1 /* 2 * Copyright 1998-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 #include "incls/_precompiled.incl" 26 #include "incls/_loopnode.cpp.incl" 27 28 //============================================================================= 29 //------------------------------is_loop_iv------------------------------------- 30 // Determine if a node is Counted loop induction variable. 31 // The method is declared in node.hpp. 32 const Node* Node::is_loop_iv() const { 33 if (this->is_Phi() && !this->as_Phi()->is_copy() && 34 this->as_Phi()->region()->is_CountedLoop() && 35 this->as_Phi()->region()->as_CountedLoop()->phi() == this) { 36 return this; 37 } else { 38 return NULL; 39 } 40 } 41 42 //============================================================================= 43 //------------------------------dump_spec-------------------------------------- 44 // Dump special per-node info 45 #ifndef PRODUCT 46 void LoopNode::dump_spec(outputStream *st) const { 47 if( is_inner_loop () ) st->print( "inner " ); 48 if( is_partial_peel_loop () ) st->print( "partial_peel " ); 49 if( partial_peel_has_failed () ) st->print( "partial_peel_failed " ); 50 } 51 #endif 52 53 //------------------------------get_early_ctrl--------------------------------- 54 // Compute earliest legal control 55 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) { 56 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" ); 57 uint i; 58 Node *early; 59 if( n->in(0) ) { 60 early = n->in(0); 61 if( !early->is_CFG() ) // Might be a non-CFG multi-def 62 early = get_ctrl(early); // So treat input as a straight data input 63 i = 1; 64 } else { 65 early = get_ctrl(n->in(1)); 66 i = 2; 67 } 68 uint e_d = dom_depth(early); 69 assert( early, "" ); 70 for( ; i < n->req(); i++ ) { 71 Node *cin = get_ctrl(n->in(i)); 72 assert( cin, "" ); 73 // Keep deepest dominator depth 74 uint c_d = dom_depth(cin); 75 if( c_d > e_d ) { // Deeper guy? 76 early = cin; // Keep deepest found so far 77 e_d = c_d; 78 } else if( c_d == e_d && // Same depth? 79 early != cin ) { // If not equal, must use slower algorithm 80 // If same depth but not equal, one _must_ dominate the other 81 // and we want the deeper (i.e., dominated) guy. 82 Node *n1 = early; 83 Node *n2 = cin; 84 while( 1 ) { 85 n1 = idom(n1); // Walk up until break cycle 86 n2 = idom(n2); 87 if( n1 == cin || // Walked early up to cin 88 dom_depth(n2) < c_d ) 89 break; // early is deeper; keep him 90 if( n2 == early || // Walked cin up to early 91 dom_depth(n1) < c_d ) { 92 early = cin; // cin is deeper; keep him 93 break; 94 } 95 } 96 e_d = dom_depth(early); // Reset depth register cache 97 } 98 } 99 100 // Return earliest legal location 101 assert(early == find_non_split_ctrl(early), "unexpected early control"); 102 103 return early; 104 } 105 106 //------------------------------set_early_ctrl--------------------------------- 107 // Set earliest legal control 108 void PhaseIdealLoop::set_early_ctrl( Node *n ) { 109 Node *early = get_early_ctrl(n); 110 111 // Record earliest legal location 112 set_ctrl(n, early); 113 } 114 115 //------------------------------set_subtree_ctrl------------------------------- 116 // set missing _ctrl entries on new nodes 117 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) { 118 // Already set? Get out. 119 if( _nodes[n->_idx] ) return; 120 // Recursively set _nodes array to indicate where the Node goes 121 uint i; 122 for( i = 0; i < n->req(); ++i ) { 123 Node *m = n->in(i); 124 if( m && m != C->root() ) 125 set_subtree_ctrl( m ); 126 } 127 128 // Fixup self 129 set_early_ctrl( n ); 130 } 131 132 //------------------------------is_counted_loop-------------------------------- 133 Node *PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) { 134 PhaseGVN *gvn = &_igvn; 135 136 // Counted loop head must be a good RegionNode with only 3 not NULL 137 // control input edges: Self, Entry, LoopBack. 138 if ( x->in(LoopNode::Self) == NULL || x->req() != 3 ) 139 return NULL; 140 141 Node *init_control = x->in(LoopNode::EntryControl); 142 Node *back_control = x->in(LoopNode::LoopBackControl); 143 if( init_control == NULL || back_control == NULL ) // Partially dead 144 return NULL; 145 // Must also check for TOP when looking for a dead loop 146 if( init_control->is_top() || back_control->is_top() ) 147 return NULL; 148 149 // Allow funny placement of Safepoint 150 if( back_control->Opcode() == Op_SafePoint ) 151 back_control = back_control->in(TypeFunc::Control); 152 153 // Controlling test for loop 154 Node *iftrue = back_control; 155 uint iftrue_op = iftrue->Opcode(); 156 if( iftrue_op != Op_IfTrue && 157 iftrue_op != Op_IfFalse ) 158 // I have a weird back-control. Probably the loop-exit test is in 159 // the middle of the loop and I am looking at some trailing control-flow 160 // merge point. To fix this I would have to partially peel the loop. 161 return NULL; // Obscure back-control 162 163 // Get boolean guarding loop-back test 164 Node *iff = iftrue->in(0); 165 if( get_loop(iff) != loop || !iff->in(1)->is_Bool() ) return NULL; 166 BoolNode *test = iff->in(1)->as_Bool(); 167 BoolTest::mask bt = test->_test._test; 168 float cl_prob = iff->as_If()->_prob; 169 if( iftrue_op == Op_IfFalse ) { 170 bt = BoolTest(bt).negate(); 171 cl_prob = 1.0 - cl_prob; 172 } 173 // Get backedge compare 174 Node *cmp = test->in(1); 175 int cmp_op = cmp->Opcode(); 176 if( cmp_op != Op_CmpI ) 177 return NULL; // Avoid pointer & float compares 178 179 // Find the trip-counter increment & limit. Limit must be loop invariant. 180 Node *incr = cmp->in(1); 181 Node *limit = cmp->in(2); 182 183 // --------- 184 // need 'loop()' test to tell if limit is loop invariant 185 // --------- 186 187 if( !is_member( loop, get_ctrl(incr) ) ) { // Swapped trip counter and limit? 188 Node *tmp = incr; // Then reverse order into the CmpI 189 incr = limit; 190 limit = tmp; 191 bt = BoolTest(bt).commute(); // And commute the exit test 192 } 193 if( is_member( loop, get_ctrl(limit) ) ) // Limit must loop-invariant 194 return NULL; 195 196 // Trip-counter increment must be commutative & associative. 197 uint incr_op = incr->Opcode(); 198 if( incr_op == Op_Phi && incr->req() == 3 ) { 199 incr = incr->in(2); // Assume incr is on backedge of Phi 200 incr_op = incr->Opcode(); 201 } 202 Node* trunc1 = NULL; 203 Node* trunc2 = NULL; 204 const TypeInt* iv_trunc_t = NULL; 205 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) { 206 return NULL; // Funny increment opcode 207 } 208 209 // Get merge point 210 Node *xphi = incr->in(1); 211 Node *stride = incr->in(2); 212 if( !stride->is_Con() ) { // Oops, swap these 213 if( !xphi->is_Con() ) // Is the other guy a constant? 214 return NULL; // Nope, unknown stride, bail out 215 Node *tmp = xphi; // 'incr' is commutative, so ok to swap 216 xphi = stride; 217 stride = tmp; 218 } 219 //if( loop(xphi) != l) return NULL;// Merge point is in inner loop?? 220 if( !xphi->is_Phi() ) return NULL; // Too much math on the trip counter 221 PhiNode *phi = xphi->as_Phi(); 222 223 // Stride must be constant 224 const Type *stride_t = stride->bottom_type(); 225 int stride_con = stride_t->is_int()->get_con(); 226 assert( stride_con, "missed some peephole opt" ); 227 228 // Phi must be of loop header; backedge must wrap to increment 229 if( phi->region() != x ) return NULL; 230 if( trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr || 231 trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1 ) { 232 return NULL; 233 } 234 Node *init_trip = phi->in(LoopNode::EntryControl); 235 //if (!init_trip->is_Con()) return NULL; // avoid rolling over MAXINT/MININT 236 237 // If iv trunc type is smaller than int, check for possible wrap. 238 if (!TypeInt::INT->higher_equal(iv_trunc_t)) { 239 assert(trunc1 != NULL, "must have found some truncation"); 240 241 // Get a better type for the phi (filtered thru if's) 242 const TypeInt* phi_ft = filtered_type(phi); 243 244 // Can iv take on a value that will wrap? 245 // 246 // Ensure iv's limit is not within "stride" of the wrap value. 247 // 248 // Example for "short" type 249 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t) 250 // If the stride is +10, then the last value of the induction 251 // variable before the increment (phi_ft->_hi) must be 252 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to 253 // ensure no truncation occurs after the increment. 254 255 if (stride_con > 0) { 256 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con || 257 iv_trunc_t->_lo > phi_ft->_lo) { 258 return NULL; // truncation may occur 259 } 260 } else if (stride_con < 0) { 261 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con || 262 iv_trunc_t->_hi < phi_ft->_hi) { 263 return NULL; // truncation may occur 264 } 265 } 266 // No possibility of wrap so truncation can be discarded 267 // Promote iv type to Int 268 } else { 269 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int"); 270 } 271 272 // ================================================= 273 // ---- SUCCESS! Found A Trip-Counted Loop! ----- 274 // 275 // Canonicalize the condition on the test. If we can exactly determine 276 // the trip-counter exit value, then set limit to that value and use 277 // a '!=' test. Otherwise use condition '<' for count-up loops and 278 // '>' for count-down loops. If the condition is inverted and we will 279 // be rolling through MININT to MAXINT, then bail out. 280 281 C->print_method("Before CountedLoop", 3); 282 283 // Check for SafePoint on backedge and remove 284 Node *sfpt = x->in(LoopNode::LoopBackControl); 285 if( sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) { 286 lazy_replace( sfpt, iftrue ); 287 loop->_tail = iftrue; 288 } 289 290 291 // If compare points to incr, we are ok. Otherwise the compare 292 // can directly point to the phi; in this case adjust the compare so that 293 // it points to the incr by adjusting the limit. 294 if( cmp->in(1) == phi || cmp->in(2) == phi ) 295 limit = gvn->transform(new (C, 3) AddINode(limit,stride)); 296 297 // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride. 298 // Final value for iterator should be: trip_count * stride + init_trip. 299 const Type *limit_t = limit->bottom_type(); 300 const Type *init_t = init_trip->bottom_type(); 301 Node *one_p = gvn->intcon( 1); 302 Node *one_m = gvn->intcon(-1); 303 304 Node *trip_count = NULL; 305 Node *hook = new (C, 6) Node(6); 306 switch( bt ) { 307 case BoolTest::eq: 308 return NULL; // Bail out, but this loop trips at most twice! 309 case BoolTest::ne: // Ahh, the case we desire 310 if( stride_con == 1 ) 311 trip_count = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 312 else if( stride_con == -1 ) 313 trip_count = gvn->transform(new (C, 3) SubINode(init_trip,limit)); 314 else 315 return NULL; // Odd stride; must prove we hit limit exactly 316 set_subtree_ctrl( trip_count ); 317 //_loop.map(trip_count->_idx,loop(limit)); 318 break; 319 case BoolTest::le: // Maybe convert to '<' case 320 limit = gvn->transform(new (C, 3) AddINode(limit,one_p)); 321 set_subtree_ctrl( limit ); 322 hook->init_req(4, limit); 323 324 bt = BoolTest::lt; 325 // Make the new limit be in the same loop nest as the old limit 326 //_loop.map(limit->_idx,limit_loop); 327 // Fall into next case 328 case BoolTest::lt: { // Maybe convert to '!=' case 329 if( stride_con < 0 ) return NULL; // Count down loop rolls through MAXINT 330 Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 331 set_subtree_ctrl( range ); 332 hook->init_req(0, range); 333 334 Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); 335 set_subtree_ctrl( bias ); 336 hook->init_req(1, bias); 337 338 Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_m)); 339 set_subtree_ctrl( bias1 ); 340 hook->init_req(2, bias1); 341 342 trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); 343 set_subtree_ctrl( trip_count ); 344 hook->init_req(3, trip_count); 345 break; 346 } 347 348 case BoolTest::ge: // Maybe convert to '>' case 349 limit = gvn->transform(new (C, 3) AddINode(limit,one_m)); 350 set_subtree_ctrl( limit ); 351 hook->init_req(4 ,limit); 352 353 bt = BoolTest::gt; 354 // Make the new limit be in the same loop nest as the old limit 355 //_loop.map(limit->_idx,limit_loop); 356 // Fall into next case 357 case BoolTest::gt: { // Maybe convert to '!=' case 358 if( stride_con > 0 ) return NULL; // count up loop rolls through MININT 359 Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); 360 set_subtree_ctrl( range ); 361 hook->init_req(0, range); 362 363 Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); 364 set_subtree_ctrl( bias ); 365 hook->init_req(1, bias); 366 367 Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_p)); 368 set_subtree_ctrl( bias1 ); 369 hook->init_req(2, bias1); 370 371 trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); 372 set_subtree_ctrl( trip_count ); 373 hook->init_req(3, trip_count); 374 break; 375 } 376 } 377 378 Node *span = gvn->transform(new (C, 3) MulINode(trip_count,stride)); 379 set_subtree_ctrl( span ); 380 hook->init_req(5, span); 381 382 limit = gvn->transform(new (C, 3) AddINode(span,init_trip)); 383 set_subtree_ctrl( limit ); 384 385 // Build a canonical trip test. 386 // Clone code, as old values may be in use. 387 incr = incr->clone(); 388 incr->set_req(1,phi); 389 incr->set_req(2,stride); 390 incr = _igvn.register_new_node_with_optimizer(incr); 391 set_early_ctrl( incr ); 392 _igvn.hash_delete(phi); 393 phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn ); 394 395 // If phi type is more restrictive than Int, raise to 396 // Int to prevent (almost) infinite recursion in igvn 397 // which can only handle integer types for constants or minint..maxint. 398 if (!TypeInt::INT->higher_equal(phi->bottom_type())) { 399 Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT); 400 nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl)); 401 nphi = _igvn.register_new_node_with_optimizer(nphi); 402 set_ctrl(nphi, get_ctrl(phi)); 403 _igvn.subsume_node(phi, nphi); 404 phi = nphi->as_Phi(); 405 } 406 cmp = cmp->clone(); 407 cmp->set_req(1,incr); 408 cmp->set_req(2,limit); 409 cmp = _igvn.register_new_node_with_optimizer(cmp); 410 set_ctrl(cmp, iff->in(0)); 411 412 Node *tmp = test->clone(); 413 assert( tmp->is_Bool(), "" ); 414 test = (BoolNode*)tmp; 415 (*(BoolTest*)&test->_test)._test = bt; //BoolTest::ne; 416 test->set_req(1,cmp); 417 _igvn.register_new_node_with_optimizer(test); 418 set_ctrl(test, iff->in(0)); 419 // If the exit test is dead, STOP! 420 if( test == NULL ) return NULL; 421 _igvn.hash_delete(iff); 422 iff->set_req_X( 1, test, &_igvn ); 423 424 // Replace the old IfNode with a new LoopEndNode 425 Node *lex = _igvn.register_new_node_with_optimizer(new (C, 2) CountedLoopEndNode( iff->in(0), iff->in(1), cl_prob, iff->as_If()->_fcnt )); 426 IfNode *le = lex->as_If(); 427 uint dd = dom_depth(iff); 428 set_idom(le, le->in(0), dd); // Update dominance for loop exit 429 set_loop(le, loop); 430 431 // Get the loop-exit control 432 Node *if_f = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue)); 433 434 // Need to swap loop-exit and loop-back control? 435 if( iftrue_op == Op_IfFalse ) { 436 Node *ift2=_igvn.register_new_node_with_optimizer(new (C, 1) IfTrueNode (le)); 437 Node *iff2=_igvn.register_new_node_with_optimizer(new (C, 1) IfFalseNode(le)); 438 439 loop->_tail = back_control = ift2; 440 set_loop(ift2, loop); 441 set_loop(iff2, get_loop(if_f)); 442 443 // Lazy update of 'get_ctrl' mechanism. 444 lazy_replace_proj( if_f , iff2 ); 445 lazy_replace_proj( iftrue, ift2 ); 446 447 // Swap names 448 if_f = iff2; 449 iftrue = ift2; 450 } else { 451 _igvn.hash_delete(if_f ); 452 _igvn.hash_delete(iftrue); 453 if_f ->set_req_X( 0, le, &_igvn ); 454 iftrue->set_req_X( 0, le, &_igvn ); 455 } 456 457 set_idom(iftrue, le, dd+1); 458 set_idom(if_f, le, dd+1); 459 460 // Now setup a new CountedLoopNode to replace the existing LoopNode 461 CountedLoopNode *l = new (C, 3) CountedLoopNode(init_control, back_control); 462 // The following assert is approximately true, and defines the intention 463 // of can_be_counted_loop. It fails, however, because phase->type 464 // is not yet initialized for this loop and its parts. 465 //assert(l->can_be_counted_loop(this), "sanity"); 466 _igvn.register_new_node_with_optimizer(l); 467 set_loop(l, loop); 468 loop->_head = l; 469 // Fix all data nodes placed at the old loop head. 470 // Uses the lazy-update mechanism of 'get_ctrl'. 471 lazy_replace( x, l ); 472 set_idom(l, init_control, dom_depth(x)); 473 474 // Check for immediately preceding SafePoint and remove 475 Node *sfpt2 = le->in(0); 476 if( sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) 477 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control)); 478 479 // Free up intermediate goo 480 _igvn.remove_dead_node(hook); 481 482 C->print_method("After CountedLoop", 3); 483 484 // Return trip counter 485 return trip_count; 486 } 487 488 489 //------------------------------Ideal------------------------------------------ 490 // Return a node which is more "ideal" than the current node. 491 // Attempt to convert into a counted-loop. 492 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 493 if (!can_be_counted_loop(phase)) { 494 phase->C->set_major_progress(); 495 } 496 return RegionNode::Ideal(phase, can_reshape); 497 } 498 499 500 //============================================================================= 501 //------------------------------Ideal------------------------------------------ 502 // Return a node which is more "ideal" than the current node. 503 // Attempt to convert into a counted-loop. 504 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { 505 return RegionNode::Ideal(phase, can_reshape); 506 } 507 508 //------------------------------dump_spec-------------------------------------- 509 // Dump special per-node info 510 #ifndef PRODUCT 511 void CountedLoopNode::dump_spec(outputStream *st) const { 512 LoopNode::dump_spec(st); 513 if( stride_is_con() ) { 514 st->print("stride: %d ",stride_con()); 515 } else { 516 st->print("stride: not constant "); 517 } 518 if( is_pre_loop () ) st->print("pre of N%d" , _main_idx ); 519 if( is_main_loop() ) st->print("main of N%d", _idx ); 520 if( is_post_loop() ) st->print("post of N%d", _main_idx ); 521 } 522 #endif 523 524 //============================================================================= 525 int CountedLoopEndNode::stride_con() const { 526 return stride()->bottom_type()->is_int()->get_con(); 527 } 528 529 530 //----------------------match_incr_with_optional_truncation-------------------- 531 // Match increment with optional truncation: 532 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16 533 // Return NULL for failure. Success returns the increment node. 534 Node* CountedLoopNode::match_incr_with_optional_truncation( 535 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) { 536 // Quick cutouts: 537 if (expr == NULL || expr->req() != 3) return false; 538 539 Node *t1 = NULL; 540 Node *t2 = NULL; 541 const TypeInt* trunc_t = TypeInt::INT; 542 Node* n1 = expr; 543 int n1op = n1->Opcode(); 544 545 // Try to strip (n1 & M) or (n1 << N >> N) from n1. 546 if (n1op == Op_AndI && 547 n1->in(2)->is_Con() && 548 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) { 549 // %%% This check should match any mask of 2**K-1. 550 t1 = n1; 551 n1 = t1->in(1); 552 n1op = n1->Opcode(); 553 trunc_t = TypeInt::CHAR; 554 } else if (n1op == Op_RShiftI && 555 n1->in(1) != NULL && 556 n1->in(1)->Opcode() == Op_LShiftI && 557 n1->in(2) == n1->in(1)->in(2) && 558 n1->in(2)->is_Con()) { 559 jint shift = n1->in(2)->bottom_type()->is_int()->get_con(); 560 // %%% This check should match any shift in [1..31]. 561 if (shift == 16 || shift == 8) { 562 t1 = n1; 563 t2 = t1->in(1); 564 n1 = t2->in(1); 565 n1op = n1->Opcode(); 566 if (shift == 16) { 567 trunc_t = TypeInt::SHORT; 568 } else if (shift == 8) { 569 trunc_t = TypeInt::BYTE; 570 } 571 } 572 } 573 574 // If (maybe after stripping) it is an AddI, we won: 575 if (n1op == Op_AddI) { 576 *trunc1 = t1; 577 *trunc2 = t2; 578 *trunc_type = trunc_t; 579 return n1; 580 } 581 582 // failed 583 return NULL; 584 } 585 586 587 //------------------------------filtered_type-------------------------------- 588 // Return a type based on condition control flow 589 // A successful return will be a type that is restricted due 590 // to a series of dominating if-tests, such as: 591 // if (i < 10) { 592 // if (i > 0) { 593 // here: "i" type is [1..10) 594 // } 595 // } 596 // or a control flow merge 597 // if (i < 10) { 598 // do { 599 // phi( , ) -- at top of loop type is [min_int..10) 600 // i = ? 601 // } while ( i < 10) 602 // 603 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) { 604 assert(n && n->bottom_type()->is_int(), "must be int"); 605 const TypeInt* filtered_t = NULL; 606 if (!n->is_Phi()) { 607 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control"); 608 filtered_t = filtered_type_from_dominators(n, n_ctrl); 609 610 } else { 611 Node* phi = n->as_Phi(); 612 Node* region = phi->in(0); 613 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region"); 614 if (region && region != C->top()) { 615 for (uint i = 1; i < phi->req(); i++) { 616 Node* val = phi->in(i); 617 Node* use_c = region->in(i); 618 const TypeInt* val_t = filtered_type_from_dominators(val, use_c); 619 if (val_t != NULL) { 620 if (filtered_t == NULL) { 621 filtered_t = val_t; 622 } else { 623 filtered_t = filtered_t->meet(val_t)->is_int(); 624 } 625 } 626 } 627 } 628 } 629 const TypeInt* n_t = _igvn.type(n)->is_int(); 630 if (filtered_t != NULL) { 631 n_t = n_t->join(filtered_t)->is_int(); 632 } 633 return n_t; 634 } 635 636 637 //------------------------------filtered_type_from_dominators-------------------------------- 638 // Return a possibly more restrictive type for val based on condition control flow of dominators 639 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) { 640 if (val->is_Con()) { 641 return val->bottom_type()->is_int(); 642 } 643 uint if_limit = 10; // Max number of dominating if's visited 644 const TypeInt* rtn_t = NULL; 645 646 if (use_ctrl && use_ctrl != C->top()) { 647 Node* val_ctrl = get_ctrl(val); 648 uint val_dom_depth = dom_depth(val_ctrl); 649 Node* pred = use_ctrl; 650 uint if_cnt = 0; 651 while (if_cnt < if_limit) { 652 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) { 653 if_cnt++; 654 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred); 655 if (if_t != NULL) { 656 if (rtn_t == NULL) { 657 rtn_t = if_t; 658 } else { 659 rtn_t = rtn_t->join(if_t)->is_int(); 660 } 661 } 662 } 663 pred = idom(pred); 664 if (pred == NULL || pred == C->top()) { 665 break; 666 } 667 // Stop if going beyond definition block of val 668 if (dom_depth(pred) < val_dom_depth) { 669 break; 670 } 671 } 672 } 673 return rtn_t; 674 } 675 676 677 //------------------------------dump_spec-------------------------------------- 678 // Dump special per-node info 679 #ifndef PRODUCT 680 void CountedLoopEndNode::dump_spec(outputStream *st) const { 681 if( in(TestValue)->is_Bool() ) { 682 BoolTest bt( test_trip()); // Added this for g++. 683 684 st->print("["); 685 bt.dump_on(st); 686 st->print("]"); 687 } 688 st->print(" "); 689 IfNode::dump_spec(st); 690 } 691 #endif 692 693 //============================================================================= 694 //------------------------------is_member-------------------------------------- 695 // Is 'l' a member of 'this'? 696 int IdealLoopTree::is_member( const IdealLoopTree *l ) const { 697 while( l->_nest > _nest ) l = l->_parent; 698 return l == this; 699 } 700 701 //------------------------------set_nest--------------------------------------- 702 // Set loop tree nesting depth. Accumulate _has_call bits. 703 int IdealLoopTree::set_nest( uint depth ) { 704 _nest = depth; 705 int bits = _has_call; 706 if( _child ) bits |= _child->set_nest(depth+1); 707 if( bits ) _has_call = 1; 708 if( _next ) bits |= _next ->set_nest(depth ); 709 return bits; 710 } 711 712 //------------------------------split_fall_in---------------------------------- 713 // Split out multiple fall-in edges from the loop header. Move them to a 714 // private RegionNode before the loop. This becomes the loop landing pad. 715 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) { 716 PhaseIterGVN &igvn = phase->_igvn; 717 uint i; 718 719 // Make a new RegionNode to be the landing pad. 720 Node *landing_pad = new (phase->C, fall_in_cnt+1) RegionNode( fall_in_cnt+1 ); 721 phase->set_loop(landing_pad,_parent); 722 // Gather all the fall-in control paths into the landing pad 723 uint icnt = fall_in_cnt; 724 uint oreq = _head->req(); 725 for( i = oreq-1; i>0; i-- ) 726 if( !phase->is_member( this, _head->in(i) ) ) 727 landing_pad->set_req(icnt--,_head->in(i)); 728 729 // Peel off PhiNode edges as well 730 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 731 Node *oj = _head->fast_out(j); 732 if( oj->is_Phi() ) { 733 PhiNode* old_phi = oj->as_Phi(); 734 assert( old_phi->region() == _head, "" ); 735 igvn.hash_delete(old_phi); // Yank from hash before hacking edges 736 Node *p = PhiNode::make_blank(landing_pad, old_phi); 737 uint icnt = fall_in_cnt; 738 for( i = oreq-1; i>0; i-- ) { 739 if( !phase->is_member( this, _head->in(i) ) ) { 740 p->init_req(icnt--, old_phi->in(i)); 741 // Go ahead and clean out old edges from old phi 742 old_phi->del_req(i); 743 } 744 } 745 // Search for CSE's here, because ZKM.jar does a lot of 746 // loop hackery and we need to be a little incremental 747 // with the CSE to avoid O(N^2) node blow-up. 748 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE 749 if( p2 ) { // Found CSE 750 p->destruct(); // Recover useless new node 751 p = p2; // Use old node 752 } else { 753 igvn.register_new_node_with_optimizer(p, old_phi); 754 } 755 // Make old Phi refer to new Phi. 756 old_phi->add_req(p); 757 // Check for the special case of making the old phi useless and 758 // disappear it. In JavaGrande I have a case where this useless 759 // Phi is the loop limit and prevents recognizing a CountedLoop 760 // which in turn prevents removing an empty loop. 761 Node *id_old_phi = old_phi->Identity( &igvn ); 762 if( id_old_phi != old_phi ) { // Found a simple identity? 763 // Note that I cannot call 'subsume_node' here, because 764 // that will yank the edge from old_phi to the Region and 765 // I'm mid-iteration over the Region's uses. 766 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) { 767 Node* use = old_phi->last_out(i); 768 igvn.hash_delete(use); 769 igvn._worklist.push(use); 770 uint uses_found = 0; 771 for (uint j = 0; j < use->len(); j++) { 772 if (use->in(j) == old_phi) { 773 if (j < use->req()) use->set_req (j, id_old_phi); 774 else use->set_prec(j, id_old_phi); 775 uses_found++; 776 } 777 } 778 i -= uses_found; // we deleted 1 or more copies of this edge 779 } 780 } 781 igvn._worklist.push(old_phi); 782 } 783 } 784 // Finally clean out the fall-in edges from the RegionNode 785 for( i = oreq-1; i>0; i-- ) { 786 if( !phase->is_member( this, _head->in(i) ) ) { 787 _head->del_req(i); 788 } 789 } 790 // Transform landing pad 791 igvn.register_new_node_with_optimizer(landing_pad, _head); 792 // Insert landing pad into the header 793 _head->add_req(landing_pad); 794 } 795 796 //------------------------------split_outer_loop------------------------------- 797 // Split out the outermost loop from this shared header. 798 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) { 799 PhaseIterGVN &igvn = phase->_igvn; 800 801 // Find index of outermost loop; it should also be my tail. 802 uint outer_idx = 1; 803 while( _head->in(outer_idx) != _tail ) outer_idx++; 804 805 // Make a LoopNode for the outermost loop. 806 Node *ctl = _head->in(LoopNode::EntryControl); 807 Node *outer = new (phase->C, 3) LoopNode( ctl, _head->in(outer_idx) ); 808 outer = igvn.register_new_node_with_optimizer(outer, _head); 809 phase->set_created_loop_node(); 810 // Outermost loop falls into '_head' loop 811 _head->set_req(LoopNode::EntryControl, outer); 812 _head->del_req(outer_idx); 813 // Split all the Phis up between '_head' loop and 'outer' loop. 814 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 815 Node *out = _head->fast_out(j); 816 if( out->is_Phi() ) { 817 PhiNode *old_phi = out->as_Phi(); 818 assert( old_phi->region() == _head, "" ); 819 Node *phi = PhiNode::make_blank(outer, old_phi); 820 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl)); 821 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx)); 822 phi = igvn.register_new_node_with_optimizer(phi, old_phi); 823 // Make old Phi point to new Phi on the fall-in path 824 igvn.hash_delete(old_phi); 825 old_phi->set_req(LoopNode::EntryControl, phi); 826 old_phi->del_req(outer_idx); 827 igvn._worklist.push(old_phi); 828 } 829 } 830 831 // Use the new loop head instead of the old shared one 832 _head = outer; 833 phase->set_loop(_head, this); 834 } 835 836 //------------------------------fix_parent------------------------------------- 837 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) { 838 loop->_parent = parent; 839 if( loop->_child ) fix_parent( loop->_child, loop ); 840 if( loop->_next ) fix_parent( loop->_next , parent ); 841 } 842 843 //------------------------------estimate_path_freq----------------------------- 844 static float estimate_path_freq( Node *n ) { 845 // Try to extract some path frequency info 846 IfNode *iff; 847 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests 848 uint nop = n->Opcode(); 849 if( nop == Op_SafePoint ) { // Skip any safepoint 850 n = n->in(0); 851 continue; 852 } 853 if( nop == Op_CatchProj ) { // Get count from a prior call 854 // Assume call does not always throw exceptions: means the call-site 855 // count is also the frequency of the fall-through path. 856 assert( n->is_CatchProj(), "" ); 857 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index ) 858 return 0.0f; // Assume call exception path is rare 859 Node *call = n->in(0)->in(0)->in(0); 860 assert( call->is_Call(), "expect a call here" ); 861 const JVMState *jvms = ((CallNode*)call)->jvms(); 862 ciMethodData* methodData = jvms->method()->method_data(); 863 if (!methodData->is_mature()) return 0.0f; // No call-site data 864 ciProfileData* data = methodData->bci_to_data(jvms->bci()); 865 if ((data == NULL) || !data->is_CounterData()) { 866 // no call profile available, try call's control input 867 n = n->in(0); 868 continue; 869 } 870 return data->as_CounterData()->count()/FreqCountInvocations; 871 } 872 // See if there's a gating IF test 873 Node *n_c = n->in(0); 874 if( !n_c->is_If() ) break; // No estimate available 875 iff = n_c->as_If(); 876 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count? 877 // Compute how much count comes on this path 878 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt; 879 // Have no count info. Skip dull uncommon-trap like branches. 880 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) || 881 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) ) 882 break; 883 // Skip through never-taken branch; look for a real loop exit. 884 n = iff->in(0); 885 } 886 return 0.0f; // No estimate available 887 } 888 889 //------------------------------merge_many_backedges--------------------------- 890 // Merge all the backedges from the shared header into a private Region. 891 // Feed that region as the one backedge to this loop. 892 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) { 893 uint i; 894 895 // Scan for the top 2 hottest backedges 896 float hotcnt = 0.0f; 897 float warmcnt = 0.0f; 898 uint hot_idx = 0; 899 // Loop starts at 2 because slot 1 is the fall-in path 900 for( i = 2; i < _head->req(); i++ ) { 901 float cnt = estimate_path_freq(_head->in(i)); 902 if( cnt > hotcnt ) { // Grab hottest path 903 warmcnt = hotcnt; 904 hotcnt = cnt; 905 hot_idx = i; 906 } else if( cnt > warmcnt ) { // And 2nd hottest path 907 warmcnt = cnt; 908 } 909 } 910 911 // See if the hottest backedge is worthy of being an inner loop 912 // by being much hotter than the next hottest backedge. 913 if( hotcnt <= 0.0001 || 914 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge 915 916 // Peel out the backedges into a private merge point; peel 917 // them all except optionally hot_idx. 918 PhaseIterGVN &igvn = phase->_igvn; 919 920 Node *hot_tail = NULL; 921 // Make a Region for the merge point 922 Node *r = new (phase->C, 1) RegionNode(1); 923 for( i = 2; i < _head->req(); i++ ) { 924 if( i != hot_idx ) 925 r->add_req( _head->in(i) ); 926 else hot_tail = _head->in(i); 927 } 928 igvn.register_new_node_with_optimizer(r, _head); 929 // Plug region into end of loop _head, followed by hot_tail 930 while( _head->req() > 3 ) _head->del_req( _head->req()-1 ); 931 _head->set_req(2, r); 932 if( hot_idx ) _head->add_req(hot_tail); 933 934 // Split all the Phis up between '_head' loop and the Region 'r' 935 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { 936 Node *out = _head->fast_out(j); 937 if( out->is_Phi() ) { 938 PhiNode* n = out->as_Phi(); 939 igvn.hash_delete(n); // Delete from hash before hacking edges 940 Node *hot_phi = NULL; 941 Node *phi = new (phase->C, r->req()) PhiNode(r, n->type(), n->adr_type()); 942 // Check all inputs for the ones to peel out 943 uint j = 1; 944 for( uint i = 2; i < n->req(); i++ ) { 945 if( i != hot_idx ) 946 phi->set_req( j++, n->in(i) ); 947 else hot_phi = n->in(i); 948 } 949 // Register the phi but do not transform until whole place transforms 950 igvn.register_new_node_with_optimizer(phi, n); 951 // Add the merge phi to the old Phi 952 while( n->req() > 3 ) n->del_req( n->req()-1 ); 953 n->set_req(2, phi); 954 if( hot_idx ) n->add_req(hot_phi); 955 } 956 } 957 958 959 // Insert a new IdealLoopTree inserted below me. Turn it into a clone 960 // of self loop tree. Turn self into a loop headed by _head and with 961 // tail being the new merge point. 962 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail ); 963 phase->set_loop(_tail,ilt); // Adjust tail 964 _tail = r; // Self's tail is new merge point 965 phase->set_loop(r,this); 966 ilt->_child = _child; // New guy has my children 967 _child = ilt; // Self has new guy as only child 968 ilt->_parent = this; // new guy has self for parent 969 ilt->_nest = _nest; // Same nesting depth (for now) 970 971 // Starting with 'ilt', look for child loop trees using the same shared 972 // header. Flatten these out; they will no longer be loops in the end. 973 IdealLoopTree **pilt = &_child; 974 while( ilt ) { 975 if( ilt->_head == _head ) { 976 uint i; 977 for( i = 2; i < _head->req(); i++ ) 978 if( _head->in(i) == ilt->_tail ) 979 break; // Still a loop 980 if( i == _head->req() ) { // No longer a loop 981 // Flatten ilt. Hang ilt's "_next" list from the end of 982 // ilt's '_child' list. Move the ilt's _child up to replace ilt. 983 IdealLoopTree **cp = &ilt->_child; 984 while( *cp ) cp = &(*cp)->_next; // Find end of child list 985 *cp = ilt->_next; // Hang next list at end of child list 986 *pilt = ilt->_child; // Move child up to replace ilt 987 ilt->_head = NULL; // Flag as a loop UNIONED into parent 988 ilt = ilt->_child; // Repeat using new ilt 989 continue; // do not advance over ilt->_child 990 } 991 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" ); 992 phase->set_loop(_head,ilt); 993 } 994 pilt = &ilt->_child; // Advance to next 995 ilt = *pilt; 996 } 997 998 if( _child ) fix_parent( _child, this ); 999 } 1000 1001 //------------------------------beautify_loops--------------------------------- 1002 // Split shared headers and insert loop landing pads. 1003 // Insert a LoopNode to replace the RegionNode. 1004 // Return TRUE if loop tree is structurally changed. 1005 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) { 1006 bool result = false; 1007 // Cache parts in locals for easy 1008 PhaseIterGVN &igvn = phase->_igvn; 1009 1010 phase->C->print_method("Before beautify loops", 3); 1011 1012 igvn.hash_delete(_head); // Yank from hash before hacking edges 1013 1014 // Check for multiple fall-in paths. Peel off a landing pad if need be. 1015 int fall_in_cnt = 0; 1016 for( uint i = 1; i < _head->req(); i++ ) 1017 if( !phase->is_member( this, _head->in(i) ) ) 1018 fall_in_cnt++; 1019 assert( fall_in_cnt, "at least 1 fall-in path" ); 1020 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins 1021 split_fall_in( phase, fall_in_cnt ); 1022 1023 // Swap inputs to the _head and all Phis to move the fall-in edge to 1024 // the left. 1025 fall_in_cnt = 1; 1026 while( phase->is_member( this, _head->in(fall_in_cnt) ) ) 1027 fall_in_cnt++; 1028 if( fall_in_cnt > 1 ) { 1029 // Since I am just swapping inputs I do not need to update def-use info 1030 Node *tmp = _head->in(1); 1031 _head->set_req( 1, _head->in(fall_in_cnt) ); 1032 _head->set_req( fall_in_cnt, tmp ); 1033 // Swap also all Phis 1034 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) { 1035 Node* phi = _head->fast_out(i); 1036 if( phi->is_Phi() ) { 1037 igvn.hash_delete(phi); // Yank from hash before hacking edges 1038 tmp = phi->in(1); 1039 phi->set_req( 1, phi->in(fall_in_cnt) ); 1040 phi->set_req( fall_in_cnt, tmp ); 1041 } 1042 } 1043 } 1044 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" ); 1045 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" ); 1046 1047 // If I am a shared header (multiple backedges), peel off the many 1048 // backedges into a private merge point and use the merge point as 1049 // the one true backedge. 1050 if( _head->req() > 3 ) { 1051 // Merge the many backedges into a single backedge. 1052 merge_many_backedges( phase ); 1053 result = true; 1054 } 1055 1056 // If I am a shared header (multiple backedges), peel off myself loop. 1057 // I better be the outermost loop. 1058 if( _head->req() > 3 ) { 1059 split_outer_loop( phase ); 1060 result = true; 1061 1062 } else if( !_head->is_Loop() && !_irreducible ) { 1063 // Make a new LoopNode to replace the old loop head 1064 Node *l = new (phase->C, 3) LoopNode( _head->in(1), _head->in(2) ); 1065 l = igvn.register_new_node_with_optimizer(l, _head); 1066 phase->set_created_loop_node(); 1067 // Go ahead and replace _head 1068 phase->_igvn.subsume_node( _head, l ); 1069 _head = l; 1070 phase->set_loop(_head, this); 1071 for (DUIterator_Fast imax, i = l->fast_outs(imax); i < imax; i++) 1072 phase->_igvn.add_users_to_worklist(l->fast_out(i)); 1073 } 1074 1075 // Now recursively beautify nested loops 1076 if( _child ) result |= _child->beautify_loops( phase ); 1077 if( _next ) result |= _next ->beautify_loops( phase ); 1078 return result; 1079 } 1080 1081 //------------------------------allpaths_check_safepts---------------------------- 1082 // Allpaths backwards scan from loop tail, terminating each path at first safepoint 1083 // encountered. Helper for check_safepts. 1084 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) { 1085 assert(stack.size() == 0, "empty stack"); 1086 stack.push(_tail); 1087 visited.Clear(); 1088 visited.set(_tail->_idx); 1089 while (stack.size() > 0) { 1090 Node* n = stack.pop(); 1091 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 1092 // Terminate this path 1093 } else if (n->Opcode() == Op_SafePoint) { 1094 if (_phase->get_loop(n) != this) { 1095 if (_required_safept == NULL) _required_safept = new Node_List(); 1096 _required_safept->push(n); // save the one closest to the tail 1097 } 1098 // Terminate this path 1099 } else { 1100 uint start = n->is_Region() ? 1 : 0; 1101 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1; 1102 for (uint i = start; i < end; i++) { 1103 Node* in = n->in(i); 1104 assert(in->is_CFG(), "must be"); 1105 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) { 1106 stack.push(in); 1107 } 1108 } 1109 } 1110 } 1111 } 1112 1113 //------------------------------check_safepts---------------------------- 1114 // Given dominators, try to find loops with calls that must always be 1115 // executed (call dominates loop tail). These loops do not need non-call 1116 // safepoints (ncsfpt). 1117 // 1118 // A complication is that a safepoint in a inner loop may be needed 1119 // by an outer loop. In the following, the inner loop sees it has a 1120 // call (block 3) on every path from the head (block 2) to the 1121 // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint) 1122 // in block 2, _but_ this leaves the outer loop without a safepoint. 1123 // 1124 // entry 0 1125 // | 1126 // v 1127 // outer 1,2 +->1 1128 // | | 1129 // | v 1130 // | 2<---+ ncsfpt in 2 1131 // |_/|\ | 1132 // | v | 1133 // inner 2,3 / 3 | call in 3 1134 // / | | 1135 // v +--+ 1136 // exit 4 1137 // 1138 // 1139 // This method creates a list (_required_safept) of ncsfpt nodes that must 1140 // be protected is created for each loop. When a ncsfpt maybe deleted, it 1141 // is first looked for in the lists for the outer loops of the current loop. 1142 // 1143 // The insights into the problem: 1144 // A) counted loops are okay 1145 // B) innermost loops are okay (only an inner loop can delete 1146 // a ncsfpt needed by an outer loop) 1147 // C) a loop is immune from an inner loop deleting a safepoint 1148 // if the loop has a call on the idom-path 1149 // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the 1150 // idom-path that is not in a nested loop 1151 // E) otherwise, an ncsfpt on the idom-path that is nested in an inner 1152 // loop needs to be prevented from deletion by an inner loop 1153 // 1154 // There are two analyses: 1155 // 1) The first, and cheaper one, scans the loop body from 1156 // tail to head following the idom (immediate dominator) 1157 // chain, looking for the cases (C,D,E) above. 1158 // Since inner loops are scanned before outer loops, there is summary 1159 // information about inner loops. Inner loops can be skipped over 1160 // when the tail of an inner loop is encountered. 1161 // 1162 // 2) The second, invoked if the first fails to find a call or ncsfpt on 1163 // the idom path (which is rare), scans all predecessor control paths 1164 // from the tail to the head, terminating a path when a call or sfpt 1165 // is encountered, to find the ncsfpt's that are closest to the tail. 1166 // 1167 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) { 1168 // Bottom up traversal 1169 IdealLoopTree* ch = _child; 1170 while (ch != NULL) { 1171 ch->check_safepts(visited, stack); 1172 ch = ch->_next; 1173 } 1174 1175 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) { 1176 bool has_call = false; // call on dom-path 1177 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth 1178 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth 1179 // Scan the dom-path nodes from tail to head 1180 for (Node* n = tail(); n != _head; n = _phase->idom(n)) { 1181 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { 1182 has_call = true; 1183 _has_sfpt = 1; // Then no need for a safept! 1184 break; 1185 } else if (n->Opcode() == Op_SafePoint) { 1186 if (_phase->get_loop(n) == this) { 1187 has_local_ncsfpt = true; 1188 break; 1189 } 1190 if (nonlocal_ncsfpt == NULL) { 1191 nonlocal_ncsfpt = n; // save the one closest to the tail 1192 } 1193 } else { 1194 IdealLoopTree* nlpt = _phase->get_loop(n); 1195 if (this != nlpt) { 1196 // If at an inner loop tail, see if the inner loop has already 1197 // recorded seeing a call on the dom-path (and stop.) If not, 1198 // jump to the head of the inner loop. 1199 assert(is_member(nlpt), "nested loop"); 1200 Node* tail = nlpt->_tail; 1201 if (tail->in(0)->is_If()) tail = tail->in(0); 1202 if (n == tail) { 1203 // If inner loop has call on dom-path, so does outer loop 1204 if (nlpt->_has_sfpt) { 1205 has_call = true; 1206 _has_sfpt = 1; 1207 break; 1208 } 1209 // Skip to head of inner loop 1210 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head"); 1211 n = nlpt->_head; 1212 } 1213 } 1214 } 1215 } 1216 // Record safept's that this loop needs preserved when an 1217 // inner loop attempts to delete it's safepoints. 1218 if (_child != NULL && !has_call && !has_local_ncsfpt) { 1219 if (nonlocal_ncsfpt != NULL) { 1220 if (_required_safept == NULL) _required_safept = new Node_List(); 1221 _required_safept->push(nonlocal_ncsfpt); 1222 } else { 1223 // Failed to find a suitable safept on the dom-path. Now use 1224 // an all paths walk from tail to head, looking for safepoints to preserve. 1225 allpaths_check_safepts(visited, stack); 1226 } 1227 } 1228 } 1229 } 1230 1231 //---------------------------is_deleteable_safept---------------------------- 1232 // Is safept not required by an outer loop? 1233 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) { 1234 assert(sfpt->Opcode() == Op_SafePoint, ""); 1235 IdealLoopTree* lp = get_loop(sfpt)->_parent; 1236 while (lp != NULL) { 1237 Node_List* sfpts = lp->_required_safept; 1238 if (sfpts != NULL) { 1239 for (uint i = 0; i < sfpts->size(); i++) { 1240 if (sfpt == sfpts->at(i)) 1241 return false; 1242 } 1243 } 1244 lp = lp->_parent; 1245 } 1246 return true; 1247 } 1248 1249 //------------------------------counted_loop----------------------------------- 1250 // Convert to counted loops where possible 1251 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) { 1252 1253 // For grins, set the inner-loop flag here 1254 if( !_child ) { 1255 if( _head->is_Loop() ) _head->as_Loop()->set_inner_loop(); 1256 } 1257 1258 if( _head->is_CountedLoop() || 1259 phase->is_counted_loop( _head, this ) ) { 1260 _has_sfpt = 1; // Indicate we do not need a safepoint here 1261 1262 // Look for a safepoint to remove 1263 for (Node* n = tail(); n != _head; n = phase->idom(n)) 1264 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && 1265 phase->is_deleteable_safept(n)) 1266 phase->lazy_replace(n,n->in(TypeFunc::Control)); 1267 1268 CountedLoopNode *cl = _head->as_CountedLoop(); 1269 Node *incr = cl->incr(); 1270 if( !incr ) return; // Dead loop? 1271 Node *init = cl->init_trip(); 1272 Node *phi = cl->phi(); 1273 // protect against stride not being a constant 1274 if( !cl->stride_is_con() ) return; 1275 int stride_con = cl->stride_con(); 1276 1277 // Look for induction variables 1278 1279 // Visit all children, looking for Phis 1280 for (DUIterator i = cl->outs(); cl->has_out(i); i++) { 1281 Node *out = cl->out(i); 1282 if (!out->is_Phi() || out == phi) continue; // Looking for other phis 1283 PhiNode* phi2 = out->as_Phi(); 1284 Node *incr2 = phi2->in( LoopNode::LoopBackControl ); 1285 // Look for induction variables of the form: X += constant 1286 if( phi2->region() != _head || 1287 incr2->req() != 3 || 1288 incr2->in(1) != phi2 || 1289 incr2 == incr || 1290 incr2->Opcode() != Op_AddI || 1291 !incr2->in(2)->is_Con() ) 1292 continue; 1293 1294 // Check for parallel induction variable (parallel to trip counter) 1295 // via an affine function. In particular, count-down loops with 1296 // count-up array indices are common. We only RCE references off 1297 // the trip-counter, so we need to convert all these to trip-counter 1298 // expressions. 1299 Node *init2 = phi2->in( LoopNode::EntryControl ); 1300 int stride_con2 = incr2->in(2)->get_int(); 1301 1302 // The general case here gets a little tricky. We want to find the 1303 // GCD of all possible parallel IV's and make a new IV using this 1304 // GCD for the loop. Then all possible IVs are simple multiples of 1305 // the GCD. In practice, this will cover very few extra loops. 1306 // Instead we require 'stride_con2' to be a multiple of 'stride_con', 1307 // where +/-1 is the common case, but other integer multiples are 1308 // also easy to handle. 1309 int ratio_con = stride_con2/stride_con; 1310 1311 if( ratio_con * stride_con == stride_con2 ) { // Check for exact 1312 // Convert to using the trip counter. The parallel induction 1313 // variable differs from the trip counter by a loop-invariant 1314 // amount, the difference between their respective initial values. 1315 // It is scaled by the 'ratio_con'. 1316 Compile* C = phase->C; 1317 Node* ratio = phase->_igvn.intcon(ratio_con); 1318 phase->set_ctrl(ratio, C->root()); 1319 Node* ratio_init = new (C, 3) MulINode(init, ratio); 1320 phase->_igvn.register_new_node_with_optimizer(ratio_init, init); 1321 phase->set_early_ctrl(ratio_init); 1322 Node* diff = new (C, 3) SubINode(init2, ratio_init); 1323 phase->_igvn.register_new_node_with_optimizer(diff, init2); 1324 phase->set_early_ctrl(diff); 1325 Node* ratio_idx = new (C, 3) MulINode(phi, ratio); 1326 phase->_igvn.register_new_node_with_optimizer(ratio_idx, phi); 1327 phase->set_ctrl(ratio_idx, cl); 1328 Node* add = new (C, 3) AddINode(ratio_idx, diff); 1329 phase->_igvn.register_new_node_with_optimizer(add); 1330 phase->set_ctrl(add, cl); 1331 phase->_igvn.hash_delete( phi2 ); 1332 phase->_igvn.subsume_node( phi2, add ); 1333 // Sometimes an induction variable is unused 1334 if (add->outcnt() == 0) { 1335 phase->_igvn.remove_dead_node(add); 1336 } 1337 --i; // deleted this phi; rescan starting with next position 1338 continue; 1339 } 1340 } 1341 } else if (_parent != NULL && !_irreducible) { 1342 // Not a counted loop. 1343 // Look for a safepoint on the idom-path to remove, preserving the first one 1344 bool found = false; 1345 Node* n = tail(); 1346 for (; n != _head && !found; n = phase->idom(n)) { 1347 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this) 1348 found = true; // Found one 1349 } 1350 // Skip past it and delete the others 1351 for (; n != _head; n = phase->idom(n)) { 1352 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && 1353 phase->is_deleteable_safept(n)) 1354 phase->lazy_replace(n,n->in(TypeFunc::Control)); 1355 } 1356 } 1357 1358 // Recursively 1359 if( _child ) _child->counted_loop( phase ); 1360 if( _next ) _next ->counted_loop( phase ); 1361 } 1362 1363 #ifndef PRODUCT 1364 //------------------------------dump_head-------------------------------------- 1365 // Dump 1 liner for loop header info 1366 void IdealLoopTree::dump_head( ) const { 1367 for( uint i=0; i<_nest; i++ ) 1368 tty->print(" "); 1369 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx); 1370 if( _irreducible ) tty->print(" IRREDUCIBLE"); 1371 if( _head->is_CountedLoop() ) { 1372 CountedLoopNode *cl = _head->as_CountedLoop(); 1373 tty->print(" counted"); 1374 if( cl->is_pre_loop () ) tty->print(" pre" ); 1375 if( cl->is_main_loop() ) tty->print(" main"); 1376 if( cl->is_post_loop() ) tty->print(" post"); 1377 } 1378 tty->cr(); 1379 } 1380 1381 //------------------------------dump------------------------------------------- 1382 // Dump loops by loop tree 1383 void IdealLoopTree::dump( ) const { 1384 dump_head(); 1385 if( _child ) _child->dump(); 1386 if( _next ) _next ->dump(); 1387 } 1388 1389 #endif 1390 1391 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) { 1392 if (loop == root) { 1393 if (loop->_child != NULL) { 1394 log->begin_head("loop_tree"); 1395 log->end_head(); 1396 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1397 log->tail("loop_tree"); 1398 assert(loop->_next == NULL, "what?"); 1399 } 1400 } else { 1401 Node* head = loop->_head; 1402 log->begin_head("loop"); 1403 log->print(" idx='%d' ", head->_idx); 1404 if (loop->_irreducible) log->print("irreducible='1' "); 1405 if (head->is_Loop()) { 1406 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' "); 1407 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' "); 1408 } 1409 if (head->is_CountedLoop()) { 1410 CountedLoopNode* cl = head->as_CountedLoop(); 1411 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx()); 1412 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx); 1413 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx()); 1414 } 1415 log->end_head(); 1416 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1417 log->tail("loop"); 1418 if( loop->_next ) log_loop_tree(root, loop->_next, log); 1419 } 1420 } 1421 1422 //============================================================================= 1423 //------------------------------PhaseIdealLoop--------------------------------- 1424 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to 1425 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups. 1426 PhaseIdealLoop::PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me, bool do_split_ifs ) 1427 : PhaseTransform(Ideal_Loop), 1428 _igvn(igvn), 1429 _dom_lca_tags(C->comp_arena()) { 1430 // Reset major-progress flag for the driver's heuristics 1431 C->clear_major_progress(); 1432 1433 #ifndef PRODUCT 1434 // Capture for later assert 1435 uint unique = C->unique(); 1436 _loop_invokes++; 1437 _loop_work += unique; 1438 #endif 1439 1440 // True if the method has at least 1 irreducible loop 1441 _has_irreducible_loops = false; 1442 1443 _created_loop_node = false; 1444 1445 Arena *a = Thread::current()->resource_area(); 1446 VectorSet visited(a); 1447 // Pre-grow the mapping from Nodes to IdealLoopTrees. 1448 _nodes.map(C->unique(), NULL); 1449 memset(_nodes.adr(), 0, wordSize * C->unique()); 1450 1451 // Pre-build the top-level outermost loop tree entry 1452 _ltree_root = new IdealLoopTree( this, C->root(), C->root() ); 1453 // Do not need a safepoint at the top level 1454 _ltree_root->_has_sfpt = 1; 1455 1456 // Empty pre-order array 1457 allocate_preorders(); 1458 1459 // Build a loop tree on the fly. Build a mapping from CFG nodes to 1460 // IdealLoopTree entries. Data nodes are NOT walked. 1461 build_loop_tree(); 1462 // Check for bailout, and return 1463 if (C->failing()) { 1464 return; 1465 } 1466 1467 // No loops after all 1468 if( !_ltree_root->_child ) C->set_has_loops(false); 1469 1470 // There should always be an outer loop containing the Root and Return nodes. 1471 // If not, we have a degenerate empty program. Bail out in this case. 1472 if (!has_node(C->root())) { 1473 C->clear_major_progress(); 1474 C->record_method_not_compilable("empty program detected during loop optimization"); 1475 return; 1476 } 1477 1478 // Nothing to do, so get out 1479 if( !C->has_loops() && !do_split_ifs && !verify_me) { 1480 _igvn.optimize(); // Cleanup NeverBranches 1481 return; 1482 } 1483 1484 // Set loop nesting depth 1485 _ltree_root->set_nest( 0 ); 1486 1487 // Split shared headers and insert loop landing pads. 1488 // Do not bother doing this on the Root loop of course. 1489 if( !verify_me && _ltree_root->_child ) { 1490 if( _ltree_root->_child->beautify_loops( this ) ) { 1491 // Re-build loop tree! 1492 _ltree_root->_child = NULL; 1493 _nodes.clear(); 1494 reallocate_preorders(); 1495 build_loop_tree(); 1496 // Check for bailout, and return 1497 if (C->failing()) { 1498 return; 1499 } 1500 // Reset loop nesting depth 1501 _ltree_root->set_nest( 0 ); 1502 1503 C->print_method("After beautify loops", 3); 1504 } 1505 } 1506 1507 // Build Dominators for elision of NULL checks & loop finding. 1508 // Since nodes do not have a slot for immediate dominator, make 1509 // a persistent side array for that info indexed on node->_idx. 1510 _idom_size = C->unique(); 1511 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size ); 1512 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size ); 1513 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth 1514 memset( _dom_depth, 0, _idom_size * sizeof(uint) ); 1515 1516 Dominators(); 1517 1518 // As a side effect, Dominators removed any unreachable CFG paths 1519 // into RegionNodes. It doesn't do this test against Root, so 1520 // we do it here. 1521 for( uint i = 1; i < C->root()->req(); i++ ) { 1522 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root? 1523 _igvn.hash_delete(C->root()); 1524 C->root()->del_req(i); 1525 _igvn._worklist.push(C->root()); 1526 i--; // Rerun same iteration on compressed edges 1527 } 1528 } 1529 1530 // Given dominators, try to find inner loops with calls that must 1531 // always be executed (call dominates loop tail). These loops do 1532 // not need a separate safepoint. 1533 Node_List cisstack(a); 1534 _ltree_root->check_safepts(visited, cisstack); 1535 1536 // Walk the DATA nodes and place into loops. Find earliest control 1537 // node. For CFG nodes, the _nodes array starts out and remains 1538 // holding the associated IdealLoopTree pointer. For DATA nodes, the 1539 // _nodes array holds the earliest legal controlling CFG node. 1540 1541 // Allocate stack with enough space to avoid frequent realloc 1542 int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats 1543 Node_Stack nstack( a, stack_size ); 1544 1545 visited.Clear(); 1546 Node_List worklist(a); 1547 // Don't need C->root() on worklist since 1548 // it will be processed among C->top() inputs 1549 worklist.push( C->top() ); 1550 visited.set( C->top()->_idx ); // Set C->top() as visited now 1551 build_loop_early( visited, worklist, nstack, verify_me ); 1552 1553 // Given early legal placement, try finding counted loops. This placement 1554 // is good enough to discover most loop invariants. 1555 if( !verify_me ) 1556 _ltree_root->counted_loop( this ); 1557 1558 // Find latest loop placement. Find ideal loop placement. 1559 visited.Clear(); 1560 init_dom_lca_tags(); 1561 // Need C->root() on worklist when processing outs 1562 worklist.push( C->root() ); 1563 NOT_PRODUCT( C->verify_graph_edges(); ) 1564 worklist.push( C->top() ); 1565 build_loop_late( visited, worklist, nstack, verify_me ); 1566 1567 // clear out the dead code 1568 while(_deadlist.size()) { 1569 igvn.remove_globally_dead_node(_deadlist.pop()); 1570 } 1571 1572 #ifndef PRODUCT 1573 C->verify_graph_edges(); 1574 if( verify_me ) { // Nested verify pass? 1575 // Check to see if the verify mode is broken 1576 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?"); 1577 return; 1578 } 1579 if( VerifyLoopOptimizations ) verify(); 1580 #endif 1581 1582 if (ReassociateInvariants) { 1583 // Reassociate invariants and prep for split_thru_phi 1584 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 1585 IdealLoopTree* lpt = iter.current(); 1586 if (!lpt->is_counted() || !lpt->is_inner()) continue; 1587 1588 lpt->reassociate_invariants(this); 1589 1590 // Because RCE opportunities can be masked by split_thru_phi, 1591 // look for RCE candidates and inhibit split_thru_phi 1592 // on just their loop-phi's for this pass of loop opts 1593 if( SplitIfBlocks && do_split_ifs ) { 1594 if (lpt->policy_range_check(this)) { 1595 lpt->_rce_candidate = 1; // = true 1596 } 1597 } 1598 } 1599 } 1600 1601 // Check for aggressive application of split-if and other transforms 1602 // that require basic-block info (like cloning through Phi's) 1603 if( SplitIfBlocks && do_split_ifs ) { 1604 visited.Clear(); 1605 split_if_with_blocks( visited, nstack ); 1606 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); ); 1607 } 1608 1609 // Perform iteration-splitting on inner loops. Split iterations to avoid 1610 // range checks or one-shot null checks. 1611 1612 // If split-if's didn't hack the graph too bad (no CFG changes) 1613 // then do loop opts. 1614 if( C->has_loops() && !C->major_progress() ) { 1615 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) ); 1616 _ltree_root->_child->iteration_split( this, worklist ); 1617 // No verify after peeling! GCM has hoisted code out of the loop. 1618 // After peeling, the hoisted code could sink inside the peeled area. 1619 // The peeling code does not try to recompute the best location for 1620 // all the code before the peeled area, so the verify pass will always 1621 // complain about it. 1622 } 1623 // Do verify graph edges in any case 1624 NOT_PRODUCT( C->verify_graph_edges(); ); 1625 1626 if( !do_split_ifs ) { 1627 // We saw major progress in Split-If to get here. We forced a 1628 // pass with unrolling and not split-if, however more split-if's 1629 // might make progress. If the unrolling didn't make progress 1630 // then the major-progress flag got cleared and we won't try 1631 // another round of Split-If. In particular the ever-common 1632 // instance-of/check-cast pattern requires at least 2 rounds of 1633 // Split-If to clear out. 1634 C->set_major_progress(); 1635 } 1636 1637 // Repeat loop optimizations if new loops were seen 1638 if (created_loop_node()) { 1639 C->set_major_progress(); 1640 } 1641 1642 // Convert scalar to superword operations 1643 1644 if (UseSuperWord && C->has_loops() && !C->major_progress()) { 1645 // SuperWord transform 1646 SuperWord sw(this); 1647 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 1648 IdealLoopTree* lpt = iter.current(); 1649 if (lpt->is_counted()) { 1650 sw.transform_loop(lpt); 1651 } 1652 } 1653 } 1654 1655 // Cleanup any modified bits 1656 _igvn.optimize(); 1657 1658 // disable assert until issue with split_flow_path is resolved (6742111) 1659 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(), 1660 // "shouldn't introduce irreducible loops"); 1661 1662 if (C->log() != NULL) { 1663 log_loop_tree(_ltree_root, _ltree_root, C->log()); 1664 } 1665 } 1666 1667 #ifndef PRODUCT 1668 //------------------------------print_statistics------------------------------- 1669 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes 1670 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique 1671 void PhaseIdealLoop::print_statistics() { 1672 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work); 1673 } 1674 1675 //------------------------------verify----------------------------------------- 1676 // Build a verify-only PhaseIdealLoop, and see that it agrees with me. 1677 static int fail; // debug only, so its multi-thread dont care 1678 void PhaseIdealLoop::verify() const { 1679 int old_progress = C->major_progress(); 1680 ResourceMark rm; 1681 PhaseIdealLoop loop_verify( _igvn, this, false ); 1682 VectorSet visited(Thread::current()->resource_area()); 1683 1684 fail = 0; 1685 verify_compare( C->root(), &loop_verify, visited ); 1686 assert( fail == 0, "verify loops failed" ); 1687 // Verify loop structure is the same 1688 _ltree_root->verify_tree(loop_verify._ltree_root, NULL); 1689 // Reset major-progress. It was cleared by creating a verify version of 1690 // PhaseIdealLoop. 1691 for( int i=0; i<old_progress; i++ ) 1692 C->set_major_progress(); 1693 } 1694 1695 //------------------------------verify_compare--------------------------------- 1696 // Make sure me and the given PhaseIdealLoop agree on key data structures 1697 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const { 1698 if( !n ) return; 1699 if( visited.test_set( n->_idx ) ) return; 1700 if( !_nodes[n->_idx] ) { // Unreachable 1701 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" ); 1702 return; 1703 } 1704 1705 uint i; 1706 for( i = 0; i < n->req(); i++ ) 1707 verify_compare( n->in(i), loop_verify, visited ); 1708 1709 // Check the '_nodes' block/loop structure 1710 i = n->_idx; 1711 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl 1712 if( _nodes[i] != loop_verify->_nodes[i] && 1713 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) { 1714 tty->print("Mismatched control setting for: "); 1715 n->dump(); 1716 if( fail++ > 10 ) return; 1717 Node *c = get_ctrl_no_update(n); 1718 tty->print("We have it as: "); 1719 if( c->in(0) ) c->dump(); 1720 else tty->print_cr("N%d",c->_idx); 1721 tty->print("Verify thinks: "); 1722 if( loop_verify->has_ctrl(n) ) 1723 loop_verify->get_ctrl_no_update(n)->dump(); 1724 else 1725 loop_verify->get_loop_idx(n)->dump(); 1726 tty->cr(); 1727 } 1728 } else { // We have a loop 1729 IdealLoopTree *us = get_loop_idx(n); 1730 if( loop_verify->has_ctrl(n) ) { 1731 tty->print("Mismatched loop setting for: "); 1732 n->dump(); 1733 if( fail++ > 10 ) return; 1734 tty->print("We have it as: "); 1735 us->dump(); 1736 tty->print("Verify thinks: "); 1737 loop_verify->get_ctrl_no_update(n)->dump(); 1738 tty->cr(); 1739 } else if (!C->major_progress()) { 1740 // Loop selection can be messed up if we did a major progress 1741 // operation, like split-if. Do not verify in that case. 1742 IdealLoopTree *them = loop_verify->get_loop_idx(n); 1743 if( us->_head != them->_head || us->_tail != them->_tail ) { 1744 tty->print("Unequals loops for: "); 1745 n->dump(); 1746 if( fail++ > 10 ) return; 1747 tty->print("We have it as: "); 1748 us->dump(); 1749 tty->print("Verify thinks: "); 1750 them->dump(); 1751 tty->cr(); 1752 } 1753 } 1754 } 1755 1756 // Check for immediate dominators being equal 1757 if( i >= _idom_size ) { 1758 if( !n->is_CFG() ) return; 1759 tty->print("CFG Node with no idom: "); 1760 n->dump(); 1761 return; 1762 } 1763 if( !n->is_CFG() ) return; 1764 if( n == C->root() ) return; // No IDOM here 1765 1766 assert(n->_idx == i, "sanity"); 1767 Node *id = idom_no_update(n); 1768 if( id != loop_verify->idom_no_update(n) ) { 1769 tty->print("Unequals idoms for: "); 1770 n->dump(); 1771 if( fail++ > 10 ) return; 1772 tty->print("We have it as: "); 1773 id->dump(); 1774 tty->print("Verify thinks: "); 1775 loop_verify->idom_no_update(n)->dump(); 1776 tty->cr(); 1777 } 1778 1779 } 1780 1781 //------------------------------verify_tree------------------------------------ 1782 // Verify that tree structures match. Because the CFG can change, siblings 1783 // within the loop tree can be reordered. We attempt to deal with that by 1784 // reordering the verify's loop tree if possible. 1785 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const { 1786 assert( _parent == parent, "Badly formed loop tree" ); 1787 1788 // Siblings not in same order? Attempt to re-order. 1789 if( _head != loop->_head ) { 1790 // Find _next pointer to update 1791 IdealLoopTree **pp = &loop->_parent->_child; 1792 while( *pp != loop ) 1793 pp = &((*pp)->_next); 1794 // Find proper sibling to be next 1795 IdealLoopTree **nn = &loop->_next; 1796 while( (*nn) && (*nn)->_head != _head ) 1797 nn = &((*nn)->_next); 1798 1799 // Check for no match. 1800 if( !(*nn) ) { 1801 // Annoyingly, irreducible loops can pick different headers 1802 // after a major_progress operation, so the rest of the loop 1803 // tree cannot be matched. 1804 if (_irreducible && Compile::current()->major_progress()) return; 1805 assert( 0, "failed to match loop tree" ); 1806 } 1807 1808 // Move (*nn) to (*pp) 1809 IdealLoopTree *hit = *nn; 1810 *nn = hit->_next; 1811 hit->_next = loop; 1812 *pp = loop; 1813 loop = hit; 1814 // Now try again to verify 1815 } 1816 1817 assert( _head == loop->_head , "mismatched loop head" ); 1818 Node *tail = _tail; // Inline a non-updating version of 1819 while( !tail->in(0) ) // the 'tail()' call. 1820 tail = tail->in(1); 1821 assert( tail == loop->_tail, "mismatched loop tail" ); 1822 1823 // Counted loops that are guarded should be able to find their guards 1824 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) { 1825 CountedLoopNode *cl = _head->as_CountedLoop(); 1826 Node *init = cl->init_trip(); 1827 Node *ctrl = cl->in(LoopNode::EntryControl); 1828 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 1829 Node *iff = ctrl->in(0); 1830 assert( iff->Opcode() == Op_If, "" ); 1831 Node *bol = iff->in(1); 1832 assert( bol->Opcode() == Op_Bool, "" ); 1833 Node *cmp = bol->in(1); 1834 assert( cmp->Opcode() == Op_CmpI, "" ); 1835 Node *add = cmp->in(1); 1836 Node *opaq; 1837 if( add->Opcode() == Op_Opaque1 ) { 1838 opaq = add; 1839 } else { 1840 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" ); 1841 assert( add == init, "" ); 1842 opaq = cmp->in(2); 1843 } 1844 assert( opaq->Opcode() == Op_Opaque1, "" ); 1845 1846 } 1847 1848 if (_child != NULL) _child->verify_tree(loop->_child, this); 1849 if (_next != NULL) _next ->verify_tree(loop->_next, parent); 1850 // Innermost loops need to verify loop bodies, 1851 // but only if no 'major_progress' 1852 int fail = 0; 1853 if (!Compile::current()->major_progress() && _child == NULL) { 1854 for( uint i = 0; i < _body.size(); i++ ) { 1855 Node *n = _body.at(i); 1856 if (n->outcnt() == 0) continue; // Ignore dead 1857 uint j; 1858 for( j = 0; j < loop->_body.size(); j++ ) 1859 if( loop->_body.at(j) == n ) 1860 break; 1861 if( j == loop->_body.size() ) { // Not found in loop body 1862 // Last ditch effort to avoid assertion: Its possible that we 1863 // have some users (so outcnt not zero) but are still dead. 1864 // Try to find from root. 1865 if (Compile::current()->root()->find(n->_idx)) { 1866 fail++; 1867 tty->print("We have that verify does not: "); 1868 n->dump(); 1869 } 1870 } 1871 } 1872 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) { 1873 Node *n = loop->_body.at(i2); 1874 if (n->outcnt() == 0) continue; // Ignore dead 1875 uint j; 1876 for( j = 0; j < _body.size(); j++ ) 1877 if( _body.at(j) == n ) 1878 break; 1879 if( j == _body.size() ) { // Not found in loop body 1880 // Last ditch effort to avoid assertion: Its possible that we 1881 // have some users (so outcnt not zero) but are still dead. 1882 // Try to find from root. 1883 if (Compile::current()->root()->find(n->_idx)) { 1884 fail++; 1885 tty->print("Verify has that we do not: "); 1886 n->dump(); 1887 } 1888 } 1889 } 1890 assert( !fail, "loop body mismatch" ); 1891 } 1892 } 1893 1894 #endif 1895 1896 //------------------------------set_idom--------------------------------------- 1897 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) { 1898 uint idx = d->_idx; 1899 if (idx >= _idom_size) { 1900 uint newsize = _idom_size<<1; 1901 while( idx >= newsize ) { 1902 newsize <<= 1; 1903 } 1904 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize); 1905 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize); 1906 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) ); 1907 _idom_size = newsize; 1908 } 1909 _idom[idx] = n; 1910 _dom_depth[idx] = dom_depth; 1911 } 1912 1913 //------------------------------recompute_dom_depth--------------------------------------- 1914 // The dominator tree is constructed with only parent pointers. 1915 // This recomputes the depth in the tree by first tagging all 1916 // nodes as "no depth yet" marker. The next pass then runs up 1917 // the dom tree from each node marked "no depth yet", and computes 1918 // the depth on the way back down. 1919 void PhaseIdealLoop::recompute_dom_depth() { 1920 uint no_depth_marker = C->unique(); 1921 uint i; 1922 // Initialize depth to "no depth yet" 1923 for (i = 0; i < _idom_size; i++) { 1924 if (_dom_depth[i] > 0 && _idom[i] != NULL) { 1925 _dom_depth[i] = no_depth_marker; 1926 } 1927 } 1928 if (_dom_stk == NULL) { 1929 uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size. 1930 if (init_size < 10) init_size = 10; 1931 _dom_stk = new (C->node_arena()) GrowableArray<uint>(C->node_arena(), init_size, 0, 0); 1932 } 1933 // Compute new depth for each node. 1934 for (i = 0; i < _idom_size; i++) { 1935 uint j = i; 1936 // Run up the dom tree to find a node with a depth 1937 while (_dom_depth[j] == no_depth_marker) { 1938 _dom_stk->push(j); 1939 j = _idom[j]->_idx; 1940 } 1941 // Compute the depth on the way back down this tree branch 1942 uint dd = _dom_depth[j] + 1; 1943 while (_dom_stk->length() > 0) { 1944 uint j = _dom_stk->pop(); 1945 _dom_depth[j] = dd; 1946 dd++; 1947 } 1948 } 1949 } 1950 1951 //------------------------------sort------------------------------------------- 1952 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the 1953 // loop tree, not the root. 1954 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) { 1955 if( !innermost ) return loop; // New innermost loop 1956 1957 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number 1958 assert( loop_preorder, "not yet post-walked loop" ); 1959 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer 1960 IdealLoopTree *l = *pp; // Do I go before or after 'l'? 1961 1962 // Insert at start of list 1963 while( l ) { // Insertion sort based on pre-order 1964 if( l == loop ) return innermost; // Already on list! 1965 int l_preorder = get_preorder(l->_head); // Cache pre-order number 1966 assert( l_preorder, "not yet post-walked l" ); 1967 // Check header pre-order number to figure proper nesting 1968 if( loop_preorder > l_preorder ) 1969 break; // End of insertion 1970 // If headers tie (e.g., shared headers) check tail pre-order numbers. 1971 // Since I split shared headers, you'd think this could not happen. 1972 // BUT: I must first do the preorder numbering before I can discover I 1973 // have shared headers, so the split headers all get the same preorder 1974 // number as the RegionNode they split from. 1975 if( loop_preorder == l_preorder && 1976 get_preorder(loop->_tail) < get_preorder(l->_tail) ) 1977 break; // Also check for shared headers (same pre#) 1978 pp = &l->_parent; // Chain up list 1979 l = *pp; 1980 } 1981 // Link into list 1982 // Point predecessor to me 1983 *pp = loop; 1984 // Point me to successor 1985 IdealLoopTree *p = loop->_parent; 1986 loop->_parent = l; // Point me to successor 1987 if( p ) sort( p, innermost ); // Insert my parents into list as well 1988 return innermost; 1989 } 1990 1991 //------------------------------build_loop_tree-------------------------------- 1992 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit 1993 // bits. The _nodes[] array is mapped by Node index and holds a NULL for 1994 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the 1995 // tightest enclosing IdealLoopTree for post-walked. 1996 // 1997 // During my forward walk I do a short 1-layer lookahead to see if I can find 1998 // a loop backedge with that doesn't have any work on the backedge. This 1999 // helps me construct nested loops with shared headers better. 2000 // 2001 // Once I've done the forward recursion, I do the post-work. For each child 2002 // I check to see if there is a backedge. Backedges define a loop! I 2003 // insert an IdealLoopTree at the target of the backedge. 2004 // 2005 // During the post-work I also check to see if I have several children 2006 // belonging to different loops. If so, then this Node is a decision point 2007 // where control flow can choose to change loop nests. It is at this 2008 // decision point where I can figure out how loops are nested. At this 2009 // time I can properly order the different loop nests from my children. 2010 // Note that there may not be any backedges at the decision point! 2011 // 2012 // Since the decision point can be far removed from the backedges, I can't 2013 // order my loops at the time I discover them. Thus at the decision point 2014 // I need to inspect loop header pre-order numbers to properly nest my 2015 // loops. This means I need to sort my childrens' loops by pre-order. 2016 // The sort is of size number-of-control-children, which generally limits 2017 // it to size 2 (i.e., I just choose between my 2 target loops). 2018 void PhaseIdealLoop::build_loop_tree() { 2019 // Allocate stack of size C->unique()/2 to avoid frequent realloc 2020 GrowableArray <Node *> bltstack(C->unique() >> 1); 2021 Node *n = C->root(); 2022 bltstack.push(n); 2023 int pre_order = 1; 2024 int stack_size; 2025 2026 while ( ( stack_size = bltstack.length() ) != 0 ) { 2027 n = bltstack.top(); // Leave node on stack 2028 if ( !is_visited(n) ) { 2029 // ---- Pre-pass Work ---- 2030 // Pre-walked but not post-walked nodes need a pre_order number. 2031 2032 set_preorder_visited( n, pre_order ); // set as visited 2033 2034 // ---- Scan over children ---- 2035 // Scan first over control projections that lead to loop headers. 2036 // This helps us find inner-to-outer loops with shared headers better. 2037 2038 // Scan children's children for loop headers. 2039 for ( int i = n->outcnt() - 1; i >= 0; --i ) { 2040 Node* m = n->raw_out(i); // Child 2041 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children 2042 // Scan over children's children to find loop 2043 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2044 Node* l = m->fast_out(j); 2045 if( is_visited(l) && // Been visited? 2046 !is_postvisited(l) && // But not post-visited 2047 get_preorder(l) < pre_order ) { // And smaller pre-order 2048 // Found! Scan the DFS down this path before doing other paths 2049 bltstack.push(m); 2050 break; 2051 } 2052 } 2053 } 2054 } 2055 pre_order++; 2056 } 2057 else if ( !is_postvisited(n) ) { 2058 // Note: build_loop_tree_impl() adds out edges on rare occasions, 2059 // such as com.sun.rsasign.am::a. 2060 // For non-recursive version, first, process current children. 2061 // On next iteration, check if additional children were added. 2062 for ( int k = n->outcnt() - 1; k >= 0; --k ) { 2063 Node* u = n->raw_out(k); 2064 if ( u->is_CFG() && !is_visited(u) ) { 2065 bltstack.push(u); 2066 } 2067 } 2068 if ( bltstack.length() == stack_size ) { 2069 // There were no additional children, post visit node now 2070 (void)bltstack.pop(); // Remove node from stack 2071 pre_order = build_loop_tree_impl( n, pre_order ); 2072 // Check for bailout 2073 if (C->failing()) { 2074 return; 2075 } 2076 // Check to grow _preorders[] array for the case when 2077 // build_loop_tree_impl() adds new nodes. 2078 check_grow_preorders(); 2079 } 2080 } 2081 else { 2082 (void)bltstack.pop(); // Remove post-visited node from stack 2083 } 2084 } 2085 } 2086 2087 //------------------------------build_loop_tree_impl--------------------------- 2088 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) { 2089 // ---- Post-pass Work ---- 2090 // Pre-walked but not post-walked nodes need a pre_order number. 2091 2092 // Tightest enclosing loop for this Node 2093 IdealLoopTree *innermost = NULL; 2094 2095 // For all children, see if any edge is a backedge. If so, make a loop 2096 // for it. Then find the tightest enclosing loop for the self Node. 2097 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 2098 Node* m = n->fast_out(i); // Child 2099 if( n == m ) continue; // Ignore control self-cycles 2100 if( !m->is_CFG() ) continue;// Ignore non-CFG edges 2101 2102 IdealLoopTree *l; // Child's loop 2103 if( !is_postvisited(m) ) { // Child visited but not post-visited? 2104 // Found a backedge 2105 assert( get_preorder(m) < pre_order, "should be backedge" ); 2106 // Check for the RootNode, which is already a LoopNode and is allowed 2107 // to have multiple "backedges". 2108 if( m == C->root()) { // Found the root? 2109 l = _ltree_root; // Root is the outermost LoopNode 2110 } else { // Else found a nested loop 2111 // Insert a LoopNode to mark this loop. 2112 l = new IdealLoopTree(this, m, n); 2113 } // End of Else found a nested loop 2114 if( !has_loop(m) ) // If 'm' does not already have a loop set 2115 set_loop(m, l); // Set loop header to loop now 2116 2117 } else { // Else not a nested loop 2118 if( !_nodes[m->_idx] ) continue; // Dead code has no loop 2119 l = get_loop(m); // Get previously determined loop 2120 // If successor is header of a loop (nest), move up-loop till it 2121 // is a member of some outer enclosing loop. Since there are no 2122 // shared headers (I've split them already) I only need to go up 2123 // at most 1 level. 2124 while( l && l->_head == m ) // Successor heads loop? 2125 l = l->_parent; // Move up 1 for me 2126 // If this loop is not properly parented, then this loop 2127 // has no exit path out, i.e. its an infinite loop. 2128 if( !l ) { 2129 // Make loop "reachable" from root so the CFG is reachable. Basically 2130 // insert a bogus loop exit that is never taken. 'm', the loop head, 2131 // points to 'n', one (of possibly many) fall-in paths. There may be 2132 // many backedges as well. 2133 2134 // Here I set the loop to be the root loop. I could have, after 2135 // inserting a bogus loop exit, restarted the recursion and found my 2136 // new loop exit. This would make the infinite loop a first-class 2137 // loop and it would then get properly optimized. What's the use of 2138 // optimizing an infinite loop? 2139 l = _ltree_root; // Oops, found infinite loop 2140 2141 // Insert the NeverBranch between 'm' and it's control user. 2142 NeverBranchNode *iff = new (C, 1) NeverBranchNode( m ); 2143 _igvn.register_new_node_with_optimizer(iff); 2144 set_loop(iff, l); 2145 Node *if_t = new (C, 1) CProjNode( iff, 0 ); 2146 _igvn.register_new_node_with_optimizer(if_t); 2147 set_loop(if_t, l); 2148 2149 Node* cfg = NULL; // Find the One True Control User of m 2150 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2151 Node* x = m->fast_out(j); 2152 if (x->is_CFG() && x != m && x != iff) 2153 { cfg = x; break; } 2154 } 2155 assert(cfg != NULL, "must find the control user of m"); 2156 uint k = 0; // Probably cfg->in(0) 2157 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region 2158 cfg->set_req( k, if_t ); // Now point to NeverBranch 2159 2160 // Now create the never-taken loop exit 2161 Node *if_f = new (C, 1) CProjNode( iff, 1 ); 2162 _igvn.register_new_node_with_optimizer(if_f); 2163 set_loop(if_f, l); 2164 // Find frame ptr for Halt. Relies on the optimizer 2165 // V-N'ing. Easier and quicker than searching through 2166 // the program structure. 2167 Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr ); 2168 _igvn.register_new_node_with_optimizer(frame); 2169 // Halt & Catch Fire 2170 Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame ); 2171 _igvn.register_new_node_with_optimizer(halt); 2172 set_loop(halt, l); 2173 C->root()->add_req(halt); 2174 set_loop(C->root(), _ltree_root); 2175 } 2176 } 2177 // Weeny check for irreducible. This child was already visited (this 2178 // IS the post-work phase). Is this child's loop header post-visited 2179 // as well? If so, then I found another entry into the loop. 2180 while( is_postvisited(l->_head) ) { 2181 // found irreducible 2182 l->_irreducible = 1; // = true 2183 l = l->_parent; 2184 _has_irreducible_loops = true; 2185 // Check for bad CFG here to prevent crash, and bailout of compile 2186 if (l == NULL) { 2187 C->record_method_not_compilable("unhandled CFG detected during loop optimization"); 2188 return pre_order; 2189 } 2190 } 2191 2192 // This Node might be a decision point for loops. It is only if 2193 // it's children belong to several different loops. The sort call 2194 // does a trivial amount of work if there is only 1 child or all 2195 // children belong to the same loop. If however, the children 2196 // belong to different loops, the sort call will properly set the 2197 // _parent pointers to show how the loops nest. 2198 // 2199 // In any case, it returns the tightest enclosing loop. 2200 innermost = sort( l, innermost ); 2201 } 2202 2203 // Def-use info will have some dead stuff; dead stuff will have no 2204 // loop decided on. 2205 2206 // Am I a loop header? If so fix up my parent's child and next ptrs. 2207 if( innermost && innermost->_head == n ) { 2208 assert( get_loop(n) == innermost, "" ); 2209 IdealLoopTree *p = innermost->_parent; 2210 IdealLoopTree *l = innermost; 2211 while( p && l->_head == n ) { 2212 l->_next = p->_child; // Put self on parents 'next child' 2213 p->_child = l; // Make self as first child of parent 2214 l = p; // Now walk up the parent chain 2215 p = l->_parent; 2216 } 2217 } else { 2218 // Note that it is possible for a LoopNode to reach here, if the 2219 // backedge has been made unreachable (hence the LoopNode no longer 2220 // denotes a Loop, and will eventually be removed). 2221 2222 // Record tightest enclosing loop for self. Mark as post-visited. 2223 set_loop(n, innermost); 2224 // Also record has_call flag early on 2225 if( innermost ) { 2226 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) { 2227 // Do not count uncommon calls 2228 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) { 2229 Node *iff = n->in(0)->in(0); 2230 if( !iff->is_If() || 2231 (n->in(0)->Opcode() == Op_IfFalse && 2232 (1.0 - iff->as_If()->_prob) >= 0.01) || 2233 (iff->as_If()->_prob >= 0.01) ) 2234 innermost->_has_call = 1; 2235 } 2236 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) { 2237 // Disable loop optimizations if the loop has a scalar replaceable 2238 // allocation. This disabling may cause a potential performance lost 2239 // if the allocation is not eliminated for some reason. 2240 innermost->_allow_optimizations = false; 2241 innermost->_has_call = 1; // = true 2242 } 2243 } 2244 } 2245 2246 // Flag as post-visited now 2247 set_postvisited(n); 2248 return pre_order; 2249 } 2250 2251 2252 //------------------------------build_loop_early------------------------------- 2253 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2254 // First pass computes the earliest controlling node possible. This is the 2255 // controlling input with the deepest dominating depth. 2256 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ) { 2257 while (worklist.size() != 0) { 2258 // Use local variables nstack_top_n & nstack_top_i to cache values 2259 // on nstack's top. 2260 Node *nstack_top_n = worklist.pop(); 2261 uint nstack_top_i = 0; 2262 //while_nstack_nonempty: 2263 while (true) { 2264 // Get parent node and next input's index from stack's top. 2265 Node *n = nstack_top_n; 2266 uint i = nstack_top_i; 2267 uint cnt = n->req(); // Count of inputs 2268 if (i == 0) { // Pre-process the node. 2269 if( has_node(n) && // Have either loop or control already? 2270 !has_ctrl(n) ) { // Have loop picked out already? 2271 // During "merge_many_backedges" we fold up several nested loops 2272 // into a single loop. This makes the members of the original 2273 // loop bodies pointing to dead loops; they need to move up 2274 // to the new UNION'd larger loop. I set the _head field of these 2275 // dead loops to NULL and the _parent field points to the owning 2276 // loop. Shades of UNION-FIND algorithm. 2277 IdealLoopTree *ilt; 2278 while( !(ilt = get_loop(n))->_head ) { 2279 // Normally I would use a set_loop here. But in this one special 2280 // case, it is legal (and expected) to change what loop a Node 2281 // belongs to. 2282 _nodes.map(n->_idx, (Node*)(ilt->_parent) ); 2283 } 2284 // Remove safepoints ONLY if I've already seen I don't need one. 2285 // (the old code here would yank a 2nd safepoint after seeing a 2286 // first one, even though the 1st did not dominate in the loop body 2287 // and thus could be avoided indefinitely) 2288 if( !verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint && 2289 is_deleteable_safept(n)) { 2290 Node *in = n->in(TypeFunc::Control); 2291 lazy_replace(n,in); // Pull safepoint now 2292 // Carry on with the recursion "as if" we are walking 2293 // only the control input 2294 if( !visited.test_set( in->_idx ) ) { 2295 worklist.push(in); // Visit this guy later, using worklist 2296 } 2297 // Get next node from nstack: 2298 // - skip n's inputs processing by setting i > cnt; 2299 // - we also will not call set_early_ctrl(n) since 2300 // has_node(n) == true (see the condition above). 2301 i = cnt + 1; 2302 } 2303 } 2304 } // if (i == 0) 2305 2306 // Visit all inputs 2307 bool done = true; // Assume all n's inputs will be processed 2308 while (i < cnt) { 2309 Node *in = n->in(i); 2310 ++i; 2311 if (in == NULL) continue; 2312 if (in->pinned() && !in->is_CFG()) 2313 set_ctrl(in, in->in(0)); 2314 int is_visited = visited.test_set( in->_idx ); 2315 if (!has_node(in)) { // No controlling input yet? 2316 assert( !in->is_CFG(), "CFG Node with no controlling input?" ); 2317 assert( !is_visited, "visit only once" ); 2318 nstack.push(n, i); // Save parent node and next input's index. 2319 nstack_top_n = in; // Process current input now. 2320 nstack_top_i = 0; 2321 done = false; // Not all n's inputs processed. 2322 break; // continue while_nstack_nonempty; 2323 } else if (!is_visited) { 2324 // This guy has a location picked out for him, but has not yet 2325 // been visited. Happens to all CFG nodes, for instance. 2326 // Visit him using the worklist instead of recursion, to break 2327 // cycles. Since he has a location already we do not need to 2328 // find his location before proceeding with the current Node. 2329 worklist.push(in); // Visit this guy later, using worklist 2330 } 2331 } 2332 if (done) { 2333 // All of n's inputs have been processed, complete post-processing. 2334 2335 // Compute earliest point this Node can go. 2336 // CFG, Phi, pinned nodes already know their controlling input. 2337 if (!has_node(n)) { 2338 // Record earliest legal location 2339 set_early_ctrl( n ); 2340 } 2341 if (nstack.is_empty()) { 2342 // Finished all nodes on stack. 2343 // Process next node on the worklist. 2344 break; 2345 } 2346 // Get saved parent node and next input's index. 2347 nstack_top_n = nstack.node(); 2348 nstack_top_i = nstack.index(); 2349 nstack.pop(); 2350 } 2351 } // while (true) 2352 } 2353 } 2354 2355 //------------------------------dom_lca_internal-------------------------------- 2356 // Pair-wise LCA 2357 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const { 2358 if( !n1 ) return n2; // Handle NULL original LCA 2359 assert( n1->is_CFG(), "" ); 2360 assert( n2->is_CFG(), "" ); 2361 // find LCA of all uses 2362 uint d1 = dom_depth(n1); 2363 uint d2 = dom_depth(n2); 2364 while (n1 != n2) { 2365 if (d1 > d2) { 2366 n1 = idom(n1); 2367 d1 = dom_depth(n1); 2368 } else if (d1 < d2) { 2369 n2 = idom(n2); 2370 d2 = dom_depth(n2); 2371 } else { 2372 // Here d1 == d2. Due to edits of the dominator-tree, sections 2373 // of the tree might have the same depth. These sections have 2374 // to be searched more carefully. 2375 2376 // Scan up all the n1's with equal depth, looking for n2. 2377 Node *t1 = idom(n1); 2378 while (dom_depth(t1) == d1) { 2379 if (t1 == n2) return n2; 2380 t1 = idom(t1); 2381 } 2382 // Scan up all the n2's with equal depth, looking for n1. 2383 Node *t2 = idom(n2); 2384 while (dom_depth(t2) == d2) { 2385 if (t2 == n1) return n1; 2386 t2 = idom(t2); 2387 } 2388 // Move up to a new dominator-depth value as well as up the dom-tree. 2389 n1 = t1; 2390 n2 = t2; 2391 d1 = dom_depth(n1); 2392 d2 = dom_depth(n2); 2393 } 2394 } 2395 return n1; 2396 } 2397 2398 //------------------------------compute_idom----------------------------------- 2399 // Locally compute IDOM using dom_lca call. Correct only if the incoming 2400 // IDOMs are correct. 2401 Node *PhaseIdealLoop::compute_idom( Node *region ) const { 2402 assert( region->is_Region(), "" ); 2403 Node *LCA = NULL; 2404 for( uint i = 1; i < region->req(); i++ ) { 2405 if( region->in(i) != C->top() ) 2406 LCA = dom_lca( LCA, region->in(i) ); 2407 } 2408 return LCA; 2409 } 2410 2411 //------------------------------get_late_ctrl---------------------------------- 2412 // Compute latest legal control. 2413 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) { 2414 assert(early != NULL, "early control should not be NULL"); 2415 2416 // Compute LCA over list of uses 2417 Node *LCA = NULL; 2418 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) { 2419 Node* c = n->fast_out(i); 2420 if (_nodes[c->_idx] == NULL) 2421 continue; // Skip the occasional dead node 2422 if( c->is_Phi() ) { // For Phis, we must land above on the path 2423 for( uint j=1; j<c->req(); j++ ) {// For all inputs 2424 if( c->in(j) == n ) { // Found matching input? 2425 Node *use = c->in(0)->in(j); 2426 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2427 } 2428 } 2429 } else { 2430 // For CFG data-users, use is in the block just prior 2431 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0); 2432 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2433 } 2434 } 2435 2436 // if this is a load, check for anti-dependent stores 2437 // We use a conservative algorithm to identify potential interfering 2438 // instructions and for rescheduling the load. The users of the memory 2439 // input of this load are examined. Any use which is not a load and is 2440 // dominated by early is considered a potentially interfering store. 2441 // This can produce false positives. 2442 if (n->is_Load() && LCA != early) { 2443 Node_List worklist; 2444 2445 Node *mem = n->in(MemNode::Memory); 2446 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { 2447 Node* s = mem->fast_out(i); 2448 worklist.push(s); 2449 } 2450 while(worklist.size() != 0 && LCA != early) { 2451 Node* s = worklist.pop(); 2452 if (s->is_Load()) { 2453 continue; 2454 } else if (s->is_MergeMem()) { 2455 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) { 2456 Node* s1 = s->fast_out(i); 2457 worklist.push(s1); 2458 } 2459 } else { 2460 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0); 2461 assert(sctrl != NULL || s->outcnt() == 0, "must have control"); 2462 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) { 2463 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n); 2464 } 2465 } 2466 } 2467 } 2468 2469 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control"); 2470 return LCA; 2471 } 2472 2473 // true if CFG node d dominates CFG node n 2474 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) { 2475 if (d == n) 2476 return true; 2477 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes"); 2478 uint dd = dom_depth(d); 2479 while (dom_depth(n) >= dd) { 2480 if (n == d) 2481 return true; 2482 n = idom(n); 2483 } 2484 return false; 2485 } 2486 2487 //------------------------------dom_lca_for_get_late_ctrl_internal------------- 2488 // Pair-wise LCA with tags. 2489 // Tag each index with the node 'tag' currently being processed 2490 // before advancing up the dominator chain using idom(). 2491 // Later calls that find a match to 'tag' know that this path has already 2492 // been considered in the current LCA (which is input 'n1' by convention). 2493 // Since get_late_ctrl() is only called once for each node, the tag array 2494 // does not need to be cleared between calls to get_late_ctrl(). 2495 // Algorithm trades a larger constant factor for better asymptotic behavior 2496 // 2497 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) { 2498 uint d1 = dom_depth(n1); 2499 uint d2 = dom_depth(n2); 2500 2501 do { 2502 if (d1 > d2) { 2503 // current lca is deeper than n2 2504 _dom_lca_tags.map(n1->_idx, tag); 2505 n1 = idom(n1); 2506 d1 = dom_depth(n1); 2507 } else if (d1 < d2) { 2508 // n2 is deeper than current lca 2509 Node *memo = _dom_lca_tags[n2->_idx]; 2510 if( memo == tag ) { 2511 return n1; // Return the current LCA 2512 } 2513 _dom_lca_tags.map(n2->_idx, tag); 2514 n2 = idom(n2); 2515 d2 = dom_depth(n2); 2516 } else { 2517 // Here d1 == d2. Due to edits of the dominator-tree, sections 2518 // of the tree might have the same depth. These sections have 2519 // to be searched more carefully. 2520 2521 // Scan up all the n1's with equal depth, looking for n2. 2522 _dom_lca_tags.map(n1->_idx, tag); 2523 Node *t1 = idom(n1); 2524 while (dom_depth(t1) == d1) { 2525 if (t1 == n2) return n2; 2526 _dom_lca_tags.map(t1->_idx, tag); 2527 t1 = idom(t1); 2528 } 2529 // Scan up all the n2's with equal depth, looking for n1. 2530 _dom_lca_tags.map(n2->_idx, tag); 2531 Node *t2 = idom(n2); 2532 while (dom_depth(t2) == d2) { 2533 if (t2 == n1) return n1; 2534 _dom_lca_tags.map(t2->_idx, tag); 2535 t2 = idom(t2); 2536 } 2537 // Move up to a new dominator-depth value as well as up the dom-tree. 2538 n1 = t1; 2539 n2 = t2; 2540 d1 = dom_depth(n1); 2541 d2 = dom_depth(n2); 2542 } 2543 } while (n1 != n2); 2544 return n1; 2545 } 2546 2547 //------------------------------init_dom_lca_tags------------------------------ 2548 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 2549 // Intended use does not involve any growth for the array, so it could 2550 // be of fixed size. 2551 void PhaseIdealLoop::init_dom_lca_tags() { 2552 uint limit = C->unique() + 1; 2553 _dom_lca_tags.map( limit, NULL ); 2554 #ifdef ASSERT 2555 for( uint i = 0; i < limit; ++i ) { 2556 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 2557 } 2558 #endif // ASSERT 2559 } 2560 2561 //------------------------------clear_dom_lca_tags------------------------------ 2562 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 2563 // Intended use does not involve any growth for the array, so it could 2564 // be of fixed size. 2565 void PhaseIdealLoop::clear_dom_lca_tags() { 2566 uint limit = C->unique() + 1; 2567 _dom_lca_tags.map( limit, NULL ); 2568 _dom_lca_tags.clear(); 2569 #ifdef ASSERT 2570 for( uint i = 0; i < limit; ++i ) { 2571 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 2572 } 2573 #endif // ASSERT 2574 } 2575 2576 //------------------------------build_loop_late-------------------------------- 2577 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2578 // Second pass finds latest legal placement, and ideal loop placement. 2579 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ) { 2580 while (worklist.size() != 0) { 2581 Node *n = worklist.pop(); 2582 // Only visit once 2583 if (visited.test_set(n->_idx)) continue; 2584 uint cnt = n->outcnt(); 2585 uint i = 0; 2586 while (true) { 2587 assert( _nodes[n->_idx], "no dead nodes" ); 2588 // Visit all children 2589 if (i < cnt) { 2590 Node* use = n->raw_out(i); 2591 ++i; 2592 // Check for dead uses. Aggressively prune such junk. It might be 2593 // dead in the global sense, but still have local uses so I cannot 2594 // easily call 'remove_dead_node'. 2595 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead? 2596 // Due to cycles, we might not hit the same fixed point in the verify 2597 // pass as we do in the regular pass. Instead, visit such phis as 2598 // simple uses of the loop head. 2599 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) { 2600 if( !visited.test(use->_idx) ) 2601 worklist.push(use); 2602 } else if( !visited.test_set(use->_idx) ) { 2603 nstack.push(n, i); // Save parent and next use's index. 2604 n = use; // Process all children of current use. 2605 cnt = use->outcnt(); 2606 i = 0; 2607 } 2608 } else { 2609 // Do not visit around the backedge of loops via data edges. 2610 // push dead code onto a worklist 2611 _deadlist.push(use); 2612 } 2613 } else { 2614 // All of n's children have been processed, complete post-processing. 2615 build_loop_late_post(n, verify_me); 2616 if (nstack.is_empty()) { 2617 // Finished all nodes on stack. 2618 // Process next node on the worklist. 2619 break; 2620 } 2621 // Get saved parent node and next use's index. Visit the rest of uses. 2622 n = nstack.node(); 2623 cnt = n->outcnt(); 2624 i = nstack.index(); 2625 nstack.pop(); 2626 } 2627 } 2628 } 2629 } 2630 2631 //------------------------------build_loop_late_post--------------------------- 2632 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2633 // Second pass finds latest legal placement, and ideal loop placement. 2634 void PhaseIdealLoop::build_loop_late_post( Node *n, const PhaseIdealLoop *verify_me ) { 2635 2636 if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress()) { 2637 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops. 2638 } 2639 2640 // CFG and pinned nodes already handled 2641 if( n->in(0) ) { 2642 if( n->in(0)->is_top() ) return; // Dead? 2643 2644 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads 2645 // _must_ be pinned (they have to observe their control edge of course). 2646 // Unlike Stores (which modify an unallocable resource, the memory 2647 // state), Mods/Loads can float around. So free them up. 2648 bool pinned = true; 2649 switch( n->Opcode() ) { 2650 case Op_DivI: 2651 case Op_DivF: 2652 case Op_DivD: 2653 case Op_ModI: 2654 case Op_ModF: 2655 case Op_ModD: 2656 case Op_LoadB: // Same with Loads; they can sink 2657 case Op_LoadUS: // during loop optimizations. 2658 case Op_LoadD: 2659 case Op_LoadF: 2660 case Op_LoadI: 2661 case Op_LoadKlass: 2662 case Op_LoadNKlass: 2663 case Op_LoadL: 2664 case Op_LoadS: 2665 case Op_LoadP: 2666 case Op_LoadN: 2667 case Op_LoadRange: 2668 case Op_LoadD_unaligned: 2669 case Op_LoadL_unaligned: 2670 case Op_StrComp: // Does a bunch of load-like effects 2671 case Op_StrEquals: 2672 case Op_StrIndexOf: 2673 case Op_AryEq: 2674 pinned = false; 2675 } 2676 if( pinned ) { 2677 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n)); 2678 if( !chosen_loop->_child ) // Inner loop? 2679 chosen_loop->_body.push(n); // Collect inner loops 2680 return; 2681 } 2682 } else { // No slot zero 2683 if( n->is_CFG() ) { // CFG with no slot 0 is dead 2684 _nodes.map(n->_idx,0); // No block setting, it's globally dead 2685 return; 2686 } 2687 assert(!n->is_CFG() || n->outcnt() == 0, ""); 2688 } 2689 2690 // Do I have a "safe range" I can select over? 2691 Node *early = get_ctrl(n);// Early location already computed 2692 2693 // Compute latest point this Node can go 2694 Node *LCA = get_late_ctrl( n, early ); 2695 // LCA is NULL due to uses being dead 2696 if( LCA == NULL ) { 2697 #ifdef ASSERT 2698 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) { 2699 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead"); 2700 } 2701 #endif 2702 _nodes.map(n->_idx, 0); // This node is useless 2703 _deadlist.push(n); 2704 return; 2705 } 2706 assert(LCA != NULL && !LCA->is_top(), "no dead nodes"); 2707 2708 Node *legal = LCA; // Walk 'legal' up the IDOM chain 2709 Node *least = legal; // Best legal position so far 2710 while( early != legal ) { // While not at earliest legal 2711 // Find least loop nesting depth 2712 legal = idom(legal); // Bump up the IDOM tree 2713 // Check for lower nesting depth 2714 if( get_loop(legal)->_nest < get_loop(least)->_nest ) 2715 least = legal; 2716 } 2717 2718 // Try not to place code on a loop entry projection 2719 // which can inhibit range check elimination. 2720 if (least != early) { 2721 Node* ctrl_out = least->unique_ctrl_out(); 2722 if (ctrl_out && ctrl_out->is_CountedLoop() && 2723 least == ctrl_out->in(LoopNode::EntryControl)) { 2724 Node* least_dom = idom(least); 2725 if (get_loop(least_dom)->is_member(get_loop(least))) { 2726 least = least_dom; 2727 } 2728 } 2729 } 2730 2731 #ifdef ASSERT 2732 // If verifying, verify that 'verify_me' has a legal location 2733 // and choose it as our location. 2734 if( verify_me ) { 2735 Node *v_ctrl = verify_me->get_ctrl_no_update(n); 2736 Node *legal = LCA; 2737 while( early != legal ) { // While not at earliest legal 2738 if( legal == v_ctrl ) break; // Check for prior good location 2739 legal = idom(legal) ;// Bump up the IDOM tree 2740 } 2741 // Check for prior good location 2742 if( legal == v_ctrl ) least = legal; // Keep prior if found 2743 } 2744 #endif 2745 2746 // Assign discovered "here or above" point 2747 least = find_non_split_ctrl(least); 2748 set_ctrl(n, least); 2749 2750 // Collect inner loop bodies 2751 IdealLoopTree *chosen_loop = get_loop(least); 2752 if( !chosen_loop->_child ) // Inner loop? 2753 chosen_loop->_body.push(n);// Collect inner loops 2754 } 2755 2756 #ifndef PRODUCT 2757 //------------------------------dump------------------------------------------- 2758 void PhaseIdealLoop::dump( ) const { 2759 ResourceMark rm; 2760 Arena* arena = Thread::current()->resource_area(); 2761 Node_Stack stack(arena, C->unique() >> 2); 2762 Node_List rpo_list; 2763 VectorSet visited(arena); 2764 visited.set(C->top()->_idx); 2765 rpo( C->root(), stack, visited, rpo_list ); 2766 // Dump root loop indexed by last element in PO order 2767 dump( _ltree_root, rpo_list.size(), rpo_list ); 2768 } 2769 2770 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const { 2771 loop->dump_head(); 2772 2773 // Now scan for CFG nodes in the same loop 2774 for( uint j=idx; j > 0; j-- ) { 2775 Node *n = rpo_list[j-1]; 2776 if( !_nodes[n->_idx] ) // Skip dead nodes 2777 continue; 2778 if( get_loop(n) != loop ) { // Wrong loop nest 2779 if( get_loop(n)->_head == n && // Found nested loop? 2780 get_loop(n)->_parent == loop ) 2781 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly 2782 continue; 2783 } 2784 2785 // Dump controlling node 2786 for( uint x = 0; x < loop->_nest; x++ ) 2787 tty->print(" "); 2788 tty->print("C"); 2789 if( n == C->root() ) { 2790 n->dump(); 2791 } else { 2792 Node* cached_idom = idom_no_update(n); 2793 Node *computed_idom = n->in(0); 2794 if( n->is_Region() ) { 2795 computed_idom = compute_idom(n); 2796 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or 2797 // any MultiBranch ctrl node), so apply a similar transform to 2798 // the cached idom returned from idom_no_update. 2799 cached_idom = find_non_split_ctrl(cached_idom); 2800 } 2801 tty->print(" ID:%d",computed_idom->_idx); 2802 n->dump(); 2803 if( cached_idom != computed_idom ) { 2804 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d", 2805 computed_idom->_idx, cached_idom->_idx); 2806 } 2807 } 2808 // Dump nodes it controls 2809 for( uint k = 0; k < _nodes.Size(); k++ ) { 2810 // (k < C->unique() && get_ctrl(find(k)) == n) 2811 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) { 2812 Node *m = C->root()->find(k); 2813 if( m && m->outcnt() > 0 ) { 2814 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) { 2815 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p", 2816 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL); 2817 } 2818 for( uint j = 0; j < loop->_nest; j++ ) 2819 tty->print(" "); 2820 tty->print(" "); 2821 m->dump(); 2822 } 2823 } 2824 } 2825 } 2826 } 2827 2828 // Collect a R-P-O for the whole CFG. 2829 // Result list is in post-order (scan backwards for RPO) 2830 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const { 2831 stk.push(start, 0); 2832 visited.set(start->_idx); 2833 2834 while (stk.is_nonempty()) { 2835 Node* m = stk.node(); 2836 uint idx = stk.index(); 2837 if (idx < m->outcnt()) { 2838 stk.set_index(idx + 1); 2839 Node* n = m->raw_out(idx); 2840 if (n->is_CFG() && !visited.test_set(n->_idx)) { 2841 stk.push(n, 0); 2842 } 2843 } else { 2844 rpo_list.push(m); 2845 stk.pop(); 2846 } 2847 } 2848 } 2849 #endif 2850 2851 2852 //============================================================================= 2853 //------------------------------LoopTreeIterator----------------------------------- 2854 2855 // Advance to next loop tree using a preorder, left-to-right traversal. 2856 void LoopTreeIterator::next() { 2857 assert(!done(), "must not be done."); 2858 if (_curnt->_child != NULL) { 2859 _curnt = _curnt->_child; 2860 } else if (_curnt->_next != NULL) { 2861 _curnt = _curnt->_next; 2862 } else { 2863 while (_curnt != _root && _curnt->_next == NULL) { 2864 _curnt = _curnt->_parent; 2865 } 2866 if (_curnt == _root) { 2867 _curnt = NULL; 2868 assert(done(), "must be done."); 2869 } else { 2870 assert(_curnt->_next != NULL, "must be more to do"); 2871 _curnt = _curnt->_next; 2872 } 2873 } 2874 }