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 ValueStack* state_before, bool substitutability_check);
94 };
95
96 void CE_Eliminator::block_do(BlockBegin* block) {
97 // 1) find conditional expression
98 // check if block ends with an If
99 If* if_ = block->end()->as_If();
100 if (if_ == nullptr) return;
101
102 // check if If works on int or object types
103 // (we cannot handle If's working on long, float or doubles yet,
104 // since IfOp doesn't support them - these If's show up if cmp
105 // operations followed by If's are eliminated)
106 ValueType* if_type = if_->x()->type();
107 if (!if_type->is_int() && !if_type->is_object()) return;
108
109 BlockBegin* t_block = if_->tsux();
110 BlockBegin* f_block = if_->fsux();
111 Instruction* t_cur = t_block->next();
112 Instruction* f_cur = f_block->next();
113
114 // one Constant may be present between BlockBegin and BlockEnd
115 Value t_const = nullptr;
116 Value f_const = nullptr;
117 if (t_cur->as_Constant() != nullptr && !t_cur->can_trap()) {
118 t_const = t_cur;
119 t_cur = t_cur->next();
120 }
121 if (f_cur->as_Constant() != nullptr && !f_cur->can_trap()) {
122 f_const = f_cur;
123 f_cur = f_cur->next();
124 }
125
126 // check if both branches end with a goto
127 Goto* t_goto = t_cur->as_Goto();
128 if (t_goto == nullptr) return;
129 Goto* f_goto = f_cur->as_Goto();
130 if (f_goto == nullptr) return;
131
132 // check if both gotos merge into the same block
133 BlockBegin* sux = t_goto->default_sux();
134 if (sux != f_goto->default_sux()) return;
135
136 // check if at least one word was pushed on sux_state
137 // inlining depths must match
138 ValueStack* if_state = if_->state();
139 ValueStack* sux_state = sux->state();
140 if (if_state->scope()->level() > sux_state->scope()->level()) {
141 while (sux_state->scope() != if_state->scope()) {
142 if_state = if_state->caller_state();
143 assert(if_state != nullptr, "states do not match up");
144 }
145 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
146 while (sux_state->scope() != if_state->scope()) {
147 sux_state = sux_state->caller_state();
148 assert(sux_state != nullptr, "states do not match up");
149 }
150 }
151
152 if (sux_state->stack_size() <= if_state->stack_size()) return;
153
154 // check if phi function is present at end of successor stack and that
155 // only this phi was pushed on the stack
156 Value sux_phi = sux_state->stack_at(if_state->stack_size());
157 if (sux_phi == nullptr || sux_phi->as_Phi() == nullptr || sux_phi->as_Phi()->block() != sux) return;
158 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
159
160 // get the values that were pushed in the true- and false-branch
161 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
162 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
163
164 // backend does not support floats
165 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
166 if (t_value->type()->is_float_kind()) return;
167
168 // check that successor has no other phi functions but sux_phi
169 // this can happen when t_block or f_block contained additional stores to local variables
170 // that are no longer represented by explicit instructions
171 for_each_phi_fun(sux, phi,
172 if (phi != sux_phi) return;
173 );
174 // true and false blocks can't have phis
175 for_each_phi_fun(t_block, phi, return; );
176 for_each_phi_fun(f_block, phi, return; );
177
178 // Only replace safepoint gotos if state_before information is available (if is a safepoint)
179 bool is_safepoint = if_->is_safepoint();
180 if (!is_safepoint && (t_goto->is_safepoint() || f_goto->is_safepoint())) {
181 return;
182 }
183
184 #ifdef ASSERT
185 #define DO_DELAYED_VERIFICATION
186 /*
187 * We need to verify the internal representation after modifying it.
188 * Verifying only the blocks that have been tampered with is cheaper than verifying the whole graph, but we must
189 * capture blocks_to_verify_later before making the changes, since they might not be reachable afterwards.
190 * DO_DELAYED_VERIFICATION ensures that the code for this is either enabled in full, or not at all.
191 */
192 #endif // ASSERT
193
194 #ifdef DO_DELAYED_VERIFICATION
195 BlockList blocks_to_verify_later;
196 blocks_to_verify_later.append(block);
197 blocks_to_verify_later.append(t_block);
198 blocks_to_verify_later.append(f_block);
199 blocks_to_verify_later.append(sux);
200 _hir->expand_with_neighborhood(blocks_to_verify_later);
201 #endif // DO_DELAYED_VERIFICATION
202
203 // 2) substitute conditional expression
204 // with an IfOp followed by a Goto
205 // cut if_ away and get node before
206 Instruction* cur_end = if_->prev();
207
208 // append constants of true- and false-block if necessary
209 // clone constants because original block must not be destroyed
210 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
211 if (t_value == t_const) {
212 t_value = new Constant(t_const->type());
213 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
214 cur_end = cur_end->set_next(t_value);
215 }
216 if (f_value == f_const) {
217 f_value = new Constant(f_const->type());
218 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
219 cur_end = cur_end->set_next(f_value);
220 }
221
222 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value,
223 if_->state_before(), if_->substitutability_check());
224 assert(result != nullptr, "make_ifop must return a non-null instruction");
225 if (!result->is_linked() && result->can_be_linked()) {
226 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
227 cur_end = cur_end->set_next(result);
228 }
229
230 // append Goto to successor
231 ValueStack* state_before = if_->state_before();
232 Goto* goto_ = new Goto(sux, state_before, is_safepoint);
233
234 // prepare state for Goto
235 ValueStack* goto_state = if_state;
236 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
237 goto_state->push(result->type(), result);
238 assert(goto_state->is_same(sux_state), "states must match now");
239 goto_->set_state(goto_state);
240
241 cur_end = cur_end->set_next(goto_, goto_state->bci());
242
243 // Adjust control flow graph
244 BlockBegin::disconnect_edge(block, t_block);
245 BlockBegin::disconnect_edge(block, f_block);
246 if (t_block->number_of_preds() == 0) {
247 BlockBegin::disconnect_edge(t_block, sux);
248 }
249 adjust_exception_edges(block, t_block);
250 if (f_block->number_of_preds() == 0) {
251 BlockBegin::disconnect_edge(f_block, sux);
252 }
253 adjust_exception_edges(block, f_block);
254
255 // update block end
256 block->set_end(goto_);
257
258 // substitute the phi if possible
259 if (sux_phi->as_Phi()->operand_count() == 1) {
260 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
261 sux_phi->set_subst(result);
262 _has_substitution = true;
263 }
264
265 // 3) successfully eliminated a conditional expression
266 _cee_count++;
267 if (PrintCEE) {
268 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());
269 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
270 }
271
272 #ifdef DO_DELAYED_VERIFICATION
273 _hir->verify_local(blocks_to_verify_later);
274 #endif // DO_DELAYED_VERIFICATION
275
276 }
277
278 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval,
279 ValueStack* state_before, bool substitutability_check) {
280 if (!OptimizeIfOps) {
281 return new IfOp(x, cond, y, tval, fval, state_before, substitutability_check);
282 }
283
284 tval = tval->subst();
285 fval = fval->subst();
286 if (tval == fval) {
287 _ifop_count++;
288 return tval;
289 }
290
291 x = x->subst();
292 y = y->subst();
293
294 Constant* y_const = y->as_Constant();
295 if (y_const != nullptr) {
296 IfOp* x_ifop = x->as_IfOp();
297 if (x_ifop != nullptr) { // x is an ifop, y is a constant
298 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
299 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
300
301 if (x_tval_const != nullptr && x_fval_const != nullptr) {
302 Instruction::Condition x_ifop_cond = x_ifop->cond();
303
304 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
305 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
306
307 // not_comparable here is a valid return in case we're comparing unloaded oop constants
308 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
309 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
310 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
311
312 _ifop_count++;
313 if (new_tval == new_fval) {
314 return new_tval;
315 } else {
316 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval, state_before, substitutability_check);
317 }
318 }
319 }
320 } else {
321 Constant* x_const = x->as_Constant();
322 if (x_const != nullptr) { // x and y are constants
323 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
324 // not_comparable here is a valid return in case we're comparing unloaded oop constants
325 if (x_compare_res != Constant::not_comparable) {
326 _ifop_count++;
327 return x_compare_res == Constant::cond_true ? tval : fval;
328 }
329 }
330 }
331 }
332 return new IfOp(x, cond, y, tval, fval, state_before, substitutability_check);
333 }
334
335 void Optimizer::eliminate_conditional_expressions() {
336 // find conditional expressions & replace them with IfOps
337 CE_Eliminator ce(ir());
338 }
339
340 // This removes others' relation to block, but doesn't empty block's lists
341 static void disconnect_from_graph(BlockBegin* block) {
342 for (int p = 0; p < block->number_of_preds(); p++) {
343 BlockBegin* pred = block->pred_at(p);
344 int idx;
345 while ((idx = pred->end()->find_sux(block)) >= 0) {
346 pred->end()->remove_sux_at(idx);
347 }
348 }
349 for (int s = 0; s < block->number_of_sux(); s++) {
350 block->sux_at(s)->remove_predecessor(block);
351 }
352 }
353
354 class BlockMerger: public BlockClosure {
355 private:
356 IR* _hir;
357 int _merge_count; // the number of block pairs successfully merged
358
359 public:
360 BlockMerger(IR* hir)
361 : _hir(hir)
362 , _merge_count(0)
363 {
364 _hir->iterate_preorder(this);
365 CompileLog* log = _hir->compilation()->log();
366 if (log != nullptr)
367 log->set_context("optimize name='eliminate_blocks'");
368 }
369
370 ~BlockMerger() {
371 CompileLog* log = _hir->compilation()->log();
372 if (log != nullptr)
373 log->clear_context(); // skip marker if nothing was printed
374 }
375
376 bool try_merge(BlockBegin* block) {
377 BlockEnd* end = block->end();
378 if (end->as_Goto() == nullptr) return false;
379
380 assert(end->number_of_sux() == 1, "end must have exactly one successor");
381 // Note: It would be sufficient to check for the number of successors (= 1)
382 // in order to decide if this block can be merged potentially. That
383 // would then also include switch statements w/ only a default case.
384 // However, in that case we would need to make sure the switch tag
385 // expression is executed if it can produce observable side effects.
386 // We should probably have the canonicalizer simplifying such switch
387 // statements and then we are sure we don't miss these merge opportunities
388 // here (was bug - gri 7/7/99).
389 BlockBegin* sux = end->default_sux();
390 if (sux->number_of_preds() != 1 || sux->is_entry_block() || end->is_safepoint()) return false;
391 // merge the two blocks
392
393 #ifdef ASSERT
394 // verify that state at the end of block and at the beginning of sux are equal
395 // no phi functions must be present at beginning of sux
396 ValueStack* sux_state = sux->state();
397 ValueStack* end_state = end->state();
398
399 assert(end_state->scope() == sux_state->scope(), "scopes must match");
400 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
401 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
402
403 int index;
404 Value sux_value;
405 for_each_stack_value(sux_state, index, sux_value) {
406 assert(sux_value == end_state->stack_at(index), "stack not equal");
407 }
408 for_each_local_value(sux_state, index, sux_value) {
409 Phi* sux_phi = sux_value->as_Phi();
410 if (sux_phi != nullptr && sux_phi->is_illegal()) continue;
411 assert(sux_value == end_state->local_at(index), "locals not equal");
412 }
413 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
414 #endif
415
416 #ifdef DO_DELAYED_VERIFICATION
417 BlockList blocks_to_verify_later;
418 blocks_to_verify_later.append(block);
419 _hir->expand_with_neighborhood(blocks_to_verify_later);
420 #endif // DO_DELAYED_VERIFICATION
421
422 // find instruction before end & append first instruction of sux block
423 Instruction* prev = end->prev();
424 Instruction* next = sux->next();
425 assert(prev->as_BlockEnd() == nullptr, "must not be a BlockEnd");
426 prev->set_next(next);
427 prev->fixup_block_pointers();
428
429 // disconnect this block from all other blocks
430 disconnect_from_graph(sux);
431 #ifdef DO_DELAYED_VERIFICATION
432 blocks_to_verify_later.remove(sux); // Sux is not part of graph anymore
433 #endif // DO_DELAYED_VERIFICATION
434 block->set_end(sux->end());
435
436 // TODO Should this be done in set_end universally?
437 // add exception handlers of deleted block, if any
438 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
439 BlockBegin* xhandler = sux->exception_handler_at(k);
440 block->add_exception_handler(xhandler);
441
442 // TODO This should be in disconnect from graph...
443 // also substitute predecessor of exception handler
444 assert(xhandler->is_predecessor(sux), "missing predecessor");
445 xhandler->remove_predecessor(sux);
446 if (!xhandler->is_predecessor(block)) {
447 xhandler->add_predecessor(block);
448 }
449 }
450
451 // debugging output
452 _merge_count++;
453 if (PrintBlockElimination) {
454 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
455 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
456 }
457
458 #ifdef DO_DELAYED_VERIFICATION
459 _hir->verify_local(blocks_to_verify_later);
460 #endif // DO_DELAYED_VERIFICATION
461
462 If* if_ = block->end()->as_If();
463 if (if_) {
464 IfOp* ifop = if_->x()->as_IfOp();
465 Constant* con = if_->y()->as_Constant();
466 bool swapped = false;
467 if (!con || !ifop) {
468 ifop = if_->y()->as_IfOp();
469 con = if_->x()->as_Constant();
470 swapped = true;
471 }
472 if (con && ifop && !ifop->substitutability_check()) {
473 Constant* tval = ifop->tval()->as_Constant();
474 Constant* fval = ifop->fval()->as_Constant();
475 if (tval && fval) {
476 // Find the instruction before if_, starting with ifop.
477 // When if_ and ifop are not in the same block, prev
478 // becomes null In such (rare) cases it is not
479 // profitable to perform the optimization.
480 Value prev = ifop;
481 while (prev != nullptr && prev->next() != if_) {
482 prev = prev->next();
483 }
484
485 if (prev != nullptr) {
486 Instruction::Condition cond = if_->cond();
487 BlockBegin* tsux = if_->tsux();
488 BlockBegin* fsux = if_->fsux();
489 if (swapped) {
490 cond = Instruction::mirror(cond);
491 }
492
493 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
494 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
495 if (tblock != fblock && !if_->is_safepoint()) {
496 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
497 tblock, fblock, if_->state_before(), if_->is_safepoint(), ifop->substitutability_check());
498 newif->set_state(if_->state()->copy());
499
500 assert(prev->next() == if_, "must be guaranteed by above search");
501 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
502 prev->set_next(newif);
503 block->set_end(newif);
504
505 _merge_count++;
506 if (PrintBlockElimination) {
507 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
508 }
509
510 #ifdef DO_DELAYED_VERIFICATION
511 _hir->verify_local(blocks_to_verify_later);
512 #endif // DO_DELAYED_VERIFICATION
513 }
514 }
515 }
516 }
517 }
518
519 return true;
520 }
521
522 virtual void block_do(BlockBegin* block) {
523 // repeat since the same block may merge again
524 while (try_merge(block)) ;
525 }
526 };
527
528 #ifdef ASSERT
529 #undef DO_DELAYED_VERIFICATION
530 #endif // ASSERT
531
532 void Optimizer::eliminate_blocks() {
533 // merge blocks if possible
534 BlockMerger bm(ir());
535 }
536
537
538 class NullCheckEliminator;
539 class NullCheckVisitor: public InstructionVisitor {
540 private:
541 NullCheckEliminator* _nce;
542 NullCheckEliminator* nce() { return _nce; }
543
544 public:
545 NullCheckVisitor() {}
546
547 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
548
549 void do_Phi (Phi* x);
550 void do_Local (Local* x);
551 void do_Constant (Constant* x);
552 void do_LoadField (LoadField* x);
553 void do_StoreField (StoreField* x);
554 void do_ArrayLength (ArrayLength* x);
555 void do_LoadIndexed (LoadIndexed* x);
556 void do_StoreIndexed (StoreIndexed* x);
557 void do_NegateOp (NegateOp* x);
558 void do_ArithmeticOp (ArithmeticOp* x);
559 void do_ShiftOp (ShiftOp* x);
560 void do_LogicOp (LogicOp* x);
561 void do_CompareOp (CompareOp* x);
562 void do_IfOp (IfOp* x);
563 void do_Convert (Convert* x);
564 void do_NullCheck (NullCheck* x);
565 void do_TypeCast (TypeCast* x);
566 void do_Invoke (Invoke* x);
567 void do_NewInstance (NewInstance* x);
568 void do_NewTypeArray (NewTypeArray* x);
569 void do_NewObjectArray (NewObjectArray* x);
570 void do_NewMultiArray (NewMultiArray* x);
571 void do_CheckCast (CheckCast* x);
572 void do_InstanceOf (InstanceOf* x);
573 void do_MonitorEnter (MonitorEnter* x);
574 void do_MonitorExit (MonitorExit* x);
575 void do_Intrinsic (Intrinsic* x);
576 void do_BlockBegin (BlockBegin* x);
577 void do_Goto (Goto* x);
578 void do_If (If* x);
579 void do_TableSwitch (TableSwitch* x);
580 void do_LookupSwitch (LookupSwitch* x);
581 void do_Return (Return* x);
582 void do_Throw (Throw* x);
583 void do_Base (Base* x);
584 void do_OsrEntry (OsrEntry* x);
585 void do_ExceptionObject(ExceptionObject* x);
586 void do_RoundFP (RoundFP* x);
587 void do_UnsafeGet (UnsafeGet* x);
588 void do_UnsafePut (UnsafePut* x);
589 void do_UnsafeGetAndSet(UnsafeGetAndSet* x);
590 void do_ProfileCall (ProfileCall* x);
591 void do_ProfileReturnType (ProfileReturnType* x);
592 void do_ProfileACmpTypes(ProfileACmpTypes* x);
593 void do_ProfileInvoke (ProfileInvoke* x);
594 void do_RuntimeCall (RuntimeCall* x);
595 void do_MemBar (MemBar* x);
596 void do_RangeCheckPredicate(RangeCheckPredicate* x);
597 #ifdef ASSERT
598 void do_Assert (Assert* x);
599 #endif
600 };
601
602
603 // Because of a static contained within (for the purpose of iteration
604 // over instructions), it is only valid to have one of these active at
605 // a time
606 class NullCheckEliminator: public ValueVisitor {
607 private:
608 Optimizer* _opt;
609
610 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
611 BlockList* _work_list; // Basic blocks to visit
612
613 bool visitable(Value x) {
614 assert(_visitable_instructions != nullptr, "check");
615 return _visitable_instructions->contains(x);
616 }
617 void mark_visited(Value x) {
618 assert(_visitable_instructions != nullptr, "check");
619 _visitable_instructions->remove(x);
620 }
621 void mark_visitable(Value x) {
622 assert(_visitable_instructions != nullptr, "check");
623 _visitable_instructions->put(x);
624 }
625 void clear_visitable_state() {
626 assert(_visitable_instructions != nullptr, "check");
627 _visitable_instructions->clear();
628 }
629
630 ValueSet* _set; // current state, propagated to subsequent BlockBegins
631 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
632 NullCheckVisitor _visitor;
633 NullCheck* _last_explicit_null_check;
634
635 bool set_contains(Value x) { assert(_set != nullptr, "check"); return _set->contains(x); }
636 void set_put (Value x) { assert(_set != nullptr, "check"); _set->put(x); }
637 void set_remove (Value x) { assert(_set != nullptr, "check"); _set->remove(x); }
638
639 BlockList* work_list() { return _work_list; }
640
641 void iterate_all();
642 void iterate_one(BlockBegin* block);
643
644 ValueSet* state() { return _set; }
645 void set_state_from (ValueSet* state) { _set->set_from(state); }
646 ValueSet* state_for (BlockBegin* block) { return _block_states.at(block->block_id()); }
647 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(block->block_id(), stack); }
648 // Returns true if caused a change in the block's state.
649 bool merge_state_for(BlockBegin* block,
650 ValueSet* incoming_state);
651
652 public:
653 // constructor
654 NullCheckEliminator(Optimizer* opt)
655 : _opt(opt)
656 , _work_list(new BlockList())
657 , _set(new ValueSet())
658 , _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), nullptr)
659 , _last_explicit_null_check(nullptr) {
660 _visitable_instructions = new ValueSet();
661 _visitor.set_eliminator(this);
662 CompileLog* log = _opt->ir()->compilation()->log();
663 if (log != nullptr)
664 log->set_context("optimize name='null_check_elimination'");
665 }
666
667 ~NullCheckEliminator() {
668 CompileLog* log = _opt->ir()->compilation()->log();
669 if (log != nullptr)
670 log->clear_context(); // skip marker if nothing was printed
671 }
672
673 Optimizer* opt() { return _opt; }
674 IR* ir () { return opt()->ir(); }
675
676 // Process a graph
677 void iterate(BlockBegin* root);
678
679 void visit(Value* f);
680
681 // In some situations (like NullCheck(x); getfield(x)) the debug
682 // information from the explicit NullCheck can be used to populate
683 // the getfield, even if the two instructions are in different
684 // scopes; this allows implicit null checks to be used but the
685 // correct exception information to be generated. We must clear the
686 // last-traversed NullCheck when we reach a potentially-exception-
687 // throwing instruction, as well as in some other cases.
688 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
689 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
690 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
691 ? _last_explicit_null_check->obj()
692 : nullptr); }
693 NullCheck* consume_last_explicit_null_check() {
694 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
695 _last_explicit_null_check->set_can_trap(false);
696 return _last_explicit_null_check;
697 }
698 void clear_last_explicit_null_check() { _last_explicit_null_check = nullptr; }
699
700 // Handlers for relevant instructions
701 // (separated out from NullCheckVisitor for clarity)
702
703 // The basic contract is that these must leave the instruction in
704 // the desired state; must not assume anything about the state of
705 // the instruction. We make multiple passes over some basic blocks
706 // and the last pass is the only one whose result is valid.
707 void handle_AccessField (AccessField* x);
708 void handle_ArrayLength (ArrayLength* x);
709 void handle_LoadIndexed (LoadIndexed* x);
710 void handle_StoreIndexed (StoreIndexed* x);
711 void handle_NullCheck (NullCheck* x);
712 void handle_Invoke (Invoke* x);
713 void handle_NewInstance (NewInstance* x);
714 void handle_NewArray (NewArray* x);
715 void handle_AccessMonitor (AccessMonitor* x);
716 void handle_Intrinsic (Intrinsic* x);
717 void handle_ExceptionObject (ExceptionObject* x);
718 void handle_Phi (Phi* x);
719 void handle_ProfileCall (ProfileCall* x);
720 void handle_ProfileReturnType (ProfileReturnType* x);
721 void handle_ProfileACmpTypes(ProfileACmpTypes* x);
722 void handle_Constant (Constant* x);
723 void handle_IfOp (IfOp* x);
724 };
725
726
727 // NEEDS_CLEANUP
728 // There may be other instructions which need to clear the last
729 // explicit null check. Anything across which we can not hoist the
730 // debug information for a NullCheck instruction must clear it. It
731 // might be safer to pattern match "NullCheck ; {AccessField,
732 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
733 // Should test to see performance hit of clearing it for all handlers
734 // with empty bodies below. If it is negligible then we should leave
735 // that in for safety, otherwise should think more about it.
736 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
737 void NullCheckVisitor::do_Local (Local* x) {}
738 void NullCheckVisitor::do_Constant (Constant* x) { nce()->handle_Constant(x); }
739 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
740 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
741 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
742 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
743 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
744 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
745 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
746 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
747 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
748 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
749 void NullCheckVisitor::do_IfOp (IfOp* x) { nce()->handle_IfOp(x); }
750 void NullCheckVisitor::do_Convert (Convert* x) {}
751 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
752 void NullCheckVisitor::do_TypeCast (TypeCast* x) {}
753 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
754 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
755 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
756 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
757 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
758 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
759 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
760 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
761 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
762 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
763 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
764 void NullCheckVisitor::do_Goto (Goto* x) {}
765 void NullCheckVisitor::do_If (If* x) {}
766 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
767 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
768 void NullCheckVisitor::do_Return (Return* x) {}
769 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
770 void NullCheckVisitor::do_Base (Base* x) {}
771 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
772 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
773 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
774 void NullCheckVisitor::do_UnsafeGet (UnsafeGet* x) {}
775 void NullCheckVisitor::do_UnsafePut (UnsafePut* x) {}
776 void NullCheckVisitor::do_UnsafeGetAndSet(UnsafeGetAndSet* x) {}
777 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check();
778 nce()->handle_ProfileCall(x); }
779 void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
780 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
781 void NullCheckVisitor::do_ProfileACmpTypes(ProfileACmpTypes* x) { nce()->handle_ProfileACmpTypes(x); }
782 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
783 void NullCheckVisitor::do_MemBar (MemBar* x) {}
784 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
785 #ifdef ASSERT
786 void NullCheckVisitor::do_Assert (Assert* x) {}
787 #endif
788
789 void NullCheckEliminator::visit(Value* p) {
790 assert(*p != nullptr, "should not find null instructions");
791 if (visitable(*p)) {
792 mark_visited(*p);
793 (*p)->visit(&_visitor);
794 }
795 }
796
797 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
798 ValueSet* state = state_for(block);
799 if (state == nullptr) {
800 state = incoming_state->copy();
801 set_state_for(block, state);
802 return true;
803 } else {
804 bool changed = state->set_intersect(incoming_state);
805 if (PrintNullCheckElimination && changed) {
806 tty->print_cr("Block %d's null check state changed", block->block_id());
807 }
808 return changed;
809 }
810 }
811
812
813 void NullCheckEliminator::iterate_all() {
814 while (work_list()->length() > 0) {
815 iterate_one(work_list()->pop());
816 }
817 }
818
819
820 void NullCheckEliminator::iterate_one(BlockBegin* block) {
821 clear_visitable_state();
822 // clear out an old explicit null checks
823 set_last_explicit_null_check(nullptr);
824
825 if (PrintNullCheckElimination) {
826 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
827 block->block_id(),
828 ir()->method()->holder()->name()->as_utf8(),
829 ir()->method()->name()->as_utf8(),
830 ir()->method()->signature()->as_symbol()->as_utf8());
831 }
832
833 // Create new state if none present (only happens at root)
834 if (state_for(block) == nullptr) {
835 ValueSet* tmp_state = new ValueSet();
836 set_state_for(block, tmp_state);
837 // Initial state is that local 0 (receiver) is non-null for
838 // non-static methods
839 ValueStack* stack = block->state();
840 IRScope* scope = stack->scope();
841 ciMethod* method = scope->method();
842 if (!method->is_static()) {
843 Local* local0 = stack->local_at(0)->as_Local();
844 assert(local0 != nullptr, "must be");
845 assert(local0->type() == objectType, "invalid type of receiver");
846
847 if (local0 != nullptr) {
848 // Local 0 is used in this scope
849 tmp_state->put(local0);
850 if (PrintNullCheckElimination) {
851 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
852 }
853 }
854 }
855 }
856
857 // Must copy block's state to avoid mutating it during iteration
858 // through the block -- otherwise "not-null" states can accidentally
859 // propagate "up" through the block during processing of backward
860 // branches and algorithm is incorrect (and does not converge)
861 set_state_from(state_for(block));
862
863 // allow visiting of Phis belonging to this block
864 for_each_phi_fun(block, phi,
865 mark_visitable(phi);
866 );
867
868 BlockEnd* e = block->end();
869 assert(e != nullptr, "incomplete graph");
870 int i;
871
872 // Propagate the state before this block into the exception
873 // handlers. They aren't true successors since we aren't guaranteed
874 // to execute the whole block before executing them. Also putting
875 // them on first seems to help reduce the amount of iteration to
876 // reach a fixed point.
877 for (i = 0; i < block->number_of_exception_handlers(); i++) {
878 BlockBegin* next = block->exception_handler_at(i);
879 if (merge_state_for(next, state())) {
880 if (!work_list()->contains(next)) {
881 work_list()->push(next);
882 }
883 }
884 }
885
886 // Iterate through block, updating state.
887 for (Instruction* instr = block; instr != nullptr; instr = instr->next()) {
888 // Mark instructions in this block as visitable as they are seen
889 // in the instruction list. This keeps the iteration from
890 // visiting instructions which are references in other blocks or
891 // visiting instructions more than once.
892 mark_visitable(instr);
893 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != nullptr)
894 || (instr->as_Constant() != nullptr && instr->as_Constant()->type()->is_object())
895 || (instr->as_IfOp() != nullptr)) {
896 mark_visited(instr);
897 instr->input_values_do(this);
898 instr->visit(&_visitor);
899 }
900 }
901
902 // Propagate state to successors if necessary
903 for (i = 0; i < e->number_of_sux(); i++) {
904 BlockBegin* next = e->sux_at(i);
905 if (merge_state_for(next, state())) {
906 if (!work_list()->contains(next)) {
907 work_list()->push(next);
908 }
909 }
910 }
911 }
912
913
914 void NullCheckEliminator::iterate(BlockBegin* block) {
915 work_list()->push(block);
916 iterate_all();
917 }
918
919 void NullCheckEliminator::handle_AccessField(AccessField* x) {
920 if (x->is_static()) {
921 if (x->as_LoadField() != nullptr) {
922 // If the field is a non-null static final object field (as is
923 // often the case for sun.misc.Unsafe), put this LoadField into
924 // the non-null map
925 ciField* field = x->field();
926 if (field->is_constant()) {
927 ciConstant field_val = field->constant_value();
928 BasicType field_type = field_val.basic_type();
929 if (is_reference_type(field_type)) {
930 ciObject* obj_val = field_val.as_object();
931 if (!obj_val->is_null_object()) {
932 if (PrintNullCheckElimination) {
933 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
934 x->id());
935 }
936 set_put(x);
937 }
938 }
939 }
940 }
941 // Be conservative
942 clear_last_explicit_null_check();
943 return;
944 }
945
946 Value obj = x->obj();
947 if (set_contains(obj)) {
948 // Value is non-null => update AccessField
949 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
950 x->set_explicit_null_check(consume_last_explicit_null_check());
951 x->set_needs_null_check(true);
952 if (PrintNullCheckElimination) {
953 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
954 x->explicit_null_check()->id(), x->id(), obj->id());
955 }
956 } else {
957 x->set_explicit_null_check(nullptr);
958 x->set_needs_null_check(false);
959 if (PrintNullCheckElimination) {
960 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
961 }
962 }
963 } else {
964 set_put(obj);
965 if (PrintNullCheckElimination) {
966 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
967 }
968 // Ensure previous passes do not cause wrong state
969 x->set_needs_null_check(true);
970 x->set_explicit_null_check(nullptr);
971 }
972 clear_last_explicit_null_check();
973 }
974
975
976 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
977 Value array = x->array();
978 if (set_contains(array)) {
979 // Value is non-null => update AccessArray
980 if (last_explicit_null_check_obj() == array) {
981 x->set_explicit_null_check(consume_last_explicit_null_check());
982 x->set_needs_null_check(true);
983 if (PrintNullCheckElimination) {
984 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
985 x->explicit_null_check()->id(), x->id(), array->id());
986 }
987 } else {
988 x->set_explicit_null_check(nullptr);
989 x->set_needs_null_check(false);
990 if (PrintNullCheckElimination) {
991 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
992 }
993 }
994 } else {
995 set_put(array);
996 if (PrintNullCheckElimination) {
997 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
998 }
999 // Ensure previous passes do not cause wrong state
1000 x->set_needs_null_check(true);
1001 x->set_explicit_null_check(nullptr);
1002 }
1003 clear_last_explicit_null_check();
1004 }
1005
1006
1007 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
1008 Value array = x->array();
1009 if (set_contains(array)) {
1010 // Value is non-null => update AccessArray
1011 if (last_explicit_null_check_obj() == array) {
1012 x->set_explicit_null_check(consume_last_explicit_null_check());
1013 x->set_needs_null_check(true);
1014 if (PrintNullCheckElimination) {
1015 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
1016 x->explicit_null_check()->id(), x->id(), array->id());
1017 }
1018 } else {
1019 x->set_explicit_null_check(nullptr);
1020 x->set_needs_null_check(false);
1021 if (PrintNullCheckElimination) {
1022 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
1023 }
1024 }
1025 } else {
1026 set_put(array);
1027 if (PrintNullCheckElimination) {
1028 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1029 }
1030 // Ensure previous passes do not cause wrong state
1031 x->set_needs_null_check(true);
1032 x->set_explicit_null_check(nullptr);
1033 }
1034 clear_last_explicit_null_check();
1035 }
1036
1037
1038 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
1039 Value array = x->array();
1040 if (set_contains(array)) {
1041 // Value is non-null => update AccessArray
1042 if (PrintNullCheckElimination) {
1043 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
1044 }
1045 x->set_needs_null_check(false);
1046 } else {
1047 set_put(array);
1048 if (PrintNullCheckElimination) {
1049 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
1050 }
1051 // Ensure previous passes do not cause wrong state
1052 x->set_needs_null_check(true);
1053 }
1054 clear_last_explicit_null_check();
1055 }
1056
1057
1058 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
1059 Value obj = x->obj();
1060 if (set_contains(obj)) {
1061 // Already proven to be non-null => this NullCheck is useless
1062 if (PrintNullCheckElimination) {
1063 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
1064 }
1065 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
1066 // The code generator won't emit LIR for a NullCheck that cannot trap.
1067 x->set_can_trap(false);
1068 } else {
1069 // May be null => add to map and set last explicit NullCheck
1070 x->set_can_trap(true);
1071 // make sure it's pinned if it can trap
1072 x->pin(Instruction::PinExplicitNullCheck);
1073 set_put(obj);
1074 set_last_explicit_null_check(x);
1075 if (PrintNullCheckElimination) {
1076 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
1077 }
1078 }
1079 }
1080
1081
1082 void NullCheckEliminator::handle_Invoke(Invoke* x) {
1083 if (!x->has_receiver()) {
1084 // Be conservative
1085 clear_last_explicit_null_check();
1086 return;
1087 }
1088
1089 Value recv = x->receiver();
1090 if (!set_contains(recv)) {
1091 set_put(recv);
1092 if (PrintNullCheckElimination) {
1093 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
1094 }
1095 }
1096 clear_last_explicit_null_check();
1097 }
1098
1099
1100 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
1101 set_put(x);
1102 if (PrintNullCheckElimination) {
1103 tty->print_cr("NewInstance %d is non-null", x->id());
1104 }
1105 }
1106
1107
1108 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1109 set_put(x);
1110 if (PrintNullCheckElimination) {
1111 tty->print_cr("NewArray %d is non-null", x->id());
1112 }
1113 }
1114
1115
1116 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1117 set_put(x);
1118 if (PrintNullCheckElimination) {
1119 tty->print_cr("ExceptionObject %d is non-null", x->id());
1120 }
1121 }
1122
1123
1124 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1125 Value obj = x->obj();
1126 if (set_contains(obj)) {
1127 // Value is non-null => update AccessMonitor
1128 if (PrintNullCheckElimination) {
1129 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1130 }
1131 x->set_needs_null_check(false);
1132 } else {
1133 set_put(obj);
1134 if (PrintNullCheckElimination) {
1135 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1136 }
1137 // Ensure previous passes do not cause wrong state
1138 x->set_needs_null_check(true);
1139 }
1140 clear_last_explicit_null_check();
1141 }
1142
1143
1144 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1145 if (!x->has_receiver()) {
1146 if (x->id() == vmIntrinsics::_arraycopy) {
1147 for (int i = 0; i < x->number_of_arguments(); i++) {
1148 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1149 }
1150 }
1151
1152 // Be conservative
1153 clear_last_explicit_null_check();
1154 return;
1155 }
1156
1157 Value recv = x->receiver();
1158 if (set_contains(recv)) {
1159 // Value is non-null => update Intrinsic
1160 if (PrintNullCheckElimination) {
1161 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", vmIntrinsics::as_int(x->id()), recv->id());
1162 }
1163 x->set_needs_null_check(false);
1164 } else {
1165 set_put(recv);
1166 if (PrintNullCheckElimination) {
1167 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", vmIntrinsics::as_int(x->id()), recv->id());
1168 }
1169 // Ensure previous passes do not cause wrong state
1170 x->set_needs_null_check(true);
1171 }
1172 clear_last_explicit_null_check();
1173 }
1174
1175
1176 void NullCheckEliminator::handle_Phi(Phi* x) {
1177 int i;
1178 bool all_non_null = true;
1179 if (x->is_illegal()) {
1180 all_non_null = false;
1181 } else {
1182 for (i = 0; i < x->operand_count(); i++) {
1183 Value input = x->operand_at(i);
1184 if (!set_contains(input)) {
1185 all_non_null = false;
1186 }
1187 }
1188 }
1189
1190 if (all_non_null) {
1191 // Value is non-null => update Phi
1192 if (PrintNullCheckElimination) {
1193 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1194 }
1195 x->set_needs_null_check(false);
1196 } else if (set_contains(x)) {
1197 set_remove(x);
1198 }
1199 }
1200
1201 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
1202 for (int i = 0; i < x->nb_profiled_args(); i++) {
1203 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
1204 }
1205 }
1206
1207 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
1208 x->set_needs_null_check(!set_contains(x->ret()));
1209 }
1210
1211 void NullCheckEliminator::handle_ProfileACmpTypes(ProfileACmpTypes* x) {
1212 x->set_left_maybe_null(!set_contains(x->left()));
1213 x->set_right_maybe_null(!set_contains(x->right()));
1214 }
1215
1216 void NullCheckEliminator::handle_Constant(Constant *x) {
1217 ObjectType* ot = x->type()->as_ObjectType();
1218 if (ot != nullptr && ot->is_loaded()) {
1219 ObjectConstant* oc = ot->as_ObjectConstant();
1220 if (oc == nullptr || !oc->value()->is_null_object()) {
1221 set_put(x);
1222 if (PrintNullCheckElimination) {
1223 tty->print_cr("Constant %d is non-null", x->id());
1224 }
1225 }
1226 }
1227 }
1228
1229 void NullCheckEliminator::handle_IfOp(IfOp *x) {
1230 if (x->type()->is_object() && set_contains(x->tval()) && set_contains(x->fval())) {
1231 set_put(x);
1232 if (PrintNullCheckElimination) {
1233 tty->print_cr("IfOp %d is non-null", x->id());
1234 }
1235 }
1236 }
1237
1238 void Optimizer::eliminate_null_checks() {
1239 ResourceMark rm;
1240
1241 NullCheckEliminator nce(this);
1242
1243 if (PrintNullCheckElimination) {
1244 tty->print_cr("Starting null check elimination for method %s::%s%s",
1245 ir()->method()->holder()->name()->as_utf8(),
1246 ir()->method()->name()->as_utf8(),
1247 ir()->method()->signature()->as_symbol()->as_utf8());
1248 }
1249
1250 // Apply to graph
1251 nce.iterate(ir()->start());
1252
1253 // walk over the graph looking for exception
1254 // handlers and iterate over them as well
1255 int nblocks = BlockBegin::number_of_blocks();
1256 BlockList blocks(nblocks);
1257 boolArray visited_block(nblocks, nblocks, false);
1258
1259 blocks.push(ir()->start());
1260 visited_block.at_put(ir()->start()->block_id(), true);
1261 for (int i = 0; i < blocks.length(); i++) {
1262 BlockBegin* b = blocks.at(i);
1263 // exception handlers need to be treated as additional roots
1264 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1265 BlockBegin* excp = b->exception_handler_at(e);
1266 int id = excp->block_id();
1267 if (!visited_block.at(id)) {
1268 blocks.push(excp);
1269 visited_block.at_put(id, true);
1270 nce.iterate(excp);
1271 }
1272 }
1273 // traverse successors
1274 BlockEnd *end = b->end();
1275 for (int s = end->number_of_sux(); s-- > 0; ) {
1276 BlockBegin* next = end->sux_at(s);
1277 int id = next->block_id();
1278 if (!visited_block.at(id)) {
1279 blocks.push(next);
1280 visited_block.at_put(id, true);
1281 }
1282 }
1283 }
1284
1285
1286 if (PrintNullCheckElimination) {
1287 tty->print_cr("Done with null check elimination for method %s::%s%s",
1288 ir()->method()->holder()->name()->as_utf8(),
1289 ir()->method()->name()->as_utf8(),
1290 ir()->method()->signature()->as_symbol()->as_utf8());
1291 }
1292 }