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 // Look for other phis (secondary IVs). Skip dead ones 1283 if (!out->is_Phi() || out == phi || !phase->has_node(out)) continue; 1284 PhiNode* phi2 = out->as_Phi(); 1285 Node *incr2 = phi2->in( LoopNode::LoopBackControl ); 1286 // Look for induction variables of the form: X += constant 1287 if( phi2->region() != _head || 1288 incr2->req() != 3 || 1289 incr2->in(1) != phi2 || 1290 incr2 == incr || 1291 incr2->Opcode() != Op_AddI || 1292 !incr2->in(2)->is_Con() ) 1293 continue; 1294 1295 // Check for parallel induction variable (parallel to trip counter) 1296 // via an affine function. In particular, count-down loops with 1297 // count-up array indices are common. We only RCE references off 1298 // the trip-counter, so we need to convert all these to trip-counter 1299 // expressions. 1300 Node *init2 = phi2->in( LoopNode::EntryControl ); 1301 int stride_con2 = incr2->in(2)->get_int(); 1302 1303 // The general case here gets a little tricky. We want to find the 1304 // GCD of all possible parallel IV's and make a new IV using this 1305 // GCD for the loop. Then all possible IVs are simple multiples of 1306 // the GCD. In practice, this will cover very few extra loops. 1307 // Instead we require 'stride_con2' to be a multiple of 'stride_con', 1308 // where +/-1 is the common case, but other integer multiples are 1309 // also easy to handle. 1310 int ratio_con = stride_con2/stride_con; 1311 1312 if( ratio_con * stride_con == stride_con2 ) { // Check for exact 1313 // Convert to using the trip counter. The parallel induction 1314 // variable differs from the trip counter by a loop-invariant 1315 // amount, the difference between their respective initial values. 1316 // It is scaled by the 'ratio_con'. 1317 Compile* C = phase->C; 1318 Node* ratio = phase->_igvn.intcon(ratio_con); 1319 phase->set_ctrl(ratio, C->root()); 1320 Node* ratio_init = new (C, 3) MulINode(init, ratio); 1321 phase->_igvn.register_new_node_with_optimizer(ratio_init, init); 1322 phase->set_early_ctrl(ratio_init); 1323 Node* diff = new (C, 3) SubINode(init2, ratio_init); 1324 phase->_igvn.register_new_node_with_optimizer(diff, init2); 1325 phase->set_early_ctrl(diff); 1326 Node* ratio_idx = new (C, 3) MulINode(phi, ratio); 1327 phase->_igvn.register_new_node_with_optimizer(ratio_idx, phi); 1328 phase->set_ctrl(ratio_idx, cl); 1329 Node* add = new (C, 3) AddINode(ratio_idx, diff); 1330 phase->_igvn.register_new_node_with_optimizer(add); 1331 phase->set_ctrl(add, cl); 1332 phase->_igvn.hash_delete( phi2 ); 1333 phase->_igvn.subsume_node( phi2, add ); 1334 // Sometimes an induction variable is unused 1335 if (add->outcnt() == 0) { 1336 phase->_igvn.remove_dead_node(add); 1337 } 1338 --i; // deleted this phi; rescan starting with next position 1339 continue; 1340 } 1341 } 1342 } else if (_parent != NULL && !_irreducible) { 1343 // Not a counted loop. 1344 // Look for a safepoint on the idom-path to remove, preserving the first one 1345 bool found = false; 1346 Node* n = tail(); 1347 for (; n != _head && !found; n = phase->idom(n)) { 1348 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this) 1349 found = true; // Found one 1350 } 1351 // Skip past it and delete the others 1352 for (; n != _head; n = phase->idom(n)) { 1353 if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && 1354 phase->is_deleteable_safept(n)) 1355 phase->lazy_replace(n,n->in(TypeFunc::Control)); 1356 } 1357 } 1358 1359 // Recursively 1360 if( _child ) _child->counted_loop( phase ); 1361 if( _next ) _next ->counted_loop( phase ); 1362 } 1363 1364 #ifndef PRODUCT 1365 //------------------------------dump_head-------------------------------------- 1366 // Dump 1 liner for loop header info 1367 void IdealLoopTree::dump_head( ) const { 1368 for( uint i=0; i<_nest; i++ ) 1369 tty->print(" "); 1370 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx); 1371 if( _irreducible ) tty->print(" IRREDUCIBLE"); 1372 if( _head->is_CountedLoop() ) { 1373 CountedLoopNode *cl = _head->as_CountedLoop(); 1374 tty->print(" counted"); 1375 if( cl->is_pre_loop () ) tty->print(" pre" ); 1376 if( cl->is_main_loop() ) tty->print(" main"); 1377 if( cl->is_post_loop() ) tty->print(" post"); 1378 } 1379 tty->cr(); 1380 } 1381 1382 //------------------------------dump------------------------------------------- 1383 // Dump loops by loop tree 1384 void IdealLoopTree::dump( ) const { 1385 dump_head(); 1386 if( _child ) _child->dump(); 1387 if( _next ) _next ->dump(); 1388 } 1389 1390 #endif 1391 1392 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) { 1393 if (loop == root) { 1394 if (loop->_child != NULL) { 1395 log->begin_head("loop_tree"); 1396 log->end_head(); 1397 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1398 log->tail("loop_tree"); 1399 assert(loop->_next == NULL, "what?"); 1400 } 1401 } else { 1402 Node* head = loop->_head; 1403 log->begin_head("loop"); 1404 log->print(" idx='%d' ", head->_idx); 1405 if (loop->_irreducible) log->print("irreducible='1' "); 1406 if (head->is_Loop()) { 1407 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' "); 1408 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' "); 1409 } 1410 if (head->is_CountedLoop()) { 1411 CountedLoopNode* cl = head->as_CountedLoop(); 1412 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx()); 1413 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx); 1414 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx()); 1415 } 1416 log->end_head(); 1417 if( loop->_child ) log_loop_tree(root, loop->_child, log); 1418 log->tail("loop"); 1419 if( loop->_next ) log_loop_tree(root, loop->_next, log); 1420 } 1421 } 1422 1423 //---------------------collect_potentially_useful_predicates----------------------- 1424 //Helper function to collect potentially useful predicates to prevent them from 1425 //being eliminated by PhaseIdealLoop::eliminate_useless_predicates 1426 void PhaseIdealLoop::collect_potentially_useful_predicates( 1427 IdealLoopTree * loop, Unique_Node_List &useful_predicates) { 1428 if (loop->_child) { // child 1429 collect_potentially_useful_predicates(loop->_child, useful_predicates); 1430 } 1431 1432 //self (only loops that we can apply loop predication may use their predicates) 1433 if (loop->_head->is_Loop() && 1434 !loop->_irreducible && 1435 !loop->tail()->is_top()) { 1436 LoopNode *lpn = loop->_head->as_Loop(); 1437 Node* entry = lpn->in(LoopNode::EntryControl); 1438 ProjNode *predicate_proj = find_predicate_insertion_point(entry); 1439 if (predicate_proj != NULL ) { //right pattern that can be used by loop predication 1440 assert(entry->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be"); 1441 useful_predicates.push(entry->in(0)->in(1)->in(1)); //good one 1442 } 1443 } 1444 1445 if( loop->_next ) { // sibling 1446 collect_potentially_useful_predicates(loop->_next, useful_predicates); 1447 } 1448 } 1449 1450 //------------------------eliminate_useless_predicates----------------------------- 1451 // Eliminate all inserted predicates if they could not be used by loop predication. 1452 void PhaseIdealLoop::eliminate_useless_predicates() { 1453 if(C->predicate_count() == 0) return; //no predicate left 1454 1455 Unique_Node_List useful_predicates; //to store useful predicates 1456 if( C->has_loops()) { 1457 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates); 1458 } 1459 1460 for (int i = C->predicate_count(); i > 0; i--) { 1461 Node * n = C->predicate_opaque1_node(i-1); 1462 assert(n->Opcode() == Op_Opaque1, "must be"); 1463 if(!useful_predicates.member(n)) { //not in the useful list 1464 _igvn.replace_node(n, n->in(1)); 1465 } 1466 } 1467 } 1468 1469 //============================================================================= 1470 //----------------------------build_and_optimize------------------------------- 1471 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to 1472 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups. 1473 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool do_loop_pred) { 1474 int old_progress = C->major_progress(); 1475 1476 // Reset major-progress flag for the driver's heuristics 1477 C->clear_major_progress(); 1478 1479 #ifndef PRODUCT 1480 // Capture for later assert 1481 uint unique = C->unique(); 1482 _loop_invokes++; 1483 _loop_work += unique; 1484 #endif 1485 1486 // True if the method has at least 1 irreducible loop 1487 _has_irreducible_loops = false; 1488 1489 _created_loop_node = false; 1490 1491 Arena *a = Thread::current()->resource_area(); 1492 VectorSet visited(a); 1493 // Pre-grow the mapping from Nodes to IdealLoopTrees. 1494 _nodes.map(C->unique(), NULL); 1495 memset(_nodes.adr(), 0, wordSize * C->unique()); 1496 1497 // Pre-build the top-level outermost loop tree entry 1498 _ltree_root = new IdealLoopTree( this, C->root(), C->root() ); 1499 // Do not need a safepoint at the top level 1500 _ltree_root->_has_sfpt = 1; 1501 1502 // Empty pre-order array 1503 allocate_preorders(); 1504 1505 // Build a loop tree on the fly. Build a mapping from CFG nodes to 1506 // IdealLoopTree entries. Data nodes are NOT walked. 1507 build_loop_tree(); 1508 // Check for bailout, and return 1509 if (C->failing()) { 1510 return; 1511 } 1512 1513 // No loops after all 1514 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false); 1515 1516 // There should always be an outer loop containing the Root and Return nodes. 1517 // If not, we have a degenerate empty program. Bail out in this case. 1518 if (!has_node(C->root())) { 1519 if (!_verify_only) { 1520 C->clear_major_progress(); 1521 C->record_method_not_compilable("empty program detected during loop optimization"); 1522 } 1523 return; 1524 } 1525 1526 // Nothing to do, so get out 1527 if( !C->has_loops() && !do_split_ifs && !_verify_me && !_verify_only ) { 1528 _igvn.optimize(); // Cleanup NeverBranches 1529 return; 1530 } 1531 1532 // Set loop nesting depth 1533 _ltree_root->set_nest( 0 ); 1534 1535 // Split shared headers and insert loop landing pads. 1536 // Do not bother doing this on the Root loop of course. 1537 if( !_verify_me && !_verify_only && _ltree_root->_child ) { 1538 if( _ltree_root->_child->beautify_loops( this ) ) { 1539 // Re-build loop tree! 1540 _ltree_root->_child = NULL; 1541 _nodes.clear(); 1542 reallocate_preorders(); 1543 build_loop_tree(); 1544 // Check for bailout, and return 1545 if (C->failing()) { 1546 return; 1547 } 1548 // Reset loop nesting depth 1549 _ltree_root->set_nest( 0 ); 1550 1551 C->print_method("After beautify loops", 3); 1552 } 1553 } 1554 1555 // Build Dominators for elision of NULL checks & loop finding. 1556 // Since nodes do not have a slot for immediate dominator, make 1557 // a persistent side array for that info indexed on node->_idx. 1558 _idom_size = C->unique(); 1559 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size ); 1560 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size ); 1561 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth 1562 memset( _dom_depth, 0, _idom_size * sizeof(uint) ); 1563 1564 Dominators(); 1565 1566 if (!_verify_only) { 1567 // As a side effect, Dominators removed any unreachable CFG paths 1568 // into RegionNodes. It doesn't do this test against Root, so 1569 // we do it here. 1570 for( uint i = 1; i < C->root()->req(); i++ ) { 1571 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root? 1572 _igvn.hash_delete(C->root()); 1573 C->root()->del_req(i); 1574 _igvn._worklist.push(C->root()); 1575 i--; // Rerun same iteration on compressed edges 1576 } 1577 } 1578 1579 // Given dominators, try to find inner loops with calls that must 1580 // always be executed (call dominates loop tail). These loops do 1581 // not need a separate safepoint. 1582 Node_List cisstack(a); 1583 _ltree_root->check_safepts(visited, cisstack); 1584 } 1585 1586 // Walk the DATA nodes and place into loops. Find earliest control 1587 // node. For CFG nodes, the _nodes array starts out and remains 1588 // holding the associated IdealLoopTree pointer. For DATA nodes, the 1589 // _nodes array holds the earliest legal controlling CFG node. 1590 1591 // Allocate stack with enough space to avoid frequent realloc 1592 int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats 1593 Node_Stack nstack( a, stack_size ); 1594 1595 visited.Clear(); 1596 Node_List worklist(a); 1597 // Don't need C->root() on worklist since 1598 // it will be processed among C->top() inputs 1599 worklist.push( C->top() ); 1600 visited.set( C->top()->_idx ); // Set C->top() as visited now 1601 build_loop_early( visited, worklist, nstack ); 1602 1603 // Given early legal placement, try finding counted loops. This placement 1604 // is good enough to discover most loop invariants. 1605 if( !_verify_me && !_verify_only ) 1606 _ltree_root->counted_loop( this ); 1607 1608 // Find latest loop placement. Find ideal loop placement. 1609 visited.Clear(); 1610 init_dom_lca_tags(); 1611 // Need C->root() on worklist when processing outs 1612 worklist.push( C->root() ); 1613 NOT_PRODUCT( C->verify_graph_edges(); ) 1614 worklist.push( C->top() ); 1615 build_loop_late( visited, worklist, nstack ); 1616 1617 if (_verify_only) { 1618 // restore major progress flag 1619 for (int i = 0; i < old_progress; i++) 1620 C->set_major_progress(); 1621 assert(C->unique() == unique, "verification mode made Nodes? ? ?"); 1622 assert(_igvn._worklist.size() == 0, "shouldn't push anything"); 1623 return; 1624 } 1625 1626 // some parser-inserted loop predicates could never be used by loop 1627 // predication. Eliminate them before loop optimization 1628 if(UseLoopPredicate) { 1629 eliminate_useless_predicates(); 1630 } 1631 1632 // clear out the dead code 1633 while(_deadlist.size()) { 1634 _igvn.remove_globally_dead_node(_deadlist.pop()); 1635 } 1636 1637 #ifndef PRODUCT 1638 C->verify_graph_edges(); 1639 if( _verify_me ) { // Nested verify pass? 1640 // Check to see if the verify mode is broken 1641 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?"); 1642 return; 1643 } 1644 if( VerifyLoopOptimizations ) verify(); 1645 #endif 1646 1647 if (ReassociateInvariants) { 1648 // Reassociate invariants and prep for split_thru_phi 1649 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 1650 IdealLoopTree* lpt = iter.current(); 1651 if (!lpt->is_counted() || !lpt->is_inner()) continue; 1652 1653 lpt->reassociate_invariants(this); 1654 1655 // Because RCE opportunities can be masked by split_thru_phi, 1656 // look for RCE candidates and inhibit split_thru_phi 1657 // on just their loop-phi's for this pass of loop opts 1658 if( SplitIfBlocks && do_split_ifs ) { 1659 if (lpt->policy_range_check(this)) { 1660 lpt->_rce_candidate = 1; // = true 1661 } 1662 } 1663 } 1664 } 1665 1666 // Check for aggressive application of split-if and other transforms 1667 // that require basic-block info (like cloning through Phi's) 1668 if( SplitIfBlocks && do_split_ifs ) { 1669 visited.Clear(); 1670 split_if_with_blocks( visited, nstack ); 1671 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); ); 1672 } 1673 1674 // Perform loop predication before iteration splitting 1675 if(do_loop_pred && C->has_loops() && !C->major_progress()) { 1676 _ltree_root->_child->loop_predication(this); 1677 } 1678 1679 // Perform iteration-splitting on inner loops. Split iterations to avoid 1680 // range checks or one-shot null checks. 1681 1682 // If split-if's didn't hack the graph too bad (no CFG changes) 1683 // then do loop opts. 1684 if( C->has_loops() && !C->major_progress() ) { 1685 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) ); 1686 _ltree_root->_child->iteration_split( this, worklist ); 1687 // No verify after peeling! GCM has hoisted code out of the loop. 1688 // After peeling, the hoisted code could sink inside the peeled area. 1689 // The peeling code does not try to recompute the best location for 1690 // all the code before the peeled area, so the verify pass will always 1691 // complain about it. 1692 } 1693 // Do verify graph edges in any case 1694 NOT_PRODUCT( C->verify_graph_edges(); ); 1695 1696 if( !do_split_ifs ) { 1697 // We saw major progress in Split-If to get here. We forced a 1698 // pass with unrolling and not split-if, however more split-if's 1699 // might make progress. If the unrolling didn't make progress 1700 // then the major-progress flag got cleared and we won't try 1701 // another round of Split-If. In particular the ever-common 1702 // instance-of/check-cast pattern requires at least 2 rounds of 1703 // Split-If to clear out. 1704 C->set_major_progress(); 1705 } 1706 1707 // Repeat loop optimizations if new loops were seen 1708 if (created_loop_node()) { 1709 C->set_major_progress(); 1710 } 1711 1712 // Convert scalar to superword operations 1713 1714 if (UseSuperWord && C->has_loops() && !C->major_progress()) { 1715 // SuperWord transform 1716 SuperWord sw(this); 1717 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 1718 IdealLoopTree* lpt = iter.current(); 1719 if (lpt->is_counted()) { 1720 sw.transform_loop(lpt); 1721 } 1722 } 1723 } 1724 1725 // Cleanup any modified bits 1726 _igvn.optimize(); 1727 1728 // disable assert until issue with split_flow_path is resolved (6742111) 1729 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(), 1730 // "shouldn't introduce irreducible loops"); 1731 1732 if (C->log() != NULL) { 1733 log_loop_tree(_ltree_root, _ltree_root, C->log()); 1734 } 1735 } 1736 1737 #ifndef PRODUCT 1738 //------------------------------print_statistics------------------------------- 1739 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes 1740 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique 1741 void PhaseIdealLoop::print_statistics() { 1742 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work); 1743 } 1744 1745 //------------------------------verify----------------------------------------- 1746 // Build a verify-only PhaseIdealLoop, and see that it agrees with me. 1747 static int fail; // debug only, so its multi-thread dont care 1748 void PhaseIdealLoop::verify() const { 1749 int old_progress = C->major_progress(); 1750 ResourceMark rm; 1751 PhaseIdealLoop loop_verify( _igvn, this ); 1752 VectorSet visited(Thread::current()->resource_area()); 1753 1754 fail = 0; 1755 verify_compare( C->root(), &loop_verify, visited ); 1756 assert( fail == 0, "verify loops failed" ); 1757 // Verify loop structure is the same 1758 _ltree_root->verify_tree(loop_verify._ltree_root, NULL); 1759 // Reset major-progress. It was cleared by creating a verify version of 1760 // PhaseIdealLoop. 1761 for( int i=0; i<old_progress; i++ ) 1762 C->set_major_progress(); 1763 } 1764 1765 //------------------------------verify_compare--------------------------------- 1766 // Make sure me and the given PhaseIdealLoop agree on key data structures 1767 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const { 1768 if( !n ) return; 1769 if( visited.test_set( n->_idx ) ) return; 1770 if( !_nodes[n->_idx] ) { // Unreachable 1771 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" ); 1772 return; 1773 } 1774 1775 uint i; 1776 for( i = 0; i < n->req(); i++ ) 1777 verify_compare( n->in(i), loop_verify, visited ); 1778 1779 // Check the '_nodes' block/loop structure 1780 i = n->_idx; 1781 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl 1782 if( _nodes[i] != loop_verify->_nodes[i] && 1783 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) { 1784 tty->print("Mismatched control setting for: "); 1785 n->dump(); 1786 if( fail++ > 10 ) return; 1787 Node *c = get_ctrl_no_update(n); 1788 tty->print("We have it as: "); 1789 if( c->in(0) ) c->dump(); 1790 else tty->print_cr("N%d",c->_idx); 1791 tty->print("Verify thinks: "); 1792 if( loop_verify->has_ctrl(n) ) 1793 loop_verify->get_ctrl_no_update(n)->dump(); 1794 else 1795 loop_verify->get_loop_idx(n)->dump(); 1796 tty->cr(); 1797 } 1798 } else { // We have a loop 1799 IdealLoopTree *us = get_loop_idx(n); 1800 if( loop_verify->has_ctrl(n) ) { 1801 tty->print("Mismatched loop setting for: "); 1802 n->dump(); 1803 if( fail++ > 10 ) return; 1804 tty->print("We have it as: "); 1805 us->dump(); 1806 tty->print("Verify thinks: "); 1807 loop_verify->get_ctrl_no_update(n)->dump(); 1808 tty->cr(); 1809 } else if (!C->major_progress()) { 1810 // Loop selection can be messed up if we did a major progress 1811 // operation, like split-if. Do not verify in that case. 1812 IdealLoopTree *them = loop_verify->get_loop_idx(n); 1813 if( us->_head != them->_head || us->_tail != them->_tail ) { 1814 tty->print("Unequals loops for: "); 1815 n->dump(); 1816 if( fail++ > 10 ) return; 1817 tty->print("We have it as: "); 1818 us->dump(); 1819 tty->print("Verify thinks: "); 1820 them->dump(); 1821 tty->cr(); 1822 } 1823 } 1824 } 1825 1826 // Check for immediate dominators being equal 1827 if( i >= _idom_size ) { 1828 if( !n->is_CFG() ) return; 1829 tty->print("CFG Node with no idom: "); 1830 n->dump(); 1831 return; 1832 } 1833 if( !n->is_CFG() ) return; 1834 if( n == C->root() ) return; // No IDOM here 1835 1836 assert(n->_idx == i, "sanity"); 1837 Node *id = idom_no_update(n); 1838 if( id != loop_verify->idom_no_update(n) ) { 1839 tty->print("Unequals idoms for: "); 1840 n->dump(); 1841 if( fail++ > 10 ) return; 1842 tty->print("We have it as: "); 1843 id->dump(); 1844 tty->print("Verify thinks: "); 1845 loop_verify->idom_no_update(n)->dump(); 1846 tty->cr(); 1847 } 1848 1849 } 1850 1851 //------------------------------verify_tree------------------------------------ 1852 // Verify that tree structures match. Because the CFG can change, siblings 1853 // within the loop tree can be reordered. We attempt to deal with that by 1854 // reordering the verify's loop tree if possible. 1855 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const { 1856 assert( _parent == parent, "Badly formed loop tree" ); 1857 1858 // Siblings not in same order? Attempt to re-order. 1859 if( _head != loop->_head ) { 1860 // Find _next pointer to update 1861 IdealLoopTree **pp = &loop->_parent->_child; 1862 while( *pp != loop ) 1863 pp = &((*pp)->_next); 1864 // Find proper sibling to be next 1865 IdealLoopTree **nn = &loop->_next; 1866 while( (*nn) && (*nn)->_head != _head ) 1867 nn = &((*nn)->_next); 1868 1869 // Check for no match. 1870 if( !(*nn) ) { 1871 // Annoyingly, irreducible loops can pick different headers 1872 // after a major_progress operation, so the rest of the loop 1873 // tree cannot be matched. 1874 if (_irreducible && Compile::current()->major_progress()) return; 1875 assert( 0, "failed to match loop tree" ); 1876 } 1877 1878 // Move (*nn) to (*pp) 1879 IdealLoopTree *hit = *nn; 1880 *nn = hit->_next; 1881 hit->_next = loop; 1882 *pp = loop; 1883 loop = hit; 1884 // Now try again to verify 1885 } 1886 1887 assert( _head == loop->_head , "mismatched loop head" ); 1888 Node *tail = _tail; // Inline a non-updating version of 1889 while( !tail->in(0) ) // the 'tail()' call. 1890 tail = tail->in(1); 1891 assert( tail == loop->_tail, "mismatched loop tail" ); 1892 1893 // Counted loops that are guarded should be able to find their guards 1894 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) { 1895 CountedLoopNode *cl = _head->as_CountedLoop(); 1896 Node *init = cl->init_trip(); 1897 Node *ctrl = cl->in(LoopNode::EntryControl); 1898 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 1899 Node *iff = ctrl->in(0); 1900 assert( iff->Opcode() == Op_If, "" ); 1901 Node *bol = iff->in(1); 1902 assert( bol->Opcode() == Op_Bool, "" ); 1903 Node *cmp = bol->in(1); 1904 assert( cmp->Opcode() == Op_CmpI, "" ); 1905 Node *add = cmp->in(1); 1906 Node *opaq; 1907 if( add->Opcode() == Op_Opaque1 ) { 1908 opaq = add; 1909 } else { 1910 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" ); 1911 assert( add == init, "" ); 1912 opaq = cmp->in(2); 1913 } 1914 assert( opaq->Opcode() == Op_Opaque1, "" ); 1915 1916 } 1917 1918 if (_child != NULL) _child->verify_tree(loop->_child, this); 1919 if (_next != NULL) _next ->verify_tree(loop->_next, parent); 1920 // Innermost loops need to verify loop bodies, 1921 // but only if no 'major_progress' 1922 int fail = 0; 1923 if (!Compile::current()->major_progress() && _child == NULL) { 1924 for( uint i = 0; i < _body.size(); i++ ) { 1925 Node *n = _body.at(i); 1926 if (n->outcnt() == 0) continue; // Ignore dead 1927 uint j; 1928 for( j = 0; j < loop->_body.size(); j++ ) 1929 if( loop->_body.at(j) == n ) 1930 break; 1931 if( j == loop->_body.size() ) { // Not found in loop body 1932 // Last ditch effort to avoid assertion: Its possible that we 1933 // have some users (so outcnt not zero) but are still dead. 1934 // Try to find from root. 1935 if (Compile::current()->root()->find(n->_idx)) { 1936 fail++; 1937 tty->print("We have that verify does not: "); 1938 n->dump(); 1939 } 1940 } 1941 } 1942 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) { 1943 Node *n = loop->_body.at(i2); 1944 if (n->outcnt() == 0) continue; // Ignore dead 1945 uint j; 1946 for( j = 0; j < _body.size(); j++ ) 1947 if( _body.at(j) == n ) 1948 break; 1949 if( j == _body.size() ) { // Not found in loop body 1950 // Last ditch effort to avoid assertion: Its possible that we 1951 // have some users (so outcnt not zero) but are still dead. 1952 // Try to find from root. 1953 if (Compile::current()->root()->find(n->_idx)) { 1954 fail++; 1955 tty->print("Verify has that we do not: "); 1956 n->dump(); 1957 } 1958 } 1959 } 1960 assert( !fail, "loop body mismatch" ); 1961 } 1962 } 1963 1964 #endif 1965 1966 //------------------------------set_idom--------------------------------------- 1967 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) { 1968 uint idx = d->_idx; 1969 if (idx >= _idom_size) { 1970 uint newsize = _idom_size<<1; 1971 while( idx >= newsize ) { 1972 newsize <<= 1; 1973 } 1974 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize); 1975 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize); 1976 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) ); 1977 _idom_size = newsize; 1978 } 1979 _idom[idx] = n; 1980 _dom_depth[idx] = dom_depth; 1981 } 1982 1983 //------------------------------recompute_dom_depth--------------------------------------- 1984 // The dominator tree is constructed with only parent pointers. 1985 // This recomputes the depth in the tree by first tagging all 1986 // nodes as "no depth yet" marker. The next pass then runs up 1987 // the dom tree from each node marked "no depth yet", and computes 1988 // the depth on the way back down. 1989 void PhaseIdealLoop::recompute_dom_depth() { 1990 uint no_depth_marker = C->unique(); 1991 uint i; 1992 // Initialize depth to "no depth yet" 1993 for (i = 0; i < _idom_size; i++) { 1994 if (_dom_depth[i] > 0 && _idom[i] != NULL) { 1995 _dom_depth[i] = no_depth_marker; 1996 } 1997 } 1998 if (_dom_stk == NULL) { 1999 uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size. 2000 if (init_size < 10) init_size = 10; 2001 _dom_stk = new (C->node_arena()) GrowableArray<uint>(C->node_arena(), init_size, 0, 0); 2002 } 2003 // Compute new depth for each node. 2004 for (i = 0; i < _idom_size; i++) { 2005 uint j = i; 2006 // Run up the dom tree to find a node with a depth 2007 while (_dom_depth[j] == no_depth_marker) { 2008 _dom_stk->push(j); 2009 j = _idom[j]->_idx; 2010 } 2011 // Compute the depth on the way back down this tree branch 2012 uint dd = _dom_depth[j] + 1; 2013 while (_dom_stk->length() > 0) { 2014 uint j = _dom_stk->pop(); 2015 _dom_depth[j] = dd; 2016 dd++; 2017 } 2018 } 2019 } 2020 2021 //------------------------------sort------------------------------------------- 2022 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the 2023 // loop tree, not the root. 2024 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) { 2025 if( !innermost ) return loop; // New innermost loop 2026 2027 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number 2028 assert( loop_preorder, "not yet post-walked loop" ); 2029 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer 2030 IdealLoopTree *l = *pp; // Do I go before or after 'l'? 2031 2032 // Insert at start of list 2033 while( l ) { // Insertion sort based on pre-order 2034 if( l == loop ) return innermost; // Already on list! 2035 int l_preorder = get_preorder(l->_head); // Cache pre-order number 2036 assert( l_preorder, "not yet post-walked l" ); 2037 // Check header pre-order number to figure proper nesting 2038 if( loop_preorder > l_preorder ) 2039 break; // End of insertion 2040 // If headers tie (e.g., shared headers) check tail pre-order numbers. 2041 // Since I split shared headers, you'd think this could not happen. 2042 // BUT: I must first do the preorder numbering before I can discover I 2043 // have shared headers, so the split headers all get the same preorder 2044 // number as the RegionNode they split from. 2045 if( loop_preorder == l_preorder && 2046 get_preorder(loop->_tail) < get_preorder(l->_tail) ) 2047 break; // Also check for shared headers (same pre#) 2048 pp = &l->_parent; // Chain up list 2049 l = *pp; 2050 } 2051 // Link into list 2052 // Point predecessor to me 2053 *pp = loop; 2054 // Point me to successor 2055 IdealLoopTree *p = loop->_parent; 2056 loop->_parent = l; // Point me to successor 2057 if( p ) sort( p, innermost ); // Insert my parents into list as well 2058 return innermost; 2059 } 2060 2061 //------------------------------build_loop_tree-------------------------------- 2062 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit 2063 // bits. The _nodes[] array is mapped by Node index and holds a NULL for 2064 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the 2065 // tightest enclosing IdealLoopTree for post-walked. 2066 // 2067 // During my forward walk I do a short 1-layer lookahead to see if I can find 2068 // a loop backedge with that doesn't have any work on the backedge. This 2069 // helps me construct nested loops with shared headers better. 2070 // 2071 // Once I've done the forward recursion, I do the post-work. For each child 2072 // I check to see if there is a backedge. Backedges define a loop! I 2073 // insert an IdealLoopTree at the target of the backedge. 2074 // 2075 // During the post-work I also check to see if I have several children 2076 // belonging to different loops. If so, then this Node is a decision point 2077 // where control flow can choose to change loop nests. It is at this 2078 // decision point where I can figure out how loops are nested. At this 2079 // time I can properly order the different loop nests from my children. 2080 // Note that there may not be any backedges at the decision point! 2081 // 2082 // Since the decision point can be far removed from the backedges, I can't 2083 // order my loops at the time I discover them. Thus at the decision point 2084 // I need to inspect loop header pre-order numbers to properly nest my 2085 // loops. This means I need to sort my childrens' loops by pre-order. 2086 // The sort is of size number-of-control-children, which generally limits 2087 // it to size 2 (i.e., I just choose between my 2 target loops). 2088 void PhaseIdealLoop::build_loop_tree() { 2089 // Allocate stack of size C->unique()/2 to avoid frequent realloc 2090 GrowableArray <Node *> bltstack(C->unique() >> 1); 2091 Node *n = C->root(); 2092 bltstack.push(n); 2093 int pre_order = 1; 2094 int stack_size; 2095 2096 while ( ( stack_size = bltstack.length() ) != 0 ) { 2097 n = bltstack.top(); // Leave node on stack 2098 if ( !is_visited(n) ) { 2099 // ---- Pre-pass Work ---- 2100 // Pre-walked but not post-walked nodes need a pre_order number. 2101 2102 set_preorder_visited( n, pre_order ); // set as visited 2103 2104 // ---- Scan over children ---- 2105 // Scan first over control projections that lead to loop headers. 2106 // This helps us find inner-to-outer loops with shared headers better. 2107 2108 // Scan children's children for loop headers. 2109 for ( int i = n->outcnt() - 1; i >= 0; --i ) { 2110 Node* m = n->raw_out(i); // Child 2111 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children 2112 // Scan over children's children to find loop 2113 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2114 Node* l = m->fast_out(j); 2115 if( is_visited(l) && // Been visited? 2116 !is_postvisited(l) && // But not post-visited 2117 get_preorder(l) < pre_order ) { // And smaller pre-order 2118 // Found! Scan the DFS down this path before doing other paths 2119 bltstack.push(m); 2120 break; 2121 } 2122 } 2123 } 2124 } 2125 pre_order++; 2126 } 2127 else if ( !is_postvisited(n) ) { 2128 // Note: build_loop_tree_impl() adds out edges on rare occasions, 2129 // such as com.sun.rsasign.am::a. 2130 // For non-recursive version, first, process current children. 2131 // On next iteration, check if additional children were added. 2132 for ( int k = n->outcnt() - 1; k >= 0; --k ) { 2133 Node* u = n->raw_out(k); 2134 if ( u->is_CFG() && !is_visited(u) ) { 2135 bltstack.push(u); 2136 } 2137 } 2138 if ( bltstack.length() == stack_size ) { 2139 // There were no additional children, post visit node now 2140 (void)bltstack.pop(); // Remove node from stack 2141 pre_order = build_loop_tree_impl( n, pre_order ); 2142 // Check for bailout 2143 if (C->failing()) { 2144 return; 2145 } 2146 // Check to grow _preorders[] array for the case when 2147 // build_loop_tree_impl() adds new nodes. 2148 check_grow_preorders(); 2149 } 2150 } 2151 else { 2152 (void)bltstack.pop(); // Remove post-visited node from stack 2153 } 2154 } 2155 } 2156 2157 //------------------------------build_loop_tree_impl--------------------------- 2158 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) { 2159 // ---- Post-pass Work ---- 2160 // Pre-walked but not post-walked nodes need a pre_order number. 2161 2162 // Tightest enclosing loop for this Node 2163 IdealLoopTree *innermost = NULL; 2164 2165 // For all children, see if any edge is a backedge. If so, make a loop 2166 // for it. Then find the tightest enclosing loop for the self Node. 2167 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 2168 Node* m = n->fast_out(i); // Child 2169 if( n == m ) continue; // Ignore control self-cycles 2170 if( !m->is_CFG() ) continue;// Ignore non-CFG edges 2171 2172 IdealLoopTree *l; // Child's loop 2173 if( !is_postvisited(m) ) { // Child visited but not post-visited? 2174 // Found a backedge 2175 assert( get_preorder(m) < pre_order, "should be backedge" ); 2176 // Check for the RootNode, which is already a LoopNode and is allowed 2177 // to have multiple "backedges". 2178 if( m == C->root()) { // Found the root? 2179 l = _ltree_root; // Root is the outermost LoopNode 2180 } else { // Else found a nested loop 2181 // Insert a LoopNode to mark this loop. 2182 l = new IdealLoopTree(this, m, n); 2183 } // End of Else found a nested loop 2184 if( !has_loop(m) ) // If 'm' does not already have a loop set 2185 set_loop(m, l); // Set loop header to loop now 2186 2187 } else { // Else not a nested loop 2188 if( !_nodes[m->_idx] ) continue; // Dead code has no loop 2189 l = get_loop(m); // Get previously determined loop 2190 // If successor is header of a loop (nest), move up-loop till it 2191 // is a member of some outer enclosing loop. Since there are no 2192 // shared headers (I've split them already) I only need to go up 2193 // at most 1 level. 2194 while( l && l->_head == m ) // Successor heads loop? 2195 l = l->_parent; // Move up 1 for me 2196 // If this loop is not properly parented, then this loop 2197 // has no exit path out, i.e. its an infinite loop. 2198 if( !l ) { 2199 // Make loop "reachable" from root so the CFG is reachable. Basically 2200 // insert a bogus loop exit that is never taken. 'm', the loop head, 2201 // points to 'n', one (of possibly many) fall-in paths. There may be 2202 // many backedges as well. 2203 2204 // Here I set the loop to be the root loop. I could have, after 2205 // inserting a bogus loop exit, restarted the recursion and found my 2206 // new loop exit. This would make the infinite loop a first-class 2207 // loop and it would then get properly optimized. What's the use of 2208 // optimizing an infinite loop? 2209 l = _ltree_root; // Oops, found infinite loop 2210 2211 if (!_verify_only) { 2212 // Insert the NeverBranch between 'm' and it's control user. 2213 NeverBranchNode *iff = new (C, 1) NeverBranchNode( m ); 2214 _igvn.register_new_node_with_optimizer(iff); 2215 set_loop(iff, l); 2216 Node *if_t = new (C, 1) CProjNode( iff, 0 ); 2217 _igvn.register_new_node_with_optimizer(if_t); 2218 set_loop(if_t, l); 2219 2220 Node* cfg = NULL; // Find the One True Control User of m 2221 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { 2222 Node* x = m->fast_out(j); 2223 if (x->is_CFG() && x != m && x != iff) 2224 { cfg = x; break; } 2225 } 2226 assert(cfg != NULL, "must find the control user of m"); 2227 uint k = 0; // Probably cfg->in(0) 2228 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region 2229 cfg->set_req( k, if_t ); // Now point to NeverBranch 2230 2231 // Now create the never-taken loop exit 2232 Node *if_f = new (C, 1) CProjNode( iff, 1 ); 2233 _igvn.register_new_node_with_optimizer(if_f); 2234 set_loop(if_f, l); 2235 // Find frame ptr for Halt. Relies on the optimizer 2236 // V-N'ing. Easier and quicker than searching through 2237 // the program structure. 2238 Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr ); 2239 _igvn.register_new_node_with_optimizer(frame); 2240 // Halt & Catch Fire 2241 Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame ); 2242 _igvn.register_new_node_with_optimizer(halt); 2243 set_loop(halt, l); 2244 C->root()->add_req(halt); 2245 } 2246 set_loop(C->root(), _ltree_root); 2247 } 2248 } 2249 // Weeny check for irreducible. This child was already visited (this 2250 // IS the post-work phase). Is this child's loop header post-visited 2251 // as well? If so, then I found another entry into the loop. 2252 if (!_verify_only) { 2253 while( is_postvisited(l->_head) ) { 2254 // found irreducible 2255 l->_irreducible = 1; // = true 2256 l = l->_parent; 2257 _has_irreducible_loops = true; 2258 // Check for bad CFG here to prevent crash, and bailout of compile 2259 if (l == NULL) { 2260 C->record_method_not_compilable("unhandled CFG detected during loop optimization"); 2261 return pre_order; 2262 } 2263 } 2264 } 2265 2266 // This Node might be a decision point for loops. It is only if 2267 // it's children belong to several different loops. The sort call 2268 // does a trivial amount of work if there is only 1 child or all 2269 // children belong to the same loop. If however, the children 2270 // belong to different loops, the sort call will properly set the 2271 // _parent pointers to show how the loops nest. 2272 // 2273 // In any case, it returns the tightest enclosing loop. 2274 innermost = sort( l, innermost ); 2275 } 2276 2277 // Def-use info will have some dead stuff; dead stuff will have no 2278 // loop decided on. 2279 2280 // Am I a loop header? If so fix up my parent's child and next ptrs. 2281 if( innermost && innermost->_head == n ) { 2282 assert( get_loop(n) == innermost, "" ); 2283 IdealLoopTree *p = innermost->_parent; 2284 IdealLoopTree *l = innermost; 2285 while( p && l->_head == n ) { 2286 l->_next = p->_child; // Put self on parents 'next child' 2287 p->_child = l; // Make self as first child of parent 2288 l = p; // Now walk up the parent chain 2289 p = l->_parent; 2290 } 2291 } else { 2292 // Note that it is possible for a LoopNode to reach here, if the 2293 // backedge has been made unreachable (hence the LoopNode no longer 2294 // denotes a Loop, and will eventually be removed). 2295 2296 // Record tightest enclosing loop for self. Mark as post-visited. 2297 set_loop(n, innermost); 2298 // Also record has_call flag early on 2299 if( innermost ) { 2300 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) { 2301 // Do not count uncommon calls 2302 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) { 2303 Node *iff = n->in(0)->in(0); 2304 if( !iff->is_If() || 2305 (n->in(0)->Opcode() == Op_IfFalse && 2306 (1.0 - iff->as_If()->_prob) >= 0.01) || 2307 (iff->as_If()->_prob >= 0.01) ) 2308 innermost->_has_call = 1; 2309 } 2310 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) { 2311 // Disable loop optimizations if the loop has a scalar replaceable 2312 // allocation. This disabling may cause a potential performance lost 2313 // if the allocation is not eliminated for some reason. 2314 innermost->_allow_optimizations = false; 2315 innermost->_has_call = 1; // = true 2316 } 2317 } 2318 } 2319 2320 // Flag as post-visited now 2321 set_postvisited(n); 2322 return pre_order; 2323 } 2324 2325 2326 //------------------------------build_loop_early------------------------------- 2327 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2328 // First pass computes the earliest controlling node possible. This is the 2329 // controlling input with the deepest dominating depth. 2330 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 2331 while (worklist.size() != 0) { 2332 // Use local variables nstack_top_n & nstack_top_i to cache values 2333 // on nstack's top. 2334 Node *nstack_top_n = worklist.pop(); 2335 uint nstack_top_i = 0; 2336 //while_nstack_nonempty: 2337 while (true) { 2338 // Get parent node and next input's index from stack's top. 2339 Node *n = nstack_top_n; 2340 uint i = nstack_top_i; 2341 uint cnt = n->req(); // Count of inputs 2342 if (i == 0) { // Pre-process the node. 2343 if( has_node(n) && // Have either loop or control already? 2344 !has_ctrl(n) ) { // Have loop picked out already? 2345 // During "merge_many_backedges" we fold up several nested loops 2346 // into a single loop. This makes the members of the original 2347 // loop bodies pointing to dead loops; they need to move up 2348 // to the new UNION'd larger loop. I set the _head field of these 2349 // dead loops to NULL and the _parent field points to the owning 2350 // loop. Shades of UNION-FIND algorithm. 2351 IdealLoopTree *ilt; 2352 while( !(ilt = get_loop(n))->_head ) { 2353 // Normally I would use a set_loop here. But in this one special 2354 // case, it is legal (and expected) to change what loop a Node 2355 // belongs to. 2356 _nodes.map(n->_idx, (Node*)(ilt->_parent) ); 2357 } 2358 // Remove safepoints ONLY if I've already seen I don't need one. 2359 // (the old code here would yank a 2nd safepoint after seeing a 2360 // first one, even though the 1st did not dominate in the loop body 2361 // and thus could be avoided indefinitely) 2362 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint && 2363 is_deleteable_safept(n)) { 2364 Node *in = n->in(TypeFunc::Control); 2365 lazy_replace(n,in); // Pull safepoint now 2366 // Carry on with the recursion "as if" we are walking 2367 // only the control input 2368 if( !visited.test_set( in->_idx ) ) { 2369 worklist.push(in); // Visit this guy later, using worklist 2370 } 2371 // Get next node from nstack: 2372 // - skip n's inputs processing by setting i > cnt; 2373 // - we also will not call set_early_ctrl(n) since 2374 // has_node(n) == true (see the condition above). 2375 i = cnt + 1; 2376 } 2377 } 2378 } // if (i == 0) 2379 2380 // Visit all inputs 2381 bool done = true; // Assume all n's inputs will be processed 2382 while (i < cnt) { 2383 Node *in = n->in(i); 2384 ++i; 2385 if (in == NULL) continue; 2386 if (in->pinned() && !in->is_CFG()) 2387 set_ctrl(in, in->in(0)); 2388 int is_visited = visited.test_set( in->_idx ); 2389 if (!has_node(in)) { // No controlling input yet? 2390 assert( !in->is_CFG(), "CFG Node with no controlling input?" ); 2391 assert( !is_visited, "visit only once" ); 2392 nstack.push(n, i); // Save parent node and next input's index. 2393 nstack_top_n = in; // Process current input now. 2394 nstack_top_i = 0; 2395 done = false; // Not all n's inputs processed. 2396 break; // continue while_nstack_nonempty; 2397 } else if (!is_visited) { 2398 // This guy has a location picked out for him, but has not yet 2399 // been visited. Happens to all CFG nodes, for instance. 2400 // Visit him using the worklist instead of recursion, to break 2401 // cycles. Since he has a location already we do not need to 2402 // find his location before proceeding with the current Node. 2403 worklist.push(in); // Visit this guy later, using worklist 2404 } 2405 } 2406 if (done) { 2407 // All of n's inputs have been processed, complete post-processing. 2408 2409 // Compute earliest point this Node can go. 2410 // CFG, Phi, pinned nodes already know their controlling input. 2411 if (!has_node(n)) { 2412 // Record earliest legal location 2413 set_early_ctrl( n ); 2414 } 2415 if (nstack.is_empty()) { 2416 // Finished all nodes on stack. 2417 // Process next node on the worklist. 2418 break; 2419 } 2420 // Get saved parent node and next input's index. 2421 nstack_top_n = nstack.node(); 2422 nstack_top_i = nstack.index(); 2423 nstack.pop(); 2424 } 2425 } // while (true) 2426 } 2427 } 2428 2429 //------------------------------dom_lca_internal-------------------------------- 2430 // Pair-wise LCA 2431 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const { 2432 if( !n1 ) return n2; // Handle NULL original LCA 2433 assert( n1->is_CFG(), "" ); 2434 assert( n2->is_CFG(), "" ); 2435 // find LCA of all uses 2436 uint d1 = dom_depth(n1); 2437 uint d2 = dom_depth(n2); 2438 while (n1 != n2) { 2439 if (d1 > d2) { 2440 n1 = idom(n1); 2441 d1 = dom_depth(n1); 2442 } else if (d1 < d2) { 2443 n2 = idom(n2); 2444 d2 = dom_depth(n2); 2445 } else { 2446 // Here d1 == d2. Due to edits of the dominator-tree, sections 2447 // of the tree might have the same depth. These sections have 2448 // to be searched more carefully. 2449 2450 // Scan up all the n1's with equal depth, looking for n2. 2451 Node *t1 = idom(n1); 2452 while (dom_depth(t1) == d1) { 2453 if (t1 == n2) return n2; 2454 t1 = idom(t1); 2455 } 2456 // Scan up all the n2's with equal depth, looking for n1. 2457 Node *t2 = idom(n2); 2458 while (dom_depth(t2) == d2) { 2459 if (t2 == n1) return n1; 2460 t2 = idom(t2); 2461 } 2462 // Move up to a new dominator-depth value as well as up the dom-tree. 2463 n1 = t1; 2464 n2 = t2; 2465 d1 = dom_depth(n1); 2466 d2 = dom_depth(n2); 2467 } 2468 } 2469 return n1; 2470 } 2471 2472 //------------------------------compute_idom----------------------------------- 2473 // Locally compute IDOM using dom_lca call. Correct only if the incoming 2474 // IDOMs are correct. 2475 Node *PhaseIdealLoop::compute_idom( Node *region ) const { 2476 assert( region->is_Region(), "" ); 2477 Node *LCA = NULL; 2478 for( uint i = 1; i < region->req(); i++ ) { 2479 if( region->in(i) != C->top() ) 2480 LCA = dom_lca( LCA, region->in(i) ); 2481 } 2482 return LCA; 2483 } 2484 2485 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) { 2486 bool had_error = false; 2487 #ifdef ASSERT 2488 if (early != C->root()) { 2489 // Make sure that there's a dominance path from use to LCA 2490 Node* d = use; 2491 while (d != LCA) { 2492 d = idom(d); 2493 if (d == C->root()) { 2494 tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx); 2495 n->dump(); 2496 use->dump(); 2497 had_error = true; 2498 break; 2499 } 2500 } 2501 } 2502 #endif 2503 return had_error; 2504 } 2505 2506 2507 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) { 2508 // Compute LCA over list of uses 2509 bool had_error = false; 2510 Node *LCA = NULL; 2511 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) { 2512 Node* c = n->fast_out(i); 2513 if (_nodes[c->_idx] == NULL) 2514 continue; // Skip the occasional dead node 2515 if( c->is_Phi() ) { // For Phis, we must land above on the path 2516 for( uint j=1; j<c->req(); j++ ) {// For all inputs 2517 if( c->in(j) == n ) { // Found matching input? 2518 Node *use = c->in(0)->in(j); 2519 if (_verify_only && use->is_top()) continue; 2520 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2521 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 2522 } 2523 } 2524 } else { 2525 // For CFG data-users, use is in the block just prior 2526 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0); 2527 LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); 2528 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; 2529 } 2530 } 2531 assert(!had_error, "bad dominance"); 2532 return LCA; 2533 } 2534 2535 //------------------------------get_late_ctrl---------------------------------- 2536 // Compute latest legal control. 2537 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) { 2538 assert(early != NULL, "early control should not be NULL"); 2539 2540 Node* LCA = compute_lca_of_uses(n, early); 2541 #ifdef ASSERT 2542 if (LCA == C->root() && LCA != early) { 2543 // def doesn't dominate uses so print some useful debugging output 2544 compute_lca_of_uses(n, early, true); 2545 } 2546 #endif 2547 2548 // if this is a load, check for anti-dependent stores 2549 // We use a conservative algorithm to identify potential interfering 2550 // instructions and for rescheduling the load. The users of the memory 2551 // input of this load are examined. Any use which is not a load and is 2552 // dominated by early is considered a potentially interfering store. 2553 // This can produce false positives. 2554 if (n->is_Load() && LCA != early) { 2555 Node_List worklist; 2556 2557 Node *mem = n->in(MemNode::Memory); 2558 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { 2559 Node* s = mem->fast_out(i); 2560 worklist.push(s); 2561 } 2562 while(worklist.size() != 0 && LCA != early) { 2563 Node* s = worklist.pop(); 2564 if (s->is_Load()) { 2565 continue; 2566 } else if (s->is_MergeMem()) { 2567 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) { 2568 Node* s1 = s->fast_out(i); 2569 worklist.push(s1); 2570 } 2571 } else { 2572 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0); 2573 assert(sctrl != NULL || s->outcnt() == 0, "must have control"); 2574 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) { 2575 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n); 2576 } 2577 } 2578 } 2579 } 2580 2581 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control"); 2582 return LCA; 2583 } 2584 2585 // true if CFG node d dominates CFG node n 2586 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) { 2587 if (d == n) 2588 return true; 2589 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes"); 2590 uint dd = dom_depth(d); 2591 while (dom_depth(n) >= dd) { 2592 if (n == d) 2593 return true; 2594 n = idom(n); 2595 } 2596 return false; 2597 } 2598 2599 //------------------------------dom_lca_for_get_late_ctrl_internal------------- 2600 // Pair-wise LCA with tags. 2601 // Tag each index with the node 'tag' currently being processed 2602 // before advancing up the dominator chain using idom(). 2603 // Later calls that find a match to 'tag' know that this path has already 2604 // been considered in the current LCA (which is input 'n1' by convention). 2605 // Since get_late_ctrl() is only called once for each node, the tag array 2606 // does not need to be cleared between calls to get_late_ctrl(). 2607 // Algorithm trades a larger constant factor for better asymptotic behavior 2608 // 2609 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) { 2610 uint d1 = dom_depth(n1); 2611 uint d2 = dom_depth(n2); 2612 2613 do { 2614 if (d1 > d2) { 2615 // current lca is deeper than n2 2616 _dom_lca_tags.map(n1->_idx, tag); 2617 n1 = idom(n1); 2618 d1 = dom_depth(n1); 2619 } else if (d1 < d2) { 2620 // n2 is deeper than current lca 2621 Node *memo = _dom_lca_tags[n2->_idx]; 2622 if( memo == tag ) { 2623 return n1; // Return the current LCA 2624 } 2625 _dom_lca_tags.map(n2->_idx, tag); 2626 n2 = idom(n2); 2627 d2 = dom_depth(n2); 2628 } else { 2629 // Here d1 == d2. Due to edits of the dominator-tree, sections 2630 // of the tree might have the same depth. These sections have 2631 // to be searched more carefully. 2632 2633 // Scan up all the n1's with equal depth, looking for n2. 2634 _dom_lca_tags.map(n1->_idx, tag); 2635 Node *t1 = idom(n1); 2636 while (dom_depth(t1) == d1) { 2637 if (t1 == n2) return n2; 2638 _dom_lca_tags.map(t1->_idx, tag); 2639 t1 = idom(t1); 2640 } 2641 // Scan up all the n2's with equal depth, looking for n1. 2642 _dom_lca_tags.map(n2->_idx, tag); 2643 Node *t2 = idom(n2); 2644 while (dom_depth(t2) == d2) { 2645 if (t2 == n1) return n1; 2646 _dom_lca_tags.map(t2->_idx, tag); 2647 t2 = idom(t2); 2648 } 2649 // Move up to a new dominator-depth value as well as up the dom-tree. 2650 n1 = t1; 2651 n2 = t2; 2652 d1 = dom_depth(n1); 2653 d2 = dom_depth(n2); 2654 } 2655 } while (n1 != n2); 2656 return n1; 2657 } 2658 2659 //------------------------------init_dom_lca_tags------------------------------ 2660 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 2661 // Intended use does not involve any growth for the array, so it could 2662 // be of fixed size. 2663 void PhaseIdealLoop::init_dom_lca_tags() { 2664 uint limit = C->unique() + 1; 2665 _dom_lca_tags.map( limit, NULL ); 2666 #ifdef ASSERT 2667 for( uint i = 0; i < limit; ++i ) { 2668 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 2669 } 2670 #endif // ASSERT 2671 } 2672 2673 //------------------------------clear_dom_lca_tags------------------------------ 2674 // Tag could be a node's integer index, 32bits instead of 64bits in some cases 2675 // Intended use does not involve any growth for the array, so it could 2676 // be of fixed size. 2677 void PhaseIdealLoop::clear_dom_lca_tags() { 2678 uint limit = C->unique() + 1; 2679 _dom_lca_tags.map( limit, NULL ); 2680 _dom_lca_tags.clear(); 2681 #ifdef ASSERT 2682 for( uint i = 0; i < limit; ++i ) { 2683 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); 2684 } 2685 #endif // ASSERT 2686 } 2687 2688 //------------------------------build_loop_late-------------------------------- 2689 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2690 // Second pass finds latest legal placement, and ideal loop placement. 2691 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { 2692 while (worklist.size() != 0) { 2693 Node *n = worklist.pop(); 2694 // Only visit once 2695 if (visited.test_set(n->_idx)) continue; 2696 uint cnt = n->outcnt(); 2697 uint i = 0; 2698 while (true) { 2699 assert( _nodes[n->_idx], "no dead nodes" ); 2700 // Visit all children 2701 if (i < cnt) { 2702 Node* use = n->raw_out(i); 2703 ++i; 2704 // Check for dead uses. Aggressively prune such junk. It might be 2705 // dead in the global sense, but still have local uses so I cannot 2706 // easily call 'remove_dead_node'. 2707 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead? 2708 // Due to cycles, we might not hit the same fixed point in the verify 2709 // pass as we do in the regular pass. Instead, visit such phis as 2710 // simple uses of the loop head. 2711 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) { 2712 if( !visited.test(use->_idx) ) 2713 worklist.push(use); 2714 } else if( !visited.test_set(use->_idx) ) { 2715 nstack.push(n, i); // Save parent and next use's index. 2716 n = use; // Process all children of current use. 2717 cnt = use->outcnt(); 2718 i = 0; 2719 } 2720 } else { 2721 // Do not visit around the backedge of loops via data edges. 2722 // push dead code onto a worklist 2723 _deadlist.push(use); 2724 } 2725 } else { 2726 // All of n's children have been processed, complete post-processing. 2727 build_loop_late_post(n); 2728 if (nstack.is_empty()) { 2729 // Finished all nodes on stack. 2730 // Process next node on the worklist. 2731 break; 2732 } 2733 // Get saved parent node and next use's index. Visit the rest of uses. 2734 n = nstack.node(); 2735 cnt = n->outcnt(); 2736 i = nstack.index(); 2737 nstack.pop(); 2738 } 2739 } 2740 } 2741 } 2742 2743 //------------------------------build_loop_late_post--------------------------- 2744 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. 2745 // Second pass finds latest legal placement, and ideal loop placement. 2746 void PhaseIdealLoop::build_loop_late_post( Node *n ) { 2747 2748 if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) { 2749 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops. 2750 } 2751 2752 // CFG and pinned nodes already handled 2753 if( n->in(0) ) { 2754 if( n->in(0)->is_top() ) return; // Dead? 2755 2756 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads 2757 // _must_ be pinned (they have to observe their control edge of course). 2758 // Unlike Stores (which modify an unallocable resource, the memory 2759 // state), Mods/Loads can float around. So free them up. 2760 bool pinned = true; 2761 switch( n->Opcode() ) { 2762 case Op_DivI: 2763 case Op_DivF: 2764 case Op_DivD: 2765 case Op_ModI: 2766 case Op_ModF: 2767 case Op_ModD: 2768 case Op_LoadB: // Same with Loads; they can sink 2769 case Op_LoadUS: // during loop optimizations. 2770 case Op_LoadD: 2771 case Op_LoadF: 2772 case Op_LoadI: 2773 case Op_LoadKlass: 2774 case Op_LoadNKlass: 2775 case Op_LoadL: 2776 case Op_LoadS: 2777 case Op_LoadP: 2778 case Op_LoadN: 2779 case Op_LoadRange: 2780 case Op_LoadD_unaligned: 2781 case Op_LoadL_unaligned: 2782 case Op_StrComp: // Does a bunch of load-like effects 2783 case Op_StrEquals: 2784 case Op_StrIndexOf: 2785 case Op_AryEq: 2786 pinned = false; 2787 } 2788 if( pinned ) { 2789 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n)); 2790 if( !chosen_loop->_child ) // Inner loop? 2791 chosen_loop->_body.push(n); // Collect inner loops 2792 return; 2793 } 2794 } else { // No slot zero 2795 if( n->is_CFG() ) { // CFG with no slot 0 is dead 2796 _nodes.map(n->_idx,0); // No block setting, it's globally dead 2797 return; 2798 } 2799 assert(!n->is_CFG() || n->outcnt() == 0, ""); 2800 } 2801 2802 // Do I have a "safe range" I can select over? 2803 Node *early = get_ctrl(n);// Early location already computed 2804 2805 // Compute latest point this Node can go 2806 Node *LCA = get_late_ctrl( n, early ); 2807 // LCA is NULL due to uses being dead 2808 if( LCA == NULL ) { 2809 #ifdef ASSERT 2810 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) { 2811 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead"); 2812 } 2813 #endif 2814 _nodes.map(n->_idx, 0); // This node is useless 2815 _deadlist.push(n); 2816 return; 2817 } 2818 assert(LCA != NULL && !LCA->is_top(), "no dead nodes"); 2819 2820 Node *legal = LCA; // Walk 'legal' up the IDOM chain 2821 Node *least = legal; // Best legal position so far 2822 while( early != legal ) { // While not at earliest legal 2823 #ifdef ASSERT 2824 if (legal->is_Start() && !early->is_Root()) { 2825 // Bad graph. Print idom path and fail. 2826 tty->print_cr( "Bad graph detected in build_loop_late"); 2827 tty->print("n: ");n->dump(); tty->cr(); 2828 tty->print("early: ");early->dump(); tty->cr(); 2829 int ct = 0; 2830 Node *dbg_legal = LCA; 2831 while(!dbg_legal->is_Start() && ct < 100) { 2832 tty->print("idom[%d] ",ct); dbg_legal->dump(); tty->cr(); 2833 ct++; 2834 dbg_legal = idom(dbg_legal); 2835 } 2836 assert(false, "Bad graph detected in build_loop_late"); 2837 } 2838 #endif 2839 // Find least loop nesting depth 2840 legal = idom(legal); // Bump up the IDOM tree 2841 // Check for lower nesting depth 2842 if( get_loop(legal)->_nest < get_loop(least)->_nest ) 2843 least = legal; 2844 } 2845 assert(early == legal || legal != C->root(), "bad dominance of inputs"); 2846 2847 // Try not to place code on a loop entry projection 2848 // which can inhibit range check elimination. 2849 if (least != early) { 2850 Node* ctrl_out = least->unique_ctrl_out(); 2851 if (ctrl_out && ctrl_out->is_CountedLoop() && 2852 least == ctrl_out->in(LoopNode::EntryControl)) { 2853 Node* least_dom = idom(least); 2854 if (get_loop(least_dom)->is_member(get_loop(least))) { 2855 least = least_dom; 2856 } 2857 } 2858 } 2859 2860 #ifdef ASSERT 2861 // If verifying, verify that 'verify_me' has a legal location 2862 // and choose it as our location. 2863 if( _verify_me ) { 2864 Node *v_ctrl = _verify_me->get_ctrl_no_update(n); 2865 Node *legal = LCA; 2866 while( early != legal ) { // While not at earliest legal 2867 if( legal == v_ctrl ) break; // Check for prior good location 2868 legal = idom(legal) ;// Bump up the IDOM tree 2869 } 2870 // Check for prior good location 2871 if( legal == v_ctrl ) least = legal; // Keep prior if found 2872 } 2873 #endif 2874 2875 // Assign discovered "here or above" point 2876 least = find_non_split_ctrl(least); 2877 set_ctrl(n, least); 2878 2879 // Collect inner loop bodies 2880 IdealLoopTree *chosen_loop = get_loop(least); 2881 if( !chosen_loop->_child ) // Inner loop? 2882 chosen_loop->_body.push(n);// Collect inner loops 2883 } 2884 2885 #ifndef PRODUCT 2886 //------------------------------dump------------------------------------------- 2887 void PhaseIdealLoop::dump( ) const { 2888 ResourceMark rm; 2889 Arena* arena = Thread::current()->resource_area(); 2890 Node_Stack stack(arena, C->unique() >> 2); 2891 Node_List rpo_list; 2892 VectorSet visited(arena); 2893 visited.set(C->top()->_idx); 2894 rpo( C->root(), stack, visited, rpo_list ); 2895 // Dump root loop indexed by last element in PO order 2896 dump( _ltree_root, rpo_list.size(), rpo_list ); 2897 } 2898 2899 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const { 2900 loop->dump_head(); 2901 2902 // Now scan for CFG nodes in the same loop 2903 for( uint j=idx; j > 0; j-- ) { 2904 Node *n = rpo_list[j-1]; 2905 if( !_nodes[n->_idx] ) // Skip dead nodes 2906 continue; 2907 if( get_loop(n) != loop ) { // Wrong loop nest 2908 if( get_loop(n)->_head == n && // Found nested loop? 2909 get_loop(n)->_parent == loop ) 2910 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly 2911 continue; 2912 } 2913 2914 // Dump controlling node 2915 for( uint x = 0; x < loop->_nest; x++ ) 2916 tty->print(" "); 2917 tty->print("C"); 2918 if( n == C->root() ) { 2919 n->dump(); 2920 } else { 2921 Node* cached_idom = idom_no_update(n); 2922 Node *computed_idom = n->in(0); 2923 if( n->is_Region() ) { 2924 computed_idom = compute_idom(n); 2925 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or 2926 // any MultiBranch ctrl node), so apply a similar transform to 2927 // the cached idom returned from idom_no_update. 2928 cached_idom = find_non_split_ctrl(cached_idom); 2929 } 2930 tty->print(" ID:%d",computed_idom->_idx); 2931 n->dump(); 2932 if( cached_idom != computed_idom ) { 2933 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d", 2934 computed_idom->_idx, cached_idom->_idx); 2935 } 2936 } 2937 // Dump nodes it controls 2938 for( uint k = 0; k < _nodes.Size(); k++ ) { 2939 // (k < C->unique() && get_ctrl(find(k)) == n) 2940 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) { 2941 Node *m = C->root()->find(k); 2942 if( m && m->outcnt() > 0 ) { 2943 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) { 2944 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p", 2945 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL); 2946 } 2947 for( uint j = 0; j < loop->_nest; j++ ) 2948 tty->print(" "); 2949 tty->print(" "); 2950 m->dump(); 2951 } 2952 } 2953 } 2954 } 2955 } 2956 2957 // Collect a R-P-O for the whole CFG. 2958 // Result list is in post-order (scan backwards for RPO) 2959 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const { 2960 stk.push(start, 0); 2961 visited.set(start->_idx); 2962 2963 while (stk.is_nonempty()) { 2964 Node* m = stk.node(); 2965 uint idx = stk.index(); 2966 if (idx < m->outcnt()) { 2967 stk.set_index(idx + 1); 2968 Node* n = m->raw_out(idx); 2969 if (n->is_CFG() && !visited.test_set(n->_idx)) { 2970 stk.push(n, 0); 2971 } 2972 } else { 2973 rpo_list.push(m); 2974 stk.pop(); 2975 } 2976 } 2977 } 2978 #endif 2979 2980 2981 //============================================================================= 2982 //------------------------------LoopTreeIterator----------------------------------- 2983 2984 // Advance to next loop tree using a preorder, left-to-right traversal. 2985 void LoopTreeIterator::next() { 2986 assert(!done(), "must not be done."); 2987 if (_curnt->_child != NULL) { 2988 _curnt = _curnt->_child; 2989 } else if (_curnt->_next != NULL) { 2990 _curnt = _curnt->_next; 2991 } else { 2992 while (_curnt != _root && _curnt->_next == NULL) { 2993 _curnt = _curnt->_parent; 2994 } 2995 if (_curnt == _root) { 2996 _curnt = NULL; 2997 assert(done(), "must be done."); 2998 } else { 2999 assert(_curnt->_next != NULL, "must be more to do"); 3000 _curnt = _curnt->_next; 3001 } 3002 } 3003 }