1 /*
   2  * Copyright (c) 2000, 2016, 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 "ci/ciTypeFlow.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "memory/resourceArea.hpp"
  29 #include "opto/addnode.hpp"
  30 #include "opto/castnode.hpp"
  31 #include "opto/cfgnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/loopnode.hpp"
  34 #include "opto/phaseX.hpp"
  35 #include "opto/runtime.hpp"
  36 #include "opto/rootnode.hpp"
  37 #include "opto/subnode.hpp"
  38 
  39 // Portions of code courtesy of Clifford Click
  40 
  41 // Optimization - Graph Style
  42 
  43 
  44 #ifndef PRODUCT
  45 extern int explicit_null_checks_elided;
  46 #endif
  47 
  48 //=============================================================================
  49 //------------------------------Value------------------------------------------
  50 // Return a tuple for whichever arm of the IF is reachable
  51 const Type* IfNode::Value(PhaseGVN* phase) const {
  52   if( !in(0) ) return Type::TOP;
  53   if( phase->type(in(0)) == Type::TOP )
  54     return Type::TOP;
  55   const Type *t = phase->type(in(1));
  56   if( t == Type::TOP )          // data is undefined
  57     return TypeTuple::IFNEITHER; // unreachable altogether
  58   if( t == TypeInt::ZERO )      // zero, or false
  59     return TypeTuple::IFFALSE;  // only false branch is reachable
  60   if( t == TypeInt::ONE )       // 1, or true
  61     return TypeTuple::IFTRUE;   // only true branch is reachable
  62   assert( t == TypeInt::BOOL, "expected boolean type" );
  63 
  64   return TypeTuple::IFBOTH;     // No progress
  65 }
  66 
  67 const RegMask &IfNode::out_RegMask() const {
  68   return RegMask::Empty;
  69 }
  70 
  71 //------------------------------split_if---------------------------------------
  72 // Look for places where we merge constants, then test on the merged value.
  73 // If the IF test will be constant folded on the path with the constant, we
  74 // win by splitting the IF to before the merge point.
  75 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  76   // I could be a lot more general here, but I'm trying to squeeze this
  77   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  78   // on the patterns I accept.  CNC
  79 
  80   // Look for a compare of a constant and a merged value
  81   Node *i1 = iff->in(1);
  82   if( !i1->is_Bool() ) return NULL;
  83   BoolNode *b = i1->as_Bool();
  84   Node *cmp = b->in(1);
  85   if( !cmp->is_Cmp() ) return NULL;
  86   i1 = cmp->in(1);
  87   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  88   PhiNode *phi = i1->as_Phi();
  89   if( phi->is_copy() ) return NULL;
  90   Node *con2 = cmp->in(2);
  91   if( !con2->is_Con() ) return NULL;
  92   // See that the merge point contains some constants
  93   Node *con1=NULL;
  94   uint i4;
  95   for( i4 = 1; i4 < phi->req(); i4++ ) {
  96     con1 = phi->in(i4);
  97     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
  98     if( con1->is_Con() ) break; // Found a constant
  99     // Also allow null-vs-not-null checks
 100     const TypePtr *tp = igvn->type(con1)->isa_ptr();
 101     if( tp && tp->_ptr == TypePtr::NotNull )
 102       break;
 103   }
 104   if( i4 >= phi->req() ) return NULL; // Found no constants
 105 
 106   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 107 
 108   // Make sure that the compare can be constant folded away
 109   Node *cmp2 = cmp->clone();
 110   cmp2->set_req(1,con1);
 111   cmp2->set_req(2,con2);
 112   const Type *t = cmp2->Value(igvn);
 113   // This compare is dead, so whack it!
 114   igvn->remove_dead_node(cmp2);
 115   if( !t->singleton() ) return NULL;
 116 
 117   // No intervening control, like a simple Call
 118   Node *r = iff->in(0);
 119   if( !r->is_Region() ) return NULL;
 120   if( phi->region() != r ) return NULL;
 121   // No other users of the cmp/bool
 122   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 123     //tty->print_cr("many users of cmp/bool");
 124     return NULL;
 125   }
 126 
 127   // Make sure we can determine where all the uses of merged values go
 128   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 129     Node* u = r->fast_out(j);
 130     if( u == r ) continue;
 131     if( u == iff ) continue;
 132     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 133     if( !u->is_Phi() ) {
 134       /*
 135       if( u->is_Start() ) {
 136         tty->print_cr("Region has inlined start use");
 137       } else {
 138         tty->print_cr("Region has odd use");
 139         u->dump(2);
 140       }*/
 141       return NULL;
 142     }
 143     if( u != phi ) {
 144       // CNC - do not allow any other merged value
 145       //tty->print_cr("Merging another value");
 146       //u->dump(2);
 147       return NULL;
 148     }
 149     // Make sure we can account for all Phi uses
 150     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 151       Node* v = u->fast_out(k); // User of the phi
 152       // CNC - Allow only really simple patterns.
 153       // In particular I disallow AddP of the Phi, a fairly common pattern
 154       if (v == cmp) continue;  // The compare is OK
 155       if (v->is_ConstraintCast()) {
 156         // If the cast is derived from data flow edges, it may not have a control edge.
 157         // If so, it should be safe to split. But follow-up code can not deal with
 158         // this (l. 359). So skip.
 159         if (v->in(0) == NULL) {
 160           return NULL;
 161         }
 162         if (v->in(0)->in(0) == iff) {
 163           continue;               // CastPP/II of the IfNode is OK
 164         }
 165       }
 166       // Disabled following code because I cannot tell if exactly one
 167       // path dominates without a real dominator check. CNC 9/9/1999
 168       //uint vop = v->Opcode();
 169       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 170       //  Node *r = v->in(0);     // Get controlling point
 171       //  if( !r ) return NULL;   // Degraded to a copy
 172       //  // Find exactly one path in (either True or False doms, but not IFF)
 173       //  int cnt = 0;
 174       //  for( uint i = 1; i < r->req(); i++ )
 175       //    if( r->in(i) && r->in(i)->in(0) == iff )
 176       //      cnt++;
 177       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 178       //}
 179       if( !v->is_Call() ) {
 180         /*
 181         if( v->Opcode() == Op_AddP ) {
 182           tty->print_cr("Phi has AddP use");
 183         } else if( v->Opcode() == Op_CastPP ) {
 184           tty->print_cr("Phi has CastPP use");
 185         } else if( v->Opcode() == Op_CastII ) {
 186           tty->print_cr("Phi has CastII use");
 187         } else {
 188           tty->print_cr("Phi has use I cant be bothered with");
 189         }
 190         */
 191       }
 192       return NULL;
 193 
 194       /* CNC - Cut out all the fancy acceptance tests
 195       // Can we clone this use when doing the transformation?
 196       // If all uses are from Phis at this merge or constants, then YES.
 197       if( !v->in(0) && v != cmp ) {
 198         tty->print_cr("Phi has free-floating use");
 199         v->dump(2);
 200         return NULL;
 201       }
 202       for( uint l = 1; l < v->req(); l++ ) {
 203         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 204             !v->in(l)->is_Con() ) {
 205           tty->print_cr("Phi has use");
 206           v->dump(2);
 207           return NULL;
 208         } // End of if Phi-use input is neither Phi nor Constant
 209       } // End of for all inputs to Phi-use
 210       */
 211     } // End of for all uses of Phi
 212   } // End of for all uses of Region
 213 
 214   // Only do this if the IF node is in a sane state
 215   if (iff->outcnt() != 2)
 216     return NULL;
 217 
 218   // Got a hit!  Do the Mondo Hack!
 219   //
 220   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 221   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 222   //     cmp - 2                         cmp - 2               cmp - 2
 223   //       bool                            bool_c                bool_x
 224   //       if                               if_c                  if_x
 225   //      T  F                              T  F                  T  F
 226   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 227   //
 228   // Split the paths coming into the merge point into 2 separate groups of
 229   // merges.  On the left will be all the paths feeding constants into the
 230   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 231   // will fold up into a constant; this will let the Cmp fold up as well as
 232   // all the control flow.  Below the original IF we have 2 control
 233   // dependent regions, 's' and 't'.  Now we will merge the two paths
 234   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 235   // likely 2 or more) will promptly constant fold away.
 236   PhaseGVN *phase = igvn;
 237 
 238   // Make a region merging constants and a region merging the rest
 239   uint req_c = 0;
 240   Node* predicate_proj = NULL;
 241   int nb_predicate_proj = 0;
 242   for (uint ii = 1; ii < r->req(); ii++) {
 243     if (phi->in(ii) == con1) {
 244       req_c++;
 245     }
 246     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
 247     if (proj != NULL) {
 248       nb_predicate_proj++;
 249       predicate_proj = proj;
 250     }
 251   }
 252 
 253   // If all the defs of the phi are the same constant, we already have the desired end state.
 254   // Skip the split that would create empty phi and region nodes.
 255   if((r->req() - req_c) == 1) {
 256     return NULL;
 257   }
 258 
 259   if (nb_predicate_proj > 1) {
 260     // Can happen in case of loop unswitching and when the loop is
 261     // optimized out: it's not a loop anymore so we don't care about
 262     // predicates.
 263     assert(!r->is_Loop(), "this must not be a loop anymore");
 264     predicate_proj = NULL;
 265   }
 266   Node* predicate_c = NULL;
 267   Node* predicate_x = NULL;
 268   bool counted_loop = r->is_CountedLoop();
 269 
 270   Node *region_c = new RegionNode(req_c + 1);
 271   Node *phi_c    = con1;
 272   uint  len      = r->req();
 273   Node *region_x = new RegionNode(len - req_c);
 274   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 275   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 276     if (phi->in(i) == con1) {
 277       region_c->init_req( i_c++, r  ->in(i) );
 278       if (r->in(i) == predicate_proj)
 279         predicate_c = predicate_proj;
 280     } else {
 281       region_x->init_req( i_x,   r  ->in(i) );
 282       phi_x   ->init_req( i_x++, phi->in(i) );
 283       if (r->in(i) == predicate_proj)
 284         predicate_x = predicate_proj;
 285     }
 286   }
 287   if (predicate_c != NULL && (req_c > 1)) {
 288     assert(predicate_x == NULL, "only one predicate entry expected");
 289     predicate_c = NULL; // Do not clone predicate below merge point
 290   }
 291   if (predicate_x != NULL && ((len - req_c) > 2)) {
 292     assert(predicate_c == NULL, "only one predicate entry expected");
 293     predicate_x = NULL; // Do not clone predicate below merge point
 294   }
 295 
 296   // Register the new RegionNodes but do not transform them.  Cannot
 297   // transform until the entire Region/Phi conglomerate has been hacked
 298   // as a single huge transform.
 299   igvn->register_new_node_with_optimizer( region_c );
 300   igvn->register_new_node_with_optimizer( region_x );
 301   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 302   // about to get one.  If this only use goes away, then phi_x will look dead.
 303   // However, he will be picking up some more uses down below.
 304   Node *hook = new Node(4);
 305   hook->init_req(0, phi_x);
 306   hook->init_req(1, phi_c);
 307   phi_x = phase->transform( phi_x );
 308 
 309   // Make the compare
 310   Node *cmp_c = phase->makecon(t);
 311   Node *cmp_x = cmp->clone();
 312   cmp_x->set_req(1,phi_x);
 313   cmp_x->set_req(2,con2);
 314   cmp_x = phase->transform(cmp_x);
 315   // Make the bool
 316   Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
 317   Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
 318   // Make the IfNode
 319   IfNode* iff_c = iff->clone()->as_If();
 320   iff_c->set_req(0, region_c);
 321   iff_c->set_req(1, b_c);
 322   igvn->set_type_bottom(iff_c);
 323   igvn->_worklist.push(iff_c);
 324   hook->init_req(2, iff_c);
 325 
 326   IfNode* iff_x = iff->clone()->as_If();
 327   iff_x->set_req(0, region_x);
 328   iff_x->set_req(1, b_x);
 329   igvn->set_type_bottom(iff_x);
 330   igvn->_worklist.push(iff_x);
 331   hook->init_req(3, iff_x);
 332 
 333   // Make the true/false arms
 334   Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
 335   Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
 336   if (predicate_c != NULL) {
 337     assert(predicate_x == NULL, "only one predicate entry expected");
 338     // Clone loop predicates to each path
 339     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
 340     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
 341   }
 342   Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
 343   Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
 344   if (predicate_x != NULL) {
 345     assert(predicate_c == NULL, "only one predicate entry expected");
 346     // Clone loop predicates to each path
 347     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
 348     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
 349   }
 350 
 351   // Merge the TRUE paths
 352   Node *region_s = new RegionNode(3);
 353   igvn->_worklist.push(region_s);
 354   region_s->init_req(1, iff_c_t);
 355   region_s->init_req(2, iff_x_t);
 356   igvn->register_new_node_with_optimizer( region_s );
 357 
 358   // Merge the FALSE paths
 359   Node *region_f = new RegionNode(3);
 360   igvn->_worklist.push(region_f);
 361   region_f->init_req(1, iff_c_f);
 362   region_f->init_req(2, iff_x_f);
 363   igvn->register_new_node_with_optimizer( region_f );
 364 
 365   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 366   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 367   cmp->set_req(2,NULL);
 368   // Check for all uses of the Phi and give them a new home.
 369   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 370   Node *phi_s = NULL;     // do not construct unless needed
 371   Node *phi_f = NULL;     // do not construct unless needed
 372   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 373     Node* v = phi->last_out(i2);// User of the phi
 374     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
 375     uint vop = v->Opcode();
 376     Node *proj = NULL;
 377     if( vop == Op_Phi ) {       // Remote merge point
 378       Node *r = v->in(0);
 379       for (uint i3 = 1; i3 < r->req(); i3++)
 380         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 381           proj = r->in(i3);
 382           break;
 383         }
 384     } else if( v->is_ConstraintCast() ) {
 385       proj = v->in(0);          // Controlling projection
 386     } else {
 387       assert( 0, "do not know how to handle this guy" );
 388     }
 389 
 390     Node *proj_path_data, *proj_path_ctrl;
 391     if( proj->Opcode() == Op_IfTrue ) {
 392       if( phi_s == NULL ) {
 393         // Only construct phi_s if needed, otherwise provides
 394         // interfering use.
 395         phi_s = PhiNode::make_blank(region_s,phi);
 396         phi_s->init_req( 1, phi_c );
 397         phi_s->init_req( 2, phi_x );
 398         hook->add_req(phi_s);
 399         phi_s = phase->transform(phi_s);
 400       }
 401       proj_path_data = phi_s;
 402       proj_path_ctrl = region_s;
 403     } else {
 404       if( phi_f == NULL ) {
 405         // Only construct phi_f if needed, otherwise provides
 406         // interfering use.
 407         phi_f = PhiNode::make_blank(region_f,phi);
 408         phi_f->init_req( 1, phi_c );
 409         phi_f->init_req( 2, phi_x );
 410         hook->add_req(phi_f);
 411         phi_f = phase->transform(phi_f);
 412       }
 413       proj_path_data = phi_f;
 414       proj_path_ctrl = region_f;
 415     }
 416 
 417     // Fixup 'v' for for the split
 418     if( vop == Op_Phi ) {       // Remote merge point
 419       uint i;
 420       for( i = 1; i < v->req(); i++ )
 421         if( v->in(i) == phi )
 422           break;
 423       v->set_req(i, proj_path_data );
 424     } else if( v->is_ConstraintCast() ) {
 425       v->set_req(0, proj_path_ctrl );
 426       v->set_req(1, proj_path_data );
 427     } else
 428       ShouldNotReachHere();
 429   }
 430 
 431   // Now replace the original iff's True/False with region_s/region_t.
 432   // This makes the original iff go dead.
 433   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 434     Node* p = iff->last_out(i3);
 435     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 436     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 437     // Replace p with u
 438     igvn->add_users_to_worklist(p);
 439     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 440       Node* x = p->last_out(l);
 441       igvn->hash_delete(x);
 442       uint uses_found = 0;
 443       for( uint j = 0; j < x->req(); j++ ) {
 444         if( x->in(j) == p ) {
 445           x->set_req(j, u);
 446           uses_found++;
 447         }
 448       }
 449       l -= uses_found;    // we deleted 1 or more copies of this edge
 450     }
 451     igvn->remove_dead_node(p);
 452   }
 453 
 454   // Force the original merge dead
 455   igvn->hash_delete(r);
 456   // First, remove region's dead users.
 457   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 458     Node* u = r->last_out(l);
 459     if( u == r ) {
 460       r->set_req(0, NULL);
 461     } else {
 462       assert(u->outcnt() == 0, "only dead users");
 463       igvn->remove_dead_node(u);
 464     }
 465     l -= 1;
 466   }
 467   igvn->remove_dead_node(r);
 468 
 469   // Now remove the bogus extra edges used to keep things alive
 470   igvn->remove_dead_node( hook );
 471 
 472   // Must return either the original node (now dead) or a new node
 473   // (Do not return a top here, since that would break the uniqueness of top.)
 474   return new ConINode(TypeInt::ZERO);
 475 }
 476 
 477 // if this IfNode follows a range check pattern return the projection
 478 // for the failed path
 479 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
 480   Node* b = in(1);
 481   if (b == NULL || !b->is_Bool())  return NULL;
 482   BoolNode* bn = b->as_Bool();
 483   Node* cmp = bn->in(1);
 484   if (cmp == NULL)  return NULL;
 485   if (cmp->Opcode() != Op_CmpU)  return NULL;
 486 
 487   l = cmp->in(1);
 488   r = cmp->in(2);
 489   flip_test = 1;
 490   if (bn->_test._test == BoolTest::le) {
 491     l = cmp->in(2);
 492     r = cmp->in(1);
 493     flip_test = 2;
 494   } else if (bn->_test._test != BoolTest::lt) {
 495     return NULL;
 496   }
 497   if (l->is_top())  return NULL;   // Top input means dead test
 498   if (r->Opcode() != Op_LoadRange && !is_RangeCheck())  return NULL;
 499 
 500   // We have recognized one of these forms:
 501   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 502   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 503 
 504   ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
 505   return iftrap;
 506 }
 507 
 508 
 509 //------------------------------is_range_check---------------------------------
 510 // Return 0 if not a range check.  Return 1 if a range check and set index and
 511 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 512 // is versus a constant.
 513 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 514   int flip_test = 0;
 515   Node* l = NULL;
 516   Node* r = NULL;
 517   ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
 518 
 519   if (iftrap == NULL) {
 520     return 0;
 521   }
 522 
 523   // Make sure it's a real range check by requiring an uncommon trap
 524   // along the OOB path.  Otherwise, it's possible that the user wrote
 525   // something which optimized to look like a range check but behaves
 526   // in some other way.
 527   if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
 528     return 0;
 529   }
 530 
 531   // Look for index+offset form
 532   Node* ind = l;
 533   jint  off = 0;
 534   if (l->is_top()) {
 535     return 0;
 536   } else if (l->Opcode() == Op_AddI) {
 537     if ((off = l->in(1)->find_int_con(0)) != 0) {
 538       ind = l->in(2)->uncast();
 539     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 540       ind = l->in(1)->uncast();
 541     }
 542   } else if ((off = l->find_int_con(-1)) >= 0) {
 543     // constant offset with no variable index
 544     ind = NULL;
 545   } else {
 546     // variable index with no constant offset (or dead negative index)
 547     off = 0;
 548   }
 549 
 550   // Return all the values:
 551   index  = ind;
 552   offset = off;
 553   range  = r;
 554   return flip_test;
 555 }
 556 
 557 //------------------------------adjust_check-----------------------------------
 558 // Adjust (widen) a prior range check
 559 static void adjust_check(Node* proj, Node* range, Node* index,
 560                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 561   PhaseGVN *gvn = igvn;
 562   // Break apart the old check
 563   Node *iff = proj->in(0);
 564   Node *bol = iff->in(1);
 565   if( bol->is_top() ) return;   // In case a partially dead range check appears
 566   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 567   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 568   if( !bol->is_Bool() ) return;
 569 
 570   Node *cmp = bol->in(1);
 571   // Compute a new check
 572   Node *new_add = gvn->intcon(off_lo);
 573   if( index ) {
 574     new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
 575   }
 576   Node *new_cmp = (flip == 1)
 577     ? new CmpUNode( new_add, range )
 578     : new CmpUNode( range, new_add );
 579   new_cmp = gvn->transform(new_cmp);
 580   // See if no need to adjust the existing check
 581   if( new_cmp == cmp ) return;
 582   // Else, adjust existing check
 583   Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 584   igvn->rehash_node_delayed( iff );
 585   iff->set_req_X( 1, new_bol, igvn );
 586 }
 587 
 588 //------------------------------up_one_dom-------------------------------------
 589 // Walk up the dominator tree one step.  Return NULL at root or true
 590 // complex merges.  Skips through small diamonds.
 591 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 592   Node *dom = curr->in(0);
 593   if( !dom )                    // Found a Region degraded to a copy?
 594     return curr->nonnull_req(); // Skip thru it
 595 
 596   if( curr != dom )             // Normal walk up one step?
 597     return dom;
 598 
 599   // Use linear_only if we are still parsing, since we cannot
 600   // trust the regions to be fully filled in.
 601   if (linear_only)
 602     return NULL;
 603 
 604   if( dom->is_Root() )
 605     return NULL;
 606 
 607   // Else hit a Region.  Check for a loop header
 608   if( dom->is_Loop() )
 609     return dom->in(1);          // Skip up thru loops
 610 
 611   // Check for small diamonds
 612   Node *din1, *din2, *din3, *din4;
 613   if( dom->req() == 3 &&        // 2-path merge point
 614       (din1 = dom ->in(1)) &&   // Left  path exists
 615       (din2 = dom ->in(2)) &&   // Right path exists
 616       (din3 = din1->in(0)) &&   // Left  path up one
 617       (din4 = din2->in(0)) ) {  // Right path up one
 618     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 619         (din3 = din3->in(0)) )
 620       din3 = din3->in(0);
 621     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 622         (din4 = din4->in(0)) )
 623       din4 = din4->in(0);
 624     if( din3 == din4 && din3->is_If() )
 625       return din3;              // Skip around diamonds
 626   }
 627 
 628   // Give up the search at true merges
 629   return NULL;                  // Dead loop?  Or hit root?
 630 }
 631 
 632 
 633 //------------------------------filtered_int_type--------------------------------
 634 // Return a possibly more restrictive type for val based on condition control flow for an if
 635 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 636   assert(if_proj &&
 637          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 638   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 639     IfNode* iff = if_proj->in(0)->as_If();
 640     if (iff->in(1) && iff->in(1)->is_Bool()) {
 641       BoolNode* bol = iff->in(1)->as_Bool();
 642       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 643         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 644         if (cmp->in(1) == val) {
 645           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 646           if (cmp2_t != NULL) {
 647             jint lo = cmp2_t->_lo;
 648             jint hi = cmp2_t->_hi;
 649             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 650             switch (msk) {
 651             case BoolTest::ne:
 652               // Can't refine type
 653               return NULL;
 654             case BoolTest::eq:
 655               return cmp2_t;
 656             case BoolTest::lt:
 657               lo = TypeInt::INT->_lo;
 658               if (hi - 1 < hi) {
 659                 hi = hi - 1;
 660               }
 661               break;
 662             case BoolTest::le:
 663               lo = TypeInt::INT->_lo;
 664               break;
 665             case BoolTest::gt:
 666               if (lo + 1 > lo) {
 667                 lo = lo + 1;
 668               }
 669               hi = TypeInt::INT->_hi;
 670               break;
 671             case BoolTest::ge:
 672               // lo unchanged
 673               hi = TypeInt::INT->_hi;
 674               break;
 675             }
 676             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 677             return rtn_t;
 678           }
 679         }
 680       }
 681     }
 682   }
 683   return NULL;
 684 }
 685 
 686 //------------------------------fold_compares----------------------------
 687 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 688 // the direction of this if is determined by the preceding if so it
 689 // can be eliminate entirely.
 690 //
 691 // Given an if testing (CmpI n v) check for an immediately control
 692 // dependent if that is testing (CmpI n v2) and has one projection
 693 // leading to this if and the other projection leading to a region
 694 // that merges one of this ifs control projections.
 695 //
 696 //                   If
 697 //                  / |
 698 //                 /  |
 699 //                /   |
 700 //              If    |
 701 //              /\    |
 702 //             /  \   |
 703 //            /    \  |
 704 //           /    Region
 705 //
 706 // Or given an if testing (CmpI n v) check for a dominating if that is
 707 // testing (CmpI n v2), both having one projection leading to an
 708 // uncommon trap. Allow Another independent guard in between to cover
 709 // an explicit range check:
 710 // if (index < 0 || index >= array.length) {
 711 // which may need a null check to guard the LoadRange
 712 //
 713 //                   If
 714 //                  / \
 715 //                 /   \
 716 //                /     \
 717 //              If      unc
 718 //              /\
 719 //             /  \
 720 //            /    \
 721 //           /      unc
 722 //
 723 
 724 // Is the comparison for this If suitable for folding?
 725 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
 726   return in(1) != NULL &&
 727     in(1)->is_Bool() &&
 728     in(1)->in(1) != NULL &&
 729     in(1)->in(1)->Opcode() == Op_CmpI &&
 730     in(1)->in(1)->in(2) != NULL &&
 731     in(1)->in(1)->in(2) != igvn->C->top() &&
 732     (in(1)->as_Bool()->_test.is_less() ||
 733      in(1)->as_Bool()->_test.is_greater());
 734 }
 735 
 736 // Is a dominating control suitable for folding with this if?
 737 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
 738   return ctrl != NULL &&
 739     ctrl->is_Proj() &&
 740     ctrl->in(0) != NULL &&
 741     ctrl->in(0)->Opcode() == Op_If &&
 742     ctrl->in(0)->outcnt() == 2 &&
 743     ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
 744     // Must compare same value
 745     ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
 746     ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
 747 }
 748 
 749 // Do this If and the dominating If share a region?
 750 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
 751   ProjNode* otherproj = proj->other_if_proj();
 752   Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
 753   RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
 754   success = NULL;
 755   fail = NULL;
 756 
 757   if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
 758     for (int i = 0; i < 2; i++) {
 759       ProjNode* proj = proj_out(i);
 760       if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 761         success = proj;
 762       } else if (fail == NULL) {
 763         fail = proj;
 764       } else {
 765         success = fail = NULL;
 766       }
 767     }
 768   }
 769   return success != NULL && fail != NULL;
 770 }
 771 
 772 // Return projection that leads to an uncommon trap if any
 773 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
 774   for (int i = 0; i < 2; i++) {
 775     call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
 776     if (call != NULL) {
 777       return proj_out(i);
 778     }
 779   }
 780   return NULL;
 781 }
 782 
 783 // Do this If and the dominating If both branch out to an uncommon trap
 784 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
 785   ProjNode* otherproj = proj->other_if_proj();
 786   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
 787 
 788   if (otherproj->outcnt() == 1 && dom_unc != NULL) {
 789     // We need to re-execute the folded Ifs after deoptimization from the merged traps
 790     if (!dom_unc->jvms()->should_reexecute()) {
 791       return false;
 792     }
 793 
 794     CallStaticJavaNode* unc = NULL;
 795     ProjNode* unc_proj = uncommon_trap_proj(unc);
 796     if (unc_proj != NULL && unc_proj->outcnt() == 1) {
 797       if (dom_unc == unc) {
 798         // Allow the uncommon trap to be shared through a region
 799         RegionNode* r = unc->in(0)->as_Region();
 800         if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
 801           return false;
 802         }
 803         assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
 804       } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
 805         return false;
 806       }
 807 
 808       // Different methods and methods containing jsrs are not supported.
 809       ciMethod* method = unc->jvms()->method();
 810       ciMethod* dom_method = dom_unc->jvms()->method();
 811       if (method != dom_method || method->has_jsrs()) {
 812         return false;
 813       }
 814       // Check that both traps are in the same activation of the method (instead
 815       // of two activations being inlined through different call sites) by verifying
 816       // that the call stacks are equal for both JVMStates.
 817       JVMState* dom_caller = dom_unc->jvms()->caller();
 818       JVMState* caller = unc->jvms()->caller();
 819       if ((dom_caller == NULL) != (caller == NULL)) {
 820         // The current method must either be inlined into both dom_caller and
 821         // caller or must not be inlined at all (top method). Bail out otherwise.
 822         return false;
 823       } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
 824         return false;
 825       }
 826       // Check that the bci of the dominating uncommon trap dominates the bci
 827       // of the dominated uncommon trap. Otherwise we may not re-execute
 828       // the dominated check after deoptimization from the merged uncommon trap.
 829       ciTypeFlow* flow = dom_method->get_flow_analysis();
 830       int bci = unc->jvms()->bci();
 831       int dom_bci = dom_unc->jvms()->bci();
 832       if (!flow->is_dominated_by(bci, dom_bci)) {
 833         return false;
 834       }
 835 
 836       // See merge_uncommon_traps: the reason of the uncommon trap
 837       // will be changed and the state of the dominating If will be
 838       // used. Checked that we didn't apply this transformation in a
 839       // previous compilation and it didn't cause too many traps
 840       if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
 841           !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
 842         success = unc_proj;
 843         fail = unc_proj->other_if_proj();
 844         return true;
 845       }
 846     }
 847   }
 848   return false;
 849 }
 850 
 851 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
 852 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 853   Node* this_cmp = in(1)->in(1);
 854   BoolNode* this_bool = in(1)->as_Bool();
 855   IfNode* dom_iff = proj->in(0)->as_If();
 856   BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 857   Node* lo = dom_iff->in(1)->in(1)->in(2);
 858   Node* hi = this_cmp->in(2);
 859   Node* n = this_cmp->in(1);
 860   ProjNode* otherproj = proj->other_if_proj();
 861 
 862   const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
 863   const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
 864 
 865   BoolTest::mask lo_test = dom_bool->_test._test;
 866   BoolTest::mask hi_test = this_bool->_test._test;
 867   BoolTest::mask cond = hi_test;
 868 
 869   // convert:
 870   //
 871   //          dom_bool = x {<,<=,>,>=} a
 872   //                           / \
 873   //     proj = {True,False}  /   \ otherproj = {False,True}
 874   //                         /
 875   //        this_bool = x {<,<=} b
 876   //                       / \
 877   //  fail = {True,False} /   \ success = {False,True}
 878   //                     /
 879   //
 880   // (Second test guaranteed canonicalized, first one may not have
 881   // been canonicalized yet)
 882   //
 883   // into:
 884   //
 885   // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
 886   //                       / \
 887   //                 fail /   \ success
 888   //                     /
 889   //
 890 
 891   // Figure out which of the two tests sets the upper bound and which
 892   // sets the lower bound if any.
 893   Node* adjusted_lim = NULL;
 894   if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
 895     assert((dom_bool->_test.is_less() && !proj->_con) ||
 896            (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
 897     // this test was canonicalized
 898     assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
 899 
 900     // this_bool = <
 901     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 902     //     x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
 903     //     lo = a, hi = b, adjusted_lim = b-a, cond = <u
 904     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 905     //     x in ]a, b[ on the fail (= True) projection, b > a:
 906     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
 907     // this_bool = <=
 908     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 909     //     x in [a, b] on the fail (= True) projection, b+1 > a-1:
 910     //     lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
 911     //     lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
 912     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 913     //     x in ]a, b] on the fail (= True) projection b+1 > a:
 914     //     lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
 915     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1
 916 
 917     if (hi_test == BoolTest::lt) {
 918       if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 919         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 920       }
 921     } else {
 922       assert(hi_test == BoolTest::le, "bad test");
 923       if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
 924         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 925         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 926         cond = BoolTest::lt;
 927       } else {
 928         assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
 929         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 930         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 931         cond = BoolTest::lt;
 932       }
 933     }
 934   } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
 935 
 936     // this_bool = <
 937     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 938     //     x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
 939     //     lo = b, hi = a, adjusted_lim = a-b, cond = >=u
 940     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 941     //     x in [b, a] on the fail (= False) projection, a+1 > b-1:
 942     //     lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
 943     //     lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
 944     // this_bool = <=
 945     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 946     //     x in ]b, a[ on the fail (= False) projection, a > b:
 947     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
 948     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 949     //     x in ]b, a] on the fail (= False) projection, a+1 > b:
 950     //     lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
 951     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >u doesn't work because a = b is possible, then b-a-1 = -1
 952 
 953     swap(lo, hi);
 954     swap(lo_type, hi_type);
 955     swap(lo_test, hi_test);
 956 
 957     assert((dom_bool->_test.is_less() && proj->_con) ||
 958            (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
 959     // this test was canonicalized
 960     assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
 961 
 962     cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
 963 
 964     if (lo_test == BoolTest::lt) {
 965       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 966         cond = BoolTest::ge;
 967       } else {
 968         assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
 969         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 970         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 971         cond = BoolTest::ge;
 972       }
 973     } else if (lo_test == BoolTest::le) {
 974       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 975         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 976         cond = BoolTest::ge;
 977       } else {
 978         assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
 979         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 980         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 981         cond = BoolTest::ge;
 982       }
 983     }
 984   } else {
 985     const TypeInt* failtype  = filtered_int_type(igvn, n, proj);
 986     if (failtype != NULL) {
 987       const TypeInt* type2 = filtered_int_type(igvn, n, fail);
 988       if (type2 != NULL) {
 989         failtype = failtype->join(type2)->is_int();
 990         if (failtype->_lo > failtype->_hi) {
 991           // previous if determines the result of this if so
 992           // replace Bool with constant
 993           igvn->_worklist.push(in(1));
 994           igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
 995           return true;
 996         }
 997       }
 998     }
 999     lo = NULL;
1000     hi = NULL;
1001   }
1002 
1003   if (lo && hi) {
1004     // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1005     Node* adjusted_val = igvn->transform(new SubINode(n,  lo));
1006     if (adjusted_lim == NULL) {
1007       adjusted_lim = igvn->transform(new SubINode(hi, lo));
1008     }
1009     Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1010     Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1011 
1012     igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1013     igvn->_worklist.push(in(1));
1014     igvn->replace_input_of(this, 1, newbool);
1015 
1016     return true;
1017   }
1018   return false;
1019 }
1020 
1021 // Merge the branches that trap for this If and the dominating If into
1022 // a single region that branches to the uncommon trap for the
1023 // dominating If
1024 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1025   Node* res = this;
1026   assert(success->in(0) == this, "bad projection");
1027 
1028   ProjNode* otherproj = proj->other_if_proj();
1029 
1030   CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1031   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1032 
1033   if (unc != dom_unc) {
1034     Node* r = new RegionNode(3);
1035 
1036     r->set_req(1, otherproj);
1037     r->set_req(2, success);
1038     r = igvn->transform(r);
1039     assert(r->is_Region(), "can't go away");
1040 
1041     // Make both If trap at the state of the first If: once the CmpI
1042     // nodes are merged, if we trap we don't know which of the CmpI
1043     // nodes would have caused the trap so we have to restart
1044     // execution at the first one
1045     igvn->replace_input_of(dom_unc, 0, r);
1046     igvn->replace_input_of(unc, 0, igvn->C->top());
1047   }
1048   int trap_request = dom_unc->uncommon_trap_request();
1049   Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1050   Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1051 
1052   int flip_test = 0;
1053   Node* l = NULL;
1054   Node* r = NULL;
1055 
1056   if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1057     // If this looks like a range check, change the trap to
1058     // Reason_range_check so the compiler recognizes it as a range
1059     // check and applies the corresponding optimizations
1060     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1061 
1062     improve_address_types(l, r, fail, igvn);
1063 
1064     res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1065   } else if (unc != dom_unc) {
1066     // If we trap we won't know what CmpI would have caused the trap
1067     // so use a special trap reason to mark this pair of CmpI nodes as
1068     // bad candidate for folding. On recompilation we won't fold them
1069     // and we may trap again but this time we'll know what branch
1070     // traps
1071     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1072   }
1073   igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1074   return res;
1075 }
1076 
1077 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1078 // of a rangecheck on index i, on 64 bit the compares may be followed
1079 // by memory accesses using i as index. In that case, the CmpU tells
1080 // us something about the values taken by i that can help the compiler
1081 // (see Compile::conv_I2X_index())
1082 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1083 #ifdef _LP64
1084   ResourceMark rm;
1085   Node_Stack stack(2);
1086 
1087   assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1088   const TypeInt* array_size = igvn->type(r)->is_int();
1089 
1090   stack.push(l, 0);
1091 
1092   while(stack.size() > 0) {
1093     Node* n = stack.node();
1094     uint start = stack.index();
1095 
1096     uint i = start;
1097     for (; i < n->outcnt(); i++) {
1098       Node* use = n->raw_out(i);
1099       if (stack.size() == 1) {
1100         if (use->Opcode() == Op_ConvI2L) {
1101           const TypeLong* bounds = use->as_Type()->type()->is_long();
1102           if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1103               (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1104             stack.set_index(i+1);
1105             stack.push(use, 0);
1106             break;
1107           }
1108         }
1109       } else if (use->is_Mem()) {
1110         Node* ctrl = use->in(0);
1111         for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1112           ctrl = up_one_dom(ctrl);
1113         }
1114         if (ctrl == fail) {
1115           Node* init_n = stack.node_at(1);
1116           assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1117           // Create a new narrow ConvI2L node that is dependent on the range check
1118           Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1119 
1120           // The type of the ConvI2L may be widen and so the new
1121           // ConvI2L may not be better than an existing ConvI2L
1122           if (new_n != init_n) {
1123             for (uint j = 2; j < stack.size(); j++) {
1124               Node* n = stack.node_at(j);
1125               Node* clone = n->clone();
1126               int rep = clone->replace_edge(init_n, new_n);
1127               assert(rep > 0, "can't find expected node?");
1128               clone = igvn->transform(clone);
1129               init_n = n;
1130               new_n = clone;
1131             }
1132             igvn->hash_delete(use);
1133             int rep = use->replace_edge(init_n, new_n);
1134             assert(rep > 0, "can't find expected node?");
1135             igvn->transform(use);
1136             if (init_n->outcnt() == 0) {
1137               igvn->_worklist.push(init_n);
1138             }
1139           }
1140         }
1141       } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1142                                         igvn->type(use)->isa_ptr())) {
1143         stack.set_index(i+1);
1144         stack.push(use, 0);
1145         break;
1146       }
1147     }
1148     if (i == n->outcnt()) {
1149       stack.pop();
1150     }
1151   }
1152 #endif
1153 }
1154 
1155 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1156   if (in(1) != NULL &&
1157       in(1)->in(1) != NULL &&
1158       in(1)->in(1)->in(2) != NULL) {
1159     Node* other = in(1)->in(1)->in(2);
1160     if (other->Opcode() == Op_LoadRange &&
1161         ((other->in(0) != NULL && other->in(0) == proj) ||
1162          (other->in(0) == NULL &&
1163           other->in(2) != NULL &&
1164           other->in(2)->is_AddP() &&
1165           other->in(2)->in(1) != NULL &&
1166           other->in(2)->in(1)->Opcode() == Op_CastPP &&
1167           other->in(2)->in(1)->in(0) == proj))) {
1168       return true;
1169     }
1170   }
1171   return false;
1172 }
1173 
1174 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1175   Node* other = in(1)->in(1)->in(2);
1176   if (other->in(MemNode::Address) != NULL &&
1177       proj->in(0)->in(1) != NULL &&
1178       proj->in(0)->in(1)->is_Bool() &&
1179       proj->in(0)->in(1)->in(1) != NULL &&
1180       proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1181       proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1182       proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1183       igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1184     return true;
1185   }
1186   return false;
1187 }
1188 
1189 // Check that the If that is in between the 2 integer comparisons has
1190 // no side effect
1191 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1192   if (proj != NULL &&
1193       proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1194       proj->outcnt() <= 2) {
1195     if (proj->outcnt() == 1 ||
1196         // Allow simple null check from LoadRange
1197         (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1198       CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1199       CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1200 
1201       // reroute_side_effect_free_unc changes the state of this
1202       // uncommon trap to restart execution at the previous
1203       // CmpI. Check that this change in a previous compilation didn't
1204       // cause too many traps.
1205       int trap_request = unc->uncommon_trap_request();
1206       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1207 
1208       if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1209         return false;
1210       }
1211 
1212       return true;
1213     }
1214   }
1215   return false;
1216 }
1217 
1218 // Make the If between the 2 integer comparisons trap at the state of
1219 // the first If: the last CmpI is the one replaced by a CmpU and the
1220 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1221 // won't be guarded by the first CmpI anymore. It can trap in cases
1222 // where the first CmpI would have prevented it from executing: on a
1223 // trap, we need to restart execution at the state of the first CmpI
1224 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1225   CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1226   ProjNode* otherproj = proj->other_if_proj();
1227   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1228   Node* call_proj = dom_unc->unique_ctrl_out();
1229   Node* halt = call_proj->unique_ctrl_out();
1230 
1231   Node* new_unc = dom_unc->clone();
1232   call_proj = call_proj->clone();
1233   halt = halt->clone();
1234   Node* c = otherproj->clone();
1235 
1236   c = igvn->transform(c);
1237   new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1238   new_unc->set_req(0, c);
1239   new_unc = igvn->transform(new_unc);
1240   call_proj->set_req(0, new_unc);
1241   call_proj = igvn->transform(call_proj);
1242   halt->set_req(0, call_proj);
1243   halt = igvn->transform(halt);
1244 
1245   igvn->replace_node(otherproj, igvn->C->top());
1246   igvn->C->root()->add_req(halt);
1247 }
1248 
1249 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1250   if (Opcode() != Op_If) return NULL;
1251 
1252   if (cmpi_folds(igvn)) {
1253     Node* ctrl = in(0);
1254     if (is_ctrl_folds(ctrl, igvn) &&
1255         ctrl->outcnt() == 1) {
1256       // A integer comparison immediately dominated by another integer
1257       // comparison
1258       ProjNode* success = NULL;
1259       ProjNode* fail = NULL;
1260       ProjNode* dom_cmp = ctrl->as_Proj();
1261       if (has_shared_region(dom_cmp, success, fail) &&
1262           // Next call modifies graph so must be last
1263           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1264         return this;
1265       }
1266       if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1267           // Next call modifies graph so must be last
1268           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1269         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1270       }
1271       return NULL;
1272     } else if (ctrl->in(0) != NULL &&
1273                ctrl->in(0)->in(0) != NULL) {
1274       ProjNode* success = NULL;
1275       ProjNode* fail = NULL;
1276       Node* dom = ctrl->in(0)->in(0);
1277       ProjNode* dom_cmp = dom->isa_Proj();
1278       ProjNode* other_cmp = ctrl->isa_Proj();
1279 
1280       // Check if it's an integer comparison dominated by another
1281       // integer comparison with another test in between
1282       if (is_ctrl_folds(dom, igvn) &&
1283           has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1284           is_side_effect_free_test(other_cmp, igvn) &&
1285           // Next call modifies graph so must be last
1286           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1287         reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1288         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1289       }
1290     }
1291   }
1292   return NULL;
1293 }
1294 
1295 //------------------------------remove_useless_bool----------------------------
1296 // Check for people making a useless boolean: things like
1297 // if( (x < y ? true : false) ) { ... }
1298 // Replace with if( x < y ) { ... }
1299 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1300   Node *i1 = iff->in(1);
1301   if( !i1->is_Bool() ) return NULL;
1302   BoolNode *bol = i1->as_Bool();
1303 
1304   Node *cmp = bol->in(1);
1305   if( cmp->Opcode() != Op_CmpI ) return NULL;
1306 
1307   // Must be comparing against a bool
1308   const Type *cmp2_t = phase->type( cmp->in(2) );
1309   if( cmp2_t != TypeInt::ZERO &&
1310       cmp2_t != TypeInt::ONE )
1311     return NULL;
1312 
1313   // Find a prior merge point merging the boolean
1314   i1 = cmp->in(1);
1315   if( !i1->is_Phi() ) return NULL;
1316   PhiNode *phi = i1->as_Phi();
1317   if( phase->type( phi ) != TypeInt::BOOL )
1318     return NULL;
1319 
1320   // Check for diamond pattern
1321   int true_path = phi->is_diamond_phi();
1322   if( true_path == 0 ) return NULL;
1323 
1324   // Make sure that iff and the control of the phi are different. This
1325   // should really only happen for dead control flow since it requires
1326   // an illegal cycle.
1327   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1328 
1329   // phi->region->if_proj->ifnode->bool->cmp
1330   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1331 
1332   // Now get the 'sense' of the test correct so we can plug in
1333   // either iff2->in(1) or its complement.
1334   int flip = 0;
1335   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1336   else if( bol->_test._test != BoolTest::eq ) return NULL;
1337   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1338 
1339   const Type *phi1_t = phase->type( phi->in(1) );
1340   const Type *phi2_t = phase->type( phi->in(2) );
1341   // Check for Phi(0,1) and flip
1342   if( phi1_t == TypeInt::ZERO ) {
1343     if( phi2_t != TypeInt::ONE ) return NULL;
1344     flip = 1-flip;
1345   } else {
1346     // Check for Phi(1,0)
1347     if( phi1_t != TypeInt::ONE  ) return NULL;
1348     if( phi2_t != TypeInt::ZERO ) return NULL;
1349   }
1350   if( true_path == 2 ) {
1351     flip = 1-flip;
1352   }
1353 
1354   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1355   assert(new_bol != iff->in(1), "must make progress");
1356   iff->set_req(1, new_bol);
1357   // Intervening diamond probably goes dead
1358   phase->C->set_major_progress();
1359   return iff;
1360 }
1361 
1362 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1363 
1364 struct RangeCheck {
1365   Node* ctl;
1366   jint off;
1367 };
1368 
1369 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1370   if (remove_dead_region(phase, can_reshape))  return this;
1371   // No Def-Use info?
1372   if (!can_reshape)  return NULL;
1373 
1374   // Don't bother trying to transform a dead if
1375   if (in(0)->is_top())  return NULL;
1376   // Don't bother trying to transform an if with a dead test
1377   if (in(1)->is_top())  return NULL;
1378   // Another variation of a dead test
1379   if (in(1)->is_Con())  return NULL;
1380   // Another variation of a dead if
1381   if (outcnt() < 2)  return NULL;
1382 
1383   // Canonicalize the test.
1384   Node* idt_if = idealize_test(phase, this);
1385   if (idt_if != NULL)  return idt_if;
1386 
1387   // Try to split the IF
1388   PhaseIterGVN *igvn = phase->is_IterGVN();
1389   Node *s = split_if(this, igvn);
1390   if (s != NULL)  return s;
1391 
1392   return NodeSentinel;
1393 }
1394 
1395 //------------------------------Ideal------------------------------------------
1396 // Return a node which is more "ideal" than the current node.  Strip out
1397 // control copies
1398 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1399   Node* res = Ideal_common(phase, can_reshape);
1400   if (res != NodeSentinel) {
1401     return res;
1402   }
1403 
1404   // Check for people making a useless boolean: things like
1405   // if( (x < y ? true : false) ) { ... }
1406   // Replace with if( x < y ) { ... }
1407   Node *bol2 = remove_useless_bool(this, phase);
1408   if( bol2 ) return bol2;
1409 
1410   if (in(0) == NULL) return NULL;     // Dead loop?
1411 
1412   PhaseIterGVN *igvn = phase->is_IterGVN();
1413   Node* result = fold_compares(igvn);
1414   if (result != NULL) {
1415     return result;
1416   }
1417 
1418   // Scan for an equivalent test
1419   Node *cmp;
1420   int dist = 0;               // Cutoff limit for search
1421   int op = Opcode();
1422   if( op == Op_If &&
1423       (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1424     if( cmp->in(2) != NULL && // make sure cmp is not already dead
1425         cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1426       dist = 64;              // Limit for null-pointer scans
1427     } else {
1428       dist = 4;               // Do not bother for random pointer tests
1429     }
1430   } else {
1431     dist = 4;                 // Limit for random junky scans
1432   }
1433 
1434   Node* prev_dom = search_identical(dist);
1435 
1436   if (prev_dom == NULL) {
1437     return NULL;
1438   }
1439 
1440   // Replace dominated IfNode
1441   return dominated_by(prev_dom, igvn);
1442 }
1443 
1444 //------------------------------dominated_by-----------------------------------
1445 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1446 #ifndef PRODUCT
1447   if (TraceIterativeGVN) {
1448     tty->print("   Removing IfNode: "); this->dump();
1449   }
1450   if (VerifyOpto && !igvn->allow_progress()) {
1451     // Found an equivalent dominating test,
1452     // we can not guarantee reaching a fix-point for these during iterativeGVN
1453     // since intervening nodes may not change.
1454     return NULL;
1455   }
1456 #endif
1457 
1458   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1459   Node *idom = in(0);
1460   // Need opcode to decide which way 'this' test goes
1461   int prev_op = prev_dom->Opcode();
1462   Node *top = igvn->C->top(); // Shortcut to top
1463 
1464   // Loop predicates may have depending checks which should not
1465   // be skipped. For example, range check predicate has two checks
1466   // for lower and upper bounds.
1467   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1468   if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)) {
1469     prev_dom = idom;
1470   }
1471 
1472   // Now walk the current IfNode's projections.
1473   // Loop ends when 'this' has no more uses.
1474   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1475     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1476     igvn->add_users_to_worklist(ifp);
1477     // Check which projection it is and set target.
1478     // Data-target is either the dominating projection of the same type
1479     // or TOP if the dominating projection is of opposite type.
1480     // Data-target will be used as the new control edge for the non-CFG
1481     // nodes like Casts and Loads.
1482     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1483     // Control-target is just the If's immediate dominator or TOP.
1484     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1485 
1486     // For each child of an IfTrue/IfFalse projection, reroute.
1487     // Loop ends when projection has no more uses.
1488     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1489       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1490       if( !s->depends_only_on_test() ) {
1491         // Find the control input matching this def-use edge.
1492         // For Regions it may not be in slot 0.
1493         uint l;
1494         for( l = 0; s->in(l) != ifp; l++ ) { }
1495         igvn->replace_input_of(s, l, ctrl_target);
1496       } else {                      // Else, for control producers,
1497         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1498       }
1499     } // End for each child of a projection
1500 
1501     igvn->remove_dead_node(ifp);
1502   } // End for each IfTrue/IfFalse child of If
1503 
1504   // Kill the IfNode
1505   igvn->remove_dead_node(this);
1506 
1507   // Must return either the original node (now dead) or a new node
1508   // (Do not return a top here, since that would break the uniqueness of top.)
1509   return new ConINode(TypeInt::ZERO);
1510 }
1511 
1512 Node* IfNode::search_identical(int dist) {
1513   // Setup to scan up the CFG looking for a dominating test
1514   Node* dom = in(0);
1515   Node* prev_dom = this;
1516   int op = Opcode();
1517   // Search up the dominator tree for an If with an identical test
1518   while (dom->Opcode() != op    ||  // Not same opcode?
1519          dom->in(1)    != in(1) ||  // Not same input 1?
1520          (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1521          prev_dom->in(0) != dom) {  // One path of test does not dominate?
1522     if (dist < 0) return NULL;
1523 
1524     dist--;
1525     prev_dom = dom;
1526     dom = up_one_dom(dom);
1527     if (!dom) return NULL;
1528   }
1529 
1530   // Check that we did not follow a loop back to ourselves
1531   if (this == dom) {
1532     return NULL;
1533   }
1534 
1535 #ifndef PRODUCT
1536   if (dist > 2) { // Add to count of NULL checks elided
1537     explicit_null_checks_elided++;
1538   }
1539 #endif
1540 
1541   return prev_dom;
1542 }
1543 
1544 //------------------------------Identity---------------------------------------
1545 // If the test is constant & we match, then we are the input Control
1546 Node* IfProjNode::Identity(PhaseGVN* phase) {
1547   // Can only optimize if cannot go the other way
1548   const TypeTuple *t = phase->type(in(0))->is_tuple();
1549   if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1550        // During parsing (GVN) we don't remove dead code aggressively.
1551        // Cut off dead branch and let PhaseRemoveUseless take care of it.
1552       (!phase->is_IterGVN() ||
1553        // During IGVN, first wait for the dead branch to be killed.
1554        // Otherwise, the IfNode's control will have two control uses (the IfNode
1555        // that doesn't go away because it still has uses and this branch of the
1556        // If) which breaks other optimizations. Node::has_special_unique_user()
1557        // will cause this node to be reprocessed once the dead branch is killed.
1558        in(0)->outcnt() == 1))) {
1559     // IfNode control
1560     return in(0)->in(0);
1561   }
1562   // no progress
1563   return this;
1564 }
1565 
1566 #ifndef PRODUCT
1567 //-------------------------------related---------------------------------------
1568 // An IfProjNode's related node set consists of its input (an IfNode) including
1569 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1570 // the restrictions for IfNode apply (see IfNode::rel).
1571 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1572   Node* ifNode = this->in(0);
1573   in_rel->append(ifNode);
1574   if (compact) {
1575     ifNode->collect_nodes(in_rel, 3, false, true);
1576   } else {
1577     ifNode->collect_nodes_in_all_data(in_rel, false);
1578   }
1579   this->collect_nodes(out_rel, -1, false, false);
1580 }
1581 
1582 //------------------------------dump_spec--------------------------------------
1583 void IfNode::dump_spec(outputStream *st) const {
1584   st->print("P=%f, C=%f",_prob,_fcnt);
1585 }
1586 
1587 //-------------------------------related---------------------------------------
1588 // For an IfNode, the set of related output nodes is just the output nodes till
1589 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1590 // The related input nodes contain no control nodes, but all data nodes
1591 // pertaining to the condition. In compact mode, the input nodes are collected
1592 // up to a depth of 3.
1593 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1594   if (compact) {
1595     this->collect_nodes(in_rel, 3, false, true);
1596   } else {
1597     this->collect_nodes_in_all_data(in_rel, false);
1598   }
1599   this->collect_nodes(out_rel, -2, false, false);
1600 }
1601 #endif
1602 
1603 //------------------------------idealize_test----------------------------------
1604 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1605 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1606 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1607 // needed.
1608 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1609   assert(iff->in(0) != NULL, "If must be live");
1610 
1611   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1612   Node* old_if_f = iff->proj_out(false);
1613   Node* old_if_t = iff->proj_out(true);
1614 
1615   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1616   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1617   // happens in count-down loops
1618   if (iff->is_CountedLoopEnd())  return NULL;
1619   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1620   BoolNode *b = iff->in(1)->as_Bool();
1621   BoolTest bt = b->_test;
1622   // Test already in good order?
1623   if( bt.is_canonical() )
1624     return NULL;
1625 
1626   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1627   // cloning the IfNode.
1628   Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1629   if( !new_b->is_Bool() ) return NULL;
1630   b = new_b->as_Bool();
1631 
1632   PhaseIterGVN *igvn = phase->is_IterGVN();
1633   assert( igvn, "Test is not canonical in parser?" );
1634 
1635   // The IF node never really changes, but it needs to be cloned
1636   iff = iff->clone()->as_If();
1637   iff->set_req(1, b);
1638   iff->_prob = 1.0-iff->_prob;
1639 
1640   Node *prior = igvn->hash_find_insert(iff);
1641   if( prior ) {
1642     igvn->remove_dead_node(iff);
1643     iff = (IfNode*)prior;
1644   } else {
1645     // Cannot call transform on it just yet
1646     igvn->set_type_bottom(iff);
1647   }
1648   igvn->_worklist.push(iff);
1649 
1650   // Now handle projections.  Cloning not required.
1651   Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1652   Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1653 
1654   igvn->register_new_node_with_optimizer(new_if_f);
1655   igvn->register_new_node_with_optimizer(new_if_t);
1656   // Flip test, so flip trailing control
1657   igvn->replace_node(old_if_f, new_if_t);
1658   igvn->replace_node(old_if_t, new_if_f);
1659 
1660   // Progress
1661   return iff;
1662 }
1663 
1664 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1665   Node* res = Ideal_common(phase, can_reshape);
1666   if (res != NodeSentinel) {
1667     return res;
1668   }
1669 
1670   PhaseIterGVN *igvn = phase->is_IterGVN();
1671   // Setup to scan up the CFG looking for a dominating test
1672   Node* prev_dom = this;
1673 
1674   // Check for range-check vs other kinds of tests
1675   Node* index1;
1676   Node* range1;
1677   jint offset1;
1678   int flip1 = is_range_check(range1, index1, offset1);
1679   if (flip1) {
1680     Node* dom = in(0);
1681     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
1682     // so all checks we inspect post-dominate the top-most check we find.
1683     // If we are going to fail the current check and we reach the top check
1684     // then we are guaranteed to fail, so just start interpreting there.
1685     // We 'expand' the top 3 range checks to include all post-dominating
1686     // checks.
1687 
1688     // The top 3 range checks seen
1689     const int NRC =3;
1690     RangeCheck prev_checks[NRC];
1691     int nb_checks = 0;
1692 
1693     // Low and high offsets seen so far
1694     jint off_lo = offset1;
1695     jint off_hi = offset1;
1696 
1697     bool found_immediate_dominator = false;
1698 
1699     // Scan for the top checks and collect range of offsets
1700     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1701       if (dom->Opcode() == Op_RangeCheck &&  // Not same opcode?
1702           prev_dom->in(0) == dom) { // One path of test does dominate?
1703         if (dom == this) return NULL; // dead loop
1704         // See if this is a range check
1705         Node* index2;
1706         Node* range2;
1707         jint offset2;
1708         int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1709         // See if this is a _matching_ range check, checking against
1710         // the same array bounds.
1711         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1712             dom->outcnt() == 2) {
1713           if (nb_checks == 0 && dom->in(1) == in(1)) {
1714             // Found an immediately dominating test at the same offset.
1715             // This kind of back-to-back test can be eliminated locally,
1716             // and there is no need to search further for dominating tests.
1717             assert(offset2 == offset1, "Same test but different offsets");
1718             found_immediate_dominator = true;
1719             break;
1720           }
1721           // Gather expanded bounds
1722           off_lo = MIN2(off_lo,offset2);
1723           off_hi = MAX2(off_hi,offset2);
1724           // Record top NRC range checks
1725           prev_checks[nb_checks%NRC].ctl = prev_dom;
1726           prev_checks[nb_checks%NRC].off = offset2;
1727           nb_checks++;
1728         }
1729       }
1730       prev_dom = dom;
1731       dom = up_one_dom(dom);
1732       if (!dom) break;
1733     }
1734 
1735     if (!found_immediate_dominator) {
1736       // Attempt to widen the dominating range check to cover some later
1737       // ones.  Since range checks "fail" by uncommon-trapping to the
1738       // interpreter, widening a check can make us speculatively enter
1739       // the interpreter.  If we see range-check deopt's, do not widen!
1740       if (!phase->C->allow_range_check_smearing())  return NULL;
1741 
1742       // Didn't find prior covering check, so cannot remove anything.
1743       if (nb_checks == 0) {
1744         return NULL;
1745       }
1746       // Constant indices only need to check the upper bound.
1747       // Non-constant indices must check both low and high.
1748       int chk0 = (nb_checks - 1) % NRC;
1749       if (index1) {
1750         if (nb_checks == 1) {
1751           return NULL;
1752         } else {
1753           // If the top range check's constant is the min or max of
1754           // all constants we widen the next one to cover the whole
1755           // range of constants.
1756           RangeCheck rc0 = prev_checks[chk0];
1757           int chk1 = (nb_checks - 2) % NRC;
1758           RangeCheck rc1 = prev_checks[chk1];
1759           if (rc0.off == off_lo) {
1760             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1761             prev_dom = rc1.ctl;
1762           } else if (rc0.off == off_hi) {
1763             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1764             prev_dom = rc1.ctl;
1765           } else {
1766             // If the top test's constant is not the min or max of all
1767             // constants, we need 3 range checks. We must leave the
1768             // top test unchanged because widening it would allow the
1769             // accesses it protects to successfully read/write out of
1770             // bounds.
1771             if (nb_checks == 2) {
1772               return NULL;
1773             }
1774             int chk2 = (nb_checks - 3) % NRC;
1775             RangeCheck rc2 = prev_checks[chk2];
1776             // The top range check a+i covers interval: -a <= i < length-a
1777             // The second range check b+i covers interval: -b <= i < length-b
1778             if (rc1.off <= rc0.off) {
1779               // if b <= a, we change the second range check to:
1780               // -min_of_all_constants <= i < length-min_of_all_constants
1781               // Together top and second range checks now cover:
1782               // -min_of_all_constants <= i < length-a
1783               // which is more restrictive than -b <= i < length-b:
1784               // -b <= -min_of_all_constants <= i < length-a <= length-b
1785               // The third check is then changed to:
1786               // -max_of_all_constants <= i < length-max_of_all_constants
1787               // so 2nd and 3rd checks restrict allowed values of i to:
1788               // -min_of_all_constants <= i < length-max_of_all_constants
1789               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1790               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1791             } else {
1792               // if b > a, we change the second range check to:
1793               // -max_of_all_constants <= i < length-max_of_all_constants
1794               // Together top and second range checks now cover:
1795               // -a <= i < length-max_of_all_constants
1796               // which is more restrictive than -b <= i < length-b:
1797               // -b < -a <= i < length-max_of_all_constants <= length-b
1798               // The third check is then changed to:
1799               // -max_of_all_constants <= i < length-max_of_all_constants
1800               // so 2nd and 3rd checks restrict allowed values of i to:
1801               // -min_of_all_constants <= i < length-max_of_all_constants
1802               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1803               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1804             }
1805             prev_dom = rc2.ctl;
1806           }
1807         }
1808       } else {
1809         RangeCheck rc0 = prev_checks[chk0];
1810         // 'Widen' the offset of the 1st and only covering check
1811         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1812         // Test is now covered by prior checks, dominate it out
1813         prev_dom = rc0.ctl;
1814       }
1815     }
1816   } else {
1817     prev_dom = search_identical(4);
1818 
1819     if (prev_dom == NULL) {
1820       return NULL;
1821     }
1822   }
1823 
1824   // Replace dominated IfNode
1825   return dominated_by(prev_dom, igvn);
1826 }