c1_Optimizer.cpp revision 4425:46f6f063b272
1/* 2 * Copyright (c) 1999, 2012, 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 "utilities/bitMap.inline.hpp" 32#include "compiler/compileLog.hpp" 33 34define_array(ValueSetArray, ValueSet*); 35define_stack(ValueSetList, ValueSetArray); 36 37 38Optimizer::Optimizer(IR* ir) { 39 assert(ir->is_valid(), "IR must be valid"); 40 _ir = ir; 41} 42 43class CE_Eliminator: public BlockClosure { 44 private: 45 IR* _hir; 46 int _cee_count; // the number of CEs successfully eliminated 47 int _ifop_count; // the number of IfOps successfully simplified 48 int _has_substitution; 49 50 public: 51 CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) { 52 _has_substitution = false; 53 _hir->iterate_preorder(this); 54 if (_has_substitution) { 55 // substituted some ifops/phis, so resolve the substitution 56 SubstitutionResolver sr(_hir); 57 } 58 59 CompileLog* log = _hir->compilation()->log(); 60 if (log != NULL) 61 log->set_context("optimize name='cee'"); 62 } 63 64 ~CE_Eliminator() { 65 CompileLog* log = _hir->compilation()->log(); 66 if (log != NULL) 67 log->clear_context(); // skip marker if nothing was printed 68 } 69 70 int cee_count() const { return _cee_count; } 71 int ifop_count() const { return _ifop_count; } 72 73 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) { 74 int e = sux->number_of_exception_handlers(); 75 for (int i = 0; i < e; i++) { 76 BlockBegin* xhandler = sux->exception_handler_at(i); 77 block->add_exception_handler(xhandler); 78 79 assert(xhandler->is_predecessor(sux), "missing predecessor"); 80 if (sux->number_of_preds() == 0) { 81 // sux is disconnected from graph so disconnect from exception handlers 82 xhandler->remove_predecessor(sux); 83 } 84 if (!xhandler->is_predecessor(block)) { 85 xhandler->add_predecessor(block); 86 } 87 } 88 } 89 90 virtual void block_do(BlockBegin* block); 91 92 private: 93 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval); 94}; 95 96void 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_ == NULL) 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 = NULL; 116 Value f_const = NULL; 117 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) { 118 t_const = t_cur; 119 t_cur = t_cur->next(); 120 } 121 if (f_cur->as_Constant() != NULL && !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 == NULL) return; 129 Goto* f_goto = f_cur->as_Goto(); 130 if (f_goto == NULL) 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 != NULL, "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 != NULL, "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 == NULL || sux_phi->as_Phi() == NULL || 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 additonal 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 // 2) substitute conditional expression 179 // with an IfOp followed by a Goto 180 // cut if_ away and get node before 181 Instruction* cur_end = if_->prev(); 182 183 // append constants of true- and false-block if necessary 184 // clone constants because original block must not be destroyed 185 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); 186 if (t_value == t_const) { 187 t_value = new Constant(t_const->type()); 188 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); 189 cur_end = cur_end->set_next(t_value); 190 } 191 if (f_value == f_const) { 192 f_value = new Constant(f_const->type()); 193 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); 194 cur_end = cur_end->set_next(f_value); 195 } 196 197 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value); 198 assert(result != NULL, "make_ifop must return a non-null instruction"); 199 if (!result->is_linked() && result->can_be_linked()) { 200 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); 201 cur_end = cur_end->set_next(result); 202 } 203 204 // append Goto to successor 205 ValueStack* state_before = if_->state_before(); 206 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint()); 207 208 // prepare state for Goto 209 ValueStack* goto_state = if_state; 210 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); 211 goto_state->push(result->type(), result); 212 assert(goto_state->is_same(sux_state), "states must match now"); 213 goto_->set_state(goto_state); 214 215 cur_end = cur_end->set_next(goto_, goto_state->bci()); 216 217 // Adjust control flow graph 218 BlockBegin::disconnect_edge(block, t_block); 219 BlockBegin::disconnect_edge(block, f_block); 220 if (t_block->number_of_preds() == 0) { 221 BlockBegin::disconnect_edge(t_block, sux); 222 } 223 adjust_exception_edges(block, t_block); 224 if (f_block->number_of_preds() == 0) { 225 BlockBegin::disconnect_edge(f_block, sux); 226 } 227 adjust_exception_edges(block, f_block); 228 229 // update block end 230 block->set_end(goto_); 231 232 // substitute the phi if possible 233 if (sux_phi->as_Phi()->operand_count() == 1) { 234 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); 235 sux_phi->set_subst(result); 236 _has_substitution = true; 237 } 238 239 // 3) successfully eliminated a conditional expression 240 _cee_count++; 241 if (PrintCEE) { 242 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()); 243 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); 244 } 245 246 _hir->verify(); 247} 248 249Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) { 250 if (!OptimizeIfOps) { 251 return new IfOp(x, cond, y, tval, fval); 252 } 253 254 tval = tval->subst(); 255 fval = fval->subst(); 256 if (tval == fval) { 257 _ifop_count++; 258 return tval; 259 } 260 261 x = x->subst(); 262 y = y->subst(); 263 264 Constant* y_const = y->as_Constant(); 265 if (y_const != NULL) { 266 IfOp* x_ifop = x->as_IfOp(); 267 if (x_ifop != NULL) { // x is an ifop, y is a constant 268 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); 269 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); 270 271 if (x_tval_const != NULL && x_fval_const != NULL) { 272 Instruction::Condition x_ifop_cond = x_ifop->cond(); 273 274 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); 275 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); 276 277 // not_comparable here is a valid return in case we're comparing unloaded oop constants 278 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) { 279 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; 280 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; 281 282 _ifop_count++; 283 if (new_tval == new_fval) { 284 return new_tval; 285 } else { 286 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval); 287 } 288 } 289 } 290 } else { 291 Constant* x_const = x->as_Constant(); 292 if (x_const != NULL) { // x and y are constants 293 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); 294 // not_comparable here is a valid return in case we're comparing unloaded oop constants 295 if (x_compare_res != Constant::not_comparable) { 296 _ifop_count++; 297 return x_compare_res == Constant::cond_true ? tval : fval; 298 } 299 } 300 } 301 } 302 return new IfOp(x, cond, y, tval, fval); 303} 304 305void Optimizer::eliminate_conditional_expressions() { 306 // find conditional expressions & replace them with IfOps 307 CE_Eliminator ce(ir()); 308} 309 310class BlockMerger: public BlockClosure { 311 private: 312 IR* _hir; 313 int _merge_count; // the number of block pairs successfully merged 314 315 public: 316 BlockMerger(IR* hir) 317 : _hir(hir) 318 , _merge_count(0) 319 { 320 _hir->iterate_preorder(this); 321 CompileLog* log = _hir->compilation()->log(); 322 if (log != NULL) 323 log->set_context("optimize name='eliminate_blocks'"); 324 } 325 326 ~BlockMerger() { 327 CompileLog* log = _hir->compilation()->log(); 328 if (log != NULL) 329 log->clear_context(); // skip marker if nothing was printed 330 } 331 332 bool try_merge(BlockBegin* block) { 333 BlockEnd* end = block->end(); 334 if (end->as_Goto() != NULL) { 335 assert(end->number_of_sux() == 1, "end must have exactly one successor"); 336 // Note: It would be sufficient to check for the number of successors (= 1) 337 // in order to decide if this block can be merged potentially. That 338 // would then also include switch statements w/ only a default case. 339 // However, in that case we would need to make sure the switch tag 340 // expression is executed if it can produce observable side effects. 341 // We should probably have the canonicalizer simplifying such switch 342 // statements and then we are sure we don't miss these merge opportunities 343 // here (was bug - gri 7/7/99). 344 BlockBegin* sux = end->default_sux(); 345 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) { 346 // merge the two blocks 347 348#ifdef ASSERT 349 // verify that state at the end of block and at the beginning of sux are equal 350 // no phi functions must be present at beginning of sux 351 ValueStack* sux_state = sux->state(); 352 ValueStack* end_state = end->state(); 353 354 assert(end_state->scope() == sux_state->scope(), "scopes must match"); 355 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); 356 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); 357 358 int index; 359 Value sux_value; 360 for_each_stack_value(sux_state, index, sux_value) { 361 assert(sux_value == end_state->stack_at(index), "stack not equal"); 362 } 363 for_each_local_value(sux_state, index, sux_value) { 364 assert(sux_value == end_state->local_at(index), "locals not equal"); 365 } 366 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); 367#endif 368 369 // find instruction before end & append first instruction of sux block 370 Instruction* prev = end->prev(); 371 Instruction* next = sux->next(); 372 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd"); 373 prev->set_next(next); 374 prev->fixup_block_pointers(); 375 sux->disconnect_from_graph(); 376 block->set_end(sux->end()); 377 // add exception handlers of deleted block, if any 378 for (int k = 0; k < sux->number_of_exception_handlers(); k++) { 379 BlockBegin* xhandler = sux->exception_handler_at(k); 380 block->add_exception_handler(xhandler); 381 382 // also substitute predecessor of exception handler 383 assert(xhandler->is_predecessor(sux), "missing predecessor"); 384 xhandler->remove_predecessor(sux); 385 if (!xhandler->is_predecessor(block)) { 386 xhandler->add_predecessor(block); 387 } 388 } 389 390 // debugging output 391 _merge_count++; 392 if (PrintBlockElimination) { 393 tty->print_cr("%d. merged B%d & B%d (stack size = %d)", 394 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); 395 } 396 397 _hir->verify(); 398 399 If* if_ = block->end()->as_If(); 400 if (if_) { 401 IfOp* ifop = if_->x()->as_IfOp(); 402 Constant* con = if_->y()->as_Constant(); 403 bool swapped = false; 404 if (!con || !ifop) { 405 ifop = if_->y()->as_IfOp(); 406 con = if_->x()->as_Constant(); 407 swapped = true; 408 } 409 if (con && ifop) { 410 Constant* tval = ifop->tval()->as_Constant(); 411 Constant* fval = ifop->fval()->as_Constant(); 412 if (tval && fval) { 413 // Find the instruction before if_, starting with ifop. 414 // When if_ and ifop are not in the same block, prev 415 // becomes NULL In such (rare) cases it is not 416 // profitable to perform the optimization. 417 Value prev = ifop; 418 while (prev != NULL && prev->next() != if_) { 419 prev = prev->next(); 420 } 421 422 if (prev != NULL) { 423 Instruction::Condition cond = if_->cond(); 424 BlockBegin* tsux = if_->tsux(); 425 BlockBegin* fsux = if_->fsux(); 426 if (swapped) { 427 cond = Instruction::mirror(cond); 428 } 429 430 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); 431 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); 432 if (tblock != fblock && !if_->is_safepoint()) { 433 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), 434 tblock, fblock, if_->state_before(), if_->is_safepoint()); 435 newif->set_state(if_->state()->copy()); 436 437 assert(prev->next() == if_, "must be guaranteed by above search"); 438 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); 439 prev->set_next(newif); 440 block->set_end(newif); 441 442 _merge_count++; 443 if (PrintBlockElimination) { 444 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); 445 } 446 447 _hir->verify(); 448 } 449 } 450 } 451 } 452 } 453 454 return true; 455 } 456 } 457 return false; 458 } 459 460 virtual void block_do(BlockBegin* block) { 461 _hir->verify(); 462 // repeat since the same block may merge again 463 while (try_merge(block)) { 464 _hir->verify(); 465 } 466 } 467}; 468 469 470void Optimizer::eliminate_blocks() { 471 // merge blocks if possible 472 BlockMerger bm(ir()); 473} 474 475 476class NullCheckEliminator; 477class NullCheckVisitor: public InstructionVisitor { 478private: 479 NullCheckEliminator* _nce; 480 NullCheckEliminator* nce() { return _nce; } 481 482public: 483 NullCheckVisitor() {} 484 485 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } 486 487 void do_Phi (Phi* x); 488 void do_Local (Local* x); 489 void do_Constant (Constant* x); 490 void do_LoadField (LoadField* x); 491 void do_StoreField (StoreField* x); 492 void do_ArrayLength (ArrayLength* x); 493 void do_LoadIndexed (LoadIndexed* x); 494 void do_StoreIndexed (StoreIndexed* x); 495 void do_NegateOp (NegateOp* x); 496 void do_ArithmeticOp (ArithmeticOp* x); 497 void do_ShiftOp (ShiftOp* x); 498 void do_LogicOp (LogicOp* x); 499 void do_CompareOp (CompareOp* x); 500 void do_IfOp (IfOp* x); 501 void do_Convert (Convert* x); 502 void do_NullCheck (NullCheck* x); 503 void do_TypeCast (TypeCast* x); 504 void do_Invoke (Invoke* x); 505 void do_NewInstance (NewInstance* x); 506 void do_NewTypeArray (NewTypeArray* x); 507 void do_NewObjectArray (NewObjectArray* x); 508 void do_NewMultiArray (NewMultiArray* x); 509 void do_CheckCast (CheckCast* x); 510 void do_InstanceOf (InstanceOf* x); 511 void do_MonitorEnter (MonitorEnter* x); 512 void do_MonitorExit (MonitorExit* x); 513 void do_Intrinsic (Intrinsic* x); 514 void do_BlockBegin (BlockBegin* x); 515 void do_Goto (Goto* x); 516 void do_If (If* x); 517 void do_IfInstanceOf (IfInstanceOf* x); 518 void do_TableSwitch (TableSwitch* x); 519 void do_LookupSwitch (LookupSwitch* x); 520 void do_Return (Return* x); 521 void do_Throw (Throw* x); 522 void do_Base (Base* x); 523 void do_OsrEntry (OsrEntry* x); 524 void do_ExceptionObject(ExceptionObject* x); 525 void do_RoundFP (RoundFP* x); 526 void do_UnsafeGetRaw (UnsafeGetRaw* x); 527 void do_UnsafePutRaw (UnsafePutRaw* x); 528 void do_UnsafeGetObject(UnsafeGetObject* x); 529 void do_UnsafePutObject(UnsafePutObject* x); 530 void do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x); 531 void do_UnsafePrefetchRead (UnsafePrefetchRead* x); 532 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x); 533 void do_ProfileCall (ProfileCall* x); 534 void do_ProfileInvoke (ProfileInvoke* x); 535 void do_RuntimeCall (RuntimeCall* x); 536 void do_MemBar (MemBar* x); 537 void do_RangeCheckPredicate(RangeCheckPredicate* x); 538 void do_Assert (Assert* x); 539}; 540 541 542// Because of a static contained within (for the purpose of iteration 543// over instructions), it is only valid to have one of these active at 544// a time 545class NullCheckEliminator: public ValueVisitor { 546 private: 547 Optimizer* _opt; 548 549 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block 550 BlockList* _work_list; // Basic blocks to visit 551 552 bool visitable(Value x) { 553 assert(_visitable_instructions != NULL, "check"); 554 return _visitable_instructions->contains(x); 555 } 556 void mark_visited(Value x) { 557 assert(_visitable_instructions != NULL, "check"); 558 _visitable_instructions->remove(x); 559 } 560 void mark_visitable(Value x) { 561 assert(_visitable_instructions != NULL, "check"); 562 _visitable_instructions->put(x); 563 } 564 void clear_visitable_state() { 565 assert(_visitable_instructions != NULL, "check"); 566 _visitable_instructions->clear(); 567 } 568 569 ValueSet* _set; // current state, propagated to subsequent BlockBegins 570 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks 571 NullCheckVisitor _visitor; 572 NullCheck* _last_explicit_null_check; 573 574 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); } 575 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); } 576 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); } 577 578 BlockList* work_list() { return _work_list; } 579 580 void iterate_all(); 581 void iterate_one(BlockBegin* block); 582 583 ValueSet* state() { return _set; } 584 void set_state_from (ValueSet* state) { _set->set_from(state); } 585 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; } 586 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; } 587 // Returns true if caused a change in the block's state. 588 bool merge_state_for(BlockBegin* block, 589 ValueSet* incoming_state); 590 591 public: 592 // constructor 593 NullCheckEliminator(Optimizer* opt) 594 : _opt(opt) 595 , _set(new ValueSet()) 596 , _last_explicit_null_check(NULL) 597 , _block_states(BlockBegin::number_of_blocks(), NULL) 598 , _work_list(new BlockList()) { 599 _visitable_instructions = new ValueSet(); 600 _visitor.set_eliminator(this); 601 CompileLog* log = _opt->ir()->compilation()->log(); 602 if (log != NULL) 603 log->set_context("optimize name='null_check_elimination'"); 604 } 605 606 ~NullCheckEliminator() { 607 CompileLog* log = _opt->ir()->compilation()->log(); 608 if (log != NULL) 609 log->clear_context(); // skip marker if nothing was printed 610 } 611 612 Optimizer* opt() { return _opt; } 613 IR* ir () { return opt()->ir(); } 614 615 // Process a graph 616 void iterate(BlockBegin* root); 617 618 void visit(Value* f); 619 620 // In some situations (like NullCheck(x); getfield(x)) the debug 621 // information from the explicit NullCheck can be used to populate 622 // the getfield, even if the two instructions are in different 623 // scopes; this allows implicit null checks to be used but the 624 // correct exception information to be generated. We must clear the 625 // last-traversed NullCheck when we reach a potentially-exception- 626 // throwing instruction, as well as in some other cases. 627 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } 628 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } 629 Value last_explicit_null_check_obj() { return (_last_explicit_null_check 630 ? _last_explicit_null_check->obj() 631 : NULL); } 632 NullCheck* consume_last_explicit_null_check() { 633 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); 634 _last_explicit_null_check->set_can_trap(false); 635 return _last_explicit_null_check; 636 } 637 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; } 638 639 // Handlers for relevant instructions 640 // (separated out from NullCheckVisitor for clarity) 641 642 // The basic contract is that these must leave the instruction in 643 // the desired state; must not assume anything about the state of 644 // the instruction. We make multiple passes over some basic blocks 645 // and the last pass is the only one whose result is valid. 646 void handle_AccessField (AccessField* x); 647 void handle_ArrayLength (ArrayLength* x); 648 void handle_LoadIndexed (LoadIndexed* x); 649 void handle_StoreIndexed (StoreIndexed* x); 650 void handle_NullCheck (NullCheck* x); 651 void handle_Invoke (Invoke* x); 652 void handle_NewInstance (NewInstance* x); 653 void handle_NewArray (NewArray* x); 654 void handle_AccessMonitor (AccessMonitor* x); 655 void handle_Intrinsic (Intrinsic* x); 656 void handle_ExceptionObject (ExceptionObject* x); 657 void handle_Phi (Phi* x); 658}; 659 660 661// NEEDS_CLEANUP 662// There may be other instructions which need to clear the last 663// explicit null check. Anything across which we can not hoist the 664// debug information for a NullCheck instruction must clear it. It 665// might be safer to pattern match "NullCheck ; {AccessField, 666// ArrayLength, LoadIndexed}" but it is more easily structured this way. 667// Should test to see performance hit of clearing it for all handlers 668// with empty bodies below. If it is negligible then we should leave 669// that in for safety, otherwise should think more about it. 670void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } 671void NullCheckVisitor::do_Local (Local* x) {} 672void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } 673void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } 674void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } 675void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } 676void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } 677void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } 678void NullCheckVisitor::do_NegateOp (NegateOp* x) {} 679void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } 680void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} 681void NullCheckVisitor::do_LogicOp (LogicOp* x) {} 682void NullCheckVisitor::do_CompareOp (CompareOp* x) {} 683void NullCheckVisitor::do_IfOp (IfOp* x) {} 684void NullCheckVisitor::do_Convert (Convert* x) {} 685void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } 686void NullCheckVisitor::do_TypeCast (TypeCast* x) {} 687void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } 688void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } 689void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } 690void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } 691void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } 692void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); } 693void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} 694void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } 695void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } 696void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); } 697void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} 698void NullCheckVisitor::do_Goto (Goto* x) {} 699void NullCheckVisitor::do_If (If* x) {} 700void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {} 701void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} 702void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} 703void NullCheckVisitor::do_Return (Return* x) {} 704void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } 705void NullCheckVisitor::do_Base (Base* x) {} 706void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} 707void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } 708void NullCheckVisitor::do_RoundFP (RoundFP* x) {} 709void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {} 710void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {} 711void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {} 712void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {} 713void NullCheckVisitor::do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x) {} 714void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {} 715void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {} 716void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); } 717void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} 718void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {} 719void NullCheckVisitor::do_MemBar (MemBar* x) {} 720void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {} 721void NullCheckVisitor::do_Assert (Assert* x) {} 722 723 724void NullCheckEliminator::visit(Value* p) { 725 assert(*p != NULL, "should not find NULL instructions"); 726 if (visitable(*p)) { 727 mark_visited(*p); 728 (*p)->visit(&_visitor); 729 } 730} 731 732bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { 733 ValueSet* state = state_for(block); 734 if (state == NULL) { 735 state = incoming_state->copy(); 736 set_state_for(block, state); 737 return true; 738 } else { 739 bool changed = state->set_intersect(incoming_state); 740 if (PrintNullCheckElimination && changed) { 741 tty->print_cr("Block %d's null check state changed", block->block_id()); 742 } 743 return changed; 744 } 745} 746 747 748void NullCheckEliminator::iterate_all() { 749 while (work_list()->length() > 0) { 750 iterate_one(work_list()->pop()); 751 } 752} 753 754 755void NullCheckEliminator::iterate_one(BlockBegin* block) { 756 clear_visitable_state(); 757 // clear out an old explicit null checks 758 set_last_explicit_null_check(NULL); 759 760 if (PrintNullCheckElimination) { 761 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", 762 block->block_id(), 763 ir()->method()->holder()->name()->as_utf8(), 764 ir()->method()->name()->as_utf8(), 765 ir()->method()->signature()->as_symbol()->as_utf8()); 766 } 767 768 // Create new state if none present (only happens at root) 769 if (state_for(block) == NULL) { 770 ValueSet* tmp_state = new ValueSet(); 771 set_state_for(block, tmp_state); 772 // Initial state is that local 0 (receiver) is non-null for 773 // non-static methods 774 ValueStack* stack = block->state(); 775 IRScope* scope = stack->scope(); 776 ciMethod* method = scope->method(); 777 if (!method->is_static()) { 778 Local* local0 = stack->local_at(0)->as_Local(); 779 assert(local0 != NULL, "must be"); 780 assert(local0->type() == objectType, "invalid type of receiver"); 781 782 if (local0 != NULL) { 783 // Local 0 is used in this scope 784 tmp_state->put(local0); 785 if (PrintNullCheckElimination) { 786 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); 787 } 788 } 789 } 790 } 791 792 // Must copy block's state to avoid mutating it during iteration 793 // through the block -- otherwise "not-null" states can accidentally 794 // propagate "up" through the block during processing of backward 795 // branches and algorithm is incorrect (and does not converge) 796 set_state_from(state_for(block)); 797 798 // allow visiting of Phis belonging to this block 799 for_each_phi_fun(block, phi, 800 mark_visitable(phi); 801 ); 802 803 BlockEnd* e = block->end(); 804 assert(e != NULL, "incomplete graph"); 805 int i; 806 807 // Propagate the state before this block into the exception 808 // handlers. They aren't true successors since we aren't guaranteed 809 // to execute the whole block before executing them. Also putting 810 // them on first seems to help reduce the amount of iteration to 811 // reach a fixed point. 812 for (i = 0; i < block->number_of_exception_handlers(); i++) { 813 BlockBegin* next = block->exception_handler_at(i); 814 if (merge_state_for(next, state())) { 815 if (!work_list()->contains(next)) { 816 work_list()->push(next); 817 } 818 } 819 } 820 821 // Iterate through block, updating state. 822 for (Instruction* instr = block; instr != NULL; instr = instr->next()) { 823 // Mark instructions in this block as visitable as they are seen 824 // in the instruction list. This keeps the iteration from 825 // visiting instructions which are references in other blocks or 826 // visiting instructions more than once. 827 mark_visitable(instr); 828 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { 829 mark_visited(instr); 830 instr->input_values_do(this); 831 instr->visit(&_visitor); 832 } 833 } 834 835 // Propagate state to successors if necessary 836 for (i = 0; i < e->number_of_sux(); i++) { 837 BlockBegin* next = e->sux_at(i); 838 if (merge_state_for(next, state())) { 839 if (!work_list()->contains(next)) { 840 work_list()->push(next); 841 } 842 } 843 } 844} 845 846 847void NullCheckEliminator::iterate(BlockBegin* block) { 848 work_list()->push(block); 849 iterate_all(); 850} 851 852void NullCheckEliminator::handle_AccessField(AccessField* x) { 853 if (x->is_static()) { 854 if (x->as_LoadField() != NULL) { 855 // If the field is a non-null static final object field (as is 856 // often the case for sun.misc.Unsafe), put this LoadField into 857 // the non-null map 858 ciField* field = x->field(); 859 if (field->is_constant()) { 860 ciConstant field_val = field->constant_value(); 861 BasicType field_type = field_val.basic_type(); 862 if (field_type == T_OBJECT || field_type == T_ARRAY) { 863 ciObject* obj_val = field_val.as_object(); 864 if (!obj_val->is_null_object()) { 865 if (PrintNullCheckElimination) { 866 tty->print_cr("AccessField %d proven non-null by static final non-null oop check", 867 x->id()); 868 } 869 set_put(x); 870 } 871 } 872 } 873 } 874 // Be conservative 875 clear_last_explicit_null_check(); 876 return; 877 } 878 879 Value obj = x->obj(); 880 if (set_contains(obj)) { 881 // Value is non-null => update AccessField 882 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { 883 x->set_explicit_null_check(consume_last_explicit_null_check()); 884 x->set_needs_null_check(true); 885 if (PrintNullCheckElimination) { 886 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", 887 x->explicit_null_check()->id(), x->id(), obj->id()); 888 } 889 } else { 890 x->set_explicit_null_check(NULL); 891 x->set_needs_null_check(false); 892 if (PrintNullCheckElimination) { 893 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); 894 } 895 } 896 } else { 897 set_put(obj); 898 if (PrintNullCheckElimination) { 899 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); 900 } 901 // Ensure previous passes do not cause wrong state 902 x->set_needs_null_check(true); 903 x->set_explicit_null_check(NULL); 904 } 905 clear_last_explicit_null_check(); 906} 907 908 909void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { 910 Value array = x->array(); 911 if (set_contains(array)) { 912 // Value is non-null => update AccessArray 913 if (last_explicit_null_check_obj() == array) { 914 x->set_explicit_null_check(consume_last_explicit_null_check()); 915 x->set_needs_null_check(true); 916 if (PrintNullCheckElimination) { 917 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", 918 x->explicit_null_check()->id(), x->id(), array->id()); 919 } 920 } else { 921 x->set_explicit_null_check(NULL); 922 x->set_needs_null_check(false); 923 if (PrintNullCheckElimination) { 924 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); 925 } 926 } 927 } else { 928 set_put(array); 929 if (PrintNullCheckElimination) { 930 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); 931 } 932 // Ensure previous passes do not cause wrong state 933 x->set_needs_null_check(true); 934 x->set_explicit_null_check(NULL); 935 } 936 clear_last_explicit_null_check(); 937} 938 939 940void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { 941 Value array = x->array(); 942 if (set_contains(array)) { 943 // Value is non-null => update AccessArray 944 if (last_explicit_null_check_obj() == array) { 945 x->set_explicit_null_check(consume_last_explicit_null_check()); 946 x->set_needs_null_check(true); 947 if (PrintNullCheckElimination) { 948 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", 949 x->explicit_null_check()->id(), x->id(), array->id()); 950 } 951 } else { 952 x->set_explicit_null_check(NULL); 953 x->set_needs_null_check(false); 954 if (PrintNullCheckElimination) { 955 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); 956 } 957 } 958 } else { 959 set_put(array); 960 if (PrintNullCheckElimination) { 961 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 962 } 963 // Ensure previous passes do not cause wrong state 964 x->set_needs_null_check(true); 965 x->set_explicit_null_check(NULL); 966 } 967 clear_last_explicit_null_check(); 968} 969 970 971void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { 972 Value array = x->array(); 973 if (set_contains(array)) { 974 // Value is non-null => update AccessArray 975 if (PrintNullCheckElimination) { 976 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); 977 } 978 x->set_needs_null_check(false); 979 } else { 980 set_put(array); 981 if (PrintNullCheckElimination) { 982 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 983 } 984 // Ensure previous passes do not cause wrong state 985 x->set_needs_null_check(true); 986 } 987 clear_last_explicit_null_check(); 988} 989 990 991void NullCheckEliminator::handle_NullCheck(NullCheck* x) { 992 Value obj = x->obj(); 993 if (set_contains(obj)) { 994 // Already proven to be non-null => this NullCheck is useless 995 if (PrintNullCheckElimination) { 996 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); 997 } 998 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. 999 // The code generator won't emit LIR for a NullCheck that cannot trap. 1000 x->set_can_trap(false); 1001 } else { 1002 // May be null => add to map and set last explicit NullCheck 1003 x->set_can_trap(true); 1004 // make sure it's pinned if it can trap 1005 x->pin(Instruction::PinExplicitNullCheck); 1006 set_put(obj); 1007 set_last_explicit_null_check(x); 1008 if (PrintNullCheckElimination) { 1009 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); 1010 } 1011 } 1012} 1013 1014 1015void NullCheckEliminator::handle_Invoke(Invoke* x) { 1016 if (!x->has_receiver()) { 1017 // Be conservative 1018 clear_last_explicit_null_check(); 1019 return; 1020 } 1021 1022 Value recv = x->receiver(); 1023 if (!set_contains(recv)) { 1024 set_put(recv); 1025 if (PrintNullCheckElimination) { 1026 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); 1027 } 1028 } 1029 clear_last_explicit_null_check(); 1030} 1031 1032 1033void NullCheckEliminator::handle_NewInstance(NewInstance* x) { 1034 set_put(x); 1035 if (PrintNullCheckElimination) { 1036 tty->print_cr("NewInstance %d is non-null", x->id()); 1037 } 1038} 1039 1040 1041void NullCheckEliminator::handle_NewArray(NewArray* x) { 1042 set_put(x); 1043 if (PrintNullCheckElimination) { 1044 tty->print_cr("NewArray %d is non-null", x->id()); 1045 } 1046} 1047 1048 1049void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { 1050 set_put(x); 1051 if (PrintNullCheckElimination) { 1052 tty->print_cr("ExceptionObject %d is non-null", x->id()); 1053 } 1054} 1055 1056 1057void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { 1058 Value obj = x->obj(); 1059 if (set_contains(obj)) { 1060 // Value is non-null => update AccessMonitor 1061 if (PrintNullCheckElimination) { 1062 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); 1063 } 1064 x->set_needs_null_check(false); 1065 } else { 1066 set_put(obj); 1067 if (PrintNullCheckElimination) { 1068 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); 1069 } 1070 // Ensure previous passes do not cause wrong state 1071 x->set_needs_null_check(true); 1072 } 1073 clear_last_explicit_null_check(); 1074} 1075 1076 1077void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { 1078 if (!x->has_receiver()) { 1079 if (x->id() == vmIntrinsics::_arraycopy) { 1080 for (int i = 0; i < x->number_of_arguments(); i++) { 1081 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i))); 1082 } 1083 } 1084 1085 // Be conservative 1086 clear_last_explicit_null_check(); 1087 return; 1088 } 1089 1090 Value recv = x->receiver(); 1091 if (set_contains(recv)) { 1092 // Value is non-null => update Intrinsic 1093 if (PrintNullCheckElimination) { 1094 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id()); 1095 } 1096 x->set_needs_null_check(false); 1097 } else { 1098 set_put(recv); 1099 if (PrintNullCheckElimination) { 1100 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id()); 1101 } 1102 // Ensure previous passes do not cause wrong state 1103 x->set_needs_null_check(true); 1104 } 1105 clear_last_explicit_null_check(); 1106} 1107 1108 1109void NullCheckEliminator::handle_Phi(Phi* x) { 1110 int i; 1111 bool all_non_null = true; 1112 if (x->is_illegal()) { 1113 all_non_null = false; 1114 } else { 1115 for (i = 0; i < x->operand_count(); i++) { 1116 Value input = x->operand_at(i); 1117 if (!set_contains(input)) { 1118 all_non_null = false; 1119 } 1120 } 1121 } 1122 1123 if (all_non_null) { 1124 // Value is non-null => update Phi 1125 if (PrintNullCheckElimination) { 1126 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); 1127 } 1128 x->set_needs_null_check(false); 1129 } else if (set_contains(x)) { 1130 set_remove(x); 1131 } 1132} 1133 1134 1135void Optimizer::eliminate_null_checks() { 1136 ResourceMark rm; 1137 1138 NullCheckEliminator nce(this); 1139 1140 if (PrintNullCheckElimination) { 1141 tty->print_cr("Starting null check elimination for method %s::%s%s", 1142 ir()->method()->holder()->name()->as_utf8(), 1143 ir()->method()->name()->as_utf8(), 1144 ir()->method()->signature()->as_symbol()->as_utf8()); 1145 } 1146 1147 // Apply to graph 1148 nce.iterate(ir()->start()); 1149 1150 // walk over the graph looking for exception 1151 // handlers and iterate over them as well 1152 int nblocks = BlockBegin::number_of_blocks(); 1153 BlockList blocks(nblocks); 1154 boolArray visited_block(nblocks, false); 1155 1156 blocks.push(ir()->start()); 1157 visited_block[ir()->start()->block_id()] = true; 1158 for (int i = 0; i < blocks.length(); i++) { 1159 BlockBegin* b = blocks[i]; 1160 // exception handlers need to be treated as additional roots 1161 for (int e = b->number_of_exception_handlers(); e-- > 0; ) { 1162 BlockBegin* excp = b->exception_handler_at(e); 1163 int id = excp->block_id(); 1164 if (!visited_block[id]) { 1165 blocks.push(excp); 1166 visited_block[id] = true; 1167 nce.iterate(excp); 1168 } 1169 } 1170 // traverse successors 1171 BlockEnd *end = b->end(); 1172 for (int s = end->number_of_sux(); s-- > 0; ) { 1173 BlockBegin* next = end->sux_at(s); 1174 int id = next->block_id(); 1175 if (!visited_block[id]) { 1176 blocks.push(next); 1177 visited_block[id] = true; 1178 } 1179 } 1180 } 1181 1182 1183 if (PrintNullCheckElimination) { 1184 tty->print_cr("Done with null check elimination for method %s::%s%s", 1185 ir()->method()->holder()->name()->as_utf8(), 1186 ir()->method()->name()->as_utf8(), 1187 ir()->method()->signature()->as_symbol()->as_utf8()); 1188 } 1189} 1190