1 /*
   2  * Copyright (c) 2000, 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 "memory/allocation.inline.hpp"
  27 #include "opto/addnode.hpp"
  28 #include "opto/cfgnode.hpp"
  29 #include "opto/connode.hpp"
  30 #include "opto/loopnode.hpp"
  31 #include "opto/phaseX.hpp"
  32 #include "opto/runtime.hpp"
  33 #include "opto/subnode.hpp"
  34 
  35 // Portions of code courtesy of Clifford Click
  36 
  37 // Optimization - Graph Style
  38 
  39 
  40 extern int explicit_null_checks_elided;
  41 
  42 //=============================================================================
  43 //------------------------------Value------------------------------------------
  44 // Return a tuple for whichever arm of the IF is reachable
  45 const Type *IfNode::Value( PhaseTransform *phase ) const {
  46   if( !in(0) ) return Type::TOP;
  47   if( phase->type(in(0)) == Type::TOP )
  48     return Type::TOP;
  49   const Type *t = phase->type(in(1));
  50   if( t == Type::TOP )          // data is undefined
  51     return TypeTuple::IFNEITHER; // unreachable altogether
  52   if( t == TypeInt::ZERO )      // zero, or false
  53     return TypeTuple::IFFALSE;  // only false branch is reachable
  54   if( t == TypeInt::ONE )       // 1, or true
  55     return TypeTuple::IFTRUE;   // only true branch is reachable
  56   assert( t == TypeInt::BOOL, "expected boolean type" );
  57 
  58   return TypeTuple::IFBOTH;     // No progress
  59 }
  60 
  61 const RegMask &IfNode::out_RegMask() const {
  62   return RegMask::Empty;
  63 }
  64 
  65 //------------------------------split_if---------------------------------------
  66 // Look for places where we merge constants, then test on the merged value.
  67 // If the IF test will be constant folded on the path with the constant, we
  68 // win by splitting the IF to before the merge point.
  69 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  70   // I could be a lot more general here, but I'm trying to squeeze this
  71   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  72   // on the patterns I accept.  CNC
  73 
  74   // Look for a compare of a constant and a merged value
  75   Node *i1 = iff->in(1);
  76   if( !i1->is_Bool() ) return NULL;
  77   BoolNode *b = i1->as_Bool();
  78   Node *cmp = b->in(1);
  79   if( !cmp->is_Cmp() ) return NULL;
  80   i1 = cmp->in(1);
  81   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  82   PhiNode *phi = i1->as_Phi();
  83   if( phi->is_copy() ) return NULL;
  84   Node *con2 = cmp->in(2);
  85   if( !con2->is_Con() ) return NULL;
  86   // See that the merge point contains some constants
  87   Node *con1=NULL;
  88   uint i4;
  89   for( i4 = 1; i4 < phi->req(); i4++ ) {
  90     con1 = phi->in(i4);
  91     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
  92     if( con1->is_Con() ) break; // Found a constant
  93     // Also allow null-vs-not-null checks
  94     const TypePtr *tp = igvn->type(con1)->isa_ptr();
  95     if( tp && tp->_ptr == TypePtr::NotNull )
  96       break;
  97   }
  98   if( i4 >= phi->req() ) return NULL; // Found no constants
  99 
 100   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 101 
 102   // Make sure that the compare can be constant folded away
 103   Node *cmp2 = cmp->clone();
 104   cmp2->set_req(1,con1);
 105   cmp2->set_req(2,con2);
 106   const Type *t = cmp2->Value(igvn);
 107   // This compare is dead, so whack it!
 108   igvn->remove_dead_node(cmp2);
 109   if( !t->singleton() ) return NULL;
 110 
 111   // No intervening control, like a simple Call
 112   Node *r = iff->in(0);
 113   if( !r->is_Region() ) return NULL;
 114   if( phi->region() != r ) return NULL;
 115   // No other users of the cmp/bool
 116   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 117     //tty->print_cr("many users of cmp/bool");
 118     return NULL;
 119   }
 120 
 121   // Make sure we can determine where all the uses of merged values go
 122   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 123     Node* u = r->fast_out(j);
 124     if( u == r ) continue;
 125     if( u == iff ) continue;
 126     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 127     if( !u->is_Phi() ) {
 128       /*
 129       if( u->is_Start() ) {
 130         tty->print_cr("Region has inlined start use");
 131       } else {
 132         tty->print_cr("Region has odd use");
 133         u->dump(2);
 134       }*/
 135       return NULL;
 136     }
 137     if( u != phi ) {
 138       // CNC - do not allow any other merged value
 139       //tty->print_cr("Merging another value");
 140       //u->dump(2);
 141       return NULL;
 142     }
 143     // Make sure we can account for all Phi uses
 144     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 145       Node* v = u->fast_out(k); // User of the phi
 146       // CNC - Allow only really simple patterns.
 147       // In particular I disallow AddP of the Phi, a fairly common pattern
 148       if( v == cmp ) continue;  // The compare is OK
 149       if( (v->is_ConstraintCast()) &&
 150           v->in(0)->in(0) == iff )
 151         continue;               // CastPP/II of the IfNode is OK
 152       // Disabled following code because I cannot tell if exactly one
 153       // path dominates without a real dominator check. CNC 9/9/1999
 154       //uint vop = v->Opcode();
 155       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 156       //  Node *r = v->in(0);     // Get controlling point
 157       //  if( !r ) return NULL;   // Degraded to a copy
 158       //  // Find exactly one path in (either True or False doms, but not IFF)
 159       //  int cnt = 0;
 160       //  for( uint i = 1; i < r->req(); i++ )
 161       //    if( r->in(i) && r->in(i)->in(0) == iff )
 162       //      cnt++;
 163       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 164       //}
 165       if( !v->is_Call() ) {
 166         /*
 167         if( v->Opcode() == Op_AddP ) {
 168           tty->print_cr("Phi has AddP use");
 169         } else if( v->Opcode() == Op_CastPP ) {
 170           tty->print_cr("Phi has CastPP use");
 171         } else if( v->Opcode() == Op_CastII ) {
 172           tty->print_cr("Phi has CastII use");
 173         } else {
 174           tty->print_cr("Phi has use I cant be bothered with");
 175         }
 176         */
 177       }
 178       return NULL;
 179 
 180       /* CNC - Cut out all the fancy acceptance tests
 181       // Can we clone this use when doing the transformation?
 182       // If all uses are from Phis at this merge or constants, then YES.
 183       if( !v->in(0) && v != cmp ) {
 184         tty->print_cr("Phi has free-floating use");
 185         v->dump(2);
 186         return NULL;
 187       }
 188       for( uint l = 1; l < v->req(); l++ ) {
 189         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 190             !v->in(l)->is_Con() ) {
 191           tty->print_cr("Phi has use");
 192           v->dump(2);
 193           return NULL;
 194         } // End of if Phi-use input is neither Phi nor Constant
 195       } // End of for all inputs to Phi-use
 196       */
 197     } // End of for all uses of Phi
 198   } // End of for all uses of Region
 199 
 200   // Only do this if the IF node is in a sane state
 201   if (iff->outcnt() != 2)
 202     return NULL;
 203 
 204   // Got a hit!  Do the Mondo Hack!
 205   //
 206   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 207   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 208   //     cmp - 2                         cmp - 2               cmp - 2
 209   //       bool                            bool_c                bool_x
 210   //       if                               if_c                  if_x
 211   //      T  F                              T  F                  T  F
 212   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 213   //
 214   // Split the paths coming into the merge point into 2 separate groups of
 215   // merges.  On the left will be all the paths feeding constants into the
 216   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 217   // will fold up into a constant; this will let the Cmp fold up as well as
 218   // all the control flow.  Below the original IF we have 2 control
 219   // dependent regions, 's' and 't'.  Now we will merge the two paths
 220   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 221   // likely 2 or more) will promptly constant fold away.
 222   PhaseGVN *phase = igvn;
 223 
 224   // Make a region merging constants and a region merging the rest
 225   uint req_c = 0;
 226   Node* predicate_proj = NULL;
 227   for (uint ii = 1; ii < r->req(); ii++) {
 228     if (phi->in(ii) == con1) {
 229       req_c++;
 230     }
 231     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
 232     if (proj != NULL) {
 233       assert(predicate_proj == NULL, "only one predicate entry expected");
 234       predicate_proj = proj;
 235     }
 236   }
 237   Node* predicate_c = NULL;
 238   Node* predicate_x = NULL;
 239   bool counted_loop = r->is_CountedLoop();
 240 
 241   Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1);
 242   Node *phi_c    = con1;
 243   uint  len      = r->req();
 244   Node *region_x = new (igvn->C, len - req_c) RegionNode(len - req_c);
 245   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 246   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 247     if (phi->in(i) == con1) {
 248       region_c->init_req( i_c++, r  ->in(i) );
 249       if (r->in(i) == predicate_proj)
 250         predicate_c = predicate_proj;
 251     } else {
 252       region_x->init_req( i_x,   r  ->in(i) );
 253       phi_x   ->init_req( i_x++, phi->in(i) );
 254       if (r->in(i) == predicate_proj)
 255         predicate_x = predicate_proj;
 256     }
 257   }
 258 
 259   // Register the new RegionNodes but do not transform them.  Cannot
 260   // transform until the entire Region/Phi conglomerate has been hacked
 261   // as a single huge transform.
 262   igvn->register_new_node_with_optimizer( region_c );
 263   igvn->register_new_node_with_optimizer( region_x );
 264   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 265   // about to get one.  If this only use goes away, then phi_x will look dead.
 266   // However, he will be picking up some more uses down below.
 267   Node *hook = new (igvn->C, 4) Node(4);
 268   hook->init_req(0, phi_x);
 269   hook->init_req(1, phi_c);
 270   phi_x = phase->transform( phi_x );
 271 
 272   // Make the compare
 273   Node *cmp_c = phase->makecon(t);
 274   Node *cmp_x = cmp->clone();
 275   cmp_x->set_req(1,phi_x);
 276   cmp_x->set_req(2,con2);
 277   cmp_x = phase->transform(cmp_x);
 278   // Make the bool
 279   Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test));
 280   Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test));
 281   // Make the IfNode
 282   IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
 283   igvn->set_type_bottom(iff_c);
 284   igvn->_worklist.push(iff_c);
 285   hook->init_req(2, iff_c);
 286 
 287   IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
 288   igvn->set_type_bottom(iff_x);
 289   igvn->_worklist.push(iff_x);
 290   hook->init_req(3, iff_x);
 291 
 292   // Make the true/false arms
 293   Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c));
 294   Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c));
 295   if (predicate_c != NULL) {
 296     assert(predicate_x == NULL, "only one predicate entry expected");
 297     // Clone loop predicates to each path
 298     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
 299     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
 300   }
 301   Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x));
 302   Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x));
 303   if (predicate_x != NULL) {
 304     assert(predicate_c == NULL, "only one predicate entry expected");
 305     // Clone loop predicates to each path
 306     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
 307     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
 308   }
 309 
 310   // Merge the TRUE paths
 311   Node *region_s = new (igvn->C, 3) RegionNode(3);
 312   igvn->_worklist.push(region_s);
 313   region_s->init_req(1, iff_c_t);
 314   region_s->init_req(2, iff_x_t);
 315   igvn->register_new_node_with_optimizer( region_s );
 316 
 317   // Merge the FALSE paths
 318   Node *region_f = new (igvn->C, 3) RegionNode(3);
 319   igvn->_worklist.push(region_f);
 320   region_f->init_req(1, iff_c_f);
 321   region_f->init_req(2, iff_x_f);
 322   igvn->register_new_node_with_optimizer( region_f );
 323 
 324   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 325   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 326   cmp->set_req(2,NULL);
 327   // Check for all uses of the Phi and give them a new home.
 328   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 329   Node *phi_s = NULL;     // do not construct unless needed
 330   Node *phi_f = NULL;     // do not construct unless needed
 331   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 332     Node* v = phi->last_out(i2);// User of the phi
 333     igvn->hash_delete(v);       // Have to fixup other Phi users
 334     igvn->_worklist.push(v);
 335     uint vop = v->Opcode();
 336     Node *proj = NULL;
 337     if( vop == Op_Phi ) {       // Remote merge point
 338       Node *r = v->in(0);
 339       for (uint i3 = 1; i3 < r->req(); i3++)
 340         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 341           proj = r->in(i3);
 342           break;
 343         }
 344     } else if( v->is_ConstraintCast() ) {
 345       proj = v->in(0);          // Controlling projection
 346     } else {
 347       assert( 0, "do not know how to handle this guy" );
 348     }
 349 
 350     Node *proj_path_data, *proj_path_ctrl;
 351     if( proj->Opcode() == Op_IfTrue ) {
 352       if( phi_s == NULL ) {
 353         // Only construct phi_s if needed, otherwise provides
 354         // interfering use.
 355         phi_s = PhiNode::make_blank(region_s,phi);
 356         phi_s->init_req( 1, phi_c );
 357         phi_s->init_req( 2, phi_x );
 358         hook->add_req(phi_s);
 359         phi_s = phase->transform(phi_s);
 360       }
 361       proj_path_data = phi_s;
 362       proj_path_ctrl = region_s;
 363     } else {
 364       if( phi_f == NULL ) {
 365         // Only construct phi_f if needed, otherwise provides
 366         // interfering use.
 367         phi_f = PhiNode::make_blank(region_f,phi);
 368         phi_f->init_req( 1, phi_c );
 369         phi_f->init_req( 2, phi_x );
 370         hook->add_req(phi_f);
 371         phi_f = phase->transform(phi_f);
 372       }
 373       proj_path_data = phi_f;
 374       proj_path_ctrl = region_f;
 375     }
 376 
 377     // Fixup 'v' for for the split
 378     if( vop == Op_Phi ) {       // Remote merge point
 379       uint i;
 380       for( i = 1; i < v->req(); i++ )
 381         if( v->in(i) == phi )
 382           break;
 383       v->set_req(i, proj_path_data );
 384     } else if( v->is_ConstraintCast() ) {
 385       v->set_req(0, proj_path_ctrl );
 386       v->set_req(1, proj_path_data );
 387     } else
 388       ShouldNotReachHere();
 389   }
 390 
 391   // Now replace the original iff's True/False with region_s/region_t.
 392   // This makes the original iff go dead.
 393   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 394     Node* p = iff->last_out(i3);
 395     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 396     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 397     // Replace p with u
 398     igvn->add_users_to_worklist(p);
 399     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 400       Node* x = p->last_out(l);
 401       igvn->hash_delete(x);
 402       uint uses_found = 0;
 403       for( uint j = 0; j < x->req(); j++ ) {
 404         if( x->in(j) == p ) {
 405           x->set_req(j, u);
 406           uses_found++;
 407         }
 408       }
 409       l -= uses_found;    // we deleted 1 or more copies of this edge
 410     }
 411     igvn->remove_dead_node(p);
 412   }
 413 
 414   // Force the original merge dead
 415   igvn->hash_delete(r);
 416   // First, remove region's dead users.
 417   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 418     Node* u = r->last_out(l);
 419     if( u == r ) {
 420       r->set_req(0, NULL);
 421     } else {
 422       assert(u->outcnt() == 0, "only dead users");
 423       igvn->remove_dead_node(u);
 424     }
 425     l -= 1;
 426   }
 427   igvn->remove_dead_node(r);
 428 
 429   // Now remove the bogus extra edges used to keep things alive
 430   igvn->remove_dead_node( hook );
 431 
 432   // Must return either the original node (now dead) or a new node
 433   // (Do not return a top here, since that would break the uniqueness of top.)
 434   return new (igvn->C, 1) ConINode(TypeInt::ZERO);
 435 }
 436 
 437 //------------------------------is_range_check---------------------------------
 438 // Return 0 if not a range check.  Return 1 if a range check and set index and
 439 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 440 // is versus a constant.
 441 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 442   Node* b = in(1);
 443   if (b == NULL || !b->is_Bool())  return 0;
 444   BoolNode* bn = b->as_Bool();
 445   Node* cmp = bn->in(1);
 446   if (cmp == NULL)  return 0;
 447   if (cmp->Opcode() != Op_CmpU)  return 0;
 448 
 449   Node* l = cmp->in(1);
 450   Node* r = cmp->in(2);
 451   int flip_test = 1;
 452   if (bn->_test._test == BoolTest::le) {
 453     l = cmp->in(2);
 454     r = cmp->in(1);
 455     flip_test = 2;
 456   } else if (bn->_test._test != BoolTest::lt) {
 457     return 0;
 458   }
 459   if (l->is_top())  return 0;   // Top input means dead test
 460   if (r->Opcode() != Op_LoadRange)  return 0;
 461 
 462   // We have recognized one of these forms:
 463   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 464   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 465 
 466   // Make sure it's a real range check by requiring an uncommon trap
 467   // along the OOB path.  Otherwise, it's possible that the user wrote
 468   // something which optimized to look like a range check but behaves
 469   // in some other way.
 470   Node* iftrap = proj_out(flip_test == 2 ? true : false);
 471   bool found_trap = false;
 472   if (iftrap != NULL) {
 473     Node* u = iftrap->unique_ctrl_out();
 474     if (u != NULL) {
 475       // It could be a merge point (Region) for uncommon trap.
 476       if (u->is_Region()) {
 477         Node* c = u->unique_ctrl_out();
 478         if (c != NULL) {
 479           iftrap = u;
 480           u = c;
 481         }
 482       }
 483       if (u->in(0) == iftrap && u->is_CallStaticJava()) {
 484         int req = u->as_CallStaticJava()->uncommon_trap_request();
 485         if (Deoptimization::trap_request_reason(req) ==
 486             Deoptimization::Reason_range_check) {
 487           found_trap = true;
 488         }
 489       }
 490     }
 491   }
 492   if (!found_trap)  return 0;   // sorry, no cigar
 493 
 494   // Look for index+offset form
 495   Node* ind = l;
 496   jint  off = 0;
 497   if (l->is_top()) {
 498     return 0;
 499   } else if (l->is_Add()) {
 500     if ((off = l->in(1)->find_int_con(0)) != 0) {
 501       ind = l->in(2);
 502     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 503       ind = l->in(1);
 504     }
 505   } else if ((off = l->find_int_con(-1)) >= 0) {
 506     // constant offset with no variable index
 507     ind = NULL;
 508   } else {
 509     // variable index with no constant offset (or dead negative index)
 510     off = 0;
 511   }
 512 
 513   // Return all the values:
 514   index  = ind;
 515   offset = off;
 516   range  = r;
 517   return flip_test;
 518 }
 519 
 520 //------------------------------adjust_check-----------------------------------
 521 // Adjust (widen) a prior range check
 522 static void adjust_check(Node* proj, Node* range, Node* index,
 523                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 524   PhaseGVN *gvn = igvn;
 525   // Break apart the old check
 526   Node *iff = proj->in(0);
 527   Node *bol = iff->in(1);
 528   if( bol->is_top() ) return;   // In case a partially dead range check appears
 529   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 530   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 531   if( !bol->is_Bool() ) return;
 532 
 533   Node *cmp = bol->in(1);
 534   // Compute a new check
 535   Node *new_add = gvn->intcon(off_lo);
 536   if( index ) {
 537     new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index;
 538   }
 539   Node *new_cmp = (flip == 1)
 540     ? new (gvn->C, 3) CmpUNode( new_add, range )
 541     : new (gvn->C, 3) CmpUNode( range, new_add );
 542   new_cmp = gvn->transform(new_cmp);
 543   // See if no need to adjust the existing check
 544   if( new_cmp == cmp ) return;
 545   // Else, adjust existing check
 546   Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 547   igvn->hash_delete( iff );
 548   iff->set_req_X( 1, new_bol, igvn );
 549 }
 550 
 551 //------------------------------up_one_dom-------------------------------------
 552 // Walk up the dominator tree one step.  Return NULL at root or true
 553 // complex merges.  Skips through small diamonds.
 554 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 555   Node *dom = curr->in(0);
 556   if( !dom )                    // Found a Region degraded to a copy?
 557     return curr->nonnull_req(); // Skip thru it
 558 
 559   if( curr != dom )             // Normal walk up one step?
 560     return dom;
 561 
 562   // Use linear_only if we are still parsing, since we cannot
 563   // trust the regions to be fully filled in.
 564   if (linear_only)
 565     return NULL;
 566 
 567   if( dom->is_Root() )
 568     return NULL;
 569 
 570   // Else hit a Region.  Check for a loop header
 571   if( dom->is_Loop() )
 572     return dom->in(1);          // Skip up thru loops
 573 
 574   // Check for small diamonds
 575   Node *din1, *din2, *din3, *din4;
 576   if( dom->req() == 3 &&        // 2-path merge point
 577       (din1 = dom ->in(1)) &&   // Left  path exists
 578       (din2 = dom ->in(2)) &&   // Right path exists
 579       (din3 = din1->in(0)) &&   // Left  path up one
 580       (din4 = din2->in(0)) ) {  // Right path up one
 581     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 582         (din3 = din3->in(0)) )
 583       din3 = din3->in(0);
 584     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 585         (din4 = din4->in(0)) )
 586       din4 = din4->in(0);
 587     if( din3 == din4 && din3->is_If() )
 588       return din3;              // Skip around diamonds
 589   }
 590 
 591   // Give up the search at true merges
 592   return NULL;                  // Dead loop?  Or hit root?
 593 }
 594 
 595 
 596 //------------------------------filtered_int_type--------------------------------
 597 // Return a possibly more restrictive type for val based on condition control flow for an if
 598 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 599   assert(if_proj &&
 600          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 601   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 602     IfNode* iff = if_proj->in(0)->as_If();
 603     if (iff->in(1) && iff->in(1)->is_Bool()) {
 604       BoolNode* bol = iff->in(1)->as_Bool();
 605       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 606         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 607         if (cmp->in(1) == val) {
 608           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 609           if (cmp2_t != NULL) {
 610             jint lo = cmp2_t->_lo;
 611             jint hi = cmp2_t->_hi;
 612             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 613             switch (msk) {
 614             case BoolTest::ne:
 615               // Can't refine type
 616               return NULL;
 617             case BoolTest::eq:
 618               return cmp2_t;
 619             case BoolTest::lt:
 620               lo = TypeInt::INT->_lo;
 621               if (hi - 1 < hi) {
 622                 hi = hi - 1;
 623               }
 624               break;
 625             case BoolTest::le:
 626               lo = TypeInt::INT->_lo;
 627               break;
 628             case BoolTest::gt:
 629               if (lo + 1 > lo) {
 630                 lo = lo + 1;
 631               }
 632               hi = TypeInt::INT->_hi;
 633               break;
 634             case BoolTest::ge:
 635               // lo unchanged
 636               hi = TypeInt::INT->_hi;
 637               break;
 638             }
 639             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 640             return rtn_t;
 641           }
 642         }
 643       }
 644     }
 645   }
 646   return NULL;
 647 }
 648 
 649 //------------------------------fold_compares----------------------------
 650 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 651 // the direction of this if is determined by the preceding if so it
 652 // can be eliminate entirely.  Given an if testing (CmpI n c) check
 653 // for an immediately control dependent if that is testing (CmpI n c2)
 654 // and has one projection leading to this if and the other projection
 655 // leading to a region that merges one of this ifs control
 656 // projections.
 657 //
 658 //                   If
 659 //                  / |
 660 //                 /  |
 661 //                /   |
 662 //              If    |
 663 //              /\    |
 664 //             /  \   |
 665 //            /    \  |
 666 //           /    Region
 667 //
 668 Node* IfNode::fold_compares(PhaseGVN* phase) {
 669   if (!EliminateAutoBox || Opcode() != Op_If) return NULL;
 670 
 671   Node* this_cmp = in(1)->in(1);
 672   if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
 673       this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
 674     Node* ctrl = in(0);
 675     BoolNode* this_bool = in(1)->as_Bool();
 676     Node* n = this_cmp->in(1);
 677     int hi = this_cmp->in(2)->get_int();
 678     if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
 679         ctrl->in(0)->is_If() &&
 680         ctrl->in(0)->outcnt() == 2 &&
 681         ctrl->in(0)->in(1)->is_Bool() &&
 682         ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
 683         ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
 684         ctrl->in(0)->in(1)->in(1)->in(1) == n) {
 685       IfNode* dom_iff = ctrl->in(0)->as_If();
 686       Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
 687       if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
 688           this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
 689         // Identify which proj goes to the region and which continues on
 690         RegionNode* region = otherproj->unique_out()->as_Region();
 691         Node* success = NULL;
 692         Node* fail = NULL;
 693         for (int i = 0; i < 2; i++) {
 694           Node* proj = proj_out(i);
 695           if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 696             success = proj;
 697           } else if (fail == NULL) {
 698             fail = proj;
 699           } else {
 700             success = fail = NULL;
 701           }
 702         }
 703         if (success != NULL && fail != NULL && !region->has_phi()) {
 704           int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
 705           BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 706           Node* dom_cmp =  dom_bool->in(1);
 707           const TypeInt* failtype  = filtered_int_type(phase, n, ctrl);
 708           if (failtype != NULL) {
 709             const TypeInt* type2 = filtered_int_type(phase, n, fail);
 710             if (type2 != NULL) {
 711               failtype = failtype->join(type2)->is_int();
 712             } else {
 713               failtype = NULL;
 714             }
 715           }
 716 
 717           if (failtype != NULL &&
 718               dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
 719             int bound = failtype->_hi - failtype->_lo + 1;
 720             if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
 721               // Merge the two compares into a single unsigned compare by building  (CmpU (n - lo) hi)
 722               BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
 723               Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo)));
 724               Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound)));
 725               Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond));
 726               phase->hash_delete(dom_iff);
 727               dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con));
 728               phase->is_IterGVN()->_worklist.push(dom_iff);
 729               phase->hash_delete(this);
 730               set_req(1, newbool);
 731               return this;
 732             }
 733             if (failtype->_lo > failtype->_hi) {
 734               // previous if determines the result of this if so
 735               // replace Bool with constant
 736               phase->hash_delete(this);
 737               set_req(1, phase->intcon(success->as_Proj()->_con));
 738               return this;
 739             }
 740           }
 741         }
 742       }
 743     }
 744   }
 745   return NULL;
 746 }
 747 
 748 //------------------------------remove_useless_bool----------------------------
 749 // Check for people making a useless boolean: things like
 750 // if( (x < y ? true : false) ) { ... }
 751 // Replace with if( x < y ) { ... }
 752 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
 753   Node *i1 = iff->in(1);
 754   if( !i1->is_Bool() ) return NULL;
 755   BoolNode *bol = i1->as_Bool();
 756 
 757   Node *cmp = bol->in(1);
 758   if( cmp->Opcode() != Op_CmpI ) return NULL;
 759 
 760   // Must be comparing against a bool
 761   const Type *cmp2_t = phase->type( cmp->in(2) );
 762   if( cmp2_t != TypeInt::ZERO &&
 763       cmp2_t != TypeInt::ONE )
 764     return NULL;
 765 
 766   // Find a prior merge point merging the boolean
 767   i1 = cmp->in(1);
 768   if( !i1->is_Phi() ) return NULL;
 769   PhiNode *phi = i1->as_Phi();
 770   if( phase->type( phi ) != TypeInt::BOOL )
 771     return NULL;
 772 
 773   // Check for diamond pattern
 774   int true_path = phi->is_diamond_phi();
 775   if( true_path == 0 ) return NULL;
 776 
 777   // Make sure that iff and the control of the phi are different. This
 778   // should really only happen for dead control flow since it requires
 779   // an illegal cycle.
 780   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
 781 
 782   // phi->region->if_proj->ifnode->bool->cmp
 783   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
 784 
 785   // Now get the 'sense' of the test correct so we can plug in
 786   // either iff2->in(1) or its complement.
 787   int flip = 0;
 788   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
 789   else if( bol->_test._test != BoolTest::eq ) return NULL;
 790   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
 791 
 792   const Type *phi1_t = phase->type( phi->in(1) );
 793   const Type *phi2_t = phase->type( phi->in(2) );
 794   // Check for Phi(0,1) and flip
 795   if( phi1_t == TypeInt::ZERO ) {
 796     if( phi2_t != TypeInt::ONE ) return NULL;
 797     flip = 1-flip;
 798   } else {
 799     // Check for Phi(1,0)
 800     if( phi1_t != TypeInt::ONE  ) return NULL;
 801     if( phi2_t != TypeInt::ZERO ) return NULL;
 802   }
 803   if( true_path == 2 ) {
 804     flip = 1-flip;
 805   }
 806 
 807   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
 808   assert(new_bol != iff->in(1), "must make progress");
 809   iff->set_req(1, new_bol);
 810   // Intervening diamond probably goes dead
 811   phase->C->set_major_progress();
 812   return iff;
 813 }
 814 
 815 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
 816 
 817 //------------------------------Ideal------------------------------------------
 818 // Return a node which is more "ideal" than the current node.  Strip out
 819 // control copies
 820 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 821   if (remove_dead_region(phase, can_reshape))  return this;
 822   // No Def-Use info?
 823   if (!can_reshape)  return NULL;
 824   PhaseIterGVN *igvn = phase->is_IterGVN();
 825 
 826   // Don't bother trying to transform a dead if
 827   if (in(0)->is_top())  return NULL;
 828   // Don't bother trying to transform an if with a dead test
 829   if (in(1)->is_top())  return NULL;
 830   // Another variation of a dead test
 831   if (in(1)->is_Con())  return NULL;
 832   // Another variation of a dead if
 833   if (outcnt() < 2)  return NULL;
 834 
 835   // Canonicalize the test.
 836   Node* idt_if = idealize_test(phase, this);
 837   if (idt_if != NULL)  return idt_if;
 838 
 839   // Try to split the IF
 840   Node *s = split_if(this, igvn);
 841   if (s != NULL)  return s;
 842 
 843   // Check for people making a useless boolean: things like
 844   // if( (x < y ? true : false) ) { ... }
 845   // Replace with if( x < y ) { ... }
 846   Node *bol2 = remove_useless_bool(this, phase);
 847   if( bol2 ) return bol2;
 848 
 849   // Setup to scan up the CFG looking for a dominating test
 850   Node *dom = in(0);
 851   Node *prev_dom = this;
 852 
 853   // Check for range-check vs other kinds of tests
 854   Node *index1, *range1;
 855   jint offset1;
 856   int flip1 = is_range_check(range1, index1, offset1);
 857   if( flip1 ) {
 858     Node *first_prev_dom = NULL;
 859 
 860     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
 861     // so all checks we inspect post-dominate the top-most check we find.
 862     // If we are going to fail the current check and we reach the top check
 863     // then we are guaranteed to fail, so just start interpreting there.
 864     // We 'expand' the top 2 range checks to include all post-dominating
 865     // checks.
 866 
 867     // The top 2 range checks seen
 868     Node *prev_chk1 = NULL;
 869     Node *prev_chk2 = NULL;
 870     // Low and high offsets seen so far
 871     jint off_lo = offset1;
 872     jint off_hi = offset1;
 873 
 874     // Scan for the top 2 checks and collect range of offsets
 875     for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
 876       if( dom->Opcode() == Op_If &&  // Not same opcode?
 877           prev_dom->in(0) == dom ) { // One path of test does dominate?
 878         if( dom == this ) return NULL; // dead loop
 879         // See if this is a range check
 880         Node *index2, *range2;
 881         jint offset2;
 882         int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
 883         // See if this is a _matching_ range check, checking against
 884         // the same array bounds.
 885         if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
 886             dom->outcnt() == 2 ) {
 887           // Gather expanded bounds
 888           off_lo = MIN2(off_lo,offset2);
 889           off_hi = MAX2(off_hi,offset2);
 890           // Record top 2 range checks
 891           prev_chk2 = prev_chk1;
 892           prev_chk1 = prev_dom;
 893           // If we match the test exactly, then the top test covers
 894           // both our lower and upper bounds.
 895           if( dom->in(1) == in(1) )
 896             prev_chk2 = prev_chk1;
 897         }
 898       }
 899       prev_dom = dom;
 900       dom = up_one_dom( dom );
 901       if( !dom ) break;
 902     }
 903 
 904 
 905     // Attempt to widen the dominating range check to cover some later
 906     // ones.  Since range checks "fail" by uncommon-trapping to the
 907     // interpreter, widening a check can make us speculative enter the
 908     // interpreter.  If we see range-check deopt's, do not widen!
 909     if (!phase->C->allow_range_check_smearing())  return NULL;
 910 
 911     // Constant indices only need to check the upper bound.
 912     // Non-constance indices must check both low and high.
 913     if( index1 ) {
 914       // Didn't find 2 prior covering checks, so cannot remove anything.
 915       if( !prev_chk2 ) return NULL;
 916       // 'Widen' the offsets of the 1st and 2nd covering check
 917       adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
 918       // Do not call adjust_check twice on the same projection
 919       // as the first call may have transformed the BoolNode to a ConI
 920       if( prev_chk1 != prev_chk2 ) {
 921         adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
 922       }
 923       // Test is now covered by prior checks, dominate it out
 924       prev_dom = prev_chk2;
 925     } else {
 926       // Didn't find prior covering check, so cannot remove anything.
 927       if( !prev_chk1 ) return NULL;
 928       // 'Widen' the offset of the 1st and only covering check
 929       adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
 930       // Test is now covered by prior checks, dominate it out
 931       prev_dom = prev_chk1;
 932     }
 933 
 934 
 935   } else {                      // Scan for an equivalent test
 936 
 937     Node *cmp;
 938     int dist = 0;               // Cutoff limit for search
 939     int op = Opcode();
 940     if( op == Op_If &&
 941         (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
 942       if( cmp->in(2) != NULL && // make sure cmp is not already dead
 943           cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
 944         dist = 64;              // Limit for null-pointer scans
 945       } else {
 946         dist = 4;               // Do not bother for random pointer tests
 947       }
 948     } else {
 949       dist = 4;                 // Limit for random junky scans
 950     }
 951 
 952     // Normal equivalent-test check.
 953     if( !dom ) return NULL;     // Dead loop?
 954 
 955     Node* result = fold_compares(phase);
 956     if (result != NULL) {
 957       return result;
 958     }
 959 
 960     // Search up the dominator tree for an If with an identical test
 961     while( dom->Opcode() != op    ||  // Not same opcode?
 962            dom->in(1)    != in(1) ||  // Not same input 1?
 963            (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
 964            prev_dom->in(0) != dom ) { // One path of test does not dominate?
 965       if( dist < 0 ) return NULL;
 966 
 967       dist--;
 968       prev_dom = dom;
 969       dom = up_one_dom( dom );
 970       if( !dom ) return NULL;
 971     }
 972 
 973     // Check that we did not follow a loop back to ourselves
 974     if( this == dom )
 975       return NULL;
 976 
 977     if( dist > 2 )              // Add to count of NULL checks elided
 978       explicit_null_checks_elided++;
 979 
 980   } // End of Else scan for an equivalent test
 981 
 982   // Hit!  Remove this IF
 983 #ifndef PRODUCT
 984   if( TraceIterativeGVN ) {
 985     tty->print("   Removing IfNode: "); this->dump();
 986   }
 987   if( VerifyOpto && !phase->allow_progress() ) {
 988     // Found an equivalent dominating test,
 989     // we can not guarantee reaching a fix-point for these during iterativeGVN
 990     // since intervening nodes may not change.
 991     return NULL;
 992   }
 993 #endif
 994 
 995   // Replace dominated IfNode
 996   dominated_by( prev_dom, igvn );
 997 
 998   // Must return either the original node (now dead) or a new node
 999   // (Do not return a top here, since that would break the uniqueness of top.)
1000   return new (phase->C, 1) ConINode(TypeInt::ZERO);
1001 }
1002 
1003 //------------------------------dominated_by-----------------------------------
1004 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1005   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1006   Node *idom = in(0);
1007   // Need opcode to decide which way 'this' test goes
1008   int prev_op = prev_dom->Opcode();
1009   Node *top = igvn->C->top(); // Shortcut to top
1010 
1011   // Now walk the current IfNode's projections.
1012   // Loop ends when 'this' has no more uses.
1013   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1014     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1015     igvn->add_users_to_worklist(ifp);
1016     // Check which projection it is and set target.
1017     // Data-target is either the dominating projection of the same type
1018     // or TOP if the dominating projection is of opposite type.
1019     // Data-target will be used as the new control edge for the non-CFG
1020     // nodes like Casts and Loads.
1021     Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top;
1022     // Control-target is just the If's immediate dominator or TOP.
1023     Node *ctrl_target = (ifp->Opcode() == prev_op ) ?     idom : top;
1024 
1025     // For each child of an IfTrue/IfFalse projection, reroute.
1026     // Loop ends when projection has no more uses.
1027     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1028       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1029       igvn->hash_delete(s);         // Yank from hash table before edge hacking
1030       if( !s->depends_only_on_test() ) {
1031         // Find the control input matching this def-use edge.
1032         // For Regions it may not be in slot 0.
1033         uint l;
1034         for( l = 0; s->in(l) != ifp; l++ ) { }
1035         s->set_req(l, ctrl_target);
1036       } else {                      // Else, for control producers,
1037         s->set_req(0, data_target); // Move child to data-target
1038       }
1039       igvn->_worklist.push(s);  // Revisit collapsed Phis
1040     } // End for each child of a projection
1041 
1042     igvn->remove_dead_node(ifp);
1043   } // End for each IfTrue/IfFalse child of If
1044 
1045   // Kill the IfNode
1046   igvn->remove_dead_node(this);
1047 }
1048 
1049 //------------------------------Identity---------------------------------------
1050 // If the test is constant & we match, then we are the input Control
1051 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1052   // Can only optimize if cannot go the other way
1053   const TypeTuple *t = phase->type(in(0))->is_tuple();
1054   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1055     ? in(0)->in(0)              // IfNode control
1056     : this;                     // no progress
1057 }
1058 
1059 //------------------------------dump_spec--------------------------------------
1060 #ifndef PRODUCT
1061 void IfNode::dump_spec(outputStream *st) const {
1062   st->print("P=%f, C=%f",_prob,_fcnt);
1063 }
1064 #endif
1065 
1066 //------------------------------idealize_test----------------------------------
1067 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1068 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1069 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1070 // needed.
1071 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1072   assert(iff->in(0) != NULL, "If must be live");
1073 
1074   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1075   Node* old_if_f = iff->proj_out(false);
1076   Node* old_if_t = iff->proj_out(true);
1077 
1078   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1079   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1080   // happens in count-down loops
1081   if (iff->is_CountedLoopEnd())  return NULL;
1082   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1083   BoolNode *b = iff->in(1)->as_Bool();
1084   BoolTest bt = b->_test;
1085   // Test already in good order?
1086   if( bt.is_canonical() )
1087     return NULL;
1088 
1089   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1090   // cloning the IfNode.
1091   Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) );
1092   if( !new_b->is_Bool() ) return NULL;
1093   b = new_b->as_Bool();
1094 
1095   PhaseIterGVN *igvn = phase->is_IterGVN();
1096   assert( igvn, "Test is not canonical in parser?" );
1097 
1098   // The IF node never really changes, but it needs to be cloned
1099   iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1100 
1101   Node *prior = igvn->hash_find_insert(iff);
1102   if( prior ) {
1103     igvn->remove_dead_node(iff);
1104     iff = (IfNode*)prior;
1105   } else {
1106     // Cannot call transform on it just yet
1107     igvn->set_type_bottom(iff);
1108   }
1109   igvn->_worklist.push(iff);
1110 
1111   // Now handle projections.  Cloning not required.
1112   Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff ));
1113   Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff ));
1114 
1115   igvn->register_new_node_with_optimizer(new_if_f);
1116   igvn->register_new_node_with_optimizer(new_if_t);
1117   // Flip test, so flip trailing control
1118   igvn->replace_node(old_if_f, new_if_t);
1119   igvn->replace_node(old_if_t, new_if_f);
1120 
1121   // Progress
1122   return iff;
1123 }
1124 
1125 //------------------------------Identity---------------------------------------
1126 // If the test is constant & we match, then we are the input Control
1127 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1128   // Can only optimize if cannot go the other way
1129   const TypeTuple *t = phase->type(in(0))->is_tuple();
1130   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1131     ? in(0)->in(0)              // IfNode control
1132     : this;                     // no progress
1133 }