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