1 /* Generic routines for manipulating SSA_NAME expressions
2 Copyright (C) 2003-2015 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)
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/>. */
22 #include "coretypes.h"
26 #include "gimple-iterator.h"
27 #include "hard-reg-set.h"
30 #include "fold-const.h"
31 #include "stor-layout.h"
32 #include "internal-fn.h"
33 #include "tree-into-ssa.h"
35 #include "tree-pass.h"
37 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
38 many of which may be thrown away shortly after their creation if jumps
39 were threaded through PHI nodes.
41 While our garbage collection mechanisms will handle this situation, it
42 is extremely wasteful to create nodes and throw them away, especially
43 when the nodes can be reused.
45 For PR 8361, we can significantly reduce the number of nodes allocated
46 and thus the total amount of memory allocated by managing SSA_NAMEs a
47 little. This additionally helps reduce the amount of work done by the
48 garbage collector. Similar results have been seen on a wider variety
49 of tests (such as the compiler itself).
51 Right now we maintain our free list on a per-function basis. It may
52 or may not make sense to maintain the free list for the duration of
55 External code should rely solely upon HIGHEST_SSA_VERSION and the
56 externally defined functions. External code should not know about
57 the details of the free list management.
59 External code should also not assume the version number on nodes is
60 monotonically increasing. We reuse the version number when we
61 reuse an SSA_NAME expression. This helps keep arrays and bitmaps
65 /* Version numbers with special meanings. We start allocating new version
66 numbers after the special ones. */
67 #define UNUSED_NAME_VERSION 0
69 unsigned int ssa_name_nodes_reused
;
70 unsigned int ssa_name_nodes_created
;
72 #define FREE_SSANAMES(fun) (fun)->gimple_df->free_ssanames
73 #define FREE_SSANAMES_QUEUE(fun) (fun)->gimple_df->free_ssanames_queue
76 /* Initialize management of SSA_NAMEs to default SIZE. If SIZE is
80 init_ssanames (struct function
*fn
, int size
)
85 vec_alloc (SSANAMES (fn
), size
);
87 /* Version 0 is special, so reserve the first slot in the table. Though
88 currently unused, we may use version 0 in alias analysis as part of
89 the heuristics used to group aliases when the alias sets are too
92 We use vec::quick_push here because we know that SSA_NAMES has at
93 least 50 elements reserved in it. */
94 SSANAMES (fn
)->quick_push (NULL_TREE
);
95 FREE_SSANAMES (fn
) = NULL
;
96 FREE_SSANAMES_QUEUE (fn
) = NULL
;
98 fn
->gimple_df
->ssa_renaming_needed
= 0;
99 fn
->gimple_df
->rename_vops
= 0;
102 /* Finalize management of SSA_NAMEs. */
107 vec_free (SSANAMES (cfun
));
108 vec_free (FREE_SSANAMES (cfun
));
109 vec_free (FREE_SSANAMES_QUEUE (cfun
));
112 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes. */
115 ssanames_print_statistics (void)
117 fprintf (stderr
, "SSA_NAME nodes allocated: %u\n", ssa_name_nodes_created
);
118 fprintf (stderr
, "SSA_NAME nodes reused: %u\n", ssa_name_nodes_reused
);
121 /* Move all SSA_NAMEs from FREE_SSA_NAMES_QUEUE to FREE_SSA_NAMES.
123 We do not, but should have a mode to verify the state of the SSA_NAMEs
124 lists. In particular at this point every name must be in the IL,
125 on the free list or in the queue. Anything else is an error. */
128 flush_ssaname_freelist (void)
130 vec_safe_splice (FREE_SSANAMES (cfun
), FREE_SSANAMES_QUEUE (cfun
));
131 vec_safe_truncate (FREE_SSANAMES_QUEUE (cfun
), 0);
134 /* Return an SSA_NAME node for variable VAR defined in statement STMT
135 in function FN. STMT may be an empty statement for artificial
136 references (e.g., default definitions created when a variable is
137 used without a preceding definition). */
140 make_ssa_name_fn (struct function
*fn
, tree var
, gimple
*stmt
)
145 gcc_assert (TREE_CODE (var
) == VAR_DECL
146 || TREE_CODE (var
) == PARM_DECL
147 || TREE_CODE (var
) == RESULT_DECL
148 || (TYPE_P (var
) && is_gimple_reg_type (var
)));
150 /* If our free list has an element, then use it. */
151 if (!vec_safe_is_empty (FREE_SSANAMES (fn
)))
153 t
= FREE_SSANAMES (fn
)->pop ();
154 ssa_name_nodes_reused
++;
156 /* The node was cleared out when we put it on the free list, so
157 there is no need to do so again here. */
158 gcc_assert ((*SSANAMES (fn
))[SSA_NAME_VERSION (t
)] == NULL
);
159 (*SSANAMES (fn
))[SSA_NAME_VERSION (t
)] = t
;
163 t
= make_node (SSA_NAME
);
164 SSA_NAME_VERSION (t
) = SSANAMES (fn
)->length ();
165 vec_safe_push (SSANAMES (fn
), t
);
166 ssa_name_nodes_created
++;
172 SET_SSA_NAME_VAR_OR_IDENTIFIER (t
, NULL_TREE
);
176 TREE_TYPE (t
) = TREE_TYPE (var
);
177 SET_SSA_NAME_VAR_OR_IDENTIFIER (t
, var
);
179 SSA_NAME_DEF_STMT (t
) = stmt
;
180 if (POINTER_TYPE_P (TREE_TYPE (t
)))
181 SSA_NAME_PTR_INFO (t
) = NULL
;
183 SSA_NAME_RANGE_INFO (t
) = NULL
;
185 SSA_NAME_IN_FREE_LIST (t
) = 0;
186 SSA_NAME_IS_DEFAULT_DEF (t
) = 0;
187 imm
= &(SSA_NAME_IMM_USE_NODE (t
));
191 imm
->loc
.ssa_name
= t
;
196 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name NAME. */
199 set_range_info (tree name
, enum value_range_type range_type
,
200 const wide_int_ref
&min
, const wide_int_ref
&max
)
202 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
203 gcc_assert (range_type
== VR_RANGE
|| range_type
== VR_ANTI_RANGE
);
204 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
205 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
207 /* Allocate if not available. */
210 size_t size
= (sizeof (range_info_def
)
211 + trailing_wide_ints
<3>::extra_size (precision
));
212 ri
= static_cast<range_info_def
*> (ggc_internal_alloc (size
));
213 ri
->ints
.set_precision (precision
);
214 SSA_NAME_RANGE_INFO (name
) = ri
;
215 ri
->set_nonzero_bits (wi::shwi (-1, precision
));
218 /* Record the range type. */
219 if (SSA_NAME_RANGE_TYPE (name
) != range_type
)
220 SSA_NAME_ANTI_RANGE_P (name
) = (range_type
== VR_ANTI_RANGE
);
222 /* Set the values. */
226 /* If it is a range, try to improve nonzero_bits from the min/max. */
227 if (range_type
== VR_RANGE
)
229 wide_int xorv
= ri
->get_min () ^ ri
->get_max ();
231 xorv
= wi::mask (precision
- wi::clz (xorv
), false, precision
);
232 ri
->set_nonzero_bits (ri
->get_nonzero_bits () & (ri
->get_min () | xorv
));
237 /* Gets range information MIN, MAX and returns enum value_range_type
238 corresponding to tree ssa_name NAME. enum value_range_type returned
239 is used to determine if MIN and MAX are valid values. */
241 enum value_range_type
242 get_range_info (const_tree name
, wide_int
*min
, wide_int
*max
)
244 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
245 gcc_assert (min
&& max
);
246 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
248 /* Return VR_VARYING for SSA_NAMEs with NULL RANGE_INFO or SSA_NAMEs
249 with integral types width > 2 * HOST_BITS_PER_WIDE_INT precision. */
250 if (!ri
|| (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (name
)))
251 > 2 * HOST_BITS_PER_WIDE_INT
))
254 *min
= ri
->get_min ();
255 *max
= ri
->get_max ();
256 return SSA_NAME_RANGE_TYPE (name
);
259 /* Change non-zero bits bitmask of NAME. */
262 set_nonzero_bits (tree name
, const wide_int_ref
&mask
)
264 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
265 if (SSA_NAME_RANGE_INFO (name
) == NULL
)
266 set_range_info (name
, VR_RANGE
,
267 TYPE_MIN_VALUE (TREE_TYPE (name
)),
268 TYPE_MAX_VALUE (TREE_TYPE (name
)));
269 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
270 ri
->set_nonzero_bits (mask
);
273 /* Return a widest_int with potentially non-zero bits in SSA_NAME
274 NAME, or -1 if unknown. */
277 get_nonzero_bits (const_tree name
)
279 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
280 if (POINTER_TYPE_P (TREE_TYPE (name
)))
282 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (name
);
284 return wi::shwi (-(HOST_WIDE_INT
) pi
->align
285 | (HOST_WIDE_INT
) pi
->misalign
, precision
);
286 return wi::shwi (-1, precision
);
289 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
291 return wi::shwi (-1, precision
);
293 return ri
->get_nonzero_bits ();
296 /* We no longer need the SSA_NAME expression VAR, release it so that
299 Note it is assumed that no calls to make_ssa_name will be made
300 until all uses of the ssa name are released and that the only
301 use of the SSA_NAME expression is to check its SSA_NAME_VAR. All
302 other fields must be assumed clobbered. */
305 release_ssa_name_fn (struct function
*fn
, tree var
)
310 /* Never release the default definition for a symbol. It's a
311 special SSA name that should always exist once it's created. */
312 if (SSA_NAME_IS_DEFAULT_DEF (var
))
315 /* If VAR has been registered for SSA updating, don't remove it.
316 After update_ssa has run, the name will be released. */
317 if (name_registered_for_update_p (var
))
319 release_ssa_name_after_update_ssa (var
);
323 /* release_ssa_name can be called multiple times on a single SSA_NAME.
324 However, it should only end up on our free list one time. We
325 keep a status bit in the SSA_NAME node itself to indicate it has
326 been put on the free list.
328 Note that once on the freelist you can not reference the SSA_NAME's
329 defining statement. */
330 if (! SSA_NAME_IN_FREE_LIST (var
))
332 tree saved_ssa_name_var
= SSA_NAME_VAR (var
);
333 int saved_ssa_name_version
= SSA_NAME_VERSION (var
);
334 use_operand_p imm
= &(SSA_NAME_IMM_USE_NODE (var
));
336 if (MAY_HAVE_DEBUG_STMTS
)
337 insert_debug_temp_for_var_def (NULL
, var
);
339 #ifdef ENABLE_CHECKING
340 verify_imm_links (stderr
, var
);
342 while (imm
->next
!= imm
)
343 delink_imm_use (imm
->next
);
345 (*SSANAMES (fn
))[SSA_NAME_VERSION (var
)] = NULL_TREE
;
346 memset (var
, 0, tree_size (var
));
350 imm
->loc
.ssa_name
= var
;
352 /* First put back the right tree node so that the tree checking
353 macros do not complain. */
354 TREE_SET_CODE (var
, SSA_NAME
);
356 /* Restore the version number. */
357 SSA_NAME_VERSION (var
) = saved_ssa_name_version
;
359 /* Hopefully this can go away once we have the new incremental
360 SSA updating code installed. */
361 SET_SSA_NAME_VAR_OR_IDENTIFIER (var
, saved_ssa_name_var
);
363 /* Note this SSA_NAME is now in the first list. */
364 SSA_NAME_IN_FREE_LIST (var
) = 1;
366 /* And finally queue it so that it will be put on the free list. */
367 vec_safe_push (FREE_SSANAMES_QUEUE (fn
), var
);
371 /* If the alignment of the pointer described by PI is known, return true and
372 store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
373 respectively. Otherwise return false. */
376 get_ptr_info_alignment (struct ptr_info_def
*pi
, unsigned int *alignp
,
377 unsigned int *misalignp
)
382 *misalignp
= pi
->misalign
;
389 /* State that the pointer described by PI has unknown alignment. */
392 mark_ptr_info_alignment_unknown (struct ptr_info_def
*pi
)
398 /* Store the power-of-two byte alignment and the deviation from that
399 alignment of pointer described by PI to ALIOGN and MISALIGN
403 set_ptr_info_alignment (struct ptr_info_def
*pi
, unsigned int align
,
404 unsigned int misalign
)
406 gcc_checking_assert (align
!= 0);
407 gcc_assert ((align
& (align
- 1)) == 0);
408 gcc_assert ((misalign
& ~(align
- 1)) == 0);
411 pi
->misalign
= misalign
;
414 /* If pointer described by PI has known alignment, increase its known
415 misalignment by INCREMENT modulo its current alignment. */
418 adjust_ptr_info_misalignment (struct ptr_info_def
*pi
,
419 unsigned int increment
)
423 pi
->misalign
+= increment
;
424 pi
->misalign
&= (pi
->align
- 1);
428 /* Return the alias information associated with pointer T. It creates a
429 new instance if none existed. */
431 struct ptr_info_def
*
432 get_ptr_info (tree t
)
434 struct ptr_info_def
*pi
;
436 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t
)));
438 pi
= SSA_NAME_PTR_INFO (t
);
441 pi
= ggc_cleared_alloc
<ptr_info_def
> ();
442 pt_solution_reset (&pi
->pt
);
443 mark_ptr_info_alignment_unknown (pi
);
444 SSA_NAME_PTR_INFO (t
) = pi
;
451 /* Creates a new SSA name using the template NAME tobe defined by
452 statement STMT in function FN. */
455 copy_ssa_name_fn (struct function
*fn
, tree name
, gimple
*stmt
)
459 if (SSA_NAME_VAR (name
))
460 new_name
= make_ssa_name_fn (fn
, SSA_NAME_VAR (name
), stmt
);
463 new_name
= make_ssa_name_fn (fn
, TREE_TYPE (name
), stmt
);
464 SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name
, SSA_NAME_IDENTIFIER (name
));
471 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
472 the SSA name NAME. */
475 duplicate_ssa_name_ptr_info (tree name
, struct ptr_info_def
*ptr_info
)
477 struct ptr_info_def
*new_ptr_info
;
479 gcc_assert (POINTER_TYPE_P (TREE_TYPE (name
)));
480 gcc_assert (!SSA_NAME_PTR_INFO (name
));
485 new_ptr_info
= ggc_alloc
<ptr_info_def
> ();
486 *new_ptr_info
= *ptr_info
;
488 SSA_NAME_PTR_INFO (name
) = new_ptr_info
;
491 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
492 RANGE_TYPE for use by the SSA name NAME. */
494 duplicate_ssa_name_range_info (tree name
, enum value_range_type range_type
,
495 struct range_info_def
*range_info
)
497 struct range_info_def
*new_range_info
;
499 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
500 gcc_assert (!SSA_NAME_RANGE_INFO (name
));
505 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
506 size_t size
= (sizeof (range_info_def
)
507 + trailing_wide_ints
<3>::extra_size (precision
));
508 new_range_info
= static_cast<range_info_def
*> (ggc_internal_alloc (size
));
509 memcpy (new_range_info
, range_info
, size
);
511 gcc_assert (range_type
== VR_RANGE
|| range_type
== VR_ANTI_RANGE
);
512 SSA_NAME_ANTI_RANGE_P (name
) = (range_type
== VR_ANTI_RANGE
);
513 SSA_NAME_RANGE_INFO (name
) = new_range_info
;
518 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
522 duplicate_ssa_name_fn (struct function
*fn
, tree name
, gimple
*stmt
)
524 tree new_name
= copy_ssa_name_fn (fn
, name
, stmt
);
525 if (POINTER_TYPE_P (TREE_TYPE (name
)))
527 struct ptr_info_def
*old_ptr_info
= SSA_NAME_PTR_INFO (name
);
530 duplicate_ssa_name_ptr_info (new_name
, old_ptr_info
);
534 struct range_info_def
*old_range_info
= SSA_NAME_RANGE_INFO (name
);
537 duplicate_ssa_name_range_info (new_name
, SSA_NAME_RANGE_TYPE (name
),
545 /* Reset all flow sensitive data on NAME such as range-info, nonzero
546 bits and alignment. */
549 reset_flow_sensitive_info (tree name
)
551 if (POINTER_TYPE_P (TREE_TYPE (name
)))
553 /* points-to info is not flow-sensitive. */
554 if (SSA_NAME_PTR_INFO (name
))
555 mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name
));
558 SSA_NAME_RANGE_INFO (name
) = NULL
;
561 /* Clear all flow sensitive data from all statements and PHI definitions
565 reset_flow_sensitive_info_in_bb (basic_block bb
)
567 for (gimple_stmt_iterator gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
);
570 gimple
*stmt
= gsi_stmt (gsi
);
573 FOR_EACH_SSA_TREE_OPERAND (op
, stmt
, i
, SSA_OP_DEF
)
574 reset_flow_sensitive_info (op
);
577 for (gphi_iterator gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
);
580 tree phi_def
= gimple_phi_result (gsi
.phi ());
581 reset_flow_sensitive_info (phi_def
);
585 /* Release all the SSA_NAMEs created by STMT. */
588 release_defs (gimple
*stmt
)
593 /* Make sure that we are in SSA. Otherwise, operand cache may point
595 gcc_assert (gimple_in_ssa_p (cfun
));
597 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
598 if (TREE_CODE (def
) == SSA_NAME
)
599 release_ssa_name (def
);
603 /* Replace the symbol associated with SSA_NAME with SYM. */
606 replace_ssa_name_symbol (tree ssa_name
, tree sym
)
608 SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name
, sym
);
609 TREE_TYPE (ssa_name
) = TREE_TYPE (sym
);
612 /* Return SSA names that are unused to GGC memory and compact the SSA
613 version namespace. This is used to keep footprint of compiler during
614 interprocedural optimization. */
618 const pass_data pass_data_release_ssa_names
=
620 GIMPLE_PASS
, /* type */
621 "release_ssa", /* name */
622 OPTGROUP_NONE
, /* optinfo_flags */
623 TV_TREE_SSA_OTHER
, /* tv_id */
624 PROP_ssa
, /* properties_required */
625 0, /* properties_provided */
626 0, /* properties_destroyed */
627 TODO_remove_unused_locals
, /* todo_flags_start */
628 0, /* todo_flags_finish */
631 class pass_release_ssa_names
: public gimple_opt_pass
634 pass_release_ssa_names (gcc::context
*ctxt
)
635 : gimple_opt_pass (pass_data_release_ssa_names
, ctxt
)
638 /* opt_pass methods: */
639 virtual unsigned int execute (function
*);
641 }; // class pass_release_ssa_names
644 pass_release_ssa_names::execute (function
*fun
)
647 int n
= vec_safe_length (FREE_SSANAMES (fun
));
649 /* Now release the freelist. */
650 vec_free (FREE_SSANAMES (fun
));
652 /* And compact the SSA number space. We make sure to not change the
653 relative order of SSA versions. */
654 for (i
= 1, j
= 1; i
< fun
->gimple_df
->ssa_names
->length (); ++i
)
656 tree name
= ssa_name (i
);
661 SSA_NAME_VERSION (name
) = j
;
662 (*fun
->gimple_df
->ssa_names
)[j
] = name
;
667 fun
->gimple_df
->ssa_names
->truncate (j
);
669 statistics_counter_event (fun
, "SSA names released", n
);
670 statistics_counter_event (fun
, "SSA name holes removed", i
- j
);
672 fprintf (dump_file
, "Released %i names, %.2f%%, removed %i holes\n",
673 n
, n
* 100.0 / num_ssa_names
, i
- j
);
680 make_pass_release_ssa_names (gcc::context
*ctxt
)
682 return new pass_release_ssa_names (ctxt
);