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 while (!vec_safe_is_empty (FREE_SSANAMES_QUEUE (cfun
)))
132 tree t
= FREE_SSANAMES_QUEUE (cfun
)->pop ();
133 vec_safe_push (FREE_SSANAMES (cfun
), t
);
137 /* Return an SSA_NAME node for variable VAR defined in statement STMT
138 in function FN. STMT may be an empty statement for artificial
139 references (e.g., default definitions created when a variable is
140 used without a preceding definition). */
143 make_ssa_name_fn (struct function
*fn
, tree var
, gimple
*stmt
)
148 gcc_assert (TREE_CODE (var
) == VAR_DECL
149 || TREE_CODE (var
) == PARM_DECL
150 || TREE_CODE (var
) == RESULT_DECL
151 || (TYPE_P (var
) && is_gimple_reg_type (var
)));
153 /* If our free list has an element, then use it. */
154 if (!vec_safe_is_empty (FREE_SSANAMES (fn
)))
156 t
= FREE_SSANAMES (fn
)->pop ();
157 if (GATHER_STATISTICS
)
158 ssa_name_nodes_reused
++;
160 /* The node was cleared out when we put it on the free list, so
161 there is no need to do so again here. */
162 gcc_assert ((*SSANAMES (fn
))[SSA_NAME_VERSION (t
)] == NULL
);
163 (*SSANAMES (fn
))[SSA_NAME_VERSION (t
)] = t
;
167 t
= make_node (SSA_NAME
);
168 SSA_NAME_VERSION (t
) = SSANAMES (fn
)->length ();
169 vec_safe_push (SSANAMES (fn
), t
);
170 if (GATHER_STATISTICS
)
171 ssa_name_nodes_created
++;
177 SET_SSA_NAME_VAR_OR_IDENTIFIER (t
, NULL_TREE
);
181 TREE_TYPE (t
) = TREE_TYPE (var
);
182 SET_SSA_NAME_VAR_OR_IDENTIFIER (t
, var
);
184 SSA_NAME_DEF_STMT (t
) = stmt
;
185 if (POINTER_TYPE_P (TREE_TYPE (t
)))
186 SSA_NAME_PTR_INFO (t
) = NULL
;
188 SSA_NAME_RANGE_INFO (t
) = NULL
;
190 SSA_NAME_IN_FREE_LIST (t
) = 0;
191 SSA_NAME_IS_DEFAULT_DEF (t
) = 0;
192 imm
= &(SSA_NAME_IMM_USE_NODE (t
));
196 imm
->loc
.ssa_name
= t
;
201 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name NAME. */
204 set_range_info (tree name
, enum value_range_type range_type
,
205 const wide_int_ref
&min
, const wide_int_ref
&max
)
207 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
208 gcc_assert (range_type
== VR_RANGE
|| range_type
== VR_ANTI_RANGE
);
209 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
210 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
212 /* Allocate if not available. */
215 size_t size
= (sizeof (range_info_def
)
216 + trailing_wide_ints
<3>::extra_size (precision
));
217 ri
= static_cast<range_info_def
*> (ggc_internal_alloc (size
));
218 ri
->ints
.set_precision (precision
);
219 SSA_NAME_RANGE_INFO (name
) = ri
;
220 ri
->set_nonzero_bits (wi::shwi (-1, precision
));
223 /* Record the range type. */
224 if (SSA_NAME_RANGE_TYPE (name
) != range_type
)
225 SSA_NAME_ANTI_RANGE_P (name
) = (range_type
== VR_ANTI_RANGE
);
227 /* Set the values. */
231 /* If it is a range, try to improve nonzero_bits from the min/max. */
232 if (range_type
== VR_RANGE
)
234 wide_int xorv
= ri
->get_min () ^ ri
->get_max ();
236 xorv
= wi::mask (precision
- wi::clz (xorv
), false, precision
);
237 ri
->set_nonzero_bits (ri
->get_nonzero_bits () & (ri
->get_min () | xorv
));
242 /* Gets range information MIN, MAX and returns enum value_range_type
243 corresponding to tree ssa_name NAME. enum value_range_type returned
244 is used to determine if MIN and MAX are valid values. */
246 enum value_range_type
247 get_range_info (const_tree name
, wide_int
*min
, wide_int
*max
)
249 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
250 gcc_assert (min
&& max
);
251 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
253 /* Return VR_VARYING for SSA_NAMEs with NULL RANGE_INFO or SSA_NAMEs
254 with integral types width > 2 * HOST_BITS_PER_WIDE_INT precision. */
255 if (!ri
|| (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (name
)))
256 > 2 * HOST_BITS_PER_WIDE_INT
))
259 *min
= ri
->get_min ();
260 *max
= ri
->get_max ();
261 return SSA_NAME_RANGE_TYPE (name
);
264 /* Change non-zero bits bitmask of NAME. */
267 set_nonzero_bits (tree name
, const wide_int_ref
&mask
)
269 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
270 if (SSA_NAME_RANGE_INFO (name
) == NULL
)
271 set_range_info (name
, VR_RANGE
,
272 TYPE_MIN_VALUE (TREE_TYPE (name
)),
273 TYPE_MAX_VALUE (TREE_TYPE (name
)));
274 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
275 ri
->set_nonzero_bits (mask
);
278 /* Return a widest_int with potentially non-zero bits in SSA_NAME
279 NAME, or -1 if unknown. */
282 get_nonzero_bits (const_tree name
)
284 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
285 if (POINTER_TYPE_P (TREE_TYPE (name
)))
287 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (name
);
289 return wi::shwi (-(HOST_WIDE_INT
) pi
->align
290 | (HOST_WIDE_INT
) pi
->misalign
, precision
);
291 return wi::shwi (-1, precision
);
294 range_info_def
*ri
= SSA_NAME_RANGE_INFO (name
);
296 return wi::shwi (-1, precision
);
298 return ri
->get_nonzero_bits ();
301 /* We no longer need the SSA_NAME expression VAR, release it so that
304 Note it is assumed that no calls to make_ssa_name will be made
305 until all uses of the ssa name are released and that the only
306 use of the SSA_NAME expression is to check its SSA_NAME_VAR. All
307 other fields must be assumed clobbered. */
310 release_ssa_name_fn (struct function
*fn
, tree var
)
315 /* Never release the default definition for a symbol. It's a
316 special SSA name that should always exist once it's created. */
317 if (SSA_NAME_IS_DEFAULT_DEF (var
))
320 /* If VAR has been registered for SSA updating, don't remove it.
321 After update_ssa has run, the name will be released. */
322 if (name_registered_for_update_p (var
))
324 release_ssa_name_after_update_ssa (var
);
328 /* release_ssa_name can be called multiple times on a single SSA_NAME.
329 However, it should only end up on our free list one time. We
330 keep a status bit in the SSA_NAME node itself to indicate it has
331 been put on the free list.
333 Note that once on the freelist you can not reference the SSA_NAME's
334 defining statement. */
335 if (! SSA_NAME_IN_FREE_LIST (var
))
337 tree saved_ssa_name_var
= SSA_NAME_VAR (var
);
338 int saved_ssa_name_version
= SSA_NAME_VERSION (var
);
339 use_operand_p imm
= &(SSA_NAME_IMM_USE_NODE (var
));
341 if (MAY_HAVE_DEBUG_STMTS
)
342 insert_debug_temp_for_var_def (NULL
, var
);
344 #ifdef ENABLE_CHECKING
345 verify_imm_links (stderr
, var
);
347 while (imm
->next
!= imm
)
348 delink_imm_use (imm
->next
);
350 (*SSANAMES (fn
))[SSA_NAME_VERSION (var
)] = NULL_TREE
;
351 memset (var
, 0, tree_size (var
));
355 imm
->loc
.ssa_name
= var
;
357 /* First put back the right tree node so that the tree checking
358 macros do not complain. */
359 TREE_SET_CODE (var
, SSA_NAME
);
361 /* Restore the version number. */
362 SSA_NAME_VERSION (var
) = saved_ssa_name_version
;
364 /* Hopefully this can go away once we have the new incremental
365 SSA updating code installed. */
366 SET_SSA_NAME_VAR_OR_IDENTIFIER (var
, saved_ssa_name_var
);
368 /* Note this SSA_NAME is now in the first list. */
369 SSA_NAME_IN_FREE_LIST (var
) = 1;
371 /* And finally queue it so that it will be put on the free list. */
372 vec_safe_push (FREE_SSANAMES_QUEUE (fn
), var
);
376 /* If the alignment of the pointer described by PI is known, return true and
377 store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
378 respectively. Otherwise return false. */
381 get_ptr_info_alignment (struct ptr_info_def
*pi
, unsigned int *alignp
,
382 unsigned int *misalignp
)
387 *misalignp
= pi
->misalign
;
394 /* State that the pointer described by PI has unknown alignment. */
397 mark_ptr_info_alignment_unknown (struct ptr_info_def
*pi
)
403 /* Store the power-of-two byte alignment and the deviation from that
404 alignment of pointer described by PI to ALIOGN and MISALIGN
408 set_ptr_info_alignment (struct ptr_info_def
*pi
, unsigned int align
,
409 unsigned int misalign
)
411 gcc_checking_assert (align
!= 0);
412 gcc_assert ((align
& (align
- 1)) == 0);
413 gcc_assert ((misalign
& ~(align
- 1)) == 0);
416 pi
->misalign
= misalign
;
419 /* If pointer described by PI has known alignment, increase its known
420 misalignment by INCREMENT modulo its current alignment. */
423 adjust_ptr_info_misalignment (struct ptr_info_def
*pi
,
424 unsigned int increment
)
428 pi
->misalign
+= increment
;
429 pi
->misalign
&= (pi
->align
- 1);
433 /* Return the alias information associated with pointer T. It creates a
434 new instance if none existed. */
436 struct ptr_info_def
*
437 get_ptr_info (tree t
)
439 struct ptr_info_def
*pi
;
441 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t
)));
443 pi
= SSA_NAME_PTR_INFO (t
);
446 pi
= ggc_cleared_alloc
<ptr_info_def
> ();
447 pt_solution_reset (&pi
->pt
);
448 mark_ptr_info_alignment_unknown (pi
);
449 SSA_NAME_PTR_INFO (t
) = pi
;
456 /* Creates a new SSA name using the template NAME tobe defined by
457 statement STMT in function FN. */
460 copy_ssa_name_fn (struct function
*fn
, tree name
, gimple
*stmt
)
464 if (SSA_NAME_VAR (name
))
465 new_name
= make_ssa_name_fn (fn
, SSA_NAME_VAR (name
), stmt
);
468 new_name
= make_ssa_name_fn (fn
, TREE_TYPE (name
), stmt
);
469 SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name
, SSA_NAME_IDENTIFIER (name
));
476 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
477 the SSA name NAME. */
480 duplicate_ssa_name_ptr_info (tree name
, struct ptr_info_def
*ptr_info
)
482 struct ptr_info_def
*new_ptr_info
;
484 gcc_assert (POINTER_TYPE_P (TREE_TYPE (name
)));
485 gcc_assert (!SSA_NAME_PTR_INFO (name
));
490 new_ptr_info
= ggc_alloc
<ptr_info_def
> ();
491 *new_ptr_info
= *ptr_info
;
493 SSA_NAME_PTR_INFO (name
) = new_ptr_info
;
496 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
497 RANGE_TYPE for use by the SSA name NAME. */
499 duplicate_ssa_name_range_info (tree name
, enum value_range_type range_type
,
500 struct range_info_def
*range_info
)
502 struct range_info_def
*new_range_info
;
504 gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name
)));
505 gcc_assert (!SSA_NAME_RANGE_INFO (name
));
506 gcc_assert (!SSA_NAME_ANTI_RANGE_P (name
));
511 unsigned int precision
= TYPE_PRECISION (TREE_TYPE (name
));
512 size_t size
= (sizeof (range_info_def
)
513 + trailing_wide_ints
<3>::extra_size (precision
));
514 new_range_info
= static_cast<range_info_def
*> (ggc_internal_alloc (size
));
515 memcpy (new_range_info
, range_info
, size
);
517 gcc_assert (range_type
== VR_RANGE
|| range_type
== VR_ANTI_RANGE
);
518 SSA_NAME_ANTI_RANGE_P (name
) = (range_type
== VR_ANTI_RANGE
);
519 SSA_NAME_RANGE_INFO (name
) = new_range_info
;
524 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
528 duplicate_ssa_name_fn (struct function
*fn
, tree name
, gimple
*stmt
)
530 tree new_name
= copy_ssa_name_fn (fn
, name
, stmt
);
531 if (POINTER_TYPE_P (TREE_TYPE (name
)))
533 struct ptr_info_def
*old_ptr_info
= SSA_NAME_PTR_INFO (name
);
536 duplicate_ssa_name_ptr_info (new_name
, old_ptr_info
);
540 struct range_info_def
*old_range_info
= SSA_NAME_RANGE_INFO (name
);
543 duplicate_ssa_name_range_info (new_name
, SSA_NAME_RANGE_TYPE (name
),
551 /* Reset all flow sensitive data on NAME such as range-info, nonzero
552 bits and alignment. */
555 reset_flow_sensitive_info (tree name
)
557 if (POINTER_TYPE_P (TREE_TYPE (name
)))
559 /* points-to info is not flow-sensitive. */
560 if (SSA_NAME_PTR_INFO (name
))
561 mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name
));
564 SSA_NAME_RANGE_INFO (name
) = NULL
;
567 /* Clear all flow sensitive data from all statements and PHI definitions
571 reset_flow_sensitive_info_in_bb (basic_block bb
)
573 for (gimple_stmt_iterator gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
);
576 gimple
*stmt
= gsi_stmt (gsi
);
579 FOR_EACH_SSA_TREE_OPERAND (op
, stmt
, i
, SSA_OP_DEF
)
580 reset_flow_sensitive_info (op
);
583 for (gphi_iterator gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
);
586 tree phi_def
= gimple_phi_result (gsi
.phi ());
587 reset_flow_sensitive_info (phi_def
);
591 /* Release all the SSA_NAMEs created by STMT. */
594 release_defs (gimple
*stmt
)
599 /* Make sure that we are in SSA. Otherwise, operand cache may point
601 gcc_assert (gimple_in_ssa_p (cfun
));
603 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
604 if (TREE_CODE (def
) == SSA_NAME
)
605 release_ssa_name (def
);
609 /* Replace the symbol associated with SSA_NAME with SYM. */
612 replace_ssa_name_symbol (tree ssa_name
, tree sym
)
614 SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name
, sym
);
615 TREE_TYPE (ssa_name
) = TREE_TYPE (sym
);
618 /* Return SSA names that are unused to GGC memory and compact the SSA
619 version namespace. This is used to keep footprint of compiler during
620 interprocedural optimization. */
624 const pass_data pass_data_release_ssa_names
=
626 GIMPLE_PASS
, /* type */
627 "release_ssa", /* name */
628 OPTGROUP_NONE
, /* optinfo_flags */
629 TV_TREE_SSA_OTHER
, /* tv_id */
630 PROP_ssa
, /* properties_required */
631 0, /* properties_provided */
632 0, /* properties_destroyed */
633 TODO_remove_unused_locals
, /* todo_flags_start */
634 0, /* todo_flags_finish */
637 class pass_release_ssa_names
: public gimple_opt_pass
640 pass_release_ssa_names (gcc::context
*ctxt
)
641 : gimple_opt_pass (pass_data_release_ssa_names
, ctxt
)
644 /* opt_pass methods: */
645 virtual unsigned int execute (function
*);
647 }; // class pass_release_ssa_names
650 pass_release_ssa_names::execute (function
*fun
)
653 flush_ssaname_freelist ();
654 int n
= vec_safe_length (FREE_SSANAMES (fun
));
656 /* Now release the freelist. */
657 vec_free (FREE_SSANAMES (fun
));
659 /* And compact the SSA number space. We make sure to not change the
660 relative order of SSA versions. */
661 for (i
= 1, j
= 1; i
< fun
->gimple_df
->ssa_names
->length (); ++i
)
663 tree name
= ssa_name (i
);
668 SSA_NAME_VERSION (name
) = j
;
669 (*fun
->gimple_df
->ssa_names
)[j
] = name
;
674 fun
->gimple_df
->ssa_names
->truncate (j
);
676 statistics_counter_event (fun
, "SSA names released", n
);
677 statistics_counter_event (fun
, "SSA name holes removed", i
- j
);
679 fprintf (dump_file
, "Released %i names, %.2f%%, removed %i holes\n",
680 n
, n
* 100.0 / num_ssa_names
, i
- j
);
687 make_pass_release_ssa_names (gcc::context
*ctxt
)
689 return new pass_release_ssa_names (ctxt
);