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