Mercurial > hg > CbC > CbC_gcc
annotate gcc/dce.c @ 129:002ebcbc1eb4
remove test_env
author | mir3636 |
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date | Tue, 15 May 2018 18:45:25 +0900 |
parents | f6334be47118 |
children | 04ced10e8804 |
rev | line source |
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0 | 1 /* RTL dead code elimination. |
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2 Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
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3 Free Software Foundation, Inc. |
0 | 4 |
5 This file is part of GCC. | |
6 | |
7 GCC is free software; you can redistribute it and/or modify it under | |
8 the terms of the GNU General Public License as published by the Free | |
9 Software Foundation; either version 3, or (at your option) any later | |
10 version. | |
11 | |
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 for more details. | |
16 | |
17 You should have received a copy of the GNU General Public License | |
18 along with GCC; see the file COPYING3. If not see | |
19 <http://www.gnu.org/licenses/>. */ | |
20 | |
21 #include "config.h" | |
22 #include "system.h" | |
23 #include "coretypes.h" | |
24 #include "hashtab.h" | |
25 #include "tm.h" | |
26 #include "rtl.h" | |
27 #include "tree.h" | |
28 #include "regs.h" | |
29 #include "hard-reg-set.h" | |
30 #include "flags.h" | |
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31 #include "except.h" |
0 | 32 #include "df.h" |
33 #include "cselib.h" | |
34 #include "dce.h" | |
35 #include "timevar.h" | |
36 #include "tree-pass.h" | |
37 #include "dbgcnt.h" | |
38 #include "tm_p.h" | |
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39 #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */ |
0 | 40 |
41 | |
42 /* ------------------------------------------------------------------------- | |
43 Core mark/delete routines | |
44 ------------------------------------------------------------------------- */ | |
45 | |
46 /* True if we are invoked while the df engine is running; in this case, | |
47 we don't want to reenter it. */ | |
48 static bool df_in_progress = false; | |
49 | |
50 /* Instructions that have been marked but whose dependencies have not | |
51 yet been processed. */ | |
52 static VEC(rtx,heap) *worklist; | |
53 | |
54 /* Bitmap of instructions marked as needed indexed by INSN_UID. */ | |
55 static sbitmap marked; | |
56 | |
57 /* Bitmap obstacks used for block processing by the fast algorithm. */ | |
58 static bitmap_obstack dce_blocks_bitmap_obstack; | |
59 static bitmap_obstack dce_tmp_bitmap_obstack; | |
60 | |
61 static bool find_call_stack_args (rtx, bool, bool, bitmap); | |
62 | |
63 /* A subroutine for which BODY is part of the instruction being tested; | |
64 either the top-level pattern, or an element of a PARALLEL. The | |
65 instruction is known not to be a bare USE or CLOBBER. */ | |
66 | |
67 static bool | |
68 deletable_insn_p_1 (rtx body) | |
69 { | |
70 switch (GET_CODE (body)) | |
71 { | |
72 case PREFETCH: | |
73 case TRAP_IF: | |
74 /* The UNSPEC case was added here because the ia-64 claims that | |
75 USEs do not work after reload and generates UNSPECS rather | |
76 than USEs. Since dce is run after reload we need to avoid | |
77 deleting these even if they are dead. If it turns out that | |
78 USEs really do work after reload, the ia-64 should be | |
79 changed, and the UNSPEC case can be removed. */ | |
80 case UNSPEC: | |
81 return false; | |
82 | |
83 default: | |
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84 return !volatile_refs_p (body); |
0 | 85 } |
86 } | |
87 | |
88 | |
89 /* Return true if INSN is a normal instruction that can be deleted by | |
90 the DCE pass. */ | |
91 | |
92 static bool | |
93 deletable_insn_p (rtx insn, bool fast, bitmap arg_stores) | |
94 { | |
95 rtx body, x; | |
96 int i; | |
97 | |
98 if (CALL_P (insn) | |
99 /* We cannot delete calls inside of the recursive dce because | |
100 this may cause basic blocks to be deleted and this messes up | |
101 the rest of the stack of optimization passes. */ | |
102 && (!df_in_progress) | |
103 /* We cannot delete pure or const sibling calls because it is | |
104 hard to see the result. */ | |
105 && (!SIBLING_CALL_P (insn)) | |
106 /* We can delete dead const or pure calls as long as they do not | |
107 infinite loop. */ | |
108 && (RTL_CONST_OR_PURE_CALL_P (insn) | |
109 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))) | |
110 return find_call_stack_args (insn, false, fast, arg_stores); | |
111 | |
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112 /* Don't delete jumps, notes and the like. */ |
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113 if (!NONJUMP_INSN_P (insn)) |
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114 return false; |
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115 |
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116 /* Don't delete insns that can throw. */ |
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117 if (!insn_nothrow_p (insn)) |
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118 return false; |
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119 |
0 | 120 body = PATTERN (insn); |
121 switch (GET_CODE (body)) | |
122 { | |
123 case USE: | |
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124 case VAR_LOCATION: |
0 | 125 return false; |
126 | |
127 case CLOBBER: | |
128 if (fast) | |
129 { | |
130 /* A CLOBBER of a dead pseudo register serves no purpose. | |
131 That is not necessarily true for hard registers until | |
132 after reload. */ | |
133 x = XEXP (body, 0); | |
134 return REG_P (x) && (!HARD_REGISTER_P (x) || reload_completed); | |
135 } | |
136 else | |
137 /* Because of the way that use-def chains are built, it is not | |
138 possible to tell if the clobber is dead because it can | |
139 never be the target of a use-def chain. */ | |
140 return false; | |
141 | |
142 case PARALLEL: | |
143 for (i = XVECLEN (body, 0) - 1; i >= 0; i--) | |
144 if (!deletable_insn_p_1 (XVECEXP (body, 0, i))) | |
145 return false; | |
146 return true; | |
147 | |
148 default: | |
149 return deletable_insn_p_1 (body); | |
150 } | |
151 } | |
152 | |
153 | |
154 /* Return true if INSN has been marked as needed. */ | |
155 | |
156 static inline int | |
157 marked_insn_p (rtx insn) | |
158 { | |
159 /* Artificial defs are always needed and they do not have an insn. | |
160 We should never see them here. */ | |
161 gcc_assert (insn); | |
162 return TEST_BIT (marked, INSN_UID (insn)); | |
163 } | |
164 | |
165 | |
166 /* If INSN has not yet been marked as needed, mark it now, and add it to | |
167 the worklist. */ | |
168 | |
169 static void | |
170 mark_insn (rtx insn, bool fast) | |
171 { | |
172 if (!marked_insn_p (insn)) | |
173 { | |
174 if (!fast) | |
175 VEC_safe_push (rtx, heap, worklist, insn); | |
176 SET_BIT (marked, INSN_UID (insn)); | |
177 if (dump_file) | |
178 fprintf (dump_file, " Adding insn %d to worklist\n", INSN_UID (insn)); | |
179 if (CALL_P (insn) | |
180 && !df_in_progress | |
181 && !SIBLING_CALL_P (insn) | |
182 && (RTL_CONST_OR_PURE_CALL_P (insn) | |
183 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))) | |
184 find_call_stack_args (insn, true, fast, NULL); | |
185 } | |
186 } | |
187 | |
188 | |
189 /* A note_stores callback used by mark_nonreg_stores. DATA is the | |
190 instruction containing DEST. */ | |
191 | |
192 static void | |
193 mark_nonreg_stores_1 (rtx dest, const_rtx pattern, void *data) | |
194 { | |
195 if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) | |
196 mark_insn ((rtx) data, true); | |
197 } | |
198 | |
199 | |
200 /* A note_stores callback used by mark_nonreg_stores. DATA is the | |
201 instruction containing DEST. */ | |
202 | |
203 static void | |
204 mark_nonreg_stores_2 (rtx dest, const_rtx pattern, void *data) | |
205 { | |
206 if (GET_CODE (pattern) != CLOBBER && !REG_P (dest)) | |
207 mark_insn ((rtx) data, false); | |
208 } | |
209 | |
210 | |
211 /* Mark INSN if BODY stores to a non-register destination. */ | |
212 | |
213 static void | |
214 mark_nonreg_stores (rtx body, rtx insn, bool fast) | |
215 { | |
216 if (fast) | |
217 note_stores (body, mark_nonreg_stores_1, insn); | |
218 else | |
219 note_stores (body, mark_nonreg_stores_2, insn); | |
220 } | |
221 | |
222 | |
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223 /* Return true if store to MEM, starting OFF bytes from stack pointer, |
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224 is a call argument store, and clear corresponding bits from SP_BYTES |
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225 bitmap if it is. */ |
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226 |
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227 static bool |
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228 check_argument_store (rtx mem, HOST_WIDE_INT off, HOST_WIDE_INT min_sp_off, |
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229 HOST_WIDE_INT max_sp_off, bitmap sp_bytes) |
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230 { |
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231 HOST_WIDE_INT byte; |
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232 for (byte = off; byte < off + GET_MODE_SIZE (GET_MODE (mem)); byte++) |
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233 { |
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234 if (byte < min_sp_off |
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235 || byte >= max_sp_off |
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236 || !bitmap_clear_bit (sp_bytes, byte - min_sp_off)) |
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237 return false; |
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238 } |
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239 return true; |
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240 } |
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241 |
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242 |
0 | 243 /* Try to find all stack stores of CALL_INSN arguments if |
244 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found | |
245 and it is therefore safe to eliminate the call, return true, | |
246 otherwise return false. This function should be first called | |
247 with DO_MARK false, and only when the CALL_INSN is actually | |
248 going to be marked called again with DO_MARK true. */ | |
249 | |
250 static bool | |
251 find_call_stack_args (rtx call_insn, bool do_mark, bool fast, | |
252 bitmap arg_stores) | |
253 { | |
254 rtx p, insn, prev_insn; | |
255 bool ret; | |
256 HOST_WIDE_INT min_sp_off, max_sp_off; | |
257 bitmap sp_bytes; | |
258 | |
259 gcc_assert (CALL_P (call_insn)); | |
260 if (!ACCUMULATE_OUTGOING_ARGS) | |
261 return true; | |
262 | |
263 if (!do_mark) | |
264 { | |
265 gcc_assert (arg_stores); | |
266 bitmap_clear (arg_stores); | |
267 } | |
268 | |
269 min_sp_off = INTTYPE_MAXIMUM (HOST_WIDE_INT); | |
270 max_sp_off = 0; | |
271 | |
272 /* First determine the minimum and maximum offset from sp for | |
273 stored arguments. */ | |
274 for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) | |
275 if (GET_CODE (XEXP (p, 0)) == USE | |
276 && MEM_P (XEXP (XEXP (p, 0), 0))) | |
277 { | |
278 rtx mem = XEXP (XEXP (p, 0), 0), addr, size; | |
279 HOST_WIDE_INT off = 0; | |
280 size = MEM_SIZE (mem); | |
281 if (size == NULL_RTX) | |
282 return false; | |
283 addr = XEXP (mem, 0); | |
284 if (GET_CODE (addr) == PLUS | |
285 && REG_P (XEXP (addr, 0)) | |
286 && CONST_INT_P (XEXP (addr, 1))) | |
287 { | |
288 off = INTVAL (XEXP (addr, 1)); | |
289 addr = XEXP (addr, 0); | |
290 } | |
291 if (addr != stack_pointer_rtx) | |
292 { | |
293 if (!REG_P (addr)) | |
294 return false; | |
295 /* If not fast, use chains to see if addr wasn't set to | |
296 sp + offset. */ | |
297 if (!fast) | |
298 { | |
299 df_ref *use_rec; | |
300 struct df_link *defs; | |
301 rtx set; | |
302 | |
303 for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++) | |
304 if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) | |
305 break; | |
306 | |
307 if (*use_rec == NULL) | |
308 return false; | |
309 | |
310 for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) | |
311 if (! DF_REF_IS_ARTIFICIAL (defs->ref)) | |
312 break; | |
313 | |
314 if (defs == NULL) | |
315 return false; | |
316 | |
317 set = single_set (DF_REF_INSN (defs->ref)); | |
318 if (!set) | |
319 return false; | |
320 | |
321 if (GET_CODE (SET_SRC (set)) != PLUS | |
322 || XEXP (SET_SRC (set), 0) != stack_pointer_rtx | |
323 || !CONST_INT_P (XEXP (SET_SRC (set), 1))) | |
324 return false; | |
325 | |
326 off += INTVAL (XEXP (SET_SRC (set), 1)); | |
327 } | |
328 else | |
329 return false; | |
330 } | |
331 min_sp_off = MIN (min_sp_off, off); | |
332 max_sp_off = MAX (max_sp_off, off + INTVAL (size)); | |
333 } | |
334 | |
335 if (min_sp_off >= max_sp_off) | |
336 return true; | |
337 sp_bytes = BITMAP_ALLOC (NULL); | |
338 | |
339 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off | |
340 which contain arguments. Checking has been done in the previous | |
341 loop. */ | |
342 for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1)) | |
343 if (GET_CODE (XEXP (p, 0)) == USE | |
344 && MEM_P (XEXP (XEXP (p, 0), 0))) | |
345 { | |
346 rtx mem = XEXP (XEXP (p, 0), 0), addr; | |
347 HOST_WIDE_INT off = 0, byte; | |
348 addr = XEXP (mem, 0); | |
349 if (GET_CODE (addr) == PLUS | |
350 && REG_P (XEXP (addr, 0)) | |
351 && CONST_INT_P (XEXP (addr, 1))) | |
352 { | |
353 off = INTVAL (XEXP (addr, 1)); | |
354 addr = XEXP (addr, 0); | |
355 } | |
356 if (addr != stack_pointer_rtx) | |
357 { | |
358 df_ref *use_rec; | |
359 struct df_link *defs; | |
360 rtx set; | |
361 | |
362 for (use_rec = DF_INSN_USES (call_insn); *use_rec; use_rec++) | |
363 if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) | |
364 break; | |
365 | |
366 for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) | |
367 if (! DF_REF_IS_ARTIFICIAL (defs->ref)) | |
368 break; | |
369 | |
370 set = single_set (DF_REF_INSN (defs->ref)); | |
371 off += INTVAL (XEXP (SET_SRC (set), 1)); | |
372 } | |
373 for (byte = off; byte < off + INTVAL (MEM_SIZE (mem)); byte++) | |
374 { | |
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375 if (!bitmap_set_bit (sp_bytes, byte - min_sp_off)) |
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376 gcc_unreachable (); |
0 | 377 } |
378 } | |
379 | |
380 /* Walk backwards, looking for argument stores. The search stops | |
381 when seeing another call, sp adjustment or memory store other than | |
382 argument store. */ | |
383 ret = false; | |
384 for (insn = PREV_INSN (call_insn); insn; insn = prev_insn) | |
385 { | |
386 rtx set, mem, addr; | |
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387 HOST_WIDE_INT off; |
0 | 388 |
389 if (insn == BB_HEAD (BLOCK_FOR_INSN (call_insn))) | |
390 prev_insn = NULL_RTX; | |
391 else | |
392 prev_insn = PREV_INSN (insn); | |
393 | |
394 if (CALL_P (insn)) | |
395 break; | |
396 | |
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397 if (!NONDEBUG_INSN_P (insn)) |
0 | 398 continue; |
399 | |
400 set = single_set (insn); | |
401 if (!set || SET_DEST (set) == stack_pointer_rtx) | |
402 break; | |
403 | |
404 if (!MEM_P (SET_DEST (set))) | |
405 continue; | |
406 | |
407 mem = SET_DEST (set); | |
408 addr = XEXP (mem, 0); | |
409 off = 0; | |
410 if (GET_CODE (addr) == PLUS | |
411 && REG_P (XEXP (addr, 0)) | |
412 && CONST_INT_P (XEXP (addr, 1))) | |
413 { | |
414 off = INTVAL (XEXP (addr, 1)); | |
415 addr = XEXP (addr, 0); | |
416 } | |
417 if (addr != stack_pointer_rtx) | |
418 { | |
419 if (!REG_P (addr)) | |
420 break; | |
421 if (!fast) | |
422 { | |
423 df_ref *use_rec; | |
424 struct df_link *defs; | |
425 rtx set; | |
426 | |
427 for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) | |
428 if (rtx_equal_p (addr, DF_REF_REG (*use_rec))) | |
429 break; | |
430 | |
431 if (*use_rec == NULL) | |
432 break; | |
433 | |
434 for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) | |
435 if (! DF_REF_IS_ARTIFICIAL (defs->ref)) | |
436 break; | |
437 | |
438 if (defs == NULL) | |
439 break; | |
440 | |
441 set = single_set (DF_REF_INSN (defs->ref)); | |
442 if (!set) | |
443 break; | |
444 | |
445 if (GET_CODE (SET_SRC (set)) != PLUS | |
446 || XEXP (SET_SRC (set), 0) != stack_pointer_rtx | |
447 || !CONST_INT_P (XEXP (SET_SRC (set), 1))) | |
448 break; | |
449 | |
450 off += INTVAL (XEXP (SET_SRC (set), 1)); | |
451 } | |
452 else | |
453 break; | |
454 } | |
455 | |
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456 if (GET_MODE_SIZE (GET_MODE (mem)) == 0 |
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457 || !check_argument_store (mem, off, min_sp_off, |
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458 max_sp_off, sp_bytes)) |
0 | 459 break; |
460 | |
461 if (!deletable_insn_p (insn, fast, NULL)) | |
462 break; | |
463 | |
464 if (do_mark) | |
465 mark_insn (insn, fast); | |
466 else | |
467 bitmap_set_bit (arg_stores, INSN_UID (insn)); | |
468 | |
469 if (bitmap_empty_p (sp_bytes)) | |
470 { | |
471 ret = true; | |
472 break; | |
473 } | |
474 } | |
475 | |
476 BITMAP_FREE (sp_bytes); | |
477 if (!ret && arg_stores) | |
478 bitmap_clear (arg_stores); | |
479 | |
480 return ret; | |
481 } | |
482 | |
483 | |
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484 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN |
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485 writes to. */ |
0 | 486 |
487 static void | |
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488 remove_reg_equal_equiv_notes_for_defs (rtx insn) |
0 | 489 { |
490 df_ref *def_rec; | |
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491 |
0 | 492 for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) |
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493 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec)); |
0 | 494 } |
495 | |
496 | |
497 /* Delete every instruction that hasn't been marked. */ | |
498 | |
499 static void | |
500 delete_unmarked_insns (void) | |
501 { | |
502 basic_block bb; | |
503 rtx insn, next; | |
504 bool must_clean = false; | |
505 | |
506 FOR_EACH_BB_REVERSE (bb) | |
507 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next) | |
508 if (INSN_P (insn)) | |
509 { | |
510 /* Always delete no-op moves. */ | |
511 if (noop_move_p (insn)) | |
512 ; | |
513 | |
514 /* Otherwise rely only on the DCE algorithm. */ | |
515 else if (marked_insn_p (insn)) | |
516 continue; | |
517 | |
518 /* Beware that reaching a dbg counter limit here can result | |
519 in miscompiled file. This occurs when a group of insns | |
520 must be deleted together, typically because the kept insn | |
521 depends on the output from the deleted insn. Deleting | |
522 this insns in reverse order (both at the bb level and | |
523 when looking at the blocks) minimizes this, but does not | |
524 eliminate it, since it is possible for the using insn to | |
525 be top of a block and the producer to be at the bottom of | |
526 the block. However, in most cases this will only result | |
527 in an uninitialized use of an insn that is dead anyway. | |
528 | |
529 However, there is one rare case that will cause a | |
530 miscompile: deletion of non-looping pure and constant | |
531 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true. | |
532 In this case it is possible to remove the call, but leave | |
533 the argument pushes to the stack. Because of the changes | |
534 to the stack pointer, this will almost always lead to a | |
535 miscompile. */ | |
536 if (!dbg_cnt (dce)) | |
537 continue; | |
538 | |
539 if (dump_file) | |
540 fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn)); | |
541 | |
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542 /* Before we delete the insn we have to remove the REG_EQUAL notes |
0 | 543 for the destination regs in order to avoid dangling notes. */ |
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544 remove_reg_equal_equiv_notes_for_defs (insn); |
0 | 545 |
546 /* If a pure or const call is deleted, this may make the cfg | |
547 have unreachable blocks. We rememeber this and call | |
548 delete_unreachable_blocks at the end. */ | |
549 if (CALL_P (insn)) | |
550 must_clean = true; | |
551 | |
552 /* Now delete the insn. */ | |
553 delete_insn_and_edges (insn); | |
554 } | |
555 | |
556 /* Deleted a pure or const call. */ | |
557 if (must_clean) | |
558 delete_unreachable_blocks (); | |
559 } | |
560 | |
561 | |
562 /* Go through the instructions and mark those whose necessity is not | |
563 dependent on inter-instruction information. Make sure all other | |
564 instructions are not marked. */ | |
565 | |
566 static void | |
567 prescan_insns_for_dce (bool fast) | |
568 { | |
569 basic_block bb; | |
570 rtx insn, prev; | |
571 bitmap arg_stores = NULL; | |
572 | |
573 if (dump_file) | |
574 fprintf (dump_file, "Finding needed instructions:\n"); | |
575 | |
576 if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS) | |
577 arg_stores = BITMAP_ALLOC (NULL); | |
578 | |
579 FOR_EACH_BB (bb) | |
580 { | |
581 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev) | |
582 if (INSN_P (insn)) | |
583 { | |
584 /* Don't mark argument stores now. They will be marked | |
585 if needed when the associated CALL is marked. */ | |
586 if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn))) | |
587 continue; | |
588 if (deletable_insn_p (insn, fast, arg_stores)) | |
589 mark_nonreg_stores (PATTERN (insn), insn, fast); | |
590 else | |
591 mark_insn (insn, fast); | |
592 } | |
593 /* find_call_stack_args only looks at argument stores in the | |
594 same bb. */ | |
595 if (arg_stores) | |
596 bitmap_clear (arg_stores); | |
597 } | |
598 | |
599 if (arg_stores) | |
600 BITMAP_FREE (arg_stores); | |
601 | |
602 if (dump_file) | |
603 fprintf (dump_file, "Finished finding needed instructions:\n"); | |
604 } | |
605 | |
606 | |
607 /* UD-based DSE routines. */ | |
608 | |
609 /* Mark instructions that define artificially-used registers, such as | |
610 the frame pointer and the stack pointer. */ | |
611 | |
612 static void | |
613 mark_artificial_uses (void) | |
614 { | |
615 basic_block bb; | |
616 struct df_link *defs; | |
617 df_ref *use_rec; | |
618 | |
619 FOR_ALL_BB (bb) | |
620 { | |
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621 for (use_rec = df_get_artificial_uses (bb->index); |
0 | 622 *use_rec; use_rec++) |
623 for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next) | |
624 if (! DF_REF_IS_ARTIFICIAL (defs->ref)) | |
625 mark_insn (DF_REF_INSN (defs->ref), false); | |
626 } | |
627 } | |
628 | |
629 | |
630 /* Mark every instruction that defines a register value that INSN uses. */ | |
631 | |
632 static void | |
633 mark_reg_dependencies (rtx insn) | |
634 { | |
635 struct df_link *defs; | |
636 df_ref *use_rec; | |
637 | |
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638 if (DEBUG_INSN_P (insn)) |
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639 return; |
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640 |
0 | 641 for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++) |
642 { | |
643 df_ref use = *use_rec; | |
644 if (dump_file) | |
645 { | |
646 fprintf (dump_file, "Processing use of "); | |
647 print_simple_rtl (dump_file, DF_REF_REG (use)); | |
648 fprintf (dump_file, " in insn %d:\n", INSN_UID (insn)); | |
649 } | |
650 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next) | |
651 if (! DF_REF_IS_ARTIFICIAL (defs->ref)) | |
652 mark_insn (DF_REF_INSN (defs->ref), false); | |
653 } | |
654 } | |
655 | |
656 | |
657 /* Initialize global variables for a new DCE pass. */ | |
658 | |
659 static void | |
660 init_dce (bool fast) | |
661 { | |
662 if (!df_in_progress) | |
663 { | |
664 if (!fast) | |
665 df_chain_add_problem (DF_UD_CHAIN); | |
666 df_analyze (); | |
667 } | |
668 | |
669 if (dump_file) | |
670 df_dump (dump_file); | |
671 | |
672 if (fast) | |
673 { | |
674 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack); | |
675 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack); | |
676 } | |
677 | |
678 marked = sbitmap_alloc (get_max_uid () + 1); | |
679 sbitmap_zero (marked); | |
680 } | |
681 | |
682 | |
683 /* Free the data allocated by init_dce. */ | |
684 | |
685 static void | |
686 fini_dce (bool fast) | |
687 { | |
688 sbitmap_free (marked); | |
689 | |
690 if (fast) | |
691 { | |
692 bitmap_obstack_release (&dce_blocks_bitmap_obstack); | |
693 bitmap_obstack_release (&dce_tmp_bitmap_obstack); | |
694 } | |
695 } | |
696 | |
697 | |
698 /* UD-chain based DCE. */ | |
699 | |
700 static unsigned int | |
701 rest_of_handle_ud_dce (void) | |
702 { | |
703 rtx insn; | |
704 | |
705 init_dce (false); | |
706 | |
707 prescan_insns_for_dce (false); | |
708 mark_artificial_uses (); | |
709 while (VEC_length (rtx, worklist) > 0) | |
710 { | |
711 insn = VEC_pop (rtx, worklist); | |
712 mark_reg_dependencies (insn); | |
713 } | |
714 VEC_free (rtx, heap, worklist); | |
715 | |
716 /* Before any insns are deleted, we must remove the chains since | |
717 they are not bidirectional. */ | |
718 df_remove_problem (df_chain); | |
719 delete_unmarked_insns (); | |
720 | |
721 fini_dce (false); | |
722 return 0; | |
723 } | |
724 | |
725 | |
726 static bool | |
727 gate_ud_dce (void) | |
728 { | |
729 return optimize > 1 && flag_dce | |
730 && dbg_cnt (dce_ud); | |
731 } | |
732 | |
733 struct rtl_opt_pass pass_ud_rtl_dce = | |
734 { | |
735 { | |
736 RTL_PASS, | |
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737 "ud dce", /* name */ |
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738 gate_ud_dce, /* gate */ |
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739 rest_of_handle_ud_dce, /* execute */ |
0 | 740 NULL, /* sub */ |
741 NULL, /* next */ | |
742 0, /* static_pass_number */ | |
743 TV_DCE, /* tv_id */ | |
744 0, /* properties_required */ | |
745 0, /* properties_provided */ | |
746 0, /* properties_destroyed */ | |
747 0, /* todo_flags_start */ | |
748 TODO_dump_func | | |
749 TODO_df_finish | TODO_verify_rtl_sharing | | |
750 TODO_ggc_collect /* todo_flags_finish */ | |
751 } | |
752 }; | |
753 | |
754 | |
755 /* ------------------------------------------------------------------------- | |
756 Fast DCE functions | |
757 ------------------------------------------------------------------------- */ | |
758 | |
759 /* Process basic block BB. Return true if the live_in set has | |
760 changed. REDO_OUT is true if the info at the bottom of the block | |
761 needs to be recalculated before starting. AU is the proper set of | |
762 artificial uses. */ | |
763 | |
764 static bool | |
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765 word_dce_process_block (basic_block bb, bool redo_out) |
0 | 766 { |
767 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack); | |
768 rtx insn; | |
769 bool block_changed; | |
770 | |
771 if (redo_out) | |
772 { | |
773 /* Need to redo the live_out set of this block if when one of | |
774 the succs of this block has had a change in it live in | |
775 set. */ | |
776 edge e; | |
777 edge_iterator ei; | |
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778 df_confluence_function_n con_fun_n = df_word_lr->problem->con_fun_n; |
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779 bitmap_clear (DF_WORD_LR_OUT (bb)); |
0 | 780 FOR_EACH_EDGE (e, ei, bb->succs) |
781 (*con_fun_n) (e); | |
782 } | |
783 | |
784 if (dump_file) | |
785 { | |
786 fprintf (dump_file, "processing block %d live out = ", bb->index); | |
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787 df_print_word_regset (dump_file, DF_WORD_LR_OUT (bb)); |
0 | 788 } |
789 | |
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790 bitmap_copy (local_live, DF_WORD_LR_OUT (bb)); |
0 | 791 |
792 FOR_BB_INSNS_REVERSE (bb, insn) | |
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793 if (NONDEBUG_INSN_P (insn)) |
0 | 794 { |
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795 bool any_changed; |
0 | 796 /* No matter if the instruction is needed or not, we remove |
797 any regno in the defs from the live set. */ | |
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798 any_changed = df_word_lr_simulate_defs (insn, local_live); |
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799 if (any_changed) |
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800 mark_insn (insn, true); |
0 | 801 |
802 /* On the other hand, we do not allow the dead uses to set | |
803 anything in local_live. */ | |
804 if (marked_insn_p (insn)) | |
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805 df_word_lr_simulate_uses (insn, local_live); |
0 | 806 |
807 if (dump_file) | |
808 { | |
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809 fprintf (dump_file, "finished processing insn %d live out = ", |
0 | 810 INSN_UID (insn)); |
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811 df_print_word_regset (dump_file, local_live); |
0 | 812 } |
813 } | |
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814 |
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815 block_changed = !bitmap_equal_p (local_live, DF_WORD_LR_IN (bb)); |
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816 if (block_changed) |
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817 bitmap_copy (DF_WORD_LR_IN (bb), local_live); |
0 | 818 |
819 BITMAP_FREE (local_live); | |
820 return block_changed; | |
821 } | |
822 | |
823 | |
824 /* Process basic block BB. Return true if the live_in set has | |
825 changed. REDO_OUT is true if the info at the bottom of the block | |
826 needs to be recalculated before starting. AU is the proper set of | |
827 artificial uses. */ | |
828 | |
829 static bool | |
830 dce_process_block (basic_block bb, bool redo_out, bitmap au) | |
831 { | |
832 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack); | |
833 rtx insn; | |
834 bool block_changed; | |
835 df_ref *def_rec; | |
836 | |
837 if (redo_out) | |
838 { | |
839 /* Need to redo the live_out set of this block if when one of | |
840 the succs of this block has had a change in it live in | |
841 set. */ | |
842 edge e; | |
843 edge_iterator ei; | |
844 df_confluence_function_n con_fun_n = df_lr->problem->con_fun_n; | |
845 bitmap_clear (DF_LR_OUT (bb)); | |
846 FOR_EACH_EDGE (e, ei, bb->succs) | |
847 (*con_fun_n) (e); | |
848 } | |
849 | |
850 if (dump_file) | |
851 { | |
852 fprintf (dump_file, "processing block %d lr out = ", bb->index); | |
853 df_print_regset (dump_file, DF_LR_OUT (bb)); | |
854 } | |
855 | |
856 bitmap_copy (local_live, DF_LR_OUT (bb)); | |
857 | |
858 df_simulate_initialize_backwards (bb, local_live); | |
859 | |
860 FOR_BB_INSNS_REVERSE (bb, insn) | |
861 if (INSN_P (insn)) | |
862 { | |
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863 bool needed = marked_insn_p (insn); |
0 | 864 |
865 /* The insn is needed if there is someone who uses the output. */ | |
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866 if (!needed) |
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867 for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++) |
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868 if (bitmap_bit_p (local_live, DF_REF_REGNO (*def_rec)) |
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869 || bitmap_bit_p (au, DF_REF_REGNO (*def_rec))) |
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870 { |
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871 needed = true; |
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872 mark_insn (insn, true); |
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873 break; |
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874 } |
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875 |
0 | 876 /* No matter if the instruction is needed or not, we remove |
877 any regno in the defs from the live set. */ | |
878 df_simulate_defs (insn, local_live); | |
879 | |
880 /* On the other hand, we do not allow the dead uses to set | |
881 anything in local_live. */ | |
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882 if (needed) |
0 | 883 df_simulate_uses (insn, local_live); |
884 } | |
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885 |
0 | 886 df_simulate_finalize_backwards (bb, local_live); |
887 | |
888 block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb)); | |
889 if (block_changed) | |
890 bitmap_copy (DF_LR_IN (bb), local_live); | |
891 | |
892 BITMAP_FREE (local_live); | |
893 return block_changed; | |
894 } | |
895 | |
896 | |
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897 /* Perform fast DCE once initialization is done. If WORD_LEVEL is |
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898 true, use the word level dce, otherwise do it at the pseudo |
0 | 899 level. */ |
900 | |
901 static void | |
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902 fast_dce (bool word_level) |
0 | 903 { |
904 int *postorder = df_get_postorder (DF_BACKWARD); | |
905 int n_blocks = df_get_n_blocks (DF_BACKWARD); | |
906 /* The set of blocks that have been seen on this iteration. */ | |
907 bitmap processed = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); | |
908 /* The set of blocks that need to have the out vectors reset because | |
909 the in of one of their successors has changed. */ | |
910 bitmap redo_out = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); | |
911 bitmap all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack); | |
912 bool global_changed = true; | |
913 | |
914 /* These regs are considered always live so if they end up dying | |
915 because of some def, we need to bring the back again. Calling | |
916 df_simulate_fixup_sets has the disadvantage of calling | |
917 bb_has_eh_pred once per insn, so we cache the information | |
918 here. */ | |
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919 bitmap au = &df->regular_block_artificial_uses; |
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920 bitmap au_eh = &df->eh_block_artificial_uses; |
0 | 921 int i; |
922 | |
923 prescan_insns_for_dce (true); | |
924 | |
925 for (i = 0; i < n_blocks; i++) | |
926 bitmap_set_bit (all_blocks, postorder[i]); | |
927 | |
928 while (global_changed) | |
929 { | |
930 global_changed = false; | |
931 | |
932 for (i = 0; i < n_blocks; i++) | |
933 { | |
934 int index = postorder[i]; | |
935 basic_block bb = BASIC_BLOCK (index); | |
936 bool local_changed; | |
937 | |
938 if (index < NUM_FIXED_BLOCKS) | |
939 { | |
940 bitmap_set_bit (processed, index); | |
941 continue; | |
942 } | |
943 | |
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944 if (word_level) |
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945 local_changed |
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946 = word_dce_process_block (bb, bitmap_bit_p (redo_out, index)); |
0 | 947 else |
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948 local_changed |
0 | 949 = dce_process_block (bb, bitmap_bit_p (redo_out, index), |
950 bb_has_eh_pred (bb) ? au_eh : au); | |
951 bitmap_set_bit (processed, index); | |
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952 |
0 | 953 if (local_changed) |
954 { | |
955 edge e; | |
956 edge_iterator ei; | |
957 FOR_EACH_EDGE (e, ei, bb->preds) | |
958 if (bitmap_bit_p (processed, e->src->index)) | |
959 /* Be tricky about when we need to iterate the | |
960 analysis. We only have redo the analysis if the | |
961 bitmaps change at the top of a block that is the | |
962 entry to a loop. */ | |
963 global_changed = true; | |
964 else | |
965 bitmap_set_bit (redo_out, e->src->index); | |
966 } | |
967 } | |
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968 |
0 | 969 if (global_changed) |
970 { | |
971 /* Turn off the RUN_DCE flag to prevent recursive calls to | |
972 dce. */ | |
973 int old_flag = df_clear_flags (DF_LR_RUN_DCE); | |
974 | |
975 /* So something was deleted that requires a redo. Do it on | |
976 the cheap. */ | |
977 delete_unmarked_insns (); | |
978 sbitmap_zero (marked); | |
979 bitmap_clear (processed); | |
980 bitmap_clear (redo_out); | |
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981 |
0 | 982 /* We do not need to rescan any instructions. We only need |
983 to redo the dataflow equations for the blocks that had a | |
984 change at the top of the block. Then we need to redo the | |
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985 iteration. */ |
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986 if (word_level) |
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987 df_analyze_problem (df_word_lr, all_blocks, postorder, n_blocks); |
0 | 988 else |
989 df_analyze_problem (df_lr, all_blocks, postorder, n_blocks); | |
990 | |
991 if (old_flag & DF_LR_RUN_DCE) | |
992 df_set_flags (DF_LR_RUN_DCE); | |
993 | |
994 prescan_insns_for_dce (true); | |
995 } | |
996 } | |
997 | |
998 delete_unmarked_insns (); | |
999 | |
1000 BITMAP_FREE (processed); | |
1001 BITMAP_FREE (redo_out); | |
1002 BITMAP_FREE (all_blocks); | |
1003 } | |
1004 | |
1005 | |
1006 /* Fast register level DCE. */ | |
1007 | |
1008 static unsigned int | |
1009 rest_of_handle_fast_dce (void) | |
1010 { | |
1011 init_dce (true); | |
1012 fast_dce (false); | |
1013 fini_dce (true); | |
1014 return 0; | |
1015 } | |
1016 | |
1017 | |
1018 /* Fast byte level DCE. */ | |
1019 | |
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1020 void |
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1021 run_word_dce (void) |
0 | 1022 { |
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1023 int old_flags; |
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1024 |
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1025 if (!flag_dce) |
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1026 return; |
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1027 |
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1028 timevar_push (TV_DCE); |
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1029 old_flags = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); |
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1030 df_word_lr_add_problem (); |
0 | 1031 init_dce (true); |
1032 fast_dce (true); | |
1033 fini_dce (true); | |
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1034 df_set_flags (old_flags); |
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1035 timevar_pop (TV_DCE); |
0 | 1036 } |
1037 | |
1038 | |
1039 /* This is an internal call that is used by the df live register | |
1040 problem to run fast dce as a side effect of creating the live | |
1041 information. The stack is organized so that the lr problem is run, | |
1042 this pass is run, which updates the live info and the df scanning | |
1043 info, and then returns to allow the rest of the problems to be run. | |
1044 | |
1045 This can be called by elsewhere but it will not update the bit | |
1046 vectors for any other problems than LR. */ | |
1047 | |
1048 void | |
1049 run_fast_df_dce (void) | |
1050 { | |
1051 if (flag_dce) | |
1052 { | |
1053 /* If dce is able to delete something, it has to happen | |
1054 immediately. Otherwise there will be problems handling the | |
1055 eq_notes. */ | |
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1056 int old_flags = |
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1057 df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN); |
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1058 |
0 | 1059 df_in_progress = true; |
1060 rest_of_handle_fast_dce (); | |
1061 df_in_progress = false; | |
1062 | |
1063 df_set_flags (old_flags); | |
1064 } | |
1065 } | |
1066 | |
1067 | |
1068 /* Run a fast DCE pass. */ | |
1069 | |
1070 void | |
1071 run_fast_dce (void) | |
1072 { | |
1073 if (flag_dce) | |
1074 rest_of_handle_fast_dce (); | |
1075 } | |
1076 | |
1077 | |
1078 static bool | |
1079 gate_fast_dce (void) | |
1080 { | |
1081 return optimize > 0 && flag_dce | |
1082 && dbg_cnt (dce_fast); | |
1083 } | |
1084 | |
1085 struct rtl_opt_pass pass_fast_rtl_dce = | |
1086 { | |
1087 { | |
1088 RTL_PASS, | |
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1089 "rtl dce", /* name */ |
0 | 1090 gate_fast_dce, /* gate */ |
1091 rest_of_handle_fast_dce, /* execute */ | |
1092 NULL, /* sub */ | |
1093 NULL, /* next */ | |
1094 0, /* static_pass_number */ | |
1095 TV_DCE, /* tv_id */ | |
1096 0, /* properties_required */ | |
1097 0, /* properties_provided */ | |
1098 0, /* properties_destroyed */ | |
1099 0, /* todo_flags_start */ | |
1100 TODO_dump_func | | |
1101 TODO_df_finish | TODO_verify_rtl_sharing | | |
1102 TODO_ggc_collect /* todo_flags_finish */ | |
1103 } | |
1104 }; |