1 /* 2 * Copyright (c) 1998, 2018, 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 "ci/ciMethodData.hpp" 27 #include "compiler/compileLog.hpp" 28 #include "gc/shared/barrierSet.hpp" 29 #include "gc/shared/c2/barrierSetC2.hpp" 30 #include "libadt/vectset.hpp" 31 #include "memory/allocation.inline.hpp" 32 #include "memory/resourceArea.hpp" 33 #include "opto/addnode.hpp" 34 #include "opto/callnode.hpp" 35 #include "opto/connode.hpp" 36 #include "opto/convertnode.hpp" 37 #include "opto/divnode.hpp" 38 #include "opto/idealGraphPrinter.hpp" 39 #include "opto/loopnode.hpp" 40 #include "opto/mulnode.hpp" 41 #include "opto/rootnode.hpp" 42 #include "opto/superword.hpp" 43 44 //============================================================================= 45 //------------------------------is_loop_iv------------------------------------- 46 // Determine if a node is Counted loop induction variable. 47 // The method is declared in node.hpp. 48 const Node* Node::is_loop_iv() const { 49 if (this->is_Phi() && !this->as_Phi()->is_copy() && 50 this->as_Phi()->region()->is_CountedLoop() && 51 this->as_Phi()->region()->as_CountedLoop()->phi() == this) { 52 return this; 53 } else { 54 return NULL; 55 } 56 } 57 58 //============================================================================= 59 //------------------------------dump_spec-------------------------------------- 60 // Dump special per-node info 61 #ifndef PRODUCT 62 void LoopNode::dump_spec(outputStream *st) const { 63 if (is_inner_loop()) st->print( "inner " ); 64 if (is_partial_peel_loop()) st->print( "partial_peel " ); 65 if (partial_peel_has_failed()) st->print( "partial_peel_failed " ); 66 } 67 #endif 68 69 //------------------------------is_valid_counted_loop------------------------- 70 bool LoopNode::is_valid_counted_loop() const { 71 if (is_CountedLoop()) { 72 CountedLoopNode* l = as_CountedLoop(); 73 CountedLoopEndNode* le = l->loopexit_or_null(); 74 if (le != NULL && 75 le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) { 76 Node* phi = l->phi(); 77 Node* exit = le->proj_out_or_null(0 /* false */); 78 if (exit != NULL && exit->Opcode() == Op_IfFalse && 79 phi != NULL && phi->is_Phi() && 80 phi->in(LoopNode::LoopBackControl) == l->incr() && 81 le->loopnode() == l && le->stride_is_con()) { 82 return true; 83 } 84 } 85 } 86 return false; 87 } 88 89 //------------------------------get_early_ctrl--------------------------------- 90 // Compute earliest legal control 91 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) { 92 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" ); 93 uint i; 94 Node *early; 95 if (n->in(0) && !n->is_expensive()) { 96 early = n->in(0); 97 if (!early->is_CFG()) // Might be a non-CFG multi-def 98 early = get_ctrl(early); // So treat input as a straight data input 99 i = 1; 100 } else { 101 early = get_ctrl(n->in(1)); 102 i = 2; 103 } 104 uint e_d = dom_depth(early); 105 assert( early, "" ); 106 for (; i < n->req(); i++) { 107 Node *cin = get_ctrl(n->in(i)); 108 assert( cin, "" ); 109 // Keep deepest dominator depth 110 uint c_d = dom_depth(cin); 111 if (c_d > e_d) { // Deeper guy? 112 early = cin; // Keep deepest found so far 113 e_d = c_d; 114 } else if (c_d == e_d && // Same depth? 115 early != cin) { // If not equal, must use slower algorithm 116 // If same depth but not equal, one _must_ dominate the other 117 // and we want the deeper (i.e., dominated) guy. 118 Node *n1 = early; 119 Node *n2 = cin; 120 while (1) { 121 n1 = idom(n1); // Walk up until break cycle 122 n2 = idom(n2); 123 if (n1 == cin || // Walked early up to cin 124 dom_depth(n2) < c_d) 125 break; // early is deeper; keep him 126 if (n2 == early || // Walked cin up to early 127 dom_depth(n1) < c_d) { 128 early = cin; // cin is deeper; keep him 129 break; 130 } 131 } 132 e_d = dom_depth(early); // Reset depth register cache 133 } 134 } 135 136 // Return earliest legal location 137 assert(early == find_non_split_ctrl(early), "unexpected early control"); 138 139 if (n->is_expensive() && !_verify_only && !_verify_me) { 140 assert(n->in(0), "should have control input"); 141 early = get_early_ctrl_for_expensive(n, early); 142 } 143 144 return early; 145 } 146 147 //------------------------------get_early_ctrl_for_expensive--------------------------------- 148 // Move node up the dominator tree as high as legal while still beneficial 149 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) { 150 assert(n->in(0) && n->is_expensive(), "expensive node with control input here"); 151 assert(OptimizeExpensiveOps, "optimization off?"); 152 153 Node* ctl = n->in(0); 154 assert(ctl->is_CFG(), "expensive input 0 must be cfg"); 155 uint min_dom_depth = dom_depth(earliest); 156 #ifdef ASSERT 157 if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) { 158 dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl); 159 assert(false, "Bad graph detected in get_early_ctrl_for_expensive"); 160 } 161 #endif 162 if (dom_depth(ctl) < min_dom_depth) { 163 return earliest; 164 } 165 166 while (1) { 167 Node *next = ctl; 168 // Moving the node out of a loop on the projection of a If 169 // confuses loop predication. So once we hit a Loop in a If branch 170 // that doesn't branch to an UNC, we stop. The code that process 171 // expensive nodes will notice the loop and skip over it to try to 172 // move the node further up. 173 if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) { 174 if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) { 175 break; 176 } 177 next = idom(ctl->in(1)->in(0)); 178 } else if (ctl->is_Proj()) { 179 // We only move it up along a projection if the projection is 180 // the single control projection for its parent: same code path, 181 // if it's a If with UNC or fallthrough of a call. 182 Node* parent_ctl = ctl->in(0); 183 if (parent_ctl == NULL) { 184 break; 185 } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) { 186 next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control(); 187 } else if (parent_ctl->is_If()) { 188 if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) { 189 break; 190 } 191 assert(idom(ctl) == parent_ctl, "strange"); 192 next = idom(parent_ctl); 193 } else if (ctl->is_CatchProj()) { 194 if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) { 195 break; 196 } 197 assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph"); 198 next = parent_ctl->in(0)->in(0)->in(0); 199 } else { 200 // Check if parent control has a single projection (this 201 // control is the only possible successor of the parent 202 // control). If so, we can try to move the node above the 203 // parent control. 204 int nb_ctl_proj = 0; 205 for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) { 206 Node *p = parent_ctl->fast_out(i); 207 if (p->is_Proj() && p->is_CFG()) { 208 nb_ctl_proj++; 209 if (nb_ctl_proj > 1) { 210 break; 211 } 212 } 213 } 214 215 if (nb_ctl_proj > 1) { 216 break; 217 } 218 assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() || 219 BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node"); 220 assert(idom(ctl) == parent_ctl, "strange"); 221 next = idom(parent_ctl); 222 } 223 } else { 224 next = idom(ctl); 225 } 226 if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) { 227 break; 228 } 229 ctl = next; 230 } 231 232 if (ctl != n->in(0)) { 233 _igvn.replace_input_of(n, 0, ctl); 234 _igvn.hash_insert(n); 235 } 236 237 return ctl; 238 } 239 240 241 //------------------------------set_early_ctrl--------------------------------- 242 // Set earliest legal control 243 void PhaseIdealLoop::set_early_ctrl( Node *n ) { 244 Node *early = get_early_ctrl(n); 245 246 // Record earliest legal location 247 set_ctrl(n, early); 248 } 249 250 //------------------------------set_subtree_ctrl------------------------------- 251 // set missing _ctrl entries on new nodes 252 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) { 253 // Already set? Get out. 254 if( _nodes[n->_idx] ) return; 255 // Recursively set _nodes array to indicate where the Node goes 256 uint i; 257 for( i = 0; i < n->req(); ++i ) { 258 Node *m = n->in(i); 259 if( m && m != C->root() ) 260 set_subtree_ctrl( m ); 261 } 262 263 // Fixup self 264 set_early_ctrl( n ); 265 } 266 267 // Create a skeleton strip mined outer loop: a Loop head before the 268 // inner strip mined loop, a safepoint and an exit condition guarded 269 // by an opaque node after the inner strip mined loop with a backedge 270 // to the loop head. The inner strip mined loop is left as it is. Only 271 // once loop optimizations are over, do we adjust the inner loop exit 272 // condition to limit its number of iterations, set the outer loop 273 // exit condition and add Phis to the outer loop head. Some loop 274 // optimizations that operate on the inner strip mined loop need to be 275 // aware of the outer strip mined loop: loop unswitching needs to 276 // clone the outer loop as well as the inner, unrolling needs to only 277 // clone the inner loop etc. No optimizations need to change the outer 278 // strip mined loop as it is only a skeleton. 279 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control, 280 IdealLoopTree* loop, float cl_prob, float le_fcnt, 281 Node*& entry_control, Node*& iffalse) { 282 Node* outer_test = _igvn.intcon(0); 283 set_ctrl(outer_test, C->root()); 284 Node *orig = iffalse; 285 iffalse = iffalse->clone(); 286 _igvn.register_new_node_with_optimizer(iffalse); 287 set_idom(iffalse, idom(orig), dom_depth(orig)); 288 289 IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt); 290 Node *outer_ift = new IfTrueNode (outer_le); 291 Node* outer_iff = orig; 292 _igvn.replace_input_of(outer_iff, 0, outer_le); 293 294 LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift); 295 entry_control = outer_l; 296 297 IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift); 298 IdealLoopTree* parent = loop->_parent; 299 IdealLoopTree* sibling = parent->_child; 300 if (sibling == loop) { 301 parent->_child = outer_ilt; 302 } else { 303 while (sibling->_next != loop) { 304 sibling = sibling->_next; 305 } 306 sibling->_next = outer_ilt; 307 } 308 outer_ilt->_next = loop->_next; 309 outer_ilt->_parent = parent; 310 outer_ilt->_child = loop; 311 outer_ilt->_nest = loop->_nest; 312 loop->_parent = outer_ilt; 313 loop->_next = NULL; 314 loop->_nest++; 315 316 set_loop(iffalse, outer_ilt); 317 register_control(outer_le, outer_ilt, iffalse); 318 register_control(outer_ift, outer_ilt, outer_le); 319 set_idom(outer_iff, outer_le, dom_depth(outer_le)); 320 _igvn.register_new_node_with_optimizer(outer_l); 321 set_loop(outer_l, outer_ilt); 322 set_idom(outer_l, init_control, dom_depth(init_control)+1); 323 324 return outer_ilt; 325 } 326 327 void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) { 328 Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL, 329 Deoptimization::Reason_loop_limit_check, 330 Op_If); 331 Node* iff = new_predicate_proj->in(0); 332 assert(iff->Opcode() == Op_If, "bad graph shape"); 333 Node* conv = iff->in(1); 334 assert(conv->Opcode() == Op_Conv2B, "bad graph shape"); 335 Node* opaq = conv->in(1); 336 assert(opaq->Opcode() == Op_Opaque1, "bad graph shape"); 337 cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit); 338 bol = _igvn.register_new_node_with_optimizer(bol); 339 set_subtree_ctrl(bol); 340 _igvn.replace_input_of(iff, 1, bol); 341 342 #ifndef PRODUCT 343 // report that the loop predication has been actually performed 344 // for this loop 345 if (TraceLoopLimitCheck) { 346 tty->print_cr("Counted Loop Limit Check generated:"); 347 debug_only( bol->dump(2); ) 348 } 349 #endif 350 } 351 352 //------------------------------is_counted_loop-------------------------------- 353 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) { 354 PhaseGVN *gvn = &_igvn; 355 356 // Counted loop head must be a good RegionNode with only 3 not NULL 357 // control input edges: Self, Entry, LoopBack. 358 if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) { 359 return false; 360 } 361 Node *init_control = x->in(LoopNode::EntryControl); 362 Node *back_control = x->in(LoopNode::LoopBackControl); 363 if (init_control == NULL || back_control == NULL) // Partially dead 364 return false; 365 // Must also check for TOP when looking for a dead loop 366 if (init_control->is_top() || back_control->is_top()) 367 return false; 368 369 // Allow funny placement of Safepoint 370 if (back_control->Opcode() == Op_SafePoint) { 371 if (LoopStripMiningIter != 0) { 372 // Leaving the safepoint on the backedge and creating a 373 // CountedLoop will confuse optimizations. We can't move the 374 // safepoint around because its jvm state wouldn't match a new 375 // location. Give up on that loop. 376 return false; 377 } 378 back_control = back_control->in(TypeFunc::Control); 379 } 380 381 // Controlling test for loop 382 Node *iftrue = back_control; 383 uint iftrue_op = iftrue->Opcode(); 384 if (iftrue_op != Op_IfTrue && 385 iftrue_op != Op_IfFalse) 386 // I have a weird back-control. Probably the loop-exit test is in 387 // the middle of the loop and I am looking at some trailing control-flow 388 // merge point. To fix this I would have to partially peel the loop. 389 return false; // Obscure back-control 390 391 // Get boolean guarding loop-back test 392 Node *iff = iftrue->in(0); 393 if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) 394 return false; 395 BoolNode *test = iff->in(1)->as_Bool(); 396 BoolTest::mask bt = test->_test._test; 397 float cl_prob = iff->as_If()->_prob; 398 if (iftrue_op == Op_IfFalse) { 399 bt = BoolTest(bt).negate(); 400 cl_prob = 1.0 - cl_prob; 401 } 402 // Get backedge compare 403 Node *cmp = test->in(1); 404 int cmp_op = cmp->Opcode(); 405 if (cmp_op != Op_CmpI) 406 return false; // Avoid pointer & float compares 407 408 // Find the trip-counter increment & limit. Limit must be loop invariant. 409 Node *incr = cmp->in(1); 410 Node *limit = cmp->in(2); 411 412 // --------- 413 // need 'loop()' test to tell if limit is loop invariant 414 // --------- 415 416 if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit? 417 Node *tmp = incr; // Then reverse order into the CmpI 418 incr = limit; 419 limit = tmp; 420 bt = BoolTest(bt).commute(); // And commute the exit test 421 } 422 if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant 423 return false; 424 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant 425 return false; 426 427 Node* phi_incr = NULL; 428 // Trip-counter increment must be commutative & associative. 429 if (incr->Opcode() == Op_CastII) { 430 incr = incr->in(1); 431 } 432 if (incr->is_Phi()) { 433 if (incr->as_Phi()->region() != x || incr->req() != 3) 434 return false; // Not simple trip counter expression 435 phi_incr = incr; 436 incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi 437 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant 438 return false; 439 } 440 441 Node* trunc1 = NULL; 442 Node* trunc2 = NULL; 443 const TypeInt* iv_trunc_t = NULL; 444 Node* orig_incr = incr; 445 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) { 446 return false; // Funny increment opcode 447 } 448 assert(incr->Opcode() == Op_AddI, "wrong increment code"); 449 450 const TypeInt* limit_t = gvn->type(limit)->is_int(); 451 if (trunc1 != NULL) { 452 // When there is a truncation, we must be sure that after the truncation 453 // the trip counter will end up higher than the limit, otherwise we are looking 454 // at an endless loop. Can happen with range checks. 455 456 // Example: 457 // int i = 0; 458 // while (true) 459 // sum + = array[i]; 460 // i++; 461 // i = i && 0x7fff; 462 // } 463 // 464 // If the array is shorter than 0x8000 this exits through a AIOOB 465 // - Counted loop transformation is ok 466 // If the array is longer then this is an endless loop 467 // - No transformation can be done. 468 469 const TypeInt* incr_t = gvn->type(orig_incr)->is_int(); 470 if (limit_t->_hi > incr_t->_hi) { 471 // if the limit can have a higher value than the increment (before the phi) 472 return false; 473 } 474 } 475 476 // Get merge point 477 Node *xphi = incr->in(1); 478 Node *stride = incr->in(2); 479 if (!stride->is_Con()) { // Oops, swap these 480 if (!xphi->is_Con()) // Is the other guy a constant? 481 return false; // Nope, unknown stride, bail out 482 Node *tmp = xphi; // 'incr' is commutative, so ok to swap 483 xphi = stride; 484 stride = tmp; 485 } 486 if (xphi->Opcode() == Op_CastII) { 487 xphi = xphi->in(1); 488 } 489 // Stride must be constant 490 int stride_con = stride->get_int(); 491 if (stride_con == 0) 492 return false; // missed some peephole opt 493 494 if (!xphi->is_Phi()) 495 return false; // Too much math on the trip counter 496 if (phi_incr != NULL && phi_incr != xphi) 497 return false; 498 PhiNode *phi = xphi->as_Phi(); 499 500 // Phi must be of loop header; backedge must wrap to increment 501 if (phi->region() != x) 502 return false; 503 if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) || 504 (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) { 505 return false; 506 } 507 Node *init_trip = phi->in(LoopNode::EntryControl); 508 509 // If iv trunc type is smaller than int, check for possible wrap. 510 if (!TypeInt::INT->higher_equal(iv_trunc_t)) { 511 assert(trunc1 != NULL, "must have found some truncation"); 512 513 // Get a better type for the phi (filtered thru if's) 514 const TypeInt* phi_ft = filtered_type(phi); 515 516 // Can iv take on a value that will wrap? 517 // 518 // Ensure iv's limit is not within "stride" of the wrap value. 519 // 520 // Example for "short" type 521 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t) 522 // If the stride is +10, then the last value of the induction 523 // variable before the increment (phi_ft->_hi) must be 524 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to 525 // ensure no truncation occurs after the increment. 526 527 if (stride_con > 0) { 528 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con || 529 iv_trunc_t->_lo > phi_ft->_lo) { 530 return false; // truncation may occur 531 } 532 } else if (stride_con < 0) { 533 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con || 534 iv_trunc_t->_hi < phi_ft->_hi) { 535 return false; // truncation may occur 536 } 537 } 538 // No possibility of wrap so truncation can be discarded 539 // Promote iv type to Int 540 } else { 541 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int"); 542 } 543 544 // If the condition is inverted and we will be rolling 545 // through MININT to MAXINT, then bail out. 546 if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice! 547 // Odd stride 548 (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) || 549 // Count down loop rolls through MAXINT 550 ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) || 551 // Count up loop rolls through MININT 552 ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) { 553 return false; // Bail out 554 } 555 556 const TypeInt* init_t = gvn->type(init_trip)->is_int(); 557 558 if (stride_con > 0) { 559 jlong init_p = (jlong)init_t->_lo + stride_con; 560 if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi) 561 return false; // cyclic loop or this loop trips only once 562 } else { 563 jlong init_p = (jlong)init_t->_hi + stride_con; 564 if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo) 565 return false; // cyclic loop or this loop trips only once 566 } 567 568 if (phi_incr != NULL && bt != BoolTest::ne) { 569 // check if there is a possiblity of IV overflowing after the first increment 570 if (stride_con > 0) { 571 if (init_t->_hi > max_jint - stride_con) { 572 return false; 573 } 574 } else { 575 if (init_t->_lo < min_jint - stride_con) { 576 return false; 577 } 578 } 579 } 580 581 // ================================================= 582 // ---- SUCCESS! Found A Trip-Counted Loop! ----- 583 // 584 assert(x->Opcode() == Op_Loop, "regular loops only"); 585 C->print_method(PHASE_BEFORE_CLOOPS, 3); 586 587 Node *hook = new Node(6); 588 589 // =================================================== 590 // Generate loop limit check to avoid integer overflow 591 // in cases like next (cyclic loops): 592 // 593 // for (i=0; i <= max_jint; i++) {} 594 // for (i=0; i < max_jint; i+=2) {} 595 // 596 // 597 // Limit check predicate depends on the loop test: 598 // 599 // for(;i != limit; i++) --> limit <= (max_jint) 600 // for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1) 601 // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride ) 602 // 603 604 // Check if limit is excluded to do more precise int overflow check. 605 bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge); 606 int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1)); 607 608 // If compare points directly to the phi we need to adjust 609 // the compare so that it points to the incr. Limit have 610 // to be adjusted to keep trip count the same and the 611 // adjusted limit should be checked for int overflow. 612 if (phi_incr != NULL) { 613 stride_m += stride_con; 614 } 615 616 if (limit->is_Con()) { 617 int limit_con = limit->get_int(); 618 if ((stride_con > 0 && limit_con > (max_jint - stride_m)) || 619 (stride_con < 0 && limit_con < (min_jint - stride_m))) { 620 // Bailout: it could be integer overflow. 621 return false; 622 } 623 } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) || 624 (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) { 625 // Limit's type may satisfy the condition, for example, 626 // when it is an array length. 627 } else { 628 // Generate loop's limit check. 629 // Loop limit check predicate should be near the loop. 630 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check); 631 if (!limit_check_proj) { 632 // The limit check predicate is not generated if this method trapped here before. 633 #ifdef ASSERT 634 if (TraceLoopLimitCheck) { 635 tty->print("missing loop limit check:"); 636 loop->dump_head(); 637 x->dump(1); 638 } 639 #endif 640 return false; 641 } 642 643 IfNode* check_iff = limit_check_proj->in(0)->as_If(); 644 645 if (!is_dominator(get_ctrl(limit), check_iff->in(0))) { 646 return false; 647 } 648 649 Node* cmp_limit; 650 Node* bol; 651 652 if (stride_con > 0) { 653 cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m)); 654 bol = new BoolNode(cmp_limit, BoolTest::le); 655 } else { 656 cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m)); 657 bol = new BoolNode(cmp_limit, BoolTest::ge); 658 } 659 660 insert_loop_limit_check(limit_check_proj, cmp_limit, bol); 661 } 662 663 // Now we need to canonicalize loop condition. 664 if (bt == BoolTest::ne) { 665 assert(stride_con == 1 || stride_con == -1, "simple increment only"); 666 if (stride_con > 0 && init_t->_hi < limit_t->_lo) { 667 // 'ne' can be replaced with 'lt' only when init < limit. 668 bt = BoolTest::lt; 669 } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) { 670 // 'ne' can be replaced with 'gt' only when init > limit. 671 bt = BoolTest::gt; 672 } else { 673 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check); 674 if (!limit_check_proj) { 675 // The limit check predicate is not generated if this method trapped here before. 676 #ifdef ASSERT 677 if (TraceLoopLimitCheck) { 678 tty->print("missing loop limit check:"); 679 loop->dump_head(); 680 x->dump(1); 681 } 682 #endif 683 return false; 684 } 685 IfNode* check_iff = limit_check_proj->in(0)->as_If(); 686 687 if (!is_dominator(get_ctrl(limit), check_iff->in(0)) || 688 !is_dominator(get_ctrl(init_trip), check_iff->in(0))) { 689 return false; 690 } 691 692 Node* cmp_limit; 693 Node* bol; 694 695 if (stride_con > 0) { 696 cmp_limit = new CmpINode(init_trip, limit); 697 bol = new BoolNode(cmp_limit, BoolTest::lt); 698 } else { 699 cmp_limit = new CmpINode(init_trip, limit); 700 bol = new BoolNode(cmp_limit, BoolTest::gt); 701 } 702 703 insert_loop_limit_check(limit_check_proj, cmp_limit, bol); 704 705 if (stride_con > 0) { 706 // 'ne' can be replaced with 'lt' only when init < limit. 707 bt = BoolTest::lt; 708 } else if (stride_con < 0) { 709 // 'ne' can be replaced with 'gt' only when init > limit. 710 bt = BoolTest::gt; 711 } 712 } 713 } 714 715 if (phi_incr != NULL) { 716 // If compare points directly to the phi we need to adjust 717 // the compare so that it points to the incr. Limit have 718 // to be adjusted to keep trip count the same and we 719 // should avoid int overflow. 720 // 721 // i = init; do {} while(i++ < limit); 722 // is converted to 723 // i = init; do {} while(++i < limit+1); 724 // 725 limit = gvn->transform(new AddINode(limit, stride)); 726 } 727 728 if (incl_limit) { 729 // The limit check guaranties that 'limit <= (max_jint - stride)' so 730 // we can convert 'i <= limit' to 'i < limit+1' since stride != 0. 731 // 732 Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1); 733 limit = gvn->transform(new AddINode(limit, one)); 734 if (bt == BoolTest::le) 735 bt = BoolTest::lt; 736 else if (bt == BoolTest::ge) 737 bt = BoolTest::gt; 738 else 739 ShouldNotReachHere(); 740 } 741 set_subtree_ctrl( limit ); 742 743 if (LoopStripMiningIter == 0) { 744 // Check for SafePoint on backedge and remove 745 Node *sfpt = x->in(LoopNode::LoopBackControl); 746 if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) { 747 lazy_replace( sfpt, iftrue ); 748 if (loop->_safepts != NULL) { 749 loop->_safepts->yank(sfpt); 750 } 751 loop->_tail = iftrue; 752 } 753 } 754 755 // Build a canonical trip test. 756 // Clone code, as old values may be in use. 757 incr = incr->clone(); 758 incr->set_req(1,phi); 759 incr->set_req(2,stride); 760 incr = _igvn.register_new_node_with_optimizer(incr); 761 set_early_ctrl( incr ); 762 _igvn.rehash_node_delayed(phi); 763 phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn ); 764 765 // If phi type is more restrictive than Int, raise to 766 // Int to prevent (almost) infinite recursion in igvn 767 // which can only handle integer types for constants or minint..maxint. 768 if (!TypeInt::INT->higher_equal(phi->bottom_type())) { 769 Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT); 770 nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl)); 771 nphi = _igvn.register_new_node_with_optimizer(nphi); 772 set_ctrl(nphi, get_ctrl(phi)); 773 _igvn.replace_node(phi, nphi); 774 phi = nphi->as_Phi(); 775 } 776 cmp = cmp->clone(); 777 cmp->set_req(1,incr); 778 cmp->set_req(2,limit); 779 cmp = _igvn.register_new_node_with_optimizer(cmp); 780 set_ctrl(cmp, iff->in(0)); 781 782 test = test->clone()->as_Bool(); 783 (*(BoolTest*)&test->_test)._test = bt; 784 test->set_req(1,cmp); 785 _igvn.register_new_node_with_optimizer(test); 786 set_ctrl(test, iff->in(0)); 787 788 // Replace the old IfNode with a new LoopEndNode 789 Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt )); 790 IfNode *le = lex->as_If(); 791 uint dd = dom_depth(iff); 792 set_idom(le, le->in(0), dd); // Update dominance for loop exit 793 set_loop(le, loop); 794 795 // Get the loop-exit control 796 Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue)); 797 798 // Need to swap loop-exit and loop-back control? 799 if (iftrue_op == Op_IfFalse) { 800 Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le)); 801 Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le)); 802 803 loop->_tail = back_control = ift2; 804 set_loop(ift2, loop); 805 set_loop(iff2, get_loop(iffalse)); 806 807 // Lazy update of 'get_ctrl' mechanism. 808 lazy_replace(iffalse, iff2); 809 lazy_replace(iftrue, ift2); 810 811 // Swap names 812 iffalse = iff2; 813 iftrue = ift2; 814 } else { 815 _igvn.rehash_node_delayed(iffalse); 816 _igvn.rehash_node_delayed(iftrue); 817 iffalse->set_req_X( 0, le, &_igvn ); 818 iftrue ->set_req_X( 0, le, &_igvn ); 819 } 820 821 set_idom(iftrue, le, dd+1); 822 set_idom(iffalse, le, dd+1); 823 assert(iff->outcnt() == 0, "should be dead now"); 824 lazy_replace( iff, le ); // fix 'get_ctrl' 825 826 Node *sfpt2 = le->in(0); 827 828 Node* entry_control = init_control; 829 bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL && 830 sfpt2->Opcode() == Op_SafePoint && !loop->_has_call; 831 IdealLoopTree* outer_ilt = NULL; 832 if (strip_mine_loop) { 833 outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop, 834 cl_prob, le->_fcnt, entry_control, 835 iffalse); 836 } 837 838 // Now setup a new CountedLoopNode to replace the existing LoopNode 839 CountedLoopNode *l = new CountedLoopNode(entry_control, back_control); 840 l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve 841 // The following assert is approximately true, and defines the intention 842 // of can_be_counted_loop. It fails, however, because phase->type 843 // is not yet initialized for this loop and its parts. 844 //assert(l->can_be_counted_loop(this), "sanity"); 845 _igvn.register_new_node_with_optimizer(l); 846 set_loop(l, loop); 847 loop->_head = l; 848 // Fix all data nodes placed at the old loop head. 849 // Uses the lazy-update mechanism of 'get_ctrl'. 850 lazy_replace( x, l ); 851 set_idom(l, entry_control, dom_depth(entry_control) + 1); 852 853 if (LoopStripMiningIter == 0 || strip_mine_loop) { 854 // Check for immediately preceding SafePoint and remove 855 if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) { 856 if (strip_mine_loop) { 857 Node* outer_le = outer_ilt->_tail->in(0); 858 Node* sfpt = sfpt2->clone(); 859 sfpt->set_req(0, iffalse); 860 outer_le->set_req(0, sfpt); 861 register_control(sfpt, outer_ilt, iffalse); 862 set_idom(outer_le, sfpt, dom_depth(sfpt)); 863 } 864 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control)); 865 if (loop->_safepts != NULL) { 866 loop->_safepts->yank(sfpt2); 867 } 868 } 869 } 870 871 // Free up intermediate goo 872 _igvn.remove_dead_node(hook); 873 874 #ifdef ASSERT 875 assert(l->is_valid_counted_loop(), "counted loop shape is messed up"); 876 assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" ); 877 #endif 878 #ifndef PRODUCT 879 if (TraceLoopOpts) { 880 tty->print("Counted "); 881 loop->dump_head(); 882 } 883 #endif 884 885 C->print_method(PHASE_AFTER_CLOOPS, 3); 886 887 // Capture bounds of the loop in the induction variable Phi before 888 // subsequent transformation (iteration splitting) obscures the 889 // bounds 890 l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn)); 891 892 if (strip_mine_loop) { 893 l->mark_strip_mined(); 894 l->verify_strip_mined(1); 895 outer_ilt->_head->as_Loop()->verify_strip_mined(1); 896 loop = outer_ilt; 897 } 898 899 return true; 900 } 901 902 //----------------------exact_limit------------------------------------------- 903 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) { 904 assert(loop->_head->is_CountedLoop(), ""); 905 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 906 assert(cl->is_valid_counted_loop(), ""); 907 908 if (ABS(cl->stride_con()) == 1 || 909 cl->limit()->Opcode() == Op_LoopLimit) { 910 // Old code has exact limit (it could be incorrect in case of int overflow). 911 // Loop limit is exact with stride == 1. And loop may already have exact limit. 912 return cl->limit(); 913 } 914 Node *limit = NULL; 915 #ifdef ASSERT 916 BoolTest::mask bt = cl->loopexit()->test_trip(); 917 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected"); 918 #endif 919 if (cl->has_exact_trip_count()) { 920 // Simple case: loop has constant boundaries. 921 // Use jlongs to avoid integer overflow. 922 int stride_con = cl->stride_con(); 923 jlong init_con = cl->init_trip()->get_int(); 924 jlong limit_con = cl->limit()->get_int(); 925 julong trip_cnt = cl->trip_count(); 926 jlong final_con = init_con + trip_cnt*stride_con; 927 int final_int = (int)final_con; 928 // The final value should be in integer range since the loop 929 // is counted and the limit was checked for overflow. 930 assert(final_con == (jlong)final_int, "final value should be integer"); 931 limit = _igvn.intcon(final_int); 932 } else { 933 // Create new LoopLimit node to get exact limit (final iv value). 934 limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride()); 935 register_new_node(limit, cl->in(LoopNode::EntryControl)); 936 } 937 assert(limit != NULL, "sanity"); 938 return limit; 939 } 940 941 //------------------------------Ideal------------------------------------------ 942 // Return a node which is more "ideal" than the current node. 943 // Attempt to convert into a counted-loop. 944 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 945 if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) { 946 phase->C->set_major_progress(); 947 } 948 return RegionNode::Ideal(phase, can_reshape); 949 } 950 951 void LoopNode::verify_strip_mined(int expect_skeleton) const { 952 #ifdef ASSERT 953 const OuterStripMinedLoopNode* outer = NULL; 954 const CountedLoopNode* inner = NULL; 955 if (is_strip_mined()) { 956 assert(is_CountedLoop(), "no Loop should be marked strip mined"); 957 inner = as_CountedLoop(); 958 outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop(); 959 } else if (is_OuterStripMinedLoop()) { 960 outer = this->as_OuterStripMinedLoop(); 961 inner = outer->unique_ctrl_out()->as_CountedLoop(); 962 assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined"); 963 } 964 if (inner != NULL || outer != NULL) { 965 assert(inner != NULL && outer != NULL, "missing loop in strip mined nest"); 966 Node* outer_tail = outer->in(LoopNode::LoopBackControl); 967 Node* outer_le = outer_tail->in(0); 968 assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If"); 969 Node* sfpt = outer_le->in(0); 970 assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?"); 971 Node* inner_out = sfpt->in(0); 972 if (inner_out->outcnt() != 1) { 973 ResourceMark rm; 974 Unique_Node_List wq; 975 976 for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) { 977 Node* u = inner_out->fast_out(i); 978 if (u == sfpt) { 979 continue; 980 } 981 wq.clear(); 982 wq.push(u); 983 bool found_sfpt = false; 984 for (uint next = 0; next < wq.size() && !found_sfpt; next++) { 985 Node *n = wq.at(next); 986 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) { 987 Node* u = n->fast_out(i); 988 if (u == sfpt) { 989 found_sfpt = true; 990 } 991 if (!u->is_CFG()) { 992 wq.push(u); 993 } 994 } 995 } 996 assert(found_sfpt, "no node in loop that's not input to safepoint"); 997 } 998 } 999 CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd(); 1000 assert(cle == inner->loopexit_or_null(), "mismatch"); 1001 bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0; 1002 if (has_skeleton) { 1003 assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node"); 1004 assert(outer->outcnt() == 2, "only phis"); 1005 } else { 1006 assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?"); 1007 uint phis = 0; 1008 for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) { 1009 Node* u = inner->fast_out(i); 1010 if (u->is_Phi()) { 1011 phis++; 1012 } 1013 } 1014 for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) { 1015 Node* u = outer->fast_out(i); 1016 assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop"); 1017 } 1018 uint stores = 0; 1019 for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) { 1020 Node* u = inner_out->fast_out(i); 1021 if (u->is_Store()) { 1022 stores++; 1023 } 1024 } 1025 assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis"); 1026 } 1027 assert(sfpt->outcnt() == 1, "no data node"); 1028 assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node"); 1029 } 1030 #endif 1031 } 1032 1033 //============================================================================= 1034 //------------------------------Ideal------------------------------------------ 1035 // Return a node which is more "ideal" than the current node. 1036 // Attempt to convert into a counted-loop. 1037 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1038 return RegionNode::Ideal(phase, can_reshape); 1039 } 1040 1041 //------------------------------dump_spec-------------------------------------- 1042 // Dump special per-node info 1043 #ifndef PRODUCT 1044 void CountedLoopNode::dump_spec(outputStream *st) const { 1045 LoopNode::dump_spec(st); 1046 if (stride_is_con()) { 1047 st->print("stride: %d ",stride_con()); 1048 } 1049 if (is_pre_loop ()) st->print("pre of N%d" , _main_idx); 1050 if (is_main_loop()) st->print("main of N%d", _idx); 1051 if (is_post_loop()) st->print("post of N%d", _main_idx); 1052 if (is_strip_mined()) st->print(" strip mined"); 1053 } 1054 #endif 1055 1056 //============================================================================= 1057 int CountedLoopEndNode::stride_con() const { 1058 return stride()->bottom_type()->is_int()->get_con(); 1059 } 1060 1061 //============================================================================= 1062 //------------------------------Value----------------------------------------- 1063 const Type* LoopLimitNode::Value(PhaseGVN* phase) const { 1064 const Type* init_t = phase->type(in(Init)); 1065 const Type* limit_t = phase->type(in(Limit)); 1066 const Type* stride_t = phase->type(in(Stride)); 1067 // Either input is TOP ==> the result is TOP 1068 if (init_t == Type::TOP) return Type::TOP; 1069 if (limit_t == Type::TOP) return Type::TOP; 1070 if (stride_t == Type::TOP) return Type::TOP; 1071 1072 int stride_con = stride_t->is_int()->get_con(); 1073 if (stride_con == 1) 1074 return NULL; // Identity 1075 1076 if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) { 1077 // Use jlongs to avoid integer overflow. 1078 jlong init_con = init_t->is_int()->get_con(); 1079 jlong limit_con = limit_t->is_int()->get_con(); 1080 int stride_m = stride_con - (stride_con > 0 ? 1 : -1); 1081 jlong trip_count = (limit_con - init_con + stride_m)/stride_con; 1082 jlong final_con = init_con + stride_con*trip_count; 1083 int final_int = (int)final_con; 1084 // The final value should be in integer range since the loop 1085 // is counted and the limit was checked for overflow. 1086 assert(final_con == (jlong)final_int, "final value should be integer"); 1087 return TypeInt::make(final_int); 1088 } 1089 1090 return bottom_type(); // TypeInt::INT 1091 } 1092 1093 //------------------------------Ideal------------------------------------------ 1094 // Return a node which is more "ideal" than the current node. 1095 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1096 if (phase->type(in(Init)) == Type::TOP || 1097 phase->type(in(Limit)) == Type::TOP || 1098 phase->type(in(Stride)) == Type::TOP) 1099 return NULL; // Dead 1100 1101 int stride_con = phase->type(in(Stride))->is_int()->get_con(); 1102 if (stride_con == 1) 1103 return NULL; // Identity 1104 1105 if (in(Init)->is_Con() && in(Limit)->is_Con()) 1106 return NULL; // Value 1107 1108 // Delay following optimizations until all loop optimizations 1109 // done to keep Ideal graph simple. 1110 if (!can_reshape || phase->C->major_progress()) 1111 return NULL; 1112 1113 const TypeInt* init_t = phase->type(in(Init) )->is_int(); 1114 const TypeInt* limit_t = phase->type(in(Limit))->is_int(); 1115 int stride_p; 1116 jlong lim, ini; 1117 julong max; 1118 if (stride_con > 0) { 1119 stride_p = stride_con; 1120 lim = limit_t->_hi; 1121 ini = init_t->_lo; 1122 max = (julong)max_jint; 1123 } else { 1124 stride_p = -stride_con; 1125 lim = init_t->_hi; 1126 ini = limit_t->_lo; 1127 max = (julong)min_jint; 1128 } 1129 julong range = lim - ini + stride_p; 1130 if (range <= max) { 1131 // Convert to integer expression if it is not overflow. 1132 Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1)); 1133 Node *range = phase->transform(new SubINode(in(Limit), in(Init))); 1134 Node *bias = phase->transform(new AddINode(range, stride_m)); 1135 Node *trip = phase->transform(new DivINode(0, bias, in(Stride))); 1136 Node *span = phase->transform(new MulINode(trip, in(Stride))); 1137 return new AddINode(span, in(Init)); // exact limit 1138 } 1139 1140 if (is_power_of_2(stride_p) || // divisor is 2^n 1141 !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node? 1142 // Convert to long expression to avoid integer overflow 1143 // and let igvn optimizer convert this division. 1144 // 1145 Node* init = phase->transform( new ConvI2LNode(in(Init))); 1146 Node* limit = phase->transform( new ConvI2LNode(in(Limit))); 1147 Node* stride = phase->longcon(stride_con); 1148 Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1)); 1149 1150 Node *range = phase->transform(new SubLNode(limit, init)); 1151 Node *bias = phase->transform(new AddLNode(range, stride_m)); 1152 Node *span; 1153 if (stride_con > 0 && is_power_of_2(stride_p)) { 1154 // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride) 1155 // and avoid generating rounding for division. Zero trip guard should 1156 // guarantee that init < limit but sometimes the guard is missing and 1157 // we can get situation when init > limit. Note, for the empty loop 1158 // optimization zero trip guard is generated explicitly which leaves 1159 // only RCE predicate where exact limit is used and the predicate 1160 // will simply fail forcing recompilation. 1161 Node* neg_stride = phase->longcon(-stride_con); 1162 span = phase->transform(new AndLNode(bias, neg_stride)); 1163 } else { 1164 Node *trip = phase->transform(new DivLNode(0, bias, stride)); 1165 span = phase->transform(new MulLNode(trip, stride)); 1166 } 1167 // Convert back to int 1168 Node *span_int = phase->transform(new ConvL2INode(span)); 1169 return new AddINode(span_int, in(Init)); // exact limit 1170 } 1171 1172 return NULL; // No progress 1173 } 1174 1175 //------------------------------Identity--------------------------------------- 1176 // If stride == 1 return limit node. 1177 Node* LoopLimitNode::Identity(PhaseGVN* phase) { 1178 int stride_con = phase->type(in(Stride))->is_int()->get_con(); 1179 if (stride_con == 1 || stride_con == -1) 1180 return in(Limit); 1181 return this; 1182 } 1183 1184 //============================================================================= 1185 //----------------------match_incr_with_optional_truncation-------------------- 1186 // Match increment with optional truncation: 1187 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16 1188 // Return NULL for failure. Success returns the increment node. 1189 Node* CountedLoopNode::match_incr_with_optional_truncation( 1190 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) { 1191 // Quick cutouts: 1192 if (expr == NULL || expr->req() != 3) return NULL; 1193 1194 Node *t1 = NULL; 1195 Node *t2 = NULL; 1196 const TypeInt* trunc_t = TypeInt::INT; 1197 Node* n1 = expr; 1198 int n1op = n1->Opcode(); 1199 1200 // Try to strip (n1 & M) or (n1 << N >> N) from n1. 1201 if (n1op == Op_AndI && 1202 n1->in(2)->is_Con() && 1203 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) { 1204 // %%% This check should match any mask of 2**K-1. 1205 t1 = n1; 1206 n1 = t1->in(1); 1207 n1op = n1->Opcode(); 1208 trunc_t = TypeInt::CHAR; 1209 } else if (n1op == Op_RShiftI && 1210 n1->in(1) != NULL && 1211 n1->in(1)->Opcode() == Op_LShiftI && 1212 n1->in(2) == n1->in(1)->in(2) && 1213 n1->in(2)->is_Con()) { 1214 jint shift = n1->in(2)->bottom_type()->is_int()->get_con(); 1215 // %%% This check should match any shift in [1..31]. 1216 if (shift == 16 || shift == 8) { 1217 t1 = n1; 1218 t2 = t1->in(1); 1219 n1 = t2->in(1); 1220 n1op = n1->Opcode(); 1221 if (shift == 16) { 1222 trunc_t = TypeInt::SHORT; 1223 } else if (shift == 8) { 1224 trunc_t = TypeInt::BYTE; 1225 } 1226 } 1227 } 1228 1229 // If (maybe after stripping) it is an AddI, we won: 1230 if (n1op == Op_AddI) { 1231 *trunc1 = t1; 1232 *trunc2 = t2; 1233 *trunc_type = trunc_t; 1234 return n1; 1235 } 1236 1237 // failed 1238 return NULL; 1239 } 1240 1241 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) { 1242 if (is_strip_mined()) { 1243 verify_strip_mined(expect_skeleton); 1244 return in(EntryControl)->as_Loop(); 1245 } 1246 return this; 1247 } 1248 1249 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const { 1250 assert(is_strip_mined(), "not a strip mined loop"); 1251 Node* c = in(EntryControl); 1252 if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) { 1253 return NULL; 1254 } 1255 return c->as_OuterStripMinedLoop(); 1256 } 1257 1258 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const { 1259 Node* c = in(LoopBackControl); 1260 if (c == NULL || c->is_top()) { 1261 return NULL; 1262 } 1263 return c->as_IfTrue(); 1264 } 1265 1266 IfTrueNode* CountedLoopNode::outer_loop_tail() const { 1267 LoopNode* l = outer_loop(); 1268 if (l == NULL) { 1269 return NULL; 1270 } 1271 return l->outer_loop_tail(); 1272 } 1273 1274 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const { 1275 IfTrueNode* proj = outer_loop_tail(); 1276 if (proj == NULL) { 1277 return NULL; 1278 } 1279 Node* c = proj->in(0); 1280 if (c == NULL || c->is_top() || c->outcnt() != 2) { 1281 return NULL; 1282 } 1283 return c->as_OuterStripMinedLoopEnd(); 1284 } 1285 1286 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const { 1287 LoopNode* l = outer_loop(); 1288 if (l == NULL) { 1289 return NULL; 1290 } 1291 return l->outer_loop_end(); 1292 } 1293 1294 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const { 1295 IfNode* le = outer_loop_end(); 1296 if (le == NULL) { 1297 return NULL; 1298 } 1299 Node* c = le->proj_out_or_null(false); 1300 if (c == NULL) { 1301 return NULL; 1302 } 1303 return c->as_IfFalse(); 1304 } 1305 1306 IfFalseNode* CountedLoopNode::outer_loop_exit() const { 1307 LoopNode* l = outer_loop(); 1308 if (l == NULL) { 1309 return NULL; 1310 } 1311 return l->outer_loop_exit(); 1312 } 1313 1314 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const { 1315 IfNode* le = outer_loop_end(); 1316 if (le == NULL) { 1317 return NULL; 1318 } 1319 Node* c = le->in(0); 1320 if (c == NULL || c->is_top()) { 1321 return NULL; 1322 } 1323 assert(c->Opcode() == Op_SafePoint, "broken outer loop"); 1324 return c->as_SafePoint(); 1325 } 1326 1327 SafePointNode* CountedLoopNode::outer_safepoint() const { 1328 LoopNode* l = outer_loop(); 1329 if (l == NULL) { 1330 return NULL; 1331 } 1332 return l->outer_safepoint(); 1333 } 1334 1335 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) { 1336 while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() && 1337 ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 && 1338 ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) { 1339 ctrl = ctrl->in(0)->in(0); 1340 } 1341 1342 return ctrl; 1343 } 1344 1345 Node* CountedLoopNode::skip_predicates() { 1346 if (is_main_loop()) { 1347 Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl); 1348 1349 return skip_predicates_from_entry(ctrl); 1350 } 1351 return in(LoopNode::EntryControl); 1352 } 1353 1354 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) { 1355 // Look for the outer & inner strip mined loop, reduce number of 1356 // iterations of the inner loop, set exit condition of outer loop, 1357 // construct required phi nodes for outer loop. 1358 CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop(); 1359 assert(inner_cl->is_strip_mined(), "inner loop should be strip mined"); 1360 Node* inner_iv_phi = inner_cl->phi(); 1361 if (inner_iv_phi == NULL) { 1362 IfNode* outer_le = outer_loop_end(); 1363 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt)); 1364 igvn->replace_node(outer_le, iff); 1365 inner_cl->clear_strip_mined(); 1366 return; 1367 } 1368 CountedLoopEndNode* inner_cle = inner_cl->loopexit(); 1369 1370 int stride = inner_cl->stride_con(); 1371 jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride); 1372 int scaled_iters = (int)scaled_iters_long; 1373 int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride); 1374 const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int(); 1375 jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo; 1376 assert(iter_estimate > 0, "broken"); 1377 if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) { 1378 // Remove outer loop and safepoint (too few iterations) 1379 Node* outer_sfpt = outer_safepoint(); 1380 Node* outer_out = outer_loop_exit(); 1381 igvn->replace_node(outer_out, outer_sfpt->in(0)); 1382 igvn->replace_input_of(outer_sfpt, 0, igvn->C->top()); 1383 inner_cl->clear_strip_mined(); 1384 return; 1385 } 1386 if (iter_estimate <= scaled_iters_long) { 1387 // We would only go through one iteration of 1388 // the outer loop: drop the outer loop but 1389 // keep the safepoint so we don't run for 1390 // too long without a safepoint 1391 IfNode* outer_le = outer_loop_end(); 1392 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt)); 1393 igvn->replace_node(outer_le, iff); 1394 inner_cl->clear_strip_mined(); 1395 return; 1396 } 1397 1398 Node* cle_tail = inner_cle->proj_out(true); 1399 ResourceMark rm; 1400 Node_List old_new; 1401 if (cle_tail->outcnt() > 1) { 1402 // Look for nodes on backedge of inner loop and clone them 1403 Unique_Node_List backedge_nodes; 1404 for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) { 1405 Node* u = cle_tail->fast_out(i); 1406 if (u != inner_cl) { 1407 assert(!u->is_CFG(), "control flow on the backedge?"); 1408 backedge_nodes.push(u); 1409 } 1410 } 1411 uint last = igvn->C->unique(); 1412 for (uint next = 0; next < backedge_nodes.size(); next++) { 1413 Node* n = backedge_nodes.at(next); 1414 old_new.map(n->_idx, n->clone()); 1415 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 1416 Node* u = n->fast_out(i); 1417 assert(!u->is_CFG(), "broken"); 1418 if (u->_idx >= last) { 1419 continue; 1420 } 1421 if (!u->is_Phi()) { 1422 backedge_nodes.push(u); 1423 } else { 1424 assert(u->in(0) == inner_cl, "strange phi on the backedge"); 1425 } 1426 } 1427 } 1428 // Put the clones on the outer loop backedge 1429 Node* le_tail = outer_loop_tail(); 1430 for (uint next = 0; next < backedge_nodes.size(); next++) { 1431 Node *n = old_new[backedge_nodes.at(next)->_idx]; 1432 for (uint i = 1; i < n->req(); i++) { 1433 if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) { 1434 n->set_req(i, old_new[n->in(i)->_idx]); 1435 } 1436 } 1437 if (n->in(0) != NULL && n->in(0) == cle_tail) { 1438 n->set_req(0, le_tail); 1439 } 1440 igvn->register_new_node_with_optimizer(n); 1441 } 1442 } 1443 1444 Node* iv_phi = NULL; 1445 // Make a clone of each phi in the inner loop 1446 // for the outer loop 1447 for (uint i = 0; i < inner_cl->outcnt(); i++) { 1448 Node* u = inner_cl->raw_out(i); 1449 if (u->is_Phi()) { 1450 assert(u->in(0) == inner_cl, "inconsistent"); 1451 Node* phi = u->clone(); 1452 phi->set_req(0, this); 1453 Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx]; 1454 if (be != NULL) { 1455 phi->set_req(LoopNode::LoopBackControl, be); 1456 } 1457 phi = igvn->transform(phi); 1458 igvn->replace_input_of(u, LoopNode::EntryControl, phi); 1459 if (u == inner_iv_phi) { 1460 iv_phi = phi; 1461 } 1462 } 1463 } 1464 Node* cle_out = inner_cle->proj_out(false); 1465 if (cle_out->outcnt() > 1) { 1466 // Look for chains of stores that were sunk 1467 // out of the inner loop and are in the outer loop 1468 for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) { 1469 Node* u = cle_out->fast_out(i); 1470 if (u->is_Store()) { 1471 Node* first = u; 1472 for(;;) { 1473 Node* next = first->in(MemNode::Memory); 1474 if (!next->is_Store() || next->in(0) != cle_out) { 1475 break; 1476 } 1477 first = next; 1478 } 1479 Node* last = u; 1480 for(;;) { 1481 Node* next = NULL; 1482 for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) { 1483 Node* uu = last->fast_out(j); 1484 if (uu->is_Store() && uu->in(0) == cle_out) { 1485 assert(next == NULL, "only one in the outer loop"); 1486 next = uu; 1487 } 1488 } 1489 if (next == NULL) { 1490 break; 1491 } 1492 last = next; 1493 } 1494 Node* phi = NULL; 1495 for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) { 1496 Node* uu = fast_out(j); 1497 if (uu->is_Phi()) { 1498 Node* be = uu->in(LoopNode::LoopBackControl); 1499 if (be->is_Store() && old_new[be->_idx] != NULL) { 1500 assert(false, "store on the backedge + sunk stores: unsupported"); 1501 // drop outer loop 1502 IfNode* outer_le = outer_loop_end(); 1503 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt)); 1504 igvn->replace_node(outer_le, iff); 1505 inner_cl->clear_strip_mined(); 1506 return; 1507 } 1508 if (be == last || be == first->in(MemNode::Memory)) { 1509 assert(phi == NULL, "only one phi"); 1510 phi = uu; 1511 } 1512 } 1513 } 1514 #ifdef ASSERT 1515 for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) { 1516 Node* uu = fast_out(j); 1517 if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) { 1518 if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) { 1519 assert(phi == uu, "what's that phi?"); 1520 } else if (uu->adr_type() == TypePtr::BOTTOM) { 1521 Node* n = uu->in(LoopNode::LoopBackControl); 1522 uint limit = igvn->C->live_nodes(); 1523 uint i = 0; 1524 while (n != uu) { 1525 i++; 1526 assert(i < limit, "infinite loop"); 1527 if (n->is_Proj()) { 1528 n = n->in(0); 1529 } else if (n->is_SafePoint() || n->is_MemBar()) { 1530 n = n->in(TypeFunc::Memory); 1531 } else if (n->is_Phi()) { 1532 n = n->in(1); 1533 } else if (n->is_MergeMem()) { 1534 n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type())); 1535 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) { 1536 n = n->in(MemNode::Memory); 1537 } else { 1538 n->dump(); 1539 ShouldNotReachHere(); 1540 } 1541 } 1542 } 1543 } 1544 } 1545 #endif 1546 if (phi == NULL) { 1547 // If the an entire chains was sunk, the 1548 // inner loop has no phi for that memory 1549 // slice, create one for the outer loop 1550 phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY, 1551 igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))); 1552 phi->set_req(LoopNode::LoopBackControl, last); 1553 phi = igvn->transform(phi); 1554 igvn->replace_input_of(first, MemNode::Memory, phi); 1555 } else { 1556 // Or fix the outer loop fix to include 1557 // that chain of stores. 1558 Node* be = phi->in(LoopNode::LoopBackControl); 1559 assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported"); 1560 if (be == first->in(MemNode::Memory)) { 1561 if (be == phi->in(LoopNode::LoopBackControl)) { 1562 igvn->replace_input_of(phi, LoopNode::LoopBackControl, last); 1563 } else { 1564 igvn->replace_input_of(be, MemNode::Memory, last); 1565 } 1566 } else { 1567 #ifdef ASSERT 1568 if (be == phi->in(LoopNode::LoopBackControl)) { 1569 assert(phi->in(LoopNode::LoopBackControl) == last, ""); 1570 } else { 1571 assert(be->in(MemNode::Memory) == last, ""); 1572 } 1573 #endif 1574 } 1575 } 1576 } 1577 } 1578 } 1579 1580 if (iv_phi != NULL) { 1581 // Now adjust the inner loop's exit condition 1582 Node* limit = inner_cl->limit(); 1583 Node* sub = NULL; 1584 if (stride > 0) { 1585 sub = igvn->transform(new SubINode(limit, iv_phi)); 1586 } else { 1587 sub = igvn->transform(new SubINode(iv_phi, limit)); 1588 } 1589 Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters))); 1590 Node* new_limit = NULL; 1591 if (stride > 0) { 1592 new_limit = igvn->transform(new AddINode(min, iv_phi)); 1593 } else { 1594 new_limit = igvn->transform(new SubINode(iv_phi, min)); 1595 } 1596 Node* cmp = inner_cle->cmp_node()->clone(); 1597 igvn->replace_input_of(cmp, 2, new_limit); 1598 Node* bol = inner_cle->in(CountedLoopEndNode::TestValue)->clone(); 1599 cmp->set_req(2, limit); 1600 bol->set_req(1, igvn->transform(cmp)); 1601 igvn->replace_input_of(outer_loop_end(), 1, igvn->transform(bol)); 1602 } else { 1603 assert(false, "should be able to adjust outer loop"); 1604 IfNode* outer_le = outer_loop_end(); 1605 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt)); 1606 igvn->replace_node(outer_le, iff); 1607 inner_cl->clear_strip_mined(); 1608 } 1609 } 1610 1611 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const { 1612 if (!in(0)) return Type::TOP; 1613 if (phase->type(in(0)) == Type::TOP) 1614 return Type::TOP; 1615 1616 return TypeTuple::IFBOTH; 1617 } 1618 1619 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1620 if (remove_dead_region(phase, can_reshape)) return this; 1621 1622 return NULL; 1623 } 1624 1625 //------------------------------filtered_type-------------------------------- 1626 // Return a type based on condition control flow 1627 // A successful return will be a type that is restricted due 1628 // to a series of dominating if-tests, such as: 1629 // if (i < 10) { 1630 // if (i > 0) { 1631 // here: "i" type is [1..10) 1632 // } 1633 // } 1634 // or a control flow merge 1635 // if (i < 10) { 1636 // do { 1637 // phi( , ) -- at top of loop type is [min_int..10) 1638 // i = ? 1639 // } while ( i < 10) 1640 // 1641 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) { 1642 assert(n && n->bottom_type()->is_int(), "must be int"); 1643 const TypeInt* filtered_t = NULL; 1644 if (!n->is_Phi()) { 1645 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control"); 1646 filtered_t = filtered_type_from_dominators(n, n_ctrl); 1647 1648 } else { 1649 Node* phi = n->as_Phi(); 1650 Node* region = phi->in(0); 1651 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region"); 1652 if (region && region != C->top()) { 1653 for (uint i = 1; i < phi->req(); i++) { 1654 Node* val = phi->in(i); 1655 Node* use_c = region->in(i); 1656 const TypeInt* val_t = filtered_type_from_dominators(val, use_c); 1657 if (val_t != NULL) { 1658 if (filtered_t == NULL) { 1659 filtered_t = val_t; 1660 } else { 1661 filtered_t = filtered_t->meet(val_t)->is_int(); 1662 } 1663 } 1664 } 1665 } 1666 } 1667 const TypeInt* n_t = _igvn.type(n)->is_int(); 1668 if (filtered_t != NULL) { 1669 n_t = n_t->join(filtered_t)->is_int(); 1670 } 1671 return n_t; 1672 } 1673 1674 1675 //------------------------------filtered_type_from_dominators-------------------------------- 1676 // Return a possibly more restrictive type for val based on condition control flow of dominators 1677 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) { 1678 if (val->is_Con()) { 1679 return val->bottom_type()->is_int(); 1680 } 1681 uint if_limit = 10; // Max number of dominating if's visited 1682 const TypeInt* rtn_t = NULL; 1683 1684 if (use_ctrl && use_ctrl != C->top()) { 1685 Node* val_ctrl = get_ctrl(val); 1686 uint val_dom_depth = dom_depth(val_ctrl); 1687 Node* pred = use_ctrl; 1688 uint if_cnt = 0; 1689 while (if_cnt < if_limit) { 1690 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) { 1691 if_cnt++; 1692 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred); 1693 if (if_t != NULL) { 1694 if (rtn_t == NULL) { 1695 rtn_t = if_t; 1696 } else { 1697 rtn_t = rtn_t->join(if_t)->is_int(); 1698 } 1699 } 1700 } 1701 pred = idom(pred); 1702 if (pred == NULL || pred == C->top()) { 1703 break; 1704 } 1705 // Stop if going beyond definition block of val 1706 if (dom_depth(pred) < val_dom_depth) { 1707 break; 1708 } 1709 } 1710 } 1711 return rtn_t; 1712 } 1713 1714 1715 //------------------------------dump_spec-------------------------------------- 1716 // Dump special per-node info 1717 #ifndef PRODUCT 1718 void CountedLoopEndNode::dump_spec(outputStream *st) const { 1719 if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) { 1720 BoolTest bt( test_trip()); // Added this for g++. 1721 1722 st->print("["); 1723 bt.dump_on(st); 1724 st->print("]"); 1725 } 1726 st->print(" "); 1727 IfNode::dump_spec(st); 1728 } 1729 #endif 1730 1731 //============================================================================= 1732 //------------------------------is_member-------------------------------------- 1733 // Is 'l' a member of 'this'? 1734 bool IdealLoopTree::is_member(const IdealLoopTree *l) const { 1735 while( l->_nest > _nest ) l = l->_parent; 1736 return l == this; 1737 } 1738 1739 //------------------------------set_nest--------------------------------------- 1740 // Set loop tree nesting depth. Accumulate _has_call bits. 1741 int IdealLoopTree::set_nest( uint depth ) { 1742 _nest = depth; 1743 int bits = _has_call; 1744 if( _child ) bits |= _child->set_nest(depth+1); 1745 if( bits ) _has_call = 1; 1746 if( _next ) bits |= _next ->set_nest(depth ); 1747 return bits; 1748 } 1749 1750 //------------------------------split_fall_in---------------------------------- 1751 // Split out multiple fall-in edges from the loop header. Move them to a 1752 // private RegionNode before the loop. This becomes the loop landing pad. 1753 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) { 1754 PhaseIterGVN &igvn = phase->_igvn; 1755 uint i; 1756 1757 // Make a new RegionNode to be the landing pad. 1758 Node *landing_pad = new RegionNode( fall_in_cnt+1 ); 1759 phase->set_loop(landing_pad,_parent); 1760 // Gather all the fall-in control paths into the landing pad 1761 uint icnt = fall_in_cnt; 1762 uint oreq = _head->req(); 1763 for( i = oreq-1; i>0; i-- ) 1764 if( !phase->is_member( this, _head->in(i) ) ) 1765 landing_pad->set_req(icnt--,_head->in(i)); 1766 1767 // Peel off PhiNode edges as well 1768 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1769 Node *oj = _head->fast_out(j); 1770 if( oj->is_Phi() ) { 1771 PhiNode* old_phi = oj->as_Phi(); 1772 assert( old_phi->region() == _head, "" ); 1773 igvn.hash_delete(old_phi); // Yank from hash before hacking edges 1774 Node *p = PhiNode::make_blank(landing_pad, old_phi); 1775 uint icnt = fall_in_cnt; 1776 for( i = oreq-1; i>0; i-- ) { 1777 if( !phase->is_member( this, _head->in(i) ) ) { 1778 p->init_req(icnt--, old_phi->in(i)); 1779 // Go ahead and clean out old edges from old phi 1780 old_phi->del_req(i); 1781 } 1782 } 1783 // Search for CSE's here, because ZKM.jar does a lot of 1784 // loop hackery and we need to be a little incremental 1785 // with the CSE to avoid O(N^2) node blow-up. 1786 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE 1787 if( p2 ) { // Found CSE 1788 p->destruct(); // Recover useless new node 1789 p = p2; // Use old node 1790 } else { 1791 igvn.register_new_node_with_optimizer(p, old_phi); 1792 } 1793 // Make old Phi refer to new Phi. 1794 old_phi->add_req(p); 1795 // Check for the special case of making the old phi useless and 1796 // disappear it. In JavaGrande I have a case where this useless 1797 // Phi is the loop limit and prevents recognizing a CountedLoop 1798 // which in turn prevents removing an empty loop. 1799 Node *id_old_phi = igvn.apply_identity(old_phi); 1800 if( id_old_phi != old_phi ) { // Found a simple identity? 1801 // Note that I cannot call 'replace_node' here, because 1802 // that will yank the edge from old_phi to the Region and 1803 // I'm mid-iteration over the Region's uses. 1804 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) { 1805 Node* use = old_phi->last_out(i); 1806 igvn.rehash_node_delayed(use); 1807 uint uses_found = 0; 1808 for (uint j = 0; j < use->len(); j++) { 1809 if (use->in(j) == old_phi) { 1810 if (j < use->req()) use->set_req (j, id_old_phi); 1811 else use->set_prec(j, id_old_phi); 1812 uses_found++; 1813 } 1814 } 1815 i -= uses_found; // we deleted 1 or more copies of this edge 1816 } 1817 } 1818 igvn._worklist.push(old_phi); 1819 } 1820 } 1821 // Finally clean out the fall-in edges from the RegionNode 1822 for( i = oreq-1; i>0; i-- ) { 1823 if( !phase->is_member( this, _head->in(i) ) ) { 1824 _head->del_req(i); 1825 } 1826 } 1827 igvn.rehash_node_delayed(_head); 1828 // Transform landing pad 1829 igvn.register_new_node_with_optimizer(landing_pad, _head); 1830 // Insert landing pad into the header 1831 _head->add_req(landing_pad); 1832 } 1833 1834 //------------------------------split_outer_loop------------------------------- 1835 // Split out the outermost loop from this shared header. 1836 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) { 1837 PhaseIterGVN &igvn = phase->_igvn; 1838 1839 // Find index of outermost loop; it should also be my tail. 1840 uint outer_idx = 1; 1841 while( _head->in(outer_idx) != _tail ) outer_idx++; 1842 1843 // Make a LoopNode for the outermost loop. 1844 Node *ctl = _head->in(LoopNode::EntryControl); 1845 Node *outer = new LoopNode( ctl, _head->in(outer_idx) ); 1846 outer = igvn.register_new_node_with_optimizer(outer, _head); 1847 phase->set_created_loop_node(); 1848 1849 // Outermost loop falls into '_head' loop 1850 _head->set_req(LoopNode::EntryControl, outer); 1851 _head->del_req(outer_idx); 1852 // Split all the Phis up between '_head' loop and 'outer' loop. 1853 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1854 Node *out = _head->fast_out(j); 1855 if( out->is_Phi() ) { 1856 PhiNode *old_phi = out->as_Phi(); 1857 assert( old_phi->region() == _head, "" ); 1858 Node *phi = PhiNode::make_blank(outer, old_phi); 1859 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl)); 1860 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx)); 1861 phi = igvn.register_new_node_with_optimizer(phi, old_phi); 1862 // Make old Phi point to new Phi on the fall-in path 1863 igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi); 1864 old_phi->del_req(outer_idx); 1865 } 1866 } 1867 1868 // Use the new loop head instead of the old shared one 1869 _head = outer; 1870 phase->set_loop(_head, this); 1871 } 1872 1873 //------------------------------fix_parent------------------------------------- 1874 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) { 1875 loop->_parent = parent; 1876 if( loop->_child ) fix_parent( loop->_child, loop ); 1877 if( loop->_next ) fix_parent( loop->_next , parent ); 1878 } 1879 1880 //------------------------------estimate_path_freq----------------------------- 1881 static float estimate_path_freq( Node *n ) { 1882 // Try to extract some path frequency info 1883 IfNode *iff; 1884 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests 1885 uint nop = n->Opcode(); 1886 if( nop == Op_SafePoint ) { // Skip any safepoint 1887 n = n->in(0); 1888 continue; 1889 } 1890 if( nop == Op_CatchProj ) { // Get count from a prior call 1891 // Assume call does not always throw exceptions: means the call-site 1892 // count is also the frequency of the fall-through path. 1893 assert( n->is_CatchProj(), "" ); 1894 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index ) 1895 return 0.0f; // Assume call exception path is rare 1896 Node *call = n->in(0)->in(0)->in(0); 1897 assert( call->is_Call(), "expect a call here" ); 1898 const JVMState *jvms = ((CallNode*)call)->jvms(); 1899 ciMethodData* methodData = jvms->method()->method_data(); 1900 if (!methodData->is_mature()) return 0.0f; // No call-site data 1901 ciProfileData* data = methodData->bci_to_data(jvms->bci()); 1902 if ((data == NULL) || !data->is_CounterData()) { 1903 // no call profile available, try call's control input 1904 n = n->in(0); 1905 continue; 1906 } 1907 return data->as_CounterData()->count()/FreqCountInvocations; 1908 } 1909 // See if there's a gating IF test 1910 Node *n_c = n->in(0); 1911 if( !n_c->is_If() ) break; // No estimate available 1912 iff = n_c->as_If(); 1913 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count? 1914 // Compute how much count comes on this path 1915 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt; 1916 // Have no count info. Skip dull uncommon-trap like branches. 1917 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) || 1918 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) ) 1919 break; 1920 // Skip through never-taken branch; look for a real loop exit. 1921 n = iff->in(0); 1922 } 1923 return 0.0f; // No estimate available 1924 } 1925 1926 //------------------------------merge_many_backedges--------------------------- 1927 // Merge all the backedges from the shared header into a private Region. 1928 // Feed that region as the one backedge to this loop. 1929 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) { 1930 uint i; 1931 1932 // Scan for the top 2 hottest backedges 1933 float hotcnt = 0.0f; 1934 float warmcnt = 0.0f; 1935 uint hot_idx = 0; 1936 // Loop starts at 2 because slot 1 is the fall-in path 1937 for( i = 2; i < _head->req(); i++ ) { 1938 float cnt = estimate_path_freq(_head->in(i)); 1939 if( cnt > hotcnt ) { // Grab hottest path 1940 warmcnt = hotcnt; 1941 hotcnt = cnt; 1942 hot_idx = i; 1943 } else if( cnt > warmcnt ) { // And 2nd hottest path 1944 warmcnt = cnt; 1945 } 1946 } 1947 1948 // See if the hottest backedge is worthy of being an inner loop 1949 // by being much hotter than the next hottest backedge. 1950 if( hotcnt <= 0.0001 || 1951 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge 1952 1953 // Peel out the backedges into a private merge point; peel 1954 // them all except optionally hot_idx. 1955 PhaseIterGVN &igvn = phase->_igvn; 1956 1957 Node *hot_tail = NULL; 1958 // Make a Region for the merge point 1959 Node *r = new RegionNode(1); 1960 for( i = 2; i < _head->req(); i++ ) { 1961 if( i != hot_idx ) 1962 r->add_req( _head->in(i) ); 1963 else hot_tail = _head->in(i); 1964 } 1965 igvn.register_new_node_with_optimizer(r, _head); 1966 // Plug region into end of loop _head, followed by hot_tail 1967 while( _head->req() > 3 ) _head->del_req( _head->req()-1 ); 1968 igvn.replace_input_of(_head, 2, r); 1969 if( hot_idx ) _head->add_req(hot_tail); 1970 1971 // Split all the Phis up between '_head' loop and the Region 'r' 1972 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1973 Node *out = _head->fast_out(j); 1974 if( out->is_Phi() ) { 1975 PhiNode* n = out->as_Phi(); 1976 igvn.hash_delete(n); // Delete from hash before hacking edges 1977 Node *hot_phi = NULL; 1978 Node *phi = new PhiNode(r, n->type(), n->adr_type()); 1979 // Check all inputs for the ones to peel out 1980 uint j = 1; 1981 for( uint i = 2; i < n->req(); i++ ) { 1982 if( i != hot_idx ) 1983 phi->set_req( j++, n->in(i) ); 1984 else hot_phi = n->in(i); 1985 } 1986 // Register the phi but do not transform until whole place transforms 1987 igvn.register_new_node_with_optimizer(phi, n); 1988 // Add the merge phi to the old Phi 1989 while( n->req() > 3 ) n->del_req( n->req()-1 ); 1990 igvn.replace_input_of(n, 2, phi); 1991 if( hot_idx ) n->add_req(hot_phi); 1992 } 1993 } 1994 1995 1996 // Insert a new IdealLoopTree inserted below me. Turn it into a clone 1997 // of self loop tree. Turn self into a loop headed by _head and with 1998 // tail being the new merge point. 1999 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail ); 2000 phase->set_loop(_tail,ilt); // Adjust tail 2001 _tail = r; // Self's tail is new merge point 2002 phase->set_loop(r,this); 2003 ilt->_child = _child; // New guy has my children 2004 _child = ilt; // Self has new guy as only child 2005 ilt->_parent = this; // new guy has self for parent 2006 ilt->_nest = _nest; // Same nesting depth (for now) 2007 2008 // Starting with 'ilt', look for child loop trees using the same shared 2009 // header. Flatten these out; they will no longer be loops in the end. 2010 IdealLoopTree **pilt = &_child; 2011 while( ilt ) { 2012 if( ilt->_head == _head ) { 2013 uint i; 2014 for( i = 2; i < _head->req(); i++ ) 2015 if( _head->in(i) == ilt->_tail ) 2016 break; // Still a loop 2017 if( i == _head->req() ) { // No longer a loop 2018 // Flatten ilt. Hang ilt's "_next" list from the end of 2019 // ilt's '_child' list. Move the ilt's _child up to replace ilt. 2020 IdealLoopTree **cp = &ilt->_child; 2021 while( *cp ) cp = &(*cp)->_next; // Find end of child list 2022 *cp = ilt->_next; // Hang next list at end of child list 2023 *pilt = ilt->_child; // Move child up to replace ilt 2024 ilt->_head = NULL; // Flag as a loop UNIONED into parent 2025 ilt = ilt->_child; // Repeat using new ilt 2026 continue; // do not advance over ilt->_child 2027 } 2028 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" ); 2029 phase->set_loop(_head,ilt); 2030 } 2031 pilt = &ilt->_child; // Advance to next 2032 ilt = *pilt; 2033 } 2034 2035 if( _child ) fix_parent( _child, this ); 2036 } 2037 2038 //------------------------------beautify_loops--------------------------------- 2039 // Split shared headers and insert loop landing pads. 2040 // Insert a LoopNode to replace the RegionNode. 2041 // Return TRUE if loop tree is structurally changed. 2042 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) { 2043 bool result = false; 2044 // Cache parts in locals for easy 2045 PhaseIterGVN &igvn = phase->_igvn; 2046 2047 igvn.hash_delete(_head); // Yank from hash before hacking edges 2048 2049 // Check for multiple fall-in paths. Peel off a landing pad if need be. 2050 int fall_in_cnt = 0; 2051 for( uint i = 1; i < _head->req(); i++ ) 2052 if( !phase->is_member( this, _head->in(i) ) ) 2053 fall_in_cnt++; 2054 assert( fall_in_cnt, "at least 1 fall-in path" ); 2055 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins 2056 split_fall_in( phase, fall_in_cnt ); 2057 2058 // Swap inputs to the _head and all Phis to move the fall-in edge to 2059 // the left. 2060 fall_in_cnt = 1; 2061 while( phase->is_member( this, _head->in(fall_in_cnt) ) ) 2062 fall_in_cnt++; 2063 if( fall_in_cnt > 1 ) { 2064 // Since I am just swapping inputs I do not need to update def-use info 2065 Node *tmp = _head->in(1); 2066 igvn.rehash_node_delayed(_head); 2067 _head->set_req( 1, _head->in(fall_in_cnt) ); 2068 _head->set_req( fall_in_cnt, tmp ); 2069 // Swap also all Phis 2070 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) { 2071 Node* phi = _head->fast_out(i); 2072 if( phi->is_Phi() ) { 2073 igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges 2074 tmp = phi->in(1); 2075 phi->set_req( 1, phi->in(fall_in_cnt) ); 2076 phi->set_req( fall_in_cnt, tmp ); 2077 } 2078 } 2079 } 2080 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" ); 2081 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" ); 2082 2083 // If I am a shared header (multiple backedges), peel off the many 2084 // backedges into a private merge point and use the merge point as 2085 // the one true backedge. 2086 if( _head->req() > 3 ) { 2087 // Merge the many backedges into a single backedge but leave 2088 // the hottest backedge as separate edge for the following peel. 2089 merge_many_backedges( phase ); 2090 result = true; 2091 } 2092 2093 // If I have one hot backedge, peel off myself loop. 2094 // I better be the outermost loop. 2095 if (_head->req() > 3 && !_irreducible) { 2096 split_outer_loop( phase ); 2097 result = true; 2098 2099 } else if (!_head->is_Loop() && !_irreducible) { 2100 // Make a new LoopNode to replace the old loop head 2101 Node *l = new LoopNode( _head->in(1), _head->in(2) ); 2102 l = igvn.register_new_node_with_optimizer(l, _head); 2103 phase->set_created_loop_node(); 2104 // Go ahead and replace _head 2105 phase->_igvn.replace_node( _head, l ); 2106 _head = l; 2107 phase->set_loop(_head, this); 2108 } 2109 2110 // Now recursively beautify nested loops 2111 if( _child ) result |= _child->beautify_loops( phase ); 2112 if( _next ) result |= _next ->beautify_loops( phase ); 2113 return result; 2114 } 2115 2116 //------------------------------allpaths_check_safepts---------------------------- 2117 // Allpaths backwards scan from loop tail, terminating each path at first safepoint 2118 // encountered. Helper for check_safepts. 2119 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) { 2120 assert(stack.size() == 0, "empty stack"); 2121 stack.push(_tail); 2122 visited.Clear(); 2123 visited.set(_tail->_idx); 2124 while (stack.size() > 0) { 2125 Node* n = stack.pop(); 2126 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 2127 // Terminate this path 2128 } else if (n->Opcode() == Op_SafePoint) { 2129 if (_phase->get_loop(n) != this) { 2130 if (_required_safept == NULL) _required_safept = new Node_List(); 2131 _required_safept->push(n); // save the one closest to the tail 2132 } 2133 // Terminate this path 2134 } else { 2135 uint start = n->is_Region() ? 1 : 0; 2136 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1; 2137 for (uint i = start; i < end; i++) { 2138 Node* in = n->in(i); 2139 assert(in->is_CFG(), "must be"); 2140 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) { 2141 stack.push(in); 2142 } 2143 } 2144 } 2145 } 2146 } 2147 2148 //------------------------------check_safepts---------------------------- 2149 // Given dominators, try to find loops with calls that must always be 2150 // executed (call dominates loop tail). These loops do not need non-call 2151 // safepoints (ncsfpt). 2152 // 2153 // A complication is that a safepoint in a inner loop may be needed 2154 // by an outer loop. In the following, the inner loop sees it has a 2155 // call (block 3) on every path from the head (block 2) to the 2156 // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint) 2157 // in block 2, _but_ this leaves the outer loop without a safepoint. 2158 // 2159 // entry 0 2160 // | 2161 // v 2162 // outer 1,2 +->1 2163 // | | 2164 // | v 2165 // | 2<---+ ncsfpt in 2 2166 // |_/|\ | 2167 // | v | 2168 // inner 2,3 / 3 | call in 3 2169 // / | | 2170 // v +--+ 2171 // exit 4 2172 // 2173 // 2174 // This method creates a list (_required_safept) of ncsfpt nodes that must 2175 // be protected is created for each loop. When a ncsfpt maybe deleted, it 2176 // is first looked for in the lists for the outer loops of the current loop. 2177 // 2178 // The insights into the problem: 2179 // A) counted loops are okay 2180 // B) innermost loops are okay (only an inner loop can delete 2181 // a ncsfpt needed by an outer loop) 2182 // C) a loop is immune from an inner loop deleting a safepoint 2183 // if the loop has a call on the idom-path 2184 // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the 2185 // idom-path that is not in a nested loop 2186 // E) otherwise, an ncsfpt on the idom-path that is nested in an inner 2187 // loop needs to be prevented from deletion by an inner loop 2188 // 2189 // There are two analyses: 2190 // 1) The first, and cheaper one, scans the loop body from 2191 // tail to head following the idom (immediate dominator) 2192 // chain, looking for the cases (C,D,E) above. 2193 // Since inner loops are scanned before outer loops, there is summary 2194 // information about inner loops. Inner loops can be skipped over 2195 // when the tail of an inner loop is encountered. 2196 // 2197 // 2) The second, invoked if the first fails to find a call or ncsfpt on 2198 // the idom path (which is rare), scans all predecessor control paths 2199 // from the tail to the head, terminating a path when a call or sfpt 2200 // is encountered, to find the ncsfpt's that are closest to the tail. 2201 // 2202 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) { 2203 // Bottom up traversal 2204 IdealLoopTree* ch = _child; 2205 if (_child) _child->check_safepts(visited, stack); 2206 if (_next) _next ->check_safepts(visited, stack); 2207 2208 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) { 2209 bool has_call = false; // call on dom-path 2210 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth 2211 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth 2212 // Scan the dom-path nodes from tail to head 2213 for (Node* n = tail(); n != _head; n = _phase->idom(n)) { 2214 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 2215 has_call = true; 2216 _has_sfpt = 1; // Then no need for a safept! 2217 break; 2218 } else if (n->Opcode() == Op_SafePoint) { 2219 if (_phase->get_loop(n) == this) { 2220 has_local_ncsfpt = true; 2221 break; 2222 } 2223 if (nonlocal_ncsfpt == NULL) { 2224 nonlocal_ncsfpt = n; // save the one closest to the tail 2225 } 2226 } else { 2227 IdealLoopTree* nlpt = _phase->get_loop(n); 2228 if (this != nlpt) { 2229 // If at an inner loop tail, see if the inner loop has already 2230 // recorded seeing a call on the dom-path (and stop.) If not, 2231 // jump to the head of the inner loop. 2232 assert(is_member(nlpt), "nested loop"); 2233 Node* tail = nlpt->_tail; 2234 if (tail->in(0)->is_If()) tail = tail->in(0); 2235 if (n == tail) { 2236 // If inner loop has call on dom-path, so does outer loop 2237 if (nlpt->_has_sfpt) { 2238 has_call = true; 2239 _has_sfpt = 1; 2240 break; 2241 } 2242 // Skip to head of inner loop 2243 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head"); 2244 n = nlpt->_head; 2245 } 2246 } 2247 } 2248 } 2249 // Record safept's that this loop needs preserved when an 2250 // inner loop attempts to delete it's safepoints. 2251 if (_child != NULL && !has_call && !has_local_ncsfpt) { 2252 if (nonlocal_ncsfpt != NULL) { 2253 if (_required_safept == NULL) _required_safept = new Node_List(); 2254 _required_safept->push(nonlocal_ncsfpt); 2255 } else { 2256 // Failed to find a suitable safept on the dom-path. Now use 2257 // an all paths walk from tail to head, looking for safepoints to preserve. 2258 allpaths_check_safepts(visited, stack); 2259 } 2260 } 2261 } 2262 } 2263 2264 //---------------------------is_deleteable_safept---------------------------- 2265 // Is safept not required by an outer loop? 2266 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) { 2267 assert(sfpt->Opcode() == Op_SafePoint, ""); 2268 IdealLoopTree* lp = get_loop(sfpt)->_parent; 2269 while (lp != NULL) { 2270 Node_List* sfpts = lp->_required_safept; 2271 if (sfpts != NULL) { 2272 for (uint i = 0; i < sfpts->size(); i++) { 2273 if (sfpt == sfpts->at(i)) 2274 return false; 2275 } 2276 } 2277 lp = lp->_parent; 2278 } 2279 return true; 2280 } 2281 2282 //---------------------------replace_parallel_iv------------------------------- 2283 // Replace parallel induction variable (parallel to trip counter) 2284 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) { 2285 assert(loop->_head->is_CountedLoop(), ""); 2286 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 2287 if (!cl->is_valid_counted_loop()) 2288 return; // skip malformed counted loop 2289 Node *incr = cl->incr(); 2290 if (incr == NULL) 2291 return; // Dead loop? 2292 Node *init = cl->init_trip(); 2293 Node *phi = cl->phi(); 2294 int stride_con = cl->stride_con(); 2295 2296 // Visit all children, looking for Phis 2297 for (DUIterator i = cl->outs(); cl->has_out(i); i++) { 2298 Node *out = cl->out(i); 2299 // Look for other phis (secondary IVs). Skip dead ones 2300 if (!out->is_Phi() || out == phi || !has_node(out)) 2301 continue; 2302 PhiNode* phi2 = out->as_Phi(); 2303 Node *incr2 = phi2->in( LoopNode::LoopBackControl ); 2304 // Look for induction variables of the form: X += constant 2305 if (phi2->region() != loop->_head || 2306 incr2->req() != 3 || 2307 incr2->in(1) != phi2 || 2308 incr2 == incr || 2309 incr2->Opcode() != Op_AddI || 2310 !incr2->in(2)->is_Con()) 2311 continue; 2312 2313 // Check for parallel induction variable (parallel to trip counter) 2314 // via an affine function. In particular, count-down loops with 2315 // count-up array indices are common. We only RCE references off 2316 // the trip-counter, so we need to convert all these to trip-counter 2317 // expressions. 2318 Node *init2 = phi2->in( LoopNode::EntryControl ); 2319 int stride_con2 = incr2->in(2)->get_int(); 2320 2321 // The ratio of the two strides cannot be represented as an int 2322 // if stride_con2 is min_int and stride_con is -1. 2323 if (stride_con2 == min_jint && stride_con == -1) { 2324 continue; 2325 } 2326 2327 // The general case here gets a little tricky. We want to find the 2328 // GCD of all possible parallel IV's and make a new IV using this 2329 // GCD for the loop. Then all possible IVs are simple multiples of 2330 // the GCD. In practice, this will cover very few extra loops. 2331 // Instead we require 'stride_con2' to be a multiple of 'stride_con', 2332 // where +/-1 is the common case, but other integer multiples are 2333 // also easy to handle. 2334 int ratio_con = stride_con2/stride_con; 2335 2336 if ((ratio_con * stride_con) == stride_con2) { // Check for exact 2337 #ifndef PRODUCT 2338 if (TraceLoopOpts) { 2339 tty->print("Parallel IV: %d ", phi2->_idx); 2340 loop->dump_head(); 2341 } 2342 #endif 2343 // Convert to using the trip counter. The parallel induction 2344 // variable differs from the trip counter by a loop-invariant 2345 // amount, the difference between their respective initial values. 2346 // It is scaled by the 'ratio_con'. 2347 Node* ratio = _igvn.intcon(ratio_con); 2348 set_ctrl(ratio, C->root()); 2349 Node* ratio_init = new MulINode(init, ratio); 2350 _igvn.register_new_node_with_optimizer(ratio_init, init); 2351 set_early_ctrl(ratio_init); 2352 Node* diff = new SubINode(init2, ratio_init); 2353 _igvn.register_new_node_with_optimizer(diff, init2); 2354 set_early_ctrl(diff); 2355 Node* ratio_idx = new MulINode(phi, ratio); 2356 _igvn.register_new_node_with_optimizer(ratio_idx, phi); 2357 set_ctrl(ratio_idx, cl); 2358 Node* add = new AddINode(ratio_idx, diff); 2359 _igvn.register_new_node_with_optimizer(add); 2360 set_ctrl(add, cl); 2361 _igvn.replace_node( phi2, add ); 2362 // Sometimes an induction variable is unused 2363 if (add->outcnt() == 0) { 2364 _igvn.remove_dead_node(add); 2365 } 2366 --i; // deleted this phi; rescan starting with next position 2367 continue; 2368 } 2369 } 2370 } 2371 2372 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) { 2373 Node* keep = NULL; 2374 if (keep_one) { 2375 // Look for a safepoint on the idom-path. 2376 for (Node* i = tail(); i != _head; i = phase->idom(i)) { 2377 if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) { 2378 keep = i; 2379 break; // Found one 2380 } 2381 } 2382 } 2383 2384 // Don't remove any safepoints if it is requested to keep a single safepoint and 2385 // no safepoint was found on idom-path. It is not safe to remove any safepoint 2386 // in this case since there's no safepoint dominating all paths in the loop body. 2387 bool prune = !keep_one || keep != NULL; 2388 2389 // Delete other safepoints in this loop. 2390 Node_List* sfpts = _safepts; 2391 if (prune && sfpts != NULL) { 2392 assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint"); 2393 for (uint i = 0; i < sfpts->size(); i++) { 2394 Node* n = sfpts->at(i); 2395 assert(phase->get_loop(n) == this, ""); 2396 if (n != keep && phase->is_deleteable_safept(n)) { 2397 phase->lazy_replace(n, n->in(TypeFunc::Control)); 2398 } 2399 } 2400 } 2401 } 2402 2403 //------------------------------counted_loop----------------------------------- 2404 // Convert to counted loops where possible 2405 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) { 2406 2407 // For grins, set the inner-loop flag here 2408 if (!_child) { 2409 if (_head->is_Loop()) _head->as_Loop()->set_inner_loop(); 2410 } 2411 2412 IdealLoopTree* loop = this; 2413 if (_head->is_CountedLoop() || 2414 phase->is_counted_loop(_head, loop)) { 2415 2416 if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) { 2417 // Indicate we do not need a safepoint here 2418 _has_sfpt = 1; 2419 } 2420 2421 // Remove safepoints 2422 bool keep_one_sfpt = !(_has_call || _has_sfpt); 2423 remove_safepoints(phase, keep_one_sfpt); 2424 2425 // Look for induction variables 2426 phase->replace_parallel_iv(this); 2427 2428 } else if (_parent != NULL && !_irreducible) { 2429 // Not a counted loop. Keep one safepoint. 2430 bool keep_one_sfpt = true; 2431 remove_safepoints(phase, keep_one_sfpt); 2432 } 2433 2434 // Recursively 2435 assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?"); 2436 assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops"); 2437 if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase); 2438 if (loop->_next) loop->_next ->counted_loop(phase); 2439 } 2440 2441 #ifndef PRODUCT 2442 //------------------------------dump_head-------------------------------------- 2443 // Dump 1 liner for loop header info 2444 void IdealLoopTree::dump_head( ) const { 2445 for (uint i=0; i<_nest; i++) 2446 tty->print(" "); 2447 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx); 2448 if (_irreducible) tty->print(" IRREDUCIBLE"); 2449 Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl); 2450 Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check); 2451 if (predicate != NULL ) { 2452 tty->print(" limit_check"); 2453 entry = PhaseIdealLoop::skip_loop_predicates(entry); 2454 } 2455 if (UseLoopPredicate) { 2456 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate); 2457 if (entry != NULL) { 2458 tty->print(" predicated"); 2459 entry = PhaseIdealLoop::skip_loop_predicates(entry); 2460 } 2461 } 2462 if (UseProfiledLoopPredicate) { 2463 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate); 2464 if (entry != NULL) { 2465 tty->print(" profile_predicated"); 2466 } 2467 } 2468 if (_head->is_CountedLoop()) { 2469 CountedLoopNode *cl = _head->as_CountedLoop(); 2470 tty->print(" counted"); 2471 2472 Node* init_n = cl->init_trip(); 2473 if (init_n != NULL && init_n->is_Con()) 2474 tty->print(" [%d,", cl->init_trip()->get_int()); 2475 else 2476 tty->print(" [int,"); 2477 Node* limit_n = cl->limit(); 2478 if (limit_n != NULL && limit_n->is_Con()) 2479 tty->print("%d),", cl->limit()->get_int()); 2480 else 2481 tty->print("int),"); 2482 int stride_con = cl->stride_con(); 2483 if (stride_con > 0) tty->print("+"); 2484 tty->print("%d", stride_con); 2485 2486 tty->print(" (%0.f iters) ", cl->profile_trip_cnt()); 2487 2488 if (cl->is_pre_loop ()) tty->print(" pre" ); 2489 if (cl->is_main_loop()) tty->print(" main"); 2490 if (cl->is_post_loop()) tty->print(" post"); 2491 if (cl->is_vectorized_loop()) tty->print(" vector"); 2492 if (cl->range_checks_present()) tty->print(" rc "); 2493 if (cl->is_multiversioned()) tty->print(" multi "); 2494 } 2495 if (_has_call) tty->print(" has_call"); 2496 if (_has_sfpt) tty->print(" has_sfpt"); 2497 if (_rce_candidate) tty->print(" rce"); 2498 if (_safepts != NULL && _safepts->size() > 0) { 2499 tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }"); 2500 } 2501 if (_required_safept != NULL && _required_safept->size() > 0) { 2502 tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }"); 2503 } 2504 if (Verbose) { 2505 tty->print(" body={"); _body.dump_simple(); tty->print(" }"); 2506 } 2507 if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) { 2508 tty->print(" strip_mined"); 2509 } 2510 tty->cr(); 2511 } 2512 2513 //------------------------------dump------------------------------------------- 2514 // Dump loops by loop tree 2515 void IdealLoopTree::dump( ) const { 2516 dump_head(); 2517 if (_child) _child->dump(); 2518 if (_next) _next ->dump(); 2519 } 2520 2521 #endif 2522 2523 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) { 2524 if (loop == root) { 2525 if (loop->_child != NULL) { 2526 log->begin_head("loop_tree"); 2527 log->end_head(); 2528 if( loop->_child ) log_loop_tree(root, loop->_child, log); 2529 log->tail("loop_tree"); 2530 assert(loop->_next == NULL, "what?"); 2531 } 2532 } else { 2533 Node* head = loop->_head; 2534 log->begin_head("loop"); 2535 log->print(" idx='%d' ", head->_idx); 2536 if (loop->_irreducible) log->print("irreducible='1' "); 2537 if (head->is_Loop()) { 2538 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' "); 2539 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' "); 2540 } 2541 if (head->is_CountedLoop()) { 2542 CountedLoopNode* cl = head->as_CountedLoop(); 2543 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx()); 2544 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx); 2545 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx()); 2546 } 2547 log->end_head(); 2548 if( loop->_child ) log_loop_tree(root, loop->_child, log); 2549 log->tail("loop"); 2550 if( loop->_next ) log_loop_tree(root, loop->_next, log); 2551 } 2552 } 2553 2554 //---------------------collect_potentially_useful_predicates----------------------- 2555 // Helper function to collect potentially useful predicates to prevent them from 2556 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates 2557 void PhaseIdealLoop::collect_potentially_useful_predicates( 2558 IdealLoopTree * loop, Unique_Node_List &useful_predicates) { 2559 if (loop->_child) { // child 2560 collect_potentially_useful_predicates(loop->_child, useful_predicates); 2561 } 2562 2563 // self (only loops that we can apply loop predication may use their predicates) 2564 if (loop->_head->is_Loop() && 2565 !loop->_irreducible && 2566 !loop->tail()->is_top()) { 2567 LoopNode* lpn = loop->_head->as_Loop(); 2568 Node* entry = lpn->in(LoopNode::EntryControl); 2569 Node* predicate_proj = find_predicate(entry); // loop_limit_check first 2570 if (predicate_proj != NULL ) { // right pattern that can be used by loop predication 2571 assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be"); 2572 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one 2573 entry = skip_loop_predicates(entry); 2574 } 2575 predicate_proj = find_predicate(entry); // Predicate 2576 if (predicate_proj != NULL ) { 2577 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one 2578 entry = skip_loop_predicates(entry); 2579 } 2580 if (UseProfiledLoopPredicate) { 2581 predicate_proj = find_predicate(entry); // Predicate 2582 if (predicate_proj != NULL ) { 2583 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one 2584 } 2585 } 2586 } 2587 2588 if (loop->_next) { // sibling 2589 collect_potentially_useful_predicates(loop->_next, useful_predicates); 2590 } 2591 } 2592 2593 //------------------------eliminate_useless_predicates----------------------------- 2594 // Eliminate all inserted predicates if they could not be used by loop predication. 2595 // Note: it will also eliminates loop limits check predicate since it also uses 2596 // Opaque1 node (see Parse::add_predicate()). 2597 void PhaseIdealLoop::eliminate_useless_predicates() { 2598 if (C->predicate_count() == 0) 2599 return; // no predicate left 2600 2601 Unique_Node_List useful_predicates; // to store useful predicates 2602 if (C->has_loops()) { 2603 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates); 2604 } 2605 2606 for (int i = C->predicate_count(); i > 0; i--) { 2607 Node * n = C->predicate_opaque1_node(i-1); 2608 assert(n->Opcode() == Op_Opaque1, "must be"); 2609 if (!useful_predicates.member(n)) { // not in the useful list 2610 _igvn.replace_node(n, n->in(1)); 2611 } 2612 } 2613 } 2614 2615 //------------------------process_expensive_nodes----------------------------- 2616 // Expensive nodes have their control input set to prevent the GVN 2617 // from commoning them and as a result forcing the resulting node to 2618 // be in a more frequent path. Use CFG information here, to change the 2619 // control inputs so that some expensive nodes can be commoned while 2620 // not executed more frequently. 2621 bool PhaseIdealLoop::process_expensive_nodes() { 2622 assert(OptimizeExpensiveOps, "optimization off?"); 2623 2624 // Sort nodes to bring similar nodes together 2625 C->sort_expensive_nodes(); 2626 2627 bool progress = false; 2628 2629 for (int i = 0; i < C->expensive_count(); ) { 2630 Node* n = C->expensive_node(i); 2631 int start = i; 2632 // Find nodes similar to n 2633 i++; 2634 for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++); 2635 int end = i; 2636 // And compare them two by two 2637 for (int j = start; j < end; j++) { 2638 Node* n1 = C->expensive_node(j); 2639 if (is_node_unreachable(n1)) { 2640 continue; 2641 } 2642 for (int k = j+1; k < end; k++) { 2643 Node* n2 = C->expensive_node(k); 2644 if (is_node_unreachable(n2)) { 2645 continue; 2646 } 2647 2648 assert(n1 != n2, "should be pair of nodes"); 2649 2650 Node* c1 = n1->in(0); 2651 Node* c2 = n2->in(0); 2652 2653 Node* parent_c1 = c1; 2654 Node* parent_c2 = c2; 2655 2656 // The call to get_early_ctrl_for_expensive() moves the 2657 // expensive nodes up but stops at loops that are in a if 2658 // branch. See whether we can exit the loop and move above the 2659 // If. 2660 if (c1->is_Loop()) { 2661 parent_c1 = c1->in(1); 2662 } 2663 if (c2->is_Loop()) { 2664 parent_c2 = c2->in(1); 2665 } 2666 2667 if (parent_c1 == parent_c2) { 2668 _igvn._worklist.push(n1); 2669 _igvn._worklist.push(n2); 2670 continue; 2671 } 2672 2673 // Look for identical expensive node up the dominator chain. 2674 if (is_dominator(c1, c2)) { 2675 c2 = c1; 2676 } else if (is_dominator(c2, c1)) { 2677 c1 = c2; 2678 } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() && 2679 parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) { 2680 // Both branches have the same expensive node so move it up 2681 // before the if. 2682 c1 = c2 = idom(parent_c1->in(0)); 2683 } 2684 // Do the actual moves 2685 if (n1->in(0) != c1) { 2686 _igvn.hash_delete(n1); 2687 n1->set_req(0, c1); 2688 _igvn.hash_insert(n1); 2689 _igvn._worklist.push(n1); 2690 progress = true; 2691 } 2692 if (n2->in(0) != c2) { 2693 _igvn.hash_delete(n2); 2694 n2->set_req(0, c2); 2695 _igvn.hash_insert(n2); 2696 _igvn._worklist.push(n2); 2697 progress = true; 2698 } 2699 } 2700 } 2701 } 2702 2703 return progress; 2704 } 2705 2706 2707 //============================================================================= 2708 //----------------------------build_and_optimize------------------------------- 2709 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to 2710 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups. 2711 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) { 2712 bool do_split_ifs = (mode == LoopOptsDefault || mode == LoopOptsLastRound); 2713 bool skip_loop_opts = (mode == LoopOptsNone); 2714 2715 ResourceMark rm; 2716 2717 int old_progress = C->major_progress(); 2718 uint orig_worklist_size = _igvn._worklist.size(); 2719 2720 // Reset major-progress flag for the driver's heuristics 2721 C->clear_major_progress(); 2722 2723 #ifndef PRODUCT 2724 // Capture for later assert 2725 uint unique = C->unique(); 2726 _loop_invokes++; 2727 _loop_work += unique; 2728 #endif 2729 2730 // True if the method has at least 1 irreducible loop 2731 _has_irreducible_loops = false; 2732 2733 _created_loop_node = false; 2734 2735 Arena *a = Thread::current()->resource_area(); 2736 VectorSet visited(a); 2737 // Pre-grow the mapping from Nodes to IdealLoopTrees. 2738 _nodes.map(C->unique(), NULL); 2739 memset(_nodes.adr(), 0, wordSize * C->unique()); 2740 2741 // Pre-build the top-level outermost loop tree entry 2742 _ltree_root = new IdealLoopTree( this, C->root(), C->root() ); 2743 // Do not need a safepoint at the top level 2744 _ltree_root->_has_sfpt = 1; 2745 2746 // Initialize Dominators. 2747 // Checked in clone_loop_predicate() during beautify_loops(). 2748 _idom_size = 0; 2749 _idom = NULL; 2750 _dom_depth = NULL; 2751 _dom_stk = NULL; 2752 2753 // Empty pre-order array 2754 allocate_preorders(); 2755 2756 // Build a loop tree on the fly. Build a mapping from CFG nodes to 2757 // IdealLoopTree entries. Data nodes are NOT walked. 2758 build_loop_tree(); 2759 // Check for bailout, and return 2760 if (C->failing()) { 2761 return; 2762 } 2763 2764 // No loops after all 2765 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false); 2766 2767 // There should always be an outer loop containing the Root and Return nodes. 2768 // If not, we have a degenerate empty program. Bail out in this case. 2769 if (!has_node(C->root())) { 2770 if (!_verify_only) { 2771 C->clear_major_progress(); 2772 C->record_method_not_compilable("empty program detected during loop optimization"); 2773 } 2774 return; 2775 } 2776 2777 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2(); 2778 // Nothing to do, so get out 2779 bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only && 2780 !bs->is_gc_specific_loop_opts_pass(mode); 2781 bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn); 2782 bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode); 2783 if (stop_early && !do_expensive_nodes) { 2784 _igvn.optimize(); // Cleanup NeverBranches 2785 return; 2786 } 2787 2788 // Set loop nesting depth 2789 _ltree_root->set_nest( 0 ); 2790 2791 // Split shared headers and insert loop landing pads. 2792 // Do not bother doing this on the Root loop of course. 2793 if( !_verify_me && !_verify_only && _ltree_root->_child ) { 2794 C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3); 2795 if( _ltree_root->_child->beautify_loops( this ) ) { 2796 // Re-build loop tree! 2797 _ltree_root->_child = NULL; 2798 _nodes.clear(); 2799 reallocate_preorders(); 2800 build_loop_tree(); 2801 // Check for bailout, and return 2802 if (C->failing()) { 2803 return; 2804 } 2805 // Reset loop nesting depth 2806 _ltree_root->set_nest( 0 ); 2807 2808 C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3); 2809 } 2810 } 2811 2812 // Build Dominators for elision of NULL checks & loop finding. 2813 // Since nodes do not have a slot for immediate dominator, make 2814 // a persistent side array for that info indexed on node->_idx. 2815 _idom_size = C->unique(); 2816 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size ); 2817 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size ); 2818 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth 2819 memset( _dom_depth, 0, _idom_size * sizeof(uint) ); 2820 2821 Dominators(); 2822 2823 if (!_verify_only) { 2824 // As a side effect, Dominators removed any unreachable CFG paths 2825 // into RegionNodes. It doesn't do this test against Root, so 2826 // we do it here. 2827 for( uint i = 1; i < C->root()->req(); i++ ) { 2828 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root? 2829 _igvn.delete_input_of(C->root(), i); 2830 i--; // Rerun same iteration on compressed edges 2831 } 2832 } 2833 2834 // Given dominators, try to find inner loops with calls that must 2835 // always be executed (call dominates loop tail). These loops do 2836 // not need a separate safepoint. 2837 Node_List cisstack(a); 2838 _ltree_root->check_safepts(visited, cisstack); 2839 } 2840 2841 // Walk the DATA nodes and place into loops. Find earliest control 2842 // node. For CFG nodes, the _nodes array starts out and remains 2843 // holding the associated IdealLoopTree pointer. For DATA nodes, the 2844 // _nodes array holds the earliest legal controlling CFG node. 2845 2846 // Allocate stack with enough space to avoid frequent realloc 2847 int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats 2848 Node_Stack nstack( a, stack_size ); 2849 2850 visited.Clear(); 2851 Node_List worklist(a); 2852 // Don't need C->root() on worklist since 2853 // it will be processed among C->top() inputs 2854 worklist.push( C->top() ); 2855 visited.set( C->top()->_idx ); // Set C->top() as visited now 2856 build_loop_early( visited, worklist, nstack ); 2857 2858 // Given early legal placement, try finding counted loops. This placement 2859 // is good enough to discover most loop invariants. 2860 if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) { 2861 _ltree_root->counted_loop( this ); 2862 } 2863 2864 // Find latest loop placement. Find ideal loop placement. 2865 visited.Clear(); 2866 init_dom_lca_tags(); 2867 // Need C->root() on worklist when processing outs 2868 worklist.push( C->root() ); 2869 NOT_PRODUCT( C->verify_graph_edges(); ) 2870 worklist.push( C->top() ); 2871 build_loop_late( visited, worklist, nstack ); 2872 2873 if (_verify_only) { 2874 // restore major progress flag 2875 for (int i = 0; i < old_progress; i++) 2876 C->set_major_progress(); 2877 assert(C->unique() == unique, "verification mode made Nodes? ? ?"); 2878 assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything"); 2879 return; 2880 } 2881 2882 // clear out the dead code after build_loop_late 2883 while (_deadlist.size()) { 2884 _igvn.remove_globally_dead_node(_deadlist.pop()); 2885 } 2886 2887 if (stop_early) { 2888 assert(do_expensive_nodes, "why are we here?"); 2889 if (process_expensive_nodes()) { 2890 // If we made some progress when processing expensive nodes then 2891 // the IGVN may modify the graph in a way that will allow us to 2892 // make some more progress: we need to try processing expensive 2893 // nodes again. 2894 C->set_major_progress(); 2895 } 2896 _igvn.optimize(); 2897 return; 2898 } 2899 2900 // Some parser-inserted loop predicates could never be used by loop 2901 // predication or they were moved away from loop during some optimizations. 2902 // For example, peeling. Eliminate them before next loop optimizations. 2903 eliminate_useless_predicates(); 2904 2905 #ifndef PRODUCT 2906 C->verify_graph_edges(); 2907 if (_verify_me) { // Nested verify pass? 2908 // Check to see if the verify mode is broken 2909 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?"); 2910 return; 2911 } 2912 if(VerifyLoopOptimizations) verify(); 2913 if(TraceLoopOpts && C->has_loops()) { 2914 _ltree_root->dump(); 2915 } 2916 #endif 2917 2918 if (skip_loop_opts) { 2919 // restore major progress flag 2920 for (int i = 0; i < old_progress; i++) { 2921 C->set_major_progress(); 2922 } 2923 2924 // Cleanup any modified bits 2925 _igvn.optimize(); 2926 2927 if (C->log() != NULL) { 2928 log_loop_tree(_ltree_root, _ltree_root, C->log()); 2929 } 2930 return; 2931 } 2932 2933 if (bs->optimize_loops(this, mode, visited, nstack, worklist)) { 2934 _igvn.optimize(); 2935 if (C->log() != NULL) { 2936 log_loop_tree(_ltree_root, _ltree_root, C->log()); 2937 } 2938 return; 2939 } 2940 2941 if (ReassociateInvariants) { 2942 // Reassociate invariants and prep for split_thru_phi 2943 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2944 IdealLoopTree* lpt = iter.current(); 2945 bool is_counted = lpt->is_counted(); 2946 if (!is_counted || !lpt->is_inner()) continue; 2947 2948 // check for vectorized loops, any reassociation of invariants was already done 2949 if (is_counted && lpt->_head->as_CountedLoop()->do_unroll_only()) continue; 2950 2951 lpt->reassociate_invariants(this); 2952 2953 // Because RCE opportunities can be masked by split_thru_phi, 2954 // look for RCE candidates and inhibit split_thru_phi 2955 // on just their loop-phi's for this pass of loop opts 2956 if (SplitIfBlocks && do_split_ifs) { 2957 if (lpt->policy_range_check(this)) { 2958 lpt->_rce_candidate = 1; // = true 2959 } 2960 } 2961 } 2962 } 2963 2964 // Check for aggressive application of split-if and other transforms 2965 // that require basic-block info (like cloning through Phi's) 2966 if( SplitIfBlocks && do_split_ifs ) { 2967 visited.Clear(); 2968 split_if_with_blocks( visited, nstack, mode == LoopOptsLastRound ); 2969 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); ); 2970 if (mode == LoopOptsLastRound) { 2971 C->set_major_progress(); 2972 } 2973 } 2974 2975 if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) { 2976 C->set_major_progress(); 2977 } 2978 2979 // Perform loop predication before iteration splitting 2980 if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) { 2981 _ltree_root->_child->loop_predication(this); 2982 } 2983 2984 if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) { 2985 if (do_intrinsify_fill()) { 2986 C->set_major_progress(); 2987 } 2988 } 2989 2990 // Perform iteration-splitting on inner loops. Split iterations to avoid 2991 // range checks or one-shot null checks. 2992 2993 // If split-if's didn't hack the graph too bad (no CFG changes) 2994 // then do loop opts. 2995 if (C->has_loops() && !C->major_progress()) { 2996 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) ); 2997 _ltree_root->_child->iteration_split( this, worklist ); 2998 // No verify after peeling! GCM has hoisted code out of the loop. 2999 // After peeling, the hoisted code could sink inside the peeled area. 3000 // The peeling code does not try to recompute the best location for 3001 // all the code before the peeled area, so the verify pass will always 3002 // complain about it. 3003 } 3004 // Do verify graph edges in any case 3005 NOT_PRODUCT( C->verify_graph_edges(); ); 3006 3007 if (!do_split_ifs) { 3008 // We saw major progress in Split-If to get here. We forced a 3009 // pass with unrolling and not split-if, however more split-if's 3010 // might make progress. If the unrolling didn't make progress 3011 // then the major-progress flag got cleared and we won't try 3012 // another round of Split-If. In particular the ever-common 3013 // instance-of/check-cast pattern requires at least 2 rounds of 3014 // Split-If to clear out. 3015 C->set_major_progress(); 3016 } 3017 3018 // Repeat loop optimizations if new loops were seen 3019 if (created_loop_node()) { 3020 C->set_major_progress(); 3021 } 3022 3023 // Keep loop predicates and perform optimizations with them 3024 // until no more loop optimizations could be done. 3025 // After that switch predicates off and do more loop optimizations. 3026 if (!C->major_progress() && (C->predicate_count() > 0)) { 3027 C->cleanup_loop_predicates(_igvn); 3028 if (TraceLoopOpts) { 3029 tty->print_cr("PredicatesOff"); 3030 } 3031 C->set_major_progress(); 3032 } 3033 3034 // Convert scalar to superword operations at the end of all loop opts. 3035 if (UseSuperWord && C->has_loops() && !C->major_progress()) { 3036 // SuperWord transform 3037 SuperWord sw(this); 3038 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 3039 IdealLoopTree* lpt = iter.current(); 3040 if (lpt->is_counted()) { 3041 CountedLoopNode *cl = lpt->_head->as_CountedLoop(); 3042 3043 if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) { 3044 // Check that the rce'd post loop is encountered first, multiversion after all 3045 // major main loop optimization are concluded 3046 if (!C->major_progress()) { 3047 IdealLoopTree *lpt_next = lpt->_next; 3048 if (lpt_next && lpt_next->is_counted()) { 3049 CountedLoopNode *cl = lpt_next->_head->as_CountedLoop(); 3050 has_range_checks(lpt_next); 3051 if (cl->is_post_loop() && cl->range_checks_present()) { 3052 if (!cl->is_multiversioned()) { 3053 if (multi_version_post_loops(lpt, lpt_next) == false) { 3054 // Cause the rce loop to be optimized away if we fail 3055 cl->mark_is_multiversioned(); 3056 cl->set_slp_max_unroll(0); 3057 poison_rce_post_loop(lpt); 3058 } 3059 } 3060 } 3061 } 3062 sw.transform_loop(lpt, true); 3063 } 3064 } else if (cl->is_main_loop()) { 3065 sw.transform_loop(lpt, true); 3066 } 3067 } 3068 } 3069 } 3070 3071 // Cleanup any modified bits 3072 _igvn.optimize(); 3073 3074 // disable assert until issue with split_flow_path is resolved (6742111) 3075 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(), 3076 // "shouldn't introduce irreducible loops"); 3077 3078 if (C->log() != NULL) { 3079 log_loop_tree(_ltree_root, _ltree_root, C->log()); 3080 } 3081 } 3082 3083 #ifndef PRODUCT 3084 //------------------------------print_statistics------------------------------- 3085 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes 3086 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique 3087 void PhaseIdealLoop::print_statistics() { 3088 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work); 3089 } 3090 3091 //------------------------------verify----------------------------------------- 3092 // Build a verify-only PhaseIdealLoop, and see that it agrees with me. 3093 static int fail; // debug only, so its multi-thread dont care 3094 void PhaseIdealLoop::verify() const { 3095 int old_progress = C->major_progress(); 3096 ResourceMark rm; 3097 PhaseIdealLoop loop_verify( _igvn, this ); 3098 VectorSet visited(Thread::current()->resource_area()); 3099 3100 fail = 0; 3101 verify_compare( C->root(), &loop_verify, visited ); 3102 assert( fail == 0, "verify loops failed" ); 3103 // Verify loop structure is the same 3104 _ltree_root->verify_tree(loop_verify._ltree_root, NULL); 3105 // Reset major-progress. It was cleared by creating a verify version of 3106 // PhaseIdealLoop. 3107 for( int i=0; i<old_progress; i++ ) 3108 C->set_major_progress(); 3109 } 3110 3111 //------------------------------verify_compare--------------------------------- 3112 // Make sure me and the given PhaseIdealLoop agree on key data structures 3113 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const { 3114 if( !n ) return; 3115 if( visited.test_set( n->_idx ) ) return; 3116 if( !_nodes[n->_idx] ) { // Unreachable 3117 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" ); 3118 return; 3119 } 3120 3121 uint i; 3122 for( i = 0; i < n->req(); i++ ) 3123 verify_compare( n->in(i), loop_verify, visited ); 3124 3125 // Check the '_nodes' block/loop structure 3126 i = n->_idx; 3127 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl 3128 if( _nodes[i] != loop_verify->_nodes[i] && 3129 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) { 3130 tty->print("Mismatched control setting for: "); 3131 n->dump(); 3132 if( fail++ > 10 ) return; 3133 Node *c = get_ctrl_no_update(n); 3134 tty->print("We have it as: "); 3135 if( c->in(0) ) c->dump(); 3136 else tty->print_cr("N%d",c->_idx); 3137 tty->print("Verify thinks: "); 3138 if( loop_verify->has_ctrl(n) ) 3139 loop_verify->get_ctrl_no_update(n)->dump(); 3140 else 3141 loop_verify->get_loop_idx(n)->dump(); 3142 tty->cr(); 3143 } 3144 } else { // We have a loop 3145 IdealLoopTree *us = get_loop_idx(n); 3146 if( loop_verify->has_ctrl(n) ) { 3147 tty->print("Mismatched loop setting for: "); 3148 n->dump(); 3149 if( fail++ > 10 ) return; 3150 tty->print("We have it as: "); 3151 us->dump(); 3152 tty->print("Verify thinks: "); 3153 loop_verify->get_ctrl_no_update(n)->dump(); 3154 tty->cr(); 3155 } else if (!C->major_progress()) { 3156 // Loop selection can be messed up if we did a major progress 3157 // operation, like split-if. Do not verify in that case. 3158 IdealLoopTree *them = loop_verify->get_loop_idx(n); 3159 if( us->_head != them->_head || us->_tail != them->_tail ) { 3160 tty->print("Unequals loops for: "); 3161 n->dump(); 3162 if( fail++ > 10 ) return; 3163 tty->print("We have it as: "); 3164 us->dump(); 3165 tty->print("Verify thinks: "); 3166 them->dump(); 3167 tty->cr(); 3168 } 3169 } 3170 } 3171 3172 // Check for immediate dominators being equal 3173 if( i >= _idom_size ) { 3174 if( !n->is_CFG() ) return; 3175 tty->print("CFG Node with no idom: "); 3176 n->dump(); 3177 return; 3178 } 3179 if( !n->is_CFG() ) return; 3180 if( n == C->root() ) return; // No IDOM here 3181 3182 assert(n->_idx == i, "sanity"); 3183 Node *id = idom_no_update(n); 3184 if( id != loop_verify->idom_no_update(n) ) { 3185 tty->print("Unequals idoms for: "); 3186 n->dump(); 3187 if( fail++ > 10 ) return; 3188 tty->print("We have it as: "); 3189 id->dump(); 3190 tty->print("Verify thinks: "); 3191 loop_verify->idom_no_update(n)->dump(); 3192 tty->cr(); 3193 } 3194 3195 } 3196 3197 //------------------------------verify_tree------------------------------------ 3198 // Verify that tree structures match. Because the CFG can change, siblings 3199 // within the loop tree can be reordered. We attempt to deal with that by 3200 // reordering the verify's loop tree if possible. 3201 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const { 3202 assert( _parent == parent, "Badly formed loop tree" ); 3203 3204 // Siblings not in same order? Attempt to re-order. 3205 if( _head != loop->_head ) { 3206 // Find _next pointer to update 3207 IdealLoopTree **pp = &loop->_parent->_child; 3208 while( *pp != loop ) 3209 pp = &((*pp)->_next); 3210 // Find proper sibling to be next 3211 IdealLoopTree **nn = &loop->_next; 3212 while( (*nn) && (*nn)->_head != _head ) 3213 nn = &((*nn)->_next); 3214 3215 // Check for no match. 3216 if( !(*nn) ) { 3217 // Annoyingly, irreducible loops can pick different headers 3218 // after a major_progress operation, so the rest of the loop 3219 // tree cannot be matched. 3220 if (_irreducible && Compile::current()->major_progress()) return; 3221 assert( 0, "failed to match loop tree" ); 3222 } 3223 3224 // Move (*nn) to (*pp) 3225 IdealLoopTree *hit = *nn; 3226 *nn = hit->_next; 3227 hit->_next = loop; 3228 *pp = loop; 3229 loop = hit; 3230 // Now try again to verify 3231 } 3232 3233 assert( _head == loop->_head , "mismatched loop head" ); 3234 Node *tail = _tail; // Inline a non-updating version of 3235 while( !tail->in(0) ) // the 'tail()' call. 3236 tail = tail->in(1); 3237 assert( tail == loop->_tail, "mismatched loop tail" ); 3238 3239 // Counted loops that are guarded should be able to find their guards 3240 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) { 3241 CountedLoopNode *cl = _head->as_CountedLoop(); 3242 Node *init = cl->init_trip(); 3243 Node *ctrl = cl->in(LoopNode::EntryControl); 3244 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 3245 Node *iff = ctrl->in(0); 3246 assert( iff->Opcode() == Op_If, "" ); 3247 Node *bol = iff->in(1); 3248 assert( bol->Opcode() == Op_Bool, "" ); 3249 Node *cmp = bol->in(1); 3250 assert( cmp->Opcode() == Op_CmpI, "" ); 3251 Node *add = cmp->in(1); 3252 Node *opaq; 3253 if( add->Opcode() == Op_Opaque1 ) { 3254 opaq = add; 3255 } else { 3256 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" ); 3257 assert( add == init, "" ); 3258 opaq = cmp->in(2); 3259 } 3260 assert( opaq->Opcode() == Op_Opaque1, "" ); 3261 3262 } 3263 3264 if (_child != NULL) _child->verify_tree(loop->_child, this); 3265 if (_next != NULL) _next ->verify_tree(loop->_next, parent); 3266 // Innermost loops need to verify loop bodies, 3267 // but only if no 'major_progress' 3268 int fail = 0; 3269 if (!Compile::current()->major_progress() && _child == NULL) { 3270 for( uint i = 0; i < _body.size(); i++ ) { 3271 Node *n = _body.at(i); 3272 if (n->outcnt() == 0) continue; // Ignore dead 3273 uint j; 3274 for( j = 0; j < loop->_body.size(); j++ ) 3275 if( loop->_body.at(j) == n ) 3276 break; 3277 if( j == loop->_body.size() ) { // Not found in loop body 3278 // Last ditch effort to avoid assertion: Its possible that we 3279 // have some users (so outcnt not zero) but are still dead. 3280 // Try to find from root. 3281 if (Compile::current()->root()->find(n->_idx)) { 3282 fail++; 3283 tty->print("We have that verify does not: "); 3284 n->dump(); 3285 } 3286 } 3287 } 3288 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) { 3289 Node *n = loop->_body.at(i2); 3290 if (n->outcnt() == 0) continue; // Ignore dead 3291 uint j; 3292 for( j = 0; j < _body.size(); j++ ) 3293 if( _body.at(j) == n ) 3294 break; 3295 if( j == _body.size() ) { // Not found in loop body 3296 // Last ditch effort to avoid assertion: Its possible that we 3297 // have some users (so outcnt not zero) but are still dead. 3298 // Try to find from root. 3299 if (Compile::current()->root()->find(n->_idx)) { 3300 fail++; 3301 tty->print("Verify has that we do not: "); 3302 n->dump(); 3303 } 3304 } 3305 } 3306 assert( !fail, "loop body mismatch" ); 3307 } 3308 } 3309 3310 #endif 3311 3312 //------------------------------set_idom--------------------------------------- 3313 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) { 3314 uint idx = d->_idx; 3315 if (idx >= _idom_size) { 3316 uint newsize = _idom_size<<1; 3317 while( idx >= newsize ) { 3318 newsize <<= 1; 3319 } 3320 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize); 3321 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize); 3322 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) ); 3323 _idom_size = newsize; 3324 } 3325 _idom[idx] = n; 3326 _dom_depth[idx] = dom_depth; 3327 } 3328 3329 //------------------------------recompute_dom_depth--------------------------------------- 3330 // The dominator tree is constructed with only parent pointers. 3331 // This recomputes the depth in the tree by first tagging all 3332 // nodes as "no depth yet" marker. The next pass then runs up 3333 // the dom tree from each node marked "no depth yet", and computes 3334 // the depth on the way back down. 3335 void PhaseIdealLoop::recompute_dom_depth() { 3336 uint no_depth_marker = C->unique(); 3337 uint i; 3338 // Initialize depth to "no depth yet" and realize all lazy updates 3339 for (i = 0; i < _idom_size; i++) { 3340 // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized). 3341 if (_dom_depth[i] > 0 && _idom[i] != NULL) { 3342 _dom_depth[i] = no_depth_marker; 3343 3344 // heal _idom if it has a fwd mapping in _nodes 3345 if (_idom[i]->in(0) == NULL) { 3346 idom(i); 3347 } 3348 } 3349 } 3350 if (_dom_stk == NULL) { 3351 uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size. 3352 if (init_size < 10) init_size = 10; 3353 _dom_stk = new GrowableArray<uint>(init_size); 3354 } 3355 // Compute new depth for each node. 3356 for (i = 0; i < _idom_size; i++) { 3357 uint j = i; 3358 // Run up the dom tree to find a node with a depth 3359 while (_dom_depth[j] == no_depth_marker) { 3360 _dom_stk->push(j); 3361 j = _idom[j]->_idx; 3362 } 3363 // Compute the depth on the way back down this tree branch 3364 uint dd = _dom_depth[j] + 1; 3365 while (_dom_stk->length() > 0) { 3366 uint j = _dom_stk->pop(); 3367 _dom_depth[j] = dd; 3368 dd++; 3369 } 3370 } 3371 } 3372 3373 //------------------------------sort------------------------------------------- 3374 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the 3375 // loop tree, not the root. 3376 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) { 3377 if( !innermost ) return loop; // New innermost loop 3378 3379 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number 3380 assert( loop_preorder, "not yet post-walked loop" ); 3381 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer 3382 IdealLoopTree *l = *pp; // Do I go before or after 'l'? 3383 3384 // Insert at start of list 3385 while( l ) { // Insertion sort based on pre-order 3386 if( l == loop ) return innermost; // Already on list! 3387 int l_preorder = get_preorder(l->_head); // Cache pre-order number 3388 assert( l_preorder, "not yet post-walked l" ); 3389 // Check header pre-order number to figure proper nesting 3390 if( loop_preorder > l_preorder ) 3391 break; // End of insertion 3392 // If headers tie (e.g., shared headers) check tail pre-order numbers. 3393 // Since I split shared headers, you'd think this could not happen. 3394 // BUT: I must first do the preorder numbering before I can discover I 3395 // have shared headers, so the split headers all get the same preorder 3396 // number as the RegionNode they split from. 3397 if( loop_preorder == l_preorder && 3398 get_preorder(loop->_tail) < get_preorder(l->_tail) ) 3399 break; // Also check for shared headers (same pre#) 3400 pp = &l->_parent; // Chain up list 3401 l = *pp; 3402 } 3403 // Link into list 3404 // Point predecessor to me 3405 *pp = loop; 3406 // Point me to successor 3407 IdealLoopTree *p = loop->_parent; 3408 loop->_parent = l; // Point me to successor 3409 if( p ) sort( p, innermost ); // Insert my parents into list as well 3410 return innermost; 3411 } 3412 3413 //------------------------------build_loop_tree-------------------------------- 3414 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit 3415 // bits. The _nodes[] array is mapped by Node index and holds a NULL for 3416 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the 3417 // tightest enclosing IdealLoopTree for post-walked. 3418 // 3419 // During my forward walk I do a short 1-layer lookahead to see if I can find 3420 // a loop backedge with that doesn't have any work on the backedge. This 3421 // helps me construct nested loops with shared headers better. 3422 // 3423 // Once I've done the forward recursion, I do the post-work. For each child 3424 // I check to see if there is a backedge. Backedges define a loop! I 3425 // insert an IdealLoopTree at the target of the backedge. 3426 // 3427 // During the post-work I also check to see if I have several children 3428 // belonging to different loops. If so, then this Node is a decision point 3429 // where control flow can choose to change loop nests. It is at this 3430 // decision point where I can figure out how loops are nested. At this 3431 // time I can properly order the different loop nests from my children. 3432 // Note that there may not be any backedges at the decision point! 3433 // 3434 // Since the decision point can be far removed from the backedges, I can't 3435 // order my loops at the time I discover them. Thus at the decision point 3436 // I need to inspect loop header pre-order numbers to properly nest my 3437 // loops. This means I need to sort my childrens' loops by pre-order. 3438 // The sort is of size number-of-control-children, which generally limits 3439 // it to size 2 (i.e., I just choose between my 2 target loops). 3440 void PhaseIdealLoop::build_loop_tree() { 3441 // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc 3442 GrowableArray <Node *> bltstack(C->live_nodes() >> 1); 3443 Node *n = C->root(); 3444 bltstack.push(n); 3445 int pre_order = 1; 3446 int stack_size; 3447 3448 while ( ( stack_size = bltstack.length() ) != 0 ) { 3449 n = bltstack.top(); // Leave node on stack 3450 if ( !is_visited(n) ) { 3451 // ---- Pre-pass Work ---- 3452 // Pre-walked but not post-walked nodes need a pre_order number. 3453 3454 set_preorder_visited( n, pre_order ); // set as visited 3455 3456 // ---- Scan over children ---- 3457 // Scan first over control projections that lead to loop headers. 3458 // This helps us find inner-to-outer loops with shared headers better. 3459 3460 // Scan children's children for loop headers. 3461 for ( int i = n->outcnt() - 1; i >= 0; --i ) { 3462 Node* m = n->raw_out(i); // Child 3463 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children 3464 // Scan over children's children to find loop 3465 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 3466 Node* l = m->fast_out(j); 3467 if( is_visited(l) && // Been visited? 3468 !is_postvisited(l) && // But not post-visited 3469 get_preorder(l) < pre_order ) { // And smaller pre-order 3470 // Found! Scan the DFS down this path before doing other paths 3471 bltstack.push(m); 3472 break; 3473 } 3474 } 3475 } 3476 } 3477 pre_order++; 3478 } 3479 else if ( !is_postvisited(n) ) { 3480 // Note: build_loop_tree_impl() adds out edges on rare occasions, 3481 // such as com.sun.rsasign.am::a. 3482 // For non-recursive version, first, process current children. 3483 // On next iteration, check if additional children were added. 3484 for ( int k = n->outcnt() - 1; k >= 0; --k ) { 3485 Node* u = n->raw_out(k); 3486 if ( u->is_CFG() && !is_visited(u) ) { 3487 bltstack.push(u); 3488 } 3489 } 3490 if ( bltstack.length() == stack_size ) { 3491 // There were no additional children, post visit node now 3492 (void)bltstack.pop(); // Remove node from stack 3493 pre_order = build_loop_tree_impl( n, pre_order ); 3494 // Check for bailout 3495 if (C->failing()) { 3496 return; 3497 } 3498 // Check to grow _preorders[] array for the case when 3499 // build_loop_tree_impl() adds new nodes. 3500 check_grow_preorders(); 3501 } 3502 } 3503 else { 3504 (void)bltstack.pop(); // Remove post-visited node from stack 3505 } 3506 } 3507 } 3508 3509 //------------------------------build_loop_tree_impl--------------------------- 3510 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) { 3511 // ---- Post-pass Work ---- 3512 // Pre-walked but not post-walked nodes need a pre_order number. 3513 3514 // Tightest enclosing loop for this Node 3515 IdealLoopTree *innermost = NULL; 3516 3517 // For all children, see if any edge is a backedge. If so, make a loop 3518 // for it. Then find the tightest enclosing loop for the self Node. 3519 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 3520 Node* m = n->fast_out(i); // Child 3521 if( n == m ) continue; // Ignore control self-cycles 3522 if( !m->is_CFG() ) continue;// Ignore non-CFG edges 3523 3524 IdealLoopTree *l; // Child's loop 3525 if( !is_postvisited(m) ) { // Child visited but not post-visited? 3526 // Found a backedge 3527 assert( get_preorder(m) < pre_order, "should be backedge" ); 3528 // Check for the RootNode, which is already a LoopNode and is allowed 3529 // to have multiple "backedges". 3530 if( m == C->root()) { // Found the root? 3531 l = _ltree_root; // Root is the outermost LoopNode 3532 } else { // Else found a nested loop 3533 // Insert a LoopNode to mark this loop. 3534 l = new IdealLoopTree(this, m, n); 3535 } // End of Else found a nested loop 3536 if( !has_loop(m) ) // If 'm' does not already have a loop set 3537 set_loop(m, l); // Set loop header to loop now 3538 3539 } else { // Else not a nested loop 3540 if( !_nodes[m->_idx] ) continue; // Dead code has no loop 3541 l = get_loop(m); // Get previously determined loop 3542 // If successor is header of a loop (nest), move up-loop till it 3543 // is a member of some outer enclosing loop. Since there are no 3544 // shared headers (I've split them already) I only need to go up 3545 // at most 1 level. 3546 while( l && l->_head == m ) // Successor heads loop? 3547 l = l->_parent; // Move up 1 for me 3548 // If this loop is not properly parented, then this loop 3549 // has no exit path out, i.e. its an infinite loop. 3550 if( !l ) { 3551 // Make loop "reachable" from root so the CFG is reachable. Basically 3552 // insert a bogus loop exit that is never taken. 'm', the loop head, 3553 // points to 'n', one (of possibly many) fall-in paths. There may be 3554 // many backedges as well. 3555 3556 // Here I set the loop to be the root loop. I could have, after 3557 // inserting a bogus loop exit, restarted the recursion and found my 3558 // new loop exit. This would make the infinite loop a first-class 3559 // loop and it would then get properly optimized. What's the use of 3560 // optimizing an infinite loop? 3561 l = _ltree_root; // Oops, found infinite loop 3562 3563 if (!_verify_only) { 3564 // Insert the NeverBranch between 'm' and it's control user. 3565 NeverBranchNode *iff = new NeverBranchNode( m ); 3566 _igvn.register_new_node_with_optimizer(iff); 3567 set_loop(iff, l); 3568 Node *if_t = new CProjNode( iff, 0 ); 3569 _igvn.register_new_node_with_optimizer(if_t); 3570 set_loop(if_t, l); 3571 3572 Node* cfg = NULL; // Find the One True Control User of m 3573 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 3574 Node* x = m->fast_out(j); 3575 if (x->is_CFG() && x != m && x != iff) 3576 { cfg = x; break; } 3577 } 3578 assert(cfg != NULL, "must find the control user of m"); 3579 uint k = 0; // Probably cfg->in(0) 3580 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region 3581 cfg->set_req( k, if_t ); // Now point to NeverBranch 3582 _igvn._worklist.push(cfg); 3583 3584 // Now create the never-taken loop exit 3585 Node *if_f = new CProjNode( iff, 1 ); 3586 _igvn.register_new_node_with_optimizer(if_f); 3587 set_loop(if_f, l); 3588 // Find frame ptr for Halt. Relies on the optimizer 3589 // V-N'ing. Easier and quicker than searching through 3590 // the program structure. 3591 Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr ); 3592 _igvn.register_new_node_with_optimizer(frame); 3593 // Halt & Catch Fire 3594 Node *halt = new HaltNode( if_f, frame ); 3595 _igvn.register_new_node_with_optimizer(halt); 3596 set_loop(halt, l); 3597 C->root()->add_req(halt); 3598 } 3599 set_loop(C->root(), _ltree_root); 3600 } 3601 } 3602 // Weeny check for irreducible. This child was already visited (this 3603 // IS the post-work phase). Is this child's loop header post-visited 3604 // as well? If so, then I found another entry into the loop. 3605 if (!_verify_only) { 3606 while( is_postvisited(l->_head) ) { 3607 // found irreducible 3608 l->_irreducible = 1; // = true 3609 l = l->_parent; 3610 _has_irreducible_loops = true; 3611 // Check for bad CFG here to prevent crash, and bailout of compile 3612 if (l == NULL) { 3613 C->record_method_not_compilable("unhandled CFG detected during loop optimization"); 3614 return pre_order; 3615 } 3616 } 3617 C->set_has_irreducible_loop(_has_irreducible_loops); 3618 } 3619 3620 // This Node might be a decision point for loops. It is only if 3621 // it's children belong to several different loops. The sort call 3622 // does a trivial amount of work if there is only 1 child or all 3623 // children belong to the same loop. If however, the children 3624 // belong to different loops, the sort call will properly set the 3625 // _parent pointers to show how the loops nest. 3626 // 3627 // In any case, it returns the tightest enclosing loop. 3628 innermost = sort( l, innermost ); 3629 } 3630 3631 // Def-use info will have some dead stuff; dead stuff will have no 3632 // loop decided on. 3633 3634 // Am I a loop header? If so fix up my parent's child and next ptrs. 3635 if( innermost && innermost->_head == n ) { 3636 assert( get_loop(n) == innermost, "" ); 3637 IdealLoopTree *p = innermost->_parent; 3638 IdealLoopTree *l = innermost; 3639 while( p && l->_head == n ) { 3640 l->_next = p->_child; // Put self on parents 'next child' 3641 p->_child = l; // Make self as first child of parent 3642 l = p; // Now walk up the parent chain 3643 p = l->_parent; 3644 } 3645 } else { 3646 // Note that it is possible for a LoopNode to reach here, if the 3647 // backedge has been made unreachable (hence the LoopNode no longer 3648 // denotes a Loop, and will eventually be removed). 3649 3650 // Record tightest enclosing loop for self. Mark as post-visited. 3651 set_loop(n, innermost); 3652 // Also record has_call flag early on 3653 if( innermost ) { 3654 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) { 3655 // Do not count uncommon calls 3656 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) { 3657 Node *iff = n->in(0)->in(0); 3658 // No any calls for vectorized loops. 3659 if( UseSuperWord || !iff->is_If() || 3660 (n->in(0)->Opcode() == Op_IfFalse && 3661 (1.0 - iff->as_If()->_prob) >= 0.01) || 3662 (iff->as_If()->_prob >= 0.01) ) 3663 innermost->_has_call = 1; 3664 } 3665 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) { 3666 // Disable loop optimizations if the loop has a scalar replaceable 3667 // allocation. This disabling may cause a potential performance lost 3668 // if the allocation is not eliminated for some reason. 3669 innermost->_allow_optimizations = false; 3670 innermost->_has_call = 1; // = true 3671 } else if (n->Opcode() == Op_SafePoint) { 3672 // Record all safepoints in this loop. 3673 if (innermost->_safepts == NULL) innermost->_safepts = new Node_List(); 3674 innermost->_safepts->push(n); 3675 } 3676 } 3677 } 3678 3679 // Flag as post-visited now 3680 set_postvisited(n); 3681 return pre_order; 3682 } 3683 3684 3685 //------------------------------build_loop_early------------------------------- 3686 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 3687 // First pass computes the earliest controlling node possible. This is the 3688 // controlling input with the deepest dominating depth. 3689 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 3690 while (worklist.size() != 0) { 3691 // Use local variables nstack_top_n & nstack_top_i to cache values 3692 // on nstack's top. 3693 Node *nstack_top_n = worklist.pop(); 3694 uint nstack_top_i = 0; 3695 //while_nstack_nonempty: 3696 while (true) { 3697 // Get parent node and next input's index from stack's top. 3698 Node *n = nstack_top_n; 3699 uint i = nstack_top_i; 3700 uint cnt = n->req(); // Count of inputs 3701 if (i == 0) { // Pre-process the node. 3702 if( has_node(n) && // Have either loop or control already? 3703 !has_ctrl(n) ) { // Have loop picked out already? 3704 // During "merge_many_backedges" we fold up several nested loops 3705 // into a single loop. This makes the members of the original 3706 // loop bodies pointing to dead loops; they need to move up 3707 // to the new UNION'd larger loop. I set the _head field of these 3708 // dead loops to NULL and the _parent field points to the owning 3709 // loop. Shades of UNION-FIND algorithm. 3710 IdealLoopTree *ilt; 3711 while( !(ilt = get_loop(n))->_head ) { 3712 // Normally I would use a set_loop here. But in this one special 3713 // case, it is legal (and expected) to change what loop a Node 3714 // belongs to. 3715 _nodes.map(n->_idx, (Node*)(ilt->_parent) ); 3716 } 3717 // Remove safepoints ONLY if I've already seen I don't need one. 3718 // (the old code here would yank a 2nd safepoint after seeing a 3719 // first one, even though the 1st did not dominate in the loop body 3720 // and thus could be avoided indefinitely) 3721 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint && 3722 is_deleteable_safept(n)) { 3723 Node *in = n->in(TypeFunc::Control); 3724 lazy_replace(n,in); // Pull safepoint now 3725 if (ilt->_safepts != NULL) { 3726 ilt->_safepts->yank(n); 3727 } 3728 // Carry on with the recursion "as if" we are walking 3729 // only the control input 3730 if( !visited.test_set( in->_idx ) ) { 3731 worklist.push(in); // Visit this guy later, using worklist 3732 } 3733 // Get next node from nstack: 3734 // - skip n's inputs processing by setting i > cnt; 3735 // - we also will not call set_early_ctrl(n) since 3736 // has_node(n) == true (see the condition above). 3737 i = cnt + 1; 3738 } 3739 } 3740 } // if (i == 0) 3741 3742 // Visit all inputs 3743 bool done = true; // Assume all n's inputs will be processed 3744 while (i < cnt) { 3745 Node *in = n->in(i); 3746 ++i; 3747 if (in == NULL) continue; 3748 if (in->pinned() && !in->is_CFG()) 3749 set_ctrl(in, in->in(0)); 3750 int is_visited = visited.test_set( in->_idx ); 3751 if (!has_node(in)) { // No controlling input yet? 3752 assert( !in->is_CFG(), "CFG Node with no controlling input?" ); 3753 assert( !is_visited, "visit only once" ); 3754 nstack.push(n, i); // Save parent node and next input's index. 3755 nstack_top_n = in; // Process current input now. 3756 nstack_top_i = 0; 3757 done = false; // Not all n's inputs processed. 3758 break; // continue while_nstack_nonempty; 3759 } else if (!is_visited) { 3760 // This guy has a location picked out for him, but has not yet 3761 // been visited. Happens to all CFG nodes, for instance. 3762 // Visit him using the worklist instead of recursion, to break 3763 // cycles. Since he has a location already we do not need to 3764 // find his location before proceeding with the current Node. 3765 worklist.push(in); // Visit this guy later, using worklist 3766 } 3767 } 3768 if (done) { 3769 // All of n's inputs have been processed, complete post-processing. 3770 3771 // Compute earliest point this Node can go. 3772 // CFG, Phi, pinned nodes already know their controlling input. 3773 if (!has_node(n)) { 3774 // Record earliest legal location 3775 set_early_ctrl( n ); 3776 } 3777 if (nstack.is_empty()) { 3778 // Finished all nodes on stack. 3779 // Process next node on the worklist. 3780 break; 3781 } 3782 // Get saved parent node and next input's index. 3783 nstack_top_n = nstack.node(); 3784 nstack_top_i = nstack.index(); 3785 nstack.pop(); 3786 } 3787 } // while (true) 3788 } 3789 } 3790 3791 //------------------------------dom_lca_internal-------------------------------- 3792 // Pair-wise LCA 3793 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const { 3794 if( !n1 ) return n2; // Handle NULL original LCA 3795 assert( n1->is_CFG(), "" ); 3796 assert( n2->is_CFG(), "" ); 3797 // find LCA of all uses 3798 uint d1 = dom_depth(n1); 3799 uint d2 = dom_depth(n2); 3800 while (n1 != n2) { 3801 if (d1 > d2) { 3802 n1 = idom(n1); 3803 d1 = dom_depth(n1); 3804 } else if (d1 < d2) { 3805 n2 = idom(n2); 3806 d2 = dom_depth(n2); 3807 } else { 3808 // Here d1 == d2. Due to edits of the dominator-tree, sections 3809 // of the tree might have the same depth. These sections have 3810 // to be searched more carefully. 3811 3812 // Scan up all the n1's with equal depth, looking for n2. 3813 Node *t1 = idom(n1); 3814 while (dom_depth(t1) == d1) { 3815 if (t1 == n2) return n2; 3816 t1 = idom(t1); 3817 } 3818 // Scan up all the n2's with equal depth, looking for n1. 3819 Node *t2 = idom(n2); 3820 while (dom_depth(t2) == d2) { 3821 if (t2 == n1) return n1; 3822 t2 = idom(t2); 3823 } 3824 // Move up to a new dominator-depth value as well as up the dom-tree. 3825 n1 = t1; 3826 n2 = t2; 3827 d1 = dom_depth(n1); 3828 d2 = dom_depth(n2); 3829 } 3830 } 3831 return n1; 3832 } 3833 3834 //------------------------------compute_idom----------------------------------- 3835 // Locally compute IDOM using dom_lca call. Correct only if the incoming 3836 // IDOMs are correct. 3837 Node *PhaseIdealLoop::compute_idom( Node *region ) const { 3838 assert( region->is_Region(), "" ); 3839 Node *LCA = NULL; 3840 for( uint i = 1; i < region->req(); i++ ) { 3841 if( region->in(i) != C->top() ) 3842 LCA = dom_lca( LCA, region->in(i) ); 3843 } 3844 return LCA; 3845 } 3846 3847 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) { 3848 bool had_error = false; 3849 #ifdef ASSERT 3850 if (early != C->root()) { 3851 // Make sure that there's a dominance path from LCA to early 3852 Node* d = LCA; 3853 while (d != early) { 3854 if (d == C->root()) { 3855 dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA); 3856 tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx); 3857 had_error = true; 3858 break; 3859 } 3860 d = idom(d); 3861 } 3862 } 3863 #endif 3864 return had_error; 3865 } 3866 3867 3868 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) { 3869 // Compute LCA over list of uses 3870 bool had_error = false; 3871 Node *LCA = NULL; 3872 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) { 3873 Node* c = n->fast_out(i); 3874 if (_nodes[c->_idx] == NULL) 3875 continue; // Skip the occasional dead node 3876 if( c->is_Phi() ) { // For Phis, we must land above on the path 3877 for( uint j=1; j<c->req(); j++ ) {// For all inputs 3878 if( c->in(j) == n ) { // Found matching input? 3879 Node *use = c->in(0)->in(j); 3880 if (_verify_only && use->is_top()) continue; 3881 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 3882 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 3883 } 3884 } 3885 } else { 3886 // For CFG data-users, use is in the block just prior 3887 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0); 3888 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 3889 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 3890 } 3891 } 3892 assert(!had_error, "bad dominance"); 3893 return LCA; 3894 } 3895 3896 // Check the shape of the graph at the loop entry. In some cases, 3897 // the shape of the graph does not match the shape outlined below. 3898 // That is caused by the Opaque1 node "protecting" the shape of 3899 // the graph being removed by, for example, the IGVN performed 3900 // in PhaseIdealLoop::build_and_optimize(). 3901 // 3902 // After the Opaque1 node has been removed, optimizations (e.g., split-if, 3903 // loop unswitching, and IGVN, or a combination of them) can freely change 3904 // the graph's shape. As a result, the graph shape outlined below cannot 3905 // be guaranteed anymore. 3906 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) { 3907 if (!cl->is_main_loop() && !cl->is_post_loop()) { 3908 return false; 3909 } 3910 Node* ctrl = cl->skip_predicates(); 3911 3912 if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) { 3913 return false; 3914 } 3915 Node* iffm = ctrl->in(0); 3916 if (iffm == NULL || !iffm->is_If()) { 3917 return false; 3918 } 3919 Node* bolzm = iffm->in(1); 3920 if (bolzm == NULL || !bolzm->is_Bool()) { 3921 return false; 3922 } 3923 Node* cmpzm = bolzm->in(1); 3924 if (cmpzm == NULL || !cmpzm->is_Cmp()) { 3925 return false; 3926 } 3927 // compares can get conditionally flipped 3928 bool found_opaque = false; 3929 for (uint i = 1; i < cmpzm->req(); i++) { 3930 Node* opnd = cmpzm->in(i); 3931 if (opnd && opnd->Opcode() == Op_Opaque1) { 3932 found_opaque = true; 3933 break; 3934 } 3935 } 3936 if (!found_opaque) { 3937 return false; 3938 } 3939 return true; 3940 } 3941 3942 //------------------------------get_late_ctrl---------------------------------- 3943 // Compute latest legal control. 3944 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) { 3945 assert(early != NULL, "early control should not be NULL"); 3946 3947 Node* LCA = compute_lca_of_uses(n, early); 3948 #ifdef ASSERT 3949 if (LCA == C->root() && LCA != early) { 3950 // def doesn't dominate uses so print some useful debugging output 3951 compute_lca_of_uses(n, early, true); 3952 } 3953 #endif 3954 3955 // if this is a load, check for anti-dependent stores 3956 // We use a conservative algorithm to identify potential interfering 3957 // instructions and for rescheduling the load. The users of the memory 3958 // input of this load are examined. Any use which is not a load and is 3959 // dominated by early is considered a potentially interfering store. 3960 // This can produce false positives. 3961 if (n->is_Load() && LCA != early) { 3962 Node_List worklist; 3963 3964 Node *mem = n->in(MemNode::Memory); 3965 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { 3966 Node* s = mem->fast_out(i); 3967 worklist.push(s); 3968 } 3969 while(worklist.size() != 0 && LCA != early) { 3970 Node* s = worklist.pop(); 3971 if (s->is_Load() || s->is_ShenandoahBarrier() || s->Opcode() == Op_SafePoint || 3972 (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) { 3973 continue; 3974 } else if (s->is_MergeMem()) { 3975 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) { 3976 Node* s1 = s->fast_out(i); 3977 worklist.push(s1); 3978 } 3979 } else { 3980 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0); 3981 assert(sctrl != NULL || s->outcnt() == 0, "must have control"); 3982 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) { 3983 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n); 3984 } 3985 } 3986 } 3987 } 3988 3989 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control"); 3990 return LCA; 3991 } 3992 3993 // true if CFG node d dominates CFG node n 3994 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) { 3995 if (d == n) 3996 return true; 3997 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes"); 3998 uint dd = dom_depth(d); 3999 while (dom_depth(n) >= dd) { 4000 if (n == d) 4001 return true; 4002 n = idom(n); 4003 } 4004 return false; 4005 } 4006 4007 //------------------------------dom_lca_for_get_late_ctrl_internal------------- 4008 // Pair-wise LCA with tags. 4009 // Tag each index with the node 'tag' currently being processed 4010 // before advancing up the dominator chain using idom(). 4011 // Later calls that find a match to 'tag' know that this path has already 4012 // been considered in the current LCA (which is input 'n1' by convention). 4013 // Since get_late_ctrl() is only called once for each node, the tag array 4014 // does not need to be cleared between calls to get_late_ctrl(). 4015 // Algorithm trades a larger constant factor for better asymptotic behavior 4016 // 4017 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) { 4018 uint d1 = dom_depth(n1); 4019 uint d2 = dom_depth(n2); 4020 4021 do { 4022 if (d1 > d2) { 4023 // current lca is deeper than n2 4024 _dom_lca_tags.map(n1->_idx, tag); 4025 n1 = idom(n1); 4026 d1 = dom_depth(n1); 4027 } else if (d1 < d2) { 4028 // n2 is deeper than current lca 4029 Node *memo = _dom_lca_tags[n2->_idx]; 4030 if( memo == tag ) { 4031 return n1; // Return the current LCA 4032 } 4033 _dom_lca_tags.map(n2->_idx, tag); 4034 n2 = idom(n2); 4035 d2 = dom_depth(n2); 4036 } else { 4037 // Here d1 == d2. Due to edits of the dominator-tree, sections 4038 // of the tree might have the same depth. These sections have 4039 // to be searched more carefully. 4040 4041 // Scan up all the n1's with equal depth, looking for n2. 4042 _dom_lca_tags.map(n1->_idx, tag); 4043 Node *t1 = idom(n1); 4044 while (dom_depth(t1) == d1) { 4045 if (t1 == n2) return n2; 4046 _dom_lca_tags.map(t1->_idx, tag); 4047 t1 = idom(t1); 4048 } 4049 // Scan up all the n2's with equal depth, looking for n1. 4050 _dom_lca_tags.map(n2->_idx, tag); 4051 Node *t2 = idom(n2); 4052 while (dom_depth(t2) == d2) { 4053 if (t2 == n1) return n1; 4054 _dom_lca_tags.map(t2->_idx, tag); 4055 t2 = idom(t2); 4056 } 4057 // Move up to a new dominator-depth value as well as up the dom-tree. 4058 n1 = t1; 4059 n2 = t2; 4060 d1 = dom_depth(n1); 4061 d2 = dom_depth(n2); 4062 } 4063 } while (n1 != n2); 4064 return n1; 4065 } 4066 4067 //------------------------------init_dom_lca_tags------------------------------ 4068 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 4069 // Intended use does not involve any growth for the array, so it could 4070 // be of fixed size. 4071 void PhaseIdealLoop::init_dom_lca_tags() { 4072 uint limit = C->unique() + 1; 4073 _dom_lca_tags.map( limit, NULL ); 4074 #ifdef ASSERT 4075 for( uint i = 0; i < limit; ++i ) { 4076 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 4077 } 4078 #endif // ASSERT 4079 } 4080 4081 //------------------------------clear_dom_lca_tags------------------------------ 4082 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 4083 // Intended use does not involve any growth for the array, so it could 4084 // be of fixed size. 4085 void PhaseIdealLoop::clear_dom_lca_tags() { 4086 uint limit = C->unique() + 1; 4087 _dom_lca_tags.map( limit, NULL ); 4088 _dom_lca_tags.clear(); 4089 #ifdef ASSERT 4090 for( uint i = 0; i < limit; ++i ) { 4091 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 4092 } 4093 #endif // ASSERT 4094 } 4095 4096 //------------------------------build_loop_late-------------------------------- 4097 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 4098 // Second pass finds latest legal placement, and ideal loop placement. 4099 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 4100 while (worklist.size() != 0) { 4101 Node *n = worklist.pop(); 4102 // Only visit once 4103 if (visited.test_set(n->_idx)) continue; 4104 uint cnt = n->outcnt(); 4105 uint i = 0; 4106 while (true) { 4107 assert( _nodes[n->_idx], "no dead nodes" ); 4108 // Visit all children 4109 if (i < cnt) { 4110 Node* use = n->raw_out(i); 4111 ++i; 4112 // Check for dead uses. Aggressively prune such junk. It might be 4113 // dead in the global sense, but still have local uses so I cannot 4114 // easily call 'remove_dead_node'. 4115 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead? 4116 // Due to cycles, we might not hit the same fixed point in the verify 4117 // pass as we do in the regular pass. Instead, visit such phis as 4118 // simple uses of the loop head. 4119 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) { 4120 if( !visited.test(use->_idx) ) 4121 worklist.push(use); 4122 } else if( !visited.test_set(use->_idx) ) { 4123 nstack.push(n, i); // Save parent and next use's index. 4124 n = use; // Process all children of current use. 4125 cnt = use->outcnt(); 4126 i = 0; 4127 } 4128 } else { 4129 // Do not visit around the backedge of loops via data edges. 4130 // push dead code onto a worklist 4131 _deadlist.push(use); 4132 } 4133 } else { 4134 // All of n's children have been processed, complete post-processing. 4135 build_loop_late_post(n); 4136 if (nstack.is_empty()) { 4137 // Finished all nodes on stack. 4138 // Process next node on the worklist. 4139 break; 4140 } 4141 // Get saved parent node and next use's index. Visit the rest of uses. 4142 n = nstack.node(); 4143 cnt = n->outcnt(); 4144 i = nstack.index(); 4145 nstack.pop(); 4146 } 4147 } 4148 } 4149 } 4150 4151 // Verify that no data node is scheduled in the outer loop of a strip 4152 // mined loop. 4153 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) { 4154 #ifdef ASSERT 4155 if (get_loop(least)->_nest == 0) { 4156 return; 4157 } 4158 IdealLoopTree* loop = get_loop(least); 4159 Node* head = loop->_head; 4160 if (head->is_OuterStripMinedLoop() && 4161 // Verification can't be applied to fully built strip mined loops 4162 head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) { 4163 Node* sfpt = head->as_Loop()->outer_safepoint(); 4164 ResourceMark rm; 4165 Unique_Node_List wq; 4166 wq.push(sfpt); 4167 for (uint i = 0; i < wq.size(); i++) { 4168 Node *m = wq.at(i); 4169 for (uint i = 1; i < m->req(); i++) { 4170 Node* nn = m->in(i); 4171 if (nn == n) { 4172 return; 4173 } 4174 if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) { 4175 wq.push(nn); 4176 } 4177 } 4178 } 4179 ShouldNotReachHere(); 4180 } 4181 #endif 4182 } 4183 4184 4185 //------------------------------build_loop_late_post--------------------------- 4186 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 4187 // Second pass finds latest legal placement, and ideal loop placement. 4188 void PhaseIdealLoop::build_loop_late_post(Node *n) { 4189 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2(); 4190 4191 if (bs->build_loop_late_post(this, n)) { 4192 return; 4193 } 4194 4195 build_loop_late_post_work(n, true); 4196 } 4197 4198 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) { 4199 4200 if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) { 4201 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops. 4202 } 4203 4204 #ifdef ASSERT 4205 if (_verify_only && !n->is_CFG()) { 4206 // Check def-use domination. 4207 compute_lca_of_uses(n, get_ctrl(n), true /* verify */); 4208 } 4209 #endif 4210 4211 // CFG and pinned nodes already handled 4212 if( n->in(0) ) { 4213 if( n->in(0)->is_top() ) return; // Dead? 4214 4215 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads 4216 // _must_ be pinned (they have to observe their control edge of course). 4217 // Unlike Stores (which modify an unallocable resource, the memory 4218 // state), Mods/Loads can float around. So free them up. 4219 switch( n->Opcode() ) { 4220 case Op_DivI: 4221 case Op_DivF: 4222 case Op_DivD: 4223 case Op_ModI: 4224 case Op_ModF: 4225 case Op_ModD: 4226 case Op_LoadB: // Same with Loads; they can sink 4227 case Op_LoadUB: // during loop optimizations. 4228 case Op_LoadUS: 4229 case Op_LoadD: 4230 case Op_LoadF: 4231 case Op_LoadI: 4232 case Op_LoadKlass: 4233 case Op_LoadNKlass: 4234 case Op_LoadL: 4235 case Op_LoadS: 4236 case Op_LoadP: 4237 case Op_LoadBarrierSlowReg: 4238 case Op_LoadBarrierWeakSlowReg: 4239 case Op_LoadN: 4240 case Op_LoadRange: 4241 case Op_LoadD_unaligned: 4242 case Op_LoadL_unaligned: 4243 case Op_StrComp: // Does a bunch of load-like effects 4244 case Op_StrEquals: 4245 case Op_StrIndexOf: 4246 case Op_StrIndexOfChar: 4247 case Op_AryEq: 4248 case Op_HasNegatives: 4249 pinned = false; 4250 } 4251 if( pinned ) { 4252 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n)); 4253 if( !chosen_loop->_child ) // Inner loop? 4254 chosen_loop->_body.push(n); // Collect inner loops 4255 return; 4256 } 4257 } else { // No slot zero 4258 if( n->is_CFG() ) { // CFG with no slot 0 is dead 4259 _nodes.map(n->_idx,0); // No block setting, it's globally dead 4260 return; 4261 } 4262 assert(!n->is_CFG() || n->outcnt() == 0, ""); 4263 } 4264 4265 // Do I have a "safe range" I can select over? 4266 Node *early = get_ctrl(n);// Early location already computed 4267 4268 // Compute latest point this Node can go 4269 Node *LCA = get_late_ctrl( n, early ); 4270 // LCA is NULL due to uses being dead 4271 if( LCA == NULL ) { 4272 #ifdef ASSERT 4273 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) { 4274 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead"); 4275 } 4276 #endif 4277 _nodes.map(n->_idx, 0); // This node is useless 4278 _deadlist.push(n); 4279 return; 4280 } 4281 assert(LCA != NULL && !LCA->is_top(), "no dead nodes"); 4282 4283 Node *legal = LCA; // Walk 'legal' up the IDOM chain 4284 Node *least = legal; // Best legal position so far 4285 while( early != legal ) { // While not at earliest legal 4286 #ifdef ASSERT 4287 if (legal->is_Start() && !early->is_Root()) { 4288 // Bad graph. Print idom path and fail. 4289 dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA); 4290 assert(false, "Bad graph detected in build_loop_late"); 4291 } 4292 #endif 4293 // Find least loop nesting depth 4294 legal = idom(legal); // Bump up the IDOM tree 4295 // Check for lower nesting depth 4296 if( get_loop(legal)->_nest < get_loop(least)->_nest ) 4297 least = legal; 4298 } 4299 assert(early == legal || legal != C->root(), "bad dominance of inputs"); 4300 4301 // Try not to place code on a loop entry projection 4302 // which can inhibit range check elimination. 4303 if (least != early) { 4304 Node* ctrl_out = least->unique_ctrl_out(); 4305 if (ctrl_out && ctrl_out->is_Loop() && 4306 least == ctrl_out->in(LoopNode::EntryControl)) { 4307 // Move the node above predicates as far up as possible so a 4308 // following pass of loop predication doesn't hoist a predicate 4309 // that depends on it above that node. 4310 Node* new_ctrl = least; 4311 for (;;) { 4312 if (!new_ctrl->is_Proj()) { 4313 break; 4314 } 4315 CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 4316 if (call == NULL) { 4317 break; 4318 } 4319 int req = call->uncommon_trap_request(); 4320 Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req); 4321 if (trap_reason != Deoptimization::Reason_loop_limit_check && 4322 trap_reason != Deoptimization::Reason_predicate && 4323 trap_reason != Deoptimization::Reason_profile_predicate) { 4324 break; 4325 } 4326 Node* c = new_ctrl->in(0)->in(0); 4327 if (is_dominator(c, early) && c != early) { 4328 break; 4329 } 4330 new_ctrl = c; 4331 } 4332 least = new_ctrl; 4333 } 4334 } 4335 4336 #ifdef ASSERT 4337 // If verifying, verify that 'verify_me' has a legal location 4338 // and choose it as our location. 4339 if( _verify_me ) { 4340 Node *v_ctrl = _verify_me->get_ctrl_no_update(n); 4341 Node *legal = LCA; 4342 while( early != legal ) { // While not at earliest legal 4343 if( legal == v_ctrl ) break; // Check for prior good location 4344 legal = idom(legal) ;// Bump up the IDOM tree 4345 } 4346 // Check for prior good location 4347 if( legal == v_ctrl ) least = legal; // Keep prior if found 4348 } 4349 #endif 4350 4351 // Assign discovered "here or above" point 4352 least = find_non_split_ctrl(least); 4353 verify_strip_mined_scheduling(n, least); 4354 set_ctrl(n, least); 4355 4356 // Collect inner loop bodies 4357 IdealLoopTree *chosen_loop = get_loop(least); 4358 if( !chosen_loop->_child ) // Inner loop? 4359 chosen_loop->_body.push(n);// Collect inner loops 4360 } 4361 4362 #ifdef ASSERT 4363 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) { 4364 tty->print_cr("%s", msg); 4365 tty->print("n: "); n->dump(); 4366 tty->print("early(n): "); early->dump(); 4367 if (n->in(0) != NULL && !n->in(0)->is_top() && 4368 n->in(0) != early && !n->in(0)->is_Root()) { 4369 tty->print("n->in(0): "); n->in(0)->dump(); 4370 } 4371 for (uint i = 1; i < n->req(); i++) { 4372 Node* in1 = n->in(i); 4373 if (in1 != NULL && in1 != n && !in1->is_top()) { 4374 tty->print("n->in(%d): ", i); in1->dump(); 4375 Node* in1_early = get_ctrl(in1); 4376 tty->print("early(n->in(%d)): ", i); in1_early->dump(); 4377 if (in1->in(0) != NULL && !in1->in(0)->is_top() && 4378 in1->in(0) != in1_early && !in1->in(0)->is_Root()) { 4379 tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump(); 4380 } 4381 for (uint j = 1; j < in1->req(); j++) { 4382 Node* in2 = in1->in(j); 4383 if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) { 4384 tty->print("n->in(%d)->in(%d): ", i, j); in2->dump(); 4385 Node* in2_early = get_ctrl(in2); 4386 tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump(); 4387 if (in2->in(0) != NULL && !in2->in(0)->is_top() && 4388 in2->in(0) != in2_early && !in2->in(0)->is_Root()) { 4389 tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump(); 4390 } 4391 } 4392 } 4393 } 4394 } 4395 tty->cr(); 4396 tty->print("LCA(n): "); LCA->dump(); 4397 for (uint i = 0; i < n->outcnt(); i++) { 4398 Node* u1 = n->raw_out(i); 4399 if (u1 == n) 4400 continue; 4401 tty->print("n->out(%d): ", i); u1->dump(); 4402 if (u1->is_CFG()) { 4403 for (uint j = 0; j < u1->outcnt(); j++) { 4404 Node* u2 = u1->raw_out(j); 4405 if (u2 != u1 && u2 != n && u2->is_CFG()) { 4406 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump(); 4407 } 4408 } 4409 } else { 4410 Node* u1_later = get_ctrl(u1); 4411 tty->print("later(n->out(%d)): ", i); u1_later->dump(); 4412 if (u1->in(0) != NULL && !u1->in(0)->is_top() && 4413 u1->in(0) != u1_later && !u1->in(0)->is_Root()) { 4414 tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump(); 4415 } 4416 for (uint j = 0; j < u1->outcnt(); j++) { 4417 Node* u2 = u1->raw_out(j); 4418 if (u2 == n || u2 == u1) 4419 continue; 4420 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump(); 4421 if (!u2->is_CFG()) { 4422 Node* u2_later = get_ctrl(u2); 4423 tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump(); 4424 if (u2->in(0) != NULL && !u2->in(0)->is_top() && 4425 u2->in(0) != u2_later && !u2->in(0)->is_Root()) { 4426 tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump(); 4427 } 4428 } 4429 } 4430 } 4431 } 4432 tty->cr(); 4433 int ct = 0; 4434 Node *dbg_legal = LCA; 4435 while(!dbg_legal->is_Start() && ct < 100) { 4436 tty->print("idom[%d] ",ct); dbg_legal->dump(); 4437 ct++; 4438 dbg_legal = idom(dbg_legal); 4439 } 4440 tty->cr(); 4441 } 4442 #endif 4443 4444 #ifndef PRODUCT 4445 //------------------------------dump------------------------------------------- 4446 void PhaseIdealLoop::dump( ) const { 4447 ResourceMark rm; 4448 Arena* arena = Thread::current()->resource_area(); 4449 Node_Stack stack(arena, C->live_nodes() >> 2); 4450 Node_List rpo_list; 4451 VectorSet visited(arena); 4452 visited.set(C->top()->_idx); 4453 rpo( C->root(), stack, visited, rpo_list ); 4454 // Dump root loop indexed by last element in PO order 4455 dump( _ltree_root, rpo_list.size(), rpo_list ); 4456 } 4457 4458 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const { 4459 loop->dump_head(); 4460 4461 // Now scan for CFG nodes in the same loop 4462 for( uint j=idx; j > 0; j-- ) { 4463 Node *n = rpo_list[j-1]; 4464 if( !_nodes[n->_idx] ) // Skip dead nodes 4465 continue; 4466 if( get_loop(n) != loop ) { // Wrong loop nest 4467 if( get_loop(n)->_head == n && // Found nested loop? 4468 get_loop(n)->_parent == loop ) 4469 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly 4470 continue; 4471 } 4472 4473 // Dump controlling node 4474 for( uint x = 0; x < loop->_nest; x++ ) 4475 tty->print(" "); 4476 tty->print("C"); 4477 if( n == C->root() ) { 4478 n->dump(); 4479 } else { 4480 Node* cached_idom = idom_no_update(n); 4481 Node *computed_idom = n->in(0); 4482 if( n->is_Region() ) { 4483 computed_idom = compute_idom(n); 4484 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or 4485 // any MultiBranch ctrl node), so apply a similar transform to 4486 // the cached idom returned from idom_no_update. 4487 cached_idom = find_non_split_ctrl(cached_idom); 4488 } 4489 tty->print(" ID:%d",computed_idom->_idx); 4490 n->dump(); 4491 if( cached_idom != computed_idom ) { 4492 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d", 4493 computed_idom->_idx, cached_idom->_idx); 4494 } 4495 } 4496 // Dump nodes it controls 4497 for( uint k = 0; k < _nodes.Size(); k++ ) { 4498 // (k < C->unique() && get_ctrl(find(k)) == n) 4499 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) { 4500 Node *m = C->root()->find(k); 4501 if( m && m->outcnt() > 0 ) { 4502 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) { 4503 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p", 4504 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL); 4505 } 4506 for( uint j = 0; j < loop->_nest; j++ ) 4507 tty->print(" "); 4508 tty->print(" "); 4509 m->dump(); 4510 } 4511 } 4512 } 4513 } 4514 } 4515 #endif 4516 4517 // Collect a R-P-O for the whole CFG. 4518 // Result list is in post-order (scan backwards for RPO) 4519 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const { 4520 stk.push(start, 0); 4521 visited.set(start->_idx); 4522 4523 while (stk.is_nonempty()) { 4524 Node* m = stk.node(); 4525 uint idx = stk.index(); 4526 if (idx < m->outcnt()) { 4527 stk.set_index(idx + 1); 4528 Node* n = m->raw_out(idx); 4529 if (n->is_CFG() && !visited.test_set(n->_idx)) { 4530 stk.push(n, 0); 4531 } 4532 } else { 4533 rpo_list.push(m); 4534 stk.pop(); 4535 } 4536 } 4537 } 4538 4539 4540 //============================================================================= 4541 //------------------------------LoopTreeIterator----------------------------------- 4542 4543 // Advance to next loop tree using a preorder, left-to-right traversal. 4544 void LoopTreeIterator::next() { 4545 assert(!done(), "must not be done."); 4546 if (_curnt->_child != NULL) { 4547 _curnt = _curnt->_child; 4548 } else if (_curnt->_next != NULL) { 4549 _curnt = _curnt->_next; 4550 } else { 4551 while (_curnt != _root && _curnt->_next == NULL) { 4552 _curnt = _curnt->_parent; 4553 } 4554 if (_curnt == _root) { 4555 _curnt = NULL; 4556 assert(done(), "must be done."); 4557 } else { 4558 assert(_curnt->_next != NULL, "must be more to do"); 4559 _curnt = _curnt->_next; 4560 } 4561 } 4562 }