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src/share/vm/c1/c1_Optimizer.cpp@c124e2e7463e
src/share/vm/c1/c1_Optimizer.cpp
Wed, 31 Aug 2011 16:46:11 -0700
- author
- never
- date
- Wed, 31 Aug 2011 16:46:11 -0700
- changeset 3099
- c124e2e7463e
- parent 2989
- 15559220ce79
- child 3386
- 7bca37d28f32
- permissions
- -rw-r--r--
7083786: dead various dead chunks of code
Reviewed-by: iveresov, kvn
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 ValueStack* sux_state = sux->state();
126 if (sux_state->stack_size() <= if_->state()->stack_size()) return;
128 // check if phi function is present at end of successor stack and that
129 // only this phi was pushed on the stack
130 Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
131 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
132 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
134 // get the values that were pushed in the true- and false-branch
135 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
136 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
138 // backend does not support floats
139 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
140 if (t_value->type()->is_float_kind()) return;
142 // check that successor has no other phi functions but sux_phi
143 // this can happen when t_block or f_block contained additonal stores to local variables
144 // that are no longer represented by explicit instructions
145 for_each_phi_fun(sux, phi,
146 if (phi != sux_phi) return;
147 );
148 // true and false blocks can't have phis
149 for_each_phi_fun(t_block, phi, return; );
150 for_each_phi_fun(f_block, phi, return; );
152 // 2) substitute conditional expression
153 // with an IfOp followed by a Goto
154 // cut if_ away and get node before
155 Instruction* cur_end = if_->prev(block);
157 // append constants of true- and false-block if necessary
158 // clone constants because original block must not be destroyed
159 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
160 if (t_value == t_const) {
161 t_value = new Constant(t_const->type());
162 NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
163 cur_end = cur_end->set_next(t_value);
164 }
165 if (f_value == f_const) {
166 f_value = new Constant(f_const->type());
167 NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
168 cur_end = cur_end->set_next(f_value);
169 }
171 Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
172 assert(result != NULL, "make_ifop must return a non-null instruction");
173 if (!result->is_linked() && result->can_be_linked()) {
174 NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
175 cur_end = cur_end->set_next(result);
176 }
178 // append Goto to successor
179 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
180 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
182 // prepare state for Goto
183 ValueStack* goto_state = if_->state();
184 while (sux_state->scope() != goto_state->scope()) {
185 goto_state = goto_state->caller_state();
186 assert(goto_state != NULL, "states do not match up");
187 }
188 goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
189 goto_state->push(result->type(), result);
190 assert(goto_state->is_same(sux_state), "states must match now");
191 goto_->set_state(goto_state);
193 cur_end = cur_end->set_next(goto_, goto_state->bci());
195 // Adjust control flow graph
196 BlockBegin::disconnect_edge(block, t_block);
197 BlockBegin::disconnect_edge(block, f_block);
198 if (t_block->number_of_preds() == 0) {
199 BlockBegin::disconnect_edge(t_block, sux);
200 }
201 adjust_exception_edges(block, t_block);
202 if (f_block->number_of_preds() == 0) {
203 BlockBegin::disconnect_edge(f_block, sux);
204 }
205 adjust_exception_edges(block, f_block);
207 // update block end
208 block->set_end(goto_);
210 // substitute the phi if possible
211 if (sux_phi->as_Phi()->operand_count() == 1) {
212 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
213 sux_phi->set_subst(result);
214 _has_substitution = true;
215 }
217 // 3) successfully eliminated a conditional expression
218 _cee_count++;
219 if (PrintCEE) {
220 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());
221 tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
222 }
224 _hir->verify();
225 }
227 Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
228 if (!OptimizeIfOps) {
229 return new IfOp(x, cond, y, tval, fval);
230 }
232 tval = tval->subst();
233 fval = fval->subst();
234 if (tval == fval) {
235 _ifop_count++;
236 return tval;
237 }
239 x = x->subst();
240 y = y->subst();
242 Constant* y_const = y->as_Constant();
243 if (y_const != NULL) {
244 IfOp* x_ifop = x->as_IfOp();
245 if (x_ifop != NULL) { // x is an ifop, y is a constant
246 Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
247 Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
249 if (x_tval_const != NULL && x_fval_const != NULL) {
250 Instruction::Condition x_ifop_cond = x_ifop->cond();
252 Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
253 Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
255 // not_comparable here is a valid return in case we're comparing unloaded oop constants
256 if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
257 Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
258 Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
260 _ifop_count++;
261 if (new_tval == new_fval) {
262 return new_tval;
263 } else {
264 return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
265 }
266 }
267 }
268 } else {
269 Constant* x_const = x->as_Constant();
270 if (x_const != NULL) { // x and y are constants
271 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
272 // not_comparable here is a valid return in case we're comparing unloaded oop constants
273 if (x_compare_res != Constant::not_comparable) {
274 _ifop_count++;
275 return x_compare_res == Constant::cond_true ? tval : fval;
276 }
277 }
278 }
279 }
280 return new IfOp(x, cond, y, tval, fval);
281 }
283 void Optimizer::eliminate_conditional_expressions() {
284 // find conditional expressions & replace them with IfOps
285 CE_Eliminator ce(ir());
286 }
288 class BlockMerger: public BlockClosure {
289 private:
290 IR* _hir;
291 int _merge_count; // the number of block pairs successfully merged
293 public:
294 BlockMerger(IR* hir)
295 : _hir(hir)
296 , _merge_count(0)
297 {
298 _hir->iterate_preorder(this);
299 }
301 bool try_merge(BlockBegin* block) {
302 BlockEnd* end = block->end();
303 if (end->as_Goto() != NULL) {
304 assert(end->number_of_sux() == 1, "end must have exactly one successor");
305 // Note: It would be sufficient to check for the number of successors (= 1)
306 // in order to decide if this block can be merged potentially. That
307 // would then also include switch statements w/ only a default case.
308 // However, in that case we would need to make sure the switch tag
309 // expression is executed if it can produce observable side effects.
310 // We should probably have the canonicalizer simplifying such switch
311 // statements and then we are sure we don't miss these merge opportunities
312 // here (was bug - gri 7/7/99).
313 BlockBegin* sux = end->default_sux();
314 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
315 // merge the two blocks
317 #ifdef ASSERT
318 // verify that state at the end of block and at the beginning of sux are equal
319 // no phi functions must be present at beginning of sux
320 ValueStack* sux_state = sux->state();
321 ValueStack* end_state = end->state();
323 assert(end_state->scope() == sux_state->scope(), "scopes must match");
324 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
325 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
327 int index;
328 Value sux_value;
329 for_each_stack_value(sux_state, index, sux_value) {
330 assert(sux_value == end_state->stack_at(index), "stack not equal");
331 }
332 for_each_local_value(sux_state, index, sux_value) {
333 assert(sux_value == end_state->local_at(index), "locals not equal");
334 }
335 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
336 #endif
338 // find instruction before end & append first instruction of sux block
339 Instruction* prev = end->prev(block);
340 Instruction* next = sux->next();
341 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
342 prev->set_next(next);
343 sux->disconnect_from_graph();
344 block->set_end(sux->end());
345 // add exception handlers of deleted block, if any
346 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
347 BlockBegin* xhandler = sux->exception_handler_at(k);
348 block->add_exception_handler(xhandler);
350 // also substitute predecessor of exception handler
351 assert(xhandler->is_predecessor(sux), "missing predecessor");
352 xhandler->remove_predecessor(sux);
353 if (!xhandler->is_predecessor(block)) {
354 xhandler->add_predecessor(block);
355 }
356 }
358 // debugging output
359 _merge_count++;
360 if (PrintBlockElimination) {
361 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
362 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
363 }
365 _hir->verify();
367 If* if_ = block->end()->as_If();
368 if (if_) {
369 IfOp* ifop = if_->x()->as_IfOp();
370 Constant* con = if_->y()->as_Constant();
371 bool swapped = false;
372 if (!con || !ifop) {
373 ifop = if_->y()->as_IfOp();
374 con = if_->x()->as_Constant();
375 swapped = true;
376 }
377 if (con && ifop) {
378 Constant* tval = ifop->tval()->as_Constant();
379 Constant* fval = ifop->fval()->as_Constant();
380 if (tval && fval) {
381 // Find the instruction before if_, starting with ifop.
382 // When if_ and ifop are not in the same block, prev
383 // becomes NULL In such (rare) cases it is not
384 // profitable to perform the optimization.
385 Value prev = ifop;
386 while (prev != NULL && prev->next() != if_) {
387 prev = prev->next();
388 }
390 if (prev != NULL) {
391 Instruction::Condition cond = if_->cond();
392 BlockBegin* tsux = if_->tsux();
393 BlockBegin* fsux = if_->fsux();
394 if (swapped) {
395 cond = Instruction::mirror(cond);
396 }
398 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
399 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
400 if (tblock != fblock && !if_->is_safepoint()) {
401 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
402 tblock, fblock, if_->state_before(), if_->is_safepoint());
403 newif->set_state(if_->state()->copy());
405 assert(prev->next() == if_, "must be guaranteed by above search");
406 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
407 prev->set_next(newif);
408 block->set_end(newif);
410 _merge_count++;
411 if (PrintBlockElimination) {
412 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
413 }
415 _hir->verify();
416 }
417 }
418 }
419 }
420 }
422 return true;
423 }
424 }
425 return false;
426 }
428 virtual void block_do(BlockBegin* block) {
429 _hir->verify();
430 // repeat since the same block may merge again
431 while (try_merge(block)) {
432 _hir->verify();
433 }
434 }
435 };
438 void Optimizer::eliminate_blocks() {
439 // merge blocks if possible
440 BlockMerger bm(ir());
441 }
444 class NullCheckEliminator;
445 class NullCheckVisitor: public InstructionVisitor {
446 private:
447 NullCheckEliminator* _nce;
448 NullCheckEliminator* nce() { return _nce; }
450 public:
451 NullCheckVisitor() {}
453 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
455 void do_Phi (Phi* x);
456 void do_Local (Local* x);
457 void do_Constant (Constant* x);
458 void do_LoadField (LoadField* x);
459 void do_StoreField (StoreField* x);
460 void do_ArrayLength (ArrayLength* x);
461 void do_LoadIndexed (LoadIndexed* x);
462 void do_StoreIndexed (StoreIndexed* x);
463 void do_NegateOp (NegateOp* x);
464 void do_ArithmeticOp (ArithmeticOp* x);
465 void do_ShiftOp (ShiftOp* x);
466 void do_LogicOp (LogicOp* x);
467 void do_CompareOp (CompareOp* x);
468 void do_IfOp (IfOp* x);
469 void do_Convert (Convert* x);
470 void do_NullCheck (NullCheck* x);
471 void do_Invoke (Invoke* x);
472 void do_NewInstance (NewInstance* x);
473 void do_NewTypeArray (NewTypeArray* x);
474 void do_NewObjectArray (NewObjectArray* x);
475 void do_NewMultiArray (NewMultiArray* x);
476 void do_CheckCast (CheckCast* x);
477 void do_InstanceOf (InstanceOf* x);
478 void do_MonitorEnter (MonitorEnter* x);
479 void do_MonitorExit (MonitorExit* x);
480 void do_Intrinsic (Intrinsic* x);
481 void do_BlockBegin (BlockBegin* x);
482 void do_Goto (Goto* x);
483 void do_If (If* x);
484 void do_IfInstanceOf (IfInstanceOf* x);
485 void do_TableSwitch (TableSwitch* x);
486 void do_LookupSwitch (LookupSwitch* x);
487 void do_Return (Return* x);
488 void do_Throw (Throw* x);
489 void do_Base (Base* x);
490 void do_OsrEntry (OsrEntry* x);
491 void do_ExceptionObject(ExceptionObject* x);
492 void do_RoundFP (RoundFP* x);
493 void do_UnsafeGetRaw (UnsafeGetRaw* x);
494 void do_UnsafePutRaw (UnsafePutRaw* x);
495 void do_UnsafeGetObject(UnsafeGetObject* x);
496 void do_UnsafePutObject(UnsafePutObject* x);
497 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
498 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
499 void do_ProfileCall (ProfileCall* x);
500 void do_ProfileInvoke (ProfileInvoke* x);
501 void do_RuntimeCall (RuntimeCall* x);
502 };
505 // Because of a static contained within (for the purpose of iteration
506 // over instructions), it is only valid to have one of these active at
507 // a time
508 class NullCheckEliminator: public ValueVisitor {
509 private:
510 Optimizer* _opt;
512 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
513 BlockList* _work_list; // Basic blocks to visit
515 bool visitable(Value x) {
516 assert(_visitable_instructions != NULL, "check");
517 return _visitable_instructions->contains(x);
518 }
519 void mark_visited(Value x) {
520 assert(_visitable_instructions != NULL, "check");
521 _visitable_instructions->remove(x);
522 }
523 void mark_visitable(Value x) {
524 assert(_visitable_instructions != NULL, "check");
525 _visitable_instructions->put(x);
526 }
527 void clear_visitable_state() {
528 assert(_visitable_instructions != NULL, "check");
529 _visitable_instructions->clear();
530 }
532 ValueSet* _set; // current state, propagated to subsequent BlockBegins
533 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
534 NullCheckVisitor _visitor;
535 NullCheck* _last_explicit_null_check;
537 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
538 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
539 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
541 BlockList* work_list() { return _work_list; }
543 void iterate_all();
544 void iterate_one(BlockBegin* block);
546 ValueSet* state() { return _set; }
547 void set_state_from (ValueSet* state) { _set->set_from(state); }
548 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
549 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
550 // Returns true if caused a change in the block's state.
551 bool merge_state_for(BlockBegin* block,
552 ValueSet* incoming_state);
554 public:
555 // constructor
556 NullCheckEliminator(Optimizer* opt)
557 : _opt(opt)
558 , _set(new ValueSet())
559 , _last_explicit_null_check(NULL)
560 , _block_states(BlockBegin::number_of_blocks(), NULL)
561 , _work_list(new BlockList()) {
562 _visitable_instructions = new ValueSet();
563 _visitor.set_eliminator(this);
564 }
566 Optimizer* opt() { return _opt; }
567 IR* ir () { return opt()->ir(); }
569 // Process a graph
570 void iterate(BlockBegin* root);
572 void visit(Value* f);
574 // In some situations (like NullCheck(x); getfield(x)) the debug
575 // information from the explicit NullCheck can be used to populate
576 // the getfield, even if the two instructions are in different
577 // scopes; this allows implicit null checks to be used but the
578 // correct exception information to be generated. We must clear the
579 // last-traversed NullCheck when we reach a potentially-exception-
580 // throwing instruction, as well as in some other cases.
581 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
582 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
583 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
584 ? _last_explicit_null_check->obj()
585 : NULL); }
586 NullCheck* consume_last_explicit_null_check() {
587 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
588 _last_explicit_null_check->set_can_trap(false);
589 return _last_explicit_null_check;
590 }
591 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
593 // Handlers for relevant instructions
594 // (separated out from NullCheckVisitor for clarity)
596 // The basic contract is that these must leave the instruction in
597 // the desired state; must not assume anything about the state of
598 // the instruction. We make multiple passes over some basic blocks
599 // and the last pass is the only one whose result is valid.
600 void handle_AccessField (AccessField* x);
601 void handle_ArrayLength (ArrayLength* x);
602 void handle_LoadIndexed (LoadIndexed* x);
603 void handle_StoreIndexed (StoreIndexed* x);
604 void handle_NullCheck (NullCheck* x);
605 void handle_Invoke (Invoke* x);
606 void handle_NewInstance (NewInstance* x);
607 void handle_NewArray (NewArray* x);
608 void handle_AccessMonitor (AccessMonitor* x);
609 void handle_Intrinsic (Intrinsic* x);
610 void handle_ExceptionObject (ExceptionObject* x);
611 void handle_Phi (Phi* x);
612 };
615 // NEEDS_CLEANUP
616 // There may be other instructions which need to clear the last
617 // explicit null check. Anything across which we can not hoist the
618 // debug information for a NullCheck instruction must clear it. It
619 // might be safer to pattern match "NullCheck ; {AccessField,
620 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
621 // Should test to see performance hit of clearing it for all handlers
622 // with empty bodies below. If it is negligible then we should leave
623 // that in for safety, otherwise should think more about it.
624 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
625 void NullCheckVisitor::do_Local (Local* x) {}
626 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
627 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
628 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
629 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
630 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
631 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
632 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
633 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
634 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
635 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
636 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
637 void NullCheckVisitor::do_IfOp (IfOp* x) {}
638 void NullCheckVisitor::do_Convert (Convert* x) {}
639 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
640 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
641 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
642 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
643 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
644 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
645 void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); }
646 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
647 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
648 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
649 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); }
650 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
651 void NullCheckVisitor::do_Goto (Goto* x) {}
652 void NullCheckVisitor::do_If (If* x) {}
653 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
654 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
655 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
656 void NullCheckVisitor::do_Return (Return* x) {}
657 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
658 void NullCheckVisitor::do_Base (Base* x) {}
659 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
660 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
661 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
662 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
663 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
664 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
665 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
666 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
667 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
668 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
669 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
670 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
673 void NullCheckEliminator::visit(Value* p) {
674 assert(*p != NULL, "should not find NULL instructions");
675 if (visitable(*p)) {
676 mark_visited(*p);
677 (*p)->visit(&_visitor);
678 }
679 }
681 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
682 ValueSet* state = state_for(block);
683 if (state == NULL) {
684 state = incoming_state->copy();
685 set_state_for(block, state);
686 return true;
687 } else {
688 bool changed = state->set_intersect(incoming_state);
689 if (PrintNullCheckElimination && changed) {
690 tty->print_cr("Block %d's null check state changed", block->block_id());
691 }
692 return changed;
693 }
694 }
697 void NullCheckEliminator::iterate_all() {
698 while (work_list()->length() > 0) {
699 iterate_one(work_list()->pop());
700 }
701 }
704 void NullCheckEliminator::iterate_one(BlockBegin* block) {
705 clear_visitable_state();
706 // clear out an old explicit null checks
707 set_last_explicit_null_check(NULL);
709 if (PrintNullCheckElimination) {
710 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
711 block->block_id(),
712 ir()->method()->holder()->name()->as_utf8(),
713 ir()->method()->name()->as_utf8(),
714 ir()->method()->signature()->as_symbol()->as_utf8());
715 }
717 // Create new state if none present (only happens at root)
718 if (state_for(block) == NULL) {
719 ValueSet* tmp_state = new ValueSet();
720 set_state_for(block, tmp_state);
721 // Initial state is that local 0 (receiver) is non-null for
722 // non-static methods
723 ValueStack* stack = block->state();
724 IRScope* scope = stack->scope();
725 ciMethod* method = scope->method();
726 if (!method->is_static()) {
727 Local* local0 = stack->local_at(0)->as_Local();
728 assert(local0 != NULL, "must be");
729 assert(local0->type() == objectType, "invalid type of receiver");
731 if (local0 != NULL) {
732 // Local 0 is used in this scope
733 tmp_state->put(local0);
734 if (PrintNullCheckElimination) {
735 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
736 }
737 }
738 }
739 }
741 // Must copy block's state to avoid mutating it during iteration
742 // through the block -- otherwise "not-null" states can accidentally
743 // propagate "up" through the block during processing of backward
744 // branches and algorithm is incorrect (and does not converge)
745 set_state_from(state_for(block));
747 // allow visiting of Phis belonging to this block
748 for_each_phi_fun(block, phi,
749 mark_visitable(phi);
750 );
752 BlockEnd* e = block->end();
753 assert(e != NULL, "incomplete graph");
754 int i;
756 // Propagate the state before this block into the exception
757 // handlers. They aren't true successors since we aren't guaranteed
758 // to execute the whole block before executing them. Also putting
759 // them on first seems to help reduce the amount of iteration to
760 // reach a fixed point.
761 for (i = 0; i < block->number_of_exception_handlers(); i++) {
762 BlockBegin* next = block->exception_handler_at(i);
763 if (merge_state_for(next, state())) {
764 if (!work_list()->contains(next)) {
765 work_list()->push(next);
766 }
767 }
768 }
770 // Iterate through block, updating state.
771 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
772 // Mark instructions in this block as visitable as they are seen
773 // in the instruction list. This keeps the iteration from
774 // visiting instructions which are references in other blocks or
775 // visiting instructions more than once.
776 mark_visitable(instr);
777 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
778 mark_visited(instr);
779 instr->input_values_do(this);
780 instr->visit(&_visitor);
781 }
782 }
784 // Propagate state to successors if necessary
785 for (i = 0; i < e->number_of_sux(); i++) {
786 BlockBegin* next = e->sux_at(i);
787 if (merge_state_for(next, state())) {
788 if (!work_list()->contains(next)) {
789 work_list()->push(next);
790 }
791 }
792 }
793 }
796 void NullCheckEliminator::iterate(BlockBegin* block) {
797 work_list()->push(block);
798 iterate_all();
799 }
801 void NullCheckEliminator::handle_AccessField(AccessField* x) {
802 if (x->is_static()) {
803 if (x->as_LoadField() != NULL) {
804 // If the field is a non-null static final object field (as is
805 // often the case for sun.misc.Unsafe), put this LoadField into
806 // the non-null map
807 ciField* field = x->field();
808 if (field->is_constant()) {
809 ciConstant field_val = field->constant_value();
810 BasicType field_type = field_val.basic_type();
811 if (field_type == T_OBJECT || field_type == T_ARRAY) {
812 ciObject* obj_val = field_val.as_object();
813 if (!obj_val->is_null_object()) {
814 if (PrintNullCheckElimination) {
815 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
816 x->id());
817 }
818 set_put(x);
819 }
820 }
821 }
822 }
823 // Be conservative
824 clear_last_explicit_null_check();
825 return;
826 }
828 Value obj = x->obj();
829 if (set_contains(obj)) {
830 // Value is non-null => update AccessField
831 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
832 x->set_explicit_null_check(consume_last_explicit_null_check());
833 x->set_needs_null_check(true);
834 if (PrintNullCheckElimination) {
835 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
836 x->explicit_null_check()->id(), x->id(), obj->id());
837 }
838 } else {
839 x->set_explicit_null_check(NULL);
840 x->set_needs_null_check(false);
841 if (PrintNullCheckElimination) {
842 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
843 }
844 }
845 } else {
846 set_put(obj);
847 if (PrintNullCheckElimination) {
848 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
849 }
850 // Ensure previous passes do not cause wrong state
851 x->set_needs_null_check(true);
852 x->set_explicit_null_check(NULL);
853 }
854 clear_last_explicit_null_check();
855 }
858 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
859 Value array = x->array();
860 if (set_contains(array)) {
861 // Value is non-null => update AccessArray
862 if (last_explicit_null_check_obj() == array) {
863 x->set_explicit_null_check(consume_last_explicit_null_check());
864 x->set_needs_null_check(true);
865 if (PrintNullCheckElimination) {
866 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
867 x->explicit_null_check()->id(), x->id(), array->id());
868 }
869 } else {
870 x->set_explicit_null_check(NULL);
871 x->set_needs_null_check(false);
872 if (PrintNullCheckElimination) {
873 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
874 }
875 }
876 } else {
877 set_put(array);
878 if (PrintNullCheckElimination) {
879 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
880 }
881 // Ensure previous passes do not cause wrong state
882 x->set_needs_null_check(true);
883 x->set_explicit_null_check(NULL);
884 }
885 clear_last_explicit_null_check();
886 }
889 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
890 Value array = x->array();
891 if (set_contains(array)) {
892 // Value is non-null => update AccessArray
893 if (last_explicit_null_check_obj() == array) {
894 x->set_explicit_null_check(consume_last_explicit_null_check());
895 x->set_needs_null_check(true);
896 if (PrintNullCheckElimination) {
897 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
898 x->explicit_null_check()->id(), x->id(), array->id());
899 }
900 } else {
901 x->set_explicit_null_check(NULL);
902 x->set_needs_null_check(false);
903 if (PrintNullCheckElimination) {
904 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
905 }
906 }
907 } else {
908 set_put(array);
909 if (PrintNullCheckElimination) {
910 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
911 }
912 // Ensure previous passes do not cause wrong state
913 x->set_needs_null_check(true);
914 x->set_explicit_null_check(NULL);
915 }
916 clear_last_explicit_null_check();
917 }
920 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
921 Value array = x->array();
922 if (set_contains(array)) {
923 // Value is non-null => update AccessArray
924 if (PrintNullCheckElimination) {
925 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
926 }
927 x->set_needs_null_check(false);
928 } else {
929 set_put(array);
930 if (PrintNullCheckElimination) {
931 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
932 }
933 // Ensure previous passes do not cause wrong state
934 x->set_needs_null_check(true);
935 }
936 clear_last_explicit_null_check();
937 }
940 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
941 Value obj = x->obj();
942 if (set_contains(obj)) {
943 // Already proven to be non-null => this NullCheck is useless
944 if (PrintNullCheckElimination) {
945 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
946 }
947 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
948 // The code generator won't emit LIR for a NullCheck that cannot trap.
949 x->set_can_trap(false);
950 } else {
951 // May be null => add to map and set last explicit NullCheck
952 x->set_can_trap(true);
953 // make sure it's pinned if it can trap
954 x->pin(Instruction::PinExplicitNullCheck);
955 set_put(obj);
956 set_last_explicit_null_check(x);
957 if (PrintNullCheckElimination) {
958 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
959 }
960 }
961 }
964 void NullCheckEliminator::handle_Invoke(Invoke* x) {
965 if (!x->has_receiver()) {
966 // Be conservative
967 clear_last_explicit_null_check();
968 return;
969 }
971 Value recv = x->receiver();
972 if (!set_contains(recv)) {
973 set_put(recv);
974 if (PrintNullCheckElimination) {
975 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
976 }
977 }
978 clear_last_explicit_null_check();
979 }
982 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
983 set_put(x);
984 if (PrintNullCheckElimination) {
985 tty->print_cr("NewInstance %d is non-null", x->id());
986 }
987 }
990 void NullCheckEliminator::handle_NewArray(NewArray* x) {
991 set_put(x);
992 if (PrintNullCheckElimination) {
993 tty->print_cr("NewArray %d is non-null", x->id());
994 }
995 }
998 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
999 set_put(x);
1000 if (PrintNullCheckElimination) {
1001 tty->print_cr("ExceptionObject %d is non-null", x->id());
1002 }
1003 }
1006 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1007 Value obj = x->obj();
1008 if (set_contains(obj)) {
1009 // Value is non-null => update AccessMonitor
1010 if (PrintNullCheckElimination) {
1011 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1012 }
1013 x->set_needs_null_check(false);
1014 } else {
1015 set_put(obj);
1016 if (PrintNullCheckElimination) {
1017 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1018 }
1019 // Ensure previous passes do not cause wrong state
1020 x->set_needs_null_check(true);
1021 }
1022 clear_last_explicit_null_check();
1023 }
1026 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1027 if (!x->has_receiver()) {
1028 if (x->id() == vmIntrinsics::_arraycopy) {
1029 for (int i = 0; i < x->number_of_arguments(); i++) {
1030 x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
1031 }
1032 }
1034 // Be conservative
1035 clear_last_explicit_null_check();
1036 return;
1037 }
1039 Value recv = x->receiver();
1040 if (set_contains(recv)) {
1041 // Value is non-null => update Intrinsic
1042 if (PrintNullCheckElimination) {
1043 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1044 }
1045 x->set_needs_null_check(false);
1046 } else {
1047 set_put(recv);
1048 if (PrintNullCheckElimination) {
1049 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1050 }
1051 // Ensure previous passes do not cause wrong state
1052 x->set_needs_null_check(true);
1053 }
1054 clear_last_explicit_null_check();
1055 }
1058 void NullCheckEliminator::handle_Phi(Phi* x) {
1059 int i;
1060 bool all_non_null = true;
1061 if (x->is_illegal()) {
1062 all_non_null = false;
1063 } else {
1064 for (i = 0; i < x->operand_count(); i++) {
1065 Value input = x->operand_at(i);
1066 if (!set_contains(input)) {
1067 all_non_null = false;
1068 }
1069 }
1070 }
1072 if (all_non_null) {
1073 // Value is non-null => update Phi
1074 if (PrintNullCheckElimination) {
1075 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1076 }
1077 x->set_needs_null_check(false);
1078 } else if (set_contains(x)) {
1079 set_remove(x);
1080 }
1081 }
1084 void Optimizer::eliminate_null_checks() {
1085 ResourceMark rm;
1087 NullCheckEliminator nce(this);
1089 if (PrintNullCheckElimination) {
1090 tty->print_cr("Starting null check elimination for method %s::%s%s",
1091 ir()->method()->holder()->name()->as_utf8(),
1092 ir()->method()->name()->as_utf8(),
1093 ir()->method()->signature()->as_symbol()->as_utf8());
1094 }
1096 // Apply to graph
1097 nce.iterate(ir()->start());
1099 // walk over the graph looking for exception
1100 // handlers and iterate over them as well
1101 int nblocks = BlockBegin::number_of_blocks();
1102 BlockList blocks(nblocks);
1103 boolArray visited_block(nblocks, false);
1105 blocks.push(ir()->start());
1106 visited_block[ir()->start()->block_id()] = true;
1107 for (int i = 0; i < blocks.length(); i++) {
1108 BlockBegin* b = blocks[i];
1109 // exception handlers need to be treated as additional roots
1110 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1111 BlockBegin* excp = b->exception_handler_at(e);
1112 int id = excp->block_id();
1113 if (!visited_block[id]) {
1114 blocks.push(excp);
1115 visited_block[id] = true;
1116 nce.iterate(excp);
1117 }
1118 }
1119 // traverse successors
1120 BlockEnd *end = b->end();
1121 for (int s = end->number_of_sux(); s-- > 0; ) {
1122 BlockBegin* next = end->sux_at(s);
1123 int id = next->block_id();
1124 if (!visited_block[id]) {
1125 blocks.push(next);
1126 visited_block[id] = true;
1127 }
1128 }
1129 }
1132 if (PrintNullCheckElimination) {
1133 tty->print_cr("Done with null check elimination for method %s::%s%s",
1134 ir()->method()->holder()->name()->as_utf8(),
1135 ir()->method()->name()->as_utf8(),
1136 ir()->method()->signature()->as_symbol()->as_utf8());
1137 }
1138 }
