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 } 550 551 //------------------------------up_one_dom------------------------------------- 552 // Walk up the dominator tree one step. Return NULL at root or true 553 // complex merges. Skips through small diamonds. 554 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { 555 Node *dom = curr->in(0); 556 if( !dom ) // Found a Region degraded to a copy? 557 return curr->nonnull_req(); // Skip thru it 558 559 if( curr != dom ) // Normal walk up one step? 560 return dom; 561 562 // Use linear_only if we are still parsing, since we cannot 563 // trust the regions to be fully filled in. 564 if (linear_only) 565 return NULL; 566 567 if( dom->is_Root() ) 568 return NULL; 569 570 // Else hit a Region. Check for a loop header 571 if( dom->is_Loop() ) 572 return dom->in(1); // Skip up thru loops 573 574 // Check for small diamonds 575 Node *din1, *din2, *din3, *din4; 576 if( dom->req() == 3 && // 2-path merge point 577 (din1 = dom ->in(1)) && // Left path exists 578 (din2 = dom ->in(2)) && // Right path exists 579 (din3 = din1->in(0)) && // Left path up one 580 (din4 = din2->in(0)) ) { // Right path up one 581 if( din3->is_Call() && // Handle a slow-path call on either arm 582 (din3 = din3->in(0)) ) 583 din3 = din3->in(0); 584 if( din4->is_Call() && // Handle a slow-path call on either arm 585 (din4 = din4->in(0)) ) 586 din4 = din4->in(0); 587 if( din3 == din4 && din3->is_If() ) 588 return din3; // Skip around diamonds 589 } 590 591 // Give up the search at true merges 592 return NULL; // Dead loop? Or hit root? 593 } 594 595 596 //------------------------------filtered_int_type-------------------------------- 597 // Return a possibly more restrictive type for val based on condition control flow for an if 598 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { 599 assert(if_proj && 600 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); 601 if (if_proj->in(0) && if_proj->in(0)->is_If()) { 602 IfNode* iff = if_proj->in(0)->as_If(); 603 if (iff->in(1) && iff->in(1)->is_Bool()) { 604 BoolNode* bol = iff->in(1)->as_Bool(); 605 if (bol->in(1) && bol->in(1)->is_Cmp()) { 606 const CmpNode* cmp = bol->in(1)->as_Cmp(); 607 if (cmp->in(1) == val) { 608 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); 609 if (cmp2_t != NULL) { 610 jint lo = cmp2_t->_lo; 611 jint hi = cmp2_t->_hi; 612 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); 613 switch (msk) { 614 case BoolTest::ne: 615 // Can't refine type 616 return NULL; 617 case BoolTest::eq: 618 return cmp2_t; 619 case BoolTest::lt: 620 lo = TypeInt::INT->_lo; 621 if (hi - 1 < hi) { 622 hi = hi - 1; 623 } 624 break; 625 case BoolTest::le: 626 lo = TypeInt::INT->_lo; 627 break; 628 case BoolTest::gt: 629 if (lo + 1 > lo) { 630 lo = lo + 1; 631 } 632 hi = TypeInt::INT->_hi; 633 break; 634 case BoolTest::ge: 635 // lo unchanged 636 hi = TypeInt::INT->_hi; 637 break; 638 } 639 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); 640 return rtn_t; 641 } 642 } 643 } 644 } 645 } 646 return NULL; 647 } 648 649 //------------------------------fold_compares---------------------------- 650 // See if a pair of CmpIs can be converted into a CmpU. In some cases 651 // the direction of this if is determined by the preceding if so it 652 // can be eliminate entirely. Given an if testing (CmpI n c) check 653 // for an immediately control dependent if that is testing (CmpI n c2) 654 // and has one projection leading to this if and the other projection 655 // leading to a region that merges one of this ifs control 656 // projections. 657 // 658 // If 659 // / | 660 // / | 661 // / | 662 // If | 663 // /\ | 664 // / \ | 665 // / \ | 666 // / Region 667 // 668 Node* IfNode::fold_compares(PhaseGVN* phase) { 669 if (!EliminateAutoBox || Opcode() != Op_If) return NULL; 670 671 Node* this_cmp = in(1)->in(1); 672 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && 673 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { 674 Node* ctrl = in(0); 675 BoolNode* this_bool = in(1)->as_Bool(); 676 Node* n = this_cmp->in(1); 677 int hi = this_cmp->in(2)->get_int(); 678 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && 679 ctrl->in(0)->is_If() && 680 ctrl->in(0)->outcnt() == 2 && 681 ctrl->in(0)->in(1)->is_Bool() && 682 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && 683 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && 684 ctrl->in(0)->in(1)->in(1)->in(1) == n) { 685 IfNode* dom_iff = ctrl->in(0)->as_If(); 686 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con); 687 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() && 688 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) { 689 // Identify which proj goes to the region and which continues on 690 RegionNode* region = otherproj->unique_out()->as_Region(); 691 Node* success = NULL; 692 Node* fail = NULL; 693 for (int i = 0; i < 2; i++) { 694 Node* proj = proj_out(i); 695 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { 696 success = proj; 697 } else if (fail == NULL) { 698 fail = proj; 699 } else { 700 success = fail = NULL; 701 } 702 } 703 if (success != NULL && fail != NULL && !region->has_phi()) { 704 int lo = dom_iff->in(1)->in(1)->in(2)->get_int(); 705 BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); 706 Node* dom_cmp = dom_bool->in(1); 707 const TypeInt* failtype = filtered_int_type(phase, n, ctrl); 708 if (failtype != NULL) { 709 const TypeInt* type2 = filtered_int_type(phase, n, fail); 710 if (type2 != NULL) { 711 failtype = failtype->join(type2)->is_int(); 712 } else { 713 failtype = NULL; 714 } 715 } 716 717 if (failtype != NULL && 718 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) { 719 int bound = failtype->_hi - failtype->_lo + 1; 720 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) { 721 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi) 722 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge; 723 Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo))); 724 Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound))); 725 Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond)); 726 phase->hash_delete(dom_iff); 727 dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con)); 728 phase->is_IterGVN()->_worklist.push(dom_iff); 729 phase->hash_delete(this); 730 set_req(1, newbool); 731 return this; 732 } 733 if (failtype->_lo > failtype->_hi) { 734 // previous if determines the result of this if so 735 // replace Bool with constant 736 phase->hash_delete(this); 737 set_req(1, phase->intcon(success->as_Proj()->_con)); 738 return this; 739 } 740 } 741 } 742 } 743 } 744 } 745 return NULL; 746 } 747 748 //------------------------------remove_useless_bool---------------------------- 749 // Check for people making a useless boolean: things like 750 // if( (x < y ? true : false) ) { ... } 751 // Replace with if( x < y ) { ... } 752 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { 753 Node *i1 = iff->in(1); 754 if( !i1->is_Bool() ) return NULL; 755 BoolNode *bol = i1->as_Bool(); 756 757 Node *cmp = bol->in(1); 758 if( cmp->Opcode() != Op_CmpI ) return NULL; 759 760 // Must be comparing against a bool 761 const Type *cmp2_t = phase->type( cmp->in(2) ); 762 if( cmp2_t != TypeInt::ZERO && 763 cmp2_t != TypeInt::ONE ) 764 return NULL; 765 766 // Find a prior merge point merging the boolean 767 i1 = cmp->in(1); 768 if( !i1->is_Phi() ) return NULL; 769 PhiNode *phi = i1->as_Phi(); 770 if( phase->type( phi ) != TypeInt::BOOL ) 771 return NULL; 772 773 // Check for diamond pattern 774 int true_path = phi->is_diamond_phi(); 775 if( true_path == 0 ) return NULL; 776 777 // Make sure that iff and the control of the phi are different. This 778 // should really only happen for dead control flow since it requires 779 // an illegal cycle. 780 if (phi->in(0)->in(1)->in(0) == iff) return NULL; 781 782 // phi->region->if_proj->ifnode->bool->cmp 783 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); 784 785 // Now get the 'sense' of the test correct so we can plug in 786 // either iff2->in(1) or its complement. 787 int flip = 0; 788 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; 789 else if( bol->_test._test != BoolTest::eq ) return NULL; 790 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; 791 792 const Type *phi1_t = phase->type( phi->in(1) ); 793 const Type *phi2_t = phase->type( phi->in(2) ); 794 // Check for Phi(0,1) and flip 795 if( phi1_t == TypeInt::ZERO ) { 796 if( phi2_t != TypeInt::ONE ) return NULL; 797 flip = 1-flip; 798 } else { 799 // Check for Phi(1,0) 800 if( phi1_t != TypeInt::ONE ) return NULL; 801 if( phi2_t != TypeInt::ZERO ) return NULL; 802 } 803 if( true_path == 2 ) { 804 flip = 1-flip; 805 } 806 807 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); 808 assert(new_bol != iff->in(1), "must make progress"); 809 iff->set_req(1, new_bol); 810 // Intervening diamond probably goes dead 811 phase->C->set_major_progress(); 812 return iff; 813 } 814 815 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); 816 817 //------------------------------Ideal------------------------------------------ 818 // Return a node which is more "ideal" than the current node. Strip out 819 // control copies 820 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { 821 if (remove_dead_region(phase, can_reshape)) return this; 822 // No Def-Use info? 823 if (!can_reshape) return NULL; 824 PhaseIterGVN *igvn = phase->is_IterGVN(); 825 826 // Don't bother trying to transform a dead if 827 if (in(0)->is_top()) return NULL; 828 // Don't bother trying to transform an if with a dead test 829 if (in(1)->is_top()) return NULL; 830 // Another variation of a dead test 831 if (in(1)->is_Con()) return NULL; 832 // Another variation of a dead if 833 if (outcnt() < 2) return NULL; 834 835 // Canonicalize the test. 836 Node* idt_if = idealize_test(phase, this); 837 if (idt_if != NULL) return idt_if; 838 839 // Try to split the IF 840 Node *s = split_if(this, igvn); 841 if (s != NULL) return s; 842 843 // Check for people making a useless boolean: things like 844 // if( (x < y ? true : false) ) { ... } 845 // Replace with if( x < y ) { ... } 846 Node *bol2 = remove_useless_bool(this, phase); 847 if( bol2 ) return bol2; 848 849 // Setup to scan up the CFG looking for a dominating test 850 Node *dom = in(0); 851 Node *prev_dom = this; 852 853 // Check for range-check vs other kinds of tests 854 Node *index1, *range1; 855 jint offset1; 856 int flip1 = is_range_check(range1, index1, offset1); 857 if( flip1 ) { 858 Node *first_prev_dom = NULL; 859 860 // Try to remove extra range checks. All 'up_one_dom' gives up at merges 861 // so all checks we inspect post-dominate the top-most check we find. 862 // If we are going to fail the current check and we reach the top check 863 // then we are guaranteed to fail, so just start interpreting there. 864 // We 'expand' the top 2 range checks to include all post-dominating 865 // checks. 866 867 // The top 2 range checks seen 868 Node *prev_chk1 = NULL; 869 Node *prev_chk2 = NULL; 870 // Low and high offsets seen so far 871 jint off_lo = offset1; 872 jint off_hi = offset1; 873 874 // Scan for the top 2 checks and collect range of offsets 875 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit 876 if( dom->Opcode() == Op_If && // Not same opcode? 877 prev_dom->in(0) == dom ) { // One path of test does dominate? 878 if( dom == this ) return NULL; // dead loop 879 // See if this is a range check 880 Node *index2, *range2; 881 jint offset2; 882 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); 883 // See if this is a _matching_ range check, checking against 884 // the same array bounds. 885 if( flip2 == flip1 && range2 == range1 && index2 == index1 && 886 dom->outcnt() == 2 ) { 887 // Gather expanded bounds 888 off_lo = MIN2(off_lo,offset2); 889 off_hi = MAX2(off_hi,offset2); 890 // Record top 2 range checks 891 prev_chk2 = prev_chk1; 892 prev_chk1 = prev_dom; 893 // If we match the test exactly, then the top test covers 894 // both our lower and upper bounds. 895 if( dom->in(1) == in(1) ) 896 prev_chk2 = prev_chk1; 897 } 898 } 899 prev_dom = dom; 900 dom = up_one_dom( dom ); 901 if( !dom ) break; 902 } 903 904 905 // Attempt to widen the dominating range check to cover some later 906 // ones. Since range checks "fail" by uncommon-trapping to the 907 // interpreter, widening a check can make us speculative enter the 908 // interpreter. If we see range-check deopt's, do not widen! 909 if (!phase->C->allow_range_check_smearing()) return NULL; 910 911 // Constant indices only need to check the upper bound. 912 // Non-constance indices must check both low and high. 913 if( index1 ) { 914 // Didn't find 2 prior covering checks, so cannot remove anything. 915 if( !prev_chk2 ) return NULL; 916 // 'Widen' the offsets of the 1st and 2nd covering check 917 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); 918 // Do not call adjust_check twice on the same projection 919 // as the first call may have transformed the BoolNode to a ConI 920 if( prev_chk1 != prev_chk2 ) { 921 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); 922 } 923 // Test is now covered by prior checks, dominate it out 924 prev_dom = prev_chk2; 925 } else { 926 // Didn't find prior covering check, so cannot remove anything. 927 if( !prev_chk1 ) return NULL; 928 // 'Widen' the offset of the 1st and only covering check 929 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); 930 // Test is now covered by prior checks, dominate it out 931 prev_dom = prev_chk1; 932 } 933 934 935 } else { // Scan for an equivalent test 936 937 Node *cmp; 938 int dist = 0; // Cutoff limit for search 939 int op = Opcode(); 940 if( op == Op_If && 941 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { 942 if( cmp->in(2) != NULL && // make sure cmp is not already dead 943 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { 944 dist = 64; // Limit for null-pointer scans 945 } else { 946 dist = 4; // Do not bother for random pointer tests 947 } 948 } else { 949 dist = 4; // Limit for random junky scans 950 } 951 952 // Normal equivalent-test check. 953 if( !dom ) return NULL; // Dead loop? 954 955 Node* result = fold_compares(phase); 956 if (result != NULL) { 957 return result; 958 } 959 960 // Search up the dominator tree for an If with an identical test 961 while( dom->Opcode() != op || // Not same opcode? 962 dom->in(1) != in(1) || // Not same input 1? 963 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? 964 prev_dom->in(0) != dom ) { // One path of test does not dominate? 965 if( dist < 0 ) return NULL; 966 967 dist--; 968 prev_dom = dom; 969 dom = up_one_dom( dom ); 970 if( !dom ) return NULL; 971 } 972 973 // Check that we did not follow a loop back to ourselves 974 if( this == dom ) 975 return NULL; 976 977 if( dist > 2 ) // Add to count of NULL checks elided 978 explicit_null_checks_elided++; 979 980 } // End of Else scan for an equivalent test 981 982 // Hit! Remove this IF 983 #ifndef PRODUCT 984 if( TraceIterativeGVN ) { 985 tty->print(" Removing IfNode: "); this->dump(); 986 } 987 if( VerifyOpto && !phase->allow_progress() ) { 988 // Found an equivalent dominating test, 989 // we can not guarantee reaching a fix-point for these during iterativeGVN 990 // since intervening nodes may not change. 991 return NULL; 992 } 993 #endif 994 995 // Replace dominated IfNode 996 dominated_by( prev_dom, igvn ); 997 998 // Must return either the original node (now dead) or a new node 999 // (Do not return a top here, since that would break the uniqueness of top.) 1000 return new (phase->C, 1) ConINode(TypeInt::ZERO); 1001 } 1002 1003 //------------------------------dominated_by----------------------------------- 1004 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { 1005 igvn->hash_delete(this); // Remove self to prevent spurious V-N 1006 Node *idom = in(0); 1007 // Need opcode to decide which way 'this' test goes 1008 int prev_op = prev_dom->Opcode(); 1009 Node *top = igvn->C->top(); // Shortcut to top 1010 1011 // Now walk the current IfNode's projections. 1012 // Loop ends when 'this' has no more uses. 1013 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { 1014 Node *ifp = last_out(i); // Get IfTrue/IfFalse 1015 igvn->add_users_to_worklist(ifp); 1016 // Check which projection it is and set target. 1017 // Data-target is either the dominating projection of the same type 1018 // or TOP if the dominating projection is of opposite type. 1019 // Data-target will be used as the new control edge for the non-CFG 1020 // nodes like Casts and Loads. 1021 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top; 1022 // Control-target is just the If's immediate dominator or TOP. 1023 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top; 1024 1025 // For each child of an IfTrue/IfFalse projection, reroute. 1026 // Loop ends when projection has no more uses. 1027 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { 1028 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse 1029 igvn->hash_delete(s); // Yank from hash table before edge hacking 1030 if( !s->depends_only_on_test() ) { 1031 // Find the control input matching this def-use edge. 1032 // For Regions it may not be in slot 0. 1033 uint l; 1034 for( l = 0; s->in(l) != ifp; l++ ) { } 1035 s->set_req(l, ctrl_target); 1036 } else { // Else, for control producers, 1037 s->set_req(0, data_target); // Move child to data-target 1038 } 1039 igvn->_worklist.push(s); // Revisit collapsed Phis 1040 } // End for each child of a projection 1041 1042 igvn->remove_dead_node(ifp); 1043 } // End for each IfTrue/IfFalse child of If 1044 1045 // Kill the IfNode 1046 igvn->remove_dead_node(this); 1047 } 1048 1049 //------------------------------Identity--------------------------------------- 1050 // If the test is constant & we match, then we are the input Control 1051 Node *IfTrueNode::Identity( PhaseTransform *phase ) { 1052 // Can only optimize if cannot go the other way 1053 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1054 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) 1055 ? in(0)->in(0) // IfNode control 1056 : this; // no progress 1057 } 1058 1059 //------------------------------dump_spec-------------------------------------- 1060 #ifndef PRODUCT 1061 void IfNode::dump_spec(outputStream *st) const { 1062 st->print("P=%f, C=%f",_prob,_fcnt); 1063 } 1064 #endif 1065 1066 //------------------------------idealize_test---------------------------------- 1067 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and 1068 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms 1069 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as 1070 // needed. 1071 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { 1072 assert(iff->in(0) != NULL, "If must be live"); 1073 1074 if (iff->outcnt() != 2) return NULL; // Malformed projections. 1075 Node* old_if_f = iff->proj_out(false); 1076 Node* old_if_t = iff->proj_out(true); 1077 1078 // CountedLoopEnds want the back-control test to be TRUE, irregardless of 1079 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition 1080 // happens in count-down loops 1081 if (iff->is_CountedLoopEnd()) return NULL; 1082 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests 1083 BoolNode *b = iff->in(1)->as_Bool(); 1084 BoolTest bt = b->_test; 1085 // Test already in good order? 1086 if( bt.is_canonical() ) 1087 return NULL; 1088 1089 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and 1090 // cloning the IfNode. 1091 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) ); 1092 if( !new_b->is_Bool() ) return NULL; 1093 b = new_b->as_Bool(); 1094 1095 PhaseIterGVN *igvn = phase->is_IterGVN(); 1096 assert( igvn, "Test is not canonical in parser?" ); 1097 1098 // The IF node never really changes, but it needs to be cloned 1099 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); 1100 1101 Node *prior = igvn->hash_find_insert(iff); 1102 if( prior ) { 1103 igvn->remove_dead_node(iff); 1104 iff = (IfNode*)prior; 1105 } else { 1106 // Cannot call transform on it just yet 1107 igvn->set_type_bottom(iff); 1108 } 1109 igvn->_worklist.push(iff); 1110 1111 // Now handle projections. Cloning not required. 1112 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff )); 1113 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); 1114 1115 igvn->register_new_node_with_optimizer(new_if_f); 1116 igvn->register_new_node_with_optimizer(new_if_t); 1117 // Flip test, so flip trailing control 1118 igvn->replace_node(old_if_f, new_if_t); 1119 igvn->replace_node(old_if_t, new_if_f); 1120 1121 // Progress 1122 return iff; 1123 } 1124 1125 //------------------------------Identity--------------------------------------- 1126 // If the test is constant & we match, then we are the input Control 1127 Node *IfFalseNode::Identity( PhaseTransform *phase ) { 1128 // Can only optimize if cannot go the other way 1129 const TypeTuple *t = phase->type(in(0))->is_tuple(); 1130 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) 1131 ? in(0)->in(0) // IfNode control 1132 : this; // no progress 1133 }