c1_Optimizer.cpp revision 1819:42a10fc37986
1/* 2 * Copyright (c) 1999, 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 "incls/_precompiled.incl" 26#include "incls/_c1_Optimizer.cpp.incl" 27 28define_array(ValueSetArray, ValueSet*); 29define_stack(ValueSetList, ValueSetArray); 30 31 32Optimizer::Optimizer(IR* ir) { 33 assert(ir->is_valid(), "IR must be valid"); 34 _ir = ir; 35} 36 37class CE_Eliminator: public BlockClosure { 38 private: 39 IR* _hir; 40 int _cee_count; // the number of CEs successfully eliminated 41 int _ifop_count; // the number of IfOps successfully simplified 42 int _has_substitution; 43 44 public: 45 CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) { 46 _has_substitution = false; 47 _hir->iterate_preorder(this); 48 if (_has_substitution) { 49 // substituted some ifops/phis, so resolve the substitution 50 SubstitutionResolver sr(_hir); 51 } 52 } 53 int cee_count() const { return _cee_count; } 54 int ifop_count() const { return _ifop_count; } 55 56 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) { 57 int e = sux->number_of_exception_handlers(); 58 for (int i = 0; i < e; i++) { 59 BlockBegin* xhandler = sux->exception_handler_at(i); 60 block->add_exception_handler(xhandler); 61 62 assert(xhandler->is_predecessor(sux), "missing predecessor"); 63 if (sux->number_of_preds() == 0) { 64 // sux is disconnected from graph so disconnect from exception handlers 65 xhandler->remove_predecessor(sux); 66 } 67 if (!xhandler->is_predecessor(block)) { 68 xhandler->add_predecessor(block); 69 } 70 } 71 } 72 73 virtual void block_do(BlockBegin* block); 74 75 private: 76 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval); 77}; 78 79void CE_Eliminator::block_do(BlockBegin* block) { 80 // 1) find conditional expression 81 // check if block ends with an If 82 If* if_ = block->end()->as_If(); 83 if (if_ == NULL) return; 84 85 // check if If works on int or object types 86 // (we cannot handle If's working on long, float or doubles yet, 87 // since IfOp doesn't support them - these If's show up if cmp 88 // operations followed by If's are eliminated) 89 ValueType* if_type = if_->x()->type(); 90 if (!if_type->is_int() && !if_type->is_object()) return; 91 92 BlockBegin* t_block = if_->tsux(); 93 BlockBegin* f_block = if_->fsux(); 94 Instruction* t_cur = t_block->next(); 95 Instruction* f_cur = f_block->next(); 96 97 // one Constant may be present between BlockBegin and BlockEnd 98 Value t_const = NULL; 99 Value f_const = NULL; 100 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) { 101 t_const = t_cur; 102 t_cur = t_cur->next(); 103 } 104 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) { 105 f_const = f_cur; 106 f_cur = f_cur->next(); 107 } 108 109 // check if both branches end with a goto 110 Goto* t_goto = t_cur->as_Goto(); 111 if (t_goto == NULL) return; 112 Goto* f_goto = f_cur->as_Goto(); 113 if (f_goto == NULL) return; 114 115 // check if both gotos merge into the same block 116 BlockBegin* sux = t_goto->default_sux(); 117 if (sux != f_goto->default_sux()) return; 118 119 // check if at least one word was pushed on sux_state 120 ValueStack* sux_state = sux->state(); 121 if (sux_state->stack_size() <= if_->state()->stack_size()) return; 122 123 // check if phi function is present at end of successor stack and that 124 // only this phi was pushed on the stack 125 Value sux_phi = sux_state->stack_at(if_->state()->stack_size()); 126 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return; 127 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return; 128 129 // get the values that were pushed in the true- and false-branch 130 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size()); 131 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size()); 132 133 // backend does not support floats 134 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types"); 135 if (t_value->type()->is_float_kind()) return; 136 137 // check that successor has no other phi functions but sux_phi 138 // this can happen when t_block or f_block contained additonal stores to local variables 139 // that are no longer represented by explicit instructions 140 for_each_phi_fun(sux, phi, 141 if (phi != sux_phi) return; 142 ); 143 // true and false blocks can't have phis 144 for_each_phi_fun(t_block, phi, return; ); 145 for_each_phi_fun(f_block, phi, return; ); 146 147 // 2) substitute conditional expression 148 // with an IfOp followed by a Goto 149 // cut if_ away and get node before 150 Instruction* cur_end = if_->prev(block); 151 152 // append constants of true- and false-block if necessary 153 // clone constants because original block must not be destroyed 154 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); 155 if (t_value == t_const) { 156 t_value = new Constant(t_const->type()); 157 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); 158 cur_end = cur_end->set_next(t_value); 159 } 160 if (f_value == f_const) { 161 f_value = new Constant(f_const->type()); 162 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); 163 cur_end = cur_end->set_next(f_value); 164 } 165 166 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value); 167 assert(result != NULL, "make_ifop must return a non-null instruction"); 168 if (!result->is_linked() && result->can_be_linked()) { 169 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); 170 cur_end = cur_end->set_next(result); 171 } 172 173 // append Goto to successor 174 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL; 175 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint()); 176 177 // prepare state for Goto 178 ValueStack* goto_state = if_->state(); 179 while (sux_state->scope() != goto_state->scope()) { 180 goto_state = goto_state->caller_state(); 181 assert(goto_state != NULL, "states do not match up"); 182 } 183 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); 184 goto_state->push(result->type(), result); 185 assert(goto_state->is_same(sux_state), "states must match now"); 186 goto_->set_state(goto_state); 187 188 cur_end = cur_end->set_next(goto_, goto_state->bci()); 189 190 // Adjust control flow graph 191 BlockBegin::disconnect_edge(block, t_block); 192 BlockBegin::disconnect_edge(block, f_block); 193 if (t_block->number_of_preds() == 0) { 194 BlockBegin::disconnect_edge(t_block, sux); 195 } 196 adjust_exception_edges(block, t_block); 197 if (f_block->number_of_preds() == 0) { 198 BlockBegin::disconnect_edge(f_block, sux); 199 } 200 adjust_exception_edges(block, f_block); 201 202 // update block end 203 block->set_end(goto_); 204 205 // substitute the phi if possible 206 if (sux_phi->as_Phi()->operand_count() == 1) { 207 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); 208 sux_phi->set_subst(result); 209 _has_substitution = true; 210 } 211 212 // 3) successfully eliminated a conditional expression 213 _cee_count++; 214 if (PrintCEE) { 215 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()); 216 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); 217 } 218 219 _hir->verify(); 220} 221 222Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) { 223 if (!OptimizeIfOps) { 224 return new IfOp(x, cond, y, tval, fval); 225 } 226 227 tval = tval->subst(); 228 fval = fval->subst(); 229 if (tval == fval) { 230 _ifop_count++; 231 return tval; 232 } 233 234 x = x->subst(); 235 y = y->subst(); 236 237 Constant* y_const = y->as_Constant(); 238 if (y_const != NULL) { 239 IfOp* x_ifop = x->as_IfOp(); 240 if (x_ifop != NULL) { // x is an ifop, y is a constant 241 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); 242 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); 243 244 if (x_tval_const != NULL && x_fval_const != NULL) { 245 Instruction::Condition x_ifop_cond = x_ifop->cond(); 246 247 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); 248 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); 249 250 guarantee(t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable, "incomparable constants in IfOp"); 251 252 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; 253 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; 254 255 _ifop_count++; 256 if (new_tval == new_fval) { 257 return new_tval; 258 } else { 259 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval); 260 } 261 } 262 } else { 263 Constant* x_const = x->as_Constant(); 264 if (x_const != NULL) { // x and y are constants 265 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); 266 guarantee(x_compare_res != Constant::not_comparable, "incomparable constants in IfOp"); 267 268 _ifop_count++; 269 return x_compare_res == Constant::cond_true ? tval : fval; 270 } 271 } 272 } 273 return new IfOp(x, cond, y, tval, fval); 274} 275 276void Optimizer::eliminate_conditional_expressions() { 277 // find conditional expressions & replace them with IfOps 278 CE_Eliminator ce(ir()); 279} 280 281class BlockMerger: public BlockClosure { 282 private: 283 IR* _hir; 284 int _merge_count; // the number of block pairs successfully merged 285 286 public: 287 BlockMerger(IR* hir) 288 : _hir(hir) 289 , _merge_count(0) 290 { 291 _hir->iterate_preorder(this); 292 } 293 294 bool try_merge(BlockBegin* block) { 295 BlockEnd* end = block->end(); 296 if (end->as_Goto() != NULL) { 297 assert(end->number_of_sux() == 1, "end must have exactly one successor"); 298 // Note: It would be sufficient to check for the number of successors (= 1) 299 // in order to decide if this block can be merged potentially. That 300 // would then also include switch statements w/ only a default case. 301 // However, in that case we would need to make sure the switch tag 302 // expression is executed if it can produce observable side effects. 303 // We should probably have the canonicalizer simplifying such switch 304 // statements and then we are sure we don't miss these merge opportunities 305 // here (was bug - gri 7/7/99). 306 BlockBegin* sux = end->default_sux(); 307 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) { 308 // merge the two blocks 309 310#ifdef ASSERT 311 // verify that state at the end of block and at the beginning of sux are equal 312 // no phi functions must be present at beginning of sux 313 ValueStack* sux_state = sux->state(); 314 ValueStack* end_state = end->state(); 315 316 assert(end_state->scope() == sux_state->scope(), "scopes must match"); 317 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); 318 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); 319 320 int index; 321 Value sux_value; 322 for_each_stack_value(sux_state, index, sux_value) { 323 assert(sux_value == end_state->stack_at(index), "stack not equal"); 324 } 325 for_each_local_value(sux_state, index, sux_value) { 326 assert(sux_value == end_state->local_at(index), "locals not equal"); 327 } 328 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); 329#endif 330 331 // find instruction before end & append first instruction of sux block 332 Instruction* prev = end->prev(block); 333 Instruction* next = sux->next(); 334 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd"); 335 prev->set_next(next); 336 sux->disconnect_from_graph(); 337 block->set_end(sux->end()); 338 // add exception handlers of deleted block, if any 339 for (int k = 0; k < sux->number_of_exception_handlers(); k++) { 340 BlockBegin* xhandler = sux->exception_handler_at(k); 341 block->add_exception_handler(xhandler); 342 343 // also substitute predecessor of exception handler 344 assert(xhandler->is_predecessor(sux), "missing predecessor"); 345 xhandler->remove_predecessor(sux); 346 if (!xhandler->is_predecessor(block)) { 347 xhandler->add_predecessor(block); 348 } 349 } 350 351 // debugging output 352 _merge_count++; 353 if (PrintBlockElimination) { 354 tty->print_cr("%d. merged B%d & B%d (stack size = %d)", 355 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); 356 } 357 358 _hir->verify(); 359 360 If* if_ = block->end()->as_If(); 361 if (if_) { 362 IfOp* ifop = if_->x()->as_IfOp(); 363 Constant* con = if_->y()->as_Constant(); 364 bool swapped = false; 365 if (!con || !ifop) { 366 ifop = if_->y()->as_IfOp(); 367 con = if_->x()->as_Constant(); 368 swapped = true; 369 } 370 if (con && ifop) { 371 Constant* tval = ifop->tval()->as_Constant(); 372 Constant* fval = ifop->fval()->as_Constant(); 373 if (tval && fval) { 374 // Find the instruction before if_, starting with ifop. 375 // When if_ and ifop are not in the same block, prev 376 // becomes NULL In such (rare) cases it is not 377 // profitable to perform the optimization. 378 Value prev = ifop; 379 while (prev != NULL && prev->next() != if_) { 380 prev = prev->next(); 381 } 382 383 if (prev != NULL) { 384 Instruction::Condition cond = if_->cond(); 385 BlockBegin* tsux = if_->tsux(); 386 BlockBegin* fsux = if_->fsux(); 387 if (swapped) { 388 cond = Instruction::mirror(cond); 389 } 390 391 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); 392 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); 393 if (tblock != fblock && !if_->is_safepoint()) { 394 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), 395 tblock, fblock, if_->state_before(), if_->is_safepoint()); 396 newif->set_state(if_->state()->copy()); 397 398 assert(prev->next() == if_, "must be guaranteed by above search"); 399 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); 400 prev->set_next(newif); 401 block->set_end(newif); 402 403 _merge_count++; 404 if (PrintBlockElimination) { 405 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); 406 } 407 408 _hir->verify(); 409 } 410 } 411 } 412 } 413 } 414 415 return true; 416 } 417 } 418 return false; 419 } 420 421 virtual void block_do(BlockBegin* block) { 422 _hir->verify(); 423 // repeat since the same block may merge again 424 while (try_merge(block)) { 425 _hir->verify(); 426 } 427 } 428}; 429 430 431void Optimizer::eliminate_blocks() { 432 // merge blocks if possible 433 BlockMerger bm(ir()); 434} 435 436 437class NullCheckEliminator; 438class NullCheckVisitor: public InstructionVisitor { 439private: 440 NullCheckEliminator* _nce; 441 NullCheckEliminator* nce() { return _nce; } 442 443public: 444 NullCheckVisitor() {} 445 446 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } 447 448 void do_Phi (Phi* x); 449 void do_Local (Local* x); 450 void do_Constant (Constant* x); 451 void do_LoadField (LoadField* x); 452 void do_StoreField (StoreField* x); 453 void do_ArrayLength (ArrayLength* x); 454 void do_LoadIndexed (LoadIndexed* x); 455 void do_StoreIndexed (StoreIndexed* x); 456 void do_NegateOp (NegateOp* x); 457 void do_ArithmeticOp (ArithmeticOp* x); 458 void do_ShiftOp (ShiftOp* x); 459 void do_LogicOp (LogicOp* x); 460 void do_CompareOp (CompareOp* x); 461 void do_IfOp (IfOp* x); 462 void do_Convert (Convert* x); 463 void do_NullCheck (NullCheck* x); 464 void do_Invoke (Invoke* x); 465 void do_NewInstance (NewInstance* x); 466 void do_NewTypeArray (NewTypeArray* x); 467 void do_NewObjectArray (NewObjectArray* x); 468 void do_NewMultiArray (NewMultiArray* x); 469 void do_CheckCast (CheckCast* x); 470 void do_InstanceOf (InstanceOf* x); 471 void do_MonitorEnter (MonitorEnter* x); 472 void do_MonitorExit (MonitorExit* x); 473 void do_Intrinsic (Intrinsic* x); 474 void do_BlockBegin (BlockBegin* x); 475 void do_Goto (Goto* x); 476 void do_If (If* x); 477 void do_IfInstanceOf (IfInstanceOf* x); 478 void do_TableSwitch (TableSwitch* x); 479 void do_LookupSwitch (LookupSwitch* x); 480 void do_Return (Return* x); 481 void do_Throw (Throw* x); 482 void do_Base (Base* x); 483 void do_OsrEntry (OsrEntry* x); 484 void do_ExceptionObject(ExceptionObject* x); 485 void do_RoundFP (RoundFP* x); 486 void do_UnsafeGetRaw (UnsafeGetRaw* x); 487 void do_UnsafePutRaw (UnsafePutRaw* x); 488 void do_UnsafeGetObject(UnsafeGetObject* x); 489 void do_UnsafePutObject(UnsafePutObject* x); 490 void do_UnsafePrefetchRead (UnsafePrefetchRead* x); 491 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x); 492 void do_ProfileCall (ProfileCall* x); 493 void do_ProfileInvoke (ProfileInvoke* x); 494}; 495 496 497// Because of a static contained within (for the purpose of iteration 498// over instructions), it is only valid to have one of these active at 499// a time 500class NullCheckEliminator: public ValueVisitor { 501 private: 502 Optimizer* _opt; 503 504 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block 505 BlockList* _work_list; // Basic blocks to visit 506 507 bool visitable(Value x) { 508 assert(_visitable_instructions != NULL, "check"); 509 return _visitable_instructions->contains(x); 510 } 511 void mark_visited(Value x) { 512 assert(_visitable_instructions != NULL, "check"); 513 _visitable_instructions->remove(x); 514 } 515 void mark_visitable(Value x) { 516 assert(_visitable_instructions != NULL, "check"); 517 _visitable_instructions->put(x); 518 } 519 void clear_visitable_state() { 520 assert(_visitable_instructions != NULL, "check"); 521 _visitable_instructions->clear(); 522 } 523 524 ValueSet* _set; // current state, propagated to subsequent BlockBegins 525 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks 526 NullCheckVisitor _visitor; 527 NullCheck* _last_explicit_null_check; 528 529 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); } 530 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); } 531 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); } 532 533 BlockList* work_list() { return _work_list; } 534 535 void iterate_all(); 536 void iterate_one(BlockBegin* block); 537 538 ValueSet* state() { return _set; } 539 void set_state_from (ValueSet* state) { _set->set_from(state); } 540 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; } 541 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; } 542 // Returns true if caused a change in the block's state. 543 bool merge_state_for(BlockBegin* block, 544 ValueSet* incoming_state); 545 546 public: 547 // constructor 548 NullCheckEliminator(Optimizer* opt) 549 : _opt(opt) 550 , _set(new ValueSet()) 551 , _last_explicit_null_check(NULL) 552 , _block_states(BlockBegin::number_of_blocks(), NULL) 553 , _work_list(new BlockList()) { 554 _visitable_instructions = new ValueSet(); 555 _visitor.set_eliminator(this); 556 } 557 558 Optimizer* opt() { return _opt; } 559 IR* ir () { return opt()->ir(); } 560 561 // Process a graph 562 void iterate(BlockBegin* root); 563 564 void visit(Value* f); 565 566 // In some situations (like NullCheck(x); getfield(x)) the debug 567 // information from the explicit NullCheck can be used to populate 568 // the getfield, even if the two instructions are in different 569 // scopes; this allows implicit null checks to be used but the 570 // correct exception information to be generated. We must clear the 571 // last-traversed NullCheck when we reach a potentially-exception- 572 // throwing instruction, as well as in some other cases. 573 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } 574 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } 575 Value last_explicit_null_check_obj() { return (_last_explicit_null_check 576 ? _last_explicit_null_check->obj() 577 : NULL); } 578 NullCheck* consume_last_explicit_null_check() { 579 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); 580 _last_explicit_null_check->set_can_trap(false); 581 return _last_explicit_null_check; 582 } 583 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; } 584 585 // Handlers for relevant instructions 586 // (separated out from NullCheckVisitor for clarity) 587 588 // The basic contract is that these must leave the instruction in 589 // the desired state; must not assume anything about the state of 590 // the instruction. We make multiple passes over some basic blocks 591 // and the last pass is the only one whose result is valid. 592 void handle_AccessField (AccessField* x); 593 void handle_ArrayLength (ArrayLength* x); 594 void handle_LoadIndexed (LoadIndexed* x); 595 void handle_StoreIndexed (StoreIndexed* x); 596 void handle_NullCheck (NullCheck* x); 597 void handle_Invoke (Invoke* x); 598 void handle_NewInstance (NewInstance* x); 599 void handle_NewArray (NewArray* x); 600 void handle_AccessMonitor (AccessMonitor* x); 601 void handle_Intrinsic (Intrinsic* x); 602 void handle_ExceptionObject (ExceptionObject* x); 603 void handle_Phi (Phi* x); 604}; 605 606 607// NEEDS_CLEANUP 608// There may be other instructions which need to clear the last 609// explicit null check. Anything across which we can not hoist the 610// debug information for a NullCheck instruction must clear it. It 611// might be safer to pattern match "NullCheck ; {AccessField, 612// ArrayLength, LoadIndexed}" but it is more easily structured this way. 613// Should test to see performance hit of clearing it for all handlers 614// with empty bodies below. If it is negligible then we should leave 615// that in for safety, otherwise should think more about it. 616void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } 617void NullCheckVisitor::do_Local (Local* x) {} 618void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } 619void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } 620void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } 621void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } 622void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } 623void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } 624void NullCheckVisitor::do_NegateOp (NegateOp* x) {} 625void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } 626void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} 627void NullCheckVisitor::do_LogicOp (LogicOp* x) {} 628void NullCheckVisitor::do_CompareOp (CompareOp* x) {} 629void NullCheckVisitor::do_IfOp (IfOp* x) {} 630void NullCheckVisitor::do_Convert (Convert* x) {} 631void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } 632void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } 633void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } 634void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } 635void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } 636void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } 637void NullCheckVisitor::do_CheckCast (CheckCast* x) {} 638void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} 639void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } 640void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } 641void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); } 642void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} 643void NullCheckVisitor::do_Goto (Goto* x) {} 644void NullCheckVisitor::do_If (If* x) {} 645void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {} 646void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} 647void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} 648void NullCheckVisitor::do_Return (Return* x) {} 649void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } 650void NullCheckVisitor::do_Base (Base* x) {} 651void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} 652void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } 653void NullCheckVisitor::do_RoundFP (RoundFP* x) {} 654void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {} 655void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {} 656void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {} 657void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {} 658void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {} 659void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {} 660void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); } 661void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} 662 663 664void NullCheckEliminator::visit(Value* p) { 665 assert(*p != NULL, "should not find NULL instructions"); 666 if (visitable(*p)) { 667 mark_visited(*p); 668 (*p)->visit(&_visitor); 669 } 670} 671 672bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { 673 ValueSet* state = state_for(block); 674 if (state == NULL) { 675 state = incoming_state->copy(); 676 set_state_for(block, state); 677 return true; 678 } else { 679 bool changed = state->set_intersect(incoming_state); 680 if (PrintNullCheckElimination && changed) { 681 tty->print_cr("Block %d's null check state changed", block->block_id()); 682 } 683 return changed; 684 } 685} 686 687 688void NullCheckEliminator::iterate_all() { 689 while (work_list()->length() > 0) { 690 iterate_one(work_list()->pop()); 691 } 692} 693 694 695void NullCheckEliminator::iterate_one(BlockBegin* block) { 696 clear_visitable_state(); 697 // clear out an old explicit null checks 698 set_last_explicit_null_check(NULL); 699 700 if (PrintNullCheckElimination) { 701 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", 702 block->block_id(), 703 ir()->method()->holder()->name()->as_utf8(), 704 ir()->method()->name()->as_utf8(), 705 ir()->method()->signature()->as_symbol()->as_utf8()); 706 } 707 708 // Create new state if none present (only happens at root) 709 if (state_for(block) == NULL) { 710 ValueSet* tmp_state = new ValueSet(); 711 set_state_for(block, tmp_state); 712 // Initial state is that local 0 (receiver) is non-null for 713 // non-static methods 714 ValueStack* stack = block->state(); 715 IRScope* scope = stack->scope(); 716 ciMethod* method = scope->method(); 717 if (!method->is_static()) { 718 Local* local0 = stack->local_at(0)->as_Local(); 719 assert(local0 != NULL, "must be"); 720 assert(local0->type() == objectType, "invalid type of receiver"); 721 722 if (local0 != NULL) { 723 // Local 0 is used in this scope 724 tmp_state->put(local0); 725 if (PrintNullCheckElimination) { 726 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); 727 } 728 } 729 } 730 } 731 732 // Must copy block's state to avoid mutating it during iteration 733 // through the block -- otherwise "not-null" states can accidentally 734 // propagate "up" through the block during processing of backward 735 // branches and algorithm is incorrect (and does not converge) 736 set_state_from(state_for(block)); 737 738 // allow visiting of Phis belonging to this block 739 for_each_phi_fun(block, phi, 740 mark_visitable(phi); 741 ); 742 743 BlockEnd* e = block->end(); 744 assert(e != NULL, "incomplete graph"); 745 int i; 746 747 // Propagate the state before this block into the exception 748 // handlers. They aren't true successors since we aren't guaranteed 749 // to execute the whole block before executing them. Also putting 750 // them on first seems to help reduce the amount of iteration to 751 // reach a fixed point. 752 for (i = 0; i < block->number_of_exception_handlers(); i++) { 753 BlockBegin* next = block->exception_handler_at(i); 754 if (merge_state_for(next, state())) { 755 if (!work_list()->contains(next)) { 756 work_list()->push(next); 757 } 758 } 759 } 760 761 // Iterate through block, updating state. 762 for (Instruction* instr = block; instr != NULL; instr = instr->next()) { 763 // Mark instructions in this block as visitable as they are seen 764 // in the instruction list. This keeps the iteration from 765 // visiting instructions which are references in other blocks or 766 // visiting instructions more than once. 767 mark_visitable(instr); 768 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { 769 mark_visited(instr); 770 instr->input_values_do(this); 771 instr->visit(&_visitor); 772 } 773 } 774 775 // Propagate state to successors if necessary 776 for (i = 0; i < e->number_of_sux(); i++) { 777 BlockBegin* next = e->sux_at(i); 778 if (merge_state_for(next, state())) { 779 if (!work_list()->contains(next)) { 780 work_list()->push(next); 781 } 782 } 783 } 784} 785 786 787void NullCheckEliminator::iterate(BlockBegin* block) { 788 work_list()->push(block); 789 iterate_all(); 790} 791 792void NullCheckEliminator::handle_AccessField(AccessField* x) { 793 if (x->is_static()) { 794 if (x->as_LoadField() != NULL) { 795 // If the field is a non-null static final object field (as is 796 // often the case for sun.misc.Unsafe), put this LoadField into 797 // the non-null map 798 ciField* field = x->field(); 799 if (field->is_constant()) { 800 ciConstant field_val = field->constant_value(); 801 BasicType field_type = field_val.basic_type(); 802 if (field_type == T_OBJECT || field_type == T_ARRAY) { 803 ciObject* obj_val = field_val.as_object(); 804 if (!obj_val->is_null_object()) { 805 if (PrintNullCheckElimination) { 806 tty->print_cr("AccessField %d proven non-null by static final non-null oop check", 807 x->id()); 808 } 809 set_put(x); 810 } 811 } 812 } 813 } 814 // Be conservative 815 clear_last_explicit_null_check(); 816 return; 817 } 818 819 Value obj = x->obj(); 820 if (set_contains(obj)) { 821 // Value is non-null => update AccessField 822 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { 823 x->set_explicit_null_check(consume_last_explicit_null_check()); 824 x->set_needs_null_check(true); 825 if (PrintNullCheckElimination) { 826 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", 827 x->explicit_null_check()->id(), x->id(), obj->id()); 828 } 829 } else { 830 x->set_explicit_null_check(NULL); 831 x->set_needs_null_check(false); 832 if (PrintNullCheckElimination) { 833 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); 834 } 835 } 836 } else { 837 set_put(obj); 838 if (PrintNullCheckElimination) { 839 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); 840 } 841 // Ensure previous passes do not cause wrong state 842 x->set_needs_null_check(true); 843 x->set_explicit_null_check(NULL); 844 } 845 clear_last_explicit_null_check(); 846} 847 848 849void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { 850 Value array = x->array(); 851 if (set_contains(array)) { 852 // Value is non-null => update AccessArray 853 if (last_explicit_null_check_obj() == array) { 854 x->set_explicit_null_check(consume_last_explicit_null_check()); 855 x->set_needs_null_check(true); 856 if (PrintNullCheckElimination) { 857 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", 858 x->explicit_null_check()->id(), x->id(), array->id()); 859 } 860 } else { 861 x->set_explicit_null_check(NULL); 862 x->set_needs_null_check(false); 863 if (PrintNullCheckElimination) { 864 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); 865 } 866 } 867 } else { 868 set_put(array); 869 if (PrintNullCheckElimination) { 870 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); 871 } 872 // Ensure previous passes do not cause wrong state 873 x->set_needs_null_check(true); 874 x->set_explicit_null_check(NULL); 875 } 876 clear_last_explicit_null_check(); 877} 878 879 880void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { 881 Value array = x->array(); 882 if (set_contains(array)) { 883 // Value is non-null => update AccessArray 884 if (last_explicit_null_check_obj() == array) { 885 x->set_explicit_null_check(consume_last_explicit_null_check()); 886 x->set_needs_null_check(true); 887 if (PrintNullCheckElimination) { 888 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", 889 x->explicit_null_check()->id(), x->id(), array->id()); 890 } 891 } else { 892 x->set_explicit_null_check(NULL); 893 x->set_needs_null_check(false); 894 if (PrintNullCheckElimination) { 895 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); 896 } 897 } 898 } else { 899 set_put(array); 900 if (PrintNullCheckElimination) { 901 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 902 } 903 // Ensure previous passes do not cause wrong state 904 x->set_needs_null_check(true); 905 x->set_explicit_null_check(NULL); 906 } 907 clear_last_explicit_null_check(); 908} 909 910 911void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { 912 Value array = x->array(); 913 if (set_contains(array)) { 914 // Value is non-null => update AccessArray 915 if (PrintNullCheckElimination) { 916 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); 917 } 918 x->set_needs_null_check(false); 919 } else { 920 set_put(array); 921 if (PrintNullCheckElimination) { 922 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 923 } 924 // Ensure previous passes do not cause wrong state 925 x->set_needs_null_check(true); 926 } 927 clear_last_explicit_null_check(); 928} 929 930 931void NullCheckEliminator::handle_NullCheck(NullCheck* x) { 932 Value obj = x->obj(); 933 if (set_contains(obj)) { 934 // Already proven to be non-null => this NullCheck is useless 935 if (PrintNullCheckElimination) { 936 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); 937 } 938 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. 939 // The code generator won't emit LIR for a NullCheck that cannot trap. 940 x->set_can_trap(false); 941 } else { 942 // May be null => add to map and set last explicit NullCheck 943 x->set_can_trap(true); 944 // make sure it's pinned if it can trap 945 x->pin(Instruction::PinExplicitNullCheck); 946 set_put(obj); 947 set_last_explicit_null_check(x); 948 if (PrintNullCheckElimination) { 949 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); 950 } 951 } 952} 953 954 955void NullCheckEliminator::handle_Invoke(Invoke* x) { 956 if (!x->has_receiver()) { 957 // Be conservative 958 clear_last_explicit_null_check(); 959 return; 960 } 961 962 Value recv = x->receiver(); 963 if (!set_contains(recv)) { 964 set_put(recv); 965 if (PrintNullCheckElimination) { 966 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); 967 } 968 } 969 clear_last_explicit_null_check(); 970} 971 972 973void NullCheckEliminator::handle_NewInstance(NewInstance* x) { 974 set_put(x); 975 if (PrintNullCheckElimination) { 976 tty->print_cr("NewInstance %d is non-null", x->id()); 977 } 978} 979 980 981void NullCheckEliminator::handle_NewArray(NewArray* x) { 982 set_put(x); 983 if (PrintNullCheckElimination) { 984 tty->print_cr("NewArray %d is non-null", x->id()); 985 } 986} 987 988 989void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { 990 set_put(x); 991 if (PrintNullCheckElimination) { 992 tty->print_cr("ExceptionObject %d is non-null", x->id()); 993 } 994} 995 996 997void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { 998 Value obj = x->obj(); 999 if (set_contains(obj)) { 1000 // Value is non-null => update AccessMonitor 1001 if (PrintNullCheckElimination) { 1002 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); 1003 } 1004 x->set_needs_null_check(false); 1005 } else { 1006 set_put(obj); 1007 if (PrintNullCheckElimination) { 1008 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); 1009 } 1010 // Ensure previous passes do not cause wrong state 1011 x->set_needs_null_check(true); 1012 } 1013 clear_last_explicit_null_check(); 1014} 1015 1016 1017void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { 1018 if (!x->has_receiver()) { 1019 // Be conservative 1020 clear_last_explicit_null_check(); 1021 return; 1022 } 1023 1024 Value recv = x->receiver(); 1025 if (set_contains(recv)) { 1026 // Value is non-null => update Intrinsic 1027 if (PrintNullCheckElimination) { 1028 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id()); 1029 } 1030 x->set_needs_null_check(false); 1031 } else { 1032 set_put(recv); 1033 if (PrintNullCheckElimination) { 1034 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id()); 1035 } 1036 // Ensure previous passes do not cause wrong state 1037 x->set_needs_null_check(true); 1038 } 1039 clear_last_explicit_null_check(); 1040} 1041 1042 1043void NullCheckEliminator::handle_Phi(Phi* x) { 1044 int i; 1045 bool all_non_null = true; 1046 if (x->is_illegal()) { 1047 all_non_null = false; 1048 } else { 1049 for (i = 0; i < x->operand_count(); i++) { 1050 Value input = x->operand_at(i); 1051 if (!set_contains(input)) { 1052 all_non_null = false; 1053 } 1054 } 1055 } 1056 1057 if (all_non_null) { 1058 // Value is non-null => update Phi 1059 if (PrintNullCheckElimination) { 1060 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); 1061 } 1062 x->set_needs_null_check(false); 1063 } else if (set_contains(x)) { 1064 set_remove(x); 1065 } 1066} 1067 1068 1069void Optimizer::eliminate_null_checks() { 1070 ResourceMark rm; 1071 1072 NullCheckEliminator nce(this); 1073 1074 if (PrintNullCheckElimination) { 1075 tty->print_cr("Starting null check elimination for method %s::%s%s", 1076 ir()->method()->holder()->name()->as_utf8(), 1077 ir()->method()->name()->as_utf8(), 1078 ir()->method()->signature()->as_symbol()->as_utf8()); 1079 } 1080 1081 // Apply to graph 1082 nce.iterate(ir()->start()); 1083 1084 // walk over the graph looking for exception 1085 // handlers and iterate over them as well 1086 int nblocks = BlockBegin::number_of_blocks(); 1087 BlockList blocks(nblocks); 1088 boolArray visited_block(nblocks, false); 1089 1090 blocks.push(ir()->start()); 1091 visited_block[ir()->start()->block_id()] = true; 1092 for (int i = 0; i < blocks.length(); i++) { 1093 BlockBegin* b = blocks[i]; 1094 // exception handlers need to be treated as additional roots 1095 for (int e = b->number_of_exception_handlers(); e-- > 0; ) { 1096 BlockBegin* excp = b->exception_handler_at(e); 1097 int id = excp->block_id(); 1098 if (!visited_block[id]) { 1099 blocks.push(excp); 1100 visited_block[id] = true; 1101 nce.iterate(excp); 1102 } 1103 } 1104 // traverse successors 1105 BlockEnd *end = b->end(); 1106 for (int s = end->number_of_sux(); s-- > 0; ) { 1107 BlockBegin* next = end->sux_at(s); 1108 int id = next->block_id(); 1109 if (!visited_block[id]) { 1110 blocks.push(next); 1111 visited_block[id] = true; 1112 } 1113 } 1114 } 1115 1116 1117 if (PrintNullCheckElimination) { 1118 tty->print_cr("Done with null check elimination for method %s::%s%s", 1119 ir()->method()->holder()->name()->as_utf8(), 1120 ir()->method()->name()->as_utf8(), 1121 ir()->method()->signature()->as_symbol()->as_utf8()); 1122 } 1123} 1124