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 "memory/allocation.inline.hpp"
  28 #include "memory/resourceArea.hpp"
  29 #include "oops/objArrayKlass.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/castnode.hpp"
  32 #include "opto/cfgnode.hpp"
  33 #include "opto/connode.hpp"
  34 #include "opto/convertnode.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/machnode.hpp"
  37 #include "opto/movenode.hpp"
  38 #include "opto/narrowptrnode.hpp"
  39 #include "opto/mulnode.hpp"
  40 #include "opto/phaseX.hpp"
  41 #include "opto/regmask.hpp"
  42 #include "opto/runtime.hpp"
  43 #include "opto/subnode.hpp"
  44 #include "utilities/vmError.hpp"




  45 
  46 // Portions of code courtesy of Clifford Click
  47 
  48 // Optimization - Graph Style
  49 
  50 //=============================================================================
  51 //------------------------------Value------------------------------------------
  52 // Compute the type of the RegionNode.
  53 const Type* RegionNode::Value(PhaseGVN* phase) const {
  54   for( uint i=1; i<req(); ++i ) {       // For all paths in
  55     Node *n = in(i);            // Get Control source
  56     if( !n ) continue;          // Missing inputs are TOP
  57     if( phase->type(n) == Type::CONTROL )
  58       return Type::CONTROL;
  59   }
  60   return Type::TOP;             // All paths dead?  Then so are we
  61 }
  62 
  63 //------------------------------Identity---------------------------------------
  64 // Check for Region being Identity.
  65 Node* RegionNode::Identity(PhaseGVN* phase) {
  66   // Cannot have Region be an identity, even if it has only 1 input.
  67   // Phi users cannot have their Region input folded away for them,
  68   // since they need to select the proper data input
  69   return this;
  70 }
  71 
  72 //------------------------------merge_region-----------------------------------
  73 // If a Region flows into a Region, merge into one big happy merge.  This is
  74 // hard to do if there is stuff that has to happen
  75 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  76   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  77     return NULL;
  78   Node *progress = NULL;        // Progress flag
  79   PhaseIterGVN *igvn = phase->is_IterGVN();
  80 
  81   uint rreq = region->req();
  82   for( uint i = 1; i < rreq; i++ ) {
  83     Node *r = region->in(i);
  84     if( r && r->Opcode() == Op_Region && // Found a region?
  85         r->in(0) == r &&        // Not already collapsed?
  86         r != region &&          // Avoid stupid situations
  87         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  88       assert(!r->as_Region()->has_phi(), "no phi users");
  89       if( !progress ) {         // No progress
  90         if (region->has_phi()) {
  91           return NULL;        // Only flatten if no Phi users
  92           // igvn->hash_delete( phi );
  93         }
  94         igvn->hash_delete( region );
  95         progress = region;      // Making progress
  96       }
  97       igvn->hash_delete( r );
  98 
  99       // Append inputs to 'r' onto 'region'
 100       for( uint j = 1; j < r->req(); j++ ) {
 101         // Move an input from 'r' to 'region'
 102         region->add_req(r->in(j));
 103         r->set_req(j, phase->C->top());
 104         // Update phis of 'region'
 105         //for( uint k = 0; k < max; k++ ) {
 106         //  Node *phi = region->out(k);
 107         //  if( phi->is_Phi() ) {
 108         //    phi->add_req(phi->in(i));
 109         //  }
 110         //}
 111 
 112         rreq++;                 // One more input to Region
 113       } // Found a region to merge into Region
 114       igvn->_worklist.push(r);
 115       // Clobber pointer to the now dead 'r'
 116       region->set_req(i, phase->C->top());
 117     }
 118   }
 119 
 120   return progress;
 121 }
 122 
 123 
 124 
 125 //--------------------------------has_phi--------------------------------------
 126 // Helper function: Return any PhiNode that uses this region or NULL
 127 PhiNode* RegionNode::has_phi() const {
 128   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 129     Node* phi = fast_out(i);
 130     if (phi->is_Phi()) {   // Check for Phi users
 131       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 132       return phi->as_Phi();  // this one is good enough
 133     }
 134   }
 135 
 136   return NULL;
 137 }
 138 
 139 
 140 //-----------------------------has_unique_phi----------------------------------
 141 // Helper function: Return the only PhiNode that uses this region or NULL
 142 PhiNode* RegionNode::has_unique_phi() const {
 143   // Check that only one use is a Phi
 144   PhiNode* only_phi = NULL;
 145   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 146     Node* phi = fast_out(i);
 147     if (phi->is_Phi()) {   // Check for Phi users
 148       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 149       if (only_phi == NULL) {
 150         only_phi = phi->as_Phi();
 151       } else {
 152         return NULL;  // multiple phis
 153       }
 154     }
 155   }
 156 
 157   return only_phi;
 158 }
 159 
 160 
 161 //------------------------------check_phi_clipping-----------------------------
 162 // Helper function for RegionNode's identification of FP clipping
 163 // Check inputs to the Phi
 164 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 165   min     = NULL;
 166   max     = NULL;
 167   val     = NULL;
 168   min_idx = 0;
 169   max_idx = 0;
 170   val_idx = 0;
 171   uint  phi_max = phi->req();
 172   if( phi_max == 4 ) {
 173     for( uint j = 1; j < phi_max; ++j ) {
 174       Node *n = phi->in(j);
 175       int opcode = n->Opcode();
 176       switch( opcode ) {
 177       case Op_ConI:
 178         {
 179           if( min == NULL ) {
 180             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 181             min_idx = j;
 182           } else {
 183             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 184             max_idx = j;
 185             if( min->get_int() > max->get_int() ) {
 186               // Swap min and max
 187               ConNode *temp;
 188               uint     temp_idx;
 189               temp     = min;     min     = max;     max     = temp;
 190               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 191             }
 192           }
 193         }
 194         break;
 195       default:
 196         {
 197           val = n;
 198           val_idx = j;
 199         }
 200         break;
 201       }
 202     }
 203   }
 204   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 205 }
 206 
 207 
 208 //------------------------------check_if_clipping------------------------------
 209 // Helper function for RegionNode's identification of FP clipping
 210 // Check that inputs to Region come from two IfNodes,
 211 //
 212 //            If
 213 //      False    True
 214 //       If        |
 215 //  False  True    |
 216 //    |      |     |
 217 //  RegionNode_inputs
 218 //
 219 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 220   top_if = NULL;
 221   bot_if = NULL;
 222 
 223   // Check control structure above RegionNode for (if  ( if  ) )
 224   Node *in1 = region->in(1);
 225   Node *in2 = region->in(2);
 226   Node *in3 = region->in(3);
 227   // Check that all inputs are projections
 228   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 229     Node *in10 = in1->in(0);
 230     Node *in20 = in2->in(0);
 231     Node *in30 = in3->in(0);
 232     // Check that #1 and #2 are ifTrue and ifFalse from same If
 233     if( in10 != NULL && in10->is_If() &&
 234         in20 != NULL && in20->is_If() &&
 235         in30 != NULL && in30->is_If() && in10 == in20 &&
 236         (in1->Opcode() != in2->Opcode()) ) {
 237       Node  *in100 = in10->in(0);
 238       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 239       // Check that control for in10 comes from other branch of IF from in3
 240       if( in1000 != NULL && in1000->is_If() &&
 241           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 242         // Control pattern checks
 243         top_if = (IfNode*)in1000;
 244         bot_if = (IfNode*)in10;
 245       }
 246     }
 247   }
 248 
 249   return (top_if != NULL);
 250 }
 251 
 252 
 253 //------------------------------check_convf2i_clipping-------------------------
 254 // Helper function for RegionNode's identification of FP clipping
 255 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 256 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 257   convf2i = NULL;
 258 
 259   // Check for the RShiftNode
 260   Node *rshift = phi->in(idx);
 261   assert( rshift, "Previous checks ensure phi input is present");
 262   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 263 
 264   // Check for the LShiftNode
 265   Node *lshift = rshift->in(1);
 266   assert( lshift, "Previous checks ensure phi input is present");
 267   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 268 
 269   // Check for the ConvF2INode
 270   Node *conv = lshift->in(1);
 271   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 272 
 273   // Check that shift amounts are only to get sign bits set after F2I
 274   jint max_cutoff     = max->get_int();
 275   jint min_cutoff     = min->get_int();
 276   jint left_shift     = lshift->in(2)->get_int();
 277   jint right_shift    = rshift->in(2)->get_int();
 278   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 279   if( left_shift != right_shift ||
 280       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 281       max_post_shift < max_cutoff ||
 282       max_post_shift < -min_cutoff ) {
 283     // Shifts are necessary but current transformation eliminates them
 284     return false;
 285   }
 286 
 287   // OK to return the result of ConvF2I without shifting
 288   convf2i = (ConvF2INode*)conv;
 289   return true;
 290 }
 291 
 292 
 293 //------------------------------check_compare_clipping-------------------------
 294 // Helper function for RegionNode's identification of FP clipping
 295 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 296   Node *i1 = iff->in(1);
 297   if ( !i1->is_Bool() ) { return false; }
 298   BoolNode *bool1 = i1->as_Bool();
 299   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 300   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 301   const Node *cmpF = bool1->in(1);
 302   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 303   // Test that the float value being compared against
 304   // is equivalent to the int value used as a limit
 305   Node *nodef = cmpF->in(2);
 306   if( nodef->Opcode() != Op_ConF ) { return false; }
 307   jfloat conf = nodef->getf();
 308   jint   coni = limit->get_int();
 309   if( ((int)conf) != coni )        { return false; }
 310   input = cmpF->in(1);
 311   return true;
 312 }
 313 
 314 //------------------------------is_unreachable_region--------------------------
 315 // Find if the Region node is reachable from the root.
 316 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
 317   assert(req() == 2, "");
 318 
 319   // First, cut the simple case of fallthrough region when NONE of
 320   // region's phis references itself directly or through a data node.
 321   uint max = outcnt();
 322   uint i;
 323   for (i = 0; i < max; i++) {
 324     Node* phi = raw_out(i);
 325     if (phi != NULL && phi->is_Phi()) {
 326       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
 327       if (phi->outcnt() == 0)
 328         continue; // Safe case - no loops
 329       if (phi->outcnt() == 1) {
 330         Node* u = phi->raw_out(0);
 331         // Skip if only one use is an other Phi or Call or Uncommon trap.
 332         // It is safe to consider this case as fallthrough.
 333         if (u != NULL && (u->is_Phi() || u->is_CFG()))
 334           continue;
 335       }
 336       // Check when phi references itself directly or through an other node.
 337       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
 338         break; // Found possible unsafe data loop.
 339     }
 340   }
 341   if (i >= max)
 342     return false; // An unsafe case was NOT found - don't need graph walk.
 343 
 344   // Unsafe case - check if the Region node is reachable from root.
 345   ResourceMark rm;
 346 
 347   Arena *a = Thread::current()->resource_area();
 348   Node_List nstack(a);
 349   VectorSet visited(a);
 350 
 351   // Mark all control nodes reachable from root outputs
 352   Node *n = (Node*)phase->C->root();
 353   nstack.push(n);
 354   visited.set(n->_idx);
 355   while (nstack.size() != 0) {
 356     n = nstack.pop();
 357     uint max = n->outcnt();
 358     for (uint i = 0; i < max; i++) {
 359       Node* m = n->raw_out(i);
 360       if (m != NULL && m->is_CFG()) {
 361         if (phase->eqv(m, this)) {
 362           return false; // We reached the Region node - it is not dead.
 363         }
 364         if (!visited.test_set(m->_idx))
 365           nstack.push(m);
 366       }
 367     }
 368   }
 369 
 370   return true; // The Region node is unreachable - it is dead.
 371 }
 372 
 373 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 374   // Incremental inlining + PhaseStringOpts sometimes produce:
 375   //
 376   // cmpP with 1 top input
 377   //           |
 378   //          If
 379   //         /  \
 380   //   IfFalse  IfTrue  /- Some Node
 381   //         \  /      /    /
 382   //        Region    / /-MergeMem
 383   //             \---Phi
 384   //
 385   //
 386   // It's expected by PhaseStringOpts that the Region goes away and is
 387   // replaced by If's control input but because there's still a Phi,
 388   // the Region stays in the graph. The top input from the cmpP is
 389   // propagated forward and a subgraph that is useful goes away. The
 390   // code below replaces the Phi with the MergeMem so that the Region
 391   // is simplified.
 392 
 393   PhiNode* phi = has_unique_phi();
 394   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 395     MergeMemNode* m = NULL;
 396     assert(phi->req() == 3, "same as region");
 397     for (uint i = 1; i < 3; ++i) {
 398       Node *mem = phi->in(i);
 399       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 400         // Nothing is control-dependent on path #i except the region itself.
 401         m = mem->as_MergeMem();
 402         uint j = 3 - i;
 403         Node* other = phi->in(j);
 404         if (other && other == m->base_memory()) {
 405           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 406           // This will allow the diamond to collapse completely.
 407           phase->is_IterGVN()->replace_node(phi, m);
 408           return true;
 409         }
 410       }
 411     }
 412   }
 413   return false;
 414 }
 415 
 416 //------------------------------Ideal------------------------------------------
 417 // Return a node which is more "ideal" than the current node.  Must preserve
 418 // the CFG, but we can still strip out dead paths.
 419 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 420   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 421   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 422 
 423   // Check for RegionNode with no Phi users and both inputs come from either
 424   // arm of the same IF.  If found, then the control-flow split is useless.
 425   bool has_phis = false;
 426   if (can_reshape) {            // Need DU info to check for Phi users
 427     has_phis = (has_phi() != NULL);       // Cache result
 428     if (has_phis && try_clean_mem_phi(phase)) {
 429       has_phis = false;
 430     }
 431 
 432     if (!has_phis) {            // No Phi users?  Nothing merging?
 433       for (uint i = 1; i < req()-1; i++) {
 434         Node *if1 = in(i);
 435         if( !if1 ) continue;
 436         Node *iff = if1->in(0);
 437         if( !iff || !iff->is_If() ) continue;
 438         for( uint j=i+1; j<req(); j++ ) {
 439           if( in(j) && in(j)->in(0) == iff &&
 440               if1->Opcode() != in(j)->Opcode() ) {
 441             // Add the IF Projections to the worklist. They (and the IF itself)
 442             // will be eliminated if dead.
 443             phase->is_IterGVN()->add_users_to_worklist(iff);
 444             set_req(i, iff->in(0));// Skip around the useless IF diamond
 445             set_req(j, NULL);
 446             return this;      // Record progress
 447           }
 448         }
 449       }
 450     }
 451   }
 452 
 453   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 454   // degrades to a copy.
 455   bool add_to_worklist = false;
 456   bool modified = false;
 457   int cnt = 0;                  // Count of values merging
 458   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 459   int del_it = 0;               // The last input path we delete
 460   // For all inputs...
 461   for( uint i=1; i<req(); ++i ){// For all paths in
 462     Node *n = in(i);            // Get the input
 463     if( n != NULL ) {
 464       // Remove useless control copy inputs
 465       if( n->is_Region() && n->as_Region()->is_copy() ) {
 466         set_req(i, n->nonnull_req());
 467         modified = true;
 468         i--;
 469         continue;
 470       }
 471       if( n->is_Proj() ) {      // Remove useless rethrows
 472         Node *call = n->in(0);
 473         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 474           set_req(i, call->in(0));
 475           modified = true;
 476           i--;
 477           continue;
 478         }
 479       }
 480       if( phase->type(n) == Type::TOP ) {
 481         set_req(i, NULL);       // Ignore TOP inputs
 482         modified = true;
 483         i--;
 484         continue;
 485       }
 486       cnt++;                    // One more value merging
 487 
 488     } else if (can_reshape) {   // Else found dead path with DU info
 489       PhaseIterGVN *igvn = phase->is_IterGVN();
 490       del_req(i);               // Yank path from self
 491       del_it = i;
 492       uint max = outcnt();
 493       DUIterator j;
 494       bool progress = true;
 495       while(progress) {         // Need to establish property over all users
 496         progress = false;
 497         for (j = outs(); has_out(j); j++) {
 498           Node *n = out(j);
 499           if( n->req() != req() && n->is_Phi() ) {
 500             assert( n->in(0) == this, "" );
 501             igvn->hash_delete(n); // Yank from hash before hacking edges
 502             n->set_req_X(i,NULL,igvn);// Correct DU info
 503             n->del_req(i);        // Yank path from Phis
 504             if( max != outcnt() ) {
 505               progress = true;
 506               j = refresh_out_pos(j);
 507               max = outcnt();
 508             }
 509           }
 510         }
 511       }
 512       add_to_worklist = true;
 513       i--;
 514     }
 515   }
 516 
 517   if (can_reshape && cnt == 1) {
 518     // Is it dead loop?
 519     // If it is LoopNopde it had 2 (+1 itself) inputs and
 520     // one of them was cut. The loop is dead if it was EntryContol.
 521     // Loop node may have only one input because entry path
 522     // is removed in PhaseIdealLoop::Dominators().
 523     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 524     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 525                              (del_it == 0 && is_unreachable_region(phase)))) ||
 526         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 527       // Yes,  the region will be removed during the next step below.
 528       // Cut the backedge input and remove phis since no data paths left.
 529       // We don't cut outputs to other nodes here since we need to put them
 530       // on the worklist.
 531       PhaseIterGVN *igvn = phase->is_IterGVN();
 532       if (in(1)->outcnt() == 1) {
 533         igvn->_worklist.push(in(1));
 534       }
 535       del_req(1);
 536       cnt = 0;
 537       assert( req() == 1, "no more inputs expected" );
 538       uint max = outcnt();
 539       bool progress = true;
 540       Node *top = phase->C->top();
 541       DUIterator j;
 542       while(progress) {
 543         progress = false;
 544         for (j = outs(); has_out(j); j++) {
 545           Node *n = out(j);
 546           if( n->is_Phi() ) {
 547             assert( igvn->eqv(n->in(0), this), "" );
 548             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 549             // Break dead loop data path.
 550             // Eagerly replace phis with top to avoid phis copies generation.
 551             igvn->replace_node(n, top);
 552             if( max != outcnt() ) {
 553               progress = true;
 554               j = refresh_out_pos(j);
 555               max = outcnt();
 556             }
 557           }
 558         }
 559       }
 560       add_to_worklist = true;
 561     }
 562   }
 563   if (add_to_worklist) {
 564     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 565   }
 566 
 567   if( cnt <= 1 ) {              // Only 1 path in?
 568     set_req(0, NULL);           // Null control input for region copy
 569     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 570       // No inputs or all inputs are NULL.
 571       return NULL;
 572     } else if (can_reshape) {   // Optimization phase - remove the node
 573       PhaseIterGVN *igvn = phase->is_IterGVN();
 574       // Strip mined (inner) loop is going away, remove outer loop.
 575       if (is_CountedLoop() &&
 576           as_Loop()->is_strip_mined()) {
 577         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 578         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 579         if (outer_sfpt != NULL && outer_out != NULL) {
 580           Node* in = outer_sfpt->in(0);
 581           igvn->replace_node(outer_out, in);
 582           LoopNode* outer = as_CountedLoop()->outer_loop();
 583           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 584         }
 585       }
 586       Node *parent_ctrl;
 587       if( cnt == 0 ) {
 588         assert( req() == 1, "no inputs expected" );
 589         // During IGVN phase such region will be subsumed by TOP node
 590         // so region's phis will have TOP as control node.
 591         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 592         // Also set other user's input to top.
 593         parent_ctrl = phase->C->top();
 594       } else {
 595         // The fallthrough case since we already checked dead loops above.
 596         parent_ctrl = in(1);
 597         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 598         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 599       }
 600       if (!add_to_worklist)
 601         igvn->add_users_to_worklist(this); // Check for further allowed opts
 602       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 603         Node* n = last_out(i);
 604         igvn->hash_delete(n); // Remove from worklist before modifying edges
 605         if( n->is_Phi() ) {   // Collapse all Phis
 606           // Eagerly replace phis to avoid copies generation.
 607           Node* in;
 608           if( cnt == 0 ) {
 609             assert( n->req() == 1, "No data inputs expected" );
 610             in = parent_ctrl; // replaced by top
 611           } else {
 612             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 613             in = n->in(1);               // replaced by unique input
 614             if( n->as_Phi()->is_unsafe_data_reference(in) )
 615               in = phase->C->top();      // replaced by top
 616           }



 617           igvn->replace_node(n, in);
 618         }
 619         else if( n->is_Region() ) { // Update all incoming edges
 620           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 621           uint uses_found = 0;
 622           for( uint k=1; k < n->req(); k++ ) {
 623             if( n->in(k) == this ) {
 624               n->set_req(k, parent_ctrl);
 625               uses_found++;
 626             }
 627           }
 628           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 629             i -= (uses_found - 1);
 630           }
 631         }
 632         else {
 633           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 634           n->set_req(0, parent_ctrl);
 635         }
 636 #ifdef ASSERT
 637         for( uint k=0; k < n->req(); k++ ) {
 638           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 639         }
 640 #endif
 641       }
 642       // Remove the RegionNode itself from DefUse info
 643       igvn->remove_dead_node(this);
 644       return NULL;
 645     }
 646     return this;                // Record progress
 647   }
 648 
 649 
 650   // If a Region flows into a Region, merge into one big happy merge.
 651   if (can_reshape) {
 652     Node *m = merge_region(this, phase);
 653     if (m != NULL)  return m;
 654   }
 655 
 656   // Check if this region is the root of a clipping idiom on floats
 657   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 658     // Check that only one use is a Phi and that it simplifies to two constants +
 659     PhiNode* phi = has_unique_phi();
 660     if (phi != NULL) {          // One Phi user
 661       // Check inputs to the Phi
 662       ConNode *min;
 663       ConNode *max;
 664       Node    *val;
 665       uint     min_idx;
 666       uint     max_idx;
 667       uint     val_idx;
 668       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 669         IfNode *top_if;
 670         IfNode *bot_if;
 671         if( check_if_clipping( this, bot_if, top_if ) ) {
 672           // Control pattern checks, now verify compares
 673           Node   *top_in = NULL;   // value being compared against
 674           Node   *bot_in = NULL;
 675           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 676               check_compare_clipping( false, top_if, max, top_in ) ) {
 677             if( bot_in == top_in ) {
 678               PhaseIterGVN *gvn = phase->is_IterGVN();
 679               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 680               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 681 
 682               // Check for the ConvF2INode
 683               ConvF2INode *convf2i;
 684               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 685                 convf2i->in(1) == bot_in ) {
 686                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 687                 // max test
 688                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 689                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 690                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 691                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 692                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 693                 // min test
 694                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 695                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 696                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 697                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 698                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 699                 // update input edges to region node
 700                 set_req_X( min_idx, if_min, gvn );
 701                 set_req_X( max_idx, if_max, gvn );
 702                 set_req_X( val_idx, ifF,    gvn );
 703                 // remove unnecessary 'LShiftI; RShiftI' idiom
 704                 gvn->hash_delete(phi);
 705                 phi->set_req_X( val_idx, convf2i, gvn );
 706                 gvn->hash_find_insert(phi);
 707                 // Return transformed region node
 708                 return this;
 709               }
 710             }
 711           }
 712         }
 713       }
 714     }
 715   }
 716 
 717   return modified ? this : NULL;
 718 }
 719 
 720 
 721 
 722 const RegMask &RegionNode::out_RegMask() const {
 723   return RegMask::Empty;
 724 }
 725 
 726 // Find the one non-null required input.  RegionNode only
 727 Node *Node::nonnull_req() const {
 728   assert( is_Region(), "" );
 729   for( uint i = 1; i < _cnt; i++ )
 730     if( in(i) )
 731       return in(i);
 732   ShouldNotReachHere();
 733   return NULL;
 734 }
 735 
 736 
 737 //=============================================================================
 738 // note that these functions assume that the _adr_type field is flattened
 739 uint PhiNode::hash() const {
 740   const Type* at = _adr_type;
 741   return TypeNode::hash() + (at ? at->hash() : 0);
 742 }
 743 uint PhiNode::cmp( const Node &n ) const {
 744   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 745 }
 746 static inline
 747 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 748   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 749   return Compile::current()->alias_type(at)->adr_type();
 750 }
 751 
 752 //----------------------------make---------------------------------------------
 753 // create a new phi with edges matching r and set (initially) to x
 754 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 755   uint preds = r->req();   // Number of predecessor paths
 756   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 757   PhiNode* p = new PhiNode(r, t, at);
 758   for (uint j = 1; j < preds; j++) {
 759     // Fill in all inputs, except those which the region does not yet have
 760     if (r->in(j) != NULL)
 761       p->init_req(j, x);
 762   }
 763   return p;
 764 }
 765 PhiNode* PhiNode::make(Node* r, Node* x) {
 766   const Type*    t  = x->bottom_type();
 767   const TypePtr* at = NULL;
 768   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 769   return make(r, x, t, at);
 770 }
 771 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 772   const Type*    t  = x->bottom_type();
 773   const TypePtr* at = NULL;
 774   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 775   return new PhiNode(r, t, at);
 776 }
 777 
 778 
 779 //------------------------slice_memory-----------------------------------------
 780 // create a new phi with narrowed memory type
 781 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 782   PhiNode* mem = (PhiNode*) clone();
 783   *(const TypePtr**)&mem->_adr_type = adr_type;
 784   // convert self-loops, or else we get a bad graph
 785   for (uint i = 1; i < req(); i++) {
 786     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 787   }
 788   mem->verify_adr_type();
 789   return mem;
 790 }
 791 
 792 //------------------------split_out_instance-----------------------------------
 793 // Split out an instance type from a bottom phi.
 794 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 795   const TypeOopPtr *t_oop = at->isa_oopptr();
 796   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 797   const TypePtr *t = adr_type();
 798   assert(type() == Type::MEMORY &&
 799          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 800           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 801           t->is_oopptr()->cast_to_exactness(true)
 802            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 803            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 804          "bottom or raw memory required");
 805 
 806   // Check if an appropriate node already exists.
 807   Node *region = in(0);
 808   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 809     Node* use = region->fast_out(k);
 810     if( use->is_Phi()) {
 811       PhiNode *phi2 = use->as_Phi();
 812       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 813         return phi2;
 814       }
 815     }
 816   }
 817   Compile *C = igvn->C;
 818   Arena *a = Thread::current()->resource_area();
 819   Node_Array node_map = new Node_Array(a);
 820   Node_Stack stack(a, C->live_nodes() >> 4);
 821   PhiNode *nphi = slice_memory(at);
 822   igvn->register_new_node_with_optimizer( nphi );
 823   node_map.map(_idx, nphi);
 824   stack.push((Node *)this, 1);
 825   while(!stack.is_empty()) {
 826     PhiNode *ophi = stack.node()->as_Phi();
 827     uint i = stack.index();
 828     assert(i >= 1, "not control edge");
 829     stack.pop();
 830     nphi = node_map[ophi->_idx]->as_Phi();
 831     for (; i < ophi->req(); i++) {
 832       Node *in = ophi->in(i);
 833       if (in == NULL || igvn->type(in) == Type::TOP)
 834         continue;
 835       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
 836       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 837       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 838         opt = node_map[optphi->_idx];
 839         if (opt == NULL) {
 840           stack.push(ophi, i);
 841           nphi = optphi->slice_memory(at);
 842           igvn->register_new_node_with_optimizer( nphi );
 843           node_map.map(optphi->_idx, nphi);
 844           ophi = optphi;
 845           i = 0; // will get incremented at top of loop
 846           continue;
 847         }
 848       }
 849       nphi->set_req(i, opt);
 850     }
 851   }
 852   return nphi;
 853 }
 854 
 855 //------------------------verify_adr_type--------------------------------------
 856 #ifdef ASSERT
 857 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
 858   if (visited.test_set(_idx))  return;  //already visited
 859 
 860   // recheck constructor invariants:
 861   verify_adr_type(false);
 862 
 863   // recheck local phi/phi consistency:
 864   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
 865          "adr_type must be consistent across phi nest");
 866 
 867   // walk around
 868   for (uint i = 1; i < req(); i++) {
 869     Node* n = in(i);
 870     if (n == NULL)  continue;
 871     const Node* np = in(i);
 872     if (np->is_Phi()) {
 873       np->as_Phi()->verify_adr_type(visited, at);
 874     } else if (n->bottom_type() == Type::TOP
 875                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
 876       // ignore top inputs
 877     } else {
 878       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
 879       // recheck phi/non-phi consistency at leaves:
 880       assert((nat != NULL) == (at != NULL), "");
 881       assert(nat == at || nat == TypePtr::BOTTOM,
 882              "adr_type must be consistent at leaves of phi nest");
 883     }
 884   }
 885 }
 886 
 887 // Verify a whole nest of phis rooted at this one.
 888 void PhiNode::verify_adr_type(bool recursive) const {
 889   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
 890   if (Node::in_dump())               return;  // muzzle asserts when printing
 891 
 892   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
 893 
 894   if (!VerifyAliases)       return;  // verify thoroughly only if requested
 895 
 896   assert(_adr_type == flatten_phi_adr_type(_adr_type),
 897          "Phi::adr_type must be pre-normalized");
 898 
 899   if (recursive) {
 900     VectorSet visited(Thread::current()->resource_area());
 901     verify_adr_type(visited, _adr_type);
 902   }
 903 }
 904 #endif
 905 
 906 
 907 //------------------------------Value------------------------------------------
 908 // Compute the type of the PhiNode
 909 const Type* PhiNode::Value(PhaseGVN* phase) const {
 910   Node *r = in(0);              // RegionNode
 911   if( !r )                      // Copy or dead
 912     return in(1) ? phase->type(in(1)) : Type::TOP;
 913 
 914   // Note: During parsing, phis are often transformed before their regions.
 915   // This means we have to use type_or_null to defend against untyped regions.
 916   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
 917     return Type::TOP;
 918 
 919   // Check for trip-counted loop.  If so, be smarter.
 920   CountedLoopNode* l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
 921   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
 922     // protect against init_trip() or limit() returning NULL
 923     if (l->can_be_counted_loop(phase)) {
 924       const Node *init   = l->init_trip();
 925       const Node *limit  = l->limit();
 926       const Node* stride = l->stride();
 927       if (init != NULL && limit != NULL && stride != NULL) {
 928         const TypeInt* lo = phase->type(init)->isa_int();
 929         const TypeInt* hi = phase->type(limit)->isa_int();
 930         const TypeInt* stride_t = phase->type(stride)->isa_int();
 931         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
 932           assert(stride_t->_hi >= stride_t->_lo, "bad stride type");
 933           BoolTest::mask bt = l->loopexit()->test_trip();
 934           // If the loop exit condition is "not equal", the condition
 935           // would not trigger if init > limit (if stride > 0) or if
 936           // init < limit if (stride > 0) so we can't deduce bounds
 937           // for the iv from the exit condition.
 938           if (bt != BoolTest::ne) {
 939             if (stride_t->_hi < 0) {          // Down-counter loop
 940               swap(lo, hi);
 941               return TypeInt::make(MIN2(lo->_lo, hi->_lo) , hi->_hi, 3);
 942             } else if (stride_t->_lo >= 0) {
 943               return TypeInt::make(lo->_lo, MAX2(lo->_hi, hi->_hi), 3);
 944             }
 945           }
 946         }
 947       }
 948     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
 949                in(LoopNode::EntryControl) != NULL &&
 950                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
 951       // During CCP, if we saturate the type of a counted loop's Phi
 952       // before the special code for counted loop above has a chance
 953       // to run (that is as long as the type of the backedge's control
 954       // is top), we might end up with non monotonic types
 955       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
 956     }
 957   }
 958 
 959   // Until we have harmony between classes and interfaces in the type
 960   // lattice, we must tread carefully around phis which implicitly
 961   // convert the one to the other.
 962   const TypePtr* ttp = _type->make_ptr();
 963   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
 964   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
 965   bool is_intf = false;
 966   if (ttip != NULL) {
 967     ciKlass* k = ttip->klass();
 968     if (k->is_loaded() && k->is_interface())
 969       is_intf = true;
 970   }
 971   if (ttkp != NULL) {
 972     ciKlass* k = ttkp->klass();
 973     if (k->is_loaded() && k->is_interface())
 974       is_intf = true;
 975   }
 976 
 977   // Default case: merge all inputs
 978   const Type *t = Type::TOP;        // Merged type starting value
 979   for (uint i = 1; i < req(); ++i) {// For all paths in
 980     // Reachable control path?
 981     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
 982       const Type* ti = phase->type(in(i));
 983       // We assume that each input of an interface-valued Phi is a true
 984       // subtype of that interface.  This might not be true of the meet
 985       // of all the input types.  The lattice is not distributive in
 986       // such cases.  Ward off asserts in type.cpp by refusing to do
 987       // meets between interfaces and proper classes.
 988       const TypePtr* tip = ti->make_ptr();
 989       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
 990       if (tiip) {
 991         bool ti_is_intf = false;
 992         ciKlass* k = tiip->klass();
 993         if (k->is_loaded() && k->is_interface())
 994           ti_is_intf = true;
 995         if (is_intf != ti_is_intf)
 996           { t = _type; break; }
 997       }
 998       t = t->meet_speculative(ti);
 999     }
1000   }
1001 
1002   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1003   // That is, we expect that "t->higher_equal(_type)" holds true.
1004   // There are various exceptions:
1005   // - Inputs which are phis might in fact be widened unnecessarily.
1006   //   For example, an input might be a widened int while the phi is a short.
1007   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1008   //   and postCCP has removed the cast which encodes the result of the check.
1009   // - The type of this phi is an interface, and the inputs are classes.
1010   // - Value calls on inputs might produce fuzzy results.
1011   //   (Occurrences of this case suggest improvements to Value methods.)
1012   //
1013   // It is not possible to see Type::BOTTOM values as phi inputs,
1014   // because the ciTypeFlow pre-pass produces verifier-quality types.
1015   const Type* ft = t->filter_speculative(_type);  // Worst case type
1016 
1017 #ifdef ASSERT
1018   // The following logic has been moved into TypeOopPtr::filter.
1019   const Type* jt = t->join_speculative(_type);
1020   if (jt->empty()) {           // Emptied out???
1021 
1022     // Check for evil case of 't' being a class and '_type' expecting an
1023     // interface.  This can happen because the bytecodes do not contain
1024     // enough type info to distinguish a Java-level interface variable
1025     // from a Java-level object variable.  If we meet 2 classes which
1026     // both implement interface I, but their meet is at 'j/l/O' which
1027     // doesn't implement I, we have no way to tell if the result should
1028     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1029     // into a Phi which "knows" it's an Interface type we'll have to
1030     // uplift the type.
1031     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1032       assert(ft == _type, ""); // Uplift to interface
1033     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1034       assert(ft == _type, ""); // Uplift to interface
1035     } else {
1036       // We also have to handle 'evil cases' of interface- vs. class-arrays
1037       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1038       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1039           assert(ft == _type, "");   // Uplift to array of interface
1040       } else {
1041         // Otherwise it's something stupid like non-overlapping int ranges
1042         // found on dying counted loops.
1043         assert(ft == Type::TOP, ""); // Canonical empty value
1044       }
1045     }
1046   }
1047 
1048   else {
1049 
1050     // If we have an interface-typed Phi and we narrow to a class type, the join
1051     // should report back the class.  However, if we have a J/L/Object
1052     // class-typed Phi and an interface flows in, it's possible that the meet &
1053     // join report an interface back out.  This isn't possible but happens
1054     // because the type system doesn't interact well with interfaces.
1055     const TypePtr *jtp = jt->make_ptr();
1056     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1057     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
1058     if( jtip && ttip ) {
1059       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1060           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1061         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1062                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1063         jt = ft;
1064       }
1065     }
1066     if( jtkp && ttkp ) {
1067       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1068           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1069           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1070         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1071                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1072         jt = ft;
1073       }
1074     }
1075     if (jt != ft && jt->base() == ft->base()) {
1076       if (jt->isa_int() &&
1077           jt->is_int()->_lo == ft->is_int()->_lo &&
1078           jt->is_int()->_hi == ft->is_int()->_hi)
1079         jt = ft;
1080       if (jt->isa_long() &&
1081           jt->is_long()->_lo == ft->is_long()->_lo &&
1082           jt->is_long()->_hi == ft->is_long()->_hi)
1083         jt = ft;
1084     }
1085     if (jt != ft) {
1086       tty->print("merge type:  "); t->dump(); tty->cr();
1087       tty->print("kill type:   "); _type->dump(); tty->cr();
1088       tty->print("join type:   "); jt->dump(); tty->cr();
1089       tty->print("filter type: "); ft->dump(); tty->cr();
1090     }
1091     assert(jt == ft, "");
1092   }
1093 #endif //ASSERT
1094 
1095   // Deal with conversion problems found in data loops.
1096   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1097 
1098   return ft;
1099 }
1100 
1101 
1102 //------------------------------is_diamond_phi---------------------------------
1103 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1104 // index of the true path or 0 otherwise.
1105 // If check_control_only is true, do not inspect the If node at the
1106 // top, and return -1 (not an edge number) on success.
1107 int PhiNode::is_diamond_phi(bool check_control_only) const {
1108   // Check for a 2-path merge
1109   Node *region = in(0);
1110   if( !region ) return 0;
1111   if( region->req() != 3 ) return 0;
1112   if(         req() != 3 ) return 0;
1113   // Check that both paths come from the same If
1114   Node *ifp1 = region->in(1);
1115   Node *ifp2 = region->in(2);
1116   if( !ifp1 || !ifp2 ) return 0;
1117   Node *iff = ifp1->in(0);
1118   if( !iff || !iff->is_If() ) return 0;
1119   if( iff != ifp2->in(0) ) return 0;
1120   if (check_control_only)  return -1;
1121   // Check for a proper bool/cmp
1122   const Node *b = iff->in(1);
1123   if( !b->is_Bool() ) return 0;
1124   const Node *cmp = b->in(1);
1125   if( !cmp->is_Cmp() ) return 0;
1126 
1127   // Check for branching opposite expected
1128   if( ifp2->Opcode() == Op_IfTrue ) {
1129     assert( ifp1->Opcode() == Op_IfFalse, "" );
1130     return 2;
1131   } else {
1132     assert( ifp1->Opcode() == Op_IfTrue, "" );
1133     return 1;
1134   }
1135 }
1136 
1137 //----------------------------check_cmove_id-----------------------------------
1138 // Check for CMove'ing a constant after comparing against the constant.
1139 // Happens all the time now, since if we compare equality vs a constant in
1140 // the parser, we "know" the variable is constant on one path and we force
1141 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1142 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1143 // general in that we don't need constants.  Since CMove's are only inserted
1144 // in very special circumstances, we do it here on generic Phi's.
1145 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1146   assert(true_path !=0, "only diamond shape graph expected");
1147 
1148   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1149   // phi->region->if_proj->ifnode->bool->cmp
1150   Node*     region = in(0);
1151   Node*     iff    = region->in(1)->in(0);
1152   BoolNode* b      = iff->in(1)->as_Bool();
1153   Node*     cmp    = b->in(1);
1154   Node*     tval   = in(true_path);
1155   Node*     fval   = in(3-true_path);
1156   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1157   if (id == NULL)
1158     return NULL;
1159 
1160   // Either value might be a cast that depends on a branch of 'iff'.
1161   // Since the 'id' value will float free of the diamond, either
1162   // decast or return failure.
1163   Node* ctl = id->in(0);
1164   if (ctl != NULL && ctl->in(0) == iff) {
1165     if (id->is_ConstraintCast()) {
1166       return id->in(1);
1167     } else {
1168       // Don't know how to disentangle this value.
1169       return NULL;
1170     }
1171   }
1172 
1173   return id;
1174 }
1175 
1176 //------------------------------Identity---------------------------------------
1177 // Check for Region being Identity.
1178 Node* PhiNode::Identity(PhaseGVN* phase) {
1179   // Check for no merging going on
1180   // (There used to be special-case code here when this->region->is_Loop.
1181   // It would check for a tributary phi on the backedge that the main phi
1182   // trivially, perhaps with a single cast.  The unique_input method
1183   // does all this and more, by reducing such tributaries to 'this'.)
1184   Node* uin = unique_input(phase, false);
1185   if (uin != NULL) {
1186     return uin;
1187   }
1188 
1189   int true_path = is_diamond_phi();
1190   if (true_path != 0) {
1191     Node* id = is_cmove_id(phase, true_path);
1192     if (id != NULL)  return id;
1193   }
1194 
1195   return this;                     // No identity
1196 }
1197 
1198 //-----------------------------unique_input------------------------------------
1199 // Find the unique value, discounting top, self-loops, and casts.
1200 // Return top if there are no inputs, and self if there are multiple.
1201 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1202   //  1) One unique direct input,
1203   // or if uncast is true:
1204   //  2) some of the inputs have an intervening ConstraintCast
1205   //  3) an input is a self loop
1206   //
1207   //  1) input   or   2) input     or   3) input __
1208   //     /   \           /   \               \  /  \
1209   //     \   /          |    cast             phi  cast
1210   //      phi            \   /               /  \  /
1211   //                      phi               /    --
1212 
1213   Node* r = in(0);                      // RegionNode
1214   if (r == NULL)  return in(1);         // Already degraded to a Copy
1215   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1216 
1217   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1218     Node* rc = r->in(i);
1219     if (rc == NULL || phase->type(rc) == Type::TOP)
1220       continue;                 // ignore unreachable control path
1221     Node* n = in(i);
1222     if (n == NULL)
1223       continue;
1224     Node* un = n;
1225     if (uncast) {
1226 #ifdef ASSERT
1227       Node* m = un->uncast();
1228 #endif
1229       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1230         Node* next = un->in(1);
1231         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1232           // risk exposing raw ptr at safepoint
1233           break;
1234         }
1235         un = next;
1236       }
1237       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1238     }
1239     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1240       continue; // ignore if top, or in(i) and "this" are in a data cycle
1241     }
1242     // Check for a unique input (maybe uncasted)
1243     if (input == NULL) {
1244       input = un;
1245     } else if (input != un) {
1246       input = NodeSentinel; // no unique input
1247     }
1248   }
1249   if (input == NULL) {
1250     return phase->C->top();        // no inputs
1251   }
1252 
1253   if (input != NodeSentinel) {
1254     return input;           // one unique direct input
1255   }
1256 
1257   // Nothing.
1258   return NULL;
1259 }
1260 
1261 //------------------------------is_x2logic-------------------------------------
1262 // Check for simple convert-to-boolean pattern
1263 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1264 // Convert Phi to an ConvIB.
1265 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1266   assert(true_path !=0, "only diamond shape graph expected");
1267   // Convert the true/false index into an expected 0/1 return.
1268   // Map 2->0 and 1->1.
1269   int flipped = 2-true_path;
1270 
1271   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1272   // phi->region->if_proj->ifnode->bool->cmp
1273   Node *region = phi->in(0);
1274   Node *iff = region->in(1)->in(0);
1275   BoolNode *b = (BoolNode*)iff->in(1);
1276   const CmpNode *cmp = (CmpNode*)b->in(1);
1277 
1278   Node *zero = phi->in(1);
1279   Node *one  = phi->in(2);
1280   const Type *tzero = phase->type( zero );
1281   const Type *tone  = phase->type( one  );
1282 
1283   // Check for compare vs 0
1284   const Type *tcmp = phase->type(cmp->in(2));
1285   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1286     // Allow cmp-vs-1 if the other input is bounded by 0-1
1287     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1288       return NULL;
1289     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1290   }
1291 
1292   // Check for setting zero/one opposite expected
1293   if( tzero == TypeInt::ZERO ) {
1294     if( tone == TypeInt::ONE ) {
1295     } else return NULL;
1296   } else if( tzero == TypeInt::ONE ) {
1297     if( tone == TypeInt::ZERO ) {
1298       flipped = 1-flipped;
1299     } else return NULL;
1300   } else return NULL;
1301 
1302   // Check for boolean test backwards
1303   if( b->_test._test == BoolTest::ne ) {
1304   } else if( b->_test._test == BoolTest::eq ) {
1305     flipped = 1-flipped;
1306   } else return NULL;
1307 
1308   // Build int->bool conversion
1309   Node *n = new Conv2BNode( cmp->in(1) );







1310   if( flipped )
1311     n = new XorINode( phase->transform(n), phase->intcon(1) );
1312 
1313   return n;
1314 }
1315 
1316 //------------------------------is_cond_add------------------------------------
1317 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1318 // To be profitable the control flow has to disappear; there can be no other
1319 // values merging here.  We replace the test-and-branch with:
1320 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1321 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1322 // Then convert Y to 0-or-Y and finally add.
1323 // This is a key transform for SpecJava _201_compress.
1324 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1325   assert(true_path !=0, "only diamond shape graph expected");
1326 
1327   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1328   // phi->region->if_proj->ifnode->bool->cmp
1329   RegionNode *region = (RegionNode*)phi->in(0);
1330   Node *iff = region->in(1)->in(0);
1331   BoolNode* b = iff->in(1)->as_Bool();
1332   const CmpNode *cmp = (CmpNode*)b->in(1);
1333 
1334   // Make sure only merging this one phi here
1335   if (region->has_unique_phi() != phi)  return NULL;
1336 
1337   // Make sure each arm of the diamond has exactly one output, which we assume
1338   // is the region.  Otherwise, the control flow won't disappear.
1339   if (region->in(1)->outcnt() != 1) return NULL;
1340   if (region->in(2)->outcnt() != 1) return NULL;
1341 
1342   // Check for "(P < Q)" of type signed int
1343   if (b->_test._test != BoolTest::lt)  return NULL;
1344   if (cmp->Opcode() != Op_CmpI)        return NULL;
1345 
1346   Node *p = cmp->in(1);
1347   Node *q = cmp->in(2);
1348   Node *n1 = phi->in(  true_path);
1349   Node *n2 = phi->in(3-true_path);
1350 
1351   int op = n1->Opcode();
1352   if( op != Op_AddI           // Need zero as additive identity
1353       /*&&op != Op_SubI &&
1354       op != Op_AddP &&
1355       op != Op_XorI &&
1356       op != Op_OrI*/ )
1357     return NULL;
1358 
1359   Node *x = n2;
1360   Node *y = NULL;
1361   if( x == n1->in(1) ) {
1362     y = n1->in(2);
1363   } else if( x == n1->in(2) ) {
1364     y = n1->in(1);
1365   } else return NULL;
1366 
1367   // Not so profitable if compare and add are constants
1368   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1369     return NULL;
1370 
1371   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1372   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1373   return new AddINode(j_and,x);
1374 }
1375 
1376 //------------------------------is_absolute------------------------------------
1377 // Check for absolute value.
1378 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1379   assert(true_path !=0, "only diamond shape graph expected");
1380 
1381   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1382   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1383 
1384   // ABS ends with the merge of 2 control flow paths.
1385   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1386   int false_path = 3 - true_path;
1387 
1388   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1389   // phi->region->if_proj->ifnode->bool->cmp
1390   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1391 
1392   // Check bool sense
1393   switch( bol->_test._test ) {
1394   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1395   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1396   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1397   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1398   default:           return NULL;                              break;
1399   }
1400 
1401   // Test is next
1402   Node *cmp = bol->in(1);
1403   const Type *tzero = NULL;
1404   switch( cmp->Opcode() ) {
1405   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1406   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1407   default: return NULL;
1408   }
1409 
1410   // Find zero input of compare; the other input is being abs'd
1411   Node *x = NULL;
1412   bool flip = false;
1413   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1414     x = cmp->in(3 - cmp_zero_idx);
1415   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1416     // The test is inverted, we should invert the result...
1417     x = cmp->in(cmp_zero_idx);
1418     flip = true;
1419   } else {
1420     return NULL;
1421   }
1422 
1423   // Next get the 2 pieces being selected, one is the original value
1424   // and the other is the negated value.
1425   if( phi_root->in(phi_x_idx) != x ) return NULL;
1426 
1427   // Check other phi input for subtract node
1428   Node *sub = phi_root->in(3 - phi_x_idx);
1429 
1430   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1431   if( tzero == TypeF::ZERO ) {
1432     if( sub->Opcode() != Op_SubF ||
1433         sub->in(2) != x ||
1434         phase->type(sub->in(1)) != tzero ) return NULL;
1435     x = new AbsFNode(x);
1436     if (flip) {
1437       x = new SubFNode(sub->in(1), phase->transform(x));
1438     }
1439   } else {
1440     if( sub->Opcode() != Op_SubD ||
1441         sub->in(2) != x ||
1442         phase->type(sub->in(1)) != tzero ) return NULL;
1443     x = new AbsDNode(x);
1444     if (flip) {
1445       x = new SubDNode(sub->in(1), phase->transform(x));
1446     }
1447   }
1448 
1449   return x;
1450 }
1451 
1452 //------------------------------split_once-------------------------------------
1453 // Helper for split_flow_path
1454 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1455   igvn->hash_delete(n);         // Remove from hash before hacking edges
1456 
1457   uint j = 1;
1458   for (uint i = phi->req()-1; i > 0; i--) {
1459     if (phi->in(i) == val) {   // Found a path with val?
1460       // Add to NEW Region/Phi, no DU info
1461       newn->set_req( j++, n->in(i) );
1462       // Remove from OLD Region/Phi
1463       n->del_req(i);
1464     }
1465   }
1466 
1467   // Register the new node but do not transform it.  Cannot transform until the
1468   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1469   igvn->register_new_node_with_optimizer( newn );
1470 
1471   // Now I can point to the new node.
1472   n->add_req(newn);
1473   igvn->_worklist.push(n);
1474 }
1475 
1476 //------------------------------split_flow_path--------------------------------
1477 // Check for merging identical values and split flow paths
1478 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1479   BasicType bt = phi->type()->basic_type();
1480   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1481     return NULL;                // Bail out on funny non-value stuff
1482   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1483     return NULL;                // third unequal input to be worth doing
1484 
1485   // Scan for a constant
1486   uint i;
1487   for( i = 1; i < phi->req()-1; i++ ) {
1488     Node *n = phi->in(i);
1489     if( !n ) return NULL;
1490     if( phase->type(n) == Type::TOP ) return NULL;
1491     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1492       break;
1493   }
1494   if( i >= phi->req() )         // Only split for constants
1495     return NULL;
1496 
1497   Node *val = phi->in(i);       // Constant to split for
1498   uint hit = 0;                 // Number of times it occurs
1499   Node *r = phi->region();
1500 
1501   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1502     Node *n = phi->in(i);
1503     if( !n ) return NULL;
1504     if( phase->type(n) == Type::TOP ) return NULL;
1505     if( phi->in(i) == val ) {
1506       hit++;
1507       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1508         return NULL;            // don't split loop entry path
1509       }
1510     }
1511   }
1512 
1513   if( hit <= 1 ||               // Make sure we find 2 or more
1514       hit == phi->req()-1 )     // and not ALL the same value
1515     return NULL;
1516 
1517   // Now start splitting out the flow paths that merge the same value.
1518   // Split first the RegionNode.
1519   PhaseIterGVN *igvn = phase->is_IterGVN();
1520   RegionNode *newr = new RegionNode(hit+1);
1521   split_once(igvn, phi, val, r, newr);
1522 
1523   // Now split all other Phis than this one
1524   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1525     Node* phi2 = r->fast_out(k);
1526     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1527       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1528       split_once(igvn, phi, val, phi2, newphi);
1529     }
1530   }
1531 
1532   // Clean up this guy
1533   igvn->hash_delete(phi);
1534   for( i = phi->req()-1; i > 0; i-- ) {
1535     if( phi->in(i) == val ) {
1536       phi->del_req(i);
1537     }
1538   }
1539   phi->add_req(val);
1540 
1541   return phi;
1542 }
1543 
1544 //=============================================================================
1545 //------------------------------simple_data_loop_check-------------------------
1546 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1547 //  Returns:
1548 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1549 // Safe       - safe case when the phi and it's inputs reference only safe data
1550 //              nodes;
1551 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1552 //              is no reference back to the phi - need a graph walk
1553 //              to determine if it is in a loop;
1554 // UnsafeLoop - unsafe case when the phi references itself directly or through
1555 //              unsafe data node.
1556 //  Note: a safe data node is a node which could/never reference itself during
1557 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1558 //  I mark Phi nodes as safe node not only because they can reference itself
1559 //  but also to prevent mistaking the fallthrough case inside an outer loop
1560 //  as dead loop when the phi references itselfs through an other phi.
1561 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1562   // It is unsafe loop if the phi node references itself directly.
1563   if (in == (Node*)this)
1564     return UnsafeLoop; // Unsafe loop
1565   // Unsafe loop if the phi node references itself through an unsafe data node.
1566   // Exclude cases with null inputs or data nodes which could reference
1567   // itself (safe for dead loops).
1568   if (in != NULL && !in->is_dead_loop_safe()) {
1569     // Check inputs of phi's inputs also.
1570     // It is much less expensive then full graph walk.
1571     uint cnt = in->req();
1572     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1573     for (; i < cnt; ++i) {
1574       Node* m = in->in(i);
1575       if (m == (Node*)this)
1576         return UnsafeLoop; // Unsafe loop
1577       if (m != NULL && !m->is_dead_loop_safe()) {
1578         // Check the most common case (about 30% of all cases):
1579         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1580         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1581         if (m1 == (Node*)this)
1582           return UnsafeLoop; // Unsafe loop
1583         if (m1 != NULL && m1 == m->in(2) &&
1584             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1585           continue; // Safe case
1586         }
1587         // The phi references an unsafe node - need full analysis.
1588         return Unsafe;
1589       }
1590     }
1591   }
1592   return Safe; // Safe case - we can optimize the phi node.
1593 }
1594 
1595 //------------------------------is_unsafe_data_reference-----------------------
1596 // If phi can be reached through the data input - it is data loop.
1597 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1598   assert(req() > 1, "");
1599   // First, check simple cases when phi references itself directly or
1600   // through an other node.
1601   LoopSafety safety = simple_data_loop_check(in);
1602   if (safety == UnsafeLoop)
1603     return true;  // phi references itself - unsafe loop
1604   else if (safety == Safe)
1605     return false; // Safe case - phi could be replaced with the unique input.
1606 
1607   // Unsafe case when we should go through data graph to determine
1608   // if the phi references itself.
1609 
1610   ResourceMark rm;
1611 
1612   Arena *a = Thread::current()->resource_area();
1613   Node_List nstack(a);
1614   VectorSet visited(a);
1615 
1616   nstack.push(in); // Start with unique input.
1617   visited.set(in->_idx);
1618   while (nstack.size() != 0) {
1619     Node* n = nstack.pop();
1620     uint cnt = n->req();
1621     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1622     for (; i < cnt; i++) {
1623       Node* m = n->in(i);
1624       if (m == (Node*)this) {
1625         return true;    // Data loop
1626       }
1627       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1628         if (!visited.test_set(m->_idx))
1629           nstack.push(m);
1630       }
1631     }
1632   }
1633   return false; // The phi is not reachable from its inputs
1634 }
1635 
1636 
1637 //------------------------------Ideal------------------------------------------
1638 // Return a node which is more "ideal" than the current node.  Must preserve
1639 // the CFG, but we can still strip out dead paths.
1640 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1641   // The next should never happen after 6297035 fix.
1642   if( is_copy() )               // Already degraded to a Copy ?
1643     return NULL;                // No change
1644 
1645   Node *r = in(0);              // RegionNode
1646   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1647 
1648   // Note: During parsing, phis are often transformed before their regions.
1649   // This means we have to use type_or_null to defend against untyped regions.
1650   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1651     return NULL;                // No change
1652 
1653   Node *top = phase->C->top();
1654   bool new_phi = (outcnt() == 0); // transforming new Phi
1655   // No change for igvn if new phi is not hooked
1656   if (new_phi && can_reshape)
1657     return NULL;
1658 
1659   // The are 2 situations when only one valid phi's input is left
1660   // (in addition to Region input).
1661   // One: region is not loop - replace phi with this input.
1662   // Two: region is loop - replace phi with top since this data path is dead
1663   //                       and we need to break the dead data loop.
1664   Node* progress = NULL;        // Record if any progress made
1665   for( uint j = 1; j < req(); ++j ){ // For all paths in
1666     // Check unreachable control paths
1667     Node* rc = r->in(j);
1668     Node* n = in(j);            // Get the input
1669     if (rc == NULL || phase->type(rc) == Type::TOP) {
1670       if (n != top) {           // Not already top?
1671         PhaseIterGVN *igvn = phase->is_IterGVN();
1672         if (can_reshape && igvn != NULL) {
1673           igvn->_worklist.push(r);
1674         }
1675         set_req(j, top);        // Nuke it down





1676         progress = this;        // Record progress
1677       }
1678     }
1679   }
1680 
1681   if (can_reshape && outcnt() == 0) {
1682     // set_req() above may kill outputs if Phi is referenced
1683     // only by itself on the dead (top) control path.
1684     return top;
1685   }
1686 
1687   bool uncasted = false;
1688   Node* uin = unique_input(phase, false);
1689   if (uin == NULL && can_reshape) {
1690     uncasted = true;
1691     uin = unique_input(phase, true);
1692   }
1693   if (uin == top) {             // Simplest case: no alive inputs.
1694     if (can_reshape)            // IGVN transformation
1695       return top;
1696     else
1697       return NULL;              // Identity will return TOP
1698   } else if (uin != NULL) {
1699     // Only one not-NULL unique input path is left.
1700     // Determine if this input is backedge of a loop.
1701     // (Skip new phis which have no uses and dead regions).
1702     if (outcnt() > 0 && r->in(0) != NULL) {
1703       // First, take the short cut when we know it is a loop and
1704       // the EntryControl data path is dead.
1705       // Loop node may have only one input because entry path
1706       // is removed in PhaseIdealLoop::Dominators().
1707       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1708       bool is_loop = (r->is_Loop() && r->req() == 3);
1709       // Then, check if there is a data loop when phi references itself directly
1710       // or through other data nodes.
1711       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1712           (!is_loop && is_unsafe_data_reference(uin))) {
1713         // Break this data loop to avoid creation of a dead loop.
1714         if (can_reshape) {
1715           return top;
1716         } else {
1717           // We can't return top if we are in Parse phase - cut inputs only
1718           // let Identity to handle the case.
1719           replace_edge(uin, top);
1720           return NULL;
1721         }
1722       }
1723     }
1724 
1725     if (uncasted) {
1726       // Add cast nodes between the phi to be removed and its unique input.
1727       // Wait until after parsing for the type information to propagate from the casts.
1728       assert(can_reshape, "Invalid during parsing");
1729       const Type* phi_type = bottom_type();
1730       assert(phi_type->isa_int() || phi_type->isa_ptr(), "bad phi type");
1731       // Add casts to carry the control dependency of the Phi that is
1732       // going away
1733       Node* cast = NULL;
1734       if (phi_type->isa_int()) {
1735         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1736       } else {
1737         const Type* uin_type = phase->type(uin);
1738         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1739           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1740         } else {
1741           // Use a CastPP for a cast to not null and a CheckCastPP for
1742           // a cast to a new klass (and both if both null-ness and
1743           // klass change).
1744 
1745           // If the type of phi is not null but the type of uin may be
1746           // null, uin's type must be casted to not null
1747           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1748               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1749             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1750           }
1751 
1752           // If the type of phi and uin, both casted to not null,
1753           // differ the klass of uin must be (check)cast'ed to match
1754           // that of phi
1755           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1756             Node* n = uin;
1757             if (cast != NULL) {
1758               cast = phase->transform(cast);
1759               n = cast;
1760             }
1761             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
1762           }
1763           if (cast == NULL) {
1764             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1765           }
1766         }
1767       }
1768       assert(cast != NULL, "cast should be set");
1769       cast = phase->transform(cast);
1770       // set all inputs to the new cast(s) so the Phi is removed by Identity
1771       PhaseIterGVN* igvn = phase->is_IterGVN();
1772       for (uint i = 1; i < req(); i++) {
1773         set_req_X(i, cast, igvn);
1774       }
1775       uin = cast;
1776     }
1777 
1778     // One unique input.
1779     debug_only(Node* ident = Identity(phase));
1780     // The unique input must eventually be detected by the Identity call.
1781 #ifdef ASSERT
1782     if (ident != uin && !ident->is_top()) {
1783       // print this output before failing assert
1784       r->dump(3);
1785       this->dump(3);
1786       ident->dump();
1787       uin->dump();
1788     }
1789 #endif
1790     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1791     return NULL;
1792   }
1793 
1794   Node* opt = NULL;
1795   int true_path = is_diamond_phi();
1796   if( true_path != 0 ) {
1797     // Check for CMove'ing identity. If it would be unsafe,
1798     // handle it here. In the safe case, let Identity handle it.
1799     Node* unsafe_id = is_cmove_id(phase, true_path);
1800     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1801       opt = unsafe_id;
1802 
1803     // Check for simple convert-to-boolean pattern
1804     if( opt == NULL )
1805       opt = is_x2logic(phase, this, true_path);
1806 
1807     // Check for absolute value
1808     if( opt == NULL )
1809       opt = is_absolute(phase, this, true_path);
1810 
1811     // Check for conditional add
1812     if( opt == NULL && can_reshape )
1813       opt = is_cond_add(phase, this, true_path);
1814 
1815     // These 4 optimizations could subsume the phi:
1816     // have to check for a dead data loop creation.
1817     if( opt != NULL ) {
1818       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
1819         // Found dead loop.
1820         if( can_reshape )
1821           return top;
1822         // We can't return top if we are in Parse phase - cut inputs only
1823         // to stop further optimizations for this phi. Identity will return TOP.
1824         assert(req() == 3, "only diamond merge phi here");
1825         set_req(1, top);
1826         set_req(2, top);
1827         return NULL;
1828       } else {
1829         return opt;
1830       }
1831     }
1832   }
1833 
1834   // Check for merging identical values and split flow paths
1835   if (can_reshape) {
1836     opt = split_flow_path(phase, this);
1837     // This optimization only modifies phi - don't need to check for dead loop.
1838     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
1839     if (opt != NULL)  return opt;
1840   }
1841 
1842   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
1843     // Try to undo Phi of AddP:
1844     // (Phi (AddP base base y) (AddP base2 base2 y))
1845     // becomes:
1846     // newbase := (Phi base base2)
1847     // (AddP newbase newbase y)
1848     //
1849     // This occurs as a result of unsuccessful split_thru_phi and
1850     // interferes with taking advantage of addressing modes. See the
1851     // clone_shift_expressions code in matcher.cpp
1852     Node* addp = in(1);
1853     const Type* type = addp->in(AddPNode::Base)->bottom_type();
1854     Node* y = addp->in(AddPNode::Offset);
1855     if (y != NULL && addp->in(AddPNode::Base) == addp->in(AddPNode::Address)) {
1856       // make sure that all the inputs are similar to the first one,
1857       // i.e. AddP with base == address and same offset as first AddP
1858       bool doit = true;
1859       for (uint i = 2; i < req(); i++) {
1860         if (in(i) == NULL ||
1861             in(i)->Opcode() != Op_AddP ||
1862             in(i)->in(AddPNode::Base) != in(i)->in(AddPNode::Address) ||
1863             in(i)->in(AddPNode::Offset) != y) {
1864           doit = false;
1865           break;
1866         }
1867         // Accumulate type for resulting Phi
1868         type = type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
1869       }
1870       Node* base = NULL;
1871       if (doit) {
1872         // Check for neighboring AddP nodes in a tree.
1873         // If they have a base, use that it.
1874         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
1875           Node* u = this->fast_out(k);
1876           if (u->is_AddP()) {
1877             Node* base2 = u->in(AddPNode::Base);
1878             if (base2 != NULL && !base2->is_top()) {
1879               if (base == NULL)
1880                 base = base2;
1881               else if (base != base2)
1882                 { doit = false; break; }
1883             }
1884           }
1885         }
1886       }
1887       if (doit) {
1888         if (base == NULL) {
1889           base = new PhiNode(in(0), type, NULL);
1890           for (uint i = 1; i < req(); i++) {
1891             base->init_req(i, in(i)->in(AddPNode::Base));
1892           }
1893           phase->is_IterGVN()->register_new_node_with_optimizer(base);
1894         }
1895         return new AddPNode(base, base, y);
1896       }
1897     }
1898   }
1899 
1900   // Split phis through memory merges, so that the memory merges will go away.
1901   // Piggy-back this transformation on the search for a unique input....
1902   // It will be as if the merged memory is the unique value of the phi.
1903   // (Do not attempt this optimization unless parsing is complete.
1904   // It would make the parser's memory-merge logic sick.)
1905   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
1906   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
1907     // see if this phi should be sliced
1908     uint merge_width = 0;
1909     bool saw_self = false;
1910     for( uint i=1; i<req(); ++i ) {// For all paths in
1911       Node *ii = in(i);
1912       // TOP inputs should not be counted as safe inputs because if the
1913       // Phi references itself through all other inputs then splitting the
1914       // Phi through memory merges would create dead loop at later stage.
1915       if (ii == top) {
1916         return NULL; // Delay optimization until graph is cleaned.
1917       }
1918       if (ii->is_MergeMem()) {
1919         MergeMemNode* n = ii->as_MergeMem();
1920         merge_width = MAX2(merge_width, n->req());
1921         saw_self = saw_self || phase->eqv(n->base_memory(), this);
1922       }
1923     }
1924 
1925     // This restriction is temporarily necessary to ensure termination:
1926     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
1927 
1928     if (merge_width > Compile::AliasIdxRaw) {
1929       // found at least one non-empty MergeMem
1930       const TypePtr* at = adr_type();
1931       if (at != TypePtr::BOTTOM) {
1932         // Patch the existing phi to select an input from the merge:
1933         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
1934         //     Phi:AT1(...m1...)
1935         int alias_idx = phase->C->get_alias_index(at);
1936         for (uint i=1; i<req(); ++i) {
1937           Node *ii = in(i);
1938           if (ii->is_MergeMem()) {
1939             MergeMemNode* n = ii->as_MergeMem();
1940             // compress paths and change unreachable cycles to TOP
1941             // If not, we can update the input infinitely along a MergeMem cycle
1942             // Equivalent code is in MemNode::Ideal_common
1943             Node *m  = phase->transform(n);
1944             if (outcnt() == 0) {  // Above transform() may kill us!
1945               return top;
1946             }
1947             // If transformed to a MergeMem, get the desired slice
1948             // Otherwise the returned node represents memory for every slice
1949             Node *new_mem = (m->is_MergeMem()) ?
1950                              m->as_MergeMem()->memory_at(alias_idx) : m;
1951             // Update input if it is progress over what we have now
1952             if (new_mem != ii) {
1953               set_req(i, new_mem);
1954               progress = this;
1955             }
1956           }
1957         }
1958       } else {
1959         // We know that at least one MergeMem->base_memory() == this
1960         // (saw_self == true). If all other inputs also references this phi
1961         // (directly or through data nodes) - it is dead loop.
1962         bool saw_safe_input = false;
1963         for (uint j = 1; j < req(); ++j) {
1964           Node *n = in(j);
1965           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
1966             continue;              // skip known cases
1967           if (!is_unsafe_data_reference(n)) {
1968             saw_safe_input = true; // found safe input
1969             break;
1970           }
1971         }
1972         if (!saw_safe_input)
1973           return top; // all inputs reference back to this phi - dead loop
1974 
1975         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
1976         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
1977         PhaseIterGVN *igvn = phase->is_IterGVN();
1978         Node* hook = new Node(1);
1979         PhiNode* new_base = (PhiNode*) clone();
1980         // Must eagerly register phis, since they participate in loops.
1981         if (igvn) {
1982           igvn->register_new_node_with_optimizer(new_base);
1983           hook->add_req(new_base);
1984         }
1985         MergeMemNode* result = MergeMemNode::make(new_base);
1986         for (uint i = 1; i < req(); ++i) {
1987           Node *ii = in(i);
1988           if (ii->is_MergeMem()) {
1989             MergeMemNode* n = ii->as_MergeMem();
1990             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
1991               // If we have not seen this slice yet, make a phi for it.
1992               bool made_new_phi = false;
1993               if (mms.is_empty()) {
1994                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
1995                 made_new_phi = true;
1996                 if (igvn) {
1997                   igvn->register_new_node_with_optimizer(new_phi);
1998                   hook->add_req(new_phi);
1999                 }
2000                 mms.set_memory(new_phi);
2001               }
2002               Node* phi = mms.memory();
2003               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2004               phi->set_req(i, mms.memory2());
2005             }
2006           }
2007         }
2008         // Distribute all self-loops.
2009         { // (Extra braces to hide mms.)
2010           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2011             Node* phi = mms.memory();
2012             for (uint i = 1; i < req(); ++i) {
2013               if (phi->in(i) == this)  phi->set_req(i, phi);
2014             }
2015           }
2016         }
2017         // now transform the new nodes, and return the mergemem
2018         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2019           Node* phi = mms.memory();
2020           mms.set_memory(phase->transform(phi));
2021         }
2022         if (igvn) { // Unhook.
2023           igvn->hash_delete(hook);
2024           for (uint i = 1; i < hook->req(); i++) {
2025             hook->set_req(i, NULL);
2026           }
2027         }
2028         // Replace self with the result.
2029         return result;
2030       }
2031     }
2032     //
2033     // Other optimizations on the memory chain
2034     //
2035     const TypePtr* at = adr_type();
2036     for( uint i=1; i<req(); ++i ) {// For all paths in
2037       Node *ii = in(i);
2038       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2039       if (ii != new_in ) {
2040         set_req(i, new_in);
2041         progress = this;
2042       }
2043     }
2044   }
2045 
2046 #ifdef _LP64
2047   // Push DecodeN/DecodeNKlass down through phi.
2048   // The rest of phi graph will transform by split EncodeP node though phis up.
2049   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2050     bool may_push = true;
2051     bool has_decodeN = false;
2052     bool is_decodeN = false;
2053     for (uint i=1; i<req(); ++i) {// For all paths in
2054       Node *ii = in(i);
2055       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2056         // Do optimization if a non dead path exist.
2057         if (ii->in(1)->bottom_type() != Type::TOP) {
2058           has_decodeN = true;
2059           is_decodeN = ii->is_DecodeN();
2060         }
2061       } else if (!ii->is_Phi()) {
2062         may_push = false;
2063       }
2064     }
2065 
2066     if (has_decodeN && may_push) {
2067       PhaseIterGVN *igvn = phase->is_IterGVN();
2068       // Make narrow type for new phi.
2069       const Type* narrow_t;
2070       if (is_decodeN) {
2071         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2072       } else {
2073         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2074       }
2075       PhiNode* new_phi = new PhiNode(r, narrow_t);
2076       uint orig_cnt = req();
2077       for (uint i=1; i<req(); ++i) {// For all paths in
2078         Node *ii = in(i);
2079         Node* new_ii = NULL;
2080         if (ii->is_DecodeNarrowPtr()) {
2081           assert(ii->bottom_type() == bottom_type(), "sanity");
2082           new_ii = ii->in(1);
2083         } else {
2084           assert(ii->is_Phi(), "sanity");
2085           if (ii->as_Phi() == this) {
2086             new_ii = new_phi;
2087           } else {
2088             if (is_decodeN) {
2089               new_ii = new EncodePNode(ii, narrow_t);
2090             } else {
2091               new_ii = new EncodePKlassNode(ii, narrow_t);
2092             }
2093             igvn->register_new_node_with_optimizer(new_ii);
2094           }
2095         }
2096         new_phi->set_req(i, new_ii);
2097       }
2098       igvn->register_new_node_with_optimizer(new_phi, this);
2099       if (is_decodeN) {
2100         progress = new DecodeNNode(new_phi, bottom_type());
2101       } else {
2102         progress = new DecodeNKlassNode(new_phi, bottom_type());
2103       }
2104     }
2105   }
2106 #endif
2107 
2108   return progress;              // Return any progress
2109 }
2110 
2111 //------------------------------is_tripcount-----------------------------------
2112 bool PhiNode::is_tripcount() const {
2113   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2114           in(0)->as_CountedLoop()->phi() == this);
2115 }
2116 
2117 //------------------------------out_RegMask------------------------------------
2118 const RegMask &PhiNode::in_RegMask(uint i) const {
2119   return i ? out_RegMask() : RegMask::Empty;
2120 }
2121 
2122 const RegMask &PhiNode::out_RegMask() const {
2123   uint ideal_reg = _type->ideal_reg();
2124   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2125   if( ideal_reg == 0 ) return RegMask::Empty;
2126   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2127   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2128 }
2129 
2130 #ifndef PRODUCT
2131 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2132   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2133   // and all outputs till level 1. In compact mode, inputs till level 1 are
2134   // collected.
2135   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2136   this->collect_nodes(out_rel, -1, false, false);
2137 }
2138 
2139 void PhiNode::dump_spec(outputStream *st) const {
2140   TypeNode::dump_spec(st);
2141   if (is_tripcount()) {
2142     st->print(" #tripcount");
2143   }
2144 }
2145 #endif
2146 
2147 
2148 //=============================================================================
2149 const Type* GotoNode::Value(PhaseGVN* phase) const {
2150   // If the input is reachable, then we are executed.
2151   // If the input is not reachable, then we are not executed.
2152   return phase->type(in(0));
2153 }
2154 
2155 Node* GotoNode::Identity(PhaseGVN* phase) {
2156   return in(0);                // Simple copy of incoming control
2157 }
2158 
2159 const RegMask &GotoNode::out_RegMask() const {
2160   return RegMask::Empty;
2161 }
2162 
2163 #ifndef PRODUCT
2164 //-----------------------------related-----------------------------------------
2165 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2166 // outputs at level 1. This is regardless of compact mode.
2167 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2168   this->collect_nodes(in_rel, 1, false, false);
2169   this->collect_nodes(out_rel, -1, false, false);
2170 }
2171 #endif
2172 
2173 
2174 //=============================================================================
2175 const RegMask &JumpNode::out_RegMask() const {
2176   return RegMask::Empty;
2177 }
2178 
2179 #ifndef PRODUCT
2180 //-----------------------------related-----------------------------------------
2181 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2182 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2183 // This is regardless of compact mode.
2184 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2185   this->collect_nodes(in_rel, 1, false, false);
2186   this->collect_nodes(out_rel, -2, false, false);
2187 }
2188 #endif
2189 
2190 //=============================================================================
2191 const RegMask &JProjNode::out_RegMask() const {
2192   return RegMask::Empty;
2193 }
2194 
2195 //=============================================================================
2196 const RegMask &CProjNode::out_RegMask() const {
2197   return RegMask::Empty;
2198 }
2199 
2200 
2201 
2202 //=============================================================================
2203 
2204 uint PCTableNode::hash() const { return Node::hash() + _size; }
2205 uint PCTableNode::cmp( const Node &n ) const
2206 { return _size == ((PCTableNode&)n)._size; }
2207 
2208 const Type *PCTableNode::bottom_type() const {
2209   const Type** f = TypeTuple::fields(_size);
2210   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2211   return TypeTuple::make(_size, f);
2212 }
2213 
2214 //------------------------------Value------------------------------------------
2215 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2216 // Control, otherwise the table targets are not reachable
2217 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2218   if( phase->type(in(0)) == Type::CONTROL )
2219     return bottom_type();
2220   return Type::TOP;             // All paths dead?  Then so are we
2221 }
2222 
2223 //------------------------------Ideal------------------------------------------
2224 // Return a node which is more "ideal" than the current node.  Strip out
2225 // control copies
2226 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2227   return remove_dead_region(phase, can_reshape) ? this : NULL;
2228 }
2229 
2230 //=============================================================================
2231 uint JumpProjNode::hash() const {
2232   return Node::hash() + _dest_bci;
2233 }
2234 
2235 uint JumpProjNode::cmp( const Node &n ) const {
2236   return ProjNode::cmp(n) &&
2237     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2238 }
2239 
2240 #ifndef PRODUCT
2241 void JumpProjNode::dump_spec(outputStream *st) const {
2242   ProjNode::dump_spec(st);
2243   st->print("@bci %d ",_dest_bci);
2244 }
2245 
2246 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2247   ProjNode::dump_compact_spec(st);
2248   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2249 }
2250 
2251 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2252   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2253   this->collect_nodes(in_rel, 1, false, false);
2254   this->collect_nodes(out_rel, -1, false, false);
2255 }
2256 #endif
2257 
2258 //=============================================================================
2259 //------------------------------Value------------------------------------------
2260 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2261 // have the default "fall_through_index" path.
2262 const Type* CatchNode::Value(PhaseGVN* phase) const {
2263   // Unreachable?  Then so are all paths from here.
2264   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2265   // First assume all paths are reachable
2266   const Type** f = TypeTuple::fields(_size);
2267   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2268   // Identify cases that will always throw an exception
2269   // () rethrow call
2270   // () virtual or interface call with NULL receiver
2271   // () call is a check cast with incompatible arguments
2272   if( in(1)->is_Proj() ) {
2273     Node *i10 = in(1)->in(0);
2274     if( i10->is_Call() ) {
2275       CallNode *call = i10->as_Call();
2276       // Rethrows always throw exceptions, never return
2277       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2278         f[CatchProjNode::fall_through_index] = Type::TOP;
2279       } else if( call->req() > TypeFunc::Parms ) {
2280         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2281         // Check for null receiver to virtual or interface calls
2282         if( call->is_CallDynamicJava() &&
2283             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2284           f[CatchProjNode::fall_through_index] = Type::TOP;
2285         }
2286       } // End of if not a runtime stub
2287     } // End of if have call above me
2288   } // End of slot 1 is not a projection
2289   return TypeTuple::make(_size, f);
2290 }
2291 
2292 //=============================================================================
2293 uint CatchProjNode::hash() const {
2294   return Node::hash() + _handler_bci;
2295 }
2296 
2297 
2298 uint CatchProjNode::cmp( const Node &n ) const {
2299   return ProjNode::cmp(n) &&
2300     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2301 }
2302 
2303 
2304 //------------------------------Identity---------------------------------------
2305 // If only 1 target is possible, choose it if it is the main control
2306 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2307   // If my value is control and no other value is, then treat as ID
2308   const TypeTuple *t = phase->type(in(0))->is_tuple();
2309   if (t->field_at(_con) != Type::CONTROL)  return this;
2310   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2311   // also remove any exception table entry.  Thus we must know the call
2312   // feeding the Catch will not really throw an exception.  This is ok for
2313   // the main fall-thru control (happens when we know a call can never throw
2314   // an exception) or for "rethrow", because a further optimization will
2315   // yank the rethrow (happens when we inline a function that can throw an
2316   // exception and the caller has no handler).  Not legal, e.g., for passing
2317   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2318   // These cases MUST throw an exception via the runtime system, so the VM
2319   // will be looking for a table entry.
2320   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2321   CallNode *call;
2322   if (_con != TypeFunc::Control && // Bail out if not the main control.
2323       !(proj->is_Proj() &&      // AND NOT a rethrow
2324         proj->in(0)->is_Call() &&
2325         (call = proj->in(0)->as_Call()) &&
2326         call->entry_point() == OptoRuntime::rethrow_stub()))
2327     return this;
2328 
2329   // Search for any other path being control
2330   for (uint i = 0; i < t->cnt(); i++) {
2331     if (i != _con && t->field_at(i) == Type::CONTROL)
2332       return this;
2333   }
2334   // Only my path is possible; I am identity on control to the jump
2335   return in(0)->in(0);
2336 }
2337 
2338 
2339 #ifndef PRODUCT
2340 void CatchProjNode::dump_spec(outputStream *st) const {
2341   ProjNode::dump_spec(st);
2342   st->print("@bci %d ",_handler_bci);
2343 }
2344 #endif
2345 
2346 //=============================================================================
2347 //------------------------------Identity---------------------------------------
2348 // Check for CreateEx being Identity.
2349 Node* CreateExNode::Identity(PhaseGVN* phase) {
2350   if( phase->type(in(1)) == Type::TOP ) return in(1);
2351   if( phase->type(in(0)) == Type::TOP ) return in(0);
2352   // We only come from CatchProj, unless the CatchProj goes away.
2353   // If the CatchProj is optimized away, then we just carry the
2354   // exception oop through.
2355   CallNode *call = in(1)->in(0)->as_Call();
2356 
2357   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2358     ? this
2359     : call->in(TypeFunc::Parms);
2360 }
2361 
2362 //=============================================================================
2363 //------------------------------Value------------------------------------------
2364 // Check for being unreachable.
2365 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2366   if (!in(0) || in(0)->is_top()) return Type::TOP;
2367   return bottom_type();
2368 }
2369 
2370 //------------------------------Ideal------------------------------------------
2371 // Check for no longer being part of a loop
2372 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2373   if (can_reshape && !in(0)->is_Loop()) {
2374     // Dead code elimination can sometimes delete this projection so
2375     // if it's not there, there's nothing to do.
2376     Node* fallthru = proj_out_or_null(0);
2377     if (fallthru != NULL) {
2378       phase->is_IterGVN()->replace_node(fallthru, in(0));
2379     }
2380     return phase->C->top();
2381   }
2382   return NULL;
2383 }
2384 
2385 #ifndef PRODUCT
2386 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2387   st->print("%s", Name());
2388 }
2389 #endif
--- EOF ---