1 /*
2 * Copyright (c) 1999, 2011, 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 _ifop_count; // the number of IfOps successfully simplified
47 int _has_substitution;
48
49 public:
50 CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) {
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 int cee_count() const { return _cee_count; }
59 int ifop_count() const { return _ifop_count; }
60
61 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
62 int e = sux->number_of_exception_handlers();
63 for (int i = 0; i < e; i++) {
64 BlockBegin* xhandler = sux->exception_handler_at(i);
65 block->add_exception_handler(xhandler);
66
67 assert(xhandler->is_predecessor(sux), "missing predecessor");
68 if (sux->number_of_preds() == 0) {
69 // sux is disconnected from graph so disconnect from exception handlers
70 xhandler->remove_predecessor(sux);
71 }
72 if (!xhandler->is_predecessor(block)) {
73 xhandler->add_predecessor(block);
74 }
75 }
76 }
77
78 virtual void block_do(BlockBegin* block);
79
80 private:
81 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
82 };
83
84 void CE_Eliminator::block_do(BlockBegin* block) {
85 // 1) find conditional expression
86 // check if block ends with an If
87 If* if_ = block->end()->as_If();
88 if (if_ == NULL) return;
89
90 // check if If works on int or object types
91 // (we cannot handle If's working on long, float or doubles yet,
92 // since IfOp doesn't support them - these If's show up if cmp
93 // operations followed by If's are eliminated)
94 ValueType* if_type = if_->x()->type();
95 if (!if_type->is_int() && !if_type->is_object()) return;
96
97 BlockBegin* t_block = if_->tsux();
98 BlockBegin* f_block = if_->fsux();
99 Instruction* t_cur = t_block->next();
100 Instruction* f_cur = f_block->next();
101
102 // one Constant may be present between BlockBegin and BlockEnd
103 Value t_const = NULL;
104 Value f_const = NULL;
105 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
106 t_const = t_cur;
107 t_cur = t_cur->next();
108 }
109 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
110 f_const = f_cur;
111 f_cur = f_cur->next();
112 }
113
114 // check if both branches end with a goto
115 Goto* t_goto = t_cur->as_Goto();
116 if (t_goto == NULL) return;
117 Goto* f_goto = f_cur->as_Goto();
118 if (f_goto == NULL) return;
119
120 // check if both gotos merge into the same block
121 BlockBegin* sux = t_goto->default_sux();
122 if (sux != f_goto->default_sux()) return;
123
124 // check if at least one word was pushed on sux_state
125 // inlining depths must match
126 ValueStack* if_state = if_->state();
127 ValueStack* sux_state = sux->state();
128 while (sux_state->scope() != if_state->scope()) {
129 if_state = if_state->caller_state();
130 assert(if_state != NULL, "states do not match up");
131 }
132
133 if (sux_state->stack_size() <= if_state->stack_size()) return;
134
135 // check if phi function is present at end of successor stack and that
136 // only this phi was pushed on the stack
137 Value sux_phi = sux_state->stack_at(if_state->stack_size());
138 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
139 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
140
141 // get the values that were pushed in the true- and false-branch
142 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
143 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
144
145 // backend does not support floats
146 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
147 if (t_value->type()->is_float_kind()) return;
148
149 // check that successor has no other phi functions but sux_phi
150 // this can happen when t_block or f_block contained additonal stores to local variables
151 // that are no longer represented by explicit instructions
152 for_each_phi_fun(sux, phi,
153 if (phi != sux_phi) return;
154 );
155 // true and false blocks can't have phis
156 for_each_phi_fun(t_block, phi, return; );
157 for_each_phi_fun(f_block, phi, return; );
158
159 // 2) substitute conditional expression
160 // with an IfOp followed by a Goto
161 // cut if_ away and get node before
162 Instruction* cur_end = if_->prev(block);
163
164 // append constants of true- and false-block if necessary
165 // clone constants because original block must not be destroyed
166 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
167 if (t_value == t_const) {
168 t_value = new Constant(t_const->type());
169 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
170 cur_end = cur_end->set_next(t_value);
171 }
172 if (f_value == f_const) {
173 f_value = new Constant(f_const->type());
174 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
175 cur_end = cur_end->set_next(f_value);
176 }
177
178 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
179 assert(result != NULL, "make_ifop must return a non-null instruction");
180 if (!result->is_linked() && result->can_be_linked()) {
181 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
182 cur_end = cur_end->set_next(result);
183 }
184
185 // append Goto to successor
186 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
187 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
188
189 // prepare state for Goto
190 ValueStack* goto_state = if_state;
191 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
192 goto_state->push(result->type(), result);
193 assert(goto_state->is_same(sux_state), "states must match now");
194 goto_->set_state(goto_state);
195
196 cur_end = cur_end->set_next(goto_, goto_state->bci());
197
198 // Adjust control flow graph
199 BlockBegin::disconnect_edge(block, t_block);
200 BlockBegin::disconnect_edge(block, f_block);
201 if (t_block->number_of_preds() == 0) {
202 BlockBegin::disconnect_edge(t_block, sux);
203 }
204 adjust_exception_edges(block, t_block);
205 if (f_block->number_of_preds() == 0) {
206 BlockBegin::disconnect_edge(f_block, sux);
207 }
208 adjust_exception_edges(block, f_block);
209
210 // update block end
211 block->set_end(goto_);
212
213 // substitute the phi if possible
214 if (sux_phi->as_Phi()->operand_count() == 1) {
215 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
216 sux_phi->set_subst(result);
217 _has_substitution = true;
218 }
219
220 // 3) successfully eliminated a conditional expression
221 _cee_count++;
222 if (PrintCEE) {
223 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());
224 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
225 }
226
227 _hir->verify();
228 }
229
230 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
231 if (!OptimizeIfOps) {
232 return new IfOp(x, cond, y, tval, fval);
233 }
234
235 tval = tval->subst();
236 fval = fval->subst();
237 if (tval == fval) {
238 _ifop_count++;
239 return tval;
240 }
241
242 x = x->subst();
243 y = y->subst();
244
245 Constant* y_const = y->as_Constant();
246 if (y_const != NULL) {
247 IfOp* x_ifop = x->as_IfOp();
248 if (x_ifop != NULL) { // x is an ifop, y is a constant
249 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
250 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
251
252 if (x_tval_const != NULL && x_fval_const != NULL) {
253 Instruction::Condition x_ifop_cond = x_ifop->cond();
254
255 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
256 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
257
258 // not_comparable here is a valid return in case we're comparing unloaded oop constants
259 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
260 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
261 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
262
263 _ifop_count++;
264 if (new_tval == new_fval) {
265 return new_tval;
266 } else {
267 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
268 }
269 }
270 }
271 } else {
272 Constant* x_const = x->as_Constant();
273 if (x_const != NULL) { // x and y are constants
274 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
275 // not_comparable here is a valid return in case we're comparing unloaded oop constants
276 if (x_compare_res != Constant::not_comparable) {
277 _ifop_count++;
278 return x_compare_res == Constant::cond_true ? tval : fval;
279 }
280 }
281 }
282 }
283 return new IfOp(x, cond, y, tval, fval);
284 }
285
286 void Optimizer::eliminate_conditional_expressions() {
287 // find conditional expressions & replace them with IfOps
288 CE_Eliminator ce(ir());
289 }
290
291 class BlockMerger: public BlockClosure {
292 private:
293 IR* _hir;
294 int _merge_count; // the number of block pairs successfully merged
295
296 public:
297 BlockMerger(IR* hir)
298 : _hir(hir)
299 , _merge_count(0)
300 {
301 _hir->iterate_preorder(this);
302 }
303
304 bool try_merge(BlockBegin* block) {
305 BlockEnd* end = block->end();
306 if (end->as_Goto() != NULL) {
307 assert(end->number_of_sux() == 1, "end must have exactly one successor");
308 // Note: It would be sufficient to check for the number of successors (= 1)
309 // in order to decide if this block can be merged potentially. That
310 // would then also include switch statements w/ only a default case.
311 // However, in that case we would need to make sure the switch tag
312 // expression is executed if it can produce observable side effects.
313 // We should probably have the canonicalizer simplifying such switch
314 // statements and then we are sure we don't miss these merge opportunities
315 // here (was bug - gri 7/7/99).
316 BlockBegin* sux = end->default_sux();
317 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
318 // merge the two blocks
319
320 #ifdef ASSERT
321 // verify that state at the end of block and at the beginning of sux are equal
322 // no phi functions must be present at beginning of sux
323 ValueStack* sux_state = sux->state();
324 ValueStack* end_state = end->state();
325
326 assert(end_state->scope() == sux_state->scope(), "scopes must match");
327 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
328 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
329
330 int index;
331 Value sux_value;
332 for_each_stack_value(sux_state, index, sux_value) {
333 assert(sux_value == end_state->stack_at(index), "stack not equal");
334 }
335 for_each_local_value(sux_state, index, sux_value) {
336 assert(sux_value == end_state->local_at(index), "locals not equal");
337 }
338 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
339 #endif
340
341 // find instruction before end & append first instruction of sux block
342 Instruction* prev = end->prev(block);
343 Instruction* next = sux->next();
344 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
345 prev->set_next(next);
346 sux->disconnect_from_graph();
347 block->set_end(sux->end());
348 // add exception handlers of deleted block, if any
349 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
350 BlockBegin* xhandler = sux->exception_handler_at(k);
351 block->add_exception_handler(xhandler);
352
353 // also substitute predecessor of exception handler
354 assert(xhandler->is_predecessor(sux), "missing predecessor");
355 xhandler->remove_predecessor(sux);
356 if (!xhandler->is_predecessor(block)) {
357 xhandler->add_predecessor(block);
358 }
359 }
360
361 // debugging output
362 _merge_count++;
363 if (PrintBlockElimination) {
364 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
365 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
366 }
367
368 _hir->verify();
369
370 If* if_ = block->end()->as_If();
371 if (if_) {
372 IfOp* ifop = if_->x()->as_IfOp();
373 Constant* con = if_->y()->as_Constant();
374 bool swapped = false;
375 if (!con || !ifop) {
376 ifop = if_->y()->as_IfOp();
377 con = if_->x()->as_Constant();
378 swapped = true;
379 }
380 if (con && ifop) {
381 Constant* tval = ifop->tval()->as_Constant();
382 Constant* fval = ifop->fval()->as_Constant();
383 if (tval && fval) {
384 // Find the instruction before if_, starting with ifop.
385 // When if_ and ifop are not in the same block, prev
386 // becomes NULL In such (rare) cases it is not
387 // profitable to perform the optimization.
388 Value prev = ifop;
389 while (prev != NULL && prev->next() != if_) {
390 prev = prev->next();
391 }
392
393 if (prev != NULL) {
394 Instruction::Condition cond = if_->cond();
395 BlockBegin* tsux = if_->tsux();
396 BlockBegin* fsux = if_->fsux();
397 if (swapped) {
398 cond = Instruction::mirror(cond);
399 }
400
401 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
402 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
403 if (tblock != fblock && !if_->is_safepoint()) {
404 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
405 tblock, fblock, if_->state_before(), if_->is_safepoint());
406 newif->set_state(if_->state()->copy());
407
408 assert(prev->next() == if_, "must be guaranteed by above search");
409 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
410 prev->set_next(newif);
411 block->set_end(newif);
412
413 _merge_count++;
414 if (PrintBlockElimination) {
415 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
416 }
417
418 _hir->verify();
419 }
420 }
421 }
422 }
423 }
424
425 return true;
426 }
427 }
428 return false;
429 }
430
431 virtual void block_do(BlockBegin* block) {
432 _hir->verify();
433 // repeat since the same block may merge again
434 while (try_merge(block)) {
435 _hir->verify();
436 }
437 }
438 };
439
440
441 void Optimizer::eliminate_blocks() {
442 // merge blocks if possible
443 BlockMerger bm(ir());
444 }
445
446
447 class NullCheckEliminator;
448 class NullCheckVisitor: public InstructionVisitor {
449 private:
450 NullCheckEliminator* _nce;
451 NullCheckEliminator* nce() { return _nce; }
452
453 public:
454 NullCheckVisitor() {}
455
456 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
457
458 void do_Phi (Phi* x);
459 void do_Local (Local* x);
460 void do_Constant (Constant* x);
461 void do_LoadField (LoadField* x);
462 void do_StoreField (StoreField* x);
463 void do_ArrayLength (ArrayLength* x);
464 void do_LoadIndexed (LoadIndexed* x);
465 void do_StoreIndexed (StoreIndexed* x);
466 void do_NegateOp (NegateOp* x);
467 void do_ArithmeticOp (ArithmeticOp* x);
468 void do_ShiftOp (ShiftOp* x);
469 void do_LogicOp (LogicOp* x);
470 void do_CompareOp (CompareOp* x);
471 void do_IfOp (IfOp* x);
472 void do_Convert (Convert* x);
473 void do_NullCheck (NullCheck* x);
474 void do_Invoke (Invoke* x);
475 void do_NewInstance (NewInstance* x);
476 void do_NewTypeArray (NewTypeArray* x);
477 void do_NewObjectArray (NewObjectArray* x);
478 void do_NewMultiArray (NewMultiArray* x);
479 void do_CheckCast (CheckCast* x);
480 void do_InstanceOf (InstanceOf* x);
481 void do_MonitorEnter (MonitorEnter* x);
482 void do_MonitorExit (MonitorExit* x);
483 void do_Intrinsic (Intrinsic* x);
484 void do_BlockBegin (BlockBegin* x);
485 void do_Goto (Goto* x);
486 void do_If (If* x);
487 void do_IfInstanceOf (IfInstanceOf* x);
488 void do_TableSwitch (TableSwitch* x);
489 void do_LookupSwitch (LookupSwitch* x);
490 void do_Return (Return* x);
491 void do_Throw (Throw* x);
492 void do_Base (Base* x);
493 void do_OsrEntry (OsrEntry* x);
494 void do_ExceptionObject(ExceptionObject* x);
495 void do_RoundFP (RoundFP* x);
496 void do_UnsafeGetRaw (UnsafeGetRaw* x);
497 void do_UnsafePutRaw (UnsafePutRaw* x);
498 void do_UnsafeGetObject(UnsafeGetObject* x);
499 void do_UnsafePutObject(UnsafePutObject* x);
500 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
501 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
502 void do_ProfileCall (ProfileCall* x);
503 void do_ProfileInvoke (ProfileInvoke* x);
504 void do_RuntimeCall (RuntimeCall* x);
505 };
506
507
508 // Because of a static contained within (for the purpose of iteration
509 // over instructions), it is only valid to have one of these active at
510 // a time
511 class NullCheckEliminator: public ValueVisitor {
512 private:
513 Optimizer* _opt;
514
515 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
516 BlockList* _work_list; // Basic blocks to visit
517
518 bool visitable(Value x) {
519 assert(_visitable_instructions != NULL, "check");
520 return _visitable_instructions->contains(x);
521 }
522 void mark_visited(Value x) {
523 assert(_visitable_instructions != NULL, "check");
524 _visitable_instructions->remove(x);
525 }
526 void mark_visitable(Value x) {
527 assert(_visitable_instructions != NULL, "check");
528 _visitable_instructions->put(x);
529 }
530 void clear_visitable_state() {
531 assert(_visitable_instructions != NULL, "check");
532 _visitable_instructions->clear();
533 }
534
535 ValueSet* _set; // current state, propagated to subsequent BlockBegins
536 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
537 NullCheckVisitor _visitor;
538 NullCheck* _last_explicit_null_check;
539
540 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
541 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
542 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
543
544 BlockList* work_list() { return _work_list; }
545
546 void iterate_all();
547 void iterate_one(BlockBegin* block);
548
549 ValueSet* state() { return _set; }
550 void set_state_from (ValueSet* state) { _set->set_from(state); }
551 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
552 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
553 // Returns true if caused a change in the block's state.
554 bool merge_state_for(BlockBegin* block,
555 ValueSet* incoming_state);
556
557 public:
558 // constructor
559 NullCheckEliminator(Optimizer* opt)
560 : _opt(opt)
561 , _set(new ValueSet())
562 , _last_explicit_null_check(NULL)
563 , _block_states(BlockBegin::number_of_blocks(), NULL)
564 , _work_list(new BlockList()) {
565 _visitable_instructions = new ValueSet();
566 _visitor.set_eliminator(this);
567 }
568
569 Optimizer* opt() { return _opt; }
570 IR* ir () { return opt()->ir(); }
571
572 // Process a graph
573 void iterate(BlockBegin* root);
574
575 void visit(Value* f);
576
577 // In some situations (like NullCheck(x); getfield(x)) the debug
578 // information from the explicit NullCheck can be used to populate
579 // the getfield, even if the two instructions are in different
580 // scopes; this allows implicit null checks to be used but the
581 // correct exception information to be generated. We must clear the
582 // last-traversed NullCheck when we reach a potentially-exception-
583 // throwing instruction, as well as in some other cases.
584 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
585 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
586 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
587 ? _last_explicit_null_check->obj()
588 : NULL); }
589 NullCheck* consume_last_explicit_null_check() {
590 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
591 _last_explicit_null_check->set_can_trap(false);
592 return _last_explicit_null_check;
593 }
594 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
595
596 // Handlers for relevant instructions
597 // (separated out from NullCheckVisitor for clarity)
598
599 // The basic contract is that these must leave the instruction in
600 // the desired state; must not assume anything about the state of
601 // the instruction. We make multiple passes over some basic blocks
602 // and the last pass is the only one whose result is valid.
603 void handle_AccessField (AccessField* x);
604 void handle_ArrayLength (ArrayLength* x);
605 void handle_LoadIndexed (LoadIndexed* x);
606 void handle_StoreIndexed (StoreIndexed* x);
607 void handle_NullCheck (NullCheck* x);
608 void handle_Invoke (Invoke* x);
609 void handle_NewInstance (NewInstance* x);
610 void handle_NewArray (NewArray* x);
611 void handle_AccessMonitor (AccessMonitor* x);
612 void handle_Intrinsic (Intrinsic* x);
613 void handle_ExceptionObject (ExceptionObject* x);
614 void handle_Phi (Phi* x);
615 };
616
617
618 // NEEDS_CLEANUP
619 // There may be other instructions which need to clear the last
620 // explicit null check. Anything across which we can not hoist the
621 // debug information for a NullCheck instruction must clear it. It
622 // might be safer to pattern match "NullCheck ; {AccessField,
623 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
624 // Should test to see performance hit of clearing it for all handlers
625 // with empty bodies below. If it is negligible then we should leave
626 // that in for safety, otherwise should think more about it.
627 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
628 void NullCheckVisitor::do_Local (Local* x) {}
629 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
630 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
631 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
632 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
633 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
634 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
635 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
636 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
637 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
638 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
639 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
640 void NullCheckVisitor::do_IfOp (IfOp* x) {}
641 void NullCheckVisitor::do_Convert (Convert* x) {}
642 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
643 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
644 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
645 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
646 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
647 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
648 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
649 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
650 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
651 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
652 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
653 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
654 void NullCheckVisitor::do_Goto (Goto* x) {}
655 void NullCheckVisitor::do_If (If* x) {}
656 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
657 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
658 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
659 void NullCheckVisitor::do_Return (Return* x) {}
660 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
661 void NullCheckVisitor::do_Base (Base* x) {}
662 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
663 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
664 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
665 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
666 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
667 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
668 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
669 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
670 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
671 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
672 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
673 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
674
675
676 void NullCheckEliminator::visit(Value* p) {
677 assert(*p != NULL, "should not find NULL instructions");
678 if (visitable(*p)) {
679 mark_visited(*p);
680 (*p)->visit(&_visitor);
681 }
682 }
683
684 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
685 ValueSet* state = state_for(block);
686 if (state == NULL) {
687 state = incoming_state->copy();
688 set_state_for(block, state);
689 return true;
690 } else {
691 bool changed = state->set_intersect(incoming_state);
692 if (PrintNullCheckElimination && changed) {
693 tty->print_cr("Block %d's null check state changed", block->block_id());
694 }
695 return changed;
696 }
697 }
698
699
700 void NullCheckEliminator::iterate_all() {
701 while (work_list()->length() > 0) {
702 iterate_one(work_list()->pop());
703 }
704 }
705
706
707 void NullCheckEliminator::iterate_one(BlockBegin* block) {
708 clear_visitable_state();
709 // clear out an old explicit null checks
710 set_last_explicit_null_check(NULL);
711
712 if (PrintNullCheckElimination) {
713 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
714 block->block_id(),
715 ir()->method()->holder()->name()->as_utf8(),
716 ir()->method()->name()->as_utf8(),
717 ir()->method()->signature()->as_symbol()->as_utf8());
718 }
719
720 // Create new state if none present (only happens at root)
721 if (state_for(block) == NULL) {
722 ValueSet* tmp_state = new ValueSet();
723 set_state_for(block, tmp_state);
724 // Initial state is that local 0 (receiver) is non-null for
725 // non-static methods
726 ValueStack* stack = block->state();
727 IRScope* scope = stack->scope();
728 ciMethod* method = scope->method();
729 if (!method->is_static()) {
730 Local* local0 = stack->local_at(0)->as_Local();
731 assert(local0 != NULL, "must be");
732 assert(local0->type() == objectType, "invalid type of receiver");
733
734 if (local0 != NULL) {
735 // Local 0 is used in this scope
736 tmp_state->put(local0);
737 if (PrintNullCheckElimination) {
738 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
739 }
740 }
741 }
742 }
743
744 // Must copy block's state to avoid mutating it during iteration
745 // through the block -- otherwise "not-null" states can accidentally
746 // propagate "up" through the block during processing of backward
747 // branches and algorithm is incorrect (and does not converge)
748 set_state_from(state_for(block));
749
750 // allow visiting of Phis belonging to this block
751 for_each_phi_fun(block, phi,
752 mark_visitable(phi);
753 );
754
755 BlockEnd* e = block->end();
756 assert(e != NULL, "incomplete graph");
757 int i;
758
759 // Propagate the state before this block into the exception
760 // handlers. They aren't true successors since we aren't guaranteed
761 // to execute the whole block before executing them. Also putting
762 // them on first seems to help reduce the amount of iteration to
763 // reach a fixed point.
764 for (i = 0; i < block->number_of_exception_handlers(); i++) {
765 BlockBegin* next = block->exception_handler_at(i);
766 if (merge_state_for(next, state())) {
767 if (!work_list()->contains(next)) {
768 work_list()->push(next);
769 }
770 }
771 }
772
773 // Iterate through block, updating state.
774 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
775 // Mark instructions in this block as visitable as they are seen
776 // in the instruction list. This keeps the iteration from
777 // visiting instructions which are references in other blocks or
778 // visiting instructions more than once.
779 mark_visitable(instr);
780 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
781 mark_visited(instr);
782 instr->input_values_do(this);
783 instr->visit(&_visitor);
784 }
785 }
786
787 // Propagate state to successors if necessary
788 for (i = 0; i < e->number_of_sux(); i++) {
789 BlockBegin* next = e->sux_at(i);
790 if (merge_state_for(next, state())) {
791 if (!work_list()->contains(next)) {
792 work_list()->push(next);
793 }
794 }
795 }
796 }
797
798
799 void NullCheckEliminator::iterate(BlockBegin* block) {
800 work_list()->push(block);
801 iterate_all();
802 }
803
804 void NullCheckEliminator::handle_AccessField(AccessField* x) {
805 if (x->is_static()) {
806 if (x->as_LoadField() != NULL) {
807 // If the field is a non-null static final object field (as is
808 // often the case for sun.misc.Unsafe), put this LoadField into
809 // the non-null map
810 ciField* field = x->field();
811 if (field->is_constant()) {
812 ciConstant field_val = field->constant_value();
813 BasicType field_type = field_val.basic_type();
814 if (field_type == T_OBJECT || field_type == T_ARRAY) {
815 ciObject* obj_val = field_val.as_object();
816 if (!obj_val->is_null_object()) {
817 if (PrintNullCheckElimination) {
818 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
819 x->id());
820 }
821 set_put(x);
822 }
823 }
824 }
825 }
826 // Be conservative
827 clear_last_explicit_null_check();
828 return;
829 }
830
831 Value obj = x->obj();
832 if (set_contains(obj)) {
833 // Value is non-null => update AccessField
834 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
835 x->set_explicit_null_check(consume_last_explicit_null_check());
836 x->set_needs_null_check(true);
837 if (PrintNullCheckElimination) {
838 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
839 x->explicit_null_check()->id(), x->id(), obj->id());
840 }
841 } else {
842 x->set_explicit_null_check(NULL);
843 x->set_needs_null_check(false);
844 if (PrintNullCheckElimination) {
845 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
846 }
847 }
848 } else {
849 set_put(obj);
850 if (PrintNullCheckElimination) {
851 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
852 }
853 // Ensure previous passes do not cause wrong state
854 x->set_needs_null_check(true);
855 x->set_explicit_null_check(NULL);
856 }
857 clear_last_explicit_null_check();
858 }
859
860
861 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
862 Value array = x->array();
863 if (set_contains(array)) {
864 // Value is non-null => update AccessArray
865 if (last_explicit_null_check_obj() == array) {
866 x->set_explicit_null_check(consume_last_explicit_null_check());
867 x->set_needs_null_check(true);
868 if (PrintNullCheckElimination) {
869 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
870 x->explicit_null_check()->id(), x->id(), array->id());
871 }
872 } else {
873 x->set_explicit_null_check(NULL);
874 x->set_needs_null_check(false);
875 if (PrintNullCheckElimination) {
876 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
877 }
878 }
879 } else {
880 set_put(array);
881 if (PrintNullCheckElimination) {
882 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
883 }
884 // Ensure previous passes do not cause wrong state
885 x->set_needs_null_check(true);
886 x->set_explicit_null_check(NULL);
887 }
888 clear_last_explicit_null_check();
889 }
890
891
892 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
893 Value array = x->array();
894 if (set_contains(array)) {
895 // Value is non-null => update AccessArray
896 if (last_explicit_null_check_obj() == array) {
897 x->set_explicit_null_check(consume_last_explicit_null_check());
898 x->set_needs_null_check(true);
899 if (PrintNullCheckElimination) {
900 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
901 x->explicit_null_check()->id(), x->id(), array->id());
902 }
903 } else {
904 x->set_explicit_null_check(NULL);
905 x->set_needs_null_check(false);
906 if (PrintNullCheckElimination) {
907 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
908 }
909 }
910 } else {
911 set_put(array);
912 if (PrintNullCheckElimination) {
913 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
914 }
915 // Ensure previous passes do not cause wrong state
916 x->set_needs_null_check(true);
917 x->set_explicit_null_check(NULL);
918 }
919 clear_last_explicit_null_check();
920 }
921
922
923 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
924 Value array = x->array();
925 if (set_contains(array)) {
926 // Value is non-null => update AccessArray
927 if (PrintNullCheckElimination) {
928 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
929 }
930 x->set_needs_null_check(false);
931 } else {
932 set_put(array);
933 if (PrintNullCheckElimination) {
934 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
935 }
936 // Ensure previous passes do not cause wrong state
937 x->set_needs_null_check(true);
938 }
939 clear_last_explicit_null_check();
940 }
941
942
943 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
944 Value obj = x->obj();
945 if (set_contains(obj)) {
946 // Already proven to be non-null => this NullCheck is useless
947 if (PrintNullCheckElimination) {
948 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
949 }
950 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
951 // The code generator won't emit LIR for a NullCheck that cannot trap.
952 x->set_can_trap(false);
953 } else {
954 // May be null => add to map and set last explicit NullCheck
955 x->set_can_trap(true);
956 // make sure it's pinned if it can trap
957 x->pin(Instruction::PinExplicitNullCheck);
958 set_put(obj);
959 set_last_explicit_null_check(x);
960 if (PrintNullCheckElimination) {
961 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
962 }
963 }
964 }
965
966
967 void NullCheckEliminator::handle_Invoke(Invoke* x) {
968 if (!x->has_receiver()) {
969 // Be conservative
970 clear_last_explicit_null_check();
971 return;
972 }
973
974 Value recv = x->receiver();
975 if (!set_contains(recv)) {
976 set_put(recv);
977 if (PrintNullCheckElimination) {
978 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
979 }
980 }
981 clear_last_explicit_null_check();
982 }
983
984
985 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
986 set_put(x);
987 if (PrintNullCheckElimination) {
988 tty->print_cr("NewInstance %d is non-null", x->id());
989 }
990 }
991
992
993 void NullCheckEliminator::handle_NewArray(NewArray* x) {
994 set_put(x);
995 if (PrintNullCheckElimination) {
996 tty->print_cr("NewArray %d is non-null", x->id());
997 }
998 }
999
1000
1001 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1002 set_put(x);
1003 if (PrintNullCheckElimination) {
1004 tty->print_cr("ExceptionObject %d is non-null", x->id());
1005 }
1006 }
1007
1008
1009 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1010 Value obj = x->obj();
1011 if (set_contains(obj)) {
1012 // Value is non-null => update AccessMonitor
1013 if (PrintNullCheckElimination) {
1014 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1015 }
1016 x->set_needs_null_check(false);
1017 } else {
1018 set_put(obj);
1019 if (PrintNullCheckElimination) {
1020 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1021 }
1022 // Ensure previous passes do not cause wrong state
1023 x->set_needs_null_check(true);
1024 }
1025 clear_last_explicit_null_check();
1026 }
1027
1028
1029 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1030 if (!x->has_receiver()) {
1031 if (x->id() == vmIntrinsics::_arraycopy) {
1032 for (int i = 0; i < x->number_of_arguments(); i++) {
1033 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1034 }
1035 }
1036
1037 // Be conservative
1038 clear_last_explicit_null_check();
1039 return;
1040 }
1041
1042 Value recv = x->receiver();
1043 if (set_contains(recv)) {
1044 // Value is non-null => update Intrinsic
1045 if (PrintNullCheckElimination) {
1046 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1047 }
1048 x->set_needs_null_check(false);
1049 } else {
1050 set_put(recv);
1051 if (PrintNullCheckElimination) {
1052 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1053 }
1054 // Ensure previous passes do not cause wrong state
1055 x->set_needs_null_check(true);
1056 }
1057 clear_last_explicit_null_check();
1058 }
1059
1060
1061 void NullCheckEliminator::handle_Phi(Phi* x) {
1062 int i;
1063 bool all_non_null = true;
1064 if (x->is_illegal()) {
1065 all_non_null = false;
1066 } else {
1067 for (i = 0; i < x->operand_count(); i++) {
1068 Value input = x->operand_at(i);
1069 if (!set_contains(input)) {
1070 all_non_null = false;
1071 }
1072 }
1073 }
1074
1075 if (all_non_null) {
1076 // Value is non-null => update Phi
1077 if (PrintNullCheckElimination) {
1078 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1079 }
1080 x->set_needs_null_check(false);
1081 } else if (set_contains(x)) {
1082 set_remove(x);
1083 }
1084 }
1085
1086
1087 void Optimizer::eliminate_null_checks() {
1088 ResourceMark rm;
1089
1090 NullCheckEliminator nce(this);
1091
1092 if (PrintNullCheckElimination) {
1093 tty->print_cr("Starting null check elimination for method %s::%s%s",
1094 ir()->method()->holder()->name()->as_utf8(),
1095 ir()->method()->name()->as_utf8(),
1096 ir()->method()->signature()->as_symbol()->as_utf8());
1097 }
1098
1099 // Apply to graph
1100 nce.iterate(ir()->start());
1101
1102 // walk over the graph looking for exception
1103 // handlers and iterate over them as well
1104 int nblocks = BlockBegin::number_of_blocks();
1105 BlockList blocks(nblocks);
1106 boolArray visited_block(nblocks, false);
1107
1108 blocks.push(ir()->start());
1109 visited_block[ir()->start()->block_id()] = true;
1110 for (int i = 0; i < blocks.length(); i++) {
1111 BlockBegin* b = blocks[i];
1112 // exception handlers need to be treated as additional roots
1113 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1114 BlockBegin* excp = b->exception_handler_at(e);
1115 int id = excp->block_id();
1116 if (!visited_block[id]) {
1117 blocks.push(excp);
1118 visited_block[id] = true;
1119 nce.iterate(excp);
1120 }
1121 }
1122 // traverse successors
1123 BlockEnd *end = b->end();
1124 for (int s = end->number_of_sux(); s-- > 0; ) {
1125 BlockBegin* next = end->sux_at(s);
1126 int id = next->block_id();
1127 if (!visited_block[id]) {
1128 blocks.push(next);
1129 visited_block[id] = true;
1130 }
1131 }
1132 }
1133
1134
1135 if (PrintNullCheckElimination) {
1136 tty->print_cr("Done with null check elimination for method %s::%s%s",
1137 ir()->method()->holder()->name()->as_utf8(),
1138 ir()->method()->name()->as_utf8(),
1139 ir()->method()->signature()->as_symbol()->as_utf8());
1140 }
1141 }