Mercurial > hg > CbC > CbC_gcc
annotate gcc/dce.c @ 88:f214c1d5b862
merge 89
| author | Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp> |
|---|---|
| date | Tue, 20 Dec 2011 18:53:46 +0900 |
| parents | f6334be47118 |
| children | 04ced10e8804 |
| rev | line source |
|---|---|
| 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 }; |