1 /* 2 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "compiler/compileLog.hpp" 27 #include "memory/allocation.inline.hpp" 28 #include "opto/addnode.hpp" 29 #include "opto/callnode.hpp" 30 #include "opto/connode.hpp" 31 #include "opto/divnode.hpp" 32 #include "opto/loopnode.hpp" 33 #include "opto/mulnode.hpp" 34 #include "opto/rootnode.hpp" 35 #include "opto/runtime.hpp" 36 #include "opto/subnode.hpp" 37 38 //------------------------------is_loop_exit----------------------------------- 39 // Given an IfNode, return the loop-exiting projection or NULL if both 40 // arms remain in the loop. 41 Node *IdealLoopTree::is_loop_exit(Node *iff) const { 42 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests 43 PhaseIdealLoop *phase = _phase; 44 // Test is an IfNode, has 2 projections. If BOTH are in the loop 45 // we need loop unswitching instead of peeling. 46 if( !is_member(phase->get_loop( iff->raw_out(0) )) ) 47 return iff->raw_out(0); 48 if( !is_member(phase->get_loop( iff->raw_out(1) )) ) 49 return iff->raw_out(1); 50 return NULL; 51 } 52 53 54 //============================================================================= 55 56 57 //------------------------------record_for_igvn---------------------------- 58 // Put loop body on igvn work list 59 void IdealLoopTree::record_for_igvn() { 60 for( uint i = 0; i < _body.size(); i++ ) { 61 Node *n = _body.at(i); 62 _phase->_igvn._worklist.push(n); 63 } 64 } 65 66 //------------------------------compute_exact_trip_count----------------------- 67 // Compute loop exact trip count if possible. Do not recalculate trip count for 68 // split loops (pre-main-post) which have their limits and inits behind Opaque node. 69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) { 70 if (!_head->as_Loop()->is_valid_counted_loop()) { 71 return; 72 } 73 CountedLoopNode* cl = _head->as_CountedLoop(); 74 // Trip count may become nonexact for iteration split loops since 75 // RCE modifies limits. Note, _trip_count value is not reset since 76 // it is used to limit unrolling of main loop. 77 cl->set_nonexact_trip_count(); 78 79 // Loop's test should be part of loop. 80 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 81 return; // Infinite loop 82 83 #ifdef ASSERT 84 BoolTest::mask bt = cl->loopexit()->test_trip(); 85 assert(bt == BoolTest::lt || bt == BoolTest::gt || 86 bt == BoolTest::ne, "canonical test is expected"); 87 #endif 88 89 Node* init_n = cl->init_trip(); 90 Node* limit_n = cl->limit(); 91 if (init_n != NULL && init_n->is_Con() && 92 limit_n != NULL && limit_n->is_Con()) { 93 // Use longs to avoid integer overflow. 94 int stride_con = cl->stride_con(); 95 jlong init_con = cl->init_trip()->get_int(); 96 jlong limit_con = cl->limit()->get_int(); 97 int stride_m = stride_con - (stride_con > 0 ? 1 : -1); 98 jlong trip_count = (limit_con - init_con + stride_m)/stride_con; 99 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) { 100 // Set exact trip count. 101 cl->set_exact_trip_count((uint)trip_count); 102 } 103 } 104 } 105 106 //------------------------------compute_profile_trip_cnt---------------------------- 107 // Compute loop trip count from profile data as 108 // (backedge_count + loop_exit_count) / loop_exit_count 109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) { 110 if (!_head->is_CountedLoop()) { 111 return; 112 } 113 CountedLoopNode* head = _head->as_CountedLoop(); 114 if (head->profile_trip_cnt() != COUNT_UNKNOWN) { 115 return; // Already computed 116 } 117 float trip_cnt = (float)max_jint; // default is big 118 119 Node* back = head->in(LoopNode::LoopBackControl); 120 while (back != head) { 121 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 122 back->in(0) && 123 back->in(0)->is_If() && 124 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN && 125 back->in(0)->as_If()->_prob != PROB_UNKNOWN) { 126 break; 127 } 128 back = phase->idom(back); 129 } 130 if (back != head) { 131 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 132 back->in(0), "if-projection exists"); 133 IfNode* back_if = back->in(0)->as_If(); 134 float loop_back_cnt = back_if->_fcnt * back_if->_prob; 135 136 // Now compute a loop exit count 137 float loop_exit_cnt = 0.0f; 138 for( uint i = 0; i < _body.size(); i++ ) { 139 Node *n = _body[i]; 140 if( n->is_If() ) { 141 IfNode *iff = n->as_If(); 142 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) { 143 Node *exit = is_loop_exit(iff); 144 if( exit ) { 145 float exit_prob = iff->_prob; 146 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob; 147 if (exit_prob > PROB_MIN) { 148 float exit_cnt = iff->_fcnt * exit_prob; 149 loop_exit_cnt += exit_cnt; 150 } 151 } 152 } 153 } 154 } 155 if (loop_exit_cnt > 0.0f) { 156 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt; 157 } else { 158 // No exit count so use 159 trip_cnt = loop_back_cnt; 160 } 161 } 162 #ifndef PRODUCT 163 if (TraceProfileTripCount) { 164 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt); 165 } 166 #endif 167 head->set_profile_trip_cnt(trip_cnt); 168 } 169 170 //---------------------is_invariant_addition----------------------------- 171 // Return nonzero index of invariant operand for an Add or Sub 172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants. 173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) { 174 int op = n->Opcode(); 175 if (op == Op_AddI || op == Op_SubI) { 176 bool in1_invar = this->is_invariant(n->in(1)); 177 bool in2_invar = this->is_invariant(n->in(2)); 178 if (in1_invar && !in2_invar) return 1; 179 if (!in1_invar && in2_invar) return 2; 180 } 181 return 0; 182 } 183 184 //---------------------reassociate_add_sub----------------------------- 185 // Reassociate invariant add and subtract expressions: 186 // 187 // inv1 + (x + inv2) => ( inv1 + inv2) + x 188 // (x + inv2) + inv1 => ( inv1 + inv2) + x 189 // inv1 + (x - inv2) => ( inv1 - inv2) + x 190 // inv1 - (inv2 - x) => ( inv1 - inv2) + x 191 // (x + inv2) - inv1 => (-inv1 + inv2) + x 192 // (x - inv2) + inv1 => ( inv1 - inv2) + x 193 // (x - inv2) - inv1 => (-inv1 - inv2) + x 194 // inv1 + (inv2 - x) => ( inv1 + inv2) - x 195 // inv1 - (x - inv2) => ( inv1 + inv2) - x 196 // (inv2 - x) + inv1 => ( inv1 + inv2) - x 197 // (inv2 - x) - inv1 => (-inv1 + inv2) - x 198 // inv1 - (x + inv2) => ( inv1 - inv2) - x 199 // 200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) { 201 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL; 202 if (is_invariant(n1)) return NULL; 203 int inv1_idx = is_invariant_addition(n1, phase); 204 if (!inv1_idx) return NULL; 205 // Don't mess with add of constant (igvn moves them to expression tree root.) 206 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL; 207 Node* inv1 = n1->in(inv1_idx); 208 Node* n2 = n1->in(3 - inv1_idx); 209 int inv2_idx = is_invariant_addition(n2, phase); 210 if (!inv2_idx) return NULL; 211 Node* x = n2->in(3 - inv2_idx); 212 Node* inv2 = n2->in(inv2_idx); 213 214 bool neg_x = n2->is_Sub() && inv2_idx == 1; 215 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2; 216 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2; 217 if (n1->is_Sub() && inv1_idx == 1) { 218 neg_x = !neg_x; 219 neg_inv2 = !neg_inv2; 220 } 221 Node* inv1_c = phase->get_ctrl(inv1); 222 Node* inv2_c = phase->get_ctrl(inv2); 223 Node* n_inv1; 224 if (neg_inv1) { 225 Node *zero = phase->_igvn.intcon(0); 226 phase->set_ctrl(zero, phase->C->root()); 227 n_inv1 = new (phase->C) SubINode(zero, inv1); 228 phase->register_new_node(n_inv1, inv1_c); 229 } else { 230 n_inv1 = inv1; 231 } 232 Node* inv; 233 if (neg_inv2) { 234 inv = new (phase->C) SubINode(n_inv1, inv2); 235 } else { 236 inv = new (phase->C) AddINode(n_inv1, inv2); 237 } 238 phase->register_new_node(inv, phase->get_early_ctrl(inv)); 239 240 Node* addx; 241 if (neg_x) { 242 addx = new (phase->C) SubINode(inv, x); 243 } else { 244 addx = new (phase->C) AddINode(x, inv); 245 } 246 phase->register_new_node(addx, phase->get_ctrl(x)); 247 phase->_igvn.replace_node(n1, addx); 248 assert(phase->get_loop(phase->get_ctrl(n1)) == this, ""); 249 _body.yank(n1); 250 return addx; 251 } 252 253 //---------------------reassociate_invariants----------------------------- 254 // Reassociate invariant expressions: 255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { 256 for (int i = _body.size() - 1; i >= 0; i--) { 257 Node *n = _body.at(i); 258 for (int j = 0; j < 5; j++) { 259 Node* nn = reassociate_add_sub(n, phase); 260 if (nn == NULL) break; 261 n = nn; // again 262 }; 263 } 264 } 265 266 //------------------------------policy_peeling--------------------------------- 267 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can 268 // make some loop-invariant test (usually a null-check) happen before the loop. 269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const { 270 Node *test = ((IdealLoopTree*)this)->tail(); 271 int body_size = ((IdealLoopTree*)this)->_body.size(); 272 int live_node_count = phase->C->live_nodes(); 273 // Peeling does loop cloning which can result in O(N^2) node construction 274 if( body_size > 255 /* Prevent overflow for large body_size */ 275 || (body_size * body_size + live_node_count > MaxNodeLimit) ) { 276 return false; // too large to safely clone 277 } 278 while( test != _head ) { // Scan till run off top of loop 279 if( test->is_If() ) { // Test? 280 Node *ctrl = phase->get_ctrl(test->in(1)); 281 if (ctrl->is_top()) 282 return false; // Found dead test on live IF? No peeling! 283 // Standard IF only has one input value to check for loop invariance 284 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added"); 285 // Condition is not a member of this loop? 286 if( !is_member(phase->get_loop(ctrl)) && 287 is_loop_exit(test) ) 288 return true; // Found reason to peel! 289 } 290 // Walk up dominators to loop _head looking for test which is 291 // executed on every path thru loop. 292 test = phase->idom(test); 293 } 294 return false; 295 } 296 297 //------------------------------peeled_dom_test_elim--------------------------- 298 // If we got the effect of peeling, either by actually peeling or by making 299 // a pre-loop which must execute at least once, we can remove all 300 // loop-invariant dominated tests in the main body. 301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) { 302 bool progress = true; 303 while( progress ) { 304 progress = false; // Reset for next iteration 305 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail(); 306 Node *test = prev->in(0); 307 while( test != loop->_head ) { // Scan till run off top of loop 308 309 int p_op = prev->Opcode(); 310 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) && 311 test->is_If() && // Test? 312 !test->in(1)->is_Con() && // And not already obvious? 313 // Condition is not a member of this loop? 314 !loop->is_member(get_loop(get_ctrl(test->in(1))))){ 315 // Walk loop body looking for instances of this test 316 for( uint i = 0; i < loop->_body.size(); i++ ) { 317 Node *n = loop->_body.at(i); 318 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) { 319 // IfNode was dominated by version in peeled loop body 320 progress = true; 321 dominated_by( old_new[prev->_idx], n ); 322 } 323 } 324 } 325 prev = test; 326 test = idom(test); 327 } // End of scan tests in loop 328 329 } // End of while( progress ) 330 } 331 332 //------------------------------do_peeling------------------------------------- 333 // Peel the first iteration of the given loop. 334 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 335 // The pre-loop illegally has 2 control users (old & new loops). 336 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 337 // Do this by making the old-loop fall-in edges act as if they came 338 // around the loopback from the prior iteration (follow the old-loop 339 // backedges) and then map to the new peeled iteration. This leaves 340 // the pre-loop with only 1 user (the new peeled iteration), but the 341 // peeled-loop backedge has 2 users. 342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 343 // extra backedge user. 344 // 345 // orig 346 // 347 // stmt1 348 // | 349 // v 350 // loop predicate 351 // | 352 // v 353 // loop<----+ 354 // | | 355 // stmt2 | 356 // | | 357 // v | 358 // if ^ 359 // / \ | 360 // / \ | 361 // v v | 362 // false true | 363 // / \ | 364 // / ----+ 365 // | 366 // v 367 // exit 368 // 369 // 370 // after clone loop 371 // 372 // stmt1 373 // | 374 // v 375 // loop predicate 376 // / \ 377 // clone / \ orig 378 // / \ 379 // / \ 380 // v v 381 // +---->loop clone loop<----+ 382 // | | | | 383 // | stmt2 clone stmt2 | 384 // | | | | 385 // | v v | 386 // ^ if clone If ^ 387 // | / \ / \ | 388 // | / \ / \ | 389 // | v v v v | 390 // | true false false true | 391 // | / \ / \ | 392 // +---- \ / ----+ 393 // \ / 394 // 1v v2 395 // region 396 // | 397 // v 398 // exit 399 // 400 // 401 // after peel and predicate move 402 // 403 // stmt1 404 // / 405 // / 406 // clone / orig 407 // / 408 // / +----------+ 409 // / | | 410 // / loop predicate | 411 // / | | 412 // v v | 413 // TOP-->loop clone loop<----+ | 414 // | | | | 415 // stmt2 clone stmt2 | | 416 // | | | ^ 417 // v v | | 418 // if clone If ^ | 419 // / \ / \ | | 420 // / \ / \ | | 421 // v v v v | | 422 // true false false true | | 423 // | \ / \ | | 424 // | \ / ----+ ^ 425 // | \ / | 426 // | 1v v2 | 427 // v region | 428 // | | | 429 // | v | 430 // | exit | 431 // | | 432 // +--------------->-----------------+ 433 // 434 // 435 // final graph 436 // 437 // stmt1 438 // | 439 // v 440 // stmt2 clone 441 // | 442 // v 443 // if clone 444 // / | 445 // / | 446 // v v 447 // false true 448 // | | 449 // | v 450 // | loop predicate 451 // | | 452 // | v 453 // | loop<----+ 454 // | | | 455 // | stmt2 | 456 // | | | 457 // | v | 458 // v if ^ 459 // | / \ | 460 // | / \ | 461 // | v v | 462 // | false true | 463 // | | \ | 464 // v v --+ 465 // region 466 // | 467 // v 468 // exit 469 // 470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) { 471 472 C->set_major_progress(); 473 // Peeling a 'main' loop in a pre/main/post situation obfuscates the 474 // 'pre' loop from the main and the 'pre' can no longer have it's 475 // iterations adjusted. Therefore, we need to declare this loop as 476 // no longer a 'main' loop; it will need new pre and post loops before 477 // we can do further RCE. 478 #ifndef PRODUCT 479 if (TraceLoopOpts) { 480 tty->print("Peel "); 481 loop->dump_head(); 482 } 483 #endif 484 Node* head = loop->_head; 485 bool counted_loop = head->is_CountedLoop(); 486 if (counted_loop) { 487 CountedLoopNode *cl = head->as_CountedLoop(); 488 assert(cl->trip_count() > 0, "peeling a fully unrolled loop"); 489 cl->set_trip_count(cl->trip_count() - 1); 490 if (cl->is_main_loop()) { 491 cl->set_normal_loop(); 492 #ifndef PRODUCT 493 if (PrintOpto && VerifyLoopOptimizations) { 494 tty->print("Peeling a 'main' loop; resetting to 'normal' "); 495 loop->dump_head(); 496 } 497 #endif 498 } 499 } 500 Node* entry = head->in(LoopNode::EntryControl); 501 502 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 503 // The pre-loop illegally has 2 control users (old & new loops). 504 clone_loop( loop, old_new, dom_depth(head) ); 505 506 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 507 // Do this by making the old-loop fall-in edges act as if they came 508 // around the loopback from the prior iteration (follow the old-loop 509 // backedges) and then map to the new peeled iteration. This leaves 510 // the pre-loop with only 1 user (the new peeled iteration), but the 511 // peeled-loop backedge has 2 users. 512 Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx]; 513 _igvn.hash_delete(head); 514 head->set_req(LoopNode::EntryControl, new_entry); 515 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) { 516 Node* old = head->fast_out(j); 517 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) { 518 Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; 519 if (!new_exit_value ) // Backedge value is ALSO loop invariant? 520 // Then loop body backedge value remains the same. 521 new_exit_value = old->in(LoopNode::LoopBackControl); 522 _igvn.hash_delete(old); 523 old->set_req(LoopNode::EntryControl, new_exit_value); 524 } 525 } 526 527 528 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 529 // extra backedge user. 530 Node* new_head = old_new[head->_idx]; 531 _igvn.hash_delete(new_head); 532 new_head->set_req(LoopNode::LoopBackControl, C->top()); 533 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) { 534 Node* use = new_head->fast_out(j2); 535 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) { 536 _igvn.hash_delete(use); 537 use->set_req(LoopNode::LoopBackControl, C->top()); 538 } 539 } 540 541 542 // Step 4: Correct dom-depth info. Set to loop-head depth. 543 int dd = dom_depth(head); 544 set_idom(head, head->in(1), dd); 545 for (uint j3 = 0; j3 < loop->_body.size(); j3++) { 546 Node *old = loop->_body.at(j3); 547 Node *nnn = old_new[old->_idx]; 548 if (!has_ctrl(nnn)) 549 set_idom(nnn, idom(nnn), dd-1); 550 } 551 552 // Now force out all loop-invariant dominating tests. The optimizer 553 // finds some, but we _know_ they are all useless. 554 peeled_dom_test_elim(loop,old_new); 555 556 loop->record_for_igvn(); 557 } 558 559 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop 560 561 //------------------------------policy_maximally_unroll------------------------ 562 // Calculate exact loop trip count and return true if loop can be maximally 563 // unrolled. 564 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const { 565 CountedLoopNode *cl = _head->as_CountedLoop(); 566 assert(cl->is_normal_loop(), ""); 567 if (!cl->is_valid_counted_loop()) 568 return false; // Malformed counted loop 569 570 if (!cl->has_exact_trip_count()) { 571 // Trip count is not exact. 572 return false; 573 } 574 575 uint trip_count = cl->trip_count(); 576 // Note, max_juint is used to indicate unknown trip count. 577 assert(trip_count > 1, "one iteration loop should be optimized out already"); 578 assert(trip_count < max_juint, "exact trip_count should be less than max_uint."); 579 580 // Real policy: if we maximally unroll, does it get too big? 581 // Allow the unrolled mess to get larger than standard loop 582 // size. After all, it will no longer be a loop. 583 uint body_size = _body.size(); 584 uint unroll_limit = (uint)LoopUnrollLimit * 4; 585 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); 586 if (trip_count > unroll_limit || body_size > unroll_limit) { 587 return false; 588 } 589 590 // Fully unroll a loop with few iterations regardless next 591 // conditions since following loop optimizations will split 592 // such loop anyway (pre-main-post). 593 if (trip_count <= 3) 594 return true; 595 596 // Take into account that after unroll conjoined heads and tails will fold, 597 // otherwise policy_unroll() may allow more unrolling than max unrolling. 598 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count; 599 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE; 600 if (body_size != tst_body_size) // Check for int overflow 601 return false; 602 if (new_body_size > unroll_limit || 603 // Unrolling can result in a large amount of node construction 604 new_body_size >= MaxNodeLimit - (uint) phase->C->live_nodes()) { 605 return false; 606 } 607 608 // Do not unroll a loop with String intrinsics code. 609 // String intrinsics are large and have loops. 610 for (uint k = 0; k < _body.size(); k++) { 611 Node* n = _body.at(k); 612 switch (n->Opcode()) { 613 case Op_StrComp: 614 case Op_StrEquals: 615 case Op_StrIndexOf: 616 case Op_EncodeISOArray: 617 case Op_AryEq: { 618 return false; 619 } 620 #if INCLUDE_RTM_OPT 621 case Op_FastLock: 622 case Op_FastUnlock: { 623 // Don't unroll RTM locking code because it is large. 624 if (UseRTMLocking) { 625 return false; 626 } 627 } 628 #endif 629 } // switch 630 } 631 632 return true; // Do maximally unroll 633 } 634 635 636 //------------------------------policy_unroll---------------------------------- 637 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if 638 // the loop is a CountedLoop and the body is small enough. 639 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const { 640 641 CountedLoopNode *cl = _head->as_CountedLoop(); 642 assert(cl->is_normal_loop() || cl->is_main_loop(), ""); 643 644 if (!cl->is_valid_counted_loop()) 645 return false; // Malformed counted loop 646 647 // Protect against over-unrolling. 648 // After split at least one iteration will be executed in pre-loop. 649 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false; 650 651 int future_unroll_ct = cl->unrolled_count() * 2; 652 if (future_unroll_ct > LoopMaxUnroll) return false; 653 654 // Check for initial stride being a small enough constant 655 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false; 656 657 // Don't unroll if the next round of unrolling would push us 658 // over the expected trip count of the loop. One is subtracted 659 // from the expected trip count because the pre-loop normally 660 // executes 1 iteration. 661 if (UnrollLimitForProfileCheck > 0 && 662 cl->profile_trip_cnt() != COUNT_UNKNOWN && 663 future_unroll_ct > UnrollLimitForProfileCheck && 664 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) { 665 return false; 666 } 667 668 // When unroll count is greater than LoopUnrollMin, don't unroll if: 669 // the residual iterations are more than 10% of the trip count 670 // and rounds of "unroll,optimize" are not making significant progress 671 // Progress defined as current size less than 20% larger than previous size. 672 if (UseSuperWord && cl->node_count_before_unroll() > 0 && 673 future_unroll_ct > LoopUnrollMin && 674 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() && 675 1.2 * cl->node_count_before_unroll() < (double)_body.size()) { 676 return false; 677 } 678 679 Node *init_n = cl->init_trip(); 680 Node *limit_n = cl->limit(); 681 int stride_con = cl->stride_con(); 682 // Non-constant bounds. 683 // Protect against over-unrolling when init or/and limit are not constant 684 // (so that trip_count's init value is maxint) but iv range is known. 685 if (init_n == NULL || !init_n->is_Con() || 686 limit_n == NULL || !limit_n->is_Con()) { 687 Node* phi = cl->phi(); 688 if (phi != NULL) { 689 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); 690 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); 691 int next_stride = stride_con * 2; // stride after this unroll 692 if (next_stride > 0) { 693 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow 694 iv_type->_lo + next_stride > iv_type->_hi) { 695 return false; // over-unrolling 696 } 697 } else if (next_stride < 0) { 698 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow 699 iv_type->_hi + next_stride < iv_type->_lo) { 700 return false; // over-unrolling 701 } 702 } 703 } 704 } 705 706 // After unroll limit will be adjusted: new_limit = limit-stride. 707 // Bailout if adjustment overflow. 708 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int(); 709 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) || 710 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo)) 711 return false; // overflow 712 713 // Adjust body_size to determine if we unroll or not 714 uint body_size = _body.size(); 715 // Key test to unroll loop in CRC32 java code 716 int xors_in_loop = 0; 717 // Also count ModL, DivL and MulL which expand mightly 718 for (uint k = 0; k < _body.size(); k++) { 719 Node* n = _body.at(k); 720 switch (n->Opcode()) { 721 case Op_XorI: xors_in_loop++; break; // CRC32 java code 722 case Op_ModL: body_size += 30; break; 723 case Op_DivL: body_size += 30; break; 724 case Op_MulL: body_size += 10; break; 725 case Op_StrComp: 726 case Op_StrEquals: 727 case Op_StrIndexOf: 728 case Op_EncodeISOArray: 729 case Op_AryEq: { 730 // Do not unroll a loop with String intrinsics code. 731 // String intrinsics are large and have loops. 732 return false; 733 } 734 #if INCLUDE_RTM_OPT 735 case Op_FastLock: 736 case Op_FastUnlock: { 737 // Don't unroll RTM locking code because it is large. 738 if (UseRTMLocking) { 739 return false; 740 } 741 } 742 #endif 743 } // switch 744 } 745 746 // Check for being too big 747 if (body_size > (uint)LoopUnrollLimit) { 748 if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true; 749 // Normal case: loop too big 750 return false; 751 } 752 753 // Unroll once! (Each trip will soon do double iterations) 754 return true; 755 } 756 757 //------------------------------policy_align----------------------------------- 758 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the 759 // expression that does the alignment. Note that only one array base can be 760 // aligned in a loop (unless the VM guarantees mutual alignment). Note that 761 // if we vectorize short memory ops into longer memory ops, we may want to 762 // increase alignment. 763 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const { 764 return false; 765 } 766 767 //------------------------------policy_range_check----------------------------- 768 // Return TRUE or FALSE if the loop should be range-check-eliminated. 769 // Actually we do iteration-splitting, a more powerful form of RCE. 770 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const { 771 if (!RangeCheckElimination) return false; 772 773 CountedLoopNode *cl = _head->as_CountedLoop(); 774 // If we unrolled with no intention of doing RCE and we later 775 // changed our minds, we got no pre-loop. Either we need to 776 // make a new pre-loop, or we gotta disallow RCE. 777 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now. 778 Node *trip_counter = cl->phi(); 779 780 // Check loop body for tests of trip-counter plus loop-invariant vs 781 // loop-invariant. 782 for (uint i = 0; i < _body.size(); i++) { 783 Node *iff = _body[i]; 784 if (iff->Opcode() == Op_If) { // Test? 785 786 // Comparing trip+off vs limit 787 Node *bol = iff->in(1); 788 if (bol->req() != 2) continue; // dead constant test 789 if (!bol->is_Bool()) { 790 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only"); 791 continue; 792 } 793 if (bol->as_Bool()->_test._test == BoolTest::ne) 794 continue; // not RC 795 796 Node *cmp = bol->in(1); 797 Node *rc_exp = cmp->in(1); 798 Node *limit = cmp->in(2); 799 800 Node *limit_c = phase->get_ctrl(limit); 801 if( limit_c == phase->C->top() ) 802 return false; // Found dead test on live IF? No RCE! 803 if( is_member(phase->get_loop(limit_c) ) ) { 804 // Compare might have operands swapped; commute them 805 rc_exp = cmp->in(2); 806 limit = cmp->in(1); 807 limit_c = phase->get_ctrl(limit); 808 if( is_member(phase->get_loop(limit_c) ) ) 809 continue; // Both inputs are loop varying; cannot RCE 810 } 811 812 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) { 813 continue; 814 } 815 // Yeah! Found a test like 'trip+off vs limit' 816 // Test is an IfNode, has 2 projections. If BOTH are in the loop 817 // we need loop unswitching instead of iteration splitting. 818 if( is_loop_exit(iff) ) 819 return true; // Found reason to split iterations 820 } // End of is IF 821 } 822 823 return false; 824 } 825 826 //------------------------------policy_peel_only------------------------------- 827 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful 828 // for unrolling loops with NO array accesses. 829 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const { 830 831 for( uint i = 0; i < _body.size(); i++ ) 832 if( _body[i]->is_Mem() ) 833 return false; 834 835 // No memory accesses at all! 836 return true; 837 } 838 839 //------------------------------clone_up_backedge_goo-------------------------- 840 // If Node n lives in the back_ctrl block and cannot float, we clone a private 841 // version of n in preheader_ctrl block and return that, otherwise return n. 842 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) { 843 if( get_ctrl(n) != back_ctrl ) return n; 844 845 // Only visit once 846 if (visited.test_set(n->_idx)) { 847 Node *x = clones.find(n->_idx); 848 if (x != NULL) 849 return x; 850 return n; 851 } 852 853 Node *x = NULL; // If required, a clone of 'n' 854 // Check for 'n' being pinned in the backedge. 855 if( n->in(0) && n->in(0) == back_ctrl ) { 856 assert(clones.find(n->_idx) == NULL, "dead loop"); 857 x = n->clone(); // Clone a copy of 'n' to preheader 858 clones.push(x, n->_idx); 859 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader 860 } 861 862 // Recursive fixup any other input edges into x. 863 // If there are no changes we can just return 'n', otherwise 864 // we need to clone a private copy and change it. 865 for( uint i = 1; i < n->req(); i++ ) { 866 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones ); 867 if( g != n->in(i) ) { 868 if( !x ) { 869 assert(clones.find(n->_idx) == NULL, "dead loop"); 870 x = n->clone(); 871 clones.push(x, n->_idx); 872 } 873 x->set_req(i, g); 874 } 875 } 876 if( x ) { // x can legally float to pre-header location 877 register_new_node( x, preheader_ctrl ); 878 return x; 879 } else { // raise n to cover LCA of uses 880 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); 881 } 882 return n; 883 } 884 885 //------------------------------insert_pre_post_loops-------------------------- 886 // Insert pre and post loops. If peel_only is set, the pre-loop can not have 887 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no 888 // alignment. Useful to unroll loops that do no array accesses. 889 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { 890 891 #ifndef PRODUCT 892 if (TraceLoopOpts) { 893 if (peel_only) 894 tty->print("PeelMainPost "); 895 else 896 tty->print("PreMainPost "); 897 loop->dump_head(); 898 } 899 #endif 900 C->set_major_progress(); 901 902 // Find common pieces of the loop being guarded with pre & post loops 903 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 904 assert( main_head->is_normal_loop(), "" ); 905 CountedLoopEndNode *main_end = main_head->loopexit(); 906 guarantee(main_end != NULL, "no loop exit node"); 907 assert( main_end->outcnt() == 2, "1 true, 1 false path only" ); 908 uint dd_main_head = dom_depth(main_head); 909 uint max = main_head->outcnt(); 910 911 Node *pre_header= main_head->in(LoopNode::EntryControl); 912 Node *init = main_head->init_trip(); 913 Node *incr = main_end ->incr(); 914 Node *limit = main_end ->limit(); 915 Node *stride = main_end ->stride(); 916 Node *cmp = main_end ->cmp_node(); 917 BoolTest::mask b_test = main_end->test_trip(); 918 919 // Need only 1 user of 'bol' because I will be hacking the loop bounds. 920 Node *bol = main_end->in(CountedLoopEndNode::TestValue); 921 if( bol->outcnt() != 1 ) { 922 bol = bol->clone(); 923 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl)); 924 _igvn.hash_delete(main_end); 925 main_end->set_req(CountedLoopEndNode::TestValue, bol); 926 } 927 // Need only 1 user of 'cmp' because I will be hacking the loop bounds. 928 if( cmp->outcnt() != 1 ) { 929 cmp = cmp->clone(); 930 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl)); 931 _igvn.hash_delete(bol); 932 bol->set_req(1, cmp); 933 } 934 935 //------------------------------ 936 // Step A: Create Post-Loop. 937 Node* main_exit = main_end->proj_out(false); 938 assert( main_exit->Opcode() == Op_IfFalse, "" ); 939 int dd_main_exit = dom_depth(main_exit); 940 941 // Step A1: Clone the loop body. The clone becomes the post-loop. The main 942 // loop pre-header illegally has 2 control users (old & new loops). 943 clone_loop( loop, old_new, dd_main_exit ); 944 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" ); 945 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop(); 946 post_head->set_post_loop(main_head); 947 948 // Reduce the post-loop trip count. 949 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 950 post_end->_prob = PROB_FAIR; 951 952 // Build the main-loop normal exit. 953 IfFalseNode *new_main_exit = new (C) IfFalseNode(main_end); 954 _igvn.register_new_node_with_optimizer( new_main_exit ); 955 set_idom(new_main_exit, main_end, dd_main_exit ); 956 set_loop(new_main_exit, loop->_parent); 957 958 // Step A2: Build a zero-trip guard for the post-loop. After leaving the 959 // main-loop, the post-loop may not execute at all. We 'opaque' the incr 960 // (the main-loop trip-counter exit value) because we will be changing 961 // the exit value (via unrolling) so we cannot constant-fold away the zero 962 // trip guard until all unrolling is done. 963 Node *zer_opaq = new (C) Opaque1Node(C, incr); 964 Node *zer_cmp = new (C) CmpINode( zer_opaq, limit ); 965 Node *zer_bol = new (C) BoolNode( zer_cmp, b_test ); 966 register_new_node( zer_opaq, new_main_exit ); 967 register_new_node( zer_cmp , new_main_exit ); 968 register_new_node( zer_bol , new_main_exit ); 969 970 // Build the IfNode 971 IfNode *zer_iff = new (C) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN ); 972 _igvn.register_new_node_with_optimizer( zer_iff ); 973 set_idom(zer_iff, new_main_exit, dd_main_exit); 974 set_loop(zer_iff, loop->_parent); 975 976 // Plug in the false-path, taken if we need to skip post-loop 977 _igvn.replace_input_of(main_exit, 0, zer_iff); 978 set_idom(main_exit, zer_iff, dd_main_exit); 979 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit); 980 // Make the true-path, must enter the post loop 981 Node *zer_taken = new (C) IfTrueNode( zer_iff ); 982 _igvn.register_new_node_with_optimizer( zer_taken ); 983 set_idom(zer_taken, zer_iff, dd_main_exit); 984 set_loop(zer_taken, loop->_parent); 985 // Plug in the true path 986 _igvn.hash_delete( post_head ); 987 post_head->set_req(LoopNode::EntryControl, zer_taken); 988 set_idom(post_head, zer_taken, dd_main_exit); 989 990 Arena *a = Thread::current()->resource_area(); 991 VectorSet visited(a); 992 Node_Stack clones(a, main_head->back_control()->outcnt()); 993 // Step A3: Make the fall-in values to the post-loop come from the 994 // fall-out values of the main-loop. 995 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) { 996 Node* main_phi = main_head->fast_out(i); 997 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) { 998 Node *post_phi = old_new[main_phi->_idx]; 999 Node *fallmain = clone_up_backedge_goo(main_head->back_control(), 1000 post_head->init_control(), 1001 main_phi->in(LoopNode::LoopBackControl), 1002 visited, clones); 1003 _igvn.hash_delete(post_phi); 1004 post_phi->set_req( LoopNode::EntryControl, fallmain ); 1005 } 1006 } 1007 1008 // Update local caches for next stanza 1009 main_exit = new_main_exit; 1010 1011 1012 //------------------------------ 1013 // Step B: Create Pre-Loop. 1014 1015 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main 1016 // loop pre-header illegally has 2 control users (old & new loops). 1017 clone_loop( loop, old_new, dd_main_head ); 1018 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop(); 1019 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 1020 pre_head->set_pre_loop(main_head); 1021 Node *pre_incr = old_new[incr->_idx]; 1022 1023 // Reduce the pre-loop trip count. 1024 pre_end->_prob = PROB_FAIR; 1025 1026 // Find the pre-loop normal exit. 1027 Node* pre_exit = pre_end->proj_out(false); 1028 assert( pre_exit->Opcode() == Op_IfFalse, "" ); 1029 IfFalseNode *new_pre_exit = new (C) IfFalseNode(pre_end); 1030 _igvn.register_new_node_with_optimizer( new_pre_exit ); 1031 set_idom(new_pre_exit, pre_end, dd_main_head); 1032 set_loop(new_pre_exit, loop->_parent); 1033 1034 // Step B2: Build a zero-trip guard for the main-loop. After leaving the 1035 // pre-loop, the main-loop may not execute at all. Later in life this 1036 // zero-trip guard will become the minimum-trip guard when we unroll 1037 // the main-loop. 1038 Node *min_opaq = new (C) Opaque1Node(C, limit); 1039 Node *min_cmp = new (C) CmpINode( pre_incr, min_opaq ); 1040 Node *min_bol = new (C) BoolNode( min_cmp, b_test ); 1041 register_new_node( min_opaq, new_pre_exit ); 1042 register_new_node( min_cmp , new_pre_exit ); 1043 register_new_node( min_bol , new_pre_exit ); 1044 1045 // Build the IfNode (assume the main-loop is executed always). 1046 IfNode *min_iff = new (C) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN ); 1047 _igvn.register_new_node_with_optimizer( min_iff ); 1048 set_idom(min_iff, new_pre_exit, dd_main_head); 1049 set_loop(min_iff, loop->_parent); 1050 1051 // Plug in the false-path, taken if we need to skip main-loop 1052 _igvn.hash_delete( pre_exit ); 1053 pre_exit->set_req(0, min_iff); 1054 set_idom(pre_exit, min_iff, dd_main_head); 1055 set_idom(pre_exit->unique_out(), min_iff, dd_main_head); 1056 // Make the true-path, must enter the main loop 1057 Node *min_taken = new (C) IfTrueNode( min_iff ); 1058 _igvn.register_new_node_with_optimizer( min_taken ); 1059 set_idom(min_taken, min_iff, dd_main_head); 1060 set_loop(min_taken, loop->_parent); 1061 // Plug in the true path 1062 _igvn.hash_delete( main_head ); 1063 main_head->set_req(LoopNode::EntryControl, min_taken); 1064 set_idom(main_head, min_taken, dd_main_head); 1065 1066 visited.Clear(); 1067 clones.clear(); 1068 // Step B3: Make the fall-in values to the main-loop come from the 1069 // fall-out values of the pre-loop. 1070 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) { 1071 Node* main_phi = main_head->fast_out(i2); 1072 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) { 1073 Node *pre_phi = old_new[main_phi->_idx]; 1074 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(), 1075 main_head->init_control(), 1076 pre_phi->in(LoopNode::LoopBackControl), 1077 visited, clones); 1078 _igvn.hash_delete(main_phi); 1079 main_phi->set_req( LoopNode::EntryControl, fallpre ); 1080 } 1081 } 1082 1083 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). 1084 // RCE and alignment may change this later. 1085 Node *cmp_end = pre_end->cmp_node(); 1086 assert( cmp_end->in(2) == limit, "" ); 1087 Node *pre_limit = new (C) AddINode( init, stride ); 1088 1089 // Save the original loop limit in this Opaque1 node for 1090 // use by range check elimination. 1091 Node *pre_opaq = new (C) Opaque1Node(C, pre_limit, limit); 1092 1093 register_new_node( pre_limit, pre_head->in(0) ); 1094 register_new_node( pre_opaq , pre_head->in(0) ); 1095 1096 // Since no other users of pre-loop compare, I can hack limit directly 1097 assert( cmp_end->outcnt() == 1, "no other users" ); 1098 _igvn.hash_delete(cmp_end); 1099 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq); 1100 1101 // Special case for not-equal loop bounds: 1102 // Change pre loop test, main loop test, and the 1103 // main loop guard test to use lt or gt depending on stride 1104 // direction: 1105 // positive stride use < 1106 // negative stride use > 1107 // 1108 // not-equal test is kept for post loop to handle case 1109 // when init > limit when stride > 0 (and reverse). 1110 1111 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) { 1112 1113 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt; 1114 // Modify pre loop end condition 1115 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1116 BoolNode* new_bol0 = new (C) BoolNode(pre_bol->in(1), new_test); 1117 register_new_node( new_bol0, pre_head->in(0) ); 1118 _igvn.hash_delete(pre_end); 1119 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0); 1120 // Modify main loop guard condition 1121 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay"); 1122 BoolNode* new_bol1 = new (C) BoolNode(min_bol->in(1), new_test); 1123 register_new_node( new_bol1, new_pre_exit ); 1124 _igvn.hash_delete(min_iff); 1125 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1); 1126 // Modify main loop end condition 1127 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 1128 BoolNode* new_bol2 = new (C) BoolNode(main_bol->in(1), new_test); 1129 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) ); 1130 _igvn.hash_delete(main_end); 1131 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2); 1132 } 1133 1134 // Flag main loop 1135 main_head->set_main_loop(); 1136 if( peel_only ) main_head->set_main_no_pre_loop(); 1137 1138 // Subtract a trip count for the pre-loop. 1139 main_head->set_trip_count(main_head->trip_count() - 1); 1140 1141 // It's difficult to be precise about the trip-counts 1142 // for the pre/post loops. They are usually very short, 1143 // so guess that 4 trips is a reasonable value. 1144 post_head->set_profile_trip_cnt(4.0); 1145 pre_head->set_profile_trip_cnt(4.0); 1146 1147 // Now force out all loop-invariant dominating tests. The optimizer 1148 // finds some, but we _know_ they are all useless. 1149 peeled_dom_test_elim(loop,old_new); 1150 loop->record_for_igvn(); 1151 } 1152 1153 //------------------------------is_invariant----------------------------- 1154 // Return true if n is invariant 1155 bool IdealLoopTree::is_invariant(Node* n) const { 1156 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n; 1157 if (n_c->is_top()) return false; 1158 return !is_member(_phase->get_loop(n_c)); 1159 } 1160 1161 1162 //------------------------------do_unroll-------------------------------------- 1163 // Unroll the loop body one step - make each trip do 2 iterations. 1164 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) { 1165 assert(LoopUnrollLimit, ""); 1166 CountedLoopNode *loop_head = loop->_head->as_CountedLoop(); 1167 CountedLoopEndNode *loop_end = loop_head->loopexit(); 1168 assert(loop_end, ""); 1169 #ifndef PRODUCT 1170 if (PrintOpto && VerifyLoopOptimizations) { 1171 tty->print("Unrolling "); 1172 loop->dump_head(); 1173 } else if (TraceLoopOpts) { 1174 if (loop_head->trip_count() < (uint)LoopUnrollLimit) { 1175 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count()); 1176 } else { 1177 tty->print("Unroll %d ", loop_head->unrolled_count()*2); 1178 } 1179 loop->dump_head(); 1180 } 1181 #endif 1182 1183 // Remember loop node count before unrolling to detect 1184 // if rounds of unroll,optimize are making progress 1185 loop_head->set_node_count_before_unroll(loop->_body.size()); 1186 1187 Node *ctrl = loop_head->in(LoopNode::EntryControl); 1188 Node *limit = loop_head->limit(); 1189 Node *init = loop_head->init_trip(); 1190 Node *stride = loop_head->stride(); 1191 1192 Node *opaq = NULL; 1193 if (adjust_min_trip) { // If not maximally unrolling, need adjustment 1194 // Search for zero-trip guard. 1195 assert( loop_head->is_main_loop(), "" ); 1196 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 1197 Node *iff = ctrl->in(0); 1198 assert( iff->Opcode() == Op_If, "" ); 1199 Node *bol = iff->in(1); 1200 assert( bol->Opcode() == Op_Bool, "" ); 1201 Node *cmp = bol->in(1); 1202 assert( cmp->Opcode() == Op_CmpI, "" ); 1203 opaq = cmp->in(2); 1204 // Occasionally it's possible for a zero-trip guard Opaque1 node to be 1205 // optimized away and then another round of loop opts attempted. 1206 // We can not optimize this particular loop in that case. 1207 if (opaq->Opcode() != Op_Opaque1) 1208 return; // Cannot find zero-trip guard! Bail out! 1209 // Zero-trip test uses an 'opaque' node which is not shared. 1210 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, ""); 1211 } 1212 1213 C->set_major_progress(); 1214 1215 Node* new_limit = NULL; 1216 if (UnrollLimitCheck) { 1217 int stride_con = stride->get_int(); 1218 int stride_p = (stride_con > 0) ? stride_con : -stride_con; 1219 uint old_trip_count = loop_head->trip_count(); 1220 // Verify that unroll policy result is still valid. 1221 assert(old_trip_count > 1 && 1222 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity"); 1223 1224 // Adjust loop limit to keep valid iterations number after unroll. 1225 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride 1226 // which may overflow. 1227 if (!adjust_min_trip) { 1228 assert(old_trip_count > 1 && (old_trip_count & 1) == 0, 1229 "odd trip count for maximally unroll"); 1230 // Don't need to adjust limit for maximally unroll since trip count is even. 1231 } else if (loop_head->has_exact_trip_count() && init->is_Con()) { 1232 // Loop's limit is constant. Loop's init could be constant when pre-loop 1233 // become peeled iteration. 1234 jlong init_con = init->get_int(); 1235 // We can keep old loop limit if iterations count stays the same: 1236 // old_trip_count == new_trip_count * 2 1237 // Note: since old_trip_count >= 2 then new_trip_count >= 1 1238 // so we also don't need to adjust zero trip test. 1239 jlong limit_con = limit->get_int(); 1240 // (stride_con*2) not overflow since stride_con <= 8. 1241 int new_stride_con = stride_con * 2; 1242 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1); 1243 jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con; 1244 // New trip count should satisfy next conditions. 1245 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity"); 1246 uint new_trip_count = (uint)trip_count; 1247 adjust_min_trip = (old_trip_count != new_trip_count*2); 1248 } 1249 1250 if (adjust_min_trip) { 1251 // Step 2: Adjust the trip limit if it is called for. 1252 // The adjustment amount is -stride. Need to make sure if the 1253 // adjustment underflows or overflows, then the main loop is skipped. 1254 Node* cmp = loop_end->cmp_node(); 1255 assert(cmp->in(2) == limit, "sanity"); 1256 assert(opaq != NULL && opaq->in(1) == limit, "sanity"); 1257 1258 // Verify that policy_unroll result is still valid. 1259 const TypeInt* limit_type = _igvn.type(limit)->is_int(); 1260 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) || 1261 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity"); 1262 1263 if (limit->is_Con()) { 1264 // The check in policy_unroll and the assert above guarantee 1265 // no underflow if limit is constant. 1266 new_limit = _igvn.intcon(limit->get_int() - stride_con); 1267 set_ctrl(new_limit, C->root()); 1268 } else { 1269 // Limit is not constant. 1270 if (loop_head->unrolled_count() == 1) { // only for first unroll 1271 // Separate limit by Opaque node in case it is an incremented 1272 // variable from previous loop to avoid using pre-incremented 1273 // value which could increase register pressure. 1274 // Otherwise reorg_offsets() optimization will create a separate 1275 // Opaque node for each use of trip-counter and as result 1276 // zero trip guard limit will be different from loop limit. 1277 assert(has_ctrl(opaq), "should have it"); 1278 Node* opaq_ctrl = get_ctrl(opaq); 1279 limit = new (C) Opaque2Node( C, limit ); 1280 register_new_node( limit, opaq_ctrl ); 1281 } 1282 if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) || 1283 stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) { 1284 // No underflow. 1285 new_limit = new (C) SubINode(limit, stride); 1286 } else { 1287 // (limit - stride) may underflow. 1288 // Clamp the adjustment value with MININT or MAXINT: 1289 // 1290 // new_limit = limit-stride 1291 // if (stride > 0) 1292 // new_limit = (limit < new_limit) ? MININT : new_limit; 1293 // else 1294 // new_limit = (limit > new_limit) ? MAXINT : new_limit; 1295 // 1296 BoolTest::mask bt = loop_end->test_trip(); 1297 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected"); 1298 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint); 1299 set_ctrl(adj_max, C->root()); 1300 Node* old_limit = NULL; 1301 Node* adj_limit = NULL; 1302 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL; 1303 if (loop_head->unrolled_count() > 1 && 1304 limit->is_CMove() && limit->Opcode() == Op_CMoveI && 1305 limit->in(CMoveNode::IfTrue) == adj_max && 1306 bol->as_Bool()->_test._test == bt && 1307 bol->in(1)->Opcode() == Op_CmpI && 1308 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) { 1309 // Loop was unrolled before. 1310 // Optimize the limit to avoid nested CMove: 1311 // use original limit as old limit. 1312 old_limit = bol->in(1)->in(1); 1313 // Adjust previous adjusted limit. 1314 adj_limit = limit->in(CMoveNode::IfFalse); 1315 adj_limit = new (C) SubINode(adj_limit, stride); 1316 } else { 1317 old_limit = limit; 1318 adj_limit = new (C) SubINode(limit, stride); 1319 } 1320 assert(old_limit != NULL && adj_limit != NULL, ""); 1321 register_new_node( adj_limit, ctrl ); // adjust amount 1322 Node* adj_cmp = new (C) CmpINode(old_limit, adj_limit); 1323 register_new_node( adj_cmp, ctrl ); 1324 Node* adj_bool = new (C) BoolNode(adj_cmp, bt); 1325 register_new_node( adj_bool, ctrl ); 1326 new_limit = new (C) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT); 1327 } 1328 register_new_node(new_limit, ctrl); 1329 } 1330 assert(new_limit != NULL, ""); 1331 // Replace in loop test. 1332 assert(loop_end->in(1)->in(1) == cmp, "sanity"); 1333 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) { 1334 // Don't need to create new test since only one user. 1335 _igvn.hash_delete(cmp); 1336 cmp->set_req(2, new_limit); 1337 } else { 1338 // Create new test since it is shared. 1339 Node* ctrl2 = loop_end->in(0); 1340 Node* cmp2 = cmp->clone(); 1341 cmp2->set_req(2, new_limit); 1342 register_new_node(cmp2, ctrl2); 1343 Node* bol2 = loop_end->in(1)->clone(); 1344 bol2->set_req(1, cmp2); 1345 register_new_node(bol2, ctrl2); 1346 _igvn.hash_delete(loop_end); 1347 loop_end->set_req(1, bol2); 1348 } 1349 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 1350 // Make it a 1-trip test (means at least 2 trips). 1351 1352 // Guard test uses an 'opaque' node which is not shared. Hence I 1353 // can edit it's inputs directly. Hammer in the new limit for the 1354 // minimum-trip guard. 1355 assert(opaq->outcnt() == 1, ""); 1356 _igvn.hash_delete(opaq); 1357 opaq->set_req(1, new_limit); 1358 } 1359 1360 // Adjust max trip count. The trip count is intentionally rounded 1361 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 1362 // the main, unrolled, part of the loop will never execute as it is protected 1363 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 1364 // and later determined that part of the unrolled loop was dead. 1365 loop_head->set_trip_count(old_trip_count / 2); 1366 1367 // Double the count of original iterations in the unrolled loop body. 1368 loop_head->double_unrolled_count(); 1369 1370 } else { // LoopLimitCheck 1371 1372 // Adjust max trip count. The trip count is intentionally rounded 1373 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 1374 // the main, unrolled, part of the loop will never execute as it is protected 1375 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 1376 // and later determined that part of the unrolled loop was dead. 1377 loop_head->set_trip_count(loop_head->trip_count() / 2); 1378 1379 // Double the count of original iterations in the unrolled loop body. 1380 loop_head->double_unrolled_count(); 1381 1382 // ----------- 1383 // Step 2: Cut back the trip counter for an unroll amount of 2. 1384 // Loop will normally trip (limit - init)/stride_con. Since it's a 1385 // CountedLoop this is exact (stride divides limit-init exactly). 1386 // We are going to double the loop body, so we want to knock off any 1387 // odd iteration: (trip_cnt & ~1). Then back compute a new limit. 1388 Node *span = new (C) SubINode( limit, init ); 1389 register_new_node( span, ctrl ); 1390 Node *trip = new (C) DivINode( 0, span, stride ); 1391 register_new_node( trip, ctrl ); 1392 Node *mtwo = _igvn.intcon(-2); 1393 set_ctrl(mtwo, C->root()); 1394 Node *rond = new (C) AndINode( trip, mtwo ); 1395 register_new_node( rond, ctrl ); 1396 Node *spn2 = new (C) MulINode( rond, stride ); 1397 register_new_node( spn2, ctrl ); 1398 new_limit = new (C) AddINode( spn2, init ); 1399 register_new_node( new_limit, ctrl ); 1400 1401 // Hammer in the new limit 1402 Node *ctrl2 = loop_end->in(0); 1403 Node *cmp2 = new (C) CmpINode( loop_head->incr(), new_limit ); 1404 register_new_node( cmp2, ctrl2 ); 1405 Node *bol2 = new (C) BoolNode( cmp2, loop_end->test_trip() ); 1406 register_new_node( bol2, ctrl2 ); 1407 _igvn.hash_delete(loop_end); 1408 loop_end->set_req(CountedLoopEndNode::TestValue, bol2); 1409 1410 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 1411 // Make it a 1-trip test (means at least 2 trips). 1412 if( adjust_min_trip ) { 1413 assert( new_limit != NULL, "" ); 1414 // Guard test uses an 'opaque' node which is not shared. Hence I 1415 // can edit it's inputs directly. Hammer in the new limit for the 1416 // minimum-trip guard. 1417 assert( opaq->outcnt() == 1, "" ); 1418 _igvn.hash_delete(opaq); 1419 opaq->set_req(1, new_limit); 1420 } 1421 } // LoopLimitCheck 1422 1423 // --------- 1424 // Step 4: Clone the loop body. Move it inside the loop. This loop body 1425 // represents the odd iterations; since the loop trips an even number of 1426 // times its backedge is never taken. Kill the backedge. 1427 uint dd = dom_depth(loop_head); 1428 clone_loop( loop, old_new, dd ); 1429 1430 // Make backedges of the clone equal to backedges of the original. 1431 // Make the fall-in from the original come from the fall-out of the clone. 1432 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) { 1433 Node* phi = loop_head->fast_out(j); 1434 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) { 1435 Node *newphi = old_new[phi->_idx]; 1436 _igvn.hash_delete( phi ); 1437 _igvn.hash_delete( newphi ); 1438 1439 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl)); 1440 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl)); 1441 phi ->set_req(LoopNode::LoopBackControl, C->top()); 1442 } 1443 } 1444 Node *clone_head = old_new[loop_head->_idx]; 1445 _igvn.hash_delete( clone_head ); 1446 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl)); 1447 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl)); 1448 loop_head ->set_req(LoopNode::LoopBackControl, C->top()); 1449 loop->_head = clone_head; // New loop header 1450 1451 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd); 1452 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd); 1453 1454 // Kill the clone's backedge 1455 Node *newcle = old_new[loop_end->_idx]; 1456 _igvn.hash_delete( newcle ); 1457 Node *one = _igvn.intcon(1); 1458 set_ctrl(one, C->root()); 1459 newcle->set_req(1, one); 1460 // Force clone into same loop body 1461 uint max = loop->_body.size(); 1462 for( uint k = 0; k < max; k++ ) { 1463 Node *old = loop->_body.at(k); 1464 Node *nnn = old_new[old->_idx]; 1465 loop->_body.push(nnn); 1466 if (!has_ctrl(old)) 1467 set_loop(nnn, loop); 1468 } 1469 1470 loop->record_for_igvn(); 1471 } 1472 1473 //------------------------------do_maximally_unroll---------------------------- 1474 1475 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) { 1476 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1477 assert(cl->has_exact_trip_count(), "trip count is not exact"); 1478 assert(cl->trip_count() > 0, ""); 1479 #ifndef PRODUCT 1480 if (TraceLoopOpts) { 1481 tty->print("MaxUnroll %d ", cl->trip_count()); 1482 loop->dump_head(); 1483 } 1484 #endif 1485 1486 // If loop is tripping an odd number of times, peel odd iteration 1487 if ((cl->trip_count() & 1) == 1) { 1488 do_peeling(loop, old_new); 1489 } 1490 1491 // Now its tripping an even number of times remaining. Double loop body. 1492 // Do not adjust pre-guards; they are not needed and do not exist. 1493 if (cl->trip_count() > 0) { 1494 assert((cl->trip_count() & 1) == 0, "missed peeling"); 1495 do_unroll(loop, old_new, false); 1496 } 1497 } 1498 1499 //------------------------------dominates_backedge--------------------------------- 1500 // Returns true if ctrl is executed on every complete iteration 1501 bool IdealLoopTree::dominates_backedge(Node* ctrl) { 1502 assert(ctrl->is_CFG(), "must be control"); 1503 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl); 1504 return _phase->dom_lca_internal(ctrl, backedge) == ctrl; 1505 } 1506 1507 //------------------------------adjust_limit----------------------------------- 1508 // Helper function for add_constraint(). 1509 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) { 1510 // Compute "I :: (limit-offset)/scale" 1511 Node *con = new (C) SubINode(rc_limit, offset); 1512 register_new_node(con, pre_ctrl); 1513 Node *X = new (C) DivINode(0, con, scale); 1514 register_new_node(X, pre_ctrl); 1515 1516 // Adjust loop limit 1517 loop_limit = (stride_con > 0) 1518 ? (Node*)(new (C) MinINode(loop_limit, X)) 1519 : (Node*)(new (C) MaxINode(loop_limit, X)); 1520 register_new_node(loop_limit, pre_ctrl); 1521 return loop_limit; 1522 } 1523 1524 //------------------------------add_constraint--------------------------------- 1525 // Constrain the main loop iterations so the conditions: 1526 // low_limit <= scale_con * I + offset < upper_limit 1527 // always holds true. That is, either increase the number of iterations in 1528 // the pre-loop or the post-loop until the condition holds true in the main 1529 // loop. Stride, scale, offset and limit are all loop invariant. Further, 1530 // stride and scale are constants (offset and limit often are). 1531 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 ) { 1532 // For positive stride, the pre-loop limit always uses a MAX function 1533 // and the main loop a MIN function. For negative stride these are 1534 // reversed. 1535 1536 // Also for positive stride*scale the affine function is increasing, so the 1537 // pre-loop must check for underflow and the post-loop for overflow. 1538 // Negative stride*scale reverses this; pre-loop checks for overflow and 1539 // post-loop for underflow. 1540 1541 Node *scale = _igvn.intcon(scale_con); 1542 set_ctrl(scale, C->root()); 1543 1544 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow 1545 // The overflow limit: scale*I+offset < upper_limit 1546 // For main-loop compute 1547 // ( if (scale > 0) /* and stride > 0 */ 1548 // I < (upper_limit-offset)/scale 1549 // else /* scale < 0 and stride < 0 */ 1550 // I > (upper_limit-offset)/scale 1551 // ) 1552 // 1553 // (upper_limit-offset) may overflow or underflow. 1554 // But it is fine since main loop will either have 1555 // less iterations or will be skipped in such case. 1556 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl); 1557 1558 // The underflow limit: low_limit <= scale*I+offset. 1559 // For pre-loop compute 1560 // NOT(scale*I+offset >= low_limit) 1561 // scale*I+offset < low_limit 1562 // ( if (scale > 0) /* and stride > 0 */ 1563 // I < (low_limit-offset)/scale 1564 // else /* scale < 0 and stride < 0 */ 1565 // I > (low_limit-offset)/scale 1566 // ) 1567 1568 if (low_limit->get_int() == -max_jint) { 1569 if (!RangeLimitCheck) return; 1570 // We need this guard when scale*pre_limit+offset >= limit 1571 // due to underflow. So we need execute pre-loop until 1572 // scale*I+offset >= min_int. But (min_int-offset) will 1573 // underflow when offset > 0 and X will be > original_limit 1574 // when stride > 0. To avoid it we replace positive offset with 0. 1575 // 1576 // Also (min_int+1 == -max_int) is used instead of min_int here 1577 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1578 Node* shift = _igvn.intcon(31); 1579 set_ctrl(shift, C->root()); 1580 Node* sign = new (C) RShiftINode(offset, shift); 1581 register_new_node(sign, pre_ctrl); 1582 offset = new (C) AndINode(offset, sign); 1583 register_new_node(offset, pre_ctrl); 1584 } else { 1585 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1586 // The only problem we have here when offset == min_int 1587 // since (0-min_int) == min_int. It may be fine for stride > 0 1588 // but for stride < 0 X will be < original_limit. To avoid it 1589 // max(pre_limit, original_limit) is used in do_range_check(). 1590 } 1591 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1592 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl); 1593 1594 } else { // stride_con*scale_con < 0 1595 // For negative stride*scale pre-loop checks for overflow and 1596 // post-loop for underflow. 1597 // 1598 // The overflow limit: scale*I+offset < upper_limit 1599 // For pre-loop compute 1600 // NOT(scale*I+offset < upper_limit) 1601 // scale*I+offset >= upper_limit 1602 // scale*I+offset+1 > upper_limit 1603 // ( if (scale < 0) /* and stride > 0 */ 1604 // I < (upper_limit-(offset+1))/scale 1605 // else /* scale > 0 and stride < 0 */ 1606 // I > (upper_limit-(offset+1))/scale 1607 // ) 1608 // 1609 // (upper_limit-offset-1) may underflow or overflow. 1610 // To avoid it min(pre_limit, original_limit) is used 1611 // in do_range_check() for stride > 0 and max() for < 0. 1612 Node *one = _igvn.intcon(1); 1613 set_ctrl(one, C->root()); 1614 1615 Node *plus_one = new (C) AddINode(offset, one); 1616 register_new_node( plus_one, pre_ctrl ); 1617 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); 1618 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl); 1619 1620 if (low_limit->get_int() == -max_jint) { 1621 if (!RangeLimitCheck) return; 1622 // We need this guard when scale*main_limit+offset >= limit 1623 // due to underflow. So we need execute main-loop while 1624 // scale*I+offset+1 > min_int. But (min_int-offset-1) will 1625 // underflow when (offset+1) > 0 and X will be < main_limit 1626 // when scale < 0 (and stride > 0). To avoid it we replace 1627 // positive (offset+1) with 0. 1628 // 1629 // Also (min_int+1 == -max_int) is used instead of min_int here 1630 // to avoid problem with scale == -1 (min_int/(-1) == min_int). 1631 Node* shift = _igvn.intcon(31); 1632 set_ctrl(shift, C->root()); 1633 Node* sign = new (C) RShiftINode(plus_one, shift); 1634 register_new_node(sign, pre_ctrl); 1635 plus_one = new (C) AndINode(plus_one, sign); 1636 register_new_node(plus_one, pre_ctrl); 1637 } else { 1638 assert(low_limit->get_int() == 0, "wrong low limit for range check"); 1639 // The only problem we have here when offset == max_int 1640 // since (max_int+1) == min_int and (0-min_int) == min_int. 1641 // But it is fine since main loop will either have 1642 // less iterations or will be skipped in such case. 1643 } 1644 // The underflow limit: low_limit <= scale*I+offset. 1645 // For main-loop compute 1646 // scale*I+offset+1 > low_limit 1647 // ( if (scale < 0) /* and stride > 0 */ 1648 // I < (low_limit-(offset+1))/scale 1649 // else /* scale > 0 and stride < 0 */ 1650 // I > (low_limit-(offset+1))/scale 1651 // ) 1652 1653 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl); 1654 } 1655 } 1656 1657 1658 //------------------------------is_scaled_iv--------------------------------- 1659 // Return true if exp is a constant times an induction var 1660 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) { 1661 if (exp == iv) { 1662 if (p_scale != NULL) { 1663 *p_scale = 1; 1664 } 1665 return true; 1666 } 1667 int opc = exp->Opcode(); 1668 if (opc == Op_MulI) { 1669 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1670 if (p_scale != NULL) { 1671 *p_scale = exp->in(2)->get_int(); 1672 } 1673 return true; 1674 } 1675 if (exp->in(2) == iv && exp->in(1)->is_Con()) { 1676 if (p_scale != NULL) { 1677 *p_scale = exp->in(1)->get_int(); 1678 } 1679 return true; 1680 } 1681 } else if (opc == Op_LShiftI) { 1682 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1683 if (p_scale != NULL) { 1684 *p_scale = 1 << exp->in(2)->get_int(); 1685 } 1686 return true; 1687 } 1688 } 1689 return false; 1690 } 1691 1692 //-----------------------------is_scaled_iv_plus_offset------------------------------ 1693 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2) 1694 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) { 1695 if (is_scaled_iv(exp, iv, p_scale)) { 1696 if (p_offset != NULL) { 1697 Node *zero = _igvn.intcon(0); 1698 set_ctrl(zero, C->root()); 1699 *p_offset = zero; 1700 } 1701 return true; 1702 } 1703 int opc = exp->Opcode(); 1704 if (opc == Op_AddI) { 1705 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1706 if (p_offset != NULL) { 1707 *p_offset = exp->in(2); 1708 } 1709 return true; 1710 } 1711 if (exp->in(2)->is_Con()) { 1712 Node* offset2 = NULL; 1713 if (depth < 2 && 1714 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale, 1715 p_offset != NULL ? &offset2 : NULL, depth+1)) { 1716 if (p_offset != NULL) { 1717 Node *ctrl_off2 = get_ctrl(offset2); 1718 Node* offset = new (C) AddINode(offset2, exp->in(2)); 1719 register_new_node(offset, ctrl_off2); 1720 *p_offset = offset; 1721 } 1722 return true; 1723 } 1724 } 1725 } else if (opc == Op_SubI) { 1726 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1727 if (p_offset != NULL) { 1728 Node *zero = _igvn.intcon(0); 1729 set_ctrl(zero, C->root()); 1730 Node *ctrl_off = get_ctrl(exp->in(2)); 1731 Node* offset = new (C) SubINode(zero, exp->in(2)); 1732 register_new_node(offset, ctrl_off); 1733 *p_offset = offset; 1734 } 1735 return true; 1736 } 1737 if (is_scaled_iv(exp->in(2), iv, p_scale)) { 1738 if (p_offset != NULL) { 1739 *p_scale *= -1; 1740 *p_offset = exp->in(1); 1741 } 1742 return true; 1743 } 1744 } 1745 return false; 1746 } 1747 1748 //------------------------------do_range_check--------------------------------- 1749 // Eliminate range-checks and other trip-counter vs loop-invariant tests. 1750 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) { 1751 #ifndef PRODUCT 1752 if (PrintOpto && VerifyLoopOptimizations) { 1753 tty->print("Range Check Elimination "); 1754 loop->dump_head(); 1755 } else if (TraceLoopOpts) { 1756 tty->print("RangeCheck "); 1757 loop->dump_head(); 1758 } 1759 #endif 1760 assert(RangeCheckElimination, ""); 1761 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1762 assert(cl->is_main_loop(), ""); 1763 1764 // protect against stride not being a constant 1765 if (!cl->stride_is_con()) 1766 return; 1767 1768 // Find the trip counter; we are iteration splitting based on it 1769 Node *trip_counter = cl->phi(); 1770 // Find the main loop limit; we will trim it's iterations 1771 // to not ever trip end tests 1772 Node *main_limit = cl->limit(); 1773 1774 // Need to find the main-loop zero-trip guard 1775 Node *ctrl = cl->in(LoopNode::EntryControl); 1776 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, ""); 1777 Node *iffm = ctrl->in(0); 1778 assert(iffm->Opcode() == Op_If, ""); 1779 Node *bolzm = iffm->in(1); 1780 assert(bolzm->Opcode() == Op_Bool, ""); 1781 Node *cmpzm = bolzm->in(1); 1782 assert(cmpzm->is_Cmp(), ""); 1783 Node *opqzm = cmpzm->in(2); 1784 // Can not optimize a loop if zero-trip Opaque1 node is optimized 1785 // away and then another round of loop opts attempted. 1786 if (opqzm->Opcode() != Op_Opaque1) 1787 return; 1788 assert(opqzm->in(1) == main_limit, "do not understand situation"); 1789 1790 // Find the pre-loop limit; we will expand it's iterations to 1791 // not ever trip low tests. 1792 Node *p_f = iffm->in(0); 1793 assert(p_f->Opcode() == Op_IfFalse, ""); 1794 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); 1795 assert(pre_end->loopnode()->is_pre_loop(), ""); 1796 Node *pre_opaq1 = pre_end->limit(); 1797 // Occasionally it's possible for a pre-loop Opaque1 node to be 1798 // optimized away and then another round of loop opts attempted. 1799 // We can not optimize this particular loop in that case. 1800 if (pre_opaq1->Opcode() != Op_Opaque1) 1801 return; 1802 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1; 1803 Node *pre_limit = pre_opaq->in(1); 1804 1805 // Where do we put new limit calculations 1806 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl); 1807 1808 // Ensure the original loop limit is available from the 1809 // pre-loop Opaque1 node. 1810 Node *orig_limit = pre_opaq->original_loop_limit(); 1811 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP) 1812 return; 1813 1814 // Must know if its a count-up or count-down loop 1815 1816 int stride_con = cl->stride_con(); 1817 Node *zero = _igvn.intcon(0); 1818 Node *one = _igvn.intcon(1); 1819 // Use symmetrical int range [-max_jint,max_jint] 1820 Node *mini = _igvn.intcon(-max_jint); 1821 set_ctrl(zero, C->root()); 1822 set_ctrl(one, C->root()); 1823 set_ctrl(mini, C->root()); 1824 1825 // Range checks that do not dominate the loop backedge (ie. 1826 // conditionally executed) can lengthen the pre loop limit beyond 1827 // the original loop limit. To prevent this, the pre limit is 1828 // (for stride > 0) MINed with the original loop limit (MAXed 1829 // stride < 0) when some range_check (rc) is conditionally 1830 // executed. 1831 bool conditional_rc = false; 1832 1833 // Check loop body for tests of trip-counter plus loop-invariant vs 1834 // loop-invariant. 1835 for( uint i = 0; i < loop->_body.size(); i++ ) { 1836 Node *iff = loop->_body[i]; 1837 if( iff->Opcode() == Op_If ) { // Test? 1838 1839 // Test is an IfNode, has 2 projections. If BOTH are in the loop 1840 // we need loop unswitching instead of iteration splitting. 1841 Node *exit = loop->is_loop_exit(iff); 1842 if( !exit ) continue; 1843 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0; 1844 1845 // Get boolean condition to test 1846 Node *i1 = iff->in(1); 1847 if( !i1->is_Bool() ) continue; 1848 BoolNode *bol = i1->as_Bool(); 1849 BoolTest b_test = bol->_test; 1850 // Flip sense of test if exit condition is flipped 1851 if( flip ) 1852 b_test = b_test.negate(); 1853 1854 // Get compare 1855 Node *cmp = bol->in(1); 1856 1857 // Look for trip_counter + offset vs limit 1858 Node *rc_exp = cmp->in(1); 1859 Node *limit = cmp->in(2); 1860 jint scale_con= 1; // Assume trip counter not scaled 1861 1862 Node *limit_c = get_ctrl(limit); 1863 if( loop->is_member(get_loop(limit_c) ) ) { 1864 // Compare might have operands swapped; commute them 1865 b_test = b_test.commute(); 1866 rc_exp = cmp->in(2); 1867 limit = cmp->in(1); 1868 limit_c = get_ctrl(limit); 1869 if( loop->is_member(get_loop(limit_c) ) ) 1870 continue; // Both inputs are loop varying; cannot RCE 1871 } 1872 // Here we know 'limit' is loop invariant 1873 1874 // 'limit' maybe pinned below the zero trip test (probably from a 1875 // previous round of rce), in which case, it can't be used in the 1876 // zero trip test expression which must occur before the zero test's if. 1877 if( limit_c == ctrl ) { 1878 continue; // Don't rce this check but continue looking for other candidates. 1879 } 1880 1881 // Check for scaled induction variable plus an offset 1882 Node *offset = NULL; 1883 1884 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) { 1885 continue; 1886 } 1887 1888 Node *offset_c = get_ctrl(offset); 1889 if( loop->is_member( get_loop(offset_c) ) ) 1890 continue; // Offset is not really loop invariant 1891 // Here we know 'offset' is loop invariant. 1892 1893 // As above for the 'limit', the 'offset' maybe pinned below the 1894 // zero trip test. 1895 if( offset_c == ctrl ) { 1896 continue; // Don't rce this check but continue looking for other candidates. 1897 } 1898 #ifdef ASSERT 1899 if (TraceRangeLimitCheck) { 1900 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":"); 1901 bol->dump(2); 1902 } 1903 #endif 1904 // At this point we have the expression as: 1905 // scale_con * trip_counter + offset :: limit 1906 // where scale_con, offset and limit are loop invariant. Trip_counter 1907 // monotonically increases by stride_con, a constant. Both (or either) 1908 // stride_con and scale_con can be negative which will flip about the 1909 // sense of the test. 1910 1911 // Adjust pre and main loop limits to guard the correct iteration set 1912 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests 1913 if( b_test._test == BoolTest::lt ) { // Range checks always use lt 1914 // The underflow and overflow limits: 0 <= scale*I+offset < limit 1915 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit ); 1916 if (!conditional_rc) { 1917 // (0-offset)/scale could be outside of loop iterations range. 1918 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck; 1919 } 1920 } else { 1921 #ifndef PRODUCT 1922 if( PrintOpto ) 1923 tty->print_cr("missed RCE opportunity"); 1924 #endif 1925 continue; // In release mode, ignore it 1926 } 1927 } else { // Otherwise work on normal compares 1928 switch( b_test._test ) { 1929 case BoolTest::gt: 1930 // Fall into GE case 1931 case BoolTest::ge: 1932 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit 1933 scale_con = -scale_con; 1934 offset = new (C) SubINode( zero, offset ); 1935 register_new_node( offset, pre_ctrl ); 1936 limit = new (C) SubINode( zero, limit ); 1937 register_new_node( limit, pre_ctrl ); 1938 // Fall into LE case 1939 case BoolTest::le: 1940 if (b_test._test != BoolTest::gt) { 1941 // Convert X <= Y to X < Y+1 1942 limit = new (C) AddINode( limit, one ); 1943 register_new_node( limit, pre_ctrl ); 1944 } 1945 // Fall into LT case 1946 case BoolTest::lt: 1947 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit 1948 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here 1949 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT. 1950 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit ); 1951 if (!conditional_rc) { 1952 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range. 1953 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could 1954 // still be outside of loop range. 1955 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck; 1956 } 1957 break; 1958 default: 1959 #ifndef PRODUCT 1960 if( PrintOpto ) 1961 tty->print_cr("missed RCE opportunity"); 1962 #endif 1963 continue; // Unhandled case 1964 } 1965 } 1966 1967 // Kill the eliminated test 1968 C->set_major_progress(); 1969 Node *kill_con = _igvn.intcon( 1-flip ); 1970 set_ctrl(kill_con, C->root()); 1971 _igvn.replace_input_of(iff, 1, kill_con); 1972 // Find surviving projection 1973 assert(iff->is_If(), ""); 1974 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip); 1975 // Find loads off the surviving projection; remove their control edge 1976 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { 1977 Node* cd = dp->fast_out(i); // Control-dependent node 1978 if (cd->is_Load() && cd->depends_only_on_test()) { // Loads can now float around in the loop 1979 // Allow the load to float around in the loop, or before it 1980 // but NOT before the pre-loop. 1981 _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL 1982 --i; 1983 --imax; 1984 } 1985 } 1986 1987 } // End of is IF 1988 1989 } 1990 1991 // Update loop limits 1992 if (conditional_rc) { 1993 pre_limit = (stride_con > 0) ? (Node*)new (C) MinINode(pre_limit, orig_limit) 1994 : (Node*)new (C) MaxINode(pre_limit, orig_limit); 1995 register_new_node(pre_limit, pre_ctrl); 1996 } 1997 _igvn.hash_delete(pre_opaq); 1998 pre_opaq->set_req(1, pre_limit); 1999 2000 // Note:: we are making the main loop limit no longer precise; 2001 // need to round up based on stride. 2002 cl->set_nonexact_trip_count(); 2003 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case 2004 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init 2005 // Hopefully, compiler will optimize for powers of 2. 2006 Node *ctrl = get_ctrl(main_limit); 2007 Node *stride = cl->stride(); 2008 Node *init = cl->init_trip(); 2009 Node *span = new (C) SubINode(main_limit,init); 2010 register_new_node(span,ctrl); 2011 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1)); 2012 Node *add = new (C) AddINode(span,rndup); 2013 register_new_node(add,ctrl); 2014 Node *div = new (C) DivINode(0,add,stride); 2015 register_new_node(div,ctrl); 2016 Node *mul = new (C) MulINode(div,stride); 2017 register_new_node(mul,ctrl); 2018 Node *newlim = new (C) AddINode(mul,init); 2019 register_new_node(newlim,ctrl); 2020 main_limit = newlim; 2021 } 2022 2023 Node *main_cle = cl->loopexit(); 2024 Node *main_bol = main_cle->in(1); 2025 // Hacking loop bounds; need private copies of exit test 2026 if( main_bol->outcnt() > 1 ) {// BoolNode shared? 2027 _igvn.hash_delete(main_cle); 2028 main_bol = main_bol->clone();// Clone a private BoolNode 2029 register_new_node( main_bol, main_cle->in(0) ); 2030 main_cle->set_req(1,main_bol); 2031 } 2032 Node *main_cmp = main_bol->in(1); 2033 if( main_cmp->outcnt() > 1 ) { // CmpNode shared? 2034 _igvn.hash_delete(main_bol); 2035 main_cmp = main_cmp->clone();// Clone a private CmpNode 2036 register_new_node( main_cmp, main_cle->in(0) ); 2037 main_bol->set_req(1,main_cmp); 2038 } 2039 // Hack the now-private loop bounds 2040 _igvn.replace_input_of(main_cmp, 2, main_limit); 2041 // The OpaqueNode is unshared by design 2042 assert( opqzm->outcnt() == 1, "cannot hack shared node" ); 2043 _igvn.replace_input_of(opqzm, 1, main_limit); 2044 } 2045 2046 //------------------------------DCE_loop_body---------------------------------- 2047 // Remove simplistic dead code from loop body 2048 void IdealLoopTree::DCE_loop_body() { 2049 for( uint i = 0; i < _body.size(); i++ ) 2050 if( _body.at(i)->outcnt() == 0 ) 2051 _body.map( i--, _body.pop() ); 2052 } 2053 2054 2055 //------------------------------adjust_loop_exit_prob-------------------------- 2056 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage. 2057 // Replace with a 1-in-10 exit guess. 2058 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) { 2059 Node *test = tail(); 2060 while( test != _head ) { 2061 uint top = test->Opcode(); 2062 if( top == Op_IfTrue || top == Op_IfFalse ) { 2063 int test_con = ((ProjNode*)test)->_con; 2064 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity"); 2065 IfNode *iff = test->in(0)->as_If(); 2066 if( iff->outcnt() == 2 ) { // Ignore dead tests 2067 Node *bol = iff->in(1); 2068 if( bol && bol->req() > 1 && bol->in(1) && 2069 ((bol->in(1)->Opcode() == Op_StorePConditional ) || 2070 (bol->in(1)->Opcode() == Op_StoreIConditional ) || 2071 (bol->in(1)->Opcode() == Op_StoreLConditional ) || 2072 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || 2073 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || 2074 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || 2075 (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) 2076 return; // Allocation loops RARELY take backedge 2077 // Find the OTHER exit path from the IF 2078 Node* ex = iff->proj_out(1-test_con); 2079 float p = iff->_prob; 2080 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) { 2081 if( top == Op_IfTrue ) { 2082 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) { 2083 iff->_prob = PROB_STATIC_FREQUENT; 2084 } 2085 } else { 2086 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) { 2087 iff->_prob = PROB_STATIC_INFREQUENT; 2088 } 2089 } 2090 } 2091 } 2092 } 2093 test = phase->idom(test); 2094 } 2095 } 2096 2097 2098 //------------------------------policy_do_remove_empty_loop-------------------- 2099 // Micro-benchmark spamming. Policy is to always remove empty loops. 2100 // The 'DO' part is to replace the trip counter with the value it will 2101 // have on the last iteration. This will break the loop. 2102 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) { 2103 // Minimum size must be empty loop 2104 if (_body.size() > EMPTY_LOOP_SIZE) 2105 return false; 2106 2107 if (!_head->is_CountedLoop()) 2108 return false; // Dead loop 2109 CountedLoopNode *cl = _head->as_CountedLoop(); 2110 if (!cl->is_valid_counted_loop()) 2111 return false; // Malformed loop 2112 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) 2113 return false; // Infinite loop 2114 2115 #ifdef ASSERT 2116 // Ensure only one phi which is the iv. 2117 Node* iv = NULL; 2118 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) { 2119 Node* n = cl->fast_out(i); 2120 if (n->Opcode() == Op_Phi) { 2121 assert(iv == NULL, "Too many phis" ); 2122 iv = n; 2123 } 2124 } 2125 assert(iv == cl->phi(), "Wrong phi" ); 2126 #endif 2127 2128 // main and post loops have explicitly created zero trip guard 2129 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop(); 2130 if (needs_guard) { 2131 // Skip guard if values not overlap. 2132 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int(); 2133 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int(); 2134 int stride_con = cl->stride_con(); 2135 if (stride_con > 0) { 2136 needs_guard = (init_t->_hi >= limit_t->_lo); 2137 } else { 2138 needs_guard = (init_t->_lo <= limit_t->_hi); 2139 } 2140 } 2141 if (needs_guard) { 2142 // Check for an obvious zero trip guard. 2143 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl)); 2144 if (inctrl->Opcode() == Op_IfTrue) { 2145 // The test should look like just the backedge of a CountedLoop 2146 Node* iff = inctrl->in(0); 2147 if (iff->is_If()) { 2148 Node* bol = iff->in(1); 2149 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) { 2150 Node* cmp = bol->in(1); 2151 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) { 2152 needs_guard = false; 2153 } 2154 } 2155 } 2156 } 2157 } 2158 2159 #ifndef PRODUCT 2160 if (PrintOpto) { 2161 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : ""); 2162 this->dump_head(); 2163 } else if (TraceLoopOpts) { 2164 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : ""); 2165 this->dump_head(); 2166 } 2167 #endif 2168 2169 if (needs_guard) { 2170 // Peel the loop to ensure there's a zero trip guard 2171 Node_List old_new; 2172 phase->do_peeling(this, old_new); 2173 } 2174 2175 // Replace the phi at loop head with the final value of the last 2176 // iteration. Then the CountedLoopEnd will collapse (backedge never 2177 // taken) and all loop-invariant uses of the exit values will be correct. 2178 Node *phi = cl->phi(); 2179 Node *exact_limit = phase->exact_limit(this); 2180 if (exact_limit != cl->limit()) { 2181 // We also need to replace the original limit to collapse loop exit. 2182 Node* cmp = cl->loopexit()->cmp_node(); 2183 assert(cl->limit() == cmp->in(2), "sanity"); 2184 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist 2185 phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist 2186 } 2187 // Note: the final value after increment should not overflow since 2188 // counted loop has limit check predicate. 2189 Node *final = new (phase->C) SubINode( exact_limit, cl->stride() ); 2190 phase->register_new_node(final,cl->in(LoopNode::EntryControl)); 2191 phase->_igvn.replace_node(phi,final); 2192 phase->C->set_major_progress(); 2193 return true; 2194 } 2195 2196 //------------------------------policy_do_one_iteration_loop------------------- 2197 // Convert one iteration loop into normal code. 2198 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) { 2199 if (!_head->as_Loop()->is_valid_counted_loop()) 2200 return false; // Only for counted loop 2201 2202 CountedLoopNode *cl = _head->as_CountedLoop(); 2203 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) { 2204 return false; 2205 } 2206 2207 #ifndef PRODUCT 2208 if(TraceLoopOpts) { 2209 tty->print("OneIteration "); 2210 this->dump_head(); 2211 } 2212 #endif 2213 2214 Node *init_n = cl->init_trip(); 2215 #ifdef ASSERT 2216 // Loop boundaries should be constant since trip count is exact. 2217 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration"); 2218 #endif 2219 // Replace the phi at loop head with the value of the init_trip. 2220 // Then the CountedLoopEnd will collapse (backedge will not be taken) 2221 // and all loop-invariant uses of the exit values will be correct. 2222 phase->_igvn.replace_node(cl->phi(), cl->init_trip()); 2223 phase->C->set_major_progress(); 2224 return true; 2225 } 2226 2227 //============================================================================= 2228 //------------------------------iteration_split_impl--------------------------- 2229 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) { 2230 // Compute exact loop trip count if possible. 2231 compute_exact_trip_count(phase); 2232 2233 // Convert one iteration loop into normal code. 2234 if (policy_do_one_iteration_loop(phase)) 2235 return true; 2236 2237 // Check and remove empty loops (spam micro-benchmarks) 2238 if (policy_do_remove_empty_loop(phase)) 2239 return true; // Here we removed an empty loop 2240 2241 bool should_peel = policy_peeling(phase); // Should we peel? 2242 2243 bool should_unswitch = policy_unswitching(phase); 2244 2245 // Non-counted loops may be peeled; exactly 1 iteration is peeled. 2246 // This removes loop-invariant tests (usually null checks). 2247 if (!_head->is_CountedLoop()) { // Non-counted loop 2248 if (PartialPeelLoop && phase->partial_peel(this, old_new)) { 2249 // Partial peel succeeded so terminate this round of loop opts 2250 return false; 2251 } 2252 if (should_peel) { // Should we peel? 2253 #ifndef PRODUCT 2254 if (PrintOpto) tty->print_cr("should_peel"); 2255 #endif 2256 phase->do_peeling(this,old_new); 2257 } else if (should_unswitch) { 2258 phase->do_unswitching(this, old_new); 2259 } 2260 return true; 2261 } 2262 CountedLoopNode *cl = _head->as_CountedLoop(); 2263 2264 if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops 2265 2266 // Do nothing special to pre- and post- loops 2267 if (cl->is_pre_loop() || cl->is_post_loop()) return true; 2268 2269 // Compute loop trip count from profile data 2270 compute_profile_trip_cnt(phase); 2271 2272 // Before attempting fancy unrolling, RCE or alignment, see if we want 2273 // to completely unroll this loop or do loop unswitching. 2274 if (cl->is_normal_loop()) { 2275 if (should_unswitch) { 2276 phase->do_unswitching(this, old_new); 2277 return true; 2278 } 2279 bool should_maximally_unroll = policy_maximally_unroll(phase); 2280 if (should_maximally_unroll) { 2281 // Here we did some unrolling and peeling. Eventually we will 2282 // completely unroll this loop and it will no longer be a loop. 2283 phase->do_maximally_unroll(this,old_new); 2284 return true; 2285 } 2286 } 2287 2288 // Skip next optimizations if running low on nodes. Note that 2289 // policy_unswitching and policy_maximally_unroll have this check. 2290 uint nodes_left = MaxNodeLimit - (uint) phase->C->live_nodes(); 2291 if ((2 * _body.size()) > nodes_left) { 2292 return true; 2293 } 2294 2295 // Counted loops may be peeled, may need some iterations run up 2296 // front for RCE, and may want to align loop refs to a cache 2297 // line. Thus we clone a full loop up front whose trip count is 2298 // at least 1 (if peeling), but may be several more. 2299 2300 // The main loop will start cache-line aligned with at least 1 2301 // iteration of the unrolled body (zero-trip test required) and 2302 // will have some range checks removed. 2303 2304 // A post-loop will finish any odd iterations (leftover after 2305 // unrolling), plus any needed for RCE purposes. 2306 2307 bool should_unroll = policy_unroll(phase); 2308 2309 bool should_rce = policy_range_check(phase); 2310 2311 bool should_align = policy_align(phase); 2312 2313 // If not RCE'ing (iteration splitting) or Aligning, then we do not 2314 // need a pre-loop. We may still need to peel an initial iteration but 2315 // we will not be needing an unknown number of pre-iterations. 2316 // 2317 // Basically, if may_rce_align reports FALSE first time through, 2318 // we will not be able to later do RCE or Aligning on this loop. 2319 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align; 2320 2321 // If we have any of these conditions (RCE, alignment, unrolling) met, then 2322 // we switch to the pre-/main-/post-loop model. This model also covers 2323 // peeling. 2324 if (should_rce || should_align || should_unroll) { 2325 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops 2326 phase->insert_pre_post_loops(this,old_new, !may_rce_align); 2327 2328 // Adjust the pre- and main-loop limits to let the pre and post loops run 2329 // with full checks, but the main-loop with no checks. Remove said 2330 // checks from the main body. 2331 if (should_rce) 2332 phase->do_range_check(this,old_new); 2333 2334 // Double loop body for unrolling. Adjust the minimum-trip test (will do 2335 // twice as many iterations as before) and the main body limit (only do 2336 // an even number of trips). If we are peeling, we might enable some RCE 2337 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if 2338 // peeling. 2339 if (should_unroll && !should_peel) 2340 phase->do_unroll(this,old_new, true); 2341 2342 // Adjust the pre-loop limits to align the main body 2343 // iterations. 2344 if (should_align) 2345 Unimplemented(); 2346 2347 } else { // Else we have an unchanged counted loop 2348 if (should_peel) // Might want to peel but do nothing else 2349 phase->do_peeling(this,old_new); 2350 } 2351 return true; 2352 } 2353 2354 2355 //============================================================================= 2356 //------------------------------iteration_split-------------------------------- 2357 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { 2358 // Recursively iteration split nested loops 2359 if (_child && !_child->iteration_split(phase, old_new)) 2360 return false; 2361 2362 // Clean out prior deadwood 2363 DCE_loop_body(); 2364 2365 2366 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. 2367 // Replace with a 1-in-10 exit guess. 2368 if (_parent /*not the root loop*/ && 2369 !_irreducible && 2370 // Also ignore the occasional dead backedge 2371 !tail()->is_top()) { 2372 adjust_loop_exit_prob(phase); 2373 } 2374 2375 // Gate unrolling, RCE and peeling efforts. 2376 if (!_child && // If not an inner loop, do not split 2377 !_irreducible && 2378 _allow_optimizations && 2379 !tail()->is_top()) { // Also ignore the occasional dead backedge 2380 if (!_has_call) { 2381 if (!iteration_split_impl(phase, old_new)) { 2382 return false; 2383 } 2384 } else if (policy_unswitching(phase)) { 2385 phase->do_unswitching(this, old_new); 2386 } 2387 } 2388 2389 // Minor offset re-organization to remove loop-fallout uses of 2390 // trip counter when there was no major reshaping. 2391 phase->reorg_offsets(this); 2392 2393 if (_next && !_next->iteration_split(phase, old_new)) 2394 return false; 2395 return true; 2396 } 2397 2398 2399 //============================================================================= 2400 // Process all the loops in the loop tree and replace any fill 2401 // patterns with an intrisc version. 2402 bool PhaseIdealLoop::do_intrinsify_fill() { 2403 bool changed = false; 2404 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 2405 IdealLoopTree* lpt = iter.current(); 2406 changed |= intrinsify_fill(lpt); 2407 } 2408 return changed; 2409 } 2410 2411 2412 // Examine an inner loop looking for a a single store of an invariant 2413 // value in a unit stride loop, 2414 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value, 2415 Node*& shift, Node*& con) { 2416 const char* msg = NULL; 2417 Node* msg_node = NULL; 2418 2419 store_value = NULL; 2420 con = NULL; 2421 shift = NULL; 2422 2423 // Process the loop looking for stores. If there are multiple 2424 // stores or extra control flow give at this point. 2425 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 2426 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2427 Node* n = lpt->_body.at(i); 2428 if (n->outcnt() == 0) continue; // Ignore dead 2429 if (n->is_Store()) { 2430 if (store != NULL) { 2431 msg = "multiple stores"; 2432 break; 2433 } 2434 int opc = n->Opcode(); 2435 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) { 2436 msg = "oop fills not handled"; 2437 break; 2438 } 2439 Node* value = n->in(MemNode::ValueIn); 2440 if (!lpt->is_invariant(value)) { 2441 msg = "variant store value"; 2442 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) { 2443 msg = "not array address"; 2444 } 2445 store = n; 2446 store_value = value; 2447 } else if (n->is_If() && n != head->loopexit()) { 2448 msg = "extra control flow"; 2449 msg_node = n; 2450 } 2451 } 2452 2453 if (store == NULL) { 2454 // No store in loop 2455 return false; 2456 } 2457 2458 if (msg == NULL && head->stride_con() != 1) { 2459 // could handle negative strides too 2460 if (head->stride_con() < 0) { 2461 msg = "negative stride"; 2462 } else { 2463 msg = "non-unit stride"; 2464 } 2465 } 2466 2467 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) { 2468 msg = "can't handle store address"; 2469 msg_node = store->in(MemNode::Address); 2470 } 2471 2472 if (msg == NULL && 2473 (!store->in(MemNode::Memory)->is_Phi() || 2474 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) { 2475 msg = "store memory isn't proper phi"; 2476 msg_node = store->in(MemNode::Memory); 2477 } 2478 2479 // Make sure there is an appropriate fill routine 2480 BasicType t = store->as_Mem()->memory_type(); 2481 const char* fill_name; 2482 if (msg == NULL && 2483 StubRoutines::select_fill_function(t, false, fill_name) == NULL) { 2484 msg = "unsupported store"; 2485 msg_node = store; 2486 } 2487 2488 if (msg != NULL) { 2489 #ifndef PRODUCT 2490 if (TraceOptimizeFill) { 2491 tty->print_cr("not fill intrinsic candidate: %s", msg); 2492 if (msg_node != NULL) msg_node->dump(); 2493 } 2494 #endif 2495 return false; 2496 } 2497 2498 // Make sure the address expression can be handled. It should be 2499 // head->phi * elsize + con. head->phi might have a ConvI2L. 2500 Node* elements[4]; 2501 Node* conv = NULL; 2502 bool found_index = false; 2503 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements)); 2504 for (int e = 0; e < count; e++) { 2505 Node* n = elements[e]; 2506 if (n->is_Con() && con == NULL) { 2507 con = n; 2508 } else if (n->Opcode() == Op_LShiftX && shift == NULL) { 2509 Node* value = n->in(1); 2510 #ifdef _LP64 2511 if (value->Opcode() == Op_ConvI2L) { 2512 conv = value; 2513 value = value->in(1); 2514 } 2515 #endif 2516 if (value != head->phi()) { 2517 msg = "unhandled shift in address"; 2518 } else { 2519 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) { 2520 msg = "scale doesn't match"; 2521 } else { 2522 found_index = true; 2523 shift = n; 2524 } 2525 } 2526 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) { 2527 if (n->in(1) == head->phi()) { 2528 found_index = true; 2529 conv = n; 2530 } else { 2531 msg = "unhandled input to ConvI2L"; 2532 } 2533 } else if (n == head->phi()) { 2534 // no shift, check below for allowed cases 2535 found_index = true; 2536 } else { 2537 msg = "unhandled node in address"; 2538 msg_node = n; 2539 } 2540 } 2541 2542 if (count == -1) { 2543 msg = "malformed address expression"; 2544 msg_node = store; 2545 } 2546 2547 if (!found_index) { 2548 msg = "missing use of index"; 2549 } 2550 2551 // byte sized items won't have a shift 2552 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) { 2553 msg = "can't find shift"; 2554 msg_node = store; 2555 } 2556 2557 if (msg != NULL) { 2558 #ifndef PRODUCT 2559 if (TraceOptimizeFill) { 2560 tty->print_cr("not fill intrinsic: %s", msg); 2561 if (msg_node != NULL) msg_node->dump(); 2562 } 2563 #endif 2564 return false; 2565 } 2566 2567 // No make sure all the other nodes in the loop can be handled 2568 VectorSet ok(Thread::current()->resource_area()); 2569 2570 // store related values are ok 2571 ok.set(store->_idx); 2572 ok.set(store->in(MemNode::Memory)->_idx); 2573 2574 CountedLoopEndNode* loop_exit = head->loopexit(); 2575 guarantee(loop_exit != NULL, "no loop exit node"); 2576 2577 // Loop structure is ok 2578 ok.set(head->_idx); 2579 ok.set(loop_exit->_idx); 2580 ok.set(head->phi()->_idx); 2581 ok.set(head->incr()->_idx); 2582 ok.set(loop_exit->cmp_node()->_idx); 2583 ok.set(loop_exit->in(1)->_idx); 2584 2585 // Address elements are ok 2586 if (con) ok.set(con->_idx); 2587 if (shift) ok.set(shift->_idx); 2588 if (conv) ok.set(conv->_idx); 2589 2590 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2591 Node* n = lpt->_body.at(i); 2592 if (n->outcnt() == 0) continue; // Ignore dead 2593 if (ok.test(n->_idx)) continue; 2594 // Backedge projection is ok 2595 if (n->is_IfTrue() && n->in(0) == loop_exit) continue; 2596 if (!n->is_AddP()) { 2597 msg = "unhandled node"; 2598 msg_node = n; 2599 break; 2600 } 2601 } 2602 2603 // Make sure no unexpected values are used outside the loop 2604 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) { 2605 Node* n = lpt->_body.at(i); 2606 // These values can be replaced with other nodes if they are used 2607 // outside the loop. 2608 if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue; 2609 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) { 2610 Node* use = iter.get(); 2611 if (!lpt->_body.contains(use)) { 2612 msg = "node is used outside loop"; 2613 // lpt->_body.dump(); 2614 msg_node = n; 2615 break; 2616 } 2617 } 2618 } 2619 2620 #ifdef ASSERT 2621 if (TraceOptimizeFill) { 2622 if (msg != NULL) { 2623 tty->print_cr("no fill intrinsic: %s", msg); 2624 if (msg_node != NULL) msg_node->dump(); 2625 } else { 2626 tty->print_cr("fill intrinsic for:"); 2627 } 2628 store->dump(); 2629 if (Verbose) { 2630 lpt->_body.dump(); 2631 } 2632 } 2633 #endif 2634 2635 return msg == NULL; 2636 } 2637 2638 2639 2640 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) { 2641 // Only for counted inner loops 2642 if (!lpt->is_counted() || !lpt->is_inner()) { 2643 return false; 2644 } 2645 2646 // Must have constant stride 2647 CountedLoopNode* head = lpt->_head->as_CountedLoop(); 2648 if (!head->is_valid_counted_loop() || !head->is_normal_loop()) { 2649 return false; 2650 } 2651 2652 // Check that the body only contains a store of a loop invariant 2653 // value that is indexed by the loop phi. 2654 Node* store = NULL; 2655 Node* store_value = NULL; 2656 Node* shift = NULL; 2657 Node* offset = NULL; 2658 if (!match_fill_loop(lpt, store, store_value, shift, offset)) { 2659 return false; 2660 } 2661 2662 #ifndef PRODUCT 2663 if (TraceLoopOpts) { 2664 tty->print("ArrayFill "); 2665 lpt->dump_head(); 2666 } 2667 #endif 2668 2669 // Now replace the whole loop body by a call to a fill routine that 2670 // covers the same region as the loop. 2671 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base); 2672 2673 // Build an expression for the beginning of the copy region 2674 Node* index = head->init_trip(); 2675 #ifdef _LP64 2676 index = new (C) ConvI2LNode(index); 2677 _igvn.register_new_node_with_optimizer(index); 2678 #endif 2679 if (shift != NULL) { 2680 // byte arrays don't require a shift but others do. 2681 index = new (C) LShiftXNode(index, shift->in(2)); 2682 _igvn.register_new_node_with_optimizer(index); 2683 } 2684 index = new (C) AddPNode(base, base, index); 2685 _igvn.register_new_node_with_optimizer(index); 2686 Node* from = new (C) AddPNode(base, index, offset); 2687 _igvn.register_new_node_with_optimizer(from); 2688 // Compute the number of elements to copy 2689 Node* len = new (C) SubINode(head->limit(), head->init_trip()); 2690 _igvn.register_new_node_with_optimizer(len); 2691 2692 BasicType t = store->as_Mem()->memory_type(); 2693 bool aligned = false; 2694 if (offset != NULL && head->init_trip()->is_Con()) { 2695 int element_size = type2aelembytes(t); 2696 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0; 2697 } 2698 2699 // Build a call to the fill routine 2700 const char* fill_name; 2701 address fill = StubRoutines::select_fill_function(t, aligned, fill_name); 2702 assert(fill != NULL, "what?"); 2703 2704 // Convert float/double to int/long for fill routines 2705 if (t == T_FLOAT) { 2706 store_value = new (C) MoveF2INode(store_value); 2707 _igvn.register_new_node_with_optimizer(store_value); 2708 } else if (t == T_DOUBLE) { 2709 store_value = new (C) MoveD2LNode(store_value); 2710 _igvn.register_new_node_with_optimizer(store_value); 2711 } 2712 2713 if (CCallingConventionRequiresIntsAsLongs && 2714 // See StubRoutines::select_fill_function for types. FLOAT has been converted to INT. 2715 (t == T_FLOAT || t == T_INT || is_subword_type(t))) { 2716 store_value = new (C) ConvI2LNode(store_value); 2717 _igvn.register_new_node_with_optimizer(store_value); 2718 } 2719 2720 Node* mem_phi = store->in(MemNode::Memory); 2721 Node* result_ctrl; 2722 Node* result_mem; 2723 const TypeFunc* call_type = OptoRuntime::array_fill_Type(); 2724 CallLeafNode *call = new (C) CallLeafNoFPNode(call_type, fill, 2725 fill_name, TypeAryPtr::get_array_body_type(t)); 2726 uint cnt = 0; 2727 call->init_req(TypeFunc::Parms + cnt++, from); 2728 call->init_req(TypeFunc::Parms + cnt++, store_value); 2729 if (CCallingConventionRequiresIntsAsLongs) { 2730 call->init_req(TypeFunc::Parms + cnt++, C->top()); 2731 } 2732 #ifdef _LP64 2733 len = new (C) ConvI2LNode(len); 2734 _igvn.register_new_node_with_optimizer(len); 2735 #endif 2736 call->init_req(TypeFunc::Parms + cnt++, len); 2737 #ifdef _LP64 2738 call->init_req(TypeFunc::Parms + cnt++, C->top()); 2739 #endif 2740 call->init_req(TypeFunc::Control, head->init_control()); 2741 call->init_req(TypeFunc::I_O, C->top()); // Does no I/O. 2742 call->init_req(TypeFunc::Memory, mem_phi->in(LoopNode::EntryControl)); 2743 call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr)); 2744 call->init_req(TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr)); 2745 _igvn.register_new_node_with_optimizer(call); 2746 result_ctrl = new (C) ProjNode(call,TypeFunc::Control); 2747 _igvn.register_new_node_with_optimizer(result_ctrl); 2748 result_mem = new (C) ProjNode(call,TypeFunc::Memory); 2749 _igvn.register_new_node_with_optimizer(result_mem); 2750 2751 /* Disable following optimization until proper fix (add missing checks). 2752 2753 // If this fill is tightly coupled to an allocation and overwrites 2754 // the whole body, allow it to take over the zeroing. 2755 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this); 2756 if (alloc != NULL && alloc->is_AllocateArray()) { 2757 Node* length = alloc->as_AllocateArray()->Ideal_length(); 2758 if (head->limit() == length && 2759 head->init_trip() == _igvn.intcon(0)) { 2760 if (TraceOptimizeFill) { 2761 tty->print_cr("Eliminated zeroing in allocation"); 2762 } 2763 alloc->maybe_set_complete(&_igvn); 2764 } else { 2765 #ifdef ASSERT 2766 if (TraceOptimizeFill) { 2767 tty->print_cr("filling array but bounds don't match"); 2768 alloc->dump(); 2769 head->init_trip()->dump(); 2770 head->limit()->dump(); 2771 length->dump(); 2772 } 2773 #endif 2774 } 2775 } 2776 */ 2777 2778 // Redirect the old control and memory edges that are outside the loop. 2779 Node* exit = head->loopexit()->proj_out(0); 2780 // Sometimes the memory phi of the head is used as the outgoing 2781 // state of the loop. It's safe in this case to replace it with the 2782 // result_mem. 2783 _igvn.replace_node(store->in(MemNode::Memory), result_mem); 2784 _igvn.replace_node(exit, result_ctrl); 2785 _igvn.replace_node(store, result_mem); 2786 // Any uses the increment outside of the loop become the loop limit. 2787 _igvn.replace_node(head->incr(), head->limit()); 2788 2789 // Disconnect the head from the loop. 2790 for (uint i = 0; i < lpt->_body.size(); i++) { 2791 Node* n = lpt->_body.at(i); 2792 _igvn.replace_node(n, C->top()); 2793 } 2794 2795 return true; 2796 }