decl.c (value_annotation_hasher::handle_cache_entry): Delete.
[gcc.git] / gcc / tree-ssanames.c
1 /* Generic routines for manipulating SSA_NAME expressions
2 Copyright (C) 2003-2015 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
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License 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 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "tm.h"
24 #include "alias.h"
25 #include "symtab.h"
26 #include "tree.h"
27 #include "fold-const.h"
28 #include "stor-layout.h"
29 #include "predict.h"
30 #include "hard-reg-set.h"
31 #include "function.h"
32 #include "basic-block.h"
33 #include "tree-ssa-alias.h"
34 #include "internal-fn.h"
35 #include "gimple-expr.h"
36 #include "gimple.h"
37 #include "gimple-ssa.h"
38 #include "tree-phinodes.h"
39 #include "ssa-iterators.h"
40 #include "stringpool.h"
41 #include "tree-ssanames.h"
42 #include "tree-into-ssa.h"
43 #include "tree-ssa.h"
44 #include "tree-pass.h"
45
46 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
47 many of which may be thrown away shortly after their creation if jumps
48 were threaded through PHI nodes.
49
50 While our garbage collection mechanisms will handle this situation, it
51 is extremely wasteful to create nodes and throw them away, especially
52 when the nodes can be reused.
53
54 For PR 8361, we can significantly reduce the number of nodes allocated
55 and thus the total amount of memory allocated by managing SSA_NAMEs a
56 little. This additionally helps reduce the amount of work done by the
57 garbage collector. Similar results have been seen on a wider variety
58 of tests (such as the compiler itself).
59
60 Right now we maintain our free list on a per-function basis. It may
61 or may not make sense to maintain the free list for the duration of
62 a compilation unit.
63
64 External code should rely solely upon HIGHEST_SSA_VERSION and the
65 externally defined functions. External code should not know about
66 the details of the free list management.
67
68 External code should also not assume the version number on nodes is
69 monotonically increasing. We reuse the version number when we
70 reuse an SSA_NAME expression. This helps keep arrays and bitmaps
71 more compact. */
72
73
74 /* Version numbers with special meanings. We start allocating new version
75 numbers after the special ones. */
76 #define UNUSED_NAME_VERSION 0
77
78 unsigned int ssa_name_nodes_reused;
79 unsigned int ssa_name_nodes_created;
80
81 #define FREE_SSANAMES(fun) (fun)->gimple_df->free_ssanames
82
83
84 /* Initialize management of SSA_NAMEs to default SIZE. If SIZE is
85 zero use default. */
86
87 void
88 init_ssanames (struct function *fn, int size)
89 {
90 if (size < 50)
91 size = 50;
92
93 vec_alloc (SSANAMES (fn), size);
94
95 /* Version 0 is special, so reserve the first slot in the table. Though
96 currently unused, we may use version 0 in alias analysis as part of
97 the heuristics used to group aliases when the alias sets are too
98 large.
99
100 We use vec::quick_push here because we know that SSA_NAMES has at
101 least 50 elements reserved in it. */
102 SSANAMES (fn)->quick_push (NULL_TREE);
103 FREE_SSANAMES (fn) = NULL;
104
105 fn->gimple_df->ssa_renaming_needed = 0;
106 fn->gimple_df->rename_vops = 0;
107 }
108
109 /* Finalize management of SSA_NAMEs. */
110
111 void
112 fini_ssanames (void)
113 {
114 vec_free (SSANAMES (cfun));
115 vec_free (FREE_SSANAMES (cfun));
116 }
117
118 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes. */
119
120 void
121 ssanames_print_statistics (void)
122 {
123 fprintf (stderr, "SSA_NAME nodes allocated: %u\n", ssa_name_nodes_created);
124 fprintf (stderr, "SSA_NAME nodes reused: %u\n", ssa_name_nodes_reused);
125 }
126
127 /* Return an SSA_NAME node for variable VAR defined in statement STMT
128 in function FN. STMT may be an empty statement for artificial
129 references (e.g., default definitions created when a variable is
130 used without a preceding definition). */
131
132 tree
133 make_ssa_name_fn (struct function *fn, tree var, gimple stmt)
134 {
135 tree t;
136 use_operand_p imm;
137
138 gcc_assert (TREE_CODE (var) == VAR_DECL
139 || TREE_CODE (var) == PARM_DECL
140 || TREE_CODE (var) == RESULT_DECL
141 || (TYPE_P (var) && is_gimple_reg_type (var)));
142
143 /* If our free list has an element, then use it. */
144 if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
145 {
146 t = FREE_SSANAMES (fn)->pop ();
147 if (GATHER_STATISTICS)
148 ssa_name_nodes_reused++;
149
150 /* The node was cleared out when we put it on the free list, so
151 there is no need to do so again here. */
152 gcc_assert ((*SSANAMES (fn))[SSA_NAME_VERSION (t)] == NULL);
153 (*SSANAMES (fn))[SSA_NAME_VERSION (t)] = t;
154 }
155 else
156 {
157 t = make_node (SSA_NAME);
158 SSA_NAME_VERSION (t) = SSANAMES (fn)->length ();
159 vec_safe_push (SSANAMES (fn), t);
160 if (GATHER_STATISTICS)
161 ssa_name_nodes_created++;
162 }
163
164 if (TYPE_P (var))
165 {
166 TREE_TYPE (t) = var;
167 SET_SSA_NAME_VAR_OR_IDENTIFIER (t, NULL_TREE);
168 }
169 else
170 {
171 TREE_TYPE (t) = TREE_TYPE (var);
172 SET_SSA_NAME_VAR_OR_IDENTIFIER (t, var);
173 }
174 SSA_NAME_DEF_STMT (t) = stmt;
175 if (POINTER_TYPE_P (TREE_TYPE (t)))
176 SSA_NAME_PTR_INFO (t) = NULL;
177 else
178 SSA_NAME_RANGE_INFO (t) = NULL;
179
180 SSA_NAME_IN_FREE_LIST (t) = 0;
181 SSA_NAME_IS_DEFAULT_DEF (t) = 0;
182 imm = &(SSA_NAME_IMM_USE_NODE (t));
183 imm->use = NULL;
184 imm->prev = imm;
185 imm->next = imm;
186 imm->loc.ssa_name = t;
187
188 return t;
189 }
190
191 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name NAME. */
192
193 void
194 set_range_info (tree name, enum value_range_type range_type,
195 const wide_int_ref &min, const wide_int_ref &max)
196 {
197 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
198 gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
199 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
200 unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
201
202 /* Allocate if not available. */
203 if (ri == NULL)
204 {
205 size_t size = (sizeof (range_info_def)
206 + trailing_wide_ints <3>::extra_size (precision));
207 ri = static_cast<range_info_def *> (ggc_internal_alloc (size));
208 ri->ints.set_precision (precision);
209 SSA_NAME_RANGE_INFO (name) = ri;
210 ri->set_nonzero_bits (wi::shwi (-1, precision));
211 }
212
213 /* Record the range type. */
214 if (SSA_NAME_RANGE_TYPE (name) != range_type)
215 SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
216
217 /* Set the values. */
218 ri->set_min (min);
219 ri->set_max (max);
220
221 /* If it is a range, try to improve nonzero_bits from the min/max. */
222 if (range_type == VR_RANGE)
223 {
224 wide_int xorv = ri->get_min () ^ ri->get_max ();
225 if (xorv != 0)
226 xorv = wi::mask (precision - wi::clz (xorv), false, precision);
227 ri->set_nonzero_bits (ri->get_nonzero_bits () & (ri->get_min () | xorv));
228 }
229 }
230
231
232 /* Gets range information MIN, MAX and returns enum value_range_type
233 corresponding to tree ssa_name NAME. enum value_range_type returned
234 is used to determine if MIN and MAX are valid values. */
235
236 enum value_range_type
237 get_range_info (const_tree name, wide_int *min, wide_int *max)
238 {
239 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
240 gcc_assert (min && max);
241 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
242
243 /* Return VR_VARYING for SSA_NAMEs with NULL RANGE_INFO or SSA_NAMEs
244 with integral types width > 2 * HOST_BITS_PER_WIDE_INT precision. */
245 if (!ri || (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (name)))
246 > 2 * HOST_BITS_PER_WIDE_INT))
247 return VR_VARYING;
248
249 *min = ri->get_min ();
250 *max = ri->get_max ();
251 return SSA_NAME_RANGE_TYPE (name);
252 }
253
254 /* Change non-zero bits bitmask of NAME. */
255
256 void
257 set_nonzero_bits (tree name, const wide_int_ref &mask)
258 {
259 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
260 if (SSA_NAME_RANGE_INFO (name) == NULL)
261 set_range_info (name, VR_RANGE,
262 TYPE_MIN_VALUE (TREE_TYPE (name)),
263 TYPE_MAX_VALUE (TREE_TYPE (name)));
264 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
265 ri->set_nonzero_bits (mask);
266 }
267
268 /* Return a widest_int with potentially non-zero bits in SSA_NAME
269 NAME, or -1 if unknown. */
270
271 wide_int
272 get_nonzero_bits (const_tree name)
273 {
274 unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
275 if (POINTER_TYPE_P (TREE_TYPE (name)))
276 {
277 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
278 if (pi && pi->align)
279 return wi::shwi (-(HOST_WIDE_INT) pi->align
280 | (HOST_WIDE_INT) pi->misalign, precision);
281 return wi::shwi (-1, precision);
282 }
283
284 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
285 if (!ri)
286 return wi::shwi (-1, precision);
287
288 return ri->get_nonzero_bits ();
289 }
290
291 /* We no longer need the SSA_NAME expression VAR, release it so that
292 it may be reused.
293
294 Note it is assumed that no calls to make_ssa_name will be made
295 until all uses of the ssa name are released and that the only
296 use of the SSA_NAME expression is to check its SSA_NAME_VAR. All
297 other fields must be assumed clobbered. */
298
299 void
300 release_ssa_name_fn (struct function *fn, tree var)
301 {
302 if (!var)
303 return;
304
305 /* Never release the default definition for a symbol. It's a
306 special SSA name that should always exist once it's created. */
307 if (SSA_NAME_IS_DEFAULT_DEF (var))
308 return;
309
310 /* If VAR has been registered for SSA updating, don't remove it.
311 After update_ssa has run, the name will be released. */
312 if (name_registered_for_update_p (var))
313 {
314 release_ssa_name_after_update_ssa (var);
315 return;
316 }
317
318 /* release_ssa_name can be called multiple times on a single SSA_NAME.
319 However, it should only end up on our free list one time. We
320 keep a status bit in the SSA_NAME node itself to indicate it has
321 been put on the free list.
322
323 Note that once on the freelist you can not reference the SSA_NAME's
324 defining statement. */
325 if (! SSA_NAME_IN_FREE_LIST (var))
326 {
327 tree saved_ssa_name_var = SSA_NAME_VAR (var);
328 int saved_ssa_name_version = SSA_NAME_VERSION (var);
329 use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (var));
330
331 if (MAY_HAVE_DEBUG_STMTS)
332 insert_debug_temp_for_var_def (NULL, var);
333
334 #ifdef ENABLE_CHECKING
335 verify_imm_links (stderr, var);
336 #endif
337 while (imm->next != imm)
338 delink_imm_use (imm->next);
339
340 (*SSANAMES (fn))[SSA_NAME_VERSION (var)] = NULL_TREE;
341 memset (var, 0, tree_size (var));
342
343 imm->prev = imm;
344 imm->next = imm;
345 imm->loc.ssa_name = var;
346
347 /* First put back the right tree node so that the tree checking
348 macros do not complain. */
349 TREE_SET_CODE (var, SSA_NAME);
350
351 /* Restore the version number. */
352 SSA_NAME_VERSION (var) = saved_ssa_name_version;
353
354 /* Hopefully this can go away once we have the new incremental
355 SSA updating code installed. */
356 SET_SSA_NAME_VAR_OR_IDENTIFIER (var, saved_ssa_name_var);
357
358 /* Note this SSA_NAME is now in the first list. */
359 SSA_NAME_IN_FREE_LIST (var) = 1;
360
361 /* And finally put it on the free list. */
362 vec_safe_push (FREE_SSANAMES (fn), var);
363 }
364 }
365
366 /* If the alignment of the pointer described by PI is known, return true and
367 store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
368 respectively. Otherwise return false. */
369
370 bool
371 get_ptr_info_alignment (struct ptr_info_def *pi, unsigned int *alignp,
372 unsigned int *misalignp)
373 {
374 if (pi->align)
375 {
376 *alignp = pi->align;
377 *misalignp = pi->misalign;
378 return true;
379 }
380 else
381 return false;
382 }
383
384 /* State that the pointer described by PI has unknown alignment. */
385
386 void
387 mark_ptr_info_alignment_unknown (struct ptr_info_def *pi)
388 {
389 pi->align = 0;
390 pi->misalign = 0;
391 }
392
393 /* Store the the power-of-two byte alignment and the deviation from that
394 alignment of pointer described by PI to ALIOGN and MISALIGN
395 respectively. */
396
397 void
398 set_ptr_info_alignment (struct ptr_info_def *pi, unsigned int align,
399 unsigned int misalign)
400 {
401 gcc_checking_assert (align != 0);
402 gcc_assert ((align & (align - 1)) == 0);
403 gcc_assert ((misalign & ~(align - 1)) == 0);
404
405 pi->align = align;
406 pi->misalign = misalign;
407 }
408
409 /* If pointer described by PI has known alignment, increase its known
410 misalignment by INCREMENT modulo its current alignment. */
411
412 void
413 adjust_ptr_info_misalignment (struct ptr_info_def *pi,
414 unsigned int increment)
415 {
416 if (pi->align != 0)
417 {
418 pi->misalign += increment;
419 pi->misalign &= (pi->align - 1);
420 }
421 }
422
423 /* Return the alias information associated with pointer T. It creates a
424 new instance if none existed. */
425
426 struct ptr_info_def *
427 get_ptr_info (tree t)
428 {
429 struct ptr_info_def *pi;
430
431 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
432
433 pi = SSA_NAME_PTR_INFO (t);
434 if (pi == NULL)
435 {
436 pi = ggc_cleared_alloc<ptr_info_def> ();
437 pt_solution_reset (&pi->pt);
438 mark_ptr_info_alignment_unknown (pi);
439 SSA_NAME_PTR_INFO (t) = pi;
440 }
441
442 return pi;
443 }
444
445
446 /* Creates a new SSA name using the template NAME tobe defined by
447 statement STMT in function FN. */
448
449 tree
450 copy_ssa_name_fn (struct function *fn, tree name, gimple stmt)
451 {
452 tree new_name;
453
454 if (SSA_NAME_VAR (name))
455 new_name = make_ssa_name_fn (fn, SSA_NAME_VAR (name), stmt);
456 else
457 {
458 new_name = make_ssa_name_fn (fn, TREE_TYPE (name), stmt);
459 SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name, SSA_NAME_IDENTIFIER (name));
460 }
461
462 return new_name;
463 }
464
465
466 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
467 the SSA name NAME. */
468
469 void
470 duplicate_ssa_name_ptr_info (tree name, struct ptr_info_def *ptr_info)
471 {
472 struct ptr_info_def *new_ptr_info;
473
474 gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
475 gcc_assert (!SSA_NAME_PTR_INFO (name));
476
477 if (!ptr_info)
478 return;
479
480 new_ptr_info = ggc_alloc<ptr_info_def> ();
481 *new_ptr_info = *ptr_info;
482
483 SSA_NAME_PTR_INFO (name) = new_ptr_info;
484 }
485
486 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
487 RANGE_TYPE for use by the SSA name NAME. */
488 void
489 duplicate_ssa_name_range_info (tree name, enum value_range_type range_type,
490 struct range_info_def *range_info)
491 {
492 struct range_info_def *new_range_info;
493
494 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
495 gcc_assert (!SSA_NAME_RANGE_INFO (name));
496 gcc_assert (!SSA_NAME_ANTI_RANGE_P (name));
497
498 if (!range_info)
499 return;
500
501 unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
502 size_t size = (sizeof (range_info_def)
503 + trailing_wide_ints <3>::extra_size (precision));
504 new_range_info = static_cast<range_info_def *> (ggc_internal_alloc (size));
505 memcpy (new_range_info, range_info, size);
506
507 gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
508 SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
509 SSA_NAME_RANGE_INFO (name) = new_range_info;
510 }
511
512
513
514 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
515 in function FN. */
516
517 tree
518 duplicate_ssa_name_fn (struct function *fn, tree name, gimple stmt)
519 {
520 tree new_name = copy_ssa_name_fn (fn, name, stmt);
521 if (POINTER_TYPE_P (TREE_TYPE (name)))
522 {
523 struct ptr_info_def *old_ptr_info = SSA_NAME_PTR_INFO (name);
524
525 if (old_ptr_info)
526 duplicate_ssa_name_ptr_info (new_name, old_ptr_info);
527 }
528 else
529 {
530 struct range_info_def *old_range_info = SSA_NAME_RANGE_INFO (name);
531
532 if (old_range_info)
533 duplicate_ssa_name_range_info (new_name, SSA_NAME_RANGE_TYPE (name),
534 old_range_info);
535 }
536
537 return new_name;
538 }
539
540
541 /* Release all the SSA_NAMEs created by STMT. */
542
543 void
544 release_defs (gimple stmt)
545 {
546 tree def;
547 ssa_op_iter iter;
548
549 /* Make sure that we are in SSA. Otherwise, operand cache may point
550 to garbage. */
551 gcc_assert (gimple_in_ssa_p (cfun));
552
553 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
554 if (TREE_CODE (def) == SSA_NAME)
555 release_ssa_name (def);
556 }
557
558
559 /* Replace the symbol associated with SSA_NAME with SYM. */
560
561 void
562 replace_ssa_name_symbol (tree ssa_name, tree sym)
563 {
564 SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name, sym);
565 TREE_TYPE (ssa_name) = TREE_TYPE (sym);
566 }
567
568 /* Return SSA names that are unused to GGC memory and compact the SSA
569 version namespace. This is used to keep footprint of compiler during
570 interprocedural optimization. */
571
572 namespace {
573
574 const pass_data pass_data_release_ssa_names =
575 {
576 GIMPLE_PASS, /* type */
577 "release_ssa", /* name */
578 OPTGROUP_NONE, /* optinfo_flags */
579 TV_TREE_SSA_OTHER, /* tv_id */
580 PROP_ssa, /* properties_required */
581 0, /* properties_provided */
582 0, /* properties_destroyed */
583 TODO_remove_unused_locals, /* todo_flags_start */
584 0, /* todo_flags_finish */
585 };
586
587 class pass_release_ssa_names : public gimple_opt_pass
588 {
589 public:
590 pass_release_ssa_names (gcc::context *ctxt)
591 : gimple_opt_pass (pass_data_release_ssa_names, ctxt)
592 {}
593
594 /* opt_pass methods: */
595 virtual unsigned int execute (function *);
596
597 }; // class pass_release_ssa_names
598
599 unsigned int
600 pass_release_ssa_names::execute (function *fun)
601 {
602 unsigned i, j;
603 int n = vec_safe_length (FREE_SSANAMES (fun));
604
605 /* Now release the freelist. */
606 vec_free (FREE_SSANAMES (fun));
607
608 /* And compact the SSA number space. We make sure to not change the
609 relative order of SSA versions. */
610 for (i = 1, j = 1; i < fun->gimple_df->ssa_names->length (); ++i)
611 {
612 tree name = ssa_name (i);
613 if (name)
614 {
615 if (i != j)
616 {
617 SSA_NAME_VERSION (name) = j;
618 (*fun->gimple_df->ssa_names)[j] = name;
619 }
620 j++;
621 }
622 }
623 fun->gimple_df->ssa_names->truncate (j);
624
625 statistics_counter_event (fun, "SSA names released", n);
626 statistics_counter_event (fun, "SSA name holes removed", i - j);
627 if (dump_file)
628 fprintf (dump_file, "Released %i names, %.2f%%, removed %i holes\n",
629 n, n * 100.0 / num_ssa_names, i - j);
630 return 0;
631 }
632
633 } // anon namespace
634
635 gimple_opt_pass *
636 make_pass_release_ssa_names (gcc::context *ctxt)
637 {
638 return new pass_release_ssa_names (ctxt);
639 }