1 /* 2 * Copyright (c) 2000, 2017, 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/castnode.hpp" 31 #include "opto/connode.hpp" 32 #include "opto/convertnode.hpp" 33 #include "opto/divnode.hpp" 34 #include "opto/loopnode.hpp" 35 #include "opto/mulnode.hpp" 36 #include "opto/movenode.hpp" 37 #include "opto/opaquenode.hpp" 38 #include "opto/rootnode.hpp" 39 #include "opto/runtime.hpp" 40 #include "opto/subnode.hpp" 41 #include "opto/superword.hpp" 42 #include "opto/vectornode.hpp" 43 44 //------------------------------is_loop_exit----------------------------------- 45 // Given an IfNode, return the loop-exiting projection or NULL if both 46 // arms remain in the loop. 47 Node *IdealLoopTree::is_loop_exit(Node *iff) const { 48 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests 49 PhaseIdealLoop *phase = _phase; 50 // Test is an IfNode, has 2 projections. If BOTH are in the loop 51 // we need loop unswitching instead of peeling. 52 if( !is_member(phase->get_loop( iff->raw_out(0) )) ) 53 return iff->raw_out(0); 54 if( !is_member(phase->get_loop( iff->raw_out(1) )) ) 55 return iff->raw_out(1); 56 return NULL; 57 } 58 59 60 //============================================================================= 61 62 63 //------------------------------record_for_igvn---------------------------- 64 // Put loop body on igvn work list 65 void IdealLoopTree::record_for_igvn() { 66 for( uint i = 0; i < _body.size(); i++ ) { 67 Node *n = _body.at(i); 68 _phase->_igvn._worklist.push(n); 69 } 70 // put body of outer strip mined loop on igvn work list as well 71 if (_head->is_CountedLoop() && _head->as_Loop()->is_strip_mined()) { 72 CountedLoopNode* l = _head->as_CountedLoop(); 73 _phase->_igvn._worklist.push(l->outer_loop()); 74 _phase->_igvn._worklist.push(l->outer_loop_tail()); 75 _phase->_igvn._worklist.push(l->outer_loop_end()); 76 _phase->_igvn._worklist.push(l->outer_safepoint()); 77 Node* cle_out = _head->as_CountedLoop()->loopexit()->proj_out(false); 78 _phase->_igvn._worklist.push(cle_out); 79 } 80 } 81 82 //------------------------------compute_exact_trip_count----------------------- 83 // Compute loop trip count if possible. Do not recalculate trip count for 84 // split loops (pre-main-post) which have their limits and inits behind Opaque node. 85 void IdealLoopTree::compute_trip_count(PhaseIdealLoop* phase) { 86 if (!_head->as_Loop()->is_valid_counted_loop()) { 87 return; 88 } 89 CountedLoopNode* cl = _head->as_CountedLoop(); 90 // Trip count may become nonexact for iteration split loops since 91 // RCE modifies limits. Note, _trip_count value is not reset since 92 // it is used to limit unrolling of main loop. 93 cl->set_nonexact_trip_count(); 94 95 // Loop's test should be part of loop. 96 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 97 return; // Infinite loop 98 99 #ifdef ASSERT 100 BoolTest::mask bt = cl->loopexit()->test_trip(); 101 assert(bt == BoolTest::lt || bt == BoolTest::gt || 102 bt == BoolTest::ne, "canonical test is expected"); 103 #endif 104 105 Node* init_n = cl->init_trip(); 106 Node* limit_n = cl->limit(); 107 if (init_n != NULL && limit_n != NULL) { 108 // Use longs to avoid integer overflow. 109 int stride_con = cl->stride_con(); 110 jlong init_con = phase->_igvn.type(init_n)->is_int()->_lo; 111 jlong limit_con = phase->_igvn.type(limit_n)->is_int()->_hi; 112 int stride_m = stride_con - (stride_con > 0 ? 1 : -1); 113 jlong trip_count = (limit_con - init_con + stride_m)/stride_con; 114 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) { 115 if (init_n->is_Con() && limit_n->is_Con()) { 116 // Set exact trip count. 117 cl->set_exact_trip_count((uint)trip_count); 118 } else if (cl->unrolled_count() == 1) { 119 // Set maximum trip count before unrolling. 120 cl->set_trip_count((uint)trip_count); 121 } 122 } 123 } 124 } 125 126 //------------------------------compute_profile_trip_cnt---------------------------- 127 // Compute loop trip count from profile data as 128 // (backedge_count + loop_exit_count) / loop_exit_count 129 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) { 130 if (!_head->is_CountedLoop()) { 131 return; 132 } 133 CountedLoopNode* head = _head->as_CountedLoop(); 134 if (head->profile_trip_cnt() != COUNT_UNKNOWN) { 135 return; // Already computed 136 } 137 float trip_cnt = (float)max_jint; // default is big 138 139 Node* back = head->in(LoopNode::LoopBackControl); 140 while (back != head) { 141 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 142 back->in(0) && 143 back->in(0)->is_If() && 144 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN && 145 back->in(0)->as_If()->_prob != PROB_UNKNOWN) { 146 break; 147 } 148 back = phase->idom(back); 149 } 150 if (back != head) { 151 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 152 back->in(0), "if-projection exists"); 153 IfNode* back_if = back->in(0)->as_If(); 154 float loop_back_cnt = back_if->_fcnt * back_if->_prob; 155 156 // Now compute a loop exit count 157 float loop_exit_cnt = 0.0f; 158 for( uint i = 0; i < _body.size(); i++ ) { 159 Node *n = _body[i]; 160 if( n->is_If() ) { 161 IfNode *iff = n->as_If(); 162 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) { 163 Node *exit = is_loop_exit(iff); 164 if( exit ) { 165 float exit_prob = iff->_prob; 166 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob; 167 if (exit_prob > PROB_MIN) { 168 float exit_cnt = iff->_fcnt * exit_prob; 169 loop_exit_cnt += exit_cnt; 170 } 171 } 172 } 173 } 174 } 175 if (loop_exit_cnt > 0.0f) { 176 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt; 177 } else { 178 // No exit count so use 179 trip_cnt = loop_back_cnt; 180 } 181 } 182 #ifndef PRODUCT 183 if (TraceProfileTripCount) { 184 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt); 185 } 186 #endif 187 head->set_profile_trip_cnt(trip_cnt); 188 } 189 190 //---------------------is_invariant_addition----------------------------- 191 // Return nonzero index of invariant operand for an Add or Sub 192 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants. 193 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) { 194 int op = n->Opcode(); 195 if (op == Op_AddI || op == Op_SubI) { 196 bool in1_invar = this->is_invariant(n->in(1)); 197 bool in2_invar = this->is_invariant(n->in(2)); 198 if (in1_invar && !in2_invar) return 1; 199 if (!in1_invar && in2_invar) return 2; 200 } 201 return 0; 202 } 203 204 //---------------------reassociate_add_sub----------------------------- 205 // Reassociate invariant add and subtract expressions: 206 // 207 // inv1 + (x + inv2) => ( inv1 + inv2) + x 208 // (x + inv2) + inv1 => ( inv1 + inv2) + x 209 // inv1 + (x - inv2) => ( inv1 - inv2) + x 210 // inv1 - (inv2 - x) => ( inv1 - inv2) + x 211 // (x + inv2) - inv1 => (-inv1 + inv2) + x 212 // (x - inv2) + inv1 => ( inv1 - inv2) + x 213 // (x - inv2) - inv1 => (-inv1 - inv2) + x 214 // inv1 + (inv2 - x) => ( inv1 + inv2) - x 215 // inv1 - (x - inv2) => ( inv1 + inv2) - x 216 // (inv2 - x) + inv1 => ( inv1 + inv2) - x 217 // (inv2 - x) - inv1 => (-inv1 + inv2) - x 218 // inv1 - (x + inv2) => ( inv1 - inv2) - x 219 // 220 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) { 221 if ((!n1->is_Add() && !n1->is_Sub()) || n1->outcnt() == 0) return NULL; 222 if (is_invariant(n1)) return NULL; 223 int inv1_idx = is_invariant_addition(n1, phase); 224 if (!inv1_idx) return NULL; 225 // Don't mess with add of constant (igvn moves them to expression tree root.) 226 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL; 227 Node* inv1 = n1->in(inv1_idx); 228 Node* n2 = n1->in(3 - inv1_idx); 229 int inv2_idx = is_invariant_addition(n2, phase); 230 if (!inv2_idx) return NULL; 231 Node* x = n2->in(3 - inv2_idx); 232 Node* inv2 = n2->in(inv2_idx); 233 234 bool neg_x = n2->is_Sub() && inv2_idx == 1; 235 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2; 236 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2; 237 if (n1->is_Sub() && inv1_idx == 1) { 238 neg_x = !neg_x; 239 neg_inv2 = !neg_inv2; 240 } 241 Node* inv1_c = phase->get_ctrl(inv1); 242 Node* inv2_c = phase->get_ctrl(inv2); 243 Node* n_inv1; 244 if (neg_inv1) { 245 Node *zero = phase->_igvn.intcon(0); 246 phase->set_ctrl(zero, phase->C->root()); 247 n_inv1 = new SubINode(zero, inv1); 248 phase->register_new_node(n_inv1, inv1_c); 249 } else { 250 n_inv1 = inv1; 251 } 252 Node* inv; 253 if (neg_inv2) { 254 inv = new SubINode(n_inv1, inv2); 255 } else { 256 inv = new AddINode(n_inv1, inv2); 257 } 258 phase->register_new_node(inv, phase->get_early_ctrl(inv)); 259 260 Node* addx; 261 if (neg_x) { 262 addx = new SubINode(inv, x); 263 } else { 264 addx = new AddINode(x, inv); 265 } 266 phase->register_new_node(addx, phase->get_ctrl(x)); 267 phase->_igvn.replace_node(n1, addx); 268 assert(phase->get_loop(phase->get_ctrl(n1)) == this, ""); 269 _body.yank(n1); 270 return addx; 271 } 272 273 //---------------------reassociate_invariants----------------------------- 274 // Reassociate invariant expressions: 275 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { 276 for (int i = _body.size() - 1; i >= 0; i--) { 277 Node *n = _body.at(i); 278 for (int j = 0; j < 5; j++) { 279 Node* nn = reassociate_add_sub(n, phase); 280 if (nn == NULL) break; 281 n = nn; // again 282 }; 283 } 284 } 285 286 //------------------------------policy_peeling--------------------------------- 287 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can 288 // make some loop-invariant test (usually a null-check) happen before the loop. 289 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const { 290 Node *test = ((IdealLoopTree*)this)->tail(); 291 int body_size = ((IdealLoopTree*)this)->_body.size(); 292 // Peeling does loop cloning which can result in O(N^2) node construction 293 if( body_size > 255 /* Prevent overflow for large body_size */ 294 || (body_size * body_size + phase->C->live_nodes()) > phase->C->max_node_limit() ) { 295 return false; // too large to safely clone 296 } 297 298 // check for vectorized loops, any peeling done was already applied 299 if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false; 300 301 while( test != _head ) { // Scan till run off top of loop 302 if( test->is_If() ) { // Test? 303 Node *ctrl = phase->get_ctrl(test->in(1)); 304 if (ctrl->is_top()) 305 return false; // Found dead test on live IF? No peeling! 306 // Standard IF only has one input value to check for loop invariance 307 assert(test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd || test->Opcode() == Op_RangeCheck, "Check this code when new subtype is added"); 308 // Condition is not a member of this loop? 309 if( !is_member(phase->get_loop(ctrl)) && 310 is_loop_exit(test) ) 311 return true; // Found reason to peel! 312 } 313 // Walk up dominators to loop _head looking for test which is 314 // executed on every path thru loop. 315 test = phase->idom(test); 316 } 317 return false; 318 } 319 320 //------------------------------peeled_dom_test_elim--------------------------- 321 // If we got the effect of peeling, either by actually peeling or by making 322 // a pre-loop which must execute at least once, we can remove all 323 // loop-invariant dominated tests in the main body. 324 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) { 325 bool progress = true; 326 while( progress ) { 327 progress = false; // Reset for next iteration 328 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail(); 329 Node *test = prev->in(0); 330 while( test != loop->_head ) { // Scan till run off top of loop 331 332 int p_op = prev->Opcode(); 333 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) && 334 test->is_If() && // Test? 335 !test->in(1)->is_Con() && // And not already obvious? 336 // Condition is not a member of this loop? 337 !loop->is_member(get_loop(get_ctrl(test->in(1))))){ 338 // Walk loop body looking for instances of this test 339 for( uint i = 0; i < loop->_body.size(); i++ ) { 340 Node *n = loop->_body.at(i); 341 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) { 342 // IfNode was dominated by version in peeled loop body 343 progress = true; 344 dominated_by( old_new[prev->_idx], n ); 345 } 346 } 347 } 348 prev = test; 349 test = idom(test); 350 } // End of scan tests in loop 351 352 } // End of while( progress ) 353 } 354 355 //------------------------------do_peeling------------------------------------- 356 // Peel the first iteration of the given loop. 357 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 358 // The pre-loop illegally has 2 control users (old & new loops). 359 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 360 // Do this by making the old-loop fall-in edges act as if they came 361 // around the loopback from the prior iteration (follow the old-loop 362 // backedges) and then map to the new peeled iteration. This leaves 363 // the pre-loop with only 1 user (the new peeled iteration), but the 364 // peeled-loop backedge has 2 users. 365 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 366 // extra backedge user. 367 // 368 // orig 369 // 370 // stmt1 371 // | 372 // v 373 // loop predicate 374 // | 375 // v 376 // loop<----+ 377 // | | 378 // stmt2 | 379 // | | 380 // v | 381 // if ^ 382 // / \ | 383 // / \ | 384 // v v | 385 // false true | 386 // / \ | 387 // / ----+ 388 // | 389 // v 390 // exit 391 // 392 // 393 // after clone loop 394 // 395 // stmt1 396 // | 397 // v 398 // loop predicate 399 // / \ 400 // clone / \ orig 401 // / \ 402 // / \ 403 // v v 404 // +---->loop clone loop<----+ 405 // | | | | 406 // | stmt2 clone stmt2 | 407 // | | | | 408 // | v v | 409 // ^ if clone If ^ 410 // | / \ / \ | 411 // | / \ / \ | 412 // | v v v v | 413 // | true false false true | 414 // | / \ / \ | 415 // +---- \ / ----+ 416 // \ / 417 // 1v v2 418 // region 419 // | 420 // v 421 // exit 422 // 423 // 424 // after peel and predicate move 425 // 426 // stmt1 427 // / 428 // / 429 // clone / orig 430 // / 431 // / +----------+ 432 // / | | 433 // / loop predicate | 434 // / | | 435 // v v | 436 // TOP-->loop clone loop<----+ | 437 // | | | | 438 // stmt2 clone stmt2 | | 439 // | | | ^ 440 // v v | | 441 // if clone If ^ | 442 // / \ / \ | | 443 // / \ / \ | | 444 // v v v v | | 445 // true false false true | | 446 // | \ / \ | | 447 // | \ / ----+ ^ 448 // | \ / | 449 // | 1v v2 | 450 // v region | 451 // | | | 452 // | v | 453 // | exit | 454 // | | 455 // +--------------->-----------------+ 456 // 457 // 458 // final graph 459 // 460 // stmt1 461 // | 462 // v 463 // stmt2 clone 464 // | 465 // v 466 // if clone 467 // / | 468 // / | 469 // v v 470 // false true 471 // | | 472 // | v 473 // | loop predicate 474 // | | 475 // | v 476 // | loop<----+ 477 // | | | 478 // | stmt2 | 479 // | | | 480 // | v | 481 // v if ^ 482 // | / \ | 483 // | / \ | 484 // | v v | 485 // | false true | 486 // | | \ | 487 // v v --+ 488 // region 489 // | 490 // v 491 // exit 492 // 493 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) { 494 495 C->set_major_progress(); 496 // Peeling a 'main' loop in a pre/main/post situation obfuscates the 497 // 'pre' loop from the main and the 'pre' can no longer have its 498 // iterations adjusted. Therefore, we need to declare this loop as 499 // no longer a 'main' loop; it will need new pre and post loops before 500 // we can do further RCE. 501 #ifndef PRODUCT 502 if (TraceLoopOpts) { 503 tty->print("Peel "); 504 loop->dump_head(); 505 } 506 #endif 507 LoopNode* head = loop->_head->as_Loop(); 508 bool counted_loop = head->is_CountedLoop(); 509 if (counted_loop) { 510 CountedLoopNode *cl = head->as_CountedLoop(); 511 assert(cl->trip_count() > 0, "peeling a fully unrolled loop"); 512 cl->set_trip_count(cl->trip_count() - 1); 513 if (cl->is_main_loop()) { 514 cl->set_normal_loop(); 515 #ifndef PRODUCT 516 if (PrintOpto && VerifyLoopOptimizations) { 517 tty->print("Peeling a 'main' loop; resetting to 'normal' "); 518 loop->dump_head(); 519 } 520 #endif 521 } 522 } 523 Node* entry = head->in(LoopNode::EntryControl); 524 525 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 526 // The pre-loop illegally has 2 control users (old & new loops). 527 clone_loop(loop, old_new, dom_depth(head->skip_strip_mined()), ControlAroundStripMined); 528 529 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 530 // Do this by making the old-loop fall-in edges act as if they came 531 // around the loopback from the prior iteration (follow the old-loop 532 // backedges) and then map to the new peeled iteration. This leaves 533 // the pre-loop with only 1 user (the new peeled iteration), but the 534 // peeled-loop backedge has 2 users. 535 Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx]; 536 _igvn.hash_delete(head->skip_strip_mined()); 537 head->skip_strip_mined()->set_req(LoopNode::EntryControl, new_entry); 538 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) { 539 Node* old = head->fast_out(j); 540 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) { 541 Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; 542 if (!new_exit_value ) // Backedge value is ALSO loop invariant? 543 // Then loop body backedge value remains the same. 544 new_exit_value = old->in(LoopNode::LoopBackControl); 545 _igvn.hash_delete(old); 546 old->set_req(LoopNode::EntryControl, new_exit_value); 547 } 548 } 549 550 551 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 552 // extra backedge user. 553 Node* new_head = old_new[head->_idx]; 554 _igvn.hash_delete(new_head); 555 new_head->set_req(LoopNode::LoopBackControl, C->top()); 556 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) { 557 Node* use = new_head->fast_out(j2); 558 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) { 559 _igvn.hash_delete(use); 560 use->set_req(LoopNode::LoopBackControl, C->top()); 561 } 562 } 563 564 565 // Step 4: Correct dom-depth info. Set to loop-head depth. 566 int dd = dom_depth(head); 567 set_idom(head, head->in(1), dd); 568 for (uint j3 = 0; j3 < loop->_body.size(); j3++) { 569 Node *old = loop->_body.at(j3); 570 Node *nnn = old_new[old->_idx]; 571 if (!has_ctrl(nnn)) 572 set_idom(nnn, idom(nnn), dd-1); 573 } 574 575 // Now force out all loop-invariant dominating tests. The optimizer 576 // finds some, but we _know_ they are all useless. 577 peeled_dom_test_elim(loop,old_new); 578 579 loop->record_for_igvn(); 580 } 581 582 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop 583 584 //------------------------------policy_maximally_unroll------------------------ 585 // Calculate exact loop trip count and return true if loop can be maximally 586 // unrolled. 587 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const { 588 CountedLoopNode *cl = _head->as_CountedLoop(); 589 assert(cl->is_normal_loop(), ""); 590 if (!cl->is_valid_counted_loop()) 591 return false; // Malformed counted loop 592 593 if (!cl->has_exact_trip_count()) { 594 // Trip count is not exact. 595 return false; 596 } 597 598 uint trip_count = cl->trip_count(); 599 // Note, max_juint is used to indicate unknown trip count. 600 assert(trip_count > 1, "one iteration loop should be optimized out already"); 601 assert(trip_count < max_juint, "exact trip_count should be less than max_uint."); 602 603 // Real policy: if we maximally unroll, does it get too big? 604 // Allow the unrolled mess to get larger than standard loop 605 // size. After all, it will no longer be a loop. 606 uint body_size = _body.size(); 607 uint unroll_limit = (uint)LoopUnrollLimit * 4; 608 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); 609 if (trip_count > unroll_limit || body_size > unroll_limit) { 610 return false; 611 } 612 613 // Fully unroll a loop with few iterations regardless next 614 // conditions since following loop optimizations will split 615 // such loop anyway (pre-main-post). 616 if (trip_count <= 3) 617 return true; 618 619 // Take into account that after unroll conjoined heads and tails will fold, 620 // otherwise policy_unroll() may allow more unrolling than max unrolling. 621 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count; 622 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE; 623 if (body_size != tst_body_size) // Check for int overflow 624 return false; 625 if (new_body_size > unroll_limit || 626 // Unrolling can result in a large amount of node construction 627 new_body_size >= phase->C->max_node_limit() - phase->C->live_nodes()) { 628 return false; 629 } 630 631 // Do not unroll a loop with String intrinsics code. 632 // String intrinsics are large and have loops. 633 for (uint k = 0; k < _body.size(); k++) { 634 Node* n = _body.at(k); 635 switch (n->Opcode()) { 636 case Op_StrComp: 637 case Op_StrEquals: 638 case Op_StrIndexOf: 639 case Op_StrIndexOfChar: 640 case Op_EncodeISOArray: 641 case Op_AryEq: 642 case Op_HasNegatives: { 643 return false; 644 } 645 #if INCLUDE_RTM_OPT 646 case Op_FastLock: 647 case Op_FastUnlock: { 648 // Don't unroll RTM locking code because it is large. 649 if (UseRTMLocking) { 650 return false; 651 } 652 } 653 #endif 654 } // switch 655 } 656 657 return true; // Do maximally unroll 658 } 659 660 661 //------------------------------policy_unroll---------------------------------- 662 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if 663 // the loop is a CountedLoop and the body is small enough. 664 bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) { 665 666 CountedLoopNode *cl = _head->as_CountedLoop(); 667 assert(cl->is_normal_loop() || cl->is_main_loop(), ""); 668 669 if (!cl->is_valid_counted_loop()) 670 return false; // Malformed counted loop 671 672 // Protect against over-unrolling. 673 // After split at least one iteration will be executed in pre-loop. 674 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false; 675 676 _local_loop_unroll_limit = LoopUnrollLimit; 677 _local_loop_unroll_factor = 4; 678 int future_unroll_ct = cl->unrolled_count() * 2; 679 if (!cl->is_vectorized_loop()) { 680 if (future_unroll_ct > LoopMaxUnroll) return false; 681 } else { 682 // obey user constraints on vector mapped loops with additional unrolling applied 683 int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1; 684 if ((future_unroll_ct / unroll_constraint) > LoopMaxUnroll) return false; 685 } 686 687 // Check for initial stride being a small enough constant 688 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false; 689 690 // Don't unroll if the next round of unrolling would push us 691 // over the expected trip count of the loop. One is subtracted 692 // from the expected trip count because the pre-loop normally 693 // executes 1 iteration. 694 if (UnrollLimitForProfileCheck > 0 && 695 cl->profile_trip_cnt() != COUNT_UNKNOWN && 696 future_unroll_ct > UnrollLimitForProfileCheck && 697 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) { 698 return false; 699 } 700 701 // When unroll count is greater than LoopUnrollMin, don't unroll if: 702 // the residual iterations are more than 10% of the trip count 703 // and rounds of "unroll,optimize" are not making significant progress 704 // Progress defined as current size less than 20% larger than previous size. 705 if (UseSuperWord && cl->node_count_before_unroll() > 0 && 706 future_unroll_ct > LoopUnrollMin && 707 (future_unroll_ct - 1) * (100 / LoopPercentProfileLimit) > cl->profile_trip_cnt() && 708 1.2 * cl->node_count_before_unroll() < (double)_body.size()) { 709 return false; 710 } 711 712 Node *init_n = cl->init_trip(); 713 Node *limit_n = cl->limit(); 714 int stride_con = cl->stride_con(); 715 // Non-constant bounds. 716 // Protect against over-unrolling when init or/and limit are not constant 717 // (so that trip_count's init value is maxint) but iv range is known. 718 if (init_n == NULL || !init_n->is_Con() || 719 limit_n == NULL || !limit_n->is_Con()) { 720 Node* phi = cl->phi(); 721 if (phi != NULL) { 722 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); 723 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); 724 int next_stride = stride_con * 2; // stride after this unroll 725 if (next_stride > 0) { 726 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow 727 iv_type->_lo + next_stride > iv_type->_hi) { 728 return false; // over-unrolling 729 } 730 } else if (next_stride < 0) { 731 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow 732 iv_type->_hi + next_stride < iv_type->_lo) { 733 return false; // over-unrolling 734 } 735 } 736 } 737 } 738 739 // After unroll limit will be adjusted: new_limit = limit-stride. 740 // Bailout if adjustment overflow. 741 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int(); 742 if ((stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi)) || 743 (stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))) 744 return false; // overflow 745 746 // Adjust body_size to determine if we unroll or not 747 uint body_size = _body.size(); 748 // Key test to unroll loop in CRC32 java code 749 int xors_in_loop = 0; 750 // Also count ModL, DivL and MulL which expand mightly 751 for (uint k = 0; k < _body.size(); k++) { 752 Node* n = _body.at(k); 753 switch (n->Opcode()) { 754 case Op_XorI: xors_in_loop++; break; // CRC32 java code 755 case Op_ModL: body_size += 30; break; 756 case Op_DivL: body_size += 30; break; 757 case Op_MulL: body_size += 10; break; 758 case Op_StrComp: 759 case Op_StrEquals: 760 case Op_StrIndexOf: 761 case Op_StrIndexOfChar: 762 case Op_EncodeISOArray: 763 case Op_AryEq: 764 case Op_HasNegatives: { 765 // Do not unroll a loop with String intrinsics code. 766 // String intrinsics are large and have loops. 767 return false; 768 } 769 #if INCLUDE_RTM_OPT 770 case Op_FastLock: 771 case Op_FastUnlock: { 772 // Don't unroll RTM locking code because it is large. 773 if (UseRTMLocking) { 774 return false; 775 } 776 } 777 #endif 778 } // switch 779 } 780 781 if (UseSuperWord) { 782 if (!cl->is_reduction_loop()) { 783 phase->mark_reductions(this); 784 } 785 786 // Only attempt slp analysis when user controls do not prohibit it 787 if (LoopMaxUnroll > _local_loop_unroll_factor) { 788 // Once policy_slp_analysis succeeds, mark the loop with the 789 // maximal unroll factor so that we minimize analysis passes 790 if (future_unroll_ct >= _local_loop_unroll_factor) { 791 policy_unroll_slp_analysis(cl, phase, future_unroll_ct); 792 } 793 } 794 } 795 796 int slp_max_unroll_factor = cl->slp_max_unroll(); 797 if ((LoopMaxUnroll < slp_max_unroll_factor) && FLAG_IS_DEFAULT(LoopMaxUnroll) && UseSubwordForMaxVector) { 798 LoopMaxUnroll = slp_max_unroll_factor; 799 } 800 if (cl->has_passed_slp()) { 801 if (slp_max_unroll_factor >= future_unroll_ct) return true; 802 // Normal case: loop too big 803 return false; 804 } 805 806 // Check for being too big 807 if (body_size > (uint)_local_loop_unroll_limit) { 808 if ((UseSubwordForMaxVector || xors_in_loop >= 4) && body_size < (uint)LoopUnrollLimit * 4) return true; 809 // Normal case: loop too big 810 return false; 811 } 812 813 if (cl->do_unroll_only()) { 814 if (TraceSuperWordLoopUnrollAnalysis) { 815 tty->print_cr("policy_unroll passed vector loop(vlen=%d,factor = %d)\n", slp_max_unroll_factor, future_unroll_ct); 816 } 817 } 818 819 // Unroll once! (Each trip will soon do double iterations) 820 return true; 821 } 822 823 void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct) { 824 // Enable this functionality target by target as needed 825 if (SuperWordLoopUnrollAnalysis) { 826 if (!cl->was_slp_analyzed()) { 827 SuperWord sw(phase); 828 sw.transform_loop(this, false); 829 830 // If the loop is slp canonical analyze it 831 if (sw.early_return() == false) { 832 sw.unrolling_analysis(_local_loop_unroll_factor); 833 } 834 } 835 836 if (cl->has_passed_slp()) { 837 int slp_max_unroll_factor = cl->slp_max_unroll(); 838 if (slp_max_unroll_factor >= future_unroll_ct) { 839 int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor; 840 if (new_limit > LoopUnrollLimit) { 841 if (TraceSuperWordLoopUnrollAnalysis) { 842 tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit); 843 } 844 _local_loop_unroll_limit = new_limit; 845 } 846 } 847 } 848 } 849 } 850 851 //------------------------------policy_align----------------------------------- 852 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the 853 // expression that does the alignment. Note that only one array base can be 854 // aligned in a loop (unless the VM guarantees mutual alignment). Note that 855 // if we vectorize short memory ops into longer memory ops, we may want to 856 // increase alignment. 857 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const { 858 return false; 859 } 860 861 //------------------------------policy_range_check----------------------------- 862 // Return TRUE or FALSE if the loop should be range-check-eliminated. 863 // Actually we do iteration-splitting, a more powerful form of RCE. 864 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const { 865 if (!RangeCheckElimination) return false; 866 867 CountedLoopNode *cl = _head->as_CountedLoop(); 868 // If we unrolled with no intention of doing RCE and we later 869 // changed our minds, we got no pre-loop. Either we need to 870 // make a new pre-loop, or we gotta disallow RCE. 871 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now. 872 Node *trip_counter = cl->phi(); 873 874 // check for vectorized loops, some opts are no longer needed 875 if (cl->do_unroll_only()) return false; 876 877 // Check loop body for tests of trip-counter plus loop-invariant vs 878 // loop-invariant. 879 for (uint i = 0; i < _body.size(); i++) { 880 Node *iff = _body[i]; 881 if (iff->Opcode() == Op_If || 882 iff->Opcode() == Op_RangeCheck) { // Test? 883 884 // Comparing trip+off vs limit 885 Node *bol = iff->in(1); 886 if (bol->req() != 2) continue; // dead constant test 887 if (!bol->is_Bool()) { 888 assert(bol->Opcode() == Op_Conv2B, "predicate check only"); 889 continue; 890 } 891 if (bol->as_Bool()->_test._test == BoolTest::ne) 892 continue; // not RC 893 894 Node *cmp = bol->in(1); 895 Node *rc_exp = cmp->in(1); 896 Node *limit = cmp->in(2); 897 898 Node *limit_c = phase->get_ctrl(limit); 899 if( limit_c == phase->C->top() ) 900 return false; // Found dead test on live IF? No RCE! 901 if( is_member(phase->get_loop(limit_c) ) ) { 902 // Compare might have operands swapped; commute them 903 rc_exp = cmp->in(2); 904 limit = cmp->in(1); 905 limit_c = phase->get_ctrl(limit); 906 if( is_member(phase->get_loop(limit_c) ) ) 907 continue; // Both inputs are loop varying; cannot RCE 908 } 909 910 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) { 911 continue; 912 } 913 // Yeah! Found a test like 'trip+off vs limit' 914 // Test is an IfNode, has 2 projections. If BOTH are in the loop 915 // we need loop unswitching instead of iteration splitting. 916 if( is_loop_exit(iff) ) 917 return true; // Found reason to split iterations 918 } // End of is IF 919 } 920 921 return false; 922 } 923 924 //------------------------------policy_peel_only------------------------------- 925 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful 926 // for unrolling loops with NO array accesses. 927 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const { 928 // check for vectorized loops, any peeling done was already applied 929 if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false; 930 931 for( uint i = 0; i < _body.size(); i++ ) 932 if( _body[i]->is_Mem() ) 933 return false; 934 935 // No memory accesses at all! 936 return true; 937 } 938 939 //------------------------------clone_up_backedge_goo-------------------------- 940 // If Node n lives in the back_ctrl block and cannot float, we clone a private 941 // version of n in preheader_ctrl block and return that, otherwise return n. 942 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) { 943 if( get_ctrl(n) != back_ctrl ) return n; 944 945 // Only visit once 946 if (visited.test_set(n->_idx)) { 947 Node *x = clones.find(n->_idx); 948 if (x != NULL) 949 return x; 950 return n; 951 } 952 953 Node *x = NULL; // If required, a clone of 'n' 954 // Check for 'n' being pinned in the backedge. 955 if( n->in(0) && n->in(0) == back_ctrl ) { 956 assert(clones.find(n->_idx) == NULL, "dead loop"); 957 x = n->clone(); // Clone a copy of 'n' to preheader 958 clones.push(x, n->_idx); 959 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader 960 } 961 962 // Recursive fixup any other input edges into x. 963 // If there are no changes we can just return 'n', otherwise 964 // we need to clone a private copy and change it. 965 for( uint i = 1; i < n->req(); i++ ) { 966 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones ); 967 if( g != n->in(i) ) { 968 if( !x ) { 969 assert(clones.find(n->_idx) == NULL, "dead loop"); 970 x = n->clone(); 971 clones.push(x, n->_idx); 972 } 973 x->set_req(i, g); 974 } 975 } 976 if( x ) { // x can legally float to pre-header location 977 register_new_node( x, preheader_ctrl ); 978 return x; 979 } else { // raise n to cover LCA of uses 980 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); 981 } 982 return n; 983 } 984 985 bool PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) { 986 Node* castii = new CastIINode(incr, TypeInt::INT, true); 987 castii->set_req(0, ctrl); 988 register_new_node(castii, ctrl); 989 for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) { 990 Node* n = incr->fast_out(i); 991 if (n->is_Phi() && n->in(0) == loop) { 992 int nrep = n->replace_edge(incr, castii); 993 return true; 994 } 995 } 996 return false; 997 } 998 999 //------------------------------insert_pre_post_loops-------------------------- 1000 // Insert pre and post loops. If peel_only is set, the pre-loop can not have 1001 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no 1002 // alignment. Useful to unroll loops that do no array accesses. 1003 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { 1004 1005 #ifndef PRODUCT 1006 if (TraceLoopOpts) { 1007 if (peel_only) 1008 tty->print("PeelMainPost "); 1009 else 1010 tty->print("PreMainPost "); 1011 loop->dump_head(); 1012 } 1013 #endif 1014 C->set_major_progress(); 1015 1016 // Find common pieces of the loop being guarded with pre & post loops 1017 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 1018 assert( main_head->is_normal_loop(), "" ); 1019 CountedLoopEndNode *main_end = main_head->loopexit(); 1020 guarantee(main_end != NULL, "no loop exit node"); 1021 assert( main_end->outcnt() == 2, "1 true, 1 false path only" ); 1022 1023 Node *pre_header= main_head->in(LoopNode::EntryControl); 1024 Node *init = main_head->init_trip(); 1025 Node *incr = main_end ->incr(); 1026 Node *limit = main_end ->limit(); 1027 Node *stride = main_end ->stride(); 1028 Node *cmp = main_end ->cmp_node(); 1029 BoolTest::mask b_test = main_end->test_trip(); 1030 1031 // Need only 1 user of 'bol' because I will be hacking the loop bounds. 1032 Node *bol = main_end->in(CountedLoopEndNode::TestValue); 1033 if( bol->outcnt() != 1 ) { 1034 bol = bol->clone(); 1035 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl)); 1036 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol); 1037 } 1038 // Need only 1 user of 'cmp' because I will be hacking the loop bounds. 1039 if( cmp->outcnt() != 1 ) { 1040 cmp = cmp->clone(); 1041 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl)); 1042 _igvn.replace_input_of(bol, 1, cmp); 1043 } 1044 1045 // Add the post loop 1046 CountedLoopNode *post_head = NULL; 1047 Node *main_exit = insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head); 1048 1049 //------------------------------ 1050 // Step B: Create Pre-Loop. 1051 1052 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main 1053 // loop pre-header illegally has 2 control users (old & new loops). 1054 LoopNode* outer_main_head = main_head; 1055 IdealLoopTree* outer_loop = loop; 1056 if (main_head->is_strip_mined()) { 1057 main_head->verify_strip_mined(1); 1058 outer_main_head = main_head->outer_loop(); 1059 outer_loop = loop->_parent; 1060 assert(outer_loop->_head == outer_main_head, "broken loop tree"); 1061 } 1062 uint dd_main_head = dom_depth(outer_main_head); 1063 clone_loop(loop, old_new, dd_main_head, ControlAroundStripMined); 1064 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop(); 1065 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 1066 pre_head->set_pre_loop(main_head); 1067 Node *pre_incr = old_new[incr->_idx]; 1068 1069 // Reduce the pre-loop trip count. 1070 pre_end->_prob = PROB_FAIR; 1071 1072 // Find the pre-loop normal exit. 1073 Node* pre_exit = pre_end->proj_out(false); 1074 assert( pre_exit->Opcode() == Op_IfFalse, "" ); 1075 IfFalseNode *new_pre_exit = new IfFalseNode(pre_end); 1076 _igvn.register_new_node_with_optimizer( new_pre_exit ); 1077 set_idom(new_pre_exit, pre_end, dd_main_head); 1078 set_loop(new_pre_exit, outer_loop->_parent); 1079 1080 // Step B2: Build a zero-trip guard for the main-loop. After leaving the 1081 // pre-loop, the main-loop may not execute at all. Later in life this 1082 // zero-trip guard will become the minimum-trip guard when we unroll 1083 // the main-loop. 1084 Node *min_opaq = new Opaque1Node(C, limit); 1085 Node *min_cmp = new CmpINode( pre_incr, min_opaq ); 1086 Node *min_bol = new BoolNode( min_cmp, b_test ); 1087 register_new_node( min_opaq, new_pre_exit ); 1088 register_new_node( min_cmp , new_pre_exit ); 1089 register_new_node( min_bol , new_pre_exit ); 1090 1091 // Build the IfNode (assume the main-loop is executed always). 1092 IfNode *min_iff = new IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN ); 1093 _igvn.register_new_node_with_optimizer( min_iff ); 1094 set_idom(min_iff, new_pre_exit, dd_main_head); 1095 set_loop(min_iff, outer_loop->_parent); 1096 1097 // Plug in the false-path, taken if we need to skip main-loop 1098 _igvn.hash_delete( pre_exit ); 1099 pre_exit->set_req(0, min_iff); 1100 set_idom(pre_exit, min_iff, dd_main_head); 1101 set_idom(pre_exit->unique_ctrl_out(), min_iff, dd_main_head); 1102 // Make the true-path, must enter the main loop 1103 Node *min_taken = new IfTrueNode( min_iff ); 1104 _igvn.register_new_node_with_optimizer( min_taken ); 1105 set_idom(min_taken, min_iff, dd_main_head); 1106 set_loop(min_taken, outer_loop->_parent); 1107 // Plug in the true path 1108 _igvn.hash_delete(outer_main_head); 1109 outer_main_head->set_req(LoopNode::EntryControl, min_taken); 1110 set_idom(outer_main_head, min_taken, dd_main_head); 1111 1112 Arena *a = Thread::current()->resource_area(); 1113 VectorSet visited(a); 1114 Node_Stack clones(a, main_head->back_control()->outcnt()); 1115 // Step B3: Make the fall-in values to the main-loop come from the 1116 // fall-out values of the pre-loop. 1117 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) { 1118 Node* main_phi = main_head->fast_out(i2); 1119 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) { 1120 Node *pre_phi = old_new[main_phi->_idx]; 1121 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(), 1122 main_head->skip_strip_mined()->in(LoopNode::EntryControl), 1123 pre_phi->in(LoopNode::LoopBackControl), 1124 visited, clones); 1125 _igvn.hash_delete(main_phi); 1126 main_phi->set_req( LoopNode::EntryControl, fallpre ); 1127 } 1128 } 1129 1130 // Nodes inside the loop may be control dependent on a predicate 1131 // that was moved before the preloop. If the back branch of the main 1132 // or post loops becomes dead, those nodes won't be dependent on the 1133 // test that guards that loop nest anymore which could lead to an 1134 // incorrect array access because it executes independently of the 1135 // test that was guarding the loop nest. We add a special CastII on 1136 // the if branch that enters the loop, between the input induction 1137 // variable value and the induction variable Phi to preserve correct 1138 // dependencies. 1139 1140 // CastII for the main loop: 1141 bool inserted = cast_incr_before_loop( pre_incr, min_taken, main_head ); 1142 assert(inserted, "no castII inserted"); 1143 1144 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). 1145 // RCE and alignment may change this later. 1146 Node *cmp_end = pre_end->cmp_node(); 1147 assert( cmp_end->in(2) == limit, "" ); 1148 Node *pre_limit = new AddINode( init, stride ); 1149 1150 // Save the original loop limit in this Opaque1 node for 1151 // use by range check elimination. 1152 Node *pre_opaq = new Opaque1Node(C, pre_limit, limit); 1153 1154 register_new_node( pre_limit, pre_head->in(0) ); 1155 register_new_node( pre_opaq , pre_head->in(0) ); 1156 1157 // Since no other users of pre-loop compare, I can hack limit directly 1158 assert( cmp_end->outcnt() == 1, "no other users" ); 1159 _igvn.hash_delete(cmp_end); 1160 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq); 1161 1162 // Special case for not-equal loop bounds: 1163 // Change pre loop test, main loop test, and the 1164 // main loop guard test to use lt or gt depending on stride 1165 // direction: 1166 // positive stride use < 1167 // negative stride use > 1168 // 1169 // not-equal test is kept for post loop to handle case 1170 // when init > limit when stride > 0 (and reverse). 1171 1172 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) { 1173 1174 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt; 1175 // Modify pre loop end condition 1176 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1177 BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test); 1178 register_new_node( new_bol0, pre_head->in(0) ); 1179 _igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0); 1180 // Modify main loop guard condition 1181 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay"); 1182 BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test); 1183 register_new_node( new_bol1, new_pre_exit ); 1184 _igvn.hash_delete(min_iff); 1185 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1); 1186 // Modify main loop end condition 1187 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1188 BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test); 1189 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) ); 1190 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2); 1191 } 1192 1193 // Flag main loop 1194 main_head->set_main_loop(); 1195 if( peel_only ) main_head->set_main_no_pre_loop(); 1196 1197 // Subtract a trip count for the pre-loop. 1198 main_head->set_trip_count(main_head->trip_count() - 1); 1199 1200 // It's difficult to be precise about the trip-counts 1201 // for the pre/post loops. They are usually very short, 1202 // so guess that 4 trips is a reasonable value. 1203 post_head->set_profile_trip_cnt(4.0); 1204 pre_head->set_profile_trip_cnt(4.0); 1205 1206 // Now force out all loop-invariant dominating tests. The optimizer 1207 // finds some, but we _know_ they are all useless. 1208 peeled_dom_test_elim(loop,old_new); 1209 loop->record_for_igvn(); 1210 } 1211 1212 //------------------------------insert_vector_post_loop------------------------ 1213 // Insert a copy of the atomic unrolled vectorized main loop as a post loop, 1214 // unroll_policy has already informed us that more unrolling is about to happen to 1215 // the main loop. The resultant post loop will serve as a vectorized drain loop. 1216 void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new) { 1217 if (!loop->_head->is_CountedLoop()) return; 1218 1219 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1220 1221 // only process vectorized main loops 1222 if (!cl->is_vectorized_loop() || !cl->is_main_loop()) return; 1223 1224 int slp_max_unroll_factor = cl->slp_max_unroll(); 1225 int cur_unroll = cl->unrolled_count(); 1226 1227 if (slp_max_unroll_factor == 0) return; 1228 1229 // only process atomic unroll vector loops (not super unrolled after vectorization) 1230 if (cur_unroll != slp_max_unroll_factor) return; 1231 1232 // we only ever process this one time 1233 if (cl->has_atomic_post_loop()) return; 1234 1235 #ifndef PRODUCT 1236 if (TraceLoopOpts) { 1237 tty->print("PostVector "); 1238 loop->dump_head(); 1239 } 1240 #endif 1241 C->set_major_progress(); 1242 1243 // Find common pieces of the loop being guarded with pre & post loops 1244 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 1245 CountedLoopEndNode *main_end = main_head->loopexit(); 1246 guarantee(main_end != NULL, "no loop exit node"); 1247 // diagnostic to show loop end is not properly formed 1248 assert(main_end->outcnt() == 2, "1 true, 1 false path only"); 1249 1250 // mark this loop as processed 1251 main_head->mark_has_atomic_post_loop(); 1252 1253 Node *incr = main_end->incr(); 1254 Node *limit = main_end->limit(); 1255 1256 // In this case we throw away the result as we are not using it to connect anything else. 1257 CountedLoopNode *post_head = NULL; 1258 insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head); 1259 1260 // It's difficult to be precise about the trip-counts 1261 // for post loops. They are usually very short, 1262 // so guess that unit vector trips is a reasonable value. 1263 post_head->set_profile_trip_cnt(cur_unroll); 1264 1265 // Now force out all loop-invariant dominating tests. The optimizer 1266 // finds some, but we _know_ they are all useless. 1267 peeled_dom_test_elim(loop, old_new); 1268 loop->record_for_igvn(); 1269 } 1270 1271 1272 //-------------------------insert_scalar_rced_post_loop------------------------ 1273 // Insert a copy of the rce'd main loop as a post loop, 1274 // We have not unrolled the main loop, so this is the right time to inject this. 1275 // Later we will examine the partner of this post loop pair which still has range checks 1276 // to see inject code which tests at runtime if the range checks are applicable. 1277 void PhaseIdealLoop::insert_scalar_rced_post_loop(IdealLoopTree *loop, Node_List &old_new) { 1278 if (!loop->_head->is_CountedLoop()) return; 1279 1280 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1281 1282 // only process RCE'd main loops 1283 if (!cl->is_main_loop() || cl->range_checks_present()) return; 1284 1285 #ifndef PRODUCT 1286 if (TraceLoopOpts) { 1287 tty->print("PostScalarRce "); 1288 loop->dump_head(); 1289 } 1290 #endif 1291 C->set_major_progress(); 1292 1293 // Find common pieces of the loop being guarded with pre & post loops 1294 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 1295 CountedLoopEndNode *main_end = main_head->loopexit(); 1296 guarantee(main_end != NULL, "no loop exit node"); 1297 // diagnostic to show loop end is not properly formed 1298 assert(main_end->outcnt() == 2, "1 true, 1 false path only"); 1299 1300 Node *incr = main_end->incr(); 1301 Node *limit = main_end->limit(); 1302 1303 // In this case we throw away the result as we are not using it to connect anything else. 1304 CountedLoopNode *post_head = NULL; 1305 insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head); 1306 1307 // It's difficult to be precise about the trip-counts 1308 // for post loops. They are usually very short, 1309 // so guess that unit vector trips is a reasonable value. 1310 post_head->set_profile_trip_cnt(4.0); 1311 post_head->set_is_rce_post_loop(); 1312 1313 // Now force out all loop-invariant dominating tests. The optimizer 1314 // finds some, but we _know_ they are all useless. 1315 peeled_dom_test_elim(loop, old_new); 1316 loop->record_for_igvn(); 1317 } 1318 1319 1320 //------------------------------insert_post_loop------------------------------- 1321 // Insert post loops. Add a post loop to the given loop passed. 1322 Node *PhaseIdealLoop::insert_post_loop(IdealLoopTree *loop, Node_List &old_new, 1323 CountedLoopNode *main_head, CountedLoopEndNode *main_end, 1324 Node *incr, Node *limit, CountedLoopNode *&post_head) { 1325 IfNode* outer_main_end = main_end; 1326 IdealLoopTree* outer_loop = loop; 1327 if (main_head->is_strip_mined()) { 1328 main_head->verify_strip_mined(1); 1329 outer_main_end = main_head->outer_loop_end(); 1330 outer_loop = loop->_parent; 1331 assert(outer_loop->_head == main_head->in(LoopNode::EntryControl), "broken loop tree"); 1332 } 1333 1334 //------------------------------ 1335 // Step A: Create a new post-Loop. 1336 Node* main_exit = outer_main_end->proj_out(false); 1337 assert(main_exit->Opcode() == Op_IfFalse, ""); 1338 int dd_main_exit = dom_depth(main_exit); 1339 1340 // Step A1: Clone the loop body of main. The clone becomes the post-loop. 1341 // The main loop pre-header illegally has 2 control users (old & new loops). 1342 clone_loop(loop, old_new, dd_main_exit, ControlAroundStripMined); 1343 assert(old_new[main_end->_idx]->Opcode() == Op_CountedLoopEnd, ""); 1344 post_head = old_new[main_head->_idx]->as_CountedLoop(); 1345 post_head->set_normal_loop(); 1346 post_head->set_post_loop(main_head); 1347 1348 // Reduce the post-loop trip count. 1349 CountedLoopEndNode* post_end = old_new[main_end->_idx]->as_CountedLoopEnd(); 1350 post_end->_prob = PROB_FAIR; 1351 1352 // Build the main-loop normal exit. 1353 IfFalseNode *new_main_exit = new IfFalseNode(outer_main_end); 1354 _igvn.register_new_node_with_optimizer(new_main_exit); 1355 set_idom(new_main_exit, outer_main_end, dd_main_exit); 1356 set_loop(new_main_exit, outer_loop->_parent); 1357 1358 // Step A2: Build a zero-trip guard for the post-loop. After leaving the 1359 // main-loop, the post-loop may not execute at all. We 'opaque' the incr 1360 // (the previous loop trip-counter exit value) because we will be changing 1361 // the exit value (via additional unrolling) so we cannot constant-fold away the zero 1362 // trip guard until all unrolling is done. 1363 Node *zer_opaq = new Opaque1Node(C, incr); 1364 Node *zer_cmp = new CmpINode(zer_opaq, limit); 1365 Node *zer_bol = new BoolNode(zer_cmp, main_end->test_trip()); 1366 register_new_node(zer_opaq, new_main_exit); 1367 register_new_node(zer_cmp, new_main_exit); 1368 register_new_node(zer_bol, new_main_exit); 1369 1370 // Build the IfNode 1371 IfNode *zer_iff = new IfNode(new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN); 1372 _igvn.register_new_node_with_optimizer(zer_iff); 1373 set_idom(zer_iff, new_main_exit, dd_main_exit); 1374 set_loop(zer_iff, outer_loop->_parent); 1375 1376 // Plug in the false-path, taken if we need to skip this post-loop 1377 _igvn.replace_input_of(main_exit, 0, zer_iff); 1378 set_idom(main_exit, zer_iff, dd_main_exit); 1379 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit); 1380 // Make the true-path, must enter this post loop 1381 Node *zer_taken = new IfTrueNode(zer_iff); 1382 _igvn.register_new_node_with_optimizer(zer_taken); 1383 set_idom(zer_taken, zer_iff, dd_main_exit); 1384 set_loop(zer_taken, outer_loop->_parent); 1385 // Plug in the true path 1386 _igvn.hash_delete(post_head); 1387 post_head->set_req(LoopNode::EntryControl, zer_taken); 1388 set_idom(post_head, zer_taken, dd_main_exit); 1389 1390 Arena *a = Thread::current()->resource_area(); 1391 VectorSet visited(a); 1392 Node_Stack clones(a, main_head->back_control()->outcnt()); 1393 // Step A3: Make the fall-in values to the post-loop come from the 1394 // fall-out values of the main-loop. 1395 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) { 1396 Node* main_phi = main_head->fast_out(i); 1397 if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0) { 1398 Node *cur_phi = old_new[main_phi->_idx]; 1399 Node *fallnew = clone_up_backedge_goo(main_head->back_control(), 1400 post_head->init_control(), 1401 main_phi->in(LoopNode::LoopBackControl), 1402 visited, clones); 1403 _igvn.hash_delete(cur_phi); 1404 cur_phi->set_req(LoopNode::EntryControl, fallnew); 1405 } 1406 } 1407 1408 // CastII for the new post loop: 1409 bool inserted = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head); 1410 assert(inserted, "no castII inserted"); 1411 1412 return new_main_exit; 1413 } 1414 1415 //------------------------------is_invariant----------------------------- 1416 // Return true if n is invariant 1417 bool IdealLoopTree::is_invariant(Node* n) const { 1418 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n; 1419 if (n_c->is_top()) return false; 1420 return !is_member(_phase->get_loop(n_c)); 1421 } 1422 1423 1424 //------------------------------do_unroll-------------------------------------- 1425 // Unroll the loop body one step - make each trip do 2 iterations. 1426 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) { 1427 assert(LoopUnrollLimit, ""); 1428 CountedLoopNode *loop_head = loop->_head->as_CountedLoop(); 1429 CountedLoopEndNode *loop_end = loop_head->loopexit(); 1430 assert(loop_end, ""); 1431 #ifndef PRODUCT 1432 if (PrintOpto && VerifyLoopOptimizations) { 1433 tty->print("Unrolling "); 1434 loop->dump_head(); 1435 } else if (TraceLoopOpts) { 1436 if (loop_head->trip_count() < (uint)LoopUnrollLimit) { 1437 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count()); 1438 } else { 1439 tty->print("Unroll %d ", loop_head->unrolled_count()*2); 1440 } 1441 loop->dump_head(); 1442 } 1443 1444 if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) { 1445 Arena* arena = Thread::current()->resource_area(); 1446 Node_Stack stack(arena, C->live_nodes() >> 2); 1447 Node_List rpo_list; 1448 VectorSet visited(arena); 1449 visited.set(loop_head->_idx); 1450 rpo( loop_head, stack, visited, rpo_list ); 1451 dump(loop, rpo_list.size(), rpo_list ); 1452 } 1453 #endif 1454 1455 // Remember loop node count before unrolling to detect 1456 // if rounds of unroll,optimize are making progress 1457 loop_head->set_node_count_before_unroll(loop->_body.size()); 1458 1459 Node *ctrl = loop_head->skip_strip_mined()->in(LoopNode::EntryControl); 1460 Node *limit = loop_head->limit(); 1461 Node *init = loop_head->init_trip(); 1462 Node *stride = loop_head->stride(); 1463 1464 Node *opaq = NULL; 1465 if (adjust_min_trip) { // If not maximally unrolling, need adjustment 1466 // Search for zero-trip guard. 1467 1468 // Check the shape of the graph at the loop entry. If an inappropriate 1469 // graph shape is encountered, the compiler bails out loop unrolling; 1470 // compilation of the method will still succeed. 1471 if (!is_canonical_loop_entry(loop_head)) { 1472 return; 1473 } 1474 opaq = ctrl->in(0)->in(1)->in(1)->in(2); 1475 // Zero-trip test uses an 'opaque' node which is not shared. 1476 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, ""); 1477 } 1478 1479 C->set_major_progress(); 1480 1481 Node* new_limit = NULL; 1482 int stride_con = stride->get_int(); 1483 int stride_p = (stride_con > 0) ? stride_con : -stride_con; 1484 uint old_trip_count = loop_head->trip_count(); 1485 // Verify that unroll policy result is still valid. 1486 assert(old_trip_count > 1 && 1487 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity"); 1488 1489 // Adjust loop limit to keep valid iterations number after unroll. 1490 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride 1491 // which may overflow. 1492 if (!adjust_min_trip) { 1493 assert(old_trip_count > 1 && (old_trip_count & 1) == 0, 1494 "odd trip count for maximally unroll"); 1495 // Don't need to adjust limit for maximally unroll since trip count is even. 1496 } else if (loop_head->has_exact_trip_count() && init->is_Con()) { 1497 // Loop's limit is constant. Loop's init could be constant when pre-loop 1498 // become peeled iteration. 1499 jlong init_con = init->get_int(); 1500 // We can keep old loop limit if iterations count stays the same: 1501 // old_trip_count == new_trip_count * 2 1502 // Note: since old_trip_count >= 2 then new_trip_count >= 1 1503 // so we also don't need to adjust zero trip test. 1504 jlong limit_con = limit->get_int(); 1505 // (stride_con*2) not overflow since stride_con <= 8. 1506 int new_stride_con = stride_con * 2; 1507 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1); 1508 jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con; 1509 // New trip count should satisfy next conditions. 1510 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity"); 1511 uint new_trip_count = (uint)trip_count; 1512 adjust_min_trip = (old_trip_count != new_trip_count*2); 1513 } 1514 1515 if (adjust_min_trip) { 1516 // Step 2: Adjust the trip limit if it is called for. 1517 // The adjustment amount is -stride. Need to make sure if the 1518 // adjustment underflows or overflows, then the main loop is skipped. 1519 Node* cmp = loop_end->cmp_node(); 1520 assert(cmp->in(2) == limit, "sanity"); 1521 assert(opaq != NULL && opaq->in(1) == limit, "sanity"); 1522 1523 // Verify that policy_unroll result is still valid. 1524 const TypeInt* limit_type = _igvn.type(limit)->is_int(); 1525 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) || 1526 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity"); 1527 1528 if (limit->is_Con()) { 1529 // The check in policy_unroll and the assert above guarantee 1530 // no underflow if limit is constant. 1531 new_limit = _igvn.intcon(limit->get_int() - stride_con); 1532 set_ctrl(new_limit, C->root()); 1533 } else { 1534 // Limit is not constant. 1535 if (loop_head->unrolled_count() == 1) { // only for first unroll 1536 // Separate limit by Opaque node in case it is an incremented 1537 // variable from previous loop to avoid using pre-incremented 1538 // value which could increase register pressure. 1539 // Otherwise reorg_offsets() optimization will create a separate 1540 // Opaque node for each use of trip-counter and as result 1541 // zero trip guard limit will be different from loop limit. 1542 assert(has_ctrl(opaq), "should have it"); 1543 Node* opaq_ctrl = get_ctrl(opaq); 1544 limit = new Opaque2Node( C, limit ); 1545 register_new_node( limit, opaq_ctrl ); 1546 } 1547 if ((stride_con > 0 && (java_subtract(limit_type->_lo, stride_con) < limit_type->_lo)) || 1548 (stride_con < 0 && (java_subtract(limit_type->_hi, stride_con) > limit_type->_hi))) { 1549 // No underflow. 1550 new_limit = new SubINode(limit, stride); 1551 } else { 1552 // (limit - stride) may underflow. 1553 // Clamp the adjustment value with MININT or MAXINT: 1554 // 1555 // new_limit = limit-stride 1556 // if (stride > 0) 1557 // new_limit = (limit < new_limit) ? MININT : new_limit; 1558 // else 1559 // new_limit = (limit > new_limit) ? MAXINT : new_limit; 1560 // 1561 BoolTest::mask bt = loop_end->test_trip(); 1562 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected"); 1563 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint); 1564 set_ctrl(adj_max, C->root()); 1565 Node* old_limit = NULL; 1566 Node* adj_limit = NULL; 1567 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL; 1568 if (loop_head->unrolled_count() > 1 && 1569 limit->is_CMove() && limit->Opcode() == Op_CMoveI && 1570 limit->in(CMoveNode::IfTrue) == adj_max && 1571 bol->as_Bool()->_test._test == bt && 1572 bol->in(1)->Opcode() == Op_CmpI && 1573 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) { 1574 // Loop was unrolled before. 1575 // Optimize the limit to avoid nested CMove: 1576 // use original limit as old limit. 1577 old_limit = bol->in(1)->in(1); 1578 // Adjust previous adjusted limit. 1579 adj_limit = limit->in(CMoveNode::IfFalse); 1580 adj_limit = new SubINode(adj_limit, stride); 1581 } else { 1582 old_limit = limit; 1583 adj_limit = new SubINode(limit, stride); 1584 } 1585 assert(old_limit != NULL && adj_limit != NULL, ""); 1586 register_new_node( adj_limit, ctrl ); // adjust amount 1587 Node* adj_cmp = new CmpINode(old_limit, adj_limit); 1588 register_new_node( adj_cmp, ctrl ); 1589 Node* adj_bool = new BoolNode(adj_cmp, bt); 1590 register_new_node( adj_bool, ctrl ); 1591 new_limit = new CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT); 1592 } 1593 register_new_node(new_limit, ctrl); 1594 } 1595 assert(new_limit != NULL, ""); 1596 // Replace in loop test. 1597 assert(loop_end->in(1)->in(1) == cmp, "sanity"); 1598 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) { 1599 // Don't need to create new test since only one user. 1600 _igvn.hash_delete(cmp); 1601 cmp->set_req(2, new_limit); 1602 } else { 1603 // Create new test since it is shared. 1604 Node* ctrl2 = loop_end->in(0); 1605 Node* cmp2 = cmp->clone(); 1606 cmp2->set_req(2, new_limit); 1607 register_new_node(cmp2, ctrl2); 1608 Node* bol2 = loop_end->in(1)->clone(); 1609 bol2->set_req(1, cmp2); 1610 register_new_node(bol2, ctrl2); 1611 _igvn.replace_input_of(loop_end, 1, bol2); 1612 } 1613 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 1614 // Make it a 1-trip test (means at least 2 trips). 1615 1616 // Guard test uses an 'opaque' node which is not shared. Hence I 1617 // can edit it's inputs directly. Hammer in the new limit for the 1618 // minimum-trip guard. 1619 assert(opaq->outcnt() == 1, ""); 1620 _igvn.replace_input_of(opaq, 1, new_limit); 1621 } 1622 1623 // Adjust max trip count. The trip count is intentionally rounded 1624 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 1625 // the main, unrolled, part of the loop will never execute as it is protected 1626 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 1627 // and later determined that part of the unrolled loop was dead. 1628 loop_head->set_trip_count(old_trip_count / 2); 1629 1630 // Double the count of original iterations in the unrolled loop body. 1631 loop_head->double_unrolled_count(); 1632 1633 // --------- 1634 // Step 4: Clone the loop body. Move it inside the loop. This loop body 1635 // represents the odd iterations; since the loop trips an even number of 1636 // times its backedge is never taken. Kill the backedge. 1637 uint dd = dom_depth(loop_head); 1638 clone_loop(loop, old_new, dd, IgnoreStripMined); 1639 1640 // Make backedges of the clone equal to backedges of the original. 1641 // Make the fall-in from the original come from the fall-out of the clone. 1642 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) { 1643 Node* phi = loop_head->fast_out(j); 1644 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) { 1645 Node *newphi = old_new[phi->_idx]; 1646 _igvn.hash_delete( phi ); 1647 _igvn.hash_delete( newphi ); 1648 1649 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl)); 1650 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl)); 1651 phi ->set_req(LoopNode::LoopBackControl, C->top()); 1652 } 1653 } 1654 Node *clone_head = old_new[loop_head->_idx]; 1655 _igvn.hash_delete( clone_head ); 1656 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl)); 1657 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl)); 1658 loop_head ->set_req(LoopNode::LoopBackControl, C->top()); 1659 loop->_head = clone_head; // New loop header 1660 1661 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd); 1662 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd); 1663 1664 // Kill the clone's backedge 1665 Node *newcle = old_new[loop_end->_idx]; 1666 _igvn.hash_delete( newcle ); 1667 Node *one = _igvn.intcon(1); 1668 set_ctrl(one, C->root()); 1669 newcle->set_req(1, one); 1670 // Force clone into same loop body 1671 uint max = loop->_body.size(); 1672 for( uint k = 0; k < max; k++ ) { 1673 Node *old = loop->_body.at(k); 1674 Node *nnn = old_new[old->_idx]; 1675 loop->_body.push(nnn); 1676 if (!has_ctrl(old)) 1677 set_loop(nnn, loop); 1678 } 1679 1680 loop->record_for_igvn(); 1681 loop_head->clear_strip_mined(); 1682 1683 #ifndef PRODUCT 1684 if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) { 1685 tty->print("\nnew loop after unroll\n"); loop->dump_head(); 1686 for (uint i = 0; i < loop->_body.size(); i++) { 1687 loop->_body.at(i)->dump(); 1688 } 1689 if(C->clone_map().is_debug()) { 1690 tty->print("\nCloneMap\n"); 1691 Dict* dict = C->clone_map().dict(); 1692 DictI i(dict); 1693 tty->print_cr("Dict@%p[%d] = ", dict, dict->Size()); 1694 for (int ii = 0; i.test(); ++i, ++ii) { 1695 NodeCloneInfo cl((uint64_t)dict->operator[]((void*)i._key)); 1696 tty->print("%d->%d:%d,", (int)(intptr_t)i._key, cl.idx(), cl.gen()); 1697 if (ii % 10 == 9) { 1698 tty->print_cr(" "); 1699 } 1700 } 1701 tty->print_cr(" "); 1702 } 1703 } 1704 #endif 1705 1706 } 1707 1708 //------------------------------do_maximally_unroll---------------------------- 1709 1710 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) { 1711 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1712 assert(cl->has_exact_trip_count(), "trip count is not exact"); 1713 assert(cl->trip_count() > 0, ""); 1714 #ifndef PRODUCT 1715 if (TraceLoopOpts) { 1716 tty->print("MaxUnroll %d ", cl->trip_count()); 1717 loop->dump_head(); 1718 } 1719 #endif 1720 1721 // If loop is tripping an odd number of times, peel odd iteration 1722 if ((cl->trip_count() & 1) == 1) { 1723 do_peeling(loop, old_new); 1724 } 1725 1726 // Now its tripping an even number of times remaining. Double loop body. 1727 // Do not adjust pre-guards; they are not needed and do not exist. 1728 if (cl->trip_count() > 0) { 1729 assert((cl->trip_count() & 1) == 0, "missed peeling"); 1730 do_unroll(loop, old_new, false); 1731 } 1732 } 1733 1734 void PhaseIdealLoop::mark_reductions(IdealLoopTree *loop) { 1735 if (SuperWordReductions == false) return; 1736 1737 CountedLoopNode* loop_head = loop->_head->as_CountedLoop(); 1738 if (loop_head->unrolled_count() > 1) { 1739 return; 1740 } 1741 1742 Node* trip_phi = loop_head->phi(); 1743 for (DUIterator_Fast imax, i = loop_head->fast_outs(imax); i < imax; i++) { 1744 Node* phi = loop_head->fast_out(i); 1745 if (phi->is_Phi() && phi->outcnt() > 0 && phi != trip_phi) { 1746 // For definitions which are loop inclusive and not tripcounts. 1747 Node* def_node = phi->in(LoopNode::LoopBackControl); 1748 1749 if (def_node != NULL) { 1750 Node* n_ctrl = get_ctrl(def_node); 1751 if (n_ctrl != NULL && loop->is_member(get_loop(n_ctrl))) { 1752 // Now test it to see if it fits the standard pattern for a reduction operator. 1753 int opc = def_node->Opcode(); 1754 if (opc != ReductionNode::opcode(opc, def_node->bottom_type()->basic_type())) { 1755 if (!def_node->is_reduction()) { // Not marked yet 1756 // To be a reduction, the arithmetic node must have the phi as input and provide a def to it 1757 bool ok = false; 1758 for (unsigned j = 1; j < def_node->req(); j++) { 1759 Node* in = def_node->in(j); 1760 if (in == phi) { 1761 ok = true; 1762 break; 1763 } 1764 } 1765 1766 // do nothing if we did not match the initial criteria 1767 if (ok == false) { 1768 continue; 1769 } 1770 1771 // The result of the reduction must not be used in the loop 1772 for (DUIterator_Fast imax, i = def_node->fast_outs(imax); i < imax && ok; i++) { 1773 Node* u = def_node->fast_out(i); 1774 if (!loop->is_member(get_loop(ctrl_or_self(u)))) { 1775 continue; 1776 } 1777 if (u == phi) { 1778 continue; 1779 } 1780 ok = false; 1781 } 1782 1783 // iff the uses conform 1784 if (ok) { 1785 def_node->add_flag(Node::Flag_is_reduction); 1786 loop_head->mark_has_reductions(); 1787 } 1788 } 1789 } 1790 } 1791 } 1792 } 1793 } 1794 } 1795 1796 //------------------------------adjust_limit----------------------------------- 1797 // Helper function for add_constraint(). 1798 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) { 1799 // Compute "I :: (limit-offset)/scale" 1800 Node *con = new SubINode(rc_limit, offset); 1801 register_new_node(con, pre_ctrl); 1802 Node *X = new DivINode(0, con, scale); 1803 register_new_node(X, pre_ctrl); 1804 1805 // Adjust loop limit 1806 loop_limit = (stride_con > 0) 1807 ? (Node*)(new MinINode(loop_limit, X)) 1808 : (Node*)(new MaxINode(loop_limit, X)); 1809 register_new_node(loop_limit, pre_ctrl); 1810 return loop_limit; 1811 } 1812 1813 //------------------------------add_constraint--------------------------------- 1814 // Constrain the main loop iterations so the conditions: 1815 // low_limit <= scale_con * I + offset < upper_limit 1816 // always holds true. That is, either increase the number of iterations in 1817 // the pre-loop or the post-loop until the condition holds true in the main 1818 // loop. Stride, scale, offset and limit are all loop invariant. Further, 1819 // stride and scale are constants (offset and limit often are). 1820 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 ) { 1821 // For positive stride, the pre-loop limit always uses a MAX function 1822 // and the main loop a MIN function. For negative stride these are 1823 // reversed. 1824 1825 // Also for positive stride*scale the affine function is increasing, so the 1826 // pre-loop must check for underflow and the post-loop for overflow. 1827 // Negative stride*scale reverses this; pre-loop checks for overflow and 1828 // post-loop for underflow. 1829 1830 Node *scale = _igvn.intcon(scale_con); 1831 set_ctrl(scale, C->root()); 1832 1833 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow 1834 // The overflow limit: scale*I+offset < upper_limit 1835 // For main-loop compute 1836 // ( if (scale > 0) /* and stride > 0 */ 1837 // I < (upper_limit-offset)/scale 1838 // else /* scale < 0 and stride < 0 */ 1839 // I > (upper_limit-offset)/scale 1840 // ) 1841 // 1842 // (upper_limit-offset) may overflow or underflow. 1843 // But it is fine since main loop will either have 1844 // less iterations or will be skipped in such case. 1845 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl); 1846 1847 // The underflow limit: low_limit <= scale*I+offset. 1848 // For pre-loop compute 1849 // NOT(scale*I+offset >= low_limit) 1850 // scale*I+offset < low_limit 1851 // ( if (scale > 0) /* and stride > 0 */ 1852 // I < (low_limit-offset)/scale 1853 // else /* scale < 0 and stride < 0 */ 1854 // I > (low_limit-offset)/scale 1855 // ) 1856 1857 if (low_limit->get_int() == -max_jint) { 1858 // We need this guard when scale*pre_limit+offset >= limit 1859 // due to underflow. So we need execute pre-loop until 1860 // scale*I+offset >= min_int. But (min_int-offset) will 1861 // underflow when offset > 0 and X will be > original_limit 1862 // when stride > 0. To avoid it we replace positive offset with 0. 1863 // 1864 // Also (min_int+1 == -max_int) is used instead of min_int here 1865 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1866 Node* shift = _igvn.intcon(31); 1867 set_ctrl(shift, C->root()); 1868 Node* sign = new RShiftINode(offset, shift); 1869 register_new_node(sign, pre_ctrl); 1870 offset = new AndINode(offset, sign); 1871 register_new_node(offset, pre_ctrl); 1872 } else { 1873 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1874 // The only problem we have here when offset == min_int 1875 // since (0-min_int) == min_int. It may be fine for stride > 0 1876 // but for stride < 0 X will be < original_limit. To avoid it 1877 // max(pre_limit, original_limit) is used in do_range_check(). 1878 } 1879 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1880 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl); 1881 1882 } else { // stride_con*scale_con < 0 1883 // For negative stride*scale pre-loop checks for overflow and 1884 // post-loop for underflow. 1885 // 1886 // The overflow limit: scale*I+offset < upper_limit 1887 // For pre-loop compute 1888 // NOT(scale*I+offset < upper_limit) 1889 // scale*I+offset >= upper_limit 1890 // scale*I+offset+1 > upper_limit 1891 // ( if (scale < 0) /* and stride > 0 */ 1892 // I < (upper_limit-(offset+1))/scale 1893 // else /* scale > 0 and stride < 0 */ 1894 // I > (upper_limit-(offset+1))/scale 1895 // ) 1896 // 1897 // (upper_limit-offset-1) may underflow or overflow. 1898 // To avoid it min(pre_limit, original_limit) is used 1899 // in do_range_check() for stride > 0 and max() for < 0. 1900 Node *one = _igvn.intcon(1); 1901 set_ctrl(one, C->root()); 1902 1903 Node *plus_one = new AddINode(offset, one); 1904 register_new_node( plus_one, pre_ctrl ); 1905 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1906 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl); 1907 1908 if (low_limit->get_int() == -max_jint) { 1909 // We need this guard when scale*main_limit+offset >= limit 1910 // due to underflow. So we need execute main-loop while 1911 // scale*I+offset+1 > min_int. But (min_int-offset-1) will 1912 // underflow when (offset+1) > 0 and X will be < main_limit 1913 // when scale < 0 (and stride > 0). To avoid it we replace 1914 // positive (offset+1) with 0. 1915 // 1916 // Also (min_int+1 == -max_int) is used instead of min_int here 1917 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1918 Node* shift = _igvn.intcon(31); 1919 set_ctrl(shift, C->root()); 1920 Node* sign = new RShiftINode(plus_one, shift); 1921 register_new_node(sign, pre_ctrl); 1922 plus_one = new AndINode(plus_one, sign); 1923 register_new_node(plus_one, pre_ctrl); 1924 } else { 1925 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1926 // The only problem we have here when offset == max_int 1927 // since (max_int+1) == min_int and (0-min_int) == min_int. 1928 // But it is fine since main loop will either have 1929 // less iterations or will be skipped in such case. 1930 } 1931 // The underflow limit: low_limit <= scale*I+offset. 1932 // For main-loop compute 1933 // scale*I+offset+1 > low_limit 1934 // ( if (scale < 0) /* and stride > 0 */ 1935 // I < (low_limit-(offset+1))/scale 1936 // else /* scale > 0 and stride < 0 */ 1937 // I > (low_limit-(offset+1))/scale 1938 // ) 1939 1940 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl); 1941 } 1942 } 1943 1944 1945 //------------------------------is_scaled_iv--------------------------------- 1946 // Return true if exp is a constant times an induction var 1947 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) { 1948 if (exp == iv) { 1949 if (p_scale != NULL) { 1950 *p_scale = 1; 1951 } 1952 return true; 1953 } 1954 int opc = exp->Opcode(); 1955 if (opc == Op_MulI) { 1956 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1957 if (p_scale != NULL) { 1958 *p_scale = exp->in(2)->get_int(); 1959 } 1960 return true; 1961 } 1962 if (exp->in(2) == iv && exp->in(1)->is_Con()) { 1963 if (p_scale != NULL) { 1964 *p_scale = exp->in(1)->get_int(); 1965 } 1966 return true; 1967 } 1968 } else if (opc == Op_LShiftI) { 1969 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1970 if (p_scale != NULL) { 1971 *p_scale = 1 << exp->in(2)->get_int(); 1972 } 1973 return true; 1974 } 1975 } 1976 return false; 1977 } 1978 1979 //-----------------------------is_scaled_iv_plus_offset------------------------------ 1980 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2) 1981 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) { 1982 if (is_scaled_iv(exp, iv, p_scale)) { 1983 if (p_offset != NULL) { 1984 Node *zero = _igvn.intcon(0); 1985 set_ctrl(zero, C->root()); 1986 *p_offset = zero; 1987 } 1988 return true; 1989 } 1990 int opc = exp->Opcode(); 1991 if (opc == Op_AddI) { 1992 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1993 if (p_offset != NULL) { 1994 *p_offset = exp->in(2); 1995 } 1996 return true; 1997 } 1998 if (is_scaled_iv(exp->in(2), iv, p_scale)) { 1999 if (p_offset != NULL) { 2000 *p_offset = exp->in(1); 2001 } 2002 return true; 2003 } 2004 if (exp->in(2)->is_Con()) { 2005 Node* offset2 = NULL; 2006 if (depth < 2 && 2007 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale, 2008 p_offset != NULL ? &offset2 : NULL, depth+1)) { 2009 if (p_offset != NULL) { 2010 Node *ctrl_off2 = get_ctrl(offset2); 2011 Node* offset = new AddINode(offset2, exp->in(2)); 2012 register_new_node(offset, ctrl_off2); 2013 *p_offset = offset; 2014 } 2015 return true; 2016 } 2017 } 2018 } else if (opc == Op_SubI) { 2019 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 2020 if (p_offset != NULL) { 2021 Node *zero = _igvn.intcon(0); 2022 set_ctrl(zero, C->root()); 2023 Node *ctrl_off = get_ctrl(exp->in(2)); 2024 Node* offset = new SubINode(zero, exp->in(2)); 2025 register_new_node(offset, ctrl_off); 2026 *p_offset = offset; 2027 } 2028 return true; 2029 } 2030 if (is_scaled_iv(exp->in(2), iv, p_scale)) { 2031 if (p_offset != NULL) { 2032 *p_scale *= -1; 2033 *p_offset = exp->in(1); 2034 } 2035 return true; 2036 } 2037 } 2038 return false; 2039 } 2040 2041 //------------------------------do_range_check--------------------------------- 2042 // Eliminate range-checks and other trip-counter vs loop-invariant tests. 2043 int PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) { 2044 #ifndef PRODUCT 2045 if (PrintOpto && VerifyLoopOptimizations) { 2046 tty->print("Range Check Elimination "); 2047 loop->dump_head(); 2048 } else if (TraceLoopOpts) { 2049 tty->print("RangeCheck "); 2050 loop->dump_head(); 2051 } 2052 #endif 2053 assert(RangeCheckElimination, ""); 2054 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 2055 // If we fail before trying to eliminate range checks, set multiversion state 2056 int closed_range_checks = 1; 2057 2058 // protect against stride not being a constant 2059 if (!cl->stride_is_con()) 2060 return closed_range_checks; 2061 2062 // Find the trip counter; we are iteration splitting based on it 2063 Node *trip_counter = cl->phi(); 2064 // Find the main loop limit; we will trim it's iterations 2065 // to not ever trip end tests 2066 Node *main_limit = cl->limit(); 2067 2068 // Check graph shape. Cannot optimize a loop if zero-trip 2069 // Opaque1 node is optimized away and then another round 2070 // of loop opts attempted. 2071 if (!is_canonical_loop_entry(cl)) { 2072 return closed_range_checks; 2073 } 2074 2075 // Need to find the main-loop zero-trip guard 2076 Node *ctrl = cl->skip_strip_mined()->in(LoopNode::EntryControl); 2077 Node *iffm = ctrl->in(0); 2078 Node *opqzm = iffm->in(1)->in(1)->in(2); 2079 assert(opqzm->in(1) == main_limit, "do not understand situation"); 2080 2081 // Find the pre-loop limit; we will expand its iterations to 2082 // not ever trip low tests. 2083 Node *p_f = iffm->in(0); 2084 // pre loop may have been optimized out 2085 if (p_f->Opcode() != Op_IfFalse) { 2086 return closed_range_checks; 2087 } 2088 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); 2089 assert(pre_end->loopnode()->is_pre_loop(), ""); 2090 Node *pre_opaq1 = pre_end->limit(); 2091 // Occasionally it's possible for a pre-loop Opaque1 node to be 2092 // optimized away and then another round of loop opts attempted. 2093 // We can not optimize this particular loop in that case. 2094 if (pre_opaq1->Opcode() != Op_Opaque1) 2095 return closed_range_checks; 2096 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1; 2097 Node *pre_limit = pre_opaq->in(1); 2098 2099 // Where do we put new limit calculations 2100 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl); 2101 2102 // Ensure the original loop limit is available from the 2103 // pre-loop Opaque1 node. 2104 Node *orig_limit = pre_opaq->original_loop_limit(); 2105 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP) 2106 return closed_range_checks; 2107 2108 // Must know if its a count-up or count-down loop 2109 2110 int stride_con = cl->stride_con(); 2111 Node *zero = _igvn.intcon(0); 2112 Node *one = _igvn.intcon(1); 2113 // Use symmetrical int range [-max_jint,max_jint] 2114 Node *mini = _igvn.intcon(-max_jint); 2115 set_ctrl(zero, C->root()); 2116 set_ctrl(one, C->root()); 2117 set_ctrl(mini, C->root()); 2118 2119 // Range checks that do not dominate the loop backedge (ie. 2120 // conditionally executed) can lengthen the pre loop limit beyond 2121 // the original loop limit. To prevent this, the pre limit is 2122 // (for stride > 0) MINed with the original loop limit (MAXed 2123 // stride < 0) when some range_check (rc) is conditionally 2124 // executed. 2125 bool conditional_rc = false; 2126 2127 // Count number of range checks and reduce by load range limits, if zero, 2128 // the loop is in canonical form to multiversion. 2129 closed_range_checks = 0; 2130 2131 // Check loop body for tests of trip-counter plus loop-invariant vs loop-variant. 2132 for( uint i = 0; i < loop->_body.size(); i++ ) { 2133 Node *iff = loop->_body[i]; 2134 if (iff->Opcode() == Op_If || 2135 iff->Opcode() == Op_RangeCheck) { // Test? 2136 // Test is an IfNode, has 2 projections. If BOTH are in the loop 2137 // we need loop unswitching instead of iteration splitting. 2138 closed_range_checks++; 2139 Node *exit = loop->is_loop_exit(iff); 2140 if( !exit ) continue; 2141 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0; 2142 2143 // Get boolean condition to test 2144 Node *i1 = iff->in(1); 2145 if( !i1->is_Bool() ) continue; 2146 BoolNode *bol = i1->as_Bool(); 2147 BoolTest b_test = bol->_test; 2148 // Flip sense of test if exit condition is flipped 2149 if( flip ) 2150 b_test = b_test.negate(); 2151 2152 // Get compare 2153 Node *cmp = bol->in(1); 2154 2155 // Look for trip_counter + offset vs limit 2156 Node *rc_exp = cmp->in(1); 2157 Node *limit = cmp->in(2); 2158 int scale_con= 1; // Assume trip counter not scaled 2159 2160 Node *limit_c = get_ctrl(limit); 2161 if( loop->is_member(get_loop(limit_c) ) ) { 2162 // Compare might have operands swapped; commute them 2163 b_test = b_test.commute(); 2164 rc_exp = cmp->in(2); 2165 limit = cmp->in(1); 2166 limit_c = get_ctrl(limit); 2167 if( loop->is_member(get_loop(limit_c) ) ) 2168 continue; // Both inputs are loop varying; cannot RCE 2169 } 2170 // Here we know 'limit' is loop invariant 2171 2172 // 'limit' maybe pinned below the zero trip test (probably from a 2173 // previous round of rce), in which case, it can't be used in the 2174 // zero trip test expression which must occur before the zero test's if. 2175 if( limit_c == ctrl ) { 2176 continue; // Don't rce this check but continue looking for other candidates. 2177 } 2178 2179 // Check for scaled induction variable plus an offset 2180 Node *offset = NULL; 2181 2182 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) { 2183 continue; 2184 } 2185 2186 Node *offset_c = get_ctrl(offset); 2187 if( loop->is_member( get_loop(offset_c) ) ) 2188 continue; // Offset is not really loop invariant 2189 // Here we know 'offset' is loop invariant. 2190 2191 // As above for the 'limit', the 'offset' maybe pinned below the 2192 // zero trip test. 2193 if( offset_c == ctrl ) { 2194 continue; // Don't rce this check but continue looking for other candidates. 2195 } 2196 #ifdef ASSERT 2197 if (TraceRangeLimitCheck) { 2198 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":"); 2199 bol->dump(2); 2200 } 2201 #endif 2202 // At this point we have the expression as: 2203 // scale_con * trip_counter + offset :: limit 2204 // where scale_con, offset and limit are loop invariant. Trip_counter 2205 // monotonically increases by stride_con, a constant. Both (or either) 2206 // stride_con and scale_con can be negative which will flip about the 2207 // sense of the test. 2208 2209 // Adjust pre and main loop limits to guard the correct iteration set 2210 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests 2211 if( b_test._test == BoolTest::lt ) { // Range checks always use lt 2212 // The underflow and overflow limits: 0 <= scale*I+offset < limit 2213 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit ); 2214 // (0-offset)/scale could be outside of loop iterations range. 2215 conditional_rc = true; 2216 } else { 2217 if (PrintOpto) { 2218 tty->print_cr("missed RCE opportunity"); 2219 } 2220 continue; // In release mode, ignore it 2221 } 2222 } else { // Otherwise work on normal compares 2223 switch( b_test._test ) { 2224 case BoolTest::gt: 2225 // Fall into GE case 2226 case BoolTest::ge: 2227 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit 2228 scale_con = -scale_con; 2229 offset = new SubINode( zero, offset ); 2230 register_new_node( offset, pre_ctrl ); 2231 limit = new SubINode( zero, limit ); 2232 register_new_node( limit, pre_ctrl ); 2233 // Fall into LE case 2234 case BoolTest::le: 2235 if (b_test._test != BoolTest::gt) { 2236 // Convert X <= Y to X < Y+1 2237 limit = new AddINode( limit, one ); 2238 register_new_node( limit, pre_ctrl ); 2239 } 2240 // Fall into LT case 2241 case BoolTest::lt: 2242 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit 2243 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here 2244 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT. 2245 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit ); 2246 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range. 2247 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could 2248 // still be outside of loop range. 2249 conditional_rc = true; 2250 break; 2251 default: 2252 if (PrintOpto) { 2253 tty->print_cr("missed RCE opportunity"); 2254 } 2255 continue; // Unhandled case 2256 } 2257 } 2258 2259 // Kill the eliminated test 2260 C->set_major_progress(); 2261 Node *kill_con = _igvn.intcon( 1-flip ); 2262 set_ctrl(kill_con, C->root()); 2263 _igvn.replace_input_of(iff, 1, kill_con); 2264 // Find surviving projection 2265 assert(iff->is_If(), ""); 2266 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip); 2267 // Find loads off the surviving projection; remove their control edge 2268 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { 2269 Node* cd = dp->fast_out(i); // Control-dependent node 2270 if (cd->is_Load() && cd->depends_only_on_test()) { // Loads can now float around in the loop 2271 // Allow the load to float around in the loop, or before it 2272 // but NOT before the pre-loop. 2273 _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL 2274 --i; 2275 --imax; 2276 } 2277 } 2278 if (limit->Opcode() == Op_LoadRange) { 2279 closed_range_checks--; 2280 } 2281 2282 } // End of is IF 2283 2284 } 2285 2286 // Update loop limits 2287 if (conditional_rc) { 2288 pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit) 2289 : (Node*)new MaxINode(pre_limit, orig_limit); 2290 register_new_node(pre_limit, pre_ctrl); 2291 } 2292 _igvn.replace_input_of(pre_opaq, 1, pre_limit); 2293 2294 // Note:: we are making the main loop limit no longer precise; 2295 // need to round up based on stride. 2296 cl->set_nonexact_trip_count(); 2297 Node *main_cle = cl->loopexit(); 2298 Node *main_bol = main_cle->in(1); 2299 // Hacking loop bounds; need private copies of exit test 2300 if( main_bol->outcnt() > 1 ) {// BoolNode shared? 2301 main_bol = main_bol->clone();// Clone a private BoolNode 2302 register_new_node( main_bol, main_cle->in(0) ); 2303 _igvn.replace_input_of(main_cle, 1, main_bol); 2304 } 2305 Node *main_cmp = main_bol->in(1); 2306 if( main_cmp->outcnt() > 1 ) { // CmpNode shared? 2307 main_cmp = main_cmp->clone();// Clone a private CmpNode 2308 register_new_node( main_cmp, main_cle->in(0) ); 2309 _igvn.replace_input_of(main_bol, 1, main_cmp); 2310 } 2311 // Hack the now-private loop bounds 2312 _igvn.replace_input_of(main_cmp, 2, main_limit); 2313 // The OpaqueNode is unshared by design 2314 assert( opqzm->outcnt() == 1, "cannot hack shared node" ); 2315 _igvn.replace_input_of(opqzm, 1, main_limit); 2316 2317 return closed_range_checks; 2318 } 2319 2320 //------------------------------has_range_checks------------------------------- 2321 // Check to see if RCE cleaned the current loop of range-checks. 2322 void PhaseIdealLoop::has_range_checks(IdealLoopTree *loop) { 2323 assert(RangeCheckElimination, ""); 2324 2325 // skip if not a counted loop 2326 if (!loop->is_counted()) return; 2327 2328 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 2329 2330 // skip this loop if it is already checked 2331 if (cl->has_been_range_checked()) return; 2332 2333 // Now check for existence of range checks 2334 for (uint i = 0; i < loop->_body.size(); i++) { 2335 Node *iff = loop->_body[i]; 2336 int iff_opc = iff->Opcode(); 2337 if (iff_opc == Op_If || iff_opc == Op_RangeCheck) { 2338 cl->mark_has_range_checks(); 2339 break; 2340 } 2341 } 2342 cl->set_has_been_range_checked(); 2343 } 2344 2345 //-------------------------multi_version_post_loops---------------------------- 2346 // Check the range checks that remain, if simple, use the bounds to guard 2347 // which version to a post loop we execute, one with range checks or one without 2348 bool PhaseIdealLoop::multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop) { 2349 bool multi_version_succeeded = false; 2350 assert(RangeCheckElimination, ""); 2351 CountedLoopNode *legacy_cl = legacy_loop->_head->as_CountedLoop(); 2352 assert(legacy_cl->is_post_loop(), ""); 2353 2354 // Check for existence of range checks using the unique instance to make a guard with 2355 Unique_Node_List worklist; 2356 for (uint i = 0; i < legacy_loop->_body.size(); i++) { 2357 Node *iff = legacy_loop->_body[i]; 2358 int iff_opc = iff->Opcode(); 2359 if (iff_opc == Op_If || iff_opc == Op_RangeCheck) { 2360 worklist.push(iff); 2361 } 2362 } 2363 2364 // Find RCE'd post loop so that we can stage its guard. 2365 if (!is_canonical_loop_entry(legacy_cl)) return multi_version_succeeded; 2366 Node* ctrl = legacy_cl->in(LoopNode::EntryControl); 2367 Node* iffm = ctrl->in(0); 2368 2369 // Now we test that both the post loops are connected 2370 Node* post_loop_region = iffm->in(0); 2371 if (post_loop_region == NULL) return multi_version_succeeded; 2372 if (!post_loop_region->is_Region()) return multi_version_succeeded; 2373 Node* covering_region = post_loop_region->in(RegionNode::Control+1); 2374 if (covering_region == NULL) return multi_version_succeeded; 2375 if (!covering_region->is_Region()) return multi_version_succeeded; 2376 Node* p_f = covering_region->in(RegionNode::Control); 2377 if (p_f == NULL) return multi_version_succeeded; 2378 if (!p_f->is_IfFalse()) return multi_version_succeeded; 2379 if (!p_f->in(0)->is_CountedLoopEnd()) return multi_version_succeeded; 2380 CountedLoopEndNode* rce_loop_end = p_f->in(0)->as_CountedLoopEnd(); 2381 if (rce_loop_end == NULL) return multi_version_succeeded; 2382 CountedLoopNode* rce_cl = rce_loop_end->loopnode(); 2383 if (rce_cl == NULL || !rce_cl->is_post_loop()) return multi_version_succeeded; 2384 CountedLoopNode *known_rce_cl = rce_loop->_head->as_CountedLoop(); 2385 if (rce_cl != known_rce_cl) return multi_version_succeeded; 2386 2387 // Then we fetch the cover entry test 2388 ctrl = rce_cl->in(LoopNode::EntryControl); 2389 if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return multi_version_succeeded; 2390 2391 #ifndef PRODUCT 2392 if (TraceLoopOpts) { 2393 tty->print("PostMultiVersion\n"); 2394 rce_loop->dump_head(); 2395 legacy_loop->dump_head(); 2396 } 2397 #endif 2398 2399 // Now fetch the limit we want to compare against 2400 Node *limit = rce_cl->limit(); 2401 bool first_time = true; 2402 2403 // If we got this far, we identified the post loop which has been RCE'd and 2404 // we have a work list. Now we will try to transform the if guard to cause 2405 // the loop pair to be multi version executed with the determination left to runtime 2406 // or the optimizer if full information is known about the given arrays at compile time. 2407 Node *last_min = NULL; 2408 multi_version_succeeded = true; 2409 while (worklist.size()) { 2410 Node* rc_iffm = worklist.pop(); 2411 if (rc_iffm->is_If()) { 2412 Node *rc_bolzm = rc_iffm->in(1); 2413 if (rc_bolzm->is_Bool()) { 2414 Node *rc_cmpzm = rc_bolzm->in(1); 2415 if (rc_cmpzm->is_Cmp()) { 2416 Node *rc_left = rc_cmpzm->in(2); 2417 if (rc_left->Opcode() != Op_LoadRange) { 2418 multi_version_succeeded = false; 2419 break; 2420 } 2421 if (first_time) { 2422 last_min = rc_left; 2423 first_time = false; 2424 } else { 2425 Node *cur_min = new MinINode(last_min, rc_left); 2426 last_min = cur_min; 2427 _igvn.register_new_node_with_optimizer(last_min); 2428 } 2429 } 2430 } 2431 } 2432 } 2433 2434 // All we have to do is update the limit of the rce loop 2435 // with the min of our expression and the current limit. 2436 // We will use this expression to replace the current limit. 2437 if (last_min && multi_version_succeeded) { 2438 Node *cur_min = new MinINode(last_min, limit); 2439 _igvn.register_new_node_with_optimizer(cur_min); 2440 Node *cmp_node = rce_loop_end->cmp_node(); 2441 _igvn.replace_input_of(cmp_node, 2, cur_min); 2442 set_ctrl(cur_min, ctrl); 2443 set_loop(cur_min, rce_loop->_parent); 2444 2445 legacy_cl->mark_is_multiversioned(); 2446 rce_cl->mark_is_multiversioned(); 2447 multi_version_succeeded = true; 2448 2449 C->set_major_progress(); 2450 } 2451 2452 return multi_version_succeeded; 2453 } 2454 2455 //-------------------------poison_rce_post_loop-------------------------------- 2456 // Causes the rce'd post loop to be optimized away if multiversioning fails 2457 void PhaseIdealLoop::poison_rce_post_loop(IdealLoopTree *rce_loop) { 2458 CountedLoopNode *rce_cl = rce_loop->_head->as_CountedLoop(); 2459 Node* ctrl = rce_cl->in(LoopNode::EntryControl); 2460 if (ctrl->is_IfTrue() || ctrl->is_IfFalse()) { 2461 Node* iffm = ctrl->in(0); 2462 if (iffm->is_If()) { 2463 Node* cur_bool = iffm->in(1); 2464 if (cur_bool->is_Bool()) { 2465 Node* cur_cmp = cur_bool->in(1); 2466 if (cur_cmp->is_Cmp()) { 2467 BoolTest::mask new_test = BoolTest::gt; 2468 BoolNode *new_bool = new BoolNode(cur_cmp, new_test); 2469 _igvn.replace_node(cur_bool, new_bool); 2470 _igvn._worklist.push(new_bool); 2471 Node* left_op = cur_cmp->in(1); 2472 _igvn.replace_input_of(cur_cmp, 2, left_op); 2473 C->set_major_progress(); 2474 } 2475 } 2476 } 2477 } 2478 } 2479 2480 //------------------------------DCE_loop_body---------------------------------- 2481 // Remove simplistic dead code from loop body 2482 void IdealLoopTree::DCE_loop_body() { 2483 for( uint i = 0; i < _body.size(); i++ ) 2484 if( _body.at(i)->outcnt() == 0 ) 2485 _body.map( i--, _body.pop() ); 2486 } 2487 2488 2489 //------------------------------adjust_loop_exit_prob-------------------------- 2490 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage. 2491 // Replace with a 1-in-10 exit guess. 2492 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) { 2493 Node *test = tail(); 2494 while( test != _head ) { 2495 uint top = test->Opcode(); 2496 if( top == Op_IfTrue || top == Op_IfFalse ) { 2497 int test_con = ((ProjNode*)test)->_con; 2498 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity"); 2499 IfNode *iff = test->in(0)->as_If(); 2500 if( iff->outcnt() == 2 ) { // Ignore dead tests 2501 Node *bol = iff->in(1); 2502 if( bol && bol->req() > 1 && bol->in(1) && 2503 ((bol->in(1)->Opcode() == Op_StorePConditional ) || 2504 (bol->in(1)->Opcode() == Op_StoreIConditional ) || 2505 (bol->in(1)->Opcode() == Op_StoreLConditional ) || 2506 (bol->in(1)->Opcode() == Op_CompareAndExchangeB ) || 2507 (bol->in(1)->Opcode() == Op_CompareAndExchangeS ) || 2508 (bol->in(1)->Opcode() == Op_CompareAndExchangeI ) || 2509 (bol->in(1)->Opcode() == Op_CompareAndExchangeL ) || 2510 (bol->in(1)->Opcode() == Op_CompareAndExchangeP ) || 2511 (bol->in(1)->Opcode() == Op_CompareAndExchangeN ) || 2512 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapB ) || 2513 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapS ) || 2514 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapI ) || 2515 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapL ) || 2516 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapP ) || 2517 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapN ) || 2518 (bol->in(1)->Opcode() == Op_CompareAndSwapB ) || 2519 (bol->in(1)->Opcode() == Op_CompareAndSwapS ) || 2520 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || 2521 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || 2522 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || 2523 (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) 2524 return; // Allocation loops RARELY take backedge 2525 // Find the OTHER exit path from the IF 2526 Node* ex = iff->proj_out(1-test_con); 2527 float p = iff->_prob; 2528 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) { 2529 if( top == Op_IfTrue ) { 2530 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) { 2531 iff->_prob = PROB_STATIC_FREQUENT; 2532 } 2533 } else { 2534 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) { 2535 iff->_prob = PROB_STATIC_INFREQUENT; 2536 } 2537 } 2538 } 2539 } 2540 } 2541 test = phase->idom(test); 2542 } 2543 } 2544 2545 #ifdef ASSERT 2546 static CountedLoopNode* locate_pre_from_main(CountedLoopNode *cl) { 2547 Node *ctrl = cl->skip_strip_mined()->in(LoopNode::EntryControl); 2548 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, ""); 2549 Node *iffm = ctrl->in(0); 2550 assert(iffm->Opcode() == Op_If, ""); 2551 Node *p_f = iffm->in(0); 2552 assert(p_f->Opcode() == Op_IfFalse, ""); 2553 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); 2554 assert(pre_end->loopnode()->is_pre_loop(), ""); 2555 return pre_end->loopnode(); 2556 } 2557 #endif 2558 2559 // Remove the main and post loops and make the pre loop execute all 2560 // iterations. Useful when the pre loop is found empty. 2561 void IdealLoopTree::remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase) { 2562 CountedLoopEndNode* pre_end = cl->loopexit(); 2563 Node* pre_cmp = pre_end->cmp_node(); 2564 if (pre_cmp->in(2)->Opcode() != Op_Opaque1) { 2565 // Only safe to remove the main loop if the compiler optimized it 2566 // out based on an unknown number of iterations 2567 return; 2568 } 2569 2570 // Can we find the main loop? 2571 if (_next == NULL) { 2572 return; 2573 } 2574 2575 Node* next_head = _next->_head; 2576 if (!next_head->is_CountedLoop()) { 2577 return; 2578 } 2579 2580 CountedLoopNode* main_head = next_head->as_CountedLoop(); 2581 if (!main_head->is_main_loop()) { 2582 return; 2583 } 2584 2585 assert(locate_pre_from_main(main_head) == cl, "bad main loop"); 2586 Node* main_iff = main_head->skip_strip_mined()->in(LoopNode::EntryControl)->in(0); 2587 2588 // Remove the Opaque1Node of the pre loop and make it execute all iterations 2589 phase->_igvn.replace_input_of(pre_cmp, 2, pre_cmp->in(2)->in(2)); 2590 // Remove the Opaque1Node of the main loop so it can be optimized out 2591 Node* main_cmp = main_iff->in(1)->in(1); 2592 assert(main_cmp->in(2)->Opcode() == Op_Opaque1, "main loop has no opaque node?"); 2593 phase->_igvn.replace_input_of(main_cmp, 2, main_cmp->in(2)->in(1)); 2594 } 2595 2596 //------------------------------policy_do_remove_empty_loop-------------------- 2597 // Micro-benchmark spamming. Policy is to always remove empty loops. 2598 // The 'DO' part is to replace the trip counter with the value it will 2599 // have on the last iteration. This will break the loop. 2600 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) { 2601 // Minimum size must be empty loop 2602 if (_body.size() > EMPTY_LOOP_SIZE) 2603 return false; 2604 2605 if (!_head->is_CountedLoop()) 2606 return false; // Dead loop 2607 CountedLoopNode *cl = _head->as_CountedLoop(); 2608 if (!cl->is_valid_counted_loop()) 2609 return false; // Malformed loop 2610 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 2611 return false; // Infinite loop 2612 2613 if (cl->is_pre_loop()) { 2614 // If the loop we are removing is a pre-loop then the main and 2615 // post loop can be removed as well 2616 remove_main_post_loops(cl, phase); 2617 } 2618 2619 #ifdef ASSERT 2620 // Ensure only one phi which is the iv. 2621 Node* iv = NULL; 2622 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) { 2623 Node* n = cl->fast_out(i); 2624 if (n->Opcode() == Op_Phi) { 2625 assert(iv == NULL, "Too many phis" ); 2626 iv = n; 2627 } 2628 } 2629 assert(iv == cl->phi(), "Wrong phi" ); 2630 #endif 2631 2632 // main and post loops have explicitly created zero trip guard 2633 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop(); 2634 if (needs_guard) { 2635 // Skip guard if values not overlap. 2636 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int(); 2637 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int(); 2638 int stride_con = cl->stride_con(); 2639 if (stride_con > 0) { 2640 needs_guard = (init_t->_hi >= limit_t->_lo); 2641 } else { 2642 needs_guard = (init_t->_lo <= limit_t->_hi); 2643 } 2644 } 2645 if (needs_guard) { 2646 // Check for an obvious zero trip guard. 2647 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->skip_strip_mined()->in(LoopNode::EntryControl)); 2648 if (inctrl->Opcode() == Op_IfTrue || inctrl->Opcode() == Op_IfFalse) { 2649 bool maybe_swapped = (inctrl->Opcode() == Op_IfFalse); 2650 // The test should look like just the backedge of a CountedLoop 2651 Node* iff = inctrl->in(0); 2652 if (iff->is_If()) { 2653 Node* bol = iff->in(1); 2654 if (bol->is_Bool()) { 2655 BoolTest test = bol->as_Bool()->_test; 2656 if (maybe_swapped) { 2657 test._test = test.commute(); 2658 test._test = test.negate(); 2659 } 2660 if (test._test == cl->loopexit()->test_trip()) { 2661 Node* cmp = bol->in(1); 2662 int init_idx = maybe_swapped ? 2 : 1; 2663 int limit_idx = maybe_swapped ? 1 : 2; 2664 if (cmp->is_Cmp() && cmp->in(init_idx) == cl->init_trip() && cmp->in(limit_idx) == cl->limit()) { 2665 needs_guard = false; 2666 } 2667 } 2668 } 2669 } 2670 } 2671 } 2672 2673 #ifndef PRODUCT 2674 if (PrintOpto) { 2675 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : ""); 2676 this->dump_head(); 2677 } else if (TraceLoopOpts) { 2678 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : ""); 2679 this->dump_head(); 2680 } 2681 #endif 2682 2683 if (needs_guard) { 2684 // Peel the loop to ensure there's a zero trip guard 2685 Node_List old_new; 2686 phase->do_peeling(this, old_new); 2687 } 2688 2689 // Replace the phi at loop head with the final value of the last 2690 // iteration. Then the CountedLoopEnd will collapse (backedge never 2691 // taken) and all loop-invariant uses of the exit values will be correct. 2692 Node *phi = cl->phi(); 2693 Node *exact_limit = phase->exact_limit(this); 2694 if (exact_limit != cl->limit()) { 2695 // We also need to replace the original limit to collapse loop exit. 2696 Node* cmp = cl->loopexit()->cmp_node(); 2697 assert(cl->limit() == cmp->in(2), "sanity"); 2698 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist 2699 phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist 2700 } 2701 // Note: the final value after increment should not overflow since 2702 // counted loop has limit check predicate. 2703 Node *final = new SubINode( exact_limit, cl->stride() ); 2704 phase->register_new_node(final,cl->in(LoopNode::EntryControl)); 2705 phase->_igvn.replace_node(phi,final); 2706 phase->C->set_major_progress(); 2707 return true; 2708 } 2709 2710 //------------------------------policy_do_one_iteration_loop------------------- 2711 // Convert one iteration loop into normal code. 2712 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) { 2713 if (!_head->as_Loop()->is_valid_counted_loop()) 2714 return false; // Only for counted loop 2715 2716 CountedLoopNode *cl = _head->as_CountedLoop(); 2717 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) { 2718 return false; 2719 } 2720 2721 #ifndef PRODUCT 2722 if(TraceLoopOpts) { 2723 tty->print("OneIteration "); 2724 this->dump_head(); 2725 } 2726 #endif 2727 2728 Node *init_n = cl->init_trip(); 2729 #ifdef ASSERT 2730 // Loop boundaries should be constant since trip count is exact. 2731 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration"); 2732 #endif 2733 // Replace the phi at loop head with the value of the init_trip. 2734 // Then the CountedLoopEnd will collapse (backedge will not be taken) 2735 // and all loop-invariant uses of the exit values will be correct. 2736 phase->_igvn.replace_node(cl->phi(), cl->init_trip()); 2737 phase->C->set_major_progress(); 2738 return true; 2739 } 2740 2741 //============================================================================= 2742 //------------------------------iteration_split_impl--------------------------- 2743 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) { 2744 // Compute loop trip count if possible. 2745 compute_trip_count(phase); 2746 2747 // Convert one iteration loop into normal code. 2748 if (policy_do_one_iteration_loop(phase)) 2749 return true; 2750 2751 // Check and remove empty loops (spam micro-benchmarks) 2752 if (policy_do_remove_empty_loop(phase)) 2753 return true; // Here we removed an empty loop 2754 2755 bool should_peel = policy_peeling(phase); // Should we peel? 2756 2757 bool should_unswitch = policy_unswitching(phase); 2758 2759 // Non-counted loops may be peeled; exactly 1 iteration is peeled. 2760 // This removes loop-invariant tests (usually null checks). 2761 if (!_head->is_CountedLoop()) { // Non-counted loop 2762 if (PartialPeelLoop && phase->partial_peel(this, old_new)) { 2763 // Partial peel succeeded so terminate this round of loop opts 2764 return false; 2765 } 2766 if (should_peel) { // Should we peel? 2767 if (PrintOpto) { tty->print_cr("should_peel"); } 2768 phase->do_peeling(this,old_new); 2769 } else if (should_unswitch) { 2770 phase->do_unswitching(this, old_new); 2771 } 2772 return true; 2773 } 2774 CountedLoopNode *cl = _head->as_CountedLoop(); 2775 2776 if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops 2777 2778 // Do nothing special to pre- and post- loops 2779 if (cl->is_pre_loop() || cl->is_post_loop()) return true; 2780 2781 // Compute loop trip count from profile data 2782 compute_profile_trip_cnt(phase); 2783 2784 // Before attempting fancy unrolling, RCE or alignment, see if we want 2785 // to completely unroll this loop or do loop unswitching. 2786 if (cl->is_normal_loop()) { 2787 if (should_unswitch) { 2788 phase->do_unswitching(this, old_new); 2789 return true; 2790 } 2791 bool should_maximally_unroll = policy_maximally_unroll(phase); 2792 if (should_maximally_unroll) { 2793 // Here we did some unrolling and peeling. Eventually we will 2794 // completely unroll this loop and it will no longer be a loop. 2795 phase->do_maximally_unroll(this,old_new); 2796 return true; 2797 } 2798 } 2799 2800 // Skip next optimizations if running low on nodes. Note that 2801 // policy_unswitching and policy_maximally_unroll have this check. 2802 int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes(); 2803 if ((int)(2 * _body.size()) > nodes_left) { 2804 return true; 2805 } 2806 2807 // Counted loops may be peeled, may need some iterations run up 2808 // front for RCE, and may want to align loop refs to a cache 2809 // line. Thus we clone a full loop up front whose trip count is 2810 // at least 1 (if peeling), but may be several more. 2811 2812 // The main loop will start cache-line aligned with at least 1 2813 // iteration of the unrolled body (zero-trip test required) and 2814 // will have some range checks removed. 2815 2816 // A post-loop will finish any odd iterations (leftover after 2817 // unrolling), plus any needed for RCE purposes. 2818 2819 bool should_unroll = policy_unroll(phase); 2820 2821 bool should_rce = policy_range_check(phase); 2822 2823 bool should_align = policy_align(phase); 2824 2825 // If not RCE'ing (iteration splitting) or Aligning, then we do not 2826 // need a pre-loop. We may still need to peel an initial iteration but 2827 // we will not be needing an unknown number of pre-iterations. 2828 // 2829 // Basically, if may_rce_align reports FALSE first time through, 2830 // we will not be able to later do RCE or Aligning on this loop. 2831 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align; 2832 2833 // If we have any of these conditions (RCE, alignment, unrolling) met, then 2834 // we switch to the pre-/main-/post-loop model. This model also covers 2835 // peeling. 2836 if (should_rce || should_align || should_unroll) { 2837 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops 2838 phase->insert_pre_post_loops(this,old_new, !may_rce_align); 2839 2840 // Adjust the pre- and main-loop limits to let the pre and post loops run 2841 // with full checks, but the main-loop with no checks. Remove said 2842 // checks from the main body. 2843 if (should_rce) { 2844 if (phase->do_range_check(this, old_new) != 0) { 2845 cl->mark_has_range_checks(); 2846 } 2847 } else if (PostLoopMultiversioning) { 2848 phase->has_range_checks(this); 2849 } 2850 2851 if (should_unroll && !should_peel && PostLoopMultiversioning) { 2852 // Try to setup multiversioning on main loops before they are unrolled 2853 if (cl->is_main_loop() && (cl->unrolled_count() == 1)) { 2854 phase->insert_scalar_rced_post_loop(this, old_new); 2855 } 2856 } 2857 2858 // Double loop body for unrolling. Adjust the minimum-trip test (will do 2859 // twice as many iterations as before) and the main body limit (only do 2860 // an even number of trips). If we are peeling, we might enable some RCE 2861 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if 2862 // peeling. 2863 if (should_unroll && !should_peel) { 2864 if (SuperWordLoopUnrollAnalysis) { 2865 phase->insert_vector_post_loop(this, old_new); 2866 } 2867 phase->do_unroll(this, old_new, true); 2868 } 2869 2870 // Adjust the pre-loop limits to align the main body 2871 // iterations. 2872 if (should_align) 2873 Unimplemented(); 2874 2875 } else { // Else we have an unchanged counted loop 2876 if (should_peel) // Might want to peel but do nothing else 2877 phase->do_peeling(this,old_new); 2878 } 2879 return true; 2880 } 2881 2882 2883 //============================================================================= 2884 //------------------------------iteration_split-------------------------------- 2885 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { 2886 // Recursively iteration split nested loops 2887 if (_child && !_child->iteration_split(phase, old_new)) 2888 return false; 2889 2890 // Clean out prior deadwood 2891 DCE_loop_body(); 2892 2893 2894 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. 2895 // Replace with a 1-in-10 exit guess. 2896 if (_parent /*not the root loop*/ && 2897 !_irreducible && 2898 // Also ignore the occasional dead backedge 2899 !tail()->is_top()) { 2900 adjust_loop_exit_prob(phase); 2901 } 2902 2903 // Gate unrolling, RCE and peeling efforts. 2904 if (!_child && // If not an inner loop, do not split 2905 !_irreducible && 2906 _allow_optimizations && 2907 !tail()->is_top()) { // Also ignore the occasional dead backedge 2908 if (!_has_call) { 2909 if (!iteration_split_impl(phase, old_new)) { 2910 return false; 2911 } 2912 } else if (policy_unswitching(phase)) { 2913 phase->do_unswitching(this, old_new); 2914 } 2915 } 2916 2917 // Minor offset re-organization to remove loop-fallout uses of 2918 // trip counter when there was no major reshaping. 2919 phase->reorg_offsets(this); 2920 2921 if (_next && !_next->iteration_split(phase, old_new)) 2922 return false; 2923 return true; 2924 } 2925 2926 2927 //============================================================================= 2928 // Process all the loops in the loop tree and replace any fill 2929 // patterns with an intrinsic version. 2930 bool PhaseIdealLoop::do_intrinsify_fill() { 2931 bool changed = false; 2932 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2933 IdealLoopTree* lpt = iter.current(); 2934 changed |= intrinsify_fill(lpt); 2935 } 2936 return changed; 2937 } 2938 2939 2940 // Examine an inner loop looking for a a single store of an invariant 2941 // value in a unit stride loop, 2942 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value, 2943 Node*& shift, Node*& con) { 2944 const char* msg = NULL; 2945 Node* msg_node = NULL; 2946 2947 store_value = NULL; 2948 con = NULL; 2949 shift = NULL; 2950 2951 // Process the loop looking for stores. If there are multiple 2952 // stores or extra control flow give at this point. 2953 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 2954 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2955 Node* n = lpt->_body.at(i); 2956 if (n->outcnt() == 0) continue; // Ignore dead 2957 if (n->is_Store()) { 2958 if (store != NULL) { 2959 msg = "multiple stores"; 2960 break; 2961 } 2962 int opc = n->Opcode(); 2963 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) { 2964 msg = "oop fills not handled"; 2965 break; 2966 } 2967 Node* value = n->in(MemNode::ValueIn); 2968 if (!lpt->is_invariant(value)) { 2969 msg = "variant store value"; 2970 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) { 2971 msg = "not array address"; 2972 } 2973 store = n; 2974 store_value = value; 2975 } else if (n->is_If() && n != head->loopexit()) { 2976 msg = "extra control flow"; 2977 msg_node = n; 2978 } 2979 } 2980 2981 if (store == NULL) { 2982 // No store in loop 2983 return false; 2984 } 2985 2986 if (msg == NULL && head->stride_con() != 1) { 2987 // could handle negative strides too 2988 if (head->stride_con() < 0) { 2989 msg = "negative stride"; 2990 } else { 2991 msg = "non-unit stride"; 2992 } 2993 } 2994 2995 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) { 2996 msg = "can't handle store address"; 2997 msg_node = store->in(MemNode::Address); 2998 } 2999 3000 if (msg == NULL && 3001 (!store->in(MemNode::Memory)->is_Phi() || 3002 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) { 3003 msg = "store memory isn't proper phi"; 3004 msg_node = store->in(MemNode::Memory); 3005 } 3006 3007 // Make sure there is an appropriate fill routine 3008 BasicType t = store->as_Mem()->memory_type(); 3009 const char* fill_name; 3010 if (msg == NULL && 3011 StubRoutines::select_fill_function(t, false, fill_name) == NULL) { 3012 msg = "unsupported store"; 3013 msg_node = store; 3014 } 3015 3016 if (msg != NULL) { 3017 #ifndef PRODUCT 3018 if (TraceOptimizeFill) { 3019 tty->print_cr("not fill intrinsic candidate: %s", msg); 3020 if (msg_node != NULL) msg_node->dump(); 3021 } 3022 #endif 3023 return false; 3024 } 3025 3026 // Make sure the address expression can be handled. It should be 3027 // head->phi * elsize + con. head->phi might have a ConvI2L(CastII()). 3028 Node* elements[4]; 3029 Node* cast = NULL; 3030 Node* conv = NULL; 3031 bool found_index = false; 3032 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements)); 3033 for (int e = 0; e < count; e++) { 3034 Node* n = elements[e]; 3035 if (n->is_Con() && con == NULL) { 3036 con = n; 3037 } else if (n->Opcode() == Op_LShiftX && shift == NULL) { 3038 Node* value = n->in(1); 3039 #ifdef _LP64 3040 if (value->Opcode() == Op_ConvI2L) { 3041 conv = value; 3042 value = value->in(1); 3043 } 3044 if (value->Opcode() == Op_CastII && 3045 value->as_CastII()->has_range_check()) { 3046 // Skip range check dependent CastII nodes 3047 cast = value; 3048 value = value->in(1); 3049 } 3050 #endif 3051 if (value != head->phi()) { 3052 msg = "unhandled shift in address"; 3053 } else { 3054 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) { 3055 msg = "scale doesn't match"; 3056 } else { 3057 found_index = true; 3058 shift = n; 3059 } 3060 } 3061 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) { 3062 conv = n; 3063 n = n->in(1); 3064 if (n->Opcode() == Op_CastII && 3065 n->as_CastII()->has_range_check()) { 3066 // Skip range check dependent CastII nodes 3067 cast = n; 3068 n = n->in(1); 3069 } 3070 if (n == head->phi()) { 3071 found_index = true; 3072 } else { 3073 msg = "unhandled input to ConvI2L"; 3074 } 3075 } else if (n == head->phi()) { 3076 // no shift, check below for allowed cases 3077 found_index = true; 3078 } else { 3079 msg = "unhandled node in address"; 3080 msg_node = n; 3081 } 3082 } 3083 3084 if (count == -1) { 3085 msg = "malformed address expression"; 3086 msg_node = store; 3087 } 3088 3089 if (!found_index) { 3090 msg = "missing use of index"; 3091 } 3092 3093 // byte sized items won't have a shift 3094 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) { 3095 msg = "can't find shift"; 3096 msg_node = store; 3097 } 3098 3099 if (msg != NULL) { 3100 #ifndef PRODUCT 3101 if (TraceOptimizeFill) { 3102 tty->print_cr("not fill intrinsic: %s", msg); 3103 if (msg_node != NULL) msg_node->dump(); 3104 } 3105 #endif 3106 return false; 3107 } 3108 3109 // No make sure all the other nodes in the loop can be handled 3110 VectorSet ok(Thread::current()->resource_area()); 3111 3112 // store related values are ok 3113 ok.set(store->_idx); 3114 ok.set(store->in(MemNode::Memory)->_idx); 3115 3116 CountedLoopEndNode* loop_exit = head->loopexit(); 3117 guarantee(loop_exit != NULL, "no loop exit node"); 3118 3119 // Loop structure is ok 3120 ok.set(head->_idx); 3121 ok.set(loop_exit->_idx); 3122 ok.set(head->phi()->_idx); 3123 ok.set(head->incr()->_idx); 3124 ok.set(loop_exit->cmp_node()->_idx); 3125 ok.set(loop_exit->in(1)->_idx); 3126 3127 // Address elements are ok 3128 if (con) ok.set(con->_idx); 3129 if (shift) ok.set(shift->_idx); 3130 if (cast) ok.set(cast->_idx); 3131 if (conv) ok.set(conv->_idx); 3132 3133 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 3134 Node* n = lpt->_body.at(i); 3135 if (n->outcnt() == 0) continue; // Ignore dead 3136 if (ok.test(n->_idx)) continue; 3137 // Backedge projection is ok 3138 if (n->is_IfTrue() && n->in(0) == loop_exit) continue; 3139 if (!n->is_AddP()) { 3140 msg = "unhandled node"; 3141 msg_node = n; 3142 break; 3143 } 3144 } 3145 3146 // Make sure no unexpected values are used outside the loop 3147 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 3148 Node* n = lpt->_body.at(i); 3149 // These values can be replaced with other nodes if they are used 3150 // outside the loop. 3151 if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue; 3152 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) { 3153 Node* use = iter.get(); 3154 if (!lpt->_body.contains(use)) { 3155 msg = "node is used outside loop"; 3156 // lpt->_body.dump(); 3157 msg_node = n; 3158 break; 3159 } 3160 } 3161 } 3162 3163 #ifdef ASSERT 3164 if (TraceOptimizeFill) { 3165 if (msg != NULL) { 3166 tty->print_cr("no fill intrinsic: %s", msg); 3167 if (msg_node != NULL) msg_node->dump(); 3168 } else { 3169 tty->print_cr("fill intrinsic for:"); 3170 } 3171 store->dump(); 3172 if (Verbose) { 3173 lpt->_body.dump(); 3174 } 3175 } 3176 #endif 3177 3178 return msg == NULL; 3179 } 3180 3181 3182 3183 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) { 3184 // Only for counted inner loops 3185 if (!lpt->is_counted() || !lpt->is_inner()) { 3186 return false; 3187 } 3188 3189 // Must have constant stride 3190 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 3191 if (!head->is_valid_counted_loop() || !head->is_normal_loop()) { 3192 return false; 3193 } 3194 3195 head->verify_strip_mined(1); 3196 3197 // Check that the body only contains a store of a loop invariant 3198 // value that is indexed by the loop phi. 3199 Node* store = NULL; 3200 Node* store_value = NULL; 3201 Node* shift = NULL; 3202 Node* offset = NULL; 3203 if (!match_fill_loop(lpt, store, store_value, shift, offset)) { 3204 return false; 3205 } 3206 3207 Node* exit = head->loopexit()->proj_out(0); 3208 if (exit == NULL) { 3209 return false; 3210 } 3211 3212 #ifndef PRODUCT 3213 if (TraceLoopOpts) { 3214 tty->print("ArrayFill "); 3215 lpt->dump_head(); 3216 } 3217 #endif 3218 3219 // Now replace the whole loop body by a call to a fill routine that 3220 // covers the same region as the loop. 3221 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base); 3222 3223 // Build an expression for the beginning of the copy region 3224 Node* index = head->init_trip(); 3225 #ifdef _LP64 3226 index = new ConvI2LNode(index); 3227 _igvn.register_new_node_with_optimizer(index); 3228 #endif 3229 if (shift != NULL) { 3230 // byte arrays don't require a shift but others do. 3231 index = new LShiftXNode(index, shift->in(2)); 3232 _igvn.register_new_node_with_optimizer(index); 3233 } 3234 index = new AddPNode(base, base, index); 3235 _igvn.register_new_node_with_optimizer(index); 3236 Node* from = new AddPNode(base, index, offset); 3237 _igvn.register_new_node_with_optimizer(from); 3238 // Compute the number of elements to copy 3239 Node* len = new SubINode(head->limit(), head->init_trip()); 3240 _igvn.register_new_node_with_optimizer(len); 3241 3242 BasicType t = store->as_Mem()->memory_type(); 3243 bool aligned = false; 3244 if (offset != NULL && head->init_trip()->is_Con()) { 3245 int element_size = type2aelembytes(t); 3246 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0; 3247 } 3248 3249 // Build a call to the fill routine 3250 const char* fill_name; 3251 address fill = StubRoutines::select_fill_function(t, aligned, fill_name); 3252 assert(fill != NULL, "what?"); 3253 3254 // Convert float/double to int/long for fill routines 3255 if (t == T_FLOAT) { 3256 store_value = new MoveF2INode(store_value); 3257 _igvn.register_new_node_with_optimizer(store_value); 3258 } else if (t == T_DOUBLE) { 3259 store_value = new MoveD2LNode(store_value); 3260 _igvn.register_new_node_with_optimizer(store_value); 3261 } 3262 3263 Node* mem_phi = store->in(MemNode::Memory); 3264 Node* result_ctrl; 3265 Node* result_mem; 3266 const TypeFunc* call_type = OptoRuntime::array_fill_Type(); 3267 CallLeafNode *call = new CallLeafNoFPNode(call_type, fill, 3268 fill_name, TypeAryPtr::get_array_body_type(t)); 3269 uint cnt = 0; 3270 call->init_req(TypeFunc::Parms + cnt++, from); 3271 call->init_req(TypeFunc::Parms + cnt++, store_value); 3272 #ifdef _LP64 3273 len = new ConvI2LNode(len); 3274 _igvn.register_new_node_with_optimizer(len); 3275 #endif 3276 call->init_req(TypeFunc::Parms + cnt++, len); 3277 #ifdef _LP64 3278 call->init_req(TypeFunc::Parms + cnt++, C->top()); 3279 #endif 3280 call->init_req(TypeFunc::Control, head->init_control()); 3281 call->init_req(TypeFunc::I_O, C->top()); // Does no I/O. 3282 call->init_req(TypeFunc::Memory, mem_phi->in(LoopNode::EntryControl)); 3283 call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr)); 3284 call->init_req(TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr)); 3285 _igvn.register_new_node_with_optimizer(call); 3286 result_ctrl = new ProjNode(call,TypeFunc::Control); 3287 _igvn.register_new_node_with_optimizer(result_ctrl); 3288 result_mem = new ProjNode(call,TypeFunc::Memory); 3289 _igvn.register_new_node_with_optimizer(result_mem); 3290 3291 /* Disable following optimization until proper fix (add missing checks). 3292 3293 // If this fill is tightly coupled to an allocation and overwrites 3294 // the whole body, allow it to take over the zeroing. 3295 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this); 3296 if (alloc != NULL && alloc->is_AllocateArray()) { 3297 Node* length = alloc->as_AllocateArray()->Ideal_length(); 3298 if (head->limit() == length && 3299 head->init_trip() == _igvn.intcon(0)) { 3300 if (TraceOptimizeFill) { 3301 tty->print_cr("Eliminated zeroing in allocation"); 3302 } 3303 alloc->maybe_set_complete(&_igvn); 3304 } else { 3305 #ifdef ASSERT 3306 if (TraceOptimizeFill) { 3307 tty->print_cr("filling array but bounds don't match"); 3308 alloc->dump(); 3309 head->init_trip()->dump(); 3310 head->limit()->dump(); 3311 length->dump(); 3312 } 3313 #endif 3314 } 3315 } 3316 */ 3317 3318 if (head->is_strip_mined()) { 3319 // Inner strip mined loop goes away so get rid of outer strip 3320 // mined loop 3321 Node* outer_sfpt = head->outer_safepoint(); 3322 Node* in = outer_sfpt->in(0); 3323 Node* outer_out = head->outer_loop_exit(); 3324 lazy_replace(outer_out, in); 3325 _igvn.replace_input_of(outer_sfpt, 0, C->top()); 3326 } 3327 3328 // Redirect the old control and memory edges that are outside the loop. 3329 // Sometimes the memory phi of the head is used as the outgoing 3330 // state of the loop. It's safe in this case to replace it with the 3331 // result_mem. 3332 _igvn.replace_node(store->in(MemNode::Memory), result_mem); 3333 lazy_replace(exit, result_ctrl); 3334 _igvn.replace_node(store, result_mem); 3335 // Any uses the increment outside of the loop become the loop limit. 3336 _igvn.replace_node(head->incr(), head->limit()); 3337 3338 // Disconnect the head from the loop. 3339 for (uint i = 0; i < lpt->_body.size(); i++) { 3340 Node* n = lpt->_body.at(i); 3341 _igvn.replace_node(n, C->top()); 3342 } 3343 3344 return true; 3345 }