1 /* 2 * Copyright (c) 1999, 2011, 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 33 define_array(ValueSetArray, ValueSet*); 34 define_stack(ValueSetList, ValueSetArray); 35 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) : _cee_count(0), _ifop_count(0), _hir(hir) { 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 int cee_count() const { return _cee_count; } 59 int ifop_count() const { return _ifop_count; } 60 61 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) { 62 int e = sux->number_of_exception_handlers(); 63 for (int i = 0; i < e; i++) { 64 BlockBegin* xhandler = sux->exception_handler_at(i); 65 block->add_exception_handler(xhandler); 66 67 assert(xhandler->is_predecessor(sux), "missing predecessor"); 68 if (sux->number_of_preds() == 0) { 69 // sux is disconnected from graph so disconnect from exception handlers 70 xhandler->remove_predecessor(sux); 71 } 72 if (!xhandler->is_predecessor(block)) { 73 xhandler->add_predecessor(block); 74 } 75 } 76 } 77 78 virtual void block_do(BlockBegin* block); 79 80 private: 81 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval); 82 }; 83 84 void CE_Eliminator::block_do(BlockBegin* block) { 85 // 1) find conditional expression 86 // check if block ends with an If 87 If* if_ = block->end()->as_If(); 88 if (if_ == NULL) return; 89 90 // check if If works on int or object types 91 // (we cannot handle If's working on long, float or doubles yet, 92 // since IfOp doesn't support them - these If's show up if cmp 93 // operations followed by If's are eliminated) 94 ValueType* if_type = if_->x()->type(); 95 if (!if_type->is_int() && !if_type->is_object()) return; 96 97 BlockBegin* t_block = if_->tsux(); 98 BlockBegin* f_block = if_->fsux(); 99 Instruction* t_cur = t_block->next(); 100 Instruction* f_cur = f_block->next(); 101 102 // one Constant may be present between BlockBegin and BlockEnd 103 Value t_const = NULL; 104 Value f_const = NULL; 105 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) { 106 t_const = t_cur; 107 t_cur = t_cur->next(); 108 } 109 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) { 110 f_const = f_cur; 111 f_cur = f_cur->next(); 112 } 113 114 // check if both branches end with a goto 115 Goto* t_goto = t_cur->as_Goto(); 116 if (t_goto == NULL) return; 117 Goto* f_goto = f_cur->as_Goto(); 118 if (f_goto == NULL) return; 119 120 // check if both gotos merge into the same block 121 BlockBegin* sux = t_goto->default_sux(); 122 if (sux != f_goto->default_sux()) return; 123 124 // check if at least one word was pushed on sux_state 125 // inlining depths must match 126 ValueStack* if_state = if_->state(); 127 ValueStack* sux_state = sux->state(); 128 while (sux_state->scope() != if_state->scope()) { 129 if_state = if_state->caller_state(); 130 assert(if_state != NULL, "states do not match up"); 131 } 132 133 if (sux_state->stack_size() <= if_state->stack_size()) return; 134 135 // check if phi function is present at end of successor stack and that 136 // only this phi was pushed on the stack 137 Value sux_phi = sux_state->stack_at(if_state->stack_size()); 138 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return; 139 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return; 140 141 // get the values that were pushed in the true- and false-branch 142 Value t_value = t_goto->state()->stack_at(if_state->stack_size()); 143 Value f_value = f_goto->state()->stack_at(if_state->stack_size()); 144 145 // backend does not support floats 146 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types"); 147 if (t_value->type()->is_float_kind()) return; 148 149 // check that successor has no other phi functions but sux_phi 150 // this can happen when t_block or f_block contained additonal stores to local variables 151 // that are no longer represented by explicit instructions 152 for_each_phi_fun(sux, phi, 153 if (phi != sux_phi) return; 154 ); 155 // true and false blocks can't have phis 156 for_each_phi_fun(t_block, phi, return; ); 157 for_each_phi_fun(f_block, phi, return; ); 158 159 // 2) substitute conditional expression 160 // with an IfOp followed by a Goto 161 // cut if_ away and get node before 162 Instruction* cur_end = if_->prev(block); 163 164 // append constants of true- and false-block if necessary 165 // clone constants because original block must not be destroyed 166 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); 167 if (t_value == t_const) { 168 t_value = new Constant(t_const->type()); 169 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); 170 cur_end = cur_end->set_next(t_value); 171 } 172 if (f_value == f_const) { 173 f_value = new Constant(f_const->type()); 174 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); 175 cur_end = cur_end->set_next(f_value); 176 } 177 178 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value); 179 assert(result != NULL, "make_ifop must return a non-null instruction"); 180 if (!result->is_linked() && result->can_be_linked()) { 181 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); 182 cur_end = cur_end->set_next(result); 183 } 184 185 // append Goto to successor 186 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL; 187 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint()); 188 189 // prepare state for Goto 190 ValueStack* goto_state = if_state; 191 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); 192 goto_state->push(result->type(), result); 193 assert(goto_state->is_same(sux_state), "states must match now"); 194 goto_->set_state(goto_state); 195 196 cur_end = cur_end->set_next(goto_, goto_state->bci()); 197 198 // Adjust control flow graph 199 BlockBegin::disconnect_edge(block, t_block); 200 BlockBegin::disconnect_edge(block, f_block); 201 if (t_block->number_of_preds() == 0) { 202 BlockBegin::disconnect_edge(t_block, sux); 203 } 204 adjust_exception_edges(block, t_block); 205 if (f_block->number_of_preds() == 0) { 206 BlockBegin::disconnect_edge(f_block, sux); 207 } 208 adjust_exception_edges(block, f_block); 209 210 // update block end 211 block->set_end(goto_); 212 213 // substitute the phi if possible 214 if (sux_phi->as_Phi()->operand_count() == 1) { 215 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); 216 sux_phi->set_subst(result); 217 _has_substitution = true; 218 } 219 220 // 3) successfully eliminated a conditional expression 221 _cee_count++; 222 if (PrintCEE) { 223 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()); 224 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); 225 } 226 227 _hir->verify(); 228 } 229 230 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) { 231 if (!OptimizeIfOps) { 232 return new IfOp(x, cond, y, tval, fval); 233 } 234 235 tval = tval->subst(); 236 fval = fval->subst(); 237 if (tval == fval) { 238 _ifop_count++; 239 return tval; 240 } 241 242 x = x->subst(); 243 y = y->subst(); 244 245 Constant* y_const = y->as_Constant(); 246 if (y_const != NULL) { 247 IfOp* x_ifop = x->as_IfOp(); 248 if (x_ifop != NULL) { // x is an ifop, y is a constant 249 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); 250 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); 251 252 if (x_tval_const != NULL && x_fval_const != NULL) { 253 Instruction::Condition x_ifop_cond = x_ifop->cond(); 254 255 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); 256 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); 257 258 // not_comparable here is a valid return in case we're comparing unloaded oop constants 259 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) { 260 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; 261 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; 262 263 _ifop_count++; 264 if (new_tval == new_fval) { 265 return new_tval; 266 } else { 267 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval); 268 } 269 } 270 } 271 } else { 272 Constant* x_const = x->as_Constant(); 273 if (x_const != NULL) { // x and y are constants 274 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); 275 // not_comparable here is a valid return in case we're comparing unloaded oop constants 276 if (x_compare_res != Constant::not_comparable) { 277 _ifop_count++; 278 return x_compare_res == Constant::cond_true ? tval : fval; 279 } 280 } 281 } 282 } 283 return new IfOp(x, cond, y, tval, fval); 284 } 285 286 void Optimizer::eliminate_conditional_expressions() { 287 // find conditional expressions & replace them with IfOps 288 CE_Eliminator ce(ir()); 289 } 290 291 class BlockMerger: public BlockClosure { 292 private: 293 IR* _hir; 294 int _merge_count; // the number of block pairs successfully merged 295 296 public: 297 BlockMerger(IR* hir) 298 : _hir(hir) 299 , _merge_count(0) 300 { 301 _hir->iterate_preorder(this); 302 } 303 304 bool try_merge(BlockBegin* block) { 305 BlockEnd* end = block->end(); 306 if (end->as_Goto() != NULL) { 307 assert(end->number_of_sux() == 1, "end must have exactly one successor"); 308 // Note: It would be sufficient to check for the number of successors (= 1) 309 // in order to decide if this block can be merged potentially. That 310 // would then also include switch statements w/ only a default case. 311 // However, in that case we would need to make sure the switch tag 312 // expression is executed if it can produce observable side effects. 313 // We should probably have the canonicalizer simplifying such switch 314 // statements and then we are sure we don't miss these merge opportunities 315 // here (was bug - gri 7/7/99). 316 BlockBegin* sux = end->default_sux(); 317 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) { 318 // merge the two blocks 319 320 #ifdef ASSERT 321 // verify that state at the end of block and at the beginning of sux are equal 322 // no phi functions must be present at beginning of sux 323 ValueStack* sux_state = sux->state(); 324 ValueStack* end_state = end->state(); 325 326 assert(end_state->scope() == sux_state->scope(), "scopes must match"); 327 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); 328 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); 329 330 int index; 331 Value sux_value; 332 for_each_stack_value(sux_state, index, sux_value) { 333 assert(sux_value == end_state->stack_at(index), "stack not equal"); 334 } 335 for_each_local_value(sux_state, index, sux_value) { 336 assert(sux_value == end_state->local_at(index), "locals not equal"); 337 } 338 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); 339 #endif 340 341 // find instruction before end & append first instruction of sux block 342 Instruction* prev = end->prev(block); 343 Instruction* next = sux->next(); 344 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd"); 345 prev->set_next(next); 346 sux->disconnect_from_graph(); 347 block->set_end(sux->end()); 348 // add exception handlers of deleted block, if any 349 for (int k = 0; k < sux->number_of_exception_handlers(); k++) { 350 BlockBegin* xhandler = sux->exception_handler_at(k); 351 block->add_exception_handler(xhandler); 352 353 // also substitute predecessor of exception handler 354 assert(xhandler->is_predecessor(sux), "missing predecessor"); 355 xhandler->remove_predecessor(sux); 356 if (!xhandler->is_predecessor(block)) { 357 xhandler->add_predecessor(block); 358 } 359 } 360 361 // debugging output 362 _merge_count++; 363 if (PrintBlockElimination) { 364 tty->print_cr("%d. merged B%d & B%d (stack size = %d)", 365 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); 366 } 367 368 _hir->verify(); 369 370 If* if_ = block->end()->as_If(); 371 if (if_) { 372 IfOp* ifop = if_->x()->as_IfOp(); 373 Constant* con = if_->y()->as_Constant(); 374 bool swapped = false; 375 if (!con || !ifop) { 376 ifop = if_->y()->as_IfOp(); 377 con = if_->x()->as_Constant(); 378 swapped = true; 379 } 380 if (con && ifop) { 381 Constant* tval = ifop->tval()->as_Constant(); 382 Constant* fval = ifop->fval()->as_Constant(); 383 if (tval && fval) { 384 // Find the instruction before if_, starting with ifop. 385 // When if_ and ifop are not in the same block, prev 386 // becomes NULL In such (rare) cases it is not 387 // profitable to perform the optimization. 388 Value prev = ifop; 389 while (prev != NULL && prev->next() != if_) { 390 prev = prev->next(); 391 } 392 393 if (prev != NULL) { 394 Instruction::Condition cond = if_->cond(); 395 BlockBegin* tsux = if_->tsux(); 396 BlockBegin* fsux = if_->fsux(); 397 if (swapped) { 398 cond = Instruction::mirror(cond); 399 } 400 401 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); 402 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); 403 if (tblock != fblock && !if_->is_safepoint()) { 404 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), 405 tblock, fblock, if_->state_before(), if_->is_safepoint()); 406 newif->set_state(if_->state()->copy()); 407 408 assert(prev->next() == if_, "must be guaranteed by above search"); 409 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); 410 prev->set_next(newif); 411 block->set_end(newif); 412 413 _merge_count++; 414 if (PrintBlockElimination) { 415 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); 416 } 417 418 _hir->verify(); 419 } 420 } 421 } 422 } 423 } 424 425 return true; 426 } 427 } 428 return false; 429 } 430 431 virtual void block_do(BlockBegin* block) { 432 _hir->verify(); 433 // repeat since the same block may merge again 434 while (try_merge(block)) { 435 _hir->verify(); 436 } 437 } 438 }; 439 440 441 void Optimizer::eliminate_blocks() { 442 // merge blocks if possible 443 BlockMerger bm(ir()); 444 } 445 446 447 class NullCheckEliminator; 448 class NullCheckVisitor: public InstructionVisitor { 449 private: 450 NullCheckEliminator* _nce; 451 NullCheckEliminator* nce() { return _nce; } 452 453 public: 454 NullCheckVisitor() {} 455 456 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } 457 458 void do_Phi (Phi* x); 459 void do_Local (Local* x); 460 void do_Constant (Constant* x); 461 void do_LoadField (LoadField* x); 462 void do_StoreField (StoreField* x); 463 void do_ArrayLength (ArrayLength* x); 464 void do_LoadIndexed (LoadIndexed* x); 465 void do_StoreIndexed (StoreIndexed* x); 466 void do_NegateOp (NegateOp* x); 467 void do_ArithmeticOp (ArithmeticOp* x); 468 void do_ShiftOp (ShiftOp* x); 469 void do_LogicOp (LogicOp* x); 470 void do_CompareOp (CompareOp* x); 471 void do_IfOp (IfOp* x); 472 void do_Convert (Convert* x); 473 void do_NullCheck (NullCheck* x); 474 void do_Invoke (Invoke* x); 475 void do_NewInstance (NewInstance* x); 476 void do_NewTypeArray (NewTypeArray* x); 477 void do_NewObjectArray (NewObjectArray* x); 478 void do_NewMultiArray (NewMultiArray* x); 479 void do_CheckCast (CheckCast* x); 480 void do_InstanceOf (InstanceOf* x); 481 void do_MonitorEnter (MonitorEnter* x); 482 void do_MonitorExit (MonitorExit* x); 483 void do_Intrinsic (Intrinsic* x); 484 void do_BlockBegin (BlockBegin* x); 485 void do_Goto (Goto* x); 486 void do_If (If* x); 487 void do_IfInstanceOf (IfInstanceOf* x); 488 void do_TableSwitch (TableSwitch* x); 489 void do_LookupSwitch (LookupSwitch* x); 490 void do_Return (Return* x); 491 void do_Throw (Throw* x); 492 void do_Base (Base* x); 493 void do_OsrEntry (OsrEntry* x); 494 void do_ExceptionObject(ExceptionObject* x); 495 void do_RoundFP (RoundFP* x); 496 void do_UnsafeGetRaw (UnsafeGetRaw* x); 497 void do_UnsafePutRaw (UnsafePutRaw* x); 498 void do_UnsafeGetObject(UnsafeGetObject* x); 499 void do_UnsafePutObject(UnsafePutObject* x); 500 void do_UnsafePrefetchRead (UnsafePrefetchRead* x); 501 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x); 502 void do_ProfileCall (ProfileCall* x); 503 void do_ProfileInvoke (ProfileInvoke* x); 504 void do_RuntimeCall (RuntimeCall* x); 505 }; 506 507 508 // Because of a static contained within (for the purpose of iteration 509 // over instructions), it is only valid to have one of these active at 510 // a time 511 class NullCheckEliminator: public ValueVisitor { 512 private: 513 Optimizer* _opt; 514 515 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block 516 BlockList* _work_list; // Basic blocks to visit 517 518 bool visitable(Value x) { 519 assert(_visitable_instructions != NULL, "check"); 520 return _visitable_instructions->contains(x); 521 } 522 void mark_visited(Value x) { 523 assert(_visitable_instructions != NULL, "check"); 524 _visitable_instructions->remove(x); 525 } 526 void mark_visitable(Value x) { 527 assert(_visitable_instructions != NULL, "check"); 528 _visitable_instructions->put(x); 529 } 530 void clear_visitable_state() { 531 assert(_visitable_instructions != NULL, "check"); 532 _visitable_instructions->clear(); 533 } 534 535 ValueSet* _set; // current state, propagated to subsequent BlockBegins 536 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks 537 NullCheckVisitor _visitor; 538 NullCheck* _last_explicit_null_check; 539 540 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); } 541 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); } 542 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); } 543 544 BlockList* work_list() { return _work_list; } 545 546 void iterate_all(); 547 void iterate_one(BlockBegin* block); 548 549 ValueSet* state() { return _set; } 550 void set_state_from (ValueSet* state) { _set->set_from(state); } 551 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; } 552 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; } 553 // Returns true if caused a change in the block's state. 554 bool merge_state_for(BlockBegin* block, 555 ValueSet* incoming_state); 556 557 public: 558 // constructor 559 NullCheckEliminator(Optimizer* opt) 560 : _opt(opt) 561 , _set(new ValueSet()) 562 , _last_explicit_null_check(NULL) 563 , _block_states(BlockBegin::number_of_blocks(), NULL) 564 , _work_list(new BlockList()) { 565 _visitable_instructions = new ValueSet(); 566 _visitor.set_eliminator(this); 567 } 568 569 Optimizer* opt() { return _opt; } 570 IR* ir () { return opt()->ir(); } 571 572 // Process a graph 573 void iterate(BlockBegin* root); 574 575 void visit(Value* f); 576 577 // In some situations (like NullCheck(x); getfield(x)) the debug 578 // information from the explicit NullCheck can be used to populate 579 // the getfield, even if the two instructions are in different 580 // scopes; this allows implicit null checks to be used but the 581 // correct exception information to be generated. We must clear the 582 // last-traversed NullCheck when we reach a potentially-exception- 583 // throwing instruction, as well as in some other cases. 584 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } 585 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } 586 Value last_explicit_null_check_obj() { return (_last_explicit_null_check 587 ? _last_explicit_null_check->obj() 588 : NULL); } 589 NullCheck* consume_last_explicit_null_check() { 590 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); 591 _last_explicit_null_check->set_can_trap(false); 592 return _last_explicit_null_check; 593 } 594 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; } 595 596 // Handlers for relevant instructions 597 // (separated out from NullCheckVisitor for clarity) 598 599 // The basic contract is that these must leave the instruction in 600 // the desired state; must not assume anything about the state of 601 // the instruction. We make multiple passes over some basic blocks 602 // and the last pass is the only one whose result is valid. 603 void handle_AccessField (AccessField* x); 604 void handle_ArrayLength (ArrayLength* x); 605 void handle_LoadIndexed (LoadIndexed* x); 606 void handle_StoreIndexed (StoreIndexed* x); 607 void handle_NullCheck (NullCheck* x); 608 void handle_Invoke (Invoke* x); 609 void handle_NewInstance (NewInstance* x); 610 void handle_NewArray (NewArray* x); 611 void handle_AccessMonitor (AccessMonitor* x); 612 void handle_Intrinsic (Intrinsic* x); 613 void handle_ExceptionObject (ExceptionObject* x); 614 void handle_Phi (Phi* x); 615 }; 616 617 618 // NEEDS_CLEANUP 619 // There may be other instructions which need to clear the last 620 // explicit null check. Anything across which we can not hoist the 621 // debug information for a NullCheck instruction must clear it. It 622 // might be safer to pattern match "NullCheck ; {AccessField, 623 // ArrayLength, LoadIndexed}" but it is more easily structured this way. 624 // Should test to see performance hit of clearing it for all handlers 625 // with empty bodies below. If it is negligible then we should leave 626 // that in for safety, otherwise should think more about it. 627 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } 628 void NullCheckVisitor::do_Local (Local* x) {} 629 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } 630 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } 631 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } 632 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } 633 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } 634 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } 635 void NullCheckVisitor::do_NegateOp (NegateOp* x) {} 636 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } 637 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} 638 void NullCheckVisitor::do_LogicOp (LogicOp* x) {} 639 void NullCheckVisitor::do_CompareOp (CompareOp* x) {} 640 void NullCheckVisitor::do_IfOp (IfOp* x) {} 641 void NullCheckVisitor::do_Convert (Convert* x) {} 642 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } 643 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } 644 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } 645 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } 646 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } 647 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } 648 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); } 649 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} 650 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } 651 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } 652 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); } 653 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} 654 void NullCheckVisitor::do_Goto (Goto* x) {} 655 void NullCheckVisitor::do_If (If* x) {} 656 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {} 657 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} 658 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} 659 void NullCheckVisitor::do_Return (Return* x) {} 660 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } 661 void NullCheckVisitor::do_Base (Base* x) {} 662 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} 663 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } 664 void NullCheckVisitor::do_RoundFP (RoundFP* x) {} 665 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {} 666 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {} 667 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {} 668 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {} 669 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {} 670 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {} 671 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); } 672 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} 673 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {} 674 675 676 void NullCheckEliminator::visit(Value* p) { 677 assert(*p != NULL, "should not find NULL instructions"); 678 if (visitable(*p)) { 679 mark_visited(*p); 680 (*p)->visit(&_visitor); 681 } 682 } 683 684 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { 685 ValueSet* state = state_for(block); 686 if (state == NULL) { 687 state = incoming_state->copy(); 688 set_state_for(block, state); 689 return true; 690 } else { 691 bool changed = state->set_intersect(incoming_state); 692 if (PrintNullCheckElimination && changed) { 693 tty->print_cr("Block %d's null check state changed", block->block_id()); 694 } 695 return changed; 696 } 697 } 698 699 700 void NullCheckEliminator::iterate_all() { 701 while (work_list()->length() > 0) { 702 iterate_one(work_list()->pop()); 703 } 704 } 705 706 707 void NullCheckEliminator::iterate_one(BlockBegin* block) { 708 clear_visitable_state(); 709 // clear out an old explicit null checks 710 set_last_explicit_null_check(NULL); 711 712 if (PrintNullCheckElimination) { 713 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", 714 block->block_id(), 715 ir()->method()->holder()->name()->as_utf8(), 716 ir()->method()->name()->as_utf8(), 717 ir()->method()->signature()->as_symbol()->as_utf8()); 718 } 719 720 // Create new state if none present (only happens at root) 721 if (state_for(block) == NULL) { 722 ValueSet* tmp_state = new ValueSet(); 723 set_state_for(block, tmp_state); 724 // Initial state is that local 0 (receiver) is non-null for 725 // non-static methods 726 ValueStack* stack = block->state(); 727 IRScope* scope = stack->scope(); 728 ciMethod* method = scope->method(); 729 if (!method->is_static()) { 730 Local* local0 = stack->local_at(0)->as_Local(); 731 assert(local0 != NULL, "must be"); 732 assert(local0->type() == objectType, "invalid type of receiver"); 733 734 if (local0 != NULL) { 735 // Local 0 is used in this scope 736 tmp_state->put(local0); 737 if (PrintNullCheckElimination) { 738 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); 739 } 740 } 741 } 742 } 743 744 // Must copy block's state to avoid mutating it during iteration 745 // through the block -- otherwise "not-null" states can accidentally 746 // propagate "up" through the block during processing of backward 747 // branches and algorithm is incorrect (and does not converge) 748 set_state_from(state_for(block)); 749 750 // allow visiting of Phis belonging to this block 751 for_each_phi_fun(block, phi, 752 mark_visitable(phi); 753 ); 754 755 BlockEnd* e = block->end(); 756 assert(e != NULL, "incomplete graph"); 757 int i; 758 759 // Propagate the state before this block into the exception 760 // handlers. They aren't true successors since we aren't guaranteed 761 // to execute the whole block before executing them. Also putting 762 // them on first seems to help reduce the amount of iteration to 763 // reach a fixed point. 764 for (i = 0; i < block->number_of_exception_handlers(); i++) { 765 BlockBegin* next = block->exception_handler_at(i); 766 if (merge_state_for(next, state())) { 767 if (!work_list()->contains(next)) { 768 work_list()->push(next); 769 } 770 } 771 } 772 773 // Iterate through block, updating state. 774 for (Instruction* instr = block; instr != NULL; instr = instr->next()) { 775 // Mark instructions in this block as visitable as they are seen 776 // in the instruction list. This keeps the iteration from 777 // visiting instructions which are references in other blocks or 778 // visiting instructions more than once. 779 mark_visitable(instr); 780 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { 781 mark_visited(instr); 782 instr->input_values_do(this); 783 instr->visit(&_visitor); 784 } 785 } 786 787 // Propagate state to successors if necessary 788 for (i = 0; i < e->number_of_sux(); i++) { 789 BlockBegin* next = e->sux_at(i); 790 if (merge_state_for(next, state())) { 791 if (!work_list()->contains(next)) { 792 work_list()->push(next); 793 } 794 } 795 } 796 } 797 798 799 void NullCheckEliminator::iterate(BlockBegin* block) { 800 work_list()->push(block); 801 iterate_all(); 802 } 803 804 void NullCheckEliminator::handle_AccessField(AccessField* x) { 805 if (x->is_static()) { 806 if (x->as_LoadField() != NULL) { 807 // If the field is a non-null static final object field (as is 808 // often the case for sun.misc.Unsafe), put this LoadField into 809 // the non-null map 810 ciField* field = x->field(); 811 if (field->is_constant()) { 812 ciConstant field_val = field->constant_value(); 813 BasicType field_type = field_val.basic_type(); 814 if (field_type == T_OBJECT || field_type == T_ARRAY) { 815 ciObject* obj_val = field_val.as_object(); 816 if (!obj_val->is_null_object()) { 817 if (PrintNullCheckElimination) { 818 tty->print_cr("AccessField %d proven non-null by static final non-null oop check", 819 x->id()); 820 } 821 set_put(x); 822 } 823 } 824 } 825 } 826 // Be conservative 827 clear_last_explicit_null_check(); 828 return; 829 } 830 831 Value obj = x->obj(); 832 if (set_contains(obj)) { 833 // Value is non-null => update AccessField 834 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { 835 x->set_explicit_null_check(consume_last_explicit_null_check()); 836 x->set_needs_null_check(true); 837 if (PrintNullCheckElimination) { 838 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", 839 x->explicit_null_check()->id(), x->id(), obj->id()); 840 } 841 } else { 842 x->set_explicit_null_check(NULL); 843 x->set_needs_null_check(false); 844 if (PrintNullCheckElimination) { 845 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); 846 } 847 } 848 } else { 849 set_put(obj); 850 if (PrintNullCheckElimination) { 851 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); 852 } 853 // Ensure previous passes do not cause wrong state 854 x->set_needs_null_check(true); 855 x->set_explicit_null_check(NULL); 856 } 857 clear_last_explicit_null_check(); 858 } 859 860 861 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { 862 Value array = x->array(); 863 if (set_contains(array)) { 864 // Value is non-null => update AccessArray 865 if (last_explicit_null_check_obj() == array) { 866 x->set_explicit_null_check(consume_last_explicit_null_check()); 867 x->set_needs_null_check(true); 868 if (PrintNullCheckElimination) { 869 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", 870 x->explicit_null_check()->id(), x->id(), array->id()); 871 } 872 } else { 873 x->set_explicit_null_check(NULL); 874 x->set_needs_null_check(false); 875 if (PrintNullCheckElimination) { 876 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); 877 } 878 } 879 } else { 880 set_put(array); 881 if (PrintNullCheckElimination) { 882 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); 883 } 884 // Ensure previous passes do not cause wrong state 885 x->set_needs_null_check(true); 886 x->set_explicit_null_check(NULL); 887 } 888 clear_last_explicit_null_check(); 889 } 890 891 892 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { 893 Value array = x->array(); 894 if (set_contains(array)) { 895 // Value is non-null => update AccessArray 896 if (last_explicit_null_check_obj() == array) { 897 x->set_explicit_null_check(consume_last_explicit_null_check()); 898 x->set_needs_null_check(true); 899 if (PrintNullCheckElimination) { 900 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", 901 x->explicit_null_check()->id(), x->id(), array->id()); 902 } 903 } else { 904 x->set_explicit_null_check(NULL); 905 x->set_needs_null_check(false); 906 if (PrintNullCheckElimination) { 907 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); 908 } 909 } 910 } else { 911 set_put(array); 912 if (PrintNullCheckElimination) { 913 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 914 } 915 // Ensure previous passes do not cause wrong state 916 x->set_needs_null_check(true); 917 x->set_explicit_null_check(NULL); 918 } 919 clear_last_explicit_null_check(); 920 } 921 922 923 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { 924 Value array = x->array(); 925 if (set_contains(array)) { 926 // Value is non-null => update AccessArray 927 if (PrintNullCheckElimination) { 928 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); 929 } 930 x->set_needs_null_check(false); 931 } else { 932 set_put(array); 933 if (PrintNullCheckElimination) { 934 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 935 } 936 // Ensure previous passes do not cause wrong state 937 x->set_needs_null_check(true); 938 } 939 clear_last_explicit_null_check(); 940 } 941 942 943 void NullCheckEliminator::handle_NullCheck(NullCheck* x) { 944 Value obj = x->obj(); 945 if (set_contains(obj)) { 946 // Already proven to be non-null => this NullCheck is useless 947 if (PrintNullCheckElimination) { 948 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); 949 } 950 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. 951 // The code generator won't emit LIR for a NullCheck that cannot trap. 952 x->set_can_trap(false); 953 } else { 954 // May be null => add to map and set last explicit NullCheck 955 x->set_can_trap(true); 956 // make sure it's pinned if it can trap 957 x->pin(Instruction::PinExplicitNullCheck); 958 set_put(obj); 959 set_last_explicit_null_check(x); 960 if (PrintNullCheckElimination) { 961 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); 962 } 963 } 964 } 965 966 967 void NullCheckEliminator::handle_Invoke(Invoke* x) { 968 if (!x->has_receiver()) { 969 // Be conservative 970 clear_last_explicit_null_check(); 971 return; 972 } 973 974 Value recv = x->receiver(); 975 if (!set_contains(recv)) { 976 set_put(recv); 977 if (PrintNullCheckElimination) { 978 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); 979 } 980 } 981 clear_last_explicit_null_check(); 982 } 983 984 985 void NullCheckEliminator::handle_NewInstance(NewInstance* x) { 986 set_put(x); 987 if (PrintNullCheckElimination) { 988 tty->print_cr("NewInstance %d is non-null", x->id()); 989 } 990 } 991 992 993 void NullCheckEliminator::handle_NewArray(NewArray* x) { 994 set_put(x); 995 if (PrintNullCheckElimination) { 996 tty->print_cr("NewArray %d is non-null", x->id()); 997 } 998 } 999 1000 1001 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { 1002 set_put(x); 1003 if (PrintNullCheckElimination) { 1004 tty->print_cr("ExceptionObject %d is non-null", x->id()); 1005 } 1006 } 1007 1008 1009 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { 1010 Value obj = x->obj(); 1011 if (set_contains(obj)) { 1012 // Value is non-null => update AccessMonitor 1013 if (PrintNullCheckElimination) { 1014 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); 1015 } 1016 x->set_needs_null_check(false); 1017 } else { 1018 set_put(obj); 1019 if (PrintNullCheckElimination) { 1020 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); 1021 } 1022 // Ensure previous passes do not cause wrong state 1023 x->set_needs_null_check(true); 1024 } 1025 clear_last_explicit_null_check(); 1026 } 1027 1028 1029 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { 1030 if (!x->has_receiver()) { 1031 if (x->id() == vmIntrinsics::_arraycopy) { 1032 for (int i = 0; i < x->number_of_arguments(); i++) { 1033 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i))); 1034 } 1035 } 1036 1037 // Be conservative 1038 clear_last_explicit_null_check(); 1039 return; 1040 } 1041 1042 Value recv = x->receiver(); 1043 if (set_contains(recv)) { 1044 // Value is non-null => update Intrinsic 1045 if (PrintNullCheckElimination) { 1046 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id()); 1047 } 1048 x->set_needs_null_check(false); 1049 } else { 1050 set_put(recv); 1051 if (PrintNullCheckElimination) { 1052 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id()); 1053 } 1054 // Ensure previous passes do not cause wrong state 1055 x->set_needs_null_check(true); 1056 } 1057 clear_last_explicit_null_check(); 1058 } 1059 1060 1061 void NullCheckEliminator::handle_Phi(Phi* x) { 1062 int i; 1063 bool all_non_null = true; 1064 if (x->is_illegal()) { 1065 all_non_null = false; 1066 } else { 1067 for (i = 0; i < x->operand_count(); i++) { 1068 Value input = x->operand_at(i); 1069 if (!set_contains(input)) { 1070 all_non_null = false; 1071 } 1072 } 1073 } 1074 1075 if (all_non_null) { 1076 // Value is non-null => update Phi 1077 if (PrintNullCheckElimination) { 1078 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); 1079 } 1080 x->set_needs_null_check(false); 1081 } else if (set_contains(x)) { 1082 set_remove(x); 1083 } 1084 } 1085 1086 1087 void Optimizer::eliminate_null_checks() { 1088 ResourceMark rm; 1089 1090 NullCheckEliminator nce(this); 1091 1092 if (PrintNullCheckElimination) { 1093 tty->print_cr("Starting null check elimination for method %s::%s%s", 1094 ir()->method()->holder()->name()->as_utf8(), 1095 ir()->method()->name()->as_utf8(), 1096 ir()->method()->signature()->as_symbol()->as_utf8()); 1097 } 1098 1099 // Apply to graph 1100 nce.iterate(ir()->start()); 1101 1102 // walk over the graph looking for exception 1103 // handlers and iterate over them as well 1104 int nblocks = BlockBegin::number_of_blocks(); 1105 BlockList blocks(nblocks); 1106 boolArray visited_block(nblocks, false); 1107 1108 blocks.push(ir()->start()); 1109 visited_block[ir()->start()->block_id()] = true; 1110 for (int i = 0; i < blocks.length(); i++) { 1111 BlockBegin* b = blocks[i]; 1112 // exception handlers need to be treated as additional roots 1113 for (int e = b->number_of_exception_handlers(); e-- > 0; ) { 1114 BlockBegin* excp = b->exception_handler_at(e); 1115 int id = excp->block_id(); 1116 if (!visited_block[id]) { 1117 blocks.push(excp); 1118 visited_block[id] = true; 1119 nce.iterate(excp); 1120 } 1121 } 1122 // traverse successors 1123 BlockEnd *end = b->end(); 1124 for (int s = end->number_of_sux(); s-- > 0; ) { 1125 BlockBegin* next = end->sux_at(s); 1126 int id = next->block_id(); 1127 if (!visited_block[id]) { 1128 blocks.push(next); 1129 visited_block[id] = true; 1130 } 1131 } 1132 } 1133 1134 1135 if (PrintNullCheckElimination) { 1136 tty->print_cr("Done with null check elimination for method %s::%s%s", 1137 ir()->method()->holder()->name()->as_utf8(), 1138 ir()->method()->name()->as_utf8(), 1139 ir()->method()->signature()->as_symbol()->as_utf8()); 1140 } 1141 }