[6/77] Make GET_MODE_WIDER return an opt_mode
[official-gcc.git] / gcc / stor-layout.c
blobf69fad8fd7599235d15cf112a233453bb6b76d1b
1 /* C-compiler utilities for types and variables storage layout
2 Copyright (C) 1987-2017 Free Software Foundation, Inc.
4 This file is part of GCC.
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.
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.
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/>. */
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 "debug.h"
45 /* Data type for the expressions representing sizes of data types.
46 It is the first integer type laid out. */
47 tree sizetype_tab[(int) stk_type_kind_last];
49 /* If nonzero, this is an upper limit on alignment of structure fields.
50 The value is measured in bits. */
51 unsigned int maximum_field_alignment = TARGET_DEFAULT_PACK_STRUCT * BITS_PER_UNIT;
53 static tree self_referential_size (tree);
54 static void finalize_record_size (record_layout_info);
55 static void finalize_type_size (tree);
56 static void place_union_field (record_layout_info, tree);
57 static int excess_unit_span (HOST_WIDE_INT, HOST_WIDE_INT, HOST_WIDE_INT,
58 HOST_WIDE_INT, tree);
59 extern void debug_rli (record_layout_info);
61 /* Given a size SIZE that may not be a constant, return a SAVE_EXPR
62 to serve as the actual size-expression for a type or decl. */
64 tree
65 variable_size (tree size)
67 /* Obviously. */
68 if (TREE_CONSTANT (size))
69 return size;
71 /* If the size is self-referential, we can't make a SAVE_EXPR (see
72 save_expr for the rationale). But we can do something else. */
73 if (CONTAINS_PLACEHOLDER_P (size))
74 return self_referential_size (size);
76 /* If we are in the global binding level, we can't make a SAVE_EXPR
77 since it may end up being shared across functions, so it is up
78 to the front-end to deal with this case. */
79 if (lang_hooks.decls.global_bindings_p ())
80 return size;
82 return save_expr (size);
85 /* An array of functions used for self-referential size computation. */
86 static GTY(()) vec<tree, va_gc> *size_functions;
88 /* Return true if T is a self-referential component reference. */
90 static bool
91 self_referential_component_ref_p (tree t)
93 if (TREE_CODE (t) != COMPONENT_REF)
94 return false;
96 while (REFERENCE_CLASS_P (t))
97 t = TREE_OPERAND (t, 0);
99 return (TREE_CODE (t) == PLACEHOLDER_EXPR);
102 /* Similar to copy_tree_r but do not copy component references involving
103 PLACEHOLDER_EXPRs. These nodes are spotted in find_placeholder_in_expr
104 and substituted in substitute_in_expr. */
106 static tree
107 copy_self_referential_tree_r (tree *tp, int *walk_subtrees, void *data)
109 enum tree_code code = TREE_CODE (*tp);
111 /* Stop at types, decls, constants like copy_tree_r. */
112 if (TREE_CODE_CLASS (code) == tcc_type
113 || TREE_CODE_CLASS (code) == tcc_declaration
114 || TREE_CODE_CLASS (code) == tcc_constant)
116 *walk_subtrees = 0;
117 return NULL_TREE;
120 /* This is the pattern built in ada/make_aligning_type. */
121 else if (code == ADDR_EXPR
122 && TREE_CODE (TREE_OPERAND (*tp, 0)) == PLACEHOLDER_EXPR)
124 *walk_subtrees = 0;
125 return NULL_TREE;
128 /* Default case: the component reference. */
129 else if (self_referential_component_ref_p (*tp))
131 *walk_subtrees = 0;
132 return NULL_TREE;
135 /* We're not supposed to have them in self-referential size trees
136 because we wouldn't properly control when they are evaluated.
137 However, not creating superfluous SAVE_EXPRs requires accurate
138 tracking of readonly-ness all the way down to here, which we
139 cannot always guarantee in practice. So punt in this case. */
140 else if (code == SAVE_EXPR)
141 return error_mark_node;
143 else if (code == STATEMENT_LIST)
144 gcc_unreachable ();
146 return copy_tree_r (tp, walk_subtrees, data);
149 /* Given a SIZE expression that is self-referential, return an equivalent
150 expression to serve as the actual size expression for a type. */
152 static tree
153 self_referential_size (tree size)
155 static unsigned HOST_WIDE_INT fnno = 0;
156 vec<tree> self_refs = vNULL;
157 tree param_type_list = NULL, param_decl_list = NULL;
158 tree t, ref, return_type, fntype, fnname, fndecl;
159 unsigned int i;
160 char buf[128];
161 vec<tree, va_gc> *args = NULL;
163 /* Do not factor out simple operations. */
164 t = skip_simple_constant_arithmetic (size);
165 if (TREE_CODE (t) == CALL_EXPR || self_referential_component_ref_p (t))
166 return size;
168 /* Collect the list of self-references in the expression. */
169 find_placeholder_in_expr (size, &self_refs);
170 gcc_assert (self_refs.length () > 0);
172 /* Obtain a private copy of the expression. */
173 t = size;
174 if (walk_tree (&t, copy_self_referential_tree_r, NULL, NULL) != NULL_TREE)
175 return size;
176 size = t;
178 /* Build the parameter and argument lists in parallel; also
179 substitute the former for the latter in the expression. */
180 vec_alloc (args, self_refs.length ());
181 FOR_EACH_VEC_ELT (self_refs, i, ref)
183 tree subst, param_name, param_type, param_decl;
185 if (DECL_P (ref))
187 /* We shouldn't have true variables here. */
188 gcc_assert (TREE_READONLY (ref));
189 subst = ref;
191 /* This is the pattern built in ada/make_aligning_type. */
192 else if (TREE_CODE (ref) == ADDR_EXPR)
193 subst = ref;
194 /* Default case: the component reference. */
195 else
196 subst = TREE_OPERAND (ref, 1);
198 sprintf (buf, "p%d", i);
199 param_name = get_identifier (buf);
200 param_type = TREE_TYPE (ref);
201 param_decl
202 = build_decl (input_location, PARM_DECL, param_name, param_type);
203 DECL_ARG_TYPE (param_decl) = param_type;
204 DECL_ARTIFICIAL (param_decl) = 1;
205 TREE_READONLY (param_decl) = 1;
207 size = substitute_in_expr (size, subst, param_decl);
209 param_type_list = tree_cons (NULL_TREE, param_type, param_type_list);
210 param_decl_list = chainon (param_decl, param_decl_list);
211 args->quick_push (ref);
214 self_refs.release ();
216 /* Append 'void' to indicate that the number of parameters is fixed. */
217 param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list);
219 /* The 3 lists have been created in reverse order. */
220 param_type_list = nreverse (param_type_list);
221 param_decl_list = nreverse (param_decl_list);
223 /* Build the function type. */
224 return_type = TREE_TYPE (size);
225 fntype = build_function_type (return_type, param_type_list);
227 /* Build the function declaration. */
228 sprintf (buf, "SZ" HOST_WIDE_INT_PRINT_UNSIGNED, fnno++);
229 fnname = get_file_function_name (buf);
230 fndecl = build_decl (input_location, FUNCTION_DECL, fnname, fntype);
231 for (t = param_decl_list; t; t = DECL_CHAIN (t))
232 DECL_CONTEXT (t) = fndecl;
233 DECL_ARGUMENTS (fndecl) = param_decl_list;
234 DECL_RESULT (fndecl)
235 = build_decl (input_location, RESULT_DECL, 0, return_type);
236 DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl;
238 /* The function has been created by the compiler and we don't
239 want to emit debug info for it. */
240 DECL_ARTIFICIAL (fndecl) = 1;
241 DECL_IGNORED_P (fndecl) = 1;
243 /* It is supposed to be "const" and never throw. */
244 TREE_READONLY (fndecl) = 1;
245 TREE_NOTHROW (fndecl) = 1;
247 /* We want it to be inlined when this is deemed profitable, as
248 well as discarded if every call has been integrated. */
249 DECL_DECLARED_INLINE_P (fndecl) = 1;
251 /* It is made up of a unique return statement. */
252 DECL_INITIAL (fndecl) = make_node (BLOCK);
253 BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
254 t = build2 (MODIFY_EXPR, return_type, DECL_RESULT (fndecl), size);
255 DECL_SAVED_TREE (fndecl) = build1 (RETURN_EXPR, void_type_node, t);
256 TREE_STATIC (fndecl) = 1;
258 /* Put it onto the list of size functions. */
259 vec_safe_push (size_functions, fndecl);
261 /* Replace the original expression with a call to the size function. */
262 return build_call_expr_loc_vec (UNKNOWN_LOCATION, fndecl, args);
265 /* Take, queue and compile all the size functions. It is essential that
266 the size functions be gimplified at the very end of the compilation
267 in order to guarantee transparent handling of self-referential sizes.
268 Otherwise the GENERIC inliner would not be able to inline them back
269 at each of their call sites, thus creating artificial non-constant
270 size expressions which would trigger nasty problems later on. */
272 void
273 finalize_size_functions (void)
275 unsigned int i;
276 tree fndecl;
278 for (i = 0; size_functions && size_functions->iterate (i, &fndecl); i++)
280 allocate_struct_function (fndecl, false);
281 set_cfun (NULL);
282 dump_function (TDI_original, fndecl);
284 /* As these functions are used to describe the layout of variable-length
285 structures, debug info generation needs their implementation. */
286 debug_hooks->size_function (fndecl);
287 gimplify_function_tree (fndecl);
288 cgraph_node::finalize_function (fndecl, false);
291 vec_free (size_functions);
294 /* Return the machine mode to use for a nonscalar of SIZE bits. The
295 mode must be in class MCLASS, and have exactly that many value bits;
296 it may have padding as well. If LIMIT is nonzero, modes of wider
297 than MAX_FIXED_MODE_SIZE will not be used. */
299 machine_mode
300 mode_for_size (unsigned int size, enum mode_class mclass, int limit)
302 machine_mode mode;
303 int i;
305 if (limit && size > MAX_FIXED_MODE_SIZE)
306 return BLKmode;
308 /* Get the first mode which has this size, in the specified class. */
309 FOR_EACH_MODE_IN_CLASS (mode, mclass)
310 if (GET_MODE_PRECISION (mode) == size)
311 return mode;
313 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
314 for (i = 0; i < NUM_INT_N_ENTS; i ++)
315 if (int_n_data[i].bitsize == size
316 && int_n_enabled_p[i])
317 return int_n_data[i].m;
319 return BLKmode;
322 /* Similar, except passed a tree node. */
324 machine_mode
325 mode_for_size_tree (const_tree size, enum mode_class mclass, int limit)
327 unsigned HOST_WIDE_INT uhwi;
328 unsigned int ui;
330 if (!tree_fits_uhwi_p (size))
331 return BLKmode;
332 uhwi = tree_to_uhwi (size);
333 ui = uhwi;
334 if (uhwi != ui)
335 return BLKmode;
336 return mode_for_size (ui, mclass, limit);
339 /* Similar, but never return BLKmode; return the narrowest mode that
340 contains at least the requested number of value bits. */
342 machine_mode
343 smallest_mode_for_size (unsigned int size, enum mode_class mclass)
345 machine_mode mode = VOIDmode;
346 int i;
348 /* Get the first mode which has at least this size, in the
349 specified class. */
350 FOR_EACH_MODE_IN_CLASS (mode, mclass)
351 if (GET_MODE_PRECISION (mode) >= size)
352 break;
354 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
355 for (i = 0; i < NUM_INT_N_ENTS; i ++)
356 if (int_n_data[i].bitsize >= size
357 && int_n_data[i].bitsize < GET_MODE_PRECISION (mode)
358 && int_n_enabled_p[i])
359 mode = int_n_data[i].m;
361 if (mode == VOIDmode)
362 gcc_unreachable ();
364 return mode;
367 /* Find an integer mode of the exact same size, or BLKmode on failure. */
369 machine_mode
370 int_mode_for_mode (machine_mode mode)
372 switch (GET_MODE_CLASS (mode))
374 case MODE_INT:
375 case MODE_PARTIAL_INT:
376 break;
378 case MODE_COMPLEX_INT:
379 case MODE_COMPLEX_FLOAT:
380 case MODE_FLOAT:
381 case MODE_DECIMAL_FLOAT:
382 case MODE_VECTOR_INT:
383 case MODE_VECTOR_FLOAT:
384 case MODE_FRACT:
385 case MODE_ACCUM:
386 case MODE_UFRACT:
387 case MODE_UACCUM:
388 case MODE_VECTOR_FRACT:
389 case MODE_VECTOR_ACCUM:
390 case MODE_VECTOR_UFRACT:
391 case MODE_VECTOR_UACCUM:
392 case MODE_POINTER_BOUNDS:
393 mode = mode_for_size (GET_MODE_BITSIZE (mode), MODE_INT, 0);
394 break;
396 case MODE_RANDOM:
397 if (mode == BLKmode)
398 break;
400 /* fall through */
402 case MODE_CC:
403 default:
404 gcc_unreachable ();
407 return mode;
410 /* Find a mode that can be used for efficient bitwise operations on MODE.
411 Return BLKmode if no such mode exists. */
413 machine_mode
414 bitwise_mode_for_mode (machine_mode mode)
416 /* Quick exit if we already have a suitable mode. */
417 unsigned int bitsize = GET_MODE_BITSIZE (mode);
418 if (SCALAR_INT_MODE_P (mode) && bitsize <= MAX_FIXED_MODE_SIZE)
419 return mode;
421 /* Reuse the sanity checks from int_mode_for_mode. */
422 gcc_checking_assert ((int_mode_for_mode (mode), true));
424 /* Try to replace complex modes with complex modes. In general we
425 expect both components to be processed independently, so we only
426 care whether there is a register for the inner mode. */
427 if (COMPLEX_MODE_P (mode))
429 machine_mode trial = mode;
430 if (GET_MODE_CLASS (mode) != MODE_COMPLEX_INT)
431 trial = mode_for_size (bitsize, MODE_COMPLEX_INT, false);
432 if (trial != BLKmode
433 && have_regs_of_mode[GET_MODE_INNER (trial)])
434 return trial;
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) || bitsize > MAX_FIXED_MODE_SIZE)
441 machine_mode trial = mode;
442 if (GET_MODE_CLASS (mode) != MODE_VECTOR_INT)
443 trial = mode_for_size (bitsize, MODE_VECTOR_INT, 0);
444 if (trial != BLKmode
445 && have_regs_of_mode[trial]
446 && targetm.vector_mode_supported_p (trial))
447 return trial;
450 /* Otherwise fall back on integers while honoring MAX_FIXED_MODE_SIZE. */
451 return mode_for_size (bitsize, MODE_INT, true);
454 /* Find a type that can be used for efficient bitwise operations on MODE.
455 Return null if no such mode exists. */
457 tree
458 bitwise_type_for_mode (machine_mode mode)
460 mode = bitwise_mode_for_mode (mode);
461 if (mode == BLKmode)
462 return NULL_TREE;
464 unsigned int inner_size = GET_MODE_UNIT_BITSIZE (mode);
465 tree inner_type = build_nonstandard_integer_type (inner_size, true);
467 if (VECTOR_MODE_P (mode))
468 return build_vector_type_for_mode (inner_type, mode);
470 if (COMPLEX_MODE_P (mode))
471 return build_complex_type (inner_type);
473 gcc_checking_assert (GET_MODE_INNER (mode) == mode);
474 return inner_type;
477 /* Find a mode that is suitable for representing a vector with
478 NUNITS elements of mode INNERMODE. Returns BLKmode if there
479 is no suitable mode. */
481 machine_mode
482 mode_for_vector (machine_mode innermode, unsigned nunits)
484 machine_mode mode;
486 /* First, look for a supported vector type. */
487 if (SCALAR_FLOAT_MODE_P (innermode))
488 mode = MIN_MODE_VECTOR_FLOAT;
489 else if (SCALAR_FRACT_MODE_P (innermode))
490 mode = MIN_MODE_VECTOR_FRACT;
491 else if (SCALAR_UFRACT_MODE_P (innermode))
492 mode = MIN_MODE_VECTOR_UFRACT;
493 else if (SCALAR_ACCUM_MODE_P (innermode))
494 mode = MIN_MODE_VECTOR_ACCUM;
495 else if (SCALAR_UACCUM_MODE_P (innermode))
496 mode = MIN_MODE_VECTOR_UACCUM;
497 else
498 mode = MIN_MODE_VECTOR_INT;
500 /* Do not check vector_mode_supported_p here. We'll do that
501 later in vector_type_mode. */
502 FOR_EACH_MODE_FROM (mode, mode)
503 if (GET_MODE_NUNITS (mode) == nunits
504 && GET_MODE_INNER (mode) == innermode)
505 break;
507 /* For integers, try mapping it to a same-sized scalar mode. */
508 if (mode == VOIDmode
509 && GET_MODE_CLASS (innermode) == MODE_INT)
510 mode = mode_for_size (nunits * GET_MODE_BITSIZE (innermode),
511 MODE_INT, 0);
513 if (mode == VOIDmode
514 || (GET_MODE_CLASS (mode) == MODE_INT
515 && !have_regs_of_mode[mode]))
516 return BLKmode;
518 return mode;
521 /* Return the alignment of MODE. This will be bounded by 1 and
522 BIGGEST_ALIGNMENT. */
524 unsigned int
525 get_mode_alignment (machine_mode mode)
527 return MIN (BIGGEST_ALIGNMENT, MAX (1, mode_base_align[mode]*BITS_PER_UNIT));
530 /* Return the natural mode of an array, given that it is SIZE bytes in
531 total and has elements of type ELEM_TYPE. */
533 static machine_mode
534 mode_for_array (tree elem_type, tree size)
536 tree elem_size;
537 unsigned HOST_WIDE_INT int_size, int_elem_size;
538 bool limit_p;
540 /* One-element arrays get the component type's mode. */
541 elem_size = TYPE_SIZE (elem_type);
542 if (simple_cst_equal (size, elem_size))
543 return TYPE_MODE (elem_type);
545 limit_p = true;
546 if (tree_fits_uhwi_p (size) && tree_fits_uhwi_p (elem_size))
548 int_size = tree_to_uhwi (size);
549 int_elem_size = tree_to_uhwi (elem_size);
550 if (int_elem_size > 0
551 && int_size % int_elem_size == 0
552 && targetm.array_mode_supported_p (TYPE_MODE (elem_type),
553 int_size / int_elem_size))
554 limit_p = false;
556 return mode_for_size_tree (size, MODE_INT, limit_p);
559 /* Subroutine of layout_decl: Force alignment required for the data type.
560 But if the decl itself wants greater alignment, don't override that. */
562 static inline void
563 do_type_align (tree type, tree decl)
565 if (TYPE_ALIGN (type) > DECL_ALIGN (decl))
567 SET_DECL_ALIGN (decl, TYPE_ALIGN (type));
568 if (TREE_CODE (decl) == FIELD_DECL)
569 DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type);
571 if (TYPE_WARN_IF_NOT_ALIGN (type) > DECL_WARN_IF_NOT_ALIGN (decl))
572 SET_DECL_WARN_IF_NOT_ALIGN (decl, TYPE_WARN_IF_NOT_ALIGN (type));
575 /* Set the size, mode and alignment of a ..._DECL node.
576 TYPE_DECL does need this for C++.
577 Note that LABEL_DECL and CONST_DECL nodes do not need this,
578 and FUNCTION_DECL nodes have them set up in a special (and simple) way.
579 Don't call layout_decl for them.
581 KNOWN_ALIGN is the amount of alignment we can assume this
582 decl has with no special effort. It is relevant only for FIELD_DECLs
583 and depends on the previous fields.
584 All that matters about KNOWN_ALIGN is which powers of 2 divide it.
585 If KNOWN_ALIGN is 0, it means, "as much alignment as you like":
586 the record will be aligned to suit. */
588 void
589 layout_decl (tree decl, unsigned int known_align)
591 tree type = TREE_TYPE (decl);
592 enum tree_code code = TREE_CODE (decl);
593 rtx rtl = NULL_RTX;
594 location_t loc = DECL_SOURCE_LOCATION (decl);
596 if (code == CONST_DECL)
597 return;
599 gcc_assert (code == VAR_DECL || code == PARM_DECL || code == RESULT_DECL
600 || code == TYPE_DECL || code == FIELD_DECL);
602 rtl = DECL_RTL_IF_SET (decl);
604 if (type == error_mark_node)
605 type = void_type_node;
607 /* Usually the size and mode come from the data type without change,
608 however, the front-end may set the explicit width of the field, so its
609 size may not be the same as the size of its type. This happens with
610 bitfields, of course (an `int' bitfield may be only 2 bits, say), but it
611 also happens with other fields. For example, the C++ front-end creates
612 zero-sized fields corresponding to empty base classes, and depends on
613 layout_type setting DECL_FIELD_BITPOS correctly for the field. Set the
614 size in bytes from the size in bits. If we have already set the mode,
615 don't set it again since we can be called twice for FIELD_DECLs. */
617 DECL_UNSIGNED (decl) = TYPE_UNSIGNED (type);
618 if (DECL_MODE (decl) == VOIDmode)
619 SET_DECL_MODE (decl, TYPE_MODE (type));
621 if (DECL_SIZE (decl) == 0)
623 DECL_SIZE (decl) = TYPE_SIZE (type);
624 DECL_SIZE_UNIT (decl) = TYPE_SIZE_UNIT (type);
626 else if (DECL_SIZE_UNIT (decl) == 0)
627 DECL_SIZE_UNIT (decl)
628 = fold_convert_loc (loc, sizetype,
629 size_binop_loc (loc, CEIL_DIV_EXPR, DECL_SIZE (decl),
630 bitsize_unit_node));
632 if (code != FIELD_DECL)
633 /* For non-fields, update the alignment from the type. */
634 do_type_align (type, decl);
635 else
636 /* For fields, it's a bit more complicated... */
638 bool old_user_align = DECL_USER_ALIGN (decl);
639 bool zero_bitfield = false;
640 bool packed_p = DECL_PACKED (decl);
641 unsigned int mfa;
643 if (DECL_BIT_FIELD (decl))
645 DECL_BIT_FIELD_TYPE (decl) = type;
647 /* A zero-length bit-field affects the alignment of the next
648 field. In essence such bit-fields are not influenced by
649 any packing due to #pragma pack or attribute packed. */
650 if (integer_zerop (DECL_SIZE (decl))
651 && ! targetm.ms_bitfield_layout_p (DECL_FIELD_CONTEXT (decl)))
653 zero_bitfield = true;
654 packed_p = false;
655 if (PCC_BITFIELD_TYPE_MATTERS)
656 do_type_align (type, decl);
657 else
659 #ifdef EMPTY_FIELD_BOUNDARY
660 if (EMPTY_FIELD_BOUNDARY > DECL_ALIGN (decl))
662 SET_DECL_ALIGN (decl, EMPTY_FIELD_BOUNDARY);
663 DECL_USER_ALIGN (decl) = 0;
665 #endif
669 /* See if we can use an ordinary integer mode for a bit-field.
670 Conditions are: a fixed size that is correct for another mode,
671 occupying a complete byte or bytes on proper boundary. */
672 if (TYPE_SIZE (type) != 0
673 && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
674 && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT)
676 machine_mode xmode
677 = mode_for_size_tree (DECL_SIZE (decl), MODE_INT, 1);
678 unsigned int xalign = GET_MODE_ALIGNMENT (xmode);
680 if (xmode != BLKmode
681 && !(xalign > BITS_PER_UNIT && DECL_PACKED (decl))
682 && (known_align == 0 || known_align >= xalign))
684 SET_DECL_ALIGN (decl, MAX (xalign, DECL_ALIGN (decl)));
685 SET_DECL_MODE (decl, xmode);
686 DECL_BIT_FIELD (decl) = 0;
690 /* Turn off DECL_BIT_FIELD if we won't need it set. */
691 if (TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode
692 && known_align >= TYPE_ALIGN (type)
693 && DECL_ALIGN (decl) >= TYPE_ALIGN (type))
694 DECL_BIT_FIELD (decl) = 0;
696 else if (packed_p && DECL_USER_ALIGN (decl))
697 /* Don't touch DECL_ALIGN. For other packed fields, go ahead and
698 round up; we'll reduce it again below. We want packing to
699 supersede USER_ALIGN inherited from the type, but defer to
700 alignment explicitly specified on the field decl. */;
701 else
702 do_type_align (type, decl);
704 /* If the field is packed and not explicitly aligned, give it the
705 minimum alignment. Note that do_type_align may set
706 DECL_USER_ALIGN, so we need to check old_user_align instead. */
707 if (packed_p
708 && !old_user_align)
709 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), BITS_PER_UNIT));
711 if (! packed_p && ! DECL_USER_ALIGN (decl))
713 /* Some targets (i.e. i386, VMS) limit struct field alignment
714 to a lower boundary than alignment of variables unless
715 it was overridden by attribute aligned. */
716 #ifdef BIGGEST_FIELD_ALIGNMENT
717 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl),
718 (unsigned) BIGGEST_FIELD_ALIGNMENT));
719 #endif
720 #ifdef ADJUST_FIELD_ALIGN
721 SET_DECL_ALIGN (decl, ADJUST_FIELD_ALIGN (decl, TREE_TYPE (decl),
722 DECL_ALIGN (decl)));
723 #endif
726 if (zero_bitfield)
727 mfa = initial_max_fld_align * BITS_PER_UNIT;
728 else
729 mfa = maximum_field_alignment;
730 /* Should this be controlled by DECL_USER_ALIGN, too? */
731 if (mfa != 0)
732 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), mfa));
735 /* Evaluate nonconstant size only once, either now or as soon as safe. */
736 if (DECL_SIZE (decl) != 0 && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
737 DECL_SIZE (decl) = variable_size (DECL_SIZE (decl));
738 if (DECL_SIZE_UNIT (decl) != 0
739 && TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST)
740 DECL_SIZE_UNIT (decl) = variable_size (DECL_SIZE_UNIT (decl));
742 /* If requested, warn about definitions of large data objects. */
743 if (warn_larger_than
744 && (code == VAR_DECL || code == PARM_DECL)
745 && ! DECL_EXTERNAL (decl))
747 tree size = DECL_SIZE_UNIT (decl);
749 if (size != 0 && TREE_CODE (size) == INTEGER_CST
750 && compare_tree_int (size, larger_than_size) > 0)
752 int size_as_int = TREE_INT_CST_LOW (size);
754 if (compare_tree_int (size, size_as_int) == 0)
755 warning (OPT_Wlarger_than_, "size of %q+D is %d bytes", decl, size_as_int);
756 else
757 warning (OPT_Wlarger_than_, "size of %q+D is larger than %wd bytes",
758 decl, larger_than_size);
762 /* If the RTL was already set, update its mode and mem attributes. */
763 if (rtl)
765 PUT_MODE (rtl, DECL_MODE (decl));
766 SET_DECL_RTL (decl, 0);
767 if (MEM_P (rtl))
768 set_mem_attributes (rtl, decl, 1);
769 SET_DECL_RTL (decl, rtl);
773 /* Given a VAR_DECL, PARM_DECL, RESULT_DECL, or FIELD_DECL, clears the
774 results of a previous call to layout_decl and calls it again. */
776 void
777 relayout_decl (tree decl)
779 DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0;
780 SET_DECL_MODE (decl, VOIDmode);
781 if (!DECL_USER_ALIGN (decl))
782 SET_DECL_ALIGN (decl, 0);
783 if (DECL_RTL_SET_P (decl))
784 SET_DECL_RTL (decl, 0);
786 layout_decl (decl, 0);
789 /* Begin laying out type T, which may be a RECORD_TYPE, UNION_TYPE, or
790 QUAL_UNION_TYPE. Return a pointer to a struct record_layout_info which
791 is to be passed to all other layout functions for this record. It is the
792 responsibility of the caller to call `free' for the storage returned.
793 Note that garbage collection is not permitted until we finish laying
794 out the record. */
796 record_layout_info
797 start_record_layout (tree t)
799 record_layout_info rli = XNEW (struct record_layout_info_s);
801 rli->t = t;
803 /* If the type has a minimum specified alignment (via an attribute
804 declaration, for example) use it -- otherwise, start with a
805 one-byte alignment. */
806 rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
807 rli->unpacked_align = rli->record_align;
808 rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT);
810 #ifdef STRUCTURE_SIZE_BOUNDARY
811 /* Packed structures don't need to have minimum size. */
812 if (! TYPE_PACKED (t))
814 unsigned tmp;
816 /* #pragma pack overrides STRUCTURE_SIZE_BOUNDARY. */
817 tmp = (unsigned) STRUCTURE_SIZE_BOUNDARY;
818 if (maximum_field_alignment != 0)
819 tmp = MIN (tmp, maximum_field_alignment);
820 rli->record_align = MAX (rli->record_align, tmp);
822 #endif
824 rli->offset = size_zero_node;
825 rli->bitpos = bitsize_zero_node;
826 rli->prev_field = 0;
827 rli->pending_statics = 0;
828 rli->packed_maybe_necessary = 0;
829 rli->remaining_in_alignment = 0;
831 return rli;
834 /* Return the combined bit position for the byte offset OFFSET and the
835 bit position BITPOS.
837 These functions operate on byte and bit positions present in FIELD_DECLs
838 and assume that these expressions result in no (intermediate) overflow.
839 This assumption is necessary to fold the expressions as much as possible,
840 so as to avoid creating artificially variable-sized types in languages
841 supporting variable-sized types like Ada. */
843 tree
844 bit_from_pos (tree offset, tree bitpos)
846 if (TREE_CODE (offset) == PLUS_EXPR)
847 offset = size_binop (PLUS_EXPR,
848 fold_convert (bitsizetype, TREE_OPERAND (offset, 0)),
849 fold_convert (bitsizetype, TREE_OPERAND (offset, 1)));
850 else
851 offset = fold_convert (bitsizetype, offset);
852 return size_binop (PLUS_EXPR, bitpos,
853 size_binop (MULT_EXPR, offset, bitsize_unit_node));
856 /* Return the combined truncated byte position for the byte offset OFFSET and
857 the bit position BITPOS. */
859 tree
860 byte_from_pos (tree offset, tree bitpos)
862 tree bytepos;
863 if (TREE_CODE (bitpos) == MULT_EXPR
864 && tree_int_cst_equal (TREE_OPERAND (bitpos, 1), bitsize_unit_node))
865 bytepos = TREE_OPERAND (bitpos, 0);
866 else
867 bytepos = size_binop (TRUNC_DIV_EXPR, bitpos, bitsize_unit_node);
868 return size_binop (PLUS_EXPR, offset, fold_convert (sizetype, bytepos));
871 /* Split the bit position POS into a byte offset *POFFSET and a bit
872 position *PBITPOS with the byte offset aligned to OFF_ALIGN bits. */
874 void
875 pos_from_bit (tree *poffset, tree *pbitpos, unsigned int off_align,
876 tree pos)
878 tree toff_align = bitsize_int (off_align);
879 if (TREE_CODE (pos) == MULT_EXPR
880 && tree_int_cst_equal (TREE_OPERAND (pos, 1), toff_align))
882 *poffset = size_binop (MULT_EXPR,
883 fold_convert (sizetype, TREE_OPERAND (pos, 0)),
884 size_int (off_align / BITS_PER_UNIT));
885 *pbitpos = bitsize_zero_node;
887 else
889 *poffset = size_binop (MULT_EXPR,
890 fold_convert (sizetype,
891 size_binop (FLOOR_DIV_EXPR, pos,
892 toff_align)),
893 size_int (off_align / BITS_PER_UNIT));
894 *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, toff_align);
898 /* Given a pointer to bit and byte offsets and an offset alignment,
899 normalize the offsets so they are within the alignment. */
901 void
902 normalize_offset (tree *poffset, tree *pbitpos, unsigned int off_align)
904 /* If the bit position is now larger than it should be, adjust it
905 downwards. */
906 if (compare_tree_int (*pbitpos, off_align) >= 0)
908 tree offset, bitpos;
909 pos_from_bit (&offset, &bitpos, off_align, *pbitpos);
910 *poffset = size_binop (PLUS_EXPR, *poffset, offset);
911 *pbitpos = bitpos;
915 /* Print debugging information about the information in RLI. */
917 DEBUG_FUNCTION void
918 debug_rli (record_layout_info rli)
920 print_node_brief (stderr, "type", rli->t, 0);
921 print_node_brief (stderr, "\noffset", rli->offset, 0);
922 print_node_brief (stderr, " bitpos", rli->bitpos, 0);
924 fprintf (stderr, "\naligns: rec = %u, unpack = %u, off = %u\n",
925 rli->record_align, rli->unpacked_align,
926 rli->offset_align);
928 /* The ms_struct code is the only that uses this. */
929 if (targetm.ms_bitfield_layout_p (rli->t))
930 fprintf (stderr, "remaining in alignment = %u\n", rli->remaining_in_alignment);
932 if (rli->packed_maybe_necessary)
933 fprintf (stderr, "packed may be necessary\n");
935 if (!vec_safe_is_empty (rli->pending_statics))
937 fprintf (stderr, "pending statics:\n");
938 debug_vec_tree (rli->pending_statics);
942 /* Given an RLI with a possibly-incremented BITPOS, adjust OFFSET and
943 BITPOS if necessary to keep BITPOS below OFFSET_ALIGN. */
945 void
946 normalize_rli (record_layout_info rli)
948 normalize_offset (&rli->offset, &rli->bitpos, rli->offset_align);
951 /* Returns the size in bytes allocated so far. */
953 tree
954 rli_size_unit_so_far (record_layout_info rli)
956 return byte_from_pos (rli->offset, rli->bitpos);
959 /* Returns the size in bits allocated so far. */
961 tree
962 rli_size_so_far (record_layout_info rli)
964 return bit_from_pos (rli->offset, rli->bitpos);
967 /* FIELD is about to be added to RLI->T. The alignment (in bits) of
968 the next available location within the record is given by KNOWN_ALIGN.
969 Update the variable alignment fields in RLI, and return the alignment
970 to give the FIELD. */
972 unsigned int
973 update_alignment_for_field (record_layout_info rli, tree field,
974 unsigned int known_align)
976 /* The alignment required for FIELD. */
977 unsigned int desired_align;
978 /* The type of this field. */
979 tree type = TREE_TYPE (field);
980 /* True if the field was explicitly aligned by the user. */
981 bool user_align;
982 bool is_bitfield;
984 /* Do not attempt to align an ERROR_MARK node */
985 if (TREE_CODE (type) == ERROR_MARK)
986 return 0;
988 /* Lay out the field so we know what alignment it needs. */
989 layout_decl (field, known_align);
990 desired_align = DECL_ALIGN (field);
991 user_align = DECL_USER_ALIGN (field);
993 is_bitfield = (type != error_mark_node
994 && DECL_BIT_FIELD_TYPE (field)
995 && ! integer_zerop (TYPE_SIZE (type)));
997 /* Record must have at least as much alignment as any field.
998 Otherwise, the alignment of the field within the record is
999 meaningless. */
1000 if (targetm.ms_bitfield_layout_p (rli->t))
1002 /* Here, the alignment of the underlying type of a bitfield can
1003 affect the alignment of a record; even a zero-sized field
1004 can do this. The alignment should be to the alignment of
1005 the type, except that for zero-size bitfields this only
1006 applies if there was an immediately prior, nonzero-size
1007 bitfield. (That's the way it is, experimentally.) */
1008 if ((!is_bitfield && !DECL_PACKED (field))
1009 || ((DECL_SIZE (field) == NULL_TREE
1010 || !integer_zerop (DECL_SIZE (field)))
1011 ? !DECL_PACKED (field)
1012 : (rli->prev_field
1013 && DECL_BIT_FIELD_TYPE (rli->prev_field)
1014 && ! integer_zerop (DECL_SIZE (rli->prev_field)))))
1016 unsigned int type_align = TYPE_ALIGN (type);
1017 type_align = MAX (type_align, desired_align);
1018 if (maximum_field_alignment != 0)
1019 type_align = MIN (type_align, maximum_field_alignment);
1020 rli->record_align = MAX (rli->record_align, type_align);
1021 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1024 else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
1026 /* Named bit-fields cause the entire structure to have the
1027 alignment implied by their type. Some targets also apply the same
1028 rules to unnamed bitfields. */
1029 if (DECL_NAME (field) != 0
1030 || targetm.align_anon_bitfield ())
1032 unsigned int type_align = TYPE_ALIGN (type);
1034 #ifdef ADJUST_FIELD_ALIGN
1035 if (! TYPE_USER_ALIGN (type))
1036 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1037 #endif
1039 /* Targets might chose to handle unnamed and hence possibly
1040 zero-width bitfield. Those are not influenced by #pragmas
1041 or packed attributes. */
1042 if (integer_zerop (DECL_SIZE (field)))
1044 if (initial_max_fld_align)
1045 type_align = MIN (type_align,
1046 initial_max_fld_align * BITS_PER_UNIT);
1048 else if (maximum_field_alignment != 0)
1049 type_align = MIN (type_align, maximum_field_alignment);
1050 else if (DECL_PACKED (field))
1051 type_align = MIN (type_align, BITS_PER_UNIT);
1053 /* The alignment of the record is increased to the maximum
1054 of the current alignment, the alignment indicated on the
1055 field (i.e., the alignment specified by an __aligned__
1056 attribute), and the alignment indicated by the type of
1057 the field. */
1058 rli->record_align = MAX (rli->record_align, desired_align);
1059 rli->record_align = MAX (rli->record_align, type_align);
1061 if (warn_packed)
1062 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1063 user_align |= TYPE_USER_ALIGN (type);
1066 else
1068 rli->record_align = MAX (rli->record_align, desired_align);
1069 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1072 TYPE_USER_ALIGN (rli->t) |= user_align;
1074 return desired_align;
1077 /* Issue a warning if the record alignment, RECORD_ALIGN, is less than
1078 the field alignment of FIELD or FIELD isn't aligned. */
1080 static void
1081 handle_warn_if_not_align (tree field, unsigned int record_align)
1083 tree type = TREE_TYPE (field);
1085 if (type == error_mark_node)
1086 return;
1088 unsigned int warn_if_not_align = 0;
1090 int opt_w = 0;
1092 if (warn_if_not_aligned)
1094 warn_if_not_align = DECL_WARN_IF_NOT_ALIGN (field);
1095 if (!warn_if_not_align)
1096 warn_if_not_align = TYPE_WARN_IF_NOT_ALIGN (type);
1097 if (warn_if_not_align)
1098 opt_w = OPT_Wif_not_aligned;
1101 if (!warn_if_not_align
1102 && warn_packed_not_aligned
1103 && TYPE_USER_ALIGN (type))
1105 warn_if_not_align = TYPE_ALIGN (type);
1106 opt_w = OPT_Wpacked_not_aligned;
1109 if (!warn_if_not_align)
1110 return;
1112 tree context = DECL_CONTEXT (field);
1114 warn_if_not_align /= BITS_PER_UNIT;
1115 record_align /= BITS_PER_UNIT;
1116 if ((record_align % warn_if_not_align) != 0)
1117 warning (opt_w, "alignment %u of %qT is less than %u",
1118 record_align, context, warn_if_not_align);
1120 unsigned HOST_WIDE_INT off
1121 = (tree_to_uhwi (DECL_FIELD_OFFSET (field))
1122 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)) / BITS_PER_UNIT);
1123 if ((off % warn_if_not_align) != 0)
1124 warning (opt_w, "%q+D offset %wu in %qT isn't aligned to %u",
1125 field, off, context, warn_if_not_align);
1128 /* Called from place_field to handle unions. */
1130 static void
1131 place_union_field (record_layout_info rli, tree field)
1133 update_alignment_for_field (rli, field, /*known_align=*/0);
1135 DECL_FIELD_OFFSET (field) = size_zero_node;
1136 DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
1137 SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);
1138 handle_warn_if_not_align (field, rli->record_align);
1140 /* If this is an ERROR_MARK return *after* having set the
1141 field at the start of the union. This helps when parsing
1142 invalid fields. */
1143 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK)
1144 return;
1146 if (AGGREGATE_TYPE_P (TREE_TYPE (field))
1147 && TYPE_TYPELESS_STORAGE (TREE_TYPE (field)))
1148 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1150 /* We assume the union's size will be a multiple of a byte so we don't
1151 bother with BITPOS. */
1152 if (TREE_CODE (rli->t) == UNION_TYPE)
1153 rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1154 else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE)
1155 rli->offset = fold_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field),
1156 DECL_SIZE_UNIT (field), rli->offset);
1159 /* A bitfield of SIZE with a required access alignment of ALIGN is allocated
1160 at BYTE_OFFSET / BIT_OFFSET. Return nonzero if the field would span more
1161 units of alignment than the underlying TYPE. */
1162 static int
1163 excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset,
1164 HOST_WIDE_INT size, HOST_WIDE_INT align, tree type)
1166 /* Note that the calculation of OFFSET might overflow; we calculate it so
1167 that we still get the right result as long as ALIGN is a power of two. */
1168 unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset;
1170 offset = offset % align;
1171 return ((offset + size + align - 1) / align
1172 > tree_to_uhwi (TYPE_SIZE (type)) / align);
1175 /* RLI contains information about the layout of a RECORD_TYPE. FIELD
1176 is a FIELD_DECL to be added after those fields already present in
1177 T. (FIELD is not actually added to the TYPE_FIELDS list here;
1178 callers that desire that behavior must manually perform that step.) */
1180 void
1181 place_field (record_layout_info rli, tree field)
1183 /* The alignment required for FIELD. */
1184 unsigned int desired_align;
1185 /* The alignment FIELD would have if we just dropped it into the
1186 record as it presently stands. */
1187 unsigned int known_align;
1188 unsigned int actual_align;
1189 /* The type of this field. */
1190 tree type = TREE_TYPE (field);
1192 gcc_assert (TREE_CODE (field) != ERROR_MARK);
1194 /* If FIELD is static, then treat it like a separate variable, not
1195 really like a structure field. If it is a FUNCTION_DECL, it's a
1196 method. In both cases, all we do is lay out the decl, and we do
1197 it *after* the record is laid out. */
1198 if (VAR_P (field))
1200 vec_safe_push (rli->pending_statics, field);
1201 return;
1204 /* Enumerators and enum types which are local to this class need not
1205 be laid out. Likewise for initialized constant fields. */
1206 else if (TREE_CODE (field) != FIELD_DECL)
1207 return;
1209 /* Unions are laid out very differently than records, so split
1210 that code off to another function. */
1211 else if (TREE_CODE (rli->t) != RECORD_TYPE)
1213 place_union_field (rli, field);
1214 return;
1217 else if (TREE_CODE (type) == ERROR_MARK)
1219 /* Place this field at the current allocation position, so we
1220 maintain monotonicity. */
1221 DECL_FIELD_OFFSET (field) = rli->offset;
1222 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1223 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1224 handle_warn_if_not_align (field, rli->record_align);
1225 return;
1228 if (AGGREGATE_TYPE_P (type)
1229 && TYPE_TYPELESS_STORAGE (type))
1230 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1232 /* Work out the known alignment so far. Note that A & (-A) is the
1233 value of the least-significant bit in A that is one. */
1234 if (! integer_zerop (rli->bitpos))
1235 known_align = least_bit_hwi (tree_to_uhwi (rli->bitpos));
1236 else if (integer_zerop (rli->offset))
1237 known_align = 0;
1238 else if (tree_fits_uhwi_p (rli->offset))
1239 known_align = (BITS_PER_UNIT
1240 * least_bit_hwi (tree_to_uhwi (rli->offset)));
1241 else
1242 known_align = rli->offset_align;
1244 desired_align = update_alignment_for_field (rli, field, known_align);
1245 if (known_align == 0)
1246 known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1248 if (warn_packed && DECL_PACKED (field))
1250 if (known_align >= TYPE_ALIGN (type))
1252 if (TYPE_ALIGN (type) > desired_align)
1254 if (STRICT_ALIGNMENT)
1255 warning (OPT_Wattributes, "packed attribute causes "
1256 "inefficient alignment for %q+D", field);
1257 /* Don't warn if DECL_PACKED was set by the type. */
1258 else if (!TYPE_PACKED (rli->t))
1259 warning (OPT_Wattributes, "packed attribute is "
1260 "unnecessary for %q+D", field);
1263 else
1264 rli->packed_maybe_necessary = 1;
1267 /* Does this field automatically have alignment it needs by virtue
1268 of the fields that precede it and the record's own alignment? */
1269 if (known_align < desired_align)
1271 /* No, we need to skip space before this field.
1272 Bump the cumulative size to multiple of field alignment. */
1274 if (!targetm.ms_bitfield_layout_p (rli->t)
1275 && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION)
1276 warning (OPT_Wpadded, "padding struct to align %q+D", field);
1278 /* If the alignment is still within offset_align, just align
1279 the bit position. */
1280 if (desired_align < rli->offset_align)
1281 rli->bitpos = round_up (rli->bitpos, desired_align);
1282 else
1284 /* First adjust OFFSET by the partial bits, then align. */
1285 rli->offset
1286 = size_binop (PLUS_EXPR, rli->offset,
1287 fold_convert (sizetype,
1288 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1289 bitsize_unit_node)));
1290 rli->bitpos = bitsize_zero_node;
1292 rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT);
1295 if (! TREE_CONSTANT (rli->offset))
1296 rli->offset_align = desired_align;
1297 if (targetm.ms_bitfield_layout_p (rli->t))
1298 rli->prev_field = NULL;
1301 /* Handle compatibility with PCC. Note that if the record has any
1302 variable-sized fields, we need not worry about compatibility. */
1303 if (PCC_BITFIELD_TYPE_MATTERS
1304 && ! targetm.ms_bitfield_layout_p (rli->t)
1305 && TREE_CODE (field) == FIELD_DECL
1306 && type != error_mark_node
1307 && DECL_BIT_FIELD (field)
1308 && (! DECL_PACKED (field)
1309 /* Enter for these packed fields only to issue a warning. */
1310 || TYPE_ALIGN (type) <= BITS_PER_UNIT)
1311 && maximum_field_alignment == 0
1312 && ! integer_zerop (DECL_SIZE (field))
1313 && tree_fits_uhwi_p (DECL_SIZE (field))
1314 && tree_fits_uhwi_p (rli->offset)
1315 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1317 unsigned int type_align = TYPE_ALIGN (type);
1318 tree dsize = DECL_SIZE (field);
1319 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1320 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1321 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1323 #ifdef ADJUST_FIELD_ALIGN
1324 if (! TYPE_USER_ALIGN (type))
1325 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1326 #endif
1328 /* A bit field may not span more units of alignment of its type
1329 than its type itself. Advance to next boundary if necessary. */
1330 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1332 if (DECL_PACKED (field))
1334 if (warn_packed_bitfield_compat == 1)
1335 inform
1336 (input_location,
1337 "offset of packed bit-field %qD has changed in GCC 4.4",
1338 field);
1340 else
1341 rli->bitpos = round_up (rli->bitpos, type_align);
1344 if (! DECL_PACKED (field))
1345 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1347 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1348 TYPE_WARN_IF_NOT_ALIGN (type));
1351 #ifdef BITFIELD_NBYTES_LIMITED
1352 if (BITFIELD_NBYTES_LIMITED
1353 && ! targetm.ms_bitfield_layout_p (rli->t)
1354 && TREE_CODE (field) == FIELD_DECL
1355 && type != error_mark_node
1356 && DECL_BIT_FIELD_TYPE (field)
1357 && ! DECL_PACKED (field)
1358 && ! integer_zerop (DECL_SIZE (field))
1359 && tree_fits_uhwi_p (DECL_SIZE (field))
1360 && tree_fits_uhwi_p (rli->offset)
1361 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1363 unsigned int type_align = TYPE_ALIGN (type);
1364 tree dsize = DECL_SIZE (field);
1365 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1366 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1367 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1369 #ifdef ADJUST_FIELD_ALIGN
1370 if (! TYPE_USER_ALIGN (type))
1371 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1372 #endif
1374 if (maximum_field_alignment != 0)
1375 type_align = MIN (type_align, maximum_field_alignment);
1376 /* ??? This test is opposite the test in the containing if
1377 statement, so this code is unreachable currently. */
1378 else if (DECL_PACKED (field))
1379 type_align = MIN (type_align, BITS_PER_UNIT);
1381 /* A bit field may not span the unit of alignment of its type.
1382 Advance to next boundary if necessary. */
1383 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1384 rli->bitpos = round_up (rli->bitpos, type_align);
1386 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1387 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1388 TYPE_WARN_IF_NOT_ALIGN (type));
1390 #endif
1392 /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
1393 A subtlety:
1394 When a bit field is inserted into a packed record, the whole
1395 size of the underlying type is used by one or more same-size
1396 adjacent bitfields. (That is, if its long:3, 32 bits is
1397 used in the record, and any additional adjacent long bitfields are
1398 packed into the same chunk of 32 bits. However, if the size
1399 changes, a new field of that size is allocated.) In an unpacked
1400 record, this is the same as using alignment, but not equivalent
1401 when packing.
1403 Note: for compatibility, we use the type size, not the type alignment
1404 to determine alignment, since that matches the documentation */
1406 if (targetm.ms_bitfield_layout_p (rli->t))
1408 tree prev_saved = rli->prev_field;
1409 tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;
1411 /* This is a bitfield if it exists. */
1412 if (rli->prev_field)
1414 /* If both are bitfields, nonzero, and the same size, this is
1415 the middle of a run. Zero declared size fields are special
1416 and handled as "end of run". (Note: it's nonzero declared
1417 size, but equal type sizes!) (Since we know that both
1418 the current and previous fields are bitfields by the
1419 time we check it, DECL_SIZE must be present for both.) */
1420 if (DECL_BIT_FIELD_TYPE (field)
1421 && !integer_zerop (DECL_SIZE (field))
1422 && !integer_zerop (DECL_SIZE (rli->prev_field))
1423 && tree_fits_shwi_p (DECL_SIZE (rli->prev_field))
1424 && tree_fits_uhwi_p (TYPE_SIZE (type))
1425 && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
1427 /* We're in the middle of a run of equal type size fields; make
1428 sure we realign if we run out of bits. (Not decl size,
1429 type size!) */
1430 HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field));
1432 if (rli->remaining_in_alignment < bitsize)
1434 HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type));
1436 /* out of bits; bump up to next 'word'. */
1437 rli->bitpos
1438 = size_binop (PLUS_EXPR, rli->bitpos,
1439 bitsize_int (rli->remaining_in_alignment));
1440 rli->prev_field = field;
1441 if (typesize < bitsize)
1442 rli->remaining_in_alignment = 0;
1443 else
1444 rli->remaining_in_alignment = typesize - bitsize;
1446 else
1447 rli->remaining_in_alignment -= bitsize;
1449 else
1451 /* End of a run: if leaving a run of bitfields of the same type
1452 size, we have to "use up" the rest of the bits of the type
1453 size.
1455 Compute the new position as the sum of the size for the prior
1456 type and where we first started working on that type.
1457 Note: since the beginning of the field was aligned then
1458 of course the end will be too. No round needed. */
1460 if (!integer_zerop (DECL_SIZE (rli->prev_field)))
1462 rli->bitpos
1463 = size_binop (PLUS_EXPR, rli->bitpos,
1464 bitsize_int (rli->remaining_in_alignment));
1466 else
1467 /* We "use up" size zero fields; the code below should behave
1468 as if the prior field was not a bitfield. */
1469 prev_saved = NULL;
1471 /* Cause a new bitfield to be captured, either this time (if
1472 currently a bitfield) or next time we see one. */
1473 if (!DECL_BIT_FIELD_TYPE (field)
1474 || integer_zerop (DECL_SIZE (field)))
1475 rli->prev_field = NULL;
1478 normalize_rli (rli);
1481 /* If we're starting a new run of same type size bitfields
1482 (or a run of non-bitfields), set up the "first of the run"
1483 fields.
1485 That is, if the current field is not a bitfield, or if there
1486 was a prior bitfield the type sizes differ, or if there wasn't
1487 a prior bitfield the size of the current field is nonzero.
1489 Note: we must be sure to test ONLY the type size if there was
1490 a prior bitfield and ONLY for the current field being zero if
1491 there wasn't. */
1493 if (!DECL_BIT_FIELD_TYPE (field)
1494 || (prev_saved != NULL
1495 ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
1496 : !integer_zerop (DECL_SIZE (field)) ))
1498 /* Never smaller than a byte for compatibility. */
1499 unsigned int type_align = BITS_PER_UNIT;
1501 /* (When not a bitfield), we could be seeing a flex array (with
1502 no DECL_SIZE). Since we won't be using remaining_in_alignment
1503 until we see a bitfield (and come by here again) we just skip
1504 calculating it. */
1505 if (DECL_SIZE (field) != NULL
1506 && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field)))
1507 && tree_fits_uhwi_p (DECL_SIZE (field)))
1509 unsigned HOST_WIDE_INT bitsize
1510 = tree_to_uhwi (DECL_SIZE (field));
1511 unsigned HOST_WIDE_INT typesize
1512 = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field)));
1514 if (typesize < bitsize)
1515 rli->remaining_in_alignment = 0;
1516 else
1517 rli->remaining_in_alignment = typesize - bitsize;
1520 /* Now align (conventionally) for the new type. */
1521 type_align = TYPE_ALIGN (TREE_TYPE (field));
1523 if (maximum_field_alignment != 0)
1524 type_align = MIN (type_align, maximum_field_alignment);
1526 rli->bitpos = round_up (rli->bitpos, type_align);
1528 /* If we really aligned, don't allow subsequent bitfields
1529 to undo that. */
1530 rli->prev_field = NULL;
1534 /* Offset so far becomes the position of this field after normalizing. */
1535 normalize_rli (rli);
1536 DECL_FIELD_OFFSET (field) = rli->offset;
1537 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1538 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1539 handle_warn_if_not_align (field, rli->record_align);
1541 /* Evaluate nonconstant offsets only once, either now or as soon as safe. */
1542 if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
1543 DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));
1545 /* If this field ended up more aligned than we thought it would be (we
1546 approximate this by seeing if its position changed), lay out the field
1547 again; perhaps we can use an integral mode for it now. */
1548 if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field)))
1549 actual_align = least_bit_hwi (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)));
1550 else if (integer_zerop (DECL_FIELD_OFFSET (field)))
1551 actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1552 else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
1553 actual_align = (BITS_PER_UNIT
1554 * least_bit_hwi (tree_to_uhwi (DECL_FIELD_OFFSET (field))));
1555 else
1556 actual_align = DECL_OFFSET_ALIGN (field);
1557 /* ACTUAL_ALIGN is still the actual alignment *within the record* .
1558 store / extract bit field operations will check the alignment of the
1559 record against the mode of bit fields. */
1561 if (known_align != actual_align)
1562 layout_decl (field, actual_align);
1564 if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field))
1565 rli->prev_field = field;
1567 /* Now add size of this field to the size of the record. If the size is
1568 not constant, treat the field as being a multiple of bytes and just
1569 adjust the offset, resetting the bit position. Otherwise, apportion the
1570 size amongst the bit position and offset. First handle the case of an
1571 unspecified size, which can happen when we have an invalid nested struct
1572 definition, such as struct j { struct j { int i; } }. The error message
1573 is printed in finish_struct. */
1574 if (DECL_SIZE (field) == 0)
1575 /* Do nothing. */;
1576 else if (TREE_CODE (DECL_SIZE (field)) != INTEGER_CST
1577 || TREE_OVERFLOW (DECL_SIZE (field)))
1579 rli->offset
1580 = size_binop (PLUS_EXPR, rli->offset,
1581 fold_convert (sizetype,
1582 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1583 bitsize_unit_node)));
1584 rli->offset
1585 = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1586 rli->bitpos = bitsize_zero_node;
1587 rli->offset_align = MIN (rli->offset_align, desired_align);
1589 else if (targetm.ms_bitfield_layout_p (rli->t))
1591 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1593 /* If we ended a bitfield before the full length of the type then
1594 pad the struct out to the full length of the last type. */
1595 if ((DECL_CHAIN (field) == NULL
1596 || TREE_CODE (DECL_CHAIN (field)) != FIELD_DECL)
1597 && DECL_BIT_FIELD_TYPE (field)
1598 && !integer_zerop (DECL_SIZE (field)))
1599 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos,
1600 bitsize_int (rli->remaining_in_alignment));
1602 normalize_rli (rli);
1604 else
1606 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1607 normalize_rli (rli);
1611 /* Assuming that all the fields have been laid out, this function uses
1612 RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type
1613 indicated by RLI. */
1615 static void
1616 finalize_record_size (record_layout_info rli)
1618 tree unpadded_size, unpadded_size_unit;
1620 /* Now we want just byte and bit offsets, so set the offset alignment
1621 to be a byte and then normalize. */
1622 rli->offset_align = BITS_PER_UNIT;
1623 normalize_rli (rli);
1625 /* Determine the desired alignment. */
1626 #ifdef ROUND_TYPE_ALIGN
1627 SET_TYPE_ALIGN (rli->t, ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t),
1628 rli->record_align));
1629 #else
1630 SET_TYPE_ALIGN (rli->t, MAX (TYPE_ALIGN (rli->t), rli->record_align));
1631 #endif
1633 /* Compute the size so far. Be sure to allow for extra bits in the
1634 size in bytes. We have guaranteed above that it will be no more
1635 than a single byte. */
1636 unpadded_size = rli_size_so_far (rli);
1637 unpadded_size_unit = rli_size_unit_so_far (rli);
1638 if (! integer_zerop (rli->bitpos))
1639 unpadded_size_unit
1640 = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node);
1642 /* Round the size up to be a multiple of the required alignment. */
1643 TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
1644 TYPE_SIZE_UNIT (rli->t)
1645 = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t));
1647 if (TREE_CONSTANT (unpadded_size)
1648 && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0
1649 && input_location != BUILTINS_LOCATION)
1650 warning (OPT_Wpadded, "padding struct size to alignment boundary");
1652 if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE
1653 && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary
1654 && TREE_CONSTANT (unpadded_size))
1656 tree unpacked_size;
1658 #ifdef ROUND_TYPE_ALIGN
1659 rli->unpacked_align
1660 = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align);
1661 #else
1662 rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align);
1663 #endif
1665 unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
1666 if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
1668 if (TYPE_NAME (rli->t))
1670 tree name;
1672 if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE)
1673 name = TYPE_NAME (rli->t);
1674 else
1675 name = DECL_NAME (TYPE_NAME (rli->t));
1677 if (STRICT_ALIGNMENT)
1678 warning (OPT_Wpacked, "packed attribute causes inefficient "
1679 "alignment for %qE", name);
1680 else
1681 warning (OPT_Wpacked,
1682 "packed attribute is unnecessary for %qE", name);
1684 else
1686 if (STRICT_ALIGNMENT)
1687 warning (OPT_Wpacked,
1688 "packed attribute causes inefficient alignment");
1689 else
1690 warning (OPT_Wpacked, "packed attribute is unnecessary");
1696 /* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE). */
1698 void
1699 compute_record_mode (tree type)
1701 tree field;
1702 machine_mode mode = VOIDmode;
1704 /* Most RECORD_TYPEs have BLKmode, so we start off assuming that.
1705 However, if possible, we use a mode that fits in a register
1706 instead, in order to allow for better optimization down the
1707 line. */
1708 SET_TYPE_MODE (type, BLKmode);
1710 if (! tree_fits_uhwi_p (TYPE_SIZE (type)))
1711 return;
1713 /* A record which has any BLKmode members must itself be
1714 BLKmode; it can't go in a register. Unless the member is
1715 BLKmode only because it isn't aligned. */
1716 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
1718 if (TREE_CODE (field) != FIELD_DECL)
1719 continue;
1721 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK
1722 || (TYPE_MODE (TREE_TYPE (field)) == BLKmode
1723 && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field))
1724 && !(TYPE_SIZE (TREE_TYPE (field)) != 0
1725 && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
1726 || ! tree_fits_uhwi_p (bit_position (field))
1727 || DECL_SIZE (field) == 0
1728 || ! tree_fits_uhwi_p (DECL_SIZE (field)))
1729 return;
1731 /* If this field is the whole struct, remember its mode so
1732 that, say, we can put a double in a class into a DF
1733 register instead of forcing it to live in the stack. */
1734 if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field)))
1735 mode = DECL_MODE (field);
1737 /* With some targets, it is sub-optimal to access an aligned
1738 BLKmode structure as a scalar. */
1739 if (targetm.member_type_forces_blk (field, mode))
1740 return;
1743 /* If we only have one real field; use its mode if that mode's size
1744 matches the type's size. This only applies to RECORD_TYPE. This
1745 does not apply to unions. */
1746 if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode
1747 && tree_fits_uhwi_p (TYPE_SIZE (type))
1748 && GET_MODE_BITSIZE (mode) == tree_to_uhwi (TYPE_SIZE (type)))
1749 SET_TYPE_MODE (type, mode);
1750 else
1751 SET_TYPE_MODE (type, mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1));
1753 /* If structure's known alignment is less than what the scalar
1754 mode would need, and it matters, then stick with BLKmode. */
1755 if (TYPE_MODE (type) != BLKmode
1756 && STRICT_ALIGNMENT
1757 && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT
1758 || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (TYPE_MODE (type))))
1760 /* If this is the only reason this type is BLKmode, then
1761 don't force containing types to be BLKmode. */
1762 TYPE_NO_FORCE_BLK (type) = 1;
1763 SET_TYPE_MODE (type, BLKmode);
1767 /* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid
1768 out. */
1770 static void
1771 finalize_type_size (tree type)
1773 /* Normally, use the alignment corresponding to the mode chosen.
1774 However, where strict alignment is not required, avoid
1775 over-aligning structures, since most compilers do not do this
1776 alignment. */
1777 if (TYPE_MODE (type) != BLKmode
1778 && TYPE_MODE (type) != VOIDmode
1779 && (STRICT_ALIGNMENT || !AGGREGATE_TYPE_P (type)))
1781 unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type));
1783 /* Don't override a larger alignment requirement coming from a user
1784 alignment of one of the fields. */
1785 if (mode_align >= TYPE_ALIGN (type))
1787 SET_TYPE_ALIGN (type, mode_align);
1788 TYPE_USER_ALIGN (type) = 0;
1792 /* Do machine-dependent extra alignment. */
1793 #ifdef ROUND_TYPE_ALIGN
1794 SET_TYPE_ALIGN (type,
1795 ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT));
1796 #endif
1798 /* If we failed to find a simple way to calculate the unit size
1799 of the type, find it by division. */
1800 if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0)
1801 /* TYPE_SIZE (type) is computed in bitsizetype. After the division, the
1802 result will fit in sizetype. We will get more efficient code using
1803 sizetype, so we force a conversion. */
1804 TYPE_SIZE_UNIT (type)
1805 = fold_convert (sizetype,
1806 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
1807 bitsize_unit_node));
1809 if (TYPE_SIZE (type) != 0)
1811 TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
1812 TYPE_SIZE_UNIT (type)
1813 = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type));
1816 /* Evaluate nonconstant sizes only once, either now or as soon as safe. */
1817 if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
1818 TYPE_SIZE (type) = variable_size (TYPE_SIZE (type));
1819 if (TYPE_SIZE_UNIT (type) != 0
1820 && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST)
1821 TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type));
1823 /* Also layout any other variants of the type. */
1824 if (TYPE_NEXT_VARIANT (type)
1825 || type != TYPE_MAIN_VARIANT (type))
1827 tree variant;
1828 /* Record layout info of this variant. */
1829 tree size = TYPE_SIZE (type);
1830 tree size_unit = TYPE_SIZE_UNIT (type);
1831 unsigned int align = TYPE_ALIGN (type);
1832 unsigned int precision = TYPE_PRECISION (type);
1833 unsigned int user_align = TYPE_USER_ALIGN (type);
1834 machine_mode mode = TYPE_MODE (type);
1836 /* Copy it into all variants. */
1837 for (variant = TYPE_MAIN_VARIANT (type);
1838 variant != 0;
1839 variant = TYPE_NEXT_VARIANT (variant))
1841 TYPE_SIZE (variant) = size;
1842 TYPE_SIZE_UNIT (variant) = size_unit;
1843 unsigned valign = align;
1844 if (TYPE_USER_ALIGN (variant))
1845 valign = MAX (valign, TYPE_ALIGN (variant));
1846 else
1847 TYPE_USER_ALIGN (variant) = user_align;
1848 SET_TYPE_ALIGN (variant, valign);
1849 TYPE_PRECISION (variant) = precision;
1850 SET_TYPE_MODE (variant, mode);
1855 /* Return a new underlying object for a bitfield started with FIELD. */
1857 static tree
1858 start_bitfield_representative (tree field)
1860 tree repr = make_node (FIELD_DECL);
1861 DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field);
1862 /* Force the representative to begin at a BITS_PER_UNIT aligned
1863 boundary - C++ may use tail-padding of a base object to
1864 continue packing bits so the bitfield region does not start
1865 at bit zero (see g++.dg/abi/bitfield5.C for example).
1866 Unallocated bits may happen for other reasons as well,
1867 for example Ada which allows explicit bit-granular structure layout. */
1868 DECL_FIELD_BIT_OFFSET (repr)
1869 = size_binop (BIT_AND_EXPR,
1870 DECL_FIELD_BIT_OFFSET (field),
1871 bitsize_int (~(BITS_PER_UNIT - 1)));
1872 SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field));
1873 DECL_SIZE (repr) = DECL_SIZE (field);
1874 DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
1875 DECL_PACKED (repr) = DECL_PACKED (field);
1876 DECL_CONTEXT (repr) = DECL_CONTEXT (field);
1877 /* There are no indirect accesses to this field. If we introduce
1878 some then they have to use the record alias set. This makes
1879 sure to properly conflict with [indirect] accesses to addressable
1880 fields of the bitfield group. */
1881 DECL_NONADDRESSABLE_P (repr) = 1;
1882 return repr;
1885 /* Finish up a bitfield group that was started by creating the underlying
1886 object REPR with the last field in the bitfield group FIELD. */
1888 static void
1889 finish_bitfield_representative (tree repr, tree field)
1891 unsigned HOST_WIDE_INT bitsize, maxbitsize;
1892 machine_mode mode;
1893 tree nextf, size;
1895 size = size_diffop (DECL_FIELD_OFFSET (field),
1896 DECL_FIELD_OFFSET (repr));
1897 while (TREE_CODE (size) == COMPOUND_EXPR)
1898 size = TREE_OPERAND (size, 1);
1899 gcc_assert (tree_fits_uhwi_p (size));
1900 bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
1901 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
1902 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))
1903 + tree_to_uhwi (DECL_SIZE (field)));
1905 /* Round up bitsize to multiples of BITS_PER_UNIT. */
1906 bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
1908 /* Now nothing tells us how to pad out bitsize ... */
1909 nextf = DECL_CHAIN (field);
1910 while (nextf && TREE_CODE (nextf) != FIELD_DECL)
1911 nextf = DECL_CHAIN (nextf);
1912 if (nextf)
1914 tree maxsize;
1915 /* If there was an error, the field may be not laid out
1916 correctly. Don't bother to do anything. */
1917 if (TREE_TYPE (nextf) == error_mark_node)
1918 return;
1919 maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
1920 DECL_FIELD_OFFSET (repr));
1921 if (tree_fits_uhwi_p (maxsize))
1923 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
1924 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf))
1925 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
1926 /* If the group ends within a bitfield nextf does not need to be
1927 aligned to BITS_PER_UNIT. Thus round up. */
1928 maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
1930 else
1931 maxbitsize = bitsize;
1933 else
1935 /* Note that if the C++ FE sets up tail-padding to be re-used it
1936 creates a as-base variant of the type with TYPE_SIZE adjusted
1937 accordingly. So it is safe to include tail-padding here. */
1938 tree aggsize = lang_hooks.types.unit_size_without_reusable_padding
1939 (DECL_CONTEXT (field));
1940 tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr));
1941 /* We cannot generally rely on maxsize to fold to an integer constant,
1942 so use bitsize as fallback for this case. */
1943 if (tree_fits_uhwi_p (maxsize))
1944 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
1945 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
1946 else
1947 maxbitsize = bitsize;
1950 /* Only if we don't artificially break up the representative in
1951 the middle of a large bitfield with different possibly
1952 overlapping representatives. And all representatives start
1953 at byte offset. */
1954 gcc_assert (maxbitsize % BITS_PER_UNIT == 0);
1956 /* Find the smallest nice mode to use. */
1957 FOR_EACH_MODE_IN_CLASS (mode, MODE_INT)
1958 if (GET_MODE_BITSIZE (mode) >= bitsize)
1959 break;
1960 if (mode != VOIDmode
1961 && (GET_MODE_BITSIZE (mode) > maxbitsize
1962 || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE))
1963 mode = VOIDmode;
1965 if (mode == VOIDmode)
1967 /* We really want a BLKmode representative only as a last resort,
1968 considering the member b in
1969 struct { int a : 7; int b : 17; int c; } __attribute__((packed));
1970 Otherwise we simply want to split the representative up
1971 allowing for overlaps within the bitfield region as required for
1972 struct { int a : 7; int b : 7;
1973 int c : 10; int d; } __attribute__((packed));
1974 [0, 15] HImode for a and b, [8, 23] HImode for c. */
1975 DECL_SIZE (repr) = bitsize_int (bitsize);
1976 DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT);
1977 SET_DECL_MODE (repr, BLKmode);
1978 TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node,
1979 bitsize / BITS_PER_UNIT);
1981 else
1983 unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode);
1984 DECL_SIZE (repr) = bitsize_int (modesize);
1985 DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT);
1986 SET_DECL_MODE (repr, mode);
1987 TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1);
1990 /* Remember whether the bitfield group is at the end of the
1991 structure or not. */
1992 DECL_CHAIN (repr) = nextf;
1995 /* Compute and set FIELD_DECLs for the underlying objects we should
1996 use for bitfield access for the structure T. */
1998 void
1999 finish_bitfield_layout (tree t)
2001 tree field, prev;
2002 tree repr = NULL_TREE;
2004 /* Unions would be special, for the ease of type-punning optimizations
2005 we could use the underlying type as hint for the representative
2006 if the bitfield would fit and the representative would not exceed
2007 the union in size. */
2008 if (TREE_CODE (t) != RECORD_TYPE)
2009 return;
2011 for (prev = NULL_TREE, field = TYPE_FIELDS (t);
2012 field; field = DECL_CHAIN (field))
2014 if (TREE_CODE (field) != FIELD_DECL)
2015 continue;
2017 /* In the C++ memory model, consecutive bit fields in a structure are
2018 considered one memory location and updating a memory location
2019 may not store into adjacent memory locations. */
2020 if (!repr
2021 && DECL_BIT_FIELD_TYPE (field))
2023 /* Start new representative. */
2024 repr = start_bitfield_representative (field);
2026 else if (repr
2027 && ! DECL_BIT_FIELD_TYPE (field))
2029 /* Finish off new representative. */
2030 finish_bitfield_representative (repr, prev);
2031 repr = NULL_TREE;
2033 else if (DECL_BIT_FIELD_TYPE (field))
2035 gcc_assert (repr != NULL_TREE);
2037 /* Zero-size bitfields finish off a representative and
2038 do not have a representative themselves. This is
2039 required by the C++ memory model. */
2040 if (integer_zerop (DECL_SIZE (field)))
2042 finish_bitfield_representative (repr, prev);
2043 repr = NULL_TREE;
2046 /* We assume that either DECL_FIELD_OFFSET of the representative
2047 and each bitfield member is a constant or they are equal.
2048 This is because we need to be able to compute the bit-offset
2049 of each field relative to the representative in get_bit_range
2050 during RTL expansion.
2051 If these constraints are not met, simply force a new
2052 representative to be generated. That will at most
2053 generate worse code but still maintain correctness with
2054 respect to the C++ memory model. */
2055 else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr))
2056 && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
2057 || operand_equal_p (DECL_FIELD_OFFSET (repr),
2058 DECL_FIELD_OFFSET (field), 0)))
2060 finish_bitfield_representative (repr, prev);
2061 repr = start_bitfield_representative (field);
2064 else
2065 continue;
2067 if (repr)
2068 DECL_BIT_FIELD_REPRESENTATIVE (field) = repr;
2070 prev = field;
2073 if (repr)
2074 finish_bitfield_representative (repr, prev);
2077 /* Do all of the work required to layout the type indicated by RLI,
2078 once the fields have been laid out. This function will call `free'
2079 for RLI, unless FREE_P is false. Passing a value other than false
2080 for FREE_P is bad practice; this option only exists to support the
2081 G++ 3.2 ABI. */
2083 void
2084 finish_record_layout (record_layout_info rli, int free_p)
2086 tree variant;
2088 /* Compute the final size. */
2089 finalize_record_size (rli);
2091 /* Compute the TYPE_MODE for the record. */
2092 compute_record_mode (rli->t);
2094 /* Perform any last tweaks to the TYPE_SIZE, etc. */
2095 finalize_type_size (rli->t);
2097 /* Compute bitfield representatives. */
2098 finish_bitfield_layout (rli->t);
2100 /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants.
2101 With C++ templates, it is too early to do this when the attribute
2102 is being parsed. */
2103 for (variant = TYPE_NEXT_VARIANT (rli->t); variant;
2104 variant = TYPE_NEXT_VARIANT (variant))
2106 TYPE_PACKED (variant) = TYPE_PACKED (rli->t);
2107 TYPE_REVERSE_STORAGE_ORDER (variant)
2108 = TYPE_REVERSE_STORAGE_ORDER (rli->t);
2111 /* Lay out any static members. This is done now because their type
2112 may use the record's type. */
2113 while (!vec_safe_is_empty (rli->pending_statics))
2114 layout_decl (rli->pending_statics->pop (), 0);
2116 /* Clean up. */
2117 if (free_p)
2119 vec_free (rli->pending_statics);
2120 free (rli);
2125 /* Finish processing a builtin RECORD_TYPE type TYPE. It's name is
2126 NAME, its fields are chained in reverse on FIELDS.
2128 If ALIGN_TYPE is non-null, it is given the same alignment as
2129 ALIGN_TYPE. */
2131 void
2132 finish_builtin_struct (tree type, const char *name, tree fields,
2133 tree align_type)
2135 tree tail, next;
2137 for (tail = NULL_TREE; fields; tail = fields, fields = next)
2139 DECL_FIELD_CONTEXT (fields) = type;
2140 next = DECL_CHAIN (fields);
2141 DECL_CHAIN (fields) = tail;
2143 TYPE_FIELDS (type) = tail;
2145 if (align_type)
2147 SET_TYPE_ALIGN (type, TYPE_ALIGN (align_type));
2148 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type);
2149 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2150 TYPE_WARN_IF_NOT_ALIGN (align_type));
2153 layout_type (type);
2154 #if 0 /* not yet, should get fixed properly later */
2155 TYPE_NAME (type) = make_type_decl (get_identifier (name), type);
2156 #else
2157 TYPE_NAME (type) = build_decl (BUILTINS_LOCATION,
2158 TYPE_DECL, get_identifier (name), type);
2159 #endif
2160 TYPE_STUB_DECL (type) = TYPE_NAME (type);
2161 layout_decl (TYPE_NAME (type), 0);
2164 /* Calculate the mode, size, and alignment for TYPE.
2165 For an array type, calculate the element separation as well.
2166 Record TYPE on the chain of permanent or temporary types
2167 so that dbxout will find out about it.
2169 TYPE_SIZE of a type is nonzero if the type has been laid out already.
2170 layout_type does nothing on such a type.
2172 If the type is incomplete, its TYPE_SIZE remains zero. */
2174 void
2175 layout_type (tree type)
2177 gcc_assert (type);
2179 if (type == error_mark_node)
2180 return;
2182 /* We don't want finalize_type_size to copy an alignment attribute to
2183 variants that don't have it. */
2184 type = TYPE_MAIN_VARIANT (type);
2186 /* Do nothing if type has been laid out before. */
2187 if (TYPE_SIZE (type))
2188 return;
2190 switch (TREE_CODE (type))
2192 case LANG_TYPE:
2193 /* This kind of type is the responsibility
2194 of the language-specific code. */
2195 gcc_unreachable ();
2197 case BOOLEAN_TYPE:
2198 case INTEGER_TYPE:
2199 case ENUMERAL_TYPE:
2200 SET_TYPE_MODE (type,
2201 smallest_mode_for_size (TYPE_PRECISION (type), MODE_INT));
2202 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2203 /* Don't set TYPE_PRECISION here, as it may be set by a bitfield. */
2204 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2205 break;
2207 case REAL_TYPE:
2208 /* Allow the caller to choose the type mode, which is how decimal
2209 floats are distinguished from binary ones. */
2210 if (TYPE_MODE (type) == VOIDmode)
2211 SET_TYPE_MODE (type,
2212 mode_for_size (TYPE_PRECISION (type), MODE_FLOAT, 0));
2213 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2214 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2215 break;
2217 case FIXED_POINT_TYPE:
2218 /* TYPE_MODE (type) has been set already. */
2219 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2220 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2221 break;
2223 case COMPLEX_TYPE:
2224 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2225 SET_TYPE_MODE (type,
2226 GET_MODE_COMPLEX_MODE (TYPE_MODE (TREE_TYPE (type))));
2228 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2229 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2230 break;
2232 case VECTOR_TYPE:
2234 int nunits = TYPE_VECTOR_SUBPARTS (type);
2235 tree innertype = TREE_TYPE (type);
2237 gcc_assert (!(nunits & (nunits - 1)));
2239 /* Find an appropriate mode for the vector type. */
2240 if (TYPE_MODE (type) == VOIDmode)
2241 SET_TYPE_MODE (type,
2242 mode_for_vector (TYPE_MODE (innertype), nunits));
2244 TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type));
2245 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2246 /* Several boolean vector elements may fit in a single unit. */
2247 if (VECTOR_BOOLEAN_TYPE_P (type)
2248 && type->type_common.mode != BLKmode)
2249 TYPE_SIZE_UNIT (type)
2250 = size_int (GET_MODE_SIZE (type->type_common.mode));
2251 else
2252 TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR,
2253 TYPE_SIZE_UNIT (innertype),
2254 size_int (nunits));
2255 TYPE_SIZE (type) = int_const_binop (MULT_EXPR,
2256 TYPE_SIZE (innertype),
2257 bitsize_int (nunits));
2259 /* For vector types, we do not default to the mode's alignment.
2260 Instead, query a target hook, defaulting to natural alignment.
2261 This prevents ABI changes depending on whether or not native
2262 vector modes are supported. */
2263 SET_TYPE_ALIGN (type, targetm.vector_alignment (type));
2265 /* However, if the underlying mode requires a bigger alignment than
2266 what the target hook provides, we cannot use the mode. For now,
2267 simply reject that case. */
2268 gcc_assert (TYPE_ALIGN (type)
2269 >= GET_MODE_ALIGNMENT (TYPE_MODE (type)));
2270 break;
2273 case VOID_TYPE:
2274 /* This is an incomplete type and so doesn't have a size. */
2275 SET_TYPE_ALIGN (type, 1);
2276 TYPE_USER_ALIGN (type) = 0;
2277 SET_TYPE_MODE (type, VOIDmode);
2278 break;
2280 case POINTER_BOUNDS_TYPE:
2281 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2282 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2283 break;
2285 case OFFSET_TYPE:
2286 TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
2287 TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS);
2288 /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be
2289 integral, which may be an __intN. */
2290 SET_TYPE_MODE (type, mode_for_size (POINTER_SIZE, MODE_INT, 0));
2291 TYPE_PRECISION (type) = POINTER_SIZE;
2292 break;
2294 case FUNCTION_TYPE:
2295 case METHOD_TYPE:
2296 /* It's hard to see what the mode and size of a function ought to
2297 be, but we do know the alignment is FUNCTION_BOUNDARY, so
2298 make it consistent with that. */
2299 SET_TYPE_MODE (type, mode_for_size (FUNCTION_BOUNDARY, MODE_INT, 0));
2300 TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY);
2301 TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT);
2302 break;
2304 case POINTER_TYPE:
2305 case REFERENCE_TYPE:
2307 machine_mode mode = TYPE_MODE (type);
2308 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2309 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2310 TYPE_UNSIGNED (type) = 1;
2311 TYPE_PRECISION (type) = GET_MODE_PRECISION (mode);
2313 break;
2315 case ARRAY_TYPE:
2317 tree index = TYPE_DOMAIN (type);
2318 tree element = TREE_TYPE (type);
2320 /* We need to know both bounds in order to compute the size. */
2321 if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index)
2322 && TYPE_SIZE (element))
2324 tree ub = TYPE_MAX_VALUE (index);
2325 tree lb = TYPE_MIN_VALUE (index);
2326 tree element_size = TYPE_SIZE (element);
2327 tree length;
2329 /* Make sure that an array of zero-sized element is zero-sized
2330 regardless of its extent. */
2331 if (integer_zerop (element_size))
2332 length = size_zero_node;
2334 /* The computation should happen in the original signedness so
2335 that (possible) negative values are handled appropriately
2336 when determining overflow. */
2337 else
2339 /* ??? When it is obvious that the range is signed
2340 represent it using ssizetype. */
2341 if (TREE_CODE (lb) == INTEGER_CST
2342 && TREE_CODE (ub) == INTEGER_CST
2343 && TYPE_UNSIGNED (TREE_TYPE (lb))
2344 && tree_int_cst_lt (ub, lb))
2346 lb = wide_int_to_tree (ssizetype,
2347 offset_int::from (lb, SIGNED));
2348 ub = wide_int_to_tree (ssizetype,
2349 offset_int::from (ub, SIGNED));
2351 length
2352 = fold_convert (sizetype,
2353 size_binop (PLUS_EXPR,
2354 build_int_cst (TREE_TYPE (lb), 1),
2355 size_binop (MINUS_EXPR, ub, lb)));
2358 /* ??? We have no way to distinguish a null-sized array from an
2359 array spanning the whole sizetype range, so we arbitrarily
2360 decide that [0, -1] is the only valid representation. */
2361 if (integer_zerop (length)
2362 && TREE_OVERFLOW (length)
2363 && integer_zerop (lb))
2364 length = size_zero_node;
2366 TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
2367 fold_convert (bitsizetype,
2368 length));
2370 /* If we know the size of the element, calculate the total size
2371 directly, rather than do some division thing below. This
2372 optimization helps Fortran assumed-size arrays (where the
2373 size of the array is determined at runtime) substantially. */
2374 if (TYPE_SIZE_UNIT (element))
2375 TYPE_SIZE_UNIT (type)
2376 = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length);
2379 /* Now round the alignment and size,
2380 using machine-dependent criteria if any. */
2382 unsigned align = TYPE_ALIGN (element);
2383 if (TYPE_USER_ALIGN (type))
2384 align = MAX (align, TYPE_ALIGN (type));
2385 else
2386 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);
2387 if (!TYPE_WARN_IF_NOT_ALIGN (type))
2388 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2389 TYPE_WARN_IF_NOT_ALIGN (element));
2390 #ifdef ROUND_TYPE_ALIGN
2391 align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT);
2392 #else
2393 align = MAX (align, BITS_PER_UNIT);
2394 #endif
2395 SET_TYPE_ALIGN (type, align);
2396 SET_TYPE_MODE (type, BLKmode);
2397 if (TYPE_SIZE (type) != 0
2398 && ! targetm.member_type_forces_blk (type, VOIDmode)
2399 /* BLKmode elements force BLKmode aggregate;
2400 else extract/store fields may lose. */
2401 && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
2402 || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
2404 SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type),
2405 TYPE_SIZE (type)));
2406 if (TYPE_MODE (type) != BLKmode
2407 && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
2408 && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
2410 TYPE_NO_FORCE_BLK (type) = 1;
2411 SET_TYPE_MODE (type, BLKmode);
2414 if (AGGREGATE_TYPE_P (element))
2415 TYPE_TYPELESS_STORAGE (type) = TYPE_TYPELESS_STORAGE (element);
2416 /* When the element size is constant, check that it is at least as
2417 large as the element alignment. */
2418 if (TYPE_SIZE_UNIT (element)
2419 && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST
2420 /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than
2421 TYPE_ALIGN_UNIT. */
2422 && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element))
2423 && !integer_zerop (TYPE_SIZE_UNIT (element))
2424 && compare_tree_int (TYPE_SIZE_UNIT (element),
2425 TYPE_ALIGN_UNIT (element)) < 0)
2426 error ("alignment of array elements is greater than element size");
2427 break;
2430 case RECORD_TYPE:
2431 case UNION_TYPE:
2432 case QUAL_UNION_TYPE:
2434 tree field;
2435 record_layout_info rli;
2437 /* Initialize the layout information. */
2438 rli = start_record_layout (type);
2440 /* If this is a QUAL_UNION_TYPE, we want to process the fields
2441 in the reverse order in building the COND_EXPR that denotes
2442 its size. We reverse them again later. */
2443 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2444 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2446 /* Place all the fields. */
2447 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
2448 place_field (rli, field);
2450 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2451 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2453 /* Finish laying out the record. */
2454 finish_record_layout (rli, /*free_p=*/true);
2456 break;
2458 default:
2459 gcc_unreachable ();
2462 /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE. For
2463 records and unions, finish_record_layout already called this
2464 function. */
2465 if (!RECORD_OR_UNION_TYPE_P (type))
2466 finalize_type_size (type);
2468 /* We should never see alias sets on incomplete aggregates. And we
2469 should not call layout_type on not incomplete aggregates. */
2470 if (AGGREGATE_TYPE_P (type))
2471 gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type));
2474 /* Return the least alignment required for type TYPE. */
2476 unsigned int
2477 min_align_of_type (tree type)
2479 unsigned int align = TYPE_ALIGN (type);
2480 if (!TYPE_USER_ALIGN (type))
2482 align = MIN (align, BIGGEST_ALIGNMENT);
2483 #ifdef BIGGEST_FIELD_ALIGNMENT
2484 align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
2485 #endif
2486 unsigned int field_align = align;
2487 #ifdef ADJUST_FIELD_ALIGN
2488 field_align = ADJUST_FIELD_ALIGN (NULL_TREE, type, field_align);
2489 #endif
2490 align = MIN (align, field_align);
2492 return align / BITS_PER_UNIT;
2495 /* Create and return a type for signed integers of PRECISION bits. */
2497 tree
2498 make_signed_type (int precision)
2500 tree type = make_node (INTEGER_TYPE);
2502 TYPE_PRECISION (type) = precision;
2504 fixup_signed_type (type);
2505 return type;
2508 /* Create and return a type for unsigned integers of PRECISION bits. */
2510 tree
2511 make_unsigned_type (int precision)
2513 tree type = make_node (INTEGER_TYPE);
2515 TYPE_PRECISION (type) = precision;
2517 fixup_unsigned_type (type);
2518 return type;
2521 /* Create and return a type for fract of PRECISION bits, UNSIGNEDP,
2522 and SATP. */
2524 tree
2525 make_fract_type (int precision, int unsignedp, int satp)
2527 tree type = make_node (FIXED_POINT_TYPE);
2529 TYPE_PRECISION (type) = precision;
2531 if (satp)
2532 TYPE_SATURATING (type) = 1;
2534 /* Lay out the type: set its alignment, size, etc. */
2535 if (unsignedp)
2537 TYPE_UNSIGNED (type) = 1;
2538 SET_TYPE_MODE (type, mode_for_size (precision, MODE_UFRACT, 0));
2540 else
2541 SET_TYPE_MODE (type, mode_for_size (precision, MODE_FRACT, 0));
2542 layout_type (type);
2544 return type;
2547 /* Create and return a type for accum of PRECISION bits, UNSIGNEDP,
2548 and SATP. */
2550 tree
2551 make_accum_type (int precision, int unsignedp, int satp)
2553 tree type = make_node (FIXED_POINT_TYPE);
2555 TYPE_PRECISION (type) = precision;
2557 if (satp)
2558 TYPE_SATURATING (type) = 1;
2560 /* Lay out the type: set its alignment, size, etc. */
2561 if (unsignedp)
2563 TYPE_UNSIGNED (type) = 1;
2564 SET_TYPE_MODE (type, mode_for_size (precision, MODE_UACCUM, 0));
2566 else
2567 SET_TYPE_MODE (type, mode_for_size (precision, MODE_ACCUM, 0));
2568 layout_type (type);
2570 return type;
2573 /* Initialize sizetypes so layout_type can use them. */
2575 void
2576 initialize_sizetypes (void)
2578 int precision, bprecision;
2580 /* Get sizetypes precision from the SIZE_TYPE target macro. */
2581 if (strcmp (SIZETYPE, "unsigned int") == 0)
2582 precision = INT_TYPE_SIZE;
2583 else if (strcmp (SIZETYPE, "long unsigned int") == 0)
2584 precision = LONG_TYPE_SIZE;
2585 else if (strcmp (SIZETYPE, "long long unsigned int") == 0)
2586 precision = LONG_LONG_TYPE_SIZE;
2587 else if (strcmp (SIZETYPE, "short unsigned int") == 0)
2588 precision = SHORT_TYPE_SIZE;
2589 else
2591 int i;
2593 precision = -1;
2594 for (i = 0; i < NUM_INT_N_ENTS; i++)
2595 if (int_n_enabled_p[i])
2597 char name[50];
2598 sprintf (name, "__int%d unsigned", int_n_data[i].bitsize);
2600 if (strcmp (name, SIZETYPE) == 0)
2602 precision = int_n_data[i].bitsize;
2605 if (precision == -1)
2606 gcc_unreachable ();
2609 bprecision
2610 = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE);
2611 bprecision
2612 = GET_MODE_PRECISION (smallest_mode_for_size (bprecision, MODE_INT));
2613 if (bprecision > HOST_BITS_PER_DOUBLE_INT)
2614 bprecision = HOST_BITS_PER_DOUBLE_INT;
2616 /* Create stubs for sizetype and bitsizetype so we can create constants. */
2617 sizetype = make_node (INTEGER_TYPE);
2618 TYPE_NAME (sizetype) = get_identifier ("sizetype");
2619 TYPE_PRECISION (sizetype) = precision;
2620 TYPE_UNSIGNED (sizetype) = 1;
2621 bitsizetype = make_node (INTEGER_TYPE);
2622 TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype");
2623 TYPE_PRECISION (bitsizetype) = bprecision;
2624 TYPE_UNSIGNED (bitsizetype) = 1;
2626 /* Now layout both types manually. */
2627 SET_TYPE_MODE (sizetype, smallest_mode_for_size (precision, MODE_INT));
2628 SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype)));
2629 TYPE_SIZE (sizetype) = bitsize_int (precision);
2630 TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (TYPE_MODE (sizetype)));
2631 set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);
2633 SET_TYPE_MODE (bitsizetype, smallest_mode_for_size (bprecision, MODE_INT));
2634 SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype)));
2635 TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
2636 TYPE_SIZE_UNIT (bitsizetype)
2637 = size_int (GET_MODE_SIZE (TYPE_MODE (bitsizetype)));
2638 set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);
2640 /* Create the signed variants of *sizetype. */
2641 ssizetype = make_signed_type (TYPE_PRECISION (sizetype));
2642 TYPE_NAME (ssizetype) = get_identifier ("ssizetype");
2643 sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype));
2644 TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype");
2647 /* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE
2648 or BOOLEAN_TYPE. Set TYPE_MIN_VALUE and TYPE_MAX_VALUE
2649 for TYPE, based on the PRECISION and whether or not the TYPE
2650 IS_UNSIGNED. PRECISION need not correspond to a width supported
2651 natively by the hardware; for example, on a machine with 8-bit,
2652 16-bit, and 32-bit register modes, PRECISION might be 7, 23, or
2653 61. */
2655 void
2656 set_min_and_max_values_for_integral_type (tree type,
2657 int precision,
2658 signop sgn)
2660 /* For bitfields with zero width we end up creating integer types
2661 with zero precision. Don't assign any minimum/maximum values
2662 to those types, they don't have any valid value. */
2663 if (precision < 1)
2664 return;
2666 TYPE_MIN_VALUE (type)
2667 = wide_int_to_tree (type, wi::min_value (precision, sgn));
2668 TYPE_MAX_VALUE (type)
2669 = wide_int_to_tree (type, wi::max_value (precision, sgn));
2672 /* Set the extreme values of TYPE based on its precision in bits,
2673 then lay it out. Used when make_signed_type won't do
2674 because the tree code is not INTEGER_TYPE. */
2676 void
2677 fixup_signed_type (tree type)
2679 int precision = TYPE_PRECISION (type);
2681 set_min_and_max_values_for_integral_type (type, precision, SIGNED);
2683 /* Lay out the type: set its alignment, size, etc. */
2684 layout_type (type);
2687 /* Set the extreme values of TYPE based on its precision in bits,
2688 then lay it out. This is used both in `make_unsigned_type'
2689 and for enumeral types. */
2691 void
2692 fixup_unsigned_type (tree type)
2694 int precision = TYPE_PRECISION (type);
2696 TYPE_UNSIGNED (type) = 1;
2698 set_min_and_max_values_for_integral_type (type, precision, UNSIGNED);
2700 /* Lay out the type: set its alignment, size, etc. */
2701 layout_type (type);
2704 /* Construct an iterator for a bitfield that spans BITSIZE bits,
2705 starting at BITPOS.
2707 BITREGION_START is the bit position of the first bit in this
2708 sequence of bit fields. BITREGION_END is the last bit in this
2709 sequence. If these two fields are non-zero, we should restrict the
2710 memory access to that range. Otherwise, we are allowed to touch
2711 any adjacent non bit-fields.
2713 ALIGN is the alignment of the underlying object in bits.
2714 VOLATILEP says whether the bitfield is volatile. */
2716 bit_field_mode_iterator
2717 ::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
2718 HOST_WIDE_INT bitregion_start,
2719 HOST_WIDE_INT bitregion_end,
2720 unsigned int align, bool volatilep)
2721 : m_mode (GET_CLASS_NARROWEST_MODE (MODE_INT)), m_bitsize (bitsize),
2722 m_bitpos (bitpos), m_bitregion_start (bitregion_start),
2723 m_bitregion_end (bitregion_end), m_align (align),
2724 m_volatilep (volatilep), m_count (0)
2726 if (!m_bitregion_end)
2728 /* We can assume that any aligned chunk of ALIGN bits that overlaps
2729 the bitfield is mapped and won't trap, provided that ALIGN isn't
2730 too large. The cap is the biggest required alignment for data,
2731 or at least the word size. And force one such chunk at least. */
2732 unsigned HOST_WIDE_INT units
2733 = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
2734 if (bitsize <= 0)
2735 bitsize = 1;
2736 m_bitregion_end = bitpos + bitsize + units - 1;
2737 m_bitregion_end -= m_bitregion_end % units + 1;
2741 /* Calls to this function return successively larger modes that can be used
2742 to represent the bitfield. Return true if another bitfield mode is
2743 available, storing it in *OUT_MODE if so. */
2745 bool
2746 bit_field_mode_iterator::next_mode (machine_mode *out_mode)
2748 for (; m_mode != VOIDmode;
2749 m_mode = GET_MODE_WIDER_MODE (m_mode).else_void ())
2751 unsigned int unit = GET_MODE_BITSIZE (m_mode);
2753 /* Skip modes that don't have full precision. */
2754 if (unit != GET_MODE_PRECISION (m_mode))
2755 continue;
2757 /* Stop if the mode is too wide to handle efficiently. */
2758 if (unit > MAX_FIXED_MODE_SIZE)
2759 break;
2761 /* Don't deliver more than one multiword mode; the smallest one
2762 should be used. */
2763 if (m_count > 0 && unit > BITS_PER_WORD)
2764 break;
2766 /* Skip modes that are too small. */
2767 unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit;
2768 unsigned HOST_WIDE_INT subend = substart + m_bitsize;
2769 if (subend > unit)
2770 continue;
2772 /* Stop if the mode goes outside the bitregion. */
2773 HOST_WIDE_INT start = m_bitpos - substart;
2774 if (m_bitregion_start && start < m_bitregion_start)
2775 break;
2776 HOST_WIDE_INT end = start + unit;
2777 if (end > m_bitregion_end + 1)
2778 break;
2780 /* Stop if the mode requires too much alignment. */
2781 if (GET_MODE_ALIGNMENT (m_mode) > m_align
2782 && SLOW_UNALIGNED_ACCESS (m_mode, m_align))
2783 break;
2785 *out_mode = m_mode;
2786 m_mode = GET_MODE_WIDER_MODE (m_mode).else_void ();
2787 m_count++;
2788 return true;
2790 return false;
2793 /* Return true if smaller modes are generally preferred for this kind
2794 of bitfield. */
2796 bool
2797 bit_field_mode_iterator::prefer_smaller_modes ()
2799 return (m_volatilep
2800 ? targetm.narrow_volatile_bitfield ()
2801 : !SLOW_BYTE_ACCESS);
2804 /* Find the best machine mode to use when referencing a bit field of length
2805 BITSIZE bits starting at BITPOS.
2807 BITREGION_START is the bit position of the first bit in this
2808 sequence of bit fields. BITREGION_END is the last bit in this
2809 sequence. If these two fields are non-zero, we should restrict the
2810 memory access to that range. Otherwise, we are allowed to touch
2811 any adjacent non bit-fields.
2813 The underlying object is known to be aligned to a boundary of ALIGN bits.
2814 If LARGEST_MODE is not VOIDmode, it means that we should not use a mode
2815 larger than LARGEST_MODE (usually SImode).
2817 If no mode meets all these conditions, we return VOIDmode.
2819 If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the
2820 smallest mode meeting these conditions.
2822 If VOLATILEP is false and SLOW_BYTE_ACCESS is true, we return the
2823 largest mode (but a mode no wider than UNITS_PER_WORD) that meets
2824 all the conditions.
2826 If VOLATILEP is true the narrow_volatile_bitfields target hook is used to
2827 decide which of the above modes should be used. */
2829 machine_mode
2830 get_best_mode (int bitsize, int bitpos,
2831 unsigned HOST_WIDE_INT bitregion_start,
2832 unsigned HOST_WIDE_INT bitregion_end,
2833 unsigned int align,
2834 machine_mode largest_mode, bool volatilep)
2836 bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start,
2837 bitregion_end, align, volatilep);
2838 machine_mode widest_mode = VOIDmode;
2839 machine_mode mode;
2840 while (iter.next_mode (&mode)
2841 /* ??? For historical reasons, reject modes that would normally
2842 receive greater alignment, even if unaligned accesses are
2843 acceptable. This has both advantages and disadvantages.
2844 Removing this check means that something like:
2846 struct s { unsigned int x; unsigned int y; };
2847 int f (struct s *s) { return s->x == 0 && s->y == 0; }
2849 can be implemented using a single load and compare on
2850 64-bit machines that have no alignment restrictions.
2851 For example, on powerpc64-linux-gnu, we would generate:
2853 ld 3,0(3)
2854 cntlzd 3,3
2855 srdi 3,3,6
2858 rather than:
2860 lwz 9,0(3)
2861 cmpwi 7,9,0
2862 bne 7,.L3
2863 lwz 3,4(3)
2864 cntlzw 3,3
2865 srwi 3,3,5
2866 extsw 3,3
2868 .p2align 4,,15
2869 .L3:
2870 li 3,0
2873 However, accessing more than one field can make life harder
2874 for the gimple optimizers. For example, gcc.dg/vect/bb-slp-5.c
2875 has a series of unsigned short copies followed by a series of
2876 unsigned short comparisons. With this check, both the copies
2877 and comparisons remain 16-bit accesses and FRE is able
2878 to eliminate the latter. Without the check, the comparisons
2879 can be done using 2 64-bit operations, which FRE isn't able
2880 to handle in the same way.
2882 Either way, it would probably be worth disabling this check
2883 during expand. One particular example where removing the
2884 check would help is the get_best_mode call in store_bit_field.
2885 If we are given a memory bitregion of 128 bits that is aligned
2886 to a 64-bit boundary, and the bitfield we want to modify is
2887 in the second half of the bitregion, this check causes
2888 store_bitfield to turn the memory into a 64-bit reference
2889 to the _first_ half of the region. We later use
2890 adjust_bitfield_address to get a reference to the correct half,
2891 but doing so looks to adjust_bitfield_address as though we are
2892 moving past the end of the original object, so it drops the
2893 associated MEM_EXPR and MEM_OFFSET. Removing the check
2894 causes store_bit_field to keep a 128-bit memory reference,
2895 so that the final bitfield reference still has a MEM_EXPR
2896 and MEM_OFFSET. */
2897 && GET_MODE_ALIGNMENT (mode) <= align
2898 && (largest_mode == VOIDmode
2899 || GET_MODE_SIZE (mode) <= GET_MODE_SIZE (largest_mode)))
2901 widest_mode = mode;
2902 if (iter.prefer_smaller_modes ())
2903 break;
2905 return widest_mode;
2908 /* Gets minimal and maximal values for MODE (signed or unsigned depending on
2909 SIGN). The returned constants are made to be usable in TARGET_MODE. */
2911 void
2912 get_mode_bounds (machine_mode mode, int sign,
2913 machine_mode target_mode,
2914 rtx *mmin, rtx *mmax)
2916 unsigned size = GET_MODE_PRECISION (mode);
2917 unsigned HOST_WIDE_INT min_val, max_val;
2919 gcc_assert (size <= HOST_BITS_PER_WIDE_INT);
2921 /* Special case BImode, which has values 0 and STORE_FLAG_VALUE. */
2922 if (mode == BImode)
2924 if (STORE_FLAG_VALUE < 0)
2926 min_val = STORE_FLAG_VALUE;
2927 max_val = 0;
2929 else
2931 min_val = 0;
2932 max_val = STORE_FLAG_VALUE;
2935 else if (sign)
2937 min_val = -(HOST_WIDE_INT_1U << (size - 1));
2938 max_val = (HOST_WIDE_INT_1U << (size - 1)) - 1;
2940 else
2942 min_val = 0;
2943 max_val = (HOST_WIDE_INT_1U << (size - 1) << 1) - 1;
2946 *mmin = gen_int_mode (min_val, target_mode);
2947 *mmax = gen_int_mode (max_val, target_mode);
2950 #include "gt-stor-layout.h"