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