1 /*
2 * Copyright (c) 1999, 2025, 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 "c1/c1_Optimizer.hpp"
26 #include "c1/c1_ValueSet.hpp"
27 #include "c1/c1_ValueStack.hpp"
28 #include "compiler/compileLog.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "utilities/bitMap.inline.hpp"
31
32 typedef GrowableArray<ValueSet*> ValueSetList;
33
34 Optimizer::Optimizer(IR* ir) {
35 assert(ir->is_valid(), "IR must be valid");
36 _ir = ir;
37 }
38
39 class CE_Eliminator: public BlockClosure {
40 private:
41 IR* _hir;
42 int _cee_count; // the number of CEs successfully eliminated
43 int _ifop_count; // the number of IfOps successfully simplified
44 int _has_substitution;
45
46 public:
47 CE_Eliminator(IR* hir) : _hir(hir), _cee_count(0), _ifop_count(0) {
48 _has_substitution = false;
49 _hir->iterate_preorder(this);
50 if (_has_substitution) {
51 // substituted some ifops/phis, so resolve the substitution
52 SubstitutionResolver sr(_hir);
53 }
54
55 CompileLog* log = _hir->compilation()->log();
56 if (log != nullptr)
57 log->set_context("optimize name='cee'");
58 }
59
60 ~CE_Eliminator() {
61 CompileLog* log = _hir->compilation()->log();
62 if (log != nullptr)
63 log->clear_context(); // skip marker if nothing was printed
64 }
65
66 int cee_count() const { return _cee_count; }
67 int ifop_count() const { return _ifop_count; }
68
69 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
70 int e = sux->number_of_exception_handlers();
71 for (int i = 0; i < e; i++) {
72 BlockBegin* xhandler = sux->exception_handler_at(i);
73 block->add_exception_handler(xhandler);
74
75 assert(xhandler->is_predecessor(sux), "missing predecessor");
76 if (sux->number_of_preds() == 0) {
77 // sux is disconnected from graph so disconnect from exception handlers
78 xhandler->remove_predecessor(sux);
79 }
80 if (!xhandler->is_predecessor(block)) {
81 xhandler->add_predecessor(block);
82 }
83 }
84 }
85
86 virtual void block_do(BlockBegin* block);
87
88 private:
89 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval,
90 ValueStack* state_before, bool substitutability_check);
91 };
92
93 void CE_Eliminator::block_do(BlockBegin* block) {
94 // 1) find conditional expression
95 // check if block ends with an If
96 If* if_ = block->end()->as_If();
97 if (if_ == nullptr) return;
98
99 // check if If works on int or object types
100 // (we cannot handle If's working on long, float or doubles yet,
101 // since IfOp doesn't support them - these If's show up if cmp
102 // operations followed by If's are eliminated)
103 ValueType* if_type = if_->x()->type();
104 if (!if_type->is_int() && !if_type->is_object()) return;
105
106 BlockBegin* t_block = if_->tsux();
107 BlockBegin* f_block = if_->fsux();
108 Instruction* t_cur = t_block->next();
109 Instruction* f_cur = f_block->next();
110
111 // one Constant may be present between BlockBegin and BlockEnd
112 Value t_const = nullptr;
113 Value f_const = nullptr;
114 if (t_cur->as_Constant() != nullptr && !t_cur->can_trap()) {
115 t_const = t_cur;
116 t_cur = t_cur->next();
117 }
118 if (f_cur->as_Constant() != nullptr && !f_cur->can_trap()) {
119 f_const = f_cur;
120 f_cur = f_cur->next();
121 }
122
123 // check if both branches end with a goto
124 Goto* t_goto = t_cur->as_Goto();
125 if (t_goto == nullptr) return;
126 Goto* f_goto = f_cur->as_Goto();
127 if (f_goto == nullptr) return;
128
129 // check if both gotos merge into the same block
130 BlockBegin* sux = t_goto->default_sux();
131 if (sux != f_goto->default_sux()) return;
132
133 // check if at least one word was pushed on sux_state
134 // inlining depths must match
135 ValueStack* if_state = if_->state();
136 ValueStack* sux_state = sux->state();
137 if (if_state->scope()->level() > sux_state->scope()->level()) {
138 while (sux_state->scope() != if_state->scope()) {
139 if_state = if_state->caller_state();
140 assert(if_state != nullptr, "states do not match up");
141 }
142 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
143 while (sux_state->scope() != if_state->scope()) {
144 sux_state = sux_state->caller_state();
145 assert(sux_state != nullptr, "states do not match up");
146 }
147 }
148
149 if (sux_state->stack_size() <= if_state->stack_size()) return;
150
151 // check if phi function is present at end of successor stack and that
152 // only this phi was pushed on the stack
153 Value sux_phi = sux_state->stack_at(if_state->stack_size());
154 if (sux_phi == nullptr || sux_phi->as_Phi() == nullptr || sux_phi->as_Phi()->block() != sux) return;
155 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
156
157 // get the values that were pushed in the true- and false-branch
158 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
159 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
160
161 // backend does not support floats
162 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
163 if (t_value->type()->is_float_kind()) return;
164
165 // check that successor has no other phi functions but sux_phi
166 // this can happen when t_block or f_block contained additional stores to local variables
167 // that are no longer represented by explicit instructions
168 for_each_phi_fun(sux, phi,
169 if (phi != sux_phi) return;
170 );
171 // true and false blocks can't have phis
172 for_each_phi_fun(t_block, phi, return; );
173 for_each_phi_fun(f_block, phi, return; );
174
175 // Only replace safepoint gotos if state_before information is available (if is a safepoint)
176 bool is_safepoint = if_->is_safepoint();
177 if (!is_safepoint && (t_goto->is_safepoint() || f_goto->is_safepoint())) {
178 return;
179 }
180
181 #ifdef ASSERT
182 #define DO_DELAYED_VERIFICATION
183 /*
184 * We need to verify the internal representation after modifying it.
185 * Verifying only the blocks that have been tampered with is cheaper than verifying the whole graph, but we must
186 * capture blocks_to_verify_later before making the changes, since they might not be reachable afterwards.
187 * DO_DELAYED_VERIFICATION ensures that the code for this is either enabled in full, or not at all.
188 */
189 #endif // ASSERT
190
191 #ifdef DO_DELAYED_VERIFICATION
192 BlockList blocks_to_verify_later;
193 blocks_to_verify_later.append(block);
194 blocks_to_verify_later.append(t_block);
195 blocks_to_verify_later.append(f_block);
196 blocks_to_verify_later.append(sux);
197 _hir->expand_with_neighborhood(blocks_to_verify_later);
198 #endif // DO_DELAYED_VERIFICATION
199
200 // 2) substitute conditional expression
201 // with an IfOp followed by a Goto
202 // cut if_ away and get node before
203 Instruction* cur_end = if_->prev();
204
205 // append constants of true- and false-block if necessary
206 // clone constants because original block must not be destroyed
207 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
208 if (t_value == t_const) {
209 t_value = new Constant(t_const->type());
210 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
211 cur_end = cur_end->set_next(t_value);
212 }
213 if (f_value == f_const) {
214 f_value = new Constant(f_const->type());
215 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
216 cur_end = cur_end->set_next(f_value);
217 }
218
219 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value,
220 if_->state_before(), if_->substitutability_check());
221 assert(result != nullptr, "make_ifop must return a non-null instruction");
222 if (!result->is_linked() && result->can_be_linked()) {
223 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
224 cur_end = cur_end->set_next(result);
225 }
226
227 // append Goto to successor
228 ValueStack* state_before = if_->state_before();
229 Goto* goto_ = new Goto(sux, state_before, is_safepoint);
230
231 // prepare state for Goto
232 ValueStack* goto_state = if_state;
233 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
234 goto_state->push(result->type(), result);
235 assert(goto_state->is_same(sux_state), "states must match now");
236 goto_->set_state(goto_state);
237
238 cur_end = cur_end->set_next(goto_, goto_state->bci());
239
240 // Adjust control flow graph
241 BlockBegin::disconnect_edge(block, t_block);
242 BlockBegin::disconnect_edge(block, f_block);
243 if (t_block->number_of_preds() == 0) {
244 BlockBegin::disconnect_edge(t_block, sux);
245 }
246 adjust_exception_edges(block, t_block);
247 if (f_block->number_of_preds() == 0) {
248 BlockBegin::disconnect_edge(f_block, sux);
249 }
250 adjust_exception_edges(block, f_block);
251
252 // update block end
253 block->set_end(goto_);
254
255 // substitute the phi if possible
256 if (sux_phi->as_Phi()->operand_count() == 1) {
257 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
258 sux_phi->set_subst(result);
259 _has_substitution = true;
260 }
261
262 // 3) successfully eliminated a conditional expression
263 _cee_count++;
264 if (PrintCEE) {
265 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());
266 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
267 }
268
269 #ifdef DO_DELAYED_VERIFICATION
270 _hir->verify_local(blocks_to_verify_later);
271 #endif // DO_DELAYED_VERIFICATION
272
273 }
274
275 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval,
276 ValueStack* state_before, bool substitutability_check) {
277 if (!OptimizeIfOps) {
278 return new IfOp(x, cond, y, tval, fval, state_before, substitutability_check);
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, state_before, substitutability_check);
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, state_before, substitutability_check);
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 && !ifop->substitutability_check()) {
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(), ifop->substitutability_check());
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_UnsafeGet (UnsafeGet* x);
584 void do_UnsafePut (UnsafePut* x);
585 void do_UnsafeGetAndSet(UnsafeGetAndSet* x);
586 void do_ProfileCall (ProfileCall* x);
587 void do_ProfileReturnType (ProfileReturnType* x);
588 void do_ProfileACmpTypes(ProfileACmpTypes* 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_ProfileACmpTypes(ProfileACmpTypes* x);
718 void handle_Constant (Constant* x);
719 void handle_IfOp (IfOp* x);
720 };
721
722
723 // NEEDS_CLEANUP
724 // There may be other instructions which need to clear the last
725 // explicit null check. Anything across which we can not hoist the
726 // debug information for a NullCheck instruction must clear it. It
727 // might be safer to pattern match "NullCheck ; {AccessField,
728 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
729 // Should test to see performance hit of clearing it for all handlers
730 // with empty bodies below. If it is negligible then we should leave
731 // that in for safety, otherwise should think more about it.
732 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
733 void NullCheckVisitor::do_Local (Local* x) {}
734 void NullCheckVisitor::do_Constant (Constant* x) { nce()->handle_Constant(x); }
735 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
736 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
737 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
738 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
739 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
740 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
741 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
742 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
743 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
744 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
745 void NullCheckVisitor::do_IfOp (IfOp* x) { nce()->handle_IfOp(x); }
746 void NullCheckVisitor::do_Convert (Convert* x) {}
747 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
748 void NullCheckVisitor::do_TypeCast (TypeCast* x) {}
749 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
750 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
751 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
752 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
753 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
754 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
755 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
756 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
757 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
758 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
759 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
760 void NullCheckVisitor::do_Goto (Goto* x) {}
761 void NullCheckVisitor::do_If (If* x) {}
762 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
763 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
764 void NullCheckVisitor::do_Return (Return* x) {}
765 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
766 void NullCheckVisitor::do_Base (Base* x) {}
767 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
768 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(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_ProfileACmpTypes(ProfileACmpTypes* x) { nce()->handle_ProfileACmpTypes(x); }
777 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
778 void NullCheckVisitor::do_MemBar (MemBar* x) {}
779 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
780 #ifdef ASSERT
781 void NullCheckVisitor::do_Assert (Assert* x) {}
782 #endif
783
784 void NullCheckEliminator::visit(Value* p) {
785 assert(*p != nullptr, "should not find null instructions");
786 if (visitable(*p)) {
787 mark_visited(*p);
788 (*p)->visit(&_visitor);
789 }
790 }
791
792 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
793 ValueSet* state = state_for(block);
794 if (state == nullptr) {
795 state = incoming_state->copy();
796 set_state_for(block, state);
797 return true;
798 } else {
799 bool changed = state->set_intersect(incoming_state);
800 if (PrintNullCheckElimination && changed) {
801 tty->print_cr("Block %d's null check state changed", block->block_id());
802 }
803 return changed;
804 }
805 }
806
807
808 void NullCheckEliminator::iterate_all() {
809 while (work_list()->length() > 0) {
810 iterate_one(work_list()->pop());
811 }
812 }
813
814
815 void NullCheckEliminator::iterate_one(BlockBegin* block) {
816 clear_visitable_state();
817 // clear out an old explicit null checks
818 set_last_explicit_null_check(nullptr);
819
820 if (PrintNullCheckElimination) {
821 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
822 block->block_id(),
823 ir()->method()->holder()->name()->as_utf8(),
824 ir()->method()->name()->as_utf8(),
825 ir()->method()->signature()->as_symbol()->as_utf8());
826 }
827
828 // Create new state if none present (only happens at root)
829 if (state_for(block) == nullptr) {
830 ValueSet* tmp_state = new ValueSet();
831 set_state_for(block, tmp_state);
832 // Initial state is that local 0 (receiver) is non-null for
833 // non-static methods
834 ValueStack* stack = block->state();
835 IRScope* scope = stack->scope();
836 ciMethod* method = scope->method();
837 if (!method->is_static()) {
838 Local* local0 = stack->local_at(0)->as_Local();
839 assert(local0 != nullptr, "must be");
840 assert(local0->type() == objectType, "invalid type of receiver");
841
842 if (local0 != nullptr) {
843 // Local 0 is used in this scope
844 tmp_state->put(local0);
845 if (PrintNullCheckElimination) {
846 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
847 }
848 }
849 }
850 }
851
852 // Must copy block's state to avoid mutating it during iteration
853 // through the block -- otherwise "not-null" states can accidentally
854 // propagate "up" through the block during processing of backward
855 // branches and algorithm is incorrect (and does not converge)
856 set_state_from(state_for(block));
857
858 // allow visiting of Phis belonging to this block
859 for_each_phi_fun(block, phi,
860 mark_visitable(phi);
861 );
862
863 BlockEnd* e = block->end();
864 assert(e != nullptr, "incomplete graph");
865 int i;
866
867 // Propagate the state before this block into the exception
868 // handlers. They aren't true successors since we aren't guaranteed
869 // to execute the whole block before executing them. Also putting
870 // them on first seems to help reduce the amount of iteration to
871 // reach a fixed point.
872 for (i = 0; i < block->number_of_exception_handlers(); i++) {
873 BlockBegin* next = block->exception_handler_at(i);
874 if (merge_state_for(next, state())) {
875 if (!work_list()->contains(next)) {
876 work_list()->push(next);
877 }
878 }
879 }
880
881 // Iterate through block, updating state.
882 for (Instruction* instr = block; instr != nullptr; instr = instr->next()) {
883 // Mark instructions in this block as visitable as they are seen
884 // in the instruction list. This keeps the iteration from
885 // visiting instructions which are references in other blocks or
886 // visiting instructions more than once.
887 mark_visitable(instr);
888 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != nullptr)
889 || (instr->as_Constant() != nullptr && instr->as_Constant()->type()->is_object())
890 || (instr->as_IfOp() != nullptr)) {
891 mark_visited(instr);
892 instr->input_values_do(this);
893 instr->visit(&_visitor);
894 }
895 }
896
897 // Propagate state to successors if necessary
898 for (i = 0; i < e->number_of_sux(); i++) {
899 BlockBegin* next = e->sux_at(i);
900 if (merge_state_for(next, state())) {
901 if (!work_list()->contains(next)) {
902 work_list()->push(next);
903 }
904 }
905 }
906 }
907
908
909 void NullCheckEliminator::iterate(BlockBegin* block) {
910 work_list()->push(block);
911 iterate_all();
912 }
913
914 void NullCheckEliminator::handle_AccessField(AccessField* x) {
915 if (x->is_static()) {
916 if (x->as_LoadField() != nullptr) {
917 // If the field is a non-null static final object field (as is
918 // often the case for sun.misc.Unsafe), put this LoadField into
919 // the non-null map
920 ciField* field = x->field();
921 if (field->is_constant()) {
922 ciConstant field_val = field->constant_value();
923 BasicType field_type = field_val.basic_type();
924 if (is_reference_type(field_type)) {
925 ciObject* obj_val = field_val.as_object();
926 if (!obj_val->is_null_object()) {
927 if (PrintNullCheckElimination) {
928 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
929 x->id());
930 }
931 set_put(x);
932 }
933 }
934 }
935 }
936 // Be conservative
937 clear_last_explicit_null_check();
938 return;
939 }
940
941 Value obj = x->obj();
942 if (set_contains(obj)) {
943 // Value is non-null => update AccessField
944 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
945 x->set_explicit_null_check(consume_last_explicit_null_check());
946 x->set_needs_null_check(true);
947 if (PrintNullCheckElimination) {
948 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
949 x->explicit_null_check()->id(), x->id(), obj->id());
950 }
951 } else {
952 x->set_explicit_null_check(nullptr);
953 x->set_needs_null_check(false);
954 if (PrintNullCheckElimination) {
955 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
956 }
957 }
958 } else {
959 set_put(obj);
960 if (PrintNullCheckElimination) {
961 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
962 }
963 // Ensure previous passes do not cause wrong state
964 x->set_needs_null_check(true);
965 x->set_explicit_null_check(nullptr);
966 }
967 clear_last_explicit_null_check();
968 }
969
970
971 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
972 Value array = x->array();
973 if (set_contains(array)) {
974 // Value is non-null => update AccessArray
975 if (last_explicit_null_check_obj() == array) {
976 x->set_explicit_null_check(consume_last_explicit_null_check());
977 x->set_needs_null_check(true);
978 if (PrintNullCheckElimination) {
979 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
980 x->explicit_null_check()->id(), x->id(), array->id());
981 }
982 } else {
983 x->set_explicit_null_check(nullptr);
984 x->set_needs_null_check(false);
985 if (PrintNullCheckElimination) {
986 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
987 }
988 }
989 } else {
990 set_put(array);
991 if (PrintNullCheckElimination) {
992 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
993 }
994 // Ensure previous passes do not cause wrong state
995 x->set_needs_null_check(true);
996 x->set_explicit_null_check(nullptr);
997 }
998 clear_last_explicit_null_check();
999 }
1000
1001
1002 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
1003 Value array = x->array();
1004 if (set_contains(array)) {
1005 // Value is non-null => update AccessArray
1006 if (last_explicit_null_check_obj() == array) {
1007 x->set_explicit_null_check(consume_last_explicit_null_check());
1008 x->set_needs_null_check(true);
1009 if (PrintNullCheckElimination) {
1010 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
1011 x->explicit_null_check()->id(), x->id(), array->id());
1012 }
1013 } else {
1014 x->set_explicit_null_check(nullptr);
1015 x->set_needs_null_check(false);
1016 if (PrintNullCheckElimination) {
1017 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
1018 }
1019 }
1020 } else {
1021 set_put(array);
1022 if (PrintNullCheckElimination) {
1023 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1024 }
1025 // Ensure previous passes do not cause wrong state
1026 x->set_needs_null_check(true);
1027 x->set_explicit_null_check(nullptr);
1028 }
1029 clear_last_explicit_null_check();
1030 }
1031
1032
1033 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
1034 Value array = x->array();
1035 if (set_contains(array)) {
1036 // Value is non-null => update AccessArray
1037 if (PrintNullCheckElimination) {
1038 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
1039 }
1040 x->set_needs_null_check(false);
1041 } else {
1042 set_put(array);
1043 if (PrintNullCheckElimination) {
1044 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1045 }
1046 // Ensure previous passes do not cause wrong state
1047 x->set_needs_null_check(true);
1048 }
1049 clear_last_explicit_null_check();
1050 }
1051
1052
1053 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
1054 Value obj = x->obj();
1055 if (set_contains(obj)) {
1056 // Already proven to be non-null => this NullCheck is useless
1057 if (PrintNullCheckElimination) {
1058 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
1059 }
1060 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
1061 // The code generator won't emit LIR for a NullCheck that cannot trap.
1062 x->set_can_trap(false);
1063 } else {
1064 // May be null => add to map and set last explicit NullCheck
1065 x->set_can_trap(true);
1066 // make sure it's pinned if it can trap
1067 x->pin(Instruction::PinExplicitNullCheck);
1068 set_put(obj);
1069 set_last_explicit_null_check(x);
1070 if (PrintNullCheckElimination) {
1071 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
1072 }
1073 }
1074 }
1075
1076
1077 void NullCheckEliminator::handle_Invoke(Invoke* x) {
1078 if (!x->has_receiver()) {
1079 // Be conservative
1080 clear_last_explicit_null_check();
1081 return;
1082 }
1083
1084 Value recv = x->receiver();
1085 if (!set_contains(recv)) {
1086 set_put(recv);
1087 if (PrintNullCheckElimination) {
1088 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
1089 }
1090 }
1091 clear_last_explicit_null_check();
1092 }
1093
1094
1095 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
1096 set_put(x);
1097 if (PrintNullCheckElimination) {
1098 tty->print_cr("NewInstance %d is non-null", x->id());
1099 }
1100 }
1101
1102
1103 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1104 set_put(x);
1105 if (PrintNullCheckElimination) {
1106 tty->print_cr("NewArray %d is non-null", x->id());
1107 }
1108 }
1109
1110
1111 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1112 set_put(x);
1113 if (PrintNullCheckElimination) {
1114 tty->print_cr("ExceptionObject %d is non-null", x->id());
1115 }
1116 }
1117
1118
1119 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1120 Value obj = x->obj();
1121 if (set_contains(obj)) {
1122 // Value is non-null => update AccessMonitor
1123 if (PrintNullCheckElimination) {
1124 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1125 }
1126 x->set_needs_null_check(false);
1127 } else {
1128 set_put(obj);
1129 if (PrintNullCheckElimination) {
1130 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1131 }
1132 // Ensure previous passes do not cause wrong state
1133 x->set_needs_null_check(true);
1134 }
1135 clear_last_explicit_null_check();
1136 }
1137
1138
1139 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1140 if (!x->has_receiver()) {
1141 if (x->id() == vmIntrinsics::_arraycopy) {
1142 for (int i = 0; i < x->number_of_arguments(); i++) {
1143 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1144 }
1145 }
1146
1147 // Be conservative
1148 clear_last_explicit_null_check();
1149 return;
1150 }
1151
1152 Value recv = x->receiver();
1153 if (set_contains(recv)) {
1154 // Value is non-null => update Intrinsic
1155 if (PrintNullCheckElimination) {
1156 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", vmIntrinsics::as_int(x->id()), recv->id());
1157 }
1158 x->set_needs_null_check(false);
1159 } else {
1160 set_put(recv);
1161 if (PrintNullCheckElimination) {
1162 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", vmIntrinsics::as_int(x->id()), recv->id());
1163 }
1164 // Ensure previous passes do not cause wrong state
1165 x->set_needs_null_check(true);
1166 }
1167 clear_last_explicit_null_check();
1168 }
1169
1170
1171 void NullCheckEliminator::handle_Phi(Phi* x) {
1172 int i;
1173 bool all_non_null = true;
1174 if (x->is_illegal()) {
1175 all_non_null = false;
1176 } else {
1177 for (i = 0; i < x->operand_count(); i++) {
1178 Value input = x->operand_at(i);
1179 if (!set_contains(input)) {
1180 all_non_null = false;
1181 }
1182 }
1183 }
1184
1185 if (all_non_null) {
1186 // Value is non-null => update Phi
1187 if (PrintNullCheckElimination) {
1188 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1189 }
1190 x->set_needs_null_check(false);
1191 } else if (set_contains(x)) {
1192 set_remove(x);
1193 }
1194 }
1195
1196 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
1197 for (int i = 0; i < x->nb_profiled_args(); i++) {
1198 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
1199 }
1200 }
1201
1202 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
1203 x->set_needs_null_check(!set_contains(x->ret()));
1204 }
1205
1206 void NullCheckEliminator::handle_ProfileACmpTypes(ProfileACmpTypes* x) {
1207 x->set_left_maybe_null(!set_contains(x->left()));
1208 x->set_right_maybe_null(!set_contains(x->right()));
1209 }
1210
1211 void NullCheckEliminator::handle_Constant(Constant *x) {
1212 ObjectType* ot = x->type()->as_ObjectType();
1213 if (ot != nullptr && ot->is_loaded()) {
1214 ObjectConstant* oc = ot->as_ObjectConstant();
1215 if (oc == nullptr || !oc->value()->is_null_object()) {
1216 set_put(x);
1217 if (PrintNullCheckElimination) {
1218 tty->print_cr("Constant %d is non-null", x->id());
1219 }
1220 }
1221 }
1222 }
1223
1224 void NullCheckEliminator::handle_IfOp(IfOp *x) {
1225 if (x->type()->is_object() && set_contains(x->tval()) && set_contains(x->fval())) {
1226 set_put(x);
1227 if (PrintNullCheckElimination) {
1228 tty->print_cr("IfOp %d is non-null", x->id());
1229 }
1230 }
1231 }
1232
1233 void Optimizer::eliminate_null_checks() {
1234 ResourceMark rm;
1235
1236 NullCheckEliminator nce(this);
1237
1238 if (PrintNullCheckElimination) {
1239 tty->print_cr("Starting null check elimination for method %s::%s%s",
1240 ir()->method()->holder()->name()->as_utf8(),
1241 ir()->method()->name()->as_utf8(),
1242 ir()->method()->signature()->as_symbol()->as_utf8());
1243 }
1244
1245 // Apply to graph
1246 nce.iterate(ir()->start());
1247
1248 // walk over the graph looking for exception
1249 // handlers and iterate over them as well
1250 int nblocks = BlockBegin::number_of_blocks();
1251 BlockList blocks(nblocks);
1252 boolArray visited_block(nblocks, nblocks, false);
1253
1254 blocks.push(ir()->start());
1255 visited_block.at_put(ir()->start()->block_id(), true);
1256 for (int i = 0; i < blocks.length(); i++) {
1257 BlockBegin* b = blocks.at(i);
1258 // exception handlers need to be treated as additional roots
1259 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1260 BlockBegin* excp = b->exception_handler_at(e);
1261 int id = excp->block_id();
1262 if (!visited_block.at(id)) {
1263 blocks.push(excp);
1264 visited_block.at_put(id, true);
1265 nce.iterate(excp);
1266 }
1267 }
1268 // traverse successors
1269 BlockEnd *end = b->end();
1270 for (int s = end->number_of_sux(); s-- > 0; ) {
1271 BlockBegin* next = end->sux_at(s);
1272 int id = next->block_id();
1273 if (!visited_block.at(id)) {
1274 blocks.push(next);
1275 visited_block.at_put(id, true);
1276 }
1277 }
1278 }
1279
1280
1281 if (PrintNullCheckElimination) {
1282 tty->print_cr("Done with null check elimination for method %s::%s%s",
1283 ir()->method()->holder()->name()->as_utf8(),
1284 ir()->method()->name()->as_utf8(),
1285 ir()->method()->signature()->as_symbol()->as_utf8());
1286 }
1287 }