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