1 /* If-conversion support.
2 Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
14 License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
19 02111-1307, USA. */
20
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "tm.h"
25
26 #include "rtl.h"
27 #include "regs.h"
28 #include "function.h"
29 #include "flags.h"
30 #include "insn-config.h"
31 #include "recog.h"
32 #include "except.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
35 #include "expr.h"
36 #include "real.h"
37 #include "output.h"
38 #include "optabs.h"
39 #include "toplev.h"
40 #include "tm_p.h"
41 #include "cfgloop.h"
42 #include "target.h"
43
44
45 #ifndef HAVE_conditional_execution
46 #define HAVE_conditional_execution 0
47 #endif
48 #ifndef HAVE_conditional_move
49 #define HAVE_conditional_move 0
50 #endif
51 #ifndef HAVE_incscc
52 #define HAVE_incscc 0
53 #endif
54 #ifndef HAVE_decscc
55 #define HAVE_decscc 0
56 #endif
57 #ifndef HAVE_trap
58 #define HAVE_trap 0
59 #endif
60 #ifndef HAVE_conditional_trap
61 #define HAVE_conditional_trap 0
62 #endif
63
64 #ifndef MAX_CONDITIONAL_EXECUTE
65 #define MAX_CONDITIONAL_EXECUTE (BRANCH_COST + 1)
66 #endif
67
68 #define NULL_EDGE ((struct edge_def *)NULL)
69 #define NULL_BLOCK ((struct basic_block_def *)NULL)
70
71 /* # of IF-THEN or IF-THEN-ELSE blocks we looked at */
72 static int num_possible_if_blocks;
73
74 /* # of IF-THEN or IF-THEN-ELSE blocks were converted to conditional
75 execution. */
76 static int num_updated_if_blocks;
77
78 /* # of changes made which require life information to be updated. */
79 static int num_true_changes;
80
81 /* Whether conditional execution changes were made. */
82 static int cond_exec_changed_p;
83
84 /* True if life data ok at present. */
85 static bool life_data_ok;
86
87 /* Forward references. */
88 static int count_bb_insns (basic_block);
89 static rtx first_active_insn (basic_block);
90 static rtx last_active_insn (basic_block, int);
91 static int seq_contains_jump (rtx);
92 static basic_block block_fallthru (basic_block);
93 static int cond_exec_process_insns (ce_if_block_t *, rtx, rtx, rtx, rtx, int);
94 static rtx cond_exec_get_condition (rtx);
95 static int cond_exec_process_if_block (ce_if_block_t *, int);
96 static rtx noce_get_condition (rtx, rtx *);
97 static int noce_operand_ok (rtx);
98 static int noce_process_if_block (ce_if_block_t *);
99 static int process_if_block (ce_if_block_t *);
100 static void merge_if_block (ce_if_block_t *);
101 static int find_cond_trap (basic_block, edge, edge);
102 static basic_block find_if_header (basic_block, int);
103 static int block_jumps_and_fallthru_p (basic_block, basic_block);
104 static int find_if_block (ce_if_block_t *);
105 static int find_if_case_1 (basic_block, edge, edge);
106 static int find_if_case_2 (basic_block, edge, edge);
107 static int find_memory (rtx *, void *);
108 static int dead_or_predicable (basic_block, basic_block, basic_block,
109 basic_block, int);
110 static void noce_emit_move_insn (rtx, rtx);
111 static rtx block_has_only_trap (basic_block);
112 static void mark_loop_exit_edges (void);
113
114 /* Sets EDGE_LOOP_EXIT flag for all loop exits. */
115 static void
mark_loop_exit_edges(void)116 mark_loop_exit_edges (void)
117 {
118 struct loops loops;
119 basic_block bb;
120 edge e;
121
122 flow_loops_find (&loops, LOOP_TREE);
123 free_dominance_info (CDI_DOMINATORS);
124
125 if (loops.num > 1)
126 {
127 FOR_EACH_BB (bb)
128 {
129 for (e = bb->succ; e; e = e->succ_next)
130 {
131 if (find_common_loop (bb->loop_father, e->dest->loop_father)
132 != bb->loop_father)
133 e->flags |= EDGE_LOOP_EXIT;
134 else
135 e->flags &= ~EDGE_LOOP_EXIT;
136 }
137 }
138 }
139
140 flow_loops_free (&loops);
141 }
142
143 /* Count the number of non-jump active insns in BB. */
144
145 static int
count_bb_insns(basic_block bb)146 count_bb_insns (basic_block bb)
147 {
148 int count = 0;
149 rtx insn = BB_HEAD (bb);
150
151 while (1)
152 {
153 if (GET_CODE (insn) == CALL_INSN || GET_CODE (insn) == INSN)
154 count++;
155
156 if (insn == BB_END (bb))
157 break;
158 insn = NEXT_INSN (insn);
159 }
160
161 return count;
162 }
163
164 /* Return the first non-jump active insn in the basic block. */
165
166 static rtx
first_active_insn(basic_block bb)167 first_active_insn (basic_block bb)
168 {
169 rtx insn = BB_HEAD (bb);
170
171 if (GET_CODE (insn) == CODE_LABEL)
172 {
173 if (insn == BB_END (bb))
174 return NULL_RTX;
175 insn = NEXT_INSN (insn);
176 }
177
178 while (GET_CODE (insn) == NOTE)
179 {
180 if (insn == BB_END (bb))
181 return NULL_RTX;
182 insn = NEXT_INSN (insn);
183 }
184
185 if (GET_CODE (insn) == JUMP_INSN)
186 return NULL_RTX;
187
188 return insn;
189 }
190
191 /* Return the last non-jump active (non-jump) insn in the basic block. */
192
193 static rtx
last_active_insn(basic_block bb,int skip_use_p)194 last_active_insn (basic_block bb, int skip_use_p)
195 {
196 rtx insn = BB_END (bb);
197 rtx head = BB_HEAD (bb);
198
199 while (GET_CODE (insn) == NOTE
200 || GET_CODE (insn) == JUMP_INSN
201 || (skip_use_p
202 && GET_CODE (insn) == INSN
203 && GET_CODE (PATTERN (insn)) == USE))
204 {
205 if (insn == head)
206 return NULL_RTX;
207 insn = PREV_INSN (insn);
208 }
209
210 if (GET_CODE (insn) == CODE_LABEL)
211 return NULL_RTX;
212
213 return insn;
214 }
215
216 /* It is possible, especially when having dealt with multi-word
217 arithmetic, for the expanders to have emitted jumps. Search
218 through the sequence and return TRUE if a jump exists so that
219 we can abort the conversion. */
220
221 static int
seq_contains_jump(rtx insn)222 seq_contains_jump (rtx insn)
223 {
224 while (insn)
225 {
226 if (GET_CODE (insn) == JUMP_INSN)
227 return 1;
228 insn = NEXT_INSN (insn);
229 }
230 return 0;
231 }
232
233 static basic_block
block_fallthru(basic_block bb)234 block_fallthru (basic_block bb)
235 {
236 edge e;
237
238 for (e = bb->succ;
239 e != NULL_EDGE && (e->flags & EDGE_FALLTHRU) == 0;
240 e = e->succ_next)
241 ;
242
243 return (e) ? e->dest : NULL_BLOCK;
244 }
245
246 /* Go through a bunch of insns, converting them to conditional
247 execution format if possible. Return TRUE if all of the non-note
248 insns were processed. */
249
250 static int
cond_exec_process_insns(ce_if_block_t * ce_info ATTRIBUTE_UNUSED,rtx start,rtx end,rtx test,rtx prob_val,int mod_ok)251 cond_exec_process_insns (ce_if_block_t *ce_info ATTRIBUTE_UNUSED,
252 /* if block information */rtx start,
253 /* first insn to look at */rtx end,
254 /* last insn to look at */rtx test,
255 /* conditional execution test */rtx prob_val,
256 /* probability of branch taken. */int mod_ok)
257 {
258 int must_be_last = FALSE;
259 rtx insn;
260 rtx xtest;
261 rtx pattern;
262
263 if (!start || !end)
264 return FALSE;
265
266 for (insn = start; ; insn = NEXT_INSN (insn))
267 {
268 if (GET_CODE (insn) == NOTE)
269 goto insn_done;
270
271 if (GET_CODE (insn) != INSN && GET_CODE (insn) != CALL_INSN)
272 abort ();
273
274 /* Remove USE insns that get in the way. */
275 if (reload_completed && GET_CODE (PATTERN (insn)) == USE)
276 {
277 /* ??? Ug. Actually unlinking the thing is problematic,
278 given what we'd have to coordinate with our callers. */
279 PUT_CODE (insn, NOTE);
280 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
281 NOTE_SOURCE_FILE (insn) = 0;
282 goto insn_done;
283 }
284
285 /* Last insn wasn't last? */
286 if (must_be_last)
287 return FALSE;
288
289 if (modified_in_p (test, insn))
290 {
291 if (!mod_ok)
292 return FALSE;
293 must_be_last = TRUE;
294 }
295
296 /* Now build the conditional form of the instruction. */
297 pattern = PATTERN (insn);
298 xtest = copy_rtx (test);
299
300 /* If this is already a COND_EXEC, rewrite the test to be an AND of the
301 two conditions. */
302 if (GET_CODE (pattern) == COND_EXEC)
303 {
304 if (GET_MODE (xtest) != GET_MODE (COND_EXEC_TEST (pattern)))
305 return FALSE;
306
307 xtest = gen_rtx_AND (GET_MODE (xtest), xtest,
308 COND_EXEC_TEST (pattern));
309 pattern = COND_EXEC_CODE (pattern);
310 }
311
312 pattern = gen_rtx_COND_EXEC (VOIDmode, xtest, pattern);
313
314 /* If the machine needs to modify the insn being conditionally executed,
315 say for example to force a constant integer operand into a temp
316 register, do so here. */
317 #ifdef IFCVT_MODIFY_INSN
318 IFCVT_MODIFY_INSN (ce_info, pattern, insn);
319 if (! pattern)
320 return FALSE;
321 #endif
322
323 validate_change (insn, &PATTERN (insn), pattern, 1);
324
325 if (GET_CODE (insn) == CALL_INSN && prob_val)
326 validate_change (insn, ®_NOTES (insn),
327 alloc_EXPR_LIST (REG_BR_PROB, prob_val,
328 REG_NOTES (insn)), 1);
329
330 insn_done:
331 if (insn == end)
332 break;
333 }
334
335 return TRUE;
336 }
337
338 /* Return the condition for a jump. Do not do any special processing. */
339
340 static rtx
cond_exec_get_condition(rtx jump)341 cond_exec_get_condition (rtx jump)
342 {
343 rtx test_if, cond;
344
345 if (any_condjump_p (jump))
346 test_if = SET_SRC (pc_set (jump));
347 else
348 return NULL_RTX;
349 cond = XEXP (test_if, 0);
350
351 /* If this branches to JUMP_LABEL when the condition is false,
352 reverse the condition. */
353 if (GET_CODE (XEXP (test_if, 2)) == LABEL_REF
354 && XEXP (XEXP (test_if, 2), 0) == JUMP_LABEL (jump))
355 {
356 enum rtx_code rev = reversed_comparison_code (cond, jump);
357 if (rev == UNKNOWN)
358 return NULL_RTX;
359
360 cond = gen_rtx_fmt_ee (rev, GET_MODE (cond), XEXP (cond, 0),
361 XEXP (cond, 1));
362 }
363
364 return cond;
365 }
366
367 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
368 to conditional execution. Return TRUE if we were successful at
369 converting the block. */
370
371 static int
cond_exec_process_if_block(ce_if_block_t * ce_info,int do_multiple_p)372 cond_exec_process_if_block (ce_if_block_t * ce_info,
373 /* if block information */int do_multiple_p)
374 {
375 basic_block test_bb = ce_info->test_bb; /* last test block */
376 basic_block then_bb = ce_info->then_bb; /* THEN */
377 basic_block else_bb = ce_info->else_bb; /* ELSE or NULL */
378 rtx test_expr; /* expression in IF_THEN_ELSE that is tested */
379 rtx then_start; /* first insn in THEN block */
380 rtx then_end; /* last insn + 1 in THEN block */
381 rtx else_start = NULL_RTX; /* first insn in ELSE block or NULL */
382 rtx else_end = NULL_RTX; /* last insn + 1 in ELSE block */
383 int max; /* max # of insns to convert. */
384 int then_mod_ok; /* whether conditional mods are ok in THEN */
385 rtx true_expr; /* test for else block insns */
386 rtx false_expr; /* test for then block insns */
387 rtx true_prob_val; /* probability of else block */
388 rtx false_prob_val; /* probability of then block */
389 int n_insns;
390 enum rtx_code false_code;
391
392 /* If test is comprised of && or || elements, and we've failed at handling
393 all of them together, just use the last test if it is the special case of
394 && elements without an ELSE block. */
395 if (!do_multiple_p && ce_info->num_multiple_test_blocks)
396 {
397 if (else_bb || ! ce_info->and_and_p)
398 return FALSE;
399
400 ce_info->test_bb = test_bb = ce_info->last_test_bb;
401 ce_info->num_multiple_test_blocks = 0;
402 ce_info->num_and_and_blocks = 0;
403 ce_info->num_or_or_blocks = 0;
404 }
405
406 /* Find the conditional jump to the ELSE or JOIN part, and isolate
407 the test. */
408 test_expr = cond_exec_get_condition (BB_END (test_bb));
409 if (! test_expr)
410 return FALSE;
411
412 /* If the conditional jump is more than just a conditional jump,
413 then we can not do conditional execution conversion on this block. */
414 if (! onlyjump_p (BB_END (test_bb)))
415 return FALSE;
416
417 /* Collect the bounds of where we're to search, skipping any labels, jumps
418 and notes at the beginning and end of the block. Then count the total
419 number of insns and see if it is small enough to convert. */
420 then_start = first_active_insn (then_bb);
421 then_end = last_active_insn (then_bb, TRUE);
422 n_insns = ce_info->num_then_insns = count_bb_insns (then_bb);
423 max = MAX_CONDITIONAL_EXECUTE;
424
425 if (else_bb)
426 {
427 max *= 2;
428 else_start = first_active_insn (else_bb);
429 else_end = last_active_insn (else_bb, TRUE);
430 n_insns += ce_info->num_else_insns = count_bb_insns (else_bb);
431 }
432
433 if (n_insns > max)
434 return FALSE;
435
436 /* Map test_expr/test_jump into the appropriate MD tests to use on
437 the conditionally executed code. */
438
439 true_expr = test_expr;
440
441 false_code = reversed_comparison_code (true_expr, BB_END (test_bb));
442 if (false_code != UNKNOWN)
443 false_expr = gen_rtx_fmt_ee (false_code, GET_MODE (true_expr),
444 XEXP (true_expr, 0), XEXP (true_expr, 1));
445 else
446 false_expr = NULL_RTX;
447
448 #ifdef IFCVT_MODIFY_TESTS
449 /* If the machine description needs to modify the tests, such as setting a
450 conditional execution register from a comparison, it can do so here. */
451 IFCVT_MODIFY_TESTS (ce_info, true_expr, false_expr);
452
453 /* See if the conversion failed. */
454 if (!true_expr || !false_expr)
455 goto fail;
456 #endif
457
458 true_prob_val = find_reg_note (BB_END (test_bb), REG_BR_PROB, NULL_RTX);
459 if (true_prob_val)
460 {
461 true_prob_val = XEXP (true_prob_val, 0);
462 false_prob_val = GEN_INT (REG_BR_PROB_BASE - INTVAL (true_prob_val));
463 }
464 else
465 false_prob_val = NULL_RTX;
466
467 /* If we have && or || tests, do them here. These tests are in the adjacent
468 blocks after the first block containing the test. */
469 if (ce_info->num_multiple_test_blocks > 0)
470 {
471 basic_block bb = test_bb;
472 basic_block last_test_bb = ce_info->last_test_bb;
473
474 if (! false_expr)
475 goto fail;
476
477 do
478 {
479 rtx start, end;
480 rtx t, f;
481
482 bb = block_fallthru (bb);
483 start = first_active_insn (bb);
484 end = last_active_insn (bb, TRUE);
485 if (start
486 && ! cond_exec_process_insns (ce_info, start, end, false_expr,
487 false_prob_val, FALSE))
488 goto fail;
489
490 /* If the conditional jump is more than just a conditional jump, then
491 we can not do conditional execution conversion on this block. */
492 if (! onlyjump_p (BB_END (bb)))
493 goto fail;
494
495 /* Find the conditional jump and isolate the test. */
496 t = cond_exec_get_condition (BB_END (bb));
497 if (! t)
498 goto fail;
499
500 f = gen_rtx_fmt_ee (reverse_condition (GET_CODE (t)),
501 GET_MODE (t),
502 XEXP (t, 0),
503 XEXP (t, 1));
504
505 if (ce_info->and_and_p)
506 {
507 t = gen_rtx_AND (GET_MODE (t), true_expr, t);
508 f = gen_rtx_IOR (GET_MODE (t), false_expr, f);
509 }
510 else
511 {
512 t = gen_rtx_IOR (GET_MODE (t), true_expr, t);
513 f = gen_rtx_AND (GET_MODE (t), false_expr, f);
514 }
515
516 /* If the machine description needs to modify the tests, such as
517 setting a conditional execution register from a comparison, it can
518 do so here. */
519 #ifdef IFCVT_MODIFY_MULTIPLE_TESTS
520 IFCVT_MODIFY_MULTIPLE_TESTS (ce_info, bb, t, f);
521
522 /* See if the conversion failed. */
523 if (!t || !f)
524 goto fail;
525 #endif
526
527 true_expr = t;
528 false_expr = f;
529 }
530 while (bb != last_test_bb);
531 }
532
533 /* For IF-THEN-ELSE blocks, we don't allow modifications of the test
534 on then THEN block. */
535 then_mod_ok = (else_bb == NULL_BLOCK);
536
537 /* Go through the THEN and ELSE blocks converting the insns if possible
538 to conditional execution. */
539
540 if (then_end
541 && (! false_expr
542 || ! cond_exec_process_insns (ce_info, then_start, then_end,
543 false_expr, false_prob_val,
544 then_mod_ok)))
545 goto fail;
546
547 if (else_bb && else_end
548 && ! cond_exec_process_insns (ce_info, else_start, else_end,
549 true_expr, true_prob_val, TRUE))
550 goto fail;
551
552 /* If we cannot apply the changes, fail. Do not go through the normal fail
553 processing, since apply_change_group will call cancel_changes. */
554 if (! apply_change_group ())
555 {
556 #ifdef IFCVT_MODIFY_CANCEL
557 /* Cancel any machine dependent changes. */
558 IFCVT_MODIFY_CANCEL (ce_info);
559 #endif
560 return FALSE;
561 }
562
563 #ifdef IFCVT_MODIFY_FINAL
564 /* Do any machine dependent final modifications. */
565 IFCVT_MODIFY_FINAL (ce_info);
566 #endif
567
568 /* Conversion succeeded. */
569 if (rtl_dump_file)
570 fprintf (rtl_dump_file, "%d insn%s converted to conditional execution.\n",
571 n_insns, (n_insns == 1) ? " was" : "s were");
572
573 /* Merge the blocks! */
574 merge_if_block (ce_info);
575 cond_exec_changed_p = TRUE;
576 return TRUE;
577
578 fail:
579 #ifdef IFCVT_MODIFY_CANCEL
580 /* Cancel any machine dependent changes. */
581 IFCVT_MODIFY_CANCEL (ce_info);
582 #endif
583
584 cancel_changes (0);
585 return FALSE;
586 }
587
588 /* Used by noce_process_if_block to communicate with its subroutines.
589
590 The subroutines know that A and B may be evaluated freely. They
591 know that X is a register. They should insert new instructions
592 before cond_earliest. */
593
594 struct noce_if_info
595 {
596 basic_block test_bb;
597 rtx insn_a, insn_b;
598 rtx x, a, b;
599 rtx jump, cond, cond_earliest;
600 };
601
602 static rtx noce_emit_store_flag (struct noce_if_info *, rtx, int, int);
603 static int noce_try_move (struct noce_if_info *);
604 static int noce_try_store_flag (struct noce_if_info *);
605 static int noce_try_addcc (struct noce_if_info *);
606 static int noce_try_store_flag_constants (struct noce_if_info *);
607 static int noce_try_store_flag_mask (struct noce_if_info *);
608 static rtx noce_emit_cmove (struct noce_if_info *, rtx, enum rtx_code, rtx,
609 rtx, rtx, rtx);
610 static int noce_try_cmove (struct noce_if_info *);
611 static int noce_try_cmove_arith (struct noce_if_info *);
612 static rtx noce_get_alt_condition (struct noce_if_info *, rtx, rtx *);
613 static int noce_try_minmax (struct noce_if_info *);
614 static int noce_try_abs (struct noce_if_info *);
615
616 /* Helper function for noce_try_store_flag*. */
617
618 static rtx
noce_emit_store_flag(struct noce_if_info * if_info,rtx x,int reversep,int normalize)619 noce_emit_store_flag (struct noce_if_info *if_info, rtx x, int reversep,
620 int normalize)
621 {
622 rtx cond = if_info->cond;
623 int cond_complex;
624 enum rtx_code code;
625
626 cond_complex = (! general_operand (XEXP (cond, 0), VOIDmode)
627 || ! general_operand (XEXP (cond, 1), VOIDmode));
628
629 /* If earliest == jump, or when the condition is complex, try to
630 build the store_flag insn directly. */
631
632 if (cond_complex)
633 cond = XEXP (SET_SRC (pc_set (if_info->jump)), 0);
634
635 if (reversep)
636 code = reversed_comparison_code (cond, if_info->jump);
637 else
638 code = GET_CODE (cond);
639
640 if ((if_info->cond_earliest == if_info->jump || cond_complex)
641 && (normalize == 0 || STORE_FLAG_VALUE == normalize))
642 {
643 rtx tmp;
644
645 tmp = gen_rtx_fmt_ee (code, GET_MODE (x), XEXP (cond, 0),
646 XEXP (cond, 1));
647 tmp = gen_rtx_SET (VOIDmode, x, tmp);
648
649 start_sequence ();
650 tmp = emit_insn (tmp);
651
652 if (recog_memoized (tmp) >= 0)
653 {
654 tmp = get_insns ();
655 end_sequence ();
656 emit_insn (tmp);
657
658 if_info->cond_earliest = if_info->jump;
659
660 return x;
661 }
662
663 end_sequence ();
664 }
665
666 /* Don't even try if the comparison operands or the mode of X are weird. */
667 if (cond_complex || !SCALAR_INT_MODE_P (GET_MODE (x)))
668 return NULL_RTX;
669
670 return emit_store_flag (x, code, XEXP (cond, 0),
671 XEXP (cond, 1), VOIDmode,
672 (code == LTU || code == LEU
673 || code == GEU || code == GTU), normalize);
674 }
675
676 /* Emit instruction to move an rtx, possibly into STRICT_LOW_PART.
677 X is the destination/target and Y is the value to copy. */
678
679 static void
noce_emit_move_insn(rtx x,rtx y)680 noce_emit_move_insn (rtx x, rtx y)
681 {
682 enum machine_mode outmode, inmode;
683 rtx outer, inner;
684 int bitpos;
685
686 if (GET_CODE (x) != STRICT_LOW_PART)
687 {
688 emit_move_insn (x, y);
689 return;
690 }
691
692 outer = XEXP (x, 0);
693 inner = XEXP (outer, 0);
694 outmode = GET_MODE (outer);
695 inmode = GET_MODE (inner);
696 bitpos = SUBREG_BYTE (outer) * BITS_PER_UNIT;
697 store_bit_field (inner, GET_MODE_BITSIZE (outmode), bitpos, outmode, y,
698 GET_MODE_BITSIZE (inmode));
699 }
700
701 /* Unshare sequence SEQ produced by if conversion. We care to mark
702 all arguments that may be shared with outer instruction stream. */
703 static void
unshare_ifcvt_sequence(struct noce_if_info * if_info,rtx seq)704 unshare_ifcvt_sequence (struct noce_if_info *if_info, rtx seq)
705 {
706 set_used_flags (if_info->x);
707 set_used_flags (if_info->cond);
708 unshare_all_rtl_in_chain (seq);
709 }
710
711 /* Convert "if (a != b) x = a; else x = b" into "x = a" and
712 "if (a == b) x = a; else x = b" into "x = b". */
713
714 static int
noce_try_move(struct noce_if_info * if_info)715 noce_try_move (struct noce_if_info *if_info)
716 {
717 rtx cond = if_info->cond;
718 enum rtx_code code = GET_CODE (cond);
719 rtx y, seq;
720
721 if (code != NE && code != EQ)
722 return FALSE;
723
724 /* This optimization isn't valid if either A or B could be a NaN
725 or a signed zero. */
726 if (HONOR_NANS (GET_MODE (if_info->x))
727 || HONOR_SIGNED_ZEROS (GET_MODE (if_info->x)))
728 return FALSE;
729
730 /* Check whether the operands of the comparison are A and in
731 either order. */
732 if ((rtx_equal_p (if_info->a, XEXP (cond, 0))
733 && rtx_equal_p (if_info->b, XEXP (cond, 1)))
734 || (rtx_equal_p (if_info->a, XEXP (cond, 1))
735 && rtx_equal_p (if_info->b, XEXP (cond, 0))))
736 {
737 y = (code == EQ) ? if_info->a : if_info->b;
738
739 /* Avoid generating the move if the source is the destination. */
740 if (! rtx_equal_p (if_info->x, y))
741 {
742 start_sequence ();
743 noce_emit_move_insn (if_info->x, y);
744 seq = get_insns ();
745 unshare_ifcvt_sequence (if_info, seq);
746 end_sequence ();
747
748 /* Make sure that all of the instructions emitted are
749 recognizable. As an excersise for the reader, build
750 a general mechanism that allows proper placement of
751 required clobbers. */
752 for (y = seq; y ; y = NEXT_INSN (y))
753 if (recog_memoized (y) == -1)
754 return FALSE;
755
756 emit_insn_before_setloc (seq, if_info->jump,
757 INSN_LOCATOR (if_info->insn_a));
758 }
759 return TRUE;
760 }
761 return FALSE;
762 }
763
764 /* Convert "if (test) x = 1; else x = 0".
765
766 Only try 0 and STORE_FLAG_VALUE here. Other combinations will be
767 tried in noce_try_store_flag_constants after noce_try_cmove has had
768 a go at the conversion. */
769
770 static int
noce_try_store_flag(struct noce_if_info * if_info)771 noce_try_store_flag (struct noce_if_info *if_info)
772 {
773 int reversep;
774 rtx target, seq;
775
776 if (GET_CODE (if_info->b) == CONST_INT
777 && INTVAL (if_info->b) == STORE_FLAG_VALUE
778 && if_info->a == const0_rtx)
779 reversep = 0;
780 else if (if_info->b == const0_rtx
781 && GET_CODE (if_info->a) == CONST_INT
782 && INTVAL (if_info->a) == STORE_FLAG_VALUE
783 && (reversed_comparison_code (if_info->cond, if_info->jump)
784 != UNKNOWN))
785 reversep = 1;
786 else
787 return FALSE;
788
789 start_sequence ();
790
791 target = noce_emit_store_flag (if_info, if_info->x, reversep, 0);
792 if (target)
793 {
794 if (target != if_info->x)
795 noce_emit_move_insn (if_info->x, target);
796
797 seq = get_insns ();
798 unshare_ifcvt_sequence (if_info, seq);
799 end_sequence ();
800 emit_insn_before_setloc (seq, if_info->jump, INSN_LOCATOR (if_info->insn_a));
801
802 return TRUE;
803 }
804 else
805 {
806 end_sequence ();
807 return FALSE;
808 }
809 }
810
811 /* Convert "if (test) x = a; else x = b", for A and B constant. */
812
813 static int
noce_try_store_flag_constants(struct noce_if_info * if_info)814 noce_try_store_flag_constants (struct noce_if_info *if_info)
815 {
816 rtx target, seq;
817 int reversep;
818 HOST_WIDE_INT itrue, ifalse, diff, tmp;
819 int normalize, can_reverse;
820 enum machine_mode mode;
821
822 if (! no_new_pseudos
823 && GET_CODE (if_info->a) == CONST_INT
824 && GET_CODE (if_info->b) == CONST_INT)
825 {
826 mode = GET_MODE (if_info->x);
827 ifalse = INTVAL (if_info->a);
828 itrue = INTVAL (if_info->b);
829
830 /* Make sure we can represent the difference between the two values. */
831 if ((itrue - ifalse > 0)
832 != ((ifalse < 0) != (itrue < 0) ? ifalse < 0 : ifalse < itrue))
833 return FALSE;
834
835 diff = trunc_int_for_mode (itrue - ifalse, mode);
836
837 can_reverse = (reversed_comparison_code (if_info->cond, if_info->jump)
838 != UNKNOWN);
839
840 reversep = 0;
841 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
842 normalize = 0;
843 else if (ifalse == 0 && exact_log2 (itrue) >= 0
844 && (STORE_FLAG_VALUE == 1
845 || BRANCH_COST >= 2))
846 normalize = 1;
847 else if (itrue == 0 && exact_log2 (ifalse) >= 0 && can_reverse
848 && (STORE_FLAG_VALUE == 1 || BRANCH_COST >= 2))
849 normalize = 1, reversep = 1;
850 else if (itrue == -1
851 && (STORE_FLAG_VALUE == -1
852 || BRANCH_COST >= 2))
853 normalize = -1;
854 else if (ifalse == -1 && can_reverse
855 && (STORE_FLAG_VALUE == -1 || BRANCH_COST >= 2))
856 normalize = -1, reversep = 1;
857 else if ((BRANCH_COST >= 2 && STORE_FLAG_VALUE == -1)
858 || BRANCH_COST >= 3)
859 normalize = -1;
860 else
861 return FALSE;
862
863 if (reversep)
864 {
865 tmp = itrue; itrue = ifalse; ifalse = tmp;
866 diff = trunc_int_for_mode (-diff, mode);
867 }
868
869 start_sequence ();
870 target = noce_emit_store_flag (if_info, if_info->x, reversep, normalize);
871 if (! target)
872 {
873 end_sequence ();
874 return FALSE;
875 }
876
877 /* if (test) x = 3; else x = 4;
878 => x = 3 + (test == 0); */
879 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
880 {
881 target = expand_simple_binop (mode,
882 (diff == STORE_FLAG_VALUE
883 ? PLUS : MINUS),
884 GEN_INT (ifalse), target, if_info->x, 0,
885 OPTAB_WIDEN);
886 }
887
888 /* if (test) x = 8; else x = 0;
889 => x = (test != 0) << 3; */
890 else if (ifalse == 0 && (tmp = exact_log2 (itrue)) >= 0)
891 {
892 target = expand_simple_binop (mode, ASHIFT,
893 target, GEN_INT (tmp), if_info->x, 0,
894 OPTAB_WIDEN);
895 }
896
897 /* if (test) x = -1; else x = b;
898 => x = -(test != 0) | b; */
899 else if (itrue == -1)
900 {
901 target = expand_simple_binop (mode, IOR,
902 target, GEN_INT (ifalse), if_info->x, 0,
903 OPTAB_WIDEN);
904 }
905
906 /* if (test) x = a; else x = b;
907 => x = (-(test != 0) & (b - a)) + a; */
908 else
909 {
910 target = expand_simple_binop (mode, AND,
911 target, GEN_INT (diff), if_info->x, 0,
912 OPTAB_WIDEN);
913 if (target)
914 target = expand_simple_binop (mode, PLUS,
915 target, GEN_INT (ifalse),
916 if_info->x, 0, OPTAB_WIDEN);
917 }
918
919 if (! target)
920 {
921 end_sequence ();
922 return FALSE;
923 }
924
925 if (target != if_info->x)
926 noce_emit_move_insn (if_info->x, target);
927
928 seq = get_insns ();
929 unshare_ifcvt_sequence (if_info, seq);
930 end_sequence ();
931
932 if (seq_contains_jump (seq))
933 return FALSE;
934
935 emit_insn_before_setloc (seq, if_info->jump, INSN_LOCATOR (if_info->insn_a));
936
937 return TRUE;
938 }
939
940 return FALSE;
941 }
942
943 /* Convert "if (test) foo++" into "foo += (test != 0)", and
944 similarly for "foo--". */
945
946 static int
noce_try_addcc(struct noce_if_info * if_info)947 noce_try_addcc (struct noce_if_info *if_info)
948 {
949 rtx target, seq;
950 int subtract, normalize;
951
952 if (! no_new_pseudos
953 && GET_CODE (if_info->a) == PLUS
954 && rtx_equal_p (XEXP (if_info->a, 0), if_info->b)
955 && (reversed_comparison_code (if_info->cond, if_info->jump)
956 != UNKNOWN))
957 {
958 rtx cond = if_info->cond;
959 enum rtx_code code = reversed_comparison_code (cond, if_info->jump);
960
961 /* First try to use addcc pattern. */
962 if (general_operand (XEXP (cond, 0), VOIDmode)
963 && general_operand (XEXP (cond, 1), VOIDmode))
964 {
965 start_sequence ();
966 target = emit_conditional_add (if_info->x, code,
967 XEXP (cond, 0),
968 XEXP (cond, 1),
969 VOIDmode,
970 if_info->b,
971 XEXP (if_info->a, 1),
972 GET_MODE (if_info->x),
973 (code == LTU || code == GEU
974 || code == LEU || code == GTU));
975 if (target)
976 {
977 if (target != if_info->x)
978 noce_emit_move_insn (if_info->x, target);
979
980 seq = get_insns ();
981 unshare_ifcvt_sequence (if_info, seq);
982 end_sequence ();
983 emit_insn_before_setloc (seq, if_info->jump,
984 INSN_LOCATOR (if_info->insn_a));
985 return TRUE;
986 }
987 end_sequence ();
988 }
989
990 /* If that fails, construct conditional increment or decrement using
991 setcc. */
992 if (BRANCH_COST >= 2
993 && (XEXP (if_info->a, 1) == const1_rtx
994 || XEXP (if_info->a, 1) == constm1_rtx))
995 {
996 start_sequence ();
997 if (STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
998 subtract = 0, normalize = 0;
999 else if (-STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
1000 subtract = 1, normalize = 0;
1001 else
1002 subtract = 0, normalize = INTVAL (XEXP (if_info->a, 1));
1003
1004
1005 target = noce_emit_store_flag (if_info,
1006 gen_reg_rtx (GET_MODE (if_info->x)),
1007 1, normalize);
1008
1009 if (target)
1010 target = expand_simple_binop (GET_MODE (if_info->x),
1011 subtract ? MINUS : PLUS,
1012 if_info->b, target, if_info->x,
1013 0, OPTAB_WIDEN);
1014 if (target)
1015 {
1016 if (target != if_info->x)
1017 noce_emit_move_insn (if_info->x, target);
1018
1019 seq = get_insns ();
1020 unshare_ifcvt_sequence (if_info, seq);
1021 end_sequence ();
1022
1023 if (seq_contains_jump (seq))
1024 return FALSE;
1025
1026 emit_insn_before_setloc (seq, if_info->jump,
1027 INSN_LOCATOR (if_info->insn_a));
1028
1029 return TRUE;
1030 }
1031 end_sequence ();
1032 }
1033 }
1034
1035 return FALSE;
1036 }
1037
1038 /* Convert "if (test) x = 0;" to "x &= -(test == 0);" */
1039
1040 static int
noce_try_store_flag_mask(struct noce_if_info * if_info)1041 noce_try_store_flag_mask (struct noce_if_info *if_info)
1042 {
1043 rtx target, seq;
1044 int reversep;
1045
1046 reversep = 0;
1047 if (! no_new_pseudos
1048 && (BRANCH_COST >= 2
1049 || STORE_FLAG_VALUE == -1)
1050 && ((if_info->a == const0_rtx
1051 && rtx_equal_p (if_info->b, if_info->x))
1052 || ((reversep = (reversed_comparison_code (if_info->cond,
1053 if_info->jump)
1054 != UNKNOWN))
1055 && if_info->b == const0_rtx
1056 && rtx_equal_p (if_info->a, if_info->x))))
1057 {
1058 start_sequence ();
1059 target = noce_emit_store_flag (if_info,
1060 gen_reg_rtx (GET_MODE (if_info->x)),
1061 reversep, -1);
1062 if (target)
1063 target = expand_simple_binop (GET_MODE (if_info->x), AND,
1064 if_info->x,
1065 target, if_info->x, 0,
1066 OPTAB_WIDEN);
1067
1068 if (target)
1069 {
1070 if (target != if_info->x)
1071 noce_emit_move_insn (if_info->x, target);
1072
1073 seq = get_insns ();
1074 unshare_ifcvt_sequence (if_info, seq);
1075 end_sequence ();
1076
1077 if (seq_contains_jump (seq))
1078 return FALSE;
1079
1080 emit_insn_before_setloc (seq, if_info->jump,
1081 INSN_LOCATOR (if_info->insn_a));
1082
1083 return TRUE;
1084 }
1085
1086 end_sequence ();
1087 }
1088
1089 return FALSE;
1090 }
1091
1092 /* Helper function for noce_try_cmove and noce_try_cmove_arith. */
1093
1094 static rtx
noce_emit_cmove(struct noce_if_info * if_info,rtx x,enum rtx_code code,rtx cmp_a,rtx cmp_b,rtx vfalse,rtx vtrue)1095 noce_emit_cmove (struct noce_if_info *if_info, rtx x, enum rtx_code code,
1096 rtx cmp_a, rtx cmp_b, rtx vfalse, rtx vtrue)
1097 {
1098 /* If earliest == jump, try to build the cmove insn directly.
1099 This is helpful when combine has created some complex condition
1100 (like for alpha's cmovlbs) that we can't hope to regenerate
1101 through the normal interface. */
1102
1103 if (if_info->cond_earliest == if_info->jump)
1104 {
1105 rtx tmp;
1106
1107 tmp = gen_rtx_fmt_ee (code, GET_MODE (if_info->cond), cmp_a, cmp_b);
1108 tmp = gen_rtx_IF_THEN_ELSE (GET_MODE (x), tmp, vtrue, vfalse);
1109 tmp = gen_rtx_SET (VOIDmode, x, tmp);
1110
1111 start_sequence ();
1112 tmp = emit_insn (tmp);
1113
1114 if (recog_memoized (tmp) >= 0)
1115 {
1116 tmp = get_insns ();
1117 end_sequence ();
1118 emit_insn (tmp);
1119
1120 return x;
1121 }
1122
1123 end_sequence ();
1124 }
1125
1126 /* Don't even try if the comparison operands are weird. */
1127 if (! general_operand (cmp_a, GET_MODE (cmp_a))
1128 || ! general_operand (cmp_b, GET_MODE (cmp_b)))
1129 return NULL_RTX;
1130
1131 #if HAVE_conditional_move
1132 return emit_conditional_move (x, code, cmp_a, cmp_b, VOIDmode,
1133 vtrue, vfalse, GET_MODE (x),
1134 (code == LTU || code == GEU
1135 || code == LEU || code == GTU));
1136 #else
1137 /* We'll never get here, as noce_process_if_block doesn't call the
1138 functions involved. Ifdef code, however, should be discouraged
1139 because it leads to typos in the code not selected. However,
1140 emit_conditional_move won't exist either. */
1141 return NULL_RTX;
1142 #endif
1143 }
1144
1145 /* Try only simple constants and registers here. More complex cases
1146 are handled in noce_try_cmove_arith after noce_try_store_flag_arith
1147 has had a go at it. */
1148
1149 static int
noce_try_cmove(struct noce_if_info * if_info)1150 noce_try_cmove (struct noce_if_info *if_info)
1151 {
1152 enum rtx_code code;
1153 rtx target, seq;
1154
1155 if ((CONSTANT_P (if_info->a) || register_operand (if_info->a, VOIDmode))
1156 && (CONSTANT_P (if_info->b) || register_operand (if_info->b, VOIDmode)))
1157 {
1158 start_sequence ();
1159
1160 code = GET_CODE (if_info->cond);
1161 target = noce_emit_cmove (if_info, if_info->x, code,
1162 XEXP (if_info->cond, 0),
1163 XEXP (if_info->cond, 1),
1164 if_info->a, if_info->b);
1165
1166 if (target)
1167 {
1168 if (target != if_info->x)
1169 noce_emit_move_insn (if_info->x, target);
1170
1171 seq = get_insns ();
1172 unshare_ifcvt_sequence (if_info, seq);
1173 end_sequence ();
1174 emit_insn_before_setloc (seq, if_info->jump,
1175 INSN_LOCATOR (if_info->insn_a));
1176 return TRUE;
1177 }
1178 else
1179 {
1180 end_sequence ();
1181 return FALSE;
1182 }
1183 }
1184
1185 return FALSE;
1186 }
1187
1188 /* Try more complex cases involving conditional_move. */
1189
1190 static int
noce_try_cmove_arith(struct noce_if_info * if_info)1191 noce_try_cmove_arith (struct noce_if_info *if_info)
1192 {
1193 rtx a = if_info->a;
1194 rtx b = if_info->b;
1195 rtx x = if_info->x;
1196 rtx insn_a, insn_b;
1197 rtx tmp, target;
1198 int is_mem = 0;
1199 enum rtx_code code;
1200
1201 /* A conditional move from two memory sources is equivalent to a
1202 conditional on their addresses followed by a load. Don't do this
1203 early because it'll screw alias analysis. Note that we've
1204 already checked for no side effects. */
1205 if (! no_new_pseudos && cse_not_expected
1206 && GET_CODE (a) == MEM && GET_CODE (b) == MEM
1207 && BRANCH_COST >= 5)
1208 {
1209 a = XEXP (a, 0);
1210 b = XEXP (b, 0);
1211 x = gen_reg_rtx (Pmode);
1212 is_mem = 1;
1213 }
1214
1215 /* ??? We could handle this if we knew that a load from A or B could
1216 not fault. This is also true if we've already loaded
1217 from the address along the path from ENTRY. */
1218 else if (may_trap_p (a) || may_trap_p (b))
1219 return FALSE;
1220
1221 /* if (test) x = a + b; else x = c - d;
1222 => y = a + b;
1223 x = c - d;
1224 if (test)
1225 x = y;
1226 */
1227
1228 code = GET_CODE (if_info->cond);
1229 insn_a = if_info->insn_a;
1230 insn_b = if_info->insn_b;
1231
1232 /* Possibly rearrange operands to make things come out more natural. */
1233 if (reversed_comparison_code (if_info->cond, if_info->jump) != UNKNOWN)
1234 {
1235 int reversep = 0;
1236 if (rtx_equal_p (b, x))
1237 reversep = 1;
1238 else if (general_operand (b, GET_MODE (b)))
1239 reversep = 1;
1240
1241 if (reversep)
1242 {
1243 code = reversed_comparison_code (if_info->cond, if_info->jump);
1244 tmp = a, a = b, b = tmp;
1245 tmp = insn_a, insn_a = insn_b, insn_b = tmp;
1246 }
1247 }
1248
1249 start_sequence ();
1250
1251 /* If either operand is complex, load it into a register first.
1252 The best way to do this is to copy the original insn. In this
1253 way we preserve any clobbers etc that the insn may have had.
1254 This is of course not possible in the IS_MEM case. */
1255 if (! general_operand (a, GET_MODE (a)))
1256 {
1257 rtx set;
1258
1259 if (no_new_pseudos)
1260 goto end_seq_and_fail;
1261
1262 if (is_mem)
1263 {
1264 tmp = gen_reg_rtx (GET_MODE (a));
1265 tmp = emit_insn (gen_rtx_SET (VOIDmode, tmp, a));
1266 }
1267 else if (! insn_a)
1268 goto end_seq_and_fail;
1269 else
1270 {
1271 a = gen_reg_rtx (GET_MODE (a));
1272 tmp = copy_rtx (insn_a);
1273 set = single_set (tmp);
1274 SET_DEST (set) = a;
1275 tmp = emit_insn (PATTERN (tmp));
1276 }
1277 if (recog_memoized (tmp) < 0)
1278 goto end_seq_and_fail;
1279 }
1280 if (! general_operand (b, GET_MODE (b)))
1281 {
1282 rtx set;
1283
1284 if (no_new_pseudos)
1285 goto end_seq_and_fail;
1286
1287 if (is_mem)
1288 {
1289 tmp = gen_reg_rtx (GET_MODE (b));
1290 tmp = emit_insn (gen_rtx_SET (VOIDmode,
1291 tmp,
1292 b));
1293 }
1294 else if (! insn_b)
1295 goto end_seq_and_fail;
1296 else
1297 {
1298 b = gen_reg_rtx (GET_MODE (b));
1299 tmp = copy_rtx (insn_b);
1300 set = single_set (tmp);
1301 SET_DEST (set) = b;
1302 tmp = emit_insn (PATTERN (tmp));
1303 }
1304 if (recog_memoized (tmp) < 0)
1305 goto end_seq_and_fail;
1306 }
1307
1308 target = noce_emit_cmove (if_info, x, code, XEXP (if_info->cond, 0),
1309 XEXP (if_info->cond, 1), a, b);
1310
1311 if (! target)
1312 goto end_seq_and_fail;
1313
1314 /* If we're handling a memory for above, emit the load now. */
1315 if (is_mem)
1316 {
1317 tmp = gen_rtx_MEM (GET_MODE (if_info->x), target);
1318
1319 /* Copy over flags as appropriate. */
1320 if (MEM_VOLATILE_P (if_info->a) || MEM_VOLATILE_P (if_info->b))
1321 MEM_VOLATILE_P (tmp) = 1;
1322 if (MEM_IN_STRUCT_P (if_info->a) && MEM_IN_STRUCT_P (if_info->b))
1323 MEM_IN_STRUCT_P (tmp) = 1;
1324 if (MEM_SCALAR_P (if_info->a) && MEM_SCALAR_P (if_info->b))
1325 MEM_SCALAR_P (tmp) = 1;
1326 if (MEM_ALIAS_SET (if_info->a) == MEM_ALIAS_SET (if_info->b))
1327 set_mem_alias_set (tmp, MEM_ALIAS_SET (if_info->a));
1328 set_mem_align (tmp,
1329 MIN (MEM_ALIGN (if_info->a), MEM_ALIGN (if_info->b)));
1330
1331 noce_emit_move_insn (if_info->x, tmp);
1332 }
1333 else if (target != x)
1334 noce_emit_move_insn (x, target);
1335
1336 tmp = get_insns ();
1337 unshare_ifcvt_sequence (if_info, tmp);
1338 end_sequence ();
1339 emit_insn_before_setloc (tmp, if_info->jump, INSN_LOCATOR (if_info->insn_a));
1340 return TRUE;
1341
1342 end_seq_and_fail:
1343 end_sequence ();
1344 return FALSE;
1345 }
1346
1347 /* For most cases, the simplified condition we found is the best
1348 choice, but this is not the case for the min/max/abs transforms.
1349 For these we wish to know that it is A or B in the condition. */
1350
1351 static rtx
noce_get_alt_condition(struct noce_if_info * if_info,rtx target,rtx * earliest)1352 noce_get_alt_condition (struct noce_if_info *if_info, rtx target,
1353 rtx *earliest)
1354 {
1355 rtx cond, set, insn;
1356 int reverse;
1357
1358 /* If target is already mentioned in the known condition, return it. */
1359 if (reg_mentioned_p (target, if_info->cond))
1360 {
1361 *earliest = if_info->cond_earliest;
1362 return if_info->cond;
1363 }
1364
1365 set = pc_set (if_info->jump);
1366 cond = XEXP (SET_SRC (set), 0);
1367 reverse
1368 = GET_CODE (XEXP (SET_SRC (set), 2)) == LABEL_REF
1369 && XEXP (XEXP (SET_SRC (set), 2), 0) == JUMP_LABEL (if_info->jump);
1370
1371 /* If we're looking for a constant, try to make the conditional
1372 have that constant in it. There are two reasons why it may
1373 not have the constant we want:
1374
1375 1. GCC may have needed to put the constant in a register, because
1376 the target can't compare directly against that constant. For
1377 this case, we look for a SET immediately before the comparison
1378 that puts a constant in that register.
1379
1380 2. GCC may have canonicalized the conditional, for example
1381 replacing "if x < 4" with "if x <= 3". We can undo that (or
1382 make equivalent types of changes) to get the constants we need
1383 if they're off by one in the right direction. */
1384
1385 if (GET_CODE (target) == CONST_INT)
1386 {
1387 enum rtx_code code = GET_CODE (if_info->cond);
1388 rtx op_a = XEXP (if_info->cond, 0);
1389 rtx op_b = XEXP (if_info->cond, 1);
1390 rtx prev_insn;
1391
1392 /* First, look to see if we put a constant in a register. */
1393 prev_insn = PREV_INSN (if_info->cond_earliest);
1394 if (prev_insn
1395 && INSN_P (prev_insn)
1396 && GET_CODE (PATTERN (prev_insn)) == SET)
1397 {
1398 rtx src = find_reg_equal_equiv_note (prev_insn);
1399 if (!src)
1400 src = SET_SRC (PATTERN (prev_insn));
1401 if (GET_CODE (src) == CONST_INT)
1402 {
1403 if (rtx_equal_p (op_a, SET_DEST (PATTERN (prev_insn))))
1404 op_a = src;
1405 else if (rtx_equal_p (op_b, SET_DEST (PATTERN (prev_insn))))
1406 op_b = src;
1407
1408 if (GET_CODE (op_a) == CONST_INT)
1409 {
1410 rtx tmp = op_a;
1411 op_a = op_b;
1412 op_b = tmp;
1413 code = swap_condition (code);
1414 }
1415 }
1416 }
1417
1418 /* Now, look to see if we can get the right constant by
1419 adjusting the conditional. */
1420 if (GET_CODE (op_b) == CONST_INT)
1421 {
1422 HOST_WIDE_INT desired_val = INTVAL (target);
1423 HOST_WIDE_INT actual_val = INTVAL (op_b);
1424
1425 switch (code)
1426 {
1427 case LT:
1428 if (actual_val == desired_val + 1)
1429 {
1430 code = LE;
1431 op_b = GEN_INT (desired_val);
1432 }
1433 break;
1434 case LE:
1435 if (actual_val == desired_val - 1)
1436 {
1437 code = LT;
1438 op_b = GEN_INT (desired_val);
1439 }
1440 break;
1441 case GT:
1442 if (actual_val == desired_val - 1)
1443 {
1444 code = GE;
1445 op_b = GEN_INT (desired_val);
1446 }
1447 break;
1448 case GE:
1449 if (actual_val == desired_val + 1)
1450 {
1451 code = GT;
1452 op_b = GEN_INT (desired_val);
1453 }
1454 break;
1455 default:
1456 break;
1457 }
1458 }
1459
1460 /* If we made any changes, generate a new conditional that is
1461 equivalent to what we started with, but has the right
1462 constants in it. */
1463 if (code != GET_CODE (if_info->cond)
1464 || op_a != XEXP (if_info->cond, 0)
1465 || op_b != XEXP (if_info->cond, 1))
1466 {
1467 cond = gen_rtx_fmt_ee (code, GET_MODE (cond), op_a, op_b);
1468 *earliest = if_info->cond_earliest;
1469 return cond;
1470 }
1471 }
1472
1473 cond = canonicalize_condition (if_info->jump, cond, reverse,
1474 earliest, target, false);
1475 if (! cond || ! reg_mentioned_p (target, cond))
1476 return NULL;
1477
1478 /* We almost certainly searched back to a different place.
1479 Need to re-verify correct lifetimes. */
1480
1481 /* X may not be mentioned in the range (cond_earliest, jump]. */
1482 for (insn = if_info->jump; insn != *earliest; insn = PREV_INSN (insn))
1483 if (INSN_P (insn) && reg_overlap_mentioned_p (if_info->x, PATTERN (insn)))
1484 return NULL;
1485
1486 /* A and B may not be modified in the range [cond_earliest, jump). */
1487 for (insn = *earliest; insn != if_info->jump; insn = NEXT_INSN (insn))
1488 if (INSN_P (insn)
1489 && (modified_in_p (if_info->a, insn)
1490 || modified_in_p (if_info->b, insn)))
1491 return NULL;
1492
1493 return cond;
1494 }
1495
1496 /* Convert "if (a < b) x = a; else x = b;" to "x = min(a, b);", etc. */
1497
1498 static int
noce_try_minmax(struct noce_if_info * if_info)1499 noce_try_minmax (struct noce_if_info *if_info)
1500 {
1501 rtx cond, earliest, target, seq;
1502 enum rtx_code code, op;
1503 int unsignedp;
1504
1505 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1506 if (no_new_pseudos)
1507 return FALSE;
1508
1509 /* ??? Reject modes with NaNs or signed zeros since we don't know how
1510 they will be resolved with an SMIN/SMAX. It wouldn't be too hard
1511 to get the target to tell us... */
1512 if (HONOR_SIGNED_ZEROS (GET_MODE (if_info->x))
1513 || HONOR_NANS (GET_MODE (if_info->x)))
1514 return FALSE;
1515
1516 cond = noce_get_alt_condition (if_info, if_info->a, &earliest);
1517 if (!cond)
1518 return FALSE;
1519
1520 /* Verify the condition is of the form we expect, and canonicalize
1521 the comparison code. */
1522 code = GET_CODE (cond);
1523 if (rtx_equal_p (XEXP (cond, 0), if_info->a))
1524 {
1525 if (! rtx_equal_p (XEXP (cond, 1), if_info->b))
1526 return FALSE;
1527 }
1528 else if (rtx_equal_p (XEXP (cond, 1), if_info->a))
1529 {
1530 if (! rtx_equal_p (XEXP (cond, 0), if_info->b))
1531 return FALSE;
1532 code = swap_condition (code);
1533 }
1534 else
1535 return FALSE;
1536
1537 /* Determine what sort of operation this is. Note that the code is for
1538 a taken branch, so the code->operation mapping appears backwards. */
1539 switch (code)
1540 {
1541 case LT:
1542 case LE:
1543 case UNLT:
1544 case UNLE:
1545 op = SMAX;
1546 unsignedp = 0;
1547 break;
1548 case GT:
1549 case GE:
1550 case UNGT:
1551 case UNGE:
1552 op = SMIN;
1553 unsignedp = 0;
1554 break;
1555 case LTU:
1556 case LEU:
1557 op = UMAX;
1558 unsignedp = 1;
1559 break;
1560 case GTU:
1561 case GEU:
1562 op = UMIN;
1563 unsignedp = 1;
1564 break;
1565 default:
1566 return FALSE;
1567 }
1568
1569 start_sequence ();
1570
1571 target = expand_simple_binop (GET_MODE (if_info->x), op,
1572 if_info->a, if_info->b,
1573 if_info->x, unsignedp, OPTAB_WIDEN);
1574 if (! target)
1575 {
1576 end_sequence ();
1577 return FALSE;
1578 }
1579 if (target != if_info->x)
1580 noce_emit_move_insn (if_info->x, target);
1581
1582 seq = get_insns ();
1583 unshare_ifcvt_sequence (if_info, seq);
1584 end_sequence ();
1585
1586 if (seq_contains_jump (seq))
1587 return FALSE;
1588
1589 emit_insn_before_setloc (seq, if_info->jump, INSN_LOCATOR (if_info->insn_a));
1590 if_info->cond = cond;
1591 if_info->cond_earliest = earliest;
1592
1593 return TRUE;
1594 }
1595
1596 /* Convert "if (a < 0) x = -a; else x = a;" to "x = abs(a);", etc. */
1597
1598 static int
noce_try_abs(struct noce_if_info * if_info)1599 noce_try_abs (struct noce_if_info *if_info)
1600 {
1601 rtx cond, earliest, target, seq, a, b, c;
1602 int negate;
1603
1604 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1605 if (no_new_pseudos)
1606 return FALSE;
1607
1608 /* Recognize A and B as constituting an ABS or NABS. */
1609 a = if_info->a;
1610 b = if_info->b;
1611 if (GET_CODE (a) == NEG && rtx_equal_p (XEXP (a, 0), b))
1612 negate = 0;
1613 else if (GET_CODE (b) == NEG && rtx_equal_p (XEXP (b, 0), a))
1614 {
1615 c = a; a = b; b = c;
1616 negate = 1;
1617 }
1618 else
1619 return FALSE;
1620
1621 cond = noce_get_alt_condition (if_info, b, &earliest);
1622 if (!cond)
1623 return FALSE;
1624
1625 /* Verify the condition is of the form we expect. */
1626 if (rtx_equal_p (XEXP (cond, 0), b))
1627 c = XEXP (cond, 1);
1628 else if (rtx_equal_p (XEXP (cond, 1), b))
1629 c = XEXP (cond, 0);
1630 else
1631 return FALSE;
1632
1633 /* Verify that C is zero. Search backward through the block for
1634 a REG_EQUAL note if necessary. */
1635 if (REG_P (c))
1636 {
1637 rtx insn, note = NULL;
1638 for (insn = earliest;
1639 insn != BB_HEAD (if_info->test_bb);
1640 insn = PREV_INSN (insn))
1641 if (INSN_P (insn)
1642 && ((note = find_reg_note (insn, REG_EQUAL, c))
1643 || (note = find_reg_note (insn, REG_EQUIV, c))))
1644 break;
1645 if (! note)
1646 return FALSE;
1647 c = XEXP (note, 0);
1648 }
1649 if (GET_CODE (c) == MEM
1650 && GET_CODE (XEXP (c, 0)) == SYMBOL_REF
1651 && CONSTANT_POOL_ADDRESS_P (XEXP (c, 0)))
1652 c = get_pool_constant (XEXP (c, 0));
1653
1654 /* Work around funny ideas get_condition has wrt canonicalization.
1655 Note that these rtx constants are known to be CONST_INT, and
1656 therefore imply integer comparisons. */
1657 if (c == constm1_rtx && GET_CODE (cond) == GT)
1658 ;
1659 else if (c == const1_rtx && GET_CODE (cond) == LT)
1660 ;
1661 else if (c != CONST0_RTX (GET_MODE (b)))
1662 return FALSE;
1663
1664 /* Determine what sort of operation this is. */
1665 switch (GET_CODE (cond))
1666 {
1667 case LT:
1668 case LE:
1669 case UNLT:
1670 case UNLE:
1671 negate = !negate;
1672 break;
1673 case GT:
1674 case GE:
1675 case UNGT:
1676 case UNGE:
1677 break;
1678 default:
1679 return FALSE;
1680 }
1681
1682 start_sequence ();
1683
1684 target = expand_abs_nojump (GET_MODE (if_info->x), b, if_info->x, 1);
1685
1686 /* ??? It's a quandary whether cmove would be better here, especially
1687 for integers. Perhaps combine will clean things up. */
1688 if (target && negate)
1689 target = expand_simple_unop (GET_MODE (target), NEG, target, if_info->x, 0);
1690
1691 if (! target)
1692 {
1693 end_sequence ();
1694 return FALSE;
1695 }
1696
1697 if (target != if_info->x)
1698 noce_emit_move_insn (if_info->x, target);
1699
1700 seq = get_insns ();
1701 unshare_ifcvt_sequence (if_info, seq);
1702 end_sequence ();
1703
1704 if (seq_contains_jump (seq))
1705 return FALSE;
1706
1707 emit_insn_before_setloc (seq, if_info->jump, INSN_LOCATOR (if_info->insn_a));
1708 if_info->cond = cond;
1709 if_info->cond_earliest = earliest;
1710
1711 return TRUE;
1712 }
1713
1714 /* Similar to get_condition, only the resulting condition must be
1715 valid at JUMP, instead of at EARLIEST. */
1716
1717 static rtx
noce_get_condition(rtx jump,rtx * earliest)1718 noce_get_condition (rtx jump, rtx *earliest)
1719 {
1720 rtx cond, set, tmp, insn;
1721 bool reverse;
1722
1723 if (! any_condjump_p (jump))
1724 return NULL_RTX;
1725
1726 set = pc_set (jump);
1727
1728 /* If this branches to JUMP_LABEL when the condition is false,
1729 reverse the condition. */
1730 reverse = (GET_CODE (XEXP (SET_SRC (set), 2)) == LABEL_REF
1731 && XEXP (XEXP (SET_SRC (set), 2), 0) == JUMP_LABEL (jump));
1732
1733 /* If the condition variable is a register and is MODE_INT, accept it. */
1734
1735 cond = XEXP (SET_SRC (set), 0);
1736 tmp = XEXP (cond, 0);
1737 if (REG_P (tmp) && GET_MODE_CLASS (GET_MODE (tmp)) == MODE_INT)
1738 {
1739 *earliest = jump;
1740
1741 if (reverse)
1742 cond = gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)),
1743 GET_MODE (cond), tmp, XEXP (cond, 1));
1744 return cond;
1745 }
1746
1747 /* Otherwise, fall back on canonicalize_condition to do the dirty
1748 work of manipulating MODE_CC values and COMPARE rtx codes. */
1749
1750 tmp = canonicalize_condition (jump, cond, reverse, earliest, NULL_RTX,
1751 false);
1752 if (!tmp)
1753 return NULL_RTX;
1754
1755 /* We are going to insert code before JUMP, not before EARLIEST.
1756 We must therefore be certain that the given condition is valid
1757 at JUMP by virtue of not having been modified since. */
1758 for (insn = *earliest; insn != jump; insn = NEXT_INSN (insn))
1759 if (INSN_P (insn) && modified_in_p (tmp, insn))
1760 break;
1761 if (insn == jump)
1762 return tmp;
1763
1764 /* The condition was modified. See if we can get a partial result
1765 that doesn't follow all the reversals. Perhaps combine can fold
1766 them together later. */
1767 tmp = XEXP (tmp, 0);
1768 if (!REG_P (tmp) || GET_MODE_CLASS (GET_MODE (tmp)) != MODE_INT)
1769 return NULL_RTX;
1770 tmp = canonicalize_condition (jump, cond, reverse, earliest, tmp,
1771 false);
1772 if (!tmp)
1773 return NULL_RTX;
1774
1775 /* For sanity's sake, re-validate the new result. */
1776 for (insn = *earliest; insn != jump; insn = NEXT_INSN (insn))
1777 if (INSN_P (insn) && modified_in_p (tmp, insn))
1778 return NULL_RTX;
1779
1780 return tmp;
1781 }
1782
1783 /* Return true if OP is ok for if-then-else processing. */
1784
1785 static int
noce_operand_ok(rtx op)1786 noce_operand_ok (rtx op)
1787 {
1788 /* We special-case memories, so handle any of them with
1789 no address side effects. */
1790 if (GET_CODE (op) == MEM)
1791 return ! side_effects_p (XEXP (op, 0));
1792
1793 if (side_effects_p (op))
1794 return FALSE;
1795
1796 return ! may_trap_p (op);
1797 }
1798
1799 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
1800 without using conditional execution. Return TRUE if we were
1801 successful at converting the block. */
1802
1803 static int
noce_process_if_block(struct ce_if_block * ce_info)1804 noce_process_if_block (struct ce_if_block * ce_info)
1805 {
1806 basic_block test_bb = ce_info->test_bb; /* test block */
1807 basic_block then_bb = ce_info->then_bb; /* THEN */
1808 basic_block else_bb = ce_info->else_bb; /* ELSE or NULL */
1809 struct noce_if_info if_info;
1810 rtx insn_a, insn_b;
1811 rtx set_a, set_b;
1812 rtx orig_x, x, a, b;
1813 rtx jump, cond;
1814
1815 /* We're looking for patterns of the form
1816
1817 (1) if (...) x = a; else x = b;
1818 (2) x = b; if (...) x = a;
1819 (3) if (...) x = a; // as if with an initial x = x.
1820
1821 The later patterns require jumps to be more expensive.
1822
1823 ??? For future expansion, look for multiple X in such patterns. */
1824
1825 /* If test is comprised of && or || elements, don't handle it unless it is
1826 the special case of && elements without an ELSE block. */
1827 if (ce_info->num_multiple_test_blocks)
1828 {
1829 if (else_bb || ! ce_info->and_and_p)
1830 return FALSE;
1831
1832 ce_info->test_bb = test_bb = ce_info->last_test_bb;
1833 ce_info->num_multiple_test_blocks = 0;
1834 ce_info->num_and_and_blocks = 0;
1835 ce_info->num_or_or_blocks = 0;
1836 }
1837
1838 /* If this is not a standard conditional jump, we can't parse it. */
1839 jump = BB_END (test_bb);
1840 cond = noce_get_condition (jump, &if_info.cond_earliest);
1841 if (! cond)
1842 return FALSE;
1843
1844 /* If the conditional jump is more than just a conditional
1845 jump, then we can not do if-conversion on this block. */
1846 if (! onlyjump_p (jump))
1847 return FALSE;
1848
1849 /* We must be comparing objects whose modes imply the size. */
1850 if (GET_MODE (XEXP (cond, 0)) == BLKmode)
1851 return FALSE;
1852
1853 /* Look for one of the potential sets. */
1854 insn_a = first_active_insn (then_bb);
1855 if (! insn_a
1856 || insn_a != last_active_insn (then_bb, FALSE)
1857 || (set_a = single_set (insn_a)) == NULL_RTX)
1858 return FALSE;
1859
1860 x = SET_DEST (set_a);
1861 a = SET_SRC (set_a);
1862
1863 /* Look for the other potential set. Make sure we've got equivalent
1864 destinations. */
1865 /* ??? This is overconservative. Storing to two different mems is
1866 as easy as conditionally computing the address. Storing to a
1867 single mem merely requires a scratch memory to use as one of the
1868 destination addresses; often the memory immediately below the
1869 stack pointer is available for this. */
1870 set_b = NULL_RTX;
1871 if (else_bb)
1872 {
1873 insn_b = first_active_insn (else_bb);
1874 if (! insn_b
1875 || insn_b != last_active_insn (else_bb, FALSE)
1876 || (set_b = single_set (insn_b)) == NULL_RTX
1877 || ! rtx_equal_p (x, SET_DEST (set_b)))
1878 return FALSE;
1879 }
1880 else
1881 {
1882 insn_b = prev_nonnote_insn (if_info.cond_earliest);
1883 /* We're going to be moving the evaluation of B down from above
1884 COND_EARLIEST to JUMP. Make sure the relevant data is still
1885 intact. */
1886 if (! insn_b
1887 || GET_CODE (insn_b) != INSN
1888 || (set_b = single_set (insn_b)) == NULL_RTX
1889 || ! rtx_equal_p (x, SET_DEST (set_b))
1890 || reg_overlap_mentioned_p (x, SET_SRC (set_b))
1891 || modified_between_p (SET_SRC (set_b),
1892 PREV_INSN (if_info.cond_earliest), jump)
1893 /* Likewise with X. In particular this can happen when
1894 noce_get_condition looks farther back in the instruction
1895 stream than one might expect. */
1896 || reg_overlap_mentioned_p (x, cond)
1897 || reg_overlap_mentioned_p (x, a)
1898 || modified_between_p (x, PREV_INSN (if_info.cond_earliest), jump))
1899 insn_b = set_b = NULL_RTX;
1900 }
1901
1902 /* If x has side effects then only the if-then-else form is safe to
1903 convert. But even in that case we would need to restore any notes
1904 (such as REG_INC) at then end. That can be tricky if
1905 noce_emit_move_insn expands to more than one insn, so disable the
1906 optimization entirely for now if there are side effects. */
1907 if (side_effects_p (x))
1908 return FALSE;
1909
1910 b = (set_b ? SET_SRC (set_b) : x);
1911
1912 /* Only operate on register destinations, and even then avoid extending
1913 the lifetime of hard registers on small register class machines. */
1914 orig_x = x;
1915 if (GET_CODE (x) != REG
1916 || (SMALL_REGISTER_CLASSES
1917 && REGNO (x) < FIRST_PSEUDO_REGISTER))
1918 {
1919 if (no_new_pseudos || GET_MODE (x) == BLKmode)
1920 return FALSE;
1921 x = gen_reg_rtx (GET_MODE (GET_CODE (x) == STRICT_LOW_PART
1922 ? XEXP (x, 0) : x));
1923 }
1924
1925 /* Don't operate on sources that may trap or are volatile. */
1926 if (! noce_operand_ok (a) || ! noce_operand_ok (b))
1927 return FALSE;
1928
1929 /* Set up the info block for our subroutines. */
1930 if_info.test_bb = test_bb;
1931 if_info.cond = cond;
1932 if_info.jump = jump;
1933 if_info.insn_a = insn_a;
1934 if_info.insn_b = insn_b;
1935 if_info.x = x;
1936 if_info.a = a;
1937 if_info.b = b;
1938
1939 /* Try optimizations in some approximation of a useful order. */
1940 /* ??? Should first look to see if X is live incoming at all. If it
1941 isn't, we don't need anything but an unconditional set. */
1942
1943 /* Look and see if A and B are really the same. Avoid creating silly
1944 cmove constructs that no one will fix up later. */
1945 if (rtx_equal_p (a, b))
1946 {
1947 /* If we have an INSN_B, we don't have to create any new rtl. Just
1948 move the instruction that we already have. If we don't have an
1949 INSN_B, that means that A == X, and we've got a noop move. In
1950 that case don't do anything and let the code below delete INSN_A. */
1951 if (insn_b && else_bb)
1952 {
1953 rtx note;
1954
1955 if (else_bb && insn_b == BB_END (else_bb))
1956 BB_END (else_bb) = PREV_INSN (insn_b);
1957 reorder_insns (insn_b, insn_b, PREV_INSN (jump));
1958
1959 /* If there was a REG_EQUAL note, delete it since it may have been
1960 true due to this insn being after a jump. */
1961 if ((note = find_reg_note (insn_b, REG_EQUAL, NULL_RTX)) != 0)
1962 remove_note (insn_b, note);
1963
1964 insn_b = NULL_RTX;
1965 }
1966 /* If we have "x = b; if (...) x = a;", and x has side-effects, then
1967 x must be executed twice. */
1968 else if (insn_b && side_effects_p (orig_x))
1969 return FALSE;
1970
1971 x = orig_x;
1972 goto success;
1973 }
1974
1975 /* Disallow the "if (...) x = a;" form (with an implicit "else x = x;")
1976 for most optimizations if writing to x may trap, i.e. its a memory
1977 other than a static var or a stack slot. */
1978 if (! set_b
1979 && GET_CODE (orig_x) == MEM
1980 && ! MEM_NOTRAP_P (orig_x)
1981 && rtx_addr_can_trap_p (XEXP (orig_x, 0)))
1982 {
1983 if (HAVE_conditional_move)
1984 {
1985 if (noce_try_cmove (&if_info))
1986 goto success;
1987 if (! HAVE_conditional_execution
1988 && noce_try_cmove_arith (&if_info))
1989 goto success;
1990 }
1991 return FALSE;
1992 }
1993
1994 if (noce_try_move (&if_info))
1995 goto success;
1996 if (noce_try_store_flag (&if_info))
1997 goto success;
1998 if (noce_try_minmax (&if_info))
1999 goto success;
2000 if (noce_try_abs (&if_info))
2001 goto success;
2002 if (HAVE_conditional_move
2003 && noce_try_cmove (&if_info))
2004 goto success;
2005 if (! HAVE_conditional_execution)
2006 {
2007 if (noce_try_store_flag_constants (&if_info))
2008 goto success;
2009 if (noce_try_addcc (&if_info))
2010 goto success;
2011 if (noce_try_store_flag_mask (&if_info))
2012 goto success;
2013 if (HAVE_conditional_move
2014 && noce_try_cmove_arith (&if_info))
2015 goto success;
2016 }
2017
2018 return FALSE;
2019
2020 success:
2021 /* The original sets may now be killed. */
2022 delete_insn (insn_a);
2023
2024 /* Several special cases here: First, we may have reused insn_b above,
2025 in which case insn_b is now NULL. Second, we want to delete insn_b
2026 if it came from the ELSE block, because follows the now correct
2027 write that appears in the TEST block. However, if we got insn_b from
2028 the TEST block, it may in fact be loading data needed for the comparison.
2029 We'll let life_analysis remove the insn if it's really dead. */
2030 if (insn_b && else_bb)
2031 delete_insn (insn_b);
2032
2033 /* The new insns will have been inserted immediately before the jump. We
2034 should be able to remove the jump with impunity, but the condition itself
2035 may have been modified by gcse to be shared across basic blocks. */
2036 delete_insn (jump);
2037
2038 /* If we used a temporary, fix it up now. */
2039 if (orig_x != x)
2040 {
2041 start_sequence ();
2042 noce_emit_move_insn (orig_x, x);
2043 insn_b = get_insns ();
2044 set_used_flags (orig_x);
2045 unshare_all_rtl_in_chain (insn_b);
2046 end_sequence ();
2047
2048 emit_insn_after_setloc (insn_b, BB_END (test_bb), INSN_LOCATOR (insn_a));
2049 }
2050
2051 /* Merge the blocks! */
2052 merge_if_block (ce_info);
2053
2054 return TRUE;
2055 }
2056
2057 /* Attempt to convert an IF-THEN or IF-THEN-ELSE block into
2058 straight line code. Return true if successful. */
2059
2060 static int
process_if_block(struct ce_if_block * ce_info)2061 process_if_block (struct ce_if_block * ce_info)
2062 {
2063 if (! reload_completed
2064 && noce_process_if_block (ce_info))
2065 return TRUE;
2066
2067 if (HAVE_conditional_execution && reload_completed)
2068 {
2069 /* If we have && and || tests, try to first handle combining the && and
2070 || tests into the conditional code, and if that fails, go back and
2071 handle it without the && and ||, which at present handles the && case
2072 if there was no ELSE block. */
2073 if (cond_exec_process_if_block (ce_info, TRUE))
2074 return TRUE;
2075
2076 if (ce_info->num_multiple_test_blocks)
2077 {
2078 cancel_changes (0);
2079
2080 if (cond_exec_process_if_block (ce_info, FALSE))
2081 return TRUE;
2082 }
2083 }
2084
2085 return FALSE;
2086 }
2087
2088 /* Merge the blocks and mark for local life update. */
2089
2090 static void
merge_if_block(struct ce_if_block * ce_info)2091 merge_if_block (struct ce_if_block * ce_info)
2092 {
2093 basic_block test_bb = ce_info->test_bb; /* last test block */
2094 basic_block then_bb = ce_info->then_bb; /* THEN */
2095 basic_block else_bb = ce_info->else_bb; /* ELSE or NULL */
2096 basic_block join_bb = ce_info->join_bb; /* join block */
2097 basic_block combo_bb;
2098
2099 /* All block merging is done into the lower block numbers. */
2100
2101 combo_bb = test_bb;
2102
2103 /* Merge any basic blocks to handle && and || subtests. Each of
2104 the blocks are on the fallthru path from the predecessor block. */
2105 if (ce_info->num_multiple_test_blocks > 0)
2106 {
2107 basic_block bb = test_bb;
2108 basic_block last_test_bb = ce_info->last_test_bb;
2109 basic_block fallthru = block_fallthru (bb);
2110
2111 do
2112 {
2113 bb = fallthru;
2114 fallthru = block_fallthru (bb);
2115 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2116 delete_from_dominance_info (CDI_POST_DOMINATORS, bb);
2117 merge_blocks (combo_bb, bb);
2118 num_true_changes++;
2119 }
2120 while (bb != last_test_bb);
2121 }
2122
2123 /* Merge TEST block into THEN block. Normally the THEN block won't have a
2124 label, but it might if there were || tests. That label's count should be
2125 zero, and it normally should be removed. */
2126
2127 if (then_bb)
2128 {
2129 if (combo_bb->global_live_at_end)
2130 COPY_REG_SET (combo_bb->global_live_at_end,
2131 then_bb->global_live_at_end);
2132 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2133 delete_from_dominance_info (CDI_POST_DOMINATORS, then_bb);
2134 merge_blocks (combo_bb, then_bb);
2135 num_true_changes++;
2136 }
2137
2138 /* The ELSE block, if it existed, had a label. That label count
2139 will almost always be zero, but odd things can happen when labels
2140 get their addresses taken. */
2141 if (else_bb)
2142 {
2143 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2144 delete_from_dominance_info (CDI_POST_DOMINATORS, else_bb);
2145 merge_blocks (combo_bb, else_bb);
2146 num_true_changes++;
2147 }
2148
2149 /* If there was no join block reported, that means it was not adjacent
2150 to the others, and so we cannot merge them. */
2151
2152 if (! join_bb)
2153 {
2154 rtx last = BB_END (combo_bb);
2155
2156 /* The outgoing edge for the current COMBO block should already
2157 be correct. Verify this. */
2158 if (combo_bb->succ == NULL_EDGE)
2159 {
2160 if (find_reg_note (last, REG_NORETURN, NULL))
2161 ;
2162 else if (GET_CODE (last) == INSN
2163 && GET_CODE (PATTERN (last)) == TRAP_IF
2164 && TRAP_CONDITION (PATTERN (last)) == const_true_rtx)
2165 ;
2166 else
2167 abort ();
2168 }
2169
2170 /* There should still be something at the end of the THEN or ELSE
2171 blocks taking us to our final destination. */
2172 else if (GET_CODE (last) == JUMP_INSN)
2173 ;
2174 else if (combo_bb->succ->dest == EXIT_BLOCK_PTR
2175 && GET_CODE (last) == CALL_INSN
2176 && SIBLING_CALL_P (last))
2177 ;
2178 else if ((combo_bb->succ->flags & EDGE_EH)
2179 && can_throw_internal (last))
2180 ;
2181 else
2182 abort ();
2183 }
2184
2185 /* The JOIN block may have had quite a number of other predecessors too.
2186 Since we've already merged the TEST, THEN and ELSE blocks, we should
2187 have only one remaining edge from our if-then-else diamond. If there
2188 is more than one remaining edge, it must come from elsewhere. There
2189 may be zero incoming edges if the THEN block didn't actually join
2190 back up (as with a call to abort). */
2191 else if ((join_bb->pred == NULL
2192 || join_bb->pred->pred_next == NULL)
2193 && join_bb != EXIT_BLOCK_PTR)
2194 {
2195 /* We can merge the JOIN. */
2196 if (combo_bb->global_live_at_end)
2197 COPY_REG_SET (combo_bb->global_live_at_end,
2198 join_bb->global_live_at_end);
2199
2200 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2201 delete_from_dominance_info (CDI_POST_DOMINATORS, join_bb);
2202 merge_blocks (combo_bb, join_bb);
2203 num_true_changes++;
2204 }
2205 else
2206 {
2207 /* We cannot merge the JOIN. */
2208
2209 /* The outgoing edge for the current COMBO block should already
2210 be correct. Verify this. */
2211 if (combo_bb->succ->succ_next != NULL_EDGE
2212 || combo_bb->succ->dest != join_bb)
2213 abort ();
2214
2215 /* Remove the jump and cruft from the end of the COMBO block. */
2216 if (join_bb != EXIT_BLOCK_PTR)
2217 tidy_fallthru_edge (combo_bb->succ, combo_bb, join_bb);
2218 }
2219
2220 num_updated_if_blocks++;
2221 }
2222
2223 /* Find a block ending in a simple IF condition and try to transform it
2224 in some way. When converting a multi-block condition, put the new code
2225 in the first such block and delete the rest. Return a pointer to this
2226 first block if some transformation was done. Return NULL otherwise. */
2227
2228 static basic_block
find_if_header(basic_block test_bb,int pass)2229 find_if_header (basic_block test_bb, int pass)
2230 {
2231 ce_if_block_t ce_info;
2232 edge then_edge;
2233 edge else_edge;
2234
2235 /* The kind of block we're looking for has exactly two successors. */
2236 if ((then_edge = test_bb->succ) == NULL_EDGE
2237 || (else_edge = then_edge->succ_next) == NULL_EDGE
2238 || else_edge->succ_next != NULL_EDGE)
2239 return NULL;
2240
2241 /* Neither edge should be abnormal. */
2242 if ((then_edge->flags & EDGE_COMPLEX)
2243 || (else_edge->flags & EDGE_COMPLEX))
2244 return NULL;
2245
2246 /* Nor exit the loop. */
2247 if ((then_edge->flags & EDGE_LOOP_EXIT)
2248 || (else_edge->flags & EDGE_LOOP_EXIT))
2249 return NULL;
2250
2251 /* The THEN edge is canonically the one that falls through. */
2252 if (then_edge->flags & EDGE_FALLTHRU)
2253 ;
2254 else if (else_edge->flags & EDGE_FALLTHRU)
2255 {
2256 edge e = else_edge;
2257 else_edge = then_edge;
2258 then_edge = e;
2259 }
2260 else
2261 /* Otherwise this must be a multiway branch of some sort. */
2262 return NULL;
2263
2264 memset (&ce_info, '\0', sizeof (ce_info));
2265 ce_info.test_bb = test_bb;
2266 ce_info.then_bb = then_edge->dest;
2267 ce_info.else_bb = else_edge->dest;
2268 ce_info.pass = pass;
2269
2270 #ifdef IFCVT_INIT_EXTRA_FIELDS
2271 IFCVT_INIT_EXTRA_FIELDS (&ce_info);
2272 #endif
2273
2274 if (find_if_block (&ce_info))
2275 goto success;
2276
2277 if (HAVE_trap && HAVE_conditional_trap
2278 && find_cond_trap (test_bb, then_edge, else_edge))
2279 goto success;
2280
2281 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY
2282 && (! HAVE_conditional_execution || reload_completed))
2283 {
2284 if (find_if_case_1 (test_bb, then_edge, else_edge))
2285 goto success;
2286 if (find_if_case_2 (test_bb, then_edge, else_edge))
2287 goto success;
2288 }
2289
2290 return NULL;
2291
2292 success:
2293 if (rtl_dump_file)
2294 fprintf (rtl_dump_file, "Conversion succeeded on pass %d.\n", pass);
2295 return ce_info.test_bb;
2296 }
2297
2298 /* Return true if a block has two edges, one of which falls through to the next
2299 block, and the other jumps to a specific block, so that we can tell if the
2300 block is part of an && test or an || test. Returns either -1 or the number
2301 of non-note, non-jump, non-USE/CLOBBER insns in the block. */
2302
2303 static int
block_jumps_and_fallthru_p(basic_block cur_bb,basic_block target_bb)2304 block_jumps_and_fallthru_p (basic_block cur_bb, basic_block target_bb)
2305 {
2306 edge cur_edge;
2307 int fallthru_p = FALSE;
2308 int jump_p = FALSE;
2309 rtx insn;
2310 rtx end;
2311 int n_insns = 0;
2312
2313 if (!cur_bb || !target_bb)
2314 return -1;
2315
2316 /* If no edges, obviously it doesn't jump or fallthru. */
2317 if (cur_bb->succ == NULL_EDGE)
2318 return FALSE;
2319
2320 for (cur_edge = cur_bb->succ;
2321 cur_edge != NULL_EDGE;
2322 cur_edge = cur_edge->succ_next)
2323 {
2324 if (cur_edge->flags & EDGE_COMPLEX)
2325 /* Anything complex isn't what we want. */
2326 return -1;
2327
2328 else if (cur_edge->flags & EDGE_FALLTHRU)
2329 fallthru_p = TRUE;
2330
2331 else if (cur_edge->dest == target_bb)
2332 jump_p = TRUE;
2333
2334 else
2335 return -1;
2336 }
2337
2338 if ((jump_p & fallthru_p) == 0)
2339 return -1;
2340
2341 /* Don't allow calls in the block, since this is used to group && and ||
2342 together for conditional execution support. ??? we should support
2343 conditional execution support across calls for IA-64 some day, but
2344 for now it makes the code simpler. */
2345 end = BB_END (cur_bb);
2346 insn = BB_HEAD (cur_bb);
2347
2348 while (insn != NULL_RTX)
2349 {
2350 if (GET_CODE (insn) == CALL_INSN)
2351 return -1;
2352
2353 if (INSN_P (insn)
2354 && GET_CODE (insn) != JUMP_INSN
2355 && GET_CODE (PATTERN (insn)) != USE
2356 && GET_CODE (PATTERN (insn)) != CLOBBER)
2357 n_insns++;
2358
2359 if (insn == end)
2360 break;
2361
2362 insn = NEXT_INSN (insn);
2363 }
2364
2365 return n_insns;
2366 }
2367
2368 /* Determine if a given basic block heads a simple IF-THEN or IF-THEN-ELSE
2369 block. If so, we'll try to convert the insns to not require the branch.
2370 Return TRUE if we were successful at converting the block. */
2371
2372 static int
find_if_block(struct ce_if_block * ce_info)2373 find_if_block (struct ce_if_block * ce_info)
2374 {
2375 basic_block test_bb = ce_info->test_bb;
2376 basic_block then_bb = ce_info->then_bb;
2377 basic_block else_bb = ce_info->else_bb;
2378 basic_block join_bb = NULL_BLOCK;
2379 edge then_succ = then_bb->succ;
2380 edge else_succ = else_bb->succ;
2381 int then_predecessors;
2382 int else_predecessors;
2383 edge cur_edge;
2384 basic_block next;
2385
2386 ce_info->last_test_bb = test_bb;
2387
2388 /* Discover if any fall through predecessors of the current test basic block
2389 were && tests (which jump to the else block) or || tests (which jump to
2390 the then block). */
2391 if (HAVE_conditional_execution && reload_completed
2392 && test_bb->pred != NULL_EDGE
2393 && test_bb->pred->pred_next == NULL_EDGE
2394 && test_bb->pred->flags == EDGE_FALLTHRU)
2395 {
2396 basic_block bb = test_bb->pred->src;
2397 basic_block target_bb;
2398 int max_insns = MAX_CONDITIONAL_EXECUTE;
2399 int n_insns;
2400
2401 /* Determine if the preceding block is an && or || block. */
2402 if ((n_insns = block_jumps_and_fallthru_p (bb, else_bb)) >= 0)
2403 {
2404 ce_info->and_and_p = TRUE;
2405 target_bb = else_bb;
2406 }
2407 else if ((n_insns = block_jumps_and_fallthru_p (bb, then_bb)) >= 0)
2408 {
2409 ce_info->and_and_p = FALSE;
2410 target_bb = then_bb;
2411 }
2412 else
2413 target_bb = NULL_BLOCK;
2414
2415 if (target_bb && n_insns <= max_insns)
2416 {
2417 int total_insns = 0;
2418 int blocks = 0;
2419
2420 ce_info->last_test_bb = test_bb;
2421
2422 /* Found at least one && or || block, look for more. */
2423 do
2424 {
2425 ce_info->test_bb = test_bb = bb;
2426 total_insns += n_insns;
2427 blocks++;
2428
2429 if (bb->pred == NULL_EDGE || bb->pred->pred_next != NULL_EDGE)
2430 break;
2431
2432 bb = bb->pred->src;
2433 n_insns = block_jumps_and_fallthru_p (bb, target_bb);
2434 }
2435 while (n_insns >= 0 && (total_insns + n_insns) <= max_insns);
2436
2437 ce_info->num_multiple_test_blocks = blocks;
2438 ce_info->num_multiple_test_insns = total_insns;
2439
2440 if (ce_info->and_and_p)
2441 ce_info->num_and_and_blocks = blocks;
2442 else
2443 ce_info->num_or_or_blocks = blocks;
2444 }
2445 }
2446
2447 /* Count the number of edges the THEN and ELSE blocks have. */
2448 then_predecessors = 0;
2449 for (cur_edge = then_bb->pred;
2450 cur_edge != NULL_EDGE;
2451 cur_edge = cur_edge->pred_next)
2452 {
2453 then_predecessors++;
2454 if (cur_edge->flags & EDGE_COMPLEX)
2455 return FALSE;
2456 }
2457
2458 else_predecessors = 0;
2459 for (cur_edge = else_bb->pred;
2460 cur_edge != NULL_EDGE;
2461 cur_edge = cur_edge->pred_next)
2462 {
2463 else_predecessors++;
2464 if (cur_edge->flags & EDGE_COMPLEX)
2465 return FALSE;
2466 }
2467
2468 /* The THEN block of an IF-THEN combo must have exactly one predecessor,
2469 other than any || blocks which jump to the THEN block. */
2470 if ((then_predecessors - ce_info->num_or_or_blocks) != 1)
2471 return FALSE;
2472
2473 /* The THEN block of an IF-THEN combo must have zero or one successors. */
2474 if (then_succ != NULL_EDGE
2475 && (then_succ->succ_next != NULL_EDGE
2476 || (then_succ->flags & EDGE_COMPLEX)
2477 || (flow2_completed && tablejump_p (BB_END (then_bb), NULL, NULL))))
2478 return FALSE;
2479
2480 /* If the THEN block has no successors, conditional execution can still
2481 make a conditional call. Don't do this unless the ELSE block has
2482 only one incoming edge -- the CFG manipulation is too ugly otherwise.
2483 Check for the last insn of the THEN block being an indirect jump, which
2484 is listed as not having any successors, but confuses the rest of the CE
2485 code processing. ??? we should fix this in the future. */
2486 if (then_succ == NULL)
2487 {
2488 if (else_bb->pred->pred_next == NULL_EDGE)
2489 {
2490 rtx last_insn = BB_END (then_bb);
2491
2492 while (last_insn
2493 && GET_CODE (last_insn) == NOTE
2494 && last_insn != BB_HEAD (then_bb))
2495 last_insn = PREV_INSN (last_insn);
2496
2497 if (last_insn
2498 && GET_CODE (last_insn) == JUMP_INSN
2499 && ! simplejump_p (last_insn))
2500 return FALSE;
2501
2502 join_bb = else_bb;
2503 else_bb = NULL_BLOCK;
2504 }
2505 else
2506 return FALSE;
2507 }
2508
2509 /* If the THEN block's successor is the other edge out of the TEST block,
2510 then we have an IF-THEN combo without an ELSE. */
2511 else if (then_succ->dest == else_bb)
2512 {
2513 join_bb = else_bb;
2514 else_bb = NULL_BLOCK;
2515 }
2516
2517 /* If the THEN and ELSE block meet in a subsequent block, and the ELSE
2518 has exactly one predecessor and one successor, and the outgoing edge
2519 is not complex, then we have an IF-THEN-ELSE combo. */
2520 else if (else_succ != NULL_EDGE
2521 && then_succ->dest == else_succ->dest
2522 && else_bb->pred->pred_next == NULL_EDGE
2523 && else_succ->succ_next == NULL_EDGE
2524 && ! (else_succ->flags & EDGE_COMPLEX)
2525 && ! (flow2_completed && tablejump_p (BB_END (else_bb), NULL, NULL)))
2526 join_bb = else_succ->dest;
2527
2528 /* Otherwise it is not an IF-THEN or IF-THEN-ELSE combination. */
2529 else
2530 return FALSE;
2531
2532 num_possible_if_blocks++;
2533
2534 if (rtl_dump_file)
2535 {
2536 fprintf (rtl_dump_file, "\nIF-THEN%s block found, pass %d, start block %d [insn %d], then %d [%d]",
2537 (else_bb) ? "-ELSE" : "",
2538 ce_info->pass,
2539 test_bb->index, (BB_HEAD (test_bb)) ? (int)INSN_UID (BB_HEAD (test_bb)) : -1,
2540 then_bb->index, (BB_HEAD (then_bb)) ? (int)INSN_UID (BB_HEAD (then_bb)) : -1);
2541
2542 if (else_bb)
2543 fprintf (rtl_dump_file, ", else %d [%d]",
2544 else_bb->index, (BB_HEAD (else_bb)) ? (int)INSN_UID (BB_HEAD (else_bb)) : -1);
2545
2546 fprintf (rtl_dump_file, ", join %d [%d]",
2547 join_bb->index, (BB_HEAD (join_bb)) ? (int)INSN_UID (BB_HEAD (join_bb)) : -1);
2548
2549 if (ce_info->num_multiple_test_blocks > 0)
2550 fprintf (rtl_dump_file, ", %d %s block%s last test %d [%d]",
2551 ce_info->num_multiple_test_blocks,
2552 (ce_info->and_and_p) ? "&&" : "||",
2553 (ce_info->num_multiple_test_blocks == 1) ? "" : "s",
2554 ce_info->last_test_bb->index,
2555 ((BB_HEAD (ce_info->last_test_bb))
2556 ? (int)INSN_UID (BB_HEAD (ce_info->last_test_bb))
2557 : -1));
2558
2559 fputc ('\n', rtl_dump_file);
2560 }
2561
2562 /* Make sure IF, THEN, and ELSE, blocks are adjacent. Actually, we get the
2563 first condition for free, since we've already asserted that there's a
2564 fallthru edge from IF to THEN. Likewise for the && and || blocks, since
2565 we checked the FALLTHRU flag, those are already adjacent to the last IF
2566 block. */
2567 /* ??? As an enhancement, move the ELSE block. Have to deal with
2568 BLOCK notes, if by no other means than aborting the merge if they
2569 exist. Sticky enough I don't want to think about it now. */
2570 next = then_bb;
2571 if (else_bb && (next = next->next_bb) != else_bb)
2572 return FALSE;
2573 if ((next = next->next_bb) != join_bb && join_bb != EXIT_BLOCK_PTR)
2574 {
2575 if (else_bb)
2576 join_bb = NULL;
2577 else
2578 return FALSE;
2579 }
2580
2581 /* Do the real work. */
2582 ce_info->else_bb = else_bb;
2583 ce_info->join_bb = join_bb;
2584
2585 return process_if_block (ce_info);
2586 }
2587
2588 /* Convert a branch over a trap, or a branch
2589 to a trap, into a conditional trap. */
2590
2591 static int
find_cond_trap(basic_block test_bb,edge then_edge,edge else_edge)2592 find_cond_trap (basic_block test_bb, edge then_edge, edge else_edge)
2593 {
2594 basic_block then_bb = then_edge->dest;
2595 basic_block else_bb = else_edge->dest;
2596 basic_block other_bb, trap_bb;
2597 rtx trap, jump, cond, cond_earliest, seq;
2598 enum rtx_code code;
2599
2600 /* Locate the block with the trap instruction. */
2601 /* ??? While we look for no successors, we really ought to allow
2602 EH successors. Need to fix merge_if_block for that to work. */
2603 if ((trap = block_has_only_trap (then_bb)) != NULL)
2604 trap_bb = then_bb, other_bb = else_bb;
2605 else if ((trap = block_has_only_trap (else_bb)) != NULL)
2606 trap_bb = else_bb, other_bb = then_bb;
2607 else
2608 return FALSE;
2609
2610 if (rtl_dump_file)
2611 {
2612 fprintf (rtl_dump_file, "\nTRAP-IF block found, start %d, trap %d\n",
2613 test_bb->index, trap_bb->index);
2614 }
2615
2616 /* If this is not a standard conditional jump, we can't parse it. */
2617 jump = BB_END (test_bb);
2618 cond = noce_get_condition (jump, &cond_earliest);
2619 if (! cond)
2620 return FALSE;
2621
2622 /* If the conditional jump is more than just a conditional jump, then
2623 we can not do if-conversion on this block. */
2624 if (! onlyjump_p (jump))
2625 return FALSE;
2626
2627 /* We must be comparing objects whose modes imply the size. */
2628 if (GET_MODE (XEXP (cond, 0)) == BLKmode)
2629 return FALSE;
2630
2631 /* Reverse the comparison code, if necessary. */
2632 code = GET_CODE (cond);
2633 if (then_bb == trap_bb)
2634 {
2635 code = reversed_comparison_code (cond, jump);
2636 if (code == UNKNOWN)
2637 return FALSE;
2638 }
2639
2640 /* Attempt to generate the conditional trap. */
2641 seq = gen_cond_trap (code, XEXP (cond, 0),
2642 XEXP (cond, 1),
2643 TRAP_CODE (PATTERN (trap)));
2644 if (seq == NULL)
2645 return FALSE;
2646
2647 num_true_changes++;
2648
2649 /* Emit the new insns before cond_earliest. */
2650 emit_insn_before_setloc (seq, cond_earliest, INSN_LOCATOR (trap));
2651
2652 /* Delete the trap block if possible. */
2653 remove_edge (trap_bb == then_bb ? then_edge : else_edge);
2654 if (trap_bb->pred == NULL)
2655 {
2656 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2657 delete_from_dominance_info (CDI_POST_DOMINATORS, trap_bb);
2658 delete_block (trap_bb);
2659 }
2660
2661 /* If the non-trap block and the test are now adjacent, merge them.
2662 Otherwise we must insert a direct branch. */
2663 if (test_bb->next_bb == other_bb)
2664 {
2665 struct ce_if_block new_ce_info;
2666 delete_insn (jump);
2667 memset (&new_ce_info, '\0', sizeof (new_ce_info));
2668 new_ce_info.test_bb = test_bb;
2669 new_ce_info.then_bb = NULL;
2670 new_ce_info.else_bb = NULL;
2671 new_ce_info.join_bb = other_bb;
2672 merge_if_block (&new_ce_info);
2673 }
2674 else
2675 {
2676 rtx lab, newjump;
2677
2678 lab = JUMP_LABEL (jump);
2679 newjump = emit_jump_insn_after (gen_jump (lab), jump);
2680 LABEL_NUSES (lab) += 1;
2681 JUMP_LABEL (newjump) = lab;
2682 emit_barrier_after (newjump);
2683
2684 delete_insn (jump);
2685 }
2686
2687 return TRUE;
2688 }
2689
2690 /* Subroutine of find_cond_trap: if BB contains only a trap insn,
2691 return it. */
2692
2693 static rtx
block_has_only_trap(basic_block bb)2694 block_has_only_trap (basic_block bb)
2695 {
2696 rtx trap;
2697
2698 /* We're not the exit block. */
2699 if (bb == EXIT_BLOCK_PTR)
2700 return NULL_RTX;
2701
2702 /* The block must have no successors. */
2703 if (bb->succ)
2704 return NULL_RTX;
2705
2706 /* The only instruction in the THEN block must be the trap. */
2707 trap = first_active_insn (bb);
2708 if (! (trap == BB_END (bb)
2709 && GET_CODE (PATTERN (trap)) == TRAP_IF
2710 && TRAP_CONDITION (PATTERN (trap)) == const_true_rtx))
2711 return NULL_RTX;
2712
2713 return trap;
2714 }
2715
2716 /* Look for IF-THEN-ELSE cases in which one of THEN or ELSE is
2717 transformable, but not necessarily the other. There need be no
2718 JOIN block.
2719
2720 Return TRUE if we were successful at converting the block.
2721
2722 Cases we'd like to look at:
2723
2724 (1)
2725 if (test) goto over; // x not live
2726 x = a;
2727 goto label;
2728 over:
2729
2730 becomes
2731
2732 x = a;
2733 if (! test) goto label;
2734
2735 (2)
2736 if (test) goto E; // x not live
2737 x = big();
2738 goto L;
2739 E:
2740 x = b;
2741 goto M;
2742
2743 becomes
2744
2745 x = b;
2746 if (test) goto M;
2747 x = big();
2748 goto L;
2749
2750 (3) // This one's really only interesting for targets that can do
2751 // multiway branching, e.g. IA-64 BBB bundles. For other targets
2752 // it results in multiple branches on a cache line, which often
2753 // does not sit well with predictors.
2754
2755 if (test1) goto E; // predicted not taken
2756 x = a;
2757 if (test2) goto F;
2758 ...
2759 E:
2760 x = b;
2761 J:
2762
2763 becomes
2764
2765 x = a;
2766 if (test1) goto E;
2767 if (test2) goto F;
2768
2769 Notes:
2770
2771 (A) Don't do (2) if the branch is predicted against the block we're
2772 eliminating. Do it anyway if we can eliminate a branch; this requires
2773 that the sole successor of the eliminated block postdominate the other
2774 side of the if.
2775
2776 (B) With CE, on (3) we can steal from both sides of the if, creating
2777
2778 if (test1) x = a;
2779 if (!test1) x = b;
2780 if (test1) goto J;
2781 if (test2) goto F;
2782 ...
2783 J:
2784
2785 Again, this is most useful if J postdominates.
2786
2787 (C) CE substitutes for helpful life information.
2788
2789 (D) These heuristics need a lot of work. */
2790
2791 /* Tests for case 1 above. */
2792
2793 static int
find_if_case_1(basic_block test_bb,edge then_edge,edge else_edge)2794 find_if_case_1 (basic_block test_bb, edge then_edge, edge else_edge)
2795 {
2796 basic_block then_bb = then_edge->dest;
2797 basic_block else_bb = else_edge->dest, new_bb;
2798 edge then_succ = then_bb->succ;
2799 int then_bb_index;
2800
2801 /* THEN has one successor. */
2802 if (!then_succ || then_succ->succ_next != NULL)
2803 return FALSE;
2804
2805 /* THEN does not fall through, but is not strange either. */
2806 if (then_succ->flags & (EDGE_COMPLEX | EDGE_FALLTHRU))
2807 return FALSE;
2808
2809 /* THEN has one predecessor. */
2810 if (then_bb->pred->pred_next != NULL)
2811 return FALSE;
2812
2813 /* THEN must do something. */
2814 if (forwarder_block_p (then_bb))
2815 return FALSE;
2816
2817 num_possible_if_blocks++;
2818 if (rtl_dump_file)
2819 fprintf (rtl_dump_file,
2820 "\nIF-CASE-1 found, start %d, then %d\n",
2821 test_bb->index, then_bb->index);
2822
2823 /* THEN is small. */
2824 if (count_bb_insns (then_bb) > BRANCH_COST)
2825 return FALSE;
2826
2827 /* Registers set are dead, or are predicable. */
2828 if (! dead_or_predicable (test_bb, then_bb, else_bb,
2829 then_bb->succ->dest, 1))
2830 return FALSE;
2831
2832 /* Conversion went ok, including moving the insns and fixing up the
2833 jump. Adjust the CFG to match. */
2834
2835 bitmap_operation (test_bb->global_live_at_end,
2836 else_bb->global_live_at_start,
2837 then_bb->global_live_at_end, BITMAP_IOR);
2838
2839 new_bb = redirect_edge_and_branch_force (FALLTHRU_EDGE (test_bb), else_bb);
2840 then_bb_index = then_bb->index;
2841 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2842 delete_from_dominance_info (CDI_POST_DOMINATORS, then_bb);
2843 delete_block (then_bb);
2844
2845 /* Make rest of code believe that the newly created block is the THEN_BB
2846 block we removed. */
2847 if (new_bb)
2848 {
2849 new_bb->index = then_bb_index;
2850 BASIC_BLOCK (then_bb_index) = new_bb;
2851 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2852 add_to_dominance_info (CDI_POST_DOMINATORS, new_bb);
2853 }
2854 /* We've possibly created jump to next insn, cleanup_cfg will solve that
2855 later. */
2856
2857 num_true_changes++;
2858 num_updated_if_blocks++;
2859
2860 return TRUE;
2861 }
2862
2863 /* Test for case 2 above. */
2864
2865 static int
find_if_case_2(basic_block test_bb,edge then_edge,edge else_edge)2866 find_if_case_2 (basic_block test_bb, edge then_edge, edge else_edge)
2867 {
2868 basic_block then_bb = then_edge->dest;
2869 basic_block else_bb = else_edge->dest;
2870 edge else_succ = else_bb->succ;
2871 rtx note;
2872
2873 /* ELSE has one successor. */
2874 if (!else_succ || else_succ->succ_next != NULL)
2875 return FALSE;
2876
2877 /* ELSE outgoing edge is not complex. */
2878 if (else_succ->flags & EDGE_COMPLEX)
2879 return FALSE;
2880
2881 /* ELSE has one predecessor. */
2882 if (else_bb->pred->pred_next != NULL)
2883 return FALSE;
2884
2885 /* THEN is not EXIT. */
2886 if (then_bb->index < 0)
2887 return FALSE;
2888
2889 /* ELSE is predicted or SUCC(ELSE) postdominates THEN. */
2890 note = find_reg_note (BB_END (test_bb), REG_BR_PROB, NULL_RTX);
2891 if (note && INTVAL (XEXP (note, 0)) >= REG_BR_PROB_BASE / 2)
2892 ;
2893 else if (else_succ->dest->index < 0
2894 || dominated_by_p (CDI_POST_DOMINATORS, then_bb,
2895 else_succ->dest))
2896 ;
2897 else
2898 return FALSE;
2899
2900 num_possible_if_blocks++;
2901 if (rtl_dump_file)
2902 fprintf (rtl_dump_file,
2903 "\nIF-CASE-2 found, start %d, else %d\n",
2904 test_bb->index, else_bb->index);
2905
2906 /* ELSE is small. */
2907 if (count_bb_insns (else_bb) > BRANCH_COST)
2908 return FALSE;
2909
2910 /* Registers set are dead, or are predicable. */
2911 if (! dead_or_predicable (test_bb, else_bb, then_bb, else_succ->dest, 0))
2912 return FALSE;
2913
2914 /* Conversion went ok, including moving the insns and fixing up the
2915 jump. Adjust the CFG to match. */
2916
2917 bitmap_operation (test_bb->global_live_at_end,
2918 then_bb->global_live_at_start,
2919 else_bb->global_live_at_end, BITMAP_IOR);
2920
2921 if (dom_computed[CDI_POST_DOMINATORS] >= DOM_NO_FAST_QUERY)
2922 delete_from_dominance_info (CDI_POST_DOMINATORS, else_bb);
2923 delete_block (else_bb);
2924
2925 num_true_changes++;
2926 num_updated_if_blocks++;
2927
2928 /* ??? We may now fallthru from one of THEN's successors into a join
2929 block. Rerun cleanup_cfg? Examine things manually? Wait? */
2930
2931 return TRUE;
2932 }
2933
2934 /* A subroutine of dead_or_predicable called through for_each_rtx.
2935 Return 1 if a memory is found. */
2936
2937 static int
find_memory(rtx * px,void * data ATTRIBUTE_UNUSED)2938 find_memory (rtx *px, void *data ATTRIBUTE_UNUSED)
2939 {
2940 return GET_CODE (*px) == MEM;
2941 }
2942
2943 /* Used by the code above to perform the actual rtl transformations.
2944 Return TRUE if successful.
2945
2946 TEST_BB is the block containing the conditional branch. MERGE_BB
2947 is the block containing the code to manipulate. NEW_DEST is the
2948 label TEST_BB should be branching to after the conversion.
2949 REVERSEP is true if the sense of the branch should be reversed. */
2950
2951 static int
dead_or_predicable(basic_block test_bb,basic_block merge_bb,basic_block other_bb,basic_block new_dest,int reversep)2952 dead_or_predicable (basic_block test_bb, basic_block merge_bb,
2953 basic_block other_bb, basic_block new_dest, int reversep)
2954 {
2955 rtx head, end, jump, earliest, old_dest, new_label = NULL_RTX;
2956
2957 jump = BB_END (test_bb);
2958
2959 /* Find the extent of the real code in the merge block. */
2960 head = BB_HEAD (merge_bb);
2961 end = BB_END (merge_bb);
2962
2963 if (GET_CODE (head) == CODE_LABEL)
2964 head = NEXT_INSN (head);
2965 if (GET_CODE (head) == NOTE)
2966 {
2967 if (head == end)
2968 {
2969 head = end = NULL_RTX;
2970 goto no_body;
2971 }
2972 head = NEXT_INSN (head);
2973 }
2974
2975 if (GET_CODE (end) == JUMP_INSN)
2976 {
2977 if (head == end)
2978 {
2979 head = end = NULL_RTX;
2980 goto no_body;
2981 }
2982 end = PREV_INSN (end);
2983 }
2984
2985 /* Disable handling dead code by conditional execution if the machine needs
2986 to do anything funny with the tests, etc. */
2987 #ifndef IFCVT_MODIFY_TESTS
2988 if (HAVE_conditional_execution)
2989 {
2990 /* In the conditional execution case, we have things easy. We know
2991 the condition is reversible. We don't have to check life info
2992 because we're going to conditionally execute the code anyway.
2993 All that's left is making sure the insns involved can actually
2994 be predicated. */
2995
2996 rtx cond, prob_val;
2997
2998 cond = cond_exec_get_condition (jump);
2999 if (! cond)
3000 return FALSE;
3001
3002 prob_val = find_reg_note (jump, REG_BR_PROB, NULL_RTX);
3003 if (prob_val)
3004 prob_val = XEXP (prob_val, 0);
3005
3006 if (reversep)
3007 {
3008 enum rtx_code rev = reversed_comparison_code (cond, jump);
3009 if (rev == UNKNOWN)
3010 return FALSE;
3011 cond = gen_rtx_fmt_ee (rev, GET_MODE (cond), XEXP (cond, 0),
3012 XEXP (cond, 1));
3013 if (prob_val)
3014 prob_val = GEN_INT (REG_BR_PROB_BASE - INTVAL (prob_val));
3015 }
3016
3017 if (! cond_exec_process_insns ((ce_if_block_t *)0, head, end, cond,
3018 prob_val, 0))
3019 goto cancel;
3020
3021 earliest = jump;
3022 }
3023 else
3024 #endif
3025 {
3026 /* In the non-conditional execution case, we have to verify that there
3027 are no trapping operations, no calls, no references to memory, and
3028 that any registers modified are dead at the branch site. */
3029
3030 rtx insn, cond, prev;
3031 regset_head merge_set_head, tmp_head, test_live_head, test_set_head;
3032 regset merge_set, tmp, test_live, test_set;
3033 struct propagate_block_info *pbi;
3034 int i, fail = 0;
3035
3036 /* Check for no calls or trapping operations. */
3037 for (insn = head; ; insn = NEXT_INSN (insn))
3038 {
3039 if (GET_CODE (insn) == CALL_INSN)
3040 return FALSE;
3041 if (INSN_P (insn))
3042 {
3043 if (may_trap_p (PATTERN (insn)))
3044 return FALSE;
3045
3046 /* ??? Even non-trapping memories such as stack frame
3047 references must be avoided. For stores, we collect
3048 no lifetime info; for reads, we'd have to assert
3049 true_dependence false against every store in the
3050 TEST range. */
3051 if (for_each_rtx (&PATTERN (insn), find_memory, NULL))
3052 return FALSE;
3053 }
3054 if (insn == end)
3055 break;
3056 }
3057
3058 if (! any_condjump_p (jump))
3059 return FALSE;
3060
3061 /* Find the extent of the conditional. */
3062 cond = noce_get_condition (jump, &earliest);
3063 if (! cond)
3064 return FALSE;
3065
3066 /* Collect:
3067 MERGE_SET = set of registers set in MERGE_BB
3068 TEST_LIVE = set of registers live at EARLIEST
3069 TEST_SET = set of registers set between EARLIEST and the
3070 end of the block. */
3071
3072 tmp = INITIALIZE_REG_SET (tmp_head);
3073 merge_set = INITIALIZE_REG_SET (merge_set_head);
3074 test_live = INITIALIZE_REG_SET (test_live_head);
3075 test_set = INITIALIZE_REG_SET (test_set_head);
3076
3077 /* ??? bb->local_set is only valid during calculate_global_regs_live,
3078 so we must recompute usage for MERGE_BB. Not so bad, I suppose,
3079 since we've already asserted that MERGE_BB is small. */
3080 propagate_block (merge_bb, tmp, merge_set, merge_set, 0);
3081
3082 /* For small register class machines, don't lengthen lifetimes of
3083 hard registers before reload. */
3084 if (SMALL_REGISTER_CLASSES && ! reload_completed)
3085 {
3086 EXECUTE_IF_SET_IN_BITMAP
3087 (merge_set, 0, i,
3088 {
3089 if (i < FIRST_PSEUDO_REGISTER
3090 && ! fixed_regs[i]
3091 && ! global_regs[i])
3092 fail = 1;
3093 });
3094 }
3095
3096 /* For TEST, we're interested in a range of insns, not a whole block.
3097 Moreover, we're interested in the insns live from OTHER_BB. */
3098
3099 COPY_REG_SET (test_live, other_bb->global_live_at_start);
3100 pbi = init_propagate_block_info (test_bb, test_live, test_set, test_set,
3101 0);
3102
3103 for (insn = jump; ; insn = prev)
3104 {
3105 prev = propagate_one_insn (pbi, insn);
3106 if (insn == earliest)
3107 break;
3108 }
3109
3110 free_propagate_block_info (pbi);
3111
3112 /* We can perform the transformation if
3113 MERGE_SET & (TEST_SET | TEST_LIVE)
3114 and
3115 TEST_SET & merge_bb->global_live_at_start
3116 are empty. */
3117
3118 bitmap_operation (tmp, test_set, test_live, BITMAP_IOR);
3119 bitmap_operation (tmp, tmp, merge_set, BITMAP_AND);
3120 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
3121
3122 bitmap_operation (tmp, test_set, merge_bb->global_live_at_start,
3123 BITMAP_AND);
3124 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
3125
3126 FREE_REG_SET (tmp);
3127 FREE_REG_SET (merge_set);
3128 FREE_REG_SET (test_live);
3129 FREE_REG_SET (test_set);
3130
3131 if (fail)
3132 return FALSE;
3133 }
3134
3135 no_body:
3136 /* We don't want to use normal invert_jump or redirect_jump because
3137 we don't want to delete_insn called. Also, we want to do our own
3138 change group management. */
3139
3140 old_dest = JUMP_LABEL (jump);
3141 if (other_bb != new_dest)
3142 {
3143 new_label = block_label (new_dest);
3144 if (reversep
3145 ? ! invert_jump_1 (jump, new_label)
3146 : ! redirect_jump_1 (jump, new_label))
3147 goto cancel;
3148 }
3149
3150 if (! apply_change_group ())
3151 return FALSE;
3152
3153 if (other_bb != new_dest)
3154 {
3155 if (old_dest)
3156 LABEL_NUSES (old_dest) -= 1;
3157 if (new_label)
3158 LABEL_NUSES (new_label) += 1;
3159 JUMP_LABEL (jump) = new_label;
3160 if (reversep)
3161 invert_br_probabilities (jump);
3162
3163 redirect_edge_succ (BRANCH_EDGE (test_bb), new_dest);
3164 if (reversep)
3165 {
3166 gcov_type count, probability;
3167 count = BRANCH_EDGE (test_bb)->count;
3168 BRANCH_EDGE (test_bb)->count = FALLTHRU_EDGE (test_bb)->count;
3169 FALLTHRU_EDGE (test_bb)->count = count;
3170 probability = BRANCH_EDGE (test_bb)->probability;
3171 BRANCH_EDGE (test_bb)->probability
3172 = FALLTHRU_EDGE (test_bb)->probability;
3173 FALLTHRU_EDGE (test_bb)->probability = probability;
3174 update_br_prob_note (test_bb);
3175 }
3176 }
3177
3178 /* Move the insns out of MERGE_BB to before the branch. */
3179 if (head != NULL)
3180 {
3181 if (end == BB_END (merge_bb))
3182 BB_END (merge_bb) = PREV_INSN (head);
3183
3184 if (squeeze_notes (&head, &end))
3185 return TRUE;
3186
3187 reorder_insns (head, end, PREV_INSN (earliest));
3188 }
3189
3190 /* Remove the jump and edge if we can. */
3191 if (other_bb == new_dest)
3192 {
3193 delete_insn (jump);
3194 remove_edge (BRANCH_EDGE (test_bb));
3195 /* ??? Can't merge blocks here, as then_bb is still in use.
3196 At minimum, the merge will get done just before bb-reorder. */
3197 }
3198
3199 return TRUE;
3200
3201 cancel:
3202 cancel_changes (0);
3203 return FALSE;
3204 }
3205
3206 /* Main entry point for all if-conversion. */
3207
3208 void
if_convert(int x_life_data_ok)3209 if_convert (int x_life_data_ok)
3210 {
3211 basic_block bb;
3212 int pass;
3213
3214 num_possible_if_blocks = 0;
3215 num_updated_if_blocks = 0;
3216 num_true_changes = 0;
3217 life_data_ok = (x_life_data_ok != 0);
3218
3219 if (! (* targetm.cannot_modify_jumps_p) ())
3220 mark_loop_exit_edges ();
3221
3222 /* Free up basic_block_for_insn so that we don't have to keep it
3223 up to date, either here or in merge_blocks. */
3224 free_basic_block_vars (1);
3225
3226 /* Compute postdominators if we think we'll use them. */
3227 if (HAVE_conditional_execution || life_data_ok)
3228 calculate_dominance_info (CDI_POST_DOMINATORS);
3229
3230 if (life_data_ok)
3231 clear_bb_flags ();
3232
3233 /* Go through each of the basic blocks looking for things to convert. If we
3234 have conditional execution, we make multiple passes to allow us to handle
3235 IF-THEN{-ELSE} blocks within other IF-THEN{-ELSE} blocks. */
3236 pass = 0;
3237 do
3238 {
3239 cond_exec_changed_p = FALSE;
3240 pass++;
3241
3242 #ifdef IFCVT_MULTIPLE_DUMPS
3243 if (rtl_dump_file && pass > 1)
3244 fprintf (rtl_dump_file, "\n\n========== Pass %d ==========\n", pass);
3245 #endif
3246
3247 FOR_EACH_BB (bb)
3248 {
3249 basic_block new_bb;
3250 while ((new_bb = find_if_header (bb, pass)))
3251 bb = new_bb;
3252 }
3253
3254 #ifdef IFCVT_MULTIPLE_DUMPS
3255 if (rtl_dump_file && cond_exec_changed_p)
3256 print_rtl_with_bb (rtl_dump_file, get_insns ());
3257 #endif
3258 }
3259 while (cond_exec_changed_p);
3260
3261 #ifdef IFCVT_MULTIPLE_DUMPS
3262 if (rtl_dump_file)
3263 fprintf (rtl_dump_file, "\n\n========== no more changes\n");
3264 #endif
3265
3266 free_dominance_info (CDI_POST_DOMINATORS);
3267
3268 if (rtl_dump_file)
3269 fflush (rtl_dump_file);
3270
3271 clear_aux_for_blocks ();
3272
3273 /* Rebuild life info for basic blocks that require it. */
3274 if (num_true_changes && life_data_ok)
3275 {
3276 /* If we allocated new pseudos, we must resize the array for sched1. */
3277 if (max_regno < max_reg_num ())
3278 {
3279 max_regno = max_reg_num ();
3280 allocate_reg_info (max_regno, FALSE, FALSE);
3281 }
3282 update_life_info_in_dirty_blocks (UPDATE_LIFE_GLOBAL_RM_NOTES,
3283 PROP_DEATH_NOTES | PROP_SCAN_DEAD_CODE
3284 | PROP_KILL_DEAD_CODE);
3285 }
3286
3287 /* Write the final stats. */
3288 if (rtl_dump_file && num_possible_if_blocks > 0)
3289 {
3290 fprintf (rtl_dump_file,
3291 "\n%d possible IF blocks searched.\n",
3292 num_possible_if_blocks);
3293 fprintf (rtl_dump_file,
3294 "%d IF blocks converted.\n",
3295 num_updated_if_blocks);
3296 fprintf (rtl_dump_file,
3297 "%d true changes made.\n\n\n",
3298 num_true_changes);
3299 }
3300
3301 #ifdef ENABLE_CHECKING
3302 verify_flow_info ();
3303 #endif
3304 }
3305