Line data Source code
1 : /* Dead and redundant store elimination
2 : Copyright (C) 2004-2026 Free Software Foundation, Inc.
3 :
4 : This file is part of GCC.
5 :
6 : GCC is free software; you can redistribute it and/or modify
7 : it under the terms of the GNU General Public License as published by
8 : the Free Software Foundation; either version 3, or (at your option)
9 : any later version.
10 :
11 : GCC is distributed in the hope that it will be useful,
12 : but WITHOUT ANY WARRANTY; without even the implied warranty of
13 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 : GNU General Public License for more details.
15 :
16 : You should have received a copy of the GNU General Public License
17 : along with GCC; see the file COPYING3. If not see
18 : <http://www.gnu.org/licenses/>. */
19 :
20 : #include "config.h"
21 : #include "system.h"
22 : #include "coretypes.h"
23 : #include "backend.h"
24 : #include "rtl.h"
25 : #include "tree.h"
26 : #include "gimple.h"
27 : #include "tree-pass.h"
28 : #include "ssa.h"
29 : #include "gimple-pretty-print.h"
30 : #include "fold-const.h"
31 : #include "gimple-iterator.h"
32 : #include "tree-cfg.h"
33 : #include "tree-dfa.h"
34 : #include "tree-cfgcleanup.h"
35 : #include "alias.h"
36 : #include "tree-ssa-loop.h"
37 : #include "tree-ssa-dse.h"
38 : #include "builtins.h"
39 : #include "gimple-fold.h"
40 : #include "gimplify.h"
41 : #include "tree-eh.h"
42 : #include "cfganal.h"
43 : #include "cgraph.h"
44 : #include "ipa-modref-tree.h"
45 : #include "ipa-modref.h"
46 : #include "target.h"
47 : #include "tree-ssa-loop-niter.h"
48 : #include "cfgloop.h"
49 : #include "tree-data-ref.h"
50 : #include "internal-fn.h"
51 : #include "tree-ssa.h"
52 :
53 : /* This file implements dead store elimination.
54 :
55 : A dead store is a store into a memory location which will later be
56 : overwritten by another store without any intervening loads. In this
57 : case the earlier store can be deleted or trimmed if the store
58 : was partially dead.
59 :
60 : A redundant store is a store into a memory location which stores
61 : the exact same value as a prior store to the same memory location.
62 : While this can often be handled by dead store elimination, removing
63 : the redundant store is often better than removing or trimming the
64 : dead store.
65 :
66 : In our SSA + virtual operand world we use immediate uses of virtual
67 : operands to detect these cases. If a store's virtual definition
68 : is used precisely once by a later store to the same location which
69 : post dominates the first store, then the first store is dead. If
70 : the data stored is the same, then the second store is redundant.
71 :
72 : The single use of the store's virtual definition ensures that
73 : there are no intervening aliased loads and the requirement that
74 : the second load post dominate the first ensures that if the earlier
75 : store executes, then the later stores will execute before the function
76 : exits.
77 :
78 : It may help to think of this as first moving the earlier store to
79 : the point immediately before the later store. Again, the single
80 : use of the virtual definition and the post-dominance relationship
81 : ensure that such movement would be safe. Clearly if there are
82 : back to back stores, then the second is makes the first dead. If
83 : the second store stores the same value, then the second store is
84 : redundant.
85 :
86 : Reviewing section 10.7.2 in Morgan's "Building an Optimizing Compiler"
87 : may also help in understanding this code since it discusses the
88 : relationship between dead store and redundant load elimination. In
89 : fact, they are the same transformation applied to different views of
90 : the CFG. */
91 :
92 : static void delete_dead_or_redundant_call (gimple_stmt_iterator *, const char *);
93 :
94 : /* Bitmap of blocks that have had EH statements cleaned. We should
95 : remove their dead edges eventually. */
96 : static bitmap need_eh_cleanup;
97 : static bitmap need_ab_cleanup;
98 :
99 : /* STMT is a statement that may write into memory. Analyze it and
100 : initialize WRITE to describe how STMT affects memory. When
101 : MAY_DEF_OK is true then the function initializes WRITE to what
102 : the stmt may define.
103 :
104 : Return TRUE if the statement was analyzed, FALSE otherwise.
105 :
106 : It is always safe to return FALSE. But typically better optimziation
107 : can be achieved by analyzing more statements. */
108 :
109 : static bool
110 232648865 : initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write, bool may_def_ok = false)
111 : {
112 : /* It's advantageous to handle certain mem* functions. */
113 232648865 : if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
114 : {
115 5351120 : switch (DECL_FUNCTION_CODE (gimple_call_fndecl (stmt)))
116 : {
117 1291010 : case BUILT_IN_MEMCPY:
118 1291010 : case BUILT_IN_MEMMOVE:
119 1291010 : case BUILT_IN_MEMSET:
120 1291010 : case BUILT_IN_MEMCPY_CHK:
121 1291010 : case BUILT_IN_MEMMOVE_CHK:
122 1291010 : case BUILT_IN_MEMSET_CHK:
123 1291010 : case BUILT_IN_STRNCPY:
124 1291010 : case BUILT_IN_STRNCPY_CHK:
125 1291010 : {
126 1291010 : tree size = gimple_call_arg (stmt, 2);
127 1291010 : tree ptr = gimple_call_arg (stmt, 0);
128 1291010 : ao_ref_init_from_ptr_and_size (write, ptr, size);
129 1291010 : return true;
130 : }
131 :
132 : /* A calloc call can never be dead, but it can make
133 : subsequent stores redundant if they store 0 into
134 : the same memory locations. */
135 3276 : case BUILT_IN_CALLOC:
136 3276 : {
137 3276 : tree nelem = gimple_call_arg (stmt, 0);
138 3276 : tree selem = gimple_call_arg (stmt, 1);
139 3276 : tree lhs;
140 3276 : if (TREE_CODE (nelem) == INTEGER_CST
141 2699 : && TREE_CODE (selem) == INTEGER_CST
142 5783 : && (lhs = gimple_call_lhs (stmt)) != NULL_TREE)
143 : {
144 2496 : tree size = fold_build2 (MULT_EXPR, TREE_TYPE (nelem),
145 : nelem, selem);
146 2496 : ao_ref_init_from_ptr_and_size (write, lhs, size);
147 2496 : return true;
148 : }
149 : }
150 :
151 : default:
152 : break;
153 : }
154 : }
155 227297745 : else if (is_gimple_call (stmt)
156 227297745 : && gimple_call_internal_p (stmt))
157 : {
158 416248 : switch (gimple_call_internal_fn (stmt))
159 : {
160 1335 : case IFN_LEN_STORE:
161 1335 : case IFN_MASK_STORE:
162 1335 : case IFN_MASK_LEN_STORE:
163 1335 : {
164 1335 : internal_fn ifn = gimple_call_internal_fn (stmt);
165 1335 : int stored_value_index = internal_fn_stored_value_index (ifn);
166 1335 : int len_index = internal_fn_len_index (ifn);
167 1335 : if (ifn == IFN_LEN_STORE)
168 : {
169 0 : tree len = gimple_call_arg (stmt, len_index);
170 0 : tree bias = gimple_call_arg (stmt, len_index + 1);
171 0 : if (tree_fits_uhwi_p (len))
172 : {
173 0 : ao_ref_init_from_ptr_and_size (write,
174 : gimple_call_arg (stmt, 0),
175 : int_const_binop (MINUS_EXPR,
176 : len, bias));
177 0 : return true;
178 : }
179 : }
180 : /* We cannot initialize a must-def ao_ref (in all cases) but we
181 : can provide a may-def variant. */
182 1335 : if (may_def_ok)
183 : {
184 1297 : ao_ref_init_from_ptr_and_range (
185 : write, gimple_call_arg (stmt, 0), true, 0, -1,
186 1297 : tree_to_poly_int64 (TYPE_SIZE (
187 : TREE_TYPE (gimple_call_arg (stmt, stored_value_index)))));
188 1297 : return true;
189 : }
190 : break;
191 : }
192 : default:;
193 : }
194 : }
195 231354062 : if (tree lhs = gimple_get_lhs (stmt))
196 : {
197 217312039 : if (TREE_CODE (lhs) != SSA_NAME
198 217312039 : && (may_def_ok || !stmt_could_throw_p (cfun, stmt)))
199 : {
200 200081147 : ao_ref_init (write, lhs);
201 200081147 : return true;
202 : }
203 : }
204 : return false;
205 : }
206 :
207 : /* Given REF from the alias oracle, return TRUE if it is a valid
208 : kill memory reference for dead store elimination, false otherwise.
209 :
210 : In particular, the reference must have a known base, known maximum
211 : size, start at a byte offset and have a size that is one or more
212 : bytes. */
213 :
214 : static bool
215 168893213 : valid_ao_ref_kill_for_dse (ao_ref *ref)
216 : {
217 168893213 : return (ao_ref_base (ref)
218 168893213 : && known_size_p (ref->max_size)
219 168578756 : && maybe_ne (ref->size, 0)
220 168560678 : && known_eq (ref->max_size, ref->size)
221 336950441 : && known_ge (ref->offset, 0));
222 : }
223 :
224 : /* Given REF from the alias oracle, return TRUE if it is a valid
225 : load or store memory reference for dead store elimination, false otherwise.
226 :
227 : Unlike for valid_ao_ref_kill_for_dse we can accept writes where max_size
228 : is not same as size since we can handle conservatively the larger range. */
229 :
230 : static bool
231 37586629 : valid_ao_ref_for_dse (ao_ref *ref)
232 : {
233 37586629 : return (ao_ref_base (ref)
234 37586629 : && known_size_p (ref->max_size)
235 74692693 : && known_ge (ref->offset, 0));
236 : }
237 :
238 : /* Initialize OFFSET and SIZE to a range known to contain REF
239 : where the boundaries are divisible by BITS_PER_UNIT (bit still in bits).
240 : Return false if this is impossible. */
241 :
242 : static bool
243 104891248 : get_byte_aligned_range_containing_ref (ao_ref *ref, poly_int64 *offset,
244 : HOST_WIDE_INT *size)
245 : {
246 0 : if (!known_size_p (ref->max_size))
247 : return false;
248 104891248 : *offset = aligned_lower_bound (ref->offset, BITS_PER_UNIT);
249 104891248 : poly_int64 end = aligned_upper_bound (ref->offset + ref->max_size,
250 : BITS_PER_UNIT);
251 104891248 : return (end - *offset).is_constant (size);
252 : }
253 :
254 : /* Initialize OFFSET and SIZE to a range known to be contained REF
255 : where the boundaries are divisible by BITS_PER_UNIT (but still in bits).
256 : Return false if this is impossible. */
257 :
258 : static bool
259 97860252 : get_byte_aligned_range_contained_in_ref (ao_ref *ref, poly_int64 *offset,
260 : HOST_WIDE_INT *size)
261 : {
262 97860252 : if (!known_size_p (ref->size)
263 97860252 : || !known_eq (ref->size, ref->max_size))
264 : return false;
265 97860252 : *offset = aligned_upper_bound (ref->offset, BITS_PER_UNIT);
266 97860252 : poly_int64 end = aligned_lower_bound (ref->offset + ref->max_size,
267 : BITS_PER_UNIT);
268 : /* For bit accesses we can get -1 here, but also 0 sized kill is not
269 : useful. */
270 97860252 : if (!known_gt (end, *offset))
271 : return false;
272 97670418 : return (end - *offset).is_constant (size);
273 : }
274 :
275 : /* Compute byte range (returned iN REF_OFFSET and RET_SIZE) for access COPY
276 : inside REF. If KILL is true, then COPY represent a kill and the byte range
277 : needs to be fully contained in bit range given by COPY. If KILL is false
278 : then the byte range returned must contain the range of COPY. */
279 :
280 : static bool
281 101470667 : get_byte_range (ao_ref *copy, ao_ref *ref, bool kill,
282 : HOST_WIDE_INT *ret_offset, HOST_WIDE_INT *ret_size)
283 : {
284 101470667 : HOST_WIDE_INT copy_size, ref_size;
285 101470667 : poly_int64 copy_offset, ref_offset;
286 101470667 : HOST_WIDE_INT diff;
287 :
288 : /* First translate from bits to bytes, rounding to bigger or smaller ranges
289 : as needed. Kills needs to be always rounded to smaller ranges while
290 : uses and stores to larger ranges. */
291 101470667 : if (kill)
292 : {
293 97860252 : if (!get_byte_aligned_range_contained_in_ref (copy, ©_offset,
294 : ©_size))
295 : return false;
296 : }
297 : else
298 : {
299 3610415 : if (!get_byte_aligned_range_containing_ref (copy, ©_offset,
300 : ©_size))
301 : return false;
302 : }
303 :
304 196560261 : if (!get_byte_aligned_range_containing_ref (ref, &ref_offset, &ref_size)
305 : || !ordered_p (copy_offset, ref_offset))
306 : return false;
307 :
308 : /* Switch sizes from bits to bytes so we do not need to care about
309 : overflows. Offset calculation needs to stay in bits until we compute
310 : the difference and can switch to HOST_WIDE_INT. */
311 101280833 : copy_size /= BITS_PER_UNIT;
312 101280833 : ref_size /= BITS_PER_UNIT;
313 :
314 : /* If COPY starts before REF, then reset the beginning of
315 : COPY to match REF and decrease the size of COPY by the
316 : number of bytes removed from COPY. */
317 101280833 : if (maybe_lt (copy_offset, ref_offset))
318 : {
319 9276805 : if (!(ref_offset - copy_offset).is_constant (&diff)
320 9276805 : || copy_size < diff / BITS_PER_UNIT)
321 : return false;
322 2716847 : copy_size -= diff / BITS_PER_UNIT;
323 2716847 : copy_offset = ref_offset;
324 : }
325 :
326 94720875 : if (!(copy_offset - ref_offset).is_constant (&diff)
327 94720875 : || ref_size <= diff / BITS_PER_UNIT)
328 : return false;
329 :
330 : /* If COPY extends beyond REF, chop off its size appropriately. */
331 6191239 : HOST_WIDE_INT limit = ref_size - diff / BITS_PER_UNIT;
332 :
333 6191239 : if (copy_size > limit)
334 1134526 : copy_size = limit;
335 6191239 : *ret_size = copy_size;
336 6191239 : if (!(copy_offset - ref_offset).is_constant (ret_offset))
337 : return false;
338 6191239 : *ret_offset /= BITS_PER_UNIT;
339 6191239 : return true;
340 : }
341 :
342 : /* Update LIVE_BYTES tracking REF for write to WRITE:
343 : Verify we have the same base memory address, the write
344 : has a known size and overlaps with REF. */
345 : static void
346 168893213 : clear_live_bytes_for_ref (sbitmap live_bytes, ao_ref *ref, ao_ref *write)
347 : {
348 168893213 : HOST_WIDE_INT start, size;
349 :
350 168893213 : if (valid_ao_ref_kill_for_dse (write)
351 168056971 : && operand_equal_p (write->base, ref->base, OEP_ADDRESS_OF)
352 266753465 : && get_byte_range (write, ref, true, &start, &size))
353 2580824 : bitmap_clear_range (live_bytes, start, size);
354 168893213 : }
355 :
356 : /* Clear any bytes written by STMT from the bitmap LIVE_BYTES. The base
357 : address written by STMT must match the one found in REF, which must
358 : have its base address previously initialized.
359 :
360 : This routine must be conservative. If we don't know the offset or
361 : actual size written, assume nothing was written. */
362 :
363 : static void
364 182905606 : clear_bytes_written_by (sbitmap live_bytes, gimple *stmt, ao_ref *ref)
365 : {
366 182905606 : ao_ref write;
367 :
368 182905606 : if (gcall *call = dyn_cast <gcall *> (stmt))
369 : {
370 5534766 : bool interposed;
371 5534766 : modref_summary *summary = get_modref_function_summary (call, &interposed);
372 :
373 5534766 : if (summary && !interposed)
374 486962 : for (auto kill : summary->kills)
375 66541 : if (kill.get_ao_ref (as_a <gcall *> (stmt), &write))
376 66517 : clear_live_bytes_for_ref (live_bytes, ref, &write);
377 : }
378 182905606 : if (!initialize_ao_ref_for_dse (stmt, &write))
379 14078910 : return;
380 :
381 168826696 : clear_live_bytes_for_ref (live_bytes, ref, &write);
382 : }
383 :
384 : /* REF is a memory write. Extract relevant information from it and
385 : initialize the LIVE_BYTES bitmap. If successful, return TRUE.
386 : Otherwise return FALSE. */
387 :
388 : static bool
389 31173965 : setup_live_bytes_from_ref (ao_ref *ref, sbitmap live_bytes)
390 : {
391 31173965 : HOST_WIDE_INT const_size;
392 31173965 : if (valid_ao_ref_for_dse (ref)
393 30719278 : && ((aligned_upper_bound (ref->offset + ref->max_size, BITS_PER_UNIT)
394 30719278 : - aligned_lower_bound (ref->offset,
395 30719278 : BITS_PER_UNIT)).is_constant (&const_size))
396 30719278 : && (const_size / BITS_PER_UNIT <= param_dse_max_object_size)
397 61574653 : && const_size > 1)
398 : {
399 30400471 : bitmap_clear (live_bytes);
400 30400471 : bitmap_set_range (live_bytes, 0, const_size / BITS_PER_UNIT);
401 30400471 : return true;
402 : }
403 : return false;
404 : }
405 :
406 : /* Compute the number of stored bytes that we can trim from the head and
407 : tail of REF. LIVE is the bitmap of stores to REF that are still live.
408 :
409 : Store the number of bytes trimmed from the head and tail in TRIM_HEAD
410 : and TRIM_TAIL respectively.
411 :
412 : STMT is the statement being trimmed and is used for debugging dump
413 : output only. */
414 :
415 : static void
416 3460918 : compute_trims (ao_ref *ref, sbitmap live, int *trim_head, int *trim_tail,
417 : gimple *stmt)
418 : {
419 3460918 : *trim_head = 0;
420 3460918 : *trim_tail = 0;
421 :
422 : /* We use bitmaps biased such that ref->offset is contained in bit zero and
423 : the bitmap extends through ref->max_size, so we know that in the original
424 : bitmap bits 0 .. ref->max_size were true. But we need to check that this
425 : covers the bytes of REF exactly. */
426 3460918 : const unsigned int align = known_alignment (ref->offset);
427 3460918 : if ((align > 0 && align < BITS_PER_UNIT)
428 3460918 : || !known_eq (ref->size, ref->max_size))
429 12388 : return;
430 :
431 : /* Now identify how much, if any of the tail we can chop off. */
432 3448530 : HOST_WIDE_INT const_size;
433 3448530 : int last_live = bitmap_last_set_bit (live);
434 3448530 : if (ref->size.is_constant (&const_size))
435 : {
436 3448530 : int last_orig = (const_size / BITS_PER_UNIT) - 1;
437 : /* We can leave inconvenient amounts on the tail as
438 : residual handling in mem* and str* functions is usually
439 : reasonably efficient. */
440 3448530 : *trim_tail = last_orig - last_live;
441 :
442 : /* But don't trim away out of bounds accesses, as this defeats
443 : proper warnings.
444 :
445 : We could have a type with no TYPE_SIZE_UNIT or we could have a VLA
446 : where TYPE_SIZE_UNIT is not a constant. */
447 3448530 : if (*trim_tail
448 10256 : && TYPE_SIZE_UNIT (TREE_TYPE (ref->base))
449 10256 : && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (ref->base))) == INTEGER_CST
450 3458785 : && compare_tree_int (TYPE_SIZE_UNIT (TREE_TYPE (ref->base)),
451 : last_orig) <= 0)
452 136 : *trim_tail = 0;
453 : }
454 :
455 : /* Identify how much, if any of the head we can chop off. */
456 3448530 : int first_orig = 0;
457 3448530 : int first_live = bitmap_first_set_bit (live);
458 3448530 : *trim_head = first_live - first_orig;
459 :
460 : /* If REF is aligned, try to maintain this alignment if it reduces
461 : the number of (power-of-two sized aligned) writes to memory. */
462 3448530 : unsigned int align_bits;
463 3448530 : unsigned HOST_WIDE_INT bitpos;
464 3359166 : if ((*trim_head || *trim_tail)
465 95160 : && last_live - first_live >= 2
466 94326 : && ao_ref_alignment (ref, &align_bits, &bitpos)
467 77212 : && align_bits >= 32
468 76864 : && bitpos == 0
469 3521645 : && align_bits % BITS_PER_UNIT == 0)
470 : {
471 73115 : unsigned int align_units = align_bits / BITS_PER_UNIT;
472 73115 : if (align_units > 16)
473 : align_units = 16;
474 75192 : while ((first_live | (align_units - 1)) > (unsigned int)last_live)
475 2077 : align_units >>= 1;
476 :
477 73115 : if (*trim_head)
478 : {
479 68447 : unsigned int pos = first_live & (align_units - 1);
480 75667 : for (unsigned int i = 1; i <= align_units; i <<= 1)
481 : {
482 75667 : unsigned int mask = ~(i - 1);
483 75667 : unsigned int bytes = align_units - (pos & mask);
484 75667 : if (wi::popcount (bytes) <= 1)
485 : {
486 68447 : *trim_head &= mask;
487 68447 : break;
488 : }
489 : }
490 : }
491 :
492 73115 : if (*trim_tail)
493 : {
494 7188 : unsigned int pos = last_live & (align_units - 1);
495 11313 : for (unsigned int i = 1; i <= align_units; i <<= 1)
496 : {
497 11313 : int mask = i - 1;
498 11313 : unsigned int bytes = (pos | mask) + 1;
499 11313 : if ((last_live | mask) > (last_live + *trim_tail))
500 : break;
501 11313 : if (wi::popcount (bytes) <= 1)
502 : {
503 7188 : unsigned int extra = (last_live | mask) - last_live;
504 7188 : *trim_tail -= extra;
505 7188 : break;
506 : }
507 : }
508 : }
509 : }
510 :
511 3448530 : if ((*trim_head || *trim_tail) && dump_file && (dump_flags & TDF_DETAILS))
512 : {
513 18 : fprintf (dump_file, " Trimming statement (head = %d, tail = %d): ",
514 : *trim_head, *trim_tail);
515 18 : print_gimple_stmt (dump_file, stmt, 0, dump_flags);
516 18 : fprintf (dump_file, "\n");
517 : }
518 : }
519 :
520 : /* STMT initializes an object from COMPLEX_CST where one or more of the bytes
521 : written may be dead stores. REF is a representation of the memory written.
522 : LIVE is the bitmap of stores to REF that are still live.
523 :
524 : Attempt to rewrite STMT so that only the real or the imaginary part of the
525 : object is actually stored. */
526 :
527 : static void
528 5518 : maybe_trim_complex_store (ao_ref *ref, sbitmap live, gimple *stmt)
529 : {
530 5518 : int trim_head, trim_tail;
531 5518 : compute_trims (ref, live, &trim_head, &trim_tail, stmt);
532 :
533 : /* The amount of data trimmed from the head or tail must be at
534 : least half the size of the object to ensure we're trimming
535 : the entire real or imaginary half. By writing things this
536 : way we avoid more O(n) bitmap operations. */
537 5518 : if (known_ge (trim_tail * 2 * BITS_PER_UNIT, ref->size))
538 : {
539 : /* TREE_REALPART is live */
540 2 : tree x = TREE_REALPART (gimple_assign_rhs1 (stmt));
541 2 : tree y = gimple_assign_lhs (stmt);
542 2 : y = build1 (REALPART_EXPR, TREE_TYPE (x), y);
543 2 : gimple_assign_set_lhs (stmt, y);
544 2 : gimple_assign_set_rhs1 (stmt, x);
545 : }
546 5516 : else if (known_ge (trim_head * 2 * BITS_PER_UNIT, ref->size))
547 : {
548 : /* TREE_IMAGPART is live */
549 3 : tree x = TREE_IMAGPART (gimple_assign_rhs1 (stmt));
550 3 : tree y = gimple_assign_lhs (stmt);
551 3 : y = build1 (IMAGPART_EXPR, TREE_TYPE (x), y);
552 3 : gimple_assign_set_lhs (stmt, y);
553 3 : gimple_assign_set_rhs1 (stmt, x);
554 : }
555 :
556 : /* Other cases indicate parts of both the real and imag subobjects
557 : are live. We do not try to optimize those cases. */
558 5518 : }
559 :
560 : /* STMT initializes an object using a CONSTRUCTOR where one or more of the
561 : bytes written are dead stores. REF is a representation of the memory
562 : written. LIVE is the bitmap of stores to REF that are still live.
563 :
564 : Attempt to rewrite STMT so that it writes fewer memory locations.
565 :
566 : The most common case for getting here is a CONSTRUCTOR with no elements
567 : being used to zero initialize an object. We do not try to handle other
568 : cases as those would force us to fully cover the object with the
569 : CONSTRUCTOR node except for the components that are dead.
570 : Also handles integer stores of 0 which can happen with memset/memcpy optimizations. */
571 :
572 : static void
573 3313301 : maybe_trim_constructor_store (ao_ref *ref, sbitmap live, gimple *stmt, bool was_integer_cst)
574 : {
575 3313301 : tree ctor = gimple_assign_rhs1 (stmt);
576 :
577 : /* This is the only case we currently handle. It actually seems to
578 : catch most cases of actual interest. */
579 3793289 : gcc_assert (was_integer_cst ? integer_zerop (ctor) : CONSTRUCTOR_NELTS (ctor) == 0);
580 :
581 3313301 : int head_trim = 0;
582 3313301 : int tail_trim = 0;
583 3313301 : compute_trims (ref, live, &head_trim, &tail_trim, stmt);
584 :
585 : /* Now we want to replace the constructor initializer
586 : with memset (object + head_trim, 0, size - head_trim - tail_trim). */
587 3313301 : if (head_trim || tail_trim)
588 : {
589 : /* We want &lhs for the MEM_REF expression. */
590 88571 : tree lhs_addr = build_fold_addr_expr (gimple_assign_lhs (stmt));
591 :
592 88571 : STRIP_USELESS_TYPE_CONVERSION (lhs_addr);
593 :
594 88571 : if (! is_gimple_min_invariant (lhs_addr))
595 17301 : return;
596 :
597 : /* The number of bytes for the new constructor. */
598 71270 : poly_int64 ref_bytes = exact_div (ref->size, BITS_PER_UNIT);
599 71270 : poly_int64 count = ref_bytes - head_trim - tail_trim;
600 :
601 : /* And the new type for the CONSTRUCTOR. Essentially it's just
602 : a char array large enough to cover the non-trimmed parts of
603 : the original CONSTRUCTOR. Note we want explicit bounds here
604 : so that we know how many bytes to clear when expanding the
605 : CONSTRUCTOR. */
606 71270 : tree type = build_array_type_nelts (char_type_node, count);
607 :
608 : /* Build a suitable alias type rather than using alias set zero
609 : to avoid pessimizing. */
610 71270 : tree alias_type = reference_alias_ptr_type (gimple_assign_lhs (stmt));
611 :
612 : /* Build a MEM_REF representing the whole accessed area, starting
613 : at the first byte not trimmed. */
614 71270 : tree exp = fold_build2 (MEM_REF, type, lhs_addr,
615 : build_int_cst (alias_type, head_trim));
616 :
617 : /* Now update STMT with a new RHS and LHS. */
618 71270 : gimple_assign_set_lhs (stmt, exp);
619 71270 : gimple_assign_set_rhs1 (stmt, build_constructor (type, NULL));
620 : }
621 : }
622 :
623 : /* STMT is a memcpy, memmove or memset. Decrement the number of bytes
624 : copied/set by DECREMENT. */
625 : static void
626 764 : decrement_count (gimple *stmt, int decrement)
627 : {
628 764 : tree *countp = gimple_call_arg_ptr (stmt, 2);
629 764 : gcc_assert (TREE_CODE (*countp) == INTEGER_CST);
630 1528 : *countp = wide_int_to_tree (TREE_TYPE (*countp), (TREE_INT_CST_LOW (*countp)
631 764 : - decrement));
632 764 : }
633 :
634 : static void
635 703 : increment_start_addr (gimple *stmt, tree *where, int increment)
636 : {
637 703 : if (tree lhs = gimple_call_lhs (stmt))
638 6 : if (where == gimple_call_arg_ptr (stmt, 0))
639 : {
640 6 : gassign *newop = gimple_build_assign (lhs, unshare_expr (*where));
641 6 : gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
642 6 : gsi_insert_after (&gsi, newop, GSI_SAME_STMT);
643 6 : gimple_call_set_lhs (stmt, NULL_TREE);
644 6 : update_stmt (stmt);
645 : }
646 :
647 703 : if (TREE_CODE (*where) == SSA_NAME)
648 : {
649 197 : tree tem = make_ssa_name (TREE_TYPE (*where));
650 197 : gassign *newop
651 197 : = gimple_build_assign (tem, POINTER_PLUS_EXPR, *where,
652 197 : build_int_cst (sizetype, increment));
653 197 : gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
654 197 : gsi_insert_before (&gsi, newop, GSI_SAME_STMT);
655 197 : *where = tem;
656 197 : update_stmt (stmt);
657 197 : return;
658 : }
659 :
660 506 : *where = build_fold_addr_expr (fold_build2 (MEM_REF, char_type_node,
661 : *where,
662 : build_int_cst (ptr_type_node,
663 : increment)));
664 506 : STRIP_USELESS_TYPE_CONVERSION (*where);
665 : }
666 :
667 : /* STMT is builtin call that writes bytes in bitmap ORIG, some bytes are dead
668 : (ORIG & ~NEW) and need not be stored. Try to rewrite STMT to reduce
669 : the amount of data it actually writes.
670 :
671 : Right now we only support trimming from the head or the tail of the
672 : memory region. In theory we could split the mem* call, but it's
673 : likely of marginal value. */
674 :
675 : static void
676 142099 : maybe_trim_memstar_call (ao_ref *ref, sbitmap live, gimple *stmt)
677 : {
678 142099 : int head_trim, tail_trim;
679 142099 : switch (DECL_FUNCTION_CODE (gimple_call_fndecl (stmt)))
680 : {
681 4613 : case BUILT_IN_STRNCPY:
682 4613 : case BUILT_IN_STRNCPY_CHK:
683 4613 : compute_trims (ref, live, &head_trim, &tail_trim, stmt);
684 4613 : if (head_trim)
685 : {
686 : /* Head trimming of strncpy is only possible if we can
687 : prove all bytes we would trim are non-zero (or we could
688 : turn the strncpy into memset if there must be zero
689 : among the head trimmed bytes). If we don't know anything
690 : about those bytes, the presence or absence of '\0' bytes
691 : in there will affect whether it acts for the non-trimmed
692 : bytes as memset or memcpy/strncpy. */
693 74 : c_strlen_data lendata = { };
694 74 : int orig_head_trim = head_trim;
695 74 : tree srcstr = gimple_call_arg (stmt, 1);
696 74 : if (!get_range_strlen (srcstr, &lendata, /*eltsize=*/1)
697 74 : || !tree_fits_uhwi_p (lendata.minlen))
698 8 : head_trim = 0;
699 66 : else if (tree_to_uhwi (lendata.minlen) < (unsigned) head_trim)
700 : {
701 60 : head_trim = tree_to_uhwi (lendata.minlen);
702 60 : if ((orig_head_trim & (UNITS_PER_WORD - 1)) == 0)
703 0 : head_trim &= ~(UNITS_PER_WORD - 1);
704 : }
705 74 : if (orig_head_trim != head_trim
706 68 : && dump_file
707 82 : && (dump_flags & TDF_DETAILS))
708 8 : fprintf (dump_file,
709 : " Adjusting strncpy trimming to (head = %d,"
710 : " tail = %d)\n", head_trim, tail_trim);
711 : }
712 4613 : goto do_memcpy;
713 :
714 99733 : case BUILT_IN_MEMCPY:
715 99733 : case BUILT_IN_MEMMOVE:
716 99733 : case BUILT_IN_MEMCPY_CHK:
717 99733 : case BUILT_IN_MEMMOVE_CHK:
718 99733 : compute_trims (ref, live, &head_trim, &tail_trim, stmt);
719 :
720 104346 : do_memcpy:
721 : /* Tail trimming is easy, we can just reduce the count. */
722 104346 : if (tail_trim)
723 72 : decrement_count (stmt, tail_trim);
724 :
725 : /* Head trimming requires adjusting all the arguments. */
726 104346 : if (head_trim)
727 : {
728 : /* For __*_chk need to adjust also the last argument. */
729 121 : if (gimple_call_num_args (stmt) == 4)
730 : {
731 49 : tree size = gimple_call_arg (stmt, 3);
732 49 : if (!tree_fits_uhwi_p (size))
733 : break;
734 7 : if (!integer_all_onesp (size))
735 : {
736 7 : unsigned HOST_WIDE_INT sz = tree_to_uhwi (size);
737 7 : if (sz < (unsigned) head_trim)
738 : break;
739 7 : tree arg = wide_int_to_tree (TREE_TYPE (size),
740 7 : sz - head_trim);
741 7 : gimple_call_set_arg (stmt, 3, arg);
742 : }
743 : }
744 79 : tree *dst = gimple_call_arg_ptr (stmt, 0);
745 79 : increment_start_addr (stmt, dst, head_trim);
746 79 : tree *src = gimple_call_arg_ptr (stmt, 1);
747 79 : increment_start_addr (stmt, src, head_trim);
748 79 : decrement_count (stmt, head_trim);
749 : }
750 : break;
751 :
752 37753 : case BUILT_IN_MEMSET:
753 37753 : case BUILT_IN_MEMSET_CHK:
754 37753 : compute_trims (ref, live, &head_trim, &tail_trim, stmt);
755 :
756 : /* Tail trimming is easy, we can just reduce the count. */
757 37753 : if (tail_trim)
758 68 : decrement_count (stmt, tail_trim);
759 :
760 : /* Head trimming requires adjusting all the arguments. */
761 37753 : if (head_trim)
762 : {
763 : /* For __*_chk need to adjust also the last argument. */
764 545 : if (gimple_call_num_args (stmt) == 4)
765 : {
766 7 : tree size = gimple_call_arg (stmt, 3);
767 7 : if (!tree_fits_uhwi_p (size))
768 : break;
769 7 : if (!integer_all_onesp (size))
770 : {
771 7 : unsigned HOST_WIDE_INT sz = tree_to_uhwi (size);
772 7 : if (sz < (unsigned) head_trim)
773 : break;
774 7 : tree arg = wide_int_to_tree (TREE_TYPE (size),
775 7 : sz - head_trim);
776 7 : gimple_call_set_arg (stmt, 3, arg);
777 : }
778 : }
779 545 : tree *dst = gimple_call_arg_ptr (stmt, 0);
780 545 : increment_start_addr (stmt, dst, head_trim);
781 545 : decrement_count (stmt, head_trim);
782 : }
783 : break;
784 :
785 : default:
786 : break;
787 : }
788 142099 : }
789 :
790 : /* STMT is a memory write where one or more bytes written are dead stores.
791 : REF is a representation of the memory written. LIVE is the bitmap of
792 : stores to REF that are still live.
793 :
794 : Attempt to rewrite STMT so that it writes fewer memory locations. Right
795 : now we only support trimming at the start or end of the memory region.
796 : It's not clear how much there is to be gained by trimming from the middle
797 : of the region. */
798 :
799 : static void
800 25999906 : maybe_trim_partially_dead_store (ao_ref *ref, sbitmap live, gimple *stmt)
801 : {
802 25999906 : if (is_gimple_assign (stmt)
803 25999906 : && TREE_CODE (gimple_assign_lhs (stmt)) != TARGET_MEM_REF)
804 : {
805 24688605 : switch (gimple_assign_rhs_code (stmt))
806 : {
807 479988 : case CONSTRUCTOR:
808 479988 : maybe_trim_constructor_store (ref, live, stmt, false);
809 479988 : break;
810 5518 : case COMPLEX_CST:
811 5518 : maybe_trim_complex_store (ref, live, stmt);
812 5518 : break;
813 8777209 : case INTEGER_CST:
814 8777209 : if (integer_zerop (gimple_assign_rhs1 (stmt))
815 8777209 : && type_has_mode_precision_p (TREE_TYPE (gimple_assign_lhs (stmt))))
816 2833313 : maybe_trim_constructor_store (ref, live, stmt, true);
817 : break;
818 : default:
819 : break;
820 : }
821 : }
822 25999906 : }
823 :
824 : /* Return TRUE if USE_REF reads bytes from LIVE where live is
825 : derived from REF, a write reference.
826 :
827 : While this routine may modify USE_REF, it's passed by value, not
828 : location. So callers do not see those modifications. */
829 :
830 : static bool
831 3610415 : live_bytes_read (ao_ref *use_ref, ao_ref *ref, sbitmap live)
832 : {
833 : /* We have already verified that USE_REF and REF hit the same object.
834 : Now verify that there's actually an overlap between USE_REF and REF. */
835 3610415 : HOST_WIDE_INT start, size;
836 3610415 : if (get_byte_range (use_ref, ref, false, &start, &size))
837 : {
838 : /* If USE_REF covers all of REF, then it will hit one or more
839 : live bytes. This avoids useless iteration over the bitmap
840 : below. */
841 3610415 : if (start == 0 && known_eq (size * 8, ref->size))
842 : return true;
843 :
844 : /* Now check if any of the remaining bits in use_ref are set in LIVE. */
845 983459 : return bitmap_any_bit_in_range_p (live, start, (start + size - 1));
846 : }
847 : return true;
848 : }
849 :
850 : /* Callback for dse_classify_store calling for_each_index. Verify that
851 : indices are invariant in the loop with backedge PHI in basic-block DATA. */
852 :
853 : static bool
854 2656244 : check_name (tree, tree *idx, void *data)
855 : {
856 2656244 : basic_block phi_bb = (basic_block) data;
857 2656244 : if (TREE_CODE (*idx) == SSA_NAME
858 1782019 : && !SSA_NAME_IS_DEFAULT_DEF (*idx)
859 4313346 : && dominated_by_p (CDI_DOMINATORS, gimple_bb (SSA_NAME_DEF_STMT (*idx)),
860 : phi_bb))
861 : return false;
862 : return true;
863 : }
864 :
865 : /* STMT stores the value 0 into one or more memory locations
866 : (via memset, empty constructor, calloc call, etc).
867 :
868 : See if there is a subsequent store of the value 0 to one
869 : or more of the same memory location(s). If so, the subsequent
870 : store is redundant and can be removed.
871 :
872 : The subsequent stores could be via memset, empty constructors,
873 : simple MEM stores, etc. */
874 :
875 : static void
876 4243133 : dse_optimize_redundant_stores (gimple *stmt)
877 : {
878 4243133 : int cnt = 0;
879 :
880 : /* TBAA state of STMT, if it is a call it is effectively alias-set zero. */
881 4243133 : alias_set_type earlier_set = 0;
882 4243133 : alias_set_type earlier_base_set = 0;
883 4243133 : if (is_gimple_assign (stmt))
884 : {
885 4184936 : ao_ref lhs_ref;
886 4184936 : ao_ref_init (&lhs_ref, gimple_assign_lhs (stmt));
887 4184936 : earlier_set = ao_ref_alias_set (&lhs_ref);
888 4184936 : earlier_base_set = ao_ref_base_alias_set (&lhs_ref);
889 : }
890 :
891 : /* We could do something fairly complex and look through PHIs
892 : like DSE_CLASSIFY_STORE, but it doesn't seem to be worth
893 : the effort.
894 :
895 : Look at all the immediate uses of the VDEF (which are obviously
896 : dominated by STMT). See if one or more stores 0 into the same
897 : memory locations a STMT, if so remove the immediate use statements. */
898 4243133 : tree defvar = gimple_vdef (stmt);
899 4243133 : imm_use_iterator ui;
900 4243133 : gimple *use_stmt;
901 13753359 : FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
902 : {
903 : /* Limit stmt walking. */
904 5288049 : if (++cnt > param_dse_max_alias_queries_per_store)
905 : break;
906 :
907 : /* If USE_STMT stores 0 into one or more of the same locations
908 : as STMT and STMT would kill USE_STMT, then we can just remove
909 : USE_STMT. */
910 5288049 : tree fndecl;
911 5288049 : if ((is_gimple_assign (use_stmt)
912 3716334 : && gimple_vdef (use_stmt)
913 3055283 : && (gimple_assign_single_p (use_stmt)
914 3055283 : && initializer_zerop (gimple_assign_rhs1 (use_stmt))))
915 7556475 : || (gimple_call_builtin_p (use_stmt, BUILT_IN_NORMAL)
916 158074 : && (fndecl = gimple_call_fndecl (use_stmt)) != NULL
917 158074 : && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET
918 136822 : || DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET_CHK)
919 21343 : && integer_zerop (gimple_call_arg (use_stmt, 1))))
920 : {
921 1466426 : ao_ref write;
922 :
923 1466426 : if (!initialize_ao_ref_for_dse (use_stmt, &write))
924 : break;
925 :
926 1445470 : if (valid_ao_ref_for_dse (&write)
927 1445470 : && stmt_kills_ref_p (stmt, &write))
928 : {
929 5448 : gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
930 5448 : if (is_gimple_assign (use_stmt))
931 : {
932 5398 : ao_ref lhs_ref;
933 5398 : ao_ref_init (&lhs_ref, gimple_assign_lhs (use_stmt));
934 5398 : if ((earlier_set == ao_ref_alias_set (&lhs_ref)
935 718 : || alias_set_subset_of (ao_ref_alias_set (&lhs_ref),
936 : earlier_set))
937 5556 : && (earlier_base_set == ao_ref_base_alias_set (&lhs_ref)
938 500 : || alias_set_subset_of
939 500 : (ao_ref_base_alias_set (&lhs_ref),
940 : earlier_base_set)))
941 4748 : delete_dead_or_redundant_assignment (&gsi, "redundant",
942 : need_eh_cleanup,
943 : need_ab_cleanup);
944 : }
945 50 : else if (is_gimple_call (use_stmt))
946 : {
947 50 : if ((earlier_set == 0
948 8 : || alias_set_subset_of (0, earlier_set))
949 50 : && (earlier_base_set == 0
950 0 : || alias_set_subset_of (0, earlier_base_set)))
951 42 : delete_dead_or_redundant_call (&gsi, "redundant");
952 : }
953 : else
954 0 : gcc_unreachable ();
955 : }
956 : }
957 4243133 : }
958 4243133 : }
959 :
960 : /* Return whether PHI contains ARG as an argument. */
961 :
962 : static bool
963 3954587 : contains_phi_arg (gphi *phi, tree arg)
964 : {
965 30249983 : for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
966 26525497 : if (gimple_phi_arg_def (phi, i) == arg)
967 : return true;
968 : return false;
969 : }
970 :
971 : /* Hash map of the memory use in a GIMPLE assignment to its
972 : data reference. If NULL data-ref analysis isn't used. */
973 : static hash_map<gimple *, data_reference_p> *dse_stmt_to_dr_map;
974 :
975 : /* A helper of dse_optimize_stmt.
976 : Given a GIMPLE_ASSIGN in STMT that writes to REF, classify it
977 : according to downstream uses and defs. Sets *BY_CLOBBER_P to true
978 : if only clobber statements influenced the classification result.
979 : Returns the classification. */
980 :
981 : static dse_store_status
982 40791478 : dse_classify_store (ao_ref *ref, gimple *stmt,
983 : bool byte_tracking_enabled, sbitmap live_bytes,
984 : bool *by_clobber_p, tree stop_at_vuse, int &cnt,
985 : bitmap visited)
986 : {
987 40791478 : gimple *temp;
988 40791478 : std::unique_ptr<data_reference, void(*)(data_reference_p)>
989 40791478 : dra (nullptr, free_data_ref);
990 :
991 40791478 : if (by_clobber_p)
992 40211823 : *by_clobber_p = true;
993 :
994 : /* Find the first dominated statement that clobbers (part of) the
995 : memory stmt stores to with no intermediate statement that may use
996 : part of the memory stmt stores. That is, find a store that may
997 : prove stmt to be a dead store. */
998 : temp = stmt;
999 518362268 : do
1000 : {
1001 279576873 : gimple *use_stmt;
1002 279576873 : imm_use_iterator ui;
1003 279576873 : bool fail = false;
1004 279576873 : tree defvar;
1005 :
1006 279576873 : if (gimple_code (temp) == GIMPLE_PHI)
1007 : {
1008 19031166 : defvar = PHI_RESULT (temp);
1009 19031166 : bitmap_set_bit (visited, SSA_NAME_VERSION (defvar));
1010 : }
1011 : else
1012 521091414 : defvar = gimple_vdef (temp);
1013 :
1014 279576873 : auto_vec<gimple *, 10> defs;
1015 279576873 : gphi *first_phi_def = NULL;
1016 279576873 : gphi *last_phi_def = NULL;
1017 :
1018 279576873 : auto_vec<tree, 10> worklist;
1019 279576873 : worklist.quick_push (defvar);
1020 :
1021 283489725 : do
1022 : {
1023 283489725 : defvar = worklist.pop ();
1024 : /* If we're instructed to stop walking at region boundary, do so. */
1025 283489725 : if (defvar == stop_at_vuse)
1026 : return DSE_STORE_LIVE;
1027 :
1028 283469944 : use_operand_p usep;
1029 889173181 : FOR_EACH_IMM_USE_FAST (usep, ui, defvar)
1030 : {
1031 351099612 : use_stmt = USE_STMT (usep);
1032 :
1033 : /* Limit stmt walking. */
1034 351099612 : if (++cnt > param_dse_max_alias_queries_per_store)
1035 : {
1036 : fail = true;
1037 : break;
1038 : }
1039 :
1040 : /* In simple cases we can look through PHI nodes, but we
1041 : have to be careful with loops and with memory references
1042 : containing operands that are also operands of PHI nodes.
1043 : See gcc.c-torture/execute/20051110-*.c. */
1044 350839232 : if (gphi *phi = dyn_cast <gphi *> (use_stmt))
1045 : {
1046 : /* Look through single-argument PHIs. */
1047 39232690 : if (gimple_phi_num_args (phi) == 1)
1048 4636710 : worklist.safe_push (gimple_phi_result (phi));
1049 : else
1050 : {
1051 : /* If we visit this PHI by following a backedge then we
1052 : have to make sure ref->ref only refers to SSA names
1053 : that are invariant with respect to the loop
1054 : represented by this PHI node. We handle irreducible
1055 : regions by relying on backedge marking and identifying
1056 : the head of the (sub-)region. */
1057 34595980 : edge e = gimple_phi_arg_edge
1058 34595980 : (phi, PHI_ARG_INDEX_FROM_USE (usep));
1059 34595980 : if (e->flags & EDGE_DFS_BACK)
1060 : {
1061 3212831 : basic_block rgn_head
1062 3212831 : = nearest_common_dominator (CDI_DOMINATORS,
1063 : gimple_bb (phi),
1064 : e->src);
1065 3212831 : if (!for_each_index (ref->ref
1066 : ? &ref->ref : &ref->base,
1067 : check_name, rgn_head))
1068 1487344 : return DSE_STORE_LIVE;
1069 : }
1070 : /* If we already visited this PHI ignore it for further
1071 : processing. But note we have to check each incoming
1072 : edge above. */
1073 66217272 : if (!bitmap_bit_p (visited,
1074 33108636 : SSA_NAME_VERSION (PHI_RESULT (phi))))
1075 : {
1076 24594781 : defs.safe_push (phi);
1077 24594781 : if (!first_phi_def)
1078 20760489 : first_phi_def = phi;;
1079 : last_phi_def = phi;
1080 : }
1081 : }
1082 : }
1083 : /* If the statement is a use the store is not dead. */
1084 311606542 : else if (ref_maybe_used_by_stmt_p (use_stmt, ref))
1085 : {
1086 27128830 : if (dse_stmt_to_dr_map
1087 5947162 : && ref->ref
1088 32970788 : && is_gimple_assign (use_stmt))
1089 : {
1090 1191808 : if (!dra)
1091 1187233 : dra.reset (create_data_ref (NULL, NULL, ref->ref, stmt,
1092 : false, false));
1093 1191808 : bool existed_p;
1094 1191808 : data_reference_p &drb
1095 1191808 : = dse_stmt_to_dr_map->get_or_insert (use_stmt,
1096 : &existed_p);
1097 1191808 : if (!existed_p)
1098 721809 : drb = create_data_ref (NULL, NULL,
1099 : gimple_assign_rhs1 (use_stmt),
1100 : use_stmt, false, false);
1101 1191808 : if (!dr_may_alias_p (dra.get (), drb, NULL))
1102 : {
1103 16576 : if (gimple_vdef (use_stmt))
1104 18 : defs.safe_push (use_stmt);
1105 8288 : continue;
1106 : }
1107 : }
1108 :
1109 : /* Handle common cases where we can easily build an ao_ref
1110 : structure for USE_STMT and in doing so we find that the
1111 : references hit non-live bytes and thus can be ignored.
1112 :
1113 : TODO: We can also use modref summary to handle calls. */
1114 27120542 : if (byte_tracking_enabled
1115 27120542 : && is_gimple_assign (use_stmt))
1116 : {
1117 4967194 : ao_ref use_ref;
1118 4967194 : ao_ref_init (&use_ref, gimple_assign_rhs1 (use_stmt));
1119 4967194 : if (valid_ao_ref_for_dse (&use_ref)
1120 4947167 : && operand_equal_p (use_ref.base, ref->base,
1121 : OEP_ADDRESS_OF)
1122 8577609 : && !live_bytes_read (&use_ref, ref, live_bytes))
1123 : {
1124 : /* If this is a store, remember it as we possibly
1125 : need to walk the defs uses. */
1126 3894 : if (gimple_vdef (use_stmt))
1127 345 : defs.safe_push (use_stmt);
1128 1947 : continue;
1129 : }
1130 : }
1131 :
1132 : fail = true;
1133 : break;
1134 : }
1135 : /* We have visited ourselves already so ignore STMT for the
1136 : purpose of chaining. */
1137 284477712 : else if (use_stmt == stmt)
1138 : ;
1139 : /* If this is a store, remember it as we possibly need to walk the
1140 : defs uses. */
1141 891015983 : else if (gimple_vdef (use_stmt))
1142 244736419 : defs.safe_push (use_stmt);
1143 1487344 : }
1144 : }
1145 563965200 : while (!fail && !worklist.is_empty ());
1146 :
1147 278069748 : if (fail)
1148 : {
1149 : /* STMT might be partially dead and we may be able to reduce
1150 : how many memory locations it stores into. */
1151 27378975 : if (byte_tracking_enabled && !gimple_clobber_p (stmt))
1152 24689678 : return DSE_STORE_MAYBE_PARTIAL_DEAD;
1153 : return DSE_STORE_LIVE;
1154 : }
1155 :
1156 : /* If we didn't find any definition this means the store is dead
1157 : if it isn't a store to global reachable memory. In this case
1158 : just pretend the stmt makes itself dead. Otherwise fail. */
1159 250690773 : if (defs.is_empty ())
1160 : {
1161 2502083 : if (ref_may_alias_global_p (ref, false))
1162 : {
1163 39655 : basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (defvar));
1164 : /* Assume that BUILT_IN_UNREACHABLE and BUILT_IN_UNREACHABLE_TRAP
1165 : do not need to keep (global) memory side-effects live.
1166 : We do not have virtual operands on BUILT_IN_UNREACHABLE
1167 : but we can do poor mans reachability when the last
1168 : definition we want to elide is in the block that ends
1169 : in such a call. */
1170 39655 : if (EDGE_COUNT (def_bb->succs) == 0)
1171 54616 : if (gcall *last = dyn_cast <gcall *> (*gsi_last_bb (def_bb)))
1172 633 : if (gimple_call_builtin_p (last, BUILT_IN_UNREACHABLE)
1173 633 : || gimple_call_builtin_p (last,
1174 : BUILT_IN_UNREACHABLE_TRAP))
1175 : {
1176 431 : if (by_clobber_p)
1177 431 : *by_clobber_p = false;
1178 431 : return DSE_STORE_DEAD;
1179 : }
1180 39224 : return DSE_STORE_LIVE;
1181 : }
1182 :
1183 2462428 : if (by_clobber_p)
1184 2459045 : *by_clobber_p = false;
1185 2462428 : return DSE_STORE_DEAD;
1186 : }
1187 :
1188 : /* Process defs and remove those we need not process further. */
1189 512349330 : for (unsigned i = 0; i < defs.length ();)
1190 : {
1191 264224985 : gimple *def = defs[i];
1192 264224985 : gimple *use_stmt;
1193 264224985 : use_operand_p use_p;
1194 264224985 : tree vdef = (gimple_code (def) == GIMPLE_PHI
1195 286764172 : ? gimple_phi_result (def) : gimple_vdef (def));
1196 264224985 : gphi *phi_def;
1197 : /* If the path to check starts with a kill we do not need to
1198 : process it further.
1199 : ??? With byte tracking we need only kill the bytes currently
1200 : live. */
1201 264224985 : if (stmt_kills_ref_p (def, ref))
1202 : {
1203 2431270 : if (by_clobber_p && !gimple_clobber_p (def))
1204 599408 : *by_clobber_p = false;
1205 2431270 : defs.unordered_remove (i);
1206 : }
1207 : /* If the path ends here we do not need to process it further.
1208 : This for example happens with calls to noreturn functions. */
1209 261793715 : else if (has_zero_uses (vdef))
1210 : {
1211 : /* But if the store is to global memory it is definitely
1212 : not dead. */
1213 2628939 : if (ref_may_alias_global_p (ref, false))
1214 64345 : return DSE_STORE_LIVE;
1215 2564594 : defs.unordered_remove (i);
1216 : }
1217 : /* In addition to kills we can remove defs whose only use
1218 : is another def in defs. That can only ever be PHIs of which
1219 : we track two for simplicity reasons, the first and last in
1220 : {first,last}_phi_def (we fail for multiple PHIs anyways).
1221 : We can also ignore defs that feed only into
1222 : already visited PHIs. */
1223 259164776 : else if (single_imm_use (vdef, &use_p, &use_stmt)
1224 259164776 : && (use_stmt == first_phi_def
1225 224793404 : || use_stmt == last_phi_def
1226 224700097 : || (gimple_code (use_stmt) == GIMPLE_PHI
1227 14271041 : && bitmap_bit_p (visited,
1228 14271041 : SSA_NAME_VERSION
1229 : (PHI_RESULT (use_stmt))))))
1230 : {
1231 5687636 : defs.unordered_remove (i);
1232 5687636 : if (def == first_phi_def)
1233 : first_phi_def = NULL;
1234 5004317 : else if (def == last_phi_def)
1235 238621 : last_phi_def = NULL;
1236 : }
1237 : /* If def is a PHI and one of its arguments is another PHI node still
1238 : in consideration we can defer processing it. */
1239 253477140 : else if ((phi_def = dyn_cast <gphi *> (def))
1240 21646309 : && ((last_phi_def
1241 21646309 : && phi_def != last_phi_def
1242 2088105 : && contains_phi_arg (phi_def,
1243 : gimple_phi_result (last_phi_def)))
1244 21536520 : || (first_phi_def
1245 21536520 : && phi_def != first_phi_def
1246 1866482 : && contains_phi_arg
1247 1866482 : (phi_def, gimple_phi_result (first_phi_def)))))
1248 : {
1249 230101 : defs.unordered_remove (i);
1250 230101 : if (phi_def == first_phi_def)
1251 : first_phi_def = NULL;
1252 160136 : else if (phi_def == last_phi_def)
1253 238621 : last_phi_def = NULL;
1254 : }
1255 : else
1256 253247039 : ++i;
1257 : }
1258 :
1259 : /* If all defs kill the ref we are done. */
1260 288915823 : if (defs.is_empty ())
1261 : return DSE_STORE_DEAD;
1262 : /* If more than one def survives we have to analyze multiple
1263 : paths. We can handle this by recursing, sharing 'visited'
1264 : to avoid redundant work and limiting it by shared 'cnt'.
1265 : For now do not bother with byte-tracking in this case. */
1266 248435009 : while (defs.length () > 1)
1267 : {
1268 9595459 : if (dse_classify_store (ref, defs.last (), false, NULL,
1269 : by_clobber_p, stop_at_vuse, cnt,
1270 : visited) != DSE_STORE_DEAD)
1271 : break;
1272 5912836 : byte_tracking_enabled = false;
1273 5912836 : defs.pop ();
1274 : }
1275 : /* If more than one def survives fail. */
1276 242522173 : if (defs.length () > 1)
1277 : {
1278 : /* STMT might be partially dead and we may be able to reduce
1279 : how many memory locations it stores into. */
1280 3682623 : if (byte_tracking_enabled && !gimple_clobber_p (stmt))
1281 1520389 : return DSE_STORE_MAYBE_PARTIAL_DEAD;
1282 : return DSE_STORE_LIVE;
1283 : }
1284 238839550 : temp = defs[0];
1285 :
1286 : /* Track partial kills. */
1287 238839550 : if (byte_tracking_enabled)
1288 : {
1289 182905606 : clear_bytes_written_by (live_bytes, temp, ref);
1290 182905606 : if (bitmap_empty_p (live_bytes))
1291 : {
1292 54155 : if (by_clobber_p && !gimple_clobber_p (temp))
1293 53993 : *by_clobber_p = false;
1294 54155 : return DSE_STORE_DEAD;
1295 : }
1296 : }
1297 279576873 : }
1298 : /* Continue walking until there are no more live bytes. */
1299 : while (1);
1300 40791478 : }
1301 :
1302 : dse_store_status
1303 31196019 : dse_classify_store (ao_ref *ref, gimple *stmt,
1304 : bool byte_tracking_enabled, sbitmap live_bytes,
1305 : bool *by_clobber_p, tree stop_at_vuse)
1306 : {
1307 31196019 : int cnt = 0;
1308 31196019 : auto_bitmap visited;
1309 31196019 : return dse_classify_store (ref, stmt, byte_tracking_enabled, live_bytes,
1310 31196019 : by_clobber_p, stop_at_vuse, cnt, visited);
1311 31196019 : }
1312 :
1313 :
1314 : /* Delete a dead call at GSI, which is mem* call of some kind. */
1315 : static void
1316 6615 : delete_dead_or_redundant_call (gimple_stmt_iterator *gsi, const char *type)
1317 : {
1318 6615 : gimple *stmt = gsi_stmt (*gsi);
1319 6615 : if (dump_file && (dump_flags & TDF_DETAILS))
1320 : {
1321 18 : fprintf (dump_file, " Deleted %s call: ", type);
1322 18 : print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1323 18 : fprintf (dump_file, "\n");
1324 : }
1325 :
1326 6615 : basic_block bb = gimple_bb (stmt);
1327 6615 : tree lhs = gimple_call_lhs (stmt);
1328 6615 : if (lhs)
1329 : {
1330 1216 : tree ptr = gimple_call_arg (stmt, 0);
1331 1216 : gimple *new_stmt = gimple_build_assign (lhs, ptr);
1332 1216 : unlink_stmt_vdef (stmt);
1333 1216 : if (gsi_replace (gsi, new_stmt, true))
1334 390 : bitmap_set_bit (need_eh_cleanup, bb->index);
1335 : }
1336 : else
1337 : {
1338 : /* Then we need to fix the operand of the consuming stmt. */
1339 5399 : unlink_stmt_vdef (stmt);
1340 :
1341 : /* Remove the dead store. */
1342 5399 : if (gsi_remove (gsi, true))
1343 0 : bitmap_set_bit (need_eh_cleanup, bb->index);
1344 5399 : release_defs (stmt);
1345 : }
1346 6615 : }
1347 :
1348 : /* Delete a dead store at GSI, which is a gimple assignment. */
1349 :
1350 : void
1351 2064762 : delete_dead_or_redundant_assignment (gimple_stmt_iterator *gsi,
1352 : const char *type,
1353 : bitmap need_eh_cleanup,
1354 : bitmap need_ab_cleanup)
1355 : {
1356 2064762 : gimple *stmt = gsi_stmt (*gsi);
1357 2064762 : if (dump_file && (dump_flags & TDF_DETAILS))
1358 : {
1359 111 : fprintf (dump_file, " Deleted %s store: ", type);
1360 111 : print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1361 111 : fprintf (dump_file, "\n");
1362 : }
1363 :
1364 : /* Then we need to fix the operand of the consuming stmt. */
1365 2064762 : unlink_stmt_vdef (stmt);
1366 :
1367 : /* Remove the dead store. */
1368 2064762 : basic_block bb = gimple_bb (stmt);
1369 2064762 : if (need_ab_cleanup && stmt_can_make_abnormal_goto (stmt))
1370 4 : bitmap_set_bit (need_ab_cleanup, bb->index);
1371 2064762 : if (gsi_remove (gsi, true) && need_eh_cleanup)
1372 91 : bitmap_set_bit (need_eh_cleanup, bb->index);
1373 :
1374 : /* And release any SSA_NAMEs set in this statement back to the
1375 : SSA_NAME manager. */
1376 2064762 : release_defs (stmt);
1377 2064762 : }
1378 :
1379 : /* Try to prove, using modref summary, that all memory written to by a call is
1380 : dead and remove it. Assume that if return value is written to memory
1381 : it is already proved to be dead. */
1382 :
1383 : static bool
1384 17208403 : dse_optimize_call (gimple_stmt_iterator *gsi, sbitmap live_bytes)
1385 : {
1386 34229627 : gcall *stmt = dyn_cast <gcall *> (gsi_stmt (*gsi));
1387 :
1388 17022610 : if (!stmt)
1389 : return false;
1390 :
1391 17022610 : tree callee = gimple_call_fndecl (stmt);
1392 :
1393 17022610 : if (!callee)
1394 : return false;
1395 :
1396 : /* Pure/const functions are optimized by normal DCE
1397 : or handled as store above. */
1398 16296005 : int flags = gimple_call_flags (stmt);
1399 16296005 : if ((flags & (ECF_PURE|ECF_CONST|ECF_NOVOPS))
1400 99 : && !(flags & (ECF_LOOPING_CONST_OR_PURE)))
1401 : return false;
1402 :
1403 16296003 : cgraph_node *node = cgraph_node::get (callee);
1404 16296003 : if (!node)
1405 : return false;
1406 :
1407 16286299 : if ((stmt_could_throw_p (cfun, stmt)
1408 7132964 : && !cfun->can_delete_dead_exceptions)
1409 18678141 : || ((gimple_call_flags (stmt) & ECF_NORETURN)
1410 2098553 : && gimple_call_ctrl_altering_p (stmt)))
1411 6839668 : return false;
1412 :
1413 : /* If return value is used the call is not dead. */
1414 9446631 : tree lhs = gimple_call_lhs (stmt);
1415 9446631 : if (lhs && TREE_CODE (lhs) == SSA_NAME)
1416 : {
1417 2368372 : imm_use_iterator ui;
1418 2368372 : gimple *use_stmt;
1419 4923212 : FOR_EACH_IMM_USE_STMT (use_stmt, ui, lhs)
1420 2507804 : if (!is_gimple_debug (use_stmt))
1421 2368372 : return false;
1422 : }
1423 :
1424 : /* Verify that there are no side-effects except for return value
1425 : and memory writes tracked by modref. */
1426 7125295 : modref_summary *summary = get_modref_function_summary (node);
1427 7125295 : if (!summary || !summary->try_dse)
1428 : return false;
1429 :
1430 71999 : bool by_clobber_p = false;
1431 :
1432 : /* Walk all memory writes and verify that they are dead. */
1433 217768 : for (auto base_node : summary->stores->bases)
1434 221035 : for (auto ref_node : base_node->refs)
1435 227091 : for (auto access_node : ref_node->accesses)
1436 : {
1437 74666 : tree arg = access_node.get_call_arg (stmt);
1438 :
1439 74666 : if (!arg || !POINTER_TYPE_P (TREE_TYPE (arg)))
1440 70613 : return false;
1441 :
1442 74665 : if (integer_zerop (arg)
1443 74676 : && !targetm.addr_space.zero_address_valid
1444 11 : (TYPE_ADDR_SPACE (TREE_TYPE (arg))))
1445 11 : continue;
1446 :
1447 74654 : ao_ref ref;
1448 :
1449 74654 : if (!access_node.get_ao_ref (stmt, &ref))
1450 : return false;
1451 74654 : ref.ref_alias_set = ref_node->ref;
1452 74654 : ref.base_alias_set = base_node->base;
1453 :
1454 74654 : bool byte_tracking_enabled
1455 74654 : = setup_live_bytes_from_ref (&ref, live_bytes);
1456 74654 : enum dse_store_status store_status;
1457 :
1458 74654 : store_status = dse_classify_store (&ref, stmt,
1459 : byte_tracking_enabled,
1460 : live_bytes, &by_clobber_p);
1461 74654 : if (store_status != DSE_STORE_DEAD)
1462 : return false;
1463 : }
1464 1386 : delete_dead_or_redundant_assignment (gsi, "dead", need_eh_cleanup,
1465 : need_ab_cleanup);
1466 1386 : return true;
1467 : }
1468 :
1469 : /* Attempt to eliminate dead stores in the statement referenced by BSI.
1470 :
1471 : A dead store is a store into a memory location which will later be
1472 : overwritten by another store without any intervening loads. In this
1473 : case the earlier store can be deleted.
1474 :
1475 : In our SSA + virtual operand world we use immediate uses of virtual
1476 : operands to detect dead stores. If a store's virtual definition
1477 : is used precisely once by a later store to the same location which
1478 : post dominates the first store, then the first store is dead. */
1479 :
1480 : static void
1481 54833327 : dse_optimize_stmt (function *fun, gimple_stmt_iterator *gsi, sbitmap live_bytes)
1482 : {
1483 54833327 : gimple *stmt = gsi_stmt (*gsi);
1484 :
1485 : /* Don't return early on *this_2(D) ={v} {CLOBBER}. */
1486 54833327 : if (gimple_has_volatile_ops (stmt)
1487 54833327 : && (!gimple_clobber_p (stmt)
1488 6342323 : || TREE_CODE (gimple_assign_lhs (stmt)) != MEM_REF))
1489 52697029 : return;
1490 :
1491 48276833 : ao_ref ref;
1492 : /* If this is not a store we can still remove dead call using
1493 : modref summary. Note we specifically allow ref to be initialized
1494 : to a conservative may-def since we are looking for followup stores
1495 : to kill all of it. */
1496 48276833 : if (!initialize_ao_ref_for_dse (stmt, &ref, true))
1497 : {
1498 17173049 : dse_optimize_call (gsi, live_bytes);
1499 17173049 : return;
1500 : }
1501 :
1502 : /* We know we have virtual definitions. We can handle assignments and
1503 : some builtin calls. */
1504 31103784 : if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL)
1505 31103784 : && !gimple_call_ctrl_altering_p (stmt))
1506 : {
1507 460722 : tree fndecl = gimple_call_fndecl (stmt);
1508 460722 : switch (DECL_FUNCTION_CODE (fndecl))
1509 : {
1510 459032 : case BUILT_IN_MEMCPY:
1511 459032 : case BUILT_IN_MEMMOVE:
1512 459032 : case BUILT_IN_STRNCPY:
1513 459032 : case BUILT_IN_MEMSET:
1514 459032 : case BUILT_IN_MEMCPY_CHK:
1515 459032 : case BUILT_IN_MEMMOVE_CHK:
1516 459032 : case BUILT_IN_STRNCPY_CHK:
1517 459032 : case BUILT_IN_MEMSET_CHK:
1518 459032 : {
1519 : /* Occasionally calls with an explicit length of zero
1520 : show up in the IL. It's pointless to do analysis
1521 : on them, they're trivially dead. */
1522 459032 : tree size = gimple_call_arg (stmt, 2);
1523 459032 : if (integer_zerop (size))
1524 : {
1525 50 : delete_dead_or_redundant_call (gsi, "dead");
1526 50 : return;
1527 : }
1528 :
1529 : /* If this is a memset call that initializes an object
1530 : to zero, it may be redundant with an earlier memset
1531 : or empty CONSTRUCTOR of a larger object. */
1532 458982 : if ((DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET
1533 361202 : || DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET_CHK)
1534 459279 : && integer_zerop (gimple_call_arg (stmt, 1)))
1535 56507 : dse_optimize_redundant_stores (stmt);
1536 :
1537 458982 : enum dse_store_status store_status;
1538 458982 : bool byte_tracking_enabled
1539 458982 : = setup_live_bytes_from_ref (&ref, live_bytes);
1540 458982 : store_status = dse_classify_store (&ref, stmt,
1541 : byte_tracking_enabled,
1542 : live_bytes);
1543 458982 : if (store_status == DSE_STORE_LIVE)
1544 : return;
1545 :
1546 148622 : if (store_status == DSE_STORE_MAYBE_PARTIAL_DEAD)
1547 : {
1548 142099 : maybe_trim_memstar_call (&ref, live_bytes, stmt);
1549 142099 : return;
1550 : }
1551 :
1552 6523 : if (store_status == DSE_STORE_DEAD)
1553 6523 : delete_dead_or_redundant_call (gsi, "dead");
1554 6523 : return;
1555 : }
1556 :
1557 1690 : case BUILT_IN_CALLOC:
1558 : /* We already know the arguments are integer constants. */
1559 1690 : dse_optimize_redundant_stores (stmt);
1560 1690 : return;
1561 :
1562 : default:
1563 : return;
1564 : }
1565 : }
1566 30643062 : else if (is_gimple_call (stmt)
1567 30643062 : && gimple_call_internal_p (stmt))
1568 : {
1569 107520 : switch (gimple_call_internal_fn (stmt))
1570 : {
1571 1297 : case IFN_LEN_STORE:
1572 1297 : case IFN_MASK_STORE:
1573 1297 : case IFN_MASK_LEN_STORE:
1574 1297 : {
1575 1297 : enum dse_store_status store_status;
1576 1297 : store_status = dse_classify_store (&ref, stmt, false, live_bytes);
1577 1297 : if (store_status == DSE_STORE_DEAD)
1578 0 : delete_dead_or_redundant_call (gsi, "dead");
1579 1297 : return;
1580 : }
1581 : default:;
1582 : }
1583 : }
1584 :
1585 30641765 : bool by_clobber_p = false;
1586 :
1587 : /* Check if this statement stores zero to a memory location,
1588 : and if there is a subsequent store of zero to the same
1589 : memory location. If so, remove the subsequent store. */
1590 30641765 : if (gimple_assign_single_p (stmt)
1591 30641765 : && initializer_zerop (gimple_assign_rhs1 (stmt)))
1592 4184936 : dse_optimize_redundant_stores (stmt);
1593 :
1594 : /* Self-assignments are zombies. */
1595 30641765 : if (is_gimple_assign (stmt)
1596 59873309 : && operand_equal_p (gimple_assign_rhs1 (stmt),
1597 29231544 : gimple_assign_lhs (stmt), 0))
1598 : ;
1599 : else
1600 : {
1601 30640329 : bool byte_tracking_enabled
1602 30640329 : = setup_live_bytes_from_ref (&ref, live_bytes);
1603 30640329 : enum dse_store_status store_status;
1604 30640329 : store_status = dse_classify_store (&ref, stmt,
1605 : byte_tracking_enabled,
1606 : live_bytes, &by_clobber_p);
1607 30640329 : if (store_status == DSE_STORE_LIVE)
1608 : return;
1609 :
1610 28195348 : if (store_status == DSE_STORE_MAYBE_PARTIAL_DEAD)
1611 : {
1612 25999906 : maybe_trim_partially_dead_store (&ref, live_bytes, stmt);
1613 25999906 : return;
1614 : }
1615 : }
1616 :
1617 : /* Now we know that use_stmt kills the LHS of stmt. */
1618 :
1619 : /* But only remove *this_2(D) ={v} {CLOBBER} if killed by
1620 : another clobber stmt. */
1621 2196878 : if (gimple_clobber_p (stmt)
1622 2196878 : && !by_clobber_p)
1623 : return;
1624 :
1625 2143463 : if (is_gimple_call (stmt)
1626 2143463 : && (gimple_has_side_effects (stmt)
1627 41455 : || (stmt_could_throw_p (fun, stmt)
1628 5 : && !fun->can_delete_dead_exceptions)))
1629 : {
1630 : /* See if we can remove complete call. */
1631 35354 : if (dse_optimize_call (gsi, live_bytes))
1632 : return;
1633 : /* Make sure we do not remove a return slot we cannot reconstruct
1634 : later. */
1635 35332 : if (gimple_call_return_slot_opt_p (as_a <gcall *>(stmt))
1636 35332 : && (TREE_ADDRESSABLE (TREE_TYPE (gimple_call_fntype (stmt)))
1637 14662 : || !poly_int_tree_p
1638 14662 : (TYPE_SIZE (TREE_TYPE (gimple_call_fntype (stmt))))))
1639 : return;
1640 28189 : if (dump_file && (dump_flags & TDF_DETAILS))
1641 : {
1642 1 : fprintf (dump_file, " Deleted dead store in call LHS: ");
1643 1 : print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1644 1 : fprintf (dump_file, "\n");
1645 : }
1646 28189 : gimple_call_set_lhs (stmt, NULL_TREE);
1647 28189 : update_stmt (stmt);
1648 : }
1649 2108109 : else if (!stmt_could_throw_p (fun, stmt)
1650 2108109 : || fun->can_delete_dead_exceptions)
1651 2058285 : delete_dead_or_redundant_assignment (gsi, "dead", need_eh_cleanup,
1652 : need_ab_cleanup);
1653 : }
1654 :
1655 : namespace {
1656 :
1657 : const pass_data pass_data_dse =
1658 : {
1659 : GIMPLE_PASS, /* type */
1660 : "dse", /* name */
1661 : OPTGROUP_NONE, /* optinfo_flags */
1662 : TV_TREE_DSE, /* tv_id */
1663 : ( PROP_cfg | PROP_ssa ), /* properties_required */
1664 : 0, /* properties_provided */
1665 : 0, /* properties_destroyed */
1666 : 0, /* todo_flags_start */
1667 : 0, /* todo_flags_finish */
1668 : };
1669 :
1670 : class pass_dse : public gimple_opt_pass
1671 : {
1672 : public:
1673 1428610 : pass_dse (gcc::context *ctxt)
1674 2857220 : : gimple_opt_pass (pass_data_dse, ctxt), use_dr_analysis_p (false)
1675 : {}
1676 :
1677 : /* opt_pass methods: */
1678 1142888 : opt_pass * clone () final override { return new pass_dse (m_ctxt); }
1679 285722 : void set_pass_param (unsigned n, bool param) final override
1680 : {
1681 285722 : gcc_assert (n == 0);
1682 285722 : use_dr_analysis_p = param;
1683 285722 : }
1684 5568844 : bool gate (function *) final override { return flag_tree_dse != 0; }
1685 : unsigned int execute (function *) final override;
1686 :
1687 : private:
1688 : bool use_dr_analysis_p;
1689 : }; // class pass_dse
1690 :
1691 : unsigned int
1692 5544176 : pass_dse::execute (function *fun)
1693 : {
1694 5544176 : unsigned todo = 0;
1695 5544176 : bool released_def = false;
1696 :
1697 5544176 : need_eh_cleanup = BITMAP_ALLOC (NULL);
1698 5544176 : need_ab_cleanup = BITMAP_ALLOC (NULL);
1699 5544176 : auto_sbitmap live_bytes (param_dse_max_object_size);
1700 5544176 : if (flag_expensive_optimizations && use_dr_analysis_p)
1701 959460 : dse_stmt_to_dr_map = new hash_map<gimple *, data_reference_p>;
1702 :
1703 5544176 : renumber_gimple_stmt_uids (fun);
1704 :
1705 5544176 : calculate_dominance_info (CDI_DOMINATORS);
1706 :
1707 : /* Dead store elimination is fundamentally a reverse program order walk. */
1708 5544176 : int *rpo = XNEWVEC (int, n_basic_blocks_for_fn (fun) - NUM_FIXED_BLOCKS);
1709 5544176 : auto_bitmap exit_bbs;
1710 5544176 : bitmap_set_bit (exit_bbs, EXIT_BLOCK);
1711 5544176 : edge entry = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (fun));
1712 5544176 : int n = rev_post_order_and_mark_dfs_back_seme (fun, entry,
1713 : exit_bbs, false, rpo, NULL);
1714 52712792 : for (int i = n; i != 0; --i)
1715 : {
1716 47168616 : basic_block bb = BASIC_BLOCK_FOR_FN (fun, rpo[i-1]);
1717 47168616 : gimple_stmt_iterator gsi;
1718 :
1719 94337232 : for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
1720 : {
1721 335224219 : gimple *stmt = gsi_stmt (gsi);
1722 :
1723 459781178 : if (gimple_vdef (stmt))
1724 54833327 : dse_optimize_stmt (fun, &gsi, live_bytes);
1725 560781784 : else if (def_operand_p
1726 280390892 : def_p = single_ssa_def_operand (stmt, SSA_OP_DEF))
1727 : {
1728 : /* When we remove dead stores make sure to also delete trivially
1729 : dead SSA defs. */
1730 63625497 : if (has_zero_uses (DEF_FROM_PTR (def_p))
1731 2091584 : && !gimple_has_side_effects (stmt)
1732 2081530 : && !is_ctrl_altering_stmt (stmt)
1733 65705339 : && (!stmt_could_throw_p (fun, stmt)
1734 91355 : || fun->can_delete_dead_exceptions))
1735 : {
1736 1988606 : if (dump_file && (dump_flags & TDF_DETAILS))
1737 : {
1738 11 : fprintf (dump_file, " Deleted trivially dead stmt: ");
1739 11 : print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1740 11 : fprintf (dump_file, "\n");
1741 : }
1742 1988606 : if (gsi_remove (&gsi, true) && need_eh_cleanup)
1743 2 : bitmap_set_bit (need_eh_cleanup, bb->index);
1744 1988606 : release_defs (stmt);
1745 1988606 : released_def = true;
1746 : }
1747 : }
1748 335224219 : if (gsi_end_p (gsi))
1749 580492 : gsi = gsi_last_bb (bb);
1750 : else
1751 717326808 : gsi_prev (&gsi);
1752 : }
1753 47168616 : bool removed_phi = false;
1754 66309310 : for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si);)
1755 : {
1756 19140694 : gphi *phi = si.phi ();
1757 19140694 : if (has_zero_uses (gimple_phi_result (phi)))
1758 : {
1759 218585 : if (dump_file && (dump_flags & TDF_DETAILS))
1760 : {
1761 0 : fprintf (dump_file, " Deleted trivially dead PHI: ");
1762 0 : print_gimple_stmt (dump_file, phi, 0, dump_flags);
1763 0 : fprintf (dump_file, "\n");
1764 : }
1765 218585 : remove_phi_node (&si, true);
1766 218585 : removed_phi = true;
1767 218585 : released_def = true;
1768 : }
1769 : else
1770 18922109 : gsi_next (&si);
1771 : }
1772 47168616 : if (removed_phi && gimple_seq_empty_p (phi_nodes (bb)))
1773 : todo |= TODO_cleanup_cfg;
1774 : }
1775 5544176 : free (rpo);
1776 :
1777 : /* Removal of stores may make some EH edges dead. Purge such edges from
1778 : the CFG as needed. */
1779 5544176 : if (!bitmap_empty_p (need_eh_cleanup))
1780 : {
1781 385 : gimple_purge_all_dead_eh_edges (need_eh_cleanup);
1782 385 : todo |= TODO_cleanup_cfg;
1783 : }
1784 5544176 : if (!bitmap_empty_p (need_ab_cleanup))
1785 : {
1786 4 : gimple_purge_all_dead_abnormal_call_edges (need_ab_cleanup);
1787 4 : todo |= TODO_cleanup_cfg;
1788 : }
1789 :
1790 5544176 : BITMAP_FREE (need_eh_cleanup);
1791 5544176 : BITMAP_FREE (need_ab_cleanup);
1792 :
1793 5544176 : if (released_def)
1794 591716 : free_numbers_of_iterations_estimates (fun);
1795 :
1796 5544176 : if (flag_expensive_optimizations && use_dr_analysis_p)
1797 : {
1798 1681269 : for (auto i = dse_stmt_to_dr_map->begin ();
1799 2403078 : i != dse_stmt_to_dr_map->end (); ++i)
1800 721809 : free_data_ref ((*i).second);
1801 1918920 : delete dse_stmt_to_dr_map;
1802 959460 : dse_stmt_to_dr_map = NULL;
1803 : }
1804 :
1805 5544176 : return todo;
1806 5544176 : }
1807 :
1808 : } // anon namespace
1809 :
1810 : gimple_opt_pass *
1811 285722 : make_pass_dse (gcc::context *ctxt)
1812 : {
1813 285722 : return new pass_dse (ctxt);
1814 : }
|
