1 #ifdef USE_PRAGMA_IDENT_SRC
   2 #pragma ident "@(#)ifnode.cpp   1.63 07/10/23 13:12:51 JVM"
   3 #endif
   4 /*
   5  * Copyright 2000-2006 Sun Microsystems, Inc.  All Rights Reserved.
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This code is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 only, as
  10  * published by the Free Software Foundation.
  11  *
  12  * This code is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  * version 2 for more details (a copy is included in the LICENSE file that
  16  * accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License version
  19  * 2 along with this work; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  25  *  
  26  */
  27 
  28 // Portions of code courtesy of Clifford Click
  29 
  30 // Optimization - Graph Style
  31 
  32 #include "incls/_precompiled.incl"
  33 #include "incls/_ifnode.cpp.incl"
  34 
  35 
  36 extern int explicit_null_checks_elided;
  37 
  38 //=============================================================================
  39 //------------------------------Value------------------------------------------
  40 // Return a tuple for whichever arm of the IF is reachable
  41 const Type *IfNode::Value( PhaseTransform *phase ) const {
  42   if( !in(0) ) return Type::TOP;
  43   if( phase->type(in(0)) == Type::TOP )
  44     return Type::TOP;
  45   const Type *t = phase->type(in(1));
  46   if( t == Type::TOP )          // data is undefined
  47     return TypeTuple::IFNEITHER; // unreachable altogether
  48   if( t == TypeInt::ZERO )      // zero, or false
  49     return TypeTuple::IFFALSE;  // only false branch is reachable
  50   if( t == TypeInt::ONE )       // 1, or true
  51     return TypeTuple::IFTRUE;   // only true branch is reachable
  52   assert( t == TypeInt::BOOL, "expected boolean type" );
  53 
  54   return TypeTuple::IFBOTH;     // No progress
  55 }
  56 
  57 const RegMask &IfNode::out_RegMask() const { 
  58   return RegMask::Empty;
  59 }
  60 
  61 //------------------------------split_if---------------------------------------
  62 // Look for places where we merge constants, then test on the merged value.
  63 // If the IF test will be constant folded on the path with the constant, we
  64 // win by splitting the IF to before the merge point.
  65 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  66   // I could be a lot more general here, but I'm trying to squeeze this
  67   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  68   // on the patterns I accept.  CNC
  69 
  70   // Look for a compare of a constant and a merged value
  71   Node *i1 = iff->in(1);
  72   if( !i1->is_Bool() ) return NULL;
  73   BoolNode *b = i1->as_Bool();
  74   Node *cmp = b->in(1);
  75   if( !cmp->is_Cmp() ) return NULL;
  76   i1 = cmp->in(1);
  77   if( i1 == NULL || !i1->is_Phi() ) return NULL;
  78   PhiNode *phi = i1->as_Phi();
  79   if( phi->is_copy() ) return NULL;
  80   Node *con2 = cmp->in(2);
  81   if( !con2->is_Con() ) return NULL;
  82   // See that the merge point contains some constants
  83   Node *con1=NULL;
  84   uint i4;
  85   for( i4 = 1; i4 < phi->req(); i4++ ) {
  86     con1 = phi->in(i4);
  87     if( !con1 ) return NULL;    // Do not optimize partially collaped merges
  88     if( con1->is_Con() ) break; // Found a constant
  89     // Also allow null-vs-not-null checks
  90     const TypePtr *tp = igvn->type(con1)->isa_ptr();
  91     if( tp && tp->_ptr == TypePtr::NotNull )
  92       break;
  93   }
  94   if( i4 >= phi->req() ) return NULL; // Found no constants
  95 
  96   igvn->C->set_has_split_ifs(true); // Has chance for split-if
  97 
  98   // Make sure that the compare can be constant folded away
  99   Node *cmp2 = cmp->clone();
 100   cmp2->set_req(1,con1);
 101   cmp2->set_req(2,con2);
 102   const Type *t = cmp2->Value(igvn);
 103   // This compare is dead, so whack it!
 104   igvn->remove_dead_node(cmp2);
 105   if( !t->singleton() ) return NULL;
 106 
 107   // No intervening control, like a simple Call
 108   Node *r = iff->in(0);
 109   if( !r->is_Region() ) return NULL;
 110   if( phi->region() != r ) return NULL;
 111   // No other users of the cmp/bool
 112   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 113     //tty->print_cr("many users of cmp/bool");
 114     return NULL;
 115   }
 116 
 117   // Make sure we can determine where all the uses of merged values go
 118   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 119     Node* u = r->fast_out(j);
 120     if( u == r ) continue;
 121     if( u == iff ) continue;
 122     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 123     if( !u->is_Phi() ) {
 124       /*
 125       if( u->is_Start() ) {
 126         tty->print_cr("Region has inlined start use");
 127       } else {
 128         tty->print_cr("Region has odd use");
 129         u->dump(2);
 130       }*/
 131       return NULL;
 132     }
 133     if( u != phi ) {
 134       // CNC - do not allow any other merged value
 135       //tty->print_cr("Merging another value");
 136       //u->dump(2);
 137       return NULL;
 138     }
 139     // Make sure we can account for all Phi uses
 140     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 141       Node* v = u->fast_out(k); // User of the phi  
 142       // CNC - Allow only really simple patterns.
 143       // In particular I disallow AddP of the Phi, a fairly common pattern
 144       if( v == cmp ) continue;  // The compare is OK
 145       if( (v->is_ConstraintCast()) &&
 146           v->in(0)->in(0) == iff ) 
 147         continue;               // CastPP/II of the IfNode is OK
 148       // Disabled following code because I cannot tell if exactly one
 149       // path dominates without a real dominator check. CNC 9/9/1999
 150       //uint vop = v->Opcode();
 151       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
 152       //  Node *r = v->in(0);     // Get controlling point
 153       //  if( !r ) return NULL;   // Degraded to a copy
 154       //  // Find exactly one path in (either True or False doms, but not IFF)
 155       //  int cnt = 0;
 156       //  for( uint i = 1; i < r->req(); i++ )
 157       //    if( r->in(i) && r->in(i)->in(0) == iff )
 158       //      cnt++;
 159       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 160       //}
 161       if( !v->is_Call() ) {
 162         /*
 163         if( v->Opcode() == Op_AddP ) {
 164           tty->print_cr("Phi has AddP use");
 165         } else if( v->Opcode() == Op_CastPP ) {
 166           tty->print_cr("Phi has CastPP use");
 167         } else if( v->Opcode() == Op_CastII ) {
 168           tty->print_cr("Phi has CastII use");
 169         } else {
 170           tty->print_cr("Phi has use I cant be bothered with");
 171         }
 172         */
 173       }
 174       return NULL;
 175 
 176       /* CNC - Cut out all the fancy acceptance tests
 177       // Can we clone this use when doing the transformation?
 178       // If all uses are from Phis at this merge or constants, then YES.
 179       if( !v->in(0) && v != cmp ) {
 180         tty->print_cr("Phi has free-floating use");
 181         v->dump(2);
 182         return NULL;
 183       }
 184       for( uint l = 1; l < v->req(); l++ ) {
 185         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 186             !v->in(l)->is_Con() ) {
 187           tty->print_cr("Phi has use");
 188           v->dump(2);
 189           return NULL;
 190         } // End of if Phi-use input is neither Phi nor Constant
 191       } // End of for all inputs to Phi-use
 192       */
 193     } // End of for all uses of Phi
 194   } // End of for all uses of Region
 195 
 196   // Only do this if the IF node is in a sane state
 197   if (iff->outcnt() != 2)
 198     return NULL;
 199 
 200   // Got a hit!  Do the Mondo Hack!
 201   //
 202   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 203   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 204   //     cmp - 2                         cmp - 2               cmp - 2
 205   //       bool                            bool_c                bool_x
 206   //       if                               if_c                  if_x
 207   //      T  F                              T  F                  T  F
 208   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 209   //
 210   // Split the paths coming into the merge point into 2 seperate groups of 
 211   // merges.  On the left will be all the paths feeding constants into the
 212   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 213   // will fold up into a constant; this will let the Cmp fold up as well as
 214   // all the control flow.  Below the original IF we have 2 control 
 215   // dependent regions, 's' and 't'.  Now we will merge the two paths
 216   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 217   // likely 2 or more) will promptly constant fold away.
 218   PhaseGVN *phase = igvn;
 219 
 220   // Make a region merging constants and a region merging the rest
 221   uint req_c = 0;
 222   for (uint ii = 1; ii < r->req(); ii++) {
 223     if( phi->in(ii) == con1 ) {
 224       req_c++;
 225     }
 226   }
 227   Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1);
 228   Node *phi_c    = con1;
 229   uint  len      = r->req();
 230   Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1);
 231   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 232   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 233     if( phi->in(i) == con1 ) {
 234       region_c->init_req( i_c++, r  ->in(i) );
 235     } else {
 236       region_x->init_req( i_x,   r  ->in(i) );
 237       phi_x   ->init_req( i_x++, phi->in(i) );
 238     }
 239   }
 240 
 241   // Register the new RegionNodes but do not transform them.  Cannot 
 242   // transform until the entire Region/Phi conglerate has been hacked 
 243   // as a single huge transform.
 244   igvn->register_new_node_with_optimizer( region_c );
 245   igvn->register_new_node_with_optimizer( region_x );
 246   phi_x = phase->transform( phi_x );
 247   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 248   // about to get one.  If this only use goes away, then phi_x will look dead.
 249   // However, he will be picking up some more uses down below.
 250   Node *hook = new (igvn->C, 4) Node(4);
 251   hook->init_req(0, phi_x);
 252   hook->init_req(1, phi_c);
 253 
 254   // Make the compare
 255   Node *cmp_c = phase->makecon(t);
 256   Node *cmp_x = cmp->clone();
 257   cmp_x->set_req(1,phi_x);
 258   cmp_x->set_req(2,con2);
 259   cmp_x = phase->transform(cmp_x);
 260   // Make the bool
 261   Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test));
 262   Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test));
 263   // Make the IfNode
 264   IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
 265   igvn->set_type_bottom(iff_c);
 266   igvn->_worklist.push(iff_c);
 267   hook->init_req(2, iff_c);
 268   
 269   IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
 270   igvn->set_type_bottom(iff_x);
 271   igvn->_worklist.push(iff_x);
 272   hook->init_req(3, iff_x);
 273   
 274   // Make the true/false arms
 275   Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c));
 276   Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c));
 277   Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x));
 278   Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x));
 279 
 280   // Merge the TRUE paths
 281   Node *region_s = new (igvn->C, 3) RegionNode(3);
 282   igvn->_worklist.push(region_s);
 283   region_s->init_req(1, iff_c_t);
 284   region_s->init_req(2, iff_x_t);
 285   igvn->register_new_node_with_optimizer( region_s );
 286 
 287   // Merge the FALSE paths
 288   Node *region_f = new (igvn->C, 3) RegionNode(3);
 289   igvn->_worklist.push(region_f);
 290   region_f->init_req(1, iff_c_f);
 291   region_f->init_req(2, iff_x_f);
 292   igvn->register_new_node_with_optimizer( region_f );
 293 
 294   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 295   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
 296   cmp->set_req(2,NULL);
 297   // Check for all uses of the Phi and give them a new home.
 298   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 299   Node *phi_s = NULL;     // do not construct unless needed
 300   Node *phi_f = NULL;     // do not construct unless needed
 301   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 302     Node* v = phi->last_out(i2);// User of the phi  
 303     igvn->hash_delete(v);       // Have to fixup other Phi users
 304     igvn->_worklist.push(v);
 305     uint vop = v->Opcode();
 306     Node *proj = NULL;
 307     if( vop == Op_Phi ) {       // Remote merge point
 308       Node *r = v->in(0);
 309       for (uint i3 = 1; i3 < r->req(); i3++)
 310         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 311           proj = r->in(i3);
 312           break;
 313         }
 314     } else if( v->is_ConstraintCast() ) {
 315       proj = v->in(0);          // Controlling projection
 316     } else {
 317       assert( 0, "do not know how to handle this guy" );
 318     }
 319 
 320     Node *proj_path_data, *proj_path_ctrl;
 321     if( proj->Opcode() == Op_IfTrue ) {
 322       if( phi_s == NULL ) {
 323         // Only construct phi_s if needed, otherwise provides
 324         // interfering use.
 325         phi_s = PhiNode::make_blank(region_s,phi);
 326         phi_s->init_req( 1, phi_c );
 327         phi_s->init_req( 2, phi_x );
 328         phi_s = phase->transform(phi_s);
 329       }
 330       proj_path_data = phi_s;
 331       proj_path_ctrl = region_s;
 332     } else {
 333       if( phi_f == NULL ) {
 334         // Only construct phi_f if needed, otherwise provides
 335         // interfering use.
 336         phi_f = PhiNode::make_blank(region_f,phi);
 337         phi_f->init_req( 1, phi_c );
 338         phi_f->init_req( 2, phi_x );
 339         phi_f = phase->transform(phi_f);
 340       }
 341       proj_path_data = phi_f;
 342       proj_path_ctrl = region_f;
 343     }
 344 
 345     // Fixup 'v' for for the split
 346     if( vop == Op_Phi ) {       // Remote merge point
 347       uint i;
 348       for( i = 1; i < v->req(); i++ )
 349         if( v->in(i) == phi )
 350           break;
 351       v->set_req(i, proj_path_data );
 352     } else if( v->is_ConstraintCast() ) {
 353       v->set_req(0, proj_path_ctrl );
 354       v->set_req(1, proj_path_data );
 355     } else 
 356       ShouldNotReachHere();
 357   }
 358 
 359   // Now replace the original iff's True/False with region_s/region_t.
 360   // This makes the original iff go dead.
 361   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 362     Node* p = iff->last_out(i3);
 363     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 364     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 365     // Replace p with u
 366     igvn->add_users_to_worklist(p);
 367     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 368       Node* x = p->last_out(l);
 369       igvn->hash_delete(x);  
 370       uint uses_found = 0;
 371       for( uint j = 0; j < x->req(); j++ ) {
 372         if( x->in(j) == p ) {
 373           x->set_req(j, u); 
 374           uses_found++;
 375         }
 376       }
 377       l -= uses_found;    // we deleted 1 or more copies of this edge
 378     }
 379     igvn->remove_dead_node(p);
 380   }
 381 
 382   // Force the original merge dead
 383   igvn->hash_delete(r);
 384   r->set_req_X(0,NULL,igvn);
 385 
 386   // Now remove the bogus extra edges used to keep things alive
 387   igvn->remove_dead_node( hook );
 388 
 389   // Must return either the original node (now dead) or a new node
 390   // (Do not return a top here, since that would break the uniqueness of top.)
 391   return new (igvn->C, 1) ConINode(TypeInt::ZERO);
 392 }
 393 
 394 //------------------------------is_range_check---------------------------------
 395 // Return 0 if not a range check.  Return 1 if a range check and set index and
 396 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 397 // is versus a constant.
 398 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 399   Node* b = in(1);
 400   if (b == NULL || !b->is_Bool())  return 0;
 401   BoolNode* bn = b->as_Bool();
 402   Node* cmp = bn->in(1);
 403   if (cmp == NULL)  return 0;
 404   if (cmp->Opcode() != Op_CmpU)  return 0;
 405 
 406   Node* l = cmp->in(1);
 407   Node* r = cmp->in(2);
 408   int flip_test = 1;
 409   if (bn->_test._test == BoolTest::le) {
 410     l = cmp->in(2);
 411     r = cmp->in(1);
 412     flip_test = 2;
 413   } else if (bn->_test._test != BoolTest::lt) {
 414     return 0;
 415   }
 416   if (l->is_top())  return 0;   // Top input means dead test
 417   if (r->Opcode() != Op_LoadRange)  return 0;
 418 
 419   // We have recognized one of these forms:
 420   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 421   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 422 
 423   // Make sure it's a real range check by requiring an uncommon trap
 424   // along the OOB path.  Otherwise, it's possible that the user wrote
 425   // something which optimized to look like a range check but behaves
 426   // in some other way.
 427   Node* iftrap = proj_out(flip_test == 2 ? true : false);
 428   bool found_trap = false;
 429   if (iftrap != NULL) {
 430     Node* u = iftrap->unique_ctrl_out();
 431     if (u != NULL) {
 432       // It could be a merge point (Region) for uncommon trap.
 433       if (u->is_Region()) {
 434         Node* c = u->unique_ctrl_out();
 435         if (c != NULL) {
 436           iftrap = u;
 437           u = c;
 438         }
 439       }
 440       if (u->in(0) == iftrap && u->is_CallStaticJava()) {
 441         int req = u->as_CallStaticJava()->uncommon_trap_request();
 442         if (Deoptimization::trap_request_reason(req) ==
 443             Deoptimization::Reason_range_check) {
 444           found_trap = true;
 445         }
 446       }
 447     }
 448   }
 449   if (!found_trap)  return 0;   // sorry, no cigar
 450 
 451   // Look for index+offset form
 452   Node* ind = l;
 453   jint  off = 0;
 454   if (l->is_top()) {
 455     return 0;                
 456   } else if (l->is_Add()) {
 457     if ((off = l->in(1)->find_int_con(0)) != 0) {
 458       ind = l->in(2);
 459     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 460       ind = l->in(1);
 461     }
 462   } else if ((off = l->find_int_con(-1)) >= 0) {
 463     // constant offset with no variable index
 464     ind = NULL;
 465   } else {
 466     // variable index with no constant offset (or dead negative index)
 467     off = 0;
 468   }
 469 
 470   // Return all the values:
 471   index  = ind;
 472   offset = off;
 473   range  = r;
 474   return flip_test;
 475 }
 476 
 477 //------------------------------adjust_check-----------------------------------
 478 // Adjust (widen) a prior range check
 479 static void adjust_check(Node* proj, Node* range, Node* index,
 480                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 481   PhaseGVN *gvn = igvn;
 482   // Break apart the old check
 483   Node *iff = proj->in(0);
 484   Node *bol = iff->in(1);
 485   if( bol->is_top() ) return;   // In case a partially dead range check appears
 486   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 487   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 488   if( !bol->is_Bool() ) return;
 489 
 490   Node *cmp = bol->in(1);
 491   // Compute a new check
 492   Node *new_add = gvn->intcon(off_lo);
 493   if( index ) {
 494     new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index;
 495   }
 496   Node *new_cmp = (flip == 1) 
 497     ? new (gvn->C, 3) CmpUNode( new_add, range ) 
 498     : new (gvn->C, 3) CmpUNode( range, new_add );
 499   new_cmp = gvn->transform(new_cmp);
 500   // See if no need to adjust the existing check
 501   if( new_cmp == cmp ) return;
 502   // Else, adjust existing check
 503   Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
 504   igvn->hash_delete( iff );
 505   iff->set_req_X( 1, new_bol, igvn );
 506 }
 507 
 508 //------------------------------up_one_dom-------------------------------------
 509 // Walk up the dominator tree one step.  Return NULL at root or true
 510 // complex merges.  Skips through small diamonds.
 511 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 512   Node *dom = curr->in(0);
 513   if( !dom )                    // Found a Region degraded to a copy?
 514     return curr->nonnull_req(); // Skip thru it
 515 
 516   if( curr != dom )             // Normal walk up one step?
 517     return dom;
 518 
 519   // Use linear_only if we are still parsing, since we cannot
 520   // trust the regions to be fully filled in.
 521   if (linear_only)
 522     return NULL;
 523 
 524   // Else hit a Region.  Check for a loop header
 525   if( dom->is_Loop() ) 
 526     return dom->in(1);          // Skip up thru loops
 527 
 528   // Check for small diamonds
 529   Node *din1, *din2, *din3, *din4;
 530   if( dom->req() == 3 &&        // 2-path merge point
 531       (din1 = dom ->in(1)) &&   // Left  path exists
 532       (din2 = dom ->in(2)) &&   // Right path exists
 533       (din3 = din1->in(0)) &&   // Left  path up one
 534       (din4 = din2->in(0)) ) {  // Right path up one
 535     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 536         (din3 = din3->in(0)) )
 537       din3 = din3->in(0);
 538     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 539         (din4 = din4->in(0)) )
 540       din4 = din4->in(0);
 541     if( din3 == din4 && din3->is_If() )
 542       return din3;              // Skip around diamonds
 543   }
 544 
 545   // Give up the search at true merges
 546   return NULL;                  // Dead loop?  Or hit root?
 547 }
 548 
 549 
 550 //------------------------------filtered_int_type--------------------------------
 551 // Return a possibly more restrictive type for val based on condition control flow for an if
 552 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
 553   assert(if_proj &&
 554          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 555   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 556     IfNode* iff = if_proj->in(0)->as_If();
 557     if (iff->in(1) && iff->in(1)->is_Bool()) {
 558       BoolNode* bol = iff->in(1)->as_Bool();
 559       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 560         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 561         if (cmp->in(1) == val) {
 562           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 563           if (cmp2_t != NULL) {
 564             jint lo = cmp2_t->_lo;
 565             jint hi = cmp2_t->_hi;
 566             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 567             switch (msk) {
 568             case BoolTest::ne:
 569               // Can't refine type
 570               return NULL;
 571             case BoolTest::eq:
 572               return cmp2_t;
 573             case BoolTest::lt:
 574               lo = TypeInt::INT->_lo;
 575               if (hi - 1 < hi) {
 576                 hi = hi - 1;
 577               }
 578               break;
 579             case BoolTest::le:
 580               lo = TypeInt::INT->_lo;
 581               break;
 582             case BoolTest::gt:
 583               if (lo + 1 > lo) {
 584                 lo = lo + 1;
 585               }
 586               hi = TypeInt::INT->_hi;
 587               break;
 588             case BoolTest::ge:
 589               // lo unchanged
 590               hi = TypeInt::INT->_hi;
 591               break;
 592             }
 593             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 594             return rtn_t;
 595           }
 596         }
 597       }
 598     }
 599   }
 600   return NULL;
 601 }
 602 
 603 //------------------------------fold_compares----------------------------
 604 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 605 // the direction of this if is determined by the preciding if so it
 606 // can be eliminate entirely.  Given an if testing (CmpI n c) check
 607 // for an immediately control dependent if that is testing (CmpI n c2)
 608 // and has one projection leading to this if and the other projection
 609 // leading to a region that merges one of this ifs control
 610 // projections.
 611 //            
 612 //                   If
 613 //                  / |
 614 //                 /  |
 615 //                /   |
 616 //              If    |
 617 //              /\    |
 618 //             /  \   |
 619 //            /    \  |
 620 //           /    Region
 621 //  
 622 Node* IfNode::fold_compares(PhaseGVN* phase) {
 623   if (!EliminateAutoBox || Opcode() != Op_If) return NULL;
 624 
 625   Node* this_cmp = in(1)->in(1);
 626   if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
 627       this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
 628     Node* ctrl = in(0);
 629     BoolNode* this_bool = in(1)->as_Bool();
 630     Node* n = this_cmp->in(1);
 631     int hi = this_cmp->in(2)->get_int();
 632     if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
 633         ctrl->in(0)->is_If() &&
 634         ctrl->in(0)->outcnt() == 2 &&
 635         ctrl->in(0)->in(1)->is_Bool() &&
 636         ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
 637         ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
 638         ctrl->in(0)->in(1)->in(1)->in(1) == n) {
 639       IfNode* dom_iff = ctrl->in(0)->as_If();
 640       Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
 641       if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
 642           this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
 643         // Identify which proj goes to the region and which continues on
 644         RegionNode* region = otherproj->unique_out()->as_Region();
 645         Node* success = NULL;
 646         Node* fail = NULL;
 647         for (int i = 0; i < 2; i++) {
 648           Node* proj = proj_out(i);
 649           if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
 650             success = proj;
 651           } else if (fail == NULL) {
 652             fail = proj;
 653           } else {
 654             success = fail = NULL;
 655           }
 656         }
 657         if (success != NULL && fail != NULL && !region->has_phi()) {
 658           int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
 659           BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 660           Node* dom_cmp =  dom_bool->in(1);
 661           const TypeInt* failtype  = filtered_int_type(phase, n, ctrl);
 662           if (failtype != NULL) {
 663             const TypeInt* type2 = filtered_int_type(phase, n, fail);
 664             if (type2 != NULL) {
 665               failtype = failtype->join(type2)->is_int();
 666             } else {
 667               failtype = NULL;
 668             }
 669           }
 670 
 671           if (failtype != NULL &&
 672               dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
 673             int bound = failtype->_hi - failtype->_lo + 1;
 674             if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
 675               // Merge the two compares into a single unsigned compare by building  (CmpU (n - lo) hi)
 676               BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
 677               Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo)));
 678               Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound)));
 679               Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond));
 680               phase->hash_delete(dom_iff);
 681               dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con));
 682               phase->is_IterGVN()->_worklist.push(dom_iff);
 683               phase->hash_delete(this);
 684               set_req(1, newbool);
 685               return this;
 686             }
 687             if (failtype->_lo > failtype->_hi) {
 688               // previous if determines the result of this if so
 689               // replace Bool with constant
 690               phase->hash_delete(this);
 691               set_req(1, phase->intcon(success->as_Proj()->_con));
 692               return this;
 693             }
 694           }
 695         }
 696       }
 697     }
 698   }
 699   return NULL;
 700 }
 701 
 702 //------------------------------remove_useless_bool----------------------------
 703 // Check for people making a useless boolean: things like
 704 // if( (x < y ? true : false) ) { ... }
 705 // Replace with if( x < y ) { ... }
 706 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
 707   Node *i1 = iff->in(1);
 708   if( !i1->is_Bool() ) return NULL;
 709   BoolNode *bol = i1->as_Bool();
 710 
 711   Node *cmp = bol->in(1);
 712   if( cmp->Opcode() != Op_CmpI ) return NULL;
 713 
 714   // Must be comparing against a bool
 715   const Type *cmp2_t = phase->type( cmp->in(2) );
 716   if( cmp2_t != TypeInt::ZERO &&
 717       cmp2_t != TypeInt::ONE )
 718     return NULL;
 719 
 720   // Find a prior merge point merging the boolean
 721   i1 = cmp->in(1);
 722   if( !i1->is_Phi() ) return NULL;
 723   PhiNode *phi = i1->as_Phi();
 724   if( phase->type( phi ) != TypeInt::BOOL )
 725     return NULL;
 726 
 727   // Check for diamond pattern
 728   int true_path = phi->is_diamond_phi();
 729   if( true_path == 0 ) return NULL;
 730 
 731   // phi->region->if_proj->ifnode->bool->cmp
 732   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
 733   
 734   // Now get the 'sense' of the test correct so we can plug in
 735   // either iff2->in(1) or its complement.
 736   int flip = 0;
 737   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
 738   else if( bol->_test._test != BoolTest::eq ) return NULL;
 739   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
 740 
 741   const Type *phi1_t = phase->type( phi->in(1) );
 742   const Type *phi2_t = phase->type( phi->in(2) );
 743   // Check for Phi(0,1) and flip
 744   if( phi1_t == TypeInt::ZERO ) {
 745     if( phi2_t != TypeInt::ONE ) return NULL;
 746     flip = 1-flip;
 747   } else {
 748     // Check for Phi(1,0)
 749     if( phi1_t != TypeInt::ONE  ) return NULL;
 750     if( phi2_t != TypeInt::ZERO ) return NULL;
 751   }
 752   if( true_path == 2 ) {
 753     flip = 1-flip;
 754   }
 755 
 756   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
 757   iff->set_req(1, new_bol);
 758   // Intervening diamond probably goes dead
 759   phase->C->set_major_progress();
 760   return iff;
 761 }
 762 
 763 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
 764 
 765 //------------------------------Ideal------------------------------------------
 766 // Return a node which is more "ideal" than the current node.  Strip out 
 767 // control copies
 768 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 769   if (remove_dead_region(phase, can_reshape))  return this;
 770   // No Def-Use info?
 771   if (!can_reshape)  return NULL;
 772   PhaseIterGVN *igvn = phase->is_IterGVN();
 773 
 774   // Don't bother trying to transform a dead if
 775   if (in(0)->is_top())  return NULL;
 776   // Don't bother trying to transform an if with a dead test
 777   if (in(1)->is_top())  return NULL;
 778   // Another variation of a dead test
 779   if (in(1)->is_Con())  return NULL;
 780   // Another variation of a dead if
 781   if (outcnt() < 2)  return NULL;
 782 
 783   // Canonicalize the test.
 784   Node* idt_if = idealize_test(phase, this);
 785   if (idt_if != NULL)  return idt_if;
 786 
 787   // Try to split the IF
 788   Node *s = split_if(this, igvn);
 789   if (s != NULL)  return s;
 790 
 791   // Check for people making a useless boolean: things like
 792   // if( (x < y ? true : false) ) { ... }
 793   // Replace with if( x < y ) { ... }
 794   Node *bol2 = remove_useless_bool(this, phase);
 795   if( bol2 ) return bol2;
 796 
 797   // Setup to scan up the CFG looking for a dominating test
 798   Node *dom = in(0);
 799   Node *prev_dom = this;
 800 
 801   // Check for range-check vs other kinds of tests
 802   Node *index1, *range1;
 803   jint offset1;
 804   int flip1 = is_range_check(range1, index1, offset1);
 805   if( flip1 ) {
 806     Node *first_prev_dom = NULL;
 807 
 808     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
 809     // so all checks we inspect post-dominate the top-most check we find.
 810     // If we are going to fail the current check and we reach the top check
 811     // then we are guarenteed to fail, so just start interpreting there.
 812     // We 'expand' the top 2 range checks to include all post-dominating 
 813     // checks.  
 814 
 815     // The top 2 range checks seen
 816     Node *prev_chk1 = NULL;
 817     Node *prev_chk2 = NULL;
 818     // Low and high offsets seen so far
 819     jint off_lo = offset1;
 820     jint off_hi = offset1;
 821 
 822     // Scan for the top 2 checks and collect range of offsets
 823     for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
 824       if( dom->Opcode() == Op_If &&  // Not same opcode?
 825           prev_dom->in(0) == dom ) { // One path of test does dominate?
 826         if( dom == this ) return NULL; // dead loop
 827         // See if this is a range check
 828         Node *index2, *range2;
 829         jint offset2;
 830         int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
 831         // See if this is a _matching_ range check, checking against
 832         // the same array bounds.
 833         if( flip2 == flip1 && range2 == range1 && index2 == index1 && 
 834             dom->outcnt() == 2 ) {
 835           // Gather expanded bounds
 836           off_lo = MIN2(off_lo,offset2);
 837           off_hi = MAX2(off_hi,offset2);
 838           // Record top 2 range checks
 839           prev_chk2 = prev_chk1;
 840           prev_chk1 = prev_dom;
 841           // If we match the test exactly, then the top test covers
 842           // both our lower and upper bounds.
 843           if( dom->in(1) == in(1) )
 844             prev_chk2 = prev_chk1;
 845         }
 846       }
 847       prev_dom = dom;
 848       dom = up_one_dom( dom );
 849       if( !dom ) break;
 850     }
 851 
 852 
 853     // Attempt to widen the dominating range check to cover some later
 854     // ones.  Since range checks "fail" by uncommon-trapping to the
 855     // interpreter, widening a check can make us speculative enter the
 856     // interpreter.  If we see range-check deopt's, do not widen!
 857     if (!phase->C->allow_range_check_smearing())  return NULL;
 858 
 859     // Constant indices only need to check the upper bound.
 860     // Non-constance indices must check both low and high.
 861     if( index1 ) {
 862       // Didn't find 2 prior covering checks, so cannot remove anything.
 863       if( !prev_chk2 ) return NULL;
 864       // 'Widen' the offsets of the 1st and 2nd covering check
 865       adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
 866       // Do not call adjust_check twice on the same projection 
 867       // as the first call may have transformed the BoolNode to a ConI
 868       if( prev_chk1 != prev_chk2 ) {
 869         adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
 870       }
 871       // Test is now covered by prior checks, dominate it out
 872       prev_dom = prev_chk2;
 873     } else {
 874       // Didn't find prior covering check, so cannot remove anything.
 875       if( !prev_chk1 ) return NULL;
 876       // 'Widen' the offset of the 1st and only covering check
 877       adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
 878       // Test is now covered by prior checks, dominate it out
 879       prev_dom = prev_chk1;
 880     }
 881 
 882 
 883   } else {                      // Scan for an equivalent test
 884 
 885     Node *cmp;
 886     int dist = 0;               // Cutoff limit for search
 887     int op = Opcode();
 888     if( op == Op_If && 
 889         (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
 890       if( cmp->in(2) != NULL && // make sure cmp is not already dead
 891           cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
 892         dist = 64;              // Limit for null-pointer scans
 893       } else {
 894         dist = 4;               // Do not bother for random pointer tests
 895       }
 896     } else {
 897       dist = 4;                 // Limit for random junky scans
 898     }
 899 
 900     // Normal equivalent-test check.
 901     if( !dom ) return NULL;     // Dead loop?
 902 
 903     Node* result = fold_compares(phase);
 904     if (result != NULL) {
 905       return result;
 906     }
 907 
 908     // Search up the dominator tree for an If with an identical test
 909     while( dom->Opcode() != op    ||  // Not same opcode?
 910            dom->in(1)    != in(1) ||  // Not same input 1?
 911            (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
 912            prev_dom->in(0) != dom ) { // One path of test does not dominate?
 913       if( dist < 0 ) return NULL;
 914 
 915       dist--;
 916       prev_dom = dom;
 917       dom = up_one_dom( dom );
 918       if( !dom ) return NULL;
 919     }
 920 
 921     // Check that we did not follow a loop back to ourselves
 922     if( this == dom ) 
 923       return NULL;
 924 
 925     if( dist > 2 )              // Add to count of NULL checks elided
 926       explicit_null_checks_elided++;
 927 
 928   } // End of Else scan for an equivalent test
 929 
 930   // Hit!  Remove this IF
 931 #ifndef PRODUCT
 932   if( TraceIterativeGVN ) {
 933     tty->print("   Removing IfNode: "); this->dump();
 934   }
 935   if( VerifyOpto && !phase->allow_progress() ) {
 936     // Found an equivalent dominating test, 
 937     // we can not guarantee reaching a fix-point for these during iterativeGVN
 938     // since intervening nodes may not change.
 939     return NULL;
 940   }
 941 #endif
 942 
 943   // Replace dominated IfNode
 944   dominated_by( prev_dom, igvn );
 945 
 946   // Must return either the original node (now dead) or a new node
 947   // (Do not return a top here, since that would break the uniqueness of top.)
 948   return new (phase->C, 1) ConINode(TypeInt::ZERO);
 949 }
 950 
 951 //------------------------------dominated_by-----------------------------------
 952 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
 953   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
 954   Node *idom = in(0);
 955   // Need opcode to decide which way 'this' test goes
 956   int prev_op = prev_dom->Opcode();
 957   Node *top = igvn->C->top(); // Shortcut to top
 958 
 959   // Now walk the current IfNode's projections.
 960   // Loop ends when 'this' has no more uses.
 961   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 962     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
 963     igvn->add_users_to_worklist(ifp);
 964     // Check which projection it is and set target.
 965     // Data-target is either the dominating projection of the same type
 966     // or TOP if the dominating projection is of opposite type.
 967     // Data-target will be used as the new control edge for the non-CFG
 968     // nodes like Casts and Loads.
 969     Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top;
 970     // Control-target is just the If's immediate dominator or TOP.
 971     Node *ctrl_target = (ifp->Opcode() == prev_op ) ?     idom : top;
 972 
 973     // For each child of an IfTrue/IfFalse projection, reroute.
 974     // Loop ends when projection has no more uses. 
 975     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
 976       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
 977       igvn->hash_delete(s);         // Yank from hash table before edge hacking
 978       if( !s->depends_only_on_test() ) {
 979         // Find the control input matching this def-use edge.
 980         // For Regions it may not be in slot 0.
 981         uint l;
 982         for( l = 0; s->in(l) != ifp; l++ ) { } 
 983         s->set_req(l, ctrl_target);
 984       } else {                      // Else, for control producers, 
 985         s->set_req(0, data_target); // Move child to data-target
 986       }
 987       igvn->_worklist.push(s);  // Revisit collapsed Phis
 988     } // End for each child of a projection
 989 
 990     igvn->remove_dead_node(ifp);
 991   } // End for each IfTrue/IfFalse child of If
 992 
 993   // Kill the IfNode
 994   igvn->remove_dead_node(this);
 995 }
 996 
 997 //------------------------------Identity---------------------------------------
 998 // If the test is constant & we match, then we are the input Control
 999 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1000   // Can only optimize if cannot go the other way
1001   const TypeTuple *t = phase->type(in(0))->is_tuple();
1002   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1003     ? in(0)->in(0)              // IfNode control
1004     : this;                     // no progress
1005 }
1006 
1007 //------------------------------dump_spec--------------------------------------
1008 #ifndef PRODUCT
1009 void IfNode::dump_spec(outputStream *st) const { 
1010   st->print("P=%f, C=%f",_prob,_fcnt);
1011 }
1012 #endif
1013 
1014 //------------------------------idealize_test----------------------------------
1015 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1016 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1017 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1018 // needed.
1019 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1020   assert(iff->in(0) != NULL, "If must be live");
1021 
1022   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
1023   Node* old_if_f = iff->proj_out(false);
1024   Node* old_if_t = iff->proj_out(true);
1025 
1026   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1027   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1028   // happens in count-down loops
1029   if (iff->is_CountedLoopEnd())  return NULL;
1030   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
1031   BoolNode *b = iff->in(1)->as_Bool();
1032   BoolTest bt = b->_test;
1033   // Test already in good order?
1034   if( bt.is_canonical() ) 
1035     return NULL;
1036 
1037   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1038   // cloning the IfNode.
1039   Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) );
1040   if( !new_b->is_Bool() ) return NULL;
1041   b = new_b->as_Bool();
1042 
1043   PhaseIterGVN *igvn = phase->is_IterGVN();
1044   assert( igvn, "Test is not canonical in parser?" );
1045   
1046   // The IF node never really changes, but it needs to be cloned
1047   iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1048 
1049   Node *prior = igvn->hash_find_insert(iff);
1050   if( prior ) {
1051     igvn->remove_dead_node(iff);
1052     iff = (IfNode*)prior;
1053   } else {
1054     // Cannot call transform on it just yet
1055     igvn->set_type_bottom(iff);
1056   }
1057   igvn->_worklist.push(iff);
1058 
1059   // Now handle projections.  Cloning not required.
1060   Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff ));
1061   Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff ));
1062 
1063   igvn->register_new_node_with_optimizer(new_if_f);
1064   igvn->register_new_node_with_optimizer(new_if_t);
1065   igvn->hash_delete(old_if_f);
1066   igvn->hash_delete(old_if_t);
1067   // Flip test, so flip trailing control 
1068   igvn->subsume_node(old_if_f, new_if_t);
1069   igvn->subsume_node(old_if_t, new_if_f);
1070 
1071   // Progress
1072   return iff;
1073 }
1074 
1075 //------------------------------Identity---------------------------------------
1076 // If the test is constant & we match, then we are the input Control
1077 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1078   // Can only optimize if cannot go the other way
1079   const TypeTuple *t = phase->type(in(0))->is_tuple();
1080   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1081     ? in(0)->in(0)              // IfNode control
1082     : this;                     // no progress
1083 }
1084