1 /*
   2  * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "memory/allocation.inline.hpp"
  27 #include "opto/callnode.hpp"
  28 #include "opto/loopnode.hpp"
  29 #include "opto/movenode.hpp"
  30 
  31 
  32 //------------------------------split_thru_region------------------------------
  33 // Split Node 'n' through merge point.
  34 Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
  35   uint wins = 0;
  36   assert( n->is_CFG(), "" );
  37   assert( region->is_Region(), "" );
  38   Node *r = new RegionNode( region->req() );
  39   IdealLoopTree *loop = get_loop( n );
  40   for( uint i = 1; i < region->req(); i++ ) {
  41     Node *x = n->clone();
  42     Node *in0 = n->in(0);
  43     if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
  44     for( uint j = 1; j < n->req(); j++ ) {
  45       Node *in = n->in(j);
  46       if( get_ctrl(in) == region )
  47         x->set_req( j, in->in(i) );
  48     }
  49     _igvn.register_new_node_with_optimizer(x);
  50     set_loop(x, loop);
  51     set_idom(x, x->in(0), dom_depth(x->in(0))+1);
  52     r->init_req(i, x);
  53   }
  54 
  55   // Record region
  56   r->set_req(0,region);         // Not a TRUE RegionNode
  57   _igvn.register_new_node_with_optimizer(r);
  58   set_loop(r, loop);
  59   if( !loop->_child )
  60     loop->_body.push(r);
  61   return r;
  62 }
  63 
  64 //------------------------------split_up---------------------------------------
  65 // Split block-local op up through the phis to empty the current block
  66 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
  67   if( n->is_CFG() ) {
  68     assert( n->in(0) != blk1, "Lousy candidate for split-if" );
  69     return false;
  70   }
  71   if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
  72     return false;               // Not block local
  73   if( n->is_Phi() ) return false; // Local PHIs are expected
  74 
  75   // Recursively split-up inputs
  76   for (uint i = 1; i < n->req(); i++) {
  77     if( split_up( n->in(i), blk1, blk2 ) ) {
  78       // Got split recursively and self went dead?
  79       if (n->outcnt() == 0)
  80         _igvn.remove_dead_node(n);
  81       return true;
  82     }
  83   }
  84 
  85   // Check for needing to clone-up a compare.  Can't do that, it forces
  86   // another (nested) split-if transform.  Instead, clone it "down".
  87   if( n->is_Cmp() ) {
  88     assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
  89     // Check for simple Cmp/Bool/CMove which we can clone-up.  Cmp/Bool/CMove
  90     // sequence can have no other users and it must all reside in the split-if
  91     // block.  Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
  92     // private, per-use versions of the Cmp and Bool are made.  These sink to
  93     // the CMove block.  If the CMove is in the split-if block, then in the
  94     // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
  95     Node *bol, *cmov;
  96     if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
  97           (bol = n->unique_out()->as_Bool()) &&
  98           (get_ctrl(bol) == blk1 ||
  99            get_ctrl(bol) == blk2) &&
 100           bol->outcnt() == 1 &&
 101           bol->unique_out()->is_CMove() &&
 102           (cmov = bol->unique_out()->as_CMove()) &&
 103           (get_ctrl(cmov) == blk1 ||
 104            get_ctrl(cmov) == blk2) ) ) {
 105 
 106       // Must clone down
 107 #ifndef PRODUCT
 108       if( PrintOpto && VerifyLoopOptimizations ) {
 109         tty->print("Cloning down: ");
 110         n->dump();
 111       }
 112 #endif
 113       // Clone down any block-local BoolNode uses of this CmpNode
 114       for (DUIterator i = n->outs(); n->has_out(i); i++) {
 115         Node* bol = n->out(i);
 116         assert( bol->is_Bool(), "" );
 117         if (bol->outcnt() == 1) {
 118           Node* use = bol->unique_out();
 119           Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
 120           if (use_c == blk1 || use_c == blk2) {
 121             continue;
 122           }
 123         }
 124         if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
 125           // Recursively sink any BoolNode
 126 #ifndef PRODUCT
 127           if( PrintOpto && VerifyLoopOptimizations ) {
 128             tty->print("Cloning down: ");
 129             bol->dump();
 130           }
 131 #endif
 132           for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
 133             // Uses are either IfNodes or CMoves
 134             Node* iff = bol->last_out(j);
 135             assert( iff->in(1) == bol, "" );
 136             // Get control block of either the CMove or the If input
 137             Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
 138             Node *x = bol->clone();
 139             register_new_node(x, iff_ctrl);
 140             _igvn.replace_input_of(iff, 1, x);
 141           }
 142           _igvn.remove_dead_node( bol );
 143           --i;
 144         }
 145       }
 146       // Clone down this CmpNode
 147       for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
 148         Node* bol = n->last_out(j);
 149         assert( bol->in(1) == n, "" );
 150         Node *x = n->clone();
 151         register_new_node(x, get_ctrl(bol));
 152         _igvn.replace_input_of(bol, 1, x);
 153       }
 154       _igvn.remove_dead_node( n );
 155 
 156       return true;
 157     }
 158   }
 159 
 160   // See if splitting-up a Store.  Any anti-dep loads must go up as
 161   // well.  An anti-dep load might be in the wrong block, because in
 162   // this particular layout/schedule we ignored anti-deps and allow
 163   // memory to be alive twice.  This only works if we do the same
 164   // operations on anti-dep loads as we do their killing stores.
 165   if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
 166     // Get store's memory slice
 167     int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
 168 
 169     // Get memory-phi anti-dep loads will be using
 170     Node *memphi = n->in(MemNode::Memory);
 171     assert( memphi->is_Phi(), "" );
 172     // Hoist any anti-dep load to the splitting block;
 173     // it will then "split-up".
 174     for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
 175       Node *load = memphi->fast_out(i);
 176       if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
 177         set_ctrl(load,blk1);
 178     }
 179   }
 180 
 181   // Found some other Node; must clone it up
 182 #ifndef PRODUCT
 183   if( PrintOpto && VerifyLoopOptimizations ) {
 184     tty->print("Cloning up: ");
 185     n->dump();
 186   }
 187 #endif
 188 
 189   // ConvI2L may have type information on it which becomes invalid if
 190   // it moves up in the graph so change any clones so widen the type
 191   // to TypeLong::INT when pushing it up.
 192   const Type* rtype = NULL;
 193   if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) {
 194     rtype = TypeLong::INT;
 195   }
 196 
 197   // Now actually split-up this guy.  One copy per control path merging.
 198   Node *phi = PhiNode::make_blank(blk1, n);
 199   for( uint j = 1; j < blk1->req(); j++ ) {
 200     Node *x = n->clone();
 201     // Widen the type of the ConvI2L when pushing up.
 202     if (rtype != NULL) x->as_Type()->set_type(rtype);
 203     if( n->in(0) && n->in(0) == blk1 )
 204       x->set_req( 0, blk1->in(j) );
 205     for( uint i = 1; i < n->req(); i++ ) {
 206       Node *m = n->in(i);
 207       if( get_ctrl(m) == blk1 ) {
 208         assert( m->in(0) == blk1, "" );
 209         x->set_req( i, m->in(j) );
 210       }
 211     }
 212     register_new_node( x, blk1->in(j) );
 213     phi->init_req( j, x );
 214   }
 215   // Announce phi to optimizer
 216   register_new_node(phi, blk1);
 217 
 218   // Remove cloned-up value from optimizer; use phi instead
 219   _igvn.replace_node( n, phi );
 220 
 221   // (There used to be a self-recursive call to split_up() here,
 222   // but it is not needed.  All necessary forward walking is done
 223   // by do_split_if() below.)
 224 
 225   return true;
 226 }
 227 
 228 //------------------------------register_new_node------------------------------
 229 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
 230   assert(!n->is_CFG(), "must be data node");
 231   _igvn.register_new_node_with_optimizer(n);
 232   set_ctrl(n, blk);
 233   IdealLoopTree *loop = get_loop(blk);
 234   if( !loop->_child )
 235     loop->_body.push(n);
 236 }
 237 
 238 //------------------------------small_cache------------------------------------
 239 struct small_cache : public Dict {
 240 
 241   small_cache() : Dict( cmpkey, hashptr ) {}
 242   Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
 243   void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
 244 };
 245 
 246 //------------------------------spinup-----------------------------------------
 247 // "Spin up" the dominator tree, starting at the use site and stopping when we
 248 // find the post-dominating point.
 249 
 250 // We must be at the merge point which post-dominates 'new_false' and
 251 // 'new_true'.  Figure out which edges into the RegionNode eventually lead up
 252 // to false and which to true.  Put in a PhiNode to merge values; plug in
 253 // the appropriate false-arm or true-arm values.  If some path leads to the
 254 // original IF, then insert a Phi recursively.
 255 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
 256   if (use_blk->is_top())        // Handle dead uses
 257     return use_blk;
 258   Node *prior_n = (Node*)0xdeadbeef;
 259   Node *n = use_blk;            // Get path input
 260   assert( use_blk != iff_dom, "" );
 261   // Here's the "spinup" the dominator tree loop.  Do a cache-check
 262   // along the way, in case we've come this way before.
 263   while( n != iff_dom ) {       // Found post-dominating point?
 264     prior_n = n;
 265     n = idom(n);                // Search higher
 266     Node *s = cache->probe( prior_n ); // Check cache
 267     if( s ) return s;           // Cache hit!
 268   }
 269 
 270   Node *phi_post;
 271   if( prior_n == new_false || prior_n == new_true ) {
 272     phi_post = def->clone();
 273     phi_post->set_req(0, prior_n );
 274     register_new_node(phi_post, prior_n);
 275   } else {
 276     // This method handles both control uses (looking for Regions) or data
 277     // uses (looking for Phis).  If looking for a control use, then we need
 278     // to insert a Region instead of a Phi; however Regions always exist
 279     // previously (the hash_find_insert below would always hit) so we can
 280     // return the existing Region.
 281     if( def->is_CFG() ) {
 282       phi_post = prior_n;       // If looking for CFG, return prior
 283     } else {
 284       assert( def->is_Phi(), "" );
 285       assert( prior_n->is_Region(), "must be a post-dominating merge point" );
 286 
 287       // Need a Phi here
 288       phi_post = PhiNode::make_blank(prior_n, def);
 289       // Search for both true and false on all paths till find one.
 290       for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
 291         phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
 292       Node *t = _igvn.hash_find_insert(phi_post);
 293       if( t ) {                 // See if we already have this one
 294         // phi_post will not be used, so kill it
 295         _igvn.remove_dead_node(phi_post);
 296         phi_post->destruct();
 297         phi_post = t;
 298       } else {
 299         register_new_node( phi_post, prior_n );
 300       }
 301     }
 302   }
 303 
 304   // Update cache everywhere
 305   prior_n = (Node*)0xdeadbeef;  // Reset IDOM walk
 306   n = use_blk;                  // Get path input
 307   // Spin-up the idom tree again, basically doing path-compression.
 308   // Insert cache entries along the way, so that if we ever hit this
 309   // point in the IDOM tree again we'll stop immediately on a cache hit.
 310   while( n != iff_dom ) {       // Found post-dominating point?
 311     prior_n = n;
 312     n = idom(n);                // Search higher
 313     cache->lru_insert( prior_n, phi_post ); // Fill cache
 314   } // End of while not gone high enough
 315 
 316   return phi_post;
 317 }
 318 
 319 //------------------------------find_use_block---------------------------------
 320 // Find the block a USE is in.  Normally USE's are in the same block as the
 321 // using instruction.  For Phi-USE's, the USE is in the predecessor block
 322 // along the corresponding path.
 323 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
 324   // CFG uses are their own block
 325   if( use->is_CFG() )
 326     return use;
 327 
 328   if( use->is_Phi() ) {         // Phi uses in prior block
 329     // Grab the first Phi use; there may be many.
 330     // Each will be handled as a separate iteration of
 331     // the "while( phi->outcnt() )" loop.
 332     uint j;
 333     for( j = 1; j < use->req(); j++ )
 334       if( use->in(j) == def )
 335         break;
 336     assert( j < use->req(), "def should be among use's inputs" );
 337     return use->in(0)->in(j);
 338   }
 339   // Normal (non-phi) use
 340   Node *use_blk = get_ctrl(use);
 341   // Some uses are directly attached to the old (and going away)
 342   // false and true branches.
 343   if( use_blk == old_false ) {
 344     use_blk = new_false;
 345     set_ctrl(use, new_false);
 346   }
 347   if( use_blk == old_true ) {
 348     use_blk = new_true;
 349     set_ctrl(use, new_true);
 350   }
 351 
 352   if (use_blk == NULL) {        // He's dead, Jim
 353     _igvn.replace_node(use, C->top());
 354   }
 355 
 356   return use_blk;
 357 }
 358 
 359 //------------------------------handle_use-------------------------------------
 360 // Handle uses of the merge point.  Basically, split-if makes the merge point
 361 // go away so all uses of the merge point must go away as well.  Most block
 362 // local uses have already been split-up, through the merge point.  Uses from
 363 // far below the merge point can't always be split up (e.g., phi-uses are
 364 // pinned) and it makes too much stuff live.  Instead we use a path-based
 365 // solution to move uses down.
 366 //
 367 // If the use is along the pre-split-CFG true branch, then the new use will
 368 // be from the post-split-CFG true merge point.  Vice-versa for the false
 369 // path.  Some uses will be along both paths; then we sink the use to the
 370 // post-dominating location; we may need to insert a Phi there.
 371 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 ) {
 372 
 373   Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
 374   if( !use_blk ) return;        // He's dead, Jim
 375 
 376   // Walk up the dominator tree until I hit either the old IfFalse, the old
 377   // IfTrue or the old If.  Insert Phis where needed.
 378   Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
 379 
 380   // Found where this USE goes.  Re-point him.
 381   uint i;
 382   for( i = 0; i < use->req(); i++ )
 383     if( use->in(i) == def )
 384       break;
 385   assert( i < use->req(), "def should be among use's inputs" );
 386   _igvn.replace_input_of(use, i, new_def);
 387 }
 388 
 389 //------------------------------do_split_if------------------------------------
 390 // Found an If getting its condition-code input from a Phi in the same block.
 391 // Split thru the Region.
 392 void PhaseIdealLoop::do_split_if( Node *iff ) {
 393   if (PrintOpto && VerifyLoopOptimizations) {
 394     tty->print_cr("Split-if");
 395   }
 396   if (TraceLoopOpts) {
 397     tty->print_cr("SplitIf");
 398   }
 399 
 400   C->set_major_progress();
 401   Node *region = iff->in(0);
 402   Node *region_dom = idom(region);
 403 
 404   // We are going to clone this test (and the control flow with it) up through
 405   // the incoming merge point.  We need to empty the current basic block.
 406   // Clone any instructions which must be in this block up through the merge
 407   // point.
 408   DUIterator i, j;
 409   bool progress = true;
 410   while (progress) {
 411     progress = false;
 412     for (i = region->outs(); region->has_out(i); i++) {
 413       Node* n = region->out(i);
 414       if( n == region ) continue;
 415       // The IF to be split is OK.
 416       if( n == iff ) continue;
 417       if( !n->is_Phi() ) {      // Found pinned memory op or such
 418         if (split_up(n, region, iff)) {
 419           i = region->refresh_out_pos(i);
 420           progress = true;
 421         }
 422         continue;
 423       }
 424       assert( n->in(0) == region, "" );
 425 
 426       // Recursively split up all users of a Phi
 427       for (j = n->outs(); n->has_out(j); j++) {
 428         Node* m = n->out(j);
 429         // If m is dead, throw it away, and declare progress
 430         if (_nodes[m->_idx] == NULL) {
 431           _igvn.remove_dead_node(m);
 432           // fall through
 433         }
 434         else if (m != iff && split_up(m, region, iff)) {
 435           // fall through
 436         } else {
 437           continue;
 438         }
 439         // Something unpredictable changed.
 440         // Tell the iterators to refresh themselves, and rerun the loop.
 441         i = region->refresh_out_pos(i);
 442         j = region->refresh_out_pos(j);
 443         progress = true;
 444       }
 445     }
 446   }
 447 
 448   // Now we have no instructions in the block containing the IF.
 449   // Split the IF.
 450   Node *new_iff = split_thru_region( iff, region );
 451 
 452   // Replace both uses of 'new_iff' with Regions merging True/False
 453   // paths.  This makes 'new_iff' go dead.
 454   Node *old_false = NULL, *old_true = NULL;
 455   Node *new_false = NULL, *new_true = NULL;
 456   for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
 457     Node *ifp = iff->last_out(j2);
 458     assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
 459     ifp->set_req(0, new_iff);
 460     Node *ifpx = split_thru_region( ifp, region );
 461 
 462     // Replace 'If' projection of a Region with a Region of
 463     // 'If' projections.
 464     ifpx->set_req(0, ifpx);       // A TRUE RegionNode
 465 
 466     // Setup dominator info
 467     set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
 468 
 469     // Check for splitting loop tails
 470     if( get_loop(iff)->tail() == ifp )
 471       get_loop(iff)->_tail = ifpx;
 472 
 473     // Replace in the graph with lazy-update mechanism
 474     new_iff->set_req(0, new_iff); // hook self so it does not go dead
 475     lazy_replace(ifp, ifpx);
 476     new_iff->set_req(0, region);
 477 
 478     // Record bits for later xforms
 479     if( ifp->Opcode() == Op_IfFalse ) {
 480       old_false = ifp;
 481       new_false = ifpx;
 482     } else {
 483       old_true = ifp;
 484       new_true = ifpx;
 485     }
 486   }
 487   _igvn.remove_dead_node(new_iff);
 488   // Lazy replace IDOM info with the region's dominator
 489   lazy_replace( iff, region_dom );
 490 
 491   // Now make the original merge point go dead, by handling all its uses.
 492   small_cache region_cache;
 493   // Preload some control flow in region-cache
 494   region_cache.lru_insert( new_false, new_false );
 495   region_cache.lru_insert( new_true , new_true  );
 496   // Now handle all uses of the splitting block
 497   for (DUIterator k = region->outs(); region->has_out(k); k++) {
 498     Node* phi = region->out(k);
 499     if (!phi->in(0)) {         // Dead phi?  Remove it
 500       _igvn.remove_dead_node(phi);
 501     } else if (phi == region) { // Found the self-reference
 502       continue;                 // No roll-back of DUIterator
 503     } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
 504       assert(phi->in(0) == region, "Inconsistent graph");
 505       // Need a per-def cache.  Phi represents a def, so make a cache
 506       small_cache phi_cache;
 507 
 508       // Inspect all Phi uses to make the Phi go dead
 509       for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
 510         Node* use = phi->last_out(l);
 511         // Compute the new DEF for this USE.  New DEF depends on the path
 512         // taken from the original DEF to the USE.  The new DEF may be some
 513         // collection of PHI's merging values from different paths.  The Phis
 514         // inserted depend only on the location of the USE.  We use a
 515         // 2-element cache to handle multiple uses from the same block.
 516         handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
 517       } // End of while phi has uses
 518       // Remove the dead Phi
 519       _igvn.remove_dead_node( phi );
 520     } else {
 521       assert(phi->in(0) == region, "Inconsistent graph");
 522       // Random memory op guarded by Region.  Compute new DEF for USE.
 523       handle_use(phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true);
 524     }
 525     // Every path above deletes a use of the region, except for the region
 526     // self-cycle (which is needed by handle_use calling find_use_block
 527     // calling get_ctrl calling get_ctrl_no_update looking for dead
 528     // regions).  So roll back the DUIterator innards.
 529     --k;
 530   } // End of while merge point has phis
 531 
 532   assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
 533   region->set_req(0, NULL);       // Break the self-cycle
 534 
 535   // Any leftover bits in the splitting block must not have depended on local
 536   // Phi inputs (these have already been split-up).  Hence it's safe to hoist
 537   // these guys to the dominating point.
 538   lazy_replace( region, region_dom );
 539 #ifndef PRODUCT
 540   if( VerifyLoopOptimizations ) verify();
 541 #endif
 542 }