1 /* 2 * Copyright (c) 2000, 2010, 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; 239 240 Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1); 241 Node *phi_c = con1; 242 uint len = r->req(); 243 Node *region_x = new (igvn->C, len - req_c) RegionNode(len - req_c); 244 Node *phi_x = PhiNode::make_blank(region_x, phi); 245 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { 246 if (phi->in(i) == con1) { 247 region_c->init_req( i_c++, r ->in(i) ); 248 if (r->in(i) == predicate_proj) 249 predicate_c = predicate_proj; 250 } else { 251 region_x->init_req( i_x, r ->in(i) ); 252 phi_x ->init_req( i_x++, phi->in(i) ); 253 if (r->in(i) == predicate_proj) 254 predicate_x = predicate_proj; 255 } 256 } 257 258 // Register the new RegionNodes but do not transform them. Cannot 259 // transform until the entire Region/Phi conglomerate has been hacked 260 // as a single huge transform. 261 igvn->register_new_node_with_optimizer( region_c ); 262 igvn->register_new_node_with_optimizer( region_x ); 263 // Prevent the untimely death of phi_x. Currently he has no uses. He is 264 // about to get one. If this only use goes away, then phi_x will look dead. 265 // However, he will be picking up some more uses down below. 266 Node *hook = new (igvn->C, 4) Node(4); 267 hook->init_req(0, phi_x); 268 hook->init_req(1, phi_c); 269 phi_x = phase->transform( phi_x ); 270 271 // Make the compare 272 Node *cmp_c = phase->makecon(t); 273 Node *cmp_x = cmp->clone(); 274 cmp_x->set_req(1,phi_x); 275 cmp_x->set_req(2,con2); 276 cmp_x = phase->transform(cmp_x); 277 // Make the bool 278 Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test)); 279 Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test)); 280 // Make the IfNode 281 IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt); 282 igvn->set_type_bottom(iff_c); 283 igvn->_worklist.push(iff_c); 284 hook->init_req(2, iff_c); 285 286 IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt); 287 igvn->set_type_bottom(iff_x); 288 igvn->_worklist.push(iff_x); 289 hook->init_req(3, iff_x); 290 291 // Make the true/false arms 292 Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c)); 293 Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c)); 294 if (predicate_c != NULL) { 295 assert(predicate_x == NULL, "only one predicate entry expected"); 296 // Clone loop predicates to each path 297 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t); 298 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f); 299 } 300 Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x)); 301 Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x)); 302 if (predicate_x != NULL) { 303 assert(predicate_c == NULL, "only one predicate entry expected"); 304 // Clone loop predicates to each path 305 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t); 306 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f); 307 } 308 309 // Merge the TRUE paths 310 Node *region_s = new (igvn->C, 3) RegionNode(3); 311 igvn->_worklist.push(region_s); 312 region_s->init_req(1, iff_c_t); 313 region_s->init_req(2, iff_x_t); 314 igvn->register_new_node_with_optimizer( region_s ); 315 316 // Merge the FALSE paths 317 Node *region_f = new (igvn->C, 3) RegionNode(3); 318 igvn->_worklist.push(region_f); 319 region_f->init_req(1, iff_c_f); 320 region_f->init_req(2, iff_x_f); 321 igvn->register_new_node_with_optimizer( region_f ); 322 323 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. 324 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead 325 cmp->set_req(2,NULL); 326 // Check for all uses of the Phi and give them a new home. 327 // The 'cmp' got cloned, but CastPP/IIs need to be moved. 328 Node *phi_s = NULL; // do not construct unless needed 329 Node *phi_f = NULL; // do not construct unless needed 330 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { 331 Node* v = phi->last_out(i2);// User of the phi 332 igvn->hash_delete(v); // Have to fixup other Phi users 333 igvn->_worklist.push(v); 334 uint vop = v->Opcode(); 335 Node *proj = NULL; 336 if( vop == Op_Phi ) { // Remote merge point 337 Node *r = v->in(0); 338 for (uint i3 = 1; i3 < r->req(); i3++) 339 if (r->in(i3) && r->in(i3)->in(0) == iff) { 340 proj = r->in(i3); 341 break; 342 } 343 } else if( v->is_ConstraintCast() ) { 344 proj = v->in(0); // Controlling projection 345 } else { 346 assert( 0, "do not know how to handle this guy" ); 347 } 348 349 Node *proj_path_data, *proj_path_ctrl; 350 if( proj->Opcode() == Op_IfTrue ) { 351 if( phi_s == NULL ) { 352 // Only construct phi_s if needed, otherwise provides 353 // interfering use. 354 phi_s = PhiNode::make_blank(region_s,phi); 355 phi_s->init_req( 1, phi_c ); 356 phi_s->init_req( 2, phi_x ); 357 hook->add_req(phi_s); 358 phi_s = phase->transform(phi_s); 359 } 360 proj_path_data = phi_s; 361 proj_path_ctrl = region_s; 362 } else { 363 if( phi_f == NULL ) { 364 // Only construct phi_f if needed, otherwise provides 365 // interfering use. 366 phi_f = PhiNode::make_blank(region_f,phi); 367 phi_f->init_req( 1, phi_c ); 368 phi_f->init_req( 2, phi_x ); 369 hook->add_req(phi_f); 370 phi_f = phase->transform(phi_f); 371 } 372 proj_path_data = phi_f; 373 proj_path_ctrl = region_f; 374 } 375 376 // Fixup 'v' for for the split 377 if( vop == Op_Phi ) { // Remote merge point 378 uint i; 379 for( i = 1; i < v->req(); i++ ) 380 if( v->in(i) == phi ) 381 break; 382 v->set_req(i, proj_path_data ); 383 } else if( v->is_ConstraintCast() ) { 384 v->set_req(0, proj_path_ctrl ); 385 v->set_req(1, proj_path_data ); 386 } else 387 ShouldNotReachHere(); 388 } 389 390 // Now replace the original iff's True/False with region_s/region_t. 391 // This makes the original iff go dead. 392 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { 393 Node* p = iff->last_out(i3); 394 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); 395 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; 396 // Replace p with u 397 igvn->add_users_to_worklist(p); 398 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { 399 Node* x = p->last_out(l); 400 igvn->hash_delete(x); 401 uint uses_found = 0; 402 for( uint j = 0; j < x->req(); j++ ) { 403 if( x->in(j) == p ) { 404 x->set_req(j, u); 405 uses_found++; 406 } 407 } 408 l -= uses_found; // we deleted 1 or more copies of this edge 409 } 410 igvn->remove_dead_node(p); 411 } 412 413 // Force the original merge dead 414 igvn->hash_delete(r); 415 // First, remove region's dead users. 416 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { 417 Node* u = r->last_out(l); 418 if( u == r ) { 419 r->set_req(0, NULL); 420 } else { 421 assert(u->outcnt() == 0, "only dead users"); 422 igvn->remove_dead_node(u); 423 } 424 l -= 1; 425 } 426 igvn->remove_dead_node(r); 427 428 // Now remove the bogus extra edges used to keep things alive 429 igvn->remove_dead_node( hook ); 430 431 // Must return either the original node (now dead) or a new node 432 // (Do not return a top here, since that would break the uniqueness of top.) 433 return new (igvn->C, 1) ConINode(TypeInt::ZERO); 434 } 435 436 //------------------------------is_range_check--------------------------------- 437 // Return 0 if not a range check. Return 1 if a range check and set index and 438 // offset. Return 2 if we had to negate the test. Index is NULL if the check 439 // is versus a constant. 440 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { 441 Node* b = in(1); 442 if (b == NULL || !b->is_Bool()) return 0; 443 BoolNode* bn = b->as_Bool(); 444 Node* cmp = bn->in(1); 445 if (cmp == NULL) return 0; 446 if (cmp->Opcode() != Op_CmpU) return 0; 447 448 Node* l = cmp->in(1); 449 Node* r = cmp->in(2); 450 int flip_test = 1; 451 if (bn->_test._test == BoolTest::le) { 452 l = cmp->in(2); 453 r = cmp->in(1); 454 flip_test = 2; 455 } else if (bn->_test._test != BoolTest::lt) { 456 return 0; 457 } 458 if (l->is_top()) return 0; // Top input means dead test 459 if (r->Opcode() != Op_LoadRange) return 0; 460 461 // We have recognized one of these forms: 462 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... 463 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... 464 465 // Make sure it's a real range check by requiring an uncommon trap 466 // along the OOB path. Otherwise, it's possible that the user wrote 467 // something which optimized to look like a range check but behaves 468 // in some other way. 469 Node* iftrap = proj_out(flip_test == 2 ? true : false); 470 bool found_trap = false; 471 if (iftrap != NULL) { 472 Node* u = iftrap->unique_ctrl_out(); 473 if (u != NULL) { 474 // It could be a merge point (Region) for uncommon trap. 475 if (u->is_Region()) { 476 Node* c = u->unique_ctrl_out(); 477 if (c != NULL) { 478 iftrap = u; 479 u = c; 480 } 481 } 482 if (u->in(0) == iftrap && u->is_CallStaticJava()) { 483 int req = u->as_CallStaticJava()->uncommon_trap_request(); 484 if (Deoptimization::trap_request_reason(req) == 485 Deoptimization::Reason_range_check) { 486 found_trap = true; 487 } 488 } 489 } 490 } 491 if (!found_trap) return 0; // sorry, no cigar 492 493 // Look for index+offset form 494 Node* ind = l; 495 jint off = 0; 496 if (l->is_top()) { 497 return 0; 498 } else if (l->is_Add()) { 499 if ((off = l->in(1)->find_int_con(0)) != 0) { 500 ind = l->in(2); 501 } else if ((off = l->in(2)->find_int_con(0)) != 0) { 502 ind = l->in(1); 503 } 504 } else if ((off = l->find_int_con(-1)) >= 0) { 505 // constant offset with no variable index 506 ind = NULL; 507 } else { 508 // variable index with no constant offset (or dead negative index) 509 off = 0; 510 } 511 512 // Return all the values: 513 index = ind; 514 offset = off; 515 range = r; 516 return flip_test; 517 } 518 519 //------------------------------adjust_check----------------------------------- 520 // Adjust (widen) a prior range check 521 static void adjust_check(Node* proj, Node* range, Node* index, 522 int flip, jint off_lo, PhaseIterGVN* igvn) { 523 PhaseGVN *gvn = igvn; 524 // Break apart the old check 525 Node *iff = proj->in(0); 526 Node *bol = iff->in(1); 527 if( bol->is_top() ) return; // In case a partially dead range check appears 528 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode 529 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) 530 if( !bol->is_Bool() ) return; 531 532 Node *cmp = bol->in(1); 533 // Compute a new check 534 Node *new_add = gvn->intcon(off_lo); 535 if( index ) { 536 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index; 537 } 538 Node *new_cmp = (flip == 1) 539 ? new (gvn->C, 3) CmpUNode( new_add, range ) 540 : new (gvn->C, 3) CmpUNode( range, new_add ); 541 new_cmp = gvn->transform(new_cmp); 542 // See if no need to adjust the existing check 543 if( new_cmp == cmp ) return; 544 // Else, adjust existing check 545 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 546 igvn->hash_delete( iff ); 547 iff->set_req_X( 1, new_bol, igvn ); 548 } 549 550 //------------------------------up_one_dom------------------------------------- 551 // Walk up the dominator tree one step. Return NULL at root or true 552 // complex merges. Skips through small diamonds. 553 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 554 Node *dom = curr->in(0); 555 if( !dom ) // Found a Region degraded to a copy? 556 return curr->nonnull_req(); // Skip thru it 557 558 if( curr != dom ) // Normal walk up one step? 559 return dom; 560 561 // Use linear_only if we are still parsing, since we cannot 562 // trust the regions to be fully filled in. 563 if (linear_only) 564 return NULL; 565 566 if( dom->is_Root() ) 567 return NULL; 568 569 // Else hit a Region. Check for a loop header 570 if( dom->is_Loop() ) 571 return dom->in(1); // Skip up thru loops 572 573 // Check for small diamonds 574 Node *din1, *din2, *din3, *din4; 575 if( dom->req() == 3 && // 2-path merge point 576 (din1 = dom ->in(1)) && // Left path exists 577 (din2 = dom ->in(2)) && // Right path exists 578 (din3 = din1->in(0)) && // Left path up one 579 (din4 = din2->in(0)) ) { // Right path up one 580 if( din3->is_Call() && // Handle a slow-path call on either arm 581 (din3 = din3->in(0)) ) 582 din3 = din3->in(0); 583 if( din4->is_Call() && // Handle a slow-path call on either arm 584 (din4 = din4->in(0)) ) 585 din4 = din4->in(0); 586 if( din3 == din4 && din3->is_If() ) 587 return din3; // Skip around diamonds 588 } 589 590 // Give up the search at true merges 591 return NULL; // Dead loop? Or hit root? 592 } 593 594 595 //------------------------------filtered_int_type-------------------------------- 596 // Return a possibly more restrictive type for val based on condition control flow for an if 597 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 598 assert(if_proj && 599 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 600 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 601 IfNode* iff = if_proj->in(0)->as_If(); 602 if (iff->in(1) && iff->in(1)->is_Bool()) { 603 BoolNode* bol = iff->in(1)->as_Bool(); 604 if (bol->in(1) && bol->in(1)->is_Cmp()) { 605 const CmpNode* cmp = bol->in(1)->as_Cmp(); 606 if (cmp->in(1) == val) { 607 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 608 if (cmp2_t != NULL) { 609 jint lo = cmp2_t->_lo; 610 jint hi = cmp2_t->_hi; 611 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 612 switch (msk) { 613 case BoolTest::ne: 614 // Can't refine type 615 return NULL; 616 case BoolTest::eq: 617 return cmp2_t; 618 case BoolTest::lt: 619 lo = TypeInt::INT->_lo; 620 if (hi - 1 < hi) { 621 hi = hi - 1; 622 } 623 break; 624 case BoolTest::le: 625 lo = TypeInt::INT->_lo; 626 break; 627 case BoolTest::gt: 628 if (lo + 1 > lo) { 629 lo = lo + 1; 630 } 631 hi = TypeInt::INT->_hi; 632 break; 633 case BoolTest::ge: 634 // lo unchanged 635 hi = TypeInt::INT->_hi; 636 break; 637 } 638 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 639 return rtn_t; 640 } 641 } 642 } 643 } 644 } 645 return NULL; 646 } 647 648 //------------------------------fold_compares---------------------------- 649 // See if a pair of CmpIs can be converted into a CmpU. In some cases 650 // the direction of this if is determined by the preceding if so it 651 // can be eliminate entirely. Given an if testing (CmpI n c) check 652 // for an immediately control dependent if that is testing (CmpI n c2) 653 // and has one projection leading to this if and the other projection 654 // leading to a region that merges one of this ifs control 655 // projections. 656 // 657 // If 658 // / | 659 // / | 660 // / | 661 // If | 662 // /\ | 663 // / \ | 664 // / \ | 665 // / Region 666 // 667 Node* IfNode::fold_compares(PhaseGVN* phase) { 668 if (!EliminateAutoBox || Opcode() != Op_If) return NULL; 669 670 Node* this_cmp = in(1)->in(1); 671 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && 672 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { 673 Node* ctrl = in(0); 674 BoolNode* this_bool = in(1)->as_Bool(); 675 Node* n = this_cmp->in(1); 676 int hi = this_cmp->in(2)->get_int(); 677 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && 678 ctrl->in(0)->is_If() && 679 ctrl->in(0)->outcnt() == 2 && 680 ctrl->in(0)->in(1)->is_Bool() && 681 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && 682 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && 683 ctrl->in(0)->in(1)->in(1)->in(1) == n) { 684 IfNode* dom_iff = ctrl->in(0)->as_If(); 685 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con); 686 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() && 687 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) { 688 // Identify which proj goes to the region and which continues on 689 RegionNode* region = otherproj->unique_out()->as_Region(); 690 Node* success = NULL; 691 Node* fail = NULL; 692 for (int i = 0; i < 2; i++) { 693 Node* proj = proj_out(i); 694 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 695 success = proj; 696 } else if (fail == NULL) { 697 fail = proj; 698 } else { 699 success = fail = NULL; 700 } 701 } 702 if (success != NULL && fail != NULL && !region->has_phi()) { 703 int lo = dom_iff->in(1)->in(1)->in(2)->get_int(); 704 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 705 Node* dom_cmp = dom_bool->in(1); 706 const TypeInt* failtype = filtered_int_type(phase, n, ctrl); 707 if (failtype != NULL) { 708 const TypeInt* type2 = filtered_int_type(phase, n, fail); 709 if (type2 != NULL) { 710 failtype = failtype->join(type2)->is_int(); 711 } else { 712 failtype = NULL; 713 } 714 } 715 716 if (failtype != NULL && 717 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) { 718 int bound = failtype->_hi - failtype->_lo + 1; 719 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) { 720 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi) 721 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge; 722 Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo))); 723 Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound))); 724 Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond)); 725 phase->hash_delete(dom_iff); 726 dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con)); 727 phase->is_IterGVN()->_worklist.push(dom_iff); 728 phase->hash_delete(this); 729 set_req(1, newbool); 730 return this; 731 } 732 if (failtype->_lo > failtype->_hi) { 733 // previous if determines the result of this if so 734 // replace Bool with constant 735 phase->hash_delete(this); 736 set_req(1, phase->intcon(success->as_Proj()->_con)); 737 return this; 738 } 739 } 740 } 741 } 742 } 743 } 744 return NULL; 745 } 746 747 //------------------------------remove_useless_bool---------------------------- 748 // Check for people making a useless boolean: things like 749 // if( (x < y ? true : false) ) { ... } 750 // Replace with if( x < y ) { ... } 751 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 752 Node *i1 = iff->in(1); 753 if( !i1->is_Bool() ) return NULL; 754 BoolNode *bol = i1->as_Bool(); 755 756 Node *cmp = bol->in(1); 757 if( cmp->Opcode() != Op_CmpI ) return NULL; 758 759 // Must be comparing against a bool 760 const Type *cmp2_t = phase->type( cmp->in(2) ); 761 if( cmp2_t != TypeInt::ZERO && 762 cmp2_t != TypeInt::ONE ) 763 return NULL; 764 765 // Find a prior merge point merging the boolean 766 i1 = cmp->in(1); 767 if( !i1->is_Phi() ) return NULL; 768 PhiNode *phi = i1->as_Phi(); 769 if( phase->type( phi ) != TypeInt::BOOL ) 770 return NULL; 771 772 // Check for diamond pattern 773 int true_path = phi->is_diamond_phi(); 774 if( true_path == 0 ) return NULL; 775 776 // Make sure that iff and the control of the phi are different. This 777 // should really only happen for dead control flow since it requires 778 // an illegal cycle. 779 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 780 781 // phi->region->if_proj->ifnode->bool->cmp 782 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 783 784 // Now get the 'sense' of the test correct so we can plug in 785 // either iff2->in(1) or its complement. 786 int flip = 0; 787 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 788 else if( bol->_test._test != BoolTest::eq ) return NULL; 789 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 790 791 const Type *phi1_t = phase->type( phi->in(1) ); 792 const Type *phi2_t = phase->type( phi->in(2) ); 793 // Check for Phi(0,1) and flip 794 if( phi1_t == TypeInt::ZERO ) { 795 if( phi2_t != TypeInt::ONE ) return NULL; 796 flip = 1-flip; 797 } else { 798 // Check for Phi(1,0) 799 if( phi1_t != TypeInt::ONE ) return NULL; 800 if( phi2_t != TypeInt::ZERO ) return NULL; 801 } 802 if( true_path == 2 ) { 803 flip = 1-flip; 804 } 805 806 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 807 assert(new_bol != iff->in(1), "must make progress"); 808 iff->set_req(1, new_bol); 809 // Intervening diamond probably goes dead 810 phase->C->set_major_progress(); 811 return iff; 812 } 813 814 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 815 816 //------------------------------Ideal------------------------------------------ 817 // Return a node which is more "ideal" than the current node. Strip out 818 // control copies 819 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 820 if (remove_dead_region(phase, can_reshape)) return this; 821 // No Def-Use info? 822 if (!can_reshape) return NULL; 823 PhaseIterGVN *igvn = phase->is_IterGVN(); 824 825 // Don't bother trying to transform a dead if 826 if (in(0)->is_top()) return NULL; 827 // Don't bother trying to transform an if with a dead test 828 if (in(1)->is_top()) return NULL; 829 // Another variation of a dead test 830 if (in(1)->is_Con()) return NULL; 831 // Another variation of a dead if 832 if (outcnt() < 2) return NULL; 833 834 // Canonicalize the test. 835 Node* idt_if = idealize_test(phase, this); 836 if (idt_if != NULL) return idt_if; 837 838 // Try to split the IF 839 Node *s = split_if(this, igvn); 840 if (s != NULL) return s; 841 842 // Check for people making a useless boolean: things like 843 // if( (x < y ? true : false) ) { ... } 844 // Replace with if( x < y ) { ... } 845 Node *bol2 = remove_useless_bool(this, phase); 846 if( bol2 ) return bol2; 847 848 // Setup to scan up the CFG looking for a dominating test 849 Node *dom = in(0); 850 Node *prev_dom = this; 851 852 // Check for range-check vs other kinds of tests 853 Node *index1, *range1; 854 jint offset1; 855 int flip1 = is_range_check(range1, index1, offset1); 856 if( flip1 ) { 857 Node *first_prev_dom = NULL; 858 859 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 860 // so all checks we inspect post-dominate the top-most check we find. 861 // If we are going to fail the current check and we reach the top check 862 // then we are guaranteed to fail, so just start interpreting there. 863 // We 'expand' the top 2 range checks to include all post-dominating 864 // checks. 865 866 // The top 2 range checks seen 867 Node *prev_chk1 = NULL; 868 Node *prev_chk2 = NULL; 869 // Low and high offsets seen so far 870 jint off_lo = offset1; 871 jint off_hi = offset1; 872 873 // Scan for the top 2 checks and collect range of offsets 874 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit 875 if( dom->Opcode() == Op_If && // Not same opcode? 876 prev_dom->in(0) == dom ) { // One path of test does dominate? 877 if( dom == this ) return NULL; // dead loop 878 // See if this is a range check 879 Node *index2, *range2; 880 jint offset2; 881 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); 882 // See if this is a _matching_ range check, checking against 883 // the same array bounds. 884 if( flip2 == flip1 && range2 == range1 && index2 == index1 && 885 dom->outcnt() == 2 ) { 886 // Gather expanded bounds 887 off_lo = MIN2(off_lo,offset2); 888 off_hi = MAX2(off_hi,offset2); 889 // Record top 2 range checks 890 prev_chk2 = prev_chk1; 891 prev_chk1 = prev_dom; 892 // If we match the test exactly, then the top test covers 893 // both our lower and upper bounds. 894 if( dom->in(1) == in(1) ) 895 prev_chk2 = prev_chk1; 896 } 897 } 898 prev_dom = dom; 899 dom = up_one_dom( dom ); 900 if( !dom ) break; 901 } 902 903 904 // Attempt to widen the dominating range check to cover some later 905 // ones. Since range checks "fail" by uncommon-trapping to the 906 // interpreter, widening a check can make us speculative enter the 907 // interpreter. If we see range-check deopt's, do not widen! 908 if (!phase->C->allow_range_check_smearing()) return NULL; 909 910 // Constant indices only need to check the upper bound. 911 // Non-constance indices must check both low and high. 912 if( index1 ) { 913 // Didn't find 2 prior covering checks, so cannot remove anything. 914 if( !prev_chk2 ) return NULL; 915 // 'Widen' the offsets of the 1st and 2nd covering check 916 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); 917 // Do not call adjust_check twice on the same projection 918 // as the first call may have transformed the BoolNode to a ConI 919 if( prev_chk1 != prev_chk2 ) { 920 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); 921 } 922 // Test is now covered by prior checks, dominate it out 923 prev_dom = prev_chk2; 924 } else { 925 // Didn't find prior covering check, so cannot remove anything. 926 if( !prev_chk1 ) return NULL; 927 // 'Widen' the offset of the 1st and only covering check 928 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); 929 // Test is now covered by prior checks, dominate it out 930 prev_dom = prev_chk1; 931 } 932 933 934 } else { // Scan for an equivalent test 935 936 Node *cmp; 937 int dist = 0; // Cutoff limit for search 938 int op = Opcode(); 939 if( op == Op_If && 940 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 941 if( cmp->in(2) != NULL && // make sure cmp is not already dead 942 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 943 dist = 64; // Limit for null-pointer scans 944 } else { 945 dist = 4; // Do not bother for random pointer tests 946 } 947 } else { 948 dist = 4; // Limit for random junky scans 949 } 950 951 // Normal equivalent-test check. 952 if( !dom ) return NULL; // Dead loop? 953 954 Node* result = fold_compares(phase); 955 if (result != NULL) { 956 return result; 957 } 958 959 // Search up the dominator tree for an If with an identical test 960 while( dom->Opcode() != op || // Not same opcode? 961 dom->in(1) != in(1) || // Not same input 1? 962 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 963 prev_dom->in(0) != dom ) { // One path of test does not dominate? 964 if( dist < 0 ) return NULL; 965 966 dist--; 967 prev_dom = dom; 968 dom = up_one_dom( dom ); 969 if( !dom ) return NULL; 970 } 971 972 // Check that we did not follow a loop back to ourselves 973 if( this == dom ) 974 return NULL; 975 976 if( dist > 2 ) // Add to count of NULL checks elided 977 explicit_null_checks_elided++; 978 979 } // End of Else scan for an equivalent test 980 981 // Hit! Remove this IF 982 #ifndef PRODUCT 983 if( TraceIterativeGVN ) { 984 tty->print(" Removing IfNode: "); this->dump(); 985 } 986 if( VerifyOpto && !phase->allow_progress() ) { 987 // Found an equivalent dominating test, 988 // we can not guarantee reaching a fix-point for these during iterativeGVN 989 // since intervening nodes may not change. 990 return NULL; 991 } 992 #endif 993 994 // Replace dominated IfNode 995 dominated_by( prev_dom, igvn ); 996 997 // Must return either the original node (now dead) or a new node 998 // (Do not return a top here, since that would break the uniqueness of top.) 999 return new (phase->C, 1) ConINode(TypeInt::ZERO); 1000 } 1001 1002 //------------------------------dominated_by----------------------------------- 1003 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { 1004 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1005 Node *idom = in(0); 1006 // Need opcode to decide which way 'this' test goes 1007 int prev_op = prev_dom->Opcode(); 1008 Node *top = igvn->C->top(); // Shortcut to top 1009 1010 // Now walk the current IfNode's projections. 1011 // Loop ends when 'this' has no more uses. 1012 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1013 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1014 igvn->add_users_to_worklist(ifp); 1015 // Check which projection it is and set target. 1016 // Data-target is either the dominating projection of the same type 1017 // or TOP if the dominating projection is of opposite type. 1018 // Data-target will be used as the new control edge for the non-CFG 1019 // nodes like Casts and Loads. 1020 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top; 1021 // Control-target is just the If's immediate dominator or TOP. 1022 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top; 1023 1024 // For each child of an IfTrue/IfFalse projection, reroute. 1025 // Loop ends when projection has no more uses. 1026 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1027 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1028 igvn->hash_delete(s); // Yank from hash table before edge hacking 1029 if( !s->depends_only_on_test() ) { 1030 // Find the control input matching this def-use edge. 1031 // For Regions it may not be in slot 0. 1032 uint l; 1033 for( l = 0; s->in(l) != ifp; l++ ) { } 1034 s->set_req(l, ctrl_target); 1035 } else { // Else, for control producers, 1036 s->set_req(0, data_target); // Move child to data-target 1037 } 1038 igvn->_worklist.push(s); // Revisit collapsed Phis 1039 } // End for each child of a projection 1040 1041 igvn->remove_dead_node(ifp); 1042 } // End for each IfTrue/IfFalse child of If 1043 1044 // Kill the IfNode 1045 igvn->remove_dead_node(this); 1046 } 1047 1048 //------------------------------Identity--------------------------------------- 1049 // If the test is constant & we match, then we are the input Control 1050 Node *IfTrueNode::Identity( PhaseTransform *phase ) { 1051 // Can only optimize if cannot go the other way 1052 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1053 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) 1054 ? in(0)->in(0) // IfNode control 1055 : this; // no progress 1056 } 1057 1058 //------------------------------dump_spec-------------------------------------- 1059 #ifndef PRODUCT 1060 void IfNode::dump_spec(outputStream *st) const { 1061 st->print("P=%f, C=%f",_prob,_fcnt); 1062 } 1063 #endif 1064 1065 //------------------------------idealize_test---------------------------------- 1066 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1067 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1068 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1069 // needed. 1070 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1071 assert(iff->in(0) != NULL, "If must be live"); 1072 1073 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1074 Node* old_if_f = iff->proj_out(false); 1075 Node* old_if_t = iff->proj_out(true); 1076 1077 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1078 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1079 // happens in count-down loops 1080 if (iff->is_CountedLoopEnd()) return NULL; 1081 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1082 BoolNode *b = iff->in(1)->as_Bool(); 1083 BoolTest bt = b->_test; 1084 // Test already in good order? 1085 if( bt.is_canonical() ) 1086 return NULL; 1087 1088 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1089 // cloning the IfNode. 1090 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) ); 1091 if( !new_b->is_Bool() ) return NULL; 1092 b = new_b->as_Bool(); 1093 1094 PhaseIterGVN *igvn = phase->is_IterGVN(); 1095 assert( igvn, "Test is not canonical in parser?" ); 1096 1097 // The IF node never really changes, but it needs to be cloned 1098 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); 1099 1100 Node *prior = igvn->hash_find_insert(iff); 1101 if( prior ) { 1102 igvn->remove_dead_node(iff); 1103 iff = (IfNode*)prior; 1104 } else { 1105 // Cannot call transform on it just yet 1106 igvn->set_type_bottom(iff); 1107 } 1108 igvn->_worklist.push(iff); 1109 1110 // Now handle projections. Cloning not required. 1111 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff )); 1112 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); 1113 1114 igvn->register_new_node_with_optimizer(new_if_f); 1115 igvn->register_new_node_with_optimizer(new_if_t); 1116 // Flip test, so flip trailing control 1117 igvn->replace_node(old_if_f, new_if_t); 1118 igvn->replace_node(old_if_t, new_if_f); 1119 1120 // Progress 1121 return iff; 1122 } 1123 1124 //------------------------------Identity--------------------------------------- 1125 // If the test is constant & we match, then we are the input Control 1126 Node *IfFalseNode::Identity( PhaseTransform *phase ) { 1127 // Can only optimize if cannot go the other way 1128 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1129 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) 1130 ? in(0)->in(0) // IfNode control 1131 : this; // no progress 1132 }