c1_Optimizer.cpp revision 1879:f95d63e2154a
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 "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 33define_array(ValueSetArray, ValueSet*); 34define_stack(ValueSetList, ValueSetArray); 35 36 37Optimizer::Optimizer(IR* ir) { 38 assert(ir->is_valid(), "IR must be valid"); 39 _ir = ir; 40} 41 42class 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 84void 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 ValueStack* sux_state = sux->state(); 126 if (sux_state->stack_size() <= if_->state()->stack_size()) return; 127 128 // check if phi function is present at end of successor stack and that 129 // only this phi was pushed on the stack 130 Value sux_phi = sux_state->stack_at(if_->state()->stack_size()); 131 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return; 132 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return; 133 134 // get the values that were pushed in the true- and false-branch 135 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size()); 136 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size()); 137 138 // backend does not support floats 139 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types"); 140 if (t_value->type()->is_float_kind()) return; 141 142 // check that successor has no other phi functions but sux_phi 143 // this can happen when t_block or f_block contained additonal stores to local variables 144 // that are no longer represented by explicit instructions 145 for_each_phi_fun(sux, phi, 146 if (phi != sux_phi) return; 147 ); 148 // true and false blocks can't have phis 149 for_each_phi_fun(t_block, phi, return; ); 150 for_each_phi_fun(f_block, phi, return; ); 151 152 // 2) substitute conditional expression 153 // with an IfOp followed by a Goto 154 // cut if_ away and get node before 155 Instruction* cur_end = if_->prev(block); 156 157 // append constants of true- and false-block if necessary 158 // clone constants because original block must not be destroyed 159 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); 160 if (t_value == t_const) { 161 t_value = new Constant(t_const->type()); 162 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); 163 cur_end = cur_end->set_next(t_value); 164 } 165 if (f_value == f_const) { 166 f_value = new Constant(f_const->type()); 167 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); 168 cur_end = cur_end->set_next(f_value); 169 } 170 171 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value); 172 assert(result != NULL, "make_ifop must return a non-null instruction"); 173 if (!result->is_linked() && result->can_be_linked()) { 174 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); 175 cur_end = cur_end->set_next(result); 176 } 177 178 // append Goto to successor 179 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL; 180 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint()); 181 182 // prepare state for Goto 183 ValueStack* goto_state = if_->state(); 184 while (sux_state->scope() != goto_state->scope()) { 185 goto_state = goto_state->caller_state(); 186 assert(goto_state != NULL, "states do not match up"); 187 } 188 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); 189 goto_state->push(result->type(), result); 190 assert(goto_state->is_same(sux_state), "states must match now"); 191 goto_->set_state(goto_state); 192 193 cur_end = cur_end->set_next(goto_, goto_state->bci()); 194 195 // Adjust control flow graph 196 BlockBegin::disconnect_edge(block, t_block); 197 BlockBegin::disconnect_edge(block, f_block); 198 if (t_block->number_of_preds() == 0) { 199 BlockBegin::disconnect_edge(t_block, sux); 200 } 201 adjust_exception_edges(block, t_block); 202 if (f_block->number_of_preds() == 0) { 203 BlockBegin::disconnect_edge(f_block, sux); 204 } 205 adjust_exception_edges(block, f_block); 206 207 // update block end 208 block->set_end(goto_); 209 210 // substitute the phi if possible 211 if (sux_phi->as_Phi()->operand_count() == 1) { 212 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); 213 sux_phi->set_subst(result); 214 _has_substitution = true; 215 } 216 217 // 3) successfully eliminated a conditional expression 218 _cee_count++; 219 if (PrintCEE) { 220 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()); 221 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); 222 } 223 224 _hir->verify(); 225} 226 227Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) { 228 if (!OptimizeIfOps) { 229 return new IfOp(x, cond, y, tval, fval); 230 } 231 232 tval = tval->subst(); 233 fval = fval->subst(); 234 if (tval == fval) { 235 _ifop_count++; 236 return tval; 237 } 238 239 x = x->subst(); 240 y = y->subst(); 241 242 Constant* y_const = y->as_Constant(); 243 if (y_const != NULL) { 244 IfOp* x_ifop = x->as_IfOp(); 245 if (x_ifop != NULL) { // x is an ifop, y is a constant 246 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); 247 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); 248 249 if (x_tval_const != NULL && x_fval_const != NULL) { 250 Instruction::Condition x_ifop_cond = x_ifop->cond(); 251 252 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); 253 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); 254 255 guarantee(t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable, "incomparable constants in IfOp"); 256 257 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; 258 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; 259 260 _ifop_count++; 261 if (new_tval == new_fval) { 262 return new_tval; 263 } else { 264 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval); 265 } 266 } 267 } else { 268 Constant* x_const = x->as_Constant(); 269 if (x_const != NULL) { // x and y are constants 270 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); 271 guarantee(x_compare_res != Constant::not_comparable, "incomparable constants in IfOp"); 272 273 _ifop_count++; 274 return x_compare_res == Constant::cond_true ? tval : fval; 275 } 276 } 277 } 278 return new IfOp(x, cond, y, tval, fval); 279} 280 281void Optimizer::eliminate_conditional_expressions() { 282 // find conditional expressions & replace them with IfOps 283 CE_Eliminator ce(ir()); 284} 285 286class BlockMerger: public BlockClosure { 287 private: 288 IR* _hir; 289 int _merge_count; // the number of block pairs successfully merged 290 291 public: 292 BlockMerger(IR* hir) 293 : _hir(hir) 294 , _merge_count(0) 295 { 296 _hir->iterate_preorder(this); 297 } 298 299 bool try_merge(BlockBegin* block) { 300 BlockEnd* end = block->end(); 301 if (end->as_Goto() != NULL) { 302 assert(end->number_of_sux() == 1, "end must have exactly one successor"); 303 // Note: It would be sufficient to check for the number of successors (= 1) 304 // in order to decide if this block can be merged potentially. That 305 // would then also include switch statements w/ only a default case. 306 // However, in that case we would need to make sure the switch tag 307 // expression is executed if it can produce observable side effects. 308 // We should probably have the canonicalizer simplifying such switch 309 // statements and then we are sure we don't miss these merge opportunities 310 // here (was bug - gri 7/7/99). 311 BlockBegin* sux = end->default_sux(); 312 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) { 313 // merge the two blocks 314 315#ifdef ASSERT 316 // verify that state at the end of block and at the beginning of sux are equal 317 // no phi functions must be present at beginning of sux 318 ValueStack* sux_state = sux->state(); 319 ValueStack* end_state = end->state(); 320 321 assert(end_state->scope() == sux_state->scope(), "scopes must match"); 322 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); 323 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); 324 325 int index; 326 Value sux_value; 327 for_each_stack_value(sux_state, index, sux_value) { 328 assert(sux_value == end_state->stack_at(index), "stack not equal"); 329 } 330 for_each_local_value(sux_state, index, sux_value) { 331 assert(sux_value == end_state->local_at(index), "locals not equal"); 332 } 333 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); 334#endif 335 336 // find instruction before end & append first instruction of sux block 337 Instruction* prev = end->prev(block); 338 Instruction* next = sux->next(); 339 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd"); 340 prev->set_next(next); 341 sux->disconnect_from_graph(); 342 block->set_end(sux->end()); 343 // add exception handlers of deleted block, if any 344 for (int k = 0; k < sux->number_of_exception_handlers(); k++) { 345 BlockBegin* xhandler = sux->exception_handler_at(k); 346 block->add_exception_handler(xhandler); 347 348 // also substitute predecessor of exception handler 349 assert(xhandler->is_predecessor(sux), "missing predecessor"); 350 xhandler->remove_predecessor(sux); 351 if (!xhandler->is_predecessor(block)) { 352 xhandler->add_predecessor(block); 353 } 354 } 355 356 // debugging output 357 _merge_count++; 358 if (PrintBlockElimination) { 359 tty->print_cr("%d. merged B%d & B%d (stack size = %d)", 360 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); 361 } 362 363 _hir->verify(); 364 365 If* if_ = block->end()->as_If(); 366 if (if_) { 367 IfOp* ifop = if_->x()->as_IfOp(); 368 Constant* con = if_->y()->as_Constant(); 369 bool swapped = false; 370 if (!con || !ifop) { 371 ifop = if_->y()->as_IfOp(); 372 con = if_->x()->as_Constant(); 373 swapped = true; 374 } 375 if (con && ifop) { 376 Constant* tval = ifop->tval()->as_Constant(); 377 Constant* fval = ifop->fval()->as_Constant(); 378 if (tval && fval) { 379 // Find the instruction before if_, starting with ifop. 380 // When if_ and ifop are not in the same block, prev 381 // becomes NULL In such (rare) cases it is not 382 // profitable to perform the optimization. 383 Value prev = ifop; 384 while (prev != NULL && prev->next() != if_) { 385 prev = prev->next(); 386 } 387 388 if (prev != NULL) { 389 Instruction::Condition cond = if_->cond(); 390 BlockBegin* tsux = if_->tsux(); 391 BlockBegin* fsux = if_->fsux(); 392 if (swapped) { 393 cond = Instruction::mirror(cond); 394 } 395 396 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); 397 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); 398 if (tblock != fblock && !if_->is_safepoint()) { 399 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), 400 tblock, fblock, if_->state_before(), if_->is_safepoint()); 401 newif->set_state(if_->state()->copy()); 402 403 assert(prev->next() == if_, "must be guaranteed by above search"); 404 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); 405 prev->set_next(newif); 406 block->set_end(newif); 407 408 _merge_count++; 409 if (PrintBlockElimination) { 410 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); 411 } 412 413 _hir->verify(); 414 } 415 } 416 } 417 } 418 } 419 420 return true; 421 } 422 } 423 return false; 424 } 425 426 virtual void block_do(BlockBegin* block) { 427 _hir->verify(); 428 // repeat since the same block may merge again 429 while (try_merge(block)) { 430 _hir->verify(); 431 } 432 } 433}; 434 435 436void Optimizer::eliminate_blocks() { 437 // merge blocks if possible 438 BlockMerger bm(ir()); 439} 440 441 442class NullCheckEliminator; 443class NullCheckVisitor: public InstructionVisitor { 444private: 445 NullCheckEliminator* _nce; 446 NullCheckEliminator* nce() { return _nce; } 447 448public: 449 NullCheckVisitor() {} 450 451 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } 452 453 void do_Phi (Phi* x); 454 void do_Local (Local* x); 455 void do_Constant (Constant* x); 456 void do_LoadField (LoadField* x); 457 void do_StoreField (StoreField* x); 458 void do_ArrayLength (ArrayLength* x); 459 void do_LoadIndexed (LoadIndexed* x); 460 void do_StoreIndexed (StoreIndexed* x); 461 void do_NegateOp (NegateOp* x); 462 void do_ArithmeticOp (ArithmeticOp* x); 463 void do_ShiftOp (ShiftOp* x); 464 void do_LogicOp (LogicOp* x); 465 void do_CompareOp (CompareOp* x); 466 void do_IfOp (IfOp* x); 467 void do_Convert (Convert* x); 468 void do_NullCheck (NullCheck* x); 469 void do_Invoke (Invoke* x); 470 void do_NewInstance (NewInstance* x); 471 void do_NewTypeArray (NewTypeArray* x); 472 void do_NewObjectArray (NewObjectArray* x); 473 void do_NewMultiArray (NewMultiArray* x); 474 void do_CheckCast (CheckCast* x); 475 void do_InstanceOf (InstanceOf* x); 476 void do_MonitorEnter (MonitorEnter* x); 477 void do_MonitorExit (MonitorExit* x); 478 void do_Intrinsic (Intrinsic* x); 479 void do_BlockBegin (BlockBegin* x); 480 void do_Goto (Goto* x); 481 void do_If (If* x); 482 void do_IfInstanceOf (IfInstanceOf* x); 483 void do_TableSwitch (TableSwitch* x); 484 void do_LookupSwitch (LookupSwitch* x); 485 void do_Return (Return* x); 486 void do_Throw (Throw* x); 487 void do_Base (Base* x); 488 void do_OsrEntry (OsrEntry* x); 489 void do_ExceptionObject(ExceptionObject* x); 490 void do_RoundFP (RoundFP* x); 491 void do_UnsafeGetRaw (UnsafeGetRaw* x); 492 void do_UnsafePutRaw (UnsafePutRaw* x); 493 void do_UnsafeGetObject(UnsafeGetObject* x); 494 void do_UnsafePutObject(UnsafePutObject* x); 495 void do_UnsafePrefetchRead (UnsafePrefetchRead* x); 496 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x); 497 void do_ProfileCall (ProfileCall* x); 498 void do_ProfileInvoke (ProfileInvoke* x); 499}; 500 501 502// Because of a static contained within (for the purpose of iteration 503// over instructions), it is only valid to have one of these active at 504// a time 505class NullCheckEliminator: public ValueVisitor { 506 private: 507 Optimizer* _opt; 508 509 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block 510 BlockList* _work_list; // Basic blocks to visit 511 512 bool visitable(Value x) { 513 assert(_visitable_instructions != NULL, "check"); 514 return _visitable_instructions->contains(x); 515 } 516 void mark_visited(Value x) { 517 assert(_visitable_instructions != NULL, "check"); 518 _visitable_instructions->remove(x); 519 } 520 void mark_visitable(Value x) { 521 assert(_visitable_instructions != NULL, "check"); 522 _visitable_instructions->put(x); 523 } 524 void clear_visitable_state() { 525 assert(_visitable_instructions != NULL, "check"); 526 _visitable_instructions->clear(); 527 } 528 529 ValueSet* _set; // current state, propagated to subsequent BlockBegins 530 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks 531 NullCheckVisitor _visitor; 532 NullCheck* _last_explicit_null_check; 533 534 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); } 535 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); } 536 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); } 537 538 BlockList* work_list() { return _work_list; } 539 540 void iterate_all(); 541 void iterate_one(BlockBegin* block); 542 543 ValueSet* state() { return _set; } 544 void set_state_from (ValueSet* state) { _set->set_from(state); } 545 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; } 546 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; } 547 // Returns true if caused a change in the block's state. 548 bool merge_state_for(BlockBegin* block, 549 ValueSet* incoming_state); 550 551 public: 552 // constructor 553 NullCheckEliminator(Optimizer* opt) 554 : _opt(opt) 555 , _set(new ValueSet()) 556 , _last_explicit_null_check(NULL) 557 , _block_states(BlockBegin::number_of_blocks(), NULL) 558 , _work_list(new BlockList()) { 559 _visitable_instructions = new ValueSet(); 560 _visitor.set_eliminator(this); 561 } 562 563 Optimizer* opt() { return _opt; } 564 IR* ir () { return opt()->ir(); } 565 566 // Process a graph 567 void iterate(BlockBegin* root); 568 569 void visit(Value* f); 570 571 // In some situations (like NullCheck(x); getfield(x)) the debug 572 // information from the explicit NullCheck can be used to populate 573 // the getfield, even if the two instructions are in different 574 // scopes; this allows implicit null checks to be used but the 575 // correct exception information to be generated. We must clear the 576 // last-traversed NullCheck when we reach a potentially-exception- 577 // throwing instruction, as well as in some other cases. 578 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } 579 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } 580 Value last_explicit_null_check_obj() { return (_last_explicit_null_check 581 ? _last_explicit_null_check->obj() 582 : NULL); } 583 NullCheck* consume_last_explicit_null_check() { 584 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); 585 _last_explicit_null_check->set_can_trap(false); 586 return _last_explicit_null_check; 587 } 588 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; } 589 590 // Handlers for relevant instructions 591 // (separated out from NullCheckVisitor for clarity) 592 593 // The basic contract is that these must leave the instruction in 594 // the desired state; must not assume anything about the state of 595 // the instruction. We make multiple passes over some basic blocks 596 // and the last pass is the only one whose result is valid. 597 void handle_AccessField (AccessField* x); 598 void handle_ArrayLength (ArrayLength* x); 599 void handle_LoadIndexed (LoadIndexed* x); 600 void handle_StoreIndexed (StoreIndexed* x); 601 void handle_NullCheck (NullCheck* x); 602 void handle_Invoke (Invoke* x); 603 void handle_NewInstance (NewInstance* x); 604 void handle_NewArray (NewArray* x); 605 void handle_AccessMonitor (AccessMonitor* x); 606 void handle_Intrinsic (Intrinsic* x); 607 void handle_ExceptionObject (ExceptionObject* x); 608 void handle_Phi (Phi* x); 609}; 610 611 612// NEEDS_CLEANUP 613// There may be other instructions which need to clear the last 614// explicit null check. Anything across which we can not hoist the 615// debug information for a NullCheck instruction must clear it. It 616// might be safer to pattern match "NullCheck ; {AccessField, 617// ArrayLength, LoadIndexed}" but it is more easily structured this way. 618// Should test to see performance hit of clearing it for all handlers 619// with empty bodies below. If it is negligible then we should leave 620// that in for safety, otherwise should think more about it. 621void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } 622void NullCheckVisitor::do_Local (Local* x) {} 623void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } 624void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } 625void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } 626void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } 627void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } 628void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } 629void NullCheckVisitor::do_NegateOp (NegateOp* x) {} 630void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } 631void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} 632void NullCheckVisitor::do_LogicOp (LogicOp* x) {} 633void NullCheckVisitor::do_CompareOp (CompareOp* x) {} 634void NullCheckVisitor::do_IfOp (IfOp* x) {} 635void NullCheckVisitor::do_Convert (Convert* x) {} 636void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } 637void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } 638void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } 639void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } 640void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } 641void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } 642void NullCheckVisitor::do_CheckCast (CheckCast* x) {} 643void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} 644void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } 645void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } 646void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); } 647void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} 648void NullCheckVisitor::do_Goto (Goto* x) {} 649void NullCheckVisitor::do_If (If* x) {} 650void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {} 651void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} 652void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} 653void NullCheckVisitor::do_Return (Return* x) {} 654void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } 655void NullCheckVisitor::do_Base (Base* x) {} 656void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} 657void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } 658void NullCheckVisitor::do_RoundFP (RoundFP* x) {} 659void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {} 660void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {} 661void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {} 662void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {} 663void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {} 664void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {} 665void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); } 666void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} 667 668 669void NullCheckEliminator::visit(Value* p) { 670 assert(*p != NULL, "should not find NULL instructions"); 671 if (visitable(*p)) { 672 mark_visited(*p); 673 (*p)->visit(&_visitor); 674 } 675} 676 677bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { 678 ValueSet* state = state_for(block); 679 if (state == NULL) { 680 state = incoming_state->copy(); 681 set_state_for(block, state); 682 return true; 683 } else { 684 bool changed = state->set_intersect(incoming_state); 685 if (PrintNullCheckElimination && changed) { 686 tty->print_cr("Block %d's null check state changed", block->block_id()); 687 } 688 return changed; 689 } 690} 691 692 693void NullCheckEliminator::iterate_all() { 694 while (work_list()->length() > 0) { 695 iterate_one(work_list()->pop()); 696 } 697} 698 699 700void NullCheckEliminator::iterate_one(BlockBegin* block) { 701 clear_visitable_state(); 702 // clear out an old explicit null checks 703 set_last_explicit_null_check(NULL); 704 705 if (PrintNullCheckElimination) { 706 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", 707 block->block_id(), 708 ir()->method()->holder()->name()->as_utf8(), 709 ir()->method()->name()->as_utf8(), 710 ir()->method()->signature()->as_symbol()->as_utf8()); 711 } 712 713 // Create new state if none present (only happens at root) 714 if (state_for(block) == NULL) { 715 ValueSet* tmp_state = new ValueSet(); 716 set_state_for(block, tmp_state); 717 // Initial state is that local 0 (receiver) is non-null for 718 // non-static methods 719 ValueStack* stack = block->state(); 720 IRScope* scope = stack->scope(); 721 ciMethod* method = scope->method(); 722 if (!method->is_static()) { 723 Local* local0 = stack->local_at(0)->as_Local(); 724 assert(local0 != NULL, "must be"); 725 assert(local0->type() == objectType, "invalid type of receiver"); 726 727 if (local0 != NULL) { 728 // Local 0 is used in this scope 729 tmp_state->put(local0); 730 if (PrintNullCheckElimination) { 731 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); 732 } 733 } 734 } 735 } 736 737 // Must copy block's state to avoid mutating it during iteration 738 // through the block -- otherwise "not-null" states can accidentally 739 // propagate "up" through the block during processing of backward 740 // branches and algorithm is incorrect (and does not converge) 741 set_state_from(state_for(block)); 742 743 // allow visiting of Phis belonging to this block 744 for_each_phi_fun(block, phi, 745 mark_visitable(phi); 746 ); 747 748 BlockEnd* e = block->end(); 749 assert(e != NULL, "incomplete graph"); 750 int i; 751 752 // Propagate the state before this block into the exception 753 // handlers. They aren't true successors since we aren't guaranteed 754 // to execute the whole block before executing them. Also putting 755 // them on first seems to help reduce the amount of iteration to 756 // reach a fixed point. 757 for (i = 0; i < block->number_of_exception_handlers(); i++) { 758 BlockBegin* next = block->exception_handler_at(i); 759 if (merge_state_for(next, state())) { 760 if (!work_list()->contains(next)) { 761 work_list()->push(next); 762 } 763 } 764 } 765 766 // Iterate through block, updating state. 767 for (Instruction* instr = block; instr != NULL; instr = instr->next()) { 768 // Mark instructions in this block as visitable as they are seen 769 // in the instruction list. This keeps the iteration from 770 // visiting instructions which are references in other blocks or 771 // visiting instructions more than once. 772 mark_visitable(instr); 773 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { 774 mark_visited(instr); 775 instr->input_values_do(this); 776 instr->visit(&_visitor); 777 } 778 } 779 780 // Propagate state to successors if necessary 781 for (i = 0; i < e->number_of_sux(); i++) { 782 BlockBegin* next = e->sux_at(i); 783 if (merge_state_for(next, state())) { 784 if (!work_list()->contains(next)) { 785 work_list()->push(next); 786 } 787 } 788 } 789} 790 791 792void NullCheckEliminator::iterate(BlockBegin* block) { 793 work_list()->push(block); 794 iterate_all(); 795} 796 797void NullCheckEliminator::handle_AccessField(AccessField* x) { 798 if (x->is_static()) { 799 if (x->as_LoadField() != NULL) { 800 // If the field is a non-null static final object field (as is 801 // often the case for sun.misc.Unsafe), put this LoadField into 802 // the non-null map 803 ciField* field = x->field(); 804 if (field->is_constant()) { 805 ciConstant field_val = field->constant_value(); 806 BasicType field_type = field_val.basic_type(); 807 if (field_type == T_OBJECT || field_type == T_ARRAY) { 808 ciObject* obj_val = field_val.as_object(); 809 if (!obj_val->is_null_object()) { 810 if (PrintNullCheckElimination) { 811 tty->print_cr("AccessField %d proven non-null by static final non-null oop check", 812 x->id()); 813 } 814 set_put(x); 815 } 816 } 817 } 818 } 819 // Be conservative 820 clear_last_explicit_null_check(); 821 return; 822 } 823 824 Value obj = x->obj(); 825 if (set_contains(obj)) { 826 // Value is non-null => update AccessField 827 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { 828 x->set_explicit_null_check(consume_last_explicit_null_check()); 829 x->set_needs_null_check(true); 830 if (PrintNullCheckElimination) { 831 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", 832 x->explicit_null_check()->id(), x->id(), obj->id()); 833 } 834 } else { 835 x->set_explicit_null_check(NULL); 836 x->set_needs_null_check(false); 837 if (PrintNullCheckElimination) { 838 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); 839 } 840 } 841 } else { 842 set_put(obj); 843 if (PrintNullCheckElimination) { 844 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); 845 } 846 // Ensure previous passes do not cause wrong state 847 x->set_needs_null_check(true); 848 x->set_explicit_null_check(NULL); 849 } 850 clear_last_explicit_null_check(); 851} 852 853 854void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { 855 Value array = x->array(); 856 if (set_contains(array)) { 857 // Value is non-null => update AccessArray 858 if (last_explicit_null_check_obj() == array) { 859 x->set_explicit_null_check(consume_last_explicit_null_check()); 860 x->set_needs_null_check(true); 861 if (PrintNullCheckElimination) { 862 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", 863 x->explicit_null_check()->id(), x->id(), array->id()); 864 } 865 } else { 866 x->set_explicit_null_check(NULL); 867 x->set_needs_null_check(false); 868 if (PrintNullCheckElimination) { 869 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); 870 } 871 } 872 } else { 873 set_put(array); 874 if (PrintNullCheckElimination) { 875 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); 876 } 877 // Ensure previous passes do not cause wrong state 878 x->set_needs_null_check(true); 879 x->set_explicit_null_check(NULL); 880 } 881 clear_last_explicit_null_check(); 882} 883 884 885void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { 886 Value array = x->array(); 887 if (set_contains(array)) { 888 // Value is non-null => update AccessArray 889 if (last_explicit_null_check_obj() == array) { 890 x->set_explicit_null_check(consume_last_explicit_null_check()); 891 x->set_needs_null_check(true); 892 if (PrintNullCheckElimination) { 893 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", 894 x->explicit_null_check()->id(), x->id(), array->id()); 895 } 896 } else { 897 x->set_explicit_null_check(NULL); 898 x->set_needs_null_check(false); 899 if (PrintNullCheckElimination) { 900 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); 901 } 902 } 903 } else { 904 set_put(array); 905 if (PrintNullCheckElimination) { 906 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 907 } 908 // Ensure previous passes do not cause wrong state 909 x->set_needs_null_check(true); 910 x->set_explicit_null_check(NULL); 911 } 912 clear_last_explicit_null_check(); 913} 914 915 916void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { 917 Value array = x->array(); 918 if (set_contains(array)) { 919 // Value is non-null => update AccessArray 920 if (PrintNullCheckElimination) { 921 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); 922 } 923 x->set_needs_null_check(false); 924 } else { 925 set_put(array); 926 if (PrintNullCheckElimination) { 927 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); 928 } 929 // Ensure previous passes do not cause wrong state 930 x->set_needs_null_check(true); 931 } 932 clear_last_explicit_null_check(); 933} 934 935 936void NullCheckEliminator::handle_NullCheck(NullCheck* x) { 937 Value obj = x->obj(); 938 if (set_contains(obj)) { 939 // Already proven to be non-null => this NullCheck is useless 940 if (PrintNullCheckElimination) { 941 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); 942 } 943 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. 944 // The code generator won't emit LIR for a NullCheck that cannot trap. 945 x->set_can_trap(false); 946 } else { 947 // May be null => add to map and set last explicit NullCheck 948 x->set_can_trap(true); 949 // make sure it's pinned if it can trap 950 x->pin(Instruction::PinExplicitNullCheck); 951 set_put(obj); 952 set_last_explicit_null_check(x); 953 if (PrintNullCheckElimination) { 954 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); 955 } 956 } 957} 958 959 960void NullCheckEliminator::handle_Invoke(Invoke* x) { 961 if (!x->has_receiver()) { 962 // Be conservative 963 clear_last_explicit_null_check(); 964 return; 965 } 966 967 Value recv = x->receiver(); 968 if (!set_contains(recv)) { 969 set_put(recv); 970 if (PrintNullCheckElimination) { 971 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); 972 } 973 } 974 clear_last_explicit_null_check(); 975} 976 977 978void NullCheckEliminator::handle_NewInstance(NewInstance* x) { 979 set_put(x); 980 if (PrintNullCheckElimination) { 981 tty->print_cr("NewInstance %d is non-null", x->id()); 982 } 983} 984 985 986void NullCheckEliminator::handle_NewArray(NewArray* x) { 987 set_put(x); 988 if (PrintNullCheckElimination) { 989 tty->print_cr("NewArray %d is non-null", x->id()); 990 } 991} 992 993 994void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { 995 set_put(x); 996 if (PrintNullCheckElimination) { 997 tty->print_cr("ExceptionObject %d is non-null", x->id()); 998 } 999} 1000 1001 1002void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { 1003 Value obj = x->obj(); 1004 if (set_contains(obj)) { 1005 // Value is non-null => update AccessMonitor 1006 if (PrintNullCheckElimination) { 1007 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); 1008 } 1009 x->set_needs_null_check(false); 1010 } else { 1011 set_put(obj); 1012 if (PrintNullCheckElimination) { 1013 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); 1014 } 1015 // Ensure previous passes do not cause wrong state 1016 x->set_needs_null_check(true); 1017 } 1018 clear_last_explicit_null_check(); 1019} 1020 1021 1022void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { 1023 if (!x->has_receiver()) { 1024 // Be conservative 1025 clear_last_explicit_null_check(); 1026 return; 1027 } 1028 1029 Value recv = x->receiver(); 1030 if (set_contains(recv)) { 1031 // Value is non-null => update Intrinsic 1032 if (PrintNullCheckElimination) { 1033 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id()); 1034 } 1035 x->set_needs_null_check(false); 1036 } else { 1037 set_put(recv); 1038 if (PrintNullCheckElimination) { 1039 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id()); 1040 } 1041 // Ensure previous passes do not cause wrong state 1042 x->set_needs_null_check(true); 1043 } 1044 clear_last_explicit_null_check(); 1045} 1046 1047 1048void NullCheckEliminator::handle_Phi(Phi* x) { 1049 int i; 1050 bool all_non_null = true; 1051 if (x->is_illegal()) { 1052 all_non_null = false; 1053 } else { 1054 for (i = 0; i < x->operand_count(); i++) { 1055 Value input = x->operand_at(i); 1056 if (!set_contains(input)) { 1057 all_non_null = false; 1058 } 1059 } 1060 } 1061 1062 if (all_non_null) { 1063 // Value is non-null => update Phi 1064 if (PrintNullCheckElimination) { 1065 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); 1066 } 1067 x->set_needs_null_check(false); 1068 } else if (set_contains(x)) { 1069 set_remove(x); 1070 } 1071} 1072 1073 1074void Optimizer::eliminate_null_checks() { 1075 ResourceMark rm; 1076 1077 NullCheckEliminator nce(this); 1078 1079 if (PrintNullCheckElimination) { 1080 tty->print_cr("Starting null check elimination for method %s::%s%s", 1081 ir()->method()->holder()->name()->as_utf8(), 1082 ir()->method()->name()->as_utf8(), 1083 ir()->method()->signature()->as_symbol()->as_utf8()); 1084 } 1085 1086 // Apply to graph 1087 nce.iterate(ir()->start()); 1088 1089 // walk over the graph looking for exception 1090 // handlers and iterate over them as well 1091 int nblocks = BlockBegin::number_of_blocks(); 1092 BlockList blocks(nblocks); 1093 boolArray visited_block(nblocks, false); 1094 1095 blocks.push(ir()->start()); 1096 visited_block[ir()->start()->block_id()] = true; 1097 for (int i = 0; i < blocks.length(); i++) { 1098 BlockBegin* b = blocks[i]; 1099 // exception handlers need to be treated as additional roots 1100 for (int e = b->number_of_exception_handlers(); e-- > 0; ) { 1101 BlockBegin* excp = b->exception_handler_at(e); 1102 int id = excp->block_id(); 1103 if (!visited_block[id]) { 1104 blocks.push(excp); 1105 visited_block[id] = true; 1106 nce.iterate(excp); 1107 } 1108 } 1109 // traverse successors 1110 BlockEnd *end = b->end(); 1111 for (int s = end->number_of_sux(); s-- > 0; ) { 1112 BlockBegin* next = end->sux_at(s); 1113 int id = next->block_id(); 1114 if (!visited_block[id]) { 1115 blocks.push(next); 1116 visited_block[id] = true; 1117 } 1118 } 1119 } 1120 1121 1122 if (PrintNullCheckElimination) { 1123 tty->print_cr("Done with null check elimination for method %s::%s%s", 1124 ir()->method()->holder()->name()->as_utf8(), 1125 ir()->method()->name()->as_utf8(), 1126 ir()->method()->signature()->as_symbol()->as_utf8()); 1127 } 1128} 1129