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