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/castnode.hpp"
  29 #include "opto/cfgnode.hpp"
  30 #include "opto/connode.hpp"
  31 #include "opto/loopnode.hpp"
  32 #include "opto/phaseX.hpp"
  33 #include "opto/runtime.hpp"
  34 #include "opto/rootnode.hpp"
  35 #include "opto/subnode.hpp"
  36 
  37 // Portions of code courtesy of Clifford Click
  38 
  39 // Optimization - Graph Style
  40 
  41 
  42 extern int explicit_null_checks_elided;
  43 
  44 //=============================================================================
  45 //------------------------------Value------------------------------------------
  46 // Return a tuple for whichever arm of the IF is reachable
  47 const Type *IfNode::Value( PhaseTransform *phase ) const {
  48   if( !in(0) ) return Type::TOP;
  49   if( phase->type(in(0)) == Type::TOP )
  50     return Type::TOP;
  51   const Type *t = phase->type(in(1));
  52   if( t == Type::TOP )          // data is undefined
  53     return TypeTuple::IFNEITHER; // unreachable altogether
  54   if( t == TypeInt::ZERO )      // zero, or false
  55     return TypeTuple::IFFALSE;  // only false branch is reachable
  56   if( t == TypeInt::ONE )       // 1, or true
  57     return TypeTuple::IFTRUE;   // only true branch is reachable
  58   assert( t == TypeInt::BOOL, "expected boolean type" );
  59 
  60   return TypeTuple::IFBOTH;     // No progress
  61 }
  62 
  63 const RegMask &IfNode::out_RegMask() const {
  64   return RegMask::Empty;
  65 }
  66 
  67 //------------------------------split_if---------------------------------------
  68 // Look for places where we merge constants, then test on the merged value.
  69 // If the IF test will be constant folded on the path with the constant, we
  70 // win by splitting the IF to before the merge point.
  71 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  72   // I could be a lot more general here, but I'm trying to squeeze this
  73   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  74   // on the patterns I accept.  CNC
  75 
  76   // Look for a compare of a constant and a merged value
  77   Node *i1 = iff->in(1);
  78   if( !i1->is_Bool() ) return NULL;
  79   BoolNode *b = i1->as_Bool();
  80   Node *cmp = b->in(1);
  81   if( !cmp->is_Cmp() ) return NULL;
  82   i1 = cmp->in(1);
  83   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  84   PhiNode *phi = i1->as_Phi();
  85   if( phi->is_copy() ) return NULL;
  86   Node *con2 = cmp->in(2);
  87   if( !con2->is_Con() ) return NULL;
  88   // See that the merge point contains some constants
  89   Node *con1=NULL;
  90   uint i4;
  91   for( i4 = 1; i4 < phi->req(); i4++ ) {
  92     con1 = phi->in(i4);
  93     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
  94     if( con1->is_Con() ) break; // Found a constant
  95     // Also allow null-vs-not-null checks
  96     const TypePtr *tp = igvn->type(con1)->isa_ptr();
  97     if( tp && tp->_ptr == TypePtr::NotNull )
  98       break;
  99   }
 100   if( i4 >= phi->req() ) return NULL; // Found no constants
 101 
 102   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 103 
 104   // Make sure that the compare can be constant folded away
 105   Node *cmp2 = cmp->clone();
 106   cmp2->set_req(1,con1);
 107   cmp2->set_req(2,con2);
 108   const Type *t = cmp2->Value(igvn);
 109   // This compare is dead, so whack it!
 110   igvn->remove_dead_node(cmp2);
 111   if( !t->singleton() ) return NULL;
 112 
 113   // No intervening control, like a simple Call
 114   Node *r = iff->in(0);
 115   if( !r->is_Region() ) return NULL;
 116   if( phi->region() != r ) return NULL;
 117   // No other users of the cmp/bool
 118   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 119     //tty->print_cr("many users of cmp/bool");
 120     return NULL;
 121   }
 122 
 123   // Make sure we can determine where all the uses of merged values go
 124   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 125     Node* u = r->fast_out(j);
 126     if( u == r ) continue;
 127     if( u == iff ) continue;
 128     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 129     if( !u->is_Phi() ) {
 130       /*
 131       if( u->is_Start() ) {
 132         tty->print_cr("Region has inlined start use");
 133       } else {
 134         tty->print_cr("Region has odd use");
 135         u->dump(2);
 136       }*/
 137       return NULL;
 138     }
 139     if( u != phi ) {
 140       // CNC - do not allow any other merged value
 141       //tty->print_cr("Merging another value");
 142       //u->dump(2);
 143       return NULL;
 144     }
 145     // Make sure we can account for all Phi uses
 146     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 147       Node* v = u->fast_out(k); // User of the phi
 148       // CNC - Allow only really simple patterns.
 149       // In particular I disallow AddP of the Phi, a fairly common pattern
 150       if (v == cmp) continue;  // The compare is OK
 151       if (v->is_ConstraintCast()) {
 152         // If the cast is derived from data flow edges, it may not have a control edge.
 153         // If so, it should be safe to split. But follow-up code can not deal with
 154         // this (l. 359). So skip.
 155         if (v->in(0) == NULL) {
 156           return NULL;
 157         }
 158         if (v->in(0)->in(0) == iff) {
 159           continue;               // CastPP/II of the IfNode is OK
 160         }
 161       }
 162       // Disabled following code because I cannot tell if exactly one
 163       // path dominates without a real dominator check. CNC 9/9/1999
 164       //uint vop = v->Opcode();
 165       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 166       //  Node *r = v->in(0);     // Get controlling point
 167       //  if( !r ) return NULL;   // Degraded to a copy
 168       //  // Find exactly one path in (either True or False doms, but not IFF)
 169       //  int cnt = 0;
 170       //  for( uint i = 1; i < r->req(); i++ )
 171       //    if( r->in(i) && r->in(i)->in(0) == iff )
 172       //      cnt++;
 173       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 174       //}
 175       if( !v->is_Call() ) {
 176         /*
 177         if( v->Opcode() == Op_AddP ) {
 178           tty->print_cr("Phi has AddP use");
 179         } else if( v->Opcode() == Op_CastPP ) {
 180           tty->print_cr("Phi has CastPP use");
 181         } else if( v->Opcode() == Op_CastII ) {
 182           tty->print_cr("Phi has CastII use");
 183         } else {
 184           tty->print_cr("Phi has use I cant be bothered with");
 185         }
 186         */
 187       }
 188       return NULL;
 189 
 190       /* CNC - Cut out all the fancy acceptance tests
 191       // Can we clone this use when doing the transformation?
 192       // If all uses are from Phis at this merge or constants, then YES.
 193       if( !v->in(0) && v != cmp ) {
 194         tty->print_cr("Phi has free-floating use");
 195         v->dump(2);
 196         return NULL;
 197       }
 198       for( uint l = 1; l < v->req(); l++ ) {
 199         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 200             !v->in(l)->is_Con() ) {
 201           tty->print_cr("Phi has use");
 202           v->dump(2);
 203           return NULL;
 204         } // End of if Phi-use input is neither Phi nor Constant
 205       } // End of for all inputs to Phi-use
 206       */
 207     } // End of for all uses of Phi
 208   } // End of for all uses of Region
 209 
 210   // Only do this if the IF node is in a sane state
 211   if (iff->outcnt() != 2)
 212     return NULL;
 213 
 214   // Got a hit!  Do the Mondo Hack!
 215   //
 216   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 217   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 218   //     cmp - 2                         cmp - 2               cmp - 2
 219   //       bool                            bool_c                bool_x
 220   //       if                               if_c                  if_x
 221   //      T  F                              T  F                  T  F
 222   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 223   //
 224   // Split the paths coming into the merge point into 2 separate groups of
 225   // merges.  On the left will be all the paths feeding constants into the
 226   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 227   // will fold up into a constant; this will let the Cmp fold up as well as
 228   // all the control flow.  Below the original IF we have 2 control
 229   // dependent regions, 's' and 't'.  Now we will merge the two paths
 230   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 231   // likely 2 or more) will promptly constant fold away.
 232   PhaseGVN *phase = igvn;
 233 
 234   // Make a region merging constants and a region merging the rest
 235   uint req_c = 0;
 236   Node* predicate_proj = NULL;
 237   for (uint ii = 1; ii < r->req(); ii++) {
 238     if (phi->in(ii) == con1) {
 239       req_c++;
 240     }
 241     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
 242     if (proj != NULL) {
 243       assert(predicate_proj == NULL, "only one predicate entry expected");
 244       predicate_proj = proj;
 245     }
 246   }
 247   Node* predicate_c = NULL;
 248   Node* predicate_x = NULL;
 249   bool counted_loop = r->is_CountedLoop();
 250 
 251   Node *region_c = new RegionNode(req_c + 1);
 252   Node *phi_c    = con1;
 253   uint  len      = r->req();
 254   Node *region_x = new RegionNode(len - req_c);
 255   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 256   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 257     if (phi->in(i) == con1) {
 258       region_c->init_req( i_c++, r  ->in(i) );
 259       if (r->in(i) == predicate_proj)
 260         predicate_c = predicate_proj;
 261     } else {
 262       region_x->init_req( i_x,   r  ->in(i) );
 263       phi_x   ->init_req( i_x++, phi->in(i) );
 264       if (r->in(i) == predicate_proj)
 265         predicate_x = predicate_proj;
 266     }
 267   }
 268   if (predicate_c != NULL && (req_c > 1)) {
 269     assert(predicate_x == NULL, "only one predicate entry expected");
 270     predicate_c = NULL; // Do not clone predicate below merge point
 271   }
 272   if (predicate_x != NULL && ((len - req_c) > 2)) {
 273     assert(predicate_c == NULL, "only one predicate entry expected");
 274     predicate_x = NULL; // Do not clone predicate below merge point
 275   }
 276 
 277   // Register the new RegionNodes but do not transform them.  Cannot
 278   // transform until the entire Region/Phi conglomerate has been hacked
 279   // as a single huge transform.
 280   igvn->register_new_node_with_optimizer( region_c );
 281   igvn->register_new_node_with_optimizer( region_x );
 282   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 283   // about to get one.  If this only use goes away, then phi_x will look dead.
 284   // However, he will be picking up some more uses down below.
 285   Node *hook = new Node(4);
 286   hook->init_req(0, phi_x);
 287   hook->init_req(1, phi_c);
 288   phi_x = phase->transform( phi_x );
 289 
 290   // Make the compare
 291   Node *cmp_c = phase->makecon(t);
 292   Node *cmp_x = cmp->clone();
 293   cmp_x->set_req(1,phi_x);
 294   cmp_x->set_req(2,con2);
 295   cmp_x = phase->transform(cmp_x);
 296   // Make the bool
 297   Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
 298   Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
 299   // Make the IfNode
 300   IfNode *iff_c = new IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
 301   igvn->set_type_bottom(iff_c);
 302   igvn->_worklist.push(iff_c);
 303   hook->init_req(2, iff_c);
 304 
 305   IfNode *iff_x = new IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
 306   igvn->set_type_bottom(iff_x);
 307   igvn->_worklist.push(iff_x);
 308   hook->init_req(3, iff_x);
 309 
 310   // Make the true/false arms
 311   Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
 312   Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
 313   if (predicate_c != NULL) {
 314     assert(predicate_x == NULL, "only one predicate entry expected");
 315     // Clone loop predicates to each path
 316     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
 317     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
 318   }
 319   Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
 320   Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
 321   if (predicate_x != NULL) {
 322     assert(predicate_c == NULL, "only one predicate entry expected");
 323     // Clone loop predicates to each path
 324     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
 325     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
 326   }
 327 
 328   // Merge the TRUE paths
 329   Node *region_s = new RegionNode(3);
 330   igvn->_worklist.push(region_s);
 331   region_s->init_req(1, iff_c_t);
 332   region_s->init_req(2, iff_x_t);
 333   igvn->register_new_node_with_optimizer( region_s );
 334 
 335   // Merge the FALSE paths
 336   Node *region_f = new RegionNode(3);
 337   igvn->_worklist.push(region_f);
 338   region_f->init_req(1, iff_c_f);
 339   region_f->init_req(2, iff_x_f);
 340   igvn->register_new_node_with_optimizer( region_f );
 341 
 342   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 343   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 344   cmp->set_req(2,NULL);
 345   // Check for all uses of the Phi and give them a new home.
 346   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 347   Node *phi_s = NULL;     // do not construct unless needed
 348   Node *phi_f = NULL;     // do not construct unless needed
 349   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 350     Node* v = phi->last_out(i2);// User of the phi
 351     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
 352     uint vop = v->Opcode();
 353     Node *proj = NULL;
 354     if( vop == Op_Phi ) {       // Remote merge point
 355       Node *r = v->in(0);
 356       for (uint i3 = 1; i3 < r->req(); i3++)
 357         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 358           proj = r->in(i3);
 359           break;
 360         }
 361     } else if( v->is_ConstraintCast() ) {
 362       proj = v->in(0);          // Controlling projection
 363     } else {
 364       assert( 0, "do not know how to handle this guy" );
 365     }
 366 
 367     Node *proj_path_data, *proj_path_ctrl;
 368     if( proj->Opcode() == Op_IfTrue ) {
 369       if( phi_s == NULL ) {
 370         // Only construct phi_s if needed, otherwise provides
 371         // interfering use.
 372         phi_s = PhiNode::make_blank(region_s,phi);
 373         phi_s->init_req( 1, phi_c );
 374         phi_s->init_req( 2, phi_x );
 375         hook->add_req(phi_s);
 376         phi_s = phase->transform(phi_s);
 377       }
 378       proj_path_data = phi_s;
 379       proj_path_ctrl = region_s;
 380     } else {
 381       if( phi_f == NULL ) {
 382         // Only construct phi_f if needed, otherwise provides
 383         // interfering use.
 384         phi_f = PhiNode::make_blank(region_f,phi);
 385         phi_f->init_req( 1, phi_c );
 386         phi_f->init_req( 2, phi_x );
 387         hook->add_req(phi_f);
 388         phi_f = phase->transform(phi_f);
 389       }
 390       proj_path_data = phi_f;
 391       proj_path_ctrl = region_f;
 392     }
 393 
 394     // Fixup 'v' for for the split
 395     if( vop == Op_Phi ) {       // Remote merge point
 396       uint i;
 397       for( i = 1; i < v->req(); i++ )
 398         if( v->in(i) == phi )
 399           break;
 400       v->set_req(i, proj_path_data );
 401     } else if( v->is_ConstraintCast() ) {
 402       v->set_req(0, proj_path_ctrl );
 403       v->set_req(1, proj_path_data );
 404     } else
 405       ShouldNotReachHere();
 406   }
 407 
 408   // Now replace the original iff's True/False with region_s/region_t.
 409   // This makes the original iff go dead.
 410   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 411     Node* p = iff->last_out(i3);
 412     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 413     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 414     // Replace p with u
 415     igvn->add_users_to_worklist(p);
 416     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 417       Node* x = p->last_out(l);
 418       igvn->hash_delete(x);
 419       uint uses_found = 0;
 420       for( uint j = 0; j < x->req(); j++ ) {
 421         if( x->in(j) == p ) {
 422           x->set_req(j, u);
 423           uses_found++;
 424         }
 425       }
 426       l -= uses_found;    // we deleted 1 or more copies of this edge
 427     }
 428     igvn->remove_dead_node(p);
 429   }
 430 
 431   // Force the original merge dead
 432   igvn->hash_delete(r);
 433   // First, remove region's dead users.
 434   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 435     Node* u = r->last_out(l);
 436     if( u == r ) {
 437       r->set_req(0, NULL);
 438     } else {
 439       assert(u->outcnt() == 0, "only dead users");
 440       igvn->remove_dead_node(u);
 441     }
 442     l -= 1;
 443   }
 444   igvn->remove_dead_node(r);
 445 
 446   // Now remove the bogus extra edges used to keep things alive
 447   igvn->remove_dead_node( hook );
 448 
 449   // Must return either the original node (now dead) or a new node
 450   // (Do not return a top here, since that would break the uniqueness of top.)
 451   return new ConINode(TypeInt::ZERO);
 452 }
 453 
 454 // if this IfNode follows a range check pattern return the projection
 455 // for the failed path
 456 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
 457   Node* b = in(1);
 458   if (b == NULL || !b->is_Bool())  return NULL;
 459   BoolNode* bn = b->as_Bool();
 460   Node* cmp = bn->in(1);
 461   if (cmp == NULL)  return NULL;
 462   if (cmp->Opcode() != Op_CmpU)  return NULL;
 463 
 464   l = cmp->in(1);
 465   r = cmp->in(2);
 466   flip_test = 1;
 467   if (bn->_test._test == BoolTest::le) {
 468     l = cmp->in(2);
 469     r = cmp->in(1);
 470     flip_test = 2;
 471   } else if (bn->_test._test != BoolTest::lt) {
 472     return NULL;
 473   }
 474   if (l->is_top())  return NULL;   // Top input means dead test
 475   if (r->Opcode() != Op_LoadRange)  return NULL;
 476 
 477   // We have recognized one of these forms:
 478   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 479   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 480 
 481   ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
 482   return iftrap;
 483 }
 484 
 485 
 486 //------------------------------is_range_check---------------------------------
 487 // Return 0 if not a range check.  Return 1 if a range check and set index and
 488 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 489 // is versus a constant.
 490 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 491   int flip_test = 0;
 492   Node* l = NULL;
 493   Node* r = NULL;
 494   ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
 495   
 496   if (iftrap == NULL) {
 497     return 0;
 498   }
 499 
 500   // Make sure it's a real range check by requiring an uncommon trap
 501   // along the OOB path.  Otherwise, it's possible that the user wrote
 502   // something which optimized to look like a range check but behaves
 503   // in some other way.
 504   if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
 505     return 0;
 506   }
 507 
 508   // Look for index+offset form
 509   Node* ind = l;
 510   jint  off = 0;
 511   if (l->is_top()) {
 512     return 0;
 513   } else if (l->Opcode() == Op_AddI) {
 514     if ((off = l->in(1)->find_int_con(0)) != 0) {
 515       ind = l->in(2);
 516     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 517       ind = l->in(1);
 518     }
 519   } else if ((off = l->find_int_con(-1)) >= 0) {
 520     // constant offset with no variable index
 521     ind = NULL;
 522   } else {
 523     // variable index with no constant offset (or dead negative index)
 524     off = 0;
 525   }
 526 
 527   // Return all the values:
 528   index  = ind;
 529   offset = off;
 530   range  = r;
 531   return flip_test;
 532 }
 533 
 534 //------------------------------adjust_check-----------------------------------
 535 // Adjust (widen) a prior range check
 536 static void adjust_check(Node* proj, Node* range, Node* index,
 537                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 538   PhaseGVN *gvn = igvn;
 539   // Break apart the old check
 540   Node *iff = proj->in(0);
 541   Node *bol = iff->in(1);
 542   if( bol->is_top() ) return;   // In case a partially dead range check appears
 543   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 544   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 545   if( !bol->is_Bool() ) return;
 546 
 547   Node *cmp = bol->in(1);
 548   // Compute a new check
 549   Node *new_add = gvn->intcon(off_lo);
 550   if( index ) {
 551     new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
 552   }
 553   Node *new_cmp = (flip == 1)
 554     ? new CmpUNode( new_add, range )
 555     : new CmpUNode( range, new_add );
 556   new_cmp = gvn->transform(new_cmp);
 557   // See if no need to adjust the existing check
 558   if( new_cmp == cmp ) return;
 559   // Else, adjust existing check
 560   Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 561   igvn->rehash_node_delayed( iff );
 562   iff->set_req_X( 1, new_bol, igvn );
 563 }
 564 
 565 //------------------------------up_one_dom-------------------------------------
 566 // Walk up the dominator tree one step.  Return NULL at root or true
 567 // complex merges.  Skips through small diamonds.
 568 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 569   Node *dom = curr->in(0);
 570   if( !dom )                    // Found a Region degraded to a copy?
 571     return curr->nonnull_req(); // Skip thru it
 572 
 573   if( curr != dom )             // Normal walk up one step?
 574     return dom;
 575 
 576   // Use linear_only if we are still parsing, since we cannot
 577   // trust the regions to be fully filled in.
 578   if (linear_only)
 579     return NULL;
 580 
 581   if( dom->is_Root() )
 582     return NULL;
 583 
 584   // Else hit a Region.  Check for a loop header
 585   if( dom->is_Loop() )
 586     return dom->in(1);          // Skip up thru loops
 587 
 588   // Check for small diamonds
 589   Node *din1, *din2, *din3, *din4;
 590   if( dom->req() == 3 &&        // 2-path merge point
 591       (din1 = dom ->in(1)) &&   // Left  path exists
 592       (din2 = dom ->in(2)) &&   // Right path exists
 593       (din3 = din1->in(0)) &&   // Left  path up one
 594       (din4 = din2->in(0)) ) {  // Right path up one
 595     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 596         (din3 = din3->in(0)) )
 597       din3 = din3->in(0);
 598     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 599         (din4 = din4->in(0)) )
 600       din4 = din4->in(0);
 601     if( din3 == din4 && din3->is_If() )
 602       return din3;              // Skip around diamonds
 603   }
 604 
 605   // Give up the search at true merges
 606   return NULL;                  // Dead loop?  Or hit root?
 607 }
 608 
 609 
 610 //------------------------------filtered_int_type--------------------------------
 611 // Return a possibly more restrictive type for val based on condition control flow for an if
 612 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 613   assert(if_proj &&
 614          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 615   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 616     IfNode* iff = if_proj->in(0)->as_If();
 617     if (iff->in(1) && iff->in(1)->is_Bool()) {
 618       BoolNode* bol = iff->in(1)->as_Bool();
 619       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 620         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 621         if (cmp->in(1) == val) {
 622           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 623           if (cmp2_t != NULL) {
 624             jint lo = cmp2_t->_lo;
 625             jint hi = cmp2_t->_hi;
 626             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 627             switch (msk) {
 628             case BoolTest::ne:
 629               // Can't refine type
 630               return NULL;
 631             case BoolTest::eq:
 632               return cmp2_t;
 633             case BoolTest::lt:
 634               lo = TypeInt::INT->_lo;
 635               if (hi - 1 < hi) {
 636                 hi = hi - 1;
 637               }
 638               break;
 639             case BoolTest::le:
 640               lo = TypeInt::INT->_lo;
 641               break;
 642             case BoolTest::gt:
 643               if (lo + 1 > lo) {
 644                 lo = lo + 1;
 645               }
 646               hi = TypeInt::INT->_hi;
 647               break;
 648             case BoolTest::ge:
 649               // lo unchanged
 650               hi = TypeInt::INT->_hi;
 651               break;
 652             }
 653             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 654             return rtn_t;
 655           }
 656         }
 657       }
 658     }
 659   }
 660   return NULL;
 661 }
 662 
 663 //------------------------------fold_compares----------------------------
 664 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 665 // the direction of this if is determined by the preceding if so it
 666 // can be eliminate entirely.
 667 //
 668 // Given an if testing (CmpI n v) check for an immediately control
 669 // dependent if that is testing (CmpI n v2) and has one projection
 670 // leading to this if and the other projection leading to a region
 671 // that merges one of this ifs control projections.
 672 //
 673 //                   If
 674 //                  / |
 675 //                 /  |
 676 //                /   |
 677 //              If    |
 678 //              /\    |
 679 //             /  \   |
 680 //            /    \  |
 681 //           /    Region
 682 //
 683 // Or given an if testing (CmpI n v) check for a dominating if that is
 684 // testing (CmpI n v2), both having one projection leading to an
 685 // uncommon trap. Allow Another independent guard in between to cover
 686 // an explicit range check:
 687 // if (index < 0 || index >= array.length) {
 688 // which may need a null check to guard the LoadRange
 689 //
 690 //                   If
 691 //                  / \
 692 //                 /   \
 693 //                /     \
 694 //              If      unc
 695 //              /\
 696 //             /  \
 697 //            /    \
 698 //           /      unc
 699 //
 700 
 701 // Is the comparison for this If suitable for folding?
 702 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
 703   return in(1) != NULL &&
 704     in(1)->is_Bool() &&
 705     in(1)->in(1) != NULL &&
 706     in(1)->in(1)->Opcode() == Op_CmpI &&
 707     in(1)->in(1)->in(2) != NULL &&
 708     in(1)->in(1)->in(2) != igvn->C->top() &&
 709     in(1)->as_Bool()->_test._test != BoolTest::ne &&
 710     in(1)->as_Bool()->_test._test != BoolTest::eq &&
 711     in(1)->as_Bool()->_test._test != BoolTest::overflow &&
 712     in(1)->as_Bool()->_test._test != BoolTest::no_overflow;
 713 }
 714 
 715 // Is a dominating control suitable for folding with this if?
 716 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
 717   return ctrl != NULL &&
 718     ctrl->is_Proj() &&
 719     ctrl->in(0) != NULL &&
 720     ctrl->in(0)->is_If() &&
 721     ctrl->in(0)->outcnt() == 2 &&
 722     ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
 723     // Must compare same value
 724     ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
 725     ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
 726 }
 727 
 728 // Do this If and the dominating If share a region?
 729 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
 730   ProjNode* otherproj = proj->other_if_proj();
 731   Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
 732   RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
 733   success = NULL;
 734   fail = NULL;
 735       
 736   if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
 737     for (int i = 0; i < 2; i++) {
 738       ProjNode* proj = proj_out(i);
 739       if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 740         success = proj;
 741       } else if (fail == NULL) {
 742         fail = proj;
 743       } else {
 744         success = fail = NULL;
 745       }
 746     }
 747   }
 748   return success != NULL && fail != NULL;
 749 }
 750 
 751 // Return projection that leads to an uncommon trap if any
 752 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
 753   for (int i = 0; i < 2; i++) {
 754     call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
 755     if (call != NULL) {
 756       return proj_out(i);
 757     }
 758   }
 759   return NULL;
 760 }
 761 
 762 // Do this If and the dominating If both branch out to an uncommon trap
 763 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
 764   ProjNode* otherproj = proj->other_if_proj();
 765   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
 766 
 767   if (otherproj->outcnt() == 1 && dom_unc != NULL) {
 768     CallStaticJavaNode* unc = NULL;
 769     ProjNode* unc_proj = uncommon_trap_proj(unc);
 770     if (unc_proj != NULL && unc_proj->outcnt() == 1) {
 771       if (dom_unc == unc) {
 772         // Allow the uncommon trap to be shared through a region
 773         RegionNode* r = unc->in(0)->as_Region();
 774         if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
 775           return false;
 776         }
 777         assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
 778       } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
 779         return false;
 780       }
 781       // See merge_uncommon_traps: the reason of the uncmmon trap will
 782       // be changed and the state of the dominating If will be
 783       // used. Checked that we didn't apply this transformation in a
 784       // previous compilation and it didn't cause too many traps
 785       if (!igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_unstable_fused_if) &&
 786           !igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_range_check)) {
 787         success = unc_proj;
 788         fail = unc_proj->other_if_proj();
 789         return true;
 790       }
 791     }
 792   }
 793   return false;
 794 }
 795 
 796 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
 797 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 798   Node* this_cmp = in(1)->in(1);
 799   BoolNode* this_bool = in(1)->as_Bool();
 800   IfNode* dom_iff = proj->in(0)->as_If();
 801   BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 802   Node* lo = dom_iff->in(1)->in(1)->in(2);
 803   Node* hi = this_cmp->in(2);
 804   Node* n = this_cmp->in(1);
 805   ProjNode* otherproj = proj->other_if_proj();
 806 
 807   const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
 808   const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
 809 
 810   BoolTest::mask lo_test = dom_bool->_test._test;
 811   BoolTest::mask hi_test = this_bool->_test._test;
 812   BoolTest::mask cond = hi_test;
 813 
 814   // Figure out which of the two tests sets the upper bound and which
 815   // sets the lower bound if any.
 816   if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
 817             
 818     assert(((lo_test == BoolTest::le || lo_test == BoolTest::lt) && !proj->_con) ||
 819            ((lo_test == BoolTest::ge || lo_test == BoolTest::gt) && proj->_con), "incorrect test");
 820     // this test was canonicalized
 821     assert((hi_test == BoolTest::le || hi_test == BoolTest::lt) && fail->_con, "incorrect test");
 822 
 823     if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 824       lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 825     }
 826   } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
 827     swap(lo, hi);
 828     swap(lo_type, hi_type);
 829     swap(lo_test, hi_test);
 830 
 831     assert(((hi_test == BoolTest::le || hi_test == BoolTest::lt) && proj->_con) ||
 832            ((hi_test == BoolTest::ge || hi_test == BoolTest::gt) && !proj->_con), "incorrect test");
 833     // this test was canonicalized
 834     assert((lo_test == BoolTest::le || lo_test == BoolTest::lt) && !fail->_con, "incorrect test");
 835             
 836     cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
 837 
 838     if (lo_test == BoolTest::le) {
 839       lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 840     }
 841 
 842   } else {
 843     const TypeInt* failtype  = filtered_int_type(igvn, n, proj);
 844     if (failtype != NULL) {
 845       const TypeInt* type2 = filtered_int_type(igvn, n, fail);
 846       if (type2 != NULL) {
 847         failtype = failtype->join(type2)->is_int();
 848         if (failtype->_lo > failtype->_hi) {
 849           // previous if determines the result of this if so
 850           // replace Bool with constant
 851           igvn->hash_delete(this);
 852           set_req(1, igvn->intcon(success->_con));
 853           return true;
 854         }
 855       }
 856     }
 857 
 858     lo = NULL;
 859     hi = NULL;
 860   }
 861 
 862   if (lo && hi) {
 863     // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
 864     Node* adjusted_val = igvn->transform(new SubINode(n,  lo));
 865     Node* adjusted_lim = igvn->transform(new SubINode(hi, lo));
 866     Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
 867     Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
 868 
 869     igvn->is_IterGVN()->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
 870     igvn->hash_delete(this);
 871     set_req(1, newbool);
 872 
 873     return true;
 874   }
 875   return false;
 876 }
 877 
 878 // Merge the branches that trap for this If and the dominating If into
 879 // a single region that branches to the uncommon trap for the
 880 // dominating If
 881 void IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 882   ProjNode* otherproj = proj->other_if_proj();
 883   
 884   CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
 885   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
 886   
 887   if (unc != dom_unc) {
 888     Node* r = new RegionNode(3);
 889 
 890     r->set_req(1, otherproj);
 891     r->set_req(2, success);
 892     r = igvn->transform(r);
 893     assert(r->is_Region(), "can't go away");
 894   
 895     // Make both If trap at the state of the first If: once the CmpI
 896     // nodes are merged, if we trap we don't know which of the CmpI
 897     // nodes would have caused the trap so we have to restart
 898     // execution at the first one
 899     igvn->replace_input_of(dom_unc, 0, r);
 900     igvn->replace_input_of(unc, 0, igvn->C->top());
 901   }
 902   int trap_request = dom_unc->uncommon_trap_request();
 903   Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
 904   Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
 905 
 906   int flip_test = 0;
 907   Node* l = NULL;
 908   Node* r = NULL;
 909 
 910   if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
 911     // If this looks like a range check, change the trap to
 912     // Reason_range_check so the compiler recognizes it as a range
 913     // check and applies the corresponding optimizations
 914     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
 915     
 916     improve_address_types(l, r, fail, igvn);
 917   } else if (unc != dom_unc) {
 918     // If we trap we won't know what CmpI would have caused the trap
 919     // so use a special trap reason to mark this pair of CmpI nodes as
 920     // bad candidate for folding. On recompilation we won't fold them
 921     // and we may trap again but this time we'll know what branch
 922     // traps
 923     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
 924   }
 925   igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
 926 }
 927 
 928 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
 929 // of a rangecheck on index i, on 64 bit the compares may be followed
 930 // by memory accesses using i as index. In that case, the CmpU tells
 931 // us something about the values taken by i that can help the compiler
 932 // (see Compile::conv_I2X_index())
 933 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
 934 #ifdef _LP64
 935   ResourceMark rm;
 936   Node_Stack stack(2);
 937 
 938   assert(r->Opcode() == Op_LoadRange, "unexpected range check");
 939   const TypeInt* array_size = igvn->type(r)->is_int();
 940 
 941   stack.push(l, 0);
 942     
 943   while(stack.size() > 0) {
 944     Node* n = stack.node();
 945     uint start = stack.index();
 946 
 947     uint i = start;
 948     for (; i < n->outcnt(); i++) {
 949       Node* use = n->raw_out(i);
 950       if (stack.size() == 1) {
 951         if (use->Opcode() == Op_ConvI2L) {
 952           const TypeLong* bounds = use->as_Type()->type()->is_long();
 953           if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
 954               (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
 955             stack.set_index(i+1);
 956             stack.push(use, 0);
 957             break;
 958           }
 959         }
 960       } else if (use->is_Mem()) {
 961         Node* ctrl = use->in(0);
 962         if (ctrl == fail) {
 963           Node* init_n = stack.node_at(1);
 964           assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
 965           Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size);
 966 
 967           for (uint j = 2; j < stack.size(); j++) {
 968             Node* n = stack.node_at(j);
 969             Node* clone = n->clone();
 970             int rep = clone->replace_edge(init_n, new_n);
 971             assert(rep > 0, "can't find expected node?");
 972             clone = igvn->transform(clone);
 973             init_n = n;
 974             new_n = clone;
 975           }
 976           igvn->hash_delete(use);
 977           int rep = use->replace_edge(init_n, new_n);
 978           assert(rep > 0, "can't find expected node?");
 979           igvn->transform(use);
 980           if (init_n->outcnt() == 0) {
 981             igvn->_worklist.push(init_n);
 982           }
 983         }
 984       } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
 985                                         igvn->type(use)->isa_ptr())) {
 986         stack.set_index(i+1);
 987         stack.push(use, 0);
 988         break;
 989       }
 990     }
 991     if (i == n->outcnt()) {
 992       stack.pop();
 993     }
 994   }
 995 #endif
 996 }
 997 
 998 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
 999   if (in(1) != NULL &&
1000       in(1)->in(1) != NULL &&
1001       in(1)->in(1)->in(2) != NULL) {
1002     Node* other = in(1)->in(1)->in(2);
1003     if (other->Opcode() == Op_LoadRange &&
1004         ((other->in(0) != NULL && other->in(0) == proj) ||
1005          (other->in(0) == NULL &&
1006           other->in(2) != NULL &&
1007           other->in(2)->is_AddP() &&
1008           other->in(2)->in(1) != NULL &&
1009           other->in(2)->in(1)->Opcode() == Op_CastPP &&
1010           other->in(2)->in(1)->in(0) == proj))) {
1011       return true;
1012     }
1013   }
1014   return false;
1015 }
1016 
1017 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1018   Node* other = in(1)->in(1)->in(2);
1019   if (other->in(MemNode::Address) != NULL &&
1020       proj->in(0)->in(1) != NULL &&
1021       proj->in(0)->in(1)->is_Bool() &&
1022       proj->in(0)->in(1)->in(1) != NULL &&
1023       proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1024       proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1025       proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1026       igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1027     return true;
1028   }
1029   return false;
1030 }
1031 
1032 // Check that the If that is in between the 2 integer comparisons has
1033 // no side effect
1034 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1035   if (proj != NULL &&
1036       proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1037       proj->outcnt() <= 2) {
1038     if (proj->outcnt() == 1 ||
1039         // Allow simple null check from LoadRange
1040         (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1041       CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1042       CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1043 
1044       // reroute_side_effect_free_unc changes the state of this
1045       // uncommon trap to restart execution at the previous
1046       // CmpI. Check that this change in a previous compilation didn't
1047       // cause too many traps.
1048       int trap_request = unc->uncommon_trap_request();
1049       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1050       
1051       if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1052         return false;
1053       }
1054 
1055       return true;
1056     }
1057   }
1058   return false;
1059 }
1060 
1061 // Make the If between the 2 integer comparisons trap at the state of
1062 // the first If: the last CmpI is the one replaced by a CmpU and the
1063 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1064 // won't be guarded by the first CmpI anymore. It can trap in cases
1065 // where the first CmpI would have prevented it from executing: on a
1066 // trap, we need to restart execution at the state of the first CmpI
1067 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1068   CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1069   ProjNode* otherproj = proj->other_if_proj();
1070   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1071   
1072   CallStaticJavaNode* new_unc = dom_unc->clone()->as_CallStaticJava();
1073   Node* call_proj = dom_unc->unique_ctrl_out();
1074   Node* halt = call_proj->unique_ctrl_out();
1075 
1076   call_proj = call_proj->clone();
1077   halt = halt->clone();
1078   Node* c = otherproj->clone();
1079   new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1080   new_unc->set_req(0, c);
1081   call_proj->set_req(0, new_unc);
1082   halt->set_req(0, call_proj);
1083 
1084   igvn->replace_node(otherproj, igvn->C->top());
1085 
1086   igvn->transform(c);
1087   igvn->transform(new_unc);
1088   igvn->transform(call_proj);
1089   igvn->transform(halt);
1090 
1091   igvn->C->root()->add_req(halt);
1092 }
1093 
1094 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1095   if (Opcode() != Op_If) return NULL;
1096 
1097   if (cmpi_folds(igvn)) {
1098     Node* ctrl = in(0);
1099     if (is_ctrl_folds(ctrl, igvn) &&
1100         ctrl->outcnt() == 1) {
1101       // A integer comparison immediately dominated by another integer
1102       // comparison
1103       ProjNode* success = NULL;
1104       ProjNode* fail = NULL;
1105       ProjNode* dom_cmp = ctrl->as_Proj();
1106       if (has_shared_region(dom_cmp, success, fail) &&
1107           // Next call modifies graph so must be last
1108           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1109         return this;
1110       }
1111       if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1112           // Next call modifies graph so must be last
1113           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1114         merge_uncommon_traps(dom_cmp, success, fail, igvn);
1115         return this;
1116       }
1117       return NULL;
1118     } else if (ctrl->in(0) != NULL &&
1119                ctrl->in(0)->in(0) != NULL) {
1120       ProjNode* success = NULL;
1121       ProjNode* fail = NULL;
1122       Node* dom = ctrl->in(0)->in(0);
1123       ProjNode* dom_cmp = dom->isa_Proj();
1124       ProjNode* other_cmp = ctrl->isa_Proj();
1125 
1126       // Check if it's an integer comparison dominated by another
1127       // integer comparison with another test in between
1128       if (is_ctrl_folds(dom, igvn) &&
1129           has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1130           is_side_effect_free_test(other_cmp, igvn) &&
1131           // Next call modifies graph so must be last
1132           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1133         reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1134         merge_uncommon_traps(dom_cmp, success, fail, igvn);          
1135         return this;
1136       }
1137     }
1138   }
1139   return NULL;
1140 }
1141 
1142 //------------------------------remove_useless_bool----------------------------
1143 // Check for people making a useless boolean: things like
1144 // if( (x < y ? true : false) ) { ... }
1145 // Replace with if( x < y ) { ... }
1146 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1147   Node *i1 = iff->in(1);
1148   if( !i1->is_Bool() ) return NULL;
1149   BoolNode *bol = i1->as_Bool();
1150 
1151   Node *cmp = bol->in(1);
1152   if( cmp->Opcode() != Op_CmpI ) return NULL;
1153 
1154   // Must be comparing against a bool
1155   const Type *cmp2_t = phase->type( cmp->in(2) );
1156   if( cmp2_t != TypeInt::ZERO &&
1157       cmp2_t != TypeInt::ONE )
1158     return NULL;
1159 
1160   // Find a prior merge point merging the boolean
1161   i1 = cmp->in(1);
1162   if( !i1->is_Phi() ) return NULL;
1163   PhiNode *phi = i1->as_Phi();
1164   if( phase->type( phi ) != TypeInt::BOOL )
1165     return NULL;
1166 
1167   // Check for diamond pattern
1168   int true_path = phi->is_diamond_phi();
1169   if( true_path == 0 ) return NULL;
1170 
1171   // Make sure that iff and the control of the phi are different. This
1172   // should really only happen for dead control flow since it requires
1173   // an illegal cycle.
1174   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1175 
1176   // phi->region->if_proj->ifnode->bool->cmp
1177   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1178 
1179   // Now get the 'sense' of the test correct so we can plug in
1180   // either iff2->in(1) or its complement.
1181   int flip = 0;
1182   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1183   else if( bol->_test._test != BoolTest::eq ) return NULL;
1184   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1185 
1186   const Type *phi1_t = phase->type( phi->in(1) );
1187   const Type *phi2_t = phase->type( phi->in(2) );
1188   // Check for Phi(0,1) and flip
1189   if( phi1_t == TypeInt::ZERO ) {
1190     if( phi2_t != TypeInt::ONE ) return NULL;
1191     flip = 1-flip;
1192   } else {
1193     // Check for Phi(1,0)
1194     if( phi1_t != TypeInt::ONE  ) return NULL;
1195     if( phi2_t != TypeInt::ZERO ) return NULL;
1196   }
1197   if( true_path == 2 ) {
1198     flip = 1-flip;
1199   }
1200 
1201   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1202   assert(new_bol != iff->in(1), "must make progress");
1203   iff->set_req(1, new_bol);
1204   // Intervening diamond probably goes dead
1205   phase->C->set_major_progress();
1206   return iff;
1207 }
1208 
1209 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1210 
1211 struct RangeCheck {
1212   Node* ctl;
1213   jint off;
1214 };
1215 
1216 //------------------------------Ideal------------------------------------------
1217 // Return a node which is more "ideal" than the current node.  Strip out
1218 // control copies
1219 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1220   if (remove_dead_region(phase, can_reshape))  return this;
1221   // No Def-Use info?
1222   if (!can_reshape)  return NULL;
1223   PhaseIterGVN *igvn = phase->is_IterGVN();
1224 
1225   // Don't bother trying to transform a dead if
1226   if (in(0)->is_top())  return NULL;
1227   // Don't bother trying to transform an if with a dead test
1228   if (in(1)->is_top())  return NULL;
1229   // Another variation of a dead test
1230   if (in(1)->is_Con())  return NULL;
1231   // Another variation of a dead if
1232   if (outcnt() < 2)  return NULL;
1233 
1234   // Canonicalize the test.
1235   Node* idt_if = idealize_test(phase, this);
1236   if (idt_if != NULL)  return idt_if;
1237 
1238   // Try to split the IF
1239   Node *s = split_if(this, igvn);
1240   if (s != NULL)  return s;
1241 
1242   // Check for people making a useless boolean: things like
1243   // if( (x < y ? true : false) ) { ... }
1244   // Replace with if( x < y ) { ... }
1245   Node *bol2 = remove_useless_bool(this, phase);
1246   if( bol2 ) return bol2;
1247 
1248   // Setup to scan up the CFG looking for a dominating test
1249   Node *dom = in(0);
1250   Node *prev_dom = this;
1251 
1252   // Check for range-check vs other kinds of tests
1253   Node *index1, *range1;
1254   jint offset1;
1255   int flip1 = is_range_check(range1, index1, offset1);
1256   if( flip1 ) {
1257     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
1258     // so all checks we inspect post-dominate the top-most check we find.
1259     // If we are going to fail the current check and we reach the top check
1260     // then we are guaranteed to fail, so just start interpreting there.
1261     // We 'expand' the top 3 range checks to include all post-dominating
1262     // checks.
1263 
1264     // The top 3 range checks seen
1265     const int NRC =3;
1266     RangeCheck prev_checks[NRC];
1267     int nb_checks = 0;
1268 
1269     // Low and high offsets seen so far
1270     jint off_lo = offset1;
1271     jint off_hi = offset1;
1272 
1273     bool found_immediate_dominator = false;
1274 
1275     // Scan for the top checks and collect range of offsets
1276     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1277       if (dom->Opcode() == Op_If &&  // Not same opcode?
1278           prev_dom->in(0) == dom) { // One path of test does dominate?
1279         if (dom == this) return NULL; // dead loop
1280         // See if this is a range check
1281         Node *index2, *range2;
1282         jint offset2;
1283         int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
1284         // See if this is a _matching_ range check, checking against
1285         // the same array bounds.
1286         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1287             dom->outcnt() == 2) {
1288           if (nb_checks == 0 && dom->in(1) == in(1)) {
1289             // Found an immediately dominating test at the same offset.
1290             // This kind of back-to-back test can be eliminated locally,
1291             // and there is no need to search further for dominating tests.
1292             assert(offset2 == offset1, "Same test but different offsets");
1293             found_immediate_dominator = true;
1294             break;
1295           }
1296           // Gather expanded bounds
1297           off_lo = MIN2(off_lo,offset2);
1298           off_hi = MAX2(off_hi,offset2);
1299           // Record top NRC range checks
1300           prev_checks[nb_checks%NRC].ctl = prev_dom;
1301           prev_checks[nb_checks%NRC].off = offset2;
1302           nb_checks++;
1303         }
1304       }
1305       prev_dom = dom;
1306       dom = up_one_dom(dom);
1307       if (!dom) break;
1308     }
1309 
1310     if (!found_immediate_dominator) {
1311       // Attempt to widen the dominating range check to cover some later
1312       // ones.  Since range checks "fail" by uncommon-trapping to the
1313       // interpreter, widening a check can make us speculatively enter
1314       // the interpreter.  If we see range-check deopt's, do not widen!
1315       if (!phase->C->allow_range_check_smearing())  return NULL;
1316 
1317       // Didn't find prior covering check, so cannot remove anything.
1318       if (nb_checks == 0) {
1319         return NULL;
1320       }
1321       // Constant indices only need to check the upper bound.
1322       // Non-constant indices must check both low and high.
1323       int chk0 = (nb_checks - 1) % NRC;
1324       if (index1) {
1325         if (nb_checks == 1) {
1326           return NULL;
1327         } else {
1328           // If the top range check's constant is the min or max of
1329           // all constants we widen the next one to cover the whole
1330           // range of constants.
1331           RangeCheck rc0 = prev_checks[chk0];
1332           int chk1 = (nb_checks - 2) % NRC;
1333           RangeCheck rc1 = prev_checks[chk1];
1334           if (rc0.off == off_lo) {
1335             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1336             prev_dom = rc1.ctl;
1337           } else if (rc0.off == off_hi) {
1338             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1339             prev_dom = rc1.ctl;
1340           } else {
1341             // If the top test's constant is not the min or max of all
1342             // constants, we need 3 range checks. We must leave the
1343             // top test unchanged because widening it would allow the
1344             // accesses it protects to successfully read/write out of
1345             // bounds.
1346             if (nb_checks == 2) {
1347               return NULL;
1348             }
1349             int chk2 = (nb_checks - 3) % NRC;
1350             RangeCheck rc2 = prev_checks[chk2];
1351             // The top range check a+i covers interval: -a <= i < length-a
1352             // The second range check b+i covers interval: -b <= i < length-b
1353             if (rc1.off <= rc0.off) {
1354               // if b <= a, we change the second range check to:
1355               // -min_of_all_constants <= i < length-min_of_all_constants
1356               // Together top and second range checks now cover:
1357               // -min_of_all_constants <= i < length-a
1358               // which is more restrictive than -b <= i < length-b:
1359               // -b <= -min_of_all_constants <= i < length-a <= length-b
1360               // The third check is then changed to:
1361               // -max_of_all_constants <= i < length-max_of_all_constants
1362               // so 2nd and 3rd checks restrict allowed values of i to:
1363               // -min_of_all_constants <= i < length-max_of_all_constants
1364               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1365               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1366             } else {
1367               // if b > a, we change the second range check to:
1368               // -max_of_all_constants <= i < length-max_of_all_constants
1369               // Together top and second range checks now cover:
1370               // -a <= i < length-max_of_all_constants
1371               // which is more restrictive than -b <= i < length-b:
1372               // -b < -a <= i < length-max_of_all_constants <= length-b
1373               // The third check is then changed to:
1374               // -max_of_all_constants <= i < length-max_of_all_constants
1375               // so 2nd and 3rd checks restrict allowed values of i to:
1376               // -min_of_all_constants <= i < length-max_of_all_constants
1377               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1378               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1379             }
1380             prev_dom = rc2.ctl;
1381           }
1382         }
1383       } else {
1384         RangeCheck rc0 = prev_checks[chk0];
1385         // 'Widen' the offset of the 1st and only covering check
1386         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1387         // Test is now covered by prior checks, dominate it out
1388         prev_dom = rc0.ctl;
1389       }
1390     }
1391 
1392   } else {                      // Scan for an equivalent test
1393 
1394     Node *cmp;
1395     int dist = 0;               // Cutoff limit for search
1396     int op = Opcode();
1397     if( op == Op_If &&
1398         (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1399       if( cmp->in(2) != NULL && // make sure cmp is not already dead
1400           cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1401         dist = 64;              // Limit for null-pointer scans
1402       } else {
1403         dist = 4;               // Do not bother for random pointer tests
1404       }
1405     } else {
1406       dist = 4;                 // Limit for random junky scans
1407     }
1408 
1409     // Normal equivalent-test check.
1410     if( !dom ) return NULL;     // Dead loop?
1411 
1412     Node* result = fold_compares(igvn);
1413     if (result != NULL) {
1414       return result;
1415     }
1416 
1417     // Search up the dominator tree for an If with an identical test
1418     while( dom->Opcode() != op    ||  // Not same opcode?
1419            dom->in(1)    != in(1) ||  // Not same input 1?
1420            (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1421            prev_dom->in(0) != dom ) { // One path of test does not dominate?
1422       if( dist < 0 ) return NULL;
1423 
1424       dist--;
1425       prev_dom = dom;
1426       dom = up_one_dom( dom );
1427       if( !dom ) return NULL;
1428     }
1429 
1430     // Check that we did not follow a loop back to ourselves
1431     if( this == dom )
1432       return NULL;
1433 
1434     if( dist > 2 )              // Add to count of NULL checks elided
1435       explicit_null_checks_elided++;
1436 
1437   } // End of Else scan for an equivalent test
1438 
1439   // Hit!  Remove this IF
1440 #ifndef PRODUCT
1441   if( TraceIterativeGVN ) {
1442     tty->print("   Removing IfNode: "); this->dump();
1443   }
1444   if( VerifyOpto && !phase->allow_progress() ) {
1445     // Found an equivalent dominating test,
1446     // we can not guarantee reaching a fix-point for these during iterativeGVN
1447     // since intervening nodes may not change.
1448     return NULL;
1449   }
1450 #endif
1451 
1452   // Replace dominated IfNode
1453   dominated_by( prev_dom, igvn );
1454 
1455   // Must return either the original node (now dead) or a new node
1456   // (Do not return a top here, since that would break the uniqueness of top.)
1457   return new ConINode(TypeInt::ZERO);
1458 }
1459 
1460 //------------------------------dominated_by-----------------------------------
1461 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1462   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1463   Node *idom = in(0);
1464   // Need opcode to decide which way 'this' test goes
1465   int prev_op = prev_dom->Opcode();
1466   Node *top = igvn->C->top(); // Shortcut to top
1467 
1468   // Loop predicates may have depending checks which should not
1469   // be skipped. For example, range check predicate has two checks
1470   // for lower and upper bounds.
1471   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1472   if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1473    prev_dom = idom;
1474 
1475   // Now walk the current IfNode's projections.
1476   // Loop ends when 'this' has no more uses.
1477   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1478     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1479     igvn->add_users_to_worklist(ifp);
1480     // Check which projection it is and set target.
1481     // Data-target is either the dominating projection of the same type
1482     // or TOP if the dominating projection is of opposite type.
1483     // Data-target will be used as the new control edge for the non-CFG
1484     // nodes like Casts and Loads.
1485     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1486     // Control-target is just the If's immediate dominator or TOP.
1487     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1488 
1489     // For each child of an IfTrue/IfFalse projection, reroute.
1490     // Loop ends when projection has no more uses.
1491     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1492       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1493       if( !s->depends_only_on_test() ) {
1494         // Find the control input matching this def-use edge.
1495         // For Regions it may not be in slot 0.
1496         uint l;
1497         for( l = 0; s->in(l) != ifp; l++ ) { }
1498         igvn->replace_input_of(s, l, ctrl_target);
1499       } else {                      // Else, for control producers,
1500         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1501       }
1502     } // End for each child of a projection
1503 
1504     igvn->remove_dead_node(ifp);
1505   } // End for each IfTrue/IfFalse child of If
1506 
1507   // Kill the IfNode
1508   igvn->remove_dead_node(this);
1509 }
1510 
1511 //------------------------------Identity---------------------------------------
1512 // If the test is constant & we match, then we are the input Control
1513 Node *IfProjNode::Identity(PhaseTransform *phase) {
1514   // Can only optimize if cannot go the other way
1515   const TypeTuple *t = phase->type(in(0))->is_tuple();
1516   if (t == TypeTuple::IFNEITHER ||
1517       // kill dead branch first otherwise the IfNode's control will
1518       // have 2 control uses (the IfNode that doesn't go away because
1519       // it still has uses and this branch of the
1520       // If). Node::has_special_unique_user() will cause this node to
1521       // be reprocessed once the dead branch is killed.
1522       (always_taken(t) && in(0)->outcnt() == 1)) {
1523     // IfNode control
1524     return in(0)->in(0);
1525   }
1526   // no progress
1527   return this;
1528 }
1529 
1530 //------------------------------dump_spec--------------------------------------
1531 #ifndef PRODUCT
1532 void IfNode::dump_spec(outputStream *st) const {
1533   st->print("P=%f, C=%f",_prob,_fcnt);
1534 }
1535 #endif
1536 
1537 //------------------------------idealize_test----------------------------------
1538 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1539 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1540 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1541 // needed.
1542 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1543   assert(iff->in(0) != NULL, "If must be live");
1544 
1545   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1546   Node* old_if_f = iff->proj_out(false);
1547   Node* old_if_t = iff->proj_out(true);
1548 
1549   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1550   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1551   // happens in count-down loops
1552   if (iff->is_CountedLoopEnd())  return NULL;
1553   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1554   BoolNode *b = iff->in(1)->as_Bool();
1555   BoolTest bt = b->_test;
1556   // Test already in good order?
1557   if( bt.is_canonical() )
1558     return NULL;
1559 
1560   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1561   // cloning the IfNode.
1562   Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1563   if( !new_b->is_Bool() ) return NULL;
1564   b = new_b->as_Bool();
1565 
1566   PhaseIterGVN *igvn = phase->is_IterGVN();
1567   assert( igvn, "Test is not canonical in parser?" );
1568 
1569   // The IF node never really changes, but it needs to be cloned
1570   iff = new IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1571 
1572   Node *prior = igvn->hash_find_insert(iff);
1573   if( prior ) {
1574     igvn->remove_dead_node(iff);
1575     iff = (IfNode*)prior;
1576   } else {
1577     // Cannot call transform on it just yet
1578     igvn->set_type_bottom(iff);
1579   }
1580   igvn->_worklist.push(iff);
1581 
1582   // Now handle projections.  Cloning not required.
1583   Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1584   Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1585 
1586   igvn->register_new_node_with_optimizer(new_if_f);
1587   igvn->register_new_node_with_optimizer(new_if_t);
1588   // Flip test, so flip trailing control
1589   igvn->replace_node(old_if_f, new_if_t);
1590   igvn->replace_node(old_if_t, new_if_f);
1591 
1592   // Progress
1593   return iff;
1594 }