1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/opto/split_if.cpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,536 @@
1.4 +/*
1.5 + * Copyright 1999-2006 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "incls/_precompiled.incl"
1.29 +#include "incls/_split_if.cpp.incl"
1.30 +
1.31 +
1.32 +//------------------------------split_thru_region------------------------------
1.33 +// Split Node 'n' through merge point.
1.34 +Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
1.35 + uint wins = 0;
1.36 + assert( n->is_CFG(), "" );
1.37 + assert( region->is_Region(), "" );
1.38 + Node *r = new (C, region->req()) RegionNode( region->req() );
1.39 + IdealLoopTree *loop = get_loop( n );
1.40 + for( uint i = 1; i < region->req(); i++ ) {
1.41 + Node *x = n->clone();
1.42 + Node *in0 = n->in(0);
1.43 + if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
1.44 + for( uint j = 1; j < n->req(); j++ ) {
1.45 + Node *in = n->in(j);
1.46 + if( get_ctrl(in) == region )
1.47 + x->set_req( j, in->in(i) );
1.48 + }
1.49 + _igvn.register_new_node_with_optimizer(x);
1.50 + set_loop(x, loop);
1.51 + set_idom(x, x->in(0), dom_depth(x->in(0))+1);
1.52 + r->init_req(i, x);
1.53 + }
1.54 +
1.55 + // Record region
1.56 + r->set_req(0,region); // Not a TRUE RegionNode
1.57 + _igvn.register_new_node_with_optimizer(r);
1.58 + set_loop(r, loop);
1.59 + if( !loop->_child )
1.60 + loop->_body.push(r);
1.61 + return r;
1.62 +}
1.63 +
1.64 +//------------------------------split_up---------------------------------------
1.65 +// Split block-local op up through the phis to empty the current block
1.66 +bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
1.67 + if( n->is_CFG() ) {
1.68 + assert( n->in(0) != blk1, "Lousy candidate for split-if" );
1.69 + return false;
1.70 + }
1.71 + if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
1.72 + return false; // Not block local
1.73 + if( n->is_Phi() ) return false; // Local PHIs are expected
1.74 +
1.75 + // Recursively split-up inputs
1.76 + for (uint i = 1; i < n->req(); i++) {
1.77 + if( split_up( n->in(i), blk1, blk2 ) ) {
1.78 + // Got split recursively and self went dead?
1.79 + if (n->outcnt() == 0)
1.80 + _igvn.remove_dead_node(n);
1.81 + return true;
1.82 + }
1.83 + }
1.84 +
1.85 + // Check for needing to clone-up a compare. Can't do that, it forces
1.86 + // another (nested) split-if transform. Instead, clone it "down".
1.87 + if( n->is_Cmp() ) {
1.88 + assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
1.89 + // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
1.90 + // sequence can have no other users and it must all reside in the split-if
1.91 + // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
1.92 + // private, per-use versions of the Cmp and Bool are made. These sink to
1.93 + // the CMove block. If the CMove is in the split-if block, then in the
1.94 + // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
1.95 + Node *bol, *cmov;
1.96 + if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
1.97 + (bol = n->unique_out()->as_Bool()) &&
1.98 + (get_ctrl(bol) == blk1 ||
1.99 + get_ctrl(bol) == blk2) &&
1.100 + bol->outcnt() == 1 &&
1.101 + bol->unique_out()->is_CMove() &&
1.102 + (cmov = bol->unique_out()->as_CMove()) &&
1.103 + (get_ctrl(cmov) == blk1 ||
1.104 + get_ctrl(cmov) == blk2) ) ) {
1.105 +
1.106 + // Must clone down
1.107 +#ifndef PRODUCT
1.108 + if( PrintOpto && VerifyLoopOptimizations ) {
1.109 + tty->print("Cloning down: ");
1.110 + n->dump();
1.111 + }
1.112 +#endif
1.113 + // Clone down any block-local BoolNode uses of this CmpNode
1.114 + for (DUIterator i = n->outs(); n->has_out(i); i++) {
1.115 + Node* bol = n->out(i);
1.116 + assert( bol->is_Bool(), "" );
1.117 + if (bol->outcnt() == 1) {
1.118 + Node* use = bol->unique_out();
1.119 + Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
1.120 + if (use_c == blk1 || use_c == blk2) {
1.121 + continue;
1.122 + }
1.123 + }
1.124 + if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
1.125 + // Recursively sink any BoolNode
1.126 +#ifndef PRODUCT
1.127 + if( PrintOpto && VerifyLoopOptimizations ) {
1.128 + tty->print("Cloning down: ");
1.129 + bol->dump();
1.130 + }
1.131 +#endif
1.132 + for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
1.133 + // Uses are either IfNodes or CMoves
1.134 + Node* iff = bol->last_out(j);
1.135 + assert( iff->in(1) == bol, "" );
1.136 + // Get control block of either the CMove or the If input
1.137 + Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
1.138 + Node *x = bol->clone();
1.139 + register_new_node(x, iff_ctrl);
1.140 + _igvn.hash_delete(iff);
1.141 + iff->set_req(1, x);
1.142 + _igvn._worklist.push(iff);
1.143 + }
1.144 + _igvn.remove_dead_node( bol );
1.145 + --i;
1.146 + }
1.147 + }
1.148 + // Clone down this CmpNode
1.149 + for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
1.150 + Node* bol = n->last_out(j);
1.151 + assert( bol->in(1) == n, "" );
1.152 + Node *x = n->clone();
1.153 + register_new_node(x, get_ctrl(bol));
1.154 + _igvn.hash_delete(bol);
1.155 + bol->set_req(1, x);
1.156 + _igvn._worklist.push(bol);
1.157 + }
1.158 + _igvn.remove_dead_node( n );
1.159 +
1.160 + return true;
1.161 + }
1.162 + }
1.163 +
1.164 + // See if splitting-up a Store. Any anti-dep loads must go up as
1.165 + // well. An anti-dep load might be in the wrong block, because in
1.166 + // this particular layout/schedule we ignored anti-deps and allow
1.167 + // memory to be alive twice. This only works if we do the same
1.168 + // operations on anti-dep loads as we do their killing stores.
1.169 + if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
1.170 + // Get store's memory slice
1.171 + int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
1.172 +
1.173 + // Get memory-phi anti-dep loads will be using
1.174 + Node *memphi = n->in(MemNode::Memory);
1.175 + assert( memphi->is_Phi(), "" );
1.176 + // Hoist any anti-dep load to the splitting block;
1.177 + // it will then "split-up".
1.178 + for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
1.179 + Node *load = memphi->fast_out(i);
1.180 + if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
1.181 + set_ctrl(load,blk1);
1.182 + }
1.183 + }
1.184 +
1.185 + // Found some other Node; must clone it up
1.186 +#ifndef PRODUCT
1.187 + if( PrintOpto && VerifyLoopOptimizations ) {
1.188 + tty->print("Cloning up: ");
1.189 + n->dump();
1.190 + }
1.191 +#endif
1.192 +
1.193 + // Now actually split-up this guy. One copy per control path merging.
1.194 + Node *phi = PhiNode::make_blank(blk1, n);
1.195 + for( uint j = 1; j < blk1->req(); j++ ) {
1.196 + Node *x = n->clone();
1.197 + if( n->in(0) && n->in(0) == blk1 )
1.198 + x->set_req( 0, blk1->in(j) );
1.199 + for( uint i = 1; i < n->req(); i++ ) {
1.200 + Node *m = n->in(i);
1.201 + if( get_ctrl(m) == blk1 ) {
1.202 + assert( m->in(0) == blk1, "" );
1.203 + x->set_req( i, m->in(j) );
1.204 + }
1.205 + }
1.206 + register_new_node( x, blk1->in(j) );
1.207 + phi->init_req( j, x );
1.208 + }
1.209 + // Announce phi to optimizer
1.210 + register_new_node(phi, blk1);
1.211 +
1.212 + // Remove cloned-up value from optimizer; use phi instead
1.213 + _igvn.hash_delete(n);
1.214 + _igvn.subsume_node( n, phi );
1.215 +
1.216 + // (There used to be a self-recursive call to split_up() here,
1.217 + // but it is not needed. All necessary forward walking is done
1.218 + // by do_split_if() below.)
1.219 +
1.220 + return true;
1.221 +}
1.222 +
1.223 +//------------------------------register_new_node------------------------------
1.224 +void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
1.225 + _igvn.register_new_node_with_optimizer(n);
1.226 + set_ctrl(n, blk);
1.227 + IdealLoopTree *loop = get_loop(blk);
1.228 + if( !loop->_child )
1.229 + loop->_body.push(n);
1.230 +}
1.231 +
1.232 +//------------------------------small_cache------------------------------------
1.233 +struct small_cache : public Dict {
1.234 +
1.235 + small_cache() : Dict( cmpkey, hashptr ) {}
1.236 + Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
1.237 + void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
1.238 +};
1.239 +
1.240 +//------------------------------spinup-----------------------------------------
1.241 +// "Spin up" the dominator tree, starting at the use site and stopping when we
1.242 +// find the post-dominating point.
1.243 +
1.244 +// We must be at the merge point which post-dominates 'new_false' and
1.245 +// 'new_true'. Figure out which edges into the RegionNode eventually lead up
1.246 +// to false and which to true. Put in a PhiNode to merge values; plug in
1.247 +// the appropriate false-arm or true-arm values. If some path leads to the
1.248 +// original IF, then insert a Phi recursively.
1.249 +Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
1.250 + if (use_blk->is_top()) // Handle dead uses
1.251 + return use_blk;
1.252 + Node *prior_n = (Node*)0xdeadbeef;
1.253 + Node *n = use_blk; // Get path input
1.254 + assert( use_blk != iff_dom, "" );
1.255 + // Here's the "spinup" the dominator tree loop. Do a cache-check
1.256 + // along the way, in case we've come this way before.
1.257 + while( n != iff_dom ) { // Found post-dominating point?
1.258 + prior_n = n;
1.259 + n = idom(n); // Search higher
1.260 + Node *s = cache->probe( prior_n ); // Check cache
1.261 + if( s ) return s; // Cache hit!
1.262 + }
1.263 +
1.264 + Node *phi_post;
1.265 + if( prior_n == new_false || prior_n == new_true ) {
1.266 + phi_post = def->clone();
1.267 + phi_post->set_req(0, prior_n );
1.268 + register_new_node(phi_post, prior_n);
1.269 + } else {
1.270 + // This method handles both control uses (looking for Regions) or data
1.271 + // uses (looking for Phis). If looking for a control use, then we need
1.272 + // to insert a Region instead of a Phi; however Regions always exist
1.273 + // previously (the hash_find_insert below would always hit) so we can
1.274 + // return the existing Region.
1.275 + if( def->is_CFG() ) {
1.276 + phi_post = prior_n; // If looking for CFG, return prior
1.277 + } else {
1.278 + assert( def->is_Phi(), "" );
1.279 + assert( prior_n->is_Region(), "must be a post-dominating merge point" );
1.280 +
1.281 + // Need a Phi here
1.282 + phi_post = PhiNode::make_blank(prior_n, def);
1.283 + // Search for both true and false on all paths till find one.
1.284 + for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
1.285 + phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
1.286 + Node *t = _igvn.hash_find_insert(phi_post);
1.287 + if( t ) { // See if we already have this one
1.288 + // phi_post will not be used, so kill it
1.289 + _igvn.remove_dead_node(phi_post);
1.290 + phi_post->destruct();
1.291 + phi_post = t;
1.292 + } else {
1.293 + register_new_node( phi_post, prior_n );
1.294 + }
1.295 + }
1.296 + }
1.297 +
1.298 + // Update cache everywhere
1.299 + prior_n = (Node*)0xdeadbeef; // Reset IDOM walk
1.300 + n = use_blk; // Get path input
1.301 + // Spin-up the idom tree again, basically doing path-compression.
1.302 + // Insert cache entries along the way, so that if we ever hit this
1.303 + // point in the IDOM tree again we'll stop immediately on a cache hit.
1.304 + while( n != iff_dom ) { // Found post-dominating point?
1.305 + prior_n = n;
1.306 + n = idom(n); // Search higher
1.307 + cache->lru_insert( prior_n, phi_post ); // Fill cache
1.308 + } // End of while not gone high enough
1.309 +
1.310 + return phi_post;
1.311 +}
1.312 +
1.313 +//------------------------------find_use_block---------------------------------
1.314 +// Find the block a USE is in. Normally USE's are in the same block as the
1.315 +// using instruction. For Phi-USE's, the USE is in the predecessor block
1.316 +// along the corresponding path.
1.317 +Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
1.318 + // CFG uses are their own block
1.319 + if( use->is_CFG() )
1.320 + return use;
1.321 +
1.322 + if( use->is_Phi() ) { // Phi uses in prior block
1.323 + // Grab the first Phi use; there may be many.
1.324 + // Each will be handled as a seperate iteration of
1.325 + // the "while( phi->outcnt() )" loop.
1.326 + uint j;
1.327 + for( j = 1; j < use->req(); j++ )
1.328 + if( use->in(j) == def )
1.329 + break;
1.330 + assert( j < use->req(), "def should be among use's inputs" );
1.331 + return use->in(0)->in(j);
1.332 + }
1.333 + // Normal (non-phi) use
1.334 + Node *use_blk = get_ctrl(use);
1.335 + // Some uses are directly attached to the old (and going away)
1.336 + // false and true branches.
1.337 + if( use_blk == old_false ) {
1.338 + use_blk = new_false;
1.339 + set_ctrl(use, new_false);
1.340 + }
1.341 + if( use_blk == old_true ) {
1.342 + use_blk = new_true;
1.343 + set_ctrl(use, new_true);
1.344 + }
1.345 +
1.346 + if (use_blk == NULL) { // He's dead, Jim
1.347 + _igvn.hash_delete(use);
1.348 + _igvn.subsume_node(use, C->top());
1.349 + }
1.350 +
1.351 + return use_blk;
1.352 +}
1.353 +
1.354 +//------------------------------handle_use-------------------------------------
1.355 +// Handle uses of the merge point. Basically, split-if makes the merge point
1.356 +// go away so all uses of the merge point must go away as well. Most block
1.357 +// local uses have already been split-up, through the merge point. Uses from
1.358 +// far below the merge point can't always be split up (e.g., phi-uses are
1.359 +// pinned) and it makes too much stuff live. Instead we use a path-based
1.360 +// solution to move uses down.
1.361 +//
1.362 +// If the use is along the pre-split-CFG true branch, then the new use will
1.363 +// be from the post-split-CFG true merge point. Vice-versa for the false
1.364 +// path. Some uses will be along both paths; then we sink the use to the
1.365 +// post-dominating location; we may need to insert a Phi there.
1.366 +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 ) {
1.367 +
1.368 + Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
1.369 + if( !use_blk ) return; // He's dead, Jim
1.370 +
1.371 + // Walk up the dominator tree until I hit either the old IfFalse, the old
1.372 + // IfTrue or the old If. Insert Phis where needed.
1.373 + Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
1.374 +
1.375 + // Found where this USE goes. Re-point him.
1.376 + uint i;
1.377 + for( i = 0; i < use->req(); i++ )
1.378 + if( use->in(i) == def )
1.379 + break;
1.380 + assert( i < use->req(), "def should be among use's inputs" );
1.381 + _igvn.hash_delete(use);
1.382 + use->set_req(i, new_def);
1.383 + _igvn._worklist.push(use);
1.384 +}
1.385 +
1.386 +//------------------------------do_split_if------------------------------------
1.387 +// Found an If getting its condition-code input from a Phi in the same block.
1.388 +// Split thru the Region.
1.389 +void PhaseIdealLoop::do_split_if( Node *iff ) {
1.390 +#ifndef PRODUCT
1.391 + if( PrintOpto && VerifyLoopOptimizations )
1.392 + tty->print_cr("Split-if");
1.393 +#endif
1.394 + C->set_major_progress();
1.395 + Node *region = iff->in(0);
1.396 + Node *region_dom = idom(region);
1.397 +
1.398 + // We are going to clone this test (and the control flow with it) up through
1.399 + // the incoming merge point. We need to empty the current basic block.
1.400 + // Clone any instructions which must be in this block up through the merge
1.401 + // point.
1.402 + DUIterator i, j;
1.403 + bool progress = true;
1.404 + while (progress) {
1.405 + progress = false;
1.406 + for (i = region->outs(); region->has_out(i); i++) {
1.407 + Node* n = region->out(i);
1.408 + if( n == region ) continue;
1.409 + // The IF to be split is OK.
1.410 + if( n == iff ) continue;
1.411 + if( !n->is_Phi() ) { // Found pinned memory op or such
1.412 + if (split_up(n, region, iff)) {
1.413 + i = region->refresh_out_pos(i);
1.414 + progress = true;
1.415 + }
1.416 + continue;
1.417 + }
1.418 + assert( n->in(0) == region, "" );
1.419 +
1.420 + // Recursively split up all users of a Phi
1.421 + for (j = n->outs(); n->has_out(j); j++) {
1.422 + Node* m = n->out(j);
1.423 + // If m is dead, throw it away, and declare progress
1.424 + if (_nodes[m->_idx] == NULL) {
1.425 + _igvn.remove_dead_node(m);
1.426 + // fall through
1.427 + }
1.428 + else if (m != iff && split_up(m, region, iff)) {
1.429 + // fall through
1.430 + } else {
1.431 + continue;
1.432 + }
1.433 + // Something unpredictable changed.
1.434 + // Tell the iterators to refresh themselves, and rerun the loop.
1.435 + i = region->refresh_out_pos(i);
1.436 + j = region->refresh_out_pos(j);
1.437 + progress = true;
1.438 + }
1.439 + }
1.440 + }
1.441 +
1.442 + // Now we have no instructions in the block containing the IF.
1.443 + // Split the IF.
1.444 + Node *new_iff = split_thru_region( iff, region );
1.445 +
1.446 + // Replace both uses of 'new_iff' with Regions merging True/False
1.447 + // paths. This makes 'new_iff' go dead.
1.448 + Node *old_false, *old_true;
1.449 + Node *new_false, *new_true;
1.450 + for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
1.451 + Node *ifp = iff->last_out(j2);
1.452 + assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
1.453 + ifp->set_req(0, new_iff);
1.454 + Node *ifpx = split_thru_region( ifp, region );
1.455 +
1.456 + // Replace 'If' projection of a Region with a Region of
1.457 + // 'If' projections.
1.458 + ifpx->set_req(0, ifpx); // A TRUE RegionNode
1.459 +
1.460 + // Setup dominator info
1.461 + set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
1.462 +
1.463 + // Check for splitting loop tails
1.464 + if( get_loop(iff)->tail() == ifp )
1.465 + get_loop(iff)->_tail = ifpx;
1.466 +
1.467 + // Replace in the graph with lazy-update mechanism
1.468 + new_iff->set_req(0, new_iff); // hook self so it does not go dead
1.469 + lazy_replace_proj( ifp, ifpx );
1.470 + new_iff->set_req(0, region);
1.471 +
1.472 + // Record bits for later xforms
1.473 + if( ifp->Opcode() == Op_IfFalse ) {
1.474 + old_false = ifp;
1.475 + new_false = ifpx;
1.476 + } else {
1.477 + old_true = ifp;
1.478 + new_true = ifpx;
1.479 + }
1.480 + }
1.481 + _igvn.remove_dead_node(new_iff);
1.482 + // Lazy replace IDOM info with the region's dominator
1.483 + lazy_replace( iff, region_dom );
1.484 +
1.485 + // Now make the original merge point go dead, by handling all its uses.
1.486 + small_cache region_cache;
1.487 + // Preload some control flow in region-cache
1.488 + region_cache.lru_insert( new_false, new_false );
1.489 + region_cache.lru_insert( new_true , new_true );
1.490 + // Now handle all uses of the splitting block
1.491 + for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {
1.492 + Node* phi = region->last_out(k);
1.493 + if( !phi->in(0) ) { // Dead phi? Remove it
1.494 + _igvn.remove_dead_node(phi);
1.495 + continue;
1.496 + }
1.497 + assert( phi->in(0) == region, "" );
1.498 + if( phi == region ) { // Found the self-reference
1.499 + phi->set_req(0, NULL);
1.500 + continue; // Break the self-cycle
1.501 + }
1.502 + // Expected common case: Phi hanging off of Region
1.503 + if( phi->is_Phi() ) {
1.504 + // Need a per-def cache. Phi represents a def, so make a cache
1.505 + small_cache phi_cache;
1.506 +
1.507 + // Inspect all Phi uses to make the Phi go dead
1.508 + for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
1.509 + Node* use = phi->last_out(l);
1.510 + // Compute the new DEF for this USE. New DEF depends on the path
1.511 + // taken from the original DEF to the USE. The new DEF may be some
1.512 + // collection of PHI's merging values from different paths. The Phis
1.513 + // inserted depend only on the location of the USE. We use a
1.514 + // 2-element cache to handle multiple uses from the same block.
1.515 + handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );
1.516 + } // End of while phi has uses
1.517 +
1.518 + // Because handle_use might relocate region->_out,
1.519 + // we must refresh the iterator.
1.520 + k = region->last_outs(kmin);
1.521 +
1.522 + // Remove the dead Phi
1.523 + _igvn.remove_dead_node( phi );
1.524 +
1.525 + } else {
1.526 + // Random memory op guarded by Region. Compute new DEF for USE.
1.527 + handle_use( phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true );
1.528 + }
1.529 +
1.530 + } // End of while merge point has phis
1.531 +
1.532 + // Any leftover bits in the splitting block must not have depended on local
1.533 + // Phi inputs (these have already been split-up). Hence it's safe to hoist
1.534 + // these guys to the dominating point.
1.535 + lazy_replace( region, region_dom );
1.536 +#ifndef PRODUCT
1.537 + if( VerifyLoopOptimizations ) verify();
1.538 +#endif
1.539 +}
