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[official-gcc.git] / gcc / tree-ssanames.c
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1 /* Generic routines for manipulating SSA_NAME expressions
2 Copyright (C) 2003-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
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.
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.
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/>. */
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "tm.h"
24 #include "tree.h"
25 #include "stor-layout.h"
26 #include "basic-block.h"
27 #include "tree-ssa-alias.h"
28 #include "internal-fn.h"
29 #include "gimple-expr.h"
30 #include "is-a.h"
31 #include "gimple.h"
32 #include "gimple-ssa.h"
33 #include "tree-phinodes.h"
34 #include "ssa-iterators.h"
35 #include "stringpool.h"
36 #include "tree-ssanames.h"
37 #include "tree-into-ssa.h"
38 #include "tree-ssa.h"
39 #include "tree-pass.h"
41 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
42 many of which may be thrown away shortly after their creation if jumps
43 were threaded through PHI nodes.
45 While our garbage collection mechanisms will handle this situation, it
46 is extremely wasteful to create nodes and throw them away, especially
47 when the nodes can be reused.
49 For PR 8361, we can significantly reduce the number of nodes allocated
50 and thus the total amount of memory allocated by managing SSA_NAMEs a
51 little. This additionally helps reduce the amount of work done by the
52 garbage collector. Similar results have been seen on a wider variety
53 of tests (such as the compiler itself).
55 Right now we maintain our free list on a per-function basis. It may
56 or may not make sense to maintain the free list for the duration of
57 a compilation unit.
59 External code should rely solely upon HIGHEST_SSA_VERSION and the
60 externally defined functions. External code should not know about
61 the details of the free list management.
63 External code should also not assume the version number on nodes is
64 monotonically increasing. We reuse the version number when we
65 reuse an SSA_NAME expression. This helps keep arrays and bitmaps
66 more compact. */
69 /* Version numbers with special meanings. We start allocating new version
70 numbers after the special ones. */
71 #define UNUSED_NAME_VERSION 0
73 unsigned int ssa_name_nodes_reused;
74 unsigned int ssa_name_nodes_created;
76 #define FREE_SSANAMES(fun) (fun)->gimple_df->free_ssanames
79 /* Initialize management of SSA_NAMEs to default SIZE. If SIZE is
80 zero use default. */
82 void
83 init_ssanames (struct function *fn, int size)
85 if (size < 50)
86 size = 50;
88 vec_alloc (SSANAMES (fn), size);
90 /* Version 0 is special, so reserve the first slot in the table. Though
91 currently unused, we may use version 0 in alias analysis as part of
92 the heuristics used to group aliases when the alias sets are too
93 large.
95 We use vec::quick_push here because we know that SSA_NAMES has at
96 least 50 elements reserved in it. */
97 SSANAMES (fn)->quick_push (NULL_TREE);
98 FREE_SSANAMES (fn) = NULL;
100 fn->gimple_df->ssa_renaming_needed = 0;
101 fn->gimple_df->rename_vops = 0;
104 /* Finalize management of SSA_NAMEs. */
106 void
107 fini_ssanames (void)
109 vec_free (SSANAMES (cfun));
110 vec_free (FREE_SSANAMES (cfun));
113 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes. */
115 void
116 ssanames_print_statistics (void)
118 fprintf (stderr, "SSA_NAME nodes allocated: %u\n", ssa_name_nodes_created);
119 fprintf (stderr, "SSA_NAME nodes reused: %u\n", ssa_name_nodes_reused);
122 /* Return an SSA_NAME node for variable VAR defined in statement STMT
123 in function FN. STMT may be an empty statement for artificial
124 references (e.g., default definitions created when a variable is
125 used without a preceding definition). */
127 tree
128 make_ssa_name_fn (struct function *fn, tree var, gimple stmt)
130 tree t;
131 use_operand_p imm;
133 gcc_assert (TREE_CODE (var) == VAR_DECL
134 || TREE_CODE (var) == PARM_DECL
135 || TREE_CODE (var) == RESULT_DECL
136 || (TYPE_P (var) && is_gimple_reg_type (var)));
138 /* If our free list has an element, then use it. */
139 if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
141 t = FREE_SSANAMES (fn)->pop ();
142 if (GATHER_STATISTICS)
143 ssa_name_nodes_reused++;
145 /* The node was cleared out when we put it on the free list, so
146 there is no need to do so again here. */
147 gcc_assert ((*SSANAMES (fn))[SSA_NAME_VERSION (t)] == NULL);
148 (*SSANAMES (fn))[SSA_NAME_VERSION (t)] = t;
150 else
152 t = make_node (SSA_NAME);
153 SSA_NAME_VERSION (t) = SSANAMES (fn)->length ();
154 vec_safe_push (SSANAMES (fn), t);
155 if (GATHER_STATISTICS)
156 ssa_name_nodes_created++;
159 if (TYPE_P (var))
161 TREE_TYPE (t) = var;
162 SET_SSA_NAME_VAR_OR_IDENTIFIER (t, NULL_TREE);
164 else
166 TREE_TYPE (t) = TREE_TYPE (var);
167 SET_SSA_NAME_VAR_OR_IDENTIFIER (t, var);
169 SSA_NAME_DEF_STMT (t) = stmt;
170 if (POINTER_TYPE_P (TREE_TYPE (t)))
171 SSA_NAME_PTR_INFO (t) = NULL;
172 else
173 SSA_NAME_RANGE_INFO (t) = NULL;
175 SSA_NAME_IN_FREE_LIST (t) = 0;
176 SSA_NAME_IS_DEFAULT_DEF (t) = 0;
177 imm = &(SSA_NAME_IMM_USE_NODE (t));
178 imm->use = NULL;
179 imm->prev = imm;
180 imm->next = imm;
181 imm->loc.ssa_name = t;
183 return t;
186 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name NAME. */
188 void
189 set_range_info (tree name, enum value_range_type range_type, double_int min,
190 double_int max)
192 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
193 gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
194 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
196 /* Allocate if not available. */
197 if (ri == NULL)
199 ri = ggc_alloc_cleared_range_info_def ();
200 SSA_NAME_RANGE_INFO (name) = ri;
201 ri->nonzero_bits = double_int::mask (TYPE_PRECISION (TREE_TYPE (name)));
204 /* Record the range type. */
205 if (SSA_NAME_RANGE_TYPE (name) != range_type)
206 SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
208 /* Set the values. */
209 ri->min = min;
210 ri->max = max;
212 /* If it is a range, try to improve nonzero_bits from the min/max. */
213 if (range_type == VR_RANGE)
215 int prec = TYPE_PRECISION (TREE_TYPE (name));
216 double_int xorv;
218 min = min.zext (prec);
219 max = max.zext (prec);
220 xorv = min ^ max;
221 if (xorv.high)
222 xorv = double_int::mask (2 * HOST_BITS_PER_WIDE_INT
223 - clz_hwi (xorv.high));
224 else if (xorv.low)
225 xorv = double_int::mask (HOST_BITS_PER_WIDE_INT
226 - clz_hwi (xorv.low));
227 ri->nonzero_bits = ri->nonzero_bits & (min | xorv);
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. */
236 enum value_range_type
237 get_range_info (const_tree name, double_int *min, double_int *max)
239 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
240 gcc_assert (min && max);
241 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
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;
249 *min = ri->min;
250 *max = ri->max;
251 return SSA_NAME_RANGE_TYPE (name);
254 /* Change non-zero bits bitmask of NAME. */
256 void
257 set_nonzero_bits (tree name, double_int mask)
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 tree_to_double_int (TYPE_MIN_VALUE (TREE_TYPE (name))),
263 tree_to_double_int (TYPE_MAX_VALUE (TREE_TYPE (name))));
264 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
265 ri->nonzero_bits
266 = mask & double_int::mask (TYPE_PRECISION (TREE_TYPE (name)));
269 /* Return a double_int with potentially non-zero bits in SSA_NAME
270 NAME, or double_int_minus_one if unknown. */
272 double_int
273 get_nonzero_bits (const_tree name)
275 if (POINTER_TYPE_P (TREE_TYPE (name)))
277 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
278 if (pi && pi->align)
280 double_int al = double_int::from_uhwi (pi->align - 1);
281 return ((double_int::mask (TYPE_PRECISION (TREE_TYPE (name))) & ~al)
282 | double_int::from_uhwi (pi->misalign));
284 return double_int_minus_one;
287 range_info_def *ri = SSA_NAME_RANGE_INFO (name);
288 if (!ri || (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (name)))
289 > 2 * HOST_BITS_PER_WIDE_INT))
290 return double_int_minus_one;
292 return ri->nonzero_bits;
295 /* We no longer need the SSA_NAME expression VAR, release it so that
296 it may be reused.
298 Note it is assumed that no calls to make_ssa_name will be made
299 until all uses of the ssa name are released and that the only
300 use of the SSA_NAME expression is to check its SSA_NAME_VAR. All
301 other fields must be assumed clobbered. */
303 void
304 release_ssa_name_fn (struct function *fn, tree var)
306 if (!var)
307 return;
309 /* Never release the default definition for a symbol. It's a
310 special SSA name that should always exist once it's created. */
311 if (SSA_NAME_IS_DEFAULT_DEF (var))
312 return;
314 /* If VAR has been registered for SSA updating, don't remove it.
315 After update_ssa has run, the name will be released. */
316 if (name_registered_for_update_p (var))
318 release_ssa_name_after_update_ssa (var);
319 return;
322 /* release_ssa_name can be called multiple times on a single SSA_NAME.
323 However, it should only end up on our free list one time. We
324 keep a status bit in the SSA_NAME node itself to indicate it has
325 been put on the free list.
327 Note that once on the freelist you can not reference the SSA_NAME's
328 defining statement. */
329 if (! SSA_NAME_IN_FREE_LIST (var))
331 tree saved_ssa_name_var = SSA_NAME_VAR (var);
332 int saved_ssa_name_version = SSA_NAME_VERSION (var);
333 use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (var));
335 if (MAY_HAVE_DEBUG_STMTS)
336 insert_debug_temp_for_var_def (NULL, var);
338 #ifdef ENABLE_CHECKING
339 verify_imm_links (stderr, var);
340 #endif
341 while (imm->next != imm)
342 delink_imm_use (imm->next);
344 (*SSANAMES (fn))[SSA_NAME_VERSION (var)] = NULL_TREE;
345 memset (var, 0, tree_size (var));
347 imm->prev = imm;
348 imm->next = imm;
349 imm->loc.ssa_name = var;
351 /* First put back the right tree node so that the tree checking
352 macros do not complain. */
353 TREE_SET_CODE (var, SSA_NAME);
355 /* Restore the version number. */
356 SSA_NAME_VERSION (var) = saved_ssa_name_version;
358 /* Hopefully this can go away once we have the new incremental
359 SSA updating code installed. */
360 SET_SSA_NAME_VAR_OR_IDENTIFIER (var, saved_ssa_name_var);
362 /* Note this SSA_NAME is now in the first list. */
363 SSA_NAME_IN_FREE_LIST (var) = 1;
365 /* And finally put it on the free list. */
366 vec_safe_push (FREE_SSANAMES (fn), var);
370 /* If the alignment of the pointer described by PI is known, return true and
371 store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
372 respectively. Otherwise return false. */
374 bool
375 get_ptr_info_alignment (struct ptr_info_def *pi, unsigned int *alignp,
376 unsigned int *misalignp)
378 if (pi->align)
380 *alignp = pi->align;
381 *misalignp = pi->misalign;
382 return true;
384 else
385 return false;
388 /* State that the pointer described by PI has unknown alignment. */
390 void
391 mark_ptr_info_alignment_unknown (struct ptr_info_def *pi)
393 pi->align = 0;
394 pi->misalign = 0;
397 /* Store the the power-of-two byte alignment and the deviation from that
398 alignment of pointer described by PI to ALIOGN and MISALIGN
399 respectively. */
401 void
402 set_ptr_info_alignment (struct ptr_info_def *pi, unsigned int align,
403 unsigned int misalign)
405 gcc_checking_assert (align != 0);
406 gcc_assert ((align & (align - 1)) == 0);
407 gcc_assert ((misalign & ~(align - 1)) == 0);
409 pi->align = align;
410 pi->misalign = misalign;
413 /* If pointer described by PI has known alignment, increase its known
414 misalignment by INCREMENT modulo its current alignment. */
416 void
417 adjust_ptr_info_misalignment (struct ptr_info_def *pi,
418 unsigned int increment)
420 if (pi->align != 0)
422 pi->misalign += increment;
423 pi->misalign &= (pi->align - 1);
427 /* Return the alias information associated with pointer T. It creates a
428 new instance if none existed. */
430 struct ptr_info_def *
431 get_ptr_info (tree t)
433 struct ptr_info_def *pi;
435 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
437 pi = SSA_NAME_PTR_INFO (t);
438 if (pi == NULL)
440 pi = ggc_alloc_cleared_ptr_info_def ();
441 pt_solution_reset (&pi->pt);
442 mark_ptr_info_alignment_unknown (pi);
443 SSA_NAME_PTR_INFO (t) = pi;
446 return pi;
450 /* Creates a new SSA name using the template NAME tobe defined by
451 statement STMT in function FN. */
453 tree
454 copy_ssa_name_fn (struct function *fn, tree name, gimple stmt)
456 tree new_name;
458 if (SSA_NAME_VAR (name))
459 new_name = make_ssa_name_fn (fn, SSA_NAME_VAR (name), stmt);
460 else
462 new_name = make_ssa_name_fn (fn, TREE_TYPE (name), stmt);
463 SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name, SSA_NAME_IDENTIFIER (name));
466 return new_name;
470 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
471 the SSA name NAME. */
473 void
474 duplicate_ssa_name_ptr_info (tree name, struct ptr_info_def *ptr_info)
476 struct ptr_info_def *new_ptr_info;
478 gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
479 gcc_assert (!SSA_NAME_PTR_INFO (name));
481 if (!ptr_info)
482 return;
484 new_ptr_info = ggc_alloc_ptr_info_def ();
485 *new_ptr_info = *ptr_info;
487 SSA_NAME_PTR_INFO (name) = new_ptr_info;
490 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
491 RANGE_TYPE for use by the SSA name NAME. */
492 void
493 duplicate_ssa_name_range_info (tree name, enum value_range_type range_type,
494 struct range_info_def *range_info)
496 struct range_info_def *new_range_info;
498 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
499 gcc_assert (!SSA_NAME_RANGE_INFO (name));
500 gcc_assert (!SSA_NAME_ANTI_RANGE_P (name));
502 if (!range_info)
503 return;
505 new_range_info = ggc_alloc_range_info_def ();
506 *new_range_info = *range_info;
508 gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
509 SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
510 SSA_NAME_RANGE_INFO (name) = new_range_info;
515 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
516 in function FN. */
518 tree
519 duplicate_ssa_name_fn (struct function *fn, tree name, gimple stmt)
521 tree new_name = copy_ssa_name_fn (fn, name, stmt);
522 if (POINTER_TYPE_P (TREE_TYPE (name)))
524 struct ptr_info_def *old_ptr_info = SSA_NAME_PTR_INFO (name);
526 if (old_ptr_info)
527 duplicate_ssa_name_ptr_info (new_name, old_ptr_info);
529 else
531 struct range_info_def *old_range_info = SSA_NAME_RANGE_INFO (name);
533 if (old_range_info)
534 duplicate_ssa_name_range_info (new_name, SSA_NAME_RANGE_TYPE (name),
535 old_range_info);
538 return new_name;
542 /* Release all the SSA_NAMEs created by STMT. */
544 void
545 release_defs (gimple stmt)
547 tree def;
548 ssa_op_iter iter;
550 /* Make sure that we are in SSA. Otherwise, operand cache may point
551 to garbage. */
552 gcc_assert (gimple_in_ssa_p (cfun));
554 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
555 if (TREE_CODE (def) == SSA_NAME)
556 release_ssa_name (def);
560 /* Replace the symbol associated with SSA_NAME with SYM. */
562 void
563 replace_ssa_name_symbol (tree ssa_name, tree sym)
565 SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name, sym);
566 TREE_TYPE (ssa_name) = TREE_TYPE (sym);
569 /* Return SSA names that are unused to GGC memory and compact the SSA
570 version namespace. This is used to keep footprint of compiler during
571 interprocedural optimization. */
572 static unsigned int
573 release_dead_ssa_names (void)
575 unsigned i, j;
576 int n = vec_safe_length (FREE_SSANAMES (cfun));
578 /* Now release the freelist. */
579 vec_free (FREE_SSANAMES (cfun));
581 /* And compact the SSA number space. We make sure to not change the
582 relative order of SSA versions. */
583 for (i = 1, j = 1; i < cfun->gimple_df->ssa_names->length (); ++i)
585 tree name = ssa_name (i);
586 if (name)
588 if (i != j)
590 SSA_NAME_VERSION (name) = j;
591 (*cfun->gimple_df->ssa_names)[j] = name;
593 j++;
596 cfun->gimple_df->ssa_names->truncate (j);
598 statistics_counter_event (cfun, "SSA names released", n);
599 statistics_counter_event (cfun, "SSA name holes removed", i - j);
600 if (dump_file)
601 fprintf (dump_file, "Released %i names, %.2f%%, removed %i holes\n",
602 n, n * 100.0 / num_ssa_names, i - j);
603 return 0;
606 namespace {
608 const pass_data pass_data_release_ssa_names =
610 GIMPLE_PASS, /* type */
611 "release_ssa", /* name */
612 OPTGROUP_NONE, /* optinfo_flags */
613 false, /* has_gate */
614 true, /* has_execute */
615 TV_TREE_SSA_OTHER, /* tv_id */
616 PROP_ssa, /* properties_required */
617 0, /* properties_provided */
618 0, /* properties_destroyed */
619 TODO_remove_unused_locals, /* todo_flags_start */
620 0, /* todo_flags_finish */
623 class pass_release_ssa_names : public gimple_opt_pass
625 public:
626 pass_release_ssa_names (gcc::context *ctxt)
627 : gimple_opt_pass (pass_data_release_ssa_names, ctxt)
630 /* opt_pass methods: */
631 unsigned int execute () { return release_dead_ssa_names (); }
633 }; // class pass_release_ssa_names
635 } // anon namespace
637 gimple_opt_pass *
638 make_pass_release_ssa_names (gcc::context *ctxt)
640 return new pass_release_ssa_names (ctxt);