duke@435: /*
duke@435:  * Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: #include "incls/_precompiled.incl"
duke@435: #include "incls/_split_if.cpp.incl"
duke@435: 
duke@435: 
duke@435: //------------------------------split_thru_region------------------------------
duke@435: // Split Node 'n' through merge point.
duke@435: Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
duke@435:   uint wins = 0;
duke@435:   assert( n->is_CFG(), "" );
duke@435:   assert( region->is_Region(), "" );
duke@435:   Node *r = new (C, region->req()) RegionNode( region->req() );
duke@435:   IdealLoopTree *loop = get_loop( n );
duke@435:   for( uint i = 1; i < region->req(); i++ ) {
duke@435:     Node *x = n->clone();
duke@435:     Node *in0 = n->in(0);
duke@435:     if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
duke@435:     for( uint j = 1; j < n->req(); j++ ) {
duke@435:       Node *in = n->in(j);
duke@435:       if( get_ctrl(in) == region )
duke@435:         x->set_req( j, in->in(i) );
duke@435:     }
duke@435:     _igvn.register_new_node_with_optimizer(x);
duke@435:     set_loop(x, loop);
duke@435:     set_idom(x, x->in(0), dom_depth(x->in(0))+1);
duke@435:     r->init_req(i, x);
duke@435:   }
duke@435: 
duke@435:   // Record region
duke@435:   r->set_req(0,region);         // Not a TRUE RegionNode
duke@435:   _igvn.register_new_node_with_optimizer(r);
duke@435:   set_loop(r, loop);
duke@435:   if( !loop->_child )
duke@435:     loop->_body.push(r);
duke@435:   return r;
duke@435: }
duke@435: 
duke@435: //------------------------------split_up---------------------------------------
duke@435: // Split block-local op up through the phis to empty the current block
duke@435: bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
duke@435:   if( n->is_CFG() ) {
duke@435:     assert( n->in(0) != blk1, "Lousy candidate for split-if" );
duke@435:     return false;
duke@435:   }
duke@435:   if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
duke@435:     return false;               // Not block local
duke@435:   if( n->is_Phi() ) return false; // Local PHIs are expected
duke@435: 
duke@435:   // Recursively split-up inputs
duke@435:   for (uint i = 1; i < n->req(); i++) {
duke@435:     if( split_up( n->in(i), blk1, blk2 ) ) {
duke@435:       // Got split recursively and self went dead?
duke@435:       if (n->outcnt() == 0)
duke@435:         _igvn.remove_dead_node(n);
duke@435:       return true;
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Check for needing to clone-up a compare.  Can't do that, it forces
duke@435:   // another (nested) split-if transform.  Instead, clone it "down".
duke@435:   if( n->is_Cmp() ) {
duke@435:     assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
duke@435:     // Check for simple Cmp/Bool/CMove which we can clone-up.  Cmp/Bool/CMove
duke@435:     // sequence can have no other users and it must all reside in the split-if
duke@435:     // block.  Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
duke@435:     // private, per-use versions of the Cmp and Bool are made.  These sink to
duke@435:     // the CMove block.  If the CMove is in the split-if block, then in the
duke@435:     // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
duke@435:     Node *bol, *cmov;
duke@435:     if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
duke@435:           (bol = n->unique_out()->as_Bool()) &&
duke@435:           (get_ctrl(bol) == blk1 ||
duke@435:            get_ctrl(bol) == blk2) &&
duke@435:           bol->outcnt() == 1 &&
duke@435:           bol->unique_out()->is_CMove() &&
duke@435:           (cmov = bol->unique_out()->as_CMove()) &&
duke@435:           (get_ctrl(cmov) == blk1 ||
duke@435:            get_ctrl(cmov) == blk2) ) ) {
duke@435: 
duke@435:       // Must clone down
duke@435: #ifndef PRODUCT
duke@435:       if( PrintOpto && VerifyLoopOptimizations ) {
duke@435:         tty->print("Cloning down: ");
duke@435:         n->dump();
duke@435:       }
duke@435: #endif
duke@435:       // Clone down any block-local BoolNode uses of this CmpNode
duke@435:       for (DUIterator i = n->outs(); n->has_out(i); i++) {
duke@435:         Node* bol = n->out(i);
duke@435:         assert( bol->is_Bool(), "" );
duke@435:         if (bol->outcnt() == 1) {
duke@435:           Node* use = bol->unique_out();
duke@435:           Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
duke@435:           if (use_c == blk1 || use_c == blk2) {
duke@435:             continue;
duke@435:           }
duke@435:         }
duke@435:         if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
duke@435:           // Recursively sink any BoolNode
duke@435: #ifndef PRODUCT
duke@435:           if( PrintOpto && VerifyLoopOptimizations ) {
duke@435:             tty->print("Cloning down: ");
duke@435:             bol->dump();
duke@435:           }
duke@435: #endif
duke@435:           for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
duke@435:             // Uses are either IfNodes or CMoves
duke@435:             Node* iff = bol->last_out(j);
duke@435:             assert( iff->in(1) == bol, "" );
duke@435:             // Get control block of either the CMove or the If input
duke@435:             Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
duke@435:             Node *x = bol->clone();
duke@435:             register_new_node(x, iff_ctrl);
duke@435:             _igvn.hash_delete(iff);
duke@435:             iff->set_req(1, x);
duke@435:             _igvn._worklist.push(iff);
duke@435:           }
duke@435:           _igvn.remove_dead_node( bol );
duke@435:           --i;
duke@435:         }
duke@435:       }
duke@435:       // Clone down this CmpNode
duke@435:       for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
duke@435:         Node* bol = n->last_out(j);
duke@435:         assert( bol->in(1) == n, "" );
duke@435:         Node *x = n->clone();
duke@435:         register_new_node(x, get_ctrl(bol));
duke@435:         _igvn.hash_delete(bol);
duke@435:         bol->set_req(1, x);
duke@435:         _igvn._worklist.push(bol);
duke@435:       }
duke@435:       _igvn.remove_dead_node( n );
duke@435: 
duke@435:       return true;
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // See if splitting-up a Store.  Any anti-dep loads must go up as
duke@435:   // well.  An anti-dep load might be in the wrong block, because in
duke@435:   // this particular layout/schedule we ignored anti-deps and allow
duke@435:   // memory to be alive twice.  This only works if we do the same
duke@435:   // operations on anti-dep loads as we do their killing stores.
duke@435:   if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
duke@435:     // Get store's memory slice
duke@435:     int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
duke@435: 
duke@435:     // Get memory-phi anti-dep loads will be using
duke@435:     Node *memphi = n->in(MemNode::Memory);
duke@435:     assert( memphi->is_Phi(), "" );
duke@435:     // Hoist any anti-dep load to the splitting block;
duke@435:     // it will then "split-up".
duke@435:     for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
duke@435:       Node *load = memphi->fast_out(i);
duke@435:       if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
duke@435:         set_ctrl(load,blk1);
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Found some other Node; must clone it up
duke@435: #ifndef PRODUCT
duke@435:   if( PrintOpto && VerifyLoopOptimizations ) {
duke@435:     tty->print("Cloning up: ");
duke@435:     n->dump();
duke@435:   }
duke@435: #endif
duke@435: 
duke@435:   // Now actually split-up this guy.  One copy per control path merging.
duke@435:   Node *phi = PhiNode::make_blank(blk1, n);
duke@435:   for( uint j = 1; j < blk1->req(); j++ ) {
duke@435:     Node *x = n->clone();
duke@435:     if( n->in(0) && n->in(0) == blk1 )
duke@435:       x->set_req( 0, blk1->in(j) );
duke@435:     for( uint i = 1; i < n->req(); i++ ) {
duke@435:       Node *m = n->in(i);
duke@435:       if( get_ctrl(m) == blk1 ) {
duke@435:         assert( m->in(0) == blk1, "" );
duke@435:         x->set_req( i, m->in(j) );
duke@435:       }
duke@435:     }
duke@435:     register_new_node( x, blk1->in(j) );
duke@435:     phi->init_req( j, x );
duke@435:   }
duke@435:   // Announce phi to optimizer
duke@435:   register_new_node(phi, blk1);
duke@435: 
duke@435:   // Remove cloned-up value from optimizer; use phi instead
duke@435:   _igvn.hash_delete(n);
duke@435:   _igvn.subsume_node( n, phi );
duke@435: 
duke@435:   // (There used to be a self-recursive call to split_up() here,
duke@435:   // but it is not needed.  All necessary forward walking is done
duke@435:   // by do_split_if() below.)
duke@435: 
duke@435:   return true;
duke@435: }
duke@435: 
duke@435: //------------------------------register_new_node------------------------------
duke@435: void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
duke@435:   _igvn.register_new_node_with_optimizer(n);
duke@435:   set_ctrl(n, blk);
duke@435:   IdealLoopTree *loop = get_loop(blk);
duke@435:   if( !loop->_child )
duke@435:     loop->_body.push(n);
duke@435: }
duke@435: 
duke@435: //------------------------------small_cache------------------------------------
duke@435: struct small_cache : public Dict {
duke@435: 
duke@435:   small_cache() : Dict( cmpkey, hashptr ) {}
duke@435:   Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
duke@435:   void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
duke@435: };
duke@435: 
duke@435: //------------------------------spinup-----------------------------------------
duke@435: // "Spin up" the dominator tree, starting at the use site and stopping when we
duke@435: // find the post-dominating point.
duke@435: 
duke@435: // We must be at the merge point which post-dominates 'new_false' and
duke@435: // 'new_true'.  Figure out which edges into the RegionNode eventually lead up
duke@435: // to false and which to true.  Put in a PhiNode to merge values; plug in
duke@435: // the appropriate false-arm or true-arm values.  If some path leads to the
duke@435: // original IF, then insert a Phi recursively.
duke@435: Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
duke@435:   if (use_blk->is_top())        // Handle dead uses
duke@435:     return use_blk;
duke@435:   Node *prior_n = (Node*)0xdeadbeef;
duke@435:   Node *n = use_blk;            // Get path input
duke@435:   assert( use_blk != iff_dom, "" );
duke@435:   // Here's the "spinup" the dominator tree loop.  Do a cache-check
duke@435:   // along the way, in case we've come this way before.
duke@435:   while( n != iff_dom ) {       // Found post-dominating point?
duke@435:     prior_n = n;
duke@435:     n = idom(n);                // Search higher
duke@435:     Node *s = cache->probe( prior_n ); // Check cache
duke@435:     if( s ) return s;           // Cache hit!
duke@435:   }
duke@435: 
duke@435:   Node *phi_post;
duke@435:   if( prior_n == new_false || prior_n == new_true ) {
duke@435:     phi_post = def->clone();
duke@435:     phi_post->set_req(0, prior_n );
duke@435:     register_new_node(phi_post, prior_n);
duke@435:   } else {
duke@435:     // This method handles both control uses (looking for Regions) or data
duke@435:     // uses (looking for Phis).  If looking for a control use, then we need
duke@435:     // to insert a Region instead of a Phi; however Regions always exist
duke@435:     // previously (the hash_find_insert below would always hit) so we can
duke@435:     // return the existing Region.
duke@435:     if( def->is_CFG() ) {
duke@435:       phi_post = prior_n;       // If looking for CFG, return prior
duke@435:     } else {
duke@435:       assert( def->is_Phi(), "" );
duke@435:       assert( prior_n->is_Region(), "must be a post-dominating merge point" );
duke@435: 
duke@435:       // Need a Phi here
duke@435:       phi_post = PhiNode::make_blank(prior_n, def);
duke@435:       // Search for both true and false on all paths till find one.
duke@435:       for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
duke@435:         phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
duke@435:       Node *t = _igvn.hash_find_insert(phi_post);
duke@435:       if( t ) {                 // See if we already have this one
duke@435:         // phi_post will not be used, so kill it
duke@435:         _igvn.remove_dead_node(phi_post);
duke@435:         phi_post->destruct();
duke@435:         phi_post = t;
duke@435:       } else {
duke@435:         register_new_node( phi_post, prior_n );
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Update cache everywhere
duke@435:   prior_n = (Node*)0xdeadbeef;  // Reset IDOM walk
duke@435:   n = use_blk;                  // Get path input
duke@435:   // Spin-up the idom tree again, basically doing path-compression.
duke@435:   // Insert cache entries along the way, so that if we ever hit this
duke@435:   // point in the IDOM tree again we'll stop immediately on a cache hit.
duke@435:   while( n != iff_dom ) {       // Found post-dominating point?
duke@435:     prior_n = n;
duke@435:     n = idom(n);                // Search higher
duke@435:     cache->lru_insert( prior_n, phi_post ); // Fill cache
duke@435:   } // End of while not gone high enough
duke@435: 
duke@435:   return phi_post;
duke@435: }
duke@435: 
duke@435: //------------------------------find_use_block---------------------------------
duke@435: // Find the block a USE is in.  Normally USE's are in the same block as the
duke@435: // using instruction.  For Phi-USE's, the USE is in the predecessor block
duke@435: // along the corresponding path.
duke@435: Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
duke@435:   // CFG uses are their own block
duke@435:   if( use->is_CFG() )
duke@435:     return use;
duke@435: 
duke@435:   if( use->is_Phi() ) {         // Phi uses in prior block
duke@435:     // Grab the first Phi use; there may be many.
twisti@1040:     // Each will be handled as a separate iteration of
duke@435:     // the "while( phi->outcnt() )" loop.
duke@435:     uint j;
duke@435:     for( j = 1; j < use->req(); j++ )
duke@435:       if( use->in(j) == def )
duke@435:         break;
duke@435:     assert( j < use->req(), "def should be among use's inputs" );
duke@435:     return use->in(0)->in(j);
duke@435:   }
duke@435:   // Normal (non-phi) use
duke@435:   Node *use_blk = get_ctrl(use);
duke@435:   // Some uses are directly attached to the old (and going away)
duke@435:   // false and true branches.
duke@435:   if( use_blk == old_false ) {
duke@435:     use_blk = new_false;
duke@435:     set_ctrl(use, new_false);
duke@435:   }
duke@435:   if( use_blk == old_true ) {
duke@435:     use_blk = new_true;
duke@435:     set_ctrl(use, new_true);
duke@435:   }
duke@435: 
duke@435:   if (use_blk == NULL) {        // He's dead, Jim
duke@435:     _igvn.hash_delete(use);
duke@435:     _igvn.subsume_node(use, C->top());
duke@435:   }
duke@435: 
duke@435:   return use_blk;
duke@435: }
duke@435: 
duke@435: //------------------------------handle_use-------------------------------------
duke@435: // Handle uses of the merge point.  Basically, split-if makes the merge point
duke@435: // go away so all uses of the merge point must go away as well.  Most block
duke@435: // local uses have already been split-up, through the merge point.  Uses from
duke@435: // far below the merge point can't always be split up (e.g., phi-uses are
duke@435: // pinned) and it makes too much stuff live.  Instead we use a path-based
duke@435: // solution to move uses down.
duke@435: //
duke@435: // If the use is along the pre-split-CFG true branch, then the new use will
duke@435: // be from the post-split-CFG true merge point.  Vice-versa for the false
duke@435: // path.  Some uses will be along both paths; then we sink the use to the
duke@435: // post-dominating location; we may need to insert a Phi there.
duke@435: void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
duke@435: 
duke@435:   Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
duke@435:   if( !use_blk ) return;        // He's dead, Jim
duke@435: 
duke@435:   // Walk up the dominator tree until I hit either the old IfFalse, the old
duke@435:   // IfTrue or the old If.  Insert Phis where needed.
duke@435:   Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
duke@435: 
duke@435:   // Found where this USE goes.  Re-point him.
duke@435:   uint i;
duke@435:   for( i = 0; i < use->req(); i++ )
duke@435:     if( use->in(i) == def )
duke@435:       break;
duke@435:   assert( i < use->req(), "def should be among use's inputs" );
duke@435:   _igvn.hash_delete(use);
duke@435:   use->set_req(i, new_def);
duke@435:   _igvn._worklist.push(use);
duke@435: }
duke@435: 
duke@435: //------------------------------do_split_if------------------------------------
duke@435: // Found an If getting its condition-code input from a Phi in the same block.
duke@435: // Split thru the Region.
duke@435: void PhaseIdealLoop::do_split_if( Node *iff ) {
duke@435: #ifndef PRODUCT
duke@435:   if( PrintOpto && VerifyLoopOptimizations )
duke@435:     tty->print_cr("Split-if");
duke@435: #endif
duke@435:   C->set_major_progress();
duke@435:   Node *region = iff->in(0);
duke@435:   Node *region_dom = idom(region);
duke@435: 
duke@435:   // We are going to clone this test (and the control flow with it) up through
duke@435:   // the incoming merge point.  We need to empty the current basic block.
duke@435:   // Clone any instructions which must be in this block up through the merge
duke@435:   // point.
duke@435:   DUIterator i, j;
duke@435:   bool progress = true;
duke@435:   while (progress) {
duke@435:     progress = false;
duke@435:     for (i = region->outs(); region->has_out(i); i++) {
duke@435:       Node* n = region->out(i);
duke@435:       if( n == region ) continue;
duke@435:       // The IF to be split is OK.
duke@435:       if( n == iff ) continue;
duke@435:       if( !n->is_Phi() ) {      // Found pinned memory op or such
duke@435:         if (split_up(n, region, iff)) {
duke@435:           i = region->refresh_out_pos(i);
duke@435:           progress = true;
duke@435:         }
duke@435:         continue;
duke@435:       }
duke@435:       assert( n->in(0) == region, "" );
duke@435: 
duke@435:       // Recursively split up all users of a Phi
duke@435:       for (j = n->outs(); n->has_out(j); j++) {
duke@435:         Node* m = n->out(j);
duke@435:         // If m is dead, throw it away, and declare progress
duke@435:         if (_nodes[m->_idx] == NULL) {
duke@435:           _igvn.remove_dead_node(m);
duke@435:           // fall through
duke@435:         }
duke@435:         else if (m != iff && split_up(m, region, iff)) {
duke@435:           // fall through
duke@435:         } else {
duke@435:           continue;
duke@435:         }
duke@435:         // Something unpredictable changed.
duke@435:         // Tell the iterators to refresh themselves, and rerun the loop.
duke@435:         i = region->refresh_out_pos(i);
duke@435:         j = region->refresh_out_pos(j);
duke@435:         progress = true;
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Now we have no instructions in the block containing the IF.
duke@435:   // Split the IF.
duke@435:   Node *new_iff = split_thru_region( iff, region );
duke@435: 
duke@435:   // Replace both uses of 'new_iff' with Regions merging True/False
duke@435:   // paths.  This makes 'new_iff' go dead.
duke@435:   Node *old_false, *old_true;
duke@435:   Node *new_false, *new_true;
duke@435:   for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
duke@435:     Node *ifp = iff->last_out(j2);
duke@435:     assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
duke@435:     ifp->set_req(0, new_iff);
duke@435:     Node *ifpx = split_thru_region( ifp, region );
duke@435: 
duke@435:     // Replace 'If' projection of a Region with a Region of
duke@435:     // 'If' projections.
duke@435:     ifpx->set_req(0, ifpx);       // A TRUE RegionNode
duke@435: 
duke@435:     // Setup dominator info
duke@435:     set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
duke@435: 
duke@435:     // Check for splitting loop tails
duke@435:     if( get_loop(iff)->tail() == ifp )
duke@435:       get_loop(iff)->_tail = ifpx;
duke@435: 
duke@435:     // Replace in the graph with lazy-update mechanism
duke@435:     new_iff->set_req(0, new_iff); // hook self so it does not go dead
duke@435:     lazy_replace_proj( ifp, ifpx );
duke@435:     new_iff->set_req(0, region);
duke@435: 
duke@435:     // Record bits for later xforms
duke@435:     if( ifp->Opcode() == Op_IfFalse ) {
duke@435:       old_false = ifp;
duke@435:       new_false = ifpx;
duke@435:     } else {
duke@435:       old_true = ifp;
duke@435:       new_true = ifpx;
duke@435:     }
duke@435:   }
duke@435:   _igvn.remove_dead_node(new_iff);
duke@435:   // Lazy replace IDOM info with the region's dominator
duke@435:   lazy_replace( iff, region_dom );
duke@435: 
duke@435:   // Now make the original merge point go dead, by handling all its uses.
duke@435:   small_cache region_cache;
duke@435:   // Preload some control flow in region-cache
duke@435:   region_cache.lru_insert( new_false, new_false );
duke@435:   region_cache.lru_insert( new_true , new_true  );
duke@435:   // Now handle all uses of the splitting block
duke@435:   for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {
duke@435:     Node* phi = region->last_out(k);
duke@435:     if( !phi->in(0) ) {         // Dead phi?  Remove it
duke@435:       _igvn.remove_dead_node(phi);
duke@435:       continue;
duke@435:     }
duke@435:     assert( phi->in(0) == region, "" );
duke@435:     if( phi == region ) {       // Found the self-reference
duke@435:       phi->set_req(0, NULL);
duke@435:       continue;                 // Break the self-cycle
duke@435:     }
duke@435:     // Expected common case: Phi hanging off of Region
duke@435:     if( phi->is_Phi() ) {
duke@435:       // Need a per-def cache.  Phi represents a def, so make a cache
duke@435:       small_cache phi_cache;
duke@435: 
duke@435:       // Inspect all Phi uses to make the Phi go dead
duke@435:       for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
duke@435:         Node* use = phi->last_out(l);
duke@435:         // Compute the new DEF for this USE.  New DEF depends on the path
duke@435:         // taken from the original DEF to the USE.  The new DEF may be some
duke@435:         // collection of PHI's merging values from different paths.  The Phis
duke@435:         // inserted depend only on the location of the USE.  We use a
duke@435:         // 2-element cache to handle multiple uses from the same block.
duke@435:         handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );
duke@435:       } // End of while phi has uses
duke@435: 
duke@435:       // Because handle_use might relocate region->_out,
duke@435:       // we must refresh the iterator.
duke@435:       k = region->last_outs(kmin);
duke@435: 
duke@435:       // Remove the dead Phi
duke@435:       _igvn.remove_dead_node( phi );
duke@435: 
duke@435:     } else {
duke@435:       // Random memory op guarded by Region.  Compute new DEF for USE.
duke@435:       handle_use( phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true );
duke@435:     }
duke@435: 
duke@435:   } // End of while merge point has phis
duke@435: 
duke@435:   // Any leftover bits in the splitting block must not have depended on local
duke@435:   // Phi inputs (these have already been split-up).  Hence it's safe to hoist
duke@435:   // these guys to the dominating point.
duke@435:   lazy_replace( region, region_dom );
duke@435: #ifndef PRODUCT
duke@435:   if( VerifyLoopOptimizations ) verify();
duke@435: #endif
duke@435: }