Thu, 22 Dec 2011 10:55:53 +0100
7123108: C1: assert(if_state != NULL) failed: states do not match up
Summary: In CEE, ensure if and common successor state are at the same inline level
Reviewed-by: never
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 */
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 };
515 // Because of a static contained within (for the purpose of iteration
516 // over instructions), it is only valid to have one of these active at
517 // a time
518 class NullCheckEliminator: public ValueVisitor {
519 private:
520 Optimizer* _opt;
522 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
523 BlockList* _work_list; // Basic blocks to visit
525 bool visitable(Value x) {
526 assert(_visitable_instructions != NULL, "check");
527 return _visitable_instructions->contains(x);
528 }
529 void mark_visited(Value x) {
530 assert(_visitable_instructions != NULL, "check");
531 _visitable_instructions->remove(x);
532 }
533 void mark_visitable(Value x) {
534 assert(_visitable_instructions != NULL, "check");
535 _visitable_instructions->put(x);
536 }
537 void clear_visitable_state() {
538 assert(_visitable_instructions != NULL, "check");
539 _visitable_instructions->clear();
540 }
542 ValueSet* _set; // current state, propagated to subsequent BlockBegins
543 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
544 NullCheckVisitor _visitor;
545 NullCheck* _last_explicit_null_check;
547 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
548 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
549 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
551 BlockList* work_list() { return _work_list; }
553 void iterate_all();
554 void iterate_one(BlockBegin* block);
556 ValueSet* state() { return _set; }
557 void set_state_from (ValueSet* state) { _set->set_from(state); }
558 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
559 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
560 // Returns true if caused a change in the block's state.
561 bool merge_state_for(BlockBegin* block,
562 ValueSet* incoming_state);
564 public:
565 // constructor
566 NullCheckEliminator(Optimizer* opt)
567 : _opt(opt)
568 , _set(new ValueSet())
569 , _last_explicit_null_check(NULL)
570 , _block_states(BlockBegin::number_of_blocks(), NULL)
571 , _work_list(new BlockList()) {
572 _visitable_instructions = new ValueSet();
573 _visitor.set_eliminator(this);
574 }
576 Optimizer* opt() { return _opt; }
577 IR* ir () { return opt()->ir(); }
579 // Process a graph
580 void iterate(BlockBegin* root);
582 void visit(Value* f);
584 // In some situations (like NullCheck(x); getfield(x)) the debug
585 // information from the explicit NullCheck can be used to populate
586 // the getfield, even if the two instructions are in different
587 // scopes; this allows implicit null checks to be used but the
588 // correct exception information to be generated. We must clear the
589 // last-traversed NullCheck when we reach a potentially-exception-
590 // throwing instruction, as well as in some other cases.
591 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
592 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
593 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
594 ? _last_explicit_null_check->obj()
595 : NULL); }
596 NullCheck* consume_last_explicit_null_check() {
597 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
598 _last_explicit_null_check->set_can_trap(false);
599 return _last_explicit_null_check;
600 }
601 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
603 // Handlers for relevant instructions
604 // (separated out from NullCheckVisitor for clarity)
606 // The basic contract is that these must leave the instruction in
607 // the desired state; must not assume anything about the state of
608 // the instruction. We make multiple passes over some basic blocks
609 // and the last pass is the only one whose result is valid.
610 void handle_AccessField (AccessField* x);
611 void handle_ArrayLength (ArrayLength* x);
612 void handle_LoadIndexed (LoadIndexed* x);
613 void handle_StoreIndexed (StoreIndexed* x);
614 void handle_NullCheck (NullCheck* x);
615 void handle_Invoke (Invoke* x);
616 void handle_NewInstance (NewInstance* x);
617 void handle_NewArray (NewArray* x);
618 void handle_AccessMonitor (AccessMonitor* x);
619 void handle_Intrinsic (Intrinsic* x);
620 void handle_ExceptionObject (ExceptionObject* x);
621 void handle_Phi (Phi* x);
622 };
625 // NEEDS_CLEANUP
626 // There may be other instructions which need to clear the last
627 // explicit null check. Anything across which we can not hoist the
628 // debug information for a NullCheck instruction must clear it. It
629 // might be safer to pattern match "NullCheck ; {AccessField,
630 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
631 // Should test to see performance hit of clearing it for all handlers
632 // with empty bodies below. If it is negligible then we should leave
633 // that in for safety, otherwise should think more about it.
634 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
635 void NullCheckVisitor::do_Local (Local* x) {}
636 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
637 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
638 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
639 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
640 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
641 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
642 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
643 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
644 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
645 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
646 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
647 void NullCheckVisitor::do_IfOp (IfOp* x) {}
648 void NullCheckVisitor::do_Convert (Convert* x) {}
649 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
650 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
651 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
652 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
653 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
654 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
655 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
656 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
657 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
658 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
659 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
660 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
661 void NullCheckVisitor::do_Goto (Goto* x) {}
662 void NullCheckVisitor::do_If (If* x) {}
663 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
664 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
665 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
666 void NullCheckVisitor::do_Return (Return* x) {}
667 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
668 void NullCheckVisitor::do_Base (Base* x) {}
669 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
670 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
671 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
672 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
673 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
674 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
675 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
676 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
677 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
678 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
679 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
680 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
683 void NullCheckEliminator::visit(Value* p) {
684 assert(*p != NULL, "should not find NULL instructions");
685 if (visitable(*p)) {
686 mark_visited(*p);
687 (*p)->visit(&_visitor);
688 }
689 }
691 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
692 ValueSet* state = state_for(block);
693 if (state == NULL) {
694 state = incoming_state->copy();
695 set_state_for(block, state);
696 return true;
697 } else {
698 bool changed = state->set_intersect(incoming_state);
699 if (PrintNullCheckElimination && changed) {
700 tty->print_cr("Block %d's null check state changed", block->block_id());
701 }
702 return changed;
703 }
704 }
707 void NullCheckEliminator::iterate_all() {
708 while (work_list()->length() > 0) {
709 iterate_one(work_list()->pop());
710 }
711 }
714 void NullCheckEliminator::iterate_one(BlockBegin* block) {
715 clear_visitable_state();
716 // clear out an old explicit null checks
717 set_last_explicit_null_check(NULL);
719 if (PrintNullCheckElimination) {
720 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
721 block->block_id(),
722 ir()->method()->holder()->name()->as_utf8(),
723 ir()->method()->name()->as_utf8(),
724 ir()->method()->signature()->as_symbol()->as_utf8());
725 }
727 // Create new state if none present (only happens at root)
728 if (state_for(block) == NULL) {
729 ValueSet* tmp_state = new ValueSet();
730 set_state_for(block, tmp_state);
731 // Initial state is that local 0 (receiver) is non-null for
732 // non-static methods
733 ValueStack* stack = block->state();
734 IRScope* scope = stack->scope();
735 ciMethod* method = scope->method();
736 if (!method->is_static()) {
737 Local* local0 = stack->local_at(0)->as_Local();
738 assert(local0 != NULL, "must be");
739 assert(local0->type() == objectType, "invalid type of receiver");
741 if (local0 != NULL) {
742 // Local 0 is used in this scope
743 tmp_state->put(local0);
744 if (PrintNullCheckElimination) {
745 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
746 }
747 }
748 }
749 }
751 // Must copy block's state to avoid mutating it during iteration
752 // through the block -- otherwise "not-null" states can accidentally
753 // propagate "up" through the block during processing of backward
754 // branches and algorithm is incorrect (and does not converge)
755 set_state_from(state_for(block));
757 // allow visiting of Phis belonging to this block
758 for_each_phi_fun(block, phi,
759 mark_visitable(phi);
760 );
762 BlockEnd* e = block->end();
763 assert(e != NULL, "incomplete graph");
764 int i;
766 // Propagate the state before this block into the exception
767 // handlers. They aren't true successors since we aren't guaranteed
768 // to execute the whole block before executing them. Also putting
769 // them on first seems to help reduce the amount of iteration to
770 // reach a fixed point.
771 for (i = 0; i < block->number_of_exception_handlers(); i++) {
772 BlockBegin* next = block->exception_handler_at(i);
773 if (merge_state_for(next, state())) {
774 if (!work_list()->contains(next)) {
775 work_list()->push(next);
776 }
777 }
778 }
780 // Iterate through block, updating state.
781 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
782 // Mark instructions in this block as visitable as they are seen
783 // in the instruction list. This keeps the iteration from
784 // visiting instructions which are references in other blocks or
785 // visiting instructions more than once.
786 mark_visitable(instr);
787 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
788 mark_visited(instr);
789 instr->input_values_do(this);
790 instr->visit(&_visitor);
791 }
792 }
794 // Propagate state to successors if necessary
795 for (i = 0; i < e->number_of_sux(); i++) {
796 BlockBegin* next = e->sux_at(i);
797 if (merge_state_for(next, state())) {
798 if (!work_list()->contains(next)) {
799 work_list()->push(next);
800 }
801 }
802 }
803 }
806 void NullCheckEliminator::iterate(BlockBegin* block) {
807 work_list()->push(block);
808 iterate_all();
809 }
811 void NullCheckEliminator::handle_AccessField(AccessField* x) {
812 if (x->is_static()) {
813 if (x->as_LoadField() != NULL) {
814 // If the field is a non-null static final object field (as is
815 // often the case for sun.misc.Unsafe), put this LoadField into
816 // the non-null map
817 ciField* field = x->field();
818 if (field->is_constant()) {
819 ciConstant field_val = field->constant_value();
820 BasicType field_type = field_val.basic_type();
821 if (field_type == T_OBJECT || field_type == T_ARRAY) {
822 ciObject* obj_val = field_val.as_object();
823 if (!obj_val->is_null_object()) {
824 if (PrintNullCheckElimination) {
825 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
826 x->id());
827 }
828 set_put(x);
829 }
830 }
831 }
832 }
833 // Be conservative
834 clear_last_explicit_null_check();
835 return;
836 }
838 Value obj = x->obj();
839 if (set_contains(obj)) {
840 // Value is non-null => update AccessField
841 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
842 x->set_explicit_null_check(consume_last_explicit_null_check());
843 x->set_needs_null_check(true);
844 if (PrintNullCheckElimination) {
845 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
846 x->explicit_null_check()->id(), x->id(), obj->id());
847 }
848 } else {
849 x->set_explicit_null_check(NULL);
850 x->set_needs_null_check(false);
851 if (PrintNullCheckElimination) {
852 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
853 }
854 }
855 } else {
856 set_put(obj);
857 if (PrintNullCheckElimination) {
858 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
859 }
860 // Ensure previous passes do not cause wrong state
861 x->set_needs_null_check(true);
862 x->set_explicit_null_check(NULL);
863 }
864 clear_last_explicit_null_check();
865 }
868 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
869 Value array = x->array();
870 if (set_contains(array)) {
871 // Value is non-null => update AccessArray
872 if (last_explicit_null_check_obj() == array) {
873 x->set_explicit_null_check(consume_last_explicit_null_check());
874 x->set_needs_null_check(true);
875 if (PrintNullCheckElimination) {
876 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
877 x->explicit_null_check()->id(), x->id(), array->id());
878 }
879 } else {
880 x->set_explicit_null_check(NULL);
881 x->set_needs_null_check(false);
882 if (PrintNullCheckElimination) {
883 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
884 }
885 }
886 } else {
887 set_put(array);
888 if (PrintNullCheckElimination) {
889 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
890 }
891 // Ensure previous passes do not cause wrong state
892 x->set_needs_null_check(true);
893 x->set_explicit_null_check(NULL);
894 }
895 clear_last_explicit_null_check();
896 }
899 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
900 Value array = x->array();
901 if (set_contains(array)) {
902 // Value is non-null => update AccessArray
903 if (last_explicit_null_check_obj() == array) {
904 x->set_explicit_null_check(consume_last_explicit_null_check());
905 x->set_needs_null_check(true);
906 if (PrintNullCheckElimination) {
907 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
908 x->explicit_null_check()->id(), x->id(), array->id());
909 }
910 } else {
911 x->set_explicit_null_check(NULL);
912 x->set_needs_null_check(false);
913 if (PrintNullCheckElimination) {
914 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
915 }
916 }
917 } else {
918 set_put(array);
919 if (PrintNullCheckElimination) {
920 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
921 }
922 // Ensure previous passes do not cause wrong state
923 x->set_needs_null_check(true);
924 x->set_explicit_null_check(NULL);
925 }
926 clear_last_explicit_null_check();
927 }
930 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
931 Value array = x->array();
932 if (set_contains(array)) {
933 // Value is non-null => update AccessArray
934 if (PrintNullCheckElimination) {
935 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
936 }
937 x->set_needs_null_check(false);
938 } else {
939 set_put(array);
940 if (PrintNullCheckElimination) {
941 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
942 }
943 // Ensure previous passes do not cause wrong state
944 x->set_needs_null_check(true);
945 }
946 clear_last_explicit_null_check();
947 }
950 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
951 Value obj = x->obj();
952 if (set_contains(obj)) {
953 // Already proven to be non-null => this NullCheck is useless
954 if (PrintNullCheckElimination) {
955 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
956 }
957 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
958 // The code generator won't emit LIR for a NullCheck that cannot trap.
959 x->set_can_trap(false);
960 } else {
961 // May be null => add to map and set last explicit NullCheck
962 x->set_can_trap(true);
963 // make sure it's pinned if it can trap
964 x->pin(Instruction::PinExplicitNullCheck);
965 set_put(obj);
966 set_last_explicit_null_check(x);
967 if (PrintNullCheckElimination) {
968 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
969 }
970 }
971 }
974 void NullCheckEliminator::handle_Invoke(Invoke* x) {
975 if (!x->has_receiver()) {
976 // Be conservative
977 clear_last_explicit_null_check();
978 return;
979 }
981 Value recv = x->receiver();
982 if (!set_contains(recv)) {
983 set_put(recv);
984 if (PrintNullCheckElimination) {
985 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
986 }
987 }
988 clear_last_explicit_null_check();
989 }
992 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
993 set_put(x);
994 if (PrintNullCheckElimination) {
995 tty->print_cr("NewInstance %d is non-null", x->id());
996 }
997 }
1000 void NullCheckEliminator::handle_NewArray(NewArray* x) {
1001 set_put(x);
1002 if (PrintNullCheckElimination) {
1003 tty->print_cr("NewArray %d is non-null", x->id());
1004 }
1005 }
1008 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
1009 set_put(x);
1010 if (PrintNullCheckElimination) {
1011 tty->print_cr("ExceptionObject %d is non-null", x->id());
1012 }
1013 }
1016 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1017 Value obj = x->obj();
1018 if (set_contains(obj)) {
1019 // Value is non-null => update AccessMonitor
1020 if (PrintNullCheckElimination) {
1021 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1022 }
1023 x->set_needs_null_check(false);
1024 } else {
1025 set_put(obj);
1026 if (PrintNullCheckElimination) {
1027 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1028 }
1029 // Ensure previous passes do not cause wrong state
1030 x->set_needs_null_check(true);
1031 }
1032 clear_last_explicit_null_check();
1033 }
1036 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1037 if (!x->has_receiver()) {
1038 if (x->id() == vmIntrinsics::_arraycopy) {
1039 for (int i = 0; i < x->number_of_arguments(); i++) {
1040 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1041 }
1042 }
1044 // Be conservative
1045 clear_last_explicit_null_check();
1046 return;
1047 }
1049 Value recv = x->receiver();
1050 if (set_contains(recv)) {
1051 // Value is non-null => update Intrinsic
1052 if (PrintNullCheckElimination) {
1053 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1054 }
1055 x->set_needs_null_check(false);
1056 } else {
1057 set_put(recv);
1058 if (PrintNullCheckElimination) {
1059 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1060 }
1061 // Ensure previous passes do not cause wrong state
1062 x->set_needs_null_check(true);
1063 }
1064 clear_last_explicit_null_check();
1065 }
1068 void NullCheckEliminator::handle_Phi(Phi* x) {
1069 int i;
1070 bool all_non_null = true;
1071 if (x->is_illegal()) {
1072 all_non_null = false;
1073 } else {
1074 for (i = 0; i < x->operand_count(); i++) {
1075 Value input = x->operand_at(i);
1076 if (!set_contains(input)) {
1077 all_non_null = false;
1078 }
1079 }
1080 }
1082 if (all_non_null) {
1083 // Value is non-null => update Phi
1084 if (PrintNullCheckElimination) {
1085 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1086 }
1087 x->set_needs_null_check(false);
1088 } else if (set_contains(x)) {
1089 set_remove(x);
1090 }
1091 }
1094 void Optimizer::eliminate_null_checks() {
1095 ResourceMark rm;
1097 NullCheckEliminator nce(this);
1099 if (PrintNullCheckElimination) {
1100 tty->print_cr("Starting null check elimination for method %s::%s%s",
1101 ir()->method()->holder()->name()->as_utf8(),
1102 ir()->method()->name()->as_utf8(),
1103 ir()->method()->signature()->as_symbol()->as_utf8());
1104 }
1106 // Apply to graph
1107 nce.iterate(ir()->start());
1109 // walk over the graph looking for exception
1110 // handlers and iterate over them as well
1111 int nblocks = BlockBegin::number_of_blocks();
1112 BlockList blocks(nblocks);
1113 boolArray visited_block(nblocks, false);
1115 blocks.push(ir()->start());
1116 visited_block[ir()->start()->block_id()] = true;
1117 for (int i = 0; i < blocks.length(); i++) {
1118 BlockBegin* b = blocks[i];
1119 // exception handlers need to be treated as additional roots
1120 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1121 BlockBegin* excp = b->exception_handler_at(e);
1122 int id = excp->block_id();
1123 if (!visited_block[id]) {
1124 blocks.push(excp);
1125 visited_block[id] = true;
1126 nce.iterate(excp);
1127 }
1128 }
1129 // traverse successors
1130 BlockEnd *end = b->end();
1131 for (int s = end->number_of_sux(); s-- > 0; ) {
1132 BlockBegin* next = end->sux_at(s);
1133 int id = next->block_id();
1134 if (!visited_block[id]) {
1135 blocks.push(next);
1136 visited_block[id] = true;
1137 }
1138 }
1139 }
1142 if (PrintNullCheckElimination) {
1143 tty->print_cr("Done with null check elimination for method %s::%s%s",
1144 ir()->method()->holder()->name()->as_utf8(),
1145 ir()->method()->name()->as_utf8(),
1146 ir()->method()->signature()->as_symbol()->as_utf8());
1147 }
1148 }