1 /*
2 * Copyright 1998-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // The MethodLiveness class performs a simple liveness analysis on a method
26 // in order to decide which locals are live (that is, will be used again) at
27 // a particular bytecode index (bci).
28 //
29 // The algorithm goes:
30 //
31 // 1. Break the method into a set of basic blocks. For each basic block we
32 // also keep track of its set of predecessors through normal control flow
33 // and predecessors through exceptional control flow.
34 //
35 // 2. For each basic block, compute two sets, gen (the set of values used before
36 // they are defined) and kill (the set of values defined before they are used)
37 // in the basic block. A basic block "needs" the locals in its gen set to
38 // perform its computation. A basic block "provides" values for the locals in
39 // its kill set, allowing a need from a successor to be ignored.
40 //
41 // 3. Liveness information (the set of locals which are needed) is pushed backwards through
42 // the program, from blocks to their predecessors. We compute and store liveness
43 // information for the normal/exceptional exit paths for each basic block. When
44 // this process reaches a fixed point, we are done.
45 //
46 // 4. When we are asked about the liveness at a particular bci with a basic block, we
47 // compute gen/kill sets which represent execution from that bci to the exit of
48 // its blocks. We then compose this range gen/kill information with the normal
49 // and exceptional exit information for the block to produce liveness information
50 // at that bci.
51 //
52 // The algorithm is approximate in many respects. Notably:
53 //
54 // 1. We do not do the analysis necessary to match jsr's with the appropriate ret.
55 // Instead we make the conservative assumption that any ret can return to any
56 // jsr return site.
57 // 2. Instead of computing the effects of exceptions at every instruction, we
58 // summarize the effects of all exceptional continuations from the block as
59 // a single set (_exception_exit), losing some information but simplifying the
60 // analysis.
61
62
63 # include "incls/_precompiled.incl"
64 # include "incls/_methodLiveness.cpp.incl"
65
66 //--------------------------------------------------------------------------
67 // The BitCounter class is used for counting the number of bits set in
68 // some BitMap. It is only used when collecting liveness statistics.
69
70 #ifndef PRODUCT
71
72 class BitCounter: public BitMapClosure {
73 private:
74 int _count;
75 public:
76 BitCounter() : _count(0) {}
77
78 // Callback when bit in map is set
79 virtual bool do_bit(size_t offset) {
80 _count++;
81 return true;
82 }
83
84 int count() {
85 return _count;
86 }
87 };
88
89
90 //--------------------------------------------------------------------------
91
92
93 // Counts
94 long MethodLiveness::_total_bytes = 0;
95 int MethodLiveness::_total_methods = 0;
96
97 long MethodLiveness::_total_blocks = 0;
98 int MethodLiveness::_max_method_blocks = 0;
99
100 long MethodLiveness::_total_edges = 0;
101 int MethodLiveness::_max_block_edges = 0;
102
103 long MethodLiveness::_total_exc_edges = 0;
104 int MethodLiveness::_max_block_exc_edges = 0;
105
106 long MethodLiveness::_total_method_locals = 0;
107 int MethodLiveness::_max_method_locals = 0;
108
109 long MethodLiveness::_total_locals_queried = 0;
110 long MethodLiveness::_total_live_locals_queried = 0;
111
112 long MethodLiveness::_total_visits = 0;
113
114 #endif
115
116 // Timers
117 elapsedTimer MethodLiveness::_time_build_graph;
118 elapsedTimer MethodLiveness::_time_gen_kill;
119 elapsedTimer MethodLiveness::_time_flow;
120 elapsedTimer MethodLiveness::_time_query;
121 elapsedTimer MethodLiveness::_time_total;
122
123 MethodLiveness::MethodLiveness(Arena* arena, ciMethod* method)
124 #ifdef COMPILER1
125 : _bci_block_start((uintptr_t*)arena->Amalloc((method->code_size() >> LogBitsPerByte) + 1), method->code_size())
126 #endif
127 {
128 _arena = arena;
129 _method = method;
130 _bit_map_size_bits = method->max_locals();
131 _bit_map_size_words = (_bit_map_size_bits / sizeof(unsigned int)) + 1;
132
133 #ifdef COMPILER1
134 _bci_block_start.clear();
135 #endif
136 }
137
138 void MethodLiveness::compute_liveness() {
139 #ifndef PRODUCT
140 if (TraceLivenessGen) {
141 tty->print_cr("################################################################");
142 tty->print("# Computing liveness information for ");
143 method()->print_short_name();
144 }
145
146 if (TimeLivenessAnalysis) _time_total.start();
147 #endif
148
149 {
150 TraceTime buildGraph(NULL, &_time_build_graph, TimeLivenessAnalysis);
151 init_basic_blocks();
152 }
153 {
154 TraceTime genKill(NULL, &_time_gen_kill, TimeLivenessAnalysis);
155 init_gen_kill();
156 }
157 {
158 TraceTime flow(NULL, &_time_flow, TimeLivenessAnalysis);
159 propagate_liveness();
160 }
161
162 #ifndef PRODUCT
163 if (TimeLivenessAnalysis) _time_total.stop();
164
165 if (TimeLivenessAnalysis) {
166 // Collect statistics
167 _total_bytes += method()->code_size();
168 _total_methods++;
169
170 int num_blocks = _block_count;
171 _total_blocks += num_blocks;
172 _max_method_blocks = MAX2(num_blocks,_max_method_blocks);
173
174 for (int i=0; i<num_blocks; i++) {
175 BasicBlock *block = _block_list[i];
176
177 int numEdges = block->_normal_predecessors->length();
178 int numExcEdges = block->_exception_predecessors->length();
179
180 _total_edges += numEdges;
181 _total_exc_edges += numExcEdges;
182 _max_block_edges = MAX2(numEdges,_max_block_edges);
183 _max_block_exc_edges = MAX2(numExcEdges,_max_block_exc_edges);
184 }
185
186 int numLocals = _bit_map_size_bits;
187 _total_method_locals += numLocals;
188 _max_method_locals = MAX2(numLocals,_max_method_locals);
189 }
190 #endif
191 }
192
193
194 void MethodLiveness::init_basic_blocks() {
195 bool bailout = false;
196
197 int method_len = method()->code_size();
198 ciMethodBlocks *mblocks = method()->get_method_blocks();
199
200 // Create an array to store the bci->BasicBlock mapping.
201 _block_map = new (arena()) GrowableArray<BasicBlock*>(arena(), method_len, method_len, NULL);
202
203 _block_count = mblocks->num_blocks();
204 _block_list = (BasicBlock **) arena()->Amalloc(sizeof(BasicBlock *) * _block_count);
205
206 // Used for patching up jsr/ret control flow.
207 GrowableArray<BasicBlock*>* jsr_exit_list = new GrowableArray<BasicBlock*>(5);
208 GrowableArray<BasicBlock*>* ret_list = new GrowableArray<BasicBlock*>(5);
209
210 // generate our block list from ciMethodBlocks
211 for (int blk = 0; blk < _block_count; blk++) {
212 ciBlock *cib = mblocks->block(blk);
213 int start_bci = cib->start_bci();
214 _block_list[blk] = new (arena()) BasicBlock(this, start_bci, cib->limit_bci());
215 _block_map->at_put(start_bci, _block_list[blk]);
216 #ifdef COMPILER1
217 // mark all bcis where a new basic block starts
218 _bci_block_start.set_bit(start_bci);
219 #endif // COMPILER1
220 }
221 // fill in the predecessors of blocks
222 ciBytecodeStream bytes(method());
223
224 for (int blk = 0; blk < _block_count; blk++) {
225 BasicBlock *current_block = _block_list[blk];
226 int bci = mblocks->block(blk)->control_bci();
227
228 if (bci == ciBlock::fall_through_bci) {
229 int limit = current_block->limit_bci();
230 if (limit < method_len) {
231 BasicBlock *next = _block_map->at(limit);
232 assert( next != NULL, "must be a block immediately following this one.");
233 next->add_normal_predecessor(current_block);
234 }
235 continue;
236 }
237 bytes.reset_to_bci(bci);
238 Bytecodes::Code code = bytes.next();
239 BasicBlock *dest;
240
241 // Now we need to interpret the instruction's effect
242 // on control flow.
243 assert (current_block != NULL, "we must have a current block");
244 switch (code) {
245 case Bytecodes::_ifeq:
246 case Bytecodes::_ifne:
247 case Bytecodes::_iflt:
248 case Bytecodes::_ifge:
249 case Bytecodes::_ifgt:
250 case Bytecodes::_ifle:
251 case Bytecodes::_if_icmpeq:
252 case Bytecodes::_if_icmpne:
253 case Bytecodes::_if_icmplt:
254 case Bytecodes::_if_icmpge:
255 case Bytecodes::_if_icmpgt:
256 case Bytecodes::_if_icmple:
257 case Bytecodes::_if_acmpeq:
258 case Bytecodes::_if_acmpne:
259 case Bytecodes::_ifnull:
260 case Bytecodes::_ifnonnull:
261 // Two way branch. Set predecessors at each destination.
262 dest = _block_map->at(bytes.next_bci());
263 assert(dest != NULL, "must be a block immediately following this one.");
264 dest->add_normal_predecessor(current_block);
265
266 dest = _block_map->at(bytes.get_dest());
267 assert(dest != NULL, "branch desination must start a block.");
268 dest->add_normal_predecessor(current_block);
269 break;
270 case Bytecodes::_goto:
271 dest = _block_map->at(bytes.get_dest());
272 assert(dest != NULL, "branch desination must start a block.");
273 dest->add_normal_predecessor(current_block);
274 break;
275 case Bytecodes::_goto_w:
276 dest = _block_map->at(bytes.get_far_dest());
277 assert(dest != NULL, "branch desination must start a block.");
278 dest->add_normal_predecessor(current_block);
279 break;
280 case Bytecodes::_tableswitch:
281 {
282 Bytecode_tableswitch *tableswitch =
283 Bytecode_tableswitch_at(bytes.cur_bcp());
284
285 int len = tableswitch->length();
286
287 dest = _block_map->at(bci + tableswitch->default_offset());
288 assert(dest != NULL, "branch desination must start a block.");
289 dest->add_normal_predecessor(current_block);
290 while (--len >= 0) {
291 dest = _block_map->at(bci + tableswitch->dest_offset_at(len));
292 assert(dest != NULL, "branch desination must start a block.");
293 dest->add_normal_predecessor(current_block);
294 }
295 break;
296 }
297
298 case Bytecodes::_lookupswitch:
299 {
300 Bytecode_lookupswitch *lookupswitch =
301 Bytecode_lookupswitch_at(bytes.cur_bcp());
302
303 int npairs = lookupswitch->number_of_pairs();
304
305 dest = _block_map->at(bci + lookupswitch->default_offset());
306 assert(dest != NULL, "branch desination must start a block.");
307 dest->add_normal_predecessor(current_block);
308 while(--npairs >= 0) {
309 LookupswitchPair *pair = lookupswitch->pair_at(npairs);
310 dest = _block_map->at( bci + pair->offset());
311 assert(dest != NULL, "branch desination must start a block.");
312 dest->add_normal_predecessor(current_block);
313 }
314 break;
315 }
316
317 case Bytecodes::_jsr:
318 {
319 assert(bytes.is_wide()==false, "sanity check");
320 dest = _block_map->at(bytes.get_dest());
321 assert(dest != NULL, "branch desination must start a block.");
322 dest->add_normal_predecessor(current_block);
323 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
324 assert(jsrExit != NULL, "jsr return bci must start a block.");
325 jsr_exit_list->append(jsrExit);
326 break;
327 }
328 case Bytecodes::_jsr_w:
329 {
330 dest = _block_map->at(bytes.get_far_dest());
331 assert(dest != NULL, "branch desination must start a block.");
332 dest->add_normal_predecessor(current_block);
333 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
334 assert(jsrExit != NULL, "jsr return bci must start a block.");
335 jsr_exit_list->append(jsrExit);
336 break;
337 }
338
339 case Bytecodes::_wide:
340 assert(false, "wide opcodes should not be seen here");
341 break;
342 case Bytecodes::_athrow:
343 case Bytecodes::_ireturn:
344 case Bytecodes::_lreturn:
345 case Bytecodes::_freturn:
346 case Bytecodes::_dreturn:
347 case Bytecodes::_areturn:
348 case Bytecodes::_return:
349 // These opcodes are not the normal predecessors of any other opcodes.
350 break;
351 case Bytecodes::_ret:
352 // We will patch up jsr/rets in a subsequent pass.
353 ret_list->append(current_block);
354 break;
355 case Bytecodes::_breakpoint:
356 // Bail out of there are breakpoints in here.
357 bailout = true;
358 break;
359 default:
360 // Do nothing.
361 break;
362 }
363 }
364 // Patch up the jsr/ret's. We conservatively assume that any ret
365 // can return to any jsr site.
366 int ret_list_len = ret_list->length();
367 int jsr_exit_list_len = jsr_exit_list->length();
368 if (ret_list_len > 0 && jsr_exit_list_len > 0) {
369 for (int i = jsr_exit_list_len - 1; i >= 0; i--) {
370 BasicBlock *jsrExit = jsr_exit_list->at(i);
371 for (int i = ret_list_len - 1; i >= 0; i--) {
372 jsrExit->add_normal_predecessor(ret_list->at(i));
373 }
374 }
375 }
376
377 // Compute exception edges.
378 for (int b=_block_count-1; b >= 0; b--) {
379 BasicBlock *block = _block_list[b];
380 int block_start = block->start_bci();
381 int block_limit = block->limit_bci();
382 ciExceptionHandlerStream handlers(method());
383 for (; !handlers.is_done(); handlers.next()) {
384 ciExceptionHandler* handler = handlers.handler();
385 int start = handler->start();
386 int limit = handler->limit();
387 int handler_bci = handler->handler_bci();
388
389 int intersect_start = MAX2(block_start, start);
390 int intersect_limit = MIN2(block_limit, limit);
391 if (intersect_start < intersect_limit) {
392 // The catch range has a nonempty intersection with this
393 // basic block. That means this basic block can be an
394 // exceptional predecessor.
395 _block_map->at(handler_bci)->add_exception_predecessor(block);
396
397 if (handler->is_catch_all()) {
398 // This is a catch-all block.
399 if (intersect_start == block_start && intersect_limit == block_limit) {
400 // The basic block is entirely contained in this catch-all block.
401 // Skip the rest of the exception handlers -- they can never be
402 // reached in execution.
403 break;
404 }
405 }
406 }
407 }
408 }
409 }
410
411 void MethodLiveness::init_gen_kill() {
412 for (int i=_block_count-1; i >= 0; i--) {
413 _block_list[i]->compute_gen_kill(method());
414 }
415 }
416
417 void MethodLiveness::propagate_liveness() {
418 int num_blocks = _block_count;
419 BasicBlock *block;
420
421 // We start our work list off with all blocks in it.
422 // Alternately, we could start off the work list with the list of all
423 // blocks which could exit the method directly, along with one block
424 // from any infinite loop. If this matters, it can be changed. It
425 // may not be clear from looking at the code, but the order of the
426 // workList will be the opposite of the creation order of the basic
427 // blocks, which should be decent for quick convergence (with the
428 // possible exception of exception handlers, which are all created
429 // early).
430 _work_list = NULL;
431 for (int i = 0; i < num_blocks; i++) {
432 block = _block_list[i];
433 block->set_next(_work_list);
434 block->set_on_work_list(true);
435 _work_list = block;
436 }
437
438
439 while ((block = work_list_get()) != NULL) {
440 block->propagate(this);
441 NOT_PRODUCT(_total_visits++;)
442 }
443 }
444
445 void MethodLiveness::work_list_add(BasicBlock *block) {
446 if (!block->on_work_list()) {
447 block->set_next(_work_list);
448 block->set_on_work_list(true);
449 _work_list = block;
450 }
451 }
452
453 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() {
454 BasicBlock *block = _work_list;
455 if (block != NULL) {
456 block->set_on_work_list(false);
457 _work_list = block->next();
458 }
459 return block;
460 }
461
462
463 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) {
464 int bci = entry_bci;
465 bool is_entry = false;
466 if (entry_bci == InvocationEntryBci) {
467 is_entry = true;
468 bci = 0;
469 }
470
471 MethodLivenessResult answer((uintptr_t*)NULL,0);
472
473 if (_block_count > 0) {
474 if (TimeLivenessAnalysis) _time_total.start();
475 if (TimeLivenessAnalysis) _time_query.start();
476
477 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" );
478 BasicBlock *block = _block_map->at(bci);
479 // We may not be at the block start, so search backwards to find the block
480 // containing bci.
481 int t = bci;
482 while (block == NULL && t > 0) {
483 block = _block_map->at(--t);
484 }
485 assert( block != NULL, "invalid bytecode index; must be instruction index" );
486 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci.");
487
488 answer = block->get_liveness_at(method(), bci);
489
490 if (is_entry && method()->is_synchronized() && !method()->is_static()) {
491 // Synchronized methods use the receiver once on entry.
492 answer.at_put(0, true);
493 }
494
495 #ifndef PRODUCT
496 if (TraceLivenessQuery) {
497 tty->print("Liveness query of ");
498 method()->print_short_name();
499 tty->print(" @ %d : result is ", bci);
500 answer.print_on(tty);
501 }
502
503 if (TimeLivenessAnalysis) _time_query.stop();
504 if (TimeLivenessAnalysis) _time_total.stop();
505 #endif
506 }
507
508 #ifndef PRODUCT
509 if (TimeLivenessAnalysis) {
510 // Collect statistics.
511 _total_locals_queried += _bit_map_size_bits;
512 BitCounter counter;
513 answer.iterate(&counter);
514 _total_live_locals_queried += counter.count();
515 }
516 #endif
517
518 return answer;
519 }
520
521
522 #ifndef PRODUCT
523
524 void MethodLiveness::print_times() {
525 tty->print_cr ("Accumulated liveness analysis times/statistics:");
526 tty->print_cr ("-----------------------------------------------");
527 tty->print_cr (" Total : %3.3f sec.", _time_total.seconds());
528 tty->print_cr (" Build graph : %3.3f sec. (%2.2f%%)", _time_build_graph.seconds(),
529 _time_build_graph.seconds() * 100 / _time_total.seconds());
530 tty->print_cr (" Gen / Kill : %3.3f sec. (%2.2f%%)", _time_gen_kill.seconds(),
531 _time_gen_kill.seconds() * 100 / _time_total.seconds());
532 tty->print_cr (" Dataflow : %3.3f sec. (%2.2f%%)", _time_flow.seconds(),
533 _time_flow.seconds() * 100 / _time_total.seconds());
534 tty->print_cr (" Query : %3.3f sec. (%2.2f%%)", _time_query.seconds(),
535 _time_query.seconds() * 100 / _time_total.seconds());
536 tty->print_cr (" #bytes : %8d (%3.0f bytes per sec)",
537 _total_bytes,
538 _total_bytes / _time_total.seconds());
539 tty->print_cr (" #methods : %8d (%3.0f methods per sec)",
540 _total_methods,
541 _total_methods / _time_total.seconds());
542 tty->print_cr (" avg locals : %3.3f max locals : %3d",
543 (float)_total_method_locals / _total_methods,
544 _max_method_locals);
545 tty->print_cr (" avg blocks : %3.3f max blocks : %3d",
546 (float)_total_blocks / _total_methods,
547 _max_method_blocks);
548 tty->print_cr (" avg bytes : %3.3f",
549 (float)_total_bytes / _total_methods);
550 tty->print_cr (" #blocks : %8d",
551 _total_blocks);
552 tty->print_cr (" avg normal predecessors : %3.3f max normal predecessors : %3d",
553 (float)_total_edges / _total_blocks,
554 _max_block_edges);
555 tty->print_cr (" avg exception predecessors : %3.3f max exception predecessors : %3d",
556 (float)_total_exc_edges / _total_blocks,
557 _max_block_exc_edges);
558 tty->print_cr (" avg visits : %3.3f",
559 (float)_total_visits / _total_blocks);
560 tty->print_cr (" #locals queried : %8d #live : %8d %%live : %2.2f%%",
561 _total_locals_queried,
562 _total_live_locals_queried,
563 100.0 * _total_live_locals_queried / _total_locals_queried);
564 }
565
566 #endif
567
568
569 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) :
570 _gen((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
571 analyzer->bit_map_size_bits()),
572 _kill((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
573 analyzer->bit_map_size_bits()),
574 _entry((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
575 analyzer->bit_map_size_bits()),
576 _normal_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
577 analyzer->bit_map_size_bits()),
578 _exception_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
579 analyzer->bit_map_size_bits()),
580 _last_bci(-1) {
581 _analyzer = analyzer;
582 _start_bci = start;
583 _limit_bci = limit;
584 _normal_predecessors =
585 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
586 _exception_predecessors =
587 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
588 _normal_exit.clear();
589 _exception_exit.clear();
590 _entry.clear();
591
592 // this initialization is not strictly necessary.
593 // _gen and _kill are cleared at the beginning of compute_gen_kill_range()
594 _gen.clear();
595 _kill.clear();
596 }
597
598
599
600 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) {
601 int start = _start_bci;
602 int limit = _limit_bci;
603
604 if (TraceLivenessGen) {
605 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci);
606 }
607
608 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors;
609
610 assert (start < split_bci && split_bci < limit, "improper split");
611
612 // Make a new block to cover the first half of the range.
613 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci);
614
615 // Assign correct values to the second half (this)
616 _normal_predecessors = first_half->_normal_predecessors;
617 _start_bci = split_bci;
618 add_normal_predecessor(first_half);
619
620 // Assign correct predecessors to the new first half
621 first_half->_normal_predecessors = save_predecessors;
622
623 return first_half;
624 }
625
626 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) {
627 ciBytecodeStream bytes(method);
628 bytes.reset_to_bci(start_bci());
629 bytes.set_max_bci(limit_bci());
630 compute_gen_kill_range(&bytes);
631
632 }
633
634 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) {
635 _gen.clear();
636 _kill.clear();
637
638 while (bytes->next() != ciBytecodeStream::EOBC()) {
639 compute_gen_kill_single(bytes);
640 }
641 }
642
643 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) {
644 int localNum;
645
646 // We prohibit _gen and _kill from having locals in common. If we
647 // know that one is definitely going to be applied before the other,
648 // we could save some computation time by relaxing this prohibition.
649
650 switch (instruction->cur_bc()) {
651 case Bytecodes::_nop:
652 case Bytecodes::_goto:
653 case Bytecodes::_goto_w:
654 case Bytecodes::_aconst_null:
655 case Bytecodes::_new:
656 case Bytecodes::_iconst_m1:
657 case Bytecodes::_iconst_0:
658 case Bytecodes::_iconst_1:
659 case Bytecodes::_iconst_2:
660 case Bytecodes::_iconst_3:
661 case Bytecodes::_iconst_4:
662 case Bytecodes::_iconst_5:
663 case Bytecodes::_fconst_0:
664 case Bytecodes::_fconst_1:
665 case Bytecodes::_fconst_2:
666 case Bytecodes::_bipush:
667 case Bytecodes::_sipush:
668 case Bytecodes::_lconst_0:
669 case Bytecodes::_lconst_1:
670 case Bytecodes::_dconst_0:
671 case Bytecodes::_dconst_1:
672 case Bytecodes::_ldc2_w:
673 case Bytecodes::_ldc:
674 case Bytecodes::_ldc_w:
675 case Bytecodes::_iaload:
676 case Bytecodes::_faload:
677 case Bytecodes::_baload:
678 case Bytecodes::_caload:
679 case Bytecodes::_saload:
680 case Bytecodes::_laload:
681 case Bytecodes::_daload:
682 case Bytecodes::_aaload:
683 case Bytecodes::_iastore:
684 case Bytecodes::_fastore:
685 case Bytecodes::_bastore:
686 case Bytecodes::_castore:
687 case Bytecodes::_sastore:
688 case Bytecodes::_lastore:
689 case Bytecodes::_dastore:
690 case Bytecodes::_aastore:
691 case Bytecodes::_pop:
692 case Bytecodes::_pop2:
693 case Bytecodes::_dup:
694 case Bytecodes::_dup_x1:
695 case Bytecodes::_dup_x2:
696 case Bytecodes::_dup2:
697 case Bytecodes::_dup2_x1:
698 case Bytecodes::_dup2_x2:
699 case Bytecodes::_swap:
700 case Bytecodes::_iadd:
701 case Bytecodes::_fadd:
702 case Bytecodes::_isub:
703 case Bytecodes::_fsub:
704 case Bytecodes::_imul:
705 case Bytecodes::_fmul:
706 case Bytecodes::_idiv:
707 case Bytecodes::_fdiv:
708 case Bytecodes::_irem:
709 case Bytecodes::_frem:
710 case Bytecodes::_ishl:
711 case Bytecodes::_ishr:
712 case Bytecodes::_iushr:
713 case Bytecodes::_iand:
714 case Bytecodes::_ior:
715 case Bytecodes::_ixor:
716 case Bytecodes::_l2f:
717 case Bytecodes::_l2i:
718 case Bytecodes::_d2f:
719 case Bytecodes::_d2i:
720 case Bytecodes::_fcmpl:
721 case Bytecodes::_fcmpg:
722 case Bytecodes::_ladd:
723 case Bytecodes::_dadd:
724 case Bytecodes::_lsub:
725 case Bytecodes::_dsub:
726 case Bytecodes::_lmul:
727 case Bytecodes::_dmul:
728 case Bytecodes::_ldiv:
729 case Bytecodes::_ddiv:
730 case Bytecodes::_lrem:
731 case Bytecodes::_drem:
732 case Bytecodes::_land:
733 case Bytecodes::_lor:
734 case Bytecodes::_lxor:
735 case Bytecodes::_ineg:
736 case Bytecodes::_fneg:
737 case Bytecodes::_i2f:
738 case Bytecodes::_f2i:
739 case Bytecodes::_i2c:
740 case Bytecodes::_i2s:
741 case Bytecodes::_i2b:
742 case Bytecodes::_lneg:
743 case Bytecodes::_dneg:
744 case Bytecodes::_l2d:
745 case Bytecodes::_d2l:
746 case Bytecodes::_lshl:
747 case Bytecodes::_lshr:
748 case Bytecodes::_lushr:
749 case Bytecodes::_i2l:
750 case Bytecodes::_i2d:
751 case Bytecodes::_f2l:
752 case Bytecodes::_f2d:
753 case Bytecodes::_lcmp:
754 case Bytecodes::_dcmpl:
755 case Bytecodes::_dcmpg:
756 case Bytecodes::_ifeq:
757 case Bytecodes::_ifne:
758 case Bytecodes::_iflt:
759 case Bytecodes::_ifge:
760 case Bytecodes::_ifgt:
761 case Bytecodes::_ifle:
762 case Bytecodes::_tableswitch:
763 case Bytecodes::_ireturn:
764 case Bytecodes::_freturn:
765 case Bytecodes::_if_icmpeq:
766 case Bytecodes::_if_icmpne:
767 case Bytecodes::_if_icmplt:
768 case Bytecodes::_if_icmpge:
769 case Bytecodes::_if_icmpgt:
770 case Bytecodes::_if_icmple:
771 case Bytecodes::_lreturn:
772 case Bytecodes::_dreturn:
773 case Bytecodes::_if_acmpeq:
774 case Bytecodes::_if_acmpne:
775 case Bytecodes::_jsr:
776 case Bytecodes::_jsr_w:
777 case Bytecodes::_getstatic:
778 case Bytecodes::_putstatic:
779 case Bytecodes::_getfield:
780 case Bytecodes::_putfield:
781 case Bytecodes::_invokevirtual:
782 case Bytecodes::_invokespecial:
783 case Bytecodes::_invokestatic:
784 case Bytecodes::_invokeinterface:
785 case Bytecodes::_invokedynamic:
786 case Bytecodes::_newarray:
787 case Bytecodes::_anewarray:
788 case Bytecodes::_checkcast:
789 case Bytecodes::_arraylength:
790 case Bytecodes::_instanceof:
791 case Bytecodes::_athrow:
792 case Bytecodes::_areturn:
793 case Bytecodes::_monitorenter:
794 case Bytecodes::_monitorexit:
795 case Bytecodes::_ifnull:
796 case Bytecodes::_ifnonnull:
797 case Bytecodes::_multianewarray:
798 case Bytecodes::_lookupswitch:
799 // These bytecodes have no effect on the method's locals.
800 break;
801
802 case Bytecodes::_return:
803 if (instruction->method()->intrinsic_id() == vmIntrinsics::_Object_init) {
804 // return from Object.init implicitly registers a finalizer
805 // for the receiver if needed, so keep it alive.
806 load_one(0);
807 }
808 break;
809
810
811 case Bytecodes::_lload:
812 case Bytecodes::_dload:
813 load_two(instruction->get_index());
814 break;
815
816 case Bytecodes::_lload_0:
817 case Bytecodes::_dload_0:
818 load_two(0);
819 break;
820
821 case Bytecodes::_lload_1:
822 case Bytecodes::_dload_1:
823 load_two(1);
824 break;
825
826 case Bytecodes::_lload_2:
827 case Bytecodes::_dload_2:
828 load_two(2);
829 break;
830
831 case Bytecodes::_lload_3:
832 case Bytecodes::_dload_3:
833 load_two(3);
834 break;
835
836 case Bytecodes::_iload:
837 case Bytecodes::_iinc:
838 case Bytecodes::_fload:
839 case Bytecodes::_aload:
840 case Bytecodes::_ret:
841 load_one(instruction->get_index());
842 break;
843
844 case Bytecodes::_iload_0:
845 case Bytecodes::_fload_0:
846 case Bytecodes::_aload_0:
847 load_one(0);
848 break;
849
850 case Bytecodes::_iload_1:
851 case Bytecodes::_fload_1:
852 case Bytecodes::_aload_1:
853 load_one(1);
854 break;
855
856 case Bytecodes::_iload_2:
857 case Bytecodes::_fload_2:
858 case Bytecodes::_aload_2:
859 load_one(2);
860 break;
861
862 case Bytecodes::_iload_3:
863 case Bytecodes::_fload_3:
864 case Bytecodes::_aload_3:
865 load_one(3);
866 break;
867
868 case Bytecodes::_lstore:
869 case Bytecodes::_dstore:
870 store_two(localNum = instruction->get_index());
871 break;
872
873 case Bytecodes::_lstore_0:
874 case Bytecodes::_dstore_0:
875 store_two(0);
876 break;
877
878 case Bytecodes::_lstore_1:
879 case Bytecodes::_dstore_1:
880 store_two(1);
881 break;
882
883 case Bytecodes::_lstore_2:
884 case Bytecodes::_dstore_2:
885 store_two(2);
886 break;
887
888 case Bytecodes::_lstore_3:
889 case Bytecodes::_dstore_3:
890 store_two(3);
891 break;
892
893 case Bytecodes::_istore:
894 case Bytecodes::_fstore:
895 case Bytecodes::_astore:
896 store_one(instruction->get_index());
897 break;
898
899 case Bytecodes::_istore_0:
900 case Bytecodes::_fstore_0:
901 case Bytecodes::_astore_0:
902 store_one(0);
903 break;
904
905 case Bytecodes::_istore_1:
906 case Bytecodes::_fstore_1:
907 case Bytecodes::_astore_1:
908 store_one(1);
909 break;
910
911 case Bytecodes::_istore_2:
912 case Bytecodes::_fstore_2:
913 case Bytecodes::_astore_2:
914 store_one(2);
915 break;
916
917 case Bytecodes::_istore_3:
918 case Bytecodes::_fstore_3:
919 case Bytecodes::_astore_3:
920 store_one(3);
921 break;
922
923 case Bytecodes::_wide:
924 fatal("Iterator should skip this bytecode");
925 break;
926
927 default:
928 tty->print("unexpected opcode: %d\n", instruction->cur_bc());
929 ShouldNotReachHere();
930 break;
931 }
932 }
933
934 void MethodLiveness::BasicBlock::load_two(int local) {
935 load_one(local);
936 load_one(local+1);
937 }
938
939 void MethodLiveness::BasicBlock::load_one(int local) {
940 if (!_kill.at(local)) {
941 _gen.at_put(local, true);
942 }
943 }
944
945 void MethodLiveness::BasicBlock::store_two(int local) {
946 store_one(local);
947 store_one(local+1);
948 }
949
950 void MethodLiveness::BasicBlock::store_one(int local) {
951 if (!_gen.at(local)) {
952 _kill.at_put(local, true);
953 }
954 }
955
956 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) {
957 // These set operations could be combined for efficiency if the
958 // performance of this analysis becomes an issue.
959 _entry.set_union(_normal_exit);
960 _entry.set_difference(_kill);
961 _entry.set_union(_gen);
962
963 // Note that we merge information from our exceptional successors
964 // just once, rather than at individual bytecodes.
965 _entry.set_union(_exception_exit);
966
967 if (TraceLivenessGen) {
968 tty->print_cr(" ** Visiting block at %d **", start_bci());
969 print_on(tty);
970 }
971
972 int i;
973 for (i=_normal_predecessors->length()-1; i>=0; i--) {
974 BasicBlock *block = _normal_predecessors->at(i);
975 if (block->merge_normal(_entry)) {
976 ml->work_list_add(block);
977 }
978 }
979 for (i=_exception_predecessors->length()-1; i>=0; i--) {
980 BasicBlock *block = _exception_predecessors->at(i);
981 if (block->merge_exception(_entry)) {
982 ml->work_list_add(block);
983 }
984 }
985 }
986
987 bool MethodLiveness::BasicBlock::merge_normal(BitMap other) {
988 return _normal_exit.set_union_with_result(other);
989 }
990
991 bool MethodLiveness::BasicBlock::merge_exception(BitMap other) {
992 return _exception_exit.set_union_with_result(other);
993 }
994
995 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) {
996 MethodLivenessResult answer(NEW_RESOURCE_ARRAY(uintptr_t, _analyzer->bit_map_size_words()),
997 _analyzer->bit_map_size_bits());
998 answer.set_is_valid();
999
1000 #ifndef ASSERT
1001 if (bci == start_bci()) {
1002 answer.set_from(_entry);
1003 return answer;
1004 }
1005 #endif
1006
1007 #ifdef ASSERT
1008 ResourceMark rm;
1009 BitMap g(_gen.size()); g.set_from(_gen);
1010 BitMap k(_kill.size()); k.set_from(_kill);
1011 #endif
1012 if (_last_bci != bci || trueInDebug) {
1013 ciBytecodeStream bytes(method);
1014 bytes.reset_to_bci(bci);
1015 bytes.set_max_bci(limit_bci());
1016 compute_gen_kill_range(&bytes);
1017 assert(_last_bci != bci ||
1018 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect");
1019 _last_bci = bci;
1020 }
1021
1022 answer.clear();
1023 answer.set_union(_normal_exit);
1024 answer.set_difference(_kill);
1025 answer.set_union(_gen);
1026 answer.set_union(_exception_exit);
1027
1028 #ifdef ASSERT
1029 if (bci == start_bci()) {
1030 assert(answer.is_same(_entry), "optimized answer must be accurate");
1031 }
1032 #endif
1033
1034 return answer;
1035 }
1036
1037 #ifndef PRODUCT
1038
1039 void MethodLiveness::BasicBlock::print_on(outputStream *os) const {
1040 os->print_cr("===================================================================");
1041 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci);
1042 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length());
1043 int i;
1044 for (i=0; i < _normal_predecessors->length(); i++) {
1045 os->print(" %4d", _normal_predecessors->at(i)->start_bci());
1046 }
1047 os->cr();
1048 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length());
1049 for (i=0; i < _exception_predecessors->length(); i++) {
1050 os->print(" %4d", _exception_predecessors->at(i)->start_bci());
1051 }
1052 os->cr();
1053 os->print (" Normal Exit : ");
1054 _normal_exit.print_on(os);
1055 os->print (" Gen : ");
1056 _gen.print_on(os);
1057 os->print (" Kill : ");
1058 _kill.print_on(os);
1059 os->print (" Exception Exit: ");
1060 _exception_exit.print_on(os);
1061 os->print (" Entry : ");
1062 _entry.print_on(os);
1063 }
1064
1065 #endif // PRODUCT