jdk8-mips64-public/hotspot: src/share/vm/opto/loopopts.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/loopopts.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/loopopts.cpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 6876: 710a3c8b516e
permissions: -rw-r--r--

Initial load
http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "memory/allocation.inline.hpp"
 #include "opto/addnode.hpp"
 #include "opto/connode.hpp"
 #include "opto/divnode.hpp"
 #include "opto/loopnode.hpp"
 #include "opto/matcher.hpp"
 #include "opto/mulnode.hpp"
 #include "opto/rootnode.hpp"
 #include "opto/subnode.hpp"
 //=============================================================================
 //------------------------------split_thru_phi---------------------------------
 // Split Node 'n' through merge point if there is enough win.
 Node *PhaseIdealLoop::split_thru_phi( Node *n, Node *region, int policy ) {
   if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::LONG) {
     // ConvI2L may have type information on it which is unsafe to push up
     // so disable this for now
     return NULL;
   }
   int wins = 0;
   assert(!n->is_CFG(), "");
   assert(region->is_Region(), "");
   const Type* type = n->bottom_type();
   const TypeOopPtr *t_oop = _igvn.type(n)->isa_oopptr();
   Node *phi;
   if (t_oop != NULL && t_oop->is_known_instance_field()) {
     int iid    = t_oop->instance_id();
     int index  = C->get_alias_index(t_oop);
     int offset = t_oop->offset();
     phi = new (C) PhiNode(region, type, NULL, iid, index, offset);
   } else {
     phi = PhiNode::make_blank(region, n);
   }
   uint old_unique = C->unique();
   for (uint i = 1; i < region->req(); i++) {
     Node *x;
     Node* the_clone = NULL;
     if (region->in(i) == C->top()) {
       x = C->top();             // Dead path?  Use a dead data op
     } else {
       x = n->clone();           // Else clone up the data op
       the_clone = x;            // Remember for possible deletion.
       // Alter data node to use pre-phi inputs
       if (n->in(0) == region)
         x->set_req( 0, region->in(i) );
       for (uint j = 1; j < n->req(); j++) {
         Node *in = n->in(j);
         if (in->is_Phi() && in->in(0) == region)
           x->set_req( j, in->in(i) ); // Use pre-Phi input for the clone
       }
     }
     // Check for a 'win' on some paths
     const Type *t = x->Value(&_igvn);
     bool singleton = t->singleton();
     // A TOP singleton indicates that there are no possible values incoming
     // along a particular edge. In most cases, this is OK, and the Phi will
     // be eliminated later in an Ideal call. However, we can't allow this to
     // happen if the singleton occurs on loop entry, as the elimination of
     // the PhiNode may cause the resulting node to migrate back to a previous
     // loop iteration.
     if (singleton && t == Type::TOP) {
       // Is_Loop() == false does not confirm the absence of a loop (e.g., an
       // irreducible loop may not be indicated by an affirmative is_Loop());
       // therefore, the only top we can split thru a phi is on a backedge of
       // a loop.
       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
     }
     if (singleton) {
       wins++;
       x = ((PhaseGVN&)_igvn).makecon(t);
     } else {
       // We now call Identity to try to simplify the cloned node.
       // Note that some Identity methods call phase->type(this).
       // Make sure that the type array is big enough for
       // our new node, even though we may throw the node away.
       // (Note: This tweaking with igvn only works because x is a new node.)
       _igvn.set_type(x, t);
       // If x is a TypeNode, capture any more-precise type permanently into Node
       // otherwise it will be not updated during igvn->transform since
       // igvn->type(x) is set to x->Value() already.
       x->raise_bottom_type(t);
       Node *y = x->Identity(&_igvn);
       if (y != x) {
         wins++;
         x = y;
       } else {
         y = _igvn.hash_find(x);
         if (y) {
           wins++;
           x = y;
         } else {
           // Else x is a new node we are keeping
           // We do not need register_new_node_with_optimizer
           // because set_type has already been called.
           _igvn._worklist.push(x);
         }
       }
     }
     if (x != the_clone && the_clone != NULL)
       _igvn.remove_dead_node(the_clone);
     phi->set_req( i, x );
   }
   // Too few wins?
   if (wins <= policy) {
     _igvn.remove_dead_node(phi);
     return NULL;
   }
   // Record Phi
   register_new_node( phi, region );
   for (uint i2 = 1; i2 < phi->req(); i2++) {
     Node *x = phi->in(i2);
     // If we commoned up the cloned 'x' with another existing Node,
     // the existing Node picks up a new use.  We need to make the
     // existing Node occur higher up so it dominates its uses.
     Node *old_ctrl;
     IdealLoopTree *old_loop;
     if (x->is_Con()) {
       // Constant's control is always root.
       set_ctrl(x, C->root());
       continue;
     }
     // The occasional new node
     if (x->_idx >= old_unique) {     // Found a new, unplaced node?
       old_ctrl = NULL;
       old_loop = NULL;               // Not in any prior loop
     } else {
       old_ctrl = get_ctrl(x);
       old_loop = get_loop(old_ctrl); // Get prior loop
     }
     // New late point must dominate new use
     Node *new_ctrl = dom_lca(old_ctrl, region->in(i2));
     if (new_ctrl == old_ctrl) // Nothing is changed
       continue;
     IdealLoopTree *new_loop = get_loop(new_ctrl);
     // Don't move x into a loop if its uses are
     // outside of loop. Otherwise x will be cloned
     // for each use outside of this loop.
     IdealLoopTree *use_loop = get_loop(region);
     if (!new_loop->is_member(use_loop) &&
         (old_loop == NULL || !new_loop->is_member(old_loop))) {
       // Take early control, later control will be recalculated
       // during next iteration of loop optimizations.
       new_ctrl = get_early_ctrl(x);
       new_loop = get_loop(new_ctrl);
     }
     // Set new location
     set_ctrl(x, new_ctrl);
     // If changing loop bodies, see if we need to collect into new body
     if (old_loop != new_loop) {
       if (old_loop && !old_loop->_child)
         old_loop->_body.yank(x);
       if (!new_loop->_child)
         new_loop->_body.push(x);  // Collect body info
     }
   }
   return phi;
 }
 //------------------------------dominated_by------------------------------------
 // Replace the dominated test with an obvious true or false.  Place it on the
 // IGVN worklist for later cleanup.  Move control-dependent data Nodes on the
 // live path up to the dominating control.
 void PhaseIdealLoop::dominated_by( Node *prevdom, Node *iff, bool flip, bool exclude_loop_predicate ) {
 #ifndef PRODUCT
   if (VerifyLoopOptimizations && PrintOpto) tty->print_cr("dominating test");
 #endif
   // prevdom is the dominating projection of the dominating test.
   assert( iff->is_If(), "" );
   assert( iff->Opcode() == Op_If || iff->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
   int pop = prevdom->Opcode();
   assert( pop == Op_IfFalse || pop == Op_IfTrue, "" );
   if (flip) {
     if (pop == Op_IfTrue)
       pop = Op_IfFalse;
     else
       pop = Op_IfTrue;
   }
   // 'con' is set to true or false to kill the dominated test.
   Node *con = _igvn.makecon(pop == Op_IfTrue ? TypeInt::ONE : TypeInt::ZERO);
   set_ctrl(con, C->root()); // Constant gets a new use
   // Hack the dominated test
   _igvn.replace_input_of(iff, 1, con);
   // If I dont have a reachable TRUE and FALSE path following the IfNode then
   // I can assume this path reaches an infinite loop.  In this case it's not
   // important to optimize the data Nodes - either the whole compilation will
   // be tossed or this path (and all data Nodes) will go dead.
   if (iff->outcnt() != 2) return;
   // Make control-dependent data Nodes on the live path (path that will remain
   // once the dominated IF is removed) become control-dependent on the
   // dominating projection.
   Node* dp = iff->as_If()->proj_out(pop == Op_IfTrue);
   // Loop predicates may have depending checks which should not
   // be skipped. For example, range check predicate has two checks
   // for lower and upper bounds.
   if (dp == NULL)
     return;
   ProjNode* dp_proj  = dp->as_Proj();
   ProjNode* unc_proj = iff->as_If()->proj_out(1 - dp_proj->_con)->as_Proj();
   if (exclude_loop_predicate &&
       unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))
     return; // Let IGVN transformation change control dependence.
   IdealLoopTree *old_loop = get_loop(dp);
   for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
     Node* cd = dp->fast_out(i); // Control-dependent node
     if (cd->depends_only_on_test()) {
       assert(cd->in(0) == dp, "");
       _igvn.replace_input_of(cd, 0, prevdom);
       set_early_ctrl(cd);
       IdealLoopTree *new_loop = get_loop(get_ctrl(cd));
       if (old_loop != new_loop) {
         if (!old_loop->_child) old_loop->_body.yank(cd);
         if (!new_loop->_child) new_loop->_body.push(cd);
       }
       --i;
       --imax;
     }
   }
 }
 //------------------------------has_local_phi_input----------------------------
 // Return TRUE if 'n' has Phi inputs from its local block and no other
 // block-local inputs (all non-local-phi inputs come from earlier blocks)
 Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
   Node *n_ctrl = get_ctrl(n);
   // See if some inputs come from a Phi in this block, or from before
   // this block.
   uint i;
   for( i = 1; i < n->req(); i++ ) {
     Node *phi = n->in(i);
     if( phi->is_Phi() && phi->in(0) == n_ctrl )
       break;
   }
   if( i >= n->req() )
     return NULL;                // No Phi inputs; nowhere to clone thru
   // Check for inputs created between 'n' and the Phi input.  These
   // must split as well; they have already been given the chance
   // (courtesy of a post-order visit) and since they did not we must
   // recover the 'cost' of splitting them by being very profitable
   // when splitting 'n'.  Since this is unlikely we simply give up.
   for( i = 1; i < n->req(); i++ ) {
     Node *m = n->in(i);
     if( get_ctrl(m) == n_ctrl && !m->is_Phi() ) {
       // We allow the special case of AddP's with no local inputs.
       // This allows us to split-up address expressions.
       if (m->is_AddP() &&
           get_ctrl(m->in(2)) != n_ctrl &&
           get_ctrl(m->in(3)) != n_ctrl) {
         // Move the AddP up to dominating point
         set_ctrl_and_loop(m, find_non_split_ctrl(idom(n_ctrl)));
         continue;
       }
       return NULL;
     }
   }
   return n_ctrl;
 }
 //------------------------------remix_address_expressions----------------------
 // Rework addressing expressions to get the most loop-invariant stuff
 // moved out.  We'd like to do all associative operators, but it's especially
 // important (common) to do address expressions.
 Node *PhaseIdealLoop::remix_address_expressions( Node *n ) {
   if (!has_ctrl(n))  return NULL;
   Node *n_ctrl = get_ctrl(n);
   IdealLoopTree *n_loop = get_loop(n_ctrl);
   // See if 'n' mixes loop-varying and loop-invariant inputs and
   // itself is loop-varying.
   // Only interested in binary ops (and AddP)
   if( n->req() < 3 || n->req() > 4 ) return NULL;
   Node *n1_ctrl = get_ctrl(n->in(                    1));
   Node *n2_ctrl = get_ctrl(n->in(                    2));
   Node *n3_ctrl = get_ctrl(n->in(n->req() == 3 ? 2 : 3));
   IdealLoopTree *n1_loop = get_loop( n1_ctrl );
   IdealLoopTree *n2_loop = get_loop( n2_ctrl );
   IdealLoopTree *n3_loop = get_loop( n3_ctrl );
   // Does one of my inputs spin in a tighter loop than self?
   if( (n_loop->is_member( n1_loop ) && n_loop != n1_loop) ||
       (n_loop->is_member( n2_loop ) && n_loop != n2_loop) ||
       (n_loop->is_member( n3_loop ) && n_loop != n3_loop) )
     return NULL;                // Leave well enough alone
   // Is at least one of my inputs loop-invariant?
   if( n1_loop == n_loop &&
       n2_loop == n_loop &&
       n3_loop == n_loop )
     return NULL;                // No loop-invariant inputs
   int n_op = n->Opcode();
   // Replace expressions like ((V+I) << 2) with (V<<2 + I<<2).
   if( n_op == Op_LShiftI ) {
     // Scale is loop invariant
     Node *scale = n->in(2);
     Node *scale_ctrl = get_ctrl(scale);
     IdealLoopTree *scale_loop = get_loop(scale_ctrl );
     if( n_loop == scale_loop || !scale_loop->is_member( n_loop ) )
       return NULL;
     const TypeInt *scale_t = scale->bottom_type()->isa_int();
     if( scale_t && scale_t->is_con() && scale_t->get_con() >= 16 )
       return NULL;              // Dont bother with byte/short masking
     // Add must vary with loop (else shift would be loop-invariant)
     Node *add = n->in(1);
     Node *add_ctrl = get_ctrl(add);
     IdealLoopTree *add_loop = get_loop(add_ctrl);
     //assert( n_loop == add_loop, "" );
     if( n_loop != add_loop ) return NULL;  // happens w/ evil ZKM loops
     // Convert I-V into I+ (0-V); same for V-I
     if( add->Opcode() == Op_SubI &&
         _igvn.type( add->in(1) ) != TypeInt::ZERO ) {
       Node *zero = _igvn.intcon(0);
       set_ctrl(zero, C->root());
       Node *neg = new (C) SubINode( _igvn.intcon(0), add->in(2) );
       register_new_node( neg, get_ctrl(add->in(2) ) );
       add = new (C) AddINode( add->in(1), neg );
       register_new_node( add, add_ctrl );
     }
     if( add->Opcode() != Op_AddI ) return NULL;
     // See if one add input is loop invariant
     Node *add_var = add->in(1);
     Node *add_var_ctrl = get_ctrl(add_var);
     IdealLoopTree *add_var_loop = get_loop(add_var_ctrl );
     Node *add_invar = add->in(2);
     Node *add_invar_ctrl = get_ctrl(add_invar);
     IdealLoopTree *add_invar_loop = get_loop(add_invar_ctrl );
     if( add_var_loop == n_loop ) {
     } else if( add_invar_loop == n_loop ) {
       // Swap to find the invariant part
       add_invar = add_var;
       add_invar_ctrl = add_var_ctrl;
       add_invar_loop = add_var_loop;
       add_var = add->in(2);
       Node *add_var_ctrl = get_ctrl(add_var);
       IdealLoopTree *add_var_loop = get_loop(add_var_ctrl );
     } else                      // Else neither input is loop invariant
       return NULL;
     if( n_loop == add_invar_loop || !add_invar_loop->is_member( n_loop ) )
       return NULL;              // No invariant part of the add?
     // Yes!  Reshape address expression!
     Node *inv_scale = new (C) LShiftINode( add_invar, scale );
     Node *inv_scale_ctrl =
       dom_depth(add_invar_ctrl) > dom_depth(scale_ctrl) ?
       add_invar_ctrl : scale_ctrl;
     register_new_node( inv_scale, inv_scale_ctrl );
     Node *var_scale = new (C) LShiftINode( add_var, scale );
     register_new_node( var_scale, n_ctrl );
     Node *var_add = new (C) AddINode( var_scale, inv_scale );
     register_new_node( var_add, n_ctrl );
     _igvn.replace_node( n, var_add );
     return var_add;
   }
   // Replace (I+V) with (V+I)
   if( n_op == Op_AddI ||
       n_op == Op_AddL ||
       n_op == Op_AddF ||
       n_op == Op_AddD ||
       n_op == Op_MulI ||
       n_op == Op_MulL ||
       n_op == Op_MulF ||
       n_op == Op_MulD ) {
     if( n2_loop == n_loop ) {
       assert( n1_loop != n_loop, "" );
       n->swap_edges(1, 2);
     }
   }
   // Replace ((I1 +p V) +p I2) with ((I1 +p I2) +p V),
   // but not if I2 is a constant.
   if( n_op == Op_AddP ) {
     if( n2_loop == n_loop && n3_loop != n_loop ) {
       if( n->in(2)->Opcode() == Op_AddP && !n->in(3)->is_Con() ) {
         Node *n22_ctrl = get_ctrl(n->in(2)->in(2));
         Node *n23_ctrl = get_ctrl(n->in(2)->in(3));
         IdealLoopTree *n22loop = get_loop( n22_ctrl );
         IdealLoopTree *n23_loop = get_loop( n23_ctrl );
         if( n22loop != n_loop && n22loop->is_member(n_loop) &&
             n23_loop == n_loop ) {
           Node *add1 = new (C) AddPNode( n->in(1), n->in(2)->in(2), n->in(3) );
           // Stuff new AddP in the loop preheader
           register_new_node( add1, n_loop->_head->in(LoopNode::EntryControl) );
           Node *add2 = new (C) AddPNode( n->in(1), add1, n->in(2)->in(3) );
           register_new_node( add2, n_ctrl );
           _igvn.replace_node( n, add2 );
           return add2;
         }
       }
     }
     // Replace (I1 +p (I2 + V)) with ((I1 +p I2) +p V)
     if( n2_loop != n_loop && n3_loop == n_loop ) {
       if( n->in(3)->Opcode() == Op_AddI ) {
         Node *V = n->in(3)->in(1);
         Node *I = n->in(3)->in(2);
         if( is_member(n_loop,get_ctrl(V)) ) {
         } else {
           Node *tmp = V; V = I; I = tmp;
         }
         if( !is_member(n_loop,get_ctrl(I)) ) {
           Node *add1 = new (C) AddPNode( n->in(1), n->in(2), I );
           // Stuff new AddP in the loop preheader
           register_new_node( add1, n_loop->_head->in(LoopNode::EntryControl) );
           Node *add2 = new (C) AddPNode( n->in(1), add1, V );
           register_new_node( add2, n_ctrl );
           _igvn.replace_node( n, add2 );
           return add2;
         }
       }
     }
   }
   return NULL;
 }
 //------------------------------conditional_move-------------------------------
 // Attempt to replace a Phi with a conditional move.  We have some pretty
 // strict profitability requirements.  All Phis at the merge point must
 // be converted, so we can remove the control flow.  We need to limit the
 // number of c-moves to a small handful.  All code that was in the side-arms
 // of the CFG diamond is now speculatively executed.  This code has to be
 // "cheap enough".  We are pretty much limited to CFG diamonds that merge
 // 1 or 2 items with a total of 1 or 2 ops executed speculatively.
 Node *PhaseIdealLoop::conditional_move( Node *region ) {
   assert(region->is_Region(), "sanity check");
   if (region->req() != 3) return NULL;
   // Check for CFG diamond
   Node *lp = region->in(1);
   Node *rp = region->in(2);
   if (!lp || !rp) return NULL;
   Node *lp_c = lp->in(0);
   if (lp_c == NULL || lp_c != rp->in(0) || !lp_c->is_If()) return NULL;
   IfNode *iff = lp_c->as_If();
   // Check for ops pinned in an arm of the diamond.
   // Can't remove the control flow in this case
   if (lp->outcnt() > 1) return NULL;
   if (rp->outcnt() > 1) return NULL;
   IdealLoopTree* r_loop = get_loop(region);
   assert(r_loop == get_loop(iff), "sanity");
   // Always convert to CMOVE if all results are used only outside this loop.
   bool used_inside_loop = (r_loop == _ltree_root);
   // Check profitability
   int cost = 0;
   int phis = 0;
   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
     Node *out = region->fast_out(i);
     if (!out->is_Phi()) continue; // Ignore other control edges, etc
     phis++;
     PhiNode* phi = out->as_Phi();
     BasicType bt = phi->type()->basic_type();
     switch (bt) {
     case T_FLOAT:
     case T_DOUBLE: {
       cost += Matcher::float_cmove_cost(); // Could be very expensive
       break;
     }
     case T_LONG: {
       cost += Matcher::long_cmove_cost(); // May encodes as 2 CMOV's
     }
     case T_INT:                 // These all CMOV fine
     case T_ADDRESS: {           // (RawPtr)
       cost++;
       break;
     }
     case T_NARROWOOP: // Fall through
     case T_OBJECT: {            // Base oops are OK, but not derived oops
       const TypeOopPtr *tp = phi->type()->make_ptr()->isa_oopptr();
       // Derived pointers are Bad (tm): what's the Base (for GC purposes) of a
       // CMOVE'd derived pointer?  It's a CMOVE'd derived base.  Thus
       // CMOVE'ing a derived pointer requires we also CMOVE the base.  If we
       // have a Phi for the base here that we convert to a CMOVE all is well
       // and good.  But if the base is dead, we'll not make a CMOVE.  Later
       // the allocator will have to produce a base by creating a CMOVE of the
       // relevant bases.  This puts the allocator in the business of
       // manufacturing expensive instructions, generally a bad plan.
       // Just Say No to Conditionally-Moved Derived Pointers.
       if (tp && tp->offset() != 0)
         return NULL;
       cost++;
       break;
     }
     default:
       return NULL;              // In particular, can't do memory or I/O
     }
     // Add in cost any speculative ops
     for (uint j = 1; j < region->req(); j++) {
       Node *proj = region->in(j);
       Node *inp = phi->in(j);
       if (get_ctrl(inp) == proj) { // Found local op
         cost++;
         // Check for a chain of dependent ops; these will all become
         // speculative in a CMOV.
         for (uint k = 1; k < inp->req(); k++)
           if (get_ctrl(inp->in(k)) == proj)
             cost += ConditionalMoveLimit; // Too much speculative goo
       }
     }
     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
     // This will likely Split-If, a higher-payoff operation.
     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
       Node* use = phi->fast_out(k);
       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
         cost += ConditionalMoveLimit;
       // Is there a use inside the loop?
       // Note: check only basic types since CMoveP is pinned.
       if (!used_inside_loop && is_java_primitive(bt)) {
         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
           used_inside_loop = true;
         }
       }
     }
   }
   Node* bol = iff->in(1);
   assert(bol->Opcode() == Op_Bool, "");
   int cmp_op = bol->in(1)->Opcode();
   // It is expensive to generate flags from a float compare.
   // Avoid duplicated float compare.
   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return NULL;
   float infrequent_prob = PROB_UNLIKELY_MAG(3);
   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
   if (used_inside_loop) {
     if (cost >= ConditionalMoveLimit) return NULL; // Too much goo
     // BlockLayoutByFrequency optimization moves infrequent branch
     // from hot path. No point in CMOV'ing in such case (110 is used
     // instead of 100 to take into account not exactness of float value).
     if (BlockLayoutByFrequency) {
       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
     }
   }
   // Check for highly predictable branch.  No point in CMOV'ing if
   // we are going to predict accurately all the time.
   if (iff->_prob < infrequent_prob ||
       iff->_prob > (1.0f - infrequent_prob))
     return NULL;
   // --------------
   // Now replace all Phis with CMOV's
   Node *cmov_ctrl = iff->in(0);
   uint flip = (lp->Opcode() == Op_IfTrue);
   while (1) {
     PhiNode* phi = NULL;
     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
       Node *out = region->fast_out(i);
       if (out->is_Phi()) {
         phi = out->as_Phi();
         break;
       }
     }
     if (phi == NULL)  break;
 #ifndef PRODUCT
     if (PrintOpto && VerifyLoopOptimizations) tty->print_cr("CMOV");
 #endif
     // Move speculative ops
     for (uint j = 1; j < region->req(); j++) {
       Node *proj = region->in(j);
       Node *inp = phi->in(j);
       if (get_ctrl(inp) == proj) { // Found local op
 #ifndef PRODUCT
         if (PrintOpto && VerifyLoopOptimizations) {
           tty->print("  speculate: ");
           inp->dump();
         }
 #endif
         set_ctrl(inp, cmov_ctrl);
       }
     }
     Node *cmov = CMoveNode::make( C, cmov_ctrl, iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi) );
     register_new_node( cmov, cmov_ctrl );
     _igvn.replace_node( phi, cmov );
 #ifndef PRODUCT
     if (TraceLoopOpts) {
       tty->print("CMOV  ");
       r_loop->dump_head();
       if (Verbose) {
         bol->in(1)->dump(1);
         cmov->dump(1);
       }
     }
     if (VerifyLoopOptimizations) verify();
 #endif
   }
   // The useless CFG diamond will fold up later; see the optimization in
   // RegionNode::Ideal.
   _igvn._worklist.push(region);
   return iff->in(1);
 }
 //------------------------------split_if_with_blocks_pre-----------------------
 // Do the real work in a non-recursive function.  Data nodes want to be
 // cloned in the pre-order so they can feed each other nicely.
 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
   // Cloning these guys is unlikely to win
   int n_op = n->Opcode();
   if( n_op == Op_MergeMem ) return n;
   if( n->is_Proj() ) return n;
   // Do not clone-up CmpFXXX variations, as these are always
   // followed by a CmpI
   if( n->is_Cmp() ) return n;
   // Attempt to use a conditional move instead of a phi/branch
   if( ConditionalMoveLimit > 0 && n_op == Op_Region ) {
     Node *cmov = conditional_move( n );
     if( cmov ) return cmov;
   }
   if( n->is_CFG() || n->is_LoadStore() )
     return n;
   if( n_op == Op_Opaque1 ||     // Opaque nodes cannot be mod'd
       n_op == Op_Opaque2 ) {
     if( !C->major_progress() )   // If chance of no more loop opts...
       _igvn._worklist.push(n);  // maybe we'll remove them
     return n;
   }
   if( n->is_Con() ) return n;   // No cloning for Con nodes
   Node *n_ctrl = get_ctrl(n);
   if( !n_ctrl ) return n;       // Dead node
   // Attempt to remix address expressions for loop invariants
   Node *m = remix_address_expressions( n );
   if( m ) return m;
   // Determine if the Node has inputs from some local Phi.
   // Returns the block to clone thru.
   Node *n_blk = has_local_phi_input( n );
   if( !n_blk ) return n;
   // Do not clone the trip counter through on a CountedLoop
   // (messes up the canonical shape).
   if( n_blk->is_CountedLoop() && n->Opcode() == Op_AddI ) return n;
   // Check for having no control input; not pinned.  Allow
   // dominating control.
   if( n->in(0) ) {
     Node *dom = idom(n_blk);
     if( dom_lca( n->in(0), dom ) != n->in(0) )
       return n;
   }
   // Policy: when is it profitable.  You must get more wins than
   // policy before it is considered profitable.  Policy is usually 0,
   // so 1 win is considered profitable.  Big merges will require big
   // cloning, so get a larger policy.
   int policy = n_blk->req() >> 2;
   // If the loop is a candidate for range check elimination,
   // delay splitting through it's phi until a later loop optimization
   if (n_blk->is_CountedLoop()) {
     IdealLoopTree *lp = get_loop(n_blk);
     if (lp && lp->_rce_candidate) {
       return n;
     }
   }
   // Use same limit as split_if_with_blocks_post
   if( C->unique() > 35000 ) return n; // Method too big
   // Split 'n' through the merge point if it is profitable
   Node *phi = split_thru_phi( n, n_blk, policy );
   if (!phi) return n;
   // Found a Phi to split thru!
   // Replace 'n' with the new phi
   _igvn.replace_node( n, phi );
   // Moved a load around the loop, 'en-registering' something.
   if (n_blk->is_Loop() && n->is_Load() &&
       !phi->in(LoopNode::LoopBackControl)->is_Load())
     C->set_major_progress();
   return phi;
 }
 static bool merge_point_too_heavy(Compile* C, Node* region) {
   // Bail out if the region and its phis have too many users.
   int weight = 0;
   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
     weight += region->fast_out(i)->outcnt();
   }
   int nodes_left = MaxNodeLimit - C->live_nodes();
   if (weight * 8 > nodes_left) {
 #ifndef PRODUCT
     if (PrintOpto)
       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
 #endif
     return true;
   } else {
     return false;
   }
 }
 static bool merge_point_safe(Node* region) {
   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
   // having a PhiNode input. This sidesteps the dangerous case where the split
   // ConvI2LNode may become TOP if the input Value() does not
   // overlap the ConvI2L range, leaving a node which may not dominate its
   // uses.
   // A better fix for this problem can be found in the BugTraq entry, but
   // expediency for Mantis demands this hack.
   // 6855164: If the merge point has a FastLockNode with a PhiNode input, we stop
   // split_if_with_blocks from splitting a block because we could not move around
   // the FastLockNode.
   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
     Node* n = region->fast_out(i);
     if (n->is_Phi()) {
       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
         Node* m = n->fast_out(j);
         if (m->is_FastLock())
           return false;
 #ifdef _LP64
         if (m->Opcode() == Op_ConvI2L)
           return false;
 #endif
       }
     }
   }
   return true;
 }
 //------------------------------place_near_use---------------------------------
 // Place some computation next to use but not inside inner loops.
 // For inner loop uses move it to the preheader area.
 Node *PhaseIdealLoop::place_near_use( Node *useblock ) const {
   IdealLoopTree *u_loop = get_loop( useblock );
   return (u_loop->_irreducible || u_loop->_child)
     ? useblock
     : u_loop->_head->in(LoopNode::EntryControl);
 }
 //------------------------------split_if_with_blocks_post----------------------
 // Do the real work in a non-recursive function.  CFG hackery wants to be
 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
 // info.
 void PhaseIdealLoop::split_if_with_blocks_post( Node *n ) {
   // Cloning Cmp through Phi's involves the split-if transform.
   // FastLock is not used by an If
   if( n->is_Cmp() && !n->is_FastLock() ) {
     if( C->unique() > 35000 ) return; // Method too big
     // Do not do 'split-if' if irreducible loops are present.
     if( _has_irreducible_loops )
       return;
     Node *n_ctrl = get_ctrl(n);
     // Determine if the Node has inputs from some local Phi.
     // Returns the block to clone thru.
     Node *n_blk = has_local_phi_input( n );
     if( n_blk != n_ctrl ) return;
     if( merge_point_too_heavy(C, n_ctrl) )
       return;
     if( n->outcnt() != 1 ) return; // Multiple bool's from 1 compare?
     Node *bol = n->unique_out();
     assert( bol->is_Bool(), "expect a bool here" );
     if( bol->outcnt() != 1 ) return;// Multiple branches from 1 compare?
     Node *iff = bol->unique_out();
     // Check some safety conditions
     if( iff->is_If() ) {        // Classic split-if?
       if( iff->in(0) != n_ctrl ) return; // Compare must be in same blk as if
     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
       // Can't split CMove with different control edge.
       if (iff->in(0) != NULL && iff->in(0) != n_ctrl ) return;
       if( get_ctrl(iff->in(2)) == n_ctrl ||
           get_ctrl(iff->in(3)) == n_ctrl )
         return;                 // Inputs not yet split-up
       if ( get_loop(n_ctrl) != get_loop(get_ctrl(iff)) ) {
         return;                 // Loop-invar test gates loop-varying CMOVE
       }
     } else {
       return;  // some other kind of node, such as an Allocate
     }
     // Do not do 'split-if' if some paths are dead.  First do dead code
     // elimination and then see if its still profitable.
     for( uint i = 1; i < n_ctrl->req(); i++ )
       if( n_ctrl->in(i) == C->top() )
         return;
     // When is split-if profitable?  Every 'win' on means some control flow
     // goes dead, so it's almost always a win.
     int policy = 0;
     // If trying to do a 'Split-If' at the loop head, it is only
     // profitable if the cmp folds up on BOTH paths.  Otherwise we
     // risk peeling a loop forever.
     // CNC - Disabled for now.  Requires careful handling of loop
     // body selection for the cloned code.  Also, make sure we check
     // for any input path not being in the same loop as n_ctrl.  For
     // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
     // because the alternative loop entry points won't be converted
     // into LoopNodes.
     IdealLoopTree *n_loop = get_loop(n_ctrl);
     for( uint j = 1; j < n_ctrl->req(); j++ )
       if( get_loop(n_ctrl->in(j)) != n_loop )
         return;
     // Check for safety of the merge point.
     if( !merge_point_safe(n_ctrl) ) {
       return;
     }
     // Split compare 'n' through the merge point if it is profitable
     Node *phi = split_thru_phi( n, n_ctrl, policy );
     if( !phi ) return;
     // Found a Phi to split thru!
     // Replace 'n' with the new phi
     _igvn.replace_node( n, phi );
     // Now split the bool up thru the phi
     Node *bolphi = split_thru_phi( bol, n_ctrl, -1 );
     guarantee(bolphi != NULL, "null boolean phi node");
     _igvn.replace_node( bol, bolphi );
     assert( iff->in(1) == bolphi, "" );
     if( bolphi->Value(&_igvn)->singleton() )
       return;
     // Conditional-move?  Must split up now
     if( !iff->is_If() ) {
       Node *cmovphi = split_thru_phi( iff, n_ctrl, -1 );
       _igvn.replace_node( iff, cmovphi );
       return;
     }
     // Now split the IF
     do_split_if( iff );
     return;
   }
   // Check for an IF ready to split; one that has its
   // condition codes input coming from a Phi at the block start.
   int n_op = n->Opcode();
   // Check for an IF being dominated by another IF same test
   if( n_op == Op_If ) {
     Node *bol = n->in(1);
     uint max = bol->outcnt();
     // Check for same test used more than once?
     if( n_op == Op_If && max > 1 && bol->is_Bool() ) {
       // Search up IDOMs to see if this IF is dominated.
       Node *cutoff = get_ctrl(bol);
       // Now search up IDOMs till cutoff, looking for a dominating test
       Node *prevdom = n;
       Node *dom = idom(prevdom);
       while( dom != cutoff ) {
         if( dom->req() > 1 && dom->in(1) == bol && prevdom->in(0) == dom ) {
           // Replace the dominated test with an obvious true or false.
           // Place it on the IGVN worklist for later cleanup.
           C->set_major_progress();
           dominated_by( prevdom, n, false, true );
 #ifndef PRODUCT
           if( VerifyLoopOptimizations ) verify();
 #endif
           return;
         }
         prevdom = dom;
         dom = idom(prevdom);
       }
     }
   }
   // See if a shared loop-varying computation has no loop-varying uses.
   // Happens if something is only used for JVM state in uncommon trap exits,
   // like various versions of induction variable+offset.  Clone the
   // computation per usage to allow it to sink out of the loop.
   if (has_ctrl(n) && !n->in(0)) {// n not dead and has no control edge (can float about)
     Node *n_ctrl = get_ctrl(n);
     IdealLoopTree *n_loop = get_loop(n_ctrl);
     if( n_loop != _ltree_root ) {
       DUIterator_Fast imax, i = n->fast_outs(imax);
       for (; i < imax; i++) {
         Node* u = n->fast_out(i);
         if( !has_ctrl(u) )     break; // Found control user
         IdealLoopTree *u_loop = get_loop(get_ctrl(u));
         if( u_loop == n_loop ) break; // Found loop-varying use
         if( n_loop->is_member( u_loop ) ) break; // Found use in inner loop
         if( u->Opcode() == Op_Opaque1 ) break; // Found loop limit, bugfix for 4677003
       }
       bool did_break = (i < imax);  // Did we break out of the previous loop?
       if (!did_break && n->outcnt() > 1) { // All uses in outer loops!
         Node *late_load_ctrl = NULL;
         if (n->is_Load()) {
           // If n is a load, get and save the result from get_late_ctrl(),
           // to be later used in calculating the control for n's clones.
           clear_dom_lca_tags();
           late_load_ctrl = get_late_ctrl(n, n_ctrl);
         }
         // If n is a load, and the late control is the same as the current
         // control, then the cloning of n is a pointless exercise, because
         // GVN will ensure that we end up where we started.
         if (!n->is_Load() || late_load_ctrl != n_ctrl) {
           for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; ) {
             Node *u = n->last_out(j); // Clone private computation per use
             _igvn.rehash_node_delayed(u);
             Node *x = n->clone(); // Clone computation
             Node *x_ctrl = NULL;
             if( u->is_Phi() ) {
               // Replace all uses of normal nodes.  Replace Phi uses
               // individually, so the separate Nodes can sink down
               // different paths.
               uint k = 1;
               while( u->in(k) != n ) k++;
               u->set_req( k, x );
               // x goes next to Phi input path
               x_ctrl = u->in(0)->in(k);
               --j;
             } else {              // Normal use
               // Replace all uses
               for( uint k = 0; k < u->req(); k++ ) {
                 if( u->in(k) == n ) {
                   u->set_req( k, x );
                   --j;
                 }
               }
               x_ctrl = get_ctrl(u);
             }
             // Find control for 'x' next to use but not inside inner loops.
             // For inner loop uses get the preheader area.
             x_ctrl = place_near_use(x_ctrl);
             if (n->is_Load()) {
               // For loads, add a control edge to a CFG node outside of the loop
               // to force them to not combine and return back inside the loop
               // during GVN optimization (4641526).
               //
               // Because we are setting the actual control input, factor in
               // the result from get_late_ctrl() so we respect any
               // anti-dependences. (6233005).
               x_ctrl = dom_lca(late_load_ctrl, x_ctrl);
               // Don't allow the control input to be a CFG splitting node.
               // Such nodes should only have ProjNodes as outs, e.g. IfNode
               // should only have IfTrueNode and IfFalseNode (4985384).
               x_ctrl = find_non_split_ctrl(x_ctrl);
               assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
               x->set_req(0, x_ctrl);
             }
             register_new_node(x, x_ctrl);
             // Some institutional knowledge is needed here: 'x' is
             // yanked because if the optimizer runs GVN on it all the
             // cloned x's will common up and undo this optimization and
             // be forced back in the loop.  This is annoying because it
             // makes +VerifyOpto report false-positives on progress.  I
             // tried setting control edges on the x's to force them to
             // not combine, but the matching gets worried when it tries
             // to fold a StoreP and an AddP together (as part of an
             // address expression) and the AddP and StoreP have
             // different controls.
             if (!x->is_Load() && !x->is_DecodeNarrowPtr()) _igvn._worklist.yank(x);
           }
           _igvn.remove_dead_node(n);
         }
       }
     }
   }
   // Check for Opaque2's who's loop has disappeared - who's input is in the
   // same loop nest as their output.  Remove 'em, they are no longer useful.
   if( n_op == Op_Opaque2 &&
       n->in(1) != NULL &&
       get_loop(get_ctrl(n)) == get_loop(get_ctrl(n->in(1))) ) {
     _igvn.replace_node( n, n->in(1) );
   }
 }
 //------------------------------split_if_with_blocks---------------------------
 // Check for aggressive application of 'split-if' optimization,
 // using basic block level info.
 void PhaseIdealLoop::split_if_with_blocks( VectorSet &visited, Node_Stack &nstack ) {
   Node *n = C->root();
   visited.set(n->_idx); // first, mark node as visited
   // Do pre-visit work for root
   n = split_if_with_blocks_pre( n );
   uint cnt = n->outcnt();
   uint i   = 0;
   while (true) {
     // Visit all children
     if (i < cnt) {
       Node* use = n->raw_out(i);
       ++i;
       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
         // Now do pre-visit work for this use
         use = split_if_with_blocks_pre( use );
         nstack.push(n, i); // Save parent and next use's index.
         n   = use;         // Process all children of current use.
         cnt = use->outcnt();
         i   = 0;
       }
     }
     else {
       // All of n's children have been processed, complete post-processing.
       if (cnt != 0 && !n->is_Con()) {
         assert(has_node(n), "no dead nodes");
         split_if_with_blocks_post( n );
       }
       if (nstack.is_empty()) {
         // Finished all nodes on stack.
         break;
       }
       // Get saved parent node and next use's index. Visit the rest of uses.
       n   = nstack.node();
       cnt = n->outcnt();
       i   = nstack.index();
       nstack.pop();
     }
   }
 }
 //=============================================================================
 //
 //                   C L O N E   A   L O O P   B O D Y
 //
 //------------------------------clone_iff--------------------------------------
 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
 // "Nearly" because all Nodes have been cloned from the original in the loop,
 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
 // through the Phi recursively, and return a Bool.
 BoolNode *PhaseIdealLoop::clone_iff( PhiNode *phi, IdealLoopTree *loop ) {
   // Convert this Phi into a Phi merging Bools
   uint i;
   for( i = 1; i < phi->req(); i++ ) {
     Node *b = phi->in(i);
     if( b->is_Phi() ) {
       _igvn.replace_input_of(phi, i, clone_iff( b->as_Phi(), loop ));
     } else {
       assert( b->is_Bool(), "" );
     }
   }
   Node *sample_bool = phi->in(1);
   Node *sample_cmp  = sample_bool->in(1);
   // Make Phis to merge the Cmp's inputs.
   PhiNode *phi1 = new (C) PhiNode( phi->in(0), Type::TOP );
   PhiNode *phi2 = new (C) PhiNode( phi->in(0), Type::TOP );
   for( i = 1; i < phi->req(); i++ ) {
     Node *n1 = phi->in(i)->in(1)->in(1);
     Node *n2 = phi->in(i)->in(1)->in(2);
     phi1->set_req( i, n1 );
     phi2->set_req( i, n2 );
     phi1->set_type( phi1->type()->meet_speculative(n1->bottom_type()));
     phi2->set_type( phi2->type()->meet_speculative(n2->bottom_type()));
   }
   // See if these Phis have been made before.
   // Register with optimizer
   Node *hit1 = _igvn.hash_find_insert(phi1);
   if( hit1 ) {                  // Hit, toss just made Phi
     _igvn.remove_dead_node(phi1); // Remove new phi
     assert( hit1->is_Phi(), "" );
     phi1 = (PhiNode*)hit1;      // Use existing phi
   } else {                      // Miss
     _igvn.register_new_node_with_optimizer(phi1);
   }
   Node *hit2 = _igvn.hash_find_insert(phi2);
   if( hit2 ) {                  // Hit, toss just made Phi
     _igvn.remove_dead_node(phi2); // Remove new phi
     assert( hit2->is_Phi(), "" );
     phi2 = (PhiNode*)hit2;      // Use existing phi
   } else {                      // Miss
     _igvn.register_new_node_with_optimizer(phi2);
   }
   // Register Phis with loop/block info
   set_ctrl(phi1, phi->in(0));
   set_ctrl(phi2, phi->in(0));
   // Make a new Cmp
   Node *cmp = sample_cmp->clone();
   cmp->set_req( 1, phi1 );
   cmp->set_req( 2, phi2 );
   _igvn.register_new_node_with_optimizer(cmp);
   set_ctrl(cmp, phi->in(0));
   // Make a new Bool
   Node *b = sample_bool->clone();
   b->set_req(1,cmp);
   _igvn.register_new_node_with_optimizer(b);
   set_ctrl(b, phi->in(0));
   assert( b->is_Bool(), "" );
   return (BoolNode*)b;
 }
 //------------------------------clone_bool-------------------------------------
 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
 // "Nearly" because all Nodes have been cloned from the original in the loop,
 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
 // through the Phi recursively, and return a Bool.
 CmpNode *PhaseIdealLoop::clone_bool( PhiNode *phi, IdealLoopTree *loop ) {
   uint i;
   // Convert this Phi into a Phi merging Bools
   for( i = 1; i < phi->req(); i++ ) {
     Node *b = phi->in(i);
     if( b->is_Phi() ) {
       _igvn.replace_input_of(phi, i, clone_bool( b->as_Phi(), loop ));
     } else {
       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
     }
   }
   Node *sample_cmp = phi->in(1);
   // Make Phis to merge the Cmp's inputs.
   PhiNode *phi1 = new (C) PhiNode( phi->in(0), Type::TOP );
   PhiNode *phi2 = new (C) PhiNode( phi->in(0), Type::TOP );
   for( uint j = 1; j < phi->req(); j++ ) {
     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
     Node *n1, *n2;
     if( cmp_top->is_Cmp() ) {
       n1 = cmp_top->in(1);
       n2 = cmp_top->in(2);
     } else {
       n1 = n2 = cmp_top;
     }
     phi1->set_req( j, n1 );
     phi2->set_req( j, n2 );
     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
   }
   // See if these Phis have been made before.
   // Register with optimizer
   Node *hit1 = _igvn.hash_find_insert(phi1);
   if( hit1 ) {                  // Hit, toss just made Phi
     _igvn.remove_dead_node(phi1); // Remove new phi
     assert( hit1->is_Phi(), "" );
     phi1 = (PhiNode*)hit1;      // Use existing phi
   } else {                      // Miss
     _igvn.register_new_node_with_optimizer(phi1);
   }
   Node *hit2 = _igvn.hash_find_insert(phi2);
   if( hit2 ) {                  // Hit, toss just made Phi
     _igvn.remove_dead_node(phi2); // Remove new phi
     assert( hit2->is_Phi(), "" );
     phi2 = (PhiNode*)hit2;      // Use existing phi
   } else {                      // Miss
     _igvn.register_new_node_with_optimizer(phi2);
   }
   // Register Phis with loop/block info
   set_ctrl(phi1, phi->in(0));
   set_ctrl(phi2, phi->in(0));
   // Make a new Cmp
   Node *cmp = sample_cmp->clone();
   cmp->set_req( 1, phi1 );
   cmp->set_req( 2, phi2 );
   _igvn.register_new_node_with_optimizer(cmp);
   set_ctrl(cmp, phi->in(0));
   assert( cmp->is_Cmp(), "" );
   return (CmpNode*)cmp;
 }
 //------------------------------sink_use---------------------------------------
 // If 'use' was in the loop-exit block, it now needs to be sunk
 // below the post-loop merge point.
 void PhaseIdealLoop::sink_use( Node *use, Node *post_loop ) {
   if (!use->is_CFG() && get_ctrl(use) == post_loop->in(2)) {
     set_ctrl(use, post_loop);
     for (DUIterator j = use->outs(); use->has_out(j); j++)
       sink_use(use->out(j), post_loop);
   }
 }
 //------------------------------clone_loop-------------------------------------
 //
 //                   C L O N E   A   L O O P   B O D Y
 //
 // This is the basic building block of the loop optimizations.  It clones an
 // entire loop body.  It makes an old_new loop body mapping; with this mapping
 // you can find the new-loop equivalent to an old-loop node.  All new-loop
 // nodes are exactly equal to their old-loop counterparts, all edges are the
 // same.  All exits from the old-loop now have a RegionNode that merges the
 // equivalent new-loop path.  This is true even for the normal "loop-exit"
 // condition.  All uses of loop-invariant old-loop values now come from (one
 // or more) Phis that merge their new-loop equivalents.
 //
 // This operation leaves the graph in an illegal state: there are two valid
 // control edges coming from the loop pre-header to both loop bodies.  I'll
 // definitely have to hack the graph after running this transform.
 //
 // From this building block I will further edit edges to perform loop peeling
 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
 //
 // Parameter side_by_size_idom:
 //   When side_by_size_idom is NULL, the dominator tree is constructed for
 //      the clone loop to dominate the original.  Used in construction of
 //      pre-main-post loop sequence.
 //   When nonnull, the clone and original are side-by-side, both are
 //      dominated by the side_by_side_idom node.  Used in construction of
 //      unswitched loops.
 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
                                  Node* side_by_side_idom) {
   // Step 1: Clone the loop body.  Make the old->new mapping.
   uint i;
   for( i = 0; i < loop->_body.size(); i++ ) {
     Node *old = loop->_body.at(i);
     Node *nnn = old->clone();
     old_new.map( old->_idx, nnn );
     _igvn.register_new_node_with_optimizer(nnn);
   }
   // Step 2: Fix the edges in the new body.  If the old input is outside the
   // loop use it.  If the old input is INside the loop, use the corresponding
   // new node instead.
   for( i = 0; i < loop->_body.size(); i++ ) {
     Node *old = loop->_body.at(i);
     Node *nnn = old_new[old->_idx];
     // Fix CFG/Loop controlling the new node
     if (has_ctrl(old)) {
       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
     } else {
       set_loop(nnn, loop->_parent);
       if (old->outcnt() > 0) {
         set_idom( nnn, old_new[idom(old)->_idx], dd );
       }
     }
     // Correct edges to the new node
     for( uint j = 0; j < nnn->req(); j++ ) {
         Node *n = nnn->in(j);
         if( n ) {
           IdealLoopTree *old_in_loop = get_loop( has_ctrl(n) ? get_ctrl(n) : n );
           if( loop->is_member( old_in_loop ) )
             nnn->set_req(j, old_new[n->_idx]);
         }
     }
     _igvn.hash_find_insert(nnn);
   }
   Node *newhead = old_new[loop->_head->_idx];
   set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
   // Step 3: Now fix control uses.  Loop varying control uses have already
   // been fixed up (as part of all input edges in Step 2).  Loop invariant
   // control uses must be either an IfFalse or an IfTrue.  Make a merge
   // point to merge the old and new IfFalse/IfTrue nodes; make the use
   // refer to this.
   ResourceArea *area = Thread::current()->resource_area();
   Node_List worklist(area);
   uint new_counter = C->unique();
   for( i = 0; i < loop->_body.size(); i++ ) {
     Node* old = loop->_body.at(i);
     if( !old->is_CFG() ) continue;
     Node* nnn = old_new[old->_idx];
     // Copy uses to a worklist, so I can munge the def-use info
     // with impunity.
     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
       worklist.push(old->fast_out(j));
     while( worklist.size() ) {  // Visit all uses
       Node *use = worklist.pop();
       if (!has_node(use))  continue; // Ignore dead nodes
       IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
       if( !loop->is_member( use_loop ) && use->is_CFG() ) {
         // Both OLD and USE are CFG nodes here.
         assert( use->is_Proj(), "" );
         // Clone the loop exit control projection
         Node *newuse = use->clone();
         newuse->set_req(0,nnn);
         _igvn.register_new_node_with_optimizer(newuse);
         set_loop(newuse, use_loop);
         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
         // We need a Region to merge the exit from the peeled body and the
         // exit from the old loop body.
         RegionNode *r = new (C) RegionNode(3);
         // Map the old use to the new merge point
         old_new.map( use->_idx, r );
         uint dd_r = MIN2(dom_depth(newuse),dom_depth(use));
         assert( dd_r >= dom_depth(dom_lca(newuse,use)), "" );
         // The original user of 'use' uses 'r' instead.
         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
           Node* useuse = use->last_out(l);
           _igvn.rehash_node_delayed(useuse);
           uint uses_found = 0;
           if( useuse->in(0) == use ) {
             useuse->set_req(0, r);
             uses_found++;
             if( useuse->is_CFG() ) {
               assert( dom_depth(useuse) > dd_r, "" );
               set_idom(useuse, r, dom_depth(useuse));
             }
           }
           for( uint k = 1; k < useuse->req(); k++ ) {
             if( useuse->in(k) == use ) {
               useuse->set_req(k, r);
               uses_found++;
             }
           }
           l -= uses_found;    // we deleted 1 or more copies of this edge
         }
         // Now finish up 'r'
         r->set_req( 1, newuse );
         r->set_req( 2,    use );
         _igvn.register_new_node_with_optimizer(r);
         set_loop(r, use_loop);
         set_idom(r, !side_by_side_idom ? newuse->in(0) : side_by_side_idom, dd_r);
       } // End of if a loop-exit test
     }
   }
   // Step 4: If loop-invariant use is not control, it must be dominated by a
   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
   // there if needed.  Make a Phi there merging old and new used values.
   Node_List *split_if_set = NULL;
   Node_List *split_bool_set = NULL;
   Node_List *split_cex_set = NULL;
   for( i = 0; i < loop->_body.size(); i++ ) {
     Node* old = loop->_body.at(i);
     Node* nnn = old_new[old->_idx];
     // Copy uses to a worklist, so I can munge the def-use info
     // with impunity.
     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
       worklist.push(old->fast_out(j));
     while( worklist.size() ) {
       Node *use = worklist.pop();
       if (!has_node(use))  continue; // Ignore dead nodes
       if (use->in(0) == C->top())  continue;
       IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
       // Check for data-use outside of loop - at least one of OLD or USE
       // must not be a CFG node.
       if( !loop->is_member( use_loop ) && (!old->is_CFG() || !use->is_CFG())) {
         // If the Data use is an IF, that means we have an IF outside of the
         // loop that is switching on a condition that is set inside of the
         // loop.  Happens if people set a loop-exit flag; then test the flag
         // in the loop to break the loop, then test is again outside of the
         // loop to determine which way the loop exited.
         // Loop predicate If node connects to Bool node through Opaque1 node.
         if (use->is_If() || use->is_CMove() || C->is_predicate_opaq(use)) {
           // Since this code is highly unlikely, we lazily build the worklist
           // of such Nodes to go split.
           if( !split_if_set )
             split_if_set = new Node_List(area);
           split_if_set->push(use);
         }
         if( use->is_Bool() ) {
           if( !split_bool_set )
             split_bool_set = new Node_List(area);
           split_bool_set->push(use);
         }
         if( use->Opcode() == Op_CreateEx ) {
           if( !split_cex_set )
             split_cex_set = new Node_List(area);
           split_cex_set->push(use);
         }
         // Get "block" use is in
         uint idx = 0;
         while( use->in(idx) != old ) idx++;
         Node *prev = use->is_CFG() ? use : get_ctrl(use);
         assert( !loop->is_member( get_loop( prev ) ), "" );
         Node *cfg = prev->_idx >= new_counter
           ? prev->in(2)
           : idom(prev);
         if( use->is_Phi() )     // Phi use is in prior block
           cfg = prev->in(idx);  // NOT in block of Phi itself
         if (cfg->is_top()) {    // Use is dead?
           _igvn.replace_input_of(use, idx, C->top());
           continue;
         }
         while( !loop->is_member( get_loop( cfg ) ) ) {
           prev = cfg;
           cfg = cfg->_idx >= new_counter ? cfg->in(2) : idom(cfg);
         }
         // If the use occurs after merging several exits from the loop, then
         // old value must have dominated all those exits.  Since the same old
         // value was used on all those exits we did not need a Phi at this
         // merge point.  NOW we do need a Phi here.  Each loop exit value
         // is now merged with the peeled body exit; each exit gets its own
         // private Phi and those Phis need to be merged here.
         Node *phi;
         if( prev->is_Region() ) {
           if( idx == 0 ) {      // Updating control edge?
             phi = prev;         // Just use existing control
           } else {              // Else need a new Phi
             phi = PhiNode::make( prev, old );
             // Now recursively fix up the new uses of old!
             for( uint i = 1; i < prev->req(); i++ ) {
               worklist.push(phi); // Onto worklist once for each 'old' input
             }
           }
         } else {
           // Get new RegionNode merging old and new loop exits
           prev = old_new[prev->_idx];
           assert( prev, "just made this in step 7" );
           if( idx == 0 ) {      // Updating control edge?
             phi = prev;         // Just use existing control
           } else {              // Else need a new Phi
             // Make a new Phi merging data values properly
             phi = PhiNode::make( prev, old );
             phi->set_req( 1, nnn );
           }
         }
         // If inserting a new Phi, check for prior hits
         if( idx != 0 ) {
           Node *hit = _igvn.hash_find_insert(phi);
           if( hit == NULL ) {
            _igvn.register_new_node_with_optimizer(phi); // Register new phi
           } else {                                      // or
             // Remove the new phi from the graph and use the hit
             _igvn.remove_dead_node(phi);
             phi = hit;                                  // Use existing phi
           }
           set_ctrl(phi, prev);
         }
         // Make 'use' use the Phi instead of the old loop body exit value
         _igvn.replace_input_of(use, idx, phi);
         if( use->_idx >= new_counter ) { // If updating new phis
           // Not needed for correctness, but prevents a weak assert
           // in AddPNode from tripping (when we end up with different
           // base & derived Phis that will become the same after
           // IGVN does CSE).
           Node *hit = _igvn.hash_find_insert(use);
           if( hit )             // Go ahead and re-hash for hits.
             _igvn.replace_node( use, hit );
         }
         // If 'use' was in the loop-exit block, it now needs to be sunk
         // below the post-loop merge point.
         sink_use( use, prev );
       }
     }
   }
   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
   // the loop uses a condition set in the loop.  The original IF probably
   // takes control from one or more OLD Regions (which in turn get from NEW
   // Regions).  In any case, there will be a set of Phis for each merge point
   // from the IF up to where the original BOOL def exists the loop.
   if( split_if_set ) {
     while( split_if_set->size() ) {
       Node *iff = split_if_set->pop();
       if( iff->in(1)->is_Phi() ) {
         BoolNode *b = clone_iff( iff->in(1)->as_Phi(), loop );
         _igvn.replace_input_of(iff, 1, b);
       }
     }
   }
   if( split_bool_set ) {
     while( split_bool_set->size() ) {
       Node *b = split_bool_set->pop();
       Node *phi = b->in(1);
       assert( phi->is_Phi(), "" );
       CmpNode *cmp = clone_bool( (PhiNode*)phi, loop );
       _igvn.replace_input_of(b, 1, cmp);
     }
   }
   if( split_cex_set ) {
     while( split_cex_set->size() ) {
       Node *b = split_cex_set->pop();
       assert( b->in(0)->is_Region(), "" );
       assert( b->in(1)->is_Phi(), "" );
       assert( b->in(0)->in(0) == b->in(1)->in(0), "" );
       split_up( b, b->in(0), NULL );
     }
   }
 }
 //---------------------- stride_of_possible_iv -------------------------------------
 // Looks for an iff/bool/comp with one operand of the compare
 // being a cycle involving an add and a phi,
 // with an optional truncation (left-shift followed by a right-shift)
 // of the add. Returns zero if not an iv.
 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
   Node* trunc1 = NULL;
   Node* trunc2 = NULL;
   const TypeInt* ttype = NULL;
   if (!iff->is_If() || iff->in(1) == NULL || !iff->in(1)->is_Bool()) {
     return 0;
   }
   BoolNode* bl = iff->in(1)->as_Bool();
   Node* cmp = bl->in(1);
   if (!cmp || cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU) {
     return 0;
   }
   // Must have an invariant operand
   if (is_member(get_loop(iff), get_ctrl(cmp->in(2)))) {
     return 0;
   }
   Node* add2 = NULL;
   Node* cmp1 = cmp->in(1);
   if (cmp1->is_Phi()) {
     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
     Node* phi = cmp1;
     for (uint i = 1; i < phi->req(); i++) {
       Node* in = phi->in(i);
       Node* add = CountedLoopNode::match_incr_with_optional_truncation(in,
                                 &trunc1, &trunc2, &ttype);
       if (add && add->in(1) == phi) {
         add2 = add->in(2);
         break;
       }
     }
   } else {
     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
     Node* addtrunc = cmp1;
     Node* add = CountedLoopNode::match_incr_with_optional_truncation(addtrunc,
                                 &trunc1, &trunc2, &ttype);
     if (add && add->in(1)->is_Phi()) {
       Node* phi = add->in(1);
       for (uint i = 1; i < phi->req(); i++) {
         if (phi->in(i) == addtrunc) {
           add2 = add->in(2);
           break;
         }
       }
     }
   }
   if (add2 != NULL) {
     const TypeInt* add2t = _igvn.type(add2)->is_int();
     if (add2t->is_con()) {
       return add2t->get_con();
     }
   }
   return 0;
 }
 //---------------------- stay_in_loop -------------------------------------
 // Return the (unique) control output node that's in the loop (if it exists.)
 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
   Node* unique = NULL;
   if (!n) return NULL;
   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
     Node* use = n->fast_out(i);
     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
       if (unique != NULL) {
         return NULL;
       }
       unique = use;
     }
   }
   return unique;
 }
 //------------------------------ register_node -------------------------------------
 // Utility to register node "n" with PhaseIdealLoop
 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth) {
   _igvn.register_new_node_with_optimizer(n);
   loop->_body.push(n);
   if (n->is_CFG()) {
     set_loop(n, loop);
     set_idom(n, pred, ddepth);
   } else {
     set_ctrl(n, pred);
   }
 }
 //------------------------------ proj_clone -------------------------------------
 // Utility to create an if-projection
 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
   ProjNode* c = p->clone()->as_Proj();
   c->set_req(0, iff);
   return c;
 }
 //------------------------------ short_circuit_if -------------------------------------
 // Force the iff control output to be the live_proj
 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
   guarantee(live_proj != NULL, "null projection");
   int proj_con = live_proj->_con;
   assert(proj_con == 0 || proj_con == 1, "false or true projection");
   Node *con = _igvn.intcon(proj_con);
   set_ctrl(con, C->root());
   if (iff) {
     iff->set_req(1, con);
   }
   return con;
 }
 //------------------------------ insert_if_before_proj -------------------------------------
 // Insert a new if before an if projection (* - new node)
 //
 // before
 //           if(test)
 //           /     \
 //          v       v
 //    other-proj   proj (arg)
 //
 // after
 //           if(test)
 //           /     \
 //          /       v
 //         |      * proj-clone
 //         v          |
 //    other-proj      v
 //                * new_if(relop(cmp[IU](left,right)))
 //                  /  \
 //                 v    v
 //         * new-proj  proj
 //         (returned)
 //
 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
   IfNode* iff = proj->in(0)->as_If();
   IdealLoopTree *loop = get_loop(proj);
   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
   int ddepth = dom_depth(proj);
   _igvn.rehash_node_delayed(iff);
   _igvn.rehash_node_delayed(proj);
   proj->set_req(0, NULL);  // temporary disconnect
   ProjNode* proj2 = proj_clone(proj, iff);
   register_node(proj2, loop, iff, ddepth);
   Node* cmp = Signed ? (Node*) new (C)CmpINode(left, right) : (Node*) new (C)CmpUNode(left, right);
   register_node(cmp, loop, proj2, ddepth);
   BoolNode* bol = new (C)BoolNode(cmp, relop);
   register_node(bol, loop, proj2, ddepth);
   IfNode* new_if = new (C)IfNode(proj2, bol, iff->_prob, iff->_fcnt);
   register_node(new_if, loop, proj2, ddepth);
   proj->set_req(0, new_if); // reattach
   set_idom(proj, new_if, ddepth);
   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
   guarantee(new_exit != NULL, "null exit node");
   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
   return new_exit;
 }
 //------------------------------ insert_region_before_proj -------------------------------------
 // Insert a region before an if projection (* - new node)
 //
 // before
 //           if(test)
 //          /      |
 //         v       |
 //       proj      v
 //               other-proj
 //
 // after
 //           if(test)
 //          /      |
 //         v       |
 // * proj-clone    v
 //         |     other-proj
 //         v
 // * new-region
 //         |
 //         v
 // *      dum_if
 //       /     \
 //      v       \
 // * dum-proj    v
 //              proj
 //
 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
   IfNode* iff = proj->in(0)->as_If();
   IdealLoopTree *loop = get_loop(proj);
   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
   int ddepth = dom_depth(proj);
   _igvn.rehash_node_delayed(iff);
   _igvn.rehash_node_delayed(proj);
   proj->set_req(0, NULL);  // temporary disconnect
   ProjNode* proj2 = proj_clone(proj, iff);
   register_node(proj2, loop, iff, ddepth);
   RegionNode* reg = new (C)RegionNode(2);
   reg->set_req(1, proj2);
   register_node(reg, loop, iff, ddepth);
   IfNode* dum_if = new (C)IfNode(reg, short_circuit_if(NULL, proj), iff->_prob, iff->_fcnt);
   register_node(dum_if, loop, reg, ddepth);
   proj->set_req(0, dum_if); // reattach
   set_idom(proj, dum_if, ddepth);
   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
   register_node(dum_proj, loop, dum_if, ddepth);
   return reg;
 }
 //------------------------------ insert_cmpi_loop_exit -------------------------------------
 // Clone a signed compare loop exit from an unsigned compare and
 // insert it before the unsigned cmp on the stay-in-loop path.
 // All new nodes inserted in the dominator tree between the original
 // if and it's projections.  The original if test is replaced with
 // a constant to force the stay-in-loop path.
 //
 // This is done to make sure that the original if and it's projections
 // still dominate the same set of control nodes, that the ctrl() relation
 // from data nodes to them is preserved, and that their loop nesting is
 // preserved.
 //
 // before
 //          if(i <u limit)    unsigned compare loop exit
 //         /       |
 //        v        v
 //   exit-proj   stay-in-loop-proj
 //
 // after
 //          if(stay-in-loop-const)  original if
 //         /       |
 //        /        v
 //       /  if(i <  limit)    new signed test
 //      /  /       |
 //     /  /        v
 //    /  /  if(i <u limit)    new cloned unsigned test
 //   /  /   /      |
 //   v  v  v       |
 //    region       |
 //        |        |
 //      dum-if     |
 //     /  |        |
 // ether  |        |
 //        v        v
 //   exit-proj   stay-in-loop-proj
 //
 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop) {
   const bool Signed   = true;
   const bool Unsigned = false;
   BoolNode* bol = if_cmpu->in(1)->as_Bool();
   if (bol->_test._test != BoolTest::lt) return NULL;
   CmpNode* cmpu = bol->in(1)->as_Cmp();
   if (cmpu->Opcode() != Op_CmpU) return NULL;
   int stride = stride_of_possible_iv(if_cmpu);
   if (stride == 0) return NULL;
   Node* lp_proj = stay_in_loop(if_cmpu, loop);
   guarantee(lp_proj != NULL, "null loop node");
   ProjNode* lp_continue = lp_proj->as_Proj();
   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
   Node* limit = NULL;
   if (stride > 0) {
     limit = cmpu->in(2);
   } else {
     limit = _igvn.makecon(TypeInt::ZERO);
     set_ctrl(limit, C->root());
   }
   // Create a new region on the exit path
   RegionNode* reg = insert_region_before_proj(lp_exit);
   guarantee(reg != NULL, "null region node");
   // Clone the if-cmpu-true-false using a signed compare
   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, limit, lp_continue);
   reg->add_req(cmpi_exit);
   // Clone the if-cmpu-true-false
   BoolTest::mask rel_u = bol->_test._test;
   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
   reg->add_req(cmpu_exit);
   // Force original if to stay in loop.
   short_circuit_if(if_cmpu, lp_continue);
   return cmpi_exit->in(0)->as_If();
 }
 //------------------------------ remove_cmpi_loop_exit -------------------------------------
 // Remove a previously inserted signed compare loop exit.
 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
   Node* lp_proj = stay_in_loop(if_cmp, loop);
   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
          stay_in_loop(lp_proj, loop)->is_If() &&
          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
   Node *con = _igvn.makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
   set_ctrl(con, C->root());
   if_cmp->set_req(1, con);
 }
 //------------------------------ scheduled_nodelist -------------------------------------
 // Create a post order schedule of nodes that are in the
 // "member" set.  The list is returned in "sched".
 // The first node in "sched" is the loop head, followed by
 // nodes which have no inputs in the "member" set, and then
 // followed by the nodes that have an immediate input dependence
 // on a node in "sched".
 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
   assert(member.test(loop->_head->_idx), "loop head must be in member set");
   Arena *a = Thread::current()->resource_area();
   VectorSet visited(a);
   Node_Stack nstack(a, loop->_body.size());
   Node* n  = loop->_head;  // top of stack is cached in "n"
   uint idx = 0;
   visited.set(n->_idx);
   // Initially push all with no inputs from within member set
   for(uint i = 0; i < loop->_body.size(); i++ ) {
     Node *elt = loop->_body.at(i);
     if (member.test(elt->_idx)) {
       bool found = false;
       for (uint j = 0; j < elt->req(); j++) {
         Node* def = elt->in(j);
         if (def && member.test(def->_idx) && def != elt) {
           found = true;
           break;
         }
       }
       if (!found && elt != loop->_head) {
         nstack.push(n, idx);
         n = elt;
         assert(!visited.test(n->_idx), "not seen yet");
         visited.set(n->_idx);
       }
     }
   }
   // traverse out's that are in the member set
   while (true) {
     if (idx < n->outcnt()) {
       Node* use = n->raw_out(idx);
       idx++;
       if (!visited.test_set(use->_idx)) {
         if (member.test(use->_idx)) {
           nstack.push(n, idx);
           n = use;
           idx = 0;
         }
       }
     } else {
       // All outputs processed
       sched.push(n);
       if (nstack.is_empty()) break;
       n   = nstack.node();
       idx = nstack.index();
       nstack.pop();
     }
   }
 }
 //------------------------------ has_use_in_set -------------------------------------
 // Has a use in the vector set
 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
     Node* use = n->fast_out(j);
     if (vset.test(use->_idx)) {
       return true;
     }
   }
   return false;
 }
 //------------------------------ has_use_internal_to_set -------------------------------------
 // Has use internal to the vector set (ie. not in a phi at the loop head)
 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
   Node* head  = loop->_head;
   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
     Node* use = n->fast_out(j);
     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
       return true;
     }
   }
   return false;
 }
 //------------------------------ clone_for_use_outside_loop -------------------------------------
 // clone "n" for uses that are outside of loop
 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
   int cloned = 0;
   assert(worklist.size() == 0, "should be empty");
   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
     Node* use = n->fast_out(j);
     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
       worklist.push(use);
     }
   }
   while( worklist.size() ) {
     Node *use = worklist.pop();
     if (!has_node(use) || use->in(0) == C->top()) continue;
     uint j;
     for (j = 0; j < use->req(); j++) {
       if (use->in(j) == n) break;
     }
     assert(j < use->req(), "must be there");
     // clone "n" and insert it between the inputs of "n" and the use outside the loop
     Node* n_clone = n->clone();
     _igvn.replace_input_of(use, j, n_clone);
     cloned++;
     Node* use_c;
     if (!use->is_Phi()) {
       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
     } else {
       // Use in a phi is considered a use in the associated predecessor block
       use_c = use->in(0)->in(j);
     }
     set_ctrl(n_clone, use_c);
     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
     get_loop(use_c)->_body.push(n_clone);
     _igvn.register_new_node_with_optimizer(n_clone);
 #if !defined(PRODUCT)
     if (TracePartialPeeling) {
       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
     }
 #endif
   }
   return cloned;
 }
 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
 // clone "n" for special uses that are in the not_peeled region.
 // If these def-uses occur in separate blocks, the code generator
 // marks the method as not compilable.  For example, if a "BoolNode"
 // is in a different basic block than the "IfNode" that uses it, then
 // the compilation is aborted in the code generator.
 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
   if (n->is_Phi() || n->is_Load()) {
     return;
   }
   assert(worklist.size() == 0, "should be empty");
   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
     Node* use = n->fast_out(j);
     if ( not_peel.test(use->_idx) &&
          (use->is_If() || use->is_CMove() || use->is_Bool()) &&
          use->in(1) == n)  {
       worklist.push(use);
     }
   }
   if (worklist.size() > 0) {
     // clone "n" and insert it between inputs of "n" and the use
     Node* n_clone = n->clone();
     loop->_body.push(n_clone);
     _igvn.register_new_node_with_optimizer(n_clone);
     set_ctrl(n_clone, get_ctrl(n));
     sink_list.push(n_clone);
     not_peel <<= n_clone->_idx;  // add n_clone to not_peel set.
 #if !defined(PRODUCT)
     if (TracePartialPeeling) {
       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
     }
 #endif
     while( worklist.size() ) {
       Node *use = worklist.pop();
       _igvn.rehash_node_delayed(use);
       for (uint j = 1; j < use->req(); j++) {
         if (use->in(j) == n) {
           use->set_req(j, n_clone);
         }
       }
     }
   }
 }
 //------------------------------ insert_phi_for_loop -------------------------------------
 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
   Node *phi = PhiNode::make(lp, back_edge_val);
   phi->set_req(LoopNode::EntryControl, lp_entry_val);
   // Use existing phi if it already exists
   Node *hit = _igvn.hash_find_insert(phi);
   if( hit == NULL ) {
     _igvn.register_new_node_with_optimizer(phi);
     set_ctrl(phi, lp);
   } else {
     // Remove the new phi from the graph and use the hit
     _igvn.remove_dead_node(phi);
     phi = hit;
   }
   _igvn.replace_input_of(use, idx, phi);
 }
 #ifdef ASSERT
 //------------------------------ is_valid_loop_partition -------------------------------------
 // Validate the loop partition sets: peel and not_peel
 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
                                               VectorSet& not_peel ) {
   uint i;
   // Check that peel_list entries are in the peel set
   for (i = 0; i < peel_list.size(); i++) {
     if (!peel.test(peel_list.at(i)->_idx)) {
       return false;
     }
   }
   // Check at loop members are in one of peel set or not_peel set
   for (i = 0; i < loop->_body.size(); i++ ) {
     Node *def  = loop->_body.at(i);
     uint di = def->_idx;
     // Check that peel set elements are in peel_list
     if (peel.test(di)) {
       if (not_peel.test(di)) {
         return false;
       }
       // Must be in peel_list also
       bool found = false;
       for (uint j = 0; j < peel_list.size(); j++) {
         if (peel_list.at(j)->_idx == di) {
           found = true;
           break;
         }
       }
       if (!found) {
         return false;
       }
     } else if (not_peel.test(di)) {
       if (peel.test(di)) {
         return false;
       }
     } else {
       return false;
     }
   }
   return true;
 }
 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
 // Ensure a use outside of loop is of the right form
 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
   return (use->is_Phi() &&
           use_c->is_Region() && use_c->req() == 3 &&
           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
 }
 //------------------------------ is_valid_clone_loop_form -------------------------------------
 // Ensure that all uses outside of loop are of the right form
 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
                                                uint orig_exit_idx, uint clone_exit_idx) {
   uint len = peel_list.size();
   for (uint i = 0; i < len; i++) {
     Node *def = peel_list.at(i);
     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
       Node *use = def->fast_out(j);
       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
       if (!loop->is_member(get_loop(use_c))) {
         // use is not in the loop, check for correct structure
         if (use->in(0) == def) {
           // Okay
         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
           return false;
         }
       }
     }
   }
   return true;
 }
 #endif
 //------------------------------ partial_peel -------------------------------------
 // Partially peel (aka loop rotation) the top portion of a loop (called
 // the peel section below) by cloning it and placing one copy just before
 // the new loop head and the other copy at the bottom of the new loop.
 //
 //    before                       after                where it came from
 //
 //    stmt1                        stmt1
 //  loop:                          stmt2                     clone
 //    stmt2                        if condA goto exitA       clone
 //    if condA goto exitA        new_loop:                   new
 //    stmt3                        stmt3                     clone
 //    if !condB goto loop          if condB goto exitB       clone
 //  exitB:                         stmt2                     orig
 //    stmt4                        if !condA goto new_loop   orig
 //  exitA:                         goto exitA
 //                               exitB:
 //                                 stmt4
 //                               exitA:
 //
 // Step 1: find the cut point: an exit test on probable
 //         induction variable.
 // Step 2: schedule (with cloning) operations in the peel
 //         section that can be executed after the cut into
 //         the section that is not peeled.  This may need
 //         to clone operations into exit blocks.  For
 //         instance, a reference to A[i] in the not-peel
 //         section and a reference to B[i] in an exit block
 //         may cause a left-shift of i by 2 to be placed
 //         in the peel block.  This step will clone the left
 //         shift into the exit block and sink the left shift
 //         from the peel to the not-peel section.
 // Step 3: clone the loop, retarget the control, and insert
 //         phis for values that are live across the new loop
 //         head.  This is very dependent on the graph structure
 //         from clone_loop.  It creates region nodes for
 //         exit control and associated phi nodes for values
 //         flow out of the loop through that exit.  The region
 //         node is dominated by the clone's control projection.
 //         So the clone's peel section is placed before the
 //         new loop head, and the clone's not-peel section is
 //         forms the top part of the new loop.  The original
 //         peel section forms the tail of the new loop.
 // Step 4: update the dominator tree and recompute the
 //         dominator depth.
 //
 //                   orig
 //
 //                   stmt1
 //                     |
 //                     v
 //               loop predicate
 //                     |
 //                     v
 //                   loop<----+
 //                     |      |
 //                   stmt2    |
 //                     |      |
 //                     v      |
 //                    ifA     |
 //                   / |      |
 //                  v  v      |
 //               false true   ^  <-- last_peel
 //               /     |      |
 //              /   ===|==cut |
 //             /     stmt3    |  <-- first_not_peel
 //            /        |      |
 //            |        v      |
 //            v       ifB     |
 //          exitA:   / \      |
 //                  /   \     |
 //                 v     v    |
 //               false true   |
 //               /       \    |
 //              /         ----+
 //             |
 //             v
 //           exitB:
 //           stmt4
 //
 //
 //            after clone loop
 //
 //                   stmt1
 //                     |
 //                     v
 //               loop predicate
 //                 /       \
 //        clone   /         \   orig
 //               /           \
 //              /             \
 //             v               v
 //   +---->loop                loop<----+
 //   |      |                    |      |
 //   |    stmt2                stmt2    |
 //   |      |                    |      |
 //   |      v                    v      |
 //   |      ifA                 ifA     |
 //   |      | \                / |      |
 //   |      v  v              v  v      |
 //   ^    true  false      false true   ^  <-- last_peel
 //   |      |   ^   \       /    |      |
 //   | cut==|==  \   \     /  ===|==cut |
 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
 //   |      |    dom   | |       |      |
 //   |      v      \  1v v2      v      |
 //   |      ifB     regionA     ifB     |
 //   |      / \        |       / \      |
 //   |     /   \       v      /   \     |
 //   |    v     v    exitA:  v     v    |
 //   |    true  false      false true   |
 //   |    /     ^   \      /       \    |
 //   +----       \   \    /         ----+
 //               dom  \  /
 //                 \  1v v2
 //                  regionB
 //                     |
 //                     v
 //                   exitB:
 //                   stmt4
 //
 //
 //           after partial peel
 //
 //                  stmt1
 //                     |
 //                     v
 //               loop predicate
 //                 /
 //        clone   /             orig
 //               /          TOP
 //              /             \
 //             v               v
 //    TOP->loop                loop----+
 //          |                    |      |
 //        stmt2                stmt2    |
 //          |                    |      |
 //          v                    v      |
 //          ifA                 ifA     |
 //          | \                / |      |
 //          v  v              v  v      |
 //        true  false      false true   |     <-- last_peel
 //          |   ^   \       /    +------|---+
 //  +->newloop   \   \     /  === ==cut |   |
 //  |     stmt3   \   \   /     TOP     |   |
 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
 //  |       v      \  1v v2      v      |   |
 //  |       ifB     regionA     ifB     ^   v
 //  |       / \        |       / \      |   |
 //  |      /   \       v      /   \     |   |
 //  |     v     v    exitA:  v     v    |   |
 //  |     true  false      false true   |   |
 //  |     /     ^   \      /       \    |   |
 //  |    |       \   \    /         v   |   |
 //  |    |       dom  \  /         TOP  |   |
 //  |    |         \  1v v2             |   |
 //  ^    v          regionB             |   |
 //  |    |             |                |   |
 //  |    |             v                ^   v
 //  |    |           exitB:             |   |
 //  |    |           stmt4              |   |
 //  |    +------------>-----------------+   |
 //  |                                       |
 //  +-----------------<---------------------+
 //
 //
 //              final graph
 //
 //                  stmt1
 //                    |
 //                    v
 //               loop predicate
 //                    |
 //                    v
 //                  stmt2 clone
 //                    |
 //                    v
 //         ........> ifA clone
 //         :        / |
 //        dom      /  |
 //         :      v   v
 //         :  false   true
 //         :  |       |
 //         :  |       v
 //         :  |    newloop<-----+
 //         :  |        |        |
 //         :  |     stmt3 clone |
 //         :  |        |        |
 //         :  |        v        |
 //         :  |       ifB       |
 //         :  |      / \        |
 //         :  |     v   v       |
 //         :  |  false true     |
 //         :  |   |     |       |
 //         :  |   v    stmt2    |
 //         :  | exitB:  |       |
 //         :  | stmt4   v       |
 //         :  |       ifA orig  |
 //         :  |      /  \       |
 //         :  |     /    \      |
 //         :  |    v     v      |
 //         :  |  false  true    |
 //         :  |  /        \     |
 //         :  v  v         -----+
 //          RegionA
 //             |
 //             v
 //           exitA
 //
 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
   if (!loop->_head->is_Loop()) {
     return false;  }
   LoopNode *head  = loop->_head->as_Loop();
   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
     return false;
   }
   // Check for complex exit control
   for(uint ii = 0; ii < loop->_body.size(); ii++ ) {
     Node *n = loop->_body.at(ii);
     int opc = n->Opcode();
     if (n->is_Call()        ||
         opc == Op_Catch     ||
         opc == Op_CatchProj ||
         opc == Op_Jump      ||
         opc == Op_JumpProj) {
 #if !defined(PRODUCT)
       if (TracePartialPeeling) {
         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
       }
 #endif
       return false;
     }
   }
   int dd = dom_depth(head);
   // Step 1: find cut point
   // Walk up dominators to loop head looking for first loop exit
   // which is executed on every path thru loop.
   IfNode *peel_if = NULL;
   IfNode *peel_if_cmpu = NULL;
   Node *iff = loop->tail();
   while( iff != head ) {
     if( iff->is_If() ) {
       Node *ctrl = get_ctrl(iff->in(1));
       if (ctrl->is_top()) return false; // Dead test on live IF.
       // If loop-varying exit-test, check for induction variable
       if( loop->is_member(get_loop(ctrl)) &&
           loop->is_loop_exit(iff) &&
           is_possible_iv_test(iff)) {
         Node* cmp = iff->in(1)->in(1);
         if (cmp->Opcode() == Op_CmpI) {
           peel_if = iff->as_If();
         } else {
           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
           peel_if_cmpu = iff->as_If();
         }
       }
     }
     iff = idom(iff);
   }
   // Prefer signed compare over unsigned compare.
   IfNode* new_peel_if = NULL;
   if (peel_if == NULL) {
     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == NULL) {
       return false;   // No peel point found
     }
     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
     if (new_peel_if == NULL) {
       return false;   // No peel point found
     }
     peel_if = new_peel_if;
   }
   Node* last_peel        = stay_in_loop(peel_if, loop);
   Node* first_not_peeled = stay_in_loop(last_peel, loop);
   if (first_not_peeled == NULL || first_not_peeled == head) {
     return false;
   }
 #if !defined(PRODUCT)
   if (TraceLoopOpts) {
     tty->print("PartialPeel  ");
     loop->dump_head();
   }
   if (TracePartialPeeling) {
     tty->print_cr("before partial peel one iteration");
     Node_List wl;
     Node* t = head->in(2);
     while (true) {
       wl.push(t);
       if (t == head) break;
       t = idom(t);
     }
     while (wl.size() > 0) {
       Node* tt = wl.pop();
       tt->dump();
       if (tt == last_peel) tty->print_cr("-- cut --");
     }
   }
 #endif
   ResourceArea *area = Thread::current()->resource_area();
   VectorSet peel(area);
   VectorSet not_peel(area);
   Node_List peel_list(area);
   Node_List worklist(area);
   Node_List sink_list(area);
   // Set of cfg nodes to peel are those that are executable from
   // the head through last_peel.
   assert(worklist.size() == 0, "should be empty");
   worklist.push(head);
   peel.set(head->_idx);
   while (worklist.size() > 0) {
     Node *n = worklist.pop();
     if (n != last_peel) {
       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
         Node* use = n->fast_out(j);
         if (use->is_CFG() &&
             loop->is_member(get_loop(use)) &&
             !peel.test_set(use->_idx)) {
           worklist.push(use);
         }
       }
     }
   }
   // Set of non-cfg nodes to peel are those that are control
   // dependent on the cfg nodes.
   uint i;
   for(i = 0; i < loop->_body.size(); i++ ) {
     Node *n = loop->_body.at(i);
     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
     if (peel.test(n_c->_idx)) {
       peel.set(n->_idx);
     } else {
       not_peel.set(n->_idx);
     }
   }
   // Step 2: move operations from the peeled section down into the
   //         not-peeled section
   // Get a post order schedule of nodes in the peel region
   // Result in right-most operand.
   scheduled_nodelist(loop, peel, peel_list );
   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
   // For future check for too many new phis
   uint old_phi_cnt = 0;
   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
     Node* use = head->fast_out(j);
     if (use->is_Phi()) old_phi_cnt++;
   }
 #if !defined(PRODUCT)
   if (TracePartialPeeling) {
     tty->print_cr("\npeeled list");
   }
 #endif
   // Evacuate nodes in peel region into the not_peeled region if possible
   uint new_phi_cnt = 0;
   uint cloned_for_outside_use = 0;
   for (i = 0; i < peel_list.size();) {
     Node* n = peel_list.at(i);
 #if !defined(PRODUCT)
   if (TracePartialPeeling) n->dump();
 #endif
     bool incr = true;
     if ( !n->is_CFG() ) {
       if ( has_use_in_set(n, not_peel) ) {
         // If not used internal to the peeled region,
         // move "n" from peeled to not_peeled region.
         if ( !has_use_internal_to_set(n, peel, loop) ) {
           // if not pinned and not a load (which maybe anti-dependent on a store)
           // and not a CMove (Matcher expects only bool->cmove).
           if ( n->in(0) == NULL && !n->is_Load() && !n->is_CMove() ) {
             cloned_for_outside_use += clone_for_use_outside_loop( loop, n, worklist );
             sink_list.push(n);
             peel     >>= n->_idx; // delete n from peel set.
             not_peel <<= n->_idx; // add n to not_peel set.
             peel_list.remove(i);
             incr = false;
 #if !defined(PRODUCT)
             if (TracePartialPeeling) {
               tty->print_cr("sink to not_peeled region: %d newbb: %d",
                             n->_idx, get_ctrl(n)->_idx);
             }
 #endif
           }
         } else {
           // Otherwise check for special def-use cases that span
           // the peel/not_peel boundary such as bool->if
           clone_for_special_use_inside_loop( loop, n, not_peel, sink_list, worklist );
           new_phi_cnt++;
         }
       }
     }
     if (incr) i++;
   }
   if (new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta) {
 #if !defined(PRODUCT)
     if (TracePartialPeeling) {
       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
                     new_phi_cnt, old_phi_cnt, new_peel_if != NULL?'T':'F');
     }
 #endif
     if (new_peel_if != NULL) {
       remove_cmpi_loop_exit(new_peel_if, loop);
     }
     // Inhibit more partial peeling on this loop
     assert(!head->is_partial_peel_loop(), "not partial peeled");
     head->mark_partial_peel_failed();
     if (cloned_for_outside_use > 0) {
       // Terminate this round of loop opts because
       // the graph outside this loop was changed.
       C->set_major_progress();
       return true;
     }
     return false;
   }
   // Step 3: clone loop, retarget control, and insert new phis
   // Create new loop head for new phis and to hang
   // the nodes being moved (sinked) from the peel region.
   LoopNode* new_head = new (C) LoopNode(last_peel, last_peel);
   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
   _igvn.register_new_node_with_optimizer(new_head);
   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
   first_not_peeled->set_req(0, new_head);
   set_loop(new_head, loop);
   loop->_body.push(new_head);
   not_peel.set(new_head->_idx);
   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
   while (sink_list.size() > 0) {
     Node* n = sink_list.pop();
     set_ctrl(n, new_head);
   }
   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
   clone_loop( loop, old_new, dd );
   const uint clone_exit_idx = 1;
   const uint orig_exit_idx  = 2;
   assert(is_valid_clone_loop_form( loop, peel_list, orig_exit_idx, clone_exit_idx ), "bad clone loop");
   Node* head_clone             = old_new[head->_idx];
   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
   Node* orig_tail_clone        = head_clone->in(2);
   // Add phi if "def" node is in peel set and "use" is not
   for(i = 0; i < peel_list.size(); i++ ) {
     Node *def  = peel_list.at(i);
     if (!def->is_CFG()) {
       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
         Node *use = def->fast_out(j);
         if (has_node(use) && use->in(0) != C->top() &&
             (!peel.test(use->_idx) ||
              (use->is_Phi() && use->in(0) == head)) ) {
           worklist.push(use);
         }
       }
       while( worklist.size() ) {
         Node *use = worklist.pop();
         for (uint j = 1; j < use->req(); j++) {
           Node* n = use->in(j);
           if (n == def) {
             // "def" is in peel set, "use" is not in peel set
             // or "use" is in the entry boundary (a phi) of the peel set
             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
             if ( loop->is_member(get_loop( use_c )) ) {
               // use is in loop
               if (old_new[use->_idx] != NULL) { // null for dead code
                 Node* use_clone = old_new[use->_idx];
                 _igvn.replace_input_of(use, j, C->top());
                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
               }
             } else {
               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
               // use is not in the loop, check if the live range includes the cut
               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
               if (not_peel.test(lp_if->_idx)) {
                 assert(j == orig_exit_idx, "use from original loop");
                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
               }
             }
           }
         }
       }
     }
   }
   // Step 3b: retarget control
   // Redirect control to the new loop head if a cloned node in
   // the not_peeled region has control that points into the peeled region.
   // This necessary because the cloned peeled region will be outside
   // the loop.
   //                            from    to
   //          cloned-peeled    <---+
   //    new_head_clone:            |    <--+
   //          cloned-not_peeled  in(0)    in(0)
   //          orig-peeled
   for(i = 0; i < loop->_body.size(); i++ ) {
     Node *n = loop->_body.at(i);
     if (!n->is_CFG()           && n->in(0) != NULL        &&
         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
       Node* n_clone = old_new[n->_idx];
       _igvn.replace_input_of(n_clone, 0, new_head_clone);
     }
   }
   // Backedge of the surviving new_head (the clone) is original last_peel
   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
   // Cut first node in original not_peel set
   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
   // Copy head_clone back-branch info to original head
   // and remove original head's loop entry and
   // clone head's back-branch
   _igvn.rehash_node_delayed(head); // Multiple edge updates
   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
   head->set_req(LoopNode::LoopBackControl, C->top());
   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
   // Similarly modify the phis
   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
     Node* use = head->fast_out(k);
     if (use->is_Phi() && use->outcnt() > 0) {
       Node* use_clone = old_new[use->_idx];
       _igvn.rehash_node_delayed(use); // Multiple edge updates
       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
       use->set_req(LoopNode::LoopBackControl, C->top());
       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
     }
   }
   // Step 4: update dominator tree and dominator depth
   set_idom(head, orig_tail_clone, dd);
   recompute_dom_depth();
   // Inhibit more partial peeling on this loop
   new_head_clone->set_partial_peel_loop();
   C->set_major_progress();
   loop->record_for_igvn();
 #if !defined(PRODUCT)
   if (TracePartialPeeling) {
     tty->print_cr("\nafter partial peel one iteration");
     Node_List wl(area);
     Node* t = last_peel;
     while (true) {
       wl.push(t);
       if (t == head_clone) break;
       t = idom(t);
     }
     while (wl.size() > 0) {
       Node* tt = wl.pop();
       if (tt == head) tty->print_cr("orig head");
       else if (tt == new_head_clone) tty->print_cr("new head");
       else if (tt == head_clone) tty->print_cr("clone head");
       tt->dump();
     }
   }
 #endif
   return true;
 }
 //------------------------------reorg_offsets----------------------------------
 // Reorganize offset computations to lower register pressure.  Mostly
 // prevent loop-fallout uses of the pre-incremented trip counter (which are
 // then alive with the post-incremented trip counter forcing an extra
 // register move)
 void PhaseIdealLoop::reorg_offsets(IdealLoopTree *loop) {
   // Perform it only for canonical counted loops.
   // Loop's shape could be messed up by iteration_split_impl.
   if (!loop->_head->is_CountedLoop())
     return;
   if (!loop->_head->as_Loop()->is_valid_counted_loop())
     return;
   CountedLoopNode *cl = loop->_head->as_CountedLoop();
   CountedLoopEndNode *cle = cl->loopexit();
   Node *exit = cle->proj_out(false);
   Node *phi = cl->phi();
   // Check for the special case of folks using the pre-incremented
   // trip-counter on the fall-out path (forces the pre-incremented
   // and post-incremented trip counter to be live at the same time).
   // Fix this by adjusting to use the post-increment trip counter.
   bool progress = true;
   while (progress) {
     progress = false;
     for (DUIterator_Fast imax, i = phi->fast_outs(imax); i < imax; i++) {
       Node* use = phi->fast_out(i);   // User of trip-counter
       if (!has_ctrl(use))  continue;
       Node *u_ctrl = get_ctrl(use);
       if (use->is_Phi()) {
         u_ctrl = NULL;
         for (uint j = 1; j < use->req(); j++)
           if (use->in(j) == phi)
             u_ctrl = dom_lca(u_ctrl, use->in(0)->in(j));
       }
       IdealLoopTree *u_loop = get_loop(u_ctrl);
       // Look for loop-invariant use
       if (u_loop == loop) continue;
       if (loop->is_member(u_loop)) continue;
       // Check that use is live out the bottom.  Assuming the trip-counter
       // update is right at the bottom, uses of of the loop middle are ok.
       if (dom_lca(exit, u_ctrl) != exit) continue;
       // Hit!  Refactor use to use the post-incremented tripcounter.
       // Compute a post-increment tripcounter.
       Node *opaq = new (C) Opaque2Node( C, cle->incr() );
       register_new_node(opaq, exit);
       Node *neg_stride = _igvn.intcon(-cle->stride_con());
       set_ctrl(neg_stride, C->root());
       Node *post = new (C) AddINode( opaq, neg_stride);
       register_new_node(post, exit);
       _igvn.rehash_node_delayed(use);
       for (uint j = 1; j < use->req(); j++) {
         if (use->in(j) == phi)
           use->set_req(j, post);
       }
       // Since DU info changed, rerun loop
       progress = true;
       break;
     }
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/loopopts.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/loopopts.cpp