1 /* GIMPLE lowering pass. Converts High GIMPLE into Low GIMPLE. 2 3 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 4 Free Software Foundation, Inc. 5 6 This file is part of GCC. 7 8 GCC is free software; you can redistribute it and/or modify it under 9 the terms of the GNU General Public License as published by the Free 10 Software Foundation; either version 3, or (at your option) any later 11 version. 12 13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 14 WARRANTY; without even the implied warranty of MERCHANTABILITY or 15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 16 for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with GCC; see the file COPYING3. If not see 20 <http://www.gnu.org/licenses/>. */ 21 22 #include "config.h" 23 #include "system.h" 24 #include "coretypes.h" 25 #include "tm.h" 26 #include "tree.h" 27 #include "gimple.h" 28 #include "tree-iterator.h" 29 #include "tree-inline.h" 30 #include "tree-flow.h" 31 #include "flags.h" 32 #include "function.h" 33 #include "diagnostic-core.h" 34 #include "tree-pass.h" 35 #include "langhooks.h" 36 37 /* The differences between High GIMPLE and Low GIMPLE are the 38 following: 39 40 1- Lexical scopes are removed (i.e., GIMPLE_BIND disappears). 41 42 2- GIMPLE_TRY and GIMPLE_CATCH are converted to abnormal control 43 flow and exception regions are built as an on-the-side region 44 hierarchy (See tree-eh.c:lower_eh_constructs). 45 46 3- Multiple identical return statements are grouped into a single 47 return and gotos to the unique return site. */ 48 49 /* Match a return statement with a label. During lowering, we identify 50 identical return statements and replace duplicates with a jump to 51 the corresponding label. */ 52 struct return_statements_t 53 { 54 tree label; 55 gimple stmt; 56 }; 57 typedef struct return_statements_t return_statements_t; 58 59 DEF_VEC_O(return_statements_t); 60 DEF_VEC_ALLOC_O(return_statements_t,heap); 61 62 struct lower_data 63 { 64 /* Block the current statement belongs to. */ 65 tree block; 66 67 /* A vector of label and return statements to be moved to the end 68 of the function. */ 69 VEC(return_statements_t,heap) *return_statements; 70 71 /* True if the current statement cannot fall through. */ 72 bool cannot_fallthru; 73 74 /* True if the function calls __builtin_setjmp. */ 75 bool calls_builtin_setjmp; 76 }; 77 78 static void lower_stmt (gimple_stmt_iterator *, struct lower_data *); 79 static void lower_gimple_bind (gimple_stmt_iterator *, struct lower_data *); 80 static void lower_gimple_return (gimple_stmt_iterator *, struct lower_data *); 81 static void lower_builtin_setjmp (gimple_stmt_iterator *); 82 83 84 /* Lower the body of current_function_decl from High GIMPLE into Low 85 GIMPLE. */ 86 87 static unsigned int 88 lower_function_body (void) 89 { 90 struct lower_data data; 91 gimple_seq body = gimple_body (current_function_decl); 92 gimple_seq lowered_body; 93 gimple_stmt_iterator i; 94 gimple bind; 95 tree t; 96 gimple x; 97 98 /* The gimplifier should've left a body of exactly one statement, 99 namely a GIMPLE_BIND. */ 100 gcc_assert (gimple_seq_first (body) == gimple_seq_last (body) 101 && gimple_code (gimple_seq_first_stmt (body)) == GIMPLE_BIND); 102 103 memset (&data, 0, sizeof (data)); 104 data.block = DECL_INITIAL (current_function_decl); 105 BLOCK_SUBBLOCKS (data.block) = NULL_TREE; 106 BLOCK_CHAIN (data.block) = NULL_TREE; 107 TREE_ASM_WRITTEN (data.block) = 1; 108 data.return_statements = VEC_alloc (return_statements_t, heap, 8); 109 110 bind = gimple_seq_first_stmt (body); 111 lowered_body = NULL; 112 gimple_seq_add_stmt (&lowered_body, bind); 113 i = gsi_start (lowered_body); 114 lower_gimple_bind (&i, &data); 115 116 /* Once the old body has been lowered, replace it with the new 117 lowered sequence. */ 118 gimple_set_body (current_function_decl, lowered_body); 119 120 i = gsi_last (lowered_body); 121 122 /* If the function falls off the end, we need a null return statement. 123 If we've already got one in the return_statements vector, we don't 124 need to do anything special. Otherwise build one by hand. */ 125 if (gimple_seq_may_fallthru (lowered_body) 126 && (VEC_empty (return_statements_t, data.return_statements) 127 || gimple_return_retval (VEC_last (return_statements_t, 128 data.return_statements)->stmt) != NULL)) 129 { 130 x = gimple_build_return (NULL); 131 gimple_set_location (x, cfun->function_end_locus); 132 gimple_set_block (x, DECL_INITIAL (current_function_decl)); 133 gsi_insert_after (&i, x, GSI_CONTINUE_LINKING); 134 } 135 136 /* If we lowered any return statements, emit the representative 137 at the end of the function. */ 138 while (!VEC_empty (return_statements_t, data.return_statements)) 139 { 140 return_statements_t t; 141 142 /* Unfortunately, we can't use VEC_pop because it returns void for 143 objects. */ 144 t = *VEC_last (return_statements_t, data.return_statements); 145 VEC_truncate (return_statements_t, 146 data.return_statements, 147 VEC_length (return_statements_t, 148 data.return_statements) - 1); 149 150 x = gimple_build_label (t.label); 151 gsi_insert_after (&i, x, GSI_CONTINUE_LINKING); 152 gsi_insert_after (&i, t.stmt, GSI_CONTINUE_LINKING); 153 } 154 155 /* If the function calls __builtin_setjmp, we need to emit the computed 156 goto that will serve as the unique dispatcher for all the receivers. */ 157 if (data.calls_builtin_setjmp) 158 { 159 tree disp_label, disp_var, arg; 160 161 /* Build 'DISP_LABEL:' and insert. */ 162 disp_label = create_artificial_label (cfun->function_end_locus); 163 /* This mark will create forward edges from every call site. */ 164 DECL_NONLOCAL (disp_label) = 1; 165 cfun->has_nonlocal_label = 1; 166 x = gimple_build_label (disp_label); 167 gsi_insert_after (&i, x, GSI_CONTINUE_LINKING); 168 169 /* Build 'DISP_VAR = __builtin_setjmp_dispatcher (DISP_LABEL);' 170 and insert. */ 171 disp_var = create_tmp_var (ptr_type_node, "setjmpvar"); 172 arg = build_addr (disp_label, current_function_decl); 173 t = builtin_decl_implicit (BUILT_IN_SETJMP_DISPATCHER); 174 x = gimple_build_call (t, 1, arg); 175 gimple_call_set_lhs (x, disp_var); 176 177 /* Build 'goto DISP_VAR;' and insert. */ 178 gsi_insert_after (&i, x, GSI_CONTINUE_LINKING); 179 x = gimple_build_goto (disp_var); 180 gsi_insert_after (&i, x, GSI_CONTINUE_LINKING); 181 } 182 183 gcc_assert (data.block == DECL_INITIAL (current_function_decl)); 184 BLOCK_SUBBLOCKS (data.block) 185 = blocks_nreverse (BLOCK_SUBBLOCKS (data.block)); 186 187 clear_block_marks (data.block); 188 VEC_free(return_statements_t, heap, data.return_statements); 189 return 0; 190 } 191 192 struct gimple_opt_pass pass_lower_cf = 193 { 194 { 195 GIMPLE_PASS, 196 "lower", /* name */ 197 NULL, /* gate */ 198 lower_function_body, /* execute */ 199 NULL, /* sub */ 200 NULL, /* next */ 201 0, /* static_pass_number */ 202 TV_NONE, /* tv_id */ 203 PROP_gimple_any, /* properties_required */ 204 PROP_gimple_lcf, /* properties_provided */ 205 0, /* properties_destroyed */ 206 0, /* todo_flags_start */ 207 0 /* todo_flags_finish */ 208 } 209 }; 210 211 212 213 /* Verify if the type of the argument matches that of the function 214 declaration. If we cannot verify this or there is a mismatch, 215 return false. */ 216 217 static bool 218 gimple_check_call_args (gimple stmt, tree fndecl) 219 { 220 tree parms, p; 221 unsigned int i, nargs; 222 223 /* Calls to internal functions always match their signature. */ 224 if (gimple_call_internal_p (stmt)) 225 return true; 226 227 nargs = gimple_call_num_args (stmt); 228 229 /* Get argument types for verification. */ 230 if (fndecl) 231 parms = TYPE_ARG_TYPES (TREE_TYPE (fndecl)); 232 else 233 parms = TYPE_ARG_TYPES (gimple_call_fntype (stmt)); 234 235 /* Verify if the type of the argument matches that of the function 236 declaration. If we cannot verify this or there is a mismatch, 237 return false. */ 238 if (fndecl && DECL_ARGUMENTS (fndecl)) 239 { 240 for (i = 0, p = DECL_ARGUMENTS (fndecl); 241 i < nargs; 242 i++, p = DECL_CHAIN (p)) 243 { 244 tree arg; 245 /* We cannot distinguish a varargs function from the case 246 of excess parameters, still deferring the inlining decision 247 to the callee is possible. */ 248 if (!p) 249 break; 250 arg = gimple_call_arg (stmt, i); 251 if (p == error_mark_node 252 || DECL_ARG_TYPE (p) == error_mark_node 253 || arg == error_mark_node 254 || (!types_compatible_p (DECL_ARG_TYPE (p), TREE_TYPE (arg)) 255 && !fold_convertible_p (DECL_ARG_TYPE (p), arg))) 256 return false; 257 } 258 } 259 else if (parms) 260 { 261 for (i = 0, p = parms; i < nargs; i++, p = TREE_CHAIN (p)) 262 { 263 tree arg; 264 /* If this is a varargs function defer inlining decision 265 to callee. */ 266 if (!p) 267 break; 268 arg = gimple_call_arg (stmt, i); 269 if (TREE_VALUE (p) == error_mark_node 270 || arg == error_mark_node 271 || TREE_CODE (TREE_VALUE (p)) == VOID_TYPE 272 || (!types_compatible_p (TREE_VALUE (p), TREE_TYPE (arg)) 273 && !fold_convertible_p (TREE_VALUE (p), arg))) 274 return false; 275 } 276 } 277 else 278 { 279 if (nargs != 0) 280 return false; 281 } 282 return true; 283 } 284 285 /* Verify if the type of the argument and lhs of CALL_STMT matches 286 that of the function declaration CALLEE. 287 If we cannot verify this or there is a mismatch, return false. */ 288 289 bool 290 gimple_check_call_matching_types (gimple call_stmt, tree callee) 291 { 292 tree lhs; 293 294 if ((DECL_RESULT (callee) 295 && !DECL_BY_REFERENCE (DECL_RESULT (callee)) 296 && (lhs = gimple_call_lhs (call_stmt)) != NULL_TREE 297 && !useless_type_conversion_p (TREE_TYPE (DECL_RESULT (callee)), 298 TREE_TYPE (lhs)) 299 && !fold_convertible_p (TREE_TYPE (DECL_RESULT (callee)), lhs)) 300 || !gimple_check_call_args (call_stmt, callee)) 301 return false; 302 return true; 303 } 304 305 /* Lower sequence SEQ. Unlike gimplification the statements are not relowered 306 when they are changed -- if this has to be done, the lowering routine must 307 do it explicitly. DATA is passed through the recursion. */ 308 309 static void 310 lower_sequence (gimple_seq seq, struct lower_data *data) 311 { 312 gimple_stmt_iterator gsi; 313 314 for (gsi = gsi_start (seq); !gsi_end_p (gsi); ) 315 lower_stmt (&gsi, data); 316 } 317 318 319 /* Lower the OpenMP directive statement pointed by GSI. DATA is 320 passed through the recursion. */ 321 322 static void 323 lower_omp_directive (gimple_stmt_iterator *gsi, struct lower_data *data) 324 { 325 gimple stmt; 326 327 stmt = gsi_stmt (*gsi); 328 329 lower_sequence (gimple_omp_body (stmt), data); 330 gsi_insert_before (gsi, stmt, GSI_SAME_STMT); 331 gsi_insert_seq_before (gsi, gimple_omp_body (stmt), GSI_SAME_STMT); 332 gimple_omp_set_body (stmt, NULL); 333 gsi_remove (gsi, false); 334 } 335 336 337 /* Lower statement GSI. DATA is passed through the recursion. We try to 338 track the fallthruness of statements and get rid of unreachable return 339 statements in order to prevent the EH lowering pass from adding useless 340 edges that can cause bogus warnings to be issued later; this guess need 341 not be 100% accurate, simply be conservative and reset cannot_fallthru 342 to false if we don't know. */ 343 344 static void 345 lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data) 346 { 347 gimple stmt = gsi_stmt (*gsi); 348 349 gimple_set_block (stmt, data->block); 350 351 switch (gimple_code (stmt)) 352 { 353 case GIMPLE_BIND: 354 lower_gimple_bind (gsi, data); 355 /* Propagate fallthruness. */ 356 return; 357 358 case GIMPLE_COND: 359 case GIMPLE_GOTO: 360 case GIMPLE_SWITCH: 361 data->cannot_fallthru = true; 362 gsi_next (gsi); 363 return; 364 365 case GIMPLE_RETURN: 366 if (data->cannot_fallthru) 367 { 368 gsi_remove (gsi, false); 369 /* Propagate fallthruness. */ 370 } 371 else 372 { 373 lower_gimple_return (gsi, data); 374 data->cannot_fallthru = true; 375 } 376 return; 377 378 case GIMPLE_TRY: 379 { 380 bool try_cannot_fallthru; 381 lower_sequence (gimple_try_eval (stmt), data); 382 try_cannot_fallthru = data->cannot_fallthru; 383 data->cannot_fallthru = false; 384 lower_sequence (gimple_try_cleanup (stmt), data); 385 /* See gimple_stmt_may_fallthru for the rationale. */ 386 if (gimple_try_kind (stmt) == GIMPLE_TRY_FINALLY) 387 { 388 data->cannot_fallthru |= try_cannot_fallthru; 389 gsi_next (gsi); 390 return; 391 } 392 } 393 break; 394 395 case GIMPLE_CATCH: 396 data->cannot_fallthru = false; 397 lower_sequence (gimple_catch_handler (stmt), data); 398 break; 399 400 case GIMPLE_EH_FILTER: 401 data->cannot_fallthru = false; 402 lower_sequence (gimple_eh_filter_failure (stmt), data); 403 break; 404 405 case GIMPLE_EH_ELSE: 406 lower_sequence (gimple_eh_else_n_body (stmt), data); 407 lower_sequence (gimple_eh_else_e_body (stmt), data); 408 break; 409 410 case GIMPLE_NOP: 411 case GIMPLE_ASM: 412 case GIMPLE_ASSIGN: 413 case GIMPLE_PREDICT: 414 case GIMPLE_LABEL: 415 case GIMPLE_EH_MUST_NOT_THROW: 416 case GIMPLE_OMP_FOR: 417 case GIMPLE_OMP_SECTIONS: 418 case GIMPLE_OMP_SECTIONS_SWITCH: 419 case GIMPLE_OMP_SECTION: 420 case GIMPLE_OMP_SINGLE: 421 case GIMPLE_OMP_MASTER: 422 case GIMPLE_OMP_ORDERED: 423 case GIMPLE_OMP_CRITICAL: 424 case GIMPLE_OMP_RETURN: 425 case GIMPLE_OMP_ATOMIC_LOAD: 426 case GIMPLE_OMP_ATOMIC_STORE: 427 case GIMPLE_OMP_CONTINUE: 428 break; 429 430 case GIMPLE_CALL: 431 { 432 tree decl = gimple_call_fndecl (stmt); 433 434 if (decl 435 && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL 436 && DECL_FUNCTION_CODE (decl) == BUILT_IN_SETJMP) 437 { 438 lower_builtin_setjmp (gsi); 439 data->cannot_fallthru = false; 440 data->calls_builtin_setjmp = true; 441 return; 442 } 443 444 if (decl && (flags_from_decl_or_type (decl) & ECF_NORETURN)) 445 { 446 data->cannot_fallthru = true; 447 gsi_next (gsi); 448 return; 449 } 450 } 451 break; 452 453 case GIMPLE_OMP_PARALLEL: 454 case GIMPLE_OMP_TASK: 455 data->cannot_fallthru = false; 456 lower_omp_directive (gsi, data); 457 data->cannot_fallthru = false; 458 return; 459 460 case GIMPLE_TRANSACTION: 461 lower_sequence (gimple_transaction_body (stmt), data); 462 break; 463 464 default: 465 gcc_unreachable (); 466 } 467 468 data->cannot_fallthru = false; 469 gsi_next (gsi); 470 } 471 472 /* Lower a bind_expr TSI. DATA is passed through the recursion. */ 473 474 static void 475 lower_gimple_bind (gimple_stmt_iterator *gsi, struct lower_data *data) 476 { 477 tree old_block = data->block; 478 gimple stmt = gsi_stmt (*gsi); 479 tree new_block = gimple_bind_block (stmt); 480 481 if (new_block) 482 { 483 if (new_block == old_block) 484 { 485 /* The outermost block of the original function may not be the 486 outermost statement chain of the gimplified function. So we 487 may see the outermost block just inside the function. */ 488 gcc_assert (new_block == DECL_INITIAL (current_function_decl)); 489 new_block = NULL; 490 } 491 else 492 { 493 /* We do not expect to handle duplicate blocks. */ 494 gcc_assert (!TREE_ASM_WRITTEN (new_block)); 495 TREE_ASM_WRITTEN (new_block) = 1; 496 497 /* Block tree may get clobbered by inlining. Normally this would 498 be fixed in rest_of_decl_compilation using block notes, but 499 since we are not going to emit them, it is up to us. */ 500 BLOCK_CHAIN (new_block) = BLOCK_SUBBLOCKS (old_block); 501 BLOCK_SUBBLOCKS (old_block) = new_block; 502 BLOCK_SUBBLOCKS (new_block) = NULL_TREE; 503 BLOCK_SUPERCONTEXT (new_block) = old_block; 504 505 data->block = new_block; 506 } 507 } 508 509 record_vars (gimple_bind_vars (stmt)); 510 lower_sequence (gimple_bind_body (stmt), data); 511 512 if (new_block) 513 { 514 gcc_assert (data->block == new_block); 515 516 BLOCK_SUBBLOCKS (new_block) 517 = blocks_nreverse (BLOCK_SUBBLOCKS (new_block)); 518 data->block = old_block; 519 } 520 521 /* The GIMPLE_BIND no longer carries any useful information -- kill it. */ 522 gsi_insert_seq_before (gsi, gimple_bind_body (stmt), GSI_SAME_STMT); 523 gsi_remove (gsi, false); 524 } 525 526 /* Try to determine whether a TRY_CATCH expression can fall through. 527 This is a subroutine of block_may_fallthru. */ 528 529 static bool 530 try_catch_may_fallthru (const_tree stmt) 531 { 532 tree_stmt_iterator i; 533 534 /* If the TRY block can fall through, the whole TRY_CATCH can 535 fall through. */ 536 if (block_may_fallthru (TREE_OPERAND (stmt, 0))) 537 return true; 538 539 i = tsi_start (TREE_OPERAND (stmt, 1)); 540 switch (TREE_CODE (tsi_stmt (i))) 541 { 542 case CATCH_EXPR: 543 /* We expect to see a sequence of CATCH_EXPR trees, each with a 544 catch expression and a body. The whole TRY_CATCH may fall 545 through iff any of the catch bodies falls through. */ 546 for (; !tsi_end_p (i); tsi_next (&i)) 547 { 548 if (block_may_fallthru (CATCH_BODY (tsi_stmt (i)))) 549 return true; 550 } 551 return false; 552 553 case EH_FILTER_EXPR: 554 /* The exception filter expression only matters if there is an 555 exception. If the exception does not match EH_FILTER_TYPES, 556 we will execute EH_FILTER_FAILURE, and we will fall through 557 if that falls through. If the exception does match 558 EH_FILTER_TYPES, the stack unwinder will continue up the 559 stack, so we will not fall through. We don't know whether we 560 will throw an exception which matches EH_FILTER_TYPES or not, 561 so we just ignore EH_FILTER_TYPES and assume that we might 562 throw an exception which doesn't match. */ 563 return block_may_fallthru (EH_FILTER_FAILURE (tsi_stmt (i))); 564 565 default: 566 /* This case represents statements to be executed when an 567 exception occurs. Those statements are implicitly followed 568 by a RESX statement to resume execution after the exception. 569 So in this case the TRY_CATCH never falls through. */ 570 return false; 571 } 572 } 573 574 575 /* Same as above, but for a GIMPLE_TRY_CATCH. */ 576 577 static bool 578 gimple_try_catch_may_fallthru (gimple stmt) 579 { 580 gimple_stmt_iterator i; 581 582 /* We don't handle GIMPLE_TRY_FINALLY. */ 583 gcc_assert (gimple_try_kind (stmt) == GIMPLE_TRY_CATCH); 584 585 /* If the TRY block can fall through, the whole TRY_CATCH can 586 fall through. */ 587 if (gimple_seq_may_fallthru (gimple_try_eval (stmt))) 588 return true; 589 590 i = gsi_start (gimple_try_cleanup (stmt)); 591 switch (gimple_code (gsi_stmt (i))) 592 { 593 case GIMPLE_CATCH: 594 /* We expect to see a sequence of GIMPLE_CATCH stmts, each with a 595 catch expression and a body. The whole try/catch may fall 596 through iff any of the catch bodies falls through. */ 597 for (; !gsi_end_p (i); gsi_next (&i)) 598 { 599 if (gimple_seq_may_fallthru (gimple_catch_handler (gsi_stmt (i)))) 600 return true; 601 } 602 return false; 603 604 case GIMPLE_EH_FILTER: 605 /* The exception filter expression only matters if there is an 606 exception. If the exception does not match EH_FILTER_TYPES, 607 we will execute EH_FILTER_FAILURE, and we will fall through 608 if that falls through. If the exception does match 609 EH_FILTER_TYPES, the stack unwinder will continue up the 610 stack, so we will not fall through. We don't know whether we 611 will throw an exception which matches EH_FILTER_TYPES or not, 612 so we just ignore EH_FILTER_TYPES and assume that we might 613 throw an exception which doesn't match. */ 614 return gimple_seq_may_fallthru (gimple_eh_filter_failure (gsi_stmt (i))); 615 616 default: 617 /* This case represents statements to be executed when an 618 exception occurs. Those statements are implicitly followed 619 by a GIMPLE_RESX to resume execution after the exception. So 620 in this case the try/catch never falls through. */ 621 return false; 622 } 623 } 624 625 626 /* Try to determine if we can fall out of the bottom of BLOCK. This guess 627 need not be 100% accurate; simply be conservative and return true if we 628 don't know. This is used only to avoid stupidly generating extra code. 629 If we're wrong, we'll just delete the extra code later. */ 630 631 bool 632 block_may_fallthru (const_tree block) 633 { 634 /* This CONST_CAST is okay because expr_last returns its argument 635 unmodified and we assign it to a const_tree. */ 636 const_tree stmt = expr_last (CONST_CAST_TREE(block)); 637 638 switch (stmt ? TREE_CODE (stmt) : ERROR_MARK) 639 { 640 case GOTO_EXPR: 641 case RETURN_EXPR: 642 /* Easy cases. If the last statement of the block implies 643 control transfer, then we can't fall through. */ 644 return false; 645 646 case SWITCH_EXPR: 647 /* If SWITCH_LABELS is set, this is lowered, and represents a 648 branch to a selected label and hence can not fall through. 649 Otherwise SWITCH_BODY is set, and the switch can fall 650 through. */ 651 return SWITCH_LABELS (stmt) == NULL_TREE; 652 653 case COND_EXPR: 654 if (block_may_fallthru (COND_EXPR_THEN (stmt))) 655 return true; 656 return block_may_fallthru (COND_EXPR_ELSE (stmt)); 657 658 case BIND_EXPR: 659 return block_may_fallthru (BIND_EXPR_BODY (stmt)); 660 661 case TRY_CATCH_EXPR: 662 return try_catch_may_fallthru (stmt); 663 664 case TRY_FINALLY_EXPR: 665 /* The finally clause is always executed after the try clause, 666 so if it does not fall through, then the try-finally will not 667 fall through. Otherwise, if the try clause does not fall 668 through, then when the finally clause falls through it will 669 resume execution wherever the try clause was going. So the 670 whole try-finally will only fall through if both the try 671 clause and the finally clause fall through. */ 672 return (block_may_fallthru (TREE_OPERAND (stmt, 0)) 673 && block_may_fallthru (TREE_OPERAND (stmt, 1))); 674 675 case MODIFY_EXPR: 676 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR) 677 stmt = TREE_OPERAND (stmt, 1); 678 else 679 return true; 680 /* FALLTHRU */ 681 682 case CALL_EXPR: 683 /* Functions that do not return do not fall through. */ 684 return (call_expr_flags (stmt) & ECF_NORETURN) == 0; 685 686 case CLEANUP_POINT_EXPR: 687 return block_may_fallthru (TREE_OPERAND (stmt, 0)); 688 689 case TARGET_EXPR: 690 return block_may_fallthru (TREE_OPERAND (stmt, 1)); 691 692 case ERROR_MARK: 693 return true; 694 695 default: 696 return lang_hooks.block_may_fallthru (stmt); 697 } 698 } 699 700 701 /* Try to determine if we can continue executing the statement 702 immediately following STMT. This guess need not be 100% accurate; 703 simply be conservative and return true if we don't know. This is 704 used only to avoid stupidly generating extra code. If we're wrong, 705 we'll just delete the extra code later. */ 706 707 bool 708 gimple_stmt_may_fallthru (gimple stmt) 709 { 710 if (!stmt) 711 return true; 712 713 switch (gimple_code (stmt)) 714 { 715 case GIMPLE_GOTO: 716 case GIMPLE_RETURN: 717 case GIMPLE_RESX: 718 /* Easy cases. If the last statement of the seq implies 719 control transfer, then we can't fall through. */ 720 return false; 721 722 case GIMPLE_SWITCH: 723 /* Switch has already been lowered and represents a branch 724 to a selected label and hence can't fall through. */ 725 return false; 726 727 case GIMPLE_COND: 728 /* GIMPLE_COND's are already lowered into a two-way branch. They 729 can't fall through. */ 730 return false; 731 732 case GIMPLE_BIND: 733 return gimple_seq_may_fallthru (gimple_bind_body (stmt)); 734 735 case GIMPLE_TRY: 736 if (gimple_try_kind (stmt) == GIMPLE_TRY_CATCH) 737 return gimple_try_catch_may_fallthru (stmt); 738 739 /* It must be a GIMPLE_TRY_FINALLY. */ 740 741 /* The finally clause is always executed after the try clause, 742 so if it does not fall through, then the try-finally will not 743 fall through. Otherwise, if the try clause does not fall 744 through, then when the finally clause falls through it will 745 resume execution wherever the try clause was going. So the 746 whole try-finally will only fall through if both the try 747 clause and the finally clause fall through. */ 748 return (gimple_seq_may_fallthru (gimple_try_eval (stmt)) 749 && gimple_seq_may_fallthru (gimple_try_cleanup (stmt))); 750 751 case GIMPLE_EH_ELSE: 752 return (gimple_seq_may_fallthru (gimple_eh_else_n_body (stmt)) 753 || gimple_seq_may_fallthru (gimple_eh_else_e_body (stmt))); 754 755 case GIMPLE_CALL: 756 /* Functions that do not return do not fall through. */ 757 return (gimple_call_flags (stmt) & ECF_NORETURN) == 0; 758 759 default: 760 return true; 761 } 762 } 763 764 765 /* Same as gimple_stmt_may_fallthru, but for the gimple sequence SEQ. */ 766 767 bool 768 gimple_seq_may_fallthru (gimple_seq seq) 769 { 770 return gimple_stmt_may_fallthru (gimple_seq_last_stmt (seq)); 771 } 772 773 774 /* Lower a GIMPLE_RETURN GSI. DATA is passed through the recursion. */ 775 776 static void 777 lower_gimple_return (gimple_stmt_iterator *gsi, struct lower_data *data) 778 { 779 gimple stmt = gsi_stmt (*gsi); 780 gimple t; 781 int i; 782 return_statements_t tmp_rs; 783 784 /* Match this up with an existing return statement that's been created. */ 785 for (i = VEC_length (return_statements_t, data->return_statements) - 1; 786 i >= 0; i--) 787 { 788 tmp_rs = *VEC_index (return_statements_t, data->return_statements, i); 789 790 if (gimple_return_retval (stmt) == gimple_return_retval (tmp_rs.stmt)) 791 { 792 /* Remove the line number from the representative return statement. 793 It now fills in for many such returns. Failure to remove this 794 will result in incorrect results for coverage analysis. */ 795 gimple_set_location (tmp_rs.stmt, UNKNOWN_LOCATION); 796 797 goto found; 798 } 799 } 800 801 /* Not found. Create a new label and record the return statement. */ 802 tmp_rs.label = create_artificial_label (cfun->function_end_locus); 803 tmp_rs.stmt = stmt; 804 VEC_safe_push (return_statements_t, heap, data->return_statements, &tmp_rs); 805 806 /* Generate a goto statement and remove the return statement. */ 807 found: 808 /* When not optimizing, make sure user returns are preserved. */ 809 if (!optimize && gimple_has_location (stmt)) 810 DECL_ARTIFICIAL (tmp_rs.label) = 0; 811 t = gimple_build_goto (tmp_rs.label); 812 gimple_set_location (t, gimple_location (stmt)); 813 gimple_set_block (t, gimple_block (stmt)); 814 gsi_insert_before (gsi, t, GSI_SAME_STMT); 815 gsi_remove (gsi, false); 816 } 817 818 /* Lower a __builtin_setjmp GSI. 819 820 __builtin_setjmp is passed a pointer to an array of five words (not 821 all will be used on all machines). It operates similarly to the C 822 library function of the same name, but is more efficient. 823 824 It is lowered into 3 other builtins, namely __builtin_setjmp_setup, 825 __builtin_setjmp_dispatcher and __builtin_setjmp_receiver, but with 826 __builtin_setjmp_dispatcher shared among all the instances; that's 827 why it is only emitted at the end by lower_function_body. 828 829 After full lowering, the body of the function should look like: 830 831 { 832 void * setjmpvar.0; 833 int D.1844; 834 int D.2844; 835 836 [...] 837 838 __builtin_setjmp_setup (&buf, &<D1847>); 839 D.1844 = 0; 840 goto <D1846>; 841 <D1847>:; 842 __builtin_setjmp_receiver (&<D1847>); 843 D.1844 = 1; 844 <D1846>:; 845 if (D.1844 == 0) goto <D1848>; else goto <D1849>; 846 847 [...] 848 849 __builtin_setjmp_setup (&buf, &<D2847>); 850 D.2844 = 0; 851 goto <D2846>; 852 <D2847>:; 853 __builtin_setjmp_receiver (&<D2847>); 854 D.2844 = 1; 855 <D2846>:; 856 if (D.2844 == 0) goto <D2848>; else goto <D2849>; 857 858 [...] 859 860 <D3850>:; 861 return; 862 <D3853>: [non-local]; 863 setjmpvar.0 = __builtin_setjmp_dispatcher (&<D3853>); 864 goto setjmpvar.0; 865 } 866 867 The dispatcher block will be both the unique destination of all the 868 abnormal call edges and the unique source of all the abnormal edges 869 to the receivers, thus keeping the complexity explosion localized. */ 870 871 static void 872 lower_builtin_setjmp (gimple_stmt_iterator *gsi) 873 { 874 gimple stmt = gsi_stmt (*gsi); 875 location_t loc = gimple_location (stmt); 876 tree cont_label = create_artificial_label (loc); 877 tree next_label = create_artificial_label (loc); 878 tree dest, t, arg; 879 gimple g; 880 881 /* NEXT_LABEL is the label __builtin_longjmp will jump to. Its address is 882 passed to both __builtin_setjmp_setup and __builtin_setjmp_receiver. */ 883 FORCED_LABEL (next_label) = 1; 884 885 dest = gimple_call_lhs (stmt); 886 887 /* Build '__builtin_setjmp_setup (BUF, NEXT_LABEL)' and insert. */ 888 arg = build_addr (next_label, current_function_decl); 889 t = builtin_decl_implicit (BUILT_IN_SETJMP_SETUP); 890 g = gimple_build_call (t, 2, gimple_call_arg (stmt, 0), arg); 891 gimple_set_location (g, loc); 892 gimple_set_block (g, gimple_block (stmt)); 893 gsi_insert_before (gsi, g, GSI_SAME_STMT); 894 895 /* Build 'DEST = 0' and insert. */ 896 if (dest) 897 { 898 g = gimple_build_assign (dest, build_zero_cst (TREE_TYPE (dest))); 899 gimple_set_location (g, loc); 900 gimple_set_block (g, gimple_block (stmt)); 901 gsi_insert_before (gsi, g, GSI_SAME_STMT); 902 } 903 904 /* Build 'goto CONT_LABEL' and insert. */ 905 g = gimple_build_goto (cont_label); 906 gsi_insert_before (gsi, g, GSI_SAME_STMT); 907 908 /* Build 'NEXT_LABEL:' and insert. */ 909 g = gimple_build_label (next_label); 910 gsi_insert_before (gsi, g, GSI_SAME_STMT); 911 912 /* Build '__builtin_setjmp_receiver (NEXT_LABEL)' and insert. */ 913 arg = build_addr (next_label, current_function_decl); 914 t = builtin_decl_implicit (BUILT_IN_SETJMP_RECEIVER); 915 g = gimple_build_call (t, 1, arg); 916 gimple_set_location (g, loc); 917 gimple_set_block (g, gimple_block (stmt)); 918 gsi_insert_before (gsi, g, GSI_SAME_STMT); 919 920 /* Build 'DEST = 1' and insert. */ 921 if (dest) 922 { 923 g = gimple_build_assign (dest, fold_convert_loc (loc, TREE_TYPE (dest), 924 integer_one_node)); 925 gimple_set_location (g, loc); 926 gimple_set_block (g, gimple_block (stmt)); 927 gsi_insert_before (gsi, g, GSI_SAME_STMT); 928 } 929 930 /* Build 'CONT_LABEL:' and insert. */ 931 g = gimple_build_label (cont_label); 932 gsi_insert_before (gsi, g, GSI_SAME_STMT); 933 934 /* Remove the call to __builtin_setjmp. */ 935 gsi_remove (gsi, false); 936 } 937 938 939 /* Record the variables in VARS into function FN. */ 940 941 void 942 record_vars_into (tree vars, tree fn) 943 { 944 if (fn != current_function_decl) 945 push_cfun (DECL_STRUCT_FUNCTION (fn)); 946 947 for (; vars; vars = DECL_CHAIN (vars)) 948 { 949 tree var = vars; 950 951 /* BIND_EXPRs contains also function/type/constant declarations 952 we don't need to care about. */ 953 if (TREE_CODE (var) != VAR_DECL) 954 continue; 955 956 /* Nothing to do in this case. */ 957 if (DECL_EXTERNAL (var)) 958 continue; 959 960 /* Record the variable. */ 961 add_local_decl (cfun, var); 962 if (gimple_referenced_vars (cfun)) 963 add_referenced_var (var); 964 } 965 966 if (fn != current_function_decl) 967 pop_cfun (); 968 } 969 970 971 /* Record the variables in VARS into current_function_decl. */ 972 973 void 974 record_vars (tree vars) 975 { 976 record_vars_into (vars, current_function_decl); 977 } 978