1 /*
2 * Copyright (c) 1998, 2014, 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 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciMethod.hpp"
27 #include "ci/ciMethodBlocks.hpp"
28 #include "ci/ciStreams.hpp"
29 #include "compiler/methodLiveness.hpp"
30 #include "interpreter/bytecode.hpp"
31 #include "interpreter/bytecodes.hpp"
32 #include "memory/allocation.inline.hpp"
33 #include "utilities/bitMap.inline.hpp"
34
35 // The MethodLiveness class performs a simple liveness analysis on a method
36 // in order to decide which locals are live (that is, will be used again) at
37 // a particular bytecode index (bci).
38 //
39 // The algorithm goes:
40 //
41 // 1. Break the method into a set of basic blocks. For each basic block we
42 // also keep track of its set of predecessors through normal control flow
43 // and predecessors through exceptional control flow.
44 //
45 // 2. For each basic block, compute two sets, gen (the set of values used before
46 // they are defined) and kill (the set of values defined before they are used)
47 // in the basic block. A basic block "needs" the locals in its gen set to
48 // perform its computation. A basic block "provides" values for the locals in
49 // its kill set, allowing a need from a successor to be ignored.
50 //
51 // 3. Liveness information (the set of locals which are needed) is pushed backwards through
52 // the program, from blocks to their predecessors. We compute and store liveness
53 // information for the normal/exceptional exit paths for each basic block. When
54 // this process reaches a fixed point, we are done.
55 //
56 // 4. When we are asked about the liveness at a particular bci with a basic block, we
57 // compute gen/kill sets which represent execution from that bci to the exit of
58 // its blocks. We then compose this range gen/kill information with the normal
59 // and exceptional exit information for the block to produce liveness information
60 // at that bci.
61 //
62 // The algorithm is approximate in many respects. Notably:
63 //
64 // 1. We do not do the analysis necessary to match jsr's with the appropriate ret.
65 // Instead we make the conservative assumption that any ret can return to any
66 // jsr return site.
67 // 2. Instead of computing the effects of exceptions at every instruction, we
68 // summarize the effects of all exceptional continuations from the block as
69 // a single set (_exception_exit), losing some information but simplifying the
70 // analysis.
71
72
73 //--------------------------------------------------------------------------
74 // The BitCounter class is used for counting the number of bits set in
75 // some BitMap. It is only used when collecting liveness statistics.
76
77 #ifndef PRODUCT
78
79 class BitCounter: public BitMapClosure {
80 private:
81 int _count;
82 public:
83 BitCounter() : _count(0) {}
84
85 // Callback when bit in map is set
86 virtual bool do_bit(size_t offset) {
87 _count++;
88 return true;
89 }
90
91 int count() {
92 return _count;
93 }
94 };
95
96
97 //--------------------------------------------------------------------------
98
99
100 // Counts
101 long MethodLiveness::_total_bytes = 0;
102 int MethodLiveness::_total_methods = 0;
103
104 long MethodLiveness::_total_blocks = 0;
105 int MethodLiveness::_max_method_blocks = 0;
106
107 long MethodLiveness::_total_edges = 0;
108 int MethodLiveness::_max_block_edges = 0;
109
110 long MethodLiveness::_total_exc_edges = 0;
111 int MethodLiveness::_max_block_exc_edges = 0;
112
113 long MethodLiveness::_total_method_locals = 0;
114 int MethodLiveness::_max_method_locals = 0;
115
116 long MethodLiveness::_total_locals_queried = 0;
117 long MethodLiveness::_total_live_locals_queried = 0;
118
119 long MethodLiveness::_total_visits = 0;
120
121 #endif
122
123 // Timers
124 elapsedTimer MethodLiveness::_time_build_graph;
125 elapsedTimer MethodLiveness::_time_gen_kill;
126 elapsedTimer MethodLiveness::_time_flow;
127 elapsedTimer MethodLiveness::_time_query;
128 elapsedTimer MethodLiveness::_time_total;
129
130 MethodLiveness::MethodLiveness(Arena* arena, ciMethod* method)
131 #ifdef COMPILER1
132 : _bci_block_start((uintptr_t*)arena->Amalloc((method->code_size() >> LogBitsPerByte) + 1), method->code_size())
133 #endif
134 {
135 _arena = arena;
136 _method = method;
137 _bit_map_size_bits = method->max_locals();
138 _bit_map_size_words = (_bit_map_size_bits / sizeof(unsigned int)) + 1;
139
140 #ifdef COMPILER1
141 _bci_block_start.clear();
142 #endif
143 }
144
145 void MethodLiveness::compute_liveness() {
146 #ifndef PRODUCT
147 if (TraceLivenessGen) {
148 tty->print_cr("################################################################");
149 tty->print("# Computing liveness information for ");
150 method()->print_short_name();
151 }
152
153 if (TimeLivenessAnalysis) _time_total.start();
154 #endif
155
156 {
157 TraceTime buildGraph(NULL, &_time_build_graph, TimeLivenessAnalysis);
158 init_basic_blocks();
159 }
160 {
161 TraceTime genKill(NULL, &_time_gen_kill, TimeLivenessAnalysis);
162 init_gen_kill();
163 }
164 {
165 TraceTime flow(NULL, &_time_flow, TimeLivenessAnalysis);
166 propagate_liveness();
167 }
168
169 #ifndef PRODUCT
170 if (TimeLivenessAnalysis) _time_total.stop();
171
172 if (TimeLivenessAnalysis) {
173 // Collect statistics
174 _total_bytes += method()->code_size();
175 _total_methods++;
176
177 int num_blocks = _block_count;
178 _total_blocks += num_blocks;
179 _max_method_blocks = MAX2(num_blocks,_max_method_blocks);
180
181 for (int i=0; i<num_blocks; i++) {
182 BasicBlock *block = _block_list[i];
183
184 int numEdges = block->_normal_predecessors->length();
185 int numExcEdges = block->_exception_predecessors->length();
186
187 _total_edges += numEdges;
188 _total_exc_edges += numExcEdges;
189 _max_block_edges = MAX2(numEdges,_max_block_edges);
190 _max_block_exc_edges = MAX2(numExcEdges,_max_block_exc_edges);
191 }
192
193 int numLocals = _bit_map_size_bits;
194 _total_method_locals += numLocals;
195 _max_method_locals = MAX2(numLocals,_max_method_locals);
196 }
197 #endif
198 }
199
200
201 void MethodLiveness::init_basic_blocks() {
202 bool bailout = false;
203
204 int method_len = method()->code_size();
205 ciMethodBlocks *mblocks = method()->get_method_blocks();
206
207 // Create an array to store the bci->BasicBlock mapping.
208 _block_map = new (arena()) GrowableArray<BasicBlock*>(arena(), method_len, method_len, NULL);
209
210 _block_count = mblocks->num_blocks();
211 _block_list = (BasicBlock **) arena()->Amalloc(sizeof(BasicBlock *) * _block_count);
212
213 // Used for patching up jsr/ret control flow.
214 GrowableArray<BasicBlock*>* jsr_exit_list = new GrowableArray<BasicBlock*>(5);
215 GrowableArray<BasicBlock*>* ret_list = new GrowableArray<BasicBlock*>(5);
216
217 // generate our block list from ciMethodBlocks
218 for (int blk = 0; blk < _block_count; blk++) {
219 ciBlock *cib = mblocks->block(blk);
220 int start_bci = cib->start_bci();
221 _block_list[blk] = new (arena()) BasicBlock(this, start_bci, cib->limit_bci());
222 _block_map->at_put(start_bci, _block_list[blk]);
223 #ifdef COMPILER1
224 // mark all bcis where a new basic block starts
225 _bci_block_start.set_bit(start_bci);
226 #endif // COMPILER1
227 }
228 // fill in the predecessors of blocks
229 ciBytecodeStream bytes(method());
230
231 for (int blk = 0; blk < _block_count; blk++) {
232 BasicBlock *current_block = _block_list[blk];
233 int bci = mblocks->block(blk)->control_bci();
234
235 if (bci == ciBlock::fall_through_bci) {
236 int limit = current_block->limit_bci();
237 if (limit < method_len) {
238 BasicBlock *next = _block_map->at(limit);
239 assert( next != NULL, "must be a block immediately following this one.");
240 next->add_normal_predecessor(current_block);
241 }
242 continue;
243 }
244 bytes.reset_to_bci(bci);
245 Bytecodes::Code code = bytes.next();
246 BasicBlock *dest;
247
248 // Now we need to interpret the instruction's effect
249 // on control flow.
250 assert (current_block != NULL, "we must have a current block");
251 switch (code) {
252 case Bytecodes::_ifeq:
253 case Bytecodes::_ifne:
254 case Bytecodes::_iflt:
255 case Bytecodes::_ifge:
256 case Bytecodes::_ifgt:
257 case Bytecodes::_ifle:
258 case Bytecodes::_if_icmpeq:
259 case Bytecodes::_if_icmpne:
260 case Bytecodes::_if_icmplt:
261 case Bytecodes::_if_icmpge:
262 case Bytecodes::_if_icmpgt:
263 case Bytecodes::_if_icmple:
264 case Bytecodes::_if_acmpeq:
265 case Bytecodes::_if_acmpne:
266 case Bytecodes::_ifnull:
267 case Bytecodes::_ifnonnull:
268 // Two way branch. Set predecessors at each destination.
269 dest = _block_map->at(bytes.next_bci());
270 assert(dest != NULL, "must be a block immediately following this one.");
271 dest->add_normal_predecessor(current_block);
272
273 dest = _block_map->at(bytes.get_dest());
274 assert(dest != NULL, "branch desination must start a block.");
275 dest->add_normal_predecessor(current_block);
276 break;
277 case Bytecodes::_goto:
278 dest = _block_map->at(bytes.get_dest());
279 assert(dest != NULL, "branch desination must start a block.");
280 dest->add_normal_predecessor(current_block);
281 break;
282 case Bytecodes::_goto_w:
283 dest = _block_map->at(bytes.get_far_dest());
284 assert(dest != NULL, "branch desination must start a block.");
285 dest->add_normal_predecessor(current_block);
286 break;
287 case Bytecodes::_tableswitch:
288 {
289 Bytecode_tableswitch tableswitch(&bytes);
290
291 int len = tableswitch.length();
292
293 dest = _block_map->at(bci + tableswitch.default_offset());
294 assert(dest != NULL, "branch desination must start a block.");
295 dest->add_normal_predecessor(current_block);
296 while (--len >= 0) {
297 dest = _block_map->at(bci + tableswitch.dest_offset_at(len));
298 assert(dest != NULL, "branch desination must start a block.");
299 dest->add_normal_predecessor(current_block);
300 }
301 break;
302 }
303
304 case Bytecodes::_lookupswitch:
305 {
306 Bytecode_lookupswitch lookupswitch(&bytes);
307
308 int npairs = lookupswitch.number_of_pairs();
309
310 dest = _block_map->at(bci + lookupswitch.default_offset());
311 assert(dest != NULL, "branch desination must start a block.");
312 dest->add_normal_predecessor(current_block);
313 while(--npairs >= 0) {
314 LookupswitchPair pair = lookupswitch.pair_at(npairs);
315 dest = _block_map->at( bci + pair.offset());
316 assert(dest != NULL, "branch desination must start a block.");
317 dest->add_normal_predecessor(current_block);
318 }
319 break;
320 }
321
322 case Bytecodes::_jsr:
323 {
324 assert(bytes.is_wide()==false, "sanity check");
325 dest = _block_map->at(bytes.get_dest());
326 assert(dest != NULL, "branch desination must start a block.");
327 dest->add_normal_predecessor(current_block);
328 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
329 assert(jsrExit != NULL, "jsr return bci must start a block.");
330 jsr_exit_list->append(jsrExit);
331 break;
332 }
333 case Bytecodes::_jsr_w:
334 {
335 dest = _block_map->at(bytes.get_far_dest());
336 assert(dest != NULL, "branch desination must start a block.");
337 dest->add_normal_predecessor(current_block);
338 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
339 assert(jsrExit != NULL, "jsr return bci must start a block.");
340 jsr_exit_list->append(jsrExit);
341 break;
342 }
343
344 case Bytecodes::_wide:
345 assert(false, "wide opcodes should not be seen here");
346 break;
347 case Bytecodes::_athrow:
348 case Bytecodes::_ireturn:
349 case Bytecodes::_lreturn:
350 case Bytecodes::_freturn:
351 case Bytecodes::_dreturn:
352 case Bytecodes::_areturn:
353 case Bytecodes::_return:
354 // These opcodes are not the normal predecessors of any other opcodes.
355 break;
356 case Bytecodes::_ret:
357 // We will patch up jsr/rets in a subsequent pass.
358 ret_list->append(current_block);
359 break;
360 case Bytecodes::_breakpoint:
361 // Bail out of there are breakpoints in here.
362 bailout = true;
363 break;
364 default:
365 // Do nothing.
366 break;
367 }
368 }
369 // Patch up the jsr/ret's. We conservatively assume that any ret
370 // can return to any jsr site.
371 int ret_list_len = ret_list->length();
372 int jsr_exit_list_len = jsr_exit_list->length();
373 if (ret_list_len > 0 && jsr_exit_list_len > 0) {
374 for (int i = jsr_exit_list_len - 1; i >= 0; i--) {
375 BasicBlock *jsrExit = jsr_exit_list->at(i);
376 for (int i = ret_list_len - 1; i >= 0; i--) {
377 jsrExit->add_normal_predecessor(ret_list->at(i));
378 }
379 }
380 }
381
382 // Compute exception edges.
383 for (int b=_block_count-1; b >= 0; b--) {
384 BasicBlock *block = _block_list[b];
385 int block_start = block->start_bci();
386 int block_limit = block->limit_bci();
387 ciExceptionHandlerStream handlers(method());
388 for (; !handlers.is_done(); handlers.next()) {
389 ciExceptionHandler* handler = handlers.handler();
390 int start = handler->start();
391 int limit = handler->limit();
392 int handler_bci = handler->handler_bci();
393
394 int intersect_start = MAX2(block_start, start);
395 int intersect_limit = MIN2(block_limit, limit);
396 if (intersect_start < intersect_limit) {
397 // The catch range has a nonempty intersection with this
398 // basic block. That means this basic block can be an
399 // exceptional predecessor.
400 _block_map->at(handler_bci)->add_exception_predecessor(block);
401
402 if (handler->is_catch_all()) {
403 // This is a catch-all block.
404 if (intersect_start == block_start && intersect_limit == block_limit) {
405 // The basic block is entirely contained in this catch-all block.
406 // Skip the rest of the exception handlers -- they can never be
407 // reached in execution.
408 break;
409 }
410 }
411 }
412 }
413 }
414 }
415
416 void MethodLiveness::init_gen_kill() {
417 for (int i=_block_count-1; i >= 0; i--) {
418 _block_list[i]->compute_gen_kill(method());
419 }
420 }
421
422 void MethodLiveness::propagate_liveness() {
423 int num_blocks = _block_count;
424 BasicBlock *block;
425
426 // We start our work list off with all blocks in it.
427 // Alternately, we could start off the work list with the list of all
428 // blocks which could exit the method directly, along with one block
429 // from any infinite loop. If this matters, it can be changed. It
430 // may not be clear from looking at the code, but the order of the
431 // workList will be the opposite of the creation order of the basic
432 // blocks, which should be decent for quick convergence (with the
433 // possible exception of exception handlers, which are all created
434 // early).
435 _work_list = NULL;
436 for (int i = 0; i < num_blocks; i++) {
437 block = _block_list[i];
438 block->set_next(_work_list);
439 block->set_on_work_list(true);
440 _work_list = block;
441 }
442
443
444 while ((block = work_list_get()) != NULL) {
445 block->propagate(this);
446 NOT_PRODUCT(_total_visits++;)
447 }
448 }
449
450 void MethodLiveness::work_list_add(BasicBlock *block) {
451 if (!block->on_work_list()) {
452 block->set_next(_work_list);
453 block->set_on_work_list(true);
454 _work_list = block;
455 }
456 }
457
458 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() {
459 BasicBlock *block = _work_list;
460 if (block != NULL) {
461 block->set_on_work_list(false);
462 _work_list = block->next();
463 }
464 return block;
465 }
466
467
468 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) {
469 int bci = entry_bci;
470 bool is_entry = false;
471 if (entry_bci == InvocationEntryBci) {
472 is_entry = true;
473 bci = 0;
474 }
475
476 MethodLivenessResult answer((BitMap::bm_word_t*)NULL,0);
477
478 if (_block_count > 0) {
479 if (TimeLivenessAnalysis) _time_total.start();
480 if (TimeLivenessAnalysis) _time_query.start();
481
482 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" );
483 BasicBlock *block = _block_map->at(bci);
484 // We may not be at the block start, so search backwards to find the block
485 // containing bci.
486 int t = bci;
487 while (block == NULL && t > 0) {
488 block = _block_map->at(--t);
489 }
490 assert( block != NULL, "invalid bytecode index; must be instruction index" );
491 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci.");
492
493 answer = block->get_liveness_at(method(), bci);
494
495 if (is_entry && method()->is_synchronized() && !method()->is_static()) {
496 // Synchronized methods use the receiver once on entry.
497 answer.at_put(0, true);
498 }
499
500 #ifndef PRODUCT
501 if (TraceLivenessQuery) {
502 tty->print("Liveness query of ");
503 method()->print_short_name();
504 tty->print(" @ %d : result is ", bci);
505 answer.print_on(tty);
506 }
507
508 if (TimeLivenessAnalysis) _time_query.stop();
509 if (TimeLivenessAnalysis) _time_total.stop();
510 #endif
511 }
512
513 #ifndef PRODUCT
514 if (TimeLivenessAnalysis) {
515 // Collect statistics.
516 _total_locals_queried += _bit_map_size_bits;
517 BitCounter counter;
518 answer.iterate(&counter);
519 _total_live_locals_queried += counter.count();
520 }
521 #endif
522
523 return answer;
524 }
525
526
527 #ifndef PRODUCT
528
529 void MethodLiveness::print_times() {
530 tty->print_cr ("Accumulated liveness analysis times/statistics:");
531 tty->print_cr ("-----------------------------------------------");
532 tty->print_cr (" Total : %3.3f sec.", _time_total.seconds());
533 tty->print_cr (" Build graph : %3.3f sec. (%2.2f%%)", _time_build_graph.seconds(),
534 _time_build_graph.seconds() * 100 / _time_total.seconds());
535 tty->print_cr (" Gen / Kill : %3.3f sec. (%2.2f%%)", _time_gen_kill.seconds(),
536 _time_gen_kill.seconds() * 100 / _time_total.seconds());
537 tty->print_cr (" Dataflow : %3.3f sec. (%2.2f%%)", _time_flow.seconds(),
538 _time_flow.seconds() * 100 / _time_total.seconds());
539 tty->print_cr (" Query : %3.3f sec. (%2.2f%%)", _time_query.seconds(),
540 _time_query.seconds() * 100 / _time_total.seconds());
541 tty->print_cr (" #bytes : %8ld (%3.0f bytes per sec)",
542 _total_bytes,
543 _total_bytes / _time_total.seconds());
544 tty->print_cr (" #methods : %8d (%3.0f methods per sec)",
545 _total_methods,
546 _total_methods / _time_total.seconds());
547 tty->print_cr (" avg locals : %3.3f max locals : %3d",
548 (float)_total_method_locals / _total_methods,
549 _max_method_locals);
550 tty->print_cr (" avg blocks : %3.3f max blocks : %3d",
551 (float)_total_blocks / _total_methods,
552 _max_method_blocks);
553 tty->print_cr (" avg bytes : %3.3f",
554 (float)_total_bytes / _total_methods);
555 tty->print_cr (" #blocks : %8ld",
556 _total_blocks);
557 tty->print_cr (" avg normal predecessors : %3.3f max normal predecessors : %3d",
558 (float)_total_edges / _total_blocks,
559 _max_block_edges);
560 tty->print_cr (" avg exception predecessors : %3.3f max exception predecessors : %3d",
561 (float)_total_exc_edges / _total_blocks,
562 _max_block_exc_edges);
563 tty->print_cr (" avg visits : %3.3f",
564 (float)_total_visits / _total_blocks);
565 tty->print_cr (" #locals queried : %8ld #live : %8ld %%live : %2.2f%%",
566 _total_locals_queried,
567 _total_live_locals_queried,
568 100.0 * _total_live_locals_queried / _total_locals_queried);
569 }
570
571 #endif
572
573
574 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) :
575 _gen((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
576 analyzer->bit_map_size_bits()),
577 _kill((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
578 analyzer->bit_map_size_bits()),
579 _entry((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
580 analyzer->bit_map_size_bits()),
581 _normal_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
582 analyzer->bit_map_size_bits()),
583 _exception_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
584 analyzer->bit_map_size_bits()),
585 _last_bci(-1) {
586 _analyzer = analyzer;
587 _start_bci = start;
588 _limit_bci = limit;
589 _normal_predecessors =
590 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
591 _exception_predecessors =
592 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
593 _normal_exit.clear();
594 _exception_exit.clear();
595 _entry.clear();
596
597 // this initialization is not strictly necessary.
598 // _gen and _kill are cleared at the beginning of compute_gen_kill_range()
599 _gen.clear();
600 _kill.clear();
601 }
602
603
604
605 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) {
606 int start = _start_bci;
607 int limit = _limit_bci;
608
609 if (TraceLivenessGen) {
610 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci);
611 }
612
613 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors;
614
615 assert (start < split_bci && split_bci < limit, "improper split");
616
617 // Make a new block to cover the first half of the range.
618 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci);
619
620 // Assign correct values to the second half (this)
621 _normal_predecessors = first_half->_normal_predecessors;
622 _start_bci = split_bci;
623 add_normal_predecessor(first_half);
624
625 // Assign correct predecessors to the new first half
626 first_half->_normal_predecessors = save_predecessors;
627
628 return first_half;
629 }
630
631 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) {
632 ciBytecodeStream bytes(method);
633 bytes.reset_to_bci(start_bci());
634 bytes.set_max_bci(limit_bci());
635 compute_gen_kill_range(&bytes);
636
637 }
638
639 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) {
640 _gen.clear();
641 _kill.clear();
642
643 while (bytes->next() != ciBytecodeStream::EOBC()) {
644 compute_gen_kill_single(bytes);
645 }
646 }
647
648 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) {
649 int localNum;
650
651 // We prohibit _gen and _kill from having locals in common. If we
652 // know that one is definitely going to be applied before the other,
653 // we could save some computation time by relaxing this prohibition.
654
655 switch (instruction->cur_bc()) {
656 case Bytecodes::_nop:
657 case Bytecodes::_goto:
658 case Bytecodes::_goto_w:
659 case Bytecodes::_aconst_null:
660 case Bytecodes::_new:
661 case Bytecodes::_iconst_m1:
662 case Bytecodes::_iconst_0:
663 case Bytecodes::_iconst_1:
664 case Bytecodes::_iconst_2:
665 case Bytecodes::_iconst_3:
666 case Bytecodes::_iconst_4:
667 case Bytecodes::_iconst_5:
668 case Bytecodes::_fconst_0:
669 case Bytecodes::_fconst_1:
670 case Bytecodes::_fconst_2:
671 case Bytecodes::_bipush:
672 case Bytecodes::_sipush:
673 case Bytecodes::_lconst_0:
674 case Bytecodes::_lconst_1:
675 case Bytecodes::_dconst_0:
676 case Bytecodes::_dconst_1:
677 case Bytecodes::_ldc2_w:
678 case Bytecodes::_ldc:
679 case Bytecodes::_ldc_w:
680 case Bytecodes::_iaload:
681 case Bytecodes::_faload:
682 case Bytecodes::_baload:
683 case Bytecodes::_caload:
684 case Bytecodes::_saload:
685 case Bytecodes::_laload:
686 case Bytecodes::_daload:
687 case Bytecodes::_aaload:
688 case Bytecodes::_iastore:
689 case Bytecodes::_fastore:
690 case Bytecodes::_bastore:
691 case Bytecodes::_castore:
692 case Bytecodes::_sastore:
693 case Bytecodes::_lastore:
694 case Bytecodes::_dastore:
695 case Bytecodes::_aastore:
696 case Bytecodes::_pop:
697 case Bytecodes::_pop2:
698 case Bytecodes::_dup:
699 case Bytecodes::_dup_x1:
700 case Bytecodes::_dup_x2:
701 case Bytecodes::_dup2:
702 case Bytecodes::_dup2_x1:
703 case Bytecodes::_dup2_x2:
704 case Bytecodes::_swap:
705 case Bytecodes::_iadd:
706 case Bytecodes::_fadd:
707 case Bytecodes::_isub:
708 case Bytecodes::_fsub:
709 case Bytecodes::_imul:
710 case Bytecodes::_fmul:
711 case Bytecodes::_idiv:
712 case Bytecodes::_fdiv:
713 case Bytecodes::_irem:
714 case Bytecodes::_frem:
715 case Bytecodes::_ishl:
716 case Bytecodes::_ishr:
717 case Bytecodes::_iushr:
718 case Bytecodes::_iand:
719 case Bytecodes::_ior:
720 case Bytecodes::_ixor:
721 case Bytecodes::_l2f:
722 case Bytecodes::_l2i:
723 case Bytecodes::_d2f:
724 case Bytecodes::_d2i:
725 case Bytecodes::_fcmpl:
726 case Bytecodes::_fcmpg:
727 case Bytecodes::_ladd:
728 case Bytecodes::_dadd:
729 case Bytecodes::_lsub:
730 case Bytecodes::_dsub:
731 case Bytecodes::_lmul:
732 case Bytecodes::_dmul:
733 case Bytecodes::_ldiv:
734 case Bytecodes::_ddiv:
735 case Bytecodes::_lrem:
736 case Bytecodes::_drem:
737 case Bytecodes::_land:
738 case Bytecodes::_lor:
739 case Bytecodes::_lxor:
740 case Bytecodes::_ineg:
741 case Bytecodes::_fneg:
742 case Bytecodes::_i2f:
743 case Bytecodes::_f2i:
744 case Bytecodes::_i2c:
745 case Bytecodes::_i2s:
746 case Bytecodes::_i2b:
747 case Bytecodes::_lneg:
748 case Bytecodes::_dneg:
749 case Bytecodes::_l2d:
750 case Bytecodes::_d2l:
751 case Bytecodes::_lshl:
752 case Bytecodes::_lshr:
753 case Bytecodes::_lushr:
754 case Bytecodes::_i2l:
755 case Bytecodes::_i2d:
756 case Bytecodes::_f2l:
757 case Bytecodes::_f2d:
758 case Bytecodes::_lcmp:
759 case Bytecodes::_dcmpl:
760 case Bytecodes::_dcmpg:
761 case Bytecodes::_ifeq:
762 case Bytecodes::_ifne:
763 case Bytecodes::_iflt:
764 case Bytecodes::_ifge:
765 case Bytecodes::_ifgt:
766 case Bytecodes::_ifle:
767 case Bytecodes::_tableswitch:
768 case Bytecodes::_ireturn:
769 case Bytecodes::_freturn:
770 case Bytecodes::_if_icmpeq:
771 case Bytecodes::_if_icmpne:
772 case Bytecodes::_if_icmplt:
773 case Bytecodes::_if_icmpge:
774 case Bytecodes::_if_icmpgt:
775 case Bytecodes::_if_icmple:
776 case Bytecodes::_lreturn:
777 case Bytecodes::_dreturn:
778 case Bytecodes::_if_acmpeq:
779 case Bytecodes::_if_acmpne:
780 case Bytecodes::_jsr:
781 case Bytecodes::_jsr_w:
782 case Bytecodes::_getstatic:
783 case Bytecodes::_putstatic:
784 case Bytecodes::_getfield:
785 case Bytecodes::_putfield:
786 case Bytecodes::_invokevirtual:
787 case Bytecodes::_invokespecial:
788 case Bytecodes::_invokestatic:
789 case Bytecodes::_invokeinterface:
790 case Bytecodes::_invokedynamic:
791 case Bytecodes::_newarray:
792 case Bytecodes::_anewarray:
793 case Bytecodes::_checkcast:
794 case Bytecodes::_arraylength:
795 case Bytecodes::_instanceof:
796 case Bytecodes::_athrow:
797 case Bytecodes::_areturn:
798 case Bytecodes::_monitorenter:
799 case Bytecodes::_monitorexit:
800 case Bytecodes::_ifnull:
801 case Bytecodes::_ifnonnull:
802 case Bytecodes::_multianewarray:
803 case Bytecodes::_lookupswitch:
804 // These bytecodes have no effect on the method's locals.
805 break;
806
807 case Bytecodes::_return:
808 if (instruction->method()->intrinsic_id() == vmIntrinsics::_Object_init) {
809 // return from Object.init implicitly registers a finalizer
810 // for the receiver if needed, so keep it alive.
811 load_one(0);
812 }
813 break;
814
815
816 case Bytecodes::_lload:
817 case Bytecodes::_dload:
818 load_two(instruction->get_index());
819 break;
820
821 case Bytecodes::_lload_0:
822 case Bytecodes::_dload_0:
823 load_two(0);
824 break;
825
826 case Bytecodes::_lload_1:
827 case Bytecodes::_dload_1:
828 load_two(1);
829 break;
830
831 case Bytecodes::_lload_2:
832 case Bytecodes::_dload_2:
833 load_two(2);
834 break;
835
836 case Bytecodes::_lload_3:
837 case Bytecodes::_dload_3:
838 load_two(3);
839 break;
840
841 case Bytecodes::_iload:
842 case Bytecodes::_iinc:
843 case Bytecodes::_fload:
844 case Bytecodes::_aload:
845 case Bytecodes::_ret:
846 load_one(instruction->get_index());
847 break;
848
849 case Bytecodes::_iload_0:
850 case Bytecodes::_fload_0:
851 case Bytecodes::_aload_0:
852 load_one(0);
853 break;
854
855 case Bytecodes::_iload_1:
856 case Bytecodes::_fload_1:
857 case Bytecodes::_aload_1:
858 load_one(1);
859 break;
860
861 case Bytecodes::_iload_2:
862 case Bytecodes::_fload_2:
863 case Bytecodes::_aload_2:
864 load_one(2);
865 break;
866
867 case Bytecodes::_iload_3:
868 case Bytecodes::_fload_3:
869 case Bytecodes::_aload_3:
870 load_one(3);
871 break;
872
873 case Bytecodes::_lstore:
874 case Bytecodes::_dstore:
875 store_two(localNum = instruction->get_index());
876 break;
877
878 case Bytecodes::_lstore_0:
879 case Bytecodes::_dstore_0:
880 store_two(0);
881 break;
882
883 case Bytecodes::_lstore_1:
884 case Bytecodes::_dstore_1:
885 store_two(1);
886 break;
887
888 case Bytecodes::_lstore_2:
889 case Bytecodes::_dstore_2:
890 store_two(2);
891 break;
892
893 case Bytecodes::_lstore_3:
894 case Bytecodes::_dstore_3:
895 store_two(3);
896 break;
897
898 case Bytecodes::_istore:
899 case Bytecodes::_fstore:
900 case Bytecodes::_astore:
901 store_one(instruction->get_index());
902 break;
903
904 case Bytecodes::_istore_0:
905 case Bytecodes::_fstore_0:
906 case Bytecodes::_astore_0:
907 store_one(0);
908 break;
909
910 case Bytecodes::_istore_1:
911 case Bytecodes::_fstore_1:
912 case Bytecodes::_astore_1:
913 store_one(1);
914 break;
915
916 case Bytecodes::_istore_2:
917 case Bytecodes::_fstore_2:
918 case Bytecodes::_astore_2:
919 store_one(2);
920 break;
921
922 case Bytecodes::_istore_3:
923 case Bytecodes::_fstore_3:
924 case Bytecodes::_astore_3:
925 store_one(3);
926 break;
927
928 case Bytecodes::_wide:
929 fatal("Iterator should skip this bytecode");
930 break;
931
932 default:
933 tty->print("unexpected opcode: %d\n", instruction->cur_bc());
934 ShouldNotReachHere();
935 break;
936 }
937 }
938
939 void MethodLiveness::BasicBlock::load_two(int local) {
940 load_one(local);
941 load_one(local+1);
942 }
943
944 void MethodLiveness::BasicBlock::load_one(int local) {
945 if (!_kill.at(local)) {
946 _gen.at_put(local, true);
947 }
948 }
949
950 void MethodLiveness::BasicBlock::store_two(int local) {
951 store_one(local);
952 store_one(local+1);
953 }
954
955 void MethodLiveness::BasicBlock::store_one(int local) {
956 if (!_gen.at(local)) {
957 _kill.at_put(local, true);
958 }
959 }
960
961 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) {
962 // These set operations could be combined for efficiency if the
963 // performance of this analysis becomes an issue.
964 _entry.set_union(_normal_exit);
965 _entry.set_difference(_kill);
966 _entry.set_union(_gen);
967
968 // Note that we merge information from our exceptional successors
969 // just once, rather than at individual bytecodes.
970 _entry.set_union(_exception_exit);
971
972 if (TraceLivenessGen) {
973 tty->print_cr(" ** Visiting block at %d **", start_bci());
974 print_on(tty);
975 }
976
977 int i;
978 for (i=_normal_predecessors->length()-1; i>=0; i--) {
979 BasicBlock *block = _normal_predecessors->at(i);
980 if (block->merge_normal(_entry)) {
981 ml->work_list_add(block);
982 }
983 }
984 for (i=_exception_predecessors->length()-1; i>=0; i--) {
985 BasicBlock *block = _exception_predecessors->at(i);
986 if (block->merge_exception(_entry)) {
987 ml->work_list_add(block);
988 }
989 }
990 }
991
992 bool MethodLiveness::BasicBlock::merge_normal(BitMap other) {
993 return _normal_exit.set_union_with_result(other);
994 }
995
996 bool MethodLiveness::BasicBlock::merge_exception(BitMap other) {
997 return _exception_exit.set_union_with_result(other);
998 }
999
1000 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) {
1001 MethodLivenessResult answer(NEW_RESOURCE_ARRAY(BitMap::bm_word_t, _analyzer->bit_map_size_words()),
1002 _analyzer->bit_map_size_bits());
1003 answer.set_is_valid();
1004
1005 #ifndef ASSERT
1006 if (bci == start_bci()) {
1007 answer.set_from(_entry);
1008 return answer;
1009 }
1010 #endif
1011
1012 #ifdef ASSERT
1013 ResourceMark rm;
1014 BitMap g(_gen.size()); g.set_from(_gen);
1015 BitMap k(_kill.size()); k.set_from(_kill);
1016 #endif
1017 if (_last_bci != bci || trueInDebug) {
1018 ciBytecodeStream bytes(method);
1019 bytes.reset_to_bci(bci);
1020 bytes.set_max_bci(limit_bci());
1021 compute_gen_kill_range(&bytes);
1022 assert(_last_bci != bci ||
1023 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect");
1024 _last_bci = bci;
1025 }
1026
1027 answer.clear();
1028 answer.set_union(_normal_exit);
1029 answer.set_difference(_kill);
1030 answer.set_union(_gen);
1031 answer.set_union(_exception_exit);
1032
1033 #ifdef ASSERT
1034 if (bci == start_bci()) {
1035 assert(answer.is_same(_entry), "optimized answer must be accurate");
1036 }
1037 #endif
1038
1039 return answer;
1040 }
1041
1042 #ifndef PRODUCT
1043
1044 void MethodLiveness::BasicBlock::print_on(outputStream *os) const {
1045 os->print_cr("===================================================================");
1046 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci);
1047 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length());
1048 int i;
1049 for (i=0; i < _normal_predecessors->length(); i++) {
1050 os->print(" %4d", _normal_predecessors->at(i)->start_bci());
1051 }
1052 os->cr();
1053 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length());
1054 for (i=0; i < _exception_predecessors->length(); i++) {
1055 os->print(" %4d", _exception_predecessors->at(i)->start_bci());
1056 }
1057 os->cr();
1058 os->print (" Normal Exit : ");
1059 _normal_exit.print_on(os);
1060 os->print (" Gen : ");
1061 _gen.print_on(os);
1062 os->print (" Kill : ");
1063 _kill.print_on(os);
1064 os->print (" Exception Exit: ");
1065 _exception_exit.print_on(os);
1066 os->print (" Entry : ");
1067 _entry.print_on(os);
1068 }
1069
1070 #endif // PRODUCT