique input.
1761   visited.set(in->_idx);
1762   while (nstack.size() != 0) {
1763     Node* n = nstack.pop();
1764     uint cnt = n->req();
1765     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1766     for (; i < cnt; i++) {
1767       Node* m = n->in(i);
1768       if (m == (Node*)this) {
1769         return true;    // Data loop
1770       }
1771       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1772         if (!visited.test_set(m->_idx))
1773           nstack.push(m);
1774       }
1775     }
1776   }
1777   return false; // The phi is not reachable from its inputs
1778 }
1779 
1780 // Is this Phi's region or some inputs to the region enqueued for IGVN
1781 // and so could cause the region to be optimized out?
1782 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1783   PhaseIterGVN* igvn = phase->is_IterGVN();
1784   Unique_Node_List& worklist = igvn->_worklist;
1785   bool delay = false;
1786   Node* r = in(0);
1787   for (uint j = 1; j < req(); j++) {
1788     Node* rc = r->in(j);
1789     Node* n = in(j);
1790     if (rc != NULL &&
1791         rc->is_Proj()) {
1792       if (worklist.member(rc)) {
1793         delay = true;
1794       } else if (rc->in(0) != NULL &&
1795                  rc->in(0)->is_If()) {
1796         if (worklist.member(rc->in(0))) {
1797           delay = true;
1798         } else if (rc->in(0)->in(1) != NULL &&
1799                    rc->in(0)->in(1)->is_Bool()) {
1800           if (worklist.member(rc->in(0)->in(1))) {
1801             delay = true;
1802           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1803                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1804             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1805               delay = true;
1806             }
1807           }
1808         }
1809       }
1810     }
1811   }
1812   if (delay) {
1813     worklist.push(this);
1814   }
1815   return delay;
1816 }
1817 
1818 //------------------------------Ideal------------------------------------------
1819 // Return a node which is more "ideal" than the current node.  Must preserve
1820 // the CFG, but we can still strip out dead paths.
1821 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1822   // The next should never happen after 6297035 fix.
1823   if( is_copy() )               // Already degraded to a Copy ?
1824     return NULL;                // No change
1825 
1826   Node *r = in(0);              // RegionNode
1827   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1828 
1829   // Note: During parsing, phis are often transformed before their regions.
1830   // This means we have to use type_or_null to defend against untyped regions.
1831   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1832     return NULL;                // No change
1833 
1834   Node *top = phase->C->top();
1835   bool new_phi = (outcnt() == 0); // transforming new Phi
1836   // No change for igvn if new phi is not hooked
1837   if (new_phi && can_reshape)
1838     return NULL;
1839 
1840   // The are 2 situations when only one valid phi's input is left
1841   // (in addition to Region input).
1842   // One: region is not loop - replace phi with this input.
1843   // Two: region is loop - replace phi with top since this data path is dead
1844   //                       and we need to break the dead data loop.
1845   Node* progress = NULL;        // Record if any progress made
1846   for( uint j = 1; j < req(); ++j ){ // For all paths in
1847     // Check unreachable control paths
1848     Node* rc = r->in(j);
1849     Node* n = in(j);            // Get the input
1850     if (rc == NULL || phase->type(rc) == Type::TOP) {
1851       if (n != top) {           // Not already top?
1852         PhaseIterGVN *igvn = phase->is_IterGVN();
1853         if (can_reshape && igvn != NULL) {
1854           igvn->_worklist.push(r);
1855         }
1856         // Nuke it down
1857         if (can_reshape) {
1858           set_req_X(j, top, igvn);
1859         } else {
1860           set_req(j, top);
1861         }
1862         progress = this;        // Record progress
1863       }
1864     }
1865   }
1866 
1867   if (can_reshape && outcnt() == 0) {
1868     // set_req() above may kill outputs if Phi is referenced
1869     // only by itself on the dead (top) control path.
1870     return top;
1871   }
1872 
1873   bool uncasted = false;
1874   Node* uin = unique_input(phase, false);
1875   if (uin == NULL && can_reshape &&
1876       // If there is a chance that the region can be optimized out do
1877       // not add a cast node that we can't remove yet.
1878       !wait_for_region_igvn(phase)) {
1879     uncasted = true;
1880     uin = unique_input(phase, true);
1881   }
1882   if (uin == top) {             // Simplest case: no alive inputs.
1883     if (can_reshape)            // IGVN transformation
1884       return top;
1885     else
1886       return NULL;              // Identity will return TOP
1887   } else if (uin != NULL) {
1888     // Only one not-NULL unique input path is left.
1889     // Determine if this input is backedge of a loop.
1890     // (Skip new phis which have no uses and dead regions).
1891     if (outcnt() > 0 && r->in(0) != NULL) {
1892       // First, take the short cut when we know it is a loop and
1893       // the EntryControl data path is dead.
1894       // Loop node may have only one input because entry path
1895       // is removed in PhaseIdealLoop::Dominators().
1896       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1897       bool is_loop = (r->is_Loop() && r->req() == 3);
1898       // Then, check if there is a data loop when phi references itself directly
1899       // or through other data nodes.
1900       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1901           (!is_loop && is_unsafe_data_reference(uin))) {
1902         // Break this data loop to avoid creation of a dead loop.
1903         if (can_reshape) {
1904           return top;
1905         } else {
1906           // We can't return top if we are in Parse phase - cut inputs only
1907           // let Identity to handle the case.
1908           replace_edge(uin, top);
1909           return NULL;
1910         }
1911       }
1912     }
1913 
1914     if (uncasted) {
1915       // Add cast nodes between the phi to be removed and its unique input.
1916       // Wait until after parsing for the type information to propagate from the casts.
1917       assert(can_reshape, "Invalid during parsing");
1918       const Type* phi_type = bottom_type();
1919       assert(phi_type->isa_int() || phi_type->isa_long() || phi_type->isa_ptr(), "bad phi type");
1920       // Add casts to carry the control dependency of the Phi that is going away
1921       Node* cast = NULL;
1922       if (phi_type->isa_int()) {
1923         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1924       } else if (phi_type->isa_long()) {
1925         cast = ConstraintCastNode::make_cast(Op_CastLL, r, uin, phi_type, true);
1926       } else {
1927         const Type* uin_type = phase->type(uin);
1928         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1929           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1930         } else {
1931           // Use a CastPP for a cast to not null and a CheckCastPP for
1932           // a cast to a new klass (and both if both null-ness and
1933           // klass change).
1934 
1935           // If the type of phi is not null but the type of uin may be
1936           // null, uin's type must be casted to not null
1937           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1938               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1939             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1940           }
1941 
1942           // If the type of phi and uin, both casted to not null,
1943           // differ the klass of uin must be (check)cast'ed to match
1944           // that of phi
1945           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1946             Node* n = uin;
1947             if (cast != NULL) {
1948               cast = phase->transform(cast);
1949               n = cast;
1950             }
1951             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
1952           }
1953           if (cast == NULL) {
1954             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1955           }
1956         }
1957       }
1958       assert(cast != NULL, "cast should be set");
1959       cast = phase->transform(cast);
1960       // set all inputs to the new cast(s) so the Phi is removed by Identity
1961       PhaseIterGVN* igvn = phase->is_IterGVN();
1962       for (uint i = 1; i < req(); i++) {
1963         set_req_X(i, cast, igvn);
1964       }
1965       uin = cast;
1966     }
1967 
1968     // One unique input.
1969     debug_only(Node* ident = Identity(phase));
1970     // The unique input must eventually be detected by the Identity call.
1971 #ifdef ASSERT
1972     if (ident != uin && !ident->is_top()) {
1973       // print this output before failing assert
1974       r->dump(3);
1975       this->dump(3);
1976       ident->dump();
1977       uin->dump();
1978     }
1979 #endif
1980     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1981     return NULL;
1982   }
1983 
1984   Node* opt = NULL;
1985   int true_path = is_diamond_phi();
1986   if( true_path != 0 ) {
1987     // Check for CMove'ing identity. If it would be unsafe,
1988     // handle it here. In the safe case, let Identity handle it.
1989     Node* unsafe_id = is_cmove_id(phase, true_path);
1990     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1991       opt = unsafe_id;
1992 
1993     // Check for simple convert-to-boolean pattern
1994     if( opt == NULL )
1995       opt = is_x2logic(phase, this, true_path);
1996 
1997     // Check for absolute value
1998     if( opt == NULL )
1999       opt = is_absolute(phase, this, true_path);
2000 
2001     // Check for conditional add
2002     if( opt == NULL && can_reshape )
2003       opt = is_cond_add(phase, this, true_path);
2004 
2005     // These 4 optimizations could subsume the phi:
2006     // have to check for a dead data loop creation.
2007     if( opt != NULL ) {
2008       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2009         // Found dead loop.
2010         if( can_reshape )
2011           return top;
2012         // We can't return top if we are in Parse phase - cut inputs only
2013         // to stop further optimizations for this phi. Identity will return TOP.
2014         assert(req() == 3, "only diamond merge phi here");
2015         set_req(1, top);
2016         set_req(2, top);
2017         return NULL;
2018       } else {
2019         return opt;
2020       }
2021     }
2022   }
2023 
2024   // Check for merging identical values and split flow paths
2025   if (can_reshape) {
2026     opt = split_flow_path(phase, this);
2027     // This optimization only modifies phi - don't need to check for dead loop.
2028     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
2029     if (opt != NULL)  return opt;
2030   }
2031 
2032   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2033     // Try to undo Phi of AddP:
2034     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2035     // becomes:
2036     // newbase := (Phi base base2)
2037     // newaddress := (Phi address address2)
2038     // newoffset := (Phi offset offset2)
2039     // (AddP newbase newaddress newoffset)
2040     //
2041     // This occurs as a result of unsuccessful split_thru_phi and
2042     // interferes with taking advantage of addressing modes. See the
2043     // clone_shift_expressions code in matcher.cpp
2044     Node* addp = in(1);
2045     Node* base = addp->in(AddPNode::Base);
2046     Node* address = addp->in(AddPNode::Address);
2047     Node* offset = addp->in(AddPNode::Offset);
2048     if (base != NULL && address != NULL && offset != NULL &&
2049         !base->is_top() && !address->is_top() && !offset->is_top()) {
2050       const Type* base_type = base->bottom_type();
2051       const Type* address_type = address->bottom_type();
2052       // make sure that all the inputs are similar to the first one,
2053       // i.e. AddP with base == address and same offset as first AddP
2054       bool doit = true;
2055       for (uint i = 2; i < req(); i++) {
2056         if (in(i) == NULL ||
2057             in(i)->Opcode() != Op_AddP ||
2058             in(i)->in(AddPNode::Base) == NULL ||
2059             in(i)->in(AddPNode::Address) == NULL ||
2060             in(i)->in(AddPNode::Offset) == NULL ||
2061             in(i)->in(AddPNode::Base)->is_top() ||
2062             in(i)->in(AddPNode::Address)->is_top() ||
2063             in(i)->in(AddPNode::Offset)->is_top()) {
2064           doit = false;
2065           break;
2066         }
2067         if (in(i)->in(AddPNode::Offset) != base) {
2068           base = NULL;
2069         }
2070         if (in(i)->in(AddPNode::Offset) != offset) {
2071           offset = NULL;
2072         }
2073         if (in(i)->in(AddPNode::Address) != address) {
2074           address = NULL;
2075         }
2076         // Accumulate type for resulting Phi
2077         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2078         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2079       }
2080       if (doit && base == NULL) {
2081         // Check for neighboring AddP nodes in a tree.
2082         // If they have a base, use that it.
2083         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2084           Node* u = this->fast_out(k);
2085           if (u->is_AddP()) {
2086             Node* base2 = u->in(AddPNode::Base);
2087             if (base2 != NULL && !base2->is_top()) {
2088               if (base == NULL)
2089                 base = base2;
2090               else if (base != base2)
2091                 { doit = false; break; }
2092             }
2093           }
2094         }
2095       }
2096       if (doit) {
2097         if (base == NULL) {
2098           base = new PhiNode(in(0), base_type, NULL);
2099           for (uint i = 1; i < req(); i++) {
2100             base->init_req(i, in(i)->in(AddPNode::Base));
2101           }
2102           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2103         }
2104         if (address == NULL) {
2105           address = new PhiNode(in(0), address_type, NULL);
2106           for (uint i = 1; i < req(); i++) {
2107             address->init_req(i, in(i)->in(AddPNode::Address));
2108           }
2109           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2110         }
2111         if (offset == NULL) {
2112           offset = new PhiNode(in(0), TypeX_X, NULL);
2113           for (uint i = 1; i < req(); i++) {
2114             offset->init_req(i, in(i)->in(AddPNode::Offset));
2115           }
2116           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2117         }
2118         return new AddPNode(base, address, offset);
2119       }
2120     }
2121   }
2122 
2123   // Split phis through memory merges, so that the memory merges will go away.
2124   // Piggy-back this transformation on the search for a unique input....
2125   // It will be as if the merged memory is the unique value of the phi.
2126   // (Do not attempt this optimization unless parsing is complete.
2127   // It would make the parser's memory-merge logic sick.)
2128   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2129   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2130     // see if this phi should be sliced
2131     uint merge_width = 0;
2132     bool saw_self = false;
2133     for( uint i=1; i<req(); ++i ) {// For all paths in
2134       Node *ii = in(i);
2135       // TOP inputs should not be counted as safe inputs because if the
2136       // Phi references itself through all other inputs then splitting the
2137       // Phi through memory merges would create dead loop at later stage.
2138       if (ii == top) {
2139         return NULL; // Delay optimization until graph is cleaned.
2140       }
2141       if (ii->is_MergeMem()) {
2142         MergeMemNode* n = ii->as_MergeMem();
2143         merge_width = MAX2(merge_width, n->req());
2144         saw_self = saw_self || phase->eqv(n->base_memory(), this);
2145       }
2146     }
2147 
2148     // This restriction is temporarily necessary to ensure termination:
2149     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2150 
2151     if (merge_width > Compile::AliasIdxRaw) {
2152       // found at least one non-empty MergeMem
2153       const TypePtr* at = adr_type();
2154       if (at != TypePtr::BOTTOM) {
2155         // Patch the existing phi to select an input from the merge:
2156         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2157         //     Phi:AT1(...m1...)
2158         int alias_idx = phase->C->get_alias_index(at);
2159         for (uint i=1; i<req(); ++i) {
2160           Node *ii = in(i);
2161           if (ii->is_MergeMem()) {
2162             MergeMemNode* n = ii->as_MergeMem();
2163             // compress paths and change unreachable cycles to TOP
2164             // If not, we can update the input infinitely along a MergeMem cycle
2165             // Equivalent code is in MemNode::Ideal_common
2166             Node *m  = phase->transform(n);
2167             if (outcnt() == 0) {  // Above transform() may kill us!
2168               return top;
2169             }
2170             // If transformed to a MergeMem, get the desired slice
2171             // Otherwise the returned node represents memory for every slice
2172             Node *new_mem = (m->is_MergeMem()) ?
2173                              m->as_MergeMem()->memory_at(alias_idx) : m;
2174             // Update input if it is progress over what we have now
2175             if (new_mem != ii) {
2176               set_req(i, new_mem);
2177               progress = this;
2178             }
2179           }
2180         }
2181       } else {
2182         // We know that at least one MergeMem->base_memory() == this
2183         // (saw_self == true). If all other inputs also references this phi
2184         // (directly or through data nodes) - it is dead loop.
2185         bool saw_safe_input = false;
2186         for (uint j = 1; j < req(); ++j) {
2187           Node *n = in(j);
2188           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
2189             continue;              // skip known cases
2190           if (!is_unsafe_data_reference(n)) {
2191             saw_safe_input = true; // found safe input
2192             break;
2193           }
2194         }
2195         if (!saw_safe_input)
2196           return top; // all inputs reference back to this phi - dead loop
2197 
2198         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2199         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2200         PhaseIterGVN *igvn = phase->is_IterGVN();
2201         Node* hook = new Node(1);
2202         PhiNode* new_base = (PhiNode*) clone();
2203         // Must eagerly register phis, since they participate in loops.
2204         if (igvn) {
2205           igvn->register_new_node_with_optimizer(new_base);
2206           hook->add_req(new_base);
2207         }
2208         MergeMemNode* result = MergeMemNode::make(new_base);
2209         for (uint i = 1; i < req(); ++i) {
2210           Node *ii = in(i);
2211           if (ii->is_MergeMem()) {
2212             MergeMemNode* n = ii->as_MergeMem();
2213             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2214               // If we have not seen this slice yet, make a phi for it.
2215               bool made_new_phi = false;
2216               if (mms.is_empty()) {
2217                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2218                 made_new_phi = true;
2219                 if (igvn) {
2220                   igvn->register_new_node_with_optimizer(new_phi);
2221                   hook->add_req(new_phi);
2222                 }
2223                 mms.set_memory(new_phi);
2224               }
2225               Node* phi = mms.memory();
2226               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2227               phi->set_req(i, mms.memory2());
2228             }
2229           }
2230         }
2231         // Distribute all self-loops.
2232         { // (Extra braces to hide mms.)
2233           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2234             Node* phi = mms.memory();
2235             for (uint i = 1; i < req(); ++i) {
2236               if (phi->in(i) == this)  phi->set_req(i, phi);
2237             }
2238           }
2239         }
2240         // now transform the new nodes, and return the mergemem
2241         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2242           Node* phi = mms.memory();
2243           mms.set_memory(phase->transform(phi));
2244         }
2245         if (igvn) { // Unhook.
2246           igvn->hash_delete(hook);
2247           for (uint i = 1; i < hook->req(); i++) {
2248             hook->set_req(i, NULL);
2249           }
2250         }
2251         // Replace self with the result.
2252         return result;
2253       }
2254     }
2255     //
2256     // Other optimizations on the memory chain
2257     //
2258     const TypePtr* at = adr_type();
2259     for( uint i=1; i<req(); ++i ) {// For all paths in
2260       Node *ii = in(i);
2261       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2262       if (ii != new_in ) {
2263         set_req(i, new_in);
2264         progress = this;
2265       }
2266     }
2267   }
2268 
2269 #ifdef _LP64
2270   // Push DecodeN/DecodeNKlass down through phi.
2271   // The rest of phi graph will transform by split EncodeP node though phis up.
2272   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2273     bool may_push = true;
2274     bool has_decodeN = false;
2275     bool is_decodeN = false;
2276     for (uint i=1; i<req(); ++i) {// For all paths in
2277       Node *ii = in(i);
2278       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2279         // Do optimization if a non dead path exist.
2280         if (ii->in(1)->bottom_type() != Type::TOP) {
2281           has_decodeN = true;
2282           is_decodeN = ii->is_DecodeN();
2283         }
2284       } else if (!ii->is_Phi()) {
2285         may_push = false;
2286       }
2287     }
2288 
2289     if (has_decodeN && may_push) {
2290       PhaseIterGVN *igvn = phase->is_IterGVN();
2291       // Make narrow type for new phi.
2292       const Type* narrow_t;
2293       if (is_decodeN) {
2294         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2295       } else {
2296         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2297       }
2298       PhiNode* new_phi = new PhiNode(r, narrow_t);
2299       uint orig_cnt = req();
2300       for (uint i=1; i<req(); ++i) {// For all paths in
2301         Node *ii = in(i);
2302         Node* new_ii = NULL;
2303         if (ii->is_DecodeNarrowPtr()) {
2304           assert(ii->bottom_type() == bottom_type(), "sanity");
2305           new_ii = ii->in(1);
2306         } else {
2307           assert(ii->is_Phi(), "sanity");
2308           if (ii->as_Phi() == this) {
2309             new_ii = new_phi;
2310           } else {
2311             if (is_decodeN) {
2312               new_ii = new EncodePNode(ii, narrow_t);
2313             } else {
2314               new_ii = new EncodePKlassNode(ii, narrow_t);
2315             }
2316             igvn->register_new_node_with_optimizer(new_ii);
2317           }
2318         }
2319         new_phi->set_req(i, new_ii);
2320       }
2321       igvn->register_new_node_with_optimizer(new_phi, this);
2322       if (is_decodeN) {
2323         progress = new DecodeNNode(new_phi, bottom_type());
2324       } else {
2325         progress = new DecodeNKlassNode(new_phi, bottom_type());
2326       }
2327     }
2328   }
2329 #endif
2330 
2331   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2332   if (EnableVectorReboxing && can_reshape && progress == NULL) {
2333     PhaseIterGVN *igvn = phase->is_IterGVN();
2334 
2335     bool all_inputs_are_equiv_vboxes = true;
2336     for (uint i = 1; i < req(); ++i) {
2337       Node *n = in(i);
2338       if (in(i)->Opcode() != Op_VectorBox) {
2339         all_inputs_are_equiv_vboxes = false;
2340         break;
2341       }
2342       // Check that vector type of vboxes is equivalent
2343       if (i != 1) {
2344         if (Type::cmp(in(i-0)->in(VectorBoxNode::Value)->bottom_type(),
2345                       in(i-1)->in(VectorBoxNode::Value)->bottom_type()) != 0) {
2346           all_inputs_are_equiv_vboxes = false;
2347           break;
2348         }
2349         if (Type::cmp(in(i-0)->in(VectorBoxNode::Box)->bottom_type(),
2350                       in(i-1)->in(VectorBoxNode::Box)->bottom_type()) != 0) {
2351           all_inputs_are_equiv_vboxes = false;
2352           break;
2353         }
2354       }
2355     }
2356 
2357     if (all_inputs_are_equiv_vboxes) {
2358       VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in(1));
2359       PhiNode* new_vbox_phi = new PhiNode(r, vbox->box_type());
2360       PhiNode* new_vect_phi = new PhiNode(r, vbox->vec_type());
2361       for (uint i = 1; i < req(); ++i) {
2362         VectorBoxNode* old_vbox = static_cast<VectorBoxNode*>(in(i));
2363         new_vbox_phi->set_req(i, old_vbox->in(VectorBoxNode::Box));
2364         new_vect_phi->set_req(i, old_vbox->in(VectorBoxNode::Value));
2365       }
2366       igvn->register_new_node_with_optimizer(new_vbox_phi, this);
2367       igvn->register_new_node_with_optimizer(new_vect_phi, this);
2368       progress = new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, vbox->box_type(), vbox->vec_type());
2369     }
2370   }
2371 
2372   return progress;              // Return any progress
2373 }
2374 
2375 //------------------------------is_tripcount-----------------------------------
2376 bool PhiNode::is_tripcount() const {
2377   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2378           in(0)->as_CountedLoop()->phi() == this);
2379 }
2380 
2381 //------------------------------out_RegMask------------------------------------
2382 const RegMask &PhiNode::in_RegMask(uint i) const {
2383   return i ? out_RegMask() : RegMask::Empty;
2384 }
2385 
2386 const RegMask &PhiNode::out_RegMask() const {
2387   uint ideal_reg = _type->ideal_reg();
2388   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2389   if( ideal_reg == 0 ) return RegMask::Empty;
2390   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2391   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2392 }
2393 
2394 #ifndef PRODUCT
2395 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2396   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2397   // and all outputs till level 1. In compact mode, inputs till level 1 are
2398   // collected.
2399   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2400   this->collect_nodes(out_rel, -1, false, false);
2401 }
2402 
2403 void PhiNode::dump_spec(outputStream *st) const {
2404   TypeNode::dump_spec(st);
2405   if (is_tripcount()) {
2406     st->print(" #tripcount");
2407   }
2408 }
2409 #endif
2410 
2411 
2412 //=============================================================================
2413 const Type* GotoNode::Value(PhaseGVN* phase) const {
2414   // If the input is reachable, then we are executed.
2415   // If the input is not reachable, then we are not executed.
2416   return phase->type(in(0));
2417 }
2418 
2419 Node* GotoNode::Identity(PhaseGVN* phase) {
2420   return in(0);                // Simple copy of incoming control
2421 }
2422 
2423 const RegMask &GotoNode::out_RegMask() const {
2424   return RegMask::Empty;
2425 }
2426 
2427 #ifndef PRODUCT
2428 //-----------------------------related-----------------------------------------
2429 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2430 // outputs at level 1. This is regardless of compact mode.
2431 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2432   this->collect_nodes(in_rel, 1, false, false);
2433   this->collect_nodes(out_rel, -1, false, false);
2434 }
2435 #endif
2436 
2437 
2438 //=============================================================================
2439 const RegMask &JumpNode::out_RegMask() const {
2440   return RegMask::Empty;
2441 }
2442 
2443 #ifndef PRODUCT
2444 //-----------------------------related-----------------------------------------
2445 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2446 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2447 // This is regardless of compact mode.
2448 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2449   this->collect_nodes(in_rel, 1, false, false);
2450   this->collect_nodes(out_rel, -2, false, false);
2451 }
2452 #endif
2453 
2454 //=============================================================================
2455 const RegMask &JProjNode::out_RegMask() const {
2456   return RegMask::Empty;
2457 }
2458 
2459 //=============================================================================
2460 const RegMask &CProjNode::out_RegMask() const {
2461   return RegMask::Empty;
2462 }
2463 
2464 
2465 
2466 //=============================================================================
2467 
2468 uint PCTableNode::hash() const { return Node::hash() + _size; }
2469 bool PCTableNode::cmp( const Node &n ) const
2470 { return _size == ((PCTableNode&)n)._size; }
2471 
2472 const Type *PCTableNode::bottom_type() const {
2473   const Type** f = TypeTuple::fields(_size);
2474   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2475   return TypeTuple::make(_size, f);
2476 }
2477 
2478 //------------------------------Value------------------------------------------
2479 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2480 // Control, otherwise the table targets are not reachable
2481 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2482   if( phase->type(in(0)) == Type::CONTROL )
2483     return bottom_type();
2484   return Type::TOP;             // All paths dead?  Then so are we
2485 }
2486 
2487 //------------------------------Ideal------------------------------------------
2488 // Return a node which is more "ideal" than the current node.  Strip out
2489 // control copies
2490 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2491   return remove_dead_region(phase, can_reshape) ? this : NULL;
2492 }
2493 
2494 //=============================================================================
2495 uint JumpProjNode::hash() const {
2496   return Node::hash() + _dest_bci;
2497 }
2498 
2499 bool JumpProjNode::cmp( const Node &n ) const {
2500   return ProjNode::cmp(n) &&
2501     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2502 }
2503 
2504 #ifndef PRODUCT
2505 void JumpProjNode::dump_spec(outputStream *st) const {
2506   ProjNode::dump_spec(st);
2507   st->print("@bci %d ",_dest_bci);
2508 }
2509 
2510 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2511   ProjNode::dump_compact_spec(st);
2512   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2513 }
2514 
2515 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2516   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2517   this->collect_nodes(in_rel, 1, false, false);
2518   this->collect_nodes(out_rel, -1, false, false);
2519 }
2520 #endif
2521 
2522 //=============================================================================
2523 //------------------------------Value------------------------------------------
2524 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2525 // have the default "fall_through_index" path.
2526 const Type* CatchNode::Value(PhaseGVN* phase) const {
2527   // Unreachable?  Then so are all paths from here.
2528   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2529   // First assume all paths are reachable
2530   const Type** f = TypeTuple::fields(_size);
2531   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2532   // Identify cases that will always throw an exception
2533   // () rethrow call
2534   // () virtual or interface call with NULL receiver
2535   // () call is a check cast with incompatible arguments
2536   if( in(1)->is_Proj() ) {
2537     Node *i10 = in(1)->in(0);
2538     if( i10->is_Call() ) {
2539       CallNode *call = i10->as_Call();
2540       // Rethrows always throw exceptions, never return
2541       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2542         f[CatchProjNode::fall_through_index] = Type::TOP;
2543       } else if( call->req() > TypeFunc::Parms ) {
2544         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2545         // Check for null receiver to virtual or interface calls
2546         if( call->is_CallDynamicJava() &&
2547             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2548           f[CatchProjNode::fall_through_index] = Type::TOP;
2549         }
2550       } // End of if not a runtime stub
2551     } // End of if have call above me
2552   } // End of slot 1 is not a projection
2553   return TypeTuple::make(_size, f);
2554 }
2555 
2556 //=============================================================================
2557 uint CatchProjNode::hash() const {
2558   return Node::hash() + _handler_bci;
2559 }
2560 
2561 
2562 bool CatchProjNode::cmp( const Node &n ) const {
2563   return ProjNode::cmp(n) &&
2564     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2565 }
2566 
2567 
2568 //------------------------------Identity---------------------------------------
2569 // If only 1 target is possible, choose it if it is the main control
2570 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2571   // If my value is control and no other value is, then treat as ID
2572   const TypeTuple *t = phase->type(in(0))->is_tuple();
2573   if (t->field_at(_con) != Type::CONTROL)  return this;
2574   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2575   // also remove any exception table entry.  Thus we must know the call
2576   // feeding the Catch will not really throw an exception.  This is ok for
2577   // the main fall-thru control (happens when we know a call can never throw
2578   // an exception) or for "rethrow", because a further optimization will
2579   // yank the rethrow (happens when we inline a function that can throw an
2580   // exception and the caller has no handler).  Not legal, e.g., for passing
2581   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2582   // These cases MUST throw an exception via the runtime system, so the VM
2583   // will be looking for a table entry.
2584   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2585   CallNode *call;
2586   if (_con != TypeFunc::Control && // Bail out if not the main control.
2587       !(proj->is_Proj() &&      // AND NOT a rethrow
2588         proj->in(0)->is_Call() &&
2589         (call = proj->in(0)->as_Call()) &&
2590         call->entry_point() == OptoRuntime::rethrow_stub()))
2591     return this;
2592 
2593   // Search for any other path being control
2594   for (uint i = 0; i < t->cnt(); i++) {
2595     if (i != _con && t->field_at(i) == Type::CONTROL)
2596       return this;
2597   }
2598   // Only my path is possible; I am identity on control to the jump
2599   return in(0)->in(0);
2600 }
2601 
2602 
2603 #ifndef PRODUCT
2604 void CatchProjNode::dump_spec(outputStream *st) const {
2605   ProjNode::dump_spec(st);
2606   st->print("@bci %d ",_handler_bci);
2607 }
2608 #endif
2609 
2610 //=============================================================================
2611 //------------------------------Identity---------------------------------------
2612 // Check for CreateEx being Identity.
2613 Node* CreateExNode::Identity(PhaseGVN* phase) {
2614   if( phase->type(in(1)) == Type::TOP ) return in(1);
2615   if( phase->type(in(0)) == Type::TOP ) return in(0);
2616   // We only come from CatchProj, unless the CatchProj goes away.
2617   // If the CatchProj is optimized away, then we just carry the
2618   // exception oop through.
2619   CallNode *call = in(1)->in(0)->as_Call();
2620 
2621   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2622     ? this
2623     : call->in(TypeFunc::Parms);
2624 }
2625 
2626 //=============================================================================
2627 //------------------------------Value------------------------------------------
2628 // Check for being unreachable.
2629 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2630   if (!in(0) || in(0)->is_top()) return Type::TOP;
2631   return bottom_type();
2632 }
2633 
2634 //------------------------------Ideal------------------------------------------
2635 // Check for no longer being part of a loop
2636 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2637   if (can_reshape && !in(0)->is_Loop()) {
2638     // Dead code elimination can sometimes delete this projection so
2639     // if it's not there, there's nothing to do.
2640     Node* fallthru = proj_out_or_null(0);
2641     if (fallthru != NULL) {
2642       phase->is_IterGVN()->replace_node(fallthru, in(0));
2643     }
2644     return phase->C->top();
2645   }
2646   return NULL;
2647 }
2648 
2649 #ifndef PRODUCT
2650 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2651   st->print("%s", Name());
2652 }
2653 #endif