1 /*
2 * Copyright (c) 1999, 2010, 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
33 define_array(ValueSetArray, ValueSet*);
34 define_stack(ValueSetList, ValueSetArray);
35
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 _has_substitution;
47
48 public:
49 CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) {
50 _has_substitution = false;
51 _hir->iterate_preorder(this);
52 if (_has_substitution) {
53 // substituted some phis so resolve the substitution
54 SubstitutionResolver sr(_hir);
55 }
56 }
57 int cee_count() const { return _cee_count; }
58
59 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
60 int e = sux->number_of_exception_handlers();
61 for (int i = 0; i < e; i++) {
62 BlockBegin* xhandler = sux->exception_handler_at(i);
63 block->add_exception_handler(xhandler);
64
65 assert(xhandler->is_predecessor(sux), "missing predecessor");
66 if (sux->number_of_preds() == 0) {
67 // sux is disconnected from graph so disconnect from exception handlers
68 xhandler->remove_predecessor(sux);
69 }
70 if (!xhandler->is_predecessor(block)) {
71 xhandler->add_predecessor(block);
72 }
73 }
74 }
75
76 virtual void block_do(BlockBegin* block) {
77 // 1) find conditional expression
78 // check if block ends with an If
79 If* if_ = block->end()->as_If();
80 if (if_ == NULL) return;
81
82 // check if If works on int or object types
83 // (we cannot handle If's working on long, float or doubles yet,
84 // since IfOp doesn't support them - these If's show up if cmp
85 // operations followed by If's are eliminated)
86 ValueType* if_type = if_->x()->type();
87 if (!if_type->is_int() && !if_type->is_object()) return;
88
89 BlockBegin* t_block = if_->tsux();
90 BlockBegin* f_block = if_->fsux();
91 Instruction* t_cur = t_block->next();
92 Instruction* f_cur = f_block->next();
93
94 // one Constant may be present between BlockBegin and BlockEnd
95 Value t_const = NULL;
96 Value f_const = NULL;
97 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
98 t_const = t_cur;
99 t_cur = t_cur->next();
100 }
101 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
102 f_const = f_cur;
103 f_cur = f_cur->next();
104 }
105
106 // check if both branches end with a goto
107 Goto* t_goto = t_cur->as_Goto();
108 if (t_goto == NULL) return;
109 Goto* f_goto = f_cur->as_Goto();
110 if (f_goto == NULL) return;
111
112 // check if both gotos merge into the same block
113 BlockBegin* sux = t_goto->default_sux();
114 if (sux != f_goto->default_sux()) return;
115
116 // check if at least one word was pushed on sux_state
117 ValueStack* sux_state = sux->state();
118 if (sux_state->stack_size() <= if_->state()->stack_size()) return;
119
120 // check if phi function is present at end of successor stack and that
121 // only this phi was pushed on the stack
122 Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
123 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
124 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
125
126 // get the values that were pushed in the true- and false-branch
127 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
128 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
129
130 // backend does not support floats
131 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
132 if (t_value->type()->is_float_kind()) return;
133
134 // check that successor has no other phi functions but sux_phi
135 // this can happen when t_block or f_block contained additonal stores to local variables
136 // that are no longer represented by explicit instructions
137 for_each_phi_fun(sux, phi,
138 if (phi != sux_phi) return;
139 );
140 // true and false blocks can't have phis
141 for_each_phi_fun(t_block, phi, return; );
142 for_each_phi_fun(f_block, phi, return; );
143
144 // 2) substitute conditional expression
145 // with an IfOp followed by a Goto
146 // cut if_ away and get node before
147 Instruction* cur_end = if_->prev(block);
148
149 // append constants of true- and false-block if necessary
150 // clone constants because original block must not be destroyed
151 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
152 if (t_value == t_const) {
153 t_value = new Constant(t_const->type());
154 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
155 cur_end = cur_end->set_next(t_value);
156 }
157 if (f_value == f_const) {
158 f_value = new Constant(f_const->type());
159 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
160 cur_end = cur_end->set_next(f_value);
161 }
162
163 // it is very unlikely that the condition can be statically decided
164 // (this was checked previously by the Canonicalizer), so always
165 // append IfOp
166 Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value);
167 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
168 cur_end = cur_end->set_next(result);
169
170 // append Goto to successor
171 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
172 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
173
174 // prepare state for Goto
175 ValueStack* goto_state = if_->state();
176 while (sux_state->scope() != goto_state->scope()) {
177 goto_state = goto_state->caller_state();
178 assert(goto_state != NULL, "states do not match up");
179 }
180 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
181 goto_state->push(result->type(), result);
182 assert(goto_state->is_same(sux_state), "states must match now");
183 goto_->set_state(goto_state);
184
185 cur_end = cur_end->set_next(goto_, goto_state->bci());
186
187 // Adjust control flow graph
188 BlockBegin::disconnect_edge(block, t_block);
189 BlockBegin::disconnect_edge(block, f_block);
190 if (t_block->number_of_preds() == 0) {
191 BlockBegin::disconnect_edge(t_block, sux);
192 }
193 adjust_exception_edges(block, t_block);
194 if (f_block->number_of_preds() == 0) {
195 BlockBegin::disconnect_edge(f_block, sux);
196 }
197 adjust_exception_edges(block, f_block);
198
199 // update block end
200 block->set_end(goto_);
201
202 // substitute the phi if possible
203 if (sux_phi->as_Phi()->operand_count() == 1) {
204 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
205 sux_phi->set_subst(result);
206 _has_substitution = true;
207 }
208
209 // 3) successfully eliminated a conditional expression
210 _cee_count++;
211 if (PrintCEE) {
212 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());
213 }
214
215 _hir->verify();
216 }
217 };
218
219
220 void Optimizer::eliminate_conditional_expressions() {
221 // find conditional expressions & replace them with IfOps
222 CE_Eliminator ce(ir());
223 }
224
225
226 class BlockMerger: public BlockClosure {
227 private:
228 IR* _hir;
229 int _merge_count; // the number of block pairs successfully merged
230
231 public:
232 BlockMerger(IR* hir)
233 : _hir(hir)
234 , _merge_count(0)
235 {
236 _hir->iterate_preorder(this);
237 }
238
239 bool try_merge(BlockBegin* block) {
240 BlockEnd* end = block->end();
241 if (end->as_Goto() != NULL) {
242 assert(end->number_of_sux() == 1, "end must have exactly one successor");
243 // Note: It would be sufficient to check for the number of successors (= 1)
244 // in order to decide if this block can be merged potentially. That
245 // would then also include switch statements w/ only a default case.
246 // However, in that case we would need to make sure the switch tag
247 // expression is executed if it can produce observable side effects.
248 // We should probably have the canonicalizer simplifying such switch
249 // statements and then we are sure we don't miss these merge opportunities
250 // here (was bug - gri 7/7/99).
251 BlockBegin* sux = end->default_sux();
252 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
253 // merge the two blocks
254
255 #ifdef ASSERT
256 // verify that state at the end of block and at the beginning of sux are equal
257 // no phi functions must be present at beginning of sux
258 ValueStack* sux_state = sux->state();
259 ValueStack* end_state = end->state();
260
261 assert(end_state->scope() == sux_state->scope(), "scopes must match");
262 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
263 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
264
265 int index;
266 Value sux_value;
267 for_each_stack_value(sux_state, index, sux_value) {
268 assert(sux_value == end_state->stack_at(index), "stack not equal");
269 }
270 for_each_local_value(sux_state, index, sux_value) {
271 assert(sux_value == end_state->local_at(index), "locals not equal");
272 }
273 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
274 #endif
275
276 // find instruction before end & append first instruction of sux block
277 Instruction* prev = end->prev(block);
278 Instruction* next = sux->next();
279 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
280 prev->set_next(next);
281 sux->disconnect_from_graph();
282 block->set_end(sux->end());
283 // add exception handlers of deleted block, if any
284 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
285 BlockBegin* xhandler = sux->exception_handler_at(k);
286 block->add_exception_handler(xhandler);
287
288 // also substitute predecessor of exception handler
289 assert(xhandler->is_predecessor(sux), "missing predecessor");
290 xhandler->remove_predecessor(sux);
291 if (!xhandler->is_predecessor(block)) {
292 xhandler->add_predecessor(block);
293 }
294 }
295
296 // debugging output
297 _merge_count++;
298 if (PrintBlockElimination) {
299 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
300 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
301 }
302
303 _hir->verify();
304
305 If* if_ = block->end()->as_If();
306 if (if_) {
307 IfOp* ifop = if_->x()->as_IfOp();
308 Constant* con = if_->y()->as_Constant();
309 bool swapped = false;
310 if (!con || !ifop) {
311 ifop = if_->y()->as_IfOp();
312 con = if_->x()->as_Constant();
313 swapped = true;
314 }
315 if (con && ifop) {
316 Constant* tval = ifop->tval()->as_Constant();
317 Constant* fval = ifop->fval()->as_Constant();
318 if (tval && fval) {
319 // Find the instruction before if_, starting with ifop.
320 // When if_ and ifop are not in the same block, prev
321 // becomes NULL In such (rare) cases it is not
322 // profitable to perform the optimization.
323 Value prev = ifop;
324 while (prev != NULL && prev->next() != if_) {
325 prev = prev->next();
326 }
327
328 if (prev != NULL) {
329 Instruction::Condition cond = if_->cond();
330 BlockBegin* tsux = if_->tsux();
331 BlockBegin* fsux = if_->fsux();
332 if (swapped) {
333 cond = Instruction::mirror(cond);
334 }
335
336 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
337 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
338 if (tblock != fblock && !if_->is_safepoint()) {
339 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
340 tblock, fblock, if_->state_before(), if_->is_safepoint());
341 newif->set_state(if_->state()->copy());
342
343 assert(prev->next() == if_, "must be guaranteed by above search");
344 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
345 prev->set_next(newif);
346 block->set_end(newif);
347
348 _merge_count++;
349 if (PrintBlockElimination) {
350 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
351 }
352
353 _hir->verify();
354 }
355 }
356 }
357 }
358 }
359
360 return true;
361 }
362 }
363 return false;
364 }
365
366 virtual void block_do(BlockBegin* block) {
367 _hir->verify();
368 // repeat since the same block may merge again
369 while (try_merge(block)) {
370 _hir->verify();
371 }
372 }
373 };
374
375
376 void Optimizer::eliminate_blocks() {
377 // merge blocks if possible
378 BlockMerger bm(ir());
379 }
380
381
382 class NullCheckEliminator;
383 class NullCheckVisitor: public InstructionVisitor {
384 private:
385 NullCheckEliminator* _nce;
386 NullCheckEliminator* nce() { return _nce; }
387
388 public:
389 NullCheckVisitor() {}
390
391 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
392
393 void do_Phi (Phi* x);
394 void do_Local (Local* x);
395 void do_Constant (Constant* x);
396 void do_LoadField (LoadField* x);
397 void do_StoreField (StoreField* x);
398 void do_ArrayLength (ArrayLength* x);
399 void do_LoadIndexed (LoadIndexed* x);
400 void do_StoreIndexed (StoreIndexed* x);
401 void do_NegateOp (NegateOp* x);
402 void do_ArithmeticOp (ArithmeticOp* x);
403 void do_ShiftOp (ShiftOp* x);
404 void do_LogicOp (LogicOp* x);
405 void do_CompareOp (CompareOp* x);
406 void do_IfOp (IfOp* x);
407 void do_Convert (Convert* x);
408 void do_NullCheck (NullCheck* x);
409 void do_Invoke (Invoke* x);
410 void do_NewInstance (NewInstance* x);
411 void do_NewTypeArray (NewTypeArray* x);
412 void do_NewObjectArray (NewObjectArray* x);
413 void do_NewMultiArray (NewMultiArray* x);
414 void do_CheckCast (CheckCast* x);
415 void do_InstanceOf (InstanceOf* x);
416 void do_MonitorEnter (MonitorEnter* x);
417 void do_MonitorExit (MonitorExit* x);
418 void do_Intrinsic (Intrinsic* x);
419 void do_BlockBegin (BlockBegin* x);
420 void do_Goto (Goto* x);
421 void do_If (If* x);
422 void do_IfInstanceOf (IfInstanceOf* x);
423 void do_TableSwitch (TableSwitch* x);
424 void do_LookupSwitch (LookupSwitch* x);
425 void do_Return (Return* x);
426 void do_Throw (Throw* x);
427 void do_Base (Base* x);
428 void do_OsrEntry (OsrEntry* x);
429 void do_ExceptionObject(ExceptionObject* x);
430 void do_RoundFP (RoundFP* x);
431 void do_UnsafeGetRaw (UnsafeGetRaw* x);
432 void do_UnsafePutRaw (UnsafePutRaw* x);
433 void do_UnsafeGetObject(UnsafeGetObject* x);
434 void do_UnsafePutObject(UnsafePutObject* x);
435 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
436 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
437 void do_ProfileCall (ProfileCall* x);
438 void do_ProfileInvoke (ProfileInvoke* x);
439 };
440
441
442 // Because of a static contained within (for the purpose of iteration
443 // over instructions), it is only valid to have one of these active at
444 // a time
445 class NullCheckEliminator: public ValueVisitor {
446 private:
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 void visit(Value* f);
510
511 // In some situations (like NullCheck(x); getfield(x)) the debug
512 // information from the explicit NullCheck can be used to populate
513 // the getfield, even if the two instructions are in different
514 // scopes; this allows implicit null checks to be used but the
515 // correct exception information to be generated. We must clear the
516 // last-traversed NullCheck when we reach a potentially-exception-
517 // throwing instruction, as well as in some other cases.
518 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
519 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
520 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
521 ? _last_explicit_null_check->obj()
522 : NULL); }
523 NullCheck* consume_last_explicit_null_check() {
524 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
525 _last_explicit_null_check->set_can_trap(false);
526 return _last_explicit_null_check;
527 }
528 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
529
530 // Handlers for relevant instructions
531 // (separated out from NullCheckVisitor for clarity)
532
533 // The basic contract is that these must leave the instruction in
534 // the desired state; must not assume anything about the state of
535 // the instruction. We make multiple passes over some basic blocks
536 // and the last pass is the only one whose result is valid.
537 void handle_AccessField (AccessField* x);
538 void handle_ArrayLength (ArrayLength* x);
539 void handle_LoadIndexed (LoadIndexed* x);
540 void handle_StoreIndexed (StoreIndexed* x);
541 void handle_NullCheck (NullCheck* x);
542 void handle_Invoke (Invoke* x);
543 void handle_NewInstance (NewInstance* x);
544 void handle_NewArray (NewArray* x);
545 void handle_AccessMonitor (AccessMonitor* x);
546 void handle_Intrinsic (Intrinsic* x);
547 void handle_ExceptionObject (ExceptionObject* x);
548 void handle_Phi (Phi* x);
549 };
550
551
552 // NEEDS_CLEANUP
553 // There may be other instructions which need to clear the last
554 // explicit null check. Anything across which we can not hoist the
555 // debug information for a NullCheck instruction must clear it. It
556 // might be safer to pattern match "NullCheck ; {AccessField,
557 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
558 // Should test to see performance hit of clearing it for all handlers
559 // with empty bodies below. If it is negligible then we should leave
560 // that in for safety, otherwise should think more about it.
561 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
562 void NullCheckVisitor::do_Local (Local* x) {}
563 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
564 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
565 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
566 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
567 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
568 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
569 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
570 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
571 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
572 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
573 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
574 void NullCheckVisitor::do_IfOp (IfOp* x) {}
575 void NullCheckVisitor::do_Convert (Convert* x) {}
576 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
577 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
578 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
579 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
580 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
581 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
582 void NullCheckVisitor::do_CheckCast (CheckCast* x) {}
583 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
584 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
585 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
586 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); }
587 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
588 void NullCheckVisitor::do_Goto (Goto* x) {}
589 void NullCheckVisitor::do_If (If* x) {}
590 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
591 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
592 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
593 void NullCheckVisitor::do_Return (Return* x) {}
594 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
595 void NullCheckVisitor::do_Base (Base* x) {}
596 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
597 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
598 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
599 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
600 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
601 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
602 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
603 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
604 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
605 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
606 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
607
608
609 void NullCheckEliminator::visit(Value* p) {
610 assert(*p != NULL, "should not find NULL instructions");
611 if (visitable(*p)) {
612 mark_visited(*p);
613 (*p)->visit(&_visitor);
614 }
615 }
616
617 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
618 ValueSet* state = state_for(block);
619 if (state == NULL) {
620 state = incoming_state->copy();
621 set_state_for(block, state);
622 return true;
623 } else {
624 bool changed = state->set_intersect(incoming_state);
625 if (PrintNullCheckElimination && changed) {
626 tty->print_cr("Block %d's null check state changed", block->block_id());
627 }
628 return changed;
629 }
630 }
631
632
633 void NullCheckEliminator::iterate_all() {
634 while (work_list()->length() > 0) {
635 iterate_one(work_list()->pop());
636 }
637 }
638
639
640 void NullCheckEliminator::iterate_one(BlockBegin* block) {
641 clear_visitable_state();
642 // clear out an old explicit null checks
643 set_last_explicit_null_check(NULL);
644
645 if (PrintNullCheckElimination) {
646 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
647 block->block_id(),
648 ir()->method()->holder()->name()->as_utf8(),
649 ir()->method()->name()->as_utf8(),
650 ir()->method()->signature()->as_symbol()->as_utf8());
651 }
652
653 // Create new state if none present (only happens at root)
654 if (state_for(block) == NULL) {
655 ValueSet* tmp_state = new ValueSet();
656 set_state_for(block, tmp_state);
657 // Initial state is that local 0 (receiver) is non-null for
658 // non-static methods
659 ValueStack* stack = block->state();
660 IRScope* scope = stack->scope();
661 ciMethod* method = scope->method();
662 if (!method->is_static()) {
663 Local* local0 = stack->local_at(0)->as_Local();
664 assert(local0 != NULL, "must be");
665 assert(local0->type() == objectType, "invalid type of receiver");
666
667 if (local0 != NULL) {
668 // Local 0 is used in this scope
669 tmp_state->put(local0);
670 if (PrintNullCheckElimination) {
671 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
672 }
673 }
674 }
675 }
676
677 // Must copy block's state to avoid mutating it during iteration
678 // through the block -- otherwise "not-null" states can accidentally
679 // propagate "up" through the block during processing of backward
680 // branches and algorithm is incorrect (and does not converge)
681 set_state_from(state_for(block));
682
683 // allow visiting of Phis belonging to this block
684 for_each_phi_fun(block, phi,
685 mark_visitable(phi);
686 );
687
688 BlockEnd* e = block->end();
689 assert(e != NULL, "incomplete graph");
690 int i;
691
692 // Propagate the state before this block into the exception
693 // handlers. They aren't true successors since we aren't guaranteed
694 // to execute the whole block before executing them. Also putting
695 // them on first seems to help reduce the amount of iteration to
696 // reach a fixed point.
697 for (i = 0; i < block->number_of_exception_handlers(); i++) {
698 BlockBegin* next = block->exception_handler_at(i);
699 if (merge_state_for(next, state())) {
700 if (!work_list()->contains(next)) {
701 work_list()->push(next);
702 }
703 }
704 }
705
706 // Iterate through block, updating state.
707 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
708 // Mark instructions in this block as visitable as they are seen
709 // in the instruction list. This keeps the iteration from
710 // visiting instructions which are references in other blocks or
711 // visiting instructions more than once.
712 mark_visitable(instr);
713 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
714 mark_visited(instr);
715 instr->input_values_do(this);
716 instr->visit(&_visitor);
717 }
718 }
719
720 // Propagate state to successors if necessary
721 for (i = 0; i < e->number_of_sux(); i++) {
722 BlockBegin* next = e->sux_at(i);
723 if (merge_state_for(next, state())) {
724 if (!work_list()->contains(next)) {
725 work_list()->push(next);
726 }
727 }
728 }
729 }
730
731
732 void NullCheckEliminator::iterate(BlockBegin* block) {
733 work_list()->push(block);
734 iterate_all();
735 }
736
737 void NullCheckEliminator::handle_AccessField(AccessField* x) {
738 if (x->is_static()) {
739 if (x->as_LoadField() != NULL) {
740 // If the field is a non-null static final object field (as is
741 // often the case for sun.misc.Unsafe), put this LoadField into
742 // the non-null map
743 ciField* field = x->field();
744 if (field->is_constant()) {
745 ciConstant field_val = field->constant_value();
746 BasicType field_type = field_val.basic_type();
747 if (field_type == T_OBJECT || field_type == T_ARRAY) {
748 ciObject* obj_val = field_val.as_object();
749 if (!obj_val->is_null_object()) {
750 if (PrintNullCheckElimination) {
751 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
752 x->id());
753 }
754 set_put(x);
755 }
756 }
757 }
758 }
759 // Be conservative
760 clear_last_explicit_null_check();
761 return;
762 }
763
764 Value obj = x->obj();
765 if (set_contains(obj)) {
766 // Value is non-null => update AccessField
767 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
768 x->set_explicit_null_check(consume_last_explicit_null_check());
769 x->set_needs_null_check(true);
770 if (PrintNullCheckElimination) {
771 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
772 x->explicit_null_check()->id(), x->id(), obj->id());
773 }
774 } else {
775 x->set_explicit_null_check(NULL);
776 x->set_needs_null_check(false);
777 if (PrintNullCheckElimination) {
778 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
779 }
780 }
781 } else {
782 set_put(obj);
783 if (PrintNullCheckElimination) {
784 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
785 }
786 // Ensure previous passes do not cause wrong state
787 x->set_needs_null_check(true);
788 x->set_explicit_null_check(NULL);
789 }
790 clear_last_explicit_null_check();
791 }
792
793
794 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
795 Value array = x->array();
796 if (set_contains(array)) {
797 // Value is non-null => update AccessArray
798 if (last_explicit_null_check_obj() == array) {
799 x->set_explicit_null_check(consume_last_explicit_null_check());
800 x->set_needs_null_check(true);
801 if (PrintNullCheckElimination) {
802 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
803 x->explicit_null_check()->id(), x->id(), array->id());
804 }
805 } else {
806 x->set_explicit_null_check(NULL);
807 x->set_needs_null_check(false);
808 if (PrintNullCheckElimination) {
809 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
810 }
811 }
812 } else {
813 set_put(array);
814 if (PrintNullCheckElimination) {
815 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
816 }
817 // Ensure previous passes do not cause wrong state
818 x->set_needs_null_check(true);
819 x->set_explicit_null_check(NULL);
820 }
821 clear_last_explicit_null_check();
822 }
823
824
825 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
826 Value array = x->array();
827 if (set_contains(array)) {
828 // Value is non-null => update AccessArray
829 if (last_explicit_null_check_obj() == array) {
830 x->set_explicit_null_check(consume_last_explicit_null_check());
831 x->set_needs_null_check(true);
832 if (PrintNullCheckElimination) {
833 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
834 x->explicit_null_check()->id(), x->id(), array->id());
835 }
836 } else {
837 x->set_explicit_null_check(NULL);
838 x->set_needs_null_check(false);
839 if (PrintNullCheckElimination) {
840 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
841 }
842 }
843 } else {
844 set_put(array);
845 if (PrintNullCheckElimination) {
846 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
847 }
848 // Ensure previous passes do not cause wrong state
849 x->set_needs_null_check(true);
850 x->set_explicit_null_check(NULL);
851 }
852 clear_last_explicit_null_check();
853 }
854
855
856 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
857 Value array = x->array();
858 if (set_contains(array)) {
859 // Value is non-null => update AccessArray
860 if (PrintNullCheckElimination) {
861 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
862 }
863 x->set_needs_null_check(false);
864 } else {
865 set_put(array);
866 if (PrintNullCheckElimination) {
867 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
868 }
869 // Ensure previous passes do not cause wrong state
870 x->set_needs_null_check(true);
871 }
872 clear_last_explicit_null_check();
873 }
874
875
876 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
877 Value obj = x->obj();
878 if (set_contains(obj)) {
879 // Already proven to be non-null => this NullCheck is useless
880 if (PrintNullCheckElimination) {
881 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
882 }
883 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
884 // The code generator won't emit LIR for a NullCheck that cannot trap.
885 x->set_can_trap(false);
886 } else {
887 // May be null => add to map and set last explicit NullCheck
888 x->set_can_trap(true);
889 // make sure it's pinned if it can trap
890 x->pin(Instruction::PinExplicitNullCheck);
891 set_put(obj);
892 set_last_explicit_null_check(x);
893 if (PrintNullCheckElimination) {
894 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
895 }
896 }
897 }
898
899
900 void NullCheckEliminator::handle_Invoke(Invoke* x) {
901 if (!x->has_receiver()) {
902 // Be conservative
903 clear_last_explicit_null_check();
904 return;
905 }
906
907 Value recv = x->receiver();
908 if (!set_contains(recv)) {
909 set_put(recv);
910 if (PrintNullCheckElimination) {
911 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
912 }
913 }
914 clear_last_explicit_null_check();
915 }
916
917
918 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
919 set_put(x);
920 if (PrintNullCheckElimination) {
921 tty->print_cr("NewInstance %d is non-null", x->id());
922 }
923 }
924
925
926 void NullCheckEliminator::handle_NewArray(NewArray* x) {
927 set_put(x);
928 if (PrintNullCheckElimination) {
929 tty->print_cr("NewArray %d is non-null", x->id());
930 }
931 }
932
933
934 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
935 set_put(x);
936 if (PrintNullCheckElimination) {
937 tty->print_cr("ExceptionObject %d is non-null", x->id());
938 }
939 }
940
941
942 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
943 Value obj = x->obj();
944 if (set_contains(obj)) {
945 // Value is non-null => update AccessMonitor
946 if (PrintNullCheckElimination) {
947 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
948 }
949 x->set_needs_null_check(false);
950 } else {
951 set_put(obj);
952 if (PrintNullCheckElimination) {
953 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
954 }
955 // Ensure previous passes do not cause wrong state
956 x->set_needs_null_check(true);
957 }
958 clear_last_explicit_null_check();
959 }
960
961
962 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
963 if (!x->has_receiver()) {
964 // Be conservative
965 clear_last_explicit_null_check();
966 return;
967 }
968
969 Value recv = x->receiver();
970 if (set_contains(recv)) {
971 // Value is non-null => update Intrinsic
972 if (PrintNullCheckElimination) {
973 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
974 }
975 x->set_needs_null_check(false);
976 } else {
977 set_put(recv);
978 if (PrintNullCheckElimination) {
979 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
980 }
981 // Ensure previous passes do not cause wrong state
982 x->set_needs_null_check(true);
983 }
984 clear_last_explicit_null_check();
985 }
986
987
988 void NullCheckEliminator::handle_Phi(Phi* x) {
989 int i;
990 bool all_non_null = true;
991 if (x->is_illegal()) {
992 all_non_null = false;
993 } else {
994 for (i = 0; i < x->operand_count(); i++) {
995 Value input = x->operand_at(i);
996 if (!set_contains(input)) {
997 all_non_null = false;
998 }
999 }
1000 }
1001
1002 if (all_non_null) {
1003 // Value is non-null => update Phi
1004 if (PrintNullCheckElimination) {
1005 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1006 }
1007 x->set_needs_null_check(false);
1008 } else if (set_contains(x)) {
1009 set_remove(x);
1010 }
1011 }
1012
1013
1014 void Optimizer::eliminate_null_checks() {
1015 ResourceMark rm;
1016
1017 NullCheckEliminator nce(this);
1018
1019 if (PrintNullCheckElimination) {
1020 tty->print_cr("Starting null check elimination for method %s::%s%s",
1021 ir()->method()->holder()->name()->as_utf8(),
1022 ir()->method()->name()->as_utf8(),
1023 ir()->method()->signature()->as_symbol()->as_utf8());
1024 }
1025
1026 // Apply to graph
1027 nce.iterate(ir()->start());
1028
1029 // walk over the graph looking for exception
1030 // handlers and iterate over them as well
1031 int nblocks = BlockBegin::number_of_blocks();
1032 BlockList blocks(nblocks);
1033 boolArray visited_block(nblocks, false);
1034
1035 blocks.push(ir()->start());
1036 visited_block[ir()->start()->block_id()] = true;
1037 for (int i = 0; i < blocks.length(); i++) {
1038 BlockBegin* b = blocks[i];
1039 // exception handlers need to be treated as additional roots
1040 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1041 BlockBegin* excp = b->exception_handler_at(e);
1042 int id = excp->block_id();
1043 if (!visited_block[id]) {
1044 blocks.push(excp);
1045 visited_block[id] = true;
1046 nce.iterate(excp);
1047 }
1048 }
1049 // traverse successors
1050 BlockEnd *end = b->end();
1051 for (int s = end->number_of_sux(); s-- > 0; ) {
1052 BlockBegin* next = end->sux_at(s);
1053 int id = next->block_id();
1054 if (!visited_block[id]) {
1055 blocks.push(next);
1056 visited_block[id] = true;
1057 }
1058 }
1059 }
1060
1061
1062 if (PrintNullCheckElimination) {
1063 tty->print_cr("Done with null check elimination for method %s::%s%s",
1064 ir()->method()->holder()->name()->as_utf8(),
1065 ir()->method()->name()->as_utf8(),
1066 ir()->method()->signature()->as_symbol()->as_utf8());
1067 }
1068 }