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c7a0240a | 1 | /* Combine stack adjustments. |
818ab71a | 2 | Copyright (C) 1987-2016 Free Software Foundation, Inc. |
c7a0240a SB |
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 | |
9dcd6f09 | 8 | Software Foundation; either version 3, or (at your option) any later |
c7a0240a SB |
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 | |
9dcd6f09 NC |
17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
c7a0240a SB |
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32 | (a) no longer valid because we've exceeded their range, (b) a | |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" | |
c7131fb2 | 44 | #include "backend.h" |
c7a0240a | 45 | #include "rtl.h" |
c7131fb2 | 46 | #include "df.h" |
c7a0240a | 47 | #include "insn-config.h" |
957060b5 AM |
48 | #include "emit-rtl.h" |
49 | #include "recog.h" | |
60393bbc | 50 | #include "cfgrtl.h" |
c7a0240a | 51 | #include "tree-pass.h" |
f8305d18 | 52 | #include "rtl-iter.h" |
c7a0240a SB |
53 | |
54 | \f | |
90588a10 JJ |
55 | /* This structure records two kinds of stack references between stack |
56 | adjusting instructions: stack references in memory addresses for | |
57 | regular insns and all stack references for debug insns. */ | |
c7a0240a | 58 | |
90588a10 | 59 | struct csa_reflist |
c7a0240a SB |
60 | { |
61 | HOST_WIDE_INT sp_offset; | |
71e88baf DM |
62 | rtx_insn *insn; |
63 | rtx *ref; | |
90588a10 | 64 | struct csa_reflist *next; |
c7a0240a SB |
65 | }; |
66 | ||
67 | static int stack_memref_p (rtx); | |
71e88baf | 68 | static rtx single_set_for_csa (rtx_insn *); |
90588a10 | 69 | static void free_csa_reflist (struct csa_reflist *); |
71e88baf | 70 | static struct csa_reflist *record_one_stack_ref (rtx_insn *, rtx *, |
90588a10 | 71 | struct csa_reflist *); |
71e88baf | 72 | static int try_apply_stack_adjustment (rtx_insn *, struct csa_reflist *, |
c7a0240a SB |
73 | HOST_WIDE_INT, HOST_WIDE_INT); |
74 | static void combine_stack_adjustments_for_block (basic_block); | |
c7a0240a SB |
75 | |
76 | ||
77 | /* Main entry point for stack adjustment combination. */ | |
78 | ||
79 | static void | |
80 | combine_stack_adjustments (void) | |
81 | { | |
82 | basic_block bb; | |
83 | ||
11cd3bed | 84 | FOR_EACH_BB_FN (bb, cfun) |
c7a0240a SB |
85 | combine_stack_adjustments_for_block (bb); |
86 | } | |
87 | ||
88 | /* Recognize a MEM of the form (sp) or (plus sp const). */ | |
89 | ||
90 | static int | |
91 | stack_memref_p (rtx x) | |
92 | { | |
93 | if (!MEM_P (x)) | |
94 | return 0; | |
95 | x = XEXP (x, 0); | |
96 | ||
97 | if (x == stack_pointer_rtx) | |
98 | return 1; | |
99 | if (GET_CODE (x) == PLUS | |
100 | && XEXP (x, 0) == stack_pointer_rtx | |
481683e1 | 101 | && CONST_INT_P (XEXP (x, 1))) |
c7a0240a SB |
102 | return 1; |
103 | ||
104 | return 0; | |
105 | } | |
106 | ||
107 | /* Recognize either normal single_set or the hack in i386.md for | |
108 | tying fp and sp adjustments. */ | |
109 | ||
110 | static rtx | |
71e88baf | 111 | single_set_for_csa (rtx_insn *insn) |
c7a0240a SB |
112 | { |
113 | int i; | |
114 | rtx tmp = single_set (insn); | |
115 | if (tmp) | |
116 | return tmp; | |
117 | ||
118 | if (!NONJUMP_INSN_P (insn) | |
119 | || GET_CODE (PATTERN (insn)) != PARALLEL) | |
120 | return NULL_RTX; | |
121 | ||
122 | tmp = PATTERN (insn); | |
123 | if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET) | |
124 | return NULL_RTX; | |
125 | ||
126 | for (i = 1; i < XVECLEN (tmp, 0); ++i) | |
127 | { | |
48c54229 | 128 | rtx this_rtx = XVECEXP (tmp, 0, i); |
c7a0240a SB |
129 | |
130 | /* The special case is allowing a no-op set. */ | |
48c54229 KG |
131 | if (GET_CODE (this_rtx) == SET |
132 | && SET_SRC (this_rtx) == SET_DEST (this_rtx)) | |
c7a0240a | 133 | ; |
48c54229 KG |
134 | else if (GET_CODE (this_rtx) != CLOBBER |
135 | && GET_CODE (this_rtx) != USE) | |
c7a0240a SB |
136 | return NULL_RTX; |
137 | } | |
138 | ||
139 | return XVECEXP (tmp, 0, 0); | |
140 | } | |
141 | ||
90588a10 | 142 | /* Free the list of csa_reflist nodes. */ |
c7a0240a SB |
143 | |
144 | static void | |
90588a10 | 145 | free_csa_reflist (struct csa_reflist *reflist) |
c7a0240a | 146 | { |
90588a10 JJ |
147 | struct csa_reflist *next; |
148 | for (; reflist ; reflist = next) | |
c7a0240a | 149 | { |
90588a10 JJ |
150 | next = reflist->next; |
151 | free (reflist); | |
c7a0240a SB |
152 | } |
153 | } | |
154 | ||
90588a10 JJ |
155 | /* Create a new csa_reflist node from the given stack reference. |
156 | It is already known that the reference is either a MEM satisfying the | |
157 | predicate stack_memref_p or a REG representing the stack pointer. */ | |
c7a0240a | 158 | |
90588a10 | 159 | static struct csa_reflist * |
71e88baf | 160 | record_one_stack_ref (rtx_insn *insn, rtx *ref, struct csa_reflist *next_reflist) |
c7a0240a | 161 | { |
90588a10 | 162 | struct csa_reflist *ml; |
c7a0240a | 163 | |
90588a10 | 164 | ml = XNEW (struct csa_reflist); |
c7a0240a | 165 | |
90588a10 | 166 | if (REG_P (*ref) || XEXP (*ref, 0) == stack_pointer_rtx) |
c7a0240a SB |
167 | ml->sp_offset = 0; |
168 | else | |
90588a10 | 169 | ml->sp_offset = INTVAL (XEXP (XEXP (*ref, 0), 1)); |
c7a0240a SB |
170 | |
171 | ml->insn = insn; | |
90588a10 JJ |
172 | ml->ref = ref; |
173 | ml->next = next_reflist; | |
c7a0240a SB |
174 | |
175 | return ml; | |
176 | } | |
177 | ||
3dce0964 RH |
178 | /* We only know how to adjust the CFA; no other frame-related changes |
179 | may appear in any insn to be deleted. */ | |
180 | ||
181 | static bool | |
182 | no_unhandled_cfa (rtx_insn *insn) | |
183 | { | |
184 | if (!RTX_FRAME_RELATED_P (insn)) | |
185 | return true; | |
186 | ||
187 | /* No CFA notes at all is a legacy interpretation like | |
188 | FRAME_RELATED_EXPR, and is context sensitive within | |
189 | the prologue state machine. We can't handle that here. */ | |
190 | bool has_cfa_adjust = false; | |
191 | ||
192 | for (rtx link = REG_NOTES (insn); link; link = XEXP (link, 1)) | |
193 | switch (REG_NOTE_KIND (link)) | |
194 | { | |
195 | default: | |
196 | break; | |
197 | case REG_CFA_ADJUST_CFA: | |
198 | has_cfa_adjust = true; | |
199 | break; | |
200 | ||
201 | case REG_FRAME_RELATED_EXPR: | |
202 | case REG_CFA_DEF_CFA: | |
203 | case REG_CFA_OFFSET: | |
204 | case REG_CFA_REGISTER: | |
205 | case REG_CFA_EXPRESSION: | |
206 | case REG_CFA_RESTORE: | |
207 | case REG_CFA_SET_VDRAP: | |
208 | case REG_CFA_WINDOW_SAVE: | |
209 | case REG_CFA_FLUSH_QUEUE: | |
210 | return false; | |
211 | } | |
212 | ||
213 | return has_cfa_adjust; | |
214 | } | |
215 | ||
c7a0240a | 216 | /* Attempt to apply ADJUST to the stack adjusting insn INSN, as well |
90588a10 JJ |
217 | as each of the memories and stack references in REFLIST. Return true |
218 | on success. */ | |
c7a0240a SB |
219 | |
220 | static int | |
71e88baf | 221 | try_apply_stack_adjustment (rtx_insn *insn, struct csa_reflist *reflist, |
90588a10 | 222 | HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta) |
c7a0240a | 223 | { |
90588a10 | 224 | struct csa_reflist *ml; |
c7a0240a SB |
225 | rtx set; |
226 | ||
227 | set = single_set_for_csa (insn); | |
1362aa31 EB |
228 | if (MEM_P (SET_DEST (set))) |
229 | validate_change (insn, &SET_DEST (set), | |
230 | replace_equiv_address (SET_DEST (set), stack_pointer_rtx), | |
231 | 1); | |
232 | else | |
233 | validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1); | |
c7a0240a | 234 | |
90588a10 JJ |
235 | for (ml = reflist; ml ; ml = ml->next) |
236 | { | |
0a81f074 RS |
237 | rtx new_addr = plus_constant (Pmode, stack_pointer_rtx, |
238 | ml->sp_offset - delta); | |
90588a10 JJ |
239 | rtx new_val; |
240 | ||
241 | if (MEM_P (*ml->ref)) | |
242 | new_val = replace_equiv_address_nv (*ml->ref, new_addr); | |
243 | else if (GET_MODE (*ml->ref) == GET_MODE (stack_pointer_rtx)) | |
244 | new_val = new_addr; | |
245 | else | |
246 | new_val = lowpart_subreg (GET_MODE (*ml->ref), new_addr, | |
247 | GET_MODE (new_addr)); | |
248 | validate_change (ml->insn, ml->ref, new_val, 1); | |
249 | } | |
c7a0240a SB |
250 | |
251 | if (apply_change_group ()) | |
252 | { | |
90588a10 JJ |
253 | /* Succeeded. Update our knowledge of the stack references. */ |
254 | for (ml = reflist; ml ; ml = ml->next) | |
c7a0240a SB |
255 | ml->sp_offset -= delta; |
256 | ||
257 | return 1; | |
258 | } | |
259 | else | |
260 | return 0; | |
261 | } | |
262 | ||
f8305d18 RS |
263 | /* For non-debug insns, record all stack memory references in INSN |
264 | and return true if there were no other (unrecorded) references to the | |
265 | stack pointer. For debug insns, record all stack references regardless | |
266 | of context and unconditionally return true. */ | |
c7a0240a | 267 | |
f8305d18 RS |
268 | static bool |
269 | record_stack_refs (rtx_insn *insn, struct csa_reflist **reflist) | |
c7a0240a | 270 | { |
f8305d18 RS |
271 | subrtx_ptr_iterator::array_type array; |
272 | FOR_EACH_SUBRTX_PTR (iter, array, &PATTERN (insn), NONCONST) | |
c7a0240a | 273 | { |
f8305d18 RS |
274 | rtx *loc = *iter; |
275 | rtx x = *loc; | |
276 | switch (GET_CODE (x)) | |
90588a10 | 277 | { |
f8305d18 RS |
278 | case MEM: |
279 | if (!reg_mentioned_p (stack_pointer_rtx, x)) | |
280 | iter.skip_subrtxes (); | |
281 | /* We are not able to handle correctly all possible memrefs | |
282 | containing stack pointer, so this check is necessary. */ | |
283 | else if (stack_memref_p (x)) | |
284 | { | |
285 | *reflist = record_one_stack_ref (insn, loc, *reflist); | |
286 | iter.skip_subrtxes (); | |
287 | } | |
288 | /* Try harder for DEBUG_INSNs, handle e.g. | |
289 | (mem (mem (sp + 16) + 4). */ | |
290 | else if (!DEBUG_INSN_P (insn)) | |
291 | return false; | |
292 | break; | |
293 | ||
294 | case REG: | |
295 | /* ??? We want be able to handle non-memory stack pointer | |
296 | references later. For now just discard all insns referring to | |
297 | stack pointer outside mem expressions. We would probably | |
298 | want to teach validate_replace to simplify expressions first. | |
299 | ||
300 | We can't just compare with STACK_POINTER_RTX because the | |
301 | reference to the stack pointer might be in some other mode. | |
302 | In particular, an explicit clobber in an asm statement will | |
303 | result in a QImode clobber. | |
304 | ||
305 | In DEBUG_INSNs, we want to replace all occurrences, otherwise | |
306 | they will cause -fcompare-debug failures. */ | |
307 | if (REGNO (x) == STACK_POINTER_REGNUM) | |
308 | { | |
309 | if (!DEBUG_INSN_P (insn)) | |
310 | return false; | |
311 | *reflist = record_one_stack_ref (insn, loc, *reflist); | |
312 | } | |
313 | break; | |
314 | ||
315 | default: | |
316 | break; | |
90588a10 | 317 | } |
c7a0240a | 318 | } |
f8305d18 | 319 | return true; |
c7a0240a SB |
320 | } |
321 | ||
4efb91df RH |
322 | /* If INSN has a REG_ARGS_SIZE note, move it to LAST. |
323 | AFTER is true iff LAST follows INSN in the instruction stream. */ | |
a182fb6b JJ |
324 | |
325 | static void | |
71e88baf | 326 | maybe_move_args_size_note (rtx_insn *last, rtx_insn *insn, bool after) |
a182fb6b | 327 | { |
9a08d230 | 328 | rtx note, last_note; |
a182fb6b | 329 | |
9a08d230 RH |
330 | note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); |
331 | if (note == NULL) | |
a182fb6b JJ |
332 | return; |
333 | ||
9a08d230 RH |
334 | last_note = find_reg_note (last, REG_ARGS_SIZE, NULL_RTX); |
335 | if (last_note) | |
4efb91df RH |
336 | { |
337 | /* The ARGS_SIZE notes are *not* cumulative. They represent an | |
338 | absolute value, and the "most recent" note wins. */ | |
339 | if (!after) | |
340 | XEXP (last_note, 0) = XEXP (note, 0); | |
341 | } | |
a182fb6b | 342 | else |
9a08d230 | 343 | add_reg_note (last, REG_ARGS_SIZE, XEXP (note, 0)); |
a182fb6b JJ |
344 | } |
345 | ||
3dce0964 RH |
346 | /* Merge any REG_CFA_ADJUST_CFA note from SRC into DST. |
347 | AFTER is true iff DST follows SRC in the instruction stream. */ | |
348 | ||
349 | static void | |
350 | maybe_merge_cfa_adjust (rtx_insn *dst, rtx_insn *src, bool after) | |
351 | { | |
352 | rtx snote = NULL, dnote = NULL; | |
353 | rtx sexp, dexp; | |
354 | rtx exp1, exp2; | |
355 | ||
356 | if (RTX_FRAME_RELATED_P (src)) | |
357 | snote = find_reg_note (src, REG_CFA_ADJUST_CFA, NULL_RTX); | |
358 | if (snote == NULL) | |
359 | return; | |
360 | sexp = XEXP (snote, 0); | |
361 | ||
362 | if (RTX_FRAME_RELATED_P (dst)) | |
363 | dnote = find_reg_note (dst, REG_CFA_ADJUST_CFA, NULL_RTX); | |
364 | if (dnote == NULL) | |
365 | { | |
366 | add_reg_note (dst, REG_CFA_ADJUST_CFA, sexp); | |
367 | return; | |
368 | } | |
369 | dexp = XEXP (dnote, 0); | |
370 | ||
371 | gcc_assert (GET_CODE (sexp) == SET); | |
372 | gcc_assert (GET_CODE (dexp) == SET); | |
373 | ||
374 | if (after) | |
375 | exp1 = dexp, exp2 = sexp; | |
376 | else | |
377 | exp1 = sexp, exp2 = dexp; | |
378 | ||
379 | SET_SRC (exp1) = simplify_replace_rtx (SET_SRC (exp1), SET_DEST (exp2), | |
380 | SET_SRC (exp2)); | |
381 | XEXP (dnote, 0) = exp1; | |
382 | } | |
383 | ||
3825692d RH |
384 | /* Return the next (or previous) active insn within BB. */ |
385 | ||
71e88baf DM |
386 | static rtx_insn * |
387 | prev_active_insn_bb (basic_block bb, rtx_insn *insn) | |
3825692d RH |
388 | { |
389 | for (insn = PREV_INSN (insn); | |
390 | insn != PREV_INSN (BB_HEAD (bb)); | |
391 | insn = PREV_INSN (insn)) | |
392 | if (active_insn_p (insn)) | |
393 | return insn; | |
71e88baf | 394 | return NULL; |
3825692d RH |
395 | } |
396 | ||
71e88baf DM |
397 | static rtx_insn * |
398 | next_active_insn_bb (basic_block bb, rtx_insn *insn) | |
3825692d RH |
399 | { |
400 | for (insn = NEXT_INSN (insn); | |
401 | insn != NEXT_INSN (BB_END (bb)); | |
402 | insn = NEXT_INSN (insn)) | |
403 | if (active_insn_p (insn)) | |
404 | return insn; | |
71e88baf | 405 | return NULL; |
3825692d RH |
406 | } |
407 | ||
408 | /* If INSN has a REG_ARGS_SIZE note, if possible move it to PREV. Otherwise | |
409 | search for a nearby candidate within BB where we can stick the note. */ | |
410 | ||
411 | static void | |
71e88baf | 412 | force_move_args_size_note (basic_block bb, rtx_insn *prev, rtx_insn *insn) |
3825692d | 413 | { |
71e88baf DM |
414 | rtx note; |
415 | rtx_insn *test, *next_candidate, *prev_candidate; | |
3825692d RH |
416 | |
417 | /* If PREV exists, tail-call to the logic in the other function. */ | |
418 | if (prev) | |
419 | { | |
420 | maybe_move_args_size_note (prev, insn, false); | |
421 | return; | |
422 | } | |
423 | ||
424 | /* First, make sure there's anything that needs doing. */ | |
425 | note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX); | |
426 | if (note == NULL) | |
427 | return; | |
428 | ||
429 | /* We need to find a spot between the previous and next exception points | |
430 | where we can place the note and "properly" deallocate the arguments. */ | |
431 | next_candidate = prev_candidate = NULL; | |
432 | ||
433 | /* It is often the case that we have insns in the order: | |
434 | call | |
435 | add sp (previous deallocation) | |
436 | sub sp (align for next arglist) | |
437 | push arg | |
438 | and the add/sub cancel. Therefore we begin by searching forward. */ | |
439 | ||
440 | test = insn; | |
441 | while ((test = next_active_insn_bb (bb, test)) != NULL) | |
442 | { | |
443 | /* Found an existing note: nothing to do. */ | |
444 | if (find_reg_note (test, REG_ARGS_SIZE, NULL_RTX)) | |
445 | return; | |
446 | /* Found something that affects unwinding. Stop searching. */ | |
447 | if (CALL_P (test) || !insn_nothrow_p (test)) | |
448 | break; | |
449 | if (next_candidate == NULL) | |
450 | next_candidate = test; | |
451 | } | |
452 | ||
453 | test = insn; | |
454 | while ((test = prev_active_insn_bb (bb, test)) != NULL) | |
455 | { | |
456 | rtx tnote; | |
457 | /* Found a place that seems logical to adjust the stack. */ | |
458 | tnote = find_reg_note (test, REG_ARGS_SIZE, NULL_RTX); | |
459 | if (tnote) | |
460 | { | |
461 | XEXP (tnote, 0) = XEXP (note, 0); | |
462 | return; | |
463 | } | |
464 | if (prev_candidate == NULL) | |
465 | prev_candidate = test; | |
466 | /* Found something that affects unwinding. Stop searching. */ | |
467 | if (CALL_P (test) || !insn_nothrow_p (test)) | |
468 | break; | |
469 | } | |
470 | ||
471 | if (prev_candidate) | |
472 | test = prev_candidate; | |
473 | else if (next_candidate) | |
474 | test = next_candidate; | |
475 | else | |
476 | { | |
477 | /* ??? We *must* have a place, lest we ICE on the lost adjustment. | |
478 | Options are: dummy clobber insn, nop, or prevent the removal of | |
65c2e636 RH |
479 | the sp += 0 insn. */ |
480 | /* TODO: Find another way to indicate to the dwarf2 code that we | |
481 | have not in fact lost an adjustment. */ | |
482 | test = emit_insn_before (gen_rtx_CLOBBER (VOIDmode, const0_rtx), insn); | |
3825692d RH |
483 | } |
484 | add_reg_note (test, REG_ARGS_SIZE, XEXP (note, 0)); | |
485 | } | |
486 | ||
c7a0240a SB |
487 | /* Subroutine of combine_stack_adjustments, called for each basic block. */ |
488 | ||
489 | static void | |
490 | combine_stack_adjustments_for_block (basic_block bb) | |
491 | { | |
492 | HOST_WIDE_INT last_sp_adjust = 0; | |
71e88baf DM |
493 | rtx_insn *last_sp_set = NULL; |
494 | rtx_insn *last2_sp_set = NULL; | |
90588a10 | 495 | struct csa_reflist *reflist = NULL; |
71e88baf DM |
496 | rtx_insn *insn, *next; |
497 | rtx set; | |
c7a0240a SB |
498 | bool end_of_block = false; |
499 | ||
500 | for (insn = BB_HEAD (bb); !end_of_block ; insn = next) | |
501 | { | |
502 | end_of_block = insn == BB_END (bb); | |
503 | next = NEXT_INSN (insn); | |
504 | ||
505 | if (! INSN_P (insn)) | |
506 | continue; | |
507 | ||
508 | set = single_set_for_csa (insn); | |
509 | if (set) | |
510 | { | |
511 | rtx dest = SET_DEST (set); | |
512 | rtx src = SET_SRC (set); | |
513 | ||
514 | /* Find constant additions to the stack pointer. */ | |
515 | if (dest == stack_pointer_rtx | |
516 | && GET_CODE (src) == PLUS | |
517 | && XEXP (src, 0) == stack_pointer_rtx | |
481683e1 | 518 | && CONST_INT_P (XEXP (src, 1))) |
c7a0240a SB |
519 | { |
520 | HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1)); | |
521 | ||
522 | /* If we've not seen an adjustment previously, record | |
523 | it now and continue. */ | |
524 | if (! last_sp_set) | |
525 | { | |
526 | last_sp_set = insn; | |
527 | last_sp_adjust = this_adjust; | |
528 | continue; | |
529 | } | |
530 | ||
90588a10 | 531 | /* If not all recorded refs can be adjusted, or the |
c7a0240a SB |
532 | adjustment is now too large for a constant addition, |
533 | we cannot merge the two stack adjustments. | |
534 | ||
535 | Also we need to be careful to not move stack pointer | |
536 | such that we create stack accesses outside the allocated | |
537 | area. We can combine an allocation into the first insn, | |
538 | or a deallocation into the second insn. We can not | |
539 | combine an allocation followed by a deallocation. | |
540 | ||
541 | The only somewhat frequent occurrence of the later is when | |
542 | a function allocates a stack frame but does not use it. | |
543 | For this case, we would need to analyze rtl stream to be | |
544 | sure that allocated area is really unused. This means not | |
545 | only checking the memory references, but also all registers | |
546 | or global memory references possibly containing a stack | |
547 | frame address. | |
548 | ||
549 | Perhaps the best way to address this problem is to teach | |
550 | gcc not to allocate stack for objects never used. */ | |
551 | ||
552 | /* Combine an allocation into the first instruction. */ | |
553 | if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0) | |
554 | { | |
3dce0964 RH |
555 | if (no_unhandled_cfa (insn) |
556 | && try_apply_stack_adjustment (last_sp_set, reflist, | |
557 | last_sp_adjust | |
558 | + this_adjust, | |
559 | this_adjust)) | |
c7a0240a SB |
560 | { |
561 | /* It worked! */ | |
3825692d | 562 | maybe_move_args_size_note (last_sp_set, insn, false); |
3dce0964 | 563 | maybe_merge_cfa_adjust (last_sp_set, insn, false); |
c7a0240a SB |
564 | delete_insn (insn); |
565 | last_sp_adjust += this_adjust; | |
566 | continue; | |
567 | } | |
568 | } | |
569 | ||
570 | /* Otherwise we have a deallocation. Do not combine with | |
571 | a previous allocation. Combine into the second insn. */ | |
572 | else if (STACK_GROWS_DOWNWARD | |
573 | ? last_sp_adjust >= 0 : last_sp_adjust <= 0) | |
574 | { | |
3dce0964 RH |
575 | if (no_unhandled_cfa (last_sp_set) |
576 | && try_apply_stack_adjustment (insn, reflist, | |
577 | last_sp_adjust | |
578 | + this_adjust, | |
579 | -last_sp_adjust)) | |
c7a0240a SB |
580 | { |
581 | /* It worked! */ | |
3825692d | 582 | maybe_move_args_size_note (insn, last_sp_set, true); |
3dce0964 | 583 | maybe_merge_cfa_adjust (insn, last_sp_set, true); |
c7a0240a SB |
584 | delete_insn (last_sp_set); |
585 | last_sp_set = insn; | |
586 | last_sp_adjust += this_adjust; | |
90588a10 JJ |
587 | free_csa_reflist (reflist); |
588 | reflist = NULL; | |
c7a0240a SB |
589 | continue; |
590 | } | |
591 | } | |
592 | ||
593 | /* Combination failed. Restart processing from here. If | |
594 | deallocation+allocation conspired to cancel, we can | |
595 | delete the old deallocation insn. */ | |
3825692d RH |
596 | if (last_sp_set) |
597 | { | |
3dce0964 | 598 | if (last_sp_adjust == 0 && no_unhandled_cfa (last_sp_set)) |
3825692d RH |
599 | { |
600 | maybe_move_args_size_note (insn, last_sp_set, true); | |
3dce0964 | 601 | maybe_merge_cfa_adjust (insn, last_sp_set, true); |
3825692d RH |
602 | delete_insn (last_sp_set); |
603 | } | |
604 | else | |
605 | last2_sp_set = last_sp_set; | |
606 | } | |
90588a10 JJ |
607 | free_csa_reflist (reflist); |
608 | reflist = NULL; | |
c7a0240a SB |
609 | last_sp_set = insn; |
610 | last_sp_adjust = this_adjust; | |
611 | continue; | |
612 | } | |
613 | ||
1362aa31 EB |
614 | /* Find a store with pre-(dec|inc)rement or pre-modify of exactly |
615 | the previous adjustment and turn it into a simple store. This | |
616 | is equivalent to anticipating the stack adjustment so this must | |
617 | be an allocation. */ | |
618 | if (MEM_P (dest) | |
619 | && ((STACK_GROWS_DOWNWARD | |
620 | ? (GET_CODE (XEXP (dest, 0)) == PRE_DEC | |
621 | && last_sp_adjust | |
622 | == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))) | |
623 | : (GET_CODE (XEXP (dest, 0)) == PRE_INC | |
624 | && last_sp_adjust | |
625 | == -(HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest)))) | |
626 | || ((STACK_GROWS_DOWNWARD | |
627 | ? last_sp_adjust >= 0 : last_sp_adjust <= 0) | |
628 | && GET_CODE (XEXP (dest, 0)) == PRE_MODIFY | |
c7a0240a | 629 | && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS |
1362aa31 EB |
630 | && XEXP (XEXP (XEXP (dest, 0), 1), 0) |
631 | == stack_pointer_rtx | |
632 | && GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1)) | |
633 | == CONST_INT | |
634 | && INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1)) | |
635 | == -last_sp_adjust)) | |
c7a0240a | 636 | && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx |
1362aa31 | 637 | && !reg_mentioned_p (stack_pointer_rtx, src) |
c7a0240a | 638 | && memory_address_p (GET_MODE (dest), stack_pointer_rtx) |
1362aa31 EB |
639 | && try_apply_stack_adjustment (insn, reflist, 0, |
640 | -last_sp_adjust)) | |
c7a0240a | 641 | { |
3825692d RH |
642 | if (last2_sp_set) |
643 | maybe_move_args_size_note (last2_sp_set, last_sp_set, false); | |
644 | else | |
645 | maybe_move_args_size_note (insn, last_sp_set, true); | |
c7a0240a | 646 | delete_insn (last_sp_set); |
90588a10 JJ |
647 | free_csa_reflist (reflist); |
648 | reflist = NULL; | |
71e88baf | 649 | last_sp_set = NULL; |
c7a0240a SB |
650 | last_sp_adjust = 0; |
651 | continue; | |
652 | } | |
653 | } | |
654 | ||
c7a0240a | 655 | if (!CALL_P (insn) && last_sp_set |
f8305d18 RS |
656 | && record_stack_refs (insn, &reflist)) |
657 | continue; | |
c7a0240a SB |
658 | |
659 | /* Otherwise, we were not able to process the instruction. | |
660 | Do not continue collecting data across such a one. */ | |
661 | if (last_sp_set | |
662 | && (CALL_P (insn) | |
663 | || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn)))) | |
664 | { | |
665 | if (last_sp_set && last_sp_adjust == 0) | |
3825692d RH |
666 | { |
667 | force_move_args_size_note (bb, last2_sp_set, last_sp_set); | |
668 | delete_insn (last_sp_set); | |
669 | } | |
90588a10 JJ |
670 | free_csa_reflist (reflist); |
671 | reflist = NULL; | |
71e88baf DM |
672 | last2_sp_set = NULL; |
673 | last_sp_set = NULL; | |
c7a0240a SB |
674 | last_sp_adjust = 0; |
675 | } | |
676 | } | |
677 | ||
678 | if (last_sp_set && last_sp_adjust == 0) | |
3825692d RH |
679 | { |
680 | force_move_args_size_note (bb, last2_sp_set, last_sp_set); | |
681 | delete_insn (last_sp_set); | |
682 | } | |
c7a0240a | 683 | |
90588a10 JJ |
684 | if (reflist) |
685 | free_csa_reflist (reflist); | |
c7a0240a SB |
686 | } |
687 | \f | |
11a687e7 RH |
688 | static unsigned int |
689 | rest_of_handle_stack_adjustments (void) | |
690 | { | |
691 | df_note_add_problem (); | |
692 | df_analyze (); | |
693 | combine_stack_adjustments (); | |
c7a0240a SB |
694 | return 0; |
695 | } | |
696 | ||
27a4cd48 DM |
697 | namespace { |
698 | ||
699 | const pass_data pass_data_stack_adjustments = | |
c7a0240a | 700 | { |
27a4cd48 DM |
701 | RTL_PASS, /* type */ |
702 | "csa", /* name */ | |
703 | OPTGROUP_NONE, /* optinfo_flags */ | |
27a4cd48 DM |
704 | TV_COMBINE_STACK_ADJUST, /* tv_id */ |
705 | 0, /* properties_required */ | |
706 | 0, /* properties_provided */ | |
707 | 0, /* properties_destroyed */ | |
708 | 0, /* todo_flags_start */ | |
3bea341f | 709 | TODO_df_finish, /* todo_flags_finish */ |
c7a0240a | 710 | }; |
27a4cd48 DM |
711 | |
712 | class pass_stack_adjustments : public rtl_opt_pass | |
713 | { | |
714 | public: | |
c3284718 RS |
715 | pass_stack_adjustments (gcc::context *ctxt) |
716 | : rtl_opt_pass (pass_data_stack_adjustments, ctxt) | |
27a4cd48 DM |
717 | {} |
718 | ||
719 | /* opt_pass methods: */ | |
1a3d085c | 720 | virtual bool gate (function *); |
be55bfe6 TS |
721 | virtual unsigned int execute (function *) |
722 | { | |
723 | return rest_of_handle_stack_adjustments (); | |
724 | } | |
27a4cd48 DM |
725 | |
726 | }; // class pass_stack_adjustments | |
727 | ||
1a3d085c TS |
728 | bool |
729 | pass_stack_adjustments::gate (function *) | |
730 | { | |
731 | /* This is kind of a heuristic. We need to run combine_stack_adjustments | |
732 | even for machines with possibly nonzero TARGET_RETURN_POPS_ARGS | |
733 | and ACCUMULATE_OUTGOING_ARGS. We expect that only ports having | |
734 | push instructions will have popping returns. */ | |
735 | #ifndef PUSH_ROUNDING | |
736 | if (ACCUMULATE_OUTGOING_ARGS) | |
737 | return false; | |
738 | #endif | |
739 | return flag_combine_stack_adjustments; | |
740 | } | |
741 | ||
27a4cd48 DM |
742 | } // anon namespace |
743 | ||
744 | rtl_opt_pass * | |
745 | make_pass_stack_adjustments (gcc::context *ctxt) | |
746 | { | |
747 | return new pass_stack_adjustments (ctxt); | |
748 | } |