1 /*
2 * Copyright 1999-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include "incls/_precompiled.incl"
26 #include "incls/_c1_Optimizer.cpp.incl"
27
28 define_array(ValueSetArray, ValueSet*);
29 define_stack(ValueSetList, ValueSetArray);
30
31
32 Optimizer::Optimizer(IR* ir) {
33 assert(ir->is_valid(), "IR must be valid");
34 _ir = ir;
35 }
36
37 class CE_Eliminator: public BlockClosure {
38 private:
39 IR* _hir;
40 int _cee_count; // the number of CEs successfully eliminated
41 int _has_substitution;
42
43 public:
44 CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) {
45 _has_substitution = false;
46 _hir->iterate_preorder(this);
47 if (_has_substitution) {
48 // substituted some phis so resolve the substitution
49 SubstitutionResolver sr(_hir);
50 }
51 }
52 int cee_count() const { return _cee_count; }
53
54 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
55 int e = sux->number_of_exception_handlers();
56 for (int i = 0; i < e; i++) {
57 BlockBegin* xhandler = sux->exception_handler_at(i);
58 block->add_exception_handler(xhandler);
59
60 assert(xhandler->is_predecessor(sux), "missing predecessor");
61 if (sux->number_of_preds() == 0) {
62 // sux is disconnected from graph so disconnect from exception handlers
63 xhandler->remove_predecessor(sux);
64 }
65 if (!xhandler->is_predecessor(block)) {
66 xhandler->add_predecessor(block);
67 }
68 }
69 }
70
71 virtual void block_do(BlockBegin* block) {
72 // 1) find conditional expression
73 // check if block ends with an If
74 If* if_ = block->end()->as_If();
75 if (if_ == NULL) return;
76
77 // check if If works on int or object types
78 // (we cannot handle If's working on long, float or doubles yet,
79 // since IfOp doesn't support them - these If's show up if cmp
80 // operations followed by If's are eliminated)
81 ValueType* if_type = if_->x()->type();
82 if (!if_type->is_int() && !if_type->is_object()) return;
83
84 BlockBegin* t_block = if_->tsux();
85 BlockBegin* f_block = if_->fsux();
86 Instruction* t_cur = t_block->next();
87 Instruction* f_cur = f_block->next();
88
89 // one Constant may be present between BlockBegin and BlockEnd
90 Value t_const = NULL;
91 Value f_const = NULL;
92 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
93 t_const = t_cur;
94 t_cur = t_cur->next();
95 }
96 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
97 f_const = f_cur;
98 f_cur = f_cur->next();
99 }
100
101 // check if both branches end with a goto
102 Goto* t_goto = t_cur->as_Goto();
103 if (t_goto == NULL) return;
104 Goto* f_goto = f_cur->as_Goto();
105 if (f_goto == NULL) return;
106
107 // check if both gotos merge into the same block
108 BlockBegin* sux = t_goto->default_sux();
109 if (sux != f_goto->default_sux()) return;
110
111 // check if at least one word was pushed on sux_state
112 ValueStack* sux_state = sux->state();
113 if (sux_state->stack_size() <= if_->state()->stack_size()) return;
114
115 // check if phi function is present at end of successor stack and that
116 // only this phi was pushed on the stack
117 Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
118 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
119 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
120
121 // get the values that were pushed in the true- and false-branch
122 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
123 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
124
125 // backend does not support floats
126 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
127 if (t_value->type()->is_float_kind()) return;
128
129 // check that successor has no other phi functions but sux_phi
130 // this can happen when t_block or f_block contained additonal stores to local variables
131 // that are no longer represented by explicit instructions
132 for_each_phi_fun(sux, phi,
133 if (phi != sux_phi) return;
134 );
135 // true and false blocks can't have phis
136 for_each_phi_fun(t_block, phi, return; );
137 for_each_phi_fun(f_block, phi, return; );
138
139 // 2) substitute conditional expression
140 // with an IfOp followed by a Goto
141 // cut if_ away and get node before
142 Instruction* cur_end = if_->prev(block);
143 int bci = if_->bci();
144
145 // append constants of true- and false-block if necessary
146 // clone constants because original block must not be destroyed
147 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
148 if (t_value == t_const) {
149 t_value = new Constant(t_const->type());
150 cur_end = cur_end->set_next(t_value, bci);
151 }
152 if (f_value == f_const) {
153 f_value = new Constant(f_const->type());
154 cur_end = cur_end->set_next(f_value, bci);
155 }
156
157 // it is very unlikely that the condition can be statically decided
158 // (this was checked previously by the Canonicalizer), so always
159 // append IfOp
160 Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value);
161 cur_end = cur_end->set_next(result, bci);
162
163 // append Goto to successor
164 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
165 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
166
167 // prepare state for Goto
168 ValueStack* goto_state = if_->state();
169 while (sux_state->scope() != goto_state->scope()) {
170 goto_state = goto_state->pop_scope();
171 assert(goto_state != NULL, "states do not match up");
172 }
173 goto_state = goto_state->copy();
174 goto_state->push(result->type(), result);
175 assert(goto_state->is_same_across_scopes(sux_state), "states must match now");
176 goto_->set_state(goto_state);
177
178 // Steal the bci for the goto from the sux
179 cur_end = cur_end->set_next(goto_, sux->bci());
180
181 // Adjust control flow graph
182 BlockBegin::disconnect_edge(block, t_block);
183 BlockBegin::disconnect_edge(block, f_block);
184 if (t_block->number_of_preds() == 0) {
185 BlockBegin::disconnect_edge(t_block, sux);
186 }
187 adjust_exception_edges(block, t_block);
188 if (f_block->number_of_preds() == 0) {
189 BlockBegin::disconnect_edge(f_block, sux);
190 }
191 adjust_exception_edges(block, f_block);
192
193 // update block end
194 block->set_end(goto_);
195
196 // substitute the phi if possible
197 if (sux_phi->as_Phi()->operand_count() == 1) {
198 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
199 sux_phi->set_subst(result);
200 _has_substitution = true;
201 }
202
203 // 3) successfully eliminated a conditional expression
204 _cee_count++;
205 if (PrintCEE) {
206 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());
207 }
208
209 _hir->verify();
210 }
211 };
212
213
214 void Optimizer::eliminate_conditional_expressions() {
215 // find conditional expressions & replace them with IfOps
216 CE_Eliminator ce(ir());
217 }
218
219
220 class BlockMerger: public BlockClosure {
221 private:
222 IR* _hir;
223 int _merge_count; // the number of block pairs successfully merged
224
225 public:
226 BlockMerger(IR* hir)
227 : _hir(hir)
228 , _merge_count(0)
229 {
230 _hir->iterate_preorder(this);
231 }
232
233 bool try_merge(BlockBegin* block) {
234 BlockEnd* end = block->end();
235 if (end->as_Goto() != NULL) {
236 assert(end->number_of_sux() == 1, "end must have exactly one successor");
237 // Note: It would be sufficient to check for the number of successors (= 1)
238 // in order to decide if this block can be merged potentially. That
239 // would then also include switch statements w/ only a default case.
240 // However, in that case we would need to make sure the switch tag
241 // expression is executed if it can produce observable side effects.
242 // We should probably have the canonicalizer simplifying such switch
243 // statements and then we are sure we don't miss these merge opportunities
244 // here (was bug - gri 7/7/99).
245 BlockBegin* sux = end->default_sux();
246 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
247 // merge the two blocks
248
249 #ifdef ASSERT
250 // verify that state at the end of block and at the beginning of sux are equal
251 // no phi functions must be present at beginning of sux
252 ValueStack* sux_state = sux->state();
253 ValueStack* end_state = end->state();
254 while (end_state->scope() != sux_state->scope()) {
255 // match up inlining level
256 end_state = end_state->pop_scope();
257 }
258 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
259 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
260
261 int index;
262 Value sux_value;
263 for_each_stack_value(sux_state, index, sux_value) {
264 assert(sux_value == end_state->stack_at(index), "stack not equal");
265 }
266 for_each_local_value(sux_state, index, sux_value) {
267 assert(sux_value == end_state->local_at(index), "locals not equal");
268 }
269 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
270 #endif
271
272 // find instruction before end & append first instruction of sux block
273 Instruction* prev = end->prev(block);
274 Instruction* next = sux->next();
275 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
276 prev->set_next(next, next->bci());
277 sux->disconnect_from_graph();
278 block->set_end(sux->end());
279 // add exception handlers of deleted block, if any
280 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
281 BlockBegin* xhandler = sux->exception_handler_at(k);
282 block->add_exception_handler(xhandler);
283
284 // also substitute predecessor of exception handler
285 assert(xhandler->is_predecessor(sux), "missing predecessor");
286 xhandler->remove_predecessor(sux);
287 if (!xhandler->is_predecessor(block)) {
288 xhandler->add_predecessor(block);
289 }
290 }
291
292 // debugging output
293 _merge_count++;
294 if (PrintBlockElimination) {
295 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
296 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
297 }
298
299 _hir->verify();
300
301 If* if_ = block->end()->as_If();
302 if (if_) {
303 IfOp* ifop = if_->x()->as_IfOp();
304 Constant* con = if_->y()->as_Constant();
305 bool swapped = false;
306 if (!con || !ifop) {
307 ifop = if_->y()->as_IfOp();
308 con = if_->x()->as_Constant();
309 swapped = true;
310 }
311 if (con && ifop) {
312 Constant* tval = ifop->tval()->as_Constant();
313 Constant* fval = ifop->fval()->as_Constant();
314 if (tval && fval) {
315 // Find the instruction before if_, starting with ifop.
316 // When if_ and ifop are not in the same block, prev
317 // becomes NULL In such (rare) cases it is not
318 // profitable to perform the optimization.
319 Value prev = ifop;
320 while (prev != NULL && prev->next() != if_) {
321 prev = prev->next();
322 }
323
324 if (prev != NULL) {
325 Instruction::Condition cond = if_->cond();
326 BlockBegin* tsux = if_->tsux();
327 BlockBegin* fsux = if_->fsux();
328 if (swapped) {
329 cond = Instruction::mirror(cond);
330 tsux = if_->fsux();
331 fsux = if_->tsux();
332 }
333
334 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
335 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
336 if (tblock != fblock && !if_->is_safepoint()) {
337 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
338 tblock, fblock, if_->state_before(), if_->is_safepoint());
339 newif->set_state(if_->state()->copy());
340
341 assert(prev->next() == if_, "must be guaranteed by above search");
342 prev->set_next(newif, if_->bci());
343 block->set_end(newif);
344
345 _merge_count++;
346 if (PrintBlockElimination) {
347 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
348 }
349
350 _hir->verify();
351 }
352 }
353 }
354 }
355 }
356
357 return true;
358 }
359 }
360 return false;
361 }
362
363 virtual void block_do(BlockBegin* block) {
364 _hir->verify();
365 // repeat since the same block may merge again
366 while (try_merge(block)) {
367 _hir->verify();
368 }
369 }
370 };
371
372
373 void Optimizer::eliminate_blocks() {
374 // merge blocks if possible
375 BlockMerger bm(ir());
376 }
377
378
379 class NullCheckEliminator;
380 class NullCheckVisitor: public InstructionVisitor {
381 private:
382 NullCheckEliminator* _nce;
383 NullCheckEliminator* nce() { return _nce; }
384
385 public:
386 NullCheckVisitor() {}
387
388 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
389
390 void do_Phi (Phi* x);
391 void do_Local (Local* x);
392 void do_Constant (Constant* x);
393 void do_LoadField (LoadField* x);
394 void do_StoreField (StoreField* x);
395 void do_ArrayLength (ArrayLength* x);
396 void do_LoadIndexed (LoadIndexed* x);
397 void do_StoreIndexed (StoreIndexed* x);
398 void do_NegateOp (NegateOp* x);
399 void do_ArithmeticOp (ArithmeticOp* x);
400 void do_ShiftOp (ShiftOp* x);
401 void do_LogicOp (LogicOp* x);
402 void do_CompareOp (CompareOp* x);
403 void do_IfOp (IfOp* x);
404 void do_Convert (Convert* x);
405 void do_NullCheck (NullCheck* x);
406 void do_Invoke (Invoke* x);
407 void do_NewInstance (NewInstance* x);
408 void do_NewTypeArray (NewTypeArray* x);
409 void do_NewObjectArray (NewObjectArray* x);
410 void do_NewMultiArray (NewMultiArray* x);
411 void do_CheckCast (CheckCast* x);
412 void do_InstanceOf (InstanceOf* x);
413 void do_MonitorEnter (MonitorEnter* x);
414 void do_MonitorExit (MonitorExit* x);
415 void do_Intrinsic (Intrinsic* x);
416 void do_BlockBegin (BlockBegin* x);
417 void do_Goto (Goto* x);
418 void do_If (If* x);
419 void do_IfInstanceOf (IfInstanceOf* x);
420 void do_TableSwitch (TableSwitch* x);
421 void do_LookupSwitch (LookupSwitch* x);
422 void do_Return (Return* x);
423 void do_Throw (Throw* x);
424 void do_Base (Base* x);
425 void do_OsrEntry (OsrEntry* x);
426 void do_ExceptionObject(ExceptionObject* x);
427 void do_RoundFP (RoundFP* x);
428 void do_UnsafeGetRaw (UnsafeGetRaw* x);
429 void do_UnsafePutRaw (UnsafePutRaw* x);
430 void do_UnsafeGetObject(UnsafeGetObject* x);
431 void do_UnsafePutObject(UnsafePutObject* x);
432 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
433 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
434 void do_ProfileCall (ProfileCall* x);
435 void do_ProfileCounter (ProfileCounter* x);
436 };
437
438
439 // Because of a static contained within (for the purpose of iteration
440 // over instructions), it is only valid to have one of these active at
441 // a time
442 class NullCheckEliminator {
443 private:
444 static NullCheckEliminator* _static_nce;
445 static void do_value(Value* vp);
446
447 Optimizer* _opt;
448
449 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
450 BlockList* _work_list; // Basic blocks to visit
451
452 bool visitable(Value x) {
453 assert(_visitable_instructions != NULL, "check");
454 return _visitable_instructions->contains(x);
455 }
456 void mark_visited(Value x) {
457 assert(_visitable_instructions != NULL, "check");
458 _visitable_instructions->remove(x);
459 }
460 void mark_visitable(Value x) {
461 assert(_visitable_instructions != NULL, "check");
462 _visitable_instructions->put(x);
463 }
464 void clear_visitable_state() {
465 assert(_visitable_instructions != NULL, "check");
466 _visitable_instructions->clear();
467 }
468
469 ValueSet* _set; // current state, propagated to subsequent BlockBegins
470 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
471 NullCheckVisitor _visitor;
472 NullCheck* _last_explicit_null_check;
473
474 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
475 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
476 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
477
478 BlockList* work_list() { return _work_list; }
479
480 void iterate_all();
481 void iterate_one(BlockBegin* block);
482
483 ValueSet* state() { return _set; }
484 void set_state_from (ValueSet* state) { _set->set_from(state); }
485 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
486 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
487 // Returns true if caused a change in the block's state.
488 bool merge_state_for(BlockBegin* block,
489 ValueSet* incoming_state);
490
491 public:
492 // constructor
493 NullCheckEliminator(Optimizer* opt)
494 : _opt(opt)
495 , _set(new ValueSet())
496 , _last_explicit_null_check(NULL)
497 , _block_states(BlockBegin::number_of_blocks(), NULL)
498 , _work_list(new BlockList()) {
499 _visitable_instructions = new ValueSet();
500 _visitor.set_eliminator(this);
501 }
502
503 Optimizer* opt() { return _opt; }
504 IR* ir () { return opt()->ir(); }
505
506 // Process a graph
507 void iterate(BlockBegin* root);
508
509 // In some situations (like NullCheck(x); getfield(x)) the debug
510 // information from the explicit NullCheck can be used to populate
511 // the getfield, even if the two instructions are in different
512 // scopes; this allows implicit null checks to be used but the
513 // correct exception information to be generated. We must clear the
514 // last-traversed NullCheck when we reach a potentially-exception-
515 // throwing instruction, as well as in some other cases.
516 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
517 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
518 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
519 ? _last_explicit_null_check->obj()
520 : NULL); }
521 NullCheck* consume_last_explicit_null_check() {
522 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
523 _last_explicit_null_check->set_can_trap(false);
524 return _last_explicit_null_check;
525 }
526 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
527
528 // Handlers for relevant instructions
529 // (separated out from NullCheckVisitor for clarity)
530
531 // The basic contract is that these must leave the instruction in
532 // the desired state; must not assume anything about the state of
533 // the instruction. We make multiple passes over some basic blocks
534 // and the last pass is the only one whose result is valid.
535 void handle_AccessField (AccessField* x);
536 void handle_ArrayLength (ArrayLength* x);
537 void handle_LoadIndexed (LoadIndexed* x);
538 void handle_StoreIndexed (StoreIndexed* x);
539 void handle_NullCheck (NullCheck* x);
540 void handle_Invoke (Invoke* x);
541 void handle_NewInstance (NewInstance* x);
542 void handle_NewArray (NewArray* x);
543 void handle_AccessMonitor (AccessMonitor* x);
544 void handle_Intrinsic (Intrinsic* x);
545 void handle_ExceptionObject (ExceptionObject* x);
546 void handle_Phi (Phi* x);
547 };
548
549
550 // NEEDS_CLEANUP
551 // There may be other instructions which need to clear the last
552 // explicit null check. Anything across which we can not hoist the
553 // debug information for a NullCheck instruction must clear it. It
554 // might be safer to pattern match "NullCheck ; {AccessField,
555 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
556 // Should test to see performance hit of clearing it for all handlers
557 // with empty bodies below. If it is negligible then we should leave
558 // that in for safety, otherwise should think more about it.
559 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
560 void NullCheckVisitor::do_Local (Local* x) {}
561 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
562 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
563 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
564 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
565 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
566 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
567 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
568 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
569 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
570 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
571 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
572 void NullCheckVisitor::do_IfOp (IfOp* x) {}
573 void NullCheckVisitor::do_Convert (Convert* x) {}
574 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
575 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
576 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
577 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
578 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
579 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
580 void NullCheckVisitor::do_CheckCast (CheckCast* x) {}
581 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
582 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
583 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
584 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); }
585 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
586 void NullCheckVisitor::do_Goto (Goto* x) {}
587 void NullCheckVisitor::do_If (If* x) {}
588 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
589 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
590 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
591 void NullCheckVisitor::do_Return (Return* x) {}
592 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
593 void NullCheckVisitor::do_Base (Base* x) {}
594 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
595 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
596 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
597 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
598 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
599 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
600 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
601 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
602 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
603 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
604 void NullCheckVisitor::do_ProfileCounter (ProfileCounter* x) {}
605
606
607 NullCheckEliminator* NullCheckEliminator::_static_nce = NULL;
608
609
610 void NullCheckEliminator::do_value(Value* p) {
611 assert(*p != NULL, "should not find NULL instructions");
612 if (_static_nce->visitable(*p)) {
613 _static_nce->mark_visited(*p);
614 (*p)->visit(&_static_nce->_visitor);
615 }
616 }
617
618 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
619 ValueSet* state = state_for(block);
620 if (state == NULL) {
621 state = incoming_state->copy();
622 set_state_for(block, state);
623 return true;
624 } else {
625 bool changed = state->set_intersect(incoming_state);
626 if (PrintNullCheckElimination && changed) {
627 tty->print_cr("Block %d's null check state changed", block->block_id());
628 }
629 return changed;
630 }
631 }
632
633
634 void NullCheckEliminator::iterate_all() {
635 while (work_list()->length() > 0) {
636 iterate_one(work_list()->pop());
637 }
638 }
639
640
641 void NullCheckEliminator::iterate_one(BlockBegin* block) {
642 _static_nce = this;
643 clear_visitable_state();
644 // clear out an old explicit null checks
645 set_last_explicit_null_check(NULL);
646
647 if (PrintNullCheckElimination) {
648 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
649 block->block_id(),
650 ir()->method()->holder()->name()->as_utf8(),
651 ir()->method()->name()->as_utf8(),
652 ir()->method()->signature()->as_symbol()->as_utf8());
653 }
654
655 // Create new state if none present (only happens at root)
656 if (state_for(block) == NULL) {
657 ValueSet* tmp_state = new ValueSet();
658 set_state_for(block, tmp_state);
659 // Initial state is that local 0 (receiver) is non-null for
660 // non-static methods
661 ValueStack* stack = block->state();
662 IRScope* scope = stack->scope();
663 ciMethod* method = scope->method();
664 if (!method->is_static()) {
665 Local* local0 = stack->local_at(0)->as_Local();
666 assert(local0 != NULL, "must be");
667 assert(local0->type() == objectType, "invalid type of receiver");
668
669 if (local0 != NULL) {
670 // Local 0 is used in this scope
671 tmp_state->put(local0);
672 if (PrintNullCheckElimination) {
673 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
674 }
675 }
676 }
677 }
678
679 // Must copy block's state to avoid mutating it during iteration
680 // through the block -- otherwise "not-null" states can accidentally
681 // propagate "up" through the block during processing of backward
682 // branches and algorithm is incorrect (and does not converge)
683 set_state_from(state_for(block));
684
685 // allow visiting of Phis belonging to this block
686 for_each_phi_fun(block, phi,
687 mark_visitable(phi);
688 );
689
690 BlockEnd* e = block->end();
691 assert(e != NULL, "incomplete graph");
692 int i;
693
694 // Propagate the state before this block into the exception
695 // handlers. They aren't true successors since we aren't guaranteed
696 // to execute the whole block before executing them. Also putting
697 // them on first seems to help reduce the amount of iteration to
698 // reach a fixed point.
699 for (i = 0; i < block->number_of_exception_handlers(); i++) {
700 BlockBegin* next = block->exception_handler_at(i);
701 if (merge_state_for(next, state())) {
702 if (!work_list()->contains(next)) {
703 work_list()->push(next);
704 }
705 }
706 }
707
708 // Iterate through block, updating state.
709 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
710 // Mark instructions in this block as visitable as they are seen
711 // in the instruction list. This keeps the iteration from
712 // visiting instructions which are references in other blocks or
713 // visiting instructions more than once.
714 mark_visitable(instr);
715 if (instr->is_root() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
716 mark_visited(instr);
717 instr->input_values_do(&NullCheckEliminator::do_value);
718 instr->visit(&_visitor);
719 }
720 }
721
722 // Propagate state to successors if necessary
723 for (i = 0; i < e->number_of_sux(); i++) {
724 BlockBegin* next = e->sux_at(i);
725 if (merge_state_for(next, state())) {
726 if (!work_list()->contains(next)) {
727 work_list()->push(next);
728 }
729 }
730 }
731 }
732
733
734 void NullCheckEliminator::iterate(BlockBegin* block) {
735 work_list()->push(block);
736 iterate_all();
737 }
738
739 void NullCheckEliminator::handle_AccessField(AccessField* x) {
740 if (x->is_static()) {
741 if (x->as_LoadField() != NULL) {
742 // If the field is a non-null static final object field (as is
743 // often the case for sun.misc.Unsafe), put this LoadField into
744 // the non-null map
745 ciField* field = x->field();
746 if (field->is_constant()) {
747 ciConstant field_val = field->constant_value();
748 BasicType field_type = field_val.basic_type();
749 if (field_type == T_OBJECT || field_type == T_ARRAY) {
750 ciObject* obj_val = field_val.as_object();
751 if (!obj_val->is_null_object()) {
752 if (PrintNullCheckElimination) {
753 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
754 x->id());
755 }
756 set_put(x);
757 }
758 }
759 }
760 }
761 // Be conservative
762 clear_last_explicit_null_check();
763 return;
764 }
765
766 Value obj = x->obj();
767 if (set_contains(obj)) {
768 // Value is non-null => update AccessField
769 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
770 x->set_explicit_null_check(consume_last_explicit_null_check());
771 x->set_needs_null_check(true);
772 if (PrintNullCheckElimination) {
773 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
774 x->explicit_null_check()->id(), x->id(), obj->id());
775 }
776 } else {
777 x->set_explicit_null_check(NULL);
778 x->set_needs_null_check(false);
779 if (PrintNullCheckElimination) {
780 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
781 }
782 }
783 } else {
784 set_put(obj);
785 if (PrintNullCheckElimination) {
786 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
787 }
788 // Ensure previous passes do not cause wrong state
789 x->set_needs_null_check(true);
790 x->set_explicit_null_check(NULL);
791 }
792 clear_last_explicit_null_check();
793 }
794
795
796 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
797 Value array = x->array();
798 if (set_contains(array)) {
799 // Value is non-null => update AccessArray
800 if (last_explicit_null_check_obj() == array) {
801 x->set_explicit_null_check(consume_last_explicit_null_check());
802 x->set_needs_null_check(true);
803 if (PrintNullCheckElimination) {
804 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
805 x->explicit_null_check()->id(), x->id(), array->id());
806 }
807 } else {
808 x->set_explicit_null_check(NULL);
809 x->set_needs_null_check(false);
810 if (PrintNullCheckElimination) {
811 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
812 }
813 }
814 } else {
815 set_put(array);
816 if (PrintNullCheckElimination) {
817 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
818 }
819 // Ensure previous passes do not cause wrong state
820 x->set_needs_null_check(true);
821 x->set_explicit_null_check(NULL);
822 }
823 clear_last_explicit_null_check();
824 }
825
826
827 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
828 Value array = x->array();
829 if (set_contains(array)) {
830 // Value is non-null => update AccessArray
831 if (last_explicit_null_check_obj() == array) {
832 x->set_explicit_null_check(consume_last_explicit_null_check());
833 x->set_needs_null_check(true);
834 if (PrintNullCheckElimination) {
835 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
836 x->explicit_null_check()->id(), x->id(), array->id());
837 }
838 } else {
839 x->set_explicit_null_check(NULL);
840 x->set_needs_null_check(false);
841 if (PrintNullCheckElimination) {
842 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
843 }
844 }
845 } else {
846 set_put(array);
847 if (PrintNullCheckElimination) {
848 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
849 }
850 // Ensure previous passes do not cause wrong state
851 x->set_needs_null_check(true);
852 x->set_explicit_null_check(NULL);
853 }
854 clear_last_explicit_null_check();
855 }
856
857
858 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
859 Value array = x->array();
860 if (set_contains(array)) {
861 // Value is non-null => update AccessArray
862 if (PrintNullCheckElimination) {
863 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
864 }
865 x->set_needs_null_check(false);
866 } else {
867 set_put(array);
868 if (PrintNullCheckElimination) {
869 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
870 }
871 // Ensure previous passes do not cause wrong state
872 x->set_needs_null_check(true);
873 }
874 clear_last_explicit_null_check();
875 }
876
877
878 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
879 Value obj = x->obj();
880 if (set_contains(obj)) {
881 // Already proven to be non-null => this NullCheck is useless
882 if (PrintNullCheckElimination) {
883 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
884 }
885 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
886 // The code generator won't emit LIR for a NullCheck that cannot trap.
887 x->set_can_trap(false);
888 } else {
889 // May be null => add to map and set last explicit NullCheck
890 x->set_can_trap(true);
891 // make sure it's pinned if it can trap
892 x->pin(Instruction::PinExplicitNullCheck);
893 set_put(obj);
894 set_last_explicit_null_check(x);
895 if (PrintNullCheckElimination) {
896 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
897 }
898 }
899 }
900
901
902 void NullCheckEliminator::handle_Invoke(Invoke* x) {
903 if (!x->has_receiver()) {
904 // Be conservative
905 clear_last_explicit_null_check();
906 return;
907 }
908
909 Value recv = x->receiver();
910 if (!set_contains(recv)) {
911 set_put(recv);
912 if (PrintNullCheckElimination) {
913 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
914 }
915 }
916 clear_last_explicit_null_check();
917 }
918
919
920 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
921 set_put(x);
922 if (PrintNullCheckElimination) {
923 tty->print_cr("NewInstance %d is non-null", x->id());
924 }
925 }
926
927
928 void NullCheckEliminator::handle_NewArray(NewArray* x) {
929 set_put(x);
930 if (PrintNullCheckElimination) {
931 tty->print_cr("NewArray %d is non-null", x->id());
932 }
933 }
934
935
936 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
937 set_put(x);
938 if (PrintNullCheckElimination) {
939 tty->print_cr("ExceptionObject %d is non-null", x->id());
940 }
941 }
942
943
944 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
945 Value obj = x->obj();
946 if (set_contains(obj)) {
947 // Value is non-null => update AccessMonitor
948 if (PrintNullCheckElimination) {
949 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
950 }
951 x->set_needs_null_check(false);
952 } else {
953 set_put(obj);
954 if (PrintNullCheckElimination) {
955 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
956 }
957 // Ensure previous passes do not cause wrong state
958 x->set_needs_null_check(true);
959 }
960 clear_last_explicit_null_check();
961 }
962
963
964 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
965 if (!x->has_receiver()) {
966 // Be conservative
967 clear_last_explicit_null_check();
968 return;
969 }
970
971 Value recv = x->receiver();
972 if (set_contains(recv)) {
973 // Value is non-null => update Intrinsic
974 if (PrintNullCheckElimination) {
975 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
976 }
977 x->set_needs_null_check(false);
978 } else {
979 set_put(recv);
980 if (PrintNullCheckElimination) {
981 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
982 }
983 // Ensure previous passes do not cause wrong state
984 x->set_needs_null_check(true);
985 }
986 clear_last_explicit_null_check();
987 }
988
989
990 void NullCheckEliminator::handle_Phi(Phi* x) {
991 int i;
992 bool all_non_null = true;
993 if (x->is_illegal()) {
994 all_non_null = false;
995 } else {
996 for (i = 0; i < x->operand_count(); i++) {
997 Value input = x->operand_at(i);
998 if (!set_contains(input)) {
999 all_non_null = false;
1000 }
1001 }
1002 }
1003
1004 if (all_non_null) {
1005 // Value is non-null => update Phi
1006 if (PrintNullCheckElimination) {
1007 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1008 }
1009 x->set_needs_null_check(false);
1010 } else if (set_contains(x)) {
1011 set_remove(x);
1012 }
1013 }
1014
1015
1016 void Optimizer::eliminate_null_checks() {
1017 ResourceMark rm;
1018
1019 NullCheckEliminator nce(this);
1020
1021 if (PrintNullCheckElimination) {
1022 tty->print_cr("Starting null check elimination for method %s::%s%s",
1023 ir()->method()->holder()->name()->as_utf8(),
1024 ir()->method()->name()->as_utf8(),
1025 ir()->method()->signature()->as_symbol()->as_utf8());
1026 }
1027
1028 // Apply to graph
1029 nce.iterate(ir()->start());
1030
1031 // walk over the graph looking for exception
1032 // handlers and iterate over them as well
1033 int nblocks = BlockBegin::number_of_blocks();
1034 BlockList blocks(nblocks);
1035 boolArray visited_block(nblocks, false);
1036
1037 blocks.push(ir()->start());
1038 visited_block[ir()->start()->block_id()] = true;
1039 for (int i = 0; i < blocks.length(); i++) {
1040 BlockBegin* b = blocks[i];
1041 // exception handlers need to be treated as additional roots
1042 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1043 BlockBegin* excp = b->exception_handler_at(e);
1044 int id = excp->block_id();
1045 if (!visited_block[id]) {
1046 blocks.push(excp);
1047 visited_block[id] = true;
1048 nce.iterate(excp);
1049 }
1050 }
1051 // traverse successors
1052 BlockEnd *end = b->end();
1053 for (int s = end->number_of_sux(); s-- > 0; ) {
1054 BlockBegin* next = end->sux_at(s);
1055 int id = next->block_id();
1056 if (!visited_block[id]) {
1057 blocks.push(next);
1058 visited_block[id] = true;
1059 }
1060 }
1061 }
1062
1063
1064 if (PrintNullCheckElimination) {
1065 tty->print_cr("Done with null check elimination for method %s::%s%s",
1066 ir()->method()->holder()->name()->as_utf8(),
1067 ir()->method()->name()->as_utf8(),
1068 ir()->method()->signature()->as_symbol()->as_utf8());
1069 }
1070 }