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a50372fe | 1 | /* Post-reload compare elimination. |
2 | Copyright (C) 2010, 2011 | |
3 | Free Software Foundation, Inc. | |
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 | /* There is a set of targets whose general-purpose move or addition | |
22 | instructions clobber the flags. These targets cannot split their | |
23 | CBRANCH/CSTORE etc patterns before reload is complete, lest reload | |
24 | itself insert these instructions in between the flags setter and user. | |
25 | Because these targets cannot split the compare from the use, they | |
26 | cannot make use of the comparison elimination offered by the combine pass. | |
27 | ||
28 | This is a small pass intended to provide comparison elimination similar to | |
29 | what is available via NOTICE_UPDATE_CC for cc0 targets. This should help | |
30 | encourage cc0 targets to convert to an explicit post-reload representation | |
31 | of the flags. | |
32 | ||
33 | This pass assumes: | |
34 | ||
35 | (0) CBRANCH/CSTORE etc have been split in pass_split_after_reload. | |
36 | ||
37 | (1) All comparison patterns are represented as | |
38 | ||
39 | [(set (reg:CC) (compare:CC (reg) (immediate)))] | |
40 | ||
41 | (2) All insn patterns that modify the flags are represented as | |
42 | ||
43 | [(set (reg) (operation) | |
44 | (clobber (reg:CC))] | |
45 | ||
46 | (3) If an insn of form (2) can usefully set the flags, there is | |
47 | another pattern of the form | |
48 | ||
49 | [(set (reg) (operation) | |
50 | (set (reg:CCM) (compare:CCM (operation) (immediate)))] | |
51 | ||
52 | The mode CCM will be chosen as if by SELECT_CC_MODE. | |
53 | ||
54 | Note that unlike NOTICE_UPDATE_CC, we do not handle memory operands. | |
55 | This could be handled as a future enhancement. | |
56 | */ | |
57 | ||
58 | #include "config.h" | |
59 | #include "system.h" | |
60 | #include "coretypes.h" | |
61 | #include "tm.h" | |
62 | #include "rtl.h" | |
63 | #include "tm_p.h" | |
64 | #include "insn-config.h" | |
65 | #include "recog.h" | |
66 | #include "flags.h" | |
67 | #include "basic-block.h" | |
68 | #include "tree-pass.h" | |
69 | #include "target.h" | |
70 | #include "df.h" | |
71 | #include "domwalk.h" | |
72 | ||
73 | \f | |
74 | /* These structures describe a comparison and how it is used. */ | |
75 | ||
76 | /* The choice of maximum 3 uses comes from wanting to eliminate the two | |
77 | duplicate compares from a three-way branch on the sign of a value. | |
78 | This is also sufficient to eliminate the duplicate compare against the | |
79 | high-part of a double-word comparison. */ | |
80 | #define MAX_CMP_USE 3 | |
81 | ||
82 | struct comparison_use | |
83 | { | |
84 | /* The instruction in which the result of the compare is used. */ | |
85 | rtx insn; | |
86 | /* The location of the flags register within the use. */ | |
87 | rtx *loc; | |
88 | /* The comparison code applied against the flags register. */ | |
89 | enum rtx_code code; | |
90 | }; | |
91 | ||
92 | struct comparison | |
93 | { | |
94 | /* The comparison instruction. */ | |
95 | rtx insn; | |
96 | ||
97 | /* The insn prior to the comparison insn that clobbers the flags. */ | |
98 | rtx prev_clobber; | |
99 | ||
100 | /* The two values being compared. These will be either REGs or | |
101 | constants. */ | |
102 | rtx in_a, in_b; | |
103 | ||
104 | /* Information about how this comparison is used. */ | |
105 | struct comparison_use uses[MAX_CMP_USE]; | |
106 | ||
107 | /* The original CC_MODE for this comparison. */ | |
108 | enum machine_mode orig_mode; | |
109 | ||
110 | /* The number of uses identified for this comparison. */ | |
111 | unsigned short n_uses; | |
112 | ||
113 | /* True if not all uses of this comparison have been identified. | |
114 | This can happen either for overflowing the array above, or if | |
115 | the flags register is used in some unusual context. */ | |
116 | bool missing_uses; | |
117 | ||
118 | /* True if its inputs are still valid at the end of the block. */ | |
119 | bool inputs_valid; | |
120 | }; | |
121 | ||
122 | typedef struct comparison *comparison_struct_p; | |
a50372fe | 123 | |
f1f41a6c | 124 | static vec<comparison_struct_p> all_compares; |
a50372fe | 125 | |
126 | /* Look for a "conforming" comparison, as defined above. If valid, return | |
127 | the rtx for the COMPARE itself. */ | |
128 | ||
129 | static rtx | |
130 | conforming_compare (rtx insn) | |
131 | { | |
132 | rtx set, src, dest; | |
133 | ||
134 | set = single_set (insn); | |
135 | if (set == NULL) | |
136 | return NULL; | |
137 | ||
138 | src = SET_SRC (set); | |
139 | if (GET_CODE (src) != COMPARE) | |
140 | return NULL; | |
141 | ||
142 | dest = SET_DEST (set); | |
143 | if (!REG_P (dest) || REGNO (dest) != targetm.flags_regnum) | |
144 | return NULL; | |
145 | ||
146 | if (REG_P (XEXP (src, 0)) | |
147 | && REG_P (XEXP (src, 0)) | |
148 | && (REG_P (XEXP (src, 1)) || CONSTANT_P (XEXP (src, 1)))) | |
149 | return src; | |
150 | ||
151 | return NULL; | |
152 | } | |
153 | ||
154 | /* Look for a pattern of the "correct" form for an insn with a flags clobber | |
155 | for which we may be able to eliminate a compare later. We're not looking | |
156 | to validate any inputs at this time, merely see that the basic shape is | |
157 | correct. The term "arithmetic" may be somewhat misleading... */ | |
158 | ||
159 | static bool | |
160 | arithmetic_flags_clobber_p (rtx insn) | |
161 | { | |
162 | rtx pat, x; | |
163 | ||
164 | if (!NONJUMP_INSN_P (insn)) | |
165 | return false; | |
166 | pat = PATTERN (insn); | |
167 | if (extract_asm_operands (pat)) | |
168 | return false; | |
169 | ||
170 | if (GET_CODE (pat) == PARALLEL && XVECLEN (pat, 0) == 2) | |
171 | { | |
172 | x = XVECEXP (pat, 0, 0); | |
173 | if (GET_CODE (x) != SET) | |
174 | return false; | |
175 | x = SET_DEST (x); | |
176 | if (!REG_P (x)) | |
177 | return false; | |
178 | ||
179 | x = XVECEXP (pat, 0, 1); | |
180 | if (GET_CODE (x) == CLOBBER) | |
181 | { | |
182 | x = XEXP (x, 0); | |
183 | if (REG_P (x) && REGNO (x) == targetm.flags_regnum) | |
184 | return true; | |
185 | } | |
186 | } | |
187 | ||
188 | return false; | |
189 | } | |
190 | ||
191 | /* Look for uses of FLAGS in INSN. If we find one we can analyze, record | |
192 | it in CMP; otherwise indicate that we've missed a use. */ | |
193 | ||
194 | static void | |
195 | find_flags_uses_in_insn (struct comparison *cmp, rtx insn) | |
196 | { | |
197 | df_ref *use_rec, use; | |
198 | ||
199 | /* If we've already lost track of uses, don't bother collecting more. */ | |
200 | if (cmp->missing_uses) | |
201 | return; | |
202 | ||
203 | /* Find a USE of the flags register. */ | |
204 | for (use_rec = DF_INSN_USES (insn); (use = *use_rec) != NULL; use_rec++) | |
205 | if (DF_REF_REGNO (use) == targetm.flags_regnum) | |
206 | { | |
207 | rtx x, *loc; | |
208 | ||
209 | /* If this is an unusual use, quit. */ | |
210 | if (DF_REF_TYPE (use) != DF_REF_REG_USE) | |
211 | goto fail; | |
212 | ||
213 | /* If we've run out of slots to record uses, quit. */ | |
214 | if (cmp->n_uses == MAX_CMP_USE) | |
215 | goto fail; | |
216 | ||
217 | /* Unfortunately the location of the flags register, while present | |
218 | in the reference structure, doesn't help. We need to find the | |
219 | comparison code that is outer to the actual flags use. */ | |
220 | loc = DF_REF_LOC (use); | |
221 | x = PATTERN (insn); | |
222 | if (GET_CODE (x) == PARALLEL) | |
223 | x = XVECEXP (x, 0, 0); | |
224 | x = SET_SRC (x); | |
225 | if (GET_CODE (x) == IF_THEN_ELSE) | |
226 | x = XEXP (x, 0); | |
227 | if (COMPARISON_P (x) | |
228 | && loc == &XEXP (x, 0) | |
229 | && XEXP (x, 1) == const0_rtx) | |
230 | { | |
231 | /* We've found a use of the flags that we understand. */ | |
232 | struct comparison_use *cuse = &cmp->uses[cmp->n_uses++]; | |
233 | cuse->insn = insn; | |
234 | cuse->loc = loc; | |
235 | cuse->code = GET_CODE (x); | |
236 | } | |
237 | else | |
238 | goto fail; | |
239 | } | |
240 | return; | |
241 | ||
242 | fail: | |
243 | /* We failed to recognize this use of the flags register. */ | |
244 | cmp->missing_uses = true; | |
245 | } | |
246 | ||
247 | /* Identify comparison instructions within BB. If the flags from the last | |
248 | compare in the BB is live at the end of the block, install the compare | |
249 | in BB->AUX. Called via walk_dominators_tree. */ | |
250 | ||
251 | static void | |
252 | find_comparisons_in_bb (struct dom_walk_data *data ATTRIBUTE_UNUSED, | |
253 | basic_block bb) | |
254 | { | |
255 | struct comparison *last_cmp; | |
256 | rtx insn, next, last_clobber; | |
257 | bool last_cmp_valid; | |
258 | bitmap killed; | |
259 | ||
260 | killed = BITMAP_ALLOC (NULL); | |
261 | ||
262 | /* The last comparison that was made. Will be reset to NULL | |
263 | once the flags are clobbered. */ | |
264 | last_cmp = NULL; | |
265 | ||
266 | /* True iff the last comparison has not been clobbered, nor | |
267 | have its inputs. Used to eliminate duplicate compares. */ | |
268 | last_cmp_valid = false; | |
269 | ||
270 | /* The last insn that clobbered the flags, if that insn is of | |
271 | a form that may be valid for eliminating a following compare. | |
272 | To be reset to NULL once the flags are set otherwise. */ | |
273 | last_clobber = NULL; | |
274 | ||
275 | /* Propagate the last live comparison throughout the extended basic block. */ | |
276 | if (single_pred_p (bb)) | |
277 | { | |
278 | last_cmp = (struct comparison *) single_pred (bb)->aux; | |
279 | if (last_cmp) | |
280 | last_cmp_valid = last_cmp->inputs_valid; | |
281 | } | |
282 | ||
283 | for (insn = BB_HEAD (bb); insn; insn = next) | |
284 | { | |
285 | rtx src; | |
286 | ||
287 | next = (insn == BB_END (bb) ? NULL_RTX : NEXT_INSN (insn)); | |
288 | if (!NONDEBUG_INSN_P (insn)) | |
289 | continue; | |
290 | ||
291 | /* Compute the set of registers modified by this instruction. */ | |
292 | bitmap_clear (killed); | |
293 | df_simulate_find_defs (insn, killed); | |
294 | ||
295 | src = conforming_compare (insn); | |
296 | if (src) | |
297 | { | |
67755ff0 | 298 | enum machine_mode src_mode = GET_MODE (src); |
299 | ||
a50372fe | 300 | /* Eliminate a compare that's redundant with the previous. */ |
301 | if (last_cmp_valid | |
302 | && rtx_equal_p (last_cmp->in_a, XEXP (src, 0)) | |
303 | && rtx_equal_p (last_cmp->in_b, XEXP (src, 1))) | |
304 | { | |
ea6ad4ae | 305 | rtx flags, x; |
306 | enum machine_mode new_mode | |
307 | = targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode); | |
308 | ||
309 | /* New mode is incompatible with the previous compare mode. */ | |
310 | if (new_mode == VOIDmode) | |
311 | continue; | |
312 | ||
313 | if (new_mode != last_cmp->orig_mode) | |
314 | { | |
315 | flags = gen_rtx_REG (src_mode, targetm.flags_regnum); | |
316 | ||
317 | /* Generate new comparison for substitution. */ | |
318 | x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1)); | |
319 | x = gen_rtx_SET (VOIDmode, flags, x); | |
320 | ||
321 | if (!validate_change (last_cmp->insn, | |
322 | &PATTERN (last_cmp->insn), x, false)) | |
323 | continue; | |
324 | ||
325 | last_cmp->orig_mode = new_mode; | |
326 | } | |
327 | ||
a50372fe | 328 | delete_insn (insn); |
329 | continue; | |
330 | } | |
331 | ||
ea6ad4ae | 332 | last_cmp = XCNEW (struct comparison); |
a50372fe | 333 | last_cmp->insn = insn; |
334 | last_cmp->prev_clobber = last_clobber; | |
335 | last_cmp->in_a = XEXP (src, 0); | |
336 | last_cmp->in_b = XEXP (src, 1); | |
67755ff0 | 337 | last_cmp->orig_mode = src_mode; |
f1f41a6c | 338 | all_compares.safe_push (last_cmp); |
a50372fe | 339 | |
340 | /* It's unusual, but be prepared for comparison patterns that | |
341 | also clobber an input, or perhaps a scratch. */ | |
342 | last_clobber = NULL; | |
343 | last_cmp_valid = true; | |
344 | } | |
345 | ||
346 | /* Notice if this instruction kills the flags register. */ | |
347 | else if (bitmap_bit_p (killed, targetm.flags_regnum)) | |
348 | { | |
349 | /* See if this insn could be the "clobber" that eliminates | |
350 | a future comparison. */ | |
351 | last_clobber = (arithmetic_flags_clobber_p (insn) ? insn : NULL); | |
352 | ||
353 | /* In either case, the previous compare is no longer valid. */ | |
354 | last_cmp = NULL; | |
355 | last_cmp_valid = false; | |
356 | continue; | |
357 | } | |
358 | ||
359 | /* Notice if this instruction uses the flags register. */ | |
360 | else if (last_cmp) | |
361 | find_flags_uses_in_insn (last_cmp, insn); | |
362 | ||
363 | /* Notice if any of the inputs to the comparison have changed. */ | |
364 | if (last_cmp_valid | |
365 | && (bitmap_bit_p (killed, REGNO (last_cmp->in_a)) | |
366 | || (REG_P (last_cmp->in_b) | |
367 | && bitmap_bit_p (killed, REGNO (last_cmp->in_b))))) | |
368 | last_cmp_valid = false; | |
369 | } | |
370 | ||
371 | BITMAP_FREE (killed); | |
372 | ||
373 | /* Remember the live comparison for subsequent members of | |
374 | the extended basic block. */ | |
375 | if (last_cmp) | |
376 | { | |
377 | bb->aux = last_cmp; | |
378 | last_cmp->inputs_valid = last_cmp_valid; | |
379 | ||
380 | /* Look to see if the flags register is live outgoing here, and | |
381 | incoming to any successor not part of the extended basic block. */ | |
7799dcb4 | 382 | if (bitmap_bit_p (df_get_live_out (bb), targetm.flags_regnum)) |
a50372fe | 383 | { |
384 | edge e; | |
385 | edge_iterator ei; | |
386 | ||
387 | FOR_EACH_EDGE (e, ei, bb->succs) | |
388 | { | |
389 | basic_block dest = e->dest; | |
7799dcb4 | 390 | if (bitmap_bit_p (df_get_live_in (bb), |
a50372fe | 391 | targetm.flags_regnum) |
392 | && !single_pred_p (dest)) | |
393 | { | |
394 | last_cmp->missing_uses = true; | |
395 | break; | |
396 | } | |
397 | } | |
398 | } | |
399 | } | |
400 | } | |
401 | ||
402 | /* Find all comparisons in the function. */ | |
403 | ||
404 | static void | |
405 | find_comparisons (void) | |
406 | { | |
407 | struct dom_walk_data data; | |
408 | ||
409 | memset (&data, 0, sizeof(data)); | |
410 | data.dom_direction = CDI_DOMINATORS; | |
411 | data.before_dom_children = find_comparisons_in_bb; | |
412 | ||
413 | calculate_dominance_info (CDI_DOMINATORS); | |
414 | ||
415 | init_walk_dominator_tree (&data); | |
416 | walk_dominator_tree (&data, ENTRY_BLOCK_PTR); | |
417 | fini_walk_dominator_tree (&data); | |
418 | ||
419 | clear_aux_for_blocks (); | |
420 | free_dominance_info (CDI_DOMINATORS); | |
421 | } | |
422 | ||
423 | /* Select an alternate CC_MODE for a comparison insn comparing A and B. | |
424 | Note that inputs are almost certainly different than the IN_A and IN_B | |
425 | stored in CMP -- we're called while attempting to eliminate the compare | |
426 | after all. Return the new FLAGS rtx if successful, else return NULL. | |
427 | Note that this function may start a change group. */ | |
428 | ||
429 | static rtx | |
97c6ec6a | 430 | maybe_select_cc_mode (struct comparison *cmp, rtx a ATTRIBUTE_UNUSED, |
431 | rtx b ATTRIBUTE_UNUSED) | |
a50372fe | 432 | { |
433 | enum machine_mode sel_mode; | |
434 | const int n = cmp->n_uses; | |
435 | rtx flags = NULL; | |
436 | ||
437 | #ifndef SELECT_CC_MODE | |
438 | /* Minimize code differences when this target macro is undefined. */ | |
439 | return NULL; | |
440 | #define SELECT_CC_MODE(A,B,C) (gcc_unreachable (), VOIDmode) | |
441 | #endif | |
442 | ||
443 | /* If we don't have access to all of the uses, we can't validate. */ | |
444 | if (cmp->missing_uses || n == 0) | |
445 | return NULL; | |
446 | ||
447 | /* Find a new mode that works for all of the uses. Special case the | |
448 | common case of exactly one use. */ | |
449 | if (n == 1) | |
450 | { | |
451 | sel_mode = SELECT_CC_MODE (cmp->uses[0].code, a, b); | |
452 | if (sel_mode != cmp->orig_mode) | |
453 | { | |
454 | flags = gen_rtx_REG (sel_mode, targetm.flags_regnum); | |
455 | validate_change (cmp->uses[0].insn, cmp->uses[0].loc, flags, true); | |
456 | } | |
457 | } | |
458 | else | |
459 | { | |
460 | int i; | |
461 | ||
462 | sel_mode = SELECT_CC_MODE (cmp->uses[0].code, a, b); | |
463 | for (i = 1; i < n; ++i) | |
464 | { | |
465 | enum machine_mode new_mode; | |
466 | new_mode = SELECT_CC_MODE (cmp->uses[i].code, a, b); | |
467 | if (new_mode != sel_mode) | |
468 | { | |
469 | sel_mode = targetm.cc_modes_compatible (sel_mode, new_mode); | |
470 | if (sel_mode == VOIDmode) | |
471 | return NULL; | |
472 | } | |
473 | } | |
474 | ||
475 | if (sel_mode != cmp->orig_mode) | |
476 | { | |
477 | flags = gen_rtx_REG (sel_mode, targetm.flags_regnum); | |
478 | for (i = 0; i < n; ++i) | |
479 | validate_change (cmp->uses[i].insn, cmp->uses[i].loc, flags, true); | |
480 | } | |
481 | } | |
482 | ||
483 | return flags; | |
484 | } | |
485 | ||
486 | /* Attempt to replace a comparison with a prior arithmetic insn that can | |
487 | compute the same flags value as the comparison itself. Return true if | |
488 | successful, having made all rtl modifications necessary. */ | |
489 | ||
490 | static bool | |
491 | try_eliminate_compare (struct comparison *cmp) | |
492 | { | |
493 | rtx x, insn, bb_head, flags, in_a, cmp_src; | |
494 | ||
9d75589a | 495 | /* We must have found an interesting "clobber" preceding the compare. */ |
a50372fe | 496 | if (cmp->prev_clobber == NULL) |
497 | return false; | |
498 | ||
499 | /* ??? For the moment we don't handle comparisons for which IN_B | |
500 | is a register. We accepted these during initial comparison | |
501 | recognition in order to eliminate duplicate compares. | |
502 | An improvement here would be to handle x = a - b; if (a cmp b). */ | |
503 | if (!CONSTANT_P (cmp->in_b)) | |
504 | return false; | |
505 | ||
506 | /* Verify that IN_A is not clobbered in between CMP and PREV_CLOBBER. | |
507 | Given that this target requires this pass, we can assume that most | |
508 | insns do clobber the flags, and so the distance between the compare | |
509 | and the clobber is likely to be small. */ | |
510 | /* ??? This is one point at which one could argue that DF_REF_CHAIN would | |
511 | be useful, but it is thought to be too heavy-weight a solution here. */ | |
512 | ||
513 | in_a = cmp->in_a; | |
514 | insn = cmp->insn; | |
515 | bb_head = BB_HEAD (BLOCK_FOR_INSN (insn)); | |
516 | for (insn = PREV_INSN (insn); | |
517 | insn != cmp->prev_clobber; | |
518 | insn = PREV_INSN (insn)) | |
519 | { | |
520 | const int abnormal_flags | |
521 | = (DF_REF_CONDITIONAL | DF_REF_PARTIAL | DF_REF_MAY_CLOBBER | |
522 | | DF_REF_MUST_CLOBBER | DF_REF_SIGN_EXTRACT | |
523 | | DF_REF_ZERO_EXTRACT | DF_REF_STRICT_LOW_PART | |
524 | | DF_REF_PRE_POST_MODIFY); | |
525 | df_ref *def_rec, def; | |
526 | ||
527 | /* Note that the BB_HEAD is always either a note or a label, but in | |
528 | any case it means that IN_A is defined outside the block. */ | |
529 | if (insn == bb_head) | |
530 | return false; | |
531 | if (NOTE_P (insn) || DEBUG_INSN_P (insn)) | |
532 | continue; | |
533 | ||
534 | /* Find a possible def of IN_A in INSN. */ | |
535 | for (def_rec = DF_INSN_DEFS (insn); (def = *def_rec) != NULL; def_rec++) | |
536 | if (DF_REF_REGNO (def) == REGNO (in_a)) | |
537 | break; | |
538 | ||
539 | /* No definitions of IN_A; continue searching. */ | |
540 | if (def == NULL) | |
541 | continue; | |
542 | ||
543 | /* Bail if this is not a totally normal set of IN_A. */ | |
544 | if (DF_REF_IS_ARTIFICIAL (def)) | |
545 | return false; | |
546 | if (DF_REF_FLAGS (def) & abnormal_flags) | |
547 | return false; | |
548 | ||
549 | /* We've found an insn between the compare and the clobber that sets | |
550 | IN_A. Given that pass_cprop_hardreg has not yet run, we still find | |
551 | situations in which we can usefully look through a copy insn. */ | |
552 | x = single_set (insn); | |
553 | if (x == NULL) | |
554 | return false; | |
555 | in_a = SET_SRC (x); | |
556 | if (!REG_P (in_a)) | |
557 | return false; | |
558 | } | |
559 | ||
560 | /* We've reached PREV_CLOBBER without finding a modification of IN_A. | |
561 | Validate that PREV_CLOBBER itself does in fact refer to IN_A. Do | |
562 | recall that we've already validated the shape of PREV_CLOBBER. */ | |
563 | x = XVECEXP (PATTERN (insn), 0, 0); | |
56cc4397 | 564 | if (rtx_equal_p (SET_DEST (x), in_a)) |
565 | cmp_src = SET_SRC (x); | |
566 | ||
567 | /* Also check operations with implicit extensions, e.g.: | |
568 | [(set (reg:DI) | |
569 | (zero_extend:DI (plus:SI (reg:SI)(reg:SI)))) | |
570 | (set (reg:CCZ flags) | |
571 | (compare:CCZ | |
572 | (plus:SI (reg:SI)(reg:SI)) | |
573 | (const_int 0)))] */ | |
574 | else if (REG_P (SET_DEST (x)) | |
575 | && REG_P (in_a) | |
576 | && REGNO (SET_DEST (x)) == REGNO (in_a) | |
577 | && (GET_CODE (SET_SRC (x)) == ZERO_EXTEND | |
578 | || GET_CODE (SET_SRC (x)) == SIGN_EXTEND) | |
579 | && GET_MODE (XEXP (SET_SRC (x), 0)) == GET_MODE (in_a)) | |
580 | cmp_src = XEXP (SET_SRC (x), 0); | |
581 | else | |
a50372fe | 582 | return false; |
56cc4397 | 583 | |
a50372fe | 584 | /* Determine if we ought to use a different CC_MODE here. */ |
585 | flags = maybe_select_cc_mode (cmp, cmp_src, cmp->in_b); | |
586 | if (flags == NULL) | |
587 | flags = gen_rtx_REG (cmp->orig_mode, targetm.flags_regnum); | |
588 | ||
589 | /* Generate a new comparison for installation in the setter. */ | |
590 | x = copy_rtx (cmp_src); | |
591 | x = gen_rtx_COMPARE (GET_MODE (flags), x, cmp->in_b); | |
592 | x = gen_rtx_SET (VOIDmode, flags, x); | |
593 | ||
594 | /* Succeed if the new instruction is valid. Note that we may have started | |
595 | a change group within maybe_select_cc_mode, therefore we must continue. */ | |
596 | validate_change (insn, &XVECEXP (PATTERN (insn), 0, 1), x, true); | |
597 | if (!apply_change_group ()) | |
598 | return false; | |
599 | ||
600 | /* Success. Delete the compare insn... */ | |
601 | delete_insn (cmp->insn); | |
602 | ||
603 | /* ... and any notes that are now invalid due to multiple sets. */ | |
604 | x = find_regno_note (insn, REG_UNUSED, targetm.flags_regnum); | |
605 | if (x) | |
606 | remove_note (insn, x); | |
607 | x = find_reg_note (insn, REG_EQUAL, NULL); | |
608 | if (x) | |
609 | remove_note (insn, x); | |
610 | x = find_reg_note (insn, REG_EQUIV, NULL); | |
611 | if (x) | |
612 | remove_note (insn, x); | |
613 | ||
614 | return true; | |
615 | } | |
616 | ||
617 | /* Main entry point to the pass. */ | |
618 | ||
619 | static unsigned int | |
620 | execute_compare_elim_after_reload (void) | |
621 | { | |
a50372fe | 622 | df_analyze (); |
623 | ||
f1f41a6c | 624 | gcc_checking_assert (!all_compares.exists ()); |
a50372fe | 625 | |
626 | /* Locate all comparisons and their uses, and eliminate duplicates. */ | |
627 | find_comparisons (); | |
f1f41a6c | 628 | if (all_compares.exists ()) |
a50372fe | 629 | { |
630 | struct comparison *cmp; | |
631 | size_t i; | |
632 | ||
633 | /* Eliminate comparisons that are redundant with flags computation. */ | |
f1f41a6c | 634 | FOR_EACH_VEC_ELT (all_compares, i, cmp) |
a50372fe | 635 | { |
636 | try_eliminate_compare (cmp); | |
637 | XDELETE (cmp); | |
638 | } | |
639 | ||
f1f41a6c | 640 | all_compares.release (); |
a50372fe | 641 | } |
642 | ||
643 | return 0; | |
644 | } | |
645 | ||
646 | static bool | |
647 | gate_compare_elim_after_reload (void) | |
648 | { | |
649 | /* Setting this target hook value is how a backend indicates the need. */ | |
650 | if (targetm.flags_regnum == INVALID_REGNUM) | |
651 | return false; | |
652 | return flag_compare_elim_after_reload; | |
653 | } | |
654 | ||
655 | struct rtl_opt_pass pass_compare_elim_after_reload = | |
656 | { | |
657 | { | |
658 | RTL_PASS, | |
659 | "cmpelim", /* name */ | |
c7875731 | 660 | OPTGROUP_NONE, /* optinfo_flags */ |
a50372fe | 661 | gate_compare_elim_after_reload, /* gate */ |
662 | execute_compare_elim_after_reload, /* execute */ | |
663 | NULL, /* sub */ | |
664 | NULL, /* next */ | |
665 | 0, /* static_pass_number */ | |
666 | TV_NONE, /* tv_id */ | |
667 | 0, /* properties_required */ | |
668 | 0, /* properties_provided */ | |
669 | 0, /* properties_destroyed */ | |
670 | 0, /* todo_flags_start */ | |
671 | TODO_df_finish | |
672 | | TODO_df_verify | |
673 | | TODO_verify_rtl_sharing | |
a50372fe | 674 | | TODO_ggc_collect /* todo_flags_finish */ |
675 | } | |
676 | }; |