PR middle-end/86864
[official-gcc.git] / gcc / dse.c
blobcfebfa0e110be56f17337dcb152984d782528889
1 /* RTL dead store elimination.
2 Copyright (C) 2005-2018 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
12 version.
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
17 for more details.
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/>. */
23 #undef BASELINE
25 #include "config.h"
26 #include "system.h"
27 #include "coretypes.h"
28 #include "backend.h"
29 #include "target.h"
30 #include "rtl.h"
31 #include "tree.h"
32 #include "gimple.h"
33 #include "predict.h"
34 #include "df.h"
35 #include "memmodel.h"
36 #include "tm_p.h"
37 #include "gimple-ssa.h"
38 #include "expmed.h"
39 #include "optabs.h"
40 #include "emit-rtl.h"
41 #include "recog.h"
42 #include "alias.h"
43 #include "stor-layout.h"
44 #include "cfgrtl.h"
45 #include "cselib.h"
46 #include "tree-pass.h"
47 #include "explow.h"
48 #include "expr.h"
49 #include "dbgcnt.h"
50 #include "params.h"
51 #include "rtl-iter.h"
52 #include "cfgcleanup.h"
54 /* This file contains three techniques for performing Dead Store
55 Elimination (dse).
57 * The first technique performs dse locally on any base address. It
58 is based on the cselib which is a local value numbering technique.
59 This technique is local to a basic block but deals with a fairly
60 general addresses.
62 * The second technique performs dse globally but is restricted to
63 base addresses that are either constant or are relative to the
64 frame_pointer.
66 * The third technique, (which is only done after register allocation)
67 processes the spill slots. This differs from the second
68 technique because it takes advantage of the fact that spilling is
69 completely free from the effects of aliasing.
71 Logically, dse is a backwards dataflow problem. A store can be
72 deleted if it if cannot be reached in the backward direction by any
73 use of the value being stored. However, the local technique uses a
74 forwards scan of the basic block because cselib requires that the
75 block be processed in that order.
77 The pass is logically broken into 7 steps:
79 0) Initialization.
81 1) The local algorithm, as well as scanning the insns for the two
82 global algorithms.
84 2) Analysis to see if the global algs are necessary. In the case
85 of stores base on a constant address, there must be at least two
86 stores to that address, to make it possible to delete some of the
87 stores. In the case of stores off of the frame or spill related
88 stores, only one store to an address is necessary because those
89 stores die at the end of the function.
91 3) Set up the global dataflow equations based on processing the
92 info parsed in the first step.
94 4) Solve the dataflow equations.
96 5) Delete the insns that the global analysis has indicated are
97 unnecessary.
99 6) Delete insns that store the same value as preceding store
100 where the earlier store couldn't be eliminated.
102 7) Cleanup.
104 This step uses cselib and canon_rtx to build the largest expression
105 possible for each address. This pass is a forwards pass through
106 each basic block. From the point of view of the global technique,
107 the first pass could examine a block in either direction. The
108 forwards ordering is to accommodate cselib.
110 We make a simplifying assumption: addresses fall into four broad
111 categories:
113 1) base has rtx_varies_p == false, offset is constant.
114 2) base has rtx_varies_p == false, offset variable.
115 3) base has rtx_varies_p == true, offset constant.
116 4) base has rtx_varies_p == true, offset variable.
118 The local passes are able to process all 4 kinds of addresses. The
119 global pass only handles 1).
121 The global problem is formulated as follows:
123 A store, S1, to address A, where A is not relative to the stack
124 frame, can be eliminated if all paths from S1 to the end of the
125 function contain another store to A before a read to A.
127 If the address A is relative to the stack frame, a store S2 to A
128 can be eliminated if there are no paths from S2 that reach the
129 end of the function that read A before another store to A. In
130 this case S2 can be deleted if there are paths from S2 to the
131 end of the function that have no reads or writes to A. This
132 second case allows stores to the stack frame to be deleted that
133 would otherwise die when the function returns. This cannot be
134 done if stores_off_frame_dead_at_return is not true. See the doc
135 for that variable for when this variable is false.
137 The global problem is formulated as a backwards set union
138 dataflow problem where the stores are the gens and reads are the
139 kills. Set union problems are rare and require some special
140 handling given our representation of bitmaps. A straightforward
141 implementation requires a lot of bitmaps filled with 1s.
142 These are expensive and cumbersome in our bitmap formulation so
143 care has been taken to avoid large vectors filled with 1s. See
144 the comments in bb_info and in the dataflow confluence functions
145 for details.
147 There are two places for further enhancements to this algorithm:
149 1) The original dse which was embedded in a pass called flow also
150 did local address forwarding. For example in
152 A <- r100
153 ... <- A
155 flow would replace the right hand side of the second insn with a
156 reference to r100. Most of the information is available to add this
157 to this pass. It has not done it because it is a lot of work in
158 the case that either r100 is assigned to between the first and
159 second insn and/or the second insn is a load of part of the value
160 stored by the first insn.
162 insn 5 in gcc.c-torture/compile/990203-1.c simple case.
163 insn 15 in gcc.c-torture/execute/20001017-2.c simple case.
164 insn 25 in gcc.c-torture/execute/20001026-1.c simple case.
165 insn 44 in gcc.c-torture/execute/20010910-1.c simple case.
167 2) The cleaning up of spill code is quite profitable. It currently
168 depends on reading tea leaves and chicken entrails left by reload.
169 This pass depends on reload creating a singleton alias set for each
170 spill slot and telling the next dse pass which of these alias sets
171 are the singletons. Rather than analyze the addresses of the
172 spills, dse's spill processing just does analysis of the loads and
173 stores that use those alias sets. There are three cases where this
174 falls short:
176 a) Reload sometimes creates the slot for one mode of access, and
177 then inserts loads and/or stores for a smaller mode. In this
178 case, the current code just punts on the slot. The proper thing
179 to do is to back out and use one bit vector position for each
180 byte of the entity associated with the slot. This depends on
181 KNOWING that reload always generates the accesses for each of the
182 bytes in some canonical (read that easy to understand several
183 passes after reload happens) way.
185 b) Reload sometimes decides that spill slot it allocated was not
186 large enough for the mode and goes back and allocates more slots
187 with the same mode and alias set. The backout in this case is a
188 little more graceful than (a). In this case the slot is unmarked
189 as being a spill slot and if final address comes out to be based
190 off the frame pointer, the global algorithm handles this slot.
192 c) For any pass that may prespill, there is currently no
193 mechanism to tell the dse pass that the slot being used has the
194 special properties that reload uses. It may be that all that is
195 required is to have those passes make the same calls that reload
196 does, assuming that the alias sets can be manipulated in the same
197 way. */
199 /* There are limits to the size of constant offsets we model for the
200 global problem. There are certainly test cases, that exceed this
201 limit, however, it is unlikely that there are important programs
202 that really have constant offsets this size. */
203 #define MAX_OFFSET (64 * 1024)
205 /* Obstack for the DSE dataflow bitmaps. We don't want to put these
206 on the default obstack because these bitmaps can grow quite large
207 (~2GB for the small (!) test case of PR54146) and we'll hold on to
208 all that memory until the end of the compiler run.
209 As a bonus, delete_tree_live_info can destroy all the bitmaps by just
210 releasing the whole obstack. */
211 static bitmap_obstack dse_bitmap_obstack;
213 /* Obstack for other data. As for above: Kinda nice to be able to
214 throw it all away at the end in one big sweep. */
215 static struct obstack dse_obstack;
217 /* Scratch bitmap for cselib's cselib_expand_value_rtx. */
218 static bitmap scratch = NULL;
220 struct insn_info_type;
222 /* This structure holds information about a candidate store. */
223 struct store_info
226 /* False means this is a clobber. */
227 bool is_set;
229 /* False if a single HOST_WIDE_INT bitmap is used for positions_needed. */
230 bool is_large;
232 /* The id of the mem group of the base address. If rtx_varies_p is
233 true, this is -1. Otherwise, it is the index into the group
234 table. */
235 int group_id;
237 /* This is the cselib value. */
238 cselib_val *cse_base;
240 /* This canonized mem. */
241 rtx mem;
243 /* Canonized MEM address for use by canon_true_dependence. */
244 rtx mem_addr;
246 /* The offset of the first byte associated with the operation. */
247 poly_int64 offset;
249 /* The number of bytes covered by the operation. This is always exact
250 and known (rather than -1). */
251 poly_int64 width;
253 union
255 /* A bitmask as wide as the number of bytes in the word that
256 contains a 1 if the byte may be needed. The store is unused if
257 all of the bits are 0. This is used if IS_LARGE is false. */
258 unsigned HOST_WIDE_INT small_bitmask;
260 struct
262 /* A bitmap with one bit per byte, or null if the number of
263 bytes isn't known at compile time. A cleared bit means
264 the position is needed. Used if IS_LARGE is true. */
265 bitmap bmap;
267 /* When BITMAP is nonnull, this counts the number of set bits
268 (i.e. unneeded bytes) in the bitmap. If it is equal to
269 WIDTH, the whole store is unused.
271 When BITMAP is null:
272 - the store is definitely not needed when COUNT == 1
273 - all the store is needed when COUNT == 0 and RHS is nonnull
274 - otherwise we don't know which parts of the store are needed. */
275 int count;
276 } large;
277 } positions_needed;
279 /* The next store info for this insn. */
280 struct store_info *next;
282 /* The right hand side of the store. This is used if there is a
283 subsequent reload of the mems address somewhere later in the
284 basic block. */
285 rtx rhs;
287 /* If rhs is or holds a constant, this contains that constant,
288 otherwise NULL. */
289 rtx const_rhs;
291 /* Set if this store stores the same constant value as REDUNDANT_REASON
292 insn stored. These aren't eliminated early, because doing that
293 might prevent the earlier larger store to be eliminated. */
294 struct insn_info_type *redundant_reason;
297 /* Return a bitmask with the first N low bits set. */
299 static unsigned HOST_WIDE_INT
300 lowpart_bitmask (int n)
302 unsigned HOST_WIDE_INT mask = HOST_WIDE_INT_M1U;
303 return mask >> (HOST_BITS_PER_WIDE_INT - n);
306 static object_allocator<store_info> cse_store_info_pool ("cse_store_info_pool");
308 static object_allocator<store_info> rtx_store_info_pool ("rtx_store_info_pool");
310 /* This structure holds information about a load. These are only
311 built for rtx bases. */
312 struct read_info_type
314 /* The id of the mem group of the base address. */
315 int group_id;
317 /* The offset of the first byte associated with the operation. */
318 poly_int64 offset;
320 /* The number of bytes covered by the operation, or -1 if not known. */
321 poly_int64 width;
323 /* The mem being read. */
324 rtx mem;
326 /* The next read_info for this insn. */
327 struct read_info_type *next;
329 typedef struct read_info_type *read_info_t;
331 static object_allocator<read_info_type> read_info_type_pool ("read_info_pool");
333 /* One of these records is created for each insn. */
335 struct insn_info_type
337 /* Set true if the insn contains a store but the insn itself cannot
338 be deleted. This is set if the insn is a parallel and there is
339 more than one non dead output or if the insn is in some way
340 volatile. */
341 bool cannot_delete;
343 /* This field is only used by the global algorithm. It is set true
344 if the insn contains any read of mem except for a (1). This is
345 also set if the insn is a call or has a clobber mem. If the insn
346 contains a wild read, the use_rec will be null. */
347 bool wild_read;
349 /* This is true only for CALL instructions which could potentially read
350 any non-frame memory location. This field is used by the global
351 algorithm. */
352 bool non_frame_wild_read;
354 /* This field is only used for the processing of const functions.
355 These functions cannot read memory, but they can read the stack
356 because that is where they may get their parms. We need to be
357 this conservative because, like the store motion pass, we don't
358 consider CALL_INSN_FUNCTION_USAGE when processing call insns.
359 Moreover, we need to distinguish two cases:
360 1. Before reload (register elimination), the stores related to
361 outgoing arguments are stack pointer based and thus deemed
362 of non-constant base in this pass. This requires special
363 handling but also means that the frame pointer based stores
364 need not be killed upon encountering a const function call.
365 2. After reload, the stores related to outgoing arguments can be
366 either stack pointer or hard frame pointer based. This means
367 that we have no other choice than also killing all the frame
368 pointer based stores upon encountering a const function call.
369 This field is set after reload for const function calls and before
370 reload for const tail function calls on targets where arg pointer
371 is the frame pointer. Having this set is less severe than a wild
372 read, it just means that all the frame related stores are killed
373 rather than all the stores. */
374 bool frame_read;
376 /* This field is only used for the processing of const functions.
377 It is set if the insn may contain a stack pointer based store. */
378 bool stack_pointer_based;
380 /* This is true if any of the sets within the store contains a
381 cselib base. Such stores can only be deleted by the local
382 algorithm. */
383 bool contains_cselib_groups;
385 /* The insn. */
386 rtx_insn *insn;
388 /* The list of mem sets or mem clobbers that are contained in this
389 insn. If the insn is deletable, it contains only one mem set.
390 But it could also contain clobbers. Insns that contain more than
391 one mem set are not deletable, but each of those mems are here in
392 order to provide info to delete other insns. */
393 store_info *store_rec;
395 /* The linked list of mem uses in this insn. Only the reads from
396 rtx bases are listed here. The reads to cselib bases are
397 completely processed during the first scan and so are never
398 created. */
399 read_info_t read_rec;
401 /* The live fixed registers. We assume only fixed registers can
402 cause trouble by being clobbered from an expanded pattern;
403 storing only the live fixed registers (rather than all registers)
404 means less memory needs to be allocated / copied for the individual
405 stores. */
406 regset fixed_regs_live;
408 /* The prev insn in the basic block. */
409 struct insn_info_type * prev_insn;
411 /* The linked list of insns that are in consideration for removal in
412 the forwards pass through the basic block. This pointer may be
413 trash as it is not cleared when a wild read occurs. The only
414 time it is guaranteed to be correct is when the traversal starts
415 at active_local_stores. */
416 struct insn_info_type * next_local_store;
418 typedef struct insn_info_type *insn_info_t;
420 static object_allocator<insn_info_type> insn_info_type_pool ("insn_info_pool");
422 /* The linked list of stores that are under consideration in this
423 basic block. */
424 static insn_info_t active_local_stores;
425 static int active_local_stores_len;
427 struct dse_bb_info_type
429 /* Pointer to the insn info for the last insn in the block. These
430 are linked so this is how all of the insns are reached. During
431 scanning this is the current insn being scanned. */
432 insn_info_t last_insn;
434 /* The info for the global dataflow problem. */
437 /* This is set if the transfer function should and in the wild_read
438 bitmap before applying the kill and gen sets. That vector knocks
439 out most of the bits in the bitmap and thus speeds up the
440 operations. */
441 bool apply_wild_read;
443 /* The following 4 bitvectors hold information about which positions
444 of which stores are live or dead. They are indexed by
445 get_bitmap_index. */
447 /* The set of store positions that exist in this block before a wild read. */
448 bitmap gen;
450 /* The set of load positions that exist in this block above the
451 same position of a store. */
452 bitmap kill;
454 /* The set of stores that reach the top of the block without being
455 killed by a read.
457 Do not represent the in if it is all ones. Note that this is
458 what the bitvector should logically be initialized to for a set
459 intersection problem. However, like the kill set, this is too
460 expensive. So initially, the in set will only be created for the
461 exit block and any block that contains a wild read. */
462 bitmap in;
464 /* The set of stores that reach the bottom of the block from it's
465 successors.
467 Do not represent the in if it is all ones. Note that this is
468 what the bitvector should logically be initialized to for a set
469 intersection problem. However, like the kill and in set, this is
470 too expensive. So what is done is that the confluence operator
471 just initializes the vector from one of the out sets of the
472 successors of the block. */
473 bitmap out;
475 /* The following bitvector is indexed by the reg number. It
476 contains the set of regs that are live at the current instruction
477 being processed. While it contains info for all of the
478 registers, only the hard registers are actually examined. It is used
479 to assure that shift and/or add sequences that are inserted do not
480 accidentally clobber live hard regs. */
481 bitmap regs_live;
484 typedef struct dse_bb_info_type *bb_info_t;
486 static object_allocator<dse_bb_info_type> dse_bb_info_type_pool
487 ("bb_info_pool");
489 /* Table to hold all bb_infos. */
490 static bb_info_t *bb_table;
492 /* There is a group_info for each rtx base that is used to reference
493 memory. There are also not many of the rtx bases because they are
494 very limited in scope. */
496 struct group_info
498 /* The actual base of the address. */
499 rtx rtx_base;
501 /* The sequential id of the base. This allows us to have a
502 canonical ordering of these that is not based on addresses. */
503 int id;
505 /* True if there are any positions that are to be processed
506 globally. */
507 bool process_globally;
509 /* True if the base of this group is either the frame_pointer or
510 hard_frame_pointer. */
511 bool frame_related;
513 /* A mem wrapped around the base pointer for the group in order to do
514 read dependency. It must be given BLKmode in order to encompass all
515 the possible offsets from the base. */
516 rtx base_mem;
518 /* Canonized version of base_mem's address. */
519 rtx canon_base_addr;
521 /* These two sets of two bitmaps are used to keep track of how many
522 stores are actually referencing that position from this base. We
523 only do this for rtx bases as this will be used to assign
524 positions in the bitmaps for the global problem. Bit N is set in
525 store1 on the first store for offset N. Bit N is set in store2
526 for the second store to offset N. This is all we need since we
527 only care about offsets that have two or more stores for them.
529 The "_n" suffix is for offsets less than 0 and the "_p" suffix is
530 for 0 and greater offsets.
532 There is one special case here, for stores into the stack frame,
533 we will or store1 into store2 before deciding which stores look
534 at globally. This is because stores to the stack frame that have
535 no other reads before the end of the function can also be
536 deleted. */
537 bitmap store1_n, store1_p, store2_n, store2_p;
539 /* These bitmaps keep track of offsets in this group escape this function.
540 An offset escapes if it corresponds to a named variable whose
541 addressable flag is set. */
542 bitmap escaped_n, escaped_p;
544 /* The positions in this bitmap have the same assignments as the in,
545 out, gen and kill bitmaps. This bitmap is all zeros except for
546 the positions that are occupied by stores for this group. */
547 bitmap group_kill;
549 /* The offset_map is used to map the offsets from this base into
550 positions in the global bitmaps. It is only created after all of
551 the all of stores have been scanned and we know which ones we
552 care about. */
553 int *offset_map_n, *offset_map_p;
554 int offset_map_size_n, offset_map_size_p;
557 static object_allocator<group_info> group_info_pool ("rtx_group_info_pool");
559 /* Index into the rtx_group_vec. */
560 static int rtx_group_next_id;
563 static vec<group_info *> rtx_group_vec;
566 /* This structure holds the set of changes that are being deferred
567 when removing read operation. See replace_read. */
568 struct deferred_change
571 /* The mem that is being replaced. */
572 rtx *loc;
574 /* The reg it is being replaced with. */
575 rtx reg;
577 struct deferred_change *next;
580 static object_allocator<deferred_change> deferred_change_pool
581 ("deferred_change_pool");
583 static deferred_change *deferred_change_list = NULL;
585 /* This is true except if cfun->stdarg -- i.e. we cannot do
586 this for vararg functions because they play games with the frame. */
587 static bool stores_off_frame_dead_at_return;
589 /* Counter for stats. */
590 static int globally_deleted;
591 static int locally_deleted;
593 static bitmap all_blocks;
595 /* Locations that are killed by calls in the global phase. */
596 static bitmap kill_on_calls;
598 /* The number of bits used in the global bitmaps. */
599 static unsigned int current_position;
601 /* Print offset range [OFFSET, OFFSET + WIDTH) to FILE. */
603 static void
604 print_range (FILE *file, poly_int64 offset, poly_int64 width)
606 fprintf (file, "[");
607 print_dec (offset, file, SIGNED);
608 fprintf (file, "..");
609 print_dec (offset + width, file, SIGNED);
610 fprintf (file, ")");
613 /*----------------------------------------------------------------------------
614 Zeroth step.
616 Initialization.
617 ----------------------------------------------------------------------------*/
620 /* Hashtable callbacks for maintaining the "bases" field of
621 store_group_info, given that the addresses are function invariants. */
623 struct invariant_group_base_hasher : nofree_ptr_hash <group_info>
625 static inline hashval_t hash (const group_info *);
626 static inline bool equal (const group_info *, const group_info *);
629 inline bool
630 invariant_group_base_hasher::equal (const group_info *gi1,
631 const group_info *gi2)
633 return rtx_equal_p (gi1->rtx_base, gi2->rtx_base);
636 inline hashval_t
637 invariant_group_base_hasher::hash (const group_info *gi)
639 int do_not_record;
640 return hash_rtx (gi->rtx_base, Pmode, &do_not_record, NULL, false);
643 /* Tables of group_info structures, hashed by base value. */
644 static hash_table<invariant_group_base_hasher> *rtx_group_table;
647 /* Get the GROUP for BASE. Add a new group if it is not there. */
649 static group_info *
650 get_group_info (rtx base)
652 struct group_info tmp_gi;
653 group_info *gi;
654 group_info **slot;
656 gcc_assert (base != NULL_RTX);
658 /* Find the store_base_info structure for BASE, creating a new one
659 if necessary. */
660 tmp_gi.rtx_base = base;
661 slot = rtx_group_table->find_slot (&tmp_gi, INSERT);
662 gi = *slot;
664 if (gi == NULL)
666 *slot = gi = group_info_pool.allocate ();
667 gi->rtx_base = base;
668 gi->id = rtx_group_next_id++;
669 gi->base_mem = gen_rtx_MEM (BLKmode, base);
670 gi->canon_base_addr = canon_rtx (base);
671 gi->store1_n = BITMAP_ALLOC (&dse_bitmap_obstack);
672 gi->store1_p = BITMAP_ALLOC (&dse_bitmap_obstack);
673 gi->store2_n = BITMAP_ALLOC (&dse_bitmap_obstack);
674 gi->store2_p = BITMAP_ALLOC (&dse_bitmap_obstack);
675 gi->escaped_p = BITMAP_ALLOC (&dse_bitmap_obstack);
676 gi->escaped_n = BITMAP_ALLOC (&dse_bitmap_obstack);
677 gi->group_kill = BITMAP_ALLOC (&dse_bitmap_obstack);
678 gi->process_globally = false;
679 gi->frame_related =
680 (base == frame_pointer_rtx) || (base == hard_frame_pointer_rtx);
681 gi->offset_map_size_n = 0;
682 gi->offset_map_size_p = 0;
683 gi->offset_map_n = NULL;
684 gi->offset_map_p = NULL;
685 rtx_group_vec.safe_push (gi);
688 return gi;
692 /* Initialization of data structures. */
694 static void
695 dse_step0 (void)
697 locally_deleted = 0;
698 globally_deleted = 0;
700 bitmap_obstack_initialize (&dse_bitmap_obstack);
701 gcc_obstack_init (&dse_obstack);
703 scratch = BITMAP_ALLOC (&reg_obstack);
704 kill_on_calls = BITMAP_ALLOC (&dse_bitmap_obstack);
707 rtx_group_table = new hash_table<invariant_group_base_hasher> (11);
709 bb_table = XNEWVEC (bb_info_t, last_basic_block_for_fn (cfun));
710 rtx_group_next_id = 0;
712 stores_off_frame_dead_at_return = !cfun->stdarg;
714 init_alias_analysis ();
719 /*----------------------------------------------------------------------------
720 First step.
722 Scan all of the insns. Any random ordering of the blocks is fine.
723 Each block is scanned in forward order to accommodate cselib which
724 is used to remove stores with non-constant bases.
725 ----------------------------------------------------------------------------*/
727 /* Delete all of the store_info recs from INSN_INFO. */
729 static void
730 free_store_info (insn_info_t insn_info)
732 store_info *cur = insn_info->store_rec;
733 while (cur)
735 store_info *next = cur->next;
736 if (cur->is_large)
737 BITMAP_FREE (cur->positions_needed.large.bmap);
738 if (cur->cse_base)
739 cse_store_info_pool.remove (cur);
740 else
741 rtx_store_info_pool.remove (cur);
742 cur = next;
745 insn_info->cannot_delete = true;
746 insn_info->contains_cselib_groups = false;
747 insn_info->store_rec = NULL;
750 struct note_add_store_info
752 rtx_insn *first, *current;
753 regset fixed_regs_live;
754 bool failure;
757 /* Callback for emit_inc_dec_insn_before via note_stores.
758 Check if a register is clobbered which is live afterwards. */
760 static void
761 note_add_store (rtx loc, const_rtx expr ATTRIBUTE_UNUSED, void *data)
763 rtx_insn *insn;
764 note_add_store_info *info = (note_add_store_info *) data;
766 if (!REG_P (loc))
767 return;
769 /* If this register is referenced by the current or an earlier insn,
770 that's OK. E.g. this applies to the register that is being incremented
771 with this addition. */
772 for (insn = info->first;
773 insn != NEXT_INSN (info->current);
774 insn = NEXT_INSN (insn))
775 if (reg_referenced_p (loc, PATTERN (insn)))
776 return;
778 /* If we come here, we have a clobber of a register that's only OK
779 if that register is not live. If we don't have liveness information
780 available, fail now. */
781 if (!info->fixed_regs_live)
783 info->failure = true;
784 return;
786 /* Now check if this is a live fixed register. */
787 unsigned int end_regno = END_REGNO (loc);
788 for (unsigned int regno = REGNO (loc); regno < end_regno; ++regno)
789 if (REGNO_REG_SET_P (info->fixed_regs_live, regno))
790 info->failure = true;
793 /* Callback for for_each_inc_dec that emits an INSN that sets DEST to
794 SRC + SRCOFF before insn ARG. */
796 static int
797 emit_inc_dec_insn_before (rtx mem ATTRIBUTE_UNUSED,
798 rtx op ATTRIBUTE_UNUSED,
799 rtx dest, rtx src, rtx srcoff, void *arg)
801 insn_info_t insn_info = (insn_info_t) arg;
802 rtx_insn *insn = insn_info->insn, *new_insn, *cur;
803 note_add_store_info info;
805 /* We can reuse all operands without copying, because we are about
806 to delete the insn that contained it. */
807 if (srcoff)
809 start_sequence ();
810 emit_insn (gen_add3_insn (dest, src, srcoff));
811 new_insn = get_insns ();
812 end_sequence ();
814 else
815 new_insn = gen_move_insn (dest, src);
816 info.first = new_insn;
817 info.fixed_regs_live = insn_info->fixed_regs_live;
818 info.failure = false;
819 for (cur = new_insn; cur; cur = NEXT_INSN (cur))
821 info.current = cur;
822 note_stores (PATTERN (cur), note_add_store, &info);
825 /* If a failure was flagged above, return 1 so that for_each_inc_dec will
826 return it immediately, communicating the failure to its caller. */
827 if (info.failure)
828 return 1;
830 emit_insn_before (new_insn, insn);
832 return 0;
835 /* Before we delete INSN_INFO->INSN, make sure that the auto inc/dec, if it
836 is there, is split into a separate insn.
837 Return true on success (or if there was nothing to do), false on failure. */
839 static bool
840 check_for_inc_dec_1 (insn_info_t insn_info)
842 rtx_insn *insn = insn_info->insn;
843 rtx note = find_reg_note (insn, REG_INC, NULL_RTX);
844 if (note)
845 return for_each_inc_dec (PATTERN (insn), emit_inc_dec_insn_before,
846 insn_info) == 0;
847 return true;
851 /* Entry point for postreload. If you work on reload_cse, or you need this
852 anywhere else, consider if you can provide register liveness information
853 and add a parameter to this function so that it can be passed down in
854 insn_info.fixed_regs_live. */
855 bool
856 check_for_inc_dec (rtx_insn *insn)
858 insn_info_type insn_info;
859 rtx note;
861 insn_info.insn = insn;
862 insn_info.fixed_regs_live = NULL;
863 note = find_reg_note (insn, REG_INC, NULL_RTX);
864 if (note)
865 return for_each_inc_dec (PATTERN (insn), emit_inc_dec_insn_before,
866 &insn_info) == 0;
867 return true;
870 /* Delete the insn and free all of the fields inside INSN_INFO. */
872 static void
873 delete_dead_store_insn (insn_info_t insn_info)
875 read_info_t read_info;
877 if (!dbg_cnt (dse))
878 return;
880 if (!check_for_inc_dec_1 (insn_info))
881 return;
882 if (dump_file && (dump_flags & TDF_DETAILS))
883 fprintf (dump_file, "Locally deleting insn %d\n",
884 INSN_UID (insn_info->insn));
886 free_store_info (insn_info);
887 read_info = insn_info->read_rec;
889 while (read_info)
891 read_info_t next = read_info->next;
892 read_info_type_pool.remove (read_info);
893 read_info = next;
895 insn_info->read_rec = NULL;
897 delete_insn (insn_info->insn);
898 locally_deleted++;
899 insn_info->insn = NULL;
901 insn_info->wild_read = false;
904 /* Return whether DECL, a local variable, can possibly escape the current
905 function scope. */
907 static bool
908 local_variable_can_escape (tree decl)
910 if (TREE_ADDRESSABLE (decl))
911 return true;
913 /* If this is a partitioned variable, we need to consider all the variables
914 in the partition. This is necessary because a store into one of them can
915 be replaced with a store into another and this may not change the outcome
916 of the escape analysis. */
917 if (cfun->gimple_df->decls_to_pointers != NULL)
919 tree *namep = cfun->gimple_df->decls_to_pointers->get (decl);
920 if (namep)
921 return TREE_ADDRESSABLE (*namep);
924 return false;
927 /* Return whether EXPR can possibly escape the current function scope. */
929 static bool
930 can_escape (tree expr)
932 tree base;
933 if (!expr)
934 return true;
935 base = get_base_address (expr);
936 if (DECL_P (base)
937 && !may_be_aliased (base)
938 && !(VAR_P (base)
939 && !DECL_EXTERNAL (base)
940 && !TREE_STATIC (base)
941 && local_variable_can_escape (base)))
942 return false;
943 return true;
946 /* Set the store* bitmaps offset_map_size* fields in GROUP based on
947 OFFSET and WIDTH. */
949 static void
950 set_usage_bits (group_info *group, poly_int64 offset, poly_int64 width,
951 tree expr)
953 /* Non-constant offsets and widths act as global kills, so there's no point
954 trying to use them to derive global DSE candidates. */
955 HOST_WIDE_INT i, const_offset, const_width;
956 bool expr_escapes = can_escape (expr);
957 if (offset.is_constant (&const_offset)
958 && width.is_constant (&const_width)
959 && const_offset > -MAX_OFFSET
960 && const_offset + const_width < MAX_OFFSET)
961 for (i = const_offset; i < const_offset + const_width; ++i)
963 bitmap store1;
964 bitmap store2;
965 bitmap escaped;
966 int ai;
967 if (i < 0)
969 store1 = group->store1_n;
970 store2 = group->store2_n;
971 escaped = group->escaped_n;
972 ai = -i;
974 else
976 store1 = group->store1_p;
977 store2 = group->store2_p;
978 escaped = group->escaped_p;
979 ai = i;
982 if (!bitmap_set_bit (store1, ai))
983 bitmap_set_bit (store2, ai);
984 else
986 if (i < 0)
988 if (group->offset_map_size_n < ai)
989 group->offset_map_size_n = ai;
991 else
993 if (group->offset_map_size_p < ai)
994 group->offset_map_size_p = ai;
997 if (expr_escapes)
998 bitmap_set_bit (escaped, ai);
1002 static void
1003 reset_active_stores (void)
1005 active_local_stores = NULL;
1006 active_local_stores_len = 0;
1009 /* Free all READ_REC of the LAST_INSN of BB_INFO. */
1011 static void
1012 free_read_records (bb_info_t bb_info)
1014 insn_info_t insn_info = bb_info->last_insn;
1015 read_info_t *ptr = &insn_info->read_rec;
1016 while (*ptr)
1018 read_info_t next = (*ptr)->next;
1019 read_info_type_pool.remove (*ptr);
1020 *ptr = next;
1024 /* Set the BB_INFO so that the last insn is marked as a wild read. */
1026 static void
1027 add_wild_read (bb_info_t bb_info)
1029 insn_info_t insn_info = bb_info->last_insn;
1030 insn_info->wild_read = true;
1031 free_read_records (bb_info);
1032 reset_active_stores ();
1035 /* Set the BB_INFO so that the last insn is marked as a wild read of
1036 non-frame locations. */
1038 static void
1039 add_non_frame_wild_read (bb_info_t bb_info)
1041 insn_info_t insn_info = bb_info->last_insn;
1042 insn_info->non_frame_wild_read = true;
1043 free_read_records (bb_info);
1044 reset_active_stores ();
1047 /* Return true if X is a constant or one of the registers that behave
1048 as a constant over the life of a function. This is equivalent to
1049 !rtx_varies_p for memory addresses. */
1051 static bool
1052 const_or_frame_p (rtx x)
1054 if (CONSTANT_P (x))
1055 return true;
1057 if (GET_CODE (x) == REG)
1059 /* Note that we have to test for the actual rtx used for the frame
1060 and arg pointers and not just the register number in case we have
1061 eliminated the frame and/or arg pointer and are using it
1062 for pseudos. */
1063 if (x == frame_pointer_rtx || x == hard_frame_pointer_rtx
1064 /* The arg pointer varies if it is not a fixed register. */
1065 || (x == arg_pointer_rtx && fixed_regs[ARG_POINTER_REGNUM])
1066 || x == pic_offset_table_rtx)
1067 return true;
1068 return false;
1071 return false;
1074 /* Take all reasonable action to put the address of MEM into the form
1075 that we can do analysis on.
1077 The gold standard is to get the address into the form: address +
1078 OFFSET where address is something that rtx_varies_p considers a
1079 constant. When we can get the address in this form, we can do
1080 global analysis on it. Note that for constant bases, address is
1081 not actually returned, only the group_id. The address can be
1082 obtained from that.
1084 If that fails, we try cselib to get a value we can at least use
1085 locally. If that fails we return false.
1087 The GROUP_ID is set to -1 for cselib bases and the index of the
1088 group for non_varying bases.
1090 FOR_READ is true if this is a mem read and false if not. */
1092 static bool
1093 canon_address (rtx mem,
1094 int *group_id,
1095 poly_int64 *offset,
1096 cselib_val **base)
1098 machine_mode address_mode = get_address_mode (mem);
1099 rtx mem_address = XEXP (mem, 0);
1100 rtx expanded_address, address;
1101 int expanded;
1103 cselib_lookup (mem_address, address_mode, 1, GET_MODE (mem));
1105 if (dump_file && (dump_flags & TDF_DETAILS))
1107 fprintf (dump_file, " mem: ");
1108 print_inline_rtx (dump_file, mem_address, 0);
1109 fprintf (dump_file, "\n");
1112 /* First see if just canon_rtx (mem_address) is const or frame,
1113 if not, try cselib_expand_value_rtx and call canon_rtx on that. */
1114 address = NULL_RTX;
1115 for (expanded = 0; expanded < 2; expanded++)
1117 if (expanded)
1119 /* Use cselib to replace all of the reg references with the full
1120 expression. This will take care of the case where we have
1122 r_x = base + offset;
1123 val = *r_x;
1125 by making it into
1127 val = *(base + offset); */
1129 expanded_address = cselib_expand_value_rtx (mem_address,
1130 scratch, 5);
1132 /* If this fails, just go with the address from first
1133 iteration. */
1134 if (!expanded_address)
1135 break;
1137 else
1138 expanded_address = mem_address;
1140 /* Split the address into canonical BASE + OFFSET terms. */
1141 address = canon_rtx (expanded_address);
1143 *offset = 0;
1145 if (dump_file && (dump_flags & TDF_DETAILS))
1147 if (expanded)
1149 fprintf (dump_file, "\n after cselib_expand address: ");
1150 print_inline_rtx (dump_file, expanded_address, 0);
1151 fprintf (dump_file, "\n");
1154 fprintf (dump_file, "\n after canon_rtx address: ");
1155 print_inline_rtx (dump_file, address, 0);
1156 fprintf (dump_file, "\n");
1159 if (GET_CODE (address) == CONST)
1160 address = XEXP (address, 0);
1162 address = strip_offset_and_add (address, offset);
1164 if (ADDR_SPACE_GENERIC_P (MEM_ADDR_SPACE (mem))
1165 && const_or_frame_p (address))
1167 group_info *group = get_group_info (address);
1169 if (dump_file && (dump_flags & TDF_DETAILS))
1171 fprintf (dump_file, " gid=%d offset=", group->id);
1172 print_dec (*offset, dump_file);
1173 fprintf (dump_file, "\n");
1175 *base = NULL;
1176 *group_id = group->id;
1177 return true;
1181 *base = cselib_lookup (address, address_mode, true, GET_MODE (mem));
1182 *group_id = -1;
1184 if (*base == NULL)
1186 if (dump_file && (dump_flags & TDF_DETAILS))
1187 fprintf (dump_file, " no cselib val - should be a wild read.\n");
1188 return false;
1190 if (dump_file && (dump_flags & TDF_DETAILS))
1192 fprintf (dump_file, " varying cselib base=%u:%u offset = ",
1193 (*base)->uid, (*base)->hash);
1194 print_dec (*offset, dump_file);
1195 fprintf (dump_file, "\n");
1197 return true;
1201 /* Clear the rhs field from the active_local_stores array. */
1203 static void
1204 clear_rhs_from_active_local_stores (void)
1206 insn_info_t ptr = active_local_stores;
1208 while (ptr)
1210 store_info *store_info = ptr->store_rec;
1211 /* Skip the clobbers. */
1212 while (!store_info->is_set)
1213 store_info = store_info->next;
1215 store_info->rhs = NULL;
1216 store_info->const_rhs = NULL;
1218 ptr = ptr->next_local_store;
1223 /* Mark byte POS bytes from the beginning of store S_INFO as unneeded. */
1225 static inline void
1226 set_position_unneeded (store_info *s_info, int pos)
1228 if (__builtin_expect (s_info->is_large, false))
1230 if (bitmap_set_bit (s_info->positions_needed.large.bmap, pos))
1231 s_info->positions_needed.large.count++;
1233 else
1234 s_info->positions_needed.small_bitmask
1235 &= ~(HOST_WIDE_INT_1U << pos);
1238 /* Mark the whole store S_INFO as unneeded. */
1240 static inline void
1241 set_all_positions_unneeded (store_info *s_info)
1243 if (__builtin_expect (s_info->is_large, false))
1245 HOST_WIDE_INT width;
1246 if (s_info->width.is_constant (&width))
1248 bitmap_set_range (s_info->positions_needed.large.bmap, 0, width);
1249 s_info->positions_needed.large.count = width;
1251 else
1253 gcc_checking_assert (!s_info->positions_needed.large.bmap);
1254 s_info->positions_needed.large.count = 1;
1257 else
1258 s_info->positions_needed.small_bitmask = HOST_WIDE_INT_0U;
1261 /* Return TRUE if any bytes from S_INFO store are needed. */
1263 static inline bool
1264 any_positions_needed_p (store_info *s_info)
1266 if (__builtin_expect (s_info->is_large, false))
1268 HOST_WIDE_INT width;
1269 if (s_info->width.is_constant (&width))
1271 gcc_checking_assert (s_info->positions_needed.large.bmap);
1272 return s_info->positions_needed.large.count < width;
1274 else
1276 gcc_checking_assert (!s_info->positions_needed.large.bmap);
1277 return s_info->positions_needed.large.count == 0;
1280 else
1281 return (s_info->positions_needed.small_bitmask != HOST_WIDE_INT_0U);
1284 /* Return TRUE if all bytes START through START+WIDTH-1 from S_INFO
1285 store are known to be needed. */
1287 static inline bool
1288 all_positions_needed_p (store_info *s_info, poly_int64 start,
1289 poly_int64 width)
1291 gcc_assert (s_info->rhs);
1292 if (!s_info->width.is_constant ())
1294 gcc_assert (s_info->is_large
1295 && !s_info->positions_needed.large.bmap);
1296 return s_info->positions_needed.large.count == 0;
1299 /* Otherwise, if START and WIDTH are non-constant, we're asking about
1300 a non-constant region of a constant-sized store. We can't say for
1301 sure that all positions are needed. */
1302 HOST_WIDE_INT const_start, const_width;
1303 if (!start.is_constant (&const_start)
1304 || !width.is_constant (&const_width))
1305 return false;
1307 if (__builtin_expect (s_info->is_large, false))
1309 for (HOST_WIDE_INT i = const_start; i < const_start + const_width; ++i)
1310 if (bitmap_bit_p (s_info->positions_needed.large.bmap, i))
1311 return false;
1312 return true;
1314 else
1316 unsigned HOST_WIDE_INT mask
1317 = lowpart_bitmask (const_width) << const_start;
1318 return (s_info->positions_needed.small_bitmask & mask) == mask;
1323 static rtx get_stored_val (store_info *, machine_mode, poly_int64,
1324 poly_int64, basic_block, bool);
1327 /* BODY is an instruction pattern that belongs to INSN. Return 1 if
1328 there is a candidate store, after adding it to the appropriate
1329 local store group if so. */
1331 static int
1332 record_store (rtx body, bb_info_t bb_info)
1334 rtx mem, rhs, const_rhs, mem_addr;
1335 poly_int64 offset = 0;
1336 poly_int64 width = 0;
1337 insn_info_t insn_info = bb_info->last_insn;
1338 store_info *store_info = NULL;
1339 int group_id;
1340 cselib_val *base = NULL;
1341 insn_info_t ptr, last, redundant_reason;
1342 bool store_is_unused;
1344 if (GET_CODE (body) != SET && GET_CODE (body) != CLOBBER)
1345 return 0;
1347 mem = SET_DEST (body);
1349 /* If this is not used, then this cannot be used to keep the insn
1350 from being deleted. On the other hand, it does provide something
1351 that can be used to prove that another store is dead. */
1352 store_is_unused
1353 = (find_reg_note (insn_info->insn, REG_UNUSED, mem) != NULL);
1355 /* Check whether that value is a suitable memory location. */
1356 if (!MEM_P (mem))
1358 /* If the set or clobber is unused, then it does not effect our
1359 ability to get rid of the entire insn. */
1360 if (!store_is_unused)
1361 insn_info->cannot_delete = true;
1362 return 0;
1365 /* At this point we know mem is a mem. */
1366 if (GET_MODE (mem) == BLKmode)
1368 HOST_WIDE_INT const_size;
1369 if (GET_CODE (XEXP (mem, 0)) == SCRATCH)
1371 if (dump_file && (dump_flags & TDF_DETAILS))
1372 fprintf (dump_file, " adding wild read for (clobber (mem:BLK (scratch))\n");
1373 add_wild_read (bb_info);
1374 insn_info->cannot_delete = true;
1375 return 0;
1377 /* Handle (set (mem:BLK (addr) [... S36 ...]) (const_int 0))
1378 as memset (addr, 0, 36); */
1379 else if (!MEM_SIZE_KNOWN_P (mem)
1380 || maybe_le (MEM_SIZE (mem), 0)
1381 /* This is a limit on the bitmap size, which is only relevant
1382 for constant-sized MEMs. */
1383 || (MEM_SIZE (mem).is_constant (&const_size)
1384 && const_size > MAX_OFFSET)
1385 || GET_CODE (body) != SET
1386 || !CONST_INT_P (SET_SRC (body)))
1388 if (!store_is_unused)
1390 /* If the set or clobber is unused, then it does not effect our
1391 ability to get rid of the entire insn. */
1392 insn_info->cannot_delete = true;
1393 clear_rhs_from_active_local_stores ();
1395 return 0;
1399 /* We can still process a volatile mem, we just cannot delete it. */
1400 if (MEM_VOLATILE_P (mem))
1401 insn_info->cannot_delete = true;
1403 if (!canon_address (mem, &group_id, &offset, &base))
1405 clear_rhs_from_active_local_stores ();
1406 return 0;
1409 if (GET_MODE (mem) == BLKmode)
1410 width = MEM_SIZE (mem);
1411 else
1412 width = GET_MODE_SIZE (GET_MODE (mem));
1414 if (!endpoint_representable_p (offset, width))
1416 clear_rhs_from_active_local_stores ();
1417 return 0;
1420 if (known_eq (width, 0))
1421 return 0;
1423 if (group_id >= 0)
1425 /* In the restrictive case where the base is a constant or the
1426 frame pointer we can do global analysis. */
1428 group_info *group
1429 = rtx_group_vec[group_id];
1430 tree expr = MEM_EXPR (mem);
1432 store_info = rtx_store_info_pool.allocate ();
1433 set_usage_bits (group, offset, width, expr);
1435 if (dump_file && (dump_flags & TDF_DETAILS))
1437 fprintf (dump_file, " processing const base store gid=%d",
1438 group_id);
1439 print_range (dump_file, offset, width);
1440 fprintf (dump_file, "\n");
1443 else
1445 if (may_be_sp_based_p (XEXP (mem, 0)))
1446 insn_info->stack_pointer_based = true;
1447 insn_info->contains_cselib_groups = true;
1449 store_info = cse_store_info_pool.allocate ();
1450 group_id = -1;
1452 if (dump_file && (dump_flags & TDF_DETAILS))
1454 fprintf (dump_file, " processing cselib store ");
1455 print_range (dump_file, offset, width);
1456 fprintf (dump_file, "\n");
1460 const_rhs = rhs = NULL_RTX;
1461 if (GET_CODE (body) == SET
1462 /* No place to keep the value after ra. */
1463 && !reload_completed
1464 && (REG_P (SET_SRC (body))
1465 || GET_CODE (SET_SRC (body)) == SUBREG
1466 || CONSTANT_P (SET_SRC (body)))
1467 && !MEM_VOLATILE_P (mem)
1468 /* Sometimes the store and reload is used for truncation and
1469 rounding. */
1470 && !(FLOAT_MODE_P (GET_MODE (mem)) && (flag_float_store)))
1472 rhs = SET_SRC (body);
1473 if (CONSTANT_P (rhs))
1474 const_rhs = rhs;
1475 else if (body == PATTERN (insn_info->insn))
1477 rtx tem = find_reg_note (insn_info->insn, REG_EQUAL, NULL_RTX);
1478 if (tem && CONSTANT_P (XEXP (tem, 0)))
1479 const_rhs = XEXP (tem, 0);
1481 if (const_rhs == NULL_RTX && REG_P (rhs))
1483 rtx tem = cselib_expand_value_rtx (rhs, scratch, 5);
1485 if (tem && CONSTANT_P (tem))
1486 const_rhs = tem;
1490 /* Check to see if this stores causes some other stores to be
1491 dead. */
1492 ptr = active_local_stores;
1493 last = NULL;
1494 redundant_reason = NULL;
1495 mem = canon_rtx (mem);
1497 if (group_id < 0)
1498 mem_addr = base->val_rtx;
1499 else
1501 group_info *group = rtx_group_vec[group_id];
1502 mem_addr = group->canon_base_addr;
1504 if (maybe_ne (offset, 0))
1505 mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
1507 while (ptr)
1509 insn_info_t next = ptr->next_local_store;
1510 struct store_info *s_info = ptr->store_rec;
1511 bool del = true;
1513 /* Skip the clobbers. We delete the active insn if this insn
1514 shadows the set. To have been put on the active list, it
1515 has exactly on set. */
1516 while (!s_info->is_set)
1517 s_info = s_info->next;
1519 if (s_info->group_id == group_id && s_info->cse_base == base)
1521 HOST_WIDE_INT i;
1522 if (dump_file && (dump_flags & TDF_DETAILS))
1524 fprintf (dump_file, " trying store in insn=%d gid=%d",
1525 INSN_UID (ptr->insn), s_info->group_id);
1526 print_range (dump_file, s_info->offset, s_info->width);
1527 fprintf (dump_file, "\n");
1530 /* Even if PTR won't be eliminated as unneeded, if both
1531 PTR and this insn store the same constant value, we might
1532 eliminate this insn instead. */
1533 if (s_info->const_rhs
1534 && const_rhs
1535 && known_subrange_p (offset, width,
1536 s_info->offset, s_info->width)
1537 && all_positions_needed_p (s_info, offset - s_info->offset,
1538 width)
1539 /* We can only remove the later store if the earlier aliases
1540 at least all accesses the later one. */
1541 && (MEM_ALIAS_SET (mem) == MEM_ALIAS_SET (s_info->mem)
1542 || alias_set_subset_of (MEM_ALIAS_SET (mem),
1543 MEM_ALIAS_SET (s_info->mem))))
1545 if (GET_MODE (mem) == BLKmode)
1547 if (GET_MODE (s_info->mem) == BLKmode
1548 && s_info->const_rhs == const_rhs)
1549 redundant_reason = ptr;
1551 else if (s_info->const_rhs == const0_rtx
1552 && const_rhs == const0_rtx)
1553 redundant_reason = ptr;
1554 else
1556 rtx val;
1557 start_sequence ();
1558 val = get_stored_val (s_info, GET_MODE (mem), offset, width,
1559 BLOCK_FOR_INSN (insn_info->insn),
1560 true);
1561 if (get_insns () != NULL)
1562 val = NULL_RTX;
1563 end_sequence ();
1564 if (val && rtx_equal_p (val, const_rhs))
1565 redundant_reason = ptr;
1569 HOST_WIDE_INT begin_unneeded, const_s_width, const_width;
1570 if (known_subrange_p (s_info->offset, s_info->width, offset, width))
1571 /* The new store touches every byte that S_INFO does. */
1572 set_all_positions_unneeded (s_info);
1573 else if ((offset - s_info->offset).is_constant (&begin_unneeded)
1574 && s_info->width.is_constant (&const_s_width)
1575 && width.is_constant (&const_width))
1577 HOST_WIDE_INT end_unneeded = begin_unneeded + const_width;
1578 begin_unneeded = MAX (begin_unneeded, 0);
1579 end_unneeded = MIN (end_unneeded, const_s_width);
1580 for (i = begin_unneeded; i < end_unneeded; ++i)
1581 set_position_unneeded (s_info, i);
1583 else
1585 /* We don't know which parts of S_INFO are needed and
1586 which aren't, so invalidate the RHS. */
1587 s_info->rhs = NULL;
1588 s_info->const_rhs = NULL;
1591 else if (s_info->rhs)
1592 /* Need to see if it is possible for this store to overwrite
1593 the value of store_info. If it is, set the rhs to NULL to
1594 keep it from being used to remove a load. */
1596 if (canon_output_dependence (s_info->mem, true,
1597 mem, GET_MODE (mem),
1598 mem_addr))
1600 s_info->rhs = NULL;
1601 s_info->const_rhs = NULL;
1605 /* An insn can be deleted if every position of every one of
1606 its s_infos is zero. */
1607 if (any_positions_needed_p (s_info))
1608 del = false;
1610 if (del)
1612 insn_info_t insn_to_delete = ptr;
1614 active_local_stores_len--;
1615 if (last)
1616 last->next_local_store = ptr->next_local_store;
1617 else
1618 active_local_stores = ptr->next_local_store;
1620 if (!insn_to_delete->cannot_delete)
1621 delete_dead_store_insn (insn_to_delete);
1623 else
1624 last = ptr;
1626 ptr = next;
1629 /* Finish filling in the store_info. */
1630 store_info->next = insn_info->store_rec;
1631 insn_info->store_rec = store_info;
1632 store_info->mem = mem;
1633 store_info->mem_addr = mem_addr;
1634 store_info->cse_base = base;
1635 HOST_WIDE_INT const_width;
1636 if (!width.is_constant (&const_width))
1638 store_info->is_large = true;
1639 store_info->positions_needed.large.count = 0;
1640 store_info->positions_needed.large.bmap = NULL;
1642 else if (const_width > HOST_BITS_PER_WIDE_INT)
1644 store_info->is_large = true;
1645 store_info->positions_needed.large.count = 0;
1646 store_info->positions_needed.large.bmap = BITMAP_ALLOC (&dse_bitmap_obstack);
1648 else
1650 store_info->is_large = false;
1651 store_info->positions_needed.small_bitmask
1652 = lowpart_bitmask (const_width);
1654 store_info->group_id = group_id;
1655 store_info->offset = offset;
1656 store_info->width = width;
1657 store_info->is_set = GET_CODE (body) == SET;
1658 store_info->rhs = rhs;
1659 store_info->const_rhs = const_rhs;
1660 store_info->redundant_reason = redundant_reason;
1662 /* If this is a clobber, we return 0. We will only be able to
1663 delete this insn if there is only one store USED store, but we
1664 can use the clobber to delete other stores earlier. */
1665 return store_info->is_set ? 1 : 0;
1669 static void
1670 dump_insn_info (const char * start, insn_info_t insn_info)
1672 fprintf (dump_file, "%s insn=%d %s\n", start,
1673 INSN_UID (insn_info->insn),
1674 insn_info->store_rec ? "has store" : "naked");
1678 /* If the modes are different and the value's source and target do not
1679 line up, we need to extract the value from lower part of the rhs of
1680 the store, shift it, and then put it into a form that can be shoved
1681 into the read_insn. This function generates a right SHIFT of a
1682 value that is at least ACCESS_SIZE bytes wide of READ_MODE. The
1683 shift sequence is returned or NULL if we failed to find a
1684 shift. */
1686 static rtx
1687 find_shift_sequence (poly_int64 access_size,
1688 store_info *store_info,
1689 machine_mode read_mode,
1690 poly_int64 shift, bool speed, bool require_cst)
1692 machine_mode store_mode = GET_MODE (store_info->mem);
1693 scalar_int_mode new_mode;
1694 rtx read_reg = NULL;
1696 /* Some machines like the x86 have shift insns for each size of
1697 operand. Other machines like the ppc or the ia-64 may only have
1698 shift insns that shift values within 32 or 64 bit registers.
1699 This loop tries to find the smallest shift insn that will right
1700 justify the value we want to read but is available in one insn on
1701 the machine. */
1703 opt_scalar_int_mode new_mode_iter;
1704 FOR_EACH_MODE_FROM (new_mode_iter,
1705 smallest_int_mode_for_size (access_size * BITS_PER_UNIT))
1707 rtx target, new_reg, new_lhs;
1708 rtx_insn *shift_seq, *insn;
1709 int cost;
1711 new_mode = new_mode_iter.require ();
1712 if (GET_MODE_BITSIZE (new_mode) > BITS_PER_WORD)
1713 break;
1715 /* If a constant was stored into memory, try to simplify it here,
1716 otherwise the cost of the shift might preclude this optimization
1717 e.g. at -Os, even when no actual shift will be needed. */
1718 if (store_info->const_rhs)
1720 poly_uint64 byte = subreg_lowpart_offset (new_mode, store_mode);
1721 rtx ret = simplify_subreg (new_mode, store_info->const_rhs,
1722 store_mode, byte);
1723 if (ret && CONSTANT_P (ret))
1725 rtx shift_rtx = gen_int_shift_amount (new_mode, shift);
1726 ret = simplify_const_binary_operation (LSHIFTRT, new_mode,
1727 ret, shift_rtx);
1728 if (ret && CONSTANT_P (ret))
1730 byte = subreg_lowpart_offset (read_mode, new_mode);
1731 ret = simplify_subreg (read_mode, ret, new_mode, byte);
1732 if (ret && CONSTANT_P (ret)
1733 && (set_src_cost (ret, read_mode, speed)
1734 <= COSTS_N_INSNS (1)))
1735 return ret;
1740 if (require_cst)
1741 return NULL_RTX;
1743 /* Try a wider mode if truncating the store mode to NEW_MODE
1744 requires a real instruction. */
1745 if (maybe_lt (GET_MODE_SIZE (new_mode), GET_MODE_SIZE (store_mode))
1746 && !TRULY_NOOP_TRUNCATION_MODES_P (new_mode, store_mode))
1747 continue;
1749 /* Also try a wider mode if the necessary punning is either not
1750 desirable or not possible. */
1751 if (!CONSTANT_P (store_info->rhs)
1752 && !targetm.modes_tieable_p (new_mode, store_mode))
1753 continue;
1755 new_reg = gen_reg_rtx (new_mode);
1757 start_sequence ();
1759 /* In theory we could also check for an ashr. Ian Taylor knows
1760 of one dsp where the cost of these two was not the same. But
1761 this really is a rare case anyway. */
1762 target = expand_binop (new_mode, lshr_optab, new_reg,
1763 gen_int_shift_amount (new_mode, shift),
1764 new_reg, 1, OPTAB_DIRECT);
1766 shift_seq = get_insns ();
1767 end_sequence ();
1769 if (target != new_reg || shift_seq == NULL)
1770 continue;
1772 cost = 0;
1773 for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
1774 if (INSN_P (insn))
1775 cost += insn_cost (insn, speed);
1777 /* The computation up to here is essentially independent
1778 of the arguments and could be precomputed. It may
1779 not be worth doing so. We could precompute if
1780 worthwhile or at least cache the results. The result
1781 technically depends on both SHIFT and ACCESS_SIZE,
1782 but in practice the answer will depend only on ACCESS_SIZE. */
1784 if (cost > COSTS_N_INSNS (1))
1785 continue;
1787 new_lhs = extract_low_bits (new_mode, store_mode,
1788 copy_rtx (store_info->rhs));
1789 if (new_lhs == NULL_RTX)
1790 continue;
1792 /* We found an acceptable shift. Generate a move to
1793 take the value from the store and put it into the
1794 shift pseudo, then shift it, then generate another
1795 move to put in into the target of the read. */
1796 emit_move_insn (new_reg, new_lhs);
1797 emit_insn (shift_seq);
1798 read_reg = extract_low_bits (read_mode, new_mode, new_reg);
1799 break;
1802 return read_reg;
1806 /* Call back for note_stores to find the hard regs set or clobbered by
1807 insn. Data is a bitmap of the hardregs set so far. */
1809 static void
1810 look_for_hardregs (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
1812 bitmap regs_set = (bitmap) data;
1814 if (REG_P (x)
1815 && HARD_REGISTER_P (x))
1816 bitmap_set_range (regs_set, REGNO (x), REG_NREGS (x));
1819 /* Helper function for replace_read and record_store.
1820 Attempt to return a value of mode READ_MODE stored in STORE_INFO,
1821 consisting of READ_WIDTH bytes starting from READ_OFFSET. Return NULL
1822 if not successful. If REQUIRE_CST is true, return always constant. */
1824 static rtx
1825 get_stored_val (store_info *store_info, machine_mode read_mode,
1826 poly_int64 read_offset, poly_int64 read_width,
1827 basic_block bb, bool require_cst)
1829 machine_mode store_mode = GET_MODE (store_info->mem);
1830 poly_int64 gap;
1831 rtx read_reg;
1833 /* To get here the read is within the boundaries of the write so
1834 shift will never be negative. Start out with the shift being in
1835 bytes. */
1836 if (store_mode == BLKmode)
1837 gap = 0;
1838 else if (BYTES_BIG_ENDIAN)
1839 gap = ((store_info->offset + store_info->width)
1840 - (read_offset + read_width));
1841 else
1842 gap = read_offset - store_info->offset;
1844 if (maybe_ne (gap, 0))
1846 poly_int64 shift = gap * BITS_PER_UNIT;
1847 poly_int64 access_size = GET_MODE_SIZE (read_mode) + gap;
1848 read_reg = find_shift_sequence (access_size, store_info, read_mode,
1849 shift, optimize_bb_for_speed_p (bb),
1850 require_cst);
1852 else if (store_mode == BLKmode)
1854 /* The store is a memset (addr, const_val, const_size). */
1855 gcc_assert (CONST_INT_P (store_info->rhs));
1856 scalar_int_mode int_store_mode;
1857 if (!int_mode_for_mode (read_mode).exists (&int_store_mode))
1858 read_reg = NULL_RTX;
1859 else if (store_info->rhs == const0_rtx)
1860 read_reg = extract_low_bits (read_mode, int_store_mode, const0_rtx);
1861 else if (GET_MODE_BITSIZE (int_store_mode) > HOST_BITS_PER_WIDE_INT
1862 || BITS_PER_UNIT >= HOST_BITS_PER_WIDE_INT)
1863 read_reg = NULL_RTX;
1864 else
1866 unsigned HOST_WIDE_INT c
1867 = INTVAL (store_info->rhs)
1868 & ((HOST_WIDE_INT_1 << BITS_PER_UNIT) - 1);
1869 int shift = BITS_PER_UNIT;
1870 while (shift < HOST_BITS_PER_WIDE_INT)
1872 c |= (c << shift);
1873 shift <<= 1;
1875 read_reg = gen_int_mode (c, int_store_mode);
1876 read_reg = extract_low_bits (read_mode, int_store_mode, read_reg);
1879 else if (store_info->const_rhs
1880 && (require_cst
1881 || GET_MODE_CLASS (read_mode) != GET_MODE_CLASS (store_mode)))
1882 read_reg = extract_low_bits (read_mode, store_mode,
1883 copy_rtx (store_info->const_rhs));
1884 else
1885 read_reg = extract_low_bits (read_mode, store_mode,
1886 copy_rtx (store_info->rhs));
1887 if (require_cst && read_reg && !CONSTANT_P (read_reg))
1888 read_reg = NULL_RTX;
1889 return read_reg;
1892 /* Take a sequence of:
1893 A <- r1
1895 ... <- A
1897 and change it into
1898 r2 <- r1
1899 A <- r1
1901 ... <- r2
1905 r3 <- extract (r1)
1906 r3 <- r3 >> shift
1907 r2 <- extract (r3)
1908 ... <- r2
1912 r2 <- extract (r1)
1913 ... <- r2
1915 Depending on the alignment and the mode of the store and
1916 subsequent load.
1919 The STORE_INFO and STORE_INSN are for the store and READ_INFO
1920 and READ_INSN are for the read. Return true if the replacement
1921 went ok. */
1923 static bool
1924 replace_read (store_info *store_info, insn_info_t store_insn,
1925 read_info_t read_info, insn_info_t read_insn, rtx *loc,
1926 bitmap regs_live)
1928 machine_mode store_mode = GET_MODE (store_info->mem);
1929 machine_mode read_mode = GET_MODE (read_info->mem);
1930 rtx_insn *insns, *this_insn;
1931 rtx read_reg;
1932 basic_block bb;
1934 if (!dbg_cnt (dse))
1935 return false;
1937 /* Create a sequence of instructions to set up the read register.
1938 This sequence goes immediately before the store and its result
1939 is read by the load.
1941 We need to keep this in perspective. We are replacing a read
1942 with a sequence of insns, but the read will almost certainly be
1943 in cache, so it is not going to be an expensive one. Thus, we
1944 are not willing to do a multi insn shift or worse a subroutine
1945 call to get rid of the read. */
1946 if (dump_file && (dump_flags & TDF_DETAILS))
1947 fprintf (dump_file, "trying to replace %smode load in insn %d"
1948 " from %smode store in insn %d\n",
1949 GET_MODE_NAME (read_mode), INSN_UID (read_insn->insn),
1950 GET_MODE_NAME (store_mode), INSN_UID (store_insn->insn));
1951 start_sequence ();
1952 bb = BLOCK_FOR_INSN (read_insn->insn);
1953 read_reg = get_stored_val (store_info,
1954 read_mode, read_info->offset, read_info->width,
1955 bb, false);
1956 if (read_reg == NULL_RTX)
1958 end_sequence ();
1959 if (dump_file && (dump_flags & TDF_DETAILS))
1960 fprintf (dump_file, " -- could not extract bits of stored value\n");
1961 return false;
1963 /* Force the value into a new register so that it won't be clobbered
1964 between the store and the load. */
1965 read_reg = copy_to_mode_reg (read_mode, read_reg);
1966 insns = get_insns ();
1967 end_sequence ();
1969 if (insns != NULL_RTX)
1971 /* Now we have to scan the set of new instructions to see if the
1972 sequence contains and sets of hardregs that happened to be
1973 live at this point. For instance, this can happen if one of
1974 the insns sets the CC and the CC happened to be live at that
1975 point. This does occasionally happen, see PR 37922. */
1976 bitmap regs_set = BITMAP_ALLOC (&reg_obstack);
1978 for (this_insn = insns; this_insn != NULL_RTX; this_insn = NEXT_INSN (this_insn))
1979 note_stores (PATTERN (this_insn), look_for_hardregs, regs_set);
1981 bitmap_and_into (regs_set, regs_live);
1982 if (!bitmap_empty_p (regs_set))
1984 if (dump_file && (dump_flags & TDF_DETAILS))
1986 fprintf (dump_file,
1987 "abandoning replacement because sequence clobbers live hardregs:");
1988 df_print_regset (dump_file, regs_set);
1991 BITMAP_FREE (regs_set);
1992 return false;
1994 BITMAP_FREE (regs_set);
1997 if (validate_change (read_insn->insn, loc, read_reg, 0))
1999 deferred_change *change = deferred_change_pool.allocate ();
2001 /* Insert this right before the store insn where it will be safe
2002 from later insns that might change it before the read. */
2003 emit_insn_before (insns, store_insn->insn);
2005 /* And now for the kludge part: cselib croaks if you just
2006 return at this point. There are two reasons for this:
2008 1) Cselib has an idea of how many pseudos there are and
2009 that does not include the new ones we just added.
2011 2) Cselib does not know about the move insn we added
2012 above the store_info, and there is no way to tell it
2013 about it, because it has "moved on".
2015 Problem (1) is fixable with a certain amount of engineering.
2016 Problem (2) is requires starting the bb from scratch. This
2017 could be expensive.
2019 So we are just going to have to lie. The move/extraction
2020 insns are not really an issue, cselib did not see them. But
2021 the use of the new pseudo read_insn is a real problem because
2022 cselib has not scanned this insn. The way that we solve this
2023 problem is that we are just going to put the mem back for now
2024 and when we are finished with the block, we undo this. We
2025 keep a table of mems to get rid of. At the end of the basic
2026 block we can put them back. */
2028 *loc = read_info->mem;
2029 change->next = deferred_change_list;
2030 deferred_change_list = change;
2031 change->loc = loc;
2032 change->reg = read_reg;
2034 /* Get rid of the read_info, from the point of view of the
2035 rest of dse, play like this read never happened. */
2036 read_insn->read_rec = read_info->next;
2037 read_info_type_pool.remove (read_info);
2038 if (dump_file && (dump_flags & TDF_DETAILS))
2040 fprintf (dump_file, " -- replaced the loaded MEM with ");
2041 print_simple_rtl (dump_file, read_reg);
2042 fprintf (dump_file, "\n");
2044 return true;
2046 else
2048 if (dump_file && (dump_flags & TDF_DETAILS))
2050 fprintf (dump_file, " -- replacing the loaded MEM with ");
2051 print_simple_rtl (dump_file, read_reg);
2052 fprintf (dump_file, " led to an invalid instruction\n");
2054 return false;
2058 /* Check the address of MEM *LOC and kill any appropriate stores that may
2059 be active. */
2061 static void
2062 check_mem_read_rtx (rtx *loc, bb_info_t bb_info)
2064 rtx mem = *loc, mem_addr;
2065 insn_info_t insn_info;
2066 poly_int64 offset = 0;
2067 poly_int64 width = 0;
2068 cselib_val *base = NULL;
2069 int group_id;
2070 read_info_t read_info;
2072 insn_info = bb_info->last_insn;
2074 if ((MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2075 || (MEM_VOLATILE_P (mem)))
2077 if (dump_file && (dump_flags & TDF_DETAILS))
2078 fprintf (dump_file, " adding wild read, volatile or barrier.\n");
2079 add_wild_read (bb_info);
2080 insn_info->cannot_delete = true;
2081 return;
2084 /* If it is reading readonly mem, then there can be no conflict with
2085 another write. */
2086 if (MEM_READONLY_P (mem))
2087 return;
2089 if (!canon_address (mem, &group_id, &offset, &base))
2091 if (dump_file && (dump_flags & TDF_DETAILS))
2092 fprintf (dump_file, " adding wild read, canon_address failure.\n");
2093 add_wild_read (bb_info);
2094 return;
2097 if (GET_MODE (mem) == BLKmode)
2098 width = -1;
2099 else
2100 width = GET_MODE_SIZE (GET_MODE (mem));
2102 if (!endpoint_representable_p (offset, known_eq (width, -1) ? 1 : width))
2104 if (dump_file && (dump_flags & TDF_DETAILS))
2105 fprintf (dump_file, " adding wild read, due to overflow.\n");
2106 add_wild_read (bb_info);
2107 return;
2110 read_info = read_info_type_pool.allocate ();
2111 read_info->group_id = group_id;
2112 read_info->mem = mem;
2113 read_info->offset = offset;
2114 read_info->width = width;
2115 read_info->next = insn_info->read_rec;
2116 insn_info->read_rec = read_info;
2117 if (group_id < 0)
2118 mem_addr = base->val_rtx;
2119 else
2121 group_info *group = rtx_group_vec[group_id];
2122 mem_addr = group->canon_base_addr;
2124 if (maybe_ne (offset, 0))
2125 mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
2127 if (group_id >= 0)
2129 /* This is the restricted case where the base is a constant or
2130 the frame pointer and offset is a constant. */
2131 insn_info_t i_ptr = active_local_stores;
2132 insn_info_t last = NULL;
2134 if (dump_file && (dump_flags & TDF_DETAILS))
2136 if (!known_size_p (width))
2137 fprintf (dump_file, " processing const load gid=%d[BLK]\n",
2138 group_id);
2139 else
2141 fprintf (dump_file, " processing const load gid=%d", group_id);
2142 print_range (dump_file, offset, width);
2143 fprintf (dump_file, "\n");
2147 while (i_ptr)
2149 bool remove = false;
2150 store_info *store_info = i_ptr->store_rec;
2152 /* Skip the clobbers. */
2153 while (!store_info->is_set)
2154 store_info = store_info->next;
2156 /* There are three cases here. */
2157 if (store_info->group_id < 0)
2158 /* We have a cselib store followed by a read from a
2159 const base. */
2160 remove
2161 = canon_true_dependence (store_info->mem,
2162 GET_MODE (store_info->mem),
2163 store_info->mem_addr,
2164 mem, mem_addr);
2166 else if (group_id == store_info->group_id)
2168 /* This is a block mode load. We may get lucky and
2169 canon_true_dependence may save the day. */
2170 if (!known_size_p (width))
2171 remove
2172 = canon_true_dependence (store_info->mem,
2173 GET_MODE (store_info->mem),
2174 store_info->mem_addr,
2175 mem, mem_addr);
2177 /* If this read is just reading back something that we just
2178 stored, rewrite the read. */
2179 else
2181 if (store_info->rhs
2182 && known_subrange_p (offset, width, store_info->offset,
2183 store_info->width)
2184 && all_positions_needed_p (store_info,
2185 offset - store_info->offset,
2186 width)
2187 && replace_read (store_info, i_ptr, read_info,
2188 insn_info, loc, bb_info->regs_live))
2189 return;
2191 /* The bases are the same, just see if the offsets
2192 could overlap. */
2193 if (ranges_maybe_overlap_p (offset, width,
2194 store_info->offset,
2195 store_info->width))
2196 remove = true;
2200 /* else
2201 The else case that is missing here is that the
2202 bases are constant but different. There is nothing
2203 to do here because there is no overlap. */
2205 if (remove)
2207 if (dump_file && (dump_flags & TDF_DETAILS))
2208 dump_insn_info ("removing from active", i_ptr);
2210 active_local_stores_len--;
2211 if (last)
2212 last->next_local_store = i_ptr->next_local_store;
2213 else
2214 active_local_stores = i_ptr->next_local_store;
2216 else
2217 last = i_ptr;
2218 i_ptr = i_ptr->next_local_store;
2221 else
2223 insn_info_t i_ptr = active_local_stores;
2224 insn_info_t last = NULL;
2225 if (dump_file && (dump_flags & TDF_DETAILS))
2227 fprintf (dump_file, " processing cselib load mem:");
2228 print_inline_rtx (dump_file, mem, 0);
2229 fprintf (dump_file, "\n");
2232 while (i_ptr)
2234 bool remove = false;
2235 store_info *store_info = i_ptr->store_rec;
2237 if (dump_file && (dump_flags & TDF_DETAILS))
2238 fprintf (dump_file, " processing cselib load against insn %d\n",
2239 INSN_UID (i_ptr->insn));
2241 /* Skip the clobbers. */
2242 while (!store_info->is_set)
2243 store_info = store_info->next;
2245 /* If this read is just reading back something that we just
2246 stored, rewrite the read. */
2247 if (store_info->rhs
2248 && store_info->group_id == -1
2249 && store_info->cse_base == base
2250 && known_subrange_p (offset, width, store_info->offset,
2251 store_info->width)
2252 && all_positions_needed_p (store_info,
2253 offset - store_info->offset, width)
2254 && replace_read (store_info, i_ptr, read_info, insn_info, loc,
2255 bb_info->regs_live))
2256 return;
2258 remove = canon_true_dependence (store_info->mem,
2259 GET_MODE (store_info->mem),
2260 store_info->mem_addr,
2261 mem, mem_addr);
2263 if (remove)
2265 if (dump_file && (dump_flags & TDF_DETAILS))
2266 dump_insn_info ("removing from active", i_ptr);
2268 active_local_stores_len--;
2269 if (last)
2270 last->next_local_store = i_ptr->next_local_store;
2271 else
2272 active_local_stores = i_ptr->next_local_store;
2274 else
2275 last = i_ptr;
2276 i_ptr = i_ptr->next_local_store;
2281 /* A note_uses callback in which DATA points the INSN_INFO for
2282 as check_mem_read_rtx. Nullify the pointer if i_m_r_m_r returns
2283 true for any part of *LOC. */
2285 static void
2286 check_mem_read_use (rtx *loc, void *data)
2288 subrtx_ptr_iterator::array_type array;
2289 FOR_EACH_SUBRTX_PTR (iter, array, loc, NONCONST)
2291 rtx *loc = *iter;
2292 if (MEM_P (*loc))
2293 check_mem_read_rtx (loc, (bb_info_t) data);
2298 /* Get arguments passed to CALL_INSN. Return TRUE if successful.
2299 So far it only handles arguments passed in registers. */
2301 static bool
2302 get_call_args (rtx call_insn, tree fn, rtx *args, int nargs)
2304 CUMULATIVE_ARGS args_so_far_v;
2305 cumulative_args_t args_so_far;
2306 tree arg;
2307 int idx;
2309 INIT_CUMULATIVE_ARGS (args_so_far_v, TREE_TYPE (fn), NULL_RTX, 0, 3);
2310 args_so_far = pack_cumulative_args (&args_so_far_v);
2312 arg = TYPE_ARG_TYPES (TREE_TYPE (fn));
2313 for (idx = 0;
2314 arg != void_list_node && idx < nargs;
2315 arg = TREE_CHAIN (arg), idx++)
2317 scalar_int_mode mode;
2318 rtx reg, link, tmp;
2320 if (!is_int_mode (TYPE_MODE (TREE_VALUE (arg)), &mode))
2321 return false;
2323 reg = targetm.calls.function_arg (args_so_far, mode, NULL_TREE, true);
2324 if (!reg || !REG_P (reg) || GET_MODE (reg) != mode)
2325 return false;
2327 for (link = CALL_INSN_FUNCTION_USAGE (call_insn);
2328 link;
2329 link = XEXP (link, 1))
2330 if (GET_CODE (XEXP (link, 0)) == USE)
2332 scalar_int_mode arg_mode;
2333 args[idx] = XEXP (XEXP (link, 0), 0);
2334 if (REG_P (args[idx])
2335 && REGNO (args[idx]) == REGNO (reg)
2336 && (GET_MODE (args[idx]) == mode
2337 || (is_int_mode (GET_MODE (args[idx]), &arg_mode)
2338 && (GET_MODE_SIZE (arg_mode) <= UNITS_PER_WORD)
2339 && (GET_MODE_SIZE (arg_mode) > GET_MODE_SIZE (mode)))))
2340 break;
2342 if (!link)
2343 return false;
2345 tmp = cselib_expand_value_rtx (args[idx], scratch, 5);
2346 if (GET_MODE (args[idx]) != mode)
2348 if (!tmp || !CONST_INT_P (tmp))
2349 return false;
2350 tmp = gen_int_mode (INTVAL (tmp), mode);
2352 if (tmp)
2353 args[idx] = tmp;
2355 targetm.calls.function_arg_advance (args_so_far, mode, NULL_TREE, true);
2357 if (arg != void_list_node || idx != nargs)
2358 return false;
2359 return true;
2362 /* Return a bitmap of the fixed registers contained in IN. */
2364 static bitmap
2365 copy_fixed_regs (const_bitmap in)
2367 bitmap ret;
2369 ret = ALLOC_REG_SET (NULL);
2370 bitmap_and (ret, in, fixed_reg_set_regset);
2371 return ret;
2374 /* Apply record_store to all candidate stores in INSN. Mark INSN
2375 if some part of it is not a candidate store and assigns to a
2376 non-register target. */
2378 static void
2379 scan_insn (bb_info_t bb_info, rtx_insn *insn)
2381 rtx body;
2382 insn_info_type *insn_info = insn_info_type_pool.allocate ();
2383 int mems_found = 0;
2384 memset (insn_info, 0, sizeof (struct insn_info_type));
2386 if (dump_file && (dump_flags & TDF_DETAILS))
2387 fprintf (dump_file, "\n**scanning insn=%d\n",
2388 INSN_UID (insn));
2390 insn_info->prev_insn = bb_info->last_insn;
2391 insn_info->insn = insn;
2392 bb_info->last_insn = insn_info;
2394 if (DEBUG_INSN_P (insn))
2396 insn_info->cannot_delete = true;
2397 return;
2400 /* Look at all of the uses in the insn. */
2401 note_uses (&PATTERN (insn), check_mem_read_use, bb_info);
2403 if (CALL_P (insn))
2405 bool const_call;
2406 rtx call, sym;
2407 tree memset_call = NULL_TREE;
2409 insn_info->cannot_delete = true;
2411 /* Const functions cannot do anything bad i.e. read memory,
2412 however, they can read their parameters which may have
2413 been pushed onto the stack.
2414 memset and bzero don't read memory either. */
2415 const_call = RTL_CONST_CALL_P (insn);
2416 if (!const_call
2417 && (call = get_call_rtx_from (insn))
2418 && (sym = XEXP (XEXP (call, 0), 0))
2419 && GET_CODE (sym) == SYMBOL_REF
2420 && SYMBOL_REF_DECL (sym)
2421 && TREE_CODE (SYMBOL_REF_DECL (sym)) == FUNCTION_DECL
2422 && fndecl_built_in_p (SYMBOL_REF_DECL (sym), BUILT_IN_MEMSET))
2423 memset_call = SYMBOL_REF_DECL (sym);
2425 if (const_call || memset_call)
2427 insn_info_t i_ptr = active_local_stores;
2428 insn_info_t last = NULL;
2430 if (dump_file && (dump_flags & TDF_DETAILS))
2431 fprintf (dump_file, "%s call %d\n",
2432 const_call ? "const" : "memset", INSN_UID (insn));
2434 /* See the head comment of the frame_read field. */
2435 if (reload_completed
2436 /* Tail calls are storing their arguments using
2437 arg pointer. If it is a frame pointer on the target,
2438 even before reload we need to kill frame pointer based
2439 stores. */
2440 || (SIBLING_CALL_P (insn)
2441 && HARD_FRAME_POINTER_IS_ARG_POINTER))
2442 insn_info->frame_read = true;
2444 /* Loop over the active stores and remove those which are
2445 killed by the const function call. */
2446 while (i_ptr)
2448 bool remove_store = false;
2450 /* The stack pointer based stores are always killed. */
2451 if (i_ptr->stack_pointer_based)
2452 remove_store = true;
2454 /* If the frame is read, the frame related stores are killed. */
2455 else if (insn_info->frame_read)
2457 store_info *store_info = i_ptr->store_rec;
2459 /* Skip the clobbers. */
2460 while (!store_info->is_set)
2461 store_info = store_info->next;
2463 if (store_info->group_id >= 0
2464 && rtx_group_vec[store_info->group_id]->frame_related)
2465 remove_store = true;
2468 if (remove_store)
2470 if (dump_file && (dump_flags & TDF_DETAILS))
2471 dump_insn_info ("removing from active", i_ptr);
2473 active_local_stores_len--;
2474 if (last)
2475 last->next_local_store = i_ptr->next_local_store;
2476 else
2477 active_local_stores = i_ptr->next_local_store;
2479 else
2480 last = i_ptr;
2482 i_ptr = i_ptr->next_local_store;
2485 if (memset_call)
2487 rtx args[3];
2488 if (get_call_args (insn, memset_call, args, 3)
2489 && CONST_INT_P (args[1])
2490 && CONST_INT_P (args[2])
2491 && INTVAL (args[2]) > 0)
2493 rtx mem = gen_rtx_MEM (BLKmode, args[0]);
2494 set_mem_size (mem, INTVAL (args[2]));
2495 body = gen_rtx_SET (mem, args[1]);
2496 mems_found += record_store (body, bb_info);
2497 if (dump_file && (dump_flags & TDF_DETAILS))
2498 fprintf (dump_file, "handling memset as BLKmode store\n");
2499 if (mems_found == 1)
2501 if (active_local_stores_len++
2502 >= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
2504 active_local_stores_len = 1;
2505 active_local_stores = NULL;
2507 insn_info->fixed_regs_live
2508 = copy_fixed_regs (bb_info->regs_live);
2509 insn_info->next_local_store = active_local_stores;
2510 active_local_stores = insn_info;
2513 else
2514 clear_rhs_from_active_local_stores ();
2517 else if (SIBLING_CALL_P (insn) && reload_completed)
2518 /* Arguments for a sibling call that are pushed to memory are passed
2519 using the incoming argument pointer of the current function. After
2520 reload that might be (and likely is) frame pointer based. */
2521 add_wild_read (bb_info);
2522 else
2523 /* Every other call, including pure functions, may read any memory
2524 that is not relative to the frame. */
2525 add_non_frame_wild_read (bb_info);
2527 return;
2530 /* Assuming that there are sets in these insns, we cannot delete
2531 them. */
2532 if ((GET_CODE (PATTERN (insn)) == CLOBBER)
2533 || volatile_refs_p (PATTERN (insn))
2534 || (!cfun->can_delete_dead_exceptions && !insn_nothrow_p (insn))
2535 || (RTX_FRAME_RELATED_P (insn))
2536 || find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX))
2537 insn_info->cannot_delete = true;
2539 body = PATTERN (insn);
2540 if (GET_CODE (body) == PARALLEL)
2542 int i;
2543 for (i = 0; i < XVECLEN (body, 0); i++)
2544 mems_found += record_store (XVECEXP (body, 0, i), bb_info);
2546 else
2547 mems_found += record_store (body, bb_info);
2549 if (dump_file && (dump_flags & TDF_DETAILS))
2550 fprintf (dump_file, "mems_found = %d, cannot_delete = %s\n",
2551 mems_found, insn_info->cannot_delete ? "true" : "false");
2553 /* If we found some sets of mems, add it into the active_local_stores so
2554 that it can be locally deleted if found dead or used for
2555 replace_read and redundant constant store elimination. Otherwise mark
2556 it as cannot delete. This simplifies the processing later. */
2557 if (mems_found == 1)
2559 if (active_local_stores_len++
2560 >= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
2562 active_local_stores_len = 1;
2563 active_local_stores = NULL;
2565 insn_info->fixed_regs_live = copy_fixed_regs (bb_info->regs_live);
2566 insn_info->next_local_store = active_local_stores;
2567 active_local_stores = insn_info;
2569 else
2570 insn_info->cannot_delete = true;
2574 /* Remove BASE from the set of active_local_stores. This is a
2575 callback from cselib that is used to get rid of the stores in
2576 active_local_stores. */
2578 static void
2579 remove_useless_values (cselib_val *base)
2581 insn_info_t insn_info = active_local_stores;
2582 insn_info_t last = NULL;
2584 while (insn_info)
2586 store_info *store_info = insn_info->store_rec;
2587 bool del = false;
2589 /* If ANY of the store_infos match the cselib group that is
2590 being deleted, then the insn can not be deleted. */
2591 while (store_info)
2593 if ((store_info->group_id == -1)
2594 && (store_info->cse_base == base))
2596 del = true;
2597 break;
2599 store_info = store_info->next;
2602 if (del)
2604 active_local_stores_len--;
2605 if (last)
2606 last->next_local_store = insn_info->next_local_store;
2607 else
2608 active_local_stores = insn_info->next_local_store;
2609 free_store_info (insn_info);
2611 else
2612 last = insn_info;
2614 insn_info = insn_info->next_local_store;
2619 /* Do all of step 1. */
2621 static void
2622 dse_step1 (void)
2624 basic_block bb;
2625 bitmap regs_live = BITMAP_ALLOC (&reg_obstack);
2627 cselib_init (0);
2628 all_blocks = BITMAP_ALLOC (NULL);
2629 bitmap_set_bit (all_blocks, ENTRY_BLOCK);
2630 bitmap_set_bit (all_blocks, EXIT_BLOCK);
2632 FOR_ALL_BB_FN (bb, cfun)
2634 insn_info_t ptr;
2635 bb_info_t bb_info = dse_bb_info_type_pool.allocate ();
2637 memset (bb_info, 0, sizeof (dse_bb_info_type));
2638 bitmap_set_bit (all_blocks, bb->index);
2639 bb_info->regs_live = regs_live;
2641 bitmap_copy (regs_live, DF_LR_IN (bb));
2642 df_simulate_initialize_forwards (bb, regs_live);
2644 bb_table[bb->index] = bb_info;
2645 cselib_discard_hook = remove_useless_values;
2647 if (bb->index >= NUM_FIXED_BLOCKS)
2649 rtx_insn *insn;
2651 active_local_stores = NULL;
2652 active_local_stores_len = 0;
2653 cselib_clear_table ();
2655 /* Scan the insns. */
2656 FOR_BB_INSNS (bb, insn)
2658 if (INSN_P (insn))
2659 scan_insn (bb_info, insn);
2660 cselib_process_insn (insn);
2661 if (INSN_P (insn))
2662 df_simulate_one_insn_forwards (bb, insn, regs_live);
2665 /* This is something of a hack, because the global algorithm
2666 is supposed to take care of the case where stores go dead
2667 at the end of the function. However, the global
2668 algorithm must take a more conservative view of block
2669 mode reads than the local alg does. So to get the case
2670 where you have a store to the frame followed by a non
2671 overlapping block more read, we look at the active local
2672 stores at the end of the function and delete all of the
2673 frame and spill based ones. */
2674 if (stores_off_frame_dead_at_return
2675 && (EDGE_COUNT (bb->succs) == 0
2676 || (single_succ_p (bb)
2677 && single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)
2678 && ! crtl->calls_eh_return)))
2680 insn_info_t i_ptr = active_local_stores;
2681 while (i_ptr)
2683 store_info *store_info = i_ptr->store_rec;
2685 /* Skip the clobbers. */
2686 while (!store_info->is_set)
2687 store_info = store_info->next;
2688 if (store_info->group_id >= 0)
2690 group_info *group = rtx_group_vec[store_info->group_id];
2691 if (group->frame_related && !i_ptr->cannot_delete)
2692 delete_dead_store_insn (i_ptr);
2695 i_ptr = i_ptr->next_local_store;
2699 /* Get rid of the loads that were discovered in
2700 replace_read. Cselib is finished with this block. */
2701 while (deferred_change_list)
2703 deferred_change *next = deferred_change_list->next;
2705 /* There is no reason to validate this change. That was
2706 done earlier. */
2707 *deferred_change_list->loc = deferred_change_list->reg;
2708 deferred_change_pool.remove (deferred_change_list);
2709 deferred_change_list = next;
2712 /* Get rid of all of the cselib based store_infos in this
2713 block and mark the containing insns as not being
2714 deletable. */
2715 ptr = bb_info->last_insn;
2716 while (ptr)
2718 if (ptr->contains_cselib_groups)
2720 store_info *s_info = ptr->store_rec;
2721 while (s_info && !s_info->is_set)
2722 s_info = s_info->next;
2723 if (s_info
2724 && s_info->redundant_reason
2725 && s_info->redundant_reason->insn
2726 && !ptr->cannot_delete)
2728 if (dump_file && (dump_flags & TDF_DETAILS))
2729 fprintf (dump_file, "Locally deleting insn %d "
2730 "because insn %d stores the "
2731 "same value and couldn't be "
2732 "eliminated\n",
2733 INSN_UID (ptr->insn),
2734 INSN_UID (s_info->redundant_reason->insn));
2735 delete_dead_store_insn (ptr);
2737 free_store_info (ptr);
2739 else
2741 store_info *s_info;
2743 /* Free at least positions_needed bitmaps. */
2744 for (s_info = ptr->store_rec; s_info; s_info = s_info->next)
2745 if (s_info->is_large)
2747 BITMAP_FREE (s_info->positions_needed.large.bmap);
2748 s_info->is_large = false;
2751 ptr = ptr->prev_insn;
2754 cse_store_info_pool.release ();
2756 bb_info->regs_live = NULL;
2759 BITMAP_FREE (regs_live);
2760 cselib_finish ();
2761 rtx_group_table->empty ();
2765 /*----------------------------------------------------------------------------
2766 Second step.
2768 Assign each byte position in the stores that we are going to
2769 analyze globally to a position in the bitmaps. Returns true if
2770 there are any bit positions assigned.
2771 ----------------------------------------------------------------------------*/
2773 static void
2774 dse_step2_init (void)
2776 unsigned int i;
2777 group_info *group;
2779 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2781 /* For all non stack related bases, we only consider a store to
2782 be deletable if there are two or more stores for that
2783 position. This is because it takes one store to make the
2784 other store redundant. However, for the stores that are
2785 stack related, we consider them if there is only one store
2786 for the position. We do this because the stack related
2787 stores can be deleted if their is no read between them and
2788 the end of the function.
2790 To make this work in the current framework, we take the stack
2791 related bases add all of the bits from store1 into store2.
2792 This has the effect of making the eligible even if there is
2793 only one store. */
2795 if (stores_off_frame_dead_at_return && group->frame_related)
2797 bitmap_ior_into (group->store2_n, group->store1_n);
2798 bitmap_ior_into (group->store2_p, group->store1_p);
2799 if (dump_file && (dump_flags & TDF_DETAILS))
2800 fprintf (dump_file, "group %d is frame related ", i);
2803 group->offset_map_size_n++;
2804 group->offset_map_n = XOBNEWVEC (&dse_obstack, int,
2805 group->offset_map_size_n);
2806 group->offset_map_size_p++;
2807 group->offset_map_p = XOBNEWVEC (&dse_obstack, int,
2808 group->offset_map_size_p);
2809 group->process_globally = false;
2810 if (dump_file && (dump_flags & TDF_DETAILS))
2812 fprintf (dump_file, "group %d(%d+%d): ", i,
2813 (int)bitmap_count_bits (group->store2_n),
2814 (int)bitmap_count_bits (group->store2_p));
2815 bitmap_print (dump_file, group->store2_n, "n ", " ");
2816 bitmap_print (dump_file, group->store2_p, "p ", "\n");
2822 /* Init the offset tables. */
2824 static bool
2825 dse_step2 (void)
2827 unsigned int i;
2828 group_info *group;
2829 /* Position 0 is unused because 0 is used in the maps to mean
2830 unused. */
2831 current_position = 1;
2832 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2834 bitmap_iterator bi;
2835 unsigned int j;
2837 memset (group->offset_map_n, 0, sizeof (int) * group->offset_map_size_n);
2838 memset (group->offset_map_p, 0, sizeof (int) * group->offset_map_size_p);
2839 bitmap_clear (group->group_kill);
2841 EXECUTE_IF_SET_IN_BITMAP (group->store2_n, 0, j, bi)
2843 bitmap_set_bit (group->group_kill, current_position);
2844 if (bitmap_bit_p (group->escaped_n, j))
2845 bitmap_set_bit (kill_on_calls, current_position);
2846 group->offset_map_n[j] = current_position++;
2847 group->process_globally = true;
2849 EXECUTE_IF_SET_IN_BITMAP (group->store2_p, 0, j, bi)
2851 bitmap_set_bit (group->group_kill, current_position);
2852 if (bitmap_bit_p (group->escaped_p, j))
2853 bitmap_set_bit (kill_on_calls, current_position);
2854 group->offset_map_p[j] = current_position++;
2855 group->process_globally = true;
2858 return current_position != 1;
2863 /*----------------------------------------------------------------------------
2864 Third step.
2866 Build the bit vectors for the transfer functions.
2867 ----------------------------------------------------------------------------*/
2870 /* Look up the bitmap index for OFFSET in GROUP_INFO. If it is not
2871 there, return 0. */
2873 static int
2874 get_bitmap_index (group_info *group_info, HOST_WIDE_INT offset)
2876 if (offset < 0)
2878 HOST_WIDE_INT offset_p = -offset;
2879 if (offset_p >= group_info->offset_map_size_n)
2880 return 0;
2881 return group_info->offset_map_n[offset_p];
2883 else
2885 if (offset >= group_info->offset_map_size_p)
2886 return 0;
2887 return group_info->offset_map_p[offset];
2892 /* Process the STORE_INFOs into the bitmaps into GEN and KILL. KILL
2893 may be NULL. */
2895 static void
2896 scan_stores (store_info *store_info, bitmap gen, bitmap kill)
2898 while (store_info)
2900 HOST_WIDE_INT i, offset, width;
2901 group_info *group_info
2902 = rtx_group_vec[store_info->group_id];
2903 /* We can (conservatively) ignore stores whose bounds aren't known;
2904 they simply don't generate new global dse opportunities. */
2905 if (group_info->process_globally
2906 && store_info->offset.is_constant (&offset)
2907 && store_info->width.is_constant (&width))
2909 HOST_WIDE_INT end = offset + width;
2910 for (i = offset; i < end; i++)
2912 int index = get_bitmap_index (group_info, i);
2913 if (index != 0)
2915 bitmap_set_bit (gen, index);
2916 if (kill)
2917 bitmap_clear_bit (kill, index);
2921 store_info = store_info->next;
2926 /* Process the READ_INFOs into the bitmaps into GEN and KILL. KILL
2927 may be NULL. */
2929 static void
2930 scan_reads (insn_info_t insn_info, bitmap gen, bitmap kill)
2932 read_info_t read_info = insn_info->read_rec;
2933 int i;
2934 group_info *group;
2936 /* If this insn reads the frame, kill all the frame related stores. */
2937 if (insn_info->frame_read)
2939 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2940 if (group->process_globally && group->frame_related)
2942 if (kill)
2943 bitmap_ior_into (kill, group->group_kill);
2944 bitmap_and_compl_into (gen, group->group_kill);
2947 if (insn_info->non_frame_wild_read)
2949 /* Kill all non-frame related stores. Kill all stores of variables that
2950 escape. */
2951 if (kill)
2952 bitmap_ior_into (kill, kill_on_calls);
2953 bitmap_and_compl_into (gen, kill_on_calls);
2954 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2955 if (group->process_globally && !group->frame_related)
2957 if (kill)
2958 bitmap_ior_into (kill, group->group_kill);
2959 bitmap_and_compl_into (gen, group->group_kill);
2962 while (read_info)
2964 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2966 if (group->process_globally)
2968 if (i == read_info->group_id)
2970 HOST_WIDE_INT offset, width;
2971 /* Reads with non-constant size kill all DSE opportunities
2972 in the group. */
2973 if (!read_info->offset.is_constant (&offset)
2974 || !read_info->width.is_constant (&width)
2975 || !known_size_p (width))
2977 /* Handle block mode reads. */
2978 if (kill)
2979 bitmap_ior_into (kill, group->group_kill);
2980 bitmap_and_compl_into (gen, group->group_kill);
2982 else
2984 /* The groups are the same, just process the
2985 offsets. */
2986 HOST_WIDE_INT j;
2987 HOST_WIDE_INT end = offset + width;
2988 for (j = offset; j < end; j++)
2990 int index = get_bitmap_index (group, j);
2991 if (index != 0)
2993 if (kill)
2994 bitmap_set_bit (kill, index);
2995 bitmap_clear_bit (gen, index);
3000 else
3002 /* The groups are different, if the alias sets
3003 conflict, clear the entire group. We only need
3004 to apply this test if the read_info is a cselib
3005 read. Anything with a constant base cannot alias
3006 something else with a different constant
3007 base. */
3008 if ((read_info->group_id < 0)
3009 && canon_true_dependence (group->base_mem,
3010 GET_MODE (group->base_mem),
3011 group->canon_base_addr,
3012 read_info->mem, NULL_RTX))
3014 if (kill)
3015 bitmap_ior_into (kill, group->group_kill);
3016 bitmap_and_compl_into (gen, group->group_kill);
3022 read_info = read_info->next;
3027 /* Return the insn in BB_INFO before the first wild read or if there
3028 are no wild reads in the block, return the last insn. */
3030 static insn_info_t
3031 find_insn_before_first_wild_read (bb_info_t bb_info)
3033 insn_info_t insn_info = bb_info->last_insn;
3034 insn_info_t last_wild_read = NULL;
3036 while (insn_info)
3038 if (insn_info->wild_read)
3040 last_wild_read = insn_info->prev_insn;
3041 /* Block starts with wild read. */
3042 if (!last_wild_read)
3043 return NULL;
3046 insn_info = insn_info->prev_insn;
3049 if (last_wild_read)
3050 return last_wild_read;
3051 else
3052 return bb_info->last_insn;
3056 /* Scan the insns in BB_INFO starting at PTR and going to the top of
3057 the block in order to build the gen and kill sets for the block.
3058 We start at ptr which may be the last insn in the block or may be
3059 the first insn with a wild read. In the latter case we are able to
3060 skip the rest of the block because it just does not matter:
3061 anything that happens is hidden by the wild read. */
3063 static void
3064 dse_step3_scan (basic_block bb)
3066 bb_info_t bb_info = bb_table[bb->index];
3067 insn_info_t insn_info;
3069 insn_info = find_insn_before_first_wild_read (bb_info);
3071 /* In the spill case or in the no_spill case if there is no wild
3072 read in the block, we will need a kill set. */
3073 if (insn_info == bb_info->last_insn)
3075 if (bb_info->kill)
3076 bitmap_clear (bb_info->kill);
3077 else
3078 bb_info->kill = BITMAP_ALLOC (&dse_bitmap_obstack);
3080 else
3081 if (bb_info->kill)
3082 BITMAP_FREE (bb_info->kill);
3084 while (insn_info)
3086 /* There may have been code deleted by the dce pass run before
3087 this phase. */
3088 if (insn_info->insn && INSN_P (insn_info->insn))
3090 scan_stores (insn_info->store_rec, bb_info->gen, bb_info->kill);
3091 scan_reads (insn_info, bb_info->gen, bb_info->kill);
3094 insn_info = insn_info->prev_insn;
3099 /* Set the gen set of the exit block, and also any block with no
3100 successors that does not have a wild read. */
3102 static void
3103 dse_step3_exit_block_scan (bb_info_t bb_info)
3105 /* The gen set is all 0's for the exit block except for the
3106 frame_pointer_group. */
3108 if (stores_off_frame_dead_at_return)
3110 unsigned int i;
3111 group_info *group;
3113 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
3115 if (group->process_globally && group->frame_related)
3116 bitmap_ior_into (bb_info->gen, group->group_kill);
3122 /* Find all of the blocks that are not backwards reachable from the
3123 exit block or any block with no successors (BB). These are the
3124 infinite loops or infinite self loops. These blocks will still
3125 have their bits set in UNREACHABLE_BLOCKS. */
3127 static void
3128 mark_reachable_blocks (sbitmap unreachable_blocks, basic_block bb)
3130 edge e;
3131 edge_iterator ei;
3133 if (bitmap_bit_p (unreachable_blocks, bb->index))
3135 bitmap_clear_bit (unreachable_blocks, bb->index);
3136 FOR_EACH_EDGE (e, ei, bb->preds)
3138 mark_reachable_blocks (unreachable_blocks, e->src);
3143 /* Build the transfer functions for the function. */
3145 static void
3146 dse_step3 ()
3148 basic_block bb;
3149 sbitmap_iterator sbi;
3150 bitmap all_ones = NULL;
3151 unsigned int i;
3153 auto_sbitmap unreachable_blocks (last_basic_block_for_fn (cfun));
3154 bitmap_ones (unreachable_blocks);
3156 FOR_ALL_BB_FN (bb, cfun)
3158 bb_info_t bb_info = bb_table[bb->index];
3159 if (bb_info->gen)
3160 bitmap_clear (bb_info->gen);
3161 else
3162 bb_info->gen = BITMAP_ALLOC (&dse_bitmap_obstack);
3164 if (bb->index == ENTRY_BLOCK)
3166 else if (bb->index == EXIT_BLOCK)
3167 dse_step3_exit_block_scan (bb_info);
3168 else
3169 dse_step3_scan (bb);
3170 if (EDGE_COUNT (bb->succs) == 0)
3171 mark_reachable_blocks (unreachable_blocks, bb);
3173 /* If this is the second time dataflow is run, delete the old
3174 sets. */
3175 if (bb_info->in)
3176 BITMAP_FREE (bb_info->in);
3177 if (bb_info->out)
3178 BITMAP_FREE (bb_info->out);
3181 /* For any block in an infinite loop, we must initialize the out set
3182 to all ones. This could be expensive, but almost never occurs in
3183 practice. However, it is common in regression tests. */
3184 EXECUTE_IF_SET_IN_BITMAP (unreachable_blocks, 0, i, sbi)
3186 if (bitmap_bit_p (all_blocks, i))
3188 bb_info_t bb_info = bb_table[i];
3189 if (!all_ones)
3191 unsigned int j;
3192 group_info *group;
3194 all_ones = BITMAP_ALLOC (&dse_bitmap_obstack);
3195 FOR_EACH_VEC_ELT (rtx_group_vec, j, group)
3196 bitmap_ior_into (all_ones, group->group_kill);
3198 if (!bb_info->out)
3200 bb_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3201 bitmap_copy (bb_info->out, all_ones);
3206 if (all_ones)
3207 BITMAP_FREE (all_ones);
3212 /*----------------------------------------------------------------------------
3213 Fourth step.
3215 Solve the bitvector equations.
3216 ----------------------------------------------------------------------------*/
3219 /* Confluence function for blocks with no successors. Create an out
3220 set from the gen set of the exit block. This block logically has
3221 the exit block as a successor. */
3225 static void
3226 dse_confluence_0 (basic_block bb)
3228 bb_info_t bb_info = bb_table[bb->index];
3230 if (bb->index == EXIT_BLOCK)
3231 return;
3233 if (!bb_info->out)
3235 bb_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3236 bitmap_copy (bb_info->out, bb_table[EXIT_BLOCK]->gen);
3240 /* Propagate the information from the in set of the dest of E to the
3241 out set of the src of E. If the various in or out sets are not
3242 there, that means they are all ones. */
3244 static bool
3245 dse_confluence_n (edge e)
3247 bb_info_t src_info = bb_table[e->src->index];
3248 bb_info_t dest_info = bb_table[e->dest->index];
3250 if (dest_info->in)
3252 if (src_info->out)
3253 bitmap_and_into (src_info->out, dest_info->in);
3254 else
3256 src_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3257 bitmap_copy (src_info->out, dest_info->in);
3260 return true;
3264 /* Propagate the info from the out to the in set of BB_INDEX's basic
3265 block. There are three cases:
3267 1) The block has no kill set. In this case the kill set is all
3268 ones. It does not matter what the out set of the block is, none of
3269 the info can reach the top. The only thing that reaches the top is
3270 the gen set and we just copy the set.
3272 2) There is a kill set but no out set and bb has successors. In
3273 this case we just return. Eventually an out set will be created and
3274 it is better to wait than to create a set of ones.
3276 3) There is both a kill and out set. We apply the obvious transfer
3277 function.
3280 static bool
3281 dse_transfer_function (int bb_index)
3283 bb_info_t bb_info = bb_table[bb_index];
3285 if (bb_info->kill)
3287 if (bb_info->out)
3289 /* Case 3 above. */
3290 if (bb_info->in)
3291 return bitmap_ior_and_compl (bb_info->in, bb_info->gen,
3292 bb_info->out, bb_info->kill);
3293 else
3295 bb_info->in = BITMAP_ALLOC (&dse_bitmap_obstack);
3296 bitmap_ior_and_compl (bb_info->in, bb_info->gen,
3297 bb_info->out, bb_info->kill);
3298 return true;
3301 else
3302 /* Case 2 above. */
3303 return false;
3305 else
3307 /* Case 1 above. If there is already an in set, nothing
3308 happens. */
3309 if (bb_info->in)
3310 return false;
3311 else
3313 bb_info->in = BITMAP_ALLOC (&dse_bitmap_obstack);
3314 bitmap_copy (bb_info->in, bb_info->gen);
3315 return true;
3320 /* Solve the dataflow equations. */
3322 static void
3323 dse_step4 (void)
3325 df_simple_dataflow (DF_BACKWARD, NULL, dse_confluence_0,
3326 dse_confluence_n, dse_transfer_function,
3327 all_blocks, df_get_postorder (DF_BACKWARD),
3328 df_get_n_blocks (DF_BACKWARD));
3329 if (dump_file && (dump_flags & TDF_DETAILS))
3331 basic_block bb;
3333 fprintf (dump_file, "\n\n*** Global dataflow info after analysis.\n");
3334 FOR_ALL_BB_FN (bb, cfun)
3336 bb_info_t bb_info = bb_table[bb->index];
3338 df_print_bb_index (bb, dump_file);
3339 if (bb_info->in)
3340 bitmap_print (dump_file, bb_info->in, " in: ", "\n");
3341 else
3342 fprintf (dump_file, " in: *MISSING*\n");
3343 if (bb_info->gen)
3344 bitmap_print (dump_file, bb_info->gen, " gen: ", "\n");
3345 else
3346 fprintf (dump_file, " gen: *MISSING*\n");
3347 if (bb_info->kill)
3348 bitmap_print (dump_file, bb_info->kill, " kill: ", "\n");
3349 else
3350 fprintf (dump_file, " kill: *MISSING*\n");
3351 if (bb_info->out)
3352 bitmap_print (dump_file, bb_info->out, " out: ", "\n");
3353 else
3354 fprintf (dump_file, " out: *MISSING*\n\n");
3361 /*----------------------------------------------------------------------------
3362 Fifth step.
3364 Delete the stores that can only be deleted using the global information.
3365 ----------------------------------------------------------------------------*/
3368 static void
3369 dse_step5 (void)
3371 basic_block bb;
3372 FOR_EACH_BB_FN (bb, cfun)
3374 bb_info_t bb_info = bb_table[bb->index];
3375 insn_info_t insn_info = bb_info->last_insn;
3376 bitmap v = bb_info->out;
3378 while (insn_info)
3380 bool deleted = false;
3381 if (dump_file && insn_info->insn)
3383 fprintf (dump_file, "starting to process insn %d\n",
3384 INSN_UID (insn_info->insn));
3385 bitmap_print (dump_file, v, " v: ", "\n");
3388 /* There may have been code deleted by the dce pass run before
3389 this phase. */
3390 if (insn_info->insn
3391 && INSN_P (insn_info->insn)
3392 && (!insn_info->cannot_delete)
3393 && (!bitmap_empty_p (v)))
3395 store_info *store_info = insn_info->store_rec;
3397 /* Try to delete the current insn. */
3398 deleted = true;
3400 /* Skip the clobbers. */
3401 while (!store_info->is_set)
3402 store_info = store_info->next;
3404 HOST_WIDE_INT i, offset, width;
3405 group_info *group_info = rtx_group_vec[store_info->group_id];
3407 if (!store_info->offset.is_constant (&offset)
3408 || !store_info->width.is_constant (&width))
3409 deleted = false;
3410 else
3412 HOST_WIDE_INT end = offset + width;
3413 for (i = offset; i < end; i++)
3415 int index = get_bitmap_index (group_info, i);
3417 if (dump_file && (dump_flags & TDF_DETAILS))
3418 fprintf (dump_file, "i = %d, index = %d\n",
3419 (int) i, index);
3420 if (index == 0 || !bitmap_bit_p (v, index))
3422 if (dump_file && (dump_flags & TDF_DETAILS))
3423 fprintf (dump_file, "failing at i = %d\n",
3424 (int) i);
3425 deleted = false;
3426 break;
3430 if (deleted)
3432 if (dbg_cnt (dse)
3433 && check_for_inc_dec_1 (insn_info))
3435 delete_insn (insn_info->insn);
3436 insn_info->insn = NULL;
3437 globally_deleted++;
3441 /* We do want to process the local info if the insn was
3442 deleted. For instance, if the insn did a wild read, we
3443 no longer need to trash the info. */
3444 if (insn_info->insn
3445 && INSN_P (insn_info->insn)
3446 && (!deleted))
3448 scan_stores (insn_info->store_rec, v, NULL);
3449 if (insn_info->wild_read)
3451 if (dump_file && (dump_flags & TDF_DETAILS))
3452 fprintf (dump_file, "wild read\n");
3453 bitmap_clear (v);
3455 else if (insn_info->read_rec
3456 || insn_info->non_frame_wild_read
3457 || insn_info->frame_read)
3459 if (dump_file && (dump_flags & TDF_DETAILS))
3461 if (!insn_info->non_frame_wild_read
3462 && !insn_info->frame_read)
3463 fprintf (dump_file, "regular read\n");
3464 if (insn_info->non_frame_wild_read)
3465 fprintf (dump_file, "non-frame wild read\n");
3466 if (insn_info->frame_read)
3467 fprintf (dump_file, "frame read\n");
3469 scan_reads (insn_info, v, NULL);
3473 insn_info = insn_info->prev_insn;
3480 /*----------------------------------------------------------------------------
3481 Sixth step.
3483 Delete stores made redundant by earlier stores (which store the same
3484 value) that couldn't be eliminated.
3485 ----------------------------------------------------------------------------*/
3487 static void
3488 dse_step6 (void)
3490 basic_block bb;
3492 FOR_ALL_BB_FN (bb, cfun)
3494 bb_info_t bb_info = bb_table[bb->index];
3495 insn_info_t insn_info = bb_info->last_insn;
3497 while (insn_info)
3499 /* There may have been code deleted by the dce pass run before
3500 this phase. */
3501 if (insn_info->insn
3502 && INSN_P (insn_info->insn)
3503 && !insn_info->cannot_delete)
3505 store_info *s_info = insn_info->store_rec;
3507 while (s_info && !s_info->is_set)
3508 s_info = s_info->next;
3509 if (s_info
3510 && s_info->redundant_reason
3511 && s_info->redundant_reason->insn
3512 && INSN_P (s_info->redundant_reason->insn))
3514 rtx_insn *rinsn = s_info->redundant_reason->insn;
3515 if (dump_file && (dump_flags & TDF_DETAILS))
3516 fprintf (dump_file, "Locally deleting insn %d "
3517 "because insn %d stores the "
3518 "same value and couldn't be "
3519 "eliminated\n",
3520 INSN_UID (insn_info->insn),
3521 INSN_UID (rinsn));
3522 delete_dead_store_insn (insn_info);
3525 insn_info = insn_info->prev_insn;
3530 /*----------------------------------------------------------------------------
3531 Seventh step.
3533 Destroy everything left standing.
3534 ----------------------------------------------------------------------------*/
3536 static void
3537 dse_step7 (void)
3539 bitmap_obstack_release (&dse_bitmap_obstack);
3540 obstack_free (&dse_obstack, NULL);
3542 end_alias_analysis ();
3543 free (bb_table);
3544 delete rtx_group_table;
3545 rtx_group_table = NULL;
3546 rtx_group_vec.release ();
3547 BITMAP_FREE (all_blocks);
3548 BITMAP_FREE (scratch);
3550 rtx_store_info_pool.release ();
3551 read_info_type_pool.release ();
3552 insn_info_type_pool.release ();
3553 dse_bb_info_type_pool.release ();
3554 group_info_pool.release ();
3555 deferred_change_pool.release ();
3559 /* -------------------------------------------------------------------------
3561 ------------------------------------------------------------------------- */
3563 /* Callback for running pass_rtl_dse. */
3565 static unsigned int
3566 rest_of_handle_dse (void)
3568 df_set_flags (DF_DEFER_INSN_RESCAN);
3570 /* Need the notes since we must track live hardregs in the forwards
3571 direction. */
3572 df_note_add_problem ();
3573 df_analyze ();
3575 dse_step0 ();
3576 dse_step1 ();
3577 dse_step2_init ();
3578 if (dse_step2 ())
3580 df_set_flags (DF_LR_RUN_DCE);
3581 df_analyze ();
3582 if (dump_file && (dump_flags & TDF_DETAILS))
3583 fprintf (dump_file, "doing global processing\n");
3584 dse_step3 ();
3585 dse_step4 ();
3586 dse_step5 ();
3589 dse_step6 ();
3590 dse_step7 ();
3592 if (dump_file)
3593 fprintf (dump_file, "dse: local deletions = %d, global deletions = %d\n",
3594 locally_deleted, globally_deleted);
3596 /* DSE can eliminate potentially-trapping MEMs.
3597 Remove any EH edges associated with them. */
3598 if ((locally_deleted || globally_deleted)
3599 && cfun->can_throw_non_call_exceptions
3600 && purge_all_dead_edges ())
3601 cleanup_cfg (0);
3603 return 0;
3606 namespace {
3608 const pass_data pass_data_rtl_dse1 =
3610 RTL_PASS, /* type */
3611 "dse1", /* name */
3612 OPTGROUP_NONE, /* optinfo_flags */
3613 TV_DSE1, /* tv_id */
3614 0, /* properties_required */
3615 0, /* properties_provided */
3616 0, /* properties_destroyed */
3617 0, /* todo_flags_start */
3618 TODO_df_finish, /* todo_flags_finish */
3621 class pass_rtl_dse1 : public rtl_opt_pass
3623 public:
3624 pass_rtl_dse1 (gcc::context *ctxt)
3625 : rtl_opt_pass (pass_data_rtl_dse1, ctxt)
3628 /* opt_pass methods: */
3629 virtual bool gate (function *)
3631 return optimize > 0 && flag_dse && dbg_cnt (dse1);
3634 virtual unsigned int execute (function *) { return rest_of_handle_dse (); }
3636 }; // class pass_rtl_dse1
3638 } // anon namespace
3640 rtl_opt_pass *
3641 make_pass_rtl_dse1 (gcc::context *ctxt)
3643 return new pass_rtl_dse1 (ctxt);
3646 namespace {
3648 const pass_data pass_data_rtl_dse2 =
3650 RTL_PASS, /* type */
3651 "dse2", /* name */
3652 OPTGROUP_NONE, /* optinfo_flags */
3653 TV_DSE2, /* tv_id */
3654 0, /* properties_required */
3655 0, /* properties_provided */
3656 0, /* properties_destroyed */
3657 0, /* todo_flags_start */
3658 TODO_df_finish, /* todo_flags_finish */
3661 class pass_rtl_dse2 : public rtl_opt_pass
3663 public:
3664 pass_rtl_dse2 (gcc::context *ctxt)
3665 : rtl_opt_pass (pass_data_rtl_dse2, ctxt)
3668 /* opt_pass methods: */
3669 virtual bool gate (function *)
3671 return optimize > 0 && flag_dse && dbg_cnt (dse2);
3674 virtual unsigned int execute (function *) { return rest_of_handle_dse (); }
3676 }; // class pass_rtl_dse2
3678 } // anon namespace
3680 rtl_opt_pass *
3681 make_pass_rtl_dse2 (gcc::context *ctxt)
3683 return new pass_rtl_dse2 (ctxt);