1 /* 2 * Copyright (c) 2000, 2013, 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_FlagsProj() ) return NULL; 80 if( !cmp->is_Cmp() ) return NULL; 81 i1 = cmp->in(1); 82 if( i1 == NULL || !i1->is_Phi() ) return NULL; 83 PhiNode *phi = i1->as_Phi(); 84 if( phi->is_copy() ) return NULL; 85 Node *con2 = cmp->in(2); 86 if( !con2->is_Con() ) return NULL; 87 // See that the merge point contains some constants 88 Node *con1=NULL; 89 uint i4; 90 for( i4 = 1; i4 < phi->req(); i4++ ) { 91 con1 = phi->in(i4); 92 if( !con1 ) return NULL; // Do not optimize partially collapsed merges 93 if( con1->is_Con() ) break; // Found a constant 94 // Also allow null-vs-not-null checks 95 const TypePtr *tp = igvn->type(con1)->isa_ptr(); 96 if( tp && tp->_ptr == TypePtr::NotNull ) 97 break; 98 } 99 if( i4 >= phi->req() ) return NULL; // Found no constants 100 101 igvn->C->set_has_split_ifs(true); // Has chance for split-if 102 103 // Make sure that the compare can be constant folded away 104 Node *cmp2 = cmp->clone(); 105 cmp2->set_req(1,con1); 106 cmp2->set_req(2,con2); 107 const Type *t = cmp2->Value(igvn); 108 // This compare is dead, so whack it! 109 igvn->remove_dead_node(cmp2); 110 if( !t->singleton() ) return NULL; 111 112 // No intervening control, like a simple Call 113 Node *r = iff->in(0); 114 if( !r->is_Region() ) return NULL; 115 if( phi->region() != r ) return NULL; 116 // No other users of the cmp/bool 117 if (b->outcnt() != 1 || cmp->outcnt() != 1) { 118 //tty->print_cr("many users of cmp/bool"); 119 return NULL; 120 } 121 122 // Make sure we can determine where all the uses of merged values go 123 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { 124 Node* u = r->fast_out(j); 125 if( u == r ) continue; 126 if( u == iff ) continue; 127 if( u->outcnt() == 0 ) continue; // use is dead & ignorable 128 if( !u->is_Phi() ) { 129 /* 130 if( u->is_Start() ) { 131 tty->print_cr("Region has inlined start use"); 132 } else { 133 tty->print_cr("Region has odd use"); 134 u->dump(2); 135 }*/ 136 return NULL; 137 } 138 if( u != phi ) { 139 // CNC - do not allow any other merged value 140 //tty->print_cr("Merging another value"); 141 //u->dump(2); 142 return NULL; 143 } 144 // Make sure we can account for all Phi uses 145 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { 146 Node* v = u->fast_out(k); // User of the phi 147 // CNC - Allow only really simple patterns. 148 // In particular I disallow AddP of the Phi, a fairly common pattern 149 if( v == cmp ) continue; // The compare is OK 150 if( (v->is_ConstraintCast()) && 151 v->in(0)->in(0) == iff ) 152 continue; // CastPP/II of the IfNode is OK 153 // Disabled following code because I cannot tell if exactly one 154 // path dominates without a real dominator check. CNC 9/9/1999 155 //uint vop = v->Opcode(); 156 //if( vop == Op_Phi ) { // Phi from another merge point might be OK 157 // Node *r = v->in(0); // Get controlling point 158 // if( !r ) return NULL; // Degraded to a copy 159 // // Find exactly one path in (either True or False doms, but not IFF) 160 // int cnt = 0; 161 // for( uint i = 1; i < r->req(); i++ ) 162 // if( r->in(i) && r->in(i)->in(0) == iff ) 163 // cnt++; 164 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi 165 //} 166 if( !v->is_Call() ) { 167 /* 168 if( v->Opcode() == Op_AddP ) { 169 tty->print_cr("Phi has AddP use"); 170 } else if( v->Opcode() == Op_CastPP ) { 171 tty->print_cr("Phi has CastPP use"); 172 } else if( v->Opcode() == Op_CastII ) { 173 tty->print_cr("Phi has CastII use"); 174 } else { 175 tty->print_cr("Phi has use I cant be bothered with"); 176 } 177 */ 178 } 179 return NULL; 180 181 /* CNC - Cut out all the fancy acceptance tests 182 // Can we clone this use when doing the transformation? 183 // If all uses are from Phis at this merge or constants, then YES. 184 if( !v->in(0) && v != cmp ) { 185 tty->print_cr("Phi has free-floating use"); 186 v->dump(2); 187 return NULL; 188 } 189 for( uint l = 1; l < v->req(); l++ ) { 190 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && 191 !v->in(l)->is_Con() ) { 192 tty->print_cr("Phi has use"); 193 v->dump(2); 194 return NULL; 195 } // End of if Phi-use input is neither Phi nor Constant 196 } // End of for all inputs to Phi-use 197 */ 198 } // End of for all uses of Phi 199 } // End of for all uses of Region 200 201 // Only do this if the IF node is in a sane state 202 if (iff->outcnt() != 2) 203 return NULL; 204 205 // Got a hit! Do the Mondo Hack! 206 // 207 //ABC a1c def ghi B 1 e h A C a c d f g i 208 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi 209 // cmp - 2 cmp - 2 cmp - 2 210 // bool bool_c bool_x 211 // if if_c if_x 212 // T F T F T F 213 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. 214 // 215 // Split the paths coming into the merge point into 2 separate groups of 216 // merges. On the left will be all the paths feeding constants into the 217 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi 218 // will fold up into a constant; this will let the Cmp fold up as well as 219 // all the control flow. Below the original IF we have 2 control 220 // dependent regions, 's' and 't'. Now we will merge the two paths 221 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite 222 // likely 2 or more) will promptly constant fold away. 223 PhaseGVN *phase = igvn; 224 225 // Make a region merging constants and a region merging the rest 226 uint req_c = 0; 227 Node* predicate_proj = NULL; 228 for (uint ii = 1; ii < r->req(); ii++) { 229 if (phi->in(ii) == con1) { 230 req_c++; 231 } 232 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii)); 233 if (proj != NULL) { 234 assert(predicate_proj == NULL, "only one predicate entry expected"); 235 predicate_proj = proj; 236 } 237 } 238 Node* predicate_c = NULL; 239 Node* predicate_x = NULL; 240 bool counted_loop = r->is_CountedLoop(); 241 242 Node *region_c = new (igvn->C) RegionNode(req_c + 1); 243 Node *phi_c = con1; 244 uint len = r->req(); 245 Node *region_x = new (igvn->C) RegionNode(len - req_c); 246 Node *phi_x = PhiNode::make_blank(region_x, phi); 247 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { 248 if (phi->in(i) == con1) { 249 region_c->init_req( i_c++, r ->in(i) ); 250 if (r->in(i) == predicate_proj) 251 predicate_c = predicate_proj; 252 } else { 253 region_x->init_req( i_x, r ->in(i) ); 254 phi_x ->init_req( i_x++, phi->in(i) ); 255 if (r->in(i) == predicate_proj) 256 predicate_x = predicate_proj; 257 } 258 } 259 if (predicate_c != NULL && (req_c > 1)) { 260 assert(predicate_x == NULL, "only one predicate entry expected"); 261 predicate_c = NULL; // Do not clone predicate below merge point 262 } 263 if (predicate_x != NULL && ((len - req_c) > 2)) { 264 assert(predicate_c == NULL, "only one predicate entry expected"); 265 predicate_x = NULL; // Do not clone predicate below merge point 266 } 267 268 // Register the new RegionNodes but do not transform them. Cannot 269 // transform until the entire Region/Phi conglomerate has been hacked 270 // as a single huge transform. 271 igvn->register_new_node_with_optimizer( region_c ); 272 igvn->register_new_node_with_optimizer( region_x ); 273 // Prevent the untimely death of phi_x. Currently he has no uses. He is 274 // about to get one. If this only use goes away, then phi_x will look dead. 275 // However, he will be picking up some more uses down below. 276 Node *hook = new (igvn->C) Node(4); 277 hook->init_req(0, phi_x); 278 hook->init_req(1, phi_c); 279 phi_x = phase->transform( phi_x ); 280 281 // Make the compare 282 Node *cmp_c = phase->makecon(t); 283 Node *cmp_x = cmp->clone(); 284 cmp_x->set_req(1,phi_x); 285 cmp_x->set_req(2,con2); 286 cmp_x = phase->transform(cmp_x); 287 // Make the bool 288 Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test)); 289 Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test)); 290 // Make the IfNode 291 IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt); 292 igvn->set_type_bottom(iff_c); 293 igvn->_worklist.push(iff_c); 294 hook->init_req(2, iff_c); 295 296 IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt); 297 igvn->set_type_bottom(iff_x); 298 igvn->_worklist.push(iff_x); 299 hook->init_req(3, iff_x); 300 301 // Make the true/false arms 302 Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c)); 303 Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c)); 304 if (predicate_c != NULL) { 305 assert(predicate_x == NULL, "only one predicate entry expected"); 306 // Clone loop predicates to each path 307 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop); 308 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop); 309 } 310 Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x)); 311 Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x)); 312 if (predicate_x != NULL) { 313 assert(predicate_c == NULL, "only one predicate entry expected"); 314 // Clone loop predicates to each path 315 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop); 316 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop); 317 } 318 319 // Merge the TRUE paths 320 Node *region_s = new (igvn->C) RegionNode(3); 321 igvn->_worklist.push(region_s); 322 region_s->init_req(1, iff_c_t); 323 region_s->init_req(2, iff_x_t); 324 igvn->register_new_node_with_optimizer( region_s ); 325 326 // Merge the FALSE paths 327 Node *region_f = new (igvn->C) RegionNode(3); 328 igvn->_worklist.push(region_f); 329 region_f->init_req(1, iff_c_f); 330 region_f->init_req(2, iff_x_f); 331 igvn->register_new_node_with_optimizer( region_f ); 332 333 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. 334 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead 335 cmp->set_req(2,NULL); 336 // Check for all uses of the Phi and give them a new home. 337 // The 'cmp' got cloned, but CastPP/IIs need to be moved. 338 Node *phi_s = NULL; // do not construct unless needed 339 Node *phi_f = NULL; // do not construct unless needed 340 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { 341 Node* v = phi->last_out(i2);// User of the phi 342 igvn->rehash_node_delayed(v); // Have to fixup other Phi users 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) 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) AddINode( index, new_add )) : index; 546 } 547 Node *new_cmp = (flip == 1) 548 ? new (gvn->C) CmpUNode( new_add, range ) 549 : new (gvn->C) 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) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); 555 igvn->rehash_node_delayed( iff ); 556 iff->set_req_X( 1, new_bol, igvn ); 557 } 558 559 //------------------------------up_one_dom------------------------------------- 560 // Walk up the dominator tree one step. Return NULL at root or true 561 // complex merges. Skips through small diamonds. 562 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 563 Node *dom = curr->in(0); 564 if( !dom ) // Found a Region degraded to a copy? 565 return curr->nonnull_req(); // Skip thru it 566 567 if( curr != dom ) // Normal walk up one step? 568 return dom; 569 570 // Use linear_only if we are still parsing, since we cannot 571 // trust the regions to be fully filled in. 572 if (linear_only) 573 return NULL; 574 575 if( dom->is_Root() ) 576 return NULL; 577 578 // Else hit a Region. Check for a loop header 579 if( dom->is_Loop() ) 580 return dom->in(1); // Skip up thru loops 581 582 // Check for small diamonds 583 Node *din1, *din2, *din3, *din4; 584 if( dom->req() == 3 && // 2-path merge point 585 (din1 = dom ->in(1)) && // Left path exists 586 (din2 = dom ->in(2)) && // Right path exists 587 (din3 = din1->in(0)) && // Left path up one 588 (din4 = din2->in(0)) ) { // Right path up one 589 if( din3->is_Call() && // Handle a slow-path call on either arm 590 (din3 = din3->in(0)) ) 591 din3 = din3->in(0); 592 if( din4->is_Call() && // Handle a slow-path call on either arm 593 (din4 = din4->in(0)) ) 594 din4 = din4->in(0); 595 if( din3 == din4 && din3->is_If() ) 596 return din3; // Skip around diamonds 597 } 598 599 // Give up the search at true merges 600 return NULL; // Dead loop? Or hit root? 601 } 602 603 604 //------------------------------filtered_int_type-------------------------------- 605 // Return a possibly more restrictive type for val based on condition control flow for an if 606 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 607 assert(if_proj && 608 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 609 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 610 IfNode* iff = if_proj->in(0)->as_If(); 611 if (iff->in(1) && iff->in(1)->is_Bool()) { 612 BoolNode* bol = iff->in(1)->as_Bool(); 613 if (bol->in(1) && bol->in(1)->is_Cmp()) { 614 const CmpNode* cmp = bol->in(1)->as_Cmp(); 615 if (cmp->in(1) == val) { 616 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 617 if (cmp2_t != NULL) { 618 jint lo = cmp2_t->_lo; 619 jint hi = cmp2_t->_hi; 620 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 621 switch (msk) { 622 case BoolTest::ne: 623 // Can't refine type 624 return NULL; 625 case BoolTest::eq: 626 return cmp2_t; 627 case BoolTest::lt: 628 lo = TypeInt::INT->_lo; 629 if (hi - 1 < hi) { 630 hi = hi - 1; 631 } 632 break; 633 case BoolTest::le: 634 lo = TypeInt::INT->_lo; 635 break; 636 case BoolTest::gt: 637 if (lo + 1 > lo) { 638 lo = lo + 1; 639 } 640 hi = TypeInt::INT->_hi; 641 break; 642 case BoolTest::ge: 643 // lo unchanged 644 hi = TypeInt::INT->_hi; 645 break; 646 } 647 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 648 return rtn_t; 649 } 650 } 651 } 652 } 653 } 654 return NULL; 655 } 656 657 //------------------------------fold_compares---------------------------- 658 // See if a pair of CmpIs can be converted into a CmpU. In some cases 659 // the direction of this if is determined by the preceding if so it 660 // can be eliminate entirely. Given an if testing (CmpI n c) check 661 // for an immediately control dependent if that is testing (CmpI n c2) 662 // and has one projection leading to this if and the other projection 663 // leading to a region that merges one of this ifs control 664 // projections. 665 // 666 // If 667 // / | 668 // / | 669 // / | 670 // If | 671 // /\ | 672 // / \ | 673 // / \ | 674 // / Region 675 // 676 Node* IfNode::fold_compares(PhaseGVN* phase) { 677 if (!phase->C->eliminate_boxing() || Opcode() != Op_If) return NULL; 678 679 Node* this_cmp = in(1)->in(1); 680 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && 681 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { 682 Node* ctrl = in(0); 683 BoolNode* this_bool = in(1)->as_Bool(); 684 Node* n = this_cmp->in(1); 685 int hi = this_cmp->in(2)->get_int(); 686 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && 687 ctrl->in(0)->is_If() && 688 ctrl->in(0)->outcnt() == 2 && 689 ctrl->in(0)->in(1)->is_Bool() && 690 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && 691 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && 692 ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() && 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) SubINode(n, phase->intcon(failtype->_lo))); 733 Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound))); 734 Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond)); 735 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con)); 736 phase->hash_delete(this); 737 set_req(1, newbool); 738 return this; 739 } 740 if (failtype->_lo > failtype->_hi) { 741 // previous if determines the result of this if so 742 // replace Bool with constant 743 phase->hash_delete(this); 744 set_req(1, phase->intcon(success->as_Proj()->_con)); 745 return this; 746 } 747 } 748 } 749 } 750 } 751 } 752 return NULL; 753 } 754 755 //------------------------------remove_useless_bool---------------------------- 756 // Check for people making a useless boolean: things like 757 // if( (x < y ? true : false) ) { ... } 758 // Replace with if( x < y ) { ... } 759 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 760 Node *i1 = iff->in(1); 761 if( !i1->is_Bool() ) return NULL; 762 BoolNode *bol = i1->as_Bool(); 763 764 Node *cmp = bol->in(1); 765 if( cmp->Opcode() != Op_CmpI ) return NULL; 766 767 // Must be comparing against a bool 768 const Type *cmp2_t = phase->type( cmp->in(2) ); 769 if( cmp2_t != TypeInt::ZERO && 770 cmp2_t != TypeInt::ONE ) 771 return NULL; 772 773 // Find a prior merge point merging the boolean 774 i1 = cmp->in(1); 775 if( !i1->is_Phi() ) return NULL; 776 PhiNode *phi = i1->as_Phi(); 777 if( phase->type( phi ) != TypeInt::BOOL ) 778 return NULL; 779 780 // Check for diamond pattern 781 int true_path = phi->is_diamond_phi(); 782 if( true_path == 0 ) return NULL; 783 784 // Make sure that iff and the control of the phi are different. This 785 // should really only happen for dead control flow since it requires 786 // an illegal cycle. 787 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 788 789 // phi->region->if_proj->ifnode->bool->cmp 790 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 791 792 // Now get the 'sense' of the test correct so we can plug in 793 // either iff2->in(1) or its complement. 794 int flip = 0; 795 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 796 else if( bol->_test._test != BoolTest::eq ) return NULL; 797 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 798 799 const Type *phi1_t = phase->type( phi->in(1) ); 800 const Type *phi2_t = phase->type( phi->in(2) ); 801 // Check for Phi(0,1) and flip 802 if( phi1_t == TypeInt::ZERO ) { 803 if( phi2_t != TypeInt::ONE ) return NULL; 804 flip = 1-flip; 805 } else { 806 // Check for Phi(1,0) 807 if( phi1_t != TypeInt::ONE ) return NULL; 808 if( phi2_t != TypeInt::ZERO ) return NULL; 809 } 810 if( true_path == 2 ) { 811 flip = 1-flip; 812 } 813 814 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 815 assert(new_bol != iff->in(1), "must make progress"); 816 iff->set_req(1, new_bol); 817 // Intervening diamond probably goes dead 818 phase->C->set_major_progress(); 819 return iff; 820 } 821 822 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 823 824 //------------------------------Ideal------------------------------------------ 825 // Return a node which is more "ideal" than the current node. Strip out 826 // control copies 827 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 828 if (remove_dead_region(phase, can_reshape)) return this; 829 // No Def-Use info? 830 if (!can_reshape) return NULL; 831 PhaseIterGVN *igvn = phase->is_IterGVN(); 832 833 // Don't bother trying to transform a dead if 834 if (in(0)->is_top()) return NULL; 835 // Don't bother trying to transform an if with a dead test 836 if (in(1)->is_top()) return NULL; 837 // Another variation of a dead test 838 if (in(1)->is_Con()) return NULL; 839 // Another variation of a dead if 840 if (outcnt() < 2) return NULL; 841 842 // Canonicalize the test. 843 Node* idt_if = idealize_test(phase, this); 844 if (idt_if != NULL) return idt_if; 845 846 // Try to split the IF 847 Node *s = split_if(this, igvn); 848 if (s != NULL) return s; 849 850 // Check for people making a useless boolean: things like 851 // if( (x < y ? true : false) ) { ... } 852 // Replace with if( x < y ) { ... } 853 Node *bol2 = remove_useless_bool(this, phase); 854 if( bol2 ) return bol2; 855 856 // Setup to scan up the CFG looking for a dominating test 857 Node *dom = in(0); 858 Node *prev_dom = this; 859 860 // Check for range-check vs other kinds of tests 861 Node *index1, *range1; 862 jint offset1; 863 int flip1 = is_range_check(range1, index1, offset1); 864 if( flip1 ) { 865 Node *first_prev_dom = NULL; 866 867 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 868 // so all checks we inspect post-dominate the top-most check we find. 869 // If we are going to fail the current check and we reach the top check 870 // then we are guaranteed to fail, so just start interpreting there. 871 // We 'expand' the top 2 range checks to include all post-dominating 872 // checks. 873 874 // The top 2 range checks seen 875 Node *prev_chk1 = NULL; 876 Node *prev_chk2 = NULL; 877 // Low and high offsets seen so far 878 jint off_lo = offset1; 879 jint off_hi = offset1; 880 881 // Scan for the top 2 checks and collect range of offsets 882 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit 883 if( dom->Opcode() == Op_If && // Not same opcode? 884 prev_dom->in(0) == dom ) { // One path of test does dominate? 885 if( dom == this ) return NULL; // dead loop 886 // See if this is a range check 887 Node *index2, *range2; 888 jint offset2; 889 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); 890 // See if this is a _matching_ range check, checking against 891 // the same array bounds. 892 if( flip2 == flip1 && range2 == range1 && index2 == index1 && 893 dom->outcnt() == 2 ) { 894 // Gather expanded bounds 895 off_lo = MIN2(off_lo,offset2); 896 off_hi = MAX2(off_hi,offset2); 897 // Record top 2 range checks 898 prev_chk2 = prev_chk1; 899 prev_chk1 = prev_dom; 900 // If we match the test exactly, then the top test covers 901 // both our lower and upper bounds. 902 if( dom->in(1) == in(1) ) 903 prev_chk2 = prev_chk1; 904 } 905 } 906 prev_dom = dom; 907 dom = up_one_dom( dom ); 908 if( !dom ) break; 909 } 910 911 912 // Attempt to widen the dominating range check to cover some later 913 // ones. Since range checks "fail" by uncommon-trapping to the 914 // interpreter, widening a check can make us speculative enter the 915 // interpreter. If we see range-check deopt's, do not widen! 916 if (!phase->C->allow_range_check_smearing()) return NULL; 917 918 // Constant indices only need to check the upper bound. 919 // Non-constance indices must check both low and high. 920 if( index1 ) { 921 // Didn't find 2 prior covering checks, so cannot remove anything. 922 if( !prev_chk2 ) return NULL; 923 // 'Widen' the offsets of the 1st and 2nd covering check 924 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); 925 // Do not call adjust_check twice on the same projection 926 // as the first call may have transformed the BoolNode to a ConI 927 if( prev_chk1 != prev_chk2 ) { 928 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); 929 } 930 // Test is now covered by prior checks, dominate it out 931 prev_dom = prev_chk2; 932 } else { 933 // Didn't find prior covering check, so cannot remove anything. 934 if( !prev_chk1 ) return NULL; 935 // 'Widen' the offset of the 1st and only covering check 936 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); 937 // Test is now covered by prior checks, dominate it out 938 prev_dom = prev_chk1; 939 } 940 941 942 } else { // Scan for an equivalent test 943 944 Node *cmp; 945 int dist = 0; // Cutoff limit for search 946 int op = Opcode(); 947 if( op == Op_If && 948 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 949 if( cmp->in(2) != NULL && // make sure cmp is not already dead 950 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 951 dist = 64; // Limit for null-pointer scans 952 } else { 953 dist = 4; // Do not bother for random pointer tests 954 } 955 } else { 956 dist = 4; // Limit for random junky scans 957 } 958 959 // Normal equivalent-test check. 960 if( !dom ) return NULL; // Dead loop? 961 962 Node* result = fold_compares(phase); 963 if (result != NULL) { 964 return result; 965 } 966 967 // Search up the dominator tree for an If with an identical test 968 while( dom->Opcode() != op || // Not same opcode? 969 dom->in(1) != in(1) || // Not same input 1? 970 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 971 prev_dom->in(0) != dom ) { // One path of test does not dominate? 972 if( dist < 0 ) return NULL; 973 974 dist--; 975 prev_dom = dom; 976 dom = up_one_dom( dom ); 977 if( !dom ) return NULL; 978 } 979 980 // Check that we did not follow a loop back to ourselves 981 if( this == dom ) 982 return NULL; 983 984 if( dist > 2 ) // Add to count of NULL checks elided 985 explicit_null_checks_elided++; 986 987 } // End of Else scan for an equivalent test 988 989 // Hit! Remove this IF 990 #ifndef PRODUCT 991 if( TraceIterativeGVN ) { 992 tty->print(" Removing IfNode: "); this->dump(); 993 } 994 if( VerifyOpto && !phase->allow_progress() ) { 995 // Found an equivalent dominating test, 996 // we can not guarantee reaching a fix-point for these during iterativeGVN 997 // since intervening nodes may not change. 998 return NULL; 999 } 1000 #endif 1001 1002 // Replace dominated IfNode 1003 dominated_by( prev_dom, igvn ); 1004 1005 // Must return either the original node (now dead) or a new node 1006 // (Do not return a top here, since that would break the uniqueness of top.) 1007 return new (phase->C) ConINode(TypeInt::ZERO); 1008 } 1009 1010 //------------------------------dominated_by----------------------------------- 1011 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { 1012 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1013 Node *idom = in(0); 1014 // Need opcode to decide which way 'this' test goes 1015 int prev_op = prev_dom->Opcode(); 1016 Node *top = igvn->C->top(); // Shortcut to top 1017 1018 // Loop predicates may have depending checks which should not 1019 // be skipped. For example, range check predicate has two checks 1020 // for lower and upper bounds. 1021 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj(); 1022 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate)) 1023 prev_dom = idom; 1024 1025 // Now walk the current IfNode's projections. 1026 // Loop ends when 'this' has no more uses. 1027 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1028 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1029 igvn->add_users_to_worklist(ifp); 1030 // Check which projection it is and set target. 1031 // Data-target is either the dominating projection of the same type 1032 // or TOP if the dominating projection is of opposite type. 1033 // Data-target will be used as the new control edge for the non-CFG 1034 // nodes like Casts and Loads. 1035 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top; 1036 // Control-target is just the If's immediate dominator or TOP. 1037 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top; 1038 1039 // For each child of an IfTrue/IfFalse projection, reroute. 1040 // Loop ends when projection has no more uses. 1041 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1042 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1043 if( !s->depends_only_on_test() ) { 1044 // Find the control input matching this def-use edge. 1045 // For Regions it may not be in slot 0. 1046 uint l; 1047 for( l = 0; s->in(l) != ifp; l++ ) { } 1048 igvn->replace_input_of(s, l, ctrl_target); 1049 } else { // Else, for control producers, 1050 igvn->replace_input_of(s, 0, data_target); // Move child to data-target 1051 } 1052 } // End for each child of a projection 1053 1054 igvn->remove_dead_node(ifp); 1055 } // End for each IfTrue/IfFalse child of If 1056 1057 // Kill the IfNode 1058 igvn->remove_dead_node(this); 1059 } 1060 1061 //------------------------------Identity--------------------------------------- 1062 // If the test is constant & we match, then we are the input Control 1063 Node *IfTrueNode::Identity( PhaseTransform *phase ) { 1064 // Can only optimize if cannot go the other way 1065 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1066 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) 1067 ? in(0)->in(0) // IfNode control 1068 : this; // no progress 1069 } 1070 1071 //------------------------------dump_spec-------------------------------------- 1072 #ifndef PRODUCT 1073 void IfNode::dump_spec(outputStream *st) const { 1074 st->print("P=%f, C=%f",_prob,_fcnt); 1075 } 1076 #endif 1077 1078 //------------------------------idealize_test---------------------------------- 1079 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1080 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1081 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1082 // needed. 1083 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1084 assert(iff->in(0) != NULL, "If must be live"); 1085 1086 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1087 Node* old_if_f = iff->proj_out(false); 1088 Node* old_if_t = iff->proj_out(true); 1089 1090 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1091 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1092 // happens in count-down loops 1093 if (iff->is_CountedLoopEnd()) return NULL; 1094 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1095 BoolNode *b = iff->in(1)->as_Bool(); 1096 BoolTest bt = b->_test; 1097 // Test already in good order? 1098 if( bt.is_canonical() ) 1099 return NULL; 1100 1101 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1102 // cloning the IfNode. 1103 Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) ); 1104 if( !new_b->is_Bool() ) return NULL; 1105 b = new_b->as_Bool(); 1106 1107 PhaseIterGVN *igvn = phase->is_IterGVN(); 1108 assert( igvn, "Test is not canonical in parser?" ); 1109 1110 // The IF node never really changes, but it needs to be cloned 1111 iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); 1112 1113 Node *prior = igvn->hash_find_insert(iff); 1114 if( prior ) { 1115 igvn->remove_dead_node(iff); 1116 iff = (IfNode*)prior; 1117 } else { 1118 // Cannot call transform on it just yet 1119 igvn->set_type_bottom(iff); 1120 } 1121 igvn->_worklist.push(iff); 1122 1123 // Now handle projections. Cloning not required. 1124 Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff )); 1125 Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff )); 1126 1127 igvn->register_new_node_with_optimizer(new_if_f); 1128 igvn->register_new_node_with_optimizer(new_if_t); 1129 // Flip test, so flip trailing control 1130 igvn->replace_node(old_if_f, new_if_t); 1131 igvn->replace_node(old_if_t, new_if_f); 1132 1133 // Progress 1134 return iff; 1135 } 1136 1137 //------------------------------Identity--------------------------------------- 1138 // If the test is constant & we match, then we are the input Control 1139 Node *IfFalseNode::Identity( PhaseTransform *phase ) { 1140 // Can only optimize if cannot go the other way 1141 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1142 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) 1143 ? in(0)->in(0) // IfNode control 1144 : this; // no progress 1145 }