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