Mercurial > hg > CbC > CbC_gcc
annotate gcc/combine-stack-adj.c @ 145:1830386684a0
gcc-9.2.0
| author | anatofuz |
|---|---|
| date | Thu, 13 Feb 2020 11:34:05 +0900 |
| parents | 84e7813d76e9 |
| children |
| rev | line source |
|---|---|
| 0 | 1 /* Combine stack adjustments. |
| 145 | 2 Copyright (C) 1987-2020 Free Software Foundation, Inc. |
| 0 | 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 /* Track stack adjustments and stack memory references. Attempt to | |
| 21 reduce the number of stack adjustments by back-propagating across | |
| 22 the memory references. | |
| 23 | |
| 24 This is intended primarily for use with targets that do not define | |
| 25 ACCUMULATE_OUTGOING_ARGS. It is of significantly more value to | |
| 26 targets that define PREFERRED_STACK_BOUNDARY more aligned than | |
| 27 STACK_BOUNDARY (e.g. x86), or if not all registers can be pushed | |
| 28 (e.g. x86 fp regs) which would ordinarily have to be implemented | |
| 29 as a sub/mov pair due to restrictions in calls.c. | |
| 30 | |
| 31 Propagation stops when any of the insns that need adjusting are | |
| 32 (a) no longer valid because we've exceeded their range, (b) a | |
| 33 non-trivial push instruction, or (c) a call instruction. | |
| 34 | |
| 35 Restriction B is based on the assumption that push instructions | |
| 36 are smaller or faster. If a port really wants to remove all | |
| 37 pushes, it should have defined ACCUMULATE_OUTGOING_ARGS. The | |
| 38 one exception that is made is for an add immediately followed | |
| 39 by a push. */ | |
| 40 | |
| 41 #include "config.h" | |
| 42 #include "system.h" | |
| 43 #include "coretypes.h" | |
| 111 | 44 #include "backend.h" |
| 0 | 45 #include "rtl.h" |
| 111 | 46 #include "df.h" |
| 0 | 47 #include "insn-config.h" |
| 111 | 48 #include "memmodel.h" |
| 49 #include "emit-rtl.h" | |
| 0 | 50 #include "recog.h" |
| 111 | 51 #include "cfgrtl.h" |
| 0 | 52 #include "tree-pass.h" |
| 111 | 53 #include "rtl-iter.h" |
| 0 | 54 |
| 55 | |
|
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56 /* This structure records two kinds of stack references between stack |
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57 adjusting instructions: stack references in memory addresses for |
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58 regular insns and all stack references for debug insns. */ |
| 0 | 59 |
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60 struct csa_reflist |
| 0 | 61 { |
| 62 HOST_WIDE_INT sp_offset; | |
| 111 | 63 rtx_insn *insn; |
| 64 rtx *ref; | |
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65 struct csa_reflist *next; |
| 0 | 66 }; |
| 67 | |
| 68 static int stack_memref_p (rtx); | |
| 111 | 69 static rtx single_set_for_csa (rtx_insn *); |
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70 static void free_csa_reflist (struct csa_reflist *); |
| 111 | 71 static struct csa_reflist *record_one_stack_ref (rtx_insn *, rtx *, |
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72 struct csa_reflist *); |
| 111 | 73 static int try_apply_stack_adjustment (rtx_insn *, struct csa_reflist *, |
| 0 | 74 HOST_WIDE_INT, HOST_WIDE_INT); |
| 75 static void combine_stack_adjustments_for_block (basic_block); | |
| 76 | |
| 77 | |
| 78 /* Main entry point for stack adjustment combination. */ | |
| 79 | |
| 80 static void | |
| 81 combine_stack_adjustments (void) | |
| 82 { | |
| 83 basic_block bb; | |
| 84 | |
| 111 | 85 FOR_EACH_BB_FN (bb, cfun) |
| 0 | 86 combine_stack_adjustments_for_block (bb); |
| 87 } | |
| 88 | |
| 89 /* Recognize a MEM of the form (sp) or (plus sp const). */ | |
| 90 | |
| 91 static int | |
| 92 stack_memref_p (rtx x) | |
| 93 { | |
| 94 if (!MEM_P (x)) | |
| 95 return 0; | |
| 96 x = XEXP (x, 0); | |
| 97 | |
| 98 if (x == stack_pointer_rtx) | |
| 99 return 1; | |
| 100 if (GET_CODE (x) == PLUS | |
| 101 && XEXP (x, 0) == stack_pointer_rtx | |
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102 && CONST_INT_P (XEXP (x, 1))) |
| 0 | 103 return 1; |
| 104 | |
| 105 return 0; | |
| 106 } | |
| 107 | |
| 108 /* Recognize either normal single_set or the hack in i386.md for | |
| 109 tying fp and sp adjustments. */ | |
| 110 | |
| 111 static rtx | |
| 111 | 112 single_set_for_csa (rtx_insn *insn) |
| 0 | 113 { |
| 114 int i; | |
| 115 rtx tmp = single_set (insn); | |
| 116 if (tmp) | |
| 117 return tmp; | |
| 118 | |
| 119 if (!NONJUMP_INSN_P (insn) | |
| 120 || GET_CODE (PATTERN (insn)) != PARALLEL) | |
| 121 return NULL_RTX; | |
| 122 | |
| 123 tmp = PATTERN (insn); | |
| 124 if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET) | |
| 125 return NULL_RTX; | |
| 126 | |
| 127 for (i = 1; i < XVECLEN (tmp, 0); ++i) | |
| 128 { | |
| 129 rtx this_rtx = XVECEXP (tmp, 0, i); | |
| 130 | |
| 131 /* The special case is allowing a no-op set. */ | |
| 132 if (GET_CODE (this_rtx) == SET | |
| 133 && SET_SRC (this_rtx) == SET_DEST (this_rtx)) | |
| 134 ; | |
| 135 else if (GET_CODE (this_rtx) != CLOBBER | |
| 136 && GET_CODE (this_rtx) != USE) | |
| 137 return NULL_RTX; | |
| 138 } | |
| 139 | |
| 140 return XVECEXP (tmp, 0, 0); | |
| 141 } | |
| 142 | |
|
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143 /* Free the list of csa_reflist nodes. */ |
| 0 | 144 |
| 145 static void | |
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146 free_csa_reflist (struct csa_reflist *reflist) |
| 0 | 147 { |
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148 struct csa_reflist *next; |
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149 for (; reflist ; reflist = next) |
| 0 | 150 { |
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151 next = reflist->next; |
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152 free (reflist); |
| 0 | 153 } |
| 154 } | |
| 155 | |
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156 /* Create a new csa_reflist node from the given stack reference. |
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157 It is already known that the reference is either a MEM satisfying the |
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158 predicate stack_memref_p or a REG representing the stack pointer. */ |
| 0 | 159 |
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160 static struct csa_reflist * |
| 111 | 161 record_one_stack_ref (rtx_insn *insn, rtx *ref, struct csa_reflist *next_reflist) |
| 0 | 162 { |
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163 struct csa_reflist *ml; |
| 0 | 164 |
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165 ml = XNEW (struct csa_reflist); |
| 0 | 166 |
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167 if (REG_P (*ref) || XEXP (*ref, 0) == stack_pointer_rtx) |
| 0 | 168 ml->sp_offset = 0; |
| 169 else | |
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170 ml->sp_offset = INTVAL (XEXP (XEXP (*ref, 0), 1)); |
| 0 | 171 |
| 172 ml->insn = insn; | |
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173 ml->ref = ref; |
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174 ml->next = next_reflist; |
| 0 | 175 |
| 176 return ml; | |
| 177 } | |
| 178 | |
| 111 | 179 /* We only know how to adjust the CFA; no other frame-related changes |
| 180 may appear in any insn to be deleted. */ | |
| 181 | |
| 182 static bool | |
| 183 no_unhandled_cfa (rtx_insn *insn) | |
| 184 { | |
| 185 if (!RTX_FRAME_RELATED_P (insn)) | |
| 186 return true; | |
| 187 | |
| 188 /* No CFA notes at all is a legacy interpretation like | |
| 189 FRAME_RELATED_EXPR, and is context sensitive within | |
| 190 the prologue state machine. We can't handle that here. */ | |
| 191 bool has_cfa_adjust = false; | |
| 192 | |
| 193 for (rtx link = REG_NOTES (insn); link; link = XEXP (link, 1)) | |
| 194 switch (REG_NOTE_KIND (link)) | |
| 195 { | |
| 196 default: | |
| 197 break; | |
| 198 case REG_CFA_ADJUST_CFA: | |
| 199 has_cfa_adjust = true; | |
| 200 break; | |
| 201 | |
| 202 case REG_FRAME_RELATED_EXPR: | |
| 203 case REG_CFA_DEF_CFA: | |
| 204 case REG_CFA_OFFSET: | |
| 205 case REG_CFA_REGISTER: | |
| 206 case REG_CFA_EXPRESSION: | |
| 207 case REG_CFA_RESTORE: | |
| 208 case REG_CFA_SET_VDRAP: | |
| 209 case REG_CFA_WINDOW_SAVE: | |
| 210 case REG_CFA_FLUSH_QUEUE: | |
| 211 case REG_CFA_TOGGLE_RA_MANGLE: | |
| 212 return false; | |
| 213 } | |
| 214 | |
| 215 return has_cfa_adjust; | |
| 216 } | |
| 217 | |
| 0 | 218 /* Attempt to apply ADJUST to the stack adjusting insn INSN, as well |
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219 as each of the memories and stack references in REFLIST. Return true |
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220 on success. */ |
| 0 | 221 |
| 222 static int | |
| 111 | 223 try_apply_stack_adjustment (rtx_insn *insn, struct csa_reflist *reflist, |
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224 HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta) |
| 0 | 225 { |
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226 struct csa_reflist *ml; |
| 0 | 227 rtx set; |
| 228 | |
| 229 set = single_set_for_csa (insn); | |
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230 if (MEM_P (SET_DEST (set))) |
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231 validate_change (insn, &SET_DEST (set), |
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232 replace_equiv_address (SET_DEST (set), stack_pointer_rtx), |
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233 1); |
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234 else |
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235 validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1); |
| 0 | 236 |
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237 for (ml = reflist; ml ; ml = ml->next) |
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238 { |
| 111 | 239 rtx new_addr = plus_constant (Pmode, stack_pointer_rtx, |
| 240 ml->sp_offset - delta); | |
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241 rtx new_val; |
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242 |
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243 if (MEM_P (*ml->ref)) |
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244 new_val = replace_equiv_address_nv (*ml->ref, new_addr); |
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245 else if (GET_MODE (*ml->ref) == GET_MODE (stack_pointer_rtx)) |
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246 new_val = new_addr; |
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247 else |
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248 new_val = lowpart_subreg (GET_MODE (*ml->ref), new_addr, |
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249 GET_MODE (new_addr)); |
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250 validate_change (ml->insn, ml->ref, new_val, 1); |
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251 } |
| 0 | 252 |
| 253 if (apply_change_group ()) | |
| 254 { | |
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255 /* Succeeded. Update our knowledge of the stack references. */ |
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256 for (ml = reflist; ml ; ml = ml->next) |
| 0 | 257 ml->sp_offset -= delta; |
| 258 | |
| 259 return 1; | |
| 260 } | |
| 261 else | |
| 262 return 0; | |
| 263 } | |
| 264 | |
| 111 | 265 /* For non-debug insns, record all stack memory references in INSN |
| 266 and return true if there were no other (unrecorded) references to the | |
| 267 stack pointer. For debug insns, record all stack references regardless | |
| 268 of context and unconditionally return true. */ | |
| 0 | 269 |
| 111 | 270 static bool |
| 271 record_stack_refs (rtx_insn *insn, struct csa_reflist **reflist) | |
| 0 | 272 { |
| 111 | 273 subrtx_ptr_iterator::array_type array; |
| 274 FOR_EACH_SUBRTX_PTR (iter, array, &PATTERN (insn), NONCONST) | |
| 0 | 275 { |
| 111 | 276 rtx *loc = *iter; |
| 277 rtx x = *loc; | |
| 278 switch (GET_CODE (x)) | |
| 0 | 279 { |
| 111 | 280 case MEM: |
| 281 if (!reg_mentioned_p (stack_pointer_rtx, x)) | |
| 282 iter.skip_subrtxes (); | |
| 283 /* We are not able to handle correctly all possible memrefs | |
| 284 containing stack pointer, so this check is necessary. */ | |
| 285 else if (stack_memref_p (x)) | |
| 286 { | |
| 287 *reflist = record_one_stack_ref (insn, loc, *reflist); | |
| 288 iter.skip_subrtxes (); | |
| 289 } | |
| 290 /* Try harder for DEBUG_INSNs, handle e.g. | |
| 291 (mem (mem (sp + 16) + 4). */ | |
| 292 else if (!DEBUG_INSN_P (insn)) | |
| 293 return false; | |
| 294 break; | |
| 295 | |
| 296 case REG: | |
| 297 /* ??? We want be able to handle non-memory stack pointer | |
| 298 references later. For now just discard all insns referring to | |
| 299 stack pointer outside mem expressions. We would probably | |
| 300 want to teach validate_replace to simplify expressions first. | |
| 301 | |
| 302 We can't just compare with STACK_POINTER_RTX because the | |
| 303 reference to the stack pointer might be in some other mode. | |
| 304 In particular, an explicit clobber in an asm statement will | |
| 305 result in a QImode clobber. | |
| 306 | |
| 307 In DEBUG_INSNs, we want to replace all occurrences, otherwise | |
| 308 they will cause -fcompare-debug failures. */ | |
| 309 if (REGNO (x) == STACK_POINTER_REGNUM) | |
| 310 { | |
| 311 if (!DEBUG_INSN_P (insn)) | |
| 312 return false; | |
| 313 *reflist = record_one_stack_ref (insn, loc, *reflist); | |
| 314 } | |
| 315 break; | |
| 316 | |
| 317 default: | |
| 318 break; | |
| 0 | 319 } |
| 111 | 320 } |
| 321 return true; | |
| 322 } | |
| 0 | 323 |
| 111 | 324 /* If INSN has a REG_ARGS_SIZE note, move it to LAST. |
| 325 AFTER is true iff LAST follows INSN in the instruction stream. */ | |
| 326 | |
| 327 static void | |
| 328 maybe_move_args_size_note (rtx_insn *last, rtx_insn *insn, bool after) | |
| 329 { | |
| 330 rtx note, last_note; | |
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331 |
| 111 | 332 note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); |
| 333 if (note == NULL) | |
| 334 return; | |
| 335 | |
| 336 last_note = find_reg_note (last, REG_ARGS_SIZE, NULL_RTX); | |
| 337 if (last_note) | |
| 338 { | |
| 339 /* The ARGS_SIZE notes are *not* cumulative. They represent an | |
| 340 absolute value, and the "most recent" note wins. */ | |
| 341 if (!after) | |
| 342 XEXP (last_note, 0) = XEXP (note, 0); | |
| 0 | 343 } |
| 111 | 344 else |
| 345 add_reg_note (last, REG_ARGS_SIZE, XEXP (note, 0)); | |
| 0 | 346 } |
| 347 | |
| 111 | 348 /* Merge any REG_CFA_ADJUST_CFA note from SRC into DST. |
| 349 AFTER is true iff DST follows SRC in the instruction stream. */ | |
| 0 | 350 |
| 351 static void | |
| 111 | 352 maybe_merge_cfa_adjust (rtx_insn *dst, rtx_insn *src, bool after) |
| 353 { | |
| 354 rtx snote = NULL, dnote = NULL; | |
| 355 rtx sexp, dexp; | |
| 356 rtx exp1, exp2; | |
| 357 | |
| 358 if (RTX_FRAME_RELATED_P (src)) | |
| 359 snote = find_reg_note (src, REG_CFA_ADJUST_CFA, NULL_RTX); | |
| 360 if (snote == NULL) | |
| 361 return; | |
| 362 sexp = XEXP (snote, 0); | |
| 363 | |
| 364 if (RTX_FRAME_RELATED_P (dst)) | |
| 365 dnote = find_reg_note (dst, REG_CFA_ADJUST_CFA, NULL_RTX); | |
| 366 if (dnote == NULL) | |
| 367 { | |
| 368 add_reg_note (dst, REG_CFA_ADJUST_CFA, sexp); | |
| 369 return; | |
| 370 } | |
| 371 dexp = XEXP (dnote, 0); | |
| 372 | |
| 373 gcc_assert (GET_CODE (sexp) == SET); | |
| 374 gcc_assert (GET_CODE (dexp) == SET); | |
| 375 | |
| 376 if (after) | |
| 377 exp1 = dexp, exp2 = sexp; | |
| 378 else | |
| 379 exp1 = sexp, exp2 = dexp; | |
| 380 | |
| 381 SET_SRC (exp1) = simplify_replace_rtx (SET_SRC (exp1), SET_DEST (exp2), | |
| 382 SET_SRC (exp2)); | |
| 383 XEXP (dnote, 0) = exp1; | |
| 384 } | |
| 385 | |
| 386 /* Return the next (or previous) active insn within BB. */ | |
| 387 | |
| 388 static rtx_insn * | |
| 389 prev_active_insn_bb (basic_block bb, rtx_insn *insn) | |
| 0 | 390 { |
| 111 | 391 for (insn = PREV_INSN (insn); |
| 392 insn != PREV_INSN (BB_HEAD (bb)); | |
| 393 insn = PREV_INSN (insn)) | |
| 394 if (active_insn_p (insn)) | |
| 395 return insn; | |
| 396 return NULL; | |
| 397 } | |
| 398 | |
| 399 static rtx_insn * | |
| 400 next_active_insn_bb (basic_block bb, rtx_insn *insn) | |
| 401 { | |
| 402 for (insn = NEXT_INSN (insn); | |
| 403 insn != NEXT_INSN (BB_END (bb)); | |
| 404 insn = NEXT_INSN (insn)) | |
| 405 if (active_insn_p (insn)) | |
| 406 return insn; | |
| 407 return NULL; | |
| 408 } | |
| 0 | 409 |
| 111 | 410 /* If INSN has a REG_ARGS_SIZE note, if possible move it to PREV. Otherwise |
| 411 search for a nearby candidate within BB where we can stick the note. */ | |
| 412 | |
| 413 static void | |
| 414 force_move_args_size_note (basic_block bb, rtx_insn *prev, rtx_insn *insn) | |
| 415 { | |
| 416 rtx note; | |
| 417 rtx_insn *test, *next_candidate, *prev_candidate; | |
| 418 | |
| 419 /* If PREV exists, tail-call to the logic in the other function. */ | |
| 420 if (prev) | |
| 421 { | |
| 422 maybe_move_args_size_note (prev, insn, false); | |
| 423 return; | |
| 424 } | |
| 425 | |
| 426 /* First, make sure there's anything that needs doing. */ | |
| 427 note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); | |
| 428 if (note == NULL) | |
| 0 | 429 return; |
| 430 | |
| 111 | 431 /* We need to find a spot between the previous and next exception points |
| 432 where we can place the note and "properly" deallocate the arguments. */ | |
| 433 next_candidate = prev_candidate = NULL; | |
| 434 | |
| 435 /* It is often the case that we have insns in the order: | |
| 436 call | |
| 437 add sp (previous deallocation) | |
| 438 sub sp (align for next arglist) | |
| 439 push arg | |
| 440 and the add/sub cancel. Therefore we begin by searching forward. */ | |
| 0 | 441 |
| 111 | 442 test = insn; |
| 443 while ((test = next_active_insn_bb (bb, test)) != NULL) | |
| 444 { | |
| 445 /* Found an existing note: nothing to do. */ | |
| 446 if (find_reg_note (test, REG_ARGS_SIZE, NULL_RTX)) | |
| 447 return; | |
| 448 /* Found something that affects unwinding. Stop searching. */ | |
| 449 if (CALL_P (test) || !insn_nothrow_p (test)) | |
| 450 break; | |
| 451 if (next_candidate == NULL) | |
| 452 next_candidate = test; | |
| 453 } | |
| 454 | |
| 455 test = insn; | |
| 456 while ((test = prev_active_insn_bb (bb, test)) != NULL) | |
| 457 { | |
| 458 rtx tnote; | |
| 459 /* Found a place that seems logical to adjust the stack. */ | |
| 460 tnote = find_reg_note (test, REG_ARGS_SIZE, NULL_RTX); | |
| 461 if (tnote) | |
| 0 | 462 { |
| 111 | 463 XEXP (tnote, 0) = XEXP (note, 0); |
| 0 | 464 return; |
| 465 } | |
| 111 | 466 if (prev_candidate == NULL) |
| 467 prev_candidate = test; | |
| 468 /* Found something that affects unwinding. Stop searching. */ | |
| 469 if (CALL_P (test) || !insn_nothrow_p (test)) | |
| 470 break; | |
| 471 } | |
| 0 | 472 |
| 111 | 473 if (prev_candidate) |
| 474 test = prev_candidate; | |
| 475 else if (next_candidate) | |
| 476 test = next_candidate; | |
| 0 | 477 else |
| 478 { | |
| 111 | 479 /* ??? We *must* have a place, lest we ICE on the lost adjustment. |
| 480 Options are: dummy clobber insn, nop, or prevent the removal of | |
| 481 the sp += 0 insn. */ | |
| 482 /* TODO: Find another way to indicate to the dwarf2 code that we | |
| 483 have not in fact lost an adjustment. */ | |
| 484 test = emit_insn_before (gen_rtx_CLOBBER (VOIDmode, const0_rtx), insn); | |
| 0 | 485 } |
| 111 | 486 add_reg_note (test, REG_ARGS_SIZE, XEXP (note, 0)); |
| 0 | 487 } |
| 488 | |
| 489 /* Subroutine of combine_stack_adjustments, called for each basic block. */ | |
| 490 | |
| 491 static void | |
| 492 combine_stack_adjustments_for_block (basic_block bb) | |
| 493 { | |
| 494 HOST_WIDE_INT last_sp_adjust = 0; | |
| 111 | 495 rtx_insn *last_sp_set = NULL; |
| 496 rtx_insn *last2_sp_set = NULL; | |
|
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497 struct csa_reflist *reflist = NULL; |
| 111 | 498 rtx_insn *insn, *next; |
| 499 rtx set; | |
| 0 | 500 bool end_of_block = false; |
| 501 | |
| 502 for (insn = BB_HEAD (bb); !end_of_block ; insn = next) | |
| 503 { | |
| 504 end_of_block = insn == BB_END (bb); | |
| 505 next = NEXT_INSN (insn); | |
| 506 | |
| 507 if (! INSN_P (insn)) | |
| 508 continue; | |
| 509 | |
| 510 set = single_set_for_csa (insn); | |
| 111 | 511 if (set && find_reg_note (insn, REG_STACK_CHECK, NULL_RTX)) |
| 512 set = NULL_RTX; | |
| 0 | 513 if (set) |
| 514 { | |
| 515 rtx dest = SET_DEST (set); | |
| 516 rtx src = SET_SRC (set); | |
| 517 | |
| 518 /* Find constant additions to the stack pointer. */ | |
| 519 if (dest == stack_pointer_rtx | |
| 520 && GET_CODE (src) == PLUS | |
| 521 && XEXP (src, 0) == stack_pointer_rtx | |
|
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522 && CONST_INT_P (XEXP (src, 1))) |
| 0 | 523 { |
| 524 HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1)); | |
| 525 | |
| 526 /* If we've not seen an adjustment previously, record | |
| 527 it now and continue. */ | |
| 528 if (! last_sp_set) | |
| 529 { | |
| 530 last_sp_set = insn; | |
| 531 last_sp_adjust = this_adjust; | |
| 532 continue; | |
| 533 } | |
| 534 | |
|
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535 /* If not all recorded refs can be adjusted, or the |
| 0 | 536 adjustment is now too large for a constant addition, |
| 537 we cannot merge the two stack adjustments. | |
| 538 | |
| 539 Also we need to be careful to not move stack pointer | |
| 540 such that we create stack accesses outside the allocated | |
| 541 area. We can combine an allocation into the first insn, | |
| 145 | 542 or a deallocation into the second insn. We cannot |
| 0 | 543 combine an allocation followed by a deallocation. |
| 544 | |
| 545 The only somewhat frequent occurrence of the later is when | |
| 546 a function allocates a stack frame but does not use it. | |
| 547 For this case, we would need to analyze rtl stream to be | |
| 548 sure that allocated area is really unused. This means not | |
| 549 only checking the memory references, but also all registers | |
| 550 or global memory references possibly containing a stack | |
| 551 frame address. | |
| 552 | |
| 553 Perhaps the best way to address this problem is to teach | |
| 554 gcc not to allocate stack for objects never used. */ | |
| 555 | |
| 556 /* Combine an allocation into the first instruction. */ | |
| 557 if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0) | |
| 558 { | |
| 111 | 559 if (no_unhandled_cfa (insn) |
| 560 && try_apply_stack_adjustment (last_sp_set, reflist, | |
| 561 last_sp_adjust | |
| 562 + this_adjust, | |
| 563 this_adjust)) | |
| 0 | 564 { |
| 565 /* It worked! */ | |
| 111 | 566 maybe_move_args_size_note (last_sp_set, insn, false); |
| 567 maybe_merge_cfa_adjust (last_sp_set, insn, false); | |
| 0 | 568 delete_insn (insn); |
| 569 last_sp_adjust += this_adjust; | |
| 570 continue; | |
| 571 } | |
| 572 } | |
| 573 | |
| 574 /* Otherwise we have a deallocation. Do not combine with | |
| 575 a previous allocation. Combine into the second insn. */ | |
| 576 else if (STACK_GROWS_DOWNWARD | |
| 577 ? last_sp_adjust >= 0 : last_sp_adjust <= 0) | |
| 578 { | |
| 111 | 579 if (no_unhandled_cfa (last_sp_set) |
| 580 && try_apply_stack_adjustment (insn, reflist, | |
| 581 last_sp_adjust | |
| 582 + this_adjust, | |
| 583 -last_sp_adjust)) | |
| 0 | 584 { |
| 585 /* It worked! */ | |
| 111 | 586 maybe_move_args_size_note (insn, last_sp_set, true); |
| 587 maybe_merge_cfa_adjust (insn, last_sp_set, true); | |
| 0 | 588 delete_insn (last_sp_set); |
| 589 last_sp_set = insn; | |
| 590 last_sp_adjust += this_adjust; | |
|
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591 free_csa_reflist (reflist); |
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592 reflist = NULL; |
| 0 | 593 continue; |
| 594 } | |
| 595 } | |
| 596 | |
| 597 /* Combination failed. Restart processing from here. If | |
| 598 deallocation+allocation conspired to cancel, we can | |
| 599 delete the old deallocation insn. */ | |
| 111 | 600 if (last_sp_set) |
| 601 { | |
| 602 if (last_sp_adjust == 0 && no_unhandled_cfa (last_sp_set)) | |
| 603 { | |
| 604 maybe_move_args_size_note (insn, last_sp_set, true); | |
| 605 maybe_merge_cfa_adjust (insn, last_sp_set, true); | |
| 606 delete_insn (last_sp_set); | |
| 607 } | |
| 608 else | |
| 609 last2_sp_set = last_sp_set; | |
| 610 } | |
|
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611 free_csa_reflist (reflist); |
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612 reflist = NULL; |
| 0 | 613 last_sp_set = insn; |
| 614 last_sp_adjust = this_adjust; | |
| 615 continue; | |
| 616 } | |
| 617 | |
|
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618 /* Find a store with pre-(dec|inc)rement or pre-modify of exactly |
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619 the previous adjustment and turn it into a simple store. This |
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620 is equivalent to anticipating the stack adjustment so this must |
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621 be an allocation. */ |
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622 if (MEM_P (dest) |
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623 && ((STACK_GROWS_DOWNWARD |
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624 ? (GET_CODE (XEXP (dest, 0)) == PRE_DEC |
| 131 | 625 && known_eq (last_sp_adjust, |
| 626 GET_MODE_SIZE (GET_MODE (dest)))) | |
|
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627 : (GET_CODE (XEXP (dest, 0)) == PRE_INC |
| 131 | 628 && known_eq (-last_sp_adjust, |
| 629 GET_MODE_SIZE (GET_MODE (dest))))) | |
|
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630 || ((STACK_GROWS_DOWNWARD |
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631 ? last_sp_adjust >= 0 : last_sp_adjust <= 0) |
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632 && GET_CODE (XEXP (dest, 0)) == PRE_MODIFY |
| 0 | 633 && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS |
|
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634 && XEXP (XEXP (XEXP (dest, 0), 1), 0) |
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635 == stack_pointer_rtx |
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636 && GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1)) |
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637 == CONST_INT |
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638 && INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1)) |
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639 == -last_sp_adjust)) |
| 0 | 640 && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx |
|
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641 && !reg_mentioned_p (stack_pointer_rtx, src) |
| 0 | 642 && memory_address_p (GET_MODE (dest), stack_pointer_rtx) |
|
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643 && try_apply_stack_adjustment (insn, reflist, 0, |
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644 -last_sp_adjust)) |
| 0 | 645 { |
| 111 | 646 if (last2_sp_set) |
| 647 maybe_move_args_size_note (last2_sp_set, last_sp_set, false); | |
| 648 else | |
| 649 maybe_move_args_size_note (insn, last_sp_set, true); | |
| 0 | 650 delete_insn (last_sp_set); |
|
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651 free_csa_reflist (reflist); |
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652 reflist = NULL; |
| 111 | 653 last_sp_set = NULL; |
| 0 | 654 last_sp_adjust = 0; |
| 655 continue; | |
| 656 } | |
| 657 } | |
| 658 | |
| 659 if (!CALL_P (insn) && last_sp_set | |
| 111 | 660 && record_stack_refs (insn, &reflist)) |
| 661 continue; | |
| 0 | 662 |
| 663 /* Otherwise, we were not able to process the instruction. | |
| 664 Do not continue collecting data across such a one. */ | |
| 665 if (last_sp_set | |
| 666 && (CALL_P (insn) | |
| 667 || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn)))) | |
| 668 { | |
| 669 if (last_sp_set && last_sp_adjust == 0) | |
| 111 | 670 { |
| 671 force_move_args_size_note (bb, last2_sp_set, last_sp_set); | |
| 672 delete_insn (last_sp_set); | |
| 673 } | |
|
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674 free_csa_reflist (reflist); |
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675 reflist = NULL; |
| 111 | 676 last2_sp_set = NULL; |
| 677 last_sp_set = NULL; | |
| 0 | 678 last_sp_adjust = 0; |
| 679 } | |
| 680 } | |
| 681 | |
| 682 if (last_sp_set && last_sp_adjust == 0) | |
| 111 | 683 { |
| 684 force_move_args_size_note (bb, last2_sp_set, last_sp_set); | |
| 685 delete_insn (last_sp_set); | |
| 686 } | |
| 0 | 687 |
|
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688 if (reflist) |
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689 free_csa_reflist (reflist); |
| 0 | 690 } |
| 691 | |
| 692 static unsigned int | |
| 693 rest_of_handle_stack_adjustments (void) | |
| 694 { | |
| 111 | 695 df_note_add_problem (); |
| 696 df_analyze (); | |
| 697 combine_stack_adjustments (); | |
| 698 return 0; | |
| 699 } | |
| 700 | |
| 701 namespace { | |
| 0 | 702 |
| 111 | 703 const pass_data pass_data_stack_adjustments = |
| 704 { | |
| 705 RTL_PASS, /* type */ | |
| 706 "csa", /* name */ | |
| 707 OPTGROUP_NONE, /* optinfo_flags */ | |
| 708 TV_COMBINE_STACK_ADJUST, /* tv_id */ | |
| 709 0, /* properties_required */ | |
| 710 0, /* properties_provided */ | |
| 711 0, /* properties_destroyed */ | |
| 712 0, /* todo_flags_start */ | |
| 713 TODO_df_finish, /* todo_flags_finish */ | |
| 714 }; | |
| 715 | |
| 716 class pass_stack_adjustments : public rtl_opt_pass | |
| 717 { | |
| 718 public: | |
| 719 pass_stack_adjustments (gcc::context *ctxt) | |
| 720 : rtl_opt_pass (pass_data_stack_adjustments, ctxt) | |
| 721 {} | |
| 722 | |
| 723 /* opt_pass methods: */ | |
| 724 virtual bool gate (function *); | |
| 725 virtual unsigned int execute (function *) | |
| 726 { | |
| 727 return rest_of_handle_stack_adjustments (); | |
| 728 } | |
| 729 | |
| 730 }; // class pass_stack_adjustments | |
| 731 | |
| 732 bool | |
| 733 pass_stack_adjustments::gate (function *) | |
| 734 { | |
| 0 | 735 /* This is kind of a heuristic. We need to run combine_stack_adjustments |
|
67
f6334be47118
update gcc from gcc-4.6-20100522 to gcc-4.6-20110318
nobuyasu <dimolto@cr.ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
736 even for machines with possibly nonzero TARGET_RETURN_POPS_ARGS |
| 0 | 737 and ACCUMULATE_OUTGOING_ARGS. We expect that only ports having |
| 738 push instructions will have popping returns. */ | |
| 739 #ifndef PUSH_ROUNDING | |
| 111 | 740 if (ACCUMULATE_OUTGOING_ARGS) |
| 741 return false; | |
| 0 | 742 #endif |
| 111 | 743 return flag_combine_stack_adjustments; |
| 0 | 744 } |
| 745 | |
| 111 | 746 } // anon namespace |
| 747 | |
| 748 rtl_opt_pass * | |
| 749 make_pass_stack_adjustments (gcc::context *ctxt) | |
| 0 | 750 { |
| 111 | 751 return new pass_stack_adjustments (ctxt); |
| 752 } |