1 /* 2 * Copyright (c) 2000, 2015, 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 "opto/addnode.hpp" 29 #include "opto/castnode.hpp" 30 #include "opto/cfgnode.hpp" 31 #include "opto/connode.hpp" 32 #include "opto/loopnode.hpp" 33 #include "opto/phaseX.hpp" 34 #include "opto/runtime.hpp" 35 #include "opto/rootnode.hpp" 36 #include "opto/subnode.hpp" 37 38 // Portions of code courtesy of Clifford Click 39 40 // Optimization - Graph Style 41 42 43 extern int explicit_null_checks_elided; 44 45 //============================================================================= 46 //------------------------------Value------------------------------------------ 47 // Return a tuple for whichever arm of the IF is reachable 48 const Type *IfNode::Value( PhaseTransform *phase ) const { 49 if( !in(0) ) return Type::TOP; 50 if( phase->type(in(0)) == Type::TOP ) 51 return Type::TOP; 52 const Type *t = phase->type(in(1)); 53 if( t == Type::TOP ) // data is undefined 54 return TypeTuple::IFNEITHER; // unreachable altogether 55 if( t == TypeInt::ZERO ) // zero, or false 56 return TypeTuple::IFFALSE; // only false branch is reachable 57 if( t == TypeInt::ONE ) // 1, or true 58 return TypeTuple::IFTRUE; // only true branch is reachable 59 assert( t == TypeInt::BOOL, "expected boolean type" ); 60 61 return TypeTuple::IFBOTH; // No progress 62 } 63 64 const RegMask &IfNode::out_RegMask() const { 65 return RegMask::Empty; 66 } 67 68 //------------------------------split_if--------------------------------------- 69 // Look for places where we merge constants, then test on the merged value. 70 // If the IF test will be constant folded on the path with the constant, we 71 // win by splitting the IF to before the merge point. 72 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) { 73 // I could be a lot more general here, but I'm trying to squeeze this 74 // in before the Christmas '98 break so I'm gonna be kinda restrictive 75 // on the patterns I accept. CNC 76 77 // Look for a compare of a constant and a merged value 78 Node *i1 = iff->in(1); 79 if( !i1->is_Bool() ) return NULL; 80 BoolNode *b = i1->as_Bool(); 81 Node *cmp = b->in(1); 82 if( !cmp->is_Cmp() ) return NULL; 83 i1 = cmp->in(1); 84 if( i1 == NULL || !i1->is_Phi() ) return NULL; 85 PhiNode *phi = i1->as_Phi(); 86 if( phi->is_copy() ) return NULL; 87 Node *con2 = cmp->in(2); 88 if( !con2->is_Con() ) return NULL; 89 // See that the merge point contains some constants 90 Node *con1=NULL; 91 uint i4; 92 for( i4 = 1; i4 < phi->req(); i4++ ) { 93 con1 = phi->in(i4); 94 if( !con1 ) return NULL; // Do not optimize partially collapsed merges 95 if( con1->is_Con() ) break; // Found a constant 96 // Also allow null-vs-not-null checks 97 const TypePtr *tp = igvn->type(con1)->isa_ptr(); 98 if( tp && tp->_ptr == TypePtr::NotNull ) 99 break; 100 } 101 if( i4 >= phi->req() ) return NULL; // Found no constants 102 103 igvn->C->set_has_split_ifs(true); // Has chance for split-if 104 105 // Make sure that the compare can be constant folded away 106 Node *cmp2 = cmp->clone(); 107 cmp2->set_req(1,con1); 108 cmp2->set_req(2,con2); 109 const Type *t = cmp2->Value(igvn); 110 // This compare is dead, so whack it! 111 igvn->remove_dead_node(cmp2); 112 if( !t->singleton() ) return NULL; 113 114 // No intervening control, like a simple Call 115 Node *r = iff->in(0); 116 if( !r->is_Region() ) return NULL; 117 if( phi->region() != r ) return NULL; 118 // No other users of the cmp/bool 119 if (b->outcnt() != 1 || cmp->outcnt() != 1) { 120 //tty->print_cr("many users of cmp/bool"); 121 return NULL; 122 } 123 124 // Make sure we can determine where all the uses of merged values go 125 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { 126 Node* u = r->fast_out(j); 127 if( u == r ) continue; 128 if( u == iff ) continue; 129 if( u->outcnt() == 0 ) continue; // use is dead & ignorable 130 if( !u->is_Phi() ) { 131 /* 132 if( u->is_Start() ) { 133 tty->print_cr("Region has inlined start use"); 134 } else { 135 tty->print_cr("Region has odd use"); 136 u->dump(2); 137 }*/ 138 return NULL; 139 } 140 if( u != phi ) { 141 // CNC - do not allow any other merged value 142 //tty->print_cr("Merging another value"); 143 //u->dump(2); 144 return NULL; 145 } 146 // Make sure we can account for all Phi uses 147 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { 148 Node* v = u->fast_out(k); // User of the phi 149 // CNC - Allow only really simple patterns. 150 // In particular I disallow AddP of the Phi, a fairly common pattern 151 if (v == cmp) continue; // The compare is OK 152 if (v->is_ConstraintCast()) { 153 // If the cast is derived from data flow edges, it may not have a control edge. 154 // If so, it should be safe to split. But follow-up code can not deal with 155 // this (l. 359). So skip. 156 if (v->in(0) == NULL) { 157 return NULL; 158 } 159 if (v->in(0)->in(0) == iff) { 160 continue; // CastPP/II of the IfNode is OK 161 } 162 } 163 // Disabled following code because I cannot tell if exactly one 164 // path dominates without a real dominator check. CNC 9/9/1999 165 //uint vop = v->Opcode(); 166 //if( vop == Op_Phi ) { // Phi from another merge point might be OK 167 // Node *r = v->in(0); // Get controlling point 168 // if( !r ) return NULL; // Degraded to a copy 169 // // Find exactly one path in (either True or False doms, but not IFF) 170 // int cnt = 0; 171 // for( uint i = 1; i < r->req(); i++ ) 172 // if( r->in(i) && r->in(i)->in(0) == iff ) 173 // cnt++; 174 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi 175 //} 176 if( !v->is_Call() ) { 177 /* 178 if( v->Opcode() == Op_AddP ) { 179 tty->print_cr("Phi has AddP use"); 180 } else if( v->Opcode() == Op_CastPP ) { 181 tty->print_cr("Phi has CastPP use"); 182 } else if( v->Opcode() == Op_CastII ) { 183 tty->print_cr("Phi has CastII use"); 184 } else { 185 tty->print_cr("Phi has use I cant be bothered with"); 186 } 187 */ 188 } 189 return NULL; 190 191 /* CNC - Cut out all the fancy acceptance tests 192 // Can we clone this use when doing the transformation? 193 // If all uses are from Phis at this merge or constants, then YES. 194 if( !v->in(0) && v != cmp ) { 195 tty->print_cr("Phi has free-floating use"); 196 v->dump(2); 197 return NULL; 198 } 199 for( uint l = 1; l < v->req(); l++ ) { 200 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && 201 !v->in(l)->is_Con() ) { 202 tty->print_cr("Phi has use"); 203 v->dump(2); 204 return NULL; 205 } // End of if Phi-use input is neither Phi nor Constant 206 } // End of for all inputs to Phi-use 207 */ 208 } // End of for all uses of Phi 209 } // End of for all uses of Region 210 211 // Only do this if the IF node is in a sane state 212 if (iff->outcnt() != 2) 213 return NULL; 214 215 // Got a hit! Do the Mondo Hack! 216 // 217 //ABC a1c def ghi B 1 e h A C a c d f g i 218 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi 219 // cmp - 2 cmp - 2 cmp - 2 220 // bool bool_c bool_x 221 // if if_c if_x 222 // T F T F T F 223 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. 224 // 225 // Split the paths coming into the merge point into 2 separate groups of 226 // merges. On the left will be all the paths feeding constants into the 227 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi 228 // will fold up into a constant; this will let the Cmp fold up as well as 229 // all the control flow. Below the original IF we have 2 control 230 // dependent regions, 's' and 't'. Now we will merge the two paths 231 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite 232 // likely 2 or more) will promptly constant fold away. 233 PhaseGVN *phase = igvn; 234 235 // Make a region merging constants and a region merging the rest 236 uint req_c = 0; 237 Node* predicate_proj = NULL; 238 int nb_predicate_proj = 0; 239 for (uint ii = 1; ii < r->req(); ii++) { 240 if (phi->in(ii) == con1) { 241 req_c++; 242 } 243 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii)); 244 if (proj != NULL) { 245 nb_predicate_proj++; 246 predicate_proj = proj; 247 } 248 } 249 if (nb_predicate_proj > 1) { 250 // Can happen in case of loop unswitching and when the loop is 251 // optimized out: it's not a loop anymore so we don't care about 252 // predicates. 253 assert(!r->is_Loop(), "this must not be a loop anymore"); 254 predicate_proj = NULL; 255 } 256 Node* predicate_c = NULL; 257 Node* predicate_x = NULL; 258 bool counted_loop = r->is_CountedLoop(); 259 260 Node *region_c = new RegionNode(req_c + 1); 261 Node *phi_c = con1; 262 uint len = r->req(); 263 Node *region_x = new RegionNode(len - req_c); 264 Node *phi_x = PhiNode::make_blank(region_x, phi); 265 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { 266 if (phi->in(i) == con1) { 267 region_c->init_req( i_c++, r ->in(i) ); 268 if (r->in(i) == predicate_proj) 269 predicate_c = predicate_proj; 270 } else { 271 region_x->init_req( i_x, r ->in(i) ); 272 phi_x ->init_req( i_x++, phi->in(i) ); 273 if (r->in(i) == predicate_proj) 274 predicate_x = predicate_proj; 275 } 276 } 277 if (predicate_c != NULL && (req_c > 1)) { 278 assert(predicate_x == NULL, "only one predicate entry expected"); 279 predicate_c = NULL; // Do not clone predicate below merge point 280 } 281 if (predicate_x != NULL && ((len - req_c) > 2)) { 282 assert(predicate_c == NULL, "only one predicate entry expected"); 283 predicate_x = NULL; // Do not clone predicate below merge point 284 } 285 286 // Register the new RegionNodes but do not transform them. Cannot 287 // transform until the entire Region/Phi conglomerate has been hacked 288 // as a single huge transform. 289 igvn->register_new_node_with_optimizer( region_c ); 290 igvn->register_new_node_with_optimizer( region_x ); 291 // Prevent the untimely death of phi_x. Currently he has no uses. He is 292 // about to get one. If this only use goes away, then phi_x will look dead. 293 // However, he will be picking up some more uses down below. 294 Node *hook = new Node(4); 295 hook->init_req(0, phi_x); 296 hook->init_req(1, phi_c); 297 phi_x = phase->transform( phi_x ); 298 299 // Make the compare 300 Node *cmp_c = phase->makecon(t); 301 Node *cmp_x = cmp->clone(); 302 cmp_x->set_req(1,phi_x); 303 cmp_x->set_req(2,con2); 304 cmp_x = phase->transform(cmp_x); 305 // Make the bool 306 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test)); 307 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test)); 308 // Make the IfNode 309 IfNode* iff_c = iff->clone()->as_If(); 310 iff_c->set_req(0, region_c); 311 iff_c->set_req(1, b_c); 312 igvn->set_type_bottom(iff_c); 313 igvn->_worklist.push(iff_c); 314 hook->init_req(2, iff_c); 315 316 IfNode* iff_x = iff->clone()->as_If(); 317 iff_x->set_req(0, region_x); 318 iff_x->set_req(1, b_x); 319 igvn->set_type_bottom(iff_x); 320 igvn->_worklist.push(iff_x); 321 hook->init_req(3, iff_x); 322 323 // Make the true/false arms 324 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c)); 325 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c)); 326 if (predicate_c != NULL) { 327 assert(predicate_x == NULL, "only one predicate entry expected"); 328 // Clone loop predicates to each path 329 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop); 330 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop); 331 } 332 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x)); 333 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x)); 334 if (predicate_x != NULL) { 335 assert(predicate_c == NULL, "only one predicate entry expected"); 336 // Clone loop predicates to each path 337 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop); 338 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop); 339 } 340 341 // Merge the TRUE paths 342 Node *region_s = new RegionNode(3); 343 igvn->_worklist.push(region_s); 344 region_s->init_req(1, iff_c_t); 345 region_s->init_req(2, iff_x_t); 346 igvn->register_new_node_with_optimizer( region_s ); 347 348 // Merge the FALSE paths 349 Node *region_f = new RegionNode(3); 350 igvn->_worklist.push(region_f); 351 region_f->init_req(1, iff_c_f); 352 region_f->init_req(2, iff_x_f); 353 igvn->register_new_node_with_optimizer( region_f ); 354 355 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. 356 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead 357 cmp->set_req(2,NULL); 358 // Check for all uses of the Phi and give them a new home. 359 // The 'cmp' got cloned, but CastPP/IIs need to be moved. 360 Node *phi_s = NULL; // do not construct unless needed 361 Node *phi_f = NULL; // do not construct unless needed 362 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { 363 Node* v = phi->last_out(i2);// User of the phi 364 igvn->rehash_node_delayed(v); // Have to fixup other Phi users 365 uint vop = v->Opcode(); 366 Node *proj = NULL; 367 if( vop == Op_Phi ) { // Remote merge point 368 Node *r = v->in(0); 369 for (uint i3 = 1; i3 < r->req(); i3++) 370 if (r->in(i3) && r->in(i3)->in(0) == iff) { 371 proj = r->in(i3); 372 break; 373 } 374 } else if( v->is_ConstraintCast() ) { 375 proj = v->in(0); // Controlling projection 376 } else { 377 assert( 0, "do not know how to handle this guy" ); 378 } 379 380 Node *proj_path_data, *proj_path_ctrl; 381 if( proj->Opcode() == Op_IfTrue ) { 382 if( phi_s == NULL ) { 383 // Only construct phi_s if needed, otherwise provides 384 // interfering use. 385 phi_s = PhiNode::make_blank(region_s,phi); 386 phi_s->init_req( 1, phi_c ); 387 phi_s->init_req( 2, phi_x ); 388 hook->add_req(phi_s); 389 phi_s = phase->transform(phi_s); 390 } 391 proj_path_data = phi_s; 392 proj_path_ctrl = region_s; 393 } else { 394 if( phi_f == NULL ) { 395 // Only construct phi_f if needed, otherwise provides 396 // interfering use. 397 phi_f = PhiNode::make_blank(region_f,phi); 398 phi_f->init_req( 1, phi_c ); 399 phi_f->init_req( 2, phi_x ); 400 hook->add_req(phi_f); 401 phi_f = phase->transform(phi_f); 402 } 403 proj_path_data = phi_f; 404 proj_path_ctrl = region_f; 405 } 406 407 // Fixup 'v' for for the split 408 if( vop == Op_Phi ) { // Remote merge point 409 uint i; 410 for( i = 1; i < v->req(); i++ ) 411 if( v->in(i) == phi ) 412 break; 413 v->set_req(i, proj_path_data ); 414 } else if( v->is_ConstraintCast() ) { 415 v->set_req(0, proj_path_ctrl ); 416 v->set_req(1, proj_path_data ); 417 } else 418 ShouldNotReachHere(); 419 } 420 421 // Now replace the original iff's True/False with region_s/region_t. 422 // This makes the original iff go dead. 423 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { 424 Node* p = iff->last_out(i3); 425 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); 426 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; 427 // Replace p with u 428 igvn->add_users_to_worklist(p); 429 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { 430 Node* x = p->last_out(l); 431 igvn->hash_delete(x); 432 uint uses_found = 0; 433 for( uint j = 0; j < x->req(); j++ ) { 434 if( x->in(j) == p ) { 435 x->set_req(j, u); 436 uses_found++; 437 } 438 } 439 l -= uses_found; // we deleted 1 or more copies of this edge 440 } 441 igvn->remove_dead_node(p); 442 } 443 444 // Force the original merge dead 445 igvn->hash_delete(r); 446 // First, remove region's dead users. 447 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { 448 Node* u = r->last_out(l); 449 if( u == r ) { 450 r->set_req(0, NULL); 451 } else { 452 assert(u->outcnt() == 0, "only dead users"); 453 igvn->remove_dead_node(u); 454 } 455 l -= 1; 456 } 457 igvn->remove_dead_node(r); 458 459 // Now remove the bogus extra edges used to keep things alive 460 igvn->remove_dead_node( hook ); 461 462 // Must return either the original node (now dead) or a new node 463 // (Do not return a top here, since that would break the uniqueness of top.) 464 return new ConINode(TypeInt::ZERO); 465 } 466 467 // if this IfNode follows a range check pattern return the projection 468 // for the failed path 469 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) { 470 Node* b = in(1); 471 if (b == NULL || !b->is_Bool()) return NULL; 472 BoolNode* bn = b->as_Bool(); 473 Node* cmp = bn->in(1); 474 if (cmp == NULL) return NULL; 475 if (cmp->Opcode() != Op_CmpU) return NULL; 476 477 l = cmp->in(1); 478 r = cmp->in(2); 479 flip_test = 1; 480 if (bn->_test._test == BoolTest::le) { 481 l = cmp->in(2); 482 r = cmp->in(1); 483 flip_test = 2; 484 } else if (bn->_test._test != BoolTest::lt) { 485 return NULL; 486 } 487 if (l->is_top()) return NULL; // Top input means dead test 488 if (r->Opcode() != Op_LoadRange) return NULL; 489 490 // We have recognized one of these forms: 491 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... 492 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... 493 494 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false); 495 return iftrap; 496 } 497 498 499 //------------------------------is_range_check--------------------------------- 500 // Return 0 if not a range check. Return 1 if a range check and set index and 501 // offset. Return 2 if we had to negate the test. Index is NULL if the check 502 // is versus a constant. 503 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) { 504 int flip_test = 0; 505 Node* l = NULL; 506 Node* r = NULL; 507 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r); 508 509 if (iftrap == NULL) { 510 return 0; 511 } 512 513 // Make sure it's a real range check by requiring an uncommon trap 514 // along the OOB path. Otherwise, it's possible that the user wrote 515 // something which optimized to look like a range check but behaves 516 // in some other way. 517 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) { 518 return 0; 519 } 520 521 // Look for index+offset form 522 Node* ind = l; 523 jint off = 0; 524 if (l->is_top()) { 525 return 0; 526 } else if (l->Opcode() == Op_AddI) { 527 if ((off = l->in(1)->find_int_con(0)) != 0) { 528 ind = l->in(2); 529 } else if ((off = l->in(2)->find_int_con(0)) != 0) { 530 ind = l->in(1); 531 } 532 } else if ((off = l->find_int_con(-1)) >= 0) { 533 // constant offset with no variable index 534 ind = NULL; 535 } else { 536 // variable index with no constant offset (or dead negative index) 537 off = 0; 538 } 539 540 // Return all the values: 541 index = ind; 542 offset = off; 543 range = r; 544 return flip_test; 545 } 546 547 //------------------------------adjust_check----------------------------------- 548 // Adjust (widen) a prior range check 549 static void adjust_check(Node* proj, Node* range, Node* index, 550 int flip, jint off_lo, PhaseIterGVN* igvn) { 551 PhaseGVN *gvn = igvn; 552 // Break apart the old check 553 Node *iff = proj->in(0); 554 Node *bol = iff->in(1); 555 if( bol->is_top() ) return; // In case a partially dead range check appears 556 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode 557 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) 558 if( !bol->is_Bool() ) return; 559 560 Node *cmp = bol->in(1); 561 // Compute a new check 562 Node *new_add = gvn->intcon(off_lo); 563 if( index ) { 564 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index; 565 } 566 Node *new_cmp = (flip == 1) 567 ? new CmpUNode( new_add, range ) 568 : new CmpUNode( range, new_add ); 569 new_cmp = gvn->transform(new_cmp); 570 // See if no need to adjust the existing check 571 if( new_cmp == cmp ) return; 572 // Else, adjust existing check 573 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 574 igvn->rehash_node_delayed( iff ); 575 iff->set_req_X( 1, new_bol, igvn ); 576 } 577 578 //------------------------------up_one_dom------------------------------------- 579 // Walk up the dominator tree one step. Return NULL at root or true 580 // complex merges. Skips through small diamonds. 581 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 582 Node *dom = curr->in(0); 583 if( !dom ) // Found a Region degraded to a copy? 584 return curr->nonnull_req(); // Skip thru it 585 586 if( curr != dom ) // Normal walk up one step? 587 return dom; 588 589 // Use linear_only if we are still parsing, since we cannot 590 // trust the regions to be fully filled in. 591 if (linear_only) 592 return NULL; 593 594 if( dom->is_Root() ) 595 return NULL; 596 597 // Else hit a Region. Check for a loop header 598 if( dom->is_Loop() ) 599 return dom->in(1); // Skip up thru loops 600 601 // Check for small diamonds 602 Node *din1, *din2, *din3, *din4; 603 if( dom->req() == 3 && // 2-path merge point 604 (din1 = dom ->in(1)) && // Left path exists 605 (din2 = dom ->in(2)) && // Right path exists 606 (din3 = din1->in(0)) && // Left path up one 607 (din4 = din2->in(0)) ) { // Right path up one 608 if( din3->is_Call() && // Handle a slow-path call on either arm 609 (din3 = din3->in(0)) ) 610 din3 = din3->in(0); 611 if( din4->is_Call() && // Handle a slow-path call on either arm 612 (din4 = din4->in(0)) ) 613 din4 = din4->in(0); 614 if( din3 == din4 && din3->is_If() ) 615 return din3; // Skip around diamonds 616 } 617 618 // Give up the search at true merges 619 return NULL; // Dead loop? Or hit root? 620 } 621 622 623 //------------------------------filtered_int_type-------------------------------- 624 // Return a possibly more restrictive type for val based on condition control flow for an if 625 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 626 assert(if_proj && 627 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 628 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 629 IfNode* iff = if_proj->in(0)->as_If(); 630 if (iff->in(1) && iff->in(1)->is_Bool()) { 631 BoolNode* bol = iff->in(1)->as_Bool(); 632 if (bol->in(1) && bol->in(1)->is_Cmp()) { 633 const CmpNode* cmp = bol->in(1)->as_Cmp(); 634 if (cmp->in(1) == val) { 635 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 636 if (cmp2_t != NULL) { 637 jint lo = cmp2_t->_lo; 638 jint hi = cmp2_t->_hi; 639 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 640 switch (msk) { 641 case BoolTest::ne: 642 // Can't refine type 643 return NULL; 644 case BoolTest::eq: 645 return cmp2_t; 646 case BoolTest::lt: 647 lo = TypeInt::INT->_lo; 648 if (hi - 1 < hi) { 649 hi = hi - 1; 650 } 651 break; 652 case BoolTest::le: 653 lo = TypeInt::INT->_lo; 654 break; 655 case BoolTest::gt: 656 if (lo + 1 > lo) { 657 lo = lo + 1; 658 } 659 hi = TypeInt::INT->_hi; 660 break; 661 case BoolTest::ge: 662 // lo unchanged 663 hi = TypeInt::INT->_hi; 664 break; 665 } 666 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 667 return rtn_t; 668 } 669 } 670 } 671 } 672 } 673 return NULL; 674 } 675 676 //------------------------------fold_compares---------------------------- 677 // See if a pair of CmpIs can be converted into a CmpU. In some cases 678 // the direction of this if is determined by the preceding if so it 679 // can be eliminate entirely. 680 // 681 // Given an if testing (CmpI n v) check for an immediately control 682 // dependent if that is testing (CmpI n v2) and has one projection 683 // leading to this if and the other projection leading to a region 684 // that merges one of this ifs control projections. 685 // 686 // If 687 // / | 688 // / | 689 // / | 690 // If | 691 // /\ | 692 // / \ | 693 // / \ | 694 // / Region 695 // 696 // Or given an if testing (CmpI n v) check for a dominating if that is 697 // testing (CmpI n v2), both having one projection leading to an 698 // uncommon trap. Allow Another independent guard in between to cover 699 // an explicit range check: 700 // if (index < 0 || index >= array.length) { 701 // which may need a null check to guard the LoadRange 702 // 703 // If 704 // / \ 705 // / \ 706 // / \ 707 // If unc 708 // /\ 709 // / \ 710 // / \ 711 // / unc 712 // 713 714 // Is the comparison for this If suitable for folding? 715 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) { 716 return in(1) != NULL && 717 in(1)->is_Bool() && 718 in(1)->in(1) != NULL && 719 in(1)->in(1)->Opcode() == Op_CmpI && 720 in(1)->in(1)->in(2) != NULL && 721 in(1)->in(1)->in(2) != igvn->C->top() && 722 (in(1)->as_Bool()->_test.is_less() || 723 in(1)->as_Bool()->_test.is_greater()); 724 } 725 726 // Is a dominating control suitable for folding with this if? 727 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) { 728 return ctrl != NULL && 729 ctrl->is_Proj() && 730 ctrl->in(0) != NULL && 731 ctrl->in(0)->Opcode() == Op_If && 732 ctrl->in(0)->outcnt() == 2 && 733 ctrl->in(0)->as_If()->cmpi_folds(igvn) && 734 // Must compare same value 735 ctrl->in(0)->in(1)->in(1)->in(1) != NULL && 736 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1); 737 } 738 739 // Do this If and the dominating If share a region? 740 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) { 741 ProjNode* otherproj = proj->other_if_proj(); 742 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out(); 743 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL; 744 success = NULL; 745 fail = NULL; 746 747 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) { 748 for (int i = 0; i < 2; i++) { 749 ProjNode* proj = proj_out(i); 750 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 751 success = proj; 752 } else if (fail == NULL) { 753 fail = proj; 754 } else { 755 success = fail = NULL; 756 } 757 } 758 } 759 return success != NULL && fail != NULL; 760 } 761 762 // Return projection that leads to an uncommon trap if any 763 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const { 764 for (int i = 0; i < 2; i++) { 765 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none); 766 if (call != NULL) { 767 return proj_out(i); 768 } 769 } 770 return NULL; 771 } 772 773 // Do this If and the dominating If both branch out to an uncommon trap 774 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) { 775 ProjNode* otherproj = proj->other_if_proj(); 776 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none); 777 778 if (otherproj->outcnt() == 1 && dom_unc != NULL) { 779 // We need to re-execute the folded Ifs after deoptimization from the merged traps 780 if (!dom_unc->jvms()->should_reexecute()) { 781 return false; 782 } 783 784 CallStaticJavaNode* unc = NULL; 785 ProjNode* unc_proj = uncommon_trap_proj(unc); 786 if (unc_proj != NULL && unc_proj->outcnt() == 1) { 787 if (dom_unc == unc) { 788 // Allow the uncommon trap to be shared through a region 789 RegionNode* r = unc->in(0)->as_Region(); 790 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) { 791 return false; 792 } 793 assert(r->has_phi() == NULL, "simple region shouldn't have a phi"); 794 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) { 795 return false; 796 } 797 798 // Different methods and methods containing jsrs are not supported. 799 ciMethod* method = unc->jvms()->method(); 800 ciMethod* dom_method = dom_unc->jvms()->method(); 801 if (method != dom_method || method->has_jsrs()) { 802 return false; 803 } 804 // Check that both traps are in the same activation of the method (instead 805 // of two activations being inlined through different call sites) by verifying 806 // that the call stacks are equal for both JVMStates. 807 JVMState* dom_caller = dom_unc->jvms()->caller(); 808 JVMState* caller = unc->jvms()->caller(); 809 if ((dom_caller == NULL) != (caller == NULL)) { 810 // Either both methods are inlined or none of them 811 return false; 812 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) { 813 return false; 814 } 815 // Check that the bci of the dominating uncommon trap dominates the bci 816 // of the dominated uncommon trap. Otherwise we may not re-execute 817 // the dominated check after deoptimization from the merged uncommon trap. 818 ciTypeFlow* flow = dom_method->get_flow_analysis(); 819 int bci = unc->jvms()->bci(); 820 int dom_bci = dom_unc->jvms()->bci(); 821 if (!flow->is_dominated_by(bci, dom_bci)) { 822 return false; 823 } 824 825 // See merge_uncommon_traps: the reason of the uncommon trap 826 // will be changed and the state of the dominating If will be 827 // used. Checked that we didn't apply this transformation in a 828 // previous compilation and it didn't cause too many traps 829 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) && 830 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) { 831 success = unc_proj; 832 fail = unc_proj->other_if_proj(); 833 return true; 834 } 835 } 836 } 837 return false; 838 } 839 840 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding 841 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) { 842 Node* this_cmp = in(1)->in(1); 843 BoolNode* this_bool = in(1)->as_Bool(); 844 IfNode* dom_iff = proj->in(0)->as_If(); 845 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 846 Node* lo = dom_iff->in(1)->in(1)->in(2); 847 Node* hi = this_cmp->in(2); 848 Node* n = this_cmp->in(1); 849 ProjNode* otherproj = proj->other_if_proj(); 850 851 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj); 852 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success); 853 854 BoolTest::mask lo_test = dom_bool->_test._test; 855 BoolTest::mask hi_test = this_bool->_test._test; 856 BoolTest::mask cond = hi_test; 857 858 // convert: 859 // 860 // dom_bool = x {<,<=,>,>=} a 861 // / \ 862 // proj = {True,False} / \ otherproj = {False,True} 863 // / 864 // this_bool = x {<,<=} b 865 // / \ 866 // fail = {True,False} / \ success = {False,True} 867 // / 868 // 869 // (Second test guaranteed canonicalized, first one may not have 870 // been canonicalized yet) 871 // 872 // into: 873 // 874 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim 875 // / \ 876 // fail / \ success 877 // / 878 // 879 880 // Figure out which of the two tests sets the upper bound and which 881 // sets the lower bound if any. 882 Node* adjusted_lim = NULL; 883 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) { 884 assert((dom_bool->_test.is_less() && !proj->_con) || 885 (dom_bool->_test.is_greater() && proj->_con), "incorrect test"); 886 // this test was canonicalized 887 assert(this_bool->_test.is_less() && fail->_con, "incorrect test"); 888 889 // this_bool = < 890 // dom_bool = >= (proj = True) or dom_bool = < (proj = False) 891 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above): 892 // lo = a, hi = b, adjusted_lim = b-a, cond = <u 893 // dom_bool = > (proj = True) or dom_bool = <= (proj = False) 894 // x in ]a, b[ on the fail (= True) projection, b > a: 895 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u 896 // this_bool = <= 897 // dom_bool = >= (proj = True) or dom_bool = < (proj = False) 898 // x in [a, b] on the fail (= True) projection, b+1 > a-1: 899 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u 900 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1 901 // dom_bool = > (proj = True) or dom_bool = <= (proj = False) 902 // x in ]a, b] on the fail (= True) projection b+1 > a: 903 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u 904 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1 905 906 if (hi_test == BoolTest::lt) { 907 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) { 908 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 909 } 910 } else { 911 assert(hi_test == BoolTest::le, "bad test"); 912 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) { 913 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 914 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1))); 915 cond = BoolTest::lt; 916 } else { 917 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test"); 918 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 919 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 920 cond = BoolTest::lt; 921 } 922 } 923 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) { 924 925 // this_bool = < 926 // dom_bool = < (proj = True) or dom_bool = >= (proj = False) 927 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above): 928 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u 929 // dom_bool = <= (proj = True) or dom_bool = > (proj = False) 930 // x in [b, a] on the fail (= False) projection, a+1 > b-1: 931 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u 932 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1 933 // this_bool = <= 934 // dom_bool = < (proj = True) or dom_bool = >= (proj = False) 935 // x in ]b, a[ on the fail (= False) projection, a > b: 936 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u 937 // dom_bool = <= (proj = True) or dom_bool = > (proj = False) 938 // x in ]b, a] on the fail (= False) projection, a+1 > b: 939 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u 940 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >u doesn't work because a = b is possible, then b-a-1 = -1 941 942 swap(lo, hi); 943 swap(lo_type, hi_type); 944 swap(lo_test, hi_test); 945 946 assert((dom_bool->_test.is_less() && proj->_con) || 947 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test"); 948 // this test was canonicalized 949 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test"); 950 951 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge; 952 953 if (lo_test == BoolTest::lt) { 954 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) { 955 cond = BoolTest::ge; 956 } else { 957 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test"); 958 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 959 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1))); 960 cond = BoolTest::ge; 961 } 962 } else if (lo_test == BoolTest::le) { 963 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) { 964 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 965 cond = BoolTest::ge; 966 } else { 967 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test"); 968 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 969 lo = igvn->transform(new AddINode(lo, igvn->intcon(1))); 970 cond = BoolTest::ge; 971 } 972 } 973 } else { 974 const TypeInt* failtype = filtered_int_type(igvn, n, proj); 975 if (failtype != NULL) { 976 const TypeInt* type2 = filtered_int_type(igvn, n, fail); 977 if (type2 != NULL) { 978 failtype = failtype->join(type2)->is_int(); 979 if (failtype->_lo > failtype->_hi) { 980 // previous if determines the result of this if so 981 // replace Bool with constant 982 igvn->_worklist.push(in(1)); 983 igvn->replace_input_of(this, 1, igvn->intcon(success->_con)); 984 return true; 985 } 986 } 987 } 988 lo = NULL; 989 hi = NULL; 990 } 991 992 if (lo && hi) { 993 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo)) 994 Node* adjusted_val = igvn->transform(new SubINode(n, lo)); 995 if (adjusted_lim == NULL) { 996 adjusted_lim = igvn->transform(new SubINode(hi, lo)); 997 } 998 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim)); 999 Node* newbool = igvn->transform(new BoolNode(newcmp, cond)); 1000 1001 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con)); 1002 igvn->_worklist.push(in(1)); 1003 igvn->replace_input_of(this, 1, newbool); 1004 1005 return true; 1006 } 1007 return false; 1008 } 1009 1010 // Merge the branches that trap for this If and the dominating If into 1011 // a single region that branches to the uncommon trap for the 1012 // dominating If 1013 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) { 1014 Node* res = this; 1015 assert(success->in(0) == this, "bad projection"); 1016 1017 ProjNode* otherproj = proj->other_if_proj(); 1018 1019 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none); 1020 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none); 1021 1022 if (unc != dom_unc) { 1023 Node* r = new RegionNode(3); 1024 1025 r->set_req(1, otherproj); 1026 r->set_req(2, success); 1027 r = igvn->transform(r); 1028 assert(r->is_Region(), "can't go away"); 1029 1030 // Make both If trap at the state of the first If: once the CmpI 1031 // nodes are merged, if we trap we don't know which of the CmpI 1032 // nodes would have caused the trap so we have to restart 1033 // execution at the first one 1034 igvn->replace_input_of(dom_unc, 0, r); 1035 igvn->replace_input_of(unc, 0, igvn->C->top()); 1036 } 1037 int trap_request = dom_unc->uncommon_trap_request(); 1038 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request); 1039 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request); 1040 1041 int flip_test = 0; 1042 Node* l = NULL; 1043 Node* r = NULL; 1044 1045 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) { 1046 // If this looks like a range check, change the trap to 1047 // Reason_range_check so the compiler recognizes it as a range 1048 // check and applies the corresponding optimizations 1049 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action); 1050 1051 improve_address_types(l, r, fail, igvn); 1052 1053 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt)); 1054 } else if (unc != dom_unc) { 1055 // If we trap we won't know what CmpI would have caused the trap 1056 // so use a special trap reason to mark this pair of CmpI nodes as 1057 // bad candidate for folding. On recompilation we won't fold them 1058 // and we may trap again but this time we'll know what branch 1059 // traps 1060 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action); 1061 } 1062 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request)); 1063 return res; 1064 } 1065 1066 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern 1067 // of a rangecheck on index i, on 64 bit the compares may be followed 1068 // by memory accesses using i as index. In that case, the CmpU tells 1069 // us something about the values taken by i that can help the compiler 1070 // (see Compile::conv_I2X_index()) 1071 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) { 1072 #ifdef _LP64 1073 ResourceMark rm; 1074 Node_Stack stack(2); 1075 1076 assert(r->Opcode() == Op_LoadRange, "unexpected range check"); 1077 const TypeInt* array_size = igvn->type(r)->is_int(); 1078 1079 stack.push(l, 0); 1080 1081 while(stack.size() > 0) { 1082 Node* n = stack.node(); 1083 uint start = stack.index(); 1084 1085 uint i = start; 1086 for (; i < n->outcnt(); i++) { 1087 Node* use = n->raw_out(i); 1088 if (stack.size() == 1) { 1089 if (use->Opcode() == Op_ConvI2L) { 1090 const TypeLong* bounds = use->as_Type()->type()->is_long(); 1091 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi && 1092 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) { 1093 stack.set_index(i+1); 1094 stack.push(use, 0); 1095 break; 1096 } 1097 } 1098 } else if (use->is_Mem()) { 1099 Node* ctrl = use->in(0); 1100 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) { 1101 ctrl = up_one_dom(ctrl); 1102 } 1103 if (ctrl == fail) { 1104 Node* init_n = stack.node_at(1); 1105 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node"); 1106 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size); 1107 1108 // The type of the ConvI2L may be widen and so the new 1109 // ConvI2L may not be better than an existing ConvI2L 1110 if (new_n != init_n) { 1111 for (uint j = 2; j < stack.size(); j++) { 1112 Node* n = stack.node_at(j); 1113 Node* clone = n->clone(); 1114 int rep = clone->replace_edge(init_n, new_n); 1115 assert(rep > 0, "can't find expected node?"); 1116 clone = igvn->transform(clone); 1117 init_n = n; 1118 new_n = clone; 1119 } 1120 igvn->hash_delete(use); 1121 int rep = use->replace_edge(init_n, new_n); 1122 assert(rep > 0, "can't find expected node?"); 1123 igvn->transform(use); 1124 if (init_n->outcnt() == 0) { 1125 igvn->_worklist.push(init_n); 1126 } 1127 } 1128 } 1129 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() || 1130 igvn->type(use)->isa_ptr())) { 1131 stack.set_index(i+1); 1132 stack.push(use, 0); 1133 break; 1134 } 1135 } 1136 if (i == n->outcnt()) { 1137 stack.pop(); 1138 } 1139 } 1140 #endif 1141 } 1142 1143 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) { 1144 if (in(1) != NULL && 1145 in(1)->in(1) != NULL && 1146 in(1)->in(1)->in(2) != NULL) { 1147 Node* other = in(1)->in(1)->in(2); 1148 if (other->Opcode() == Op_LoadRange && 1149 ((other->in(0) != NULL && other->in(0) == proj) || 1150 (other->in(0) == NULL && 1151 other->in(2) != NULL && 1152 other->in(2)->is_AddP() && 1153 other->in(2)->in(1) != NULL && 1154 other->in(2)->in(1)->Opcode() == Op_CastPP && 1155 other->in(2)->in(1)->in(0) == proj))) { 1156 return true; 1157 } 1158 } 1159 return false; 1160 } 1161 1162 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) { 1163 Node* other = in(1)->in(1)->in(2); 1164 if (other->in(MemNode::Address) != NULL && 1165 proj->in(0)->in(1) != NULL && 1166 proj->in(0)->in(1)->is_Bool() && 1167 proj->in(0)->in(1)->in(1) != NULL && 1168 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP && 1169 proj->in(0)->in(1)->in(1)->in(2) != NULL && 1170 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() && 1171 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) { 1172 return true; 1173 } 1174 return false; 1175 } 1176 1177 // Check that the If that is in between the 2 integer comparisons has 1178 // no side effect 1179 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) { 1180 if (proj != NULL && 1181 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) && 1182 proj->outcnt() <= 2) { 1183 if (proj->outcnt() == 1 || 1184 // Allow simple null check from LoadRange 1185 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) { 1186 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1187 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1188 1189 // reroute_side_effect_free_unc changes the state of this 1190 // uncommon trap to restart execution at the previous 1191 // CmpI. Check that this change in a previous compilation didn't 1192 // cause too many traps. 1193 int trap_request = unc->uncommon_trap_request(); 1194 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request); 1195 1196 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) { 1197 return false; 1198 } 1199 1200 return true; 1201 } 1202 } 1203 return false; 1204 } 1205 1206 // Make the If between the 2 integer comparisons trap at the state of 1207 // the first If: the last CmpI is the one replaced by a CmpU and the 1208 // first CmpI is eliminated, so the test between the 2 CmpI nodes 1209 // won't be guarded by the first CmpI anymore. It can trap in cases 1210 // where the first CmpI would have prevented it from executing: on a 1211 // trap, we need to restart execution at the state of the first CmpI 1212 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) { 1213 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1214 ProjNode* otherproj = proj->other_if_proj(); 1215 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none); 1216 Node* call_proj = dom_unc->unique_ctrl_out(); 1217 Node* halt = call_proj->unique_ctrl_out(); 1218 1219 Node* new_unc = dom_unc->clone(); 1220 call_proj = call_proj->clone(); 1221 halt = halt->clone(); 1222 Node* c = otherproj->clone(); 1223 1224 c = igvn->transform(c); 1225 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms)); 1226 new_unc->set_req(0, c); 1227 new_unc = igvn->transform(new_unc); 1228 call_proj->set_req(0, new_unc); 1229 call_proj = igvn->transform(call_proj); 1230 halt->set_req(0, call_proj); 1231 halt = igvn->transform(halt); 1232 1233 igvn->replace_node(otherproj, igvn->C->top()); 1234 igvn->C->root()->add_req(halt); 1235 } 1236 1237 Node* IfNode::fold_compares(PhaseIterGVN* igvn) { 1238 if (Opcode() != Op_If) return NULL; 1239 1240 if (cmpi_folds(igvn)) { 1241 Node* ctrl = in(0); 1242 if (is_ctrl_folds(ctrl, igvn) && 1243 ctrl->outcnt() == 1) { 1244 // A integer comparison immediately dominated by another integer 1245 // comparison 1246 ProjNode* success = NULL; 1247 ProjNode* fail = NULL; 1248 ProjNode* dom_cmp = ctrl->as_Proj(); 1249 if (has_shared_region(dom_cmp, success, fail) && 1250 // Next call modifies graph so must be last 1251 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1252 return this; 1253 } 1254 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) && 1255 // Next call modifies graph so must be last 1256 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1257 return merge_uncommon_traps(dom_cmp, success, fail, igvn); 1258 } 1259 return NULL; 1260 } else if (ctrl->in(0) != NULL && 1261 ctrl->in(0)->in(0) != NULL) { 1262 ProjNode* success = NULL; 1263 ProjNode* fail = NULL; 1264 Node* dom = ctrl->in(0)->in(0); 1265 ProjNode* dom_cmp = dom->isa_Proj(); 1266 ProjNode* other_cmp = ctrl->isa_Proj(); 1267 1268 // Check if it's an integer comparison dominated by another 1269 // integer comparison with another test in between 1270 if (is_ctrl_folds(dom, igvn) && 1271 has_only_uncommon_traps(dom_cmp, success, fail, igvn) && 1272 is_side_effect_free_test(other_cmp, igvn) && 1273 // Next call modifies graph so must be last 1274 fold_compares_helper(dom_cmp, success, fail, igvn)) { 1275 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn); 1276 return merge_uncommon_traps(dom_cmp, success, fail, igvn); 1277 } 1278 } 1279 } 1280 return NULL; 1281 } 1282 1283 //------------------------------remove_useless_bool---------------------------- 1284 // Check for people making a useless boolean: things like 1285 // if( (x < y ? true : false) ) { ... } 1286 // Replace with if( x < y ) { ... } 1287 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 1288 Node *i1 = iff->in(1); 1289 if( !i1->is_Bool() ) return NULL; 1290 BoolNode *bol = i1->as_Bool(); 1291 1292 Node *cmp = bol->in(1); 1293 if( cmp->Opcode() != Op_CmpI ) return NULL; 1294 1295 // Must be comparing against a bool 1296 const Type *cmp2_t = phase->type( cmp->in(2) ); 1297 if( cmp2_t != TypeInt::ZERO && 1298 cmp2_t != TypeInt::ONE ) 1299 return NULL; 1300 1301 // Find a prior merge point merging the boolean 1302 i1 = cmp->in(1); 1303 if( !i1->is_Phi() ) return NULL; 1304 PhiNode *phi = i1->as_Phi(); 1305 if( phase->type( phi ) != TypeInt::BOOL ) 1306 return NULL; 1307 1308 // Check for diamond pattern 1309 int true_path = phi->is_diamond_phi(); 1310 if( true_path == 0 ) return NULL; 1311 1312 // Make sure that iff and the control of the phi are different. This 1313 // should really only happen for dead control flow since it requires 1314 // an illegal cycle. 1315 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 1316 1317 // phi->region->if_proj->ifnode->bool->cmp 1318 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 1319 1320 // Now get the 'sense' of the test correct so we can plug in 1321 // either iff2->in(1) or its complement. 1322 int flip = 0; 1323 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 1324 else if( bol->_test._test != BoolTest::eq ) return NULL; 1325 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 1326 1327 const Type *phi1_t = phase->type( phi->in(1) ); 1328 const Type *phi2_t = phase->type( phi->in(2) ); 1329 // Check for Phi(0,1) and flip 1330 if( phi1_t == TypeInt::ZERO ) { 1331 if( phi2_t != TypeInt::ONE ) return NULL; 1332 flip = 1-flip; 1333 } else { 1334 // Check for Phi(1,0) 1335 if( phi1_t != TypeInt::ONE ) return NULL; 1336 if( phi2_t != TypeInt::ZERO ) return NULL; 1337 } 1338 if( true_path == 2 ) { 1339 flip = 1-flip; 1340 } 1341 1342 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 1343 assert(new_bol != iff->in(1), "must make progress"); 1344 iff->set_req(1, new_bol); 1345 // Intervening diamond probably goes dead 1346 phase->C->set_major_progress(); 1347 return iff; 1348 } 1349 1350 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 1351 1352 struct RangeCheck { 1353 Node* ctl; 1354 jint off; 1355 }; 1356 1357 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) { 1358 if (remove_dead_region(phase, can_reshape)) return this; 1359 // No Def-Use info? 1360 if (!can_reshape) return NULL; 1361 1362 // Don't bother trying to transform a dead if 1363 if (in(0)->is_top()) return NULL; 1364 // Don't bother trying to transform an if with a dead test 1365 if (in(1)->is_top()) return NULL; 1366 // Another variation of a dead test 1367 if (in(1)->is_Con()) return NULL; 1368 // Another variation of a dead if 1369 if (outcnt() < 2) return NULL; 1370 1371 // Canonicalize the test. 1372 Node* idt_if = idealize_test(phase, this); 1373 if (idt_if != NULL) return idt_if; 1374 1375 // Try to split the IF 1376 PhaseIterGVN *igvn = phase->is_IterGVN(); 1377 Node *s = split_if(this, igvn); 1378 if (s != NULL) return s; 1379 1380 return NodeSentinel; 1381 } 1382 1383 //------------------------------Ideal------------------------------------------ 1384 // Return a node which is more "ideal" than the current node. Strip out 1385 // control copies 1386 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1387 Node* res = Ideal_common(phase, can_reshape); 1388 if (res != NodeSentinel) { 1389 return res; 1390 } 1391 1392 // Check for people making a useless boolean: things like 1393 // if( (x < y ? true : false) ) { ... } 1394 // Replace with if( x < y ) { ... } 1395 Node *bol2 = remove_useless_bool(this, phase); 1396 if( bol2 ) return bol2; 1397 1398 if (in(0) == NULL) return NULL; // Dead loop? 1399 1400 PhaseIterGVN *igvn = phase->is_IterGVN(); 1401 Node* result = fold_compares(igvn); 1402 if (result != NULL) { 1403 return result; 1404 } 1405 1406 // Scan for an equivalent test 1407 Node *cmp; 1408 int dist = 0; // Cutoff limit for search 1409 int op = Opcode(); 1410 if( op == Op_If && 1411 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 1412 if( cmp->in(2) != NULL && // make sure cmp is not already dead 1413 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 1414 dist = 64; // Limit for null-pointer scans 1415 } else { 1416 dist = 4; // Do not bother for random pointer tests 1417 } 1418 } else { 1419 dist = 4; // Limit for random junky scans 1420 } 1421 1422 Node* prev_dom = search_identical(dist); 1423 1424 if (prev_dom == NULL) { 1425 return NULL; 1426 } 1427 1428 // Replace dominated IfNode 1429 return dominated_by(prev_dom, igvn); 1430 } 1431 1432 //------------------------------dominated_by----------------------------------- 1433 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) { 1434 #ifndef PRODUCT 1435 if (TraceIterativeGVN) { 1436 tty->print(" Removing IfNode: "); this->dump(); 1437 } 1438 if (VerifyOpto && !igvn->allow_progress()) { 1439 // Found an equivalent dominating test, 1440 // we can not guarantee reaching a fix-point for these during iterativeGVN 1441 // since intervening nodes may not change. 1442 return NULL; 1443 } 1444 #endif 1445 1446 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1447 Node *idom = in(0); 1448 // Need opcode to decide which way 'this' test goes 1449 int prev_op = prev_dom->Opcode(); 1450 Node *top = igvn->C->top(); // Shortcut to top 1451 1452 // Loop predicates may have depending checks which should not 1453 // be skipped. For example, range check predicate has two checks 1454 // for lower and upper bounds. 1455 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj(); 1456 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL) 1457 prev_dom = idom; 1458 1459 // Now walk the current IfNode's projections. 1460 // Loop ends when 'this' has no more uses. 1461 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1462 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1463 igvn->add_users_to_worklist(ifp); 1464 // Check which projection it is and set target. 1465 // Data-target is either the dominating projection of the same type 1466 // or TOP if the dominating projection is of opposite type. 1467 // Data-target will be used as the new control edge for the non-CFG 1468 // nodes like Casts and Loads. 1469 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top; 1470 // Control-target is just the If's immediate dominator or TOP. 1471 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top; 1472 1473 // For each child of an IfTrue/IfFalse projection, reroute. 1474 // Loop ends when projection has no more uses. 1475 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1476 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1477 if( !s->depends_only_on_test() ) { 1478 // Find the control input matching this def-use edge. 1479 // For Regions it may not be in slot 0. 1480 uint l; 1481 for( l = 0; s->in(l) != ifp; l++ ) { } 1482 igvn->replace_input_of(s, l, ctrl_target); 1483 } else { // Else, for control producers, 1484 igvn->replace_input_of(s, 0, data_target); // Move child to data-target 1485 } 1486 } // End for each child of a projection 1487 1488 igvn->remove_dead_node(ifp); 1489 } // End for each IfTrue/IfFalse child of If 1490 1491 // Kill the IfNode 1492 igvn->remove_dead_node(this); 1493 1494 // Must return either the original node (now dead) or a new node 1495 // (Do not return a top here, since that would break the uniqueness of top.) 1496 return new ConINode(TypeInt::ZERO); 1497 } 1498 1499 Node* IfNode::search_identical(int dist) { 1500 // Setup to scan up the CFG looking for a dominating test 1501 Node* dom = in(0); 1502 Node* prev_dom = this; 1503 int op = Opcode(); 1504 // Search up the dominator tree for an If with an identical test 1505 while( dom->Opcode() != op || // Not same opcode? 1506 dom->in(1) != in(1) || // Not same input 1? 1507 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 1508 prev_dom->in(0) != dom ) { // One path of test does not dominate? 1509 if( dist < 0 ) return NULL; 1510 1511 dist--; 1512 prev_dom = dom; 1513 dom = up_one_dom( dom ); 1514 if( !dom ) return NULL; 1515 } 1516 1517 // Check that we did not follow a loop back to ourselves 1518 if( this == dom ) 1519 return NULL; 1520 1521 if( dist > 2 ) // Add to count of NULL checks elided 1522 explicit_null_checks_elided++; 1523 1524 return prev_dom; 1525 } 1526 1527 //------------------------------Identity--------------------------------------- 1528 // If the test is constant & we match, then we are the input Control 1529 Node *IfProjNode::Identity(PhaseTransform *phase) { 1530 // Can only optimize if cannot go the other way 1531 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1532 if (t == TypeTuple::IFNEITHER || 1533 // kill dead branch first otherwise the IfNode's control will 1534 // have 2 control uses (the IfNode that doesn't go away because 1535 // it still has uses and this branch of the 1536 // If). Node::has_special_unique_user() will cause this node to 1537 // be reprocessed once the dead branch is killed. 1538 (always_taken(t) && in(0)->outcnt() == 1)) { 1539 // IfNode control 1540 return in(0)->in(0); 1541 } 1542 // no progress 1543 return this; 1544 } 1545 1546 #ifndef PRODUCT 1547 //-------------------------------related--------------------------------------- 1548 // An IfProjNode's related node set consists of its input (an IfNode) including 1549 // the IfNode's condition, plus all of its outputs at level 1. In compact mode, 1550 // the restrictions for IfNode apply (see IfNode::rel). 1551 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const { 1552 Node* ifNode = this->in(0); 1553 in_rel->append(ifNode); 1554 if (compact) { 1555 ifNode->collect_nodes(in_rel, 3, false, true); 1556 } else { 1557 ifNode->collect_nodes_in_all_data(in_rel, false); 1558 } 1559 this->collect_nodes(out_rel, -1, false, false); 1560 } 1561 1562 //------------------------------dump_spec-------------------------------------- 1563 void IfNode::dump_spec(outputStream *st) const { 1564 st->print("P=%f, C=%f",_prob,_fcnt); 1565 } 1566 1567 //-------------------------------related--------------------------------------- 1568 // For an IfNode, the set of related output nodes is just the output nodes till 1569 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer. 1570 // The related input nodes contain no control nodes, but all data nodes 1571 // pertaining to the condition. In compact mode, the input nodes are collected 1572 // up to a depth of 3. 1573 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const { 1574 if (compact) { 1575 this->collect_nodes(in_rel, 3, false, true); 1576 } else { 1577 this->collect_nodes_in_all_data(in_rel, false); 1578 } 1579 this->collect_nodes(out_rel, -2, false, false); 1580 } 1581 #endif 1582 1583 //------------------------------idealize_test---------------------------------- 1584 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1585 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1586 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1587 // needed. 1588 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1589 assert(iff->in(0) != NULL, "If must be live"); 1590 1591 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1592 Node* old_if_f = iff->proj_out(false); 1593 Node* old_if_t = iff->proj_out(true); 1594 1595 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1596 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1597 // happens in count-down loops 1598 if (iff->is_CountedLoopEnd()) return NULL; 1599 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1600 BoolNode *b = iff->in(1)->as_Bool(); 1601 BoolTest bt = b->_test; 1602 // Test already in good order? 1603 if( bt.is_canonical() ) 1604 return NULL; 1605 1606 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1607 // cloning the IfNode. 1608 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) ); 1609 if( !new_b->is_Bool() ) return NULL; 1610 b = new_b->as_Bool(); 1611 1612 PhaseIterGVN *igvn = phase->is_IterGVN(); 1613 assert( igvn, "Test is not canonical in parser?" ); 1614 1615 // The IF node never really changes, but it needs to be cloned 1616 iff = iff->clone()->as_If(); 1617 iff->set_req(1, b); 1618 iff->_prob = 1.0-iff->_prob; 1619 1620 Node *prior = igvn->hash_find_insert(iff); 1621 if( prior ) { 1622 igvn->remove_dead_node(iff); 1623 iff = (IfNode*)prior; 1624 } else { 1625 // Cannot call transform on it just yet 1626 igvn->set_type_bottom(iff); 1627 } 1628 igvn->_worklist.push(iff); 1629 1630 // Now handle projections. Cloning not required. 1631 Node* new_if_f = (Node*)(new IfFalseNode( iff )); 1632 Node* new_if_t = (Node*)(new IfTrueNode ( iff )); 1633 1634 igvn->register_new_node_with_optimizer(new_if_f); 1635 igvn->register_new_node_with_optimizer(new_if_t); 1636 // Flip test, so flip trailing control 1637 igvn->replace_node(old_if_f, new_if_t); 1638 igvn->replace_node(old_if_t, new_if_f); 1639 1640 // Progress 1641 return iff; 1642 } 1643 1644 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) { 1645 Node* res = Ideal_common(phase, can_reshape); 1646 if (res != NodeSentinel) { 1647 return res; 1648 } 1649 1650 PhaseIterGVN *igvn = phase->is_IterGVN(); 1651 // Setup to scan up the CFG looking for a dominating test 1652 Node* prev_dom = this; 1653 1654 // Check for range-check vs other kinds of tests 1655 Node* index1; 1656 Node* range1; 1657 jint offset1; 1658 int flip1 = is_range_check(range1, index1, offset1); 1659 if (flip1) { 1660 Node* dom = in(0); 1661 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 1662 // so all checks we inspect post-dominate the top-most check we find. 1663 // If we are going to fail the current check and we reach the top check 1664 // then we are guaranteed to fail, so just start interpreting there. 1665 // We 'expand' the top 3 range checks to include all post-dominating 1666 // checks. 1667 1668 // The top 3 range checks seen 1669 const int NRC =3; 1670 RangeCheck prev_checks[NRC]; 1671 int nb_checks = 0; 1672 1673 // Low and high offsets seen so far 1674 jint off_lo = offset1; 1675 jint off_hi = offset1; 1676 1677 bool found_immediate_dominator = false; 1678 1679 // Scan for the top checks and collect range of offsets 1680 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit 1681 if (dom->Opcode() == Op_RangeCheck && // Not same opcode? 1682 prev_dom->in(0) == dom) { // One path of test does dominate? 1683 if (dom == this) return NULL; // dead loop 1684 // See if this is a range check 1685 Node* index2; 1686 Node* range2; 1687 jint offset2; 1688 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2); 1689 // See if this is a _matching_ range check, checking against 1690 // the same array bounds. 1691 if (flip2 == flip1 && range2 == range1 && index2 == index1 && 1692 dom->outcnt() == 2) { 1693 if (nb_checks == 0 && dom->in(1) == in(1)) { 1694 // Found an immediately dominating test at the same offset. 1695 // This kind of back-to-back test can be eliminated locally, 1696 // and there is no need to search further for dominating tests. 1697 assert(offset2 == offset1, "Same test but different offsets"); 1698 found_immediate_dominator = true; 1699 break; 1700 } 1701 // Gather expanded bounds 1702 off_lo = MIN2(off_lo,offset2); 1703 off_hi = MAX2(off_hi,offset2); 1704 // Record top NRC range checks 1705 prev_checks[nb_checks%NRC].ctl = prev_dom; 1706 prev_checks[nb_checks%NRC].off = offset2; 1707 nb_checks++; 1708 } 1709 } 1710 prev_dom = dom; 1711 dom = up_one_dom(dom); 1712 if (!dom) break; 1713 } 1714 1715 if (!found_immediate_dominator) { 1716 // Attempt to widen the dominating range check to cover some later 1717 // ones. Since range checks "fail" by uncommon-trapping to the 1718 // interpreter, widening a check can make us speculatively enter 1719 // the interpreter. If we see range-check deopt's, do not widen! 1720 if (!phase->C->allow_range_check_smearing()) return NULL; 1721 1722 // Didn't find prior covering check, so cannot remove anything. 1723 if (nb_checks == 0) { 1724 return NULL; 1725 } 1726 // Constant indices only need to check the upper bound. 1727 // Non-constant indices must check both low and high. 1728 int chk0 = (nb_checks - 1) % NRC; 1729 if (index1) { 1730 if (nb_checks == 1) { 1731 return NULL; 1732 } else { 1733 // If the top range check's constant is the min or max of 1734 // all constants we widen the next one to cover the whole 1735 // range of constants. 1736 RangeCheck rc0 = prev_checks[chk0]; 1737 int chk1 = (nb_checks - 2) % NRC; 1738 RangeCheck rc1 = prev_checks[chk1]; 1739 if (rc0.off == off_lo) { 1740 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); 1741 prev_dom = rc1.ctl; 1742 } else if (rc0.off == off_hi) { 1743 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); 1744 prev_dom = rc1.ctl; 1745 } else { 1746 // If the top test's constant is not the min or max of all 1747 // constants, we need 3 range checks. We must leave the 1748 // top test unchanged because widening it would allow the 1749 // accesses it protects to successfully read/write out of 1750 // bounds. 1751 if (nb_checks == 2) { 1752 return NULL; 1753 } 1754 int chk2 = (nb_checks - 3) % NRC; 1755 RangeCheck rc2 = prev_checks[chk2]; 1756 // The top range check a+i covers interval: -a <= i < length-a 1757 // The second range check b+i covers interval: -b <= i < length-b 1758 if (rc1.off <= rc0.off) { 1759 // if b <= a, we change the second range check to: 1760 // -min_of_all_constants <= i < length-min_of_all_constants 1761 // Together top and second range checks now cover: 1762 // -min_of_all_constants <= i < length-a 1763 // which is more restrictive than -b <= i < length-b: 1764 // -b <= -min_of_all_constants <= i < length-a <= length-b 1765 // The third check is then changed to: 1766 // -max_of_all_constants <= i < length-max_of_all_constants 1767 // so 2nd and 3rd checks restrict allowed values of i to: 1768 // -min_of_all_constants <= i < length-max_of_all_constants 1769 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); 1770 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn); 1771 } else { 1772 // if b > a, we change the second range check to: 1773 // -max_of_all_constants <= i < length-max_of_all_constants 1774 // Together top and second range checks now cover: 1775 // -a <= i < length-max_of_all_constants 1776 // which is more restrictive than -b <= i < length-b: 1777 // -b < -a <= i < length-max_of_all_constants <= length-b 1778 // The third check is then changed to: 1779 // -max_of_all_constants <= i < length-max_of_all_constants 1780 // so 2nd and 3rd checks restrict allowed values of i to: 1781 // -min_of_all_constants <= i < length-max_of_all_constants 1782 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); 1783 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn); 1784 } 1785 prev_dom = rc2.ctl; 1786 } 1787 } 1788 } else { 1789 RangeCheck rc0 = prev_checks[chk0]; 1790 // 'Widen' the offset of the 1st and only covering check 1791 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn); 1792 // Test is now covered by prior checks, dominate it out 1793 prev_dom = rc0.ctl; 1794 } 1795 } 1796 } else { 1797 prev_dom = search_identical(4); 1798 1799 if (prev_dom == NULL) { 1800 return NULL; 1801 } 1802 } 1803 1804 // Replace dominated IfNode 1805 return dominated_by(prev_dom, igvn); 1806 }