1 /* 2 * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "ci/ciTypeFlow.hpp" 27 #include "memory/allocation.inline.hpp" 28 #include "memory/resourceArea.hpp" 29 #include "opto/addnode.hpp" 30 #include "opto/castnode.hpp" 31 #include "opto/cfgnode.hpp" 32 #include "opto/connode.hpp" 33 #include "opto/loopnode.hpp" 34 #include "opto/phaseX.hpp" 35 #include "opto/runtime.hpp" 36 #include "opto/rootnode.hpp" 37 #include "opto/subnode.hpp" 38 39 // Portions of code courtesy of Clifford Click 40 41 // Optimization - Graph Style 42 43 44 #ifndef PRODUCT 45 extern int explicit_null_checks_elided; 46 #endif 47 48 //============================================================================= 49 //------------------------------Value------------------------------------------ 50 // Return a tuple for whichever arm of the IF is reachable 51 const Type* IfNode::Value(PhaseGVN* phase) const { 52 if( !in(0) ) return Type::TOP; 53 if( phase->type(in(0)) == Type::TOP ) 54 return Type::TOP; 55 const Type *t = phase->type(in(1)); 56 if( t == Type::TOP ) // data is undefined 57 return TypeTuple::IFNEITHER; // unreachable altogether 58 if( t == TypeInt::ZERO ) // zero, or false 59 return TypeTuple::IFFALSE; // only false branch is reachable 60 if( t == TypeInt::ONE ) // 1, or true 61 return TypeTuple::IFTRUE; // only true branch is reachable 62 assert( t == TypeInt::BOOL, "expected boolean type" ); 63 64 return TypeTuple::IFBOTH; // No progress 65 } 66 67 const RegMask &IfNode::out_RegMask() const { 68 return RegMask::Empty; 69 } 70 71 //------------------------------split_if--------------------------------------- 72 // Look for places where we merge constants, then test on the merged value. 73 // If the IF test will be constant folded on the path with the constant, we 74 // win by splitting the IF to before the merge point. 75 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) { 76 // I could be a lot more general here, but I'm trying to squeeze this 77 // in before the Christmas '98 break so I'm gonna be kinda restrictive 78 // on the patterns I accept. CNC 79 80 // Look for a compare of a constant and a merged value 81 Node *i1 = iff->in(1); 82 if( !i1->is_Bool() ) return NULL; 83 BoolNode *b = i1->as_Bool(); 84 Node *cmp = b->in(1); 85 if( !cmp->is_Cmp() ) return NULL; 86 i1 = cmp->in(1); 87 if( i1 == NULL || !i1->is_Phi() ) return NULL; 88 PhiNode *phi = i1->as_Phi(); 89 if( phi->is_copy() ) return NULL; 90 Node *con2 = cmp->in(2); 91 if( !con2->is_Con() ) return NULL; 92 // See that the merge point contains some constants 93 Node *con1=NULL; 94 uint i4; 95 for( i4 = 1; i4 < phi->req(); i4++ ) { 96 con1 = phi->in(i4); 97 if( !con1 ) return NULL; // Do not optimize partially collapsed merges 98 if( con1->is_Con() ) break; // Found a constant 99 // Also allow null-vs-not-null checks 100 const TypePtr *tp = igvn->type(con1)->isa_ptr(); 101 if( tp && tp->_ptr == TypePtr::NotNull ) 102 break; 103 } 104 if( i4 >= phi->req() ) return NULL; // Found no constants 105 106 igvn->C->set_has_split_ifs(true); // Has chance for split-if 107 108 // Make sure that the compare can be constant folded away 109 Node *cmp2 = cmp->clone(); 110 cmp2->set_req(1,con1); 111 cmp2->set_req(2,con2); 112 const Type *t = cmp2->Value(igvn); 113 // This compare is dead, so whack it! 114 igvn->remove_dead_node(cmp2); 115 if( !t->singleton() ) return NULL; 116 117 // No intervening control, like a simple Call 118 Node *r = iff->in(0); 119 if( !r->is_Region() ) return NULL; 120 if (r->is_Loop() && r->in(LoopNode::LoopBackControl)->is_top()) return NULL; // going away anyway 121 if( phi->region() != r ) return NULL; 122 // No other users of the cmp/bool 123 if (b->outcnt() != 1 || cmp->outcnt() != 1) { 124 //tty->print_cr("many users of cmp/bool"); 125 return NULL; 126 } 127 128 // Make sure we can determine where all the uses of merged values go 129 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { 130 Node* u = r->fast_out(j); 131 if( u == r ) continue; 132 if( u == iff ) continue; 133 if( u->outcnt() == 0 ) continue; // use is dead & ignorable 134 if( !u->is_Phi() ) { 135 /* 136 if( u->is_Start() ) { 137 tty->print_cr("Region has inlined start use"); 138 } else { 139 tty->print_cr("Region has odd use"); 140 u->dump(2); 141 }*/ 142 return NULL; 143 } 144 if( u != phi ) { 145 // CNC - do not allow any other merged value 146 //tty->print_cr("Merging another value"); 147 //u->dump(2); 148 return NULL; 149 } 150 // Make sure we can account for all Phi uses 151 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { 152 Node* v = u->fast_out(k); // User of the phi 153 // CNC - Allow only really simple patterns. 154 // In particular I disallow AddP of the Phi, a fairly common pattern 155 if (v == cmp) continue; // The compare is OK 156 if (v->is_ConstraintCast()) { 157 // If the cast is derived from data flow edges, it may not have a control edge. 158 // If so, it should be safe to split. But follow-up code can not deal with 159 // this (l. 359). So skip. 160 if (v->in(0) == NULL) { 161 return NULL; 162 } 163 if (v->in(0)->in(0) == iff) { 164 continue; // CastPP/II of the IfNode is OK 165 } 166 } 167 // Disabled following code because I cannot tell if exactly one 168 // path dominates without a real dominator check. CNC 9/9/1999 169 //uint vop = v->Opcode(); 170 //if( vop == Op_Phi ) { // Phi from another merge point might be OK 171 // Node *r = v->in(0); // Get controlling point 172 // if( !r ) return NULL; // Degraded to a copy 173 // // Find exactly one path in (either True or False doms, but not IFF) 174 // int cnt = 0; 175 // for( uint i = 1; i < r->req(); i++ ) 176 // if( r->in(i) && r->in(i)->in(0) == iff ) 177 // cnt++; 178 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi 179 //} 180 if( !v->is_Call() ) { 181 /* 182 if( v->Opcode() == Op_AddP ) { 183 tty->print_cr("Phi has AddP use"); 184 } else if( v->Opcode() == Op_CastPP ) { 185 tty->print_cr("Phi has CastPP use"); 186 } else if( v->Opcode() == Op_CastII ) { 187 tty->print_cr("Phi has CastII use"); 188 } else { 189 tty->print_cr("Phi has use I cant be bothered with"); 190 } 191 */ 192 } 193 return NULL; 194 195 /* CNC - Cut out all the fancy acceptance tests 196 // Can we clone this use when doing the transformation? 197 // If all uses are from Phis at this merge or constants, then YES. 198 if( !v->in(0) && v != cmp ) { 199 tty->print_cr("Phi has free-floating use"); 200 v->dump(2); 201 return NULL; 202 } 203 for( uint l = 1; l < v->req(); l++ ) { 204 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && 205 !v->in(l)->is_Con() ) { 206 tty->print_cr("Phi has use"); 207 v->dump(2); 208 return NULL; 209 } // End of if Phi-use input is neither Phi nor Constant 210 } // End of for all inputs to Phi-use 211 */ 212 } // End of for all uses of Phi 213 } // End of for all uses of Region 214 215 // Only do this if the IF node is in a sane state 216 if (iff->outcnt() != 2) 217 return NULL; 218 219 // Got a hit! Do the Mondo Hack! 220 // 221 //ABC a1c def ghi B 1 e h A C a c d f g i 222 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi 223 // cmp - 2 cmp - 2 cmp - 2 224 // bool bool_c bool_x 225 // if if_c if_x 226 // T F T F T F 227 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. 228 // 229 // Split the paths coming into the merge point into 2 separate groups of 230 // merges. On the left will be all the paths feeding constants into the 231 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi 232 // will fold up into a constant; this will let the Cmp fold up as well as 233 // all the control flow. Below the original IF we have 2 control 234 // dependent regions, 's' and 't'. Now we will merge the two paths 235 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite 236 // likely 2 or more) will promptly constant fold away. 237 PhaseGVN *phase = igvn; 238 239 // Make a region merging constants and a region merging the rest 240 uint req_c = 0; 241 Node* predicate_proj = NULL; 242 int nb_predicate_proj = 0; 243 for (uint ii = 1; ii < r->req(); ii++) { 244 if (phi->in(ii) == con1) { 245 req_c++; 246 } 247 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii)); 248 if (proj != NULL) { 249 nb_predicate_proj++; 250 predicate_proj = proj; 251 } 252 } 253 254 // If all the defs of the phi are the same constant, we already have the desired end state. 255 // Skip the split that would create empty phi and region nodes. 256 if((r->req() - req_c) == 1) { 257 return NULL; 258 } 259 260 if (nb_predicate_proj > 1) { 261 // Can happen in case of loop unswitching and when the loop is 262 // optimized out: it's not a loop anymore so we don't care about 263 // predicates. 264 assert(!r->is_Loop(), "this must not be a loop anymore"); 265 predicate_proj = NULL; 266 } 267 Node* predicate_c = NULL; 268 Node* predicate_x = NULL; 269 bool counted_loop = r->is_CountedLoop(); 270 271 Node *region_c = new RegionNode(req_c + 1); 272 Node *phi_c = con1; 273 uint len = r->req(); 274 Node *region_x = new RegionNode(len - req_c); 275 Node *phi_x = PhiNode::make_blank(region_x, phi); 276 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { 277 if (phi->in(i) == con1) { 278 region_c->init_req( i_c++, r ->in(i) ); 279 if (r->in(i) == predicate_proj) 280 predicate_c = predicate_proj; 281 } else { 282 region_x->init_req( i_x, r ->in(i) ); 283 phi_x ->init_req( i_x++, phi->in(i) ); 284 if (r->in(i) == predicate_proj) 285 predicate_x = predicate_proj; 286 } 287 } 288 if (predicate_c != NULL && (req_c > 1)) { 289 assert(predicate_x == NULL, "only one predicate entry expected"); 290 predicate_c = NULL; // Do not clone predicate below merge point 291 } 292 if (predicate_x != NULL && ((len - req_c) > 2)) { 293 assert(predicate_c == NULL, "only one predicate entry expected"); 294 predicate_x = NULL; // Do not clone predicate below merge point 295 } 296 297 // Register the new RegionNodes but do not transform them. Cannot 298 // transform until the entire Region/Phi conglomerate has been hacked 299 // as a single huge transform. 300 igvn->register_new_node_with_optimizer( region_c ); 301 igvn->register_new_node_with_optimizer( region_x ); 302 // Prevent the untimely death of phi_x. Currently he has no uses. He is 303 // about to get one. If this only use goes away, then phi_x will look dead. 304 // However, he will be picking up some more uses down below. 305 Node *hook = new Node(4); 306 hook->init_req(0, phi_x); 307 hook->init_req(1, phi_c); 308 phi_x = phase->transform( phi_x ); 309 310 // Make the compare 311 Node *cmp_c = phase->makecon(t); 312 Node *cmp_x = cmp->clone(); 313 cmp_x->set_req(1,phi_x); 314 cmp_x->set_req(2,con2); 315 cmp_x = phase->transform(cmp_x); 316 // Make the bool 317 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test)); 318 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test)); 319 // Make the IfNode 320 IfNode* iff_c = iff->clone()->as_If(); 321 iff_c->set_req(0, region_c); 322 iff_c->set_req(1, b_c); 323 igvn->set_type_bottom(iff_c); 324 igvn->_worklist.push(iff_c); 325 hook->init_req(2, iff_c); 326 327 IfNode* iff_x = iff->clone()->as_If(); 328 iff_x->set_req(0, region_x); 329 iff_x->set_req(1, b_x); 330 igvn->set_type_bottom(iff_x); 331 igvn->_worklist.push(iff_x); 332 hook->init_req(3, iff_x); 333 334 // Make the true/false arms 335 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c)); 336 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c)); 337 if (predicate_c != NULL) { 338 assert(predicate_x == NULL, "only one predicate entry expected"); 339 // Clone loop predicates to each path 340 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop); 341 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop); 342 } 343 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x)); 344 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x)); 345 if (predicate_x != NULL) { 346 assert(predicate_c == NULL, "only one predicate entry expected"); 347 // Clone loop predicates to each path 348 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop); 349 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop); 350 } 351 352 // Merge the TRUE paths 353 Node *region_s = new RegionNode(3); 354 igvn->_worklist.push(region_s); 355 region_s->init_req(1, iff_c_t); 356 region_s->init_req(2, iff_x_t); 357 igvn->register_new_node_with_optimizer( region_s ); 358 359 // Merge the FALSE paths 360 Node *region_f = new RegionNode(3); 361 igvn->_worklist.push(region_f); 362 region_f->init_req(1, iff_c_f); 363 region_f->init_req(2, iff_x_f); 364 igvn->register_new_node_with_optimizer( region_f ); 365 366 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. 367 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead 368 cmp->set_req(2,NULL); 369 // Check for all uses of the Phi and give them a new home. 370 // The 'cmp' got cloned, but CastPP/IIs need to be moved. 371 Node *phi_s = NULL; // do not construct unless needed 372 Node *phi_f = NULL; // do not construct unless needed 373 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { 374 Node* v = phi->last_out(i2);// User of the phi 375 igvn->rehash_node_delayed(v); // Have to fixup other Phi users 376 uint vop = v->Opcode(); 377 Node *proj = NULL; 378 if( vop == Op_Phi ) { // Remote merge point 379 Node *r = v->in(0); 380 for (uint i3 = 1; i3 < r->req(); i3++) 381 if (r->in(i3) && r->in(i3)->in(0) == iff) { 382 proj = r->in(i3); 383 break; 384 } 385 } else if( v->is_ConstraintCast() ) { 386 proj = v->in(0); // Controlling projection 387 } else { 388 assert( 0, "do not know how to handle this guy" ); 389 } 390 391 Node *proj_path_data, *proj_path_ctrl; 392 if( proj->Opcode() == Op_IfTrue ) { 393 if( phi_s == NULL ) { 394 // Only construct phi_s if needed, otherwise provides 395 // interfering use. 396 phi_s = PhiNode::make_blank(region_s,phi); 397 phi_s->init_req( 1, phi_c ); 398 phi_s->init_req( 2, phi_x ); 399 hook->add_req(phi_s); 400 phi_s = phase->transform(phi_s); 401 } 402 proj_path_data = phi_s; 403 proj_path_ctrl = region_s; 404 } else { 405 if( phi_f == NULL ) { 406 // Only construct phi_f if needed, otherwise provides 407 // interfering use. 408 phi_f = PhiNode::make_blank(region_f,phi); 409 phi_f->init_req( 1, phi_c ); 410 phi_f->init_req( 2, phi_x ); 411 hook->add_req(phi_f); 412 phi_f = phase->transform(phi_f); 413 } 414 proj_path_data = phi_f; 415 proj_path_ctrl = region_f; 416 } 417 418 // Fixup 'v' for for the split 419 if( vop == Op_Phi ) { // Remote merge point 420 uint i; 421 for( i = 1; i < v->req(); i++ ) 422 if( v->in(i) == phi ) 423 break; 424 v->set_req(i, proj_path_data ); 425 } else if( v->is_ConstraintCast() ) { 426 v->set_req(0, proj_path_ctrl ); 427 v->set_req(1, proj_path_data ); 428 } else 429 ShouldNotReachHere(); 430 } 431 432 // Now replace the original iff's True/False with region_s/region_t. 433 // This makes the original iff go dead. 434 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { 435 Node* p = iff->last_out(i3); 436 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); 437 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; 438 // Replace p with u 439 igvn->add_users_to_worklist(p); 440 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { 441 Node* x = p->last_out(l); 442 igvn->hash_delete(x); 443 uint uses_found = 0; 444 for( uint j = 0; j < x->req(); j++ ) { 445 if( x->in(j) == p ) { 446 x->set_req(j, u); 447 uses_found++; 448 } 449 } 450 l -= uses_found; // we deleted 1 or more copies of this edge 451 } 452 igvn->remove_dead_node(p); 453 } 454 455 // Force the original merge dead 456 igvn->hash_delete(r); 457 // First, remove region's dead users. 458 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { 459 Node* u = r->last_out(l); 460 if( u == r ) { 461 r->set_req(0, NULL); 462 } else { 463 assert(u->outcnt() == 0, "only dead users"); 464 igvn->remove_dead_node(u); 465 } 466 l -= 1; 467 } 468 igvn->remove_dead_node(r); 469 470 // Now remove the bogus extra edges used to keep things alive 471 igvn->remove_dead_node( hook ); 472 473 // Must return either the original node (now dead) or a new node 474 // (Do not return a top here, since that would break the uniqueness of top.) 475 return new ConINode(TypeInt::ZERO); 476 } 477 478 // if this IfNode follows a range check pattern return the projection 479 // for the failed path 480 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) { 481 if (outcnt() != 2) { 482 return NULL; 483 } 484 Node* b = in(1); 485 if (b == NULL || !b->is_Bool()) return NULL; 486 BoolNode* bn = b->as_Bool(); 487 Node* cmp = bn->in(1); 488 if (cmp == NULL) return NULL; 489 if (cmp->Opcode() != Op_CmpU) return NULL; 490 491 l = cmp->in(1); 492 r = cmp->in(2); 493 flip_test = 1; 494 if (bn->_test._test == BoolTest::le) { 495 l = cmp->in(2); 496 r = cmp->in(1); 497 flip_test = 2; 498 } else if (bn->_test._test != BoolTest::lt) { 499 return NULL; 500 } 501 if (l->is_top()) return NULL; // Top input means dead test 502 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return NULL; 503 504 // We have recognized one of these forms: 505 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... 506 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... 507 508 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false); 509 return iftrap; 510 } 511 512 513 //------------------------------is_range_check--------------------------------- 514 // Return 0 if not a range check. Return 1 if a range check and set index and 515 // offset. Return 2 if we had to negate the test. Index is NULL if the check 516 // is versus a constant. 517 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) { 518 int flip_test = 0; 519 Node* l = NULL; 520 Node* r = NULL; 521 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r); 522 523 if (iftrap == NULL) { 524 return 0; 525 } 526 527 // Make sure it's a real range check by requiring an uncommon trap 528 // along the OOB path. Otherwise, it's possible that the user wrote 529 // something which optimized to look like a range check but behaves 530 // in some other way. 531 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) { 532 return 0; 533 } 534 535 // Look for index+offset form 536 Node* ind = l; 537 jint off = 0; 538 if (l->is_top()) { 539 return 0; 540 } else if (l->Opcode() == Op_AddI) { 541 if ((off = l->in(1)->find_int_con(0)) != 0) { 542 ind = l->in(2)->uncast(); 543 } else if ((off = l->in(2)->find_int_con(0)) != 0) { 544 ind = l->in(1)->uncast(); 545 } 546 } else if ((off = l->find_int_con(-1)) >= 0) { 547 // constant offset with no variable index 548 ind = NULL; 549 } else { 550 // variable index with no constant offset (or dead negative index) 551 off = 0; 552 } 553 554 // Return all the values: 555 index = ind; 556 offset = off; 557 range = r; 558 return flip_test; 559 } 560 561 //------------------------------adjust_check----------------------------------- 562 // Adjust (widen) a prior range check 563 static void adjust_check(Node* proj, Node* range, Node* index, 564 int flip, jint off_lo, PhaseIterGVN* igvn) { 565 PhaseGVN *gvn = igvn; 566 // Break apart the old check 567 Node *iff = proj->in(0); 568 Node *bol = iff->in(1); 569 if( bol->is_top() ) return; // In case a partially dead range check appears 570 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode 571 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) 572 if( !bol->is_Bool() ) return; 573 574 Node *cmp = bol->in(1); 575 // Compute a new check 576 Node *new_add = gvn->intcon(off_lo); 577 if( index ) { 578 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index; 579 } 580 Node *new_cmp = (flip == 1) 581 ? new CmpUNode( new_add, range ) 582 : new CmpUNode( range, new_add ); 583 new_cmp = gvn->transform(new_cmp); 584 // See if no need to adjust the existing check 585 if( new_cmp == cmp ) return; 586 // Else, adjust existing check 587 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 588 igvn->rehash_node_delayed( iff ); 589 iff->set_req_X( 1, new_bol, igvn ); 590 } 591 592 //------------------------------up_one_dom------------------------------------- 593 // Walk up the dominator tree one step. Return NULL at root or true 594 // complex merges. Skips through small diamonds. 595 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 596 Node *dom = curr->in(0); 597 if( !dom ) // Found a Region degraded to a copy? 598 return curr->nonnull_req(); // Skip thru it 599 600 if( curr != dom ) // Normal walk up one step? 601 return dom; 602 603 // Use linear_only if we are still parsing, since we cannot 604 // trust the regions to be fully filled in. 605 if (linear_only) 606 return NULL; 607 608 if( dom->is_Root() ) 609 return NULL; 610 611 // Else hit a Region. Check for a loop header 612 if( dom->is_Loop() ) 613 return dom->in(1); // Skip up thru loops 614 615 // Check for small diamonds 616 Node *din1, *din2, *din3, *din4; 617 if( dom->req() == 3 && // 2-path merge point 618 (din1 = dom ->in(1)) && // Left path exists 619 (din2 = dom ->in(2)) && // Right path exists 620 (din3 = din1->in(0)) && // Left path up one 621 (din4 = din2->in(0)) ) { // Right path up one 622 if( din3->is_Call() && // Handle a slow-path call on either arm 623 (din3 = din3->in(0)) ) 624 din3 = din3->in(0); 625 if( din4->is_Call() && // Handle a slow-path call on either arm 626 (din4 = din4->in(0)) ) 627 din4 = din4->in(0); 628 if( din3 == din4 && din3->is_If() ) 629 return din3; // Skip around diamonds 630 } 631 632 // Give up the search at true merges 633 return NULL; // Dead loop? Or hit root? 634 } 635 636 637 //------------------------------filtered_int_type-------------------------------- 638 // Return a possibly more restrictive type for val based on condition control flow for an if 639 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 640 assert(if_proj && 641 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 642 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 643 IfNode* iff = if_proj->in(0)->as_If(); 644 if (iff->in(1) && iff->in(1)->is_Bool()) { 645 BoolNode* bol = iff->in(1)->as_Bool(); 646 if (bol->in(1) && bol->in(1)->is_Cmp()) { 647 const CmpNode* cmp = bol->in(1)->as_Cmp(); 648 if (cmp->in(1) == val) { 649 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 650 if (cmp2_t != NULL) { 651 jint lo = cmp2_t->_lo; 652 jint hi = cmp2_t->_hi; 653 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 654 switch (msk) { 655 case BoolTest::ne: 656 // Can't refine type 657 return NULL; 658 case BoolTest::eq: 659 return cmp2_t; 660 case BoolTest::lt: 661 lo = TypeInt::INT->_lo; 662 if (hi - 1 < hi) { 663 hi = hi - 1; 664 } 665 break; 666 case BoolTest::le: 667 lo = TypeInt::INT->_lo; 668 break; 669 case BoolTest::gt: 670 if (lo + 1 > lo) { 671 lo = lo + 1; 672 } 673 hi = TypeInt::INT->_hi; 674 break; 675 case BoolTest::ge: 676 // lo unchanged 677 hi = TypeInt::INT->_hi; 678 break; 679 default: 680 break; 681 } 682 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 683 return rtn_t; 684 } 685 } 686 } 687 } 688 } 689 return NULL; 690 } 691 692 //------------------------------fold_compares---------------------------- 693 // See if a pair of CmpIs can be converted into a CmpU. In some cases 694 // the direction of this if is determined by the preceding if so it 695 // can be eliminate entirely. 696 // 697 // Given an if testing (CmpI n v) check for an immediately control 698 // dependent if that is testing (CmpI n v2) and has one projection 699 // leading to this if and the other projection leading to a region 700 // that merges one of this ifs control projections. 701 // 702 // If 703 // / | 704 // / | 705 // / | 706 // If | 707 // /\ | 708 // / \ | 709 // / \ | 710 // / Region 711 // 712 // Or given an if testing (CmpI n v) check for a dominating if that is 713 // testing (CmpI n v2), both having one projection leading to an 714 // uncommon trap. Allow Another independent guard in between to cover 715 // an explicit range check: 716 // if (index < 0 || index >= array.length) { 717 // which may need a null check to guard the LoadRange 718 // 719 // If 720 // / \ 721 // / \ 722 // / \ 723 // If unc 724 // /\ 725 // / \ 726 // / \ 727 // / unc 728 // 729 730 // Is the comparison for this If suitable for folding? 731 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) { 732 return in(1) != NULL && 733 in(1)->is_Bool() && 734 in(1)->in(1) != NULL && 735 in(1)->in(1)->Opcode() == Op_CmpI && 736 in(1)->in(1)->in(2) != NULL && 737 in(1)->in(1)->in(2) != igvn->C->top() && 738 (in(1)->as_Bool()->_test.is_less() || 739 in(1)->as_Bool()->_test.is_greater()); 740 } 741 742 // Is a dominating control suitable for folding with this if? 743 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) { 744 return ctrl != NULL && 745 ctrl->is_Proj() && 746 ctrl->in(0) != NULL && 747 ctrl->in(0)->Opcode() == Op_If && 748 ctrl->in(0)->outcnt() == 2 && 749 ctrl->in(0)->as_If()->cmpi_folds(igvn) && 750 // Must compare same value 751 ctrl->in(0)->in(1)->in(1)->in(1) != NULL && 752 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1); 753 } 754 755 // Do this If and the dominating If share a region? 756 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) { 757 ProjNode* otherproj = proj->other_if_proj(); 758 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out(); 759 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL; 760 success = NULL; 761 fail = NULL; 762 763 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) { 764 for (int i = 0; i < 2; i++) { 765 ProjNode* proj = proj_out(i); 766 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 767 success = proj; 768 } else if (fail == NULL) { 769 fail = proj; 770 } else { 771 success = fail = NULL; 772 } 773 } 774 } 775 return success != NULL && fail != NULL; 776 } 777 778 // Return projection that leads to an uncommon trap if any 779 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const { 780 for (int i = 0; i < 2; i++) { 781 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none); 782 if (call != NULL) { 783 return proj_out(i); 784 } 785 } 786 return NULL; 787 } 788 789 // Do this If and the dominating If both branch out to an uncommon trap 790 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) { 791 ProjNode* otherproj = proj->other_if_proj(); 792 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none); 793 794 if (otherproj->outcnt() == 1 && dom_unc != NULL) { 795 // We need to re-execute the folded Ifs after deoptimization from the merged traps 796 if (!dom_unc->jvms()->should_reexecute()) { 797 return false; 798 } 799 800 CallStaticJavaNode* unc = NULL; 801 ProjNode* unc_proj = uncommon_trap_proj(unc); 802 if (unc_proj != NULL && unc_proj->outcnt() == 1) { 803 if (dom_unc == unc) { 804 // Allow the uncommon trap to be shared through a region 805 RegionNode* r = unc->in(0)->as_Region(); 806 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) { 807 return false; 808 } 809 assert(r->has_phi() == NULL, "simple region shouldn't have a phi"); 810 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) { 811 return false; 812 } 813 814 // Different methods and methods containing jsrs are not supported. 815 ciMethod* method = unc->jvms()->method(); 816 ciMethod* dom_method = dom_unc->jvms()->method(); 817 if (method != dom_method || method->has_jsrs()) { 818 return false; 819 } 820 // Check that both traps are in the same activation of the method (instead 821 // of two activations being inlined through different call sites) by verifying 822 // that the call stacks are equal for both JVMStates. 823 JVMState* dom_caller = dom_unc->jvms()->caller(); 824 JVMState* caller = unc->jvms()->caller(); 825 if ((dom_caller == NULL) != (caller == NULL)) { 826 // The current method must either be inlined into both dom_caller and 827 // caller or must not be inlined at all (top method). Bail out otherwise. 828 return false; 829 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) { 830 return false; 831 } 832 // Check that the bci of the dominating uncommon trap dominates the bci 833 // of the dominated uncommon trap. Otherwise we may not re-execute 834 // the dominated check after deoptimization from the merged uncommon trap. 835 ciTypeFlow* flow = dom_method->get_flow_analysis(); 836 int bci = unc->jvms()->bci(); 837 int dom_bci = dom_unc->jvms()->bci(); 838 if (!flow->is_dominated_by(bci, dom_bci)) { 839 return false; 840 } 841 842 // See merge_uncommon_traps: the reason of the uncommon trap 843 // will be changed and the state of the dominating If will be 844 // used. Checked that we didn't apply this transformation in a 845 // previous compilation and it didn't cause too many traps 846 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) && 847 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) { 848 success = unc_proj; 849 fail = unc_proj->other_if_proj(); 850 return true; 851 } 852 } 853 } 854 return false; 855 } 856 857 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding 858 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) { 859 Node* this_cmp = in(1)->in(1); 860 BoolNode* this_bool = in(1)->as_Bool(); 861 IfNode* dom_iff = proj->in(0)->as_If(); 862 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 863 Node* lo = dom_iff->in(1)->in(1)->in(2); 864 Node* hi = this_cmp->in(2); 865 Node* n = this_cmp->in(1); 866 ProjNode* otherproj = proj->other_if_proj(); 867 868 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj); 869 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success); 870 871 BoolTest::mask lo_test = dom_bool->_test._test; 872 BoolTest::mask hi_test = this_bool->_test._test; 873 BoolTest::mask cond = hi_test; 874 875 // convert: 876 // 877 // dom_bool = x {<,<=,>,>=} a 878 // / \ 879 // proj = {True,False} / \ otherproj = {False,True} 880 // / 881 // this_bool = x {<,<=} b 882 // / \ 883 // fail = {True,False} / \ success = {False,True} 884 // / 885 // 886 // (Second test guaranteed canonicalized, first one may not have 887 // been canonicalized yet) 888 // 889 // into: 890 // 891 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim 892 // / \ 893 // fail / \ success 894 // / 895 // 896 897 // Figure out which of the two tests sets the upper bound and which 898 // sets the lower bound if any. 899 Node* adjusted_lim = NULL; 900 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) { 901 assert((dom_bool->_test.is_less() && !proj->_con) || 902 (dom_bool->_test.is_greater() && proj->_con), "incorrect test"); 903 // this test was canonicalized 904 assert(this_bool->_test.is_less() && fail->_con, "incorrect test"); 905 906 // this_bool = < 907 // dom_bool = >= (proj = True) or dom_bool = < (proj = False) 908 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above): 909 // lo = a, hi = b, adjusted_lim = b-a, cond = <u 910 // dom_bool = > (proj = True) or dom_bool = <= (proj = False) 911 // x in ]a, b[ on the fail (= True) projection, b > a: 912 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u 913 // this_bool = <= 914 // dom_bool = >= (proj = True) or dom_bool = < (proj = False) 915 // x in [a, b] on the fail (= True) projection, b+1 > a-1: 916 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u 917 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1 918 // dom_bool = > (proj = True) or dom_bool = <= (proj = False) 919 // x in ]a, b] on the fail (= True) projection b+1 > a: 920 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u 921 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1 922 923 if (hi_test == BoolTest::lt) { 924 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) { 925 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 926 } 927 } else { 928 assert(hi_test == BoolTest::le, "bad test"); 929 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) { 930 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 931 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1))); 932 cond = BoolTest::lt; 933 } else { 934 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test"); 935 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 936 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 937 cond = BoolTest::lt; 938 } 939 } 940 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) { 941 942 // this_bool = < 943 // dom_bool = < (proj = True) or dom_bool = >= (proj = False) 944 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above): 945 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u 946 // dom_bool = <= (proj = True) or dom_bool = > (proj = False) 947 // x in [b, a] on the fail (= False) projection, a+1 > b-1: 948 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u 949 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1 950 // this_bool = <= 951 // dom_bool = < (proj = True) or dom_bool = >= (proj = False) 952 // x in ]b, a[ on the fail (= False) projection, a > b: 953 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u 954 // dom_bool = <= (proj = True) or dom_bool = > (proj = False) 955 // x in ]b, a] on the fail (= False) projection, a+1 > b: 956 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u 957 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >u doesn't work because a = b is possible, then b-a-1 = -1 958 959 swap(lo, hi); 960 swap(lo_type, hi_type); 961 swap(lo_test, hi_test); 962 963 assert((dom_bool->_test.is_less() && proj->_con) || 964 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test"); 965 // this test was canonicalized 966 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test"); 967 968 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge; 969 970 if (lo_test == BoolTest::lt) { 971 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) { 972 cond = BoolTest::ge; 973 } else { 974 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test"); 975 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 976 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1))); 977 cond = BoolTest::ge; 978 } 979 } else if (lo_test == BoolTest::le) { 980 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) { 981 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 982 cond = BoolTest::ge; 983 } else { 984 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test"); 985 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 986 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 987 cond = BoolTest::ge; 988 } 989 } 990 } else { 991 const TypeInt* failtype = filtered_int_type(igvn, n, proj); 992 if (failtype != NULL) { 993 const TypeInt* type2 = filtered_int_type(igvn, n, fail); 994 if (type2 != NULL) { 995 failtype = failtype->join(type2)->is_int(); 996 if (failtype->_lo > failtype->_hi) { 997 // previous if determines the result of this if so 998 // replace Bool with constant 999 igvn->_worklist.push(in(1)); 1000 igvn->replace_input_of(this, 1, igvn->intcon(success->_con)); 1001 return true; 1002 } 1003 } 1004 } 1005 lo = NULL; 1006 hi = NULL; 1007 } 1008 1009 if (lo && hi) { 1010 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo)) 1011 Node* adjusted_val = igvn->transform(new SubINode(n, lo)); 1012 if (adjusted_lim == NULL) { 1013 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 1014 } 1015 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim)); 1016 Node* newbool = igvn->transform(new BoolNode(newcmp, cond)); 1017 1018 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con)); 1019 igvn->_worklist.push(in(1)); 1020 igvn->replace_input_of(this, 1, newbool); 1021 1022 return true; 1023 } 1024 return false; 1025 } 1026 1027 // Merge the branches that trap for this If and the dominating If into 1028 // a single region that branches to the uncommon trap for the 1029 // dominating If 1030 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) { 1031 Node* res = this; 1032 assert(success->in(0) == this, "bad projection"); 1033 1034 ProjNode* otherproj = proj->other_if_proj(); 1035 1036 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none); 1037 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none); 1038 1039 if (unc != dom_unc) { 1040 Node* r = new RegionNode(3); 1041 1042 r->set_req(1, otherproj); 1043 r->set_req(2, success); 1044 r = igvn->transform(r); 1045 assert(r->is_Region(), "can't go away"); 1046 1047 // Make both If trap at the state of the first If: once the CmpI 1048 // nodes are merged, if we trap we don't know which of the CmpI 1049 // nodes would have caused the trap so we have to restart 1050 // execution at the first one 1051 igvn->replace_input_of(dom_unc, 0, r); 1052 igvn->replace_input_of(unc, 0, igvn->C->top()); 1053 } 1054 int trap_request = dom_unc->uncommon_trap_request(); 1055 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request); 1056 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request); 1057 1058 int flip_test = 0; 1059 Node* l = NULL; 1060 Node* r = NULL; 1061 1062 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) { 1063 // If this looks like a range check, change the trap to 1064 // Reason_range_check so the compiler recognizes it as a range 1065 // check and applies the corresponding optimizations 1066 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action); 1067 1068 improve_address_types(l, r, fail, igvn); 1069 1070 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt)); 1071 } else if (unc != dom_unc) { 1072 // If we trap we won't know what CmpI would have caused the trap 1073 // so use a special trap reason to mark this pair of CmpI nodes as 1074 // bad candidate for folding. On recompilation we won't fold them 1075 // and we may trap again but this time we'll know what branch 1076 // traps 1077 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action); 1078 } 1079 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request)); 1080 return res; 1081 } 1082 1083 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern 1084 // of a rangecheck on index i, on 64 bit the compares may be followed 1085 // by memory accesses using i as index. In that case, the CmpU tells 1086 // us something about the values taken by i that can help the compiler 1087 // (see Compile::conv_I2X_index()) 1088 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) { 1089 #ifdef _LP64 1090 ResourceMark rm; 1091 Node_Stack stack(2); 1092 1093 assert(r->Opcode() == Op_LoadRange, "unexpected range check"); 1094 const TypeInt* array_size = igvn->type(r)->is_int(); 1095 1096 stack.push(l, 0); 1097 1098 while(stack.size() > 0) { 1099 Node* n = stack.node(); 1100 uint start = stack.index(); 1101 1102 uint i = start; 1103 for (; i < n->outcnt(); i++) { 1104 Node* use = n->raw_out(i); 1105 if (stack.size() == 1) { 1106 if (use->Opcode() == Op_ConvI2L) { 1107 const TypeLong* bounds = use->as_Type()->type()->is_long(); 1108 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi && 1109 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) { 1110 stack.set_index(i+1); 1111 stack.push(use, 0); 1112 break; 1113 } 1114 } 1115 } else if (use->is_Mem()) { 1116 Node* ctrl = use->in(0); 1117 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) { 1118 ctrl = up_one_dom(ctrl); 1119 } 1120 if (ctrl == fail) { 1121 Node* init_n = stack.node_at(1); 1122 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node"); 1123 // Create a new narrow ConvI2L node that is dependent on the range check 1124 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail); 1125 1126 // The type of the ConvI2L may be widen and so the new 1127 // ConvI2L may not be better than an existing ConvI2L 1128 if (new_n != init_n) { 1129 for (uint j = 2; j < stack.size(); j++) { 1130 Node* n = stack.node_at(j); 1131 Node* clone = n->clone(); 1132 int rep = clone->replace_edge(init_n, new_n); 1133 assert(rep > 0, "can't find expected node?"); 1134 clone = igvn->transform(clone); 1135 init_n = n; 1136 new_n = clone; 1137 } 1138 igvn->hash_delete(use); 1139 int rep = use->replace_edge(init_n, new_n); 1140 assert(rep > 0, "can't find expected node?"); 1141 igvn->transform(use); 1142 if (init_n->outcnt() == 0) { 1143 igvn->_worklist.push(init_n); 1144 } 1145 } 1146 } 1147 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() || 1148 igvn->type(use)->isa_ptr())) { 1149 stack.set_index(i+1); 1150 stack.push(use, 0); 1151 break; 1152 } 1153 } 1154 if (i == n->outcnt()) { 1155 stack.pop(); 1156 } 1157 } 1158 #endif 1159 } 1160 1161 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) { 1162 if (in(1) != NULL && 1163 in(1)->in(1) != NULL && 1164 in(1)->in(1)->in(2) != NULL) { 1165 Node* other = in(1)->in(1)->in(2); 1166 if (other->Opcode() == Op_LoadRange && 1167 ((other->in(0) != NULL && other->in(0) == proj) || 1168 (other->in(0) == NULL && 1169 other->in(2) != NULL && 1170 other->in(2)->is_AddP() && 1171 other->in(2)->in(1) != NULL && 1172 other->in(2)->in(1)->Opcode() == Op_CastPP && 1173 other->in(2)->in(1)->in(0) == proj))) { 1174 return true; 1175 } 1176 } 1177 return false; 1178 } 1179 1180 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) { 1181 Node* other = in(1)->in(1)->in(2); 1182 if (other->in(MemNode::Address) != NULL && 1183 proj->in(0)->in(1) != NULL && 1184 proj->in(0)->in(1)->is_Bool() && 1185 proj->in(0)->in(1)->in(1) != NULL && 1186 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP && 1187 proj->in(0)->in(1)->in(1)->in(2) != NULL && 1188 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() && 1189 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) { 1190 return true; 1191 } 1192 return false; 1193 } 1194 1195 // Check that the If that is in between the 2 integer comparisons has 1196 // no side effect 1197 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) { 1198 if (proj != NULL && 1199 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) && 1200 proj->outcnt() <= 2) { 1201 if (proj->outcnt() == 1 || 1202 // Allow simple null check from LoadRange 1203 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) { 1204 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1205 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1206 1207 // reroute_side_effect_free_unc changes the state of this 1208 // uncommon trap to restart execution at the previous 1209 // CmpI. Check that this change in a previous compilation didn't 1210 // cause too many traps. 1211 int trap_request = unc->uncommon_trap_request(); 1212 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request); 1213 1214 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) { 1215 return false; 1216 } 1217 1218 return true; 1219 } 1220 } 1221 return false; 1222 } 1223 1224 // Make the If between the 2 integer comparisons trap at the state of 1225 // the first If: the last CmpI is the one replaced by a CmpU and the 1226 // first CmpI is eliminated, so the test between the 2 CmpI nodes 1227 // won't be guarded by the first CmpI anymore. It can trap in cases 1228 // where the first CmpI would have prevented it from executing: on a 1229 // trap, we need to restart execution at the state of the first CmpI 1230 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) { 1231 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1232 ProjNode* otherproj = proj->other_if_proj(); 1233 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1234 Node* call_proj = dom_unc->unique_ctrl_out(); 1235 Node* halt = call_proj->unique_ctrl_out(); 1236 1237 Node* new_unc = dom_unc->clone(); 1238 call_proj = call_proj->clone(); 1239 halt = halt->clone(); 1240 Node* c = otherproj->clone(); 1241 1242 c = igvn->transform(c); 1243 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms)); 1244 new_unc->set_req(0, c); 1245 new_unc = igvn->transform(new_unc); 1246 call_proj->set_req(0, new_unc); 1247 call_proj = igvn->transform(call_proj); 1248 halt->set_req(0, call_proj); 1249 halt = igvn->transform(halt); 1250 1251 igvn->replace_node(otherproj, igvn->C->top()); 1252 igvn->C->root()->add_req(halt); 1253 } 1254 1255 Node* IfNode::fold_compares(PhaseIterGVN* igvn) { 1256 if (Opcode() != Op_If) return NULL; 1257 1258 if (cmpi_folds(igvn)) { 1259 Node* ctrl = in(0); 1260 if (is_ctrl_folds(ctrl, igvn) && 1261 ctrl->outcnt() == 1) { 1262 // A integer comparison immediately dominated by another integer 1263 // comparison 1264 ProjNode* success = NULL; 1265 ProjNode* fail = NULL; 1266 ProjNode* dom_cmp = ctrl->as_Proj(); 1267 if (has_shared_region(dom_cmp, success, fail) && 1268 // Next call modifies graph so must be last 1269 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1270 return this; 1271 } 1272 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) && 1273 // Next call modifies graph so must be last 1274 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1275 return merge_uncommon_traps(dom_cmp, success, fail, igvn); 1276 } 1277 return NULL; 1278 } else if (ctrl->in(0) != NULL && 1279 ctrl->in(0)->in(0) != NULL) { 1280 ProjNode* success = NULL; 1281 ProjNode* fail = NULL; 1282 Node* dom = ctrl->in(0)->in(0); 1283 ProjNode* dom_cmp = dom->isa_Proj(); 1284 ProjNode* other_cmp = ctrl->isa_Proj(); 1285 1286 // Check if it's an integer comparison dominated by another 1287 // integer comparison with another test in between 1288 if (is_ctrl_folds(dom, igvn) && 1289 has_only_uncommon_traps(dom_cmp, success, fail, igvn) && 1290 is_side_effect_free_test(other_cmp, igvn) && 1291 // Next call modifies graph so must be last 1292 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1293 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn); 1294 return merge_uncommon_traps(dom_cmp, success, fail, igvn); 1295 } 1296 } 1297 } 1298 return NULL; 1299 } 1300 1301 //------------------------------remove_useless_bool---------------------------- 1302 // Check for people making a useless boolean: things like 1303 // if( (x < y ? true : false) ) { ... } 1304 // Replace with if( x < y ) { ... } 1305 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 1306 Node *i1 = iff->in(1); 1307 if( !i1->is_Bool() ) return NULL; 1308 BoolNode *bol = i1->as_Bool(); 1309 1310 Node *cmp = bol->in(1); 1311 if( cmp->Opcode() != Op_CmpI ) return NULL; 1312 1313 // Must be comparing against a bool 1314 const Type *cmp2_t = phase->type( cmp->in(2) ); 1315 if( cmp2_t != TypeInt::ZERO && 1316 cmp2_t != TypeInt::ONE ) 1317 return NULL; 1318 1319 // Find a prior merge point merging the boolean 1320 i1 = cmp->in(1); 1321 if( !i1->is_Phi() ) return NULL; 1322 PhiNode *phi = i1->as_Phi(); 1323 if( phase->type( phi ) != TypeInt::BOOL ) 1324 return NULL; 1325 1326 // Check for diamond pattern 1327 int true_path = phi->is_diamond_phi(); 1328 if( true_path == 0 ) return NULL; 1329 1330 // Make sure that iff and the control of the phi are different. This 1331 // should really only happen for dead control flow since it requires 1332 // an illegal cycle. 1333 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 1334 1335 // phi->region->if_proj->ifnode->bool->cmp 1336 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 1337 1338 // Now get the 'sense' of the test correct so we can plug in 1339 // either iff2->in(1) or its complement. 1340 int flip = 0; 1341 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 1342 else if( bol->_test._test != BoolTest::eq ) return NULL; 1343 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 1344 1345 const Type *phi1_t = phase->type( phi->in(1) ); 1346 const Type *phi2_t = phase->type( phi->in(2) ); 1347 // Check for Phi(0,1) and flip 1348 if( phi1_t == TypeInt::ZERO ) { 1349 if( phi2_t != TypeInt::ONE ) return NULL; 1350 flip = 1-flip; 1351 } else { 1352 // Check for Phi(1,0) 1353 if( phi1_t != TypeInt::ONE ) return NULL; 1354 if( phi2_t != TypeInt::ZERO ) return NULL; 1355 } 1356 if( true_path == 2 ) { 1357 flip = 1-flip; 1358 } 1359 1360 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 1361 assert(new_bol != iff->in(1), "must make progress"); 1362 iff->set_req(1, new_bol); 1363 // Intervening diamond probably goes dead 1364 phase->C->set_major_progress(); 1365 return iff; 1366 } 1367 1368 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 1369 1370 struct RangeCheck { 1371 Node* ctl; 1372 jint off; 1373 }; 1374 1375 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) { 1376 if (remove_dead_region(phase, can_reshape)) return this; 1377 // No Def-Use info? 1378 if (!can_reshape) return NULL; 1379 1380 // Don't bother trying to transform a dead if 1381 if (in(0)->is_top()) return NULL; 1382 // Don't bother trying to transform an if with a dead test 1383 if (in(1)->is_top()) return NULL; 1384 // Another variation of a dead test 1385 if (in(1)->is_Con()) return NULL; 1386 // Another variation of a dead if 1387 if (outcnt() < 2) return NULL; 1388 1389 // Canonicalize the test. 1390 Node* idt_if = idealize_test(phase, this); 1391 if (idt_if != NULL) return idt_if; 1392 1393 // Try to split the IF 1394 PhaseIterGVN *igvn = phase->is_IterGVN(); 1395 Node *s = split_if(this, igvn); 1396 if (s != NULL) return s; 1397 1398 return NodeSentinel; 1399 } 1400 1401 //------------------------------Ideal------------------------------------------ 1402 // Return a node which is more "ideal" than the current node. Strip out 1403 // control copies 1404 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1405 Node* res = Ideal_common(phase, can_reshape); 1406 if (res != NodeSentinel) { 1407 return res; 1408 } 1409 1410 // Check for people making a useless boolean: things like 1411 // if( (x < y ? true : false) ) { ... } 1412 // Replace with if( x < y ) { ... } 1413 Node *bol2 = remove_useless_bool(this, phase); 1414 if( bol2 ) return bol2; 1415 1416 if (in(0) == NULL) return NULL; // Dead loop? 1417 1418 PhaseIterGVN *igvn = phase->is_IterGVN(); 1419 Node* result = fold_compares(igvn); 1420 if (result != NULL) { 1421 return result; 1422 } 1423 1424 // Scan for an equivalent test 1425 Node *cmp; 1426 int dist = 0; // Cutoff limit for search 1427 int op = Opcode(); 1428 if( op == Op_If && 1429 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 1430 if( cmp->in(2) != NULL && // make sure cmp is not already dead 1431 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 1432 dist = 64; // Limit for null-pointer scans 1433 } else { 1434 dist = 4; // Do not bother for random pointer tests 1435 } 1436 } else { 1437 dist = 4; // Limit for random junky scans 1438 } 1439 1440 Node* prev_dom = search_identical(dist); 1441 1442 if (prev_dom == NULL) { 1443 return NULL; 1444 } 1445 1446 // Replace dominated IfNode 1447 return dominated_by(prev_dom, igvn); 1448 } 1449 1450 //------------------------------dominated_by----------------------------------- 1451 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) { 1452 #ifndef PRODUCT 1453 if (TraceIterativeGVN) { 1454 tty->print(" Removing IfNode: "); this->dump(); 1455 } 1456 if (VerifyOpto && !igvn->allow_progress()) { 1457 // Found an equivalent dominating test, 1458 // we can not guarantee reaching a fix-point for these during iterativeGVN 1459 // since intervening nodes may not change. 1460 return NULL; 1461 } 1462 #endif 1463 1464 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1465 Node *idom = in(0); 1466 // Need opcode to decide which way 'this' test goes 1467 int prev_op = prev_dom->Opcode(); 1468 Node *top = igvn->C->top(); // Shortcut to top 1469 1470 // Loop predicates may have depending checks which should not 1471 // be skipped. For example, range check predicate has two checks 1472 // for lower and upper bounds. 1473 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj(); 1474 if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)) { 1475 prev_dom = idom; 1476 } 1477 1478 // Now walk the current IfNode's projections. 1479 // Loop ends when 'this' has no more uses. 1480 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1481 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1482 igvn->add_users_to_worklist(ifp); 1483 // Check which projection it is and set target. 1484 // Data-target is either the dominating projection of the same type 1485 // or TOP if the dominating projection is of opposite type. 1486 // Data-target will be used as the new control edge for the non-CFG 1487 // nodes like Casts and Loads. 1488 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top; 1489 // Control-target is just the If's immediate dominator or TOP. 1490 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top; 1491 1492 // For each child of an IfTrue/IfFalse projection, reroute. 1493 // Loop ends when projection has no more uses. 1494 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1495 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1496 if( !s->depends_only_on_test() ) { 1497 // Find the control input matching this def-use edge. 1498 // For Regions it may not be in slot 0. 1499 uint l; 1500 for( l = 0; s->in(l) != ifp; l++ ) { } 1501 igvn->replace_input_of(s, l, ctrl_target); 1502 } else { // Else, for control producers, 1503 igvn->replace_input_of(s, 0, data_target); // Move child to data-target 1504 } 1505 } // End for each child of a projection 1506 1507 igvn->remove_dead_node(ifp); 1508 } // End for each IfTrue/IfFalse child of If 1509 1510 // Kill the IfNode 1511 igvn->remove_dead_node(this); 1512 1513 // Must return either the original node (now dead) or a new node 1514 // (Do not return a top here, since that would break the uniqueness of top.) 1515 return new ConINode(TypeInt::ZERO); 1516 } 1517 1518 Node* IfNode::search_identical(int dist) { 1519 // Setup to scan up the CFG looking for a dominating test 1520 Node* dom = in(0); 1521 Node* prev_dom = this; 1522 int op = Opcode(); 1523 // Search up the dominator tree for an If with an identical test 1524 while (dom->Opcode() != op || // Not same opcode? 1525 dom->in(1) != in(1) || // Not same input 1? 1526 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 1527 prev_dom->in(0) != dom) { // One path of test does not dominate? 1528 if (dist < 0) return NULL; 1529 1530 dist--; 1531 prev_dom = dom; 1532 dom = up_one_dom(dom); 1533 if (!dom) return NULL; 1534 } 1535 1536 // Check that we did not follow a loop back to ourselves 1537 if (this == dom) { 1538 return NULL; 1539 } 1540 1541 #ifndef PRODUCT 1542 if (dist > 2) { // Add to count of NULL checks elided 1543 explicit_null_checks_elided++; 1544 } 1545 #endif 1546 1547 return prev_dom; 1548 } 1549 1550 //------------------------------Identity--------------------------------------- 1551 // If the test is constant & we match, then we are the input Control 1552 Node* IfProjNode::Identity(PhaseGVN* phase) { 1553 // Can only optimize if cannot go the other way 1554 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1555 if (t == TypeTuple::IFNEITHER || (always_taken(t) && 1556 // During parsing (GVN) we don't remove dead code aggressively. 1557 // Cut off dead branch and let PhaseRemoveUseless take care of it. 1558 (!phase->is_IterGVN() || 1559 // During IGVN, first wait for the dead branch to be killed. 1560 // Otherwise, the IfNode's control will have two control uses (the IfNode 1561 // that doesn't go away because it still has uses and this branch of the 1562 // If) which breaks other optimizations. Node::has_special_unique_user() 1563 // will cause this node to be reprocessed once the dead branch is killed. 1564 in(0)->outcnt() == 1))) { 1565 // IfNode control 1566 return in(0)->in(0); 1567 } 1568 // no progress 1569 return this; 1570 } 1571 1572 #ifndef PRODUCT 1573 //-------------------------------related--------------------------------------- 1574 // An IfProjNode's related node set consists of its input (an IfNode) including 1575 // the IfNode's condition, plus all of its outputs at level 1. In compact mode, 1576 // the restrictions for IfNode apply (see IfNode::rel). 1577 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const { 1578 Node* ifNode = this->in(0); 1579 in_rel->append(ifNode); 1580 if (compact) { 1581 ifNode->collect_nodes(in_rel, 3, false, true); 1582 } else { 1583 ifNode->collect_nodes_in_all_data(in_rel, false); 1584 } 1585 this->collect_nodes(out_rel, -1, false, false); 1586 } 1587 1588 //------------------------------dump_spec-------------------------------------- 1589 void IfNode::dump_spec(outputStream *st) const { 1590 st->print("P=%f, C=%f",_prob,_fcnt); 1591 } 1592 1593 //-------------------------------related--------------------------------------- 1594 // For an IfNode, the set of related output nodes is just the output nodes till 1595 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer. 1596 // The related input nodes contain no control nodes, but all data nodes 1597 // pertaining to the condition. In compact mode, the input nodes are collected 1598 // up to a depth of 3. 1599 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const { 1600 if (compact) { 1601 this->collect_nodes(in_rel, 3, false, true); 1602 } else { 1603 this->collect_nodes_in_all_data(in_rel, false); 1604 } 1605 this->collect_nodes(out_rel, -2, false, false); 1606 } 1607 #endif 1608 1609 //------------------------------idealize_test---------------------------------- 1610 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1611 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1612 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1613 // needed. 1614 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1615 assert(iff->in(0) != NULL, "If must be live"); 1616 1617 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1618 Node* old_if_f = iff->proj_out(false); 1619 Node* old_if_t = iff->proj_out(true); 1620 1621 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1622 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1623 // happens in count-down loops 1624 if (iff->is_CountedLoopEnd()) return NULL; 1625 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1626 BoolNode *b = iff->in(1)->as_Bool(); 1627 BoolTest bt = b->_test; 1628 // Test already in good order? 1629 if( bt.is_canonical() ) 1630 return NULL; 1631 1632 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1633 // cloning the IfNode. 1634 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) ); 1635 if( !new_b->is_Bool() ) return NULL; 1636 b = new_b->as_Bool(); 1637 1638 PhaseIterGVN *igvn = phase->is_IterGVN(); 1639 assert( igvn, "Test is not canonical in parser?" ); 1640 1641 // The IF node never really changes, but it needs to be cloned 1642 iff = iff->clone()->as_If(); 1643 iff->set_req(1, b); 1644 iff->_prob = 1.0-iff->_prob; 1645 1646 Node *prior = igvn->hash_find_insert(iff); 1647 if( prior ) { 1648 igvn->remove_dead_node(iff); 1649 iff = (IfNode*)prior; 1650 } else { 1651 // Cannot call transform on it just yet 1652 igvn->set_type_bottom(iff); 1653 } 1654 igvn->_worklist.push(iff); 1655 1656 // Now handle projections. Cloning not required. 1657 Node* new_if_f = (Node*)(new IfFalseNode( iff )); 1658 Node* new_if_t = (Node*)(new IfTrueNode ( iff )); 1659 1660 igvn->register_new_node_with_optimizer(new_if_f); 1661 igvn->register_new_node_with_optimizer(new_if_t); 1662 // Flip test, so flip trailing control 1663 igvn->replace_node(old_if_f, new_if_t); 1664 igvn->replace_node(old_if_t, new_if_f); 1665 1666 // Progress 1667 return iff; 1668 } 1669 1670 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1671 Node* res = Ideal_common(phase, can_reshape); 1672 if (res != NodeSentinel) { 1673 return res; 1674 } 1675 1676 PhaseIterGVN *igvn = phase->is_IterGVN(); 1677 // Setup to scan up the CFG looking for a dominating test 1678 Node* prev_dom = this; 1679 1680 // Check for range-check vs other kinds of tests 1681 Node* index1; 1682 Node* range1; 1683 jint offset1; 1684 int flip1 = is_range_check(range1, index1, offset1); 1685 if (flip1) { 1686 Node* dom = in(0); 1687 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 1688 // so all checks we inspect post-dominate the top-most check we find. 1689 // If we are going to fail the current check and we reach the top check 1690 // then we are guaranteed to fail, so just start interpreting there. 1691 // We 'expand' the top 3 range checks to include all post-dominating 1692 // checks. 1693 1694 // The top 3 range checks seen 1695 const int NRC =3; 1696 RangeCheck prev_checks[NRC]; 1697 int nb_checks = 0; 1698 1699 // Low and high offsets seen so far 1700 jint off_lo = offset1; 1701 jint off_hi = offset1; 1702 1703 bool found_immediate_dominator = false; 1704 1705 // Scan for the top checks and collect range of offsets 1706 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit 1707 if (dom->Opcode() == Op_RangeCheck && // Not same opcode? 1708 prev_dom->in(0) == dom) { // One path of test does dominate? 1709 if (dom == this) return NULL; // dead loop 1710 // See if this is a range check 1711 Node* index2; 1712 Node* range2; 1713 jint offset2; 1714 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2); 1715 // See if this is a _matching_ range check, checking against 1716 // the same array bounds. 1717 if (flip2 == flip1 && range2 == range1 && index2 == index1 && 1718 dom->outcnt() == 2) { 1719 if (nb_checks == 0 && dom->in(1) == in(1)) { 1720 // Found an immediately dominating test at the same offset. 1721 // This kind of back-to-back test can be eliminated locally, 1722 // and there is no need to search further for dominating tests. 1723 assert(offset2 == offset1, "Same test but different offsets"); 1724 found_immediate_dominator = true; 1725 break; 1726 } 1727 // Gather expanded bounds 1728 off_lo = MIN2(off_lo,offset2); 1729 off_hi = MAX2(off_hi,offset2); 1730 // Record top NRC range checks 1731 prev_checks[nb_checks%NRC].ctl = prev_dom; 1732 prev_checks[nb_checks%NRC].off = offset2; 1733 nb_checks++; 1734 } 1735 } 1736 prev_dom = dom; 1737 dom = up_one_dom(dom); 1738 if (!dom) break; 1739 } 1740 1741 if (!found_immediate_dominator) { 1742 // Attempt to widen the dominating range check to cover some later 1743 // ones. Since range checks "fail" by uncommon-trapping to the 1744 // interpreter, widening a check can make us speculatively enter 1745 // the interpreter. If we see range-check deopt's, do not widen! 1746 if (!phase->C->allow_range_check_smearing()) return NULL; 1747 1748 // Didn't find prior covering check, so cannot remove anything. 1749 if (nb_checks == 0) { 1750 return NULL; 1751 } 1752 // Constant indices only need to check the upper bound. 1753 // Non-constant indices must check both low and high. 1754 int chk0 = (nb_checks - 1) % NRC; 1755 if (index1) { 1756 if (nb_checks == 1) { 1757 return NULL; 1758 } else { 1759 // If the top range check's constant is the min or max of 1760 // all constants we widen the next one to cover the whole 1761 // range of constants. 1762 RangeCheck rc0 = prev_checks[chk0]; 1763 int chk1 = (nb_checks - 2) % NRC; 1764 RangeCheck rc1 = prev_checks[chk1]; 1765 if (rc0.off == off_lo) { 1766 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); 1767 prev_dom = rc1.ctl; 1768 } else if (rc0.off == off_hi) { 1769 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); 1770 prev_dom = rc1.ctl; 1771 } else { 1772 // If the top test's constant is not the min or max of all 1773 // constants, we need 3 range checks. We must leave the 1774 // top test unchanged because widening it would allow the 1775 // accesses it protects to successfully read/write out of 1776 // bounds. 1777 if (nb_checks == 2) { 1778 return NULL; 1779 } 1780 int chk2 = (nb_checks - 3) % NRC; 1781 RangeCheck rc2 = prev_checks[chk2]; 1782 // The top range check a+i covers interval: -a <= i < length-a 1783 // The second range check b+i covers interval: -b <= i < length-b 1784 if (rc1.off <= rc0.off) { 1785 // if b <= a, we change the second range check to: 1786 // -min_of_all_constants <= i < length-min_of_all_constants 1787 // Together top and second range checks now cover: 1788 // -min_of_all_constants <= i < length-a 1789 // which is more restrictive than -b <= i < length-b: 1790 // -b <= -min_of_all_constants <= i < length-a <= length-b 1791 // The third check is then changed to: 1792 // -max_of_all_constants <= i < length-max_of_all_constants 1793 // so 2nd and 3rd checks restrict allowed values of i to: 1794 // -min_of_all_constants <= i < length-max_of_all_constants 1795 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); 1796 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn); 1797 } else { 1798 // if b > a, we change the second range check to: 1799 // -max_of_all_constants <= i < length-max_of_all_constants 1800 // Together top and second range checks now cover: 1801 // -a <= i < length-max_of_all_constants 1802 // which is more restrictive than -b <= i < length-b: 1803 // -b < -a <= i < length-max_of_all_constants <= length-b 1804 // The third check is then changed to: 1805 // -max_of_all_constants <= i < length-max_of_all_constants 1806 // so 2nd and 3rd checks restrict allowed values of i to: 1807 // -min_of_all_constants <= i < length-max_of_all_constants 1808 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); 1809 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn); 1810 } 1811 prev_dom = rc2.ctl; 1812 } 1813 } 1814 } else { 1815 RangeCheck rc0 = prev_checks[chk0]; 1816 // 'Widen' the offset of the 1st and only covering check 1817 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn); 1818 // Test is now covered by prior checks, dominate it out 1819 prev_dom = rc0.ctl; 1820 } 1821 } 1822 } else { 1823 prev_dom = search_identical(4); 1824 1825 if (prev_dom == NULL) { 1826 return NULL; 1827 } 1828 } 1829 1830 // Replace dominated IfNode 1831 return dominated_by(prev_dom, igvn); 1832 }