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 #include "utilities/macros.hpp"
  46 #if INCLUDE_SHENANDOAHGC
  47 #include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
  48 #endif
  49 
  50 // Portions of code courtesy of Clifford Click
  51 
  52 // Optimization - Graph Style
  53 
  54 //=============================================================================
  55 //------------------------------Value------------------------------------------
  56 // Compute the type of the RegionNode.
  57 const Type* RegionNode::Value(PhaseGVN* phase) const {
  58   for( uint i=1; i<req(); ++i ) {       // For all paths in
  59     Node *n = in(i);            // Get Control source
  60     if( !n ) continue;          // Missing inputs are TOP
  61     if( phase->type(n) == Type::CONTROL )
  62       return Type::CONTROL;
  63   }
  64   return Type::TOP;             // All paths dead?  Then so are we
  65 }
  66 
  67 //------------------------------Identity---------------------------------------
  68 // Check for Region being Identity.
  69 Node* RegionNode::Identity(PhaseGVN* phase) {
  70   // Cannot have Region be an identity, even if it has only 1 input.
  71   // Phi users cannot have their Region input folded away for them,
  72   // since they need to select the proper data input
  73   return this;
  74 }
  75 
  76 //------------------------------merge_region-----------------------------------
  77 // If a Region flows into a Region, merge into one big happy merge.  This is
  78 // hard to do if there is stuff that has to happen
  79 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  80   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  81     return NULL;
  82   Node *progress = NULL;        // Progress flag
  83   PhaseIterGVN *igvn = phase->is_IterGVN();
  84 
  85   uint rreq = region->req();
  86   for( uint i = 1; i < rreq; i++ ) {
  87     Node *r = region->in(i);
  88     if( r && r->Opcode() == Op_Region && // Found a region?
  89         r->in(0) == r &&        // Not already collapsed?
  90         r != region &&          // Avoid stupid situations
  91         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  92       assert(!r->as_Region()->has_phi(), "no phi users");
  93       if( !progress ) {         // No progress
  94         if (region->has_phi()) {
  95           return NULL;        // Only flatten if no Phi users
  96           // igvn->hash_delete( phi );
  97         }
  98         igvn->hash_delete( region );
  99         progress = region;      // Making progress
 100       }
 101       igvn->hash_delete( r );
 102 
 103       // Append inputs to 'r' onto 'region'
 104       for( uint j = 1; j < r->req(); j++ ) {
 105         // Move an input from 'r' to 'region'
 106         region->add_req(r->in(j));
 107         r->set_req(j, phase->C->top());
 108         // Update phis of 'region'
 109         //for( uint k = 0; k < max; k++ ) {
 110         //  Node *phi = region->out(k);
 111         //  if( phi->is_Phi() ) {
 112         //    phi->add_req(phi->in(i));
 113         //  }
 114         //}
 115 
 116         rreq++;                 // One more input to Region
 117       } // Found a region to merge into Region
 118       igvn->_worklist.push(r);
 119       // Clobber pointer to the now dead 'r'
 120       region->set_req(i, phase->C->top());
 121     }
 122   }
 123 
 124   return progress;
 125 }
 126 
 127 
 128 
 129 //--------------------------------has_phi--------------------------------------
 130 // Helper function: Return any PhiNode that uses this region or NULL
 131 PhiNode* RegionNode::has_phi() const {
 132   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 133     Node* phi = fast_out(i);
 134     if (phi->is_Phi()) {   // Check for Phi users
 135       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 136       return phi->as_Phi();  // this one is good enough
 137     }
 138   }
 139 
 140   return NULL;
 141 }
 142 
 143 
 144 //-----------------------------has_unique_phi----------------------------------
 145 // Helper function: Return the only PhiNode that uses this region or NULL
 146 PhiNode* RegionNode::has_unique_phi() const {
 147   // Check that only one use is a Phi
 148   PhiNode* only_phi = NULL;
 149   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 150     Node* phi = fast_out(i);
 151     if (phi->is_Phi()) {   // Check for Phi users
 152       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 153       if (only_phi == NULL) {
 154         only_phi = phi->as_Phi();
 155       } else {
 156         return NULL;  // multiple phis
 157       }
 158     }
 159   }
 160 
 161   return only_phi;
 162 }
 163 
 164 
 165 //------------------------------check_phi_clipping-----------------------------
 166 // Helper function for RegionNode's identification of FP clipping
 167 // Check inputs to the Phi
 168 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 169   min     = NULL;
 170   max     = NULL;
 171   val     = NULL;
 172   min_idx = 0;
 173   max_idx = 0;
 174   val_idx = 0;
 175   uint  phi_max = phi->req();
 176   if( phi_max == 4 ) {
 177     for( uint j = 1; j < phi_max; ++j ) {
 178       Node *n = phi->in(j);
 179       int opcode = n->Opcode();
 180       switch( opcode ) {
 181       case Op_ConI:
 182         {
 183           if( min == NULL ) {
 184             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 185             min_idx = j;
 186           } else {
 187             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 188             max_idx = j;
 189             if( min->get_int() > max->get_int() ) {
 190               // Swap min and max
 191               ConNode *temp;
 192               uint     temp_idx;
 193               temp     = min;     min     = max;     max     = temp;
 194               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 195             }
 196           }
 197         }
 198         break;
 199       default:
 200         {
 201           val = n;
 202           val_idx = j;
 203         }
 204         break;
 205       }
 206     }
 207   }
 208   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 209 }
 210 
 211 
 212 //------------------------------check_if_clipping------------------------------
 213 // Helper function for RegionNode's identification of FP clipping
 214 // Check that inputs to Region come from two IfNodes,
 215 //
 216 //            If
 217 //      False    True
 218 //       If        |
 219 //  False  True    |
 220 //    |      |     |
 221 //  RegionNode_inputs
 222 //
 223 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 224   top_if = NULL;
 225   bot_if = NULL;
 226 
 227   // Check control structure above RegionNode for (if  ( if  ) )
 228   Node *in1 = region->in(1);
 229   Node *in2 = region->in(2);
 230   Node *in3 = region->in(3);
 231   // Check that all inputs are projections
 232   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 233     Node *in10 = in1->in(0);
 234     Node *in20 = in2->in(0);
 235     Node *in30 = in3->in(0);
 236     // Check that #1 and #2 are ifTrue and ifFalse from same If
 237     if( in10 != NULL && in10->is_If() &&
 238         in20 != NULL && in20->is_If() &&
 239         in30 != NULL && in30->is_If() && in10 == in20 &&
 240         (in1->Opcode() != in2->Opcode()) ) {
 241       Node  *in100 = in10->in(0);
 242       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 243       // Check that control for in10 comes from other branch of IF from in3
 244       if( in1000 != NULL && in1000->is_If() &&
 245           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 246         // Control pattern checks
 247         top_if = (IfNode*)in1000;
 248         bot_if = (IfNode*)in10;
 249       }
 250     }
 251   }
 252 
 253   return (top_if != NULL);
 254 }
 255 
 256 
 257 //------------------------------check_convf2i_clipping-------------------------
 258 // Helper function for RegionNode's identification of FP clipping
 259 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 260 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 261   convf2i = NULL;
 262 
 263   // Check for the RShiftNode
 264   Node *rshift = phi->in(idx);
 265   assert( rshift, "Previous checks ensure phi input is present");
 266   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 267 
 268   // Check for the LShiftNode
 269   Node *lshift = rshift->in(1);
 270   assert( lshift, "Previous checks ensure phi input is present");
 271   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 272 
 273   // Check for the ConvF2INode
 274   Node *conv = lshift->in(1);
 275   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 276 
 277   // Check that shift amounts are only to get sign bits set after F2I
 278   jint max_cutoff     = max->get_int();
 279   jint min_cutoff     = min->get_int();
 280   jint left_shift     = lshift->in(2)->get_int();
 281   jint right_shift    = rshift->in(2)->get_int();
 282   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 283   if( left_shift != right_shift ||
 284       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 285       max_post_shift < max_cutoff ||
 286       max_post_shift < -min_cutoff ) {
 287     // Shifts are necessary but current transformation eliminates them
 288     return false;
 289   }
 290 
 291   // OK to return the result of ConvF2I without shifting
 292   convf2i = (ConvF2INode*)conv;
 293   return true;
 294 }
 295 
 296 
 297 //------------------------------check_compare_clipping-------------------------
 298 // Helper function for RegionNode's identification of FP clipping
 299 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 300   Node *i1 = iff->in(1);
 301   if ( !i1->is_Bool() ) { return false; }
 302   BoolNode *bool1 = i1->as_Bool();
 303   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 304   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 305   const Node *cmpF = bool1->in(1);
 306   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 307   // Test that the float value being compared against
 308   // is equivalent to the int value used as a limit
 309   Node *nodef = cmpF->in(2);
 310   if( nodef->Opcode() != Op_ConF ) { return false; }
 311   jfloat conf = nodef->getf();
 312   jint   coni = limit->get_int();
 313   if( ((int)conf) != coni )        { return false; }
 314   input = cmpF->in(1);
 315   return true;
 316 }
 317 
 318 //------------------------------is_unreachable_region--------------------------
 319 // Find if the Region node is reachable from the root.
 320 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
 321   assert(req() == 2, "");
 322 
 323   // First, cut the simple case of fallthrough region when NONE of
 324   // region's phis references itself directly or through a data node.
 325   uint max = outcnt();
 326   uint i;
 327   for (i = 0; i < max; i++) {
 328     Node* phi = raw_out(i);
 329     if (phi != NULL && phi->is_Phi()) {
 330       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
 331       if (phi->outcnt() == 0)
 332         continue; // Safe case - no loops
 333       if (phi->outcnt() == 1) {
 334         Node* u = phi->raw_out(0);
 335         // Skip if only one use is an other Phi or Call or Uncommon trap.
 336         // It is safe to consider this case as fallthrough.
 337         if (u != NULL && (u->is_Phi() || u->is_CFG()))
 338           continue;
 339       }
 340       // Check when phi references itself directly or through an other node.
 341       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
 342         break; // Found possible unsafe data loop.
 343     }
 344   }
 345   if (i >= max)
 346     return false; // An unsafe case was NOT found - don't need graph walk.
 347 
 348   // Unsafe case - check if the Region node is reachable from root.
 349   ResourceMark rm;
 350 
 351   Arena *a = Thread::current()->resource_area();
 352   Node_List nstack(a);
 353   VectorSet visited(a);
 354 
 355   // Mark all control nodes reachable from root outputs
 356   Node *n = (Node*)phase->C->root();
 357   nstack.push(n);
 358   visited.set(n->_idx);
 359   while (nstack.size() != 0) {
 360     n = nstack.pop();
 361     uint max = n->outcnt();
 362     for (uint i = 0; i < max; i++) {
 363       Node* m = n->raw_out(i);
 364       if (m != NULL && m->is_CFG()) {
 365         if (phase->eqv(m, this)) {
 366           return false; // We reached the Region node - it is not dead.
 367         }
 368         if (!visited.test_set(m->_idx))
 369           nstack.push(m);
 370       }
 371     }
 372   }
 373 
 374   return true; // The Region node is unreachable - it is dead.
 375 }
 376 
 377 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 378   // Incremental inlining + PhaseStringOpts sometimes produce:
 379   //
 380   // cmpP with 1 top input
 381   //           |
 382   //          If
 383   //         /  \
 384   //   IfFalse  IfTrue  /- Some Node
 385   //         \  /      /    /
 386   //        Region    / /-MergeMem
 387   //             \---Phi
 388   //
 389   //
 390   // It's expected by PhaseStringOpts that the Region goes away and is
 391   // replaced by If's control input but because there's still a Phi,
 392   // the Region stays in the graph. The top input from the cmpP is
 393   // propagated forward and a subgraph that is useful goes away. The
 394   // code below replaces the Phi with the MergeMem so that the Region
 395   // is simplified.
 396 
 397   PhiNode* phi = has_unique_phi();
 398   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 399     MergeMemNode* m = NULL;
 400     assert(phi->req() == 3, "same as region");
 401     for (uint i = 1; i < 3; ++i) {
 402       Node *mem = phi->in(i);
 403       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 404         // Nothing is control-dependent on path #i except the region itself.
 405         m = mem->as_MergeMem();
 406         uint j = 3 - i;
 407         Node* other = phi->in(j);
 408         if (other && other == m->base_memory()) {
 409           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 410           // This will allow the diamond to collapse completely.
 411           phase->is_IterGVN()->replace_node(phi, m);
 412           return true;
 413         }
 414       }
 415     }
 416   }
 417   return false;
 418 }
 419 
 420 //------------------------------Ideal------------------------------------------
 421 // Return a node which is more "ideal" than the current node.  Must preserve
 422 // the CFG, but we can still strip out dead paths.
 423 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 424   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 425   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 426 
 427   // Check for RegionNode with no Phi users and both inputs come from either
 428   // arm of the same IF.  If found, then the control-flow split is useless.
 429   bool has_phis = false;
 430   if (can_reshape) {            // Need DU info to check for Phi users
 431     has_phis = (has_phi() != NULL);       // Cache result
 432     if (has_phis && try_clean_mem_phi(phase)) {
 433       has_phis = false;
 434     }
 435 
 436     if (!has_phis) {            // No Phi users?  Nothing merging?
 437       for (uint i = 1; i < req()-1; i++) {
 438         Node *if1 = in(i);
 439         if( !if1 ) continue;
 440         Node *iff = if1->in(0);
 441         if( !iff || !iff->is_If() ) continue;
 442         for( uint j=i+1; j<req(); j++ ) {
 443           if( in(j) && in(j)->in(0) == iff &&
 444               if1->Opcode() != in(j)->Opcode() ) {
 445             // Add the IF Projections to the worklist. They (and the IF itself)
 446             // will be eliminated if dead.
 447             phase->is_IterGVN()->add_users_to_worklist(iff);
 448             set_req(i, iff->in(0));// Skip around the useless IF diamond
 449             set_req(j, NULL);
 450             return this;      // Record progress
 451           }
 452         }
 453       }
 454     }
 455   }
 456 
 457   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 458   // degrades to a copy.
 459   bool add_to_worklist = false;
 460   bool modified = false;
 461   int cnt = 0;                  // Count of values merging
 462   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 463   int del_it = 0;               // The last input path we delete
 464   // For all inputs...
 465   for( uint i=1; i<req(); ++i ){// For all paths in
 466     Node *n = in(i);            // Get the input
 467     if( n != NULL ) {
 468       // Remove useless control copy inputs
 469       if( n->is_Region() && n->as_Region()->is_copy() ) {
 470         set_req(i, n->nonnull_req());
 471         modified = true;
 472         i--;
 473         continue;
 474       }
 475       if( n->is_Proj() ) {      // Remove useless rethrows
 476         Node *call = n->in(0);
 477         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 478           set_req(i, call->in(0));
 479           modified = true;
 480           i--;
 481           continue;
 482         }
 483       }
 484       if( phase->type(n) == Type::TOP ) {
 485         set_req(i, NULL);       // Ignore TOP inputs
 486         modified = true;
 487         i--;
 488         continue;
 489       }
 490       cnt++;                    // One more value merging
 491 
 492     } else if (can_reshape) {   // Else found dead path with DU info
 493       PhaseIterGVN *igvn = phase->is_IterGVN();
 494       del_req(i);               // Yank path from self
 495       del_it = i;
 496       uint max = outcnt();
 497       DUIterator j;
 498       bool progress = true;
 499       while(progress) {         // Need to establish property over all users
 500         progress = false;
 501         for (j = outs(); has_out(j); j++) {
 502           Node *n = out(j);
 503           if( n->req() != req() && n->is_Phi() ) {
 504             assert( n->in(0) == this, "" );
 505             igvn->hash_delete(n); // Yank from hash before hacking edges
 506             n->set_req_X(i,NULL,igvn);// Correct DU info
 507             n->del_req(i);        // Yank path from Phis
 508             if( max != outcnt() ) {
 509               progress = true;
 510               j = refresh_out_pos(j);
 511               max = outcnt();
 512             }
 513           }
 514         }
 515       }
 516       add_to_worklist = true;
 517       i--;
 518     }
 519   }
 520 
 521   if (can_reshape && cnt == 1) {
 522     // Is it dead loop?
 523     // If it is LoopNopde it had 2 (+1 itself) inputs and
 524     // one of them was cut. The loop is dead if it was EntryContol.
 525     // Loop node may have only one input because entry path
 526     // is removed in PhaseIdealLoop::Dominators().
 527     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 528     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 529                              (del_it == 0 && is_unreachable_region(phase)))) ||
 530         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 531       // Yes,  the region will be removed during the next step below.
 532       // Cut the backedge input and remove phis since no data paths left.
 533       // We don't cut outputs to other nodes here since we need to put them
 534       // on the worklist.
 535       PhaseIterGVN *igvn = phase->is_IterGVN();
 536       if (in(1)->outcnt() == 1) {
 537         igvn->_worklist.push(in(1));
 538       }
 539       del_req(1);
 540       cnt = 0;
 541       assert( req() == 1, "no more inputs expected" );
 542       uint max = outcnt();
 543       bool progress = true;
 544       Node *top = phase->C->top();
 545       DUIterator j;
 546       while(progress) {
 547         progress = false;
 548         for (j = outs(); has_out(j); j++) {
 549           Node *n = out(j);
 550           if( n->is_Phi() ) {
 551             assert( igvn->eqv(n->in(0), this), "" );
 552             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 553             // Break dead loop data path.
 554             // Eagerly replace phis with top to avoid phis copies generation.
 555             igvn->replace_node(n, top);
 556             if( max != outcnt() ) {
 557               progress = true;
 558               j = refresh_out_pos(j);
 559               max = outcnt();
 560             }
 561           }
 562         }
 563       }
 564       add_to_worklist = true;
 565     }
 566   }
 567   if (add_to_worklist) {
 568     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 569   }
 570 
 571   if( cnt <= 1 ) {              // Only 1 path in?
 572     set_req(0, NULL);           // Null control input for region copy
 573     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 574       // No inputs or all inputs are NULL.
 575       return NULL;
 576     } else if (can_reshape) {   // Optimization phase - remove the node
 577       PhaseIterGVN *igvn = phase->is_IterGVN();
 578       // Strip mined (inner) loop is going away, remove outer loop.
 579       if (is_CountedLoop() &&
 580           as_Loop()->is_strip_mined()) {
 581         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 582         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 583         if (outer_sfpt != NULL && outer_out != NULL) {
 584           Node* in = outer_sfpt->in(0);
 585           igvn->replace_node(outer_out, in);
 586           LoopNode* outer = as_CountedLoop()->outer_loop();
 587           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 588         }
 589       }
 590       Node *parent_ctrl;
 591       if( cnt == 0 ) {
 592         assert( req() == 1, "no inputs expected" );
 593         // During IGVN phase such region will be subsumed by TOP node
 594         // so region's phis will have TOP as control node.
 595         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 596         // Also set other user's input to top.
 597         parent_ctrl = phase->C->top();
 598       } else {
 599         // The fallthrough case since we already checked dead loops above.
 600         parent_ctrl = in(1);
 601         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 602         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 603       }
 604       if (!add_to_worklist)
 605         igvn->add_users_to_worklist(this); // Check for further allowed opts
 606       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 607         Node* n = last_out(i);
 608         igvn->hash_delete(n); // Remove from worklist before modifying edges
 609         if( n->is_Phi() ) {   // Collapse all Phis
 610           // Eagerly replace phis to avoid copies generation.
 611           Node* in;
 612           if( cnt == 0 ) {
 613             assert( n->req() == 1, "No data inputs expected" );
 614             in = parent_ctrl; // replaced by top
 615           } else {
 616             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 617             in = n->in(1);               // replaced by unique input
 618             if( n->as_Phi()->is_unsafe_data_reference(in) )
 619               in = phase->C->top();      // replaced by top
 620           }
 621           igvn->replace_node(n, in);
 622         }
 623         else if( n->is_Region() ) { // Update all incoming edges
 624           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 625           uint uses_found = 0;
 626           for( uint k=1; k < n->req(); k++ ) {
 627             if( n->in(k) == this ) {
 628               n->set_req(k, parent_ctrl);
 629               uses_found++;
 630             }
 631           }
 632           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 633             i -= (uses_found - 1);
 634           }
 635         }
 636         else {
 637           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 638           n->set_req(0, parent_ctrl);
 639         }
 640 #ifdef ASSERT
 641         for( uint k=0; k < n->req(); k++ ) {
 642           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 643         }
 644 #endif
 645       }
 646       // Remove the RegionNode itself from DefUse info
 647       igvn->remove_dead_node(this);
 648       return NULL;
 649     }
 650     return this;                // Record progress
 651   }
 652 
 653 
 654   // If a Region flows into a Region, merge into one big happy merge.
 655   if (can_reshape) {
 656     Node *m = merge_region(this, phase);
 657     if (m != NULL)  return m;
 658   }
 659 
 660   // Check if this region is the root of a clipping idiom on floats
 661   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 662     // Check that only one use is a Phi and that it simplifies to two constants +
 663     PhiNode* phi = has_unique_phi();
 664     if (phi != NULL) {          // One Phi user
 665       // Check inputs to the Phi
 666       ConNode *min;
 667       ConNode *max;
 668       Node    *val;
 669       uint     min_idx;
 670       uint     max_idx;
 671       uint     val_idx;
 672       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 673         IfNode *top_if;
 674         IfNode *bot_if;
 675         if( check_if_clipping( this, bot_if, top_if ) ) {
 676           // Control pattern checks, now verify compares
 677           Node   *top_in = NULL;   // value being compared against
 678           Node   *bot_in = NULL;
 679           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 680               check_compare_clipping( false, top_if, max, top_in ) ) {
 681             if( bot_in == top_in ) {
 682               PhaseIterGVN *gvn = phase->is_IterGVN();
 683               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 684               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 685 
 686               // Check for the ConvF2INode
 687               ConvF2INode *convf2i;
 688               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 689                 convf2i->in(1) == bot_in ) {
 690                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 691                 // max test
 692                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 693                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 694                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 695                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 696                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 697                 // min test
 698                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 699                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 700                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 701                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 702                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 703                 // update input edges to region node
 704                 set_req_X( min_idx, if_min, gvn );
 705                 set_req_X( max_idx, if_max, gvn );
 706                 set_req_X( val_idx, ifF,    gvn );
 707                 // remove unnecessary 'LShiftI; RShiftI' idiom
 708                 gvn->hash_delete(phi);
 709                 phi->set_req_X( val_idx, convf2i, gvn );
 710                 gvn->hash_find_insert(phi);
 711                 // Return transformed region node
 712                 return this;
 713               }
 714             }
 715           }
 716         }
 717       }
 718     }
 719   }
 720 
 721   return modified ? this : NULL;
 722 }
 723 
 724 
 725 
 726 const RegMask &RegionNode::out_RegMask() const {
 727   return RegMask::Empty;
 728 }
 729 
 730 // Find the one non-null required input.  RegionNode only
 731 Node *Node::nonnull_req() const {
 732   assert( is_Region(), "" );
 733   for( uint i = 1; i < _cnt; i++ )
 734     if( in(i) )
 735       return in(i);
 736   ShouldNotReachHere();
 737   return NULL;
 738 }
 739 
 740 
 741 //=============================================================================
 742 // note that these functions assume that the _adr_type field is flattened
 743 uint PhiNode::hash() const {
 744   const Type* at = _adr_type;
 745   return TypeNode::hash() + (at ? at->hash() : 0);
 746 }
 747 uint PhiNode::cmp( const Node &n ) const {
 748   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 749 }
 750 static inline
 751 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 752   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 753   return Compile::current()->alias_type(at)->adr_type();
 754 }
 755 
 756 //----------------------------make---------------------------------------------
 757 // create a new phi with edges matching r and set (initially) to x
 758 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 759   uint preds = r->req();   // Number of predecessor paths
 760   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 761   PhiNode* p = new PhiNode(r, t, at);
 762   for (uint j = 1; j < preds; j++) {
 763     // Fill in all inputs, except those which the region does not yet have
 764     if (r->in(j) != NULL)
 765       p->init_req(j, x);
 766   }
 767   return p;
 768 }
 769 PhiNode* PhiNode::make(Node* r, Node* x) {
 770   const Type*    t  = x->bottom_type();
 771   const TypePtr* at = NULL;
 772   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 773   return make(r, x, t, at);
 774 }
 775 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 776   const Type*    t  = x->bottom_type();
 777   const TypePtr* at = NULL;
 778   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 779   return new PhiNode(r, t, at);
 780 }
 781 
 782 
 783 //------------------------slice_memory-----------------------------------------
 784 // create a new phi with narrowed memory type
 785 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 786   PhiNode* mem = (PhiNode*) clone();
 787   *(const TypePtr**)&mem->_adr_type = adr_type;
 788   // convert self-loops, or else we get a bad graph
 789   for (uint i = 1; i < req(); i++) {
 790     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 791   }
 792   mem->verify_adr_type();
 793   return mem;
 794 }
 795 
 796 //------------------------split_out_instance-----------------------------------
 797 // Split out an instance type from a bottom phi.
 798 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 799   const TypeOopPtr *t_oop = at->isa_oopptr();
 800   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 801   const TypePtr *t = adr_type();
 802   assert(type() == Type::MEMORY &&
 803          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 804           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 805           t->is_oopptr()->cast_to_exactness(true)
 806            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 807            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 808          "bottom or raw memory required");
 809 
 810   // Check if an appropriate node already exists.
 811   Node *region = in(0);
 812   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 813     Node* use = region->fast_out(k);
 814     if( use->is_Phi()) {
 815       PhiNode *phi2 = use->as_Phi();
 816       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 817         return phi2;
 818       }
 819     }
 820   }
 821   Compile *C = igvn->C;
 822   Arena *a = Thread::current()->resource_area();
 823   Node_Array node_map = new Node_Array(a);
 824   Node_Stack stack(a, C->live_nodes() >> 4);
 825   PhiNode *nphi = slice_memory(at);
 826   igvn->register_new_node_with_optimizer( nphi );
 827   node_map.map(_idx, nphi);
 828   stack.push((Node *)this, 1);
 829   while(!stack.is_empty()) {
 830     PhiNode *ophi = stack.node()->as_Phi();
 831     uint i = stack.index();
 832     assert(i >= 1, "not control edge");
 833     stack.pop();
 834     nphi = node_map[ophi->_idx]->as_Phi();
 835     for (; i < ophi->req(); i++) {
 836       Node *in = ophi->in(i);
 837       if (in == NULL || igvn->type(in) == Type::TOP)
 838         continue;
 839       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
 840       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 841       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 842         opt = node_map[optphi->_idx];
 843         if (opt == NULL) {
 844           stack.push(ophi, i);
 845           nphi = optphi->slice_memory(at);
 846           igvn->register_new_node_with_optimizer( nphi );
 847           node_map.map(optphi->_idx, nphi);
 848           ophi = optphi;
 849           i = 0; // will get incremented at top of loop
 850           continue;
 851         }
 852       }
 853       nphi->set_req(i, opt);
 854     }
 855   }
 856   return nphi;
 857 }
 858 
 859 //------------------------verify_adr_type--------------------------------------
 860 #ifdef ASSERT
 861 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
 862   if (visited.test_set(_idx))  return;  //already visited
 863 
 864   // recheck constructor invariants:
 865   verify_adr_type(false);
 866 
 867   // recheck local phi/phi consistency:
 868   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
 869          "adr_type must be consistent across phi nest");
 870 
 871   // walk around
 872   for (uint i = 1; i < req(); i++) {
 873     Node* n = in(i);
 874     if (n == NULL)  continue;
 875     const Node* np = in(i);
 876     if (np->is_Phi()) {
 877       np->as_Phi()->verify_adr_type(visited, at);
 878     } else if (n->bottom_type() == Type::TOP
 879                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
 880       // ignore top inputs
 881     } else {
 882       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
 883       // recheck phi/non-phi consistency at leaves:
 884       assert((nat != NULL) == (at != NULL), "");
 885       assert(nat == at || nat == TypePtr::BOTTOM,
 886              "adr_type must be consistent at leaves of phi nest");
 887     }
 888   }
 889 }
 890 
 891 // Verify a whole nest of phis rooted at this one.
 892 void PhiNode::verify_adr_type(bool recursive) const {
 893   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
 894   if (Node::in_dump())               return;  // muzzle asserts when printing
 895 
 896   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
 897 
 898   if (!VerifyAliases)       return;  // verify thoroughly only if requested
 899 
 900   assert(_adr_type == flatten_phi_adr_type(_adr_type),
 901          "Phi::adr_type must be pre-normalized");
 902 
 903   if (recursive) {
 904     VectorSet visited(Thread::current()->resource_area());
 905     verify_adr_type(visited, _adr_type);
 906   }
 907 }
 908 #endif
 909 
 910 
 911 //------------------------------Value------------------------------------------
 912 // Compute the type of the PhiNode
 913 const Type* PhiNode::Value(PhaseGVN* phase) const {
 914   Node *r = in(0);              // RegionNode
 915   if( !r )                      // Copy or dead
 916     return in(1) ? phase->type(in(1)) : Type::TOP;
 917 
 918   // Note: During parsing, phis are often transformed before their regions.
 919   // This means we have to use type_or_null to defend against untyped regions.
 920   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
 921     return Type::TOP;
 922 
 923   // Check for trip-counted loop.  If so, be smarter.
 924   CountedLoopNode* l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
 925   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
 926     // protect against init_trip() or limit() returning NULL
 927     if (l->can_be_counted_loop(phase)) {
 928       const Node *init   = l->init_trip();
 929       const Node *limit  = l->limit();
 930       const Node* stride = l->stride();
 931       if (init != NULL && limit != NULL && stride != NULL) {
 932         const TypeInt* lo = phase->type(init)->isa_int();
 933         const TypeInt* hi = phase->type(limit)->isa_int();
 934         const TypeInt* stride_t = phase->type(stride)->isa_int();
 935         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
 936           assert(stride_t->_hi >= stride_t->_lo, "bad stride type");
 937           BoolTest::mask bt = l->loopexit()->test_trip();
 938           // If the loop exit condition is "not equal", the condition
 939           // would not trigger if init > limit (if stride > 0) or if
 940           // init < limit if (stride > 0) so we can't deduce bounds
 941           // for the iv from the exit condition.
 942           if (bt != BoolTest::ne) {
 943             if (stride_t->_hi < 0) {          // Down-counter loop
 944               swap(lo, hi);
 945               return TypeInt::make(MIN2(lo->_lo, hi->_lo) , hi->_hi, 3);
 946             } else if (stride_t->_lo >= 0) {
 947               return TypeInt::make(lo->_lo, MAX2(lo->_hi, hi->_hi), 3);
 948             }
 949           }
 950         }
 951       }
 952     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
 953                in(LoopNode::EntryControl) != NULL &&
 954                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
 955       // During CCP, if we saturate the type of a counted loop's Phi
 956       // before the special code for counted loop above has a chance
 957       // to run (that is as long as the type of the backedge's control
 958       // is top), we might end up with non monotonic types
 959       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
 960     }
 961   }
 962 
 963   // Until we have harmony between classes and interfaces in the type
 964   // lattice, we must tread carefully around phis which implicitly
 965   // convert the one to the other.
 966   const TypePtr* ttp = _type->make_ptr();
 967   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
 968   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
 969   bool is_intf = false;
 970   if (ttip != NULL) {
 971     ciKlass* k = ttip->klass();
 972     if (k->is_loaded() && k->is_interface())
 973       is_intf = true;
 974   }
 975   if (ttkp != NULL) {
 976     ciKlass* k = ttkp->klass();
 977     if (k->is_loaded() && k->is_interface())
 978       is_intf = true;
 979   }
 980 
 981   // Default case: merge all inputs
 982   const Type *t = Type::TOP;        // Merged type starting value
 983   for (uint i = 1; i < req(); ++i) {// For all paths in
 984     // Reachable control path?
 985     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
 986       const Type* ti = phase->type(in(i));
 987       // We assume that each input of an interface-valued Phi is a true
 988       // subtype of that interface.  This might not be true of the meet
 989       // of all the input types.  The lattice is not distributive in
 990       // such cases.  Ward off asserts in type.cpp by refusing to do
 991       // meets between interfaces and proper classes.
 992       const TypePtr* tip = ti->make_ptr();
 993       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
 994       if (tiip) {
 995         bool ti_is_intf = false;
 996         ciKlass* k = tiip->klass();
 997         if (k->is_loaded() && k->is_interface())
 998           ti_is_intf = true;
 999         if (is_intf != ti_is_intf)
1000           { t = _type; break; }
1001       }
1002       t = t->meet_speculative(ti);
1003     }
1004   }
1005 
1006   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1007   // That is, we expect that "t->higher_equal(_type)" holds true.
1008   // There are various exceptions:
1009   // - Inputs which are phis might in fact be widened unnecessarily.
1010   //   For example, an input might be a widened int while the phi is a short.
1011   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1012   //   and postCCP has removed the cast which encodes the result of the check.
1013   // - The type of this phi is an interface, and the inputs are classes.
1014   // - Value calls on inputs might produce fuzzy results.
1015   //   (Occurrences of this case suggest improvements to Value methods.)
1016   //
1017   // It is not possible to see Type::BOTTOM values as phi inputs,
1018   // because the ciTypeFlow pre-pass produces verifier-quality types.
1019   const Type* ft = t->filter_speculative(_type);  // Worst case type
1020 
1021 #ifdef ASSERT
1022   // The following logic has been moved into TypeOopPtr::filter.
1023   const Type* jt = t->join_speculative(_type);
1024   if (jt->empty()) {           // Emptied out???
1025 
1026     // Check for evil case of 't' being a class and '_type' expecting an
1027     // interface.  This can happen because the bytecodes do not contain
1028     // enough type info to distinguish a Java-level interface variable
1029     // from a Java-level object variable.  If we meet 2 classes which
1030     // both implement interface I, but their meet is at 'j/l/O' which
1031     // doesn't implement I, we have no way to tell if the result should
1032     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1033     // into a Phi which "knows" it's an Interface type we'll have to
1034     // uplift the type.
1035     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1036       assert(ft == _type, ""); // Uplift to interface
1037     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1038       assert(ft == _type, ""); // Uplift to interface
1039     } else {
1040       // We also have to handle 'evil cases' of interface- vs. class-arrays
1041       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1042       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1043           assert(ft == _type, "");   // Uplift to array of interface
1044       } else {
1045         // Otherwise it's something stupid like non-overlapping int ranges
1046         // found on dying counted loops.
1047         assert(ft == Type::TOP, ""); // Canonical empty value
1048       }
1049     }
1050   }
1051 
1052   else {
1053 
1054     // If we have an interface-typed Phi and we narrow to a class type, the join
1055     // should report back the class.  However, if we have a J/L/Object
1056     // class-typed Phi and an interface flows in, it's possible that the meet &
1057     // join report an interface back out.  This isn't possible but happens
1058     // because the type system doesn't interact well with interfaces.
1059     const TypePtr *jtp = jt->make_ptr();
1060     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1061     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
1062     if( jtip && ttip ) {
1063       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1064           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1065         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1066                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1067         jt = ft;
1068       }
1069     }
1070     if( jtkp && ttkp ) {
1071       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1072           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1073           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1074         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1075                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1076         jt = ft;
1077       }
1078     }
1079     if (jt != ft && jt->base() == ft->base()) {
1080       if (jt->isa_int() &&
1081           jt->is_int()->_lo == ft->is_int()->_lo &&
1082           jt->is_int()->_hi == ft->is_int()->_hi)
1083         jt = ft;
1084       if (jt->isa_long() &&
1085           jt->is_long()->_lo == ft->is_long()->_lo &&
1086           jt->is_long()->_hi == ft->is_long()->_hi)
1087         jt = ft;
1088     }
1089     if (jt != ft) {
1090       tty->print("merge type:  "); t->dump(); tty->cr();
1091       tty->print("kill type:   "); _type->dump(); tty->cr();
1092       tty->print("join type:   "); jt->dump(); tty->cr();
1093       tty->print("filter type: "); ft->dump(); tty->cr();
1094     }
1095     assert(jt == ft, "");
1096   }
1097 #endif //ASSERT
1098 
1099   // Deal with conversion problems found in data loops.
1100   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1101 
1102   return ft;
1103 }
1104 
1105 
1106 //------------------------------is_diamond_phi---------------------------------
1107 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1108 // index of the true path or 0 otherwise.
1109 // If check_control_only is true, do not inspect the If node at the
1110 // top, and return -1 (not an edge number) on success.
1111 int PhiNode::is_diamond_phi(bool check_control_only) const {
1112   // Check for a 2-path merge
1113   Node *region = in(0);
1114   if( !region ) return 0;
1115   if( region->req() != 3 ) return 0;
1116   if(         req() != 3 ) return 0;
1117   // Check that both paths come from the same If
1118   Node *ifp1 = region->in(1);
1119   Node *ifp2 = region->in(2);
1120   if( !ifp1 || !ifp2 ) return 0;
1121   Node *iff = ifp1->in(0);
1122   if( !iff || !iff->is_If() ) return 0;
1123   if( iff != ifp2->in(0) ) return 0;
1124   if (check_control_only)  return -1;
1125   // Check for a proper bool/cmp
1126   const Node *b = iff->in(1);
1127   if( !b->is_Bool() ) return 0;
1128   const Node *cmp = b->in(1);
1129   if( !cmp->is_Cmp() ) return 0;
1130 
1131   // Check for branching opposite expected
1132   if( ifp2->Opcode() == Op_IfTrue ) {
1133     assert( ifp1->Opcode() == Op_IfFalse, "" );
1134     return 2;
1135   } else {
1136     assert( ifp1->Opcode() == Op_IfTrue, "" );
1137     return 1;
1138   }
1139 }
1140 
1141 //----------------------------check_cmove_id-----------------------------------
1142 // Check for CMove'ing a constant after comparing against the constant.
1143 // Happens all the time now, since if we compare equality vs a constant in
1144 // the parser, we "know" the variable is constant on one path and we force
1145 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1146 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1147 // general in that we don't need constants.  Since CMove's are only inserted
1148 // in very special circumstances, we do it here on generic Phi's.
1149 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1150   assert(true_path !=0, "only diamond shape graph expected");
1151 
1152   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1153   // phi->region->if_proj->ifnode->bool->cmp
1154   Node*     region = in(0);
1155   Node*     iff    = region->in(1)->in(0);
1156   BoolNode* b      = iff->in(1)->as_Bool();
1157   Node*     cmp    = b->in(1);
1158   Node*     tval   = in(true_path);
1159   Node*     fval   = in(3-true_path);
1160   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1161   if (id == NULL)
1162     return NULL;
1163 
1164   // Either value might be a cast that depends on a branch of 'iff'.
1165   // Since the 'id' value will float free of the diamond, either
1166   // decast or return failure.
1167   Node* ctl = id->in(0);
1168   if (ctl != NULL && ctl->in(0) == iff) {
1169     if (id->is_ConstraintCast()) {
1170       return id->in(1);
1171     } else {
1172       // Don't know how to disentangle this value.
1173       return NULL;
1174     }
1175   }
1176 
1177   return id;
1178 }
1179 
1180 //------------------------------Identity---------------------------------------
1181 // Check for Region being Identity.
1182 Node* PhiNode::Identity(PhaseGVN* phase) {
1183   // Check for no merging going on
1184   // (There used to be special-case code here when this->region->is_Loop.
1185   // It would check for a tributary phi on the backedge that the main phi
1186   // trivially, perhaps with a single cast.  The unique_input method
1187   // does all this and more, by reducing such tributaries to 'this'.)
1188   Node* uin = unique_input(phase, false);
1189   if (uin != NULL) {
1190     return uin;
1191   }
1192 
1193   int true_path = is_diamond_phi();
1194   if (true_path != 0) {
1195     Node* id = is_cmove_id(phase, true_path);
1196     if (id != NULL)  return id;
1197   }
1198 
1199   return this;                     // No identity
1200 }
1201 
1202 //-----------------------------unique_input------------------------------------
1203 // Find the unique value, discounting top, self-loops, and casts.
1204 // Return top if there are no inputs, and self if there are multiple.
1205 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1206   //  1) One unique direct input,
1207   // or if uncast is true:
1208   //  2) some of the inputs have an intervening ConstraintCast
1209   //  3) an input is a self loop
1210   //
1211   //  1) input   or   2) input     or   3) input __
1212   //     /   \           /   \               \  /  \
1213   //     \   /          |    cast             phi  cast
1214   //      phi            \   /               /  \  /
1215   //                      phi               /    --
1216 
1217   Node* r = in(0);                      // RegionNode
1218   if (r == NULL)  return in(1);         // Already degraded to a Copy
1219   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1220 
1221   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1222     Node* rc = r->in(i);
1223     if (rc == NULL || phase->type(rc) == Type::TOP)
1224       continue;                 // ignore unreachable control path
1225     Node* n = in(i);
1226     if (n == NULL)
1227       continue;
1228     Node* un = n;
1229     if (uncast) {
1230 #ifdef ASSERT
1231       Node* m = un->uncast();
1232 #endif
1233       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1234         Node* next = un->in(1);
1235         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1236           // risk exposing raw ptr at safepoint
1237           break;
1238         }
1239         un = next;
1240       }
1241       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1242     }
1243     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1244       continue; // ignore if top, or in(i) and "this" are in a data cycle
1245     }
1246     // Check for a unique input (maybe uncasted)
1247     if (input == NULL) {
1248       input = un;
1249     } else if (input != un) {
1250       input = NodeSentinel; // no unique input
1251     }
1252   }
1253   if (input == NULL) {
1254     return phase->C->top();        // no inputs
1255   }
1256 
1257   if (input != NodeSentinel) {
1258     return input;           // one unique direct input
1259   }
1260 
1261   // Nothing.
1262   return NULL;
1263 }
1264 
1265 //------------------------------is_x2logic-------------------------------------
1266 // Check for simple convert-to-boolean pattern
1267 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1268 // Convert Phi to an ConvIB.
1269 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1270   assert(true_path !=0, "only diamond shape graph expected");
1271   // Convert the true/false index into an expected 0/1 return.
1272   // Map 2->0 and 1->1.
1273   int flipped = 2-true_path;
1274 
1275   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1276   // phi->region->if_proj->ifnode->bool->cmp
1277   Node *region = phi->in(0);
1278   Node *iff = region->in(1)->in(0);
1279   BoolNode *b = (BoolNode*)iff->in(1);
1280   const CmpNode *cmp = (CmpNode*)b->in(1);
1281 
1282   Node *zero = phi->in(1);
1283   Node *one  = phi->in(2);
1284   const Type *tzero = phase->type( zero );
1285   const Type *tone  = phase->type( one  );
1286 
1287   // Check for compare vs 0
1288   const Type *tcmp = phase->type(cmp->in(2));
1289   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1290     // Allow cmp-vs-1 if the other input is bounded by 0-1
1291     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1292       return NULL;
1293     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1294   }
1295 
1296   // Check for setting zero/one opposite expected
1297   if( tzero == TypeInt::ZERO ) {
1298     if( tone == TypeInt::ONE ) {
1299     } else return NULL;
1300   } else if( tzero == TypeInt::ONE ) {
1301     if( tone == TypeInt::ZERO ) {
1302       flipped = 1-flipped;
1303     } else return NULL;
1304   } else return NULL;
1305 
1306   // Check for boolean test backwards
1307   if( b->_test._test == BoolTest::ne ) {
1308   } else if( b->_test._test == BoolTest::eq ) {
1309     flipped = 1-flipped;
1310   } else return NULL;
1311 
1312   // Build int->bool concfgversion
1313   Node *n = new Conv2BNode(cmp->in(1));
1314   if( flipped )
1315     n = new XorINode( phase->transform(n), phase->intcon(1) );
1316 
1317   return n;
1318 }
1319 
1320 //------------------------------is_cond_add------------------------------------
1321 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1322 // To be profitable the control flow has to disappear; there can be no other
1323 // values merging here.  We replace the test-and-branch with:
1324 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1325 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1326 // Then convert Y to 0-or-Y and finally add.
1327 // This is a key transform for SpecJava _201_compress.
1328 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1329   assert(true_path !=0, "only diamond shape graph expected");
1330 
1331   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1332   // phi->region->if_proj->ifnode->bool->cmp
1333   RegionNode *region = (RegionNode*)phi->in(0);
1334   Node *iff = region->in(1)->in(0);
1335   BoolNode* b = iff->in(1)->as_Bool();
1336   const CmpNode *cmp = (CmpNode*)b->in(1);
1337 
1338   // Make sure only merging this one phi here
1339   if (region->has_unique_phi() != phi)  return NULL;
1340 
1341   // Make sure each arm of the diamond has exactly one output, which we assume
1342   // is the region.  Otherwise, the control flow won't disappear.
1343   if (region->in(1)->outcnt() != 1) return NULL;
1344   if (region->in(2)->outcnt() != 1) return NULL;
1345 
1346   // Check for "(P < Q)" of type signed int
1347   if (b->_test._test != BoolTest::lt)  return NULL;
1348   if (cmp->Opcode() != Op_CmpI)        return NULL;
1349 
1350   Node *p = cmp->in(1);
1351   Node *q = cmp->in(2);
1352   Node *n1 = phi->in(  true_path);
1353   Node *n2 = phi->in(3-true_path);
1354 
1355   int op = n1->Opcode();
1356   if( op != Op_AddI           // Need zero as additive identity
1357       /*&&op != Op_SubI &&
1358       op != Op_AddP &&
1359       op != Op_XorI &&
1360       op != Op_OrI*/ )
1361     return NULL;
1362 
1363   Node *x = n2;
1364   Node *y = NULL;
1365   if( x == n1->in(1) ) {
1366     y = n1->in(2);
1367   } else if( x == n1->in(2) ) {
1368     y = n1->in(1);
1369   } else return NULL;
1370 
1371   // Not so profitable if compare and add are constants
1372   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1373     return NULL;
1374 
1375   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1376   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1377   return new AddINode(j_and,x);
1378 }
1379 
1380 //------------------------------is_absolute------------------------------------
1381 // Check for absolute value.
1382 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1383   assert(true_path !=0, "only diamond shape graph expected");
1384 
1385   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1386   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1387 
1388   // ABS ends with the merge of 2 control flow paths.
1389   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1390   int false_path = 3 - true_path;
1391 
1392   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1393   // phi->region->if_proj->ifnode->bool->cmp
1394   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1395 
1396   // Check bool sense
1397   switch( bol->_test._test ) {
1398   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1399   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1400   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1401   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1402   default:           return NULL;                              break;
1403   }
1404 
1405   // Test is next
1406   Node *cmp = bol->in(1);
1407   const Type *tzero = NULL;
1408   switch( cmp->Opcode() ) {
1409   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1410   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1411   default: return NULL;
1412   }
1413 
1414   // Find zero input of compare; the other input is being abs'd
1415   Node *x = NULL;
1416   bool flip = false;
1417   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1418     x = cmp->in(3 - cmp_zero_idx);
1419   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1420     // The test is inverted, we should invert the result...
1421     x = cmp->in(cmp_zero_idx);
1422     flip = true;
1423   } else {
1424     return NULL;
1425   }
1426 
1427   // Next get the 2 pieces being selected, one is the original value
1428   // and the other is the negated value.
1429   if( phi_root->in(phi_x_idx) != x ) return NULL;
1430 
1431   // Check other phi input for subtract node
1432   Node *sub = phi_root->in(3 - phi_x_idx);
1433 
1434   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1435   if( tzero == TypeF::ZERO ) {
1436     if( sub->Opcode() != Op_SubF ||
1437         sub->in(2) != x ||
1438         phase->type(sub->in(1)) != tzero ) return NULL;
1439     x = new AbsFNode(x);
1440     if (flip) {
1441       x = new SubFNode(sub->in(1), phase->transform(x));
1442     }
1443   } else {
1444     if( sub->Opcode() != Op_SubD ||
1445         sub->in(2) != x ||
1446         phase->type(sub->in(1)) != tzero ) return NULL;
1447     x = new AbsDNode(x);
1448     if (flip) {
1449       x = new SubDNode(sub->in(1), phase->transform(x));
1450     }
1451   }
1452 
1453   return x;
1454 }
1455 
1456 //------------------------------split_once-------------------------------------
1457 // Helper for split_flow_path
1458 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1459   igvn->hash_delete(n);         // Remove from hash before hacking edges
1460 
1461   uint j = 1;
1462   for (uint i = phi->req()-1; i > 0; i--) {
1463     if (phi->in(i) == val) {   // Found a path with val?
1464       // Add to NEW Region/Phi, no DU info
1465       newn->set_req( j++, n->in(i) );
1466       // Remove from OLD Region/Phi
1467       n->del_req(i);
1468     }
1469   }
1470 
1471   // Register the new node but do not transform it.  Cannot transform until the
1472   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1473   igvn->register_new_node_with_optimizer( newn );
1474 
1475   // Now I can point to the new node.
1476   n->add_req(newn);
1477   igvn->_worklist.push(n);
1478 }
1479 
1480 //------------------------------split_flow_path--------------------------------
1481 // Check for merging identical values and split flow paths
1482 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1483   BasicType bt = phi->type()->basic_type();
1484   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1485     return NULL;                // Bail out on funny non-value stuff
1486   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1487     return NULL;                // third unequal input to be worth doing
1488 
1489   // Scan for a constant
1490   uint i;
1491   for( i = 1; i < phi->req()-1; i++ ) {
1492     Node *n = phi->in(i);
1493     if( !n ) return NULL;
1494     if( phase->type(n) == Type::TOP ) return NULL;
1495     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1496       break;
1497   }
1498   if( i >= phi->req() )         // Only split for constants
1499     return NULL;
1500 
1501   Node *val = phi->in(i);       // Constant to split for
1502   uint hit = 0;                 // Number of times it occurs
1503   Node *r = phi->region();
1504 
1505   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1506     Node *n = phi->in(i);
1507     if( !n ) return NULL;
1508     if( phase->type(n) == Type::TOP ) return NULL;
1509     if( phi->in(i) == val ) {
1510       hit++;
1511       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1512         return NULL;            // don't split loop entry path
1513       }
1514     }
1515   }
1516 
1517   if( hit <= 1 ||               // Make sure we find 2 or more
1518       hit == phi->req()-1 )     // and not ALL the same value
1519     return NULL;
1520 
1521   // Now start splitting out the flow paths that merge the same value.
1522   // Split first the RegionNode.
1523   PhaseIterGVN *igvn = phase->is_IterGVN();
1524   RegionNode *newr = new RegionNode(hit+1);
1525   split_once(igvn, phi, val, r, newr);
1526 
1527   // Now split all other Phis than this one
1528   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1529     Node* phi2 = r->fast_out(k);
1530     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1531       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1532       split_once(igvn, phi, val, phi2, newphi);
1533     }
1534   }
1535 
1536   // Clean up this guy
1537   igvn->hash_delete(phi);
1538   for( i = phi->req()-1; i > 0; i-- ) {
1539     if( phi->in(i) == val ) {
1540       phi->del_req(i);
1541     }
1542   }
1543   phi->add_req(val);
1544 
1545   return phi;
1546 }
1547 
1548 //=============================================================================
1549 //------------------------------simple_data_loop_check-------------------------
1550 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1551 //  Returns:
1552 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1553 // Safe       - safe case when the phi and it's inputs reference only safe data
1554 //              nodes;
1555 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1556 //              is no reference back to the phi - need a graph walk
1557 //              to determine if it is in a loop;
1558 // UnsafeLoop - unsafe case when the phi references itself directly or through
1559 //              unsafe data node.
1560 //  Note: a safe data node is a node which could/never reference itself during
1561 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1562 //  I mark Phi nodes as safe node not only because they can reference itself
1563 //  but also to prevent mistaking the fallthrough case inside an outer loop
1564 //  as dead loop when the phi references itselfs through an other phi.
1565 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1566   // It is unsafe loop if the phi node references itself directly.
1567   if (in == (Node*)this)
1568     return UnsafeLoop; // Unsafe loop
1569   // Unsafe loop if the phi node references itself through an unsafe data node.
1570   // Exclude cases with null inputs or data nodes which could reference
1571   // itself (safe for dead loops).
1572   if (in != NULL && !in->is_dead_loop_safe()) {
1573     // Check inputs of phi's inputs also.
1574     // It is much less expensive then full graph walk.
1575     uint cnt = in->req();
1576     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1577     for (; i < cnt; ++i) {
1578       Node* m = in->in(i);
1579       if (m == (Node*)this)
1580         return UnsafeLoop; // Unsafe loop
1581       if (m != NULL && !m->is_dead_loop_safe()) {
1582         // Check the most common case (about 30% of all cases):
1583         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1584         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1585         if (m1 == (Node*)this)
1586           return UnsafeLoop; // Unsafe loop
1587         if (m1 != NULL && m1 == m->in(2) &&
1588             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1589           continue; // Safe case
1590         }
1591         // The phi references an unsafe node - need full analysis.
1592         return Unsafe;
1593       }
1594     }
1595   }
1596   return Safe; // Safe case - we can optimize the phi node.
1597 }
1598 
1599 //------------------------------is_unsafe_data_reference-----------------------
1600 // If phi can be reached through the data input - it is data loop.
1601 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1602   assert(req() > 1, "");
1603   // First, check simple cases when phi references itself directly or
1604   // through an other node.
1605   LoopSafety safety = simple_data_loop_check(in);
1606   if (safety == UnsafeLoop)
1607     return true;  // phi references itself - unsafe loop
1608   else if (safety == Safe)
1609     return false; // Safe case - phi could be replaced with the unique input.
1610 
1611   // Unsafe case when we should go through data graph to determine
1612   // if the phi references itself.
1613 
1614   ResourceMark rm;
1615 
1616   Arena *a = Thread::current()->resource_area();
1617   Node_List nstack(a);
1618   VectorSet visited(a);
1619 
1620   nstack.push(in); // Start with unique input.
1621   visited.set(in->_idx);
1622   while (nstack.size() != 0) {
1623     Node* n = nstack.pop();
1624     uint cnt = n->req();
1625     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1626     for (; i < cnt; i++) {
1627       Node* m = n->in(i);
1628       if (m == (Node*)this) {
1629         return true;    // Data loop
1630       }
1631       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1632         if (!visited.test_set(m->_idx))
1633           nstack.push(m);
1634       }
1635     }
1636   }
1637   return false; // The phi is not reachable from its inputs
1638 }
1639 
1640 
1641 //------------------------------Ideal------------------------------------------
1642 // Return a node which is more "ideal" than the current node.  Must preserve
1643 // the CFG, but we can still strip out dead paths.
1644 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1645   // The next should never happen after 6297035 fix.
1646   if( is_copy() )               // Already degraded to a Copy ?
1647     return NULL;                // No change
1648 
1649   Node *r = in(0);              // RegionNode
1650   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1651 
1652   // Note: During parsing, phis are often transformed before their regions.
1653   // This means we have to use type_or_null to defend against untyped regions.
1654   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1655     return NULL;                // No change
1656 
1657   Node *top = phase->C->top();
1658   bool new_phi = (outcnt() == 0); // transforming new Phi
1659   // No change for igvn if new phi is not hooked
1660   if (new_phi && can_reshape)
1661     return NULL;
1662 
1663   // The are 2 situations when only one valid phi's input is left
1664   // (in addition to Region input).
1665   // One: region is not loop - replace phi with this input.
1666   // Two: region is loop - replace phi with top since this data path is dead
1667   //                       and we need to break the dead data loop.
1668   Node* progress = NULL;        // Record if any progress made
1669   for( uint j = 1; j < req(); ++j ){ // For all paths in
1670     // Check unreachable control paths
1671     Node* rc = r->in(j);
1672     Node* n = in(j);            // Get the input
1673     if (rc == NULL || phase->type(rc) == Type::TOP) {
1674       if (n != top) {           // Not already top?
1675         PhaseIterGVN *igvn = phase->is_IterGVN();
1676         if (can_reshape && igvn != NULL) {
1677           igvn->_worklist.push(r);
1678         }
1679         set_req(j, top);        // Nuke it down
1680         progress = this;        // Record progress
1681       }
1682     }
1683   }
1684 
1685   if (can_reshape && outcnt() == 0) {
1686     // set_req() above may kill outputs if Phi is referenced
1687     // only by itself on the dead (top) control path.
1688     return top;
1689   }
1690 
1691   bool uncasted = false;
1692   Node* uin = unique_input(phase, false);
1693   if (uin == NULL && can_reshape) {
1694     uncasted = true;
1695     uin = unique_input(phase, true);
1696   }
1697   if (uin == top) {             // Simplest case: no alive inputs.
1698     if (can_reshape)            // IGVN transformation
1699       return top;
1700     else
1701       return NULL;              // Identity will return TOP
1702   } else if (uin != NULL) {
1703     // Only one not-NULL unique input path is left.
1704     // Determine if this input is backedge of a loop.
1705     // (Skip new phis which have no uses and dead regions).
1706     if (outcnt() > 0 && r->in(0) != NULL) {
1707       // First, take the short cut when we know it is a loop and
1708       // the EntryControl data path is dead.
1709       // Loop node may have only one input because entry path
1710       // is removed in PhaseIdealLoop::Dominators().
1711       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1712       bool is_loop = (r->is_Loop() && r->req() == 3);
1713       // Then, check if there is a data loop when phi references itself directly
1714       // or through other data nodes.
1715       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1716           (!is_loop && is_unsafe_data_reference(uin))) {
1717         // Break this data loop to avoid creation of a dead loop.
1718         if (can_reshape) {
1719           return top;
1720         } else {
1721           // We can't return top if we are in Parse phase - cut inputs only
1722           // let Identity to handle the case.
1723           replace_edge(uin, top);
1724           return NULL;
1725         }
1726       }
1727     }
1728 
1729     if (uncasted) {
1730       // Add cast nodes between the phi to be removed and its unique input.
1731       // Wait until after parsing for the type information to propagate from the casts.
1732       assert(can_reshape, "Invalid during parsing");
1733       const Type* phi_type = bottom_type();
1734       assert(phi_type->isa_int() || phi_type->isa_ptr(), "bad phi type");
1735       // Add casts to carry the control dependency of the Phi that is
1736       // going away
1737       Node* cast = NULL;
1738       if (phi_type->isa_int()) {
1739         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1740       } else {
1741         const Type* uin_type = phase->type(uin);
1742         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1743           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1744         } else {
1745           // Use a CastPP for a cast to not null and a CheckCastPP for
1746           // a cast to a new klass (and both if both null-ness and
1747           // klass change).
1748 
1749           // If the type of phi is not null but the type of uin may be
1750           // null, uin's type must be casted to not null
1751           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1752               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1753             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1754           }
1755 
1756           // If the type of phi and uin, both casted to not null,
1757           // differ the klass of uin must be (check)cast'ed to match
1758           // that of phi
1759           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1760             Node* n = uin;
1761             if (cast != NULL) {
1762               cast = phase->transform(cast);
1763               n = cast;
1764             }
1765             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
1766           }
1767           if (cast == NULL) {
1768             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1769           }
1770         }
1771       }
1772       assert(cast != NULL, "cast should be set");
1773       cast = phase->transform(cast);
1774       // set all inputs to the new cast(s) so the Phi is removed by Identity
1775       PhaseIterGVN* igvn = phase->is_IterGVN();
1776       for (uint i = 1; i < req(); i++) {
1777         set_req_X(i, cast, igvn);
1778       }
1779       uin = cast;
1780     }
1781 
1782     // One unique input.
1783     debug_only(Node* ident = Identity(phase));
1784     // The unique input must eventually be detected by the Identity call.
1785 #ifdef ASSERT
1786     if (ident != uin && !ident->is_top()) {
1787       // print this output before failing assert
1788       r->dump(3);
1789       this->dump(3);
1790       ident->dump();
1791       uin->dump();
1792     }
1793 #endif
1794     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1795     return NULL;
1796   }
1797 
1798   Node* opt = NULL;
1799   int true_path = is_diamond_phi();
1800   if( true_path != 0 ) {
1801     // Check for CMove'ing identity. If it would be unsafe,
1802     // handle it here. In the safe case, let Identity handle it.
1803     Node* unsafe_id = is_cmove_id(phase, true_path);
1804     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1805       opt = unsafe_id;
1806 
1807     // Check for simple convert-to-boolean pattern
1808     if( opt == NULL )
1809       opt = is_x2logic(phase, this, true_path);
1810 
1811     // Check for absolute value
1812     if( opt == NULL )
1813       opt = is_absolute(phase, this, true_path);
1814 
1815     // Check for conditional add
1816     if( opt == NULL && can_reshape )
1817       opt = is_cond_add(phase, this, true_path);
1818 
1819     // These 4 optimizations could subsume the phi:
1820     // have to check for a dead data loop creation.
1821     if( opt != NULL ) {
1822       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
1823         // Found dead loop.
1824         if( can_reshape )
1825           return top;
1826         // We can't return top if we are in Parse phase - cut inputs only
1827         // to stop further optimizations for this phi. Identity will return TOP.
1828         assert(req() == 3, "only diamond merge phi here");
1829         set_req(1, top);
1830         set_req(2, top);
1831         return NULL;
1832       } else {
1833         return opt;
1834       }
1835     }
1836   }
1837 
1838   // Check for merging identical values and split flow paths
1839   if (can_reshape) {
1840     opt = split_flow_path(phase, this);
1841     // This optimization only modifies phi - don't need to check for dead loop.
1842     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
1843     if (opt != NULL)  return opt;
1844   }
1845 
1846   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
1847     // Try to undo Phi of AddP:
1848     // (Phi (AddP base base y) (AddP base2 base2 y))
1849     // becomes:
1850     // newbase := (Phi base base2)
1851     // (AddP newbase newbase y)
1852     //
1853     // This occurs as a result of unsuccessful split_thru_phi and
1854     // interferes with taking advantage of addressing modes. See the
1855     // clone_shift_expressions code in matcher.cpp
1856     Node* addp = in(1);
1857     const Type* type = addp->in(AddPNode::Base)->bottom_type();
1858     Node* y = addp->in(AddPNode::Offset);
1859     if (y != NULL && addp->in(AddPNode::Base) == addp->in(AddPNode::Address)) {
1860       // make sure that all the inputs are similar to the first one,
1861       // i.e. AddP with base == address and same offset as first AddP
1862       bool doit = true;
1863       for (uint i = 2; i < req(); i++) {
1864         if (in(i) == NULL ||
1865             in(i)->Opcode() != Op_AddP ||
1866             in(i)->in(AddPNode::Base) != in(i)->in(AddPNode::Address) ||
1867             in(i)->in(AddPNode::Offset) != y) {
1868           doit = false;
1869           break;
1870         }
1871         // Accumulate type for resulting Phi
1872         type = type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
1873       }
1874       Node* base = NULL;
1875       if (doit) {
1876         // Check for neighboring AddP nodes in a tree.
1877         // If they have a base, use that it.
1878         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
1879           Node* u = this->fast_out(k);
1880           if (u->is_AddP()) {
1881             Node* base2 = u->in(AddPNode::Base);
1882             if (base2 != NULL && !base2->is_top()) {
1883               if (base == NULL)
1884                 base = base2;
1885               else if (base != base2)
1886                 { doit = false; break; }
1887             }
1888           }
1889         }
1890       }
1891       if (doit) {
1892         if (base == NULL) {
1893           base = new PhiNode(in(0), type, NULL);
1894           for (uint i = 1; i < req(); i++) {
1895             base->init_req(i, in(i)->in(AddPNode::Base));
1896           }
1897           phase->is_IterGVN()->register_new_node_with_optimizer(base);
1898         }
1899         return new AddPNode(base, base, y);
1900       }
1901     }
1902   }
1903 
1904   // Split phis through memory merges, so that the memory merges will go away.
1905   // Piggy-back this transformation on the search for a unique input....
1906   // It will be as if the merged memory is the unique value of the phi.
1907   // (Do not attempt this optimization unless parsing is complete.
1908   // It would make the parser's memory-merge logic sick.)
1909   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
1910   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
1911     // see if this phi should be sliced
1912     uint merge_width = 0;
1913     bool saw_self = false;
1914     for( uint i=1; i<req(); ++i ) {// For all paths in
1915       Node *ii = in(i);
1916       // TOP inputs should not be counted as safe inputs because if the
1917       // Phi references itself through all other inputs then splitting the
1918       // Phi through memory merges would create dead loop at later stage.
1919       if (ii == top) {
1920         return NULL; // Delay optimization until graph is cleaned.
1921       }
1922       if (ii->is_MergeMem()) {
1923         MergeMemNode* n = ii->as_MergeMem();
1924         merge_width = MAX2(merge_width, n->req());
1925         saw_self = saw_self || phase->eqv(n->base_memory(), this);
1926       }
1927     }
1928 
1929     // This restriction is temporarily necessary to ensure termination:
1930     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
1931 
1932     if (merge_width > Compile::AliasIdxRaw) {
1933       // found at least one non-empty MergeMem
1934       const TypePtr* at = adr_type();
1935       if (at != TypePtr::BOTTOM) {
1936         // Patch the existing phi to select an input from the merge:
1937         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
1938         //     Phi:AT1(...m1...)
1939         int alias_idx = phase->C->get_alias_index(at);
1940         for (uint i=1; i<req(); ++i) {
1941           Node *ii = in(i);
1942           if (ii->is_MergeMem()) {
1943             MergeMemNode* n = ii->as_MergeMem();
1944             // compress paths and change unreachable cycles to TOP
1945             // If not, we can update the input infinitely along a MergeMem cycle
1946             // Equivalent code is in MemNode::Ideal_common
1947             Node *m  = phase->transform(n);
1948             if (outcnt() == 0) {  // Above transform() may kill us!
1949               return top;
1950             }
1951             // If transformed to a MergeMem, get the desired slice
1952             // Otherwise the returned node represents memory for every slice
1953             Node *new_mem = (m->is_MergeMem()) ?
1954                              m->as_MergeMem()->memory_at(alias_idx) : m;
1955             // Update input if it is progress over what we have now
1956             if (new_mem != ii) {
1957               set_req(i, new_mem);
1958               progress = this;
1959             }
1960           }
1961         }
1962       } else {
1963         // We know that at least one MergeMem->base_memory() == this
1964         // (saw_self == true). If all other inputs also references this phi
1965         // (directly or through data nodes) - it is dead loop.
1966         bool saw_safe_input = false;
1967         for (uint j = 1; j < req(); ++j) {
1968           Node *n = in(j);
1969           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
1970             continue;              // skip known cases
1971           if (!is_unsafe_data_reference(n)) {
1972             saw_safe_input = true; // found safe input
1973             break;
1974           }
1975         }
1976         if (!saw_safe_input)
1977           return top; // all inputs reference back to this phi - dead loop
1978 
1979         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
1980         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
1981         PhaseIterGVN *igvn = phase->is_IterGVN();
1982         Node* hook = new Node(1);
1983         PhiNode* new_base = (PhiNode*) clone();
1984         // Must eagerly register phis, since they participate in loops.
1985         if (igvn) {
1986           igvn->register_new_node_with_optimizer(new_base);
1987           hook->add_req(new_base);
1988         }
1989         MergeMemNode* result = MergeMemNode::make(new_base);
1990         for (uint i = 1; i < req(); ++i) {
1991           Node *ii = in(i);
1992           if (ii->is_MergeMem()) {
1993             MergeMemNode* n = ii->as_MergeMem();
1994             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
1995               // If we have not seen this slice yet, make a phi for it.
1996               bool made_new_phi = false;
1997               if (mms.is_empty()) {
1998                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
1999                 made_new_phi = true;
2000                 if (igvn) {
2001                   igvn->register_new_node_with_optimizer(new_phi);
2002                   hook->add_req(new_phi);
2003                 }
2004                 mms.set_memory(new_phi);
2005               }
2006               Node* phi = mms.memory();
2007               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2008               phi->set_req(i, mms.memory2());
2009             }
2010           }
2011         }
2012         // Distribute all self-loops.
2013         { // (Extra braces to hide mms.)
2014           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2015             Node* phi = mms.memory();
2016             for (uint i = 1; i < req(); ++i) {
2017               if (phi->in(i) == this)  phi->set_req(i, phi);
2018             }
2019           }
2020         }
2021         // now transform the new nodes, and return the mergemem
2022         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2023           Node* phi = mms.memory();
2024           mms.set_memory(phase->transform(phi));
2025         }
2026         if (igvn) { // Unhook.
2027           igvn->hash_delete(hook);
2028           for (uint i = 1; i < hook->req(); i++) {
2029             hook->set_req(i, NULL);
2030           }
2031         }
2032         // Replace self with the result.
2033         return result;
2034       }
2035     }
2036     //
2037     // Other optimizations on the memory chain
2038     //
2039     const TypePtr* at = adr_type();
2040     for( uint i=1; i<req(); ++i ) {// For all paths in
2041       Node *ii = in(i);
2042       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2043       if (ii != new_in ) {
2044         set_req(i, new_in);
2045         progress = this;
2046       }
2047     }
2048   }
2049 
2050 #ifdef _LP64
2051   // Push DecodeN/DecodeNKlass down through phi.
2052   // The rest of phi graph will transform by split EncodeP node though phis up.
2053   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2054     bool may_push = true;
2055     bool has_decodeN = false;
2056     bool is_decodeN = false;
2057     for (uint i=1; i<req(); ++i) {// For all paths in
2058       Node *ii = in(i);
2059       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2060         // Do optimization if a non dead path exist.
2061         if (ii->in(1)->bottom_type() != Type::TOP) {
2062           has_decodeN = true;
2063           is_decodeN = ii->is_DecodeN();
2064         }
2065       } else if (!ii->is_Phi()) {
2066         may_push = false;
2067       }
2068     }
2069 
2070     if (has_decodeN && may_push) {
2071       PhaseIterGVN *igvn = phase->is_IterGVN();
2072       // Make narrow type for new phi.
2073       const Type* narrow_t;
2074       if (is_decodeN) {
2075         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2076       } else {
2077         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2078       }
2079       PhiNode* new_phi = new PhiNode(r, narrow_t);
2080       uint orig_cnt = req();
2081       for (uint i=1; i<req(); ++i) {// For all paths in
2082         Node *ii = in(i);
2083         Node* new_ii = NULL;
2084         if (ii->is_DecodeNarrowPtr()) {
2085           assert(ii->bottom_type() == bottom_type(), "sanity");
2086           new_ii = ii->in(1);
2087         } else {
2088           assert(ii->is_Phi(), "sanity");
2089           if (ii->as_Phi() == this) {
2090             new_ii = new_phi;
2091           } else {
2092             if (is_decodeN) {
2093               new_ii = new EncodePNode(ii, narrow_t);
2094             } else {
2095               new_ii = new EncodePKlassNode(ii, narrow_t);
2096             }
2097             igvn->register_new_node_with_optimizer(new_ii);
2098           }
2099         }
2100         new_phi->set_req(i, new_ii);
2101       }
2102       igvn->register_new_node_with_optimizer(new_phi, this);
2103       if (is_decodeN) {
2104         progress = new DecodeNNode(new_phi, bottom_type());
2105       } else {
2106         progress = new DecodeNKlassNode(new_phi, bottom_type());
2107       }
2108     }
2109   }
2110 #endif
2111 
2112   return progress;              // Return any progress
2113 }
2114 
2115 //------------------------------is_tripcount-----------------------------------
2116 bool PhiNode::is_tripcount() const {
2117   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2118           in(0)->as_CountedLoop()->phi() == this);
2119 }
2120 
2121 //------------------------------out_RegMask------------------------------------
2122 const RegMask &PhiNode::in_RegMask(uint i) const {
2123   return i ? out_RegMask() : RegMask::Empty;
2124 }
2125 
2126 const RegMask &PhiNode::out_RegMask() const {
2127   uint ideal_reg = _type->ideal_reg();
2128   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2129   if( ideal_reg == 0 ) return RegMask::Empty;
2130   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2131   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2132 }
2133 
2134 #ifndef PRODUCT
2135 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2136   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2137   // and all outputs till level 1. In compact mode, inputs till level 1 are
2138   // collected.
2139   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2140   this->collect_nodes(out_rel, -1, false, false);
2141 }
2142 
2143 void PhiNode::dump_spec(outputStream *st) const {
2144   TypeNode::dump_spec(st);
2145   if (is_tripcount()) {
2146     st->print(" #tripcount");
2147   }
2148 }
2149 #endif
2150 
2151 
2152 //=============================================================================
2153 const Type* GotoNode::Value(PhaseGVN* phase) const {
2154   // If the input is reachable, then we are executed.
2155   // If the input is not reachable, then we are not executed.
2156   return phase->type(in(0));
2157 }
2158 
2159 Node* GotoNode::Identity(PhaseGVN* phase) {
2160   return in(0);                // Simple copy of incoming control
2161 }
2162 
2163 const RegMask &GotoNode::out_RegMask() const {
2164   return RegMask::Empty;
2165 }
2166 
2167 #ifndef PRODUCT
2168 //-----------------------------related-----------------------------------------
2169 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2170 // outputs at level 1. This is regardless of compact mode.
2171 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2172   this->collect_nodes(in_rel, 1, false, false);
2173   this->collect_nodes(out_rel, -1, false, false);
2174 }
2175 #endif
2176 
2177 
2178 //=============================================================================
2179 const RegMask &JumpNode::out_RegMask() const {
2180   return RegMask::Empty;
2181 }
2182 
2183 #ifndef PRODUCT
2184 //-----------------------------related-----------------------------------------
2185 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2186 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2187 // This is regardless of compact mode.
2188 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2189   this->collect_nodes(in_rel, 1, false, false);
2190   this->collect_nodes(out_rel, -2, false, false);
2191 }
2192 #endif
2193 
2194 //=============================================================================
2195 const RegMask &JProjNode::out_RegMask() const {
2196   return RegMask::Empty;
2197 }
2198 
2199 //=============================================================================
2200 const RegMask &CProjNode::out_RegMask() const {
2201   return RegMask::Empty;
2202 }
2203 
2204 
2205 
2206 //=============================================================================
2207 
2208 uint PCTableNode::hash() const { return Node::hash() + _size; }
2209 uint PCTableNode::cmp( const Node &n ) const
2210 { return _size == ((PCTableNode&)n)._size; }
2211 
2212 const Type *PCTableNode::bottom_type() const {
2213   const Type** f = TypeTuple::fields(_size);
2214   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2215   return TypeTuple::make(_size, f);
2216 }
2217 
2218 //------------------------------Value------------------------------------------
2219 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2220 // Control, otherwise the table targets are not reachable
2221 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2222   if( phase->type(in(0)) == Type::CONTROL )
2223     return bottom_type();
2224   return Type::TOP;             // All paths dead?  Then so are we
2225 }
2226 
2227 //------------------------------Ideal------------------------------------------
2228 // Return a node which is more "ideal" than the current node.  Strip out
2229 // control copies
2230 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2231   return remove_dead_region(phase, can_reshape) ? this : NULL;
2232 }
2233 
2234 //=============================================================================
2235 uint JumpProjNode::hash() const {
2236   return Node::hash() + _dest_bci;
2237 }
2238 
2239 uint JumpProjNode::cmp( const Node &n ) const {
2240   return ProjNode::cmp(n) &&
2241     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2242 }
2243 
2244 #ifndef PRODUCT
2245 void JumpProjNode::dump_spec(outputStream *st) const {
2246   ProjNode::dump_spec(st);
2247   st->print("@bci %d ",_dest_bci);
2248 }
2249 
2250 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2251   ProjNode::dump_compact_spec(st);
2252   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2253 }
2254 
2255 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2256   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2257   this->collect_nodes(in_rel, 1, false, false);
2258   this->collect_nodes(out_rel, -1, false, false);
2259 }
2260 #endif
2261 
2262 //=============================================================================
2263 //------------------------------Value------------------------------------------
2264 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2265 // have the default "fall_through_index" path.
2266 const Type* CatchNode::Value(PhaseGVN* phase) const {
2267   // Unreachable?  Then so are all paths from here.
2268   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2269   // First assume all paths are reachable
2270   const Type** f = TypeTuple::fields(_size);
2271   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2272   // Identify cases that will always throw an exception
2273   // () rethrow call
2274   // () virtual or interface call with NULL receiver
2275   // () call is a check cast with incompatible arguments
2276   if( in(1)->is_Proj() ) {
2277     Node *i10 = in(1)->in(0);
2278     if( i10->is_Call() ) {
2279       CallNode *call = i10->as_Call();
2280       // Rethrows always throw exceptions, never return
2281       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2282         f[CatchProjNode::fall_through_index] = Type::TOP;
2283       } else if( call->req() > TypeFunc::Parms ) {
2284         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2285         // Check for null receiver to virtual or interface calls
2286         if( call->is_CallDynamicJava() &&
2287             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2288           f[CatchProjNode::fall_through_index] = Type::TOP;
2289         }
2290       } // End of if not a runtime stub
2291     } // End of if have call above me
2292   } // End of slot 1 is not a projection
2293   return TypeTuple::make(_size, f);
2294 }
2295 
2296 //=============================================================================
2297 uint CatchProjNode::hash() const {
2298   return Node::hash() + _handler_bci;
2299 }
2300 
2301 
2302 uint CatchProjNode::cmp( const Node &n ) const {
2303   return ProjNode::cmp(n) &&
2304     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2305 }
2306 
2307 
2308 //------------------------------Identity---------------------------------------
2309 // If only 1 target is possible, choose it if it is the main control
2310 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2311   // If my value is control and no other value is, then treat as ID
2312   const TypeTuple *t = phase->type(in(0))->is_tuple();
2313   if (t->field_at(_con) != Type::CONTROL)  return this;
2314   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2315   // also remove any exception table entry.  Thus we must know the call
2316   // feeding the Catch will not really throw an exception.  This is ok for
2317   // the main fall-thru control (happens when we know a call can never throw
2318   // an exception) or for "rethrow", because a further optimization will
2319   // yank the rethrow (happens when we inline a function that can throw an
2320   // exception and the caller has no handler).  Not legal, e.g., for passing
2321   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2322   // These cases MUST throw an exception via the runtime system, so the VM
2323   // will be looking for a table entry.
2324   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2325   CallNode *call;
2326   if (_con != TypeFunc::Control && // Bail out if not the main control.
2327       !(proj->is_Proj() &&      // AND NOT a rethrow
2328         proj->in(0)->is_Call() &&
2329         (call = proj->in(0)->as_Call()) &&
2330         call->entry_point() == OptoRuntime::rethrow_stub()))
2331     return this;
2332 
2333   // Search for any other path being control
2334   for (uint i = 0; i < t->cnt(); i++) {
2335     if (i != _con && t->field_at(i) == Type::CONTROL)
2336       return this;
2337   }
2338   // Only my path is possible; I am identity on control to the jump
2339   return in(0)->in(0);
2340 }
2341 
2342 
2343 #ifndef PRODUCT
2344 void CatchProjNode::dump_spec(outputStream *st) const {
2345   ProjNode::dump_spec(st);
2346   st->print("@bci %d ",_handler_bci);
2347 }
2348 #endif
2349 
2350 //=============================================================================
2351 //------------------------------Identity---------------------------------------
2352 // Check for CreateEx being Identity.
2353 Node* CreateExNode::Identity(PhaseGVN* phase) {
2354   if( phase->type(in(1)) == Type::TOP ) return in(1);
2355   if( phase->type(in(0)) == Type::TOP ) return in(0);
2356   // We only come from CatchProj, unless the CatchProj goes away.
2357   // If the CatchProj is optimized away, then we just carry the
2358   // exception oop through.
2359   CallNode *call = in(1)->in(0)->as_Call();
2360 
2361   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2362     ? this
2363     : call->in(TypeFunc::Parms);
2364 }
2365 
2366 //=============================================================================
2367 //------------------------------Value------------------------------------------
2368 // Check for being unreachable.
2369 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2370   if (!in(0) || in(0)->is_top()) return Type::TOP;
2371   return bottom_type();
2372 }
2373 
2374 //------------------------------Ideal------------------------------------------
2375 // Check for no longer being part of a loop
2376 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2377   if (can_reshape && !in(0)->is_Loop()) {
2378     // Dead code elimination can sometimes delete this projection so
2379     // if it's not there, there's nothing to do.
2380     Node* fallthru = proj_out_or_null(0);
2381     if (fallthru != NULL) {
2382       phase->is_IterGVN()->replace_node(fallthru, in(0));
2383     }
2384     return phase->C->top();
2385   }
2386   return NULL;
2387 }
2388 
2389 #ifndef PRODUCT
2390 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2391   st->print("%s", Name());
2392 }
2393 #endif