Daily bump.
[official-gcc.git] / gcc / stor-layout.c
blobad970019e0198ec5afea71b77c886728d82b4cb9
1 /* C-compiler utilities for types and variables storage layout
2 Copyright (C) 1987-2018 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 "attribs.h"
44 #include "debug.h"
46 /* Data type for the expressions representing sizes of data types.
47 It is the first integer type laid out. */
48 tree sizetype_tab[(int) stk_type_kind_last];
50 /* If nonzero, this is an upper limit on alignment of structure fields.
51 The value is measured in bits. */
52 unsigned int maximum_field_alignment = TARGET_DEFAULT_PACK_STRUCT * BITS_PER_UNIT;
54 static tree self_referential_size (tree);
55 static void finalize_record_size (record_layout_info);
56 static void finalize_type_size (tree);
57 static void place_union_field (record_layout_info, tree);
58 static int excess_unit_span (HOST_WIDE_INT, HOST_WIDE_INT, HOST_WIDE_INT,
59 HOST_WIDE_INT, tree);
60 extern void debug_rli (record_layout_info);
62 /* Given a size SIZE that may not be a constant, return a SAVE_EXPR
63 to serve as the actual size-expression for a type or decl. */
65 tree
66 variable_size (tree size)
68 /* Obviously. */
69 if (TREE_CONSTANT (size))
70 return size;
72 /* If the size is self-referential, we can't make a SAVE_EXPR (see
73 save_expr for the rationale). But we can do something else. */
74 if (CONTAINS_PLACEHOLDER_P (size))
75 return self_referential_size (size);
77 /* If we are in the global binding level, we can't make a SAVE_EXPR
78 since it may end up being shared across functions, so it is up
79 to the front-end to deal with this case. */
80 if (lang_hooks.decls.global_bindings_p ())
81 return size;
83 return save_expr (size);
86 /* An array of functions used for self-referential size computation. */
87 static GTY(()) vec<tree, va_gc> *size_functions;
89 /* Return true if T is a self-referential component reference. */
91 static bool
92 self_referential_component_ref_p (tree t)
94 if (TREE_CODE (t) != COMPONENT_REF)
95 return false;
97 while (REFERENCE_CLASS_P (t))
98 t = TREE_OPERAND (t, 0);
100 return (TREE_CODE (t) == PLACEHOLDER_EXPR);
103 /* Similar to copy_tree_r but do not copy component references involving
104 PLACEHOLDER_EXPRs. These nodes are spotted in find_placeholder_in_expr
105 and substituted in substitute_in_expr. */
107 static tree
108 copy_self_referential_tree_r (tree *tp, int *walk_subtrees, void *data)
110 enum tree_code code = TREE_CODE (*tp);
112 /* Stop at types, decls, constants like copy_tree_r. */
113 if (TREE_CODE_CLASS (code) == tcc_type
114 || TREE_CODE_CLASS (code) == tcc_declaration
115 || TREE_CODE_CLASS (code) == tcc_constant)
117 *walk_subtrees = 0;
118 return NULL_TREE;
121 /* This is the pattern built in ada/make_aligning_type. */
122 else if (code == ADDR_EXPR
123 && TREE_CODE (TREE_OPERAND (*tp, 0)) == PLACEHOLDER_EXPR)
125 *walk_subtrees = 0;
126 return NULL_TREE;
129 /* Default case: the component reference. */
130 else if (self_referential_component_ref_p (*tp))
132 *walk_subtrees = 0;
133 return NULL_TREE;
136 /* We're not supposed to have them in self-referential size trees
137 because we wouldn't properly control when they are evaluated.
138 However, not creating superfluous SAVE_EXPRs requires accurate
139 tracking of readonly-ness all the way down to here, which we
140 cannot always guarantee in practice. So punt in this case. */
141 else if (code == SAVE_EXPR)
142 return error_mark_node;
144 else if (code == STATEMENT_LIST)
145 gcc_unreachable ();
147 return copy_tree_r (tp, walk_subtrees, data);
150 /* Given a SIZE expression that is self-referential, return an equivalent
151 expression to serve as the actual size expression for a type. */
153 static tree
154 self_referential_size (tree size)
156 static unsigned HOST_WIDE_INT fnno = 0;
157 vec<tree> self_refs = vNULL;
158 tree param_type_list = NULL, param_decl_list = NULL;
159 tree t, ref, return_type, fntype, fnname, fndecl;
160 unsigned int i;
161 char buf[128];
162 vec<tree, va_gc> *args = NULL;
164 /* Do not factor out simple operations. */
165 t = skip_simple_constant_arithmetic (size);
166 if (TREE_CODE (t) == CALL_EXPR || self_referential_component_ref_p (t))
167 return size;
169 /* Collect the list of self-references in the expression. */
170 find_placeholder_in_expr (size, &self_refs);
171 gcc_assert (self_refs.length () > 0);
173 /* Obtain a private copy of the expression. */
174 t = size;
175 if (walk_tree (&t, copy_self_referential_tree_r, NULL, NULL) != NULL_TREE)
176 return size;
177 size = t;
179 /* Build the parameter and argument lists in parallel; also
180 substitute the former for the latter in the expression. */
181 vec_alloc (args, self_refs.length ());
182 FOR_EACH_VEC_ELT (self_refs, i, ref)
184 tree subst, param_name, param_type, param_decl;
186 if (DECL_P (ref))
188 /* We shouldn't have true variables here. */
189 gcc_assert (TREE_READONLY (ref));
190 subst = ref;
192 /* This is the pattern built in ada/make_aligning_type. */
193 else if (TREE_CODE (ref) == ADDR_EXPR)
194 subst = ref;
195 /* Default case: the component reference. */
196 else
197 subst = TREE_OPERAND (ref, 1);
199 sprintf (buf, "p%d", i);
200 param_name = get_identifier (buf);
201 param_type = TREE_TYPE (ref);
202 param_decl
203 = build_decl (input_location, PARM_DECL, param_name, param_type);
204 DECL_ARG_TYPE (param_decl) = param_type;
205 DECL_ARTIFICIAL (param_decl) = 1;
206 TREE_READONLY (param_decl) = 1;
208 size = substitute_in_expr (size, subst, param_decl);
210 param_type_list = tree_cons (NULL_TREE, param_type, param_type_list);
211 param_decl_list = chainon (param_decl, param_decl_list);
212 args->quick_push (ref);
215 self_refs.release ();
217 /* Append 'void' to indicate that the number of parameters is fixed. */
218 param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list);
220 /* The 3 lists have been created in reverse order. */
221 param_type_list = nreverse (param_type_list);
222 param_decl_list = nreverse (param_decl_list);
224 /* Build the function type. */
225 return_type = TREE_TYPE (size);
226 fntype = build_function_type (return_type, param_type_list);
228 /* Build the function declaration. */
229 sprintf (buf, "SZ" HOST_WIDE_INT_PRINT_UNSIGNED, fnno++);
230 fnname = get_file_function_name (buf);
231 fndecl = build_decl (input_location, FUNCTION_DECL, fnname, fntype);
232 for (t = param_decl_list; t; t = DECL_CHAIN (t))
233 DECL_CONTEXT (t) = fndecl;
234 DECL_ARGUMENTS (fndecl) = param_decl_list;
235 DECL_RESULT (fndecl)
236 = build_decl (input_location, RESULT_DECL, 0, return_type);
237 DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl;
239 /* The function has been created by the compiler and we don't
240 want to emit debug info for it. */
241 DECL_ARTIFICIAL (fndecl) = 1;
242 DECL_IGNORED_P (fndecl) = 1;
244 /* It is supposed to be "const" and never throw. */
245 TREE_READONLY (fndecl) = 1;
246 TREE_NOTHROW (fndecl) = 1;
248 /* We want it to be inlined when this is deemed profitable, as
249 well as discarded if every call has been integrated. */
250 DECL_DECLARED_INLINE_P (fndecl) = 1;
252 /* It is made up of a unique return statement. */
253 DECL_INITIAL (fndecl) = make_node (BLOCK);
254 BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
255 t = build2 (MODIFY_EXPR, return_type, DECL_RESULT (fndecl), size);
256 DECL_SAVED_TREE (fndecl) = build1 (RETURN_EXPR, void_type_node, t);
257 TREE_STATIC (fndecl) = 1;
259 /* Put it onto the list of size functions. */
260 vec_safe_push (size_functions, fndecl);
262 /* Replace the original expression with a call to the size function. */
263 return build_call_expr_loc_vec (UNKNOWN_LOCATION, fndecl, args);
266 /* Take, queue and compile all the size functions. It is essential that
267 the size functions be gimplified at the very end of the compilation
268 in order to guarantee transparent handling of self-referential sizes.
269 Otherwise the GENERIC inliner would not be able to inline them back
270 at each of their call sites, thus creating artificial non-constant
271 size expressions which would trigger nasty problems later on. */
273 void
274 finalize_size_functions (void)
276 unsigned int i;
277 tree fndecl;
279 for (i = 0; size_functions && size_functions->iterate (i, &fndecl); i++)
281 allocate_struct_function (fndecl, false);
282 set_cfun (NULL);
283 dump_function (TDI_original, fndecl);
285 /* As these functions are used to describe the layout of variable-length
286 structures, debug info generation needs their implementation. */
287 debug_hooks->size_function (fndecl);
288 gimplify_function_tree (fndecl);
289 cgraph_node::finalize_function (fndecl, false);
292 vec_free (size_functions);
295 /* Return a machine mode of class MCLASS with SIZE bits of precision,
296 if one exists. The mode may have padding bits as well the SIZE
297 value bits. If LIMIT is nonzero, disregard modes wider than
298 MAX_FIXED_MODE_SIZE. */
300 opt_machine_mode
301 mode_for_size (poly_uint64 size, enum mode_class mclass, int limit)
303 machine_mode mode;
304 int i;
306 if (limit && maybe_gt (size, (unsigned int) MAX_FIXED_MODE_SIZE))
307 return opt_machine_mode ();
309 /* Get the first mode which has this size, in the specified class. */
310 FOR_EACH_MODE_IN_CLASS (mode, mclass)
311 if (known_eq (GET_MODE_PRECISION (mode), size))
312 return mode;
314 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
315 for (i = 0; i < NUM_INT_N_ENTS; i ++)
316 if (known_eq (int_n_data[i].bitsize, size)
317 && int_n_enabled_p[i])
318 return int_n_data[i].m;
320 return opt_machine_mode ();
323 /* Similar, except passed a tree node. */
325 opt_machine_mode
326 mode_for_size_tree (const_tree size, enum mode_class mclass, int limit)
328 unsigned HOST_WIDE_INT uhwi;
329 unsigned int ui;
331 if (!tree_fits_uhwi_p (size))
332 return opt_machine_mode ();
333 uhwi = tree_to_uhwi (size);
334 ui = uhwi;
335 if (uhwi != ui)
336 return opt_machine_mode ();
337 return mode_for_size (ui, mclass, limit);
340 /* Return the narrowest mode of class MCLASS that contains at least
341 SIZE bits. Abort if no such mode exists. */
343 machine_mode
344 smallest_mode_for_size (poly_uint64 size, enum mode_class mclass)
346 machine_mode mode = VOIDmode;
347 int i;
349 /* Get the first mode which has at least this size, in the
350 specified class. */
351 FOR_EACH_MODE_IN_CLASS (mode, mclass)
352 if (known_ge (GET_MODE_PRECISION (mode), size))
353 break;
355 gcc_assert (mode != VOIDmode);
357 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
358 for (i = 0; i < NUM_INT_N_ENTS; i ++)
359 if (known_ge (int_n_data[i].bitsize, size)
360 && known_lt (int_n_data[i].bitsize, GET_MODE_PRECISION (mode))
361 && int_n_enabled_p[i])
362 mode = int_n_data[i].m;
364 return mode;
367 /* Return an integer mode of exactly the same size as MODE, if one exists. */
369 opt_scalar_int_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 return as_a <scalar_int_mode> (mode);
378 case MODE_COMPLEX_INT:
379 case MODE_COMPLEX_FLOAT:
380 case MODE_FLOAT:
381 case MODE_DECIMAL_FLOAT:
382 case MODE_FRACT:
383 case MODE_ACCUM:
384 case MODE_UFRACT:
385 case MODE_UACCUM:
386 case MODE_VECTOR_BOOL:
387 case MODE_VECTOR_INT:
388 case MODE_VECTOR_FLOAT:
389 case MODE_VECTOR_FRACT:
390 case MODE_VECTOR_ACCUM:
391 case MODE_VECTOR_UFRACT:
392 case MODE_VECTOR_UACCUM:
393 case MODE_POINTER_BOUNDS:
394 return int_mode_for_size (GET_MODE_BITSIZE (mode), 0);
396 case MODE_RANDOM:
397 if (mode == BLKmode)
398 return opt_scalar_int_mode ();
400 /* fall through */
402 case MODE_CC:
403 default:
404 gcc_unreachable ();
408 /* Find a mode that can be used for efficient bitwise operations on MODE,
409 if one exists. */
411 opt_machine_mode
412 bitwise_mode_for_mode (machine_mode mode)
414 /* Quick exit if we already have a suitable mode. */
415 scalar_int_mode int_mode;
416 if (is_a <scalar_int_mode> (mode, &int_mode)
417 && GET_MODE_BITSIZE (int_mode) <= MAX_FIXED_MODE_SIZE)
418 return int_mode;
420 /* Reuse the sanity checks from int_mode_for_mode. */
421 gcc_checking_assert ((int_mode_for_mode (mode), true));
423 poly_int64 bitsize = GET_MODE_BITSIZE (mode);
425 /* Try to replace complex modes with complex modes. In general we
426 expect both components to be processed independently, so we only
427 care whether there is a register for the inner mode. */
428 if (COMPLEX_MODE_P (mode))
430 machine_mode trial = mode;
431 if ((GET_MODE_CLASS (trial) == MODE_COMPLEX_INT
432 || mode_for_size (bitsize, MODE_COMPLEX_INT, false).exists (&trial))
433 && have_regs_of_mode[GET_MODE_INNER (trial)])
434 return trial;
437 /* Try to replace vector modes with vector modes. Also try using vector
438 modes if an integer mode would be too big. */
439 if (VECTOR_MODE_P (mode)
440 || maybe_gt (bitsize, MAX_FIXED_MODE_SIZE))
442 machine_mode trial = mode;
443 if ((GET_MODE_CLASS (trial) == MODE_VECTOR_INT
444 || mode_for_size (bitsize, MODE_VECTOR_INT, 0).exists (&trial))
445 && have_regs_of_mode[trial]
446 && targetm.vector_mode_supported_p (trial))
447 return trial;
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 if (!bitwise_mode_for_mode (mode).exists (&mode))
461 return NULL_TREE;
463 unsigned int inner_size = GET_MODE_UNIT_BITSIZE (mode);
464 tree inner_type = build_nonstandard_integer_type (inner_size, true);
466 if (VECTOR_MODE_P (mode))
467 return build_vector_type_for_mode (inner_type, mode);
469 if (COMPLEX_MODE_P (mode))
470 return build_complex_type (inner_type);
472 gcc_checking_assert (GET_MODE_INNER (mode) == mode);
473 return inner_type;
476 /* Find a mode that is suitable for representing a vector with NUNITS
477 elements of mode INNERMODE, if one exists. The returned mode can be
478 either an integer mode or a vector mode. */
480 opt_machine_mode
481 mode_for_vector (scalar_mode innermode, poly_uint64 nunits)
483 machine_mode mode;
485 /* First, look for a supported vector type. */
486 if (SCALAR_FLOAT_MODE_P (innermode))
487 mode = MIN_MODE_VECTOR_FLOAT;
488 else if (SCALAR_FRACT_MODE_P (innermode))
489 mode = MIN_MODE_VECTOR_FRACT;
490 else if (SCALAR_UFRACT_MODE_P (innermode))
491 mode = MIN_MODE_VECTOR_UFRACT;
492 else if (SCALAR_ACCUM_MODE_P (innermode))
493 mode = MIN_MODE_VECTOR_ACCUM;
494 else if (SCALAR_UACCUM_MODE_P (innermode))
495 mode = MIN_MODE_VECTOR_UACCUM;
496 else
497 mode = MIN_MODE_VECTOR_INT;
499 /* Do not check vector_mode_supported_p here. We'll do that
500 later in vector_type_mode. */
501 FOR_EACH_MODE_FROM (mode, mode)
502 if (known_eq (GET_MODE_NUNITS (mode), nunits)
503 && GET_MODE_INNER (mode) == innermode)
504 return mode;
506 /* For integers, try mapping it to a same-sized scalar mode. */
507 if (GET_MODE_CLASS (innermode) == MODE_INT)
509 poly_uint64 nbits = nunits * GET_MODE_BITSIZE (innermode);
510 if (int_mode_for_size (nbits, 0).exists (&mode)
511 && have_regs_of_mode[mode])
512 return mode;
515 return opt_machine_mode ();
518 /* Return the mode for a vector that has NUNITS integer elements of
519 INT_BITS bits each, if such a mode exists. The mode can be either
520 an integer mode or a vector mode. */
522 opt_machine_mode
523 mode_for_int_vector (unsigned int int_bits, poly_uint64 nunits)
525 scalar_int_mode int_mode;
526 machine_mode vec_mode;
527 if (int_mode_for_size (int_bits, 0).exists (&int_mode)
528 && mode_for_vector (int_mode, nunits).exists (&vec_mode))
529 return vec_mode;
530 return opt_machine_mode ();
533 /* Return the alignment of MODE. This will be bounded by 1 and
534 BIGGEST_ALIGNMENT. */
536 unsigned int
537 get_mode_alignment (machine_mode mode)
539 return MIN (BIGGEST_ALIGNMENT, MAX (1, mode_base_align[mode]*BITS_PER_UNIT));
542 /* Return the natural mode of an array, given that it is SIZE bytes in
543 total and has elements of type ELEM_TYPE. */
545 static machine_mode
546 mode_for_array (tree elem_type, tree size)
548 tree elem_size;
549 poly_uint64 int_size, int_elem_size;
550 unsigned HOST_WIDE_INT num_elems;
551 bool limit_p;
553 /* One-element arrays get the component type's mode. */
554 elem_size = TYPE_SIZE (elem_type);
555 if (simple_cst_equal (size, elem_size))
556 return TYPE_MODE (elem_type);
558 limit_p = true;
559 if (poly_int_tree_p (size, &int_size)
560 && poly_int_tree_p (elem_size, &int_elem_size)
561 && maybe_ne (int_elem_size, 0U)
562 && constant_multiple_p (int_size, int_elem_size, &num_elems))
564 machine_mode elem_mode = TYPE_MODE (elem_type);
565 machine_mode mode;
566 if (targetm.array_mode (elem_mode, num_elems).exists (&mode))
567 return mode;
568 if (targetm.array_mode_supported_p (elem_mode, num_elems))
569 limit_p = false;
571 return mode_for_size_tree (size, MODE_INT, limit_p).else_blk ();
574 /* Subroutine of layout_decl: Force alignment required for the data type.
575 But if the decl itself wants greater alignment, don't override that. */
577 static inline void
578 do_type_align (tree type, tree decl)
580 if (TYPE_ALIGN (type) > DECL_ALIGN (decl))
582 SET_DECL_ALIGN (decl, TYPE_ALIGN (type));
583 if (TREE_CODE (decl) == FIELD_DECL)
584 DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type);
586 if (TYPE_WARN_IF_NOT_ALIGN (type) > DECL_WARN_IF_NOT_ALIGN (decl))
587 SET_DECL_WARN_IF_NOT_ALIGN (decl, TYPE_WARN_IF_NOT_ALIGN (type));
590 /* Set the size, mode and alignment of a ..._DECL node.
591 TYPE_DECL does need this for C++.
592 Note that LABEL_DECL and CONST_DECL nodes do not need this,
593 and FUNCTION_DECL nodes have them set up in a special (and simple) way.
594 Don't call layout_decl for them.
596 KNOWN_ALIGN is the amount of alignment we can assume this
597 decl has with no special effort. It is relevant only for FIELD_DECLs
598 and depends on the previous fields.
599 All that matters about KNOWN_ALIGN is which powers of 2 divide it.
600 If KNOWN_ALIGN is 0, it means, "as much alignment as you like":
601 the record will be aligned to suit. */
603 void
604 layout_decl (tree decl, unsigned int known_align)
606 tree type = TREE_TYPE (decl);
607 enum tree_code code = TREE_CODE (decl);
608 rtx rtl = NULL_RTX;
609 location_t loc = DECL_SOURCE_LOCATION (decl);
611 if (code == CONST_DECL)
612 return;
614 gcc_assert (code == VAR_DECL || code == PARM_DECL || code == RESULT_DECL
615 || code == TYPE_DECL || code == FIELD_DECL);
617 rtl = DECL_RTL_IF_SET (decl);
619 if (type == error_mark_node)
620 type = void_type_node;
622 /* Usually the size and mode come from the data type without change,
623 however, the front-end may set the explicit width of the field, so its
624 size may not be the same as the size of its type. This happens with
625 bitfields, of course (an `int' bitfield may be only 2 bits, say), but it
626 also happens with other fields. For example, the C++ front-end creates
627 zero-sized fields corresponding to empty base classes, and depends on
628 layout_type setting DECL_FIELD_BITPOS correctly for the field. Set the
629 size in bytes from the size in bits. If we have already set the mode,
630 don't set it again since we can be called twice for FIELD_DECLs. */
632 DECL_UNSIGNED (decl) = TYPE_UNSIGNED (type);
633 if (DECL_MODE (decl) == VOIDmode)
634 SET_DECL_MODE (decl, TYPE_MODE (type));
636 if (DECL_SIZE (decl) == 0)
638 DECL_SIZE (decl) = TYPE_SIZE (type);
639 DECL_SIZE_UNIT (decl) = TYPE_SIZE_UNIT (type);
641 else if (DECL_SIZE_UNIT (decl) == 0)
642 DECL_SIZE_UNIT (decl)
643 = fold_convert_loc (loc, sizetype,
644 size_binop_loc (loc, CEIL_DIV_EXPR, DECL_SIZE (decl),
645 bitsize_unit_node));
647 if (code != FIELD_DECL)
648 /* For non-fields, update the alignment from the type. */
649 do_type_align (type, decl);
650 else
651 /* For fields, it's a bit more complicated... */
653 bool old_user_align = DECL_USER_ALIGN (decl);
654 bool zero_bitfield = false;
655 bool packed_p = DECL_PACKED (decl);
656 unsigned int mfa;
658 if (DECL_BIT_FIELD (decl))
660 DECL_BIT_FIELD_TYPE (decl) = type;
662 /* A zero-length bit-field affects the alignment of the next
663 field. In essence such bit-fields are not influenced by
664 any packing due to #pragma pack or attribute packed. */
665 if (integer_zerop (DECL_SIZE (decl))
666 && ! targetm.ms_bitfield_layout_p (DECL_FIELD_CONTEXT (decl)))
668 zero_bitfield = true;
669 packed_p = false;
670 if (PCC_BITFIELD_TYPE_MATTERS)
671 do_type_align (type, decl);
672 else
674 #ifdef EMPTY_FIELD_BOUNDARY
675 if (EMPTY_FIELD_BOUNDARY > DECL_ALIGN (decl))
677 SET_DECL_ALIGN (decl, EMPTY_FIELD_BOUNDARY);
678 DECL_USER_ALIGN (decl) = 0;
680 #endif
684 /* See if we can use an ordinary integer mode for a bit-field.
685 Conditions are: a fixed size that is correct for another mode,
686 occupying a complete byte or bytes on proper boundary. */
687 if (TYPE_SIZE (type) != 0
688 && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
689 && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT)
691 machine_mode xmode;
692 if (mode_for_size_tree (DECL_SIZE (decl),
693 MODE_INT, 1).exists (&xmode))
695 unsigned int xalign = GET_MODE_ALIGNMENT (xmode);
696 if (!(xalign > BITS_PER_UNIT && DECL_PACKED (decl))
697 && (known_align == 0 || known_align >= xalign))
699 SET_DECL_ALIGN (decl, MAX (xalign, DECL_ALIGN (decl)));
700 SET_DECL_MODE (decl, xmode);
701 DECL_BIT_FIELD (decl) = 0;
706 /* Turn off DECL_BIT_FIELD if we won't need it set. */
707 if (TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode
708 && known_align >= TYPE_ALIGN (type)
709 && DECL_ALIGN (decl) >= TYPE_ALIGN (type))
710 DECL_BIT_FIELD (decl) = 0;
712 else if (packed_p && DECL_USER_ALIGN (decl))
713 /* Don't touch DECL_ALIGN. For other packed fields, go ahead and
714 round up; we'll reduce it again below. We want packing to
715 supersede USER_ALIGN inherited from the type, but defer to
716 alignment explicitly specified on the field decl. */;
717 else
718 do_type_align (type, decl);
720 /* If the field is packed and not explicitly aligned, give it the
721 minimum alignment. Note that do_type_align may set
722 DECL_USER_ALIGN, so we need to check old_user_align instead. */
723 if (packed_p
724 && !old_user_align)
725 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), BITS_PER_UNIT));
727 if (! packed_p && ! DECL_USER_ALIGN (decl))
729 /* Some targets (i.e. i386, VMS) limit struct field alignment
730 to a lower boundary than alignment of variables unless
731 it was overridden by attribute aligned. */
732 #ifdef BIGGEST_FIELD_ALIGNMENT
733 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl),
734 (unsigned) BIGGEST_FIELD_ALIGNMENT));
735 #endif
736 #ifdef ADJUST_FIELD_ALIGN
737 SET_DECL_ALIGN (decl, ADJUST_FIELD_ALIGN (decl, TREE_TYPE (decl),
738 DECL_ALIGN (decl)));
739 #endif
742 if (zero_bitfield)
743 mfa = initial_max_fld_align * BITS_PER_UNIT;
744 else
745 mfa = maximum_field_alignment;
746 /* Should this be controlled by DECL_USER_ALIGN, too? */
747 if (mfa != 0)
748 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), mfa));
751 /* Evaluate nonconstant size only once, either now or as soon as safe. */
752 if (DECL_SIZE (decl) != 0 && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
753 DECL_SIZE (decl) = variable_size (DECL_SIZE (decl));
754 if (DECL_SIZE_UNIT (decl) != 0
755 && TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST)
756 DECL_SIZE_UNIT (decl) = variable_size (DECL_SIZE_UNIT (decl));
758 /* If requested, warn about definitions of large data objects. */
759 if (warn_larger_than
760 && (code == VAR_DECL || code == PARM_DECL)
761 && ! DECL_EXTERNAL (decl))
763 tree size = DECL_SIZE_UNIT (decl);
765 if (size != 0 && TREE_CODE (size) == INTEGER_CST
766 && compare_tree_int (size, larger_than_size) > 0)
768 int size_as_int = TREE_INT_CST_LOW (size);
770 if (compare_tree_int (size, size_as_int) == 0)
771 warning (OPT_Wlarger_than_, "size of %q+D is %d bytes", decl, size_as_int);
772 else
773 warning (OPT_Wlarger_than_, "size of %q+D is larger than %wd bytes",
774 decl, larger_than_size);
778 /* If the RTL was already set, update its mode and mem attributes. */
779 if (rtl)
781 PUT_MODE (rtl, DECL_MODE (decl));
782 SET_DECL_RTL (decl, 0);
783 if (MEM_P (rtl))
784 set_mem_attributes (rtl, decl, 1);
785 SET_DECL_RTL (decl, rtl);
789 /* Given a VAR_DECL, PARM_DECL, RESULT_DECL, or FIELD_DECL, clears the
790 results of a previous call to layout_decl and calls it again. */
792 void
793 relayout_decl (tree decl)
795 DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0;
796 SET_DECL_MODE (decl, VOIDmode);
797 if (!DECL_USER_ALIGN (decl))
798 SET_DECL_ALIGN (decl, 0);
799 if (DECL_RTL_SET_P (decl))
800 SET_DECL_RTL (decl, 0);
802 layout_decl (decl, 0);
805 /* Begin laying out type T, which may be a RECORD_TYPE, UNION_TYPE, or
806 QUAL_UNION_TYPE. Return a pointer to a struct record_layout_info which
807 is to be passed to all other layout functions for this record. It is the
808 responsibility of the caller to call `free' for the storage returned.
809 Note that garbage collection is not permitted until we finish laying
810 out the record. */
812 record_layout_info
813 start_record_layout (tree t)
815 record_layout_info rli = XNEW (struct record_layout_info_s);
817 rli->t = t;
819 /* If the type has a minimum specified alignment (via an attribute
820 declaration, for example) use it -- otherwise, start with a
821 one-byte alignment. */
822 rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
823 rli->unpacked_align = rli->record_align;
824 rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT);
826 #ifdef STRUCTURE_SIZE_BOUNDARY
827 /* Packed structures don't need to have minimum size. */
828 if (! TYPE_PACKED (t))
830 unsigned tmp;
832 /* #pragma pack overrides STRUCTURE_SIZE_BOUNDARY. */
833 tmp = (unsigned) STRUCTURE_SIZE_BOUNDARY;
834 if (maximum_field_alignment != 0)
835 tmp = MIN (tmp, maximum_field_alignment);
836 rli->record_align = MAX (rli->record_align, tmp);
838 #endif
840 rli->offset = size_zero_node;
841 rli->bitpos = bitsize_zero_node;
842 rli->prev_field = 0;
843 rli->pending_statics = 0;
844 rli->packed_maybe_necessary = 0;
845 rli->remaining_in_alignment = 0;
847 return rli;
850 /* Fold sizetype value X to bitsizetype, given that X represents a type
851 size or offset. */
853 static tree
854 bits_from_bytes (tree x)
856 if (POLY_INT_CST_P (x))
857 /* The runtime calculation isn't allowed to overflow sizetype;
858 increasing the runtime values must always increase the size
859 or offset of the object. This means that the object imposes
860 a maximum value on the runtime parameters, but we don't record
861 what that is. */
862 return build_poly_int_cst
863 (bitsizetype,
864 poly_wide_int::from (poly_int_cst_value (x),
865 TYPE_PRECISION (bitsizetype),
866 TYPE_SIGN (TREE_TYPE (x))));
867 x = fold_convert (bitsizetype, x);
868 gcc_checking_assert (x);
869 return x;
872 /* Return the combined bit position for the byte offset OFFSET and the
873 bit position BITPOS.
875 These functions operate on byte and bit positions present in FIELD_DECLs
876 and assume that these expressions result in no (intermediate) overflow.
877 This assumption is necessary to fold the expressions as much as possible,
878 so as to avoid creating artificially variable-sized types in languages
879 supporting variable-sized types like Ada. */
881 tree
882 bit_from_pos (tree offset, tree bitpos)
884 return size_binop (PLUS_EXPR, bitpos,
885 size_binop (MULT_EXPR, bits_from_bytes (offset),
886 bitsize_unit_node));
889 /* Return the combined truncated byte position for the byte offset OFFSET and
890 the bit position BITPOS. */
892 tree
893 byte_from_pos (tree offset, tree bitpos)
895 tree bytepos;
896 if (TREE_CODE (bitpos) == MULT_EXPR
897 && tree_int_cst_equal (TREE_OPERAND (bitpos, 1), bitsize_unit_node))
898 bytepos = TREE_OPERAND (bitpos, 0);
899 else
900 bytepos = size_binop (TRUNC_DIV_EXPR, bitpos, bitsize_unit_node);
901 return size_binop (PLUS_EXPR, offset, fold_convert (sizetype, bytepos));
904 /* Split the bit position POS into a byte offset *POFFSET and a bit
905 position *PBITPOS with the byte offset aligned to OFF_ALIGN bits. */
907 void
908 pos_from_bit (tree *poffset, tree *pbitpos, unsigned int off_align,
909 tree pos)
911 tree toff_align = bitsize_int (off_align);
912 if (TREE_CODE (pos) == MULT_EXPR
913 && tree_int_cst_equal (TREE_OPERAND (pos, 1), toff_align))
915 *poffset = size_binop (MULT_EXPR,
916 fold_convert (sizetype, TREE_OPERAND (pos, 0)),
917 size_int (off_align / BITS_PER_UNIT));
918 *pbitpos = bitsize_zero_node;
920 else
922 *poffset = size_binop (MULT_EXPR,
923 fold_convert (sizetype,
924 size_binop (FLOOR_DIV_EXPR, pos,
925 toff_align)),
926 size_int (off_align / BITS_PER_UNIT));
927 *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, toff_align);
931 /* Given a pointer to bit and byte offsets and an offset alignment,
932 normalize the offsets so they are within the alignment. */
934 void
935 normalize_offset (tree *poffset, tree *pbitpos, unsigned int off_align)
937 /* If the bit position is now larger than it should be, adjust it
938 downwards. */
939 if (compare_tree_int (*pbitpos, off_align) >= 0)
941 tree offset, bitpos;
942 pos_from_bit (&offset, &bitpos, off_align, *pbitpos);
943 *poffset = size_binop (PLUS_EXPR, *poffset, offset);
944 *pbitpos = bitpos;
948 /* Print debugging information about the information in RLI. */
950 DEBUG_FUNCTION void
951 debug_rli (record_layout_info rli)
953 print_node_brief (stderr, "type", rli->t, 0);
954 print_node_brief (stderr, "\noffset", rli->offset, 0);
955 print_node_brief (stderr, " bitpos", rli->bitpos, 0);
957 fprintf (stderr, "\naligns: rec = %u, unpack = %u, off = %u\n",
958 rli->record_align, rli->unpacked_align,
959 rli->offset_align);
961 /* The ms_struct code is the only that uses this. */
962 if (targetm.ms_bitfield_layout_p (rli->t))
963 fprintf (stderr, "remaining in alignment = %u\n", rli->remaining_in_alignment);
965 if (rli->packed_maybe_necessary)
966 fprintf (stderr, "packed may be necessary\n");
968 if (!vec_safe_is_empty (rli->pending_statics))
970 fprintf (stderr, "pending statics:\n");
971 debug (rli->pending_statics);
975 /* Given an RLI with a possibly-incremented BITPOS, adjust OFFSET and
976 BITPOS if necessary to keep BITPOS below OFFSET_ALIGN. */
978 void
979 normalize_rli (record_layout_info rli)
981 normalize_offset (&rli->offset, &rli->bitpos, rli->offset_align);
984 /* Returns the size in bytes allocated so far. */
986 tree
987 rli_size_unit_so_far (record_layout_info rli)
989 return byte_from_pos (rli->offset, rli->bitpos);
992 /* Returns the size in bits allocated so far. */
994 tree
995 rli_size_so_far (record_layout_info rli)
997 return bit_from_pos (rli->offset, rli->bitpos);
1000 /* FIELD is about to be added to RLI->T. The alignment (in bits) of
1001 the next available location within the record is given by KNOWN_ALIGN.
1002 Update the variable alignment fields in RLI, and return the alignment
1003 to give the FIELD. */
1005 unsigned int
1006 update_alignment_for_field (record_layout_info rli, tree field,
1007 unsigned int known_align)
1009 /* The alignment required for FIELD. */
1010 unsigned int desired_align;
1011 /* The type of this field. */
1012 tree type = TREE_TYPE (field);
1013 /* True if the field was explicitly aligned by the user. */
1014 bool user_align;
1015 bool is_bitfield;
1017 /* Do not attempt to align an ERROR_MARK node */
1018 if (TREE_CODE (type) == ERROR_MARK)
1019 return 0;
1021 /* Lay out the field so we know what alignment it needs. */
1022 layout_decl (field, known_align);
1023 desired_align = DECL_ALIGN (field);
1024 user_align = DECL_USER_ALIGN (field);
1026 is_bitfield = (type != error_mark_node
1027 && DECL_BIT_FIELD_TYPE (field)
1028 && ! integer_zerop (TYPE_SIZE (type)));
1030 /* Record must have at least as much alignment as any field.
1031 Otherwise, the alignment of the field within the record is
1032 meaningless. */
1033 if (targetm.ms_bitfield_layout_p (rli->t))
1035 /* Here, the alignment of the underlying type of a bitfield can
1036 affect the alignment of a record; even a zero-sized field
1037 can do this. The alignment should be to the alignment of
1038 the type, except that for zero-size bitfields this only
1039 applies if there was an immediately prior, nonzero-size
1040 bitfield. (That's the way it is, experimentally.) */
1041 if (!is_bitfield
1042 || ((DECL_SIZE (field) == NULL_TREE
1043 || !integer_zerop (DECL_SIZE (field)))
1044 ? !DECL_PACKED (field)
1045 : (rli->prev_field
1046 && DECL_BIT_FIELD_TYPE (rli->prev_field)
1047 && ! integer_zerop (DECL_SIZE (rli->prev_field)))))
1049 unsigned int type_align = TYPE_ALIGN (type);
1050 if (!is_bitfield && DECL_PACKED (field))
1051 type_align = desired_align;
1052 else
1053 type_align = MAX (type_align, desired_align);
1054 if (maximum_field_alignment != 0)
1055 type_align = MIN (type_align, maximum_field_alignment);
1056 rli->record_align = MAX (rli->record_align, type_align);
1057 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1060 else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
1062 /* Named bit-fields cause the entire structure to have the
1063 alignment implied by their type. Some targets also apply the same
1064 rules to unnamed bitfields. */
1065 if (DECL_NAME (field) != 0
1066 || targetm.align_anon_bitfield ())
1068 unsigned int type_align = TYPE_ALIGN (type);
1070 #ifdef ADJUST_FIELD_ALIGN
1071 if (! TYPE_USER_ALIGN (type))
1072 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1073 #endif
1075 /* Targets might chose to handle unnamed and hence possibly
1076 zero-width bitfield. Those are not influenced by #pragmas
1077 or packed attributes. */
1078 if (integer_zerop (DECL_SIZE (field)))
1080 if (initial_max_fld_align)
1081 type_align = MIN (type_align,
1082 initial_max_fld_align * BITS_PER_UNIT);
1084 else if (maximum_field_alignment != 0)
1085 type_align = MIN (type_align, maximum_field_alignment);
1086 else if (DECL_PACKED (field))
1087 type_align = MIN (type_align, BITS_PER_UNIT);
1089 /* The alignment of the record is increased to the maximum
1090 of the current alignment, the alignment indicated on the
1091 field (i.e., the alignment specified by an __aligned__
1092 attribute), and the alignment indicated by the type of
1093 the field. */
1094 rli->record_align = MAX (rli->record_align, desired_align);
1095 rli->record_align = MAX (rli->record_align, type_align);
1097 if (warn_packed)
1098 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1099 user_align |= TYPE_USER_ALIGN (type);
1102 else
1104 rli->record_align = MAX (rli->record_align, desired_align);
1105 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1108 TYPE_USER_ALIGN (rli->t) |= user_align;
1110 return desired_align;
1113 /* Issue a warning if the record alignment, RECORD_ALIGN, is less than
1114 the field alignment of FIELD or FIELD isn't aligned. */
1116 static void
1117 handle_warn_if_not_align (tree field, unsigned int record_align)
1119 tree type = TREE_TYPE (field);
1121 if (type == error_mark_node)
1122 return;
1124 unsigned int warn_if_not_align = 0;
1126 int opt_w = 0;
1128 if (warn_if_not_aligned)
1130 warn_if_not_align = DECL_WARN_IF_NOT_ALIGN (field);
1131 if (!warn_if_not_align)
1132 warn_if_not_align = TYPE_WARN_IF_NOT_ALIGN (type);
1133 if (warn_if_not_align)
1134 opt_w = OPT_Wif_not_aligned;
1137 if (!warn_if_not_align
1138 && warn_packed_not_aligned
1139 && lookup_attribute ("aligned", TYPE_ATTRIBUTES (type)))
1141 warn_if_not_align = TYPE_ALIGN (type);
1142 opt_w = OPT_Wpacked_not_aligned;
1145 if (!warn_if_not_align)
1146 return;
1148 tree context = DECL_CONTEXT (field);
1150 warn_if_not_align /= BITS_PER_UNIT;
1151 record_align /= BITS_PER_UNIT;
1152 if ((record_align % warn_if_not_align) != 0)
1153 warning (opt_w, "alignment %u of %qT is less than %u",
1154 record_align, context, warn_if_not_align);
1156 tree off = byte_position (field);
1157 if (!multiple_of_p (TREE_TYPE (off), off, size_int (warn_if_not_align)))
1159 if (TREE_CODE (off) == INTEGER_CST)
1160 warning (opt_w, "%q+D offset %E in %qT isn%'t aligned to %u",
1161 field, off, context, warn_if_not_align);
1162 else
1163 warning (opt_w, "%q+D offset %E in %qT may not be aligned to %u",
1164 field, off, context, warn_if_not_align);
1168 /* Called from place_field to handle unions. */
1170 static void
1171 place_union_field (record_layout_info rli, tree field)
1173 update_alignment_for_field (rli, field, /*known_align=*/0);
1175 DECL_FIELD_OFFSET (field) = size_zero_node;
1176 DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
1177 SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);
1178 handle_warn_if_not_align (field, rli->record_align);
1180 /* If this is an ERROR_MARK return *after* having set the
1181 field at the start of the union. This helps when parsing
1182 invalid fields. */
1183 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK)
1184 return;
1186 if (AGGREGATE_TYPE_P (TREE_TYPE (field))
1187 && TYPE_TYPELESS_STORAGE (TREE_TYPE (field)))
1188 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1190 /* We assume the union's size will be a multiple of a byte so we don't
1191 bother with BITPOS. */
1192 if (TREE_CODE (rli->t) == UNION_TYPE)
1193 rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1194 else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE)
1195 rli->offset = fold_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field),
1196 DECL_SIZE_UNIT (field), rli->offset);
1199 /* A bitfield of SIZE with a required access alignment of ALIGN is allocated
1200 at BYTE_OFFSET / BIT_OFFSET. Return nonzero if the field would span more
1201 units of alignment than the underlying TYPE. */
1202 static int
1203 excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset,
1204 HOST_WIDE_INT size, HOST_WIDE_INT align, tree type)
1206 /* Note that the calculation of OFFSET might overflow; we calculate it so
1207 that we still get the right result as long as ALIGN is a power of two. */
1208 unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset;
1210 offset = offset % align;
1211 return ((offset + size + align - 1) / align
1212 > tree_to_uhwi (TYPE_SIZE (type)) / align);
1215 /* RLI contains information about the layout of a RECORD_TYPE. FIELD
1216 is a FIELD_DECL to be added after those fields already present in
1217 T. (FIELD is not actually added to the TYPE_FIELDS list here;
1218 callers that desire that behavior must manually perform that step.) */
1220 void
1221 place_field (record_layout_info rli, tree field)
1223 /* The alignment required for FIELD. */
1224 unsigned int desired_align;
1225 /* The alignment FIELD would have if we just dropped it into the
1226 record as it presently stands. */
1227 unsigned int known_align;
1228 unsigned int actual_align;
1229 /* The type of this field. */
1230 tree type = TREE_TYPE (field);
1232 gcc_assert (TREE_CODE (field) != ERROR_MARK);
1234 /* If FIELD is static, then treat it like a separate variable, not
1235 really like a structure field. If it is a FUNCTION_DECL, it's a
1236 method. In both cases, all we do is lay out the decl, and we do
1237 it *after* the record is laid out. */
1238 if (VAR_P (field))
1240 vec_safe_push (rli->pending_statics, field);
1241 return;
1244 /* Enumerators and enum types which are local to this class need not
1245 be laid out. Likewise for initialized constant fields. */
1246 else if (TREE_CODE (field) != FIELD_DECL)
1247 return;
1249 /* Unions are laid out very differently than records, so split
1250 that code off to another function. */
1251 else if (TREE_CODE (rli->t) != RECORD_TYPE)
1253 place_union_field (rli, field);
1254 return;
1257 else if (TREE_CODE (type) == ERROR_MARK)
1259 /* Place this field at the current allocation position, so we
1260 maintain monotonicity. */
1261 DECL_FIELD_OFFSET (field) = rli->offset;
1262 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1263 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1264 handle_warn_if_not_align (field, rli->record_align);
1265 return;
1268 if (AGGREGATE_TYPE_P (type)
1269 && TYPE_TYPELESS_STORAGE (type))
1270 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1272 /* Work out the known alignment so far. Note that A & (-A) is the
1273 value of the least-significant bit in A that is one. */
1274 if (! integer_zerop (rli->bitpos))
1275 known_align = least_bit_hwi (tree_to_uhwi (rli->bitpos));
1276 else if (integer_zerop (rli->offset))
1277 known_align = 0;
1278 else if (tree_fits_uhwi_p (rli->offset))
1279 known_align = (BITS_PER_UNIT
1280 * least_bit_hwi (tree_to_uhwi (rli->offset)));
1281 else
1282 known_align = rli->offset_align;
1284 desired_align = update_alignment_for_field (rli, field, known_align);
1285 if (known_align == 0)
1286 known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1288 if (warn_packed && DECL_PACKED (field))
1290 if (known_align >= TYPE_ALIGN (type))
1292 if (TYPE_ALIGN (type) > desired_align)
1294 if (STRICT_ALIGNMENT)
1295 warning (OPT_Wattributes, "packed attribute causes "
1296 "inefficient alignment for %q+D", field);
1297 /* Don't warn if DECL_PACKED was set by the type. */
1298 else if (!TYPE_PACKED (rli->t))
1299 warning (OPT_Wattributes, "packed attribute is "
1300 "unnecessary for %q+D", field);
1303 else
1304 rli->packed_maybe_necessary = 1;
1307 /* Does this field automatically have alignment it needs by virtue
1308 of the fields that precede it and the record's own alignment? */
1309 if (known_align < desired_align
1310 && (! targetm.ms_bitfield_layout_p (rli->t)
1311 || rli->prev_field == NULL))
1313 /* No, we need to skip space before this field.
1314 Bump the cumulative size to multiple of field alignment. */
1316 if (!targetm.ms_bitfield_layout_p (rli->t)
1317 && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION)
1318 warning (OPT_Wpadded, "padding struct to align %q+D", field);
1320 /* If the alignment is still within offset_align, just align
1321 the bit position. */
1322 if (desired_align < rli->offset_align)
1323 rli->bitpos = round_up (rli->bitpos, desired_align);
1324 else
1326 /* First adjust OFFSET by the partial bits, then align. */
1327 rli->offset
1328 = size_binop (PLUS_EXPR, rli->offset,
1329 fold_convert (sizetype,
1330 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1331 bitsize_unit_node)));
1332 rli->bitpos = bitsize_zero_node;
1334 rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT);
1337 if (! TREE_CONSTANT (rli->offset))
1338 rli->offset_align = desired_align;
1341 /* Handle compatibility with PCC. Note that if the record has any
1342 variable-sized fields, we need not worry about compatibility. */
1343 if (PCC_BITFIELD_TYPE_MATTERS
1344 && ! targetm.ms_bitfield_layout_p (rli->t)
1345 && TREE_CODE (field) == FIELD_DECL
1346 && type != error_mark_node
1347 && DECL_BIT_FIELD (field)
1348 && (! DECL_PACKED (field)
1349 /* Enter for these packed fields only to issue a warning. */
1350 || TYPE_ALIGN (type) <= BITS_PER_UNIT)
1351 && maximum_field_alignment == 0
1352 && ! integer_zerop (DECL_SIZE (field))
1353 && tree_fits_uhwi_p (DECL_SIZE (field))
1354 && tree_fits_uhwi_p (rli->offset)
1355 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1357 unsigned int type_align = TYPE_ALIGN (type);
1358 tree dsize = DECL_SIZE (field);
1359 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1360 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1361 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1363 #ifdef ADJUST_FIELD_ALIGN
1364 if (! TYPE_USER_ALIGN (type))
1365 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1366 #endif
1368 /* A bit field may not span more units of alignment of its type
1369 than its type itself. Advance to next boundary if necessary. */
1370 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1372 if (DECL_PACKED (field))
1374 if (warn_packed_bitfield_compat == 1)
1375 inform
1376 (input_location,
1377 "offset of packed bit-field %qD has changed in GCC 4.4",
1378 field);
1380 else
1381 rli->bitpos = round_up (rli->bitpos, type_align);
1384 if (! DECL_PACKED (field))
1385 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));
1391 #ifdef BITFIELD_NBYTES_LIMITED
1392 if (BITFIELD_NBYTES_LIMITED
1393 && ! targetm.ms_bitfield_layout_p (rli->t)
1394 && TREE_CODE (field) == FIELD_DECL
1395 && type != error_mark_node
1396 && DECL_BIT_FIELD_TYPE (field)
1397 && ! DECL_PACKED (field)
1398 && ! integer_zerop (DECL_SIZE (field))
1399 && tree_fits_uhwi_p (DECL_SIZE (field))
1400 && tree_fits_uhwi_p (rli->offset)
1401 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1403 unsigned int type_align = TYPE_ALIGN (type);
1404 tree dsize = DECL_SIZE (field);
1405 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1406 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1407 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1409 #ifdef ADJUST_FIELD_ALIGN
1410 if (! TYPE_USER_ALIGN (type))
1411 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1412 #endif
1414 if (maximum_field_alignment != 0)
1415 type_align = MIN (type_align, maximum_field_alignment);
1416 /* ??? This test is opposite the test in the containing if
1417 statement, so this code is unreachable currently. */
1418 else if (DECL_PACKED (field))
1419 type_align = MIN (type_align, BITS_PER_UNIT);
1421 /* A bit field may not span the unit of alignment of its type.
1422 Advance to next boundary if necessary. */
1423 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1424 rli->bitpos = round_up (rli->bitpos, type_align);
1426 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1427 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1428 TYPE_WARN_IF_NOT_ALIGN (type));
1430 #endif
1432 /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
1433 A subtlety:
1434 When a bit field is inserted into a packed record, the whole
1435 size of the underlying type is used by one or more same-size
1436 adjacent bitfields. (That is, if its long:3, 32 bits is
1437 used in the record, and any additional adjacent long bitfields are
1438 packed into the same chunk of 32 bits. However, if the size
1439 changes, a new field of that size is allocated.) In an unpacked
1440 record, this is the same as using alignment, but not equivalent
1441 when packing.
1443 Note: for compatibility, we use the type size, not the type alignment
1444 to determine alignment, since that matches the documentation */
1446 if (targetm.ms_bitfield_layout_p (rli->t))
1448 tree prev_saved = rli->prev_field;
1449 tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;
1451 /* This is a bitfield if it exists. */
1452 if (rli->prev_field)
1454 bool realign_p = known_align < desired_align;
1456 /* If both are bitfields, nonzero, and the same size, this is
1457 the middle of a run. Zero declared size fields are special
1458 and handled as "end of run". (Note: it's nonzero declared
1459 size, but equal type sizes!) (Since we know that both
1460 the current and previous fields are bitfields by the
1461 time we check it, DECL_SIZE must be present for both.) */
1462 if (DECL_BIT_FIELD_TYPE (field)
1463 && !integer_zerop (DECL_SIZE (field))
1464 && !integer_zerop (DECL_SIZE (rli->prev_field))
1465 && tree_fits_shwi_p (DECL_SIZE (rli->prev_field))
1466 && tree_fits_uhwi_p (TYPE_SIZE (type))
1467 && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
1469 /* We're in the middle of a run of equal type size fields; make
1470 sure we realign if we run out of bits. (Not decl size,
1471 type size!) */
1472 HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field));
1474 if (rli->remaining_in_alignment < bitsize)
1476 HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type));
1478 /* out of bits; bump up to next 'word'. */
1479 rli->bitpos
1480 = size_binop (PLUS_EXPR, rli->bitpos,
1481 bitsize_int (rli->remaining_in_alignment));
1482 rli->prev_field = field;
1483 if (typesize < bitsize)
1484 rli->remaining_in_alignment = 0;
1485 else
1486 rli->remaining_in_alignment = typesize - bitsize;
1488 else
1490 rli->remaining_in_alignment -= bitsize;
1491 realign_p = false;
1494 else
1496 /* End of a run: if leaving a run of bitfields of the same type
1497 size, we have to "use up" the rest of the bits of the type
1498 size.
1500 Compute the new position as the sum of the size for the prior
1501 type and where we first started working on that type.
1502 Note: since the beginning of the field was aligned then
1503 of course the end will be too. No round needed. */
1505 if (!integer_zerop (DECL_SIZE (rli->prev_field)))
1507 rli->bitpos
1508 = size_binop (PLUS_EXPR, rli->bitpos,
1509 bitsize_int (rli->remaining_in_alignment));
1511 else
1512 /* We "use up" size zero fields; the code below should behave
1513 as if the prior field was not a bitfield. */
1514 prev_saved = NULL;
1516 /* Cause a new bitfield to be captured, either this time (if
1517 currently a bitfield) or next time we see one. */
1518 if (!DECL_BIT_FIELD_TYPE (field)
1519 || integer_zerop (DECL_SIZE (field)))
1520 rli->prev_field = NULL;
1523 /* Does this field automatically have alignment it needs by virtue
1524 of the fields that precede it and the record's own alignment? */
1525 if (realign_p)
1527 /* If the alignment is still within offset_align, just align
1528 the bit position. */
1529 if (desired_align < rli->offset_align)
1530 rli->bitpos = round_up (rli->bitpos, desired_align);
1531 else
1533 /* First adjust OFFSET by the partial bits, then align. */
1534 tree d = size_binop (CEIL_DIV_EXPR, rli->bitpos,
1535 bitsize_unit_node);
1536 rli->offset = size_binop (PLUS_EXPR, rli->offset,
1537 fold_convert (sizetype, d));
1538 rli->bitpos = bitsize_zero_node;
1540 rli->offset = round_up (rli->offset,
1541 desired_align / BITS_PER_UNIT);
1544 if (! TREE_CONSTANT (rli->offset))
1545 rli->offset_align = desired_align;
1548 normalize_rli (rli);
1551 /* If we're starting a new run of same type size bitfields
1552 (or a run of non-bitfields), set up the "first of the run"
1553 fields.
1555 That is, if the current field is not a bitfield, or if there
1556 was a prior bitfield the type sizes differ, or if there wasn't
1557 a prior bitfield the size of the current field is nonzero.
1559 Note: we must be sure to test ONLY the type size if there was
1560 a prior bitfield and ONLY for the current field being zero if
1561 there wasn't. */
1563 if (!DECL_BIT_FIELD_TYPE (field)
1564 || (prev_saved != NULL
1565 ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
1566 : !integer_zerop (DECL_SIZE (field))))
1568 /* Never smaller than a byte for compatibility. */
1569 unsigned int type_align = BITS_PER_UNIT;
1571 /* (When not a bitfield), we could be seeing a flex array (with
1572 no DECL_SIZE). Since we won't be using remaining_in_alignment
1573 until we see a bitfield (and come by here again) we just skip
1574 calculating it. */
1575 if (DECL_SIZE (field) != NULL
1576 && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field)))
1577 && tree_fits_uhwi_p (DECL_SIZE (field)))
1579 unsigned HOST_WIDE_INT bitsize
1580 = tree_to_uhwi (DECL_SIZE (field));
1581 unsigned HOST_WIDE_INT typesize
1582 = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field)));
1584 if (typesize < bitsize)
1585 rli->remaining_in_alignment = 0;
1586 else
1587 rli->remaining_in_alignment = typesize - bitsize;
1590 /* Now align (conventionally) for the new type. */
1591 if (! DECL_PACKED (field))
1592 type_align = TYPE_ALIGN (TREE_TYPE (field));
1594 if (maximum_field_alignment != 0)
1595 type_align = MIN (type_align, maximum_field_alignment);
1597 rli->bitpos = round_up (rli->bitpos, type_align);
1599 /* If we really aligned, don't allow subsequent bitfields
1600 to undo that. */
1601 rli->prev_field = NULL;
1605 /* Offset so far becomes the position of this field after normalizing. */
1606 normalize_rli (rli);
1607 DECL_FIELD_OFFSET (field) = rli->offset;
1608 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1609 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1610 handle_warn_if_not_align (field, rli->record_align);
1612 /* Evaluate nonconstant offsets only once, either now or as soon as safe. */
1613 if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
1614 DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));
1616 /* If this field ended up more aligned than we thought it would be (we
1617 approximate this by seeing if its position changed), lay out the field
1618 again; perhaps we can use an integral mode for it now. */
1619 if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field)))
1620 actual_align = least_bit_hwi (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)));
1621 else if (integer_zerop (DECL_FIELD_OFFSET (field)))
1622 actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1623 else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
1624 actual_align = (BITS_PER_UNIT
1625 * least_bit_hwi (tree_to_uhwi (DECL_FIELD_OFFSET (field))));
1626 else
1627 actual_align = DECL_OFFSET_ALIGN (field);
1628 /* ACTUAL_ALIGN is still the actual alignment *within the record* .
1629 store / extract bit field operations will check the alignment of the
1630 record against the mode of bit fields. */
1632 if (known_align != actual_align)
1633 layout_decl (field, actual_align);
1635 if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field))
1636 rli->prev_field = field;
1638 /* Now add size of this field to the size of the record. If the size is
1639 not constant, treat the field as being a multiple of bytes and just
1640 adjust the offset, resetting the bit position. Otherwise, apportion the
1641 size amongst the bit position and offset. First handle the case of an
1642 unspecified size, which can happen when we have an invalid nested struct
1643 definition, such as struct j { struct j { int i; } }. The error message
1644 is printed in finish_struct. */
1645 if (DECL_SIZE (field) == 0)
1646 /* Do nothing. */;
1647 else if (TREE_CODE (DECL_SIZE (field)) != INTEGER_CST
1648 || TREE_OVERFLOW (DECL_SIZE (field)))
1650 rli->offset
1651 = size_binop (PLUS_EXPR, rli->offset,
1652 fold_convert (sizetype,
1653 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1654 bitsize_unit_node)));
1655 rli->offset
1656 = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1657 rli->bitpos = bitsize_zero_node;
1658 rli->offset_align = MIN (rli->offset_align, desired_align);
1660 if (!multiple_of_p (bitsizetype, DECL_SIZE (field),
1661 bitsize_int (rli->offset_align)))
1663 tree type = strip_array_types (TREE_TYPE (field));
1664 /* The above adjusts offset_align just based on the start of the
1665 field. The field might not have a size that is a multiple of
1666 that offset_align though. If the field is an array of fixed
1667 sized elements, assume there can be any multiple of those
1668 sizes. If it is a variable length aggregate or array of
1669 variable length aggregates, assume worst that the end is
1670 just BITS_PER_UNIT aligned. */
1671 if (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
1673 if (TREE_INT_CST_LOW (TYPE_SIZE (type)))
1675 unsigned HOST_WIDE_INT sz
1676 = least_bit_hwi (TREE_INT_CST_LOW (TYPE_SIZE (type)));
1677 rli->offset_align = MIN (rli->offset_align, sz);
1680 else
1681 rli->offset_align = MIN (rli->offset_align, BITS_PER_UNIT);
1684 else if (targetm.ms_bitfield_layout_p (rli->t))
1686 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1688 /* If we ended a bitfield before the full length of the type then
1689 pad the struct out to the full length of the last type. */
1690 if ((DECL_CHAIN (field) == NULL
1691 || TREE_CODE (DECL_CHAIN (field)) != FIELD_DECL)
1692 && DECL_BIT_FIELD_TYPE (field)
1693 && !integer_zerop (DECL_SIZE (field)))
1694 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos,
1695 bitsize_int (rli->remaining_in_alignment));
1697 normalize_rli (rli);
1699 else
1701 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1702 normalize_rli (rli);
1706 /* Assuming that all the fields have been laid out, this function uses
1707 RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type
1708 indicated by RLI. */
1710 static void
1711 finalize_record_size (record_layout_info rli)
1713 tree unpadded_size, unpadded_size_unit;
1715 /* Now we want just byte and bit offsets, so set the offset alignment
1716 to be a byte and then normalize. */
1717 rli->offset_align = BITS_PER_UNIT;
1718 normalize_rli (rli);
1720 /* Determine the desired alignment. */
1721 #ifdef ROUND_TYPE_ALIGN
1722 SET_TYPE_ALIGN (rli->t, ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t),
1723 rli->record_align));
1724 #else
1725 SET_TYPE_ALIGN (rli->t, MAX (TYPE_ALIGN (rli->t), rli->record_align));
1726 #endif
1728 /* Compute the size so far. Be sure to allow for extra bits in the
1729 size in bytes. We have guaranteed above that it will be no more
1730 than a single byte. */
1731 unpadded_size = rli_size_so_far (rli);
1732 unpadded_size_unit = rli_size_unit_so_far (rli);
1733 if (! integer_zerop (rli->bitpos))
1734 unpadded_size_unit
1735 = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node);
1737 /* Round the size up to be a multiple of the required alignment. */
1738 TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
1739 TYPE_SIZE_UNIT (rli->t)
1740 = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t));
1742 if (TREE_CONSTANT (unpadded_size)
1743 && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0
1744 && input_location != BUILTINS_LOCATION)
1745 warning (OPT_Wpadded, "padding struct size to alignment boundary");
1747 if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE
1748 && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary
1749 && TREE_CONSTANT (unpadded_size))
1751 tree unpacked_size;
1753 #ifdef ROUND_TYPE_ALIGN
1754 rli->unpacked_align
1755 = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align);
1756 #else
1757 rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align);
1758 #endif
1760 unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
1761 if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
1763 if (TYPE_NAME (rli->t))
1765 tree name;
1767 if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE)
1768 name = TYPE_NAME (rli->t);
1769 else
1770 name = DECL_NAME (TYPE_NAME (rli->t));
1772 if (STRICT_ALIGNMENT)
1773 warning (OPT_Wpacked, "packed attribute causes inefficient "
1774 "alignment for %qE", name);
1775 else
1776 warning (OPT_Wpacked,
1777 "packed attribute is unnecessary for %qE", name);
1779 else
1781 if (STRICT_ALIGNMENT)
1782 warning (OPT_Wpacked,
1783 "packed attribute causes inefficient alignment");
1784 else
1785 warning (OPT_Wpacked, "packed attribute is unnecessary");
1791 /* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE). */
1793 void
1794 compute_record_mode (tree type)
1796 tree field;
1797 machine_mode mode = VOIDmode;
1799 /* Most RECORD_TYPEs have BLKmode, so we start off assuming that.
1800 However, if possible, we use a mode that fits in a register
1801 instead, in order to allow for better optimization down the
1802 line. */
1803 SET_TYPE_MODE (type, BLKmode);
1805 if (! tree_fits_uhwi_p (TYPE_SIZE (type)))
1806 return;
1808 /* A record which has any BLKmode members must itself be
1809 BLKmode; it can't go in a register. Unless the member is
1810 BLKmode only because it isn't aligned. */
1811 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
1813 if (TREE_CODE (field) != FIELD_DECL)
1814 continue;
1816 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK
1817 || (TYPE_MODE (TREE_TYPE (field)) == BLKmode
1818 && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field))
1819 && !(TYPE_SIZE (TREE_TYPE (field)) != 0
1820 && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
1821 || ! tree_fits_uhwi_p (bit_position (field))
1822 || DECL_SIZE (field) == 0
1823 || ! tree_fits_uhwi_p (DECL_SIZE (field)))
1824 return;
1826 /* If this field is the whole struct, remember its mode so
1827 that, say, we can put a double in a class into a DF
1828 register instead of forcing it to live in the stack. */
1829 if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field)))
1830 mode = DECL_MODE (field);
1832 /* With some targets, it is sub-optimal to access an aligned
1833 BLKmode structure as a scalar. */
1834 if (targetm.member_type_forces_blk (field, mode))
1835 return;
1838 /* If we only have one real field; use its mode if that mode's size
1839 matches the type's size. This only applies to RECORD_TYPE. This
1840 does not apply to unions. */
1841 poly_uint64 type_size;
1842 if (TREE_CODE (type) == RECORD_TYPE
1843 && mode != VOIDmode
1844 && poly_int_tree_p (TYPE_SIZE (type), &type_size)
1845 && known_eq (GET_MODE_BITSIZE (mode), type_size))
1847 else
1848 mode = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1).else_blk ();
1850 /* If structure's known alignment is less than what the scalar
1851 mode would need, and it matters, then stick with BLKmode. */
1852 if (mode != BLKmode
1853 && STRICT_ALIGNMENT
1854 && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT
1855 || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (mode)))
1857 /* If this is the only reason this type is BLKmode, then
1858 don't force containing types to be BLKmode. */
1859 TYPE_NO_FORCE_BLK (type) = 1;
1860 mode = BLKmode;
1863 SET_TYPE_MODE (type, mode);
1866 /* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid
1867 out. */
1869 static void
1870 finalize_type_size (tree type)
1872 /* Normally, use the alignment corresponding to the mode chosen.
1873 However, where strict alignment is not required, avoid
1874 over-aligning structures, since most compilers do not do this
1875 alignment. */
1876 if (TYPE_MODE (type) != BLKmode
1877 && TYPE_MODE (type) != VOIDmode
1878 && (STRICT_ALIGNMENT || !AGGREGATE_TYPE_P (type)))
1880 unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type));
1882 /* Don't override a larger alignment requirement coming from a user
1883 alignment of one of the fields. */
1884 if (mode_align >= TYPE_ALIGN (type))
1886 SET_TYPE_ALIGN (type, mode_align);
1887 TYPE_USER_ALIGN (type) = 0;
1891 /* Do machine-dependent extra alignment. */
1892 #ifdef ROUND_TYPE_ALIGN
1893 SET_TYPE_ALIGN (type,
1894 ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT));
1895 #endif
1897 /* If we failed to find a simple way to calculate the unit size
1898 of the type, find it by division. */
1899 if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0)
1900 /* TYPE_SIZE (type) is computed in bitsizetype. After the division, the
1901 result will fit in sizetype. We will get more efficient code using
1902 sizetype, so we force a conversion. */
1903 TYPE_SIZE_UNIT (type)
1904 = fold_convert (sizetype,
1905 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
1906 bitsize_unit_node));
1908 if (TYPE_SIZE (type) != 0)
1910 TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
1911 TYPE_SIZE_UNIT (type)
1912 = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type));
1915 /* Evaluate nonconstant sizes only once, either now or as soon as safe. */
1916 if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
1917 TYPE_SIZE (type) = variable_size (TYPE_SIZE (type));
1918 if (TYPE_SIZE_UNIT (type) != 0
1919 && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST)
1920 TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type));
1922 /* Handle empty records as per the x86-64 psABI. */
1923 TYPE_EMPTY_P (type) = targetm.calls.empty_record_p (type);
1925 /* Also layout any other variants of the type. */
1926 if (TYPE_NEXT_VARIANT (type)
1927 || type != TYPE_MAIN_VARIANT (type))
1929 tree variant;
1930 /* Record layout info of this variant. */
1931 tree size = TYPE_SIZE (type);
1932 tree size_unit = TYPE_SIZE_UNIT (type);
1933 unsigned int align = TYPE_ALIGN (type);
1934 unsigned int precision = TYPE_PRECISION (type);
1935 unsigned int user_align = TYPE_USER_ALIGN (type);
1936 machine_mode mode = TYPE_MODE (type);
1937 bool empty_p = TYPE_EMPTY_P (type);
1939 /* Copy it into all variants. */
1940 for (variant = TYPE_MAIN_VARIANT (type);
1941 variant != 0;
1942 variant = TYPE_NEXT_VARIANT (variant))
1944 TYPE_SIZE (variant) = size;
1945 TYPE_SIZE_UNIT (variant) = size_unit;
1946 unsigned valign = align;
1947 if (TYPE_USER_ALIGN (variant))
1948 valign = MAX (valign, TYPE_ALIGN (variant));
1949 else
1950 TYPE_USER_ALIGN (variant) = user_align;
1951 SET_TYPE_ALIGN (variant, valign);
1952 TYPE_PRECISION (variant) = precision;
1953 SET_TYPE_MODE (variant, mode);
1954 TYPE_EMPTY_P (variant) = empty_p;
1959 /* Return a new underlying object for a bitfield started with FIELD. */
1961 static tree
1962 start_bitfield_representative (tree field)
1964 tree repr = make_node (FIELD_DECL);
1965 DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field);
1966 /* Force the representative to begin at a BITS_PER_UNIT aligned
1967 boundary - C++ may use tail-padding of a base object to
1968 continue packing bits so the bitfield region does not start
1969 at bit zero (see g++.dg/abi/bitfield5.C for example).
1970 Unallocated bits may happen for other reasons as well,
1971 for example Ada which allows explicit bit-granular structure layout. */
1972 DECL_FIELD_BIT_OFFSET (repr)
1973 = size_binop (BIT_AND_EXPR,
1974 DECL_FIELD_BIT_OFFSET (field),
1975 bitsize_int (~(BITS_PER_UNIT - 1)));
1976 SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field));
1977 DECL_SIZE (repr) = DECL_SIZE (field);
1978 DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
1979 DECL_PACKED (repr) = DECL_PACKED (field);
1980 DECL_CONTEXT (repr) = DECL_CONTEXT (field);
1981 /* There are no indirect accesses to this field. If we introduce
1982 some then they have to use the record alias set. This makes
1983 sure to properly conflict with [indirect] accesses to addressable
1984 fields of the bitfield group. */
1985 DECL_NONADDRESSABLE_P (repr) = 1;
1986 return repr;
1989 /* Finish up a bitfield group that was started by creating the underlying
1990 object REPR with the last field in the bitfield group FIELD. */
1992 static void
1993 finish_bitfield_representative (tree repr, tree field)
1995 unsigned HOST_WIDE_INT bitsize, maxbitsize;
1996 tree nextf, size;
1998 size = size_diffop (DECL_FIELD_OFFSET (field),
1999 DECL_FIELD_OFFSET (repr));
2000 while (TREE_CODE (size) == COMPOUND_EXPR)
2001 size = TREE_OPERAND (size, 1);
2002 gcc_assert (tree_fits_uhwi_p (size));
2003 bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
2004 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
2005 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))
2006 + tree_to_uhwi (DECL_SIZE (field)));
2008 /* Round up bitsize to multiples of BITS_PER_UNIT. */
2009 bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
2011 /* Now nothing tells us how to pad out bitsize ... */
2012 nextf = DECL_CHAIN (field);
2013 while (nextf && TREE_CODE (nextf) != FIELD_DECL)
2014 nextf = DECL_CHAIN (nextf);
2015 if (nextf)
2017 tree maxsize;
2018 /* If there was an error, the field may be not laid out
2019 correctly. Don't bother to do anything. */
2020 if (TREE_TYPE (nextf) == error_mark_node)
2021 return;
2022 maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
2023 DECL_FIELD_OFFSET (repr));
2024 if (tree_fits_uhwi_p (maxsize))
2026 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
2027 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf))
2028 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
2029 /* If the group ends within a bitfield nextf does not need to be
2030 aligned to BITS_PER_UNIT. Thus round up. */
2031 maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
2033 else
2034 maxbitsize = bitsize;
2036 else
2038 /* Note that if the C++ FE sets up tail-padding to be re-used it
2039 creates a as-base variant of the type with TYPE_SIZE adjusted
2040 accordingly. So it is safe to include tail-padding here. */
2041 tree aggsize = lang_hooks.types.unit_size_without_reusable_padding
2042 (DECL_CONTEXT (field));
2043 tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr));
2044 /* We cannot generally rely on maxsize to fold to an integer constant,
2045 so use bitsize as fallback for this case. */
2046 if (tree_fits_uhwi_p (maxsize))
2047 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
2048 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
2049 else
2050 maxbitsize = bitsize;
2053 /* Only if we don't artificially break up the representative in
2054 the middle of a large bitfield with different possibly
2055 overlapping representatives. And all representatives start
2056 at byte offset. */
2057 gcc_assert (maxbitsize % BITS_PER_UNIT == 0);
2059 /* Find the smallest nice mode to use. */
2060 opt_scalar_int_mode mode_iter;
2061 FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_INT)
2062 if (GET_MODE_BITSIZE (mode_iter.require ()) >= bitsize)
2063 break;
2065 scalar_int_mode mode;
2066 if (!mode_iter.exists (&mode)
2067 || GET_MODE_BITSIZE (mode) > maxbitsize
2068 || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE)
2070 /* We really want a BLKmode representative only as a last resort,
2071 considering the member b in
2072 struct { int a : 7; int b : 17; int c; } __attribute__((packed));
2073 Otherwise we simply want to split the representative up
2074 allowing for overlaps within the bitfield region as required for
2075 struct { int a : 7; int b : 7;
2076 int c : 10; int d; } __attribute__((packed));
2077 [0, 15] HImode for a and b, [8, 23] HImode for c. */
2078 DECL_SIZE (repr) = bitsize_int (bitsize);
2079 DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT);
2080 SET_DECL_MODE (repr, BLKmode);
2081 TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node,
2082 bitsize / BITS_PER_UNIT);
2084 else
2086 unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode);
2087 DECL_SIZE (repr) = bitsize_int (modesize);
2088 DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT);
2089 SET_DECL_MODE (repr, mode);
2090 TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1);
2093 /* Remember whether the bitfield group is at the end of the
2094 structure or not. */
2095 DECL_CHAIN (repr) = nextf;
2098 /* Compute and set FIELD_DECLs for the underlying objects we should
2099 use for bitfield access for the structure T. */
2101 void
2102 finish_bitfield_layout (tree t)
2104 tree field, prev;
2105 tree repr = NULL_TREE;
2107 /* Unions would be special, for the ease of type-punning optimizations
2108 we could use the underlying type as hint for the representative
2109 if the bitfield would fit and the representative would not exceed
2110 the union in size. */
2111 if (TREE_CODE (t) != RECORD_TYPE)
2112 return;
2114 for (prev = NULL_TREE, field = TYPE_FIELDS (t);
2115 field; field = DECL_CHAIN (field))
2117 if (TREE_CODE (field) != FIELD_DECL)
2118 continue;
2120 /* In the C++ memory model, consecutive bit fields in a structure are
2121 considered one memory location and updating a memory location
2122 may not store into adjacent memory locations. */
2123 if (!repr
2124 && DECL_BIT_FIELD_TYPE (field))
2126 /* Start new representative. */
2127 repr = start_bitfield_representative (field);
2129 else if (repr
2130 && ! DECL_BIT_FIELD_TYPE (field))
2132 /* Finish off new representative. */
2133 finish_bitfield_representative (repr, prev);
2134 repr = NULL_TREE;
2136 else if (DECL_BIT_FIELD_TYPE (field))
2138 gcc_assert (repr != NULL_TREE);
2140 /* Zero-size bitfields finish off a representative and
2141 do not have a representative themselves. This is
2142 required by the C++ memory model. */
2143 if (integer_zerop (DECL_SIZE (field)))
2145 finish_bitfield_representative (repr, prev);
2146 repr = NULL_TREE;
2149 /* We assume that either DECL_FIELD_OFFSET of the representative
2150 and each bitfield member is a constant or they are equal.
2151 This is because we need to be able to compute the bit-offset
2152 of each field relative to the representative in get_bit_range
2153 during RTL expansion.
2154 If these constraints are not met, simply force a new
2155 representative to be generated. That will at most
2156 generate worse code but still maintain correctness with
2157 respect to the C++ memory model. */
2158 else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr))
2159 && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
2160 || operand_equal_p (DECL_FIELD_OFFSET (repr),
2161 DECL_FIELD_OFFSET (field), 0)))
2163 finish_bitfield_representative (repr, prev);
2164 repr = start_bitfield_representative (field);
2167 else
2168 continue;
2170 if (repr)
2171 DECL_BIT_FIELD_REPRESENTATIVE (field) = repr;
2173 prev = field;
2176 if (repr)
2177 finish_bitfield_representative (repr, prev);
2180 /* Do all of the work required to layout the type indicated by RLI,
2181 once the fields have been laid out. This function will call `free'
2182 for RLI, unless FREE_P is false. Passing a value other than false
2183 for FREE_P is bad practice; this option only exists to support the
2184 G++ 3.2 ABI. */
2186 void
2187 finish_record_layout (record_layout_info rli, int free_p)
2189 tree variant;
2191 /* Compute the final size. */
2192 finalize_record_size (rli);
2194 /* Compute the TYPE_MODE for the record. */
2195 compute_record_mode (rli->t);
2197 /* Perform any last tweaks to the TYPE_SIZE, etc. */
2198 finalize_type_size (rli->t);
2200 /* Compute bitfield representatives. */
2201 finish_bitfield_layout (rli->t);
2203 /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants.
2204 With C++ templates, it is too early to do this when the attribute
2205 is being parsed. */
2206 for (variant = TYPE_NEXT_VARIANT (rli->t); variant;
2207 variant = TYPE_NEXT_VARIANT (variant))
2209 TYPE_PACKED (variant) = TYPE_PACKED (rli->t);
2210 TYPE_REVERSE_STORAGE_ORDER (variant)
2211 = TYPE_REVERSE_STORAGE_ORDER (rli->t);
2214 /* Lay out any static members. This is done now because their type
2215 may use the record's type. */
2216 while (!vec_safe_is_empty (rli->pending_statics))
2217 layout_decl (rli->pending_statics->pop (), 0);
2219 /* Clean up. */
2220 if (free_p)
2222 vec_free (rli->pending_statics);
2223 free (rli);
2228 /* Finish processing a builtin RECORD_TYPE type TYPE. It's name is
2229 NAME, its fields are chained in reverse on FIELDS.
2231 If ALIGN_TYPE is non-null, it is given the same alignment as
2232 ALIGN_TYPE. */
2234 void
2235 finish_builtin_struct (tree type, const char *name, tree fields,
2236 tree align_type)
2238 tree tail, next;
2240 for (tail = NULL_TREE; fields; tail = fields, fields = next)
2242 DECL_FIELD_CONTEXT (fields) = type;
2243 next = DECL_CHAIN (fields);
2244 DECL_CHAIN (fields) = tail;
2246 TYPE_FIELDS (type) = tail;
2248 if (align_type)
2250 SET_TYPE_ALIGN (type, TYPE_ALIGN (align_type));
2251 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type);
2252 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2253 TYPE_WARN_IF_NOT_ALIGN (align_type));
2256 layout_type (type);
2257 #if 0 /* not yet, should get fixed properly later */
2258 TYPE_NAME (type) = make_type_decl (get_identifier (name), type);
2259 #else
2260 TYPE_NAME (type) = build_decl (BUILTINS_LOCATION,
2261 TYPE_DECL, get_identifier (name), type);
2262 #endif
2263 TYPE_STUB_DECL (type) = TYPE_NAME (type);
2264 layout_decl (TYPE_NAME (type), 0);
2267 /* Calculate the mode, size, and alignment for TYPE.
2268 For an array type, calculate the element separation as well.
2269 Record TYPE on the chain of permanent or temporary types
2270 so that dbxout will find out about it.
2272 TYPE_SIZE of a type is nonzero if the type has been laid out already.
2273 layout_type does nothing on such a type.
2275 If the type is incomplete, its TYPE_SIZE remains zero. */
2277 void
2278 layout_type (tree type)
2280 gcc_assert (type);
2282 if (type == error_mark_node)
2283 return;
2285 /* We don't want finalize_type_size to copy an alignment attribute to
2286 variants that don't have it. */
2287 type = TYPE_MAIN_VARIANT (type);
2289 /* Do nothing if type has been laid out before. */
2290 if (TYPE_SIZE (type))
2291 return;
2293 switch (TREE_CODE (type))
2295 case LANG_TYPE:
2296 /* This kind of type is the responsibility
2297 of the language-specific code. */
2298 gcc_unreachable ();
2300 case BOOLEAN_TYPE:
2301 case INTEGER_TYPE:
2302 case ENUMERAL_TYPE:
2304 scalar_int_mode mode
2305 = smallest_int_mode_for_size (TYPE_PRECISION (type));
2306 SET_TYPE_MODE (type, mode);
2307 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2308 /* Don't set TYPE_PRECISION here, as it may be set by a bitfield. */
2309 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2310 break;
2313 case REAL_TYPE:
2315 /* Allow the caller to choose the type mode, which is how decimal
2316 floats are distinguished from binary ones. */
2317 if (TYPE_MODE (type) == VOIDmode)
2318 SET_TYPE_MODE
2319 (type, float_mode_for_size (TYPE_PRECISION (type)).require ());
2320 scalar_float_mode mode = as_a <scalar_float_mode> (TYPE_MODE (type));
2321 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2322 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2323 break;
2326 case FIXED_POINT_TYPE:
2328 /* TYPE_MODE (type) has been set already. */
2329 scalar_mode mode = SCALAR_TYPE_MODE (type);
2330 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2331 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2332 break;
2335 case COMPLEX_TYPE:
2336 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2337 SET_TYPE_MODE (type,
2338 GET_MODE_COMPLEX_MODE (TYPE_MODE (TREE_TYPE (type))));
2340 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2341 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2342 break;
2344 case VECTOR_TYPE:
2346 poly_uint64 nunits = TYPE_VECTOR_SUBPARTS (type);
2347 tree innertype = TREE_TYPE (type);
2349 /* Find an appropriate mode for the vector type. */
2350 if (TYPE_MODE (type) == VOIDmode)
2351 SET_TYPE_MODE (type,
2352 mode_for_vector (SCALAR_TYPE_MODE (innertype),
2353 nunits).else_blk ());
2355 TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type));
2356 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2357 /* Several boolean vector elements may fit in a single unit. */
2358 if (VECTOR_BOOLEAN_TYPE_P (type)
2359 && type->type_common.mode != BLKmode)
2360 TYPE_SIZE_UNIT (type)
2361 = size_int (GET_MODE_SIZE (type->type_common.mode));
2362 else
2363 TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR,
2364 TYPE_SIZE_UNIT (innertype),
2365 size_int (nunits));
2366 TYPE_SIZE (type) = int_const_binop
2367 (MULT_EXPR,
2368 bits_from_bytes (TYPE_SIZE_UNIT (type)),
2369 bitsize_int (BITS_PER_UNIT));
2371 /* For vector types, we do not default to the mode's alignment.
2372 Instead, query a target hook, defaulting to natural alignment.
2373 This prevents ABI changes depending on whether or not native
2374 vector modes are supported. */
2375 SET_TYPE_ALIGN (type, targetm.vector_alignment (type));
2377 /* However, if the underlying mode requires a bigger alignment than
2378 what the target hook provides, we cannot use the mode. For now,
2379 simply reject that case. */
2380 gcc_assert (TYPE_ALIGN (type)
2381 >= GET_MODE_ALIGNMENT (TYPE_MODE (type)));
2382 break;
2385 case VOID_TYPE:
2386 /* This is an incomplete type and so doesn't have a size. */
2387 SET_TYPE_ALIGN (type, 1);
2388 TYPE_USER_ALIGN (type) = 0;
2389 SET_TYPE_MODE (type, VOIDmode);
2390 break;
2392 case OFFSET_TYPE:
2393 TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
2394 TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS);
2395 /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be
2396 integral, which may be an __intN. */
2397 SET_TYPE_MODE (type, int_mode_for_size (POINTER_SIZE, 0).require ());
2398 TYPE_PRECISION (type) = POINTER_SIZE;
2399 break;
2401 case FUNCTION_TYPE:
2402 case METHOD_TYPE:
2403 /* It's hard to see what the mode and size of a function ought to
2404 be, but we do know the alignment is FUNCTION_BOUNDARY, so
2405 make it consistent with that. */
2406 SET_TYPE_MODE (type,
2407 int_mode_for_size (FUNCTION_BOUNDARY, 0).else_blk ());
2408 TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY);
2409 TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT);
2410 break;
2412 case POINTER_TYPE:
2413 case REFERENCE_TYPE:
2415 scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
2416 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2417 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2418 TYPE_UNSIGNED (type) = 1;
2419 TYPE_PRECISION (type) = GET_MODE_PRECISION (mode);
2421 break;
2423 case ARRAY_TYPE:
2425 tree index = TYPE_DOMAIN (type);
2426 tree element = TREE_TYPE (type);
2428 /* We need to know both bounds in order to compute the size. */
2429 if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index)
2430 && TYPE_SIZE (element))
2432 tree ub = TYPE_MAX_VALUE (index);
2433 tree lb = TYPE_MIN_VALUE (index);
2434 tree element_size = TYPE_SIZE (element);
2435 tree length;
2437 /* Make sure that an array of zero-sized element is zero-sized
2438 regardless of its extent. */
2439 if (integer_zerop (element_size))
2440 length = size_zero_node;
2442 /* The computation should happen in the original signedness so
2443 that (possible) negative values are handled appropriately
2444 when determining overflow. */
2445 else
2447 /* ??? When it is obvious that the range is signed
2448 represent it using ssizetype. */
2449 if (TREE_CODE (lb) == INTEGER_CST
2450 && TREE_CODE (ub) == INTEGER_CST
2451 && TYPE_UNSIGNED (TREE_TYPE (lb))
2452 && tree_int_cst_lt (ub, lb))
2454 lb = wide_int_to_tree (ssizetype,
2455 offset_int::from (wi::to_wide (lb),
2456 SIGNED));
2457 ub = wide_int_to_tree (ssizetype,
2458 offset_int::from (wi::to_wide (ub),
2459 SIGNED));
2461 length
2462 = fold_convert (sizetype,
2463 size_binop (PLUS_EXPR,
2464 build_int_cst (TREE_TYPE (lb), 1),
2465 size_binop (MINUS_EXPR, ub, lb)));
2468 /* ??? We have no way to distinguish a null-sized array from an
2469 array spanning the whole sizetype range, so we arbitrarily
2470 decide that [0, -1] is the only valid representation. */
2471 if (integer_zerop (length)
2472 && TREE_OVERFLOW (length)
2473 && integer_zerop (lb))
2474 length = size_zero_node;
2476 TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
2477 bits_from_bytes (length));
2479 /* If we know the size of the element, calculate the total size
2480 directly, rather than do some division thing below. This
2481 optimization helps Fortran assumed-size arrays (where the
2482 size of the array is determined at runtime) substantially. */
2483 if (TYPE_SIZE_UNIT (element))
2484 TYPE_SIZE_UNIT (type)
2485 = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length);
2488 /* Now round the alignment and size,
2489 using machine-dependent criteria if any. */
2491 unsigned align = TYPE_ALIGN (element);
2492 if (TYPE_USER_ALIGN (type))
2493 align = MAX (align, TYPE_ALIGN (type));
2494 else
2495 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);
2496 if (!TYPE_WARN_IF_NOT_ALIGN (type))
2497 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2498 TYPE_WARN_IF_NOT_ALIGN (element));
2499 #ifdef ROUND_TYPE_ALIGN
2500 align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT);
2501 #else
2502 align = MAX (align, BITS_PER_UNIT);
2503 #endif
2504 SET_TYPE_ALIGN (type, align);
2505 SET_TYPE_MODE (type, BLKmode);
2506 if (TYPE_SIZE (type) != 0
2507 && ! targetm.member_type_forces_blk (type, VOIDmode)
2508 /* BLKmode elements force BLKmode aggregate;
2509 else extract/store fields may lose. */
2510 && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
2511 || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
2513 SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type),
2514 TYPE_SIZE (type)));
2515 if (TYPE_MODE (type) != BLKmode
2516 && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
2517 && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
2519 TYPE_NO_FORCE_BLK (type) = 1;
2520 SET_TYPE_MODE (type, BLKmode);
2523 if (AGGREGATE_TYPE_P (element))
2524 TYPE_TYPELESS_STORAGE (type) = TYPE_TYPELESS_STORAGE (element);
2525 /* When the element size is constant, check that it is at least as
2526 large as the element alignment. */
2527 if (TYPE_SIZE_UNIT (element)
2528 && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST
2529 /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than
2530 TYPE_ALIGN_UNIT. */
2531 && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element))
2532 && !integer_zerop (TYPE_SIZE_UNIT (element))
2533 && compare_tree_int (TYPE_SIZE_UNIT (element),
2534 TYPE_ALIGN_UNIT (element)) < 0)
2535 error ("alignment of array elements is greater than element size");
2536 break;
2539 case RECORD_TYPE:
2540 case UNION_TYPE:
2541 case QUAL_UNION_TYPE:
2543 tree field;
2544 record_layout_info rli;
2546 /* Initialize the layout information. */
2547 rli = start_record_layout (type);
2549 /* If this is a QUAL_UNION_TYPE, we want to process the fields
2550 in the reverse order in building the COND_EXPR that denotes
2551 its size. We reverse them again later. */
2552 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2553 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2555 /* Place all the fields. */
2556 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
2557 place_field (rli, field);
2559 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2560 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2562 /* Finish laying out the record. */
2563 finish_record_layout (rli, /*free_p=*/true);
2565 break;
2567 default:
2568 gcc_unreachable ();
2571 /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE. For
2572 records and unions, finish_record_layout already called this
2573 function. */
2574 if (!RECORD_OR_UNION_TYPE_P (type))
2575 finalize_type_size (type);
2577 /* We should never see alias sets on incomplete aggregates. And we
2578 should not call layout_type on not incomplete aggregates. */
2579 if (AGGREGATE_TYPE_P (type))
2580 gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type));
2583 /* Return the least alignment required for type TYPE. */
2585 unsigned int
2586 min_align_of_type (tree type)
2588 unsigned int align = TYPE_ALIGN (type);
2589 if (!TYPE_USER_ALIGN (type))
2591 align = MIN (align, BIGGEST_ALIGNMENT);
2592 #ifdef BIGGEST_FIELD_ALIGNMENT
2593 align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
2594 #endif
2595 unsigned int field_align = align;
2596 #ifdef ADJUST_FIELD_ALIGN
2597 field_align = ADJUST_FIELD_ALIGN (NULL_TREE, type, field_align);
2598 #endif
2599 align = MIN (align, field_align);
2601 return align / BITS_PER_UNIT;
2604 /* Create and return a type for signed integers of PRECISION bits. */
2606 tree
2607 make_signed_type (int precision)
2609 tree type = make_node (INTEGER_TYPE);
2611 TYPE_PRECISION (type) = precision;
2613 fixup_signed_type (type);
2614 return type;
2617 /* Create and return a type for unsigned integers of PRECISION bits. */
2619 tree
2620 make_unsigned_type (int precision)
2622 tree type = make_node (INTEGER_TYPE);
2624 TYPE_PRECISION (type) = precision;
2626 fixup_unsigned_type (type);
2627 return type;
2630 /* Create and return a type for fract of PRECISION bits, UNSIGNEDP,
2631 and SATP. */
2633 tree
2634 make_fract_type (int precision, int unsignedp, int satp)
2636 tree type = make_node (FIXED_POINT_TYPE);
2638 TYPE_PRECISION (type) = precision;
2640 if (satp)
2641 TYPE_SATURATING (type) = 1;
2643 /* Lay out the type: set its alignment, size, etc. */
2644 TYPE_UNSIGNED (type) = unsignedp;
2645 enum mode_class mclass = unsignedp ? MODE_UFRACT : MODE_FRACT;
2646 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2647 layout_type (type);
2649 return type;
2652 /* Create and return a type for accum of PRECISION bits, UNSIGNEDP,
2653 and SATP. */
2655 tree
2656 make_accum_type (int precision, int unsignedp, int satp)
2658 tree type = make_node (FIXED_POINT_TYPE);
2660 TYPE_PRECISION (type) = precision;
2662 if (satp)
2663 TYPE_SATURATING (type) = 1;
2665 /* Lay out the type: set its alignment, size, etc. */
2666 TYPE_UNSIGNED (type) = unsignedp;
2667 enum mode_class mclass = unsignedp ? MODE_UACCUM : MODE_ACCUM;
2668 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2669 layout_type (type);
2671 return type;
2674 /* Initialize sizetypes so layout_type can use them. */
2676 void
2677 initialize_sizetypes (void)
2679 int precision, bprecision;
2681 /* Get sizetypes precision from the SIZE_TYPE target macro. */
2682 if (strcmp (SIZETYPE, "unsigned int") == 0)
2683 precision = INT_TYPE_SIZE;
2684 else if (strcmp (SIZETYPE, "long unsigned int") == 0)
2685 precision = LONG_TYPE_SIZE;
2686 else if (strcmp (SIZETYPE, "long long unsigned int") == 0)
2687 precision = LONG_LONG_TYPE_SIZE;
2688 else if (strcmp (SIZETYPE, "short unsigned int") == 0)
2689 precision = SHORT_TYPE_SIZE;
2690 else
2692 int i;
2694 precision = -1;
2695 for (i = 0; i < NUM_INT_N_ENTS; i++)
2696 if (int_n_enabled_p[i])
2698 char name[50];
2699 sprintf (name, "__int%d unsigned", int_n_data[i].bitsize);
2701 if (strcmp (name, SIZETYPE) == 0)
2703 precision = int_n_data[i].bitsize;
2706 if (precision == -1)
2707 gcc_unreachable ();
2710 bprecision
2711 = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE);
2712 bprecision = GET_MODE_PRECISION (smallest_int_mode_for_size (bprecision));
2713 if (bprecision > HOST_BITS_PER_DOUBLE_INT)
2714 bprecision = HOST_BITS_PER_DOUBLE_INT;
2716 /* Create stubs for sizetype and bitsizetype so we can create constants. */
2717 sizetype = make_node (INTEGER_TYPE);
2718 TYPE_NAME (sizetype) = get_identifier ("sizetype");
2719 TYPE_PRECISION (sizetype) = precision;
2720 TYPE_UNSIGNED (sizetype) = 1;
2721 bitsizetype = make_node (INTEGER_TYPE);
2722 TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype");
2723 TYPE_PRECISION (bitsizetype) = bprecision;
2724 TYPE_UNSIGNED (bitsizetype) = 1;
2726 /* Now layout both types manually. */
2727 scalar_int_mode mode = smallest_int_mode_for_size (precision);
2728 SET_TYPE_MODE (sizetype, mode);
2729 SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype)));
2730 TYPE_SIZE (sizetype) = bitsize_int (precision);
2731 TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (mode));
2732 set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);
2734 mode = smallest_int_mode_for_size (bprecision);
2735 SET_TYPE_MODE (bitsizetype, mode);
2736 SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype)));
2737 TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
2738 TYPE_SIZE_UNIT (bitsizetype) = size_int (GET_MODE_SIZE (mode));
2739 set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);
2741 /* Create the signed variants of *sizetype. */
2742 ssizetype = make_signed_type (TYPE_PRECISION (sizetype));
2743 TYPE_NAME (ssizetype) = get_identifier ("ssizetype");
2744 sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype));
2745 TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype");
2748 /* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE
2749 or BOOLEAN_TYPE. Set TYPE_MIN_VALUE and TYPE_MAX_VALUE
2750 for TYPE, based on the PRECISION and whether or not the TYPE
2751 IS_UNSIGNED. PRECISION need not correspond to a width supported
2752 natively by the hardware; for example, on a machine with 8-bit,
2753 16-bit, and 32-bit register modes, PRECISION might be 7, 23, or
2754 61. */
2756 void
2757 set_min_and_max_values_for_integral_type (tree type,
2758 int precision,
2759 signop sgn)
2761 /* For bitfields with zero width we end up creating integer types
2762 with zero precision. Don't assign any minimum/maximum values
2763 to those types, they don't have any valid value. */
2764 if (precision < 1)
2765 return;
2767 TYPE_MIN_VALUE (type)
2768 = wide_int_to_tree (type, wi::min_value (precision, sgn));
2769 TYPE_MAX_VALUE (type)
2770 = wide_int_to_tree (type, wi::max_value (precision, sgn));
2773 /* Set the extreme values of TYPE based on its precision in bits,
2774 then lay it out. Used when make_signed_type won't do
2775 because the tree code is not INTEGER_TYPE. */
2777 void
2778 fixup_signed_type (tree type)
2780 int precision = TYPE_PRECISION (type);
2782 set_min_and_max_values_for_integral_type (type, precision, SIGNED);
2784 /* Lay out the type: set its alignment, size, etc. */
2785 layout_type (type);
2788 /* Set the extreme values of TYPE based on its precision in bits,
2789 then lay it out. This is used both in `make_unsigned_type'
2790 and for enumeral types. */
2792 void
2793 fixup_unsigned_type (tree type)
2795 int precision = TYPE_PRECISION (type);
2797 TYPE_UNSIGNED (type) = 1;
2799 set_min_and_max_values_for_integral_type (type, precision, UNSIGNED);
2801 /* Lay out the type: set its alignment, size, etc. */
2802 layout_type (type);
2805 /* Construct an iterator for a bitfield that spans BITSIZE bits,
2806 starting at BITPOS.
2808 BITREGION_START is the bit position of the first bit in this
2809 sequence of bit fields. BITREGION_END is the last bit in this
2810 sequence. If these two fields are non-zero, we should restrict the
2811 memory access to that range. Otherwise, we are allowed to touch
2812 any adjacent non bit-fields.
2814 ALIGN is the alignment of the underlying object in bits.
2815 VOLATILEP says whether the bitfield is volatile. */
2817 bit_field_mode_iterator
2818 ::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
2819 poly_int64 bitregion_start,
2820 poly_int64 bitregion_end,
2821 unsigned int align, bool volatilep)
2822 : m_mode (NARROWEST_INT_MODE), m_bitsize (bitsize),
2823 m_bitpos (bitpos), m_bitregion_start (bitregion_start),
2824 m_bitregion_end (bitregion_end), m_align (align),
2825 m_volatilep (volatilep), m_count (0)
2827 if (known_eq (m_bitregion_end, 0))
2829 /* We can assume that any aligned chunk of ALIGN bits that overlaps
2830 the bitfield is mapped and won't trap, provided that ALIGN isn't
2831 too large. The cap is the biggest required alignment for data,
2832 or at least the word size. And force one such chunk at least. */
2833 unsigned HOST_WIDE_INT units
2834 = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
2835 if (bitsize <= 0)
2836 bitsize = 1;
2837 HOST_WIDE_INT end = bitpos + bitsize + units - 1;
2838 m_bitregion_end = end - end % units - 1;
2842 /* Calls to this function return successively larger modes that can be used
2843 to represent the bitfield. Return true if another bitfield mode is
2844 available, storing it in *OUT_MODE if so. */
2846 bool
2847 bit_field_mode_iterator::next_mode (scalar_int_mode *out_mode)
2849 scalar_int_mode mode;
2850 for (; m_mode.exists (&mode); m_mode = GET_MODE_WIDER_MODE (mode))
2852 unsigned int unit = GET_MODE_BITSIZE (mode);
2854 /* Skip modes that don't have full precision. */
2855 if (unit != GET_MODE_PRECISION (mode))
2856 continue;
2858 /* Stop if the mode is too wide to handle efficiently. */
2859 if (unit > MAX_FIXED_MODE_SIZE)
2860 break;
2862 /* Don't deliver more than one multiword mode; the smallest one
2863 should be used. */
2864 if (m_count > 0 && unit > BITS_PER_WORD)
2865 break;
2867 /* Skip modes that are too small. */
2868 unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit;
2869 unsigned HOST_WIDE_INT subend = substart + m_bitsize;
2870 if (subend > unit)
2871 continue;
2873 /* Stop if the mode goes outside the bitregion. */
2874 HOST_WIDE_INT start = m_bitpos - substart;
2875 if (maybe_ne (m_bitregion_start, 0)
2876 && maybe_lt (start, m_bitregion_start))
2877 break;
2878 HOST_WIDE_INT end = start + unit;
2879 if (maybe_gt (end, m_bitregion_end + 1))
2880 break;
2882 /* Stop if the mode requires too much alignment. */
2883 if (GET_MODE_ALIGNMENT (mode) > m_align
2884 && targetm.slow_unaligned_access (mode, m_align))
2885 break;
2887 *out_mode = mode;
2888 m_mode = GET_MODE_WIDER_MODE (mode);
2889 m_count++;
2890 return true;
2892 return false;
2895 /* Return true if smaller modes are generally preferred for this kind
2896 of bitfield. */
2898 bool
2899 bit_field_mode_iterator::prefer_smaller_modes ()
2901 return (m_volatilep
2902 ? targetm.narrow_volatile_bitfield ()
2903 : !SLOW_BYTE_ACCESS);
2906 /* Find the best machine mode to use when referencing a bit field of length
2907 BITSIZE bits starting at BITPOS.
2909 BITREGION_START is the bit position of the first bit in this
2910 sequence of bit fields. BITREGION_END is the last bit in this
2911 sequence. If these two fields are non-zero, we should restrict the
2912 memory access to that range. Otherwise, we are allowed to touch
2913 any adjacent non bit-fields.
2915 The chosen mode must have no more than LARGEST_MODE_BITSIZE bits.
2916 INT_MAX is a suitable value for LARGEST_MODE_BITSIZE if the caller
2917 doesn't want to apply a specific limit.
2919 If no mode meets all these conditions, we return VOIDmode.
2921 The underlying object is known to be aligned to a boundary of ALIGN bits.
2923 If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the
2924 smallest mode meeting these conditions.
2926 If VOLATILEP is false and SLOW_BYTE_ACCESS is true, we return the
2927 largest mode (but a mode no wider than UNITS_PER_WORD) that meets
2928 all the conditions.
2930 If VOLATILEP is true the narrow_volatile_bitfields target hook is used to
2931 decide which of the above modes should be used. */
2933 bool
2934 get_best_mode (int bitsize, int bitpos,
2935 poly_uint64 bitregion_start, poly_uint64 bitregion_end,
2936 unsigned int align,
2937 unsigned HOST_WIDE_INT largest_mode_bitsize, bool volatilep,
2938 scalar_int_mode *best_mode)
2940 bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start,
2941 bitregion_end, align, volatilep);
2942 scalar_int_mode mode;
2943 bool found = false;
2944 while (iter.next_mode (&mode)
2945 /* ??? For historical reasons, reject modes that would normally
2946 receive greater alignment, even if unaligned accesses are
2947 acceptable. This has both advantages and disadvantages.
2948 Removing this check means that something like:
2950 struct s { unsigned int x; unsigned int y; };
2951 int f (struct s *s) { return s->x == 0 && s->y == 0; }
2953 can be implemented using a single load and compare on
2954 64-bit machines that have no alignment restrictions.
2955 For example, on powerpc64-linux-gnu, we would generate:
2957 ld 3,0(3)
2958 cntlzd 3,3
2959 srdi 3,3,6
2962 rather than:
2964 lwz 9,0(3)
2965 cmpwi 7,9,0
2966 bne 7,.L3
2967 lwz 3,4(3)
2968 cntlzw 3,3
2969 srwi 3,3,5
2970 extsw 3,3
2972 .p2align 4,,15
2973 .L3:
2974 li 3,0
2977 However, accessing more than one field can make life harder
2978 for the gimple optimizers. For example, gcc.dg/vect/bb-slp-5.c
2979 has a series of unsigned short copies followed by a series of
2980 unsigned short comparisons. With this check, both the copies
2981 and comparisons remain 16-bit accesses and FRE is able
2982 to eliminate the latter. Without the check, the comparisons
2983 can be done using 2 64-bit operations, which FRE isn't able
2984 to handle in the same way.
2986 Either way, it would probably be worth disabling this check
2987 during expand. One particular example where removing the
2988 check would help is the get_best_mode call in store_bit_field.
2989 If we are given a memory bitregion of 128 bits that is aligned
2990 to a 64-bit boundary, and the bitfield we want to modify is
2991 in the second half of the bitregion, this check causes
2992 store_bitfield to turn the memory into a 64-bit reference
2993 to the _first_ half of the region. We later use
2994 adjust_bitfield_address to get a reference to the correct half,
2995 but doing so looks to adjust_bitfield_address as though we are
2996 moving past the end of the original object, so it drops the
2997 associated MEM_EXPR and MEM_OFFSET. Removing the check
2998 causes store_bit_field to keep a 128-bit memory reference,
2999 so that the final bitfield reference still has a MEM_EXPR
3000 and MEM_OFFSET. */
3001 && GET_MODE_ALIGNMENT (mode) <= align
3002 && GET_MODE_BITSIZE (mode) <= largest_mode_bitsize)
3004 *best_mode = mode;
3005 found = true;
3006 if (iter.prefer_smaller_modes ())
3007 break;
3010 return found;
3013 /* Gets minimal and maximal values for MODE (signed or unsigned depending on
3014 SIGN). The returned constants are made to be usable in TARGET_MODE. */
3016 void
3017 get_mode_bounds (scalar_int_mode mode, int sign,
3018 scalar_int_mode target_mode,
3019 rtx *mmin, rtx *mmax)
3021 unsigned size = GET_MODE_PRECISION (mode);
3022 unsigned HOST_WIDE_INT min_val, max_val;
3024 gcc_assert (size <= HOST_BITS_PER_WIDE_INT);
3026 /* Special case BImode, which has values 0 and STORE_FLAG_VALUE. */
3027 if (mode == BImode)
3029 if (STORE_FLAG_VALUE < 0)
3031 min_val = STORE_FLAG_VALUE;
3032 max_val = 0;
3034 else
3036 min_val = 0;
3037 max_val = STORE_FLAG_VALUE;
3040 else if (sign)
3042 min_val = -(HOST_WIDE_INT_1U << (size - 1));
3043 max_val = (HOST_WIDE_INT_1U << (size - 1)) - 1;
3045 else
3047 min_val = 0;
3048 max_val = (HOST_WIDE_INT_1U << (size - 1) << 1) - 1;
3051 *mmin = gen_int_mode (min_val, target_mode);
3052 *mmax = gen_int_mode (max_val, target_mode);
3055 #include "gt-stor-layout.h"