1 /* 2 * Copyright (c) 1999, 2023, 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 "opto/addnode.hpp" 26 #include "opto/node.hpp" 27 #include "precompiled.hpp" 28 #include "memory/allocation.inline.hpp" 29 #include "opto/callnode.hpp" 30 #include "opto/loopnode.hpp" 31 #include "opto/movenode.hpp" 32 #include "opto/opaquenode.hpp" 33 34 35 //------------------------------split_thru_region------------------------------ 36 // Split Node 'n' through merge point. 37 RegionNode* PhaseIdealLoop::split_thru_region(Node* n, RegionNode* region) { 38 assert(n->is_CFG(), ""); 39 RegionNode* r = new RegionNode(region->req()); 40 IdealLoopTree* loop = get_loop(n); 41 for (uint i = 1; i < region->req(); i++) { 42 Node* x = n->clone(); 43 Node* in0 = n->in(0); 44 if (in0->in(0) == region) x->set_req(0, in0->in(i)); 45 for (uint j = 1; j < n->req(); j++) { 46 Node* in = n->in(j); 47 if (get_ctrl(in) == region) { 48 x->set_req(j, in->in(i)); 49 } 50 } 51 _igvn.register_new_node_with_optimizer(x); 52 set_loop(x, loop); 53 set_idom(x, x->in(0), dom_depth(x->in(0))+1); 54 r->init_req(i, x); 55 } 56 57 // Record region 58 r->set_req(0,region); // Not a TRUE RegionNode 59 _igvn.register_new_node_with_optimizer(r); 60 set_loop(r, loop); 61 if (!loop->_child) { 62 loop->_body.push(r); 63 } 64 return r; 65 } 66 67 //------------------------------split_up--------------------------------------- 68 // Split block-local op up through the phis to empty the current block 69 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) { 70 if( n->is_CFG() ) { 71 assert( n->in(0) != blk1, "Lousy candidate for split-if" ); 72 return false; 73 } 74 if (!at_relevant_ctrl(n, blk1, blk2)) 75 return false; // Not block local 76 if( n->is_Phi() ) return false; // Local PHIs are expected 77 78 // Recursively split-up inputs 79 for (uint i = 1; i < n->req(); i++) { 80 if( split_up( n->in(i), blk1, blk2 ) ) { 81 // Got split recursively and self went dead? 82 if (n->outcnt() == 0) 83 _igvn.remove_dead_node(n); 84 return true; 85 } 86 } 87 88 if (clone_cmp_loadklass_down(n, blk1, blk2)) { 89 return true; 90 } 91 92 // Check for needing to clone-up a compare. Can't do that, it forces 93 // another (nested) split-if transform. Instead, clone it "down". 94 if (clone_cmp_down(n, blk1, blk2)) { 95 return true; 96 } 97 98 if (subgraph_has_opaque(n)) { 99 Unique_Node_List wq; 100 wq.push(n); 101 for (uint i = 0; i < wq.size(); i++) { 102 Node* m = wq.at(i); 103 if (m->is_If()) { 104 assert(assertion_predicate_has_loop_opaque_node(m->as_If()), "opaque node not reachable from if?"); 105 Node* bol = create_bool_from_template_assertion_predicate(m, nullptr, nullptr, m->in(0)); 106 _igvn.replace_input_of(m, 1, bol); 107 } else { 108 assert(!m->is_CFG(), "not CFG expected"); 109 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 110 Node* u = m->fast_out(j); 111 wq.push(u); 112 } 113 } 114 } 115 } 116 117 if (n->Opcode() == Op_OpaqueZeroTripGuard) { 118 // If this Opaque1 is part of the zero trip guard for a loop: 119 // 1- it can't be shared 120 // 2- the zero trip guard can't be the if that's being split 121 // As a consequence, this node could be assigned control anywhere between its current control and the zero trip guard. 122 // Move it down to get it out of the way of split if and avoid breaking the zero trip guard shape. 123 Node* cmp = n->unique_out(); 124 assert(cmp->Opcode() == Op_CmpI, "bad zero trip guard shape"); 125 Node* bol = cmp->unique_out(); 126 assert(bol->Opcode() == Op_Bool, "bad zero trip guard shape"); 127 Node* iff = bol->unique_out(); 128 assert(iff->Opcode() == Op_If, "bad zero trip guard shape"); 129 set_ctrl(n, iff->in(0)); 130 set_ctrl(cmp, iff->in(0)); 131 set_ctrl(bol, iff->in(0)); 132 return true; 133 } 134 135 // See if splitting-up a Store. Any anti-dep loads must go up as 136 // well. An anti-dep load might be in the wrong block, because in 137 // this particular layout/schedule we ignored anti-deps and allow 138 // memory to be alive twice. This only works if we do the same 139 // operations on anti-dep loads as we do their killing stores. 140 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) { 141 // Get store's memory slice 142 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr()); 143 144 // Get memory-phi anti-dep loads will be using 145 Node *memphi = n->in(MemNode::Memory); 146 assert( memphi->is_Phi(), "" ); 147 // Hoist any anti-dep load to the splitting block; 148 // it will then "split-up". 149 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) { 150 Node *load = memphi->fast_out(i); 151 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) ) 152 set_ctrl(load,blk1); 153 } 154 } 155 156 // Found some other Node; must clone it up 157 #ifndef PRODUCT 158 if( PrintOpto && VerifyLoopOptimizations ) { 159 tty->print("Cloning up: "); 160 n->dump(); 161 } 162 #endif 163 164 // ConvI2L may have type information on it which becomes invalid if 165 // it moves up in the graph so change any clones so widen the type 166 // to TypeLong::INT when pushing it up. 167 const Type* rtype = nullptr; 168 if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) { 169 rtype = TypeLong::INT; 170 } 171 172 // Now actually split-up this guy. One copy per control path merging. 173 Node *phi = PhiNode::make_blank(blk1, n); 174 for( uint j = 1; j < blk1->req(); j++ ) { 175 Node *x = n->clone(); 176 // Widen the type of the ConvI2L when pushing up. 177 if (rtype != nullptr) x->as_Type()->set_type(rtype); 178 if( n->in(0) && n->in(0) == blk1 ) 179 x->set_req( 0, blk1->in(j) ); 180 for( uint i = 1; i < n->req(); i++ ) { 181 Node *m = n->in(i); 182 if( get_ctrl(m) == blk1 ) { 183 assert( m->in(0) == blk1, "" ); 184 x->set_req( i, m->in(j) ); 185 } 186 } 187 register_new_node( x, blk1->in(j) ); 188 phi->init_req( j, x ); 189 } 190 // Announce phi to optimizer 191 register_new_node(phi, blk1); 192 193 // Remove cloned-up value from optimizer; use phi instead 194 _igvn.replace_node( n, phi ); 195 196 // (There used to be a self-recursive call to split_up() here, 197 // but it is not needed. All necessary forward walking is done 198 // by do_split_if() below.) 199 200 return true; 201 } 202 203 // Look for a (If .. (Bool(CmpP (LoadKlass .. (AddP obj ..)) ..))) and clone all of it down. 204 // There's likely a CheckCastPP on one of the branches of the If, with obj as input. 205 // If the (LoadKlass .. (AddP obj ..)) is not cloned down, then split if transforms this to: (If .. (Bool(CmpP phi1 ..))) 206 // and the CheckCastPP to (CheckCastPP phi2). It's possible then that phi2 is transformed to a CheckCastPP 207 // (through PhiNode::Ideal) and that that CheckCastPP is replaced by another narrower CheckCastPP at the same control 208 // (through ConstraintCastNode::Identity). That could cause the CheckCastPP at the If to become top while (CmpP phi1) 209 // wouldn't constant fold because it's using a different data path. Cloning the whole subgraph down guarantees both the 210 // AddP and CheckCastPP have the same obj input after split if. 211 bool PhaseIdealLoop::clone_cmp_loadklass_down(Node* n, const Node* blk1, const Node* blk2) { 212 if (n->Opcode() == Op_AddP && at_relevant_ctrl(n, blk1, blk2)) { 213 Node_List cmp_nodes; 214 uint old = C->unique(); 215 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 216 Node* u1 = n->fast_out(i); 217 if (u1->Opcode() == Op_LoadNKlass && at_relevant_ctrl(u1, blk1, blk2)) { 218 for (DUIterator_Fast jmax, j = u1->fast_outs(jmax); j < jmax; j++) { 219 Node* u2 = u1->fast_out(j); 220 if (u2->Opcode() == Op_DecodeNKlass && at_relevant_ctrl(u2, blk1, blk2)) { 221 for (DUIterator k = u2->outs(); u2->has_out(k); k++) { 222 Node* u3 = u2->out(k); 223 if (at_relevant_ctrl(u3, blk1, blk2) && clone_cmp_down(u3, blk1, blk2)) { 224 --k; 225 } 226 } 227 for (DUIterator_Fast kmax, k = u2->fast_outs(kmax); k < kmax; k++) { 228 Node* u3 = u2->fast_out(k); 229 if (u3->_idx >= old) { 230 cmp_nodes.push(u3); 231 } 232 } 233 } 234 } 235 } else if (u1->Opcode() == Op_LoadKlass && at_relevant_ctrl(u1, blk1, blk2)) { 236 for (DUIterator j = u1->outs(); u1->has_out(j); j++) { 237 Node* u2 = u1->out(j); 238 if (at_relevant_ctrl(u2, blk1, blk2) && clone_cmp_down(u2, blk1, blk2)) { 239 --j; 240 } 241 } 242 for (DUIterator_Fast kmax, k = u1->fast_outs(kmax); k < kmax; k++) { 243 Node* u2 = u1->fast_out(k); 244 if (u2->_idx >= old) { 245 cmp_nodes.push(u2); 246 } 247 } 248 } 249 } 250 251 for (uint i = 0; i < cmp_nodes.size(); ++i) { 252 Node* cmp = cmp_nodes.at(i); 253 clone_loadklass_nodes_at_cmp_index(n, cmp, 1); 254 clone_loadklass_nodes_at_cmp_index(n, cmp, 2); 255 } 256 if (n->outcnt() == 0) { 257 assert(n->is_dead(), ""); 258 return true; 259 } 260 } 261 return false; 262 } 263 264 bool PhaseIdealLoop::at_relevant_ctrl(Node* n, const Node* blk1, const Node* blk2) { 265 return ctrl_or_self(n) == blk1 || ctrl_or_self(n) == blk2; 266 } 267 268 void PhaseIdealLoop::clone_loadklass_nodes_at_cmp_index(const Node* n, Node* cmp, int i) { 269 Node* decode = cmp->in(i); 270 if (decode->Opcode() == Op_DecodeNKlass) { 271 Node* loadklass = decode->in(1); 272 if (loadklass->Opcode() == Op_LoadNKlass) { 273 Node* addp = loadklass->in(MemNode::Address); 274 if (addp == n) { 275 Node* ctrl = get_ctrl(cmp); 276 Node* decode_clone = decode->clone(); 277 Node* loadklass_clone = loadklass->clone(); 278 Node* addp_clone = addp->clone(); 279 register_new_node(decode_clone, ctrl); 280 register_new_node(loadklass_clone, ctrl); 281 register_new_node(addp_clone, ctrl); 282 _igvn.replace_input_of(cmp, i, decode_clone); 283 _igvn.replace_input_of(decode_clone, 1, loadklass_clone); 284 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone); 285 if (decode->outcnt() == 0) { 286 _igvn.remove_dead_node(decode); 287 } 288 } 289 } 290 } else { 291 Node* loadklass = cmp->in(i); 292 if (loadklass->Opcode() == Op_LoadKlass) { 293 Node* addp = loadklass->in(MemNode::Address); 294 if (addp == n) { 295 Node* ctrl = get_ctrl(cmp); 296 Node* loadklass_clone = loadklass->clone(); 297 Node* addp_clone = addp->clone(); 298 register_new_node(loadklass_clone, ctrl); 299 register_new_node(addp_clone, ctrl); 300 _igvn.replace_input_of(cmp, i, loadklass_clone); 301 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone); 302 if (loadklass->outcnt() == 0) { 303 _igvn.remove_dead_node(loadklass); 304 } 305 } 306 } 307 } 308 } 309 310 bool PhaseIdealLoop::clone_cmp_down(Node* n, const Node* blk1, const Node* blk2) { 311 if( n->is_Cmp() ) { 312 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF"); 313 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove 314 // sequence can have no other users and it must all reside in the split-if 315 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below - 316 // private, per-use versions of the Cmp and Bool are made. These sink to 317 // the CMove block. If the CMove is in the split-if block, then in the 318 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up. 319 Node *bol, *cmov; 320 if (!(n->outcnt() == 1 && n->unique_out()->is_Bool() && 321 (bol = n->unique_out()->as_Bool()) && 322 (at_relevant_ctrl(bol, blk1, blk2) && 323 bol->outcnt() == 1 && 324 bol->unique_out()->is_CMove() && 325 (cmov = bol->unique_out()->as_CMove()) && 326 at_relevant_ctrl(cmov, blk1, blk2)))) { 327 328 // Must clone down 329 #ifndef PRODUCT 330 if( PrintOpto && VerifyLoopOptimizations ) { 331 tty->print("Cloning down: "); 332 n->dump(); 333 } 334 #endif 335 if (!n->is_FastLock()) { 336 // Clone down any block-local BoolNode uses of this CmpNode 337 for (DUIterator i = n->outs(); n->has_out(i); i++) { 338 Node* bol = n->out(i); 339 assert( bol->is_Bool(), "" ); 340 if (bol->outcnt() == 1) { 341 Node* use = bol->unique_out(); 342 if (use->Opcode() == Op_Opaque4) { 343 if (use->outcnt() == 1) { 344 Node* iff = use->unique_out(); 345 assert(iff->is_If(), "unexpected node type"); 346 Node *use_c = iff->in(0); 347 if (use_c == blk1 || use_c == blk2) { 348 continue; 349 } 350 } 351 } else { 352 // We might see an Opaque1 from a loop limit check here 353 assert(use->is_If() || use->is_CMove() || use->Opcode() == Op_Opaque1 || use->is_AllocateArray(), "unexpected node type"); 354 Node *use_c = (use->is_If() || use->is_AllocateArray()) ? use->in(0) : get_ctrl(use); 355 if (use_c == blk1 || use_c == blk2) { 356 assert(use->is_CMove(), "unexpected node type"); 357 continue; 358 } 359 } 360 } 361 if (at_relevant_ctrl(bol, blk1, blk2)) { 362 // Recursively sink any BoolNode 363 #ifndef PRODUCT 364 if( PrintOpto && VerifyLoopOptimizations ) { 365 tty->print("Cloning down: "); 366 bol->dump(); 367 } 368 #endif 369 for (DUIterator j = bol->outs(); bol->has_out(j); j++) { 370 Node* u = bol->out(j); 371 // Uses are either IfNodes, CMoves or Opaque4 372 if (u->Opcode() == Op_Opaque4) { 373 assert(u->in(1) == bol, "bad input"); 374 for (DUIterator_Last kmin, k = u->last_outs(kmin); k >= kmin; --k) { 375 Node* iff = u->last_out(k); 376 assert(iff->is_If() || iff->is_CMove(), "unexpected node type"); 377 assert( iff->in(1) == u, "" ); 378 // Get control block of either the CMove or the If input 379 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff); 380 Node *x1 = bol->clone(); 381 Node *x2 = u->clone(); 382 register_new_node(x1, iff_ctrl); 383 register_new_node(x2, iff_ctrl); 384 _igvn.replace_input_of(x2, 1, x1); 385 _igvn.replace_input_of(iff, 1, x2); 386 } 387 _igvn.remove_dead_node(u); 388 --j; 389 } else { 390 // We might see an Opaque1 from a loop limit check here 391 assert(u->is_If() || u->is_CMove() || u->Opcode() == Op_Opaque1 || u->is_AllocateArray(), "unexpected node type"); 392 assert(u->is_AllocateArray() || u->in(1) == bol, ""); 393 assert(!u->is_AllocateArray() || u->in(AllocateNode::ValidLengthTest) == bol, "wrong input to AllocateArray"); 394 // Get control block of either the CMove or the If input 395 Node *u_ctrl = (u->is_If() || u->is_AllocateArray()) ? u->in(0) : get_ctrl(u); 396 assert((u_ctrl != blk1 && u_ctrl != blk2) || u->is_CMove(), "won't converge"); 397 Node *x = bol->clone(); 398 register_new_node(x, u_ctrl); 399 _igvn.replace_input_of(u, u->is_AllocateArray() ? AllocateNode::ValidLengthTest : 1, x); 400 --j; 401 } 402 } 403 _igvn.remove_dead_node(bol); 404 --i; 405 } 406 } 407 } 408 // Clone down this CmpNode 409 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) { 410 Node* use = n->last_out(j); 411 uint pos = 1; 412 if (n->is_FastLock()) { 413 pos = TypeFunc::Parms + 2; 414 assert(use->is_Lock(), "FastLock only used by LockNode"); 415 } 416 assert(use->in(pos) == n, "" ); 417 Node *x = n->clone(); 418 register_new_node(x, ctrl_or_self(use)); 419 _igvn.replace_input_of(use, pos, x); 420 } 421 _igvn.remove_dead_node(n); 422 423 return true; 424 } 425 } 426 return false; 427 } 428 429 //------------------------------register_new_node------------------------------ 430 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) { 431 assert(!n->is_CFG(), "must be data node"); 432 _igvn.register_new_node_with_optimizer(n); 433 set_ctrl(n, blk); 434 IdealLoopTree *loop = get_loop(blk); 435 if( !loop->_child ) 436 loop->_body.push(n); 437 } 438 439 //------------------------------small_cache------------------------------------ 440 struct small_cache : public Dict { 441 442 small_cache() : Dict( cmpkey, hashptr ) {} 443 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); } 444 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); } 445 }; 446 447 //------------------------------spinup----------------------------------------- 448 // "Spin up" the dominator tree, starting at the use site and stopping when we 449 // find the post-dominating point. 450 451 // We must be at the merge point which post-dominates 'new_false' and 452 // 'new_true'. Figure out which edges into the RegionNode eventually lead up 453 // to false and which to true. Put in a PhiNode to merge values; plug in 454 // the appropriate false-arm or true-arm values. If some path leads to the 455 // original IF, then insert a Phi recursively. 456 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) { 457 if (use_blk->is_top()) // Handle dead uses 458 return use_blk; 459 Node *prior_n = (Node*)((intptr_t)0xdeadbeef); 460 Node *n = use_blk; // Get path input 461 assert( use_blk != iff_dom, "" ); 462 // Here's the "spinup" the dominator tree loop. Do a cache-check 463 // along the way, in case we've come this way before. 464 while( n != iff_dom ) { // Found post-dominating point? 465 prior_n = n; 466 n = idom(n); // Search higher 467 Node *s = cache->probe( prior_n ); // Check cache 468 if( s ) return s; // Cache hit! 469 } 470 471 Node *phi_post; 472 if( prior_n == new_false || prior_n == new_true ) { 473 phi_post = def->clone(); 474 phi_post->set_req(0, prior_n ); 475 register_new_node(phi_post, prior_n); 476 } else { 477 // This method handles both control uses (looking for Regions) or data 478 // uses (looking for Phis). If looking for a control use, then we need 479 // to insert a Region instead of a Phi; however Regions always exist 480 // previously (the hash_find_insert below would always hit) so we can 481 // return the existing Region. 482 if( def->is_CFG() ) { 483 phi_post = prior_n; // If looking for CFG, return prior 484 } else { 485 assert( def->is_Phi(), "" ); 486 assert( prior_n->is_Region(), "must be a post-dominating merge point" ); 487 488 // Need a Phi here 489 phi_post = PhiNode::make_blank(prior_n, def); 490 // Search for both true and false on all paths till find one. 491 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths 492 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) ); 493 Node *t = _igvn.hash_find_insert(phi_post); 494 if( t ) { // See if we already have this one 495 // phi_post will not be used, so kill it 496 _igvn.remove_dead_node(phi_post); 497 phi_post->destruct(&_igvn); 498 phi_post = t; 499 } else { 500 register_new_node( phi_post, prior_n ); 501 } 502 } 503 } 504 505 // Update cache everywhere 506 prior_n = (Node*)((intptr_t)0xdeadbeef); // Reset IDOM walk 507 n = use_blk; // Get path input 508 // Spin-up the idom tree again, basically doing path-compression. 509 // Insert cache entries along the way, so that if we ever hit this 510 // point in the IDOM tree again we'll stop immediately on a cache hit. 511 while( n != iff_dom ) { // Found post-dominating point? 512 prior_n = n; 513 n = idom(n); // Search higher 514 cache->lru_insert( prior_n, phi_post ); // Fill cache 515 } // End of while not gone high enough 516 517 return phi_post; 518 } 519 520 //------------------------------find_use_block--------------------------------- 521 // Find the block a USE is in. Normally USE's are in the same block as the 522 // using instruction. For Phi-USE's, the USE is in the predecessor block 523 // along the corresponding path. 524 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) { 525 // CFG uses are their own block 526 if( use->is_CFG() ) 527 return use; 528 529 if( use->is_Phi() ) { // Phi uses in prior block 530 // Grab the first Phi use; there may be many. 531 // Each will be handled as a separate iteration of 532 // the "while( phi->outcnt() )" loop. 533 uint j; 534 for( j = 1; j < use->req(); j++ ) 535 if( use->in(j) == def ) 536 break; 537 assert( j < use->req(), "def should be among use's inputs" ); 538 return use->in(0)->in(j); 539 } 540 // Normal (non-phi) use 541 Node *use_blk = get_ctrl(use); 542 // Some uses are directly attached to the old (and going away) 543 // false and true branches. 544 if( use_blk == old_false ) { 545 use_blk = new_false; 546 set_ctrl(use, new_false); 547 } 548 if( use_blk == old_true ) { 549 use_blk = new_true; 550 set_ctrl(use, new_true); 551 } 552 553 if (use_blk == nullptr) { // He's dead, Jim 554 _igvn.replace_node(use, C->top()); 555 } 556 557 return use_blk; 558 } 559 560 //------------------------------handle_use------------------------------------- 561 // Handle uses of the merge point. Basically, split-if makes the merge point 562 // go away so all uses of the merge point must go away as well. Most block 563 // local uses have already been split-up, through the merge point. Uses from 564 // far below the merge point can't always be split up (e.g., phi-uses are 565 // pinned) and it makes too much stuff live. Instead we use a path-based 566 // solution to move uses down. 567 // 568 // If the use is along the pre-split-CFG true branch, then the new use will 569 // be from the post-split-CFG true merge point. Vice-versa for the false 570 // path. Some uses will be along both paths; then we sink the use to the 571 // post-dominating location; we may need to insert a Phi there. 572 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 ) { 573 574 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true); 575 if( !use_blk ) return; // He's dead, Jim 576 577 // Walk up the dominator tree until I hit either the old IfFalse, the old 578 // IfTrue or the old If. Insert Phis where needed. 579 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache ); 580 581 // Found where this USE goes. Re-point him. 582 uint i; 583 for( i = 0; i < use->req(); i++ ) 584 if( use->in(i) == def ) 585 break; 586 assert( i < use->req(), "def should be among use's inputs" ); 587 _igvn.replace_input_of(use, i, new_def); 588 } 589 590 //------------------------------do_split_if------------------------------------ 591 // Found an If getting its condition-code input from a Phi in the same block. 592 // Split thru the Region. 593 void PhaseIdealLoop::do_split_if(Node* iff, RegionNode** new_false_region, RegionNode** new_true_region) { 594 if (PrintOpto && VerifyLoopOptimizations) { 595 tty->print_cr("Split-if"); 596 } 597 if (TraceLoopOpts) { 598 tty->print_cr("SplitIf"); 599 } 600 601 C->set_major_progress(); 602 RegionNode *region = iff->in(0)->as_Region(); 603 Node *region_dom = idom(region); 604 605 // We are going to clone this test (and the control flow with it) up through 606 // the incoming merge point. We need to empty the current basic block. 607 // Clone any instructions which must be in this block up through the merge 608 // point. 609 DUIterator i, j; 610 bool progress = true; 611 while (progress) { 612 progress = false; 613 for (i = region->outs(); region->has_out(i); i++) { 614 Node* n = region->out(i); 615 if( n == region ) continue; 616 // The IF to be split is OK. 617 if( n == iff ) continue; 618 if( !n->is_Phi() ) { // Found pinned memory op or such 619 if (split_up(n, region, iff)) { 620 i = region->refresh_out_pos(i); 621 progress = true; 622 } 623 continue; 624 } 625 assert( n->in(0) == region, "" ); 626 627 // Recursively split up all users of a Phi 628 for (j = n->outs(); n->has_out(j); j++) { 629 Node* m = n->out(j); 630 // If m is dead, throw it away, and declare progress 631 if (_loop_or_ctrl[m->_idx] == nullptr) { 632 _igvn.remove_dead_node(m); 633 // fall through 634 } 635 else if (m != iff && split_up(m, region, iff)) { 636 // fall through 637 } else { 638 continue; 639 } 640 // Something unpredictable changed. 641 // Tell the iterators to refresh themselves, and rerun the loop. 642 i = region->refresh_out_pos(i); 643 j = region->refresh_out_pos(j); 644 progress = true; 645 } 646 } 647 } 648 649 // Now we have no instructions in the block containing the IF. 650 // Split the IF. 651 RegionNode *new_iff = split_thru_region(iff, region); 652 653 // Replace both uses of 'new_iff' with Regions merging True/False 654 // paths. This makes 'new_iff' go dead. 655 Node *old_false = nullptr, *old_true = nullptr; 656 RegionNode* new_false = nullptr; 657 RegionNode* new_true = nullptr; 658 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) { 659 Node *ifp = iff->last_out(j2); 660 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" ); 661 ifp->set_req(0, new_iff); 662 RegionNode* ifpx = split_thru_region(ifp, region); 663 664 // Replace 'If' projection of a Region with a Region of 665 // 'If' projections. 666 ifpx->set_req(0, ifpx); // A TRUE RegionNode 667 668 // Setup dominator info 669 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1); 670 671 // Check for splitting loop tails 672 if( get_loop(iff)->tail() == ifp ) 673 get_loop(iff)->_tail = ifpx; 674 675 // Replace in the graph with lazy-update mechanism 676 new_iff->set_req(0, new_iff); // hook self so it does not go dead 677 lazy_replace(ifp, ifpx); 678 new_iff->set_req(0, region); 679 680 // Record bits for later xforms 681 if( ifp->Opcode() == Op_IfFalse ) { 682 old_false = ifp; 683 new_false = ifpx; 684 } else { 685 old_true = ifp; 686 new_true = ifpx; 687 } 688 } 689 _igvn.remove_dead_node(new_iff); 690 // Lazy replace IDOM info with the region's dominator 691 lazy_replace(iff, region_dom); 692 lazy_update(region, region_dom); // idom must be update before handle_uses 693 region->set_req(0, nullptr); // Break the self-cycle. Required for lazy_update to work on region 694 695 // Now make the original merge point go dead, by handling all its uses. 696 small_cache region_cache; 697 // Preload some control flow in region-cache 698 region_cache.lru_insert( new_false, new_false ); 699 region_cache.lru_insert( new_true , new_true ); 700 // Now handle all uses of the splitting block 701 for (DUIterator k = region->outs(); region->has_out(k); k++) { 702 Node* phi = region->out(k); 703 if (!phi->in(0)) { // Dead phi? Remove it 704 _igvn.remove_dead_node(phi); 705 } else if (phi == region) { // Found the self-reference 706 continue; // No roll-back of DUIterator 707 } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region 708 assert(phi->in(0) == region, "Inconsistent graph"); 709 // Need a per-def cache. Phi represents a def, so make a cache 710 small_cache phi_cache; 711 712 // Inspect all Phi uses to make the Phi go dead 713 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) { 714 Node* use = phi->last_out(l); 715 // Compute the new DEF for this USE. New DEF depends on the path 716 // taken from the original DEF to the USE. The new DEF may be some 717 // collection of PHI's merging values from different paths. The Phis 718 // inserted depend only on the location of the USE. We use a 719 // 2-element cache to handle multiple uses from the same block. 720 handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true); 721 } // End of while phi has uses 722 // Remove the dead Phi 723 _igvn.remove_dead_node( phi ); 724 } else { 725 assert(phi->in(0) == region, "Inconsistent graph"); 726 // Random memory op guarded by Region. Compute new DEF for USE. 727 handle_use(phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true); 728 } 729 // Every path above deletes a use of the region, except for the region 730 // self-cycle (which is needed by handle_use calling find_use_block 731 // calling get_ctrl calling get_ctrl_no_update looking for dead 732 // regions). So roll back the DUIterator innards. 733 --k; 734 } // End of while merge point has phis 735 736 _igvn.remove_dead_node(region); 737 738 if (new_false_region != nullptr) { 739 *new_false_region = new_false; 740 } 741 if (new_true_region != nullptr) { 742 *new_true_region = new_true; 743 } 744 745 DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } ); 746 }