1 /*
   2  * Copyright (c) 2000, 2015, 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 "opto/addnode.hpp"
  29 #include "opto/castnode.hpp"
  30 #include "opto/cfgnode.hpp"
  31 #include "opto/connode.hpp"
  32 #include "opto/loopnode.hpp"
  33 #include "opto/phaseX.hpp"
  34 #include "opto/runtime.hpp"
  35 #include "opto/rootnode.hpp"
  36 #include "opto/subnode.hpp"
  37 
  38 // Portions of code courtesy of Clifford Click
  39 
  40 // Optimization - Graph Style
  41 
  42 
  43 extern int explicit_null_checks_elided;
  44 
  45 //=============================================================================
  46 //------------------------------Value------------------------------------------
  47 // Return a tuple for whichever arm of the IF is reachable
  48 const Type* IfNode::Value(PhaseGVN* phase) const {
  49   if( !in(0) ) return Type::TOP;
  50   if( phase->type(in(0)) == Type::TOP )
  51     return Type::TOP;
  52   const Type *t = phase->type(in(1));
  53   if( t == Type::TOP )          // data is undefined
  54     return TypeTuple::IFNEITHER; // unreachable altogether
  55   if( t == TypeInt::ZERO )      // zero, or false
  56     return TypeTuple::IFFALSE;  // only false branch is reachable
  57   if( t == TypeInt::ONE )       // 1, or true
  58     return TypeTuple::IFTRUE;   // only true branch is reachable
  59   assert( t == TypeInt::BOOL, "expected boolean type" );
  60 
  61   return TypeTuple::IFBOTH;     // No progress
  62 }
  63 
  64 const RegMask &IfNode::out_RegMask() const {
  65   return RegMask::Empty;
  66 }
  67 
  68 //------------------------------split_if---------------------------------------
  69 // Look for places where we merge constants, then test on the merged value.
  70 // If the IF test will be constant folded on the path with the constant, we
  71 // win by splitting the IF to before the merge point.
  72 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  73   // I could be a lot more general here, but I'm trying to squeeze this
  74   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  75   // on the patterns I accept.  CNC
  76 
  77   // Look for a compare of a constant and a merged value
  78   Node *i1 = iff->in(1);
  79   if( !i1->is_Bool() ) return NULL;
  80   BoolNode *b = i1->as_Bool();
  81   Node *cmp = b->in(1);
  82   if( !cmp->is_Cmp() ) return NULL;
  83   i1 = cmp->in(1);
  84   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  85   PhiNode *phi = i1->as_Phi();
  86   if( phi->is_copy() ) return NULL;
  87   Node *con2 = cmp->in(2);
  88   if( !con2->is_Con() ) return NULL;
  89   // See that the merge point contains some constants
  90   Node *con1=NULL;
  91   uint i4;
  92   for( i4 = 1; i4 < phi->req(); i4++ ) {
  93     con1 = phi->in(i4);
  94     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
  95     if( con1->is_Con() ) break; // Found a constant
  96     // Also allow null-vs-not-null checks
  97     const TypePtr *tp = igvn->type(con1)->isa_ptr();
  98     if( tp && tp->_ptr == TypePtr::NotNull )
  99       break;
 100   }
 101   if( i4 >= phi->req() ) return NULL; // Found no constants
 102 
 103   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 104 
 105   // Make sure that the compare can be constant folded away
 106   Node *cmp2 = cmp->clone();
 107   cmp2->set_req(1,con1);
 108   cmp2->set_req(2,con2);
 109   const Type *t = cmp2->Value(igvn);
 110   // This compare is dead, so whack it!
 111   igvn->remove_dead_node(cmp2);
 112   if( !t->singleton() ) return NULL;
 113 
 114   // No intervening control, like a simple Call
 115   Node *r = iff->in(0);
 116   if( !r->is_Region() ) return NULL;
 117   if( phi->region() != r ) return NULL;
 118   // No other users of the cmp/bool
 119   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 120     //tty->print_cr("many users of cmp/bool");
 121     return NULL;
 122   }
 123 
 124   // Make sure we can determine where all the uses of merged values go
 125   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 126     Node* u = r->fast_out(j);
 127     if( u == r ) continue;
 128     if( u == iff ) continue;
 129     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 130     if( !u->is_Phi() ) {
 131       /*
 132       if( u->is_Start() ) {
 133         tty->print_cr("Region has inlined start use");
 134       } else {
 135         tty->print_cr("Region has odd use");
 136         u->dump(2);
 137       }*/
 138       return NULL;
 139     }
 140     if( u != phi ) {
 141       // CNC - do not allow any other merged value
 142       //tty->print_cr("Merging another value");
 143       //u->dump(2);
 144       return NULL;
 145     }
 146     // Make sure we can account for all Phi uses
 147     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 148       Node* v = u->fast_out(k); // User of the phi
 149       // CNC - Allow only really simple patterns.
 150       // In particular I disallow AddP of the Phi, a fairly common pattern
 151       if (v == cmp) continue;  // The compare is OK
 152       if (v->is_ConstraintCast()) {
 153         // If the cast is derived from data flow edges, it may not have a control edge.
 154         // If so, it should be safe to split. But follow-up code can not deal with
 155         // this (l. 359). So skip.
 156         if (v->in(0) == NULL) {
 157           return NULL;
 158         }
 159         if (v->in(0)->in(0) == iff) {
 160           continue;               // CastPP/II of the IfNode is OK
 161         }
 162       }
 163       // Disabled following code because I cannot tell if exactly one
 164       // path dominates without a real dominator check. CNC 9/9/1999
 165       //uint vop = v->Opcode();
 166       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 167       //  Node *r = v->in(0);     // Get controlling point
 168       //  if( !r ) return NULL;   // Degraded to a copy
 169       //  // Find exactly one path in (either True or False doms, but not IFF)
 170       //  int cnt = 0;
 171       //  for( uint i = 1; i < r->req(); i++ )
 172       //    if( r->in(i) && r->in(i)->in(0) == iff )
 173       //      cnt++;
 174       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 175       //}
 176       if( !v->is_Call() ) {
 177         /*
 178         if( v->Opcode() == Op_AddP ) {
 179           tty->print_cr("Phi has AddP use");
 180         } else if( v->Opcode() == Op_CastPP ) {
 181           tty->print_cr("Phi has CastPP use");
 182         } else if( v->Opcode() == Op_CastII ) {
 183           tty->print_cr("Phi has CastII use");
 184         } else {
 185           tty->print_cr("Phi has use I cant be bothered with");
 186         }
 187         */
 188       }
 189       return NULL;
 190 
 191       /* CNC - Cut out all the fancy acceptance tests
 192       // Can we clone this use when doing the transformation?
 193       // If all uses are from Phis at this merge or constants, then YES.
 194       if( !v->in(0) && v != cmp ) {
 195         tty->print_cr("Phi has free-floating use");
 196         v->dump(2);
 197         return NULL;
 198       }
 199       for( uint l = 1; l < v->req(); l++ ) {
 200         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 201             !v->in(l)->is_Con() ) {
 202           tty->print_cr("Phi has use");
 203           v->dump(2);
 204           return NULL;
 205         } // End of if Phi-use input is neither Phi nor Constant
 206       } // End of for all inputs to Phi-use
 207       */
 208     } // End of for all uses of Phi
 209   } // End of for all uses of Region
 210 
 211   // Only do this if the IF node is in a sane state
 212   if (iff->outcnt() != 2)
 213     return NULL;
 214 
 215   // Got a hit!  Do the Mondo Hack!
 216   //
 217   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 218   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 219   //     cmp - 2                         cmp - 2               cmp - 2
 220   //       bool                            bool_c                bool_x
 221   //       if                               if_c                  if_x
 222   //      T  F                              T  F                  T  F
 223   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 224   //
 225   // Split the paths coming into the merge point into 2 separate groups of
 226   // merges.  On the left will be all the paths feeding constants into the
 227   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 228   // will fold up into a constant; this will let the Cmp fold up as well as
 229   // all the control flow.  Below the original IF we have 2 control
 230   // dependent regions, 's' and 't'.  Now we will merge the two paths
 231   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 232   // likely 2 or more) will promptly constant fold away.
 233   PhaseGVN *phase = igvn;
 234 
 235   // Make a region merging constants and a region merging the rest
 236   uint req_c = 0;
 237   Node* predicate_proj = NULL;
 238   int nb_predicate_proj = 0;
 239   for (uint ii = 1; ii < r->req(); ii++) {
 240     if (phi->in(ii) == con1) {
 241       req_c++;
 242     }
 243     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
 244     if (proj != NULL) {
 245       nb_predicate_proj++;
 246       predicate_proj = proj;
 247     }
 248   }
 249   if (nb_predicate_proj > 1) {
 250     // Can happen in case of loop unswitching and when the loop is
 251     // optimized out: it's not a loop anymore so we don't care about
 252     // predicates.
 253     assert(!r->is_Loop(), "this must not be a loop anymore");
 254     predicate_proj = NULL;
 255   }
 256   Node* predicate_c = NULL;
 257   Node* predicate_x = NULL;
 258   bool counted_loop = r->is_CountedLoop();
 259 
 260   Node *region_c = new RegionNode(req_c + 1);
 261   Node *phi_c    = con1;
 262   uint  len      = r->req();
 263   Node *region_x = new RegionNode(len - req_c);
 264   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 265   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 266     if (phi->in(i) == con1) {
 267       region_c->init_req( i_c++, r  ->in(i) );
 268       if (r->in(i) == predicate_proj)
 269         predicate_c = predicate_proj;
 270     } else {
 271       region_x->init_req( i_x,   r  ->in(i) );
 272       phi_x   ->init_req( i_x++, phi->in(i) );
 273       if (r->in(i) == predicate_proj)
 274         predicate_x = predicate_proj;
 275     }
 276   }
 277   if (predicate_c != NULL && (req_c > 1)) {
 278     assert(predicate_x == NULL, "only one predicate entry expected");
 279     predicate_c = NULL; // Do not clone predicate below merge point
 280   }
 281   if (predicate_x != NULL && ((len - req_c) > 2)) {
 282     assert(predicate_c == NULL, "only one predicate entry expected");
 283     predicate_x = NULL; // Do not clone predicate below merge point
 284   }
 285 
 286   // Register the new RegionNodes but do not transform them.  Cannot
 287   // transform until the entire Region/Phi conglomerate has been hacked
 288   // as a single huge transform.
 289   igvn->register_new_node_with_optimizer( region_c );
 290   igvn->register_new_node_with_optimizer( region_x );
 291   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 292   // about to get one.  If this only use goes away, then phi_x will look dead.
 293   // However, he will be picking up some more uses down below.
 294   Node *hook = new Node(4);
 295   hook->init_req(0, phi_x);
 296   hook->init_req(1, phi_c);
 297   phi_x = phase->transform( phi_x );
 298 
 299   // Make the compare
 300   Node *cmp_c = phase->makecon(t);
 301   Node *cmp_x = cmp->clone();
 302   cmp_x->set_req(1,phi_x);
 303   cmp_x->set_req(2,con2);
 304   cmp_x = phase->transform(cmp_x);
 305   // Make the bool
 306   Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
 307   Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
 308   // Make the IfNode
 309   IfNode* iff_c = iff->clone()->as_If();
 310   iff_c->set_req(0, region_c);
 311   iff_c->set_req(1, b_c);
 312   igvn->set_type_bottom(iff_c);
 313   igvn->_worklist.push(iff_c);
 314   hook->init_req(2, iff_c);
 315 
 316   IfNode* iff_x = iff->clone()->as_If();
 317   iff_x->set_req(0, region_x);
 318   iff_x->set_req(1, b_x);
 319   igvn->set_type_bottom(iff_x);
 320   igvn->_worklist.push(iff_x);
 321   hook->init_req(3, iff_x);
 322 
 323   // Make the true/false arms
 324   Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
 325   Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
 326   if (predicate_c != NULL) {
 327     assert(predicate_x == NULL, "only one predicate entry expected");
 328     // Clone loop predicates to each path
 329     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
 330     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
 331   }
 332   Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
 333   Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
 334   if (predicate_x != NULL) {
 335     assert(predicate_c == NULL, "only one predicate entry expected");
 336     // Clone loop predicates to each path
 337     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
 338     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
 339   }
 340 
 341   // Merge the TRUE paths
 342   Node *region_s = new RegionNode(3);
 343   igvn->_worklist.push(region_s);
 344   region_s->init_req(1, iff_c_t);
 345   region_s->init_req(2, iff_x_t);
 346   igvn->register_new_node_with_optimizer( region_s );
 347 
 348   // Merge the FALSE paths
 349   Node *region_f = new RegionNode(3);
 350   igvn->_worklist.push(region_f);
 351   region_f->init_req(1, iff_c_f);
 352   region_f->init_req(2, iff_x_f);
 353   igvn->register_new_node_with_optimizer( region_f );
 354 
 355   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 356   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 357   cmp->set_req(2,NULL);
 358   // Check for all uses of the Phi and give them a new home.
 359   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 360   Node *phi_s = NULL;     // do not construct unless needed
 361   Node *phi_f = NULL;     // do not construct unless needed
 362   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 363     Node* v = phi->last_out(i2);// User of the phi
 364     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
 365     uint vop = v->Opcode();
 366     Node *proj = NULL;
 367     if( vop == Op_Phi ) {       // Remote merge point
 368       Node *r = v->in(0);
 369       for (uint i3 = 1; i3 < r->req(); i3++)
 370         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 371           proj = r->in(i3);
 372           break;
 373         }
 374     } else if( v->is_ConstraintCast() ) {
 375       proj = v->in(0);          // Controlling projection
 376     } else {
 377       assert( 0, "do not know how to handle this guy" );
 378     }
 379 
 380     Node *proj_path_data, *proj_path_ctrl;
 381     if( proj->Opcode() == Op_IfTrue ) {
 382       if( phi_s == NULL ) {
 383         // Only construct phi_s if needed, otherwise provides
 384         // interfering use.
 385         phi_s = PhiNode::make_blank(region_s,phi);
 386         phi_s->init_req( 1, phi_c );
 387         phi_s->init_req( 2, phi_x );
 388         hook->add_req(phi_s);
 389         phi_s = phase->transform(phi_s);
 390       }
 391       proj_path_data = phi_s;
 392       proj_path_ctrl = region_s;
 393     } else {
 394       if( phi_f == NULL ) {
 395         // Only construct phi_f if needed, otherwise provides
 396         // interfering use.
 397         phi_f = PhiNode::make_blank(region_f,phi);
 398         phi_f->init_req( 1, phi_c );
 399         phi_f->init_req( 2, phi_x );
 400         hook->add_req(phi_f);
 401         phi_f = phase->transform(phi_f);
 402       }
 403       proj_path_data = phi_f;
 404       proj_path_ctrl = region_f;
 405     }
 406 
 407     // Fixup 'v' for for the split
 408     if( vop == Op_Phi ) {       // Remote merge point
 409       uint i;
 410       for( i = 1; i < v->req(); i++ )
 411         if( v->in(i) == phi )
 412           break;
 413       v->set_req(i, proj_path_data );
 414     } else if( v->is_ConstraintCast() ) {
 415       v->set_req(0, proj_path_ctrl );
 416       v->set_req(1, proj_path_data );
 417     } else
 418       ShouldNotReachHere();
 419   }
 420 
 421   // Now replace the original iff's True/False with region_s/region_t.
 422   // This makes the original iff go dead.
 423   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 424     Node* p = iff->last_out(i3);
 425     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 426     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 427     // Replace p with u
 428     igvn->add_users_to_worklist(p);
 429     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 430       Node* x = p->last_out(l);
 431       igvn->hash_delete(x);
 432       uint uses_found = 0;
 433       for( uint j = 0; j < x->req(); j++ ) {
 434         if( x->in(j) == p ) {
 435           x->set_req(j, u);
 436           uses_found++;
 437         }
 438       }
 439       l -= uses_found;    // we deleted 1 or more copies of this edge
 440     }
 441     igvn->remove_dead_node(p);
 442   }
 443 
 444   // Force the original merge dead
 445   igvn->hash_delete(r);
 446   // First, remove region's dead users.
 447   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 448     Node* u = r->last_out(l);
 449     if( u == r ) {
 450       r->set_req(0, NULL);
 451     } else {
 452       assert(u->outcnt() == 0, "only dead users");
 453       igvn->remove_dead_node(u);
 454     }
 455     l -= 1;
 456   }
 457   igvn->remove_dead_node(r);
 458 
 459   // Now remove the bogus extra edges used to keep things alive
 460   igvn->remove_dead_node( hook );
 461 
 462   // Must return either the original node (now dead) or a new node
 463   // (Do not return a top here, since that would break the uniqueness of top.)
 464   return new ConINode(TypeInt::ZERO);
 465 }
 466 
 467 // if this IfNode follows a range check pattern return the projection
 468 // for the failed path
 469 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
 470   Node* b = in(1);
 471   if (b == NULL || !b->is_Bool())  return NULL;
 472   BoolNode* bn = b->as_Bool();
 473   Node* cmp = bn->in(1);
 474   if (cmp == NULL)  return NULL;
 475   if (cmp->Opcode() != Op_CmpU)  return NULL;
 476 
 477   l = cmp->in(1);
 478   r = cmp->in(2);
 479   flip_test = 1;
 480   if (bn->_test._test == BoolTest::le) {
 481     l = cmp->in(2);
 482     r = cmp->in(1);
 483     flip_test = 2;
 484   } else if (bn->_test._test != BoolTest::lt) {
 485     return NULL;
 486   }
 487   if (l->is_top())  return NULL;   // Top input means dead test
 488   if (r->Opcode() != Op_LoadRange && !is_RangeCheck())  return NULL;
 489 
 490   // We have recognized one of these forms:
 491   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 492   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 493 
 494   ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
 495   return iftrap;
 496 }
 497 
 498 
 499 //------------------------------is_range_check---------------------------------
 500 // Return 0 if not a range check.  Return 1 if a range check and set index and
 501 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 502 // is versus a constant.
 503 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 504   int flip_test = 0;
 505   Node* l = NULL;
 506   Node* r = NULL;
 507   ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
 508 
 509   if (iftrap == NULL) {
 510     return 0;
 511   }
 512 
 513   // Make sure it's a real range check by requiring an uncommon trap
 514   // along the OOB path.  Otherwise, it's possible that the user wrote
 515   // something which optimized to look like a range check but behaves
 516   // in some other way.
 517   if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
 518     return 0;
 519   }
 520 
 521   // Look for index+offset form
 522   Node* ind = l;
 523   jint  off = 0;
 524   if (l->is_top()) {
 525     return 0;
 526   } else if (l->Opcode() == Op_AddI) {
 527     if ((off = l->in(1)->find_int_con(0)) != 0) {
 528       ind = l->in(2)->uncast();
 529     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 530       ind = l->in(1)->uncast();
 531     }
 532   } else if ((off = l->find_int_con(-1)) >= 0) {
 533     // constant offset with no variable index
 534     ind = NULL;
 535   } else {
 536     // variable index with no constant offset (or dead negative index)
 537     off = 0;
 538   }
 539 
 540   // Return all the values:
 541   index  = ind;
 542   offset = off;
 543   range  = r;
 544   return flip_test;
 545 }
 546 
 547 //------------------------------adjust_check-----------------------------------
 548 // Adjust (widen) a prior range check
 549 static void adjust_check(Node* proj, Node* range, Node* index,
 550                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 551   PhaseGVN *gvn = igvn;
 552   // Break apart the old check
 553   Node *iff = proj->in(0);
 554   Node *bol = iff->in(1);
 555   if( bol->is_top() ) return;   // In case a partially dead range check appears
 556   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 557   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 558   if( !bol->is_Bool() ) return;
 559 
 560   Node *cmp = bol->in(1);
 561   // Compute a new check
 562   Node *new_add = gvn->intcon(off_lo);
 563   if( index ) {
 564     new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
 565   }
 566   Node *new_cmp = (flip == 1)
 567     ? new CmpUNode( new_add, range )
 568     : new CmpUNode( range, new_add );
 569   new_cmp = gvn->transform(new_cmp);
 570   // See if no need to adjust the existing check
 571   if( new_cmp == cmp ) return;
 572   // Else, adjust existing check
 573   Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 574   igvn->rehash_node_delayed( iff );
 575   iff->set_req_X( 1, new_bol, igvn );
 576 }
 577 
 578 //------------------------------up_one_dom-------------------------------------
 579 // Walk up the dominator tree one step.  Return NULL at root or true
 580 // complex merges.  Skips through small diamonds.
 581 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 582   Node *dom = curr->in(0);
 583   if( !dom )                    // Found a Region degraded to a copy?
 584     return curr->nonnull_req(); // Skip thru it
 585 
 586   if( curr != dom )             // Normal walk up one step?
 587     return dom;
 588 
 589   // Use linear_only if we are still parsing, since we cannot
 590   // trust the regions to be fully filled in.
 591   if (linear_only)
 592     return NULL;
 593 
 594   if( dom->is_Root() )
 595     return NULL;
 596 
 597   // Else hit a Region.  Check for a loop header
 598   if( dom->is_Loop() )
 599     return dom->in(1);          // Skip up thru loops
 600 
 601   // Check for small diamonds
 602   Node *din1, *din2, *din3, *din4;
 603   if( dom->req() == 3 &&        // 2-path merge point
 604       (din1 = dom ->in(1)) &&   // Left  path exists
 605       (din2 = dom ->in(2)) &&   // Right path exists
 606       (din3 = din1->in(0)) &&   // Left  path up one
 607       (din4 = din2->in(0)) ) {  // Right path up one
 608     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 609         (din3 = din3->in(0)) )
 610       din3 = din3->in(0);
 611     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 612         (din4 = din4->in(0)) )
 613       din4 = din4->in(0);
 614     if( din3 == din4 && din3->is_If() )
 615       return din3;              // Skip around diamonds
 616   }
 617 
 618   // Give up the search at true merges
 619   return NULL;                  // Dead loop?  Or hit root?
 620 }
 621 
 622 
 623 //------------------------------filtered_int_type--------------------------------
 624 // Return a possibly more restrictive type for val based on condition control flow for an if
 625 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 626   assert(if_proj &&
 627          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 628   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 629     IfNode* iff = if_proj->in(0)->as_If();
 630     if (iff->in(1) && iff->in(1)->is_Bool()) {
 631       BoolNode* bol = iff->in(1)->as_Bool();
 632       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 633         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 634         if (cmp->in(1) == val) {
 635           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 636           if (cmp2_t != NULL) {
 637             jint lo = cmp2_t->_lo;
 638             jint hi = cmp2_t->_hi;
 639             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 640             switch (msk) {
 641             case BoolTest::ne:
 642               // Can't refine type
 643               return NULL;
 644             case BoolTest::eq:
 645               return cmp2_t;
 646             case BoolTest::lt:
 647               lo = TypeInt::INT->_lo;
 648               if (hi - 1 < hi) {
 649                 hi = hi - 1;
 650               }
 651               break;
 652             case BoolTest::le:
 653               lo = TypeInt::INT->_lo;
 654               break;
 655             case BoolTest::gt:
 656               if (lo + 1 > lo) {
 657                 lo = lo + 1;
 658               }
 659               hi = TypeInt::INT->_hi;
 660               break;
 661             case BoolTest::ge:
 662               // lo unchanged
 663               hi = TypeInt::INT->_hi;
 664               break;
 665             }
 666             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 667             return rtn_t;
 668           }
 669         }
 670       }
 671     }
 672   }
 673   return NULL;
 674 }
 675 
 676 //------------------------------fold_compares----------------------------
 677 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 678 // the direction of this if is determined by the preceding if so it
 679 // can be eliminate entirely.
 680 //
 681 // Given an if testing (CmpI n v) check for an immediately control
 682 // dependent if that is testing (CmpI n v2) and has one projection
 683 // leading to this if and the other projection leading to a region
 684 // that merges one of this ifs control projections.
 685 //
 686 //                   If
 687 //                  / |
 688 //                 /  |
 689 //                /   |
 690 //              If    |
 691 //              /\    |
 692 //             /  \   |
 693 //            /    \  |
 694 //           /    Region
 695 //
 696 // Or given an if testing (CmpI n v) check for a dominating if that is
 697 // testing (CmpI n v2), both having one projection leading to an
 698 // uncommon trap. Allow Another independent guard in between to cover
 699 // an explicit range check:
 700 // if (index < 0 || index >= array.length) {
 701 // which may need a null check to guard the LoadRange
 702 //
 703 //                   If
 704 //                  / \
 705 //                 /   \
 706 //                /     \
 707 //              If      unc
 708 //              /\
 709 //             /  \
 710 //            /    \
 711 //           /      unc
 712 //
 713 
 714 // Is the comparison for this If suitable for folding?
 715 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
 716   return in(1) != NULL &&
 717     in(1)->is_Bool() &&
 718     in(1)->in(1) != NULL &&
 719     in(1)->in(1)->Opcode() == Op_CmpI &&
 720     in(1)->in(1)->in(2) != NULL &&
 721     in(1)->in(1)->in(2) != igvn->C->top() &&
 722     (in(1)->as_Bool()->_test.is_less() ||
 723      in(1)->as_Bool()->_test.is_greater());
 724 }
 725 
 726 // Is a dominating control suitable for folding with this if?
 727 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
 728   return ctrl != NULL &&
 729     ctrl->is_Proj() &&
 730     ctrl->in(0) != NULL &&
 731     ctrl->in(0)->Opcode() == Op_If &&
 732     ctrl->in(0)->outcnt() == 2 &&
 733     ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
 734     // Must compare same value
 735     ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
 736     ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
 737 }
 738 
 739 // Do this If and the dominating If share a region?
 740 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
 741   ProjNode* otherproj = proj->other_if_proj();
 742   Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
 743   RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
 744   success = NULL;
 745   fail = NULL;
 746 
 747   if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
 748     for (int i = 0; i < 2; i++) {
 749       ProjNode* proj = proj_out(i);
 750       if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 751         success = proj;
 752       } else if (fail == NULL) {
 753         fail = proj;
 754       } else {
 755         success = fail = NULL;
 756       }
 757     }
 758   }
 759   return success != NULL && fail != NULL;
 760 }
 761 
 762 // Return projection that leads to an uncommon trap if any
 763 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
 764   for (int i = 0; i < 2; i++) {
 765     call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
 766     if (call != NULL) {
 767       return proj_out(i);
 768     }
 769   }
 770   return NULL;
 771 }
 772 
 773 // Do this If and the dominating If both branch out to an uncommon trap
 774 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
 775   ProjNode* otherproj = proj->other_if_proj();
 776   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
 777 
 778   if (otherproj->outcnt() == 1 && dom_unc != NULL) {
 779     // We need to re-execute the folded Ifs after deoptimization from the merged traps
 780     if (!dom_unc->jvms()->should_reexecute()) {
 781       return false;
 782     }
 783 
 784     CallStaticJavaNode* unc = NULL;
 785     ProjNode* unc_proj = uncommon_trap_proj(unc);
 786     if (unc_proj != NULL && unc_proj->outcnt() == 1) {
 787       if (dom_unc == unc) {
 788         // Allow the uncommon trap to be shared through a region
 789         RegionNode* r = unc->in(0)->as_Region();
 790         if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
 791           return false;
 792         }
 793         assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
 794       } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
 795         return false;
 796       }
 797 
 798       // Different methods and methods containing jsrs are not supported.
 799       ciMethod* method = unc->jvms()->method();
 800       ciMethod* dom_method = dom_unc->jvms()->method();
 801       if (method != dom_method || method->has_jsrs()) {
 802         return false;
 803       }
 804       // Check that both traps are in the same activation of the method (instead
 805       // of two activations being inlined through different call sites) by verifying
 806       // that the call stacks are equal for both JVMStates.
 807       JVMState* dom_caller = dom_unc->jvms()->caller();
 808       JVMState* caller = unc->jvms()->caller();
 809       if ((dom_caller == NULL) != (caller == NULL)) {
 810         // The current method must either be inlined into both dom_caller and
 811         // caller or must not be inlined at all (top method). Bail out otherwise.
 812         return false;
 813       } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
 814         return false;
 815       }
 816       // Check that the bci of the dominating uncommon trap dominates the bci
 817       // of the dominated uncommon trap. Otherwise we may not re-execute
 818       // the dominated check after deoptimization from the merged uncommon trap.
 819       ciTypeFlow* flow = dom_method->get_flow_analysis();
 820       int bci = unc->jvms()->bci();
 821       int dom_bci = dom_unc->jvms()->bci();
 822       if (!flow->is_dominated_by(bci, dom_bci)) {
 823         return false;
 824       }
 825 
 826       // See merge_uncommon_traps: the reason of the uncommon trap
 827       // will be changed and the state of the dominating If will be
 828       // used. Checked that we didn't apply this transformation in a
 829       // previous compilation and it didn't cause too many traps
 830       if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
 831           !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
 832         success = unc_proj;
 833         fail = unc_proj->other_if_proj();
 834         return true;
 835       }
 836     }
 837   }
 838   return false;
 839 }
 840 
 841 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
 842 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 843   Node* this_cmp = in(1)->in(1);
 844   BoolNode* this_bool = in(1)->as_Bool();
 845   IfNode* dom_iff = proj->in(0)->as_If();
 846   BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 847   Node* lo = dom_iff->in(1)->in(1)->in(2);
 848   Node* hi = this_cmp->in(2);
 849   Node* n = this_cmp->in(1);
 850   ProjNode* otherproj = proj->other_if_proj();
 851 
 852   const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
 853   const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
 854 
 855   BoolTest::mask lo_test = dom_bool->_test._test;
 856   BoolTest::mask hi_test = this_bool->_test._test;
 857   BoolTest::mask cond = hi_test;
 858 
 859   // convert:
 860   //
 861   //          dom_bool = x {<,<=,>,>=} a
 862   //                           / \
 863   //     proj = {True,False}  /   \ otherproj = {False,True}
 864   //                         /
 865   //        this_bool = x {<,<=} b
 866   //                       / \
 867   //  fail = {True,False} /   \ success = {False,True}
 868   //                     /
 869   //
 870   // (Second test guaranteed canonicalized, first one may not have
 871   // been canonicalized yet)
 872   //
 873   // into:
 874   //
 875   // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
 876   //                       / \
 877   //                 fail /   \ success
 878   //                     /
 879   //
 880 
 881   // Figure out which of the two tests sets the upper bound and which
 882   // sets the lower bound if any.
 883   Node* adjusted_lim = NULL;
 884   if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
 885     assert((dom_bool->_test.is_less() && !proj->_con) ||
 886            (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
 887     // this test was canonicalized
 888     assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
 889 
 890     // this_bool = <
 891     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 892     //     x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
 893     //     lo = a, hi = b, adjusted_lim = b-a, cond = <u
 894     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 895     //     x in ]a, b[ on the fail (= True) projection, b > a:
 896     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
 897     // this_bool = <=
 898     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 899     //     x in [a, b] on the fail (= True) projection, b+1 > a-1:
 900     //     lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
 901     //     lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
 902     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 903     //     x in ]a, b] on the fail (= True) projection b+1 > a:
 904     //     lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
 905     //     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
 906 
 907     if (hi_test == BoolTest::lt) {
 908       if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 909         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 910       }
 911     } else {
 912       assert(hi_test == BoolTest::le, "bad test");
 913       if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
 914         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 915         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 916         cond = BoolTest::lt;
 917       } else {
 918         assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
 919         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 920         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 921         cond = BoolTest::lt;
 922       }
 923     }
 924   } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
 925 
 926     // this_bool = <
 927     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 928     //     x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
 929     //     lo = b, hi = a, adjusted_lim = a-b, cond = >=u
 930     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 931     //     x in [b, a] on the fail (= False) projection, a+1 > b-1:
 932     //     lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
 933     //     lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
 934     // this_bool = <=
 935     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 936     //     x in ]b, a[ on the fail (= False) projection, a > b:
 937     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
 938     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 939     //     x in ]b, a] on the fail (= False) projection, a+1 > b:
 940     //     lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
 941     //     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
 942 
 943     swap(lo, hi);
 944     swap(lo_type, hi_type);
 945     swap(lo_test, hi_test);
 946 
 947     assert((dom_bool->_test.is_less() && proj->_con) ||
 948            (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
 949     // this test was canonicalized
 950     assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
 951 
 952     cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
 953 
 954     if (lo_test == BoolTest::lt) {
 955       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 956         cond = BoolTest::ge;
 957       } else {
 958         assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
 959         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 960         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 961         cond = BoolTest::ge;
 962       }
 963     } else if (lo_test == BoolTest::le) {
 964       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 965         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 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         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 971         cond = BoolTest::ge;
 972       }
 973     }
 974   } else {
 975     const TypeInt* failtype  = filtered_int_type(igvn, n, proj);
 976     if (failtype != NULL) {
 977       const TypeInt* type2 = filtered_int_type(igvn, n, fail);
 978       if (type2 != NULL) {
 979         failtype = failtype->join(type2)->is_int();
 980         if (failtype->_lo > failtype->_hi) {
 981           // previous if determines the result of this if so
 982           // replace Bool with constant
 983           igvn->_worklist.push(in(1));
 984           igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
 985           return true;
 986         }
 987       }
 988     }
 989     lo = NULL;
 990     hi = NULL;
 991   }
 992 
 993   if (lo && hi) {
 994     // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
 995     Node* adjusted_val = igvn->transform(new SubINode(n,  lo));
 996     if (adjusted_lim == NULL) {
 997       adjusted_lim = igvn->transform(new SubINode(hi, lo));
 998     }
 999     Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1000     Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1001 
1002     igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1003     igvn->_worklist.push(in(1));
1004     igvn->replace_input_of(this, 1, newbool);
1005 
1006     return true;
1007   }
1008   return false;
1009 }
1010 
1011 // Merge the branches that trap for this If and the dominating If into
1012 // a single region that branches to the uncommon trap for the
1013 // dominating If
1014 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1015   Node* res = this;
1016   assert(success->in(0) == this, "bad projection");
1017 
1018   ProjNode* otherproj = proj->other_if_proj();
1019 
1020   CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1021   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1022 
1023   if (unc != dom_unc) {
1024     Node* r = new RegionNode(3);
1025 
1026     r->set_req(1, otherproj);
1027     r->set_req(2, success);
1028     r = igvn->transform(r);
1029     assert(r->is_Region(), "can't go away");
1030 
1031     // Make both If trap at the state of the first If: once the CmpI
1032     // nodes are merged, if we trap we don't know which of the CmpI
1033     // nodes would have caused the trap so we have to restart
1034     // execution at the first one
1035     igvn->replace_input_of(dom_unc, 0, r);
1036     igvn->replace_input_of(unc, 0, igvn->C->top());
1037   }
1038   int trap_request = dom_unc->uncommon_trap_request();
1039   Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1040   Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1041 
1042   int flip_test = 0;
1043   Node* l = NULL;
1044   Node* r = NULL;
1045 
1046   if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1047     // If this looks like a range check, change the trap to
1048     // Reason_range_check so the compiler recognizes it as a range
1049     // check and applies the corresponding optimizations
1050     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1051 
1052     improve_address_types(l, r, fail, igvn);
1053 
1054     res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1055   } else if (unc != dom_unc) {
1056     // If we trap we won't know what CmpI would have caused the trap
1057     // so use a special trap reason to mark this pair of CmpI nodes as
1058     // bad candidate for folding. On recompilation we won't fold them
1059     // and we may trap again but this time we'll know what branch
1060     // traps
1061     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1062   }
1063   igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1064   return res;
1065 }
1066 
1067 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1068 // of a rangecheck on index i, on 64 bit the compares may be followed
1069 // by memory accesses using i as index. In that case, the CmpU tells
1070 // us something about the values taken by i that can help the compiler
1071 // (see Compile::conv_I2X_index())
1072 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1073 #ifdef _LP64
1074   ResourceMark rm;
1075   Node_Stack stack(2);
1076 
1077   assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1078   const TypeInt* array_size = igvn->type(r)->is_int();
1079 
1080   stack.push(l, 0);
1081 
1082   while(stack.size() > 0) {
1083     Node* n = stack.node();
1084     uint start = stack.index();
1085 
1086     uint i = start;
1087     for (; i < n->outcnt(); i++) {
1088       Node* use = n->raw_out(i);
1089       if (stack.size() == 1) {
1090         if (use->Opcode() == Op_ConvI2L) {
1091           const TypeLong* bounds = use->as_Type()->type()->is_long();
1092           if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1093               (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1094             stack.set_index(i+1);
1095             stack.push(use, 0);
1096             break;
1097           }
1098         }
1099       } else if (use->is_Mem()) {
1100         Node* ctrl = use->in(0);
1101         for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1102           ctrl = up_one_dom(ctrl);
1103         }
1104         if (ctrl == fail) {
1105           Node* init_n = stack.node_at(1);
1106           assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1107           // Create a new narrow ConvI2L node that is dependent on the range check
1108           Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1109 
1110           // The type of the ConvI2L may be widen and so the new
1111           // ConvI2L may not be better than an existing ConvI2L
1112           if (new_n != init_n) {
1113             for (uint j = 2; j < stack.size(); j++) {
1114               Node* n = stack.node_at(j);
1115               Node* clone = n->clone();
1116               int rep = clone->replace_edge(init_n, new_n);
1117               assert(rep > 0, "can't find expected node?");
1118               clone = igvn->transform(clone);
1119               init_n = n;
1120               new_n = clone;
1121             }
1122             igvn->hash_delete(use);
1123             int rep = use->replace_edge(init_n, new_n);
1124             assert(rep > 0, "can't find expected node?");
1125             igvn->transform(use);
1126             if (init_n->outcnt() == 0) {
1127               igvn->_worklist.push(init_n);
1128             }
1129           }
1130         }
1131       } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1132                                         igvn->type(use)->isa_ptr())) {
1133         stack.set_index(i+1);
1134         stack.push(use, 0);
1135         break;
1136       }
1137     }
1138     if (i == n->outcnt()) {
1139       stack.pop();
1140     }
1141   }
1142 #endif
1143 }
1144 
1145 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1146   if (in(1) != NULL &&
1147       in(1)->in(1) != NULL &&
1148       in(1)->in(1)->in(2) != NULL) {
1149     Node* other = in(1)->in(1)->in(2);
1150     if (other->Opcode() == Op_LoadRange &&
1151         ((other->in(0) != NULL && other->in(0) == proj) ||
1152          (other->in(0) == NULL &&
1153           other->in(2) != NULL &&
1154           other->in(2)->is_AddP() &&
1155           other->in(2)->in(1) != NULL &&
1156           other->in(2)->in(1)->Opcode() == Op_CastPP &&
1157           other->in(2)->in(1)->in(0) == proj))) {
1158       return true;
1159     }
1160   }
1161   return false;
1162 }
1163 
1164 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1165   Node* other = in(1)->in(1)->in(2);
1166   if (other->in(MemNode::Address) != NULL &&
1167       proj->in(0)->in(1) != NULL &&
1168       proj->in(0)->in(1)->is_Bool() &&
1169       proj->in(0)->in(1)->in(1) != NULL &&
1170       proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1171       proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1172       proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1173       igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1174     return true;
1175   }
1176   return false;
1177 }
1178 
1179 // Check that the If that is in between the 2 integer comparisons has
1180 // no side effect
1181 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1182   if (proj != NULL &&
1183       proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1184       proj->outcnt() <= 2) {
1185     if (proj->outcnt() == 1 ||
1186         // Allow simple null check from LoadRange
1187         (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1188       CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1189       CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1190 
1191       // reroute_side_effect_free_unc changes the state of this
1192       // uncommon trap to restart execution at the previous
1193       // CmpI. Check that this change in a previous compilation didn't
1194       // cause too many traps.
1195       int trap_request = unc->uncommon_trap_request();
1196       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1197 
1198       if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1199         return false;
1200       }
1201 
1202       return true;
1203     }
1204   }
1205   return false;
1206 }
1207 
1208 // Make the If between the 2 integer comparisons trap at the state of
1209 // the first If: the last CmpI is the one replaced by a CmpU and the
1210 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1211 // won't be guarded by the first CmpI anymore. It can trap in cases
1212 // where the first CmpI would have prevented it from executing: on a
1213 // trap, we need to restart execution at the state of the first CmpI
1214 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1215   CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1216   ProjNode* otherproj = proj->other_if_proj();
1217   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1218   Node* call_proj = dom_unc->unique_ctrl_out();
1219   Node* halt = call_proj->unique_ctrl_out();
1220 
1221   Node* new_unc = dom_unc->clone();
1222   call_proj = call_proj->clone();
1223   halt = halt->clone();
1224   Node* c = otherproj->clone();
1225 
1226   c = igvn->transform(c);
1227   new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1228   new_unc->set_req(0, c);
1229   new_unc = igvn->transform(new_unc);
1230   call_proj->set_req(0, new_unc);
1231   call_proj = igvn->transform(call_proj);
1232   halt->set_req(0, call_proj);
1233   halt = igvn->transform(halt);
1234 
1235   igvn->replace_node(otherproj, igvn->C->top());
1236   igvn->C->root()->add_req(halt);
1237 }
1238 
1239 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1240   if (Opcode() != Op_If) return NULL;
1241 
1242   if (cmpi_folds(igvn)) {
1243     Node* ctrl = in(0);
1244     if (is_ctrl_folds(ctrl, igvn) &&
1245         ctrl->outcnt() == 1) {
1246       // A integer comparison immediately dominated by another integer
1247       // comparison
1248       ProjNode* success = NULL;
1249       ProjNode* fail = NULL;
1250       ProjNode* dom_cmp = ctrl->as_Proj();
1251       if (has_shared_region(dom_cmp, success, fail) &&
1252           // Next call modifies graph so must be last
1253           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1254         return this;
1255       }
1256       if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1257           // Next call modifies graph so must be last
1258           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1259         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1260       }
1261       return NULL;
1262     } else if (ctrl->in(0) != NULL &&
1263                ctrl->in(0)->in(0) != NULL) {
1264       ProjNode* success = NULL;
1265       ProjNode* fail = NULL;
1266       Node* dom = ctrl->in(0)->in(0);
1267       ProjNode* dom_cmp = dom->isa_Proj();
1268       ProjNode* other_cmp = ctrl->isa_Proj();
1269 
1270       // Check if it's an integer comparison dominated by another
1271       // integer comparison with another test in between
1272       if (is_ctrl_folds(dom, igvn) &&
1273           has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1274           is_side_effect_free_test(other_cmp, igvn) &&
1275           // Next call modifies graph so must be last
1276           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1277         reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1278         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1279       }
1280     }
1281   }
1282   return NULL;
1283 }
1284 
1285 //------------------------------remove_useless_bool----------------------------
1286 // Check for people making a useless boolean: things like
1287 // if( (x < y ? true : false) ) { ... }
1288 // Replace with if( x < y ) { ... }
1289 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1290   Node *i1 = iff->in(1);
1291   if( !i1->is_Bool() ) return NULL;
1292   BoolNode *bol = i1->as_Bool();
1293 
1294   Node *cmp = bol->in(1);
1295   if( cmp->Opcode() != Op_CmpI ) return NULL;
1296 
1297   // Must be comparing against a bool
1298   const Type *cmp2_t = phase->type( cmp->in(2) );
1299   if( cmp2_t != TypeInt::ZERO &&
1300       cmp2_t != TypeInt::ONE )
1301     return NULL;
1302 
1303   // Find a prior merge point merging the boolean
1304   i1 = cmp->in(1);
1305   if( !i1->is_Phi() ) return NULL;
1306   PhiNode *phi = i1->as_Phi();
1307   if( phase->type( phi ) != TypeInt::BOOL )
1308     return NULL;
1309 
1310   // Check for diamond pattern
1311   int true_path = phi->is_diamond_phi();
1312   if( true_path == 0 ) return NULL;
1313 
1314   // Make sure that iff and the control of the phi are different. This
1315   // should really only happen for dead control flow since it requires
1316   // an illegal cycle.
1317   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1318 
1319   // phi->region->if_proj->ifnode->bool->cmp
1320   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1321 
1322   // Now get the 'sense' of the test correct so we can plug in
1323   // either iff2->in(1) or its complement.
1324   int flip = 0;
1325   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1326   else if( bol->_test._test != BoolTest::eq ) return NULL;
1327   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1328 
1329   const Type *phi1_t = phase->type( phi->in(1) );
1330   const Type *phi2_t = phase->type( phi->in(2) );
1331   // Check for Phi(0,1) and flip
1332   if( phi1_t == TypeInt::ZERO ) {
1333     if( phi2_t != TypeInt::ONE ) return NULL;
1334     flip = 1-flip;
1335   } else {
1336     // Check for Phi(1,0)
1337     if( phi1_t != TypeInt::ONE  ) return NULL;
1338     if( phi2_t != TypeInt::ZERO ) return NULL;
1339   }
1340   if( true_path == 2 ) {
1341     flip = 1-flip;
1342   }
1343 
1344   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1345   assert(new_bol != iff->in(1), "must make progress");
1346   iff->set_req(1, new_bol);
1347   // Intervening diamond probably goes dead
1348   phase->C->set_major_progress();
1349   return iff;
1350 }
1351 
1352 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1353 
1354 struct RangeCheck {
1355   Node* ctl;
1356   jint off;
1357 };
1358 
1359 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1360   if (remove_dead_region(phase, can_reshape))  return this;
1361   // No Def-Use info?
1362   if (!can_reshape)  return NULL;
1363 
1364   // Don't bother trying to transform a dead if
1365   if (in(0)->is_top())  return NULL;
1366   // Don't bother trying to transform an if with a dead test
1367   if (in(1)->is_top())  return NULL;
1368   // Another variation of a dead test
1369   if (in(1)->is_Con())  return NULL;
1370   // Another variation of a dead if
1371   if (outcnt() < 2)  return NULL;
1372 
1373   // Canonicalize the test.
1374   Node* idt_if = idealize_test(phase, this);
1375   if (idt_if != NULL)  return idt_if;
1376 
1377   // Try to split the IF
1378   PhaseIterGVN *igvn = phase->is_IterGVN();
1379   Node *s = split_if(this, igvn);
1380   if (s != NULL)  return s;
1381 
1382   return NodeSentinel;
1383 }
1384 
1385 //------------------------------Ideal------------------------------------------
1386 // Return a node which is more "ideal" than the current node.  Strip out
1387 // control copies
1388 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1389   Node* res = Ideal_common(phase, can_reshape);
1390   if (res != NodeSentinel) {
1391     return res;
1392   }
1393 
1394   // Check for people making a useless boolean: things like
1395   // if( (x < y ? true : false) ) { ... }
1396   // Replace with if( x < y ) { ... }
1397   Node *bol2 = remove_useless_bool(this, phase);
1398   if( bol2 ) return bol2;
1399 
1400   if (in(0) == NULL) return NULL;     // Dead loop?
1401 
1402   PhaseIterGVN *igvn = phase->is_IterGVN();
1403   Node* result = fold_compares(igvn);
1404   if (result != NULL) {
1405     return result;
1406   }
1407 
1408   // Scan for an equivalent test
1409   Node *cmp;
1410   int dist = 0;               // Cutoff limit for search
1411   int op = Opcode();
1412   if( op == Op_If &&
1413       (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1414     if( cmp->in(2) != NULL && // make sure cmp is not already dead
1415         cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1416       dist = 64;              // Limit for null-pointer scans
1417     } else {
1418       dist = 4;               // Do not bother for random pointer tests
1419     }
1420   } else {
1421     dist = 4;                 // Limit for random junky scans
1422   }
1423 
1424   Node* prev_dom = search_identical(dist);
1425 
1426   if (prev_dom == NULL) {
1427     return NULL;
1428   }
1429 
1430   // Replace dominated IfNode
1431   return dominated_by(prev_dom, igvn);
1432 }
1433 
1434 //------------------------------dominated_by-----------------------------------
1435 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1436 #ifndef PRODUCT
1437   if (TraceIterativeGVN) {
1438     tty->print("   Removing IfNode: "); this->dump();
1439   }
1440   if (VerifyOpto && !igvn->allow_progress()) {
1441     // Found an equivalent dominating test,
1442     // we can not guarantee reaching a fix-point for these during iterativeGVN
1443     // since intervening nodes may not change.
1444     return NULL;
1445   }
1446 #endif
1447 
1448   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1449   Node *idom = in(0);
1450   // Need opcode to decide which way 'this' test goes
1451   int prev_op = prev_dom->Opcode();
1452   Node *top = igvn->C->top(); // Shortcut to top
1453 
1454   // Loop predicates may have depending checks which should not
1455   // be skipped. For example, range check predicate has two checks
1456   // for lower and upper bounds.
1457   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1458   if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1459    prev_dom = idom;
1460 
1461   // Now walk the current IfNode's projections.
1462   // Loop ends when 'this' has no more uses.
1463   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1464     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1465     igvn->add_users_to_worklist(ifp);
1466     // Check which projection it is and set target.
1467     // Data-target is either the dominating projection of the same type
1468     // or TOP if the dominating projection is of opposite type.
1469     // Data-target will be used as the new control edge for the non-CFG
1470     // nodes like Casts and Loads.
1471     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1472     // Control-target is just the If's immediate dominator or TOP.
1473     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1474 
1475     // For each child of an IfTrue/IfFalse projection, reroute.
1476     // Loop ends when projection has no more uses.
1477     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1478       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1479       if( !s->depends_only_on_test() ) {
1480         // Find the control input matching this def-use edge.
1481         // For Regions it may not be in slot 0.
1482         uint l;
1483         for( l = 0; s->in(l) != ifp; l++ ) { }
1484         igvn->replace_input_of(s, l, ctrl_target);
1485       } else {                      // Else, for control producers,
1486         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1487       }
1488     } // End for each child of a projection
1489 
1490     igvn->remove_dead_node(ifp);
1491   } // End for each IfTrue/IfFalse child of If
1492 
1493   // Kill the IfNode
1494   igvn->remove_dead_node(this);
1495 
1496   // Must return either the original node (now dead) or a new node
1497   // (Do not return a top here, since that would break the uniqueness of top.)
1498   return new ConINode(TypeInt::ZERO);
1499 }
1500 
1501 Node* IfNode::search_identical(int dist) {
1502   // Setup to scan up the CFG looking for a dominating test
1503   Node* dom = in(0);
1504   Node* prev_dom = this;
1505   int op = Opcode();
1506   // Search up the dominator tree for an If with an identical test
1507   while( dom->Opcode() != op    ||  // Not same opcode?
1508          dom->in(1)    != in(1) ||  // Not same input 1?
1509          (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1510          prev_dom->in(0) != dom ) { // One path of test does not dominate?
1511     if( dist < 0 ) return NULL;
1512 
1513     dist--;
1514     prev_dom = dom;
1515     dom = up_one_dom( dom );
1516     if( !dom ) return NULL;
1517   }
1518 
1519   // Check that we did not follow a loop back to ourselves
1520   if( this == dom )
1521     return NULL;
1522 
1523   if( dist > 2 )              // Add to count of NULL checks elided
1524     explicit_null_checks_elided++;
1525 
1526   return prev_dom;
1527 }
1528 
1529 //------------------------------Identity---------------------------------------
1530 // If the test is constant & we match, then we are the input Control
1531 Node* IfProjNode::Identity(PhaseGVN* phase) {
1532   // Can only optimize if cannot go the other way
1533   const TypeTuple *t = phase->type(in(0))->is_tuple();
1534   if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1535        // During parsing (GVN) we don't remove dead code aggressively.
1536        // Cut off dead branch and let PhaseRemoveUseless take care of it.
1537       (!phase->is_IterGVN() ||
1538        // During IGVN, first wait for the dead branch to be killed.
1539        // Otherwise, the IfNode's control will have two control uses (the IfNode
1540        // that doesn't go away because it still has uses and this branch of the
1541        // If) which breaks other optimizations. Node::has_special_unique_user()
1542        // will cause this node to be reprocessed once the dead branch is killed.
1543        in(0)->outcnt() == 1))) {
1544     // IfNode control
1545     return in(0)->in(0);
1546   }
1547   // no progress
1548   return this;
1549 }
1550 
1551 #ifndef PRODUCT
1552 //-------------------------------related---------------------------------------
1553 // An IfProjNode's related node set consists of its input (an IfNode) including
1554 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1555 // the restrictions for IfNode apply (see IfNode::rel).
1556 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1557   Node* ifNode = this->in(0);
1558   in_rel->append(ifNode);
1559   if (compact) {
1560     ifNode->collect_nodes(in_rel, 3, false, true);
1561   } else {
1562     ifNode->collect_nodes_in_all_data(in_rel, false);
1563   }
1564   this->collect_nodes(out_rel, -1, false, false);
1565 }
1566 
1567 //------------------------------dump_spec--------------------------------------
1568 void IfNode::dump_spec(outputStream *st) const {
1569   st->print("P=%f, C=%f",_prob,_fcnt);
1570 }
1571 
1572 //-------------------------------related---------------------------------------
1573 // For an IfNode, the set of related output nodes is just the output nodes till
1574 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1575 // The related input nodes contain no control nodes, but all data nodes
1576 // pertaining to the condition. In compact mode, the input nodes are collected
1577 // up to a depth of 3.
1578 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1579   if (compact) {
1580     this->collect_nodes(in_rel, 3, false, true);
1581   } else {
1582     this->collect_nodes_in_all_data(in_rel, false);
1583   }
1584   this->collect_nodes(out_rel, -2, false, false);
1585 }
1586 #endif
1587 
1588 //------------------------------idealize_test----------------------------------
1589 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1590 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1591 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1592 // needed.
1593 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1594   assert(iff->in(0) != NULL, "If must be live");
1595 
1596   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1597   Node* old_if_f = iff->proj_out(false);
1598   Node* old_if_t = iff->proj_out(true);
1599 
1600   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1601   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1602   // happens in count-down loops
1603   if (iff->is_CountedLoopEnd())  return NULL;
1604   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1605   BoolNode *b = iff->in(1)->as_Bool();
1606   BoolTest bt = b->_test;
1607   // Test already in good order?
1608   if( bt.is_canonical() )
1609     return NULL;
1610 
1611   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1612   // cloning the IfNode.
1613   Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1614   if( !new_b->is_Bool() ) return NULL;
1615   b = new_b->as_Bool();
1616 
1617   PhaseIterGVN *igvn = phase->is_IterGVN();
1618   assert( igvn, "Test is not canonical in parser?" );
1619 
1620   // The IF node never really changes, but it needs to be cloned
1621   iff = iff->clone()->as_If();
1622   iff->set_req(1, b);
1623   iff->_prob = 1.0-iff->_prob;
1624 
1625   Node *prior = igvn->hash_find_insert(iff);
1626   if( prior ) {
1627     igvn->remove_dead_node(iff);
1628     iff = (IfNode*)prior;
1629   } else {
1630     // Cannot call transform on it just yet
1631     igvn->set_type_bottom(iff);
1632   }
1633   igvn->_worklist.push(iff);
1634 
1635   // Now handle projections.  Cloning not required.
1636   Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1637   Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1638 
1639   igvn->register_new_node_with_optimizer(new_if_f);
1640   igvn->register_new_node_with_optimizer(new_if_t);
1641   // Flip test, so flip trailing control
1642   igvn->replace_node(old_if_f, new_if_t);
1643   igvn->replace_node(old_if_t, new_if_f);
1644 
1645   // Progress
1646   return iff;
1647 }
1648 
1649 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1650   Node* res = Ideal_common(phase, can_reshape);
1651   if (res != NodeSentinel) {
1652     return res;
1653   }
1654 
1655   PhaseIterGVN *igvn = phase->is_IterGVN();
1656   // Setup to scan up the CFG looking for a dominating test
1657   Node* prev_dom = this;
1658 
1659   // Check for range-check vs other kinds of tests
1660   Node* index1;
1661   Node* range1;
1662   jint offset1;
1663   int flip1 = is_range_check(range1, index1, offset1);
1664   if (flip1) {
1665     Node* dom = in(0);
1666     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
1667     // so all checks we inspect post-dominate the top-most check we find.
1668     // If we are going to fail the current check and we reach the top check
1669     // then we are guaranteed to fail, so just start interpreting there.
1670     // We 'expand' the top 3 range checks to include all post-dominating
1671     // checks.
1672 
1673     // The top 3 range checks seen
1674     const int NRC =3;
1675     RangeCheck prev_checks[NRC];
1676     int nb_checks = 0;
1677 
1678     // Low and high offsets seen so far
1679     jint off_lo = offset1;
1680     jint off_hi = offset1;
1681 
1682     bool found_immediate_dominator = false;
1683 
1684     // Scan for the top checks and collect range of offsets
1685     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1686       if (dom->Opcode() == Op_RangeCheck &&  // Not same opcode?
1687           prev_dom->in(0) == dom) { // One path of test does dominate?
1688         if (dom == this) return NULL; // dead loop
1689         // See if this is a range check
1690         Node* index2;
1691         Node* range2;
1692         jint offset2;
1693         int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1694         // See if this is a _matching_ range check, checking against
1695         // the same array bounds.
1696         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1697             dom->outcnt() == 2) {
1698           if (nb_checks == 0 && dom->in(1) == in(1)) {
1699             // Found an immediately dominating test at the same offset.
1700             // This kind of back-to-back test can be eliminated locally,
1701             // and there is no need to search further for dominating tests.
1702             assert(offset2 == offset1, "Same test but different offsets");
1703             found_immediate_dominator = true;
1704             break;
1705           }
1706           // Gather expanded bounds
1707           off_lo = MIN2(off_lo,offset2);
1708           off_hi = MAX2(off_hi,offset2);
1709           // Record top NRC range checks
1710           prev_checks[nb_checks%NRC].ctl = prev_dom;
1711           prev_checks[nb_checks%NRC].off = offset2;
1712           nb_checks++;
1713         }
1714       }
1715       prev_dom = dom;
1716       dom = up_one_dom(dom);
1717       if (!dom) break;
1718     }
1719 
1720     if (!found_immediate_dominator) {
1721       // Attempt to widen the dominating range check to cover some later
1722       // ones.  Since range checks "fail" by uncommon-trapping to the
1723       // interpreter, widening a check can make us speculatively enter
1724       // the interpreter.  If we see range-check deopt's, do not widen!
1725       if (!phase->C->allow_range_check_smearing())  return NULL;
1726 
1727       // Didn't find prior covering check, so cannot remove anything.
1728       if (nb_checks == 0) {
1729         return NULL;
1730       }
1731       // Constant indices only need to check the upper bound.
1732       // Non-constant indices must check both low and high.
1733       int chk0 = (nb_checks - 1) % NRC;
1734       if (index1) {
1735         if (nb_checks == 1) {
1736           return NULL;
1737         } else {
1738           // If the top range check's constant is the min or max of
1739           // all constants we widen the next one to cover the whole
1740           // range of constants.
1741           RangeCheck rc0 = prev_checks[chk0];
1742           int chk1 = (nb_checks - 2) % NRC;
1743           RangeCheck rc1 = prev_checks[chk1];
1744           if (rc0.off == off_lo) {
1745             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1746             prev_dom = rc1.ctl;
1747           } else if (rc0.off == off_hi) {
1748             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1749             prev_dom = rc1.ctl;
1750           } else {
1751             // If the top test's constant is not the min or max of all
1752             // constants, we need 3 range checks. We must leave the
1753             // top test unchanged because widening it would allow the
1754             // accesses it protects to successfully read/write out of
1755             // bounds.
1756             if (nb_checks == 2) {
1757               return NULL;
1758             }
1759             int chk2 = (nb_checks - 3) % NRC;
1760             RangeCheck rc2 = prev_checks[chk2];
1761             // The top range check a+i covers interval: -a <= i < length-a
1762             // The second range check b+i covers interval: -b <= i < length-b
1763             if (rc1.off <= rc0.off) {
1764               // if b <= a, we change the second range check to:
1765               // -min_of_all_constants <= i < length-min_of_all_constants
1766               // Together top and second range checks now cover:
1767               // -min_of_all_constants <= i < length-a
1768               // which is more restrictive than -b <= i < length-b:
1769               // -b <= -min_of_all_constants <= i < length-a <= length-b
1770               // The third check is then changed to:
1771               // -max_of_all_constants <= i < length-max_of_all_constants
1772               // so 2nd and 3rd checks restrict allowed values of i to:
1773               // -min_of_all_constants <= i < length-max_of_all_constants
1774               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1775               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1776             } else {
1777               // if b > a, we change the second range check to:
1778               // -max_of_all_constants <= i < length-max_of_all_constants
1779               // Together top and second range checks now cover:
1780               // -a <= i < length-max_of_all_constants
1781               // which is more restrictive than -b <= i < length-b:
1782               // -b < -a <= i < length-max_of_all_constants <= length-b
1783               // The third check is then changed to:
1784               // -max_of_all_constants <= i < length-max_of_all_constants
1785               // so 2nd and 3rd checks restrict allowed values of i to:
1786               // -min_of_all_constants <= i < length-max_of_all_constants
1787               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1788               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1789             }
1790             prev_dom = rc2.ctl;
1791           }
1792         }
1793       } else {
1794         RangeCheck rc0 = prev_checks[chk0];
1795         // 'Widen' the offset of the 1st and only covering check
1796         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1797         // Test is now covered by prior checks, dominate it out
1798         prev_dom = rc0.ctl;
1799       }
1800     }
1801   } else {
1802     prev_dom = search_identical(4);
1803 
1804     if (prev_dom == NULL) {
1805       return NULL;
1806     }
1807   }
1808 
1809   // Replace dominated IfNode
1810   return dominated_by(prev_dom, igvn);
1811 }
--- EOF ---