1 /*
   2  * Copyright (c) 1999, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "memory/allocation.inline.hpp"
  27 #include "opto/addnode.hpp"
  28 #include "opto/connode.hpp"
  29 #include "opto/divnode.hpp"
  30 #include "opto/loopnode.hpp"
  31 #include "opto/matcher.hpp"
  32 #include "opto/mulnode.hpp"
  33 #include "opto/movenode.hpp"
  34 #include "opto/opaquenode.hpp"
  35 #include "opto/rootnode.hpp"
  36 #include "opto/shenandoahSupport.hpp"
  37 #include "opto/subnode.hpp"
  38 
  39 //=============================================================================
  40 //------------------------------split_thru_phi---------------------------------
  41 // Split Node 'n' through merge point if there is enough win.
  42 Node *PhaseIdealLoop::split_thru_phi( Node *n, Node *region, int policy ) {
  43   if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::LONG) {
  44     // ConvI2L may have type information on it which is unsafe to push up
  45     // so disable this for now
  46     return NULL;
  47   }
  48 
  49   int wins = 0;
  50   assert(!n->is_CFG(), "");
  51   assert(region->is_Region(), "");
  52 
  53   const Type* type = n->bottom_type();
  54   const TypeOopPtr *t_oop = _igvn.type(n)->isa_oopptr();
  55   Node *phi;
  56   if (t_oop != NULL && t_oop->is_known_instance_field()) {
  57     int iid    = t_oop->instance_id();
  58     int index  = C->get_alias_index(t_oop);
  59     int offset = t_oop->offset();
  60     phi = new PhiNode(region, type, NULL, iid, index, offset);
  61   } else {
  62     phi = PhiNode::make_blank(region, n);
  63   }
  64   uint old_unique = C->unique();
  65   for (uint i = 1; i < region->req(); i++) {
  66     Node *x;
  67     Node* the_clone = NULL;
  68     if (region->in(i) == C->top()) {
  69       x = C->top();             // Dead path?  Use a dead data op
  70     } else {
  71 #ifdef ASSERT
  72       if (n->is_ShenandoahBarrier()) { n->as_ShenandoahBarrier()->check_invariants(); }
  73 #endif
  74       x = n->clone();           // Else clone up the data op
  75       the_clone = x;            // Remember for possible deletion.
  76       // Alter data node to use pre-phi inputs
  77       if (n->in(0) == region)
  78         x->set_req( 0, region->in(i) );
  79       for (uint j = 1; j < n->req(); j++) {
  80         Node *in = n->in(j);
  81         if (in->is_Phi() && in->in(0) == region)
  82           x->set_req( j, in->in(i) ); // Use pre-Phi input for the clone
  83       }
  84     }
  85     // Check for a 'win' on some paths
  86     const Type *t = x->Value(&_igvn);
  87 
  88     bool singleton = t->singleton();
  89 
  90     // A TOP singleton indicates that there are no possible values incoming
  91     // along a particular edge. In most cases, this is OK, and the Phi will
  92     // be eliminated later in an Ideal call. However, we can't allow this to
  93     // happen if the singleton occurs on loop entry, as the elimination of
  94     // the PhiNode may cause the resulting node to migrate back to a previous
  95     // loop iteration.
  96     if (singleton && t == Type::TOP) {
  97       // Is_Loop() == false does not confirm the absence of a loop (e.g., an
  98       // irreducible loop may not be indicated by an affirmative is_Loop());
  99       // therefore, the only top we can split thru a phi is on a backedge of
 100       // a loop.
 101       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
 102     }
 103 
 104     if (singleton) {
 105       wins++;
 106       x = ((PhaseGVN&)_igvn).makecon(t);
 107     } else {
 108       // We now call Identity to try to simplify the cloned node.
 109       // Note that some Identity methods call phase->type(this).
 110       // Make sure that the type array is big enough for
 111       // our new node, even though we may throw the node away.
 112       // (Note: This tweaking with igvn only works because x is a new node.)
 113       _igvn.set_type(x, t);
 114       // If x is a TypeNode, capture any more-precise type permanently into Node
 115       // otherwise it will be not updated during igvn->transform since
 116       // igvn->type(x) is set to x->Value() already.
 117       x->raise_bottom_type(t);
 118       if (x->Opcode() != Op_ShenandoahWriteBarrier) {
 119         Node *y = x->Identity(&_igvn);
 120         if (y != x) {
 121           wins++;
 122           x = y;
 123         } else {
 124           y = _igvn.hash_find(x);
 125           if (y) {
 126             wins++;
 127             x = y;
 128           } else {
 129             // Else x is a new node we are keeping
 130             // We do not need register_new_node_with_optimizer
 131             // because set_type has already been called.
 132             _igvn._worklist.push(x);
 133           }
 134         }
 135       } else {
 136         // wins++;
 137         _igvn._worklist.push(x);
 138       }
 139     }
 140     if (x != the_clone && the_clone != NULL)
 141       _igvn.remove_dead_node(the_clone);
 142     phi->set_req( i, x );
 143   }
 144   // Too few wins?
 145   if (wins <= policy) {
 146     _igvn.remove_dead_node(phi);
 147     return NULL;
 148   }
 149 
 150   // Record Phi
 151   register_new_node( phi, region );
 152 
 153   for (uint i2 = 1; i2 < phi->req(); i2++) {
 154     Node *x = phi->in(i2);
 155     // If we commoned up the cloned 'x' with another existing Node,
 156     // the existing Node picks up a new use.  We need to make the
 157     // existing Node occur higher up so it dominates its uses.
 158     Node *old_ctrl;
 159     IdealLoopTree *old_loop;
 160 
 161     if (x->is_Con()) {
 162       // Constant's control is always root.
 163       set_ctrl(x, C->root());
 164       continue;
 165     }
 166     // The occasional new node
 167     if (x->_idx >= old_unique) {     // Found a new, unplaced node?
 168       old_ctrl = NULL;
 169       old_loop = NULL;               // Not in any prior loop
 170     } else {
 171       old_ctrl = get_ctrl(x);
 172       old_loop = get_loop(old_ctrl); // Get prior loop
 173     }
 174     // New late point must dominate new use
 175     Node *new_ctrl = dom_lca(old_ctrl, region->in(i2));
 176     if (new_ctrl == old_ctrl) // Nothing is changed
 177       continue;
 178 
 179     IdealLoopTree *new_loop = get_loop(new_ctrl);
 180 
 181     // Don't move x into a loop if its uses are
 182     // outside of loop. Otherwise x will be cloned
 183     // for each use outside of this loop.
 184     IdealLoopTree *use_loop = get_loop(region);
 185     if (!new_loop->is_member(use_loop) &&
 186         (old_loop == NULL || !new_loop->is_member(old_loop))) {
 187       // Take early control, later control will be recalculated
 188       // during next iteration of loop optimizations.
 189       new_ctrl = get_early_ctrl(x);
 190       new_loop = get_loop(new_ctrl);
 191     }
 192     // Set new location
 193     set_ctrl(x, new_ctrl);
 194     // If changing loop bodies, see if we need to collect into new body
 195     if (old_loop != new_loop) {
 196       if (old_loop && !old_loop->_child)
 197         old_loop->_body.yank(x);
 198       if (!new_loop->_child)
 199         new_loop->_body.push(x);  // Collect body info
 200     }
 201   }
 202 
 203   return phi;
 204 }
 205 
 206 void PhaseIdealLoop::split_mem_thru_phi(Node* n, Node* r, Node* phi) {
 207   if (n->Opcode() == Op_ShenandoahWriteBarrier) {
 208 #ifdef ASSERT
 209     n->as_ShenandoahBarrier()->check_invariants();
 210 #endif
 211     if (n->has_out_with(Op_ShenandoahWBMemProj)) {
 212       Node* old_mem_phi = n->in(ShenandoahBarrierNode::Memory);
 213       assert(r->is_Region(), "need region to control phi");
 214       assert(phi->is_Phi(), "expect phi");
 215       Node* memphi = PhiNode::make(r, old_mem_phi, Type::MEMORY, C->alias_type(n->adr_type())->adr_type());
 216       for (uint i = 1; i < r->req(); i++) {
 217         Node* wb = phi->in(i);
 218         if (wb->Opcode() == Op_ShenandoahWriteBarrier) {
 219           assert(! wb->has_out_with(Op_ShenandoahWBMemProj), "new clone does not have mem proj");
 220           Node* new_proj = new ShenandoahWBMemProjNode(wb);
 221           register_new_node(new_proj, r->in(i));
 222           memphi->set_req(i, new_proj);
 223         } else {
 224           if (old_mem_phi->is_Phi() && old_mem_phi->in(0) == r) {
 225             memphi->set_req(i, old_mem_phi->in(i));
 226           }
 227         }
 228       }
 229       register_new_node(memphi, r);
 230       Node* old_mem_out = n->find_out_with(Op_ShenandoahWBMemProj);
 231       assert(old_mem_out != NULL, "expect memory projection");
 232       _igvn.replace_node(old_mem_out, memphi);
 233     }
 234     assert(! n->has_out_with(Op_ShenandoahWBMemProj), "no more memory outs");
 235   }
 236 }
 237 
 238 //------------------------------dominated_by------------------------------------
 239 // Replace the dominated test with an obvious true or false.  Place it on the
 240 // IGVN worklist for later cleanup.  Move control-dependent data Nodes on the
 241 // live path up to the dominating control.
 242 void PhaseIdealLoop::dominated_by( Node *prevdom, Node *iff, bool flip, bool exclude_loop_predicate ) {
 243 #ifndef PRODUCT
 244   if (VerifyLoopOptimizations && PrintOpto) tty->print_cr("dominating test");
 245 #endif
 246 
 247 
 248   // prevdom is the dominating projection of the dominating test.
 249   assert( iff->is_If(), "" );
 250   assert( iff->Opcode() == Op_If || iff->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
 251   int pop = prevdom->Opcode();
 252   assert( pop == Op_IfFalse || pop == Op_IfTrue, "" );
 253   if (flip) {
 254     if (pop == Op_IfTrue)
 255       pop = Op_IfFalse;
 256     else
 257       pop = Op_IfTrue;
 258   }
 259   // 'con' is set to true or false to kill the dominated test.
 260   Node *con = _igvn.makecon(pop == Op_IfTrue ? TypeInt::ONE : TypeInt::ZERO);
 261   set_ctrl(con, C->root()); // Constant gets a new use
 262   // Hack the dominated test
 263   _igvn.replace_input_of(iff, 1, con);
 264 
 265   // If I dont have a reachable TRUE and FALSE path following the IfNode then
 266   // I can assume this path reaches an infinite loop.  In this case it's not
 267   // important to optimize the data Nodes - either the whole compilation will
 268   // be tossed or this path (and all data Nodes) will go dead.
 269   if (iff->outcnt() != 2) return;
 270 
 271   // Make control-dependent data Nodes on the live path (path that will remain
 272   // once the dominated IF is removed) become control-dependent on the
 273   // dominating projection.
 274   Node* dp = iff->as_If()->proj_out(pop == Op_IfTrue);
 275 
 276   // Loop predicates may have depending checks which should not
 277   // be skipped. For example, range check predicate has two checks
 278   // for lower and upper bounds.
 279   if (dp == NULL)
 280     return;
 281 
 282   ProjNode* dp_proj  = dp->as_Proj();
 283   ProjNode* unc_proj = iff->as_If()->proj_out(1 - dp_proj->_con)->as_Proj();
 284   if (exclude_loop_predicate &&
 285       (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL ||
 286        unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_range_check) != NULL)) {
 287     // If this is a range check (IfNode::is_range_check), do not
 288     // reorder because Compile::allow_range_check_smearing might have
 289     // changed the check.
 290     return; // Let IGVN transformation change control dependence.
 291   }
 292 
 293   IdealLoopTree *old_loop = get_loop(dp);
 294 
 295   for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
 296     Node* cd = dp->fast_out(i); // Control-dependent node
 297     if (cd->depends_only_on_test()) {
 298       assert(cd->in(0) == dp, "");
 299       _igvn.replace_input_of(cd, 0, prevdom);
 300       set_early_ctrl(cd);
 301       IdealLoopTree *new_loop = get_loop(get_ctrl(cd));
 302       if (old_loop != new_loop) {
 303         if (!old_loop->_child) old_loop->_body.yank(cd);
 304         if (!new_loop->_child) new_loop->_body.push(cd);
 305       }
 306       --i;
 307       --imax;
 308     }
 309   }
 310 }
 311 
 312 //------------------------------has_local_phi_input----------------------------
 313 // Return TRUE if 'n' has Phi inputs from its local block and no other
 314 // block-local inputs (all non-local-phi inputs come from earlier blocks)
 315 Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
 316   Node *n_ctrl = get_ctrl(n);
 317   // See if some inputs come from a Phi in this block, or from before
 318   // this block.
 319   uint i;
 320   for( i = 1; i < n->req(); i++ ) {
 321     Node *phi = n->in(i);
 322     if( phi->is_Phi() && phi->in(0) == n_ctrl )
 323       break;
 324   }
 325   if( i >= n->req() )
 326     return NULL;                // No Phi inputs; nowhere to clone thru
 327 
 328   // Check for inputs created between 'n' and the Phi input.  These
 329   // must split as well; they have already been given the chance
 330   // (courtesy of a post-order visit) and since they did not we must
 331   // recover the 'cost' of splitting them by being very profitable
 332   // when splitting 'n'.  Since this is unlikely we simply give up.
 333   for( i = 1; i < n->req(); i++ ) {
 334     Node *m = n->in(i);
 335     if( get_ctrl(m) == n_ctrl && !m->is_Phi() ) {
 336       // We allow the special case of AddP's with no local inputs.
 337       // This allows us to split-up address expressions.
 338       if (m->is_AddP() &&
 339           get_ctrl(m->in(2)) != n_ctrl &&
 340           get_ctrl(m->in(3)) != n_ctrl) {
 341         // Move the AddP up to dominating point
 342         set_ctrl_and_loop(m, find_non_split_ctrl(idom(n_ctrl)));
 343         continue;
 344       }
 345       return NULL;
 346     }
 347   }
 348 
 349   return n_ctrl;
 350 }
 351 
 352 //------------------------------remix_address_expressions----------------------
 353 // Rework addressing expressions to get the most loop-invariant stuff
 354 // moved out.  We'd like to do all associative operators, but it's especially
 355 // important (common) to do address expressions.
 356 Node *PhaseIdealLoop::remix_address_expressions( Node *n ) {
 357   if (!has_ctrl(n))  return NULL;
 358   Node *n_ctrl = get_ctrl(n);
 359   IdealLoopTree *n_loop = get_loop(n_ctrl);
 360 
 361   // See if 'n' mixes loop-varying and loop-invariant inputs and
 362   // itself is loop-varying.
 363 
 364   // Only interested in binary ops (and AddP)
 365   if( n->req() < 3 || n->req() > 4 ) return NULL;
 366 
 367   Node *n1_ctrl = get_ctrl(n->in(                    1));
 368   Node *n2_ctrl = get_ctrl(n->in(                    2));
 369   Node *n3_ctrl = get_ctrl(n->in(n->req() == 3 ? 2 : 3));
 370   IdealLoopTree *n1_loop = get_loop( n1_ctrl );
 371   IdealLoopTree *n2_loop = get_loop( n2_ctrl );
 372   IdealLoopTree *n3_loop = get_loop( n3_ctrl );
 373 
 374   // Does one of my inputs spin in a tighter loop than self?
 375   if( (n_loop->is_member( n1_loop ) && n_loop != n1_loop) ||
 376       (n_loop->is_member( n2_loop ) && n_loop != n2_loop) ||
 377       (n_loop->is_member( n3_loop ) && n_loop != n3_loop) )
 378     return NULL;                // Leave well enough alone
 379 
 380   // Is at least one of my inputs loop-invariant?
 381   if( n1_loop == n_loop &&
 382       n2_loop == n_loop &&
 383       n3_loop == n_loop )
 384     return NULL;                // No loop-invariant inputs
 385 
 386 
 387   int n_op = n->Opcode();
 388 
 389   // Replace expressions like ((V+I) << 2) with (V<<2 + I<<2).
 390   if( n_op == Op_LShiftI ) {
 391     // Scale is loop invariant
 392     Node *scale = n->in(2);
 393     Node *scale_ctrl = get_ctrl(scale);
 394     IdealLoopTree *scale_loop = get_loop(scale_ctrl );
 395     if( n_loop == scale_loop || !scale_loop->is_member( n_loop ) )
 396       return NULL;
 397     const TypeInt *scale_t = scale->bottom_type()->isa_int();
 398     if( scale_t && scale_t->is_con() && scale_t->get_con() >= 16 )
 399       return NULL;              // Dont bother with byte/short masking
 400     // Add must vary with loop (else shift would be loop-invariant)
 401     Node *add = n->in(1);
 402     Node *add_ctrl = get_ctrl(add);
 403     IdealLoopTree *add_loop = get_loop(add_ctrl);
 404     //assert( n_loop == add_loop, "" );
 405     if( n_loop != add_loop ) return NULL;  // happens w/ evil ZKM loops
 406 
 407     // Convert I-V into I+ (0-V); same for V-I
 408     if( add->Opcode() == Op_SubI &&
 409         _igvn.type( add->in(1) ) != TypeInt::ZERO ) {
 410       Node *zero = _igvn.intcon(0);
 411       set_ctrl(zero, C->root());
 412       Node *neg = new SubINode( _igvn.intcon(0), add->in(2) );
 413       register_new_node( neg, get_ctrl(add->in(2) ) );
 414       add = new AddINode( add->in(1), neg );
 415       register_new_node( add, add_ctrl );
 416     }
 417     if( add->Opcode() != Op_AddI ) return NULL;
 418     // See if one add input is loop invariant
 419     Node *add_var = add->in(1);
 420     Node *add_var_ctrl = get_ctrl(add_var);
 421     IdealLoopTree *add_var_loop = get_loop(add_var_ctrl );
 422     Node *add_invar = add->in(2);
 423     Node *add_invar_ctrl = get_ctrl(add_invar);
 424     IdealLoopTree *add_invar_loop = get_loop(add_invar_ctrl );
 425     if( add_var_loop == n_loop ) {
 426     } else if( add_invar_loop == n_loop ) {
 427       // Swap to find the invariant part
 428       add_invar = add_var;
 429       add_invar_ctrl = add_var_ctrl;
 430       add_invar_loop = add_var_loop;
 431       add_var = add->in(2);
 432       Node *add_var_ctrl = get_ctrl(add_var);
 433       IdealLoopTree *add_var_loop = get_loop(add_var_ctrl );
 434     } else                      // Else neither input is loop invariant
 435       return NULL;
 436     if( n_loop == add_invar_loop || !add_invar_loop->is_member( n_loop ) )
 437       return NULL;              // No invariant part of the add?
 438 
 439     // Yes!  Reshape address expression!
 440     Node *inv_scale = new LShiftINode( add_invar, scale );
 441     Node *inv_scale_ctrl =
 442       dom_depth(add_invar_ctrl) > dom_depth(scale_ctrl) ?
 443       add_invar_ctrl : scale_ctrl;
 444     register_new_node( inv_scale, inv_scale_ctrl );
 445     Node *var_scale = new LShiftINode( add_var, scale );
 446     register_new_node( var_scale, n_ctrl );
 447     Node *var_add = new AddINode( var_scale, inv_scale );
 448     register_new_node( var_add, n_ctrl );
 449     _igvn.replace_node( n, var_add );
 450     return var_add;
 451   }
 452 
 453   // Replace (I+V) with (V+I)
 454   if( n_op == Op_AddI ||
 455       n_op == Op_AddL ||
 456       n_op == Op_AddF ||
 457       n_op == Op_AddD ||
 458       n_op == Op_MulI ||
 459       n_op == Op_MulL ||
 460       n_op == Op_MulF ||
 461       n_op == Op_MulD ) {
 462     if( n2_loop == n_loop ) {
 463       assert( n1_loop != n_loop, "" );
 464       n->swap_edges(1, 2);
 465     }
 466   }
 467 
 468   // Replace ((I1 +p V) +p I2) with ((I1 +p I2) +p V),
 469   // but not if I2 is a constant.
 470   if( n_op == Op_AddP ) {
 471     if( n2_loop == n_loop && n3_loop != n_loop ) {
 472       if( n->in(2)->Opcode() == Op_AddP && !n->in(3)->is_Con() ) {
 473         Node *n22_ctrl = get_ctrl(n->in(2)->in(2));
 474         Node *n23_ctrl = get_ctrl(n->in(2)->in(3));
 475         IdealLoopTree *n22loop = get_loop( n22_ctrl );
 476         IdealLoopTree *n23_loop = get_loop( n23_ctrl );
 477         if( n22loop != n_loop && n22loop->is_member(n_loop) &&
 478             n23_loop == n_loop ) {
 479           Node *add1 = new AddPNode( n->in(1), n->in(2)->in(2), n->in(3) );
 480           // Stuff new AddP in the loop preheader
 481           register_new_node( add1, n_loop->_head->in(LoopNode::EntryControl) );
 482           Node *add2 = new AddPNode( n->in(1), add1, n->in(2)->in(3) );
 483           register_new_node( add2, n_ctrl );
 484           _igvn.replace_node( n, add2 );
 485           return add2;
 486         }
 487       }
 488     }
 489 
 490     // Replace (I1 +p (I2 + V)) with ((I1 +p I2) +p V)
 491     if( n2_loop != n_loop && n3_loop == n_loop ) {
 492       if( n->in(3)->Opcode() == Op_AddI ) {
 493         Node *V = n->in(3)->in(1);
 494         Node *I = n->in(3)->in(2);
 495         if( is_member(n_loop,get_ctrl(V)) ) {
 496         } else {
 497           Node *tmp = V; V = I; I = tmp;
 498         }
 499         if( !is_member(n_loop,get_ctrl(I)) ) {
 500           Node *add1 = new AddPNode( n->in(1), n->in(2), I );
 501           // Stuff new AddP in the loop preheader
 502           register_new_node( add1, n_loop->_head->in(LoopNode::EntryControl) );
 503           Node *add2 = new AddPNode( n->in(1), add1, V );
 504           register_new_node( add2, n_ctrl );
 505           _igvn.replace_node( n, add2 );
 506           return add2;
 507         }
 508       }
 509     }
 510   }
 511 
 512   return NULL;
 513 }
 514 
 515 //------------------------------conditional_move-------------------------------
 516 // Attempt to replace a Phi with a conditional move.  We have some pretty
 517 // strict profitability requirements.  All Phis at the merge point must
 518 // be converted, so we can remove the control flow.  We need to limit the
 519 // number of c-moves to a small handful.  All code that was in the side-arms
 520 // of the CFG diamond is now speculatively executed.  This code has to be
 521 // "cheap enough".  We are pretty much limited to CFG diamonds that merge
 522 // 1 or 2 items with a total of 1 or 2 ops executed speculatively.
 523 Node *PhaseIdealLoop::conditional_move( Node *region ) {
 524 
 525   assert(region->is_Region(), "sanity check");
 526   if (region->req() != 3) return NULL;
 527 
 528   // Check for CFG diamond
 529   Node *lp = region->in(1);
 530   Node *rp = region->in(2);
 531   if (!lp || !rp) return NULL;
 532   Node *lp_c = lp->in(0);
 533   if (lp_c == NULL || lp_c != rp->in(0) || !lp_c->is_If()) return NULL;
 534   IfNode *iff = lp_c->as_If();
 535 
 536   // Check for ops pinned in an arm of the diamond.
 537   // Can't remove the control flow in this case
 538   if (lp->outcnt() > 1) return NULL;
 539   if (rp->outcnt() > 1) return NULL;
 540 
 541   IdealLoopTree* r_loop = get_loop(region);
 542   assert(r_loop == get_loop(iff), "sanity");
 543   // Always convert to CMOVE if all results are used only outside this loop.
 544   bool used_inside_loop = (r_loop == _ltree_root);
 545 
 546   // Check profitability
 547   int cost = 0;
 548   int phis = 0;
 549   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 550     Node *out = region->fast_out(i);
 551     if (!out->is_Phi()) continue; // Ignore other control edges, etc
 552     phis++;
 553     PhiNode* phi = out->as_Phi();
 554     BasicType bt = phi->type()->basic_type();
 555     switch (bt) {
 556     case T_FLOAT:
 557     case T_DOUBLE: {
 558       cost += Matcher::float_cmove_cost(); // Could be very expensive
 559       break;
 560     }
 561     case T_LONG: {
 562       cost += Matcher::long_cmove_cost(); // May encodes as 2 CMOV's
 563     }
 564     case T_INT:                 // These all CMOV fine
 565     case T_ADDRESS: {           // (RawPtr)
 566       cost++;
 567       break;
 568     }
 569     case T_NARROWOOP: // Fall through
 570     case T_OBJECT: {            // Base oops are OK, but not derived oops
 571       const TypeOopPtr *tp = phi->type()->make_ptr()->isa_oopptr();
 572       // Derived pointers are Bad (tm): what's the Base (for GC purposes) of a
 573       // CMOVE'd derived pointer?  It's a CMOVE'd derived base.  Thus
 574       // CMOVE'ing a derived pointer requires we also CMOVE the base.  If we
 575       // have a Phi for the base here that we convert to a CMOVE all is well
 576       // and good.  But if the base is dead, we'll not make a CMOVE.  Later
 577       // the allocator will have to produce a base by creating a CMOVE of the
 578       // relevant bases.  This puts the allocator in the business of
 579       // manufacturing expensive instructions, generally a bad plan.
 580       // Just Say No to Conditionally-Moved Derived Pointers.
 581       if (tp && tp->offset() != 0)
 582         return NULL;
 583       cost++;
 584       break;
 585     }
 586     default:
 587       return NULL;              // In particular, can't do memory or I/O
 588     }
 589     // Add in cost any speculative ops
 590     for (uint j = 1; j < region->req(); j++) {
 591       Node *proj = region->in(j);
 592       Node *inp = phi->in(j);
 593       if (get_ctrl(inp) == proj) { // Found local op
 594         cost++;
 595         // Check for a chain of dependent ops; these will all become
 596         // speculative in a CMOV.
 597         for (uint k = 1; k < inp->req(); k++)
 598           if (get_ctrl(inp->in(k)) == proj)
 599             cost += ConditionalMoveLimit; // Too much speculative goo
 600       }
 601     }
 602     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
 603     // This will likely Split-If, a higher-payoff operation.
 604     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
 605       Node* use = phi->fast_out(k);
 606       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
 607         cost += ConditionalMoveLimit;
 608       // Is there a use inside the loop?
 609       // Note: check only basic types since CMoveP is pinned.
 610       if (!used_inside_loop && is_java_primitive(bt)) {
 611         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
 612         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
 613           used_inside_loop = true;
 614         }
 615       }
 616     }
 617   }
 618   Node* bol = iff->in(1);
 619   assert(bol->Opcode() == Op_Bool, "");
 620   int cmp_op = bol->in(1)->Opcode();
 621   // It is expensive to generate flags from a float compare.
 622   // Avoid duplicated float compare.
 623   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return NULL;
 624 
 625   float infrequent_prob = PROB_UNLIKELY_MAG(3);
 626   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
 627   if (used_inside_loop) {
 628     if (cost >= ConditionalMoveLimit) return NULL; // Too much goo
 629 
 630     // BlockLayoutByFrequency optimization moves infrequent branch
 631     // from hot path. No point in CMOV'ing in such case (110 is used
 632     // instead of 100 to take into account not exactness of float value).
 633     if (BlockLayoutByFrequency) {
 634       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
 635     }
 636   }
 637   // Check for highly predictable branch.  No point in CMOV'ing if
 638   // we are going to predict accurately all the time.
 639   if (iff->_prob < infrequent_prob ||
 640       iff->_prob > (1.0f - infrequent_prob))
 641     return NULL;
 642 
 643   // --------------
 644   // Now replace all Phis with CMOV's
 645   Node *cmov_ctrl = iff->in(0);
 646   uint flip = (lp->Opcode() == Op_IfTrue);
 647   while (1) {
 648     PhiNode* phi = NULL;
 649     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 650       Node *out = region->fast_out(i);
 651       if (out->is_Phi()) {
 652         phi = out->as_Phi();
 653         break;
 654       }
 655     }
 656     if (phi == NULL)  break;
 657 #ifndef PRODUCT
 658     if (PrintOpto && VerifyLoopOptimizations) tty->print_cr("CMOV");
 659 #endif
 660     // Move speculative ops
 661     for (uint j = 1; j < region->req(); j++) {
 662       Node *proj = region->in(j);
 663       Node *inp = phi->in(j);
 664       if (get_ctrl(inp) == proj) { // Found local op
 665 #ifndef PRODUCT
 666         if (PrintOpto && VerifyLoopOptimizations) {
 667           tty->print("  speculate: ");
 668           inp->dump();
 669         }
 670 #endif
 671         set_ctrl(inp, cmov_ctrl);
 672       }
 673     }
 674     Node *cmov = CMoveNode::make(cmov_ctrl, iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi));
 675     register_new_node( cmov, cmov_ctrl );
 676     _igvn.replace_node( phi, cmov );
 677 #ifndef PRODUCT
 678     if (TraceLoopOpts) {
 679       tty->print("CMOV  ");
 680       r_loop->dump_head();
 681       if (Verbose) {
 682         bol->in(1)->dump(1);
 683         cmov->dump(1);
 684       }
 685     }
 686     if (VerifyLoopOptimizations) verify();
 687 #endif
 688   }
 689 
 690   // The useless CFG diamond will fold up later; see the optimization in
 691   // RegionNode::Ideal.
 692   _igvn._worklist.push(region);
 693 
 694   return iff->in(1);
 695 }
 696 
 697 #ifdef ASSERT
 698 static void enqueue_cfg_uses(Node* m, Unique_Node_List& wq) {
 699   for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
 700     Node* u = m->fast_out(i);
 701     if (u->is_CFG()) {
 702       if (u->Opcode() == Op_NeverBranch) {
 703         u = ((NeverBranchNode*)u)->proj_out(0);
 704         enqueue_cfg_uses(u, wq);
 705       } else {
 706         wq.push(u);
 707       }
 708     }
 709   }
 710 }
 711 #endif
 712 
 713 // Try moving a store out of a loop, right before the loop
 714 Node* PhaseIdealLoop::try_move_store_before_loop(Node* n, Node *n_ctrl) {
 715   // Store has to be first in the loop body
 716   IdealLoopTree *n_loop = get_loop(n_ctrl);
 717   if (n->is_Store() && n_loop != _ltree_root && n_loop->is_loop() && n->in(0) != NULL) {
 718     Node* address = n->in(MemNode::Address);
 719     Node* value = n->in(MemNode::ValueIn);
 720     Node* mem = n->in(MemNode::Memory);
 721     IdealLoopTree* address_loop = get_loop(get_ctrl(address));
 722     IdealLoopTree* value_loop = get_loop(get_ctrl(value));
 723 
 724     // - address and value must be loop invariant
 725     // - memory must be a memory Phi for the loop
 726     // - Store must be the only store on this memory slice in the
 727     // loop: if there's another store following this one then value
 728     // written at iteration i by the second store could be overwritten
 729     // at iteration i+n by the first store: it's not safe to move the
 730     // first store out of the loop
 731     // - nothing must observe the Phi memory: it guarantees no read
 732     // before the store and no early exit out of the loop
 733     // With those conditions, we are also guaranteed the store post
 734     // dominates the loop head. Otherwise there would be extra Phi
 735     // involved between the loop's Phi and the store.
 736 
 737     if (!n_loop->is_member(address_loop) &&
 738         !n_loop->is_member(value_loop) &&
 739         mem->is_Phi() && mem->in(0) == n_loop->_head &&
 740         mem->outcnt() == 1 &&
 741         mem->in(LoopNode::LoopBackControl) == n) {
 742 
 743 #ifdef ASSERT
 744       // Verify that store's control does post dominate loop entry and
 745       // that there's no early exit of the loop before the store.
 746       bool ctrl_ok = false;
 747       {
 748         // Follow control from loop head until n, we exit the loop or
 749         // we reach the tail
 750         ResourceMark rm;
 751         Unique_Node_List wq;
 752         wq.push(n_loop->_head);
 753         assert(n_loop->_tail != NULL, "need a tail");
 754         for (uint next = 0; next < wq.size(); ++next) {
 755           Node *m = wq.at(next);
 756           if (m == n->in(0)) {
 757             ctrl_ok = true;
 758             continue;
 759           }
 760           assert(!has_ctrl(m), "should be CFG");
 761           if (!n_loop->is_member(get_loop(m)) || m == n_loop->_tail) {
 762             ctrl_ok = false;
 763             break;
 764           }
 765           enqueue_cfg_uses(m, wq);
 766         }
 767       }
 768       assert(ctrl_ok, "bad control");
 769 #endif
 770 
 771       // move the Store
 772       _igvn.replace_input_of(mem, LoopNode::LoopBackControl, mem);
 773       _igvn.replace_input_of(n, 0, n_loop->_head->in(LoopNode::EntryControl));
 774       _igvn.replace_input_of(n, MemNode::Memory, mem->in(LoopNode::EntryControl));
 775       // Disconnect the phi now. An empty phi can confuse other
 776       // optimizations in this pass of loop opts.
 777       _igvn.replace_node(mem, mem->in(LoopNode::EntryControl));
 778       n_loop->_body.yank(mem);
 779 
 780       IdealLoopTree* new_loop = get_loop(n->in(0));
 781       set_ctrl_and_loop(n, n->in(0));
 782 
 783       return n;
 784     }
 785   }
 786   return NULL;
 787 }
 788 
 789 // Try moving a store out of a loop, right after the loop
 790 void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
 791   if (n->is_Store() && n->in(0) != NULL) {
 792     Node *n_ctrl = get_ctrl(n);
 793     IdealLoopTree *n_loop = get_loop(n_ctrl);
 794     // Store must be in a loop
 795     if (n_loop != _ltree_root && !n_loop->_irreducible) {
 796       Node* address = n->in(MemNode::Address);
 797       Node* value = n->in(MemNode::ValueIn);
 798       IdealLoopTree* address_loop = get_loop(get_ctrl(address));
 799       // address must be loop invariant
 800       if (!n_loop->is_member(address_loop)) {
 801         // Store must be last on this memory slice in the loop and
 802         // nothing in the loop must observe it
 803         Node* phi = NULL;
 804         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 805           Node* u = n->fast_out(i);
 806           if (has_ctrl(u)) { // control use?
 807             IdealLoopTree *u_loop = get_loop(get_ctrl(u));
 808             if (!n_loop->is_member(u_loop)) {
 809               continue;
 810             }
 811             if (u->is_Phi() && u->in(0) == n_loop->_head) {
 812               assert(_igvn.type(u) == Type::MEMORY, "bad phi");
 813               assert(phi == NULL, "already found");
 814               phi = u;
 815               continue;
 816             }
 817           }
 818           phi = NULL;
 819           break;
 820         }
 821         if (phi != NULL) {
 822           // Nothing in the loop before the store (next iteration)
 823           // must observe the stored value
 824           bool mem_ok = true;
 825           {
 826             ResourceMark rm;
 827             Unique_Node_List wq;
 828             wq.push(phi);
 829             for (uint next = 0; next < wq.size() && mem_ok; ++next) {
 830               Node *m = wq.at(next);
 831               for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax && mem_ok; i++) {
 832                 Node* u = m->fast_out(i);
 833                 if (u->is_Store() || u->is_Phi()) {
 834                   if (u != n) {
 835                     wq.push(u);
 836                     mem_ok = (wq.size() <= 10);
 837                   }
 838                 } else {
 839                   mem_ok = false;
 840                   break;
 841                 }
 842               }
 843             }
 844           }
 845           if (mem_ok) {
 846             // Move the Store out of the loop creating clones along
 847             // all paths out of the loop that observe the stored value
 848             _igvn.rehash_node_delayed(phi);
 849             int count = phi->replace_edge(n, n->in(MemNode::Memory));
 850             assert(count > 0, "inconsistent phi");
 851             for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 852               Node* u = n->fast_out(i);
 853               Node* c = get_ctrl(u);
 854 
 855               if (u->is_Phi()) {
 856                 c = u->in(0)->in(u->find_edge(n));
 857               }
 858               IdealLoopTree *u_loop = get_loop(c);
 859               assert (!n_loop->is_member(u_loop), "only the phi should have been a use in the loop");
 860               while(true) {
 861                 Node* next_c = find_non_split_ctrl(idom(c));
 862                 if (n_loop->is_member(get_loop(next_c))) {
 863                   break;
 864                 }
 865                 c = next_c;
 866               }
 867 
 868               Node* st = n->clone();
 869               st->set_req(0, c);
 870               _igvn.register_new_node_with_optimizer(st);
 871 
 872               set_ctrl(st, c);
 873               IdealLoopTree* new_loop = get_loop(c);
 874               assert(new_loop != n_loop, "should be moved out of loop");
 875               if (new_loop->_child == NULL) new_loop->_body.push(st);
 876 
 877               _igvn.replace_input_of(u, u->find_edge(n), st);
 878               --imax;
 879               --i;
 880             }
 881 
 882 
 883             assert(n->outcnt() == 0, "all uses should be gone");
 884             _igvn.replace_input_of(n, MemNode::Memory, C->top());
 885             // Disconnect the phi now. An empty phi can confuse other
 886             // optimizations in this pass of loop opts..
 887             if (phi->in(LoopNode::LoopBackControl) == phi) {
 888               _igvn.replace_node(phi, phi->in(LoopNode::EntryControl));
 889               n_loop->_body.yank(phi);
 890             }
 891           }
 892         }
 893       }
 894     }
 895   }
 896 }
 897 
 898 //------------------------------split_if_with_blocks_pre-----------------------
 899 // Do the real work in a non-recursive function.  Data nodes want to be
 900 // cloned in the pre-order so they can feed each other nicely.
 901 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
 902   // Cloning these guys is unlikely to win
 903   int n_op = n->Opcode();
 904   if( n_op == Op_MergeMem ) return n;
 905   if( n->is_Proj() ) return n;
 906   // Do not clone-up CmpFXXX variations, as these are always
 907   // followed by a CmpI
 908   if( n->is_Cmp() ) return n;
 909   // Attempt to use a conditional move instead of a phi/branch
 910   if( ConditionalMoveLimit > 0 && n_op == Op_Region ) {
 911     Node *cmov = conditional_move( n );
 912     if( cmov ) return cmov;
 913   }
 914   if( n->is_CFG() || n->is_LoadStore() )
 915     return n;
 916   if( n_op == Op_Opaque1 ||     // Opaque nodes cannot be mod'd
 917       n_op == Op_Opaque2 ) {
 918     if( !C->major_progress() )   // If chance of no more loop opts...
 919       _igvn._worklist.push(n);  // maybe we'll remove them
 920     return n;
 921   }
 922 
 923   if( n->is_Con() ) return n;   // No cloning for Con nodes
 924 
 925   Node *n_ctrl = get_ctrl(n);
 926   if( !n_ctrl ) return n;       // Dead node
 927 
 928   Node* res = try_move_store_before_loop(n, n_ctrl);
 929   if (res != NULL) {
 930     return n;
 931   }
 932 
 933   // Attempt to remix address expressions for loop invariants
 934   Node *m = remix_address_expressions( n );
 935   if( m ) return m;
 936 
 937   // Determine if the Node has inputs from some local Phi.
 938   // Returns the block to clone thru.
 939   Node *n_blk = has_local_phi_input( n );
 940   if( !n_blk ) return n;
 941 
 942   // Do not clone the trip counter through on a CountedLoop
 943   // (messes up the canonical shape).
 944   if( n_blk->is_CountedLoop() && n->Opcode() == Op_AddI ) return n;
 945 
 946   // Check for having no control input; not pinned.  Allow
 947   // dominating control.
 948   if (n->in(0)) {
 949     Node *dom = idom(n_blk);
 950     if (dom_lca(n->in(0), dom) != n->in(0)) {
 951       return n;
 952     }
 953   }
 954   // Policy: when is it profitable.  You must get more wins than
 955   // policy before it is considered profitable.  Policy is usually 0,
 956   // so 1 win is considered profitable.  Big merges will require big
 957   // cloning, so get a larger policy.
 958   int policy = n_blk->req() >> 2;
 959 
 960   // If the loop is a candidate for range check elimination,
 961   // delay splitting through it's phi until a later loop optimization
 962   if (n_blk->is_CountedLoop()) {
 963     IdealLoopTree *lp = get_loop(n_blk);
 964     if (lp && lp->_rce_candidate) {
 965       return n;
 966     }
 967   }
 968 
 969   // Use same limit as split_if_with_blocks_post
 970   if( C->live_nodes() > 35000 ) return n; // Method too big
 971 
 972   // Split 'n' through the merge point if it is profitable
 973   Node *phi = split_thru_phi( n, n_blk, policy );
 974   if (!phi) return n;
 975 
 976   // Found a Phi to split thru!
 977   // Replace 'n' with the new phi
 978   split_mem_thru_phi(n, n_blk, phi);
 979   _igvn.replace_node( n, phi );
 980   // Moved a load around the loop, 'en-registering' something.
 981   if (n_blk->is_Loop() && n->is_Load() &&
 982       !phi->in(LoopNode::LoopBackControl)->is_Load())
 983     C->set_major_progress();
 984 
 985   // Moved a barrier around the loop, 'en-registering' something.
 986   if (n_blk->is_Loop() && n->is_ShenandoahBarrier() &&
 987       !phi->in(LoopNode::LoopBackControl)->is_ShenandoahBarrier())
 988     C->set_major_progress();
 989 
 990   return phi;
 991 }
 992 
 993 static bool merge_point_too_heavy(Compile* C, Node* region) {
 994   // Bail out if the region and its phis have too many users.
 995   int weight = 0;
 996   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 997     weight += region->fast_out(i)->outcnt();
 998   }
 999   int nodes_left = C->max_node_limit() - C->live_nodes();
1000   if (weight * 8 > nodes_left) {
1001 #ifndef PRODUCT
1002     if (PrintOpto)
1003       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
1004 #endif
1005     return true;
1006   } else {
1007     return false;
1008   }
1009 }
1010 
1011 static bool merge_point_safe(Node* region) {
1012   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
1013   // having a PhiNode input. This sidesteps the dangerous case where the split
1014   // ConvI2LNode may become TOP if the input Value() does not
1015   // overlap the ConvI2L range, leaving a node which may not dominate its
1016   // uses.
1017   // A better fix for this problem can be found in the BugTraq entry, but
1018   // expediency for Mantis demands this hack.
1019   // 6855164: If the merge point has a FastLockNode with a PhiNode input, we stop
1020   // split_if_with_blocks from splitting a block because we could not move around
1021   // the FastLockNode.
1022   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1023     Node* n = region->fast_out(i);
1024     if (n->is_Phi()) {
1025       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
1026         Node* m = n->fast_out(j);
1027         if (m->is_FastLock())
1028           return false;
1029 #ifdef _LP64
1030         if (m->Opcode() == Op_ConvI2L)
1031           return false;
1032 #endif
1033       }
1034     }
1035   }
1036   return true;
1037 }
1038 
1039 
1040 //------------------------------place_near_use---------------------------------
1041 // Place some computation next to use but not inside inner loops.
1042 // For inner loop uses move it to the preheader area.
1043 Node *PhaseIdealLoop::place_near_use( Node *useblock ) const {
1044   IdealLoopTree *u_loop = get_loop( useblock );
1045   return (u_loop->_irreducible || u_loop->_child)
1046     ? useblock
1047     : u_loop->_head->in(LoopNode::EntryControl);
1048 }
1049 
1050 
1051 //------------------------------split_if_with_blocks_post----------------------
1052 // Do the real work in a non-recursive function.  CFG hackery wants to be
1053 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
1054 // info.
1055 void PhaseIdealLoop::split_if_with_blocks_post( Node *n ) {
1056 
1057   // Cloning Cmp through Phi's involves the split-if transform.
1058   // FastLock is not used by an If
1059   if( n->is_Cmp() && !n->is_FastLock() ) {
1060     if( C->live_nodes() > 35000 ) return; // Method too big
1061 
1062     // Do not do 'split-if' if irreducible loops are present.
1063     if( _has_irreducible_loops )
1064       return;
1065 
1066     Node *n_ctrl = get_ctrl(n);
1067     // Determine if the Node has inputs from some local Phi.
1068     // Returns the block to clone thru.
1069     Node *n_blk = has_local_phi_input( n );
1070     if( n_blk != n_ctrl ) return;
1071 
1072     if( merge_point_too_heavy(C, n_ctrl) )
1073       return;
1074 
1075     if( n->outcnt() != 1 ) return; // Multiple bool's from 1 compare?
1076     Node *bol = n->unique_out();
1077     assert( bol->is_Bool(), "expect a bool here" );
1078     if( bol->outcnt() != 1 ) return;// Multiple branches from 1 compare?
1079     Node *iff = bol->unique_out();
1080 
1081     // Check some safety conditions
1082     if( iff->is_If() ) {        // Classic split-if?
1083       if( iff->in(0) != n_ctrl ) return; // Compare must be in same blk as if
1084     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
1085       // Can't split CMove with different control edge.
1086       if (iff->in(0) != NULL && iff->in(0) != n_ctrl ) return;
1087       if( get_ctrl(iff->in(2)) == n_ctrl ||
1088           get_ctrl(iff->in(3)) == n_ctrl )
1089         return;                 // Inputs not yet split-up
1090       if ( get_loop(n_ctrl) != get_loop(get_ctrl(iff)) ) {
1091         return;                 // Loop-invar test gates loop-varying CMOVE
1092       }
1093     } else {
1094       return;  // some other kind of node, such as an Allocate
1095     }
1096 
1097     // Do not do 'split-if' if some paths are dead.  First do dead code
1098     // elimination and then see if its still profitable.
1099     for( uint i = 1; i < n_ctrl->req(); i++ )
1100       if( n_ctrl->in(i) == C->top() )
1101         return;
1102 
1103     // When is split-if profitable?  Every 'win' on means some control flow
1104     // goes dead, so it's almost always a win.
1105     int policy = 0;
1106     // If trying to do a 'Split-If' at the loop head, it is only
1107     // profitable if the cmp folds up on BOTH paths.  Otherwise we
1108     // risk peeling a loop forever.
1109 
1110     // CNC - Disabled for now.  Requires careful handling of loop
1111     // body selection for the cloned code.  Also, make sure we check
1112     // for any input path not being in the same loop as n_ctrl.  For
1113     // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
1114     // because the alternative loop entry points won't be converted
1115     // into LoopNodes.
1116     IdealLoopTree *n_loop = get_loop(n_ctrl);
1117     for( uint j = 1; j < n_ctrl->req(); j++ )
1118       if( get_loop(n_ctrl->in(j)) != n_loop )
1119         return;
1120 
1121     // Check for safety of the merge point.
1122     if( !merge_point_safe(n_ctrl) ) {
1123       return;
1124     }
1125 
1126     // Split compare 'n' through the merge point if it is profitable
1127     Node *phi = split_thru_phi( n, n_ctrl, policy );
1128     if( !phi ) return;
1129 
1130     // Found a Phi to split thru!
1131     // Replace 'n' with the new phi
1132     assert(n->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers yet");
1133     _igvn.replace_node( n, phi );
1134 
1135     // Now split the bool up thru the phi
1136     assert(bol->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers yet");
1137     Node *bolphi = split_thru_phi( bol, n_ctrl, -1 );
1138     guarantee(bolphi != NULL, "null boolean phi node");
1139 
1140     _igvn.replace_node( bol, bolphi );
1141     assert( iff->in(1) == bolphi, "" );
1142 
1143     if( bolphi->Value(&_igvn)->singleton() )
1144       return;
1145 
1146     // Conditional-move?  Must split up now
1147     if( !iff->is_If() ) {
1148       assert(iff->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers yet");
1149       Node *cmovphi = split_thru_phi( iff, n_ctrl, -1 );
1150       _igvn.replace_node( iff, cmovphi );
1151       return;
1152     }
1153 
1154     // Now split the IF
1155     do_split_if( iff );
1156     return;
1157   }
1158 
1159   // Check for an IF ready to split; one that has its
1160   // condition codes input coming from a Phi at the block start.
1161   int n_op = n->Opcode();
1162 
1163   // Check for an IF being dominated by another IF same test
1164   if (n_op == Op_If) {
1165     Node *bol = n->in(1);
1166     uint max = bol->outcnt();
1167     // Check for same test used more than once?
1168     if (max > 1 && bol->is_Bool()) {
1169       // Search up IDOMs to see if this IF is dominated.
1170       Node *cutoff = get_ctrl(bol);
1171 
1172       // Now search up IDOMs till cutoff, looking for a dominating test
1173       Node *prevdom = n;
1174       Node *dom = idom(prevdom);
1175       while (dom != cutoff) {
1176         if (dom->req() > 1 && dom->in(1) == bol && prevdom->in(0) == dom) {
1177           // Replace the dominated test with an obvious true or false.
1178           // Place it on the IGVN worklist for later cleanup.
1179           C->set_major_progress();
1180           dominated_by(prevdom, n, false, true);
1181 #ifndef PRODUCT
1182           if( VerifyLoopOptimizations ) verify();
1183 #endif
1184           return;
1185         }
1186         prevdom = dom;
1187         dom = idom(prevdom);
1188       }
1189     }
1190   }
1191 
1192   // See if a shared loop-varying computation has no loop-varying uses.
1193   // Happens if something is only used for JVM state in uncommon trap exits,
1194   // like various versions of induction variable+offset.  Clone the
1195   // computation per usage to allow it to sink out of the loop.
1196   if (has_ctrl(n) && !n->in(0)) {// n not dead and has no control edge (can float about)
1197     Node *n_ctrl = get_ctrl(n);
1198     IdealLoopTree *n_loop = get_loop(n_ctrl);
1199     if( n_loop != _ltree_root ) {
1200       DUIterator_Fast imax, i = n->fast_outs(imax);
1201       for (; i < imax; i++) {
1202         Node* u = n->fast_out(i);
1203         if( !has_ctrl(u) )     break; // Found control user
1204         IdealLoopTree *u_loop = get_loop(get_ctrl(u));
1205         if( u_loop == n_loop ) break; // Found loop-varying use
1206         if( n_loop->is_member( u_loop ) ) break; // Found use in inner loop
1207         if( u->Opcode() == Op_Opaque1 ) break; // Found loop limit, bugfix for 4677003
1208       }
1209       bool did_break = (i < imax);  // Did we break out of the previous loop?
1210       if (!did_break && n->outcnt() > 1) { // All uses in outer loops!
1211         Node *late_load_ctrl = NULL;
1212         if (n->is_Load()) {
1213           // If n is a load, get and save the result from get_late_ctrl(),
1214           // to be later used in calculating the control for n's clones.
1215           clear_dom_lca_tags();
1216           late_load_ctrl = get_late_ctrl(n, n_ctrl);
1217         }
1218         // If n is a load, and the late control is the same as the current
1219         // control, then the cloning of n is a pointless exercise, because
1220         // GVN will ensure that we end up where we started.
1221         if (!n->is_Load() || late_load_ctrl != n_ctrl) {
1222           for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; ) {
1223             Node *u = n->last_out(j); // Clone private computation per use
1224             _igvn.rehash_node_delayed(u);
1225             Node *x = n->clone(); // Clone computation
1226             Node *x_ctrl = NULL;
1227             if( u->is_Phi() ) {
1228               // Replace all uses of normal nodes.  Replace Phi uses
1229               // individually, so the separate Nodes can sink down
1230               // different paths.
1231               uint k = 1;
1232               while( u->in(k) != n ) k++;
1233               u->set_req( k, x );
1234               // x goes next to Phi input path
1235               x_ctrl = u->in(0)->in(k);
1236               --j;
1237             } else {              // Normal use
1238               // Replace all uses
1239               for( uint k = 0; k < u->req(); k++ ) {
1240                 if( u->in(k) == n ) {
1241                   u->set_req( k, x );
1242                   --j;
1243                 }
1244               }
1245               x_ctrl = get_ctrl(u);
1246             }
1247 
1248             // Find control for 'x' next to use but not inside inner loops.
1249             // For inner loop uses get the preheader area.
1250             x_ctrl = place_near_use(x_ctrl);
1251 
1252             if (n->is_Load()) {
1253               // For loads, add a control edge to a CFG node outside of the loop
1254               // to force them to not combine and return back inside the loop
1255               // during GVN optimization (4641526).
1256               //
1257               // Because we are setting the actual control input, factor in
1258               // the result from get_late_ctrl() so we respect any
1259               // anti-dependences. (6233005).
1260               x_ctrl = dom_lca(late_load_ctrl, x_ctrl);
1261 
1262               // Don't allow the control input to be a CFG splitting node.
1263               // Such nodes should only have ProjNodes as outs, e.g. IfNode
1264               // should only have IfTrueNode and IfFalseNode (4985384).
1265               x_ctrl = find_non_split_ctrl(x_ctrl);
1266               assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
1267 
1268               x->set_req(0, x_ctrl);
1269             }
1270             register_new_node(x, x_ctrl);
1271 
1272             // Some institutional knowledge is needed here: 'x' is
1273             // yanked because if the optimizer runs GVN on it all the
1274             // cloned x's will common up and undo this optimization and
1275             // be forced back in the loop.  This is annoying because it
1276             // makes +VerifyOpto report false-positives on progress.  I
1277             // tried setting control edges on the x's to force them to
1278             // not combine, but the matching gets worried when it tries
1279             // to fold a StoreP and an AddP together (as part of an
1280             // address expression) and the AddP and StoreP have
1281             // different controls.
1282             if (!x->is_Load() && !x->is_DecodeNarrowPtr() && !x->is_ShenandoahBarrier()) _igvn._worklist.yank(x);
1283           }
1284           _igvn.remove_dead_node(n);
1285         }
1286       }
1287     }
1288   }
1289 
1290   try_move_store_after_loop(n);
1291 
1292   // Check for Opaque2's who's loop has disappeared - who's input is in the
1293   // same loop nest as their output.  Remove 'em, they are no longer useful.
1294   if( n_op == Op_Opaque2 &&
1295       n->in(1) != NULL &&
1296       get_loop(get_ctrl(n)) == get_loop(get_ctrl(n->in(1))) ) {
1297     _igvn.replace_node( n, n->in(1) );
1298   }
1299 }
1300 
1301 //------------------------------split_if_with_blocks---------------------------
1302 // Check for aggressive application of 'split-if' optimization,
1303 // using basic block level info.
1304 void PhaseIdealLoop::split_if_with_blocks( VectorSet &visited, Node_Stack &nstack ) {
1305   Node *n = C->root();
1306   visited.set(n->_idx); // first, mark node as visited
1307   // Do pre-visit work for root
1308   n = split_if_with_blocks_pre( n );
1309   uint cnt = n->outcnt();
1310   uint i   = 0;
1311   while (true) {
1312     // Visit all children
1313     if (i < cnt) {
1314       Node* use = n->raw_out(i);
1315       ++i;
1316       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
1317         // Now do pre-visit work for this use
1318         use = split_if_with_blocks_pre( use );
1319         nstack.push(n, i); // Save parent and next use's index.
1320         n   = use;         // Process all children of current use.
1321         cnt = use->outcnt();
1322         i   = 0;
1323       }
1324     }
1325     else {
1326       // All of n's children have been processed, complete post-processing.
1327       if (cnt != 0 && !n->is_Con()) {
1328         assert(has_node(n), "no dead nodes");
1329         split_if_with_blocks_post( n );
1330       }
1331       if (nstack.is_empty()) {
1332         // Finished all nodes on stack.
1333         break;
1334       }
1335       // Get saved parent node and next use's index. Visit the rest of uses.
1336       n   = nstack.node();
1337       cnt = n->outcnt();
1338       i   = nstack.index();
1339       nstack.pop();
1340     }
1341   }
1342 }
1343 
1344 
1345 //=============================================================================
1346 //
1347 //                   C L O N E   A   L O O P   B O D Y
1348 //
1349 
1350 //------------------------------clone_iff--------------------------------------
1351 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1352 // "Nearly" because all Nodes have been cloned from the original in the loop,
1353 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1354 // through the Phi recursively, and return a Bool.
1355 BoolNode *PhaseIdealLoop::clone_iff( PhiNode *phi, IdealLoopTree *loop ) {
1356 
1357   // Convert this Phi into a Phi merging Bools
1358   uint i;
1359   for( i = 1; i < phi->req(); i++ ) {
1360     Node *b = phi->in(i);
1361     if( b->is_Phi() ) {
1362       _igvn.replace_input_of(phi, i, clone_iff( b->as_Phi(), loop ));
1363     } else {
1364       assert( b->is_Bool(), "" );
1365     }
1366   }
1367 
1368   Node *sample_bool = phi->in(1);
1369   Node *sample_cmp  = sample_bool->in(1);
1370 
1371   // Make Phis to merge the Cmp's inputs.
1372   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
1373   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
1374   for( i = 1; i < phi->req(); i++ ) {
1375     Node *n1 = phi->in(i)->in(1)->in(1);
1376     Node *n2 = phi->in(i)->in(1)->in(2);
1377     phi1->set_req( i, n1 );
1378     phi2->set_req( i, n2 );
1379     phi1->set_type( phi1->type()->meet_speculative(n1->bottom_type()));
1380     phi2->set_type( phi2->type()->meet_speculative(n2->bottom_type()));
1381   }
1382   // See if these Phis have been made before.
1383   // Register with optimizer
1384   Node *hit1 = _igvn.hash_find_insert(phi1);
1385   if( hit1 ) {                  // Hit, toss just made Phi
1386     _igvn.remove_dead_node(phi1); // Remove new phi
1387     assert( hit1->is_Phi(), "" );
1388     phi1 = (PhiNode*)hit1;      // Use existing phi
1389   } else {                      // Miss
1390     _igvn.register_new_node_with_optimizer(phi1);
1391   }
1392   Node *hit2 = _igvn.hash_find_insert(phi2);
1393   if( hit2 ) {                  // Hit, toss just made Phi
1394     _igvn.remove_dead_node(phi2); // Remove new phi
1395     assert( hit2->is_Phi(), "" );
1396     phi2 = (PhiNode*)hit2;      // Use existing phi
1397   } else {                      // Miss
1398     _igvn.register_new_node_with_optimizer(phi2);
1399   }
1400   // Register Phis with loop/block info
1401   set_ctrl(phi1, phi->in(0));
1402   set_ctrl(phi2, phi->in(0));
1403   // Make a new Cmp
1404   Node *cmp = sample_cmp->clone();
1405   cmp->set_req( 1, phi1 );
1406   cmp->set_req( 2, phi2 );
1407   _igvn.register_new_node_with_optimizer(cmp);
1408   set_ctrl(cmp, phi->in(0));
1409 
1410   // Make a new Bool
1411   Node *b = sample_bool->clone();
1412   b->set_req(1,cmp);
1413   _igvn.register_new_node_with_optimizer(b);
1414   set_ctrl(b, phi->in(0));
1415 
1416   assert( b->is_Bool(), "" );
1417   return (BoolNode*)b;
1418 }
1419 
1420 //------------------------------clone_bool-------------------------------------
1421 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1422 // "Nearly" because all Nodes have been cloned from the original in the loop,
1423 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1424 // through the Phi recursively, and return a Bool.
1425 CmpNode *PhaseIdealLoop::clone_bool( PhiNode *phi, IdealLoopTree *loop ) {
1426   uint i;
1427   // Convert this Phi into a Phi merging Bools
1428   for( i = 1; i < phi->req(); i++ ) {
1429     Node *b = phi->in(i);
1430     if( b->is_Phi() ) {
1431       _igvn.replace_input_of(phi, i, clone_bool( b->as_Phi(), loop ));
1432     } else {
1433       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
1434     }
1435   }
1436 
1437   Node *sample_cmp = phi->in(1);
1438 
1439   // Make Phis to merge the Cmp's inputs.
1440   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
1441   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
1442   for( uint j = 1; j < phi->req(); j++ ) {
1443     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
1444     Node *n1, *n2;
1445     if( cmp_top->is_Cmp() ) {
1446       n1 = cmp_top->in(1);
1447       n2 = cmp_top->in(2);
1448     } else {
1449       n1 = n2 = cmp_top;
1450     }
1451     phi1->set_req( j, n1 );
1452     phi2->set_req( j, n2 );
1453     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
1454     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
1455   }
1456 
1457   // See if these Phis have been made before.
1458   // Register with optimizer
1459   Node *hit1 = _igvn.hash_find_insert(phi1);
1460   if( hit1 ) {                  // Hit, toss just made Phi
1461     _igvn.remove_dead_node(phi1); // Remove new phi
1462     assert( hit1->is_Phi(), "" );
1463     phi1 = (PhiNode*)hit1;      // Use existing phi
1464   } else {                      // Miss
1465     _igvn.register_new_node_with_optimizer(phi1);
1466   }
1467   Node *hit2 = _igvn.hash_find_insert(phi2);
1468   if( hit2 ) {                  // Hit, toss just made Phi
1469     _igvn.remove_dead_node(phi2); // Remove new phi
1470     assert( hit2->is_Phi(), "" );
1471     phi2 = (PhiNode*)hit2;      // Use existing phi
1472   } else {                      // Miss
1473     _igvn.register_new_node_with_optimizer(phi2);
1474   }
1475   // Register Phis with loop/block info
1476   set_ctrl(phi1, phi->in(0));
1477   set_ctrl(phi2, phi->in(0));
1478   // Make a new Cmp
1479   Node *cmp = sample_cmp->clone();
1480   cmp->set_req( 1, phi1 );
1481   cmp->set_req( 2, phi2 );
1482   _igvn.register_new_node_with_optimizer(cmp);
1483   set_ctrl(cmp, phi->in(0));
1484 
1485   assert( cmp->is_Cmp(), "" );
1486   return (CmpNode*)cmp;
1487 }
1488 
1489 //------------------------------sink_use---------------------------------------
1490 // If 'use' was in the loop-exit block, it now needs to be sunk
1491 // below the post-loop merge point.
1492 void PhaseIdealLoop::sink_use( Node *use, Node *post_loop ) {
1493   if (!use->is_CFG() && get_ctrl(use) == post_loop->in(2)) {
1494     set_ctrl(use, post_loop);
1495     for (DUIterator j = use->outs(); use->has_out(j); j++)
1496       sink_use(use->out(j), post_loop);
1497   }
1498 }
1499 
1500 //------------------------------clone_loop-------------------------------------
1501 //
1502 //                   C L O N E   A   L O O P   B O D Y
1503 //
1504 // This is the basic building block of the loop optimizations.  It clones an
1505 // entire loop body.  It makes an old_new loop body mapping; with this mapping
1506 // you can find the new-loop equivalent to an old-loop node.  All new-loop
1507 // nodes are exactly equal to their old-loop counterparts, all edges are the
1508 // same.  All exits from the old-loop now have a RegionNode that merges the
1509 // equivalent new-loop path.  This is true even for the normal "loop-exit"
1510 // condition.  All uses of loop-invariant old-loop values now come from (one
1511 // or more) Phis that merge their new-loop equivalents.
1512 //
1513 // This operation leaves the graph in an illegal state: there are two valid
1514 // control edges coming from the loop pre-header to both loop bodies.  I'll
1515 // definitely have to hack the graph after running this transform.
1516 //
1517 // From this building block I will further edit edges to perform loop peeling
1518 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
1519 //
1520 // Parameter side_by_size_idom:
1521 //   When side_by_size_idom is NULL, the dominator tree is constructed for
1522 //      the clone loop to dominate the original.  Used in construction of
1523 //      pre-main-post loop sequence.
1524 //   When nonnull, the clone and original are side-by-side, both are
1525 //      dominated by the side_by_side_idom node.  Used in construction of
1526 //      unswitched loops.
1527 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
1528                                  Node* side_by_side_idom) {
1529 
1530 #ifndef PRODUCT
1531   if (C->do_vector_loop() && PrintOpto) {
1532     const char* mname = C->method()->name()->as_quoted_ascii();
1533     if (mname != NULL) {
1534       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
1535     }
1536   }
1537 #endif
1538 
1539   CloneMap& cm = C->clone_map();
1540   Dict* dict = cm.dict();
1541   if (C->do_vector_loop()) {
1542     cm.set_clone_idx(cm.max_gen()+1);
1543 #ifndef PRODUCT
1544     if (PrintOpto) {
1545       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
1546       loop->dump_head();
1547     }
1548 #endif
1549   }
1550 
1551   // Step 1: Clone the loop body.  Make the old->new mapping.
1552   uint i;
1553   for( i = 0; i < loop->_body.size(); i++ ) {
1554     Node *old = loop->_body.at(i);
1555 #ifdef ASSERT
1556     if (old->Opcode() == Op_ShenandoahWriteBarrier) {
1557       Node* memproj = old->find_out_with(Op_ShenandoahWBMemProj);
1558       assert(memproj == NULL || (loop->is_member(get_loop(has_ctrl(memproj) ? get_ctrl(memproj) : memproj))), "WB's mem-proj must be in loop too");
1559     }
1560     if (old->Opcode() == Op_ShenandoahWBMemProj) {
1561       Node* wb = old->in(0);
1562       assert(loop->is_member(get_loop(has_ctrl(wb) ? get_ctrl(wb) : wb)), "WB must be in loop too");
1563     }
1564 #endif
1565     Node *nnn = old->clone();
1566     old_new.map( old->_idx, nnn );
1567     if (C->do_vector_loop()) {
1568       cm.verify_insert_and_clone(old, nnn, cm.clone_idx());
1569     }
1570     _igvn.register_new_node_with_optimizer(nnn);
1571   }
1572 
1573 
1574   // Step 2: Fix the edges in the new body.  If the old input is outside the
1575   // loop use it.  If the old input is INside the loop, use the corresponding
1576   // new node instead.
1577   for( i = 0; i < loop->_body.size(); i++ ) {
1578     Node *old = loop->_body.at(i);
1579     Node *nnn = old_new[old->_idx];
1580     // Fix CFG/Loop controlling the new node
1581     if (has_ctrl(old)) {
1582       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
1583     } else {
1584       set_loop(nnn, loop->_parent);
1585       if (old->outcnt() > 0) {
1586         set_idom( nnn, old_new[idom(old)->_idx], dd );
1587       }
1588     }
1589     // Correct edges to the new node
1590     for( uint j = 0; j < nnn->req(); j++ ) {
1591         Node *n = nnn->in(j);
1592         if( n ) {
1593           IdealLoopTree *old_in_loop = get_loop( has_ctrl(n) ? get_ctrl(n) : n );
1594           if( loop->is_member( old_in_loop ) )
1595             nnn->set_req(j, old_new[n->_idx]);
1596         }
1597     }
1598     _igvn.hash_find_insert(nnn);
1599   }
1600   Node *newhead = old_new[loop->_head->_idx];
1601   set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
1602 
1603 
1604   // Step 3: Now fix control uses.  Loop varying control uses have already
1605   // been fixed up (as part of all input edges in Step 2).  Loop invariant
1606   // control uses must be either an IfFalse or an IfTrue.  Make a merge
1607   // point to merge the old and new IfFalse/IfTrue nodes; make the use
1608   // refer to this.
1609   ResourceArea *area = Thread::current()->resource_area();
1610   Node_List worklist(area);
1611   uint new_counter = C->unique();
1612   for( i = 0; i < loop->_body.size(); i++ ) {
1613     Node* old = loop->_body.at(i);
1614     if( !old->is_CFG() ) continue;
1615     Node* nnn = old_new[old->_idx];
1616 
1617     // Copy uses to a worklist, so I can munge the def-use info
1618     // with impunity.
1619     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
1620       worklist.push(old->fast_out(j));
1621 
1622     while( worklist.size() ) {  // Visit all uses
1623       Node *use = worklist.pop();
1624       if (!has_node(use))  continue; // Ignore dead nodes
1625       IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
1626       if( !loop->is_member( use_loop ) && use->is_CFG() ) {
1627         // Both OLD and USE are CFG nodes here.
1628         assert( use->is_Proj(), "" );
1629 
1630         // Clone the loop exit control projection
1631         Node *newuse = use->clone();
1632         if (C->do_vector_loop()) {
1633           cm.verify_insert_and_clone(use, newuse, cm.clone_idx());
1634         }
1635         newuse->set_req(0,nnn);
1636         _igvn.register_new_node_with_optimizer(newuse);
1637         set_loop(newuse, use_loop);
1638         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
1639 
1640         // We need a Region to merge the exit from the peeled body and the
1641         // exit from the old loop body.
1642         RegionNode *r = new RegionNode(3);
1643         // Map the old use to the new merge point
1644         old_new.map( use->_idx, r );
1645         uint dd_r = MIN2(dom_depth(newuse),dom_depth(use));
1646         assert( dd_r >= dom_depth(dom_lca(newuse,use)), "" );
1647 
1648         // The original user of 'use' uses 'r' instead.
1649         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
1650           Node* useuse = use->last_out(l);
1651           _igvn.rehash_node_delayed(useuse);
1652           uint uses_found = 0;
1653           if( useuse->in(0) == use ) {
1654             useuse->set_req(0, r);
1655             uses_found++;
1656             if( useuse->is_CFG() ) {
1657               assert( dom_depth(useuse) > dd_r, "" );
1658               set_idom(useuse, r, dom_depth(useuse));
1659             }
1660           }
1661           for( uint k = 1; k < useuse->req(); k++ ) {
1662             if( useuse->in(k) == use ) {
1663               useuse->set_req(k, r);
1664               uses_found++;
1665             }
1666           }
1667           l -= uses_found;    // we deleted 1 or more copies of this edge
1668         }
1669 
1670         // Now finish up 'r'
1671         r->set_req( 1, newuse );
1672         r->set_req( 2,    use );
1673         _igvn.register_new_node_with_optimizer(r);
1674         set_loop(r, use_loop);
1675         set_idom(r, !side_by_side_idom ? newuse->in(0) : side_by_side_idom, dd_r);
1676       } // End of if a loop-exit test
1677     }
1678   }
1679 
1680   // Step 4: If loop-invariant use is not control, it must be dominated by a
1681   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
1682   // there if needed.  Make a Phi there merging old and new used values.
1683   Node_List *split_if_set = NULL;
1684   Node_List *split_bool_set = NULL;
1685   Node_List *split_cex_set = NULL;
1686   for( i = 0; i < loop->_body.size(); i++ ) {
1687     Node* old = loop->_body.at(i);
1688     Node* nnn = old_new[old->_idx];
1689     // Copy uses to a worklist, so I can munge the def-use info
1690     // with impunity.
1691     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
1692       worklist.push(old->fast_out(j));
1693 
1694     while( worklist.size() ) {
1695       Node *use = worklist.pop();
1696       if (!has_node(use))  continue; // Ignore dead nodes
1697       if (use->in(0) == C->top())  continue;
1698       IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
1699       // Check for data-use outside of loop - at least one of OLD or USE
1700       // must not be a CFG node.
1701       if( !loop->is_member( use_loop ) && (!old->is_CFG() || !use->is_CFG())) {
1702 
1703         // If the Data use is an IF, that means we have an IF outside of the
1704         // loop that is switching on a condition that is set inside of the
1705         // loop.  Happens if people set a loop-exit flag; then test the flag
1706         // in the loop to break the loop, then test is again outside of the
1707         // loop to determine which way the loop exited.
1708         // Loop predicate If node connects to Bool node through Opaque1 node.
1709         if (use->is_If() || use->is_CMove() || C->is_predicate_opaq(use)) {
1710           // Since this code is highly unlikely, we lazily build the worklist
1711           // of such Nodes to go split.
1712           if( !split_if_set )
1713             split_if_set = new Node_List(area);
1714           split_if_set->push(use);
1715         }
1716         if( use->is_Bool() ) {
1717           if( !split_bool_set )
1718             split_bool_set = new Node_List(area);
1719           split_bool_set->push(use);
1720         }
1721         if( use->Opcode() == Op_CreateEx ) {
1722           if( !split_cex_set )
1723             split_cex_set = new Node_List(area);
1724           split_cex_set->push(use);
1725         }
1726 
1727 
1728         // Get "block" use is in
1729         uint idx = 0;
1730         while( use->in(idx) != old ) idx++;
1731         Node *prev = use->is_CFG() ? use : get_ctrl(use);
1732         assert( !loop->is_member( get_loop( prev ) ), "" );
1733         Node *cfg = prev->_idx >= new_counter
1734           ? prev->in(2)
1735           : idom(prev);
1736         if( use->is_Phi() )     // Phi use is in prior block
1737           cfg = prev->in(idx);  // NOT in block of Phi itself
1738         if (cfg->is_top()) {    // Use is dead?
1739           _igvn.replace_input_of(use, idx, C->top());
1740           continue;
1741         }
1742 
1743         while( !loop->is_member( get_loop( cfg ) ) ) {
1744           prev = cfg;
1745           cfg = cfg->_idx >= new_counter ? cfg->in(2) : idom(cfg);
1746         }
1747         // If the use occurs after merging several exits from the loop, then
1748         // old value must have dominated all those exits.  Since the same old
1749         // value was used on all those exits we did not need a Phi at this
1750         // merge point.  NOW we do need a Phi here.  Each loop exit value
1751         // is now merged with the peeled body exit; each exit gets its own
1752         // private Phi and those Phis need to be merged here.
1753         Node *phi;
1754         if( prev->is_Region() ) {
1755           if( idx == 0  && use->Opcode() != Op_ShenandoahWBMemProj) {      // Updating control edge?
1756             phi = prev;         // Just use existing control
1757           } else {              // Else need a new Phi
1758             phi = PhiNode::make( prev, old );
1759             // Now recursively fix up the new uses of old!
1760             uint first = use->Opcode() != Op_ShenandoahWBMemProj ? 1 : 0;
1761             for( uint i = first; i < prev->req(); i++ ) {
1762               worklist.push(phi); // Onto worklist once for each 'old' input
1763             }
1764           }
1765         } else {
1766           // Get new RegionNode merging old and new loop exits
1767           prev = old_new[prev->_idx];
1768           assert( prev, "just made this in step 7" );
1769           if( idx == 0 && use->Opcode() != Op_ShenandoahWBMemProj) {      // Updating control edge?
1770             phi = prev;         // Just use existing control
1771           } else {              // Else need a new Phi
1772             // Make a new Phi merging data values properly
1773             phi = PhiNode::make( prev, old );
1774             phi->set_req( 1, nnn );
1775           }
1776         }
1777         // If inserting a new Phi, check for prior hits
1778         if( idx != 0 ) {
1779           Node *hit = _igvn.hash_find_insert(phi);
1780           if( hit == NULL ) {
1781            _igvn.register_new_node_with_optimizer(phi); // Register new phi
1782           } else {                                      // or
1783             // Remove the new phi from the graph and use the hit
1784             _igvn.remove_dead_node(phi);
1785             phi = hit;                                  // Use existing phi
1786           }
1787           set_ctrl(phi, prev);
1788         }
1789         // Make 'use' use the Phi instead of the old loop body exit value
1790         _igvn.replace_input_of(use, idx, phi);
1791         if( use->_idx >= new_counter ) { // If updating new phis
1792           // Not needed for correctness, but prevents a weak assert
1793           // in AddPNode from tripping (when we end up with different
1794           // base & derived Phis that will become the same after
1795           // IGVN does CSE).
1796           Node *hit = _igvn.hash_find_insert(use);
1797           if( hit )             // Go ahead and re-hash for hits.
1798             _igvn.replace_node( use, hit );
1799         }
1800 
1801         // If 'use' was in the loop-exit block, it now needs to be sunk
1802         // below the post-loop merge point.
1803         sink_use( use, prev );
1804       }
1805     }
1806   }
1807 
1808   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
1809   // the loop uses a condition set in the loop.  The original IF probably
1810   // takes control from one or more OLD Regions (which in turn get from NEW
1811   // Regions).  In any case, there will be a set of Phis for each merge point
1812   // from the IF up to where the original BOOL def exists the loop.
1813   if( split_if_set ) {
1814     while( split_if_set->size() ) {
1815       Node *iff = split_if_set->pop();
1816       if( iff->in(1)->is_Phi() ) {
1817         BoolNode *b = clone_iff( iff->in(1)->as_Phi(), loop );
1818         _igvn.replace_input_of(iff, 1, b);
1819       }
1820     }
1821   }
1822   if( split_bool_set ) {
1823     while( split_bool_set->size() ) {
1824       Node *b = split_bool_set->pop();
1825       Node *phi = b->in(1);
1826       assert( phi->is_Phi(), "" );
1827       CmpNode *cmp = clone_bool( (PhiNode*)phi, loop );
1828       _igvn.replace_input_of(b, 1, cmp);
1829     }
1830   }
1831   if( split_cex_set ) {
1832     while( split_cex_set->size() ) {
1833       Node *b = split_cex_set->pop();
1834       assert( b->in(0)->is_Region(), "" );
1835       assert( b->in(1)->is_Phi(), "" );
1836       assert( b->in(0)->in(0) == b->in(1)->in(0), "" );
1837       split_up( b, b->in(0), NULL );
1838     }
1839   }
1840 
1841 }
1842 
1843 
1844 //---------------------- stride_of_possible_iv -------------------------------------
1845 // Looks for an iff/bool/comp with one operand of the compare
1846 // being a cycle involving an add and a phi,
1847 // with an optional truncation (left-shift followed by a right-shift)
1848 // of the add. Returns zero if not an iv.
1849 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
1850   Node* trunc1 = NULL;
1851   Node* trunc2 = NULL;
1852   const TypeInt* ttype = NULL;
1853   if (!iff->is_If() || iff->in(1) == NULL || !iff->in(1)->is_Bool()) {
1854     return 0;
1855   }
1856   BoolNode* bl = iff->in(1)->as_Bool();
1857   Node* cmp = bl->in(1);
1858   if (!cmp || cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU) {
1859     return 0;
1860   }
1861   // Must have an invariant operand
1862   if (is_member(get_loop(iff), get_ctrl(cmp->in(2)))) {
1863     return 0;
1864   }
1865   Node* add2 = NULL;
1866   Node* cmp1 = cmp->in(1);
1867   if (cmp1->is_Phi()) {
1868     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
1869     Node* phi = cmp1;
1870     for (uint i = 1; i < phi->req(); i++) {
1871       Node* in = phi->in(i);
1872       Node* add = CountedLoopNode::match_incr_with_optional_truncation(in,
1873                                 &trunc1, &trunc2, &ttype);
1874       if (add && add->in(1) == phi) {
1875         add2 = add->in(2);
1876         break;
1877       }
1878     }
1879   } else {
1880     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
1881     Node* addtrunc = cmp1;
1882     Node* add = CountedLoopNode::match_incr_with_optional_truncation(addtrunc,
1883                                 &trunc1, &trunc2, &ttype);
1884     if (add && add->in(1)->is_Phi()) {
1885       Node* phi = add->in(1);
1886       for (uint i = 1; i < phi->req(); i++) {
1887         if (phi->in(i) == addtrunc) {
1888           add2 = add->in(2);
1889           break;
1890         }
1891       }
1892     }
1893   }
1894   if (add2 != NULL) {
1895     const TypeInt* add2t = _igvn.type(add2)->is_int();
1896     if (add2t->is_con()) {
1897       return add2t->get_con();
1898     }
1899   }
1900   return 0;
1901 }
1902 
1903 
1904 //---------------------- stay_in_loop -------------------------------------
1905 // Return the (unique) control output node that's in the loop (if it exists.)
1906 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
1907   Node* unique = NULL;
1908   if (!n) return NULL;
1909   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1910     Node* use = n->fast_out(i);
1911     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
1912       if (unique != NULL) {
1913         return NULL;
1914       }
1915       unique = use;
1916     }
1917   }
1918   return unique;
1919 }
1920 
1921 //------------------------------ register_node -------------------------------------
1922 // Utility to register node "n" with PhaseIdealLoop
1923 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth) {
1924   _igvn.register_new_node_with_optimizer(n);
1925   loop->_body.push(n);
1926   if (n->is_CFG()) {
1927     set_loop(n, loop);
1928     set_idom(n, pred, ddepth);
1929   } else {
1930     set_ctrl(n, pred);
1931   }
1932 }
1933 
1934 //------------------------------ proj_clone -------------------------------------
1935 // Utility to create an if-projection
1936 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
1937   ProjNode* c = p->clone()->as_Proj();
1938   c->set_req(0, iff);
1939   return c;
1940 }
1941 
1942 //------------------------------ short_circuit_if -------------------------------------
1943 // Force the iff control output to be the live_proj
1944 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
1945   guarantee(live_proj != NULL, "null projection");
1946   int proj_con = live_proj->_con;
1947   assert(proj_con == 0 || proj_con == 1, "false or true projection");
1948   Node *con = _igvn.intcon(proj_con);
1949   set_ctrl(con, C->root());
1950   if (iff) {
1951     iff->set_req(1, con);
1952   }
1953   return con;
1954 }
1955 
1956 //------------------------------ insert_if_before_proj -------------------------------------
1957 // Insert a new if before an if projection (* - new node)
1958 //
1959 // before
1960 //           if(test)
1961 //           /     \
1962 //          v       v
1963 //    other-proj   proj (arg)
1964 //
1965 // after
1966 //           if(test)
1967 //           /     \
1968 //          /       v
1969 //         |      * proj-clone
1970 //         v          |
1971 //    other-proj      v
1972 //                * new_if(relop(cmp[IU](left,right)))
1973 //                  /  \
1974 //                 v    v
1975 //         * new-proj  proj
1976 //         (returned)
1977 //
1978 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
1979   IfNode* iff = proj->in(0)->as_If();
1980   IdealLoopTree *loop = get_loop(proj);
1981   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
1982   int ddepth = dom_depth(proj);
1983 
1984   _igvn.rehash_node_delayed(iff);
1985   _igvn.rehash_node_delayed(proj);
1986 
1987   proj->set_req(0, NULL);  // temporary disconnect
1988   ProjNode* proj2 = proj_clone(proj, iff);
1989   register_node(proj2, loop, iff, ddepth);
1990 
1991   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
1992   register_node(cmp, loop, proj2, ddepth);
1993 
1994   BoolNode* bol = new BoolNode(cmp, relop);
1995   register_node(bol, loop, proj2, ddepth);
1996 
1997   IfNode* new_if = new IfNode(proj2, bol, iff->_prob, iff->_fcnt);
1998   register_node(new_if, loop, proj2, ddepth);
1999 
2000   proj->set_req(0, new_if); // reattach
2001   set_idom(proj, new_if, ddepth);
2002 
2003   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
2004   guarantee(new_exit != NULL, "null exit node");
2005   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
2006 
2007   return new_exit;
2008 }
2009 
2010 //------------------------------ insert_region_before_proj -------------------------------------
2011 // Insert a region before an if projection (* - new node)
2012 //
2013 // before
2014 //           if(test)
2015 //          /      |
2016 //         v       |
2017 //       proj      v
2018 //               other-proj
2019 //
2020 // after
2021 //           if(test)
2022 //          /      |
2023 //         v       |
2024 // * proj-clone    v
2025 //         |     other-proj
2026 //         v
2027 // * new-region
2028 //         |
2029 //         v
2030 // *      dum_if
2031 //       /     \
2032 //      v       \
2033 // * dum-proj    v
2034 //              proj
2035 //
2036 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
2037   IfNode* iff = proj->in(0)->as_If();
2038   IdealLoopTree *loop = get_loop(proj);
2039   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
2040   int ddepth = dom_depth(proj);
2041 
2042   _igvn.rehash_node_delayed(iff);
2043   _igvn.rehash_node_delayed(proj);
2044 
2045   proj->set_req(0, NULL);  // temporary disconnect
2046   ProjNode* proj2 = proj_clone(proj, iff);
2047   register_node(proj2, loop, iff, ddepth);
2048 
2049   RegionNode* reg = new RegionNode(2);
2050   reg->set_req(1, proj2);
2051   register_node(reg, loop, iff, ddepth);
2052 
2053   IfNode* dum_if = new IfNode(reg, short_circuit_if(NULL, proj), iff->_prob, iff->_fcnt);
2054   register_node(dum_if, loop, reg, ddepth);
2055 
2056   proj->set_req(0, dum_if); // reattach
2057   set_idom(proj, dum_if, ddepth);
2058 
2059   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
2060   register_node(dum_proj, loop, dum_if, ddepth);
2061 
2062   return reg;
2063 }
2064 
2065 //------------------------------ insert_cmpi_loop_exit -------------------------------------
2066 // Clone a signed compare loop exit from an unsigned compare and
2067 // insert it before the unsigned cmp on the stay-in-loop path.
2068 // All new nodes inserted in the dominator tree between the original
2069 // if and it's projections.  The original if test is replaced with
2070 // a constant to force the stay-in-loop path.
2071 //
2072 // This is done to make sure that the original if and it's projections
2073 // still dominate the same set of control nodes, that the ctrl() relation
2074 // from data nodes to them is preserved, and that their loop nesting is
2075 // preserved.
2076 //
2077 // before
2078 //          if(i <u limit)    unsigned compare loop exit
2079 //         /       |
2080 //        v        v
2081 //   exit-proj   stay-in-loop-proj
2082 //
2083 // after
2084 //          if(stay-in-loop-const)  original if
2085 //         /       |
2086 //        /        v
2087 //       /  if(i <  limit)    new signed test
2088 //      /  /       |
2089 //     /  /        v
2090 //    /  /  if(i <u limit)    new cloned unsigned test
2091 //   /  /   /      |
2092 //   v  v  v       |
2093 //    region       |
2094 //        |        |
2095 //      dum-if     |
2096 //     /  |        |
2097 // ether  |        |
2098 //        v        v
2099 //   exit-proj   stay-in-loop-proj
2100 //
2101 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop) {
2102   const bool Signed   = true;
2103   const bool Unsigned = false;
2104 
2105   BoolNode* bol = if_cmpu->in(1)->as_Bool();
2106   if (bol->_test._test != BoolTest::lt) return NULL;
2107   CmpNode* cmpu = bol->in(1)->as_Cmp();
2108   if (cmpu->Opcode() != Op_CmpU) return NULL;
2109   int stride = stride_of_possible_iv(if_cmpu);
2110   if (stride == 0) return NULL;
2111 
2112   Node* lp_proj = stay_in_loop(if_cmpu, loop);
2113   guarantee(lp_proj != NULL, "null loop node");
2114 
2115   ProjNode* lp_continue = lp_proj->as_Proj();
2116   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
2117 
2118   Node* limit = NULL;
2119   if (stride > 0) {
2120     limit = cmpu->in(2);
2121   } else {
2122     limit = _igvn.makecon(TypeInt::ZERO);
2123     set_ctrl(limit, C->root());
2124   }
2125   // Create a new region on the exit path
2126   RegionNode* reg = insert_region_before_proj(lp_exit);
2127   guarantee(reg != NULL, "null region node");
2128 
2129   // Clone the if-cmpu-true-false using a signed compare
2130   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
2131   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, limit, lp_continue);
2132   reg->add_req(cmpi_exit);
2133 
2134   // Clone the if-cmpu-true-false
2135   BoolTest::mask rel_u = bol->_test._test;
2136   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
2137   reg->add_req(cmpu_exit);
2138 
2139   // Force original if to stay in loop.
2140   short_circuit_if(if_cmpu, lp_continue);
2141 
2142   return cmpi_exit->in(0)->as_If();
2143 }
2144 
2145 //------------------------------ remove_cmpi_loop_exit -------------------------------------
2146 // Remove a previously inserted signed compare loop exit.
2147 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
2148   Node* lp_proj = stay_in_loop(if_cmp, loop);
2149   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
2150          stay_in_loop(lp_proj, loop)->is_If() &&
2151          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
2152   Node *con = _igvn.makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
2153   set_ctrl(con, C->root());
2154   if_cmp->set_req(1, con);
2155 }
2156 
2157 //------------------------------ scheduled_nodelist -------------------------------------
2158 // Create a post order schedule of nodes that are in the
2159 // "member" set.  The list is returned in "sched".
2160 // The first node in "sched" is the loop head, followed by
2161 // nodes which have no inputs in the "member" set, and then
2162 // followed by the nodes that have an immediate input dependence
2163 // on a node in "sched".
2164 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
2165 
2166   assert(member.test(loop->_head->_idx), "loop head must be in member set");
2167   Arena *a = Thread::current()->resource_area();
2168   VectorSet visited(a);
2169   Node_Stack nstack(a, loop->_body.size());
2170 
2171   Node* n  = loop->_head;  // top of stack is cached in "n"
2172   uint idx = 0;
2173   visited.set(n->_idx);
2174 
2175   // Initially push all with no inputs from within member set
2176   for(uint i = 0; i < loop->_body.size(); i++ ) {
2177     Node *elt = loop->_body.at(i);
2178     if (member.test(elt->_idx)) {
2179       bool found = false;
2180       for (uint j = 0; j < elt->req(); j++) {
2181         Node* def = elt->in(j);
2182         if (def && member.test(def->_idx) && def != elt) {
2183           found = true;
2184           break;
2185         }
2186       }
2187       if (!found && elt != loop->_head) {
2188         nstack.push(n, idx);
2189         n = elt;
2190         assert(!visited.test(n->_idx), "not seen yet");
2191         visited.set(n->_idx);
2192       }
2193     }
2194   }
2195 
2196   // traverse out's that are in the member set
2197   while (true) {
2198     if (idx < n->outcnt()) {
2199       Node* use = n->raw_out(idx);
2200       idx++;
2201       if (!visited.test_set(use->_idx)) {
2202         if (member.test(use->_idx)) {
2203           nstack.push(n, idx);
2204           n = use;
2205           idx = 0;
2206         }
2207       }
2208     } else {
2209       // All outputs processed
2210       sched.push(n);
2211       if (nstack.is_empty()) break;
2212       n   = nstack.node();
2213       idx = nstack.index();
2214       nstack.pop();
2215     }
2216   }
2217 }
2218 
2219 
2220 //------------------------------ has_use_in_set -------------------------------------
2221 // Has a use in the vector set
2222 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
2223   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2224     Node* use = n->fast_out(j);
2225     if (vset.test(use->_idx)) {
2226       return true;
2227     }
2228   }
2229   return false;
2230 }
2231 
2232 
2233 //------------------------------ has_use_internal_to_set -------------------------------------
2234 // Has use internal to the vector set (ie. not in a phi at the loop head)
2235 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
2236   Node* head  = loop->_head;
2237   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2238     Node* use = n->fast_out(j);
2239     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
2240       return true;
2241     }
2242   }
2243   return false;
2244 }
2245 
2246 
2247 //------------------------------ clone_for_use_outside_loop -------------------------------------
2248 // clone "n" for uses that are outside of loop
2249 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
2250   int cloned = 0;
2251   assert(worklist.size() == 0, "should be empty");
2252   assert(n->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers yet");
2253   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2254     Node* use = n->fast_out(j);
2255     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
2256       worklist.push(use);
2257     }
2258   }
2259   while( worklist.size() ) {
2260     Node *use = worklist.pop();
2261     if (!has_node(use) || use->in(0) == C->top()) continue;
2262     uint j;
2263     for (j = 0; j < use->req(); j++) {
2264       if (use->in(j) == n) break;
2265     }
2266     assert(j < use->req(), "must be there");
2267 
2268     // clone "n" and insert it between the inputs of "n" and the use outside the loop
2269     assert(n->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers");
2270     Node* n_clone = n->clone();
2271     _igvn.replace_input_of(use, j, n_clone);
2272     cloned++;
2273     Node* use_c;
2274     if (!use->is_Phi()) {
2275       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
2276     } else {
2277       // Use in a phi is considered a use in the associated predecessor block
2278       use_c = use->in(0)->in(j);
2279     }
2280     set_ctrl(n_clone, use_c);
2281     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
2282     get_loop(use_c)->_body.push(n_clone);
2283     _igvn.register_new_node_with_optimizer(n_clone);
2284 #if !defined(PRODUCT)
2285     if (TracePartialPeeling) {
2286       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
2287     }
2288 #endif
2289   }
2290   return cloned;
2291 }
2292 
2293 
2294 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
2295 // clone "n" for special uses that are in the not_peeled region.
2296 // If these def-uses occur in separate blocks, the code generator
2297 // marks the method as not compilable.  For example, if a "BoolNode"
2298 // is in a different basic block than the "IfNode" that uses it, then
2299 // the compilation is aborted in the code generator.
2300 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
2301                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
2302   if (n->is_Phi() || n->is_Load()) {
2303     return;
2304   }
2305   assert(worklist.size() == 0, "should be empty");
2306   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2307     Node* use = n->fast_out(j);
2308     if ( not_peel.test(use->_idx) &&
2309          (use->is_If() || use->is_CMove() || use->is_Bool()) &&
2310          use->in(1) == n)  {
2311       worklist.push(use);
2312     }
2313   }
2314   if (worklist.size() > 0) {
2315     // clone "n" and insert it between inputs of "n" and the use
2316     assert(n->Opcode() != Op_ShenandoahWriteBarrier, "not with write barriers");
2317     Node* n_clone = n->clone();
2318     loop->_body.push(n_clone);
2319     _igvn.register_new_node_with_optimizer(n_clone);
2320     set_ctrl(n_clone, get_ctrl(n));
2321     sink_list.push(n_clone);
2322     not_peel <<= n_clone->_idx;  // add n_clone to not_peel set.
2323 #if !defined(PRODUCT)
2324     if (TracePartialPeeling) {
2325       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
2326     }
2327 #endif
2328     while( worklist.size() ) {
2329       Node *use = worklist.pop();
2330       _igvn.rehash_node_delayed(use);
2331       for (uint j = 1; j < use->req(); j++) {
2332         if (use->in(j) == n) {
2333           use->set_req(j, n_clone);
2334         }
2335       }
2336     }
2337   }
2338 }
2339 
2340 
2341 //------------------------------ insert_phi_for_loop -------------------------------------
2342 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
2343 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
2344   Node *phi = PhiNode::make(lp, back_edge_val);
2345   phi->set_req(LoopNode::EntryControl, lp_entry_val);
2346   // Use existing phi if it already exists
2347   Node *hit = _igvn.hash_find_insert(phi);
2348   if( hit == NULL ) {
2349     _igvn.register_new_node_with_optimizer(phi);
2350     set_ctrl(phi, lp);
2351   } else {
2352     // Remove the new phi from the graph and use the hit
2353     _igvn.remove_dead_node(phi);
2354     phi = hit;
2355   }
2356   _igvn.replace_input_of(use, idx, phi);
2357 }
2358 
2359 #ifdef ASSERT
2360 //------------------------------ is_valid_loop_partition -------------------------------------
2361 // Validate the loop partition sets: peel and not_peel
2362 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
2363                                               VectorSet& not_peel ) {
2364   uint i;
2365   // Check that peel_list entries are in the peel set
2366   for (i = 0; i < peel_list.size(); i++) {
2367     if (!peel.test(peel_list.at(i)->_idx)) {
2368       return false;
2369     }
2370   }
2371   // Check at loop members are in one of peel set or not_peel set
2372   for (i = 0; i < loop->_body.size(); i++ ) {
2373     Node *def  = loop->_body.at(i);
2374     uint di = def->_idx;
2375     // Check that peel set elements are in peel_list
2376     if (peel.test(di)) {
2377       if (not_peel.test(di)) {
2378         return false;
2379       }
2380       // Must be in peel_list also
2381       bool found = false;
2382       for (uint j = 0; j < peel_list.size(); j++) {
2383         if (peel_list.at(j)->_idx == di) {
2384           found = true;
2385           break;
2386         }
2387       }
2388       if (!found) {
2389         return false;
2390       }
2391     } else if (not_peel.test(di)) {
2392       if (peel.test(di)) {
2393         return false;
2394       }
2395     } else {
2396       return false;
2397     }
2398   }
2399   return true;
2400 }
2401 
2402 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
2403 // Ensure a use outside of loop is of the right form
2404 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
2405   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
2406   return (use->is_Phi() &&
2407           use_c->is_Region() && use_c->req() == 3 &&
2408           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
2409            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
2410            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
2411           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
2412 }
2413 
2414 //------------------------------ is_valid_clone_loop_form -------------------------------------
2415 // Ensure that all uses outside of loop are of the right form
2416 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
2417                                                uint orig_exit_idx, uint clone_exit_idx) {
2418   uint len = peel_list.size();
2419   for (uint i = 0; i < len; i++) {
2420     Node *def = peel_list.at(i);
2421 
2422     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
2423       Node *use = def->fast_out(j);
2424       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
2425       if (!loop->is_member(get_loop(use_c))) {
2426         // use is not in the loop, check for correct structure
2427         if (use->in(0) == def) {
2428           // Okay
2429         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
2430           return false;
2431         }
2432       }
2433     }
2434   }
2435   return true;
2436 }
2437 #endif
2438 
2439 //------------------------------ partial_peel -------------------------------------
2440 // Partially peel (aka loop rotation) the top portion of a loop (called
2441 // the peel section below) by cloning it and placing one copy just before
2442 // the new loop head and the other copy at the bottom of the new loop.
2443 //
2444 //    before                       after                where it came from
2445 //
2446 //    stmt1                        stmt1
2447 //  loop:                          stmt2                     clone
2448 //    stmt2                        if condA goto exitA       clone
2449 //    if condA goto exitA        new_loop:                   new
2450 //    stmt3                        stmt3                     clone
2451 //    if !condB goto loop          if condB goto exitB       clone
2452 //  exitB:                         stmt2                     orig
2453 //    stmt4                        if !condA goto new_loop   orig
2454 //  exitA:                         goto exitA
2455 //                               exitB:
2456 //                                 stmt4
2457 //                               exitA:
2458 //
2459 // Step 1: find the cut point: an exit test on probable
2460 //         induction variable.
2461 // Step 2: schedule (with cloning) operations in the peel
2462 //         section that can be executed after the cut into
2463 //         the section that is not peeled.  This may need
2464 //         to clone operations into exit blocks.  For
2465 //         instance, a reference to A[i] in the not-peel
2466 //         section and a reference to B[i] in an exit block
2467 //         may cause a left-shift of i by 2 to be placed
2468 //         in the peel block.  This step will clone the left
2469 //         shift into the exit block and sink the left shift
2470 //         from the peel to the not-peel section.
2471 // Step 3: clone the loop, retarget the control, and insert
2472 //         phis for values that are live across the new loop
2473 //         head.  This is very dependent on the graph structure
2474 //         from clone_loop.  It creates region nodes for
2475 //         exit control and associated phi nodes for values
2476 //         flow out of the loop through that exit.  The region
2477 //         node is dominated by the clone's control projection.
2478 //         So the clone's peel section is placed before the
2479 //         new loop head, and the clone's not-peel section is
2480 //         forms the top part of the new loop.  The original
2481 //         peel section forms the tail of the new loop.
2482 // Step 4: update the dominator tree and recompute the
2483 //         dominator depth.
2484 //
2485 //                   orig
2486 //
2487 //                   stmt1
2488 //                     |
2489 //                     v
2490 //               loop predicate
2491 //                     |
2492 //                     v
2493 //                   loop<----+
2494 //                     |      |
2495 //                   stmt2    |
2496 //                     |      |
2497 //                     v      |
2498 //                    ifA     |
2499 //                   / |      |
2500 //                  v  v      |
2501 //               false true   ^  <-- last_peel
2502 //               /     |      |
2503 //              /   ===|==cut |
2504 //             /     stmt3    |  <-- first_not_peel
2505 //            /        |      |
2506 //            |        v      |
2507 //            v       ifB     |
2508 //          exitA:   / \      |
2509 //                  /   \     |
2510 //                 v     v    |
2511 //               false true   |
2512 //               /       \    |
2513 //              /         ----+
2514 //             |
2515 //             v
2516 //           exitB:
2517 //           stmt4
2518 //
2519 //
2520 //            after clone loop
2521 //
2522 //                   stmt1
2523 //                     |
2524 //                     v
2525 //               loop predicate
2526 //                 /       \
2527 //        clone   /         \   orig
2528 //               /           \
2529 //              /             \
2530 //             v               v
2531 //   +---->loop                loop<----+
2532 //   |      |                    |      |
2533 //   |    stmt2                stmt2    |
2534 //   |      |                    |      |
2535 //   |      v                    v      |
2536 //   |      ifA                 ifA     |
2537 //   |      | \                / |      |
2538 //   |      v  v              v  v      |
2539 //   ^    true  false      false true   ^  <-- last_peel
2540 //   |      |   ^   \       /    |      |
2541 //   | cut==|==  \   \     /  ===|==cut |
2542 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
2543 //   |      |    dom   | |       |      |
2544 //   |      v      \  1v v2      v      |
2545 //   |      ifB     regionA     ifB     |
2546 //   |      / \        |       / \      |
2547 //   |     /   \       v      /   \     |
2548 //   |    v     v    exitA:  v     v    |
2549 //   |    true  false      false true   |
2550 //   |    /     ^   \      /       \    |
2551 //   +----       \   \    /         ----+
2552 //               dom  \  /
2553 //                 \  1v v2
2554 //                  regionB
2555 //                     |
2556 //                     v
2557 //                   exitB:
2558 //                   stmt4
2559 //
2560 //
2561 //           after partial peel
2562 //
2563 //                  stmt1
2564 //                     |
2565 //                     v
2566 //               loop predicate
2567 //                 /
2568 //        clone   /             orig
2569 //               /          TOP
2570 //              /             \
2571 //             v               v
2572 //    TOP->loop                loop----+
2573 //          |                    |      |
2574 //        stmt2                stmt2    |
2575 //          |                    |      |
2576 //          v                    v      |
2577 //          ifA                 ifA     |
2578 //          | \                / |      |
2579 //          v  v              v  v      |
2580 //        true  false      false true   |     <-- last_peel
2581 //          |   ^   \       /    +------|---+
2582 //  +->newloop   \   \     /  === ==cut |   |
2583 //  |     stmt3   \   \   /     TOP     |   |
2584 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
2585 //  |       v      \  1v v2      v      |   |
2586 //  |       ifB     regionA     ifB     ^   v
2587 //  |       / \        |       / \      |   |
2588 //  |      /   \       v      /   \     |   |
2589 //  |     v     v    exitA:  v     v    |   |
2590 //  |     true  false      false true   |   |
2591 //  |     /     ^   \      /       \    |   |
2592 //  |    |       \   \    /         v   |   |
2593 //  |    |       dom  \  /         TOP  |   |
2594 //  |    |         \  1v v2             |   |
2595 //  ^    v          regionB             |   |
2596 //  |    |             |                |   |
2597 //  |    |             v                ^   v
2598 //  |    |           exitB:             |   |
2599 //  |    |           stmt4              |   |
2600 //  |    +------------>-----------------+   |
2601 //  |                                       |
2602 //  +-----------------<---------------------+
2603 //
2604 //
2605 //              final graph
2606 //
2607 //                  stmt1
2608 //                    |
2609 //                    v
2610 //               loop predicate
2611 //                    |
2612 //                    v
2613 //                  stmt2 clone
2614 //                    |
2615 //                    v
2616 //         ........> ifA clone
2617 //         :        / |
2618 //        dom      /  |
2619 //         :      v   v
2620 //         :  false   true
2621 //         :  |       |
2622 //         :  |       v
2623 //         :  |    newloop<-----+
2624 //         :  |        |        |
2625 //         :  |     stmt3 clone |
2626 //         :  |        |        |
2627 //         :  |        v        |
2628 //         :  |       ifB       |
2629 //         :  |      / \        |
2630 //         :  |     v   v       |
2631 //         :  |  false true     |
2632 //         :  |   |     |       |
2633 //         :  |   v    stmt2    |
2634 //         :  | exitB:  |       |
2635 //         :  | stmt4   v       |
2636 //         :  |       ifA orig  |
2637 //         :  |      /  \       |
2638 //         :  |     /    \      |
2639 //         :  |    v     v      |
2640 //         :  |  false  true    |
2641 //         :  |  /        \     |
2642 //         :  v  v         -----+
2643 //          RegionA
2644 //             |
2645 //             v
2646 //           exitA
2647 //
2648 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
2649 
2650   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
2651   if (!loop->_head->is_Loop()) {
2652     return false;  }
2653 
2654   LoopNode *head  = loop->_head->as_Loop();
2655 
2656   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
2657     return false;
2658   }
2659 
2660   // Check for complex exit control
2661   for(uint ii = 0; ii < loop->_body.size(); ii++ ) {
2662     Node *n = loop->_body.at(ii);
2663     int opc = n->Opcode();
2664     if (n->is_Call()        ||
2665         opc == Op_Catch     ||
2666         opc == Op_CatchProj ||
2667         opc == Op_Jump      ||
2668         opc == Op_JumpProj) {
2669 #if !defined(PRODUCT)
2670       if (TracePartialPeeling) {
2671         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
2672       }
2673 #endif
2674       return false;
2675     }
2676   }
2677 
2678   int dd = dom_depth(head);
2679 
2680   // Step 1: find cut point
2681 
2682   // Walk up dominators to loop head looking for first loop exit
2683   // which is executed on every path thru loop.
2684   IfNode *peel_if = NULL;
2685   IfNode *peel_if_cmpu = NULL;
2686 
2687   Node *iff = loop->tail();
2688   while( iff != head ) {
2689     if( iff->is_If() ) {
2690       Node *ctrl = get_ctrl(iff->in(1));
2691       if (ctrl->is_top()) return false; // Dead test on live IF.
2692       // If loop-varying exit-test, check for induction variable
2693       if( loop->is_member(get_loop(ctrl)) &&
2694           loop->is_loop_exit(iff) &&
2695           is_possible_iv_test(iff)) {
2696         Node* cmp = iff->in(1)->in(1);
2697         if (cmp->Opcode() == Op_CmpI) {
2698           peel_if = iff->as_If();
2699         } else {
2700           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
2701           peel_if_cmpu = iff->as_If();
2702         }
2703       }
2704     }
2705     iff = idom(iff);
2706   }
2707   // Prefer signed compare over unsigned compare.
2708   IfNode* new_peel_if = NULL;
2709   if (peel_if == NULL) {
2710     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == NULL) {
2711       return false;   // No peel point found
2712     }
2713     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
2714     if (new_peel_if == NULL) {
2715       return false;   // No peel point found
2716     }
2717     peel_if = new_peel_if;
2718   }
2719   Node* last_peel        = stay_in_loop(peel_if, loop);
2720   Node* first_not_peeled = stay_in_loop(last_peel, loop);
2721   if (first_not_peeled == NULL || first_not_peeled == head) {
2722     return false;
2723   }
2724 
2725 #if !defined(PRODUCT)
2726   if (TraceLoopOpts) {
2727     tty->print("PartialPeel  ");
2728     loop->dump_head();
2729   }
2730 
2731   if (TracePartialPeeling) {
2732     tty->print_cr("before partial peel one iteration");
2733     Node_List wl;
2734     Node* t = head->in(2);
2735     while (true) {
2736       wl.push(t);
2737       if (t == head) break;
2738       t = idom(t);
2739     }
2740     while (wl.size() > 0) {
2741       Node* tt = wl.pop();
2742       tt->dump();
2743       if (tt == last_peel) tty->print_cr("-- cut --");
2744     }
2745   }
2746 #endif
2747   ResourceArea *area = Thread::current()->resource_area();
2748   VectorSet peel(area);
2749   VectorSet not_peel(area);
2750   Node_List peel_list(area);
2751   Node_List worklist(area);
2752   Node_List sink_list(area);
2753 
2754   // Set of cfg nodes to peel are those that are executable from
2755   // the head through last_peel.
2756   assert(worklist.size() == 0, "should be empty");
2757   worklist.push(head);
2758   peel.set(head->_idx);
2759   while (worklist.size() > 0) {
2760     Node *n = worklist.pop();
2761     if (n != last_peel) {
2762       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2763         Node* use = n->fast_out(j);
2764         if (use->is_CFG() &&
2765             loop->is_member(get_loop(use)) &&
2766             !peel.test_set(use->_idx)) {
2767           worklist.push(use);
2768         }
2769       }
2770     }
2771   }
2772 
2773   // Set of non-cfg nodes to peel are those that are control
2774   // dependent on the cfg nodes.
2775   uint i;
2776   for(i = 0; i < loop->_body.size(); i++ ) {
2777     Node *n = loop->_body.at(i);
2778     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
2779     if (peel.test(n_c->_idx)) {
2780       peel.set(n->_idx);
2781     } else {
2782       not_peel.set(n->_idx);
2783     }
2784   }
2785 
2786   // Step 2: move operations from the peeled section down into the
2787   //         not-peeled section
2788 
2789   // Get a post order schedule of nodes in the peel region
2790   // Result in right-most operand.
2791   scheduled_nodelist(loop, peel, peel_list );
2792 
2793   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
2794 
2795   // For future check for too many new phis
2796   uint old_phi_cnt = 0;
2797   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
2798     Node* use = head->fast_out(j);
2799     if (use->is_Phi()) old_phi_cnt++;
2800   }
2801 
2802 #if !defined(PRODUCT)
2803   if (TracePartialPeeling) {
2804     tty->print_cr("\npeeled list");
2805   }
2806 #endif
2807 
2808   // Evacuate nodes in peel region into the not_peeled region if possible
2809   uint new_phi_cnt = 0;
2810   uint cloned_for_outside_use = 0;
2811   for (i = 0; i < peel_list.size();) {
2812     Node* n = peel_list.at(i);
2813 #if !defined(PRODUCT)
2814   if (TracePartialPeeling) n->dump();
2815 #endif
2816     bool incr = true;
2817     if ( !n->is_CFG() ) {
2818 
2819       if ( has_use_in_set(n, not_peel) ) {
2820 
2821         // If not used internal to the peeled region,
2822         // move "n" from peeled to not_peeled region.
2823 
2824         if ( !has_use_internal_to_set(n, peel, loop) ) {
2825 
2826           // if not pinned and not a load (which maybe anti-dependent on a store)
2827           // and not a CMove (Matcher expects only bool->cmove).
2828           if ( n->in(0) == NULL && !n->is_Load() && !n->is_CMove() ) {
2829             cloned_for_outside_use += clone_for_use_outside_loop( loop, n, worklist );
2830             sink_list.push(n);
2831             peel     >>= n->_idx; // delete n from peel set.
2832             not_peel <<= n->_idx; // add n to not_peel set.
2833             peel_list.remove(i);
2834             incr = false;
2835 #if !defined(PRODUCT)
2836             if (TracePartialPeeling) {
2837               tty->print_cr("sink to not_peeled region: %d newbb: %d",
2838                             n->_idx, get_ctrl(n)->_idx);
2839             }
2840 #endif
2841           }
2842         } else {
2843           // Otherwise check for special def-use cases that span
2844           // the peel/not_peel boundary such as bool->if
2845           clone_for_special_use_inside_loop( loop, n, not_peel, sink_list, worklist );
2846           new_phi_cnt++;
2847         }
2848       }
2849     }
2850     if (incr) i++;
2851   }
2852 
2853   if (new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta) {
2854 #if !defined(PRODUCT)
2855     if (TracePartialPeeling) {
2856       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
2857                     new_phi_cnt, old_phi_cnt, new_peel_if != NULL?'T':'F');
2858     }
2859 #endif
2860     if (new_peel_if != NULL) {
2861       remove_cmpi_loop_exit(new_peel_if, loop);
2862     }
2863     // Inhibit more partial peeling on this loop
2864     assert(!head->is_partial_peel_loop(), "not partial peeled");
2865     head->mark_partial_peel_failed();
2866     if (cloned_for_outside_use > 0) {
2867       // Terminate this round of loop opts because
2868       // the graph outside this loop was changed.
2869       C->set_major_progress();
2870       return true;
2871     }
2872     return false;
2873   }
2874 
2875   // Step 3: clone loop, retarget control, and insert new phis
2876 
2877   // Create new loop head for new phis and to hang
2878   // the nodes being moved (sinked) from the peel region.
2879   LoopNode* new_head = new LoopNode(last_peel, last_peel);
2880   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
2881   _igvn.register_new_node_with_optimizer(new_head);
2882   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
2883   _igvn.replace_input_of(first_not_peeled, 0, new_head);
2884   set_loop(new_head, loop);
2885   loop->_body.push(new_head);
2886   not_peel.set(new_head->_idx);
2887   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
2888   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
2889 
2890   while (sink_list.size() > 0) {
2891     Node* n = sink_list.pop();
2892     set_ctrl(n, new_head);
2893   }
2894 
2895   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
2896 
2897   clone_loop( loop, old_new, dd );
2898 
2899   const uint clone_exit_idx = 1;
2900   const uint orig_exit_idx  = 2;
2901   assert(is_valid_clone_loop_form( loop, peel_list, orig_exit_idx, clone_exit_idx ), "bad clone loop");
2902 
2903   Node* head_clone             = old_new[head->_idx];
2904   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
2905   Node* orig_tail_clone        = head_clone->in(2);
2906 
2907   // Add phi if "def" node is in peel set and "use" is not
2908 
2909   for(i = 0; i < peel_list.size(); i++ ) {
2910     Node *def  = peel_list.at(i);
2911     if (!def->is_CFG()) {
2912       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
2913         Node *use = def->fast_out(j);
2914         if (has_node(use) && use->in(0) != C->top() &&
2915             (!peel.test(use->_idx) ||
2916              (use->is_Phi() && use->in(0) == head)) ) {
2917           worklist.push(use);
2918         }
2919       }
2920       while( worklist.size() ) {
2921         Node *use = worklist.pop();
2922         for (uint j = 1; j < use->req(); j++) {
2923           Node* n = use->in(j);
2924           if (n == def) {
2925 
2926             // "def" is in peel set, "use" is not in peel set
2927             // or "use" is in the entry boundary (a phi) of the peel set
2928 
2929             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
2930 
2931             if ( loop->is_member(get_loop( use_c )) ) {
2932               // use is in loop
2933               if (old_new[use->_idx] != NULL) { // null for dead code
2934                 Node* use_clone = old_new[use->_idx];
2935                 _igvn.replace_input_of(use, j, C->top());
2936                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
2937               }
2938             } else {
2939               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
2940               // use is not in the loop, check if the live range includes the cut
2941               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
2942               if (not_peel.test(lp_if->_idx)) {
2943                 assert(j == orig_exit_idx, "use from original loop");
2944                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
2945               }
2946             }
2947           }
2948         }
2949       }
2950     }
2951   }
2952 
2953   // Step 3b: retarget control
2954 
2955   // Redirect control to the new loop head if a cloned node in
2956   // the not_peeled region has control that points into the peeled region.
2957   // This necessary because the cloned peeled region will be outside
2958   // the loop.
2959   //                            from    to
2960   //          cloned-peeled    <---+
2961   //    new_head_clone:            |    <--+
2962   //          cloned-not_peeled  in(0)    in(0)
2963   //          orig-peeled
2964 
2965   for(i = 0; i < loop->_body.size(); i++ ) {
2966     Node *n = loop->_body.at(i);
2967     if (!n->is_CFG()           && n->in(0) != NULL        &&
2968         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
2969       Node* n_clone = old_new[n->_idx];
2970       _igvn.replace_input_of(n_clone, 0, new_head_clone);
2971     }
2972   }
2973 
2974   // Backedge of the surviving new_head (the clone) is original last_peel
2975   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
2976 
2977   // Cut first node in original not_peel set
2978   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
2979   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
2980   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
2981 
2982   // Copy head_clone back-branch info to original head
2983   // and remove original head's loop entry and
2984   // clone head's back-branch
2985   _igvn.rehash_node_delayed(head); // Multiple edge updates
2986   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
2987   head->set_req(LoopNode::LoopBackControl, C->top());
2988   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
2989 
2990   // Similarly modify the phis
2991   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
2992     Node* use = head->fast_out(k);
2993     if (use->is_Phi() && use->outcnt() > 0) {
2994       Node* use_clone = old_new[use->_idx];
2995       _igvn.rehash_node_delayed(use); // Multiple edge updates
2996       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
2997       use->set_req(LoopNode::LoopBackControl, C->top());
2998       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
2999     }
3000   }
3001 
3002   // Step 4: update dominator tree and dominator depth
3003 
3004   set_idom(head, orig_tail_clone, dd);
3005   recompute_dom_depth();
3006 
3007   // Inhibit more partial peeling on this loop
3008   new_head_clone->set_partial_peel_loop();
3009   C->set_major_progress();
3010   loop->record_for_igvn();
3011 
3012 #if !defined(PRODUCT)
3013   if (TracePartialPeeling) {
3014     tty->print_cr("\nafter partial peel one iteration");
3015     Node_List wl(area);
3016     Node* t = last_peel;
3017     while (true) {
3018       wl.push(t);
3019       if (t == head_clone) break;
3020       t = idom(t);
3021     }
3022     while (wl.size() > 0) {
3023       Node* tt = wl.pop();
3024       if (tt == head) tty->print_cr("orig head");
3025       else if (tt == new_head_clone) tty->print_cr("new head");
3026       else if (tt == head_clone) tty->print_cr("clone head");
3027       tt->dump();
3028     }
3029   }
3030 #endif
3031   return true;
3032 }
3033 
3034 //------------------------------reorg_offsets----------------------------------
3035 // Reorganize offset computations to lower register pressure.  Mostly
3036 // prevent loop-fallout uses of the pre-incremented trip counter (which are
3037 // then alive with the post-incremented trip counter forcing an extra
3038 // register move)
3039 void PhaseIdealLoop::reorg_offsets(IdealLoopTree *loop) {
3040   // Perform it only for canonical counted loops.
3041   // Loop's shape could be messed up by iteration_split_impl.
3042   if (!loop->_head->is_CountedLoop())
3043     return;
3044   if (!loop->_head->as_Loop()->is_valid_counted_loop())
3045     return;
3046 
3047   CountedLoopNode *cl = loop->_head->as_CountedLoop();
3048   CountedLoopEndNode *cle = cl->loopexit();
3049   Node *exit = cle->proj_out(false);
3050   Node *phi = cl->phi();
3051 
3052   // Check for the special case of folks using the pre-incremented
3053   // trip-counter on the fall-out path (forces the pre-incremented
3054   // and post-incremented trip counter to be live at the same time).
3055   // Fix this by adjusting to use the post-increment trip counter.
3056 
3057   bool progress = true;
3058   while (progress) {
3059     progress = false;
3060     for (DUIterator_Fast imax, i = phi->fast_outs(imax); i < imax; i++) {
3061       Node* use = phi->fast_out(i);   // User of trip-counter
3062       if (!has_ctrl(use))  continue;
3063       Node *u_ctrl = get_ctrl(use);
3064       if (use->is_Phi()) {
3065         u_ctrl = NULL;
3066         for (uint j = 1; j < use->req(); j++)
3067           if (use->in(j) == phi)
3068             u_ctrl = dom_lca(u_ctrl, use->in(0)->in(j));
3069       }
3070       IdealLoopTree *u_loop = get_loop(u_ctrl);
3071       // Look for loop-invariant use
3072       if (u_loop == loop) continue;
3073       if (loop->is_member(u_loop)) continue;
3074       // Check that use is live out the bottom.  Assuming the trip-counter
3075       // update is right at the bottom, uses of of the loop middle are ok.
3076       if (dom_lca(exit, u_ctrl) != exit) continue;
3077       // Hit!  Refactor use to use the post-incremented tripcounter.
3078       // Compute a post-increment tripcounter.
3079       Node *opaq = new Opaque2Node( C, cle->incr() );
3080       register_new_node(opaq, exit);
3081       Node *neg_stride = _igvn.intcon(-cle->stride_con());
3082       set_ctrl(neg_stride, C->root());
3083       Node *post = new AddINode( opaq, neg_stride);
3084       register_new_node(post, exit);
3085       _igvn.rehash_node_delayed(use);
3086       for (uint j = 1; j < use->req(); j++) {
3087         if (use->in(j) == phi)
3088           use->set_req(j, post);
3089       }
3090       // Since DU info changed, rerun loop
3091       progress = true;
3092       break;
3093     }
3094   }
3095 
3096 }