1 /*
   2  * Copyright (c) 2000, 2017, 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             default:
 676               break;
 677             }
 678             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 679             return rtn_t;
 680           }
 681         }
 682       }
 683     }
 684   }
 685   return NULL;
 686 }
 687 
 688 //------------------------------fold_compares----------------------------
 689 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 690 // the direction of this if is determined by the preceding if so it
 691 // can be eliminate entirely.
 692 //
 693 // Given an if testing (CmpI n v) check for an immediately control
 694 // dependent if that is testing (CmpI n v2) and has one projection
 695 // leading to this if and the other projection leading to a region
 696 // that merges one of this ifs control projections.
 697 //
 698 //                   If
 699 //                  / |
 700 //                 /  |
 701 //                /   |
 702 //              If    |
 703 //              /\    |
 704 //             /  \   |
 705 //            /    \  |
 706 //           /    Region
 707 //
 708 // Or given an if testing (CmpI n v) check for a dominating if that is
 709 // testing (CmpI n v2), both having one projection leading to an
 710 // uncommon trap. Allow Another independent guard in between to cover
 711 // an explicit range check:
 712 // if (index < 0 || index >= array.length) {
 713 // which may need a null check to guard the LoadRange
 714 //
 715 //                   If
 716 //                  / \
 717 //                 /   \
 718 //                /     \
 719 //              If      unc
 720 //              /\
 721 //             /  \
 722 //            /    \
 723 //           /      unc
 724 //
 725 
 726 // Is the comparison for this If suitable for folding?
 727 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
 728   return in(1) != NULL &&
 729     in(1)->is_Bool() &&
 730     in(1)->in(1) != NULL &&
 731     in(1)->in(1)->Opcode() == Op_CmpI &&
 732     in(1)->in(1)->in(2) != NULL &&
 733     in(1)->in(1)->in(2) != igvn->C->top() &&
 734     (in(1)->as_Bool()->_test.is_less() ||
 735      in(1)->as_Bool()->_test.is_greater());
 736 }
 737 
 738 // Is a dominating control suitable for folding with this if?
 739 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
 740   return ctrl != NULL &&
 741     ctrl->is_Proj() &&
 742     ctrl->in(0) != NULL &&
 743     ctrl->in(0)->Opcode() == Op_If &&
 744     ctrl->in(0)->outcnt() == 2 &&
 745     ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
 746     // Must compare same value
 747     ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
 748     ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
 749 }
 750 
 751 // Do this If and the dominating If share a region?
 752 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
 753   ProjNode* otherproj = proj->other_if_proj();
 754   Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
 755   RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
 756   success = NULL;
 757   fail = NULL;
 758 
 759   if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
 760     for (int i = 0; i < 2; i++) {
 761       ProjNode* proj = proj_out(i);
 762       if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 763         success = proj;
 764       } else if (fail == NULL) {
 765         fail = proj;
 766       } else {
 767         success = fail = NULL;
 768       }
 769     }
 770   }
 771   return success != NULL && fail != NULL;
 772 }
 773 
 774 // Return projection that leads to an uncommon trap if any
 775 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
 776   for (int i = 0; i < 2; i++) {
 777     call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
 778     if (call != NULL) {
 779       return proj_out(i);
 780     }
 781   }
 782   return NULL;
 783 }
 784 
 785 // Do this If and the dominating If both branch out to an uncommon trap
 786 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
 787   ProjNode* otherproj = proj->other_if_proj();
 788   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
 789 
 790   if (otherproj->outcnt() == 1 && dom_unc != NULL) {
 791     // We need to re-execute the folded Ifs after deoptimization from the merged traps
 792     if (!dom_unc->jvms()->should_reexecute()) {
 793       return false;
 794     }
 795 
 796     CallStaticJavaNode* unc = NULL;
 797     ProjNode* unc_proj = uncommon_trap_proj(unc);
 798     if (unc_proj != NULL && unc_proj->outcnt() == 1) {
 799       if (dom_unc == unc) {
 800         // Allow the uncommon trap to be shared through a region
 801         RegionNode* r = unc->in(0)->as_Region();
 802         if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
 803           return false;
 804         }
 805         assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
 806       } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
 807         return false;
 808       }
 809 
 810       // Different methods and methods containing jsrs are not supported.
 811       ciMethod* method = unc->jvms()->method();
 812       ciMethod* dom_method = dom_unc->jvms()->method();
 813       if (method != dom_method || method->has_jsrs()) {
 814         return false;
 815       }
 816       // Check that both traps are in the same activation of the method (instead
 817       // of two activations being inlined through different call sites) by verifying
 818       // that the call stacks are equal for both JVMStates.
 819       JVMState* dom_caller = dom_unc->jvms()->caller();
 820       JVMState* caller = unc->jvms()->caller();
 821       if ((dom_caller == NULL) != (caller == NULL)) {
 822         // The current method must either be inlined into both dom_caller and
 823         // caller or must not be inlined at all (top method). Bail out otherwise.
 824         return false;
 825       } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
 826         return false;
 827       }
 828       // Check that the bci of the dominating uncommon trap dominates the bci
 829       // of the dominated uncommon trap. Otherwise we may not re-execute
 830       // the dominated check after deoptimization from the merged uncommon trap.
 831       ciTypeFlow* flow = dom_method->get_flow_analysis();
 832       int bci = unc->jvms()->bci();
 833       int dom_bci = dom_unc->jvms()->bci();
 834       if (!flow->is_dominated_by(bci, dom_bci)) {
 835         return false;
 836       }
 837 
 838       // See merge_uncommon_traps: the reason of the uncommon trap
 839       // will be changed and the state of the dominating If will be
 840       // used. Checked that we didn't apply this transformation in a
 841       // previous compilation and it didn't cause too many traps
 842       if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
 843           !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
 844         success = unc_proj;
 845         fail = unc_proj->other_if_proj();
 846         return true;
 847       }
 848     }
 849   }
 850   return false;
 851 }
 852 
 853 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
 854 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 855   Node* this_cmp = in(1)->in(1);
 856   BoolNode* this_bool = in(1)->as_Bool();
 857   IfNode* dom_iff = proj->in(0)->as_If();
 858   BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 859   Node* lo = dom_iff->in(1)->in(1)->in(2);
 860   Node* hi = this_cmp->in(2);
 861   Node* n = this_cmp->in(1);
 862   ProjNode* otherproj = proj->other_if_proj();
 863 
 864   const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
 865   const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
 866 
 867   BoolTest::mask lo_test = dom_bool->_test._test;
 868   BoolTest::mask hi_test = this_bool->_test._test;
 869   BoolTest::mask cond = hi_test;
 870 
 871   // convert:
 872   //
 873   //          dom_bool = x {<,<=,>,>=} a
 874   //                           / \
 875   //     proj = {True,False}  /   \ otherproj = {False,True}
 876   //                         /
 877   //        this_bool = x {<,<=} b
 878   //                       / \
 879   //  fail = {True,False} /   \ success = {False,True}
 880   //                     /
 881   //
 882   // (Second test guaranteed canonicalized, first one may not have
 883   // been canonicalized yet)
 884   //
 885   // into:
 886   //
 887   // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
 888   //                       / \
 889   //                 fail /   \ success
 890   //                     /
 891   //
 892 
 893   // Figure out which of the two tests sets the upper bound and which
 894   // sets the lower bound if any.
 895   Node* adjusted_lim = NULL;
 896   if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
 897     assert((dom_bool->_test.is_less() && !proj->_con) ||
 898            (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
 899     // this test was canonicalized
 900     assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
 901 
 902     // this_bool = <
 903     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 904     //     x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
 905     //     lo = a, hi = b, adjusted_lim = b-a, cond = <u
 906     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 907     //     x in ]a, b[ on the fail (= True) projection, b > a:
 908     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
 909     // this_bool = <=
 910     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 911     //     x in [a, b] on the fail (= True) projection, b+1 > a-1:
 912     //     lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
 913     //     lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
 914     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 915     //     x in ]a, b] on the fail (= True) projection b+1 > a:
 916     //     lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
 917     //     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
 918 
 919     if (hi_test == BoolTest::lt) {
 920       if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 921         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 922       }
 923     } else {
 924       assert(hi_test == BoolTest::le, "bad test");
 925       if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
 926         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 927         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 928         cond = BoolTest::lt;
 929       } else {
 930         assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
 931         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 932         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 933         cond = BoolTest::lt;
 934       }
 935     }
 936   } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
 937 
 938     // this_bool = <
 939     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 940     //     x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
 941     //     lo = b, hi = a, adjusted_lim = a-b, cond = >=u
 942     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 943     //     x in [b, a] on the fail (= False) projection, a+1 > b-1:
 944     //     lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
 945     //     lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
 946     // this_bool = <=
 947     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 948     //     x in ]b, a[ on the fail (= False) projection, a > b:
 949     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
 950     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 951     //     x in ]b, a] on the fail (= False) projection, a+1 > b:
 952     //     lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
 953     //     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
 954 
 955     swap(lo, hi);
 956     swap(lo_type, hi_type);
 957     swap(lo_test, hi_test);
 958 
 959     assert((dom_bool->_test.is_less() && proj->_con) ||
 960            (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
 961     // this test was canonicalized
 962     assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
 963 
 964     cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
 965 
 966     if (lo_test == BoolTest::lt) {
 967       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 968         cond = BoolTest::ge;
 969       } else {
 970         assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
 971         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 972         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 973         cond = BoolTest::ge;
 974       }
 975     } else if (lo_test == BoolTest::le) {
 976       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
 977         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 978         cond = BoolTest::ge;
 979       } else {
 980         assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
 981         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 982         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 983         cond = BoolTest::ge;
 984       }
 985     }
 986   } else {
 987     const TypeInt* failtype  = filtered_int_type(igvn, n, proj);
 988     if (failtype != NULL) {
 989       const TypeInt* type2 = filtered_int_type(igvn, n, fail);
 990       if (type2 != NULL) {
 991         failtype = failtype->join(type2)->is_int();
 992         if (failtype->_lo > failtype->_hi) {
 993           // previous if determines the result of this if so
 994           // replace Bool with constant
 995           igvn->_worklist.push(in(1));
 996           igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
 997           return true;
 998         }
 999       }
1000     }
1001     lo = NULL;
1002     hi = NULL;
1003   }
1004 
1005   if (lo && hi) {
1006     // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1007     Node* adjusted_val = igvn->transform(new SubINode(n,  lo));
1008     if (adjusted_lim == NULL) {
1009       adjusted_lim = igvn->transform(new SubINode(hi, lo));
1010     }
1011     Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1012     Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1013 
1014     igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1015     igvn->_worklist.push(in(1));
1016     igvn->replace_input_of(this, 1, newbool);
1017 
1018     return true;
1019   }
1020   return false;
1021 }
1022 
1023 // Merge the branches that trap for this If and the dominating If into
1024 // a single region that branches to the uncommon trap for the
1025 // dominating If
1026 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1027   Node* res = this;
1028   assert(success->in(0) == this, "bad projection");
1029 
1030   ProjNode* otherproj = proj->other_if_proj();
1031 
1032   CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1033   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1034 
1035   if (unc != dom_unc) {
1036     Node* r = new RegionNode(3);
1037 
1038     r->set_req(1, otherproj);
1039     r->set_req(2, success);
1040     r = igvn->transform(r);
1041     assert(r->is_Region(), "can't go away");
1042 
1043     // Make both If trap at the state of the first If: once the CmpI
1044     // nodes are merged, if we trap we don't know which of the CmpI
1045     // nodes would have caused the trap so we have to restart
1046     // execution at the first one
1047     igvn->replace_input_of(dom_unc, 0, r);
1048     igvn->replace_input_of(unc, 0, igvn->C->top());
1049   }
1050   int trap_request = dom_unc->uncommon_trap_request();
1051   Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1052   Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1053 
1054   int flip_test = 0;
1055   Node* l = NULL;
1056   Node* r = NULL;
1057 
1058   if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1059     // If this looks like a range check, change the trap to
1060     // Reason_range_check so the compiler recognizes it as a range
1061     // check and applies the corresponding optimizations
1062     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1063 
1064     improve_address_types(l, r, fail, igvn);
1065 
1066     res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1067   } else if (unc != dom_unc) {
1068     // If we trap we won't know what CmpI would have caused the trap
1069     // so use a special trap reason to mark this pair of CmpI nodes as
1070     // bad candidate for folding. On recompilation we won't fold them
1071     // and we may trap again but this time we'll know what branch
1072     // traps
1073     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1074   }
1075   igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1076   return res;
1077 }
1078 
1079 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1080 // of a rangecheck on index i, on 64 bit the compares may be followed
1081 // by memory accesses using i as index. In that case, the CmpU tells
1082 // us something about the values taken by i that can help the compiler
1083 // (see Compile::conv_I2X_index())
1084 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1085 #ifdef _LP64
1086   ResourceMark rm;
1087   Node_Stack stack(2);
1088 
1089   assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1090   const TypeInt* array_size = igvn->type(r)->is_int();
1091 
1092   stack.push(l, 0);
1093 
1094   while(stack.size() > 0) {
1095     Node* n = stack.node();
1096     uint start = stack.index();
1097 
1098     uint i = start;
1099     for (; i < n->outcnt(); i++) {
1100       Node* use = n->raw_out(i);
1101       if (stack.size() == 1) {
1102         if (use->Opcode() == Op_ConvI2L) {
1103           const TypeLong* bounds = use->as_Type()->type()->is_long();
1104           if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1105               (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1106             stack.set_index(i+1);
1107             stack.push(use, 0);
1108             break;
1109           }
1110         }
1111       } else if (use->is_Mem()) {
1112         Node* ctrl = use->in(0);
1113         for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1114           ctrl = up_one_dom(ctrl);
1115         }
1116         if (ctrl == fail) {
1117           Node* init_n = stack.node_at(1);
1118           assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1119           // Create a new narrow ConvI2L node that is dependent on the range check
1120           Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1121 
1122           // The type of the ConvI2L may be widen and so the new
1123           // ConvI2L may not be better than an existing ConvI2L
1124           if (new_n != init_n) {
1125             for (uint j = 2; j < stack.size(); j++) {
1126               Node* n = stack.node_at(j);
1127               Node* clone = n->clone();
1128               int rep = clone->replace_edge(init_n, new_n);
1129               assert(rep > 0, "can't find expected node?");
1130               clone = igvn->transform(clone);
1131               init_n = n;
1132               new_n = clone;
1133             }
1134             igvn->hash_delete(use);
1135             int rep = use->replace_edge(init_n, new_n);
1136             assert(rep > 0, "can't find expected node?");
1137             igvn->transform(use);
1138             if (init_n->outcnt() == 0) {
1139               igvn->_worklist.push(init_n);
1140             }
1141           }
1142         }
1143       } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1144                                         igvn->type(use)->isa_ptr())) {
1145         stack.set_index(i+1);
1146         stack.push(use, 0);
1147         break;
1148       }
1149     }
1150     if (i == n->outcnt()) {
1151       stack.pop();
1152     }
1153   }
1154 #endif
1155 }
1156 
1157 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1158   if (in(1) != NULL &&
1159       in(1)->in(1) != NULL &&
1160       in(1)->in(1)->in(2) != NULL) {
1161     Node* other = in(1)->in(1)->in(2);
1162     if (other->Opcode() == Op_LoadRange &&
1163         ((other->in(0) != NULL && other->in(0) == proj) ||
1164          (other->in(0) == NULL &&
1165           other->in(2) != NULL &&
1166           other->in(2)->is_AddP() &&
1167           other->in(2)->in(1) != NULL &&
1168           other->in(2)->in(1)->Opcode() == Op_CastPP &&
1169           other->in(2)->in(1)->in(0) == proj))) {
1170       return true;
1171     }
1172   }
1173   return false;
1174 }
1175 
1176 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1177   Node* other = in(1)->in(1)->in(2);
1178   if (other->in(MemNode::Address) != NULL &&
1179       proj->in(0)->in(1) != NULL &&
1180       proj->in(0)->in(1)->is_Bool() &&
1181       proj->in(0)->in(1)->in(1) != NULL &&
1182       proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1183       proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1184       proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1185       igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1186     return true;
1187   }
1188   return false;
1189 }
1190 
1191 // Check that the If that is in between the 2 integer comparisons has
1192 // no side effect
1193 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1194   if (proj != NULL &&
1195       proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1196       proj->outcnt() <= 2) {
1197     if (proj->outcnt() == 1 ||
1198         // Allow simple null check from LoadRange
1199         (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1200       CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1201       CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1202 
1203       // reroute_side_effect_free_unc changes the state of this
1204       // uncommon trap to restart execution at the previous
1205       // CmpI. Check that this change in a previous compilation didn't
1206       // cause too many traps.
1207       int trap_request = unc->uncommon_trap_request();
1208       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1209 
1210       if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1211         return false;
1212       }
1213 
1214       return true;
1215     }
1216   }
1217   return false;
1218 }
1219 
1220 // Make the If between the 2 integer comparisons trap at the state of
1221 // the first If: the last CmpI is the one replaced by a CmpU and the
1222 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1223 // won't be guarded by the first CmpI anymore. It can trap in cases
1224 // where the first CmpI would have prevented it from executing: on a
1225 // trap, we need to restart execution at the state of the first CmpI
1226 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1227   CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1228   ProjNode* otherproj = proj->other_if_proj();
1229   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1230   Node* call_proj = dom_unc->unique_ctrl_out();
1231   Node* halt = call_proj->unique_ctrl_out();
1232 
1233   Node* new_unc = dom_unc->clone();
1234   call_proj = call_proj->clone();
1235   halt = halt->clone();
1236   Node* c = otherproj->clone();
1237 
1238   c = igvn->transform(c);
1239   new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1240   new_unc->set_req(0, c);
1241   new_unc = igvn->transform(new_unc);
1242   call_proj->set_req(0, new_unc);
1243   call_proj = igvn->transform(call_proj);
1244   halt->set_req(0, call_proj);
1245   halt = igvn->transform(halt);
1246 
1247   igvn->replace_node(otherproj, igvn->C->top());
1248   igvn->C->root()->add_req(halt);
1249 }
1250 
1251 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1252   if (Opcode() != Op_If) return NULL;
1253 
1254   if (cmpi_folds(igvn)) {
1255     Node* ctrl = in(0);
1256     if (is_ctrl_folds(ctrl, igvn) &&
1257         ctrl->outcnt() == 1) {
1258       // A integer comparison immediately dominated by another integer
1259       // comparison
1260       ProjNode* success = NULL;
1261       ProjNode* fail = NULL;
1262       ProjNode* dom_cmp = ctrl->as_Proj();
1263       if (has_shared_region(dom_cmp, success, fail) &&
1264           // Next call modifies graph so must be last
1265           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1266         return this;
1267       }
1268       if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1269           // Next call modifies graph so must be last
1270           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1271         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1272       }
1273       return NULL;
1274     } else if (ctrl->in(0) != NULL &&
1275                ctrl->in(0)->in(0) != NULL) {
1276       ProjNode* success = NULL;
1277       ProjNode* fail = NULL;
1278       Node* dom = ctrl->in(0)->in(0);
1279       ProjNode* dom_cmp = dom->isa_Proj();
1280       ProjNode* other_cmp = ctrl->isa_Proj();
1281 
1282       // Check if it's an integer comparison dominated by another
1283       // integer comparison with another test in between
1284       if (is_ctrl_folds(dom, igvn) &&
1285           has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1286           is_side_effect_free_test(other_cmp, igvn) &&
1287           // Next call modifies graph so must be last
1288           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1289         reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1290         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1291       }
1292     }
1293   }
1294   return NULL;
1295 }
1296 
1297 //------------------------------remove_useless_bool----------------------------
1298 // Check for people making a useless boolean: things like
1299 // if( (x < y ? true : false) ) { ... }
1300 // Replace with if( x < y ) { ... }
1301 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1302   Node *i1 = iff->in(1);
1303   if( !i1->is_Bool() ) return NULL;
1304   BoolNode *bol = i1->as_Bool();
1305 
1306   Node *cmp = bol->in(1);
1307   if( cmp->Opcode() != Op_CmpI ) return NULL;
1308 
1309   // Must be comparing against a bool
1310   const Type *cmp2_t = phase->type( cmp->in(2) );
1311   if( cmp2_t != TypeInt::ZERO &&
1312       cmp2_t != TypeInt::ONE )
1313     return NULL;
1314 
1315   // Find a prior merge point merging the boolean
1316   i1 = cmp->in(1);
1317   if( !i1->is_Phi() ) return NULL;
1318   PhiNode *phi = i1->as_Phi();
1319   if( phase->type( phi ) != TypeInt::BOOL )
1320     return NULL;
1321 
1322   // Check for diamond pattern
1323   int true_path = phi->is_diamond_phi();
1324   if( true_path == 0 ) return NULL;
1325 
1326   // Make sure that iff and the control of the phi are different. This
1327   // should really only happen for dead control flow since it requires
1328   // an illegal cycle.
1329   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1330 
1331   // phi->region->if_proj->ifnode->bool->cmp
1332   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1333 
1334   // Now get the 'sense' of the test correct so we can plug in
1335   // either iff2->in(1) or its complement.
1336   int flip = 0;
1337   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1338   else if( bol->_test._test != BoolTest::eq ) return NULL;
1339   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1340 
1341   const Type *phi1_t = phase->type( phi->in(1) );
1342   const Type *phi2_t = phase->type( phi->in(2) );
1343   // Check for Phi(0,1) and flip
1344   if( phi1_t == TypeInt::ZERO ) {
1345     if( phi2_t != TypeInt::ONE ) return NULL;
1346     flip = 1-flip;
1347   } else {
1348     // Check for Phi(1,0)
1349     if( phi1_t != TypeInt::ONE  ) return NULL;
1350     if( phi2_t != TypeInt::ZERO ) return NULL;
1351   }
1352   if( true_path == 2 ) {
1353     flip = 1-flip;
1354   }
1355 
1356   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1357   assert(new_bol != iff->in(1), "must make progress");
1358   iff->set_req(1, new_bol);
1359   // Intervening diamond probably goes dead
1360   phase->C->set_major_progress();
1361   return iff;
1362 }
1363 
1364 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1365 
1366 struct RangeCheck {
1367   Node* ctl;
1368   jint off;
1369 };
1370 
1371 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1372   if (remove_dead_region(phase, can_reshape))  return this;
1373   // No Def-Use info?
1374   if (!can_reshape)  return NULL;
1375 
1376   // Don't bother trying to transform a dead if
1377   if (in(0)->is_top())  return NULL;
1378   // Don't bother trying to transform an if with a dead test
1379   if (in(1)->is_top())  return NULL;
1380   // Another variation of a dead test
1381   if (in(1)->is_Con())  return NULL;
1382   // Another variation of a dead if
1383   if (outcnt() < 2)  return NULL;
1384 
1385   // Canonicalize the test.
1386   Node* idt_if = idealize_test(phase, this);
1387   if (idt_if != NULL)  return idt_if;
1388 
1389   // Try to split the IF
1390   PhaseIterGVN *igvn = phase->is_IterGVN();
1391   Node *s = split_if(this, igvn);
1392   if (s != NULL)  return s;
1393 
1394   return NodeSentinel;
1395 }
1396 
1397 //------------------------------Ideal------------------------------------------
1398 // Return a node which is more "ideal" than the current node.  Strip out
1399 // control copies
1400 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1401   Node* res = Ideal_common(phase, can_reshape);
1402   if (res != NodeSentinel) {
1403     return res;
1404   }
1405 
1406   // Check for people making a useless boolean: things like
1407   // if( (x < y ? true : false) ) { ... }
1408   // Replace with if( x < y ) { ... }
1409   Node *bol2 = remove_useless_bool(this, phase);
1410   if( bol2 ) return bol2;
1411 
1412   if (in(0) == NULL) return NULL;     // Dead loop?
1413 
1414   PhaseIterGVN *igvn = phase->is_IterGVN();
1415   Node* result = fold_compares(igvn);
1416   if (result != NULL) {
1417     return result;
1418   }
1419 
1420   // Scan for an equivalent test
1421   Node *cmp;
1422   int dist = 0;               // Cutoff limit for search
1423   int op = Opcode();
1424   if( op == Op_If &&
1425       (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1426     if( cmp->in(2) != NULL && // make sure cmp is not already dead
1427         cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1428       dist = 64;              // Limit for null-pointer scans
1429     } else {
1430       dist = 4;               // Do not bother for random pointer tests
1431     }
1432   } else {
1433     dist = 4;                 // Limit for random junky scans
1434   }
1435 
1436   Node* prev_dom = search_identical(dist);
1437 
1438   if (prev_dom == NULL) {
1439     return NULL;
1440   }
1441 
1442   // Replace dominated IfNode
1443   return dominated_by(prev_dom, igvn);
1444 }
1445 
1446 //------------------------------dominated_by-----------------------------------
1447 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1448 #ifndef PRODUCT
1449   if (TraceIterativeGVN) {
1450     tty->print("   Removing IfNode: "); this->dump();
1451   }
1452   if (VerifyOpto && !igvn->allow_progress()) {
1453     // Found an equivalent dominating test,
1454     // we can not guarantee reaching a fix-point for these during iterativeGVN
1455     // since intervening nodes may not change.
1456     return NULL;
1457   }
1458 #endif
1459 
1460   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1461   Node *idom = in(0);
1462   // Need opcode to decide which way 'this' test goes
1463   int prev_op = prev_dom->Opcode();
1464   Node *top = igvn->C->top(); // Shortcut to top
1465 
1466   // Loop predicates may have depending checks which should not
1467   // be skipped. For example, range check predicate has two checks
1468   // for lower and upper bounds.
1469   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1470   if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)) {
1471     prev_dom = idom;
1472   }
1473 
1474   // Now walk the current IfNode's projections.
1475   // Loop ends when 'this' has no more uses.
1476   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1477     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1478     igvn->add_users_to_worklist(ifp);
1479     // Check which projection it is and set target.
1480     // Data-target is either the dominating projection of the same type
1481     // or TOP if the dominating projection is of opposite type.
1482     // Data-target will be used as the new control edge for the non-CFG
1483     // nodes like Casts and Loads.
1484     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1485     // Control-target is just the If's immediate dominator or TOP.
1486     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1487 
1488     // For each child of an IfTrue/IfFalse projection, reroute.
1489     // Loop ends when projection has no more uses.
1490     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1491       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1492       if( !s->depends_only_on_test() ) {
1493         // Find the control input matching this def-use edge.
1494         // For Regions it may not be in slot 0.
1495         uint l;
1496         for( l = 0; s->in(l) != ifp; l++ ) { }
1497         igvn->replace_input_of(s, l, ctrl_target);
1498       } else {                      // Else, for control producers,
1499         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1500       }
1501     } // End for each child of a projection
1502 
1503     igvn->remove_dead_node(ifp);
1504   } // End for each IfTrue/IfFalse child of If
1505 
1506   // Kill the IfNode
1507   igvn->remove_dead_node(this);
1508 
1509   // Must return either the original node (now dead) or a new node
1510   // (Do not return a top here, since that would break the uniqueness of top.)
1511   return new ConINode(TypeInt::ZERO);
1512 }
1513 
1514 Node* IfNode::search_identical(int dist) {
1515   // Setup to scan up the CFG looking for a dominating test
1516   Node* dom = in(0);
1517   Node* prev_dom = this;
1518   int op = Opcode();
1519   // Search up the dominator tree for an If with an identical test
1520   while (dom->Opcode() != op    ||  // Not same opcode?
1521          dom->in(1)    != in(1) ||  // Not same input 1?
1522          (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1523          prev_dom->in(0) != dom) {  // One path of test does not dominate?
1524     if (dist < 0) return NULL;
1525 
1526     dist--;
1527     prev_dom = dom;
1528     dom = up_one_dom(dom);
1529     if (!dom) return NULL;
1530   }
1531 
1532   // Check that we did not follow a loop back to ourselves
1533   if (this == dom) {
1534     return NULL;
1535   }
1536 
1537 #ifndef PRODUCT
1538   if (dist > 2) { // Add to count of NULL checks elided
1539     explicit_null_checks_elided++;
1540   }
1541 #endif
1542 
1543   return prev_dom;
1544 }
1545 
1546 //------------------------------Identity---------------------------------------
1547 // If the test is constant & we match, then we are the input Control
1548 Node* IfProjNode::Identity(PhaseGVN* phase) {
1549   // Can only optimize if cannot go the other way
1550   const TypeTuple *t = phase->type(in(0))->is_tuple();
1551   if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1552        // During parsing (GVN) we don't remove dead code aggressively.
1553        // Cut off dead branch and let PhaseRemoveUseless take care of it.
1554       (!phase->is_IterGVN() ||
1555        // During IGVN, first wait for the dead branch to be killed.
1556        // Otherwise, the IfNode's control will have two control uses (the IfNode
1557        // that doesn't go away because it still has uses and this branch of the
1558        // If) which breaks other optimizations. Node::has_special_unique_user()
1559        // will cause this node to be reprocessed once the dead branch is killed.
1560        in(0)->outcnt() == 1))) {
1561     // IfNode control
1562     return in(0)->in(0);
1563   }
1564   // no progress
1565   return this;
1566 }
1567 
1568 #ifndef PRODUCT
1569 //-------------------------------related---------------------------------------
1570 // An IfProjNode's related node set consists of its input (an IfNode) including
1571 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1572 // the restrictions for IfNode apply (see IfNode::rel).
1573 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1574   Node* ifNode = this->in(0);
1575   in_rel->append(ifNode);
1576   if (compact) {
1577     ifNode->collect_nodes(in_rel, 3, false, true);
1578   } else {
1579     ifNode->collect_nodes_in_all_data(in_rel, false);
1580   }
1581   this->collect_nodes(out_rel, -1, false, false);
1582 }
1583 
1584 //------------------------------dump_spec--------------------------------------
1585 void IfNode::dump_spec(outputStream *st) const {
1586   st->print("P=%f, C=%f",_prob,_fcnt);
1587 }
1588 
1589 //-------------------------------related---------------------------------------
1590 // For an IfNode, the set of related output nodes is just the output nodes till
1591 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1592 // The related input nodes contain no control nodes, but all data nodes
1593 // pertaining to the condition. In compact mode, the input nodes are collected
1594 // up to a depth of 3.
1595 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1596   if (compact) {
1597     this->collect_nodes(in_rel, 3, false, true);
1598   } else {
1599     this->collect_nodes_in_all_data(in_rel, false);
1600   }
1601   this->collect_nodes(out_rel, -2, false, false);
1602 }
1603 #endif
1604 
1605 //------------------------------idealize_test----------------------------------
1606 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1607 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1608 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1609 // needed.
1610 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1611   assert(iff->in(0) != NULL, "If must be live");
1612 
1613   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1614   Node* old_if_f = iff->proj_out(false);
1615   Node* old_if_t = iff->proj_out(true);
1616 
1617   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1618   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1619   // happens in count-down loops
1620   if (iff->is_CountedLoopEnd())  return NULL;
1621   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1622   BoolNode *b = iff->in(1)->as_Bool();
1623   BoolTest bt = b->_test;
1624   // Test already in good order?
1625   if( bt.is_canonical() )
1626     return NULL;
1627 
1628   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1629   // cloning the IfNode.
1630   Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1631   if( !new_b->is_Bool() ) return NULL;
1632   b = new_b->as_Bool();
1633 
1634   PhaseIterGVN *igvn = phase->is_IterGVN();
1635   assert( igvn, "Test is not canonical in parser?" );
1636 
1637   // The IF node never really changes, but it needs to be cloned
1638   iff = iff->clone()->as_If();
1639   iff->set_req(1, b);
1640   iff->_prob = 1.0-iff->_prob;
1641 
1642   Node *prior = igvn->hash_find_insert(iff);
1643   if( prior ) {
1644     igvn->remove_dead_node(iff);
1645     iff = (IfNode*)prior;
1646   } else {
1647     // Cannot call transform on it just yet
1648     igvn->set_type_bottom(iff);
1649   }
1650   igvn->_worklist.push(iff);
1651 
1652   // Now handle projections.  Cloning not required.
1653   Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1654   Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1655 
1656   igvn->register_new_node_with_optimizer(new_if_f);
1657   igvn->register_new_node_with_optimizer(new_if_t);
1658   // Flip test, so flip trailing control
1659   igvn->replace_node(old_if_f, new_if_t);
1660   igvn->replace_node(old_if_t, new_if_f);
1661 
1662   // Progress
1663   return iff;
1664 }
1665 
1666 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1667   Node* res = Ideal_common(phase, can_reshape);
1668   if (res != NodeSentinel) {
1669     return res;
1670   }
1671 
1672   PhaseIterGVN *igvn = phase->is_IterGVN();
1673   // Setup to scan up the CFG looking for a dominating test
1674   Node* prev_dom = this;
1675 
1676   // Check for range-check vs other kinds of tests
1677   Node* index1;
1678   Node* range1;
1679   jint offset1;
1680   int flip1 = is_range_check(range1, index1, offset1);
1681   if (flip1) {
1682     Node* dom = in(0);
1683     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
1684     // so all checks we inspect post-dominate the top-most check we find.
1685     // If we are going to fail the current check and we reach the top check
1686     // then we are guaranteed to fail, so just start interpreting there.
1687     // We 'expand' the top 3 range checks to include all post-dominating
1688     // checks.
1689 
1690     // The top 3 range checks seen
1691     const int NRC =3;
1692     RangeCheck prev_checks[NRC];
1693     int nb_checks = 0;
1694 
1695     // Low and high offsets seen so far
1696     jint off_lo = offset1;
1697     jint off_hi = offset1;
1698 
1699     bool found_immediate_dominator = false;
1700 
1701     // Scan for the top checks and collect range of offsets
1702     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1703       if (dom->Opcode() == Op_RangeCheck &&  // Not same opcode?
1704           prev_dom->in(0) == dom) { // One path of test does dominate?
1705         if (dom == this) return NULL; // dead loop
1706         // See if this is a range check
1707         Node* index2;
1708         Node* range2;
1709         jint offset2;
1710         int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1711         // See if this is a _matching_ range check, checking against
1712         // the same array bounds.
1713         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1714             dom->outcnt() == 2) {
1715           if (nb_checks == 0 && dom->in(1) == in(1)) {
1716             // Found an immediately dominating test at the same offset.
1717             // This kind of back-to-back test can be eliminated locally,
1718             // and there is no need to search further for dominating tests.
1719             assert(offset2 == offset1, "Same test but different offsets");
1720             found_immediate_dominator = true;
1721             break;
1722           }
1723           // Gather expanded bounds
1724           off_lo = MIN2(off_lo,offset2);
1725           off_hi = MAX2(off_hi,offset2);
1726           // Record top NRC range checks
1727           prev_checks[nb_checks%NRC].ctl = prev_dom;
1728           prev_checks[nb_checks%NRC].off = offset2;
1729           nb_checks++;
1730         }
1731       }
1732       prev_dom = dom;
1733       dom = up_one_dom(dom);
1734       if (!dom) break;
1735     }
1736 
1737     if (!found_immediate_dominator) {
1738       // Attempt to widen the dominating range check to cover some later
1739       // ones.  Since range checks "fail" by uncommon-trapping to the
1740       // interpreter, widening a check can make us speculatively enter
1741       // the interpreter.  If we see range-check deopt's, do not widen!
1742       if (!phase->C->allow_range_check_smearing())  return NULL;
1743 
1744       // Didn't find prior covering check, so cannot remove anything.
1745       if (nb_checks == 0) {
1746         return NULL;
1747       }
1748       // Constant indices only need to check the upper bound.
1749       // Non-constant indices must check both low and high.
1750       int chk0 = (nb_checks - 1) % NRC;
1751       if (index1) {
1752         if (nb_checks == 1) {
1753           return NULL;
1754         } else {
1755           // If the top range check's constant is the min or max of
1756           // all constants we widen the next one to cover the whole
1757           // range of constants.
1758           RangeCheck rc0 = prev_checks[chk0];
1759           int chk1 = (nb_checks - 2) % NRC;
1760           RangeCheck rc1 = prev_checks[chk1];
1761           if (rc0.off == off_lo) {
1762             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1763             prev_dom = rc1.ctl;
1764           } else if (rc0.off == off_hi) {
1765             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1766             prev_dom = rc1.ctl;
1767           } else {
1768             // If the top test's constant is not the min or max of all
1769             // constants, we need 3 range checks. We must leave the
1770             // top test unchanged because widening it would allow the
1771             // accesses it protects to successfully read/write out of
1772             // bounds.
1773             if (nb_checks == 2) {
1774               return NULL;
1775             }
1776             int chk2 = (nb_checks - 3) % NRC;
1777             RangeCheck rc2 = prev_checks[chk2];
1778             // The top range check a+i covers interval: -a <= i < length-a
1779             // The second range check b+i covers interval: -b <= i < length-b
1780             if (rc1.off <= rc0.off) {
1781               // if b <= a, we change the second range check to:
1782               // -min_of_all_constants <= i < length-min_of_all_constants
1783               // Together top and second range checks now cover:
1784               // -min_of_all_constants <= i < length-a
1785               // which is more restrictive than -b <= i < length-b:
1786               // -b <= -min_of_all_constants <= i < length-a <= length-b
1787               // The third check is then changed to:
1788               // -max_of_all_constants <= i < length-max_of_all_constants
1789               // so 2nd and 3rd checks restrict allowed values of i to:
1790               // -min_of_all_constants <= i < length-max_of_all_constants
1791               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1792               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1793             } else {
1794               // if b > a, we change the second range check to:
1795               // -max_of_all_constants <= i < length-max_of_all_constants
1796               // Together top and second range checks now cover:
1797               // -a <= i < length-max_of_all_constants
1798               // which is more restrictive than -b <= i < length-b:
1799               // -b < -a <= i < length-max_of_all_constants <= length-b
1800               // The third check is then changed to:
1801               // -max_of_all_constants <= i < length-max_of_all_constants
1802               // so 2nd and 3rd checks restrict allowed values of i to:
1803               // -min_of_all_constants <= i < length-max_of_all_constants
1804               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1805               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1806             }
1807             prev_dom = rc2.ctl;
1808           }
1809         }
1810       } else {
1811         RangeCheck rc0 = prev_checks[chk0];
1812         // 'Widen' the offset of the 1st and only covering check
1813         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1814         // Test is now covered by prior checks, dominate it out
1815         prev_dom = rc0.ctl;
1816       }
1817     }
1818   } else {
1819     prev_dom = search_identical(4);
1820 
1821     if (prev_dom == NULL) {
1822       return NULL;
1823     }
1824   }
1825 
1826   // Replace dominated IfNode
1827   return dominated_by(prev_dom, igvn);
1828 }