* cfgloop.c (flow_loop_entry_edges_find): Fix typo.
[official-gcc.git] / gcc / ifcvt.c
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1 /* If-conversion support.
2 Copyright (C) 2000, 2001 Free Software Foundation, Inc.
4 This file is part of GCC.
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.
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.
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. */
21 #include "config.h"
22 #include "system.h"
24 #include "rtl.h"
25 #include "regs.h"
26 #include "function.h"
27 #include "flags.h"
28 #include "insn-config.h"
29 #include "recog.h"
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
32 #include "expr.h"
33 #include "real.h"
34 #include "output.h"
35 #include "toplev.h"
36 #include "tm_p.h"
39 #ifndef HAVE_conditional_execution
40 #define HAVE_conditional_execution 0
41 #endif
42 #ifndef HAVE_conditional_move
43 #define HAVE_conditional_move 0
44 #endif
45 #ifndef HAVE_incscc
46 #define HAVE_incscc 0
47 #endif
48 #ifndef HAVE_decscc
49 #define HAVE_decscc 0
50 #endif
51 #ifndef HAVE_trap
52 #define HAVE_trap 0
53 #endif
54 #ifndef HAVE_conditional_trap
55 #define HAVE_conditional_trap 0
56 #endif
58 #ifndef MAX_CONDITIONAL_EXECUTE
59 #define MAX_CONDITIONAL_EXECUTE (BRANCH_COST + 1)
60 #endif
62 #define NULL_EDGE ((struct edge_def *)NULL)
63 #define NULL_BLOCK ((struct basic_block_def *)NULL)
65 /* # of IF-THEN or IF-THEN-ELSE blocks we looked at */
66 static int num_possible_if_blocks;
68 /* # of IF-THEN or IF-THEN-ELSE blocks were converted to conditional
69 execution. */
70 static int num_updated_if_blocks;
72 /* # of basic blocks that were removed. */
73 static int num_removed_blocks;
75 /* True if life data ok at present. */
76 static bool life_data_ok;
78 /* The post-dominator relation on the original block numbers. */
79 static sbitmap *post_dominators;
81 /* Forward references. */
82 static int count_bb_insns PARAMS ((basic_block));
83 static rtx first_active_insn PARAMS ((basic_block));
84 static int last_active_insn_p PARAMS ((basic_block, rtx));
85 static int seq_contains_jump PARAMS ((rtx));
87 static int cond_exec_process_insns PARAMS ((rtx, rtx, rtx, rtx, int));
88 static rtx cond_exec_get_condition PARAMS ((rtx));
89 static int cond_exec_process_if_block PARAMS ((basic_block, basic_block,
90 basic_block, basic_block));
92 static rtx noce_get_condition PARAMS ((rtx, rtx *));
93 static int noce_operand_ok PARAMS ((rtx));
94 static int noce_process_if_block PARAMS ((basic_block, basic_block,
95 basic_block, basic_block));
97 static int process_if_block PARAMS ((basic_block, basic_block,
98 basic_block, basic_block));
99 static void merge_if_block PARAMS ((basic_block, basic_block,
100 basic_block, basic_block));
102 static int find_if_header PARAMS ((basic_block));
103 static int find_if_block PARAMS ((basic_block, edge, edge));
104 static int find_if_case_1 PARAMS ((basic_block, edge, edge));
105 static int find_if_case_2 PARAMS ((basic_block, edge, edge));
106 static int find_cond_trap PARAMS ((basic_block, edge, edge));
107 static int find_memory PARAMS ((rtx *, void *));
108 static int dead_or_predicable PARAMS ((basic_block, basic_block,
109 basic_block, basic_block, int));
110 static void noce_emit_move_insn PARAMS ((rtx, rtx));
112 /* Abuse the basic_block AUX field to store the original block index,
113 as well as a flag indicating that the block should be rescaned for
114 life analysis. */
116 #define SET_ORIG_INDEX(BB,I) ((BB)->aux = (void *)((size_t)(I) << 1))
117 #define ORIG_INDEX(BB) ((size_t)(BB)->aux >> 1)
118 #define SET_UPDATE_LIFE(BB) ((BB)->aux = (void *)((size_t)(BB)->aux | 1))
119 #define UPDATE_LIFE(BB) ((size_t)(BB)->aux & 1)
122 /* Count the number of non-jump active insns in BB. */
124 static int
125 count_bb_insns (bb)
126 basic_block bb;
128 int count = 0;
129 rtx insn = bb->head;
131 while (1)
133 if (GET_CODE (insn) == CALL_INSN || GET_CODE (insn) == INSN)
134 count++;
136 if (insn == bb->end)
137 break;
138 insn = NEXT_INSN (insn);
141 return count;
144 /* Return the first non-jump active insn in the basic block. */
146 static rtx
147 first_active_insn (bb)
148 basic_block bb;
150 rtx insn = bb->head;
152 if (GET_CODE (insn) == CODE_LABEL)
154 if (insn == bb->end)
155 return NULL_RTX;
156 insn = NEXT_INSN (insn);
159 while (GET_CODE (insn) == NOTE)
161 if (insn == bb->end)
162 return NULL_RTX;
163 insn = NEXT_INSN (insn);
166 if (GET_CODE (insn) == JUMP_INSN)
167 return NULL_RTX;
169 return insn;
172 /* Return true if INSN is the last active non-jump insn in BB. */
174 static int
175 last_active_insn_p (bb, insn)
176 basic_block bb;
177 rtx insn;
181 if (insn == bb->end)
182 return TRUE;
183 insn = NEXT_INSN (insn);
185 while (GET_CODE (insn) == NOTE);
187 return GET_CODE (insn) == JUMP_INSN;
190 /* It is possible, especially when having dealt with multi-word
191 arithmetic, for the expanders to have emitted jumps. Search
192 through the sequence and return TRUE if a jump exists so that
193 we can abort the conversion. */
195 static int
196 seq_contains_jump (insn)
197 rtx insn;
199 while (insn)
201 if (GET_CODE (insn) == JUMP_INSN)
202 return 1;
203 insn = NEXT_INSN (insn);
205 return 0;
208 /* Go through a bunch of insns, converting them to conditional
209 execution format if possible. Return TRUE if all of the non-note
210 insns were processed. */
212 static int
213 cond_exec_process_insns (start, end, test, prob_val, mod_ok)
214 rtx start; /* first insn to look at */
215 rtx end; /* last insn to look at */
216 rtx test; /* conditional execution test */
217 rtx prob_val; /* probability of branch taken. */
218 int mod_ok; /* true if modifications ok last insn. */
220 int must_be_last = FALSE;
221 rtx insn;
222 rtx pattern;
224 for (insn = start; ; insn = NEXT_INSN (insn))
226 if (GET_CODE (insn) == NOTE)
227 goto insn_done;
229 if (GET_CODE (insn) != INSN && GET_CODE (insn) != CALL_INSN)
230 abort ();
232 /* Remove USE insns that get in the way. */
233 if (reload_completed && GET_CODE (PATTERN (insn)) == USE)
235 /* ??? Ug. Actually unlinking the thing is problematic,
236 given what we'd have to coordinate with our callers. */
237 PUT_CODE (insn, NOTE);
238 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
239 NOTE_SOURCE_FILE (insn) = 0;
240 goto insn_done;
243 /* Last insn wasn't last? */
244 if (must_be_last)
245 return FALSE;
247 if (modified_in_p (test, insn))
249 if (!mod_ok)
250 return FALSE;
251 must_be_last = TRUE;
254 /* Now build the conditional form of the instruction. */
255 pattern = PATTERN (insn);
257 /* If the machine needs to modify the insn being conditionally executed,
258 say for example to force a constant integer operand into a temp
259 register, do so here. */
260 #ifdef IFCVT_MODIFY_INSN
261 IFCVT_MODIFY_INSN (pattern, insn);
262 if (! pattern)
263 return FALSE;
264 #endif
266 validate_change (insn, &PATTERN (insn),
267 gen_rtx_COND_EXEC (VOIDmode, copy_rtx (test),
268 pattern), 1);
270 if (GET_CODE (insn) == CALL_INSN && prob_val)
271 validate_change (insn, &REG_NOTES (insn),
272 alloc_EXPR_LIST (REG_BR_PROB, prob_val,
273 REG_NOTES (insn)), 1);
275 insn_done:
276 if (insn == end)
277 break;
280 return TRUE;
283 /* Return the condition for a jump. Do not do any special processing. */
285 static rtx
286 cond_exec_get_condition (jump)
287 rtx jump;
289 rtx test_if, cond;
291 if (any_condjump_p (jump))
292 test_if = SET_SRC (pc_set (jump));
293 else
294 return NULL_RTX;
295 cond = XEXP (test_if, 0);
297 /* If this branches to JUMP_LABEL when the condition is false,
298 reverse the condition. */
299 if (GET_CODE (XEXP (test_if, 2)) == LABEL_REF
300 && XEXP (XEXP (test_if, 2), 0) == JUMP_LABEL (jump))
302 enum rtx_code rev = reversed_comparison_code (cond, jump);
303 if (rev == UNKNOWN)
304 return NULL_RTX;
306 cond = gen_rtx_fmt_ee (rev, GET_MODE (cond), XEXP (cond, 0),
307 XEXP (cond, 1));
310 return cond;
313 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
314 to conditional execution. Return TRUE if we were successful at
315 converting the the block. */
317 static int
318 cond_exec_process_if_block (test_bb, then_bb, else_bb, join_bb)
319 basic_block test_bb; /* Basic block test is in */
320 basic_block then_bb; /* Basic block for THEN block */
321 basic_block else_bb; /* Basic block for ELSE block */
322 basic_block join_bb; /* Basic block the join label is in */
324 rtx test_expr; /* expression in IF_THEN_ELSE that is tested */
325 rtx then_start; /* first insn in THEN block */
326 rtx then_end; /* last insn + 1 in THEN block */
327 rtx else_start = NULL_RTX; /* first insn in ELSE block or NULL */
328 rtx else_end = NULL_RTX; /* last insn + 1 in ELSE block */
329 int max; /* max # of insns to convert. */
330 int then_mod_ok; /* whether conditional mods are ok in THEN */
331 rtx true_expr; /* test for else block insns */
332 rtx false_expr; /* test for then block insns */
333 rtx true_prob_val; /* probability of else block */
334 rtx false_prob_val; /* probability of then block */
335 int n_insns;
336 enum rtx_code false_code;
338 /* Find the conditional jump to the ELSE or JOIN part, and isolate
339 the test. */
340 test_expr = cond_exec_get_condition (test_bb->end);
341 if (! test_expr)
342 return FALSE;
344 /* If the conditional jump is more than just a conditional jump,
345 then we can not do conditional execution conversion on this block. */
346 if (!onlyjump_p (test_bb->end))
347 return FALSE;
349 /* Collect the bounds of where we're to search. */
351 then_start = then_bb->head;
352 then_end = then_bb->end;
354 /* Skip a label heading THEN block. */
355 if (GET_CODE (then_start) == CODE_LABEL)
356 then_start = NEXT_INSN (then_start);
358 /* Skip a (use (const_int 0)) or branch as the final insn. */
359 if (GET_CODE (then_end) == INSN
360 && GET_CODE (PATTERN (then_end)) == USE
361 && GET_CODE (XEXP (PATTERN (then_end), 0)) == CONST_INT)
362 then_end = PREV_INSN (then_end);
363 else if (GET_CODE (then_end) == JUMP_INSN)
364 then_end = PREV_INSN (then_end);
366 if (else_bb)
368 /* Skip the ELSE block's label. */
369 else_start = NEXT_INSN (else_bb->head);
370 else_end = else_bb->end;
372 /* Skip a (use (const_int 0)) or branch as the final insn. */
373 if (GET_CODE (else_end) == INSN
374 && GET_CODE (PATTERN (else_end)) == USE
375 && GET_CODE (XEXP (PATTERN (else_end), 0)) == CONST_INT)
376 else_end = PREV_INSN (else_end);
377 else if (GET_CODE (else_end) == JUMP_INSN)
378 else_end = PREV_INSN (else_end);
381 /* How many instructions should we convert in total? */
382 n_insns = 0;
383 if (else_bb)
385 max = 2 * MAX_CONDITIONAL_EXECUTE;
386 n_insns = count_bb_insns (else_bb);
388 else
389 max = MAX_CONDITIONAL_EXECUTE;
390 n_insns += count_bb_insns (then_bb);
391 if (n_insns > max)
392 return FALSE;
394 /* Map test_expr/test_jump into the appropriate MD tests to use on
395 the conditionally executed code. */
397 true_expr = test_expr;
399 false_code = reversed_comparison_code (true_expr, test_bb->end);
400 if (false_code != UNKNOWN)
401 false_expr = gen_rtx_fmt_ee (false_code, GET_MODE (true_expr),
402 XEXP (true_expr, 0), XEXP (true_expr, 1));
403 else
404 false_expr = NULL_RTX;
406 #ifdef IFCVT_MODIFY_TESTS
407 /* If the machine description needs to modify the tests, such as setting a
408 conditional execution register from a comparison, it can do so here. */
409 IFCVT_MODIFY_TESTS (true_expr, false_expr, test_bb, then_bb, else_bb,
410 join_bb);
412 /* See if the conversion failed */
413 if (!true_expr || !false_expr)
414 goto fail;
415 #endif
417 true_prob_val = find_reg_note (test_bb->end, REG_BR_PROB, NULL_RTX);
418 if (true_prob_val)
420 true_prob_val = XEXP (true_prob_val, 0);
421 false_prob_val = GEN_INT (REG_BR_PROB_BASE - INTVAL (true_prob_val));
423 else
424 false_prob_val = NULL_RTX;
426 /* For IF-THEN-ELSE blocks, we don't allow modifications of the test
427 on then THEN block. */
428 then_mod_ok = (else_bb == NULL_BLOCK);
430 /* Go through the THEN and ELSE blocks converting the insns if possible
431 to conditional execution. */
433 if (then_end
434 && (! false_expr
435 || ! cond_exec_process_insns (then_start, then_end, false_expr,
436 false_prob_val, then_mod_ok)))
437 goto fail;
439 if (else_bb
440 && ! cond_exec_process_insns (else_start, else_end,
441 true_expr, true_prob_val, TRUE))
442 goto fail;
444 if (! apply_change_group ())
445 return FALSE;
447 #ifdef IFCVT_MODIFY_FINAL
448 /* Do any machine dependent final modifications */
449 IFCVT_MODIFY_FINAL (test_bb, then_bb, else_bb, join_bb);
450 #endif
452 /* Conversion succeeded. */
453 if (rtl_dump_file)
454 fprintf (rtl_dump_file, "%d insn%s converted to conditional execution.\n",
455 n_insns, (n_insns == 1) ? " was" : "s were");
457 /* Merge the blocks! */
458 merge_if_block (test_bb, then_bb, else_bb, join_bb);
459 return TRUE;
461 fail:
462 #ifdef IFCVT_MODIFY_CANCEL
463 /* Cancel any machine dependent changes. */
464 IFCVT_MODIFY_CANCEL (test_bb, then_bb, else_bb, join_bb);
465 #endif
467 cancel_changes (0);
468 return FALSE;
471 /* Used by noce_process_if_block to communicate with its subroutines.
473 The subroutines know that A and B may be evaluated freely. They
474 know that X is a register. They should insert new instructions
475 before cond_earliest. */
477 struct noce_if_info
479 basic_block test_bb;
480 rtx insn_a, insn_b;
481 rtx x, a, b;
482 rtx jump, cond, cond_earliest;
485 static rtx noce_emit_store_flag PARAMS ((struct noce_if_info *,
486 rtx, int, int));
487 static int noce_try_store_flag PARAMS ((struct noce_if_info *));
488 static int noce_try_store_flag_inc PARAMS ((struct noce_if_info *));
489 static int noce_try_store_flag_constants PARAMS ((struct noce_if_info *));
490 static int noce_try_store_flag_mask PARAMS ((struct noce_if_info *));
491 static rtx noce_emit_cmove PARAMS ((struct noce_if_info *,
492 rtx, enum rtx_code, rtx,
493 rtx, rtx, rtx));
494 static int noce_try_cmove PARAMS ((struct noce_if_info *));
495 static int noce_try_cmove_arith PARAMS ((struct noce_if_info *));
496 static rtx noce_get_alt_condition PARAMS ((struct noce_if_info *,
497 rtx, rtx *));
498 static int noce_try_minmax PARAMS ((struct noce_if_info *));
499 static int noce_try_abs PARAMS ((struct noce_if_info *));
501 /* Helper function for noce_try_store_flag*. */
503 static rtx
504 noce_emit_store_flag (if_info, x, reversep, normalize)
505 struct noce_if_info *if_info;
506 rtx x;
507 int reversep, normalize;
509 rtx cond = if_info->cond;
510 int cond_complex;
511 enum rtx_code code;
513 cond_complex = (! general_operand (XEXP (cond, 0), VOIDmode)
514 || ! general_operand (XEXP (cond, 1), VOIDmode));
516 /* If earliest == jump, or when the condition is complex, try to
517 build the store_flag insn directly. */
519 if (cond_complex)
520 cond = XEXP (SET_SRC (pc_set (if_info->jump)), 0);
522 if (reversep)
523 code = reversed_comparison_code (cond, if_info->jump);
524 else
525 code = GET_CODE (cond);
527 if ((if_info->cond_earliest == if_info->jump || cond_complex)
528 && (normalize == 0 || STORE_FLAG_VALUE == normalize))
530 rtx tmp;
532 tmp = gen_rtx_fmt_ee (code, GET_MODE (x), XEXP (cond, 0),
533 XEXP (cond, 1));
534 tmp = gen_rtx_SET (VOIDmode, x, tmp);
536 start_sequence ();
537 tmp = emit_insn (tmp);
539 if (recog_memoized (tmp) >= 0)
541 tmp = get_insns ();
542 end_sequence ();
543 emit_insns (tmp);
545 if_info->cond_earliest = if_info->jump;
547 return x;
550 end_sequence ();
553 /* Don't even try if the comparison operands are weird. */
554 if (cond_complex)
555 return NULL_RTX;
557 return emit_store_flag (x, code, XEXP (cond, 0),
558 XEXP (cond, 1), VOIDmode,
559 (code == LTU || code == LEU
560 || code == GEU || code == GTU), normalize);
563 /* Emit instruction to move an rtx into STRICT_LOW_PART. */
564 static void
565 noce_emit_move_insn (x, y)
566 rtx x, y;
568 enum machine_mode outmode, inmode;
569 rtx outer, inner;
570 int bitpos;
572 if (GET_CODE (x) != STRICT_LOW_PART)
574 emit_move_insn (x, y);
575 return;
578 outer = XEXP (x, 0);
579 inner = XEXP (outer, 0);
580 outmode = GET_MODE (outer);
581 inmode = GET_MODE (inner);
582 bitpos = SUBREG_BYTE (outer) * BITS_PER_UNIT;
583 store_bit_field (inner, GET_MODE_BITSIZE (outmode), bitpos, outmode, y,
584 GET_MODE_BITSIZE (inmode));
587 /* Convert "if (test) x = 1; else x = 0".
589 Only try 0 and STORE_FLAG_VALUE here. Other combinations will be
590 tried in noce_try_store_flag_constants after noce_try_cmove has had
591 a go at the conversion. */
593 static int
594 noce_try_store_flag (if_info)
595 struct noce_if_info *if_info;
597 int reversep;
598 rtx target, seq;
600 if (GET_CODE (if_info->b) == CONST_INT
601 && INTVAL (if_info->b) == STORE_FLAG_VALUE
602 && if_info->a == const0_rtx)
603 reversep = 0;
604 else if (if_info->b == const0_rtx
605 && GET_CODE (if_info->a) == CONST_INT
606 && INTVAL (if_info->a) == STORE_FLAG_VALUE
607 && (reversed_comparison_code (if_info->cond, if_info->jump)
608 != UNKNOWN))
609 reversep = 1;
610 else
611 return FALSE;
613 start_sequence ();
615 target = noce_emit_store_flag (if_info, if_info->x, reversep, 0);
616 if (target)
618 if (target != if_info->x)
619 noce_emit_move_insn (if_info->x, target);
621 seq = get_insns ();
622 end_sequence ();
623 emit_insns_before (seq, if_info->cond_earliest);
625 return TRUE;
627 else
629 end_sequence ();
630 return FALSE;
634 /* Convert "if (test) x = a; else x = b", for A and B constant. */
636 static int
637 noce_try_store_flag_constants (if_info)
638 struct noce_if_info *if_info;
640 rtx target, seq;
641 int reversep;
642 HOST_WIDE_INT itrue, ifalse, diff, tmp;
643 int normalize, can_reverse;
644 enum machine_mode mode;
646 if (! no_new_pseudos
647 && GET_CODE (if_info->a) == CONST_INT
648 && GET_CODE (if_info->b) == CONST_INT)
650 mode = GET_MODE (if_info->x);
651 ifalse = INTVAL (if_info->a);
652 itrue = INTVAL (if_info->b);
654 /* Make sure we can represent the difference between the two values. */
655 if ((itrue - ifalse > 0)
656 != ((ifalse < 0) != (itrue < 0) ? ifalse < 0 : ifalse < itrue))
657 return FALSE;
659 diff = trunc_int_for_mode (itrue - ifalse, mode);
661 can_reverse = (reversed_comparison_code (if_info->cond, if_info->jump)
662 != UNKNOWN);
664 reversep = 0;
665 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
666 normalize = 0;
667 else if (ifalse == 0 && exact_log2 (itrue) >= 0
668 && (STORE_FLAG_VALUE == 1
669 || BRANCH_COST >= 2))
670 normalize = 1;
671 else if (itrue == 0 && exact_log2 (ifalse) >= 0 && can_reverse
672 && (STORE_FLAG_VALUE == 1 || BRANCH_COST >= 2))
673 normalize = 1, reversep = 1;
674 else if (itrue == -1
675 && (STORE_FLAG_VALUE == -1
676 || BRANCH_COST >= 2))
677 normalize = -1;
678 else if (ifalse == -1 && can_reverse
679 && (STORE_FLAG_VALUE == -1 || BRANCH_COST >= 2))
680 normalize = -1, reversep = 1;
681 else if ((BRANCH_COST >= 2 && STORE_FLAG_VALUE == -1)
682 || BRANCH_COST >= 3)
683 normalize = -1;
684 else
685 return FALSE;
687 if (reversep)
689 tmp = itrue; itrue = ifalse; ifalse = tmp;
690 diff = trunc_int_for_mode (-diff, mode);
693 start_sequence ();
694 target = noce_emit_store_flag (if_info, if_info->x, reversep, normalize);
695 if (! target)
697 end_sequence ();
698 return FALSE;
701 /* if (test) x = 3; else x = 4;
702 => x = 3 + (test == 0); */
703 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
705 target = expand_simple_binop (mode,
706 (diff == STORE_FLAG_VALUE
707 ? PLUS : MINUS),
708 GEN_INT (ifalse), target, if_info->x, 0,
709 OPTAB_WIDEN);
712 /* if (test) x = 8; else x = 0;
713 => x = (test != 0) << 3; */
714 else if (ifalse == 0 && (tmp = exact_log2 (itrue)) >= 0)
716 target = expand_simple_binop (mode, ASHIFT,
717 target, GEN_INT (tmp), if_info->x, 0,
718 OPTAB_WIDEN);
721 /* if (test) x = -1; else x = b;
722 => x = -(test != 0) | b; */
723 else if (itrue == -1)
725 target = expand_simple_binop (mode, IOR,
726 target, GEN_INT (ifalse), if_info->x, 0,
727 OPTAB_WIDEN);
730 /* if (test) x = a; else x = b;
731 => x = (-(test != 0) & (b - a)) + a; */
732 else
734 target = expand_simple_binop (mode, AND,
735 target, GEN_INT (diff), if_info->x, 0,
736 OPTAB_WIDEN);
737 if (target)
738 target = expand_simple_binop (mode, PLUS,
739 target, GEN_INT (ifalse),
740 if_info->x, 0, OPTAB_WIDEN);
743 if (! target)
745 end_sequence ();
746 return FALSE;
749 if (target != if_info->x)
750 noce_emit_move_insn (if_info->x, target);
752 seq = get_insns ();
753 end_sequence ();
755 if (seq_contains_jump (seq))
756 return FALSE;
758 emit_insns_before (seq, if_info->cond_earliest);
760 return TRUE;
763 return FALSE;
766 /* Convert "if (test) foo++" into "foo += (test != 0)", and
767 similarly for "foo--". */
769 static int
770 noce_try_store_flag_inc (if_info)
771 struct noce_if_info *if_info;
773 rtx target, seq;
774 int subtract, normalize;
776 if (! no_new_pseudos
777 && (BRANCH_COST >= 2
778 || HAVE_incscc
779 || HAVE_decscc)
780 /* Should be no `else' case to worry about. */
781 && if_info->b == if_info->x
782 && GET_CODE (if_info->a) == PLUS
783 && (XEXP (if_info->a, 1) == const1_rtx
784 || XEXP (if_info->a, 1) == constm1_rtx)
785 && rtx_equal_p (XEXP (if_info->a, 0), if_info->x)
786 && (reversed_comparison_code (if_info->cond, if_info->jump)
787 != UNKNOWN))
789 if (STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
790 subtract = 0, normalize = 0;
791 else if (-STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
792 subtract = 1, normalize = 0;
793 else
794 subtract = 0, normalize = INTVAL (XEXP (if_info->a, 1));
796 start_sequence ();
798 target = noce_emit_store_flag (if_info,
799 gen_reg_rtx (GET_MODE (if_info->x)),
800 1, normalize);
802 if (target)
803 target = expand_simple_binop (GET_MODE (if_info->x),
804 subtract ? MINUS : PLUS,
805 if_info->x, target, if_info->x,
806 0, OPTAB_WIDEN);
807 if (target)
809 if (target != if_info->x)
810 noce_emit_move_insn (if_info->x, target);
812 seq = get_insns ();
813 end_sequence ();
815 if (seq_contains_jump (seq))
816 return FALSE;
818 emit_insns_before (seq, if_info->cond_earliest);
820 return TRUE;
823 end_sequence ();
826 return FALSE;
829 /* Convert "if (test) x = 0;" to "x &= -(test == 0);" */
831 static int
832 noce_try_store_flag_mask (if_info)
833 struct noce_if_info *if_info;
835 rtx target, seq;
836 int reversep;
838 reversep = 0;
839 if (! no_new_pseudos
840 && (BRANCH_COST >= 2
841 || STORE_FLAG_VALUE == -1)
842 && ((if_info->a == const0_rtx
843 && rtx_equal_p (if_info->b, if_info->x))
844 || ((reversep = (reversed_comparison_code (if_info->cond,
845 if_info->jump)
846 != UNKNOWN))
847 && if_info->b == const0_rtx
848 && rtx_equal_p (if_info->a, if_info->x))))
850 start_sequence ();
851 target = noce_emit_store_flag (if_info,
852 gen_reg_rtx (GET_MODE (if_info->x)),
853 reversep, -1);
854 if (target)
855 target = expand_simple_binop (GET_MODE (if_info->x), AND,
856 if_info->x, target, if_info->x, 0,
857 OPTAB_WIDEN);
859 if (target)
861 if (target != if_info->x)
862 noce_emit_move_insn (if_info->x, target);
864 seq = get_insns ();
865 end_sequence ();
867 if (seq_contains_jump (seq))
868 return FALSE;
870 emit_insns_before (seq, if_info->cond_earliest);
872 return TRUE;
875 end_sequence ();
878 return FALSE;
881 /* Helper function for noce_try_cmove and noce_try_cmove_arith. */
883 static rtx
884 noce_emit_cmove (if_info, x, code, cmp_a, cmp_b, vfalse, vtrue)
885 struct noce_if_info *if_info;
886 rtx x, cmp_a, cmp_b, vfalse, vtrue;
887 enum rtx_code code;
889 /* If earliest == jump, try to build the cmove insn directly.
890 This is helpful when combine has created some complex condition
891 (like for alpha's cmovlbs) that we can't hope to regenerate
892 through the normal interface. */
894 if (if_info->cond_earliest == if_info->jump)
896 rtx tmp;
898 tmp = gen_rtx_fmt_ee (code, GET_MODE (if_info->cond), cmp_a, cmp_b);
899 tmp = gen_rtx_IF_THEN_ELSE (GET_MODE (x), tmp, vtrue, vfalse);
900 tmp = gen_rtx_SET (VOIDmode, x, tmp);
902 start_sequence ();
903 tmp = emit_insn (tmp);
905 if (recog_memoized (tmp) >= 0)
907 tmp = get_insns ();
908 end_sequence ();
909 emit_insns (tmp);
911 return x;
914 end_sequence ();
917 /* Don't even try if the comparison operands are weird. */
918 if (! general_operand (cmp_a, GET_MODE (cmp_a))
919 || ! general_operand (cmp_b, GET_MODE (cmp_b)))
920 return NULL_RTX;
922 #if HAVE_conditional_move
923 return emit_conditional_move (x, code, cmp_a, cmp_b, VOIDmode,
924 vtrue, vfalse, GET_MODE (x),
925 (code == LTU || code == GEU
926 || code == LEU || code == GTU));
927 #else
928 /* We'll never get here, as noce_process_if_block doesn't call the
929 functions involved. Ifdef code, however, should be discouraged
930 because it leads to typos in the code not selected. However,
931 emit_conditional_move won't exist either. */
932 return NULL_RTX;
933 #endif
936 /* Try only simple constants and registers here. More complex cases
937 are handled in noce_try_cmove_arith after noce_try_store_flag_arith
938 has had a go at it. */
940 static int
941 noce_try_cmove (if_info)
942 struct noce_if_info *if_info;
944 enum rtx_code code;
945 rtx target, seq;
947 if ((CONSTANT_P (if_info->a) || register_operand (if_info->a, VOIDmode))
948 && (CONSTANT_P (if_info->b) || register_operand (if_info->b, VOIDmode)))
950 start_sequence ();
952 code = GET_CODE (if_info->cond);
953 target = noce_emit_cmove (if_info, if_info->x, code,
954 XEXP (if_info->cond, 0),
955 XEXP (if_info->cond, 1),
956 if_info->a, if_info->b);
958 if (target)
960 if (target != if_info->x)
961 noce_emit_move_insn (if_info->x, target);
963 seq = get_insns ();
964 end_sequence ();
965 emit_insns_before (seq, if_info->cond_earliest);
966 return TRUE;
968 else
970 end_sequence ();
971 return FALSE;
975 return FALSE;
978 /* Try more complex cases involving conditional_move. */
980 static int
981 noce_try_cmove_arith (if_info)
982 struct noce_if_info *if_info;
984 rtx a = if_info->a;
985 rtx b = if_info->b;
986 rtx x = if_info->x;
987 rtx insn_a, insn_b;
988 rtx tmp, target;
989 int is_mem = 0;
990 enum rtx_code code;
992 /* A conditional move from two memory sources is equivalent to a
993 conditional on their addresses followed by a load. Don't do this
994 early because it'll screw alias analysis. Note that we've
995 already checked for no side effects. */
996 if (! no_new_pseudos && cse_not_expected
997 && GET_CODE (a) == MEM && GET_CODE (b) == MEM
998 && BRANCH_COST >= 5)
1000 a = XEXP (a, 0);
1001 b = XEXP (b, 0);
1002 x = gen_reg_rtx (Pmode);
1003 is_mem = 1;
1006 /* ??? We could handle this if we knew that a load from A or B could
1007 not fault. This is also true if we've already loaded
1008 from the address along the path from ENTRY. */
1009 else if (may_trap_p (a) || may_trap_p (b))
1010 return FALSE;
1012 /* if (test) x = a + b; else x = c - d;
1013 => y = a + b;
1014 x = c - d;
1015 if (test)
1016 x = y;
1019 code = GET_CODE (if_info->cond);
1020 insn_a = if_info->insn_a;
1021 insn_b = if_info->insn_b;
1023 /* Possibly rearrange operands to make things come out more natural. */
1024 if (reversed_comparison_code (if_info->cond, if_info->jump) != UNKNOWN)
1026 int reversep = 0;
1027 if (rtx_equal_p (b, x))
1028 reversep = 1;
1029 else if (general_operand (b, GET_MODE (b)))
1030 reversep = 1;
1032 if (reversep)
1034 code = reversed_comparison_code (if_info->cond, if_info->jump);
1035 tmp = a, a = b, b = tmp;
1036 tmp = insn_a, insn_a = insn_b, insn_b = tmp;
1040 start_sequence ();
1042 /* If either operand is complex, load it into a register first.
1043 The best way to do this is to copy the original insn. In this
1044 way we preserve any clobbers etc that the insn may have had.
1045 This is of course not possible in the IS_MEM case. */
1046 if (! general_operand (a, GET_MODE (a)))
1048 rtx set;
1050 if (no_new_pseudos)
1051 goto end_seq_and_fail;
1053 if (is_mem)
1055 tmp = gen_reg_rtx (GET_MODE (a));
1056 tmp = emit_insn (gen_rtx_SET (VOIDmode, tmp, a));
1058 else if (! insn_a)
1059 goto end_seq_and_fail;
1060 else
1062 a = gen_reg_rtx (GET_MODE (a));
1063 tmp = copy_rtx (insn_a);
1064 set = single_set (tmp);
1065 SET_DEST (set) = a;
1066 tmp = emit_insn (PATTERN (tmp));
1068 if (recog_memoized (tmp) < 0)
1069 goto end_seq_and_fail;
1071 if (! general_operand (b, GET_MODE (b)))
1073 rtx set;
1075 if (no_new_pseudos)
1076 goto end_seq_and_fail;
1078 if (is_mem)
1080 tmp = gen_reg_rtx (GET_MODE (b));
1081 tmp = emit_insn (gen_rtx_SET (VOIDmode, tmp, b));
1083 else if (! insn_b)
1084 goto end_seq_and_fail;
1085 else
1087 b = gen_reg_rtx (GET_MODE (b));
1088 tmp = copy_rtx (insn_b);
1089 set = single_set (tmp);
1090 SET_DEST (set) = b;
1091 tmp = emit_insn (PATTERN (tmp));
1093 if (recog_memoized (tmp) < 0)
1094 goto end_seq_and_fail;
1097 target = noce_emit_cmove (if_info, x, code, XEXP (if_info->cond, 0),
1098 XEXP (if_info->cond, 1), a, b);
1100 if (! target)
1101 goto end_seq_and_fail;
1103 /* If we're handling a memory for above, emit the load now. */
1104 if (is_mem)
1106 tmp = gen_rtx_MEM (GET_MODE (if_info->x), target);
1108 /* Copy over flags as appropriate. */
1109 if (MEM_VOLATILE_P (if_info->a) || MEM_VOLATILE_P (if_info->b))
1110 MEM_VOLATILE_P (tmp) = 1;
1111 if (MEM_IN_STRUCT_P (if_info->a) && MEM_IN_STRUCT_P (if_info->b))
1112 MEM_IN_STRUCT_P (tmp) = 1;
1113 if (MEM_SCALAR_P (if_info->a) && MEM_SCALAR_P (if_info->b))
1114 MEM_SCALAR_P (tmp) = 1;
1115 if (MEM_ALIAS_SET (if_info->a) == MEM_ALIAS_SET (if_info->b))
1116 set_mem_alias_set (tmp, MEM_ALIAS_SET (if_info->a));
1117 set_mem_align (tmp,
1118 MIN (MEM_ALIGN (if_info->a), MEM_ALIGN (if_info->b)));
1120 noce_emit_move_insn (if_info->x, tmp);
1122 else if (target != x)
1123 noce_emit_move_insn (x, target);
1125 tmp = get_insns ();
1126 end_sequence ();
1127 emit_insns_before (tmp, if_info->cond_earliest);
1128 return TRUE;
1130 end_seq_and_fail:
1131 end_sequence ();
1132 return FALSE;
1135 /* For most cases, the simplified condition we found is the best
1136 choice, but this is not the case for the min/max/abs transforms.
1137 For these we wish to know that it is A or B in the condition. */
1139 static rtx
1140 noce_get_alt_condition (if_info, target, earliest)
1141 struct noce_if_info *if_info;
1142 rtx target;
1143 rtx *earliest;
1145 rtx cond, set, insn;
1146 int reverse;
1148 /* If target is already mentioned in the known condition, return it. */
1149 if (reg_mentioned_p (target, if_info->cond))
1151 *earliest = if_info->cond_earliest;
1152 return if_info->cond;
1155 set = pc_set (if_info->jump);
1156 cond = XEXP (SET_SRC (set), 0);
1157 reverse
1158 = GET_CODE (XEXP (SET_SRC (set), 2)) == LABEL_REF
1159 && XEXP (XEXP (SET_SRC (set), 2), 0) == JUMP_LABEL (if_info->jump);
1161 /* If we're looking for a constant, try to make the conditional
1162 have that constant in it. There are two reasons why it may
1163 not have the constant we want:
1165 1. GCC may have needed to put the constant in a register, because
1166 the target can't compare directly against that constant. For
1167 this case, we look for a SET immediately before the comparison
1168 that puts a constant in that register.
1170 2. GCC may have canonicalized the conditional, for example
1171 replacing "if x < 4" with "if x <= 3". We can undo that (or
1172 make equivalent types of changes) to get the constants we need
1173 if they're off by one in the right direction. */
1175 if (GET_CODE (target) == CONST_INT)
1177 enum rtx_code code = GET_CODE (if_info->cond);
1178 rtx op_a = XEXP (if_info->cond, 0);
1179 rtx op_b = XEXP (if_info->cond, 1);
1180 rtx prev_insn;
1182 /* First, look to see if we put a constant in a register. */
1183 prev_insn = PREV_INSN (if_info->cond_earliest);
1184 if (prev_insn
1185 && INSN_P (prev_insn)
1186 && GET_CODE (PATTERN (prev_insn)) == SET)
1188 rtx src = find_reg_equal_equiv_note (prev_insn);
1189 if (!src)
1190 src = SET_SRC (PATTERN (prev_insn));
1191 if (GET_CODE (src) == CONST_INT)
1193 if (rtx_equal_p (op_a, SET_DEST (PATTERN (prev_insn))))
1194 op_a = src;
1195 else if (rtx_equal_p (op_b, SET_DEST (PATTERN (prev_insn))))
1196 op_b = src;
1198 if (GET_CODE (op_a) == CONST_INT)
1200 rtx tmp = op_a;
1201 op_a = op_b;
1202 op_b = tmp;
1203 code = swap_condition (code);
1208 /* Now, look to see if we can get the right constant by
1209 adjusting the conditional. */
1210 if (GET_CODE (op_b) == CONST_INT)
1212 HOST_WIDE_INT desired_val = INTVAL (target);
1213 HOST_WIDE_INT actual_val = INTVAL (op_b);
1215 switch (code)
1217 case LT:
1218 if (actual_val == desired_val + 1)
1220 code = LE;
1221 op_b = GEN_INT (desired_val);
1223 break;
1224 case LE:
1225 if (actual_val == desired_val - 1)
1227 code = LT;
1228 op_b = GEN_INT (desired_val);
1230 break;
1231 case GT:
1232 if (actual_val == desired_val - 1)
1234 code = GE;
1235 op_b = GEN_INT (desired_val);
1237 break;
1238 case GE:
1239 if (actual_val == desired_val + 1)
1241 code = GT;
1242 op_b = GEN_INT (desired_val);
1244 break;
1245 default:
1246 break;
1250 /* If we made any changes, generate a new conditional that is
1251 equivalent to what we started with, but has the right
1252 constants in it. */
1253 if (code != GET_CODE (if_info->cond)
1254 || op_a != XEXP (if_info->cond, 0)
1255 || op_b != XEXP (if_info->cond, 1))
1257 cond = gen_rtx_fmt_ee (code, GET_MODE (cond), op_a, op_b);
1258 *earliest = if_info->cond_earliest;
1259 return cond;
1263 cond = canonicalize_condition (if_info->jump, cond, reverse,
1264 earliest, target);
1265 if (! cond || ! reg_mentioned_p (target, cond))
1266 return NULL;
1268 /* We almost certainly searched back to a different place.
1269 Need to re-verify correct lifetimes. */
1271 /* X may not be mentioned in the range (cond_earliest, jump]. */
1272 for (insn = if_info->jump; insn != *earliest; insn = PREV_INSN (insn))
1273 if (INSN_P (insn) && reg_mentioned_p (if_info->x, insn))
1274 return NULL;
1276 /* A and B may not be modified in the range [cond_earliest, jump). */
1277 for (insn = *earliest; insn != if_info->jump; insn = NEXT_INSN (insn))
1278 if (INSN_P (insn)
1279 && (modified_in_p (if_info->a, insn)
1280 || modified_in_p (if_info->b, insn)))
1281 return NULL;
1283 return cond;
1286 /* Convert "if (a < b) x = a; else x = b;" to "x = min(a, b);", etc. */
1288 static int
1289 noce_try_minmax (if_info)
1290 struct noce_if_info *if_info;
1292 rtx cond, earliest, target, seq;
1293 enum rtx_code code, op;
1294 int unsignedp;
1296 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1297 if (no_new_pseudos)
1298 return FALSE;
1300 /* ??? Reject FP modes since we don't know how 0 vs -0 or NaNs
1301 will be resolved with an SMIN/SMAX. It wouldn't be too hard
1302 to get the target to tell us... */
1303 if (FLOAT_MODE_P (GET_MODE (if_info->x))
1304 && TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
1305 && ! flag_unsafe_math_optimizations)
1306 return FALSE;
1308 cond = noce_get_alt_condition (if_info, if_info->a, &earliest);
1309 if (!cond)
1310 return FALSE;
1312 /* Verify the condition is of the form we expect, and canonicalize
1313 the comparison code. */
1314 code = GET_CODE (cond);
1315 if (rtx_equal_p (XEXP (cond, 0), if_info->a))
1317 if (! rtx_equal_p (XEXP (cond, 1), if_info->b))
1318 return FALSE;
1320 else if (rtx_equal_p (XEXP (cond, 1), if_info->a))
1322 if (! rtx_equal_p (XEXP (cond, 0), if_info->b))
1323 return FALSE;
1324 code = swap_condition (code);
1326 else
1327 return FALSE;
1329 /* Determine what sort of operation this is. Note that the code is for
1330 a taken branch, so the code->operation mapping appears backwards. */
1331 switch (code)
1333 case LT:
1334 case LE:
1335 case UNLT:
1336 case UNLE:
1337 op = SMAX;
1338 unsignedp = 0;
1339 break;
1340 case GT:
1341 case GE:
1342 case UNGT:
1343 case UNGE:
1344 op = SMIN;
1345 unsignedp = 0;
1346 break;
1347 case LTU:
1348 case LEU:
1349 op = UMAX;
1350 unsignedp = 1;
1351 break;
1352 case GTU:
1353 case GEU:
1354 op = UMIN;
1355 unsignedp = 1;
1356 break;
1357 default:
1358 return FALSE;
1361 start_sequence ();
1363 target = expand_simple_binop (GET_MODE (if_info->x), op,
1364 if_info->a, if_info->b,
1365 if_info->x, unsignedp, OPTAB_WIDEN);
1366 if (! target)
1368 end_sequence ();
1369 return FALSE;
1371 if (target != if_info->x)
1372 noce_emit_move_insn (if_info->x, target);
1374 seq = get_insns ();
1375 end_sequence ();
1377 if (seq_contains_jump (seq))
1378 return FALSE;
1380 emit_insns_before (seq, earliest);
1381 if_info->cond = cond;
1382 if_info->cond_earliest = earliest;
1384 return TRUE;
1387 /* Convert "if (a < 0) x = -a; else x = a;" to "x = abs(a);", etc. */
1389 static int
1390 noce_try_abs (if_info)
1391 struct noce_if_info *if_info;
1393 rtx cond, earliest, target, seq, a, b, c;
1394 int negate;
1396 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1397 if (no_new_pseudos)
1398 return FALSE;
1400 /* Recognize A and B as constituting an ABS or NABS. */
1401 a = if_info->a;
1402 b = if_info->b;
1403 if (GET_CODE (a) == NEG && rtx_equal_p (XEXP (a, 0), b))
1404 negate = 0;
1405 else if (GET_CODE (b) == NEG && rtx_equal_p (XEXP (b, 0), a))
1407 c = a; a = b; b = c;
1408 negate = 1;
1410 else
1411 return FALSE;
1413 cond = noce_get_alt_condition (if_info, b, &earliest);
1414 if (!cond)
1415 return FALSE;
1417 /* Verify the condition is of the form we expect. */
1418 if (rtx_equal_p (XEXP (cond, 0), b))
1419 c = XEXP (cond, 1);
1420 else if (rtx_equal_p (XEXP (cond, 1), b))
1421 c = XEXP (cond, 0);
1422 else
1423 return FALSE;
1425 /* Verify that C is zero. Search backward through the block for
1426 a REG_EQUAL note if necessary. */
1427 if (REG_P (c))
1429 rtx insn, note = NULL;
1430 for (insn = earliest;
1431 insn != if_info->test_bb->head;
1432 insn = PREV_INSN (insn))
1433 if (INSN_P (insn)
1434 && ((note = find_reg_note (insn, REG_EQUAL, c))
1435 || (note = find_reg_note (insn, REG_EQUIV, c))))
1436 break;
1437 if (! note)
1438 return FALSE;
1439 c = XEXP (note, 0);
1441 if (GET_CODE (c) == MEM
1442 && GET_CODE (XEXP (c, 0)) == SYMBOL_REF
1443 && CONSTANT_POOL_ADDRESS_P (XEXP (c, 0)))
1444 c = get_pool_constant (XEXP (c, 0));
1446 /* Work around funny ideas get_condition has wrt canonicalization.
1447 Note that these rtx constants are known to be CONST_INT, and
1448 therefore imply integer comparisons. */
1449 if (c == constm1_rtx && GET_CODE (cond) == GT)
1451 else if (c == const1_rtx && GET_CODE (cond) == LT)
1453 else if (c != CONST0_RTX (GET_MODE (b)))
1454 return FALSE;
1456 /* Determine what sort of operation this is. */
1457 switch (GET_CODE (cond))
1459 case LT:
1460 case LE:
1461 case UNLT:
1462 case UNLE:
1463 negate = !negate;
1464 break;
1465 case GT:
1466 case GE:
1467 case UNGT:
1468 case UNGE:
1469 break;
1470 default:
1471 return FALSE;
1474 start_sequence ();
1476 target = expand_simple_unop (GET_MODE (if_info->x), ABS, b, if_info->x, 0);
1478 /* ??? It's a quandry whether cmove would be better here, especially
1479 for integers. Perhaps combine will clean things up. */
1480 if (target && negate)
1481 target = expand_simple_unop (GET_MODE (target), NEG, target, if_info->x, 0);
1483 if (! target)
1485 end_sequence ();
1486 return FALSE;
1489 if (target != if_info->x)
1490 noce_emit_move_insn (if_info->x, target);
1492 seq = get_insns ();
1493 end_sequence ();
1495 if (seq_contains_jump (seq))
1496 return FALSE;
1498 emit_insns_before (seq, earliest);
1499 if_info->cond = cond;
1500 if_info->cond_earliest = earliest;
1502 return TRUE;
1505 /* Look for the condition for the jump first. We'd prefer to avoid
1506 get_condition if we can -- it tries to look back for the contents
1507 of an original compare. On targets that use normal integers for
1508 comparisons, e.g. alpha, this is wasteful. */
1510 static rtx
1511 noce_get_condition (jump, earliest)
1512 rtx jump;
1513 rtx *earliest;
1515 rtx cond;
1516 rtx set;
1518 /* If the condition variable is a register and is MODE_INT, accept it.
1519 Otherwise, fall back on get_condition. */
1521 if (! any_condjump_p (jump))
1522 return NULL_RTX;
1524 set = pc_set (jump);
1526 cond = XEXP (SET_SRC (set), 0);
1527 if (GET_CODE (XEXP (cond, 0)) == REG
1528 && GET_MODE_CLASS (GET_MODE (XEXP (cond, 0))) == MODE_INT)
1530 *earliest = jump;
1532 /* If this branches to JUMP_LABEL when the condition is false,
1533 reverse the condition. */
1534 if (GET_CODE (XEXP (SET_SRC (set), 2)) == LABEL_REF
1535 && XEXP (XEXP (SET_SRC (set), 2), 0) == JUMP_LABEL (jump))
1536 cond = gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)),
1537 GET_MODE (cond), XEXP (cond, 0),
1538 XEXP (cond, 1));
1540 else
1541 cond = get_condition (jump, earliest);
1543 return cond;
1546 /* Return true if OP is ok for if-then-else processing. */
1548 static int
1549 noce_operand_ok (op)
1550 rtx op;
1552 /* We special-case memories, so handle any of them with
1553 no address side effects. */
1554 if (GET_CODE (op) == MEM)
1555 return ! side_effects_p (XEXP (op, 0));
1557 if (side_effects_p (op))
1558 return FALSE;
1560 /* ??? Unfortuantely may_trap_p can't look at flag_trapping_math, due to
1561 being linked into the genfoo programs. This is probably a mistake.
1562 With finite operands, most fp operations don't trap. */
1563 if (!flag_trapping_math && FLOAT_MODE_P (GET_MODE (op)))
1564 switch (GET_CODE (op))
1566 case DIV:
1567 case MOD:
1568 case UDIV:
1569 case UMOD:
1570 /* ??? This is kinda lame -- almost every target will have forced
1571 the constant into a register first. But given the expense of
1572 division, this is probably for the best. */
1573 return (CONSTANT_P (XEXP (op, 1))
1574 && XEXP (op, 1) != CONST0_RTX (GET_MODE (op))
1575 && ! may_trap_p (XEXP (op, 0)));
1577 default:
1578 switch (GET_RTX_CLASS (GET_CODE (op)))
1580 case '1':
1581 return ! may_trap_p (XEXP (op, 0));
1582 case 'c':
1583 case '2':
1584 return ! may_trap_p (XEXP (op, 0)) && ! may_trap_p (XEXP (op, 1));
1586 break;
1589 return ! may_trap_p (op);
1592 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
1593 without using conditional execution. Return TRUE if we were
1594 successful at converting the the block. */
1596 static int
1597 noce_process_if_block (test_bb, then_bb, else_bb, join_bb)
1598 basic_block test_bb; /* Basic block test is in */
1599 basic_block then_bb; /* Basic block for THEN block */
1600 basic_block else_bb; /* Basic block for ELSE block */
1601 basic_block join_bb; /* Basic block the join label is in */
1603 /* We're looking for patterns of the form
1605 (1) if (...) x = a; else x = b;
1606 (2) x = b; if (...) x = a;
1607 (3) if (...) x = a; // as if with an initial x = x.
1609 The later patterns require jumps to be more expensive.
1611 ??? For future expansion, look for multiple X in such patterns. */
1613 struct noce_if_info if_info;
1614 rtx insn_a, insn_b;
1615 rtx set_a, set_b;
1616 rtx orig_x, x, a, b;
1617 rtx jump, cond, insn;
1619 /* If this is not a standard conditional jump, we can't parse it. */
1620 jump = test_bb->end;
1621 cond = noce_get_condition (jump, &if_info.cond_earliest);
1622 if (! cond)
1623 return FALSE;
1625 /* If the conditional jump is more than just a conditional jump,
1626 then we can not do if-conversion on this block. */
1627 if (! onlyjump_p (jump))
1628 return FALSE;
1630 /* We must be comparing objects whose modes imply the size. */
1631 if (GET_MODE (XEXP (cond, 0)) == BLKmode)
1632 return FALSE;
1634 /* Look for one of the potential sets. */
1635 insn_a = first_active_insn (then_bb);
1636 if (! insn_a
1637 || ! last_active_insn_p (then_bb, insn_a)
1638 || (set_a = single_set (insn_a)) == NULL_RTX)
1639 return FALSE;
1641 x = SET_DEST (set_a);
1642 a = SET_SRC (set_a);
1644 /* Look for the other potential set. Make sure we've got equivalent
1645 destinations. */
1646 /* ??? This is overconservative. Storing to two different mems is
1647 as easy as conditionally computing the address. Storing to a
1648 single mem merely requires a scratch memory to use as one of the
1649 destination addresses; often the memory immediately below the
1650 stack pointer is available for this. */
1651 set_b = NULL_RTX;
1652 if (else_bb)
1654 insn_b = first_active_insn (else_bb);
1655 if (! insn_b
1656 || ! last_active_insn_p (else_bb, insn_b)
1657 || (set_b = single_set (insn_b)) == NULL_RTX
1658 || ! rtx_equal_p (x, SET_DEST (set_b)))
1659 return FALSE;
1661 else
1663 insn_b = prev_nonnote_insn (if_info.cond_earliest);
1664 if (! insn_b
1665 || GET_CODE (insn_b) != INSN
1666 || (set_b = single_set (insn_b)) == NULL_RTX
1667 || ! rtx_equal_p (x, SET_DEST (set_b))
1668 || reg_mentioned_p (x, cond)
1669 || reg_mentioned_p (x, a)
1670 || reg_mentioned_p (x, SET_SRC (set_b)))
1671 insn_b = set_b = NULL_RTX;
1673 b = (set_b ? SET_SRC (set_b) : x);
1675 /* X may not be mentioned in the range (cond_earliest, jump]. */
1676 for (insn = jump; insn != if_info.cond_earliest; insn = PREV_INSN (insn))
1677 if (INSN_P (insn) && reg_mentioned_p (x, insn))
1678 return FALSE;
1680 /* A and B may not be modified in the range [cond_earliest, jump). */
1681 for (insn = if_info.cond_earliest; insn != jump; insn = NEXT_INSN (insn))
1682 if (INSN_P (insn)
1683 && (modified_in_p (a, insn) || modified_in_p (b, insn)))
1684 return FALSE;
1686 /* Only operate on register destinations, and even then avoid extending
1687 the lifetime of hard registers on small register class machines. */
1688 orig_x = x;
1689 if (GET_CODE (x) != REG
1690 || (SMALL_REGISTER_CLASSES
1691 && REGNO (x) < FIRST_PSEUDO_REGISTER))
1693 if (no_new_pseudos)
1694 return FALSE;
1695 x = gen_reg_rtx (GET_MODE (GET_CODE (x) == STRICT_LOW_PART
1696 ? XEXP (x, 0) : x));
1699 /* Don't operate on sources that may trap or are volatile. */
1700 if (! noce_operand_ok (a) || ! noce_operand_ok (b))
1701 return FALSE;
1703 /* Set up the info block for our subroutines. */
1704 if_info.test_bb = test_bb;
1705 if_info.cond = cond;
1706 if_info.jump = jump;
1707 if_info.insn_a = insn_a;
1708 if_info.insn_b = insn_b;
1709 if_info.x = x;
1710 if_info.a = a;
1711 if_info.b = b;
1713 /* Try optimizations in some approximation of a useful order. */
1714 /* ??? Should first look to see if X is live incoming at all. If it
1715 isn't, we don't need anything but an unconditional set. */
1717 /* Look and see if A and B are really the same. Avoid creating silly
1718 cmove constructs that no one will fix up later. */
1719 if (rtx_equal_p (a, b))
1721 /* If we have an INSN_B, we don't have to create any new rtl. Just
1722 move the instruction that we already have. If we don't have an
1723 INSN_B, that means that A == X, and we've got a noop move. In
1724 that case don't do anything and let the code below delete INSN_A. */
1725 if (insn_b && else_bb)
1727 rtx note;
1729 if (else_bb && insn_b == else_bb->end)
1730 else_bb->end = PREV_INSN (insn_b);
1731 reorder_insns (insn_b, insn_b, PREV_INSN (if_info.cond_earliest));
1733 /* If there was a REG_EQUAL note, delete it since it may have been
1734 true due to this insn being after a jump. */
1735 if ((note = find_reg_note (insn_b, REG_EQUAL, NULL_RTX)) != 0)
1736 remove_note (insn_b, note);
1738 insn_b = NULL_RTX;
1740 /* If we have "x = b; if (...) x = a;", and x has side-effects, then
1741 x must be executed twice. */
1742 else if (insn_b && side_effects_p (orig_x))
1743 return FALSE;
1745 x = orig_x;
1746 goto success;
1749 if (noce_try_store_flag (&if_info))
1750 goto success;
1751 if (noce_try_minmax (&if_info))
1752 goto success;
1753 if (noce_try_abs (&if_info))
1754 goto success;
1755 if (HAVE_conditional_move
1756 && noce_try_cmove (&if_info))
1757 goto success;
1758 if (! HAVE_conditional_execution)
1760 if (noce_try_store_flag_constants (&if_info))
1761 goto success;
1762 if (noce_try_store_flag_inc (&if_info))
1763 goto success;
1764 if (noce_try_store_flag_mask (&if_info))
1765 goto success;
1766 if (HAVE_conditional_move
1767 && noce_try_cmove_arith (&if_info))
1768 goto success;
1771 return FALSE;
1773 success:
1774 /* The original sets may now be killed. */
1775 delete_insn (insn_a);
1777 /* Several special cases here: First, we may have reused insn_b above,
1778 in which case insn_b is now NULL. Second, we want to delete insn_b
1779 if it came from the ELSE block, because follows the now correct
1780 write that appears in the TEST block. However, if we got insn_b from
1781 the TEST block, it may in fact be loading data needed for the comparison.
1782 We'll let life_analysis remove the insn if it's really dead. */
1783 if (insn_b && else_bb)
1784 delete_insn (insn_b);
1786 /* The new insns will have been inserted before cond_earliest. We should
1787 be able to remove the jump with impunity, but the condition itself may
1788 have been modified by gcse to be shared across basic blocks. */
1789 delete_insn (jump);
1791 /* If we used a temporary, fix it up now. */
1792 if (orig_x != x)
1794 start_sequence ();
1795 noce_emit_move_insn (orig_x, x);
1796 insn_b = gen_sequence ();
1797 end_sequence ();
1799 emit_insn_after (insn_b, test_bb->end);
1802 /* Merge the blocks! */
1803 merge_if_block (test_bb, then_bb, else_bb, join_bb);
1805 return TRUE;
1808 /* Attempt to convert an IF-THEN or IF-THEN-ELSE block into
1809 straight line code. Return true if successful. */
1811 static int
1812 process_if_block (test_bb, then_bb, else_bb, join_bb)
1813 basic_block test_bb; /* Basic block test is in */
1814 basic_block then_bb; /* Basic block for THEN block */
1815 basic_block else_bb; /* Basic block for ELSE block */
1816 basic_block join_bb; /* Basic block the join label is in */
1818 if (! reload_completed
1819 && noce_process_if_block (test_bb, then_bb, else_bb, join_bb))
1820 return TRUE;
1822 if (HAVE_conditional_execution
1823 && reload_completed
1824 && cond_exec_process_if_block (test_bb, then_bb, else_bb, join_bb))
1825 return TRUE;
1827 return FALSE;
1830 /* Merge the blocks and mark for local life update. */
1832 static void
1833 merge_if_block (test_bb, then_bb, else_bb, join_bb)
1834 basic_block test_bb; /* Basic block test is in */
1835 basic_block then_bb; /* Basic block for THEN block */
1836 basic_block else_bb; /* Basic block for ELSE block */
1837 basic_block join_bb; /* Basic block the join label is in */
1839 basic_block combo_bb;
1841 /* All block merging is done into the lower block numbers. */
1843 combo_bb = test_bb;
1845 /* First merge TEST block into THEN block. This is a no-brainer since
1846 the THEN block did not have a code label to begin with. */
1848 if (life_data_ok)
1849 COPY_REG_SET (combo_bb->global_live_at_end, then_bb->global_live_at_end);
1850 merge_blocks_nomove (combo_bb, then_bb);
1851 num_removed_blocks++;
1853 /* The ELSE block, if it existed, had a label. That label count
1854 will almost always be zero, but odd things can happen when labels
1855 get their addresses taken. */
1856 if (else_bb)
1858 merge_blocks_nomove (combo_bb, else_bb);
1859 num_removed_blocks++;
1862 /* If there was no join block reported, that means it was not adjacent
1863 to the others, and so we cannot merge them. */
1865 if (! join_bb)
1867 /* The outgoing edge for the current COMBO block should already
1868 be correct. Verify this. */
1869 if (combo_bb->succ == NULL_EDGE)
1870 abort ();
1872 /* There should still be a branch at the end of the THEN or ELSE
1873 blocks taking us to our final destination. */
1874 if (GET_CODE (combo_bb->end) != JUMP_INSN)
1875 abort ();
1878 /* The JOIN block may have had quite a number of other predecessors too.
1879 Since we've already merged the TEST, THEN and ELSE blocks, we should
1880 have only one remaining edge from our if-then-else diamond. If there
1881 is more than one remaining edge, it must come from elsewhere. There
1882 may be zero incoming edges if the THEN block didn't actually join
1883 back up (as with a call to abort). */
1884 else if ((join_bb->pred == NULL
1885 || join_bb->pred->pred_next == NULL)
1886 && join_bb != EXIT_BLOCK_PTR)
1888 /* We can merge the JOIN. */
1889 if (life_data_ok)
1890 COPY_REG_SET (combo_bb->global_live_at_end,
1891 join_bb->global_live_at_end);
1892 merge_blocks_nomove (combo_bb, join_bb);
1893 num_removed_blocks++;
1895 else
1897 /* We cannot merge the JOIN. */
1899 /* The outgoing edge for the current COMBO block should already
1900 be correct. Verify this. */
1901 if (combo_bb->succ->succ_next != NULL_EDGE
1902 || combo_bb->succ->dest != join_bb)
1903 abort ();
1905 /* Remove the jump and cruft from the end of the COMBO block. */
1906 if (join_bb != EXIT_BLOCK_PTR)
1907 tidy_fallthru_edge (combo_bb->succ, combo_bb, join_bb);
1910 /* Make sure we update life info properly. */
1911 SET_UPDATE_LIFE (combo_bb);
1913 num_updated_if_blocks++;
1916 /* Find a block ending in a simple IF condition. Return TRUE if
1917 we were able to transform it in some way. */
1919 static int
1920 find_if_header (test_bb)
1921 basic_block test_bb;
1923 edge then_edge;
1924 edge else_edge;
1926 /* The kind of block we're looking for has exactly two successors. */
1927 if ((then_edge = test_bb->succ) == NULL_EDGE
1928 || (else_edge = then_edge->succ_next) == NULL_EDGE
1929 || else_edge->succ_next != NULL_EDGE)
1930 return FALSE;
1932 /* Neither edge should be abnormal. */
1933 if ((then_edge->flags & EDGE_COMPLEX)
1934 || (else_edge->flags & EDGE_COMPLEX))
1935 return FALSE;
1937 /* The THEN edge is canonically the one that falls through. */
1938 if (then_edge->flags & EDGE_FALLTHRU)
1940 else if (else_edge->flags & EDGE_FALLTHRU)
1942 edge e = else_edge;
1943 else_edge = then_edge;
1944 then_edge = e;
1946 else
1947 /* Otherwise this must be a multiway branch of some sort. */
1948 return FALSE;
1950 if (find_if_block (test_bb, then_edge, else_edge))
1951 goto success;
1952 if (HAVE_trap && HAVE_conditional_trap
1953 && find_cond_trap (test_bb, then_edge, else_edge))
1954 goto success;
1955 if (post_dominators
1956 && (! HAVE_conditional_execution || reload_completed))
1958 if (find_if_case_1 (test_bb, then_edge, else_edge))
1959 goto success;
1960 if (find_if_case_2 (test_bb, then_edge, else_edge))
1961 goto success;
1964 return FALSE;
1966 success:
1967 if (rtl_dump_file)
1968 fprintf (rtl_dump_file, "Conversion succeeded.\n");
1969 return TRUE;
1972 /* Determine if a given basic block heads a simple IF-THEN or IF-THEN-ELSE
1973 block. If so, we'll try to convert the insns to not require the branch.
1974 Return TRUE if we were successful at converting the the block. */
1976 static int
1977 find_if_block (test_bb, then_edge, else_edge)
1978 basic_block test_bb;
1979 edge then_edge, else_edge;
1981 basic_block then_bb = then_edge->dest;
1982 basic_block else_bb = else_edge->dest;
1983 basic_block join_bb = NULL_BLOCK;
1984 edge then_succ = then_bb->succ;
1985 edge else_succ = else_bb->succ;
1986 int next_index;
1988 /* The THEN block of an IF-THEN combo must have exactly one predecessor. */
1989 if (then_bb->pred->pred_next != NULL_EDGE)
1990 return FALSE;
1992 /* The THEN block of an IF-THEN combo must have zero or one successors. */
1993 if (then_succ != NULL_EDGE
1994 && (then_succ->succ_next != NULL_EDGE
1995 || (then_succ->flags & EDGE_COMPLEX)))
1996 return FALSE;
1998 /* If the THEN block has no successors, conditional execution can still
1999 make a conditional call. Don't do this unless the ELSE block has
2000 only one incoming edge -- the CFG manipulation is too ugly otherwise.
2001 Check for the last insn of the THEN block being an indirect jump, which
2002 is listed as not having any successors, but confuses the rest of the CE
2003 code processing. XXX we should fix this in the future. */
2004 if (then_succ == NULL)
2006 if (else_bb->pred->pred_next == NULL_EDGE)
2008 rtx last_insn = then_bb->end;
2010 while (last_insn
2011 && GET_CODE (last_insn) == NOTE
2012 && last_insn != then_bb->head)
2013 last_insn = PREV_INSN (last_insn);
2015 if (last_insn
2016 && GET_CODE (last_insn) == JUMP_INSN
2017 && ! simplejump_p (last_insn))
2018 return FALSE;
2020 join_bb = else_bb;
2021 else_bb = NULL_BLOCK;
2023 else
2024 return FALSE;
2027 /* If the THEN block's successor is the other edge out of the TEST block,
2028 then we have an IF-THEN combo without an ELSE. */
2029 else if (then_succ->dest == else_bb)
2031 join_bb = else_bb;
2032 else_bb = NULL_BLOCK;
2035 /* If the THEN and ELSE block meet in a subsequent block, and the ELSE
2036 has exactly one predecessor and one successor, and the outgoing edge
2037 is not complex, then we have an IF-THEN-ELSE combo. */
2038 else if (else_succ != NULL_EDGE
2039 && then_succ->dest == else_succ->dest
2040 && else_bb->pred->pred_next == NULL_EDGE
2041 && else_succ->succ_next == NULL_EDGE
2042 && ! (else_succ->flags & EDGE_COMPLEX))
2043 join_bb = else_succ->dest;
2045 /* Otherwise it is not an IF-THEN or IF-THEN-ELSE combination. */
2046 else
2047 return FALSE;
2049 num_possible_if_blocks++;
2051 if (rtl_dump_file)
2053 if (else_bb)
2054 fprintf (rtl_dump_file,
2055 "\nIF-THEN-ELSE block found, start %d, then %d, else %d, join %d\n",
2056 test_bb->index, then_bb->index, else_bb->index,
2057 join_bb->index);
2058 else
2059 fprintf (rtl_dump_file,
2060 "\nIF-THEN block found, start %d, then %d, join %d\n",
2061 test_bb->index, then_bb->index, join_bb->index);
2064 /* Make sure IF, THEN, and ELSE, blocks are adjacent. Actually, we
2065 get the first condition for free, since we've already asserted that
2066 there's a fallthru edge from IF to THEN. */
2067 /* ??? As an enhancement, move the ELSE block. Have to deal with
2068 BLOCK notes, if by no other means than aborting the merge if they
2069 exist. Sticky enough I don't want to think about it now. */
2070 next_index = then_bb->index;
2071 if (else_bb && ++next_index != else_bb->index)
2072 return FALSE;
2073 if (++next_index != join_bb->index && join_bb->index != EXIT_BLOCK)
2075 if (else_bb)
2076 join_bb = NULL;
2077 else
2078 return FALSE;
2081 /* Do the real work. */
2082 return process_if_block (test_bb, then_bb, else_bb, join_bb);
2085 /* Convert a branch over a trap, or a branch to a trap,
2086 into a conditional trap. */
2088 static int
2089 find_cond_trap (test_bb, then_edge, else_edge)
2090 basic_block test_bb;
2091 edge then_edge, else_edge;
2093 basic_block then_bb, else_bb, join_bb, trap_bb;
2094 rtx trap, jump, cond, cond_earliest, seq;
2095 enum rtx_code code;
2097 then_bb = then_edge->dest;
2098 else_bb = else_edge->dest;
2099 join_bb = NULL;
2101 /* Locate the block with the trap instruction. */
2102 /* ??? While we look for no successors, we really ought to allow
2103 EH successors. Need to fix merge_if_block for that to work. */
2104 /* ??? We can't currently handle merging the blocks if they are not
2105 already adjacent. Prevent losage in merge_if_block by detecting
2106 this now. */
2107 if (then_bb->succ == NULL)
2109 trap_bb = then_bb;
2110 if (else_bb->index != then_bb->index + 1)
2111 return FALSE;
2112 join_bb = else_bb;
2113 else_bb = NULL;
2115 else if (else_bb->succ == NULL)
2117 trap_bb = else_bb;
2118 if (else_bb->index != then_bb->index + 1)
2119 else_bb = NULL;
2120 else if (then_bb->succ
2121 && ! then_bb->succ->succ_next
2122 && ! (then_bb->succ->flags & EDGE_COMPLEX)
2123 && then_bb->succ->dest->index == else_bb->index + 1)
2124 join_bb = then_bb->succ->dest;
2126 else
2127 return FALSE;
2129 /* Don't confuse a conditional return with something we want to
2130 optimize here. */
2131 if (trap_bb == EXIT_BLOCK_PTR)
2132 return FALSE;
2134 /* The only instruction in the THEN block must be the trap. */
2135 trap = first_active_insn (trap_bb);
2136 if (! (trap == trap_bb->end
2137 && GET_CODE (PATTERN (trap)) == TRAP_IF
2138 && TRAP_CONDITION (PATTERN (trap)) == const_true_rtx))
2139 return FALSE;
2141 if (rtl_dump_file)
2143 if (trap_bb == then_bb)
2144 fprintf (rtl_dump_file,
2145 "\nTRAP-IF block found, start %d, trap %d",
2146 test_bb->index, then_bb->index);
2147 else
2148 fprintf (rtl_dump_file,
2149 "\nTRAP-IF block found, start %d, then %d, trap %d",
2150 test_bb->index, then_bb->index, trap_bb->index);
2151 if (join_bb)
2152 fprintf (rtl_dump_file, ", join %d\n", join_bb->index);
2153 else
2154 fputc ('\n', rtl_dump_file);
2157 /* If this is not a standard conditional jump, we can't parse it. */
2158 jump = test_bb->end;
2159 cond = noce_get_condition (jump, &cond_earliest);
2160 if (! cond)
2161 return FALSE;
2163 /* If the conditional jump is more than just a conditional jump,
2164 then we can not do if-conversion on this block. */
2165 if (! onlyjump_p (jump))
2166 return FALSE;
2168 /* We must be comparing objects whose modes imply the size. */
2169 if (GET_MODE (XEXP (cond, 0)) == BLKmode)
2170 return FALSE;
2172 /* Reverse the comparison code, if necessary. */
2173 code = GET_CODE (cond);
2174 if (then_bb == trap_bb)
2176 code = reversed_comparison_code (cond, jump);
2177 if (code == UNKNOWN)
2178 return FALSE;
2181 /* Attempt to generate the conditional trap. */
2182 seq = gen_cond_trap (code, XEXP (cond, 0), XEXP (cond, 1),
2183 TRAP_CODE (PATTERN (trap)));
2184 if (seq == NULL)
2185 return FALSE;
2187 /* Emit the new insns before cond_earliest; delete the old jump
2188 and trap insns. */
2190 emit_insn_before (seq, cond_earliest);
2192 delete_insn (jump);
2194 delete_insn (trap);
2196 /* Merge the blocks! */
2197 if (trap_bb != then_bb && ! else_bb)
2199 flow_delete_block (trap_bb);
2200 num_removed_blocks++;
2202 merge_if_block (test_bb, then_bb, else_bb, join_bb);
2204 return TRUE;
2207 /* Look for IF-THEN-ELSE cases in which one of THEN or ELSE is
2208 transformable, but not necessarily the other. There need be no
2209 JOIN block.
2211 Return TRUE if we were successful at converting the the block.
2213 Cases we'd like to look at:
2216 if (test) goto over; // x not live
2217 x = a;
2218 goto label;
2219 over:
2221 becomes
2223 x = a;
2224 if (! test) goto label;
2227 if (test) goto E; // x not live
2228 x = big();
2229 goto L;
2231 x = b;
2232 goto M;
2234 becomes
2236 x = b;
2237 if (test) goto M;
2238 x = big();
2239 goto L;
2241 (3) // This one's really only interesting for targets that can do
2242 // multiway branching, e.g. IA-64 BBB bundles. For other targets
2243 // it results in multiple branches on a cache line, which often
2244 // does not sit well with predictors.
2246 if (test1) goto E; // predicted not taken
2247 x = a;
2248 if (test2) goto F;
2251 x = b;
2254 becomes
2256 x = a;
2257 if (test1) goto E;
2258 if (test2) goto F;
2260 Notes:
2262 (A) Don't do (2) if the branch is predicted against the block we're
2263 eliminating. Do it anyway if we can eliminate a branch; this requires
2264 that the sole successor of the eliminated block postdominate the other
2265 side of the if.
2267 (B) With CE, on (3) we can steal from both sides of the if, creating
2269 if (test1) x = a;
2270 if (!test1) x = b;
2271 if (test1) goto J;
2272 if (test2) goto F;
2276 Again, this is most useful if J postdominates.
2278 (C) CE substitutes for helpful life information.
2280 (D) These heuristics need a lot of work. */
2282 /* Tests for case 1 above. */
2284 static int
2285 find_if_case_1 (test_bb, then_edge, else_edge)
2286 basic_block test_bb;
2287 edge then_edge, else_edge;
2289 basic_block then_bb = then_edge->dest;
2290 basic_block else_bb = else_edge->dest, new_bb;
2291 edge then_succ = then_bb->succ;
2293 /* THEN has one successor. */
2294 if (!then_succ || then_succ->succ_next != NULL)
2295 return FALSE;
2297 /* THEN does not fall through, but is not strange either. */
2298 if (then_succ->flags & (EDGE_COMPLEX | EDGE_FALLTHRU))
2299 return FALSE;
2301 /* THEN has one predecessor. */
2302 if (then_bb->pred->pred_next != NULL)
2303 return FALSE;
2305 /* THEN must do something. */
2306 if (forwarder_block_p (then_bb))
2307 return FALSE;
2309 num_possible_if_blocks++;
2310 if (rtl_dump_file)
2311 fprintf (rtl_dump_file,
2312 "\nIF-CASE-1 found, start %d, then %d\n",
2313 test_bb->index, then_bb->index);
2315 /* THEN is small. */
2316 if (count_bb_insns (then_bb) > BRANCH_COST)
2317 return FALSE;
2319 /* Registers set are dead, or are predicable. */
2320 if (! dead_or_predicable (test_bb, then_bb, else_bb,
2321 then_bb->succ->dest, 1))
2322 return FALSE;
2324 /* Conversion went ok, including moving the insns and fixing up the
2325 jump. Adjust the CFG to match. */
2327 SET_UPDATE_LIFE (test_bb);
2328 bitmap_operation (test_bb->global_live_at_end,
2329 else_bb->global_live_at_start,
2330 then_bb->global_live_at_end, BITMAP_IOR);
2332 new_bb = redirect_edge_and_branch_force (FALLTHRU_EDGE (test_bb), else_bb);
2333 /* Make rest of code believe that the newly created block is the THEN_BB
2334 block we are going to remove. */
2335 if (new_bb)
2337 new_bb->aux = then_bb->aux;
2338 SET_UPDATE_LIFE (then_bb);
2340 flow_delete_block (then_bb);
2341 /* We've possibly created jump to next insn, cleanup_cfg will solve that
2342 later. */
2344 num_removed_blocks++;
2345 num_updated_if_blocks++;
2347 return TRUE;
2350 /* Test for case 2 above. */
2352 static int
2353 find_if_case_2 (test_bb, then_edge, else_edge)
2354 basic_block test_bb;
2355 edge then_edge, else_edge;
2357 basic_block then_bb = then_edge->dest;
2358 basic_block else_bb = else_edge->dest;
2359 edge else_succ = else_bb->succ;
2360 rtx note;
2362 /* ELSE has one successor. */
2363 if (!else_succ || else_succ->succ_next != NULL)
2364 return FALSE;
2366 /* ELSE outgoing edge is not complex. */
2367 if (else_succ->flags & EDGE_COMPLEX)
2368 return FALSE;
2370 /* ELSE has one predecessor. */
2371 if (else_bb->pred->pred_next != NULL)
2372 return FALSE;
2374 /* THEN is not EXIT. */
2375 if (then_bb->index < 0)
2376 return FALSE;
2378 /* ELSE is predicted or SUCC(ELSE) postdominates THEN. */
2379 note = find_reg_note (test_bb->end, REG_BR_PROB, NULL_RTX);
2380 if (note && INTVAL (XEXP (note, 0)) >= REG_BR_PROB_BASE / 2)
2382 else if (else_succ->dest->index < 0
2383 || TEST_BIT (post_dominators[ORIG_INDEX (then_bb)],
2384 ORIG_INDEX (else_succ->dest)))
2386 else
2387 return FALSE;
2389 num_possible_if_blocks++;
2390 if (rtl_dump_file)
2391 fprintf (rtl_dump_file,
2392 "\nIF-CASE-2 found, start %d, else %d\n",
2393 test_bb->index, else_bb->index);
2395 /* ELSE is small. */
2396 if (count_bb_insns (then_bb) > BRANCH_COST)
2397 return FALSE;
2399 /* Registers set are dead, or are predicable. */
2400 if (! dead_or_predicable (test_bb, else_bb, then_bb, else_succ->dest, 0))
2401 return FALSE;
2403 /* Conversion went ok, including moving the insns and fixing up the
2404 jump. Adjust the CFG to match. */
2406 SET_UPDATE_LIFE (test_bb);
2407 bitmap_operation (test_bb->global_live_at_end,
2408 then_bb->global_live_at_start,
2409 else_bb->global_live_at_end, BITMAP_IOR);
2411 flow_delete_block (else_bb);
2413 num_removed_blocks++;
2414 num_updated_if_blocks++;
2416 /* ??? We may now fallthru from one of THEN's successors into a join
2417 block. Rerun cleanup_cfg? Examine things manually? Wait? */
2419 return TRUE;
2422 /* A subroutine of dead_or_predicable called through for_each_rtx.
2423 Return 1 if a memory is found. */
2425 static int
2426 find_memory (px, data)
2427 rtx *px;
2428 void *data ATTRIBUTE_UNUSED;
2430 return GET_CODE (*px) == MEM;
2433 /* Used by the code above to perform the actual rtl transformations.
2434 Return TRUE if successful.
2436 TEST_BB is the block containing the conditional branch. MERGE_BB
2437 is the block containing the code to manipulate. NEW_DEST is the
2438 label TEST_BB should be branching to after the conversion.
2439 REVERSEP is true if the sense of the branch should be reversed. */
2441 static int
2442 dead_or_predicable (test_bb, merge_bb, other_bb, new_dest, reversep)
2443 basic_block test_bb, merge_bb, other_bb;
2444 basic_block new_dest;
2445 int reversep;
2447 rtx head, end, jump, earliest, old_dest, new_label;
2449 jump = test_bb->end;
2451 /* Find the extent of the real code in the merge block. */
2452 head = merge_bb->head;
2453 end = merge_bb->end;
2455 if (GET_CODE (head) == CODE_LABEL)
2456 head = NEXT_INSN (head);
2457 if (GET_CODE (head) == NOTE)
2459 if (head == end)
2461 head = end = NULL_RTX;
2462 goto no_body;
2464 head = NEXT_INSN (head);
2467 if (GET_CODE (end) == JUMP_INSN)
2469 if (head == end)
2471 head = end = NULL_RTX;
2472 goto no_body;
2474 end = PREV_INSN (end);
2477 /* Disable handling dead code by conditional execution if the machine needs
2478 to do anything funny with the tests, etc. */
2479 #ifndef IFCVT_MODIFY_TESTS
2480 if (HAVE_conditional_execution)
2482 /* In the conditional execution case, we have things easy. We know
2483 the condition is reversable. We don't have to check life info,
2484 becase we're going to conditionally execute the code anyway.
2485 All that's left is making sure the insns involved can actually
2486 be predicated. */
2488 rtx cond, prob_val;
2490 cond = cond_exec_get_condition (jump);
2491 if (! cond)
2492 return FALSE;
2494 prob_val = find_reg_note (jump, REG_BR_PROB, NULL_RTX);
2495 if (prob_val)
2496 prob_val = XEXP (prob_val, 0);
2498 if (reversep)
2500 enum rtx_code rev = reversed_comparison_code (cond, jump);
2501 if (rev == UNKNOWN)
2502 return FALSE;
2503 cond = gen_rtx_fmt_ee (rev, GET_MODE (cond), XEXP (cond, 0),
2504 XEXP (cond, 1));
2505 if (prob_val)
2506 prob_val = GEN_INT (REG_BR_PROB_BASE - INTVAL (prob_val));
2509 if (! cond_exec_process_insns (head, end, cond, prob_val, 0))
2510 goto cancel;
2512 earliest = jump;
2514 else
2515 #endif
2517 /* In the non-conditional execution case, we have to verify that there
2518 are no trapping operations, no calls, no references to memory, and
2519 that any registers modified are dead at the branch site. */
2521 rtx insn, cond, prev;
2522 regset_head merge_set_head, tmp_head, test_live_head, test_set_head;
2523 regset merge_set, tmp, test_live, test_set;
2524 struct propagate_block_info *pbi;
2525 int i, fail = 0;
2527 /* Check for no calls or trapping operations. */
2528 for (insn = head; ; insn = NEXT_INSN (insn))
2530 if (GET_CODE (insn) == CALL_INSN)
2531 return FALSE;
2532 if (INSN_P (insn))
2534 if (may_trap_p (PATTERN (insn)))
2535 return FALSE;
2537 /* ??? Even non-trapping memories such as stack frame
2538 references must be avoided. For stores, we collect
2539 no lifetime info; for reads, we'd have to assert
2540 true_dependence false against every store in the
2541 TEST range. */
2542 if (for_each_rtx (&PATTERN (insn), find_memory, NULL))
2543 return FALSE;
2545 if (insn == end)
2546 break;
2549 if (! any_condjump_p (jump))
2550 return FALSE;
2552 /* Find the extent of the conditional. */
2553 cond = noce_get_condition (jump, &earliest);
2554 if (! cond)
2555 return FALSE;
2557 /* Collect:
2558 MERGE_SET = set of registers set in MERGE_BB
2559 TEST_LIVE = set of registers live at EARLIEST
2560 TEST_SET = set of registers set between EARLIEST and the
2561 end of the block. */
2563 tmp = INITIALIZE_REG_SET (tmp_head);
2564 merge_set = INITIALIZE_REG_SET (merge_set_head);
2565 test_live = INITIALIZE_REG_SET (test_live_head);
2566 test_set = INITIALIZE_REG_SET (test_set_head);
2568 /* ??? bb->local_set is only valid during calculate_global_regs_live,
2569 so we must recompute usage for MERGE_BB. Not so bad, I suppose,
2570 since we've already asserted that MERGE_BB is small. */
2571 propagate_block (merge_bb, tmp, merge_set, merge_set, 0);
2573 /* For small register class machines, don't lengthen lifetimes of
2574 hard registers before reload. */
2575 if (SMALL_REGISTER_CLASSES && ! reload_completed)
2577 EXECUTE_IF_SET_IN_BITMAP
2578 (merge_set, 0, i,
2580 if (i < FIRST_PSEUDO_REGISTER
2581 && ! fixed_regs[i]
2582 && ! global_regs[i])
2583 fail = 1;
2587 /* For TEST, we're interested in a range of insns, not a whole block.
2588 Moreover, we're interested in the insns live from OTHER_BB. */
2590 COPY_REG_SET (test_live, other_bb->global_live_at_start);
2591 pbi = init_propagate_block_info (test_bb, test_live, test_set, test_set,
2594 for (insn = jump; ; insn = prev)
2596 prev = propagate_one_insn (pbi, insn);
2597 if (insn == earliest)
2598 break;
2601 free_propagate_block_info (pbi);
2603 /* We can perform the transformation if
2604 MERGE_SET & (TEST_SET | TEST_LIVE)
2606 TEST_SET & merge_bb->global_live_at_start
2607 are empty. */
2609 bitmap_operation (tmp, test_set, test_live, BITMAP_IOR);
2610 bitmap_operation (tmp, tmp, merge_set, BITMAP_AND);
2611 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
2613 bitmap_operation (tmp, test_set, merge_bb->global_live_at_start,
2614 BITMAP_AND);
2615 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
2617 FREE_REG_SET (tmp);
2618 FREE_REG_SET (merge_set);
2619 FREE_REG_SET (test_live);
2620 FREE_REG_SET (test_set);
2622 if (fail)
2623 return FALSE;
2626 no_body:
2627 /* We don't want to use normal invert_jump or redirect_jump because
2628 we don't want to delete_insn called. Also, we want to do our own
2629 change group management. */
2631 old_dest = JUMP_LABEL (jump);
2632 new_label = block_label (new_dest);
2633 if (reversep
2634 ? ! invert_jump_1 (jump, new_label)
2635 : ! redirect_jump_1 (jump, new_label))
2636 goto cancel;
2638 if (! apply_change_group ())
2639 return FALSE;
2641 if (old_dest)
2642 LABEL_NUSES (old_dest) -= 1;
2643 if (new_label)
2644 LABEL_NUSES (new_label) += 1;
2645 JUMP_LABEL (jump) = new_label;
2647 if (reversep)
2648 invert_br_probabilities (jump);
2650 redirect_edge_succ (BRANCH_EDGE (test_bb), new_dest);
2651 if (reversep)
2653 gcov_type count, probability;
2654 count = BRANCH_EDGE (test_bb)->count;
2655 BRANCH_EDGE (test_bb)->count = FALLTHRU_EDGE (test_bb)->count;
2656 FALLTHRU_EDGE (test_bb)->count = count;
2657 probability = BRANCH_EDGE (test_bb)->probability;
2658 BRANCH_EDGE (test_bb)->probability = FALLTHRU_EDGE (test_bb)->probability;
2659 FALLTHRU_EDGE (test_bb)->probability = probability;
2662 /* Move the insns out of MERGE_BB to before the branch. */
2663 if (head != NULL)
2665 if (end == merge_bb->end)
2666 merge_bb->end = PREV_INSN (head);
2668 if (squeeze_notes (&head, &end))
2669 return TRUE;
2671 reorder_insns (head, end, PREV_INSN (earliest));
2673 return TRUE;
2675 cancel:
2676 cancel_changes (0);
2677 return FALSE;
2680 /* Main entry point for all if-conversion. */
2682 void
2683 if_convert (x_life_data_ok)
2684 int x_life_data_ok;
2686 int block_num;
2688 num_possible_if_blocks = 0;
2689 num_updated_if_blocks = 0;
2690 num_removed_blocks = 0;
2691 life_data_ok = (x_life_data_ok != 0);
2693 /* Free up basic_block_for_insn so that we don't have to keep it
2694 up to date, either here or in merge_blocks_nomove. */
2695 free_basic_block_vars (1);
2697 /* Compute postdominators if we think we'll use them. */
2698 post_dominators = NULL;
2699 if (HAVE_conditional_execution || life_data_ok)
2701 post_dominators = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
2702 calculate_dominance_info (NULL, post_dominators, CDI_POST_DOMINATORS);
2705 /* Record initial block numbers. */
2706 for (block_num = 0; block_num < n_basic_blocks; block_num++)
2707 SET_ORIG_INDEX (BASIC_BLOCK (block_num), block_num);
2709 /* Go through each of the basic blocks looking for things to convert. */
2710 for (block_num = 0; block_num < n_basic_blocks; )
2712 basic_block bb = BASIC_BLOCK (block_num);
2713 if (find_if_header (bb))
2714 block_num = bb->index;
2715 else
2716 block_num++;
2719 if (post_dominators)
2720 sbitmap_vector_free (post_dominators);
2722 if (rtl_dump_file)
2723 fflush (rtl_dump_file);
2725 /* Rebuild life info for basic blocks that require it. */
2726 if (num_removed_blocks && life_data_ok)
2728 sbitmap update_life_blocks = sbitmap_alloc (n_basic_blocks);
2729 sbitmap_zero (update_life_blocks);
2731 /* If we allocated new pseudos, we must resize the array for sched1. */
2732 if (max_regno < max_reg_num ())
2734 max_regno = max_reg_num ();
2735 allocate_reg_info (max_regno, FALSE, FALSE);
2738 for (block_num = 0; block_num < n_basic_blocks; block_num++)
2739 if (UPDATE_LIFE (BASIC_BLOCK (block_num)))
2740 SET_BIT (update_life_blocks, block_num);
2742 count_or_remove_death_notes (update_life_blocks, 1);
2743 /* ??? See about adding a mode that verifies that the initial
2744 set of blocks don't let registers come live. */
2745 update_life_info (update_life_blocks, UPDATE_LIFE_GLOBAL,
2746 PROP_DEATH_NOTES | PROP_SCAN_DEAD_CODE
2747 | PROP_KILL_DEAD_CODE);
2749 sbitmap_free (update_life_blocks);
2751 clear_aux_for_blocks ();
2753 /* Write the final stats. */
2754 if (rtl_dump_file && num_possible_if_blocks > 0)
2756 fprintf (rtl_dump_file,
2757 "\n%d possible IF blocks searched.\n",
2758 num_possible_if_blocks);
2759 fprintf (rtl_dump_file,
2760 "%d IF blocks converted.\n",
2761 num_updated_if_blocks);
2762 fprintf (rtl_dump_file,
2763 "%d basic blocks deleted.\n\n\n",
2764 num_removed_blocks);
2767 #ifdef ENABLE_CHECKING
2768 verify_flow_info ();
2769 #endif