1 /* 2 * Copyright (c) 1999, 2023, 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 "c1/c1_Canonicalizer.hpp" 27 #include "c1/c1_Optimizer.hpp" 28 #include "c1/c1_ValueMap.hpp" 29 #include "c1/c1_ValueSet.hpp" 30 #include "c1/c1_ValueStack.hpp" 31 #include "memory/resourceArea.hpp" 32 #include "utilities/bitMap.inline.hpp" 33 #include "compiler/compileLog.hpp" 34 35 typedef GrowableArray<ValueSet*> ValueSetList; 36 37 Optimizer::Optimizer(IR* ir) { 38 assert(ir->is_valid(), "IR must be valid"); 39 _ir = ir; 40 } 41 42 class CE_Eliminator: public BlockClosure { 43 private: 44 IR* _hir; 45 int _cee_count; // the number of CEs successfully eliminated 46 int _ifop_count; // the number of IfOps successfully simplified 47 int _has_substitution; 48 49 public: 50 CE_Eliminator(IR* hir) : _hir(hir), _cee_count(0), _ifop_count(0) { 51 _has_substitution = false; 52 _hir->iterate_preorder(this); 53 if (_has_substitution) { 54 // substituted some ifops/phis, so resolve the substitution 55 SubstitutionResolver sr(_hir); 56 } 57 58 CompileLog* log = _hir->compilation()->log(); 59 if (log != nullptr) 60 log->set_context("optimize name='cee'"); 61 } 62 63 ~CE_Eliminator() { 64 CompileLog* log = _hir->compilation()->log(); 65 if (log != nullptr) 66 log->clear_context(); // skip marker if nothing was printed 67 } 68 69 int cee_count() const { return _cee_count; } 70 int ifop_count() const { return _ifop_count; } 71 72 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) { 73 int e = sux->number_of_exception_handlers(); 74 for (int i = 0; i < e; i++) { 75 BlockBegin* xhandler = sux->exception_handler_at(i); 76 block->add_exception_handler(xhandler); 77 78 assert(xhandler->is_predecessor(sux), "missing predecessor"); 79 if (sux->number_of_preds() == 0) { 80 // sux is disconnected from graph so disconnect from exception handlers 81 xhandler->remove_predecessor(sux); 82 } 83 if (!xhandler->is_predecessor(block)) { 84 xhandler->add_predecessor(block); 85 } 86 } 87 } 88 89 virtual void block_do(BlockBegin* block); 90 91 private: 92 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval, 93 ValueStack* state_before, bool substitutability_check); 94 }; 95 96 void CE_Eliminator::block_do(BlockBegin* block) { 97 // 1) find conditional expression 98 // check if block ends with an If 99 If* if_ = block->end()->as_If(); 100 if (if_ == nullptr) return; 101 102 // check if If works on int or object types 103 // (we cannot handle If's working on long, float or doubles yet, 104 // since IfOp doesn't support them - these If's show up if cmp 105 // operations followed by If's are eliminated) 106 ValueType* if_type = if_->x()->type(); 107 if (!if_type->is_int() && !if_type->is_object()) return; 108 109 BlockBegin* t_block = if_->tsux(); 110 BlockBegin* f_block = if_->fsux(); 111 Instruction* t_cur = t_block->next(); 112 Instruction* f_cur = f_block->next(); 113 114 // one Constant may be present between BlockBegin and BlockEnd 115 Value t_const = nullptr; 116 Value f_const = nullptr; 117 if (t_cur->as_Constant() != nullptr && !t_cur->can_trap()) { 118 t_const = t_cur; 119 t_cur = t_cur->next(); 120 } 121 if (f_cur->as_Constant() != nullptr && !f_cur->can_trap()) { 122 f_const = f_cur; 123 f_cur = f_cur->next(); 124 } 125 126 // check if both branches end with a goto 127 Goto* t_goto = t_cur->as_Goto(); 128 if (t_goto == nullptr) return; 129 Goto* f_goto = f_cur->as_Goto(); 130 if (f_goto == nullptr) return; 131 132 // check if both gotos merge into the same block 133 BlockBegin* sux = t_goto->default_sux(); 134 if (sux != f_goto->default_sux()) return; 135 136 // check if at least one word was pushed on sux_state 137 // inlining depths must match 138 ValueStack* if_state = if_->state(); 139 ValueStack* sux_state = sux->state(); 140 if (if_state->scope()->level() > sux_state->scope()->level()) { 141 while (sux_state->scope() != if_state->scope()) { 142 if_state = if_state->caller_state(); 143 assert(if_state != nullptr, "states do not match up"); 144 } 145 } else if (if_state->scope()->level() < sux_state->scope()->level()) { 146 while (sux_state->scope() != if_state->scope()) { 147 sux_state = sux_state->caller_state(); 148 assert(sux_state != nullptr, "states do not match up"); 149 } 150 } 151 152 if (sux_state->stack_size() <= if_state->stack_size()) return; 153 154 // check if phi function is present at end of successor stack and that 155 // only this phi was pushed on the stack 156 Value sux_phi = sux_state->stack_at(if_state->stack_size()); 157 if (sux_phi == nullptr || sux_phi->as_Phi() == nullptr || sux_phi->as_Phi()->block() != sux) return; 158 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return; 159 160 // get the values that were pushed in the true- and false-branch 161 Value t_value = t_goto->state()->stack_at(if_state->stack_size()); 162 Value f_value = f_goto->state()->stack_at(if_state->stack_size()); 163 164 // backend does not support floats 165 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types"); 166 if (t_value->type()->is_float_kind()) return; 167 168 // check that successor has no other phi functions but sux_phi 169 // this can happen when t_block or f_block contained additional stores to local variables 170 // that are no longer represented by explicit instructions 171 for_each_phi_fun(sux, phi, 172 if (phi != sux_phi) return; 173 ); 174 // true and false blocks can't have phis 175 for_each_phi_fun(t_block, phi, return; ); 176 for_each_phi_fun(f_block, phi, return; ); 177 178 // Only replace safepoint gotos if state_before information is available (if is a safepoint) 179 bool is_safepoint = if_->is_safepoint(); 180 if (!is_safepoint && (t_goto->is_safepoint() || f_goto->is_safepoint())) { 181 return; 182 } 183 184 #ifdef ASSERT 185 #define DO_DELAYED_VERIFICATION 186 /* 187 * We need to verify the internal representation after modifying it. 188 * Verifying only the blocks that have been tampered with is cheaper than verifying the whole graph, but we must 189 * capture blocks_to_verify_later before making the changes, since they might not be reachable afterwards. 190 * DO_DELAYED_VERIFICATION ensures that the code for this is either enabled in full, or not at all. 191 */ 192 #endif // ASSERT 193 194 #ifdef DO_DELAYED_VERIFICATION 195 BlockList blocks_to_verify_later; 196 blocks_to_verify_later.append(block); 197 blocks_to_verify_later.append(t_block); 198 blocks_to_verify_later.append(f_block); 199 blocks_to_verify_later.append(sux); 200 _hir->expand_with_neighborhood(blocks_to_verify_later); 201 #endif // DO_DELAYED_VERIFICATION 202 203 // 2) substitute conditional expression 204 // with an IfOp followed by a Goto 205 // cut if_ away and get node before 206 Instruction* cur_end = if_->prev(); 207 208 // append constants of true- and false-block if necessary 209 // clone constants because original block must not be destroyed 210 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); 211 if (t_value == t_const) { 212 t_value = new Constant(t_const->type()); 213 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); 214 cur_end = cur_end->set_next(t_value); 215 } 216 if (f_value == f_const) { 217 f_value = new Constant(f_const->type()); 218 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); 219 cur_end = cur_end->set_next(f_value); 220 } 221 222 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value, 223 if_->state_before(), if_->substitutability_check()); 224 assert(result != nullptr, "make_ifop must return a non-null instruction"); 225 if (!result->is_linked() && result->can_be_linked()) { 226 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); 227 cur_end = cur_end->set_next(result); 228 } 229 230 // append Goto to successor 231 ValueStack* state_before = if_->state_before(); 232 Goto* goto_ = new Goto(sux, state_before, is_safepoint); 233 234 // prepare state for Goto 235 ValueStack* goto_state = if_state; 236 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); 237 goto_state->push(result->type(), result); 238 assert(goto_state->is_same(sux_state), "states must match now"); 239 goto_->set_state(goto_state); 240 241 cur_end = cur_end->set_next(goto_, goto_state->bci()); 242 243 // Adjust control flow graph 244 BlockBegin::disconnect_edge(block, t_block); 245 BlockBegin::disconnect_edge(block, f_block); 246 if (t_block->number_of_preds() == 0) { 247 BlockBegin::disconnect_edge(t_block, sux); 248 } 249 adjust_exception_edges(block, t_block); 250 if (f_block->number_of_preds() == 0) { 251 BlockBegin::disconnect_edge(f_block, sux); 252 } 253 adjust_exception_edges(block, f_block); 254 255 // update block end 256 block->set_end(goto_); 257 258 // substitute the phi if possible 259 if (sux_phi->as_Phi()->operand_count() == 1) { 260 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); 261 sux_phi->set_subst(result); 262 _has_substitution = true; 263 } 264 265 // 3) successfully eliminated a conditional expression 266 _cee_count++; 267 if (PrintCEE) { 268 tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id()); 269 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); 270 } 271 272 #ifdef DO_DELAYED_VERIFICATION 273 _hir->verify_local(blocks_to_verify_later); 274 #endif // DO_DELAYED_VERIFICATION 275 276 } 277 278 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval, 279 ValueStack* state_before, bool substitutability_check) { 280 if (!OptimizeIfOps) { 281 return new IfOp(x, cond, y, tval, fval, state_before, substitutability_check); 282 } 283 284 tval = tval->subst(); 285 fval = fval->subst(); 286 if (tval == fval) { 287 _ifop_count++; 288 return tval; 289 } 290 291 x = x->subst(); 292 y = y->subst(); 293 294 Constant* y_const = y->as_Constant(); 295 if (y_const != nullptr) { 296 IfOp* x_ifop = x->as_IfOp(); 297 if (x_ifop != nullptr) { // x is an ifop, y is a constant 298 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); 299 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); 300 301 if (x_tval_const != nullptr && x_fval_const != nullptr) { 302 Instruction::Condition x_ifop_cond = x_ifop->cond(); 303 304 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); 305 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); 306 307 // not_comparable here is a valid return in case we're comparing unloaded oop constants 308 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) { 309 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; 310 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; 311 312 _ifop_count++; 313 if (new_tval == new_fval) { 314 return new_tval; 315 } else { 316 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval, state_before, substitutability_check); 317 } 318 } 319 } 320 } else { 321 Constant* x_const = x->as_Constant(); 322 if (x_const != nullptr) { // x and y are constants 323 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); 324 // not_comparable here is a valid return in case we're comparing unloaded oop constants 325 if (x_compare_res != Constant::not_comparable) { 326 _ifop_count++; 327 return x_compare_res == Constant::cond_true ? tval : fval; 328 } 329 } 330 } 331 } 332 return new IfOp(x, cond, y, tval, fval, state_before, substitutability_check); 333 } 334 335 void Optimizer::eliminate_conditional_expressions() { 336 // find conditional expressions & replace them with IfOps 337 CE_Eliminator ce(ir()); 338 } 339 340 // This removes others' relation to block, but doesn't empty block's lists 341 void disconnect_from_graph(BlockBegin* block) { 342 for (int p = 0; p < block->number_of_preds(); p++) { 343 BlockBegin* pred = block->pred_at(p); 344 int idx; 345 while ((idx = pred->end()->find_sux(block)) >= 0) { 346 pred->end()->remove_sux_at(idx); 347 } 348 } 349 for (int s = 0; s < block->number_of_sux(); s++) { 350 block->sux_at(s)->remove_predecessor(block); 351 } 352 } 353 354 class BlockMerger: public BlockClosure { 355 private: 356 IR* _hir; 357 int _merge_count; // the number of block pairs successfully merged 358 359 public: 360 BlockMerger(IR* hir) 361 : _hir(hir) 362 , _merge_count(0) 363 { 364 _hir->iterate_preorder(this); 365 CompileLog* log = _hir->compilation()->log(); 366 if (log != nullptr) 367 log->set_context("optimize name='eliminate_blocks'"); 368 } 369 370 ~BlockMerger() { 371 CompileLog* log = _hir->compilation()->log(); 372 if (log != nullptr) 373 log->clear_context(); // skip marker if nothing was printed 374 } 375 376 bool try_merge(BlockBegin* block) { 377 BlockEnd* end = block->end(); 378 if (end->as_Goto() == nullptr) return false; 379 380 assert(end->number_of_sux() == 1, "end must have exactly one successor"); 381 // Note: It would be sufficient to check for the number of successors (= 1) 382 // in order to decide if this block can be merged potentially. That 383 // would then also include switch statements w/ only a default case. 384 // However, in that case we would need to make sure the switch tag 385 // expression is executed if it can produce observable side effects. 386 // We should probably have the canonicalizer simplifying such switch 387 // statements and then we are sure we don't miss these merge opportunities 388 // here (was bug - gri 7/7/99). 389 BlockBegin* sux = end->default_sux(); 390 if (sux->number_of_preds() != 1 || sux->is_entry_block() || end->is_safepoint()) return false; 391 // merge the two blocks 392 393 #ifdef ASSERT 394 // verify that state at the end of block and at the beginning of sux are equal 395 // no phi functions must be present at beginning of sux 396 ValueStack* sux_state = sux->state(); 397 ValueStack* end_state = end->state(); 398 399 assert(end_state->scope() == sux_state->scope(), "scopes must match"); 400 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); 401 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); 402 403 int index; 404 Value sux_value; 405 for_each_stack_value(sux_state, index, sux_value) { 406 assert(sux_value == end_state->stack_at(index), "stack not equal"); 407 } 408 for_each_local_value(sux_state, index, sux_value) { 409 Phi* sux_phi = sux_value->as_Phi(); 410 if (sux_phi != nullptr && sux_phi->is_illegal()) continue; 411 assert(sux_value == end_state->local_at(index), "locals not equal"); 412 } 413 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); 414 #endif 415 416 #ifdef DO_DELAYED_VERIFICATION 417 BlockList blocks_to_verify_later; 418 blocks_to_verify_later.append(block); 419 _hir->expand_with_neighborhood(blocks_to_verify_later); 420 #endif // DO_DELAYED_VERIFICATION 421 422 // find instruction before end & append first instruction of sux block 423 Instruction* prev = end->prev(); 424 Instruction* next = sux->next(); 425 assert(prev->as_BlockEnd() == nullptr, "must not be a BlockEnd"); 426 prev->set_next(next); 427 prev->fixup_block_pointers(); 428 429 // disconnect this block from all other blocks 430 disconnect_from_graph(sux); 431 #ifdef DO_DELAYED_VERIFICATION 432 blocks_to_verify_later.remove(sux); // Sux is not part of graph anymore 433 #endif // DO_DELAYED_VERIFICATION 434 block->set_end(sux->end()); 435 436 // TODO Should this be done in set_end universally? 437 // add exception handlers of deleted block, if any 438 for (int k = 0; k < sux->number_of_exception_handlers(); k++) { 439 BlockBegin* xhandler = sux->exception_handler_at(k); 440 block->add_exception_handler(xhandler); 441 442 // TODO This should be in disconnect from graph... 443 // also substitute predecessor of exception handler 444 assert(xhandler->is_predecessor(sux), "missing predecessor"); 445 xhandler->remove_predecessor(sux); 446 if (!xhandler->is_predecessor(block)) { 447 xhandler->add_predecessor(block); 448 } 449 } 450 451 // debugging output 452 _merge_count++; 453 if (PrintBlockElimination) { 454 tty->print_cr("%d. merged B%d & B%d (stack size = %d)", 455 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); 456 } 457 458 #ifdef DO_DELAYED_VERIFICATION 459 _hir->verify_local(blocks_to_verify_later); 460 #endif // DO_DELAYED_VERIFICATION 461 462 If* if_ = block->end()->as_If(); 463 if (if_) { 464 IfOp* ifop = if_->x()->as_IfOp(); 465 Constant* con = if_->y()->as_Constant(); 466 bool swapped = false; 467 if (!con || !ifop) { 468 ifop = if_->y()->as_IfOp(); 469 con = if_->x()->as_Constant(); 470 swapped = true; 471 } 472 if (con && ifop && !ifop->substitutability_check()) { 473 Constant* tval = ifop->tval()->as_Constant(); 474 Constant* fval = ifop->fval()->as_Constant(); 475 if (tval && fval) { 476 // Find the instruction before if_, starting with ifop. 477 // When if_ and ifop are not in the same block, prev 478 // becomes null In such (rare) cases it is not 479 // profitable to perform the optimization. 480 Value prev = ifop; 481 while (prev != nullptr && prev->next() != if_) { 482 prev = prev->next(); 483 } 484 485 if (prev != nullptr) { 486 Instruction::Condition cond = if_->cond(); 487 BlockBegin* tsux = if_->tsux(); 488 BlockBegin* fsux = if_->fsux(); 489 if (swapped) { 490 cond = Instruction::mirror(cond); 491 } 492 493 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); 494 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); 495 if (tblock != fblock && !if_->is_safepoint()) { 496 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), 497 tblock, fblock, if_->state_before(), if_->is_safepoint(), ifop->substitutability_check()); 498 newif->set_state(if_->state()->copy()); 499 500 assert(prev->next() == if_, "must be guaranteed by above search"); 501 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); 502 prev->set_next(newif); 503 block->set_end(newif); 504 505 _merge_count++; 506 if (PrintBlockElimination) { 507 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); 508 } 509 510 #ifdef DO_DELAYED_VERIFICATION 511 _hir->verify_local(blocks_to_verify_later); 512 #endif // DO_DELAYED_VERIFICATION 513 } 514 } 515 } 516 } 517 } 518 519 return true; 520 } 521 522 virtual void block_do(BlockBegin* block) { 523 // repeat since the same block may merge again 524 while (try_merge(block)) ; 525 } 526 }; 527 528 #ifdef ASSERT 529 #undef DO_DELAYED_VERIFICATION 530 #endif // ASSERT 531 532 void Optimizer::eliminate_blocks() { 533 // merge blocks if possible 534 BlockMerger bm(ir()); 535 } 536 537 538 class NullCheckEliminator; 539 class NullCheckVisitor: public InstructionVisitor { 540 private: 541 NullCheckEliminator* _nce; 542 NullCheckEliminator* nce() { return _nce; } 543 544 public: 545 NullCheckVisitor() {} 546 547 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } 548 549 void do_Phi (Phi* x); 550 void do_Local (Local* x); 551 void do_Constant (Constant* x); 552 void do_LoadField (LoadField* x); 553 void do_StoreField (StoreField* x); 554 void do_ArrayLength (ArrayLength* x); 555 void do_LoadIndexed (LoadIndexed* x); 556 void do_StoreIndexed (StoreIndexed* x); 557 void do_NegateOp (NegateOp* x); 558 void do_ArithmeticOp (ArithmeticOp* x); 559 void do_ShiftOp (ShiftOp* x); 560 void do_LogicOp (LogicOp* x); 561 void do_CompareOp (CompareOp* x); 562 void do_IfOp (IfOp* x); 563 void do_Convert (Convert* x); 564 void do_NullCheck (NullCheck* x); 565 void do_TypeCast (TypeCast* x); 566 void do_Invoke (Invoke* x); 567 void do_NewInstance (NewInstance* x); 568 void do_NewInlineTypeInstance(NewInlineTypeInstance* x); 569 void do_NewTypeArray (NewTypeArray* x); 570 void do_NewObjectArray (NewObjectArray* x); 571 void do_NewMultiArray (NewMultiArray* x); 572 void do_Deoptimize (Deoptimize* x); 573 void do_CheckCast (CheckCast* x); 574 void do_InstanceOf (InstanceOf* x); 575 void do_MonitorEnter (MonitorEnter* x); 576 void do_MonitorExit (MonitorExit* x); 577 void do_Intrinsic (Intrinsic* x); 578 void do_BlockBegin (BlockBegin* x); 579 void do_Goto (Goto* x); 580 void do_If (If* x); 581 void do_TableSwitch (TableSwitch* x); 582 void do_LookupSwitch (LookupSwitch* x); 583 void do_Return (Return* x); 584 void do_Throw (Throw* x); 585 void do_Base (Base* x); 586 void do_OsrEntry (OsrEntry* x); 587 void do_ExceptionObject(ExceptionObject* x); 588 void do_RoundFP (RoundFP* x); 589 void do_UnsafeGet (UnsafeGet* x); 590 void do_UnsafePut (UnsafePut* x); 591 void do_UnsafeGetAndSet(UnsafeGetAndSet* x); 592 void do_ProfileCall (ProfileCall* x); 593 void do_ProfileReturnType (ProfileReturnType* x); 594 void do_ProfileACmpTypes(ProfileACmpTypes* x); 595 void do_ProfileInvoke (ProfileInvoke* x); 596 void do_RuntimeCall (RuntimeCall* x); 597 void do_MemBar (MemBar* x); 598 void do_RangeCheckPredicate(RangeCheckPredicate* x); 599 #ifdef ASSERT 600 void do_Assert (Assert* x); 601 #endif 602 }; 603 604 605 // Because of a static contained within (for the purpose of iteration 606 // over instructions), it is only valid to have one of these active at 607 // a time 608 class NullCheckEliminator: public ValueVisitor { 609 private: 610 Optimizer* _opt; 611 612 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block 613 BlockList* _work_list; // Basic blocks to visit 614 615 bool visitable(Value x) { 616 assert(_visitable_instructions != nullptr, "check"); 617 return _visitable_instructions->contains(x); 618 } 619 void mark_visited(Value x) { 620 assert(_visitable_instructions != nullptr, "check"); 621 _visitable_instructions->remove(x); 622 } 623 void mark_visitable(Value x) { 624 assert(_visitable_instructions != nullptr, "check"); 625 _visitable_instructions->put(x); 626 } 627 void clear_visitable_state() { 628 assert(_visitable_instructions != nullptr, "check"); 629 _visitable_instructions->clear(); 630 } 631 632 ValueSet* _set; // current state, propagated to subsequent BlockBegins 633 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks 634 NullCheckVisitor _visitor; 635 NullCheck* _last_explicit_null_check; 636 637 bool set_contains(Value x) { assert(_set != nullptr, "check"); return _set->contains(x); } 638 void set_put (Value x) { assert(_set != nullptr, "check"); _set->put(x); } 639 void set_remove (Value x) { assert(_set != nullptr, "check"); _set->remove(x); } 640 641 BlockList* work_list() { return _work_list; } 642 643 void iterate_all(); 644 void iterate_one(BlockBegin* block); 645 646 ValueSet* state() { return _set; } 647 void set_state_from (ValueSet* state) { _set->set_from(state); } 648 ValueSet* state_for (BlockBegin* block) { return _block_states.at(block->block_id()); } 649 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(block->block_id(), stack); } 650 // Returns true if caused a change in the block's state. 651 bool merge_state_for(BlockBegin* block, 652 ValueSet* incoming_state); 653 654 public: 655 // constructor 656 NullCheckEliminator(Optimizer* opt) 657 : _opt(opt) 658 , _work_list(new BlockList()) 659 , _set(new ValueSet()) 660 , _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), nullptr) 661 , _last_explicit_null_check(nullptr) { 662 _visitable_instructions = new ValueSet(); 663 _visitor.set_eliminator(this); 664 CompileLog* log = _opt->ir()->compilation()->log(); 665 if (log != nullptr) 666 log->set_context("optimize name='null_check_elimination'"); 667 } 668 669 ~NullCheckEliminator() { 670 CompileLog* log = _opt->ir()->compilation()->log(); 671 if (log != nullptr) 672 log->clear_context(); // skip marker if nothing was printed 673 } 674 675 Optimizer* opt() { return _opt; } 676 IR* ir () { return opt()->ir(); } 677 678 // Process a graph 679 void iterate(BlockBegin* root); 680 681 void visit(Value* f); 682 683 // In some situations (like NullCheck(x); getfield(x)) the debug 684 // information from the explicit NullCheck can be used to populate 685 // the getfield, even if the two instructions are in different 686 // scopes; this allows implicit null checks to be used but the 687 // correct exception information to be generated. We must clear the 688 // last-traversed NullCheck when we reach a potentially-exception- 689 // throwing instruction, as well as in some other cases. 690 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } 691 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } 692 Value last_explicit_null_check_obj() { return (_last_explicit_null_check 693 ? _last_explicit_null_check->obj() 694 : nullptr); } 695 NullCheck* consume_last_explicit_null_check() { 696 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); 697 _last_explicit_null_check->set_can_trap(false); 698 return _last_explicit_null_check; 699 } 700 void clear_last_explicit_null_check() { _last_explicit_null_check = nullptr; } 701 702 // Handlers for relevant instructions 703 // (separated out from NullCheckVisitor for clarity) 704 705 // The basic contract is that these must leave the instruction in 706 // the desired state; must not assume anything about the state of 707 // the instruction. We make multiple passes over some basic blocks 708 // and the last pass is the only one whose result is valid. 709 void handle_AccessField (AccessField* x); 710 void handle_ArrayLength (ArrayLength* x); 711 void handle_LoadIndexed (LoadIndexed* x); 712 void handle_StoreIndexed (StoreIndexed* x); 713 void handle_NullCheck (NullCheck* x); 714 void handle_Invoke (Invoke* x); 715 void handle_NewInstance (NewInstance* x); 716 void handle_NewInlineTypeInstance(NewInlineTypeInstance* x); 717 void handle_NewArray (NewArray* x); 718 void handle_AccessMonitor (AccessMonitor* x); 719 void handle_Intrinsic (Intrinsic* x); 720 void handle_ExceptionObject (ExceptionObject* x); 721 void handle_Phi (Phi* x); 722 void handle_ProfileCall (ProfileCall* x); 723 void handle_ProfileReturnType (ProfileReturnType* x); 724 void handle_ProfileACmpTypes(ProfileACmpTypes* x); 725 }; 726 727 728 // NEEDS_CLEANUP 729 // There may be other instructions which need to clear the last 730 // explicit null check. Anything across which we can not hoist the 731 // debug information for a NullCheck instruction must clear it. It 732 // might be safer to pattern match "NullCheck ; {AccessField, 733 // ArrayLength, LoadIndexed}" but it is more easily structured this way. 734 // Should test to see performance hit of clearing it for all handlers 735 // with empty bodies below. If it is negligible then we should leave 736 // that in for safety, otherwise should think more about it. 737 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } 738 void NullCheckVisitor::do_Local (Local* x) {} 739 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } 740 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } 741 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } 742 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } 743 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } 744 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } 745 void NullCheckVisitor::do_NegateOp (NegateOp* x) {} 746 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } 747 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} 748 void NullCheckVisitor::do_LogicOp (LogicOp* x) {} 749 void NullCheckVisitor::do_CompareOp (CompareOp* x) {} 750 void NullCheckVisitor::do_IfOp (IfOp* x) {} 751 void NullCheckVisitor::do_Convert (Convert* x) {} 752 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } 753 void NullCheckVisitor::do_TypeCast (TypeCast* x) {} 754 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } 755 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } 756 void NullCheckVisitor::do_NewInlineTypeInstance(NewInlineTypeInstance* x) { nce()->handle_NewInlineTypeInstance(x); } 757 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } 758 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } 759 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } 760 void NullCheckVisitor::do_Deoptimize (Deoptimize* x) {} 761 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); } 762 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} 763 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } 764 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } 765 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); } 766 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} 767 void NullCheckVisitor::do_Goto (Goto* x) {} 768 void NullCheckVisitor::do_If (If* x) {} 769 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} 770 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} 771 void NullCheckVisitor::do_Return (Return* x) {} 772 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } 773 void NullCheckVisitor::do_Base (Base* x) {} 774 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} 775 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } 776 void NullCheckVisitor::do_RoundFP (RoundFP* x) {} 777 void NullCheckVisitor::do_UnsafeGet (UnsafeGet* x) {} 778 void NullCheckVisitor::do_UnsafePut (UnsafePut* x) {} 779 void NullCheckVisitor::do_UnsafeGetAndSet(UnsafeGetAndSet* x) {} 780 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); 781 nce()->handle_ProfileCall(x); } 782 void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); } 783 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} 784 void NullCheckVisitor::do_ProfileACmpTypes(ProfileACmpTypes* x) { nce()->handle_ProfileACmpTypes(x); } 785 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {} 786 void NullCheckVisitor::do_MemBar (MemBar* x) {} 787 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {} 788 #ifdef ASSERT 789 void NullCheckVisitor::do_Assert (Assert* x) {} 790 #endif 791 792 void NullCheckEliminator::visit(Value* p) { 793 assert(*p != nullptr, "should not find null instructions"); 794 if (visitable(*p)) { 795 mark_visited(*p); 796 (*p)->visit(&_visitor); 797 } 798 } 799 800 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { 801 ValueSet* state = state_for(block); 802 if (state == nullptr) { 803 state = incoming_state->copy(); 804 set_state_for(block, state); 805 return true; 806 } else { 807 bool changed = state->set_intersect(incoming_state); 808 if (PrintNullCheckElimination && changed) { 809 tty->print_cr("Block %d's null check state changed", block->block_id()); 810 } 811 return changed; 812 } 813 } 814 815 816 void NullCheckEliminator::iterate_all() { 817 while (work_list()->length() > 0) { 818 iterate_one(work_list()->pop()); 819 } 820 } 821 822 823 void NullCheckEliminator::iterate_one(BlockBegin* block) { 824 clear_visitable_state(); 825 // clear out an old explicit null checks 826 set_last_explicit_null_check(nullptr); 827 828 if (PrintNullCheckElimination) { 829 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", 830 block->block_id(), 831 ir()->method()->holder()->name()->as_utf8(), 832 ir()->method()->name()->as_utf8(), 833 ir()->method()->signature()->as_symbol()->as_utf8()); 834 } 835 836 // Create new state if none present (only happens at root) 837 if (state_for(block) == nullptr) { 838 ValueSet* tmp_state = new ValueSet(); 839 set_state_for(block, tmp_state); 840 // Initial state is that local 0 (receiver) is non-null for 841 // non-static methods 842 ValueStack* stack = block->state(); 843 IRScope* scope = stack->scope(); 844 ciMethod* method = scope->method(); 845 if (!method->is_static()) { 846 Local* local0 = stack->local_at(0)->as_Local(); 847 assert(local0 != nullptr, "must be"); 848 assert(local0->type() == objectType, "invalid type of receiver"); 849 850 if (local0 != nullptr) { 851 // Local 0 is used in this scope 852 tmp_state->put(local0); 853 if (PrintNullCheckElimination) { 854 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); 855 } 856 } 857 } 858 } 859 860 // Must copy block's state to avoid mutating it during iteration 861 // through the block -- otherwise "not-null" states can accidentally 862 // propagate "up" through the block during processing of backward 863 // branches and algorithm is incorrect (and does not converge) 864 set_state_from(state_for(block)); 865 866 // allow visiting of Phis belonging to this block 867 for_each_phi_fun(block, phi, 868 mark_visitable(phi); 869 ); 870 871 BlockEnd* e = block->end(); 872 assert(e != nullptr, "incomplete graph"); 873 int i; 874 875 // Propagate the state before this block into the exception 876 // handlers. They aren't true successors since we aren't guaranteed 877 // to execute the whole block before executing them. Also putting 878 // them on first seems to help reduce the amount of iteration to 879 // reach a fixed point. 880 for (i = 0; i < block->number_of_exception_handlers(); i++) { 881 BlockBegin* next = block->exception_handler_at(i); 882 if (merge_state_for(next, state())) { 883 if (!work_list()->contains(next)) { 884 work_list()->push(next); 885 } 886 } 887 } 888 889 // Iterate through block, updating state. 890 for (Instruction* instr = block; instr != nullptr; instr = instr->next()) { 891 // Mark instructions in this block as visitable as they are seen 892 // in the instruction list. This keeps the iteration from 893 // visiting instructions which are references in other blocks or 894 // visiting instructions more than once. 895 mark_visitable(instr); 896 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != nullptr)) { 897 mark_visited(instr); 898 instr->input_values_do(this); 899 instr->visit(&_visitor); 900 } 901 } 902 903 // Propagate state to successors if necessary 904 for (i = 0; i < e->number_of_sux(); i++) { 905 BlockBegin* next = e->sux_at(i); 906 if (merge_state_for(next, state())) { 907 if (!work_list()->contains(next)) { 908 work_list()->push(next); 909 } 910 } 911 } 912 } 913 914 915 void NullCheckEliminator::iterate(BlockBegin* block) { 916 work_list()->push(block); 917 iterate_all(); 918 } 919 920 void NullCheckEliminator::handle_AccessField(AccessField* x) { 921 if (x->is_static()) { 922 if (x->as_LoadField() != nullptr) { 923 // If the field is a non-null static final object field (as is 924 // often the case for sun.misc.Unsafe), put this LoadField into 925 // the non-null map 926 ciField* field = x->field(); 927 if (field->is_constant()) { 928 ciConstant field_val = field->constant_value(); 929 BasicType field_type = field_val.basic_type(); 930 if (is_reference_type(field_type)) { 931 ciObject* obj_val = field_val.as_object(); 932 if (!obj_val->is_null_object()) { 933 if (PrintNullCheckElimination) { 934 tty->print_cr("AccessField %d proven non-null by static final non-null oop check", 935 x->id()); 936 } 937 set_put(x); 938 } 939 } 940 } 941 } 942 // Be conservative 943 clear_last_explicit_null_check(); 944 return; 945 } 946 947 Value obj = x->obj(); 948 if (set_contains(obj)) { 949 // Value is non-null => update AccessField 950 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { 951 x->set_explicit_null_check(consume_last_explicit_null_check()); 952 x->set_needs_null_check(true); 953 if (PrintNullCheckElimination) { 954 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", 955 x->explicit_null_check()->id(), x->id(), obj->id()); 956 } 957 } else { 958 x->set_explicit_null_check(nullptr); 959 x->set_needs_null_check(false); 960 if (PrintNullCheckElimination) { 961 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); 962 } 963 } 964 } else { 965 set_put(obj); 966 if (PrintNullCheckElimination) { 967 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); 968 } 969 // Ensure previous passes do not cause wrong state 970 x->set_needs_null_check(true); 971 x->set_explicit_null_check(nullptr); 972 } 973 clear_last_explicit_null_check(); 974 } 975 976 977 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { 978 Value array = x->array(); 979 if (set_contains(array)) { 980 // Value is non-null => update AccessArray 981 if (last_explicit_null_check_obj() == array) { 982 x->set_explicit_null_check(consume_last_explicit_null_check()); 983 x->set_needs_null_check(true); 984 if (PrintNullCheckElimination) { 985 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", 986 x->explicit_null_check()->id(), x->id(), array->id()); 987 } 988 } else { 989 x->set_explicit_null_check(nullptr); 990 x->set_needs_null_check(false); 991 if (PrintNullCheckElimination) { 992 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); 993 } 994 } 995 } else { 996 set_put(array); 997 if (PrintNullCheckElimination) { 998 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); 999 } 1000 // Ensure previous passes do not cause wrong state 1001 x->set_needs_null_check(true); 1002 x->set_explicit_null_check(nullptr); 1003 } 1004 clear_last_explicit_null_check(); 1005 } 1006 1007 1008 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { 1009 Value array = x->array(); 1010 if (set_contains(array)) { 1011 // Value is non-null => update AccessArray 1012 if (last_explicit_null_check_obj() == array) { 1013 x->set_explicit_null_check(consume_last_explicit_null_check()); 1014 x->set_needs_null_check(true); 1015 if (PrintNullCheckElimination) { 1016 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", 1017 x->explicit_null_check()->id(), x->id(), array->id()); 1018 } 1019 } else { 1020 x->set_explicit_null_check(nullptr); 1021 x->set_needs_null_check(false); 1022 if (PrintNullCheckElimination) { 1023 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); 1024 } 1025 } 1026 } else { 1027 set_put(array); 1028 if (PrintNullCheckElimination) { 1029 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 1030 } 1031 // Ensure previous passes do not cause wrong state 1032 x->set_needs_null_check(true); 1033 x->set_explicit_null_check(nullptr); 1034 } 1035 clear_last_explicit_null_check(); 1036 } 1037 1038 1039 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { 1040 Value array = x->array(); 1041 if (set_contains(array)) { 1042 // Value is non-null => update AccessArray 1043 if (PrintNullCheckElimination) { 1044 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); 1045 } 1046 x->set_needs_null_check(false); 1047 } else { 1048 set_put(array); 1049 if (PrintNullCheckElimination) { 1050 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 1051 } 1052 // Ensure previous passes do not cause wrong state 1053 x->set_needs_null_check(true); 1054 } 1055 clear_last_explicit_null_check(); 1056 } 1057 1058 1059 void NullCheckEliminator::handle_NullCheck(NullCheck* x) { 1060 Value obj = x->obj(); 1061 if (set_contains(obj)) { 1062 // Already proven to be non-null => this NullCheck is useless 1063 if (PrintNullCheckElimination) { 1064 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); 1065 } 1066 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. 1067 // The code generator won't emit LIR for a NullCheck that cannot trap. 1068 x->set_can_trap(false); 1069 } else { 1070 // May be null => add to map and set last explicit NullCheck 1071 x->set_can_trap(true); 1072 // make sure it's pinned if it can trap 1073 x->pin(Instruction::PinExplicitNullCheck); 1074 set_put(obj); 1075 set_last_explicit_null_check(x); 1076 if (PrintNullCheckElimination) { 1077 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); 1078 } 1079 } 1080 } 1081 1082 1083 void NullCheckEliminator::handle_Invoke(Invoke* x) { 1084 if (!x->has_receiver()) { 1085 // Be conservative 1086 clear_last_explicit_null_check(); 1087 return; 1088 } 1089 1090 Value recv = x->receiver(); 1091 if (!set_contains(recv)) { 1092 set_put(recv); 1093 if (PrintNullCheckElimination) { 1094 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); 1095 } 1096 } 1097 clear_last_explicit_null_check(); 1098 } 1099 1100 1101 void NullCheckEliminator::handle_NewInstance(NewInstance* x) { 1102 set_put(x); 1103 if (PrintNullCheckElimination) { 1104 tty->print_cr("NewInstance %d is non-null", x->id()); 1105 } 1106 } 1107 1108 void NullCheckEliminator::handle_NewInlineTypeInstance(NewInlineTypeInstance* x) { 1109 set_put(x); 1110 if (PrintNullCheckElimination) { 1111 tty->print_cr("NewInlineTypeInstance %d is non-null", x->id()); 1112 } 1113 } 1114 1115 1116 void NullCheckEliminator::handle_NewArray(NewArray* x) { 1117 set_put(x); 1118 if (PrintNullCheckElimination) { 1119 tty->print_cr("NewArray %d is non-null", x->id()); 1120 } 1121 } 1122 1123 1124 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { 1125 set_put(x); 1126 if (PrintNullCheckElimination) { 1127 tty->print_cr("ExceptionObject %d is non-null", x->id()); 1128 } 1129 } 1130 1131 1132 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { 1133 Value obj = x->obj(); 1134 if (set_contains(obj)) { 1135 // Value is non-null => update AccessMonitor 1136 if (PrintNullCheckElimination) { 1137 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); 1138 } 1139 x->set_needs_null_check(false); 1140 } else { 1141 set_put(obj); 1142 if (PrintNullCheckElimination) { 1143 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); 1144 } 1145 // Ensure previous passes do not cause wrong state 1146 x->set_needs_null_check(true); 1147 } 1148 clear_last_explicit_null_check(); 1149 } 1150 1151 1152 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { 1153 if (!x->has_receiver()) { 1154 if (x->id() == vmIntrinsics::_arraycopy) { 1155 for (int i = 0; i < x->number_of_arguments(); i++) { 1156 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i))); 1157 } 1158 } 1159 1160 // Be conservative 1161 clear_last_explicit_null_check(); 1162 return; 1163 } 1164 1165 Value recv = x->receiver(); 1166 if (set_contains(recv)) { 1167 // Value is non-null => update Intrinsic 1168 if (PrintNullCheckElimination) { 1169 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", vmIntrinsics::as_int(x->id()), recv->id()); 1170 } 1171 x->set_needs_null_check(false); 1172 } else { 1173 set_put(recv); 1174 if (PrintNullCheckElimination) { 1175 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", vmIntrinsics::as_int(x->id()), recv->id()); 1176 } 1177 // Ensure previous passes do not cause wrong state 1178 x->set_needs_null_check(true); 1179 } 1180 clear_last_explicit_null_check(); 1181 } 1182 1183 1184 void NullCheckEliminator::handle_Phi(Phi* x) { 1185 int i; 1186 bool all_non_null = true; 1187 if (x->is_illegal()) { 1188 all_non_null = false; 1189 } else { 1190 for (i = 0; i < x->operand_count(); i++) { 1191 Value input = x->operand_at(i); 1192 if (!set_contains(input)) { 1193 all_non_null = false; 1194 } 1195 } 1196 } 1197 1198 if (all_non_null) { 1199 // Value is non-null => update Phi 1200 if (PrintNullCheckElimination) { 1201 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); 1202 } 1203 x->set_needs_null_check(false); 1204 } else if (set_contains(x)) { 1205 set_remove(x); 1206 } 1207 } 1208 1209 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) { 1210 for (int i = 0; i < x->nb_profiled_args(); i++) { 1211 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i))); 1212 } 1213 } 1214 1215 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) { 1216 x->set_needs_null_check(!set_contains(x->ret())); 1217 } 1218 1219 void NullCheckEliminator::handle_ProfileACmpTypes(ProfileACmpTypes* x) { 1220 x->set_left_maybe_null(!set_contains(x->left())); 1221 x->set_right_maybe_null(!set_contains(x->right())); 1222 } 1223 1224 void Optimizer::eliminate_null_checks() { 1225 ResourceMark rm; 1226 1227 NullCheckEliminator nce(this); 1228 1229 if (PrintNullCheckElimination) { 1230 tty->print_cr("Starting null check elimination for method %s::%s%s", 1231 ir()->method()->holder()->name()->as_utf8(), 1232 ir()->method()->name()->as_utf8(), 1233 ir()->method()->signature()->as_symbol()->as_utf8()); 1234 } 1235 1236 // Apply to graph 1237 nce.iterate(ir()->start()); 1238 1239 // walk over the graph looking for exception 1240 // handlers and iterate over them as well 1241 int nblocks = BlockBegin::number_of_blocks(); 1242 BlockList blocks(nblocks); 1243 boolArray visited_block(nblocks, nblocks, false); 1244 1245 blocks.push(ir()->start()); 1246 visited_block.at_put(ir()->start()->block_id(), true); 1247 for (int i = 0; i < blocks.length(); i++) { 1248 BlockBegin* b = blocks.at(i); 1249 // exception handlers need to be treated as additional roots 1250 for (int e = b->number_of_exception_handlers(); e-- > 0; ) { 1251 BlockBegin* excp = b->exception_handler_at(e); 1252 int id = excp->block_id(); 1253 if (!visited_block.at(id)) { 1254 blocks.push(excp); 1255 visited_block.at_put(id, true); 1256 nce.iterate(excp); 1257 } 1258 } 1259 // traverse successors 1260 BlockEnd *end = b->end(); 1261 for (int s = end->number_of_sux(); s-- > 0; ) { 1262 BlockBegin* next = end->sux_at(s); 1263 int id = next->block_id(); 1264 if (!visited_block.at(id)) { 1265 blocks.push(next); 1266 visited_block.at_put(id, true); 1267 } 1268 } 1269 } 1270 1271 1272 if (PrintNullCheckElimination) { 1273 tty->print_cr("Done with null check elimination for method %s::%s%s", 1274 ir()->method()->holder()->name()->as_utf8(), 1275 ir()->method()->name()->as_utf8(), 1276 ir()->method()->signature()->as_symbol()->as_utf8()); 1277 } 1278 }