1 | /* RTL dead code elimination. |
2 | Copyright (C) 2005-2023 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 it under |
7 | the terms of the GNU General Public License as published by the Free |
8 | Software Foundation; either version 3, or (at your option) any later |
9 | version. |
10 | |
11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or |
13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
14 | 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 "predict.h" |
27 | #include "df.h" |
28 | #include "memmodel.h" |
29 | #include "tm_p.h" |
30 | #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */ |
31 | #include "cfgrtl.h" |
32 | #include "cfgbuild.h" |
33 | #include "cfgcleanup.h" |
34 | #include "dce.h" |
35 | #include "valtrack.h" |
36 | #include "tree-pass.h" |
37 | #include "dbgcnt.h" |
38 | #include "rtl-iter.h" |
39 | |
40 | |
41 | /* ------------------------------------------------------------------------- |
42 | Core mark/delete routines |
43 | ------------------------------------------------------------------------- */ |
44 | |
45 | /* True if we are invoked while the df engine is running; in this case, |
46 | we don't want to reenter it. */ |
47 | static bool df_in_progress = false; |
48 | |
49 | /* True if we are allowed to alter the CFG in this pass. */ |
50 | static bool can_alter_cfg = false; |
51 | |
52 | /* Instructions that have been marked but whose dependencies have not |
53 | yet been processed. */ |
54 | static vec<rtx_insn *> worklist; |
55 | |
56 | /* Bitmap of instructions marked as needed indexed by INSN_UID. */ |
57 | static sbitmap marked; |
58 | |
59 | /* Bitmap obstacks used for block processing by the fast algorithm. */ |
60 | static bitmap_obstack dce_blocks_bitmap_obstack; |
61 | static bitmap_obstack dce_tmp_bitmap_obstack; |
62 | |
63 | static bool find_call_stack_args (rtx_call_insn *, bool, bool, bitmap); |
64 | |
65 | /* A subroutine for which BODY is part of the instruction being tested; |
66 | either the top-level pattern, or an element of a PARALLEL. The |
67 | instruction is known not to be a bare USE or CLOBBER. */ |
68 | |
69 | static bool |
70 | deletable_insn_p_1 (rtx body) |
71 | { |
72 | switch (GET_CODE (body)) |
73 | { |
74 | case PREFETCH: |
75 | case TRAP_IF: |
76 | /* The UNSPEC case was added here because the ia-64 claims that |
77 | USEs do not work after reload and generates UNSPECS rather |
78 | than USEs. Since dce is run after reload we need to avoid |
79 | deleting these even if they are dead. If it turns out that |
80 | USEs really do work after reload, the ia-64 should be |
81 | changed, and the UNSPEC case can be removed. */ |
82 | case UNSPEC: |
83 | return false; |
84 | |
85 | default: |
86 | return !volatile_refs_p (body); |
87 | } |
88 | } |
89 | |
90 | /* Don't delete calls that may throw if we cannot do so. */ |
91 | |
92 | static bool |
93 | can_delete_call (rtx_insn *insn) |
94 | { |
95 | if (cfun->can_delete_dead_exceptions && can_alter_cfg) |
96 | return true; |
97 | if (!insn_nothrow_p (insn)) |
98 | return false; |
99 | if (can_alter_cfg) |
100 | return true; |
101 | /* If we can't alter cfg, even when the call can't throw exceptions, it |
102 | might have EDGE_ABNORMAL_CALL edges and so we shouldn't delete such |
103 | calls. */ |
104 | gcc_assert (CALL_P (insn)); |
105 | if (BLOCK_FOR_INSN (insn) && BB_END (BLOCK_FOR_INSN (insn)) == insn) |
106 | { |
107 | edge e; |
108 | edge_iterator ei; |
109 | |
110 | FOR_EACH_EDGE (e, ei, BLOCK_FOR_INSN (insn)->succs) |
111 | if ((e->flags & EDGE_ABNORMAL_CALL) != 0) |
112 | return false; |
113 | } |
114 | return true; |
115 | } |
116 | |
117 | /* Return true if INSN is a normal instruction that can be deleted by |
118 | the DCE pass. */ |
119 | |
120 | static bool |
121 | deletable_insn_p (rtx_insn *insn, bool fast, bitmap arg_stores) |
122 | { |
123 | rtx body, x; |
124 | int i; |
125 | df_ref def; |
126 | |
127 | if (CALL_P (insn) |
128 | /* We cannot delete calls inside of the recursive dce because |
129 | this may cause basic blocks to be deleted and this messes up |
130 | the rest of the stack of optimization passes. */ |
131 | && (!df_in_progress) |
132 | /* We cannot delete pure or const sibling calls because it is |
133 | hard to see the result. */ |
134 | && (!SIBLING_CALL_P (insn)) |
135 | /* We can delete dead const or pure calls as long as they do not |
136 | infinite loop. */ |
137 | && (RTL_CONST_OR_PURE_CALL_P (insn) |
138 | && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)) |
139 | /* Don't delete calls that may throw if we cannot do so. */ |
140 | && can_delete_call (insn)) |
141 | return find_call_stack_args (as_a <rtx_call_insn *> (p: insn), false, |
142 | fast, arg_stores); |
143 | |
144 | /* Don't delete jumps, notes and the like. */ |
145 | if (!NONJUMP_INSN_P (insn)) |
146 | return false; |
147 | |
148 | /* Don't delete insns that may throw if we cannot do so. */ |
149 | if (!(cfun->can_delete_dead_exceptions && can_alter_cfg) |
150 | && !insn_nothrow_p (insn)) |
151 | return false; |
152 | |
153 | /* If INSN sets a global_reg, leave it untouched. */ |
154 | FOR_EACH_INSN_DEF (def, insn) |
155 | if (HARD_REGISTER_NUM_P (DF_REF_REGNO (def)) |
156 | && global_regs[DF_REF_REGNO (def)]) |
157 | return false; |
158 | /* Initialization of pseudo PIC register should never be removed. */ |
159 | else if (DF_REF_REG (def) == pic_offset_table_rtx |
160 | && REGNO (pic_offset_table_rtx) >= FIRST_PSEUDO_REGISTER) |
161 | return false; |
162 | |
163 | /* Callee-save restores are needed. */ |
164 | if (RTX_FRAME_RELATED_P (insn) |
165 | && crtl->shrink_wrapped_separate |
166 | && find_reg_note (insn, REG_CFA_RESTORE, NULL)) |
167 | return false; |
168 | |
169 | body = PATTERN (insn); |
170 | switch (GET_CODE (body)) |
171 | { |
172 | case USE: |
173 | case VAR_LOCATION: |
174 | return false; |
175 | |
176 | case CLOBBER: |
177 | if (fast) |
178 | { |
179 | /* A CLOBBER of a dead pseudo register serves no purpose. |
180 | That is not necessarily true for hard registers until |
181 | after reload. */ |
182 | x = XEXP (body, 0); |
183 | return REG_P (x) && (!HARD_REGISTER_P (x) || reload_completed); |
184 | } |
185 | else |
186 | /* Because of the way that use-def chains are built, it is not |
187 | possible to tell if the clobber is dead because it can |
188 | never be the target of a use-def chain. */ |
189 | return false; |
190 | |
191 | case PARALLEL: |
192 | for (i = XVECLEN (body, 0) - 1; i >= 0; i--) |
193 | if (!deletable_insn_p_1 (XVECEXP (body, 0, i))) |
194 | return false; |
195 | return true; |
196 | |
197 | default: |
198 | return deletable_insn_p_1 (body); |
199 | } |
200 | } |
201 | |
202 | |
203 | /* Return true if INSN has been marked as needed. */ |
204 | |
205 | static inline int |
206 | marked_insn_p (rtx_insn *insn) |
207 | { |
208 | /* Artificial defs are always needed and they do not have an insn. |
209 | We should never see them here. */ |
210 | gcc_assert (insn); |
211 | return bitmap_bit_p (map: marked, bitno: INSN_UID (insn)); |
212 | } |
213 | |
214 | |
215 | /* If INSN has not yet been marked as needed, mark it now, and add it to |
216 | the worklist. */ |
217 | |
218 | static void |
219 | mark_insn (rtx_insn *insn, bool fast) |
220 | { |
221 | if (!marked_insn_p (insn)) |
222 | { |
223 | if (!fast) |
224 | worklist.safe_push (obj: insn); |
225 | bitmap_set_bit (map: marked, bitno: INSN_UID (insn)); |
226 | if (dump_file) |
227 | fprintf (stream: dump_file, format: " Adding insn %d to worklist\n" , INSN_UID (insn)); |
228 | if (CALL_P (insn) |
229 | && !df_in_progress |
230 | && !SIBLING_CALL_P (insn) |
231 | && (RTL_CONST_OR_PURE_CALL_P (insn) |
232 | && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)) |
233 | && can_delete_call (insn)) |
234 | find_call_stack_args (as_a <rtx_call_insn *> (p: insn), true, fast, NULL); |
235 | } |
236 | } |
237 | |
238 | |
239 | /* A note_stores callback used by mark_nonreg_stores. DATA is the |
240 | instruction containing DEST. */ |
241 | |
242 | static void |
243 | mark_nonreg_stores_1 (rtx dest, const_rtx pattern, void *data) |
244 | { |
245 | if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) |
246 | mark_insn (insn: (rtx_insn *) data, fast: true); |
247 | } |
248 | |
249 | |
250 | /* A note_stores callback used by mark_nonreg_stores. DATA is the |
251 | instruction containing DEST. */ |
252 | |
253 | static void |
254 | mark_nonreg_stores_2 (rtx dest, const_rtx pattern, void *data) |
255 | { |
256 | if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) |
257 | mark_insn (insn: (rtx_insn *) data, fast: false); |
258 | } |
259 | |
260 | |
261 | /* Mark INSN if it stores to a non-register destination. */ |
262 | |
263 | static void |
264 | mark_nonreg_stores (rtx_insn *insn, bool fast) |
265 | { |
266 | if (fast) |
267 | note_stores (insn, mark_nonreg_stores_1, insn); |
268 | else |
269 | note_stores (insn, mark_nonreg_stores_2, insn); |
270 | } |
271 | |
272 | |
273 | /* Return true if a store to SIZE bytes, starting OFF bytes from stack pointer, |
274 | is a call argument store, and clear corresponding bits from SP_BYTES |
275 | bitmap if it is. */ |
276 | |
277 | static bool |
278 | check_argument_store (HOST_WIDE_INT size, HOST_WIDE_INT off, |
279 | HOST_WIDE_INT min_sp_off, HOST_WIDE_INT max_sp_off, |
280 | bitmap sp_bytes) |
281 | { |
282 | HOST_WIDE_INT byte; |
283 | for (byte = off; byte < off + size; byte++) |
284 | { |
285 | if (byte < min_sp_off |
286 | || byte >= max_sp_off |
287 | || !bitmap_clear_bit (sp_bytes, byte - min_sp_off)) |
288 | return false; |
289 | } |
290 | return true; |
291 | } |
292 | |
293 | /* If MEM has sp address, return 0, if it has sp + const address, |
294 | return that const, if it has reg address where reg is set to sp + const |
295 | and FAST is false, return const, otherwise return |
296 | INTTYPE_MINUMUM (HOST_WIDE_INT). */ |
297 | |
298 | static HOST_WIDE_INT |
299 | sp_based_mem_offset (rtx_call_insn *call_insn, const_rtx mem, bool fast) |
300 | { |
301 | HOST_WIDE_INT off = 0; |
302 | rtx addr = XEXP (mem, 0); |
303 | if (GET_CODE (addr) == PLUS |
304 | && REG_P (XEXP (addr, 0)) |
305 | && CONST_INT_P (XEXP (addr, 1))) |
306 | { |
307 | off = INTVAL (XEXP (addr, 1)); |
308 | addr = XEXP (addr, 0); |
309 | } |
310 | if (addr == stack_pointer_rtx) |
311 | return off; |
312 | |
313 | if (!REG_P (addr) || fast) |
314 | return INTTYPE_MINIMUM (HOST_WIDE_INT); |
315 | |
316 | /* If not fast, use chains to see if addr wasn't set to sp + offset. */ |
317 | df_ref use; |
318 | FOR_EACH_INSN_USE (use, call_insn) |
319 | if (rtx_equal_p (addr, DF_REF_REG (use))) |
320 | break; |
321 | |
322 | if (use == NULL) |
323 | return INTTYPE_MINIMUM (HOST_WIDE_INT); |
324 | |
325 | struct df_link *defs; |
326 | for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) |
327 | if (! DF_REF_IS_ARTIFICIAL (defs->ref)) |
328 | break; |
329 | |
330 | if (defs == NULL) |
331 | return INTTYPE_MINIMUM (HOST_WIDE_INT); |
332 | |
333 | rtx set = single_set (DF_REF_INSN (defs->ref)); |
334 | if (!set) |
335 | return INTTYPE_MINIMUM (HOST_WIDE_INT); |
336 | |
337 | if (GET_CODE (SET_SRC (set)) != PLUS |
338 | || XEXP (SET_SRC (set), 0) != stack_pointer_rtx |
339 | || !CONST_INT_P (XEXP (SET_SRC (set), 1))) |
340 | return INTTYPE_MINIMUM (HOST_WIDE_INT); |
341 | |
342 | off += INTVAL (XEXP (SET_SRC (set), 1)); |
343 | return off; |
344 | } |
345 | |
346 | /* Data for check_argument_load called via note_uses. */ |
347 | struct check_argument_load_data { |
348 | bitmap sp_bytes; |
349 | HOST_WIDE_INT min_sp_off, max_sp_off; |
350 | rtx_call_insn *call_insn; |
351 | bool fast; |
352 | bool load_found; |
353 | }; |
354 | |
355 | /* Helper function for find_call_stack_args. Check if there are |
356 | any loads from the argument slots in between the const/pure call |
357 | and store to the argument slot, set LOAD_FOUND if any is found. */ |
358 | |
359 | static void |
360 | check_argument_load (rtx *loc, void *data) |
361 | { |
362 | struct check_argument_load_data *d |
363 | = (struct check_argument_load_data *) data; |
364 | subrtx_iterator::array_type array; |
365 | FOR_EACH_SUBRTX (iter, array, *loc, NONCONST) |
366 | { |
367 | const_rtx mem = *iter; |
368 | HOST_WIDE_INT size; |
369 | if (MEM_P (mem) |
370 | && MEM_SIZE_KNOWN_P (mem) |
371 | && MEM_SIZE (mem).is_constant (const_value: &size)) |
372 | { |
373 | HOST_WIDE_INT off = sp_based_mem_offset (call_insn: d->call_insn, mem, fast: d->fast); |
374 | if (off != INTTYPE_MINIMUM (HOST_WIDE_INT) |
375 | && off < d->max_sp_off |
376 | && off + size > d->min_sp_off) |
377 | for (HOST_WIDE_INT byte = MAX (off, d->min_sp_off); |
378 | byte < MIN (off + size, d->max_sp_off); byte++) |
379 | if (bitmap_bit_p (d->sp_bytes, byte - d->min_sp_off)) |
380 | { |
381 | d->load_found = true; |
382 | return; |
383 | } |
384 | } |
385 | } |
386 | } |
387 | |
388 | /* Try to find all stack stores of CALL_INSN arguments if |
389 | ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found |
390 | and it is therefore safe to eliminate the call, return true, |
391 | otherwise return false. This function should be first called |
392 | with DO_MARK false, and only when the CALL_INSN is actually |
393 | going to be marked called again with DO_MARK true. */ |
394 | |
395 | static bool |
396 | find_call_stack_args (rtx_call_insn *call_insn, bool do_mark, bool fast, |
397 | bitmap arg_stores) |
398 | { |
399 | rtx p; |
400 | rtx_insn *insn, *prev_insn; |
401 | bool ret; |
402 | HOST_WIDE_INT min_sp_off, max_sp_off; |
403 | bitmap sp_bytes; |
404 | |
405 | gcc_assert (CALL_P (call_insn)); |
406 | if (!ACCUMULATE_OUTGOING_ARGS) |
407 | return true; |
408 | |
409 | if (!do_mark) |
410 | { |
411 | gcc_assert (arg_stores); |
412 | bitmap_clear (arg_stores); |
413 | } |
414 | |
415 | min_sp_off = INTTYPE_MAXIMUM (HOST_WIDE_INT); |
416 | max_sp_off = 0; |
417 | |
418 | /* First determine the minimum and maximum offset from sp for |
419 | stored arguments. */ |
420 | for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) |
421 | if (GET_CODE (XEXP (p, 0)) == USE |
422 | && MEM_P (XEXP (XEXP (p, 0), 0))) |
423 | { |
424 | rtx mem = XEXP (XEXP (p, 0), 0); |
425 | HOST_WIDE_INT size; |
426 | if (!MEM_SIZE_KNOWN_P (mem) || !MEM_SIZE (mem).is_constant (const_value: &size)) |
427 | return false; |
428 | HOST_WIDE_INT off = sp_based_mem_offset (call_insn, mem, fast); |
429 | if (off == INTTYPE_MINIMUM (HOST_WIDE_INT)) |
430 | return false; |
431 | min_sp_off = MIN (min_sp_off, off); |
432 | max_sp_off = MAX (max_sp_off, off + size); |
433 | } |
434 | |
435 | if (min_sp_off >= max_sp_off) |
436 | return true; |
437 | sp_bytes = BITMAP_ALLOC (NULL); |
438 | |
439 | /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off |
440 | which contain arguments. Checking has been done in the previous |
441 | loop. */ |
442 | for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) |
443 | if (GET_CODE (XEXP (p, 0)) == USE |
444 | && MEM_P (XEXP (XEXP (p, 0), 0))) |
445 | { |
446 | rtx mem = XEXP (XEXP (p, 0), 0); |
447 | /* Checked in the previous iteration. */ |
448 | HOST_WIDE_INT size = MEM_SIZE (mem).to_constant (); |
449 | HOST_WIDE_INT off = sp_based_mem_offset (call_insn, mem, fast); |
450 | gcc_checking_assert (off != INTTYPE_MINIMUM (HOST_WIDE_INT)); |
451 | for (HOST_WIDE_INT byte = off; byte < off + size; byte++) |
452 | if (!bitmap_set_bit (sp_bytes, byte - min_sp_off)) |
453 | gcc_unreachable (); |
454 | } |
455 | |
456 | /* Walk backwards, looking for argument stores. The search stops |
457 | when seeing another call, sp adjustment, memory store other than |
458 | argument store or a read from an argument stack slot. */ |
459 | struct check_argument_load_data data |
460 | = { .sp_bytes: sp_bytes, .min_sp_off: min_sp_off, .max_sp_off: max_sp_off, .call_insn: call_insn, .fast: fast, .load_found: false }; |
461 | ret = false; |
462 | for (insn = PREV_INSN (insn: call_insn); insn; insn = prev_insn) |
463 | { |
464 | if (insn == BB_HEAD (BLOCK_FOR_INSN (call_insn))) |
465 | prev_insn = NULL; |
466 | else |
467 | prev_insn = PREV_INSN (insn); |
468 | |
469 | if (CALL_P (insn)) |
470 | break; |
471 | |
472 | if (!NONDEBUG_INSN_P (insn)) |
473 | continue; |
474 | |
475 | rtx set = single_set (insn); |
476 | if (!set || SET_DEST (set) == stack_pointer_rtx) |
477 | break; |
478 | |
479 | note_uses (&PATTERN (insn), check_argument_load, &data); |
480 | if (data.load_found) |
481 | break; |
482 | |
483 | if (!MEM_P (SET_DEST (set))) |
484 | continue; |
485 | |
486 | rtx mem = SET_DEST (set); |
487 | HOST_WIDE_INT off = sp_based_mem_offset (call_insn, mem, fast); |
488 | if (off == INTTYPE_MINIMUM (HOST_WIDE_INT)) |
489 | break; |
490 | |
491 | HOST_WIDE_INT size; |
492 | if (!MEM_SIZE_KNOWN_P (mem) |
493 | || !MEM_SIZE (mem).is_constant (const_value: &size) |
494 | || !check_argument_store (size, off, min_sp_off, |
495 | max_sp_off, sp_bytes)) |
496 | break; |
497 | |
498 | if (!deletable_insn_p (insn, fast, NULL)) |
499 | break; |
500 | |
501 | if (do_mark) |
502 | mark_insn (insn, fast); |
503 | else |
504 | bitmap_set_bit (arg_stores, INSN_UID (insn)); |
505 | |
506 | if (bitmap_empty_p (map: sp_bytes)) |
507 | { |
508 | ret = true; |
509 | break; |
510 | } |
511 | } |
512 | |
513 | BITMAP_FREE (sp_bytes); |
514 | if (!ret && arg_stores) |
515 | bitmap_clear (arg_stores); |
516 | |
517 | return ret; |
518 | } |
519 | |
520 | |
521 | /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN |
522 | writes to. */ |
523 | |
524 | static void |
525 | remove_reg_equal_equiv_notes_for_defs (rtx_insn *insn) |
526 | { |
527 | df_ref def; |
528 | |
529 | FOR_EACH_INSN_DEF (def, insn) |
530 | remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (def)); |
531 | } |
532 | |
533 | /* Scan all BBs for debug insns and reset those that reference values |
534 | defined in unmarked insns. */ |
535 | |
536 | static void |
537 | reset_unmarked_insns_debug_uses (void) |
538 | { |
539 | basic_block bb; |
540 | rtx_insn *insn, *next; |
541 | |
542 | FOR_EACH_BB_REVERSE_FN (bb, cfun) |
543 | FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next) |
544 | if (DEBUG_INSN_P (insn)) |
545 | { |
546 | df_ref use; |
547 | |
548 | FOR_EACH_INSN_USE (use, insn) |
549 | { |
550 | struct df_link *defs; |
551 | for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) |
552 | { |
553 | rtx_insn *ref_insn; |
554 | if (DF_REF_IS_ARTIFICIAL (defs->ref)) |
555 | continue; |
556 | ref_insn = DF_REF_INSN (defs->ref); |
557 | if (!marked_insn_p (insn: ref_insn)) |
558 | break; |
559 | } |
560 | if (!defs) |
561 | continue; |
562 | /* ??? FIXME could we propagate the values assigned to |
563 | each of the DEFs? */ |
564 | INSN_VAR_LOCATION_LOC (insn) = gen_rtx_UNKNOWN_VAR_LOC (); |
565 | df_insn_rescan_debug_internal (insn); |
566 | break; |
567 | } |
568 | } |
569 | } |
570 | |
571 | /* Delete every instruction that hasn't been marked. */ |
572 | |
573 | static void |
574 | delete_unmarked_insns (void) |
575 | { |
576 | basic_block bb; |
577 | rtx_insn *insn, *next; |
578 | bool must_clean = false; |
579 | |
580 | FOR_EACH_BB_REVERSE_FN (bb, cfun) |
581 | FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next) |
582 | if (NONDEBUG_INSN_P (insn)) |
583 | { |
584 | rtx turn_into_use = NULL_RTX; |
585 | |
586 | /* Always delete no-op moves. */ |
587 | if (noop_move_p (insn) |
588 | /* Unless the no-op move can throw and we are not allowed |
589 | to alter cfg. */ |
590 | && (!cfun->can_throw_non_call_exceptions |
591 | || (cfun->can_delete_dead_exceptions && can_alter_cfg) |
592 | || insn_nothrow_p (insn))) |
593 | { |
594 | if (RTX_FRAME_RELATED_P (insn)) |
595 | turn_into_use |
596 | = find_reg_note (insn, REG_CFA_RESTORE, NULL); |
597 | if (turn_into_use && REG_P (XEXP (turn_into_use, 0))) |
598 | turn_into_use = XEXP (turn_into_use, 0); |
599 | else |
600 | turn_into_use = NULL_RTX; |
601 | } |
602 | |
603 | /* Otherwise rely only on the DCE algorithm. */ |
604 | else if (marked_insn_p (insn)) |
605 | continue; |
606 | |
607 | /* Beware that reaching a dbg counter limit here can result |
608 | in miscompiled file. This occurs when a group of insns |
609 | must be deleted together, typically because the kept insn |
610 | depends on the output from the deleted insn. Deleting |
611 | this insns in reverse order (both at the bb level and |
612 | when looking at the blocks) minimizes this, but does not |
613 | eliminate it, since it is possible for the using insn to |
614 | be top of a block and the producer to be at the bottom of |
615 | the block. However, in most cases this will only result |
616 | in an uninitialized use of an insn that is dead anyway. |
617 | |
618 | However, there is one rare case that will cause a |
619 | miscompile: deletion of non-looping pure and constant |
620 | calls on a machine where ACCUMULATE_OUTGOING_ARGS is true. |
621 | In this case it is possible to remove the call, but leave |
622 | the argument pushes to the stack. Because of the changes |
623 | to the stack pointer, this will almost always lead to a |
624 | miscompile. */ |
625 | if (!dbg_cnt (index: dce)) |
626 | continue; |
627 | |
628 | if (dump_file) |
629 | fprintf (stream: dump_file, format: "DCE: Deleting insn %d\n" , INSN_UID (insn)); |
630 | |
631 | /* Before we delete the insn we have to remove the REG_EQUAL notes |
632 | for the destination regs in order to avoid dangling notes. */ |
633 | remove_reg_equal_equiv_notes_for_defs (insn); |
634 | |
635 | if (turn_into_use) |
636 | { |
637 | /* Don't remove frame related noop moves if they cary |
638 | REG_CFA_RESTORE note, while we don't need to emit any code, |
639 | we need it to emit the CFI restore note. */ |
640 | PATTERN (insn) |
641 | = gen_rtx_USE (GET_MODE (turn_into_use), turn_into_use); |
642 | INSN_CODE (insn) = -1; |
643 | df_insn_rescan (insn); |
644 | } |
645 | else |
646 | /* Now delete the insn. */ |
647 | must_clean |= delete_insn_and_edges (insn); |
648 | } |
649 | |
650 | /* Deleted a pure or const call. */ |
651 | if (must_clean) |
652 | { |
653 | gcc_assert (can_alter_cfg); |
654 | delete_unreachable_blocks (); |
655 | free_dominance_info (CDI_DOMINATORS); |
656 | } |
657 | } |
658 | |
659 | |
660 | /* Go through the instructions and mark those whose necessity is not |
661 | dependent on inter-instruction information. Make sure all other |
662 | instructions are not marked. */ |
663 | |
664 | static void |
665 | prescan_insns_for_dce (bool fast) |
666 | { |
667 | basic_block bb; |
668 | rtx_insn *insn, *prev; |
669 | bitmap arg_stores = NULL; |
670 | |
671 | if (dump_file) |
672 | fprintf (stream: dump_file, format: "Finding needed instructions:\n" ); |
673 | |
674 | if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS) |
675 | arg_stores = BITMAP_ALLOC (NULL); |
676 | |
677 | FOR_EACH_BB_FN (bb, cfun) |
678 | { |
679 | FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev) |
680 | if (NONDEBUG_INSN_P (insn)) |
681 | { |
682 | /* Don't mark argument stores now. They will be marked |
683 | if needed when the associated CALL is marked. */ |
684 | if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn))) |
685 | continue; |
686 | if (deletable_insn_p (insn, fast, arg_stores)) |
687 | mark_nonreg_stores (insn, fast); |
688 | else |
689 | mark_insn (insn, fast); |
690 | } |
691 | /* find_call_stack_args only looks at argument stores in the |
692 | same bb. */ |
693 | if (arg_stores) |
694 | bitmap_clear (arg_stores); |
695 | } |
696 | |
697 | if (arg_stores) |
698 | BITMAP_FREE (arg_stores); |
699 | |
700 | if (dump_file) |
701 | fprintf (stream: dump_file, format: "Finished finding needed instructions:\n" ); |
702 | } |
703 | |
704 | |
705 | /* UD-based DSE routines. */ |
706 | |
707 | /* Mark instructions that define artificially-used registers, such as |
708 | the frame pointer and the stack pointer. */ |
709 | |
710 | static void |
711 | mark_artificial_uses (void) |
712 | { |
713 | basic_block bb; |
714 | struct df_link *defs; |
715 | df_ref use; |
716 | |
717 | FOR_ALL_BB_FN (bb, cfun) |
718 | FOR_EACH_ARTIFICIAL_USE (use, bb->index) |
719 | for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) |
720 | if (!DF_REF_IS_ARTIFICIAL (defs->ref)) |
721 | mark_insn (DF_REF_INSN (defs->ref), fast: false); |
722 | } |
723 | |
724 | |
725 | /* Mark every instruction that defines a register value that INSN uses. */ |
726 | |
727 | static void |
728 | mark_reg_dependencies (rtx_insn *insn) |
729 | { |
730 | struct df_link *defs; |
731 | df_ref use; |
732 | |
733 | if (DEBUG_INSN_P (insn)) |
734 | return; |
735 | |
736 | FOR_EACH_INSN_USE (use, insn) |
737 | { |
738 | if (dump_file) |
739 | { |
740 | fprintf (stream: dump_file, format: "Processing use of " ); |
741 | print_simple_rtl (dump_file, DF_REF_REG (use)); |
742 | fprintf (stream: dump_file, format: " in insn %d:\n" , INSN_UID (insn)); |
743 | } |
744 | for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) |
745 | if (! DF_REF_IS_ARTIFICIAL (defs->ref)) |
746 | mark_insn (DF_REF_INSN (defs->ref), fast: false); |
747 | } |
748 | } |
749 | |
750 | |
751 | /* Initialize global variables for a new DCE pass. */ |
752 | |
753 | static void |
754 | init_dce (bool fast) |
755 | { |
756 | if (!df_in_progress) |
757 | { |
758 | if (!fast) |
759 | { |
760 | df_set_flags (DF_RD_PRUNE_DEAD_DEFS); |
761 | df_chain_add_problem (DF_UD_CHAIN); |
762 | } |
763 | df_analyze (); |
764 | } |
765 | |
766 | if (dump_file) |
767 | df_dump (dump_file); |
768 | |
769 | if (fast) |
770 | { |
771 | bitmap_obstack_initialize (&dce_blocks_bitmap_obstack); |
772 | bitmap_obstack_initialize (&dce_tmp_bitmap_obstack); |
773 | can_alter_cfg = false; |
774 | } |
775 | else |
776 | can_alter_cfg = true; |
777 | |
778 | marked = sbitmap_alloc (get_max_uid () + 1); |
779 | bitmap_clear (marked); |
780 | } |
781 | |
782 | |
783 | /* Free the data allocated by init_dce. */ |
784 | |
785 | static void |
786 | fini_dce (bool fast) |
787 | { |
788 | sbitmap_free (map: marked); |
789 | |
790 | if (fast) |
791 | { |
792 | bitmap_obstack_release (&dce_blocks_bitmap_obstack); |
793 | bitmap_obstack_release (&dce_tmp_bitmap_obstack); |
794 | } |
795 | } |
796 | |
797 | |
798 | /* UD-chain based DCE. */ |
799 | |
800 | static unsigned int |
801 | rest_of_handle_ud_dce (void) |
802 | { |
803 | rtx_insn *insn; |
804 | |
805 | init_dce (fast: false); |
806 | |
807 | prescan_insns_for_dce (fast: false); |
808 | mark_artificial_uses (); |
809 | while (worklist.length () > 0) |
810 | { |
811 | insn = worklist.pop (); |
812 | mark_reg_dependencies (insn); |
813 | } |
814 | worklist.release (); |
815 | |
816 | if (MAY_HAVE_DEBUG_BIND_INSNS) |
817 | reset_unmarked_insns_debug_uses (); |
818 | |
819 | /* Before any insns are deleted, we must remove the chains since |
820 | they are not bidirectional. */ |
821 | df_remove_problem (df_chain); |
822 | delete_unmarked_insns (); |
823 | |
824 | fini_dce (fast: false); |
825 | return 0; |
826 | } |
827 | |
828 | |
829 | namespace { |
830 | |
831 | const pass_data pass_data_ud_rtl_dce = |
832 | { |
833 | .type: RTL_PASS, /* type */ |
834 | .name: "ud_dce" , /* name */ |
835 | .optinfo_flags: OPTGROUP_NONE, /* optinfo_flags */ |
836 | .tv_id: TV_DCE, /* tv_id */ |
837 | .properties_required: 0, /* properties_required */ |
838 | .properties_provided: 0, /* properties_provided */ |
839 | .properties_destroyed: 0, /* properties_destroyed */ |
840 | .todo_flags_start: 0, /* todo_flags_start */ |
841 | TODO_df_finish, /* todo_flags_finish */ |
842 | }; |
843 | |
844 | class pass_ud_rtl_dce : public rtl_opt_pass |
845 | { |
846 | public: |
847 | pass_ud_rtl_dce (gcc::context *ctxt) |
848 | : rtl_opt_pass (pass_data_ud_rtl_dce, ctxt) |
849 | {} |
850 | |
851 | /* opt_pass methods: */ |
852 | bool gate (function *) final override |
853 | { |
854 | return optimize > 1 && flag_dce && dbg_cnt (index: dce_ud); |
855 | } |
856 | |
857 | unsigned int execute (function *) final override |
858 | { |
859 | return rest_of_handle_ud_dce (); |
860 | } |
861 | |
862 | }; // class pass_ud_rtl_dce |
863 | |
864 | } // anon namespace |
865 | |
866 | rtl_opt_pass * |
867 | make_pass_ud_rtl_dce (gcc::context *ctxt) |
868 | { |
869 | return new pass_ud_rtl_dce (ctxt); |
870 | } |
871 | |
872 | |
873 | /* ------------------------------------------------------------------------- |
874 | Fast DCE functions |
875 | ------------------------------------------------------------------------- */ |
876 | |
877 | /* Process basic block BB. Return true if the live_in set has |
878 | changed. REDO_OUT is true if the info at the bottom of the block |
879 | needs to be recalculated before starting. AU is the proper set of |
880 | artificial uses. Track global substitution of uses of dead pseudos |
881 | in debug insns using GLOBAL_DEBUG. */ |
882 | |
883 | static bool |
884 | word_dce_process_block (basic_block bb, bool redo_out, |
885 | struct dead_debug_global *global_debug) |
886 | { |
887 | bitmap local_live = BITMAP_ALLOC (obstack: &dce_tmp_bitmap_obstack); |
888 | rtx_insn *insn; |
889 | bool block_changed; |
890 | struct dead_debug_local debug; |
891 | |
892 | if (redo_out) |
893 | { |
894 | /* Need to redo the live_out set of this block if when one of |
895 | the succs of this block has had a change in it live in |
896 | set. */ |
897 | edge e; |
898 | edge_iterator ei; |
899 | df_confluence_function_n con_fun_n = df_word_lr->problem->con_fun_n; |
900 | bitmap_clear (DF_WORD_LR_OUT (bb)); |
901 | FOR_EACH_EDGE (e, ei, bb->succs) |
902 | (*con_fun_n) (e); |
903 | } |
904 | |
905 | if (dump_file) |
906 | { |
907 | fprintf (stream: dump_file, format: "processing block %d live out = " , bb->index); |
908 | df_print_word_regset (file: dump_file, DF_WORD_LR_OUT (bb)); |
909 | } |
910 | |
911 | bitmap_copy (local_live, DF_WORD_LR_OUT (bb)); |
912 | dead_debug_local_init (&debug, NULL, global_debug); |
913 | |
914 | FOR_BB_INSNS_REVERSE (bb, insn) |
915 | if (DEBUG_INSN_P (insn)) |
916 | { |
917 | df_ref use; |
918 | FOR_EACH_INSN_USE (use, insn) |
919 | if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER |
920 | && known_eq (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use))), |
921 | 2 * UNITS_PER_WORD) |
922 | && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (use)) |
923 | && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (use) + 1)) |
924 | dead_debug_add (&debug, use, DF_REF_REGNO (use)); |
925 | } |
926 | else if (INSN_P (insn)) |
927 | { |
928 | bool any_changed; |
929 | |
930 | /* No matter if the instruction is needed or not, we remove |
931 | any regno in the defs from the live set. */ |
932 | any_changed = df_word_lr_simulate_defs (insn, local_live); |
933 | if (any_changed) |
934 | mark_insn (insn, fast: true); |
935 | |
936 | /* On the other hand, we do not allow the dead uses to set |
937 | anything in local_live. */ |
938 | if (marked_insn_p (insn)) |
939 | df_word_lr_simulate_uses (insn, local_live); |
940 | |
941 | /* Insert debug temps for dead REGs used in subsequent debug |
942 | insns. We may have to emit a debug temp even if the insn |
943 | was marked, in case the debug use was after the point of |
944 | death. */ |
945 | if (debug.used && !bitmap_empty_p (map: debug.used)) |
946 | { |
947 | df_ref def; |
948 | |
949 | FOR_EACH_INSN_DEF (def, insn) |
950 | dead_debug_insert_temp (&debug, DF_REF_REGNO (def), insn, |
951 | marked_insn_p (insn) |
952 | && !control_flow_insn_p (insn) |
953 | ? DEBUG_TEMP_AFTER_WITH_REG_FORCE |
954 | : DEBUG_TEMP_BEFORE_WITH_VALUE); |
955 | } |
956 | |
957 | if (dump_file) |
958 | { |
959 | fprintf (stream: dump_file, format: "finished processing insn %d live out = " , |
960 | INSN_UID (insn)); |
961 | df_print_word_regset (file: dump_file, r: local_live); |
962 | } |
963 | } |
964 | |
965 | block_changed = !bitmap_equal_p (local_live, DF_WORD_LR_IN (bb)); |
966 | if (block_changed) |
967 | bitmap_copy (DF_WORD_LR_IN (bb), local_live); |
968 | |
969 | dead_debug_local_finish (&debug, NULL); |
970 | BITMAP_FREE (local_live); |
971 | return block_changed; |
972 | } |
973 | |
974 | |
975 | /* Process basic block BB. Return true if the live_in set has |
976 | changed. REDO_OUT is true if the info at the bottom of the block |
977 | needs to be recalculated before starting. AU is the proper set of |
978 | artificial uses. Track global substitution of uses of dead pseudos |
979 | in debug insns using GLOBAL_DEBUG. */ |
980 | |
981 | static bool |
982 | dce_process_block (basic_block bb, bool redo_out, bitmap au, |
983 | struct dead_debug_global *global_debug) |
984 | { |
985 | bitmap local_live = BITMAP_ALLOC (obstack: &dce_tmp_bitmap_obstack); |
986 | rtx_insn *insn; |
987 | bool block_changed; |
988 | df_ref def; |
989 | struct dead_debug_local debug; |
990 | |
991 | if (redo_out) |
992 | { |
993 | /* Need to redo the live_out set of this block if when one of |
994 | the succs of this block has had a change in it live in |
995 | set. */ |
996 | edge e; |
997 | edge_iterator ei; |
998 | df_confluence_function_n con_fun_n = df_lr->problem->con_fun_n; |
999 | bitmap_clear (DF_LR_OUT (bb)); |
1000 | FOR_EACH_EDGE (e, ei, bb->succs) |
1001 | (*con_fun_n) (e); |
1002 | } |
1003 | |
1004 | if (dump_file) |
1005 | { |
1006 | fprintf (stream: dump_file, format: "processing block %d lr out = " , bb->index); |
1007 | df_print_regset (file: dump_file, DF_LR_OUT (bb)); |
1008 | } |
1009 | |
1010 | bitmap_copy (local_live, DF_LR_OUT (bb)); |
1011 | |
1012 | df_simulate_initialize_backwards (bb, local_live); |
1013 | dead_debug_local_init (&debug, NULL, global_debug); |
1014 | |
1015 | FOR_BB_INSNS_REVERSE (bb, insn) |
1016 | if (DEBUG_INSN_P (insn)) |
1017 | { |
1018 | df_ref use; |
1019 | FOR_EACH_INSN_USE (use, insn) |
1020 | if (!bitmap_bit_p (local_live, DF_REF_REGNO (use)) |
1021 | && !bitmap_bit_p (au, DF_REF_REGNO (use))) |
1022 | dead_debug_add (&debug, use, DF_REF_REGNO (use)); |
1023 | } |
1024 | else if (INSN_P (insn)) |
1025 | { |
1026 | bool needed = marked_insn_p (insn); |
1027 | |
1028 | /* The insn is needed if there is someone who uses the output. */ |
1029 | if (!needed) |
1030 | FOR_EACH_INSN_DEF (def, insn) |
1031 | if (bitmap_bit_p (local_live, DF_REF_REGNO (def)) |
1032 | || bitmap_bit_p (au, DF_REF_REGNO (def))) |
1033 | { |
1034 | needed = true; |
1035 | mark_insn (insn, fast: true); |
1036 | break; |
1037 | } |
1038 | |
1039 | /* No matter if the instruction is needed or not, we remove |
1040 | any regno in the defs from the live set. */ |
1041 | df_simulate_defs (insn, local_live); |
1042 | |
1043 | /* On the other hand, we do not allow the dead uses to set |
1044 | anything in local_live. */ |
1045 | if (needed) |
1046 | df_simulate_uses (insn, local_live); |
1047 | |
1048 | /* Insert debug temps for dead REGs used in subsequent debug |
1049 | insns. We may have to emit a debug temp even if the insn |
1050 | was marked, in case the debug use was after the point of |
1051 | death. */ |
1052 | if (debug.used && !bitmap_empty_p (map: debug.used)) |
1053 | FOR_EACH_INSN_DEF (def, insn) |
1054 | dead_debug_insert_temp (&debug, DF_REF_REGNO (def), insn, |
1055 | needed && !control_flow_insn_p (insn) |
1056 | ? DEBUG_TEMP_AFTER_WITH_REG_FORCE |
1057 | : DEBUG_TEMP_BEFORE_WITH_VALUE); |
1058 | } |
1059 | |
1060 | dead_debug_local_finish (&debug, NULL); |
1061 | df_simulate_finalize_backwards (bb, local_live); |
1062 | |
1063 | block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb)); |
1064 | if (block_changed) |
1065 | bitmap_copy (DF_LR_IN (bb), local_live); |
1066 | |
1067 | BITMAP_FREE (local_live); |
1068 | return block_changed; |
1069 | } |
1070 | |
1071 | |
1072 | /* Perform fast DCE once initialization is done. If WORD_LEVEL is |
1073 | true, use the word level dce, otherwise do it at the pseudo |
1074 | level. */ |
1075 | |
1076 | static void |
1077 | fast_dce (bool word_level) |
1078 | { |
1079 | int *postorder = df_get_postorder (DF_BACKWARD); |
1080 | int n_blocks = df_get_n_blocks (DF_BACKWARD); |
1081 | /* The set of blocks that have been seen on this iteration. */ |
1082 | bitmap processed = BITMAP_ALLOC (obstack: &dce_blocks_bitmap_obstack); |
1083 | /* The set of blocks that need to have the out vectors reset because |
1084 | the in of one of their successors has changed. */ |
1085 | bitmap redo_out = BITMAP_ALLOC (obstack: &dce_blocks_bitmap_obstack); |
1086 | bitmap all_blocks = BITMAP_ALLOC (obstack: &dce_blocks_bitmap_obstack); |
1087 | bool global_changed = true; |
1088 | |
1089 | /* These regs are considered always live so if they end up dying |
1090 | because of some def, we need to bring the back again. Calling |
1091 | df_simulate_fixup_sets has the disadvantage of calling |
1092 | bb_has_eh_pred once per insn, so we cache the information |
1093 | here. */ |
1094 | bitmap au = &df->regular_block_artificial_uses; |
1095 | bitmap au_eh = &df->eh_block_artificial_uses; |
1096 | int i; |
1097 | struct dead_debug_global global_debug; |
1098 | |
1099 | prescan_insns_for_dce (fast: true); |
1100 | |
1101 | for (i = 0; i < n_blocks; i++) |
1102 | bitmap_set_bit (all_blocks, postorder[i]); |
1103 | |
1104 | dead_debug_global_init (&global_debug, NULL); |
1105 | |
1106 | while (global_changed) |
1107 | { |
1108 | global_changed = false; |
1109 | |
1110 | for (i = 0; i < n_blocks; i++) |
1111 | { |
1112 | int index = postorder[i]; |
1113 | basic_block bb = BASIC_BLOCK_FOR_FN (cfun, index); |
1114 | bool local_changed; |
1115 | |
1116 | if (index < NUM_FIXED_BLOCKS) |
1117 | { |
1118 | bitmap_set_bit (processed, index); |
1119 | continue; |
1120 | } |
1121 | |
1122 | if (word_level) |
1123 | local_changed |
1124 | = word_dce_process_block (bb, redo_out: bitmap_bit_p (redo_out, index), |
1125 | global_debug: &global_debug); |
1126 | else |
1127 | local_changed |
1128 | = dce_process_block (bb, redo_out: bitmap_bit_p (redo_out, index), |
1129 | au: bb_has_eh_pred (bb) ? au_eh : au, |
1130 | global_debug: &global_debug); |
1131 | bitmap_set_bit (processed, index); |
1132 | |
1133 | if (local_changed) |
1134 | { |
1135 | edge e; |
1136 | edge_iterator ei; |
1137 | FOR_EACH_EDGE (e, ei, bb->preds) |
1138 | if (bitmap_bit_p (processed, e->src->index)) |
1139 | /* Be tricky about when we need to iterate the |
1140 | analysis. We only have redo the analysis if the |
1141 | bitmaps change at the top of a block that is the |
1142 | entry to a loop. */ |
1143 | global_changed = true; |
1144 | else |
1145 | bitmap_set_bit (redo_out, e->src->index); |
1146 | } |
1147 | } |
1148 | |
1149 | if (global_changed) |
1150 | { |
1151 | /* Turn off the RUN_DCE flag to prevent recursive calls to |
1152 | dce. */ |
1153 | int old_flag = df_clear_flags (DF_LR_RUN_DCE); |
1154 | |
1155 | /* So something was deleted that requires a redo. Do it on |
1156 | the cheap. */ |
1157 | delete_unmarked_insns (); |
1158 | bitmap_clear (marked); |
1159 | bitmap_clear (processed); |
1160 | bitmap_clear (redo_out); |
1161 | |
1162 | /* We do not need to rescan any instructions. We only need |
1163 | to redo the dataflow equations for the blocks that had a |
1164 | change at the top of the block. Then we need to redo the |
1165 | iteration. */ |
1166 | if (word_level) |
1167 | df_analyze_problem (df_word_lr, all_blocks, postorder, n_blocks); |
1168 | else |
1169 | df_analyze_problem (df_lr, all_blocks, postorder, n_blocks); |
1170 | |
1171 | if (old_flag & DF_LR_RUN_DCE) |
1172 | df_set_flags (DF_LR_RUN_DCE); |
1173 | |
1174 | prescan_insns_for_dce (fast: true); |
1175 | } |
1176 | } |
1177 | |
1178 | dead_debug_global_finish (&global_debug, NULL); |
1179 | |
1180 | delete_unmarked_insns (); |
1181 | |
1182 | BITMAP_FREE (processed); |
1183 | BITMAP_FREE (redo_out); |
1184 | BITMAP_FREE (all_blocks); |
1185 | } |
1186 | |
1187 | |
1188 | /* Fast register level DCE. */ |
1189 | |
1190 | static unsigned int |
1191 | rest_of_handle_fast_dce (void) |
1192 | { |
1193 | init_dce (fast: true); |
1194 | fast_dce (word_level: false); |
1195 | fini_dce (fast: true); |
1196 | return 0; |
1197 | } |
1198 | |
1199 | |
1200 | /* Fast byte level DCE. */ |
1201 | |
1202 | void |
1203 | run_word_dce (void) |
1204 | { |
1205 | int old_flags; |
1206 | |
1207 | if (!flag_dce) |
1208 | return; |
1209 | |
1210 | timevar_push (tv: TV_DCE); |
1211 | old_flags = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); |
1212 | df_word_lr_add_problem (); |
1213 | init_dce (fast: true); |
1214 | fast_dce (word_level: true); |
1215 | fini_dce (fast: true); |
1216 | df_set_flags (old_flags); |
1217 | timevar_pop (tv: TV_DCE); |
1218 | } |
1219 | |
1220 | |
1221 | /* This is an internal call that is used by the df live register |
1222 | problem to run fast dce as a side effect of creating the live |
1223 | information. The stack is organized so that the lr problem is run, |
1224 | this pass is run, which updates the live info and the df scanning |
1225 | info, and then returns to allow the rest of the problems to be run. |
1226 | |
1227 | This can be called by elsewhere but it will not update the bit |
1228 | vectors for any other problems than LR. */ |
1229 | |
1230 | void |
1231 | run_fast_df_dce (void) |
1232 | { |
1233 | if (flag_dce) |
1234 | { |
1235 | /* If dce is able to delete something, it has to happen |
1236 | immediately. Otherwise there will be problems handling the |
1237 | eq_notes. */ |
1238 | int old_flags = |
1239 | df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); |
1240 | |
1241 | df_in_progress = true; |
1242 | rest_of_handle_fast_dce (); |
1243 | df_in_progress = false; |
1244 | |
1245 | df_set_flags (old_flags); |
1246 | } |
1247 | } |
1248 | |
1249 | |
1250 | /* Run a fast DCE pass. */ |
1251 | |
1252 | void |
1253 | run_fast_dce (void) |
1254 | { |
1255 | if (flag_dce) |
1256 | rest_of_handle_fast_dce (); |
1257 | } |
1258 | |
1259 | |
1260 | namespace { |
1261 | |
1262 | const pass_data pass_data_fast_rtl_dce = |
1263 | { |
1264 | .type: RTL_PASS, /* type */ |
1265 | .name: "rtl_dce" , /* name */ |
1266 | .optinfo_flags: OPTGROUP_NONE, /* optinfo_flags */ |
1267 | .tv_id: TV_DCE, /* tv_id */ |
1268 | .properties_required: 0, /* properties_required */ |
1269 | .properties_provided: 0, /* properties_provided */ |
1270 | .properties_destroyed: 0, /* properties_destroyed */ |
1271 | .todo_flags_start: 0, /* todo_flags_start */ |
1272 | TODO_df_finish, /* todo_flags_finish */ |
1273 | }; |
1274 | |
1275 | class pass_fast_rtl_dce : public rtl_opt_pass |
1276 | { |
1277 | public: |
1278 | pass_fast_rtl_dce (gcc::context *ctxt) |
1279 | : rtl_opt_pass (pass_data_fast_rtl_dce, ctxt) |
1280 | {} |
1281 | |
1282 | /* opt_pass methods: */ |
1283 | bool gate (function *) final override |
1284 | { |
1285 | return optimize > 0 && flag_dce && dbg_cnt (index: dce_fast); |
1286 | } |
1287 | |
1288 | unsigned int execute (function *) final override |
1289 | { |
1290 | return rest_of_handle_fast_dce (); |
1291 | } |
1292 | |
1293 | }; // class pass_fast_rtl_dce |
1294 | |
1295 | } // anon namespace |
1296 | |
1297 | rtl_opt_pass * |
1298 | make_pass_fast_rtl_dce (gcc::context *ctxt) |
1299 | { |
1300 | return new pass_fast_rtl_dce (ctxt); |
1301 | } |
1302 | |