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 bool counted_loop = r->is_CountedLoop(); 240 241 Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1); 242 Node *phi_c = con1; 243 uint len = r->req(); 244 Node *region_x = new (igvn->C, len - req_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, 4) 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, 2) BoolNode(cmp_c,b->_test._test)); 288 Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test)); 289 // Make the IfNode 290 IfNode *iff_c = new (igvn->C, 2) 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, 2) 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, 1) IfTrueNode (iff_c)); 302 Node *iff_c_f = phase->transform(new (igvn->C, 1) 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, 1) IfTrueNode (iff_x)); 310 Node *iff_x_f = phase->transform(new (igvn->C, 1) 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, 3) 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, 3) 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->hash_delete(v); // Have to fixup other Phi users 342 igvn->_worklist.push(v); 343 uint vop = v->Opcode(); 344 Node *proj = NULL; 345 if( vop == Op_Phi ) { // Remote merge point 346 Node *r = v->in(0); 347 for (uint i3 = 1; i3 < r->req(); i3++) 348 if (r->in(i3) && r->in(i3)->in(0) == iff) { 349 proj = r->in(i3); 350 break; 351 } 352 } else if( v->is_ConstraintCast() ) { 353 proj = v->in(0); // Controlling projection 354 } else { 355 assert( 0, "do not know how to handle this guy" ); 356 } 357 358 Node *proj_path_data, *proj_path_ctrl; 359 if( proj->Opcode() == Op_IfTrue ) { 360 if( phi_s == NULL ) { 361 // Only construct phi_s if needed, otherwise provides 362 // interfering use. 363 phi_s = PhiNode::make_blank(region_s,phi); 364 phi_s->init_req( 1, phi_c ); 365 phi_s->init_req( 2, phi_x ); 366 hook->add_req(phi_s); 367 phi_s = phase->transform(phi_s); 368 } 369 proj_path_data = phi_s; 370 proj_path_ctrl = region_s; 371 } else { 372 if( phi_f == NULL ) { 373 // Only construct phi_f if needed, otherwise provides 374 // interfering use. 375 phi_f = PhiNode::make_blank(region_f,phi); 376 phi_f->init_req( 1, phi_c ); 377 phi_f->init_req( 2, phi_x ); 378 hook->add_req(phi_f); 379 phi_f = phase->transform(phi_f); 380 } 381 proj_path_data = phi_f; 382 proj_path_ctrl = region_f; 383 } 384 385 // Fixup 'v' for for the split 386 if( vop == Op_Phi ) { // Remote merge point 387 uint i; 388 for( i = 1; i < v->req(); i++ ) 389 if( v->in(i) == phi ) 390 break; 391 v->set_req(i, proj_path_data ); 392 } else if( v->is_ConstraintCast() ) { 393 v->set_req(0, proj_path_ctrl ); 394 v->set_req(1, proj_path_data ); 395 } else 396 ShouldNotReachHere(); 397 } 398 399 // Now replace the original iff's True/False with region_s/region_t. 400 // This makes the original iff go dead. 401 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { 402 Node* p = iff->last_out(i3); 403 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); 404 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; 405 // Replace p with u 406 igvn->add_users_to_worklist(p); 407 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { 408 Node* x = p->last_out(l); 409 igvn->hash_delete(x); 410 uint uses_found = 0; 411 for( uint j = 0; j < x->req(); j++ ) { 412 if( x->in(j) == p ) { 413 x->set_req(j, u); 414 uses_found++; 415 } 416 } 417 l -= uses_found; // we deleted 1 or more copies of this edge 418 } 419 igvn->remove_dead_node(p); 420 } 421 422 // Force the original merge dead 423 igvn->hash_delete(r); 424 // First, remove region's dead users. 425 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { 426 Node* u = r->last_out(l); 427 if( u == r ) { 428 r->set_req(0, NULL); 429 } else { 430 assert(u->outcnt() == 0, "only dead users"); 431 igvn->remove_dead_node(u); 432 } 433 l -= 1; 434 } 435 igvn->remove_dead_node(r); 436 437 // Now remove the bogus extra edges used to keep things alive 438 igvn->remove_dead_node( hook ); 439 440 // Must return either the original node (now dead) or a new node 441 // (Do not return a top here, since that would break the uniqueness of top.) 442 return new (igvn->C, 1) ConINode(TypeInt::ZERO); 443 } 444 445 //------------------------------is_range_check--------------------------------- 446 // Return 0 if not a range check. Return 1 if a range check and set index and 447 // offset. Return 2 if we had to negate the test. Index is NULL if the check 448 // is versus a constant. 449 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { 450 Node* b = in(1); 451 if (b == NULL || !b->is_Bool()) return 0; 452 BoolNode* bn = b->as_Bool(); 453 Node* cmp = bn->in(1); 454 if (cmp == NULL) return 0; 455 if (cmp->Opcode() != Op_CmpU) return 0; 456 457 Node* l = cmp->in(1); 458 Node* r = cmp->in(2); 459 int flip_test = 1; 460 if (bn->_test._test == BoolTest::le) { 461 l = cmp->in(2); 462 r = cmp->in(1); 463 flip_test = 2; 464 } else if (bn->_test._test != BoolTest::lt) { 465 return 0; 466 } 467 if (l->is_top()) return 0; // Top input means dead test 468 if (r->Opcode() != Op_LoadRange) return 0; 469 470 // We have recognized one of these forms: 471 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... 472 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... 473 474 // Make sure it's a real range check by requiring an uncommon trap 475 // along the OOB path. Otherwise, it's possible that the user wrote 476 // something which optimized to look like a range check but behaves 477 // in some other way. 478 Node* iftrap = proj_out(flip_test == 2 ? true : false); 479 bool found_trap = false; 480 if (iftrap != NULL) { 481 Node* u = iftrap->unique_ctrl_out(); 482 if (u != NULL) { 483 // It could be a merge point (Region) for uncommon trap. 484 if (u->is_Region()) { 485 Node* c = u->unique_ctrl_out(); 486 if (c != NULL) { 487 iftrap = u; 488 u = c; 489 } 490 } 491 if (u->in(0) == iftrap && u->is_CallStaticJava()) { 492 int req = u->as_CallStaticJava()->uncommon_trap_request(); 493 if (Deoptimization::trap_request_reason(req) == 494 Deoptimization::Reason_range_check) { 495 found_trap = true; 496 } 497 } 498 } 499 } 500 if (!found_trap) return 0; // sorry, no cigar 501 502 // Look for index+offset form 503 Node* ind = l; 504 jint off = 0; 505 if (l->is_top()) { 506 return 0; 507 } else if (l->is_Add()) { 508 if ((off = l->in(1)->find_int_con(0)) != 0) { 509 ind = l->in(2); 510 } else if ((off = l->in(2)->find_int_con(0)) != 0) { 511 ind = l->in(1); 512 } 513 } else if ((off = l->find_int_con(-1)) >= 0) { 514 // constant offset with no variable index 515 ind = NULL; 516 } else { 517 // variable index with no constant offset (or dead negative index) 518 off = 0; 519 } 520 521 // Return all the values: 522 index = ind; 523 offset = off; 524 range = r; 525 return flip_test; 526 } 527 528 //------------------------------adjust_check----------------------------------- 529 // Adjust (widen) a prior range check 530 static void adjust_check(Node* proj, Node* range, Node* index, 531 int flip, jint off_lo, PhaseIterGVN* igvn) { 532 PhaseGVN *gvn = igvn; 533 // Break apart the old check 534 Node *iff = proj->in(0); 535 Node *bol = iff->in(1); 536 if( bol->is_top() ) return; // In case a partially dead range check appears 537 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode 538 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) 539 if( !bol->is_Bool() ) return; 540 541 Node *cmp = bol->in(1); 542 // Compute a new check 543 Node *new_add = gvn->intcon(off_lo); 544 if( index ) { 545 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index; 546 } 547 Node *new_cmp = (flip == 1) 548 ? new (gvn->C, 3) CmpUNode( new_add, range ) 549 : new (gvn->C, 3) CmpUNode( range, new_add ); 550 new_cmp = gvn->transform(new_cmp); 551 // See if no need to adjust the existing check 552 if( new_cmp == cmp ) return; 553 // Else, adjust existing check 554 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 555 igvn->hash_delete( iff ); 556 iff->set_req_X( 1, new_bol, igvn ); 557 igvn->_worklist.push( iff ); 558 } 559 560 //------------------------------up_one_dom------------------------------------- 561 // Walk up the dominator tree one step. Return NULL at root or true 562 // complex merges. Skips through small diamonds. 563 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 564 Node *dom = curr->in(0); 565 if( !dom ) // Found a Region degraded to a copy? 566 return curr->nonnull_req(); // Skip thru it 567 568 if( curr != dom ) // Normal walk up one step? 569 return dom; 570 571 // Use linear_only if we are still parsing, since we cannot 572 // trust the regions to be fully filled in. 573 if (linear_only) 574 return NULL; 575 576 if( dom->is_Root() ) 577 return NULL; 578 579 // Else hit a Region. Check for a loop header 580 if( dom->is_Loop() ) 581 return dom->in(1); // Skip up thru loops 582 583 // Check for small diamonds 584 Node *din1, *din2, *din3, *din4; 585 if( dom->req() == 3 && // 2-path merge point 586 (din1 = dom ->in(1)) && // Left path exists 587 (din2 = dom ->in(2)) && // Right path exists 588 (din3 = din1->in(0)) && // Left path up one 589 (din4 = din2->in(0)) ) { // Right path up one 590 if( din3->is_Call() && // Handle a slow-path call on either arm 591 (din3 = din3->in(0)) ) 592 din3 = din3->in(0); 593 if( din4->is_Call() && // Handle a slow-path call on either arm 594 (din4 = din4->in(0)) ) 595 din4 = din4->in(0); 596 if( din3 == din4 && din3->is_If() ) 597 return din3; // Skip around diamonds 598 } 599 600 // Give up the search at true merges 601 return NULL; // Dead loop? Or hit root? 602 } 603 604 605 //------------------------------filtered_int_type-------------------------------- 606 // Return a possibly more restrictive type for val based on condition control flow for an if 607 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 608 assert(if_proj && 609 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 610 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 611 IfNode* iff = if_proj->in(0)->as_If(); 612 if (iff->in(1) && iff->in(1)->is_Bool()) { 613 BoolNode* bol = iff->in(1)->as_Bool(); 614 if (bol->in(1) && bol->in(1)->is_Cmp()) { 615 const CmpNode* cmp = bol->in(1)->as_Cmp(); 616 if (cmp->in(1) == val) { 617 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 618 if (cmp2_t != NULL) { 619 jint lo = cmp2_t->_lo; 620 jint hi = cmp2_t->_hi; 621 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 622 switch (msk) { 623 case BoolTest::ne: 624 // Can't refine type 625 return NULL; 626 case BoolTest::eq: 627 return cmp2_t; 628 case BoolTest::lt: 629 lo = TypeInt::INT->_lo; 630 if (hi - 1 < hi) { 631 hi = hi - 1; 632 } 633 break; 634 case BoolTest::le: 635 lo = TypeInt::INT->_lo; 636 break; 637 case BoolTest::gt: 638 if (lo + 1 > lo) { 639 lo = lo + 1; 640 } 641 hi = TypeInt::INT->_hi; 642 break; 643 case BoolTest::ge: 644 // lo unchanged 645 hi = TypeInt::INT->_hi; 646 break; 647 } 648 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 649 return rtn_t; 650 } 651 } 652 } 653 } 654 } 655 return NULL; 656 } 657 658 //------------------------------fold_compares---------------------------- 659 // See if a pair of CmpIs can be converted into a CmpU. In some cases 660 // the direction of this if is determined by the preceding if so it 661 // can be eliminate entirely. Given an if testing (CmpI n c) check 662 // for an immediately control dependent if that is testing (CmpI n c2) 663 // and has one projection leading to this if and the other projection 664 // leading to a region that merges one of this ifs control 665 // projections. 666 // 667 // If 668 // / | 669 // / | 670 // / | 671 // If | 672 // /\ | 673 // / \ | 674 // / \ | 675 // / Region 676 // 677 Node* IfNode::fold_compares(PhaseGVN* phase) { 678 if (!EliminateAutoBox || Opcode() != Op_If) return NULL; 679 680 Node* this_cmp = in(1)->in(1); 681 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && 682 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { 683 Node* ctrl = in(0); 684 BoolNode* this_bool = in(1)->as_Bool(); 685 Node* n = this_cmp->in(1); 686 int hi = this_cmp->in(2)->get_int(); 687 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && 688 ctrl->in(0)->is_If() && 689 ctrl->in(0)->outcnt() == 2 && 690 ctrl->in(0)->in(1)->is_Bool() && 691 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && 692 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && 693 ctrl->in(0)->in(1)->in(1)->in(1) == n) { 694 IfNode* dom_iff = ctrl->in(0)->as_If(); 695 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con); 696 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() && 697 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) { 698 // Identify which proj goes to the region and which continues on 699 RegionNode* region = otherproj->unique_out()->as_Region(); 700 Node* success = NULL; 701 Node* fail = NULL; 702 for (int i = 0; i < 2; i++) { 703 Node* proj = proj_out(i); 704 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 705 success = proj; 706 } else if (fail == NULL) { 707 fail = proj; 708 } else { 709 success = fail = NULL; 710 } 711 } 712 if (success != NULL && fail != NULL && !region->has_phi()) { 713 int lo = dom_iff->in(1)->in(1)->in(2)->get_int(); 714 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 715 Node* dom_cmp = dom_bool->in(1); 716 const TypeInt* failtype = filtered_int_type(phase, n, ctrl); 717 if (failtype != NULL) { 718 const TypeInt* type2 = filtered_int_type(phase, n, fail); 719 if (type2 != NULL) { 720 failtype = failtype->join(type2)->is_int(); 721 } else { 722 failtype = NULL; 723 } 724 } 725 726 if (failtype != NULL && 727 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) { 728 int bound = failtype->_hi - failtype->_lo + 1; 729 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) { 730 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi) 731 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge; 732 Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo))); 733 Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound))); 734 Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond)); 735 phase->hash_delete(dom_iff); 736 dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con)); 737 phase->is_IterGVN()->_worklist.push(dom_iff); 738 phase->hash_delete(this); 739 set_req(1, newbool); 740 return this; 741 } 742 if (failtype->_lo > failtype->_hi) { 743 // previous if determines the result of this if so 744 // replace Bool with constant 745 phase->hash_delete(this); 746 set_req(1, phase->intcon(success->as_Proj()->_con)); 747 return this; 748 } 749 } 750 } 751 } 752 } 753 } 754 return NULL; 755 } 756 757 //------------------------------remove_useless_bool---------------------------- 758 // Check for people making a useless boolean: things like 759 // if( (x < y ? true : false) ) { ... } 760 // Replace with if( x < y ) { ... } 761 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 762 Node *i1 = iff->in(1); 763 if( !i1->is_Bool() ) return NULL; 764 BoolNode *bol = i1->as_Bool(); 765 766 Node *cmp = bol->in(1); 767 if( cmp->Opcode() != Op_CmpI ) return NULL; 768 769 // Must be comparing against a bool 770 const Type *cmp2_t = phase->type( cmp->in(2) ); 771 if( cmp2_t != TypeInt::ZERO && 772 cmp2_t != TypeInt::ONE ) 773 return NULL; 774 775 // Find a prior merge point merging the boolean 776 i1 = cmp->in(1); 777 if( !i1->is_Phi() ) return NULL; 778 PhiNode *phi = i1->as_Phi(); 779 if( phase->type( phi ) != TypeInt::BOOL ) 780 return NULL; 781 782 // Check for diamond pattern 783 int true_path = phi->is_diamond_phi(); 784 if( true_path == 0 ) return NULL; 785 786 // Make sure that iff and the control of the phi are different. This 787 // should really only happen for dead control flow since it requires 788 // an illegal cycle. 789 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 790 791 // phi->region->if_proj->ifnode->bool->cmp 792 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 793 794 // Now get the 'sense' of the test correct so we can plug in 795 // either iff2->in(1) or its complement. 796 int flip = 0; 797 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 798 else if( bol->_test._test != BoolTest::eq ) return NULL; 799 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 800 801 const Type *phi1_t = phase->type( phi->in(1) ); 802 const Type *phi2_t = phase->type( phi->in(2) ); 803 // Check for Phi(0,1) and flip 804 if( phi1_t == TypeInt::ZERO ) { 805 if( phi2_t != TypeInt::ONE ) return NULL; 806 flip = 1-flip; 807 } else { 808 // Check for Phi(1,0) 809 if( phi1_t != TypeInt::ONE ) return NULL; 810 if( phi2_t != TypeInt::ZERO ) return NULL; 811 } 812 if( true_path == 2 ) { 813 flip = 1-flip; 814 } 815 816 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 817 assert(new_bol != iff->in(1), "must make progress"); 818 iff->set_req(1, new_bol); 819 // Intervening diamond probably goes dead 820 phase->C->set_major_progress(); 821 return iff; 822 } 823 824 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 825 826 //------------------------------Ideal------------------------------------------ 827 // Return a node which is more "ideal" than the current node. Strip out 828 // control copies 829 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 830 if (remove_dead_region(phase, can_reshape)) return this; 831 // No Def-Use info? 832 if (!can_reshape) return NULL; 833 PhaseIterGVN *igvn = phase->is_IterGVN(); 834 835 // Don't bother trying to transform a dead if 836 if (in(0)->is_top()) return NULL; 837 // Don't bother trying to transform an if with a dead test 838 if (in(1)->is_top()) return NULL; 839 // Another variation of a dead test 840 if (in(1)->is_Con()) return NULL; 841 // Another variation of a dead if 842 if (outcnt() < 2) return NULL; 843 844 // Canonicalize the test. 845 Node* idt_if = idealize_test(phase, this); 846 if (idt_if != NULL) return idt_if; 847 848 // Try to split the IF 849 Node *s = split_if(this, igvn); 850 if (s != NULL) return s; 851 852 // Check for people making a useless boolean: things like 853 // if( (x < y ? true : false) ) { ... } 854 // Replace with if( x < y ) { ... } 855 Node *bol2 = remove_useless_bool(this, phase); 856 if( bol2 ) return bol2; 857 858 // Setup to scan up the CFG looking for a dominating test 859 Node *dom = in(0); 860 Node *prev_dom = this; 861 862 // Check for range-check vs other kinds of tests 863 Node *index1, *range1; 864 jint offset1; 865 int flip1 = is_range_check(range1, index1, offset1); 866 if( flip1 ) { 867 Node *first_prev_dom = NULL; 868 869 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 870 // so all checks we inspect post-dominate the top-most check we find. 871 // If we are going to fail the current check and we reach the top check 872 // then we are guaranteed to fail, so just start interpreting there. 873 // We 'expand' the top 2 range checks to include all post-dominating 874 // checks. 875 876 // The top 2 range checks seen 877 Node *prev_chk1 = NULL; 878 Node *prev_chk2 = NULL; 879 // Low and high offsets seen so far 880 jint off_lo = offset1; 881 jint off_hi = offset1; 882 883 // Scan for the top 2 checks and collect range of offsets 884 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit 885 if( dom->Opcode() == Op_If && // Not same opcode? 886 prev_dom->in(0) == dom ) { // One path of test does dominate? 887 if( dom == this ) return NULL; // dead loop 888 // See if this is a range check 889 Node *index2, *range2; 890 jint offset2; 891 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); 892 // See if this is a _matching_ range check, checking against 893 // the same array bounds. 894 if( flip2 == flip1 && range2 == range1 && index2 == index1 && 895 dom->outcnt() == 2 ) { 896 // Gather expanded bounds 897 off_lo = MIN2(off_lo,offset2); 898 off_hi = MAX2(off_hi,offset2); 899 // Record top 2 range checks 900 prev_chk2 = prev_chk1; 901 prev_chk1 = prev_dom; 902 // If we match the test exactly, then the top test covers 903 // both our lower and upper bounds. 904 if( dom->in(1) == in(1) ) 905 prev_chk2 = prev_chk1; 906 } 907 } 908 prev_dom = dom; 909 dom = up_one_dom( dom ); 910 if( !dom ) break; 911 } 912 913 914 // Attempt to widen the dominating range check to cover some later 915 // ones. Since range checks "fail" by uncommon-trapping to the 916 // interpreter, widening a check can make us speculative enter the 917 // interpreter. If we see range-check deopt's, do not widen! 918 if (!phase->C->allow_range_check_smearing()) return NULL; 919 920 // Constant indices only need to check the upper bound. 921 // Non-constance indices must check both low and high. 922 if( index1 ) { 923 // Didn't find 2 prior covering checks, so cannot remove anything. 924 if( !prev_chk2 ) return NULL; 925 // 'Widen' the offsets of the 1st and 2nd covering check 926 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); 927 // Do not call adjust_check twice on the same projection 928 // as the first call may have transformed the BoolNode to a ConI 929 if( prev_chk1 != prev_chk2 ) { 930 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); 931 } 932 // Test is now covered by prior checks, dominate it out 933 prev_dom = prev_chk2; 934 } else { 935 // Didn't find prior covering check, so cannot remove anything. 936 if( !prev_chk1 ) return NULL; 937 // 'Widen' the offset of the 1st and only covering check 938 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); 939 // Test is now covered by prior checks, dominate it out 940 prev_dom = prev_chk1; 941 } 942 943 944 } else { // Scan for an equivalent test 945 946 Node *cmp; 947 int dist = 0; // Cutoff limit for search 948 int op = Opcode(); 949 if( op == Op_If && 950 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 951 if( cmp->in(2) != NULL && // make sure cmp is not already dead 952 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 953 dist = 64; // Limit for null-pointer scans 954 } else { 955 dist = 4; // Do not bother for random pointer tests 956 } 957 } else { 958 dist = 4; // Limit for random junky scans 959 } 960 961 // Normal equivalent-test check. 962 if( !dom ) return NULL; // Dead loop? 963 964 Node* result = fold_compares(phase); 965 if (result != NULL) { 966 return result; 967 } 968 969 // Search up the dominator tree for an If with an identical test 970 while( dom->Opcode() != op || // Not same opcode? 971 dom->in(1) != in(1) || // Not same input 1? 972 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 973 prev_dom->in(0) != dom ) { // One path of test does not dominate? 974 if( dist < 0 ) return NULL; 975 976 dist--; 977 prev_dom = dom; 978 dom = up_one_dom( dom ); 979 if( !dom ) return NULL; 980 } 981 982 // Check that we did not follow a loop back to ourselves 983 if( this == dom ) 984 return NULL; 985 986 if( dist > 2 ) // Add to count of NULL checks elided 987 explicit_null_checks_elided++; 988 989 } // End of Else scan for an equivalent test 990 991 // Hit! Remove this IF 992 #ifndef PRODUCT 993 if( TraceIterativeGVN ) { 994 tty->print(" Removing IfNode: "); this->dump(); 995 } 996 if( VerifyOpto && !phase->allow_progress() ) { 997 // Found an equivalent dominating test, 998 // we can not guarantee reaching a fix-point for these during iterativeGVN 999 // since intervening nodes may not change. 1000 return NULL; 1001 } 1002 #endif 1003 1004 // Replace dominated IfNode 1005 dominated_by( prev_dom, igvn ); 1006 1007 // Must return either the original node (now dead) or a new node 1008 // (Do not return a top here, since that would break the uniqueness of top.) 1009 return new (phase->C, 1) ConINode(TypeInt::ZERO); 1010 } 1011 1012 //------------------------------dominated_by----------------------------------- 1013 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { 1014 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1015 Node *idom = in(0); 1016 // Need opcode to decide which way 'this' test goes 1017 int prev_op = prev_dom->Opcode(); 1018 Node *top = igvn->C->top(); // Shortcut to top 1019 1020 // Now walk the current IfNode's projections. 1021 // Loop ends when 'this' has no more uses. 1022 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1023 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1024 igvn->add_users_to_worklist(ifp); 1025 // Check which projection it is and set target. 1026 // Data-target is either the dominating projection of the same type 1027 // or TOP if the dominating projection is of opposite type. 1028 // Data-target will be used as the new control edge for the non-CFG 1029 // nodes like Casts and Loads. 1030 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top; 1031 // Control-target is just the If's immediate dominator or TOP. 1032 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top; 1033 1034 // For each child of an IfTrue/IfFalse projection, reroute. 1035 // Loop ends when projection has no more uses. 1036 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1037 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1038 igvn->hash_delete(s); // Yank from hash table before edge hacking 1039 if( !s->depends_only_on_test() ) { 1040 // Find the control input matching this def-use edge. 1041 // For Regions it may not be in slot 0. 1042 uint l; 1043 for( l = 0; s->in(l) != ifp; l++ ) { } 1044 s->set_req(l, ctrl_target); 1045 } else { // Else, for control producers, 1046 s->set_req(0, data_target); // Move child to data-target 1047 } 1048 igvn->_worklist.push(s); // Revisit collapsed Phis 1049 } // End for each child of a projection 1050 1051 igvn->remove_dead_node(ifp); 1052 } // End for each IfTrue/IfFalse child of If 1053 1054 // Kill the IfNode 1055 igvn->remove_dead_node(this); 1056 } 1057 1058 //------------------------------Identity--------------------------------------- 1059 // If the test is constant & we match, then we are the input Control 1060 Node *IfTrueNode::Identity( PhaseTransform *phase ) { 1061 // Can only optimize if cannot go the other way 1062 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1063 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) 1064 ? in(0)->in(0) // IfNode control 1065 : this; // no progress 1066 } 1067 1068 //------------------------------dump_spec-------------------------------------- 1069 #ifndef PRODUCT 1070 void IfNode::dump_spec(outputStream *st) const { 1071 st->print("P=%f, C=%f",_prob,_fcnt); 1072 } 1073 #endif 1074 1075 //------------------------------idealize_test---------------------------------- 1076 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1077 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1078 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1079 // needed. 1080 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1081 assert(iff->in(0) != NULL, "If must be live"); 1082 1083 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1084 Node* old_if_f = iff->proj_out(false); 1085 Node* old_if_t = iff->proj_out(true); 1086 1087 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1088 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1089 // happens in count-down loops 1090 if (iff->is_CountedLoopEnd()) return NULL; 1091 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1092 BoolNode *b = iff->in(1)->as_Bool(); 1093 BoolTest bt = b->_test; 1094 // Test already in good order? 1095 if( bt.is_canonical() ) 1096 return NULL; 1097 1098 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1099 // cloning the IfNode. 1100 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) ); 1101 if( !new_b->is_Bool() ) return NULL; 1102 b = new_b->as_Bool(); 1103 1104 PhaseIterGVN *igvn = phase->is_IterGVN(); 1105 assert( igvn, "Test is not canonical in parser?" ); 1106 1107 // The IF node never really changes, but it needs to be cloned 1108 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); 1109 1110 Node *prior = igvn->hash_find_insert(iff); 1111 if( prior ) { 1112 igvn->remove_dead_node(iff); 1113 iff = (IfNode*)prior; 1114 } else { 1115 // Cannot call transform on it just yet 1116 igvn->set_type_bottom(iff); 1117 } 1118 igvn->_worklist.push(iff); 1119 1120 // Now handle projections. Cloning not required. 1121 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff )); 1122 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); 1123 1124 igvn->register_new_node_with_optimizer(new_if_f); 1125 igvn->register_new_node_with_optimizer(new_if_t); 1126 // Flip test, so flip trailing control 1127 igvn->replace_node(old_if_f, new_if_t); 1128 igvn->replace_node(old_if_t, new_if_f); 1129 1130 // Progress 1131 return iff; 1132 } 1133 1134 //------------------------------Identity--------------------------------------- 1135 // If the test is constant & we match, then we are the input Control 1136 Node *IfFalseNode::Identity( PhaseTransform *phase ) { 1137 // Can only optimize if cannot go the other way 1138 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1139 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) 1140 ? in(0)->in(0) // IfNode control 1141 : this; // no progress 1142 }