1 /* 2 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "compiler/compileLog.hpp" 27 #include "memory/allocation.inline.hpp" 28 #include "opto/addnode.hpp" 29 #include "opto/callnode.hpp" 30 #include "opto/connode.hpp" 31 #include "opto/divnode.hpp" 32 #include "opto/loopnode.hpp" 33 #include "opto/mulnode.hpp" 34 #include "opto/rootnode.hpp" 35 #include "opto/runtime.hpp" 36 #include "opto/subnode.hpp" 37 38 //------------------------------is_loop_exit----------------------------------- 39 // Given an IfNode, return the loop-exiting projection or NULL if both 40 // arms remain in the loop. 41 Node *IdealLoopTree::is_loop_exit(Node *iff) const { 42 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests 43 PhaseIdealLoop *phase = _phase; 44 // Test is an IfNode, has 2 projections. If BOTH are in the loop 45 // we need loop unswitching instead of peeling. 46 if( !is_member(phase->get_loop( iff->raw_out(0) )) ) 47 return iff->raw_out(0); 48 if( !is_member(phase->get_loop( iff->raw_out(1) )) ) 49 return iff->raw_out(1); 50 return NULL; 51 } 52 53 54 //============================================================================= 55 56 57 //------------------------------record_for_igvn---------------------------- 58 // Put loop body on igvn work list 59 void IdealLoopTree::record_for_igvn() { 60 for( uint i = 0; i < _body.size(); i++ ) { 61 Node *n = _body.at(i); 62 _phase->_igvn._worklist.push(n); 63 } 64 } 65 66 //------------------------------compute_exact_trip_count----------------------- 67 // Compute loop exact trip count if possible. Do not recalculate trip count for 68 // split loops (pre-main-post) which have their limits and inits behind Opaque node. 69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) { 70 if (!_head->as_Loop()->is_valid_counted_loop()) { 71 return; 72 } 73 CountedLoopNode* cl = _head->as_CountedLoop(); 74 // Trip count may become nonexact for iteration split loops since 75 // RCE modifies limits. Note, _trip_count value is not reset since 76 // it is used to limit unrolling of main loop. 77 cl->set_nonexact_trip_count(); 78 79 // Loop's test should be part of loop. 80 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 81 return; // Infinite loop 82 83 #ifdef ASSERT 84 BoolTest::mask bt = cl->loopexit()->test_trip(); 85 assert(bt == BoolTest::lt || bt == BoolTest::gt || 86 bt == BoolTest::ne, "canonical test is expected"); 87 #endif 88 89 Node* init_n = cl->init_trip(); 90 Node* limit_n = cl->limit(); 91 if (init_n != NULL && init_n->is_Con() && 92 limit_n != NULL && limit_n->is_Con()) { 93 // Use longs to avoid integer overflow. 94 int stride_con = cl->stride_con(); 95 long init_con = cl->init_trip()->get_int(); 96 long limit_con = cl->limit()->get_int(); 97 int stride_m = stride_con - (stride_con > 0 ? 1 : -1); 98 long trip_count = (limit_con - init_con + stride_m)/stride_con; 99 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) { 100 // Set exact trip count. 101 cl->set_exact_trip_count((uint)trip_count); 102 } 103 } 104 } 105 106 //------------------------------compute_profile_trip_cnt---------------------------- 107 // Compute loop trip count from profile data as 108 // (backedge_count + loop_exit_count) / loop_exit_count 109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) { 110 if (!_head->is_CountedLoop()) { 111 return; 112 } 113 CountedLoopNode* head = _head->as_CountedLoop(); 114 if (head->profile_trip_cnt() != COUNT_UNKNOWN) { 115 return; // Already computed 116 } 117 float trip_cnt = (float)max_jint; // default is big 118 119 Node* back = head->in(LoopNode::LoopBackControl); 120 while (back != head) { 121 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 122 back->in(0) && 123 back->in(0)->is_If() && 124 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN && 125 back->in(0)->as_If()->_prob != PROB_UNKNOWN) { 126 break; 127 } 128 back = phase->idom(back); 129 } 130 if (back != head) { 131 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 132 back->in(0), "if-projection exists"); 133 IfNode* back_if = back->in(0)->as_If(); 134 float loop_back_cnt = back_if->_fcnt * back_if->_prob; 135 136 // Now compute a loop exit count 137 float loop_exit_cnt = 0.0f; 138 for( uint i = 0; i < _body.size(); i++ ) { 139 Node *n = _body[i]; 140 if( n->is_If() ) { 141 IfNode *iff = n->as_If(); 142 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) { 143 Node *exit = is_loop_exit(iff); 144 if( exit ) { 145 float exit_prob = iff->_prob; 146 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob; 147 if (exit_prob > PROB_MIN) { 148 float exit_cnt = iff->_fcnt * exit_prob; 149 loop_exit_cnt += exit_cnt; 150 } 151 } 152 } 153 } 154 } 155 if (loop_exit_cnt > 0.0f) { 156 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt; 157 } else { 158 // No exit count so use 159 trip_cnt = loop_back_cnt; 160 } 161 } 162 #ifndef PRODUCT 163 if (TraceProfileTripCount) { 164 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt); 165 } 166 #endif 167 head->set_profile_trip_cnt(trip_cnt); 168 } 169 170 //---------------------is_invariant_addition----------------------------- 171 // Return nonzero index of invariant operand for an Add or Sub 172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants. 173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) { 174 int op = n->Opcode(); 175 if (op == Op_AddI || op == Op_SubI) { 176 bool in1_invar = this->is_invariant(n->in(1)); 177 bool in2_invar = this->is_invariant(n->in(2)); 178 if (in1_invar && !in2_invar) return 1; 179 if (!in1_invar && in2_invar) return 2; 180 } 181 return 0; 182 } 183 184 //---------------------reassociate_add_sub----------------------------- 185 // Reassociate invariant add and subtract expressions: 186 // 187 // inv1 + (x + inv2) => ( inv1 + inv2) + x 188 // (x + inv2) + inv1 => ( inv1 + inv2) + x 189 // inv1 + (x - inv2) => ( inv1 - inv2) + x 190 // inv1 - (inv2 - x) => ( inv1 - inv2) + x 191 // (x + inv2) - inv1 => (-inv1 + inv2) + x 192 // (x - inv2) + inv1 => ( inv1 - inv2) + x 193 // (x - inv2) - inv1 => (-inv1 - inv2) + x 194 // inv1 + (inv2 - x) => ( inv1 + inv2) - x 195 // inv1 - (x - inv2) => ( inv1 + inv2) - x 196 // (inv2 - x) + inv1 => ( inv1 + inv2) - x 197 // (inv2 - x) - inv1 => (-inv1 + inv2) - x 198 // inv1 - (x + inv2) => ( inv1 - inv2) - x 199 // 200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) { 201 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL; 202 if (is_invariant(n1)) return NULL; 203 int inv1_idx = is_invariant_addition(n1, phase); 204 if (!inv1_idx) return NULL; 205 // Don't mess with add of constant (igvn moves them to expression tree root.) 206 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL; 207 Node* inv1 = n1->in(inv1_idx); 208 Node* n2 = n1->in(3 - inv1_idx); 209 int inv2_idx = is_invariant_addition(n2, phase); 210 if (!inv2_idx) return NULL; 211 Node* x = n2->in(3 - inv2_idx); 212 Node* inv2 = n2->in(inv2_idx); 213 214 bool neg_x = n2->is_Sub() && inv2_idx == 1; 215 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2; 216 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2; 217 if (n1->is_Sub() && inv1_idx == 1) { 218 neg_x = !neg_x; 219 neg_inv2 = !neg_inv2; 220 } 221 Node* inv1_c = phase->get_ctrl(inv1); 222 Node* inv2_c = phase->get_ctrl(inv2); 223 Node* n_inv1; 224 if (neg_inv1) { 225 Node *zero = phase->_igvn.intcon(0); 226 phase->set_ctrl(zero, phase->C->root()); 227 n_inv1 = new (phase->C, 3) SubINode(zero, inv1); 228 phase->register_new_node(n_inv1, inv1_c); 229 } else { 230 n_inv1 = inv1; 231 } 232 Node* inv; 233 if (neg_inv2) { 234 inv = new (phase->C, 3) SubINode(n_inv1, inv2); 235 } else { 236 inv = new (phase->C, 3) AddINode(n_inv1, inv2); 237 } 238 phase->register_new_node(inv, phase->get_early_ctrl(inv)); 239 240 Node* addx; 241 if (neg_x) { 242 addx = new (phase->C, 3) SubINode(inv, x); 243 } else { 244 addx = new (phase->C, 3) AddINode(x, inv); 245 } 246 phase->register_new_node(addx, phase->get_ctrl(x)); 247 phase->_igvn.replace_node(n1, addx); 248 assert(phase->get_loop(phase->get_ctrl(n1)) == this, ""); 249 _body.yank(n1); 250 return addx; 251 } 252 253 //---------------------reassociate_invariants----------------------------- 254 // Reassociate invariant expressions: 255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { 256 for (int i = _body.size() - 1; i >= 0; i--) { 257 Node *n = _body.at(i); 258 for (int j = 0; j < 5; j++) { 259 Node* nn = reassociate_add_sub(n, phase); 260 if (nn == NULL) break; 261 n = nn; // again 262 }; 263 } 264 } 265 266 //------------------------------policy_peeling--------------------------------- 267 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can 268 // make some loop-invariant test (usually a null-check) happen before the loop. 269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const { 270 Node *test = ((IdealLoopTree*)this)->tail(); 271 int body_size = ((IdealLoopTree*)this)->_body.size(); 272 int uniq = phase->C->unique(); 273 // Peeling does loop cloning which can result in O(N^2) node construction 274 if( body_size > 255 /* Prevent overflow for large body_size */ 275 || (body_size * body_size + uniq > MaxNodeLimit) ) { 276 return false; // too large to safely clone 277 } 278 while( test != _head ) { // Scan till run off top of loop 279 if( test->is_If() ) { // Test? 280 Node *ctrl = phase->get_ctrl(test->in(1)); 281 if (ctrl->is_top()) 282 return false; // Found dead test on live IF? No peeling! 283 // Standard IF only has one input value to check for loop invariance 284 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added"); 285 // Condition is not a member of this loop? 286 if( !is_member(phase->get_loop(ctrl)) && 287 is_loop_exit(test) ) 288 return true; // Found reason to peel! 289 } 290 // Walk up dominators to loop _head looking for test which is 291 // executed on every path thru loop. 292 test = phase->idom(test); 293 } 294 return false; 295 } 296 297 //------------------------------peeled_dom_test_elim--------------------------- 298 // If we got the effect of peeling, either by actually peeling or by making 299 // a pre-loop which must execute at least once, we can remove all 300 // loop-invariant dominated tests in the main body. 301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) { 302 bool progress = true; 303 while( progress ) { 304 progress = false; // Reset for next iteration 305 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail(); 306 Node *test = prev->in(0); 307 while( test != loop->_head ) { // Scan till run off top of loop 308 309 int p_op = prev->Opcode(); 310 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) && 311 test->is_If() && // Test? 312 !test->in(1)->is_Con() && // And not already obvious? 313 // Condition is not a member of this loop? 314 !loop->is_member(get_loop(get_ctrl(test->in(1))))){ 315 // Walk loop body looking for instances of this test 316 for( uint i = 0; i < loop->_body.size(); i++ ) { 317 Node *n = loop->_body.at(i); 318 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) { 319 // IfNode was dominated by version in peeled loop body 320 progress = true; 321 dominated_by( old_new[prev->_idx], n ); 322 } 323 } 324 } 325 prev = test; 326 test = idom(test); 327 } // End of scan tests in loop 328 329 } // End of while( progress ) 330 } 331 332 //------------------------------do_peeling------------------------------------- 333 // Peel the first iteration of the given loop. 334 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 335 // The pre-loop illegally has 2 control users (old & new loops). 336 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 337 // Do this by making the old-loop fall-in edges act as if they came 338 // around the loopback from the prior iteration (follow the old-loop 339 // backedges) and then map to the new peeled iteration. This leaves 340 // the pre-loop with only 1 user (the new peeled iteration), but the 341 // peeled-loop backedge has 2 users. 342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 343 // extra backedge user. 344 // 345 // orig 346 // 347 // stmt1 348 // | 349 // v 350 // loop predicate 351 // | 352 // v 353 // loop<----+ 354 // | | 355 // stmt2 | 356 // | | 357 // v | 358 // if ^ 359 // / \ | 360 // / \ | 361 // v v | 362 // false true | 363 // / \ | 364 // / ----+ 365 // | 366 // v 367 // exit 368 // 369 // 370 // after clone loop 371 // 372 // stmt1 373 // | 374 // v 375 // loop predicate 376 // / \ 377 // clone / \ orig 378 // / \ 379 // / \ 380 // v v 381 // +---->loop clone loop<----+ 382 // | | | | 383 // | stmt2 clone stmt2 | 384 // | | | | 385 // | v v | 386 // ^ if clone If ^ 387 // | / \ / \ | 388 // | / \ / \ | 389 // | v v v v | 390 // | true false false true | 391 // | / \ / \ | 392 // +---- \ / ----+ 393 // \ / 394 // 1v v2 395 // region 396 // | 397 // v 398 // exit 399 // 400 // 401 // after peel and predicate move 402 // 403 // stmt1 404 // / 405 // / 406 // clone / orig 407 // / 408 // / +----------+ 409 // / | | 410 // / loop predicate | 411 // / | | 412 // v v | 413 // TOP-->loop clone loop<----+ | 414 // | | | | 415 // stmt2 clone stmt2 | | 416 // | | | ^ 417 // v v | | 418 // if clone If ^ | 419 // / \ / \ | | 420 // / \ / \ | | 421 // v v v v | | 422 // true false false true | | 423 // | \ / \ | | 424 // | \ / ----+ ^ 425 // | \ / | 426 // | 1v v2 | 427 // v region | 428 // | | | 429 // | v | 430 // | exit | 431 // | | 432 // +--------------->-----------------+ 433 // 434 // 435 // final graph 436 // 437 // stmt1 438 // | 439 // v 440 // stmt2 clone 441 // | 442 // v 443 // if clone 444 // / | 445 // / | 446 // v v 447 // false true 448 // | | 449 // | v 450 // | loop predicate 451 // | | 452 // | v 453 // | loop<----+ 454 // | | | 455 // | stmt2 | 456 // | | | 457 // | v | 458 // v if ^ 459 // | / \ | 460 // | / \ | 461 // | v v | 462 // | false true | 463 // | | \ | 464 // v v --+ 465 // region 466 // | 467 // v 468 // exit 469 // 470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) { 471 472 C->set_major_progress(); 473 // Peeling a 'main' loop in a pre/main/post situation obfuscates the 474 // 'pre' loop from the main and the 'pre' can no longer have it's 475 // iterations adjusted. Therefore, we need to declare this loop as 476 // no longer a 'main' loop; it will need new pre and post loops before 477 // we can do further RCE. 478 #ifndef PRODUCT 479 if (TraceLoopOpts) { 480 tty->print("Peel "); 481 loop->dump_head(); 482 } 483 #endif 484 Node* head = loop->_head; 485 bool counted_loop = head->is_CountedLoop(); 486 if (counted_loop) { 487 CountedLoopNode *cl = head->as_CountedLoop(); 488 assert(cl->trip_count() > 0, "peeling a fully unrolled loop"); 489 cl->set_trip_count(cl->trip_count() - 1); 490 if (cl->is_main_loop()) { 491 cl->set_normal_loop(); 492 #ifndef PRODUCT 493 if (PrintOpto && VerifyLoopOptimizations) { 494 tty->print("Peeling a 'main' loop; resetting to 'normal' "); 495 loop->dump_head(); 496 } 497 #endif 498 } 499 } 500 Node* entry = head->in(LoopNode::EntryControl); 501 502 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 503 // The pre-loop illegally has 2 control users (old & new loops). 504 clone_loop( loop, old_new, dom_depth(head) ); 505 506 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 507 // Do this by making the old-loop fall-in edges act as if they came 508 // around the loopback from the prior iteration (follow the old-loop 509 // backedges) and then map to the new peeled iteration. This leaves 510 // the pre-loop with only 1 user (the new peeled iteration), but the 511 // peeled-loop backedge has 2 users. 512 Node* new_exit_value = old_new[head->in(LoopNode::LoopBackControl)->_idx]; 513 new_exit_value = move_loop_predicates(entry, new_exit_value, !counted_loop); 514 _igvn.hash_delete(head); 515 head->set_req(LoopNode::EntryControl, new_exit_value); 516 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) { 517 Node* old = head->fast_out(j); 518 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) { 519 new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; 520 if (!new_exit_value ) // Backedge value is ALSO loop invariant? 521 // Then loop body backedge value remains the same. 522 new_exit_value = old->in(LoopNode::LoopBackControl); 523 _igvn.hash_delete(old); 524 old->set_req(LoopNode::EntryControl, new_exit_value); 525 } 526 } 527 528 529 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 530 // extra backedge user. 531 Node* new_head = old_new[head->_idx]; 532 _igvn.hash_delete(new_head); 533 new_head->set_req(LoopNode::LoopBackControl, C->top()); 534 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) { 535 Node* use = new_head->fast_out(j2); 536 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) { 537 _igvn.hash_delete(use); 538 use->set_req(LoopNode::LoopBackControl, C->top()); 539 } 540 } 541 542 543 // Step 4: Correct dom-depth info. Set to loop-head depth. 544 int dd = dom_depth(head); 545 set_idom(head, head->in(1), dd); 546 for (uint j3 = 0; j3 < loop->_body.size(); j3++) { 547 Node *old = loop->_body.at(j3); 548 Node *nnn = old_new[old->_idx]; 549 if (!has_ctrl(nnn)) 550 set_idom(nnn, idom(nnn), dd-1); 551 // While we're at it, remove any SafePoints from the peeled code 552 if (old->Opcode() == Op_SafePoint) { 553 Node *nnn = old_new[old->_idx]; 554 lazy_replace(nnn,nnn->in(TypeFunc::Control)); 555 } 556 } 557 558 // Now force out all loop-invariant dominating tests. The optimizer 559 // finds some, but we _know_ they are all useless. 560 peeled_dom_test_elim(loop,old_new); 561 562 loop->record_for_igvn(); 563 } 564 565 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop 566 567 //------------------------------policy_maximally_unroll------------------------ 568 // Calculate exact loop trip count and return true if loop can be maximally 569 // unrolled. 570 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const { 571 CountedLoopNode *cl = _head->as_CountedLoop(); 572 assert(cl->is_normal_loop(), ""); 573 if (!cl->is_valid_counted_loop()) 574 return false; // Malformed counted loop 575 576 if (!cl->has_exact_trip_count()) { 577 // Trip count is not exact. 578 return false; 579 } 580 581 uint trip_count = cl->trip_count(); 582 // Note, max_juint is used to indicate unknown trip count. 583 assert(trip_count > 1, "one iteration loop should be optimized out already"); 584 assert(trip_count < max_juint, "exact trip_count should be less than max_uint."); 585 586 // Real policy: if we maximally unroll, does it get too big? 587 // Allow the unrolled mess to get larger than standard loop 588 // size. After all, it will no longer be a loop. 589 uint body_size = _body.size(); 590 uint unroll_limit = (uint)LoopUnrollLimit * 4; 591 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); 592 if (trip_count > unroll_limit || body_size > unroll_limit) { 593 return false; 594 } 595 596 // Fully unroll a loop with few iterations regardless next 597 // conditions since following loop optimizations will split 598 // such loop anyway (pre-main-post). 599 if (trip_count <= 3) 600 return true; 601 602 // Take into account that after unroll conjoined heads and tails will fold, 603 // otherwise policy_unroll() may allow more unrolling than max unrolling. 604 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count; 605 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE; 606 if (body_size != tst_body_size) // Check for int overflow 607 return false; 608 if (new_body_size > unroll_limit || 609 // Unrolling can result in a large amount of node construction 610 new_body_size >= MaxNodeLimit - phase->C->unique()) { 611 return false; 612 } 613 614 // Do not unroll a loop with String intrinsics code. 615 // String intrinsics are large and have loops. 616 for (uint k = 0; k < _body.size(); k++) { 617 Node* n = _body.at(k); 618 switch (n->Opcode()) { 619 case Op_StrComp: 620 case Op_StrEquals: 621 case Op_StrIndexOf: 622 case Op_AryEq: { 623 return false; 624 } 625 } // switch 626 } 627 628 return true; // Do maximally unroll 629 } 630 631 632 #define MAX_UNROLL 16 // maximum number of unrolls for main loop 633 634 //------------------------------policy_unroll---------------------------------- 635 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if 636 // the loop is a CountedLoop and the body is small enough. 637 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const { 638 639 CountedLoopNode *cl = _head->as_CountedLoop(); 640 assert(cl->is_normal_loop() || cl->is_main_loop(), ""); 641 642 if (!cl->is_valid_counted_loop()) 643 return false; // Malformed counted loop 644 645 // Protect against over-unrolling. 646 // After split at least one iteration will be executed in pre-loop. 647 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false; 648 649 int future_unroll_ct = cl->unrolled_count() * 2; 650 if (future_unroll_ct > MAX_UNROLL) return false; 651 652 // Check for initial stride being a small enough constant 653 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false; 654 655 // Don't unroll if the next round of unrolling would push us 656 // over the expected trip count of the loop. One is subtracted 657 // from the expected trip count because the pre-loop normally 658 // executes 1 iteration. 659 if (UnrollLimitForProfileCheck > 0 && 660 cl->profile_trip_cnt() != COUNT_UNKNOWN && 661 future_unroll_ct > UnrollLimitForProfileCheck && 662 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) { 663 return false; 664 } 665 666 // When unroll count is greater than LoopUnrollMin, don't unroll if: 667 // the residual iterations are more than 10% of the trip count 668 // and rounds of "unroll,optimize" are not making significant progress 669 // Progress defined as current size less than 20% larger than previous size. 670 if (UseSuperWord && cl->node_count_before_unroll() > 0 && 671 future_unroll_ct > LoopUnrollMin && 672 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() && 673 1.2 * cl->node_count_before_unroll() < (double)_body.size()) { 674 return false; 675 } 676 677 Node *init_n = cl->init_trip(); 678 Node *limit_n = cl->limit(); 679 int stride_con = cl->stride_con(); 680 // Non-constant bounds. 681 // Protect against over-unrolling when init or/and limit are not constant 682 // (so that trip_count's init value is maxint) but iv range is known. 683 if (init_n == NULL || !init_n->is_Con() || 684 limit_n == NULL || !limit_n->is_Con()) { 685 Node* phi = cl->phi(); 686 if (phi != NULL) { 687 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); 688 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); 689 int next_stride = stride_con * 2; // stride after this unroll 690 if (next_stride > 0) { 691 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow 692 iv_type->_lo + next_stride > iv_type->_hi) { 693 return false; // over-unrolling 694 } 695 } else if (next_stride < 0) { 696 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow 697 iv_type->_hi + next_stride < iv_type->_lo) { 698 return false; // over-unrolling 699 } 700 } 701 } 702 } 703 704 // After unroll limit will be adjusted: new_limit = limit-stride. 705 // Bailout if adjustment overflow. 706 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int(); 707 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) || 708 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo)) 709 return false; // overflow 710 711 // Adjust body_size to determine if we unroll or not 712 uint body_size = _body.size(); 713 // Also count ModL, DivL and MulL which expand mightly 714 for (uint k = 0; k < _body.size(); k++) { 715 Node* n = _body.at(k); 716 switch (n->Opcode()) { 717 case Op_ModL: body_size += 30; break; 718 case Op_DivL: body_size += 30; break; 719 case Op_MulL: body_size += 10; break; 720 case Op_StrComp: 721 case Op_StrEquals: 722 case Op_StrIndexOf: 723 case Op_AryEq: { 724 // Do not unroll a loop with String intrinsics code. 725 // String intrinsics are large and have loops. 726 return false; 727 } 728 } // switch 729 } 730 731 // Check for being too big 732 if (body_size > (uint)LoopUnrollLimit) { 733 // Normal case: loop too big 734 return false; 735 } 736 737 // Unroll once! (Each trip will soon do double iterations) 738 return true; 739 } 740 741 //------------------------------policy_align----------------------------------- 742 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the 743 // expression that does the alignment. Note that only one array base can be 744 // aligned in a loop (unless the VM guarantees mutual alignment). Note that 745 // if we vectorize short memory ops into longer memory ops, we may want to 746 // increase alignment. 747 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const { 748 return false; 749 } 750 751 //------------------------------policy_range_check----------------------------- 752 // Return TRUE or FALSE if the loop should be range-check-eliminated. 753 // Actually we do iteration-splitting, a more powerful form of RCE. 754 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const { 755 if (!RangeCheckElimination) return false; 756 757 CountedLoopNode *cl = _head->as_CountedLoop(); 758 // If we unrolled with no intention of doing RCE and we later 759 // changed our minds, we got no pre-loop. Either we need to 760 // make a new pre-loop, or we gotta disallow RCE. 761 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now. 762 Node *trip_counter = cl->phi(); 763 764 // Check loop body for tests of trip-counter plus loop-invariant vs 765 // loop-invariant. 766 for (uint i = 0; i < _body.size(); i++) { 767 Node *iff = _body[i]; 768 if (iff->Opcode() == Op_If) { // Test? 769 770 // Comparing trip+off vs limit 771 Node *bol = iff->in(1); 772 if (bol->req() != 2) continue; // dead constant test 773 if (!bol->is_Bool()) { 774 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only"); 775 continue; 776 } 777 if (bol->as_Bool()->_test._test == BoolTest::ne) 778 continue; // not RC 779 780 Node *cmp = bol->in(1); 781 782 Node *rc_exp = cmp->in(1); 783 Node *limit = cmp->in(2); 784 785 Node *limit_c = phase->get_ctrl(limit); 786 if( limit_c == phase->C->top() ) 787 return false; // Found dead test on live IF? No RCE! 788 if( is_member(phase->get_loop(limit_c) ) ) { 789 // Compare might have operands swapped; commute them 790 rc_exp = cmp->in(2); 791 limit = cmp->in(1); 792 limit_c = phase->get_ctrl(limit); 793 if( is_member(phase->get_loop(limit_c) ) ) 794 continue; // Both inputs are loop varying; cannot RCE 795 } 796 797 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) { 798 continue; 799 } 800 // Yeah! Found a test like 'trip+off vs limit' 801 // Test is an IfNode, has 2 projections. If BOTH are in the loop 802 // we need loop unswitching instead of iteration splitting. 803 if( is_loop_exit(iff) ) 804 return true; // Found reason to split iterations 805 } // End of is IF 806 } 807 808 return false; 809 } 810 811 //------------------------------policy_peel_only------------------------------- 812 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful 813 // for unrolling loops with NO array accesses. 814 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const { 815 816 for( uint i = 0; i < _body.size(); i++ ) 817 if( _body[i]->is_Mem() ) 818 return false; 819 820 // No memory accesses at all! 821 return true; 822 } 823 824 //------------------------------clone_up_backedge_goo-------------------------- 825 // If Node n lives in the back_ctrl block and cannot float, we clone a private 826 // version of n in preheader_ctrl block and return that, otherwise return n. 827 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) { 828 if( get_ctrl(n) != back_ctrl ) return n; 829 830 // Only visit once 831 if (visited.test_set(n->_idx)) { 832 Node *x = clones.find(n->_idx); 833 if (x != NULL) 834 return x; 835 return n; 836 } 837 838 Node *x = NULL; // If required, a clone of 'n' 839 // Check for 'n' being pinned in the backedge. 840 if( n->in(0) && n->in(0) == back_ctrl ) { 841 assert(clones.find(n->_idx) == NULL, "dead loop"); 842 x = n->clone(); // Clone a copy of 'n' to preheader 843 clones.push(x, n->_idx); 844 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader 845 } 846 847 // Recursive fixup any other input edges into x. 848 // If there are no changes we can just return 'n', otherwise 849 // we need to clone a private copy and change it. 850 for( uint i = 1; i < n->req(); i++ ) { 851 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones ); 852 if( g != n->in(i) ) { 853 if( !x ) { 854 assert(clones.find(n->_idx) == NULL, "dead loop"); 855 x = n->clone(); 856 clones.push(x, n->_idx); 857 } 858 x->set_req(i, g); 859 } 860 } 861 if( x ) { // x can legally float to pre-header location 862 register_new_node( x, preheader_ctrl ); 863 return x; 864 } else { // raise n to cover LCA of uses 865 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); 866 } 867 return n; 868 } 869 870 //------------------------------insert_pre_post_loops-------------------------- 871 // Insert pre and post loops. If peel_only is set, the pre-loop can not have 872 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no 873 // alignment. Useful to unroll loops that do no array accesses. 874 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { 875 876 #ifndef PRODUCT 877 if (TraceLoopOpts) { 878 if (peel_only) 879 tty->print("PeelMainPost "); 880 else 881 tty->print("PreMainPost "); 882 loop->dump_head(); 883 } 884 #endif 885 C->set_major_progress(); 886 887 // Find common pieces of the loop being guarded with pre & post loops 888 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 889 assert( main_head->is_normal_loop(), "" ); 890 CountedLoopEndNode *main_end = main_head->loopexit(); 891 assert( main_end->outcnt() == 2, "1 true, 1 false path only" ); 892 uint dd_main_head = dom_depth(main_head); 893 uint max = main_head->outcnt(); 894 895 Node *pre_header= main_head->in(LoopNode::EntryControl); 896 Node *init = main_head->init_trip(); 897 Node *incr = main_end ->incr(); 898 Node *limit = main_end ->limit(); 899 Node *stride = main_end ->stride(); 900 Node *cmp = main_end ->cmp_node(); 901 BoolTest::mask b_test = main_end->test_trip(); 902 903 // Need only 1 user of 'bol' because I will be hacking the loop bounds. 904 Node *bol = main_end->in(CountedLoopEndNode::TestValue); 905 if( bol->outcnt() != 1 ) { 906 bol = bol->clone(); 907 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl)); 908 _igvn.hash_delete(main_end); 909 main_end->set_req(CountedLoopEndNode::TestValue, bol); 910 } 911 // Need only 1 user of 'cmp' because I will be hacking the loop bounds. 912 if( cmp->outcnt() != 1 ) { 913 cmp = cmp->clone(); 914 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl)); 915 _igvn.hash_delete(bol); 916 bol->set_req(1, cmp); 917 } 918 919 //------------------------------ 920 // Step A: Create Post-Loop. 921 Node* main_exit = main_end->proj_out(false); 922 assert( main_exit->Opcode() == Op_IfFalse, "" ); 923 int dd_main_exit = dom_depth(main_exit); 924 925 // Step A1: Clone the loop body. The clone becomes the post-loop. The main 926 // loop pre-header illegally has 2 control users (old & new loops). 927 clone_loop( loop, old_new, dd_main_exit ); 928 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" ); 929 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop(); 930 post_head->set_post_loop(main_head); 931 932 // Reduce the post-loop trip count. 933 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 934 post_end->_prob = PROB_FAIR; 935 936 // Build the main-loop normal exit. 937 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end); 938 _igvn.register_new_node_with_optimizer( new_main_exit ); 939 set_idom(new_main_exit, main_end, dd_main_exit ); 940 set_loop(new_main_exit, loop->_parent); 941 942 // Step A2: Build a zero-trip guard for the post-loop. After leaving the 943 // main-loop, the post-loop may not execute at all. We 'opaque' the incr 944 // (the main-loop trip-counter exit value) because we will be changing 945 // the exit value (via unrolling) so we cannot constant-fold away the zero 946 // trip guard until all unrolling is done. 947 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr); 948 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit ); 949 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test ); 950 register_new_node( zer_opaq, new_main_exit ); 951 register_new_node( zer_cmp , new_main_exit ); 952 register_new_node( zer_bol , new_main_exit ); 953 954 // Build the IfNode 955 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN ); 956 _igvn.register_new_node_with_optimizer( zer_iff ); 957 set_idom(zer_iff, new_main_exit, dd_main_exit); 958 set_loop(zer_iff, loop->_parent); 959 960 // Plug in the false-path, taken if we need to skip post-loop 961 _igvn.hash_delete( main_exit ); 962 main_exit->set_req(0, zer_iff); 963 _igvn._worklist.push(main_exit); 964 set_idom(main_exit, zer_iff, dd_main_exit); 965 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit); 966 // Make the true-path, must enter the post loop 967 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff ); 968 _igvn.register_new_node_with_optimizer( zer_taken ); 969 set_idom(zer_taken, zer_iff, dd_main_exit); 970 set_loop(zer_taken, loop->_parent); 971 // Plug in the true path 972 _igvn.hash_delete( post_head ); 973 post_head->set_req(LoopNode::EntryControl, zer_taken); 974 set_idom(post_head, zer_taken, dd_main_exit); 975 976 Arena *a = Thread::current()->resource_area(); 977 VectorSet visited(a); 978 Node_Stack clones(a, main_head->back_control()->outcnt()); 979 // Step A3: Make the fall-in values to the post-loop come from the 980 // fall-out values of the main-loop. 981 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) { 982 Node* main_phi = main_head->fast_out(i); 983 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) { 984 Node *post_phi = old_new[main_phi->_idx]; 985 Node *fallmain = clone_up_backedge_goo(main_head->back_control(), 986 post_head->init_control(), 987 main_phi->in(LoopNode::LoopBackControl), 988 visited, clones); 989 _igvn.hash_delete(post_phi); 990 post_phi->set_req( LoopNode::EntryControl, fallmain ); 991 } 992 } 993 994 // Update local caches for next stanza 995 main_exit = new_main_exit; 996 997 998 //------------------------------ 999 // Step B: Create Pre-Loop. 1000 1001 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main 1002 // loop pre-header illegally has 2 control users (old & new loops). 1003 clone_loop( loop, old_new, dd_main_head ); 1004 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop(); 1005 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 1006 pre_head->set_pre_loop(main_head); 1007 Node *pre_incr = old_new[incr->_idx]; 1008 1009 // Reduce the pre-loop trip count. 1010 pre_end->_prob = PROB_FAIR; 1011 1012 // Find the pre-loop normal exit. 1013 Node* pre_exit = pre_end->proj_out(false); 1014 assert( pre_exit->Opcode() == Op_IfFalse, "" ); 1015 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end); 1016 _igvn.register_new_node_with_optimizer( new_pre_exit ); 1017 set_idom(new_pre_exit, pre_end, dd_main_head); 1018 set_loop(new_pre_exit, loop->_parent); 1019 1020 // Step B2: Build a zero-trip guard for the main-loop. After leaving the 1021 // pre-loop, the main-loop may not execute at all. Later in life this 1022 // zero-trip guard will become the minimum-trip guard when we unroll 1023 // the main-loop. 1024 Node *min_opaq = new (C, 2) Opaque1Node(C, limit); 1025 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq ); 1026 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test ); 1027 register_new_node( min_opaq, new_pre_exit ); 1028 register_new_node( min_cmp , new_pre_exit ); 1029 register_new_node( min_bol , new_pre_exit ); 1030 1031 // Build the IfNode (assume the main-loop is executed always). 1032 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN ); 1033 _igvn.register_new_node_with_optimizer( min_iff ); 1034 set_idom(min_iff, new_pre_exit, dd_main_head); 1035 set_loop(min_iff, loop->_parent); 1036 1037 // Plug in the false-path, taken if we need to skip main-loop 1038 _igvn.hash_delete( pre_exit ); 1039 pre_exit->set_req(0, min_iff); 1040 set_idom(pre_exit, min_iff, dd_main_head); 1041 set_idom(pre_exit->unique_out(), min_iff, dd_main_head); 1042 // Make the true-path, must enter the main loop 1043 Node *min_taken = new (C, 1) IfTrueNode( min_iff ); 1044 _igvn.register_new_node_with_optimizer( min_taken ); 1045 set_idom(min_taken, min_iff, dd_main_head); 1046 set_loop(min_taken, loop->_parent); 1047 // Plug in the true path 1048 _igvn.hash_delete( main_head ); 1049 main_head->set_req(LoopNode::EntryControl, min_taken); 1050 set_idom(main_head, min_taken, dd_main_head); 1051 1052 visited.Clear(); 1053 clones.clear(); 1054 // Step B3: Make the fall-in values to the main-loop come from the 1055 // fall-out values of the pre-loop. 1056 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) { 1057 Node* main_phi = main_head->fast_out(i2); 1058 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) { 1059 Node *pre_phi = old_new[main_phi->_idx]; 1060 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(), 1061 main_head->init_control(), 1062 pre_phi->in(LoopNode::LoopBackControl), 1063 visited, clones); 1064 _igvn.hash_delete(main_phi); 1065 main_phi->set_req( LoopNode::EntryControl, fallpre ); 1066 } 1067 } 1068 1069 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). 1070 // RCE and alignment may change this later. 1071 Node *cmp_end = pre_end->cmp_node(); 1072 assert( cmp_end->in(2) == limit, "" ); 1073 Node *pre_limit = new (C, 3) AddINode( init, stride ); 1074 1075 // Save the original loop limit in this Opaque1 node for 1076 // use by range check elimination. 1077 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit); 1078 1079 register_new_node( pre_limit, pre_head->in(0) ); 1080 register_new_node( pre_opaq , pre_head->in(0) ); 1081 1082 // Since no other users of pre-loop compare, I can hack limit directly 1083 assert( cmp_end->outcnt() == 1, "no other users" ); 1084 _igvn.hash_delete(cmp_end); 1085 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq); 1086 1087 // Special case for not-equal loop bounds: 1088 // Change pre loop test, main loop test, and the 1089 // main loop guard test to use lt or gt depending on stride 1090 // direction: 1091 // positive stride use < 1092 // negative stride use > 1093 // 1094 // not-equal test is kept for post loop to handle case 1095 // when init > limit when stride > 0 (and reverse). 1096 1097 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) { 1098 1099 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt; 1100 // Modify pre loop end condition 1101 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1102 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test); 1103 register_new_node( new_bol0, pre_head->in(0) ); 1104 _igvn.hash_delete(pre_end); 1105 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0); 1106 // Modify main loop guard condition 1107 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay"); 1108 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test); 1109 register_new_node( new_bol1, new_pre_exit ); 1110 _igvn.hash_delete(min_iff); 1111 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1); 1112 // Modify main loop end condition 1113 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1114 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test); 1115 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) ); 1116 _igvn.hash_delete(main_end); 1117 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2); 1118 } 1119 1120 // Flag main loop 1121 main_head->set_main_loop(); 1122 if( peel_only ) main_head->set_main_no_pre_loop(); 1123 1124 // Subtract a trip count for the pre-loop. 1125 main_head->set_trip_count(main_head->trip_count() - 1); 1126 1127 // It's difficult to be precise about the trip-counts 1128 // for the pre/post loops. They are usually very short, 1129 // so guess that 4 trips is a reasonable value. 1130 post_head->set_profile_trip_cnt(4.0); 1131 pre_head->set_profile_trip_cnt(4.0); 1132 1133 // Now force out all loop-invariant dominating tests. The optimizer 1134 // finds some, but we _know_ they are all useless. 1135 peeled_dom_test_elim(loop,old_new); 1136 } 1137 1138 //------------------------------is_invariant----------------------------- 1139 // Return true if n is invariant 1140 bool IdealLoopTree::is_invariant(Node* n) const { 1141 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n; 1142 if (n_c->is_top()) return false; 1143 return !is_member(_phase->get_loop(n_c)); 1144 } 1145 1146 1147 //------------------------------do_unroll-------------------------------------- 1148 // Unroll the loop body one step - make each trip do 2 iterations. 1149 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) { 1150 assert(LoopUnrollLimit, ""); 1151 CountedLoopNode *loop_head = loop->_head->as_CountedLoop(); 1152 CountedLoopEndNode *loop_end = loop_head->loopexit(); 1153 assert(loop_end, ""); 1154 #ifndef PRODUCT 1155 if (PrintOpto && VerifyLoopOptimizations) { 1156 tty->print("Unrolling "); 1157 loop->dump_head(); 1158 } else if (TraceLoopOpts) { 1159 if (loop_head->trip_count() < (uint)LoopUnrollLimit) { 1160 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count()); 1161 } else { 1162 tty->print("Unroll %d ", loop_head->unrolled_count()*2); 1163 } 1164 loop->dump_head(); 1165 } 1166 #endif 1167 1168 // Remember loop node count before unrolling to detect 1169 // if rounds of unroll,optimize are making progress 1170 loop_head->set_node_count_before_unroll(loop->_body.size()); 1171 1172 Node *ctrl = loop_head->in(LoopNode::EntryControl); 1173 Node *limit = loop_head->limit(); 1174 Node *init = loop_head->init_trip(); 1175 Node *stride = loop_head->stride(); 1176 1177 Node *opaq = NULL; 1178 if (adjust_min_trip) { // If not maximally unrolling, need adjustment 1179 // Search for zero-trip guard. 1180 assert( loop_head->is_main_loop(), "" ); 1181 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 1182 Node *iff = ctrl->in(0); 1183 assert( iff->Opcode() == Op_If, "" ); 1184 Node *bol = iff->in(1); 1185 assert( bol->Opcode() == Op_Bool, "" ); 1186 Node *cmp = bol->in(1); 1187 assert( cmp->Opcode() == Op_CmpI, "" ); 1188 opaq = cmp->in(2); 1189 // Occasionally it's possible for a zero-trip guard Opaque1 node to be 1190 // optimized away and then another round of loop opts attempted. 1191 // We can not optimize this particular loop in that case. 1192 if (opaq->Opcode() != Op_Opaque1) 1193 return; // Cannot find zero-trip guard! Bail out! 1194 // Zero-trip test uses an 'opaque' node which is not shared. 1195 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, ""); 1196 } 1197 1198 C->set_major_progress(); 1199 1200 Node* new_limit = NULL; 1201 if (UnrollLimitCheck) { 1202 int stride_con = stride->get_int(); 1203 int stride_p = (stride_con > 0) ? stride_con : -stride_con; 1204 uint old_trip_count = loop_head->trip_count(); 1205 // Verify that unroll policy result is still valid. 1206 assert(old_trip_count > 1 && 1207 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity"); 1208 1209 // Adjust loop limit to keep valid iterations number after unroll. 1210 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride 1211 // which may overflow. 1212 if (!adjust_min_trip) { 1213 assert(old_trip_count > 1 && (old_trip_count & 1) == 0, 1214 "odd trip count for maximally unroll"); 1215 // Don't need to adjust limit for maximally unroll since trip count is even. 1216 } else if (loop_head->has_exact_trip_count() && init->is_Con()) { 1217 // Loop's limit is constant. Loop's init could be constant when pre-loop 1218 // become peeled iteration. 1219 long init_con = init->get_int(); 1220 // We can keep old loop limit if iterations count stays the same: 1221 // old_trip_count == new_trip_count * 2 1222 // Note: since old_trip_count >= 2 then new_trip_count >= 1 1223 // so we also don't need to adjust zero trip test. 1224 long limit_con = limit->get_int(); 1225 // (stride_con*2) not overflow since stride_con <= 8. 1226 int new_stride_con = stride_con * 2; 1227 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1); 1228 long trip_count = (limit_con - init_con + stride_m)/new_stride_con; 1229 // New trip count should satisfy next conditions. 1230 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity"); 1231 uint new_trip_count = (uint)trip_count; 1232 adjust_min_trip = (old_trip_count != new_trip_count*2); 1233 } 1234 1235 if (adjust_min_trip) { 1236 // Step 2: Adjust the trip limit if it is called for. 1237 // The adjustment amount is -stride. Need to make sure if the 1238 // adjustment underflows or overflows, then the main loop is skipped. 1239 Node* cmp = loop_end->cmp_node(); 1240 assert(cmp->in(2) == limit, "sanity"); 1241 assert(opaq != NULL && opaq->in(1) == limit, "sanity"); 1242 1243 // Verify that policy_unroll result is still valid. 1244 const TypeInt* limit_type = _igvn.type(limit)->is_int(); 1245 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) || 1246 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity"); 1247 1248 if (limit->is_Con()) { 1249 // The check in policy_unroll and the assert above guarantee 1250 // no underflow if limit is constant. 1251 new_limit = _igvn.intcon(limit->get_int() - stride_con); 1252 set_ctrl(new_limit, C->root()); 1253 } else { 1254 // Limit is not constant. 1255 if (loop_head->unrolled_count() == 1) { // only for first unroll 1256 // Separate limit by Opaque node in case it is an incremented 1257 // variable from previous loop to avoid using pre-incremented 1258 // value which could increase register pressure. 1259 // Otherwise reorg_offsets() optimization will create a separate 1260 // Opaque node for each use of trip-counter and as result 1261 // zero trip guard limit will be different from loop limit. 1262 assert(has_ctrl(opaq), "should have it"); 1263 Node* opaq_ctrl = get_ctrl(opaq); 1264 limit = new (C, 2) Opaque2Node( C, limit ); 1265 register_new_node( limit, opaq_ctrl ); 1266 } 1267 if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) || 1268 stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) { 1269 // No underflow. 1270 new_limit = new (C, 3) SubINode(limit, stride); 1271 } else { 1272 // (limit - stride) may underflow. 1273 // Clamp the adjustment value with MININT or MAXINT: 1274 // 1275 // new_limit = limit-stride 1276 // if (stride > 0) 1277 // new_limit = (limit < new_limit) ? MININT : new_limit; 1278 // else 1279 // new_limit = (limit > new_limit) ? MAXINT : new_limit; 1280 // 1281 BoolTest::mask bt = loop_end->test_trip(); 1282 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected"); 1283 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint); 1284 set_ctrl(adj_max, C->root()); 1285 Node* old_limit = NULL; 1286 Node* adj_limit = NULL; 1287 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL; 1288 if (loop_head->unrolled_count() > 1 && 1289 limit->is_CMove() && limit->Opcode() == Op_CMoveI && 1290 limit->in(CMoveNode::IfTrue) == adj_max && 1291 bol->as_Bool()->_test._test == bt && 1292 bol->in(1)->Opcode() == Op_CmpI && 1293 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) { 1294 // Loop was unrolled before. 1295 // Optimize the limit to avoid nested CMove: 1296 // use original limit as old limit. 1297 old_limit = bol->in(1)->in(1); 1298 // Adjust previous adjusted limit. 1299 adj_limit = limit->in(CMoveNode::IfFalse); 1300 adj_limit = new (C, 3) SubINode(adj_limit, stride); 1301 } else { 1302 old_limit = limit; 1303 adj_limit = new (C, 3) SubINode(limit, stride); 1304 } 1305 assert(old_limit != NULL && adj_limit != NULL, ""); 1306 register_new_node( adj_limit, ctrl ); // adjust amount 1307 Node* adj_cmp = new (C, 3) CmpINode(old_limit, adj_limit); 1308 register_new_node( adj_cmp, ctrl ); 1309 Node* adj_bool = new (C, 2) BoolNode(adj_cmp, bt); 1310 register_new_node( adj_bool, ctrl ); 1311 new_limit = new (C, 4) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT); 1312 } 1313 register_new_node(new_limit, ctrl); 1314 } 1315 assert(new_limit != NULL, ""); 1316 // Replace in loop test. 1317 assert(loop_end->in(1)->in(1) == cmp, "sanity"); 1318 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) { 1319 // Don't need to create new test since only one user. 1320 _igvn.hash_delete(cmp); 1321 cmp->set_req(2, new_limit); 1322 } else { 1323 // Create new test since it is shared. 1324 Node* ctrl2 = loop_end->in(0); 1325 Node* cmp2 = cmp->clone(); 1326 cmp2->set_req(2, new_limit); 1327 register_new_node(cmp2, ctrl2); 1328 Node* bol2 = loop_end->in(1)->clone(); 1329 bol2->set_req(1, cmp2); 1330 register_new_node(bol2, ctrl2); 1331 _igvn.hash_delete(loop_end); 1332 loop_end->set_req(1, bol2); 1333 } 1334 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 1335 // Make it a 1-trip test (means at least 2 trips). 1336 1337 // Guard test uses an 'opaque' node which is not shared. Hence I 1338 // can edit it's inputs directly. Hammer in the new limit for the 1339 // minimum-trip guard. 1340 assert(opaq->outcnt() == 1, ""); 1341 _igvn.hash_delete(opaq); 1342 opaq->set_req(1, new_limit); 1343 } 1344 1345 // Adjust max trip count. The trip count is intentionally rounded 1346 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 1347 // the main, unrolled, part of the loop will never execute as it is protected 1348 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 1349 // and later determined that part of the unrolled loop was dead. 1350 loop_head->set_trip_count(old_trip_count / 2); 1351 1352 // Double the count of original iterations in the unrolled loop body. 1353 loop_head->double_unrolled_count(); 1354 1355 } else { // LoopLimitCheck 1356 1357 // Adjust max trip count. The trip count is intentionally rounded 1358 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 1359 // the main, unrolled, part of the loop will never execute as it is protected 1360 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 1361 // and later determined that part of the unrolled loop was dead. 1362 loop_head->set_trip_count(loop_head->trip_count() / 2); 1363 1364 // Double the count of original iterations in the unrolled loop body. 1365 loop_head->double_unrolled_count(); 1366 1367 // ----------- 1368 // Step 2: Cut back the trip counter for an unroll amount of 2. 1369 // Loop will normally trip (limit - init)/stride_con. Since it's a 1370 // CountedLoop this is exact (stride divides limit-init exactly). 1371 // We are going to double the loop body, so we want to knock off any 1372 // odd iteration: (trip_cnt & ~1). Then back compute a new limit. 1373 Node *span = new (C, 3) SubINode( limit, init ); 1374 register_new_node( span, ctrl ); 1375 Node *trip = new (C, 3) DivINode( 0, span, stride ); 1376 register_new_node( trip, ctrl ); 1377 Node *mtwo = _igvn.intcon(-2); 1378 set_ctrl(mtwo, C->root()); 1379 Node *rond = new (C, 3) AndINode( trip, mtwo ); 1380 register_new_node( rond, ctrl ); 1381 Node *spn2 = new (C, 3) MulINode( rond, stride ); 1382 register_new_node( spn2, ctrl ); 1383 new_limit = new (C, 3) AddINode( spn2, init ); 1384 register_new_node( new_limit, ctrl ); 1385 1386 // Hammer in the new limit 1387 Node *ctrl2 = loop_end->in(0); 1388 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), new_limit ); 1389 register_new_node( cmp2, ctrl2 ); 1390 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() ); 1391 register_new_node( bol2, ctrl2 ); 1392 _igvn.hash_delete(loop_end); 1393 loop_end->set_req(CountedLoopEndNode::TestValue, bol2); 1394 1395 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 1396 // Make it a 1-trip test (means at least 2 trips). 1397 if( adjust_min_trip ) { 1398 assert( new_limit != NULL, "" ); 1399 // Guard test uses an 'opaque' node which is not shared. Hence I 1400 // can edit it's inputs directly. Hammer in the new limit for the 1401 // minimum-trip guard. 1402 assert( opaq->outcnt() == 1, "" ); 1403 _igvn.hash_delete(opaq); 1404 opaq->set_req(1, new_limit); 1405 } 1406 } // LoopLimitCheck 1407 1408 // --------- 1409 // Step 4: Clone the loop body. Move it inside the loop. This loop body 1410 // represents the odd iterations; since the loop trips an even number of 1411 // times its backedge is never taken. Kill the backedge. 1412 uint dd = dom_depth(loop_head); 1413 clone_loop( loop, old_new, dd ); 1414 1415 // Make backedges of the clone equal to backedges of the original. 1416 // Make the fall-in from the original come from the fall-out of the clone. 1417 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) { 1418 Node* phi = loop_head->fast_out(j); 1419 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) { 1420 Node *newphi = old_new[phi->_idx]; 1421 _igvn.hash_delete( phi ); 1422 _igvn.hash_delete( newphi ); 1423 1424 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl)); 1425 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl)); 1426 phi ->set_req(LoopNode::LoopBackControl, C->top()); 1427 } 1428 } 1429 Node *clone_head = old_new[loop_head->_idx]; 1430 _igvn.hash_delete( clone_head ); 1431 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl)); 1432 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl)); 1433 loop_head ->set_req(LoopNode::LoopBackControl, C->top()); 1434 loop->_head = clone_head; // New loop header 1435 1436 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd); 1437 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd); 1438 1439 // Kill the clone's backedge 1440 Node *newcle = old_new[loop_end->_idx]; 1441 _igvn.hash_delete( newcle ); 1442 Node *one = _igvn.intcon(1); 1443 set_ctrl(one, C->root()); 1444 newcle->set_req(1, one); 1445 // Force clone into same loop body 1446 uint max = loop->_body.size(); 1447 for( uint k = 0; k < max; k++ ) { 1448 Node *old = loop->_body.at(k); 1449 Node *nnn = old_new[old->_idx]; 1450 loop->_body.push(nnn); 1451 if (!has_ctrl(old)) 1452 set_loop(nnn, loop); 1453 } 1454 1455 loop->record_for_igvn(); 1456 } 1457 1458 //------------------------------do_maximally_unroll---------------------------- 1459 1460 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) { 1461 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1462 assert(cl->has_exact_trip_count(), "trip count is not exact"); 1463 assert(cl->trip_count() > 0, ""); 1464 #ifndef PRODUCT 1465 if (TraceLoopOpts) { 1466 tty->print("MaxUnroll %d ", cl->trip_count()); 1467 loop->dump_head(); 1468 } 1469 #endif 1470 1471 // If loop is tripping an odd number of times, peel odd iteration 1472 if ((cl->trip_count() & 1) == 1) { 1473 do_peeling(loop, old_new); 1474 } 1475 1476 // Now its tripping an even number of times remaining. Double loop body. 1477 // Do not adjust pre-guards; they are not needed and do not exist. 1478 if (cl->trip_count() > 0) { 1479 assert((cl->trip_count() & 1) == 0, "missed peeling"); 1480 do_unroll(loop, old_new, false); 1481 } 1482 } 1483 1484 //------------------------------dominates_backedge--------------------------------- 1485 // Returns true if ctrl is executed on every complete iteration 1486 bool IdealLoopTree::dominates_backedge(Node* ctrl) { 1487 assert(ctrl->is_CFG(), "must be control"); 1488 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl); 1489 return _phase->dom_lca_internal(ctrl, backedge) == ctrl; 1490 } 1491 1492 //------------------------------adjust_limit----------------------------------- 1493 // Helper function for add_constraint(). 1494 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) { 1495 // Compute "I :: (limit-offset)/scale" 1496 Node *con = new (C, 3) SubINode(rc_limit, offset); 1497 register_new_node(con, pre_ctrl); 1498 Node *X = new (C, 3) DivINode(0, con, scale); 1499 register_new_node(X, pre_ctrl); 1500 1501 // Adjust loop limit 1502 loop_limit = (stride_con > 0) 1503 ? (Node*)(new (C, 3) MinINode(loop_limit, X)) 1504 : (Node*)(new (C, 3) MaxINode(loop_limit, X)); 1505 register_new_node(loop_limit, pre_ctrl); 1506 return loop_limit; 1507 } 1508 1509 //------------------------------add_constraint--------------------------------- 1510 // Constrain the main loop iterations so the conditions: 1511 // low_limit <= scale_con * I + offset < upper_limit 1512 // always holds true. That is, either increase the number of iterations in 1513 // the pre-loop or the post-loop until the condition holds true in the main 1514 // loop. Stride, scale, offset and limit are all loop invariant. Further, 1515 // stride and scale are constants (offset and limit often are). 1516 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) { 1517 // For positive stride, the pre-loop limit always uses a MAX function 1518 // and the main loop a MIN function. For negative stride these are 1519 // reversed. 1520 1521 // Also for positive stride*scale the affine function is increasing, so the 1522 // pre-loop must check for underflow and the post-loop for overflow. 1523 // Negative stride*scale reverses this; pre-loop checks for overflow and 1524 // post-loop for underflow. 1525 1526 Node *scale = _igvn.intcon(scale_con); 1527 set_ctrl(scale, C->root()); 1528 1529 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow 1530 // The overflow limit: scale*I+offset < upper_limit 1531 // For main-loop compute 1532 // ( if (scale > 0) /* and stride > 0 */ 1533 // I < (upper_limit-offset)/scale 1534 // else /* scale < 0 and stride < 0 */ 1535 // I > (upper_limit-offset)/scale 1536 // ) 1537 // 1538 // (upper_limit-offset) may overflow or underflow. 1539 // But it is fine since main loop will either have 1540 // less iterations or will be skipped in such case. 1541 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl); 1542 1543 // The underflow limit: low_limit <= scale*I+offset. 1544 // For pre-loop compute 1545 // NOT(scale*I+offset >= low_limit) 1546 // scale*I+offset < low_limit 1547 // ( if (scale > 0) /* and stride > 0 */ 1548 // I < (low_limit-offset)/scale 1549 // else /* scale < 0 and stride < 0 */ 1550 // I > (low_limit-offset)/scale 1551 // ) 1552 1553 if (low_limit->get_int() == -max_jint) { 1554 if (!RangeLimitCheck) return; 1555 // We need this guard when scale*pre_limit+offset >= limit 1556 // due to underflow. So we need execute pre-loop until 1557 // scale*I+offset >= min_int. But (min_int-offset) will 1558 // underflow when offset > 0 and X will be > original_limit 1559 // when stride > 0. To avoid it we replace positive offset with 0. 1560 // 1561 // Also (min_int+1 == -max_int) is used instead of min_int here 1562 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1563 Node* shift = _igvn.intcon(31); 1564 set_ctrl(shift, C->root()); 1565 Node* sign = new (C, 3) RShiftINode(offset, shift); 1566 register_new_node(sign, pre_ctrl); 1567 offset = new (C, 3) AndINode(offset, sign); 1568 register_new_node(offset, pre_ctrl); 1569 } else { 1570 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1571 // The only problem we have here when offset == min_int 1572 // since (0-min_int) == min_int. It may be fine for stride > 0 1573 // but for stride < 0 X will be < original_limit. To avoid it 1574 // max(pre_limit, original_limit) is used in do_range_check(). 1575 } 1576 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1577 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl); 1578 1579 } else { // stride_con*scale_con < 0 1580 // For negative stride*scale pre-loop checks for overflow and 1581 // post-loop for underflow. 1582 // 1583 // The overflow limit: scale*I+offset < upper_limit 1584 // For pre-loop compute 1585 // NOT(scale*I+offset < upper_limit) 1586 // scale*I+offset >= upper_limit 1587 // scale*I+offset+1 > upper_limit 1588 // ( if (scale < 0) /* and stride > 0 */ 1589 // I < (upper_limit-(offset+1))/scale 1590 // else /* scale > 0 and stride < 0 */ 1591 // I > (upper_limit-(offset+1))/scale 1592 // ) 1593 // 1594 // (upper_limit-offset-1) may underflow or overflow. 1595 // To avoid it min(pre_limit, original_limit) is used 1596 // in do_range_check() for stride > 0 and max() for < 0. 1597 Node *one = _igvn.intcon(1); 1598 set_ctrl(one, C->root()); 1599 1600 Node *plus_one = new (C, 3) AddINode(offset, one); 1601 register_new_node( plus_one, pre_ctrl ); 1602 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1603 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl); 1604 1605 if (low_limit->get_int() == -max_jint) { 1606 if (!RangeLimitCheck) return; 1607 // We need this guard when scale*main_limit+offset >= limit 1608 // due to underflow. So we need execute main-loop while 1609 // scale*I+offset+1 > min_int. But (min_int-offset-1) will 1610 // underflow when (offset+1) > 0 and X will be < main_limit 1611 // when scale < 0 (and stride > 0). To avoid it we replace 1612 // positive (offset+1) with 0. 1613 // 1614 // Also (min_int+1 == -max_int) is used instead of min_int here 1615 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1616 Node* shift = _igvn.intcon(31); 1617 set_ctrl(shift, C->root()); 1618 Node* sign = new (C, 3) RShiftINode(plus_one, shift); 1619 register_new_node(sign, pre_ctrl); 1620 plus_one = new (C, 3) AndINode(plus_one, sign); 1621 register_new_node(plus_one, pre_ctrl); 1622 } else { 1623 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1624 // The only problem we have here when offset == max_int 1625 // since (max_int+1) == min_int and (0-min_int) == min_int. 1626 // But it is fine since main loop will either have 1627 // less iterations or will be skipped in such case. 1628 } 1629 // The underflow limit: low_limit <= scale*I+offset. 1630 // For main-loop compute 1631 // scale*I+offset+1 > low_limit 1632 // ( if (scale < 0) /* and stride > 0 */ 1633 // I < (low_limit-(offset+1))/scale 1634 // else /* scale > 0 and stride < 0 */ 1635 // I > (low_limit-(offset+1))/scale 1636 // ) 1637 1638 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl); 1639 } 1640 } 1641 1642 1643 //------------------------------is_scaled_iv--------------------------------- 1644 // Return true if exp is a constant times an induction var 1645 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) { 1646 if (exp == iv) { 1647 if (p_scale != NULL) { 1648 *p_scale = 1; 1649 } 1650 return true; 1651 } 1652 int opc = exp->Opcode(); 1653 if (opc == Op_MulI) { 1654 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1655 if (p_scale != NULL) { 1656 *p_scale = exp->in(2)->get_int(); 1657 } 1658 return true; 1659 } 1660 if (exp->in(2) == iv && exp->in(1)->is_Con()) { 1661 if (p_scale != NULL) { 1662 *p_scale = exp->in(1)->get_int(); 1663 } 1664 return true; 1665 } 1666 } else if (opc == Op_LShiftI) { 1667 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1668 if (p_scale != NULL) { 1669 *p_scale = 1 << exp->in(2)->get_int(); 1670 } 1671 return true; 1672 } 1673 } 1674 return false; 1675 } 1676 1677 //-----------------------------is_scaled_iv_plus_offset------------------------------ 1678 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2) 1679 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) { 1680 if (is_scaled_iv(exp, iv, p_scale)) { 1681 if (p_offset != NULL) { 1682 Node *zero = _igvn.intcon(0); 1683 set_ctrl(zero, C->root()); 1684 *p_offset = zero; 1685 } 1686 return true; 1687 } 1688 int opc = exp->Opcode(); 1689 if (opc == Op_AddI) { 1690 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1691 if (p_offset != NULL) { 1692 *p_offset = exp->in(2); 1693 } 1694 return true; 1695 } 1696 if (exp->in(2)->is_Con()) { 1697 Node* offset2 = NULL; 1698 if (depth < 2 && 1699 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale, 1700 p_offset != NULL ? &offset2 : NULL, depth+1)) { 1701 if (p_offset != NULL) { 1702 Node *ctrl_off2 = get_ctrl(offset2); 1703 Node* offset = new (C, 3) AddINode(offset2, exp->in(2)); 1704 register_new_node(offset, ctrl_off2); 1705 *p_offset = offset; 1706 } 1707 return true; 1708 } 1709 } 1710 } else if (opc == Op_SubI) { 1711 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1712 if (p_offset != NULL) { 1713 Node *zero = _igvn.intcon(0); 1714 set_ctrl(zero, C->root()); 1715 Node *ctrl_off = get_ctrl(exp->in(2)); 1716 Node* offset = new (C, 3) SubINode(zero, exp->in(2)); 1717 register_new_node(offset, ctrl_off); 1718 *p_offset = offset; 1719 } 1720 return true; 1721 } 1722 if (is_scaled_iv(exp->in(2), iv, p_scale)) { 1723 if (p_offset != NULL) { 1724 *p_scale *= -1; 1725 *p_offset = exp->in(1); 1726 } 1727 return true; 1728 } 1729 } 1730 return false; 1731 } 1732 1733 //------------------------------do_range_check--------------------------------- 1734 // Eliminate range-checks and other trip-counter vs loop-invariant tests. 1735 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) { 1736 #ifndef PRODUCT 1737 if (PrintOpto && VerifyLoopOptimizations) { 1738 tty->print("Range Check Elimination "); 1739 loop->dump_head(); 1740 } else if (TraceLoopOpts) { 1741 tty->print("RangeCheck "); 1742 loop->dump_head(); 1743 } 1744 #endif 1745 assert(RangeCheckElimination, ""); 1746 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1747 assert(cl->is_main_loop(), ""); 1748 1749 // protect against stride not being a constant 1750 if (!cl->stride_is_con()) 1751 return; 1752 1753 // Find the trip counter; we are iteration splitting based on it 1754 Node *trip_counter = cl->phi(); 1755 // Find the main loop limit; we will trim it's iterations 1756 // to not ever trip end tests 1757 Node *main_limit = cl->limit(); 1758 1759 // Need to find the main-loop zero-trip guard 1760 Node *ctrl = cl->in(LoopNode::EntryControl); 1761 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, ""); 1762 Node *iffm = ctrl->in(0); 1763 assert(iffm->Opcode() == Op_If, ""); 1764 Node *bolzm = iffm->in(1); 1765 assert(bolzm->Opcode() == Op_Bool, ""); 1766 Node *cmpzm = bolzm->in(1); 1767 assert(cmpzm->is_Cmp(), ""); 1768 Node *opqzm = cmpzm->in(2); 1769 // Can not optimize a loop if zero-trip Opaque1 node is optimized 1770 // away and then another round of loop opts attempted. 1771 if (opqzm->Opcode() != Op_Opaque1) 1772 return; 1773 assert(opqzm->in(1) == main_limit, "do not understand situation"); 1774 1775 // Find the pre-loop limit; we will expand it's iterations to 1776 // not ever trip low tests. 1777 Node *p_f = iffm->in(0); 1778 assert(p_f->Opcode() == Op_IfFalse, ""); 1779 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); 1780 assert(pre_end->loopnode()->is_pre_loop(), ""); 1781 Node *pre_opaq1 = pre_end->limit(); 1782 // Occasionally it's possible for a pre-loop Opaque1 node to be 1783 // optimized away and then another round of loop opts attempted. 1784 // We can not optimize this particular loop in that case. 1785 if (pre_opaq1->Opcode() != Op_Opaque1) 1786 return; 1787 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1; 1788 Node *pre_limit = pre_opaq->in(1); 1789 1790 // Where do we put new limit calculations 1791 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl); 1792 1793 // Ensure the original loop limit is available from the 1794 // pre-loop Opaque1 node. 1795 Node *orig_limit = pre_opaq->original_loop_limit(); 1796 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP) 1797 return; 1798 1799 // Must know if its a count-up or count-down loop 1800 1801 int stride_con = cl->stride_con(); 1802 Node *zero = _igvn.intcon(0); 1803 Node *one = _igvn.intcon(1); 1804 // Use symmetrical int range [-max_jint,max_jint] 1805 Node *mini = _igvn.intcon(-max_jint); 1806 set_ctrl(zero, C->root()); 1807 set_ctrl(one, C->root()); 1808 set_ctrl(mini, C->root()); 1809 1810 // Range checks that do not dominate the loop backedge (ie. 1811 // conditionally executed) can lengthen the pre loop limit beyond 1812 // the original loop limit. To prevent this, the pre limit is 1813 // (for stride > 0) MINed with the original loop limit (MAXed 1814 // stride < 0) when some range_check (rc) is conditionally 1815 // executed. 1816 bool conditional_rc = false; 1817 1818 // Check loop body for tests of trip-counter plus loop-invariant vs 1819 // loop-invariant. 1820 for( uint i = 0; i < loop->_body.size(); i++ ) { 1821 Node *iff = loop->_body[i]; 1822 if( iff->Opcode() == Op_If ) { // Test? 1823 1824 // Test is an IfNode, has 2 projections. If BOTH are in the loop 1825 // we need loop unswitching instead of iteration splitting. 1826 Node *exit = loop->is_loop_exit(iff); 1827 if( !exit ) continue; 1828 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0; 1829 1830 // Get boolean condition to test 1831 Node *i1 = iff->in(1); 1832 if( !i1->is_Bool() ) continue; 1833 BoolNode *bol = i1->as_Bool(); 1834 BoolTest b_test = bol->_test; 1835 // Flip sense of test if exit condition is flipped 1836 if( flip ) 1837 b_test = b_test.negate(); 1838 1839 // Get compare 1840 Node *cmp = bol->in(1); 1841 1842 // Look for trip_counter + offset vs limit 1843 Node *rc_exp = cmp->in(1); 1844 Node *limit = cmp->in(2); 1845 jint scale_con= 1; // Assume trip counter not scaled 1846 1847 Node *limit_c = get_ctrl(limit); 1848 if( loop->is_member(get_loop(limit_c) ) ) { 1849 // Compare might have operands swapped; commute them 1850 b_test = b_test.commute(); 1851 rc_exp = cmp->in(2); 1852 limit = cmp->in(1); 1853 limit_c = get_ctrl(limit); 1854 if( loop->is_member(get_loop(limit_c) ) ) 1855 continue; // Both inputs are loop varying; cannot RCE 1856 } 1857 // Here we know 'limit' is loop invariant 1858 1859 // 'limit' maybe pinned below the zero trip test (probably from a 1860 // previous round of rce), in which case, it can't be used in the 1861 // zero trip test expression which must occur before the zero test's if. 1862 if( limit_c == ctrl ) { 1863 continue; // Don't rce this check but continue looking for other candidates. 1864 } 1865 1866 // Check for scaled induction variable plus an offset 1867 Node *offset = NULL; 1868 1869 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) { 1870 continue; 1871 } 1872 1873 Node *offset_c = get_ctrl(offset); 1874 if( loop->is_member( get_loop(offset_c) ) ) 1875 continue; // Offset is not really loop invariant 1876 // Here we know 'offset' is loop invariant. 1877 1878 // As above for the 'limit', the 'offset' maybe pinned below the 1879 // zero trip test. 1880 if( offset_c == ctrl ) { 1881 continue; // Don't rce this check but continue looking for other candidates. 1882 } 1883 #ifdef ASSERT 1884 if (TraceRangeLimitCheck) { 1885 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":"); 1886 bol->dump(2); 1887 } 1888 #endif 1889 // At this point we have the expression as: 1890 // scale_con * trip_counter + offset :: limit 1891 // where scale_con, offset and limit are loop invariant. Trip_counter 1892 // monotonically increases by stride_con, a constant. Both (or either) 1893 // stride_con and scale_con can be negative which will flip about the 1894 // sense of the test. 1895 1896 // Adjust pre and main loop limits to guard the correct iteration set 1897 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests 1898 if( b_test._test == BoolTest::lt ) { // Range checks always use lt 1899 // The underflow and overflow limits: 0 <= scale*I+offset < limit 1900 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit ); 1901 if (!conditional_rc) { 1902 // (0-offset)/scale could be outside of loop iterations range. 1903 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck; 1904 } 1905 } else { 1906 #ifndef PRODUCT 1907 if( PrintOpto ) 1908 tty->print_cr("missed RCE opportunity"); 1909 #endif 1910 continue; // In release mode, ignore it 1911 } 1912 } else { // Otherwise work on normal compares 1913 switch( b_test._test ) { 1914 case BoolTest::gt: 1915 // Fall into GE case 1916 case BoolTest::ge: 1917 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit 1918 scale_con = -scale_con; 1919 offset = new (C, 3) SubINode( zero, offset ); 1920 register_new_node( offset, pre_ctrl ); 1921 limit = new (C, 3) SubINode( zero, limit ); 1922 register_new_node( limit, pre_ctrl ); 1923 // Fall into LE case 1924 case BoolTest::le: 1925 if (b_test._test != BoolTest::gt) { 1926 // Convert X <= Y to X < Y+1 1927 limit = new (C, 3) AddINode( limit, one ); 1928 register_new_node( limit, pre_ctrl ); 1929 } 1930 // Fall into LT case 1931 case BoolTest::lt: 1932 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit 1933 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here 1934 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT. 1935 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit ); 1936 if (!conditional_rc) { 1937 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range. 1938 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could 1939 // still be outside of loop range. 1940 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck; 1941 } 1942 break; 1943 default: 1944 #ifndef PRODUCT 1945 if( PrintOpto ) 1946 tty->print_cr("missed RCE opportunity"); 1947 #endif 1948 continue; // Unhandled case 1949 } 1950 } 1951 1952 // Kill the eliminated test 1953 C->set_major_progress(); 1954 Node *kill_con = _igvn.intcon( 1-flip ); 1955 set_ctrl(kill_con, C->root()); 1956 _igvn.hash_delete(iff); 1957 iff->set_req(1, kill_con); 1958 _igvn._worklist.push(iff); 1959 // Find surviving projection 1960 assert(iff->is_If(), ""); 1961 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip); 1962 // Find loads off the surviving projection; remove their control edge 1963 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { 1964 Node* cd = dp->fast_out(i); // Control-dependent node 1965 if( cd->is_Load() ) { // Loads can now float around in the loop 1966 _igvn.hash_delete(cd); 1967 // Allow the load to float around in the loop, or before it 1968 // but NOT before the pre-loop. 1969 cd->set_req(0, ctrl); // ctrl, not NULL 1970 _igvn._worklist.push(cd); 1971 --i; 1972 --imax; 1973 } 1974 } 1975 1976 } // End of is IF 1977 1978 } 1979 1980 // Update loop limits 1981 if (conditional_rc) { 1982 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit) 1983 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit); 1984 register_new_node(pre_limit, pre_ctrl); 1985 } 1986 _igvn.hash_delete(pre_opaq); 1987 pre_opaq->set_req(1, pre_limit); 1988 1989 // Note:: we are making the main loop limit no longer precise; 1990 // need to round up based on stride. 1991 cl->set_nonexact_trip_count(); 1992 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case 1993 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init 1994 // Hopefully, compiler will optimize for powers of 2. 1995 Node *ctrl = get_ctrl(main_limit); 1996 Node *stride = cl->stride(); 1997 Node *init = cl->init_trip(); 1998 Node *span = new (C, 3) SubINode(main_limit,init); 1999 register_new_node(span,ctrl); 2000 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1)); 2001 Node *add = new (C, 3) AddINode(span,rndup); 2002 register_new_node(add,ctrl); 2003 Node *div = new (C, 3) DivINode(0,add,stride); 2004 register_new_node(div,ctrl); 2005 Node *mul = new (C, 3) MulINode(div,stride); 2006 register_new_node(mul,ctrl); 2007 Node *newlim = new (C, 3) AddINode(mul,init); 2008 register_new_node(newlim,ctrl); 2009 main_limit = newlim; 2010 } 2011 2012 Node *main_cle = cl->loopexit(); 2013 Node *main_bol = main_cle->in(1); 2014 // Hacking loop bounds; need private copies of exit test 2015 if( main_bol->outcnt() > 1 ) {// BoolNode shared? 2016 _igvn.hash_delete(main_cle); 2017 main_bol = main_bol->clone();// Clone a private BoolNode 2018 register_new_node( main_bol, main_cle->in(0) ); 2019 main_cle->set_req(1,main_bol); 2020 } 2021 Node *main_cmp = main_bol->in(1); 2022 if( main_cmp->outcnt() > 1 ) { // CmpNode shared? 2023 _igvn.hash_delete(main_bol); 2024 main_cmp = main_cmp->clone();// Clone a private CmpNode 2025 register_new_node( main_cmp, main_cle->in(0) ); 2026 main_bol->set_req(1,main_cmp); 2027 } 2028 // Hack the now-private loop bounds 2029 _igvn.hash_delete(main_cmp); 2030 main_cmp->set_req(2, main_limit); 2031 _igvn._worklist.push(main_cmp); 2032 // The OpaqueNode is unshared by design 2033 _igvn.hash_delete(opqzm); 2034 assert( opqzm->outcnt() == 1, "cannot hack shared node" ); 2035 opqzm->set_req(1,main_limit); 2036 _igvn._worklist.push(opqzm); 2037 } 2038 2039 //------------------------------DCE_loop_body---------------------------------- 2040 // Remove simplistic dead code from loop body 2041 void IdealLoopTree::DCE_loop_body() { 2042 for( uint i = 0; i < _body.size(); i++ ) 2043 if( _body.at(i)->outcnt() == 0 ) 2044 _body.map( i--, _body.pop() ); 2045 } 2046 2047 2048 //------------------------------adjust_loop_exit_prob-------------------------- 2049 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage. 2050 // Replace with a 1-in-10 exit guess. 2051 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) { 2052 Node *test = tail(); 2053 while( test != _head ) { 2054 uint top = test->Opcode(); 2055 if( top == Op_IfTrue || top == Op_IfFalse ) { 2056 int test_con = ((ProjNode*)test)->_con; 2057 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity"); 2058 IfNode *iff = test->in(0)->as_If(); 2059 if( iff->outcnt() == 2 ) { // Ignore dead tests 2060 Node *bol = iff->in(1); 2061 if( bol && bol->req() > 1 && bol->in(1) && 2062 ((bol->in(1)->Opcode() == Op_StorePConditional ) || 2063 (bol->in(1)->Opcode() == Op_StoreIConditional ) || 2064 (bol->in(1)->Opcode() == Op_StoreLConditional ) || 2065 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || 2066 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || 2067 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || 2068 (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) 2069 return; // Allocation loops RARELY take backedge 2070 // Find the OTHER exit path from the IF 2071 Node* ex = iff->proj_out(1-test_con); 2072 float p = iff->_prob; 2073 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) { 2074 if( top == Op_IfTrue ) { 2075 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) { 2076 iff->_prob = PROB_STATIC_FREQUENT; 2077 } 2078 } else { 2079 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) { 2080 iff->_prob = PROB_STATIC_INFREQUENT; 2081 } 2082 } 2083 } 2084 } 2085 } 2086 test = phase->idom(test); 2087 } 2088 } 2089 2090 2091 //------------------------------policy_do_remove_empty_loop-------------------- 2092 // Micro-benchmark spamming. Policy is to always remove empty loops. 2093 // The 'DO' part is to replace the trip counter with the value it will 2094 // have on the last iteration. This will break the loop. 2095 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) { 2096 // Minimum size must be empty loop 2097 if (_body.size() > EMPTY_LOOP_SIZE) 2098 return false; 2099 2100 if (!_head->is_CountedLoop()) 2101 return false; // Dead loop 2102 CountedLoopNode *cl = _head->as_CountedLoop(); 2103 if (!cl->loopexit()) 2104 return false; // Malformed loop 2105 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 2106 return false; // Infinite loop 2107 2108 #ifdef ASSERT 2109 // Ensure only one phi which is the iv. 2110 Node* iv = NULL; 2111 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) { 2112 Node* n = cl->fast_out(i); 2113 if (n->Opcode() == Op_Phi) { 2114 assert(iv == NULL, "Too many phis" ); 2115 iv = n; 2116 } 2117 } 2118 assert(iv == cl->phi(), "Wrong phi" ); 2119 #endif 2120 2121 // main and post loops have explicitly created zero trip guard 2122 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop(); 2123 if (needs_guard) { 2124 // Skip guard if values not overlap. 2125 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int(); 2126 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int(); 2127 int stride_con = cl->stride_con(); 2128 if (stride_con > 0) { 2129 needs_guard = (init_t->_hi >= limit_t->_lo); 2130 } else { 2131 needs_guard = (init_t->_lo <= limit_t->_hi); 2132 } 2133 } 2134 if (needs_guard) { 2135 // Check for an obvious zero trip guard. 2136 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl)); 2137 if (inctrl->Opcode() == Op_IfTrue) { 2138 // The test should look like just the backedge of a CountedLoop 2139 Node* iff = inctrl->in(0); 2140 if (iff->is_If()) { 2141 Node* bol = iff->in(1); 2142 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) { 2143 Node* cmp = bol->in(1); 2144 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) { 2145 needs_guard = false; 2146 } 2147 } 2148 } 2149 } 2150 } 2151 2152 #ifndef PRODUCT 2153 if (PrintOpto) { 2154 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : ""); 2155 this->dump_head(); 2156 } else if (TraceLoopOpts) { 2157 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : ""); 2158 this->dump_head(); 2159 } 2160 #endif 2161 2162 if (needs_guard) { 2163 // Peel the loop to ensure there's a zero trip guard 2164 Node_List old_new; 2165 phase->do_peeling(this, old_new); 2166 } 2167 2168 // Replace the phi at loop head with the final value of the last 2169 // iteration. Then the CountedLoopEnd will collapse (backedge never 2170 // taken) and all loop-invariant uses of the exit values will be correct. 2171 Node *phi = cl->phi(); 2172 Node *exact_limit = phase->exact_limit(this); 2173 if (exact_limit != cl->limit()) { 2174 // We also need to replace the original limit to collapse loop exit. 2175 Node* cmp = cl->loopexit()->cmp_node(); 2176 assert(cl->limit() == cmp->in(2), "sanity"); 2177 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist 2178 phase->_igvn.hash_delete(cmp); 2179 cmp->set_req(2, exact_limit); 2180 phase->_igvn._worklist.push(cmp); // put cmp on worklist 2181 } 2182 // Note: the final value after increment should not overflow since 2183 // counted loop has limit check predicate. 2184 Node *final = new (phase->C, 3) SubINode( exact_limit, cl->stride() ); 2185 phase->register_new_node(final,cl->in(LoopNode::EntryControl)); 2186 phase->_igvn.replace_node(phi,final); 2187 phase->C->set_major_progress(); 2188 return true; 2189 } 2190 2191 //------------------------------policy_do_one_iteration_loop------------------- 2192 // Convert one iteration loop into normal code. 2193 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) { 2194 if (!_head->as_Loop()->is_valid_counted_loop()) 2195 return false; // Only for counted loop 2196 2197 CountedLoopNode *cl = _head->as_CountedLoop(); 2198 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) { 2199 return false; 2200 } 2201 2202 #ifndef PRODUCT 2203 if(TraceLoopOpts) { 2204 tty->print("OneIteration "); 2205 this->dump_head(); 2206 } 2207 #endif 2208 2209 Node *init_n = cl->init_trip(); 2210 #ifdef ASSERT 2211 // Loop boundaries should be constant since trip count is exact. 2212 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration"); 2213 #endif 2214 // Replace the phi at loop head with the value of the init_trip. 2215 // Then the CountedLoopEnd will collapse (backedge will not be taken) 2216 // and all loop-invariant uses of the exit values will be correct. 2217 phase->_igvn.replace_node(cl->phi(), cl->init_trip()); 2218 phase->C->set_major_progress(); 2219 return true; 2220 } 2221 2222 //============================================================================= 2223 //------------------------------iteration_split_impl--------------------------- 2224 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) { 2225 // Compute exact loop trip count if possible. 2226 compute_exact_trip_count(phase); 2227 2228 // Convert one iteration loop into normal code. 2229 if (policy_do_one_iteration_loop(phase)) 2230 return true; 2231 2232 // Check and remove empty loops (spam micro-benchmarks) 2233 if (policy_do_remove_empty_loop(phase)) 2234 return true; // Here we removed an empty loop 2235 2236 bool should_peel = policy_peeling(phase); // Should we peel? 2237 2238 bool should_unswitch = policy_unswitching(phase); 2239 2240 // Non-counted loops may be peeled; exactly 1 iteration is peeled. 2241 // This removes loop-invariant tests (usually null checks). 2242 if (!_head->is_CountedLoop()) { // Non-counted loop 2243 if (PartialPeelLoop && phase->partial_peel(this, old_new)) { 2244 // Partial peel succeeded so terminate this round of loop opts 2245 return false; 2246 } 2247 if (should_peel) { // Should we peel? 2248 #ifndef PRODUCT 2249 if (PrintOpto) tty->print_cr("should_peel"); 2250 #endif 2251 phase->do_peeling(this,old_new); 2252 } else if (should_unswitch) { 2253 phase->do_unswitching(this, old_new); 2254 } 2255 return true; 2256 } 2257 CountedLoopNode *cl = _head->as_CountedLoop(); 2258 2259 if (!cl->loopexit()) return true; // Ignore various kinds of broken loops 2260 2261 // Do nothing special to pre- and post- loops 2262 if (cl->is_pre_loop() || cl->is_post_loop()) return true; 2263 2264 // Compute loop trip count from profile data 2265 compute_profile_trip_cnt(phase); 2266 2267 // Before attempting fancy unrolling, RCE or alignment, see if we want 2268 // to completely unroll this loop or do loop unswitching. 2269 if (cl->is_normal_loop()) { 2270 if (should_unswitch) { 2271 phase->do_unswitching(this, old_new); 2272 return true; 2273 } 2274 bool should_maximally_unroll = policy_maximally_unroll(phase); 2275 if (should_maximally_unroll) { 2276 // Here we did some unrolling and peeling. Eventually we will 2277 // completely unroll this loop and it will no longer be a loop. 2278 phase->do_maximally_unroll(this,old_new); 2279 return true; 2280 } 2281 } 2282 2283 // Skip next optimizations if running low on nodes. Note that 2284 // policy_unswitching and policy_maximally_unroll have this check. 2285 uint nodes_left = MaxNodeLimit - phase->C->unique(); 2286 if ((2 * _body.size()) > nodes_left) { 2287 return true; 2288 } 2289 2290 // Counted loops may be peeled, may need some iterations run up 2291 // front for RCE, and may want to align loop refs to a cache 2292 // line. Thus we clone a full loop up front whose trip count is 2293 // at least 1 (if peeling), but may be several more. 2294 2295 // The main loop will start cache-line aligned with at least 1 2296 // iteration of the unrolled body (zero-trip test required) and 2297 // will have some range checks removed. 2298 2299 // A post-loop will finish any odd iterations (leftover after 2300 // unrolling), plus any needed for RCE purposes. 2301 2302 bool should_unroll = policy_unroll(phase); 2303 2304 bool should_rce = policy_range_check(phase); 2305 2306 bool should_align = policy_align(phase); 2307 2308 // If not RCE'ing (iteration splitting) or Aligning, then we do not 2309 // need a pre-loop. We may still need to peel an initial iteration but 2310 // we will not be needing an unknown number of pre-iterations. 2311 // 2312 // Basically, if may_rce_align reports FALSE first time through, 2313 // we will not be able to later do RCE or Aligning on this loop. 2314 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align; 2315 2316 // If we have any of these conditions (RCE, alignment, unrolling) met, then 2317 // we switch to the pre-/main-/post-loop model. This model also covers 2318 // peeling. 2319 if (should_rce || should_align || should_unroll) { 2320 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops 2321 phase->insert_pre_post_loops(this,old_new, !may_rce_align); 2322 2323 // Adjust the pre- and main-loop limits to let the pre and post loops run 2324 // with full checks, but the main-loop with no checks. Remove said 2325 // checks from the main body. 2326 if (should_rce) 2327 phase->do_range_check(this,old_new); 2328 2329 // Double loop body for unrolling. Adjust the minimum-trip test (will do 2330 // twice as many iterations as before) and the main body limit (only do 2331 // an even number of trips). If we are peeling, we might enable some RCE 2332 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if 2333 // peeling. 2334 if (should_unroll && !should_peel) 2335 phase->do_unroll(this,old_new, true); 2336 2337 // Adjust the pre-loop limits to align the main body 2338 // iterations. 2339 if (should_align) 2340 Unimplemented(); 2341 2342 } else { // Else we have an unchanged counted loop 2343 if (should_peel) // Might want to peel but do nothing else 2344 phase->do_peeling(this,old_new); 2345 } 2346 return true; 2347 } 2348 2349 2350 //============================================================================= 2351 //------------------------------iteration_split-------------------------------- 2352 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { 2353 // Recursively iteration split nested loops 2354 if (_child && !_child->iteration_split(phase, old_new)) 2355 return false; 2356 2357 // Clean out prior deadwood 2358 DCE_loop_body(); 2359 2360 2361 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. 2362 // Replace with a 1-in-10 exit guess. 2363 if (_parent /*not the root loop*/ && 2364 !_irreducible && 2365 // Also ignore the occasional dead backedge 2366 !tail()->is_top()) { 2367 adjust_loop_exit_prob(phase); 2368 } 2369 2370 // Gate unrolling, RCE and peeling efforts. 2371 if (!_child && // If not an inner loop, do not split 2372 !_irreducible && 2373 _allow_optimizations && 2374 !tail()->is_top()) { // Also ignore the occasional dead backedge 2375 if (!_has_call) { 2376 if (!iteration_split_impl(phase, old_new)) { 2377 return false; 2378 } 2379 } else if (policy_unswitching(phase)) { 2380 phase->do_unswitching(this, old_new); 2381 } 2382 } 2383 2384 // Minor offset re-organization to remove loop-fallout uses of 2385 // trip counter when there was no major reshaping. 2386 phase->reorg_offsets(this); 2387 2388 if (_next && !_next->iteration_split(phase, old_new)) 2389 return false; 2390 return true; 2391 } 2392 2393 2394 //============================================================================= 2395 // Process all the loops in the loop tree and replace any fill 2396 // patterns with an intrisc version. 2397 bool PhaseIdealLoop::do_intrinsify_fill() { 2398 bool changed = false; 2399 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2400 IdealLoopTree* lpt = iter.current(); 2401 changed |= intrinsify_fill(lpt); 2402 } 2403 return changed; 2404 } 2405 2406 2407 // Examine an inner loop looking for a a single store of an invariant 2408 // value in a unit stride loop, 2409 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value, 2410 Node*& shift, Node*& con) { 2411 const char* msg = NULL; 2412 Node* msg_node = NULL; 2413 2414 store_value = NULL; 2415 con = NULL; 2416 shift = NULL; 2417 2418 // Process the loop looking for stores. If there are multiple 2419 // stores or extra control flow give at this point. 2420 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 2421 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2422 Node* n = lpt->_body.at(i); 2423 if (n->outcnt() == 0) continue; // Ignore dead 2424 if (n->is_Store()) { 2425 if (store != NULL) { 2426 msg = "multiple stores"; 2427 break; 2428 } 2429 int opc = n->Opcode(); 2430 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreCM) { 2431 msg = "oop fills not handled"; 2432 break; 2433 } 2434 Node* value = n->in(MemNode::ValueIn); 2435 if (!lpt->is_invariant(value)) { 2436 msg = "variant store value"; 2437 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) { 2438 msg = "not array address"; 2439 } 2440 store = n; 2441 store_value = value; 2442 } else if (n->is_If() && n != head->loopexit()) { 2443 msg = "extra control flow"; 2444 msg_node = n; 2445 } 2446 } 2447 2448 if (store == NULL) { 2449 // No store in loop 2450 return false; 2451 } 2452 2453 if (msg == NULL && head->stride_con() != 1) { 2454 // could handle negative strides too 2455 if (head->stride_con() < 0) { 2456 msg = "negative stride"; 2457 } else { 2458 msg = "non-unit stride"; 2459 } 2460 } 2461 2462 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) { 2463 msg = "can't handle store address"; 2464 msg_node = store->in(MemNode::Address); 2465 } 2466 2467 if (msg == NULL && 2468 (!store->in(MemNode::Memory)->is_Phi() || 2469 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) { 2470 msg = "store memory isn't proper phi"; 2471 msg_node = store->in(MemNode::Memory); 2472 } 2473 2474 // Make sure there is an appropriate fill routine 2475 BasicType t = store->as_Mem()->memory_type(); 2476 const char* fill_name; 2477 if (msg == NULL && 2478 StubRoutines::select_fill_function(t, false, fill_name) == NULL) { 2479 msg = "unsupported store"; 2480 msg_node = store; 2481 } 2482 2483 if (msg != NULL) { 2484 #ifndef PRODUCT 2485 if (TraceOptimizeFill) { 2486 tty->print_cr("not fill intrinsic candidate: %s", msg); 2487 if (msg_node != NULL) msg_node->dump(); 2488 } 2489 #endif 2490 return false; 2491 } 2492 2493 // Make sure the address expression can be handled. It should be 2494 // head->phi * elsize + con. head->phi might have a ConvI2L. 2495 Node* elements[4]; 2496 Node* conv = NULL; 2497 bool found_index = false; 2498 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements)); 2499 for (int e = 0; e < count; e++) { 2500 Node* n = elements[e]; 2501 if (n->is_Con() && con == NULL) { 2502 con = n; 2503 } else if (n->Opcode() == Op_LShiftX && shift == NULL) { 2504 Node* value = n->in(1); 2505 #ifdef _LP64 2506 if (value->Opcode() == Op_ConvI2L) { 2507 conv = value; 2508 value = value->in(1); 2509 } 2510 #endif 2511 if (value != head->phi()) { 2512 msg = "unhandled shift in address"; 2513 } else { 2514 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) { 2515 msg = "scale doesn't match"; 2516 } else { 2517 found_index = true; 2518 shift = n; 2519 } 2520 } 2521 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) { 2522 if (n->in(1) == head->phi()) { 2523 found_index = true; 2524 conv = n; 2525 } else { 2526 msg = "unhandled input to ConvI2L"; 2527 } 2528 } else if (n == head->phi()) { 2529 // no shift, check below for allowed cases 2530 found_index = true; 2531 } else { 2532 msg = "unhandled node in address"; 2533 msg_node = n; 2534 } 2535 } 2536 2537 if (count == -1) { 2538 msg = "malformed address expression"; 2539 msg_node = store; 2540 } 2541 2542 if (!found_index) { 2543 msg = "missing use of index"; 2544 } 2545 2546 // byte sized items won't have a shift 2547 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) { 2548 msg = "can't find shift"; 2549 msg_node = store; 2550 } 2551 2552 if (msg != NULL) { 2553 #ifndef PRODUCT 2554 if (TraceOptimizeFill) { 2555 tty->print_cr("not fill intrinsic: %s", msg); 2556 if (msg_node != NULL) msg_node->dump(); 2557 } 2558 #endif 2559 return false; 2560 } 2561 2562 // No make sure all the other nodes in the loop can be handled 2563 VectorSet ok(Thread::current()->resource_area()); 2564 2565 // store related values are ok 2566 ok.set(store->_idx); 2567 ok.set(store->in(MemNode::Memory)->_idx); 2568 2569 // Loop structure is ok 2570 ok.set(head->_idx); 2571 ok.set(head->loopexit()->_idx); 2572 ok.set(head->phi()->_idx); 2573 ok.set(head->incr()->_idx); 2574 ok.set(head->loopexit()->cmp_node()->_idx); 2575 ok.set(head->loopexit()->in(1)->_idx); 2576 2577 // Address elements are ok 2578 if (con) ok.set(con->_idx); 2579 if (shift) ok.set(shift->_idx); 2580 if (conv) ok.set(conv->_idx); 2581 2582 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2583 Node* n = lpt->_body.at(i); 2584 if (n->outcnt() == 0) continue; // Ignore dead 2585 if (ok.test(n->_idx)) continue; 2586 // Backedge projection is ok 2587 if (n->is_IfTrue() && n->in(0) == head->loopexit()) continue; 2588 if (!n->is_AddP()) { 2589 msg = "unhandled node"; 2590 msg_node = n; 2591 break; 2592 } 2593 } 2594 2595 // Make sure no unexpected values are used outside the loop 2596 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2597 Node* n = lpt->_body.at(i); 2598 // These values can be replaced with other nodes if they are used 2599 // outside the loop. 2600 if (n == store || n == head->loopexit() || n == head->incr() || n == store->in(MemNode::Memory)) continue; 2601 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) { 2602 Node* use = iter.get(); 2603 if (!lpt->_body.contains(use)) { 2604 msg = "node is used outside loop"; 2605 // lpt->_body.dump(); 2606 msg_node = n; 2607 break; 2608 } 2609 } 2610 } 2611 2612 #ifdef ASSERT 2613 if (TraceOptimizeFill) { 2614 if (msg != NULL) { 2615 tty->print_cr("no fill intrinsic: %s", msg); 2616 if (msg_node != NULL) msg_node->dump(); 2617 } else { 2618 tty->print_cr("fill intrinsic for:"); 2619 } 2620 store->dump(); 2621 if (Verbose) { 2622 lpt->_body.dump(); 2623 } 2624 } 2625 #endif 2626 2627 return msg == NULL; 2628 } 2629 2630 2631 2632 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) { 2633 // Only for counted inner loops 2634 if (!lpt->is_counted() || !lpt->is_inner()) { 2635 return false; 2636 } 2637 2638 // Must have constant stride 2639 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 2640 if (!head->stride_is_con() || !head->is_normal_loop()) { 2641 return false; 2642 } 2643 2644 // Check that the body only contains a store of a loop invariant 2645 // value that is indexed by the loop phi. 2646 Node* store = NULL; 2647 Node* store_value = NULL; 2648 Node* shift = NULL; 2649 Node* offset = NULL; 2650 if (!match_fill_loop(lpt, store, store_value, shift, offset)) { 2651 return false; 2652 } 2653 2654 #ifndef PRODUCT 2655 if (TraceLoopOpts) { 2656 tty->print("ArrayFill "); 2657 lpt->dump_head(); 2658 } 2659 #endif 2660 2661 // Now replace the whole loop body by a call to a fill routine that 2662 // covers the same region as the loop. 2663 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base); 2664 2665 // Build an expression for the beginning of the copy region 2666 Node* index = head->init_trip(); 2667 #ifdef _LP64 2668 index = new (C, 2) ConvI2LNode(index); 2669 _igvn.register_new_node_with_optimizer(index); 2670 #endif 2671 if (shift != NULL) { 2672 // byte arrays don't require a shift but others do. 2673 index = new (C, 3) LShiftXNode(index, shift->in(2)); 2674 _igvn.register_new_node_with_optimizer(index); 2675 } 2676 index = new (C, 4) AddPNode(base, base, index); 2677 _igvn.register_new_node_with_optimizer(index); 2678 Node* from = new (C, 4) AddPNode(base, index, offset); 2679 _igvn.register_new_node_with_optimizer(from); 2680 // Compute the number of elements to copy 2681 Node* len = new (C, 3) SubINode(head->limit(), head->init_trip()); 2682 _igvn.register_new_node_with_optimizer(len); 2683 2684 BasicType t = store->as_Mem()->memory_type(); 2685 bool aligned = false; 2686 if (offset != NULL && head->init_trip()->is_Con()) { 2687 int element_size = type2aelembytes(t); 2688 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0; 2689 } 2690 2691 // Build a call to the fill routine 2692 const char* fill_name; 2693 address fill = StubRoutines::select_fill_function(t, aligned, fill_name); 2694 assert(fill != NULL, "what?"); 2695 2696 // Convert float/double to int/long for fill routines 2697 if (t == T_FLOAT) { 2698 store_value = new (C, 2) MoveF2INode(store_value); 2699 _igvn.register_new_node_with_optimizer(store_value); 2700 } else if (t == T_DOUBLE) { 2701 store_value = new (C, 2) MoveD2LNode(store_value); 2702 _igvn.register_new_node_with_optimizer(store_value); 2703 } 2704 2705 Node* mem_phi = store->in(MemNode::Memory); 2706 Node* result_ctrl; 2707 Node* result_mem; 2708 const TypeFunc* call_type = OptoRuntime::array_fill_Type(); 2709 int size = call_type->domain()->cnt(); 2710 CallLeafNode *call = new (C, size) CallLeafNoFPNode(call_type, fill, 2711 fill_name, TypeAryPtr::get_array_body_type(t)); 2712 call->init_req(TypeFunc::Parms+0, from); 2713 call->init_req(TypeFunc::Parms+1, store_value); 2714 #ifdef _LP64 2715 len = new (C, 2) ConvI2LNode(len); 2716 _igvn.register_new_node_with_optimizer(len); 2717 #endif 2718 call->init_req(TypeFunc::Parms+2, len); 2719 #ifdef _LP64 2720 call->init_req(TypeFunc::Parms+3, C->top()); 2721 #endif 2722 call->init_req( TypeFunc::Control, head->init_control()); 2723 call->init_req( TypeFunc::I_O , C->top() ) ; // does no i/o 2724 call->init_req( TypeFunc::Memory , mem_phi->in(LoopNode::EntryControl) ); 2725 call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) ); 2726 call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) ); 2727 _igvn.register_new_node_with_optimizer(call); 2728 result_ctrl = new (C, 1) ProjNode(call,TypeFunc::Control); 2729 _igvn.register_new_node_with_optimizer(result_ctrl); 2730 result_mem = new (C, 1) ProjNode(call,TypeFunc::Memory); 2731 _igvn.register_new_node_with_optimizer(result_mem); 2732 2733 // If this fill is tightly coupled to an allocation and overwrites 2734 // the whole body, allow it to take over the zeroing. 2735 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this); 2736 if (alloc != NULL && alloc->is_AllocateArray()) { 2737 Node* length = alloc->as_AllocateArray()->Ideal_length(); 2738 if (head->limit() == length && 2739 head->init_trip() == _igvn.intcon(0)) { 2740 if (TraceOptimizeFill) { 2741 tty->print_cr("Eliminated zeroing in allocation"); 2742 } 2743 alloc->maybe_set_complete(&_igvn); 2744 } else { 2745 #ifdef ASSERT 2746 if (TraceOptimizeFill) { 2747 tty->print_cr("filling array but bounds don't match"); 2748 alloc->dump(); 2749 head->init_trip()->dump(); 2750 head->limit()->dump(); 2751 length->dump(); 2752 } 2753 #endif 2754 } 2755 } 2756 2757 // Redirect the old control and memory edges that are outside the loop. 2758 Node* exit = head->loopexit()->proj_out(0); 2759 // Sometimes the memory phi of the head is used as the outgoing 2760 // state of the loop. It's safe in this case to replace it with the 2761 // result_mem. 2762 _igvn.replace_node(store->in(MemNode::Memory), result_mem); 2763 _igvn.replace_node(exit, result_ctrl); 2764 _igvn.replace_node(store, result_mem); 2765 // Any uses the increment outside of the loop become the loop limit. 2766 _igvn.replace_node(head->incr(), head->limit()); 2767 2768 // Disconnect the head from the loop. 2769 for (uint i = 0; i < lpt->_body.size(); i++) { 2770 Node* n = lpt->_body.at(i); 2771 _igvn.replace_node(n, C->top()); 2772 } 2773 2774 return true; 2775 }