Wed, 02 Feb 2011 11:35:26 -0500
7016023: Enable building ARM and PPC from src/closed repository
Reviewed-by: dholmes, bdelsart
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,
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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 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 guarantee(t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable, "incomparable constants in IfOp");
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 } else {
268 Constant* x_const = x->as_Constant();
269 if (x_const != NULL) { // x and y are constants
270 Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
271 guarantee(x_compare_res != Constant::not_comparable, "incomparable constants in IfOp");
273 _ifop_count++;
274 return x_compare_res == Constant::cond_true ? tval : fval;
275 }
276 }
277 }
278 return new IfOp(x, cond, y, tval, fval);
279 }
281 void Optimizer::eliminate_conditional_expressions() {
282 // find conditional expressions & replace them with IfOps
283 CE_Eliminator ce(ir());
284 }
286 class BlockMerger: public BlockClosure {
287 private:
288 IR* _hir;
289 int _merge_count; // the number of block pairs successfully merged
291 public:
292 BlockMerger(IR* hir)
293 : _hir(hir)
294 , _merge_count(0)
295 {
296 _hir->iterate_preorder(this);
297 }
299 bool try_merge(BlockBegin* block) {
300 BlockEnd* end = block->end();
301 if (end->as_Goto() != NULL) {
302 assert(end->number_of_sux() == 1, "end must have exactly one successor");
303 // Note: It would be sufficient to check for the number of successors (= 1)
304 // in order to decide if this block can be merged potentially. That
305 // would then also include switch statements w/ only a default case.
306 // However, in that case we would need to make sure the switch tag
307 // expression is executed if it can produce observable side effects.
308 // We should probably have the canonicalizer simplifying such switch
309 // statements and then we are sure we don't miss these merge opportunities
310 // here (was bug - gri 7/7/99).
311 BlockBegin* sux = end->default_sux();
312 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
313 // merge the two blocks
315 #ifdef ASSERT
316 // verify that state at the end of block and at the beginning of sux are equal
317 // no phi functions must be present at beginning of sux
318 ValueStack* sux_state = sux->state();
319 ValueStack* end_state = end->state();
321 assert(end_state->scope() == sux_state->scope(), "scopes must match");
322 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
323 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
325 int index;
326 Value sux_value;
327 for_each_stack_value(sux_state, index, sux_value) {
328 assert(sux_value == end_state->stack_at(index), "stack not equal");
329 }
330 for_each_local_value(sux_state, index, sux_value) {
331 assert(sux_value == end_state->local_at(index), "locals not equal");
332 }
333 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
334 #endif
336 // find instruction before end & append first instruction of sux block
337 Instruction* prev = end->prev(block);
338 Instruction* next = sux->next();
339 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
340 prev->set_next(next);
341 sux->disconnect_from_graph();
342 block->set_end(sux->end());
343 // add exception handlers of deleted block, if any
344 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
345 BlockBegin* xhandler = sux->exception_handler_at(k);
346 block->add_exception_handler(xhandler);
348 // also substitute predecessor of exception handler
349 assert(xhandler->is_predecessor(sux), "missing predecessor");
350 xhandler->remove_predecessor(sux);
351 if (!xhandler->is_predecessor(block)) {
352 xhandler->add_predecessor(block);
353 }
354 }
356 // debugging output
357 _merge_count++;
358 if (PrintBlockElimination) {
359 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
360 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
361 }
363 _hir->verify();
365 If* if_ = block->end()->as_If();
366 if (if_) {
367 IfOp* ifop = if_->x()->as_IfOp();
368 Constant* con = if_->y()->as_Constant();
369 bool swapped = false;
370 if (!con || !ifop) {
371 ifop = if_->y()->as_IfOp();
372 con = if_->x()->as_Constant();
373 swapped = true;
374 }
375 if (con && ifop) {
376 Constant* tval = ifop->tval()->as_Constant();
377 Constant* fval = ifop->fval()->as_Constant();
378 if (tval && fval) {
379 // Find the instruction before if_, starting with ifop.
380 // When if_ and ifop are not in the same block, prev
381 // becomes NULL In such (rare) cases it is not
382 // profitable to perform the optimization.
383 Value prev = ifop;
384 while (prev != NULL && prev->next() != if_) {
385 prev = prev->next();
386 }
388 if (prev != NULL) {
389 Instruction::Condition cond = if_->cond();
390 BlockBegin* tsux = if_->tsux();
391 BlockBegin* fsux = if_->fsux();
392 if (swapped) {
393 cond = Instruction::mirror(cond);
394 }
396 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
397 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
398 if (tblock != fblock && !if_->is_safepoint()) {
399 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
400 tblock, fblock, if_->state_before(), if_->is_safepoint());
401 newif->set_state(if_->state()->copy());
403 assert(prev->next() == if_, "must be guaranteed by above search");
404 NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
405 prev->set_next(newif);
406 block->set_end(newif);
408 _merge_count++;
409 if (PrintBlockElimination) {
410 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
411 }
413 _hir->verify();
414 }
415 }
416 }
417 }
418 }
420 return true;
421 }
422 }
423 return false;
424 }
426 virtual void block_do(BlockBegin* block) {
427 _hir->verify();
428 // repeat since the same block may merge again
429 while (try_merge(block)) {
430 _hir->verify();
431 }
432 }
433 };
436 void Optimizer::eliminate_blocks() {
437 // merge blocks if possible
438 BlockMerger bm(ir());
439 }
442 class NullCheckEliminator;
443 class NullCheckVisitor: public InstructionVisitor {
444 private:
445 NullCheckEliminator* _nce;
446 NullCheckEliminator* nce() { return _nce; }
448 public:
449 NullCheckVisitor() {}
451 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
453 void do_Phi (Phi* x);
454 void do_Local (Local* x);
455 void do_Constant (Constant* x);
456 void do_LoadField (LoadField* x);
457 void do_StoreField (StoreField* x);
458 void do_ArrayLength (ArrayLength* x);
459 void do_LoadIndexed (LoadIndexed* x);
460 void do_StoreIndexed (StoreIndexed* x);
461 void do_NegateOp (NegateOp* x);
462 void do_ArithmeticOp (ArithmeticOp* x);
463 void do_ShiftOp (ShiftOp* x);
464 void do_LogicOp (LogicOp* x);
465 void do_CompareOp (CompareOp* x);
466 void do_IfOp (IfOp* x);
467 void do_Convert (Convert* x);
468 void do_NullCheck (NullCheck* x);
469 void do_Invoke (Invoke* x);
470 void do_NewInstance (NewInstance* x);
471 void do_NewTypeArray (NewTypeArray* x);
472 void do_NewObjectArray (NewObjectArray* x);
473 void do_NewMultiArray (NewMultiArray* x);
474 void do_CheckCast (CheckCast* x);
475 void do_InstanceOf (InstanceOf* x);
476 void do_MonitorEnter (MonitorEnter* x);
477 void do_MonitorExit (MonitorExit* x);
478 void do_Intrinsic (Intrinsic* x);
479 void do_BlockBegin (BlockBegin* x);
480 void do_Goto (Goto* x);
481 void do_If (If* x);
482 void do_IfInstanceOf (IfInstanceOf* x);
483 void do_TableSwitch (TableSwitch* x);
484 void do_LookupSwitch (LookupSwitch* x);
485 void do_Return (Return* x);
486 void do_Throw (Throw* x);
487 void do_Base (Base* x);
488 void do_OsrEntry (OsrEntry* x);
489 void do_ExceptionObject(ExceptionObject* x);
490 void do_RoundFP (RoundFP* x);
491 void do_UnsafeGetRaw (UnsafeGetRaw* x);
492 void do_UnsafePutRaw (UnsafePutRaw* x);
493 void do_UnsafeGetObject(UnsafeGetObject* x);
494 void do_UnsafePutObject(UnsafePutObject* x);
495 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
496 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
497 void do_ProfileCall (ProfileCall* x);
498 void do_ProfileInvoke (ProfileInvoke* x);
499 void do_RuntimeCall (RuntimeCall* x);
500 };
503 // Because of a static contained within (for the purpose of iteration
504 // over instructions), it is only valid to have one of these active at
505 // a time
506 class NullCheckEliminator: public ValueVisitor {
507 private:
508 Optimizer* _opt;
510 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
511 BlockList* _work_list; // Basic blocks to visit
513 bool visitable(Value x) {
514 assert(_visitable_instructions != NULL, "check");
515 return _visitable_instructions->contains(x);
516 }
517 void mark_visited(Value x) {
518 assert(_visitable_instructions != NULL, "check");
519 _visitable_instructions->remove(x);
520 }
521 void mark_visitable(Value x) {
522 assert(_visitable_instructions != NULL, "check");
523 _visitable_instructions->put(x);
524 }
525 void clear_visitable_state() {
526 assert(_visitable_instructions != NULL, "check");
527 _visitable_instructions->clear();
528 }
530 ValueSet* _set; // current state, propagated to subsequent BlockBegins
531 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
532 NullCheckVisitor _visitor;
533 NullCheck* _last_explicit_null_check;
535 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
536 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
537 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
539 BlockList* work_list() { return _work_list; }
541 void iterate_all();
542 void iterate_one(BlockBegin* block);
544 ValueSet* state() { return _set; }
545 void set_state_from (ValueSet* state) { _set->set_from(state); }
546 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
547 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
548 // Returns true if caused a change in the block's state.
549 bool merge_state_for(BlockBegin* block,
550 ValueSet* incoming_state);
552 public:
553 // constructor
554 NullCheckEliminator(Optimizer* opt)
555 : _opt(opt)
556 , _set(new ValueSet())
557 , _last_explicit_null_check(NULL)
558 , _block_states(BlockBegin::number_of_blocks(), NULL)
559 , _work_list(new BlockList()) {
560 _visitable_instructions = new ValueSet();
561 _visitor.set_eliminator(this);
562 }
564 Optimizer* opt() { return _opt; }
565 IR* ir () { return opt()->ir(); }
567 // Process a graph
568 void iterate(BlockBegin* root);
570 void visit(Value* f);
572 // In some situations (like NullCheck(x); getfield(x)) the debug
573 // information from the explicit NullCheck can be used to populate
574 // the getfield, even if the two instructions are in different
575 // scopes; this allows implicit null checks to be used but the
576 // correct exception information to be generated. We must clear the
577 // last-traversed NullCheck when we reach a potentially-exception-
578 // throwing instruction, as well as in some other cases.
579 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
580 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
581 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
582 ? _last_explicit_null_check->obj()
583 : NULL); }
584 NullCheck* consume_last_explicit_null_check() {
585 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
586 _last_explicit_null_check->set_can_trap(false);
587 return _last_explicit_null_check;
588 }
589 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
591 // Handlers for relevant instructions
592 // (separated out from NullCheckVisitor for clarity)
594 // The basic contract is that these must leave the instruction in
595 // the desired state; must not assume anything about the state of
596 // the instruction. We make multiple passes over some basic blocks
597 // and the last pass is the only one whose result is valid.
598 void handle_AccessField (AccessField* x);
599 void handle_ArrayLength (ArrayLength* x);
600 void handle_LoadIndexed (LoadIndexed* x);
601 void handle_StoreIndexed (StoreIndexed* x);
602 void handle_NullCheck (NullCheck* x);
603 void handle_Invoke (Invoke* x);
604 void handle_NewInstance (NewInstance* x);
605 void handle_NewArray (NewArray* x);
606 void handle_AccessMonitor (AccessMonitor* x);
607 void handle_Intrinsic (Intrinsic* x);
608 void handle_ExceptionObject (ExceptionObject* x);
609 void handle_Phi (Phi* x);
610 };
613 // NEEDS_CLEANUP
614 // There may be other instructions which need to clear the last
615 // explicit null check. Anything across which we can not hoist the
616 // debug information for a NullCheck instruction must clear it. It
617 // might be safer to pattern match "NullCheck ; {AccessField,
618 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
619 // Should test to see performance hit of clearing it for all handlers
620 // with empty bodies below. If it is negligible then we should leave
621 // that in for safety, otherwise should think more about it.
622 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
623 void NullCheckVisitor::do_Local (Local* x) {}
624 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
625 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
626 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
627 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
628 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
629 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
630 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
631 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
632 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
633 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
634 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
635 void NullCheckVisitor::do_IfOp (IfOp* x) {}
636 void NullCheckVisitor::do_Convert (Convert* x) {}
637 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
638 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
639 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
640 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
641 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
642 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
643 void NullCheckVisitor::do_CheckCast (CheckCast* x) {}
644 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
645 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
646 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
647 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); }
648 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
649 void NullCheckVisitor::do_Goto (Goto* x) {}
650 void NullCheckVisitor::do_If (If* x) {}
651 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
652 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
653 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
654 void NullCheckVisitor::do_Return (Return* x) {}
655 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
656 void NullCheckVisitor::do_Base (Base* x) {}
657 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
658 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
659 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
660 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
661 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
662 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
663 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
664 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
665 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
666 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
667 void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
668 void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
671 void NullCheckEliminator::visit(Value* p) {
672 assert(*p != NULL, "should not find NULL instructions");
673 if (visitable(*p)) {
674 mark_visited(*p);
675 (*p)->visit(&_visitor);
676 }
677 }
679 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
680 ValueSet* state = state_for(block);
681 if (state == NULL) {
682 state = incoming_state->copy();
683 set_state_for(block, state);
684 return true;
685 } else {
686 bool changed = state->set_intersect(incoming_state);
687 if (PrintNullCheckElimination && changed) {
688 tty->print_cr("Block %d's null check state changed", block->block_id());
689 }
690 return changed;
691 }
692 }
695 void NullCheckEliminator::iterate_all() {
696 while (work_list()->length() > 0) {
697 iterate_one(work_list()->pop());
698 }
699 }
702 void NullCheckEliminator::iterate_one(BlockBegin* block) {
703 clear_visitable_state();
704 // clear out an old explicit null checks
705 set_last_explicit_null_check(NULL);
707 if (PrintNullCheckElimination) {
708 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
709 block->block_id(),
710 ir()->method()->holder()->name()->as_utf8(),
711 ir()->method()->name()->as_utf8(),
712 ir()->method()->signature()->as_symbol()->as_utf8());
713 }
715 // Create new state if none present (only happens at root)
716 if (state_for(block) == NULL) {
717 ValueSet* tmp_state = new ValueSet();
718 set_state_for(block, tmp_state);
719 // Initial state is that local 0 (receiver) is non-null for
720 // non-static methods
721 ValueStack* stack = block->state();
722 IRScope* scope = stack->scope();
723 ciMethod* method = scope->method();
724 if (!method->is_static()) {
725 Local* local0 = stack->local_at(0)->as_Local();
726 assert(local0 != NULL, "must be");
727 assert(local0->type() == objectType, "invalid type of receiver");
729 if (local0 != NULL) {
730 // Local 0 is used in this scope
731 tmp_state->put(local0);
732 if (PrintNullCheckElimination) {
733 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
734 }
735 }
736 }
737 }
739 // Must copy block's state to avoid mutating it during iteration
740 // through the block -- otherwise "not-null" states can accidentally
741 // propagate "up" through the block during processing of backward
742 // branches and algorithm is incorrect (and does not converge)
743 set_state_from(state_for(block));
745 // allow visiting of Phis belonging to this block
746 for_each_phi_fun(block, phi,
747 mark_visitable(phi);
748 );
750 BlockEnd* e = block->end();
751 assert(e != NULL, "incomplete graph");
752 int i;
754 // Propagate the state before this block into the exception
755 // handlers. They aren't true successors since we aren't guaranteed
756 // to execute the whole block before executing them. Also putting
757 // them on first seems to help reduce the amount of iteration to
758 // reach a fixed point.
759 for (i = 0; i < block->number_of_exception_handlers(); i++) {
760 BlockBegin* next = block->exception_handler_at(i);
761 if (merge_state_for(next, state())) {
762 if (!work_list()->contains(next)) {
763 work_list()->push(next);
764 }
765 }
766 }
768 // Iterate through block, updating state.
769 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
770 // Mark instructions in this block as visitable as they are seen
771 // in the instruction list. This keeps the iteration from
772 // visiting instructions which are references in other blocks or
773 // visiting instructions more than once.
774 mark_visitable(instr);
775 if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
776 mark_visited(instr);
777 instr->input_values_do(this);
778 instr->visit(&_visitor);
779 }
780 }
782 // Propagate state to successors if necessary
783 for (i = 0; i < e->number_of_sux(); i++) {
784 BlockBegin* next = e->sux_at(i);
785 if (merge_state_for(next, state())) {
786 if (!work_list()->contains(next)) {
787 work_list()->push(next);
788 }
789 }
790 }
791 }
794 void NullCheckEliminator::iterate(BlockBegin* block) {
795 work_list()->push(block);
796 iterate_all();
797 }
799 void NullCheckEliminator::handle_AccessField(AccessField* x) {
800 if (x->is_static()) {
801 if (x->as_LoadField() != NULL) {
802 // If the field is a non-null static final object field (as is
803 // often the case for sun.misc.Unsafe), put this LoadField into
804 // the non-null map
805 ciField* field = x->field();
806 if (field->is_constant()) {
807 ciConstant field_val = field->constant_value();
808 BasicType field_type = field_val.basic_type();
809 if (field_type == T_OBJECT || field_type == T_ARRAY) {
810 ciObject* obj_val = field_val.as_object();
811 if (!obj_val->is_null_object()) {
812 if (PrintNullCheckElimination) {
813 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
814 x->id());
815 }
816 set_put(x);
817 }
818 }
819 }
820 }
821 // Be conservative
822 clear_last_explicit_null_check();
823 return;
824 }
826 Value obj = x->obj();
827 if (set_contains(obj)) {
828 // Value is non-null => update AccessField
829 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
830 x->set_explicit_null_check(consume_last_explicit_null_check());
831 x->set_needs_null_check(true);
832 if (PrintNullCheckElimination) {
833 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
834 x->explicit_null_check()->id(), x->id(), obj->id());
835 }
836 } else {
837 x->set_explicit_null_check(NULL);
838 x->set_needs_null_check(false);
839 if (PrintNullCheckElimination) {
840 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
841 }
842 }
843 } else {
844 set_put(obj);
845 if (PrintNullCheckElimination) {
846 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
847 }
848 // Ensure previous passes do not cause wrong state
849 x->set_needs_null_check(true);
850 x->set_explicit_null_check(NULL);
851 }
852 clear_last_explicit_null_check();
853 }
856 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
857 Value array = x->array();
858 if (set_contains(array)) {
859 // Value is non-null => update AccessArray
860 if (last_explicit_null_check_obj() == array) {
861 x->set_explicit_null_check(consume_last_explicit_null_check());
862 x->set_needs_null_check(true);
863 if (PrintNullCheckElimination) {
864 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
865 x->explicit_null_check()->id(), x->id(), array->id());
866 }
867 } else {
868 x->set_explicit_null_check(NULL);
869 x->set_needs_null_check(false);
870 if (PrintNullCheckElimination) {
871 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
872 }
873 }
874 } else {
875 set_put(array);
876 if (PrintNullCheckElimination) {
877 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
878 }
879 // Ensure previous passes do not cause wrong state
880 x->set_needs_null_check(true);
881 x->set_explicit_null_check(NULL);
882 }
883 clear_last_explicit_null_check();
884 }
887 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
888 Value array = x->array();
889 if (set_contains(array)) {
890 // Value is non-null => update AccessArray
891 if (last_explicit_null_check_obj() == array) {
892 x->set_explicit_null_check(consume_last_explicit_null_check());
893 x->set_needs_null_check(true);
894 if (PrintNullCheckElimination) {
895 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
896 x->explicit_null_check()->id(), x->id(), array->id());
897 }
898 } else {
899 x->set_explicit_null_check(NULL);
900 x->set_needs_null_check(false);
901 if (PrintNullCheckElimination) {
902 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
903 }
904 }
905 } else {
906 set_put(array);
907 if (PrintNullCheckElimination) {
908 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
909 }
910 // Ensure previous passes do not cause wrong state
911 x->set_needs_null_check(true);
912 x->set_explicit_null_check(NULL);
913 }
914 clear_last_explicit_null_check();
915 }
918 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
919 Value array = x->array();
920 if (set_contains(array)) {
921 // Value is non-null => update AccessArray
922 if (PrintNullCheckElimination) {
923 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
924 }
925 x->set_needs_null_check(false);
926 } else {
927 set_put(array);
928 if (PrintNullCheckElimination) {
929 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
930 }
931 // Ensure previous passes do not cause wrong state
932 x->set_needs_null_check(true);
933 }
934 clear_last_explicit_null_check();
935 }
938 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
939 Value obj = x->obj();
940 if (set_contains(obj)) {
941 // Already proven to be non-null => this NullCheck is useless
942 if (PrintNullCheckElimination) {
943 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
944 }
945 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
946 // The code generator won't emit LIR for a NullCheck that cannot trap.
947 x->set_can_trap(false);
948 } else {
949 // May be null => add to map and set last explicit NullCheck
950 x->set_can_trap(true);
951 // make sure it's pinned if it can trap
952 x->pin(Instruction::PinExplicitNullCheck);
953 set_put(obj);
954 set_last_explicit_null_check(x);
955 if (PrintNullCheckElimination) {
956 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
957 }
958 }
959 }
962 void NullCheckEliminator::handle_Invoke(Invoke* x) {
963 if (!x->has_receiver()) {
964 // Be conservative
965 clear_last_explicit_null_check();
966 return;
967 }
969 Value recv = x->receiver();
970 if (!set_contains(recv)) {
971 set_put(recv);
972 if (PrintNullCheckElimination) {
973 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
974 }
975 }
976 clear_last_explicit_null_check();
977 }
980 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
981 set_put(x);
982 if (PrintNullCheckElimination) {
983 tty->print_cr("NewInstance %d is non-null", x->id());
984 }
985 }
988 void NullCheckEliminator::handle_NewArray(NewArray* x) {
989 set_put(x);
990 if (PrintNullCheckElimination) {
991 tty->print_cr("NewArray %d is non-null", x->id());
992 }
993 }
996 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
997 set_put(x);
998 if (PrintNullCheckElimination) {
999 tty->print_cr("ExceptionObject %d is non-null", x->id());
1000 }
1001 }
1004 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
1005 Value obj = x->obj();
1006 if (set_contains(obj)) {
1007 // Value is non-null => update AccessMonitor
1008 if (PrintNullCheckElimination) {
1009 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
1010 }
1011 x->set_needs_null_check(false);
1012 } else {
1013 set_put(obj);
1014 if (PrintNullCheckElimination) {
1015 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
1016 }
1017 // Ensure previous passes do not cause wrong state
1018 x->set_needs_null_check(true);
1019 }
1020 clear_last_explicit_null_check();
1021 }
1024 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
1025 if (!x->has_receiver()) {
1026 // Be conservative
1027 clear_last_explicit_null_check();
1028 return;
1029 }
1031 Value recv = x->receiver();
1032 if (set_contains(recv)) {
1033 // Value is non-null => update Intrinsic
1034 if (PrintNullCheckElimination) {
1035 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
1036 }
1037 x->set_needs_null_check(false);
1038 } else {
1039 set_put(recv);
1040 if (PrintNullCheckElimination) {
1041 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
1042 }
1043 // Ensure previous passes do not cause wrong state
1044 x->set_needs_null_check(true);
1045 }
1046 clear_last_explicit_null_check();
1047 }
1050 void NullCheckEliminator::handle_Phi(Phi* x) {
1051 int i;
1052 bool all_non_null = true;
1053 if (x->is_illegal()) {
1054 all_non_null = false;
1055 } else {
1056 for (i = 0; i < x->operand_count(); i++) {
1057 Value input = x->operand_at(i);
1058 if (!set_contains(input)) {
1059 all_non_null = false;
1060 }
1061 }
1062 }
1064 if (all_non_null) {
1065 // Value is non-null => update Phi
1066 if (PrintNullCheckElimination) {
1067 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
1068 }
1069 x->set_needs_null_check(false);
1070 } else if (set_contains(x)) {
1071 set_remove(x);
1072 }
1073 }
1076 void Optimizer::eliminate_null_checks() {
1077 ResourceMark rm;
1079 NullCheckEliminator nce(this);
1081 if (PrintNullCheckElimination) {
1082 tty->print_cr("Starting null check elimination for method %s::%s%s",
1083 ir()->method()->holder()->name()->as_utf8(),
1084 ir()->method()->name()->as_utf8(),
1085 ir()->method()->signature()->as_symbol()->as_utf8());
1086 }
1088 // Apply to graph
1089 nce.iterate(ir()->start());
1091 // walk over the graph looking for exception
1092 // handlers and iterate over them as well
1093 int nblocks = BlockBegin::number_of_blocks();
1094 BlockList blocks(nblocks);
1095 boolArray visited_block(nblocks, false);
1097 blocks.push(ir()->start());
1098 visited_block[ir()->start()->block_id()] = true;
1099 for (int i = 0; i < blocks.length(); i++) {
1100 BlockBegin* b = blocks[i];
1101 // exception handlers need to be treated as additional roots
1102 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
1103 BlockBegin* excp = b->exception_handler_at(e);
1104 int id = excp->block_id();
1105 if (!visited_block[id]) {
1106 blocks.push(excp);
1107 visited_block[id] = true;
1108 nce.iterate(excp);
1109 }
1110 }
1111 // traverse successors
1112 BlockEnd *end = b->end();
1113 for (int s = end->number_of_sux(); s-- > 0; ) {
1114 BlockBegin* next = end->sux_at(s);
1115 int id = next->block_id();
1116 if (!visited_block[id]) {
1117 blocks.push(next);
1118 visited_block[id] = true;
1119 }
1120 }
1121 }
1124 if (PrintNullCheckElimination) {
1125 tty->print_cr("Done with null check elimination for method %s::%s%s",
1126 ir()->method()->holder()->name()->as_utf8(),
1127 ir()->method()->name()->as_utf8(),
1128 ir()->method()->signature()->as_symbol()->as_utf8());
1129 }
1130 }