1 /* RTL dead store elimination.
2 Copyright (C) 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
4 Contributed by Richard Sandiford <rsandifor@codesourcery.com>
5 and Kenneth Zadeck <zadeck@naturalbridge.com>
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it under
10 the terms of the GNU General Public License as published by the Free
11 Software Foundation; either version 3, or (at your option) any later
14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
27 #include "coretypes.h"
34 #include "hard-reg-set.h"
39 #include "tree-pass.h"
40 #include "alloc-pool.h"
42 #include "insn-config.h"
49 /* This file contains three techniques for performing Dead Store
52 * The first technique performs dse locally on any base address. It
53 is based on the cselib which is a local value numbering technique.
54 This technique is local to a basic block but deals with a fairly
57 * The second technique performs dse globally but is restricted to
58 base addresses that are either constant or are relative to the
61 * The third technique, (which is only done after register allocation)
62 processes the spill spill slots. This differs from the second
63 technique because it takes advantage of the fact that spilling is
64 completely free from the effects of aliasing.
66 Logically, dse is a backwards dataflow problem. A store can be
67 deleted if it if cannot be reached in the backward direction by any
68 use of the value being stored. However, the local technique uses a
69 forwards scan of the basic block because cselib requires that the
70 block be processed in that order.
72 The pass is logically broken into 7 steps:
76 1) The local algorithm, as well as scanning the insns for the two
79 2) Analysis to see if the global algs are necessary. In the case
80 of stores base on a constant address, there must be at least two
81 stores to that address, to make it possible to delete some of the
82 stores. In the case of stores off of the frame or spill related
83 stores, only one store to an address is necessary because those
84 stores die at the end of the function.
86 3) Set up the global dataflow equations based on processing the
87 info parsed in the first step.
89 4) Solve the dataflow equations.
91 5) Delete the insns that the global analysis has indicated are
96 This step uses cselib and canon_rtx to build the largest expression
97 possible for each address. This pass is a forwards pass through
98 each basic block. From the point of view of the global technique,
99 the first pass could examine a block in either direction. The
100 forwards ordering is to accommodate cselib.
102 We a simplifying assumption: addresses fall into four broad
105 1) base has rtx_varies_p == false, offset is constant.
106 2) base has rtx_varies_p == false, offset variable.
107 3) base has rtx_varies_p == true, offset constant.
108 4) base has rtx_varies_p == true, offset variable.
110 The local passes are able to process all 4 kinds of addresses. The
111 global pass only handles (1).
113 The global problem is formulated as follows:
115 A store, S1, to address A, where A is not relative to the stack
116 frame, can be eliminated if all paths from S1 to the end of the
117 of the function contain another store to A before a read to A.
119 If the address A is relative to the stack frame, a store S2 to A
120 can be eliminated if there are no paths from S1 that reach the
121 end of the function that read A before another store to A. In
122 this case S2 can be deleted if there are paths to from S2 to the
123 end of the function that have no reads or writes to A. This
124 second case allows stores to the stack frame to be deleted that
125 would otherwise die when the function returns. This cannot be
126 done if stores_off_frame_dead_at_return is not true. See the doc
127 for that variable for when this variable is false.
129 The global problem is formulated as a backwards set union
130 dataflow problem where the stores are the gens and reads are the
131 kills. Set union problems are rare and require some special
132 handling given our representation of bitmaps. A straightforward
133 implementation of requires a lot of bitmaps filled with 1s.
134 These are expensive and cumbersome in our bitmap formulation so
135 care has been taken to avoid large vectors filled with 1s. See
136 the comments in bb_info and in the dataflow confluence functions
139 There are two places for further enhancements to this algorithm:
141 1) The original dse which was embedded in a pass called flow also
142 did local address forwarding. For example in
147 flow would replace the right hand side of the second insn with a
148 reference to r100. Most of the information is available to add this
149 to this pass. It has not done it because it is a lot of work in
150 the case that either r100 is assigned to between the first and
151 second insn and/or the second insn is a load of part of the value
152 stored by the first insn.
154 insn 5 in gcc.c-torture/compile/990203-1.c simple case.
155 insn 15 in gcc.c-torture/execute/20001017-2.c simple case.
156 insn 25 in gcc.c-torture/execute/20001026-1.c simple case.
157 insn 44 in gcc.c-torture/execute/20010910-1.c simple case.
159 2) The cleaning up of spill code is quite profitable. It currently
160 depends on reading tea leaves and chicken entrails left by reload.
161 This pass depends on reload creating a singleton alias set for each
162 spill slot and telling the next dse pass which of these alias sets
163 are the singletons. Rather than analyze the addresses of the
164 spills, dse's spill processing just does analysis of the loads and
165 stores that use those alias sets. There are three cases where this
168 a) Reload sometimes creates the slot for one mode of access, and
169 then inserts loads and/or stores for a smaller mode. In this
170 case, the current code just punts on the slot. The proper thing
171 to do is to back out and use one bit vector position for each
172 byte of the entity associated with the slot. This depends on
173 KNOWING that reload always generates the accesses for each of the
174 bytes in some canonical (read that easy to understand several
175 passes after reload happens) way.
177 b) Reload sometimes decides that spill slot it allocated was not
178 large enough for the mode and goes back and allocates more slots
179 with the same mode and alias set. The backout in this case is a
180 little more graceful than (a). In this case the slot is unmarked
181 as being a spill slot and if final address comes out to be based
182 off the frame pointer, the global algorithm handles this slot.
184 c) For any pass that may prespill, there is currently no
185 mechanism to tell the dse pass that the slot being used has the
186 special properties that reload uses. It may be that all that is
187 required is to have those passes make the same calls that reload
188 does, assuming that the alias sets can be manipulated in the same
191 /* There are limits to the size of constant offsets we model for the
192 global problem. There are certainly test cases, that exceed this
193 limit, however, it is unlikely that there are important programs
194 that really have constant offsets this size. */
195 #define MAX_OFFSET (64 * 1024)
198 static bitmap scratch = NULL;
201 /* This structure holds information about a candidate store. */
205 /* False means this is a clobber. */
208 /* The id of the mem group of the base address. If rtx_varies_p is
209 true, this is -1. Otherwise, it is the index into the group
213 /* This is the cselib value. */
214 cselib_val *cse_base;
216 /* This canonized mem. */
219 /* The result of get_addr on mem. */
222 /* If this is non-zero, it is the alias set of a spill location. */
223 alias_set_type alias_set;
225 /* The offset of the first and byte before the last byte associated
226 with the operation. */
229 /* An bitmask as wide as the number of bytes in the word that
230 contains a 1 if the byte may be needed. The store is unused if
231 all of the bits are 0. */
232 unsigned HOST_WIDE_INT positions_needed;
234 /* The next store info for this insn. */
235 struct store_info *next;
237 /* The right hand side of the store. This is used if there is a
238 subsequent reload of the mems address somewhere later in the
243 /* Return a bitmask with the first N low bits set. */
245 static unsigned HOST_WIDE_INT
246 lowpart_bitmask (int n)
248 unsigned HOST_WIDE_INT mask = ~(unsigned HOST_WIDE_INT) 0;
249 return mask >> (HOST_BITS_PER_WIDE_INT - n);
252 typedef struct store_info *store_info_t;
253 static alloc_pool cse_store_info_pool;
254 static alloc_pool rtx_store_info_pool;
256 /* This structure holds information about a load. These are only
257 built for rtx bases. */
260 /* The id of the mem group of the base address. */
263 /* If this is non-zero, it is the alias set of a spill location. */
264 alias_set_type alias_set;
266 /* The offset of the first and byte after the last byte associated
267 with the operation. If begin == end == 0, the read did not have
268 a constant offset. */
271 /* The mem being read. */
274 /* The next read_info for this insn. */
275 struct read_info *next;
277 typedef struct read_info *read_info_t;
278 static alloc_pool read_info_pool;
281 /* One of these records is created for each insn. */
285 /* Set true if the insn contains a store but the insn itself cannot
286 be deleted. This is set if the insn is a parallel and there is
287 more than one non dead output or if the insn is in some way
291 /* This field is only used by the global algorithm. It is set true
292 if the insn contains any read of mem except for a (1). This is
293 also set if the insn is a call or has a clobber mem. If the insn
294 contains a wild read, the use_rec will be null. */
297 /* This field is only used for the processing of const functions.
298 These functions cannot read memory, but they can read the stack
299 because that is where they may get their parms. We need to be
300 this conservative because, like the store motion pass, we don't
301 consider CALL_INSN_FUNCTION_USAGE when processing call insns.
302 Moreover, we need to distinguish two cases:
303 1. Before reload (register elimination), the stores related to
304 outgoing arguments are stack pointer based and thus deemed
305 of non-constant base in this pass. This requires special
306 handling but also means that the frame pointer based stores
307 need not be killed upon encountering a const function call.
308 2. After reload, the stores related to outgoing arguments can be
309 either stack pointer or hard frame pointer based. This means
310 that we have no other choice than also killing all the frame
311 pointer based stores upon encountering a const function call.
312 This field is set after reload for const function calls. Having
313 this set is less severe than a wild read, it just means that all
314 the frame related stores are killed rather than all the stores. */
317 /* This field is only used for the processing of const functions.
318 It is set if the insn may contain a stack pointer based store. */
319 bool stack_pointer_based;
321 /* This is true if any of the sets within the store contains a
322 cselib base. Such stores can only be deleted by the local
324 bool contains_cselib_groups;
329 /* The list of mem sets or mem clobbers that are contained in this
330 insn. If the insn is deletable, it contains only one mem set.
331 But it could also contain clobbers. Insns that contain more than
332 one mem set are not deletable, but each of those mems are here in
333 order to provide info to delete other insns. */
334 store_info_t store_rec;
336 /* The linked list of mem uses in this insn. Only the reads from
337 rtx bases are listed here. The reads to cselib bases are
338 completely processed during the first scan and so are never
340 read_info_t read_rec;
342 /* The prev insn in the basic block. */
343 struct insn_info * prev_insn;
345 /* The linked list of insns that are in consideration for removal in
346 the forwards pass thru the basic block. This pointer may be
347 trash as it is not cleared when a wild read occurs. The only
348 time it is guaranteed to be correct is when the traversal starts
349 at active_local_stores. */
350 struct insn_info * next_local_store;
353 typedef struct insn_info *insn_info_t;
354 static alloc_pool insn_info_pool;
356 /* The linked list of stores that are under consideration in this
358 static insn_info_t active_local_stores;
363 /* Pointer to the insn info for the last insn in the block. These
364 are linked so this is how all of the insns are reached. During
365 scanning this is the current insn being scanned. */
366 insn_info_t last_insn;
368 /* The info for the global dataflow problem. */
371 /* This is set if the transfer function should and in the wild_read
372 bitmap before applying the kill and gen sets. That vector knocks
373 out most of the bits in the bitmap and thus speeds up the
375 bool apply_wild_read;
377 /* The set of store positions that exist in this block before a wild read. */
380 /* The set of load positions that exist in this block above the
381 same position of a store. */
384 /* The set of stores that reach the top of the block without being
387 Do not represent the in if it is all ones. Note that this is
388 what the bitvector should logically be initialized to for a set
389 intersection problem. However, like the kill set, this is too
390 expensive. So initially, the in set will only be created for the
391 exit block and any block that contains a wild read. */
394 /* The set of stores that reach the bottom of the block from it's
397 Do not represent the in if it is all ones. Note that this is
398 what the bitvector should logically be initialized to for a set
399 intersection problem. However, like the kill and in set, this is
400 too expensive. So what is done is that the confluence operator
401 just initializes the vector from one of the out sets of the
402 successors of the block. */
406 typedef struct bb_info *bb_info_t;
407 static alloc_pool bb_info_pool;
409 /* Table to hold all bb_infos. */
410 static bb_info_t *bb_table;
412 /* There is a group_info for each rtx base that is used to reference
413 memory. There are also not many of the rtx bases because they are
414 very limited in scope. */
418 /* The actual base of the address. */
421 /* The sequential id of the base. This allows us to have a
422 canonical ordering of these that is not based on addresses. */
425 /* A mem wrapped around the base pointer for the group in order to
426 do read dependency. */
429 /* Canonized version of base_mem, most likely the same thing. */
432 /* These two sets of two bitmaps are used to keep track of how many
433 stores are actually referencing that position from this base. We
434 only do this for rtx bases as this will be used to assign
435 positions in the bitmaps for the global problem. Bit N is set in
436 store1 on the first store for offset N. Bit N is set in store2
437 for the second store to offset N. This is all we need since we
438 only care about offsets that have two or more stores for them.
440 The "_n" suffix is for offsets less than 0 and the "_p" suffix is
441 for 0 and greater offsets.
443 There is one special case here, for stores into the stack frame,
444 we will or store1 into store2 before deciding which stores look
445 at globally. This is because stores to the stack frame that have
446 no other reads before the end of the function can also be
448 bitmap store1_n, store1_p, store2_n, store2_p;
450 /* The positions in this bitmap have the same assignments as the in,
451 out, gen and kill bitmaps. This bitmap is all zeros except for
452 the positions that are occupied by stores for this group. */
455 /* True if there are any positions that are to be processed
457 bool process_globally;
459 /* True if the base of this group is either the frame_pointer or
460 hard_frame_pointer. */
463 /* The offset_map is used to map the offsets from this base into
464 positions in the global bitmaps. It is only created after all of
465 the all of stores have been scanned and we know which ones we
467 int *offset_map_n, *offset_map_p;
468 int offset_map_size_n, offset_map_size_p;
470 typedef struct group_info *group_info_t;
471 typedef const struct group_info *const_group_info_t;
472 static alloc_pool rtx_group_info_pool;
474 /* Tables of group_info structures, hashed by base value. */
475 static htab_t rtx_group_table;
477 /* Index into the rtx_group_vec. */
478 static int rtx_group_next_id;
480 DEF_VEC_P(group_info_t);
481 DEF_VEC_ALLOC_P(group_info_t,heap);
483 static VEC(group_info_t,heap) *rtx_group_vec;
486 /* This structure holds the set of changes that are being deferred
487 when removing read operation. See replace_read. */
488 struct deferred_change
491 /* The mem that is being replaced. */
494 /* The reg it is being replaced with. */
497 struct deferred_change *next;
500 typedef struct deferred_change *deferred_change_t;
501 static alloc_pool deferred_change_pool;
503 static deferred_change_t deferred_change_list = NULL;
505 /* This are used to hold the alias sets of spill variables. Since
506 these are never aliased and there may be a lot of them, it makes
507 sense to treat them specially. This bitvector is only allocated in
508 calls from dse_record_singleton_alias_set which currently is only
509 made during reload1. So when dse is called before reload this
510 mechanism does nothing. */
512 static bitmap clear_alias_sets = NULL;
514 /* The set of clear_alias_sets that have been disqualified because
515 there are loads or stores using a different mode than the alias set
516 was registered with. */
517 static bitmap disqualified_clear_alias_sets = NULL;
519 /* The group that holds all of the clear_alias_sets. */
520 static group_info_t clear_alias_group;
522 /* The modes of the clear_alias_sets. */
523 static htab_t clear_alias_mode_table;
525 /* Hash table element to look up the mode for an alias set. */
526 struct clear_alias_mode_holder
528 alias_set_type alias_set;
529 enum machine_mode mode;
532 static alloc_pool clear_alias_mode_pool;
534 /* This is true except if cfun->stdarg -- i.e. we cannot do
535 this for vararg functions because they play games with the frame. */
536 static bool stores_off_frame_dead_at_return;
538 /* Counter for stats. */
539 static int globally_deleted;
540 static int locally_deleted;
541 static int spill_deleted;
543 static bitmap all_blocks;
545 /* The number of bits used in the global bitmaps. */
546 static unsigned int current_position;
549 static bool gate_dse (void);
550 static bool gate_dse1 (void);
551 static bool gate_dse2 (void);
554 /*----------------------------------------------------------------------------
558 ----------------------------------------------------------------------------*/
560 /* Hashtable callbacks for maintaining the "bases" field of
561 store_group_info, given that the addresses are function invariants. */
564 clear_alias_mode_eq (const void *p1, const void *p2)
566 const struct clear_alias_mode_holder * h1
567 = (const struct clear_alias_mode_holder *) p1;
568 const struct clear_alias_mode_holder * h2
569 = (const struct clear_alias_mode_holder *) p2;
570 return h1->alias_set == h2->alias_set;
575 clear_alias_mode_hash (const void *p)
577 const struct clear_alias_mode_holder *holder
578 = (const struct clear_alias_mode_holder *) p;
579 return holder->alias_set;
583 /* Find the entry associated with ALIAS_SET. */
585 static struct clear_alias_mode_holder *
586 clear_alias_set_lookup (alias_set_type alias_set)
588 struct clear_alias_mode_holder tmp_holder;
591 tmp_holder.alias_set = alias_set;
592 slot = htab_find_slot (clear_alias_mode_table, &tmp_holder, NO_INSERT);
595 return (struct clear_alias_mode_holder *) *slot;
599 /* Hashtable callbacks for maintaining the "bases" field of
600 store_group_info, given that the addresses are function invariants. */
603 invariant_group_base_eq (const void *p1, const void *p2)
605 const_group_info_t gi1 = (const_group_info_t) p1;
606 const_group_info_t gi2 = (const_group_info_t) p2;
607 return rtx_equal_p (gi1->rtx_base, gi2->rtx_base);
612 invariant_group_base_hash (const void *p)
614 const_group_info_t gi = (const_group_info_t) p;
616 return hash_rtx (gi->rtx_base, Pmode, &do_not_record, NULL, false);
620 /* Get the GROUP for BASE. Add a new group if it is not there. */
623 get_group_info (rtx base)
625 struct group_info tmp_gi;
631 /* Find the store_base_info structure for BASE, creating a new one
633 tmp_gi.rtx_base = base;
634 slot = htab_find_slot (rtx_group_table, &tmp_gi, INSERT);
635 gi = (group_info_t) *slot;
639 if (!clear_alias_group)
641 clear_alias_group = gi =
642 (group_info_t) pool_alloc (rtx_group_info_pool);
643 memset (gi, 0, sizeof (struct group_info));
644 gi->id = rtx_group_next_id++;
645 gi->store1_n = BITMAP_ALLOC (NULL);
646 gi->store1_p = BITMAP_ALLOC (NULL);
647 gi->store2_n = BITMAP_ALLOC (NULL);
648 gi->store2_p = BITMAP_ALLOC (NULL);
649 gi->group_kill = BITMAP_ALLOC (NULL);
650 gi->process_globally = false;
651 gi->offset_map_size_n = 0;
652 gi->offset_map_size_p = 0;
653 gi->offset_map_n = NULL;
654 gi->offset_map_p = NULL;
655 VEC_safe_push (group_info_t, heap, rtx_group_vec, gi);
657 return clear_alias_group;
662 *slot = gi = (group_info_t) pool_alloc (rtx_group_info_pool);
664 gi->id = rtx_group_next_id++;
665 gi->base_mem = gen_rtx_MEM (QImode, base);
666 gi->canon_base_mem = canon_rtx (gi->base_mem);
667 gi->store1_n = BITMAP_ALLOC (NULL);
668 gi->store1_p = BITMAP_ALLOC (NULL);
669 gi->store2_n = BITMAP_ALLOC (NULL);
670 gi->store2_p = BITMAP_ALLOC (NULL);
671 gi->group_kill = BITMAP_ALLOC (NULL);
672 gi->process_globally = false;
674 (base == frame_pointer_rtx) || (base == hard_frame_pointer_rtx);
675 gi->offset_map_size_n = 0;
676 gi->offset_map_size_p = 0;
677 gi->offset_map_n = NULL;
678 gi->offset_map_p = NULL;
679 VEC_safe_push (group_info_t, heap, rtx_group_vec, gi);
686 /* Initialization of data structures. */
692 globally_deleted = 0;
695 scratch = BITMAP_ALLOC (NULL);
698 = create_alloc_pool ("rtx_store_info_pool",
699 sizeof (struct store_info), 100);
701 = create_alloc_pool ("read_info_pool",
702 sizeof (struct read_info), 100);
704 = create_alloc_pool ("insn_info_pool",
705 sizeof (struct insn_info), 100);
707 = create_alloc_pool ("bb_info_pool",
708 sizeof (struct bb_info), 100);
710 = create_alloc_pool ("rtx_group_info_pool",
711 sizeof (struct group_info), 100);
713 = create_alloc_pool ("deferred_change_pool",
714 sizeof (struct deferred_change), 10);
716 rtx_group_table = htab_create (11, invariant_group_base_hash,
717 invariant_group_base_eq, NULL);
719 bb_table = XCNEWVEC (bb_info_t, last_basic_block);
720 rtx_group_next_id = 0;
722 stores_off_frame_dead_at_return = !cfun->stdarg;
724 init_alias_analysis ();
726 if (clear_alias_sets)
727 clear_alias_group = get_group_info (NULL);
729 clear_alias_group = NULL;
734 /*----------------------------------------------------------------------------
737 Scan all of the insns. Any random ordering of the blocks is fine.
738 Each block is scanned in forward order to accommodate cselib which
739 is used to remove stores with non-constant bases.
740 ----------------------------------------------------------------------------*/
742 /* Delete all of the store_info recs from INSN_INFO. */
745 free_store_info (insn_info_t insn_info)
747 store_info_t store_info = insn_info->store_rec;
750 store_info_t next = store_info->next;
751 if (store_info->cse_base)
752 pool_free (cse_store_info_pool, store_info);
754 pool_free (rtx_store_info_pool, store_info);
758 insn_info->cannot_delete = true;
759 insn_info->contains_cselib_groups = false;
760 insn_info->store_rec = NULL;
770 /* Add an insn to do the add inside a x if it is a
771 PRE/POST-INC/DEC/MODIFY. D is an structure containing the insn and
772 the size of the mode of the MEM that this is inside of. */
775 replace_inc_dec (rtx *r, void *d)
778 struct insn_size *data = (struct insn_size *)d;
779 switch (GET_CODE (x))
784 rtx r1 = XEXP (x, 0);
785 rtx c = gen_int_mode (Pmode, data->size);
786 add_insn_before (data->insn,
787 gen_rtx_SET (Pmode, r1,
788 gen_rtx_PLUS (Pmode, r1, c)),
796 rtx r1 = XEXP (x, 0);
797 rtx c = gen_int_mode (Pmode, -data->size);
798 add_insn_before (data->insn,
799 gen_rtx_SET (Pmode, r1,
800 gen_rtx_PLUS (Pmode, r1, c)),
808 /* We can reuse the add because we are about to delete the
809 insn that contained it. */
810 rtx add = XEXP (x, 0);
811 rtx r1 = XEXP (add, 0);
812 add_insn_before (data->insn,
813 gen_rtx_SET (Pmode, r1, add), NULL);
823 /* If X is a MEM, check the address to see if it is PRE/POST-INC/DEC/MODIFY
824 and generate an add to replace that. */
827 replace_inc_dec_mem (rtx *r, void *d)
830 if (GET_CODE (x) == MEM)
832 struct insn_size data;
834 data.size = GET_MODE_SIZE (GET_MODE (x));
837 for_each_rtx (&XEXP (x, 0), replace_inc_dec, &data);
844 /* Before we delete INSN, make sure that the auto inc/dec, if it is
845 there, is split into a separate insn. */
848 check_for_inc_dec (rtx insn)
850 rtx note = find_reg_note (insn, REG_INC, NULL_RTX);
852 for_each_rtx (&insn, replace_inc_dec_mem, insn);
856 /* Delete the insn and free all of the fields inside INSN_INFO. */
859 delete_dead_store_insn (insn_info_t insn_info)
861 read_info_t read_info;
866 check_for_inc_dec (insn_info->insn);
869 fprintf (dump_file, "Locally deleting insn %d ",
870 INSN_UID (insn_info->insn));
871 if (insn_info->store_rec->alias_set)
872 fprintf (dump_file, "alias set %d\n",
873 (int) insn_info->store_rec->alias_set);
875 fprintf (dump_file, "\n");
878 free_store_info (insn_info);
879 read_info = insn_info->read_rec;
883 read_info_t next = read_info->next;
884 pool_free (read_info_pool, read_info);
887 insn_info->read_rec = NULL;
889 delete_insn (insn_info->insn);
891 insn_info->insn = NULL;
893 insn_info->wild_read = false;
897 /* Set the store* bitmaps offset_map_size* fields in GROUP based on
901 set_usage_bits (group_info_t group, HOST_WIDE_INT offset, HOST_WIDE_INT width)
905 if ((offset > -MAX_OFFSET) && (offset < MAX_OFFSET))
906 for (i=offset; i<offset+width; i++)
913 store1 = group->store1_n;
914 store2 = group->store2_n;
919 store1 = group->store1_p;
920 store2 = group->store2_p;
924 if (bitmap_bit_p (store1, ai))
925 bitmap_set_bit (store2, ai);
928 bitmap_set_bit (store1, ai);
931 if (group->offset_map_size_n < ai)
932 group->offset_map_size_n = ai;
936 if (group->offset_map_size_p < ai)
937 group->offset_map_size_p = ai;
944 /* Set the BB_INFO so that the last insn is marked as a wild read. */
947 add_wild_read (bb_info_t bb_info)
949 insn_info_t insn_info = bb_info->last_insn;
950 read_info_t *ptr = &insn_info->read_rec;
954 read_info_t next = (*ptr)->next;
955 if ((*ptr)->alias_set == 0)
957 pool_free (read_info_pool, *ptr);
963 insn_info->wild_read = true;
964 active_local_stores = NULL;
968 /* Return true if X is a constant or one of the registers that behave
969 as a constant over the life of a function. This is equivalent to
970 !rtx_varies_p for memory addresses. */
973 const_or_frame_p (rtx x)
975 switch (GET_CODE (x))
978 return MEM_READONLY_P (x);
989 /* Note that we have to test for the actual rtx used for the frame
990 and arg pointers and not just the register number in case we have
991 eliminated the frame and/or arg pointer and are using it
993 if (x == frame_pointer_rtx || x == hard_frame_pointer_rtx
994 /* The arg pointer varies if it is not a fixed register. */
995 || (x == arg_pointer_rtx && fixed_regs[ARG_POINTER_REGNUM])
996 || x == pic_offset_table_rtx)
1005 /* Take all reasonable action to put the address of MEM into the form
1006 that we can do analysis on.
1008 The gold standard is to get the address into the form: address +
1009 OFFSET where address is something that rtx_varies_p considers a
1010 constant. When we can get the address in this form, we can do
1011 global analysis on it. Note that for constant bases, address is
1012 not actually returned, only the group_id. The address can be
1015 If that fails, we try cselib to get a value we can at least use
1016 locally. If that fails we return false.
1018 The GROUP_ID is set to -1 for cselib bases and the index of the
1019 group for non_varying bases.
1021 FOR_READ is true if this is a mem read and false if not. */
1024 canon_address (rtx mem,
1025 alias_set_type *alias_set_out,
1027 HOST_WIDE_INT *offset,
1030 rtx mem_address = XEXP (mem, 0);
1031 rtx expanded_address, address;
1032 /* Make sure that cselib is has initialized all of the operands of
1033 the address before asking it to do the subst. */
1035 if (clear_alias_sets)
1037 /* If this is a spill, do not do any further processing. */
1038 alias_set_type alias_set = MEM_ALIAS_SET (mem);
1040 fprintf (dump_file, "found alias set %d\n", (int) alias_set);
1041 if (bitmap_bit_p (clear_alias_sets, alias_set))
1043 struct clear_alias_mode_holder *entry
1044 = clear_alias_set_lookup (alias_set);
1046 /* If the modes do not match, we cannot process this set. */
1047 if (entry->mode != GET_MODE (mem))
1051 "disqualifying alias set %d, (%s) != (%s)\n",
1052 (int) alias_set, GET_MODE_NAME (entry->mode),
1053 GET_MODE_NAME (GET_MODE (mem)));
1055 bitmap_set_bit (disqualified_clear_alias_sets, alias_set);
1059 *alias_set_out = alias_set;
1060 *group_id = clear_alias_group->id;
1067 cselib_lookup (mem_address, Pmode, 1);
1071 fprintf (dump_file, " mem: ");
1072 print_inline_rtx (dump_file, mem_address, 0);
1073 fprintf (dump_file, "\n");
1076 /* Use cselib to replace all of the reg references with the full
1077 expression. This will take care of the case where we have
1079 r_x = base + offset;
1084 val = *(base + offset);
1087 expanded_address = cselib_expand_value_rtx (mem_address, scratch, 5);
1089 /* If this fails, just go with the mem_address. */
1090 if (!expanded_address)
1091 expanded_address = mem_address;
1093 /* Split the address into canonical BASE + OFFSET terms. */
1094 address = canon_rtx (expanded_address);
1100 fprintf (dump_file, "\n after cselib_expand address: ");
1101 print_inline_rtx (dump_file, expanded_address, 0);
1102 fprintf (dump_file, "\n");
1104 fprintf (dump_file, "\n after canon_rtx address: ");
1105 print_inline_rtx (dump_file, address, 0);
1106 fprintf (dump_file, "\n");
1109 if (GET_CODE (address) == CONST)
1110 address = XEXP (address, 0);
1112 if (GET_CODE (address) == PLUS && GET_CODE (XEXP (address, 1)) == CONST_INT)
1114 *offset = INTVAL (XEXP (address, 1));
1115 address = XEXP (address, 0);
1118 if (const_or_frame_p (address))
1120 group_info_t group = get_group_info (address);
1123 fprintf (dump_file, " gid=%d offset=%d \n", group->id, (int)*offset);
1125 *group_id = group->id;
1129 *base = cselib_lookup (address, Pmode, true);
1135 fprintf (dump_file, " no cselib val - should be a wild read.\n");
1139 fprintf (dump_file, " varying cselib base=%d offset = %d\n",
1140 (*base)->value, (int)*offset);
1146 /* Clear the rhs field from the active_local_stores array. */
1149 clear_rhs_from_active_local_stores (void)
1151 insn_info_t ptr = active_local_stores;
1155 store_info_t store_info = ptr->store_rec;
1156 /* Skip the clobbers. */
1157 while (!store_info->is_set)
1158 store_info = store_info->next;
1160 store_info->rhs = NULL;
1162 ptr = ptr->next_local_store;
1167 /* BODY is an instruction pattern that belongs to INSN. Return 1 if
1168 there is a candidate store, after adding it to the appropriate
1169 local store group if so. */
1172 record_store (rtx body, bb_info_t bb_info)
1175 HOST_WIDE_INT offset = 0;
1176 HOST_WIDE_INT width = 0;
1177 alias_set_type spill_alias_set;
1178 insn_info_t insn_info = bb_info->last_insn;
1179 store_info_t store_info = NULL;
1181 cselib_val *base = NULL;
1182 insn_info_t ptr, last;
1183 bool store_is_unused;
1185 if (GET_CODE (body) != SET && GET_CODE (body) != CLOBBER)
1188 /* If this is not used, then this cannot be used to keep the insn
1189 from being deleted. On the other hand, it does provide something
1190 that can be used to prove that another store is dead. */
1192 = (find_reg_note (insn_info->insn, REG_UNUSED, body) != NULL);
1194 /* Check whether that value is a suitable memory location. */
1195 mem = SET_DEST (body);
1198 /* If the set or clobber is unused, then it does not effect our
1199 ability to get rid of the entire insn. */
1200 if (!store_is_unused)
1201 insn_info->cannot_delete = true;
1205 /* At this point we know mem is a mem. */
1206 if (GET_MODE (mem) == BLKmode)
1208 if (GET_CODE (XEXP (mem, 0)) == SCRATCH)
1211 fprintf (dump_file, " adding wild read for (clobber (mem:BLK (scratch))\n");
1212 add_wild_read (bb_info);
1213 insn_info->cannot_delete = true;
1215 else if (!store_is_unused)
1217 /* If the set or clobber is unused, then it does not effect our
1218 ability to get rid of the entire insn. */
1219 insn_info->cannot_delete = true;
1220 clear_rhs_from_active_local_stores ();
1225 /* We can still process a volatile mem, we just cannot delete it. */
1226 if (MEM_VOLATILE_P (mem))
1227 insn_info->cannot_delete = true;
1229 if (!canon_address (mem, &spill_alias_set, &group_id, &offset, &base))
1231 clear_rhs_from_active_local_stores ();
1235 width = GET_MODE_SIZE (GET_MODE (mem));
1237 if (spill_alias_set)
1239 bitmap store1 = clear_alias_group->store1_p;
1240 bitmap store2 = clear_alias_group->store2_p;
1242 if (bitmap_bit_p (store1, spill_alias_set))
1243 bitmap_set_bit (store2, spill_alias_set);
1245 bitmap_set_bit (store1, spill_alias_set);
1247 if (clear_alias_group->offset_map_size_p < spill_alias_set)
1248 clear_alias_group->offset_map_size_p = spill_alias_set;
1250 store_info = (store_info_t) pool_alloc (rtx_store_info_pool);
1253 fprintf (dump_file, " processing spill store %d(%s)\n",
1254 (int) spill_alias_set, GET_MODE_NAME (GET_MODE (mem)));
1256 else if (group_id >= 0)
1258 /* In the restrictive case where the base is a constant or the
1259 frame pointer we can do global analysis. */
1262 = VEC_index (group_info_t, rtx_group_vec, group_id);
1264 store_info = (store_info_t) pool_alloc (rtx_store_info_pool);
1265 set_usage_bits (group, offset, width);
1268 fprintf (dump_file, " processing const base store gid=%d[%d..%d)\n",
1269 group_id, (int)offset, (int)(offset+width));
1273 rtx base_term = find_base_term (XEXP (mem, 0));
1275 || (GET_CODE (base_term) == ADDRESS
1276 && GET_MODE (base_term) == Pmode
1277 && XEXP (base_term, 0) == stack_pointer_rtx))
1278 insn_info->stack_pointer_based = true;
1279 insn_info->contains_cselib_groups = true;
1281 store_info = (store_info_t) pool_alloc (cse_store_info_pool);
1285 fprintf (dump_file, " processing cselib store [%d..%d)\n",
1286 (int)offset, (int)(offset+width));
1289 /* Check to see if this stores causes some other stores to be
1291 ptr = active_local_stores;
1296 insn_info_t next = ptr->next_local_store;
1297 store_info_t s_info = ptr->store_rec;
1300 /* Skip the clobbers. We delete the active insn if this insn
1301 shadows the set. To have been put on the active list, it
1302 has exactly on set. */
1303 while (!s_info->is_set)
1304 s_info = s_info->next;
1306 if (s_info->alias_set != spill_alias_set)
1308 else if (s_info->alias_set)
1310 struct clear_alias_mode_holder *entry
1311 = clear_alias_set_lookup (s_info->alias_set);
1312 /* Generally, spills cannot be processed if and of the
1313 references to the slot have a different mode. But if
1314 we are in the same block and mode is exactly the same
1315 between this store and one before in the same block,
1316 we can still delete it. */
1317 if ((GET_MODE (mem) == GET_MODE (s_info->mem))
1318 && (GET_MODE (mem) == entry->mode))
1321 s_info->positions_needed = (unsigned HOST_WIDE_INT) 0;
1324 fprintf (dump_file, " trying spill store in insn=%d alias_set=%d\n",
1325 INSN_UID (ptr->insn), (int) s_info->alias_set);
1327 else if ((s_info->group_id == group_id)
1328 && (s_info->cse_base == base))
1332 fprintf (dump_file, " trying store in insn=%d gid=%d[%d..%d)\n",
1333 INSN_UID (ptr->insn), s_info->group_id,
1334 (int)s_info->begin, (int)s_info->end);
1335 for (i = offset; i < offset+width; i++)
1336 if (i >= s_info->begin && i < s_info->end)
1337 s_info->positions_needed
1338 &= ~(((unsigned HOST_WIDE_INT) 1) << (i - s_info->begin));
1340 else if (s_info->rhs)
1341 /* Need to see if it is possible for this store to overwrite
1342 the value of store_info. If it is, set the rhs to NULL to
1343 keep it from being used to remove a load. */
1345 if (canon_true_dependence (s_info->mem,
1346 GET_MODE (s_info->mem),
1352 /* An insn can be deleted if every position of every one of
1353 its s_infos is zero. */
1354 if (s_info->positions_needed != (unsigned HOST_WIDE_INT) 0)
1359 insn_info_t insn_to_delete = ptr;
1362 last->next_local_store = ptr->next_local_store;
1364 active_local_stores = ptr->next_local_store;
1366 delete_dead_store_insn (insn_to_delete);
1374 gcc_assert ((unsigned) width <= HOST_BITS_PER_WIDE_INT);
1376 /* Finish filling in the store_info. */
1377 store_info->next = insn_info->store_rec;
1378 insn_info->store_rec = store_info;
1379 store_info->mem = canon_rtx (mem);
1380 store_info->alias_set = spill_alias_set;
1381 store_info->mem_addr = get_addr (XEXP (mem, 0));
1382 store_info->cse_base = base;
1383 store_info->positions_needed = lowpart_bitmask (width);
1384 store_info->group_id = group_id;
1385 store_info->begin = offset;
1386 store_info->end = offset + width;
1387 store_info->is_set = GET_CODE (body) == SET;
1389 if (store_info->is_set
1390 /* No place to keep the value after ra. */
1391 && !reload_completed
1392 && (REG_P (SET_SRC (body))
1393 || GET_CODE (SET_SRC (body)) == SUBREG
1394 || CONSTANT_P (SET_SRC (body)))
1395 /* Sometimes the store and reload is used for truncation and
1397 && !(FLOAT_MODE_P (GET_MODE (mem)) && (flag_float_store)))
1398 store_info->rhs = SET_SRC (body);
1400 store_info->rhs = NULL;
1402 /* If this is a clobber, we return 0. We will only be able to
1403 delete this insn if there is only one store USED store, but we
1404 can use the clobber to delete other stores earlier. */
1405 return store_info->is_set ? 1 : 0;
1410 dump_insn_info (const char * start, insn_info_t insn_info)
1412 fprintf (dump_file, "%s insn=%d %s\n", start,
1413 INSN_UID (insn_info->insn),
1414 insn_info->store_rec ? "has store" : "naked");
1418 /* If the modes are different and the value's source and target do not
1419 line up, we need to extract the value from lower part of the rhs of
1420 the store, shift it, and then put it into a form that can be shoved
1421 into the read_insn. This function generates a right SHIFT of a
1422 value that is at least ACCESS_SIZE bytes wide of READ_MODE. The
1423 shift sequence is returned or NULL if we failed to find a
1427 find_shift_sequence (int access_size,
1428 store_info_t store_info,
1429 read_info_t read_info,
1432 enum machine_mode store_mode = GET_MODE (store_info->mem);
1433 enum machine_mode read_mode = GET_MODE (read_info->mem);
1434 enum machine_mode new_mode;
1435 rtx read_reg = NULL;
1437 /* Some machines like the x86 have shift insns for each size of
1438 operand. Other machines like the ppc or the ia-64 may only have
1439 shift insns that shift values within 32 or 64 bit registers.
1440 This loop tries to find the smallest shift insn that will right
1441 justify the value we want to read but is available in one insn on
1444 for (new_mode = smallest_mode_for_size (access_size * BITS_PER_UNIT,
1446 GET_MODE_BITSIZE (new_mode) <= BITS_PER_WORD;
1447 new_mode = GET_MODE_WIDER_MODE (new_mode))
1449 rtx target, new_reg, shift_seq, insn, new_lhs;
1452 /* Try a wider mode if truncating the store mode to NEW_MODE
1453 requires a real instruction. */
1454 if (GET_MODE_BITSIZE (new_mode) < GET_MODE_BITSIZE (store_mode)
1455 && !TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (new_mode),
1456 GET_MODE_BITSIZE (store_mode)))
1459 /* Also try a wider mode if the necessary punning is either not
1460 desirable or not possible. */
1461 if (!CONSTANT_P (store_info->rhs)
1462 && !MODES_TIEABLE_P (new_mode, store_mode))
1464 offset = subreg_lowpart_offset (new_mode, store_mode);
1465 new_lhs = simplify_gen_subreg (new_mode, copy_rtx (store_info->rhs),
1466 store_mode, offset);
1467 if (new_lhs == NULL_RTX)
1470 new_reg = gen_reg_rtx (new_mode);
1474 /* In theory we could also check for an ashr. Ian Taylor knows
1475 of one dsp where the cost of these two was not the same. But
1476 this really is a rare case anyway. */
1477 target = expand_binop (new_mode, lshr_optab, new_reg,
1478 GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
1480 shift_seq = get_insns ();
1483 if (target != new_reg || shift_seq == NULL)
1487 for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
1489 cost += insn_rtx_cost (PATTERN (insn));
1491 /* The computation up to here is essentially independent
1492 of the arguments and could be precomputed. It may
1493 not be worth doing so. We could precompute if
1494 worthwhile or at least cache the results. The result
1495 technically depends on both SHIFT and ACCESS_SIZE,
1496 but in practice the answer will depend only on ACCESS_SIZE. */
1498 if (cost > COSTS_N_INSNS (1))
1501 /* We found an acceptable shift. Generate a move to
1502 take the value from the store and put it into the
1503 shift pseudo, then shift it, then generate another
1504 move to put in into the target of the read. */
1505 emit_move_insn (new_reg, new_lhs);
1506 emit_insn (shift_seq);
1507 read_reg = extract_low_bits (read_mode, new_mode, new_reg);
1515 /* Take a sequence of:
1538 Depending on the alignment and the mode of the store and
1542 The STORE_INFO and STORE_INSN are for the store and READ_INFO
1543 and READ_INSN are for the read. Return true if the replacement
1547 replace_read (store_info_t store_info, insn_info_t store_insn,
1548 read_info_t read_info, insn_info_t read_insn, rtx *loc)
1550 enum machine_mode store_mode = GET_MODE (store_info->mem);
1551 enum machine_mode read_mode = GET_MODE (read_info->mem);
1553 int access_size; /* In bytes. */
1554 rtx insns, read_reg;
1559 /* To get here the read is within the boundaries of the write so
1560 shift will never be negative. Start out with the shift being in
1562 if (BYTES_BIG_ENDIAN)
1563 shift = store_info->end - read_info->end;
1565 shift = read_info->begin - store_info->begin;
1567 access_size = shift + GET_MODE_SIZE (read_mode);
1569 /* From now on it is bits. */
1570 shift *= BITS_PER_UNIT;
1572 /* Create a sequence of instructions to set up the read register.
1573 This sequence goes immediately before the store and its result
1574 is read by the load.
1576 We need to keep this in perspective. We are replacing a read
1577 with a sequence of insns, but the read will almost certainly be
1578 in cache, so it is not going to be an expensive one. Thus, we
1579 are not willing to do a multi insn shift or worse a subroutine
1580 call to get rid of the read. */
1582 fprintf (dump_file, "trying to replace %smode load in insn %d"
1583 " from %smode store in insn %d\n",
1584 GET_MODE_NAME (read_mode), INSN_UID (read_insn->insn),
1585 GET_MODE_NAME (store_mode), INSN_UID (store_insn->insn));
1588 read_reg = find_shift_sequence (access_size, store_info, read_info, shift);
1590 read_reg = extract_low_bits (read_mode, store_mode,
1591 copy_rtx (store_info->rhs));
1592 if (read_reg == NULL_RTX)
1596 fprintf (dump_file, " -- could not extract bits of stored value\n");
1599 /* Force the value into a new register so that it won't be clobbered
1600 between the store and the load. */
1601 read_reg = copy_to_mode_reg (read_mode, read_reg);
1602 insns = get_insns ();
1605 if (validate_change (read_insn->insn, loc, read_reg, 0))
1607 deferred_change_t deferred_change =
1608 (deferred_change_t) pool_alloc (deferred_change_pool);
1610 /* Insert this right before the store insn where it will be safe
1611 from later insns that might change it before the read. */
1612 emit_insn_before (insns, store_insn->insn);
1614 /* And now for the kludge part: cselib croaks if you just
1615 return at this point. There are two reasons for this:
1617 1) Cselib has an idea of how many pseudos there are and
1618 that does not include the new ones we just added.
1620 2) Cselib does not know about the move insn we added
1621 above the store_info, and there is no way to tell it
1622 about it, because it has "moved on".
1624 Problem (1) is fixable with a certain amount of engineering.
1625 Problem (2) is requires starting the bb from scratch. This
1628 So we are just going to have to lie. The move/extraction
1629 insns are not really an issue, cselib did not see them. But
1630 the use of the new pseudo read_insn is a real problem because
1631 cselib has not scanned this insn. The way that we solve this
1632 problem is that we are just going to put the mem back for now
1633 and when we are finished with the block, we undo this. We
1634 keep a table of mems to get rid of. At the end of the basic
1635 block we can put them back. */
1637 *loc = read_info->mem;
1638 deferred_change->next = deferred_change_list;
1639 deferred_change_list = deferred_change;
1640 deferred_change->loc = loc;
1641 deferred_change->reg = read_reg;
1643 /* Get rid of the read_info, from the point of view of the
1644 rest of dse, play like this read never happened. */
1645 read_insn->read_rec = read_info->next;
1646 pool_free (read_info_pool, read_info);
1649 fprintf (dump_file, " -- replaced the loaded MEM with ");
1650 print_simple_rtl (dump_file, read_reg);
1651 fprintf (dump_file, "\n");
1659 fprintf (dump_file, " -- replacing the loaded MEM with ");
1660 print_simple_rtl (dump_file, read_reg);
1661 fprintf (dump_file, " led to an invalid instruction\n");
1667 /* A for_each_rtx callback in which DATA is the bb_info. Check to see
1668 if LOC is a mem and if it is look at the address and kill any
1669 appropriate stores that may be active. */
1672 check_mem_read_rtx (rtx *loc, void *data)
1676 insn_info_t insn_info;
1677 HOST_WIDE_INT offset = 0;
1678 HOST_WIDE_INT width = 0;
1679 alias_set_type spill_alias_set = 0;
1680 cselib_val *base = NULL;
1682 read_info_t read_info;
1684 if (!mem || !MEM_P (mem))
1687 bb_info = (bb_info_t) data;
1688 insn_info = bb_info->last_insn;
1690 if ((MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
1691 || (MEM_VOLATILE_P (mem)))
1694 fprintf (dump_file, " adding wild read, volatile or barrier.\n");
1695 add_wild_read (bb_info);
1696 insn_info->cannot_delete = true;
1700 /* If it is reading readonly mem, then there can be no conflict with
1702 if (MEM_READONLY_P (mem))
1705 if (!canon_address (mem, &spill_alias_set, &group_id, &offset, &base))
1708 fprintf (dump_file, " adding wild read, canon_address failure.\n");
1709 add_wild_read (bb_info);
1713 if (GET_MODE (mem) == BLKmode)
1716 width = GET_MODE_SIZE (GET_MODE (mem));
1718 read_info = (read_info_t) pool_alloc (read_info_pool);
1719 read_info->group_id = group_id;
1720 read_info->mem = mem;
1721 read_info->alias_set = spill_alias_set;
1722 read_info->begin = offset;
1723 read_info->end = offset + width;
1724 read_info->next = insn_info->read_rec;
1725 insn_info->read_rec = read_info;
1727 /* We ignore the clobbers in store_info. The is mildly aggressive,
1728 but there really should not be a clobber followed by a read. */
1730 if (spill_alias_set)
1732 insn_info_t i_ptr = active_local_stores;
1733 insn_info_t last = NULL;
1736 fprintf (dump_file, " processing spill load %d\n",
1737 (int) spill_alias_set);
1741 store_info_t store_info = i_ptr->store_rec;
1743 /* Skip the clobbers. */
1744 while (!store_info->is_set)
1745 store_info = store_info->next;
1747 if (store_info->alias_set == spill_alias_set)
1750 dump_insn_info ("removing from active", i_ptr);
1753 last->next_local_store = i_ptr->next_local_store;
1755 active_local_stores = i_ptr->next_local_store;
1759 i_ptr = i_ptr->next_local_store;
1762 else if (group_id >= 0)
1764 /* This is the restricted case where the base is a constant or
1765 the frame pointer and offset is a constant. */
1766 insn_info_t i_ptr = active_local_stores;
1767 insn_info_t last = NULL;
1772 fprintf (dump_file, " processing const load gid=%d[BLK]\n",
1775 fprintf (dump_file, " processing const load gid=%d[%d..%d)\n",
1776 group_id, (int)offset, (int)(offset+width));
1781 bool remove = false;
1782 store_info_t store_info = i_ptr->store_rec;
1784 /* Skip the clobbers. */
1785 while (!store_info->is_set)
1786 store_info = store_info->next;
1788 /* There are three cases here. */
1789 if (store_info->group_id < 0)
1790 /* We have a cselib store followed by a read from a
1793 = canon_true_dependence (store_info->mem,
1794 GET_MODE (store_info->mem),
1795 store_info->mem_addr,
1798 else if (group_id == store_info->group_id)
1800 /* This is a block mode load. We may get lucky and
1801 canon_true_dependence may save the day. */
1804 = canon_true_dependence (store_info->mem,
1805 GET_MODE (store_info->mem),
1806 store_info->mem_addr,
1809 /* If this read is just reading back something that we just
1810 stored, rewrite the read. */
1814 && (offset >= store_info->begin)
1815 && (offset + width <= store_info->end))
1817 unsigned HOST_WIDE_INT mask
1818 = (lowpart_bitmask (width)
1819 << (offset - store_info->begin));
1821 if ((store_info->positions_needed & mask) == mask
1822 && replace_read (store_info, i_ptr,
1823 read_info, insn_info, loc))
1826 /* The bases are the same, just see if the offsets
1828 if ((offset < store_info->end)
1829 && (offset + width > store_info->begin))
1835 The else case that is missing here is that the
1836 bases are constant but different. There is nothing
1837 to do here because there is no overlap. */
1842 dump_insn_info ("removing from active", i_ptr);
1845 last->next_local_store = i_ptr->next_local_store;
1847 active_local_stores = i_ptr->next_local_store;
1851 i_ptr = i_ptr->next_local_store;
1856 insn_info_t i_ptr = active_local_stores;
1857 insn_info_t last = NULL;
1860 fprintf (dump_file, " processing cselib load mem:");
1861 print_inline_rtx (dump_file, mem, 0);
1862 fprintf (dump_file, "\n");
1867 bool remove = false;
1868 store_info_t store_info = i_ptr->store_rec;
1871 fprintf (dump_file, " processing cselib load against insn %d\n",
1872 INSN_UID (i_ptr->insn));
1874 /* Skip the clobbers. */
1875 while (!store_info->is_set)
1876 store_info = store_info->next;
1878 /* If this read is just reading back something that we just
1879 stored, rewrite the read. */
1881 && store_info->group_id == -1
1882 && store_info->cse_base == base
1883 && (offset >= store_info->begin)
1884 && (offset + width <= store_info->end))
1886 unsigned HOST_WIDE_INT mask
1887 = (lowpart_bitmask (width)
1888 << (offset - store_info->begin));
1890 if ((store_info->positions_needed & mask) == mask
1891 && replace_read (store_info, i_ptr,
1892 read_info, insn_info, loc))
1896 if (!store_info->alias_set)
1897 remove = canon_true_dependence (store_info->mem,
1898 GET_MODE (store_info->mem),
1899 store_info->mem_addr,
1905 dump_insn_info ("removing from active", i_ptr);
1908 last->next_local_store = i_ptr->next_local_store;
1910 active_local_stores = i_ptr->next_local_store;
1914 i_ptr = i_ptr->next_local_store;
1920 /* A for_each_rtx callback in which DATA points the INSN_INFO for
1921 as check_mem_read_rtx. Nullify the pointer if i_m_r_m_r returns
1922 true for any part of *LOC. */
1925 check_mem_read_use (rtx *loc, void *data)
1927 for_each_rtx (loc, check_mem_read_rtx, data);
1930 /* Apply record_store to all candidate stores in INSN. Mark INSN
1931 if some part of it is not a candidate store and assigns to a
1932 non-register target. */
1935 scan_insn (bb_info_t bb_info, rtx insn)
1938 insn_info_t insn_info = (insn_info_t) pool_alloc (insn_info_pool);
1940 memset (insn_info, 0, sizeof (struct insn_info));
1943 fprintf (dump_file, "\n**scanning insn=%d\n",
1946 insn_info->prev_insn = bb_info->last_insn;
1947 insn_info->insn = insn;
1948 bb_info->last_insn = insn_info;
1951 /* Cselib clears the table for this case, so we have to essentially
1953 if (NONJUMP_INSN_P (insn)
1954 && GET_CODE (PATTERN (insn)) == ASM_OPERANDS
1955 && MEM_VOLATILE_P (PATTERN (insn)))
1957 add_wild_read (bb_info);
1958 insn_info->cannot_delete = true;
1962 /* Look at all of the uses in the insn. */
1963 note_uses (&PATTERN (insn), check_mem_read_use, bb_info);
1967 insn_info->cannot_delete = true;
1969 /* Const functions cannot do anything bad i.e. read memory,
1970 however, they can read their parameters which may have
1971 been pushed onto the stack. */
1972 if (RTL_CONST_CALL_P (insn))
1974 insn_info_t i_ptr = active_local_stores;
1975 insn_info_t last = NULL;
1978 fprintf (dump_file, "const call %d\n", INSN_UID (insn));
1980 /* See the head comment of the frame_read field. */
1981 if (reload_completed)
1982 insn_info->frame_read = true;
1984 /* Loop over the active stores and remove those which are
1985 killed by the const function call. */
1988 bool remove_store = false;
1990 /* The stack pointer based stores are always killed. */
1991 if (i_ptr->stack_pointer_based)
1992 remove_store = true;
1994 /* If the frame is read, the frame related stores are killed. */
1995 else if (insn_info->frame_read)
1997 store_info_t store_info = i_ptr->store_rec;
1999 /* Skip the clobbers. */
2000 while (!store_info->is_set)
2001 store_info = store_info->next;
2003 if (store_info->group_id >= 0
2004 && VEC_index (group_info_t, rtx_group_vec,
2005 store_info->group_id)->frame_related)
2006 remove_store = true;
2012 dump_insn_info ("removing from active", i_ptr);
2015 last->next_local_store = i_ptr->next_local_store;
2017 active_local_stores = i_ptr->next_local_store;
2022 i_ptr = i_ptr->next_local_store;
2027 /* Every other call, including pure functions, may read memory. */
2028 add_wild_read (bb_info);
2033 /* Assuming that there are sets in these insns, we cannot delete
2035 if ((GET_CODE (PATTERN (insn)) == CLOBBER)
2036 || volatile_refs_p (PATTERN (insn))
2037 || (flag_non_call_exceptions && may_trap_p (PATTERN (insn)))
2038 || (RTX_FRAME_RELATED_P (insn))
2039 || find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX))
2040 insn_info->cannot_delete = true;
2042 body = PATTERN (insn);
2043 if (GET_CODE (body) == PARALLEL)
2046 for (i = 0; i < XVECLEN (body, 0); i++)
2047 mems_found += record_store (XVECEXP (body, 0, i), bb_info);
2050 mems_found += record_store (body, bb_info);
2053 fprintf (dump_file, "mems_found = %d, cannot_delete = %s\n",
2054 mems_found, insn_info->cannot_delete ? "true" : "false");
2056 /* If we found some sets of mems, and the insn has not been marked
2057 cannot delete, add it into the active_local_stores so that it can
2058 be locally deleted if found dead. Otherwise mark it as cannot
2059 delete. This simplifies the processing later. */
2060 if (mems_found == 1 && !insn_info->cannot_delete)
2062 insn_info->next_local_store = active_local_stores;
2063 active_local_stores = insn_info;
2066 insn_info->cannot_delete = true;
2070 /* Remove BASE from the set of active_local_stores. This is a
2071 callback from cselib that is used to get rid of the stores in
2072 active_local_stores. */
2075 remove_useless_values (cselib_val *base)
2077 insn_info_t insn_info = active_local_stores;
2078 insn_info_t last = NULL;
2082 store_info_t store_info = insn_info->store_rec;
2083 bool delete = false;
2085 /* If ANY of the store_infos match the cselib group that is
2086 being deleted, then the insn can not be deleted. */
2089 if ((store_info->group_id == -1)
2090 && (store_info->cse_base == base))
2095 store_info = store_info->next;
2101 last->next_local_store = insn_info->next_local_store;
2103 active_local_stores = insn_info->next_local_store;
2104 free_store_info (insn_info);
2109 insn_info = insn_info->next_local_store;
2114 /* Do all of step 1. */
2121 cselib_init (false);
2122 all_blocks = BITMAP_ALLOC (NULL);
2123 bitmap_set_bit (all_blocks, ENTRY_BLOCK);
2124 bitmap_set_bit (all_blocks, EXIT_BLOCK);
2129 bb_info_t bb_info = (bb_info_t) pool_alloc (bb_info_pool);
2131 memset (bb_info, 0, sizeof (struct bb_info));
2132 bitmap_set_bit (all_blocks, bb->index);
2134 bb_table[bb->index] = bb_info;
2135 cselib_discard_hook = remove_useless_values;
2137 if (bb->index >= NUM_FIXED_BLOCKS)
2142 = create_alloc_pool ("cse_store_info_pool",
2143 sizeof (struct store_info), 100);
2144 active_local_stores = NULL;
2145 cselib_clear_table ();
2147 /* Scan the insns. */
2148 FOR_BB_INSNS (bb, insn)
2151 scan_insn (bb_info, insn);
2152 cselib_process_insn (insn);
2155 /* This is something of a hack, because the global algorithm
2156 is supposed to take care of the case where stores go dead
2157 at the end of the function. However, the global
2158 algorithm must take a more conservative view of block
2159 mode reads than the local alg does. So to get the case
2160 where you have a store to the frame followed by a non
2161 overlapping block more read, we look at the active local
2162 stores at the end of the function and delete all of the
2163 frame and spill based ones. */
2164 if (stores_off_frame_dead_at_return
2165 && (EDGE_COUNT (bb->succs) == 0
2166 || (single_succ_p (bb)
2167 && single_succ (bb) == EXIT_BLOCK_PTR
2168 && ! crtl->calls_eh_return)))
2170 insn_info_t i_ptr = active_local_stores;
2173 store_info_t store_info = i_ptr->store_rec;
2175 /* Skip the clobbers. */
2176 while (!store_info->is_set)
2177 store_info = store_info->next;
2178 if (store_info->alias_set)
2179 delete_dead_store_insn (i_ptr);
2181 if (store_info->group_id >= 0)
2184 = VEC_index (group_info_t, rtx_group_vec, store_info->group_id);
2185 if (group->frame_related)
2186 delete_dead_store_insn (i_ptr);
2189 i_ptr = i_ptr->next_local_store;
2193 /* Get rid of the loads that were discovered in
2194 replace_read. Cselib is finished with this block. */
2195 while (deferred_change_list)
2197 deferred_change_t next = deferred_change_list->next;
2199 /* There is no reason to validate this change. That was
2201 *deferred_change_list->loc = deferred_change_list->reg;
2202 pool_free (deferred_change_pool, deferred_change_list);
2203 deferred_change_list = next;
2206 /* Get rid of all of the cselib based store_infos in this
2207 block and mark the containing insns as not being
2209 ptr = bb_info->last_insn;
2212 if (ptr->contains_cselib_groups)
2213 free_store_info (ptr);
2214 ptr = ptr->prev_insn;
2217 free_alloc_pool (cse_store_info_pool);
2222 htab_empty (rtx_group_table);
2226 /*----------------------------------------------------------------------------
2229 Assign each byte position in the stores that we are going to
2230 analyze globally to a position in the bitmaps. Returns true if
2231 there are any bit positions assigned.
2232 ----------------------------------------------------------------------------*/
2235 dse_step2_init (void)
2240 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
2242 /* For all non stack related bases, we only consider a store to
2243 be deletable if there are two or more stores for that
2244 position. This is because it takes one store to make the
2245 other store redundant. However, for the stores that are
2246 stack related, we consider them if there is only one store
2247 for the position. We do this because the stack related
2248 stores can be deleted if their is no read between them and
2249 the end of the function.
2251 To make this work in the current framework, we take the stack
2252 related bases add all of the bits from store1 into store2.
2253 This has the effect of making the eligible even if there is
2256 if (stores_off_frame_dead_at_return && group->frame_related)
2258 bitmap_ior_into (group->store2_n, group->store1_n);
2259 bitmap_ior_into (group->store2_p, group->store1_p);
2261 fprintf (dump_file, "group %d is frame related ", i);
2264 group->offset_map_size_n++;
2265 group->offset_map_n = XNEWVEC (int, group->offset_map_size_n);
2266 group->offset_map_size_p++;
2267 group->offset_map_p = XNEWVEC (int, group->offset_map_size_p);
2268 group->process_globally = false;
2271 fprintf (dump_file, "group %d(%d+%d): ", i,
2272 (int)bitmap_count_bits (group->store2_n),
2273 (int)bitmap_count_bits (group->store2_p));
2274 bitmap_print (dump_file, group->store2_n, "n ", " ");
2275 bitmap_print (dump_file, group->store2_p, "p ", "\n");
2281 /* Init the offset tables for the normal case. */
2284 dse_step2_nospill (void)
2288 /* Position 0 is unused because 0 is used in the maps to mean
2290 current_position = 1;
2292 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
2297 if (group == clear_alias_group)
2300 memset (group->offset_map_n, 0, sizeof(int) * group->offset_map_size_n);
2301 memset (group->offset_map_p, 0, sizeof(int) * group->offset_map_size_p);
2302 bitmap_clear (group->group_kill);
2304 EXECUTE_IF_SET_IN_BITMAP (group->store2_n, 0, j, bi)
2306 bitmap_set_bit (group->group_kill, current_position);
2307 group->offset_map_n[j] = current_position++;
2308 group->process_globally = true;
2310 EXECUTE_IF_SET_IN_BITMAP (group->store2_p, 0, j, bi)
2312 bitmap_set_bit (group->group_kill, current_position);
2313 group->offset_map_p[j] = current_position++;
2314 group->process_globally = true;
2317 return current_position != 1;
2321 /* Init the offset tables for the spill case. */
2324 dse_step2_spill (void)
2327 group_info_t group = clear_alias_group;
2330 /* Position 0 is unused because 0 is used in the maps to mean
2332 current_position = 1;
2336 bitmap_print (dump_file, clear_alias_sets,
2337 "clear alias sets ", "\n");
2338 bitmap_print (dump_file, disqualified_clear_alias_sets,
2339 "disqualified clear alias sets ", "\n");
2342 memset (group->offset_map_n, 0, sizeof(int) * group->offset_map_size_n);
2343 memset (group->offset_map_p, 0, sizeof(int) * group->offset_map_size_p);
2344 bitmap_clear (group->group_kill);
2346 /* Remove the disqualified positions from the store2_p set. */
2347 bitmap_and_compl_into (group->store2_p, disqualified_clear_alias_sets);
2349 /* We do not need to process the store2_n set because
2350 alias_sets are always positive. */
2351 EXECUTE_IF_SET_IN_BITMAP (group->store2_p, 0, j, bi)
2353 bitmap_set_bit (group->group_kill, current_position);
2354 group->offset_map_p[j] = current_position++;
2355 group->process_globally = true;
2358 return current_position != 1;
2363 /*----------------------------------------------------------------------------
2366 Build the bit vectors for the transfer functions.
2367 ----------------------------------------------------------------------------*/
2370 /* Note that this is NOT a general purpose function. Any mem that has
2371 an alias set registered here expected to be COMPLETELY unaliased:
2372 i.e it's addresses are not and need not be examined.
2374 It is known that all references to this address will have this
2375 alias set and there are NO other references to this address in the
2378 Currently the only place that is known to be clean enough to use
2379 this interface is the code that assigns the spill locations.
2381 All of the mems that have alias_sets registered are subjected to a
2382 very powerful form of dse where function calls, volatile reads and
2383 writes, and reads from random location are not taken into account.
2385 It is also assumed that these locations go dead when the function
2386 returns. This assumption could be relaxed if there were found to
2387 be places that this assumption was not correct.
2389 The MODE is passed in and saved. The mode of each load or store to
2390 a mem with ALIAS_SET is checked against MEM. If the size of that
2391 load or store is different from MODE, processing is halted on this
2392 alias set. For the vast majority of aliases sets, all of the loads
2393 and stores will use the same mode. But vectors are treated
2394 differently: the alias set is established for the entire vector,
2395 but reload will insert loads and stores for individual elements and
2396 we do not necessarily have the information to track those separate
2397 elements. So when we see a mode mismatch, we just bail. */
2401 dse_record_singleton_alias_set (alias_set_type alias_set,
2402 enum machine_mode mode)
2404 struct clear_alias_mode_holder tmp_holder;
2405 struct clear_alias_mode_holder *entry;
2408 /* If we are not going to run dse, we need to return now or there
2409 will be problems with allocating the bitmaps. */
2410 if ((!gate_dse()) || !alias_set)
2413 if (!clear_alias_sets)
2415 clear_alias_sets = BITMAP_ALLOC (NULL);
2416 disqualified_clear_alias_sets = BITMAP_ALLOC (NULL);
2417 clear_alias_mode_table = htab_create (11, clear_alias_mode_hash,
2418 clear_alias_mode_eq, NULL);
2419 clear_alias_mode_pool = create_alloc_pool ("clear_alias_mode_pool",
2420 sizeof (struct clear_alias_mode_holder), 100);
2423 bitmap_set_bit (clear_alias_sets, alias_set);
2425 tmp_holder.alias_set = alias_set;
2427 slot = htab_find_slot (clear_alias_mode_table, &tmp_holder, INSERT);
2428 gcc_assert (*slot == NULL);
2431 (struct clear_alias_mode_holder *) pool_alloc (clear_alias_mode_pool);
2432 entry->alias_set = alias_set;
2437 /* Remove ALIAS_SET from the sets of stack slots being considered. */
2440 dse_invalidate_singleton_alias_set (alias_set_type alias_set)
2442 if ((!gate_dse()) || !alias_set)
2445 bitmap_clear_bit (clear_alias_sets, alias_set);
2449 /* Look up the bitmap index for OFFSET in GROUP_INFO. If it is not
2453 get_bitmap_index (group_info_t group_info, HOST_WIDE_INT offset)
2457 HOST_WIDE_INT offset_p = -offset;
2458 if (offset_p >= group_info->offset_map_size_n)
2460 return group_info->offset_map_n[offset_p];
2464 if (offset >= group_info->offset_map_size_p)
2466 return group_info->offset_map_p[offset];
2471 /* Process the STORE_INFOs into the bitmaps into GEN and KILL. KILL
2475 scan_stores_nospill (store_info_t store_info, bitmap gen, bitmap kill)
2480 group_info_t group_info
2481 = VEC_index (group_info_t, rtx_group_vec, store_info->group_id);
2482 if (group_info->process_globally)
2483 for (i = store_info->begin; i < store_info->end; i++)
2485 int index = get_bitmap_index (group_info, i);
2488 bitmap_set_bit (gen, index);
2490 bitmap_clear_bit (kill, index);
2493 store_info = store_info->next;
2498 /* Process the STORE_INFOs into the bitmaps into GEN and KILL. KILL
2502 scan_stores_spill (store_info_t store_info, bitmap gen, bitmap kill)
2506 if (store_info->alias_set)
2508 int index = get_bitmap_index (clear_alias_group,
2509 store_info->alias_set);
2512 bitmap_set_bit (gen, index);
2514 bitmap_clear_bit (kill, index);
2517 store_info = store_info->next;
2522 /* Process the READ_INFOs into the bitmaps into GEN and KILL. KILL
2526 scan_reads_nospill (insn_info_t insn_info, bitmap gen, bitmap kill)
2528 read_info_t read_info = insn_info->read_rec;
2532 /* If this insn reads the frame, kill all the frame related stores. */
2533 if (insn_info->frame_read)
2535 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
2536 if (group->process_globally && group->frame_related)
2539 bitmap_ior_into (kill, group->group_kill);
2540 bitmap_and_compl_into (gen, group->group_kill);
2546 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
2548 if (group->process_globally)
2550 if (i == read_info->group_id)
2552 if (read_info->begin > read_info->end)
2554 /* Begin > end for block mode reads. */
2556 bitmap_ior_into (kill, group->group_kill);
2557 bitmap_and_compl_into (gen, group->group_kill);
2561 /* The groups are the same, just process the
2564 for (j = read_info->begin; j < read_info->end; j++)
2566 int index = get_bitmap_index (group, j);
2570 bitmap_set_bit (kill, index);
2571 bitmap_clear_bit (gen, index);
2578 /* The groups are different, if the alias sets
2579 conflict, clear the entire group. We only need
2580 to apply this test if the read_info is a cselib
2581 read. Anything with a constant base cannot alias
2582 something else with a different constant
2584 if ((read_info->group_id < 0)
2585 && canon_true_dependence (group->base_mem,
2587 group->canon_base_mem,
2588 read_info->mem, rtx_varies_p))
2591 bitmap_ior_into (kill, group->group_kill);
2592 bitmap_and_compl_into (gen, group->group_kill);
2598 read_info = read_info->next;
2602 /* Process the READ_INFOs into the bitmaps into GEN and KILL. KILL
2606 scan_reads_spill (read_info_t read_info, bitmap gen, bitmap kill)
2610 if (read_info->alias_set)
2612 int index = get_bitmap_index (clear_alias_group,
2613 read_info->alias_set);
2617 bitmap_set_bit (kill, index);
2618 bitmap_clear_bit (gen, index);
2622 read_info = read_info->next;
2627 /* Return the insn in BB_INFO before the first wild read or if there
2628 are no wild reads in the block, return the last insn. */
2631 find_insn_before_first_wild_read (bb_info_t bb_info)
2633 insn_info_t insn_info = bb_info->last_insn;
2634 insn_info_t last_wild_read = NULL;
2638 if (insn_info->wild_read)
2640 last_wild_read = insn_info->prev_insn;
2641 /* Block starts with wild read. */
2642 if (!last_wild_read)
2646 insn_info = insn_info->prev_insn;
2650 return last_wild_read;
2652 return bb_info->last_insn;
2656 /* Scan the insns in BB_INFO starting at PTR and going to the top of
2657 the block in order to build the gen and kill sets for the block.
2658 We start at ptr which may be the last insn in the block or may be
2659 the first insn with a wild read. In the latter case we are able to
2660 skip the rest of the block because it just does not matter:
2661 anything that happens is hidden by the wild read. */
2664 dse_step3_scan (bool for_spills, basic_block bb)
2666 bb_info_t bb_info = bb_table[bb->index];
2667 insn_info_t insn_info;
2670 /* There are no wild reads in the spill case. */
2671 insn_info = bb_info->last_insn;
2673 insn_info = find_insn_before_first_wild_read (bb_info);
2675 /* In the spill case or in the no_spill case if there is no wild
2676 read in the block, we will need a kill set. */
2677 if (insn_info == bb_info->last_insn)
2680 bitmap_clear (bb_info->kill);
2682 bb_info->kill = BITMAP_ALLOC (NULL);
2686 BITMAP_FREE (bb_info->kill);
2690 /* There may have been code deleted by the dce pass run before
2692 if (insn_info->insn && INSN_P (insn_info->insn))
2694 /* Process the read(s) last. */
2697 scan_stores_spill (insn_info->store_rec, bb_info->gen, bb_info->kill);
2698 scan_reads_spill (insn_info->read_rec, bb_info->gen, bb_info->kill);
2702 scan_stores_nospill (insn_info->store_rec, bb_info->gen, bb_info->kill);
2703 scan_reads_nospill (insn_info, bb_info->gen, bb_info->kill);
2707 insn_info = insn_info->prev_insn;
2712 /* Set the gen set of the exit block, and also any block with no
2713 successors that does not have a wild read. */
2716 dse_step3_exit_block_scan (bb_info_t bb_info)
2718 /* The gen set is all 0's for the exit block except for the
2719 frame_pointer_group. */
2721 if (stores_off_frame_dead_at_return)
2726 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
2728 if (group->process_globally && group->frame_related)
2729 bitmap_ior_into (bb_info->gen, group->group_kill);
2735 /* Find all of the blocks that are not backwards reachable from the
2736 exit block or any block with no successors (BB). These are the
2737 infinite loops or infinite self loops. These blocks will still
2738 have their bits set in UNREACHABLE_BLOCKS. */
2741 mark_reachable_blocks (sbitmap unreachable_blocks, basic_block bb)
2746 if (TEST_BIT (unreachable_blocks, bb->index))
2748 RESET_BIT (unreachable_blocks, bb->index);
2749 FOR_EACH_EDGE (e, ei, bb->preds)
2751 mark_reachable_blocks (unreachable_blocks, e->src);
2756 /* Build the transfer functions for the function. */
2759 dse_step3 (bool for_spills)
2762 sbitmap unreachable_blocks = sbitmap_alloc (last_basic_block);
2763 sbitmap_iterator sbi;
2764 bitmap all_ones = NULL;
2767 sbitmap_ones (unreachable_blocks);
2771 bb_info_t bb_info = bb_table[bb->index];
2773 bitmap_clear (bb_info->gen);
2775 bb_info->gen = BITMAP_ALLOC (NULL);
2777 if (bb->index == ENTRY_BLOCK)
2779 else if (bb->index == EXIT_BLOCK)
2780 dse_step3_exit_block_scan (bb_info);
2782 dse_step3_scan (for_spills, bb);
2783 if (EDGE_COUNT (bb->succs) == 0)
2784 mark_reachable_blocks (unreachable_blocks, bb);
2786 /* If this is the second time dataflow is run, delete the old
2789 BITMAP_FREE (bb_info->in);
2791 BITMAP_FREE (bb_info->out);
2794 /* For any block in an infinite loop, we must initialize the out set
2795 to all ones. This could be expensive, but almost never occurs in
2796 practice. However, it is common in regression tests. */
2797 EXECUTE_IF_SET_IN_SBITMAP (unreachable_blocks, 0, i, sbi)
2799 if (bitmap_bit_p (all_blocks, i))
2801 bb_info_t bb_info = bb_table[i];
2807 all_ones = BITMAP_ALLOC (NULL);
2808 for (j = 0; VEC_iterate (group_info_t, rtx_group_vec, j, group); j++)
2809 bitmap_ior_into (all_ones, group->group_kill);
2813 bb_info->out = BITMAP_ALLOC (NULL);
2814 bitmap_copy (bb_info->out, all_ones);
2820 BITMAP_FREE (all_ones);
2821 sbitmap_free (unreachable_blocks);
2826 /*----------------------------------------------------------------------------
2829 Solve the bitvector equations.
2830 ----------------------------------------------------------------------------*/
2833 /* Confluence function for blocks with no successors. Create an out
2834 set from the gen set of the exit block. This block logically has
2835 the exit block as a successor. */
2840 dse_confluence_0 (basic_block bb)
2842 bb_info_t bb_info = bb_table[bb->index];
2844 if (bb->index == EXIT_BLOCK)
2849 bb_info->out = BITMAP_ALLOC (NULL);
2850 bitmap_copy (bb_info->out, bb_table[EXIT_BLOCK]->gen);
2854 /* Propagate the information from the in set of the dest of E to the
2855 out set of the src of E. If the various in or out sets are not
2856 there, that means they are all ones. */
2859 dse_confluence_n (edge e)
2861 bb_info_t src_info = bb_table[e->src->index];
2862 bb_info_t dest_info = bb_table[e->dest->index];
2867 bitmap_and_into (src_info->out, dest_info->in);
2870 src_info->out = BITMAP_ALLOC (NULL);
2871 bitmap_copy (src_info->out, dest_info->in);
2877 /* Propagate the info from the out to the in set of BB_INDEX's basic
2878 block. There are three cases:
2880 1) The block has no kill set. In this case the kill set is all
2881 ones. It does not matter what the out set of the block is, none of
2882 the info can reach the top. The only thing that reaches the top is
2883 the gen set and we just copy the set.
2885 2) There is a kill set but no out set and bb has successors. In
2886 this case we just return. Eventually an out set will be created and
2887 it is better to wait than to create a set of ones.
2889 3) There is both a kill and out set. We apply the obvious transfer
2894 dse_transfer_function (int bb_index)
2896 bb_info_t bb_info = bb_table[bb_index];
2904 return bitmap_ior_and_compl (bb_info->in, bb_info->gen,
2905 bb_info->out, bb_info->kill);
2908 bb_info->in = BITMAP_ALLOC (NULL);
2909 bitmap_ior_and_compl (bb_info->in, bb_info->gen,
2910 bb_info->out, bb_info->kill);
2920 /* Case 1 above. If there is already an in set, nothing
2926 bb_info->in = BITMAP_ALLOC (NULL);
2927 bitmap_copy (bb_info->in, bb_info->gen);
2933 /* Solve the dataflow equations. */
2938 df_simple_dataflow (DF_BACKWARD, NULL, dse_confluence_0,
2939 dse_confluence_n, dse_transfer_function,
2940 all_blocks, df_get_postorder (DF_BACKWARD),
2941 df_get_n_blocks (DF_BACKWARD));
2946 fprintf (dump_file, "\n\n*** Global dataflow info after analysis.\n");
2949 bb_info_t bb_info = bb_table[bb->index];
2951 df_print_bb_index (bb, dump_file);
2953 bitmap_print (dump_file, bb_info->in, " in: ", "\n");
2955 fprintf (dump_file, " in: *MISSING*\n");
2957 bitmap_print (dump_file, bb_info->gen, " gen: ", "\n");
2959 fprintf (dump_file, " gen: *MISSING*\n");
2961 bitmap_print (dump_file, bb_info->kill, " kill: ", "\n");
2963 fprintf (dump_file, " kill: *MISSING*\n");
2965 bitmap_print (dump_file, bb_info->out, " out: ", "\n");
2967 fprintf (dump_file, " out: *MISSING*\n\n");
2974 /*----------------------------------------------------------------------------
2977 Delete the stores that can only be deleted using the global information.
2978 ----------------------------------------------------------------------------*/
2982 dse_step5_nospill (void)
2987 bb_info_t bb_info = bb_table[bb->index];
2988 insn_info_t insn_info = bb_info->last_insn;
2989 bitmap v = bb_info->out;
2993 bool deleted = false;
2994 if (dump_file && insn_info->insn)
2996 fprintf (dump_file, "starting to process insn %d\n",
2997 INSN_UID (insn_info->insn));
2998 bitmap_print (dump_file, v, " v: ", "\n");
3001 /* There may have been code deleted by the dce pass run before
3004 && INSN_P (insn_info->insn)
3005 && (!insn_info->cannot_delete)
3006 && (!bitmap_empty_p (v)))
3008 store_info_t store_info = insn_info->store_rec;
3010 /* Try to delete the current insn. */
3013 /* Skip the clobbers. */
3014 while (!store_info->is_set)
3015 store_info = store_info->next;
3017 if (store_info->alias_set)
3022 group_info_t group_info
3023 = VEC_index (group_info_t, rtx_group_vec, store_info->group_id);
3025 for (i = store_info->begin; i < store_info->end; i++)
3027 int index = get_bitmap_index (group_info, i);
3030 fprintf (dump_file, "i = %d, index = %d\n", (int)i, index);
3031 if (index == 0 || !bitmap_bit_p (v, index))
3034 fprintf (dump_file, "failing at i = %d\n", (int)i);
3044 check_for_inc_dec (insn_info->insn);
3045 delete_insn (insn_info->insn);
3046 insn_info->insn = NULL;
3051 /* We do want to process the local info if the insn was
3052 deleted. For instance, if the insn did a wild read, we
3053 no longer need to trash the info. */
3055 && INSN_P (insn_info->insn)
3058 scan_stores_nospill (insn_info->store_rec, v, NULL);
3059 if (insn_info->wild_read)
3062 fprintf (dump_file, "wild read\n");
3065 else if (insn_info->read_rec)
3068 fprintf (dump_file, "regular read\n");
3069 scan_reads_nospill (insn_info, v, NULL);
3073 insn_info = insn_info->prev_insn;
3080 dse_step5_spill (void)
3085 bb_info_t bb_info = bb_table[bb->index];
3086 insn_info_t insn_info = bb_info->last_insn;
3087 bitmap v = bb_info->out;
3091 bool deleted = false;
3092 /* There may have been code deleted by the dce pass run before
3095 && INSN_P (insn_info->insn)
3096 && (!insn_info->cannot_delete)
3097 && (!bitmap_empty_p (v)))
3099 /* Try to delete the current insn. */
3100 store_info_t store_info = insn_info->store_rec;
3105 if (store_info->alias_set)
3107 int index = get_bitmap_index (clear_alias_group,
3108 store_info->alias_set);
3109 if (index == 0 || !bitmap_bit_p (v, index))
3117 store_info = store_info->next;
3119 if (deleted && dbg_cnt (dse))
3122 fprintf (dump_file, "Spill deleting insn %d\n",
3123 INSN_UID (insn_info->insn));
3124 check_for_inc_dec (insn_info->insn);
3125 delete_insn (insn_info->insn);
3127 insn_info->insn = NULL;
3132 && INSN_P (insn_info->insn)
3135 scan_stores_spill (insn_info->store_rec, v, NULL);
3136 scan_reads_spill (insn_info->read_rec, v, NULL);
3139 insn_info = insn_info->prev_insn;
3146 /*----------------------------------------------------------------------------
3149 Destroy everything left standing.
3150 ----------------------------------------------------------------------------*/
3153 dse_step6 (bool global_done)
3159 for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
3161 free (group->offset_map_n);
3162 free (group->offset_map_p);
3163 BITMAP_FREE (group->store1_n);
3164 BITMAP_FREE (group->store1_p);
3165 BITMAP_FREE (group->store2_n);
3166 BITMAP_FREE (group->store2_p);
3167 BITMAP_FREE (group->group_kill);
3173 bb_info_t bb_info = bb_table[bb->index];
3174 BITMAP_FREE (bb_info->gen);
3176 BITMAP_FREE (bb_info->kill);
3178 BITMAP_FREE (bb_info->in);
3180 BITMAP_FREE (bb_info->out);
3183 if (clear_alias_sets)
3185 BITMAP_FREE (clear_alias_sets);
3186 BITMAP_FREE (disqualified_clear_alias_sets);
3187 free_alloc_pool (clear_alias_mode_pool);
3188 htab_delete (clear_alias_mode_table);
3191 end_alias_analysis ();
3193 htab_delete (rtx_group_table);
3194 VEC_free (group_info_t, heap, rtx_group_vec);
3195 BITMAP_FREE (all_blocks);
3196 BITMAP_FREE (scratch);
3198 free_alloc_pool (rtx_store_info_pool);
3199 free_alloc_pool (read_info_pool);
3200 free_alloc_pool (insn_info_pool);
3201 free_alloc_pool (bb_info_pool);
3202 free_alloc_pool (rtx_group_info_pool);
3203 free_alloc_pool (deferred_change_pool);
3207 /* -------------------------------------------------------------------------
3209 ------------------------------------------------------------------------- */
3211 /* Callback for running pass_rtl_dse. */
3214 rest_of_handle_dse (void)
3216 bool did_global = false;
3218 df_set_flags (DF_DEFER_INSN_RESCAN);
3223 if (dse_step2_nospill ())
3225 df_set_flags (DF_LR_RUN_DCE);
3229 fprintf (dump_file, "doing global processing\n");
3232 dse_step5_nospill ();
3235 /* For the instance of dse that runs after reload, we make a special
3236 pass to process the spills. These are special in that they are
3237 totally transparent, i.e, there is no aliasing issues that need
3238 to be considered. This means that the wild reads that kill
3239 everything else do not apply here. */
3240 if (clear_alias_sets && dse_step2_spill ())
3244 df_set_flags (DF_LR_RUN_DCE);
3249 fprintf (dump_file, "doing global spill processing\n");
3255 dse_step6 (did_global);
3258 fprintf (dump_file, "dse: local deletions = %d, global deletions = %d, spill deletions = %d\n",
3259 locally_deleted, globally_deleted, spill_deleted);
3266 return gate_dse1 () || gate_dse2 ();
3272 return optimize > 0 && flag_dse
3279 return optimize > 0 && flag_dse
3283 struct rtl_opt_pass pass_rtl_dse1 =
3288 gate_dse1, /* gate */
3289 rest_of_handle_dse, /* execute */
3292 0, /* static_pass_number */
3293 TV_DSE1, /* tv_id */
3294 0, /* properties_required */
3295 0, /* properties_provided */
3296 0, /* properties_destroyed */
3297 0, /* todo_flags_start */
3299 TODO_df_finish | TODO_verify_rtl_sharing |
3300 TODO_ggc_collect /* todo_flags_finish */
3304 struct rtl_opt_pass pass_rtl_dse2 =
3309 gate_dse2, /* gate */
3310 rest_of_handle_dse, /* execute */
3313 0, /* static_pass_number */
3314 TV_DSE2, /* tv_id */
3315 0, /* properties_required */
3316 0, /* properties_provided */
3317 0, /* properties_destroyed */
3318 0, /* todo_flags_start */
3320 TODO_df_finish | TODO_verify_rtl_sharing |
3321 TODO_ggc_collect /* todo_flags_finish */