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