1 /*
2 * Copyright (c) 1998, 2016, 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 "memory/resourceArea.hpp"
34 #include "utilities/bitMap.inline.hpp"
35
36 // The MethodLiveness class performs a simple liveness analysis on a method
37 // in order to decide which locals are live (that is, will be used again) at
38 // a particular bytecode index (bci).
39 //
40 // The algorithm goes:
41 //
42 // 1. Break the method into a set of basic blocks. For each basic block we
43 // also keep track of its set of predecessors through normal control flow
44 // and predecessors through exceptional control flow.
45 //
46 // 2. For each basic block, compute two sets, gen (the set of values used before
47 // they are defined) and kill (the set of values defined before they are used)
48 // in the basic block. A basic block "needs" the locals in its gen set to
49 // perform its computation. A basic block "provides" values for the locals in
50 // its kill set, allowing a need from a successor to be ignored.
51 //
52 // 3. Liveness information (the set of locals which are needed) is pushed backwards through
53 // the program, from blocks to their predecessors. We compute and store liveness
54 // information for the normal/exceptional exit paths for each basic block. When
55 // this process reaches a fixed point, we are done.
56 //
57 // 4. When we are asked about the liveness at a particular bci with a basic block, we
58 // compute gen/kill sets which represent execution from that bci to the exit of
59 // its blocks. We then compose this range gen/kill information with the normal
60 // and exceptional exit information for the block to produce liveness information
61 // at that bci.
62 //
63 // The algorithm is approximate in many respects. Notably:
64 //
65 // 1. We do not do the analysis necessary to match jsr's with the appropriate ret.
66 // Instead we make the conservative assumption that any ret can return to any
67 // jsr return site.
68 // 2. Instead of computing the effects of exceptions at every instruction, we
69 // summarize the effects of all exceptional continuations from the block as
70 // a single set (_exception_exit), losing some information but simplifying the
71 // analysis.
72
73
74 //--------------------------------------------------------------------------
75 // The BitCounter class is used for counting the number of bits set in
76 // some BitMap. It is only used when collecting liveness statistics.
77
78 #ifndef PRODUCT
79
80 class BitCounter: public BitMapClosure {
81 private:
82 int _count;
83 public:
84 BitCounter() : _count(0) {}
85
86 // Callback when bit in map is set
87 virtual bool do_bit(size_t offset) {
88 _count++;
89 return true;
90 }
91
92 int count() {
93 return _count;
94 }
95 };
96
97
98 //--------------------------------------------------------------------------
99
100
101 // Counts
102 long MethodLiveness::_total_bytes = 0;
103 int MethodLiveness::_total_methods = 0;
104
105 long MethodLiveness::_total_blocks = 0;
106 int MethodLiveness::_max_method_blocks = 0;
107
108 long MethodLiveness::_total_edges = 0;
109 int MethodLiveness::_max_block_edges = 0;
110
111 long MethodLiveness::_total_exc_edges = 0;
112 int MethodLiveness::_max_block_exc_edges = 0;
113
114 long MethodLiveness::_total_method_locals = 0;
115 int MethodLiveness::_max_method_locals = 0;
116
117 long MethodLiveness::_total_locals_queried = 0;
118 long MethodLiveness::_total_live_locals_queried = 0;
119
120 long MethodLiveness::_total_visits = 0;
121
122 #endif
123
124 // Timers
125 elapsedTimer MethodLiveness::_time_build_graph;
126 elapsedTimer MethodLiveness::_time_gen_kill;
127 elapsedTimer MethodLiveness::_time_flow;
128 elapsedTimer MethodLiveness::_time_query;
129 elapsedTimer MethodLiveness::_time_total;
130
131 MethodLiveness::MethodLiveness(Arena* arena, ciMethod* method)
132 #ifdef COMPILER1
133 : _bci_block_start((uintptr_t*)arena->Amalloc((method->code_size() >> LogBitsPerByte) + 1), method->code_size())
134 #endif
135 {
136 _arena = arena;
137 _method = method;
138 _bit_map_size_bits = method->max_locals();
139 _bit_map_size_words = (_bit_map_size_bits / sizeof(unsigned int)) + 1;
140
141 #ifdef COMPILER1
142 _bci_block_start.clear();
143 #endif
144 }
145
146 void MethodLiveness::compute_liveness() {
147 #ifndef PRODUCT
148 if (TraceLivenessGen) {
149 tty->print_cr("################################################################");
150 tty->print("# Computing liveness information for ");
151 method()->print_short_name();
152 }
153
154 if (TimeLivenessAnalysis) _time_total.start();
155 #endif
156
157 {
158 TraceTime buildGraph(NULL, &_time_build_graph, TimeLivenessAnalysis);
159 init_basic_blocks();
160 }
161 {
162 TraceTime genKill(NULL, &_time_gen_kill, TimeLivenessAnalysis);
163 init_gen_kill();
164 }
165 {
166 TraceTime flow(NULL, &_time_flow, TimeLivenessAnalysis);
167 propagate_liveness();
168 }
169
170 #ifndef PRODUCT
171 if (TimeLivenessAnalysis) _time_total.stop();
172
173 if (TimeLivenessAnalysis) {
174 // Collect statistics
175 _total_bytes += method()->code_size();
176 _total_methods++;
177
178 int num_blocks = _block_count;
179 _total_blocks += num_blocks;
180 _max_method_blocks = MAX2(num_blocks,_max_method_blocks);
181
182 for (int i=0; i<num_blocks; i++) {
183 BasicBlock *block = _block_list[i];
184
185 int numEdges = block->_normal_predecessors->length();
186 int numExcEdges = block->_exception_predecessors->length();
187
188 _total_edges += numEdges;
189 _total_exc_edges += numExcEdges;
190 _max_block_edges = MAX2(numEdges,_max_block_edges);
191 _max_block_exc_edges = MAX2(numExcEdges,_max_block_exc_edges);
192 }
193
194 int numLocals = _bit_map_size_bits;
195 _total_method_locals += numLocals;
196 _max_method_locals = MAX2(numLocals,_max_method_locals);
197 }
198 #endif
199 }
200
201
202 void MethodLiveness::init_basic_blocks() {
203 bool bailout = false;
204
205 int method_len = method()->code_size();
206 ciMethodBlocks *mblocks = method()->get_method_blocks();
207
208 // Create an array to store the bci->BasicBlock mapping.
209 _block_map = new (arena()) GrowableArray<BasicBlock*>(arena(), method_len, method_len, NULL);
210
211 _block_count = mblocks->num_blocks();
212 _block_list = (BasicBlock **) arena()->Amalloc(sizeof(BasicBlock *) * _block_count);
213
214 // Used for patching up jsr/ret control flow.
215 GrowableArray<BasicBlock*>* jsr_exit_list = new GrowableArray<BasicBlock*>(5);
216 GrowableArray<BasicBlock*>* ret_list = new GrowableArray<BasicBlock*>(5);
217
218 // generate our block list from ciMethodBlocks
219 for (int blk = 0; blk < _block_count; blk++) {
220 ciBlock *cib = mblocks->block(blk);
221 int start_bci = cib->start_bci();
222 _block_list[blk] = new (arena()) BasicBlock(this, start_bci, cib->limit_bci());
223 _block_map->at_put(start_bci, _block_list[blk]);
224 #ifdef COMPILER1
225 // mark all bcis where a new basic block starts
226 _bci_block_start.set_bit(start_bci);
227 #endif // COMPILER1
228 }
229 // fill in the predecessors of blocks
230 ciBytecodeStream bytes(method());
231
232 for (int blk = 0; blk < _block_count; blk++) {
233 BasicBlock *current_block = _block_list[blk];
234 int bci = mblocks->block(blk)->control_bci();
235
236 if (bci == ciBlock::fall_through_bci) {
237 int limit = current_block->limit_bci();
238 if (limit < method_len) {
239 BasicBlock *next = _block_map->at(limit);
240 assert( next != NULL, "must be a block immediately following this one.");
241 next->add_normal_predecessor(current_block);
242 }
243 continue;
244 }
245 bytes.reset_to_bci(bci);
246 Bytecodes::Code code = bytes.next();
247 BasicBlock *dest;
248
249 // Now we need to interpret the instruction's effect
250 // on control flow.
251 assert (current_block != NULL, "we must have a current block");
252 switch (code) {
253 case Bytecodes::_ifeq:
254 case Bytecodes::_ifne:
255 case Bytecodes::_iflt:
256 case Bytecodes::_ifge:
257 case Bytecodes::_ifgt:
258 case Bytecodes::_ifle:
259 case Bytecodes::_if_icmpeq:
260 case Bytecodes::_if_icmpne:
261 case Bytecodes::_if_icmplt:
262 case Bytecodes::_if_icmpge:
263 case Bytecodes::_if_icmpgt:
264 case Bytecodes::_if_icmple:
265 case Bytecodes::_if_acmpeq:
266 case Bytecodes::_if_acmpne:
267 case Bytecodes::_ifnull:
268 case Bytecodes::_ifnonnull:
269 // Two way branch. Set predecessors at each destination.
270 dest = _block_map->at(bytes.next_bci());
271 assert(dest != NULL, "must be a block immediately following this one.");
272 dest->add_normal_predecessor(current_block);
273
274 dest = _block_map->at(bytes.get_dest());
275 assert(dest != NULL, "branch desination must start a block.");
276 dest->add_normal_predecessor(current_block);
277 break;
278 case Bytecodes::_goto:
279 dest = _block_map->at(bytes.get_dest());
280 assert(dest != NULL, "branch desination must start a block.");
281 dest->add_normal_predecessor(current_block);
282 break;
283 case Bytecodes::_goto_w:
284 dest = _block_map->at(bytes.get_far_dest());
285 assert(dest != NULL, "branch desination must start a block.");
286 dest->add_normal_predecessor(current_block);
287 break;
288 case Bytecodes::_tableswitch:
289 {
290 Bytecode_tableswitch tableswitch(&bytes);
291
292 int len = tableswitch.length();
293
294 dest = _block_map->at(bci + tableswitch.default_offset());
295 assert(dest != NULL, "branch desination must start a block.");
296 dest->add_normal_predecessor(current_block);
297 while (--len >= 0) {
298 dest = _block_map->at(bci + tableswitch.dest_offset_at(len));
299 assert(dest != NULL, "branch desination must start a block.");
300 dest->add_normal_predecessor(current_block);
301 }
302 break;
303 }
304
305 case Bytecodes::_lookupswitch:
306 {
307 Bytecode_lookupswitch lookupswitch(&bytes);
308
309 int npairs = lookupswitch.number_of_pairs();
310
311 dest = _block_map->at(bci + lookupswitch.default_offset());
312 assert(dest != NULL, "branch desination must start a block.");
313 dest->add_normal_predecessor(current_block);
314 while(--npairs >= 0) {
315 LookupswitchPair pair = lookupswitch.pair_at(npairs);
316 dest = _block_map->at( bci + pair.offset());
317 assert(dest != NULL, "branch desination must start a block.");
318 dest->add_normal_predecessor(current_block);
319 }
320 break;
321 }
322
323 case Bytecodes::_jsr:
324 {
325 assert(bytes.is_wide()==false, "sanity check");
326 dest = _block_map->at(bytes.get_dest());
327 assert(dest != NULL, "branch desination must start a block.");
328 dest->add_normal_predecessor(current_block);
329 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
330 assert(jsrExit != NULL, "jsr return bci must start a block.");
331 jsr_exit_list->append(jsrExit);
332 break;
333 }
334 case Bytecodes::_jsr_w:
335 {
336 dest = _block_map->at(bytes.get_far_dest());
337 assert(dest != NULL, "branch desination must start a block.");
338 dest->add_normal_predecessor(current_block);
339 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
340 assert(jsrExit != NULL, "jsr return bci must start a block.");
341 jsr_exit_list->append(jsrExit);
342 break;
343 }
344
345 case Bytecodes::_wide:
346 assert(false, "wide opcodes should not be seen here");
347 break;
348 case Bytecodes::_athrow:
349 case Bytecodes::_ireturn:
350 case Bytecodes::_lreturn:
351 case Bytecodes::_freturn:
352 case Bytecodes::_dreturn:
353 case Bytecodes::_areturn:
354 case Bytecodes::_return:
355 // These opcodes are not the normal predecessors of any other opcodes.
356 break;
357 case Bytecodes::_ret:
358 // We will patch up jsr/rets in a subsequent pass.
359 ret_list->append(current_block);
360 break;
361 case Bytecodes::_breakpoint:
362 // Bail out of there are breakpoints in here.
363 bailout = true;
364 break;
365 default:
366 // Do nothing.
367 break;
368 }
369 }
370 // Patch up the jsr/ret's. We conservatively assume that any ret
371 // can return to any jsr site.
372 int ret_list_len = ret_list->length();
373 int jsr_exit_list_len = jsr_exit_list->length();
374 if (ret_list_len > 0 && jsr_exit_list_len > 0) {
375 for (int i = jsr_exit_list_len - 1; i >= 0; i--) {
376 BasicBlock *jsrExit = jsr_exit_list->at(i);
377 for (int i = ret_list_len - 1; i >= 0; i--) {
378 jsrExit->add_normal_predecessor(ret_list->at(i));
379 }
380 }
381 }
382
383 // Compute exception edges.
384 for (int b=_block_count-1; b >= 0; b--) {
385 BasicBlock *block = _block_list[b];
386 int block_start = block->start_bci();
387 int block_limit = block->limit_bci();
388 ciExceptionHandlerStream handlers(method());
389 for (; !handlers.is_done(); handlers.next()) {
390 ciExceptionHandler* handler = handlers.handler();
391 int start = handler->start();
392 int limit = handler->limit();
393 int handler_bci = handler->handler_bci();
394
395 int intersect_start = MAX2(block_start, start);
396 int intersect_limit = MIN2(block_limit, limit);
397 if (intersect_start < intersect_limit) {
398 // The catch range has a nonempty intersection with this
399 // basic block. That means this basic block can be an
400 // exceptional predecessor.
401 _block_map->at(handler_bci)->add_exception_predecessor(block);
402
403 if (handler->is_catch_all()) {
404 // This is a catch-all block.
405 if (intersect_start == block_start && intersect_limit == block_limit) {
406 // The basic block is entirely contained in this catch-all block.
407 // Skip the rest of the exception handlers -- they can never be
408 // reached in execution.
409 break;
410 }
411 }
412 }
413 }
414 }
415 }
416
417 void MethodLiveness::init_gen_kill() {
418 for (int i=_block_count-1; i >= 0; i--) {
419 _block_list[i]->compute_gen_kill(method());
420 }
421 }
422
423 void MethodLiveness::propagate_liveness() {
424 int num_blocks = _block_count;
425 BasicBlock *block;
426
427 // We start our work list off with all blocks in it.
428 // Alternately, we could start off the work list with the list of all
429 // blocks which could exit the method directly, along with one block
430 // from any infinite loop. If this matters, it can be changed. It
431 // may not be clear from looking at the code, but the order of the
432 // workList will be the opposite of the creation order of the basic
433 // blocks, which should be decent for quick convergence (with the
434 // possible exception of exception handlers, which are all created
435 // early).
436 _work_list = NULL;
437 for (int i = 0; i < num_blocks; i++) {
438 block = _block_list[i];
439 block->set_next(_work_list);
440 block->set_on_work_list(true);
441 _work_list = block;
442 }
443
444
445 while ((block = work_list_get()) != NULL) {
446 block->propagate(this);
447 NOT_PRODUCT(_total_visits++;)
448 }
449 }
450
451 void MethodLiveness::work_list_add(BasicBlock *block) {
452 if (!block->on_work_list()) {
453 block->set_next(_work_list);
454 block->set_on_work_list(true);
455 _work_list = block;
456 }
457 }
458
459 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() {
460 BasicBlock *block = _work_list;
461 if (block != NULL) {
462 block->set_on_work_list(false);
463 _work_list = block->next();
464 }
465 return block;
466 }
467
468
469 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) {
470 int bci = entry_bci;
471 bool is_entry = false;
472 if (entry_bci == InvocationEntryBci) {
473 is_entry = true;
474 bci = 0;
475 }
476
477 MethodLivenessResult answer((BitMap::bm_word_t*)NULL,0);
478
479 if (_block_count > 0) {
480 if (TimeLivenessAnalysis) _time_total.start();
481 if (TimeLivenessAnalysis) _time_query.start();
482
483 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" );
484 BasicBlock *block = _block_map->at(bci);
485 // We may not be at the block start, so search backwards to find the block
486 // containing bci.
487 int t = bci;
488 while (block == NULL && t > 0) {
489 block = _block_map->at(--t);
490 }
491 assert( block != NULL, "invalid bytecode index; must be instruction index" );
492 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci.");
493
494 answer = block->get_liveness_at(method(), bci);
495
496 if (is_entry && method()->is_synchronized() && !method()->is_static()) {
497 // Synchronized methods use the receiver once on entry.
498 answer.at_put(0, true);
499 }
500
501 #ifndef PRODUCT
502 if (TraceLivenessQuery) {
503 tty->print("Liveness query of ");
504 method()->print_short_name();
505 tty->print(" @ %d : result is ", bci);
506 answer.print_on(tty);
507 }
508
509 if (TimeLivenessAnalysis) _time_query.stop();
510 if (TimeLivenessAnalysis) _time_total.stop();
511 #endif
512 }
513
514 #ifndef PRODUCT
515 if (TimeLivenessAnalysis) {
516 // Collect statistics.
517 _total_locals_queried += _bit_map_size_bits;
518 BitCounter counter;
519 answer.iterate(&counter);
520 _total_live_locals_queried += counter.count();
521 }
522 #endif
523
524 return answer;
525 }
526
527
528 #ifndef PRODUCT
529
530 void MethodLiveness::print_times() {
531 tty->print_cr ("Accumulated liveness analysis times/statistics:");
532 tty->print_cr ("-----------------------------------------------");
533 tty->print_cr (" Total : %3.3f sec.", _time_total.seconds());
534 tty->print_cr (" Build graph : %3.3f sec. (%2.2f%%)", _time_build_graph.seconds(),
535 _time_build_graph.seconds() * 100 / _time_total.seconds());
536 tty->print_cr (" Gen / Kill : %3.3f sec. (%2.2f%%)", _time_gen_kill.seconds(),
537 _time_gen_kill.seconds() * 100 / _time_total.seconds());
538 tty->print_cr (" Dataflow : %3.3f sec. (%2.2f%%)", _time_flow.seconds(),
539 _time_flow.seconds() * 100 / _time_total.seconds());
540 tty->print_cr (" Query : %3.3f sec. (%2.2f%%)", _time_query.seconds(),
541 _time_query.seconds() * 100 / _time_total.seconds());
542 tty->print_cr (" #bytes : %8ld (%3.0f bytes per sec)",
543 _total_bytes,
544 _total_bytes / _time_total.seconds());
545 tty->print_cr (" #methods : %8d (%3.0f methods per sec)",
546 _total_methods,
547 _total_methods / _time_total.seconds());
548 tty->print_cr (" avg locals : %3.3f max locals : %3d",
549 (float)_total_method_locals / _total_methods,
550 _max_method_locals);
551 tty->print_cr (" avg blocks : %3.3f max blocks : %3d",
552 (float)_total_blocks / _total_methods,
553 _max_method_blocks);
554 tty->print_cr (" avg bytes : %3.3f",
555 (float)_total_bytes / _total_methods);
556 tty->print_cr (" #blocks : %8ld",
557 _total_blocks);
558 tty->print_cr (" avg normal predecessors : %3.3f max normal predecessors : %3d",
559 (float)_total_edges / _total_blocks,
560 _max_block_edges);
561 tty->print_cr (" avg exception predecessors : %3.3f max exception predecessors : %3d",
562 (float)_total_exc_edges / _total_blocks,
563 _max_block_exc_edges);
564 tty->print_cr (" avg visits : %3.3f",
565 (float)_total_visits / _total_blocks);
566 tty->print_cr (" #locals queried : %8ld #live : %8ld %%live : %2.2f%%",
567 _total_locals_queried,
568 _total_live_locals_queried,
569 100.0 * _total_live_locals_queried / _total_locals_queried);
570 }
571
572 #endif
573
574
575 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) :
576 _gen((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
577 analyzer->bit_map_size_bits()),
578 _kill((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
579 analyzer->bit_map_size_bits()),
580 _entry((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
581 analyzer->bit_map_size_bits()),
582 _normal_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
583 analyzer->bit_map_size_bits()),
584 _exception_exit((uintptr_t*)analyzer->arena()->Amalloc(BytesPerWord * analyzer->bit_map_size_words()),
585 analyzer->bit_map_size_bits()),
586 _last_bci(-1) {
587 _analyzer = analyzer;
588 _start_bci = start;
589 _limit_bci = limit;
590 _normal_predecessors =
591 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
592 _exception_predecessors =
593 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, NULL);
594 _normal_exit.clear();
595 _exception_exit.clear();
596 _entry.clear();
597
598 // this initialization is not strictly necessary.
599 // _gen and _kill are cleared at the beginning of compute_gen_kill_range()
600 _gen.clear();
601 _kill.clear();
602 }
603
604
605
606 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) {
607 int start = _start_bci;
608 int limit = _limit_bci;
609
610 if (TraceLivenessGen) {
611 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci);
612 }
613
614 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors;
615
616 assert (start < split_bci && split_bci < limit, "improper split");
617
618 // Make a new block to cover the first half of the range.
619 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci);
620
621 // Assign correct values to the second half (this)
622 _normal_predecessors = first_half->_normal_predecessors;
623 _start_bci = split_bci;
624 add_normal_predecessor(first_half);
625
626 // Assign correct predecessors to the new first half
627 first_half->_normal_predecessors = save_predecessors;
628
629 return first_half;
630 }
631
632 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) {
633 ciBytecodeStream bytes(method);
634 bytes.reset_to_bci(start_bci());
635 bytes.set_max_bci(limit_bci());
636 compute_gen_kill_range(&bytes);
637
638 }
639
640 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) {
641 _gen.clear();
642 _kill.clear();
643
644 while (bytes->next() != ciBytecodeStream::EOBC()) {
645 compute_gen_kill_single(bytes);
646 }
647 }
648
649 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) {
650 int localNum;
651
652 // We prohibit _gen and _kill from having locals in common. If we
653 // know that one is definitely going to be applied before the other,
654 // we could save some computation time by relaxing this prohibition.
655
656 switch (instruction->cur_bc()) {
657 case Bytecodes::_nop:
658 case Bytecodes::_goto:
659 case Bytecodes::_goto_w:
660 case Bytecodes::_aconst_null:
661 case Bytecodes::_new:
662 case Bytecodes::_iconst_m1:
663 case Bytecodes::_iconst_0:
664 case Bytecodes::_iconst_1:
665 case Bytecodes::_iconst_2:
666 case Bytecodes::_iconst_3:
667 case Bytecodes::_iconst_4:
668 case Bytecodes::_iconst_5:
669 case Bytecodes::_fconst_0:
670 case Bytecodes::_fconst_1:
671 case Bytecodes::_fconst_2:
672 case Bytecodes::_bipush:
673 case Bytecodes::_sipush:
674 case Bytecodes::_lconst_0:
675 case Bytecodes::_lconst_1:
676 case Bytecodes::_dconst_0:
677 case Bytecodes::_dconst_1:
678 case Bytecodes::_ldc2_w:
679 case Bytecodes::_ldc:
680 case Bytecodes::_ldc_w:
681 case Bytecodes::_iaload:
682 case Bytecodes::_faload:
683 case Bytecodes::_baload:
684 case Bytecodes::_caload:
685 case Bytecodes::_saload:
686 case Bytecodes::_laload:
687 case Bytecodes::_daload:
688 case Bytecodes::_aaload:
689 case Bytecodes::_iastore:
690 case Bytecodes::_fastore:
691 case Bytecodes::_bastore:
692 case Bytecodes::_castore:
693 case Bytecodes::_sastore:
694 case Bytecodes::_lastore:
695 case Bytecodes::_dastore:
696 case Bytecodes::_aastore:
697 case Bytecodes::_pop:
698 case Bytecodes::_pop2:
699 case Bytecodes::_dup:
700 case Bytecodes::_dup_x1:
701 case Bytecodes::_dup_x2:
702 case Bytecodes::_dup2:
703 case Bytecodes::_dup2_x1:
704 case Bytecodes::_dup2_x2:
705 case Bytecodes::_swap:
706 case Bytecodes::_iadd:
707 case Bytecodes::_fadd:
708 case Bytecodes::_isub:
709 case Bytecodes::_fsub:
710 case Bytecodes::_imul:
711 case Bytecodes::_fmul:
712 case Bytecodes::_idiv:
713 case Bytecodes::_fdiv:
714 case Bytecodes::_irem:
715 case Bytecodes::_frem:
716 case Bytecodes::_ishl:
717 case Bytecodes::_ishr:
718 case Bytecodes::_iushr:
719 case Bytecodes::_iand:
720 case Bytecodes::_ior:
721 case Bytecodes::_ixor:
722 case Bytecodes::_l2f:
723 case Bytecodes::_l2i:
724 case Bytecodes::_d2f:
725 case Bytecodes::_d2i:
726 case Bytecodes::_fcmpl:
727 case Bytecodes::_fcmpg:
728 case Bytecodes::_ladd:
729 case Bytecodes::_dadd:
730 case Bytecodes::_lsub:
731 case Bytecodes::_dsub:
732 case Bytecodes::_lmul:
733 case Bytecodes::_dmul:
734 case Bytecodes::_ldiv:
735 case Bytecodes::_ddiv:
736 case Bytecodes::_lrem:
737 case Bytecodes::_drem:
738 case Bytecodes::_land:
739 case Bytecodes::_lor:
740 case Bytecodes::_lxor:
741 case Bytecodes::_ineg:
742 case Bytecodes::_fneg:
743 case Bytecodes::_i2f:
744 case Bytecodes::_f2i:
745 case Bytecodes::_i2c:
746 case Bytecodes::_i2s:
747 case Bytecodes::_i2b:
748 case Bytecodes::_lneg:
749 case Bytecodes::_dneg:
750 case Bytecodes::_l2d:
751 case Bytecodes::_d2l:
752 case Bytecodes::_lshl:
753 case Bytecodes::_lshr:
754 case Bytecodes::_lushr:
755 case Bytecodes::_i2l:
756 case Bytecodes::_i2d:
757 case Bytecodes::_f2l:
758 case Bytecodes::_f2d:
759 case Bytecodes::_lcmp:
760 case Bytecodes::_dcmpl:
761 case Bytecodes::_dcmpg:
762 case Bytecodes::_ifeq:
763 case Bytecodes::_ifne:
764 case Bytecodes::_iflt:
765 case Bytecodes::_ifge:
766 case Bytecodes::_ifgt:
767 case Bytecodes::_ifle:
768 case Bytecodes::_tableswitch:
769 case Bytecodes::_ireturn:
770 case Bytecodes::_freturn:
771 case Bytecodes::_if_icmpeq:
772 case Bytecodes::_if_icmpne:
773 case Bytecodes::_if_icmplt:
774 case Bytecodes::_if_icmpge:
775 case Bytecodes::_if_icmpgt:
776 case Bytecodes::_if_icmple:
777 case Bytecodes::_lreturn:
778 case Bytecodes::_dreturn:
779 case Bytecodes::_if_acmpeq:
780 case Bytecodes::_if_acmpne:
781 case Bytecodes::_jsr:
782 case Bytecodes::_jsr_w:
783 case Bytecodes::_getstatic:
784 case Bytecodes::_putstatic:
785 case Bytecodes::_getfield:
786 case Bytecodes::_putfield:
787 case Bytecodes::_invokevirtual:
788 case Bytecodes::_invokespecial:
789 case Bytecodes::_invokestatic:
790 case Bytecodes::_invokeinterface:
791 case Bytecodes::_invokedynamic:
792 case Bytecodes::_newarray:
793 case Bytecodes::_anewarray:
794 case Bytecodes::_checkcast:
795 case Bytecodes::_arraylength:
796 case Bytecodes::_instanceof:
797 case Bytecodes::_athrow:
798 case Bytecodes::_areturn:
799 case Bytecodes::_monitorenter:
800 case Bytecodes::_monitorexit:
801 case Bytecodes::_ifnull:
802 case Bytecodes::_ifnonnull:
803 case Bytecodes::_multianewarray:
804 case Bytecodes::_lookupswitch:
805 // These bytecodes have no effect on the method's locals.
806 break;
807
808 case Bytecodes::_return:
809 if (instruction->method()->intrinsic_id() == vmIntrinsics::_Object_init) {
810 // return from Object.init implicitly registers a finalizer
811 // for the receiver if needed, so keep it alive.
812 load_one(0);
813 }
814 break;
815
816
817 case Bytecodes::_lload:
818 case Bytecodes::_dload:
819 load_two(instruction->get_index());
820 break;
821
822 case Bytecodes::_lload_0:
823 case Bytecodes::_dload_0:
824 load_two(0);
825 break;
826
827 case Bytecodes::_lload_1:
828 case Bytecodes::_dload_1:
829 load_two(1);
830 break;
831
832 case Bytecodes::_lload_2:
833 case Bytecodes::_dload_2:
834 load_two(2);
835 break;
836
837 case Bytecodes::_lload_3:
838 case Bytecodes::_dload_3:
839 load_two(3);
840 break;
841
842 case Bytecodes::_iload:
843 case Bytecodes::_iinc:
844 case Bytecodes::_fload:
845 case Bytecodes::_aload:
846 case Bytecodes::_ret:
847 load_one(instruction->get_index());
848 break;
849
850 case Bytecodes::_iload_0:
851 case Bytecodes::_fload_0:
852 case Bytecodes::_aload_0:
853 load_one(0);
854 break;
855
856 case Bytecodes::_iload_1:
857 case Bytecodes::_fload_1:
858 case Bytecodes::_aload_1:
859 load_one(1);
860 break;
861
862 case Bytecodes::_iload_2:
863 case Bytecodes::_fload_2:
864 case Bytecodes::_aload_2:
865 load_one(2);
866 break;
867
868 case Bytecodes::_iload_3:
869 case Bytecodes::_fload_3:
870 case Bytecodes::_aload_3:
871 load_one(3);
872 break;
873
874 case Bytecodes::_lstore:
875 case Bytecodes::_dstore:
876 store_two(localNum = instruction->get_index());
877 break;
878
879 case Bytecodes::_lstore_0:
880 case Bytecodes::_dstore_0:
881 store_two(0);
882 break;
883
884 case Bytecodes::_lstore_1:
885 case Bytecodes::_dstore_1:
886 store_two(1);
887 break;
888
889 case Bytecodes::_lstore_2:
890 case Bytecodes::_dstore_2:
891 store_two(2);
892 break;
893
894 case Bytecodes::_lstore_3:
895 case Bytecodes::_dstore_3:
896 store_two(3);
897 break;
898
899 case Bytecodes::_istore:
900 case Bytecodes::_fstore:
901 case Bytecodes::_astore:
902 store_one(instruction->get_index());
903 break;
904
905 case Bytecodes::_istore_0:
906 case Bytecodes::_fstore_0:
907 case Bytecodes::_astore_0:
908 store_one(0);
909 break;
910
911 case Bytecodes::_istore_1:
912 case Bytecodes::_fstore_1:
913 case Bytecodes::_astore_1:
914 store_one(1);
915 break;
916
917 case Bytecodes::_istore_2:
918 case Bytecodes::_fstore_2:
919 case Bytecodes::_astore_2:
920 store_one(2);
921 break;
922
923 case Bytecodes::_istore_3:
924 case Bytecodes::_fstore_3:
925 case Bytecodes::_astore_3:
926 store_one(3);
927 break;
928
929 case Bytecodes::_wide:
930 fatal("Iterator should skip this bytecode");
931 break;
932
933 default:
934 tty->print("unexpected opcode: %d\n", instruction->cur_bc());
935 ShouldNotReachHere();
936 break;
937 }
938 }
939
940 void MethodLiveness::BasicBlock::load_two(int local) {
941 load_one(local);
942 load_one(local+1);
943 }
944
945 void MethodLiveness::BasicBlock::load_one(int local) {
946 if (!_kill.at(local)) {
947 _gen.at_put(local, true);
948 }
949 }
950
951 void MethodLiveness::BasicBlock::store_two(int local) {
952 store_one(local);
953 store_one(local+1);
954 }
955
956 void MethodLiveness::BasicBlock::store_one(int local) {
957 if (!_gen.at(local)) {
958 _kill.at_put(local, true);
959 }
960 }
961
962 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) {
963 // These set operations could be combined for efficiency if the
964 // performance of this analysis becomes an issue.
965 _entry.set_union(_normal_exit);
966 _entry.set_difference(_kill);
967 _entry.set_union(_gen);
968
969 // Note that we merge information from our exceptional successors
970 // just once, rather than at individual bytecodes.
971 _entry.set_union(_exception_exit);
972
973 if (TraceLivenessGen) {
974 tty->print_cr(" ** Visiting block at %d **", start_bci());
975 print_on(tty);
976 }
977
978 int i;
979 for (i=_normal_predecessors->length()-1; i>=0; i--) {
980 BasicBlock *block = _normal_predecessors->at(i);
981 if (block->merge_normal(_entry)) {
982 ml->work_list_add(block);
983 }
984 }
985 for (i=_exception_predecessors->length()-1; i>=0; i--) {
986 BasicBlock *block = _exception_predecessors->at(i);
987 if (block->merge_exception(_entry)) {
988 ml->work_list_add(block);
989 }
990 }
991 }
992
993 bool MethodLiveness::BasicBlock::merge_normal(BitMap other) {
994 return _normal_exit.set_union_with_result(other);
995 }
996
997 bool MethodLiveness::BasicBlock::merge_exception(BitMap other) {
998 return _exception_exit.set_union_with_result(other);
999 }
1000
1001 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) {
1002 MethodLivenessResult answer(NEW_RESOURCE_ARRAY(BitMap::bm_word_t, _analyzer->bit_map_size_words()),
1003 _analyzer->bit_map_size_bits());
1004 answer.set_is_valid();
1005
1006 #ifndef ASSERT
1007 if (bci == start_bci()) {
1008 answer.set_from(_entry);
1009 return answer;
1010 }
1011 #endif
1012
1013 #ifdef ASSERT
1014 ResourceMark rm;
1015 BitMap g(_gen.size()); g.set_from(_gen);
1016 BitMap k(_kill.size()); k.set_from(_kill);
1017 #endif
1018 if (_last_bci != bci || trueInDebug) {
1019 ciBytecodeStream bytes(method);
1020 bytes.reset_to_bci(bci);
1021 bytes.set_max_bci(limit_bci());
1022 compute_gen_kill_range(&bytes);
1023 assert(_last_bci != bci ||
1024 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect");
1025 _last_bci = bci;
1026 }
1027
1028 answer.clear();
1029 answer.set_union(_normal_exit);
1030 answer.set_difference(_kill);
1031 answer.set_union(_gen);
1032 answer.set_union(_exception_exit);
1033
1034 #ifdef ASSERT
1035 if (bci == start_bci()) {
1036 assert(answer.is_same(_entry), "optimized answer must be accurate");
1037 }
1038 #endif
1039
1040 return answer;
1041 }
1042
1043 #ifndef PRODUCT
1044
1045 void MethodLiveness::BasicBlock::print_on(outputStream *os) const {
1046 os->print_cr("===================================================================");
1047 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci);
1048 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length());
1049 int i;
1050 for (i=0; i < _normal_predecessors->length(); i++) {
1051 os->print(" %4d", _normal_predecessors->at(i)->start_bci());
1052 }
1053 os->cr();
1054 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length());
1055 for (i=0; i < _exception_predecessors->length(); i++) {
1056 os->print(" %4d", _exception_predecessors->at(i)->start_bci());
1057 }
1058 os->cr();
1059 os->print (" Normal Exit : ");
1060 _normal_exit.print_on(os);
1061 os->print (" Gen : ");
1062 _gen.print_on(os);
1063 os->print (" Kill : ");
1064 _kill.print_on(os);
1065 os->print (" Exception Exit: ");
1066 _exception_exit.print_on(os);
1067 os->print (" Entry : ");
1068 _entry.print_on(os);
1069 }
1070
1071 #endif // PRODUCT