1 /*
2 * Copyright (c) 1998, 2025, 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 "ci/ciMethod.hpp"
26 #include "ci/ciMethodBlocks.hpp"
27 #include "ci/ciStreams.hpp"
28 #include "classfile/vmIntrinsics.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 MethodLiveness::MethodLiveness(Arena* arena, ciMethod* method)
74 #ifdef COMPILER1
75 : _bci_block_start(arena, method->code_size())
76 #endif
77 {
78 _arena = arena;
79 _method = method;
80 _bit_map_size_bits = method->max_locals();
81 }
82
83 void MethodLiveness::compute_liveness() {
84 #ifndef PRODUCT
85 if (TraceLivenessGen) {
86 tty->print_cr("################################################################");
87 tty->print("# Computing liveness information for ");
88 method()->print_short_name();
89 }
90 #endif
91
92 init_basic_blocks();
93 init_gen_kill();
94 propagate_liveness();
95 }
96
97
98 void MethodLiveness::init_basic_blocks() {
99 int method_len = method()->code_size();
100 ciMethodBlocks *mblocks = method()->get_method_blocks();
101
102 // Create an array to store the bci->BasicBlock mapping.
103 _block_map = new (arena()) GrowableArray<BasicBlock*>(arena(), method_len, method_len, nullptr);
104
105 _block_count = mblocks->num_blocks();
106 _block_list = (BasicBlock **) arena()->Amalloc(sizeof(BasicBlock *) * _block_count);
107
108 // Used for patching up jsr/ret control flow.
109 GrowableArray<BasicBlock*>* jsr_exit_list = new GrowableArray<BasicBlock*>(5);
110 GrowableArray<BasicBlock*>* ret_list = new GrowableArray<BasicBlock*>(5);
111
112 // generate our block list from ciMethodBlocks
113 for (int blk = 0; blk < _block_count; blk++) {
114 ciBlock *cib = mblocks->block(blk);
115 int start_bci = cib->start_bci();
116 _block_list[blk] = new (arena()) BasicBlock(this, start_bci, cib->limit_bci());
117 _block_map->at_put(start_bci, _block_list[blk]);
118 #ifdef COMPILER1
119 // mark all bcis where a new basic block starts
120 _bci_block_start.set_bit(start_bci);
121 #endif // COMPILER1
122 }
123 // fill in the predecessors of blocks
124 ciBytecodeStream bytes(method());
125
126 for (int blk = 0; blk < _block_count; blk++) {
127 BasicBlock *current_block = _block_list[blk];
128 int bci = mblocks->block(blk)->control_bci();
129
130 if (bci == ciBlock::fall_through_bci) {
131 int limit = current_block->limit_bci();
132 if (limit < method_len) {
133 BasicBlock *next = _block_map->at(limit);
134 assert( next != nullptr, "must be a block immediately following this one.");
135 next->add_normal_predecessor(current_block);
136 }
137 continue;
138 }
139 bytes.reset_to_bci(bci);
140 Bytecodes::Code code = bytes.next();
141 BasicBlock *dest;
142
143 // Now we need to interpret the instruction's effect
144 // on control flow.
145 assert (current_block != nullptr, "we must have a current block");
146 switch (code) {
147 case Bytecodes::_ifeq:
148 case Bytecodes::_ifne:
149 case Bytecodes::_iflt:
150 case Bytecodes::_ifge:
151 case Bytecodes::_ifgt:
152 case Bytecodes::_ifle:
153 case Bytecodes::_if_icmpeq:
154 case Bytecodes::_if_icmpne:
155 case Bytecodes::_if_icmplt:
156 case Bytecodes::_if_icmpge:
157 case Bytecodes::_if_icmpgt:
158 case Bytecodes::_if_icmple:
159 case Bytecodes::_if_acmpeq:
160 case Bytecodes::_if_acmpne:
161 case Bytecodes::_ifnull:
162 case Bytecodes::_ifnonnull:
163 // Two way branch. Set predecessors at each destination.
164 if (bytes.next_bci() < method_len) {
165 dest = _block_map->at(bytes.next_bci());
166 assert(dest != nullptr, "must be a block immediately following this one.");
167 dest->add_normal_predecessor(current_block);
168 }
169 dest = _block_map->at(bytes.get_dest());
170 assert(dest != nullptr, "branch destination must start a block.");
171 dest->add_normal_predecessor(current_block);
172 break;
173 case Bytecodes::_goto:
174 dest = _block_map->at(bytes.get_dest());
175 assert(dest != nullptr, "branch destination must start a block.");
176 dest->add_normal_predecessor(current_block);
177 break;
178 case Bytecodes::_goto_w:
179 dest = _block_map->at(bytes.get_far_dest());
180 assert(dest != nullptr, "branch destination must start a block.");
181 dest->add_normal_predecessor(current_block);
182 break;
183 case Bytecodes::_tableswitch:
184 {
185 Bytecode_tableswitch tableswitch(&bytes);
186
187 int len = tableswitch.length();
188
189 dest = _block_map->at(bci + tableswitch.default_offset());
190 assert(dest != nullptr, "branch destination must start a block.");
191 dest->add_normal_predecessor(current_block);
192 while (--len >= 0) {
193 dest = _block_map->at(bci + tableswitch.dest_offset_at(len));
194 assert(dest != nullptr, "branch destination must start a block.");
195 dest->add_normal_predecessor(current_block);
196 }
197 break;
198 }
199
200 case Bytecodes::_lookupswitch:
201 {
202 Bytecode_lookupswitch lookupswitch(&bytes);
203
204 int npairs = lookupswitch.number_of_pairs();
205
206 dest = _block_map->at(bci + lookupswitch.default_offset());
207 assert(dest != nullptr, "branch destination must start a block.");
208 dest->add_normal_predecessor(current_block);
209 while(--npairs >= 0) {
210 LookupswitchPair pair = lookupswitch.pair_at(npairs);
211 dest = _block_map->at( bci + pair.offset());
212 assert(dest != nullptr, "branch destination must start a block.");
213 dest->add_normal_predecessor(current_block);
214 }
215 break;
216 }
217
218 case Bytecodes::_jsr:
219 {
220 assert(bytes.is_wide()==false, "sanity check");
221 dest = _block_map->at(bytes.get_dest());
222 assert(dest != nullptr, "branch destination must start a block.");
223 dest->add_normal_predecessor(current_block);
224 if (bci + Bytecodes::length_for(code) >= method_len) {
225 break;
226 }
227 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
228 assert(jsrExit != nullptr, "jsr return bci must start a block.");
229 jsr_exit_list->append(jsrExit);
230 break;
231 }
232 case Bytecodes::_jsr_w:
233 {
234 dest = _block_map->at(bytes.get_far_dest());
235 assert(dest != nullptr, "branch destination must start a block.");
236 dest->add_normal_predecessor(current_block);
237 if (bci + Bytecodes::length_for(code) >= method_len) {
238 break;
239 }
240 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
241 assert(jsrExit != nullptr, "jsr return bci must start a block.");
242 jsr_exit_list->append(jsrExit);
243 break;
244 }
245
246 case Bytecodes::_wide:
247 assert(false, "wide opcodes should not be seen here");
248 break;
249 case Bytecodes::_athrow:
250 case Bytecodes::_ireturn:
251 case Bytecodes::_lreturn:
252 case Bytecodes::_freturn:
253 case Bytecodes::_dreturn:
254 case Bytecodes::_areturn:
255 case Bytecodes::_return:
256 // These opcodes are not the normal predecessors of any other opcodes.
257 break;
258 case Bytecodes::_ret:
259 // We will patch up jsr/rets in a subsequent pass.
260 ret_list->append(current_block);
261 break;
262 default:
263 // Do nothing.
264 break;
265 }
266 }
267 // Patch up the jsr/ret's. We conservatively assume that any ret
268 // can return to any jsr site.
269 int ret_list_len = ret_list->length();
270 int jsr_exit_list_len = jsr_exit_list->length();
271 if (ret_list_len > 0 && jsr_exit_list_len > 0) {
272 for (int i = jsr_exit_list_len - 1; i >= 0; i--) {
273 BasicBlock *jsrExit = jsr_exit_list->at(i);
274 for (int i = ret_list_len - 1; i >= 0; i--) {
275 jsrExit->add_normal_predecessor(ret_list->at(i));
276 }
277 }
278 }
279
280 // Compute exception edges.
281 for (int b=_block_count-1; b >= 0; b--) {
282 BasicBlock *block = _block_list[b];
283 int block_start = block->start_bci();
284 int block_limit = block->limit_bci();
285 ciExceptionHandlerStream handlers(method());
286 for (; !handlers.is_done(); handlers.next()) {
287 ciExceptionHandler* handler = handlers.handler();
288 int start = handler->start();
289 int limit = handler->limit();
290 int handler_bci = handler->handler_bci();
291
292 int intersect_start = MAX2(block_start, start);
293 int intersect_limit = MIN2(block_limit, limit);
294 if (intersect_start < intersect_limit) {
295 // The catch range has a nonempty intersection with this
296 // basic block. That means this basic block can be an
297 // exceptional predecessor.
298 _block_map->at(handler_bci)->add_exception_predecessor(block);
299
300 if (handler->is_catch_all()) {
301 // This is a catch-all block.
302 if (intersect_start == block_start && intersect_limit == block_limit) {
303 // The basic block is entirely contained in this catch-all block.
304 // Skip the rest of the exception handlers -- they can never be
305 // reached in execution.
306 break;
307 }
308 }
309 }
310 }
311 }
312 }
313
314 void MethodLiveness::init_gen_kill() {
315 for (int i=_block_count-1; i >= 0; i--) {
316 _block_list[i]->compute_gen_kill(method());
317 }
318 }
319
320 void MethodLiveness::propagate_liveness() {
321 int num_blocks = _block_count;
322 BasicBlock *block;
323
324 // We start our work list off with all blocks in it.
325 // Alternately, we could start off the work list with the list of all
326 // blocks which could exit the method directly, along with one block
327 // from any infinite loop. If this matters, it can be changed. It
328 // may not be clear from looking at the code, but the order of the
329 // workList will be the opposite of the creation order of the basic
330 // blocks, which should be decent for quick convergence (with the
331 // possible exception of exception handlers, which are all created
332 // early).
333 _work_list = nullptr;
334 for (int i = 0; i < num_blocks; i++) {
335 block = _block_list[i];
336 block->set_next(_work_list);
337 block->set_on_work_list(true);
338 _work_list = block;
339 }
340
341
342 while ((block = work_list_get()) != nullptr) {
343 block->propagate(this);
344 }
345 }
346
347 void MethodLiveness::work_list_add(BasicBlock *block) {
348 if (!block->on_work_list()) {
349 block->set_next(_work_list);
350 block->set_on_work_list(true);
351 _work_list = block;
352 }
353 }
354
355 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() {
356 BasicBlock *block = _work_list;
357 if (block != nullptr) {
358 block->set_on_work_list(false);
359 _work_list = block->next();
360 }
361 return block;
362 }
363
364
365 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) {
366 int bci = entry_bci;
367 bool is_entry = false;
368 if (entry_bci == InvocationEntryBci) {
369 is_entry = true;
370 bci = 0;
371 }
372
373 MethodLivenessResult answer;
374
375 if (_block_count > 0) {
376
377 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" );
378 BasicBlock *block = _block_map->at(bci);
379 // We may not be at the block start, so search backwards to find the block
380 // containing bci.
381 int t = bci;
382 while (block == nullptr && t > 0) {
383 block = _block_map->at(--t);
384 }
385 guarantee(block != nullptr, "invalid bytecode index; must be instruction index");
386 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci.");
387
388 answer = block->get_liveness_at(method(), bci);
389
390 if (is_entry && method()->is_synchronized() && !method()->is_static()) {
391 // Synchronized methods use the receiver once on entry.
392 answer.at_put(0, true);
393 }
394
395 #ifndef PRODUCT
396 if (TraceLivenessQuery) {
397 tty->print("Liveness query of ");
398 method()->print_short_name();
399 tty->print(" @ %d : result is ", bci);
400 answer.print_on(tty);
401 }
402 #endif
403 }
404
405 return answer;
406 }
407
408 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) :
409 _entry(analyzer->arena(), analyzer->bit_map_size_bits()),
410 _normal_exit(analyzer->arena(), analyzer->bit_map_size_bits()),
411 _exception_exit(analyzer->arena(), analyzer->bit_map_size_bits()),
412 _gen(analyzer->arena(), analyzer->bit_map_size_bits()),
413 _kill(analyzer->arena(), analyzer->bit_map_size_bits()),
414 _last_bci(-1) {
415 _analyzer = analyzer;
416 _start_bci = start;
417 _limit_bci = limit;
418 _normal_predecessors =
419 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr);
420 _exception_predecessors =
421 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr);
422 }
423
424
425
426 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) {
427 int start = _start_bci;
428 int limit = _limit_bci;
429
430 if (TraceLivenessGen) {
431 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci);
432 }
433
434 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors;
435
436 assert (start < split_bci && split_bci < limit, "improper split");
437
438 // Make a new block to cover the first half of the range.
439 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci);
440
441 // Assign correct values to the second half (this)
442 _normal_predecessors = first_half->_normal_predecessors;
443 _start_bci = split_bci;
444 add_normal_predecessor(first_half);
445
446 // Assign correct predecessors to the new first half
447 first_half->_normal_predecessors = save_predecessors;
448
449 return first_half;
450 }
451
452 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) {
453 ciBytecodeStream bytes(method);
454 bytes.reset_to_bci(start_bci());
455 bytes.set_max_bci(limit_bci());
456 compute_gen_kill_range(&bytes);
457
458 }
459
460 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) {
461 _gen.clear();
462 _kill.clear();
463
464 while (bytes->next() != ciBytecodeStream::EOBC()) {
465 compute_gen_kill_single(bytes);
466 }
467 }
468
469 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) {
470 // We prohibit _gen and _kill from having locals in common. If we
471 // know that one is definitely going to be applied before the other,
472 // we could save some computation time by relaxing this prohibition.
473
474 switch (instruction->cur_bc()) {
475 case Bytecodes::_nop:
476 case Bytecodes::_goto:
477 case Bytecodes::_goto_w:
478 case Bytecodes::_aconst_null:
479 case Bytecodes::_new:
480 case Bytecodes::_iconst_m1:
481 case Bytecodes::_iconst_0:
482 case Bytecodes::_iconst_1:
483 case Bytecodes::_iconst_2:
484 case Bytecodes::_iconst_3:
485 case Bytecodes::_iconst_4:
486 case Bytecodes::_iconst_5:
487 case Bytecodes::_fconst_0:
488 case Bytecodes::_fconst_1:
489 case Bytecodes::_fconst_2:
490 case Bytecodes::_bipush:
491 case Bytecodes::_sipush:
492 case Bytecodes::_lconst_0:
493 case Bytecodes::_lconst_1:
494 case Bytecodes::_dconst_0:
495 case Bytecodes::_dconst_1:
496 case Bytecodes::_ldc2_w:
497 case Bytecodes::_ldc:
498 case Bytecodes::_ldc_w:
499 case Bytecodes::_iaload:
500 case Bytecodes::_faload:
501 case Bytecodes::_baload:
502 case Bytecodes::_caload:
503 case Bytecodes::_saload:
504 case Bytecodes::_laload:
505 case Bytecodes::_daload:
506 case Bytecodes::_aaload:
507 case Bytecodes::_iastore:
508 case Bytecodes::_fastore:
509 case Bytecodes::_bastore:
510 case Bytecodes::_castore:
511 case Bytecodes::_sastore:
512 case Bytecodes::_lastore:
513 case Bytecodes::_dastore:
514 case Bytecodes::_aastore:
515 case Bytecodes::_pop:
516 case Bytecodes::_pop2:
517 case Bytecodes::_dup:
518 case Bytecodes::_dup_x1:
519 case Bytecodes::_dup_x2:
520 case Bytecodes::_dup2:
521 case Bytecodes::_dup2_x1:
522 case Bytecodes::_dup2_x2:
523 case Bytecodes::_swap:
524 case Bytecodes::_iadd:
525 case Bytecodes::_fadd:
526 case Bytecodes::_isub:
527 case Bytecodes::_fsub:
528 case Bytecodes::_imul:
529 case Bytecodes::_fmul:
530 case Bytecodes::_idiv:
531 case Bytecodes::_fdiv:
532 case Bytecodes::_irem:
533 case Bytecodes::_frem:
534 case Bytecodes::_ishl:
535 case Bytecodes::_ishr:
536 case Bytecodes::_iushr:
537 case Bytecodes::_iand:
538 case Bytecodes::_ior:
539 case Bytecodes::_ixor:
540 case Bytecodes::_l2f:
541 case Bytecodes::_l2i:
542 case Bytecodes::_d2f:
543 case Bytecodes::_d2i:
544 case Bytecodes::_fcmpl:
545 case Bytecodes::_fcmpg:
546 case Bytecodes::_ladd:
547 case Bytecodes::_dadd:
548 case Bytecodes::_lsub:
549 case Bytecodes::_dsub:
550 case Bytecodes::_lmul:
551 case Bytecodes::_dmul:
552 case Bytecodes::_ldiv:
553 case Bytecodes::_ddiv:
554 case Bytecodes::_lrem:
555 case Bytecodes::_drem:
556 case Bytecodes::_land:
557 case Bytecodes::_lor:
558 case Bytecodes::_lxor:
559 case Bytecodes::_ineg:
560 case Bytecodes::_fneg:
561 case Bytecodes::_i2f:
562 case Bytecodes::_f2i:
563 case Bytecodes::_i2c:
564 case Bytecodes::_i2s:
565 case Bytecodes::_i2b:
566 case Bytecodes::_lneg:
567 case Bytecodes::_dneg:
568 case Bytecodes::_l2d:
569 case Bytecodes::_d2l:
570 case Bytecodes::_lshl:
571 case Bytecodes::_lshr:
572 case Bytecodes::_lushr:
573 case Bytecodes::_i2l:
574 case Bytecodes::_i2d:
575 case Bytecodes::_f2l:
576 case Bytecodes::_f2d:
577 case Bytecodes::_lcmp:
578 case Bytecodes::_dcmpl:
579 case Bytecodes::_dcmpg:
580 case Bytecodes::_ifeq:
581 case Bytecodes::_ifne:
582 case Bytecodes::_iflt:
583 case Bytecodes::_ifge:
584 case Bytecodes::_ifgt:
585 case Bytecodes::_ifle:
586 case Bytecodes::_tableswitch:
587 case Bytecodes::_ireturn:
588 case Bytecodes::_freturn:
589 case Bytecodes::_if_icmpeq:
590 case Bytecodes::_if_icmpne:
591 case Bytecodes::_if_icmplt:
592 case Bytecodes::_if_icmpge:
593 case Bytecodes::_if_icmpgt:
594 case Bytecodes::_if_icmple:
595 case Bytecodes::_lreturn:
596 case Bytecodes::_dreturn:
597 case Bytecodes::_if_acmpeq:
598 case Bytecodes::_if_acmpne:
599 case Bytecodes::_jsr:
600 case Bytecodes::_jsr_w:
601 case Bytecodes::_getstatic:
602 case Bytecodes::_putstatic:
603 case Bytecodes::_getfield:
604 case Bytecodes::_putfield:
605 case Bytecodes::_invokevirtual:
606 case Bytecodes::_invokespecial:
607 case Bytecodes::_invokestatic:
608 case Bytecodes::_invokeinterface:
609 case Bytecodes::_invokedynamic:
610 case Bytecodes::_newarray:
611 case Bytecodes::_anewarray:
612 case Bytecodes::_checkcast:
613 case Bytecodes::_arraylength:
614 case Bytecodes::_instanceof:
615 case Bytecodes::_athrow:
616 case Bytecodes::_areturn:
617 case Bytecodes::_monitorenter:
618 case Bytecodes::_monitorexit:
619 case Bytecodes::_ifnull:
620 case Bytecodes::_ifnonnull:
621 case Bytecodes::_multianewarray:
622 case Bytecodes::_lookupswitch:
623 // These bytecodes have no effect on the method's locals.
624 break;
625
626 case Bytecodes::_return: {627 ciMethod* method = instruction->method();628 ciInstanceKlass* holder = method->holder();629 const bool abstract_klass = holder->is_abstract();630 const bool concrete_value_klass = !abstract_klass && holder->is_inlinetype();631 if (method->intrinsic_id() == vmIntrinsics::_Object_init ||632 (method->is_object_constructor() && (concrete_value_klass || abstract_klass))) {633 // Returning from Object.<init> implicitly registers a finalizer for the receiver if needed, to keep it alive.634 // Value class constructors update the scalarized receiver. We need to keep it live so that we can find it after635 // (chained) constructor calls and propagate updates to the caller. If the holder of the constructor is abstract,636 // we do not know if the constructor was called on a value class or not. We therefore keep the receiver of all637 // abstract constructors live.
638 load_one(0);
639 }
640 break;
641 }
642 case Bytecodes::_lload:
643 case Bytecodes::_dload:
644 load_two(instruction->get_index());
645 break;
646
647 case Bytecodes::_lload_0:
648 case Bytecodes::_dload_0:
649 load_two(0);
650 break;
651
652 case Bytecodes::_lload_1:
653 case Bytecodes::_dload_1:
654 load_two(1);
655 break;
656
657 case Bytecodes::_lload_2:
658 case Bytecodes::_dload_2:
659 load_two(2);
660 break;
661
662 case Bytecodes::_lload_3:
663 case Bytecodes::_dload_3:
664 load_two(3);
665 break;
666
667 case Bytecodes::_iload:
668 case Bytecodes::_iinc:
669 case Bytecodes::_fload:
670 case Bytecodes::_aload:
671 case Bytecodes::_ret:
672 load_one(instruction->get_index());
673 break;
674
675 case Bytecodes::_iload_0:
676 case Bytecodes::_fload_0:
677 case Bytecodes::_aload_0:
678 load_one(0);
679 break;
680
681 case Bytecodes::_iload_1:
682 case Bytecodes::_fload_1:
683 case Bytecodes::_aload_1:
684 load_one(1);
685 break;
686
687 case Bytecodes::_iload_2:
688 case Bytecodes::_fload_2:
689 case Bytecodes::_aload_2:
690 load_one(2);
691 break;
692
693 case Bytecodes::_iload_3:
694 case Bytecodes::_fload_3:
695 case Bytecodes::_aload_3:
696 load_one(3);
697 break;
698
699 case Bytecodes::_lstore:
700 case Bytecodes::_dstore:
701 store_two(instruction->get_index());
702 break;
703
704 case Bytecodes::_lstore_0:
705 case Bytecodes::_dstore_0:
706 store_two(0);
707 break;
708
709 case Bytecodes::_lstore_1:
710 case Bytecodes::_dstore_1:
711 store_two(1);
712 break;
713
714 case Bytecodes::_lstore_2:
715 case Bytecodes::_dstore_2:
716 store_two(2);
717 break;
718
719 case Bytecodes::_lstore_3:
720 case Bytecodes::_dstore_3:
721 store_two(3);
722 break;
723
724 case Bytecodes::_istore:
725 case Bytecodes::_fstore:
726 case Bytecodes::_astore:
727 store_one(instruction->get_index());
728 break;
729
730 case Bytecodes::_istore_0:
731 case Bytecodes::_fstore_0:
732 case Bytecodes::_astore_0:
733 store_one(0);
734 break;
735
736 case Bytecodes::_istore_1:
737 case Bytecodes::_fstore_1:
738 case Bytecodes::_astore_1:
739 store_one(1);
740 break;
741
742 case Bytecodes::_istore_2:
743 case Bytecodes::_fstore_2:
744 case Bytecodes::_astore_2:
745 store_one(2);
746 break;
747
748 case Bytecodes::_istore_3:
749 case Bytecodes::_fstore_3:
750 case Bytecodes::_astore_3:
751 store_one(3);
752 break;
753
754 case Bytecodes::_wide:
755 fatal("Iterator should skip this bytecode");
756 break;
757
758 default:
759 tty->print("unexpected opcode: %d\n", instruction->cur_bc());
760 ShouldNotReachHere();
761 break;
762 }
763 }
764
765 void MethodLiveness::BasicBlock::load_two(int local) {
766 load_one(local);
767 load_one(local+1);
768 }
769
770 void MethodLiveness::BasicBlock::load_one(int local) {
771 if (!_kill.at(local)) {
772 _gen.at_put(local, true);
773 }
774 }
775
776 void MethodLiveness::BasicBlock::store_two(int local) {
777 store_one(local);
778 store_one(local+1);
779 }
780
781 void MethodLiveness::BasicBlock::store_one(int local) {
782 if (!_gen.at(local)) {
783 _kill.at_put(local, true);
784 }
785 }
786
787 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) {
788 // These set operations could be combined for efficiency if the
789 // performance of this analysis becomes an issue.
790 _entry.set_union(_normal_exit);
791 _entry.set_difference(_kill);
792 _entry.set_union(_gen);
793
794 // Note that we merge information from our exceptional successors
795 // just once, rather than at individual bytecodes.
796 _entry.set_union(_exception_exit);
797
798 if (TraceLivenessGen) {
799 tty->print_cr(" ** Visiting block at %d **", start_bci());
800 print_on(tty);
801 }
802
803 int i;
804 for (i=_normal_predecessors->length()-1; i>=0; i--) {
805 BasicBlock *block = _normal_predecessors->at(i);
806 if (block->merge_normal(_entry)) {
807 ml->work_list_add(block);
808 }
809 }
810 for (i=_exception_predecessors->length()-1; i>=0; i--) {
811 BasicBlock *block = _exception_predecessors->at(i);
812 if (block->merge_exception(_entry)) {
813 ml->work_list_add(block);
814 }
815 }
816 }
817
818 bool MethodLiveness::BasicBlock::merge_normal(const BitMap& other) {
819 return _normal_exit.set_union_with_result(other);
820 }
821
822 bool MethodLiveness::BasicBlock::merge_exception(const BitMap& other) {
823 return _exception_exit.set_union_with_result(other);
824 }
825
826 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) {
827 MethodLivenessResult answer(_analyzer->bit_map_size_bits());
828 answer.set_is_valid();
829
830 #ifndef ASSERT
831 if (bci == start_bci()) {
832 answer.set_from(_entry);
833 return answer;
834 }
835 #endif
836
837 #ifdef ASSERT
838 ResourceMark rm;
839 ResourceBitMap g(_gen.size(), false); g.set_from(_gen);
840 ResourceBitMap k(_kill.size(), false); k.set_from(_kill);
841 #endif
842 if (_last_bci != bci || trueInDebug) {
843 ciBytecodeStream bytes(method);
844 bytes.reset_to_bci(bci);
845 bytes.set_max_bci(limit_bci());
846 compute_gen_kill_range(&bytes);
847 assert(_last_bci != bci ||
848 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect");
849 _last_bci = bci;
850 }
851
852 answer.set_union(_normal_exit);
853 answer.set_difference(_kill);
854 answer.set_union(_gen);
855 answer.set_union(_exception_exit);
856
857 #ifdef ASSERT
858 if (bci == start_bci()) {
859 assert(answer.is_same(_entry), "optimized answer must be accurate");
860 }
861 #endif
862
863 return answer;
864 }
865
866 #ifndef PRODUCT
867
868 void MethodLiveness::BasicBlock::print_on(outputStream *os) const {
869 os->print_cr("===================================================================");
870 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci);
871 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length());
872 int i;
873 for (i=0; i < _normal_predecessors->length(); i++) {
874 os->print(" %4d", _normal_predecessors->at(i)->start_bci());
875 }
876 os->cr();
877 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length());
878 for (i=0; i < _exception_predecessors->length(); i++) {
879 os->print(" %4d", _exception_predecessors->at(i)->start_bci());
880 }
881 os->cr();
882 os->print (" Normal Exit : ");
883 _normal_exit.print_on(os);
884 os->print (" Gen : ");
885 _gen.print_on(os);
886 os->print (" Kill : ");
887 _kill.print_on(os);
888 os->print (" Exception Exit: ");
889 _exception_exit.print_on(os);
890 os->print (" Entry : ");
891 _entry.print_on(os);
892 }
893
894 #endif // PRODUCT
--- EOF ---