1 /*
2 * Copyright (c) 1999, 2017, 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.inline.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 != NULL)
60 log->set_context("optimize name='cee'");
61 }
62
63 ~CE_Eliminator() {
64 CompileLog* log = _hir->compilation()->log();
65 if (log != NULL)
66 log->clear_context(); // skip marker if nothing was printed
67 }
68
69 int cee_count() const { return _cee_count; }
70 int ifop_count() const { return _ifop_count; }
71
72 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
73 int e = sux->number_of_exception_handlers();
74 for (int i = 0; i < e; i++) {
75 BlockBegin* xhandler = sux->exception_handler_at(i);
76 block->add_exception_handler(xhandler);
77
78 assert(xhandler->is_predecessor(sux), "missing predecessor");
79 if (sux->number_of_preds() == 0) {
80 // sux is disconnected from graph so disconnect from exception handlers
81 xhandler->remove_predecessor(sux);
82 }
83 if (!xhandler->is_predecessor(block)) {
84 xhandler->add_predecessor(block);
85 }
86 }
87 }
88
89 virtual void block_do(BlockBegin* block);
90
91 private:
92 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
93 };
94
95 void CE_Eliminator::block_do(BlockBegin* block) {
96 // 1) find conditional expression
97 // check if block ends with an If
98 If* if_ = block->end()->as_If();
99 if (if_ == NULL) return;
100
101 // check if If works on int or object types
102 // (we cannot handle If's working on long, float or doubles yet,
103 // since IfOp doesn't support them - these If's show up if cmp
104 // operations followed by If's are eliminated)
105 ValueType* if_type = if_->x()->type();
106 if (!if_type->is_int() && !if_type->is_object()) return;
107
108 BlockBegin* t_block = if_->tsux();
109 BlockBegin* f_block = if_->fsux();
110 Instruction* t_cur = t_block->next();
111 Instruction* f_cur = f_block->next();
112
113 // one Constant may be present between BlockBegin and BlockEnd
114 Value t_const = NULL;
115 Value f_const = NULL;
116 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
117 t_const = t_cur;
118 t_cur = t_cur->next();
119 }
120 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
121 f_const = f_cur;
122 f_cur = f_cur->next();
123 }
124
125 // check if both branches end with a goto
126 Goto* t_goto = t_cur->as_Goto();
127 if (t_goto == NULL) return;
128 Goto* f_goto = f_cur->as_Goto();
129 if (f_goto == NULL) return;
130
131 // check if both gotos merge into the same block
132 BlockBegin* sux = t_goto->default_sux();
133 if (sux != f_goto->default_sux()) return;
134
135 // check if at least one word was pushed on sux_state
136 // inlining depths must match
137 ValueStack* if_state = if_->state();
138 ValueStack* sux_state = sux->state();
139 if (if_state->scope()->level() > sux_state->scope()->level()) {
140 while (sux_state->scope() != if_state->scope()) {
141 if_state = if_state->caller_state();
142 assert(if_state != NULL, "states do not match up");
143 }
144 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
145 while (sux_state->scope() != if_state->scope()) {
146 sux_state = sux_state->caller_state();
147 assert(sux_state != NULL, "states do not match up");
148 }
149 }
150
151 if (sux_state->stack_size() <= if_state->stack_size()) return;
152
153 // check if phi function is present at end of successor stack and that
154 // only this phi was pushed on the stack
155 Value sux_phi = sux_state->stack_at(if_state->stack_size());
156 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
157 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
158
159 // get the values that were pushed in the true- and false-branch
160 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
161 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
162
163 // backend does not support floats
164 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
165 if (t_value->type()->is_float_kind()) return;
166
167 // check that successor has no other phi functions but sux_phi
168 // this can happen when t_block or f_block contained additonal stores to local variables
169 // that are no longer represented by explicit instructions
170 for_each_phi_fun(sux, phi,
171 if (phi != sux_phi) return;
172 );
173 // true and false blocks can't have phis
174 for_each_phi_fun(t_block, phi, return; );
175 for_each_phi_fun(f_block, phi, return; );
176
177 // 2) substitute conditional expression
178 // with an IfOp followed by a Goto
179 // cut if_ away and get node before
180 Instruction* cur_end = if_->prev();
181
182 // append constants of true- and false-block if necessary
183 // clone constants because original block must not be destroyed
184 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
185 if (t_value == t_const) {
186 t_value = new Constant(t_const->type());
187 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
188 cur_end = cur_end->set_next(t_value);
189 }
190 if (f_value == f_const) {
191 f_value = new Constant(f_const->type());
192 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
193 cur_end = cur_end->set_next(f_value);
194 }
195
196 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
197 assert(result != NULL, "make_ifop must return a non-null instruction");
198 if (!result->is_linked() && result->can_be_linked()) {
199 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
200 cur_end = cur_end->set_next(result);
201 }
202
203 // append Goto to successor
204 ValueStack* state_before = if_->state_before();
205 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
206
207 // prepare state for Goto
208 ValueStack* goto_state = if_state;
209 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
210 goto_state->push(result->type(), result);
211 assert(goto_state->is_same(sux_state), "states must match now");
212 goto_->set_state(goto_state);
213
214 cur_end = cur_end->set_next(goto_, goto_state->bci());
215
216 // Adjust control flow graph
217 BlockBegin::disconnect_edge(block, t_block);
218 BlockBegin::disconnect_edge(block, f_block);
219 if (t_block->number_of_preds() == 0) {
220 BlockBegin::disconnect_edge(t_block, sux);
221 }
222 adjust_exception_edges(block, t_block);
223 if (f_block->number_of_preds() == 0) {
224 BlockBegin::disconnect_edge(f_block, sux);
225 }
226 adjust_exception_edges(block, f_block);
227
228 // update block end
229 block->set_end(goto_);
230
231 // substitute the phi if possible
232 if (sux_phi->as_Phi()->operand_count() == 1) {
233 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
234 sux_phi->set_subst(result);
235 _has_substitution = true;
236 }
237
238 // 3) successfully eliminated a conditional expression
239 _cee_count++;
240 if (PrintCEE) {
241 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());
242 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
243 }
244
245 _hir->verify();
246 }
247
248 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
249 if (!OptimizeIfOps) {
250 return new IfOp(x, cond, y, tval, fval);
251 }
252
253 tval = tval->subst();
254 fval = fval->subst();
255 if (tval == fval) {
256 _ifop_count++;
257 return tval;
258 }
259
260 x = x->subst();
261 y = y->subst();
262
263 Constant* y_const = y->as_Constant();
264 if (y_const != NULL) {
265 IfOp* x_ifop = x->as_IfOp();
266 if (x_ifop != NULL) { // x is an ifop, y is a constant
267 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
268 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
269
270 if (x_tval_const != NULL && x_fval_const != NULL) {
271 Instruction::Condition x_ifop_cond = x_ifop->cond();
272
273 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
274 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
275
276 // not_comparable here is a valid return in case we're comparing unloaded oop constants
277 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
278 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
279 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
280
281 _ifop_count++;
282 if (new_tval == new_fval) {
283 return new_tval;
284 } else {
285 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
286 }
287 }
288 }
289 } else {
290 Constant* x_const = x->as_Constant();
291 if (x_const != NULL) { // x and y are constants
292 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
293 // not_comparable here is a valid return in case we're comparing unloaded oop constants
294 if (x_compare_res != Constant::not_comparable) {
295 _ifop_count++;
296 return x_compare_res == Constant::cond_true ? tval : fval;
297 }
298 }
299 }
300 }
301 return new IfOp(x, cond, y, tval, fval);
302 }
303
304 void Optimizer::eliminate_conditional_expressions() {
305 // find conditional expressions & replace them with IfOps
306 CE_Eliminator ce(ir());
307 }
308
309 class BlockMerger: public BlockClosure {
310 private:
311 IR* _hir;
312 int _merge_count; // the number of block pairs successfully merged
313
314 public:
315 BlockMerger(IR* hir)
316 : _hir(hir)
317 , _merge_count(0)
318 {
319 _hir->iterate_preorder(this);
320 CompileLog* log = _hir->compilation()->log();
321 if (log != NULL)
322 log->set_context("optimize name='eliminate_blocks'");
323 }
324
325 ~BlockMerger() {
326 CompileLog* log = _hir->compilation()->log();
327 if (log != NULL)
328 log->clear_context(); // skip marker if nothing was printed
329 }
330
331 bool try_merge(BlockBegin* block) {
332 BlockEnd* end = block->end();
333 if (end->as_Goto() != NULL) {
334 assert(end->number_of_sux() == 1, "end must have exactly one successor");
335 // Note: It would be sufficient to check for the number of successors (= 1)
336 // in order to decide if this block can be merged potentially. That
337 // would then also include switch statements w/ only a default case.
338 // However, in that case we would need to make sure the switch tag
339 // expression is executed if it can produce observable side effects.
340 // We should probably have the canonicalizer simplifying such switch
341 // statements and then we are sure we don't miss these merge opportunities
342 // here (was bug - gri 7/7/99).
343 BlockBegin* sux = end->default_sux();
344 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
345 // merge the two blocks
346
347 #ifdef ASSERT
348 // verify that state at the end of block and at the beginning of sux are equal
349 // no phi functions must be present at beginning of sux
350 ValueStack* sux_state = sux->state();
351 ValueStack* end_state = end->state();
352
353 assert(end_state->scope() == sux_state->scope(), "scopes must match");
354 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
355 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
356
357 int index;
358 Value sux_value;
359 for_each_stack_value(sux_state, index, sux_value) {
360 assert(sux_value == end_state->stack_at(index), "stack not equal");
361 }
362 for_each_local_value(sux_state, index, sux_value) {
363 assert(sux_value == end_state->local_at(index), "locals not equal");
364 }
365 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
366 #endif
367
368 // find instruction before end & append first instruction of sux block
369 Instruction* prev = end->prev();
370 Instruction* next = sux->next();
371 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
372 prev->set_next(next);
373 prev->fixup_block_pointers();
374 sux->disconnect_from_graph();
375 block->set_end(sux->end());
376 // add exception handlers of deleted block, if any
377 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
378 BlockBegin* xhandler = sux->exception_handler_at(k);
379 block->add_exception_handler(xhandler);
380
381 // also substitute predecessor of exception handler
382 assert(xhandler->is_predecessor(sux), "missing predecessor");
383 xhandler->remove_predecessor(sux);
384 if (!xhandler->is_predecessor(block)) {
385 xhandler->add_predecessor(block);
386 }
387 }
388
389 // debugging output
390 _merge_count++;
391 if (PrintBlockElimination) {
392 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
393 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
394 }
395
396 _hir->verify();
397
398 If* if_ = block->end()->as_If();
399 if (if_) {
400 IfOp* ifop = if_->x()->as_IfOp();
401 Constant* con = if_->y()->as_Constant();
402 bool swapped = false;
403 if (!con || !ifop) {
404 ifop = if_->y()->as_IfOp();
405 con = if_->x()->as_Constant();
406 swapped = true;
407 }
408 if (con && ifop) {
409 Constant* tval = ifop->tval()->as_Constant();
410 Constant* fval = ifop->fval()->as_Constant();
411 if (tval && fval) {
412 // Find the instruction before if_, starting with ifop.
413 // When if_ and ifop are not in the same block, prev
414 // becomes NULL In such (rare) cases it is not
415 // profitable to perform the optimization.
416 Value prev = ifop;
417 while (prev != NULL && prev->next() != if_) {
418 prev = prev->next();
419 }
420
421 if (prev != NULL) {
422 Instruction::Condition cond = if_->cond();
423 BlockBegin* tsux = if_->tsux();
424 BlockBegin* fsux = if_->fsux();
425 if (swapped) {
426 cond = Instruction::mirror(cond);
427 }
428
429 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
430 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
431 if (tblock != fblock && !if_->is_safepoint()) {
432 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
433 tblock, fblock, if_->state_before(), if_->is_safepoint());
434 newif->set_state(if_->state()->copy());
435
436 assert(prev->next() == if_, "must be guaranteed by above search");
437 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
438 prev->set_next(newif);
439 block->set_end(newif);
440
441 _merge_count++;
442 if (PrintBlockElimination) {
443 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
444 }
445
446 _hir->verify();
447 }
448 }
449 }
450 }
451 }
452
453 return true;
454 }
455 }
456 return false;
457 }
458
459 virtual void block_do(BlockBegin* block) {
460 _hir->verify();
461 // repeat since the same block may merge again
462 while (try_merge(block)) {
463 _hir->verify();
464 }
465 }
466 };
467
468
469 void Optimizer::eliminate_blocks() {
470 // merge blocks if possible
471 BlockMerger bm(ir());
472 }
473
474
475 class NullCheckEliminator;
476 class NullCheckVisitor: public InstructionVisitor {
477 private:
478 NullCheckEliminator* _nce;
479 NullCheckEliminator* nce() { return _nce; }
480
481 public:
482 NullCheckVisitor() {}
483
484 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
485
486 void do_Phi (Phi* x);
487 void do_Local (Local* x);
488 void do_Constant (Constant* x);
489 void do_LoadField (LoadField* x);
490 void do_StoreField (StoreField* x);
491 void do_ArrayLength (ArrayLength* x);
492 void do_LoadIndexed (LoadIndexed* x);
493 void do_StoreIndexed (StoreIndexed* x);
494 void do_NegateOp (NegateOp* x);
495 void do_ArithmeticOp (ArithmeticOp* x);
496 void do_ShiftOp (ShiftOp* x);
497 void do_LogicOp (LogicOp* x);
498 void do_CompareOp (CompareOp* x);
499 void do_IfOp (IfOp* x);
500 void do_Convert (Convert* x);
501 void do_NullCheck (NullCheck* x);
502 void do_TypeCast (TypeCast* x);
503 void do_Invoke (Invoke* x);
504 void do_NewInstance (NewInstance* x);
505 void do_NewTypeArray (NewTypeArray* x);
506 void do_NewObjectArray (NewObjectArray* x);
507 void do_NewMultiArray (NewMultiArray* x);
508 void do_CheckCast (CheckCast* x);
509 void do_InstanceOf (InstanceOf* x);
510 void do_MonitorEnter (MonitorEnter* x);
511 void do_MonitorExit (MonitorExit* x);
512 void do_Intrinsic (Intrinsic* x);
513 void do_BlockBegin (BlockBegin* x);
514 void do_Goto (Goto* x);
515 void do_If (If* x);
516 void do_IfInstanceOf (IfInstanceOf* x);
517 void do_TableSwitch (TableSwitch* x);
518 void do_LookupSwitch (LookupSwitch* x);
519 void do_Return (Return* x);
520 void do_Throw (Throw* x);
521 void do_Base (Base* x);
522 void do_OsrEntry (OsrEntry* x);
523 void do_ExceptionObject(ExceptionObject* x);
524 void do_RoundFP (RoundFP* x);
525 void do_UnsafeGetRaw (UnsafeGetRaw* x);
526 void do_UnsafePutRaw (UnsafePutRaw* x);
527 void do_UnsafeGetObject(UnsafeGetObject* x);
528 void do_UnsafePutObject(UnsafePutObject* x);
529 void do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x);
530 void do_ProfileCall (ProfileCall* x);
531 void do_ProfileReturnType (ProfileReturnType* x);
532 void do_ProfileInvoke (ProfileInvoke* x);
533 void do_RuntimeCall (RuntimeCall* x);
534 void do_MemBar (MemBar* x);
535 void do_RangeCheckPredicate(RangeCheckPredicate* x);
536 #ifdef ASSERT
537 void do_Assert (Assert* x);
538 #endif
539 };
540
541
542 // Because of a static contained within (for the purpose of iteration
543 // over instructions), it is only valid to have one of these active at
544 // a time
545 class NullCheckEliminator: public ValueVisitor {
546 private:
547 Optimizer* _opt;
548
549 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
550 BlockList* _work_list; // Basic blocks to visit
551
552 bool visitable(Value x) {
553 assert(_visitable_instructions != NULL, "check");
554 return _visitable_instructions->contains(x);
555 }
556 void mark_visited(Value x) {
557 assert(_visitable_instructions != NULL, "check");
558 _visitable_instructions->remove(x);
559 }
560 void mark_visitable(Value x) {
561 assert(_visitable_instructions != NULL, "check");
562 _visitable_instructions->put(x);
563 }
564 void clear_visitable_state() {
565 assert(_visitable_instructions != NULL, "check");
566 _visitable_instructions->clear();
567 }
568
569 ValueSet* _set; // current state, propagated to subsequent BlockBegins
570 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
571 NullCheckVisitor _visitor;
572 NullCheck* _last_explicit_null_check;
573
574 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
575 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
576 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
577
578 BlockList* work_list() { return _work_list; }
579
580 void iterate_all();
581 void iterate_one(BlockBegin* block);
582
583 ValueSet* state() { return _set; }
584 void set_state_from (ValueSet* state) { _set->set_from(state); }
585 ValueSet* state_for (BlockBegin* block) { return _block_states.at(block->block_id()); }
586 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(block->block_id(), stack); }
587 // Returns true if caused a change in the block's state.
588 bool merge_state_for(BlockBegin* block,
589 ValueSet* incoming_state);
590
591 public:
592 // constructor
593 NullCheckEliminator(Optimizer* opt)
594 : _opt(opt)
595 , _work_list(new BlockList())
596 , _set(new ValueSet())
597 , _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), NULL)
598 , _last_explicit_null_check(NULL) {
599 _visitable_instructions = new ValueSet();
600 _visitor.set_eliminator(this);
601 CompileLog* log = _opt->ir()->compilation()->log();
602 if (log != NULL)
603 log->set_context("optimize name='null_check_elimination'");
604 }
605
606 ~NullCheckEliminator() {
607 CompileLog* log = _opt->ir()->compilation()->log();
608 if (log != NULL)
609 log->clear_context(); // skip marker if nothing was printed
610 }
611
612 Optimizer* opt() { return _opt; }
613 IR* ir () { return opt()->ir(); }
614
615 // Process a graph
616 void iterate(BlockBegin* root);
617
618 void visit(Value* f);
619
620 // In some situations (like NullCheck(x); getfield(x)) the debug
621 // information from the explicit NullCheck can be used to populate
622 // the getfield, even if the two instructions are in different
623 // scopes; this allows implicit null checks to be used but the
624 // correct exception information to be generated. We must clear the
625 // last-traversed NullCheck when we reach a potentially-exception-
626 // throwing instruction, as well as in some other cases.
627 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
628 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
629 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
630 ? _last_explicit_null_check->obj()
631 : NULL); }
632 NullCheck* consume_last_explicit_null_check() {
633 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
634 _last_explicit_null_check->set_can_trap(false);
635 return _last_explicit_null_check;
636 }
637 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
638
639 // Handlers for relevant instructions
640 // (separated out from NullCheckVisitor for clarity)
641
642 // The basic contract is that these must leave the instruction in
643 // the desired state; must not assume anything about the state of
644 // the instruction. We make multiple passes over some basic blocks
645 // and the last pass is the only one whose result is valid.
646 void handle_AccessField (AccessField* x);
647 void handle_ArrayLength (ArrayLength* x);
648 void handle_LoadIndexed (LoadIndexed* x);
649 void handle_StoreIndexed (StoreIndexed* x);
650 void handle_NullCheck (NullCheck* x);
651 void handle_Invoke (Invoke* x);
652 void handle_NewInstance (NewInstance* x);
653 void handle_NewArray (NewArray* x);
654 void handle_AccessMonitor (AccessMonitor* x);
655 void handle_Intrinsic (Intrinsic* x);
656 void handle_ExceptionObject (ExceptionObject* x);
657 void handle_Phi (Phi* x);
658 void handle_ProfileCall (ProfileCall* x);
659 void handle_ProfileReturnType (ProfileReturnType* x);
660 };
661
662
663 // NEEDS_CLEANUP
664 // There may be other instructions which need to clear the last
665 // explicit null check. Anything across which we can not hoist the
666 // debug information for a NullCheck instruction must clear it. It
667 // might be safer to pattern match "NullCheck ; {AccessField,
668 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
669 // Should test to see performance hit of clearing it for all handlers
670 // with empty bodies below. If it is negligible then we should leave
671 // that in for safety, otherwise should think more about it.
672 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
673 void NullCheckVisitor::do_Local (Local* x) {}
674 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
675 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
676 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
677 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
678 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
679 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
680 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
681 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
682 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
683 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
684 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
685 void NullCheckVisitor::do_IfOp (IfOp* x) {}
686 void NullCheckVisitor::do_Convert (Convert* x) {}
687 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
688 void NullCheckVisitor::do_TypeCast (TypeCast* x) {}
689 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
690 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
691 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
692 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
693 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
694 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
695 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
696 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
697 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
698 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
699 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
700 void NullCheckVisitor::do_Goto (Goto* x) {}
701 void NullCheckVisitor::do_If (If* x) {}
702 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
703 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
704 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
705 void NullCheckVisitor::do_Return (Return* x) {}
706 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
707 void NullCheckVisitor::do_Base (Base* x) {}
708 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
709 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
710 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
711 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
712 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
713 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
714 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
715 void NullCheckVisitor::do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x) {}
716 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check();
717 nce()->handle_ProfileCall(x); }
718 void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
719 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
720 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
721 void NullCheckVisitor::do_MemBar (MemBar* x) {}
722 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
723 #ifdef ASSERT
724 void NullCheckVisitor::do_Assert (Assert* x) {}
725 #endif
726
727 void NullCheckEliminator::visit(Value* p) {
728 assert(*p != NULL, "should not find NULL instructions");
729 if (visitable(*p)) {
730 mark_visited(*p);
731 (*p)->visit(&_visitor);
732 }
733 }
734
735 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
736 ValueSet* state = state_for(block);
737 if (state == NULL) {
738 state = incoming_state->copy();
739 set_state_for(block, state);
740 return true;
741 } else {
742 bool changed = state->set_intersect(incoming_state);
743 if (PrintNullCheckElimination && changed) {
744 tty->print_cr("Block %d's null check state changed", block->block_id());
745 }
746 return changed;
747 }
748 }
749
750
751 void NullCheckEliminator::iterate_all() {
752 while (work_list()->length() > 0) {
753 iterate_one(work_list()->pop());
754 }
755 }
756
757
758 void NullCheckEliminator::iterate_one(BlockBegin* block) {
759 clear_visitable_state();
760 // clear out an old explicit null checks
761 set_last_explicit_null_check(NULL);
762
763 if (PrintNullCheckElimination) {
764 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
765 block->block_id(),
766 ir()->method()->holder()->name()->as_utf8(),
767 ir()->method()->name()->as_utf8(),
768 ir()->method()->signature()->as_symbol()->as_utf8());
769 }
770
771 // Create new state if none present (only happens at root)
772 if (state_for(block) == NULL) {
773 ValueSet* tmp_state = new ValueSet();
774 set_state_for(block, tmp_state);
775 // Initial state is that local 0 (receiver) is non-null for
776 // non-static methods
777 ValueStack* stack = block->state();
778 IRScope* scope = stack->scope();
779 ciMethod* method = scope->method();
780 if (!method->is_static()) {
781 Local* local0 = stack->local_at(0)->as_Local();
782 assert(local0 != NULL, "must be");
783 assert(local0->type() == objectType, "invalid type of receiver");
784
785 if (local0 != NULL) {
786 // Local 0 is used in this scope
787 tmp_state->put(local0);
788 if (PrintNullCheckElimination) {
789 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
790 }
791 }
792 }
793 }
794
795 // Must copy block's state to avoid mutating it during iteration
796 // through the block -- otherwise "not-null" states can accidentally
797 // propagate "up" through the block during processing of backward
798 // branches and algorithm is incorrect (and does not converge)
799 set_state_from(state_for(block));
800
801 // allow visiting of Phis belonging to this block
802 for_each_phi_fun(block, phi,
803 mark_visitable(phi);
804 );
805
806 BlockEnd* e = block->end();
807 assert(e != NULL, "incomplete graph");
808 int i;
809
810 // Propagate the state before this block into the exception
811 // handlers. They aren't true successors since we aren't guaranteed
812 // to execute the whole block before executing them. Also putting
813 // them on first seems to help reduce the amount of iteration to
814 // reach a fixed point.
815 for (i = 0; i < block->number_of_exception_handlers(); i++) {
816 BlockBegin* next = block->exception_handler_at(i);
817 if (merge_state_for(next, state())) {
818 if (!work_list()->contains(next)) {
819 work_list()->push(next);
820 }
821 }
822 }
823
824 // Iterate through block, updating state.
825 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
826 // Mark instructions in this block as visitable as they are seen
827 // in the instruction list. This keeps the iteration from
828 // visiting instructions which are references in other blocks or
829 // visiting instructions more than once.
830 mark_visitable(instr);
831 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
832 mark_visited(instr);
833 instr->input_values_do(this);
834 instr->visit(&_visitor);
835 }
836 }
837
838 // Propagate state to successors if necessary
839 for (i = 0; i < e->number_of_sux(); i++) {
840 BlockBegin* next = e->sux_at(i);
841 if (merge_state_for(next, state())) {
842 if (!work_list()->contains(next)) {
843 work_list()->push(next);
844 }
845 }
846 }
847 }
848
849
850 void NullCheckEliminator::iterate(BlockBegin* block) {
851 work_list()->push(block);
852 iterate_all();
853 }
854
855 void NullCheckEliminator::handle_AccessField(AccessField* x) {
856 if (x->is_static()) {
857 if (x->as_LoadField() != NULL) {
858 // If the field is a non-null static final object field (as is
859 // often the case for sun.misc.Unsafe), put this LoadField into
860 // the non-null map
861 ciField* field = x->field();
862 if (field->is_constant()) {
863 ciConstant field_val = field->constant_value();
864 BasicType field_type = field_val.basic_type();
865 if (field_type == T_OBJECT || field_type == T_ARRAY) {
866 ciObject* obj_val = field_val.as_object();
867 if (!obj_val->is_null_object()) {
868 if (PrintNullCheckElimination) {
869 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
870 x->id());
871 }
872 set_put(x);
873 }
874 }
875 }
876 }
877 // Be conservative
878 clear_last_explicit_null_check();
879 return;
880 }
881
882 Value obj = x->obj();
883 if (set_contains(obj)) {
884 // Value is non-null => update AccessField
885 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
886 x->set_explicit_null_check(consume_last_explicit_null_check());
887 x->set_needs_null_check(true);
888 if (PrintNullCheckElimination) {
889 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
890 x->explicit_null_check()->id(), x->id(), obj->id());
891 }
892 } else {
893 x->set_explicit_null_check(NULL);
894 x->set_needs_null_check(false);
895 if (PrintNullCheckElimination) {
896 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
897 }
898 }
899 } else {
900 set_put(obj);
901 if (PrintNullCheckElimination) {
902 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
903 }
904 // Ensure previous passes do not cause wrong state
905 x->set_needs_null_check(true);
906 x->set_explicit_null_check(NULL);
907 }
908 clear_last_explicit_null_check();
909 }
910
911
912 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
913 Value array = x->array();
914 if (set_contains(array)) {
915 // Value is non-null => update AccessArray
916 if (last_explicit_null_check_obj() == array) {
917 x->set_explicit_null_check(consume_last_explicit_null_check());
918 x->set_needs_null_check(true);
919 if (PrintNullCheckElimination) {
920 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
921 x->explicit_null_check()->id(), x->id(), array->id());
922 }
923 } else {
924 x->set_explicit_null_check(NULL);
925 x->set_needs_null_check(false);
926 if (PrintNullCheckElimination) {
927 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
928 }
929 }
930 } else {
931 set_put(array);
932 if (PrintNullCheckElimination) {
933 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
934 }
935 // Ensure previous passes do not cause wrong state
936 x->set_needs_null_check(true);
937 x->set_explicit_null_check(NULL);
938 }
939 clear_last_explicit_null_check();
940 }
941
942
943 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
944 Value array = x->array();
945 if (set_contains(array)) {
946 // Value is non-null => update AccessArray
947 if (last_explicit_null_check_obj() == array) {
948 x->set_explicit_null_check(consume_last_explicit_null_check());
949 x->set_needs_null_check(true);
950 if (PrintNullCheckElimination) {
951 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
952 x->explicit_null_check()->id(), x->id(), array->id());
953 }
954 } else {
955 x->set_explicit_null_check(NULL);
956 x->set_needs_null_check(false);
957 if (PrintNullCheckElimination) {
958 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
959 }
960 }
961 } else {
962 set_put(array);
963 if (PrintNullCheckElimination) {
964 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
965 }
966 // Ensure previous passes do not cause wrong state
967 x->set_needs_null_check(true);
968 x->set_explicit_null_check(NULL);
969 }
970 clear_last_explicit_null_check();
971 }
972
973
974 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
975 Value array = x->array();
976 if (set_contains(array)) {
977 // Value is non-null => update AccessArray
978 if (PrintNullCheckElimination) {
979 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
980 }
981 x->set_needs_null_check(false);
982 } else {
983 set_put(array);
984 if (PrintNullCheckElimination) {
985 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
986 }
987 // Ensure previous passes do not cause wrong state
988 x->set_needs_null_check(true);
989 }
990 clear_last_explicit_null_check();
991 }
992
993
994 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
995 Value obj = x->obj();
996 if (set_contains(obj)) {
997 // Already proven to be non-null => this NullCheck is useless
998 if (PrintNullCheckElimination) {
999 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
1000 }
1001 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
1002 // The code generator won't emit LIR for a NullCheck that cannot trap.
1003 x->set_can_trap(false);
1004 } else {
1005 // May be null => add to map and set last explicit NullCheck
1006 x->set_can_trap(true);
1007 // make sure it's pinned if it can trap
1008 x->pin(Instruction::PinExplicitNullCheck);
1009 set_put(obj);
1010 set_last_explicit_null_check(x);
1011 if (PrintNullCheckElimination) {
1012 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
1013 }
1014 }
1015 }
1016
1017
1018 void NullCheckEliminator::handle_Invoke(Invoke* x) {
1019 if (!x->has_receiver()) {
1020 // Be conservative
1021 clear_last_explicit_null_check();
1022 return;
1023 }
1024
1025 Value recv = x->receiver();
1026 if (!set_contains(recv)) {
1027 set_put(recv);
1028 if (PrintNullCheckElimination) {
1029 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
1030 }
1031 }
1032 clear_last_explicit_null_check();
1033 }
1034
1035
1036 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
1037 set_put(x);
1038 if (PrintNullCheckElimination) {
1039 tty->print_cr("NewInstance %d is non-null", x->id());
1040 }
1041 }
1042
1043
1044 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1045 set_put(x);
1046 if (PrintNullCheckElimination) {
1047 tty->print_cr("NewArray %d is non-null", x->id());
1048 }
1049 }
1050
1051
1052 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1053 set_put(x);
1054 if (PrintNullCheckElimination) {
1055 tty->print_cr("ExceptionObject %d is non-null", x->id());
1056 }
1057 }
1058
1059
1060 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1061 Value obj = x->obj();
1062 if (set_contains(obj)) {
1063 // Value is non-null => update AccessMonitor
1064 if (PrintNullCheckElimination) {
1065 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1066 }
1067 x->set_needs_null_check(false);
1068 } else {
1069 set_put(obj);
1070 if (PrintNullCheckElimination) {
1071 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1072 }
1073 // Ensure previous passes do not cause wrong state
1074 x->set_needs_null_check(true);
1075 }
1076 clear_last_explicit_null_check();
1077 }
1078
1079
1080 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1081 if (!x->has_receiver()) {
1082 if (x->id() == vmIntrinsics::_arraycopy) {
1083 for (int i = 0; i < x->number_of_arguments(); i++) {
1084 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1085 }
1086 }
1087
1088 // Be conservative
1089 clear_last_explicit_null_check();
1090 return;
1091 }
1092
1093 Value recv = x->receiver();
1094 if (set_contains(recv)) {
1095 // Value is non-null => update Intrinsic
1096 if (PrintNullCheckElimination) {
1097 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1098 }
1099 x->set_needs_null_check(false);
1100 } else {
1101 set_put(recv);
1102 if (PrintNullCheckElimination) {
1103 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1104 }
1105 // Ensure previous passes do not cause wrong state
1106 x->set_needs_null_check(true);
1107 }
1108 clear_last_explicit_null_check();
1109 }
1110
1111
1112 void NullCheckEliminator::handle_Phi(Phi* x) {
1113 int i;
1114 bool all_non_null = true;
1115 if (x->is_illegal()) {
1116 all_non_null = false;
1117 } else {
1118 for (i = 0; i < x->operand_count(); i++) {
1119 Value input = x->operand_at(i);
1120 if (!set_contains(input)) {
1121 all_non_null = false;
1122 }
1123 }
1124 }
1125
1126 if (all_non_null) {
1127 // Value is non-null => update Phi
1128 if (PrintNullCheckElimination) {
1129 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1130 }
1131 x->set_needs_null_check(false);
1132 } else if (set_contains(x)) {
1133 set_remove(x);
1134 }
1135 }
1136
1137 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
1138 for (int i = 0; i < x->nb_profiled_args(); i++) {
1139 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
1140 }
1141 }
1142
1143 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
1144 x->set_needs_null_check(!set_contains(x->ret()));
1145 }
1146
1147 void Optimizer::eliminate_null_checks() {
1148 ResourceMark rm;
1149
1150 NullCheckEliminator nce(this);
1151
1152 if (PrintNullCheckElimination) {
1153 tty->print_cr("Starting null check elimination for method %s::%s%s",
1154 ir()->method()->holder()->name()->as_utf8(),
1155 ir()->method()->name()->as_utf8(),
1156 ir()->method()->signature()->as_symbol()->as_utf8());
1157 }
1158
1159 // Apply to graph
1160 nce.iterate(ir()->start());
1161
1162 // walk over the graph looking for exception
1163 // handlers and iterate over them as well
1164 int nblocks = BlockBegin::number_of_blocks();
1165 BlockList blocks(nblocks);
1166 boolArray visited_block(nblocks, nblocks, false);
1167
1168 blocks.push(ir()->start());
1169 visited_block.at_put(ir()->start()->block_id(), true);
1170 for (int i = 0; i < blocks.length(); i++) {
1171 BlockBegin* b = blocks.at(i);
1172 // exception handlers need to be treated as additional roots
1173 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1174 BlockBegin* excp = b->exception_handler_at(e);
1175 int id = excp->block_id();
1176 if (!visited_block.at(id)) {
1177 blocks.push(excp);
1178 visited_block.at_put(id, true);
1179 nce.iterate(excp);
1180 }
1181 }
1182 // traverse successors
1183 BlockEnd *end = b->end();
1184 for (int s = end->number_of_sux(); s-- > 0; ) {
1185 BlockBegin* next = end->sux_at(s);
1186 int id = next->block_id();
1187 if (!visited_block.at(id)) {
1188 blocks.push(next);
1189 visited_block.at_put(id, true);
1190 }
1191 }
1192 }
1193
1194
1195 if (PrintNullCheckElimination) {
1196 tty->print_cr("Done with null check elimination for method %s::%s%s",
1197 ir()->method()->holder()->name()->as_utf8(),
1198 ir()->method()->name()->as_utf8(),
1199 ir()->method()->signature()->as_symbol()->as_utf8());
1200 }
1201 }