rev 5902 : 8027754: Enable loop optimizations for loops with MathExact inside

   1 /*
   2  * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
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  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_FlagsProj() ) return NULL;
  80   if( !cmp->is_Cmp() ) return NULL;
  81   i1 = cmp->in(1);
  82   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  83   PhiNode *phi = i1->as_Phi();
  84   if( phi->is_copy() ) return NULL;
  85   Node *con2 = cmp->in(2);
  86   if( !con2->is_Con() ) return NULL;
  87   // See that the merge point contains some constants
  88   Node *con1=NULL;
  89   uint i4;
  90   for( i4 = 1; i4 < phi->req(); i4++ ) {
  91     con1 = phi->in(i4);
  92     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
  93     if( con1->is_Con() ) break; // Found a constant
  94     // Also allow null-vs-not-null checks
  95     const TypePtr *tp = igvn->type(con1)->isa_ptr();
  96     if( tp && tp->_ptr == TypePtr::NotNull )
  97       break;
  98   }
  99   if( i4 >= phi->req() ) return NULL; // Found no constants
 100 
 101   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 102 
 103   // Make sure that the compare can be constant folded away
 104   Node *cmp2 = cmp->clone();
 105   cmp2->set_req(1,con1);
 106   cmp2->set_req(2,con2);
 107   const Type *t = cmp2->Value(igvn);
 108   // This compare is dead, so whack it!
 109   igvn->remove_dead_node(cmp2);
 110   if( !t->singleton() ) return NULL;
 111 
 112   // No intervening control, like a simple Call
 113   Node *r = iff->in(0);
 114   if( !r->is_Region() ) return NULL;
 115   if( phi->region() != r ) return NULL;
 116   // No other users of the cmp/bool
 117   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 118     //tty->print_cr("many users of cmp/bool");
 119     return NULL;
 120   }
 121 
 122   // Make sure we can determine where all the uses of merged values go
 123   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 124     Node* u = r->fast_out(j);
 125     if( u == r ) continue;
 126     if( u == iff ) continue;
 127     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 128     if( !u->is_Phi() ) {
 129       /*
 130       if( u->is_Start() ) {
 131         tty->print_cr("Region has inlined start use");
 132       } else {
 133         tty->print_cr("Region has odd use");
 134         u->dump(2);
 135       }*/
 136       return NULL;
 137     }
 138     if( u != phi ) {
 139       // CNC - do not allow any other merged value
 140       //tty->print_cr("Merging another value");
 141       //u->dump(2);
 142       return NULL;
 143     }
 144     // Make sure we can account for all Phi uses
 145     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 146       Node* v = u->fast_out(k); // User of the phi
 147       // CNC - Allow only really simple patterns.
 148       // In particular I disallow AddP of the Phi, a fairly common pattern
 149       if( v == cmp ) continue;  // The compare is OK
 150       if( (v->is_ConstraintCast()) &&
 151           v->in(0)->in(0) == iff )
 152         continue;               // CastPP/II of the IfNode is OK
 153       // Disabled following code because I cannot tell if exactly one
 154       // path dominates without a real dominator check. CNC 9/9/1999
 155       //uint vop = v->Opcode();
 156       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 157       //  Node *r = v->in(0);     // Get controlling point
 158       //  if( !r ) return NULL;   // Degraded to a copy
 159       //  // Find exactly one path in (either True or False doms, but not IFF)
 160       //  int cnt = 0;
 161       //  for( uint i = 1; i < r->req(); i++ )
 162       //    if( r->in(i) && r->in(i)->in(0) == iff )
 163       //      cnt++;
 164       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 165       //}
 166       if( !v->is_Call() ) {
 167         /*
 168         if( v->Opcode() == Op_AddP ) {
 169           tty->print_cr("Phi has AddP use");
 170         } else if( v->Opcode() == Op_CastPP ) {
 171           tty->print_cr("Phi has CastPP use");
 172         } else if( v->Opcode() == Op_CastII ) {
 173           tty->print_cr("Phi has CastII use");
 174         } else {
 175           tty->print_cr("Phi has use I cant be bothered with");
 176         }
 177         */
 178       }
 179       return NULL;
 180 
 181       /* CNC - Cut out all the fancy acceptance tests
 182       // Can we clone this use when doing the transformation?
 183       // If all uses are from Phis at this merge or constants, then YES.
 184       if( !v->in(0) && v != cmp ) {
 185         tty->print_cr("Phi has free-floating use");
 186         v->dump(2);
 187         return NULL;
 188       }
 189       for( uint l = 1; l < v->req(); l++ ) {
 190         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 191             !v->in(l)->is_Con() ) {
 192           tty->print_cr("Phi has use");
 193           v->dump(2);
 194           return NULL;
 195         } // End of if Phi-use input is neither Phi nor Constant
 196       } // End of for all inputs to Phi-use
 197       */
 198     } // End of for all uses of Phi
 199   } // End of for all uses of Region
 200 
 201   // Only do this if the IF node is in a sane state
 202   if (iff->outcnt() != 2)
 203     return NULL;
 204 
 205   // Got a hit!  Do the Mondo Hack!
 206   //
 207   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 208   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 209   //     cmp - 2                         cmp - 2               cmp - 2
 210   //       bool                            bool_c                bool_x
 211   //       if                               if_c                  if_x
 212   //      T  F                              T  F                  T  F
 213   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 214   //
 215   // Split the paths coming into the merge point into 2 separate groups of
 216   // merges.  On the left will be all the paths feeding constants into the
 217   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 218   // will fold up into a constant; this will let the Cmp fold up as well as
 219   // all the control flow.  Below the original IF we have 2 control
 220   // dependent regions, 's' and 't'.  Now we will merge the two paths
 221   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 222   // likely 2 or more) will promptly constant fold away.
 223   PhaseGVN *phase = igvn;
 224 
 225   // Make a region merging constants and a region merging the rest
 226   uint req_c = 0;
 227   Node* predicate_proj = NULL;
 228   for (uint ii = 1; ii < r->req(); ii++) {
 229     if (phi->in(ii) == con1) {
 230       req_c++;
 231     }
 232     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
 233     if (proj != NULL) {
 234       assert(predicate_proj == NULL, "only one predicate entry expected");
 235       predicate_proj = proj;
 236     }
 237   }
 238   Node* predicate_c = NULL;
 239   Node* predicate_x = NULL;
 240   bool counted_loop = r->is_CountedLoop();
 241 
 242   Node *region_c = new (igvn->C) RegionNode(req_c + 1);
 243   Node *phi_c    = con1;
 244   uint  len      = r->req();
 245   Node *region_x = new (igvn->C) RegionNode(len - req_c);
 246   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 247   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 248     if (phi->in(i) == con1) {
 249       region_c->init_req( i_c++, r  ->in(i) );
 250       if (r->in(i) == predicate_proj)
 251         predicate_c = predicate_proj;
 252     } else {
 253       region_x->init_req( i_x,   r  ->in(i) );
 254       phi_x   ->init_req( i_x++, phi->in(i) );
 255       if (r->in(i) == predicate_proj)
 256         predicate_x = predicate_proj;
 257     }
 258   }
 259   if (predicate_c != NULL && (req_c > 1)) {
 260     assert(predicate_x == NULL, "only one predicate entry expected");
 261     predicate_c = NULL; // Do not clone predicate below merge point
 262   }
 263   if (predicate_x != NULL && ((len - req_c) > 2)) {
 264     assert(predicate_c == NULL, "only one predicate entry expected");
 265     predicate_x = NULL; // Do not clone predicate below merge point
 266   }
 267 
 268   // Register the new RegionNodes but do not transform them.  Cannot
 269   // transform until the entire Region/Phi conglomerate has been hacked
 270   // as a single huge transform.
 271   igvn->register_new_node_with_optimizer( region_c );
 272   igvn->register_new_node_with_optimizer( region_x );
 273   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 274   // about to get one.  If this only use goes away, then phi_x will look dead.
 275   // However, he will be picking up some more uses down below.
 276   Node *hook = new (igvn->C) Node(4);
 277   hook->init_req(0, phi_x);
 278   hook->init_req(1, phi_c);
 279   phi_x = phase->transform( phi_x );
 280 
 281   // Make the compare
 282   Node *cmp_c = phase->makecon(t);
 283   Node *cmp_x = cmp->clone();
 284   cmp_x->set_req(1,phi_x);
 285   cmp_x->set_req(2,con2);
 286   cmp_x = phase->transform(cmp_x);
 287   // Make the bool
 288   Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test));
 289   Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test));
 290   // Make the IfNode
 291   IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
 292   igvn->set_type_bottom(iff_c);
 293   igvn->_worklist.push(iff_c);
 294   hook->init_req(2, iff_c);
 295 
 296   IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
 297   igvn->set_type_bottom(iff_x);
 298   igvn->_worklist.push(iff_x);
 299   hook->init_req(3, iff_x);
 300 
 301   // Make the true/false arms
 302   Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c));
 303   Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c));
 304   if (predicate_c != NULL) {
 305     assert(predicate_x == NULL, "only one predicate entry expected");
 306     // Clone loop predicates to each path
 307     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
 308     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
 309   }
 310   Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x));
 311   Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x));
 312   if (predicate_x != NULL) {
 313     assert(predicate_c == NULL, "only one predicate entry expected");
 314     // Clone loop predicates to each path
 315     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
 316     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
 317   }
 318 
 319   // Merge the TRUE paths
 320   Node *region_s = new (igvn->C) RegionNode(3);
 321   igvn->_worklist.push(region_s);
 322   region_s->init_req(1, iff_c_t);
 323   region_s->init_req(2, iff_x_t);
 324   igvn->register_new_node_with_optimizer( region_s );
 325 
 326   // Merge the FALSE paths
 327   Node *region_f = new (igvn->C) RegionNode(3);
 328   igvn->_worklist.push(region_f);
 329   region_f->init_req(1, iff_c_f);
 330   region_f->init_req(2, iff_x_f);
 331   igvn->register_new_node_with_optimizer( region_f );
 332 
 333   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 334   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 335   cmp->set_req(2,NULL);
 336   // Check for all uses of the Phi and give them a new home.
 337   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 338   Node *phi_s = NULL;     // do not construct unless needed
 339   Node *phi_f = NULL;     // do not construct unless needed
 340   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 341     Node* v = phi->last_out(i2);// User of the phi
 342     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
 343     uint vop = v->Opcode();
 344     Node *proj = NULL;
 345     if( vop == Op_Phi ) {       // Remote merge point
 346       Node *r = v->in(0);
 347       for (uint i3 = 1; i3 < r->req(); i3++)
 348         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 349           proj = r->in(i3);
 350           break;
 351         }
 352     } else if( v->is_ConstraintCast() ) {
 353       proj = v->in(0);          // Controlling projection
 354     } else {
 355       assert( 0, "do not know how to handle this guy" );
 356     }
 357 
 358     Node *proj_path_data, *proj_path_ctrl;
 359     if( proj->Opcode() == Op_IfTrue ) {
 360       if( phi_s == NULL ) {
 361         // Only construct phi_s if needed, otherwise provides
 362         // interfering use.
 363         phi_s = PhiNode::make_blank(region_s,phi);
 364         phi_s->init_req( 1, phi_c );
 365         phi_s->init_req( 2, phi_x );
 366         hook->add_req(phi_s);
 367         phi_s = phase->transform(phi_s);
 368       }
 369       proj_path_data = phi_s;
 370       proj_path_ctrl = region_s;
 371     } else {
 372       if( phi_f == NULL ) {
 373         // Only construct phi_f if needed, otherwise provides
 374         // interfering use.
 375         phi_f = PhiNode::make_blank(region_f,phi);
 376         phi_f->init_req( 1, phi_c );
 377         phi_f->init_req( 2, phi_x );
 378         hook->add_req(phi_f);
 379         phi_f = phase->transform(phi_f);
 380       }
 381       proj_path_data = phi_f;
 382       proj_path_ctrl = region_f;
 383     }
 384 
 385     // Fixup 'v' for for the split
 386     if( vop == Op_Phi ) {       // Remote merge point
 387       uint i;
 388       for( i = 1; i < v->req(); i++ )
 389         if( v->in(i) == phi )
 390           break;
 391       v->set_req(i, proj_path_data );
 392     } else if( v->is_ConstraintCast() ) {
 393       v->set_req(0, proj_path_ctrl );
 394       v->set_req(1, proj_path_data );
 395     } else
 396       ShouldNotReachHere();
 397   }
 398 
 399   // Now replace the original iff's True/False with region_s/region_t.
 400   // This makes the original iff go dead.
 401   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 402     Node* p = iff->last_out(i3);
 403     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 404     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 405     // Replace p with u
 406     igvn->add_users_to_worklist(p);
 407     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 408       Node* x = p->last_out(l);
 409       igvn->hash_delete(x);
 410       uint uses_found = 0;
 411       for( uint j = 0; j < x->req(); j++ ) {
 412         if( x->in(j) == p ) {
 413           x->set_req(j, u);
 414           uses_found++;
 415         }
 416       }
 417       l -= uses_found;    // we deleted 1 or more copies of this edge
 418     }
 419     igvn->remove_dead_node(p);
 420   }
 421 
 422   // Force the original merge dead
 423   igvn->hash_delete(r);
 424   // First, remove region's dead users.
 425   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 426     Node* u = r->last_out(l);
 427     if( u == r ) {
 428       r->set_req(0, NULL);
 429     } else {
 430       assert(u->outcnt() == 0, "only dead users");
 431       igvn->remove_dead_node(u);
 432     }
 433     l -= 1;
 434   }
 435   igvn->remove_dead_node(r);
 436 
 437   // Now remove the bogus extra edges used to keep things alive
 438   igvn->remove_dead_node( hook );
 439 
 440   // Must return either the original node (now dead) or a new node
 441   // (Do not return a top here, since that would break the uniqueness of top.)
 442   return new (igvn->C) ConINode(TypeInt::ZERO);
 443 }
 444 
 445 //------------------------------is_range_check---------------------------------
 446 // Return 0 if not a range check.  Return 1 if a range check and set index and
 447 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 448 // is versus a constant.
 449 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 450   Node* b = in(1);
 451   if (b == NULL || !b->is_Bool())  return 0;
 452   BoolNode* bn = b->as_Bool();
 453   Node* cmp = bn->in(1);
 454   if (cmp == NULL)  return 0;
 455   if (cmp->Opcode() != Op_CmpU)  return 0;
 456 
 457   Node* l = cmp->in(1);
 458   Node* r = cmp->in(2);
 459   int flip_test = 1;
 460   if (bn->_test._test == BoolTest::le) {
 461     l = cmp->in(2);
 462     r = cmp->in(1);
 463     flip_test = 2;
 464   } else if (bn->_test._test != BoolTest::lt) {
 465     return 0;
 466   }
 467   if (l->is_top())  return 0;   // Top input means dead test
 468   if (r->Opcode() != Op_LoadRange)  return 0;
 469 
 470   // We have recognized one of these forms:
 471   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 472   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 473 
 474   // Make sure it's a real range check by requiring an uncommon trap
 475   // along the OOB path.  Otherwise, it's possible that the user wrote
 476   // something which optimized to look like a range check but behaves
 477   // in some other way.
 478   Node* iftrap = proj_out(flip_test == 2 ? true : false);
 479   bool found_trap = false;
 480   if (iftrap != NULL) {
 481     Node* u = iftrap->unique_ctrl_out();
 482     if (u != NULL) {
 483       // It could be a merge point (Region) for uncommon trap.
 484       if (u->is_Region()) {
 485         Node* c = u->unique_ctrl_out();
 486         if (c != NULL) {
 487           iftrap = u;
 488           u = c;
 489         }
 490       }
 491       if (u->in(0) == iftrap && u->is_CallStaticJava()) {
 492         int req = u->as_CallStaticJava()->uncommon_trap_request();
 493         if (Deoptimization::trap_request_reason(req) ==
 494             Deoptimization::Reason_range_check) {
 495           found_trap = true;
 496         }
 497       }
 498     }
 499   }
 500   if (!found_trap)  return 0;   // sorry, no cigar
 501 
 502   // Look for index+offset form
 503   Node* ind = l;
 504   jint  off = 0;
 505   if (l->is_top()) {
 506     return 0;
 507   } else if (l->is_Add()) {
 508     if ((off = l->in(1)->find_int_con(0)) != 0) {
 509       ind = l->in(2);
 510     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 511       ind = l->in(1);
 512     }
 513   } else if ((off = l->find_int_con(-1)) >= 0) {
 514     // constant offset with no variable index
 515     ind = NULL;
 516   } else {
 517     // variable index with no constant offset (or dead negative index)
 518     off = 0;
 519   }
 520 
 521   // Return all the values:
 522   index  = ind;
 523   offset = off;
 524   range  = r;
 525   return flip_test;
 526 }
 527 
 528 //------------------------------adjust_check-----------------------------------
 529 // Adjust (widen) a prior range check
 530 static void adjust_check(Node* proj, Node* range, Node* index,
 531                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 532   PhaseGVN *gvn = igvn;
 533   // Break apart the old check
 534   Node *iff = proj->in(0);
 535   Node *bol = iff->in(1);
 536   if( bol->is_top() ) return;   // In case a partially dead range check appears
 537   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 538   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 539   if( !bol->is_Bool() ) return;
 540 
 541   Node *cmp = bol->in(1);
 542   // Compute a new check
 543   Node *new_add = gvn->intcon(off_lo);
 544   if( index ) {
 545     new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index;
 546   }
 547   Node *new_cmp = (flip == 1)
 548     ? new (gvn->C) CmpUNode( new_add, range )
 549     : new (gvn->C) CmpUNode( range, new_add );
 550   new_cmp = gvn->transform(new_cmp);
 551   // See if no need to adjust the existing check
 552   if( new_cmp == cmp ) return;
 553   // Else, adjust existing check
 554   Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 555   igvn->rehash_node_delayed( iff );
 556   iff->set_req_X( 1, new_bol, igvn );
 557 }
 558 
 559 //------------------------------up_one_dom-------------------------------------
 560 // Walk up the dominator tree one step.  Return NULL at root or true
 561 // complex merges.  Skips through small diamonds.
 562 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 563   Node *dom = curr->in(0);
 564   if( !dom )                    // Found a Region degraded to a copy?
 565     return curr->nonnull_req(); // Skip thru it
 566 
 567   if( curr != dom )             // Normal walk up one step?
 568     return dom;
 569 
 570   // Use linear_only if we are still parsing, since we cannot
 571   // trust the regions to be fully filled in.
 572   if (linear_only)
 573     return NULL;
 574 
 575   if( dom->is_Root() )
 576     return NULL;
 577 
 578   // Else hit a Region.  Check for a loop header
 579   if( dom->is_Loop() )
 580     return dom->in(1);          // Skip up thru loops
 581 
 582   // Check for small diamonds
 583   Node *din1, *din2, *din3, *din4;
 584   if( dom->req() == 3 &&        // 2-path merge point
 585       (din1 = dom ->in(1)) &&   // Left  path exists
 586       (din2 = dom ->in(2)) &&   // Right path exists
 587       (din3 = din1->in(0)) &&   // Left  path up one
 588       (din4 = din2->in(0)) ) {  // Right path up one
 589     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 590         (din3 = din3->in(0)) )
 591       din3 = din3->in(0);
 592     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 593         (din4 = din4->in(0)) )
 594       din4 = din4->in(0);
 595     if( din3 == din4 && din3->is_If() )
 596       return din3;              // Skip around diamonds
 597   }
 598 
 599   // Give up the search at true merges
 600   return NULL;                  // Dead loop?  Or hit root?
 601 }
 602 
 603 
 604 //------------------------------filtered_int_type--------------------------------
 605 // Return a possibly more restrictive type for val based on condition control flow for an if
 606 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 607   assert(if_proj &&
 608          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 609   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 610     IfNode* iff = if_proj->in(0)->as_If();
 611     if (iff->in(1) && iff->in(1)->is_Bool()) {
 612       BoolNode* bol = iff->in(1)->as_Bool();
 613       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 614         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 615         if (cmp->in(1) == val) {
 616           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 617           if (cmp2_t != NULL) {
 618             jint lo = cmp2_t->_lo;
 619             jint hi = cmp2_t->_hi;
 620             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 621             switch (msk) {
 622             case BoolTest::ne:
 623               // Can't refine type
 624               return NULL;
 625             case BoolTest::eq:
 626               return cmp2_t;
 627             case BoolTest::lt:
 628               lo = TypeInt::INT->_lo;
 629               if (hi - 1 < hi) {
 630                 hi = hi - 1;
 631               }
 632               break;
 633             case BoolTest::le:
 634               lo = TypeInt::INT->_lo;
 635               break;
 636             case BoolTest::gt:
 637               if (lo + 1 > lo) {
 638                 lo = lo + 1;
 639               }
 640               hi = TypeInt::INT->_hi;
 641               break;
 642             case BoolTest::ge:
 643               // lo unchanged
 644               hi = TypeInt::INT->_hi;
 645               break;
 646             }
 647             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 648             return rtn_t;
 649           }
 650         }
 651       }
 652     }
 653   }
 654   return NULL;
 655 }
 656 
 657 //------------------------------fold_compares----------------------------
 658 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 659 // the direction of this if is determined by the preceding if so it
 660 // can be eliminate entirely.  Given an if testing (CmpI n c) check
 661 // for an immediately control dependent if that is testing (CmpI n c2)
 662 // and has one projection leading to this if and the other projection
 663 // leading to a region that merges one of this ifs control
 664 // projections.
 665 //
 666 //                   If
 667 //                  / |
 668 //                 /  |
 669 //                /   |
 670 //              If    |
 671 //              /\    |
 672 //             /  \   |
 673 //            /    \  |
 674 //           /    Region
 675 //
 676 Node* IfNode::fold_compares(PhaseGVN* phase) {
 677   if (!phase->C->eliminate_boxing() || Opcode() != Op_If) return NULL;
 678 
 679   Node* this_cmp = in(1)->in(1);
 680   if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
 681       this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
 682     Node* ctrl = in(0);
 683     BoolNode* this_bool = in(1)->as_Bool();
 684     Node* n = this_cmp->in(1);
 685     int hi = this_cmp->in(2)->get_int();
 686     if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
 687         ctrl->in(0)->is_If() &&
 688         ctrl->in(0)->outcnt() == 2 &&
 689         ctrl->in(0)->in(1)->is_Bool() &&
 690         ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
 691         ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
 692         ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
 693         ctrl->in(0)->in(1)->in(1)->in(1) == n) {
 694       IfNode* dom_iff = ctrl->in(0)->as_If();
 695       Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
 696       if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
 697           this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
 698         // Identify which proj goes to the region and which continues on
 699         RegionNode* region = otherproj->unique_out()->as_Region();
 700         Node* success = NULL;
 701         Node* fail = NULL;
 702         for (int i = 0; i < 2; i++) {
 703           Node* proj = proj_out(i);
 704           if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 705             success = proj;
 706           } else if (fail == NULL) {
 707             fail = proj;
 708           } else {
 709             success = fail = NULL;
 710           }
 711         }
 712         if (success != NULL && fail != NULL && !region->has_phi()) {
 713           int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
 714           BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 715           Node* dom_cmp =  dom_bool->in(1);
 716           const TypeInt* failtype  = filtered_int_type(phase, n, ctrl);
 717           if (failtype != NULL) {
 718             const TypeInt* type2 = filtered_int_type(phase, n, fail);
 719             if (type2 != NULL) {
 720               failtype = failtype->join(type2)->is_int();
 721             } else {
 722               failtype = NULL;
 723             }
 724           }
 725 
 726           if (failtype != NULL &&
 727               dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
 728             int bound = failtype->_hi - failtype->_lo + 1;
 729             if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
 730               // Merge the two compares into a single unsigned compare by building  (CmpU (n - lo) hi)
 731               BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
 732               Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo)));
 733               Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound)));
 734               Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond));
 735               phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
 736               phase->hash_delete(this);
 737               set_req(1, newbool);
 738               return this;
 739             }
 740             if (failtype->_lo > failtype->_hi) {
 741               // previous if determines the result of this if so
 742               // replace Bool with constant
 743               phase->hash_delete(this);
 744               set_req(1, phase->intcon(success->as_Proj()->_con));
 745               return this;
 746             }
 747           }
 748         }
 749       }
 750     }
 751   }
 752   return NULL;
 753 }
 754 
 755 //------------------------------remove_useless_bool----------------------------
 756 // Check for people making a useless boolean: things like
 757 // if( (x < y ? true : false) ) { ... }
 758 // Replace with if( x < y ) { ... }
 759 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
 760   Node *i1 = iff->in(1);
 761   if( !i1->is_Bool() ) return NULL;
 762   BoolNode *bol = i1->as_Bool();
 763 
 764   Node *cmp = bol->in(1);
 765   if( cmp->Opcode() != Op_CmpI ) return NULL;
 766 
 767   // Must be comparing against a bool
 768   const Type *cmp2_t = phase->type( cmp->in(2) );
 769   if( cmp2_t != TypeInt::ZERO &&
 770       cmp2_t != TypeInt::ONE )
 771     return NULL;
 772 
 773   // Find a prior merge point merging the boolean
 774   i1 = cmp->in(1);
 775   if( !i1->is_Phi() ) return NULL;
 776   PhiNode *phi = i1->as_Phi();
 777   if( phase->type( phi ) != TypeInt::BOOL )
 778     return NULL;
 779 
 780   // Check for diamond pattern
 781   int true_path = phi->is_diamond_phi();
 782   if( true_path == 0 ) return NULL;
 783 
 784   // Make sure that iff and the control of the phi are different. This
 785   // should really only happen for dead control flow since it requires
 786   // an illegal cycle.
 787   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
 788 
 789   // phi->region->if_proj->ifnode->bool->cmp
 790   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
 791 
 792   // Now get the 'sense' of the test correct so we can plug in
 793   // either iff2->in(1) or its complement.
 794   int flip = 0;
 795   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
 796   else if( bol->_test._test != BoolTest::eq ) return NULL;
 797   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
 798 
 799   const Type *phi1_t = phase->type( phi->in(1) );
 800   const Type *phi2_t = phase->type( phi->in(2) );
 801   // Check for Phi(0,1) and flip
 802   if( phi1_t == TypeInt::ZERO ) {
 803     if( phi2_t != TypeInt::ONE ) return NULL;
 804     flip = 1-flip;
 805   } else {
 806     // Check for Phi(1,0)
 807     if( phi1_t != TypeInt::ONE  ) return NULL;
 808     if( phi2_t != TypeInt::ZERO ) return NULL;
 809   }
 810   if( true_path == 2 ) {
 811     flip = 1-flip;
 812   }
 813 
 814   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
 815   assert(new_bol != iff->in(1), "must make progress");
 816   iff->set_req(1, new_bol);
 817   // Intervening diamond probably goes dead
 818   phase->C->set_major_progress();
 819   return iff;
 820 }
 821 
 822 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
 823 
 824 //------------------------------Ideal------------------------------------------
 825 // Return a node which is more "ideal" than the current node.  Strip out
 826 // control copies
 827 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 828   if (remove_dead_region(phase, can_reshape))  return this;
 829   // No Def-Use info?
 830   if (!can_reshape)  return NULL;
 831   PhaseIterGVN *igvn = phase->is_IterGVN();
 832 
 833   // Don't bother trying to transform a dead if
 834   if (in(0)->is_top())  return NULL;
 835   // Don't bother trying to transform an if with a dead test
 836   if (in(1)->is_top())  return NULL;
 837   // Another variation of a dead test
 838   if (in(1)->is_Con())  return NULL;
 839   // Another variation of a dead if
 840   if (outcnt() < 2)  return NULL;
 841 
 842   // Canonicalize the test.
 843   Node* idt_if = idealize_test(phase, this);
 844   if (idt_if != NULL)  return idt_if;
 845 
 846   // Try to split the IF
 847   Node *s = split_if(this, igvn);
 848   if (s != NULL)  return s;
 849 
 850   // Check for people making a useless boolean: things like
 851   // if( (x < y ? true : false) ) { ... }
 852   // Replace with if( x < y ) { ... }
 853   Node *bol2 = remove_useless_bool(this, phase);
 854   if( bol2 ) return bol2;
 855 
 856   // Setup to scan up the CFG looking for a dominating test
 857   Node *dom = in(0);
 858   Node *prev_dom = this;
 859 
 860   // Check for range-check vs other kinds of tests
 861   Node *index1, *range1;
 862   jint offset1;
 863   int flip1 = is_range_check(range1, index1, offset1);
 864   if( flip1 ) {
 865     Node *first_prev_dom = NULL;
 866 
 867     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
 868     // so all checks we inspect post-dominate the top-most check we find.
 869     // If we are going to fail the current check and we reach the top check
 870     // then we are guaranteed to fail, so just start interpreting there.
 871     // We 'expand' the top 2 range checks to include all post-dominating
 872     // checks.
 873 
 874     // The top 2 range checks seen
 875     Node *prev_chk1 = NULL;
 876     Node *prev_chk2 = NULL;
 877     // Low and high offsets seen so far
 878     jint off_lo = offset1;
 879     jint off_hi = offset1;
 880 
 881     // Scan for the top 2 checks and collect range of offsets
 882     for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
 883       if( dom->Opcode() == Op_If &&  // Not same opcode?
 884           prev_dom->in(0) == dom ) { // One path of test does dominate?
 885         if( dom == this ) return NULL; // dead loop
 886         // See if this is a range check
 887         Node *index2, *range2;
 888         jint offset2;
 889         int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
 890         // See if this is a _matching_ range check, checking against
 891         // the same array bounds.
 892         if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
 893             dom->outcnt() == 2 ) {
 894           // Gather expanded bounds
 895           off_lo = MIN2(off_lo,offset2);
 896           off_hi = MAX2(off_hi,offset2);
 897           // Record top 2 range checks
 898           prev_chk2 = prev_chk1;
 899           prev_chk1 = prev_dom;
 900           // If we match the test exactly, then the top test covers
 901           // both our lower and upper bounds.
 902           if( dom->in(1) == in(1) )
 903             prev_chk2 = prev_chk1;
 904         }
 905       }
 906       prev_dom = dom;
 907       dom = up_one_dom( dom );
 908       if( !dom ) break;
 909     }
 910 
 911 
 912     // Attempt to widen the dominating range check to cover some later
 913     // ones.  Since range checks "fail" by uncommon-trapping to the
 914     // interpreter, widening a check can make us speculative enter the
 915     // interpreter.  If we see range-check deopt's, do not widen!
 916     if (!phase->C->allow_range_check_smearing())  return NULL;
 917 
 918     // Constant indices only need to check the upper bound.
 919     // Non-constance indices must check both low and high.
 920     if( index1 ) {
 921       // Didn't find 2 prior covering checks, so cannot remove anything.
 922       if( !prev_chk2 ) return NULL;
 923       // 'Widen' the offsets of the 1st and 2nd covering check
 924       adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
 925       // Do not call adjust_check twice on the same projection
 926       // as the first call may have transformed the BoolNode to a ConI
 927       if( prev_chk1 != prev_chk2 ) {
 928         adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
 929       }
 930       // Test is now covered by prior checks, dominate it out
 931       prev_dom = prev_chk2;
 932     } else {
 933       // Didn't find prior covering check, so cannot remove anything.
 934       if( !prev_chk1 ) return NULL;
 935       // 'Widen' the offset of the 1st and only covering check
 936       adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
 937       // Test is now covered by prior checks, dominate it out
 938       prev_dom = prev_chk1;
 939     }
 940 
 941 
 942   } else {                      // Scan for an equivalent test
 943 
 944     Node *cmp;
 945     int dist = 0;               // Cutoff limit for search
 946     int op = Opcode();
 947     if( op == Op_If &&
 948         (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
 949       if( cmp->in(2) != NULL && // make sure cmp is not already dead
 950           cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
 951         dist = 64;              // Limit for null-pointer scans
 952       } else {
 953         dist = 4;               // Do not bother for random pointer tests
 954       }
 955     } else {
 956       dist = 4;                 // Limit for random junky scans
 957     }
 958 
 959     // Normal equivalent-test check.
 960     if( !dom ) return NULL;     // Dead loop?
 961 
 962     Node* result = fold_compares(phase);
 963     if (result != NULL) {
 964       return result;
 965     }
 966 
 967     // Search up the dominator tree for an If with an identical test
 968     while( dom->Opcode() != op    ||  // Not same opcode?
 969            dom->in(1)    != in(1) ||  // Not same input 1?
 970            (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
 971            prev_dom->in(0) != dom ) { // One path of test does not dominate?
 972       if( dist < 0 ) return NULL;
 973 
 974       dist--;
 975       prev_dom = dom;
 976       dom = up_one_dom( dom );
 977       if( !dom ) return NULL;
 978     }
 979 
 980     // Check that we did not follow a loop back to ourselves
 981     if( this == dom )
 982       return NULL;
 983 
 984     if( dist > 2 )              // Add to count of NULL checks elided
 985       explicit_null_checks_elided++;
 986 
 987   } // End of Else scan for an equivalent test
 988 
 989   // Hit!  Remove this IF
 990 #ifndef PRODUCT
 991   if( TraceIterativeGVN ) {
 992     tty->print("   Removing IfNode: "); this->dump();
 993   }
 994   if( VerifyOpto && !phase->allow_progress() ) {
 995     // Found an equivalent dominating test,
 996     // we can not guarantee reaching a fix-point for these during iterativeGVN
 997     // since intervening nodes may not change.
 998     return NULL;
 999   }
1000 #endif
1001 
1002   // Replace dominated IfNode
1003   dominated_by( prev_dom, igvn );
1004 
1005   // Must return either the original node (now dead) or a new node
1006   // (Do not return a top here, since that would break the uniqueness of top.)
1007   return new (phase->C) ConINode(TypeInt::ZERO);
1008 }
1009 
1010 //------------------------------dominated_by-----------------------------------
1011 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1012   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1013   Node *idom = in(0);
1014   // Need opcode to decide which way 'this' test goes
1015   int prev_op = prev_dom->Opcode();
1016   Node *top = igvn->C->top(); // Shortcut to top
1017 
1018   // Loop predicates may have depending checks which should not
1019   // be skipped. For example, range check predicate has two checks
1020   // for lower and upper bounds.
1021   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1022   if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))
1023     prev_dom = idom;
1024 
1025   // Now walk the current IfNode's projections.
1026   // Loop ends when 'this' has no more uses.
1027   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1028     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1029     igvn->add_users_to_worklist(ifp);
1030     // Check which projection it is and set target.
1031     // Data-target is either the dominating projection of the same type
1032     // or TOP if the dominating projection is of opposite type.
1033     // Data-target will be used as the new control edge for the non-CFG
1034     // nodes like Casts and Loads.
1035     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1036     // Control-target is just the If's immediate dominator or TOP.
1037     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1038 
1039     // For each child of an IfTrue/IfFalse projection, reroute.
1040     // Loop ends when projection has no more uses.
1041     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1042       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1043       if( !s->depends_only_on_test() ) {
1044         // Find the control input matching this def-use edge.
1045         // For Regions it may not be in slot 0.
1046         uint l;
1047         for( l = 0; s->in(l) != ifp; l++ ) { }
1048         igvn->replace_input_of(s, l, ctrl_target);
1049       } else {                      // Else, for control producers,
1050         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1051       }
1052     } // End for each child of a projection
1053 
1054     igvn->remove_dead_node(ifp);
1055   } // End for each IfTrue/IfFalse child of If
1056 
1057   // Kill the IfNode
1058   igvn->remove_dead_node(this);
1059 }
1060 
1061 //------------------------------Identity---------------------------------------
1062 // If the test is constant & we match, then we are the input Control
1063 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1064   // Can only optimize if cannot go the other way
1065   const TypeTuple *t = phase->type(in(0))->is_tuple();
1066   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1067     ? in(0)->in(0)              // IfNode control
1068     : this;                     // no progress
1069 }
1070 
1071 //------------------------------dump_spec--------------------------------------
1072 #ifndef PRODUCT
1073 void IfNode::dump_spec(outputStream *st) const {
1074   st->print("P=%f, C=%f",_prob,_fcnt);
1075 }
1076 #endif
1077 
1078 //------------------------------idealize_test----------------------------------
1079 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1080 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1081 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1082 // needed.
1083 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1084   assert(iff->in(0) != NULL, "If must be live");
1085 
1086   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1087   Node* old_if_f = iff->proj_out(false);
1088   Node* old_if_t = iff->proj_out(true);
1089 
1090   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1091   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1092   // happens in count-down loops
1093   if (iff->is_CountedLoopEnd())  return NULL;
1094   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1095   BoolNode *b = iff->in(1)->as_Bool();
1096   BoolTest bt = b->_test;
1097   // Test already in good order?
1098   if( bt.is_canonical() )
1099     return NULL;
1100 
1101   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1102   // cloning the IfNode.
1103   Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) );
1104   if( !new_b->is_Bool() ) return NULL;
1105   b = new_b->as_Bool();
1106 
1107   PhaseIterGVN *igvn = phase->is_IterGVN();
1108   assert( igvn, "Test is not canonical in parser?" );
1109 
1110   // The IF node never really changes, but it needs to be cloned
1111   iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1112 
1113   Node *prior = igvn->hash_find_insert(iff);
1114   if( prior ) {
1115     igvn->remove_dead_node(iff);
1116     iff = (IfNode*)prior;
1117   } else {
1118     // Cannot call transform on it just yet
1119     igvn->set_type_bottom(iff);
1120   }
1121   igvn->_worklist.push(iff);
1122 
1123   // Now handle projections.  Cloning not required.
1124   Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff ));
1125   Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff ));
1126 
1127   igvn->register_new_node_with_optimizer(new_if_f);
1128   igvn->register_new_node_with_optimizer(new_if_t);
1129   // Flip test, so flip trailing control
1130   igvn->replace_node(old_if_f, new_if_t);
1131   igvn->replace_node(old_if_t, new_if_f);
1132 
1133   // Progress
1134   return iff;
1135 }
1136 
1137 //------------------------------Identity---------------------------------------
1138 // If the test is constant & we match, then we are the input Control
1139 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1140   // Can only optimize if cannot go the other way
1141   const TypeTuple *t = phase->type(in(0))->is_tuple();
1142   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1143     ? in(0)->in(0)              // IfNode control
1144     : this;                     // no progress
1145 }
--- EOF ---