1 /* C-compiler utilities for types and variables storage layout 2 Copyright (C) 1987-2018 Free Software Foundation, Inc. 3 4 This file is part of GCC. 5 6 GCC is free software; you can redistribute it and/or modify it under 7 the terms of the GNU General Public License as published by the Free 8 Software Foundation; either version 3, or (at your option) any later 9 version. 10 11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 12 WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GCC; see the file COPYING3. If not see 18 <http://www.gnu.org/licenses/>. */ 19 20 21 #include "config.h" 22 #include "system.h" 23 #include "coretypes.h" 24 #include "target.h" 25 #include "function.h" 26 #include "rtl.h" 27 #include "tree.h" 28 #include "memmodel.h" 29 #include "tm_p.h" 30 #include "stringpool.h" 31 #include "regs.h" 32 #include "emit-rtl.h" 33 #include "cgraph.h" 34 #include "diagnostic-core.h" 35 #include "fold-const.h" 36 #include "stor-layout.h" 37 #include "varasm.h" 38 #include "print-tree.h" 39 #include "langhooks.h" 40 #include "tree-inline.h" 41 #include "dumpfile.h" 42 #include "gimplify.h" 43 #include "attribs.h" 44 #include "debug.h" 45 46 /* Data type for the expressions representing sizes of data types. 47 It is the first integer type laid out. */ 48 tree sizetype_tab[(int) stk_type_kind_last]; 49 50 /* If nonzero, this is an upper limit on alignment of structure fields. 51 The value is measured in bits. */ 52 unsigned int maximum_field_alignment = TARGET_DEFAULT_PACK_STRUCT * BITS_PER_UNIT; 53 54 static tree self_referential_size (tree); 55 static void finalize_record_size (record_layout_info); 56 static void finalize_type_size (tree); 57 static void place_union_field (record_layout_info, tree); 58 static int excess_unit_span (HOST_WIDE_INT, HOST_WIDE_INT, HOST_WIDE_INT, 59 HOST_WIDE_INT, tree); 60 extern void debug_rli (record_layout_info); 61 62 /* Given a size SIZE that may not be a constant, return a SAVE_EXPR 63 to serve as the actual size-expression for a type or decl. */ 64 65 tree 66 variable_size (tree size) 67 { 68 /* Obviously. */ 69 if (TREE_CONSTANT (size)) 70 return size; 71 72 /* If the size is self-referential, we can't make a SAVE_EXPR (see 73 save_expr for the rationale). But we can do something else. */ 74 if (CONTAINS_PLACEHOLDER_P (size)) 75 return self_referential_size (size); 76 77 /* If we are in the global binding level, we can't make a SAVE_EXPR 78 since it may end up being shared across functions, so it is up 79 to the front-end to deal with this case. */ 80 if (lang_hooks.decls.global_bindings_p ()) 81 return size; 82 83 return save_expr (size); 84 } 85 86 /* An array of functions used for self-referential size computation. */ 87 static GTY(()) vec<tree, va_gc> *size_functions; 88 89 /* Return true if T is a self-referential component reference. */ 90 91 static bool 92 self_referential_component_ref_p (tree t) 93 { 94 if (TREE_CODE (t) != COMPONENT_REF) 95 return false; 96 97 while (REFERENCE_CLASS_P (t)) 98 t = TREE_OPERAND (t, 0); 99 100 return (TREE_CODE (t) == PLACEHOLDER_EXPR); 101 } 102 103 /* Similar to copy_tree_r but do not copy component references involving 104 PLACEHOLDER_EXPRs. These nodes are spotted in find_placeholder_in_expr 105 and substituted in substitute_in_expr. */ 106 107 static tree 108 copy_self_referential_tree_r (tree *tp, int *walk_subtrees, void *data) 109 { 110 enum tree_code code = TREE_CODE (*tp); 111 112 /* Stop at types, decls, constants like copy_tree_r. */ 113 if (TREE_CODE_CLASS (code) == tcc_type 114 || TREE_CODE_CLASS (code) == tcc_declaration 115 || TREE_CODE_CLASS (code) == tcc_constant) 116 { 117 *walk_subtrees = 0; 118 return NULL_TREE; 119 } 120 121 /* This is the pattern built in ada/make_aligning_type. */ 122 else if (code == ADDR_EXPR 123 && TREE_CODE (TREE_OPERAND (*tp, 0)) == PLACEHOLDER_EXPR) 124 { 125 *walk_subtrees = 0; 126 return NULL_TREE; 127 } 128 129 /* Default case: the component reference. */ 130 else if (self_referential_component_ref_p (*tp)) 131 { 132 *walk_subtrees = 0; 133 return NULL_TREE; 134 } 135 136 /* We're not supposed to have them in self-referential size trees 137 because we wouldn't properly control when they are evaluated. 138 However, not creating superfluous SAVE_EXPRs requires accurate 139 tracking of readonly-ness all the way down to here, which we 140 cannot always guarantee in practice. So punt in this case. */ 141 else if (code == SAVE_EXPR) 142 return error_mark_node; 143 144 else if (code == STATEMENT_LIST) 145 gcc_unreachable (); 146 147 return copy_tree_r (tp, walk_subtrees, data); 148 } 149 150 /* Given a SIZE expression that is self-referential, return an equivalent 151 expression to serve as the actual size expression for a type. */ 152 153 static tree 154 self_referential_size (tree size) 155 { 156 static unsigned HOST_WIDE_INT fnno = 0; 157 vec<tree> self_refs = vNULL; 158 tree param_type_list = NULL, param_decl_list = NULL; 159 tree t, ref, return_type, fntype, fnname, fndecl; 160 unsigned int i; 161 char buf[128]; 162 vec<tree, va_gc> *args = NULL; 163 164 /* Do not factor out simple operations. */ 165 t = skip_simple_constant_arithmetic (size); 166 if (TREE_CODE (t) == CALL_EXPR || self_referential_component_ref_p (t)) 167 return size; 168 169 /* Collect the list of self-references in the expression. */ 170 find_placeholder_in_expr (size, &self_refs); 171 gcc_assert (self_refs.length () > 0); 172 173 /* Obtain a private copy of the expression. */ 174 t = size; 175 if (walk_tree (&t, copy_self_referential_tree_r, NULL, NULL) != NULL_TREE) 176 return size; 177 size = t; 178 179 /* Build the parameter and argument lists in parallel; also 180 substitute the former for the latter in the expression. */ 181 vec_alloc (args, self_refs.length ()); 182 FOR_EACH_VEC_ELT (self_refs, i, ref) 183 { 184 tree subst, param_name, param_type, param_decl; 185 186 if (DECL_P (ref)) 187 { 188 /* We shouldn't have true variables here. */ 189 gcc_assert (TREE_READONLY (ref)); 190 subst = ref; 191 } 192 /* This is the pattern built in ada/make_aligning_type. */ 193 else if (TREE_CODE (ref) == ADDR_EXPR) 194 subst = ref; 195 /* Default case: the component reference. */ 196 else 197 subst = TREE_OPERAND (ref, 1); 198 199 sprintf (buf, "p%d", i); 200 param_name = get_identifier (buf); 201 param_type = TREE_TYPE (ref); 202 param_decl 203 = build_decl (input_location, PARM_DECL, param_name, param_type); 204 DECL_ARG_TYPE (param_decl) = param_type; 205 DECL_ARTIFICIAL (param_decl) = 1; 206 TREE_READONLY (param_decl) = 1; 207 208 size = substitute_in_expr (size, subst, param_decl); 209 210 param_type_list = tree_cons (NULL_TREE, param_type, param_type_list); 211 param_decl_list = chainon (param_decl, param_decl_list); 212 args->quick_push (ref); 213 } 214 215 self_refs.release (); 216 217 /* Append 'void' to indicate that the number of parameters is fixed. */ 218 param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list); 219 220 /* The 3 lists have been created in reverse order. */ 221 param_type_list = nreverse (param_type_list); 222 param_decl_list = nreverse (param_decl_list); 223 224 /* Build the function type. */ 225 return_type = TREE_TYPE (size); 226 fntype = build_function_type (return_type, param_type_list); 227 228 /* Build the function declaration. */ 229 sprintf (buf, "SZ" HOST_WIDE_INT_PRINT_UNSIGNED, fnno++); 230 fnname = get_file_function_name (buf); 231 fndecl = build_decl (input_location, FUNCTION_DECL, fnname, fntype); 232 for (t = param_decl_list; t; t = DECL_CHAIN (t)) 233 DECL_CONTEXT (t) = fndecl; 234 DECL_ARGUMENTS (fndecl) = param_decl_list; 235 DECL_RESULT (fndecl) 236 = build_decl (input_location, RESULT_DECL, 0, return_type); 237 DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl; 238 239 /* The function has been created by the compiler and we don't 240 want to emit debug info for it. */ 241 DECL_ARTIFICIAL (fndecl) = 1; 242 DECL_IGNORED_P (fndecl) = 1; 243 244 /* It is supposed to be "const" and never throw. */ 245 TREE_READONLY (fndecl) = 1; 246 TREE_NOTHROW (fndecl) = 1; 247 248 /* We want it to be inlined when this is deemed profitable, as 249 well as discarded if every call has been integrated. */ 250 DECL_DECLARED_INLINE_P (fndecl) = 1; 251 252 /* It is made up of a unique return statement. */ 253 DECL_INITIAL (fndecl) = make_node (BLOCK); 254 BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl; 255 t = build2 (MODIFY_EXPR, return_type, DECL_RESULT (fndecl), size); 256 DECL_SAVED_TREE (fndecl) = build1 (RETURN_EXPR, void_type_node, t); 257 TREE_STATIC (fndecl) = 1; 258 259 /* Put it onto the list of size functions. */ 260 vec_safe_push (size_functions, fndecl); 261 262 /* Replace the original expression with a call to the size function. */ 263 return build_call_expr_loc_vec (UNKNOWN_LOCATION, fndecl, args); 264 } 265 266 /* Take, queue and compile all the size functions. It is essential that 267 the size functions be gimplified at the very end of the compilation 268 in order to guarantee transparent handling of self-referential sizes. 269 Otherwise the GENERIC inliner would not be able to inline them back 270 at each of their call sites, thus creating artificial non-constant 271 size expressions which would trigger nasty problems later on. */ 272 273 void 274 finalize_size_functions (void) 275 { 276 unsigned int i; 277 tree fndecl; 278 279 for (i = 0; size_functions && size_functions->iterate (i, &fndecl); i++) 280 { 281 allocate_struct_function (fndecl, false); 282 set_cfun (NULL); 283 dump_function (TDI_original, fndecl); 284 285 /* As these functions are used to describe the layout of variable-length 286 structures, debug info generation needs their implementation. */ 287 debug_hooks->size_function (fndecl); 288 gimplify_function_tree (fndecl); 289 cgraph_node::finalize_function (fndecl, false); 290 } 291 292 vec_free (size_functions); 293 } 294 295 /* Return a machine mode of class MCLASS with SIZE bits of precision, 296 if one exists. The mode may have padding bits as well the SIZE 297 value bits. If LIMIT is nonzero, disregard modes wider than 298 MAX_FIXED_MODE_SIZE. */ 299 300 opt_machine_mode 301 mode_for_size (poly_uint64 size, enum mode_class mclass, int limit) 302 { 303 machine_mode mode; 304 int i; 305 306 if (limit && maybe_gt (size, (unsigned int) MAX_FIXED_MODE_SIZE)) 307 return opt_machine_mode (); 308 309 /* Get the first mode which has this size, in the specified class. */ 310 FOR_EACH_MODE_IN_CLASS (mode, mclass) 311 if (known_eq (GET_MODE_PRECISION (mode), size)) 312 return mode; 313 314 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT) 315 for (i = 0; i < NUM_INT_N_ENTS; i ++) 316 if (known_eq (int_n_data[i].bitsize, size) 317 && int_n_enabled_p[i]) 318 return int_n_data[i].m; 319 320 return opt_machine_mode (); 321 } 322 323 /* Similar, except passed a tree node. */ 324 325 opt_machine_mode 326 mode_for_size_tree (const_tree size, enum mode_class mclass, int limit) 327 { 328 unsigned HOST_WIDE_INT uhwi; 329 unsigned int ui; 330 331 if (!tree_fits_uhwi_p (size)) 332 return opt_machine_mode (); 333 uhwi = tree_to_uhwi (size); 334 ui = uhwi; 335 if (uhwi != ui) 336 return opt_machine_mode (); 337 return mode_for_size (ui, mclass, limit); 338 } 339 340 /* Return the narrowest mode of class MCLASS that contains at least 341 SIZE bits. Abort if no such mode exists. */ 342 343 machine_mode 344 smallest_mode_for_size (poly_uint64 size, enum mode_class mclass) 345 { 346 machine_mode mode = VOIDmode; 347 int i; 348 349 /* Get the first mode which has at least this size, in the 350 specified class. */ 351 FOR_EACH_MODE_IN_CLASS (mode, mclass) 352 if (known_ge (GET_MODE_PRECISION (mode), size)) 353 break; 354 355 gcc_assert (mode != VOIDmode); 356 357 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT) 358 for (i = 0; i < NUM_INT_N_ENTS; i ++) 359 if (known_ge (int_n_data[i].bitsize, size) 360 && known_lt (int_n_data[i].bitsize, GET_MODE_PRECISION (mode)) 361 && int_n_enabled_p[i]) 362 mode = int_n_data[i].m; 363 364 return mode; 365 } 366 367 /* Return an integer mode of exactly the same size as MODE, if one exists. */ 368 369 opt_scalar_int_mode 370 int_mode_for_mode (machine_mode mode) 371 { 372 switch (GET_MODE_CLASS (mode)) 373 { 374 case MODE_INT: 375 case MODE_PARTIAL_INT: 376 return as_a <scalar_int_mode> (mode); 377 378 case MODE_COMPLEX_INT: 379 case MODE_COMPLEX_FLOAT: 380 case MODE_FLOAT: 381 case MODE_DECIMAL_FLOAT: 382 case MODE_FRACT: 383 case MODE_ACCUM: 384 case MODE_UFRACT: 385 case MODE_UACCUM: 386 case MODE_VECTOR_BOOL: 387 case MODE_VECTOR_INT: 388 case MODE_VECTOR_FLOAT: 389 case MODE_VECTOR_FRACT: 390 case MODE_VECTOR_ACCUM: 391 case MODE_VECTOR_UFRACT: 392 case MODE_VECTOR_UACCUM: 393 case MODE_POINTER_BOUNDS: 394 return int_mode_for_size (GET_MODE_BITSIZE (mode), 0); 395 396 case MODE_RANDOM: 397 if (mode == BLKmode) 398 return opt_scalar_int_mode (); 399 400 /* fall through */ 401 402 case MODE_CC: 403 default: 404 gcc_unreachable (); 405 } 406 } 407 408 /* Find a mode that can be used for efficient bitwise operations on MODE, 409 if one exists. */ 410 411 opt_machine_mode 412 bitwise_mode_for_mode (machine_mode mode) 413 { 414 /* Quick exit if we already have a suitable mode. */ 415 scalar_int_mode int_mode; 416 if (is_a <scalar_int_mode> (mode, &int_mode) 417 && GET_MODE_BITSIZE (int_mode) <= MAX_FIXED_MODE_SIZE) 418 return int_mode; 419 420 /* Reuse the sanity checks from int_mode_for_mode. */ 421 gcc_checking_assert ((int_mode_for_mode (mode), true)); 422 423 poly_int64 bitsize = GET_MODE_BITSIZE (mode); 424 425 /* Try to replace complex modes with complex modes. In general we 426 expect both components to be processed independently, so we only 427 care whether there is a register for the inner mode. */ 428 if (COMPLEX_MODE_P (mode)) 429 { 430 machine_mode trial = mode; 431 if ((GET_MODE_CLASS (trial) == MODE_COMPLEX_INT 432 || mode_for_size (bitsize, MODE_COMPLEX_INT, false).exists (&trial)) 433 && have_regs_of_mode[GET_MODE_INNER (trial)]) 434 return trial; 435 } 436 437 /* Try to replace vector modes with vector modes. Also try using vector 438 modes if an integer mode would be too big. */ 439 if (VECTOR_MODE_P (mode) 440 || maybe_gt (bitsize, MAX_FIXED_MODE_SIZE)) 441 { 442 machine_mode trial = mode; 443 if ((GET_MODE_CLASS (trial) == MODE_VECTOR_INT 444 || mode_for_size (bitsize, MODE_VECTOR_INT, 0).exists (&trial)) 445 && have_regs_of_mode[trial] 446 && targetm.vector_mode_supported_p (trial)) 447 return trial; 448 } 449 450 /* Otherwise fall back on integers while honoring MAX_FIXED_MODE_SIZE. */ 451 return mode_for_size (bitsize, MODE_INT, true); 452 } 453 454 /* Find a type that can be used for efficient bitwise operations on MODE. 455 Return null if no such mode exists. */ 456 457 tree 458 bitwise_type_for_mode (machine_mode mode) 459 { 460 if (!bitwise_mode_for_mode (mode).exists (&mode)) 461 return NULL_TREE; 462 463 unsigned int inner_size = GET_MODE_UNIT_BITSIZE (mode); 464 tree inner_type = build_nonstandard_integer_type (inner_size, true); 465 466 if (VECTOR_MODE_P (mode)) 467 return build_vector_type_for_mode (inner_type, mode); 468 469 if (COMPLEX_MODE_P (mode)) 470 return build_complex_type (inner_type); 471 472 gcc_checking_assert (GET_MODE_INNER (mode) == mode); 473 return inner_type; 474 } 475 476 /* Find a mode that is suitable for representing a vector with NUNITS 477 elements of mode INNERMODE, if one exists. The returned mode can be 478 either an integer mode or a vector mode. */ 479 480 opt_machine_mode 481 mode_for_vector (scalar_mode innermode, poly_uint64 nunits) 482 { 483 machine_mode mode; 484 485 /* First, look for a supported vector type. */ 486 if (SCALAR_FLOAT_MODE_P (innermode)) 487 mode = MIN_MODE_VECTOR_FLOAT; 488 else if (SCALAR_FRACT_MODE_P (innermode)) 489 mode = MIN_MODE_VECTOR_FRACT; 490 else if (SCALAR_UFRACT_MODE_P (innermode)) 491 mode = MIN_MODE_VECTOR_UFRACT; 492 else if (SCALAR_ACCUM_MODE_P (innermode)) 493 mode = MIN_MODE_VECTOR_ACCUM; 494 else if (SCALAR_UACCUM_MODE_P (innermode)) 495 mode = MIN_MODE_VECTOR_UACCUM; 496 else 497 mode = MIN_MODE_VECTOR_INT; 498 499 /* Do not check vector_mode_supported_p here. We'll do that 500 later in vector_type_mode. */ 501 FOR_EACH_MODE_FROM (mode, mode) 502 if (known_eq (GET_MODE_NUNITS (mode), nunits) 503 && GET_MODE_INNER (mode) == innermode) 504 return mode; 505 506 /* For integers, try mapping it to a same-sized scalar mode. */ 507 if (GET_MODE_CLASS (innermode) == MODE_INT) 508 { 509 poly_uint64 nbits = nunits * GET_MODE_BITSIZE (innermode); 510 if (int_mode_for_size (nbits, 0).exists (&mode) 511 && have_regs_of_mode[mode]) 512 return mode; 513 } 514 515 return opt_machine_mode (); 516 } 517 518 /* Return the mode for a vector that has NUNITS integer elements of 519 INT_BITS bits each, if such a mode exists. The mode can be either 520 an integer mode or a vector mode. */ 521 522 opt_machine_mode 523 mode_for_int_vector (unsigned int int_bits, poly_uint64 nunits) 524 { 525 scalar_int_mode int_mode; 526 machine_mode vec_mode; 527 if (int_mode_for_size (int_bits, 0).exists (&int_mode) 528 && mode_for_vector (int_mode, nunits).exists (&vec_mode)) 529 return vec_mode; 530 return opt_machine_mode (); 531 } 532 533 /* Return the alignment of MODE. This will be bounded by 1 and 534 BIGGEST_ALIGNMENT. */ 535 536 unsigned int 537 get_mode_alignment (machine_mode mode) 538 { 539 return MIN (BIGGEST_ALIGNMENT, MAX (1, mode_base_align[mode]*BITS_PER_UNIT)); 540 } 541 542 /* Return the natural mode of an array, given that it is SIZE bytes in 543 total and has elements of type ELEM_TYPE. */ 544 545 static machine_mode 546 mode_for_array (tree elem_type, tree size) 547 { 548 tree elem_size; 549 poly_uint64 int_size, int_elem_size; 550 unsigned HOST_WIDE_INT num_elems; 551 bool limit_p; 552 553 /* One-element arrays get the component type's mode. */ 554 elem_size = TYPE_SIZE (elem_type); 555 if (simple_cst_equal (size, elem_size)) 556 return TYPE_MODE (elem_type); 557 558 limit_p = true; 559 if (poly_int_tree_p (size, &int_size) 560 && poly_int_tree_p (elem_size, &int_elem_size) 561 && maybe_ne (int_elem_size, 0U) 562 && constant_multiple_p (int_size, int_elem_size, &num_elems)) 563 { 564 machine_mode elem_mode = TYPE_MODE (elem_type); 565 machine_mode mode; 566 if (targetm.array_mode (elem_mode, num_elems).exists (&mode)) 567 return mode; 568 if (targetm.array_mode_supported_p (elem_mode, num_elems)) 569 limit_p = false; 570 } 571 return mode_for_size_tree (size, MODE_INT, limit_p).else_blk (); 572 } 573 574 /* Subroutine of layout_decl: Force alignment required for the data type. 575 But if the decl itself wants greater alignment, don't override that. */ 576 577 static inline void 578 do_type_align (tree type, tree decl) 579 { 580 if (TYPE_ALIGN (type) > DECL_ALIGN (decl)) 581 { 582 SET_DECL_ALIGN (decl, TYPE_ALIGN (type)); 583 if (TREE_CODE (decl) == FIELD_DECL) 584 DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type); 585 } 586 if (TYPE_WARN_IF_NOT_ALIGN (type) > DECL_WARN_IF_NOT_ALIGN (decl)) 587 SET_DECL_WARN_IF_NOT_ALIGN (decl, TYPE_WARN_IF_NOT_ALIGN (type)); 588 } 589 590 /* Set the size, mode and alignment of a ..._DECL node. 591 TYPE_DECL does need this for C++. 592 Note that LABEL_DECL and CONST_DECL nodes do not need this, 593 and FUNCTION_DECL nodes have them set up in a special (and simple) way. 594 Don't call layout_decl for them. 595 596 KNOWN_ALIGN is the amount of alignment we can assume this 597 decl has with no special effort. It is relevant only for FIELD_DECLs 598 and depends on the previous fields. 599 All that matters about KNOWN_ALIGN is which powers of 2 divide it. 600 If KNOWN_ALIGN is 0, it means, "as much alignment as you like": 601 the record will be aligned to suit. */ 602 603 void 604 layout_decl (tree decl, unsigned int known_align) 605 { 606 tree type = TREE_TYPE (decl); 607 enum tree_code code = TREE_CODE (decl); 608 rtx rtl = NULL_RTX; 609 location_t loc = DECL_SOURCE_LOCATION (decl); 610 611 if (code == CONST_DECL) 612 return; 613 614 gcc_assert (code == VAR_DECL || code == PARM_DECL || code == RESULT_DECL 615 || code == TYPE_DECL || code == FIELD_DECL); 616 617 rtl = DECL_RTL_IF_SET (decl); 618 619 if (type == error_mark_node) 620 type = void_type_node; 621 622 /* Usually the size and mode come from the data type without change, 623 however, the front-end may set the explicit width of the field, so its 624 size may not be the same as the size of its type. This happens with 625 bitfields, of course (an `int' bitfield may be only 2 bits, say), but it 626 also happens with other fields. For example, the C++ front-end creates 627 zero-sized fields corresponding to empty base classes, and depends on 628 layout_type setting DECL_FIELD_BITPOS correctly for the field. Set the 629 size in bytes from the size in bits. If we have already set the mode, 630 don't set it again since we can be called twice for FIELD_DECLs. */ 631 632 DECL_UNSIGNED (decl) = TYPE_UNSIGNED (type); 633 if (DECL_MODE (decl) == VOIDmode) 634 SET_DECL_MODE (decl, TYPE_MODE (type)); 635 636 if (DECL_SIZE (decl) == 0) 637 { 638 DECL_SIZE (decl) = TYPE_SIZE (type); 639 DECL_SIZE_UNIT (decl) = TYPE_SIZE_UNIT (type); 640 } 641 else if (DECL_SIZE_UNIT (decl) == 0) 642 DECL_SIZE_UNIT (decl) 643 = fold_convert_loc (loc, sizetype, 644 size_binop_loc (loc, CEIL_DIV_EXPR, DECL_SIZE (decl), 645 bitsize_unit_node)); 646 647 if (code != FIELD_DECL) 648 /* For non-fields, update the alignment from the type. */ 649 do_type_align (type, decl); 650 else 651 /* For fields, it's a bit more complicated... */ 652 { 653 bool old_user_align = DECL_USER_ALIGN (decl); 654 bool zero_bitfield = false; 655 bool packed_p = DECL_PACKED (decl); 656 unsigned int mfa; 657 658 if (DECL_BIT_FIELD (decl)) 659 { 660 DECL_BIT_FIELD_TYPE (decl) = type; 661 662 /* A zero-length bit-field affects the alignment of the next 663 field. In essence such bit-fields are not influenced by 664 any packing due to #pragma pack or attribute packed. */ 665 if (integer_zerop (DECL_SIZE (decl)) 666 && ! targetm.ms_bitfield_layout_p (DECL_FIELD_CONTEXT (decl))) 667 { 668 zero_bitfield = true; 669 packed_p = false; 670 if (PCC_BITFIELD_TYPE_MATTERS) 671 do_type_align (type, decl); 672 else 673 { 674 #ifdef EMPTY_FIELD_BOUNDARY 675 if (EMPTY_FIELD_BOUNDARY > DECL_ALIGN (decl)) 676 { 677 SET_DECL_ALIGN (decl, EMPTY_FIELD_BOUNDARY); 678 DECL_USER_ALIGN (decl) = 0; 679 } 680 #endif 681 } 682 } 683 684 /* See if we can use an ordinary integer mode for a bit-field. 685 Conditions are: a fixed size that is correct for another mode, 686 occupying a complete byte or bytes on proper boundary. */ 687 if (TYPE_SIZE (type) != 0 688 && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST 689 && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT) 690 { 691 machine_mode xmode; 692 if (mode_for_size_tree (DECL_SIZE (decl), 693 MODE_INT, 1).exists (&xmode)) 694 { 695 unsigned int xalign = GET_MODE_ALIGNMENT (xmode); 696 if (!(xalign > BITS_PER_UNIT && DECL_PACKED (decl)) 697 && (known_align == 0 || known_align >= xalign)) 698 { 699 SET_DECL_ALIGN (decl, MAX (xalign, DECL_ALIGN (decl))); 700 SET_DECL_MODE (decl, xmode); 701 DECL_BIT_FIELD (decl) = 0; 702 } 703 } 704 } 705 706 /* Turn off DECL_BIT_FIELD if we won't need it set. */ 707 if (TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode 708 && known_align >= TYPE_ALIGN (type) 709 && DECL_ALIGN (decl) >= TYPE_ALIGN (type)) 710 DECL_BIT_FIELD (decl) = 0; 711 } 712 else if (packed_p && DECL_USER_ALIGN (decl)) 713 /* Don't touch DECL_ALIGN. For other packed fields, go ahead and 714 round up; we'll reduce it again below. We want packing to 715 supersede USER_ALIGN inherited from the type, but defer to 716 alignment explicitly specified on the field decl. */; 717 else 718 do_type_align (type, decl); 719 720 /* If the field is packed and not explicitly aligned, give it the 721 minimum alignment. Note that do_type_align may set 722 DECL_USER_ALIGN, so we need to check old_user_align instead. */ 723 if (packed_p 724 && !old_user_align) 725 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), BITS_PER_UNIT)); 726 727 if (! packed_p && ! DECL_USER_ALIGN (decl)) 728 { 729 /* Some targets (i.e. i386, VMS) limit struct field alignment 730 to a lower boundary than alignment of variables unless 731 it was overridden by attribute aligned. */ 732 #ifdef BIGGEST_FIELD_ALIGNMENT 733 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), 734 (unsigned) BIGGEST_FIELD_ALIGNMENT)); 735 #endif 736 #ifdef ADJUST_FIELD_ALIGN 737 SET_DECL_ALIGN (decl, ADJUST_FIELD_ALIGN (decl, TREE_TYPE (decl), 738 DECL_ALIGN (decl))); 739 #endif 740 } 741 742 if (zero_bitfield) 743 mfa = initial_max_fld_align * BITS_PER_UNIT; 744 else 745 mfa = maximum_field_alignment; 746 /* Should this be controlled by DECL_USER_ALIGN, too? */ 747 if (mfa != 0) 748 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), mfa)); 749 } 750 751 /* Evaluate nonconstant size only once, either now or as soon as safe. */ 752 if (DECL_SIZE (decl) != 0 && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST) 753 DECL_SIZE (decl) = variable_size (DECL_SIZE (decl)); 754 if (DECL_SIZE_UNIT (decl) != 0 755 && TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST) 756 DECL_SIZE_UNIT (decl) = variable_size (DECL_SIZE_UNIT (decl)); 757 758 /* If requested, warn about definitions of large data objects. */ 759 if (warn_larger_than 760 && (code == VAR_DECL || code == PARM_DECL) 761 && ! DECL_EXTERNAL (decl)) 762 { 763 tree size = DECL_SIZE_UNIT (decl); 764 765 if (size != 0 && TREE_CODE (size) == INTEGER_CST 766 && compare_tree_int (size, larger_than_size) > 0) 767 { 768 int size_as_int = TREE_INT_CST_LOW (size); 769 770 if (compare_tree_int (size, size_as_int) == 0) 771 warning (OPT_Wlarger_than_, "size of %q+D is %d bytes", decl, size_as_int); 772 else 773 warning (OPT_Wlarger_than_, "size of %q+D is larger than %wd bytes", 774 decl, larger_than_size); 775 } 776 } 777 778 /* If the RTL was already set, update its mode and mem attributes. */ 779 if (rtl) 780 { 781 PUT_MODE (rtl, DECL_MODE (decl)); 782 SET_DECL_RTL (decl, 0); 783 if (MEM_P (rtl)) 784 set_mem_attributes (rtl, decl, 1); 785 SET_DECL_RTL (decl, rtl); 786 } 787 } 788 789 /* Given a VAR_DECL, PARM_DECL, RESULT_DECL, or FIELD_DECL, clears the 790 results of a previous call to layout_decl and calls it again. */ 791 792 void 793 relayout_decl (tree decl) 794 { 795 DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0; 796 SET_DECL_MODE (decl, VOIDmode); 797 if (!DECL_USER_ALIGN (decl)) 798 SET_DECL_ALIGN (decl, 0); 799 if (DECL_RTL_SET_P (decl)) 800 SET_DECL_RTL (decl, 0); 801 802 layout_decl (decl, 0); 803 } 804 805 /* Begin laying out type T, which may be a RECORD_TYPE, UNION_TYPE, or 806 QUAL_UNION_TYPE. Return a pointer to a struct record_layout_info which 807 is to be passed to all other layout functions for this record. It is the 808 responsibility of the caller to call `free' for the storage returned. 809 Note that garbage collection is not permitted until we finish laying 810 out the record. */ 811 812 record_layout_info 813 start_record_layout (tree t) 814 { 815 record_layout_info rli = XNEW (struct record_layout_info_s); 816 817 rli->t = t; 818 819 /* If the type has a minimum specified alignment (via an attribute 820 declaration, for example) use it -- otherwise, start with a 821 one-byte alignment. */ 822 rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t)); 823 rli->unpacked_align = rli->record_align; 824 rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT); 825 826 #ifdef STRUCTURE_SIZE_BOUNDARY 827 /* Packed structures don't need to have minimum size. */ 828 if (! TYPE_PACKED (t)) 829 { 830 unsigned tmp; 831 832 /* #pragma pack overrides STRUCTURE_SIZE_BOUNDARY. */ 833 tmp = (unsigned) STRUCTURE_SIZE_BOUNDARY; 834 if (maximum_field_alignment != 0) 835 tmp = MIN (tmp, maximum_field_alignment); 836 rli->record_align = MAX (rli->record_align, tmp); 837 } 838 #endif 839 840 rli->offset = size_zero_node; 841 rli->bitpos = bitsize_zero_node; 842 rli->prev_field = 0; 843 rli->pending_statics = 0; 844 rli->packed_maybe_necessary = 0; 845 rli->remaining_in_alignment = 0; 846 847 return rli; 848 } 849 850 /* Fold sizetype value X to bitsizetype, given that X represents a type 851 size or offset. */ 852 853 static tree 854 bits_from_bytes (tree x) 855 { 856 if (POLY_INT_CST_P (x)) 857 /* The runtime calculation isn't allowed to overflow sizetype; 858 increasing the runtime values must always increase the size 859 or offset of the object. This means that the object imposes 860 a maximum value on the runtime parameters, but we don't record 861 what that is. */ 862 return build_poly_int_cst 863 (bitsizetype, 864 poly_wide_int::from (poly_int_cst_value (x), 865 TYPE_PRECISION (bitsizetype), 866 TYPE_SIGN (TREE_TYPE (x)))); 867 x = fold_convert (bitsizetype, x); 868 gcc_checking_assert (x); 869 return x; 870 } 871 872 /* Return the combined bit position for the byte offset OFFSET and the 873 bit position BITPOS. 874 875 These functions operate on byte and bit positions present in FIELD_DECLs 876 and assume that these expressions result in no (intermediate) overflow. 877 This assumption is necessary to fold the expressions as much as possible, 878 so as to avoid creating artificially variable-sized types in languages 879 supporting variable-sized types like Ada. */ 880 881 tree 882 bit_from_pos (tree offset, tree bitpos) 883 { 884 return size_binop (PLUS_EXPR, bitpos, 885 size_binop (MULT_EXPR, bits_from_bytes (offset), 886 bitsize_unit_node)); 887 } 888 889 /* Return the combined truncated byte position for the byte offset OFFSET and 890 the bit position BITPOS. */ 891 892 tree 893 byte_from_pos (tree offset, tree bitpos) 894 { 895 tree bytepos; 896 if (TREE_CODE (bitpos) == MULT_EXPR 897 && tree_int_cst_equal (TREE_OPERAND (bitpos, 1), bitsize_unit_node)) 898 bytepos = TREE_OPERAND (bitpos, 0); 899 else 900 bytepos = size_binop (TRUNC_DIV_EXPR, bitpos, bitsize_unit_node); 901 return size_binop (PLUS_EXPR, offset, fold_convert (sizetype, bytepos)); 902 } 903 904 /* Split the bit position POS into a byte offset *POFFSET and a bit 905 position *PBITPOS with the byte offset aligned to OFF_ALIGN bits. */ 906 907 void 908 pos_from_bit (tree *poffset, tree *pbitpos, unsigned int off_align, 909 tree pos) 910 { 911 tree toff_align = bitsize_int (off_align); 912 if (TREE_CODE (pos) == MULT_EXPR 913 && tree_int_cst_equal (TREE_OPERAND (pos, 1), toff_align)) 914 { 915 *poffset = size_binop (MULT_EXPR, 916 fold_convert (sizetype, TREE_OPERAND (pos, 0)), 917 size_int (off_align / BITS_PER_UNIT)); 918 *pbitpos = bitsize_zero_node; 919 } 920 else 921 { 922 *poffset = size_binop (MULT_EXPR, 923 fold_convert (sizetype, 924 size_binop (FLOOR_DIV_EXPR, pos, 925 toff_align)), 926 size_int (off_align / BITS_PER_UNIT)); 927 *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, toff_align); 928 } 929 } 930 931 /* Given a pointer to bit and byte offsets and an offset alignment, 932 normalize the offsets so they are within the alignment. */ 933 934 void 935 normalize_offset (tree *poffset, tree *pbitpos, unsigned int off_align) 936 { 937 /* If the bit position is now larger than it should be, adjust it 938 downwards. */ 939 if (compare_tree_int (*pbitpos, off_align) >= 0) 940 { 941 tree offset, bitpos; 942 pos_from_bit (&offset, &bitpos, off_align, *pbitpos); 943 *poffset = size_binop (PLUS_EXPR, *poffset, offset); 944 *pbitpos = bitpos; 945 } 946 } 947 948 /* Print debugging information about the information in RLI. */ 949 950 DEBUG_FUNCTION void 951 debug_rli (record_layout_info rli) 952 { 953 print_node_brief (stderr, "type", rli->t, 0); 954 print_node_brief (stderr, "\noffset", rli->offset, 0); 955 print_node_brief (stderr, " bitpos", rli->bitpos, 0); 956 957 fprintf (stderr, "\naligns: rec = %u, unpack = %u, off = %u\n", 958 rli->record_align, rli->unpacked_align, 959 rli->offset_align); 960 961 /* The ms_struct code is the only that uses this. */ 962 if (targetm.ms_bitfield_layout_p (rli->t)) 963 fprintf (stderr, "remaining in alignment = %u\n", rli->remaining_in_alignment); 964 965 if (rli->packed_maybe_necessary) 966 fprintf (stderr, "packed may be necessary\n"); 967 968 if (!vec_safe_is_empty (rli->pending_statics)) 969 { 970 fprintf (stderr, "pending statics:\n"); 971 debug (rli->pending_statics); 972 } 973 } 974 975 /* Given an RLI with a possibly-incremented BITPOS, adjust OFFSET and 976 BITPOS if necessary to keep BITPOS below OFFSET_ALIGN. */ 977 978 void 979 normalize_rli (record_layout_info rli) 980 { 981 normalize_offset (&rli->offset, &rli->bitpos, rli->offset_align); 982 } 983 984 /* Returns the size in bytes allocated so far. */ 985 986 tree 987 rli_size_unit_so_far (record_layout_info rli) 988 { 989 return byte_from_pos (rli->offset, rli->bitpos); 990 } 991 992 /* Returns the size in bits allocated so far. */ 993 994 tree 995 rli_size_so_far (record_layout_info rli) 996 { 997 return bit_from_pos (rli->offset, rli->bitpos); 998 } 999 1000 /* FIELD is about to be added to RLI->T. The alignment (in bits) of 1001 the next available location within the record is given by KNOWN_ALIGN. 1002 Update the variable alignment fields in RLI, and return the alignment 1003 to give the FIELD. */ 1004 1005 unsigned int 1006 update_alignment_for_field (record_layout_info rli, tree field, 1007 unsigned int known_align) 1008 { 1009 /* The alignment required for FIELD. */ 1010 unsigned int desired_align; 1011 /* The type of this field. */ 1012 tree type = TREE_TYPE (field); 1013 /* True if the field was explicitly aligned by the user. */ 1014 bool user_align; 1015 bool is_bitfield; 1016 1017 /* Do not attempt to align an ERROR_MARK node */ 1018 if (TREE_CODE (type) == ERROR_MARK) 1019 return 0; 1020 1021 /* Lay out the field so we know what alignment it needs. */ 1022 layout_decl (field, known_align); 1023 desired_align = DECL_ALIGN (field); 1024 user_align = DECL_USER_ALIGN (field); 1025 1026 is_bitfield = (type != error_mark_node 1027 && DECL_BIT_FIELD_TYPE (field) 1028 && ! integer_zerop (TYPE_SIZE (type))); 1029 1030 /* Record must have at least as much alignment as any field. 1031 Otherwise, the alignment of the field within the record is 1032 meaningless. */ 1033 if (targetm.ms_bitfield_layout_p (rli->t)) 1034 { 1035 /* Here, the alignment of the underlying type of a bitfield can 1036 affect the alignment of a record; even a zero-sized field 1037 can do this. The alignment should be to the alignment of 1038 the type, except that for zero-size bitfields this only 1039 applies if there was an immediately prior, nonzero-size 1040 bitfield. (That's the way it is, experimentally.) */ 1041 if (!is_bitfield 1042 || ((DECL_SIZE (field) == NULL_TREE 1043 || !integer_zerop (DECL_SIZE (field))) 1044 ? !DECL_PACKED (field) 1045 : (rli->prev_field 1046 && DECL_BIT_FIELD_TYPE (rli->prev_field) 1047 && ! integer_zerop (DECL_SIZE (rli->prev_field))))) 1048 { 1049 unsigned int type_align = TYPE_ALIGN (type); 1050 if (!is_bitfield && DECL_PACKED (field)) 1051 type_align = desired_align; 1052 else 1053 type_align = MAX (type_align, desired_align); 1054 if (maximum_field_alignment != 0) 1055 type_align = MIN (type_align, maximum_field_alignment); 1056 rli->record_align = MAX (rli->record_align, type_align); 1057 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type)); 1058 } 1059 } 1060 else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS) 1061 { 1062 /* Named bit-fields cause the entire structure to have the 1063 alignment implied by their type. Some targets also apply the same 1064 rules to unnamed bitfields. */ 1065 if (DECL_NAME (field) != 0 1066 || targetm.align_anon_bitfield ()) 1067 { 1068 unsigned int type_align = TYPE_ALIGN (type); 1069 1070 #ifdef ADJUST_FIELD_ALIGN 1071 if (! TYPE_USER_ALIGN (type)) 1072 type_align = ADJUST_FIELD_ALIGN (field, type, type_align); 1073 #endif 1074 1075 /* Targets might chose to handle unnamed and hence possibly 1076 zero-width bitfield. Those are not influenced by #pragmas 1077 or packed attributes. */ 1078 if (integer_zerop (DECL_SIZE (field))) 1079 { 1080 if (initial_max_fld_align) 1081 type_align = MIN (type_align, 1082 initial_max_fld_align * BITS_PER_UNIT); 1083 } 1084 else if (maximum_field_alignment != 0) 1085 type_align = MIN (type_align, maximum_field_alignment); 1086 else if (DECL_PACKED (field)) 1087 type_align = MIN (type_align, BITS_PER_UNIT); 1088 1089 /* The alignment of the record is increased to the maximum 1090 of the current alignment, the alignment indicated on the 1091 field (i.e., the alignment specified by an __aligned__ 1092 attribute), and the alignment indicated by the type of 1093 the field. */ 1094 rli->record_align = MAX (rli->record_align, desired_align); 1095 rli->record_align = MAX (rli->record_align, type_align); 1096 1097 if (warn_packed) 1098 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type)); 1099 user_align |= TYPE_USER_ALIGN (type); 1100 } 1101 } 1102 else 1103 { 1104 rli->record_align = MAX (rli->record_align, desired_align); 1105 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type)); 1106 } 1107 1108 TYPE_USER_ALIGN (rli->t) |= user_align; 1109 1110 return desired_align; 1111 } 1112 1113 /* Issue a warning if the record alignment, RECORD_ALIGN, is less than 1114 the field alignment of FIELD or FIELD isn't aligned. */ 1115 1116 static void 1117 handle_warn_if_not_align (tree field, unsigned int record_align) 1118 { 1119 tree type = TREE_TYPE (field); 1120 1121 if (type == error_mark_node) 1122 return; 1123 1124 unsigned int warn_if_not_align = 0; 1125 1126 int opt_w = 0; 1127 1128 if (warn_if_not_aligned) 1129 { 1130 warn_if_not_align = DECL_WARN_IF_NOT_ALIGN (field); 1131 if (!warn_if_not_align) 1132 warn_if_not_align = TYPE_WARN_IF_NOT_ALIGN (type); 1133 if (warn_if_not_align) 1134 opt_w = OPT_Wif_not_aligned; 1135 } 1136 1137 if (!warn_if_not_align 1138 && warn_packed_not_aligned 1139 && lookup_attribute ("aligned", TYPE_ATTRIBUTES (type))) 1140 { 1141 warn_if_not_align = TYPE_ALIGN (type); 1142 opt_w = OPT_Wpacked_not_aligned; 1143 } 1144 1145 if (!warn_if_not_align) 1146 return; 1147 1148 tree context = DECL_CONTEXT (field); 1149 1150 warn_if_not_align /= BITS_PER_UNIT; 1151 record_align /= BITS_PER_UNIT; 1152 if ((record_align % warn_if_not_align) != 0) 1153 warning (opt_w, "alignment %u of %qT is less than %u", 1154 record_align, context, warn_if_not_align); 1155 1156 tree off = byte_position (field); 1157 if (!multiple_of_p (TREE_TYPE (off), off, size_int (warn_if_not_align))) 1158 { 1159 if (TREE_CODE (off) == INTEGER_CST) 1160 warning (opt_w, "%q+D offset %E in %qT isn%'t aligned to %u", 1161 field, off, context, warn_if_not_align); 1162 else 1163 warning (opt_w, "%q+D offset %E in %qT may not be aligned to %u", 1164 field, off, context, warn_if_not_align); 1165 } 1166 } 1167 1168 /* Called from place_field to handle unions. */ 1169 1170 static void 1171 place_union_field (record_layout_info rli, tree field) 1172 { 1173 update_alignment_for_field (rli, field, /*known_align=*/0); 1174 1175 DECL_FIELD_OFFSET (field) = size_zero_node; 1176 DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node; 1177 SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT); 1178 handle_warn_if_not_align (field, rli->record_align); 1179 1180 /* If this is an ERROR_MARK return *after* having set the 1181 field at the start of the union. This helps when parsing 1182 invalid fields. */ 1183 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK) 1184 return; 1185 1186 if (AGGREGATE_TYPE_P (TREE_TYPE (field)) 1187 && TYPE_TYPELESS_STORAGE (TREE_TYPE (field))) 1188 TYPE_TYPELESS_STORAGE (rli->t) = 1; 1189 1190 /* We assume the union's size will be a multiple of a byte so we don't 1191 bother with BITPOS. */ 1192 if (TREE_CODE (rli->t) == UNION_TYPE) 1193 rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field)); 1194 else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE) 1195 rli->offset = fold_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field), 1196 DECL_SIZE_UNIT (field), rli->offset); 1197 } 1198 1199 /* A bitfield of SIZE with a required access alignment of ALIGN is allocated 1200 at BYTE_OFFSET / BIT_OFFSET. Return nonzero if the field would span more 1201 units of alignment than the underlying TYPE. */ 1202 static int 1203 excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset, 1204 HOST_WIDE_INT size, HOST_WIDE_INT align, tree type) 1205 { 1206 /* Note that the calculation of OFFSET might overflow; we calculate it so 1207 that we still get the right result as long as ALIGN is a power of two. */ 1208 unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset; 1209 1210 offset = offset % align; 1211 return ((offset + size + align - 1) / align 1212 > tree_to_uhwi (TYPE_SIZE (type)) / align); 1213 } 1214 1215 /* RLI contains information about the layout of a RECORD_TYPE. FIELD 1216 is a FIELD_DECL to be added after those fields already present in 1217 T. (FIELD is not actually added to the TYPE_FIELDS list here; 1218 callers that desire that behavior must manually perform that step.) */ 1219 1220 void 1221 place_field (record_layout_info rli, tree field) 1222 { 1223 /* The alignment required for FIELD. */ 1224 unsigned int desired_align; 1225 /* The alignment FIELD would have if we just dropped it into the 1226 record as it presently stands. */ 1227 unsigned int known_align; 1228 unsigned int actual_align; 1229 /* The type of this field. */ 1230 tree type = TREE_TYPE (field); 1231 1232 gcc_assert (TREE_CODE (field) != ERROR_MARK); 1233 1234 /* If FIELD is static, then treat it like a separate variable, not 1235 really like a structure field. If it is a FUNCTION_DECL, it's a 1236 method. In both cases, all we do is lay out the decl, and we do 1237 it *after* the record is laid out. */ 1238 if (VAR_P (field)) 1239 { 1240 vec_safe_push (rli->pending_statics, field); 1241 return; 1242 } 1243 1244 /* Enumerators and enum types which are local to this class need not 1245 be laid out. Likewise for initialized constant fields. */ 1246 else if (TREE_CODE (field) != FIELD_DECL) 1247 return; 1248 1249 /* Unions are laid out very differently than records, so split 1250 that code off to another function. */ 1251 else if (TREE_CODE (rli->t) != RECORD_TYPE) 1252 { 1253 place_union_field (rli, field); 1254 return; 1255 } 1256 1257 else if (TREE_CODE (type) == ERROR_MARK) 1258 { 1259 /* Place this field at the current allocation position, so we 1260 maintain monotonicity. */ 1261 DECL_FIELD_OFFSET (field) = rli->offset; 1262 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos; 1263 SET_DECL_OFFSET_ALIGN (field, rli->offset_align); 1264 handle_warn_if_not_align (field, rli->record_align); 1265 return; 1266 } 1267 1268 if (AGGREGATE_TYPE_P (type) 1269 && TYPE_TYPELESS_STORAGE (type)) 1270 TYPE_TYPELESS_STORAGE (rli->t) = 1; 1271 1272 /* Work out the known alignment so far. Note that A & (-A) is the 1273 value of the least-significant bit in A that is one. */ 1274 if (! integer_zerop (rli->bitpos)) 1275 known_align = least_bit_hwi (tree_to_uhwi (rli->bitpos)); 1276 else if (integer_zerop (rli->offset)) 1277 known_align = 0; 1278 else if (tree_fits_uhwi_p (rli->offset)) 1279 known_align = (BITS_PER_UNIT 1280 * least_bit_hwi (tree_to_uhwi (rli->offset))); 1281 else 1282 known_align = rli->offset_align; 1283 1284 desired_align = update_alignment_for_field (rli, field, known_align); 1285 if (known_align == 0) 1286 known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align); 1287 1288 if (warn_packed && DECL_PACKED (field)) 1289 { 1290 if (known_align >= TYPE_ALIGN (type)) 1291 { 1292 if (TYPE_ALIGN (type) > desired_align) 1293 { 1294 if (STRICT_ALIGNMENT) 1295 warning (OPT_Wattributes, "packed attribute causes " 1296 "inefficient alignment for %q+D", field); 1297 /* Don't warn if DECL_PACKED was set by the type. */ 1298 else if (!TYPE_PACKED (rli->t)) 1299 warning (OPT_Wattributes, "packed attribute is " 1300 "unnecessary for %q+D", field); 1301 } 1302 } 1303 else 1304 rli->packed_maybe_necessary = 1; 1305 } 1306 1307 /* Does this field automatically have alignment it needs by virtue 1308 of the fields that precede it and the record's own alignment? */ 1309 if (known_align < desired_align 1310 && (! targetm.ms_bitfield_layout_p (rli->t) 1311 || rli->prev_field == NULL)) 1312 { 1313 /* No, we need to skip space before this field. 1314 Bump the cumulative size to multiple of field alignment. */ 1315 1316 if (!targetm.ms_bitfield_layout_p (rli->t) 1317 && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION) 1318 warning (OPT_Wpadded, "padding struct to align %q+D", field); 1319 1320 /* If the alignment is still within offset_align, just align 1321 the bit position. */ 1322 if (desired_align < rli->offset_align) 1323 rli->bitpos = round_up (rli->bitpos, desired_align); 1324 else 1325 { 1326 /* First adjust OFFSET by the partial bits, then align. */ 1327 rli->offset 1328 = size_binop (PLUS_EXPR, rli->offset, 1329 fold_convert (sizetype, 1330 size_binop (CEIL_DIV_EXPR, rli->bitpos, 1331 bitsize_unit_node))); 1332 rli->bitpos = bitsize_zero_node; 1333 1334 rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT); 1335 } 1336 1337 if (! TREE_CONSTANT (rli->offset)) 1338 rli->offset_align = desired_align; 1339 } 1340 1341 /* Handle compatibility with PCC. Note that if the record has any 1342 variable-sized fields, we need not worry about compatibility. */ 1343 if (PCC_BITFIELD_TYPE_MATTERS 1344 && ! targetm.ms_bitfield_layout_p (rli->t) 1345 && TREE_CODE (field) == FIELD_DECL 1346 && type != error_mark_node 1347 && DECL_BIT_FIELD (field) 1348 && (! DECL_PACKED (field) 1349 /* Enter for these packed fields only to issue a warning. */ 1350 || TYPE_ALIGN (type) <= BITS_PER_UNIT) 1351 && maximum_field_alignment == 0 1352 && ! integer_zerop (DECL_SIZE (field)) 1353 && tree_fits_uhwi_p (DECL_SIZE (field)) 1354 && tree_fits_uhwi_p (rli->offset) 1355 && tree_fits_uhwi_p (TYPE_SIZE (type))) 1356 { 1357 unsigned int type_align = TYPE_ALIGN (type); 1358 tree dsize = DECL_SIZE (field); 1359 HOST_WIDE_INT field_size = tree_to_uhwi (dsize); 1360 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset); 1361 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos); 1362 1363 #ifdef ADJUST_FIELD_ALIGN 1364 if (! TYPE_USER_ALIGN (type)) 1365 type_align = ADJUST_FIELD_ALIGN (field, type, type_align); 1366 #endif 1367 1368 /* A bit field may not span more units of alignment of its type 1369 than its type itself. Advance to next boundary if necessary. */ 1370 if (excess_unit_span (offset, bit_offset, field_size, type_align, type)) 1371 { 1372 if (DECL_PACKED (field)) 1373 { 1374 if (warn_packed_bitfield_compat == 1) 1375 inform 1376 (input_location, 1377 "offset of packed bit-field %qD has changed in GCC 4.4", 1378 field); 1379 } 1380 else 1381 rli->bitpos = round_up (rli->bitpos, type_align); 1382 } 1383 1384 if (! DECL_PACKED (field)) 1385 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type); 1386 1387 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t, 1388 TYPE_WARN_IF_NOT_ALIGN (type)); 1389 } 1390 1391 #ifdef BITFIELD_NBYTES_LIMITED 1392 if (BITFIELD_NBYTES_LIMITED 1393 && ! targetm.ms_bitfield_layout_p (rli->t) 1394 && TREE_CODE (field) == FIELD_DECL 1395 && type != error_mark_node 1396 && DECL_BIT_FIELD_TYPE (field) 1397 && ! DECL_PACKED (field) 1398 && ! integer_zerop (DECL_SIZE (field)) 1399 && tree_fits_uhwi_p (DECL_SIZE (field)) 1400 && tree_fits_uhwi_p (rli->offset) 1401 && tree_fits_uhwi_p (TYPE_SIZE (type))) 1402 { 1403 unsigned int type_align = TYPE_ALIGN (type); 1404 tree dsize = DECL_SIZE (field); 1405 HOST_WIDE_INT field_size = tree_to_uhwi (dsize); 1406 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset); 1407 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos); 1408 1409 #ifdef ADJUST_FIELD_ALIGN 1410 if (! TYPE_USER_ALIGN (type)) 1411 type_align = ADJUST_FIELD_ALIGN (field, type, type_align); 1412 #endif 1413 1414 if (maximum_field_alignment != 0) 1415 type_align = MIN (type_align, maximum_field_alignment); 1416 /* ??? This test is opposite the test in the containing if 1417 statement, so this code is unreachable currently. */ 1418 else if (DECL_PACKED (field)) 1419 type_align = MIN (type_align, BITS_PER_UNIT); 1420 1421 /* A bit field may not span the unit of alignment of its type. 1422 Advance to next boundary if necessary. */ 1423 if (excess_unit_span (offset, bit_offset, field_size, type_align, type)) 1424 rli->bitpos = round_up (rli->bitpos, type_align); 1425 1426 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type); 1427 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t, 1428 TYPE_WARN_IF_NOT_ALIGN (type)); 1429 } 1430 #endif 1431 1432 /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details. 1433 A subtlety: 1434 When a bit field is inserted into a packed record, the whole 1435 size of the underlying type is used by one or more same-size 1436 adjacent bitfields. (That is, if its long:3, 32 bits is 1437 used in the record, and any additional adjacent long bitfields are 1438 packed into the same chunk of 32 bits. However, if the size 1439 changes, a new field of that size is allocated.) In an unpacked 1440 record, this is the same as using alignment, but not equivalent 1441 when packing. 1442 1443 Note: for compatibility, we use the type size, not the type alignment 1444 to determine alignment, since that matches the documentation */ 1445 1446 if (targetm.ms_bitfield_layout_p (rli->t)) 1447 { 1448 tree prev_saved = rli->prev_field; 1449 tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL; 1450 1451 /* This is a bitfield if it exists. */ 1452 if (rli->prev_field) 1453 { 1454 bool realign_p = known_align < desired_align; 1455 1456 /* If both are bitfields, nonzero, and the same size, this is 1457 the middle of a run. Zero declared size fields are special 1458 and handled as "end of run". (Note: it's nonzero declared 1459 size, but equal type sizes!) (Since we know that both 1460 the current and previous fields are bitfields by the 1461 time we check it, DECL_SIZE must be present for both.) */ 1462 if (DECL_BIT_FIELD_TYPE (field) 1463 && !integer_zerop (DECL_SIZE (field)) 1464 && !integer_zerop (DECL_SIZE (rli->prev_field)) 1465 && tree_fits_shwi_p (DECL_SIZE (rli->prev_field)) 1466 && tree_fits_uhwi_p (TYPE_SIZE (type)) 1467 && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))) 1468 { 1469 /* We're in the middle of a run of equal type size fields; make 1470 sure we realign if we run out of bits. (Not decl size, 1471 type size!) */ 1472 HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field)); 1473 1474 if (rli->remaining_in_alignment < bitsize) 1475 { 1476 HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type)); 1477 1478 /* out of bits; bump up to next 'word'. */ 1479 rli->bitpos 1480 = size_binop (PLUS_EXPR, rli->bitpos, 1481 bitsize_int (rli->remaining_in_alignment)); 1482 rli->prev_field = field; 1483 if (typesize < bitsize) 1484 rli->remaining_in_alignment = 0; 1485 else 1486 rli->remaining_in_alignment = typesize - bitsize; 1487 } 1488 else 1489 { 1490 rli->remaining_in_alignment -= bitsize; 1491 realign_p = false; 1492 } 1493 } 1494 else 1495 { 1496 /* End of a run: if leaving a run of bitfields of the same type 1497 size, we have to "use up" the rest of the bits of the type 1498 size. 1499 1500 Compute the new position as the sum of the size for the prior 1501 type and where we first started working on that type. 1502 Note: since the beginning of the field was aligned then 1503 of course the end will be too. No round needed. */ 1504 1505 if (!integer_zerop (DECL_SIZE (rli->prev_field))) 1506 { 1507 rli->bitpos 1508 = size_binop (PLUS_EXPR, rli->bitpos, 1509 bitsize_int (rli->remaining_in_alignment)); 1510 } 1511 else 1512 /* We "use up" size zero fields; the code below should behave 1513 as if the prior field was not a bitfield. */ 1514 prev_saved = NULL; 1515 1516 /* Cause a new bitfield to be captured, either this time (if 1517 currently a bitfield) or next time we see one. */ 1518 if (!DECL_BIT_FIELD_TYPE (field) 1519 || integer_zerop (DECL_SIZE (field))) 1520 rli->prev_field = NULL; 1521 } 1522 1523 /* Does this field automatically have alignment it needs by virtue 1524 of the fields that precede it and the record's own alignment? */ 1525 if (realign_p) 1526 { 1527 /* If the alignment is still within offset_align, just align 1528 the bit position. */ 1529 if (desired_align < rli->offset_align) 1530 rli->bitpos = round_up (rli->bitpos, desired_align); 1531 else 1532 { 1533 /* First adjust OFFSET by the partial bits, then align. */ 1534 tree d = size_binop (CEIL_DIV_EXPR, rli->bitpos, 1535 bitsize_unit_node); 1536 rli->offset = size_binop (PLUS_EXPR, rli->offset, 1537 fold_convert (sizetype, d)); 1538 rli->bitpos = bitsize_zero_node; 1539 1540 rli->offset = round_up (rli->offset, 1541 desired_align / BITS_PER_UNIT); 1542 } 1543 1544 if (! TREE_CONSTANT (rli->offset)) 1545 rli->offset_align = desired_align; 1546 } 1547 1548 normalize_rli (rli); 1549 } 1550 1551 /* If we're starting a new run of same type size bitfields 1552 (or a run of non-bitfields), set up the "first of the run" 1553 fields. 1554 1555 That is, if the current field is not a bitfield, or if there 1556 was a prior bitfield the type sizes differ, or if there wasn't 1557 a prior bitfield the size of the current field is nonzero. 1558 1559 Note: we must be sure to test ONLY the type size if there was 1560 a prior bitfield and ONLY for the current field being zero if 1561 there wasn't. */ 1562 1563 if (!DECL_BIT_FIELD_TYPE (field) 1564 || (prev_saved != NULL 1565 ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)) 1566 : !integer_zerop (DECL_SIZE (field)))) 1567 { 1568 /* Never smaller than a byte for compatibility. */ 1569 unsigned int type_align = BITS_PER_UNIT; 1570 1571 /* (When not a bitfield), we could be seeing a flex array (with 1572 no DECL_SIZE). Since we won't be using remaining_in_alignment 1573 until we see a bitfield (and come by here again) we just skip 1574 calculating it. */ 1575 if (DECL_SIZE (field) != NULL 1576 && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field))) 1577 && tree_fits_uhwi_p (DECL_SIZE (field))) 1578 { 1579 unsigned HOST_WIDE_INT bitsize 1580 = tree_to_uhwi (DECL_SIZE (field)); 1581 unsigned HOST_WIDE_INT typesize 1582 = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field))); 1583 1584 if (typesize < bitsize) 1585 rli->remaining_in_alignment = 0; 1586 else 1587 rli->remaining_in_alignment = typesize - bitsize; 1588 } 1589 1590 /* Now align (conventionally) for the new type. */ 1591 if (! DECL_PACKED (field)) 1592 type_align = TYPE_ALIGN (TREE_TYPE (field)); 1593 1594 if (maximum_field_alignment != 0) 1595 type_align = MIN (type_align, maximum_field_alignment); 1596 1597 rli->bitpos = round_up (rli->bitpos, type_align); 1598 1599 /* If we really aligned, don't allow subsequent bitfields 1600 to undo that. */ 1601 rli->prev_field = NULL; 1602 } 1603 } 1604 1605 /* Offset so far becomes the position of this field after normalizing. */ 1606 normalize_rli (rli); 1607 DECL_FIELD_OFFSET (field) = rli->offset; 1608 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos; 1609 SET_DECL_OFFSET_ALIGN (field, rli->offset_align); 1610 handle_warn_if_not_align (field, rli->record_align); 1611 1612 /* Evaluate nonconstant offsets only once, either now or as soon as safe. */ 1613 if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST) 1614 DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field)); 1615 1616 /* If this field ended up more aligned than we thought it would be (we 1617 approximate this by seeing if its position changed), lay out the field 1618 again; perhaps we can use an integral mode for it now. */ 1619 if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field))) 1620 actual_align = least_bit_hwi (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))); 1621 else if (integer_zerop (DECL_FIELD_OFFSET (field))) 1622 actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align); 1623 else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field))) 1624 actual_align = (BITS_PER_UNIT 1625 * least_bit_hwi (tree_to_uhwi (DECL_FIELD_OFFSET (field)))); 1626 else 1627 actual_align = DECL_OFFSET_ALIGN (field); 1628 /* ACTUAL_ALIGN is still the actual alignment *within the record* . 1629 store / extract bit field operations will check the alignment of the 1630 record against the mode of bit fields. */ 1631 1632 if (known_align != actual_align) 1633 layout_decl (field, actual_align); 1634 1635 if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field)) 1636 rli->prev_field = field; 1637 1638 /* Now add size of this field to the size of the record. If the size is 1639 not constant, treat the field as being a multiple of bytes and just 1640 adjust the offset, resetting the bit position. Otherwise, apportion the 1641 size amongst the bit position and offset. First handle the case of an 1642 unspecified size, which can happen when we have an invalid nested struct 1643 definition, such as struct j { struct j { int i; } }. The error message 1644 is printed in finish_struct. */ 1645 if (DECL_SIZE (field) == 0) 1646 /* Do nothing. */; 1647 else if (TREE_CODE (DECL_SIZE (field)) != INTEGER_CST 1648 || TREE_OVERFLOW (DECL_SIZE (field))) 1649 { 1650 rli->offset 1651 = size_binop (PLUS_EXPR, rli->offset, 1652 fold_convert (sizetype, 1653 size_binop (CEIL_DIV_EXPR, rli->bitpos, 1654 bitsize_unit_node))); 1655 rli->offset 1656 = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field)); 1657 rli->bitpos = bitsize_zero_node; 1658 rli->offset_align = MIN (rli->offset_align, desired_align); 1659 1660 if (!multiple_of_p (bitsizetype, DECL_SIZE (field), 1661 bitsize_int (rli->offset_align))) 1662 { 1663 tree type = strip_array_types (TREE_TYPE (field)); 1664 /* The above adjusts offset_align just based on the start of the 1665 field. The field might not have a size that is a multiple of 1666 that offset_align though. If the field is an array of fixed 1667 sized elements, assume there can be any multiple of those 1668 sizes. If it is a variable length aggregate or array of 1669 variable length aggregates, assume worst that the end is 1670 just BITS_PER_UNIT aligned. */ 1671 if (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST) 1672 { 1673 if (TREE_INT_CST_LOW (TYPE_SIZE (type))) 1674 { 1675 unsigned HOST_WIDE_INT sz 1676 = least_bit_hwi (TREE_INT_CST_LOW (TYPE_SIZE (type))); 1677 rli->offset_align = MIN (rli->offset_align, sz); 1678 } 1679 } 1680 else 1681 rli->offset_align = MIN (rli->offset_align, BITS_PER_UNIT); 1682 } 1683 } 1684 else if (targetm.ms_bitfield_layout_p (rli->t)) 1685 { 1686 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field)); 1687 1688 /* If we ended a bitfield before the full length of the type then 1689 pad the struct out to the full length of the last type. */ 1690 if ((DECL_CHAIN (field) == NULL 1691 || TREE_CODE (DECL_CHAIN (field)) != FIELD_DECL) 1692 && DECL_BIT_FIELD_TYPE (field) 1693 && !integer_zerop (DECL_SIZE (field))) 1694 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, 1695 bitsize_int (rli->remaining_in_alignment)); 1696 1697 normalize_rli (rli); 1698 } 1699 else 1700 { 1701 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field)); 1702 normalize_rli (rli); 1703 } 1704 } 1705 1706 /* Assuming that all the fields have been laid out, this function uses 1707 RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type 1708 indicated by RLI. */ 1709 1710 static void 1711 finalize_record_size (record_layout_info rli) 1712 { 1713 tree unpadded_size, unpadded_size_unit; 1714 1715 /* Now we want just byte and bit offsets, so set the offset alignment 1716 to be a byte and then normalize. */ 1717 rli->offset_align = BITS_PER_UNIT; 1718 normalize_rli (rli); 1719 1720 /* Determine the desired alignment. */ 1721 #ifdef ROUND_TYPE_ALIGN 1722 SET_TYPE_ALIGN (rli->t, ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), 1723 rli->record_align)); 1724 #else 1725 SET_TYPE_ALIGN (rli->t, MAX (TYPE_ALIGN (rli->t), rli->record_align)); 1726 #endif 1727 1728 /* Compute the size so far. Be sure to allow for extra bits in the 1729 size in bytes. We have guaranteed above that it will be no more 1730 than a single byte. */ 1731 unpadded_size = rli_size_so_far (rli); 1732 unpadded_size_unit = rli_size_unit_so_far (rli); 1733 if (! integer_zerop (rli->bitpos)) 1734 unpadded_size_unit 1735 = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node); 1736 1737 /* Round the size up to be a multiple of the required alignment. */ 1738 TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t)); 1739 TYPE_SIZE_UNIT (rli->t) 1740 = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t)); 1741 1742 if (TREE_CONSTANT (unpadded_size) 1743 && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0 1744 && input_location != BUILTINS_LOCATION) 1745 warning (OPT_Wpadded, "padding struct size to alignment boundary"); 1746 1747 if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE 1748 && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary 1749 && TREE_CONSTANT (unpadded_size)) 1750 { 1751 tree unpacked_size; 1752 1753 #ifdef ROUND_TYPE_ALIGN 1754 rli->unpacked_align 1755 = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align); 1756 #else 1757 rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align); 1758 #endif 1759 1760 unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align); 1761 if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t))) 1762 { 1763 if (TYPE_NAME (rli->t)) 1764 { 1765 tree name; 1766 1767 if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE) 1768 name = TYPE_NAME (rli->t); 1769 else 1770 name = DECL_NAME (TYPE_NAME (rli->t)); 1771 1772 if (STRICT_ALIGNMENT) 1773 warning (OPT_Wpacked, "packed attribute causes inefficient " 1774 "alignment for %qE", name); 1775 else 1776 warning (OPT_Wpacked, 1777 "packed attribute is unnecessary for %qE", name); 1778 } 1779 else 1780 { 1781 if (STRICT_ALIGNMENT) 1782 warning (OPT_Wpacked, 1783 "packed attribute causes inefficient alignment"); 1784 else 1785 warning (OPT_Wpacked, "packed attribute is unnecessary"); 1786 } 1787 } 1788 } 1789 } 1790 1791 /* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE). */ 1792 1793 void 1794 compute_record_mode (tree type) 1795 { 1796 tree field; 1797 machine_mode mode = VOIDmode; 1798 1799 /* Most RECORD_TYPEs have BLKmode, so we start off assuming that. 1800 However, if possible, we use a mode that fits in a register 1801 instead, in order to allow for better optimization down the 1802 line. */ 1803 SET_TYPE_MODE (type, BLKmode); 1804 1805 if (! tree_fits_uhwi_p (TYPE_SIZE (type))) 1806 return; 1807 1808 /* A record which has any BLKmode members must itself be 1809 BLKmode; it can't go in a register. Unless the member is 1810 BLKmode only because it isn't aligned. */ 1811 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field)) 1812 { 1813 if (TREE_CODE (field) != FIELD_DECL) 1814 continue; 1815 1816 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK 1817 || (TYPE_MODE (TREE_TYPE (field)) == BLKmode 1818 && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field)) 1819 && !(TYPE_SIZE (TREE_TYPE (field)) != 0 1820 && integer_zerop (TYPE_SIZE (TREE_TYPE (field))))) 1821 || ! tree_fits_uhwi_p (bit_position (field)) 1822 || DECL_SIZE (field) == 0 1823 || ! tree_fits_uhwi_p (DECL_SIZE (field))) 1824 return; 1825 1826 /* If this field is the whole struct, remember its mode so 1827 that, say, we can put a double in a class into a DF 1828 register instead of forcing it to live in the stack. */ 1829 if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field))) 1830 mode = DECL_MODE (field); 1831 1832 /* With some targets, it is sub-optimal to access an aligned 1833 BLKmode structure as a scalar. */ 1834 if (targetm.member_type_forces_blk (field, mode)) 1835 return; 1836 } 1837 1838 /* If we only have one real field; use its mode if that mode's size 1839 matches the type's size. This only applies to RECORD_TYPE. This 1840 does not apply to unions. */ 1841 if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode 1842 && tree_fits_uhwi_p (TYPE_SIZE (type)) 1843 && known_eq (GET_MODE_BITSIZE (mode), tree_to_uhwi (TYPE_SIZE (type)))) 1844 ; 1845 else 1846 mode = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1).else_blk (); 1847 1848 /* If structure's known alignment is less than what the scalar 1849 mode would need, and it matters, then stick with BLKmode. */ 1850 if (mode != BLKmode 1851 && STRICT_ALIGNMENT 1852 && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT 1853 || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (mode))) 1854 { 1855 /* If this is the only reason this type is BLKmode, then 1856 don't force containing types to be BLKmode. */ 1857 TYPE_NO_FORCE_BLK (type) = 1; 1858 mode = BLKmode; 1859 } 1860 1861 SET_TYPE_MODE (type, mode); 1862 } 1863 1864 /* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid 1865 out. */ 1866 1867 static void 1868 finalize_type_size (tree type) 1869 { 1870 /* Normally, use the alignment corresponding to the mode chosen. 1871 However, where strict alignment is not required, avoid 1872 over-aligning structures, since most compilers do not do this 1873 alignment. */ 1874 if (TYPE_MODE (type) != BLKmode 1875 && TYPE_MODE (type) != VOIDmode 1876 && (STRICT_ALIGNMENT || !AGGREGATE_TYPE_P (type))) 1877 { 1878 unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type)); 1879 1880 /* Don't override a larger alignment requirement coming from a user 1881 alignment of one of the fields. */ 1882 if (mode_align >= TYPE_ALIGN (type)) 1883 { 1884 SET_TYPE_ALIGN (type, mode_align); 1885 TYPE_USER_ALIGN (type) = 0; 1886 } 1887 } 1888 1889 /* Do machine-dependent extra alignment. */ 1890 #ifdef ROUND_TYPE_ALIGN 1891 SET_TYPE_ALIGN (type, 1892 ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT)); 1893 #endif 1894 1895 /* If we failed to find a simple way to calculate the unit size 1896 of the type, find it by division. */ 1897 if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0) 1898 /* TYPE_SIZE (type) is computed in bitsizetype. After the division, the 1899 result will fit in sizetype. We will get more efficient code using 1900 sizetype, so we force a conversion. */ 1901 TYPE_SIZE_UNIT (type) 1902 = fold_convert (sizetype, 1903 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type), 1904 bitsize_unit_node)); 1905 1906 if (TYPE_SIZE (type) != 0) 1907 { 1908 TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type)); 1909 TYPE_SIZE_UNIT (type) 1910 = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type)); 1911 } 1912 1913 /* Evaluate nonconstant sizes only once, either now or as soon as safe. */ 1914 if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST) 1915 TYPE_SIZE (type) = variable_size (TYPE_SIZE (type)); 1916 if (TYPE_SIZE_UNIT (type) != 0 1917 && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST) 1918 TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type)); 1919 1920 /* Handle empty records as per the x86-64 psABI. */ 1921 TYPE_EMPTY_P (type) = targetm.calls.empty_record_p (type); 1922 1923 /* Also layout any other variants of the type. */ 1924 if (TYPE_NEXT_VARIANT (type) 1925 || type != TYPE_MAIN_VARIANT (type)) 1926 { 1927 tree variant; 1928 /* Record layout info of this variant. */ 1929 tree size = TYPE_SIZE (type); 1930 tree size_unit = TYPE_SIZE_UNIT (type); 1931 unsigned int align = TYPE_ALIGN (type); 1932 unsigned int precision = TYPE_PRECISION (type); 1933 unsigned int user_align = TYPE_USER_ALIGN (type); 1934 machine_mode mode = TYPE_MODE (type); 1935 bool empty_p = TYPE_EMPTY_P (type); 1936 1937 /* Copy it into all variants. */ 1938 for (variant = TYPE_MAIN_VARIANT (type); 1939 variant != 0; 1940 variant = TYPE_NEXT_VARIANT (variant)) 1941 { 1942 TYPE_SIZE (variant) = size; 1943 TYPE_SIZE_UNIT (variant) = size_unit; 1944 unsigned valign = align; 1945 if (TYPE_USER_ALIGN (variant)) 1946 valign = MAX (valign, TYPE_ALIGN (variant)); 1947 else 1948 TYPE_USER_ALIGN (variant) = user_align; 1949 SET_TYPE_ALIGN (variant, valign); 1950 TYPE_PRECISION (variant) = precision; 1951 SET_TYPE_MODE (variant, mode); 1952 TYPE_EMPTY_P (variant) = empty_p; 1953 } 1954 } 1955 } 1956 1957 /* Return a new underlying object for a bitfield started with FIELD. */ 1958 1959 static tree 1960 start_bitfield_representative (tree field) 1961 { 1962 tree repr = make_node (FIELD_DECL); 1963 DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field); 1964 /* Force the representative to begin at a BITS_PER_UNIT aligned 1965 boundary - C++ may use tail-padding of a base object to 1966 continue packing bits so the bitfield region does not start 1967 at bit zero (see g++.dg/abi/bitfield5.C for example). 1968 Unallocated bits may happen for other reasons as well, 1969 for example Ada which allows explicit bit-granular structure layout. */ 1970 DECL_FIELD_BIT_OFFSET (repr) 1971 = size_binop (BIT_AND_EXPR, 1972 DECL_FIELD_BIT_OFFSET (field), 1973 bitsize_int (~(BITS_PER_UNIT - 1))); 1974 SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field)); 1975 DECL_SIZE (repr) = DECL_SIZE (field); 1976 DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field); 1977 DECL_PACKED (repr) = DECL_PACKED (field); 1978 DECL_CONTEXT (repr) = DECL_CONTEXT (field); 1979 /* There are no indirect accesses to this field. If we introduce 1980 some then they have to use the record alias set. This makes 1981 sure to properly conflict with [indirect] accesses to addressable 1982 fields of the bitfield group. */ 1983 DECL_NONADDRESSABLE_P (repr) = 1; 1984 return repr; 1985 } 1986 1987 /* Finish up a bitfield group that was started by creating the underlying 1988 object REPR with the last field in the bitfield group FIELD. */ 1989 1990 static void 1991 finish_bitfield_representative (tree repr, tree field) 1992 { 1993 unsigned HOST_WIDE_INT bitsize, maxbitsize; 1994 tree nextf, size; 1995 1996 size = size_diffop (DECL_FIELD_OFFSET (field), 1997 DECL_FIELD_OFFSET (repr)); 1998 while (TREE_CODE (size) == COMPOUND_EXPR) 1999 size = TREE_OPERAND (size, 1); 2000 gcc_assert (tree_fits_uhwi_p (size)); 2001 bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT 2002 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)) 2003 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)) 2004 + tree_to_uhwi (DECL_SIZE (field))); 2005 2006 /* Round up bitsize to multiples of BITS_PER_UNIT. */ 2007 bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1); 2008 2009 /* Now nothing tells us how to pad out bitsize ... */ 2010 nextf = DECL_CHAIN (field); 2011 while (nextf && TREE_CODE (nextf) != FIELD_DECL) 2012 nextf = DECL_CHAIN (nextf); 2013 if (nextf) 2014 { 2015 tree maxsize; 2016 /* If there was an error, the field may be not laid out 2017 correctly. Don't bother to do anything. */ 2018 if (TREE_TYPE (nextf) == error_mark_node) 2019 return; 2020 maxsize = size_diffop (DECL_FIELD_OFFSET (nextf), 2021 DECL_FIELD_OFFSET (repr)); 2022 if (tree_fits_uhwi_p (maxsize)) 2023 { 2024 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT 2025 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf)) 2026 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))); 2027 /* If the group ends within a bitfield nextf does not need to be 2028 aligned to BITS_PER_UNIT. Thus round up. */ 2029 maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1); 2030 } 2031 else 2032 maxbitsize = bitsize; 2033 } 2034 else 2035 { 2036 /* Note that if the C++ FE sets up tail-padding to be re-used it 2037 creates a as-base variant of the type with TYPE_SIZE adjusted 2038 accordingly. So it is safe to include tail-padding here. */ 2039 tree aggsize = lang_hooks.types.unit_size_without_reusable_padding 2040 (DECL_CONTEXT (field)); 2041 tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr)); 2042 /* We cannot generally rely on maxsize to fold to an integer constant, 2043 so use bitsize as fallback for this case. */ 2044 if (tree_fits_uhwi_p (maxsize)) 2045 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT 2046 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))); 2047 else 2048 maxbitsize = bitsize; 2049 } 2050 2051 /* Only if we don't artificially break up the representative in 2052 the middle of a large bitfield with different possibly 2053 overlapping representatives. And all representatives start 2054 at byte offset. */ 2055 gcc_assert (maxbitsize % BITS_PER_UNIT == 0); 2056 2057 /* Find the smallest nice mode to use. */ 2058 opt_scalar_int_mode mode_iter; 2059 FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_INT) 2060 if (GET_MODE_BITSIZE (mode_iter.require ()) >= bitsize) 2061 break; 2062 2063 scalar_int_mode mode; 2064 if (!mode_iter.exists (&mode) 2065 || GET_MODE_BITSIZE (mode) > maxbitsize 2066 || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE) 2067 { 2068 /* We really want a BLKmode representative only as a last resort, 2069 considering the member b in 2070 struct { int a : 7; int b : 17; int c; } __attribute__((packed)); 2071 Otherwise we simply want to split the representative up 2072 allowing for overlaps within the bitfield region as required for 2073 struct { int a : 7; int b : 7; 2074 int c : 10; int d; } __attribute__((packed)); 2075 [0, 15] HImode for a and b, [8, 23] HImode for c. */ 2076 DECL_SIZE (repr) = bitsize_int (bitsize); 2077 DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT); 2078 SET_DECL_MODE (repr, BLKmode); 2079 TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node, 2080 bitsize / BITS_PER_UNIT); 2081 } 2082 else 2083 { 2084 unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode); 2085 DECL_SIZE (repr) = bitsize_int (modesize); 2086 DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT); 2087 SET_DECL_MODE (repr, mode); 2088 TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1); 2089 } 2090 2091 /* Remember whether the bitfield group is at the end of the 2092 structure or not. */ 2093 DECL_CHAIN (repr) = nextf; 2094 } 2095 2096 /* Compute and set FIELD_DECLs for the underlying objects we should 2097 use for bitfield access for the structure T. */ 2098 2099 void 2100 finish_bitfield_layout (tree t) 2101 { 2102 tree field, prev; 2103 tree repr = NULL_TREE; 2104 2105 /* Unions would be special, for the ease of type-punning optimizations 2106 we could use the underlying type as hint for the representative 2107 if the bitfield would fit and the representative would not exceed 2108 the union in size. */ 2109 if (TREE_CODE (t) != RECORD_TYPE) 2110 return; 2111 2112 for (prev = NULL_TREE, field = TYPE_FIELDS (t); 2113 field; field = DECL_CHAIN (field)) 2114 { 2115 if (TREE_CODE (field) != FIELD_DECL) 2116 continue; 2117 2118 /* In the C++ memory model, consecutive bit fields in a structure are 2119 considered one memory location and updating a memory location 2120 may not store into adjacent memory locations. */ 2121 if (!repr 2122 && DECL_BIT_FIELD_TYPE (field)) 2123 { 2124 /* Start new representative. */ 2125 repr = start_bitfield_representative (field); 2126 } 2127 else if (repr 2128 && ! DECL_BIT_FIELD_TYPE (field)) 2129 { 2130 /* Finish off new representative. */ 2131 finish_bitfield_representative (repr, prev); 2132 repr = NULL_TREE; 2133 } 2134 else if (DECL_BIT_FIELD_TYPE (field)) 2135 { 2136 gcc_assert (repr != NULL_TREE); 2137 2138 /* Zero-size bitfields finish off a representative and 2139 do not have a representative themselves. This is 2140 required by the C++ memory model. */ 2141 if (integer_zerop (DECL_SIZE (field))) 2142 { 2143 finish_bitfield_representative (repr, prev); 2144 repr = NULL_TREE; 2145 } 2146 2147 /* We assume that either DECL_FIELD_OFFSET of the representative 2148 and each bitfield member is a constant or they are equal. 2149 This is because we need to be able to compute the bit-offset 2150 of each field relative to the representative in get_bit_range 2151 during RTL expansion. 2152 If these constraints are not met, simply force a new 2153 representative to be generated. That will at most 2154 generate worse code but still maintain correctness with 2155 respect to the C++ memory model. */ 2156 else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr)) 2157 && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field))) 2158 || operand_equal_p (DECL_FIELD_OFFSET (repr), 2159 DECL_FIELD_OFFSET (field), 0))) 2160 { 2161 finish_bitfield_representative (repr, prev); 2162 repr = start_bitfield_representative (field); 2163 } 2164 } 2165 else 2166 continue; 2167 2168 if (repr) 2169 DECL_BIT_FIELD_REPRESENTATIVE (field) = repr; 2170 2171 prev = field; 2172 } 2173 2174 if (repr) 2175 finish_bitfield_representative (repr, prev); 2176 } 2177 2178 /* Do all of the work required to layout the type indicated by RLI, 2179 once the fields have been laid out. This function will call `free' 2180 for RLI, unless FREE_P is false. Passing a value other than false 2181 for FREE_P is bad practice; this option only exists to support the 2182 G++ 3.2 ABI. */ 2183 2184 void 2185 finish_record_layout (record_layout_info rli, int free_p) 2186 { 2187 tree variant; 2188 2189 /* Compute the final size. */ 2190 finalize_record_size (rli); 2191 2192 /* Compute the TYPE_MODE for the record. */ 2193 compute_record_mode (rli->t); 2194 2195 /* Perform any last tweaks to the TYPE_SIZE, etc. */ 2196 finalize_type_size (rli->t); 2197 2198 /* Compute bitfield representatives. */ 2199 finish_bitfield_layout (rli->t); 2200 2201 /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants. 2202 With C++ templates, it is too early to do this when the attribute 2203 is being parsed. */ 2204 for (variant = TYPE_NEXT_VARIANT (rli->t); variant; 2205 variant = TYPE_NEXT_VARIANT (variant)) 2206 { 2207 TYPE_PACKED (variant) = TYPE_PACKED (rli->t); 2208 TYPE_REVERSE_STORAGE_ORDER (variant) 2209 = TYPE_REVERSE_STORAGE_ORDER (rli->t); 2210 } 2211 2212 /* Lay out any static members. This is done now because their type 2213 may use the record's type. */ 2214 while (!vec_safe_is_empty (rli->pending_statics)) 2215 layout_decl (rli->pending_statics->pop (), 0); 2216 2217 /* Clean up. */ 2218 if (free_p) 2219 { 2220 vec_free (rli->pending_statics); 2221 free (rli); 2222 } 2223 } 2224 2225 2226 /* Finish processing a builtin RECORD_TYPE type TYPE. It's name is 2227 NAME, its fields are chained in reverse on FIELDS. 2228 2229 If ALIGN_TYPE is non-null, it is given the same alignment as 2230 ALIGN_TYPE. */ 2231 2232 void 2233 finish_builtin_struct (tree type, const char *name, tree fields, 2234 tree align_type) 2235 { 2236 tree tail, next; 2237 2238 for (tail = NULL_TREE; fields; tail = fields, fields = next) 2239 { 2240 DECL_FIELD_CONTEXT (fields) = type; 2241 next = DECL_CHAIN (fields); 2242 DECL_CHAIN (fields) = tail; 2243 } 2244 TYPE_FIELDS (type) = tail; 2245 2246 if (align_type) 2247 { 2248 SET_TYPE_ALIGN (type, TYPE_ALIGN (align_type)); 2249 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type); 2250 SET_TYPE_WARN_IF_NOT_ALIGN (type, 2251 TYPE_WARN_IF_NOT_ALIGN (align_type)); 2252 } 2253 2254 layout_type (type); 2255 #if 0 /* not yet, should get fixed properly later */ 2256 TYPE_NAME (type) = make_type_decl (get_identifier (name), type); 2257 #else 2258 TYPE_NAME (type) = build_decl (BUILTINS_LOCATION, 2259 TYPE_DECL, get_identifier (name), type); 2260 #endif 2261 TYPE_STUB_DECL (type) = TYPE_NAME (type); 2262 layout_decl (TYPE_NAME (type), 0); 2263 } 2264 2265 /* Calculate the mode, size, and alignment for TYPE. 2266 For an array type, calculate the element separation as well. 2267 Record TYPE on the chain of permanent or temporary types 2268 so that dbxout will find out about it. 2269 2270 TYPE_SIZE of a type is nonzero if the type has been laid out already. 2271 layout_type does nothing on such a type. 2272 2273 If the type is incomplete, its TYPE_SIZE remains zero. */ 2274 2275 void 2276 layout_type (tree type) 2277 { 2278 gcc_assert (type); 2279 2280 if (type == error_mark_node) 2281 return; 2282 2283 /* We don't want finalize_type_size to copy an alignment attribute to 2284 variants that don't have it. */ 2285 type = TYPE_MAIN_VARIANT (type); 2286 2287 /* Do nothing if type has been laid out before. */ 2288 if (TYPE_SIZE (type)) 2289 return; 2290 2291 switch (TREE_CODE (type)) 2292 { 2293 case LANG_TYPE: 2294 /* This kind of type is the responsibility 2295 of the language-specific code. */ 2296 gcc_unreachable (); 2297 2298 case BOOLEAN_TYPE: 2299 case INTEGER_TYPE: 2300 case ENUMERAL_TYPE: 2301 { 2302 scalar_int_mode mode 2303 = smallest_int_mode_for_size (TYPE_PRECISION (type)); 2304 SET_TYPE_MODE (type, mode); 2305 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode)); 2306 /* Don't set TYPE_PRECISION here, as it may be set by a bitfield. */ 2307 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode)); 2308 break; 2309 } 2310 2311 case REAL_TYPE: 2312 { 2313 /* Allow the caller to choose the type mode, which is how decimal 2314 floats are distinguished from binary ones. */ 2315 if (TYPE_MODE (type) == VOIDmode) 2316 SET_TYPE_MODE 2317 (type, float_mode_for_size (TYPE_PRECISION (type)).require ()); 2318 scalar_float_mode mode = as_a <scalar_float_mode> (TYPE_MODE (type)); 2319 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode)); 2320 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode)); 2321 break; 2322 } 2323 2324 case FIXED_POINT_TYPE: 2325 { 2326 /* TYPE_MODE (type) has been set already. */ 2327 scalar_mode mode = SCALAR_TYPE_MODE (type); 2328 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode)); 2329 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode)); 2330 break; 2331 } 2332 2333 case COMPLEX_TYPE: 2334 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type)); 2335 SET_TYPE_MODE (type, 2336 GET_MODE_COMPLEX_MODE (TYPE_MODE (TREE_TYPE (type)))); 2337 2338 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type))); 2339 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type))); 2340 break; 2341 2342 case VECTOR_TYPE: 2343 { 2344 poly_uint64 nunits = TYPE_VECTOR_SUBPARTS (type); 2345 tree innertype = TREE_TYPE (type); 2346 2347 /* Find an appropriate mode for the vector type. */ 2348 if (TYPE_MODE (type) == VOIDmode) 2349 SET_TYPE_MODE (type, 2350 mode_for_vector (SCALAR_TYPE_MODE (innertype), 2351 nunits).else_blk ()); 2352 2353 TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type)); 2354 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type)); 2355 /* Several boolean vector elements may fit in a single unit. */ 2356 if (VECTOR_BOOLEAN_TYPE_P (type) 2357 && type->type_common.mode != BLKmode) 2358 TYPE_SIZE_UNIT (type) 2359 = size_int (GET_MODE_SIZE (type->type_common.mode)); 2360 else 2361 TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR, 2362 TYPE_SIZE_UNIT (innertype), 2363 size_int (nunits)); 2364 TYPE_SIZE (type) = int_const_binop 2365 (MULT_EXPR, 2366 bits_from_bytes (TYPE_SIZE_UNIT (type)), 2367 bitsize_int (BITS_PER_UNIT)); 2368 2369 /* For vector types, we do not default to the mode's alignment. 2370 Instead, query a target hook, defaulting to natural alignment. 2371 This prevents ABI changes depending on whether or not native 2372 vector modes are supported. */ 2373 SET_TYPE_ALIGN (type, targetm.vector_alignment (type)); 2374 2375 /* However, if the underlying mode requires a bigger alignment than 2376 what the target hook provides, we cannot use the mode. For now, 2377 simply reject that case. */ 2378 gcc_assert (TYPE_ALIGN (type) 2379 >= GET_MODE_ALIGNMENT (TYPE_MODE (type))); 2380 break; 2381 } 2382 2383 case VOID_TYPE: 2384 /* This is an incomplete type and so doesn't have a size. */ 2385 SET_TYPE_ALIGN (type, 1); 2386 TYPE_USER_ALIGN (type) = 0; 2387 SET_TYPE_MODE (type, VOIDmode); 2388 break; 2389 2390 case POINTER_BOUNDS_TYPE: 2391 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type))); 2392 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type))); 2393 break; 2394 2395 case OFFSET_TYPE: 2396 TYPE_SIZE (type) = bitsize_int (POINTER_SIZE); 2397 TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS); 2398 /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be 2399 integral, which may be an __intN. */ 2400 SET_TYPE_MODE (type, int_mode_for_size (POINTER_SIZE, 0).require ()); 2401 TYPE_PRECISION (type) = POINTER_SIZE; 2402 break; 2403 2404 case FUNCTION_TYPE: 2405 case METHOD_TYPE: 2406 /* It's hard to see what the mode and size of a function ought to 2407 be, but we do know the alignment is FUNCTION_BOUNDARY, so 2408 make it consistent with that. */ 2409 SET_TYPE_MODE (type, 2410 int_mode_for_size (FUNCTION_BOUNDARY, 0).else_blk ()); 2411 TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY); 2412 TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT); 2413 break; 2414 2415 case POINTER_TYPE: 2416 case REFERENCE_TYPE: 2417 { 2418 scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type); 2419 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode)); 2420 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode)); 2421 TYPE_UNSIGNED (type) = 1; 2422 TYPE_PRECISION (type) = GET_MODE_PRECISION (mode); 2423 } 2424 break; 2425 2426 case ARRAY_TYPE: 2427 { 2428 tree index = TYPE_DOMAIN (type); 2429 tree element = TREE_TYPE (type); 2430 2431 /* We need to know both bounds in order to compute the size. */ 2432 if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index) 2433 && TYPE_SIZE (element)) 2434 { 2435 tree ub = TYPE_MAX_VALUE (index); 2436 tree lb = TYPE_MIN_VALUE (index); 2437 tree element_size = TYPE_SIZE (element); 2438 tree length; 2439 2440 /* Make sure that an array of zero-sized element is zero-sized 2441 regardless of its extent. */ 2442 if (integer_zerop (element_size)) 2443 length = size_zero_node; 2444 2445 /* The computation should happen in the original signedness so 2446 that (possible) negative values are handled appropriately 2447 when determining overflow. */ 2448 else 2449 { 2450 /* ??? When it is obvious that the range is signed 2451 represent it using ssizetype. */ 2452 if (TREE_CODE (lb) == INTEGER_CST 2453 && TREE_CODE (ub) == INTEGER_CST 2454 && TYPE_UNSIGNED (TREE_TYPE (lb)) 2455 && tree_int_cst_lt (ub, lb)) 2456 { 2457 lb = wide_int_to_tree (ssizetype, 2458 offset_int::from (wi::to_wide (lb), 2459 SIGNED)); 2460 ub = wide_int_to_tree (ssizetype, 2461 offset_int::from (wi::to_wide (ub), 2462 SIGNED)); 2463 } 2464 length 2465 = fold_convert (sizetype, 2466 size_binop (PLUS_EXPR, 2467 build_int_cst (TREE_TYPE (lb), 1), 2468 size_binop (MINUS_EXPR, ub, lb))); 2469 } 2470 2471 /* ??? We have no way to distinguish a null-sized array from an 2472 array spanning the whole sizetype range, so we arbitrarily 2473 decide that [0, -1] is the only valid representation. */ 2474 if (integer_zerop (length) 2475 && TREE_OVERFLOW (length) 2476 && integer_zerop (lb)) 2477 length = size_zero_node; 2478 2479 TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size, 2480 bits_from_bytes (length)); 2481 2482 /* If we know the size of the element, calculate the total size 2483 directly, rather than do some division thing below. This 2484 optimization helps Fortran assumed-size arrays (where the 2485 size of the array is determined at runtime) substantially. */ 2486 if (TYPE_SIZE_UNIT (element)) 2487 TYPE_SIZE_UNIT (type) 2488 = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length); 2489 } 2490 2491 /* Now round the alignment and size, 2492 using machine-dependent criteria if any. */ 2493 2494 unsigned align = TYPE_ALIGN (element); 2495 if (TYPE_USER_ALIGN (type)) 2496 align = MAX (align, TYPE_ALIGN (type)); 2497 else 2498 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element); 2499 if (!TYPE_WARN_IF_NOT_ALIGN (type)) 2500 SET_TYPE_WARN_IF_NOT_ALIGN (type, 2501 TYPE_WARN_IF_NOT_ALIGN (element)); 2502 #ifdef ROUND_TYPE_ALIGN 2503 align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT); 2504 #else 2505 align = MAX (align, BITS_PER_UNIT); 2506 #endif 2507 SET_TYPE_ALIGN (type, align); 2508 SET_TYPE_MODE (type, BLKmode); 2509 if (TYPE_SIZE (type) != 0 2510 && ! targetm.member_type_forces_blk (type, VOIDmode) 2511 /* BLKmode elements force BLKmode aggregate; 2512 else extract/store fields may lose. */ 2513 && (TYPE_MODE (TREE_TYPE (type)) != BLKmode 2514 || TYPE_NO_FORCE_BLK (TREE_TYPE (type)))) 2515 { 2516 SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type), 2517 TYPE_SIZE (type))); 2518 if (TYPE_MODE (type) != BLKmode 2519 && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT 2520 && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type))) 2521 { 2522 TYPE_NO_FORCE_BLK (type) = 1; 2523 SET_TYPE_MODE (type, BLKmode); 2524 } 2525 } 2526 if (AGGREGATE_TYPE_P (element)) 2527 TYPE_TYPELESS_STORAGE (type) = TYPE_TYPELESS_STORAGE (element); 2528 /* When the element size is constant, check that it is at least as 2529 large as the element alignment. */ 2530 if (TYPE_SIZE_UNIT (element) 2531 && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST 2532 /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than 2533 TYPE_ALIGN_UNIT. */ 2534 && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element)) 2535 && !integer_zerop (TYPE_SIZE_UNIT (element)) 2536 && compare_tree_int (TYPE_SIZE_UNIT (element), 2537 TYPE_ALIGN_UNIT (element)) < 0) 2538 error ("alignment of array elements is greater than element size"); 2539 break; 2540 } 2541 2542 case RECORD_TYPE: 2543 case UNION_TYPE: 2544 case QUAL_UNION_TYPE: 2545 { 2546 tree field; 2547 record_layout_info rli; 2548 2549 /* Initialize the layout information. */ 2550 rli = start_record_layout (type); 2551 2552 /* If this is a QUAL_UNION_TYPE, we want to process the fields 2553 in the reverse order in building the COND_EXPR that denotes 2554 its size. We reverse them again later. */ 2555 if (TREE_CODE (type) == QUAL_UNION_TYPE) 2556 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type)); 2557 2558 /* Place all the fields. */ 2559 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field)) 2560 place_field (rli, field); 2561 2562 if (TREE_CODE (type) == QUAL_UNION_TYPE) 2563 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type)); 2564 2565 /* Finish laying out the record. */ 2566 finish_record_layout (rli, /*free_p=*/true); 2567 } 2568 break; 2569 2570 default: 2571 gcc_unreachable (); 2572 } 2573 2574 /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE. For 2575 records and unions, finish_record_layout already called this 2576 function. */ 2577 if (!RECORD_OR_UNION_TYPE_P (type)) 2578 finalize_type_size (type); 2579 2580 /* We should never see alias sets on incomplete aggregates. And we 2581 should not call layout_type on not incomplete aggregates. */ 2582 if (AGGREGATE_TYPE_P (type)) 2583 gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type)); 2584 } 2585 2586 /* Return the least alignment required for type TYPE. */ 2587 2588 unsigned int 2589 min_align_of_type (tree type) 2590 { 2591 unsigned int align = TYPE_ALIGN (type); 2592 if (!TYPE_USER_ALIGN (type)) 2593 { 2594 align = MIN (align, BIGGEST_ALIGNMENT); 2595 #ifdef BIGGEST_FIELD_ALIGNMENT 2596 align = MIN (align, BIGGEST_FIELD_ALIGNMENT); 2597 #endif 2598 unsigned int field_align = align; 2599 #ifdef ADJUST_FIELD_ALIGN 2600 field_align = ADJUST_FIELD_ALIGN (NULL_TREE, type, field_align); 2601 #endif 2602 align = MIN (align, field_align); 2603 } 2604 return align / BITS_PER_UNIT; 2605 } 2606 2607 /* Create and return a type for signed integers of PRECISION bits. */ 2608 2609 tree 2610 make_signed_type (int precision) 2611 { 2612 tree type = make_node (INTEGER_TYPE); 2613 2614 TYPE_PRECISION (type) = precision; 2615 2616 fixup_signed_type (type); 2617 return type; 2618 } 2619 2620 /* Create and return a type for unsigned integers of PRECISION bits. */ 2621 2622 tree 2623 make_unsigned_type (int precision) 2624 { 2625 tree type = make_node (INTEGER_TYPE); 2626 2627 TYPE_PRECISION (type) = precision; 2628 2629 fixup_unsigned_type (type); 2630 return type; 2631 } 2632 2633 /* Create and return a type for fract of PRECISION bits, UNSIGNEDP, 2634 and SATP. */ 2635 2636 tree 2637 make_fract_type (int precision, int unsignedp, int satp) 2638 { 2639 tree type = make_node (FIXED_POINT_TYPE); 2640 2641 TYPE_PRECISION (type) = precision; 2642 2643 if (satp) 2644 TYPE_SATURATING (type) = 1; 2645 2646 /* Lay out the type: set its alignment, size, etc. */ 2647 TYPE_UNSIGNED (type) = unsignedp; 2648 enum mode_class mclass = unsignedp ? MODE_UFRACT : MODE_FRACT; 2649 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ()); 2650 layout_type (type); 2651 2652 return type; 2653 } 2654 2655 /* Create and return a type for accum of PRECISION bits, UNSIGNEDP, 2656 and SATP. */ 2657 2658 tree 2659 make_accum_type (int precision, int unsignedp, int satp) 2660 { 2661 tree type = make_node (FIXED_POINT_TYPE); 2662 2663 TYPE_PRECISION (type) = precision; 2664 2665 if (satp) 2666 TYPE_SATURATING (type) = 1; 2667 2668 /* Lay out the type: set its alignment, size, etc. */ 2669 TYPE_UNSIGNED (type) = unsignedp; 2670 enum mode_class mclass = unsignedp ? MODE_UACCUM : MODE_ACCUM; 2671 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ()); 2672 layout_type (type); 2673 2674 return type; 2675 } 2676 2677 /* Initialize sizetypes so layout_type can use them. */ 2678 2679 void 2680 initialize_sizetypes (void) 2681 { 2682 int precision, bprecision; 2683 2684 /* Get sizetypes precision from the SIZE_TYPE target macro. */ 2685 if (strcmp (SIZETYPE, "unsigned int") == 0) 2686 precision = INT_TYPE_SIZE; 2687 else if (strcmp (SIZETYPE, "long unsigned int") == 0) 2688 precision = LONG_TYPE_SIZE; 2689 else if (strcmp (SIZETYPE, "long long unsigned int") == 0) 2690 precision = LONG_LONG_TYPE_SIZE; 2691 else if (strcmp (SIZETYPE, "short unsigned int") == 0) 2692 precision = SHORT_TYPE_SIZE; 2693 else 2694 { 2695 int i; 2696 2697 precision = -1; 2698 for (i = 0; i < NUM_INT_N_ENTS; i++) 2699 if (int_n_enabled_p[i]) 2700 { 2701 char name[50]; 2702 sprintf (name, "__int%d unsigned", int_n_data[i].bitsize); 2703 2704 if (strcmp (name, SIZETYPE) == 0) 2705 { 2706 precision = int_n_data[i].bitsize; 2707 } 2708 } 2709 if (precision == -1) 2710 gcc_unreachable (); 2711 } 2712 2713 bprecision 2714 = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE); 2715 bprecision = GET_MODE_PRECISION (smallest_int_mode_for_size (bprecision)); 2716 if (bprecision > HOST_BITS_PER_DOUBLE_INT) 2717 bprecision = HOST_BITS_PER_DOUBLE_INT; 2718 2719 /* Create stubs for sizetype and bitsizetype so we can create constants. */ 2720 sizetype = make_node (INTEGER_TYPE); 2721 TYPE_NAME (sizetype) = get_identifier ("sizetype"); 2722 TYPE_PRECISION (sizetype) = precision; 2723 TYPE_UNSIGNED (sizetype) = 1; 2724 bitsizetype = make_node (INTEGER_TYPE); 2725 TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype"); 2726 TYPE_PRECISION (bitsizetype) = bprecision; 2727 TYPE_UNSIGNED (bitsizetype) = 1; 2728 2729 /* Now layout both types manually. */ 2730 scalar_int_mode mode = smallest_int_mode_for_size (precision); 2731 SET_TYPE_MODE (sizetype, mode); 2732 SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype))); 2733 TYPE_SIZE (sizetype) = bitsize_int (precision); 2734 TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (mode)); 2735 set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED); 2736 2737 mode = smallest_int_mode_for_size (bprecision); 2738 SET_TYPE_MODE (bitsizetype, mode); 2739 SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype))); 2740 TYPE_SIZE (bitsizetype) = bitsize_int (bprecision); 2741 TYPE_SIZE_UNIT (bitsizetype) = size_int (GET_MODE_SIZE (mode)); 2742 set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED); 2743 2744 /* Create the signed variants of *sizetype. */ 2745 ssizetype = make_signed_type (TYPE_PRECISION (sizetype)); 2746 TYPE_NAME (ssizetype) = get_identifier ("ssizetype"); 2747 sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype)); 2748 TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype"); 2749 } 2750 2751 /* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE 2752 or BOOLEAN_TYPE. Set TYPE_MIN_VALUE and TYPE_MAX_VALUE 2753 for TYPE, based on the PRECISION and whether or not the TYPE 2754 IS_UNSIGNED. PRECISION need not correspond to a width supported 2755 natively by the hardware; for example, on a machine with 8-bit, 2756 16-bit, and 32-bit register modes, PRECISION might be 7, 23, or 2757 61. */ 2758 2759 void 2760 set_min_and_max_values_for_integral_type (tree type, 2761 int precision, 2762 signop sgn) 2763 { 2764 /* For bitfields with zero width we end up creating integer types 2765 with zero precision. Don't assign any minimum/maximum values 2766 to those types, they don't have any valid value. */ 2767 if (precision < 1) 2768 return; 2769 2770 TYPE_MIN_VALUE (type) 2771 = wide_int_to_tree (type, wi::min_value (precision, sgn)); 2772 TYPE_MAX_VALUE (type) 2773 = wide_int_to_tree (type, wi::max_value (precision, sgn)); 2774 } 2775 2776 /* Set the extreme values of TYPE based on its precision in bits, 2777 then lay it out. Used when make_signed_type won't do 2778 because the tree code is not INTEGER_TYPE. */ 2779 2780 void 2781 fixup_signed_type (tree type) 2782 { 2783 int precision = TYPE_PRECISION (type); 2784 2785 set_min_and_max_values_for_integral_type (type, precision, SIGNED); 2786 2787 /* Lay out the type: set its alignment, size, etc. */ 2788 layout_type (type); 2789 } 2790 2791 /* Set the extreme values of TYPE based on its precision in bits, 2792 then lay it out. This is used both in `make_unsigned_type' 2793 and for enumeral types. */ 2794 2795 void 2796 fixup_unsigned_type (tree type) 2797 { 2798 int precision = TYPE_PRECISION (type); 2799 2800 TYPE_UNSIGNED (type) = 1; 2801 2802 set_min_and_max_values_for_integral_type (type, precision, UNSIGNED); 2803 2804 /* Lay out the type: set its alignment, size, etc. */ 2805 layout_type (type); 2806 } 2807 2808 /* Construct an iterator for a bitfield that spans BITSIZE bits, 2809 starting at BITPOS. 2810 2811 BITREGION_START is the bit position of the first bit in this 2812 sequence of bit fields. BITREGION_END is the last bit in this 2813 sequence. If these two fields are non-zero, we should restrict the 2814 memory access to that range. Otherwise, we are allowed to touch 2815 any adjacent non bit-fields. 2816 2817 ALIGN is the alignment of the underlying object in bits. 2818 VOLATILEP says whether the bitfield is volatile. */ 2819 2820 bit_field_mode_iterator 2821 ::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos, 2822 poly_int64 bitregion_start, 2823 poly_int64 bitregion_end, 2824 unsigned int align, bool volatilep) 2825 : m_mode (NARROWEST_INT_MODE), m_bitsize (bitsize), 2826 m_bitpos (bitpos), m_bitregion_start (bitregion_start), 2827 m_bitregion_end (bitregion_end), m_align (align), 2828 m_volatilep (volatilep), m_count (0) 2829 { 2830 if (known_eq (m_bitregion_end, 0)) 2831 { 2832 /* We can assume that any aligned chunk of ALIGN bits that overlaps 2833 the bitfield is mapped and won't trap, provided that ALIGN isn't 2834 too large. The cap is the biggest required alignment for data, 2835 or at least the word size. And force one such chunk at least. */ 2836 unsigned HOST_WIDE_INT units 2837 = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD)); 2838 if (bitsize <= 0) 2839 bitsize = 1; 2840 HOST_WIDE_INT end = bitpos + bitsize + units - 1; 2841 m_bitregion_end = end - end % units - 1; 2842 } 2843 } 2844 2845 /* Calls to this function return successively larger modes that can be used 2846 to represent the bitfield. Return true if another bitfield mode is 2847 available, storing it in *OUT_MODE if so. */ 2848 2849 bool 2850 bit_field_mode_iterator::next_mode (scalar_int_mode *out_mode) 2851 { 2852 scalar_int_mode mode; 2853 for (; m_mode.exists (&mode); m_mode = GET_MODE_WIDER_MODE (mode)) 2854 { 2855 unsigned int unit = GET_MODE_BITSIZE (mode); 2856 2857 /* Skip modes that don't have full precision. */ 2858 if (unit != GET_MODE_PRECISION (mode)) 2859 continue; 2860 2861 /* Stop if the mode is too wide to handle efficiently. */ 2862 if (unit > MAX_FIXED_MODE_SIZE) 2863 break; 2864 2865 /* Don't deliver more than one multiword mode; the smallest one 2866 should be used. */ 2867 if (m_count > 0 && unit > BITS_PER_WORD) 2868 break; 2869 2870 /* Skip modes that are too small. */ 2871 unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit; 2872 unsigned HOST_WIDE_INT subend = substart + m_bitsize; 2873 if (subend > unit) 2874 continue; 2875 2876 /* Stop if the mode goes outside the bitregion. */ 2877 HOST_WIDE_INT start = m_bitpos - substart; 2878 if (maybe_ne (m_bitregion_start, 0) 2879 && maybe_lt (start, m_bitregion_start)) 2880 break; 2881 HOST_WIDE_INT end = start + unit; 2882 if (maybe_gt (end, m_bitregion_end + 1)) 2883 break; 2884 2885 /* Stop if the mode requires too much alignment. */ 2886 if (GET_MODE_ALIGNMENT (mode) > m_align 2887 && targetm.slow_unaligned_access (mode, m_align)) 2888 break; 2889 2890 *out_mode = mode; 2891 m_mode = GET_MODE_WIDER_MODE (mode); 2892 m_count++; 2893 return true; 2894 } 2895 return false; 2896 } 2897 2898 /* Return true if smaller modes are generally preferred for this kind 2899 of bitfield. */ 2900 2901 bool 2902 bit_field_mode_iterator::prefer_smaller_modes () 2903 { 2904 return (m_volatilep 2905 ? targetm.narrow_volatile_bitfield () 2906 : !SLOW_BYTE_ACCESS); 2907 } 2908 2909 /* Find the best machine mode to use when referencing a bit field of length 2910 BITSIZE bits starting at BITPOS. 2911 2912 BITREGION_START is the bit position of the first bit in this 2913 sequence of bit fields. BITREGION_END is the last bit in this 2914 sequence. If these two fields are non-zero, we should restrict the 2915 memory access to that range. Otherwise, we are allowed to touch 2916 any adjacent non bit-fields. 2917 2918 The chosen mode must have no more than LARGEST_MODE_BITSIZE bits. 2919 INT_MAX is a suitable value for LARGEST_MODE_BITSIZE if the caller 2920 doesn't want to apply a specific limit. 2921 2922 If no mode meets all these conditions, we return VOIDmode. 2923 2924 The underlying object is known to be aligned to a boundary of ALIGN bits. 2925 2926 If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the 2927 smallest mode meeting these conditions. 2928 2929 If VOLATILEP is false and SLOW_BYTE_ACCESS is true, we return the 2930 largest mode (but a mode no wider than UNITS_PER_WORD) that meets 2931 all the conditions. 2932 2933 If VOLATILEP is true the narrow_volatile_bitfields target hook is used to 2934 decide which of the above modes should be used. */ 2935 2936 bool 2937 get_best_mode (int bitsize, int bitpos, 2938 poly_uint64 bitregion_start, poly_uint64 bitregion_end, 2939 unsigned int align, 2940 unsigned HOST_WIDE_INT largest_mode_bitsize, bool volatilep, 2941 scalar_int_mode *best_mode) 2942 { 2943 bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start, 2944 bitregion_end, align, volatilep); 2945 scalar_int_mode mode; 2946 bool found = false; 2947 while (iter.next_mode (&mode) 2948 /* ??? For historical reasons, reject modes that would normally 2949 receive greater alignment, even if unaligned accesses are 2950 acceptable. This has both advantages and disadvantages. 2951 Removing this check means that something like: 2952 2953 struct s { unsigned int x; unsigned int y; }; 2954 int f (struct s *s) { return s->x == 0 && s->y == 0; } 2955 2956 can be implemented using a single load and compare on 2957 64-bit machines that have no alignment restrictions. 2958 For example, on powerpc64-linux-gnu, we would generate: 2959 2960 ld 3,0(3) 2961 cntlzd 3,3 2962 srdi 3,3,6 2963 blr 2964 2965 rather than: 2966 2967 lwz 9,0(3) 2968 cmpwi 7,9,0 2969 bne 7,.L3 2970 lwz 3,4(3) 2971 cntlzw 3,3 2972 srwi 3,3,5 2973 extsw 3,3 2974 blr 2975 .p2align 4,,15 2976 .L3: 2977 li 3,0 2978 blr 2979 2980 However, accessing more than one field can make life harder 2981 for the gimple optimizers. For example, gcc.dg/vect/bb-slp-5.c 2982 has a series of unsigned short copies followed by a series of 2983 unsigned short comparisons. With this check, both the copies 2984 and comparisons remain 16-bit accesses and FRE is able 2985 to eliminate the latter. Without the check, the comparisons 2986 can be done using 2 64-bit operations, which FRE isn't able 2987 to handle in the same way. 2988 2989 Either way, it would probably be worth disabling this check 2990 during expand. One particular example where removing the 2991 check would help is the get_best_mode call in store_bit_field. 2992 If we are given a memory bitregion of 128 bits that is aligned 2993 to a 64-bit boundary, and the bitfield we want to modify is 2994 in the second half of the bitregion, this check causes 2995 store_bitfield to turn the memory into a 64-bit reference 2996 to the _first_ half of the region. We later use 2997 adjust_bitfield_address to get a reference to the correct half, 2998 but doing so looks to adjust_bitfield_address as though we are 2999 moving past the end of the original object, so it drops the 3000 associated MEM_EXPR and MEM_OFFSET. Removing the check 3001 causes store_bit_field to keep a 128-bit memory reference, 3002 so that the final bitfield reference still has a MEM_EXPR 3003 and MEM_OFFSET. */ 3004 && GET_MODE_ALIGNMENT (mode) <= align 3005 && GET_MODE_BITSIZE (mode) <= largest_mode_bitsize) 3006 { 3007 *best_mode = mode; 3008 found = true; 3009 if (iter.prefer_smaller_modes ()) 3010 break; 3011 } 3012 3013 return found; 3014 } 3015 3016 /* Gets minimal and maximal values for MODE (signed or unsigned depending on 3017 SIGN). The returned constants are made to be usable in TARGET_MODE. */ 3018 3019 void 3020 get_mode_bounds (scalar_int_mode mode, int sign, 3021 scalar_int_mode target_mode, 3022 rtx *mmin, rtx *mmax) 3023 { 3024 unsigned size = GET_MODE_PRECISION (mode); 3025 unsigned HOST_WIDE_INT min_val, max_val; 3026 3027 gcc_assert (size <= HOST_BITS_PER_WIDE_INT); 3028 3029 /* Special case BImode, which has values 0 and STORE_FLAG_VALUE. */ 3030 if (mode == BImode) 3031 { 3032 if (STORE_FLAG_VALUE < 0) 3033 { 3034 min_val = STORE_FLAG_VALUE; 3035 max_val = 0; 3036 } 3037 else 3038 { 3039 min_val = 0; 3040 max_val = STORE_FLAG_VALUE; 3041 } 3042 } 3043 else if (sign) 3044 { 3045 min_val = -(HOST_WIDE_INT_1U << (size - 1)); 3046 max_val = (HOST_WIDE_INT_1U << (size - 1)) - 1; 3047 } 3048 else 3049 { 3050 min_val = 0; 3051 max_val = (HOST_WIDE_INT_1U << (size - 1) << 1) - 1; 3052 } 3053 3054 *mmin = gen_int_mode (min_val, target_mode); 3055 *mmax = gen_int_mode (max_val, target_mode); 3056 } 3057 3058 #include "gt-stor-layout.h" 3059