Tue, 21 Feb 2012 13:14:55 -0500
7120481: storeStore barrier in constructor with final field
Summary: Issue storestore barrier before constructor return if the constructor write final field.
Reviewed-by: dholmes, jrose, roland, coleenp
Contributed-by: Jiangli Zhou <jiangli.zhou@oracle.com>
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.
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23 */
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"
33 define_array(ValueSetArray, ValueSet*);
34 define_stack(ValueSetList, ValueSetArray);
37 Optimizer::Optimizer(IR* ir) {
38 assert(ir->is_valid(), "IR must be valid");
39 _ir = ir;
40 }
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;
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; }
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);
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 }
78 virtual void block_do(BlockBegin* block);
80 private:
81 Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
82 };
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;
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;
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();
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 }
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;
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;
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 if (if_state->scope()->level() > sux_state->scope()->level()) {
129 while (sux_state->scope() != if_state->scope()) {
130 if_state = if_state->caller_state();
131 assert(if_state != NULL, "states do not match up");
132 }
133 } else if (if_state->scope()->level() < sux_state->scope()->level()) {
134 while (sux_state->scope() != if_state->scope()) {
135 sux_state = sux_state->caller_state();
136 assert(sux_state != NULL, "states do not match up");
137 }
138 }
140 if (sux_state->stack_size() <= if_state->stack_size()) return;
142 // check if phi function is present at end of successor stack and that
143 // only this phi was pushed on the stack
144 Value sux_phi = sux_state->stack_at(if_state->stack_size());
145 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
146 if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
148 // get the values that were pushed in the true- and false-branch
149 Value t_value = t_goto->state()->stack_at(if_state->stack_size());
150 Value f_value = f_goto->state()->stack_at(if_state->stack_size());
152 // backend does not support floats
153 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
154 if (t_value->type()->is_float_kind()) return;
156 // check that successor has no other phi functions but sux_phi
157 // this can happen when t_block or f_block contained additonal stores to local variables
158 // that are no longer represented by explicit instructions
159 for_each_phi_fun(sux, phi,
160 if (phi != sux_phi) return;
161 );
162 // true and false blocks can't have phis
163 for_each_phi_fun(t_block, phi, return; );
164 for_each_phi_fun(f_block, phi, return; );
166 // 2) substitute conditional expression
167 // with an IfOp followed by a Goto
168 // cut if_ away and get node before
169 Instruction* cur_end = if_->prev(block);
171 // append constants of true- and false-block if necessary
172 // clone constants because original block must not be destroyed
173 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
174 if (t_value == t_const) {
175 t_value = new Constant(t_const->type());
176 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
177 cur_end = cur_end->set_next(t_value);
178 }
179 if (f_value == f_const) {
180 f_value = new Constant(f_const->type());
181 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
182 cur_end = cur_end->set_next(f_value);
183 }
185 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
186 assert(result != NULL, "make_ifop must return a non-null instruction");
187 if (!result->is_linked() && result->can_be_linked()) {
188 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
189 cur_end = cur_end->set_next(result);
190 }
192 // append Goto to successor
193 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
194 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
196 // prepare state for Goto
197 ValueStack* goto_state = if_state;
198 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
199 goto_state->push(result->type(), result);
200 assert(goto_state->is_same(sux_state), "states must match now");
201 goto_->set_state(goto_state);
203 cur_end = cur_end->set_next(goto_, goto_state->bci());
205 // Adjust control flow graph
206 BlockBegin::disconnect_edge(block, t_block);
207 BlockBegin::disconnect_edge(block, f_block);
208 if (t_block->number_of_preds() == 0) {
209 BlockBegin::disconnect_edge(t_block, sux);
210 }
211 adjust_exception_edges(block, t_block);
212 if (f_block->number_of_preds() == 0) {
213 BlockBegin::disconnect_edge(f_block, sux);
214 }
215 adjust_exception_edges(block, f_block);
217 // update block end
218 block->set_end(goto_);
220 // substitute the phi if possible
221 if (sux_phi->as_Phi()->operand_count() == 1) {
222 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
223 sux_phi->set_subst(result);
224 _has_substitution = true;
225 }
227 // 3) successfully eliminated a conditional expression
228 _cee_count++;
229 if (PrintCEE) {
230 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());
231 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
232 }
234 _hir->verify();
235 }
237 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
238 if (!OptimizeIfOps) {
239 return new IfOp(x, cond, y, tval, fval);
240 }
242 tval = tval->subst();
243 fval = fval->subst();
244 if (tval == fval) {
245 _ifop_count++;
246 return tval;
247 }
249 x = x->subst();
250 y = y->subst();
252 Constant* y_const = y->as_Constant();
253 if (y_const != NULL) {
254 IfOp* x_ifop = x->as_IfOp();
255 if (x_ifop != NULL) { // x is an ifop, y is a constant
256 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
257 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
259 if (x_tval_const != NULL && x_fval_const != NULL) {
260 Instruction::Condition x_ifop_cond = x_ifop->cond();
262 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
263 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
265 // not_comparable here is a valid return in case we're comparing unloaded oop constants
266 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
267 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
268 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
270 _ifop_count++;
271 if (new_tval == new_fval) {
272 return new_tval;
273 } else {
274 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
275 }
276 }
277 }
278 } else {
279 Constant* x_const = x->as_Constant();
280 if (x_const != NULL) { // x and y are constants
281 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
282 // not_comparable here is a valid return in case we're comparing unloaded oop constants
283 if (x_compare_res != Constant::not_comparable) {
284 _ifop_count++;
285 return x_compare_res == Constant::cond_true ? tval : fval;
286 }
287 }
288 }
289 }
290 return new IfOp(x, cond, y, tval, fval);
291 }
293 void Optimizer::eliminate_conditional_expressions() {
294 // find conditional expressions & replace them with IfOps
295 CE_Eliminator ce(ir());
296 }
298 class BlockMerger: public BlockClosure {
299 private:
300 IR* _hir;
301 int _merge_count; // the number of block pairs successfully merged
303 public:
304 BlockMerger(IR* hir)
305 : _hir(hir)
306 , _merge_count(0)
307 {
308 _hir->iterate_preorder(this);
309 }
311 bool try_merge(BlockBegin* block) {
312 BlockEnd* end = block->end();
313 if (end->as_Goto() != NULL) {
314 assert(end->number_of_sux() == 1, "end must have exactly one successor");
315 // Note: It would be sufficient to check for the number of successors (= 1)
316 // in order to decide if this block can be merged potentially. That
317 // would then also include switch statements w/ only a default case.
318 // However, in that case we would need to make sure the switch tag
319 // expression is executed if it can produce observable side effects.
320 // We should probably have the canonicalizer simplifying such switch
321 // statements and then we are sure we don't miss these merge opportunities
322 // here (was bug - gri 7/7/99).
323 BlockBegin* sux = end->default_sux();
324 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
325 // merge the two blocks
327 #ifdef ASSERT
328 // verify that state at the end of block and at the beginning of sux are equal
329 // no phi functions must be present at beginning of sux
330 ValueStack* sux_state = sux->state();
331 ValueStack* end_state = end->state();
333 assert(end_state->scope() == sux_state->scope(), "scopes must match");
334 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
335 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
337 int index;
338 Value sux_value;
339 for_each_stack_value(sux_state, index, sux_value) {
340 assert(sux_value == end_state->stack_at(index), "stack not equal");
341 }
342 for_each_local_value(sux_state, index, sux_value) {
343 assert(sux_value == end_state->local_at(index), "locals not equal");
344 }
345 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
346 #endif
348 // find instruction before end & append first instruction of sux block
349 Instruction* prev = end->prev(block);
350 Instruction* next = sux->next();
351 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
352 prev->set_next(next);
353 sux->disconnect_from_graph();
354 block->set_end(sux->end());
355 // add exception handlers of deleted block, if any
356 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
357 BlockBegin* xhandler = sux->exception_handler_at(k);
358 block->add_exception_handler(xhandler);
360 // also substitute predecessor of exception handler
361 assert(xhandler->is_predecessor(sux), "missing predecessor");
362 xhandler->remove_predecessor(sux);
363 if (!xhandler->is_predecessor(block)) {
364 xhandler->add_predecessor(block);
365 }
366 }
368 // debugging output
369 _merge_count++;
370 if (PrintBlockElimination) {
371 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
372 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
373 }
375 _hir->verify();
377 If* if_ = block->end()->as_If();
378 if (if_) {
379 IfOp* ifop = if_->x()->as_IfOp();
380 Constant* con = if_->y()->as_Constant();
381 bool swapped = false;
382 if (!con || !ifop) {
383 ifop = if_->y()->as_IfOp();
384 con = if_->x()->as_Constant();
385 swapped = true;
386 }
387 if (con && ifop) {
388 Constant* tval = ifop->tval()->as_Constant();
389 Constant* fval = ifop->fval()->as_Constant();
390 if (tval && fval) {
391 // Find the instruction before if_, starting with ifop.
392 // When if_ and ifop are not in the same block, prev
393 // becomes NULL In such (rare) cases it is not
394 // profitable to perform the optimization.
395 Value prev = ifop;
396 while (prev != NULL && prev->next() != if_) {
397 prev = prev->next();
398 }
400 if (prev != NULL) {
401 Instruction::Condition cond = if_->cond();
402 BlockBegin* tsux = if_->tsux();
403 BlockBegin* fsux = if_->fsux();
404 if (swapped) {
405 cond = Instruction::mirror(cond);
406 }
408 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
409 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
410 if (tblock != fblock && !if_->is_safepoint()) {
411 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
412 tblock, fblock, if_->state_before(), if_->is_safepoint());
413 newif->set_state(if_->state()->copy());
415 assert(prev->next() == if_, "must be guaranteed by above search");
416 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
417 prev->set_next(newif);
418 block->set_end(newif);
420 _merge_count++;
421 if (PrintBlockElimination) {
422 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
423 }
425 _hir->verify();
426 }
427 }
428 }
429 }
430 }
432 return true;
433 }
434 }
435 return false;
436 }
438 virtual void block_do(BlockBegin* block) {
439 _hir->verify();
440 // repeat since the same block may merge again
441 while (try_merge(block)) {
442 _hir->verify();
443 }
444 }
445 };
448 void Optimizer::eliminate_blocks() {
449 // merge blocks if possible
450 BlockMerger bm(ir());
451 }
454 class NullCheckEliminator;
455 class NullCheckVisitor: public InstructionVisitor {
456 private:
457 NullCheckEliminator* _nce;
458 NullCheckEliminator* nce() { return _nce; }
460 public:
461 NullCheckVisitor() {}
463 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
465 void do_Phi (Phi* x);
466 void do_Local (Local* x);
467 void do_Constant (Constant* x);
468 void do_LoadField (LoadField* x);
469 void do_StoreField (StoreField* x);
470 void do_ArrayLength (ArrayLength* x);
471 void do_LoadIndexed (LoadIndexed* x);
472 void do_StoreIndexed (StoreIndexed* x);
473 void do_NegateOp (NegateOp* x);
474 void do_ArithmeticOp (ArithmeticOp* x);
475 void do_ShiftOp (ShiftOp* x);
476 void do_LogicOp (LogicOp* x);
477 void do_CompareOp (CompareOp* x);
478 void do_IfOp (IfOp* x);
479 void do_Convert (Convert* x);
480 void do_NullCheck (NullCheck* x);
481 void do_Invoke (Invoke* x);
482 void do_NewInstance (NewInstance* x);
483 void do_NewTypeArray (NewTypeArray* x);
484 void do_NewObjectArray (NewObjectArray* x);
485 void do_NewMultiArray (NewMultiArray* x);
486 void do_CheckCast (CheckCast* x);
487 void do_InstanceOf (InstanceOf* x);
488 void do_MonitorEnter (MonitorEnter* x);
489 void do_MonitorExit (MonitorExit* x);
490 void do_Intrinsic (Intrinsic* x);
491 void do_BlockBegin (BlockBegin* x);
492 void do_Goto (Goto* x);
493 void do_If (If* x);
494 void do_IfInstanceOf (IfInstanceOf* x);
495 void do_TableSwitch (TableSwitch* x);
496 void do_LookupSwitch (LookupSwitch* x);
497 void do_Return (Return* x);
498 void do_Throw (Throw* x);
499 void do_Base (Base* x);
500 void do_OsrEntry (OsrEntry* x);
501 void do_ExceptionObject(ExceptionObject* x);
502 void do_RoundFP (RoundFP* x);
503 void do_UnsafeGetRaw (UnsafeGetRaw* x);
504 void do_UnsafePutRaw (UnsafePutRaw* x);
505 void do_UnsafeGetObject(UnsafeGetObject* x);
506 void do_UnsafePutObject(UnsafePutObject* x);
507 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
508 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
509 void do_ProfileCall (ProfileCall* x);
510 void do_ProfileInvoke (ProfileInvoke* x);
511 void do_RuntimeCall (RuntimeCall* x);
512 void do_MemBar (MemBar* x);
513 };
516 // Because of a static contained within (for the purpose of iteration
517 // over instructions), it is only valid to have one of these active at
518 // a time
519 class NullCheckEliminator: public ValueVisitor {
520 private:
521 Optimizer* _opt;
523 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
524 BlockList* _work_list; // Basic blocks to visit
526 bool visitable(Value x) {
527 assert(_visitable_instructions != NULL, "check");
528 return _visitable_instructions->contains(x);
529 }
530 void mark_visited(Value x) {
531 assert(_visitable_instructions != NULL, "check");
532 _visitable_instructions->remove(x);
533 }
534 void mark_visitable(Value x) {
535 assert(_visitable_instructions != NULL, "check");
536 _visitable_instructions->put(x);
537 }
538 void clear_visitable_state() {
539 assert(_visitable_instructions != NULL, "check");
540 _visitable_instructions->clear();
541 }
543 ValueSet* _set; // current state, propagated to subsequent BlockBegins
544 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
545 NullCheckVisitor _visitor;
546 NullCheck* _last_explicit_null_check;
548 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
549 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
550 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
552 BlockList* work_list() { return _work_list; }
554 void iterate_all();
555 void iterate_one(BlockBegin* block);
557 ValueSet* state() { return _set; }
558 void set_state_from (ValueSet* state) { _set->set_from(state); }
559 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
560 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
561 // Returns true if caused a change in the block's state.
562 bool merge_state_for(BlockBegin* block,
563 ValueSet* incoming_state);
565 public:
566 // constructor
567 NullCheckEliminator(Optimizer* opt)
568 : _opt(opt)
569 , _set(new ValueSet())
570 , _last_explicit_null_check(NULL)
571 , _block_states(BlockBegin::number_of_blocks(), NULL)
572 , _work_list(new BlockList()) {
573 _visitable_instructions = new ValueSet();
574 _visitor.set_eliminator(this);
575 }
577 Optimizer* opt() { return _opt; }
578 IR* ir () { return opt()->ir(); }
580 // Process a graph
581 void iterate(BlockBegin* root);
583 void visit(Value* f);
585 // In some situations (like NullCheck(x); getfield(x)) the debug
586 // information from the explicit NullCheck can be used to populate
587 // the getfield, even if the two instructions are in different
588 // scopes; this allows implicit null checks to be used but the
589 // correct exception information to be generated. We must clear the
590 // last-traversed NullCheck when we reach a potentially-exception-
591 // throwing instruction, as well as in some other cases.
592 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
593 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
594 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
595 ? _last_explicit_null_check->obj()
596 : NULL); }
597 NullCheck* consume_last_explicit_null_check() {
598 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
599 _last_explicit_null_check->set_can_trap(false);
600 return _last_explicit_null_check;
601 }
602 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
604 // Handlers for relevant instructions
605 // (separated out from NullCheckVisitor for clarity)
607 // The basic contract is that these must leave the instruction in
608 // the desired state; must not assume anything about the state of
609 // the instruction. We make multiple passes over some basic blocks
610 // and the last pass is the only one whose result is valid.
611 void handle_AccessField (AccessField* x);
612 void handle_ArrayLength (ArrayLength* x);
613 void handle_LoadIndexed (LoadIndexed* x);
614 void handle_StoreIndexed (StoreIndexed* x);
615 void handle_NullCheck (NullCheck* x);
616 void handle_Invoke (Invoke* x);
617 void handle_NewInstance (NewInstance* x);
618 void handle_NewArray (NewArray* x);
619 void handle_AccessMonitor (AccessMonitor* x);
620 void handle_Intrinsic (Intrinsic* x);
621 void handle_ExceptionObject (ExceptionObject* x);
622 void handle_Phi (Phi* x);
623 };
626 // NEEDS_CLEANUP
627 // There may be other instructions which need to clear the last
628 // explicit null check. Anything across which we can not hoist the
629 // debug information for a NullCheck instruction must clear it. It
630 // might be safer to pattern match "NullCheck ; {AccessField,
631 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
632 // Should test to see performance hit of clearing it for all handlers
633 // with empty bodies below. If it is negligible then we should leave
634 // that in for safety, otherwise should think more about it.
635 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
636 void NullCheckVisitor::do_Local (Local* x) {}
637 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
638 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
639 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
640 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
641 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
642 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
643 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
644 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
645 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
646 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
647 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
648 void NullCheckVisitor::do_IfOp (IfOp* x) {}
649 void NullCheckVisitor::do_Convert (Convert* x) {}
650 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
651 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
652 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
653 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
654 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
655 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
656 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
657 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
658 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
659 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
660 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
661 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
662 void NullCheckVisitor::do_Goto (Goto* x) {}
663 void NullCheckVisitor::do_If (If* x) {}
664 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
665 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
666 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
667 void NullCheckVisitor::do_Return (Return* x) {}
668 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
669 void NullCheckVisitor::do_Base (Base* x) {}
670 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
671 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
672 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
673 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
674 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
675 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
676 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
677 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
678 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
679 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
680 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
681 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
682 void NullCheckVisitor::do_MemBar (MemBar* x) {}
685 void NullCheckEliminator::visit(Value* p) {
686 assert(*p != NULL, "should not find NULL instructions");
687 if (visitable(*p)) {
688 mark_visited(*p);
689 (*p)->visit(&_visitor);
690 }
691 }
693 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
694 ValueSet* state = state_for(block);
695 if (state == NULL) {
696 state = incoming_state->copy();
697 set_state_for(block, state);
698 return true;
699 } else {
700 bool changed = state->set_intersect(incoming_state);
701 if (PrintNullCheckElimination && changed) {
702 tty->print_cr("Block %d's null check state changed", block->block_id());
703 }
704 return changed;
705 }
706 }
709 void NullCheckEliminator::iterate_all() {
710 while (work_list()->length() > 0) {
711 iterate_one(work_list()->pop());
712 }
713 }
716 void NullCheckEliminator::iterate_one(BlockBegin* block) {
717 clear_visitable_state();
718 // clear out an old explicit null checks
719 set_last_explicit_null_check(NULL);
721 if (PrintNullCheckElimination) {
722 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
723 block->block_id(),
724 ir()->method()->holder()->name()->as_utf8(),
725 ir()->method()->name()->as_utf8(),
726 ir()->method()->signature()->as_symbol()->as_utf8());
727 }
729 // Create new state if none present (only happens at root)
730 if (state_for(block) == NULL) {
731 ValueSet* tmp_state = new ValueSet();
732 set_state_for(block, tmp_state);
733 // Initial state is that local 0 (receiver) is non-null for
734 // non-static methods
735 ValueStack* stack = block->state();
736 IRScope* scope = stack->scope();
737 ciMethod* method = scope->method();
738 if (!method->is_static()) {
739 Local* local0 = stack->local_at(0)->as_Local();
740 assert(local0 != NULL, "must be");
741 assert(local0->type() == objectType, "invalid type of receiver");
743 if (local0 != NULL) {
744 // Local 0 is used in this scope
745 tmp_state->put(local0);
746 if (PrintNullCheckElimination) {
747 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
748 }
749 }
750 }
751 }
753 // Must copy block's state to avoid mutating it during iteration
754 // through the block -- otherwise "not-null" states can accidentally
755 // propagate "up" through the block during processing of backward
756 // branches and algorithm is incorrect (and does not converge)
757 set_state_from(state_for(block));
759 // allow visiting of Phis belonging to this block
760 for_each_phi_fun(block, phi,
761 mark_visitable(phi);
762 );
764 BlockEnd* e = block->end();
765 assert(e != NULL, "incomplete graph");
766 int i;
768 // Propagate the state before this block into the exception
769 // handlers. They aren't true successors since we aren't guaranteed
770 // to execute the whole block before executing them. Also putting
771 // them on first seems to help reduce the amount of iteration to
772 // reach a fixed point.
773 for (i = 0; i < block->number_of_exception_handlers(); i++) {
774 BlockBegin* next = block->exception_handler_at(i);
775 if (merge_state_for(next, state())) {
776 if (!work_list()->contains(next)) {
777 work_list()->push(next);
778 }
779 }
780 }
782 // Iterate through block, updating state.
783 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
784 // Mark instructions in this block as visitable as they are seen
785 // in the instruction list. This keeps the iteration from
786 // visiting instructions which are references in other blocks or
787 // visiting instructions more than once.
788 mark_visitable(instr);
789 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
790 mark_visited(instr);
791 instr->input_values_do(this);
792 instr->visit(&_visitor);
793 }
794 }
796 // Propagate state to successors if necessary
797 for (i = 0; i < e->number_of_sux(); i++) {
798 BlockBegin* next = e->sux_at(i);
799 if (merge_state_for(next, state())) {
800 if (!work_list()->contains(next)) {
801 work_list()->push(next);
802 }
803 }
804 }
805 }
808 void NullCheckEliminator::iterate(BlockBegin* block) {
809 work_list()->push(block);
810 iterate_all();
811 }
813 void NullCheckEliminator::handle_AccessField(AccessField* x) {
814 if (x->is_static()) {
815 if (x->as_LoadField() != NULL) {
816 // If the field is a non-null static final object field (as is
817 // often the case for sun.misc.Unsafe), put this LoadField into
818 // the non-null map
819 ciField* field = x->field();
820 if (field->is_constant()) {
821 ciConstant field_val = field->constant_value();
822 BasicType field_type = field_val.basic_type();
823 if (field_type == T_OBJECT || field_type == T_ARRAY) {
824 ciObject* obj_val = field_val.as_object();
825 if (!obj_val->is_null_object()) {
826 if (PrintNullCheckElimination) {
827 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
828 x->id());
829 }
830 set_put(x);
831 }
832 }
833 }
834 }
835 // Be conservative
836 clear_last_explicit_null_check();
837 return;
838 }
840 Value obj = x->obj();
841 if (set_contains(obj)) {
842 // Value is non-null => update AccessField
843 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
844 x->set_explicit_null_check(consume_last_explicit_null_check());
845 x->set_needs_null_check(true);
846 if (PrintNullCheckElimination) {
847 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
848 x->explicit_null_check()->id(), x->id(), obj->id());
849 }
850 } else {
851 x->set_explicit_null_check(NULL);
852 x->set_needs_null_check(false);
853 if (PrintNullCheckElimination) {
854 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
855 }
856 }
857 } else {
858 set_put(obj);
859 if (PrintNullCheckElimination) {
860 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
861 }
862 // Ensure previous passes do not cause wrong state
863 x->set_needs_null_check(true);
864 x->set_explicit_null_check(NULL);
865 }
866 clear_last_explicit_null_check();
867 }
870 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
871 Value array = x->array();
872 if (set_contains(array)) {
873 // Value is non-null => update AccessArray
874 if (last_explicit_null_check_obj() == array) {
875 x->set_explicit_null_check(consume_last_explicit_null_check());
876 x->set_needs_null_check(true);
877 if (PrintNullCheckElimination) {
878 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
879 x->explicit_null_check()->id(), x->id(), array->id());
880 }
881 } else {
882 x->set_explicit_null_check(NULL);
883 x->set_needs_null_check(false);
884 if (PrintNullCheckElimination) {
885 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
886 }
887 }
888 } else {
889 set_put(array);
890 if (PrintNullCheckElimination) {
891 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
892 }
893 // Ensure previous passes do not cause wrong state
894 x->set_needs_null_check(true);
895 x->set_explicit_null_check(NULL);
896 }
897 clear_last_explicit_null_check();
898 }
901 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
902 Value array = x->array();
903 if (set_contains(array)) {
904 // Value is non-null => update AccessArray
905 if (last_explicit_null_check_obj() == array) {
906 x->set_explicit_null_check(consume_last_explicit_null_check());
907 x->set_needs_null_check(true);
908 if (PrintNullCheckElimination) {
909 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
910 x->explicit_null_check()->id(), x->id(), array->id());
911 }
912 } else {
913 x->set_explicit_null_check(NULL);
914 x->set_needs_null_check(false);
915 if (PrintNullCheckElimination) {
916 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
917 }
918 }
919 } else {
920 set_put(array);
921 if (PrintNullCheckElimination) {
922 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
923 }
924 // Ensure previous passes do not cause wrong state
925 x->set_needs_null_check(true);
926 x->set_explicit_null_check(NULL);
927 }
928 clear_last_explicit_null_check();
929 }
932 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
933 Value array = x->array();
934 if (set_contains(array)) {
935 // Value is non-null => update AccessArray
936 if (PrintNullCheckElimination) {
937 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
938 }
939 x->set_needs_null_check(false);
940 } else {
941 set_put(array);
942 if (PrintNullCheckElimination) {
943 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
944 }
945 // Ensure previous passes do not cause wrong state
946 x->set_needs_null_check(true);
947 }
948 clear_last_explicit_null_check();
949 }
952 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
953 Value obj = x->obj();
954 if (set_contains(obj)) {
955 // Already proven to be non-null => this NullCheck is useless
956 if (PrintNullCheckElimination) {
957 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
958 }
959 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
960 // The code generator won't emit LIR for a NullCheck that cannot trap.
961 x->set_can_trap(false);
962 } else {
963 // May be null => add to map and set last explicit NullCheck
964 x->set_can_trap(true);
965 // make sure it's pinned if it can trap
966 x->pin(Instruction::PinExplicitNullCheck);
967 set_put(obj);
968 set_last_explicit_null_check(x);
969 if (PrintNullCheckElimination) {
970 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
971 }
972 }
973 }
976 void NullCheckEliminator::handle_Invoke(Invoke* x) {
977 if (!x->has_receiver()) {
978 // Be conservative
979 clear_last_explicit_null_check();
980 return;
981 }
983 Value recv = x->receiver();
984 if (!set_contains(recv)) {
985 set_put(recv);
986 if (PrintNullCheckElimination) {
987 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
988 }
989 }
990 clear_last_explicit_null_check();
991 }
994 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
995 set_put(x);
996 if (PrintNullCheckElimination) {
997 tty->print_cr("NewInstance %d is non-null", x->id());
998 }
999 }
1002 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1003 set_put(x);
1004 if (PrintNullCheckElimination) {
1005 tty->print_cr("NewArray %d is non-null", x->id());
1006 }
1007 }
1010 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1011 set_put(x);
1012 if (PrintNullCheckElimination) {
1013 tty->print_cr("ExceptionObject %d is non-null", x->id());
1014 }
1015 }
1018 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1019 Value obj = x->obj();
1020 if (set_contains(obj)) {
1021 // Value is non-null => update AccessMonitor
1022 if (PrintNullCheckElimination) {
1023 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1024 }
1025 x->set_needs_null_check(false);
1026 } else {
1027 set_put(obj);
1028 if (PrintNullCheckElimination) {
1029 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1030 }
1031 // Ensure previous passes do not cause wrong state
1032 x->set_needs_null_check(true);
1033 }
1034 clear_last_explicit_null_check();
1035 }
1038 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1039 if (!x->has_receiver()) {
1040 if (x->id() == vmIntrinsics::_arraycopy) {
1041 for (int i = 0; i < x->number_of_arguments(); i++) {
1042 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1043 }
1044 }
1046 // Be conservative
1047 clear_last_explicit_null_check();
1048 return;
1049 }
1051 Value recv = x->receiver();
1052 if (set_contains(recv)) {
1053 // Value is non-null => update Intrinsic
1054 if (PrintNullCheckElimination) {
1055 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1056 }
1057 x->set_needs_null_check(false);
1058 } else {
1059 set_put(recv);
1060 if (PrintNullCheckElimination) {
1061 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1062 }
1063 // Ensure previous passes do not cause wrong state
1064 x->set_needs_null_check(true);
1065 }
1066 clear_last_explicit_null_check();
1067 }
1070 void NullCheckEliminator::handle_Phi(Phi* x) {
1071 int i;
1072 bool all_non_null = true;
1073 if (x->is_illegal()) {
1074 all_non_null = false;
1075 } else {
1076 for (i = 0; i < x->operand_count(); i++) {
1077 Value input = x->operand_at(i);
1078 if (!set_contains(input)) {
1079 all_non_null = false;
1080 }
1081 }
1082 }
1084 if (all_non_null) {
1085 // Value is non-null => update Phi
1086 if (PrintNullCheckElimination) {
1087 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1088 }
1089 x->set_needs_null_check(false);
1090 } else if (set_contains(x)) {
1091 set_remove(x);
1092 }
1093 }
1096 void Optimizer::eliminate_null_checks() {
1097 ResourceMark rm;
1099 NullCheckEliminator nce(this);
1101 if (PrintNullCheckElimination) {
1102 tty->print_cr("Starting null check elimination for method %s::%s%s",
1103 ir()->method()->holder()->name()->as_utf8(),
1104 ir()->method()->name()->as_utf8(),
1105 ir()->method()->signature()->as_symbol()->as_utf8());
1106 }
1108 // Apply to graph
1109 nce.iterate(ir()->start());
1111 // walk over the graph looking for exception
1112 // handlers and iterate over them as well
1113 int nblocks = BlockBegin::number_of_blocks();
1114 BlockList blocks(nblocks);
1115 boolArray visited_block(nblocks, false);
1117 blocks.push(ir()->start());
1118 visited_block[ir()->start()->block_id()] = true;
1119 for (int i = 0; i < blocks.length(); i++) {
1120 BlockBegin* b = blocks[i];
1121 // exception handlers need to be treated as additional roots
1122 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1123 BlockBegin* excp = b->exception_handler_at(e);
1124 int id = excp->block_id();
1125 if (!visited_block[id]) {
1126 blocks.push(excp);
1127 visited_block[id] = true;
1128 nce.iterate(excp);
1129 }
1130 }
1131 // traverse successors
1132 BlockEnd *end = b->end();
1133 for (int s = end->number_of_sux(); s-- > 0; ) {
1134 BlockBegin* next = end->sux_at(s);
1135 int id = next->block_id();
1136 if (!visited_block[id]) {
1137 blocks.push(next);
1138 visited_block[id] = true;
1139 }
1140 }
1141 }
1144 if (PrintNullCheckElimination) {
1145 tty->print_cr("Done with null check elimination for method %s::%s%s",
1146 ir()->method()->holder()->name()->as_utf8(),
1147 ir()->method()->name()->as_utf8(),
1148 ir()->method()->signature()->as_symbol()->as_utf8());
1149 }
1150 }