1 /*
   2  * Copyright (c) 1997, 2010, 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 //------------------------------Ideal------------------------------------------
 367 // Return a node which is more "ideal" than the current node.  Must preserve
 368 // the CFG, but we can still strip out dead paths.
 369 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 370   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 371   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 372 
 373   // Check for RegionNode with no Phi users and both inputs come from either
 374   // arm of the same IF.  If found, then the control-flow split is useless.
 375   bool has_phis = false;
 376   if (can_reshape) {            // Need DU info to check for Phi users
 377     has_phis = (has_phi() != NULL);       // Cache result
 378     if (!has_phis) {            // No Phi users?  Nothing merging?
 379       for (uint i = 1; i < req()-1; i++) {
 380         Node *if1 = in(i);
 381         if( !if1 ) continue;
 382         Node *iff = if1->in(0);
 383         if( !iff || !iff->is_If() ) continue;
 384         for( uint j=i+1; j<req(); j++ ) {
 385           if( in(j) && in(j)->in(0) == iff &&
 386               if1->Opcode() != in(j)->Opcode() ) {
 387             // Add the IF Projections to the worklist. They (and the IF itself)
 388             // will be eliminated if dead.
 389             phase->is_IterGVN()->add_users_to_worklist(iff);
 390             set_req(i, iff->in(0));// Skip around the useless IF diamond
 391             set_req(j, NULL);
 392             return this;      // Record progress
 393           }
 394         }
 395       }
 396     }
 397   }
 398 
 399   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 400   // degrades to a copy.
 401   bool add_to_worklist = false;
 402   int cnt = 0;                  // Count of values merging
 403   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 404   int del_it = 0;               // The last input path we delete
 405   // For all inputs...
 406   for( uint i=1; i<req(); ++i ){// For all paths in
 407     Node *n = in(i);            // Get the input
 408     if( n != NULL ) {
 409       // Remove useless control copy inputs
 410       if( n->is_Region() && n->as_Region()->is_copy() ) {
 411         set_req(i, n->nonnull_req());
 412         i--;
 413         continue;
 414       }
 415       if( n->is_Proj() ) {      // Remove useless rethrows
 416         Node *call = n->in(0);
 417         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 418           set_req(i, call->in(0));
 419           i--;
 420           continue;
 421         }
 422       }
 423       if( phase->type(n) == Type::TOP ) {
 424         set_req(i, NULL);       // Ignore TOP inputs
 425         i--;
 426         continue;
 427       }
 428       cnt++;                    // One more value merging
 429 
 430     } else if (can_reshape) {   // Else found dead path with DU info
 431       PhaseIterGVN *igvn = phase->is_IterGVN();
 432       del_req(i);               // Yank path from self
 433       del_it = i;
 434       uint max = outcnt();
 435       DUIterator j;
 436       bool progress = true;
 437       while(progress) {         // Need to establish property over all users
 438         progress = false;
 439         for (j = outs(); has_out(j); j++) {
 440           Node *n = out(j);
 441           if( n->req() != req() && n->is_Phi() ) {
 442             assert( n->in(0) == this, "" );
 443             igvn->hash_delete(n); // Yank from hash before hacking edges
 444             n->set_req_X(i,NULL,igvn);// Correct DU info
 445             n->del_req(i);        // Yank path from Phis
 446             if( max != outcnt() ) {
 447               progress = true;
 448               j = refresh_out_pos(j);
 449               max = outcnt();
 450             }
 451           }
 452         }
 453       }
 454       add_to_worklist = true;
 455       i--;
 456     }
 457   }
 458 
 459   if (can_reshape && cnt == 1) {
 460     // Is it dead loop?
 461     // If it is LoopNopde it had 2 (+1 itself) inputs and
 462     // one of them was cut. The loop is dead if it was EntryContol.
 463     assert(!this->is_Loop() || cnt_orig == 3, "Loop node should have 3 inputs");
 464     if (this->is_Loop() && del_it == LoopNode::EntryControl ||
 465        !this->is_Loop() && has_phis && is_unreachable_region(phase)) {
 466       // Yes,  the region will be removed during the next step below.
 467       // Cut the backedge input and remove phis since no data paths left.
 468       // We don't cut outputs to other nodes here since we need to put them
 469       // on the worklist.
 470       del_req(1);
 471       cnt = 0;
 472       assert( req() == 1, "no more inputs expected" );
 473       uint max = outcnt();
 474       bool progress = true;
 475       Node *top = phase->C->top();
 476       PhaseIterGVN *igvn = phase->is_IterGVN();
 477       DUIterator j;
 478       while(progress) {
 479         progress = false;
 480         for (j = outs(); has_out(j); j++) {
 481           Node *n = out(j);
 482           if( n->is_Phi() ) {
 483             assert( igvn->eqv(n->in(0), this), "" );
 484             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 485             // Break dead loop data path.
 486             // Eagerly replace phis with top to avoid phis copies generation.
 487             igvn->replace_node(n, top);
 488             if( max != outcnt() ) {
 489               progress = true;
 490               j = refresh_out_pos(j);
 491               max = outcnt();
 492             }
 493           }
 494         }
 495       }
 496       add_to_worklist = true;
 497     }
 498   }
 499   if (add_to_worklist) {
 500     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 501   }
 502 
 503   if( cnt <= 1 ) {              // Only 1 path in?
 504     set_req(0, NULL);           // Null control input for region copy
 505     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 506       // No inputs or all inputs are NULL.
 507       return NULL;
 508     } else if (can_reshape) {   // Optimization phase - remove the node
 509       PhaseIterGVN *igvn = phase->is_IterGVN();
 510       Node *parent_ctrl;
 511       if( cnt == 0 ) {
 512         assert( req() == 1, "no inputs expected" );
 513         // During IGVN phase such region will be subsumed by TOP node
 514         // so region's phis will have TOP as control node.
 515         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 516         // Also set other user's input to top.
 517         parent_ctrl = phase->C->top();
 518       } else {
 519         // The fallthrough case since we already checked dead loops above.
 520         parent_ctrl = in(1);
 521         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 522         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 523       }
 524       if (!add_to_worklist)
 525         igvn->add_users_to_worklist(this); // Check for further allowed opts
 526       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 527         Node* n = last_out(i);
 528         igvn->hash_delete(n); // Remove from worklist before modifying edges
 529         if( n->is_Phi() ) {   // Collapse all Phis
 530           // Eagerly replace phis to avoid copies generation.
 531           Node* in;
 532           if( cnt == 0 ) {
 533             assert( n->req() == 1, "No data inputs expected" );
 534             in = parent_ctrl; // replaced by top
 535           } else {
 536             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 537             in = n->in(1);               // replaced by unique input
 538             if( n->as_Phi()->is_unsafe_data_reference(in) )
 539               in = phase->C->top();      // replaced by top
 540           }
 541           igvn->replace_node(n, in);
 542         }
 543         else if( n->is_Region() ) { // Update all incoming edges
 544           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 545           uint uses_found = 0;
 546           for( uint k=1; k < n->req(); k++ ) {
 547             if( n->in(k) == this ) {
 548               n->set_req(k, parent_ctrl);
 549               uses_found++;
 550             }
 551           }
 552           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 553             i -= (uses_found - 1);
 554           }
 555         }
 556         else {
 557           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 558           n->set_req(0, parent_ctrl);
 559         }
 560 #ifdef ASSERT
 561         for( uint k=0; k < n->req(); k++ ) {
 562           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 563         }
 564 #endif
 565       }
 566       // Remove the RegionNode itself from DefUse info
 567       igvn->remove_dead_node(this);
 568       return NULL;
 569     }
 570     return this;                // Record progress
 571   }
 572 
 573 
 574   // If a Region flows into a Region, merge into one big happy merge.
 575   if (can_reshape) {
 576     Node *m = merge_region(this, phase);
 577     if (m != NULL)  return m;
 578   }
 579 
 580   // Check if this region is the root of a clipping idiom on floats
 581   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 582     // Check that only one use is a Phi and that it simplifies to two constants +
 583     PhiNode* phi = has_unique_phi();
 584     if (phi != NULL) {          // One Phi user
 585       // Check inputs to the Phi
 586       ConNode *min;
 587       ConNode *max;
 588       Node    *val;
 589       uint     min_idx;
 590       uint     max_idx;
 591       uint     val_idx;
 592       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 593         IfNode *top_if;
 594         IfNode *bot_if;
 595         if( check_if_clipping( this, bot_if, top_if ) ) {
 596           // Control pattern checks, now verify compares
 597           Node   *top_in = NULL;   // value being compared against
 598           Node   *bot_in = NULL;
 599           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 600               check_compare_clipping( false, top_if, max, top_in ) ) {
 601             if( bot_in == top_in ) {
 602               PhaseIterGVN *gvn = phase->is_IterGVN();
 603               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 604               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 605 
 606               // Check for the ConvF2INode
 607               ConvF2INode *convf2i;
 608               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 609                 convf2i->in(1) == bot_in ) {
 610                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 611                 // max test
 612                 Node *cmp   = gvn->register_new_node_with_optimizer(new (phase->C, 3) CmpINode( convf2i, min ));
 613                 Node *boo   = gvn->register_new_node_with_optimizer(new (phase->C, 2) BoolNode( cmp, BoolTest::lt ));
 614                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C, 2) IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 615                 Node *if_min= gvn->register_new_node_with_optimizer(new (phase->C, 1) IfTrueNode (iff));
 616                 Node *ifF   = gvn->register_new_node_with_optimizer(new (phase->C, 1) IfFalseNode(iff));
 617                 // min test
 618                 cmp         = gvn->register_new_node_with_optimizer(new (phase->C, 3) CmpINode( convf2i, max ));
 619                 boo         = gvn->register_new_node_with_optimizer(new (phase->C, 2) BoolNode( cmp, BoolTest::gt ));
 620                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C, 2) IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 621                 Node *if_max= gvn->register_new_node_with_optimizer(new (phase->C, 1) IfTrueNode (iff));
 622                 ifF         = gvn->register_new_node_with_optimizer(new (phase->C, 1) IfFalseNode(iff));
 623                 // update input edges to region node
 624                 set_req_X( min_idx, if_min, gvn );
 625                 set_req_X( max_idx, if_max, gvn );
 626                 set_req_X( val_idx, ifF,    gvn );
 627                 // remove unnecessary 'LShiftI; RShiftI' idiom
 628                 gvn->hash_delete(phi);
 629                 phi->set_req_X( val_idx, convf2i, gvn );
 630                 gvn->hash_find_insert(phi);
 631                 // Return transformed region node
 632                 return this;
 633               }
 634             }
 635           }
 636         }
 637       }
 638     }
 639   }
 640 
 641   return NULL;
 642 }
 643 
 644 
 645 
 646 const RegMask &RegionNode::out_RegMask() const {
 647   return RegMask::Empty;
 648 }
 649 
 650 // Find the one non-null required input.  RegionNode only
 651 Node *Node::nonnull_req() const {
 652   assert( is_Region(), "" );
 653   for( uint i = 1; i < _cnt; i++ )
 654     if( in(i) )
 655       return in(i);
 656   ShouldNotReachHere();
 657   return NULL;
 658 }
 659 
 660 
 661 //=============================================================================
 662 // note that these functions assume that the _adr_type field is flattened
 663 uint PhiNode::hash() const {
 664   const Type* at = _adr_type;
 665   return TypeNode::hash() + (at ? at->hash() : 0);
 666 }
 667 uint PhiNode::cmp( const Node &n ) const {
 668   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 669 }
 670 static inline
 671 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 672   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 673   return Compile::current()->alias_type(at)->adr_type();
 674 }
 675 
 676 //----------------------------make---------------------------------------------
 677 // create a new phi with edges matching r and set (initially) to x
 678 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 679   uint preds = r->req();   // Number of predecessor paths
 680   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 681   PhiNode* p = new (Compile::current(), preds) PhiNode(r, t, at);
 682   for (uint j = 1; j < preds; j++) {
 683     // Fill in all inputs, except those which the region does not yet have
 684     if (r->in(j) != NULL)
 685       p->init_req(j, x);
 686   }
 687   return p;
 688 }
 689 PhiNode* PhiNode::make(Node* r, Node* x) {
 690   const Type*    t  = x->bottom_type();
 691   const TypePtr* at = NULL;
 692   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 693   return make(r, x, t, at);
 694 }
 695 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 696   const Type*    t  = x->bottom_type();
 697   const TypePtr* at = NULL;
 698   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 699   return new (Compile::current(), r->req()) PhiNode(r, t, at);
 700 }
 701 
 702 
 703 //------------------------slice_memory-----------------------------------------
 704 // create a new phi with narrowed memory type
 705 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 706   PhiNode* mem = (PhiNode*) clone();
 707   *(const TypePtr**)&mem->_adr_type = adr_type;
 708   // convert self-loops, or else we get a bad graph
 709   for (uint i = 1; i < req(); i++) {
 710     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 711   }
 712   mem->verify_adr_type();
 713   return mem;
 714 }
 715 
 716 //------------------------split_out_instance-----------------------------------
 717 // Split out an instance type from a bottom phi.
 718 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 719   const TypeOopPtr *t_oop = at->isa_oopptr();
 720   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 721   const TypePtr *t = adr_type();
 722   assert(type() == Type::MEMORY &&
 723          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 724           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 725           t->is_oopptr()->cast_to_exactness(true)
 726            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 727            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 728          "bottom or raw memory required");
 729 
 730   // Check if an appropriate node already exists.
 731   Node *region = in(0);
 732   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 733     Node* use = region->fast_out(k);
 734     if( use->is_Phi()) {
 735       PhiNode *phi2 = use->as_Phi();
 736       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 737         return phi2;
 738       }
 739     }
 740   }
 741   Compile *C = igvn->C;
 742   Arena *a = Thread::current()->resource_area();
 743   Node_Array node_map = new Node_Array(a);
 744   Node_Stack stack(a, C->unique() >> 4);
 745   PhiNode *nphi = slice_memory(at);
 746   igvn->register_new_node_with_optimizer( nphi );
 747   node_map.map(_idx, nphi);
 748   stack.push((Node *)this, 1);
 749   while(!stack.is_empty()) {
 750     PhiNode *ophi = stack.node()->as_Phi();
 751     uint i = stack.index();
 752     assert(i >= 1, "not control edge");
 753     stack.pop();
 754     nphi = node_map[ophi->_idx]->as_Phi();
 755     for (; i < ophi->req(); i++) {
 756       Node *in = ophi->in(i);
 757       if (in == NULL || igvn->type(in) == Type::TOP)
 758         continue;
 759       Node *opt = MemNode::optimize_simple_memory_chain(in, at, igvn);
 760       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 761       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 762         opt = node_map[optphi->_idx];
 763         if (opt == NULL) {
 764           stack.push(ophi, i);
 765           nphi = optphi->slice_memory(at);
 766           igvn->register_new_node_with_optimizer( nphi );
 767           node_map.map(optphi->_idx, nphi);
 768           ophi = optphi;
 769           i = 0; // will get incremented at top of loop
 770           continue;
 771         }
 772       }
 773       nphi->set_req(i, opt);
 774     }
 775   }
 776   return nphi;
 777 }
 778 
 779 //------------------------verify_adr_type--------------------------------------
 780 #ifdef ASSERT
 781 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
 782   if (visited.test_set(_idx))  return;  //already visited
 783 
 784   // recheck constructor invariants:
 785   verify_adr_type(false);
 786 
 787   // recheck local phi/phi consistency:
 788   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
 789          "adr_type must be consistent across phi nest");
 790 
 791   // walk around
 792   for (uint i = 1; i < req(); i++) {
 793     Node* n = in(i);
 794     if (n == NULL)  continue;
 795     const Node* np = in(i);
 796     if (np->is_Phi()) {
 797       np->as_Phi()->verify_adr_type(visited, at);
 798     } else if (n->bottom_type() == Type::TOP
 799                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
 800       // ignore top inputs
 801     } else {
 802       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
 803       // recheck phi/non-phi consistency at leaves:
 804       assert((nat != NULL) == (at != NULL), "");
 805       assert(nat == at || nat == TypePtr::BOTTOM,
 806              "adr_type must be consistent at leaves of phi nest");
 807     }
 808   }
 809 }
 810 
 811 // Verify a whole nest of phis rooted at this one.
 812 void PhiNode::verify_adr_type(bool recursive) const {
 813   if (is_error_reported())  return;  // muzzle asserts when debugging an error
 814   if (Node::in_dump())      return;  // muzzle asserts when printing
 815 
 816   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
 817 
 818   if (!VerifyAliases)       return;  // verify thoroughly only if requested
 819 
 820   assert(_adr_type == flatten_phi_adr_type(_adr_type),
 821          "Phi::adr_type must be pre-normalized");
 822 
 823   if (recursive) {
 824     VectorSet visited(Thread::current()->resource_area());
 825     verify_adr_type(visited, _adr_type);
 826   }
 827 }
 828 #endif
 829 
 830 
 831 //------------------------------Value------------------------------------------
 832 // Compute the type of the PhiNode
 833 const Type *PhiNode::Value( PhaseTransform *phase ) const {
 834   Node *r = in(0);              // RegionNode
 835   if( !r )                      // Copy or dead
 836     return in(1) ? phase->type(in(1)) : Type::TOP;
 837 
 838   // Note: During parsing, phis are often transformed before their regions.
 839   // This means we have to use type_or_null to defend against untyped regions.
 840   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
 841     return Type::TOP;
 842 
 843   // Check for trip-counted loop.  If so, be smarter.
 844   CountedLoopNode *l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
 845   if( l && l->can_be_counted_loop(phase) &&
 846       ((const Node*)l->phi() == this) ) { // Trip counted loop!
 847     // protect against init_trip() or limit() returning NULL
 848     const Node *init   = l->init_trip();
 849     const Node *limit  = l->limit();
 850     if( init != NULL && limit != NULL && l->stride_is_con() ) {
 851       const TypeInt *lo = init ->bottom_type()->isa_int();
 852       const TypeInt *hi = limit->bottom_type()->isa_int();
 853       if( lo && hi ) {            // Dying loops might have TOP here
 854         int stride = l->stride_con();
 855         if( stride < 0 ) {          // Down-counter loop
 856           const TypeInt *tmp = lo; lo = hi; hi = tmp;
 857           stride = -stride;
 858         }
 859         if( lo->_hi < hi->_lo )     // Reversed endpoints are well defined :-(
 860           return TypeInt::make(lo->_lo,hi->_hi,3);
 861       }
 862     }
 863   }
 864 
 865   // Until we have harmony between classes and interfaces in the type
 866   // lattice, we must tread carefully around phis which implicitly
 867   // convert the one to the other.
 868   const TypePtr* ttp = _type->make_ptr();
 869   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
 870   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
 871   bool is_intf = false;
 872   if (ttip != NULL) {
 873     ciKlass* k = ttip->klass();
 874     if (k->is_loaded() && k->is_interface())
 875       is_intf = true;
 876   }
 877   if (ttkp != NULL) {
 878     ciKlass* k = ttkp->klass();
 879     if (k->is_loaded() && k->is_interface())
 880       is_intf = true;
 881   }
 882 
 883   // Default case: merge all inputs
 884   const Type *t = Type::TOP;        // Merged type starting value
 885   for (uint i = 1; i < req(); ++i) {// For all paths in
 886     // Reachable control path?
 887     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
 888       const Type* ti = phase->type(in(i));
 889       // We assume that each input of an interface-valued Phi is a true
 890       // subtype of that interface.  This might not be true of the meet
 891       // of all the input types.  The lattice is not distributive in
 892       // such cases.  Ward off asserts in type.cpp by refusing to do
 893       // meets between interfaces and proper classes.
 894       const TypePtr* tip = ti->make_ptr();
 895       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
 896       if (tiip) {
 897         bool ti_is_intf = false;
 898         ciKlass* k = tiip->klass();
 899         if (k->is_loaded() && k->is_interface())
 900           ti_is_intf = true;
 901         if (is_intf != ti_is_intf)
 902           { t = _type; break; }
 903       }
 904       t = t->meet(ti);
 905     }
 906   }
 907 
 908   // The worst-case type (from ciTypeFlow) should be consistent with "t".
 909   // That is, we expect that "t->higher_equal(_type)" holds true.
 910   // There are various exceptions:
 911   // - Inputs which are phis might in fact be widened unnecessarily.
 912   //   For example, an input might be a widened int while the phi is a short.
 913   // - Inputs might be BotPtrs but this phi is dependent on a null check,
 914   //   and postCCP has removed the cast which encodes the result of the check.
 915   // - The type of this phi is an interface, and the inputs are classes.
 916   // - Value calls on inputs might produce fuzzy results.
 917   //   (Occurrences of this case suggest improvements to Value methods.)
 918   //
 919   // It is not possible to see Type::BOTTOM values as phi inputs,
 920   // because the ciTypeFlow pre-pass produces verifier-quality types.
 921   const Type* ft = t->filter(_type);  // Worst case type
 922 
 923 #ifdef ASSERT
 924   // The following logic has been moved into TypeOopPtr::filter.
 925   const Type* jt = t->join(_type);
 926   if( jt->empty() ) {           // Emptied out???
 927 
 928     // Check for evil case of 't' being a class and '_type' expecting an
 929     // interface.  This can happen because the bytecodes do not contain
 930     // enough type info to distinguish a Java-level interface variable
 931     // from a Java-level object variable.  If we meet 2 classes which
 932     // both implement interface I, but their meet is at 'j/l/O' which
 933     // doesn't implement I, we have no way to tell if the result should
 934     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
 935     // into a Phi which "knows" it's an Interface type we'll have to
 936     // uplift the type.
 937     if( !t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface() )
 938       { assert(ft == _type, ""); } // Uplift to interface
 939     else if( !t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface() )
 940       { assert(ft == _type, ""); } // Uplift to interface
 941     // Otherwise it's something stupid like non-overlapping int ranges
 942     // found on dying counted loops.
 943     else
 944       { assert(ft == Type::TOP, ""); } // Canonical empty value
 945   }
 946 
 947   else {
 948 
 949     // If we have an interface-typed Phi and we narrow to a class type, the join
 950     // should report back the class.  However, if we have a J/L/Object
 951     // class-typed Phi and an interface flows in, it's possible that the meet &
 952     // join report an interface back out.  This isn't possible but happens
 953     // because the type system doesn't interact well with interfaces.
 954     const TypePtr *jtp = jt->make_ptr();
 955     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
 956     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
 957     if( jtip && ttip ) {
 958       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
 959           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
 960         // Happens in a CTW of rt.jar, 320-341, no extra flags
 961         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
 962                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
 963         jt = ft;
 964       }
 965     }
 966     if( jtkp && ttkp ) {
 967       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
 968           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
 969           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
 970         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
 971                ft->isa_narrowoop() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
 972         jt = ft;
 973       }
 974     }
 975     if (jt != ft && jt->base() == ft->base()) {
 976       if (jt->isa_int() &&
 977           jt->is_int()->_lo == ft->is_int()->_lo &&
 978           jt->is_int()->_hi == ft->is_int()->_hi)
 979         jt = ft;
 980       if (jt->isa_long() &&
 981           jt->is_long()->_lo == ft->is_long()->_lo &&
 982           jt->is_long()->_hi == ft->is_long()->_hi)
 983         jt = ft;
 984     }
 985     if (jt != ft) {
 986       tty->print("merge type:  "); t->dump(); tty->cr();
 987       tty->print("kill type:   "); _type->dump(); tty->cr();
 988       tty->print("join type:   "); jt->dump(); tty->cr();
 989       tty->print("filter type: "); ft->dump(); tty->cr();
 990     }
 991     assert(jt == ft, "");
 992   }
 993 #endif //ASSERT
 994 
 995   // Deal with conversion problems found in data loops.
 996   ft = phase->saturate(ft, phase->type_or_null(this), _type);
 997 
 998   return ft;
 999 }
1000 
1001 
1002 //------------------------------is_diamond_phi---------------------------------
1003 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1004 // index of the true path or 0 otherwise.
1005 int PhiNode::is_diamond_phi() const {
1006   // Check for a 2-path merge
1007   Node *region = in(0);
1008   if( !region ) return 0;
1009   if( region->req() != 3 ) return 0;
1010   if(         req() != 3 ) return 0;
1011   // Check that both paths come from the same If
1012   Node *ifp1 = region->in(1);
1013   Node *ifp2 = region->in(2);
1014   if( !ifp1 || !ifp2 ) return 0;
1015   Node *iff = ifp1->in(0);
1016   if( !iff || !iff->is_If() ) return 0;
1017   if( iff != ifp2->in(0) ) return 0;
1018   // Check for a proper bool/cmp
1019   const Node *b = iff->in(1);
1020   if( !b->is_Bool() ) return 0;
1021   const Node *cmp = b->in(1);
1022   if( !cmp->is_Cmp() ) return 0;
1023 
1024   // Check for branching opposite expected
1025   if( ifp2->Opcode() == Op_IfTrue ) {
1026     assert( ifp1->Opcode() == Op_IfFalse, "" );
1027     return 2;
1028   } else {
1029     assert( ifp1->Opcode() == Op_IfTrue, "" );
1030     return 1;
1031   }
1032 }
1033 
1034 //----------------------------check_cmove_id-----------------------------------
1035 // Check for CMove'ing a constant after comparing against the constant.
1036 // Happens all the time now, since if we compare equality vs a constant in
1037 // the parser, we "know" the variable is constant on one path and we force
1038 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1039 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1040 // general in that we don't need constants.  Since CMove's are only inserted
1041 // in very special circumstances, we do it here on generic Phi's.
1042 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1043   assert(true_path !=0, "only diamond shape graph expected");
1044 
1045   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1046   // phi->region->if_proj->ifnode->bool->cmp
1047   Node*     region = in(0);
1048   Node*     iff    = region->in(1)->in(0);
1049   BoolNode* b      = iff->in(1)->as_Bool();
1050   Node*     cmp    = b->in(1);
1051   Node*     tval   = in(true_path);
1052   Node*     fval   = in(3-true_path);
1053   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1054   if (id == NULL)
1055     return NULL;
1056 
1057   // Either value might be a cast that depends on a branch of 'iff'.
1058   // Since the 'id' value will float free of the diamond, either
1059   // decast or return failure.
1060   Node* ctl = id->in(0);
1061   if (ctl != NULL && ctl->in(0) == iff) {
1062     if (id->is_ConstraintCast()) {
1063       return id->in(1);
1064     } else {
1065       // Don't know how to disentangle this value.
1066       return NULL;
1067     }
1068   }
1069 
1070   return id;
1071 }
1072 
1073 //------------------------------Identity---------------------------------------
1074 // Check for Region being Identity.
1075 Node *PhiNode::Identity( PhaseTransform *phase ) {
1076   // Check for no merging going on
1077   // (There used to be special-case code here when this->region->is_Loop.
1078   // It would check for a tributary phi on the backedge that the main phi
1079   // trivially, perhaps with a single cast.  The unique_input method
1080   // does all this and more, by reducing such tributaries to 'this'.)
1081   Node* uin = unique_input(phase);
1082   if (uin != NULL) {
1083     return uin;
1084   }
1085 
1086   int true_path = is_diamond_phi();
1087   if (true_path != 0) {
1088     Node* id = is_cmove_id(phase, true_path);
1089     if (id != NULL)  return id;
1090   }
1091 
1092   return this;                     // No identity
1093 }
1094 
1095 //-----------------------------unique_input------------------------------------
1096 // Find the unique value, discounting top, self-loops, and casts.
1097 // Return top if there are no inputs, and self if there are multiple.
1098 Node* PhiNode::unique_input(PhaseTransform* phase) {
1099   //  1) One unique direct input, or
1100   //  2) some of the inputs have an intervening ConstraintCast and
1101   //     the type of input is the same or sharper (more specific)
1102   //     than the phi's type.
1103   //  3) an input is a self loop
1104   //
1105   //  1) input   or   2) input     or   3) input __
1106   //     /   \           /   \               \  /  \
1107   //     \   /          |    cast             phi  cast
1108   //      phi            \   /               /  \  /
1109   //                      phi               /    --
1110 
1111   Node* r = in(0);                      // RegionNode
1112   if (r == NULL)  return in(1);         // Already degraded to a Copy
1113   Node* uncasted_input = NULL; // The unique uncasted input (ConstraintCasts removed)
1114   Node* direct_input   = NULL; // The unique direct input
1115 
1116   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1117     Node* rc = r->in(i);
1118     if (rc == NULL || phase->type(rc) == Type::TOP)
1119       continue;                 // ignore unreachable control path
1120     Node* n = in(i);
1121     if (n == NULL)
1122       continue;
1123     Node* un = n->uncast();
1124     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1125       continue; // ignore if top, or in(i) and "this" are in a data cycle
1126     }
1127     // Check for a unique uncasted input
1128     if (uncasted_input == NULL) {
1129       uncasted_input = un;
1130     } else if (uncasted_input != un) {
1131       uncasted_input = NodeSentinel; // no unique uncasted input
1132     }
1133     // Check for a unique direct input
1134     if (direct_input == NULL) {
1135       direct_input = n;
1136     } else if (direct_input != n) {
1137       direct_input = NodeSentinel; // no unique direct input
1138     }
1139   }
1140   if (direct_input == NULL) {
1141     return phase->C->top();        // no inputs
1142   }
1143   assert(uncasted_input != NULL,"");
1144 
1145   if (direct_input != NodeSentinel) {
1146     return direct_input;           // one unique direct input
1147   }
1148   if (uncasted_input != NodeSentinel &&
1149       phase->type(uncasted_input)->higher_equal(type())) {
1150     return uncasted_input;         // one unique uncasted input
1151   }
1152 
1153   // Nothing.
1154   return NULL;
1155 }
1156 
1157 //------------------------------is_x2logic-------------------------------------
1158 // Check for simple convert-to-boolean pattern
1159 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1160 // Convert Phi to an ConvIB.
1161 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1162   assert(true_path !=0, "only diamond shape graph expected");
1163   // Convert the true/false index into an expected 0/1 return.
1164   // Map 2->0 and 1->1.
1165   int flipped = 2-true_path;
1166 
1167   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1168   // phi->region->if_proj->ifnode->bool->cmp
1169   Node *region = phi->in(0);
1170   Node *iff = region->in(1)->in(0);
1171   BoolNode *b = (BoolNode*)iff->in(1);
1172   const CmpNode *cmp = (CmpNode*)b->in(1);
1173 
1174   Node *zero = phi->in(1);
1175   Node *one  = phi->in(2);
1176   const Type *tzero = phase->type( zero );
1177   const Type *tone  = phase->type( one  );
1178 
1179   // Check for compare vs 0
1180   const Type *tcmp = phase->type(cmp->in(2));
1181   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1182     // Allow cmp-vs-1 if the other input is bounded by 0-1
1183     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1184       return NULL;
1185     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1186   }
1187 
1188   // Check for setting zero/one opposite expected
1189   if( tzero == TypeInt::ZERO ) {
1190     if( tone == TypeInt::ONE ) {
1191     } else return NULL;
1192   } else if( tzero == TypeInt::ONE ) {
1193     if( tone == TypeInt::ZERO ) {
1194       flipped = 1-flipped;
1195     } else return NULL;
1196   } else return NULL;
1197 
1198   // Check for boolean test backwards
1199   if( b->_test._test == BoolTest::ne ) {
1200   } else if( b->_test._test == BoolTest::eq ) {
1201     flipped = 1-flipped;
1202   } else return NULL;
1203 
1204   // Build int->bool conversion
1205   Node *n = new (phase->C, 2) Conv2BNode( cmp->in(1) );
1206   if( flipped )
1207     n = new (phase->C, 3) XorINode( phase->transform(n), phase->intcon(1) );
1208 
1209   return n;
1210 }
1211 
1212 //------------------------------is_cond_add------------------------------------
1213 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1214 // To be profitable the control flow has to disappear; there can be no other
1215 // values merging here.  We replace the test-and-branch with:
1216 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1217 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1218 // Then convert Y to 0-or-Y and finally add.
1219 // This is a key transform for SpecJava _201_compress.
1220 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1221   assert(true_path !=0, "only diamond shape graph expected");
1222 
1223   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1224   // phi->region->if_proj->ifnode->bool->cmp
1225   RegionNode *region = (RegionNode*)phi->in(0);
1226   Node *iff = region->in(1)->in(0);
1227   BoolNode* b = iff->in(1)->as_Bool();
1228   const CmpNode *cmp = (CmpNode*)b->in(1);
1229 
1230   // Make sure only merging this one phi here
1231   if (region->has_unique_phi() != phi)  return NULL;
1232 
1233   // Make sure each arm of the diamond has exactly one output, which we assume
1234   // is the region.  Otherwise, the control flow won't disappear.
1235   if (region->in(1)->outcnt() != 1) return NULL;
1236   if (region->in(2)->outcnt() != 1) return NULL;
1237 
1238   // Check for "(P < Q)" of type signed int
1239   if (b->_test._test != BoolTest::lt)  return NULL;
1240   if (cmp->Opcode() != Op_CmpI)        return NULL;
1241 
1242   Node *p = cmp->in(1);
1243   Node *q = cmp->in(2);
1244   Node *n1 = phi->in(  true_path);
1245   Node *n2 = phi->in(3-true_path);
1246 
1247   int op = n1->Opcode();
1248   if( op != Op_AddI           // Need zero as additive identity
1249       /*&&op != Op_SubI &&
1250       op != Op_AddP &&
1251       op != Op_XorI &&
1252       op != Op_OrI*/ )
1253     return NULL;
1254 
1255   Node *x = n2;
1256   Node *y = n1->in(1);
1257   if( n2 == n1->in(1) ) {
1258     y = n1->in(2);
1259   } else if( n2 == n1->in(1) ) {
1260   } else return NULL;
1261 
1262   // Not so profitable if compare and add are constants
1263   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1264     return NULL;
1265 
1266   Node *cmplt = phase->transform( new (phase->C, 3) CmpLTMaskNode(p,q) );
1267   Node *j_and   = phase->transform( new (phase->C, 3) AndINode(cmplt,y) );
1268   return new (phase->C, 3) AddINode(j_and,x);
1269 }
1270 
1271 //------------------------------is_absolute------------------------------------
1272 // Check for absolute value.
1273 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1274   assert(true_path !=0, "only diamond shape graph expected");
1275 
1276   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1277   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1278 
1279   // ABS ends with the merge of 2 control flow paths.
1280   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1281   int false_path = 3 - true_path;
1282 
1283   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1284   // phi->region->if_proj->ifnode->bool->cmp
1285   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1286 
1287   // Check bool sense
1288   switch( bol->_test._test ) {
1289   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1290   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1291   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1292   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1293   default:           return NULL;                              break;
1294   }
1295 
1296   // Test is next
1297   Node *cmp = bol->in(1);
1298   const Type *tzero = NULL;
1299   switch( cmp->Opcode() ) {
1300   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1301   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1302   default: return NULL;
1303   }
1304 
1305   // Find zero input of compare; the other input is being abs'd
1306   Node *x = NULL;
1307   bool flip = false;
1308   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1309     x = cmp->in(3 - cmp_zero_idx);
1310   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1311     // The test is inverted, we should invert the result...
1312     x = cmp->in(cmp_zero_idx);
1313     flip = true;
1314   } else {
1315     return NULL;
1316   }
1317 
1318   // Next get the 2 pieces being selected, one is the original value
1319   // and the other is the negated value.
1320   if( phi_root->in(phi_x_idx) != x ) return NULL;
1321 
1322   // Check other phi input for subtract node
1323   Node *sub = phi_root->in(3 - phi_x_idx);
1324 
1325   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1326   if( tzero == TypeF::ZERO ) {
1327     if( sub->Opcode() != Op_SubF ||
1328         sub->in(2) != x ||
1329         phase->type(sub->in(1)) != tzero ) return NULL;
1330     x = new (phase->C, 2) AbsFNode(x);
1331     if (flip) {
1332       x = new (phase->C, 3) SubFNode(sub->in(1), phase->transform(x));
1333     }
1334   } else {
1335     if( sub->Opcode() != Op_SubD ||
1336         sub->in(2) != x ||
1337         phase->type(sub->in(1)) != tzero ) return NULL;
1338     x = new (phase->C, 2) AbsDNode(x);
1339     if (flip) {
1340       x = new (phase->C, 3) SubDNode(sub->in(1), phase->transform(x));
1341     }
1342   }
1343 
1344   return x;
1345 }
1346 
1347 //------------------------------split_once-------------------------------------
1348 // Helper for split_flow_path
1349 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1350   igvn->hash_delete(n);         // Remove from hash before hacking edges
1351 
1352   Node* predicate_proj = NULL;
1353   uint j = 1;
1354   for (uint i = phi->req()-1; i > 0; i--) {
1355     if (phi->in(i) == val) {   // Found a path with val?
1356       if (n->is_Region()) {
1357         Node* proj = PhaseIdealLoop::find_predicate(n->in(i));
1358         if (proj != NULL) {
1359           assert(predicate_proj == NULL, "only one predicate entry expected");
1360           predicate_proj = proj;
1361         }
1362       }
1363       // Add to NEW Region/Phi, no DU info
1364       newn->set_req( j++, n->in(i) );
1365       // Remove from OLD Region/Phi
1366       n->del_req(i);
1367     }
1368   }
1369 
1370   // Register the new node but do not transform it.  Cannot transform until the
1371   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1372   igvn->register_new_node_with_optimizer( newn );
1373 
1374   // Clone loop predicates
1375   if (predicate_proj != NULL) {
1376     newn = igvn->clone_loop_predicates(predicate_proj, newn, !n->is_CountedLoop());
1377   }
1378 
1379   // Now I can point to the new node.
1380   n->add_req(newn);
1381   igvn->_worklist.push(n);
1382 }
1383 
1384 //------------------------------split_flow_path--------------------------------
1385 // Check for merging identical values and split flow paths
1386 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1387   BasicType bt = phi->type()->basic_type();
1388   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1389     return NULL;                // Bail out on funny non-value stuff
1390   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1391     return NULL;                // third unequal input to be worth doing
1392 
1393   // Scan for a constant
1394   uint i;
1395   for( i = 1; i < phi->req()-1; i++ ) {
1396     Node *n = phi->in(i);
1397     if( !n ) return NULL;
1398     if( phase->type(n) == Type::TOP ) return NULL;
1399     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN )
1400       break;
1401   }
1402   if( i >= phi->req() )         // Only split for constants
1403     return NULL;
1404 
1405   Node *val = phi->in(i);       // Constant to split for
1406   uint hit = 0;                 // Number of times it occurs
1407 
1408   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1409     Node *n = phi->in(i);
1410     if( !n ) return NULL;
1411     if( phase->type(n) == Type::TOP ) return NULL;
1412     if( phi->in(i) == val )
1413       hit++;
1414   }
1415 
1416   if( hit <= 1 ||               // Make sure we find 2 or more
1417       hit == phi->req()-1 )     // and not ALL the same value
1418     return NULL;
1419 
1420   // Now start splitting out the flow paths that merge the same value.
1421   // Split first the RegionNode.
1422   PhaseIterGVN *igvn = phase->is_IterGVN();
1423   Node *r = phi->region();
1424   RegionNode *newr = new (phase->C, hit+1) RegionNode(hit+1);
1425   split_once(igvn, phi, val, r, newr);
1426 
1427   // Now split all other Phis than this one
1428   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1429     Node* phi2 = r->fast_out(k);
1430     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1431       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1432       split_once(igvn, phi, val, phi2, newphi);
1433     }
1434   }
1435 
1436   // Clean up this guy
1437   igvn->hash_delete(phi);
1438   for( i = phi->req()-1; i > 0; i-- ) {
1439     if( phi->in(i) == val ) {
1440       phi->del_req(i);
1441     }
1442   }
1443   phi->add_req(val);
1444 
1445   return phi;
1446 }
1447 
1448 //=============================================================================
1449 //------------------------------simple_data_loop_check-------------------------
1450 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1451 //  Returns:
1452 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1453 // Safe       - safe case when the phi and it's inputs reference only safe data
1454 //              nodes;
1455 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1456 //              is no reference back to the phi - need a graph walk
1457 //              to determine if it is in a loop;
1458 // UnsafeLoop - unsafe case when the phi references itself directly or through
1459 //              unsafe data node.
1460 //  Note: a safe data node is a node which could/never reference itself during
1461 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1462 //  I mark Phi nodes as safe node not only because they can reference itself
1463 //  but also to prevent mistaking the fallthrough case inside an outer loop
1464 //  as dead loop when the phi references itselfs through an other phi.
1465 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1466   // It is unsafe loop if the phi node references itself directly.
1467   if (in == (Node*)this)
1468     return UnsafeLoop; // Unsafe loop
1469   // Unsafe loop if the phi node references itself through an unsafe data node.
1470   // Exclude cases with null inputs or data nodes which could reference
1471   // itself (safe for dead loops).
1472   if (in != NULL && !in->is_dead_loop_safe()) {
1473     // Check inputs of phi's inputs also.
1474     // It is much less expensive then full graph walk.
1475     uint cnt = in->req();
1476     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1477     for (; i < cnt; ++i) {
1478       Node* m = in->in(i);
1479       if (m == (Node*)this)
1480         return UnsafeLoop; // Unsafe loop
1481       if (m != NULL && !m->is_dead_loop_safe()) {
1482         // Check the most common case (about 30% of all cases):
1483         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1484         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1485         if (m1 == (Node*)this)
1486           return UnsafeLoop; // Unsafe loop
1487         if (m1 != NULL && m1 == m->in(2) &&
1488             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1489           continue; // Safe case
1490         }
1491         // The phi references an unsafe node - need full analysis.
1492         return Unsafe;
1493       }
1494     }
1495   }
1496   return Safe; // Safe case - we can optimize the phi node.
1497 }
1498 
1499 //------------------------------is_unsafe_data_reference-----------------------
1500 // If phi can be reached through the data input - it is data loop.
1501 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1502   assert(req() > 1, "");
1503   // First, check simple cases when phi references itself directly or
1504   // through an other node.
1505   LoopSafety safety = simple_data_loop_check(in);
1506   if (safety == UnsafeLoop)
1507     return true;  // phi references itself - unsafe loop
1508   else if (safety == Safe)
1509     return false; // Safe case - phi could be replaced with the unique input.
1510 
1511   // Unsafe case when we should go through data graph to determine
1512   // if the phi references itself.
1513 
1514   ResourceMark rm;
1515 
1516   Arena *a = Thread::current()->resource_area();
1517   Node_List nstack(a);
1518   VectorSet visited(a);
1519 
1520   nstack.push(in); // Start with unique input.
1521   visited.set(in->_idx);
1522   while (nstack.size() != 0) {
1523     Node* n = nstack.pop();
1524     uint cnt = n->req();
1525     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1526     for (; i < cnt; i++) {
1527       Node* m = n->in(i);
1528       if (m == (Node*)this) {
1529         return true;    // Data loop
1530       }
1531       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1532         if (!visited.test_set(m->_idx))
1533           nstack.push(m);
1534       }
1535     }
1536   }
1537   return false; // The phi is not reachable from its inputs
1538 }
1539 
1540 
1541 //------------------------------Ideal------------------------------------------
1542 // Return a node which is more "ideal" than the current node.  Must preserve
1543 // the CFG, but we can still strip out dead paths.
1544 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1545   // The next should never happen after 6297035 fix.
1546   if( is_copy() )               // Already degraded to a Copy ?
1547     return NULL;                // No change
1548 
1549   Node *r = in(0);              // RegionNode
1550   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1551 
1552   // Note: During parsing, phis are often transformed before their regions.
1553   // This means we have to use type_or_null to defend against untyped regions.
1554   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1555     return NULL;                // No change
1556 
1557   Node *top = phase->C->top();
1558   bool new_phi = (outcnt() == 0); // transforming new Phi
1559   assert(!can_reshape || !new_phi, "for igvn new phi should be hooked");
1560 
1561   // The are 2 situations when only one valid phi's input is left
1562   // (in addition to Region input).
1563   // One: region is not loop - replace phi with this input.
1564   // Two: region is loop - replace phi with top since this data path is dead
1565   //                       and we need to break the dead data loop.
1566   Node* progress = NULL;        // Record if any progress made
1567   for( uint j = 1; j < req(); ++j ){ // For all paths in
1568     // Check unreachable control paths
1569     Node* rc = r->in(j);
1570     Node* n = in(j);            // Get the input
1571     if (rc == NULL || phase->type(rc) == Type::TOP) {
1572       if (n != top) {           // Not already top?
1573         set_req(j, top);        // Nuke it down
1574         progress = this;        // Record progress
1575       }
1576     }
1577   }
1578 
1579   if (can_reshape && outcnt() == 0) {
1580     // set_req() above may kill outputs if Phi is referenced
1581     // only by itself on the dead (top) control path.
1582     return top;
1583   }
1584 
1585   Node* uin = unique_input(phase);
1586   if (uin == top) {             // Simplest case: no alive inputs.
1587     if (can_reshape)            // IGVN transformation
1588       return top;
1589     else
1590       return NULL;              // Identity will return TOP
1591   } else if (uin != NULL) {
1592     // Only one not-NULL unique input path is left.
1593     // Determine if this input is backedge of a loop.
1594     // (Skip new phis which have no uses and dead regions).
1595     if( outcnt() > 0 && r->in(0) != NULL ) {
1596       // First, take the short cut when we know it is a loop and
1597       // the EntryControl data path is dead.
1598       assert(!r->is_Loop() || r->req() == 3, "Loop node should have 3 inputs");
1599       // Then, check if there is a data loop when phi references itself directly
1600       // or through other data nodes.
1601       if( r->is_Loop() && !phase->eqv_uncast(uin, in(LoopNode::EntryControl)) ||
1602          !r->is_Loop() && is_unsafe_data_reference(uin) ) {
1603         // Break this data loop to avoid creation of a dead loop.
1604         if (can_reshape) {
1605           return top;
1606         } else {
1607           // We can't return top if we are in Parse phase - cut inputs only
1608           // let Identity to handle the case.
1609           replace_edge(uin, top);
1610           return NULL;
1611         }
1612       }
1613     }
1614 
1615     // One unique input.
1616     debug_only(Node* ident = Identity(phase));
1617     // The unique input must eventually be detected by the Identity call.
1618 #ifdef ASSERT
1619     if (ident != uin && !ident->is_top()) {
1620       // print this output before failing assert
1621       r->dump(3);
1622       this->dump(3);
1623       ident->dump();
1624       uin->dump();
1625     }
1626 #endif
1627     assert(ident == uin || ident->is_top(), "Identity must clean this up");
1628     return NULL;
1629   }
1630 
1631 
1632   Node* opt = NULL;
1633   int true_path = is_diamond_phi();
1634   if( true_path != 0 ) {
1635     // Check for CMove'ing identity. If it would be unsafe,
1636     // handle it here. In the safe case, let Identity handle it.
1637     Node* unsafe_id = is_cmove_id(phase, true_path);
1638     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
1639       opt = unsafe_id;
1640 
1641     // Check for simple convert-to-boolean pattern
1642     if( opt == NULL )
1643       opt = is_x2logic(phase, this, true_path);
1644 
1645     // Check for absolute value
1646     if( opt == NULL )
1647       opt = is_absolute(phase, this, true_path);
1648 
1649     // Check for conditional add
1650     if( opt == NULL && can_reshape )
1651       opt = is_cond_add(phase, this, true_path);
1652 
1653     // These 4 optimizations could subsume the phi:
1654     // have to check for a dead data loop creation.
1655     if( opt != NULL ) {
1656       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
1657         // Found dead loop.
1658         if( can_reshape )
1659           return top;
1660         // We can't return top if we are in Parse phase - cut inputs only
1661         // to stop further optimizations for this phi. Identity will return TOP.
1662         assert(req() == 3, "only diamond merge phi here");
1663         set_req(1, top);
1664         set_req(2, top);
1665         return NULL;
1666       } else {
1667         return opt;
1668       }
1669     }
1670   }
1671 
1672   // Check for merging identical values and split flow paths
1673   if (can_reshape) {
1674     opt = split_flow_path(phase, this);
1675     // This optimization only modifies phi - don't need to check for dead loop.
1676     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
1677     if (opt != NULL)  return opt;
1678   }
1679 
1680   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
1681     // Try to undo Phi of AddP:
1682     // (Phi (AddP base base y) (AddP base2 base2 y))
1683     // becomes:
1684     // newbase := (Phi base base2)
1685     // (AddP newbase newbase y)
1686     //
1687     // This occurs as a result of unsuccessful split_thru_phi and
1688     // interferes with taking advantage of addressing modes. See the
1689     // clone_shift_expressions code in matcher.cpp
1690     Node* addp = in(1);
1691     const Type* type = addp->in(AddPNode::Base)->bottom_type();
1692     Node* y = addp->in(AddPNode::Offset);
1693     if (y != NULL && addp->in(AddPNode::Base) == addp->in(AddPNode::Address)) {
1694       // make sure that all the inputs are similar to the first one,
1695       // i.e. AddP with base == address and same offset as first AddP
1696       bool doit = true;
1697       for (uint i = 2; i < req(); i++) {
1698         if (in(i) == NULL ||
1699             in(i)->Opcode() != Op_AddP ||
1700             in(i)->in(AddPNode::Base) != in(i)->in(AddPNode::Address) ||
1701             in(i)->in(AddPNode::Offset) != y) {
1702           doit = false;
1703           break;
1704         }
1705         // Accumulate type for resulting Phi
1706         type = type->meet(in(i)->in(AddPNode::Base)->bottom_type());
1707       }
1708       Node* base = NULL;
1709       if (doit) {
1710         // Check for neighboring AddP nodes in a tree.
1711         // If they have a base, use that it.
1712         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
1713           Node* u = this->fast_out(k);
1714           if (u->is_AddP()) {
1715             Node* base2 = u->in(AddPNode::Base);
1716             if (base2 != NULL && !base2->is_top()) {
1717               if (base == NULL)
1718                 base = base2;
1719               else if (base != base2)
1720                 { doit = false; break; }
1721             }
1722           }
1723         }
1724       }
1725       if (doit) {
1726         if (base == NULL) {
1727           base = new (phase->C, in(0)->req()) PhiNode(in(0), type, NULL);
1728           for (uint i = 1; i < req(); i++) {
1729             base->init_req(i, in(i)->in(AddPNode::Base));
1730           }
1731           phase->is_IterGVN()->register_new_node_with_optimizer(base);
1732         }
1733         return new (phase->C, 4) AddPNode(base, base, y);
1734       }
1735     }
1736   }
1737 
1738   // Split phis through memory merges, so that the memory merges will go away.
1739   // Piggy-back this transformation on the search for a unique input....
1740   // It will be as if the merged memory is the unique value of the phi.
1741   // (Do not attempt this optimization unless parsing is complete.
1742   // It would make the parser's memory-merge logic sick.)
1743   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
1744   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
1745     // see if this phi should be sliced
1746     uint merge_width = 0;
1747     bool saw_self = false;
1748     for( uint i=1; i<req(); ++i ) {// For all paths in
1749       Node *ii = in(i);
1750       if (ii->is_MergeMem()) {
1751         MergeMemNode* n = ii->as_MergeMem();
1752         merge_width = MAX2(merge_width, n->req());
1753         saw_self = saw_self || phase->eqv(n->base_memory(), this);
1754       }
1755     }
1756 
1757     // This restriction is temporarily necessary to ensure termination:
1758     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
1759 
1760     if (merge_width > Compile::AliasIdxRaw) {
1761       // found at least one non-empty MergeMem
1762       const TypePtr* at = adr_type();
1763       if (at != TypePtr::BOTTOM) {
1764         // Patch the existing phi to select an input from the merge:
1765         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
1766         //     Phi:AT1(...m1...)
1767         int alias_idx = phase->C->get_alias_index(at);
1768         for (uint i=1; i<req(); ++i) {
1769           Node *ii = in(i);
1770           if (ii->is_MergeMem()) {
1771             MergeMemNode* n = ii->as_MergeMem();
1772             // compress paths and change unreachable cycles to TOP
1773             // If not, we can update the input infinitely along a MergeMem cycle
1774             // Equivalent code is in MemNode::Ideal_common
1775             Node *m  = phase->transform(n);
1776             if (outcnt() == 0) {  // Above transform() may kill us!
1777               return top;
1778             }
1779             // If transformed to a MergeMem, get the desired slice
1780             // Otherwise the returned node represents memory for every slice
1781             Node *new_mem = (m->is_MergeMem()) ?
1782                              m->as_MergeMem()->memory_at(alias_idx) : m;
1783             // Update input if it is progress over what we have now
1784             if (new_mem != ii) {
1785               set_req(i, new_mem);
1786               progress = this;
1787             }
1788           }
1789         }
1790       } else {
1791         // We know that at least one MergeMem->base_memory() == this
1792         // (saw_self == true). If all other inputs also references this phi
1793         // (directly or through data nodes) - it is dead loop.
1794         bool saw_safe_input = false;
1795         for (uint j = 1; j < req(); ++j) {
1796           Node *n = in(j);
1797           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
1798             continue;              // skip known cases
1799           if (!is_unsafe_data_reference(n)) {
1800             saw_safe_input = true; // found safe input
1801             break;
1802           }
1803         }
1804         if (!saw_safe_input)
1805           return top; // all inputs reference back to this phi - dead loop
1806 
1807         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
1808         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
1809         PhaseIterGVN *igvn = phase->is_IterGVN();
1810         Node* hook = new (phase->C, 1) Node(1);
1811         PhiNode* new_base = (PhiNode*) clone();
1812         // Must eagerly register phis, since they participate in loops.
1813         if (igvn) {
1814           igvn->register_new_node_with_optimizer(new_base);
1815           hook->add_req(new_base);
1816         }
1817         MergeMemNode* result = MergeMemNode::make(phase->C, new_base);
1818         for (uint i = 1; i < req(); ++i) {
1819           Node *ii = in(i);
1820           if (ii->is_MergeMem()) {
1821             MergeMemNode* n = ii->as_MergeMem();
1822             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
1823               // If we have not seen this slice yet, make a phi for it.
1824               bool made_new_phi = false;
1825               if (mms.is_empty()) {
1826                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
1827                 made_new_phi = true;
1828                 if (igvn) {
1829                   igvn->register_new_node_with_optimizer(new_phi);
1830                   hook->add_req(new_phi);
1831                 }
1832                 mms.set_memory(new_phi);
1833               }
1834               Node* phi = mms.memory();
1835               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
1836               phi->set_req(i, mms.memory2());
1837             }
1838           }
1839         }
1840         // Distribute all self-loops.
1841         { // (Extra braces to hide mms.)
1842           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
1843             Node* phi = mms.memory();
1844             for (uint i = 1; i < req(); ++i) {
1845               if (phi->in(i) == this)  phi->set_req(i, phi);
1846             }
1847           }
1848         }
1849         // now transform the new nodes, and return the mergemem
1850         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
1851           Node* phi = mms.memory();
1852           mms.set_memory(phase->transform(phi));
1853         }
1854         if (igvn) { // Unhook.
1855           igvn->hash_delete(hook);
1856           for (uint i = 1; i < hook->req(); i++) {
1857             hook->set_req(i, NULL);
1858           }
1859         }
1860         // Replace self with the result.
1861         return result;
1862       }
1863     }
1864     //
1865     // Other optimizations on the memory chain
1866     //
1867     const TypePtr* at = adr_type();
1868     for( uint i=1; i<req(); ++i ) {// For all paths in
1869       Node *ii = in(i);
1870       Node *new_in = MemNode::optimize_memory_chain(ii, at, phase);
1871       if (ii != new_in ) {
1872         set_req(i, new_in);
1873         progress = this;
1874       }
1875     }
1876   }
1877 
1878 #ifdef _LP64
1879   // Push DecodeN down through phi.
1880   // The rest of phi graph will transform by split EncodeP node though phis up.
1881   if (UseCompressedOops && can_reshape && progress == NULL) {
1882     bool may_push = true;
1883     bool has_decodeN = false;
1884     for (uint i=1; i<req(); ++i) {// For all paths in
1885       Node *ii = in(i);
1886       if (ii->is_DecodeN() && ii->bottom_type() == bottom_type()) {
1887         // Do optimization if a non dead path exist.
1888         if (ii->in(1)->bottom_type() != Type::TOP) {
1889           has_decodeN = true;
1890         }
1891       } else if (!ii->is_Phi()) {
1892         may_push = false;
1893       }
1894     }
1895 
1896     if (has_decodeN && may_push) {
1897       PhaseIterGVN *igvn = phase->is_IterGVN();
1898       // Make narrow type for new phi.
1899       const Type* narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
1900       PhiNode* new_phi = new (phase->C, r->req()) PhiNode(r, narrow_t);
1901       uint orig_cnt = req();
1902       for (uint i=1; i<req(); ++i) {// For all paths in
1903         Node *ii = in(i);
1904         Node* new_ii = NULL;
1905         if (ii->is_DecodeN()) {
1906           assert(ii->bottom_type() == bottom_type(), "sanity");
1907           new_ii = ii->in(1);
1908         } else {
1909           assert(ii->is_Phi(), "sanity");
1910           if (ii->as_Phi() == this) {
1911             new_ii = new_phi;
1912           } else {
1913             new_ii = new (phase->C, 2) EncodePNode(ii, narrow_t);
1914             igvn->register_new_node_with_optimizer(new_ii);
1915           }
1916         }
1917         new_phi->set_req(i, new_ii);
1918       }
1919       igvn->register_new_node_with_optimizer(new_phi, this);
1920       progress = new (phase->C, 2) DecodeNNode(new_phi, bottom_type());
1921     }
1922   }
1923 #endif
1924 
1925   return progress;              // Return any progress
1926 }
1927 
1928 //------------------------------is_tripcount-----------------------------------
1929 bool PhiNode::is_tripcount() const {
1930   return (in(0) != NULL && in(0)->is_CountedLoop() &&
1931           in(0)->as_CountedLoop()->phi() == this);
1932 }
1933 
1934 //------------------------------out_RegMask------------------------------------
1935 const RegMask &PhiNode::in_RegMask(uint i) const {
1936   return i ? out_RegMask() : RegMask::Empty;
1937 }
1938 
1939 const RegMask &PhiNode::out_RegMask() const {
1940   uint ideal_reg = Matcher::base2reg[_type->base()];
1941   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
1942   if( ideal_reg == 0 ) return RegMask::Empty;
1943   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
1944 }
1945 
1946 #ifndef PRODUCT
1947 void PhiNode::dump_spec(outputStream *st) const {
1948   TypeNode::dump_spec(st);
1949   if (is_tripcount()) {
1950     st->print(" #tripcount");
1951   }
1952 }
1953 #endif
1954 
1955 
1956 //=============================================================================
1957 const Type *GotoNode::Value( PhaseTransform *phase ) const {
1958   // If the input is reachable, then we are executed.
1959   // If the input is not reachable, then we are not executed.
1960   return phase->type(in(0));
1961 }
1962 
1963 Node *GotoNode::Identity( PhaseTransform *phase ) {
1964   return in(0);                // Simple copy of incoming control
1965 }
1966 
1967 const RegMask &GotoNode::out_RegMask() const {
1968   return RegMask::Empty;
1969 }
1970 
1971 //=============================================================================
1972 const RegMask &JumpNode::out_RegMask() const {
1973   return RegMask::Empty;
1974 }
1975 
1976 //=============================================================================
1977 const RegMask &JProjNode::out_RegMask() const {
1978   return RegMask::Empty;
1979 }
1980 
1981 //=============================================================================
1982 const RegMask &CProjNode::out_RegMask() const {
1983   return RegMask::Empty;
1984 }
1985 
1986 
1987 
1988 //=============================================================================
1989 
1990 uint PCTableNode::hash() const { return Node::hash() + _size; }
1991 uint PCTableNode::cmp( const Node &n ) const
1992 { return _size == ((PCTableNode&)n)._size; }
1993 
1994 const Type *PCTableNode::bottom_type() const {
1995   const Type** f = TypeTuple::fields(_size);
1996   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
1997   return TypeTuple::make(_size, f);
1998 }
1999 
2000 //------------------------------Value------------------------------------------
2001 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2002 // Control, otherwise the table targets are not reachable
2003 const Type *PCTableNode::Value( PhaseTransform *phase ) const {
2004   if( phase->type(in(0)) == Type::CONTROL )
2005     return bottom_type();
2006   return Type::TOP;             // All paths dead?  Then so are we
2007 }
2008 
2009 //------------------------------Ideal------------------------------------------
2010 // Return a node which is more "ideal" than the current node.  Strip out
2011 // control copies
2012 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2013   return remove_dead_region(phase, can_reshape) ? this : NULL;
2014 }
2015 
2016 //=============================================================================
2017 uint JumpProjNode::hash() const {
2018   return Node::hash() + _dest_bci;
2019 }
2020 
2021 uint JumpProjNode::cmp( const Node &n ) const {
2022   return ProjNode::cmp(n) &&
2023     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2024 }
2025 
2026 #ifndef PRODUCT
2027 void JumpProjNode::dump_spec(outputStream *st) const {
2028   ProjNode::dump_spec(st);
2029    st->print("@bci %d ",_dest_bci);
2030 }
2031 #endif
2032 
2033 //=============================================================================
2034 //------------------------------Value------------------------------------------
2035 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2036 // have the default "fall_through_index" path.
2037 const Type *CatchNode::Value( PhaseTransform *phase ) const {
2038   // Unreachable?  Then so are all paths from here.
2039   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2040   // First assume all paths are reachable
2041   const Type** f = TypeTuple::fields(_size);
2042   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2043   // Identify cases that will always throw an exception
2044   // () rethrow call
2045   // () virtual or interface call with NULL receiver
2046   // () call is a check cast with incompatible arguments
2047   if( in(1)->is_Proj() ) {
2048     Node *i10 = in(1)->in(0);
2049     if( i10->is_Call() ) {
2050       CallNode *call = i10->as_Call();
2051       // Rethrows always throw exceptions, never return
2052       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2053         f[CatchProjNode::fall_through_index] = Type::TOP;
2054       } else if( call->req() > TypeFunc::Parms ) {
2055         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2056         // Check for null receiver to virtual or interface calls
2057         if( call->is_CallDynamicJava() &&
2058             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2059           f[CatchProjNode::fall_through_index] = Type::TOP;
2060         }
2061       } // End of if not a runtime stub
2062     } // End of if have call above me
2063   } // End of slot 1 is not a projection
2064   return TypeTuple::make(_size, f);
2065 }
2066 
2067 //=============================================================================
2068 uint CatchProjNode::hash() const {
2069   return Node::hash() + _handler_bci;
2070 }
2071 
2072 
2073 uint CatchProjNode::cmp( const Node &n ) const {
2074   return ProjNode::cmp(n) &&
2075     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2076 }
2077 
2078 
2079 //------------------------------Identity---------------------------------------
2080 // If only 1 target is possible, choose it if it is the main control
2081 Node *CatchProjNode::Identity( PhaseTransform *phase ) {
2082   // If my value is control and no other value is, then treat as ID
2083   const TypeTuple *t = phase->type(in(0))->is_tuple();
2084   if (t->field_at(_con) != Type::CONTROL)  return this;
2085   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2086   // also remove any exception table entry.  Thus we must know the call
2087   // feeding the Catch will not really throw an exception.  This is ok for
2088   // the main fall-thru control (happens when we know a call can never throw
2089   // an exception) or for "rethrow", because a further optimization will
2090   // yank the rethrow (happens when we inline a function that can throw an
2091   // exception and the caller has no handler).  Not legal, e.g., for passing
2092   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2093   // These cases MUST throw an exception via the runtime system, so the VM
2094   // will be looking for a table entry.
2095   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2096   CallNode *call;
2097   if (_con != TypeFunc::Control && // Bail out if not the main control.
2098       !(proj->is_Proj() &&      // AND NOT a rethrow
2099         proj->in(0)->is_Call() &&
2100         (call = proj->in(0)->as_Call()) &&
2101         call->entry_point() == OptoRuntime::rethrow_stub()))
2102     return this;
2103 
2104   // Search for any other path being control
2105   for (uint i = 0; i < t->cnt(); i++) {
2106     if (i != _con && t->field_at(i) == Type::CONTROL)
2107       return this;
2108   }
2109   // Only my path is possible; I am identity on control to the jump
2110   return in(0)->in(0);
2111 }
2112 
2113 
2114 #ifndef PRODUCT
2115 void CatchProjNode::dump_spec(outputStream *st) const {
2116   ProjNode::dump_spec(st);
2117   st->print("@bci %d ",_handler_bci);
2118 }
2119 #endif
2120 
2121 //=============================================================================
2122 //------------------------------Identity---------------------------------------
2123 // Check for CreateEx being Identity.
2124 Node *CreateExNode::Identity( PhaseTransform *phase ) {
2125   if( phase->type(in(1)) == Type::TOP ) return in(1);
2126   if( phase->type(in(0)) == Type::TOP ) return in(0);
2127   // We only come from CatchProj, unless the CatchProj goes away.
2128   // If the CatchProj is optimized away, then we just carry the
2129   // exception oop through.
2130   CallNode *call = in(1)->in(0)->as_Call();
2131 
2132   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2133     ? this
2134     : call->in(TypeFunc::Parms);
2135 }
2136 
2137 //=============================================================================
2138 //------------------------------Value------------------------------------------
2139 // Check for being unreachable.
2140 const Type *NeverBranchNode::Value( PhaseTransform *phase ) const {
2141   if (!in(0) || in(0)->is_top()) return Type::TOP;
2142   return bottom_type();
2143 }
2144 
2145 //------------------------------Ideal------------------------------------------
2146 // Check for no longer being part of a loop
2147 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2148   if (can_reshape && !in(0)->is_Loop()) {
2149     // Dead code elimination can sometimes delete this projection so
2150     // if it's not there, there's nothing to do.
2151     Node* fallthru = proj_out(0);
2152     if (fallthru != NULL) {
2153       phase->is_IterGVN()->replace_node(fallthru, in(0));
2154     }
2155     return phase->C->top();
2156   }
2157   return NULL;
2158 }
2159 
2160 #ifndef PRODUCT
2161 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2162   st->print("%s", Name());
2163 }
2164 #endif