runtime: allow preemption in fast syscall return
[official-gcc.git] / gcc / stor-layout.c
blob5fdf81a9a25f567301215b57fff957aca23d8b40
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 && !DECL_PACKED (field))
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 type_align = MAX (type_align, desired_align);
1051 if (maximum_field_alignment != 0)
1052 type_align = MIN (type_align, maximum_field_alignment);
1053 rli->record_align = MAX (rli->record_align, type_align);
1054 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1057 else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
1059 /* Named bit-fields cause the entire structure to have the
1060 alignment implied by their type. Some targets also apply the same
1061 rules to unnamed bitfields. */
1062 if (DECL_NAME (field) != 0
1063 || targetm.align_anon_bitfield ())
1065 unsigned int type_align = TYPE_ALIGN (type);
1067 #ifdef ADJUST_FIELD_ALIGN
1068 if (! TYPE_USER_ALIGN (type))
1069 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1070 #endif
1072 /* Targets might chose to handle unnamed and hence possibly
1073 zero-width bitfield. Those are not influenced by #pragmas
1074 or packed attributes. */
1075 if (integer_zerop (DECL_SIZE (field)))
1077 if (initial_max_fld_align)
1078 type_align = MIN (type_align,
1079 initial_max_fld_align * BITS_PER_UNIT);
1081 else if (maximum_field_alignment != 0)
1082 type_align = MIN (type_align, maximum_field_alignment);
1083 else if (DECL_PACKED (field))
1084 type_align = MIN (type_align, BITS_PER_UNIT);
1086 /* The alignment of the record is increased to the maximum
1087 of the current alignment, the alignment indicated on the
1088 field (i.e., the alignment specified by an __aligned__
1089 attribute), and the alignment indicated by the type of
1090 the field. */
1091 rli->record_align = MAX (rli->record_align, desired_align);
1092 rli->record_align = MAX (rli->record_align, type_align);
1094 if (warn_packed)
1095 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1096 user_align |= TYPE_USER_ALIGN (type);
1099 else
1101 rli->record_align = MAX (rli->record_align, desired_align);
1102 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1105 TYPE_USER_ALIGN (rli->t) |= user_align;
1107 return desired_align;
1110 /* Issue a warning if the record alignment, RECORD_ALIGN, is less than
1111 the field alignment of FIELD or FIELD isn't aligned. */
1113 static void
1114 handle_warn_if_not_align (tree field, unsigned int record_align)
1116 tree type = TREE_TYPE (field);
1118 if (type == error_mark_node)
1119 return;
1121 unsigned int warn_if_not_align = 0;
1123 int opt_w = 0;
1125 if (warn_if_not_aligned)
1127 warn_if_not_align = DECL_WARN_IF_NOT_ALIGN (field);
1128 if (!warn_if_not_align)
1129 warn_if_not_align = TYPE_WARN_IF_NOT_ALIGN (type);
1130 if (warn_if_not_align)
1131 opt_w = OPT_Wif_not_aligned;
1134 if (!warn_if_not_align
1135 && warn_packed_not_aligned
1136 && lookup_attribute ("aligned", TYPE_ATTRIBUTES (type)))
1138 warn_if_not_align = TYPE_ALIGN (type);
1139 opt_w = OPT_Wpacked_not_aligned;
1142 if (!warn_if_not_align)
1143 return;
1145 tree context = DECL_CONTEXT (field);
1147 warn_if_not_align /= BITS_PER_UNIT;
1148 record_align /= BITS_PER_UNIT;
1149 if ((record_align % warn_if_not_align) != 0)
1150 warning (opt_w, "alignment %u of %qT is less than %u",
1151 record_align, context, warn_if_not_align);
1153 tree off = byte_position (field);
1154 if (!multiple_of_p (TREE_TYPE (off), off, size_int (warn_if_not_align)))
1156 if (TREE_CODE (off) == INTEGER_CST)
1157 warning (opt_w, "%q+D offset %E in %qT isn%'t aligned to %u",
1158 field, off, context, warn_if_not_align);
1159 else
1160 warning (opt_w, "%q+D offset %E in %qT may not be aligned to %u",
1161 field, off, context, warn_if_not_align);
1165 /* Called from place_field to handle unions. */
1167 static void
1168 place_union_field (record_layout_info rli, tree field)
1170 update_alignment_for_field (rli, field, /*known_align=*/0);
1172 DECL_FIELD_OFFSET (field) = size_zero_node;
1173 DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
1174 SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);
1175 handle_warn_if_not_align (field, rli->record_align);
1177 /* If this is an ERROR_MARK return *after* having set the
1178 field at the start of the union. This helps when parsing
1179 invalid fields. */
1180 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK)
1181 return;
1183 if (AGGREGATE_TYPE_P (TREE_TYPE (field))
1184 && TYPE_TYPELESS_STORAGE (TREE_TYPE (field)))
1185 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1187 /* We assume the union's size will be a multiple of a byte so we don't
1188 bother with BITPOS. */
1189 if (TREE_CODE (rli->t) == UNION_TYPE)
1190 rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1191 else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE)
1192 rli->offset = fold_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field),
1193 DECL_SIZE_UNIT (field), rli->offset);
1196 /* A bitfield of SIZE with a required access alignment of ALIGN is allocated
1197 at BYTE_OFFSET / BIT_OFFSET. Return nonzero if the field would span more
1198 units of alignment than the underlying TYPE. */
1199 static int
1200 excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset,
1201 HOST_WIDE_INT size, HOST_WIDE_INT align, tree type)
1203 /* Note that the calculation of OFFSET might overflow; we calculate it so
1204 that we still get the right result as long as ALIGN is a power of two. */
1205 unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset;
1207 offset = offset % align;
1208 return ((offset + size + align - 1) / align
1209 > tree_to_uhwi (TYPE_SIZE (type)) / align);
1212 /* RLI contains information about the layout of a RECORD_TYPE. FIELD
1213 is a FIELD_DECL to be added after those fields already present in
1214 T. (FIELD is not actually added to the TYPE_FIELDS list here;
1215 callers that desire that behavior must manually perform that step.) */
1217 void
1218 place_field (record_layout_info rli, tree field)
1220 /* The alignment required for FIELD. */
1221 unsigned int desired_align;
1222 /* The alignment FIELD would have if we just dropped it into the
1223 record as it presently stands. */
1224 unsigned int known_align;
1225 unsigned int actual_align;
1226 /* The type of this field. */
1227 tree type = TREE_TYPE (field);
1229 gcc_assert (TREE_CODE (field) != ERROR_MARK);
1231 /* If FIELD is static, then treat it like a separate variable, not
1232 really like a structure field. If it is a FUNCTION_DECL, it's a
1233 method. In both cases, all we do is lay out the decl, and we do
1234 it *after* the record is laid out. */
1235 if (VAR_P (field))
1237 vec_safe_push (rli->pending_statics, field);
1238 return;
1241 /* Enumerators and enum types which are local to this class need not
1242 be laid out. Likewise for initialized constant fields. */
1243 else if (TREE_CODE (field) != FIELD_DECL)
1244 return;
1246 /* Unions are laid out very differently than records, so split
1247 that code off to another function. */
1248 else if (TREE_CODE (rli->t) != RECORD_TYPE)
1250 place_union_field (rli, field);
1251 return;
1254 else if (TREE_CODE (type) == ERROR_MARK)
1256 /* Place this field at the current allocation position, so we
1257 maintain monotonicity. */
1258 DECL_FIELD_OFFSET (field) = rli->offset;
1259 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1260 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1261 handle_warn_if_not_align (field, rli->record_align);
1262 return;
1265 if (AGGREGATE_TYPE_P (type)
1266 && TYPE_TYPELESS_STORAGE (type))
1267 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1269 /* Work out the known alignment so far. Note that A & (-A) is the
1270 value of the least-significant bit in A that is one. */
1271 if (! integer_zerop (rli->bitpos))
1272 known_align = least_bit_hwi (tree_to_uhwi (rli->bitpos));
1273 else if (integer_zerop (rli->offset))
1274 known_align = 0;
1275 else if (tree_fits_uhwi_p (rli->offset))
1276 known_align = (BITS_PER_UNIT
1277 * least_bit_hwi (tree_to_uhwi (rli->offset)));
1278 else
1279 known_align = rli->offset_align;
1281 desired_align = update_alignment_for_field (rli, field, known_align);
1282 if (known_align == 0)
1283 known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1285 if (warn_packed && DECL_PACKED (field))
1287 if (known_align >= TYPE_ALIGN (type))
1289 if (TYPE_ALIGN (type) > desired_align)
1291 if (STRICT_ALIGNMENT)
1292 warning (OPT_Wattributes, "packed attribute causes "
1293 "inefficient alignment for %q+D", field);
1294 /* Don't warn if DECL_PACKED was set by the type. */
1295 else if (!TYPE_PACKED (rli->t))
1296 warning (OPT_Wattributes, "packed attribute is "
1297 "unnecessary for %q+D", field);
1300 else
1301 rli->packed_maybe_necessary = 1;
1304 /* Does this field automatically have alignment it needs by virtue
1305 of the fields that precede it and the record's own alignment? */
1306 if (known_align < desired_align)
1308 /* No, we need to skip space before this field.
1309 Bump the cumulative size to multiple of field alignment. */
1311 if (!targetm.ms_bitfield_layout_p (rli->t)
1312 && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION)
1313 warning (OPT_Wpadded, "padding struct to align %q+D", field);
1315 /* If the alignment is still within offset_align, just align
1316 the bit position. */
1317 if (desired_align < rli->offset_align)
1318 rli->bitpos = round_up (rli->bitpos, desired_align);
1319 else
1321 /* First adjust OFFSET by the partial bits, then align. */
1322 rli->offset
1323 = size_binop (PLUS_EXPR, rli->offset,
1324 fold_convert (sizetype,
1325 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1326 bitsize_unit_node)));
1327 rli->bitpos = bitsize_zero_node;
1329 rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT);
1332 if (! TREE_CONSTANT (rli->offset))
1333 rli->offset_align = desired_align;
1334 if (targetm.ms_bitfield_layout_p (rli->t))
1335 rli->prev_field = NULL;
1338 /* Handle compatibility with PCC. Note that if the record has any
1339 variable-sized fields, we need not worry about compatibility. */
1340 if (PCC_BITFIELD_TYPE_MATTERS
1341 && ! targetm.ms_bitfield_layout_p (rli->t)
1342 && TREE_CODE (field) == FIELD_DECL
1343 && type != error_mark_node
1344 && DECL_BIT_FIELD (field)
1345 && (! DECL_PACKED (field)
1346 /* Enter for these packed fields only to issue a warning. */
1347 || TYPE_ALIGN (type) <= BITS_PER_UNIT)
1348 && maximum_field_alignment == 0
1349 && ! integer_zerop (DECL_SIZE (field))
1350 && tree_fits_uhwi_p (DECL_SIZE (field))
1351 && tree_fits_uhwi_p (rli->offset)
1352 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1354 unsigned int type_align = TYPE_ALIGN (type);
1355 tree dsize = DECL_SIZE (field);
1356 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1357 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1358 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1360 #ifdef ADJUST_FIELD_ALIGN
1361 if (! TYPE_USER_ALIGN (type))
1362 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1363 #endif
1365 /* A bit field may not span more units of alignment of its type
1366 than its type itself. Advance to next boundary if necessary. */
1367 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1369 if (DECL_PACKED (field))
1371 if (warn_packed_bitfield_compat == 1)
1372 inform
1373 (input_location,
1374 "offset of packed bit-field %qD has changed in GCC 4.4",
1375 field);
1377 else
1378 rli->bitpos = round_up (rli->bitpos, type_align);
1381 if (! DECL_PACKED (field))
1382 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1384 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1385 TYPE_WARN_IF_NOT_ALIGN (type));
1388 #ifdef BITFIELD_NBYTES_LIMITED
1389 if (BITFIELD_NBYTES_LIMITED
1390 && ! targetm.ms_bitfield_layout_p (rli->t)
1391 && TREE_CODE (field) == FIELD_DECL
1392 && type != error_mark_node
1393 && DECL_BIT_FIELD_TYPE (field)
1394 && ! DECL_PACKED (field)
1395 && ! integer_zerop (DECL_SIZE (field))
1396 && tree_fits_uhwi_p (DECL_SIZE (field))
1397 && tree_fits_uhwi_p (rli->offset)
1398 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1400 unsigned int type_align = TYPE_ALIGN (type);
1401 tree dsize = DECL_SIZE (field);
1402 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1403 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1404 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1406 #ifdef ADJUST_FIELD_ALIGN
1407 if (! TYPE_USER_ALIGN (type))
1408 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1409 #endif
1411 if (maximum_field_alignment != 0)
1412 type_align = MIN (type_align, maximum_field_alignment);
1413 /* ??? This test is opposite the test in the containing if
1414 statement, so this code is unreachable currently. */
1415 else if (DECL_PACKED (field))
1416 type_align = MIN (type_align, BITS_PER_UNIT);
1418 /* A bit field may not span the unit of alignment of its type.
1419 Advance to next boundary if necessary. */
1420 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1421 rli->bitpos = round_up (rli->bitpos, type_align);
1423 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1424 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1425 TYPE_WARN_IF_NOT_ALIGN (type));
1427 #endif
1429 /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
1430 A subtlety:
1431 When a bit field is inserted into a packed record, the whole
1432 size of the underlying type is used by one or more same-size
1433 adjacent bitfields. (That is, if its long:3, 32 bits is
1434 used in the record, and any additional adjacent long bitfields are
1435 packed into the same chunk of 32 bits. However, if the size
1436 changes, a new field of that size is allocated.) In an unpacked
1437 record, this is the same as using alignment, but not equivalent
1438 when packing.
1440 Note: for compatibility, we use the type size, not the type alignment
1441 to determine alignment, since that matches the documentation */
1443 if (targetm.ms_bitfield_layout_p (rli->t))
1445 tree prev_saved = rli->prev_field;
1446 tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;
1448 /* This is a bitfield if it exists. */
1449 if (rli->prev_field)
1451 /* If both are bitfields, nonzero, and the same size, this is
1452 the middle of a run. Zero declared size fields are special
1453 and handled as "end of run". (Note: it's nonzero declared
1454 size, but equal type sizes!) (Since we know that both
1455 the current and previous fields are bitfields by the
1456 time we check it, DECL_SIZE must be present for both.) */
1457 if (DECL_BIT_FIELD_TYPE (field)
1458 && !integer_zerop (DECL_SIZE (field))
1459 && !integer_zerop (DECL_SIZE (rli->prev_field))
1460 && tree_fits_shwi_p (DECL_SIZE (rli->prev_field))
1461 && tree_fits_uhwi_p (TYPE_SIZE (type))
1462 && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
1464 /* We're in the middle of a run of equal type size fields; make
1465 sure we realign if we run out of bits. (Not decl size,
1466 type size!) */
1467 HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field));
1469 if (rli->remaining_in_alignment < bitsize)
1471 HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type));
1473 /* out of bits; bump up to next 'word'. */
1474 rli->bitpos
1475 = size_binop (PLUS_EXPR, rli->bitpos,
1476 bitsize_int (rli->remaining_in_alignment));
1477 rli->prev_field = field;
1478 if (typesize < bitsize)
1479 rli->remaining_in_alignment = 0;
1480 else
1481 rli->remaining_in_alignment = typesize - bitsize;
1483 else
1484 rli->remaining_in_alignment -= bitsize;
1486 else
1488 /* End of a run: if leaving a run of bitfields of the same type
1489 size, we have to "use up" the rest of the bits of the type
1490 size.
1492 Compute the new position as the sum of the size for the prior
1493 type and where we first started working on that type.
1494 Note: since the beginning of the field was aligned then
1495 of course the end will be too. No round needed. */
1497 if (!integer_zerop (DECL_SIZE (rli->prev_field)))
1499 rli->bitpos
1500 = size_binop (PLUS_EXPR, rli->bitpos,
1501 bitsize_int (rli->remaining_in_alignment));
1503 else
1504 /* We "use up" size zero fields; the code below should behave
1505 as if the prior field was not a bitfield. */
1506 prev_saved = NULL;
1508 /* Cause a new bitfield to be captured, either this time (if
1509 currently a bitfield) or next time we see one. */
1510 if (!DECL_BIT_FIELD_TYPE (field)
1511 || integer_zerop (DECL_SIZE (field)))
1512 rli->prev_field = NULL;
1515 normalize_rli (rli);
1518 /* If we're starting a new run of same type size bitfields
1519 (or a run of non-bitfields), set up the "first of the run"
1520 fields.
1522 That is, if the current field is not a bitfield, or if there
1523 was a prior bitfield the type sizes differ, or if there wasn't
1524 a prior bitfield the size of the current field is nonzero.
1526 Note: we must be sure to test ONLY the type size if there was
1527 a prior bitfield and ONLY for the current field being zero if
1528 there wasn't. */
1530 if (!DECL_BIT_FIELD_TYPE (field)
1531 || (prev_saved != NULL
1532 ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
1533 : !integer_zerop (DECL_SIZE (field)) ))
1535 /* Never smaller than a byte for compatibility. */
1536 unsigned int type_align = BITS_PER_UNIT;
1538 /* (When not a bitfield), we could be seeing a flex array (with
1539 no DECL_SIZE). Since we won't be using remaining_in_alignment
1540 until we see a bitfield (and come by here again) we just skip
1541 calculating it. */
1542 if (DECL_SIZE (field) != NULL
1543 && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field)))
1544 && tree_fits_uhwi_p (DECL_SIZE (field)))
1546 unsigned HOST_WIDE_INT bitsize
1547 = tree_to_uhwi (DECL_SIZE (field));
1548 unsigned HOST_WIDE_INT typesize
1549 = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field)));
1551 if (typesize < bitsize)
1552 rli->remaining_in_alignment = 0;
1553 else
1554 rli->remaining_in_alignment = typesize - bitsize;
1557 /* Now align (conventionally) for the new type. */
1558 type_align = TYPE_ALIGN (TREE_TYPE (field));
1560 if (maximum_field_alignment != 0)
1561 type_align = MIN (type_align, maximum_field_alignment);
1563 rli->bitpos = round_up (rli->bitpos, type_align);
1565 /* If we really aligned, don't allow subsequent bitfields
1566 to undo that. */
1567 rli->prev_field = NULL;
1571 /* Offset so far becomes the position of this field after normalizing. */
1572 normalize_rli (rli);
1573 DECL_FIELD_OFFSET (field) = rli->offset;
1574 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1575 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1576 handle_warn_if_not_align (field, rli->record_align);
1578 /* Evaluate nonconstant offsets only once, either now or as soon as safe. */
1579 if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
1580 DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));
1582 /* If this field ended up more aligned than we thought it would be (we
1583 approximate this by seeing if its position changed), lay out the field
1584 again; perhaps we can use an integral mode for it now. */
1585 if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field)))
1586 actual_align = least_bit_hwi (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)));
1587 else if (integer_zerop (DECL_FIELD_OFFSET (field)))
1588 actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1589 else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
1590 actual_align = (BITS_PER_UNIT
1591 * least_bit_hwi (tree_to_uhwi (DECL_FIELD_OFFSET (field))));
1592 else
1593 actual_align = DECL_OFFSET_ALIGN (field);
1594 /* ACTUAL_ALIGN is still the actual alignment *within the record* .
1595 store / extract bit field operations will check the alignment of the
1596 record against the mode of bit fields. */
1598 if (known_align != actual_align)
1599 layout_decl (field, actual_align);
1601 if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field))
1602 rli->prev_field = field;
1604 /* Now add size of this field to the size of the record. If the size is
1605 not constant, treat the field as being a multiple of bytes and just
1606 adjust the offset, resetting the bit position. Otherwise, apportion the
1607 size amongst the bit position and offset. First handle the case of an
1608 unspecified size, which can happen when we have an invalid nested struct
1609 definition, such as struct j { struct j { int i; } }. The error message
1610 is printed in finish_struct. */
1611 if (DECL_SIZE (field) == 0)
1612 /* Do nothing. */;
1613 else if (TREE_CODE (DECL_SIZE (field)) != INTEGER_CST
1614 || TREE_OVERFLOW (DECL_SIZE (field)))
1616 rli->offset
1617 = size_binop (PLUS_EXPR, rli->offset,
1618 fold_convert (sizetype,
1619 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1620 bitsize_unit_node)));
1621 rli->offset
1622 = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1623 rli->bitpos = bitsize_zero_node;
1624 rli->offset_align = MIN (rli->offset_align, desired_align);
1626 if (!multiple_of_p (bitsizetype, DECL_SIZE (field),
1627 bitsize_int (rli->offset_align)))
1629 tree type = strip_array_types (TREE_TYPE (field));
1630 /* The above adjusts offset_align just based on the start of the
1631 field. The field might not have a size that is a multiple of
1632 that offset_align though. If the field is an array of fixed
1633 sized elements, assume there can be any multiple of those
1634 sizes. If it is a variable length aggregate or array of
1635 variable length aggregates, assume worst that the end is
1636 just BITS_PER_UNIT aligned. */
1637 if (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
1639 if (TREE_INT_CST_LOW (TYPE_SIZE (type)))
1641 unsigned HOST_WIDE_INT sz
1642 = least_bit_hwi (TREE_INT_CST_LOW (TYPE_SIZE (type)));
1643 rli->offset_align = MIN (rli->offset_align, sz);
1646 else
1647 rli->offset_align = MIN (rli->offset_align, BITS_PER_UNIT);
1650 else if (targetm.ms_bitfield_layout_p (rli->t))
1652 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1654 /* If we ended a bitfield before the full length of the type then
1655 pad the struct out to the full length of the last type. */
1656 if ((DECL_CHAIN (field) == NULL
1657 || TREE_CODE (DECL_CHAIN (field)) != FIELD_DECL)
1658 && DECL_BIT_FIELD_TYPE (field)
1659 && !integer_zerop (DECL_SIZE (field)))
1660 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos,
1661 bitsize_int (rli->remaining_in_alignment));
1663 normalize_rli (rli);
1665 else
1667 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1668 normalize_rli (rli);
1672 /* Assuming that all the fields have been laid out, this function uses
1673 RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type
1674 indicated by RLI. */
1676 static void
1677 finalize_record_size (record_layout_info rli)
1679 tree unpadded_size, unpadded_size_unit;
1681 /* Now we want just byte and bit offsets, so set the offset alignment
1682 to be a byte and then normalize. */
1683 rli->offset_align = BITS_PER_UNIT;
1684 normalize_rli (rli);
1686 /* Determine the desired alignment. */
1687 #ifdef ROUND_TYPE_ALIGN
1688 SET_TYPE_ALIGN (rli->t, ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t),
1689 rli->record_align));
1690 #else
1691 SET_TYPE_ALIGN (rli->t, MAX (TYPE_ALIGN (rli->t), rli->record_align));
1692 #endif
1694 /* Compute the size so far. Be sure to allow for extra bits in the
1695 size in bytes. We have guaranteed above that it will be no more
1696 than a single byte. */
1697 unpadded_size = rli_size_so_far (rli);
1698 unpadded_size_unit = rli_size_unit_so_far (rli);
1699 if (! integer_zerop (rli->bitpos))
1700 unpadded_size_unit
1701 = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node);
1703 /* Round the size up to be a multiple of the required alignment. */
1704 TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
1705 TYPE_SIZE_UNIT (rli->t)
1706 = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t));
1708 if (TREE_CONSTANT (unpadded_size)
1709 && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0
1710 && input_location != BUILTINS_LOCATION)
1711 warning (OPT_Wpadded, "padding struct size to alignment boundary");
1713 if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE
1714 && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary
1715 && TREE_CONSTANT (unpadded_size))
1717 tree unpacked_size;
1719 #ifdef ROUND_TYPE_ALIGN
1720 rli->unpacked_align
1721 = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align);
1722 #else
1723 rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align);
1724 #endif
1726 unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
1727 if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
1729 if (TYPE_NAME (rli->t))
1731 tree name;
1733 if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE)
1734 name = TYPE_NAME (rli->t);
1735 else
1736 name = DECL_NAME (TYPE_NAME (rli->t));
1738 if (STRICT_ALIGNMENT)
1739 warning (OPT_Wpacked, "packed attribute causes inefficient "
1740 "alignment for %qE", name);
1741 else
1742 warning (OPT_Wpacked,
1743 "packed attribute is unnecessary for %qE", name);
1745 else
1747 if (STRICT_ALIGNMENT)
1748 warning (OPT_Wpacked,
1749 "packed attribute causes inefficient alignment");
1750 else
1751 warning (OPT_Wpacked, "packed attribute is unnecessary");
1757 /* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE). */
1759 void
1760 compute_record_mode (tree type)
1762 tree field;
1763 machine_mode mode = VOIDmode;
1765 /* Most RECORD_TYPEs have BLKmode, so we start off assuming that.
1766 However, if possible, we use a mode that fits in a register
1767 instead, in order to allow for better optimization down the
1768 line. */
1769 SET_TYPE_MODE (type, BLKmode);
1771 if (! tree_fits_uhwi_p (TYPE_SIZE (type)))
1772 return;
1774 /* A record which has any BLKmode members must itself be
1775 BLKmode; it can't go in a register. Unless the member is
1776 BLKmode only because it isn't aligned. */
1777 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
1779 if (TREE_CODE (field) != FIELD_DECL)
1780 continue;
1782 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK
1783 || (TYPE_MODE (TREE_TYPE (field)) == BLKmode
1784 && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field))
1785 && !(TYPE_SIZE (TREE_TYPE (field)) != 0
1786 && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
1787 || ! tree_fits_uhwi_p (bit_position (field))
1788 || DECL_SIZE (field) == 0
1789 || ! tree_fits_uhwi_p (DECL_SIZE (field)))
1790 return;
1792 /* If this field is the whole struct, remember its mode so
1793 that, say, we can put a double in a class into a DF
1794 register instead of forcing it to live in the stack. */
1795 if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field)))
1796 mode = DECL_MODE (field);
1798 /* With some targets, it is sub-optimal to access an aligned
1799 BLKmode structure as a scalar. */
1800 if (targetm.member_type_forces_blk (field, mode))
1801 return;
1804 /* If we only have one real field; use its mode if that mode's size
1805 matches the type's size. This only applies to RECORD_TYPE. This
1806 does not apply to unions. */
1807 if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode
1808 && tree_fits_uhwi_p (TYPE_SIZE (type))
1809 && known_eq (GET_MODE_BITSIZE (mode), tree_to_uhwi (TYPE_SIZE (type))))
1811 else
1812 mode = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1).else_blk ();
1814 /* If structure's known alignment is less than what the scalar
1815 mode would need, and it matters, then stick with BLKmode. */
1816 if (mode != BLKmode
1817 && STRICT_ALIGNMENT
1818 && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT
1819 || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (mode)))
1821 /* If this is the only reason this type is BLKmode, then
1822 don't force containing types to be BLKmode. */
1823 TYPE_NO_FORCE_BLK (type) = 1;
1824 mode = BLKmode;
1827 SET_TYPE_MODE (type, mode);
1830 /* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid
1831 out. */
1833 static void
1834 finalize_type_size (tree type)
1836 /* Normally, use the alignment corresponding to the mode chosen.
1837 However, where strict alignment is not required, avoid
1838 over-aligning structures, since most compilers do not do this
1839 alignment. */
1840 if (TYPE_MODE (type) != BLKmode
1841 && TYPE_MODE (type) != VOIDmode
1842 && (STRICT_ALIGNMENT || !AGGREGATE_TYPE_P (type)))
1844 unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type));
1846 /* Don't override a larger alignment requirement coming from a user
1847 alignment of one of the fields. */
1848 if (mode_align >= TYPE_ALIGN (type))
1850 SET_TYPE_ALIGN (type, mode_align);
1851 TYPE_USER_ALIGN (type) = 0;
1855 /* Do machine-dependent extra alignment. */
1856 #ifdef ROUND_TYPE_ALIGN
1857 SET_TYPE_ALIGN (type,
1858 ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT));
1859 #endif
1861 /* If we failed to find a simple way to calculate the unit size
1862 of the type, find it by division. */
1863 if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0)
1864 /* TYPE_SIZE (type) is computed in bitsizetype. After the division, the
1865 result will fit in sizetype. We will get more efficient code using
1866 sizetype, so we force a conversion. */
1867 TYPE_SIZE_UNIT (type)
1868 = fold_convert (sizetype,
1869 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
1870 bitsize_unit_node));
1872 if (TYPE_SIZE (type) != 0)
1874 TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
1875 TYPE_SIZE_UNIT (type)
1876 = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type));
1879 /* Evaluate nonconstant sizes only once, either now or as soon as safe. */
1880 if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
1881 TYPE_SIZE (type) = variable_size (TYPE_SIZE (type));
1882 if (TYPE_SIZE_UNIT (type) != 0
1883 && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST)
1884 TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type));
1886 /* Also layout any other variants of the type. */
1887 if (TYPE_NEXT_VARIANT (type)
1888 || type != TYPE_MAIN_VARIANT (type))
1890 tree variant;
1891 /* Record layout info of this variant. */
1892 tree size = TYPE_SIZE (type);
1893 tree size_unit = TYPE_SIZE_UNIT (type);
1894 unsigned int align = TYPE_ALIGN (type);
1895 unsigned int precision = TYPE_PRECISION (type);
1896 unsigned int user_align = TYPE_USER_ALIGN (type);
1897 machine_mode mode = TYPE_MODE (type);
1899 /* Copy it into all variants. */
1900 for (variant = TYPE_MAIN_VARIANT (type);
1901 variant != 0;
1902 variant = TYPE_NEXT_VARIANT (variant))
1904 TYPE_SIZE (variant) = size;
1905 TYPE_SIZE_UNIT (variant) = size_unit;
1906 unsigned valign = align;
1907 if (TYPE_USER_ALIGN (variant))
1908 valign = MAX (valign, TYPE_ALIGN (variant));
1909 else
1910 TYPE_USER_ALIGN (variant) = user_align;
1911 SET_TYPE_ALIGN (variant, valign);
1912 TYPE_PRECISION (variant) = precision;
1913 SET_TYPE_MODE (variant, mode);
1917 /* Handle empty records as per the x86-64 psABI. */
1918 TYPE_EMPTY_P (type) = targetm.calls.empty_record_p (type);
1921 /* Return a new underlying object for a bitfield started with FIELD. */
1923 static tree
1924 start_bitfield_representative (tree field)
1926 tree repr = make_node (FIELD_DECL);
1927 DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field);
1928 /* Force the representative to begin at a BITS_PER_UNIT aligned
1929 boundary - C++ may use tail-padding of a base object to
1930 continue packing bits so the bitfield region does not start
1931 at bit zero (see g++.dg/abi/bitfield5.C for example).
1932 Unallocated bits may happen for other reasons as well,
1933 for example Ada which allows explicit bit-granular structure layout. */
1934 DECL_FIELD_BIT_OFFSET (repr)
1935 = size_binop (BIT_AND_EXPR,
1936 DECL_FIELD_BIT_OFFSET (field),
1937 bitsize_int (~(BITS_PER_UNIT - 1)));
1938 SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field));
1939 DECL_SIZE (repr) = DECL_SIZE (field);
1940 DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
1941 DECL_PACKED (repr) = DECL_PACKED (field);
1942 DECL_CONTEXT (repr) = DECL_CONTEXT (field);
1943 /* There are no indirect accesses to this field. If we introduce
1944 some then they have to use the record alias set. This makes
1945 sure to properly conflict with [indirect] accesses to addressable
1946 fields of the bitfield group. */
1947 DECL_NONADDRESSABLE_P (repr) = 1;
1948 return repr;
1951 /* Finish up a bitfield group that was started by creating the underlying
1952 object REPR with the last field in the bitfield group FIELD. */
1954 static void
1955 finish_bitfield_representative (tree repr, tree field)
1957 unsigned HOST_WIDE_INT bitsize, maxbitsize;
1958 tree nextf, size;
1960 size = size_diffop (DECL_FIELD_OFFSET (field),
1961 DECL_FIELD_OFFSET (repr));
1962 while (TREE_CODE (size) == COMPOUND_EXPR)
1963 size = TREE_OPERAND (size, 1);
1964 gcc_assert (tree_fits_uhwi_p (size));
1965 bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
1966 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
1967 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))
1968 + tree_to_uhwi (DECL_SIZE (field)));
1970 /* Round up bitsize to multiples of BITS_PER_UNIT. */
1971 bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
1973 /* Now nothing tells us how to pad out bitsize ... */
1974 nextf = DECL_CHAIN (field);
1975 while (nextf && TREE_CODE (nextf) != FIELD_DECL)
1976 nextf = DECL_CHAIN (nextf);
1977 if (nextf)
1979 tree maxsize;
1980 /* If there was an error, the field may be not laid out
1981 correctly. Don't bother to do anything. */
1982 if (TREE_TYPE (nextf) == error_mark_node)
1983 return;
1984 maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
1985 DECL_FIELD_OFFSET (repr));
1986 if (tree_fits_uhwi_p (maxsize))
1988 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
1989 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf))
1990 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
1991 /* If the group ends within a bitfield nextf does not need to be
1992 aligned to BITS_PER_UNIT. Thus round up. */
1993 maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
1995 else
1996 maxbitsize = bitsize;
1998 else
2000 /* Note that if the C++ FE sets up tail-padding to be re-used it
2001 creates a as-base variant of the type with TYPE_SIZE adjusted
2002 accordingly. So it is safe to include tail-padding here. */
2003 tree aggsize = lang_hooks.types.unit_size_without_reusable_padding
2004 (DECL_CONTEXT (field));
2005 tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr));
2006 /* We cannot generally rely on maxsize to fold to an integer constant,
2007 so use bitsize as fallback for this case. */
2008 if (tree_fits_uhwi_p (maxsize))
2009 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
2010 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
2011 else
2012 maxbitsize = bitsize;
2015 /* Only if we don't artificially break up the representative in
2016 the middle of a large bitfield with different possibly
2017 overlapping representatives. And all representatives start
2018 at byte offset. */
2019 gcc_assert (maxbitsize % BITS_PER_UNIT == 0);
2021 /* Find the smallest nice mode to use. */
2022 opt_scalar_int_mode mode_iter;
2023 FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_INT)
2024 if (GET_MODE_BITSIZE (mode_iter.require ()) >= bitsize)
2025 break;
2027 scalar_int_mode mode;
2028 if (!mode_iter.exists (&mode)
2029 || GET_MODE_BITSIZE (mode) > maxbitsize
2030 || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE)
2032 /* We really want a BLKmode representative only as a last resort,
2033 considering the member b in
2034 struct { int a : 7; int b : 17; int c; } __attribute__((packed));
2035 Otherwise we simply want to split the representative up
2036 allowing for overlaps within the bitfield region as required for
2037 struct { int a : 7; int b : 7;
2038 int c : 10; int d; } __attribute__((packed));
2039 [0, 15] HImode for a and b, [8, 23] HImode for c. */
2040 DECL_SIZE (repr) = bitsize_int (bitsize);
2041 DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT);
2042 SET_DECL_MODE (repr, BLKmode);
2043 TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node,
2044 bitsize / BITS_PER_UNIT);
2046 else
2048 unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode);
2049 DECL_SIZE (repr) = bitsize_int (modesize);
2050 DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT);
2051 SET_DECL_MODE (repr, mode);
2052 TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1);
2055 /* Remember whether the bitfield group is at the end of the
2056 structure or not. */
2057 DECL_CHAIN (repr) = nextf;
2060 /* Compute and set FIELD_DECLs for the underlying objects we should
2061 use for bitfield access for the structure T. */
2063 void
2064 finish_bitfield_layout (tree t)
2066 tree field, prev;
2067 tree repr = NULL_TREE;
2069 /* Unions would be special, for the ease of type-punning optimizations
2070 we could use the underlying type as hint for the representative
2071 if the bitfield would fit and the representative would not exceed
2072 the union in size. */
2073 if (TREE_CODE (t) != RECORD_TYPE)
2074 return;
2076 for (prev = NULL_TREE, field = TYPE_FIELDS (t);
2077 field; field = DECL_CHAIN (field))
2079 if (TREE_CODE (field) != FIELD_DECL)
2080 continue;
2082 /* In the C++ memory model, consecutive bit fields in a structure are
2083 considered one memory location and updating a memory location
2084 may not store into adjacent memory locations. */
2085 if (!repr
2086 && DECL_BIT_FIELD_TYPE (field))
2088 /* Start new representative. */
2089 repr = start_bitfield_representative (field);
2091 else if (repr
2092 && ! DECL_BIT_FIELD_TYPE (field))
2094 /* Finish off new representative. */
2095 finish_bitfield_representative (repr, prev);
2096 repr = NULL_TREE;
2098 else if (DECL_BIT_FIELD_TYPE (field))
2100 gcc_assert (repr != NULL_TREE);
2102 /* Zero-size bitfields finish off a representative and
2103 do not have a representative themselves. This is
2104 required by the C++ memory model. */
2105 if (integer_zerop (DECL_SIZE (field)))
2107 finish_bitfield_representative (repr, prev);
2108 repr = NULL_TREE;
2111 /* We assume that either DECL_FIELD_OFFSET of the representative
2112 and each bitfield member is a constant or they are equal.
2113 This is because we need to be able to compute the bit-offset
2114 of each field relative to the representative in get_bit_range
2115 during RTL expansion.
2116 If these constraints are not met, simply force a new
2117 representative to be generated. That will at most
2118 generate worse code but still maintain correctness with
2119 respect to the C++ memory model. */
2120 else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr))
2121 && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
2122 || operand_equal_p (DECL_FIELD_OFFSET (repr),
2123 DECL_FIELD_OFFSET (field), 0)))
2125 finish_bitfield_representative (repr, prev);
2126 repr = start_bitfield_representative (field);
2129 else
2130 continue;
2132 if (repr)
2133 DECL_BIT_FIELD_REPRESENTATIVE (field) = repr;
2135 prev = field;
2138 if (repr)
2139 finish_bitfield_representative (repr, prev);
2142 /* Do all of the work required to layout the type indicated by RLI,
2143 once the fields have been laid out. This function will call `free'
2144 for RLI, unless FREE_P is false. Passing a value other than false
2145 for FREE_P is bad practice; this option only exists to support the
2146 G++ 3.2 ABI. */
2148 void
2149 finish_record_layout (record_layout_info rli, int free_p)
2151 tree variant;
2153 /* Compute the final size. */
2154 finalize_record_size (rli);
2156 /* Compute the TYPE_MODE for the record. */
2157 compute_record_mode (rli->t);
2159 /* Perform any last tweaks to the TYPE_SIZE, etc. */
2160 finalize_type_size (rli->t);
2162 /* Compute bitfield representatives. */
2163 finish_bitfield_layout (rli->t);
2165 /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants.
2166 With C++ templates, it is too early to do this when the attribute
2167 is being parsed. */
2168 for (variant = TYPE_NEXT_VARIANT (rli->t); variant;
2169 variant = TYPE_NEXT_VARIANT (variant))
2171 TYPE_PACKED (variant) = TYPE_PACKED (rli->t);
2172 TYPE_REVERSE_STORAGE_ORDER (variant)
2173 = TYPE_REVERSE_STORAGE_ORDER (rli->t);
2176 /* Lay out any static members. This is done now because their type
2177 may use the record's type. */
2178 while (!vec_safe_is_empty (rli->pending_statics))
2179 layout_decl (rli->pending_statics->pop (), 0);
2181 /* Clean up. */
2182 if (free_p)
2184 vec_free (rli->pending_statics);
2185 free (rli);
2190 /* Finish processing a builtin RECORD_TYPE type TYPE. It's name is
2191 NAME, its fields are chained in reverse on FIELDS.
2193 If ALIGN_TYPE is non-null, it is given the same alignment as
2194 ALIGN_TYPE. */
2196 void
2197 finish_builtin_struct (tree type, const char *name, tree fields,
2198 tree align_type)
2200 tree tail, next;
2202 for (tail = NULL_TREE; fields; tail = fields, fields = next)
2204 DECL_FIELD_CONTEXT (fields) = type;
2205 next = DECL_CHAIN (fields);
2206 DECL_CHAIN (fields) = tail;
2208 TYPE_FIELDS (type) = tail;
2210 if (align_type)
2212 SET_TYPE_ALIGN (type, TYPE_ALIGN (align_type));
2213 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type);
2214 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2215 TYPE_WARN_IF_NOT_ALIGN (align_type));
2218 layout_type (type);
2219 #if 0 /* not yet, should get fixed properly later */
2220 TYPE_NAME (type) = make_type_decl (get_identifier (name), type);
2221 #else
2222 TYPE_NAME (type) = build_decl (BUILTINS_LOCATION,
2223 TYPE_DECL, get_identifier (name), type);
2224 #endif
2225 TYPE_STUB_DECL (type) = TYPE_NAME (type);
2226 layout_decl (TYPE_NAME (type), 0);
2229 /* Calculate the mode, size, and alignment for TYPE.
2230 For an array type, calculate the element separation as well.
2231 Record TYPE on the chain of permanent or temporary types
2232 so that dbxout will find out about it.
2234 TYPE_SIZE of a type is nonzero if the type has been laid out already.
2235 layout_type does nothing on such a type.
2237 If the type is incomplete, its TYPE_SIZE remains zero. */
2239 void
2240 layout_type (tree type)
2242 gcc_assert (type);
2244 if (type == error_mark_node)
2245 return;
2247 /* We don't want finalize_type_size to copy an alignment attribute to
2248 variants that don't have it. */
2249 type = TYPE_MAIN_VARIANT (type);
2251 /* Do nothing if type has been laid out before. */
2252 if (TYPE_SIZE (type))
2253 return;
2255 switch (TREE_CODE (type))
2257 case LANG_TYPE:
2258 /* This kind of type is the responsibility
2259 of the language-specific code. */
2260 gcc_unreachable ();
2262 case BOOLEAN_TYPE:
2263 case INTEGER_TYPE:
2264 case ENUMERAL_TYPE:
2266 scalar_int_mode mode
2267 = smallest_int_mode_for_size (TYPE_PRECISION (type));
2268 SET_TYPE_MODE (type, mode);
2269 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2270 /* Don't set TYPE_PRECISION here, as it may be set by a bitfield. */
2271 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2272 break;
2275 case REAL_TYPE:
2277 /* Allow the caller to choose the type mode, which is how decimal
2278 floats are distinguished from binary ones. */
2279 if (TYPE_MODE (type) == VOIDmode)
2280 SET_TYPE_MODE
2281 (type, float_mode_for_size (TYPE_PRECISION (type)).require ());
2282 scalar_float_mode mode = as_a <scalar_float_mode> (TYPE_MODE (type));
2283 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2284 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2285 break;
2288 case FIXED_POINT_TYPE:
2290 /* TYPE_MODE (type) has been set already. */
2291 scalar_mode mode = SCALAR_TYPE_MODE (type);
2292 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2293 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2294 break;
2297 case COMPLEX_TYPE:
2298 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2299 SET_TYPE_MODE (type,
2300 GET_MODE_COMPLEX_MODE (TYPE_MODE (TREE_TYPE (type))));
2302 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2303 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2304 break;
2306 case VECTOR_TYPE:
2308 poly_uint64 nunits = TYPE_VECTOR_SUBPARTS (type);
2309 tree innertype = TREE_TYPE (type);
2311 /* Find an appropriate mode for the vector type. */
2312 if (TYPE_MODE (type) == VOIDmode)
2313 SET_TYPE_MODE (type,
2314 mode_for_vector (SCALAR_TYPE_MODE (innertype),
2315 nunits).else_blk ());
2317 TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type));
2318 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2319 /* Several boolean vector elements may fit in a single unit. */
2320 if (VECTOR_BOOLEAN_TYPE_P (type)
2321 && type->type_common.mode != BLKmode)
2322 TYPE_SIZE_UNIT (type)
2323 = size_int (GET_MODE_SIZE (type->type_common.mode));
2324 else
2325 TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR,
2326 TYPE_SIZE_UNIT (innertype),
2327 size_int (nunits));
2328 TYPE_SIZE (type) = int_const_binop
2329 (MULT_EXPR,
2330 bits_from_bytes (TYPE_SIZE_UNIT (type)),
2331 bitsize_int (BITS_PER_UNIT));
2333 /* For vector types, we do not default to the mode's alignment.
2334 Instead, query a target hook, defaulting to natural alignment.
2335 This prevents ABI changes depending on whether or not native
2336 vector modes are supported. */
2337 SET_TYPE_ALIGN (type, targetm.vector_alignment (type));
2339 /* However, if the underlying mode requires a bigger alignment than
2340 what the target hook provides, we cannot use the mode. For now,
2341 simply reject that case. */
2342 gcc_assert (TYPE_ALIGN (type)
2343 >= GET_MODE_ALIGNMENT (TYPE_MODE (type)));
2344 break;
2347 case VOID_TYPE:
2348 /* This is an incomplete type and so doesn't have a size. */
2349 SET_TYPE_ALIGN (type, 1);
2350 TYPE_USER_ALIGN (type) = 0;
2351 SET_TYPE_MODE (type, VOIDmode);
2352 break;
2354 case POINTER_BOUNDS_TYPE:
2355 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2356 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2357 break;
2359 case OFFSET_TYPE:
2360 TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
2361 TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS);
2362 /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be
2363 integral, which may be an __intN. */
2364 SET_TYPE_MODE (type, int_mode_for_size (POINTER_SIZE, 0).require ());
2365 TYPE_PRECISION (type) = POINTER_SIZE;
2366 break;
2368 case FUNCTION_TYPE:
2369 case METHOD_TYPE:
2370 /* It's hard to see what the mode and size of a function ought to
2371 be, but we do know the alignment is FUNCTION_BOUNDARY, so
2372 make it consistent with that. */
2373 SET_TYPE_MODE (type,
2374 int_mode_for_size (FUNCTION_BOUNDARY, 0).else_blk ());
2375 TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY);
2376 TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT);
2377 break;
2379 case POINTER_TYPE:
2380 case REFERENCE_TYPE:
2382 scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
2383 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2384 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2385 TYPE_UNSIGNED (type) = 1;
2386 TYPE_PRECISION (type) = GET_MODE_PRECISION (mode);
2388 break;
2390 case ARRAY_TYPE:
2392 tree index = TYPE_DOMAIN (type);
2393 tree element = TREE_TYPE (type);
2395 /* We need to know both bounds in order to compute the size. */
2396 if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index)
2397 && TYPE_SIZE (element))
2399 tree ub = TYPE_MAX_VALUE (index);
2400 tree lb = TYPE_MIN_VALUE (index);
2401 tree element_size = TYPE_SIZE (element);
2402 tree length;
2404 /* Make sure that an array of zero-sized element is zero-sized
2405 regardless of its extent. */
2406 if (integer_zerop (element_size))
2407 length = size_zero_node;
2409 /* The computation should happen in the original signedness so
2410 that (possible) negative values are handled appropriately
2411 when determining overflow. */
2412 else
2414 /* ??? When it is obvious that the range is signed
2415 represent it using ssizetype. */
2416 if (TREE_CODE (lb) == INTEGER_CST
2417 && TREE_CODE (ub) == INTEGER_CST
2418 && TYPE_UNSIGNED (TREE_TYPE (lb))
2419 && tree_int_cst_lt (ub, lb))
2421 lb = wide_int_to_tree (ssizetype,
2422 offset_int::from (wi::to_wide (lb),
2423 SIGNED));
2424 ub = wide_int_to_tree (ssizetype,
2425 offset_int::from (wi::to_wide (ub),
2426 SIGNED));
2428 length
2429 = fold_convert (sizetype,
2430 size_binop (PLUS_EXPR,
2431 build_int_cst (TREE_TYPE (lb), 1),
2432 size_binop (MINUS_EXPR, ub, lb)));
2435 /* ??? We have no way to distinguish a null-sized array from an
2436 array spanning the whole sizetype range, so we arbitrarily
2437 decide that [0, -1] is the only valid representation. */
2438 if (integer_zerop (length)
2439 && TREE_OVERFLOW (length)
2440 && integer_zerop (lb))
2441 length = size_zero_node;
2443 TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
2444 bits_from_bytes (length));
2446 /* If we know the size of the element, calculate the total size
2447 directly, rather than do some division thing below. This
2448 optimization helps Fortran assumed-size arrays (where the
2449 size of the array is determined at runtime) substantially. */
2450 if (TYPE_SIZE_UNIT (element))
2451 TYPE_SIZE_UNIT (type)
2452 = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length);
2455 /* Now round the alignment and size,
2456 using machine-dependent criteria if any. */
2458 unsigned align = TYPE_ALIGN (element);
2459 if (TYPE_USER_ALIGN (type))
2460 align = MAX (align, TYPE_ALIGN (type));
2461 else
2462 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);
2463 if (!TYPE_WARN_IF_NOT_ALIGN (type))
2464 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2465 TYPE_WARN_IF_NOT_ALIGN (element));
2466 #ifdef ROUND_TYPE_ALIGN
2467 align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT);
2468 #else
2469 align = MAX (align, BITS_PER_UNIT);
2470 #endif
2471 SET_TYPE_ALIGN (type, align);
2472 SET_TYPE_MODE (type, BLKmode);
2473 if (TYPE_SIZE (type) != 0
2474 && ! targetm.member_type_forces_blk (type, VOIDmode)
2475 /* BLKmode elements force BLKmode aggregate;
2476 else extract/store fields may lose. */
2477 && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
2478 || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
2480 SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type),
2481 TYPE_SIZE (type)));
2482 if (TYPE_MODE (type) != BLKmode
2483 && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
2484 && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
2486 TYPE_NO_FORCE_BLK (type) = 1;
2487 SET_TYPE_MODE (type, BLKmode);
2490 if (AGGREGATE_TYPE_P (element))
2491 TYPE_TYPELESS_STORAGE (type) = TYPE_TYPELESS_STORAGE (element);
2492 /* When the element size is constant, check that it is at least as
2493 large as the element alignment. */
2494 if (TYPE_SIZE_UNIT (element)
2495 && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST
2496 /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than
2497 TYPE_ALIGN_UNIT. */
2498 && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element))
2499 && !integer_zerop (TYPE_SIZE_UNIT (element))
2500 && compare_tree_int (TYPE_SIZE_UNIT (element),
2501 TYPE_ALIGN_UNIT (element)) < 0)
2502 error ("alignment of array elements is greater than element size");
2503 break;
2506 case RECORD_TYPE:
2507 case UNION_TYPE:
2508 case QUAL_UNION_TYPE:
2510 tree field;
2511 record_layout_info rli;
2513 /* Initialize the layout information. */
2514 rli = start_record_layout (type);
2516 /* If this is a QUAL_UNION_TYPE, we want to process the fields
2517 in the reverse order in building the COND_EXPR that denotes
2518 its size. We reverse them again later. */
2519 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2520 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2522 /* Place all the fields. */
2523 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
2524 place_field (rli, field);
2526 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2527 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2529 /* Finish laying out the record. */
2530 finish_record_layout (rli, /*free_p=*/true);
2532 break;
2534 default:
2535 gcc_unreachable ();
2538 /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE. For
2539 records and unions, finish_record_layout already called this
2540 function. */
2541 if (!RECORD_OR_UNION_TYPE_P (type))
2542 finalize_type_size (type);
2544 /* We should never see alias sets on incomplete aggregates. And we
2545 should not call layout_type on not incomplete aggregates. */
2546 if (AGGREGATE_TYPE_P (type))
2547 gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type));
2550 /* Return the least alignment required for type TYPE. */
2552 unsigned int
2553 min_align_of_type (tree type)
2555 unsigned int align = TYPE_ALIGN (type);
2556 if (!TYPE_USER_ALIGN (type))
2558 align = MIN (align, BIGGEST_ALIGNMENT);
2559 #ifdef BIGGEST_FIELD_ALIGNMENT
2560 align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
2561 #endif
2562 unsigned int field_align = align;
2563 #ifdef ADJUST_FIELD_ALIGN
2564 field_align = ADJUST_FIELD_ALIGN (NULL_TREE, type, field_align);
2565 #endif
2566 align = MIN (align, field_align);
2568 return align / BITS_PER_UNIT;
2571 /* Create and return a type for signed integers of PRECISION bits. */
2573 tree
2574 make_signed_type (int precision)
2576 tree type = make_node (INTEGER_TYPE);
2578 TYPE_PRECISION (type) = precision;
2580 fixup_signed_type (type);
2581 return type;
2584 /* Create and return a type for unsigned integers of PRECISION bits. */
2586 tree
2587 make_unsigned_type (int precision)
2589 tree type = make_node (INTEGER_TYPE);
2591 TYPE_PRECISION (type) = precision;
2593 fixup_unsigned_type (type);
2594 return type;
2597 /* Create and return a type for fract of PRECISION bits, UNSIGNEDP,
2598 and SATP. */
2600 tree
2601 make_fract_type (int precision, int unsignedp, int satp)
2603 tree type = make_node (FIXED_POINT_TYPE);
2605 TYPE_PRECISION (type) = precision;
2607 if (satp)
2608 TYPE_SATURATING (type) = 1;
2610 /* Lay out the type: set its alignment, size, etc. */
2611 TYPE_UNSIGNED (type) = unsignedp;
2612 enum mode_class mclass = unsignedp ? MODE_UFRACT : MODE_FRACT;
2613 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2614 layout_type (type);
2616 return type;
2619 /* Create and return a type for accum of PRECISION bits, UNSIGNEDP,
2620 and SATP. */
2622 tree
2623 make_accum_type (int precision, int unsignedp, int satp)
2625 tree type = make_node (FIXED_POINT_TYPE);
2627 TYPE_PRECISION (type) = precision;
2629 if (satp)
2630 TYPE_SATURATING (type) = 1;
2632 /* Lay out the type: set its alignment, size, etc. */
2633 TYPE_UNSIGNED (type) = unsignedp;
2634 enum mode_class mclass = unsignedp ? MODE_UACCUM : MODE_ACCUM;
2635 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2636 layout_type (type);
2638 return type;
2641 /* Initialize sizetypes so layout_type can use them. */
2643 void
2644 initialize_sizetypes (void)
2646 int precision, bprecision;
2648 /* Get sizetypes precision from the SIZE_TYPE target macro. */
2649 if (strcmp (SIZETYPE, "unsigned int") == 0)
2650 precision = INT_TYPE_SIZE;
2651 else if (strcmp (SIZETYPE, "long unsigned int") == 0)
2652 precision = LONG_TYPE_SIZE;
2653 else if (strcmp (SIZETYPE, "long long unsigned int") == 0)
2654 precision = LONG_LONG_TYPE_SIZE;
2655 else if (strcmp (SIZETYPE, "short unsigned int") == 0)
2656 precision = SHORT_TYPE_SIZE;
2657 else
2659 int i;
2661 precision = -1;
2662 for (i = 0; i < NUM_INT_N_ENTS; i++)
2663 if (int_n_enabled_p[i])
2665 char name[50];
2666 sprintf (name, "__int%d unsigned", int_n_data[i].bitsize);
2668 if (strcmp (name, SIZETYPE) == 0)
2670 precision = int_n_data[i].bitsize;
2673 if (precision == -1)
2674 gcc_unreachable ();
2677 bprecision
2678 = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE);
2679 bprecision = GET_MODE_PRECISION (smallest_int_mode_for_size (bprecision));
2680 if (bprecision > HOST_BITS_PER_DOUBLE_INT)
2681 bprecision = HOST_BITS_PER_DOUBLE_INT;
2683 /* Create stubs for sizetype and bitsizetype so we can create constants. */
2684 sizetype = make_node (INTEGER_TYPE);
2685 TYPE_NAME (sizetype) = get_identifier ("sizetype");
2686 TYPE_PRECISION (sizetype) = precision;
2687 TYPE_UNSIGNED (sizetype) = 1;
2688 bitsizetype = make_node (INTEGER_TYPE);
2689 TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype");
2690 TYPE_PRECISION (bitsizetype) = bprecision;
2691 TYPE_UNSIGNED (bitsizetype) = 1;
2693 /* Now layout both types manually. */
2694 scalar_int_mode mode = smallest_int_mode_for_size (precision);
2695 SET_TYPE_MODE (sizetype, mode);
2696 SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype)));
2697 TYPE_SIZE (sizetype) = bitsize_int (precision);
2698 TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (mode));
2699 set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);
2701 mode = smallest_int_mode_for_size (bprecision);
2702 SET_TYPE_MODE (bitsizetype, mode);
2703 SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype)));
2704 TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
2705 TYPE_SIZE_UNIT (bitsizetype) = size_int (GET_MODE_SIZE (mode));
2706 set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);
2708 /* Create the signed variants of *sizetype. */
2709 ssizetype = make_signed_type (TYPE_PRECISION (sizetype));
2710 TYPE_NAME (ssizetype) = get_identifier ("ssizetype");
2711 sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype));
2712 TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype");
2715 /* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE
2716 or BOOLEAN_TYPE. Set TYPE_MIN_VALUE and TYPE_MAX_VALUE
2717 for TYPE, based on the PRECISION and whether or not the TYPE
2718 IS_UNSIGNED. PRECISION need not correspond to a width supported
2719 natively by the hardware; for example, on a machine with 8-bit,
2720 16-bit, and 32-bit register modes, PRECISION might be 7, 23, or
2721 61. */
2723 void
2724 set_min_and_max_values_for_integral_type (tree type,
2725 int precision,
2726 signop sgn)
2728 /* For bitfields with zero width we end up creating integer types
2729 with zero precision. Don't assign any minimum/maximum values
2730 to those types, they don't have any valid value. */
2731 if (precision < 1)
2732 return;
2734 TYPE_MIN_VALUE (type)
2735 = wide_int_to_tree (type, wi::min_value (precision, sgn));
2736 TYPE_MAX_VALUE (type)
2737 = wide_int_to_tree (type, wi::max_value (precision, sgn));
2740 /* Set the extreme values of TYPE based on its precision in bits,
2741 then lay it out. Used when make_signed_type won't do
2742 because the tree code is not INTEGER_TYPE. */
2744 void
2745 fixup_signed_type (tree type)
2747 int precision = TYPE_PRECISION (type);
2749 set_min_and_max_values_for_integral_type (type, precision, SIGNED);
2751 /* Lay out the type: set its alignment, size, etc. */
2752 layout_type (type);
2755 /* Set the extreme values of TYPE based on its precision in bits,
2756 then lay it out. This is used both in `make_unsigned_type'
2757 and for enumeral types. */
2759 void
2760 fixup_unsigned_type (tree type)
2762 int precision = TYPE_PRECISION (type);
2764 TYPE_UNSIGNED (type) = 1;
2766 set_min_and_max_values_for_integral_type (type, precision, UNSIGNED);
2768 /* Lay out the type: set its alignment, size, etc. */
2769 layout_type (type);
2772 /* Construct an iterator for a bitfield that spans BITSIZE bits,
2773 starting at BITPOS.
2775 BITREGION_START is the bit position of the first bit in this
2776 sequence of bit fields. BITREGION_END is the last bit in this
2777 sequence. If these two fields are non-zero, we should restrict the
2778 memory access to that range. Otherwise, we are allowed to touch
2779 any adjacent non bit-fields.
2781 ALIGN is the alignment of the underlying object in bits.
2782 VOLATILEP says whether the bitfield is volatile. */
2784 bit_field_mode_iterator
2785 ::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
2786 poly_int64 bitregion_start,
2787 poly_int64 bitregion_end,
2788 unsigned int align, bool volatilep)
2789 : m_mode (NARROWEST_INT_MODE), m_bitsize (bitsize),
2790 m_bitpos (bitpos), m_bitregion_start (bitregion_start),
2791 m_bitregion_end (bitregion_end), m_align (align),
2792 m_volatilep (volatilep), m_count (0)
2794 if (known_eq (m_bitregion_end, 0))
2796 /* We can assume that any aligned chunk of ALIGN bits that overlaps
2797 the bitfield is mapped and won't trap, provided that ALIGN isn't
2798 too large. The cap is the biggest required alignment for data,
2799 or at least the word size. And force one such chunk at least. */
2800 unsigned HOST_WIDE_INT units
2801 = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
2802 if (bitsize <= 0)
2803 bitsize = 1;
2804 HOST_WIDE_INT end = bitpos + bitsize + units - 1;
2805 m_bitregion_end = end - end % units - 1;
2809 /* Calls to this function return successively larger modes that can be used
2810 to represent the bitfield. Return true if another bitfield mode is
2811 available, storing it in *OUT_MODE if so. */
2813 bool
2814 bit_field_mode_iterator::next_mode (scalar_int_mode *out_mode)
2816 scalar_int_mode mode;
2817 for (; m_mode.exists (&mode); m_mode = GET_MODE_WIDER_MODE (mode))
2819 unsigned int unit = GET_MODE_BITSIZE (mode);
2821 /* Skip modes that don't have full precision. */
2822 if (unit != GET_MODE_PRECISION (mode))
2823 continue;
2825 /* Stop if the mode is too wide to handle efficiently. */
2826 if (unit > MAX_FIXED_MODE_SIZE)
2827 break;
2829 /* Don't deliver more than one multiword mode; the smallest one
2830 should be used. */
2831 if (m_count > 0 && unit > BITS_PER_WORD)
2832 break;
2834 /* Skip modes that are too small. */
2835 unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit;
2836 unsigned HOST_WIDE_INT subend = substart + m_bitsize;
2837 if (subend > unit)
2838 continue;
2840 /* Stop if the mode goes outside the bitregion. */
2841 HOST_WIDE_INT start = m_bitpos - substart;
2842 if (maybe_ne (m_bitregion_start, 0)
2843 && maybe_lt (start, m_bitregion_start))
2844 break;
2845 HOST_WIDE_INT end = start + unit;
2846 if (maybe_gt (end, m_bitregion_end + 1))
2847 break;
2849 /* Stop if the mode requires too much alignment. */
2850 if (GET_MODE_ALIGNMENT (mode) > m_align
2851 && targetm.slow_unaligned_access (mode, m_align))
2852 break;
2854 *out_mode = mode;
2855 m_mode = GET_MODE_WIDER_MODE (mode);
2856 m_count++;
2857 return true;
2859 return false;
2862 /* Return true if smaller modes are generally preferred for this kind
2863 of bitfield. */
2865 bool
2866 bit_field_mode_iterator::prefer_smaller_modes ()
2868 return (m_volatilep
2869 ? targetm.narrow_volatile_bitfield ()
2870 : !SLOW_BYTE_ACCESS);
2873 /* Find the best machine mode to use when referencing a bit field of length
2874 BITSIZE bits starting at BITPOS.
2876 BITREGION_START is the bit position of the first bit in this
2877 sequence of bit fields. BITREGION_END is the last bit in this
2878 sequence. If these two fields are non-zero, we should restrict the
2879 memory access to that range. Otherwise, we are allowed to touch
2880 any adjacent non bit-fields.
2882 The chosen mode must have no more than LARGEST_MODE_BITSIZE bits.
2883 INT_MAX is a suitable value for LARGEST_MODE_BITSIZE if the caller
2884 doesn't want to apply a specific limit.
2886 If no mode meets all these conditions, we return VOIDmode.
2888 The underlying object is known to be aligned to a boundary of ALIGN bits.
2890 If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the
2891 smallest mode meeting these conditions.
2893 If VOLATILEP is false and SLOW_BYTE_ACCESS is true, we return the
2894 largest mode (but a mode no wider than UNITS_PER_WORD) that meets
2895 all the conditions.
2897 If VOLATILEP is true the narrow_volatile_bitfields target hook is used to
2898 decide which of the above modes should be used. */
2900 bool
2901 get_best_mode (int bitsize, int bitpos,
2902 poly_uint64 bitregion_start, poly_uint64 bitregion_end,
2903 unsigned int align,
2904 unsigned HOST_WIDE_INT largest_mode_bitsize, bool volatilep,
2905 scalar_int_mode *best_mode)
2907 bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start,
2908 bitregion_end, align, volatilep);
2909 scalar_int_mode mode;
2910 bool found = false;
2911 while (iter.next_mode (&mode)
2912 /* ??? For historical reasons, reject modes that would normally
2913 receive greater alignment, even if unaligned accesses are
2914 acceptable. This has both advantages and disadvantages.
2915 Removing this check means that something like:
2917 struct s { unsigned int x; unsigned int y; };
2918 int f (struct s *s) { return s->x == 0 && s->y == 0; }
2920 can be implemented using a single load and compare on
2921 64-bit machines that have no alignment restrictions.
2922 For example, on powerpc64-linux-gnu, we would generate:
2924 ld 3,0(3)
2925 cntlzd 3,3
2926 srdi 3,3,6
2929 rather than:
2931 lwz 9,0(3)
2932 cmpwi 7,9,0
2933 bne 7,.L3
2934 lwz 3,4(3)
2935 cntlzw 3,3
2936 srwi 3,3,5
2937 extsw 3,3
2939 .p2align 4,,15
2940 .L3:
2941 li 3,0
2944 However, accessing more than one field can make life harder
2945 for the gimple optimizers. For example, gcc.dg/vect/bb-slp-5.c
2946 has a series of unsigned short copies followed by a series of
2947 unsigned short comparisons. With this check, both the copies
2948 and comparisons remain 16-bit accesses and FRE is able
2949 to eliminate the latter. Without the check, the comparisons
2950 can be done using 2 64-bit operations, which FRE isn't able
2951 to handle in the same way.
2953 Either way, it would probably be worth disabling this check
2954 during expand. One particular example where removing the
2955 check would help is the get_best_mode call in store_bit_field.
2956 If we are given a memory bitregion of 128 bits that is aligned
2957 to a 64-bit boundary, and the bitfield we want to modify is
2958 in the second half of the bitregion, this check causes
2959 store_bitfield to turn the memory into a 64-bit reference
2960 to the _first_ half of the region. We later use
2961 adjust_bitfield_address to get a reference to the correct half,
2962 but doing so looks to adjust_bitfield_address as though we are
2963 moving past the end of the original object, so it drops the
2964 associated MEM_EXPR and MEM_OFFSET. Removing the check
2965 causes store_bit_field to keep a 128-bit memory reference,
2966 so that the final bitfield reference still has a MEM_EXPR
2967 and MEM_OFFSET. */
2968 && GET_MODE_ALIGNMENT (mode) <= align
2969 && GET_MODE_BITSIZE (mode) <= largest_mode_bitsize)
2971 *best_mode = mode;
2972 found = true;
2973 if (iter.prefer_smaller_modes ())
2974 break;
2977 return found;
2980 /* Gets minimal and maximal values for MODE (signed or unsigned depending on
2981 SIGN). The returned constants are made to be usable in TARGET_MODE. */
2983 void
2984 get_mode_bounds (scalar_int_mode mode, int sign,
2985 scalar_int_mode target_mode,
2986 rtx *mmin, rtx *mmax)
2988 unsigned size = GET_MODE_PRECISION (mode);
2989 unsigned HOST_WIDE_INT min_val, max_val;
2991 gcc_assert (size <= HOST_BITS_PER_WIDE_INT);
2993 /* Special case BImode, which has values 0 and STORE_FLAG_VALUE. */
2994 if (mode == BImode)
2996 if (STORE_FLAG_VALUE < 0)
2998 min_val = STORE_FLAG_VALUE;
2999 max_val = 0;
3001 else
3003 min_val = 0;
3004 max_val = STORE_FLAG_VALUE;
3007 else if (sign)
3009 min_val = -(HOST_WIDE_INT_1U << (size - 1));
3010 max_val = (HOST_WIDE_INT_1U << (size - 1)) - 1;
3012 else
3014 min_val = 0;
3015 max_val = (HOST_WIDE_INT_1U << (size - 1) << 1) - 1;
3018 *mmin = gen_int_mode (min_val, target_mode);
3019 *mmax = gen_int_mode (max_val, target_mode);
3022 #include "gt-stor-layout.h"