1 /*
2 * Copyright (c) 1999, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "c1/c1_Canonicalizer.hpp"
27 #include "c1/c1_Optimizer.hpp"
28 #include "c1/c1_ValueMap.hpp"
29 #include "c1/c1_ValueSet.hpp"
30 #include "c1/c1_ValueStack.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "utilities/bitMap.inline.hpp"
33 #include "compiler/compileLog.hpp"
34
35 typedef GrowableArray<ValueSet*> ValueSetList;
36
37 Optimizer::Optimizer(IR* ir) {
38 assert(ir->is_valid(), "IR must be valid");
39 _ir = ir;
40 }
41
42 class CE_Eliminator: public BlockClosure {
43 private:
44 IR* _hir;
45 int _cee_count; // the number of CEs successfully eliminated
46 int _ifop_count; // the number of IfOps successfully simplified
47 int _has_substitution;
48
49 public:
50 CE_Eliminator(IR* hir) : _hir(hir), _cee_count(0), _ifop_count(0) {
51 _has_substitution = false;
52 _hir->iterate_preorder(this);
53 if (_has_substitution) {
54 // substituted some ifops/phis, so resolve the substitution
55 SubstitutionResolver sr(_hir);
56 }
57
58 CompileLog* log = _hir->compilation()->log();
59 if (log != nullptr)
60 log->set_context("optimize name='cee'");
61 }
62
63 ~CE_Eliminator() {
64 CompileLog* log = _hir->compilation()->log();
65 if (log != nullptr)
66 log->clear_context(); // skip marker if nothing was printed
67 }
68
69 int cee_count() const { return _cee_count; }
70 int ifop_count() const { return _ifop_count; }
71
72 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
73 int e = sux->number_of_exception_handlers();
74 for (int i = 0; i < e; i++) {
75 BlockBegin* xhandler = sux->exception_handler_at(i);
76 block->add_exception_handler(xhandler);
77
78 assert(xhandler->is_predecessor(sux), "missing predecessor");
79 if (sux->number_of_preds() == 0) {
80 // sux is disconnected from graph so disconnect from exception handlers
81 xhandler->remove_predecessor(sux);
82 }
83 if (!xhandler->is_predecessor(block)) {
84 xhandler->add_predecessor(block);
85 }
86 }
87 }
88
89 virtual void block_do(BlockBegin* block);
90
91 private:
92 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
93 };
94
95 void CE_Eliminator::block_do(BlockBegin* block) {
96 // 1) find conditional expression
97 // check if block ends with an If
98 If* if_ = block->end()->as_If();
99 if (if_ == nullptr) return;
100
101 // check if If works on int or object types
102 // (we cannot handle If's working on long, float or doubles yet,
103 // since IfOp doesn't support them - these If's show up if cmp
104 // operations followed by If's are eliminated)
105 ValueType* if_type = if_->x()->type();
106 if (!if_type->is_int() && !if_type->is_object()) return;
107
108 BlockBegin* t_block = if_->tsux();
109 BlockBegin* f_block = if_->fsux();
110 Instruction* t_cur = t_block->next();
111 Instruction* f_cur = f_block->next();
112
113 // one Constant may be present between BlockBegin and BlockEnd
114 Value t_const = nullptr;
115 Value f_const = nullptr;
116 if (t_cur->as_Constant() != nullptr && !t_cur->can_trap()) {
117 t_const = t_cur;
118 t_cur = t_cur->next();
119 }
120 if (f_cur->as_Constant() != nullptr && !f_cur->can_trap()) {
121 f_const = f_cur;
122 f_cur = f_cur->next();
123 }
124
125 // check if both branches end with a goto
126 Goto* t_goto = t_cur->as_Goto();
127 if (t_goto == nullptr) return;
128 Goto* f_goto = f_cur->as_Goto();
129 if (f_goto == nullptr) return;
130
131 // check if both gotos merge into the same block
132 BlockBegin* sux = t_goto->default_sux();
133 if (sux != f_goto->default_sux()) return;
134
135 // check if at least one word was pushed on sux_state
136 // inlining depths must match
137 ValueStack* if_state = if_->state();
138 ValueStack* sux_state = sux->state();
139 if (if_state->scope()->level() > sux_state->scope()->level()) {
140 while (sux_state->scope() != if_state->scope()) {
141 if_state = if_state->caller_state();
142 assert(if_state != nullptr, "states do not match up");
143 }
144 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
145 while (sux_state->scope() != if_state->scope()) {
146 sux_state = sux_state->caller_state();
147 assert(sux_state != nullptr, "states do not match up");
148 }
149 }
150
151 if (sux_state->stack_size() <= if_state->stack_size()) return;
152
153 // check if phi function is present at end of successor stack and that
154 // only this phi was pushed on the stack
155 Value sux_phi = sux_state->stack_at(if_state->stack_size());
156 if (sux_phi == nullptr || sux_phi->as_Phi() == nullptr || sux_phi->as_Phi()->block() != sux) return;
157 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
158
159 // get the values that were pushed in the true- and false-branch
160 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
161 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
162
163 // backend does not support floats
164 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
165 if (t_value->type()->is_float_kind()) return;
166
167 // check that successor has no other phi functions but sux_phi
168 // this can happen when t_block or f_block contained additional stores to local variables
169 // that are no longer represented by explicit instructions
170 for_each_phi_fun(sux, phi,
171 if (phi != sux_phi) return;
172 );
173 // true and false blocks can't have phis
174 for_each_phi_fun(t_block, phi, return; );
175 for_each_phi_fun(f_block, phi, return; );
176
177 // Only replace safepoint gotos if state_before information is available (if is a safepoint)
178 bool is_safepoint = if_->is_safepoint();
179 if (!is_safepoint && (t_goto->is_safepoint() || f_goto->is_safepoint())) {
180 return;
181 }
182
183 #ifdef ASSERT
184 #define DO_DELAYED_VERIFICATION
185 /*
186 * We need to verify the internal representation after modifying it.
187 * Verifying only the blocks that have been tampered with is cheaper than verifying the whole graph, but we must
188 * capture blocks_to_verify_later before making the changes, since they might not be reachable afterwards.
189 * DO_DELAYED_VERIFICATION ensures that the code for this is either enabled in full, or not at all.
190 */
191 #endif // ASSERT
192
193 #ifdef DO_DELAYED_VERIFICATION
194 BlockList blocks_to_verify_later;
195 blocks_to_verify_later.append(block);
196 blocks_to_verify_later.append(t_block);
197 blocks_to_verify_later.append(f_block);
198 blocks_to_verify_later.append(sux);
199 _hir->expand_with_neighborhood(blocks_to_verify_later);
200 #endif // DO_DELAYED_VERIFICATION
201
202 // 2) substitute conditional expression
203 // with an IfOp followed by a Goto
204 // cut if_ away and get node before
205 Instruction* cur_end = if_->prev();
206
207 // append constants of true- and false-block if necessary
208 // clone constants because original block must not be destroyed
209 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
210 if (t_value == t_const) {
211 t_value = new Constant(t_const->type());
212 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
213 cur_end = cur_end->set_next(t_value);
214 }
215 if (f_value == f_const) {
216 f_value = new Constant(f_const->type());
217 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
218 cur_end = cur_end->set_next(f_value);
219 }
220
221 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
222 assert(result != nullptr, "make_ifop must return a non-null instruction");
223 if (!result->is_linked() && result->can_be_linked()) {
224 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
225 cur_end = cur_end->set_next(result);
226 }
227
228 // append Goto to successor
229 ValueStack* state_before = if_->state_before();
230 Goto* goto_ = new Goto(sux, state_before, is_safepoint);
231
232 // prepare state for Goto
233 ValueStack* goto_state = if_state;
234 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
235 goto_state->push(result->type(), result);
236 assert(goto_state->is_same(sux_state), "states must match now");
237 goto_->set_state(goto_state);
238
239 cur_end = cur_end->set_next(goto_, goto_state->bci());
240
241 // Adjust control flow graph
242 BlockBegin::disconnect_edge(block, t_block);
243 BlockBegin::disconnect_edge(block, f_block);
244 if (t_block->number_of_preds() == 0) {
245 BlockBegin::disconnect_edge(t_block, sux);
246 }
247 adjust_exception_edges(block, t_block);
248 if (f_block->number_of_preds() == 0) {
249 BlockBegin::disconnect_edge(f_block, sux);
250 }
251 adjust_exception_edges(block, f_block);
252
253 // update block end
254 block->set_end(goto_);
255
256 // substitute the phi if possible
257 if (sux_phi->as_Phi()->operand_count() == 1) {
258 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
259 sux_phi->set_subst(result);
260 _has_substitution = true;
261 }
262
263 // 3) successfully eliminated a conditional expression
264 _cee_count++;
265 if (PrintCEE) {
266 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());
267 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
268 }
269
270 #ifdef DO_DELAYED_VERIFICATION
271 _hir->verify_local(blocks_to_verify_later);
272 #endif // DO_DELAYED_VERIFICATION
273
274 }
275
276 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
277 if (!OptimizeIfOps) {
278 return new IfOp(x, cond, y, tval, fval);
279 }
280
281 tval = tval->subst();
282 fval = fval->subst();
283 if (tval == fval) {
284 _ifop_count++;
285 return tval;
286 }
287
288 x = x->subst();
289 y = y->subst();
290
291 Constant* y_const = y->as_Constant();
292 if (y_const != nullptr) {
293 IfOp* x_ifop = x->as_IfOp();
294 if (x_ifop != nullptr) { // x is an ifop, y is a constant
295 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
296 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
297
298 if (x_tval_const != nullptr && x_fval_const != nullptr) {
299 Instruction::Condition x_ifop_cond = x_ifop->cond();
300
301 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
302 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
303
304 // not_comparable here is a valid return in case we're comparing unloaded oop constants
305 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
306 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
307 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
308
309 _ifop_count++;
310 if (new_tval == new_fval) {
311 return new_tval;
312 } else {
313 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
314 }
315 }
316 }
317 } else {
318 Constant* x_const = x->as_Constant();
319 if (x_const != nullptr) { // x and y are constants
320 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
321 // not_comparable here is a valid return in case we're comparing unloaded oop constants
322 if (x_compare_res != Constant::not_comparable) {
323 _ifop_count++;
324 return x_compare_res == Constant::cond_true ? tval : fval;
325 }
326 }
327 }
328 }
329 return new IfOp(x, cond, y, tval, fval);
330 }
331
332 void Optimizer::eliminate_conditional_expressions() {
333 // find conditional expressions & replace them with IfOps
334 CE_Eliminator ce(ir());
335 }
336
337 // This removes others' relation to block, but doesn't empty block's lists
338 static void disconnect_from_graph(BlockBegin* block) {
339 for (int p = 0; p < block->number_of_preds(); p++) {
340 BlockBegin* pred = block->pred_at(p);
341 int idx;
342 while ((idx = pred->end()->find_sux(block)) >= 0) {
343 pred->end()->remove_sux_at(idx);
344 }
345 }
346 for (int s = 0; s < block->number_of_sux(); s++) {
347 block->sux_at(s)->remove_predecessor(block);
348 }
349 }
350
351 class BlockMerger: public BlockClosure {
352 private:
353 IR* _hir;
354 int _merge_count; // the number of block pairs successfully merged
355
356 public:
357 BlockMerger(IR* hir)
358 : _hir(hir)
359 , _merge_count(0)
360 {
361 _hir->iterate_preorder(this);
362 CompileLog* log = _hir->compilation()->log();
363 if (log != nullptr)
364 log->set_context("optimize name='eliminate_blocks'");
365 }
366
367 ~BlockMerger() {
368 CompileLog* log = _hir->compilation()->log();
369 if (log != nullptr)
370 log->clear_context(); // skip marker if nothing was printed
371 }
372
373 bool try_merge(BlockBegin* block) {
374 BlockEnd* end = block->end();
375 if (end->as_Goto() == nullptr) return false;
376
377 assert(end->number_of_sux() == 1, "end must have exactly one successor");
378 // Note: It would be sufficient to check for the number of successors (= 1)
379 // in order to decide if this block can be merged potentially. That
380 // would then also include switch statements w/ only a default case.
381 // However, in that case we would need to make sure the switch tag
382 // expression is executed if it can produce observable side effects.
383 // We should probably have the canonicalizer simplifying such switch
384 // statements and then we are sure we don't miss these merge opportunities
385 // here (was bug - gri 7/7/99).
386 BlockBegin* sux = end->default_sux();
387 if (sux->number_of_preds() != 1 || sux->is_entry_block() || end->is_safepoint()) return false;
388 // merge the two blocks
389
390 #ifdef ASSERT
391 // verify that state at the end of block and at the beginning of sux are equal
392 // no phi functions must be present at beginning of sux
393 ValueStack* sux_state = sux->state();
394 ValueStack* end_state = end->state();
395
396 assert(end_state->scope() == sux_state->scope(), "scopes must match");
397 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
398 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
399
400 int index;
401 Value sux_value;
402 for_each_stack_value(sux_state, index, sux_value) {
403 assert(sux_value == end_state->stack_at(index), "stack not equal");
404 }
405 for_each_local_value(sux_state, index, sux_value) {
406 Phi* sux_phi = sux_value->as_Phi();
407 if (sux_phi != nullptr && sux_phi->is_illegal()) continue;
408 assert(sux_value == end_state->local_at(index), "locals not equal");
409 }
410 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
411 #endif
412
413 #ifdef DO_DELAYED_VERIFICATION
414 BlockList blocks_to_verify_later;
415 blocks_to_verify_later.append(block);
416 _hir->expand_with_neighborhood(blocks_to_verify_later);
417 #endif // DO_DELAYED_VERIFICATION
418
419 // find instruction before end & append first instruction of sux block
420 Instruction* prev = end->prev();
421 Instruction* next = sux->next();
422 assert(prev->as_BlockEnd() == nullptr, "must not be a BlockEnd");
423 prev->set_next(next);
424 prev->fixup_block_pointers();
425
426 // disconnect this block from all other blocks
427 disconnect_from_graph(sux);
428 #ifdef DO_DELAYED_VERIFICATION
429 blocks_to_verify_later.remove(sux); // Sux is not part of graph anymore
430 #endif // DO_DELAYED_VERIFICATION
431 block->set_end(sux->end());
432
433 // TODO Should this be done in set_end universally?
434 // add exception handlers of deleted block, if any
435 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
436 BlockBegin* xhandler = sux->exception_handler_at(k);
437 block->add_exception_handler(xhandler);
438
439 // TODO This should be in disconnect from graph...
440 // also substitute predecessor of exception handler
441 assert(xhandler->is_predecessor(sux), "missing predecessor");
442 xhandler->remove_predecessor(sux);
443 if (!xhandler->is_predecessor(block)) {
444 xhandler->add_predecessor(block);
445 }
446 }
447
448 // debugging output
449 _merge_count++;
450 if (PrintBlockElimination) {
451 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
452 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
453 }
454
455 #ifdef DO_DELAYED_VERIFICATION
456 _hir->verify_local(blocks_to_verify_later);
457 #endif // DO_DELAYED_VERIFICATION
458
459 If* if_ = block->end()->as_If();
460 if (if_) {
461 IfOp* ifop = if_->x()->as_IfOp();
462 Constant* con = if_->y()->as_Constant();
463 bool swapped = false;
464 if (!con || !ifop) {
465 ifop = if_->y()->as_IfOp();
466 con = if_->x()->as_Constant();
467 swapped = true;
468 }
469 if (con && ifop) {
470 Constant* tval = ifop->tval()->as_Constant();
471 Constant* fval = ifop->fval()->as_Constant();
472 if (tval && fval) {
473 // Find the instruction before if_, starting with ifop.
474 // When if_ and ifop are not in the same block, prev
475 // becomes null In such (rare) cases it is not
476 // profitable to perform the optimization.
477 Value prev = ifop;
478 while (prev != nullptr && prev->next() != if_) {
479 prev = prev->next();
480 }
481
482 if (prev != nullptr) {
483 Instruction::Condition cond = if_->cond();
484 BlockBegin* tsux = if_->tsux();
485 BlockBegin* fsux = if_->fsux();
486 if (swapped) {
487 cond = Instruction::mirror(cond);
488 }
489
490 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
491 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
492 if (tblock != fblock && !if_->is_safepoint()) {
493 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
494 tblock, fblock, if_->state_before(), if_->is_safepoint());
495 newif->set_state(if_->state()->copy());
496
497 assert(prev->next() == if_, "must be guaranteed by above search");
498 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
499 prev->set_next(newif);
500 block->set_end(newif);
501
502 _merge_count++;
503 if (PrintBlockElimination) {
504 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
505 }
506
507 #ifdef DO_DELAYED_VERIFICATION
508 _hir->verify_local(blocks_to_verify_later);
509 #endif // DO_DELAYED_VERIFICATION
510 }
511 }
512 }
513 }
514 }
515
516 return true;
517 }
518
519 virtual void block_do(BlockBegin* block) {
520 // repeat since the same block may merge again
521 while (try_merge(block)) ;
522 }
523 };
524
525 #ifdef ASSERT
526 #undef DO_DELAYED_VERIFICATION
527 #endif // ASSERT
528
529 void Optimizer::eliminate_blocks() {
530 // merge blocks if possible
531 BlockMerger bm(ir());
532 }
533
534
535 class NullCheckEliminator;
536 class NullCheckVisitor: public InstructionVisitor {
537 private:
538 NullCheckEliminator* _nce;
539 NullCheckEliminator* nce() { return _nce; }
540
541 public:
542 NullCheckVisitor() {}
543
544 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
545
546 void do_Phi (Phi* x);
547 void do_Local (Local* x);
548 void do_Constant (Constant* x);
549 void do_LoadField (LoadField* x);
550 void do_StoreField (StoreField* x);
551 void do_ArrayLength (ArrayLength* x);
552 void do_LoadIndexed (LoadIndexed* x);
553 void do_StoreIndexed (StoreIndexed* x);
554 void do_NegateOp (NegateOp* x);
555 void do_ArithmeticOp (ArithmeticOp* x);
556 void do_ShiftOp (ShiftOp* x);
557 void do_LogicOp (LogicOp* x);
558 void do_CompareOp (CompareOp* x);
559 void do_IfOp (IfOp* x);
560 void do_Convert (Convert* x);
561 void do_NullCheck (NullCheck* x);
562 void do_TypeCast (TypeCast* x);
563 void do_Invoke (Invoke* x);
564 void do_NewInstance (NewInstance* x);
565 void do_NewTypeArray (NewTypeArray* x);
566 void do_NewObjectArray (NewObjectArray* x);
567 void do_NewMultiArray (NewMultiArray* x);
568 void do_CheckCast (CheckCast* x);
569 void do_InstanceOf (InstanceOf* x);
570 void do_MonitorEnter (MonitorEnter* x);
571 void do_MonitorExit (MonitorExit* x);
572 void do_Intrinsic (Intrinsic* x);
573 void do_BlockBegin (BlockBegin* x);
574 void do_Goto (Goto* x);
575 void do_If (If* x);
576 void do_TableSwitch (TableSwitch* x);
577 void do_LookupSwitch (LookupSwitch* x);
578 void do_Return (Return* x);
579 void do_Throw (Throw* x);
580 void do_Base (Base* x);
581 void do_OsrEntry (OsrEntry* x);
582 void do_ExceptionObject(ExceptionObject* x);
583 void do_RoundFP (RoundFP* x);
584 void do_UnsafeGet (UnsafeGet* x);
585 void do_UnsafePut (UnsafePut* x);
586 void do_UnsafeGetAndSet(UnsafeGetAndSet* x);
587 void do_ProfileCall (ProfileCall* x);
588 void do_ProfileReturnType (ProfileReturnType* x);
589 void do_ProfileInvoke (ProfileInvoke* x);
590 void do_RuntimeCall (RuntimeCall* x);
591 void do_MemBar (MemBar* x);
592 void do_RangeCheckPredicate(RangeCheckPredicate* x);
593 #ifdef ASSERT
594 void do_Assert (Assert* x);
595 #endif
596 };
597
598
599 // Because of a static contained within (for the purpose of iteration
600 // over instructions), it is only valid to have one of these active at
601 // a time
602 class NullCheckEliminator: public ValueVisitor {
603 private:
604 Optimizer* _opt;
605
606 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
607 BlockList* _work_list; // Basic blocks to visit
608
609 bool visitable(Value x) {
610 assert(_visitable_instructions != nullptr, "check");
611 return _visitable_instructions->contains(x);
612 }
613 void mark_visited(Value x) {
614 assert(_visitable_instructions != nullptr, "check");
615 _visitable_instructions->remove(x);
616 }
617 void mark_visitable(Value x) {
618 assert(_visitable_instructions != nullptr, "check");
619 _visitable_instructions->put(x);
620 }
621 void clear_visitable_state() {
622 assert(_visitable_instructions != nullptr, "check");
623 _visitable_instructions->clear();
624 }
625
626 ValueSet* _set; // current state, propagated to subsequent BlockBegins
627 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
628 NullCheckVisitor _visitor;
629 NullCheck* _last_explicit_null_check;
630
631 bool set_contains(Value x) { assert(_set != nullptr, "check"); return _set->contains(x); }
632 void set_put (Value x) { assert(_set != nullptr, "check"); _set->put(x); }
633 void set_remove (Value x) { assert(_set != nullptr, "check"); _set->remove(x); }
634
635 BlockList* work_list() { return _work_list; }
636
637 void iterate_all();
638 void iterate_one(BlockBegin* block);
639
640 ValueSet* state() { return _set; }
641 void set_state_from (ValueSet* state) { _set->set_from(state); }
642 ValueSet* state_for (BlockBegin* block) { return _block_states.at(block->block_id()); }
643 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(block->block_id(), stack); }
644 // Returns true if caused a change in the block's state.
645 bool merge_state_for(BlockBegin* block,
646 ValueSet* incoming_state);
647
648 public:
649 // constructor
650 NullCheckEliminator(Optimizer* opt)
651 : _opt(opt)
652 , _work_list(new BlockList())
653 , _set(new ValueSet())
654 , _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), nullptr)
655 , _last_explicit_null_check(nullptr) {
656 _visitable_instructions = new ValueSet();
657 _visitor.set_eliminator(this);
658 CompileLog* log = _opt->ir()->compilation()->log();
659 if (log != nullptr)
660 log->set_context("optimize name='null_check_elimination'");
661 }
662
663 ~NullCheckEliminator() {
664 CompileLog* log = _opt->ir()->compilation()->log();
665 if (log != nullptr)
666 log->clear_context(); // skip marker if nothing was printed
667 }
668
669 Optimizer* opt() { return _opt; }
670 IR* ir () { return opt()->ir(); }
671
672 // Process a graph
673 void iterate(BlockBegin* root);
674
675 void visit(Value* f);
676
677 // In some situations (like NullCheck(x); getfield(x)) the debug
678 // information from the explicit NullCheck can be used to populate
679 // the getfield, even if the two instructions are in different
680 // scopes; this allows implicit null checks to be used but the
681 // correct exception information to be generated. We must clear the
682 // last-traversed NullCheck when we reach a potentially-exception-
683 // throwing instruction, as well as in some other cases.
684 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
685 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
686 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
687 ? _last_explicit_null_check->obj()
688 : nullptr); }
689 NullCheck* consume_last_explicit_null_check() {
690 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
691 _last_explicit_null_check->set_can_trap(false);
692 return _last_explicit_null_check;
693 }
694 void clear_last_explicit_null_check() { _last_explicit_null_check = nullptr; }
695
696 // Handlers for relevant instructions
697 // (separated out from NullCheckVisitor for clarity)
698
699 // The basic contract is that these must leave the instruction in
700 // the desired state; must not assume anything about the state of
701 // the instruction. We make multiple passes over some basic blocks
702 // and the last pass is the only one whose result is valid.
703 void handle_AccessField (AccessField* x);
704 void handle_ArrayLength (ArrayLength* x);
705 void handle_LoadIndexed (LoadIndexed* x);
706 void handle_StoreIndexed (StoreIndexed* x);
707 void handle_NullCheck (NullCheck* x);
708 void handle_Invoke (Invoke* x);
709 void handle_NewInstance (NewInstance* x);
710 void handle_NewArray (NewArray* x);
711 void handle_AccessMonitor (AccessMonitor* x);
712 void handle_Intrinsic (Intrinsic* x);
713 void handle_ExceptionObject (ExceptionObject* x);
714 void handle_Phi (Phi* x);
715 void handle_ProfileCall (ProfileCall* x);
716 void handle_ProfileReturnType (ProfileReturnType* x);
717 void handle_Constant (Constant* x);
718 void handle_IfOp (IfOp* x);
719 };
720
721
722 // NEEDS_CLEANUP
723 // There may be other instructions which need to clear the last
724 // explicit null check. Anything across which we can not hoist the
725 // debug information for a NullCheck instruction must clear it. It
726 // might be safer to pattern match "NullCheck ; {AccessField,
727 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
728 // Should test to see performance hit of clearing it for all handlers
729 // with empty bodies below. If it is negligible then we should leave
730 // that in for safety, otherwise should think more about it.
731 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
732 void NullCheckVisitor::do_Local (Local* x) {}
733 void NullCheckVisitor::do_Constant (Constant* x) { nce()->handle_Constant(x); }
734 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
735 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
736 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
737 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
738 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
739 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
740 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
741 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
742 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
743 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
744 void NullCheckVisitor::do_IfOp (IfOp* x) { nce()->handle_IfOp(x); }
745 void NullCheckVisitor::do_Convert (Convert* x) {}
746 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
747 void NullCheckVisitor::do_TypeCast (TypeCast* x) {}
748 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
749 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
750 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
751 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
752 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
753 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
754 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
755 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
756 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
757 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
758 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
759 void NullCheckVisitor::do_Goto (Goto* x) {}
760 void NullCheckVisitor::do_If (If* x) {}
761 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
762 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
763 void NullCheckVisitor::do_Return (Return* x) {}
764 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
765 void NullCheckVisitor::do_Base (Base* x) {}
766 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
767 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
768 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
769 void NullCheckVisitor::do_UnsafeGet (UnsafeGet* x) {}
770 void NullCheckVisitor::do_UnsafePut (UnsafePut* x) {}
771 void NullCheckVisitor::do_UnsafeGetAndSet(UnsafeGetAndSet* x) {}
772 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check();
773 nce()->handle_ProfileCall(x); }
774 void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
775 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
776 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
777 void NullCheckVisitor::do_MemBar (MemBar* x) {}
778 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
779 #ifdef ASSERT
780 void NullCheckVisitor::do_Assert (Assert* x) {}
781 #endif
782
783 void NullCheckEliminator::visit(Value* p) {
784 assert(*p != nullptr, "should not find null instructions");
785 if (visitable(*p)) {
786 mark_visited(*p);
787 (*p)->visit(&_visitor);
788 }
789 }
790
791 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
792 ValueSet* state = state_for(block);
793 if (state == nullptr) {
794 state = incoming_state->copy();
795 set_state_for(block, state);
796 return true;
797 } else {
798 bool changed = state->set_intersect(incoming_state);
799 if (PrintNullCheckElimination && changed) {
800 tty->print_cr("Block %d's null check state changed", block->block_id());
801 }
802 return changed;
803 }
804 }
805
806
807 void NullCheckEliminator::iterate_all() {
808 while (work_list()->length() > 0) {
809 iterate_one(work_list()->pop());
810 }
811 }
812
813
814 void NullCheckEliminator::iterate_one(BlockBegin* block) {
815 clear_visitable_state();
816 // clear out an old explicit null checks
817 set_last_explicit_null_check(nullptr);
818
819 if (PrintNullCheckElimination) {
820 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
821 block->block_id(),
822 ir()->method()->holder()->name()->as_utf8(),
823 ir()->method()->name()->as_utf8(),
824 ir()->method()->signature()->as_symbol()->as_utf8());
825 }
826
827 // Create new state if none present (only happens at root)
828 if (state_for(block) == nullptr) {
829 ValueSet* tmp_state = new ValueSet();
830 set_state_for(block, tmp_state);
831 // Initial state is that local 0 (receiver) is non-null for
832 // non-static methods
833 ValueStack* stack = block->state();
834 IRScope* scope = stack->scope();
835 ciMethod* method = scope->method();
836 if (!method->is_static()) {
837 Local* local0 = stack->local_at(0)->as_Local();
838 assert(local0 != nullptr, "must be");
839 assert(local0->type() == objectType, "invalid type of receiver");
840
841 if (local0 != nullptr) {
842 // Local 0 is used in this scope
843 tmp_state->put(local0);
844 if (PrintNullCheckElimination) {
845 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
846 }
847 }
848 }
849 }
850
851 // Must copy block's state to avoid mutating it during iteration
852 // through the block -- otherwise "not-null" states can accidentally
853 // propagate "up" through the block during processing of backward
854 // branches and algorithm is incorrect (and does not converge)
855 set_state_from(state_for(block));
856
857 // allow visiting of Phis belonging to this block
858 for_each_phi_fun(block, phi,
859 mark_visitable(phi);
860 );
861
862 BlockEnd* e = block->end();
863 assert(e != nullptr, "incomplete graph");
864 int i;
865
866 // Propagate the state before this block into the exception
867 // handlers. They aren't true successors since we aren't guaranteed
868 // to execute the whole block before executing them. Also putting
869 // them on first seems to help reduce the amount of iteration to
870 // reach a fixed point.
871 for (i = 0; i < block->number_of_exception_handlers(); i++) {
872 BlockBegin* next = block->exception_handler_at(i);
873 if (merge_state_for(next, state())) {
874 if (!work_list()->contains(next)) {
875 work_list()->push(next);
876 }
877 }
878 }
879
880 // Iterate through block, updating state.
881 for (Instruction* instr = block; instr != nullptr; instr = instr->next()) {
882 // Mark instructions in this block as visitable as they are seen
883 // in the instruction list. This keeps the iteration from
884 // visiting instructions which are references in other blocks or
885 // visiting instructions more than once.
886 mark_visitable(instr);
887 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != nullptr)
888 || (instr->as_Constant() != nullptr && instr->as_Constant()->type()->is_object())
889 || (instr->as_IfOp() != nullptr)) {
890 mark_visited(instr);
891 instr->input_values_do(this);
892 instr->visit(&_visitor);
893 }
894 }
895
896 // Propagate state to successors if necessary
897 for (i = 0; i < e->number_of_sux(); i++) {
898 BlockBegin* next = e->sux_at(i);
899 if (merge_state_for(next, state())) {
900 if (!work_list()->contains(next)) {
901 work_list()->push(next);
902 }
903 }
904 }
905 }
906
907
908 void NullCheckEliminator::iterate(BlockBegin* block) {
909 work_list()->push(block);
910 iterate_all();
911 }
912
913 void NullCheckEliminator::handle_AccessField(AccessField* x) {
914 if (x->is_static()) {
915 if (x->as_LoadField() != nullptr) {
916 // If the field is a non-null static final object field (as is
917 // often the case for sun.misc.Unsafe), put this LoadField into
918 // the non-null map
919 ciField* field = x->field();
920 if (field->is_constant()) {
921 ciConstant field_val = field->constant_value();
922 BasicType field_type = field_val.basic_type();
923 if (is_reference_type(field_type)) {
924 ciObject* obj_val = field_val.as_object();
925 if (!obj_val->is_null_object()) {
926 if (PrintNullCheckElimination) {
927 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
928 x->id());
929 }
930 set_put(x);
931 }
932 }
933 }
934 }
935 // Be conservative
936 clear_last_explicit_null_check();
937 return;
938 }
939
940 Value obj = x->obj();
941 if (set_contains(obj)) {
942 // Value is non-null => update AccessField
943 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
944 x->set_explicit_null_check(consume_last_explicit_null_check());
945 x->set_needs_null_check(true);
946 if (PrintNullCheckElimination) {
947 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
948 x->explicit_null_check()->id(), x->id(), obj->id());
949 }
950 } else {
951 x->set_explicit_null_check(nullptr);
952 x->set_needs_null_check(false);
953 if (PrintNullCheckElimination) {
954 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
955 }
956 }
957 } else {
958 set_put(obj);
959 if (PrintNullCheckElimination) {
960 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
961 }
962 // Ensure previous passes do not cause wrong state
963 x->set_needs_null_check(true);
964 x->set_explicit_null_check(nullptr);
965 }
966 clear_last_explicit_null_check();
967 }
968
969
970 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
971 Value array = x->array();
972 if (set_contains(array)) {
973 // Value is non-null => update AccessArray
974 if (last_explicit_null_check_obj() == array) {
975 x->set_explicit_null_check(consume_last_explicit_null_check());
976 x->set_needs_null_check(true);
977 if (PrintNullCheckElimination) {
978 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
979 x->explicit_null_check()->id(), x->id(), array->id());
980 }
981 } else {
982 x->set_explicit_null_check(nullptr);
983 x->set_needs_null_check(false);
984 if (PrintNullCheckElimination) {
985 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
986 }
987 }
988 } else {
989 set_put(array);
990 if (PrintNullCheckElimination) {
991 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
992 }
993 // Ensure previous passes do not cause wrong state
994 x->set_needs_null_check(true);
995 x->set_explicit_null_check(nullptr);
996 }
997 clear_last_explicit_null_check();
998 }
999
1000
1001 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
1002 Value array = x->array();
1003 if (set_contains(array)) {
1004 // Value is non-null => update AccessArray
1005 if (last_explicit_null_check_obj() == array) {
1006 x->set_explicit_null_check(consume_last_explicit_null_check());
1007 x->set_needs_null_check(true);
1008 if (PrintNullCheckElimination) {
1009 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
1010 x->explicit_null_check()->id(), x->id(), array->id());
1011 }
1012 } else {
1013 x->set_explicit_null_check(nullptr);
1014 x->set_needs_null_check(false);
1015 if (PrintNullCheckElimination) {
1016 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
1017 }
1018 }
1019 } else {
1020 set_put(array);
1021 if (PrintNullCheckElimination) {
1022 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1023 }
1024 // Ensure previous passes do not cause wrong state
1025 x->set_needs_null_check(true);
1026 x->set_explicit_null_check(nullptr);
1027 }
1028 clear_last_explicit_null_check();
1029 }
1030
1031
1032 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
1033 Value array = x->array();
1034 if (set_contains(array)) {
1035 // Value is non-null => update AccessArray
1036 if (PrintNullCheckElimination) {
1037 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
1038 }
1039 x->set_needs_null_check(false);
1040 } else {
1041 set_put(array);
1042 if (PrintNullCheckElimination) {
1043 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1044 }
1045 // Ensure previous passes do not cause wrong state
1046 x->set_needs_null_check(true);
1047 }
1048 clear_last_explicit_null_check();
1049 }
1050
1051
1052 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
1053 Value obj = x->obj();
1054 if (set_contains(obj)) {
1055 // Already proven to be non-null => this NullCheck is useless
1056 if (PrintNullCheckElimination) {
1057 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
1058 }
1059 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
1060 // The code generator won't emit LIR for a NullCheck that cannot trap.
1061 x->set_can_trap(false);
1062 } else {
1063 // May be null => add to map and set last explicit NullCheck
1064 x->set_can_trap(true);
1065 // make sure it's pinned if it can trap
1066 x->pin(Instruction::PinExplicitNullCheck);
1067 set_put(obj);
1068 set_last_explicit_null_check(x);
1069 if (PrintNullCheckElimination) {
1070 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
1071 }
1072 }
1073 }
1074
1075
1076 void NullCheckEliminator::handle_Invoke(Invoke* x) {
1077 if (!x->has_receiver()) {
1078 // Be conservative
1079 clear_last_explicit_null_check();
1080 return;
1081 }
1082
1083 Value recv = x->receiver();
1084 if (!set_contains(recv)) {
1085 set_put(recv);
1086 if (PrintNullCheckElimination) {
1087 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
1088 }
1089 }
1090 clear_last_explicit_null_check();
1091 }
1092
1093
1094 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
1095 set_put(x);
1096 if (PrintNullCheckElimination) {
1097 tty->print_cr("NewInstance %d is non-null", x->id());
1098 }
1099 }
1100
1101
1102 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1103 set_put(x);
1104 if (PrintNullCheckElimination) {
1105 tty->print_cr("NewArray %d is non-null", x->id());
1106 }
1107 }
1108
1109
1110 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1111 set_put(x);
1112 if (PrintNullCheckElimination) {
1113 tty->print_cr("ExceptionObject %d is non-null", x->id());
1114 }
1115 }
1116
1117
1118 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1119 Value obj = x->obj();
1120 if (set_contains(obj)) {
1121 // Value is non-null => update AccessMonitor
1122 if (PrintNullCheckElimination) {
1123 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1124 }
1125 x->set_needs_null_check(false);
1126 } else {
1127 set_put(obj);
1128 if (PrintNullCheckElimination) {
1129 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1130 }
1131 // Ensure previous passes do not cause wrong state
1132 x->set_needs_null_check(true);
1133 }
1134 clear_last_explicit_null_check();
1135 }
1136
1137
1138 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1139 if (!x->has_receiver()) {
1140 if (x->id() == vmIntrinsics::_arraycopy) {
1141 for (int i = 0; i < x->number_of_arguments(); i++) {
1142 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1143 }
1144 }
1145
1146 // Be conservative
1147 clear_last_explicit_null_check();
1148 return;
1149 }
1150
1151 Value recv = x->receiver();
1152 if (set_contains(recv)) {
1153 // Value is non-null => update Intrinsic
1154 if (PrintNullCheckElimination) {
1155 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", vmIntrinsics::as_int(x->id()), recv->id());
1156 }
1157 x->set_needs_null_check(false);
1158 } else {
1159 set_put(recv);
1160 if (PrintNullCheckElimination) {
1161 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", vmIntrinsics::as_int(x->id()), recv->id());
1162 }
1163 // Ensure previous passes do not cause wrong state
1164 x->set_needs_null_check(true);
1165 }
1166 clear_last_explicit_null_check();
1167 }
1168
1169
1170 void NullCheckEliminator::handle_Phi(Phi* x) {
1171 int i;
1172 bool all_non_null = true;
1173 if (x->is_illegal()) {
1174 all_non_null = false;
1175 } else {
1176 for (i = 0; i < x->operand_count(); i++) {
1177 Value input = x->operand_at(i);
1178 if (!set_contains(input)) {
1179 all_non_null = false;
1180 }
1181 }
1182 }
1183
1184 if (all_non_null) {
1185 // Value is non-null => update Phi
1186 if (PrintNullCheckElimination) {
1187 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1188 }
1189 x->set_needs_null_check(false);
1190 } else if (set_contains(x)) {
1191 set_remove(x);
1192 }
1193 }
1194
1195 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
1196 for (int i = 0; i < x->nb_profiled_args(); i++) {
1197 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
1198 }
1199 }
1200
1201 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
1202 x->set_needs_null_check(!set_contains(x->ret()));
1203 }
1204
1205 void NullCheckEliminator::handle_Constant(Constant *x) {
1206 ObjectType* ot = x->type()->as_ObjectType();
1207 if (ot != nullptr && ot->is_loaded()) {
1208 ObjectConstant* oc = ot->as_ObjectConstant();
1209 if (oc == nullptr || !oc->value()->is_null_object()) {
1210 set_put(x);
1211 if (PrintNullCheckElimination) {
1212 tty->print_cr("Constant %d is non-null", x->id());
1213 }
1214 }
1215 }
1216 }
1217
1218 void NullCheckEliminator::handle_IfOp(IfOp *x) {
1219 if (x->type()->is_object() && set_contains(x->tval()) && set_contains(x->fval())) {
1220 set_put(x);
1221 if (PrintNullCheckElimination) {
1222 tty->print_cr("IfOp %d is non-null", x->id());
1223 }
1224 }
1225 }
1226
1227 void Optimizer::eliminate_null_checks() {
1228 ResourceMark rm;
1229
1230 NullCheckEliminator nce(this);
1231
1232 if (PrintNullCheckElimination) {
1233 tty->print_cr("Starting null check elimination for method %s::%s%s",
1234 ir()->method()->holder()->name()->as_utf8(),
1235 ir()->method()->name()->as_utf8(),
1236 ir()->method()->signature()->as_symbol()->as_utf8());
1237 }
1238
1239 // Apply to graph
1240 nce.iterate(ir()->start());
1241
1242 // walk over the graph looking for exception
1243 // handlers and iterate over them as well
1244 int nblocks = BlockBegin::number_of_blocks();
1245 BlockList blocks(nblocks);
1246 boolArray visited_block(nblocks, nblocks, false);
1247
1248 blocks.push(ir()->start());
1249 visited_block.at_put(ir()->start()->block_id(), true);
1250 for (int i = 0; i < blocks.length(); i++) {
1251 BlockBegin* b = blocks.at(i);
1252 // exception handlers need to be treated as additional roots
1253 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1254 BlockBegin* excp = b->exception_handler_at(e);
1255 int id = excp->block_id();
1256 if (!visited_block.at(id)) {
1257 blocks.push(excp);
1258 visited_block.at_put(id, true);
1259 nce.iterate(excp);
1260 }
1261 }
1262 // traverse successors
1263 BlockEnd *end = b->end();
1264 for (int s = end->number_of_sux(); s-- > 0; ) {
1265 BlockBegin* next = end->sux_at(s);
1266 int id = next->block_id();
1267 if (!visited_block.at(id)) {
1268 blocks.push(next);
1269 visited_block.at_put(id, true);
1270 }
1271 }
1272 }
1273
1274
1275 if (PrintNullCheckElimination) {
1276 tty->print_cr("Done with null check elimination for method %s::%s%s",
1277 ir()->method()->holder()->name()->as_utf8(),
1278 ir()->method()->name()->as_utf8(),
1279 ir()->method()->signature()->as_symbol()->as_utf8());
1280 }
1281 }