1 /*
2 * Copyright (c) 1999, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "c1/c1_Canonicalizer.hpp"
27 #include "c1/c1_Optimizer.hpp"
28 #include "c1/c1_ValueMap.hpp"
29 #include "c1/c1_ValueSet.hpp"
30 #include "c1/c1_ValueStack.hpp"
31 #include "utilities/bitMap.inline.hpp"
32 #include "compiler/compileLog.hpp"
33
34 typedef GrowableArray<ValueSet*> ValueSetList;
35
36 Optimizer::Optimizer(IR* ir) {
37 assert(ir->is_valid(), "IR must be valid");
38 _ir = ir;
39 }
40
41 class CE_Eliminator: public BlockClosure {
42 private:
43 IR* _hir;
44 int _cee_count; // the number of CEs successfully eliminated
45 int _ifop_count; // the number of IfOps successfully simplified
46 int _has_substitution;
47
48 public:
49 CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) {
50 _has_substitution = false;
51 _hir->iterate_preorder(this);
52 if (_has_substitution) {
53 // substituted some ifops/phis, so resolve the substitution
54 SubstitutionResolver sr(_hir);
55 }
56
57 CompileLog* log = _hir->compilation()->log();
58 if (log != NULL)
59 log->set_context("optimize name='cee'");
60 }
61
62 ~CE_Eliminator() {
63 CompileLog* log = _hir->compilation()->log();
64 if (log != NULL)
65 log->clear_context(); // skip marker if nothing was printed
66 }
67
68 int cee_count() const { return _cee_count; }
69 int ifop_count() const { return _ifop_count; }
70
71 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
72 int e = sux->number_of_exception_handlers();
73 for (int i = 0; i < e; i++) {
74 BlockBegin* xhandler = sux->exception_handler_at(i);
75 block->add_exception_handler(xhandler);
76
77 assert(xhandler->is_predecessor(sux), "missing predecessor");
78 if (sux->number_of_preds() == 0) {
79 // sux is disconnected from graph so disconnect from exception handlers
80 xhandler->remove_predecessor(sux);
81 }
82 if (!xhandler->is_predecessor(block)) {
83 xhandler->add_predecessor(block);
84 }
85 }
86 }
87
88 virtual void block_do(BlockBegin* block);
89
90 private:
91 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
92 };
93
94 void CE_Eliminator::block_do(BlockBegin* block) {
95 // 1) find conditional expression
96 // check if block ends with an If
97 If* if_ = block->end()->as_If();
98 if (if_ == NULL) return;
99
100 // check if If works on int or object types
101 // (we cannot handle If's working on long, float or doubles yet,
102 // since IfOp doesn't support them - these If's show up if cmp
103 // operations followed by If's are eliminated)
104 ValueType* if_type = if_->x()->type();
105 if (!if_type->is_int() && !if_type->is_object()) return;
106
107 BlockBegin* t_block = if_->tsux();
108 BlockBegin* f_block = if_->fsux();
109 Instruction* t_cur = t_block->next();
110 Instruction* f_cur = f_block->next();
111
112 // one Constant may be present between BlockBegin and BlockEnd
113 Value t_const = NULL;
114 Value f_const = NULL;
115 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
116 t_const = t_cur;
117 t_cur = t_cur->next();
118 }
119 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
120 f_const = f_cur;
121 f_cur = f_cur->next();
122 }
123
124 // check if both branches end with a goto
125 Goto* t_goto = t_cur->as_Goto();
126 if (t_goto == NULL) return;
127 Goto* f_goto = f_cur->as_Goto();
128 if (f_goto == NULL) return;
129
130 // check if both gotos merge into the same block
131 BlockBegin* sux = t_goto->default_sux();
132 if (sux != f_goto->default_sux()) return;
133
134 // check if at least one word was pushed on sux_state
135 // inlining depths must match
136 ValueStack* if_state = if_->state();
137 ValueStack* sux_state = sux->state();
138 if (if_state->scope()->level() > sux_state->scope()->level()) {
139 while (sux_state->scope() != if_state->scope()) {
140 if_state = if_state->caller_state();
141 assert(if_state != NULL, "states do not match up");
142 }
143 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
144 while (sux_state->scope() != if_state->scope()) {
145 sux_state = sux_state->caller_state();
146 assert(sux_state != NULL, "states do not match up");
147 }
148 }
149
150 if (sux_state->stack_size() <= if_state->stack_size()) return;
151
152 // check if phi function is present at end of successor stack and that
153 // only this phi was pushed on the stack
154 Value sux_phi = sux_state->stack_at(if_state->stack_size());
155 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
156 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
157
158 // get the values that were pushed in the true- and false-branch
159 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
160 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
161
162 // backend does not support floats
163 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
164 if (t_value->type()->is_float_kind()) return;
165
166 // check that successor has no other phi functions but sux_phi
167 // this can happen when t_block or f_block contained additonal stores to local variables
168 // that are no longer represented by explicit instructions
169 for_each_phi_fun(sux, phi,
170 if (phi != sux_phi) return;
171 );
172 // true and false blocks can't have phis
173 for_each_phi_fun(t_block, phi, return; );
174 for_each_phi_fun(f_block, phi, return; );
175
176 // 2) substitute conditional expression
177 // with an IfOp followed by a Goto
178 // cut if_ away and get node before
179 Instruction* cur_end = if_->prev();
180
181 // append constants of true- and false-block if necessary
182 // clone constants because original block must not be destroyed
183 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
184 if (t_value == t_const) {
185 t_value = new Constant(t_const->type());
186 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
187 cur_end = cur_end->set_next(t_value);
188 }
189 if (f_value == f_const) {
190 f_value = new Constant(f_const->type());
191 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
192 cur_end = cur_end->set_next(f_value);
193 }
194
195 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
196 assert(result != NULL, "make_ifop must return a non-null instruction");
197 if (!result->is_linked() && result->can_be_linked()) {
198 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
199 cur_end = cur_end->set_next(result);
200 }
201
202 // append Goto to successor
203 ValueStack* state_before = if_->state_before();
204 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
205
206 // prepare state for Goto
207 ValueStack* goto_state = if_state;
208 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
209 goto_state->push(result->type(), result);
210 assert(goto_state->is_same(sux_state), "states must match now");
211 goto_->set_state(goto_state);
212
213 cur_end = cur_end->set_next(goto_, goto_state->bci());
214
215 // Adjust control flow graph
216 BlockBegin::disconnect_edge(block, t_block);
217 BlockBegin::disconnect_edge(block, f_block);
218 if (t_block->number_of_preds() == 0) {
219 BlockBegin::disconnect_edge(t_block, sux);
220 }
221 adjust_exception_edges(block, t_block);
222 if (f_block->number_of_preds() == 0) {
223 BlockBegin::disconnect_edge(f_block, sux);
224 }
225 adjust_exception_edges(block, f_block);
226
227 // update block end
228 block->set_end(goto_);
229
230 // substitute the phi if possible
231 if (sux_phi->as_Phi()->operand_count() == 1) {
232 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
233 sux_phi->set_subst(result);
234 _has_substitution = true;
235 }
236
237 // 3) successfully eliminated a conditional expression
238 _cee_count++;
239 if (PrintCEE) {
240 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());
241 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
242 }
243
244 _hir->verify();
245 }
246
247 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
248 if (!OptimizeIfOps) {
249 return new IfOp(x, cond, y, tval, fval);
250 }
251
252 tval = tval->subst();
253 fval = fval->subst();
254 if (tval == fval) {
255 _ifop_count++;
256 return tval;
257 }
258
259 x = x->subst();
260 y = y->subst();
261
262 Constant* y_const = y->as_Constant();
263 if (y_const != NULL) {
264 IfOp* x_ifop = x->as_IfOp();
265 if (x_ifop != NULL) { // x is an ifop, y is a constant
266 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
267 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
268
269 if (x_tval_const != NULL && x_fval_const != NULL) {
270 Instruction::Condition x_ifop_cond = x_ifop->cond();
271
272 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
273 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
274
275 // not_comparable here is a valid return in case we're comparing unloaded oop constants
276 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
277 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
278 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
279
280 _ifop_count++;
281 if (new_tval == new_fval) {
282 return new_tval;
283 } else {
284 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
285 }
286 }
287 }
288 } else {
289 Constant* x_const = x->as_Constant();
290 if (x_const != NULL) { // x and y are constants
291 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
292 // not_comparable here is a valid return in case we're comparing unloaded oop constants
293 if (x_compare_res != Constant::not_comparable) {
294 _ifop_count++;
295 return x_compare_res == Constant::cond_true ? tval : fval;
296 }
297 }
298 }
299 }
300 return new IfOp(x, cond, y, tval, fval);
301 }
302
303 void Optimizer::eliminate_conditional_expressions() {
304 // find conditional expressions & replace them with IfOps
305 CE_Eliminator ce(ir());
306 }
307
308 class BlockMerger: public BlockClosure {
309 private:
310 IR* _hir;
311 int _merge_count; // the number of block pairs successfully merged
312
313 public:
314 BlockMerger(IR* hir)
315 : _hir(hir)
316 , _merge_count(0)
317 {
318 _hir->iterate_preorder(this);
319 CompileLog* log = _hir->compilation()->log();
320 if (log != NULL)
321 log->set_context("optimize name='eliminate_blocks'");
322 }
323
324 ~BlockMerger() {
325 CompileLog* log = _hir->compilation()->log();
326 if (log != NULL)
327 log->clear_context(); // skip marker if nothing was printed
328 }
329
330 bool try_merge(BlockBegin* block) {
331 BlockEnd* end = block->end();
332 if (end->as_Goto() != NULL) {
333 assert(end->number_of_sux() == 1, "end must have exactly one successor");
334 // Note: It would be sufficient to check for the number of successors (= 1)
335 // in order to decide if this block can be merged potentially. That
336 // would then also include switch statements w/ only a default case.
337 // However, in that case we would need to make sure the switch tag
338 // expression is executed if it can produce observable side effects.
339 // We should probably have the canonicalizer simplifying such switch
340 // statements and then we are sure we don't miss these merge opportunities
341 // here (was bug - gri 7/7/99).
342 BlockBegin* sux = end->default_sux();
343 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
344 // merge the two blocks
345
346 #ifdef ASSERT
347 // verify that state at the end of block and at the beginning of sux are equal
348 // no phi functions must be present at beginning of sux
349 ValueStack* sux_state = sux->state();
350 ValueStack* end_state = end->state();
351
352 assert(end_state->scope() == sux_state->scope(), "scopes must match");
353 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
354 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
355
356 int index;
357 Value sux_value;
358 for_each_stack_value(sux_state, index, sux_value) {
359 assert(sux_value == end_state->stack_at(index), "stack not equal");
360 }
361 for_each_local_value(sux_state, index, sux_value) {
362 assert(sux_value == end_state->local_at(index), "locals not equal");
363 }
364 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
365 #endif
366
367 // find instruction before end & append first instruction of sux block
368 Instruction* prev = end->prev();
369 Instruction* next = sux->next();
370 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
371 prev->set_next(next);
372 prev->fixup_block_pointers();
373 sux->disconnect_from_graph();
374 block->set_end(sux->end());
375 // add exception handlers of deleted block, if any
376 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
377 BlockBegin* xhandler = sux->exception_handler_at(k);
378 block->add_exception_handler(xhandler);
379
380 // also substitute predecessor of exception handler
381 assert(xhandler->is_predecessor(sux), "missing predecessor");
382 xhandler->remove_predecessor(sux);
383 if (!xhandler->is_predecessor(block)) {
384 xhandler->add_predecessor(block);
385 }
386 }
387
388 // debugging output
389 _merge_count++;
390 if (PrintBlockElimination) {
391 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
392 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
393 }
394
395 _hir->verify();
396
397 If* if_ = block->end()->as_If();
398 if (if_) {
399 IfOp* ifop = if_->x()->as_IfOp();
400 Constant* con = if_->y()->as_Constant();
401 bool swapped = false;
402 if (!con || !ifop) {
403 ifop = if_->y()->as_IfOp();
404 con = if_->x()->as_Constant();
405 swapped = true;
406 }
407 if (con && ifop) {
408 Constant* tval = ifop->tval()->as_Constant();
409 Constant* fval = ifop->fval()->as_Constant();
410 if (tval && fval) {
411 // Find the instruction before if_, starting with ifop.
412 // When if_ and ifop are not in the same block, prev
413 // becomes NULL In such (rare) cases it is not
414 // profitable to perform the optimization.
415 Value prev = ifop;
416 while (prev != NULL && prev->next() != if_) {
417 prev = prev->next();
418 }
419
420 if (prev != NULL) {
421 Instruction::Condition cond = if_->cond();
422 BlockBegin* tsux = if_->tsux();
423 BlockBegin* fsux = if_->fsux();
424 if (swapped) {
425 cond = Instruction::mirror(cond);
426 }
427
428 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
429 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
430 if (tblock != fblock && !if_->is_safepoint()) {
431 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
432 tblock, fblock, if_->state_before(), if_->is_safepoint());
433 newif->set_state(if_->state()->copy());
434
435 assert(prev->next() == if_, "must be guaranteed by above search");
436 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
437 prev->set_next(newif);
438 block->set_end(newif);
439
440 _merge_count++;
441 if (PrintBlockElimination) {
442 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
443 }
444
445 _hir->verify();
446 }
447 }
448 }
449 }
450 }
451
452 return true;
453 }
454 }
455 return false;
456 }
457
458 virtual void block_do(BlockBegin* block) {
459 _hir->verify();
460 // repeat since the same block may merge again
461 while (try_merge(block)) {
462 _hir->verify();
463 }
464 }
465 };
466
467
468 void Optimizer::eliminate_blocks() {
469 // merge blocks if possible
470 BlockMerger bm(ir());
471 }
472
473
474 class NullCheckEliminator;
475 class NullCheckVisitor: public InstructionVisitor {
476 private:
477 NullCheckEliminator* _nce;
478 NullCheckEliminator* nce() { return _nce; }
479
480 public:
481 NullCheckVisitor() {}
482
483 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
484
485 void do_Phi (Phi* x);
486 void do_Local (Local* x);
487 void do_Constant (Constant* x);
488 void do_LoadField (LoadField* x);
489 void do_StoreField (StoreField* x);
490 void do_ArrayLength (ArrayLength* x);
491 void do_LoadIndexed (LoadIndexed* x);
492 void do_StoreIndexed (StoreIndexed* x);
493 void do_NegateOp (NegateOp* x);
494 void do_ArithmeticOp (ArithmeticOp* x);
495 void do_ShiftOp (ShiftOp* x);
496 void do_LogicOp (LogicOp* x);
497 void do_CompareOp (CompareOp* x);
498 void do_IfOp (IfOp* x);
499 void do_Convert (Convert* x);
500 void do_NullCheck (NullCheck* x);
501 void do_TypeCast (TypeCast* x);
502 void do_Invoke (Invoke* x);
503 void do_NewInstance (NewInstance* x);
504 void do_NewTypeArray (NewTypeArray* x);
505 void do_NewObjectArray (NewObjectArray* x);
506 void do_NewMultiArray (NewMultiArray* x);
507 void do_CheckCast (CheckCast* x);
508 void do_InstanceOf (InstanceOf* x);
509 void do_MonitorEnter (MonitorEnter* x);
510 void do_MonitorExit (MonitorExit* x);
511 void do_Intrinsic (Intrinsic* x);
512 void do_BlockBegin (BlockBegin* x);
513 void do_Goto (Goto* x);
514 void do_If (If* x);
515 void do_IfInstanceOf (IfInstanceOf* x);
516 void do_TableSwitch (TableSwitch* x);
517 void do_LookupSwitch (LookupSwitch* x);
518 void do_Return (Return* x);
519 void do_Throw (Throw* x);
520 void do_Base (Base* x);
521 void do_OsrEntry (OsrEntry* x);
522 void do_ExceptionObject(ExceptionObject* x);
523 void do_RoundFP (RoundFP* x);
524 void do_UnsafeGetRaw (UnsafeGetRaw* x);
525 void do_UnsafePutRaw (UnsafePutRaw* x);
526 void do_UnsafeGetObject(UnsafeGetObject* x);
527 void do_UnsafePutObject(UnsafePutObject* x);
528 void do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x);
529 void do_ProfileCall (ProfileCall* x);
530 void do_ProfileReturnType (ProfileReturnType* x);
531 void do_ProfileInvoke (ProfileInvoke* x);
532 void do_RuntimeCall (RuntimeCall* x);
533 void do_MemBar (MemBar* x);
534 void do_RangeCheckPredicate(RangeCheckPredicate* x);
535 #ifdef ASSERT
536 void do_Assert (Assert* x);
537 #endif
538 };
539
540
541 // Because of a static contained within (for the purpose of iteration
542 // over instructions), it is only valid to have one of these active at
543 // a time
544 class NullCheckEliminator: public ValueVisitor {
545 private:
546 Optimizer* _opt;
547
548 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
549 BlockList* _work_list; // Basic blocks to visit
550
551 bool visitable(Value x) {
552 assert(_visitable_instructions != NULL, "check");
553 return _visitable_instructions->contains(x);
554 }
555 void mark_visited(Value x) {
556 assert(_visitable_instructions != NULL, "check");
557 _visitable_instructions->remove(x);
558 }
559 void mark_visitable(Value x) {
560 assert(_visitable_instructions != NULL, "check");
561 _visitable_instructions->put(x);
562 }
563 void clear_visitable_state() {
564 assert(_visitable_instructions != NULL, "check");
565 _visitable_instructions->clear();
566 }
567
568 ValueSet* _set; // current state, propagated to subsequent BlockBegins
569 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
570 NullCheckVisitor _visitor;
571 NullCheck* _last_explicit_null_check;
572
573 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
574 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
575 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
576
577 BlockList* work_list() { return _work_list; }
578
579 void iterate_all();
580 void iterate_one(BlockBegin* block);
581
582 ValueSet* state() { return _set; }
583 void set_state_from (ValueSet* state) { _set->set_from(state); }
584 ValueSet* state_for (BlockBegin* block) { return _block_states.at(block->block_id()); }
585 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(block->block_id(), stack); }
586 // Returns true if caused a change in the block's state.
587 bool merge_state_for(BlockBegin* block,
588 ValueSet* incoming_state);
589
590 public:
591 // constructor
592 NullCheckEliminator(Optimizer* opt)
593 : _opt(opt)
594 , _set(new ValueSet())
595 , _last_explicit_null_check(NULL)
596 , _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), NULL)
597 , _work_list(new BlockList()) {
598 _visitable_instructions = new ValueSet();
599 _visitor.set_eliminator(this);
600 CompileLog* log = _opt->ir()->compilation()->log();
601 if (log != NULL)
602 log->set_context("optimize name='null_check_elimination'");
603 }
604
605 ~NullCheckEliminator() {
606 CompileLog* log = _opt->ir()->compilation()->log();
607 if (log != NULL)
608 log->clear_context(); // skip marker if nothing was printed
609 }
610
611 Optimizer* opt() { return _opt; }
612 IR* ir () { return opt()->ir(); }
613
614 // Process a graph
615 void iterate(BlockBegin* root);
616
617 void visit(Value* f);
618
619 // In some situations (like NullCheck(x); getfield(x)) the debug
620 // information from the explicit NullCheck can be used to populate
621 // the getfield, even if the two instructions are in different
622 // scopes; this allows implicit null checks to be used but the
623 // correct exception information to be generated. We must clear the
624 // last-traversed NullCheck when we reach a potentially-exception-
625 // throwing instruction, as well as in some other cases.
626 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
627 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
628 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
629 ? _last_explicit_null_check->obj()
630 : NULL); }
631 NullCheck* consume_last_explicit_null_check() {
632 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
633 _last_explicit_null_check->set_can_trap(false);
634 return _last_explicit_null_check;
635 }
636 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
637
638 // Handlers for relevant instructions
639 // (separated out from NullCheckVisitor for clarity)
640
641 // The basic contract is that these must leave the instruction in
642 // the desired state; must not assume anything about the state of
643 // the instruction. We make multiple passes over some basic blocks
644 // and the last pass is the only one whose result is valid.
645 void handle_AccessField (AccessField* x);
646 void handle_ArrayLength (ArrayLength* x);
647 void handle_LoadIndexed (LoadIndexed* x);
648 void handle_StoreIndexed (StoreIndexed* x);
649 void handle_NullCheck (NullCheck* x);
650 void handle_Invoke (Invoke* x);
651 void handle_NewInstance (NewInstance* x);
652 void handle_NewArray (NewArray* x);
653 void handle_AccessMonitor (AccessMonitor* x);
654 void handle_Intrinsic (Intrinsic* x);
655 void handle_ExceptionObject (ExceptionObject* x);
656 void handle_Phi (Phi* x);
657 void handle_ProfileCall (ProfileCall* x);
658 void handle_ProfileReturnType (ProfileReturnType* x);
659 };
660
661
662 // NEEDS_CLEANUP
663 // There may be other instructions which need to clear the last
664 // explicit null check. Anything across which we can not hoist the
665 // debug information for a NullCheck instruction must clear it. It
666 // might be safer to pattern match "NullCheck ; {AccessField,
667 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
668 // Should test to see performance hit of clearing it for all handlers
669 // with empty bodies below. If it is negligible then we should leave
670 // that in for safety, otherwise should think more about it.
671 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
672 void NullCheckVisitor::do_Local (Local* x) {}
673 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
674 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
675 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
676 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
677 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
678 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
679 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
680 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
681 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
682 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
683 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
684 void NullCheckVisitor::do_IfOp (IfOp* x) {}
685 void NullCheckVisitor::do_Convert (Convert* x) {}
686 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
687 void NullCheckVisitor::do_TypeCast (TypeCast* x) {}
688 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
689 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
690 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
691 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
692 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
693 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
694 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
695 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
696 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
697 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
698 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
699 void NullCheckVisitor::do_Goto (Goto* x) {}
700 void NullCheckVisitor::do_If (If* x) {}
701 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
702 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
703 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
704 void NullCheckVisitor::do_Return (Return* x) {}
705 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
706 void NullCheckVisitor::do_Base (Base* x) {}
707 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
708 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
709 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
710 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
711 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
712 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
713 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
714 void NullCheckVisitor::do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x) {}
715 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check();
716 nce()->handle_ProfileCall(x); }
717 void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
718 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
719 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
720 void NullCheckVisitor::do_MemBar (MemBar* x) {}
721 void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
722 #ifdef ASSERT
723 void NullCheckVisitor::do_Assert (Assert* x) {}
724 #endif
725
726 void NullCheckEliminator::visit(Value* p) {
727 assert(*p != NULL, "should not find NULL instructions");
728 if (visitable(*p)) {
729 mark_visited(*p);
730 (*p)->visit(&_visitor);
731 }
732 }
733
734 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
735 ValueSet* state = state_for(block);
736 if (state == NULL) {
737 state = incoming_state->copy();
738 set_state_for(block, state);
739 return true;
740 } else {
741 bool changed = state->set_intersect(incoming_state);
742 if (PrintNullCheckElimination && changed) {
743 tty->print_cr("Block %d's null check state changed", block->block_id());
744 }
745 return changed;
746 }
747 }
748
749
750 void NullCheckEliminator::iterate_all() {
751 while (work_list()->length() > 0) {
752 iterate_one(work_list()->pop());
753 }
754 }
755
756
757 void NullCheckEliminator::iterate_one(BlockBegin* block) {
758 clear_visitable_state();
759 // clear out an old explicit null checks
760 set_last_explicit_null_check(NULL);
761
762 if (PrintNullCheckElimination) {
763 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
764 block->block_id(),
765 ir()->method()->holder()->name()->as_utf8(),
766 ir()->method()->name()->as_utf8(),
767 ir()->method()->signature()->as_symbol()->as_utf8());
768 }
769
770 // Create new state if none present (only happens at root)
771 if (state_for(block) == NULL) {
772 ValueSet* tmp_state = new ValueSet();
773 set_state_for(block, tmp_state);
774 // Initial state is that local 0 (receiver) is non-null for
775 // non-static methods
776 ValueStack* stack = block->state();
777 IRScope* scope = stack->scope();
778 ciMethod* method = scope->method();
779 if (!method->is_static()) {
780 Local* local0 = stack->local_at(0)->as_Local();
781 assert(local0 != NULL, "must be");
782 assert(local0->type() == objectType, "invalid type of receiver");
783
784 if (local0 != NULL) {
785 // Local 0 is used in this scope
786 tmp_state->put(local0);
787 if (PrintNullCheckElimination) {
788 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
789 }
790 }
791 }
792 }
793
794 // Must copy block's state to avoid mutating it during iteration
795 // through the block -- otherwise "not-null" states can accidentally
796 // propagate "up" through the block during processing of backward
797 // branches and algorithm is incorrect (and does not converge)
798 set_state_from(state_for(block));
799
800 // allow visiting of Phis belonging to this block
801 for_each_phi_fun(block, phi,
802 mark_visitable(phi);
803 );
804
805 BlockEnd* e = block->end();
806 assert(e != NULL, "incomplete graph");
807 int i;
808
809 // Propagate the state before this block into the exception
810 // handlers. They aren't true successors since we aren't guaranteed
811 // to execute the whole block before executing them. Also putting
812 // them on first seems to help reduce the amount of iteration to
813 // reach a fixed point.
814 for (i = 0; i < block->number_of_exception_handlers(); i++) {
815 BlockBegin* next = block->exception_handler_at(i);
816 if (merge_state_for(next, state())) {
817 if (!work_list()->contains(next)) {
818 work_list()->push(next);
819 }
820 }
821 }
822
823 // Iterate through block, updating state.
824 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
825 // Mark instructions in this block as visitable as they are seen
826 // in the instruction list. This keeps the iteration from
827 // visiting instructions which are references in other blocks or
828 // visiting instructions more than once.
829 mark_visitable(instr);
830 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
831 mark_visited(instr);
832 instr->input_values_do(this);
833 instr->visit(&_visitor);
834 }
835 }
836
837 // Propagate state to successors if necessary
838 for (i = 0; i < e->number_of_sux(); i++) {
839 BlockBegin* next = e->sux_at(i);
840 if (merge_state_for(next, state())) {
841 if (!work_list()->contains(next)) {
842 work_list()->push(next);
843 }
844 }
845 }
846 }
847
848
849 void NullCheckEliminator::iterate(BlockBegin* block) {
850 work_list()->push(block);
851 iterate_all();
852 }
853
854 void NullCheckEliminator::handle_AccessField(AccessField* x) {
855 if (x->is_static()) {
856 if (x->as_LoadField() != NULL) {
857 // If the field is a non-null static final object field (as is
858 // often the case for sun.misc.Unsafe), put this LoadField into
859 // the non-null map
860 ciField* field = x->field();
861 if (field->is_constant()) {
862 ciConstant field_val = field->constant_value();
863 BasicType field_type = field_val.basic_type();
864 if (field_type == T_OBJECT || field_type == T_ARRAY) {
865 ciObject* obj_val = field_val.as_object();
866 if (!obj_val->is_null_object()) {
867 if (PrintNullCheckElimination) {
868 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
869 x->id());
870 }
871 set_put(x);
872 }
873 }
874 }
875 }
876 // Be conservative
877 clear_last_explicit_null_check();
878 return;
879 }
880
881 Value obj = x->obj();
882 if (set_contains(obj)) {
883 // Value is non-null => update AccessField
884 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
885 x->set_explicit_null_check(consume_last_explicit_null_check());
886 x->set_needs_null_check(true);
887 if (PrintNullCheckElimination) {
888 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
889 x->explicit_null_check()->id(), x->id(), obj->id());
890 }
891 } else {
892 x->set_explicit_null_check(NULL);
893 x->set_needs_null_check(false);
894 if (PrintNullCheckElimination) {
895 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
896 }
897 }
898 } else {
899 set_put(obj);
900 if (PrintNullCheckElimination) {
901 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
902 }
903 // Ensure previous passes do not cause wrong state
904 x->set_needs_null_check(true);
905 x->set_explicit_null_check(NULL);
906 }
907 clear_last_explicit_null_check();
908 }
909
910
911 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
912 Value array = x->array();
913 if (set_contains(array)) {
914 // Value is non-null => update AccessArray
915 if (last_explicit_null_check_obj() == array) {
916 x->set_explicit_null_check(consume_last_explicit_null_check());
917 x->set_needs_null_check(true);
918 if (PrintNullCheckElimination) {
919 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
920 x->explicit_null_check()->id(), x->id(), array->id());
921 }
922 } else {
923 x->set_explicit_null_check(NULL);
924 x->set_needs_null_check(false);
925 if (PrintNullCheckElimination) {
926 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
927 }
928 }
929 } else {
930 set_put(array);
931 if (PrintNullCheckElimination) {
932 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
933 }
934 // Ensure previous passes do not cause wrong state
935 x->set_needs_null_check(true);
936 x->set_explicit_null_check(NULL);
937 }
938 clear_last_explicit_null_check();
939 }
940
941
942 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
943 Value array = x->array();
944 if (set_contains(array)) {
945 // Value is non-null => update AccessArray
946 if (last_explicit_null_check_obj() == array) {
947 x->set_explicit_null_check(consume_last_explicit_null_check());
948 x->set_needs_null_check(true);
949 if (PrintNullCheckElimination) {
950 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
951 x->explicit_null_check()->id(), x->id(), array->id());
952 }
953 } else {
954 x->set_explicit_null_check(NULL);
955 x->set_needs_null_check(false);
956 if (PrintNullCheckElimination) {
957 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
958 }
959 }
960 } else {
961 set_put(array);
962 if (PrintNullCheckElimination) {
963 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
964 }
965 // Ensure previous passes do not cause wrong state
966 x->set_needs_null_check(true);
967 x->set_explicit_null_check(NULL);
968 }
969 clear_last_explicit_null_check();
970 }
971
972
973 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
974 Value array = x->array();
975 if (set_contains(array)) {
976 // Value is non-null => update AccessArray
977 if (PrintNullCheckElimination) {
978 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
979 }
980 x->set_needs_null_check(false);
981 } else {
982 set_put(array);
983 if (PrintNullCheckElimination) {
984 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
985 }
986 // Ensure previous passes do not cause wrong state
987 x->set_needs_null_check(true);
988 }
989 clear_last_explicit_null_check();
990 }
991
992
993 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
994 Value obj = x->obj();
995 if (set_contains(obj)) {
996 // Already proven to be non-null => this NullCheck is useless
997 if (PrintNullCheckElimination) {
998 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
999 }
1000 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
1001 // The code generator won't emit LIR for a NullCheck that cannot trap.
1002 x->set_can_trap(false);
1003 } else {
1004 // May be null => add to map and set last explicit NullCheck
1005 x->set_can_trap(true);
1006 // make sure it's pinned if it can trap
1007 x->pin(Instruction::PinExplicitNullCheck);
1008 set_put(obj);
1009 set_last_explicit_null_check(x);
1010 if (PrintNullCheckElimination) {
1011 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
1012 }
1013 }
1014 }
1015
1016
1017 void NullCheckEliminator::handle_Invoke(Invoke* x) {
1018 if (!x->has_receiver()) {
1019 // Be conservative
1020 clear_last_explicit_null_check();
1021 return;
1022 }
1023
1024 Value recv = x->receiver();
1025 if (!set_contains(recv)) {
1026 set_put(recv);
1027 if (PrintNullCheckElimination) {
1028 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
1029 }
1030 }
1031 clear_last_explicit_null_check();
1032 }
1033
1034
1035 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
1036 set_put(x);
1037 if (PrintNullCheckElimination) {
1038 tty->print_cr("NewInstance %d is non-null", x->id());
1039 }
1040 }
1041
1042
1043 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1044 set_put(x);
1045 if (PrintNullCheckElimination) {
1046 tty->print_cr("NewArray %d is non-null", x->id());
1047 }
1048 }
1049
1050
1051 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1052 set_put(x);
1053 if (PrintNullCheckElimination) {
1054 tty->print_cr("ExceptionObject %d is non-null", x->id());
1055 }
1056 }
1057
1058
1059 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1060 Value obj = x->obj();
1061 if (set_contains(obj)) {
1062 // Value is non-null => update AccessMonitor
1063 if (PrintNullCheckElimination) {
1064 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1065 }
1066 x->set_needs_null_check(false);
1067 } else {
1068 set_put(obj);
1069 if (PrintNullCheckElimination) {
1070 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1071 }
1072 // Ensure previous passes do not cause wrong state
1073 x->set_needs_null_check(true);
1074 }
1075 clear_last_explicit_null_check();
1076 }
1077
1078
1079 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1080 if (!x->has_receiver()) {
1081 if (x->id() == vmIntrinsics::_arraycopy) {
1082 for (int i = 0; i < x->number_of_arguments(); i++) {
1083 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1084 }
1085 }
1086
1087 // Be conservative
1088 clear_last_explicit_null_check();
1089 return;
1090 }
1091
1092 Value recv = x->receiver();
1093 if (set_contains(recv)) {
1094 // Value is non-null => update Intrinsic
1095 if (PrintNullCheckElimination) {
1096 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1097 }
1098 x->set_needs_null_check(false);
1099 } else {
1100 set_put(recv);
1101 if (PrintNullCheckElimination) {
1102 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1103 }
1104 // Ensure previous passes do not cause wrong state
1105 x->set_needs_null_check(true);
1106 }
1107 clear_last_explicit_null_check();
1108 }
1109
1110
1111 void NullCheckEliminator::handle_Phi(Phi* x) {
1112 int i;
1113 bool all_non_null = true;
1114 if (x->is_illegal()) {
1115 all_non_null = false;
1116 } else {
1117 for (i = 0; i < x->operand_count(); i++) {
1118 Value input = x->operand_at(i);
1119 if (!set_contains(input)) {
1120 all_non_null = false;
1121 }
1122 }
1123 }
1124
1125 if (all_non_null) {
1126 // Value is non-null => update Phi
1127 if (PrintNullCheckElimination) {
1128 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1129 }
1130 x->set_needs_null_check(false);
1131 } else if (set_contains(x)) {
1132 set_remove(x);
1133 }
1134 }
1135
1136 void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
1137 for (int i = 0; i < x->nb_profiled_args(); i++) {
1138 x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
1139 }
1140 }
1141
1142 void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
1143 x->set_needs_null_check(!set_contains(x->ret()));
1144 }
1145
1146 void Optimizer::eliminate_null_checks() {
1147 ResourceMark rm;
1148
1149 NullCheckEliminator nce(this);
1150
1151 if (PrintNullCheckElimination) {
1152 tty->print_cr("Starting null check elimination for method %s::%s%s",
1153 ir()->method()->holder()->name()->as_utf8(),
1154 ir()->method()->name()->as_utf8(),
1155 ir()->method()->signature()->as_symbol()->as_utf8());
1156 }
1157
1158 // Apply to graph
1159 nce.iterate(ir()->start());
1160
1161 // walk over the graph looking for exception
1162 // handlers and iterate over them as well
1163 int nblocks = BlockBegin::number_of_blocks();
1164 BlockList blocks(nblocks);
1165 boolArray visited_block(nblocks, nblocks, false);
1166
1167 blocks.push(ir()->start());
1168 visited_block.at_put(ir()->start()->block_id(), true);
1169 for (int i = 0; i < blocks.length(); i++) {
1170 BlockBegin* b = blocks.at(i);
1171 // exception handlers need to be treated as additional roots
1172 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1173 BlockBegin* excp = b->exception_handler_at(e);
1174 int id = excp->block_id();
1175 if (!visited_block.at(id)) {
1176 blocks.push(excp);
1177 visited_block.at_put(id, true);
1178 nce.iterate(excp);
1179 }
1180 }
1181 // traverse successors
1182 BlockEnd *end = b->end();
1183 for (int s = end->number_of_sux(); s-- > 0; ) {
1184 BlockBegin* next = end->sux_at(s);
1185 int id = next->block_id();
1186 if (!visited_block.at(id)) {
1187 blocks.push(next);
1188 visited_block.at_put(id, true);
1189 }
1190 }
1191 }
1192
1193
1194 if (PrintNullCheckElimination) {
1195 tty->print_cr("Done with null check elimination for method %s::%s%s",
1196 ir()->method()->holder()->name()->as_utf8(),
1197 ir()->method()->name()->as_utf8(),
1198 ir()->method()->signature()->as_symbol()->as_utf8());
1199 }
1200 }