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