1 /* C-compiler utilities for types and variables storage layout
2 Copyright (C) 1987-2018 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "target.h"
25 #include "function.h"
26 #include "rtl.h"
27 #include "tree.h"
28 #include "memmodel.h"
29 #include "tm_p.h"
30 #include "stringpool.h"
31 #include "regs.h"
32 #include "emit-rtl.h"
33 #include "cgraph.h"
34 #include "diagnostic-core.h"
35 #include "fold-const.h"
36 #include "stor-layout.h"
37 #include "varasm.h"
38 #include "print-tree.h"
39 #include "langhooks.h"
40 #include "tree-inline.h"
41 #include "dumpfile.h"
42 #include "gimplify.h"
43 #include "attribs.h"
44 #include "debug.h"
45
46 /* Data type for the expressions representing sizes of data types.
47 It is the first integer type laid out. */
48 tree sizetype_tab[(int) stk_type_kind_last];
49
50 /* If nonzero, this is an upper limit on alignment of structure fields.
51 The value is measured in bits. */
52 unsigned int maximum_field_alignment = TARGET_DEFAULT_PACK_STRUCT * BITS_PER_UNIT;
53
54 static tree self_referential_size (tree);
55 static void finalize_record_size (record_layout_info);
56 static void finalize_type_size (tree);
57 static void place_union_field (record_layout_info, tree);
58 static int excess_unit_span (HOST_WIDE_INT, HOST_WIDE_INT, HOST_WIDE_INT,
59 HOST_WIDE_INT, tree);
60 extern void debug_rli (record_layout_info);
61
62 /* Given a size SIZE that may not be a constant, return a SAVE_EXPR
63 to serve as the actual size-expression for a type or decl. */
64
65 tree
variable_size(tree size)66 variable_size (tree size)
67 {
68 /* Obviously. */
69 if (TREE_CONSTANT (size))
70 return size;
71
72 /* If the size is self-referential, we can't make a SAVE_EXPR (see
73 save_expr for the rationale). But we can do something else. */
74 if (CONTAINS_PLACEHOLDER_P (size))
75 return self_referential_size (size);
76
77 /* If we are in the global binding level, we can't make a SAVE_EXPR
78 since it may end up being shared across functions, so it is up
79 to the front-end to deal with this case. */
80 if (lang_hooks.decls.global_bindings_p ())
81 return size;
82
83 return save_expr (size);
84 }
85
86 /* An array of functions used for self-referential size computation. */
87 static GTY(()) vec<tree, va_gc> *size_functions;
88
89 /* Return true if T is a self-referential component reference. */
90
91 static bool
self_referential_component_ref_p(tree t)92 self_referential_component_ref_p (tree t)
93 {
94 if (TREE_CODE (t) != COMPONENT_REF)
95 return false;
96
97 while (REFERENCE_CLASS_P (t))
98 t = TREE_OPERAND (t, 0);
99
100 return (TREE_CODE (t) == PLACEHOLDER_EXPR);
101 }
102
103 /* Similar to copy_tree_r but do not copy component references involving
104 PLACEHOLDER_EXPRs. These nodes are spotted in find_placeholder_in_expr
105 and substituted in substitute_in_expr. */
106
107 static tree
copy_self_referential_tree_r(tree * tp,int * walk_subtrees,void * data)108 copy_self_referential_tree_r (tree *tp, int *walk_subtrees, void *data)
109 {
110 enum tree_code code = TREE_CODE (*tp);
111
112 /* Stop at types, decls, constants like copy_tree_r. */
113 if (TREE_CODE_CLASS (code) == tcc_type
114 || TREE_CODE_CLASS (code) == tcc_declaration
115 || TREE_CODE_CLASS (code) == tcc_constant)
116 {
117 *walk_subtrees = 0;
118 return NULL_TREE;
119 }
120
121 /* This is the pattern built in ada/make_aligning_type. */
122 else if (code == ADDR_EXPR
123 && TREE_CODE (TREE_OPERAND (*tp, 0)) == PLACEHOLDER_EXPR)
124 {
125 *walk_subtrees = 0;
126 return NULL_TREE;
127 }
128
129 /* Default case: the component reference. */
130 else if (self_referential_component_ref_p (*tp))
131 {
132 *walk_subtrees = 0;
133 return NULL_TREE;
134 }
135
136 /* We're not supposed to have them in self-referential size trees
137 because we wouldn't properly control when they are evaluated.
138 However, not creating superfluous SAVE_EXPRs requires accurate
139 tracking of readonly-ness all the way down to here, which we
140 cannot always guarantee in practice. So punt in this case. */
141 else if (code == SAVE_EXPR)
142 return error_mark_node;
143
144 else if (code == STATEMENT_LIST)
145 gcc_unreachable ();
146
147 return copy_tree_r (tp, walk_subtrees, data);
148 }
149
150 /* Given a SIZE expression that is self-referential, return an equivalent
151 expression to serve as the actual size expression for a type. */
152
153 static tree
self_referential_size(tree size)154 self_referential_size (tree size)
155 {
156 static unsigned HOST_WIDE_INT fnno = 0;
157 vec<tree> self_refs = vNULL;
158 tree param_type_list = NULL, param_decl_list = NULL;
159 tree t, ref, return_type, fntype, fnname, fndecl;
160 unsigned int i;
161 char buf[128];
162 vec<tree, va_gc> *args = NULL;
163
164 /* Do not factor out simple operations. */
165 t = skip_simple_constant_arithmetic (size);
166 if (TREE_CODE (t) == CALL_EXPR || self_referential_component_ref_p (t))
167 return size;
168
169 /* Collect the list of self-references in the expression. */
170 find_placeholder_in_expr (size, &self_refs);
171 gcc_assert (self_refs.length () > 0);
172
173 /* Obtain a private copy of the expression. */
174 t = size;
175 if (walk_tree (&t, copy_self_referential_tree_r, NULL, NULL) != NULL_TREE)
176 return size;
177 size = t;
178
179 /* Build the parameter and argument lists in parallel; also
180 substitute the former for the latter in the expression. */
181 vec_alloc (args, self_refs.length ());
182 FOR_EACH_VEC_ELT (self_refs, i, ref)
183 {
184 tree subst, param_name, param_type, param_decl;
185
186 if (DECL_P (ref))
187 {
188 /* We shouldn't have true variables here. */
189 gcc_assert (TREE_READONLY (ref));
190 subst = ref;
191 }
192 /* This is the pattern built in ada/make_aligning_type. */
193 else if (TREE_CODE (ref) == ADDR_EXPR)
194 subst = ref;
195 /* Default case: the component reference. */
196 else
197 subst = TREE_OPERAND (ref, 1);
198
199 sprintf (buf, "p%d", i);
200 param_name = get_identifier (buf);
201 param_type = TREE_TYPE (ref);
202 param_decl
203 = build_decl (input_location, PARM_DECL, param_name, param_type);
204 DECL_ARG_TYPE (param_decl) = param_type;
205 DECL_ARTIFICIAL (param_decl) = 1;
206 TREE_READONLY (param_decl) = 1;
207
208 size = substitute_in_expr (size, subst, param_decl);
209
210 param_type_list = tree_cons (NULL_TREE, param_type, param_type_list);
211 param_decl_list = chainon (param_decl, param_decl_list);
212 args->quick_push (ref);
213 }
214
215 self_refs.release ();
216
217 /* Append 'void' to indicate that the number of parameters is fixed. */
218 param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list);
219
220 /* The 3 lists have been created in reverse order. */
221 param_type_list = nreverse (param_type_list);
222 param_decl_list = nreverse (param_decl_list);
223
224 /* Build the function type. */
225 return_type = TREE_TYPE (size);
226 fntype = build_function_type (return_type, param_type_list);
227
228 /* Build the function declaration. */
229 sprintf (buf, "SZ" HOST_WIDE_INT_PRINT_UNSIGNED, fnno++);
230 fnname = get_file_function_name (buf);
231 fndecl = build_decl (input_location, FUNCTION_DECL, fnname, fntype);
232 for (t = param_decl_list; t; t = DECL_CHAIN (t))
233 DECL_CONTEXT (t) = fndecl;
234 DECL_ARGUMENTS (fndecl) = param_decl_list;
235 DECL_RESULT (fndecl)
236 = build_decl (input_location, RESULT_DECL, 0, return_type);
237 DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl;
238
239 /* The function has been created by the compiler and we don't
240 want to emit debug info for it. */
241 DECL_ARTIFICIAL (fndecl) = 1;
242 DECL_IGNORED_P (fndecl) = 1;
243
244 /* It is supposed to be "const" and never throw. */
245 TREE_READONLY (fndecl) = 1;
246 TREE_NOTHROW (fndecl) = 1;
247
248 /* We want it to be inlined when this is deemed profitable, as
249 well as discarded if every call has been integrated. */
250 DECL_DECLARED_INLINE_P (fndecl) = 1;
251
252 /* It is made up of a unique return statement. */
253 DECL_INITIAL (fndecl) = make_node (BLOCK);
254 BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
255 t = build2 (MODIFY_EXPR, return_type, DECL_RESULT (fndecl), size);
256 DECL_SAVED_TREE (fndecl) = build1 (RETURN_EXPR, void_type_node, t);
257 TREE_STATIC (fndecl) = 1;
258
259 /* Put it onto the list of size functions. */
260 vec_safe_push (size_functions, fndecl);
261
262 /* Replace the original expression with a call to the size function. */
263 return build_call_expr_loc_vec (UNKNOWN_LOCATION, fndecl, args);
264 }
265
266 /* Take, queue and compile all the size functions. It is essential that
267 the size functions be gimplified at the very end of the compilation
268 in order to guarantee transparent handling of self-referential sizes.
269 Otherwise the GENERIC inliner would not be able to inline them back
270 at each of their call sites, thus creating artificial non-constant
271 size expressions which would trigger nasty problems later on. */
272
273 void
finalize_size_functions(void)274 finalize_size_functions (void)
275 {
276 unsigned int i;
277 tree fndecl;
278
279 for (i = 0; size_functions && size_functions->iterate (i, &fndecl); i++)
280 {
281 allocate_struct_function (fndecl, false);
282 set_cfun (NULL);
283 dump_function (TDI_original, fndecl);
284
285 /* As these functions are used to describe the layout of variable-length
286 structures, debug info generation needs their implementation. */
287 debug_hooks->size_function (fndecl);
288 gimplify_function_tree (fndecl);
289 cgraph_node::finalize_function (fndecl, false);
290 }
291
292 vec_free (size_functions);
293 }
294
295 /* Return a machine mode of class MCLASS with SIZE bits of precision,
296 if one exists. The mode may have padding bits as well the SIZE
297 value bits. If LIMIT is nonzero, disregard modes wider than
298 MAX_FIXED_MODE_SIZE. */
299
300 opt_machine_mode
mode_for_size(poly_uint64 size,enum mode_class mclass,int limit)301 mode_for_size (poly_uint64 size, enum mode_class mclass, int limit)
302 {
303 machine_mode mode;
304 int i;
305
306 if (limit && maybe_gt (size, (unsigned int) MAX_FIXED_MODE_SIZE))
307 return opt_machine_mode ();
308
309 /* Get the first mode which has this size, in the specified class. */
310 FOR_EACH_MODE_IN_CLASS (mode, mclass)
311 if (known_eq (GET_MODE_PRECISION (mode), size))
312 return mode;
313
314 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
315 for (i = 0; i < NUM_INT_N_ENTS; i ++)
316 if (known_eq (int_n_data[i].bitsize, size)
317 && int_n_enabled_p[i])
318 return int_n_data[i].m;
319
320 return opt_machine_mode ();
321 }
322
323 /* Similar, except passed a tree node. */
324
325 opt_machine_mode
mode_for_size_tree(const_tree size,enum mode_class mclass,int limit)326 mode_for_size_tree (const_tree size, enum mode_class mclass, int limit)
327 {
328 unsigned HOST_WIDE_INT uhwi;
329 unsigned int ui;
330
331 if (!tree_fits_uhwi_p (size))
332 return opt_machine_mode ();
333 uhwi = tree_to_uhwi (size);
334 ui = uhwi;
335 if (uhwi != ui)
336 return opt_machine_mode ();
337 return mode_for_size (ui, mclass, limit);
338 }
339
340 /* Return the narrowest mode of class MCLASS that contains at least
341 SIZE bits. Abort if no such mode exists. */
342
343 machine_mode
smallest_mode_for_size(poly_uint64 size,enum mode_class mclass)344 smallest_mode_for_size (poly_uint64 size, enum mode_class mclass)
345 {
346 machine_mode mode = VOIDmode;
347 int i;
348
349 /* Get the first mode which has at least this size, in the
350 specified class. */
351 FOR_EACH_MODE_IN_CLASS (mode, mclass)
352 if (known_ge (GET_MODE_PRECISION (mode), size))
353 break;
354
355 gcc_assert (mode != VOIDmode);
356
357 if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
358 for (i = 0; i < NUM_INT_N_ENTS; i ++)
359 if (known_ge (int_n_data[i].bitsize, size)
360 && known_lt (int_n_data[i].bitsize, GET_MODE_PRECISION (mode))
361 && int_n_enabled_p[i])
362 mode = int_n_data[i].m;
363
364 return mode;
365 }
366
367 /* Return an integer mode of exactly the same size as MODE, if one exists. */
368
369 opt_scalar_int_mode
int_mode_for_mode(machine_mode mode)370 int_mode_for_mode (machine_mode mode)
371 {
372 switch (GET_MODE_CLASS (mode))
373 {
374 case MODE_INT:
375 case MODE_PARTIAL_INT:
376 return as_a <scalar_int_mode> (mode);
377
378 case MODE_COMPLEX_INT:
379 case MODE_COMPLEX_FLOAT:
380 case MODE_FLOAT:
381 case MODE_DECIMAL_FLOAT:
382 case MODE_FRACT:
383 case MODE_ACCUM:
384 case MODE_UFRACT:
385 case MODE_UACCUM:
386 case MODE_VECTOR_BOOL:
387 case MODE_VECTOR_INT:
388 case MODE_VECTOR_FLOAT:
389 case MODE_VECTOR_FRACT:
390 case MODE_VECTOR_ACCUM:
391 case MODE_VECTOR_UFRACT:
392 case MODE_VECTOR_UACCUM:
393 case MODE_POINTER_BOUNDS:
394 return int_mode_for_size (GET_MODE_BITSIZE (mode), 0);
395
396 case MODE_RANDOM:
397 if (mode == BLKmode)
398 return opt_scalar_int_mode ();
399
400 /* fall through */
401
402 case MODE_CC:
403 default:
404 gcc_unreachable ();
405 }
406 }
407
408 /* Find a mode that can be used for efficient bitwise operations on MODE,
409 if one exists. */
410
411 opt_machine_mode
bitwise_mode_for_mode(machine_mode mode)412 bitwise_mode_for_mode (machine_mode mode)
413 {
414 /* Quick exit if we already have a suitable mode. */
415 scalar_int_mode int_mode;
416 if (is_a <scalar_int_mode> (mode, &int_mode)
417 && GET_MODE_BITSIZE (int_mode) <= MAX_FIXED_MODE_SIZE)
418 return int_mode;
419
420 /* Reuse the sanity checks from int_mode_for_mode. */
421 gcc_checking_assert ((int_mode_for_mode (mode), true));
422
423 poly_int64 bitsize = GET_MODE_BITSIZE (mode);
424
425 /* Try to replace complex modes with complex modes. In general we
426 expect both components to be processed independently, so we only
427 care whether there is a register for the inner mode. */
428 if (COMPLEX_MODE_P (mode))
429 {
430 machine_mode trial = mode;
431 if ((GET_MODE_CLASS (trial) == MODE_COMPLEX_INT
432 || mode_for_size (bitsize, MODE_COMPLEX_INT, false).exists (&trial))
433 && have_regs_of_mode[GET_MODE_INNER (trial)])
434 return trial;
435 }
436
437 /* Try to replace vector modes with vector modes. Also try using vector
438 modes if an integer mode would be too big. */
439 if (VECTOR_MODE_P (mode)
440 || maybe_gt (bitsize, MAX_FIXED_MODE_SIZE))
441 {
442 machine_mode trial = mode;
443 if ((GET_MODE_CLASS (trial) == MODE_VECTOR_INT
444 || mode_for_size (bitsize, MODE_VECTOR_INT, 0).exists (&trial))
445 && have_regs_of_mode[trial]
446 && targetm.vector_mode_supported_p (trial))
447 return trial;
448 }
449
450 /* Otherwise fall back on integers while honoring MAX_FIXED_MODE_SIZE. */
451 return mode_for_size (bitsize, MODE_INT, true);
452 }
453
454 /* Find a type that can be used for efficient bitwise operations on MODE.
455 Return null if no such mode exists. */
456
457 tree
bitwise_type_for_mode(machine_mode mode)458 bitwise_type_for_mode (machine_mode mode)
459 {
460 if (!bitwise_mode_for_mode (mode).exists (&mode))
461 return NULL_TREE;
462
463 unsigned int inner_size = GET_MODE_UNIT_BITSIZE (mode);
464 tree inner_type = build_nonstandard_integer_type (inner_size, true);
465
466 if (VECTOR_MODE_P (mode))
467 return build_vector_type_for_mode (inner_type, mode);
468
469 if (COMPLEX_MODE_P (mode))
470 return build_complex_type (inner_type);
471
472 gcc_checking_assert (GET_MODE_INNER (mode) == mode);
473 return inner_type;
474 }
475
476 /* Find a mode that is suitable for representing a vector with NUNITS
477 elements of mode INNERMODE, if one exists. The returned mode can be
478 either an integer mode or a vector mode. */
479
480 opt_machine_mode
mode_for_vector(scalar_mode innermode,poly_uint64 nunits)481 mode_for_vector (scalar_mode innermode, poly_uint64 nunits)
482 {
483 machine_mode mode;
484
485 /* First, look for a supported vector type. */
486 if (SCALAR_FLOAT_MODE_P (innermode))
487 mode = MIN_MODE_VECTOR_FLOAT;
488 else if (SCALAR_FRACT_MODE_P (innermode))
489 mode = MIN_MODE_VECTOR_FRACT;
490 else if (SCALAR_UFRACT_MODE_P (innermode))
491 mode = MIN_MODE_VECTOR_UFRACT;
492 else if (SCALAR_ACCUM_MODE_P (innermode))
493 mode = MIN_MODE_VECTOR_ACCUM;
494 else if (SCALAR_UACCUM_MODE_P (innermode))
495 mode = MIN_MODE_VECTOR_UACCUM;
496 else
497 mode = MIN_MODE_VECTOR_INT;
498
499 /* Do not check vector_mode_supported_p here. We'll do that
500 later in vector_type_mode. */
501 FOR_EACH_MODE_FROM (mode, mode)
502 if (known_eq (GET_MODE_NUNITS (mode), nunits)
503 && GET_MODE_INNER (mode) == innermode)
504 return mode;
505
506 /* For integers, try mapping it to a same-sized scalar mode. */
507 if (GET_MODE_CLASS (innermode) == MODE_INT)
508 {
509 poly_uint64 nbits = nunits * GET_MODE_BITSIZE (innermode);
510 if (int_mode_for_size (nbits, 0).exists (&mode)
511 && have_regs_of_mode[mode])
512 return mode;
513 }
514
515 return opt_machine_mode ();
516 }
517
518 /* Return the mode for a vector that has NUNITS integer elements of
519 INT_BITS bits each, if such a mode exists. The mode can be either
520 an integer mode or a vector mode. */
521
522 opt_machine_mode
mode_for_int_vector(unsigned int int_bits,poly_uint64 nunits)523 mode_for_int_vector (unsigned int int_bits, poly_uint64 nunits)
524 {
525 scalar_int_mode int_mode;
526 machine_mode vec_mode;
527 if (int_mode_for_size (int_bits, 0).exists (&int_mode)
528 && mode_for_vector (int_mode, nunits).exists (&vec_mode))
529 return vec_mode;
530 return opt_machine_mode ();
531 }
532
533 /* Return the alignment of MODE. This will be bounded by 1 and
534 BIGGEST_ALIGNMENT. */
535
536 unsigned int
get_mode_alignment(machine_mode mode)537 get_mode_alignment (machine_mode mode)
538 {
539 return MIN (BIGGEST_ALIGNMENT, MAX (1, mode_base_align[mode]*BITS_PER_UNIT));
540 }
541
542 /* Return the natural mode of an array, given that it is SIZE bytes in
543 total and has elements of type ELEM_TYPE. */
544
545 static machine_mode
mode_for_array(tree elem_type,tree size)546 mode_for_array (tree elem_type, tree size)
547 {
548 tree elem_size;
549 poly_uint64 int_size, int_elem_size;
550 unsigned HOST_WIDE_INT num_elems;
551 bool limit_p;
552
553 /* One-element arrays get the component type's mode. */
554 elem_size = TYPE_SIZE (elem_type);
555 if (simple_cst_equal (size, elem_size))
556 return TYPE_MODE (elem_type);
557
558 limit_p = true;
559 if (poly_int_tree_p (size, &int_size)
560 && poly_int_tree_p (elem_size, &int_elem_size)
561 && maybe_ne (int_elem_size, 0U)
562 && constant_multiple_p (int_size, int_elem_size, &num_elems))
563 {
564 machine_mode elem_mode = TYPE_MODE (elem_type);
565 machine_mode mode;
566 if (targetm.array_mode (elem_mode, num_elems).exists (&mode))
567 return mode;
568 if (targetm.array_mode_supported_p (elem_mode, num_elems))
569 limit_p = false;
570 }
571 return mode_for_size_tree (size, MODE_INT, limit_p).else_blk ();
572 }
573
574 /* Subroutine of layout_decl: Force alignment required for the data type.
575 But if the decl itself wants greater alignment, don't override that. */
576
577 static inline void
do_type_align(tree type,tree decl)578 do_type_align (tree type, tree decl)
579 {
580 if (TYPE_ALIGN (type) > DECL_ALIGN (decl))
581 {
582 SET_DECL_ALIGN (decl, TYPE_ALIGN (type));
583 if (TREE_CODE (decl) == FIELD_DECL)
584 DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type);
585 }
586 if (TYPE_WARN_IF_NOT_ALIGN (type) > DECL_WARN_IF_NOT_ALIGN (decl))
587 SET_DECL_WARN_IF_NOT_ALIGN (decl, TYPE_WARN_IF_NOT_ALIGN (type));
588 }
589
590 /* Set the size, mode and alignment of a ..._DECL node.
591 TYPE_DECL does need this for C++.
592 Note that LABEL_DECL and CONST_DECL nodes do not need this,
593 and FUNCTION_DECL nodes have them set up in a special (and simple) way.
594 Don't call layout_decl for them.
595
596 KNOWN_ALIGN is the amount of alignment we can assume this
597 decl has with no special effort. It is relevant only for FIELD_DECLs
598 and depends on the previous fields.
599 All that matters about KNOWN_ALIGN is which powers of 2 divide it.
600 If KNOWN_ALIGN is 0, it means, "as much alignment as you like":
601 the record will be aligned to suit. */
602
603 void
layout_decl(tree decl,unsigned int known_align)604 layout_decl (tree decl, unsigned int known_align)
605 {
606 tree type = TREE_TYPE (decl);
607 enum tree_code code = TREE_CODE (decl);
608 rtx rtl = NULL_RTX;
609 location_t loc = DECL_SOURCE_LOCATION (decl);
610
611 if (code == CONST_DECL)
612 return;
613
614 gcc_assert (code == VAR_DECL || code == PARM_DECL || code == RESULT_DECL
615 || code == TYPE_DECL || code == FIELD_DECL);
616
617 rtl = DECL_RTL_IF_SET (decl);
618
619 if (type == error_mark_node)
620 type = void_type_node;
621
622 /* Usually the size and mode come from the data type without change,
623 however, the front-end may set the explicit width of the field, so its
624 size may not be the same as the size of its type. This happens with
625 bitfields, of course (an `int' bitfield may be only 2 bits, say), but it
626 also happens with other fields. For example, the C++ front-end creates
627 zero-sized fields corresponding to empty base classes, and depends on
628 layout_type setting DECL_FIELD_BITPOS correctly for the field. Set the
629 size in bytes from the size in bits. If we have already set the mode,
630 don't set it again since we can be called twice for FIELD_DECLs. */
631
632 DECL_UNSIGNED (decl) = TYPE_UNSIGNED (type);
633 if (DECL_MODE (decl) == VOIDmode)
634 SET_DECL_MODE (decl, TYPE_MODE (type));
635
636 if (DECL_SIZE (decl) == 0)
637 {
638 DECL_SIZE (decl) = TYPE_SIZE (type);
639 DECL_SIZE_UNIT (decl) = TYPE_SIZE_UNIT (type);
640 }
641 else if (DECL_SIZE_UNIT (decl) == 0)
642 DECL_SIZE_UNIT (decl)
643 = fold_convert_loc (loc, sizetype,
644 size_binop_loc (loc, CEIL_DIV_EXPR, DECL_SIZE (decl),
645 bitsize_unit_node));
646
647 if (code != FIELD_DECL)
648 /* For non-fields, update the alignment from the type. */
649 do_type_align (type, decl);
650 else
651 /* For fields, it's a bit more complicated... */
652 {
653 bool old_user_align = DECL_USER_ALIGN (decl);
654 bool zero_bitfield = false;
655 bool packed_p = DECL_PACKED (decl);
656 unsigned int mfa;
657
658 if (DECL_BIT_FIELD (decl))
659 {
660 DECL_BIT_FIELD_TYPE (decl) = type;
661
662 /* A zero-length bit-field affects the alignment of the next
663 field. In essence such bit-fields are not influenced by
664 any packing due to #pragma pack or attribute packed. */
665 if (integer_zerop (DECL_SIZE (decl))
666 && ! targetm.ms_bitfield_layout_p (DECL_FIELD_CONTEXT (decl)))
667 {
668 zero_bitfield = true;
669 packed_p = false;
670 if (PCC_BITFIELD_TYPE_MATTERS)
671 do_type_align (type, decl);
672 else
673 {
674 #ifdef EMPTY_FIELD_BOUNDARY
675 if (EMPTY_FIELD_BOUNDARY > DECL_ALIGN (decl))
676 {
677 SET_DECL_ALIGN (decl, EMPTY_FIELD_BOUNDARY);
678 DECL_USER_ALIGN (decl) = 0;
679 }
680 #endif
681 }
682 }
683
684 /* See if we can use an ordinary integer mode for a bit-field.
685 Conditions are: a fixed size that is correct for another mode,
686 occupying a complete byte or bytes on proper boundary. */
687 if (TYPE_SIZE (type) != 0
688 && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
689 && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT)
690 {
691 machine_mode xmode;
692 if (mode_for_size_tree (DECL_SIZE (decl),
693 MODE_INT, 1).exists (&xmode))
694 {
695 unsigned int xalign = GET_MODE_ALIGNMENT (xmode);
696 if (!(xalign > BITS_PER_UNIT && DECL_PACKED (decl))
697 && (known_align == 0 || known_align >= xalign))
698 {
699 SET_DECL_ALIGN (decl, MAX (xalign, DECL_ALIGN (decl)));
700 SET_DECL_MODE (decl, xmode);
701 DECL_BIT_FIELD (decl) = 0;
702 }
703 }
704 }
705
706 /* Turn off DECL_BIT_FIELD if we won't need it set. */
707 if (TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode
708 && known_align >= TYPE_ALIGN (type)
709 && DECL_ALIGN (decl) >= TYPE_ALIGN (type))
710 DECL_BIT_FIELD (decl) = 0;
711 }
712 else if (packed_p && DECL_USER_ALIGN (decl))
713 /* Don't touch DECL_ALIGN. For other packed fields, go ahead and
714 round up; we'll reduce it again below. We want packing to
715 supersede USER_ALIGN inherited from the type, but defer to
716 alignment explicitly specified on the field decl. */;
717 else
718 do_type_align (type, decl);
719
720 /* If the field is packed and not explicitly aligned, give it the
721 minimum alignment. Note that do_type_align may set
722 DECL_USER_ALIGN, so we need to check old_user_align instead. */
723 if (packed_p
724 && !old_user_align)
725 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), BITS_PER_UNIT));
726
727 if (! packed_p && ! DECL_USER_ALIGN (decl))
728 {
729 /* Some targets (i.e. i386, VMS) limit struct field alignment
730 to a lower boundary than alignment of variables unless
731 it was overridden by attribute aligned. */
732 #ifdef BIGGEST_FIELD_ALIGNMENT
733 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl),
734 (unsigned) BIGGEST_FIELD_ALIGNMENT));
735 #endif
736 #ifdef ADJUST_FIELD_ALIGN
737 SET_DECL_ALIGN (decl, ADJUST_FIELD_ALIGN (decl, TREE_TYPE (decl),
738 DECL_ALIGN (decl)));
739 #endif
740 }
741
742 if (zero_bitfield)
743 mfa = initial_max_fld_align * BITS_PER_UNIT;
744 else
745 mfa = maximum_field_alignment;
746 /* Should this be controlled by DECL_USER_ALIGN, too? */
747 if (mfa != 0)
748 SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), mfa));
749 }
750
751 /* Evaluate nonconstant size only once, either now or as soon as safe. */
752 if (DECL_SIZE (decl) != 0 && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
753 DECL_SIZE (decl) = variable_size (DECL_SIZE (decl));
754 if (DECL_SIZE_UNIT (decl) != 0
755 && TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST)
756 DECL_SIZE_UNIT (decl) = variable_size (DECL_SIZE_UNIT (decl));
757
758 /* If requested, warn about definitions of large data objects. */
759 if (warn_larger_than
760 && (code == VAR_DECL || code == PARM_DECL)
761 && ! DECL_EXTERNAL (decl))
762 {
763 tree size = DECL_SIZE_UNIT (decl);
764
765 if (size != 0 && TREE_CODE (size) == INTEGER_CST
766 && compare_tree_int (size, larger_than_size) > 0)
767 {
768 int size_as_int = TREE_INT_CST_LOW (size);
769
770 if (compare_tree_int (size, size_as_int) == 0)
771 warning (OPT_Wlarger_than_, "size of %q+D is %d bytes", decl, size_as_int);
772 else
773 warning (OPT_Wlarger_than_, "size of %q+D is larger than %wd bytes",
774 decl, larger_than_size);
775 }
776 }
777
778 /* If the RTL was already set, update its mode and mem attributes. */
779 if (rtl)
780 {
781 PUT_MODE (rtl, DECL_MODE (decl));
782 SET_DECL_RTL (decl, 0);
783 if (MEM_P (rtl))
784 set_mem_attributes (rtl, decl, 1);
785 SET_DECL_RTL (decl, rtl);
786 }
787 }
788
789 /* Given a VAR_DECL, PARM_DECL, RESULT_DECL, or FIELD_DECL, clears the
790 results of a previous call to layout_decl and calls it again. */
791
792 void
relayout_decl(tree decl)793 relayout_decl (tree decl)
794 {
795 DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0;
796 SET_DECL_MODE (decl, VOIDmode);
797 if (!DECL_USER_ALIGN (decl))
798 SET_DECL_ALIGN (decl, 0);
799 if (DECL_RTL_SET_P (decl))
800 SET_DECL_RTL (decl, 0);
801
802 layout_decl (decl, 0);
803 }
804
805 /* Begin laying out type T, which may be a RECORD_TYPE, UNION_TYPE, or
806 QUAL_UNION_TYPE. Return a pointer to a struct record_layout_info which
807 is to be passed to all other layout functions for this record. It is the
808 responsibility of the caller to call `free' for the storage returned.
809 Note that garbage collection is not permitted until we finish laying
810 out the record. */
811
812 record_layout_info
start_record_layout(tree t)813 start_record_layout (tree t)
814 {
815 record_layout_info rli = XNEW (struct record_layout_info_s);
816
817 rli->t = t;
818
819 /* If the type has a minimum specified alignment (via an attribute
820 declaration, for example) use it -- otherwise, start with a
821 one-byte alignment. */
822 rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
823 rli->unpacked_align = rli->record_align;
824 rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT);
825
826 #ifdef STRUCTURE_SIZE_BOUNDARY
827 /* Packed structures don't need to have minimum size. */
828 if (! TYPE_PACKED (t))
829 {
830 unsigned tmp;
831
832 /* #pragma pack overrides STRUCTURE_SIZE_BOUNDARY. */
833 tmp = (unsigned) STRUCTURE_SIZE_BOUNDARY;
834 if (maximum_field_alignment != 0)
835 tmp = MIN (tmp, maximum_field_alignment);
836 rli->record_align = MAX (rli->record_align, tmp);
837 }
838 #endif
839
840 rli->offset = size_zero_node;
841 rli->bitpos = bitsize_zero_node;
842 rli->prev_field = 0;
843 rli->pending_statics = 0;
844 rli->packed_maybe_necessary = 0;
845 rli->remaining_in_alignment = 0;
846
847 return rli;
848 }
849
850 /* Fold sizetype value X to bitsizetype, given that X represents a type
851 size or offset. */
852
853 static tree
bits_from_bytes(tree x)854 bits_from_bytes (tree x)
855 {
856 if (POLY_INT_CST_P (x))
857 /* The runtime calculation isn't allowed to overflow sizetype;
858 increasing the runtime values must always increase the size
859 or offset of the object. This means that the object imposes
860 a maximum value on the runtime parameters, but we don't record
861 what that is. */
862 return build_poly_int_cst
863 (bitsizetype,
864 poly_wide_int::from (poly_int_cst_value (x),
865 TYPE_PRECISION (bitsizetype),
866 TYPE_SIGN (TREE_TYPE (x))));
867 x = fold_convert (bitsizetype, x);
868 gcc_checking_assert (x);
869 return x;
870 }
871
872 /* Return the combined bit position for the byte offset OFFSET and the
873 bit position BITPOS.
874
875 These functions operate on byte and bit positions present in FIELD_DECLs
876 and assume that these expressions result in no (intermediate) overflow.
877 This assumption is necessary to fold the expressions as much as possible,
878 so as to avoid creating artificially variable-sized types in languages
879 supporting variable-sized types like Ada. */
880
881 tree
bit_from_pos(tree offset,tree bitpos)882 bit_from_pos (tree offset, tree bitpos)
883 {
884 return size_binop (PLUS_EXPR, bitpos,
885 size_binop (MULT_EXPR, bits_from_bytes (offset),
886 bitsize_unit_node));
887 }
888
889 /* Return the combined truncated byte position for the byte offset OFFSET and
890 the bit position BITPOS. */
891
892 tree
byte_from_pos(tree offset,tree bitpos)893 byte_from_pos (tree offset, tree bitpos)
894 {
895 tree bytepos;
896 if (TREE_CODE (bitpos) == MULT_EXPR
897 && tree_int_cst_equal (TREE_OPERAND (bitpos, 1), bitsize_unit_node))
898 bytepos = TREE_OPERAND (bitpos, 0);
899 else
900 bytepos = size_binop (TRUNC_DIV_EXPR, bitpos, bitsize_unit_node);
901 return size_binop (PLUS_EXPR, offset, fold_convert (sizetype, bytepos));
902 }
903
904 /* Split the bit position POS into a byte offset *POFFSET and a bit
905 position *PBITPOS with the byte offset aligned to OFF_ALIGN bits. */
906
907 void
pos_from_bit(tree * poffset,tree * pbitpos,unsigned int off_align,tree pos)908 pos_from_bit (tree *poffset, tree *pbitpos, unsigned int off_align,
909 tree pos)
910 {
911 tree toff_align = bitsize_int (off_align);
912 if (TREE_CODE (pos) == MULT_EXPR
913 && tree_int_cst_equal (TREE_OPERAND (pos, 1), toff_align))
914 {
915 *poffset = size_binop (MULT_EXPR,
916 fold_convert (sizetype, TREE_OPERAND (pos, 0)),
917 size_int (off_align / BITS_PER_UNIT));
918 *pbitpos = bitsize_zero_node;
919 }
920 else
921 {
922 *poffset = size_binop (MULT_EXPR,
923 fold_convert (sizetype,
924 size_binop (FLOOR_DIV_EXPR, pos,
925 toff_align)),
926 size_int (off_align / BITS_PER_UNIT));
927 *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, toff_align);
928 }
929 }
930
931 /* Given a pointer to bit and byte offsets and an offset alignment,
932 normalize the offsets so they are within the alignment. */
933
934 void
normalize_offset(tree * poffset,tree * pbitpos,unsigned int off_align)935 normalize_offset (tree *poffset, tree *pbitpos, unsigned int off_align)
936 {
937 /* If the bit position is now larger than it should be, adjust it
938 downwards. */
939 if (compare_tree_int (*pbitpos, off_align) >= 0)
940 {
941 tree offset, bitpos;
942 pos_from_bit (&offset, &bitpos, off_align, *pbitpos);
943 *poffset = size_binop (PLUS_EXPR, *poffset, offset);
944 *pbitpos = bitpos;
945 }
946 }
947
948 /* Print debugging information about the information in RLI. */
949
950 DEBUG_FUNCTION void
debug_rli(record_layout_info rli)951 debug_rli (record_layout_info rli)
952 {
953 print_node_brief (stderr, "type", rli->t, 0);
954 print_node_brief (stderr, "\noffset", rli->offset, 0);
955 print_node_brief (stderr, " bitpos", rli->bitpos, 0);
956
957 fprintf (stderr, "\naligns: rec = %u, unpack = %u, off = %u\n",
958 rli->record_align, rli->unpacked_align,
959 rli->offset_align);
960
961 /* The ms_struct code is the only that uses this. */
962 if (targetm.ms_bitfield_layout_p (rli->t))
963 fprintf (stderr, "remaining in alignment = %u\n", rli->remaining_in_alignment);
964
965 if (rli->packed_maybe_necessary)
966 fprintf (stderr, "packed may be necessary\n");
967
968 if (!vec_safe_is_empty (rli->pending_statics))
969 {
970 fprintf (stderr, "pending statics:\n");
971 debug (rli->pending_statics);
972 }
973 }
974
975 /* Given an RLI with a possibly-incremented BITPOS, adjust OFFSET and
976 BITPOS if necessary to keep BITPOS below OFFSET_ALIGN. */
977
978 void
normalize_rli(record_layout_info rli)979 normalize_rli (record_layout_info rli)
980 {
981 normalize_offset (&rli->offset, &rli->bitpos, rli->offset_align);
982 }
983
984 /* Returns the size in bytes allocated so far. */
985
986 tree
rli_size_unit_so_far(record_layout_info rli)987 rli_size_unit_so_far (record_layout_info rli)
988 {
989 return byte_from_pos (rli->offset, rli->bitpos);
990 }
991
992 /* Returns the size in bits allocated so far. */
993
994 tree
rli_size_so_far(record_layout_info rli)995 rli_size_so_far (record_layout_info rli)
996 {
997 return bit_from_pos (rli->offset, rli->bitpos);
998 }
999
1000 /* FIELD is about to be added to RLI->T. The alignment (in bits) of
1001 the next available location within the record is given by KNOWN_ALIGN.
1002 Update the variable alignment fields in RLI, and return the alignment
1003 to give the FIELD. */
1004
1005 unsigned int
update_alignment_for_field(record_layout_info rli,tree field,unsigned int known_align)1006 update_alignment_for_field (record_layout_info rli, tree field,
1007 unsigned int known_align)
1008 {
1009 /* The alignment required for FIELD. */
1010 unsigned int desired_align;
1011 /* The type of this field. */
1012 tree type = TREE_TYPE (field);
1013 /* True if the field was explicitly aligned by the user. */
1014 bool user_align;
1015 bool is_bitfield;
1016
1017 /* Do not attempt to align an ERROR_MARK node */
1018 if (TREE_CODE (type) == ERROR_MARK)
1019 return 0;
1020
1021 /* Lay out the field so we know what alignment it needs. */
1022 layout_decl (field, known_align);
1023 desired_align = DECL_ALIGN (field);
1024 user_align = DECL_USER_ALIGN (field);
1025
1026 is_bitfield = (type != error_mark_node
1027 && DECL_BIT_FIELD_TYPE (field)
1028 && ! integer_zerop (TYPE_SIZE (type)));
1029
1030 /* Record must have at least as much alignment as any field.
1031 Otherwise, the alignment of the field within the record is
1032 meaningless. */
1033 if (targetm.ms_bitfield_layout_p (rli->t))
1034 {
1035 /* Here, the alignment of the underlying type of a bitfield can
1036 affect the alignment of a record; even a zero-sized field
1037 can do this. The alignment should be to the alignment of
1038 the type, except that for zero-size bitfields this only
1039 applies if there was an immediately prior, nonzero-size
1040 bitfield. (That's the way it is, experimentally.) */
1041 if (!is_bitfield
1042 || ((DECL_SIZE (field) == NULL_TREE
1043 || !integer_zerop (DECL_SIZE (field)))
1044 ? !DECL_PACKED (field)
1045 : (rli->prev_field
1046 && DECL_BIT_FIELD_TYPE (rli->prev_field)
1047 && ! integer_zerop (DECL_SIZE (rli->prev_field)))))
1048 {
1049 unsigned int type_align = TYPE_ALIGN (type);
1050 if (!is_bitfield && DECL_PACKED (field))
1051 type_align = desired_align;
1052 else
1053 type_align = MAX (type_align, desired_align);
1054 if (maximum_field_alignment != 0)
1055 type_align = MIN (type_align, maximum_field_alignment);
1056 rli->record_align = MAX (rli->record_align, type_align);
1057 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1058 }
1059 }
1060 else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
1061 {
1062 /* Named bit-fields cause the entire structure to have the
1063 alignment implied by their type. Some targets also apply the same
1064 rules to unnamed bitfields. */
1065 if (DECL_NAME (field) != 0
1066 || targetm.align_anon_bitfield ())
1067 {
1068 unsigned int type_align = TYPE_ALIGN (type);
1069
1070 #ifdef ADJUST_FIELD_ALIGN
1071 if (! TYPE_USER_ALIGN (type))
1072 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1073 #endif
1074
1075 /* Targets might chose to handle unnamed and hence possibly
1076 zero-width bitfield. Those are not influenced by #pragmas
1077 or packed attributes. */
1078 if (integer_zerop (DECL_SIZE (field)))
1079 {
1080 if (initial_max_fld_align)
1081 type_align = MIN (type_align,
1082 initial_max_fld_align * BITS_PER_UNIT);
1083 }
1084 else if (maximum_field_alignment != 0)
1085 type_align = MIN (type_align, maximum_field_alignment);
1086 else if (DECL_PACKED (field))
1087 type_align = MIN (type_align, BITS_PER_UNIT);
1088
1089 /* The alignment of the record is increased to the maximum
1090 of the current alignment, the alignment indicated on the
1091 field (i.e., the alignment specified by an __aligned__
1092 attribute), and the alignment indicated by the type of
1093 the field. */
1094 rli->record_align = MAX (rli->record_align, desired_align);
1095 rli->record_align = MAX (rli->record_align, type_align);
1096
1097 if (warn_packed)
1098 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1099 user_align |= TYPE_USER_ALIGN (type);
1100 }
1101 }
1102 else
1103 {
1104 rli->record_align = MAX (rli->record_align, desired_align);
1105 rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
1106 }
1107
1108 TYPE_USER_ALIGN (rli->t) |= user_align;
1109
1110 return desired_align;
1111 }
1112
1113 /* Issue a warning if the record alignment, RECORD_ALIGN, is less than
1114 the field alignment of FIELD or FIELD isn't aligned. */
1115
1116 static void
handle_warn_if_not_align(tree field,unsigned int record_align)1117 handle_warn_if_not_align (tree field, unsigned int record_align)
1118 {
1119 tree type = TREE_TYPE (field);
1120
1121 if (type == error_mark_node)
1122 return;
1123
1124 unsigned int warn_if_not_align = 0;
1125
1126 int opt_w = 0;
1127
1128 if (warn_if_not_aligned)
1129 {
1130 warn_if_not_align = DECL_WARN_IF_NOT_ALIGN (field);
1131 if (!warn_if_not_align)
1132 warn_if_not_align = TYPE_WARN_IF_NOT_ALIGN (type);
1133 if (warn_if_not_align)
1134 opt_w = OPT_Wif_not_aligned;
1135 }
1136
1137 if (!warn_if_not_align
1138 && warn_packed_not_aligned
1139 && lookup_attribute ("aligned", TYPE_ATTRIBUTES (type)))
1140 {
1141 warn_if_not_align = TYPE_ALIGN (type);
1142 opt_w = OPT_Wpacked_not_aligned;
1143 }
1144
1145 if (!warn_if_not_align)
1146 return;
1147
1148 tree context = DECL_CONTEXT (field);
1149
1150 warn_if_not_align /= BITS_PER_UNIT;
1151 record_align /= BITS_PER_UNIT;
1152 if ((record_align % warn_if_not_align) != 0)
1153 warning (opt_w, "alignment %u of %qT is less than %u",
1154 record_align, context, warn_if_not_align);
1155
1156 tree off = byte_position (field);
1157 if (!multiple_of_p (TREE_TYPE (off), off, size_int (warn_if_not_align)))
1158 {
1159 if (TREE_CODE (off) == INTEGER_CST)
1160 warning (opt_w, "%q+D offset %E in %qT isn%'t aligned to %u",
1161 field, off, context, warn_if_not_align);
1162 else
1163 warning (opt_w, "%q+D offset %E in %qT may not be aligned to %u",
1164 field, off, context, warn_if_not_align);
1165 }
1166 }
1167
1168 /* Called from place_field to handle unions. */
1169
1170 static void
place_union_field(record_layout_info rli,tree field)1171 place_union_field (record_layout_info rli, tree field)
1172 {
1173 update_alignment_for_field (rli, field, /*known_align=*/0);
1174
1175 DECL_FIELD_OFFSET (field) = size_zero_node;
1176 DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
1177 SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);
1178 handle_warn_if_not_align (field, rli->record_align);
1179
1180 /* If this is an ERROR_MARK return *after* having set the
1181 field at the start of the union. This helps when parsing
1182 invalid fields. */
1183 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK)
1184 return;
1185
1186 if (AGGREGATE_TYPE_P (TREE_TYPE (field))
1187 && TYPE_TYPELESS_STORAGE (TREE_TYPE (field)))
1188 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1189
1190 /* We assume the union's size will be a multiple of a byte so we don't
1191 bother with BITPOS. */
1192 if (TREE_CODE (rli->t) == UNION_TYPE)
1193 rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1194 else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE)
1195 rli->offset = fold_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field),
1196 DECL_SIZE_UNIT (field), rli->offset);
1197 }
1198
1199 /* A bitfield of SIZE with a required access alignment of ALIGN is allocated
1200 at BYTE_OFFSET / BIT_OFFSET. Return nonzero if the field would span more
1201 units of alignment than the underlying TYPE. */
1202 static int
excess_unit_span(HOST_WIDE_INT byte_offset,HOST_WIDE_INT bit_offset,HOST_WIDE_INT size,HOST_WIDE_INT align,tree type)1203 excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset,
1204 HOST_WIDE_INT size, HOST_WIDE_INT align, tree type)
1205 {
1206 /* Note that the calculation of OFFSET might overflow; we calculate it so
1207 that we still get the right result as long as ALIGN is a power of two. */
1208 unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset;
1209
1210 offset = offset % align;
1211 return ((offset + size + align - 1) / align
1212 > tree_to_uhwi (TYPE_SIZE (type)) / align);
1213 }
1214
1215 /* RLI contains information about the layout of a RECORD_TYPE. FIELD
1216 is a FIELD_DECL to be added after those fields already present in
1217 T. (FIELD is not actually added to the TYPE_FIELDS list here;
1218 callers that desire that behavior must manually perform that step.) */
1219
1220 void
place_field(record_layout_info rli,tree field)1221 place_field (record_layout_info rli, tree field)
1222 {
1223 /* The alignment required for FIELD. */
1224 unsigned int desired_align;
1225 /* The alignment FIELD would have if we just dropped it into the
1226 record as it presently stands. */
1227 unsigned int known_align;
1228 unsigned int actual_align;
1229 /* The type of this field. */
1230 tree type = TREE_TYPE (field);
1231
1232 gcc_assert (TREE_CODE (field) != ERROR_MARK);
1233
1234 /* If FIELD is static, then treat it like a separate variable, not
1235 really like a structure field. If it is a FUNCTION_DECL, it's a
1236 method. In both cases, all we do is lay out the decl, and we do
1237 it *after* the record is laid out. */
1238 if (VAR_P (field))
1239 {
1240 vec_safe_push (rli->pending_statics, field);
1241 return;
1242 }
1243
1244 /* Enumerators and enum types which are local to this class need not
1245 be laid out. Likewise for initialized constant fields. */
1246 else if (TREE_CODE (field) != FIELD_DECL)
1247 return;
1248
1249 /* Unions are laid out very differently than records, so split
1250 that code off to another function. */
1251 else if (TREE_CODE (rli->t) != RECORD_TYPE)
1252 {
1253 place_union_field (rli, field);
1254 return;
1255 }
1256
1257 else if (TREE_CODE (type) == ERROR_MARK)
1258 {
1259 /* Place this field at the current allocation position, so we
1260 maintain monotonicity. */
1261 DECL_FIELD_OFFSET (field) = rli->offset;
1262 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1263 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1264 handle_warn_if_not_align (field, rli->record_align);
1265 return;
1266 }
1267
1268 if (AGGREGATE_TYPE_P (type)
1269 && TYPE_TYPELESS_STORAGE (type))
1270 TYPE_TYPELESS_STORAGE (rli->t) = 1;
1271
1272 /* Work out the known alignment so far. Note that A & (-A) is the
1273 value of the least-significant bit in A that is one. */
1274 if (! integer_zerop (rli->bitpos))
1275 known_align = least_bit_hwi (tree_to_uhwi (rli->bitpos));
1276 else if (integer_zerop (rli->offset))
1277 known_align = 0;
1278 else if (tree_fits_uhwi_p (rli->offset))
1279 known_align = (BITS_PER_UNIT
1280 * least_bit_hwi (tree_to_uhwi (rli->offset)));
1281 else
1282 known_align = rli->offset_align;
1283
1284 desired_align = update_alignment_for_field (rli, field, known_align);
1285 if (known_align == 0)
1286 known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1287
1288 if (warn_packed && DECL_PACKED (field))
1289 {
1290 if (known_align >= TYPE_ALIGN (type))
1291 {
1292 if (TYPE_ALIGN (type) > desired_align)
1293 {
1294 if (STRICT_ALIGNMENT)
1295 warning (OPT_Wattributes, "packed attribute causes "
1296 "inefficient alignment for %q+D", field);
1297 /* Don't warn if DECL_PACKED was set by the type. */
1298 else if (!TYPE_PACKED (rli->t))
1299 warning (OPT_Wattributes, "packed attribute is "
1300 "unnecessary for %q+D", field);
1301 }
1302 }
1303 else
1304 rli->packed_maybe_necessary = 1;
1305 }
1306
1307 /* Does this field automatically have alignment it needs by virtue
1308 of the fields that precede it and the record's own alignment? */
1309 if (known_align < desired_align
1310 && (! targetm.ms_bitfield_layout_p (rli->t)
1311 || rli->prev_field == NULL))
1312 {
1313 /* No, we need to skip space before this field.
1314 Bump the cumulative size to multiple of field alignment. */
1315
1316 if (!targetm.ms_bitfield_layout_p (rli->t)
1317 && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION)
1318 warning (OPT_Wpadded, "padding struct to align %q+D", field);
1319
1320 /* If the alignment is still within offset_align, just align
1321 the bit position. */
1322 if (desired_align < rli->offset_align)
1323 rli->bitpos = round_up (rli->bitpos, desired_align);
1324 else
1325 {
1326 /* First adjust OFFSET by the partial bits, then align. */
1327 rli->offset
1328 = size_binop (PLUS_EXPR, rli->offset,
1329 fold_convert (sizetype,
1330 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1331 bitsize_unit_node)));
1332 rli->bitpos = bitsize_zero_node;
1333
1334 rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT);
1335 }
1336
1337 if (! TREE_CONSTANT (rli->offset))
1338 rli->offset_align = desired_align;
1339 }
1340
1341 /* Handle compatibility with PCC. Note that if the record has any
1342 variable-sized fields, we need not worry about compatibility. */
1343 if (PCC_BITFIELD_TYPE_MATTERS
1344 && ! targetm.ms_bitfield_layout_p (rli->t)
1345 && TREE_CODE (field) == FIELD_DECL
1346 && type != error_mark_node
1347 && DECL_BIT_FIELD (field)
1348 && (! DECL_PACKED (field)
1349 /* Enter for these packed fields only to issue a warning. */
1350 || TYPE_ALIGN (type) <= BITS_PER_UNIT)
1351 && maximum_field_alignment == 0
1352 && ! integer_zerop (DECL_SIZE (field))
1353 && tree_fits_uhwi_p (DECL_SIZE (field))
1354 && tree_fits_uhwi_p (rli->offset)
1355 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1356 {
1357 unsigned int type_align = TYPE_ALIGN (type);
1358 tree dsize = DECL_SIZE (field);
1359 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1360 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1361 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1362
1363 #ifdef ADJUST_FIELD_ALIGN
1364 if (! TYPE_USER_ALIGN (type))
1365 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1366 #endif
1367
1368 /* A bit field may not span more units of alignment of its type
1369 than its type itself. Advance to next boundary if necessary. */
1370 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1371 {
1372 if (DECL_PACKED (field))
1373 {
1374 if (warn_packed_bitfield_compat == 1)
1375 inform
1376 (input_location,
1377 "offset of packed bit-field %qD has changed in GCC 4.4",
1378 field);
1379 }
1380 else
1381 rli->bitpos = round_up (rli->bitpos, type_align);
1382 }
1383
1384 if (! DECL_PACKED (field))
1385 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1386
1387 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1388 TYPE_WARN_IF_NOT_ALIGN (type));
1389 }
1390
1391 #ifdef BITFIELD_NBYTES_LIMITED
1392 if (BITFIELD_NBYTES_LIMITED
1393 && ! targetm.ms_bitfield_layout_p (rli->t)
1394 && TREE_CODE (field) == FIELD_DECL
1395 && type != error_mark_node
1396 && DECL_BIT_FIELD_TYPE (field)
1397 && ! DECL_PACKED (field)
1398 && ! integer_zerop (DECL_SIZE (field))
1399 && tree_fits_uhwi_p (DECL_SIZE (field))
1400 && tree_fits_uhwi_p (rli->offset)
1401 && tree_fits_uhwi_p (TYPE_SIZE (type)))
1402 {
1403 unsigned int type_align = TYPE_ALIGN (type);
1404 tree dsize = DECL_SIZE (field);
1405 HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
1406 HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
1407 HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);
1408
1409 #ifdef ADJUST_FIELD_ALIGN
1410 if (! TYPE_USER_ALIGN (type))
1411 type_align = ADJUST_FIELD_ALIGN (field, type, type_align);
1412 #endif
1413
1414 if (maximum_field_alignment != 0)
1415 type_align = MIN (type_align, maximum_field_alignment);
1416 /* ??? This test is opposite the test in the containing if
1417 statement, so this code is unreachable currently. */
1418 else if (DECL_PACKED (field))
1419 type_align = MIN (type_align, BITS_PER_UNIT);
1420
1421 /* A bit field may not span the unit of alignment of its type.
1422 Advance to next boundary if necessary. */
1423 if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
1424 rli->bitpos = round_up (rli->bitpos, type_align);
1425
1426 TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
1427 SET_TYPE_WARN_IF_NOT_ALIGN (rli->t,
1428 TYPE_WARN_IF_NOT_ALIGN (type));
1429 }
1430 #endif
1431
1432 /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
1433 A subtlety:
1434 When a bit field is inserted into a packed record, the whole
1435 size of the underlying type is used by one or more same-size
1436 adjacent bitfields. (That is, if its long:3, 32 bits is
1437 used in the record, and any additional adjacent long bitfields are
1438 packed into the same chunk of 32 bits. However, if the size
1439 changes, a new field of that size is allocated.) In an unpacked
1440 record, this is the same as using alignment, but not equivalent
1441 when packing.
1442
1443 Note: for compatibility, we use the type size, not the type alignment
1444 to determine alignment, since that matches the documentation */
1445
1446 if (targetm.ms_bitfield_layout_p (rli->t))
1447 {
1448 tree prev_saved = rli->prev_field;
1449 tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;
1450
1451 /* This is a bitfield if it exists. */
1452 if (rli->prev_field)
1453 {
1454 bool realign_p = known_align < desired_align;
1455
1456 /* If both are bitfields, nonzero, and the same size, this is
1457 the middle of a run. Zero declared size fields are special
1458 and handled as "end of run". (Note: it's nonzero declared
1459 size, but equal type sizes!) (Since we know that both
1460 the current and previous fields are bitfields by the
1461 time we check it, DECL_SIZE must be present for both.) */
1462 if (DECL_BIT_FIELD_TYPE (field)
1463 && !integer_zerop (DECL_SIZE (field))
1464 && !integer_zerop (DECL_SIZE (rli->prev_field))
1465 && tree_fits_shwi_p (DECL_SIZE (rli->prev_field))
1466 && tree_fits_uhwi_p (TYPE_SIZE (type))
1467 && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
1468 {
1469 /* We're in the middle of a run of equal type size fields; make
1470 sure we realign if we run out of bits. (Not decl size,
1471 type size!) */
1472 HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field));
1473
1474 if (rli->remaining_in_alignment < bitsize)
1475 {
1476 HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type));
1477
1478 /* out of bits; bump up to next 'word'. */
1479 rli->bitpos
1480 = size_binop (PLUS_EXPR, rli->bitpos,
1481 bitsize_int (rli->remaining_in_alignment));
1482 rli->prev_field = field;
1483 if (typesize < bitsize)
1484 rli->remaining_in_alignment = 0;
1485 else
1486 rli->remaining_in_alignment = typesize - bitsize;
1487 }
1488 else
1489 {
1490 rli->remaining_in_alignment -= bitsize;
1491 realign_p = false;
1492 }
1493 }
1494 else
1495 {
1496 /* End of a run: if leaving a run of bitfields of the same type
1497 size, we have to "use up" the rest of the bits of the type
1498 size.
1499
1500 Compute the new position as the sum of the size for the prior
1501 type and where we first started working on that type.
1502 Note: since the beginning of the field was aligned then
1503 of course the end will be too. No round needed. */
1504
1505 if (!integer_zerop (DECL_SIZE (rli->prev_field)))
1506 {
1507 rli->bitpos
1508 = size_binop (PLUS_EXPR, rli->bitpos,
1509 bitsize_int (rli->remaining_in_alignment));
1510 }
1511 else
1512 /* We "use up" size zero fields; the code below should behave
1513 as if the prior field was not a bitfield. */
1514 prev_saved = NULL;
1515
1516 /* Cause a new bitfield to be captured, either this time (if
1517 currently a bitfield) or next time we see one. */
1518 if (!DECL_BIT_FIELD_TYPE (field)
1519 || integer_zerop (DECL_SIZE (field)))
1520 rli->prev_field = NULL;
1521 }
1522
1523 /* Does this field automatically have alignment it needs by virtue
1524 of the fields that precede it and the record's own alignment? */
1525 if (realign_p)
1526 {
1527 /* If the alignment is still within offset_align, just align
1528 the bit position. */
1529 if (desired_align < rli->offset_align)
1530 rli->bitpos = round_up (rli->bitpos, desired_align);
1531 else
1532 {
1533 /* First adjust OFFSET by the partial bits, then align. */
1534 tree d = size_binop (CEIL_DIV_EXPR, rli->bitpos,
1535 bitsize_unit_node);
1536 rli->offset = size_binop (PLUS_EXPR, rli->offset,
1537 fold_convert (sizetype, d));
1538 rli->bitpos = bitsize_zero_node;
1539
1540 rli->offset = round_up (rli->offset,
1541 desired_align / BITS_PER_UNIT);
1542 }
1543
1544 if (! TREE_CONSTANT (rli->offset))
1545 rli->offset_align = desired_align;
1546 }
1547
1548 normalize_rli (rli);
1549 }
1550
1551 /* If we're starting a new run of same type size bitfields
1552 (or a run of non-bitfields), set up the "first of the run"
1553 fields.
1554
1555 That is, if the current field is not a bitfield, or if there
1556 was a prior bitfield the type sizes differ, or if there wasn't
1557 a prior bitfield the size of the current field is nonzero.
1558
1559 Note: we must be sure to test ONLY the type size if there was
1560 a prior bitfield and ONLY for the current field being zero if
1561 there wasn't. */
1562
1563 if (!DECL_BIT_FIELD_TYPE (field)
1564 || (prev_saved != NULL
1565 ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
1566 : !integer_zerop (DECL_SIZE (field))))
1567 {
1568 /* Never smaller than a byte for compatibility. */
1569 unsigned int type_align = BITS_PER_UNIT;
1570
1571 /* (When not a bitfield), we could be seeing a flex array (with
1572 no DECL_SIZE). Since we won't be using remaining_in_alignment
1573 until we see a bitfield (and come by here again) we just skip
1574 calculating it. */
1575 if (DECL_SIZE (field) != NULL
1576 && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field)))
1577 && tree_fits_uhwi_p (DECL_SIZE (field)))
1578 {
1579 unsigned HOST_WIDE_INT bitsize
1580 = tree_to_uhwi (DECL_SIZE (field));
1581 unsigned HOST_WIDE_INT typesize
1582 = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field)));
1583
1584 if (typesize < bitsize)
1585 rli->remaining_in_alignment = 0;
1586 else
1587 rli->remaining_in_alignment = typesize - bitsize;
1588 }
1589
1590 /* Now align (conventionally) for the new type. */
1591 if (! DECL_PACKED (field))
1592 type_align = TYPE_ALIGN (TREE_TYPE (field));
1593
1594 if (maximum_field_alignment != 0)
1595 type_align = MIN (type_align, maximum_field_alignment);
1596
1597 rli->bitpos = round_up (rli->bitpos, type_align);
1598
1599 /* If we really aligned, don't allow subsequent bitfields
1600 to undo that. */
1601 rli->prev_field = NULL;
1602 }
1603 }
1604
1605 /* Offset so far becomes the position of this field after normalizing. */
1606 normalize_rli (rli);
1607 DECL_FIELD_OFFSET (field) = rli->offset;
1608 DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
1609 SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
1610 handle_warn_if_not_align (field, rli->record_align);
1611
1612 /* Evaluate nonconstant offsets only once, either now or as soon as safe. */
1613 if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
1614 DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));
1615
1616 /* If this field ended up more aligned than we thought it would be (we
1617 approximate this by seeing if its position changed), lay out the field
1618 again; perhaps we can use an integral mode for it now. */
1619 if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field)))
1620 actual_align = least_bit_hwi (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)));
1621 else if (integer_zerop (DECL_FIELD_OFFSET (field)))
1622 actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
1623 else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
1624 actual_align = (BITS_PER_UNIT
1625 * least_bit_hwi (tree_to_uhwi (DECL_FIELD_OFFSET (field))));
1626 else
1627 actual_align = DECL_OFFSET_ALIGN (field);
1628 /* ACTUAL_ALIGN is still the actual alignment *within the record* .
1629 store / extract bit field operations will check the alignment of the
1630 record against the mode of bit fields. */
1631
1632 if (known_align != actual_align)
1633 layout_decl (field, actual_align);
1634
1635 if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field))
1636 rli->prev_field = field;
1637
1638 /* Now add size of this field to the size of the record. If the size is
1639 not constant, treat the field as being a multiple of bytes and just
1640 adjust the offset, resetting the bit position. Otherwise, apportion the
1641 size amongst the bit position and offset. First handle the case of an
1642 unspecified size, which can happen when we have an invalid nested struct
1643 definition, such as struct j { struct j { int i; } }. The error message
1644 is printed in finish_struct. */
1645 if (DECL_SIZE (field) == 0)
1646 /* Do nothing. */;
1647 else if (TREE_CODE (DECL_SIZE (field)) != INTEGER_CST
1648 || TREE_OVERFLOW (DECL_SIZE (field)))
1649 {
1650 rli->offset
1651 = size_binop (PLUS_EXPR, rli->offset,
1652 fold_convert (sizetype,
1653 size_binop (CEIL_DIV_EXPR, rli->bitpos,
1654 bitsize_unit_node)));
1655 rli->offset
1656 = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field));
1657 rli->bitpos = bitsize_zero_node;
1658 rli->offset_align = MIN (rli->offset_align, desired_align);
1659
1660 if (!multiple_of_p (bitsizetype, DECL_SIZE (field),
1661 bitsize_int (rli->offset_align)))
1662 {
1663 tree type = strip_array_types (TREE_TYPE (field));
1664 /* The above adjusts offset_align just based on the start of the
1665 field. The field might not have a size that is a multiple of
1666 that offset_align though. If the field is an array of fixed
1667 sized elements, assume there can be any multiple of those
1668 sizes. If it is a variable length aggregate or array of
1669 variable length aggregates, assume worst that the end is
1670 just BITS_PER_UNIT aligned. */
1671 if (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
1672 {
1673 if (TREE_INT_CST_LOW (TYPE_SIZE (type)))
1674 {
1675 unsigned HOST_WIDE_INT sz
1676 = least_bit_hwi (TREE_INT_CST_LOW (TYPE_SIZE (type)));
1677 rli->offset_align = MIN (rli->offset_align, sz);
1678 }
1679 }
1680 else
1681 rli->offset_align = MIN (rli->offset_align, BITS_PER_UNIT);
1682 }
1683 }
1684 else if (targetm.ms_bitfield_layout_p (rli->t))
1685 {
1686 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1687
1688 /* If FIELD is the last field and doesn't end at the full length
1689 of the type then pad the struct out to the full length of the
1690 last type. */
1691 if (DECL_BIT_FIELD_TYPE (field)
1692 && !integer_zerop (DECL_SIZE (field)))
1693 {
1694 /* We have to scan, because non-field DECLS are also here. */
1695 tree probe = field;
1696 while ((probe = DECL_CHAIN (probe)))
1697 if (TREE_CODE (probe) == FIELD_DECL)
1698 break;
1699 if (!probe)
1700 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos,
1701 bitsize_int (rli->remaining_in_alignment));
1702 }
1703
1704 normalize_rli (rli);
1705 }
1706 else
1707 {
1708 rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
1709 normalize_rli (rli);
1710 }
1711 }
1712
1713 /* Assuming that all the fields have been laid out, this function uses
1714 RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type
1715 indicated by RLI. */
1716
1717 static void
finalize_record_size(record_layout_info rli)1718 finalize_record_size (record_layout_info rli)
1719 {
1720 tree unpadded_size, unpadded_size_unit;
1721
1722 /* Now we want just byte and bit offsets, so set the offset alignment
1723 to be a byte and then normalize. */
1724 rli->offset_align = BITS_PER_UNIT;
1725 normalize_rli (rli);
1726
1727 /* Determine the desired alignment. */
1728 #ifdef ROUND_TYPE_ALIGN
1729 SET_TYPE_ALIGN (rli->t, ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t),
1730 rli->record_align));
1731 #else
1732 SET_TYPE_ALIGN (rli->t, MAX (TYPE_ALIGN (rli->t), rli->record_align));
1733 #endif
1734
1735 /* Compute the size so far. Be sure to allow for extra bits in the
1736 size in bytes. We have guaranteed above that it will be no more
1737 than a single byte. */
1738 unpadded_size = rli_size_so_far (rli);
1739 unpadded_size_unit = rli_size_unit_so_far (rli);
1740 if (! integer_zerop (rli->bitpos))
1741 unpadded_size_unit
1742 = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node);
1743
1744 /* Round the size up to be a multiple of the required alignment. */
1745 TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
1746 TYPE_SIZE_UNIT (rli->t)
1747 = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t));
1748
1749 if (TREE_CONSTANT (unpadded_size)
1750 && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0
1751 && input_location != BUILTINS_LOCATION)
1752 warning (OPT_Wpadded, "padding struct size to alignment boundary");
1753
1754 if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE
1755 && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary
1756 && TREE_CONSTANT (unpadded_size))
1757 {
1758 tree unpacked_size;
1759
1760 #ifdef ROUND_TYPE_ALIGN
1761 rli->unpacked_align
1762 = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align);
1763 #else
1764 rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align);
1765 #endif
1766
1767 unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
1768 if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
1769 {
1770 if (TYPE_NAME (rli->t))
1771 {
1772 tree name;
1773
1774 if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE)
1775 name = TYPE_NAME (rli->t);
1776 else
1777 name = DECL_NAME (TYPE_NAME (rli->t));
1778
1779 if (STRICT_ALIGNMENT)
1780 warning (OPT_Wpacked, "packed attribute causes inefficient "
1781 "alignment for %qE", name);
1782 else
1783 warning (OPT_Wpacked,
1784 "packed attribute is unnecessary for %qE", name);
1785 }
1786 else
1787 {
1788 if (STRICT_ALIGNMENT)
1789 warning (OPT_Wpacked,
1790 "packed attribute causes inefficient alignment");
1791 else
1792 warning (OPT_Wpacked, "packed attribute is unnecessary");
1793 }
1794 }
1795 }
1796 }
1797
1798 /* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE). */
1799
1800 void
compute_record_mode(tree type)1801 compute_record_mode (tree type)
1802 {
1803 tree field;
1804 machine_mode mode = VOIDmode;
1805
1806 /* Most RECORD_TYPEs have BLKmode, so we start off assuming that.
1807 However, if possible, we use a mode that fits in a register
1808 instead, in order to allow for better optimization down the
1809 line. */
1810 SET_TYPE_MODE (type, BLKmode);
1811
1812 if (! tree_fits_uhwi_p (TYPE_SIZE (type)))
1813 return;
1814
1815 /* A record which has any BLKmode members must itself be
1816 BLKmode; it can't go in a register. Unless the member is
1817 BLKmode only because it isn't aligned. */
1818 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
1819 {
1820 if (TREE_CODE (field) != FIELD_DECL)
1821 continue;
1822
1823 if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK
1824 || (TYPE_MODE (TREE_TYPE (field)) == BLKmode
1825 && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field))
1826 && !(TYPE_SIZE (TREE_TYPE (field)) != 0
1827 && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
1828 || ! tree_fits_uhwi_p (bit_position (field))
1829 || DECL_SIZE (field) == 0
1830 || ! tree_fits_uhwi_p (DECL_SIZE (field)))
1831 return;
1832
1833 /* If this field is the whole struct, remember its mode so
1834 that, say, we can put a double in a class into a DF
1835 register instead of forcing it to live in the stack. */
1836 if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field)))
1837 mode = DECL_MODE (field);
1838
1839 /* With some targets, it is sub-optimal to access an aligned
1840 BLKmode structure as a scalar. */
1841 if (targetm.member_type_forces_blk (field, mode))
1842 return;
1843 }
1844
1845 /* If we only have one real field; use its mode if that mode's size
1846 matches the type's size. This only applies to RECORD_TYPE. This
1847 does not apply to unions. */
1848 if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode
1849 && tree_fits_uhwi_p (TYPE_SIZE (type))
1850 && known_eq (GET_MODE_BITSIZE (mode), tree_to_uhwi (TYPE_SIZE (type))))
1851 ;
1852 else
1853 mode = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1).else_blk ();
1854
1855 /* If structure's known alignment is less than what the scalar
1856 mode would need, and it matters, then stick with BLKmode. */
1857 if (mode != BLKmode
1858 && STRICT_ALIGNMENT
1859 && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT
1860 || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (mode)))
1861 {
1862 /* If this is the only reason this type is BLKmode, then
1863 don't force containing types to be BLKmode. */
1864 TYPE_NO_FORCE_BLK (type) = 1;
1865 mode = BLKmode;
1866 }
1867
1868 SET_TYPE_MODE (type, mode);
1869 }
1870
1871 /* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid
1872 out. */
1873
1874 static void
finalize_type_size(tree type)1875 finalize_type_size (tree type)
1876 {
1877 /* Normally, use the alignment corresponding to the mode chosen.
1878 However, where strict alignment is not required, avoid
1879 over-aligning structures, since most compilers do not do this
1880 alignment. */
1881 if (TYPE_MODE (type) != BLKmode
1882 && TYPE_MODE (type) != VOIDmode
1883 && (STRICT_ALIGNMENT || !AGGREGATE_TYPE_P (type)))
1884 {
1885 unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type));
1886
1887 /* Don't override a larger alignment requirement coming from a user
1888 alignment of one of the fields. */
1889 if (mode_align >= TYPE_ALIGN (type))
1890 {
1891 SET_TYPE_ALIGN (type, mode_align);
1892 TYPE_USER_ALIGN (type) = 0;
1893 }
1894 }
1895
1896 /* Do machine-dependent extra alignment. */
1897 #ifdef ROUND_TYPE_ALIGN
1898 SET_TYPE_ALIGN (type,
1899 ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT));
1900 #endif
1901
1902 /* If we failed to find a simple way to calculate the unit size
1903 of the type, find it by division. */
1904 if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0)
1905 /* TYPE_SIZE (type) is computed in bitsizetype. After the division, the
1906 result will fit in sizetype. We will get more efficient code using
1907 sizetype, so we force a conversion. */
1908 TYPE_SIZE_UNIT (type)
1909 = fold_convert (sizetype,
1910 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
1911 bitsize_unit_node));
1912
1913 if (TYPE_SIZE (type) != 0)
1914 {
1915 TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
1916 TYPE_SIZE_UNIT (type)
1917 = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type));
1918 }
1919
1920 /* Evaluate nonconstant sizes only once, either now or as soon as safe. */
1921 if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
1922 TYPE_SIZE (type) = variable_size (TYPE_SIZE (type));
1923 if (TYPE_SIZE_UNIT (type) != 0
1924 && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST)
1925 TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type));
1926
1927 /* Handle empty records as per the x86-64 psABI. */
1928 TYPE_EMPTY_P (type) = targetm.calls.empty_record_p (type);
1929
1930 /* Also layout any other variants of the type. */
1931 if (TYPE_NEXT_VARIANT (type)
1932 || type != TYPE_MAIN_VARIANT (type))
1933 {
1934 tree variant;
1935 /* Record layout info of this variant. */
1936 tree size = TYPE_SIZE (type);
1937 tree size_unit = TYPE_SIZE_UNIT (type);
1938 unsigned int align = TYPE_ALIGN (type);
1939 unsigned int precision = TYPE_PRECISION (type);
1940 unsigned int user_align = TYPE_USER_ALIGN (type);
1941 machine_mode mode = TYPE_MODE (type);
1942 bool empty_p = TYPE_EMPTY_P (type);
1943
1944 /* Copy it into all variants. */
1945 for (variant = TYPE_MAIN_VARIANT (type);
1946 variant != 0;
1947 variant = TYPE_NEXT_VARIANT (variant))
1948 {
1949 TYPE_SIZE (variant) = size;
1950 TYPE_SIZE_UNIT (variant) = size_unit;
1951 unsigned valign = align;
1952 if (TYPE_USER_ALIGN (variant))
1953 valign = MAX (valign, TYPE_ALIGN (variant));
1954 else
1955 TYPE_USER_ALIGN (variant) = user_align;
1956 SET_TYPE_ALIGN (variant, valign);
1957 TYPE_PRECISION (variant) = precision;
1958 SET_TYPE_MODE (variant, mode);
1959 TYPE_EMPTY_P (variant) = empty_p;
1960 }
1961 }
1962 }
1963
1964 /* Return a new underlying object for a bitfield started with FIELD. */
1965
1966 static tree
start_bitfield_representative(tree field)1967 start_bitfield_representative (tree field)
1968 {
1969 tree repr = make_node (FIELD_DECL);
1970 DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field);
1971 /* Force the representative to begin at a BITS_PER_UNIT aligned
1972 boundary - C++ may use tail-padding of a base object to
1973 continue packing bits so the bitfield region does not start
1974 at bit zero (see g++.dg/abi/bitfield5.C for example).
1975 Unallocated bits may happen for other reasons as well,
1976 for example Ada which allows explicit bit-granular structure layout. */
1977 DECL_FIELD_BIT_OFFSET (repr)
1978 = size_binop (BIT_AND_EXPR,
1979 DECL_FIELD_BIT_OFFSET (field),
1980 bitsize_int (~(BITS_PER_UNIT - 1)));
1981 SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field));
1982 DECL_SIZE (repr) = DECL_SIZE (field);
1983 DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
1984 DECL_PACKED (repr) = DECL_PACKED (field);
1985 DECL_CONTEXT (repr) = DECL_CONTEXT (field);
1986 /* There are no indirect accesses to this field. If we introduce
1987 some then they have to use the record alias set. This makes
1988 sure to properly conflict with [indirect] accesses to addressable
1989 fields of the bitfield group. */
1990 DECL_NONADDRESSABLE_P (repr) = 1;
1991 return repr;
1992 }
1993
1994 /* Finish up a bitfield group that was started by creating the underlying
1995 object REPR with the last field in the bitfield group FIELD. */
1996
1997 static void
finish_bitfield_representative(tree repr,tree field)1998 finish_bitfield_representative (tree repr, tree field)
1999 {
2000 unsigned HOST_WIDE_INT bitsize, maxbitsize;
2001 tree nextf, size;
2002
2003 size = size_diffop (DECL_FIELD_OFFSET (field),
2004 DECL_FIELD_OFFSET (repr));
2005 while (TREE_CODE (size) == COMPOUND_EXPR)
2006 size = TREE_OPERAND (size, 1);
2007 gcc_assert (tree_fits_uhwi_p (size));
2008 bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
2009 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
2010 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))
2011 + tree_to_uhwi (DECL_SIZE (field)));
2012
2013 /* Round up bitsize to multiples of BITS_PER_UNIT. */
2014 bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
2015
2016 /* Now nothing tells us how to pad out bitsize ... */
2017 nextf = DECL_CHAIN (field);
2018 while (nextf && TREE_CODE (nextf) != FIELD_DECL)
2019 nextf = DECL_CHAIN (nextf);
2020 if (nextf)
2021 {
2022 tree maxsize;
2023 /* If there was an error, the field may be not laid out
2024 correctly. Don't bother to do anything. */
2025 if (TREE_TYPE (nextf) == error_mark_node)
2026 return;
2027 maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
2028 DECL_FIELD_OFFSET (repr));
2029 if (tree_fits_uhwi_p (maxsize))
2030 {
2031 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
2032 + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf))
2033 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
2034 /* If the group ends within a bitfield nextf does not need to be
2035 aligned to BITS_PER_UNIT. Thus round up. */
2036 maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
2037 }
2038 else
2039 maxbitsize = bitsize;
2040 }
2041 else
2042 {
2043 /* Note that if the C++ FE sets up tail-padding to be re-used it
2044 creates a as-base variant of the type with TYPE_SIZE adjusted
2045 accordingly. So it is safe to include tail-padding here. */
2046 tree aggsize = lang_hooks.types.unit_size_without_reusable_padding
2047 (DECL_CONTEXT (field));
2048 tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr));
2049 /* We cannot generally rely on maxsize to fold to an integer constant,
2050 so use bitsize as fallback for this case. */
2051 if (tree_fits_uhwi_p (maxsize))
2052 maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
2053 - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
2054 else
2055 maxbitsize = bitsize;
2056 }
2057
2058 /* Only if we don't artificially break up the representative in
2059 the middle of a large bitfield with different possibly
2060 overlapping representatives. And all representatives start
2061 at byte offset. */
2062 gcc_assert (maxbitsize % BITS_PER_UNIT == 0);
2063
2064 /* Find the smallest nice mode to use. */
2065 opt_scalar_int_mode mode_iter;
2066 FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_INT)
2067 if (GET_MODE_BITSIZE (mode_iter.require ()) >= bitsize)
2068 break;
2069
2070 scalar_int_mode mode;
2071 if (!mode_iter.exists (&mode)
2072 || GET_MODE_BITSIZE (mode) > maxbitsize
2073 || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE)
2074 {
2075 /* We really want a BLKmode representative only as a last resort,
2076 considering the member b in
2077 struct { int a : 7; int b : 17; int c; } __attribute__((packed));
2078 Otherwise we simply want to split the representative up
2079 allowing for overlaps within the bitfield region as required for
2080 struct { int a : 7; int b : 7;
2081 int c : 10; int d; } __attribute__((packed));
2082 [0, 15] HImode for a and b, [8, 23] HImode for c. */
2083 DECL_SIZE (repr) = bitsize_int (bitsize);
2084 DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT);
2085 SET_DECL_MODE (repr, BLKmode);
2086 TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node,
2087 bitsize / BITS_PER_UNIT);
2088 }
2089 else
2090 {
2091 unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode);
2092 DECL_SIZE (repr) = bitsize_int (modesize);
2093 DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT);
2094 SET_DECL_MODE (repr, mode);
2095 TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1);
2096 }
2097
2098 /* Remember whether the bitfield group is at the end of the
2099 structure or not. */
2100 DECL_CHAIN (repr) = nextf;
2101 }
2102
2103 /* Compute and set FIELD_DECLs for the underlying objects we should
2104 use for bitfield access for the structure T. */
2105
2106 void
finish_bitfield_layout(tree t)2107 finish_bitfield_layout (tree t)
2108 {
2109 tree field, prev;
2110 tree repr = NULL_TREE;
2111
2112 /* Unions would be special, for the ease of type-punning optimizations
2113 we could use the underlying type as hint for the representative
2114 if the bitfield would fit and the representative would not exceed
2115 the union in size. */
2116 if (TREE_CODE (t) != RECORD_TYPE)
2117 return;
2118
2119 for (prev = NULL_TREE, field = TYPE_FIELDS (t);
2120 field; field = DECL_CHAIN (field))
2121 {
2122 if (TREE_CODE (field) != FIELD_DECL)
2123 continue;
2124
2125 /* In the C++ memory model, consecutive bit fields in a structure are
2126 considered one memory location and updating a memory location
2127 may not store into adjacent memory locations. */
2128 if (!repr
2129 && DECL_BIT_FIELD_TYPE (field))
2130 {
2131 /* Start new representative. */
2132 repr = start_bitfield_representative (field);
2133 }
2134 else if (repr
2135 && ! DECL_BIT_FIELD_TYPE (field))
2136 {
2137 /* Finish off new representative. */
2138 finish_bitfield_representative (repr, prev);
2139 repr = NULL_TREE;
2140 }
2141 else if (DECL_BIT_FIELD_TYPE (field))
2142 {
2143 gcc_assert (repr != NULL_TREE);
2144
2145 /* Zero-size bitfields finish off a representative and
2146 do not have a representative themselves. This is
2147 required by the C++ memory model. */
2148 if (integer_zerop (DECL_SIZE (field)))
2149 {
2150 finish_bitfield_representative (repr, prev);
2151 repr = NULL_TREE;
2152 }
2153
2154 /* We assume that either DECL_FIELD_OFFSET of the representative
2155 and each bitfield member is a constant or they are equal.
2156 This is because we need to be able to compute the bit-offset
2157 of each field relative to the representative in get_bit_range
2158 during RTL expansion.
2159 If these constraints are not met, simply force a new
2160 representative to be generated. That will at most
2161 generate worse code but still maintain correctness with
2162 respect to the C++ memory model. */
2163 else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr))
2164 && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
2165 || operand_equal_p (DECL_FIELD_OFFSET (repr),
2166 DECL_FIELD_OFFSET (field), 0)))
2167 {
2168 finish_bitfield_representative (repr, prev);
2169 repr = start_bitfield_representative (field);
2170 }
2171 }
2172 else
2173 continue;
2174
2175 if (repr)
2176 DECL_BIT_FIELD_REPRESENTATIVE (field) = repr;
2177
2178 prev = field;
2179 }
2180
2181 if (repr)
2182 finish_bitfield_representative (repr, prev);
2183 }
2184
2185 /* Do all of the work required to layout the type indicated by RLI,
2186 once the fields have been laid out. This function will call `free'
2187 for RLI, unless FREE_P is false. Passing a value other than false
2188 for FREE_P is bad practice; this option only exists to support the
2189 G++ 3.2 ABI. */
2190
2191 void
finish_record_layout(record_layout_info rli,int free_p)2192 finish_record_layout (record_layout_info rli, int free_p)
2193 {
2194 tree variant;
2195
2196 /* Compute the final size. */
2197 finalize_record_size (rli);
2198
2199 /* Compute the TYPE_MODE for the record. */
2200 compute_record_mode (rli->t);
2201
2202 /* Perform any last tweaks to the TYPE_SIZE, etc. */
2203 finalize_type_size (rli->t);
2204
2205 /* Compute bitfield representatives. */
2206 finish_bitfield_layout (rli->t);
2207
2208 /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants.
2209 With C++ templates, it is too early to do this when the attribute
2210 is being parsed. */
2211 for (variant = TYPE_NEXT_VARIANT (rli->t); variant;
2212 variant = TYPE_NEXT_VARIANT (variant))
2213 {
2214 TYPE_PACKED (variant) = TYPE_PACKED (rli->t);
2215 TYPE_REVERSE_STORAGE_ORDER (variant)
2216 = TYPE_REVERSE_STORAGE_ORDER (rli->t);
2217 }
2218
2219 /* Lay out any static members. This is done now because their type
2220 may use the record's type. */
2221 while (!vec_safe_is_empty (rli->pending_statics))
2222 layout_decl (rli->pending_statics->pop (), 0);
2223
2224 /* Clean up. */
2225 if (free_p)
2226 {
2227 vec_free (rli->pending_statics);
2228 free (rli);
2229 }
2230 }
2231
2232
2233 /* Finish processing a builtin RECORD_TYPE type TYPE. It's name is
2234 NAME, its fields are chained in reverse on FIELDS.
2235
2236 If ALIGN_TYPE is non-null, it is given the same alignment as
2237 ALIGN_TYPE. */
2238
2239 void
finish_builtin_struct(tree type,const char * name,tree fields,tree align_type)2240 finish_builtin_struct (tree type, const char *name, tree fields,
2241 tree align_type)
2242 {
2243 tree tail, next;
2244
2245 for (tail = NULL_TREE; fields; tail = fields, fields = next)
2246 {
2247 DECL_FIELD_CONTEXT (fields) = type;
2248 next = DECL_CHAIN (fields);
2249 DECL_CHAIN (fields) = tail;
2250 }
2251 TYPE_FIELDS (type) = tail;
2252
2253 if (align_type)
2254 {
2255 SET_TYPE_ALIGN (type, TYPE_ALIGN (align_type));
2256 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type);
2257 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2258 TYPE_WARN_IF_NOT_ALIGN (align_type));
2259 }
2260
2261 layout_type (type);
2262 #if 0 /* not yet, should get fixed properly later */
2263 TYPE_NAME (type) = make_type_decl (get_identifier (name), type);
2264 #else
2265 TYPE_NAME (type) = build_decl (BUILTINS_LOCATION,
2266 TYPE_DECL, get_identifier (name), type);
2267 #endif
2268 TYPE_STUB_DECL (type) = TYPE_NAME (type);
2269 layout_decl (TYPE_NAME (type), 0);
2270 }
2271
2272 /* Calculate the mode, size, and alignment for TYPE.
2273 For an array type, calculate the element separation as well.
2274 Record TYPE on the chain of permanent or temporary types
2275 so that dbxout will find out about it.
2276
2277 TYPE_SIZE of a type is nonzero if the type has been laid out already.
2278 layout_type does nothing on such a type.
2279
2280 If the type is incomplete, its TYPE_SIZE remains zero. */
2281
2282 void
layout_type(tree type)2283 layout_type (tree type)
2284 {
2285 gcc_assert (type);
2286
2287 if (type == error_mark_node)
2288 return;
2289
2290 /* We don't want finalize_type_size to copy an alignment attribute to
2291 variants that don't have it. */
2292 type = TYPE_MAIN_VARIANT (type);
2293
2294 /* Do nothing if type has been laid out before. */
2295 if (TYPE_SIZE (type))
2296 return;
2297
2298 switch (TREE_CODE (type))
2299 {
2300 case LANG_TYPE:
2301 /* This kind of type is the responsibility
2302 of the language-specific code. */
2303 gcc_unreachable ();
2304
2305 case BOOLEAN_TYPE:
2306 case INTEGER_TYPE:
2307 case ENUMERAL_TYPE:
2308 {
2309 scalar_int_mode mode
2310 = smallest_int_mode_for_size (TYPE_PRECISION (type));
2311 SET_TYPE_MODE (type, mode);
2312 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2313 /* Don't set TYPE_PRECISION here, as it may be set by a bitfield. */
2314 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2315 break;
2316 }
2317
2318 case REAL_TYPE:
2319 {
2320 /* Allow the caller to choose the type mode, which is how decimal
2321 floats are distinguished from binary ones. */
2322 if (TYPE_MODE (type) == VOIDmode)
2323 SET_TYPE_MODE
2324 (type, float_mode_for_size (TYPE_PRECISION (type)).require ());
2325 scalar_float_mode mode = as_a <scalar_float_mode> (TYPE_MODE (type));
2326 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2327 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2328 break;
2329 }
2330
2331 case FIXED_POINT_TYPE:
2332 {
2333 /* TYPE_MODE (type) has been set already. */
2334 scalar_mode mode = SCALAR_TYPE_MODE (type);
2335 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2336 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2337 break;
2338 }
2339
2340 case COMPLEX_TYPE:
2341 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2342 SET_TYPE_MODE (type,
2343 GET_MODE_COMPLEX_MODE (TYPE_MODE (TREE_TYPE (type))));
2344
2345 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2346 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2347 break;
2348
2349 case VECTOR_TYPE:
2350 {
2351 poly_uint64 nunits = TYPE_VECTOR_SUBPARTS (type);
2352 tree innertype = TREE_TYPE (type);
2353
2354 /* Find an appropriate mode for the vector type. */
2355 if (TYPE_MODE (type) == VOIDmode)
2356 SET_TYPE_MODE (type,
2357 mode_for_vector (SCALAR_TYPE_MODE (innertype),
2358 nunits).else_blk ());
2359
2360 TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type));
2361 TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
2362 /* Several boolean vector elements may fit in a single unit. */
2363 if (VECTOR_BOOLEAN_TYPE_P (type)
2364 && type->type_common.mode != BLKmode)
2365 TYPE_SIZE_UNIT (type)
2366 = size_int (GET_MODE_SIZE (type->type_common.mode));
2367 else
2368 TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR,
2369 TYPE_SIZE_UNIT (innertype),
2370 size_int (nunits));
2371 TYPE_SIZE (type) = int_const_binop
2372 (MULT_EXPR,
2373 bits_from_bytes (TYPE_SIZE_UNIT (type)),
2374 bitsize_int (BITS_PER_UNIT));
2375
2376 /* For vector types, we do not default to the mode's alignment.
2377 Instead, query a target hook, defaulting to natural alignment.
2378 This prevents ABI changes depending on whether or not native
2379 vector modes are supported. */
2380 SET_TYPE_ALIGN (type, targetm.vector_alignment (type));
2381
2382 /* However, if the underlying mode requires a bigger alignment than
2383 what the target hook provides, we cannot use the mode. For now,
2384 simply reject that case. */
2385 gcc_assert (TYPE_ALIGN (type)
2386 >= GET_MODE_ALIGNMENT (TYPE_MODE (type)));
2387 break;
2388 }
2389
2390 case VOID_TYPE:
2391 /* This is an incomplete type and so doesn't have a size. */
2392 SET_TYPE_ALIGN (type, 1);
2393 TYPE_USER_ALIGN (type) = 0;
2394 SET_TYPE_MODE (type, VOIDmode);
2395 break;
2396
2397 case POINTER_BOUNDS_TYPE:
2398 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
2399 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
2400 break;
2401
2402 case OFFSET_TYPE:
2403 TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
2404 TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS);
2405 /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be
2406 integral, which may be an __intN. */
2407 SET_TYPE_MODE (type, int_mode_for_size (POINTER_SIZE, 0).require ());
2408 TYPE_PRECISION (type) = POINTER_SIZE;
2409 break;
2410
2411 case FUNCTION_TYPE:
2412 case METHOD_TYPE:
2413 /* It's hard to see what the mode and size of a function ought to
2414 be, but we do know the alignment is FUNCTION_BOUNDARY, so
2415 make it consistent with that. */
2416 SET_TYPE_MODE (type,
2417 int_mode_for_size (FUNCTION_BOUNDARY, 0).else_blk ());
2418 TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY);
2419 TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT);
2420 break;
2421
2422 case POINTER_TYPE:
2423 case REFERENCE_TYPE:
2424 {
2425 scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
2426 TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
2427 TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
2428 TYPE_UNSIGNED (type) = 1;
2429 TYPE_PRECISION (type) = GET_MODE_PRECISION (mode);
2430 }
2431 break;
2432
2433 case ARRAY_TYPE:
2434 {
2435 tree index = TYPE_DOMAIN (type);
2436 tree element = TREE_TYPE (type);
2437
2438 /* We need to know both bounds in order to compute the size. */
2439 if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index)
2440 && TYPE_SIZE (element))
2441 {
2442 tree ub = TYPE_MAX_VALUE (index);
2443 tree lb = TYPE_MIN_VALUE (index);
2444 tree element_size = TYPE_SIZE (element);
2445 tree length;
2446
2447 /* Make sure that an array of zero-sized element is zero-sized
2448 regardless of its extent. */
2449 if (integer_zerop (element_size))
2450 length = size_zero_node;
2451
2452 /* The computation should happen in the original signedness so
2453 that (possible) negative values are handled appropriately
2454 when determining overflow. */
2455 else
2456 {
2457 /* ??? When it is obvious that the range is signed
2458 represent it using ssizetype. */
2459 if (TREE_CODE (lb) == INTEGER_CST
2460 && TREE_CODE (ub) == INTEGER_CST
2461 && TYPE_UNSIGNED (TREE_TYPE (lb))
2462 && tree_int_cst_lt (ub, lb))
2463 {
2464 lb = wide_int_to_tree (ssizetype,
2465 offset_int::from (wi::to_wide (lb),
2466 SIGNED));
2467 ub = wide_int_to_tree (ssizetype,
2468 offset_int::from (wi::to_wide (ub),
2469 SIGNED));
2470 }
2471 length
2472 = fold_convert (sizetype,
2473 size_binop (PLUS_EXPR,
2474 build_int_cst (TREE_TYPE (lb), 1),
2475 size_binop (MINUS_EXPR, ub, lb)));
2476 }
2477
2478 /* ??? We have no way to distinguish a null-sized array from an
2479 array spanning the whole sizetype range, so we arbitrarily
2480 decide that [0, -1] is the only valid representation. */
2481 if (integer_zerop (length)
2482 && TREE_OVERFLOW (length)
2483 && integer_zerop (lb))
2484 length = size_zero_node;
2485
2486 TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
2487 bits_from_bytes (length));
2488
2489 /* If we know the size of the element, calculate the total size
2490 directly, rather than do some division thing below. This
2491 optimization helps Fortran assumed-size arrays (where the
2492 size of the array is determined at runtime) substantially. */
2493 if (TYPE_SIZE_UNIT (element))
2494 TYPE_SIZE_UNIT (type)
2495 = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length);
2496 }
2497
2498 /* Now round the alignment and size,
2499 using machine-dependent criteria if any. */
2500
2501 unsigned align = TYPE_ALIGN (element);
2502 if (TYPE_USER_ALIGN (type))
2503 align = MAX (align, TYPE_ALIGN (type));
2504 else
2505 TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);
2506 if (!TYPE_WARN_IF_NOT_ALIGN (type))
2507 SET_TYPE_WARN_IF_NOT_ALIGN (type,
2508 TYPE_WARN_IF_NOT_ALIGN (element));
2509 #ifdef ROUND_TYPE_ALIGN
2510 align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT);
2511 #else
2512 align = MAX (align, BITS_PER_UNIT);
2513 #endif
2514 SET_TYPE_ALIGN (type, align);
2515 SET_TYPE_MODE (type, BLKmode);
2516 if (TYPE_SIZE (type) != 0
2517 && ! targetm.member_type_forces_blk (type, VOIDmode)
2518 /* BLKmode elements force BLKmode aggregate;
2519 else extract/store fields may lose. */
2520 && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
2521 || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
2522 {
2523 SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type),
2524 TYPE_SIZE (type)));
2525 if (TYPE_MODE (type) != BLKmode
2526 && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
2527 && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
2528 {
2529 TYPE_NO_FORCE_BLK (type) = 1;
2530 SET_TYPE_MODE (type, BLKmode);
2531 }
2532 }
2533 if (AGGREGATE_TYPE_P (element))
2534 TYPE_TYPELESS_STORAGE (type) = TYPE_TYPELESS_STORAGE (element);
2535 /* When the element size is constant, check that it is at least as
2536 large as the element alignment. */
2537 if (TYPE_SIZE_UNIT (element)
2538 && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST
2539 /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than
2540 TYPE_ALIGN_UNIT. */
2541 && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element))
2542 && !integer_zerop (TYPE_SIZE_UNIT (element))
2543 && compare_tree_int (TYPE_SIZE_UNIT (element),
2544 TYPE_ALIGN_UNIT (element)) < 0)
2545 error ("alignment of array elements is greater than element size");
2546 break;
2547 }
2548
2549 case RECORD_TYPE:
2550 case UNION_TYPE:
2551 case QUAL_UNION_TYPE:
2552 {
2553 tree field;
2554 record_layout_info rli;
2555
2556 /* Initialize the layout information. */
2557 rli = start_record_layout (type);
2558
2559 /* If this is a QUAL_UNION_TYPE, we want to process the fields
2560 in the reverse order in building the COND_EXPR that denotes
2561 its size. We reverse them again later. */
2562 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2563 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2564
2565 /* Place all the fields. */
2566 for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
2567 place_field (rli, field);
2568
2569 if (TREE_CODE (type) == QUAL_UNION_TYPE)
2570 TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));
2571
2572 /* Finish laying out the record. */
2573 finish_record_layout (rli, /*free_p=*/true);
2574 }
2575 break;
2576
2577 default:
2578 gcc_unreachable ();
2579 }
2580
2581 /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE. For
2582 records and unions, finish_record_layout already called this
2583 function. */
2584 if (!RECORD_OR_UNION_TYPE_P (type))
2585 finalize_type_size (type);
2586
2587 /* We should never see alias sets on incomplete aggregates. And we
2588 should not call layout_type on not incomplete aggregates. */
2589 if (AGGREGATE_TYPE_P (type))
2590 gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type));
2591 }
2592
2593 /* Return the least alignment required for type TYPE. */
2594
2595 unsigned int
min_align_of_type(tree type)2596 min_align_of_type (tree type)
2597 {
2598 unsigned int align = TYPE_ALIGN (type);
2599 if (!TYPE_USER_ALIGN (type))
2600 {
2601 align = MIN (align, BIGGEST_ALIGNMENT);
2602 #ifdef BIGGEST_FIELD_ALIGNMENT
2603 align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
2604 #endif
2605 unsigned int field_align = align;
2606 #ifdef ADJUST_FIELD_ALIGN
2607 field_align = ADJUST_FIELD_ALIGN (NULL_TREE, type, field_align);
2608 #endif
2609 align = MIN (align, field_align);
2610 }
2611 return align / BITS_PER_UNIT;
2612 }
2613
2614 /* Create and return a type for signed integers of PRECISION bits. */
2615
2616 tree
make_signed_type(int precision)2617 make_signed_type (int precision)
2618 {
2619 tree type = make_node (INTEGER_TYPE);
2620
2621 TYPE_PRECISION (type) = precision;
2622
2623 fixup_signed_type (type);
2624 return type;
2625 }
2626
2627 /* Create and return a type for unsigned integers of PRECISION bits. */
2628
2629 tree
make_unsigned_type(int precision)2630 make_unsigned_type (int precision)
2631 {
2632 tree type = make_node (INTEGER_TYPE);
2633
2634 TYPE_PRECISION (type) = precision;
2635
2636 fixup_unsigned_type (type);
2637 return type;
2638 }
2639
2640 /* Create and return a type for fract of PRECISION bits, UNSIGNEDP,
2641 and SATP. */
2642
2643 tree
make_fract_type(int precision,int unsignedp,int satp)2644 make_fract_type (int precision, int unsignedp, int satp)
2645 {
2646 tree type = make_node (FIXED_POINT_TYPE);
2647
2648 TYPE_PRECISION (type) = precision;
2649
2650 if (satp)
2651 TYPE_SATURATING (type) = 1;
2652
2653 /* Lay out the type: set its alignment, size, etc. */
2654 TYPE_UNSIGNED (type) = unsignedp;
2655 enum mode_class mclass = unsignedp ? MODE_UFRACT : MODE_FRACT;
2656 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2657 layout_type (type);
2658
2659 return type;
2660 }
2661
2662 /* Create and return a type for accum of PRECISION bits, UNSIGNEDP,
2663 and SATP. */
2664
2665 tree
make_accum_type(int precision,int unsignedp,int satp)2666 make_accum_type (int precision, int unsignedp, int satp)
2667 {
2668 tree type = make_node (FIXED_POINT_TYPE);
2669
2670 TYPE_PRECISION (type) = precision;
2671
2672 if (satp)
2673 TYPE_SATURATING (type) = 1;
2674
2675 /* Lay out the type: set its alignment, size, etc. */
2676 TYPE_UNSIGNED (type) = unsignedp;
2677 enum mode_class mclass = unsignedp ? MODE_UACCUM : MODE_ACCUM;
2678 SET_TYPE_MODE (type, mode_for_size (precision, mclass, 0).require ());
2679 layout_type (type);
2680
2681 return type;
2682 }
2683
2684 /* Initialize sizetypes so layout_type can use them. */
2685
2686 void
initialize_sizetypes(void)2687 initialize_sizetypes (void)
2688 {
2689 int precision, bprecision;
2690
2691 /* Get sizetypes precision from the SIZE_TYPE target macro. */
2692 if (strcmp (SIZETYPE, "unsigned int") == 0)
2693 precision = INT_TYPE_SIZE;
2694 else if (strcmp (SIZETYPE, "long unsigned int") == 0)
2695 precision = LONG_TYPE_SIZE;
2696 else if (strcmp (SIZETYPE, "long long unsigned int") == 0)
2697 precision = LONG_LONG_TYPE_SIZE;
2698 else if (strcmp (SIZETYPE, "short unsigned int") == 0)
2699 precision = SHORT_TYPE_SIZE;
2700 else
2701 {
2702 int i;
2703
2704 precision = -1;
2705 for (i = 0; i < NUM_INT_N_ENTS; i++)
2706 if (int_n_enabled_p[i])
2707 {
2708 char name[50];
2709 sprintf (name, "__int%d unsigned", int_n_data[i].bitsize);
2710
2711 if (strcmp (name, SIZETYPE) == 0)
2712 {
2713 precision = int_n_data[i].bitsize;
2714 }
2715 }
2716 if (precision == -1)
2717 gcc_unreachable ();
2718 }
2719
2720 bprecision
2721 = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE);
2722 bprecision = GET_MODE_PRECISION (smallest_int_mode_for_size (bprecision));
2723 if (bprecision > HOST_BITS_PER_DOUBLE_INT)
2724 bprecision = HOST_BITS_PER_DOUBLE_INT;
2725
2726 /* Create stubs for sizetype and bitsizetype so we can create constants. */
2727 sizetype = make_node (INTEGER_TYPE);
2728 TYPE_NAME (sizetype) = get_identifier ("sizetype");
2729 TYPE_PRECISION (sizetype) = precision;
2730 TYPE_UNSIGNED (sizetype) = 1;
2731 bitsizetype = make_node (INTEGER_TYPE);
2732 TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype");
2733 TYPE_PRECISION (bitsizetype) = bprecision;
2734 TYPE_UNSIGNED (bitsizetype) = 1;
2735
2736 /* Now layout both types manually. */
2737 scalar_int_mode mode = smallest_int_mode_for_size (precision);
2738 SET_TYPE_MODE (sizetype, mode);
2739 SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype)));
2740 TYPE_SIZE (sizetype) = bitsize_int (precision);
2741 TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (mode));
2742 set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);
2743
2744 mode = smallest_int_mode_for_size (bprecision);
2745 SET_TYPE_MODE (bitsizetype, mode);
2746 SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype)));
2747 TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
2748 TYPE_SIZE_UNIT (bitsizetype) = size_int (GET_MODE_SIZE (mode));
2749 set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);
2750
2751 /* Create the signed variants of *sizetype. */
2752 ssizetype = make_signed_type (TYPE_PRECISION (sizetype));
2753 TYPE_NAME (ssizetype) = get_identifier ("ssizetype");
2754 sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype));
2755 TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype");
2756 }
2757
2758 /* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE
2759 or BOOLEAN_TYPE. Set TYPE_MIN_VALUE and TYPE_MAX_VALUE
2760 for TYPE, based on the PRECISION and whether or not the TYPE
2761 IS_UNSIGNED. PRECISION need not correspond to a width supported
2762 natively by the hardware; for example, on a machine with 8-bit,
2763 16-bit, and 32-bit register modes, PRECISION might be 7, 23, or
2764 61. */
2765
2766 void
set_min_and_max_values_for_integral_type(tree type,int precision,signop sgn)2767 set_min_and_max_values_for_integral_type (tree type,
2768 int precision,
2769 signop sgn)
2770 {
2771 /* For bitfields with zero width we end up creating integer types
2772 with zero precision. Don't assign any minimum/maximum values
2773 to those types, they don't have any valid value. */
2774 if (precision < 1)
2775 return;
2776
2777 TYPE_MIN_VALUE (type)
2778 = wide_int_to_tree (type, wi::min_value (precision, sgn));
2779 TYPE_MAX_VALUE (type)
2780 = wide_int_to_tree (type, wi::max_value (precision, sgn));
2781 }
2782
2783 /* Set the extreme values of TYPE based on its precision in bits,
2784 then lay it out. Used when make_signed_type won't do
2785 because the tree code is not INTEGER_TYPE. */
2786
2787 void
fixup_signed_type(tree type)2788 fixup_signed_type (tree type)
2789 {
2790 int precision = TYPE_PRECISION (type);
2791
2792 set_min_and_max_values_for_integral_type (type, precision, SIGNED);
2793
2794 /* Lay out the type: set its alignment, size, etc. */
2795 layout_type (type);
2796 }
2797
2798 /* Set the extreme values of TYPE based on its precision in bits,
2799 then lay it out. This is used both in `make_unsigned_type'
2800 and for enumeral types. */
2801
2802 void
fixup_unsigned_type(tree type)2803 fixup_unsigned_type (tree type)
2804 {
2805 int precision = TYPE_PRECISION (type);
2806
2807 TYPE_UNSIGNED (type) = 1;
2808
2809 set_min_and_max_values_for_integral_type (type, precision, UNSIGNED);
2810
2811 /* Lay out the type: set its alignment, size, etc. */
2812 layout_type (type);
2813 }
2814
2815 /* Construct an iterator for a bitfield that spans BITSIZE bits,
2816 starting at BITPOS.
2817
2818 BITREGION_START is the bit position of the first bit in this
2819 sequence of bit fields. BITREGION_END is the last bit in this
2820 sequence. If these two fields are non-zero, we should restrict the
2821 memory access to that range. Otherwise, we are allowed to touch
2822 any adjacent non bit-fields.
2823
2824 ALIGN is the alignment of the underlying object in bits.
2825 VOLATILEP says whether the bitfield is volatile. */
2826
2827 bit_field_mode_iterator
bit_field_mode_iterator(HOST_WIDE_INT bitsize,HOST_WIDE_INT bitpos,poly_int64 bitregion_start,poly_int64 bitregion_end,unsigned int align,bool volatilep)2828 ::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
2829 poly_int64 bitregion_start,
2830 poly_int64 bitregion_end,
2831 unsigned int align, bool volatilep)
2832 : m_mode (NARROWEST_INT_MODE), m_bitsize (bitsize),
2833 m_bitpos (bitpos), m_bitregion_start (bitregion_start),
2834 m_bitregion_end (bitregion_end), m_align (align),
2835 m_volatilep (volatilep), m_count (0)
2836 {
2837 if (known_eq (m_bitregion_end, 0))
2838 {
2839 /* We can assume that any aligned chunk of ALIGN bits that overlaps
2840 the bitfield is mapped and won't trap, provided that ALIGN isn't
2841 too large. The cap is the biggest required alignment for data,
2842 or at least the word size. And force one such chunk at least. */
2843 unsigned HOST_WIDE_INT units
2844 = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
2845 if (bitsize <= 0)
2846 bitsize = 1;
2847 HOST_WIDE_INT end = bitpos + bitsize + units - 1;
2848 m_bitregion_end = end - end % units - 1;
2849 }
2850 }
2851
2852 /* Calls to this function return successively larger modes that can be used
2853 to represent the bitfield. Return true if another bitfield mode is
2854 available, storing it in *OUT_MODE if so. */
2855
2856 bool
next_mode(scalar_int_mode * out_mode)2857 bit_field_mode_iterator::next_mode (scalar_int_mode *out_mode)
2858 {
2859 scalar_int_mode mode;
2860 for (; m_mode.exists (&mode); m_mode = GET_MODE_WIDER_MODE (mode))
2861 {
2862 unsigned int unit = GET_MODE_BITSIZE (mode);
2863
2864 /* Skip modes that don't have full precision. */
2865 if (unit != GET_MODE_PRECISION (mode))
2866 continue;
2867
2868 /* Stop if the mode is too wide to handle efficiently. */
2869 if (unit > MAX_FIXED_MODE_SIZE)
2870 break;
2871
2872 /* Don't deliver more than one multiword mode; the smallest one
2873 should be used. */
2874 if (m_count > 0 && unit > BITS_PER_WORD)
2875 break;
2876
2877 /* Skip modes that are too small. */
2878 unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit;
2879 unsigned HOST_WIDE_INT subend = substart + m_bitsize;
2880 if (subend > unit)
2881 continue;
2882
2883 /* Stop if the mode goes outside the bitregion. */
2884 HOST_WIDE_INT start = m_bitpos - substart;
2885 if (maybe_ne (m_bitregion_start, 0)
2886 && maybe_lt (start, m_bitregion_start))
2887 break;
2888 HOST_WIDE_INT end = start + unit;
2889 if (maybe_gt (end, m_bitregion_end + 1))
2890 break;
2891
2892 /* Stop if the mode requires too much alignment. */
2893 if (GET_MODE_ALIGNMENT (mode) > m_align
2894 && targetm.slow_unaligned_access (mode, m_align))
2895 break;
2896
2897 *out_mode = mode;
2898 m_mode = GET_MODE_WIDER_MODE (mode);
2899 m_count++;
2900 return true;
2901 }
2902 return false;
2903 }
2904
2905 /* Return true if smaller modes are generally preferred for this kind
2906 of bitfield. */
2907
2908 bool
prefer_smaller_modes()2909 bit_field_mode_iterator::prefer_smaller_modes ()
2910 {
2911 return (m_volatilep
2912 ? targetm.narrow_volatile_bitfield ()
2913 : !SLOW_BYTE_ACCESS);
2914 }
2915
2916 /* Find the best machine mode to use when referencing a bit field of length
2917 BITSIZE bits starting at BITPOS.
2918
2919 BITREGION_START is the bit position of the first bit in this
2920 sequence of bit fields. BITREGION_END is the last bit in this
2921 sequence. If these two fields are non-zero, we should restrict the
2922 memory access to that range. Otherwise, we are allowed to touch
2923 any adjacent non bit-fields.
2924
2925 The chosen mode must have no more than LARGEST_MODE_BITSIZE bits.
2926 INT_MAX is a suitable value for LARGEST_MODE_BITSIZE if the caller
2927 doesn't want to apply a specific limit.
2928
2929 If no mode meets all these conditions, we return VOIDmode.
2930
2931 The underlying object is known to be aligned to a boundary of ALIGN bits.
2932
2933 If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the
2934 smallest mode meeting these conditions.
2935
2936 If VOLATILEP is false and SLOW_BYTE_ACCESS is true, we return the
2937 largest mode (but a mode no wider than UNITS_PER_WORD) that meets
2938 all the conditions.
2939
2940 If VOLATILEP is true the narrow_volatile_bitfields target hook is used to
2941 decide which of the above modes should be used. */
2942
2943 bool
get_best_mode(int bitsize,int bitpos,poly_uint64 bitregion_start,poly_uint64 bitregion_end,unsigned int align,unsigned HOST_WIDE_INT largest_mode_bitsize,bool volatilep,scalar_int_mode * best_mode)2944 get_best_mode (int bitsize, int bitpos,
2945 poly_uint64 bitregion_start, poly_uint64 bitregion_end,
2946 unsigned int align,
2947 unsigned HOST_WIDE_INT largest_mode_bitsize, bool volatilep,
2948 scalar_int_mode *best_mode)
2949 {
2950 bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start,
2951 bitregion_end, align, volatilep);
2952 scalar_int_mode mode;
2953 bool found = false;
2954 while (iter.next_mode (&mode)
2955 /* ??? For historical reasons, reject modes that would normally
2956 receive greater alignment, even if unaligned accesses are
2957 acceptable. This has both advantages and disadvantages.
2958 Removing this check means that something like:
2959
2960 struct s { unsigned int x; unsigned int y; };
2961 int f (struct s *s) { return s->x == 0 && s->y == 0; }
2962
2963 can be implemented using a single load and compare on
2964 64-bit machines that have no alignment restrictions.
2965 For example, on powerpc64-linux-gnu, we would generate:
2966
2967 ld 3,0(3)
2968 cntlzd 3,3
2969 srdi 3,3,6
2970 blr
2971
2972 rather than:
2973
2974 lwz 9,0(3)
2975 cmpwi 7,9,0
2976 bne 7,.L3
2977 lwz 3,4(3)
2978 cntlzw 3,3
2979 srwi 3,3,5
2980 extsw 3,3
2981 blr
2982 .p2align 4,,15
2983 .L3:
2984 li 3,0
2985 blr
2986
2987 However, accessing more than one field can make life harder
2988 for the gimple optimizers. For example, gcc.dg/vect/bb-slp-5.c
2989 has a series of unsigned short copies followed by a series of
2990 unsigned short comparisons. With this check, both the copies
2991 and comparisons remain 16-bit accesses and FRE is able
2992 to eliminate the latter. Without the check, the comparisons
2993 can be done using 2 64-bit operations, which FRE isn't able
2994 to handle in the same way.
2995
2996 Either way, it would probably be worth disabling this check
2997 during expand. One particular example where removing the
2998 check would help is the get_best_mode call in store_bit_field.
2999 If we are given a memory bitregion of 128 bits that is aligned
3000 to a 64-bit boundary, and the bitfield we want to modify is
3001 in the second half of the bitregion, this check causes
3002 store_bitfield to turn the memory into a 64-bit reference
3003 to the _first_ half of the region. We later use
3004 adjust_bitfield_address to get a reference to the correct half,
3005 but doing so looks to adjust_bitfield_address as though we are
3006 moving past the end of the original object, so it drops the
3007 associated MEM_EXPR and MEM_OFFSET. Removing the check
3008 causes store_bit_field to keep a 128-bit memory reference,
3009 so that the final bitfield reference still has a MEM_EXPR
3010 and MEM_OFFSET. */
3011 && GET_MODE_ALIGNMENT (mode) <= align
3012 && GET_MODE_BITSIZE (mode) <= largest_mode_bitsize)
3013 {
3014 *best_mode = mode;
3015 found = true;
3016 if (iter.prefer_smaller_modes ())
3017 break;
3018 }
3019
3020 return found;
3021 }
3022
3023 /* Gets minimal and maximal values for MODE (signed or unsigned depending on
3024 SIGN). The returned constants are made to be usable in TARGET_MODE. */
3025
3026 void
get_mode_bounds(scalar_int_mode mode,int sign,scalar_int_mode target_mode,rtx * mmin,rtx * mmax)3027 get_mode_bounds (scalar_int_mode mode, int sign,
3028 scalar_int_mode target_mode,
3029 rtx *mmin, rtx *mmax)
3030 {
3031 unsigned size = GET_MODE_PRECISION (mode);
3032 unsigned HOST_WIDE_INT min_val, max_val;
3033
3034 gcc_assert (size <= HOST_BITS_PER_WIDE_INT);
3035
3036 /* Special case BImode, which has values 0 and STORE_FLAG_VALUE. */
3037 if (mode == BImode)
3038 {
3039 if (STORE_FLAG_VALUE < 0)
3040 {
3041 min_val = STORE_FLAG_VALUE;
3042 max_val = 0;
3043 }
3044 else
3045 {
3046 min_val = 0;
3047 max_val = STORE_FLAG_VALUE;
3048 }
3049 }
3050 else if (sign)
3051 {
3052 min_val = -(HOST_WIDE_INT_1U << (size - 1));
3053 max_val = (HOST_WIDE_INT_1U << (size - 1)) - 1;
3054 }
3055 else
3056 {
3057 min_val = 0;
3058 max_val = (HOST_WIDE_INT_1U << (size - 1) << 1) - 1;
3059 }
3060
3061 *mmin = gen_int_mode (min_val, target_mode);
3062 *mmax = gen_int_mode (max_val, target_mode);
3063 }
3064
3065 #include "gt-stor-layout.h"
3066