Daily bump.
[official-gcc.git] / gcc / dse.c
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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 && DECL_BUILT_IN_CLASS (SYMBOL_REF_DECL (sym)) == BUILT_IN_NORMAL
2423 && DECL_FUNCTION_CODE (SYMBOL_REF_DECL (sym)) == BUILT_IN_MEMSET)
2424 memset_call = SYMBOL_REF_DECL (sym);
2426 if (const_call || memset_call)
2428 insn_info_t i_ptr = active_local_stores;
2429 insn_info_t last = NULL;
2431 if (dump_file && (dump_flags & TDF_DETAILS))
2432 fprintf (dump_file, "%s call %d\n",
2433 const_call ? "const" : "memset", INSN_UID (insn));
2435 /* See the head comment of the frame_read field. */
2436 if (reload_completed
2437 /* Tail calls are storing their arguments using
2438 arg pointer. If it is a frame pointer on the target,
2439 even before reload we need to kill frame pointer based
2440 stores. */
2441 || (SIBLING_CALL_P (insn)
2442 && HARD_FRAME_POINTER_IS_ARG_POINTER))
2443 insn_info->frame_read = true;
2445 /* Loop over the active stores and remove those which are
2446 killed by the const function call. */
2447 while (i_ptr)
2449 bool remove_store = false;
2451 /* The stack pointer based stores are always killed. */
2452 if (i_ptr->stack_pointer_based)
2453 remove_store = true;
2455 /* If the frame is read, the frame related stores are killed. */
2456 else if (insn_info->frame_read)
2458 store_info *store_info = i_ptr->store_rec;
2460 /* Skip the clobbers. */
2461 while (!store_info->is_set)
2462 store_info = store_info->next;
2464 if (store_info->group_id >= 0
2465 && rtx_group_vec[store_info->group_id]->frame_related)
2466 remove_store = true;
2469 if (remove_store)
2471 if (dump_file && (dump_flags & TDF_DETAILS))
2472 dump_insn_info ("removing from active", i_ptr);
2474 active_local_stores_len--;
2475 if (last)
2476 last->next_local_store = i_ptr->next_local_store;
2477 else
2478 active_local_stores = i_ptr->next_local_store;
2480 else
2481 last = i_ptr;
2483 i_ptr = i_ptr->next_local_store;
2486 if (memset_call)
2488 rtx args[3];
2489 if (get_call_args (insn, memset_call, args, 3)
2490 && CONST_INT_P (args[1])
2491 && CONST_INT_P (args[2])
2492 && INTVAL (args[2]) > 0)
2494 rtx mem = gen_rtx_MEM (BLKmode, args[0]);
2495 set_mem_size (mem, INTVAL (args[2]));
2496 body = gen_rtx_SET (mem, args[1]);
2497 mems_found += record_store (body, bb_info);
2498 if (dump_file && (dump_flags & TDF_DETAILS))
2499 fprintf (dump_file, "handling memset as BLKmode store\n");
2500 if (mems_found == 1)
2502 if (active_local_stores_len++
2503 >= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
2505 active_local_stores_len = 1;
2506 active_local_stores = NULL;
2508 insn_info->fixed_regs_live
2509 = copy_fixed_regs (bb_info->regs_live);
2510 insn_info->next_local_store = active_local_stores;
2511 active_local_stores = insn_info;
2514 else
2515 clear_rhs_from_active_local_stores ();
2518 else if (SIBLING_CALL_P (insn) && reload_completed)
2519 /* Arguments for a sibling call that are pushed to memory are passed
2520 using the incoming argument pointer of the current function. After
2521 reload that might be (and likely is) frame pointer based. */
2522 add_wild_read (bb_info);
2523 else
2524 /* Every other call, including pure functions, may read any memory
2525 that is not relative to the frame. */
2526 add_non_frame_wild_read (bb_info);
2528 return;
2531 /* Assuming that there are sets in these insns, we cannot delete
2532 them. */
2533 if ((GET_CODE (PATTERN (insn)) == CLOBBER)
2534 || volatile_refs_p (PATTERN (insn))
2535 || (!cfun->can_delete_dead_exceptions && !insn_nothrow_p (insn))
2536 || (RTX_FRAME_RELATED_P (insn))
2537 || find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX))
2538 insn_info->cannot_delete = true;
2540 body = PATTERN (insn);
2541 if (GET_CODE (body) == PARALLEL)
2543 int i;
2544 for (i = 0; i < XVECLEN (body, 0); i++)
2545 mems_found += record_store (XVECEXP (body, 0, i), bb_info);
2547 else
2548 mems_found += record_store (body, bb_info);
2550 if (dump_file && (dump_flags & TDF_DETAILS))
2551 fprintf (dump_file, "mems_found = %d, cannot_delete = %s\n",
2552 mems_found, insn_info->cannot_delete ? "true" : "false");
2554 /* If we found some sets of mems, add it into the active_local_stores so
2555 that it can be locally deleted if found dead or used for
2556 replace_read and redundant constant store elimination. Otherwise mark
2557 it as cannot delete. This simplifies the processing later. */
2558 if (mems_found == 1)
2560 if (active_local_stores_len++
2561 >= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
2563 active_local_stores_len = 1;
2564 active_local_stores = NULL;
2566 insn_info->fixed_regs_live = copy_fixed_regs (bb_info->regs_live);
2567 insn_info->next_local_store = active_local_stores;
2568 active_local_stores = insn_info;
2570 else
2571 insn_info->cannot_delete = true;
2575 /* Remove BASE from the set of active_local_stores. This is a
2576 callback from cselib that is used to get rid of the stores in
2577 active_local_stores. */
2579 static void
2580 remove_useless_values (cselib_val *base)
2582 insn_info_t insn_info = active_local_stores;
2583 insn_info_t last = NULL;
2585 while (insn_info)
2587 store_info *store_info = insn_info->store_rec;
2588 bool del = false;
2590 /* If ANY of the store_infos match the cselib group that is
2591 being deleted, then the insn can not be deleted. */
2592 while (store_info)
2594 if ((store_info->group_id == -1)
2595 && (store_info->cse_base == base))
2597 del = true;
2598 break;
2600 store_info = store_info->next;
2603 if (del)
2605 active_local_stores_len--;
2606 if (last)
2607 last->next_local_store = insn_info->next_local_store;
2608 else
2609 active_local_stores = insn_info->next_local_store;
2610 free_store_info (insn_info);
2612 else
2613 last = insn_info;
2615 insn_info = insn_info->next_local_store;
2620 /* Do all of step 1. */
2622 static void
2623 dse_step1 (void)
2625 basic_block bb;
2626 bitmap regs_live = BITMAP_ALLOC (&reg_obstack);
2628 cselib_init (0);
2629 all_blocks = BITMAP_ALLOC (NULL);
2630 bitmap_set_bit (all_blocks, ENTRY_BLOCK);
2631 bitmap_set_bit (all_blocks, EXIT_BLOCK);
2633 FOR_ALL_BB_FN (bb, cfun)
2635 insn_info_t ptr;
2636 bb_info_t bb_info = dse_bb_info_type_pool.allocate ();
2638 memset (bb_info, 0, sizeof (dse_bb_info_type));
2639 bitmap_set_bit (all_blocks, bb->index);
2640 bb_info->regs_live = regs_live;
2642 bitmap_copy (regs_live, DF_LR_IN (bb));
2643 df_simulate_initialize_forwards (bb, regs_live);
2645 bb_table[bb->index] = bb_info;
2646 cselib_discard_hook = remove_useless_values;
2648 if (bb->index >= NUM_FIXED_BLOCKS)
2650 rtx_insn *insn;
2652 active_local_stores = NULL;
2653 active_local_stores_len = 0;
2654 cselib_clear_table ();
2656 /* Scan the insns. */
2657 FOR_BB_INSNS (bb, insn)
2659 if (INSN_P (insn))
2660 scan_insn (bb_info, insn);
2661 cselib_process_insn (insn);
2662 if (INSN_P (insn))
2663 df_simulate_one_insn_forwards (bb, insn, regs_live);
2666 /* This is something of a hack, because the global algorithm
2667 is supposed to take care of the case where stores go dead
2668 at the end of the function. However, the global
2669 algorithm must take a more conservative view of block
2670 mode reads than the local alg does. So to get the case
2671 where you have a store to the frame followed by a non
2672 overlapping block more read, we look at the active local
2673 stores at the end of the function and delete all of the
2674 frame and spill based ones. */
2675 if (stores_off_frame_dead_at_return
2676 && (EDGE_COUNT (bb->succs) == 0
2677 || (single_succ_p (bb)
2678 && single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)
2679 && ! crtl->calls_eh_return)))
2681 insn_info_t i_ptr = active_local_stores;
2682 while (i_ptr)
2684 store_info *store_info = i_ptr->store_rec;
2686 /* Skip the clobbers. */
2687 while (!store_info->is_set)
2688 store_info = store_info->next;
2689 if (store_info->group_id >= 0)
2691 group_info *group = rtx_group_vec[store_info->group_id];
2692 if (group->frame_related && !i_ptr->cannot_delete)
2693 delete_dead_store_insn (i_ptr);
2696 i_ptr = i_ptr->next_local_store;
2700 /* Get rid of the loads that were discovered in
2701 replace_read. Cselib is finished with this block. */
2702 while (deferred_change_list)
2704 deferred_change *next = deferred_change_list->next;
2706 /* There is no reason to validate this change. That was
2707 done earlier. */
2708 *deferred_change_list->loc = deferred_change_list->reg;
2709 deferred_change_pool.remove (deferred_change_list);
2710 deferred_change_list = next;
2713 /* Get rid of all of the cselib based store_infos in this
2714 block and mark the containing insns as not being
2715 deletable. */
2716 ptr = bb_info->last_insn;
2717 while (ptr)
2719 if (ptr->contains_cselib_groups)
2721 store_info *s_info = ptr->store_rec;
2722 while (s_info && !s_info->is_set)
2723 s_info = s_info->next;
2724 if (s_info
2725 && s_info->redundant_reason
2726 && s_info->redundant_reason->insn
2727 && !ptr->cannot_delete)
2729 if (dump_file && (dump_flags & TDF_DETAILS))
2730 fprintf (dump_file, "Locally deleting insn %d "
2731 "because insn %d stores the "
2732 "same value and couldn't be "
2733 "eliminated\n",
2734 INSN_UID (ptr->insn),
2735 INSN_UID (s_info->redundant_reason->insn));
2736 delete_dead_store_insn (ptr);
2738 free_store_info (ptr);
2740 else
2742 store_info *s_info;
2744 /* Free at least positions_needed bitmaps. */
2745 for (s_info = ptr->store_rec; s_info; s_info = s_info->next)
2746 if (s_info->is_large)
2748 BITMAP_FREE (s_info->positions_needed.large.bmap);
2749 s_info->is_large = false;
2752 ptr = ptr->prev_insn;
2755 cse_store_info_pool.release ();
2757 bb_info->regs_live = NULL;
2760 BITMAP_FREE (regs_live);
2761 cselib_finish ();
2762 rtx_group_table->empty ();
2766 /*----------------------------------------------------------------------------
2767 Second step.
2769 Assign each byte position in the stores that we are going to
2770 analyze globally to a position in the bitmaps. Returns true if
2771 there are any bit positions assigned.
2772 ----------------------------------------------------------------------------*/
2774 static void
2775 dse_step2_init (void)
2777 unsigned int i;
2778 group_info *group;
2780 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2782 /* For all non stack related bases, we only consider a store to
2783 be deletable if there are two or more stores for that
2784 position. This is because it takes one store to make the
2785 other store redundant. However, for the stores that are
2786 stack related, we consider them if there is only one store
2787 for the position. We do this because the stack related
2788 stores can be deleted if their is no read between them and
2789 the end of the function.
2791 To make this work in the current framework, we take the stack
2792 related bases add all of the bits from store1 into store2.
2793 This has the effect of making the eligible even if there is
2794 only one store. */
2796 if (stores_off_frame_dead_at_return && group->frame_related)
2798 bitmap_ior_into (group->store2_n, group->store1_n);
2799 bitmap_ior_into (group->store2_p, group->store1_p);
2800 if (dump_file && (dump_flags & TDF_DETAILS))
2801 fprintf (dump_file, "group %d is frame related ", i);
2804 group->offset_map_size_n++;
2805 group->offset_map_n = XOBNEWVEC (&dse_obstack, int,
2806 group->offset_map_size_n);
2807 group->offset_map_size_p++;
2808 group->offset_map_p = XOBNEWVEC (&dse_obstack, int,
2809 group->offset_map_size_p);
2810 group->process_globally = false;
2811 if (dump_file && (dump_flags & TDF_DETAILS))
2813 fprintf (dump_file, "group %d(%d+%d): ", i,
2814 (int)bitmap_count_bits (group->store2_n),
2815 (int)bitmap_count_bits (group->store2_p));
2816 bitmap_print (dump_file, group->store2_n, "n ", " ");
2817 bitmap_print (dump_file, group->store2_p, "p ", "\n");
2823 /* Init the offset tables. */
2825 static bool
2826 dse_step2 (void)
2828 unsigned int i;
2829 group_info *group;
2830 /* Position 0 is unused because 0 is used in the maps to mean
2831 unused. */
2832 current_position = 1;
2833 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2835 bitmap_iterator bi;
2836 unsigned int j;
2838 memset (group->offset_map_n, 0, sizeof (int) * group->offset_map_size_n);
2839 memset (group->offset_map_p, 0, sizeof (int) * group->offset_map_size_p);
2840 bitmap_clear (group->group_kill);
2842 EXECUTE_IF_SET_IN_BITMAP (group->store2_n, 0, j, bi)
2844 bitmap_set_bit (group->group_kill, current_position);
2845 if (bitmap_bit_p (group->escaped_n, j))
2846 bitmap_set_bit (kill_on_calls, current_position);
2847 group->offset_map_n[j] = current_position++;
2848 group->process_globally = true;
2850 EXECUTE_IF_SET_IN_BITMAP (group->store2_p, 0, j, bi)
2852 bitmap_set_bit (group->group_kill, current_position);
2853 if (bitmap_bit_p (group->escaped_p, j))
2854 bitmap_set_bit (kill_on_calls, current_position);
2855 group->offset_map_p[j] = current_position++;
2856 group->process_globally = true;
2859 return current_position != 1;
2864 /*----------------------------------------------------------------------------
2865 Third step.
2867 Build the bit vectors for the transfer functions.
2868 ----------------------------------------------------------------------------*/
2871 /* Look up the bitmap index for OFFSET in GROUP_INFO. If it is not
2872 there, return 0. */
2874 static int
2875 get_bitmap_index (group_info *group_info, HOST_WIDE_INT offset)
2877 if (offset < 0)
2879 HOST_WIDE_INT offset_p = -offset;
2880 if (offset_p >= group_info->offset_map_size_n)
2881 return 0;
2882 return group_info->offset_map_n[offset_p];
2884 else
2886 if (offset >= group_info->offset_map_size_p)
2887 return 0;
2888 return group_info->offset_map_p[offset];
2893 /* Process the STORE_INFOs into the bitmaps into GEN and KILL. KILL
2894 may be NULL. */
2896 static void
2897 scan_stores (store_info *store_info, bitmap gen, bitmap kill)
2899 while (store_info)
2901 HOST_WIDE_INT i, offset, width;
2902 group_info *group_info
2903 = rtx_group_vec[store_info->group_id];
2904 /* We can (conservatively) ignore stores whose bounds aren't known;
2905 they simply don't generate new global dse opportunities. */
2906 if (group_info->process_globally
2907 && store_info->offset.is_constant (&offset)
2908 && store_info->width.is_constant (&width))
2910 HOST_WIDE_INT end = offset + width;
2911 for (i = offset; i < end; i++)
2913 int index = get_bitmap_index (group_info, i);
2914 if (index != 0)
2916 bitmap_set_bit (gen, index);
2917 if (kill)
2918 bitmap_clear_bit (kill, index);
2922 store_info = store_info->next;
2927 /* Process the READ_INFOs into the bitmaps into GEN and KILL. KILL
2928 may be NULL. */
2930 static void
2931 scan_reads (insn_info_t insn_info, bitmap gen, bitmap kill)
2933 read_info_t read_info = insn_info->read_rec;
2934 int i;
2935 group_info *group;
2937 /* If this insn reads the frame, kill all the frame related stores. */
2938 if (insn_info->frame_read)
2940 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2941 if (group->process_globally && group->frame_related)
2943 if (kill)
2944 bitmap_ior_into (kill, group->group_kill);
2945 bitmap_and_compl_into (gen, group->group_kill);
2948 if (insn_info->non_frame_wild_read)
2950 /* Kill all non-frame related stores. Kill all stores of variables that
2951 escape. */
2952 if (kill)
2953 bitmap_ior_into (kill, kill_on_calls);
2954 bitmap_and_compl_into (gen, kill_on_calls);
2955 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2956 if (group->process_globally && !group->frame_related)
2958 if (kill)
2959 bitmap_ior_into (kill, group->group_kill);
2960 bitmap_and_compl_into (gen, group->group_kill);
2963 while (read_info)
2965 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
2967 if (group->process_globally)
2969 if (i == read_info->group_id)
2971 HOST_WIDE_INT offset, width;
2972 /* Reads with non-constant size kill all DSE opportunities
2973 in the group. */
2974 if (!read_info->offset.is_constant (&offset)
2975 || !read_info->width.is_constant (&width)
2976 || !known_size_p (width))
2978 /* Handle block mode reads. */
2979 if (kill)
2980 bitmap_ior_into (kill, group->group_kill);
2981 bitmap_and_compl_into (gen, group->group_kill);
2983 else
2985 /* The groups are the same, just process the
2986 offsets. */
2987 HOST_WIDE_INT j;
2988 HOST_WIDE_INT end = offset + width;
2989 for (j = offset; j < end; j++)
2991 int index = get_bitmap_index (group, j);
2992 if (index != 0)
2994 if (kill)
2995 bitmap_set_bit (kill, index);
2996 bitmap_clear_bit (gen, index);
3001 else
3003 /* The groups are different, if the alias sets
3004 conflict, clear the entire group. We only need
3005 to apply this test if the read_info is a cselib
3006 read. Anything with a constant base cannot alias
3007 something else with a different constant
3008 base. */
3009 if ((read_info->group_id < 0)
3010 && canon_true_dependence (group->base_mem,
3011 GET_MODE (group->base_mem),
3012 group->canon_base_addr,
3013 read_info->mem, NULL_RTX))
3015 if (kill)
3016 bitmap_ior_into (kill, group->group_kill);
3017 bitmap_and_compl_into (gen, group->group_kill);
3023 read_info = read_info->next;
3028 /* Return the insn in BB_INFO before the first wild read or if there
3029 are no wild reads in the block, return the last insn. */
3031 static insn_info_t
3032 find_insn_before_first_wild_read (bb_info_t bb_info)
3034 insn_info_t insn_info = bb_info->last_insn;
3035 insn_info_t last_wild_read = NULL;
3037 while (insn_info)
3039 if (insn_info->wild_read)
3041 last_wild_read = insn_info->prev_insn;
3042 /* Block starts with wild read. */
3043 if (!last_wild_read)
3044 return NULL;
3047 insn_info = insn_info->prev_insn;
3050 if (last_wild_read)
3051 return last_wild_read;
3052 else
3053 return bb_info->last_insn;
3057 /* Scan the insns in BB_INFO starting at PTR and going to the top of
3058 the block in order to build the gen and kill sets for the block.
3059 We start at ptr which may be the last insn in the block or may be
3060 the first insn with a wild read. In the latter case we are able to
3061 skip the rest of the block because it just does not matter:
3062 anything that happens is hidden by the wild read. */
3064 static void
3065 dse_step3_scan (basic_block bb)
3067 bb_info_t bb_info = bb_table[bb->index];
3068 insn_info_t insn_info;
3070 insn_info = find_insn_before_first_wild_read (bb_info);
3072 /* In the spill case or in the no_spill case if there is no wild
3073 read in the block, we will need a kill set. */
3074 if (insn_info == bb_info->last_insn)
3076 if (bb_info->kill)
3077 bitmap_clear (bb_info->kill);
3078 else
3079 bb_info->kill = BITMAP_ALLOC (&dse_bitmap_obstack);
3081 else
3082 if (bb_info->kill)
3083 BITMAP_FREE (bb_info->kill);
3085 while (insn_info)
3087 /* There may have been code deleted by the dce pass run before
3088 this phase. */
3089 if (insn_info->insn && INSN_P (insn_info->insn))
3091 scan_stores (insn_info->store_rec, bb_info->gen, bb_info->kill);
3092 scan_reads (insn_info, bb_info->gen, bb_info->kill);
3095 insn_info = insn_info->prev_insn;
3100 /* Set the gen set of the exit block, and also any block with no
3101 successors that does not have a wild read. */
3103 static void
3104 dse_step3_exit_block_scan (bb_info_t bb_info)
3106 /* The gen set is all 0's for the exit block except for the
3107 frame_pointer_group. */
3109 if (stores_off_frame_dead_at_return)
3111 unsigned int i;
3112 group_info *group;
3114 FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
3116 if (group->process_globally && group->frame_related)
3117 bitmap_ior_into (bb_info->gen, group->group_kill);
3123 /* Find all of the blocks that are not backwards reachable from the
3124 exit block or any block with no successors (BB). These are the
3125 infinite loops or infinite self loops. These blocks will still
3126 have their bits set in UNREACHABLE_BLOCKS. */
3128 static void
3129 mark_reachable_blocks (sbitmap unreachable_blocks, basic_block bb)
3131 edge e;
3132 edge_iterator ei;
3134 if (bitmap_bit_p (unreachable_blocks, bb->index))
3136 bitmap_clear_bit (unreachable_blocks, bb->index);
3137 FOR_EACH_EDGE (e, ei, bb->preds)
3139 mark_reachable_blocks (unreachable_blocks, e->src);
3144 /* Build the transfer functions for the function. */
3146 static void
3147 dse_step3 ()
3149 basic_block bb;
3150 sbitmap_iterator sbi;
3151 bitmap all_ones = NULL;
3152 unsigned int i;
3154 auto_sbitmap unreachable_blocks (last_basic_block_for_fn (cfun));
3155 bitmap_ones (unreachable_blocks);
3157 FOR_ALL_BB_FN (bb, cfun)
3159 bb_info_t bb_info = bb_table[bb->index];
3160 if (bb_info->gen)
3161 bitmap_clear (bb_info->gen);
3162 else
3163 bb_info->gen = BITMAP_ALLOC (&dse_bitmap_obstack);
3165 if (bb->index == ENTRY_BLOCK)
3167 else if (bb->index == EXIT_BLOCK)
3168 dse_step3_exit_block_scan (bb_info);
3169 else
3170 dse_step3_scan (bb);
3171 if (EDGE_COUNT (bb->succs) == 0)
3172 mark_reachable_blocks (unreachable_blocks, bb);
3174 /* If this is the second time dataflow is run, delete the old
3175 sets. */
3176 if (bb_info->in)
3177 BITMAP_FREE (bb_info->in);
3178 if (bb_info->out)
3179 BITMAP_FREE (bb_info->out);
3182 /* For any block in an infinite loop, we must initialize the out set
3183 to all ones. This could be expensive, but almost never occurs in
3184 practice. However, it is common in regression tests. */
3185 EXECUTE_IF_SET_IN_BITMAP (unreachable_blocks, 0, i, sbi)
3187 if (bitmap_bit_p (all_blocks, i))
3189 bb_info_t bb_info = bb_table[i];
3190 if (!all_ones)
3192 unsigned int j;
3193 group_info *group;
3195 all_ones = BITMAP_ALLOC (&dse_bitmap_obstack);
3196 FOR_EACH_VEC_ELT (rtx_group_vec, j, group)
3197 bitmap_ior_into (all_ones, group->group_kill);
3199 if (!bb_info->out)
3201 bb_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3202 bitmap_copy (bb_info->out, all_ones);
3207 if (all_ones)
3208 BITMAP_FREE (all_ones);
3213 /*----------------------------------------------------------------------------
3214 Fourth step.
3216 Solve the bitvector equations.
3217 ----------------------------------------------------------------------------*/
3220 /* Confluence function for blocks with no successors. Create an out
3221 set from the gen set of the exit block. This block logically has
3222 the exit block as a successor. */
3226 static void
3227 dse_confluence_0 (basic_block bb)
3229 bb_info_t bb_info = bb_table[bb->index];
3231 if (bb->index == EXIT_BLOCK)
3232 return;
3234 if (!bb_info->out)
3236 bb_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3237 bitmap_copy (bb_info->out, bb_table[EXIT_BLOCK]->gen);
3241 /* Propagate the information from the in set of the dest of E to the
3242 out set of the src of E. If the various in or out sets are not
3243 there, that means they are all ones. */
3245 static bool
3246 dse_confluence_n (edge e)
3248 bb_info_t src_info = bb_table[e->src->index];
3249 bb_info_t dest_info = bb_table[e->dest->index];
3251 if (dest_info->in)
3253 if (src_info->out)
3254 bitmap_and_into (src_info->out, dest_info->in);
3255 else
3257 src_info->out = BITMAP_ALLOC (&dse_bitmap_obstack);
3258 bitmap_copy (src_info->out, dest_info->in);
3261 return true;
3265 /* Propagate the info from the out to the in set of BB_INDEX's basic
3266 block. There are three cases:
3268 1) The block has no kill set. In this case the kill set is all
3269 ones. It does not matter what the out set of the block is, none of
3270 the info can reach the top. The only thing that reaches the top is
3271 the gen set and we just copy the set.
3273 2) There is a kill set but no out set and bb has successors. In
3274 this case we just return. Eventually an out set will be created and
3275 it is better to wait than to create a set of ones.
3277 3) There is both a kill and out set. We apply the obvious transfer
3278 function.
3281 static bool
3282 dse_transfer_function (int bb_index)
3284 bb_info_t bb_info = bb_table[bb_index];
3286 if (bb_info->kill)
3288 if (bb_info->out)
3290 /* Case 3 above. */
3291 if (bb_info->in)
3292 return bitmap_ior_and_compl (bb_info->in, bb_info->gen,
3293 bb_info->out, bb_info->kill);
3294 else
3296 bb_info->in = BITMAP_ALLOC (&dse_bitmap_obstack);
3297 bitmap_ior_and_compl (bb_info->in, bb_info->gen,
3298 bb_info->out, bb_info->kill);
3299 return true;
3302 else
3303 /* Case 2 above. */
3304 return false;
3306 else
3308 /* Case 1 above. If there is already an in set, nothing
3309 happens. */
3310 if (bb_info->in)
3311 return false;
3312 else
3314 bb_info->in = BITMAP_ALLOC (&dse_bitmap_obstack);
3315 bitmap_copy (bb_info->in, bb_info->gen);
3316 return true;
3321 /* Solve the dataflow equations. */
3323 static void
3324 dse_step4 (void)
3326 df_simple_dataflow (DF_BACKWARD, NULL, dse_confluence_0,
3327 dse_confluence_n, dse_transfer_function,
3328 all_blocks, df_get_postorder (DF_BACKWARD),
3329 df_get_n_blocks (DF_BACKWARD));
3330 if (dump_file && (dump_flags & TDF_DETAILS))
3332 basic_block bb;
3334 fprintf (dump_file, "\n\n*** Global dataflow info after analysis.\n");
3335 FOR_ALL_BB_FN (bb, cfun)
3337 bb_info_t bb_info = bb_table[bb->index];
3339 df_print_bb_index (bb, dump_file);
3340 if (bb_info->in)
3341 bitmap_print (dump_file, bb_info->in, " in: ", "\n");
3342 else
3343 fprintf (dump_file, " in: *MISSING*\n");
3344 if (bb_info->gen)
3345 bitmap_print (dump_file, bb_info->gen, " gen: ", "\n");
3346 else
3347 fprintf (dump_file, " gen: *MISSING*\n");
3348 if (bb_info->kill)
3349 bitmap_print (dump_file, bb_info->kill, " kill: ", "\n");
3350 else
3351 fprintf (dump_file, " kill: *MISSING*\n");
3352 if (bb_info->out)
3353 bitmap_print (dump_file, bb_info->out, " out: ", "\n");
3354 else
3355 fprintf (dump_file, " out: *MISSING*\n\n");
3362 /*----------------------------------------------------------------------------
3363 Fifth step.
3365 Delete the stores that can only be deleted using the global information.
3366 ----------------------------------------------------------------------------*/
3369 static void
3370 dse_step5 (void)
3372 basic_block bb;
3373 FOR_EACH_BB_FN (bb, cfun)
3375 bb_info_t bb_info = bb_table[bb->index];
3376 insn_info_t insn_info = bb_info->last_insn;
3377 bitmap v = bb_info->out;
3379 while (insn_info)
3381 bool deleted = false;
3382 if (dump_file && insn_info->insn)
3384 fprintf (dump_file, "starting to process insn %d\n",
3385 INSN_UID (insn_info->insn));
3386 bitmap_print (dump_file, v, " v: ", "\n");
3389 /* There may have been code deleted by the dce pass run before
3390 this phase. */
3391 if (insn_info->insn
3392 && INSN_P (insn_info->insn)
3393 && (!insn_info->cannot_delete)
3394 && (!bitmap_empty_p (v)))
3396 store_info *store_info = insn_info->store_rec;
3398 /* Try to delete the current insn. */
3399 deleted = true;
3401 /* Skip the clobbers. */
3402 while (!store_info->is_set)
3403 store_info = store_info->next;
3405 HOST_WIDE_INT i, offset, width;
3406 group_info *group_info = rtx_group_vec[store_info->group_id];
3408 if (!store_info->offset.is_constant (&offset)
3409 || !store_info->width.is_constant (&width))
3410 deleted = false;
3411 else
3413 HOST_WIDE_INT end = offset + width;
3414 for (i = offset; i < end; i++)
3416 int index = get_bitmap_index (group_info, i);
3418 if (dump_file && (dump_flags & TDF_DETAILS))
3419 fprintf (dump_file, "i = %d, index = %d\n",
3420 (int) i, index);
3421 if (index == 0 || !bitmap_bit_p (v, index))
3423 if (dump_file && (dump_flags & TDF_DETAILS))
3424 fprintf (dump_file, "failing at i = %d\n",
3425 (int) i);
3426 deleted = false;
3427 break;
3431 if (deleted)
3433 if (dbg_cnt (dse)
3434 && check_for_inc_dec_1 (insn_info))
3436 delete_insn (insn_info->insn);
3437 insn_info->insn = NULL;
3438 globally_deleted++;
3442 /* We do want to process the local info if the insn was
3443 deleted. For instance, if the insn did a wild read, we
3444 no longer need to trash the info. */
3445 if (insn_info->insn
3446 && INSN_P (insn_info->insn)
3447 && (!deleted))
3449 scan_stores (insn_info->store_rec, v, NULL);
3450 if (insn_info->wild_read)
3452 if (dump_file && (dump_flags & TDF_DETAILS))
3453 fprintf (dump_file, "wild read\n");
3454 bitmap_clear (v);
3456 else if (insn_info->read_rec
3457 || insn_info->non_frame_wild_read
3458 || insn_info->frame_read)
3460 if (dump_file && (dump_flags & TDF_DETAILS))
3462 if (!insn_info->non_frame_wild_read
3463 && !insn_info->frame_read)
3464 fprintf (dump_file, "regular read\n");
3465 if (insn_info->non_frame_wild_read)
3466 fprintf (dump_file, "non-frame wild read\n");
3467 if (insn_info->frame_read)
3468 fprintf (dump_file, "frame read\n");
3470 scan_reads (insn_info, v, NULL);
3474 insn_info = insn_info->prev_insn;
3481 /*----------------------------------------------------------------------------
3482 Sixth step.
3484 Delete stores made redundant by earlier stores (which store the same
3485 value) that couldn't be eliminated.
3486 ----------------------------------------------------------------------------*/
3488 static void
3489 dse_step6 (void)
3491 basic_block bb;
3493 FOR_ALL_BB_FN (bb, cfun)
3495 bb_info_t bb_info = bb_table[bb->index];
3496 insn_info_t insn_info = bb_info->last_insn;
3498 while (insn_info)
3500 /* There may have been code deleted by the dce pass run before
3501 this phase. */
3502 if (insn_info->insn
3503 && INSN_P (insn_info->insn)
3504 && !insn_info->cannot_delete)
3506 store_info *s_info = insn_info->store_rec;
3508 while (s_info && !s_info->is_set)
3509 s_info = s_info->next;
3510 if (s_info
3511 && s_info->redundant_reason
3512 && s_info->redundant_reason->insn
3513 && INSN_P (s_info->redundant_reason->insn))
3515 rtx_insn *rinsn = s_info->redundant_reason->insn;
3516 if (dump_file && (dump_flags & TDF_DETAILS))
3517 fprintf (dump_file, "Locally deleting insn %d "
3518 "because insn %d stores the "
3519 "same value and couldn't be "
3520 "eliminated\n",
3521 INSN_UID (insn_info->insn),
3522 INSN_UID (rinsn));
3523 delete_dead_store_insn (insn_info);
3526 insn_info = insn_info->prev_insn;
3531 /*----------------------------------------------------------------------------
3532 Seventh step.
3534 Destroy everything left standing.
3535 ----------------------------------------------------------------------------*/
3537 static void
3538 dse_step7 (void)
3540 bitmap_obstack_release (&dse_bitmap_obstack);
3541 obstack_free (&dse_obstack, NULL);
3543 end_alias_analysis ();
3544 free (bb_table);
3545 delete rtx_group_table;
3546 rtx_group_table = NULL;
3547 rtx_group_vec.release ();
3548 BITMAP_FREE (all_blocks);
3549 BITMAP_FREE (scratch);
3551 rtx_store_info_pool.release ();
3552 read_info_type_pool.release ();
3553 insn_info_type_pool.release ();
3554 dse_bb_info_type_pool.release ();
3555 group_info_pool.release ();
3556 deferred_change_pool.release ();
3560 /* -------------------------------------------------------------------------
3562 ------------------------------------------------------------------------- */
3564 /* Callback for running pass_rtl_dse. */
3566 static unsigned int
3567 rest_of_handle_dse (void)
3569 df_set_flags (DF_DEFER_INSN_RESCAN);
3571 /* Need the notes since we must track live hardregs in the forwards
3572 direction. */
3573 df_note_add_problem ();
3574 df_analyze ();
3576 dse_step0 ();
3577 dse_step1 ();
3578 dse_step2_init ();
3579 if (dse_step2 ())
3581 df_set_flags (DF_LR_RUN_DCE);
3582 df_analyze ();
3583 if (dump_file && (dump_flags & TDF_DETAILS))
3584 fprintf (dump_file, "doing global processing\n");
3585 dse_step3 ();
3586 dse_step4 ();
3587 dse_step5 ();
3590 dse_step6 ();
3591 dse_step7 ();
3593 if (dump_file)
3594 fprintf (dump_file, "dse: local deletions = %d, global deletions = %d\n",
3595 locally_deleted, globally_deleted);
3597 /* DSE can eliminate potentially-trapping MEMs.
3598 Remove any EH edges associated with them. */
3599 if ((locally_deleted || globally_deleted)
3600 && cfun->can_throw_non_call_exceptions
3601 && purge_all_dead_edges ())
3602 cleanup_cfg (0);
3604 return 0;
3607 namespace {
3609 const pass_data pass_data_rtl_dse1 =
3611 RTL_PASS, /* type */
3612 "dse1", /* name */
3613 OPTGROUP_NONE, /* optinfo_flags */
3614 TV_DSE1, /* tv_id */
3615 0, /* properties_required */
3616 0, /* properties_provided */
3617 0, /* properties_destroyed */
3618 0, /* todo_flags_start */
3619 TODO_df_finish, /* todo_flags_finish */
3622 class pass_rtl_dse1 : public rtl_opt_pass
3624 public:
3625 pass_rtl_dse1 (gcc::context *ctxt)
3626 : rtl_opt_pass (pass_data_rtl_dse1, ctxt)
3629 /* opt_pass methods: */
3630 virtual bool gate (function *)
3632 return optimize > 0 && flag_dse && dbg_cnt (dse1);
3635 virtual unsigned int execute (function *) { return rest_of_handle_dse (); }
3637 }; // class pass_rtl_dse1
3639 } // anon namespace
3641 rtl_opt_pass *
3642 make_pass_rtl_dse1 (gcc::context *ctxt)
3644 return new pass_rtl_dse1 (ctxt);
3647 namespace {
3649 const pass_data pass_data_rtl_dse2 =
3651 RTL_PASS, /* type */
3652 "dse2", /* name */
3653 OPTGROUP_NONE, /* optinfo_flags */
3654 TV_DSE2, /* tv_id */
3655 0, /* properties_required */
3656 0, /* properties_provided */
3657 0, /* properties_destroyed */
3658 0, /* todo_flags_start */
3659 TODO_df_finish, /* todo_flags_finish */
3662 class pass_rtl_dse2 : public rtl_opt_pass
3664 public:
3665 pass_rtl_dse2 (gcc::context *ctxt)
3666 : rtl_opt_pass (pass_data_rtl_dse2, ctxt)
3669 /* opt_pass methods: */
3670 virtual bool gate (function *)
3672 return optimize > 0 && flag_dse && dbg_cnt (dse2);
3675 virtual unsigned int execute (function *) { return rest_of_handle_dse (); }
3677 }; // class pass_rtl_dse2
3679 } // anon namespace
3681 rtl_opt_pass *
3682 make_pass_rtl_dse2 (gcc::context *ctxt)
3684 return new pass_rtl_dse2 (ctxt);