1 /*
2 * Copyright (c) 1998, 2024, 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 "classfile/vmIntrinsics.hpp"
30 #include "compiler/methodLiveness.hpp"
31 #include "interpreter/bytecode.hpp"
32 #include "interpreter/bytecodes.hpp"
33 #include "memory/allocation.inline.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "utilities/bitMap.inline.hpp"
36
37 // The MethodLiveness class performs a simple liveness analysis on a method
38 // in order to decide which locals are live (that is, will be used again) at
39 // a particular bytecode index (bci).
40 //
41 // The algorithm goes:
42 //
43 // 1. Break the method into a set of basic blocks. For each basic block we
44 // also keep track of its set of predecessors through normal control flow
45 // and predecessors through exceptional control flow.
46 //
47 // 2. For each basic block, compute two sets, gen (the set of values used before
48 // they are defined) and kill (the set of values defined before they are used)
49 // in the basic block. A basic block "needs" the locals in its gen set to
50 // perform its computation. A basic block "provides" values for the locals in
51 // its kill set, allowing a need from a successor to be ignored.
52 //
53 // 3. Liveness information (the set of locals which are needed) is pushed backwards through
54 // the program, from blocks to their predecessors. We compute and store liveness
55 // information for the normal/exceptional exit paths for each basic block. When
56 // this process reaches a fixed point, we are done.
57 //
58 // 4. When we are asked about the liveness at a particular bci with a basic block, we
59 // compute gen/kill sets which represent execution from that bci to the exit of
60 // its blocks. We then compose this range gen/kill information with the normal
61 // and exceptional exit information for the block to produce liveness information
62 // at that bci.
63 //
64 // The algorithm is approximate in many respects. Notably:
65 //
66 // 1. We do not do the analysis necessary to match jsr's with the appropriate ret.
67 // Instead we make the conservative assumption that any ret can return to any
68 // jsr return site.
69 // 2. Instead of computing the effects of exceptions at every instruction, we
70 // summarize the effects of all exceptional continuations from the block as
71 // a single set (_exception_exit), losing some information but simplifying the
72 // analysis.
73
74 MethodLiveness::MethodLiveness(Arena* arena, ciMethod* method)
75 #ifdef COMPILER1
76 : _bci_block_start(arena, method->code_size())
77 #endif
78 {
79 _arena = arena;
80 _method = method;
81 _bit_map_size_bits = method->max_locals();
82 }
83
84 void MethodLiveness::compute_liveness() {
85 #ifndef PRODUCT
86 if (TraceLivenessGen) {
87 tty->print_cr("################################################################");
88 tty->print("# Computing liveness information for ");
89 method()->print_short_name();
90 }
91 #endif
92
93 init_basic_blocks();
94 init_gen_kill();
95 propagate_liveness();
96 }
97
98
99 void MethodLiveness::init_basic_blocks() {
100 int method_len = method()->code_size();
101 ciMethodBlocks *mblocks = method()->get_method_blocks();
102
103 // Create an array to store the bci->BasicBlock mapping.
104 _block_map = new (arena()) GrowableArray<BasicBlock*>(arena(), method_len, method_len, nullptr);
105
106 _block_count = mblocks->num_blocks();
107 _block_list = (BasicBlock **) arena()->Amalloc(sizeof(BasicBlock *) * _block_count);
108
109 // Used for patching up jsr/ret control flow.
110 GrowableArray<BasicBlock*>* jsr_exit_list = new GrowableArray<BasicBlock*>(5);
111 GrowableArray<BasicBlock*>* ret_list = new GrowableArray<BasicBlock*>(5);
112
113 // generate our block list from ciMethodBlocks
114 for (int blk = 0; blk < _block_count; blk++) {
115 ciBlock *cib = mblocks->block(blk);
116 int start_bci = cib->start_bci();
117 _block_list[blk] = new (arena()) BasicBlock(this, start_bci, cib->limit_bci());
118 _block_map->at_put(start_bci, _block_list[blk]);
119 #ifdef COMPILER1
120 // mark all bcis where a new basic block starts
121 _bci_block_start.set_bit(start_bci);
122 #endif // COMPILER1
123 }
124 // fill in the predecessors of blocks
125 ciBytecodeStream bytes(method());
126
127 for (int blk = 0; blk < _block_count; blk++) {
128 BasicBlock *current_block = _block_list[blk];
129 int bci = mblocks->block(blk)->control_bci();
130
131 if (bci == ciBlock::fall_through_bci) {
132 int limit = current_block->limit_bci();
133 if (limit < method_len) {
134 BasicBlock *next = _block_map->at(limit);
135 assert( next != nullptr, "must be a block immediately following this one.");
136 next->add_normal_predecessor(current_block);
137 }
138 continue;
139 }
140 bytes.reset_to_bci(bci);
141 Bytecodes::Code code = bytes.next();
142 BasicBlock *dest;
143
144 // Now we need to interpret the instruction's effect
145 // on control flow.
146 assert (current_block != nullptr, "we must have a current block");
147 switch (code) {
148 case Bytecodes::_ifeq:
149 case Bytecodes::_ifne:
150 case Bytecodes::_iflt:
151 case Bytecodes::_ifge:
152 case Bytecodes::_ifgt:
153 case Bytecodes::_ifle:
154 case Bytecodes::_if_icmpeq:
155 case Bytecodes::_if_icmpne:
156 case Bytecodes::_if_icmplt:
157 case Bytecodes::_if_icmpge:
158 case Bytecodes::_if_icmpgt:
159 case Bytecodes::_if_icmple:
160 case Bytecodes::_if_acmpeq:
161 case Bytecodes::_if_acmpne:
162 case Bytecodes::_ifnull:
163 case Bytecodes::_ifnonnull:
164 // Two way branch. Set predecessors at each destination.
165 if (bytes.next_bci() < method_len) {
166 dest = _block_map->at(bytes.next_bci());
167 assert(dest != nullptr, "must be a block immediately following this one.");
168 dest->add_normal_predecessor(current_block);
169 }
170 dest = _block_map->at(bytes.get_dest());
171 assert(dest != nullptr, "branch destination must start a block.");
172 dest->add_normal_predecessor(current_block);
173 break;
174 case Bytecodes::_goto:
175 dest = _block_map->at(bytes.get_dest());
176 assert(dest != nullptr, "branch destination must start a block.");
177 dest->add_normal_predecessor(current_block);
178 break;
179 case Bytecodes::_goto_w:
180 dest = _block_map->at(bytes.get_far_dest());
181 assert(dest != nullptr, "branch destination must start a block.");
182 dest->add_normal_predecessor(current_block);
183 break;
184 case Bytecodes::_tableswitch:
185 {
186 Bytecode_tableswitch tableswitch(&bytes);
187
188 int len = tableswitch.length();
189
190 dest = _block_map->at(bci + tableswitch.default_offset());
191 assert(dest != nullptr, "branch destination must start a block.");
192 dest->add_normal_predecessor(current_block);
193 while (--len >= 0) {
194 dest = _block_map->at(bci + tableswitch.dest_offset_at(len));
195 assert(dest != nullptr, "branch destination must start a block.");
196 dest->add_normal_predecessor(current_block);
197 }
198 break;
199 }
200
201 case Bytecodes::_lookupswitch:
202 {
203 Bytecode_lookupswitch lookupswitch(&bytes);
204
205 int npairs = lookupswitch.number_of_pairs();
206
207 dest = _block_map->at(bci + lookupswitch.default_offset());
208 assert(dest != nullptr, "branch destination must start a block.");
209 dest->add_normal_predecessor(current_block);
210 while(--npairs >= 0) {
211 LookupswitchPair pair = lookupswitch.pair_at(npairs);
212 dest = _block_map->at( bci + pair.offset());
213 assert(dest != nullptr, "branch destination must start a block.");
214 dest->add_normal_predecessor(current_block);
215 }
216 break;
217 }
218
219 case Bytecodes::_jsr:
220 {
221 assert(bytes.is_wide()==false, "sanity check");
222 dest = _block_map->at(bytes.get_dest());
223 assert(dest != nullptr, "branch destination must start a block.");
224 dest->add_normal_predecessor(current_block);
225 if (bci + Bytecodes::length_for(code) >= method_len) {
226 break;
227 }
228 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
229 assert(jsrExit != nullptr, "jsr return bci must start a block.");
230 jsr_exit_list->append(jsrExit);
231 break;
232 }
233 case Bytecodes::_jsr_w:
234 {
235 dest = _block_map->at(bytes.get_far_dest());
236 assert(dest != nullptr, "branch destination must start a block.");
237 dest->add_normal_predecessor(current_block);
238 if (bci + Bytecodes::length_for(code) >= method_len) {
239 break;
240 }
241 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci());
242 assert(jsrExit != nullptr, "jsr return bci must start a block.");
243 jsr_exit_list->append(jsrExit);
244 break;
245 }
246
247 case Bytecodes::_wide:
248 assert(false, "wide opcodes should not be seen here");
249 break;
250 case Bytecodes::_athrow:
251 case Bytecodes::_ireturn:
252 case Bytecodes::_lreturn:
253 case Bytecodes::_freturn:
254 case Bytecodes::_dreturn:
255 case Bytecodes::_areturn:
256 case Bytecodes::_return:
257 // These opcodes are not the normal predecessors of any other opcodes.
258 break;
259 case Bytecodes::_ret:
260 // We will patch up jsr/rets in a subsequent pass.
261 ret_list->append(current_block);
262 break;
263 default:
264 // Do nothing.
265 break;
266 }
267 }
268 // Patch up the jsr/ret's. We conservatively assume that any ret
269 // can return to any jsr site.
270 int ret_list_len = ret_list->length();
271 int jsr_exit_list_len = jsr_exit_list->length();
272 if (ret_list_len > 0 && jsr_exit_list_len > 0) {
273 for (int i = jsr_exit_list_len - 1; i >= 0; i--) {
274 BasicBlock *jsrExit = jsr_exit_list->at(i);
275 for (int i = ret_list_len - 1; i >= 0; i--) {
276 jsrExit->add_normal_predecessor(ret_list->at(i));
277 }
278 }
279 }
280
281 // Compute exception edges.
282 for (int b=_block_count-1; b >= 0; b--) {
283 BasicBlock *block = _block_list[b];
284 int block_start = block->start_bci();
285 int block_limit = block->limit_bci();
286 ciExceptionHandlerStream handlers(method());
287 for (; !handlers.is_done(); handlers.next()) {
288 ciExceptionHandler* handler = handlers.handler();
289 int start = handler->start();
290 int limit = handler->limit();
291 int handler_bci = handler->handler_bci();
292
293 int intersect_start = MAX2(block_start, start);
294 int intersect_limit = MIN2(block_limit, limit);
295 if (intersect_start < intersect_limit) {
296 // The catch range has a nonempty intersection with this
297 // basic block. That means this basic block can be an
298 // exceptional predecessor.
299 _block_map->at(handler_bci)->add_exception_predecessor(block);
300
301 if (handler->is_catch_all()) {
302 // This is a catch-all block.
303 if (intersect_start == block_start && intersect_limit == block_limit) {
304 // The basic block is entirely contained in this catch-all block.
305 // Skip the rest of the exception handlers -- they can never be
306 // reached in execution.
307 break;
308 }
309 }
310 }
311 }
312 }
313 }
314
315 void MethodLiveness::init_gen_kill() {
316 for (int i=_block_count-1; i >= 0; i--) {
317 _block_list[i]->compute_gen_kill(method());
318 }
319 }
320
321 void MethodLiveness::propagate_liveness() {
322 int num_blocks = _block_count;
323 BasicBlock *block;
324
325 // We start our work list off with all blocks in it.
326 // Alternately, we could start off the work list with the list of all
327 // blocks which could exit the method directly, along with one block
328 // from any infinite loop. If this matters, it can be changed. It
329 // may not be clear from looking at the code, but the order of the
330 // workList will be the opposite of the creation order of the basic
331 // blocks, which should be decent for quick convergence (with the
332 // possible exception of exception handlers, which are all created
333 // early).
334 _work_list = nullptr;
335 for (int i = 0; i < num_blocks; i++) {
336 block = _block_list[i];
337 block->set_next(_work_list);
338 block->set_on_work_list(true);
339 _work_list = block;
340 }
341
342
343 while ((block = work_list_get()) != nullptr) {
344 block->propagate(this);
345 }
346 }
347
348 void MethodLiveness::work_list_add(BasicBlock *block) {
349 if (!block->on_work_list()) {
350 block->set_next(_work_list);
351 block->set_on_work_list(true);
352 _work_list = block;
353 }
354 }
355
356 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() {
357 BasicBlock *block = _work_list;
358 if (block != nullptr) {
359 block->set_on_work_list(false);
360 _work_list = block->next();
361 }
362 return block;
363 }
364
365
366 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) {
367 int bci = entry_bci;
368 bool is_entry = false;
369 if (entry_bci == InvocationEntryBci) {
370 is_entry = true;
371 bci = 0;
372 }
373
374 MethodLivenessResult answer;
375
376 if (_block_count > 0) {
377
378 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" );
379 BasicBlock *block = _block_map->at(bci);
380 // We may not be at the block start, so search backwards to find the block
381 // containing bci.
382 int t = bci;
383 while (block == nullptr && t > 0) {
384 block = _block_map->at(--t);
385 }
386 guarantee(block != nullptr, "invalid bytecode index; must be instruction index");
387 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci.");
388
389 answer = block->get_liveness_at(method(), bci);
390
391 if (is_entry && method()->is_synchronized() && !method()->is_static()) {
392 // Synchronized methods use the receiver once on entry.
393 answer.at_put(0, true);
394 }
395
396 #ifndef PRODUCT
397 if (TraceLivenessQuery) {
398 tty->print("Liveness query of ");
399 method()->print_short_name();
400 tty->print(" @ %d : result is ", bci);
401 answer.print_on(tty);
402 }
403 #endif
404 }
405
406 return answer;
407 }
408
409 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) :
410 _entry(analyzer->arena(), analyzer->bit_map_size_bits()),
411 _normal_exit(analyzer->arena(), analyzer->bit_map_size_bits()),
412 _exception_exit(analyzer->arena(), analyzer->bit_map_size_bits()),
413 _gen(analyzer->arena(), analyzer->bit_map_size_bits()),
414 _kill(analyzer->arena(), analyzer->bit_map_size_bits()),
415 _last_bci(-1) {
416 _analyzer = analyzer;
417 _start_bci = start;
418 _limit_bci = limit;
419 _normal_predecessors =
420 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr);
421 _exception_predecessors =
422 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr);
423 }
424
425
426
427 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) {
428 int start = _start_bci;
429 int limit = _limit_bci;
430
431 if (TraceLivenessGen) {
432 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci);
433 }
434
435 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors;
436
437 assert (start < split_bci && split_bci < limit, "improper split");
438
439 // Make a new block to cover the first half of the range.
440 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci);
441
442 // Assign correct values to the second half (this)
443 _normal_predecessors = first_half->_normal_predecessors;
444 _start_bci = split_bci;
445 add_normal_predecessor(first_half);
446
447 // Assign correct predecessors to the new first half
448 first_half->_normal_predecessors = save_predecessors;
449
450 return first_half;
451 }
452
453 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) {
454 ciBytecodeStream bytes(method);
455 bytes.reset_to_bci(start_bci());
456 bytes.set_max_bci(limit_bci());
457 compute_gen_kill_range(&bytes);
458
459 }
460
461 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) {
462 _gen.clear();
463 _kill.clear();
464
465 while (bytes->next() != ciBytecodeStream::EOBC()) {
466 compute_gen_kill_single(bytes);
467 }
468 }
469
470 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) {
471 // We prohibit _gen and _kill from having locals in common. If we
472 // know that one is definitely going to be applied before the other,
473 // we could save some computation time by relaxing this prohibition.
474
475 switch (instruction->cur_bc()) {
476 case Bytecodes::_nop:
477 case Bytecodes::_goto:
478 case Bytecodes::_goto_w:
479 case Bytecodes::_aconst_null:
480 case Bytecodes::_new:
481 case Bytecodes::_iconst_m1:
482 case Bytecodes::_iconst_0:
483 case Bytecodes::_iconst_1:
484 case Bytecodes::_iconst_2:
485 case Bytecodes::_iconst_3:
486 case Bytecodes::_iconst_4:
487 case Bytecodes::_iconst_5:
488 case Bytecodes::_fconst_0:
489 case Bytecodes::_fconst_1:
490 case Bytecodes::_fconst_2:
491 case Bytecodes::_bipush:
492 case Bytecodes::_sipush:
493 case Bytecodes::_lconst_0:
494 case Bytecodes::_lconst_1:
495 case Bytecodes::_dconst_0:
496 case Bytecodes::_dconst_1:
497 case Bytecodes::_ldc2_w:
498 case Bytecodes::_ldc:
499 case Bytecodes::_ldc_w:
500 case Bytecodes::_iaload:
501 case Bytecodes::_faload:
502 case Bytecodes::_baload:
503 case Bytecodes::_caload:
504 case Bytecodes::_saload:
505 case Bytecodes::_laload:
506 case Bytecodes::_daload:
507 case Bytecodes::_aaload:
508 case Bytecodes::_iastore:
509 case Bytecodes::_fastore:
510 case Bytecodes::_bastore:
511 case Bytecodes::_castore:
512 case Bytecodes::_sastore:
513 case Bytecodes::_lastore:
514 case Bytecodes::_dastore:
515 case Bytecodes::_aastore:
516 case Bytecodes::_pop:
517 case Bytecodes::_pop2:
518 case Bytecodes::_dup:
519 case Bytecodes::_dup_x1:
520 case Bytecodes::_dup_x2:
521 case Bytecodes::_dup2:
522 case Bytecodes::_dup2_x1:
523 case Bytecodes::_dup2_x2:
524 case Bytecodes::_swap:
525 case Bytecodes::_iadd:
526 case Bytecodes::_fadd:
527 case Bytecodes::_isub:
528 case Bytecodes::_fsub:
529 case Bytecodes::_imul:
530 case Bytecodes::_fmul:
531 case Bytecodes::_idiv:
532 case Bytecodes::_fdiv:
533 case Bytecodes::_irem:
534 case Bytecodes::_frem:
535 case Bytecodes::_ishl:
536 case Bytecodes::_ishr:
537 case Bytecodes::_iushr:
538 case Bytecodes::_iand:
539 case Bytecodes::_ior:
540 case Bytecodes::_ixor:
541 case Bytecodes::_l2f:
542 case Bytecodes::_l2i:
543 case Bytecodes::_d2f:
544 case Bytecodes::_d2i:
545 case Bytecodes::_fcmpl:
546 case Bytecodes::_fcmpg:
547 case Bytecodes::_ladd:
548 case Bytecodes::_dadd:
549 case Bytecodes::_lsub:
550 case Bytecodes::_dsub:
551 case Bytecodes::_lmul:
552 case Bytecodes::_dmul:
553 case Bytecodes::_ldiv:
554 case Bytecodes::_ddiv:
555 case Bytecodes::_lrem:
556 case Bytecodes::_drem:
557 case Bytecodes::_land:
558 case Bytecodes::_lor:
559 case Bytecodes::_lxor:
560 case Bytecodes::_ineg:
561 case Bytecodes::_fneg:
562 case Bytecodes::_i2f:
563 case Bytecodes::_f2i:
564 case Bytecodes::_i2c:
565 case Bytecodes::_i2s:
566 case Bytecodes::_i2b:
567 case Bytecodes::_lneg:
568 case Bytecodes::_dneg:
569 case Bytecodes::_l2d:
570 case Bytecodes::_d2l:
571 case Bytecodes::_lshl:
572 case Bytecodes::_lshr:
573 case Bytecodes::_lushr:
574 case Bytecodes::_i2l:
575 case Bytecodes::_i2d:
576 case Bytecodes::_f2l:
577 case Bytecodes::_f2d:
578 case Bytecodes::_lcmp:
579 case Bytecodes::_dcmpl:
580 case Bytecodes::_dcmpg:
581 case Bytecodes::_ifeq:
582 case Bytecodes::_ifne:
583 case Bytecodes::_iflt:
584 case Bytecodes::_ifge:
585 case Bytecodes::_ifgt:
586 case Bytecodes::_ifle:
587 case Bytecodes::_tableswitch:
588 case Bytecodes::_ireturn:
589 case Bytecodes::_freturn:
590 case Bytecodes::_if_icmpeq:
591 case Bytecodes::_if_icmpne:
592 case Bytecodes::_if_icmplt:
593 case Bytecodes::_if_icmpge:
594 case Bytecodes::_if_icmpgt:
595 case Bytecodes::_if_icmple:
596 case Bytecodes::_lreturn:
597 case Bytecodes::_dreturn:
598 case Bytecodes::_if_acmpeq:
599 case Bytecodes::_if_acmpne:
600 case Bytecodes::_jsr:
601 case Bytecodes::_jsr_w:
602 case Bytecodes::_getstatic:
603 case Bytecodes::_putstatic:
604 case Bytecodes::_getfield:
605 case Bytecodes::_putfield:
606 case Bytecodes::_invokevirtual:
607 case Bytecodes::_invokespecial:
608 case Bytecodes::_invokestatic:
609 case Bytecodes::_invokeinterface:
610 case Bytecodes::_invokedynamic:
611 case Bytecodes::_newarray:
612 case Bytecodes::_anewarray:
613 case Bytecodes::_checkcast:
614 case Bytecodes::_arraylength:
615 case Bytecodes::_instanceof:
616 case Bytecodes::_athrow:
617 case Bytecodes::_areturn:
618 case Bytecodes::_monitorenter:
619 case Bytecodes::_monitorexit:
620 case Bytecodes::_ifnull:
621 case Bytecodes::_ifnonnull:
622 case Bytecodes::_multianewarray:
623 case Bytecodes::_lookupswitch:
624 // These bytecodes have no effect on the method's locals.
625 break;
626
627 case Bytecodes::_return: {
628 ciMethod* method = instruction->method();
629 ciInstanceKlass* holder = method->holder();
630 const bool abstract_klass = holder->is_abstract();
631 const bool concrete_value_klass = !abstract_klass && holder->is_inlinetype();
632 if (method->intrinsic_id() == vmIntrinsics::_Object_init ||
633 (method->is_object_constructor() && (concrete_value_klass || abstract_klass))) {
634 // Returning from Object.<init> implicitly registers a finalizer for the receiver if needed, to keep it alive.
635 // Value class constructors update the scalarized receiver. We need to keep it live so that we can find it after
636 // (chained) constructor calls and propagate updates to the caller. If the holder of the constructor is abstract,
637 // we do not know if the constructor was called on a value class or not. We therefore keep the receiver of all
638 // abstract constructors live.
639 load_one(0);
640 }
641 break;
642 }
643 case Bytecodes::_lload:
644 case Bytecodes::_dload:
645 load_two(instruction->get_index());
646 break;
647
648 case Bytecodes::_lload_0:
649 case Bytecodes::_dload_0:
650 load_two(0);
651 break;
652
653 case Bytecodes::_lload_1:
654 case Bytecodes::_dload_1:
655 load_two(1);
656 break;
657
658 case Bytecodes::_lload_2:
659 case Bytecodes::_dload_2:
660 load_two(2);
661 break;
662
663 case Bytecodes::_lload_3:
664 case Bytecodes::_dload_3:
665 load_two(3);
666 break;
667
668 case Bytecodes::_iload:
669 case Bytecodes::_iinc:
670 case Bytecodes::_fload:
671 case Bytecodes::_aload:
672 case Bytecodes::_ret:
673 load_one(instruction->get_index());
674 break;
675
676 case Bytecodes::_iload_0:
677 case Bytecodes::_fload_0:
678 case Bytecodes::_aload_0:
679 load_one(0);
680 break;
681
682 case Bytecodes::_iload_1:
683 case Bytecodes::_fload_1:
684 case Bytecodes::_aload_1:
685 load_one(1);
686 break;
687
688 case Bytecodes::_iload_2:
689 case Bytecodes::_fload_2:
690 case Bytecodes::_aload_2:
691 load_one(2);
692 break;
693
694 case Bytecodes::_iload_3:
695 case Bytecodes::_fload_3:
696 case Bytecodes::_aload_3:
697 load_one(3);
698 break;
699
700 case Bytecodes::_lstore:
701 case Bytecodes::_dstore:
702 store_two(instruction->get_index());
703 break;
704
705 case Bytecodes::_lstore_0:
706 case Bytecodes::_dstore_0:
707 store_two(0);
708 break;
709
710 case Bytecodes::_lstore_1:
711 case Bytecodes::_dstore_1:
712 store_two(1);
713 break;
714
715 case Bytecodes::_lstore_2:
716 case Bytecodes::_dstore_2:
717 store_two(2);
718 break;
719
720 case Bytecodes::_lstore_3:
721 case Bytecodes::_dstore_3:
722 store_two(3);
723 break;
724
725 case Bytecodes::_istore:
726 case Bytecodes::_fstore:
727 case Bytecodes::_astore:
728 store_one(instruction->get_index());
729 break;
730
731 case Bytecodes::_istore_0:
732 case Bytecodes::_fstore_0:
733 case Bytecodes::_astore_0:
734 store_one(0);
735 break;
736
737 case Bytecodes::_istore_1:
738 case Bytecodes::_fstore_1:
739 case Bytecodes::_astore_1:
740 store_one(1);
741 break;
742
743 case Bytecodes::_istore_2:
744 case Bytecodes::_fstore_2:
745 case Bytecodes::_astore_2:
746 store_one(2);
747 break;
748
749 case Bytecodes::_istore_3:
750 case Bytecodes::_fstore_3:
751 case Bytecodes::_astore_3:
752 store_one(3);
753 break;
754
755 case Bytecodes::_wide:
756 fatal("Iterator should skip this bytecode");
757 break;
758
759 default:
760 tty->print("unexpected opcode: %d\n", instruction->cur_bc());
761 ShouldNotReachHere();
762 break;
763 }
764 }
765
766 void MethodLiveness::BasicBlock::load_two(int local) {
767 load_one(local);
768 load_one(local+1);
769 }
770
771 void MethodLiveness::BasicBlock::load_one(int local) {
772 if (!_kill.at(local)) {
773 _gen.at_put(local, true);
774 }
775 }
776
777 void MethodLiveness::BasicBlock::store_two(int local) {
778 store_one(local);
779 store_one(local+1);
780 }
781
782 void MethodLiveness::BasicBlock::store_one(int local) {
783 if (!_gen.at(local)) {
784 _kill.at_put(local, true);
785 }
786 }
787
788 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) {
789 // These set operations could be combined for efficiency if the
790 // performance of this analysis becomes an issue.
791 _entry.set_union(_normal_exit);
792 _entry.set_difference(_kill);
793 _entry.set_union(_gen);
794
795 // Note that we merge information from our exceptional successors
796 // just once, rather than at individual bytecodes.
797 _entry.set_union(_exception_exit);
798
799 if (TraceLivenessGen) {
800 tty->print_cr(" ** Visiting block at %d **", start_bci());
801 print_on(tty);
802 }
803
804 int i;
805 for (i=_normal_predecessors->length()-1; i>=0; i--) {
806 BasicBlock *block = _normal_predecessors->at(i);
807 if (block->merge_normal(_entry)) {
808 ml->work_list_add(block);
809 }
810 }
811 for (i=_exception_predecessors->length()-1; i>=0; i--) {
812 BasicBlock *block = _exception_predecessors->at(i);
813 if (block->merge_exception(_entry)) {
814 ml->work_list_add(block);
815 }
816 }
817 }
818
819 bool MethodLiveness::BasicBlock::merge_normal(const BitMap& other) {
820 return _normal_exit.set_union_with_result(other);
821 }
822
823 bool MethodLiveness::BasicBlock::merge_exception(const BitMap& other) {
824 return _exception_exit.set_union_with_result(other);
825 }
826
827 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) {
828 MethodLivenessResult answer(_analyzer->bit_map_size_bits());
829 answer.set_is_valid();
830
831 #ifndef ASSERT
832 if (bci == start_bci()) {
833 answer.set_from(_entry);
834 return answer;
835 }
836 #endif
837
838 #ifdef ASSERT
839 ResourceMark rm;
840 ResourceBitMap g(_gen.size(), false); g.set_from(_gen);
841 ResourceBitMap k(_kill.size(), false); k.set_from(_kill);
842 #endif
843 if (_last_bci != bci || trueInDebug) {
844 ciBytecodeStream bytes(method);
845 bytes.reset_to_bci(bci);
846 bytes.set_max_bci(limit_bci());
847 compute_gen_kill_range(&bytes);
848 assert(_last_bci != bci ||
849 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect");
850 _last_bci = bci;
851 }
852
853 answer.set_union(_normal_exit);
854 answer.set_difference(_kill);
855 answer.set_union(_gen);
856 answer.set_union(_exception_exit);
857
858 #ifdef ASSERT
859 if (bci == start_bci()) {
860 assert(answer.is_same(_entry), "optimized answer must be accurate");
861 }
862 #endif
863
864 return answer;
865 }
866
867 #ifndef PRODUCT
868
869 void MethodLiveness::BasicBlock::print_on(outputStream *os) const {
870 os->print_cr("===================================================================");
871 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci);
872 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length());
873 int i;
874 for (i=0; i < _normal_predecessors->length(); i++) {
875 os->print(" %4d", _normal_predecessors->at(i)->start_bci());
876 }
877 os->cr();
878 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length());
879 for (i=0; i < _exception_predecessors->length(); i++) {
880 os->print(" %4d", _exception_predecessors->at(i)->start_bci());
881 }
882 os->cr();
883 os->print (" Normal Exit : ");
884 _normal_exit.print_on(os);
885 os->print (" Gen : ");
886 _gen.print_on(os);
887 os->print (" Kill : ");
888 _kill.print_on(os);
889 os->print (" Exception Exit: ");
890 _exception_exit.print_on(os);
891 os->print (" Entry : ");
892 _entry.print_on(os);
893 }
894
895 #endif // PRODUCT