1 /* 2 * Copyright (c) 1998, 2023, 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 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci()); 226 assert(jsrExit != nullptr, "jsr return bci must start a block."); 227 jsr_exit_list->append(jsrExit); 228 break; 229 } 230 case Bytecodes::_jsr_w: 231 { 232 dest = _block_map->at(bytes.get_far_dest()); 233 assert(dest != nullptr, "branch destination must start a block."); 234 dest->add_normal_predecessor(current_block); 235 BasicBlock *jsrExit = _block_map->at(current_block->limit_bci()); 236 assert(jsrExit != nullptr, "jsr return bci must start a block."); 237 jsr_exit_list->append(jsrExit); 238 break; 239 } 240 241 case Bytecodes::_wide: 242 assert(false, "wide opcodes should not be seen here"); 243 break; 244 case Bytecodes::_athrow: 245 case Bytecodes::_ireturn: 246 case Bytecodes::_lreturn: 247 case Bytecodes::_freturn: 248 case Bytecodes::_dreturn: 249 case Bytecodes::_areturn: 250 case Bytecodes::_return: 251 // These opcodes are not the normal predecessors of any other opcodes. 252 break; 253 case Bytecodes::_ret: 254 // We will patch up jsr/rets in a subsequent pass. 255 ret_list->append(current_block); 256 break; 257 default: 258 // Do nothing. 259 break; 260 } 261 } 262 // Patch up the jsr/ret's. We conservatively assume that any ret 263 // can return to any jsr site. 264 int ret_list_len = ret_list->length(); 265 int jsr_exit_list_len = jsr_exit_list->length(); 266 if (ret_list_len > 0 && jsr_exit_list_len > 0) { 267 for (int i = jsr_exit_list_len - 1; i >= 0; i--) { 268 BasicBlock *jsrExit = jsr_exit_list->at(i); 269 for (int i = ret_list_len - 1; i >= 0; i--) { 270 jsrExit->add_normal_predecessor(ret_list->at(i)); 271 } 272 } 273 } 274 275 // Compute exception edges. 276 for (int b=_block_count-1; b >= 0; b--) { 277 BasicBlock *block = _block_list[b]; 278 int block_start = block->start_bci(); 279 int block_limit = block->limit_bci(); 280 ciExceptionHandlerStream handlers(method()); 281 for (; !handlers.is_done(); handlers.next()) { 282 ciExceptionHandler* handler = handlers.handler(); 283 int start = handler->start(); 284 int limit = handler->limit(); 285 int handler_bci = handler->handler_bci(); 286 287 int intersect_start = MAX2(block_start, start); 288 int intersect_limit = MIN2(block_limit, limit); 289 if (intersect_start < intersect_limit) { 290 // The catch range has a nonempty intersection with this 291 // basic block. That means this basic block can be an 292 // exceptional predecessor. 293 _block_map->at(handler_bci)->add_exception_predecessor(block); 294 295 if (handler->is_catch_all()) { 296 // This is a catch-all block. 297 if (intersect_start == block_start && intersect_limit == block_limit) { 298 // The basic block is entirely contained in this catch-all block. 299 // Skip the rest of the exception handlers -- they can never be 300 // reached in execution. 301 break; 302 } 303 } 304 } 305 } 306 } 307 } 308 309 void MethodLiveness::init_gen_kill() { 310 for (int i=_block_count-1; i >= 0; i--) { 311 _block_list[i]->compute_gen_kill(method()); 312 } 313 } 314 315 void MethodLiveness::propagate_liveness() { 316 int num_blocks = _block_count; 317 BasicBlock *block; 318 319 // We start our work list off with all blocks in it. 320 // Alternately, we could start off the work list with the list of all 321 // blocks which could exit the method directly, along with one block 322 // from any infinite loop. If this matters, it can be changed. It 323 // may not be clear from looking at the code, but the order of the 324 // workList will be the opposite of the creation order of the basic 325 // blocks, which should be decent for quick convergence (with the 326 // possible exception of exception handlers, which are all created 327 // early). 328 _work_list = nullptr; 329 for (int i = 0; i < num_blocks; i++) { 330 block = _block_list[i]; 331 block->set_next(_work_list); 332 block->set_on_work_list(true); 333 _work_list = block; 334 } 335 336 337 while ((block = work_list_get()) != nullptr) { 338 block->propagate(this); 339 } 340 } 341 342 void MethodLiveness::work_list_add(BasicBlock *block) { 343 if (!block->on_work_list()) { 344 block->set_next(_work_list); 345 block->set_on_work_list(true); 346 _work_list = block; 347 } 348 } 349 350 MethodLiveness::BasicBlock *MethodLiveness::work_list_get() { 351 BasicBlock *block = _work_list; 352 if (block != nullptr) { 353 block->set_on_work_list(false); 354 _work_list = block->next(); 355 } 356 return block; 357 } 358 359 360 MethodLivenessResult MethodLiveness::get_liveness_at(int entry_bci) { 361 int bci = entry_bci; 362 bool is_entry = false; 363 if (entry_bci == InvocationEntryBci) { 364 is_entry = true; 365 bci = 0; 366 } 367 368 MethodLivenessResult answer; 369 370 if (_block_count > 0) { 371 372 assert( 0 <= bci && bci < method()->code_size(), "bci out of range" ); 373 BasicBlock *block = _block_map->at(bci); 374 // We may not be at the block start, so search backwards to find the block 375 // containing bci. 376 int t = bci; 377 while (block == nullptr && t > 0) { 378 block = _block_map->at(--t); 379 } 380 guarantee(block != nullptr, "invalid bytecode index; must be instruction index"); 381 assert(bci >= block->start_bci() && bci < block->limit_bci(), "block must contain bci."); 382 383 answer = block->get_liveness_at(method(), bci); 384 385 if (is_entry && method()->is_synchronized() && !method()->is_static()) { 386 // Synchronized methods use the receiver once on entry. 387 answer.at_put(0, true); 388 } 389 390 #ifndef PRODUCT 391 if (TraceLivenessQuery) { 392 tty->print("Liveness query of "); 393 method()->print_short_name(); 394 tty->print(" @ %d : result is ", bci); 395 answer.print_on(tty); 396 } 397 #endif 398 } 399 400 return answer; 401 } 402 403 MethodLiveness::BasicBlock::BasicBlock(MethodLiveness *analyzer, int start, int limit) : 404 _entry(analyzer->arena(), analyzer->bit_map_size_bits()), 405 _normal_exit(analyzer->arena(), analyzer->bit_map_size_bits()), 406 _exception_exit(analyzer->arena(), analyzer->bit_map_size_bits()), 407 _gen(analyzer->arena(), analyzer->bit_map_size_bits()), 408 _kill(analyzer->arena(), analyzer->bit_map_size_bits()), 409 _last_bci(-1) { 410 _analyzer = analyzer; 411 _start_bci = start; 412 _limit_bci = limit; 413 _normal_predecessors = 414 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr); 415 _exception_predecessors = 416 new (analyzer->arena()) GrowableArray<MethodLiveness::BasicBlock*>(analyzer->arena(), 5, 0, nullptr); 417 } 418 419 420 421 MethodLiveness::BasicBlock *MethodLiveness::BasicBlock::split(int split_bci) { 422 int start = _start_bci; 423 int limit = _limit_bci; 424 425 if (TraceLivenessGen) { 426 tty->print_cr(" ** Splitting block (%d,%d) at %d", start, limit, split_bci); 427 } 428 429 GrowableArray<BasicBlock*>* save_predecessors = _normal_predecessors; 430 431 assert (start < split_bci && split_bci < limit, "improper split"); 432 433 // Make a new block to cover the first half of the range. 434 BasicBlock *first_half = new (_analyzer->arena()) BasicBlock(_analyzer, start, split_bci); 435 436 // Assign correct values to the second half (this) 437 _normal_predecessors = first_half->_normal_predecessors; 438 _start_bci = split_bci; 439 add_normal_predecessor(first_half); 440 441 // Assign correct predecessors to the new first half 442 first_half->_normal_predecessors = save_predecessors; 443 444 return first_half; 445 } 446 447 void MethodLiveness::BasicBlock::compute_gen_kill(ciMethod* method) { 448 ciBytecodeStream bytes(method); 449 bytes.reset_to_bci(start_bci()); 450 bytes.set_max_bci(limit_bci()); 451 compute_gen_kill_range(&bytes); 452 453 } 454 455 void MethodLiveness::BasicBlock::compute_gen_kill_range(ciBytecodeStream *bytes) { 456 _gen.clear(); 457 _kill.clear(); 458 459 while (bytes->next() != ciBytecodeStream::EOBC()) { 460 compute_gen_kill_single(bytes); 461 } 462 } 463 464 void MethodLiveness::BasicBlock::compute_gen_kill_single(ciBytecodeStream *instruction) { 465 // We prohibit _gen and _kill from having locals in common. If we 466 // know that one is definitely going to be applied before the other, 467 // we could save some computation time by relaxing this prohibition. 468 469 switch (instruction->cur_bc()) { 470 case Bytecodes::_nop: 471 case Bytecodes::_goto: 472 case Bytecodes::_goto_w: 473 case Bytecodes::_aconst_null: 474 case Bytecodes::_new: 475 case Bytecodes::_iconst_m1: 476 case Bytecodes::_iconst_0: 477 case Bytecodes::_iconst_1: 478 case Bytecodes::_iconst_2: 479 case Bytecodes::_iconst_3: 480 case Bytecodes::_iconst_4: 481 case Bytecodes::_iconst_5: 482 case Bytecodes::_fconst_0: 483 case Bytecodes::_fconst_1: 484 case Bytecodes::_fconst_2: 485 case Bytecodes::_bipush: 486 case Bytecodes::_sipush: 487 case Bytecodes::_lconst_0: 488 case Bytecodes::_lconst_1: 489 case Bytecodes::_dconst_0: 490 case Bytecodes::_dconst_1: 491 case Bytecodes::_ldc2_w: 492 case Bytecodes::_ldc: 493 case Bytecodes::_ldc_w: 494 case Bytecodes::_iaload: 495 case Bytecodes::_faload: 496 case Bytecodes::_baload: 497 case Bytecodes::_caload: 498 case Bytecodes::_saload: 499 case Bytecodes::_laload: 500 case Bytecodes::_daload: 501 case Bytecodes::_aaload: 502 case Bytecodes::_iastore: 503 case Bytecodes::_fastore: 504 case Bytecodes::_bastore: 505 case Bytecodes::_castore: 506 case Bytecodes::_sastore: 507 case Bytecodes::_lastore: 508 case Bytecodes::_dastore: 509 case Bytecodes::_aastore: 510 case Bytecodes::_pop: 511 case Bytecodes::_pop2: 512 case Bytecodes::_dup: 513 case Bytecodes::_dup_x1: 514 case Bytecodes::_dup_x2: 515 case Bytecodes::_dup2: 516 case Bytecodes::_dup2_x1: 517 case Bytecodes::_dup2_x2: 518 case Bytecodes::_swap: 519 case Bytecodes::_iadd: 520 case Bytecodes::_fadd: 521 case Bytecodes::_isub: 522 case Bytecodes::_fsub: 523 case Bytecodes::_imul: 524 case Bytecodes::_fmul: 525 case Bytecodes::_idiv: 526 case Bytecodes::_fdiv: 527 case Bytecodes::_irem: 528 case Bytecodes::_frem: 529 case Bytecodes::_ishl: 530 case Bytecodes::_ishr: 531 case Bytecodes::_iushr: 532 case Bytecodes::_iand: 533 case Bytecodes::_ior: 534 case Bytecodes::_ixor: 535 case Bytecodes::_l2f: 536 case Bytecodes::_l2i: 537 case Bytecodes::_d2f: 538 case Bytecodes::_d2i: 539 case Bytecodes::_fcmpl: 540 case Bytecodes::_fcmpg: 541 case Bytecodes::_ladd: 542 case Bytecodes::_dadd: 543 case Bytecodes::_lsub: 544 case Bytecodes::_dsub: 545 case Bytecodes::_lmul: 546 case Bytecodes::_dmul: 547 case Bytecodes::_ldiv: 548 case Bytecodes::_ddiv: 549 case Bytecodes::_lrem: 550 case Bytecodes::_drem: 551 case Bytecodes::_land: 552 case Bytecodes::_lor: 553 case Bytecodes::_lxor: 554 case Bytecodes::_ineg: 555 case Bytecodes::_fneg: 556 case Bytecodes::_i2f: 557 case Bytecodes::_f2i: 558 case Bytecodes::_i2c: 559 case Bytecodes::_i2s: 560 case Bytecodes::_i2b: 561 case Bytecodes::_lneg: 562 case Bytecodes::_dneg: 563 case Bytecodes::_l2d: 564 case Bytecodes::_d2l: 565 case Bytecodes::_lshl: 566 case Bytecodes::_lshr: 567 case Bytecodes::_lushr: 568 case Bytecodes::_i2l: 569 case Bytecodes::_i2d: 570 case Bytecodes::_f2l: 571 case Bytecodes::_f2d: 572 case Bytecodes::_lcmp: 573 case Bytecodes::_dcmpl: 574 case Bytecodes::_dcmpg: 575 case Bytecodes::_ifeq: 576 case Bytecodes::_ifne: 577 case Bytecodes::_iflt: 578 case Bytecodes::_ifge: 579 case Bytecodes::_ifgt: 580 case Bytecodes::_ifle: 581 case Bytecodes::_tableswitch: 582 case Bytecodes::_ireturn: 583 case Bytecodes::_freturn: 584 case Bytecodes::_if_icmpeq: 585 case Bytecodes::_if_icmpne: 586 case Bytecodes::_if_icmplt: 587 case Bytecodes::_if_icmpge: 588 case Bytecodes::_if_icmpgt: 589 case Bytecodes::_if_icmple: 590 case Bytecodes::_lreturn: 591 case Bytecodes::_dreturn: 592 case Bytecodes::_if_acmpeq: 593 case Bytecodes::_if_acmpne: 594 case Bytecodes::_jsr: 595 case Bytecodes::_jsr_w: 596 case Bytecodes::_getstatic: 597 case Bytecodes::_putstatic: 598 case Bytecodes::_getfield: 599 case Bytecodes::_putfield: 600 case Bytecodes::_invokevirtual: 601 case Bytecodes::_invokespecial: 602 case Bytecodes::_invokestatic: 603 case Bytecodes::_invokeinterface: 604 case Bytecodes::_invokedynamic: 605 case Bytecodes::_newarray: 606 case Bytecodes::_anewarray: 607 case Bytecodes::_checkcast: 608 case Bytecodes::_arraylength: 609 case Bytecodes::_instanceof: 610 case Bytecodes::_athrow: 611 case Bytecodes::_areturn: 612 case Bytecodes::_monitorenter: 613 case Bytecodes::_monitorexit: 614 case Bytecodes::_ifnull: 615 case Bytecodes::_ifnonnull: 616 case Bytecodes::_multianewarray: 617 case Bytecodes::_lookupswitch: 618 // These bytecodes have no effect on the method's locals. 619 break; 620 621 case Bytecodes::_return: { 622 ciMethod* method = instruction->method(); 623 ciInstanceKlass* holder = method->holder(); 624 const bool abstract_klass = holder->is_abstract(); 625 const bool concrete_value_klass = !abstract_klass && holder->is_inlinetype(); 626 if (method->intrinsic_id() == vmIntrinsics::_Object_init || 627 (method->is_object_constructor() && (concrete_value_klass || abstract_klass))) { 628 // Returning from Object.<init> implicitly registers a finalizer for the receiver if needed, to keep it alive. 629 // Value class constructors update the scalarized receiver. We need to keep it live so that we can find it after 630 // (chained) constructor calls and propagate updates to the caller. If the holder of the constructor is abstract, 631 // we do not know if the constructor was called on a value class or not. We therefore keep the receiver of all 632 // abstract constructors live. 633 load_one(0); 634 } 635 break; 636 } 637 case Bytecodes::_lload: 638 case Bytecodes::_dload: 639 load_two(instruction->get_index()); 640 break; 641 642 case Bytecodes::_lload_0: 643 case Bytecodes::_dload_0: 644 load_two(0); 645 break; 646 647 case Bytecodes::_lload_1: 648 case Bytecodes::_dload_1: 649 load_two(1); 650 break; 651 652 case Bytecodes::_lload_2: 653 case Bytecodes::_dload_2: 654 load_two(2); 655 break; 656 657 case Bytecodes::_lload_3: 658 case Bytecodes::_dload_3: 659 load_two(3); 660 break; 661 662 case Bytecodes::_iload: 663 case Bytecodes::_iinc: 664 case Bytecodes::_fload: 665 case Bytecodes::_aload: 666 case Bytecodes::_ret: 667 load_one(instruction->get_index()); 668 break; 669 670 case Bytecodes::_iload_0: 671 case Bytecodes::_fload_0: 672 case Bytecodes::_aload_0: 673 load_one(0); 674 break; 675 676 case Bytecodes::_iload_1: 677 case Bytecodes::_fload_1: 678 case Bytecodes::_aload_1: 679 load_one(1); 680 break; 681 682 case Bytecodes::_iload_2: 683 case Bytecodes::_fload_2: 684 case Bytecodes::_aload_2: 685 load_one(2); 686 break; 687 688 case Bytecodes::_iload_3: 689 case Bytecodes::_fload_3: 690 case Bytecodes::_aload_3: 691 load_one(3); 692 break; 693 694 case Bytecodes::_lstore: 695 case Bytecodes::_dstore: 696 store_two(instruction->get_index()); 697 break; 698 699 case Bytecodes::_lstore_0: 700 case Bytecodes::_dstore_0: 701 store_two(0); 702 break; 703 704 case Bytecodes::_lstore_1: 705 case Bytecodes::_dstore_1: 706 store_two(1); 707 break; 708 709 case Bytecodes::_lstore_2: 710 case Bytecodes::_dstore_2: 711 store_two(2); 712 break; 713 714 case Bytecodes::_lstore_3: 715 case Bytecodes::_dstore_3: 716 store_two(3); 717 break; 718 719 case Bytecodes::_istore: 720 case Bytecodes::_fstore: 721 case Bytecodes::_astore: 722 store_one(instruction->get_index()); 723 break; 724 725 case Bytecodes::_istore_0: 726 case Bytecodes::_fstore_0: 727 case Bytecodes::_astore_0: 728 store_one(0); 729 break; 730 731 case Bytecodes::_istore_1: 732 case Bytecodes::_fstore_1: 733 case Bytecodes::_astore_1: 734 store_one(1); 735 break; 736 737 case Bytecodes::_istore_2: 738 case Bytecodes::_fstore_2: 739 case Bytecodes::_astore_2: 740 store_one(2); 741 break; 742 743 case Bytecodes::_istore_3: 744 case Bytecodes::_fstore_3: 745 case Bytecodes::_astore_3: 746 store_one(3); 747 break; 748 749 case Bytecodes::_wide: 750 fatal("Iterator should skip this bytecode"); 751 break; 752 753 default: 754 tty->print("unexpected opcode: %d\n", instruction->cur_bc()); 755 ShouldNotReachHere(); 756 break; 757 } 758 } 759 760 void MethodLiveness::BasicBlock::load_two(int local) { 761 load_one(local); 762 load_one(local+1); 763 } 764 765 void MethodLiveness::BasicBlock::load_one(int local) { 766 if (!_kill.at(local)) { 767 _gen.at_put(local, true); 768 } 769 } 770 771 void MethodLiveness::BasicBlock::store_two(int local) { 772 store_one(local); 773 store_one(local+1); 774 } 775 776 void MethodLiveness::BasicBlock::store_one(int local) { 777 if (!_gen.at(local)) { 778 _kill.at_put(local, true); 779 } 780 } 781 782 void MethodLiveness::BasicBlock::propagate(MethodLiveness *ml) { 783 // These set operations could be combined for efficiency if the 784 // performance of this analysis becomes an issue. 785 _entry.set_union(_normal_exit); 786 _entry.set_difference(_kill); 787 _entry.set_union(_gen); 788 789 // Note that we merge information from our exceptional successors 790 // just once, rather than at individual bytecodes. 791 _entry.set_union(_exception_exit); 792 793 if (TraceLivenessGen) { 794 tty->print_cr(" ** Visiting block at %d **", start_bci()); 795 print_on(tty); 796 } 797 798 int i; 799 for (i=_normal_predecessors->length()-1; i>=0; i--) { 800 BasicBlock *block = _normal_predecessors->at(i); 801 if (block->merge_normal(_entry)) { 802 ml->work_list_add(block); 803 } 804 } 805 for (i=_exception_predecessors->length()-1; i>=0; i--) { 806 BasicBlock *block = _exception_predecessors->at(i); 807 if (block->merge_exception(_entry)) { 808 ml->work_list_add(block); 809 } 810 } 811 } 812 813 bool MethodLiveness::BasicBlock::merge_normal(const BitMap& other) { 814 return _normal_exit.set_union_with_result(other); 815 } 816 817 bool MethodLiveness::BasicBlock::merge_exception(const BitMap& other) { 818 return _exception_exit.set_union_with_result(other); 819 } 820 821 MethodLivenessResult MethodLiveness::BasicBlock::get_liveness_at(ciMethod* method, int bci) { 822 MethodLivenessResult answer(_analyzer->bit_map_size_bits()); 823 answer.set_is_valid(); 824 825 #ifndef ASSERT 826 if (bci == start_bci()) { 827 answer.set_from(_entry); 828 return answer; 829 } 830 #endif 831 832 #ifdef ASSERT 833 ResourceMark rm; 834 ResourceBitMap g(_gen.size(), false); g.set_from(_gen); 835 ResourceBitMap k(_kill.size(), false); k.set_from(_kill); 836 #endif 837 if (_last_bci != bci || trueInDebug) { 838 ciBytecodeStream bytes(method); 839 bytes.reset_to_bci(bci); 840 bytes.set_max_bci(limit_bci()); 841 compute_gen_kill_range(&bytes); 842 assert(_last_bci != bci || 843 (g.is_same(_gen) && k.is_same(_kill)), "cached computation is incorrect"); 844 _last_bci = bci; 845 } 846 847 answer.set_union(_normal_exit); 848 answer.set_difference(_kill); 849 answer.set_union(_gen); 850 answer.set_union(_exception_exit); 851 852 #ifdef ASSERT 853 if (bci == start_bci()) { 854 assert(answer.is_same(_entry), "optimized answer must be accurate"); 855 } 856 #endif 857 858 return answer; 859 } 860 861 #ifndef PRODUCT 862 863 void MethodLiveness::BasicBlock::print_on(outputStream *os) const { 864 os->print_cr("==================================================================="); 865 os->print_cr(" Block start: %4d, limit: %4d", _start_bci, _limit_bci); 866 os->print (" Normal predecessors (%2d) @", _normal_predecessors->length()); 867 int i; 868 for (i=0; i < _normal_predecessors->length(); i++) { 869 os->print(" %4d", _normal_predecessors->at(i)->start_bci()); 870 } 871 os->cr(); 872 os->print (" Exceptional predecessors (%2d) @", _exception_predecessors->length()); 873 for (i=0; i < _exception_predecessors->length(); i++) { 874 os->print(" %4d", _exception_predecessors->at(i)->start_bci()); 875 } 876 os->cr(); 877 os->print (" Normal Exit : "); 878 _normal_exit.print_on(os); 879 os->print (" Gen : "); 880 _gen.print_on(os); 881 os->print (" Kill : "); 882 _kill.print_on(os); 883 os->print (" Exception Exit: "); 884 _exception_exit.print_on(os); 885 os->print (" Entry : "); 886 _entry.print_on(os); 887 } 888 889 #endif // PRODUCT