1 /* 2 * Copyright (c) 1998, 2011, 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 "libadt/vectset.hpp" 29 #include "memory/allocation.inline.hpp" 30 #include "opto/addnode.hpp" 31 #include "opto/callnode.hpp" 32 #include "opto/connode.hpp" 33 #include "opto/divnode.hpp" 34 #include "opto/idealGraphPrinter.hpp" 35 #include "opto/loopnode.hpp" 36 #include "opto/mulnode.hpp" 37 #include "opto/rootnode.hpp" 38 #include "opto/superword.hpp" 39 40 //============================================================================= 41 //------------------------------is_loop_iv------------------------------------- 42 // Determine if a node is Counted loop induction variable. 43 // The method is declared in node.hpp. 44 const Node* Node::is_loop_iv() const { 45 if (this->is_Phi() && !this->as_Phi()->is_copy() && 46 this->as_Phi()->region()->is_CountedLoop() && 47 this->as_Phi()->region()->as_CountedLoop()->phi() == this) { 48 return this; 49 } else { 50 return NULL; 51 } 52 } 53 54 //============================================================================= 55 //------------------------------dump_spec-------------------------------------- 56 // Dump special per-node info 57 #ifndef PRODUCT 58 void LoopNode::dump_spec(outputStream *st) const { 59 if (is_inner_loop()) st->print( "inner " ); 60 if (is_partial_peel_loop()) st->print( "partial_peel " ); 61 if (partial_peel_has_failed()) st->print( "partial_peel_failed " ); 62 } 63 #endif 64 65 //------------------------------is_valid_counted_loop------------------------- 66 bool LoopNode::is_valid_counted_loop() const { 67 if (is_CountedLoop()) { 68 CountedLoopNode* l = as_CountedLoop(); 69 CountedLoopEndNode* le = l->loopexit(); 70 if (le != NULL && 71 le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) { 72 Node* phi = l->phi(); 73 Node* exit = le->proj_out(0 /* false */); 74 if (exit != NULL && exit->Opcode() == Op_IfFalse && 75 phi != NULL && phi->is_Phi() && 76 phi->in(LoopNode::LoopBackControl) == l->incr() && 77 le->loopnode() == l && le->stride_is_con()) { 78 return true; 79 } 80 } 81 } 82 return false; 83 } 84 85 //------------------------------get_early_ctrl--------------------------------- 86 // Compute earliest legal control 87 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) { 88 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" ); 89 uint i; 90 Node *early; 91 if( n->in(0) ) { 92 early = n->in(0); 93 if( !early->is_CFG() ) // Might be a non-CFG multi-def 94 early = get_ctrl(early); // So treat input as a straight data input 95 i = 1; 96 } else { 97 early = get_ctrl(n->in(1)); 98 i = 2; 99 } 100 uint e_d = dom_depth(early); 101 assert( early, "" ); 102 for( ; i < n->req(); i++ ) { 103 Node *cin = get_ctrl(n->in(i)); 104 assert( cin, "" ); 105 // Keep deepest dominator depth 106 uint c_d = dom_depth(cin); 107 if( c_d > e_d ) { // Deeper guy? 108 early = cin; // Keep deepest found so far 109 e_d = c_d; 110 } else if( c_d == e_d && // Same depth? 111 early != cin ) { // If not equal, must use slower algorithm 112 // If same depth but not equal, one _must_ dominate the other 113 // and we want the deeper (i.e., dominated) guy. 114 Node *n1 = early; 115 Node *n2 = cin; 116 while( 1 ) { 117 n1 = idom(n1); // Walk up until break cycle 118 n2 = idom(n2); 119 if( n1 == cin || // Walked early up to cin 120 dom_depth(n2) < c_d ) 121 break; // early is deeper; keep him 122 if( n2 == early || // Walked cin up to early 123 dom_depth(n1) < c_d ) { 124 early = cin; // cin is deeper; keep him 125 break; 126 } 127 } 128 e_d = dom_depth(early); // Reset depth register cache 129 } 130 } 131 132 // Return earliest legal location 133 assert(early == find_non_split_ctrl(early), "unexpected early control"); 134 135 return early; 136 } 137 138 //------------------------------set_early_ctrl--------------------------------- 139 // Set earliest legal control 140 void PhaseIdealLoop::set_early_ctrl( Node *n ) { 141 Node *early = get_early_ctrl(n); 142 143 // Record earliest legal location 144 set_ctrl(n, early); 145 } 146 147 //------------------------------set_subtree_ctrl------------------------------- 148 // set missing _ctrl entries on new nodes 149 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) { 150 // Already set? Get out. 151 if( _nodes[n->_idx] ) return; 152 // Recursively set _nodes array to indicate where the Node goes 153 uint i; 154 for( i = 0; i < n->req(); ++i ) { 155 Node *m = n->in(i); 156 if( m && m != C->root() ) 157 set_subtree_ctrl( m ); 158 } 159 160 // Fixup self 161 set_early_ctrl( n ); 162 } 163 164 //------------------------------is_counted_loop-------------------------------- 165 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) { 166 PhaseGVN *gvn = &_igvn; 167 168 // Counted loop head must be a good RegionNode with only 3 not NULL 169 // control input edges: Self, Entry, LoopBack. 170 if (x->in(LoopNode::Self) == NULL || x->req() != 3) 171 return false; 172 173 Node *init_control = x->in(LoopNode::EntryControl); 174 Node *back_control = x->in(LoopNode::LoopBackControl); 175 if (init_control == NULL || back_control == NULL) // Partially dead 176 return false; 177 // Must also check for TOP when looking for a dead loop 178 if (init_control->is_top() || back_control->is_top()) 179 return false; 180 181 // Allow funny placement of Safepoint 182 if (back_control->Opcode() == Op_SafePoint) 183 back_control = back_control->in(TypeFunc::Control); 184 185 // Controlling test for loop 186 Node *iftrue = back_control; 187 uint iftrue_op = iftrue->Opcode(); 188 if (iftrue_op != Op_IfTrue && 189 iftrue_op != Op_IfFalse) 190 // I have a weird back-control. Probably the loop-exit test is in 191 // the middle of the loop and I am looking at some trailing control-flow 192 // merge point. To fix this I would have to partially peel the loop. 193 return false; // Obscure back-control 194 195 // Get boolean guarding loop-back test 196 Node *iff = iftrue->in(0); 197 if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) 198 return false; 199 BoolNode *test = iff->in(1)->as_Bool(); 200 BoolTest::mask bt = test->_test._test; 201 float cl_prob = iff->as_If()->_prob; 202 if (iftrue_op == Op_IfFalse) { 203 bt = BoolTest(bt).negate(); 204 cl_prob = 1.0 - cl_prob; 205 } 206 // Get backedge compare 207 Node *cmp = test->in(1); 208 int cmp_op = cmp->Opcode(); 209 if (cmp_op != Op_CmpI) 210 return false; // Avoid pointer & float compares 211 212 // Find the trip-counter increment & limit. Limit must be loop invariant. 213 Node *incr = cmp->in(1); 214 Node *limit = cmp->in(2); 215 216 // --------- 217 // need 'loop()' test to tell if limit is loop invariant 218 // --------- 219 220 if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit? 221 Node *tmp = incr; // Then reverse order into the CmpI 222 incr = limit; 223 limit = tmp; 224 bt = BoolTest(bt).commute(); // And commute the exit test 225 } 226 if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant 227 return false; 228 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant 229 return false; 230 231 Node* phi_incr = NULL; 232 // Trip-counter increment must be commutative & associative. 233 if (incr->is_Phi()) { 234 if (incr->as_Phi()->region() != x || incr->req() != 3) 235 return false; // Not simple trip counter expression 236 phi_incr = incr; 237 incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi 238 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant 239 return false; 240 } 241 242 Node* trunc1 = NULL; 243 Node* trunc2 = NULL; 244 const TypeInt* iv_trunc_t = NULL; 245 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) { 246 return false; // Funny increment opcode 247 } 248 assert(incr->Opcode() == Op_AddI, "wrong increment code"); 249 250 // Get merge point 251 Node *xphi = incr->in(1); 252 Node *stride = incr->in(2); 253 if (!stride->is_Con()) { // Oops, swap these 254 if (!xphi->is_Con()) // Is the other guy a constant? 255 return false; // Nope, unknown stride, bail out 256 Node *tmp = xphi; // 'incr' is commutative, so ok to swap 257 xphi = stride; 258 stride = tmp; 259 } 260 // Stride must be constant 261 int stride_con = stride->get_int(); 262 if (stride_con == 0) 263 return false; // missed some peephole opt 264 265 if (!xphi->is_Phi()) 266 return false; // Too much math on the trip counter 267 if (phi_incr != NULL && phi_incr != xphi) 268 return false; 269 PhiNode *phi = xphi->as_Phi(); 270 271 // Phi must be of loop header; backedge must wrap to increment 272 if (phi->region() != x) 273 return false; 274 if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr || 275 trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) { 276 return false; 277 } 278 Node *init_trip = phi->in(LoopNode::EntryControl); 279 280 // If iv trunc type is smaller than int, check for possible wrap. 281 if (!TypeInt::INT->higher_equal(iv_trunc_t)) { 282 assert(trunc1 != NULL, "must have found some truncation"); 283 284 // Get a better type for the phi (filtered thru if's) 285 const TypeInt* phi_ft = filtered_type(phi); 286 287 // Can iv take on a value that will wrap? 288 // 289 // Ensure iv's limit is not within "stride" of the wrap value. 290 // 291 // Example for "short" type 292 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t) 293 // If the stride is +10, then the last value of the induction 294 // variable before the increment (phi_ft->_hi) must be 295 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to 296 // ensure no truncation occurs after the increment. 297 298 if (stride_con > 0) { 299 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con || 300 iv_trunc_t->_lo > phi_ft->_lo) { 301 return false; // truncation may occur 302 } 303 } else if (stride_con < 0) { 304 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con || 305 iv_trunc_t->_hi < phi_ft->_hi) { 306 return false; // truncation may occur 307 } 308 } 309 // No possibility of wrap so truncation can be discarded 310 // Promote iv type to Int 311 } else { 312 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int"); 313 } 314 315 // If the condition is inverted and we will be rolling 316 // through MININT to MAXINT, then bail out. 317 if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice! 318 // Odd stride 319 bt == BoolTest::ne && stride_con != 1 && stride_con != -1 || 320 // Count down loop rolls through MAXINT 321 (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 || 322 // Count up loop rolls through MININT 323 (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) { 324 return false; // Bail out 325 } 326 327 const TypeInt* init_t = gvn->type(init_trip)->is_int(); 328 const TypeInt* limit_t = gvn->type(limit)->is_int(); 329 330 if (stride_con > 0) { 331 long init_p = (long)init_t->_lo + stride_con; 332 if (init_p > (long)max_jint || init_p > (long)limit_t->_hi) 333 return false; // cyclic loop or this loop trips only once 334 } else { 335 long init_p = (long)init_t->_hi + stride_con; 336 if (init_p < (long)min_jint || init_p < (long)limit_t->_lo) 337 return false; // cyclic loop or this loop trips only once 338 } 339 340 // ================================================= 341 // ---- SUCCESS! Found A Trip-Counted Loop! ----- 342 // 343 assert(x->Opcode() == Op_Loop, "regular loops only"); 344 C->print_method("Before CountedLoop", 3); 345 346 Node *hook = new (C, 6) Node(6); 347 348 if (LoopLimitCheck) { 349 350 // =================================================== 351 // Generate loop limit check to avoid integer overflow 352 // in cases like next (cyclic loops): 353 // 354 // for (i=0; i <= max_jint; i++) {} 355 // for (i=0; i < max_jint; i+=2) {} 356 // 357 // 358 // Limit check predicate depends on the loop test: 359 // 360 // for(;i != limit; i++) --> limit <= (max_jint) 361 // for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1) 362 // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride ) 363 // 364 365 // Check if limit is excluded to do more precise int overflow check. 366 bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge); 367 int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1)); 368 369 // If compare points directly to the phi we need to adjust 370 // the compare so that it points to the incr. Limit have 371 // to be adjusted to keep trip count the same and the 372 // adjusted limit should be checked for int overflow. 373 if (phi_incr != NULL) { 374 stride_m += stride_con; 375 } 376 377 if (limit->is_Con()) { 378 int limit_con = limit->get_int(); 379 if ((stride_con > 0 && limit_con > (max_jint - stride_m)) || 380 (stride_con < 0 && limit_con < (min_jint - stride_m))) { 381 // Bailout: it could be integer overflow. 382 return false; 383 } 384 } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) || 385 (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) { 386 // Limit's type may satisfy the condition, for example, 387 // when it is an array length. 388 } else { 389 // Generate loop's limit check. 390 // Loop limit check predicate should be near the loop. 391 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check); 392 if (!limit_check_proj) { 393 // The limit check predicate is not generated if this method trapped here before. 394 #ifdef ASSERT 395 if (TraceLoopLimitCheck) { 396 tty->print("missing loop limit check:"); 397 loop->dump_head(); 398 x->dump(1); 399 } 400 #endif 401 return false; 402 } 403 404 IfNode* check_iff = limit_check_proj->in(0)->as_If(); 405 Node* cmp_limit; 406 Node* bol; 407 408 if (stride_con > 0) { 409 cmp_limit = new (C, 3) CmpINode(limit, _igvn.intcon(max_jint - stride_m)); 410 bol = new (C, 2) BoolNode(cmp_limit, BoolTest::le); 411 } else { 412 cmp_limit = new (C, 3) CmpINode(limit, _igvn.intcon(min_jint - stride_m)); 413 bol = new (C, 2) BoolNode(cmp_limit, BoolTest::ge); 414 } 415 cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit); 416 bol = _igvn.register_new_node_with_optimizer(bol); 417 set_subtree_ctrl(bol); 418 419 // Replace condition in original predicate but preserve Opaque node 420 // so that previous predicates could be found. 421 assert(check_iff->in(1)->Opcode() == Op_Conv2B && 422 check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, ""); 423 Node* opq = check_iff->in(1)->in(1); 424 _igvn.hash_delete(opq); 425 opq->set_req(1, bol); 426 // Update ctrl. 427 set_ctrl(opq, check_iff->in(0)); 428 set_ctrl(check_iff->in(1), check_iff->in(0)); 429 430 #ifndef PRODUCT 431 // report that the loop predication has been actually performed 432 // for this loop 433 if (TraceLoopLimitCheck) { 434 tty->print_cr("Counted Loop Limit Check generated:"); 435 debug_only( bol->dump(2); ) 436 } 437 #endif 438 } 439 440 if (phi_incr != NULL) { 441 // If compare points directly to the phi we need to adjust 442 // the compare so that it points to the incr. Limit have 443 // to be adjusted to keep trip count the same and we 444 // should avoid int overflow. 445 // 446 // i = init; do {} while(i++ < limit); 447 // is converted to 448 // i = init; do {} while(++i < limit+1); 449 // 450 limit = gvn->transform(new (C, 3) AddINode(limit, stride)); 451 } 452 453 // Now we need to canonicalize loop condition. 454 if (bt == BoolTest::ne) { 455 assert(stride_con == 1 || stride_con == -1, "simple increment only"); 456 // 'ne' can be replaced with 'lt' only when init < limit. 457 if (stride_con > 0 && init_t->_hi < limit_t->_lo) 458 bt = BoolTest::lt; 459 // 'ne' can be replaced with 'gt' only when init > limit. 460 if (stride_con < 0 && init_t->_lo > limit_t->_hi) 461 bt = BoolTest::gt; 462 } 463 464 if (incl_limit) { 465 // The limit check guaranties that 'limit <= (max_jint - stride)' so 466 // we can convert 'i <= limit' to 'i < limit+1' since stride != 0. 467 // 468 Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1); 469 limit = gvn->transform(new (C, 3) AddINode(limit, one)); 470 if (bt == BoolTest::le) 471 bt = BoolTest::lt; 472 else if (bt == BoolTest::ge) 473 bt = BoolTest::gt; 474 else 475 ShouldNotReachHere(); 476 } 477 set_subtree_ctrl( limit ); 478 479 } else { // LoopLimitCheck 480 481 // If compare points to incr, we are ok. Otherwise the compare 482 // can directly point to the phi; in this case adjust the compare so that 483 // it points to the incr by adjusting the limit. 484 if (cmp->in(1) == phi || cmp->in(2) == phi) 485 limit = gvn->transform(new (C, 3) AddINode(limit,stride)); 486 487 // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride. 488 // Final value for iterator should be: trip_count * stride + init_trip. 489 Node *one_p = gvn->intcon( 1); 490 Node *one_m = gvn->intcon(-1); 491 492 Node *trip_count = NULL; 493 switch( bt ) { 494 case BoolTest::eq: 495 ShouldNotReachHere(); 496 case BoolTest::ne: // Ahh, the case we desire 497 if (stride_con == 1) 498 trip_count = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 499 else if (stride_con == -1) 500 trip_count = gvn->transform(new (C, 3) SubINode(init_trip,limit)); 501 else 502 ShouldNotReachHere(); 503 set_subtree_ctrl(trip_count); 504 //_loop.map(trip_count->_idx,loop(limit)); 505 break; 506 case BoolTest::le: // Maybe convert to '<' case 507 limit = gvn->transform(new (C, 3) AddINode(limit,one_p)); 508 set_subtree_ctrl( limit ); 509 hook->init_req(4, limit); 510 511 bt = BoolTest::lt; 512 // Make the new limit be in the same loop nest as the old limit 513 //_loop.map(limit->_idx,limit_loop); 514 // Fall into next case 515 case BoolTest::lt: { // Maybe convert to '!=' case 516 if (stride_con < 0) // Count down loop rolls through MAXINT 517 ShouldNotReachHere(); 518 Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 519 set_subtree_ctrl( range ); 520 hook->init_req(0, range); 521 522 Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); 523 set_subtree_ctrl( bias ); 524 hook->init_req(1, bias); 525 526 Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_m)); 527 set_subtree_ctrl( bias1 ); 528 hook->init_req(2, bias1); 529 530 trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); 531 set_subtree_ctrl( trip_count ); 532 hook->init_req(3, trip_count); 533 break; 534 } 535 536 case BoolTest::ge: // Maybe convert to '>' case 537 limit = gvn->transform(new (C, 3) AddINode(limit,one_m)); 538 set_subtree_ctrl( limit ); 539 hook->init_req(4 ,limit); 540 541 bt = BoolTest::gt; 542 // Make the new limit be in the same loop nest as the old limit 543 //_loop.map(limit->_idx,limit_loop); 544 // Fall into next case 545 case BoolTest::gt: { // Maybe convert to '!=' case 546 if (stride_con > 0) // count up loop rolls through MININT 547 ShouldNotReachHere(); 548 Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 549 set_subtree_ctrl( range ); 550 hook->init_req(0, range); 551 552 Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); 553 set_subtree_ctrl( bias ); 554 hook->init_req(1, bias); 555 556 Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_p)); 557 set_subtree_ctrl( bias1 ); 558 hook->init_req(2, bias1); 559 560 trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); 561 set_subtree_ctrl( trip_count ); 562 hook->init_req(3, trip_count); 563 break; 564 } 565 } // switch( bt ) 566 567 Node *span = gvn->transform(new (C, 3) MulINode(trip_count,stride)); 568 set_subtree_ctrl( span ); 569 hook->init_req(5, span); 570 571 limit = gvn->transform(new (C, 3) AddINode(span,init_trip)); 572 set_subtree_ctrl( limit ); 573 574 } // LoopLimitCheck 575 576 // Check for SafePoint on backedge and remove 577 Node *sfpt = x->in(LoopNode::LoopBackControl); 578 if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) { 579 lazy_replace( sfpt, iftrue ); 580 loop->_tail = iftrue; 581 } 582 583 // Build a canonical trip test. 584 // Clone code, as old values may be in use. 585 Node* nphi = PhiNode::make(x, init_trip, TypeInt::INT); 586 nphi = _igvn.register_new_node_with_optimizer(nphi); 587 set_ctrl(nphi, get_ctrl(phi)); 588 589 incr = incr->clone(); 590 incr->set_req(1,nphi); 591 incr->set_req(2,stride); 592 incr = _igvn.register_new_node_with_optimizer(incr); 593 set_early_ctrl( incr ); 594 595 nphi->set_req(LoopNode::LoopBackControl, incr); 596 _igvn.replace_node(phi, nphi); 597 phi = nphi->as_Phi(); 598 599 cmp = cmp->clone(); 600 cmp->set_req(1,incr); 601 cmp->set_req(2,limit); 602 cmp = _igvn.register_new_node_with_optimizer(cmp); 603 set_ctrl(cmp, iff->in(0)); 604 605 test = test->clone()->as_Bool(); 606 (*(BoolTest*)&test->_test)._test = bt; 607 test->set_req(1,cmp); 608 _igvn.register_new_node_with_optimizer(test); 609 set_ctrl(test, iff->in(0)); 610 611 // Replace the old IfNode with a new LoopEndNode 612 Node *lex = _igvn.register_new_node_with_optimizer(new (C, 2) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt )); 613 IfNode *le = lex->as_If(); 614 uint dd = dom_depth(iff); 615 set_idom(le, le->in(0), dd); // Update dominance for loop exit 616 set_loop(le, loop); 617 618 // Get the loop-exit control 619 Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue)); 620 621 // Need to swap loop-exit and loop-back control? 622 if (iftrue_op == Op_IfFalse) { 623 Node *ift2=_igvn.register_new_node_with_optimizer(new (C, 1) IfTrueNode (le)); 624 Node *iff2=_igvn.register_new_node_with_optimizer(new (C, 1) IfFalseNode(le)); 625 626 loop->_tail = back_control = ift2; 627 set_loop(ift2, loop); 628 set_loop(iff2, get_loop(iffalse)); 629 630 // Lazy update of 'get_ctrl' mechanism. 631 lazy_replace_proj( iffalse, iff2 ); 632 lazy_replace_proj( iftrue, ift2 ); 633 634 // Swap names 635 iffalse = iff2; 636 iftrue = ift2; 637 } else { 638 _igvn.hash_delete(iffalse); 639 _igvn.hash_delete(iftrue); 640 iffalse->set_req_X( 0, le, &_igvn ); 641 iftrue ->set_req_X( 0, le, &_igvn ); 642 } 643 644 set_idom(iftrue, le, dd+1); 645 set_idom(iffalse, le, dd+1); 646 assert(iff->outcnt() == 0, "should be dead now"); 647 lazy_replace( iff, le ); // fix 'get_ctrl' 648 649 // Now setup a new CountedLoopNode to replace the existing LoopNode 650 CountedLoopNode *l = new (C, 3) CountedLoopNode(init_control, back_control); 651 l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve 652 // The following assert is approximately true, and defines the intention 653 // of can_be_counted_loop. It fails, however, because phase->type 654 // is not yet initialized for this loop and its parts. 655 //assert(l->can_be_counted_loop(this), "sanity"); 656 _igvn.register_new_node_with_optimizer(l); 657 set_loop(l, loop); 658 loop->_head = l; 659 // Fix all data nodes placed at the old loop head. 660 // Uses the lazy-update mechanism of 'get_ctrl'. 661 lazy_replace( x, l ); 662 set_idom(l, init_control, dom_depth(x)); 663 664 // Check for immediately preceding SafePoint and remove 665 Node *sfpt2 = le->in(0); 666 if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) 667 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control)); 668 669 // Free up intermediate goo 670 _igvn.remove_dead_node(hook); 671 672 #ifdef ASSERT 673 assert(l->is_valid_counted_loop(), "counted loop shape is messed up"); 674 assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" ); 675 #endif 676 #ifndef PRODUCT 677 if (TraceLoopOpts) { 678 tty->print("Counted "); 679 loop->dump_head(); 680 } 681 #endif 682 683 C->print_method("After CountedLoop", 3); 684 685 return true; 686 } 687 688 //----------------------exact_limit------------------------------------------- 689 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) { 690 assert(loop->_head->is_CountedLoop(), ""); 691 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 692 assert(cl->is_valid_counted_loop(), ""); 693 694 if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 || 695 cl->limit()->Opcode() == Op_LoopLimit) { 696 // Old code has exact limit (it could be incorrect in case of int overflow). 697 // Loop limit is exact with stride == 1. And loop may already have exact limit. 698 return cl->limit(); 699 } 700 Node *limit = NULL; 701 #ifdef ASSERT 702 BoolTest::mask bt = cl->loopexit()->test_trip(); 703 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected"); 704 #endif 705 if (cl->has_exact_trip_count()) { 706 // Simple case: loop has constant boundaries. 707 // Use longs to avoid integer overflow. 708 int stride_con = cl->stride_con(); 709 long init_con = cl->init_trip()->get_int(); 710 long limit_con = cl->limit()->get_int(); 711 julong trip_cnt = cl->trip_count(); 712 long final_con = init_con + trip_cnt*stride_con; 713 final_con -= stride_con; 714 int final_int = (int)final_con; 715 // The final value should be in integer range since the loop 716 // is counted and the limit was checked for overflow. 717 assert(final_con == (long)final_int, "final value should be integer"); 718 limit = _igvn.intcon(final_int); 719 } else { 720 // Create new LoopLimit node to get exact limit (final iv value). 721 limit = new (C, 4) LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride()); 722 register_new_node(limit, cl->in(LoopNode::EntryControl)); 723 } 724 assert(limit != NULL, "sanity"); 725 return limit; 726 } 727 728 //------------------------------Ideal------------------------------------------ 729 // Return a node which is more "ideal" than the current node. 730 // Attempt to convert into a counted-loop. 731 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 732 if (!can_be_counted_loop(phase)) { 733 phase->C->set_major_progress(); 734 } 735 return RegionNode::Ideal(phase, can_reshape); 736 } 737 738 739 //============================================================================= 740 //------------------------------Ideal------------------------------------------ 741 // Return a node which is more "ideal" than the current node. 742 // Attempt to convert into a counted-loop. 743 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 744 return RegionNode::Ideal(phase, can_reshape); 745 } 746 747 //------------------------------dump_spec-------------------------------------- 748 // Dump special per-node info 749 #ifndef PRODUCT 750 void CountedLoopNode::dump_spec(outputStream *st) const { 751 LoopNode::dump_spec(st); 752 if (stride_is_con()) { 753 st->print("stride: %d ",stride_con()); 754 } 755 if (is_pre_loop ()) st->print("pre of N%d" , _main_idx); 756 if (is_main_loop()) st->print("main of N%d", _idx); 757 if (is_post_loop()) st->print("post of N%d", _main_idx); 758 } 759 #endif 760 761 //============================================================================= 762 int CountedLoopEndNode::stride_con() const { 763 return stride()->bottom_type()->is_int()->get_con(); 764 } 765 766 //============================================================================= 767 //------------------------------Value----------------------------------------- 768 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const { 769 const Type* init_t = phase->type(in(Init)); 770 const Type* limit_t = phase->type(in(Limit)); 771 const Type* stride_t = phase->type(in(Stride)); 772 // Either input is TOP ==> the result is TOP 773 if (init_t == Type::TOP) return Type::TOP; 774 if (limit_t == Type::TOP) return Type::TOP; 775 if (stride_t == Type::TOP) return Type::TOP; 776 777 int stride_con = stride_t->is_int()->get_con(); 778 if (stride_con == 1) 779 return NULL; // Identity 780 781 if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) { 782 // Use longs to avoid integer overflow. 783 long init_con = init_t->is_int()->get_con(); 784 long limit_con = limit_t->is_int()->get_con(); 785 int stride_m = stride_con - (stride_con > 0 ? 1 : -1); 786 long trip_count = (limit_con - init_con + stride_m)/stride_con; 787 long final_con = init_con + stride_con*trip_count; 788 int final_int = (int)final_con; 789 // The final value should be in integer range since the loop 790 // is counted and the limit was checked for overflow. 791 assert(final_con == (long)final_int, "final value should be integer"); 792 return TypeInt::make(final_int); 793 } 794 795 return bottom_type(); // TypeInt::INT 796 } 797 798 //------------------------------Ideal------------------------------------------ 799 // Return a node which is more "ideal" than the current node. 800 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) { 801 if (phase->type(in(Init)) == Type::TOP || 802 phase->type(in(Limit)) == Type::TOP || 803 phase->type(in(Stride)) == Type::TOP) 804 return NULL; // Dead 805 806 int stride_con = phase->type(in(Stride))->is_int()->get_con(); 807 if (stride_con == 1) 808 return NULL; // Identity 809 810 if (in(Init)->is_Con() && in(Limit)->is_Con()) 811 return NULL; // Value 812 813 // Delay following optimizations until all loop optimizations 814 // done to keep Ideal graph simple. 815 if (!can_reshape || phase->C->major_progress()) 816 return NULL; 817 818 const TypeInt* init_t = phase->type(in(Init) )->is_int(); 819 const TypeInt* limit_t = phase->type(in(Limit))->is_int(); 820 int stride_p; 821 long lim, ini; 822 julong max; 823 if (stride_con > 0) { 824 stride_p = stride_con; 825 lim = limit_t->_hi; 826 ini = init_t->_lo; 827 max = (julong)max_jint; 828 } else { 829 stride_p = -stride_con; 830 lim = init_t->_hi; 831 ini = limit_t->_lo; 832 max = (julong)min_jint; 833 } 834 julong range = lim - ini + stride_p; 835 if (range <= max) { 836 // Convert to integer expression if it is not overflow. 837 Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1)); 838 Node *range = phase->transform(new (phase->C, 3) SubINode(in(Limit), in(Init))); 839 Node *bias = phase->transform(new (phase->C, 3) AddINode(range, stride_m)); 840 Node *trip = phase->transform(new (phase->C, 3) DivINode(0, bias, in(Stride))); 841 Node *span = phase->transform(new (phase->C, 3) MulINode(trip, in(Stride))); 842 return new (phase->C, 3) AddINode(span, in(Init)); // exact limit 843 } 844 845 if (is_power_of_2(stride_p) || // divisor is 2^n 846 !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node? 847 // Convert to long expression to avoid integer overflow 848 // and let igvn optimizer convert this division. 849 // 850 Node* init = phase->transform( new (phase->C, 2) ConvI2LNode(in(Init))); 851 Node* limit = phase->transform( new (phase->C, 2) ConvI2LNode(in(Limit))); 852 Node* stride = phase->longcon(stride_con); 853 Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1)); 854 855 Node *range = phase->transform(new (phase->C, 3) SubLNode(limit, init)); 856 Node *bias = phase->transform(new (phase->C, 3) AddLNode(range, stride_m)); 857 Node *span; 858 if (stride_con > 0 && is_power_of_2(stride_p)) { 859 // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride) 860 // and avoid generating rounding for division. Zero trip guard should 861 // guarantee that init < limit but sometimes the guard is missing and 862 // we can get situation when init > limit. Note, for the empty loop 863 // optimization zero trip guard is generated explicitly which leaves 864 // only RCE predicate where exact limit is used and the predicate 865 // will simply fail forcing recompilation. 866 Node* neg_stride = phase->longcon(-stride_con); 867 span = phase->transform(new (phase->C, 3) AndLNode(bias, neg_stride)); 868 } else { 869 Node *trip = phase->transform(new (phase->C, 3) DivLNode(0, bias, stride)); 870 span = phase->transform(new (phase->C, 3) MulLNode(trip, stride)); 871 } 872 // Convert back to int 873 Node *span_int = phase->transform(new (phase->C, 2) ConvL2INode(span)); 874 return new (phase->C, 3) AddINode(span_int, in(Init)); // exact limit 875 } 876 877 return NULL; // No progress 878 } 879 880 //------------------------------Identity--------------------------------------- 881 // If stride == 1 return limit node. 882 Node *LoopLimitNode::Identity( PhaseTransform *phase ) { 883 int stride_con = phase->type(in(Stride))->is_int()->get_con(); 884 if (stride_con == 1 || stride_con == -1) 885 return in(Limit); 886 return this; 887 } 888 889 //============================================================================= 890 //----------------------match_incr_with_optional_truncation-------------------- 891 // Match increment with optional truncation: 892 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16 893 // Return NULL for failure. Success returns the increment node. 894 Node* CountedLoopNode::match_incr_with_optional_truncation( 895 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) { 896 // Quick cutouts: 897 if (expr == NULL || expr->req() != 3) return false; 898 899 Node *t1 = NULL; 900 Node *t2 = NULL; 901 const TypeInt* trunc_t = TypeInt::INT; 902 Node* n1 = expr; 903 int n1op = n1->Opcode(); 904 905 // Try to strip (n1 & M) or (n1 << N >> N) from n1. 906 if (n1op == Op_AndI && 907 n1->in(2)->is_Con() && 908 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) { 909 // %%% This check should match any mask of 2**K-1. 910 t1 = n1; 911 n1 = t1->in(1); 912 n1op = n1->Opcode(); 913 trunc_t = TypeInt::CHAR; 914 } else if (n1op == Op_RShiftI && 915 n1->in(1) != NULL && 916 n1->in(1)->Opcode() == Op_LShiftI && 917 n1->in(2) == n1->in(1)->in(2) && 918 n1->in(2)->is_Con()) { 919 jint shift = n1->in(2)->bottom_type()->is_int()->get_con(); 920 // %%% This check should match any shift in [1..31]. 921 if (shift == 16 || shift == 8) { 922 t1 = n1; 923 t2 = t1->in(1); 924 n1 = t2->in(1); 925 n1op = n1->Opcode(); 926 if (shift == 16) { 927 trunc_t = TypeInt::SHORT; 928 } else if (shift == 8) { 929 trunc_t = TypeInt::BYTE; 930 } 931 } 932 } 933 934 // If (maybe after stripping) it is an AddI, we won: 935 if (n1op == Op_AddI) { 936 *trunc1 = t1; 937 *trunc2 = t2; 938 *trunc_type = trunc_t; 939 return n1; 940 } 941 942 // failed 943 return NULL; 944 } 945 946 947 //------------------------------filtered_type-------------------------------- 948 // Return a type based on condition control flow 949 // A successful return will be a type that is restricted due 950 // to a series of dominating if-tests, such as: 951 // if (i < 10) { 952 // if (i > 0) { 953 // here: "i" type is [1..10) 954 // } 955 // } 956 // or a control flow merge 957 // if (i < 10) { 958 // do { 959 // phi( , ) -- at top of loop type is [min_int..10) 960 // i = ? 961 // } while ( i < 10) 962 // 963 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) { 964 assert(n && n->bottom_type()->is_int(), "must be int"); 965 const TypeInt* filtered_t = NULL; 966 if (!n->is_Phi()) { 967 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control"); 968 filtered_t = filtered_type_from_dominators(n, n_ctrl); 969 970 } else { 971 Node* phi = n->as_Phi(); 972 Node* region = phi->in(0); 973 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region"); 974 if (region && region != C->top()) { 975 for (uint i = 1; i < phi->req(); i++) { 976 Node* val = phi->in(i); 977 Node* use_c = region->in(i); 978 const TypeInt* val_t = filtered_type_from_dominators(val, use_c); 979 if (val_t != NULL) { 980 if (filtered_t == NULL) { 981 filtered_t = val_t; 982 } else { 983 filtered_t = filtered_t->meet(val_t)->is_int(); 984 } 985 } 986 } 987 } 988 } 989 const TypeInt* n_t = _igvn.type(n)->is_int(); 990 if (filtered_t != NULL) { 991 n_t = n_t->join(filtered_t)->is_int(); 992 } 993 return n_t; 994 } 995 996 997 //------------------------------filtered_type_from_dominators-------------------------------- 998 // Return a possibly more restrictive type for val based on condition control flow of dominators 999 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) { 1000 if (val->is_Con()) { 1001 return val->bottom_type()->is_int(); 1002 } 1003 uint if_limit = 10; // Max number of dominating if's visited 1004 const TypeInt* rtn_t = NULL; 1005 1006 if (use_ctrl && use_ctrl != C->top()) { 1007 Node* val_ctrl = get_ctrl(val); 1008 uint val_dom_depth = dom_depth(val_ctrl); 1009 Node* pred = use_ctrl; 1010 uint if_cnt = 0; 1011 while (if_cnt < if_limit) { 1012 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) { 1013 if_cnt++; 1014 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred); 1015 if (if_t != NULL) { 1016 if (rtn_t == NULL) { 1017 rtn_t = if_t; 1018 } else { 1019 rtn_t = rtn_t->join(if_t)->is_int(); 1020 } 1021 } 1022 } 1023 pred = idom(pred); 1024 if (pred == NULL || pred == C->top()) { 1025 break; 1026 } 1027 // Stop if going beyond definition block of val 1028 if (dom_depth(pred) < val_dom_depth) { 1029 break; 1030 } 1031 } 1032 } 1033 return rtn_t; 1034 } 1035 1036 1037 //------------------------------dump_spec-------------------------------------- 1038 // Dump special per-node info 1039 #ifndef PRODUCT 1040 void CountedLoopEndNode::dump_spec(outputStream *st) const { 1041 if( in(TestValue)->is_Bool() ) { 1042 BoolTest bt( test_trip()); // Added this for g++. 1043 1044 st->print("["); 1045 bt.dump_on(st); 1046 st->print("]"); 1047 } 1048 st->print(" "); 1049 IfNode::dump_spec(st); 1050 } 1051 #endif 1052 1053 //============================================================================= 1054 //------------------------------is_member-------------------------------------- 1055 // Is 'l' a member of 'this'? 1056 int IdealLoopTree::is_member( const IdealLoopTree *l ) const { 1057 while( l->_nest > _nest ) l = l->_parent; 1058 return l == this; 1059 } 1060 1061 //------------------------------set_nest--------------------------------------- 1062 // Set loop tree nesting depth. Accumulate _has_call bits. 1063 int IdealLoopTree::set_nest( uint depth ) { 1064 _nest = depth; 1065 int bits = _has_call; 1066 if( _child ) bits |= _child->set_nest(depth+1); 1067 if( bits ) _has_call = 1; 1068 if( _next ) bits |= _next ->set_nest(depth ); 1069 return bits; 1070 } 1071 1072 //------------------------------split_fall_in---------------------------------- 1073 // Split out multiple fall-in edges from the loop header. Move them to a 1074 // private RegionNode before the loop. This becomes the loop landing pad. 1075 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) { 1076 PhaseIterGVN &igvn = phase->_igvn; 1077 uint i; 1078 1079 // Make a new RegionNode to be the landing pad. 1080 Node *landing_pad = new (phase->C, fall_in_cnt+1) RegionNode( fall_in_cnt+1 ); 1081 phase->set_loop(landing_pad,_parent); 1082 // Gather all the fall-in control paths into the landing pad 1083 uint icnt = fall_in_cnt; 1084 uint oreq = _head->req(); 1085 for( i = oreq-1; i>0; i-- ) 1086 if( !phase->is_member( this, _head->in(i) ) ) 1087 landing_pad->set_req(icnt--,_head->in(i)); 1088 1089 // Peel off PhiNode edges as well 1090 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1091 Node *oj = _head->fast_out(j); 1092 if( oj->is_Phi() ) { 1093 PhiNode* old_phi = oj->as_Phi(); 1094 assert( old_phi->region() == _head, "" ); 1095 igvn.hash_delete(old_phi); // Yank from hash before hacking edges 1096 Node *p = PhiNode::make_blank(landing_pad, old_phi); 1097 uint icnt = fall_in_cnt; 1098 for( i = oreq-1; i>0; i-- ) { 1099 if( !phase->is_member( this, _head->in(i) ) ) { 1100 p->init_req(icnt--, old_phi->in(i)); 1101 // Go ahead and clean out old edges from old phi 1102 old_phi->del_req(i); 1103 } 1104 } 1105 // Search for CSE's here, because ZKM.jar does a lot of 1106 // loop hackery and we need to be a little incremental 1107 // with the CSE to avoid O(N^2) node blow-up. 1108 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE 1109 if( p2 ) { // Found CSE 1110 p->destruct(); // Recover useless new node 1111 p = p2; // Use old node 1112 } else { 1113 igvn.register_new_node_with_optimizer(p, old_phi); 1114 } 1115 // Make old Phi refer to new Phi. 1116 old_phi->add_req(p); 1117 // Check for the special case of making the old phi useless and 1118 // disappear it. In JavaGrande I have a case where this useless 1119 // Phi is the loop limit and prevents recognizing a CountedLoop 1120 // which in turn prevents removing an empty loop. 1121 Node *id_old_phi = old_phi->Identity( &igvn ); 1122 if( id_old_phi != old_phi ) { // Found a simple identity? 1123 // Note that I cannot call 'replace_node' here, because 1124 // that will yank the edge from old_phi to the Region and 1125 // I'm mid-iteration over the Region's uses. 1126 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) { 1127 Node* use = old_phi->last_out(i); 1128 igvn.hash_delete(use); 1129 igvn._worklist.push(use); 1130 uint uses_found = 0; 1131 for (uint j = 0; j < use->len(); j++) { 1132 if (use->in(j) == old_phi) { 1133 if (j < use->req()) use->set_req (j, id_old_phi); 1134 else use->set_prec(j, id_old_phi); 1135 uses_found++; 1136 } 1137 } 1138 i -= uses_found; // we deleted 1 or more copies of this edge 1139 } 1140 } 1141 igvn._worklist.push(old_phi); 1142 } 1143 } 1144 // Finally clean out the fall-in edges from the RegionNode 1145 for( i = oreq-1; i>0; i-- ) { 1146 if( !phase->is_member( this, _head->in(i) ) ) { 1147 _head->del_req(i); 1148 } 1149 } 1150 // Transform landing pad 1151 igvn.register_new_node_with_optimizer(landing_pad, _head); 1152 // Insert landing pad into the header 1153 _head->add_req(landing_pad); 1154 } 1155 1156 //------------------------------split_outer_loop------------------------------- 1157 // Split out the outermost loop from this shared header. 1158 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) { 1159 PhaseIterGVN &igvn = phase->_igvn; 1160 1161 // Find index of outermost loop; it should also be my tail. 1162 uint outer_idx = 1; 1163 while( _head->in(outer_idx) != _tail ) outer_idx++; 1164 1165 // Make a LoopNode for the outermost loop. 1166 Node *ctl = _head->in(LoopNode::EntryControl); 1167 Node *outer = new (phase->C, 3) LoopNode( ctl, _head->in(outer_idx) ); 1168 outer = igvn.register_new_node_with_optimizer(outer, _head); 1169 phase->set_created_loop_node(); 1170 1171 // Outermost loop falls into '_head' loop 1172 _head->set_req(LoopNode::EntryControl, outer); 1173 _head->del_req(outer_idx); 1174 // Split all the Phis up between '_head' loop and 'outer' loop. 1175 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1176 Node *out = _head->fast_out(j); 1177 if( out->is_Phi() ) { 1178 PhiNode *old_phi = out->as_Phi(); 1179 assert( old_phi->region() == _head, "" ); 1180 Node *phi = PhiNode::make_blank(outer, old_phi); 1181 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl)); 1182 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx)); 1183 phi = igvn.register_new_node_with_optimizer(phi, old_phi); 1184 // Make old Phi point to new Phi on the fall-in path 1185 igvn.hash_delete(old_phi); 1186 old_phi->set_req(LoopNode::EntryControl, phi); 1187 old_phi->del_req(outer_idx); 1188 igvn._worklist.push(old_phi); 1189 } 1190 } 1191 1192 // Use the new loop head instead of the old shared one 1193 _head = outer; 1194 phase->set_loop(_head, this); 1195 } 1196 1197 //------------------------------fix_parent------------------------------------- 1198 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) { 1199 loop->_parent = parent; 1200 if( loop->_child ) fix_parent( loop->_child, loop ); 1201 if( loop->_next ) fix_parent( loop->_next , parent ); 1202 } 1203 1204 //------------------------------estimate_path_freq----------------------------- 1205 static float estimate_path_freq( Node *n ) { 1206 // Try to extract some path frequency info 1207 IfNode *iff; 1208 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests 1209 uint nop = n->Opcode(); 1210 if( nop == Op_SafePoint ) { // Skip any safepoint 1211 n = n->in(0); 1212 continue; 1213 } 1214 if( nop == Op_CatchProj ) { // Get count from a prior call 1215 // Assume call does not always throw exceptions: means the call-site 1216 // count is also the frequency of the fall-through path. 1217 assert( n->is_CatchProj(), "" ); 1218 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index ) 1219 return 0.0f; // Assume call exception path is rare 1220 Node *call = n->in(0)->in(0)->in(0); 1221 assert( call->is_Call(), "expect a call here" ); 1222 const JVMState *jvms = ((CallNode*)call)->jvms(); 1223 ciMethodData* methodData = jvms->method()->method_data(); 1224 if (!methodData->is_mature()) return 0.0f; // No call-site data 1225 ciProfileData* data = methodData->bci_to_data(jvms->bci()); 1226 if ((data == NULL) || !data->is_CounterData()) { 1227 // no call profile available, try call's control input 1228 n = n->in(0); 1229 continue; 1230 } 1231 return data->as_CounterData()->count()/FreqCountInvocations; 1232 } 1233 // See if there's a gating IF test 1234 Node *n_c = n->in(0); 1235 if( !n_c->is_If() ) break; // No estimate available 1236 iff = n_c->as_If(); 1237 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count? 1238 // Compute how much count comes on this path 1239 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt; 1240 // Have no count info. Skip dull uncommon-trap like branches. 1241 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) || 1242 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) ) 1243 break; 1244 // Skip through never-taken branch; look for a real loop exit. 1245 n = iff->in(0); 1246 } 1247 return 0.0f; // No estimate available 1248 } 1249 1250 //------------------------------merge_many_backedges--------------------------- 1251 // Merge all the backedges from the shared header into a private Region. 1252 // Feed that region as the one backedge to this loop. 1253 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) { 1254 uint i; 1255 1256 // Scan for the top 2 hottest backedges 1257 float hotcnt = 0.0f; 1258 float warmcnt = 0.0f; 1259 uint hot_idx = 0; 1260 // Loop starts at 2 because slot 1 is the fall-in path 1261 for( i = 2; i < _head->req(); i++ ) { 1262 float cnt = estimate_path_freq(_head->in(i)); 1263 if( cnt > hotcnt ) { // Grab hottest path 1264 warmcnt = hotcnt; 1265 hotcnt = cnt; 1266 hot_idx = i; 1267 } else if( cnt > warmcnt ) { // And 2nd hottest path 1268 warmcnt = cnt; 1269 } 1270 } 1271 1272 // See if the hottest backedge is worthy of being an inner loop 1273 // by being much hotter than the next hottest backedge. 1274 if( hotcnt <= 0.0001 || 1275 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge 1276 1277 // Peel out the backedges into a private merge point; peel 1278 // them all except optionally hot_idx. 1279 PhaseIterGVN &igvn = phase->_igvn; 1280 1281 Node *hot_tail = NULL; 1282 // Make a Region for the merge point 1283 Node *r = new (phase->C, 1) RegionNode(1); 1284 for( i = 2; i < _head->req(); i++ ) { 1285 if( i != hot_idx ) 1286 r->add_req( _head->in(i) ); 1287 else hot_tail = _head->in(i); 1288 } 1289 igvn.register_new_node_with_optimizer(r, _head); 1290 // Plug region into end of loop _head, followed by hot_tail 1291 while( _head->req() > 3 ) _head->del_req( _head->req()-1 ); 1292 _head->set_req(2, r); 1293 if( hot_idx ) _head->add_req(hot_tail); 1294 1295 // Split all the Phis up between '_head' loop and the Region 'r' 1296 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 1297 Node *out = _head->fast_out(j); 1298 if( out->is_Phi() ) { 1299 PhiNode* n = out->as_Phi(); 1300 igvn.hash_delete(n); // Delete from hash before hacking edges 1301 Node *hot_phi = NULL; 1302 Node *phi = new (phase->C, r->req()) PhiNode(r, n->type(), n->adr_type()); 1303 // Check all inputs for the ones to peel out 1304 uint j = 1; 1305 for( uint i = 2; i < n->req(); i++ ) { 1306 if( i != hot_idx ) 1307 phi->set_req( j++, n->in(i) ); 1308 else hot_phi = n->in(i); 1309 } 1310 // Register the phi but do not transform until whole place transforms 1311 igvn.register_new_node_with_optimizer(phi, n); 1312 // Add the merge phi to the old Phi 1313 while( n->req() > 3 ) n->del_req( n->req()-1 ); 1314 n->set_req(2, phi); 1315 if( hot_idx ) n->add_req(hot_phi); 1316 } 1317 } 1318 1319 1320 // Insert a new IdealLoopTree inserted below me. Turn it into a clone 1321 // of self loop tree. Turn self into a loop headed by _head and with 1322 // tail being the new merge point. 1323 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail ); 1324 phase->set_loop(_tail,ilt); // Adjust tail 1325 _tail = r; // Self's tail is new merge point 1326 phase->set_loop(r,this); 1327 ilt->_child = _child; // New guy has my children 1328 _child = ilt; // Self has new guy as only child 1329 ilt->_parent = this; // new guy has self for parent 1330 ilt->_nest = _nest; // Same nesting depth (for now) 1331 1332 // Starting with 'ilt', look for child loop trees using the same shared 1333 // header. Flatten these out; they will no longer be loops in the end. 1334 IdealLoopTree **pilt = &_child; 1335 while( ilt ) { 1336 if( ilt->_head == _head ) { 1337 uint i; 1338 for( i = 2; i < _head->req(); i++ ) 1339 if( _head->in(i) == ilt->_tail ) 1340 break; // Still a loop 1341 if( i == _head->req() ) { // No longer a loop 1342 // Flatten ilt. Hang ilt's "_next" list from the end of 1343 // ilt's '_child' list. Move the ilt's _child up to replace ilt. 1344 IdealLoopTree **cp = &ilt->_child; 1345 while( *cp ) cp = &(*cp)->_next; // Find end of child list 1346 *cp = ilt->_next; // Hang next list at end of child list 1347 *pilt = ilt->_child; // Move child up to replace ilt 1348 ilt->_head = NULL; // Flag as a loop UNIONED into parent 1349 ilt = ilt->_child; // Repeat using new ilt 1350 continue; // do not advance over ilt->_child 1351 } 1352 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" ); 1353 phase->set_loop(_head,ilt); 1354 } 1355 pilt = &ilt->_child; // Advance to next 1356 ilt = *pilt; 1357 } 1358 1359 if( _child ) fix_parent( _child, this ); 1360 } 1361 1362 //------------------------------beautify_loops--------------------------------- 1363 // Split shared headers and insert loop landing pads. 1364 // Insert a LoopNode to replace the RegionNode. 1365 // Return TRUE if loop tree is structurally changed. 1366 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) { 1367 bool result = false; 1368 // Cache parts in locals for easy 1369 PhaseIterGVN &igvn = phase->_igvn; 1370 1371 igvn.hash_delete(_head); // Yank from hash before hacking edges 1372 1373 // Check for multiple fall-in paths. Peel off a landing pad if need be. 1374 int fall_in_cnt = 0; 1375 for( uint i = 1; i < _head->req(); i++ ) 1376 if( !phase->is_member( this, _head->in(i) ) ) 1377 fall_in_cnt++; 1378 assert( fall_in_cnt, "at least 1 fall-in path" ); 1379 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins 1380 split_fall_in( phase, fall_in_cnt ); 1381 1382 // Swap inputs to the _head and all Phis to move the fall-in edge to 1383 // the left. 1384 fall_in_cnt = 1; 1385 while( phase->is_member( this, _head->in(fall_in_cnt) ) ) 1386 fall_in_cnt++; 1387 if( fall_in_cnt > 1 ) { 1388 // Since I am just swapping inputs I do not need to update def-use info 1389 Node *tmp = _head->in(1); 1390 _head->set_req( 1, _head->in(fall_in_cnt) ); 1391 _head->set_req( fall_in_cnt, tmp ); 1392 // Swap also all Phis 1393 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) { 1394 Node* phi = _head->fast_out(i); 1395 if( phi->is_Phi() ) { 1396 igvn.hash_delete(phi); // Yank from hash before hacking edges 1397 tmp = phi->in(1); 1398 phi->set_req( 1, phi->in(fall_in_cnt) ); 1399 phi->set_req( fall_in_cnt, tmp ); 1400 } 1401 } 1402 } 1403 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" ); 1404 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" ); 1405 1406 // If I am a shared header (multiple backedges), peel off the many 1407 // backedges into a private merge point and use the merge point as 1408 // the one true backedge. 1409 if( _head->req() > 3 ) { 1410 // Merge the many backedges into a single backedge but leave 1411 // the hottest backedge as separate edge for the following peel. 1412 merge_many_backedges( phase ); 1413 result = true; 1414 } 1415 1416 // If I have one hot backedge, peel off myself loop. 1417 // I better be the outermost loop. 1418 if( _head->req() > 3 ) { 1419 split_outer_loop( phase ); 1420 result = true; 1421 1422 } else if( !_head->is_Loop() && !_irreducible ) { 1423 // Make a new LoopNode to replace the old loop head 1424 Node *l = new (phase->C, 3) LoopNode( _head->in(1), _head->in(2) ); 1425 l = igvn.register_new_node_with_optimizer(l, _head); 1426 phase->set_created_loop_node(); 1427 // Go ahead and replace _head 1428 phase->_igvn.replace_node( _head, l ); 1429 _head = l; 1430 phase->set_loop(_head, this); 1431 } 1432 1433 // Now recursively beautify nested loops 1434 if( _child ) result |= _child->beautify_loops( phase ); 1435 if( _next ) result |= _next ->beautify_loops( phase ); 1436 return result; 1437 } 1438 1439 //------------------------------allpaths_check_safepts---------------------------- 1440 // Allpaths backwards scan from loop tail, terminating each path at first safepoint 1441 // encountered. Helper for check_safepts. 1442 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) { 1443 assert(stack.size() == 0, "empty stack"); 1444 stack.push(_tail); 1445 visited.Clear(); 1446 visited.set(_tail->_idx); 1447 while (stack.size() > 0) { 1448 Node* n = stack.pop(); 1449 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 1450 // Terminate this path 1451 } else if (n->Opcode() == Op_SafePoint) { 1452 if (_phase->get_loop(n) != this) { 1453 if (_required_safept == NULL) _required_safept = new Node_List(); 1454 _required_safept->push(n); // save the one closest to the tail 1455 } 1456 // Terminate this path 1457 } else { 1458 uint start = n->is_Region() ? 1 : 0; 1459 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1; 1460 for (uint i = start; i < end; i++) { 1461 Node* in = n->in(i); 1462 assert(in->is_CFG(), "must be"); 1463 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) { 1464 stack.push(in); 1465 } 1466 } 1467 } 1468 } 1469 } 1470 1471 //------------------------------check_safepts---------------------------- 1472 // Given dominators, try to find loops with calls that must always be 1473 // executed (call dominates loop tail). These loops do not need non-call 1474 // safepoints (ncsfpt). 1475 // 1476 // A complication is that a safepoint in a inner loop may be needed 1477 // by an outer loop. In the following, the inner loop sees it has a 1478 // call (block 3) on every path from the head (block 2) to the 1479 // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint) 1480 // in block 2, _but_ this leaves the outer loop without a safepoint. 1481 // 1482 // entry 0 1483 // | 1484 // v 1485 // outer 1,2 +->1 1486 // | | 1487 // | v 1488 // | 2<---+ ncsfpt in 2 1489 // |_/|\ | 1490 // | v | 1491 // inner 2,3 / 3 | call in 3 1492 // / | | 1493 // v +--+ 1494 // exit 4 1495 // 1496 // 1497 // This method creates a list (_required_safept) of ncsfpt nodes that must 1498 // be protected is created for each loop. When a ncsfpt maybe deleted, it 1499 // is first looked for in the lists for the outer loops of the current loop. 1500 // 1501 // The insights into the problem: 1502 // A) counted loops are okay 1503 // B) innermost loops are okay (only an inner loop can delete 1504 // a ncsfpt needed by an outer loop) 1505 // C) a loop is immune from an inner loop deleting a safepoint 1506 // if the loop has a call on the idom-path 1507 // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the 1508 // idom-path that is not in a nested loop 1509 // E) otherwise, an ncsfpt on the idom-path that is nested in an inner 1510 // loop needs to be prevented from deletion by an inner loop 1511 // 1512 // There are two analyses: 1513 // 1) The first, and cheaper one, scans the loop body from 1514 // tail to head following the idom (immediate dominator) 1515 // chain, looking for the cases (C,D,E) above. 1516 // Since inner loops are scanned before outer loops, there is summary 1517 // information about inner loops. Inner loops can be skipped over 1518 // when the tail of an inner loop is encountered. 1519 // 1520 // 2) The second, invoked if the first fails to find a call or ncsfpt on 1521 // the idom path (which is rare), scans all predecessor control paths 1522 // from the tail to the head, terminating a path when a call or sfpt 1523 // is encountered, to find the ncsfpt's that are closest to the tail. 1524 // 1525 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) { 1526 // Bottom up traversal 1527 IdealLoopTree* ch = _child; 1528 while (ch != NULL) { 1529 ch->check_safepts(visited, stack); 1530 ch = ch->_next; 1531 } 1532 1533 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) { 1534 bool has_call = false; // call on dom-path 1535 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth 1536 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth 1537 // Scan the dom-path nodes from tail to head 1538 for (Node* n = tail(); n != _head; n = _phase->idom(n)) { 1539 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 1540 has_call = true; 1541 _has_sfpt = 1; // Then no need for a safept! 1542 break; 1543 } else if (n->Opcode() == Op_SafePoint) { 1544 if (_phase->get_loop(n) == this) { 1545 has_local_ncsfpt = true; 1546 break; 1547 } 1548 if (nonlocal_ncsfpt == NULL) { 1549 nonlocal_ncsfpt = n; // save the one closest to the tail 1550 } 1551 } else { 1552 IdealLoopTree* nlpt = _phase->get_loop(n); 1553 if (this != nlpt) { 1554 // If at an inner loop tail, see if the inner loop has already 1555 // recorded seeing a call on the dom-path (and stop.) If not, 1556 // jump to the head of the inner loop. 1557 assert(is_member(nlpt), "nested loop"); 1558 Node* tail = nlpt->_tail; 1559 if (tail->in(0)->is_If()) tail = tail->in(0); 1560 if (n == tail) { 1561 // If inner loop has call on dom-path, so does outer loop 1562 if (nlpt->_has_sfpt) { 1563 has_call = true; 1564 _has_sfpt = 1; 1565 break; 1566 } 1567 // Skip to head of inner loop 1568 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head"); 1569 n = nlpt->_head; 1570 } 1571 } 1572 } 1573 } 1574 // Record safept's that this loop needs preserved when an 1575 // inner loop attempts to delete it's safepoints. 1576 if (_child != NULL && !has_call && !has_local_ncsfpt) { 1577 if (nonlocal_ncsfpt != NULL) { 1578 if (_required_safept == NULL) _required_safept = new Node_List(); 1579 _required_safept->push(nonlocal_ncsfpt); 1580 } else { 1581 // Failed to find a suitable safept on the dom-path. Now use 1582 // an all paths walk from tail to head, looking for safepoints to preserve. 1583 allpaths_check_safepts(visited, stack); 1584 } 1585 } 1586 } 1587 } 1588 1589 //---------------------------is_deleteable_safept---------------------------- 1590 // Is safept not required by an outer loop? 1591 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) { 1592 assert(sfpt->Opcode() == Op_SafePoint, ""); 1593 IdealLoopTree* lp = get_loop(sfpt)->_parent; 1594 while (lp != NULL) { 1595 Node_List* sfpts = lp->_required_safept; 1596 if (sfpts != NULL) { 1597 for (uint i = 0; i < sfpts->size(); i++) { 1598 if (sfpt == sfpts->at(i)) 1599 return false; 1600 } 1601 } 1602 lp = lp->_parent; 1603 } 1604 return true; 1605 } 1606 1607 //---------------------------replace_parallel_iv------------------------------- 1608 // Replace parallel induction variable (parallel to trip counter) 1609 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) { 1610 assert(loop->_head->is_CountedLoop(), ""); 1611 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1612 if (!cl->is_valid_counted_loop()) 1613 return; // skip malformed counted loop 1614 Node *incr = cl->incr(); 1615 if (incr == NULL) 1616 return; // Dead loop? 1617 Node *init = cl->init_trip(); 1618 Node *phi = cl->phi(); 1619 int stride_con = cl->stride_con(); 1620 1621 PhaseGVN *gvn = &_igvn; 1622 1623 // Visit all children, looking for Phis 1624 for (DUIterator i = cl->outs(); cl->has_out(i); i++) { 1625 Node *out = cl->out(i); 1626 // Look for other phis (secondary IVs). Skip dead ones 1627 if (!out->is_Phi() || out == phi || !has_node(out)) 1628 continue; 1629 PhiNode* phi2 = out->as_Phi(); 1630 Node *incr2 = phi2->in( LoopNode::LoopBackControl ); 1631 // Look for induction variables of the form: X += constant 1632 if (phi2->region() != loop->_head || 1633 incr2->req() != 3 || 1634 incr2->in(1) != phi2 || 1635 incr2 == incr || 1636 incr2->Opcode() != Op_AddI || 1637 !incr2->in(2)->is_Con()) 1638 continue; 1639 1640 // Check for parallel induction variable (parallel to trip counter) 1641 // via an affine function. In particular, count-down loops with 1642 // count-up array indices are common. We only RCE references off 1643 // the trip-counter, so we need to convert all these to trip-counter 1644 // expressions. 1645 Node *init2 = phi2->in( LoopNode::EntryControl ); 1646 int stride_con2 = incr2->in(2)->get_int(); 1647 1648 // The general case here gets a little tricky. We want to find the 1649 // GCD of all possible parallel IV's and make a new IV using this 1650 // GCD for the loop. Then all possible IVs are simple multiples of 1651 // the GCD. In practice, this will cover very few extra loops. 1652 // Instead we require 'stride_con2' to be a multiple of 'stride_con', 1653 // where +/-1 is the common case, but other integer multiples are 1654 // also easy to handle. 1655 int ratio_con = stride_con2/stride_con; 1656 1657 if ((ratio_con * stride_con) == stride_con2) { // Check for exact 1658 // Convert to using the trip counter. The parallel induction 1659 // variable differs from the trip counter by a loop-invariant 1660 // amount, the difference between their respective initial values. 1661 // It is scaled by the 'ratio_con'. 1662 // Perform local Ideal transformation since in most cases ratio == 1. 1663 Node* ratio = _igvn.intcon(ratio_con); 1664 set_ctrl(ratio, C->root()); 1665 Node* hook = new (C, 3) Node(3); 1666 Node* ratio_init = gvn->transform(new (C, 3) MulINode(init, ratio)); 1667 hook->init_req(0, ratio_init); 1668 Node* diff = gvn->transform(new (C, 3) SubINode(init2, ratio_init)); 1669 hook->init_req(1, diff); 1670 Node* ratio_idx = gvn->transform(new (C, 3) MulINode(phi, ratio)); 1671 hook->init_req(2, ratio_idx); 1672 Node* add = gvn->transform(new (C, 3) AddINode(ratio_idx, diff)); 1673 set_subtree_ctrl(add); 1674 _igvn.replace_node( phi2, add ); 1675 // Free up intermediate goo 1676 _igvn.remove_dead_node(hook); 1677 // Sometimes an induction variable is unused 1678 if (add->outcnt() == 0) { 1679 _igvn.remove_dead_node(add); 1680 } 1681 --i; // deleted this phi; rescan starting with next position 1682 continue; 1683 } 1684 } 1685 } 1686 1687 //------------------------------counted_loop----------------------------------- 1688 // Convert to counted loops where possible 1689 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) { 1690 1691 // For grins, set the inner-loop flag here 1692 if (!_child) { 1693 if (_head->is_Loop()) _head->as_Loop()->set_inner_loop(); 1694 } 1695 1696 if (_head->is_CountedLoop() || 1697 phase->is_counted_loop(_head, this)) { 1698 _has_sfpt = 1; // Indicate we do not need a safepoint here 1699 1700 // Look for a safepoint to remove 1701 for (Node* n = tail(); n != _head; n = phase->idom(n)) 1702 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && 1703 phase->is_deleteable_safept(n)) 1704 phase->lazy_replace(n,n->in(TypeFunc::Control)); 1705 1706 // Look for induction variables 1707 phase->replace_parallel_iv(this); 1708 1709 } else if (_parent != NULL && !_irreducible) { 1710 // Not a counted loop. 1711 // Look for a safepoint on the idom-path to remove, preserving the first one 1712 bool found = false; 1713 Node* n = tail(); 1714 for (; n != _head && !found; n = phase->idom(n)) { 1715 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this) 1716 found = true; // Found one 1717 } 1718 // Skip past it and delete the others 1719 for (; n != _head; n = phase->idom(n)) { 1720 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && 1721 phase->is_deleteable_safept(n)) 1722 phase->lazy_replace(n,n->in(TypeFunc::Control)); 1723 } 1724 } 1725 1726 // Recursively 1727 if (_child) _child->counted_loop( phase ); 1728 if (_next) _next ->counted_loop( phase ); 1729 } 1730 1731 #ifndef PRODUCT 1732 //------------------------------dump_head-------------------------------------- 1733 // Dump 1 liner for loop header info 1734 void IdealLoopTree::dump_head( ) const { 1735 for (uint i=0; i<_nest; i++) 1736 tty->print(" "); 1737 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx); 1738 if (_irreducible) tty->print(" IRREDUCIBLE"); 1739 Node* entry = _head->in(LoopNode::EntryControl); 1740 if (LoopLimitCheck) { 1741 Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check); 1742 if (predicate != NULL ) { 1743 tty->print(" limit_check"); 1744 entry = entry->in(0)->in(0); 1745 } 1746 } 1747 if (UseLoopPredicate) { 1748 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate); 1749 if (entry != NULL) { 1750 tty->print(" predicated"); 1751 } 1752 } 1753 if (_head->is_CountedLoop()) { 1754 CountedLoopNode *cl = _head->as_CountedLoop(); 1755 tty->print(" counted"); 1756 1757 Node* init_n = cl->init_trip(); 1758 if (init_n != NULL && init_n->is_Con()) 1759 tty->print(" [%d,", cl->init_trip()->get_int()); 1760 else 1761 tty->print(" [int,"); 1762 Node* limit_n = cl->limit(); 1763 if (limit_n != NULL && limit_n->is_Con()) 1764 tty->print("%d),", cl->limit()->get_int()); 1765 else 1766 tty->print("int),"); 1767 int stride_con = cl->stride_con(); 1768 if (stride_con > 0) tty->print("+"); 1769 tty->print("%d", stride_con); 1770 1771 if (cl->is_pre_loop ()) tty->print(" pre" ); 1772 if (cl->is_main_loop()) tty->print(" main"); 1773 if (cl->is_post_loop()) tty->print(" post"); 1774 } 1775 tty->cr(); 1776 } 1777 1778 //------------------------------dump------------------------------------------- 1779 // Dump loops by loop tree 1780 void IdealLoopTree::dump( ) const { 1781 dump_head(); 1782 if (_child) _child->dump(); 1783 if (_next) _next ->dump(); 1784 } 1785 1786 #endif 1787 1788 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) { 1789 if (loop == root) { 1790 if (loop->_child != NULL) { 1791 log->begin_head("loop_tree"); 1792 log->end_head(); 1793 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1794 log->tail("loop_tree"); 1795 assert(loop->_next == NULL, "what?"); 1796 } 1797 } else { 1798 Node* head = loop->_head; 1799 log->begin_head("loop"); 1800 log->print(" idx='%d' ", head->_idx); 1801 if (loop->_irreducible) log->print("irreducible='1' "); 1802 if (head->is_Loop()) { 1803 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' "); 1804 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' "); 1805 } 1806 if (head->is_CountedLoop()) { 1807 CountedLoopNode* cl = head->as_CountedLoop(); 1808 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx()); 1809 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx); 1810 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx()); 1811 } 1812 log->end_head(); 1813 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1814 log->tail("loop"); 1815 if( loop->_next ) log_loop_tree(root, loop->_next, log); 1816 } 1817 } 1818 1819 //---------------------collect_potentially_useful_predicates----------------------- 1820 // Helper function to collect potentially useful predicates to prevent them from 1821 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates 1822 void PhaseIdealLoop::collect_potentially_useful_predicates( 1823 IdealLoopTree * loop, Unique_Node_List &useful_predicates) { 1824 if (loop->_child) { // child 1825 collect_potentially_useful_predicates(loop->_child, useful_predicates); 1826 } 1827 1828 // self (only loops that we can apply loop predication may use their predicates) 1829 if (loop->_head->is_Loop() && 1830 !loop->_irreducible && 1831 !loop->tail()->is_top()) { 1832 LoopNode* lpn = loop->_head->as_Loop(); 1833 Node* entry = lpn->in(LoopNode::EntryControl); 1834 Node* predicate_proj = find_predicate(entry); // loop_limit_check first 1835 if (predicate_proj != NULL ) { // right pattern that can be used by loop predication 1836 assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be"); 1837 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one 1838 entry = entry->in(0)->in(0); 1839 } 1840 predicate_proj = find_predicate(entry); // Predicate 1841 if (predicate_proj != NULL ) { 1842 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one 1843 } 1844 } 1845 1846 if (loop->_next) { // sibling 1847 collect_potentially_useful_predicates(loop->_next, useful_predicates); 1848 } 1849 } 1850 1851 //------------------------eliminate_useless_predicates----------------------------- 1852 // Eliminate all inserted predicates if they could not be used by loop predication. 1853 // Note: it will also eliminates loop limits check predicate since it also uses 1854 // Opaque1 node (see Parse::add_predicate()). 1855 void PhaseIdealLoop::eliminate_useless_predicates() { 1856 if (C->predicate_count() == 0) 1857 return; // no predicate left 1858 1859 Unique_Node_List useful_predicates; // to store useful predicates 1860 if (C->has_loops()) { 1861 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates); 1862 } 1863 1864 for (int i = C->predicate_count(); i > 0; i--) { 1865 Node * n = C->predicate_opaque1_node(i-1); 1866 assert(n->Opcode() == Op_Opaque1, "must be"); 1867 if (!useful_predicates.member(n)) { // not in the useful list 1868 _igvn.replace_node(n, n->in(1)); 1869 } 1870 } 1871 } 1872 1873 //============================================================================= 1874 //----------------------------build_and_optimize------------------------------- 1875 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to 1876 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups. 1877 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs) { 1878 ResourceMark rm; 1879 1880 int old_progress = C->major_progress(); 1881 uint orig_worklist_size = _igvn._worklist.size(); 1882 1883 // Reset major-progress flag for the driver's heuristics 1884 C->clear_major_progress(); 1885 1886 #ifndef PRODUCT 1887 // Capture for later assert 1888 uint unique = C->unique(); 1889 _loop_invokes++; 1890 _loop_work += unique; 1891 #endif 1892 1893 // True if the method has at least 1 irreducible loop 1894 _has_irreducible_loops = false; 1895 1896 _created_loop_node = false; 1897 1898 Arena *a = Thread::current()->resource_area(); 1899 VectorSet visited(a); 1900 // Pre-grow the mapping from Nodes to IdealLoopTrees. 1901 _nodes.map(C->unique(), NULL); 1902 memset(_nodes.adr(), 0, wordSize * C->unique()); 1903 1904 // Pre-build the top-level outermost loop tree entry 1905 _ltree_root = new IdealLoopTree( this, C->root(), C->root() ); 1906 // Do not need a safepoint at the top level 1907 _ltree_root->_has_sfpt = 1; 1908 1909 // Initialize Dominators. 1910 // Checked in clone_loop_predicate() during beautify_loops(). 1911 _idom_size = 0; 1912 _idom = NULL; 1913 _dom_depth = NULL; 1914 _dom_stk = NULL; 1915 1916 // Empty pre-order array 1917 allocate_preorders(); 1918 1919 // Build a loop tree on the fly. Build a mapping from CFG nodes to 1920 // IdealLoopTree entries. Data nodes are NOT walked. 1921 build_loop_tree(); 1922 // Check for bailout, and return 1923 if (C->failing()) { 1924 return; 1925 } 1926 1927 // No loops after all 1928 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false); 1929 1930 // There should always be an outer loop containing the Root and Return nodes. 1931 // If not, we have a degenerate empty program. Bail out in this case. 1932 if (!has_node(C->root())) { 1933 if (!_verify_only) { 1934 C->clear_major_progress(); 1935 C->record_method_not_compilable("empty program detected during loop optimization"); 1936 } 1937 return; 1938 } 1939 1940 // Nothing to do, so get out 1941 if( !C->has_loops() && !do_split_ifs && !_verify_me && !_verify_only ) { 1942 _igvn.optimize(); // Cleanup NeverBranches 1943 return; 1944 } 1945 1946 // Set loop nesting depth 1947 _ltree_root->set_nest( 0 ); 1948 1949 // Split shared headers and insert loop landing pads. 1950 // Do not bother doing this on the Root loop of course. 1951 if( !_verify_me && !_verify_only && _ltree_root->_child ) { 1952 C->print_method("Before beautify loops", 3); 1953 if( _ltree_root->_child->beautify_loops( this ) ) { 1954 // Re-build loop tree! 1955 _ltree_root->_child = NULL; 1956 _nodes.clear(); 1957 reallocate_preorders(); 1958 build_loop_tree(); 1959 // Check for bailout, and return 1960 if (C->failing()) { 1961 return; 1962 } 1963 // Reset loop nesting depth 1964 _ltree_root->set_nest( 0 ); 1965 1966 C->print_method("After beautify loops", 3); 1967 } 1968 } 1969 1970 // Build Dominators for elision of NULL checks & loop finding. 1971 // Since nodes do not have a slot for immediate dominator, make 1972 // a persistent side array for that info indexed on node->_idx. 1973 _idom_size = C->unique(); 1974 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size ); 1975 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size ); 1976 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth 1977 memset( _dom_depth, 0, _idom_size * sizeof(uint) ); 1978 1979 Dominators(); 1980 1981 if (!_verify_only) { 1982 // As a side effect, Dominators removed any unreachable CFG paths 1983 // into RegionNodes. It doesn't do this test against Root, so 1984 // we do it here. 1985 for( uint i = 1; i < C->root()->req(); i++ ) { 1986 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root? 1987 _igvn.hash_delete(C->root()); 1988 C->root()->del_req(i); 1989 _igvn._worklist.push(C->root()); 1990 i--; // Rerun same iteration on compressed edges 1991 } 1992 } 1993 1994 // Given dominators, try to find inner loops with calls that must 1995 // always be executed (call dominates loop tail). These loops do 1996 // not need a separate safepoint. 1997 Node_List cisstack(a); 1998 _ltree_root->check_safepts(visited, cisstack); 1999 } 2000 2001 // Walk the DATA nodes and place into loops. Find earliest control 2002 // node. For CFG nodes, the _nodes array starts out and remains 2003 // holding the associated IdealLoopTree pointer. For DATA nodes, the 2004 // _nodes array holds the earliest legal controlling CFG node. 2005 2006 // Allocate stack with enough space to avoid frequent realloc 2007 int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats 2008 Node_Stack nstack( a, stack_size ); 2009 2010 visited.Clear(); 2011 Node_List worklist(a); 2012 // Don't need C->root() on worklist since 2013 // it will be processed among C->top() inputs 2014 worklist.push( C->top() ); 2015 visited.set( C->top()->_idx ); // Set C->top() as visited now 2016 build_loop_early( visited, worklist, nstack ); 2017 2018 // Given early legal placement, try finding counted loops. This placement 2019 // is good enough to discover most loop invariants. 2020 if( !_verify_me && !_verify_only ) 2021 _ltree_root->counted_loop( this ); 2022 2023 // Find latest loop placement. Find ideal loop placement. 2024 visited.Clear(); 2025 init_dom_lca_tags(); 2026 // Need C->root() on worklist when processing outs 2027 worklist.push( C->root() ); 2028 NOT_PRODUCT( C->verify_graph_edges(); ) 2029 worklist.push( C->top() ); 2030 build_loop_late( visited, worklist, nstack ); 2031 2032 if (_verify_only) { 2033 // restore major progress flag 2034 for (int i = 0; i < old_progress; i++) 2035 C->set_major_progress(); 2036 assert(C->unique() == unique, "verification mode made Nodes? ? ?"); 2037 assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything"); 2038 return; 2039 } 2040 2041 // Some parser-inserted loop predicates could never be used by loop 2042 // predication or they were moved away from loop during some optimizations. 2043 // For example, peeling. Eliminate them before next loop optimizations. 2044 if (UseLoopPredicate || LoopLimitCheck) { 2045 eliminate_useless_predicates(); 2046 } 2047 2048 // clear out the dead code 2049 while(_deadlist.size()) { 2050 _igvn.remove_globally_dead_node(_deadlist.pop()); 2051 } 2052 2053 #ifndef PRODUCT 2054 C->verify_graph_edges(); 2055 if (_verify_me) { // Nested verify pass? 2056 // Check to see if the verify mode is broken 2057 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?"); 2058 return; 2059 } 2060 if(VerifyLoopOptimizations) verify(); 2061 if(TraceLoopOpts && C->has_loops()) { 2062 _ltree_root->dump(); 2063 } 2064 #endif 2065 2066 if (ReassociateInvariants) { 2067 // Reassociate invariants and prep for split_thru_phi 2068 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2069 IdealLoopTree* lpt = iter.current(); 2070 if (!lpt->is_counted() || !lpt->is_inner()) continue; 2071 2072 lpt->reassociate_invariants(this); 2073 2074 // Because RCE opportunities can be masked by split_thru_phi, 2075 // look for RCE candidates and inhibit split_thru_phi 2076 // on just their loop-phi's for this pass of loop opts 2077 if (SplitIfBlocks && do_split_ifs) { 2078 if (lpt->policy_range_check(this)) { 2079 lpt->_rce_candidate = 1; // = true 2080 } 2081 } 2082 } 2083 } 2084 2085 // Check for aggressive application of split-if and other transforms 2086 // that require basic-block info (like cloning through Phi's) 2087 if( SplitIfBlocks && do_split_ifs ) { 2088 visited.Clear(); 2089 split_if_with_blocks( visited, nstack ); 2090 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); ); 2091 } 2092 2093 // Perform loop predication before iteration splitting 2094 if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) { 2095 _ltree_root->_child->loop_predication(this); 2096 } 2097 2098 if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) { 2099 if (do_intrinsify_fill()) { 2100 C->set_major_progress(); 2101 } 2102 } 2103 2104 // Perform iteration-splitting on inner loops. Split iterations to avoid 2105 // range checks or one-shot null checks. 2106 2107 // If split-if's didn't hack the graph too bad (no CFG changes) 2108 // then do loop opts. 2109 if (C->has_loops() && !C->major_progress()) { 2110 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) ); 2111 _ltree_root->_child->iteration_split( this, worklist ); 2112 // No verify after peeling! GCM has hoisted code out of the loop. 2113 // After peeling, the hoisted code could sink inside the peeled area. 2114 // The peeling code does not try to recompute the best location for 2115 // all the code before the peeled area, so the verify pass will always 2116 // complain about it. 2117 } 2118 // Do verify graph edges in any case 2119 NOT_PRODUCT( C->verify_graph_edges(); ); 2120 2121 if (!do_split_ifs) { 2122 // We saw major progress in Split-If to get here. We forced a 2123 // pass with unrolling and not split-if, however more split-if's 2124 // might make progress. If the unrolling didn't make progress 2125 // then the major-progress flag got cleared and we won't try 2126 // another round of Split-If. In particular the ever-common 2127 // instance-of/check-cast pattern requires at least 2 rounds of 2128 // Split-If to clear out. 2129 C->set_major_progress(); 2130 } 2131 2132 // Repeat loop optimizations if new loops were seen 2133 if (created_loop_node()) { 2134 C->set_major_progress(); 2135 } 2136 2137 // Keep loop predicates and perform optimizations with them 2138 // until no more loop optimizations could be done. 2139 // After that switch predicates off and do more loop optimizations. 2140 if (!C->major_progress() && (C->predicate_count() > 0)) { 2141 C->cleanup_loop_predicates(_igvn); 2142 #ifndef PRODUCT 2143 if (TraceLoopOpts) { 2144 tty->print_cr("PredicatesOff"); 2145 } 2146 #endif 2147 C->set_major_progress(); 2148 } 2149 2150 // Convert scalar to superword operations at the end of all loop opts. 2151 if (UseSuperWord && C->has_loops() && !C->major_progress()) { 2152 // SuperWord transform 2153 SuperWord sw(this); 2154 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2155 IdealLoopTree* lpt = iter.current(); 2156 if (lpt->is_counted()) { 2157 sw.transform_loop(lpt); 2158 } 2159 } 2160 } 2161 2162 // Cleanup any modified bits 2163 _igvn.optimize(); 2164 2165 // disable assert until issue with split_flow_path is resolved (6742111) 2166 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(), 2167 // "shouldn't introduce irreducible loops"); 2168 2169 if (C->log() != NULL) { 2170 log_loop_tree(_ltree_root, _ltree_root, C->log()); 2171 } 2172 } 2173 2174 #ifndef PRODUCT 2175 //------------------------------print_statistics------------------------------- 2176 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes 2177 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique 2178 void PhaseIdealLoop::print_statistics() { 2179 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work); 2180 } 2181 2182 //------------------------------verify----------------------------------------- 2183 // Build a verify-only PhaseIdealLoop, and see that it agrees with me. 2184 static int fail; // debug only, so its multi-thread dont care 2185 void PhaseIdealLoop::verify() const { 2186 int old_progress = C->major_progress(); 2187 ResourceMark rm; 2188 PhaseIdealLoop loop_verify( _igvn, this ); 2189 VectorSet visited(Thread::current()->resource_area()); 2190 2191 fail = 0; 2192 verify_compare( C->root(), &loop_verify, visited ); 2193 assert( fail == 0, "verify loops failed" ); 2194 // Verify loop structure is the same 2195 _ltree_root->verify_tree(loop_verify._ltree_root, NULL); 2196 // Reset major-progress. It was cleared by creating a verify version of 2197 // PhaseIdealLoop. 2198 for( int i=0; i<old_progress; i++ ) 2199 C->set_major_progress(); 2200 } 2201 2202 //------------------------------verify_compare--------------------------------- 2203 // Make sure me and the given PhaseIdealLoop agree on key data structures 2204 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const { 2205 if( !n ) return; 2206 if( visited.test_set( n->_idx ) ) return; 2207 if( !_nodes[n->_idx] ) { // Unreachable 2208 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" ); 2209 return; 2210 } 2211 2212 uint i; 2213 for( i = 0; i < n->req(); i++ ) 2214 verify_compare( n->in(i), loop_verify, visited ); 2215 2216 // Check the '_nodes' block/loop structure 2217 i = n->_idx; 2218 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl 2219 if( _nodes[i] != loop_verify->_nodes[i] && 2220 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) { 2221 tty->print("Mismatched control setting for: "); 2222 n->dump(); 2223 if( fail++ > 10 ) return; 2224 Node *c = get_ctrl_no_update(n); 2225 tty->print("We have it as: "); 2226 if( c->in(0) ) c->dump(); 2227 else tty->print_cr("N%d",c->_idx); 2228 tty->print("Verify thinks: "); 2229 if( loop_verify->has_ctrl(n) ) 2230 loop_verify->get_ctrl_no_update(n)->dump(); 2231 else 2232 loop_verify->get_loop_idx(n)->dump(); 2233 tty->cr(); 2234 } 2235 } else { // We have a loop 2236 IdealLoopTree *us = get_loop_idx(n); 2237 if( loop_verify->has_ctrl(n) ) { 2238 tty->print("Mismatched loop setting for: "); 2239 n->dump(); 2240 if( fail++ > 10 ) return; 2241 tty->print("We have it as: "); 2242 us->dump(); 2243 tty->print("Verify thinks: "); 2244 loop_verify->get_ctrl_no_update(n)->dump(); 2245 tty->cr(); 2246 } else if (!C->major_progress()) { 2247 // Loop selection can be messed up if we did a major progress 2248 // operation, like split-if. Do not verify in that case. 2249 IdealLoopTree *them = loop_verify->get_loop_idx(n); 2250 if( us->_head != them->_head || us->_tail != them->_tail ) { 2251 tty->print("Unequals loops for: "); 2252 n->dump(); 2253 if( fail++ > 10 ) return; 2254 tty->print("We have it as: "); 2255 us->dump(); 2256 tty->print("Verify thinks: "); 2257 them->dump(); 2258 tty->cr(); 2259 } 2260 } 2261 } 2262 2263 // Check for immediate dominators being equal 2264 if( i >= _idom_size ) { 2265 if( !n->is_CFG() ) return; 2266 tty->print("CFG Node with no idom: "); 2267 n->dump(); 2268 return; 2269 } 2270 if( !n->is_CFG() ) return; 2271 if( n == C->root() ) return; // No IDOM here 2272 2273 assert(n->_idx == i, "sanity"); 2274 Node *id = idom_no_update(n); 2275 if( id != loop_verify->idom_no_update(n) ) { 2276 tty->print("Unequals idoms for: "); 2277 n->dump(); 2278 if( fail++ > 10 ) return; 2279 tty->print("We have it as: "); 2280 id->dump(); 2281 tty->print("Verify thinks: "); 2282 loop_verify->idom_no_update(n)->dump(); 2283 tty->cr(); 2284 } 2285 2286 } 2287 2288 //------------------------------verify_tree------------------------------------ 2289 // Verify that tree structures match. Because the CFG can change, siblings 2290 // within the loop tree can be reordered. We attempt to deal with that by 2291 // reordering the verify's loop tree if possible. 2292 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const { 2293 assert( _parent == parent, "Badly formed loop tree" ); 2294 2295 // Siblings not in same order? Attempt to re-order. 2296 if( _head != loop->_head ) { 2297 // Find _next pointer to update 2298 IdealLoopTree **pp = &loop->_parent->_child; 2299 while( *pp != loop ) 2300 pp = &((*pp)->_next); 2301 // Find proper sibling to be next 2302 IdealLoopTree **nn = &loop->_next; 2303 while( (*nn) && (*nn)->_head != _head ) 2304 nn = &((*nn)->_next); 2305 2306 // Check for no match. 2307 if( !(*nn) ) { 2308 // Annoyingly, irreducible loops can pick different headers 2309 // after a major_progress operation, so the rest of the loop 2310 // tree cannot be matched. 2311 if (_irreducible && Compile::current()->major_progress()) return; 2312 assert( 0, "failed to match loop tree" ); 2313 } 2314 2315 // Move (*nn) to (*pp) 2316 IdealLoopTree *hit = *nn; 2317 *nn = hit->_next; 2318 hit->_next = loop; 2319 *pp = loop; 2320 loop = hit; 2321 // Now try again to verify 2322 } 2323 2324 assert( _head == loop->_head , "mismatched loop head" ); 2325 Node *tail = _tail; // Inline a non-updating version of 2326 while( !tail->in(0) ) // the 'tail()' call. 2327 tail = tail->in(1); 2328 assert( tail == loop->_tail, "mismatched loop tail" ); 2329 2330 // Counted loops that are guarded should be able to find their guards 2331 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) { 2332 CountedLoopNode *cl = _head->as_CountedLoop(); 2333 Node *init = cl->init_trip(); 2334 Node *ctrl = cl->in(LoopNode::EntryControl); 2335 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 2336 Node *iff = ctrl->in(0); 2337 assert( iff->Opcode() == Op_If, "" ); 2338 Node *bol = iff->in(1); 2339 assert( bol->Opcode() == Op_Bool, "" ); 2340 Node *cmp = bol->in(1); 2341 assert( cmp->Opcode() == Op_CmpI, "" ); 2342 Node *add = cmp->in(1); 2343 Node *opaq; 2344 if( add->Opcode() == Op_Opaque1 ) { 2345 opaq = add; 2346 } else { 2347 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" ); 2348 assert( add == init, "" ); 2349 opaq = cmp->in(2); 2350 } 2351 assert( opaq->Opcode() == Op_Opaque1, "" ); 2352 2353 } 2354 2355 if (_child != NULL) _child->verify_tree(loop->_child, this); 2356 if (_next != NULL) _next ->verify_tree(loop->_next, parent); 2357 // Innermost loops need to verify loop bodies, 2358 // but only if no 'major_progress' 2359 int fail = 0; 2360 if (!Compile::current()->major_progress() && _child == NULL) { 2361 for( uint i = 0; i < _body.size(); i++ ) { 2362 Node *n = _body.at(i); 2363 if (n->outcnt() == 0) continue; // Ignore dead 2364 uint j; 2365 for( j = 0; j < loop->_body.size(); j++ ) 2366 if( loop->_body.at(j) == n ) 2367 break; 2368 if( j == loop->_body.size() ) { // Not found in loop body 2369 // Last ditch effort to avoid assertion: Its possible that we 2370 // have some users (so outcnt not zero) but are still dead. 2371 // Try to find from root. 2372 if (Compile::current()->root()->find(n->_idx)) { 2373 fail++; 2374 tty->print("We have that verify does not: "); 2375 n->dump(); 2376 } 2377 } 2378 } 2379 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) { 2380 Node *n = loop->_body.at(i2); 2381 if (n->outcnt() == 0) continue; // Ignore dead 2382 uint j; 2383 for( j = 0; j < _body.size(); j++ ) 2384 if( _body.at(j) == n ) 2385 break; 2386 if( j == _body.size() ) { // Not found in loop body 2387 // Last ditch effort to avoid assertion: Its possible that we 2388 // have some users (so outcnt not zero) but are still dead. 2389 // Try to find from root. 2390 if (Compile::current()->root()->find(n->_idx)) { 2391 fail++; 2392 tty->print("Verify has that we do not: "); 2393 n->dump(); 2394 } 2395 } 2396 } 2397 assert( !fail, "loop body mismatch" ); 2398 } 2399 } 2400 2401 #endif 2402 2403 //------------------------------set_idom--------------------------------------- 2404 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) { 2405 uint idx = d->_idx; 2406 if (idx >= _idom_size) { 2407 uint newsize = _idom_size<<1; 2408 while( idx >= newsize ) { 2409 newsize <<= 1; 2410 } 2411 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize); 2412 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize); 2413 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) ); 2414 _idom_size = newsize; 2415 } 2416 _idom[idx] = n; 2417 _dom_depth[idx] = dom_depth; 2418 } 2419 2420 //------------------------------recompute_dom_depth--------------------------------------- 2421 // The dominator tree is constructed with only parent pointers. 2422 // This recomputes the depth in the tree by first tagging all 2423 // nodes as "no depth yet" marker. The next pass then runs up 2424 // the dom tree from each node marked "no depth yet", and computes 2425 // the depth on the way back down. 2426 void PhaseIdealLoop::recompute_dom_depth() { 2427 uint no_depth_marker = C->unique(); 2428 uint i; 2429 // Initialize depth to "no depth yet" 2430 for (i = 0; i < _idom_size; i++) { 2431 if (_dom_depth[i] > 0 && _idom[i] != NULL) { 2432 _dom_depth[i] = no_depth_marker; 2433 } 2434 } 2435 if (_dom_stk == NULL) { 2436 uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size. 2437 if (init_size < 10) init_size = 10; 2438 _dom_stk = new GrowableArray<uint>(init_size); 2439 } 2440 // Compute new depth for each node. 2441 for (i = 0; i < _idom_size; i++) { 2442 uint j = i; 2443 // Run up the dom tree to find a node with a depth 2444 while (_dom_depth[j] == no_depth_marker) { 2445 _dom_stk->push(j); 2446 j = _idom[j]->_idx; 2447 } 2448 // Compute the depth on the way back down this tree branch 2449 uint dd = _dom_depth[j] + 1; 2450 while (_dom_stk->length() > 0) { 2451 uint j = _dom_stk->pop(); 2452 _dom_depth[j] = dd; 2453 dd++; 2454 } 2455 } 2456 } 2457 2458 //------------------------------sort------------------------------------------- 2459 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the 2460 // loop tree, not the root. 2461 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) { 2462 if( !innermost ) return loop; // New innermost loop 2463 2464 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number 2465 assert( loop_preorder, "not yet post-walked loop" ); 2466 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer 2467 IdealLoopTree *l = *pp; // Do I go before or after 'l'? 2468 2469 // Insert at start of list 2470 while( l ) { // Insertion sort based on pre-order 2471 if( l == loop ) return innermost; // Already on list! 2472 int l_preorder = get_preorder(l->_head); // Cache pre-order number 2473 assert( l_preorder, "not yet post-walked l" ); 2474 // Check header pre-order number to figure proper nesting 2475 if( loop_preorder > l_preorder ) 2476 break; // End of insertion 2477 // If headers tie (e.g., shared headers) check tail pre-order numbers. 2478 // Since I split shared headers, you'd think this could not happen. 2479 // BUT: I must first do the preorder numbering before I can discover I 2480 // have shared headers, so the split headers all get the same preorder 2481 // number as the RegionNode they split from. 2482 if( loop_preorder == l_preorder && 2483 get_preorder(loop->_tail) < get_preorder(l->_tail) ) 2484 break; // Also check for shared headers (same pre#) 2485 pp = &l->_parent; // Chain up list 2486 l = *pp; 2487 } 2488 // Link into list 2489 // Point predecessor to me 2490 *pp = loop; 2491 // Point me to successor 2492 IdealLoopTree *p = loop->_parent; 2493 loop->_parent = l; // Point me to successor 2494 if( p ) sort( p, innermost ); // Insert my parents into list as well 2495 return innermost; 2496 } 2497 2498 //------------------------------build_loop_tree-------------------------------- 2499 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit 2500 // bits. The _nodes[] array is mapped by Node index and holds a NULL for 2501 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the 2502 // tightest enclosing IdealLoopTree for post-walked. 2503 // 2504 // During my forward walk I do a short 1-layer lookahead to see if I can find 2505 // a loop backedge with that doesn't have any work on the backedge. This 2506 // helps me construct nested loops with shared headers better. 2507 // 2508 // Once I've done the forward recursion, I do the post-work. For each child 2509 // I check to see if there is a backedge. Backedges define a loop! I 2510 // insert an IdealLoopTree at the target of the backedge. 2511 // 2512 // During the post-work I also check to see if I have several children 2513 // belonging to different loops. If so, then this Node is a decision point 2514 // where control flow can choose to change loop nests. It is at this 2515 // decision point where I can figure out how loops are nested. At this 2516 // time I can properly order the different loop nests from my children. 2517 // Note that there may not be any backedges at the decision point! 2518 // 2519 // Since the decision point can be far removed from the backedges, I can't 2520 // order my loops at the time I discover them. Thus at the decision point 2521 // I need to inspect loop header pre-order numbers to properly nest my 2522 // loops. This means I need to sort my childrens' loops by pre-order. 2523 // The sort is of size number-of-control-children, which generally limits 2524 // it to size 2 (i.e., I just choose between my 2 target loops). 2525 void PhaseIdealLoop::build_loop_tree() { 2526 // Allocate stack of size C->unique()/2 to avoid frequent realloc 2527 GrowableArray <Node *> bltstack(C->unique() >> 1); 2528 Node *n = C->root(); 2529 bltstack.push(n); 2530 int pre_order = 1; 2531 int stack_size; 2532 2533 while ( ( stack_size = bltstack.length() ) != 0 ) { 2534 n = bltstack.top(); // Leave node on stack 2535 if ( !is_visited(n) ) { 2536 // ---- Pre-pass Work ---- 2537 // Pre-walked but not post-walked nodes need a pre_order number. 2538 2539 set_preorder_visited( n, pre_order ); // set as visited 2540 2541 // ---- Scan over children ---- 2542 // Scan first over control projections that lead to loop headers. 2543 // This helps us find inner-to-outer loops with shared headers better. 2544 2545 // Scan children's children for loop headers. 2546 for ( int i = n->outcnt() - 1; i >= 0; --i ) { 2547 Node* m = n->raw_out(i); // Child 2548 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children 2549 // Scan over children's children to find loop 2550 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2551 Node* l = m->fast_out(j); 2552 if( is_visited(l) && // Been visited? 2553 !is_postvisited(l) && // But not post-visited 2554 get_preorder(l) < pre_order ) { // And smaller pre-order 2555 // Found! Scan the DFS down this path before doing other paths 2556 bltstack.push(m); 2557 break; 2558 } 2559 } 2560 } 2561 } 2562 pre_order++; 2563 } 2564 else if ( !is_postvisited(n) ) { 2565 // Note: build_loop_tree_impl() adds out edges on rare occasions, 2566 // such as com.sun.rsasign.am::a. 2567 // For non-recursive version, first, process current children. 2568 // On next iteration, check if additional children were added. 2569 for ( int k = n->outcnt() - 1; k >= 0; --k ) { 2570 Node* u = n->raw_out(k); 2571 if ( u->is_CFG() && !is_visited(u) ) { 2572 bltstack.push(u); 2573 } 2574 } 2575 if ( bltstack.length() == stack_size ) { 2576 // There were no additional children, post visit node now 2577 (void)bltstack.pop(); // Remove node from stack 2578 pre_order = build_loop_tree_impl( n, pre_order ); 2579 // Check for bailout 2580 if (C->failing()) { 2581 return; 2582 } 2583 // Check to grow _preorders[] array for the case when 2584 // build_loop_tree_impl() adds new nodes. 2585 check_grow_preorders(); 2586 } 2587 } 2588 else { 2589 (void)bltstack.pop(); // Remove post-visited node from stack 2590 } 2591 } 2592 } 2593 2594 //------------------------------build_loop_tree_impl--------------------------- 2595 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) { 2596 // ---- Post-pass Work ---- 2597 // Pre-walked but not post-walked nodes need a pre_order number. 2598 2599 // Tightest enclosing loop for this Node 2600 IdealLoopTree *innermost = NULL; 2601 2602 // For all children, see if any edge is a backedge. If so, make a loop 2603 // for it. Then find the tightest enclosing loop for the self Node. 2604 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 2605 Node* m = n->fast_out(i); // Child 2606 if( n == m ) continue; // Ignore control self-cycles 2607 if( !m->is_CFG() ) continue;// Ignore non-CFG edges 2608 2609 IdealLoopTree *l; // Child's loop 2610 if( !is_postvisited(m) ) { // Child visited but not post-visited? 2611 // Found a backedge 2612 assert( get_preorder(m) < pre_order, "should be backedge" ); 2613 // Check for the RootNode, which is already a LoopNode and is allowed 2614 // to have multiple "backedges". 2615 if( m == C->root()) { // Found the root? 2616 l = _ltree_root; // Root is the outermost LoopNode 2617 } else { // Else found a nested loop 2618 // Insert a LoopNode to mark this loop. 2619 l = new IdealLoopTree(this, m, n); 2620 } // End of Else found a nested loop 2621 if( !has_loop(m) ) // If 'm' does not already have a loop set 2622 set_loop(m, l); // Set loop header to loop now 2623 2624 } else { // Else not a nested loop 2625 if( !_nodes[m->_idx] ) continue; // Dead code has no loop 2626 l = get_loop(m); // Get previously determined loop 2627 // If successor is header of a loop (nest), move up-loop till it 2628 // is a member of some outer enclosing loop. Since there are no 2629 // shared headers (I've split them already) I only need to go up 2630 // at most 1 level. 2631 while( l && l->_head == m ) // Successor heads loop? 2632 l = l->_parent; // Move up 1 for me 2633 // If this loop is not properly parented, then this loop 2634 // has no exit path out, i.e. its an infinite loop. 2635 if( !l ) { 2636 // Make loop "reachable" from root so the CFG is reachable. Basically 2637 // insert a bogus loop exit that is never taken. 'm', the loop head, 2638 // points to 'n', one (of possibly many) fall-in paths. There may be 2639 // many backedges as well. 2640 2641 // Here I set the loop to be the root loop. I could have, after 2642 // inserting a bogus loop exit, restarted the recursion and found my 2643 // new loop exit. This would make the infinite loop a first-class 2644 // loop and it would then get properly optimized. What's the use of 2645 // optimizing an infinite loop? 2646 l = _ltree_root; // Oops, found infinite loop 2647 2648 if (!_verify_only) { 2649 // Insert the NeverBranch between 'm' and it's control user. 2650 NeverBranchNode *iff = new (C, 1) NeverBranchNode( m ); 2651 _igvn.register_new_node_with_optimizer(iff); 2652 set_loop(iff, l); 2653 Node *if_t = new (C, 1) CProjNode( iff, 0 ); 2654 _igvn.register_new_node_with_optimizer(if_t); 2655 set_loop(if_t, l); 2656 2657 Node* cfg = NULL; // Find the One True Control User of m 2658 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2659 Node* x = m->fast_out(j); 2660 if (x->is_CFG() && x != m && x != iff) 2661 { cfg = x; break; } 2662 } 2663 assert(cfg != NULL, "must find the control user of m"); 2664 uint k = 0; // Probably cfg->in(0) 2665 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region 2666 cfg->set_req( k, if_t ); // Now point to NeverBranch 2667 2668 // Now create the never-taken loop exit 2669 Node *if_f = new (C, 1) CProjNode( iff, 1 ); 2670 _igvn.register_new_node_with_optimizer(if_f); 2671 set_loop(if_f, l); 2672 // Find frame ptr for Halt. Relies on the optimizer 2673 // V-N'ing. Easier and quicker than searching through 2674 // the program structure. 2675 Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr ); 2676 _igvn.register_new_node_with_optimizer(frame); 2677 // Halt & Catch Fire 2678 Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame ); 2679 _igvn.register_new_node_with_optimizer(halt); 2680 set_loop(halt, l); 2681 C->root()->add_req(halt); 2682 } 2683 set_loop(C->root(), _ltree_root); 2684 } 2685 } 2686 // Weeny check for irreducible. This child was already visited (this 2687 // IS the post-work phase). Is this child's loop header post-visited 2688 // as well? If so, then I found another entry into the loop. 2689 if (!_verify_only) { 2690 while( is_postvisited(l->_head) ) { 2691 // found irreducible 2692 l->_irreducible = 1; // = true 2693 l = l->_parent; 2694 _has_irreducible_loops = true; 2695 // Check for bad CFG here to prevent crash, and bailout of compile 2696 if (l == NULL) { 2697 C->record_method_not_compilable("unhandled CFG detected during loop optimization"); 2698 return pre_order; 2699 } 2700 } 2701 } 2702 2703 // This Node might be a decision point for loops. It is only if 2704 // it's children belong to several different loops. The sort call 2705 // does a trivial amount of work if there is only 1 child or all 2706 // children belong to the same loop. If however, the children 2707 // belong to different loops, the sort call will properly set the 2708 // _parent pointers to show how the loops nest. 2709 // 2710 // In any case, it returns the tightest enclosing loop. 2711 innermost = sort( l, innermost ); 2712 } 2713 2714 // Def-use info will have some dead stuff; dead stuff will have no 2715 // loop decided on. 2716 2717 // Am I a loop header? If so fix up my parent's child and next ptrs. 2718 if( innermost && innermost->_head == n ) { 2719 assert( get_loop(n) == innermost, "" ); 2720 IdealLoopTree *p = innermost->_parent; 2721 IdealLoopTree *l = innermost; 2722 while( p && l->_head == n ) { 2723 l->_next = p->_child; // Put self on parents 'next child' 2724 p->_child = l; // Make self as first child of parent 2725 l = p; // Now walk up the parent chain 2726 p = l->_parent; 2727 } 2728 } else { 2729 // Note that it is possible for a LoopNode to reach here, if the 2730 // backedge has been made unreachable (hence the LoopNode no longer 2731 // denotes a Loop, and will eventually be removed). 2732 2733 // Record tightest enclosing loop for self. Mark as post-visited. 2734 set_loop(n, innermost); 2735 // Also record has_call flag early on 2736 if( innermost ) { 2737 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) { 2738 // Do not count uncommon calls 2739 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) { 2740 Node *iff = n->in(0)->in(0); 2741 if( !iff->is_If() || 2742 (n->in(0)->Opcode() == Op_IfFalse && 2743 (1.0 - iff->as_If()->_prob) >= 0.01) || 2744 (iff->as_If()->_prob >= 0.01) ) 2745 innermost->_has_call = 1; 2746 } 2747 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) { 2748 // Disable loop optimizations if the loop has a scalar replaceable 2749 // allocation. This disabling may cause a potential performance lost 2750 // if the allocation is not eliminated for some reason. 2751 innermost->_allow_optimizations = false; 2752 innermost->_has_call = 1; // = true 2753 } 2754 } 2755 } 2756 2757 // Flag as post-visited now 2758 set_postvisited(n); 2759 return pre_order; 2760 } 2761 2762 2763 //------------------------------build_loop_early------------------------------- 2764 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2765 // First pass computes the earliest controlling node possible. This is the 2766 // controlling input with the deepest dominating depth. 2767 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 2768 while (worklist.size() != 0) { 2769 // Use local variables nstack_top_n & nstack_top_i to cache values 2770 // on nstack's top. 2771 Node *nstack_top_n = worklist.pop(); 2772 uint nstack_top_i = 0; 2773 //while_nstack_nonempty: 2774 while (true) { 2775 // Get parent node and next input's index from stack's top. 2776 Node *n = nstack_top_n; 2777 uint i = nstack_top_i; 2778 uint cnt = n->req(); // Count of inputs 2779 if (i == 0) { // Pre-process the node. 2780 if( has_node(n) && // Have either loop or control already? 2781 !has_ctrl(n) ) { // Have loop picked out already? 2782 // During "merge_many_backedges" we fold up several nested loops 2783 // into a single loop. This makes the members of the original 2784 // loop bodies pointing to dead loops; they need to move up 2785 // to the new UNION'd larger loop. I set the _head field of these 2786 // dead loops to NULL and the _parent field points to the owning 2787 // loop. Shades of UNION-FIND algorithm. 2788 IdealLoopTree *ilt; 2789 while( !(ilt = get_loop(n))->_head ) { 2790 // Normally I would use a set_loop here. But in this one special 2791 // case, it is legal (and expected) to change what loop a Node 2792 // belongs to. 2793 _nodes.map(n->_idx, (Node*)(ilt->_parent) ); 2794 } 2795 // Remove safepoints ONLY if I've already seen I don't need one. 2796 // (the old code here would yank a 2nd safepoint after seeing a 2797 // first one, even though the 1st did not dominate in the loop body 2798 // and thus could be avoided indefinitely) 2799 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint && 2800 is_deleteable_safept(n)) { 2801 Node *in = n->in(TypeFunc::Control); 2802 lazy_replace(n,in); // Pull safepoint now 2803 // Carry on with the recursion "as if" we are walking 2804 // only the control input 2805 if( !visited.test_set( in->_idx ) ) { 2806 worklist.push(in); // Visit this guy later, using worklist 2807 } 2808 // Get next node from nstack: 2809 // - skip n's inputs processing by setting i > cnt; 2810 // - we also will not call set_early_ctrl(n) since 2811 // has_node(n) == true (see the condition above). 2812 i = cnt + 1; 2813 } 2814 } 2815 } // if (i == 0) 2816 2817 // Visit all inputs 2818 bool done = true; // Assume all n's inputs will be processed 2819 while (i < cnt) { 2820 Node *in = n->in(i); 2821 ++i; 2822 if (in == NULL) continue; 2823 if (in->pinned() && !in->is_CFG()) 2824 set_ctrl(in, in->in(0)); 2825 int is_visited = visited.test_set( in->_idx ); 2826 if (!has_node(in)) { // No controlling input yet? 2827 assert( !in->is_CFG(), "CFG Node with no controlling input?" ); 2828 assert( !is_visited, "visit only once" ); 2829 nstack.push(n, i); // Save parent node and next input's index. 2830 nstack_top_n = in; // Process current input now. 2831 nstack_top_i = 0; 2832 done = false; // Not all n's inputs processed. 2833 break; // continue while_nstack_nonempty; 2834 } else if (!is_visited) { 2835 // This guy has a location picked out for him, but has not yet 2836 // been visited. Happens to all CFG nodes, for instance. 2837 // Visit him using the worklist instead of recursion, to break 2838 // cycles. Since he has a location already we do not need to 2839 // find his location before proceeding with the current Node. 2840 worklist.push(in); // Visit this guy later, using worklist 2841 } 2842 } 2843 if (done) { 2844 // All of n's inputs have been processed, complete post-processing. 2845 2846 // Compute earliest point this Node can go. 2847 // CFG, Phi, pinned nodes already know their controlling input. 2848 if (!has_node(n)) { 2849 // Record earliest legal location 2850 set_early_ctrl( n ); 2851 } 2852 if (nstack.is_empty()) { 2853 // Finished all nodes on stack. 2854 // Process next node on the worklist. 2855 break; 2856 } 2857 // Get saved parent node and next input's index. 2858 nstack_top_n = nstack.node(); 2859 nstack_top_i = nstack.index(); 2860 nstack.pop(); 2861 } 2862 } // while (true) 2863 } 2864 } 2865 2866 //------------------------------dom_lca_internal-------------------------------- 2867 // Pair-wise LCA 2868 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const { 2869 if( !n1 ) return n2; // Handle NULL original LCA 2870 assert( n1->is_CFG(), "" ); 2871 assert( n2->is_CFG(), "" ); 2872 // find LCA of all uses 2873 uint d1 = dom_depth(n1); 2874 uint d2 = dom_depth(n2); 2875 while (n1 != n2) { 2876 if (d1 > d2) { 2877 n1 = idom(n1); 2878 d1 = dom_depth(n1); 2879 } else if (d1 < d2) { 2880 n2 = idom(n2); 2881 d2 = dom_depth(n2); 2882 } else { 2883 // Here d1 == d2. Due to edits of the dominator-tree, sections 2884 // of the tree might have the same depth. These sections have 2885 // to be searched more carefully. 2886 2887 // Scan up all the n1's with equal depth, looking for n2. 2888 Node *t1 = idom(n1); 2889 while (dom_depth(t1) == d1) { 2890 if (t1 == n2) return n2; 2891 t1 = idom(t1); 2892 } 2893 // Scan up all the n2's with equal depth, looking for n1. 2894 Node *t2 = idom(n2); 2895 while (dom_depth(t2) == d2) { 2896 if (t2 == n1) return n1; 2897 t2 = idom(t2); 2898 } 2899 // Move up to a new dominator-depth value as well as up the dom-tree. 2900 n1 = t1; 2901 n2 = t2; 2902 d1 = dom_depth(n1); 2903 d2 = dom_depth(n2); 2904 } 2905 } 2906 return n1; 2907 } 2908 2909 //------------------------------compute_idom----------------------------------- 2910 // Locally compute IDOM using dom_lca call. Correct only if the incoming 2911 // IDOMs are correct. 2912 Node *PhaseIdealLoop::compute_idom( Node *region ) const { 2913 assert( region->is_Region(), "" ); 2914 Node *LCA = NULL; 2915 for( uint i = 1; i < region->req(); i++ ) { 2916 if( region->in(i) != C->top() ) 2917 LCA = dom_lca( LCA, region->in(i) ); 2918 } 2919 return LCA; 2920 } 2921 2922 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) { 2923 bool had_error = false; 2924 #ifdef ASSERT 2925 if (early != C->root()) { 2926 // Make sure that there's a dominance path from use to LCA 2927 Node* d = use; 2928 while (d != LCA) { 2929 d = idom(d); 2930 if (d == C->root()) { 2931 tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx); 2932 n->dump(); 2933 use->dump(); 2934 had_error = true; 2935 break; 2936 } 2937 } 2938 } 2939 #endif 2940 return had_error; 2941 } 2942 2943 2944 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) { 2945 // Compute LCA over list of uses 2946 bool had_error = false; 2947 Node *LCA = NULL; 2948 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) { 2949 Node* c = n->fast_out(i); 2950 if (_nodes[c->_idx] == NULL) 2951 continue; // Skip the occasional dead node 2952 if( c->is_Phi() ) { // For Phis, we must land above on the path 2953 for( uint j=1; j<c->req(); j++ ) {// For all inputs 2954 if( c->in(j) == n ) { // Found matching input? 2955 Node *use = c->in(0)->in(j); 2956 if (_verify_only && use->is_top()) continue; 2957 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2958 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 2959 } 2960 } 2961 } else { 2962 // For CFG data-users, use is in the block just prior 2963 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0); 2964 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2965 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 2966 } 2967 } 2968 assert(!had_error, "bad dominance"); 2969 return LCA; 2970 } 2971 2972 //------------------------------get_late_ctrl---------------------------------- 2973 // Compute latest legal control. 2974 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) { 2975 assert(early != NULL, "early control should not be NULL"); 2976 2977 Node* LCA = compute_lca_of_uses(n, early); 2978 #ifdef ASSERT 2979 if (LCA == C->root() && LCA != early) { 2980 // def doesn't dominate uses so print some useful debugging output 2981 compute_lca_of_uses(n, early, true); 2982 } 2983 #endif 2984 2985 // if this is a load, check for anti-dependent stores 2986 // We use a conservative algorithm to identify potential interfering 2987 // instructions and for rescheduling the load. The users of the memory 2988 // input of this load are examined. Any use which is not a load and is 2989 // dominated by early is considered a potentially interfering store. 2990 // This can produce false positives. 2991 if (n->is_Load() && LCA != early) { 2992 Node_List worklist; 2993 2994 Node *mem = n->in(MemNode::Memory); 2995 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { 2996 Node* s = mem->fast_out(i); 2997 worklist.push(s); 2998 } 2999 while(worklist.size() != 0 && LCA != early) { 3000 Node* s = worklist.pop(); 3001 if (s->is_Load()) { 3002 continue; 3003 } else if (s->is_MergeMem()) { 3004 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) { 3005 Node* s1 = s->fast_out(i); 3006 worklist.push(s1); 3007 } 3008 } else { 3009 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0); 3010 assert(sctrl != NULL || s->outcnt() == 0, "must have control"); 3011 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) { 3012 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n); 3013 } 3014 } 3015 } 3016 } 3017 3018 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control"); 3019 return LCA; 3020 } 3021 3022 // true if CFG node d dominates CFG node n 3023 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) { 3024 if (d == n) 3025 return true; 3026 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes"); 3027 uint dd = dom_depth(d); 3028 while (dom_depth(n) >= dd) { 3029 if (n == d) 3030 return true; 3031 n = idom(n); 3032 } 3033 return false; 3034 } 3035 3036 //------------------------------dom_lca_for_get_late_ctrl_internal------------- 3037 // Pair-wise LCA with tags. 3038 // Tag each index with the node 'tag' currently being processed 3039 // before advancing up the dominator chain using idom(). 3040 // Later calls that find a match to 'tag' know that this path has already 3041 // been considered in the current LCA (which is input 'n1' by convention). 3042 // Since get_late_ctrl() is only called once for each node, the tag array 3043 // does not need to be cleared between calls to get_late_ctrl(). 3044 // Algorithm trades a larger constant factor for better asymptotic behavior 3045 // 3046 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) { 3047 uint d1 = dom_depth(n1); 3048 uint d2 = dom_depth(n2); 3049 3050 do { 3051 if (d1 > d2) { 3052 // current lca is deeper than n2 3053 _dom_lca_tags.map(n1->_idx, tag); 3054 n1 = idom(n1); 3055 d1 = dom_depth(n1); 3056 } else if (d1 < d2) { 3057 // n2 is deeper than current lca 3058 Node *memo = _dom_lca_tags[n2->_idx]; 3059 if( memo == tag ) { 3060 return n1; // Return the current LCA 3061 } 3062 _dom_lca_tags.map(n2->_idx, tag); 3063 n2 = idom(n2); 3064 d2 = dom_depth(n2); 3065 } else { 3066 // Here d1 == d2. Due to edits of the dominator-tree, sections 3067 // of the tree might have the same depth. These sections have 3068 // to be searched more carefully. 3069 3070 // Scan up all the n1's with equal depth, looking for n2. 3071 _dom_lca_tags.map(n1->_idx, tag); 3072 Node *t1 = idom(n1); 3073 while (dom_depth(t1) == d1) { 3074 if (t1 == n2) return n2; 3075 _dom_lca_tags.map(t1->_idx, tag); 3076 t1 = idom(t1); 3077 } 3078 // Scan up all the n2's with equal depth, looking for n1. 3079 _dom_lca_tags.map(n2->_idx, tag); 3080 Node *t2 = idom(n2); 3081 while (dom_depth(t2) == d2) { 3082 if (t2 == n1) return n1; 3083 _dom_lca_tags.map(t2->_idx, tag); 3084 t2 = idom(t2); 3085 } 3086 // Move up to a new dominator-depth value as well as up the dom-tree. 3087 n1 = t1; 3088 n2 = t2; 3089 d1 = dom_depth(n1); 3090 d2 = dom_depth(n2); 3091 } 3092 } while (n1 != n2); 3093 return n1; 3094 } 3095 3096 //------------------------------init_dom_lca_tags------------------------------ 3097 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 3098 // Intended use does not involve any growth for the array, so it could 3099 // be of fixed size. 3100 void PhaseIdealLoop::init_dom_lca_tags() { 3101 uint limit = C->unique() + 1; 3102 _dom_lca_tags.map( limit, NULL ); 3103 #ifdef ASSERT 3104 for( uint i = 0; i < limit; ++i ) { 3105 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 3106 } 3107 #endif // ASSERT 3108 } 3109 3110 //------------------------------clear_dom_lca_tags------------------------------ 3111 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 3112 // Intended use does not involve any growth for the array, so it could 3113 // be of fixed size. 3114 void PhaseIdealLoop::clear_dom_lca_tags() { 3115 uint limit = C->unique() + 1; 3116 _dom_lca_tags.map( limit, NULL ); 3117 _dom_lca_tags.clear(); 3118 #ifdef ASSERT 3119 for( uint i = 0; i < limit; ++i ) { 3120 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 3121 } 3122 #endif // ASSERT 3123 } 3124 3125 //------------------------------build_loop_late-------------------------------- 3126 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 3127 // Second pass finds latest legal placement, and ideal loop placement. 3128 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 3129 while (worklist.size() != 0) { 3130 Node *n = worklist.pop(); 3131 // Only visit once 3132 if (visited.test_set(n->_idx)) continue; 3133 uint cnt = n->outcnt(); 3134 uint i = 0; 3135 while (true) { 3136 assert( _nodes[n->_idx], "no dead nodes" ); 3137 // Visit all children 3138 if (i < cnt) { 3139 Node* use = n->raw_out(i); 3140 ++i; 3141 // Check for dead uses. Aggressively prune such junk. It might be 3142 // dead in the global sense, but still have local uses so I cannot 3143 // easily call 'remove_dead_node'. 3144 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead? 3145 // Due to cycles, we might not hit the same fixed point in the verify 3146 // pass as we do in the regular pass. Instead, visit such phis as 3147 // simple uses of the loop head. 3148 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) { 3149 if( !visited.test(use->_idx) ) 3150 worklist.push(use); 3151 } else if( !visited.test_set(use->_idx) ) { 3152 nstack.push(n, i); // Save parent and next use's index. 3153 n = use; // Process all children of current use. 3154 cnt = use->outcnt(); 3155 i = 0; 3156 } 3157 } else { 3158 // Do not visit around the backedge of loops via data edges. 3159 // push dead code onto a worklist 3160 _deadlist.push(use); 3161 } 3162 } else { 3163 // All of n's children have been processed, complete post-processing. 3164 build_loop_late_post(n); 3165 if (nstack.is_empty()) { 3166 // Finished all nodes on stack. 3167 // Process next node on the worklist. 3168 break; 3169 } 3170 // Get saved parent node and next use's index. Visit the rest of uses. 3171 n = nstack.node(); 3172 cnt = n->outcnt(); 3173 i = nstack.index(); 3174 nstack.pop(); 3175 } 3176 } 3177 } 3178 } 3179 3180 //------------------------------build_loop_late_post--------------------------- 3181 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 3182 // Second pass finds latest legal placement, and ideal loop placement. 3183 void PhaseIdealLoop::build_loop_late_post( Node *n ) { 3184 3185 if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) { 3186 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops. 3187 } 3188 3189 // CFG and pinned nodes already handled 3190 if( n->in(0) ) { 3191 if( n->in(0)->is_top() ) return; // Dead? 3192 3193 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads 3194 // _must_ be pinned (they have to observe their control edge of course). 3195 // Unlike Stores (which modify an unallocable resource, the memory 3196 // state), Mods/Loads can float around. So free them up. 3197 bool pinned = true; 3198 switch( n->Opcode() ) { 3199 case Op_DivI: 3200 case Op_DivF: 3201 case Op_DivD: 3202 case Op_ModI: 3203 case Op_ModF: 3204 case Op_ModD: 3205 case Op_LoadB: // Same with Loads; they can sink 3206 case Op_LoadUS: // during loop optimizations. 3207 case Op_LoadD: 3208 case Op_LoadF: 3209 case Op_LoadI: 3210 case Op_LoadKlass: 3211 case Op_LoadNKlass: 3212 case Op_LoadL: 3213 case Op_LoadS: 3214 case Op_LoadP: 3215 case Op_LoadN: 3216 case Op_LoadRange: 3217 case Op_LoadD_unaligned: 3218 case Op_LoadL_unaligned: 3219 case Op_StrComp: // Does a bunch of load-like effects 3220 case Op_StrEquals: 3221 case Op_StrIndexOf: 3222 case Op_AryEq: 3223 pinned = false; 3224 } 3225 if( pinned ) { 3226 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n)); 3227 if( !chosen_loop->_child ) // Inner loop? 3228 chosen_loop->_body.push(n); // Collect inner loops 3229 return; 3230 } 3231 } else { // No slot zero 3232 if( n->is_CFG() ) { // CFG with no slot 0 is dead 3233 _nodes.map(n->_idx,0); // No block setting, it's globally dead 3234 return; 3235 } 3236 assert(!n->is_CFG() || n->outcnt() == 0, ""); 3237 } 3238 3239 // Do I have a "safe range" I can select over? 3240 Node *early = get_ctrl(n);// Early location already computed 3241 3242 // Compute latest point this Node can go 3243 Node *LCA = get_late_ctrl( n, early ); 3244 // LCA is NULL due to uses being dead 3245 if( LCA == NULL ) { 3246 #ifdef ASSERT 3247 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) { 3248 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead"); 3249 } 3250 #endif 3251 _nodes.map(n->_idx, 0); // This node is useless 3252 _deadlist.push(n); 3253 return; 3254 } 3255 assert(LCA != NULL && !LCA->is_top(), "no dead nodes"); 3256 3257 Node *legal = LCA; // Walk 'legal' up the IDOM chain 3258 Node *least = legal; // Best legal position so far 3259 while( early != legal ) { // While not at earliest legal 3260 #ifdef ASSERT 3261 if (legal->is_Start() && !early->is_Root()) { 3262 // Bad graph. Print idom path and fail. 3263 tty->print_cr( "Bad graph detected in build_loop_late"); 3264 tty->print("n: ");n->dump(); tty->cr(); 3265 tty->print("early: ");early->dump(); tty->cr(); 3266 int ct = 0; 3267 Node *dbg_legal = LCA; 3268 while(!dbg_legal->is_Start() && ct < 100) { 3269 tty->print("idom[%d] ",ct); dbg_legal->dump(); tty->cr(); 3270 ct++; 3271 dbg_legal = idom(dbg_legal); 3272 } 3273 assert(false, "Bad graph detected in build_loop_late"); 3274 } 3275 #endif 3276 // Find least loop nesting depth 3277 legal = idom(legal); // Bump up the IDOM tree 3278 // Check for lower nesting depth 3279 if( get_loop(legal)->_nest < get_loop(least)->_nest ) 3280 least = legal; 3281 } 3282 assert(early == legal || legal != C->root(), "bad dominance of inputs"); 3283 3284 // Try not to place code on a loop entry projection 3285 // which can inhibit range check elimination. 3286 if (least != early) { 3287 Node* ctrl_out = least->unique_ctrl_out(); 3288 if (ctrl_out && ctrl_out->is_CountedLoop() && 3289 least == ctrl_out->in(LoopNode::EntryControl)) { 3290 Node* least_dom = idom(least); 3291 if (get_loop(least_dom)->is_member(get_loop(least))) { 3292 least = least_dom; 3293 } 3294 } 3295 } 3296 3297 #ifdef ASSERT 3298 // If verifying, verify that 'verify_me' has a legal location 3299 // and choose it as our location. 3300 if( _verify_me ) { 3301 Node *v_ctrl = _verify_me->get_ctrl_no_update(n); 3302 Node *legal = LCA; 3303 while( early != legal ) { // While not at earliest legal 3304 if( legal == v_ctrl ) break; // Check for prior good location 3305 legal = idom(legal) ;// Bump up the IDOM tree 3306 } 3307 // Check for prior good location 3308 if( legal == v_ctrl ) least = legal; // Keep prior if found 3309 } 3310 #endif 3311 3312 // Assign discovered "here or above" point 3313 least = find_non_split_ctrl(least); 3314 set_ctrl(n, least); 3315 3316 // Collect inner loop bodies 3317 IdealLoopTree *chosen_loop = get_loop(least); 3318 if( !chosen_loop->_child ) // Inner loop? 3319 chosen_loop->_body.push(n);// Collect inner loops 3320 } 3321 3322 #ifndef PRODUCT 3323 //------------------------------dump------------------------------------------- 3324 void PhaseIdealLoop::dump( ) const { 3325 ResourceMark rm; 3326 Arena* arena = Thread::current()->resource_area(); 3327 Node_Stack stack(arena, C->unique() >> 2); 3328 Node_List rpo_list; 3329 VectorSet visited(arena); 3330 visited.set(C->top()->_idx); 3331 rpo( C->root(), stack, visited, rpo_list ); 3332 // Dump root loop indexed by last element in PO order 3333 dump( _ltree_root, rpo_list.size(), rpo_list ); 3334 } 3335 3336 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const { 3337 loop->dump_head(); 3338 3339 // Now scan for CFG nodes in the same loop 3340 for( uint j=idx; j > 0; j-- ) { 3341 Node *n = rpo_list[j-1]; 3342 if( !_nodes[n->_idx] ) // Skip dead nodes 3343 continue; 3344 if( get_loop(n) != loop ) { // Wrong loop nest 3345 if( get_loop(n)->_head == n && // Found nested loop? 3346 get_loop(n)->_parent == loop ) 3347 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly 3348 continue; 3349 } 3350 3351 // Dump controlling node 3352 for( uint x = 0; x < loop->_nest; x++ ) 3353 tty->print(" "); 3354 tty->print("C"); 3355 if( n == C->root() ) { 3356 n->dump(); 3357 } else { 3358 Node* cached_idom = idom_no_update(n); 3359 Node *computed_idom = n->in(0); 3360 if( n->is_Region() ) { 3361 computed_idom = compute_idom(n); 3362 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or 3363 // any MultiBranch ctrl node), so apply a similar transform to 3364 // the cached idom returned from idom_no_update. 3365 cached_idom = find_non_split_ctrl(cached_idom); 3366 } 3367 tty->print(" ID:%d",computed_idom->_idx); 3368 n->dump(); 3369 if( cached_idom != computed_idom ) { 3370 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d", 3371 computed_idom->_idx, cached_idom->_idx); 3372 } 3373 } 3374 // Dump nodes it controls 3375 for( uint k = 0; k < _nodes.Size(); k++ ) { 3376 // (k < C->unique() && get_ctrl(find(k)) == n) 3377 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) { 3378 Node *m = C->root()->find(k); 3379 if( m && m->outcnt() > 0 ) { 3380 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) { 3381 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p", 3382 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL); 3383 } 3384 for( uint j = 0; j < loop->_nest; j++ ) 3385 tty->print(" "); 3386 tty->print(" "); 3387 m->dump(); 3388 } 3389 } 3390 } 3391 } 3392 } 3393 3394 // Collect a R-P-O for the whole CFG. 3395 // Result list is in post-order (scan backwards for RPO) 3396 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const { 3397 stk.push(start, 0); 3398 visited.set(start->_idx); 3399 3400 while (stk.is_nonempty()) { 3401 Node* m = stk.node(); 3402 uint idx = stk.index(); 3403 if (idx < m->outcnt()) { 3404 stk.set_index(idx + 1); 3405 Node* n = m->raw_out(idx); 3406 if (n->is_CFG() && !visited.test_set(n->_idx)) { 3407 stk.push(n, 0); 3408 } 3409 } else { 3410 rpo_list.push(m); 3411 stk.pop(); 3412 } 3413 } 3414 } 3415 #endif 3416 3417 3418 //============================================================================= 3419 //------------------------------LoopTreeIterator----------------------------------- 3420 3421 // Advance to next loop tree using a preorder, left-to-right traversal. 3422 void LoopTreeIterator::next() { 3423 assert(!done(), "must not be done."); 3424 if (_curnt->_child != NULL) { 3425 _curnt = _curnt->_child; 3426 } else if (_curnt->_next != NULL) { 3427 _curnt = _curnt->_next; 3428 } else { 3429 while (_curnt != _root && _curnt->_next == NULL) { 3430 _curnt = _curnt->_parent; 3431 } 3432 if (_curnt == _root) { 3433 _curnt = NULL; 3434 assert(done(), "must be done."); 3435 } else { 3436 assert(_curnt->_next != NULL, "must be more to do"); 3437 _curnt = _curnt->_next; 3438 } 3439 } 3440 }