split_if.cpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 1999, 2010, 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 "incls/_precompiled.incl" 26#include "incls/_split_if.cpp.incl" 27 28 29//------------------------------split_thru_region------------------------------ 30// Split Node 'n' through merge point. 31Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) { 32 uint wins = 0; 33 assert( n->is_CFG(), "" ); 34 assert( region->is_Region(), "" ); 35 Node *r = new (C, region->req()) RegionNode( region->req() ); 36 IdealLoopTree *loop = get_loop( n ); 37 for( uint i = 1; i < region->req(); i++ ) { 38 Node *x = n->clone(); 39 Node *in0 = n->in(0); 40 if( in0->in(0) == region ) x->set_req( 0, in0->in(i) ); 41 for( uint j = 1; j < n->req(); j++ ) { 42 Node *in = n->in(j); 43 if( get_ctrl(in) == region ) 44 x->set_req( j, in->in(i) ); 45 } 46 _igvn.register_new_node_with_optimizer(x); 47 set_loop(x, loop); 48 set_idom(x, x->in(0), dom_depth(x->in(0))+1); 49 r->init_req(i, x); 50 } 51 52 // Record region 53 r->set_req(0,region); // Not a TRUE RegionNode 54 _igvn.register_new_node_with_optimizer(r); 55 set_loop(r, loop); 56 if( !loop->_child ) 57 loop->_body.push(r); 58 return r; 59} 60 61//------------------------------split_up--------------------------------------- 62// Split block-local op up through the phis to empty the current block 63bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) { 64 if( n->is_CFG() ) { 65 assert( n->in(0) != blk1, "Lousy candidate for split-if" ); 66 return false; 67 } 68 if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 ) 69 return false; // Not block local 70 if( n->is_Phi() ) return false; // Local PHIs are expected 71 72 // Recursively split-up inputs 73 for (uint i = 1; i < n->req(); i++) { 74 if( split_up( n->in(i), blk1, blk2 ) ) { 75 // Got split recursively and self went dead? 76 if (n->outcnt() == 0) 77 _igvn.remove_dead_node(n); 78 return true; 79 } 80 } 81 82 // Check for needing to clone-up a compare. Can't do that, it forces 83 // another (nested) split-if transform. Instead, clone it "down". 84 if( n->is_Cmp() ) { 85 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF"); 86 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove 87 // sequence can have no other users and it must all reside in the split-if 88 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below - 89 // private, per-use versions of the Cmp and Bool are made. These sink to 90 // the CMove block. If the CMove is in the split-if block, then in the 91 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up. 92 Node *bol, *cmov; 93 if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() && 94 (bol = n->unique_out()->as_Bool()) && 95 (get_ctrl(bol) == blk1 || 96 get_ctrl(bol) == blk2) && 97 bol->outcnt() == 1 && 98 bol->unique_out()->is_CMove() && 99 (cmov = bol->unique_out()->as_CMove()) && 100 (get_ctrl(cmov) == blk1 || 101 get_ctrl(cmov) == blk2) ) ) { 102 103 // Must clone down 104#ifndef PRODUCT 105 if( PrintOpto && VerifyLoopOptimizations ) { 106 tty->print("Cloning down: "); 107 n->dump(); 108 } 109#endif 110 // Clone down any block-local BoolNode uses of this CmpNode 111 for (DUIterator i = n->outs(); n->has_out(i); i++) { 112 Node* bol = n->out(i); 113 assert( bol->is_Bool(), "" ); 114 if (bol->outcnt() == 1) { 115 Node* use = bol->unique_out(); 116 Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use); 117 if (use_c == blk1 || use_c == blk2) { 118 continue; 119 } 120 } 121 if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) { 122 // Recursively sink any BoolNode 123#ifndef PRODUCT 124 if( PrintOpto && VerifyLoopOptimizations ) { 125 tty->print("Cloning down: "); 126 bol->dump(); 127 } 128#endif 129 for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) { 130 // Uses are either IfNodes or CMoves 131 Node* iff = bol->last_out(j); 132 assert( iff->in(1) == bol, "" ); 133 // Get control block of either the CMove or the If input 134 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff); 135 Node *x = bol->clone(); 136 register_new_node(x, iff_ctrl); 137 _igvn.hash_delete(iff); 138 iff->set_req(1, x); 139 _igvn._worklist.push(iff); 140 } 141 _igvn.remove_dead_node( bol ); 142 --i; 143 } 144 } 145 // Clone down this CmpNode 146 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) { 147 Node* bol = n->last_out(j); 148 assert( bol->in(1) == n, "" ); 149 Node *x = n->clone(); 150 register_new_node(x, get_ctrl(bol)); 151 _igvn.hash_delete(bol); 152 bol->set_req(1, x); 153 _igvn._worklist.push(bol); 154 } 155 _igvn.remove_dead_node( n ); 156 157 return true; 158 } 159 } 160 161 // See if splitting-up a Store. Any anti-dep loads must go up as 162 // well. An anti-dep load might be in the wrong block, because in 163 // this particular layout/schedule we ignored anti-deps and allow 164 // memory to be alive twice. This only works if we do the same 165 // operations on anti-dep loads as we do their killing stores. 166 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) { 167 // Get store's memory slice 168 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr()); 169 170 // Get memory-phi anti-dep loads will be using 171 Node *memphi = n->in(MemNode::Memory); 172 assert( memphi->is_Phi(), "" ); 173 // Hoist any anti-dep load to the splitting block; 174 // it will then "split-up". 175 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) { 176 Node *load = memphi->fast_out(i); 177 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) ) 178 set_ctrl(load,blk1); 179 } 180 } 181 182 // Found some other Node; must clone it up 183#ifndef PRODUCT 184 if( PrintOpto && VerifyLoopOptimizations ) { 185 tty->print("Cloning up: "); 186 n->dump(); 187 } 188#endif 189 190 // ConvI2L may have type information on it which becomes invalid if 191 // it moves up in the graph so change any clones so widen the type 192 // to TypeLong::INT when pushing it up. 193 const Type* rtype = NULL; 194 if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) { 195 rtype = TypeLong::INT; 196 } 197 198 // Now actually split-up this guy. One copy per control path merging. 199 Node *phi = PhiNode::make_blank(blk1, n); 200 for( uint j = 1; j < blk1->req(); j++ ) { 201 Node *x = n->clone(); 202 // Widen the type of the ConvI2L when pushing up. 203 if (rtype != NULL) x->as_Type()->set_type(rtype); 204 if( n->in(0) && n->in(0) == blk1 ) 205 x->set_req( 0, blk1->in(j) ); 206 for( uint i = 1; i < n->req(); i++ ) { 207 Node *m = n->in(i); 208 if( get_ctrl(m) == blk1 ) { 209 assert( m->in(0) == blk1, "" ); 210 x->set_req( i, m->in(j) ); 211 } 212 } 213 register_new_node( x, blk1->in(j) ); 214 phi->init_req( j, x ); 215 } 216 // Announce phi to optimizer 217 register_new_node(phi, blk1); 218 219 // Remove cloned-up value from optimizer; use phi instead 220 _igvn.hash_delete(n); 221 _igvn.subsume_node( n, phi ); 222 223 // (There used to be a self-recursive call to split_up() here, 224 // but it is not needed. All necessary forward walking is done 225 // by do_split_if() below.) 226 227 return true; 228} 229 230//------------------------------register_new_node------------------------------ 231void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) { 232 assert(!n->is_CFG(), "must be data node"); 233 _igvn.register_new_node_with_optimizer(n); 234 set_ctrl(n, blk); 235 IdealLoopTree *loop = get_loop(blk); 236 if( !loop->_child ) 237 loop->_body.push(n); 238} 239 240//------------------------------small_cache------------------------------------ 241struct small_cache : public Dict { 242 243 small_cache() : Dict( cmpkey, hashptr ) {} 244 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); } 245 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); } 246}; 247 248//------------------------------spinup----------------------------------------- 249// "Spin up" the dominator tree, starting at the use site and stopping when we 250// find the post-dominating point. 251 252// We must be at the merge point which post-dominates 'new_false' and 253// 'new_true'. Figure out which edges into the RegionNode eventually lead up 254// to false and which to true. Put in a PhiNode to merge values; plug in 255// the appropriate false-arm or true-arm values. If some path leads to the 256// original IF, then insert a Phi recursively. 257Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) { 258 if (use_blk->is_top()) // Handle dead uses 259 return use_blk; 260 Node *prior_n = (Node*)0xdeadbeef; 261 Node *n = use_blk; // Get path input 262 assert( use_blk != iff_dom, "" ); 263 // Here's the "spinup" the dominator tree loop. Do a cache-check 264 // along the way, in case we've come this way before. 265 while( n != iff_dom ) { // Found post-dominating point? 266 prior_n = n; 267 n = idom(n); // Search higher 268 Node *s = cache->probe( prior_n ); // Check cache 269 if( s ) return s; // Cache hit! 270 } 271 272 Node *phi_post; 273 if( prior_n == new_false || prior_n == new_true ) { 274 phi_post = def->clone(); 275 phi_post->set_req(0, prior_n ); 276 register_new_node(phi_post, prior_n); 277 } else { 278 // This method handles both control uses (looking for Regions) or data 279 // uses (looking for Phis). If looking for a control use, then we need 280 // to insert a Region instead of a Phi; however Regions always exist 281 // previously (the hash_find_insert below would always hit) so we can 282 // return the existing Region. 283 if( def->is_CFG() ) { 284 phi_post = prior_n; // If looking for CFG, return prior 285 } else { 286 assert( def->is_Phi(), "" ); 287 assert( prior_n->is_Region(), "must be a post-dominating merge point" ); 288 289 // Need a Phi here 290 phi_post = PhiNode::make_blank(prior_n, def); 291 // Search for both true and false on all paths till find one. 292 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths 293 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) ); 294 Node *t = _igvn.hash_find_insert(phi_post); 295 if( t ) { // See if we already have this one 296 // phi_post will not be used, so kill it 297 _igvn.remove_dead_node(phi_post); 298 phi_post->destruct(); 299 phi_post = t; 300 } else { 301 register_new_node( phi_post, prior_n ); 302 } 303 } 304 } 305 306 // Update cache everywhere 307 prior_n = (Node*)0xdeadbeef; // Reset IDOM walk 308 n = use_blk; // Get path input 309 // Spin-up the idom tree again, basically doing path-compression. 310 // Insert cache entries along the way, so that if we ever hit this 311 // point in the IDOM tree again we'll stop immediately on a cache hit. 312 while( n != iff_dom ) { // Found post-dominating point? 313 prior_n = n; 314 n = idom(n); // Search higher 315 cache->lru_insert( prior_n, phi_post ); // Fill cache 316 } // End of while not gone high enough 317 318 return phi_post; 319} 320 321//------------------------------find_use_block--------------------------------- 322// Find the block a USE is in. Normally USE's are in the same block as the 323// using instruction. For Phi-USE's, the USE is in the predecessor block 324// along the corresponding path. 325Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) { 326 // CFG uses are their own block 327 if( use->is_CFG() ) 328 return use; 329 330 if( use->is_Phi() ) { // Phi uses in prior block 331 // Grab the first Phi use; there may be many. 332 // Each will be handled as a separate iteration of 333 // the "while( phi->outcnt() )" loop. 334 uint j; 335 for( j = 1; j < use->req(); j++ ) 336 if( use->in(j) == def ) 337 break; 338 assert( j < use->req(), "def should be among use's inputs" ); 339 return use->in(0)->in(j); 340 } 341 // Normal (non-phi) use 342 Node *use_blk = get_ctrl(use); 343 // Some uses are directly attached to the old (and going away) 344 // false and true branches. 345 if( use_blk == old_false ) { 346 use_blk = new_false; 347 set_ctrl(use, new_false); 348 } 349 if( use_blk == old_true ) { 350 use_blk = new_true; 351 set_ctrl(use, new_true); 352 } 353 354 if (use_blk == NULL) { // He's dead, Jim 355 _igvn.hash_delete(use); 356 _igvn.subsume_node(use, C->top()); 357 } 358 359 return use_blk; 360} 361 362//------------------------------handle_use------------------------------------- 363// Handle uses of the merge point. Basically, split-if makes the merge point 364// go away so all uses of the merge point must go away as well. Most block 365// local uses have already been split-up, through the merge point. Uses from 366// far below the merge point can't always be split up (e.g., phi-uses are 367// pinned) and it makes too much stuff live. Instead we use a path-based 368// solution to move uses down. 369// 370// If the use is along the pre-split-CFG true branch, then the new use will 371// be from the post-split-CFG true merge point. Vice-versa for the false 372// path. Some uses will be along both paths; then we sink the use to the 373// post-dominating location; we may need to insert a Phi there. 374void 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 ) { 375 376 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true); 377 if( !use_blk ) return; // He's dead, Jim 378 379 // Walk up the dominator tree until I hit either the old IfFalse, the old 380 // IfTrue or the old If. Insert Phis where needed. 381 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache ); 382 383 // Found where this USE goes. Re-point him. 384 uint i; 385 for( i = 0; i < use->req(); i++ ) 386 if( use->in(i) == def ) 387 break; 388 assert( i < use->req(), "def should be among use's inputs" ); 389 _igvn.hash_delete(use); 390 use->set_req(i, new_def); 391 _igvn._worklist.push(use); 392} 393 394//------------------------------do_split_if------------------------------------ 395// Found an If getting its condition-code input from a Phi in the same block. 396// Split thru the Region. 397void PhaseIdealLoop::do_split_if( Node *iff ) { 398#ifndef PRODUCT 399 if( PrintOpto && VerifyLoopOptimizations ) 400 tty->print_cr("Split-if"); 401#endif 402 C->set_major_progress(); 403 Node *region = iff->in(0); 404 Node *region_dom = idom(region); 405 406 // We are going to clone this test (and the control flow with it) up through 407 // the incoming merge point. We need to empty the current basic block. 408 // Clone any instructions which must be in this block up through the merge 409 // point. 410 DUIterator i, j; 411 bool progress = true; 412 while (progress) { 413 progress = false; 414 for (i = region->outs(); region->has_out(i); i++) { 415 Node* n = region->out(i); 416 if( n == region ) continue; 417 // The IF to be split is OK. 418 if( n == iff ) continue; 419 if( !n->is_Phi() ) { // Found pinned memory op or such 420 if (split_up(n, region, iff)) { 421 i = region->refresh_out_pos(i); 422 progress = true; 423 } 424 continue; 425 } 426 assert( n->in(0) == region, "" ); 427 428 // Recursively split up all users of a Phi 429 for (j = n->outs(); n->has_out(j); j++) { 430 Node* m = n->out(j); 431 // If m is dead, throw it away, and declare progress 432 if (_nodes[m->_idx] == NULL) { 433 _igvn.remove_dead_node(m); 434 // fall through 435 } 436 else if (m != iff && split_up(m, region, iff)) { 437 // fall through 438 } else { 439 continue; 440 } 441 // Something unpredictable changed. 442 // Tell the iterators to refresh themselves, and rerun the loop. 443 i = region->refresh_out_pos(i); 444 j = region->refresh_out_pos(j); 445 progress = true; 446 } 447 } 448 } 449 450 // Now we have no instructions in the block containing the IF. 451 // Split the IF. 452 Node *new_iff = split_thru_region( iff, region ); 453 454 // Replace both uses of 'new_iff' with Regions merging True/False 455 // paths. This makes 'new_iff' go dead. 456 Node *old_false, *old_true; 457 Node *new_false, *new_true; 458 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) { 459 Node *ifp = iff->last_out(j2); 460 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" ); 461 ifp->set_req(0, new_iff); 462 Node *ifpx = split_thru_region( ifp, region ); 463 464 // Replace 'If' projection of a Region with a Region of 465 // 'If' projections. 466 ifpx->set_req(0, ifpx); // A TRUE RegionNode 467 468 // Setup dominator info 469 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1); 470 471 // Check for splitting loop tails 472 if( get_loop(iff)->tail() == ifp ) 473 get_loop(iff)->_tail = ifpx; 474 475 // Replace in the graph with lazy-update mechanism 476 new_iff->set_req(0, new_iff); // hook self so it does not go dead 477 lazy_replace_proj( ifp, ifpx ); 478 new_iff->set_req(0, region); 479 480 // Record bits for later xforms 481 if( ifp->Opcode() == Op_IfFalse ) { 482 old_false = ifp; 483 new_false = ifpx; 484 } else { 485 old_true = ifp; 486 new_true = ifpx; 487 } 488 } 489 _igvn.remove_dead_node(new_iff); 490 // Lazy replace IDOM info with the region's dominator 491 lazy_replace( iff, region_dom ); 492 493 // Now make the original merge point go dead, by handling all its uses. 494 small_cache region_cache; 495 // Preload some control flow in region-cache 496 region_cache.lru_insert( new_false, new_false ); 497 region_cache.lru_insert( new_true , new_true ); 498 // Now handle all uses of the splitting block 499 for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) { 500 Node* phi = region->last_out(k); 501 if( !phi->in(0) ) { // Dead phi? Remove it 502 _igvn.remove_dead_node(phi); 503 continue; 504 } 505 assert( phi->in(0) == region, "" ); 506 if( phi == region ) { // Found the self-reference 507 phi->set_req(0, NULL); 508 continue; // Break the self-cycle 509 } 510 // Expected common case: Phi hanging off of Region 511 if( phi->is_Phi() ) { 512 // Need a per-def cache. Phi represents a def, so make a cache 513 small_cache phi_cache; 514 515 // Inspect all Phi uses to make the Phi go dead 516 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) { 517 Node* use = phi->last_out(l); 518 // Compute the new DEF for this USE. New DEF depends on the path 519 // taken from the original DEF to the USE. The new DEF may be some 520 // collection of PHI's merging values from different paths. The Phis 521 // inserted depend only on the location of the USE. We use a 522 // 2-element cache to handle multiple uses from the same block. 523 handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true ); 524 } // End of while phi has uses 525 526 // Because handle_use might relocate region->_out, 527 // we must refresh the iterator. 528 k = region->last_outs(kmin); 529 530 // Remove the dead Phi 531 _igvn.remove_dead_node( phi ); 532 533 } else { 534 // Random memory op guarded by Region. Compute new DEF for USE. 535 handle_use( phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true ); 536 } 537 538 } // End of while merge point has phis 539 540 // Any leftover bits in the splitting block must not have depended on local 541 // Phi inputs (these have already been split-up). Hence it's safe to hoist 542 // these guys to the dominating point. 543 lazy_replace( region, region_dom ); 544#ifndef PRODUCT 545 if( VerifyLoopOptimizations ) verify(); 546#endif 547} 548