1 /* 2 * Copyright 2000-2009 Sun Microsystems, Inc. All Rights Reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 #include "incls/_precompiled.incl" 26 #include "incls/_loopTransform.cpp.incl" 27 28 //------------------------------is_loop_exit----------------------------------- 29 // Given an IfNode, return the loop-exiting projection or NULL if both 30 // arms remain in the loop. 31 Node *IdealLoopTree::is_loop_exit(Node *iff) const { 32 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests 33 PhaseIdealLoop *phase = _phase; 34 // Test is an IfNode, has 2 projections. If BOTH are in the loop 35 // we need loop unswitching instead of peeling. 36 if( !is_member(phase->get_loop( iff->raw_out(0) )) ) 37 return iff->raw_out(0); 38 if( !is_member(phase->get_loop( iff->raw_out(1) )) ) 39 return iff->raw_out(1); 40 return NULL; 41 } 42 43 44 //============================================================================= 45 46 47 //------------------------------record_for_igvn---------------------------- 48 // Put loop body on igvn work list 49 void IdealLoopTree::record_for_igvn() { 50 for( uint i = 0; i < _body.size(); i++ ) { 51 Node *n = _body.at(i); 52 _phase->_igvn._worklist.push(n); 53 } 54 } 55 56 //------------------------------compute_profile_trip_cnt---------------------------- 57 // Compute loop trip count from profile data as 58 // (backedge_count + loop_exit_count) / loop_exit_count 59 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) { 60 if (!_head->is_CountedLoop()) { 61 return; 62 } 63 CountedLoopNode* head = _head->as_CountedLoop(); 64 if (head->profile_trip_cnt() != COUNT_UNKNOWN) { 65 return; // Already computed 66 } 67 float trip_cnt = (float)max_jint; // default is big 68 69 Node* back = head->in(LoopNode::LoopBackControl); 70 while (back != head) { 71 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 72 back->in(0) && 73 back->in(0)->is_If() && 74 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN && 75 back->in(0)->as_If()->_prob != PROB_UNKNOWN) { 76 break; 77 } 78 back = phase->idom(back); 79 } 80 if (back != head) { 81 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && 82 back->in(0), "if-projection exists"); 83 IfNode* back_if = back->in(0)->as_If(); 84 float loop_back_cnt = back_if->_fcnt * back_if->_prob; 85 86 // Now compute a loop exit count 87 float loop_exit_cnt = 0.0f; 88 for( uint i = 0; i < _body.size(); i++ ) { 89 Node *n = _body[i]; 90 if( n->is_If() ) { 91 IfNode *iff = n->as_If(); 92 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) { 93 Node *exit = is_loop_exit(iff); 94 if( exit ) { 95 float exit_prob = iff->_prob; 96 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob; 97 if (exit_prob > PROB_MIN) { 98 float exit_cnt = iff->_fcnt * exit_prob; 99 loop_exit_cnt += exit_cnt; 100 } 101 } 102 } 103 } 104 } 105 if (loop_exit_cnt > 0.0f) { 106 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt; 107 } else { 108 // No exit count so use 109 trip_cnt = loop_back_cnt; 110 } 111 } 112 #ifndef PRODUCT 113 if (TraceProfileTripCount) { 114 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt); 115 } 116 #endif 117 head->set_profile_trip_cnt(trip_cnt); 118 } 119 120 //---------------------is_invariant_addition----------------------------- 121 // Return nonzero index of invariant operand for an Add or Sub 122 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants. 123 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) { 124 int op = n->Opcode(); 125 if (op == Op_AddI || op == Op_SubI) { 126 bool in1_invar = this->is_invariant(n->in(1)); 127 bool in2_invar = this->is_invariant(n->in(2)); 128 if (in1_invar && !in2_invar) return 1; 129 if (!in1_invar && in2_invar) return 2; 130 } 131 return 0; 132 } 133 134 //---------------------reassociate_add_sub----------------------------- 135 // Reassociate invariant add and subtract expressions: 136 // 137 // inv1 + (x + inv2) => ( inv1 + inv2) + x 138 // (x + inv2) + inv1 => ( inv1 + inv2) + x 139 // inv1 + (x - inv2) => ( inv1 - inv2) + x 140 // inv1 - (inv2 - x) => ( inv1 - inv2) + x 141 // (x + inv2) - inv1 => (-inv1 + inv2) + x 142 // (x - inv2) + inv1 => ( inv1 - inv2) + x 143 // (x - inv2) - inv1 => (-inv1 - inv2) + x 144 // inv1 + (inv2 - x) => ( inv1 + inv2) - x 145 // inv1 - (x - inv2) => ( inv1 + inv2) - x 146 // (inv2 - x) + inv1 => ( inv1 + inv2) - x 147 // (inv2 - x) - inv1 => (-inv1 + inv2) - x 148 // inv1 - (x + inv2) => ( inv1 - inv2) - x 149 // 150 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) { 151 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL; 152 if (is_invariant(n1)) return NULL; 153 int inv1_idx = is_invariant_addition(n1, phase); 154 if (!inv1_idx) return NULL; 155 // Don't mess with add of constant (igvn moves them to expression tree root.) 156 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL; 157 Node* inv1 = n1->in(inv1_idx); 158 Node* n2 = n1->in(3 - inv1_idx); 159 int inv2_idx = is_invariant_addition(n2, phase); 160 if (!inv2_idx) return NULL; 161 Node* x = n2->in(3 - inv2_idx); 162 Node* inv2 = n2->in(inv2_idx); 163 164 bool neg_x = n2->is_Sub() && inv2_idx == 1; 165 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2; 166 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2; 167 if (n1->is_Sub() && inv1_idx == 1) { 168 neg_x = !neg_x; 169 neg_inv2 = !neg_inv2; 170 } 171 Node* inv1_c = phase->get_ctrl(inv1); 172 Node* inv2_c = phase->get_ctrl(inv2); 173 Node* n_inv1; 174 if (neg_inv1) { 175 Node *zero = phase->_igvn.intcon(0); 176 phase->set_ctrl(zero, phase->C->root()); 177 n_inv1 = new (phase->C, 3) SubINode(zero, inv1); 178 phase->register_new_node(n_inv1, inv1_c); 179 } else { 180 n_inv1 = inv1; 181 } 182 Node* inv; 183 if (neg_inv2) { 184 inv = new (phase->C, 3) SubINode(n_inv1, inv2); 185 } else { 186 inv = new (phase->C, 3) AddINode(n_inv1, inv2); 187 } 188 phase->register_new_node(inv, phase->get_early_ctrl(inv)); 189 190 Node* addx; 191 if (neg_x) { 192 addx = new (phase->C, 3) SubINode(inv, x); 193 } else { 194 addx = new (phase->C, 3) AddINode(x, inv); 195 } 196 phase->register_new_node(addx, phase->get_ctrl(x)); 197 phase->_igvn.hash_delete(n1); 198 phase->_igvn.subsume_node(n1, addx); 199 return addx; 200 } 201 202 //---------------------reassociate_invariants----------------------------- 203 // Reassociate invariant expressions: 204 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { 205 for (int i = _body.size() - 1; i >= 0; i--) { 206 Node *n = _body.at(i); 207 for (int j = 0; j < 5; j++) { 208 Node* nn = reassociate_add_sub(n, phase); 209 if (nn == NULL) break; 210 n = nn; // again 211 }; 212 } 213 } 214 215 //------------------------------policy_peeling--------------------------------- 216 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can 217 // make some loop-invariant test (usually a null-check) happen before the loop. 218 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const { 219 Node *test = ((IdealLoopTree*)this)->tail(); 220 int body_size = ((IdealLoopTree*)this)->_body.size(); 221 int uniq = phase->C->unique(); 222 // Peeling does loop cloning which can result in O(N^2) node construction 223 if( body_size > 255 /* Prevent overflow for large body_size */ 224 || (body_size * body_size + uniq > MaxNodeLimit) ) { 225 return false; // too large to safely clone 226 } 227 while( test != _head ) { // Scan till run off top of loop 228 if( test->is_If() ) { // Test? 229 Node *ctrl = phase->get_ctrl(test->in(1)); 230 if (ctrl->is_top()) 231 return false; // Found dead test on live IF? No peeling! 232 // Standard IF only has one input value to check for loop invariance 233 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added"); 234 // Condition is not a member of this loop? 235 if( !is_member(phase->get_loop(ctrl)) && 236 is_loop_exit(test) ) 237 return true; // Found reason to peel! 238 } 239 // Walk up dominators to loop _head looking for test which is 240 // executed on every path thru loop. 241 test = phase->idom(test); 242 } 243 return false; 244 } 245 246 //------------------------------peeled_dom_test_elim--------------------------- 247 // If we got the effect of peeling, either by actually peeling or by making 248 // a pre-loop which must execute at least once, we can remove all 249 // loop-invariant dominated tests in the main body. 250 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) { 251 bool progress = true; 252 while( progress ) { 253 progress = false; // Reset for next iteration 254 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail(); 255 Node *test = prev->in(0); 256 while( test != loop->_head ) { // Scan till run off top of loop 257 258 int p_op = prev->Opcode(); 259 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) && 260 test->is_If() && // Test? 261 !test->in(1)->is_Con() && // And not already obvious? 262 // Condition is not a member of this loop? 263 !loop->is_member(get_loop(get_ctrl(test->in(1))))){ 264 // Walk loop body looking for instances of this test 265 for( uint i = 0; i < loop->_body.size(); i++ ) { 266 Node *n = loop->_body.at(i); 267 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) { 268 // IfNode was dominated by version in peeled loop body 269 progress = true; 270 dominated_by( old_new[prev->_idx], n ); 271 } 272 } 273 } 274 prev = test; 275 test = idom(test); 276 } // End of scan tests in loop 277 278 } // End of while( progress ) 279 } 280 281 //------------------------------do_peeling------------------------------------- 282 // Peel the first iteration of the given loop. 283 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 284 // The pre-loop illegally has 2 control users (old & new loops). 285 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 286 // Do this by making the old-loop fall-in edges act as if they came 287 // around the loopback from the prior iteration (follow the old-loop 288 // backedges) and then map to the new peeled iteration. This leaves 289 // the pre-loop with only 1 user (the new peeled iteration), but the 290 // peeled-loop backedge has 2 users. 291 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 292 // extra backedge user. 293 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) { 294 295 C->set_major_progress(); 296 // Peeling a 'main' loop in a pre/main/post situation obfuscates the 297 // 'pre' loop from the main and the 'pre' can no longer have it's 298 // iterations adjusted. Therefore, we need to declare this loop as 299 // no longer a 'main' loop; it will need new pre and post loops before 300 // we can do further RCE. 301 Node *h = loop->_head; 302 if( h->is_CountedLoop() ) { 303 CountedLoopNode *cl = h->as_CountedLoop(); 304 assert(cl->trip_count() > 0, "peeling a fully unrolled loop"); 305 cl->set_trip_count(cl->trip_count() - 1); 306 if( cl->is_main_loop() ) { 307 cl->set_normal_loop(); 308 #ifndef PRODUCT 309 if( PrintOpto && VerifyLoopOptimizations ) { 310 tty->print("Peeling a 'main' loop; resetting to 'normal' "); 311 loop->dump_head(); 312 } 313 #endif 314 } 315 } 316 317 // Step 1: Clone the loop body. The clone becomes the peeled iteration. 318 // The pre-loop illegally has 2 control users (old & new loops). 319 clone_loop( loop, old_new, dom_depth(loop->_head) ); 320 321 322 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. 323 // Do this by making the old-loop fall-in edges act as if they came 324 // around the loopback from the prior iteration (follow the old-loop 325 // backedges) and then map to the new peeled iteration. This leaves 326 // the pre-loop with only 1 user (the new peeled iteration), but the 327 // peeled-loop backedge has 2 users. 328 for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) { 329 Node* old = loop->_head->fast_out(j); 330 if( old->in(0) == loop->_head && old->req() == 3 && 331 (old->is_Loop() || old->is_Phi()) ) { 332 Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; 333 if( !new_exit_value ) // Backedge value is ALSO loop invariant? 334 // Then loop body backedge value remains the same. 335 new_exit_value = old->in(LoopNode::LoopBackControl); 336 _igvn.hash_delete(old); 337 old->set_req(LoopNode::EntryControl, new_exit_value); 338 } 339 } 340 341 342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the 343 // extra backedge user. 344 Node *nnn = old_new[loop->_head->_idx]; 345 _igvn.hash_delete(nnn); 346 nnn->set_req(LoopNode::LoopBackControl, C->top()); 347 for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) { 348 Node* use = nnn->fast_out(j2); 349 if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) { 350 _igvn.hash_delete(use); 351 use->set_req(LoopNode::LoopBackControl, C->top()); 352 } 353 } 354 355 356 // Step 4: Correct dom-depth info. Set to loop-head depth. 357 int dd = dom_depth(loop->_head); 358 set_idom(loop->_head, loop->_head->in(1), dd); 359 for (uint j3 = 0; j3 < loop->_body.size(); j3++) { 360 Node *old = loop->_body.at(j3); 361 Node *nnn = old_new[old->_idx]; 362 if (!has_ctrl(nnn)) 363 set_idom(nnn, idom(nnn), dd-1); 364 // While we're at it, remove any SafePoints from the peeled code 365 if( old->Opcode() == Op_SafePoint ) { 366 Node *nnn = old_new[old->_idx]; 367 lazy_replace(nnn,nnn->in(TypeFunc::Control)); 368 } 369 } 370 371 // Now force out all loop-invariant dominating tests. The optimizer 372 // finds some, but we _know_ they are all useless. 373 peeled_dom_test_elim(loop,old_new); 374 375 loop->record_for_igvn(); 376 } 377 378 //------------------------------policy_maximally_unroll------------------------ 379 // Return exact loop trip count, or 0 if not maximally unrolling 380 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const { 381 CountedLoopNode *cl = _head->as_CountedLoop(); 382 assert( cl->is_normal_loop(), "" ); 383 384 Node *init_n = cl->init_trip(); 385 Node *limit_n = cl->limit(); 386 387 // Non-constant bounds 388 if( init_n == NULL || !init_n->is_Con() || 389 limit_n == NULL || !limit_n->is_Con() || 390 // protect against stride not being a constant 391 !cl->stride_is_con() ) { 392 return false; 393 } 394 int init = init_n->get_int(); 395 int limit = limit_n->get_int(); 396 int span = limit - init; 397 int stride = cl->stride_con(); 398 399 if (init >= limit || stride > span) { 400 // return a false (no maximally unroll) and the regular unroll/peel 401 // route will make a small mess which CCP will fold away. 402 return false; 403 } 404 uint trip_count = span/stride; // trip_count can be greater than 2 Gig. 405 assert( (int)trip_count*stride == span, "must divide evenly" ); 406 407 // Real policy: if we maximally unroll, does it get too big? 408 // Allow the unrolled mess to get larger than standard loop 409 // size. After all, it will no longer be a loop. 410 uint body_size = _body.size(); 411 uint unroll_limit = (uint)LoopUnrollLimit * 4; 412 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); 413 cl->set_trip_count(trip_count); 414 if( trip_count <= unroll_limit && body_size <= unroll_limit ) { 415 uint new_body_size = body_size * trip_count; 416 if (new_body_size <= unroll_limit && 417 body_size == new_body_size / trip_count && 418 // Unrolling can result in a large amount of node construction 419 new_body_size < MaxNodeLimit - phase->C->unique()) { 420 return true; // maximally unroll 421 } 422 } 423 424 return false; // Do not maximally unroll 425 } 426 427 428 //------------------------------policy_unroll---------------------------------- 429 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if 430 // the loop is a CountedLoop and the body is small enough. 431 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const { 432 433 CountedLoopNode *cl = _head->as_CountedLoop(); 434 assert( cl->is_normal_loop() || cl->is_main_loop(), "" ); 435 436 // protect against stride not being a constant 437 if( !cl->stride_is_con() ) return false; 438 439 // protect against over-unrolling 440 if( cl->trip_count() <= 1 ) return false; 441 442 int future_unroll_ct = cl->unrolled_count() * 2; 443 444 // Don't unroll if the next round of unrolling would push us 445 // over the expected trip count of the loop. One is subtracted 446 // from the expected trip count because the pre-loop normally 447 // executes 1 iteration. 448 if (UnrollLimitForProfileCheck > 0 && 449 cl->profile_trip_cnt() != COUNT_UNKNOWN && 450 future_unroll_ct > UnrollLimitForProfileCheck && 451 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) { 452 return false; 453 } 454 455 // When unroll count is greater than LoopUnrollMin, don't unroll if: 456 // the residual iterations are more than 10% of the trip count 457 // and rounds of "unroll,optimize" are not making significant progress 458 // Progress defined as current size less than 20% larger than previous size. 459 if (UseSuperWord && cl->node_count_before_unroll() > 0 && 460 future_unroll_ct > LoopUnrollMin && 461 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() && 462 1.2 * cl->node_count_before_unroll() < (double)_body.size()) { 463 return false; 464 } 465 466 Node *init_n = cl->init_trip(); 467 Node *limit_n = cl->limit(); 468 // Non-constant bounds. 469 // Protect against over-unrolling when init or/and limit are not constant 470 // (so that trip_count's init value is maxint) but iv range is known. 471 if( init_n == NULL || !init_n->is_Con() || 472 limit_n == NULL || !limit_n->is_Con() ) { 473 Node* phi = cl->phi(); 474 if( phi != NULL ) { 475 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); 476 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); 477 int next_stride = cl->stride_con() * 2; // stride after this unroll 478 if( next_stride > 0 ) { 479 if( iv_type->_lo + next_stride <= iv_type->_lo || // overflow 480 iv_type->_lo + next_stride > iv_type->_hi ) { 481 return false; // over-unrolling 482 } 483 } else if( next_stride < 0 ) { 484 if( iv_type->_hi + next_stride >= iv_type->_hi || // overflow 485 iv_type->_hi + next_stride < iv_type->_lo ) { 486 return false; // over-unrolling 487 } 488 } 489 } 490 } 491 492 // Adjust body_size to determine if we unroll or not 493 uint body_size = _body.size(); 494 // Key test to unroll CaffeineMark's Logic test 495 int xors_in_loop = 0; 496 // Also count ModL, DivL and MulL which expand mightly 497 for( uint k = 0; k < _body.size(); k++ ) { 498 switch( _body.at(k)->Opcode() ) { 499 case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test 500 case Op_ModL: body_size += 30; break; 501 case Op_DivL: body_size += 30; break; 502 case Op_MulL: body_size += 10; break; 503 } 504 } 505 506 // Check for being too big 507 if( body_size > (uint)LoopUnrollLimit ) { 508 if( xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true; 509 // Normal case: loop too big 510 return false; 511 } 512 513 // Check for stride being a small enough constant 514 if( abs(cl->stride_con()) > (1<<3) ) return false; 515 516 // Unroll once! (Each trip will soon do double iterations) 517 return true; 518 } 519 520 //------------------------------policy_align----------------------------------- 521 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the 522 // expression that does the alignment. Note that only one array base can be 523 // aligned in a loop (unless the VM guarantees mutual alignment). Note that 524 // if we vectorize short memory ops into longer memory ops, we may want to 525 // increase alignment. 526 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const { 527 return false; 528 } 529 530 //------------------------------policy_range_check----------------------------- 531 // Return TRUE or FALSE if the loop should be range-check-eliminated. 532 // Actually we do iteration-splitting, a more powerful form of RCE. 533 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const { 534 if( !RangeCheckElimination ) return false; 535 536 CountedLoopNode *cl = _head->as_CountedLoop(); 537 // If we unrolled with no intention of doing RCE and we later 538 // changed our minds, we got no pre-loop. Either we need to 539 // make a new pre-loop, or we gotta disallow RCE. 540 if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now. 541 Node *trip_counter = cl->phi(); 542 543 // Check loop body for tests of trip-counter plus loop-invariant vs 544 // loop-invariant. 545 for( uint i = 0; i < _body.size(); i++ ) { 546 Node *iff = _body[i]; 547 if( iff->Opcode() == Op_If ) { // Test? 548 549 // Comparing trip+off vs limit 550 Node *bol = iff->in(1); 551 if( bol->req() != 2 ) continue; // dead constant test 552 if (!bol->is_Bool()) { 553 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only"); 554 continue; 555 } 556 Node *cmp = bol->in(1); 557 558 Node *rc_exp = cmp->in(1); 559 Node *limit = cmp->in(2); 560 561 Node *limit_c = phase->get_ctrl(limit); 562 if( limit_c == phase->C->top() ) 563 return false; // Found dead test on live IF? No RCE! 564 if( is_member(phase->get_loop(limit_c) ) ) { 565 // Compare might have operands swapped; commute them 566 rc_exp = cmp->in(2); 567 limit = cmp->in(1); 568 limit_c = phase->get_ctrl(limit); 569 if( is_member(phase->get_loop(limit_c) ) ) 570 continue; // Both inputs are loop varying; cannot RCE 571 } 572 573 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) { 574 continue; 575 } 576 // Yeah! Found a test like 'trip+off vs limit' 577 // Test is an IfNode, has 2 projections. If BOTH are in the loop 578 // we need loop unswitching instead of iteration splitting. 579 if( is_loop_exit(iff) ) 580 return true; // Found reason to split iterations 581 } // End of is IF 582 } 583 584 return false; 585 } 586 587 //------------------------------policy_peel_only------------------------------- 588 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful 589 // for unrolling loops with NO array accesses. 590 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const { 591 592 for( uint i = 0; i < _body.size(); i++ ) 593 if( _body[i]->is_Mem() ) 594 return false; 595 596 // No memory accesses at all! 597 return true; 598 } 599 600 //------------------------------clone_up_backedge_goo-------------------------- 601 // If Node n lives in the back_ctrl block and cannot float, we clone a private 602 // version of n in preheader_ctrl block and return that, otherwise return n. 603 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) { 604 if( get_ctrl(n) != back_ctrl ) return n; 605 606 Node *x = NULL; // If required, a clone of 'n' 607 // Check for 'n' being pinned in the backedge. 608 if( n->in(0) && n->in(0) == back_ctrl ) { 609 x = n->clone(); // Clone a copy of 'n' to preheader 610 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader 611 } 612 613 // Recursive fixup any other input edges into x. 614 // If there are no changes we can just return 'n', otherwise 615 // we need to clone a private copy and change it. 616 for( uint i = 1; i < n->req(); i++ ) { 617 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) ); 618 if( g != n->in(i) ) { 619 if( !x ) 620 x = n->clone(); 621 x->set_req(i, g); 622 } 623 } 624 if( x ) { // x can legally float to pre-header location 625 register_new_node( x, preheader_ctrl ); 626 return x; 627 } else { // raise n to cover LCA of uses 628 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); 629 } 630 return n; 631 } 632 633 //------------------------------insert_pre_post_loops-------------------------- 634 // Insert pre and post loops. If peel_only is set, the pre-loop can not have 635 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no 636 // alignment. Useful to unroll loops that do no array accesses. 637 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { 638 639 C->set_major_progress(); 640 641 // Find common pieces of the loop being guarded with pre & post loops 642 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); 643 assert( main_head->is_normal_loop(), "" ); 644 CountedLoopEndNode *main_end = main_head->loopexit(); 645 assert( main_end->outcnt() == 2, "1 true, 1 false path only" ); 646 uint dd_main_head = dom_depth(main_head); 647 uint max = main_head->outcnt(); 648 649 Node *pre_header= main_head->in(LoopNode::EntryControl); 650 Node *init = main_head->init_trip(); 651 Node *incr = main_end ->incr(); 652 Node *limit = main_end ->limit(); 653 Node *stride = main_end ->stride(); 654 Node *cmp = main_end ->cmp_node(); 655 BoolTest::mask b_test = main_end->test_trip(); 656 657 // Need only 1 user of 'bol' because I will be hacking the loop bounds. 658 Node *bol = main_end->in(CountedLoopEndNode::TestValue); 659 if( bol->outcnt() != 1 ) { 660 bol = bol->clone(); 661 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl)); 662 _igvn.hash_delete(main_end); 663 main_end->set_req(CountedLoopEndNode::TestValue, bol); 664 } 665 // Need only 1 user of 'cmp' because I will be hacking the loop bounds. 666 if( cmp->outcnt() != 1 ) { 667 cmp = cmp->clone(); 668 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl)); 669 _igvn.hash_delete(bol); 670 bol->set_req(1, cmp); 671 } 672 673 //------------------------------ 674 // Step A: Create Post-Loop. 675 Node* main_exit = main_end->proj_out(false); 676 assert( main_exit->Opcode() == Op_IfFalse, "" ); 677 int dd_main_exit = dom_depth(main_exit); 678 679 // Step A1: Clone the loop body. The clone becomes the post-loop. The main 680 // loop pre-header illegally has 2 control users (old & new loops). 681 clone_loop( loop, old_new, dd_main_exit ); 682 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" ); 683 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop(); 684 post_head->set_post_loop(main_head); 685 686 // Reduce the post-loop trip count. 687 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 688 post_end->_prob = PROB_FAIR; 689 690 // Build the main-loop normal exit. 691 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end); 692 _igvn.register_new_node_with_optimizer( new_main_exit ); 693 set_idom(new_main_exit, main_end, dd_main_exit ); 694 set_loop(new_main_exit, loop->_parent); 695 696 // Step A2: Build a zero-trip guard for the post-loop. After leaving the 697 // main-loop, the post-loop may not execute at all. We 'opaque' the incr 698 // (the main-loop trip-counter exit value) because we will be changing 699 // the exit value (via unrolling) so we cannot constant-fold away the zero 700 // trip guard until all unrolling is done. 701 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr); 702 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit ); 703 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test ); 704 register_new_node( zer_opaq, new_main_exit ); 705 register_new_node( zer_cmp , new_main_exit ); 706 register_new_node( zer_bol , new_main_exit ); 707 708 // Build the IfNode 709 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN ); 710 _igvn.register_new_node_with_optimizer( zer_iff ); 711 set_idom(zer_iff, new_main_exit, dd_main_exit); 712 set_loop(zer_iff, loop->_parent); 713 714 // Plug in the false-path, taken if we need to skip post-loop 715 _igvn.hash_delete( main_exit ); 716 main_exit->set_req(0, zer_iff); 717 _igvn._worklist.push(main_exit); 718 set_idom(main_exit, zer_iff, dd_main_exit); 719 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit); 720 // Make the true-path, must enter the post loop 721 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff ); 722 _igvn.register_new_node_with_optimizer( zer_taken ); 723 set_idom(zer_taken, zer_iff, dd_main_exit); 724 set_loop(zer_taken, loop->_parent); 725 // Plug in the true path 726 _igvn.hash_delete( post_head ); 727 post_head->set_req(LoopNode::EntryControl, zer_taken); 728 set_idom(post_head, zer_taken, dd_main_exit); 729 730 // Step A3: Make the fall-in values to the post-loop come from the 731 // fall-out values of the main-loop. 732 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) { 733 Node* main_phi = main_head->fast_out(i); 734 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) { 735 Node *post_phi = old_new[main_phi->_idx]; 736 Node *fallmain = clone_up_backedge_goo(main_head->back_control(), 737 post_head->init_control(), 738 main_phi->in(LoopNode::LoopBackControl)); 739 _igvn.hash_delete(post_phi); 740 post_phi->set_req( LoopNode::EntryControl, fallmain ); 741 } 742 } 743 744 // Update local caches for next stanza 745 main_exit = new_main_exit; 746 747 748 //------------------------------ 749 // Step B: Create Pre-Loop. 750 751 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main 752 // loop pre-header illegally has 2 control users (old & new loops). 753 clone_loop( loop, old_new, dd_main_head ); 754 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop(); 755 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); 756 pre_head->set_pre_loop(main_head); 757 Node *pre_incr = old_new[incr->_idx]; 758 759 // Reduce the pre-loop trip count. 760 pre_end->_prob = PROB_FAIR; 761 762 // Find the pre-loop normal exit. 763 Node* pre_exit = pre_end->proj_out(false); 764 assert( pre_exit->Opcode() == Op_IfFalse, "" ); 765 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end); 766 _igvn.register_new_node_with_optimizer( new_pre_exit ); 767 set_idom(new_pre_exit, pre_end, dd_main_head); 768 set_loop(new_pre_exit, loop->_parent); 769 770 // Step B2: Build a zero-trip guard for the main-loop. After leaving the 771 // pre-loop, the main-loop may not execute at all. Later in life this 772 // zero-trip guard will become the minimum-trip guard when we unroll 773 // the main-loop. 774 Node *min_opaq = new (C, 2) Opaque1Node(C, limit); 775 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq ); 776 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test ); 777 register_new_node( min_opaq, new_pre_exit ); 778 register_new_node( min_cmp , new_pre_exit ); 779 register_new_node( min_bol , new_pre_exit ); 780 781 // Build the IfNode (assume the main-loop is executed always). 782 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN ); 783 _igvn.register_new_node_with_optimizer( min_iff ); 784 set_idom(min_iff, new_pre_exit, dd_main_head); 785 set_loop(min_iff, loop->_parent); 786 787 // Plug in the false-path, taken if we need to skip main-loop 788 _igvn.hash_delete( pre_exit ); 789 pre_exit->set_req(0, min_iff); 790 set_idom(pre_exit, min_iff, dd_main_head); 791 set_idom(pre_exit->unique_out(), min_iff, dd_main_head); 792 // Make the true-path, must enter the main loop 793 Node *min_taken = new (C, 1) IfTrueNode( min_iff ); 794 _igvn.register_new_node_with_optimizer( min_taken ); 795 set_idom(min_taken, min_iff, dd_main_head); 796 set_loop(min_taken, loop->_parent); 797 // Plug in the true path 798 _igvn.hash_delete( main_head ); 799 main_head->set_req(LoopNode::EntryControl, min_taken); 800 set_idom(main_head, min_taken, dd_main_head); 801 802 // Step B3: Make the fall-in values to the main-loop come from the 803 // fall-out values of the pre-loop. 804 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) { 805 Node* main_phi = main_head->fast_out(i2); 806 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) { 807 Node *pre_phi = old_new[main_phi->_idx]; 808 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(), 809 main_head->init_control(), 810 pre_phi->in(LoopNode::LoopBackControl)); 811 _igvn.hash_delete(main_phi); 812 main_phi->set_req( LoopNode::EntryControl, fallpre ); 813 } 814 } 815 816 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). 817 // RCE and alignment may change this later. 818 Node *cmp_end = pre_end->cmp_node(); 819 assert( cmp_end->in(2) == limit, "" ); 820 Node *pre_limit = new (C, 3) AddINode( init, stride ); 821 822 // Save the original loop limit in this Opaque1 node for 823 // use by range check elimination. 824 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit); 825 826 register_new_node( pre_limit, pre_head->in(0) ); 827 register_new_node( pre_opaq , pre_head->in(0) ); 828 829 // Since no other users of pre-loop compare, I can hack limit directly 830 assert( cmp_end->outcnt() == 1, "no other users" ); 831 _igvn.hash_delete(cmp_end); 832 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq); 833 834 // Special case for not-equal loop bounds: 835 // Change pre loop test, main loop test, and the 836 // main loop guard test to use lt or gt depending on stride 837 // direction: 838 // positive stride use < 839 // negative stride use > 840 841 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) { 842 843 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt; 844 // Modify pre loop end condition 845 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 846 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test); 847 register_new_node( new_bol0, pre_head->in(0) ); 848 _igvn.hash_delete(pre_end); 849 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0); 850 // Modify main loop guard condition 851 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay"); 852 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test); 853 register_new_node( new_bol1, new_pre_exit ); 854 _igvn.hash_delete(min_iff); 855 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1); 856 // Modify main loop end condition 857 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool(); 858 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test); 859 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) ); 860 _igvn.hash_delete(main_end); 861 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2); 862 } 863 864 // Flag main loop 865 main_head->set_main_loop(); 866 if( peel_only ) main_head->set_main_no_pre_loop(); 867 868 // It's difficult to be precise about the trip-counts 869 // for the pre/post loops. They are usually very short, 870 // so guess that 4 trips is a reasonable value. 871 post_head->set_profile_trip_cnt(4.0); 872 pre_head->set_profile_trip_cnt(4.0); 873 874 // Now force out all loop-invariant dominating tests. The optimizer 875 // finds some, but we _know_ they are all useless. 876 peeled_dom_test_elim(loop,old_new); 877 } 878 879 //------------------------------is_invariant----------------------------- 880 // Return true if n is invariant 881 bool IdealLoopTree::is_invariant(Node* n) const { 882 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n; 883 if (n_c->is_top()) return false; 884 return !is_member(_phase->get_loop(n_c)); 885 } 886 887 888 //------------------------------do_unroll-------------------------------------- 889 // Unroll the loop body one step - make each trip do 2 iterations. 890 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) { 891 assert( LoopUnrollLimit, "" ); 892 #ifndef PRODUCT 893 if( PrintOpto && VerifyLoopOptimizations ) { 894 tty->print("Unrolling "); 895 loop->dump_head(); 896 } 897 #endif 898 CountedLoopNode *loop_head = loop->_head->as_CountedLoop(); 899 CountedLoopEndNode *loop_end = loop_head->loopexit(); 900 assert( loop_end, "" ); 901 902 // Remember loop node count before unrolling to detect 903 // if rounds of unroll,optimize are making progress 904 loop_head->set_node_count_before_unroll(loop->_body.size()); 905 906 Node *ctrl = loop_head->in(LoopNode::EntryControl); 907 Node *limit = loop_head->limit(); 908 Node *init = loop_head->init_trip(); 909 Node *strid = loop_head->stride(); 910 911 Node *opaq = NULL; 912 if( adjust_min_trip ) { // If not maximally unrolling, need adjustment 913 assert( loop_head->is_main_loop(), "" ); 914 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 915 Node *iff = ctrl->in(0); 916 assert( iff->Opcode() == Op_If, "" ); 917 Node *bol = iff->in(1); 918 assert( bol->Opcode() == Op_Bool, "" ); 919 Node *cmp = bol->in(1); 920 assert( cmp->Opcode() == Op_CmpI, "" ); 921 opaq = cmp->in(2); 922 // Occasionally it's possible for a pre-loop Opaque1 node to be 923 // optimized away and then another round of loop opts attempted. 924 // We can not optimize this particular loop in that case. 925 if( opaq->Opcode() != Op_Opaque1 ) 926 return; // Cannot find pre-loop! Bail out! 927 } 928 929 C->set_major_progress(); 930 931 // Adjust max trip count. The trip count is intentionally rounded 932 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, 933 // the main, unrolled, part of the loop will never execute as it is protected 934 // by the min-trip test. See bug 4834191 for a case where we over-unrolled 935 // and later determined that part of the unrolled loop was dead. 936 loop_head->set_trip_count(loop_head->trip_count() / 2); 937 938 // Double the count of original iterations in the unrolled loop body. 939 loop_head->double_unrolled_count(); 940 941 // ----------- 942 // Step 2: Cut back the trip counter for an unroll amount of 2. 943 // Loop will normally trip (limit - init)/stride_con. Since it's a 944 // CountedLoop this is exact (stride divides limit-init exactly). 945 // We are going to double the loop body, so we want to knock off any 946 // odd iteration: (trip_cnt & ~1). Then back compute a new limit. 947 Node *span = new (C, 3) SubINode( limit, init ); 948 register_new_node( span, ctrl ); 949 Node *trip = new (C, 3) DivINode( 0, span, strid ); 950 register_new_node( trip, ctrl ); 951 Node *mtwo = _igvn.intcon(-2); 952 set_ctrl(mtwo, C->root()); 953 Node *rond = new (C, 3) AndINode( trip, mtwo ); 954 register_new_node( rond, ctrl ); 955 Node *spn2 = new (C, 3) MulINode( rond, strid ); 956 register_new_node( spn2, ctrl ); 957 Node *lim2 = new (C, 3) AddINode( spn2, init ); 958 register_new_node( lim2, ctrl ); 959 960 // Hammer in the new limit 961 Node *ctrl2 = loop_end->in(0); 962 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 ); 963 register_new_node( cmp2, ctrl2 ); 964 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() ); 965 register_new_node( bol2, ctrl2 ); 966 _igvn.hash_delete(loop_end); 967 loop_end->set_req(CountedLoopEndNode::TestValue, bol2); 968 969 // Step 3: Find the min-trip test guaranteed before a 'main' loop. 970 // Make it a 1-trip test (means at least 2 trips). 971 if( adjust_min_trip ) { 972 // Guard test uses an 'opaque' node which is not shared. Hence I 973 // can edit it's inputs directly. Hammer in the new limit for the 974 // minimum-trip guard. 975 assert( opaq->outcnt() == 1, "" ); 976 _igvn.hash_delete(opaq); 977 opaq->set_req(1, lim2); 978 } 979 980 // --------- 981 // Step 4: Clone the loop body. Move it inside the loop. This loop body 982 // represents the odd iterations; since the loop trips an even number of 983 // times its backedge is never taken. Kill the backedge. 984 uint dd = dom_depth(loop_head); 985 clone_loop( loop, old_new, dd ); 986 987 // Make backedges of the clone equal to backedges of the original. 988 // Make the fall-in from the original come from the fall-out of the clone. 989 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) { 990 Node* phi = loop_head->fast_out(j); 991 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) { 992 Node *newphi = old_new[phi->_idx]; 993 _igvn.hash_delete( phi ); 994 _igvn.hash_delete( newphi ); 995 996 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl)); 997 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl)); 998 phi ->set_req(LoopNode::LoopBackControl, C->top()); 999 } 1000 } 1001 Node *clone_head = old_new[loop_head->_idx]; 1002 _igvn.hash_delete( clone_head ); 1003 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl)); 1004 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl)); 1005 loop_head ->set_req(LoopNode::LoopBackControl, C->top()); 1006 loop->_head = clone_head; // New loop header 1007 1008 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd); 1009 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd); 1010 1011 // Kill the clone's backedge 1012 Node *newcle = old_new[loop_end->_idx]; 1013 _igvn.hash_delete( newcle ); 1014 Node *one = _igvn.intcon(1); 1015 set_ctrl(one, C->root()); 1016 newcle->set_req(1, one); 1017 // Force clone into same loop body 1018 uint max = loop->_body.size(); 1019 for( uint k = 0; k < max; k++ ) { 1020 Node *old = loop->_body.at(k); 1021 Node *nnn = old_new[old->_idx]; 1022 loop->_body.push(nnn); 1023 if (!has_ctrl(old)) 1024 set_loop(nnn, loop); 1025 } 1026 1027 loop->record_for_igvn(); 1028 } 1029 1030 //------------------------------do_maximally_unroll---------------------------- 1031 1032 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) { 1033 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1034 assert( cl->trip_count() > 0, ""); 1035 1036 // If loop is tripping an odd number of times, peel odd iteration 1037 if( (cl->trip_count() & 1) == 1 ) { 1038 do_peeling( loop, old_new ); 1039 } 1040 1041 // Now its tripping an even number of times remaining. Double loop body. 1042 // Do not adjust pre-guards; they are not needed and do not exist. 1043 if( cl->trip_count() > 0 ) { 1044 do_unroll( loop, old_new, false ); 1045 } 1046 } 1047 1048 //------------------------------dominates_backedge--------------------------------- 1049 // Returns true if ctrl is executed on every complete iteration 1050 bool IdealLoopTree::dominates_backedge(Node* ctrl) { 1051 assert(ctrl->is_CFG(), "must be control"); 1052 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl); 1053 return _phase->dom_lca_internal(ctrl, backedge) == ctrl; 1054 } 1055 1056 //------------------------------add_constraint--------------------------------- 1057 // Constrain the main loop iterations so the condition: 1058 // scale_con * I + offset < limit 1059 // always holds true. That is, either increase the number of iterations in 1060 // the pre-loop or the post-loop until the condition holds true in the main 1061 // loop. Stride, scale, offset and limit are all loop invariant. Further, 1062 // stride and scale are constants (offset and limit often are). 1063 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) { 1064 1065 // Compute "I :: (limit-offset)/scale_con" 1066 Node *con = new (C, 3) SubINode( limit, offset ); 1067 register_new_node( con, pre_ctrl ); 1068 Node *scale = _igvn.intcon(scale_con); 1069 set_ctrl(scale, C->root()); 1070 Node *X = new (C, 3) DivINode( 0, con, scale ); 1071 register_new_node( X, pre_ctrl ); 1072 1073 // For positive stride, the pre-loop limit always uses a MAX function 1074 // and the main loop a MIN function. For negative stride these are 1075 // reversed. 1076 1077 // Also for positive stride*scale the affine function is increasing, so the 1078 // pre-loop must check for underflow and the post-loop for overflow. 1079 // Negative stride*scale reverses this; pre-loop checks for overflow and 1080 // post-loop for underflow. 1081 if( stride_con*scale_con > 0 ) { 1082 // Compute I < (limit-offset)/scale_con 1083 // Adjust main-loop last iteration to be MIN/MAX(main_loop,X) 1084 *main_limit = (stride_con > 0) 1085 ? (Node*)(new (C, 3) MinINode( *main_limit, X )) 1086 : (Node*)(new (C, 3) MaxINode( *main_limit, X )); 1087 register_new_node( *main_limit, pre_ctrl ); 1088 1089 } else { 1090 // Compute (limit-offset)/scale_con + SGN(-scale_con) <= I 1091 // Add the negation of the main-loop constraint to the pre-loop. 1092 // See footnote [++] below for a derivation of the limit expression. 1093 Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1); 1094 set_ctrl(incr, C->root()); 1095 Node *adj = new (C, 3) AddINode( X, incr ); 1096 register_new_node( adj, pre_ctrl ); 1097 *pre_limit = (scale_con > 0) 1098 ? (Node*)new (C, 3) MinINode( *pre_limit, adj ) 1099 : (Node*)new (C, 3) MaxINode( *pre_limit, adj ); 1100 register_new_node( *pre_limit, pre_ctrl ); 1101 1102 // [++] Here's the algebra that justifies the pre-loop limit expression: 1103 // 1104 // NOT( scale_con * I + offset < limit ) 1105 // == 1106 // scale_con * I + offset >= limit 1107 // == 1108 // SGN(scale_con) * I >= (limit-offset)/|scale_con| 1109 // == 1110 // (limit-offset)/|scale_con| <= I * SGN(scale_con) 1111 // == 1112 // (limit-offset)/|scale_con|-1 < I * SGN(scale_con) 1113 // == 1114 // ( if (scale_con > 0) /*common case*/ 1115 // (limit-offset)/scale_con - 1 < I 1116 // else 1117 // (limit-offset)/scale_con + 1 > I 1118 // ) 1119 // ( if (scale_con > 0) /*common case*/ 1120 // (limit-offset)/scale_con + SGN(-scale_con) < I 1121 // else 1122 // (limit-offset)/scale_con + SGN(-scale_con) > I 1123 } 1124 } 1125 1126 1127 //------------------------------is_scaled_iv--------------------------------- 1128 // Return true if exp is a constant times an induction var 1129 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) { 1130 if (exp == iv) { 1131 if (p_scale != NULL) { 1132 *p_scale = 1; 1133 } 1134 return true; 1135 } 1136 int opc = exp->Opcode(); 1137 if (opc == Op_MulI) { 1138 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1139 if (p_scale != NULL) { 1140 *p_scale = exp->in(2)->get_int(); 1141 } 1142 return true; 1143 } 1144 if (exp->in(2) == iv && exp->in(1)->is_Con()) { 1145 if (p_scale != NULL) { 1146 *p_scale = exp->in(1)->get_int(); 1147 } 1148 return true; 1149 } 1150 } else if (opc == Op_LShiftI) { 1151 if (exp->in(1) == iv && exp->in(2)->is_Con()) { 1152 if (p_scale != NULL) { 1153 *p_scale = 1 << exp->in(2)->get_int(); 1154 } 1155 return true; 1156 } 1157 } 1158 return false; 1159 } 1160 1161 //-----------------------------is_scaled_iv_plus_offset------------------------------ 1162 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2) 1163 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) { 1164 if (is_scaled_iv(exp, iv, p_scale)) { 1165 if (p_offset != NULL) { 1166 Node *zero = _igvn.intcon(0); 1167 set_ctrl(zero, C->root()); 1168 *p_offset = zero; 1169 } 1170 return true; 1171 } 1172 int opc = exp->Opcode(); 1173 if (opc == Op_AddI) { 1174 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1175 if (p_offset != NULL) { 1176 *p_offset = exp->in(2); 1177 } 1178 return true; 1179 } 1180 if (exp->in(2)->is_Con()) { 1181 Node* offset2 = NULL; 1182 if (depth < 2 && 1183 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale, 1184 p_offset != NULL ? &offset2 : NULL, depth+1)) { 1185 if (p_offset != NULL) { 1186 Node *ctrl_off2 = get_ctrl(offset2); 1187 Node* offset = new (C, 3) AddINode(offset2, exp->in(2)); 1188 register_new_node(offset, ctrl_off2); 1189 *p_offset = offset; 1190 } 1191 return true; 1192 } 1193 } 1194 } else if (opc == Op_SubI) { 1195 if (is_scaled_iv(exp->in(1), iv, p_scale)) { 1196 if (p_offset != NULL) { 1197 Node *zero = _igvn.intcon(0); 1198 set_ctrl(zero, C->root()); 1199 Node *ctrl_off = get_ctrl(exp->in(2)); 1200 Node* offset = new (C, 3) SubINode(zero, exp->in(2)); 1201 register_new_node(offset, ctrl_off); 1202 *p_offset = offset; 1203 } 1204 return true; 1205 } 1206 if (is_scaled_iv(exp->in(2), iv, p_scale)) { 1207 if (p_offset != NULL) { 1208 *p_scale *= -1; 1209 *p_offset = exp->in(1); 1210 } 1211 return true; 1212 } 1213 } 1214 return false; 1215 } 1216 1217 //------------------------------do_range_check--------------------------------- 1218 // Eliminate range-checks and other trip-counter vs loop-invariant tests. 1219 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) { 1220 #ifndef PRODUCT 1221 if( PrintOpto && VerifyLoopOptimizations ) { 1222 tty->print("Range Check Elimination "); 1223 loop->dump_head(); 1224 } 1225 #endif 1226 assert( RangeCheckElimination, "" ); 1227 CountedLoopNode *cl = loop->_head->as_CountedLoop(); 1228 assert( cl->is_main_loop(), "" ); 1229 1230 // Find the trip counter; we are iteration splitting based on it 1231 Node *trip_counter = cl->phi(); 1232 // Find the main loop limit; we will trim it's iterations 1233 // to not ever trip end tests 1234 Node *main_limit = cl->limit(); 1235 // Find the pre-loop limit; we will expand it's iterations to 1236 // not ever trip low tests. 1237 Node *ctrl = cl->in(LoopNode::EntryControl); 1238 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); 1239 Node *iffm = ctrl->in(0); 1240 assert( iffm->Opcode() == Op_If, "" ); 1241 Node *p_f = iffm->in(0); 1242 assert( p_f->Opcode() == Op_IfFalse, "" ); 1243 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); 1244 assert( pre_end->loopnode()->is_pre_loop(), "" ); 1245 Node *pre_opaq1 = pre_end->limit(); 1246 // Occasionally it's possible for a pre-loop Opaque1 node to be 1247 // optimized away and then another round of loop opts attempted. 1248 // We can not optimize this particular loop in that case. 1249 if( pre_opaq1->Opcode() != Op_Opaque1 ) 1250 return; 1251 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1; 1252 Node *pre_limit = pre_opaq->in(1); 1253 1254 // Where do we put new limit calculations 1255 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl); 1256 1257 // Ensure the original loop limit is available from the 1258 // pre-loop Opaque1 node. 1259 Node *orig_limit = pre_opaq->original_loop_limit(); 1260 if( orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP ) 1261 return; 1262 1263 // Need to find the main-loop zero-trip guard 1264 Node *bolzm = iffm->in(1); 1265 assert( bolzm->Opcode() == Op_Bool, "" ); 1266 Node *cmpzm = bolzm->in(1); 1267 assert( cmpzm->is_Cmp(), "" ); 1268 Node *opqzm = cmpzm->in(2); 1269 if( opqzm->Opcode() != Op_Opaque1 ) 1270 return; 1271 assert( opqzm->in(1) == main_limit, "do not understand situation" ); 1272 1273 // Must know if its a count-up or count-down loop 1274 1275 // protect against stride not being a constant 1276 if ( !cl->stride_is_con() ) { 1277 return; 1278 } 1279 int stride_con = cl->stride_con(); 1280 Node *zero = _igvn.intcon(0); 1281 Node *one = _igvn.intcon(1); 1282 set_ctrl(zero, C->root()); 1283 set_ctrl(one, C->root()); 1284 1285 // Range checks that do not dominate the loop backedge (ie. 1286 // conditionally executed) can lengthen the pre loop limit beyond 1287 // the original loop limit. To prevent this, the pre limit is 1288 // (for stride > 0) MINed with the original loop limit (MAXed 1289 // stride < 0) when some range_check (rc) is conditionally 1290 // executed. 1291 bool conditional_rc = false; 1292 1293 // Check loop body for tests of trip-counter plus loop-invariant vs 1294 // loop-invariant. 1295 for( uint i = 0; i < loop->_body.size(); i++ ) { 1296 Node *iff = loop->_body[i]; 1297 if( iff->Opcode() == Op_If ) { // Test? 1298 1299 // Test is an IfNode, has 2 projections. If BOTH are in the loop 1300 // we need loop unswitching instead of iteration splitting. 1301 Node *exit = loop->is_loop_exit(iff); 1302 if( !exit ) continue; 1303 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0; 1304 1305 // Get boolean condition to test 1306 Node *i1 = iff->in(1); 1307 if( !i1->is_Bool() ) continue; 1308 BoolNode *bol = i1->as_Bool(); 1309 BoolTest b_test = bol->_test; 1310 // Flip sense of test if exit condition is flipped 1311 if( flip ) 1312 b_test = b_test.negate(); 1313 1314 // Get compare 1315 Node *cmp = bol->in(1); 1316 1317 // Look for trip_counter + offset vs limit 1318 Node *rc_exp = cmp->in(1); 1319 Node *limit = cmp->in(2); 1320 jint scale_con= 1; // Assume trip counter not scaled 1321 1322 Node *limit_c = get_ctrl(limit); 1323 if( loop->is_member(get_loop(limit_c) ) ) { 1324 // Compare might have operands swapped; commute them 1325 b_test = b_test.commute(); 1326 rc_exp = cmp->in(2); 1327 limit = cmp->in(1); 1328 limit_c = get_ctrl(limit); 1329 if( loop->is_member(get_loop(limit_c) ) ) 1330 continue; // Both inputs are loop varying; cannot RCE 1331 } 1332 // Here we know 'limit' is loop invariant 1333 1334 // 'limit' maybe pinned below the zero trip test (probably from a 1335 // previous round of rce), in which case, it can't be used in the 1336 // zero trip test expression which must occur before the zero test's if. 1337 if( limit_c == ctrl ) { 1338 continue; // Don't rce this check but continue looking for other candidates. 1339 } 1340 1341 // Check for scaled induction variable plus an offset 1342 Node *offset = NULL; 1343 1344 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) { 1345 continue; 1346 } 1347 1348 Node *offset_c = get_ctrl(offset); 1349 if( loop->is_member( get_loop(offset_c) ) ) 1350 continue; // Offset is not really loop invariant 1351 // Here we know 'offset' is loop invariant. 1352 1353 // As above for the 'limit', the 'offset' maybe pinned below the 1354 // zero trip test. 1355 if( offset_c == ctrl ) { 1356 continue; // Don't rce this check but continue looking for other candidates. 1357 } 1358 1359 // At this point we have the expression as: 1360 // scale_con * trip_counter + offset :: limit 1361 // where scale_con, offset and limit are loop invariant. Trip_counter 1362 // monotonically increases by stride_con, a constant. Both (or either) 1363 // stride_con and scale_con can be negative which will flip about the 1364 // sense of the test. 1365 1366 // Adjust pre and main loop limits to guard the correct iteration set 1367 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests 1368 if( b_test._test == BoolTest::lt ) { // Range checks always use lt 1369 // The overflow limit: scale*I+offset < limit 1370 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit ); 1371 // The underflow limit: 0 <= scale*I+offset. 1372 // Some math yields: -scale*I-(offset+1) < 0 1373 Node *plus_one = new (C, 3) AddINode( offset, one ); 1374 register_new_node( plus_one, pre_ctrl ); 1375 Node *neg_offset = new (C, 3) SubINode( zero, plus_one ); 1376 register_new_node( neg_offset, pre_ctrl ); 1377 add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit ); 1378 if (!conditional_rc) { 1379 conditional_rc = !loop->dominates_backedge(iff); 1380 } 1381 } else { 1382 #ifndef PRODUCT 1383 if( PrintOpto ) 1384 tty->print_cr("missed RCE opportunity"); 1385 #endif 1386 continue; // In release mode, ignore it 1387 } 1388 } else { // Otherwise work on normal compares 1389 switch( b_test._test ) { 1390 case BoolTest::ge: // Convert X >= Y to -X <= -Y 1391 scale_con = -scale_con; 1392 offset = new (C, 3) SubINode( zero, offset ); 1393 register_new_node( offset, pre_ctrl ); 1394 limit = new (C, 3) SubINode( zero, limit ); 1395 register_new_node( limit, pre_ctrl ); 1396 // Fall into LE case 1397 case BoolTest::le: // Convert X <= Y to X < Y+1 1398 limit = new (C, 3) AddINode( limit, one ); 1399 register_new_node( limit, pre_ctrl ); 1400 // Fall into LT case 1401 case BoolTest::lt: 1402 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit ); 1403 if (!conditional_rc) { 1404 conditional_rc = !loop->dominates_backedge(iff); 1405 } 1406 break; 1407 default: 1408 #ifndef PRODUCT 1409 if( PrintOpto ) 1410 tty->print_cr("missed RCE opportunity"); 1411 #endif 1412 continue; // Unhandled case 1413 } 1414 } 1415 1416 // Kill the eliminated test 1417 C->set_major_progress(); 1418 Node *kill_con = _igvn.intcon( 1-flip ); 1419 set_ctrl(kill_con, C->root()); 1420 _igvn.hash_delete(iff); 1421 iff->set_req(1, kill_con); 1422 _igvn._worklist.push(iff); 1423 // Find surviving projection 1424 assert(iff->is_If(), ""); 1425 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip); 1426 // Find loads off the surviving projection; remove their control edge 1427 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { 1428 Node* cd = dp->fast_out(i); // Control-dependent node 1429 if( cd->is_Load() ) { // Loads can now float around in the loop 1430 _igvn.hash_delete(cd); 1431 // Allow the load to float around in the loop, or before it 1432 // but NOT before the pre-loop. 1433 cd->set_req(0, ctrl); // ctrl, not NULL 1434 _igvn._worklist.push(cd); 1435 --i; 1436 --imax; 1437 } 1438 } 1439 1440 } // End of is IF 1441 1442 } 1443 1444 // Update loop limits 1445 if (conditional_rc) { 1446 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit) 1447 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit); 1448 register_new_node(pre_limit, pre_ctrl); 1449 } 1450 _igvn.hash_delete(pre_opaq); 1451 pre_opaq->set_req(1, pre_limit); 1452 1453 // Note:: we are making the main loop limit no longer precise; 1454 // need to round up based on stride. 1455 if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case 1456 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init 1457 // Hopefully, compiler will optimize for powers of 2. 1458 Node *ctrl = get_ctrl(main_limit); 1459 Node *stride = cl->stride(); 1460 Node *init = cl->init_trip(); 1461 Node *span = new (C, 3) SubINode(main_limit,init); 1462 register_new_node(span,ctrl); 1463 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1)); 1464 Node *add = new (C, 3) AddINode(span,rndup); 1465 register_new_node(add,ctrl); 1466 Node *div = new (C, 3) DivINode(0,add,stride); 1467 register_new_node(div,ctrl); 1468 Node *mul = new (C, 3) MulINode(div,stride); 1469 register_new_node(mul,ctrl); 1470 Node *newlim = new (C, 3) AddINode(mul,init); 1471 register_new_node(newlim,ctrl); 1472 main_limit = newlim; 1473 } 1474 1475 Node *main_cle = cl->loopexit(); 1476 Node *main_bol = main_cle->in(1); 1477 // Hacking loop bounds; need private copies of exit test 1478 if( main_bol->outcnt() > 1 ) {// BoolNode shared? 1479 _igvn.hash_delete(main_cle); 1480 main_bol = main_bol->clone();// Clone a private BoolNode 1481 register_new_node( main_bol, main_cle->in(0) ); 1482 main_cle->set_req(1,main_bol); 1483 } 1484 Node *main_cmp = main_bol->in(1); 1485 if( main_cmp->outcnt() > 1 ) { // CmpNode shared? 1486 _igvn.hash_delete(main_bol); 1487 main_cmp = main_cmp->clone();// Clone a private CmpNode 1488 register_new_node( main_cmp, main_cle->in(0) ); 1489 main_bol->set_req(1,main_cmp); 1490 } 1491 // Hack the now-private loop bounds 1492 _igvn.hash_delete(main_cmp); 1493 main_cmp->set_req(2, main_limit); 1494 _igvn._worklist.push(main_cmp); 1495 // The OpaqueNode is unshared by design 1496 _igvn.hash_delete(opqzm); 1497 assert( opqzm->outcnt() == 1, "cannot hack shared node" ); 1498 opqzm->set_req(1,main_limit); 1499 _igvn._worklist.push(opqzm); 1500 } 1501 1502 //------------------------------DCE_loop_body---------------------------------- 1503 // Remove simplistic dead code from loop body 1504 void IdealLoopTree::DCE_loop_body() { 1505 for( uint i = 0; i < _body.size(); i++ ) 1506 if( _body.at(i)->outcnt() == 0 ) 1507 _body.map( i--, _body.pop() ); 1508 } 1509 1510 1511 //------------------------------adjust_loop_exit_prob-------------------------- 1512 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage. 1513 // Replace with a 1-in-10 exit guess. 1514 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) { 1515 Node *test = tail(); 1516 while( test != _head ) { 1517 uint top = test->Opcode(); 1518 if( top == Op_IfTrue || top == Op_IfFalse ) { 1519 int test_con = ((ProjNode*)test)->_con; 1520 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity"); 1521 IfNode *iff = test->in(0)->as_If(); 1522 if( iff->outcnt() == 2 ) { // Ignore dead tests 1523 Node *bol = iff->in(1); 1524 if( bol && bol->req() > 1 && bol->in(1) && 1525 ((bol->in(1)->Opcode() == Op_StorePConditional ) || 1526 (bol->in(1)->Opcode() == Op_StoreIConditional ) || 1527 (bol->in(1)->Opcode() == Op_StoreLConditional ) || 1528 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || 1529 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || 1530 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || 1531 (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) 1532 return; // Allocation loops RARELY take backedge 1533 // Find the OTHER exit path from the IF 1534 Node* ex = iff->proj_out(1-test_con); 1535 float p = iff->_prob; 1536 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) { 1537 if( top == Op_IfTrue ) { 1538 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) { 1539 iff->_prob = PROB_STATIC_FREQUENT; 1540 } 1541 } else { 1542 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) { 1543 iff->_prob = PROB_STATIC_INFREQUENT; 1544 } 1545 } 1546 } 1547 } 1548 } 1549 test = phase->idom(test); 1550 } 1551 } 1552 1553 1554 //------------------------------policy_do_remove_empty_loop-------------------- 1555 // Micro-benchmark spamming. Policy is to always remove empty loops. 1556 // The 'DO' part is to replace the trip counter with the value it will 1557 // have on the last iteration. This will break the loop. 1558 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) { 1559 // Minimum size must be empty loop 1560 if( _body.size() > 7/*number of nodes in an empty loop*/ ) return false; 1561 1562 if( !_head->is_CountedLoop() ) return false; // Dead loop 1563 CountedLoopNode *cl = _head->as_CountedLoop(); 1564 if( !cl->loopexit() ) return false; // Malformed loop 1565 if( !phase->is_member(this,phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)) ) ) 1566 return false; // Infinite loop 1567 #ifndef PRODUCT 1568 if( PrintOpto ) 1569 tty->print_cr("Removing empty loop"); 1570 #endif 1571 #ifdef ASSERT 1572 // Ensure only one phi which is the iv. 1573 Node* iv = NULL; 1574 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) { 1575 Node* n = cl->fast_out(i); 1576 if (n->Opcode() == Op_Phi) { 1577 assert(iv == NULL, "Too many phis" ); 1578 iv = n; 1579 } 1580 } 1581 assert(iv == cl->phi(), "Wrong phi" ); 1582 #endif 1583 // Replace the phi at loop head with the final value of the last 1584 // iteration. Then the CountedLoopEnd will collapse (backedge never 1585 // taken) and all loop-invariant uses of the exit values will be correct. 1586 Node *phi = cl->phi(); 1587 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() ); 1588 phase->register_new_node(final,cl->in(LoopNode::EntryControl)); 1589 phase->_igvn.hash_delete(phi); 1590 phase->_igvn.subsume_node(phi,final); 1591 phase->C->set_major_progress(); 1592 return true; 1593 } 1594 1595 1596 //============================================================================= 1597 //------------------------------iteration_split_impl--------------------------- 1598 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) { 1599 // Check and remove empty loops (spam micro-benchmarks) 1600 if( policy_do_remove_empty_loop(phase) ) 1601 return true; // Here we removed an empty loop 1602 1603 bool should_peel = policy_peeling(phase); // Should we peel? 1604 1605 bool should_unswitch = policy_unswitching(phase); 1606 1607 // Non-counted loops may be peeled; exactly 1 iteration is peeled. 1608 // This removes loop-invariant tests (usually null checks). 1609 if( !_head->is_CountedLoop() ) { // Non-counted loop 1610 if (PartialPeelLoop && phase->partial_peel(this, old_new)) { 1611 // Partial peel succeeded so terminate this round of loop opts 1612 return false; 1613 } 1614 if( should_peel ) { // Should we peel? 1615 #ifndef PRODUCT 1616 if (PrintOpto) tty->print_cr("should_peel"); 1617 #endif 1618 phase->do_peeling(this,old_new); 1619 } else if( should_unswitch ) { 1620 phase->do_unswitching(this, old_new); 1621 } 1622 return true; 1623 } 1624 CountedLoopNode *cl = _head->as_CountedLoop(); 1625 1626 if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops 1627 1628 // Do nothing special to pre- and post- loops 1629 if( cl->is_pre_loop() || cl->is_post_loop() ) return true; 1630 1631 // Compute loop trip count from profile data 1632 compute_profile_trip_cnt(phase); 1633 1634 // Before attempting fancy unrolling, RCE or alignment, see if we want 1635 // to completely unroll this loop or do loop unswitching. 1636 if( cl->is_normal_loop() ) { 1637 if (should_unswitch) { 1638 phase->do_unswitching(this, old_new); 1639 return true; 1640 } 1641 bool should_maximally_unroll = policy_maximally_unroll(phase); 1642 if( should_maximally_unroll ) { 1643 // Here we did some unrolling and peeling. Eventually we will 1644 // completely unroll this loop and it will no longer be a loop. 1645 phase->do_maximally_unroll(this,old_new); 1646 return true; 1647 } 1648 } 1649 1650 1651 // Counted loops may be peeled, may need some iterations run up 1652 // front for RCE, and may want to align loop refs to a cache 1653 // line. Thus we clone a full loop up front whose trip count is 1654 // at least 1 (if peeling), but may be several more. 1655 1656 // The main loop will start cache-line aligned with at least 1 1657 // iteration of the unrolled body (zero-trip test required) and 1658 // will have some range checks removed. 1659 1660 // A post-loop will finish any odd iterations (leftover after 1661 // unrolling), plus any needed for RCE purposes. 1662 1663 bool should_unroll = policy_unroll(phase); 1664 1665 bool should_rce = policy_range_check(phase); 1666 1667 bool should_align = policy_align(phase); 1668 1669 // If not RCE'ing (iteration splitting) or Aligning, then we do not 1670 // need a pre-loop. We may still need to peel an initial iteration but 1671 // we will not be needing an unknown number of pre-iterations. 1672 // 1673 // Basically, if may_rce_align reports FALSE first time through, 1674 // we will not be able to later do RCE or Aligning on this loop. 1675 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align; 1676 1677 // If we have any of these conditions (RCE, alignment, unrolling) met, then 1678 // we switch to the pre-/main-/post-loop model. This model also covers 1679 // peeling. 1680 if( should_rce || should_align || should_unroll ) { 1681 if( cl->is_normal_loop() ) // Convert to 'pre/main/post' loops 1682 phase->insert_pre_post_loops(this,old_new, !may_rce_align); 1683 1684 // Adjust the pre- and main-loop limits to let the pre and post loops run 1685 // with full checks, but the main-loop with no checks. Remove said 1686 // checks from the main body. 1687 if( should_rce ) 1688 phase->do_range_check(this,old_new); 1689 1690 // Double loop body for unrolling. Adjust the minimum-trip test (will do 1691 // twice as many iterations as before) and the main body limit (only do 1692 // an even number of trips). If we are peeling, we might enable some RCE 1693 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if 1694 // peeling. 1695 if( should_unroll && !should_peel ) 1696 phase->do_unroll(this,old_new, true); 1697 1698 // Adjust the pre-loop limits to align the main body 1699 // iterations. 1700 if( should_align ) 1701 Unimplemented(); 1702 1703 } else { // Else we have an unchanged counted loop 1704 if( should_peel ) // Might want to peel but do nothing else 1705 phase->do_peeling(this,old_new); 1706 } 1707 return true; 1708 } 1709 1710 1711 //============================================================================= 1712 //------------------------------iteration_split-------------------------------- 1713 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { 1714 // Recursively iteration split nested loops 1715 if( _child && !_child->iteration_split( phase, old_new )) 1716 return false; 1717 1718 // Clean out prior deadwood 1719 DCE_loop_body(); 1720 1721 1722 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. 1723 // Replace with a 1-in-10 exit guess. 1724 if( _parent /*not the root loop*/ && 1725 !_irreducible && 1726 // Also ignore the occasional dead backedge 1727 !tail()->is_top() ) { 1728 adjust_loop_exit_prob(phase); 1729 } 1730 1731 1732 // Gate unrolling, RCE and peeling efforts. 1733 if( !_child && // If not an inner loop, do not split 1734 !_irreducible && 1735 _allow_optimizations && 1736 !tail()->is_top() ) { // Also ignore the occasional dead backedge 1737 if (!_has_call) { 1738 if (!iteration_split_impl( phase, old_new )) { 1739 return false; 1740 } 1741 } else if (policy_unswitching(phase)) { 1742 phase->do_unswitching(this, old_new); 1743 } 1744 } 1745 1746 // Minor offset re-organization to remove loop-fallout uses of 1747 // trip counter. 1748 if( _head->is_CountedLoop() ) phase->reorg_offsets( this ); 1749 if( _next && !_next->iteration_split( phase, old_new )) 1750 return false; 1751 return true; 1752 } 1753 1754 //-------------------------------is_uncommon_trap_proj---------------------------- 1755 // Return true if proj is the form of "proj->[region->..]call_uct" 1756 bool PhaseIdealLoop::is_uncommon_trap_proj(ProjNode* proj, bool must_reason_predicate) { 1757 int path_limit = 10; 1758 assert(proj, "invalid argument"); 1759 Node* out = proj; 1760 for (int ct = 0; ct < path_limit; ct++) { 1761 out = out->unique_ctrl_out(); 1762 if (out == NULL || out->is_Root() || out->is_Start()) 1763 return false; 1764 if (out->is_CallStaticJava()) { 1765 int req = out->as_CallStaticJava()->uncommon_trap_request(); 1766 if (req != 0) { 1767 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(req); 1768 if (!must_reason_predicate || reason == Deoptimization::Reason_predicate){ 1769 return true; 1770 } 1771 } 1772 return false; // don't do further after call 1773 } 1774 } 1775 return false; 1776 } 1777 1778 //-------------------------------is_uncommon_trap_if_pattern------------------------- 1779 // Return true for "if(test)-> proj -> ... 1780 // | 1781 // V 1782 // other_proj->[region->..]call_uct" 1783 // 1784 // "must_reason_predicate" means the uct reason must be Reason_predicate 1785 bool PhaseIdealLoop::is_uncommon_trap_if_pattern(ProjNode *proj, bool must_reason_predicate) { 1786 Node *in0 = proj->in(0); 1787 if (!in0->is_If()) return false; 1788 // Variation of a dead If node. 1789 if (in0->outcnt() < 2) return false; 1790 IfNode* iff = in0->as_If(); 1791 1792 // we need "If(Conv2B(Opaque1(...)))" pattern for must_reason_predicate 1793 if (must_reason_predicate) { 1794 if (iff->in(1)->Opcode() != Op_Conv2B || 1795 iff->in(1)->in(1)->Opcode() != Op_Opaque1) { 1796 return false; 1797 } 1798 } 1799 1800 ProjNode* other_proj = iff->proj_out(1-proj->_con)->as_Proj(); 1801 return is_uncommon_trap_proj(other_proj, must_reason_predicate); 1802 } 1803 1804 //------------------------------create_new_if_for_predicate------------------------ 1805 // create a new if above the uct_if_pattern for the predicate to be promoted. 1806 // 1807 // before after 1808 // ---------- ---------- 1809 // ctrl ctrl 1810 // | | 1811 // | | 1812 // v v 1813 // iff new_iff 1814 // / \ / \ 1815 // / \ / \ 1816 // v v v v 1817 // uncommon_proj cont_proj if_uct if_cont 1818 // \ | | | | 1819 // \ | | | | 1820 // v v v | v 1821 // rgn loop | iff 1822 // | | / \ 1823 // | | / \ 1824 // v | v v 1825 // uncommon_trap | uncommon_proj cont_proj 1826 // \ \ | | 1827 // \ \ | | 1828 // v v v v 1829 // rgn loop 1830 // | 1831 // | 1832 // v 1833 // uncommon_trap 1834 // 1835 // 1836 // We will create a region to guard the uct call if there is no one there. 1837 // The true projecttion (if_cont) of the new_iff is returned. 1838 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj) { 1839 assert(is_uncommon_trap_if_pattern(cont_proj, true), "must be a uct if pattern!"); 1840 IfNode* iff = cont_proj->in(0)->as_If(); 1841 1842 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con); 1843 Node *rgn = uncommon_proj->unique_ctrl_out(); 1844 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct"); 1845 1846 if (!rgn->is_Region()) { // create a region to guard the call 1847 assert(rgn->is_Call(), "must be call uct"); 1848 CallNode* call = rgn->as_Call(); 1849 rgn = new (C, 1) RegionNode(1); 1850 _igvn.set_type(rgn, rgn->bottom_type()); 1851 rgn->add_req(uncommon_proj); 1852 set_idom(rgn, idom(uncommon_proj), dom_depth(uncommon_proj)+1); 1853 _igvn.hash_delete(call); 1854 call->set_req(0, rgn); 1855 } 1856 1857 // Create new_iff 1858 uint iffdd = dom_depth(iff); 1859 IdealLoopTree* lp = get_loop(iff); 1860 IfNode *new_iff = new (C, 2) IfNode(iff->in(0), NULL, iff->_prob, iff->_fcnt); 1861 register_node(new_iff, lp, idom(iff), iffdd); 1862 Node *if_cont = new (C, 1) IfTrueNode(new_iff); 1863 Node *if_uct = new (C, 1) IfFalseNode(new_iff); 1864 if (cont_proj->is_IfFalse()) { 1865 // Swap 1866 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp; 1867 } 1868 register_node(if_cont, lp, new_iff, iffdd); 1869 register_node(if_uct, get_loop(rgn), new_iff, iffdd); 1870 1871 // if_cont to iff 1872 _igvn.hash_delete(iff); 1873 iff->set_req(0, if_cont); 1874 set_idom(iff, if_cont, dom_depth(iff)); 1875 1876 // if_uct to rgn 1877 _igvn.hash_delete(rgn); 1878 rgn->add_req(if_uct); 1879 Node* ridom = idom(rgn); 1880 Node* nrdom = dom_lca(ridom, new_iff); 1881 set_idom(rgn, nrdom, dom_depth(rgn)); 1882 1883 // rgn must have no phis 1884 assert(!rgn->as_Region()->has_phi(), "region must have no phis"); 1885 1886 return if_cont->as_Proj(); 1887 } 1888 1889 //------------------------------find_predicate_insertion_point-------------------------- 1890 // Find a good location to insert a predicate 1891 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c) { 1892 if (start_c == C->root() || !start_c->is_Proj()) 1893 return NULL; 1894 if (is_uncommon_trap_if_pattern(start_c->as_Proj(), true/*Reason_Predicate*/)) { 1895 return start_c->as_Proj(); 1896 } 1897 return NULL; 1898 } 1899 1900 //------------------------------Invariance----------------------------------- 1901 // Helper class for loop_predication_impl to compute invariance on the fly and 1902 // clone invariants. 1903 class Invariance : public StackObj { 1904 VectorSet _visited, _invariant; 1905 Node_Stack _stack; 1906 VectorSet _clone_visited; 1907 Node_List _old_new; // map of old to new (clone) 1908 IdealLoopTree* _lpt; 1909 PhaseIdealLoop* _phase; 1910 1911 // Helper function to set up the invariance for invariance computation 1912 // If n is a known invariant, set up directly. Otherwise, look up the 1913 // the possibility to push n onto the stack for further processing. 1914 void visit(Node* use, Node* n) { 1915 if (_lpt->is_invariant(n)) { // known invariant 1916 _invariant.set(n->_idx); 1917 } else if (!n->is_CFG()) { 1918 Node *n_ctrl = _phase->ctrl_or_self(n); 1919 Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG 1920 if (_phase->is_dominator(n_ctrl, u_ctrl)) { 1921 _stack.push(n, n->in(0) == NULL ? 1 : 0); 1922 } 1923 } 1924 } 1925 1926 // Compute invariance for "the_node" and (possibly) all its inputs recursively 1927 // on the fly 1928 void compute_invariance(Node* n) { 1929 assert(_visited.test(n->_idx), "must be"); 1930 visit(n, n); 1931 while (_stack.is_nonempty()) { 1932 Node* n = _stack.node(); 1933 uint idx = _stack.index(); 1934 if (idx == n->req()) { // all inputs are processed 1935 _stack.pop(); 1936 // n is invariant if it's inputs are all invariant 1937 bool all_inputs_invariant = true; 1938 for (uint i = 0; i < n->req(); i++) { 1939 Node* in = n->in(i); 1940 if (in == NULL) continue; 1941 assert(_visited.test(in->_idx), "must have visited input"); 1942 if (!_invariant.test(in->_idx)) { // bad guy 1943 all_inputs_invariant = false; 1944 break; 1945 } 1946 } 1947 if (all_inputs_invariant) { 1948 _invariant.set(n->_idx); // I am a invariant too 1949 } 1950 } else { // process next input 1951 _stack.set_index(idx + 1); 1952 Node* m = n->in(idx); 1953 if (m != NULL && !_visited.test_set(m->_idx)) { 1954 visit(n, m); 1955 } 1956 } 1957 } 1958 } 1959 1960 // Helper function to set up _old_new map for clone_nodes. 1961 // If n is a known invariant, set up directly ("clone" of n == n). 1962 // Otherwise, push n onto the stack for real cloning. 1963 void clone_visit(Node* n) { 1964 assert(_invariant.test(n->_idx), "must be invariant"); 1965 if (_lpt->is_invariant(n)) { // known invariant 1966 _old_new.map(n->_idx, n); 1967 } else{ // to be cloned 1968 assert (!n->is_CFG(), "should not see CFG here"); 1969 _stack.push(n, n->in(0) == NULL ? 1 : 0); 1970 } 1971 } 1972 1973 // Clone "n" and (possibly) all its inputs recursively 1974 void clone_nodes(Node* n, Node* ctrl) { 1975 clone_visit(n); 1976 while (_stack.is_nonempty()) { 1977 Node* n = _stack.node(); 1978 uint idx = _stack.index(); 1979 if (idx == n->req()) { // all inputs processed, clone n! 1980 _stack.pop(); 1981 // clone invariant node 1982 Node* n_cl = n->clone(); 1983 _old_new.map(n->_idx, n_cl); 1984 _phase->register_new_node(n_cl, ctrl); 1985 for (uint i = 0; i < n->req(); i++) { 1986 Node* in = n_cl->in(i); 1987 if (in == NULL) continue; 1988 n_cl->set_req(i, _old_new[in->_idx]); 1989 } 1990 } else { // process next input 1991 _stack.set_index(idx + 1); 1992 Node* m = n->in(idx); 1993 if (m != NULL && !_clone_visited.test_set(m->_idx)) { 1994 clone_visit(m); // visit the input 1995 } 1996 } 1997 } 1998 } 1999 2000 public: 2001 Invariance(Arena* area, IdealLoopTree* lpt) : 2002 _lpt(lpt), _phase(lpt->_phase), 2003 _visited(area), _invariant(area), _stack(area, 10 /* guess */), 2004 _clone_visited(area), _old_new(area) 2005 {} 2006 2007 // Map old to n for invariance computation and clone 2008 void map_ctrl(Node* old, Node* n) { 2009 assert(old->is_CFG() && n->is_CFG(), "must be"); 2010 _old_new.map(old->_idx, n); // "clone" of old is n 2011 _invariant.set(old->_idx); // old is invariant 2012 _clone_visited.set(old->_idx); 2013 } 2014 2015 // Driver function to compute invariance 2016 bool is_invariant(Node* n) { 2017 if (!_visited.test_set(n->_idx)) 2018 compute_invariance(n); 2019 return (_invariant.test(n->_idx) != 0); 2020 } 2021 2022 // Driver function to clone invariant 2023 Node* clone(Node* n, Node* ctrl) { 2024 assert(ctrl->is_CFG(), "must be"); 2025 assert(_invariant.test(n->_idx), "must be an invariant"); 2026 if (!_clone_visited.test(n->_idx)) 2027 clone_nodes(n, ctrl); 2028 return _old_new[n->_idx]; 2029 } 2030 }; 2031 2032 //------------------------------is_range_check_if ----------------------------------- 2033 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format 2034 // Note: this function is particularly designed for loop predication. We require load_range 2035 // and offset to be loop invariant computed on the fly by "invar" 2036 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const { 2037 if (!is_loop_exit(iff)) { 2038 return false; 2039 } 2040 if (!iff->in(1)->is_Bool()) { 2041 return false; 2042 } 2043 const BoolNode *bol = iff->in(1)->as_Bool(); 2044 if (bol->_test._test != BoolTest::lt) { 2045 return false; 2046 } 2047 if (!bol->in(1)->is_Cmp()) { 2048 return false; 2049 } 2050 const CmpNode *cmp = bol->in(1)->as_Cmp(); 2051 if (cmp->Opcode() != Op_CmpU ) { 2052 return false; 2053 } 2054 if (cmp->in(2)->Opcode() != Op_LoadRange) { 2055 return false; 2056 } 2057 LoadRangeNode* lr = (LoadRangeNode*)cmp->in(2); 2058 if (!invar.is_invariant(lr)) { // loadRange must be invariant 2059 return false; 2060 } 2061 Node *iv = _head->as_CountedLoop()->phi(); 2062 int scale = 0; 2063 Node *offset = NULL; 2064 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) { 2065 return false; 2066 } 2067 if(offset && !invar.is_invariant(offset)) { // offset must be invariant 2068 return false; 2069 } 2070 return true; 2071 } 2072 2073 //------------------------------rc_predicate----------------------------------- 2074 // Create a range check predicate 2075 // 2076 // for (i = init; i < limit; i += stride) { 2077 // a[scale*i+offset] 2078 // } 2079 // 2080 // Compute max(scale*i + offset) for init <= i < limit and build the predicate 2081 // as "max(scale*i + offset) u< a.length". 2082 // 2083 // There are two cases for max(scale*i + offset): 2084 // (1) stride*scale > 0 2085 // max(scale*i + offset) = scale*(limit-stride) + offset 2086 // (2) stride*scale < 0 2087 // max(scale*i + offset) = scale*init + offset 2088 BoolNode* PhaseIdealLoop::rc_predicate(Node* ctrl, 2089 int scale, Node* offset, 2090 Node* init, Node* limit, Node* stride, 2091 Node* range) { 2092 Node* max_idx_expr = init; 2093 int stride_con = stride->get_int(); 2094 if ((stride_con > 0) == (scale > 0)) { 2095 max_idx_expr = new (C, 3) SubINode(limit, stride); 2096 register_new_node(max_idx_expr, ctrl); 2097 } 2098 2099 if (scale != 1) { 2100 ConNode* con_scale = _igvn.intcon(scale); 2101 max_idx_expr = new (C, 3) MulINode(max_idx_expr, con_scale); 2102 register_new_node(max_idx_expr, ctrl); 2103 } 2104 2105 if (offset && (!offset->is_Con() || offset->get_int() != 0)){ 2106 max_idx_expr = new (C, 3) AddINode(max_idx_expr, offset); 2107 register_new_node(max_idx_expr, ctrl); 2108 } 2109 2110 CmpUNode* cmp = new (C, 3) CmpUNode(max_idx_expr, range); 2111 register_new_node(cmp, ctrl); 2112 BoolNode* bol = new (C, 2) BoolNode(cmp, BoolTest::lt); 2113 register_new_node(bol, ctrl); 2114 return bol; 2115 } 2116 2117 //------------------------------ loop_predication_impl-------------------------- 2118 // Insert loop predicates for null checks and range checks 2119 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) { 2120 if (!UseLoopPredicate) return false; 2121 2122 if (!loop->_head->is_Loop()) { 2123 // Could be a simple region when irreducible loops are present. 2124 return false; 2125 } 2126 2127 CountedLoopNode *cl = NULL; 2128 if (loop->_head->is_CountedLoop()) { 2129 cl = loop->_head->as_CountedLoop(); 2130 // do nothing for iteration-splitted loops 2131 if (!cl->is_normal_loop()) return false; 2132 } 2133 2134 // Too many traps seen? 2135 bool tmt = C->too_many_traps(C->method(), 0, Deoptimization::Reason_predicate); 2136 int tc = C->trap_count(Deoptimization::Reason_predicate); 2137 if (tmt || tc > 0) { 2138 if (TraceLoopPredicate) { 2139 tty->print_cr("too many predicate traps: %d", tc); 2140 C->method()->print(); // which method has too many predicate traps 2141 tty->print_cr(""); 2142 } 2143 return false; 2144 } 2145 2146 LoopNode *lpn = loop->_head->as_Loop(); 2147 Node* entry = lpn->in(LoopNode::EntryControl); 2148 2149 ProjNode *predicate_proj = find_predicate_insertion_point(entry); 2150 if (!predicate_proj){ 2151 #ifndef PRODUCT 2152 if (TraceLoopPredicate) { 2153 tty->print("missing predicate:"); 2154 loop->dump_head(); 2155 } 2156 #endif 2157 return false; 2158 } 2159 2160 ConNode* zero = _igvn.intcon(0); 2161 set_ctrl(zero, C->root()); 2162 Node *cond_false = new (C, 2) Conv2BNode(zero); 2163 register_new_node(cond_false, C->root()); 2164 ConNode* one = _igvn.intcon(1); 2165 set_ctrl(one, C->root()); 2166 Node *cond_true = new (C, 2) Conv2BNode(one); 2167 register_new_node(cond_true, C->root()); 2168 2169 ResourceArea *area = Thread::current()->resource_area(); 2170 Invariance invar(area, loop); 2171 2172 // Create list of if-projs such that a newer proj dominates all older 2173 // projs in the list, and they all dominate loop->tail() 2174 Node_List if_proj_list(area); 2175 LoopNode *head = loop->_head->as_Loop(); 2176 Node *current_proj = loop->tail(); //start from tail 2177 while ( current_proj != head ) { 2178 if (loop == get_loop(current_proj) && // still in the loop ? 2179 current_proj->is_Proj() && // is a projection ? 2180 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ? 2181 if_proj_list.push(current_proj); 2182 } 2183 current_proj = idom(current_proj); 2184 } 2185 2186 bool hoisted = false; // true if at least one proj is promoted 2187 while (if_proj_list.size() > 0) { 2188 // Following are changed to nonnull when a predicate can be hoisted 2189 ProjNode* new_predicate_proj = NULL; 2190 BoolNode* new_predicate_bol = NULL; 2191 2192 ProjNode* proj = if_proj_list.pop()->as_Proj(); 2193 IfNode* iff = proj->in(0)->as_If(); 2194 2195 if (!is_uncommon_trap_if_pattern(proj)) { 2196 if (loop->is_loop_exit(iff)) { 2197 // stop processing the remaining projs in the list because the execution of them 2198 // depends on the condition of "iff" (iff->in(1)). 2199 break; 2200 } else { 2201 // Both arms are inside the loop. There are two cases: 2202 // (1) there is one backward branch. In this case, any remaining proj 2203 // in the if_proj list post-dominates "iff". So, the condition of "iff" 2204 // does not determine the execution the remining projs directly, and we 2205 // can safely continue. 2206 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj" 2207 // does not dominate loop->tail(), so it can not be in the if_proj list. 2208 continue; 2209 } 2210 } 2211 2212 Node* test = iff->in(1); 2213 if (!test->is_Bool()){ //Conv2B, ... 2214 continue; 2215 } 2216 BoolNode* bol = test->as_Bool(); 2217 if (invar.is_invariant(bol)) { 2218 // Invariant test 2219 new_predicate_proj = create_new_if_for_predicate(predicate_proj); 2220 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0); 2221 new_predicate_bol = invar.clone(bol, ctrl)->as_Bool(); 2222 if (TraceLoopPredicate) tty->print("invariant"); 2223 } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) { 2224 // Range check (only for counted loops) 2225 new_predicate_proj = create_new_if_for_predicate(predicate_proj); 2226 Node *ctrl = new_predicate_proj->in(0)->as_If()->in(0); 2227 const Node* cmp = bol->in(1)->as_Cmp(); 2228 Node* idx = cmp->in(1); 2229 assert(!invar.is_invariant(idx), "index is variant"); 2230 assert(cmp->in(2)->Opcode() == Op_LoadRange, "must be"); 2231 LoadRangeNode* ld_rng = (LoadRangeNode*)cmp->in(2); // LoadRangeNode 2232 assert(invar.is_invariant(ld_rng), "load range must be invariant"); 2233 ld_rng = (LoadRangeNode*)invar.clone(ld_rng, ctrl); 2234 int scale = 1; 2235 Node* offset = zero; 2236 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset); 2237 assert(ok, "must be index expression"); 2238 if (offset && offset != zero) { 2239 assert(invar.is_invariant(offset), "offset must be loop invariant"); 2240 offset = invar.clone(offset, ctrl); 2241 } 2242 Node* init = cl->init_trip(); 2243 Node* limit = cl->limit(); 2244 Node* stride = cl->stride(); 2245 new_predicate_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, ld_rng); 2246 if (TraceLoopPredicate) tty->print("range check"); 2247 } 2248 2249 if (new_predicate_proj == NULL) { 2250 // The other proj of the "iff" is a uncommon trap projection, and we can assume 2251 // the other proj will not be executed ("executed" means uct raised). 2252 continue; 2253 } else { 2254 // Success - attach condition (new_predicate_bol) to predicate if 2255 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate 2256 IfNode* new_iff = new_predicate_proj->in(0)->as_If(); 2257 2258 // Negate test if necessary 2259 if (proj->_con != predicate_proj->_con) { 2260 new_predicate_bol = new (C, 2) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate()); 2261 register_new_node(new_predicate_bol, new_iff->in(0)); 2262 if (TraceLoopPredicate) tty->print_cr(" if negated: %d", iff->_idx); 2263 } else { 2264 if (TraceLoopPredicate) tty->print_cr(" if: %d", iff->_idx); 2265 } 2266 2267 _igvn.hash_delete(new_iff); 2268 new_iff->set_req(1, new_predicate_bol); 2269 2270 _igvn.hash_delete(iff); 2271 iff->set_req(1, proj->is_IfFalse() ? cond_false : cond_true); 2272 2273 Node* ctrl = new_predicate_proj; // new control 2274 ProjNode* dp = proj; // old control 2275 assert(get_loop(dp) == loop, "guarenteed at the time of collecting proj"); 2276 // Find nodes (depends only on the test) off the surviving projection; 2277 // move them outside the loop with the control of proj_clone 2278 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { 2279 Node* cd = dp->fast_out(i); // Control-dependent node 2280 if (cd->depends_only_on_test()) { 2281 assert(cd->in(0) == dp, ""); 2282 _igvn.hash_delete(cd); 2283 cd->set_req(0, ctrl); // ctrl, not NULL 2284 set_early_ctrl(cd); 2285 _igvn._worklist.push(cd); 2286 IdealLoopTree *new_loop = get_loop(get_ctrl(cd)); 2287 if (new_loop != loop) { 2288 if (!loop->_child) loop->_body.yank(cd); 2289 if (!new_loop->_child ) new_loop->_body.push(cd); 2290 } 2291 --i; 2292 --imax; 2293 } 2294 } 2295 2296 hoisted = true; 2297 C->set_major_progress(); 2298 } 2299 } // end while 2300 2301 #ifndef PRODUCT 2302 // report that the loop predication has been actually performed 2303 // for this loop 2304 if (TraceLoopPredicate && hoisted) { 2305 tty->print("Loop Predication Performed:"); 2306 loop->dump_head(); 2307 } 2308 #endif 2309 2310 return hoisted; 2311 } 2312 2313 //------------------------------loop_predication-------------------------------- 2314 // driver routine for loop predication optimization 2315 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) { 2316 bool hoisted = false; 2317 // Recursively promote predicates 2318 if ( _child ) { 2319 hoisted = _child->loop_predication( phase); 2320 } 2321 2322 // self 2323 if (!_irreducible && !tail()->is_top()) { 2324 hoisted |= phase->loop_predication_impl(this); 2325 } 2326 2327 if ( _next ) { //sibling 2328 hoisted |= _next->loop_predication( phase); 2329 } 2330 2331 return hoisted; 2332 }