1 /* 2 * Copyright (c) 2000, 2012, 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 "memory/allocation.inline.hpp" 27 #include "opto/addnode.hpp" 28 #include "opto/cfgnode.hpp" 29 #include "opto/connode.hpp" 30 #include "opto/loopnode.hpp" 31 #include "opto/phaseX.hpp" 32 #include "opto/runtime.hpp" 33 #include "opto/subnode.hpp" 34 35 // Portions of code courtesy of Clifford Click 36 37 // Optimization - Graph Style 38 39 40 extern int explicit_null_checks_elided; 41 42 //============================================================================= 43 //------------------------------Value------------------------------------------ 44 // Return a tuple for whichever arm of the IF is reachable 45 const Type *IfNode::Value( PhaseTransform *phase ) const { 46 if( !in(0) ) return Type::TOP; 47 if( phase->type(in(0)) == Type::TOP ) 48 return Type::TOP; 49 const Type *t = phase->type(in(1)); 50 if( t == Type::TOP ) // data is undefined 51 return TypeTuple::IFNEITHER; // unreachable altogether 52 if( t == TypeInt::ZERO ) // zero, or false 53 return TypeTuple::IFFALSE; // only false branch is reachable 54 if( t == TypeInt::ONE ) // 1, or true 55 return TypeTuple::IFTRUE; // only true branch is reachable 56 assert( t == TypeInt::BOOL, "expected boolean type" ); 57 58 return TypeTuple::IFBOTH; // No progress 59 } 60 61 const RegMask &IfNode::out_RegMask() const { 62 return RegMask::Empty; 63 } 64 65 //------------------------------split_if--------------------------------------- 66 // Look for places where we merge constants, then test on the merged value. 67 // If the IF test will be constant folded on the path with the constant, we 68 // win by splitting the IF to before the merge point. 69 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) { 70 // I could be a lot more general here, but I'm trying to squeeze this 71 // in before the Christmas '98 break so I'm gonna be kinda restrictive 72 // on the patterns I accept. CNC 73 74 // Look for a compare of a constant and a merged value 75 Node *i1 = iff->in(1); 76 if( !i1->is_Bool() ) return NULL; 77 BoolNode *b = i1->as_Bool(); 78 Node *cmp = b->in(1); 79 if( !cmp->is_Cmp() ) return NULL; 80 i1 = cmp->in(1); 81 if( i1 == NULL || !i1->is_Phi() ) return NULL; 82 PhiNode *phi = i1->as_Phi(); 83 if( phi->is_copy() ) return NULL; 84 Node *con2 = cmp->in(2); 85 if( !con2->is_Con() ) return NULL; 86 // See that the merge point contains some constants 87 Node *con1=NULL; 88 uint i4; 89 for( i4 = 1; i4 < phi->req(); i4++ ) { 90 con1 = phi->in(i4); 91 if( !con1 ) return NULL; // Do not optimize partially collapsed merges 92 if( con1->is_Con() ) break; // Found a constant 93 // Also allow null-vs-not-null checks 94 const TypePtr *tp = igvn->type(con1)->isa_ptr(); 95 if( tp && tp->_ptr == TypePtr::NotNull ) 96 break; 97 } 98 if( i4 >= phi->req() ) return NULL; // Found no constants 99 100 igvn->C->set_has_split_ifs(true); // Has chance for split-if 101 102 // Make sure that the compare can be constant folded away 103 Node *cmp2 = cmp->clone(); 104 cmp2->set_req(1,con1); 105 cmp2->set_req(2,con2); 106 const Type *t = cmp2->Value(igvn); 107 // This compare is dead, so whack it! 108 igvn->remove_dead_node(cmp2); 109 if( !t->singleton() ) return NULL; 110 111 // No intervening control, like a simple Call 112 Node *r = iff->in(0); 113 if( !r->is_Region() ) return NULL; 114 if( phi->region() != r ) return NULL; 115 // No other users of the cmp/bool 116 if (b->outcnt() != 1 || cmp->outcnt() != 1) { 117 //tty->print_cr("many users of cmp/bool"); 118 return NULL; 119 } 120 121 // Make sure we can determine where all the uses of merged values go 122 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { 123 Node* u = r->fast_out(j); 124 if( u == r ) continue; 125 if( u == iff ) continue; 126 if( u->outcnt() == 0 ) continue; // use is dead & ignorable 127 if( !u->is_Phi() ) { 128 /* 129 if( u->is_Start() ) { 130 tty->print_cr("Region has inlined start use"); 131 } else { 132 tty->print_cr("Region has odd use"); 133 u->dump(2); 134 }*/ 135 return NULL; 136 } 137 if( u != phi ) { 138 // CNC - do not allow any other merged value 139 //tty->print_cr("Merging another value"); 140 //u->dump(2); 141 return NULL; 142 } 143 // Make sure we can account for all Phi uses 144 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { 145 Node* v = u->fast_out(k); // User of the phi 146 // CNC - Allow only really simple patterns. 147 // In particular I disallow AddP of the Phi, a fairly common pattern 148 if( v == cmp ) continue; // The compare is OK 149 if( (v->is_ConstraintCast()) && 150 v->in(0)->in(0) == iff ) 151 continue; // CastPP/II of the IfNode is OK 152 // Disabled following code because I cannot tell if exactly one 153 // path dominates without a real dominator check. CNC 9/9/1999 154 //uint vop = v->Opcode(); 155 //if( vop == Op_Phi ) { // Phi from another merge point might be OK 156 // Node *r = v->in(0); // Get controlling point 157 // if( !r ) return NULL; // Degraded to a copy 158 // // Find exactly one path in (either True or False doms, but not IFF) 159 // int cnt = 0; 160 // for( uint i = 1; i < r->req(); i++ ) 161 // if( r->in(i) && r->in(i)->in(0) == iff ) 162 // cnt++; 163 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi 164 //} 165 if( !v->is_Call() ) { 166 /* 167 if( v->Opcode() == Op_AddP ) { 168 tty->print_cr("Phi has AddP use"); 169 } else if( v->Opcode() == Op_CastPP ) { 170 tty->print_cr("Phi has CastPP use"); 171 } else if( v->Opcode() == Op_CastII ) { 172 tty->print_cr("Phi has CastII use"); 173 } else { 174 tty->print_cr("Phi has use I cant be bothered with"); 175 } 176 */ 177 } 178 return NULL; 179 180 /* CNC - Cut out all the fancy acceptance tests 181 // Can we clone this use when doing the transformation? 182 // If all uses are from Phis at this merge or constants, then YES. 183 if( !v->in(0) && v != cmp ) { 184 tty->print_cr("Phi has free-floating use"); 185 v->dump(2); 186 return NULL; 187 } 188 for( uint l = 1; l < v->req(); l++ ) { 189 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && 190 !v->in(l)->is_Con() ) { 191 tty->print_cr("Phi has use"); 192 v->dump(2); 193 return NULL; 194 } // End of if Phi-use input is neither Phi nor Constant 195 } // End of for all inputs to Phi-use 196 */ 197 } // End of for all uses of Phi 198 } // End of for all uses of Region 199 200 // Only do this if the IF node is in a sane state 201 if (iff->outcnt() != 2) 202 return NULL; 203 204 // Got a hit! Do the Mondo Hack! 205 // 206 //ABC a1c def ghi B 1 e h A C a c d f g i 207 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi 208 // cmp - 2 cmp - 2 cmp - 2 209 // bool bool_c bool_x 210 // if if_c if_x 211 // T F T F T F 212 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. 213 // 214 // Split the paths coming into the merge point into 2 separate groups of 215 // merges. On the left will be all the paths feeding constants into the 216 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi 217 // will fold up into a constant; this will let the Cmp fold up as well as 218 // all the control flow. Below the original IF we have 2 control 219 // dependent regions, 's' and 't'. Now we will merge the two paths 220 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite 221 // likely 2 or more) will promptly constant fold away. 222 PhaseGVN *phase = igvn; 223 224 // Make a region merging constants and a region merging the rest 225 uint req_c = 0; 226 Node* predicate_proj = NULL; 227 for (uint ii = 1; ii < r->req(); ii++) { 228 if (phi->in(ii) == con1) { 229 req_c++; 230 } 231 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii)); 232 if (proj != NULL) { 233 assert(predicate_proj == NULL, "only one predicate entry expected"); 234 predicate_proj = proj; 235 } 236 } 237 Node* predicate_c = NULL; 238 Node* predicate_x = NULL; 239 bool counted_loop = r->is_CountedLoop(); 240 241 Node *region_c = new (igvn->C) RegionNode(req_c + 1); 242 Node *phi_c = con1; 243 uint len = r->req(); 244 Node *region_x = new (igvn->C) RegionNode(len - req_c); 245 Node *phi_x = PhiNode::make_blank(region_x, phi); 246 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { 247 if (phi->in(i) == con1) { 248 region_c->init_req( i_c++, r ->in(i) ); 249 if (r->in(i) == predicate_proj) 250 predicate_c = predicate_proj; 251 } else { 252 region_x->init_req( i_x, r ->in(i) ); 253 phi_x ->init_req( i_x++, phi->in(i) ); 254 if (r->in(i) == predicate_proj) 255 predicate_x = predicate_proj; 256 } 257 } 258 if (predicate_c != NULL && (req_c > 1)) { 259 assert(predicate_x == NULL, "only one predicate entry expected"); 260 predicate_c = NULL; // Do not clone predicate below merge point 261 } 262 if (predicate_x != NULL && ((len - req_c) > 2)) { 263 assert(predicate_c == NULL, "only one predicate entry expected"); 264 predicate_x = NULL; // Do not clone predicate below merge point 265 } 266 267 // Register the new RegionNodes but do not transform them. Cannot 268 // transform until the entire Region/Phi conglomerate has been hacked 269 // as a single huge transform. 270 igvn->register_new_node_with_optimizer( region_c ); 271 igvn->register_new_node_with_optimizer( region_x ); 272 // Prevent the untimely death of phi_x. Currently he has no uses. He is 273 // about to get one. If this only use goes away, then phi_x will look dead. 274 // However, he will be picking up some more uses down below. 275 Node *hook = new (igvn->C) Node(4); 276 hook->init_req(0, phi_x); 277 hook->init_req(1, phi_c); 278 phi_x = phase->transform( phi_x ); 279 280 // Make the compare 281 Node *cmp_c = phase->makecon(t); 282 Node *cmp_x = cmp->clone(); 283 cmp_x->set_req(1,phi_x); 284 cmp_x->set_req(2,con2); 285 cmp_x = phase->transform(cmp_x); 286 // Make the bool 287 Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test)); 288 Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test)); 289 // Make the IfNode 290 IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt); 291 igvn->set_type_bottom(iff_c); 292 igvn->_worklist.push(iff_c); 293 hook->init_req(2, iff_c); 294 295 IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt); 296 igvn->set_type_bottom(iff_x); 297 igvn->_worklist.push(iff_x); 298 hook->init_req(3, iff_x); 299 300 // Make the true/false arms 301 Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c)); 302 Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c)); 303 if (predicate_c != NULL) { 304 assert(predicate_x == NULL, "only one predicate entry expected"); 305 // Clone loop predicates to each path 306 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop); 307 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop); 308 } 309 Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x)); 310 Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x)); 311 if (predicate_x != NULL) { 312 assert(predicate_c == NULL, "only one predicate entry expected"); 313 // Clone loop predicates to each path 314 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop); 315 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop); 316 } 317 318 // Merge the TRUE paths 319 Node *region_s = new (igvn->C) RegionNode(3); 320 igvn->_worklist.push(region_s); 321 region_s->init_req(1, iff_c_t); 322 region_s->init_req(2, iff_x_t); 323 igvn->register_new_node_with_optimizer( region_s ); 324 325 // Merge the FALSE paths 326 Node *region_f = new (igvn->C) RegionNode(3); 327 igvn->_worklist.push(region_f); 328 region_f->init_req(1, iff_c_f); 329 region_f->init_req(2, iff_x_f); 330 igvn->register_new_node_with_optimizer( region_f ); 331 332 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. 333 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead 334 cmp->set_req(2,NULL); 335 // Check for all uses of the Phi and give them a new home. 336 // The 'cmp' got cloned, but CastPP/IIs need to be moved. 337 Node *phi_s = NULL; // do not construct unless needed 338 Node *phi_f = NULL; // do not construct unless needed 339 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { 340 Node* v = phi->last_out(i2);// User of the phi 341 igvn->rehash_node_delayed(v); // Have to fixup other Phi users 342 uint vop = v->Opcode(); 343 Node *proj = NULL; 344 if( vop == Op_Phi ) { // Remote merge point 345 Node *r = v->in(0); 346 for (uint i3 = 1; i3 < r->req(); i3++) 347 if (r->in(i3) && r->in(i3)->in(0) == iff) { 348 proj = r->in(i3); 349 break; 350 } 351 } else if( v->is_ConstraintCast() ) { 352 proj = v->in(0); // Controlling projection 353 } else { 354 assert( 0, "do not know how to handle this guy" ); 355 } 356 357 Node *proj_path_data, *proj_path_ctrl; 358 if( proj->Opcode() == Op_IfTrue ) { 359 if( phi_s == NULL ) { 360 // Only construct phi_s if needed, otherwise provides 361 // interfering use. 362 phi_s = PhiNode::make_blank(region_s,phi); 363 phi_s->init_req( 1, phi_c ); 364 phi_s->init_req( 2, phi_x ); 365 hook->add_req(phi_s); 366 phi_s = phase->transform(phi_s); 367 } 368 proj_path_data = phi_s; 369 proj_path_ctrl = region_s; 370 } else { 371 if( phi_f == NULL ) { 372 // Only construct phi_f if needed, otherwise provides 373 // interfering use. 374 phi_f = PhiNode::make_blank(region_f,phi); 375 phi_f->init_req( 1, phi_c ); 376 phi_f->init_req( 2, phi_x ); 377 hook->add_req(phi_f); 378 phi_f = phase->transform(phi_f); 379 } 380 proj_path_data = phi_f; 381 proj_path_ctrl = region_f; 382 } 383 384 // Fixup 'v' for for the split 385 if( vop == Op_Phi ) { // Remote merge point 386 uint i; 387 for( i = 1; i < v->req(); i++ ) 388 if( v->in(i) == phi ) 389 break; 390 v->set_req(i, proj_path_data ); 391 } else if( v->is_ConstraintCast() ) { 392 v->set_req(0, proj_path_ctrl ); 393 v->set_req(1, proj_path_data ); 394 } else 395 ShouldNotReachHere(); 396 } 397 398 // Now replace the original iff's True/False with region_s/region_t. 399 // This makes the original iff go dead. 400 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { 401 Node* p = iff->last_out(i3); 402 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); 403 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; 404 // Replace p with u 405 igvn->add_users_to_worklist(p); 406 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { 407 Node* x = p->last_out(l); 408 igvn->hash_delete(x); 409 uint uses_found = 0; 410 for( uint j = 0; j < x->req(); j++ ) { 411 if( x->in(j) == p ) { 412 x->set_req(j, u); 413 uses_found++; 414 } 415 } 416 l -= uses_found; // we deleted 1 or more copies of this edge 417 } 418 igvn->remove_dead_node(p); 419 } 420 421 // Force the original merge dead 422 igvn->hash_delete(r); 423 // First, remove region's dead users. 424 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { 425 Node* u = r->last_out(l); 426 if( u == r ) { 427 r->set_req(0, NULL); 428 } else { 429 assert(u->outcnt() == 0, "only dead users"); 430 igvn->remove_dead_node(u); 431 } 432 l -= 1; 433 } 434 igvn->remove_dead_node(r); 435 436 // Now remove the bogus extra edges used to keep things alive 437 igvn->remove_dead_node( hook ); 438 439 // Must return either the original node (now dead) or a new node 440 // (Do not return a top here, since that would break the uniqueness of top.) 441 return new (igvn->C) ConINode(TypeInt::ZERO); 442 } 443 444 //------------------------------is_range_check--------------------------------- 445 // Return 0 if not a range check. Return 1 if a range check and set index and 446 // offset. Return 2 if we had to negate the test. Index is NULL if the check 447 // is versus a constant. 448 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { 449 Node* b = in(1); 450 if (b == NULL || !b->is_Bool()) return 0; 451 BoolNode* bn = b->as_Bool(); 452 Node* cmp = bn->in(1); 453 if (cmp == NULL) return 0; 454 if (cmp->Opcode() != Op_CmpU) return 0; 455 456 Node* l = cmp->in(1); 457 Node* r = cmp->in(2); 458 int flip_test = 1; 459 if (bn->_test._test == BoolTest::le) { 460 l = cmp->in(2); 461 r = cmp->in(1); 462 flip_test = 2; 463 } else if (bn->_test._test != BoolTest::lt) { 464 return 0; 465 } 466 if (l->is_top()) return 0; // Top input means dead test 467 if (r->Opcode() != Op_LoadRange) return 0; 468 469 // We have recognized one of these forms: 470 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... 471 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... 472 473 // Make sure it's a real range check by requiring an uncommon trap 474 // along the OOB path. Otherwise, it's possible that the user wrote 475 // something which optimized to look like a range check but behaves 476 // in some other way. 477 Node* iftrap = proj_out(flip_test == 2 ? true : false); 478 bool found_trap = false; 479 if (iftrap != NULL) { 480 Node* u = iftrap->unique_ctrl_out(); 481 if (u != NULL) { 482 // It could be a merge point (Region) for uncommon trap. 483 if (u->is_Region()) { 484 Node* c = u->unique_ctrl_out(); 485 if (c != NULL) { 486 iftrap = u; 487 u = c; 488 } 489 } 490 if (u->in(0) == iftrap && u->is_CallStaticJava()) { 491 int req = u->as_CallStaticJava()->uncommon_trap_request(); 492 if (Deoptimization::trap_request_reason(req) == 493 Deoptimization::Reason_range_check) { 494 found_trap = true; 495 } 496 } 497 } 498 } 499 if (!found_trap) return 0; // sorry, no cigar 500 501 // Look for index+offset form 502 Node* ind = l; 503 jint off = 0; 504 if (l->is_top()) { 505 return 0; 506 } else if (l->is_Add()) { 507 if ((off = l->in(1)->find_int_con(0)) != 0) { 508 ind = l->in(2); 509 } else if ((off = l->in(2)->find_int_con(0)) != 0) { 510 ind = l->in(1); 511 } 512 } else if ((off = l->find_int_con(-1)) >= 0) { 513 // constant offset with no variable index 514 ind = NULL; 515 } else { 516 // variable index with no constant offset (or dead negative index) 517 off = 0; 518 } 519 520 // Return all the values: 521 index = ind; 522 offset = off; 523 range = r; 524 return flip_test; 525 } 526 527 //------------------------------adjust_check----------------------------------- 528 // Adjust (widen) a prior range check 529 static void adjust_check(Node* proj, Node* range, Node* index, 530 int flip, jint off_lo, PhaseIterGVN* igvn) { 531 PhaseGVN *gvn = igvn; 532 // Break apart the old check 533 Node *iff = proj->in(0); 534 Node *bol = iff->in(1); 535 if( bol->is_top() ) return; // In case a partially dead range check appears 536 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode 537 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) 538 if( !bol->is_Bool() ) return; 539 540 Node *cmp = bol->in(1); 541 // Compute a new check 542 Node *new_add = gvn->intcon(off_lo); 543 if( index ) { 544 new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index; 545 } 546 Node *new_cmp = (flip == 1) 547 ? new (gvn->C) CmpUNode( new_add, range ) 548 : new (gvn->C) CmpUNode( range, new_add ); 549 new_cmp = gvn->transform(new_cmp); 550 // See if no need to adjust the existing check 551 if( new_cmp == cmp ) return; 552 // Else, adjust existing check 553 Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 554 igvn->rehash_node_delayed( iff ); 555 iff->set_req_X( 1, new_bol, igvn ); 556 } 557 558 //------------------------------up_one_dom------------------------------------- 559 // Walk up the dominator tree one step. Return NULL at root or true 560 // complex merges. Skips through small diamonds. 561 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 562 Node *dom = curr->in(0); 563 if( !dom ) // Found a Region degraded to a copy? 564 return curr->nonnull_req(); // Skip thru it 565 566 if( curr != dom ) // Normal walk up one step? 567 return dom; 568 569 // Use linear_only if we are still parsing, since we cannot 570 // trust the regions to be fully filled in. 571 if (linear_only) 572 return NULL; 573 574 if( dom->is_Root() ) 575 return NULL; 576 577 // Else hit a Region. Check for a loop header 578 if( dom->is_Loop() ) 579 return dom->in(1); // Skip up thru loops 580 581 // Check for small diamonds 582 Node *din1, *din2, *din3, *din4; 583 if( dom->req() == 3 && // 2-path merge point 584 (din1 = dom ->in(1)) && // Left path exists 585 (din2 = dom ->in(2)) && // Right path exists 586 (din3 = din1->in(0)) && // Left path up one 587 (din4 = din2->in(0)) ) { // Right path up one 588 if( din3->is_Call() && // Handle a slow-path call on either arm 589 (din3 = din3->in(0)) ) 590 din3 = din3->in(0); 591 if( din4->is_Call() && // Handle a slow-path call on either arm 592 (din4 = din4->in(0)) ) 593 din4 = din4->in(0); 594 if( din3 == din4 && din3->is_If() ) 595 return din3; // Skip around diamonds 596 } 597 598 // Give up the search at true merges 599 return NULL; // Dead loop? Or hit root? 600 } 601 602 603 //------------------------------filtered_int_type-------------------------------- 604 // Return a possibly more restrictive type for val based on condition control flow for an if 605 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 606 assert(if_proj && 607 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 608 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 609 IfNode* iff = if_proj->in(0)->as_If(); 610 if (iff->in(1) && iff->in(1)->is_Bool()) { 611 BoolNode* bol = iff->in(1)->as_Bool(); 612 if (bol->in(1) && bol->in(1)->is_Cmp()) { 613 const CmpNode* cmp = bol->in(1)->as_Cmp(); 614 if (cmp->in(1) == val) { 615 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 616 if (cmp2_t != NULL) { 617 jint lo = cmp2_t->_lo; 618 jint hi = cmp2_t->_hi; 619 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 620 switch (msk) { 621 case BoolTest::ne: 622 // Can't refine type 623 return NULL; 624 case BoolTest::eq: 625 return cmp2_t; 626 case BoolTest::lt: 627 lo = TypeInt::INT->_lo; 628 if (hi - 1 < hi) { 629 hi = hi - 1; 630 } 631 break; 632 case BoolTest::le: 633 lo = TypeInt::INT->_lo; 634 break; 635 case BoolTest::gt: 636 if (lo + 1 > lo) { 637 lo = lo + 1; 638 } 639 hi = TypeInt::INT->_hi; 640 break; 641 case BoolTest::ge: 642 // lo unchanged 643 hi = TypeInt::INT->_hi; 644 break; 645 } 646 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 647 return rtn_t; 648 } 649 } 650 } 651 } 652 } 653 return NULL; 654 } 655 656 //------------------------------fold_compares---------------------------- 657 // See if a pair of CmpIs can be converted into a CmpU. In some cases 658 // the direction of this if is determined by the preceding if so it 659 // can be eliminate entirely. Given an if testing (CmpI n c) check 660 // for an immediately control dependent if that is testing (CmpI n c2) 661 // and has one projection leading to this if and the other projection 662 // leading to a region that merges one of this ifs control 663 // projections. 664 // 665 // If 666 // / | 667 // / | 668 // / | 669 // If | 670 // /\ | 671 // / \ | 672 // / \ | 673 // / Region 674 // 675 Node* IfNode::fold_compares(PhaseGVN* phase) { 676 if (!phase->C->eliminate_boxing() || Opcode() != Op_If) return NULL; 677 678 Node* this_cmp = in(1)->in(1); 679 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && 680 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { 681 Node* ctrl = in(0); 682 BoolNode* this_bool = in(1)->as_Bool(); 683 Node* n = this_cmp->in(1); 684 int hi = this_cmp->in(2)->get_int(); 685 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && 686 ctrl->in(0)->is_If() && 687 ctrl->in(0)->outcnt() == 2 && 688 ctrl->in(0)->in(1)->is_Bool() && 689 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && 690 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && 691 ctrl->in(0)->in(1)->in(1)->in(1) == n) { 692 IfNode* dom_iff = ctrl->in(0)->as_If(); 693 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con); 694 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() && 695 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) { 696 // Identify which proj goes to the region and which continues on 697 RegionNode* region = otherproj->unique_out()->as_Region(); 698 Node* success = NULL; 699 Node* fail = NULL; 700 for (int i = 0; i < 2; i++) { 701 Node* proj = proj_out(i); 702 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 703 success = proj; 704 } else if (fail == NULL) { 705 fail = proj; 706 } else { 707 success = fail = NULL; 708 } 709 } 710 if (success != NULL && fail != NULL && !region->has_phi()) { 711 int lo = dom_iff->in(1)->in(1)->in(2)->get_int(); 712 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 713 Node* dom_cmp = dom_bool->in(1); 714 const TypeInt* failtype = filtered_int_type(phase, n, ctrl); 715 if (failtype != NULL) { 716 const TypeInt* type2 = filtered_int_type(phase, n, fail); 717 if (type2 != NULL) { 718 failtype = failtype->join(type2)->is_int(); 719 } else { 720 failtype = NULL; 721 } 722 } 723 724 if (failtype != NULL && 725 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) { 726 int bound = failtype->_hi - failtype->_lo + 1; 727 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) { 728 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi) 729 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge; 730 Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo))); 731 Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound))); 732 Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond)); 733 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con)); 734 phase->hash_delete(this); 735 set_req(1, newbool); 736 return this; 737 } 738 if (failtype->_lo > failtype->_hi) { 739 // previous if determines the result of this if so 740 // replace Bool with constant 741 phase->hash_delete(this); 742 set_req(1, phase->intcon(success->as_Proj()->_con)); 743 return this; 744 } 745 } 746 } 747 } 748 } 749 } 750 return NULL; 751 } 752 753 //------------------------------remove_useless_bool---------------------------- 754 // Check for people making a useless boolean: things like 755 // if( (x < y ? true : false) ) { ... } 756 // Replace with if( x < y ) { ... } 757 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 758 Node *i1 = iff->in(1); 759 if( !i1->is_Bool() ) return NULL; 760 BoolNode *bol = i1->as_Bool(); 761 762 Node *cmp = bol->in(1); 763 if( cmp->Opcode() != Op_CmpI ) return NULL; 764 765 // Must be comparing against a bool 766 const Type *cmp2_t = phase->type( cmp->in(2) ); 767 if( cmp2_t != TypeInt::ZERO && 768 cmp2_t != TypeInt::ONE ) 769 return NULL; 770 771 // Find a prior merge point merging the boolean 772 i1 = cmp->in(1); 773 if( !i1->is_Phi() ) return NULL; 774 PhiNode *phi = i1->as_Phi(); 775 if( phase->type( phi ) != TypeInt::BOOL ) 776 return NULL; 777 778 // Check for diamond pattern 779 int true_path = phi->is_diamond_phi(); 780 if( true_path == 0 ) return NULL; 781 782 // Make sure that iff and the control of the phi are different. This 783 // should really only happen for dead control flow since it requires 784 // an illegal cycle. 785 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 786 787 // phi->region->if_proj->ifnode->bool->cmp 788 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 789 790 // Now get the 'sense' of the test correct so we can plug in 791 // either iff2->in(1) or its complement. 792 int flip = 0; 793 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 794 else if( bol->_test._test != BoolTest::eq ) return NULL; 795 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 796 797 const Type *phi1_t = phase->type( phi->in(1) ); 798 const Type *phi2_t = phase->type( phi->in(2) ); 799 // Check for Phi(0,1) and flip 800 if( phi1_t == TypeInt::ZERO ) { 801 if( phi2_t != TypeInt::ONE ) return NULL; 802 flip = 1-flip; 803 } else { 804 // Check for Phi(1,0) 805 if( phi1_t != TypeInt::ONE ) return NULL; 806 if( phi2_t != TypeInt::ZERO ) return NULL; 807 } 808 if( true_path == 2 ) { 809 flip = 1-flip; 810 } 811 812 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 813 assert(new_bol != iff->in(1), "must make progress"); 814 iff->set_req(1, new_bol); 815 // Intervening diamond probably goes dead 816 phase->C->set_major_progress(); 817 return iff; 818 } 819 820 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 821 822 //------------------------------Ideal------------------------------------------ 823 // Return a node which is more "ideal" than the current node. Strip out 824 // control copies 825 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 826 if (remove_dead_region(phase, can_reshape)) return this; 827 // No Def-Use info? 828 if (!can_reshape) return NULL; 829 PhaseIterGVN *igvn = phase->is_IterGVN(); 830 831 // Don't bother trying to transform a dead if 832 if (in(0)->is_top()) return NULL; 833 // Don't bother trying to transform an if with a dead test 834 if (in(1)->is_top()) return NULL; 835 // Another variation of a dead test 836 if (in(1)->is_Con()) return NULL; 837 // Another variation of a dead if 838 if (outcnt() < 2) return NULL; 839 840 // Canonicalize the test. 841 Node* idt_if = idealize_test(phase, this); 842 if (idt_if != NULL) return idt_if; 843 844 // Try to split the IF 845 Node *s = split_if(this, igvn); 846 if (s != NULL) return s; 847 848 // Check for people making a useless boolean: things like 849 // if( (x < y ? true : false) ) { ... } 850 // Replace with if( x < y ) { ... } 851 Node *bol2 = remove_useless_bool(this, phase); 852 if( bol2 ) return bol2; 853 854 // Setup to scan up the CFG looking for a dominating test 855 Node *dom = in(0); 856 Node *prev_dom = this; 857 858 // Check for range-check vs other kinds of tests 859 Node *index1, *range1; 860 jint offset1; 861 int flip1 = is_range_check(range1, index1, offset1); 862 if( flip1 ) { 863 Node *first_prev_dom = NULL; 864 865 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 866 // so all checks we inspect post-dominate the top-most check we find. 867 // If we are going to fail the current check and we reach the top check 868 // then we are guaranteed to fail, so just start interpreting there. 869 // We 'expand' the top 2 range checks to include all post-dominating 870 // checks. 871 872 // The top 2 range checks seen 873 Node *prev_chk1 = NULL; 874 Node *prev_chk2 = NULL; 875 // Low and high offsets seen so far 876 jint off_lo = offset1; 877 jint off_hi = offset1; 878 879 // Scan for the top 2 checks and collect range of offsets 880 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit 881 if( dom->Opcode() == Op_If && // Not same opcode? 882 prev_dom->in(0) == dom ) { // One path of test does dominate? 883 if( dom == this ) return NULL; // dead loop 884 // See if this is a range check 885 Node *index2, *range2; 886 jint offset2; 887 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); 888 // See if this is a _matching_ range check, checking against 889 // the same array bounds. 890 if( flip2 == flip1 && range2 == range1 && index2 == index1 && 891 dom->outcnt() == 2 ) { 892 // Gather expanded bounds 893 off_lo = MIN2(off_lo,offset2); 894 off_hi = MAX2(off_hi,offset2); 895 // Record top 2 range checks 896 prev_chk2 = prev_chk1; 897 prev_chk1 = prev_dom; 898 // If we match the test exactly, then the top test covers 899 // both our lower and upper bounds. 900 if( dom->in(1) == in(1) ) 901 prev_chk2 = prev_chk1; 902 } 903 } 904 prev_dom = dom; 905 dom = up_one_dom( dom ); 906 if( !dom ) break; 907 } 908 909 910 // Attempt to widen the dominating range check to cover some later 911 // ones. Since range checks "fail" by uncommon-trapping to the 912 // interpreter, widening a check can make us speculative enter the 913 // interpreter. If we see range-check deopt's, do not widen! 914 if (!phase->C->allow_range_check_smearing()) return NULL; 915 916 // Constant indices only need to check the upper bound. 917 // Non-constance indices must check both low and high. 918 if( index1 ) { 919 // Didn't find 2 prior covering checks, so cannot remove anything. 920 if( !prev_chk2 ) return NULL; 921 // 'Widen' the offsets of the 1st and 2nd covering check 922 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); 923 // Do not call adjust_check twice on the same projection 924 // as the first call may have transformed the BoolNode to a ConI 925 if( prev_chk1 != prev_chk2 ) { 926 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); 927 } 928 // Test is now covered by prior checks, dominate it out 929 prev_dom = prev_chk2; 930 } else { 931 // Didn't find prior covering check, so cannot remove anything. 932 if( !prev_chk1 ) return NULL; 933 // 'Widen' the offset of the 1st and only covering check 934 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); 935 // Test is now covered by prior checks, dominate it out 936 prev_dom = prev_chk1; 937 } 938 939 940 } else { // Scan for an equivalent test 941 942 Node *cmp; 943 int dist = 0; // Cutoff limit for search 944 int op = Opcode(); 945 if( op == Op_If && 946 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 947 if( cmp->in(2) != NULL && // make sure cmp is not already dead 948 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 949 dist = 64; // Limit for null-pointer scans 950 } else { 951 dist = 4; // Do not bother for random pointer tests 952 } 953 } else { 954 dist = 4; // Limit for random junky scans 955 } 956 957 // Normal equivalent-test check. 958 if( !dom ) return NULL; // Dead loop? 959 960 Node* result = fold_compares(phase); 961 if (result != NULL) { 962 return result; 963 } 964 965 // Search up the dominator tree for an If with an identical test 966 while( dom->Opcode() != op || // Not same opcode? 967 dom->in(1) != in(1) || // Not same input 1? 968 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 969 prev_dom->in(0) != dom ) { // One path of test does not dominate? 970 if( dist < 0 ) return NULL; 971 972 dist--; 973 prev_dom = dom; 974 dom = up_one_dom( dom ); 975 if( !dom ) return NULL; 976 } 977 978 // Check that we did not follow a loop back to ourselves 979 if( this == dom ) 980 return NULL; 981 982 if( dist > 2 ) // Add to count of NULL checks elided 983 explicit_null_checks_elided++; 984 985 } // End of Else scan for an equivalent test 986 987 // Hit! Remove this IF 988 #ifndef PRODUCT 989 if( TraceIterativeGVN ) { 990 tty->print(" Removing IfNode: "); this->dump(); 991 } 992 if( VerifyOpto && !phase->allow_progress() ) { 993 // Found an equivalent dominating test, 994 // we can not guarantee reaching a fix-point for these during iterativeGVN 995 // since intervening nodes may not change. 996 return NULL; 997 } 998 #endif 999 1000 // Replace dominated IfNode 1001 dominated_by( prev_dom, igvn ); 1002 1003 // Must return either the original node (now dead) or a new node 1004 // (Do not return a top here, since that would break the uniqueness of top.) 1005 return new (phase->C) ConINode(TypeInt::ZERO); 1006 } 1007 1008 //------------------------------dominated_by----------------------------------- 1009 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { 1010 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1011 Node *idom = in(0); 1012 // Need opcode to decide which way 'this' test goes 1013 int prev_op = prev_dom->Opcode(); 1014 Node *top = igvn->C->top(); // Shortcut to top 1015 1016 // Loop predicates may have depending checks which should not 1017 // be skipped. For example, range check predicate has two checks 1018 // for lower and upper bounds. 1019 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj(); 1020 if (PhaseIdealLoop::is_uncommon_trap_proj(unc_proj, Deoptimization::Reason_predicate)) 1021 prev_dom = idom; 1022 1023 // Now walk the current IfNode's projections. 1024 // Loop ends when 'this' has no more uses. 1025 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1026 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1027 igvn->add_users_to_worklist(ifp); 1028 // Check which projection it is and set target. 1029 // Data-target is either the dominating projection of the same type 1030 // or TOP if the dominating projection is of opposite type. 1031 // Data-target will be used as the new control edge for the non-CFG 1032 // nodes like Casts and Loads. 1033 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top; 1034 // Control-target is just the If's immediate dominator or TOP. 1035 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top; 1036 1037 // For each child of an IfTrue/IfFalse projection, reroute. 1038 // Loop ends when projection has no more uses. 1039 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1040 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1041 if( !s->depends_only_on_test() ) { 1042 // Find the control input matching this def-use edge. 1043 // For Regions it may not be in slot 0. 1044 uint l; 1045 for( l = 0; s->in(l) != ifp; l++ ) { } 1046 igvn->replace_input_of(s, l, ctrl_target); 1047 } else { // Else, for control producers, 1048 igvn->replace_input_of(s, 0, data_target); // Move child to data-target 1049 } 1050 } // End for each child of a projection 1051 1052 igvn->remove_dead_node(ifp); 1053 } // End for each IfTrue/IfFalse child of If 1054 1055 // Kill the IfNode 1056 igvn->remove_dead_node(this); 1057 } 1058 1059 //------------------------------Identity--------------------------------------- 1060 // If the test is constant & we match, then we are the input Control 1061 Node *IfTrueNode::Identity( PhaseTransform *phase ) { 1062 // Can only optimize if cannot go the other way 1063 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1064 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) 1065 ? in(0)->in(0) // IfNode control 1066 : this; // no progress 1067 } 1068 1069 //------------------------------dump_spec-------------------------------------- 1070 #ifndef PRODUCT 1071 void IfNode::dump_spec(outputStream *st) const { 1072 st->print("P=%f, C=%f",_prob,_fcnt); 1073 } 1074 #endif 1075 1076 //------------------------------idealize_test---------------------------------- 1077 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1078 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1079 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1080 // needed. 1081 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1082 assert(iff->in(0) != NULL, "If must be live"); 1083 1084 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1085 Node* old_if_f = iff->proj_out(false); 1086 Node* old_if_t = iff->proj_out(true); 1087 1088 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1089 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1090 // happens in count-down loops 1091 if (iff->is_CountedLoopEnd()) return NULL; 1092 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1093 BoolNode *b = iff->in(1)->as_Bool(); 1094 BoolTest bt = b->_test; 1095 // Test already in good order? 1096 if( bt.is_canonical() ) 1097 return NULL; 1098 1099 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1100 // cloning the IfNode. 1101 Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) ); 1102 if( !new_b->is_Bool() ) return NULL; 1103 b = new_b->as_Bool(); 1104 1105 PhaseIterGVN *igvn = phase->is_IterGVN(); 1106 assert( igvn, "Test is not canonical in parser?" ); 1107 1108 // The IF node never really changes, but it needs to be cloned 1109 iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); 1110 1111 Node *prior = igvn->hash_find_insert(iff); 1112 if( prior ) { 1113 igvn->remove_dead_node(iff); 1114 iff = (IfNode*)prior; 1115 } else { 1116 // Cannot call transform on it just yet 1117 igvn->set_type_bottom(iff); 1118 } 1119 igvn->_worklist.push(iff); 1120 1121 // Now handle projections. Cloning not required. 1122 Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff )); 1123 Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff )); 1124 1125 igvn->register_new_node_with_optimizer(new_if_f); 1126 igvn->register_new_node_with_optimizer(new_if_t); 1127 // Flip test, so flip trailing control 1128 igvn->replace_node(old_if_f, new_if_t); 1129 igvn->replace_node(old_if_t, new_if_f); 1130 1131 // Progress 1132 return iff; 1133 } 1134 1135 //------------------------------Identity--------------------------------------- 1136 // If the test is constant & we match, then we are the input Control 1137 Node *IfFalseNode::Identity( PhaseTransform *phase ) { 1138 // Can only optimize if cannot go the other way 1139 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1140 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) 1141 ? in(0)->in(0) // IfNode control 1142 : this; // no progress 1143 }