1 /* If-conversion support.
2 Copyright (C) 2000 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
28 #include "insn-config.h"
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
38 #ifndef HAVE_conditional_execution
39 #define HAVE_conditional_execution 0
41 #ifndef HAVE_conditional_move
42 #define HAVE_conditional_move 0
51 #ifndef MAX_CONDITIONAL_EXECUTE
52 #define MAX_CONDITIONAL_EXECUTE (BRANCH_COST + 1)
55 #define NULL_EDGE ((struct edge_def *)NULL)
56 #define NULL_BLOCK ((struct basic_block_def *)NULL)
58 /* # of IF-THEN or IF-THEN-ELSE blocks we looked at */
59 static int num_possible_if_blocks
;
61 /* # of IF-THEN or IF-THEN-ELSE blocks were converted to conditional
63 static int num_updated_if_blocks
;
65 /* # of basic blocks that were removed. */
66 static int num_removed_blocks
;
68 /* The post-dominator relation on the original block numbers. */
69 static sbitmap
*post_dominators
;
71 /* Forward references. */
72 static int count_bb_insns
PARAMS ((basic_block
));
73 static rtx first_active_insn
PARAMS ((basic_block
));
74 static int last_active_insn_p
PARAMS ((basic_block
, rtx
));
75 static int seq_contains_jump
PARAMS ((rtx
));
77 static int cond_exec_process_insns
PARAMS ((rtx
, rtx
, rtx
, rtx
, int));
78 static rtx cond_exec_get_condition
PARAMS ((rtx
));
79 static int cond_exec_process_if_block
PARAMS ((basic_block
, basic_block
,
80 basic_block
, basic_block
));
82 static rtx noce_get_condition
PARAMS ((rtx
, rtx
*));
83 static int noce_operand_ok
PARAMS ((rtx
));
84 static int noce_process_if_block
PARAMS ((basic_block
, basic_block
,
85 basic_block
, basic_block
));
87 static int process_if_block
PARAMS ((basic_block
, basic_block
,
88 basic_block
, basic_block
));
89 static void merge_if_block
PARAMS ((basic_block
, basic_block
,
90 basic_block
, basic_block
));
92 static int find_if_header
PARAMS ((basic_block
));
93 static int find_if_block
PARAMS ((basic_block
, edge
, edge
));
94 static int find_if_case_1
PARAMS ((basic_block
, edge
, edge
));
95 static int find_if_case_2
PARAMS ((basic_block
, edge
, edge
));
96 static int find_memory
PARAMS ((rtx
*, void *));
97 static int dead_or_predicable
PARAMS ((basic_block
, basic_block
,
98 basic_block
, rtx
, int));
100 /* Abuse the basic_block AUX field to store the original block index,
101 as well as a flag indicating that the block should be rescaned for
104 #define SET_ORIG_INDEX(BB,I) ((BB)->aux = (void *)((size_t)(I) << 1))
105 #define ORIG_INDEX(BB) ((size_t)(BB)->aux >> 1)
106 #define SET_UPDATE_LIFE(BB) ((BB)->aux = (void *)((size_t)(BB)->aux | 1))
107 #define UPDATE_LIFE(BB) ((size_t)(BB)->aux & 1)
110 /* Count the number of non-jump active insns in BB. */
121 if (GET_CODE (insn
) == CALL_INSN
|| GET_CODE (insn
) == INSN
)
126 insn
= NEXT_INSN (insn
);
132 /* Return the first non-jump active insn in the basic block. */
135 first_active_insn (bb
)
140 if (GET_CODE (insn
) == CODE_LABEL
)
144 insn
= NEXT_INSN (insn
);
147 while (GET_CODE (insn
) == NOTE
)
151 insn
= NEXT_INSN (insn
);
154 if (GET_CODE (insn
) == JUMP_INSN
)
160 /* Return true if INSN is the last active non-jump insn in BB. */
163 last_active_insn_p (bb
, insn
)
171 insn
= NEXT_INSN (insn
);
173 while (GET_CODE (insn
) == NOTE
);
175 return GET_CODE (insn
) == JUMP_INSN
;
178 /* It is possible, especially when having dealt with multi-word
179 arithmetic, for the expanders to have emitted jumps. Search
180 through the sequence and return TRUE if a jump exists so that
181 we can abort the conversion. */
184 seq_contains_jump (insn
)
189 if (GET_CODE (insn
) == JUMP_INSN
)
191 insn
= NEXT_INSN (insn
);
196 /* Go through a bunch of insns, converting them to conditional
197 execution format if possible. Return TRUE if all of the non-note
198 insns were processed. */
201 cond_exec_process_insns (start
, end
, test
, prob_val
, mod_ok
)
202 rtx start
; /* first insn to look at */
203 rtx end
; /* last insn to look at */
204 rtx test
; /* conditional execution test */
205 rtx prob_val
; /* probability of branch taken. */
206 int mod_ok
; /* true if modifications ok last insn. */
208 int must_be_last
= FALSE
;
212 for (insn
= start
; ; insn
= NEXT_INSN (insn
))
214 if (GET_CODE (insn
) == NOTE
)
217 if (GET_CODE (insn
) != INSN
&& GET_CODE (insn
) != CALL_INSN
)
220 /* Remove USE insns that get in the way. */
221 if (reload_completed
&& GET_CODE (PATTERN (insn
)) == USE
)
223 /* ??? Ug. Actually unlinking the thing is problematic,
224 given what we'd have to coordinate with our callers. */
225 PUT_CODE (insn
, NOTE
);
226 NOTE_LINE_NUMBER (insn
) = NOTE_INSN_DELETED
;
227 NOTE_SOURCE_FILE (insn
) = 0;
231 /* Last insn wasn't last? */
235 if (modified_in_p (test
, insn
))
242 /* Now build the conditional form of the instruction. */
243 pattern
= PATTERN (insn
);
245 /* If the machine needs to modify the insn being conditionally executed,
246 say for example to force a constant integer operand into a temp
247 register, do so here. */
248 #ifdef IFCVT_MODIFY_INSN
249 IFCVT_MODIFY_INSN (pattern
, insn
);
254 validate_change (insn
, &PATTERN (insn
),
255 gen_rtx_COND_EXEC (VOIDmode
, copy_rtx (test
),
258 if (GET_CODE (insn
) == CALL_INSN
&& prob_val
)
259 validate_change (insn
, ®_NOTES (insn
),
260 alloc_EXPR_LIST (REG_BR_PROB
, prob_val
,
261 REG_NOTES (insn
)), 1);
271 /* Return the condition for a jump. Do not do any special processing. */
274 cond_exec_get_condition (jump
)
279 if (any_condjump_p (jump
))
280 test_if
= SET_SRC (pc_set (jump
));
283 cond
= XEXP (test_if
, 0);
285 /* If this branches to JUMP_LABEL when the condition is false,
286 reverse the condition. */
287 if (GET_CODE (XEXP (test_if
, 2)) == LABEL_REF
288 && XEXP (XEXP (test_if
, 2), 0) == JUMP_LABEL (jump
))
289 cond
= gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond
)),
290 GET_MODE (cond
), XEXP (cond
, 0),
296 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
297 to conditional execution. Return TRUE if we were successful at
298 converting the the block. */
301 cond_exec_process_if_block (test_bb
, then_bb
, else_bb
, join_bb
)
302 basic_block test_bb
; /* Basic block test is in */
303 basic_block then_bb
; /* Basic block for THEN block */
304 basic_block else_bb
; /* Basic block for ELSE block */
305 basic_block join_bb
; /* Basic block the join label is in */
307 rtx test_expr
; /* expression in IF_THEN_ELSE that is tested */
308 rtx then_start
; /* first insn in THEN block */
309 rtx then_end
; /* last insn + 1 in THEN block */
310 rtx else_start
= NULL_RTX
; /* first insn in ELSE block or NULL */
311 rtx else_end
= NULL_RTX
; /* last insn + 1 in ELSE block */
312 int max
; /* max # of insns to convert. */
313 int then_mod_ok
; /* whether conditional mods are ok in THEN */
314 rtx true_expr
; /* test for else block insns */
315 rtx false_expr
; /* test for then block insns */
316 rtx true_prob_val
; /* probability of else block */
317 rtx false_prob_val
; /* probability of then block */
320 /* Find the conditional jump to the ELSE or JOIN part, and isolate
322 test_expr
= cond_exec_get_condition (test_bb
->end
);
326 /* If the conditional jump is more than just a conditional jump,
327 then we can not do conditional execution conversion on this block. */
328 if (!onlyjump_p (test_bb
->end
))
331 /* Collect the bounds of where we're to search. */
333 then_start
= then_bb
->head
;
334 then_end
= then_bb
->end
;
336 /* Skip a label heading THEN block. */
337 if (GET_CODE (then_start
) == CODE_LABEL
)
338 then_start
= NEXT_INSN (then_start
);
340 /* Skip a (use (const_int 0)) or branch as the final insn. */
341 if (GET_CODE (then_end
) == INSN
342 && GET_CODE (PATTERN (then_end
)) == USE
343 && GET_CODE (XEXP (PATTERN (then_end
), 0)) == CONST_INT
)
344 then_end
= PREV_INSN (then_end
);
345 else if (GET_CODE (then_end
) == JUMP_INSN
)
346 then_end
= PREV_INSN (then_end
);
350 /* Skip the ELSE block's label. */
351 else_start
= NEXT_INSN (else_bb
->head
);
352 else_end
= else_bb
->end
;
354 /* Skip a (use (const_int 0)) or branch as the final insn. */
355 if (GET_CODE (else_end
) == INSN
356 && GET_CODE (PATTERN (else_end
)) == USE
357 && GET_CODE (XEXP (PATTERN (else_end
), 0)) == CONST_INT
)
358 else_end
= PREV_INSN (else_end
);
359 else if (GET_CODE (else_end
) == JUMP_INSN
)
360 else_end
= PREV_INSN (else_end
);
363 /* How many instructions should we convert in total? */
367 max
= 2 * MAX_CONDITIONAL_EXECUTE
;
368 n_insns
= count_bb_insns (else_bb
);
371 max
= MAX_CONDITIONAL_EXECUTE
;
372 n_insns
+= count_bb_insns (then_bb
);
376 /* Map test_expr/test_jump into the appropriate MD tests to use on
377 the conditionally executed code. */
379 true_expr
= test_expr
;
380 false_expr
= gen_rtx_fmt_ee (reverse_condition (GET_CODE (true_expr
)),
381 GET_MODE (true_expr
), XEXP (true_expr
, 0),
382 XEXP (true_expr
, 1));
384 #ifdef IFCVT_MODIFY_TESTS
385 /* If the machine description needs to modify the tests, such as setting a
386 conditional execution register from a comparison, it can do so here. */
387 IFCVT_MODIFY_TESTS (true_expr
, false_expr
, test_bb
, then_bb
, else_bb
,
390 /* See if the conversion failed */
391 if (!true_expr
|| !false_expr
)
395 true_prob_val
= find_reg_note (test_bb
->end
, REG_BR_PROB
, NULL_RTX
);
398 true_prob_val
= XEXP (true_prob_val
, 0);
399 false_prob_val
= GEN_INT (REG_BR_PROB_BASE
- INTVAL (true_prob_val
));
402 false_prob_val
= NULL_RTX
;
404 /* For IF-THEN-ELSE blocks, we don't allow modifications of the test
405 on then THEN block. */
406 then_mod_ok
= (else_bb
== NULL_BLOCK
);
408 /* Go through the THEN and ELSE blocks converting the insns if possible
409 to conditional execution. */
412 && ! cond_exec_process_insns (then_start
, then_end
,
413 false_expr
, false_prob_val
, then_mod_ok
))
417 && ! cond_exec_process_insns (else_start
, else_end
,
418 true_expr
, true_prob_val
, TRUE
))
421 if (! apply_change_group ())
424 #ifdef IFCVT_MODIFY_FINAL
425 /* Do any machine dependent final modifications */
426 IFCVT_MODIFY_FINAL (test_bb
, then_bb
, else_bb
, join_bb
);
429 /* Conversion succeeded. */
431 fprintf (rtl_dump_file
, "%d insn%s converted to conditional execution.\n",
432 n_insns
, (n_insns
== 1) ? " was" : "s were");
434 /* Merge the blocks! */
435 merge_if_block (test_bb
, then_bb
, else_bb
, join_bb
);
439 #ifdef IFCVT_MODIFY_CANCEL
440 /* Cancel any machine dependent changes. */
441 IFCVT_MODIFY_CANCEL (test_bb
, then_bb
, else_bb
, join_bb
);
448 /* Used by noce_process_if_block to communicate with its subroutines.
450 The subroutines know that A and B may be evaluated freely. They
451 know that X is a register. They should insert new instructions
452 before cond_earliest. */
459 rtx jump
, cond
, cond_earliest
;
462 static rtx noce_emit_store_flag
PARAMS ((struct noce_if_info
*,
464 static int noce_try_store_flag
PARAMS ((struct noce_if_info
*));
465 static int noce_try_store_flag_inc
PARAMS ((struct noce_if_info
*));
466 static int noce_try_store_flag_constants
PARAMS ((struct noce_if_info
*));
467 static int noce_try_store_flag_mask
PARAMS ((struct noce_if_info
*));
468 static rtx noce_emit_cmove
PARAMS ((struct noce_if_info
*,
469 rtx
, enum rtx_code
, rtx
,
471 static int noce_try_cmove
PARAMS ((struct noce_if_info
*));
472 static int noce_try_cmove_arith
PARAMS ((struct noce_if_info
*));
473 static rtx noce_get_alt_condition
PARAMS ((struct noce_if_info
*,
475 static int noce_try_minmax
PARAMS ((struct noce_if_info
*));
476 static int noce_try_abs
PARAMS ((struct noce_if_info
*));
478 /* Helper function for noce_try_store_flag*. */
481 noce_emit_store_flag (if_info
, x
, reversep
, normalize
)
482 struct noce_if_info
*if_info
;
484 int reversep
, normalize
;
486 rtx cond
= if_info
->cond
;
490 cond_complex
= (! general_operand (XEXP (cond
, 0), VOIDmode
)
491 || ! general_operand (XEXP (cond
, 1), VOIDmode
));
493 /* If earliest == jump, or when the condition is complex, try to
494 build the store_flag insn directly. */
497 cond
= XEXP (SET_SRC (pc_set (if_info
->jump
)), 0);
499 if ((if_info
->cond_earliest
== if_info
->jump
|| cond_complex
)
500 && (normalize
== 0 || STORE_FLAG_VALUE
== normalize
))
504 code
= GET_CODE (cond
);
506 code
= reverse_condition (code
);
508 tmp
= gen_rtx_fmt_ee (code
, GET_MODE (x
), XEXP (cond
, 0),
510 tmp
= gen_rtx_SET (VOIDmode
, x
, tmp
);
513 tmp
= emit_insn (tmp
);
515 if (recog_memoized (tmp
) >= 0)
521 if_info
->cond_earliest
= if_info
->jump
;
529 /* Don't even try if the comparison operands are weird. */
533 code
= GET_CODE (cond
);
535 code
= reverse_condition (code
);
537 return emit_store_flag (x
, code
, XEXP (cond
, 0),
538 XEXP (cond
, 1), VOIDmode
,
539 (code
== LTU
|| code
== LEU
540 || code
== GEU
|| code
== GTU
), normalize
);
543 /* Convert "if (test) x = 1; else x = 0".
545 Only try 0 and STORE_FLAG_VALUE here. Other combinations will be
546 tried in noce_try_store_flag_constants after noce_try_cmove has had
547 a go at the conversion. */
550 noce_try_store_flag (if_info
)
551 struct noce_if_info
*if_info
;
556 if (GET_CODE (if_info
->b
) == CONST_INT
557 && INTVAL (if_info
->b
) == STORE_FLAG_VALUE
558 && if_info
->a
== const0_rtx
)
560 else if (if_info
->b
== const0_rtx
561 && GET_CODE (if_info
->a
) == CONST_INT
562 && INTVAL (if_info
->a
) == STORE_FLAG_VALUE
563 && can_reverse_comparison_p (if_info
->cond
, if_info
->jump
))
570 target
= noce_emit_store_flag (if_info
, if_info
->x
, reversep
, 0);
573 if (target
!= if_info
->x
)
574 emit_move_insn (if_info
->x
, target
);
578 emit_insns_before (seq
, if_info
->cond_earliest
);
589 /* Convert "if (test) x = a; else x = b", for A and B constant. */
592 noce_try_store_flag_constants (if_info
)
593 struct noce_if_info
*if_info
;
597 HOST_WIDE_INT itrue
, ifalse
, diff
, tmp
;
598 int normalize
, can_reverse
;
601 && GET_CODE (if_info
->a
) == CONST_INT
602 && GET_CODE (if_info
->b
) == CONST_INT
)
604 ifalse
= INTVAL (if_info
->a
);
605 itrue
= INTVAL (if_info
->b
);
606 diff
= itrue
- ifalse
;
608 can_reverse
= can_reverse_comparison_p (if_info
->cond
, if_info
->jump
);
611 if (diff
== STORE_FLAG_VALUE
|| diff
== -STORE_FLAG_VALUE
)
613 else if (ifalse
== 0 && exact_log2 (itrue
) >= 0
614 && (STORE_FLAG_VALUE
== 1
615 || BRANCH_COST
>= 2))
617 else if (itrue
== 0 && exact_log2 (ifalse
) >= 0 && can_reverse
618 && (STORE_FLAG_VALUE
== 1 || BRANCH_COST
>= 2))
619 normalize
= 1, reversep
= 1;
621 && (STORE_FLAG_VALUE
== -1
622 || BRANCH_COST
>= 2))
624 else if (ifalse
== -1 && can_reverse
625 && (STORE_FLAG_VALUE
== -1 || BRANCH_COST
>= 2))
626 normalize
= -1, reversep
= 1;
627 else if ((BRANCH_COST
>= 2 && STORE_FLAG_VALUE
== -1)
635 tmp
= itrue
; itrue
= ifalse
; ifalse
= tmp
;
640 target
= noce_emit_store_flag (if_info
, if_info
->x
, reversep
, normalize
);
647 /* if (test) x = 3; else x = 4;
648 => x = 3 + (test == 0); */
649 if (diff
== STORE_FLAG_VALUE
|| diff
== -STORE_FLAG_VALUE
)
651 target
= expand_binop (GET_MODE (if_info
->x
),
652 (diff
== STORE_FLAG_VALUE
653 ? add_optab
: sub_optab
),
654 GEN_INT (ifalse
), target
, if_info
->x
, 0,
658 /* if (test) x = 8; else x = 0;
659 => x = (test != 0) << 3; */
660 else if (ifalse
== 0 && (tmp
= exact_log2 (itrue
)) >= 0)
662 target
= expand_binop (GET_MODE (if_info
->x
), ashl_optab
,
663 target
, GEN_INT (tmp
), if_info
->x
, 0,
667 /* if (test) x = -1; else x = b;
668 => x = -(test != 0) | b; */
669 else if (itrue
== -1)
671 target
= expand_binop (GET_MODE (if_info
->x
), ior_optab
,
672 target
, GEN_INT (ifalse
), if_info
->x
, 0,
676 /* if (test) x = a; else x = b;
677 => x = (-(test != 0) & (b - a)) + a; */
680 target
= expand_binop (GET_MODE (if_info
->x
), and_optab
,
681 target
, GEN_INT (diff
), if_info
->x
, 0,
684 target
= expand_binop (GET_MODE (if_info
->x
), add_optab
,
685 target
, GEN_INT (ifalse
), if_info
->x
, 0,
695 if (target
!= if_info
->x
)
696 emit_move_insn (if_info
->x
, target
);
701 if (seq_contains_jump (seq
))
704 emit_insns_before (seq
, if_info
->cond_earliest
);
712 /* Convert "if (test) foo++" into "foo += (test != 0)", and
713 similarly for "foo--". */
716 noce_try_store_flag_inc (if_info
)
717 struct noce_if_info
*if_info
;
720 int subtract
, normalize
;
726 /* Should be no `else' case to worry about. */
727 && if_info
->b
== if_info
->x
728 && GET_CODE (if_info
->a
) == PLUS
729 && (XEXP (if_info
->a
, 1) == const1_rtx
730 || XEXP (if_info
->a
, 1) == constm1_rtx
)
731 && rtx_equal_p (XEXP (if_info
->a
, 0), if_info
->x
)
732 && can_reverse_comparison_p (if_info
->cond
, if_info
->jump
))
734 if (STORE_FLAG_VALUE
== INTVAL (XEXP (if_info
->a
, 1)))
735 subtract
= 0, normalize
= 0;
736 else if (-STORE_FLAG_VALUE
== INTVAL (XEXP (if_info
->a
, 1)))
737 subtract
= 1, normalize
= 0;
739 subtract
= 0, normalize
= INTVAL (XEXP (if_info
->a
, 1));
743 target
= noce_emit_store_flag (if_info
,
744 gen_reg_rtx (GET_MODE (if_info
->x
)),
748 target
= expand_binop (GET_MODE (if_info
->x
),
749 subtract
? sub_optab
: add_optab
,
750 if_info
->x
, target
, if_info
->x
, 0, OPTAB_WIDEN
);
753 if (target
!= if_info
->x
)
754 emit_move_insn (if_info
->x
, target
);
759 if (seq_contains_jump (seq
))
762 emit_insns_before (seq
, if_info
->cond_earliest
);
773 /* Convert "if (test) x = 0;" to "x &= -(test == 0);" */
776 noce_try_store_flag_mask (if_info
)
777 struct noce_if_info
*if_info
;
785 || STORE_FLAG_VALUE
== -1)
786 && ((if_info
->a
== const0_rtx
787 && rtx_equal_p (if_info
->b
, if_info
->x
))
788 || ((reversep
= can_reverse_comparison_p (if_info
->cond
,
790 && if_info
->b
== const0_rtx
791 && rtx_equal_p (if_info
->a
, if_info
->x
))))
794 target
= noce_emit_store_flag (if_info
,
795 gen_reg_rtx (GET_MODE (if_info
->x
)),
798 target
= expand_binop (GET_MODE (if_info
->x
), and_optab
,
799 if_info
->x
, target
, if_info
->x
, 0,
804 if (target
!= if_info
->x
)
805 emit_move_insn (if_info
->x
, target
);
810 if (seq_contains_jump (seq
))
813 emit_insns_before (seq
, if_info
->cond_earliest
);
824 /* Helper function for noce_try_cmove and noce_try_cmove_arith. */
827 noce_emit_cmove (if_info
, x
, code
, cmp_a
, cmp_b
, vfalse
, vtrue
)
828 struct noce_if_info
*if_info
;
829 rtx x
, cmp_a
, cmp_b
, vfalse
, vtrue
;
832 /* If earliest == jump, try to build the cmove insn directly.
833 This is helpful when combine has created some complex condition
834 (like for alpha's cmovlbs) that we can't hope to regenerate
835 through the normal interface. */
837 if (if_info
->cond_earliest
== if_info
->jump
)
841 tmp
= gen_rtx_fmt_ee (code
, GET_MODE (if_info
->cond
), cmp_a
, cmp_b
);
842 tmp
= gen_rtx_IF_THEN_ELSE (GET_MODE (x
), tmp
, vtrue
, vfalse
);
843 tmp
= gen_rtx_SET (VOIDmode
, x
, tmp
);
846 tmp
= emit_insn (tmp
);
848 if (recog_memoized (tmp
) >= 0)
860 /* Don't even try if the comparison operands are weird. */
861 if (! general_operand (cmp_a
, GET_MODE (cmp_a
))
862 || ! general_operand (cmp_b
, GET_MODE (cmp_b
)))
865 #if HAVE_conditional_move
866 return emit_conditional_move (x
, code
, cmp_a
, cmp_b
, VOIDmode
,
867 vtrue
, vfalse
, GET_MODE (x
),
868 (code
== LTU
|| code
== GEU
869 || code
== LEU
|| code
== GTU
));
871 /* We'll never get here, as noce_process_if_block doesn't call the
872 functions involved. Ifdef code, however, should be discouraged
873 because it leads to typos in the code not selected. However,
874 emit_conditional_move won't exist either. */
879 /* Try only simple constants and registers here. More complex cases
880 are handled in noce_try_cmove_arith after noce_try_store_flag_arith
881 has had a go at it. */
884 noce_try_cmove (if_info
)
885 struct noce_if_info
*if_info
;
890 if ((CONSTANT_P (if_info
->a
) || register_operand (if_info
->a
, VOIDmode
))
891 && (CONSTANT_P (if_info
->b
) || register_operand (if_info
->b
, VOIDmode
)))
895 code
= GET_CODE (if_info
->cond
);
896 target
= noce_emit_cmove (if_info
, if_info
->x
, code
,
897 XEXP (if_info
->cond
, 0),
898 XEXP (if_info
->cond
, 1),
899 if_info
->a
, if_info
->b
);
903 if (target
!= if_info
->x
)
904 emit_move_insn (if_info
->x
, target
);
908 emit_insns_before (seq
, if_info
->cond_earliest
);
921 /* Try more complex cases involving conditional_move. */
924 noce_try_cmove_arith (if_info
)
925 struct noce_if_info
*if_info
;
935 /* A conditional move from two memory sources is equivalent to a
936 conditional on their addresses followed by a load. Don't do this
937 early because it'll screw alias analysis. Note that we've
938 already checked for no side effects. */
939 if (! no_new_pseudos
&& cse_not_expected
940 && GET_CODE (a
) == MEM
&& GET_CODE (b
) == MEM
945 x
= gen_reg_rtx (Pmode
);
949 /* ??? We could handle this if we knew that a load from A or B could
950 not fault. This is also true if we've already loaded
951 from the address along the path from ENTRY. */
952 else if (may_trap_p (a
) || may_trap_p (b
))
955 /* if (test) x = a + b; else x = c - d;
962 code
= GET_CODE (if_info
->cond
);
963 insn_a
= if_info
->insn_a
;
964 insn_b
= if_info
->insn_b
;
966 /* Possibly rearrange operands to make things come out more natural. */
967 if (can_reverse_comparison_p (if_info
->cond
, if_info
->jump
))
970 if (rtx_equal_p (b
, x
))
972 else if (general_operand (b
, GET_MODE (b
)))
977 code
= reverse_condition (code
);
978 tmp
= a
, a
= b
, b
= tmp
;
979 tmp
= insn_a
, insn_a
= insn_b
, insn_b
= tmp
;
985 /* If either operand is complex, load it into a register first.
986 The best way to do this is to copy the original insn. In this
987 way we preserve any clobbers etc that the insn may have had.
988 This is of course not possible in the IS_MEM case. */
989 if (! general_operand (a
, GET_MODE (a
)))
994 goto end_seq_and_fail
;
998 tmp
= gen_reg_rtx (GET_MODE (a
));
999 tmp
= emit_insn (gen_rtx_SET (VOIDmode
, tmp
, a
));
1002 goto end_seq_and_fail
;
1005 a
= gen_reg_rtx (GET_MODE (a
));
1006 tmp
= copy_rtx (insn_a
);
1007 set
= single_set (tmp
);
1009 tmp
= emit_insn (PATTERN (tmp
));
1011 if (recog_memoized (tmp
) < 0)
1012 goto end_seq_and_fail
;
1014 if (! general_operand (b
, GET_MODE (b
)))
1019 goto end_seq_and_fail
;
1023 tmp
= gen_reg_rtx (GET_MODE (b
));
1024 tmp
= emit_insn (gen_rtx_SET (VOIDmode
, tmp
, b
));
1027 goto end_seq_and_fail
;
1030 b
= gen_reg_rtx (GET_MODE (b
));
1031 tmp
= copy_rtx (insn_b
);
1032 set
= single_set (tmp
);
1034 tmp
= emit_insn (PATTERN (tmp
));
1036 if (recog_memoized (tmp
) < 0)
1037 goto end_seq_and_fail
;
1040 target
= noce_emit_cmove (if_info
, x
, code
, XEXP (if_info
->cond
, 0),
1041 XEXP (if_info
->cond
, 1), a
, b
);
1044 goto end_seq_and_fail
;
1046 /* If we're handling a memory for above, emit the load now. */
1049 tmp
= gen_rtx_MEM (GET_MODE (if_info
->x
), target
);
1051 /* Copy over flags as appropriate. */
1052 if (MEM_VOLATILE_P (if_info
->a
) || MEM_VOLATILE_P (if_info
->b
))
1053 MEM_VOLATILE_P (tmp
) = 1;
1054 if (MEM_IN_STRUCT_P (if_info
->a
) && MEM_IN_STRUCT_P (if_info
->b
))
1055 MEM_IN_STRUCT_P (tmp
) = 1;
1056 if (MEM_SCALAR_P (if_info
->a
) && MEM_SCALAR_P (if_info
->b
))
1057 MEM_SCALAR_P (tmp
) = 1;
1058 if (MEM_ALIAS_SET (if_info
->a
) == MEM_ALIAS_SET (if_info
->b
))
1059 MEM_ALIAS_SET (tmp
) = MEM_ALIAS_SET (if_info
->a
);
1061 emit_move_insn (if_info
->x
, tmp
);
1063 else if (target
!= x
)
1064 emit_move_insn (x
, target
);
1068 emit_insns_before (tmp
, if_info
->cond_earliest
);
1076 /* For most cases, the simplified condition we found is the best
1077 choice, but this is not the case for the min/max/abs transforms.
1078 For these we wish to know that it is A or B in the condition. */
1081 noce_get_alt_condition (if_info
, target
, earliest
)
1082 struct noce_if_info
*if_info
;
1086 rtx cond
, set
, insn
;
1089 /* If target is already mentioned in the known condition, return it. */
1090 if (reg_mentioned_p (target
, if_info
->cond
))
1092 *earliest
= if_info
->cond_earliest
;
1093 return if_info
->cond
;
1096 set
= pc_set (if_info
->jump
);
1097 cond
= XEXP (SET_SRC (set
), 0);
1099 = GET_CODE (XEXP (SET_SRC (set
), 2)) == LABEL_REF
1100 && XEXP (XEXP (SET_SRC (set
), 2), 0) == JUMP_LABEL (if_info
->jump
);
1102 cond
= canonicalize_condition (if_info
->jump
, cond
, reverse
,
1104 if (! cond
|| ! reg_mentioned_p (target
, cond
))
1107 /* We almost certainly searched back to a different place.
1108 Need to re-verify correct lifetimes. */
1110 /* X may not be mentioned in the range (cond_earliest, jump]. */
1111 for (insn
= if_info
->jump
; insn
!= *earliest
; insn
= PREV_INSN (insn
))
1112 if (INSN_P (insn
) && reg_mentioned_p (if_info
->x
, insn
))
1115 /* A and B may not be modified in the range [cond_earliest, jump). */
1116 for (insn
= *earliest
; insn
!= if_info
->jump
; insn
= NEXT_INSN (insn
))
1118 && (modified_in_p (if_info
->a
, insn
)
1119 || modified_in_p (if_info
->b
, insn
)))
1125 /* Convert "if (a < b) x = a; else x = b;" to "x = min(a, b);", etc. */
1128 noce_try_minmax (if_info
)
1129 struct noce_if_info
*if_info
;
1131 rtx cond
, earliest
, target
, seq
;
1136 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1140 /* ??? Reject FP modes since we don't know how 0 vs -0 or NaNs
1141 will be resolved with an SMIN/SMAX. It wouldn't be too hard
1142 to get the target to tell us... */
1143 if (FLOAT_MODE_P (GET_MODE (if_info
->x
))
1144 && TARGET_FLOAT_FORMAT
== IEEE_FLOAT_FORMAT
1145 && ! flag_fast_math
)
1148 cond
= noce_get_alt_condition (if_info
, if_info
->a
, &earliest
);
1152 /* Verify the condition is of the form we expect, and canonicalize
1153 the comparison code. */
1154 code
= GET_CODE (cond
);
1155 if (rtx_equal_p (XEXP (cond
, 0), if_info
->a
))
1157 if (! rtx_equal_p (XEXP (cond
, 1), if_info
->b
))
1160 else if (rtx_equal_p (XEXP (cond
, 1), if_info
->a
))
1162 if (! rtx_equal_p (XEXP (cond
, 0), if_info
->b
))
1164 code
= swap_condition (code
);
1169 /* Determine what sort of operation this is. Note that the code is for
1170 a taken branch, so the code->operation mapping appears backwards. */
1203 target
= expand_binop (GET_MODE (if_info
->x
), op
, if_info
->a
, if_info
->b
,
1204 if_info
->x
, unsignedp
, OPTAB_WIDEN
);
1210 if (target
!= if_info
->x
)
1211 emit_move_insn (if_info
->x
, target
);
1216 if (seq_contains_jump (seq
))
1219 emit_insns_before (seq
, earliest
);
1220 if_info
->cond
= cond
;
1221 if_info
->cond_earliest
= earliest
;
1226 /* Convert "if (a < 0) x = -a; else x = a;" to "x = abs(a);", etc. */
1229 noce_try_abs (if_info
)
1230 struct noce_if_info
*if_info
;
1232 rtx cond
, earliest
, target
, seq
, a
, b
, c
;
1235 /* ??? Can't guarantee that expand_binop won't create pseudos. */
1239 /* Recognize A and B as constituting an ABS or NABS. */
1242 if (GET_CODE (a
) == NEG
&& rtx_equal_p (XEXP (a
, 0), b
))
1244 else if (GET_CODE (b
) == NEG
&& rtx_equal_p (XEXP (b
, 0), a
))
1246 c
= a
; a
= b
; b
= c
;
1252 cond
= noce_get_alt_condition (if_info
, b
, &earliest
);
1256 /* Verify the condition is of the form we expect. */
1257 if (rtx_equal_p (XEXP (cond
, 0), b
))
1259 else if (rtx_equal_p (XEXP (cond
, 1), b
))
1264 /* Verify that C is zero. Search backward through the block for
1265 a REG_EQUAL note if necessary. */
1268 rtx insn
, note
= NULL
;
1269 for (insn
= earliest
;
1270 insn
!= if_info
->test_bb
->head
;
1271 insn
= PREV_INSN (insn
))
1273 && ((note
= find_reg_note (insn
, REG_EQUAL
, c
))
1274 || (note
= find_reg_note (insn
, REG_EQUIV
, c
))))
1280 if (GET_CODE (c
) == MEM
1281 && GET_CODE (XEXP (c
, 0)) == SYMBOL_REF
1282 && CONSTANT_POOL_ADDRESS_P (XEXP (c
, 0)))
1283 c
= get_pool_constant (XEXP (c
, 0));
1285 /* Work around funny ideas get_condition has wrt canonicalization.
1286 Note that these rtx constants are known to be CONST_INT, and
1287 therefore imply integer comparisons. */
1288 if (c
== constm1_rtx
&& GET_CODE (cond
) == GT
)
1290 else if (c
== const1_rtx
&& GET_CODE (cond
) == LT
)
1292 else if (c
!= CONST0_RTX (GET_MODE (b
)))
1295 /* Determine what sort of operation this is. */
1296 switch (GET_CODE (cond
))
1315 target
= expand_unop (GET_MODE (if_info
->x
), abs_optab
, b
, if_info
->x
, 0);
1317 /* ??? It's a quandry whether cmove would be better here, especially
1318 for integers. Perhaps combine will clean things up. */
1319 if (target
&& negate
)
1320 target
= expand_unop (GET_MODE (target
), neg_optab
, target
, if_info
->x
, 0);
1328 if (target
!= if_info
->x
)
1329 emit_move_insn (if_info
->x
, target
);
1334 if (seq_contains_jump (seq
))
1337 emit_insns_before (seq
, earliest
);
1338 if_info
->cond
= cond
;
1339 if_info
->cond_earliest
= earliest
;
1344 /* Look for the condition for the jump first. We'd prefer to avoid
1345 get_condition if we can -- it tries to look back for the contents
1346 of an original compare. On targets that use normal integers for
1347 comparisons, e.g. alpha, this is wasteful. */
1350 noce_get_condition (jump
, earliest
)
1357 /* If the condition variable is a register and is MODE_INT, accept it.
1358 Otherwise, fall back on get_condition. */
1360 if (! any_condjump_p (jump
))
1363 set
= pc_set (jump
);
1365 cond
= XEXP (SET_SRC (set
), 0);
1366 if (GET_CODE (XEXP (cond
, 0)) == REG
1367 && GET_MODE_CLASS (GET_MODE (XEXP (cond
, 0))) == MODE_INT
)
1371 /* If this branches to JUMP_LABEL when the condition is false,
1372 reverse the condition. */
1373 if (GET_CODE (XEXP (SET_SRC (set
), 2)) == LABEL_REF
1374 && XEXP (XEXP (SET_SRC (set
), 2), 0) == JUMP_LABEL (jump
))
1375 cond
= gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond
)),
1376 GET_MODE (cond
), XEXP (cond
, 0),
1380 cond
= get_condition (jump
, earliest
);
1385 /* Return true if OP is ok for if-then-else processing. */
1388 noce_operand_ok (op
)
1391 /* We special-case memories, so handle any of them with
1392 no address side effects. */
1393 if (GET_CODE (op
) == MEM
)
1394 return ! side_effects_p (XEXP (op
, 0));
1396 if (side_effects_p (op
))
1399 /* ??? Unfortuantely may_trap_p can't look at flag_fast_math, due to
1400 being linked into the genfoo programs. This is probably a mistake.
1401 With finite operands, most fp operations don't trap. */
1402 if (flag_fast_math
&& FLOAT_MODE_P (GET_MODE (op
)))
1403 switch (GET_CODE (op
))
1409 /* ??? This is kinda lame -- almost every target will have forced
1410 the constant into a register first. But given the expense of
1411 division, this is probably for the best. */
1412 return (CONSTANT_P (XEXP (op
, 1))
1413 && XEXP (op
, 1) != CONST0_RTX (GET_MODE (op
))
1414 && ! may_trap_p (XEXP (op
, 0)));
1417 switch (GET_RTX_CLASS (GET_CODE (op
)))
1422 return ! may_trap_p (XEXP (op
, 0)) && ! may_trap_p (XEXP (op
, 1));
1427 return ! may_trap_p (op
);
1430 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
1431 without using conditional execution. Return TRUE if we were
1432 successful at converting the the block. */
1435 noce_process_if_block (test_bb
, then_bb
, else_bb
, join_bb
)
1436 basic_block test_bb
; /* Basic block test is in */
1437 basic_block then_bb
; /* Basic block for THEN block */
1438 basic_block else_bb
; /* Basic block for ELSE block */
1439 basic_block join_bb
; /* Basic block the join label is in */
1441 /* We're looking for patterns of the form
1443 (1) if (...) x = a; else x = b;
1444 (2) x = b; if (...) x = a;
1445 (3) if (...) x = a; // as if with an initial x = x.
1447 The later patterns require jumps to be more expensive.
1449 ??? For future expansion, look for multiple X in such patterns. */
1451 struct noce_if_info if_info
;
1454 rtx orig_x
, x
, a
, b
;
1455 rtx jump
, cond
, insn
;
1457 /* If this is not a standard conditional jump, we can't parse it. */
1458 jump
= test_bb
->end
;
1459 cond
= noce_get_condition (jump
, &if_info
.cond_earliest
);
1463 /* If the conditional jump is more than just a conditional jump,
1464 then we can not do if-conversion on this block. */
1465 if (! onlyjump_p (jump
))
1468 /* We must be comparing objects whose modes imply the size. */
1469 if (GET_MODE (XEXP (cond
, 0)) == BLKmode
)
1472 /* Look for one of the potential sets. */
1473 insn_a
= first_active_insn (then_bb
);
1475 || ! last_active_insn_p (then_bb
, insn_a
)
1476 || (set_a
= single_set (insn_a
)) == NULL_RTX
)
1479 x
= SET_DEST (set_a
);
1480 a
= SET_SRC (set_a
);
1482 /* Look for the other potential set. Make sure we've got equivalent
1484 /* ??? This is overconservative. Storing to two different mems is
1485 as easy as conditionally computing the address. Storing to a
1486 single mem merely requires a scratch memory to use as one of the
1487 destination addresses; often the memory immediately below the
1488 stack pointer is available for this. */
1492 insn_b
= first_active_insn (else_bb
);
1494 || ! last_active_insn_p (else_bb
, insn_b
)
1495 || (set_b
= single_set (insn_b
)) == NULL_RTX
1496 || ! rtx_equal_p (x
, SET_DEST (set_b
)))
1501 insn_b
= prev_nonnote_insn (if_info
.cond_earliest
);
1503 || GET_CODE (insn_b
) != INSN
1504 || (set_b
= single_set (insn_b
)) == NULL_RTX
1505 || ! rtx_equal_p (x
, SET_DEST (set_b
))
1506 || reg_mentioned_p (x
, cond
)
1507 || reg_mentioned_p (x
, a
)
1508 || reg_mentioned_p (x
, SET_SRC (set_b
)))
1509 insn_b
= set_b
= NULL_RTX
;
1511 b
= (set_b
? SET_SRC (set_b
) : x
);
1513 /* X may not be mentioned in the range (cond_earliest, jump]. */
1514 for (insn
= jump
; insn
!= if_info
.cond_earliest
; insn
= PREV_INSN (insn
))
1515 if (INSN_P (insn
) && reg_mentioned_p (x
, insn
))
1518 /* A and B may not be modified in the range [cond_earliest, jump). */
1519 for (insn
= if_info
.cond_earliest
; insn
!= jump
; insn
= NEXT_INSN (insn
))
1521 && (modified_in_p (a
, insn
) || modified_in_p (b
, insn
)))
1524 /* Only operate on register destinations, and even then avoid extending
1525 the lifetime of hard registers on small register class machines. */
1527 if (GET_CODE (x
) != REG
1528 || (SMALL_REGISTER_CLASSES
1529 && REGNO (x
) < FIRST_PSEUDO_REGISTER
))
1533 x
= gen_reg_rtx (GET_MODE (x
));
1536 /* Don't operate on sources that may trap or are volatile. */
1537 if (! noce_operand_ok (a
) || ! noce_operand_ok (b
))
1540 /* Set up the info block for our subroutines. */
1541 if_info
.test_bb
= test_bb
;
1542 if_info
.cond
= cond
;
1543 if_info
.jump
= jump
;
1544 if_info
.insn_a
= insn_a
;
1545 if_info
.insn_b
= insn_b
;
1550 /* Try optimizations in some approximation of a useful order. */
1551 /* ??? Should first look to see if X is live incoming at all. If it
1552 isn't, we don't need anything but an unconditional set. */
1554 /* Look and see if A and B are really the same. Avoid creating silly
1555 cmove constructs that no one will fix up later. */
1556 if (rtx_equal_p (a
, b
))
1558 /* If we have an INSN_B, we don't have to create any new rtl. Just
1559 move the instruction that we already have. If we don't have an
1560 INSN_B, that means that A == X, and we've got a noop move. In
1561 that case don't do anything and let the code below delete INSN_A. */
1562 if (insn_b
&& else_bb
)
1564 if (else_bb
&& insn_b
== else_bb
->end
)
1565 else_bb
->end
= PREV_INSN (insn_b
);
1566 reorder_insns (insn_b
, insn_b
, PREV_INSN (if_info
.cond_earliest
));
1569 /* If we have "x = b; if (...) x = a;", and x has side-effects, then
1570 x must be executed twice. */
1571 else if (insn_b
&& side_effects_p (orig_x
))
1578 if (noce_try_store_flag (&if_info
))
1580 if (noce_try_minmax (&if_info
))
1582 if (noce_try_abs (&if_info
))
1584 if (HAVE_conditional_move
1585 && noce_try_cmove (&if_info
))
1587 if (! HAVE_conditional_execution
)
1589 if (noce_try_store_flag_constants (&if_info
))
1591 if (noce_try_store_flag_inc (&if_info
))
1593 if (noce_try_store_flag_mask (&if_info
))
1595 if (HAVE_conditional_move
1596 && noce_try_cmove_arith (&if_info
))
1603 /* The original sets may now be killed. */
1604 if (insn_a
== then_bb
->end
)
1605 then_bb
->end
= PREV_INSN (insn_a
);
1606 flow_delete_insn (insn_a
);
1608 /* Several special cases here: First, we may have reused insn_b above,
1609 in which case insn_b is now NULL. Second, we want to delete insn_b
1610 if it came from the ELSE block, because follows the now correct
1611 write that appears in the TEST block. However, if we got insn_b from
1612 the TEST block, it may in fact be loading data needed for the comparison.
1613 We'll let life_analysis remove the insn if it's really dead. */
1614 if (insn_b
&& else_bb
)
1616 if (insn_b
== else_bb
->end
)
1617 else_bb
->end
= PREV_INSN (insn_b
);
1618 flow_delete_insn (insn_b
);
1621 /* The new insns will have been inserted before cond_earliest. We should
1622 be able to remove the jump with impunity, but the condition itself may
1623 have been modified by gcse to be shared across basic blocks. */
1624 test_bb
->end
= PREV_INSN (jump
);
1625 flow_delete_insn (jump
);
1627 /* If we used a temporary, fix it up now. */
1631 emit_move_insn (orig_x
, x
);
1632 insn_b
= gen_sequence ();
1635 test_bb
->end
= emit_insn_after (insn_b
, test_bb
->end
);
1638 /* Merge the blocks! */
1639 merge_if_block (test_bb
, then_bb
, else_bb
, join_bb
);
1644 /* Attempt to convert an IF-THEN or IF-THEN-ELSE block into
1645 straight line code. Return true if successful. */
1648 process_if_block (test_bb
, then_bb
, else_bb
, join_bb
)
1649 basic_block test_bb
; /* Basic block test is in */
1650 basic_block then_bb
; /* Basic block for THEN block */
1651 basic_block else_bb
; /* Basic block for ELSE block */
1652 basic_block join_bb
; /* Basic block the join label is in */
1654 if (! reload_completed
1655 && noce_process_if_block (test_bb
, then_bb
, else_bb
, join_bb
))
1658 if (HAVE_conditional_execution
1660 && cond_exec_process_if_block (test_bb
, then_bb
, else_bb
, join_bb
))
1666 /* Merge the blocks and mark for local life update. */
1669 merge_if_block (test_bb
, then_bb
, else_bb
, join_bb
)
1670 basic_block test_bb
; /* Basic block test is in */
1671 basic_block then_bb
; /* Basic block for THEN block */
1672 basic_block else_bb
; /* Basic block for ELSE block */
1673 basic_block join_bb
; /* Basic block the join label is in */
1675 basic_block combo_bb
;
1677 /* All block merging is done into the lower block numbers. */
1681 /* First merge TEST block into THEN block. This is a no-brainer since
1682 the THEN block did not have a code label to begin with. */
1684 if (combo_bb
->global_live_at_end
)
1685 COPY_REG_SET (combo_bb
->global_live_at_end
, then_bb
->global_live_at_end
);
1686 merge_blocks_nomove (combo_bb
, then_bb
);
1687 num_removed_blocks
++;
1689 /* The ELSE block, if it existed, had a label. That label count
1690 will almost always be zero, but odd things can happen when labels
1691 get their addresses taken. */
1694 merge_blocks_nomove (combo_bb
, else_bb
);
1695 num_removed_blocks
++;
1698 /* If there was no join block reported, that means it was not adjacent
1699 to the others, and so we cannot merge them. */
1703 /* The outgoing edge for the current COMBO block should already
1704 be correct. Verify this. */
1705 if (combo_bb
->succ
== NULL_EDGE
)
1708 /* There should sill be a branch at the end of the THEN or ELSE
1709 blocks taking us to our final destination. */
1710 if (! simplejump_p (combo_bb
->end
)
1711 && ! returnjump_p (combo_bb
->end
))
1715 /* The JOIN block may have had quite a number of other predecessors too.
1716 Since we've already merged the TEST, THEN and ELSE blocks, we should
1717 have only one remaining edge from our if-then-else diamond. If there
1718 is more than one remaining edge, it must come from elsewhere. There
1719 may be zero incoming edges if the THEN block didn't actually join
1720 back up (as with a call to abort). */
1721 else if (join_bb
->pred
== NULL
|| join_bb
->pred
->pred_next
== NULL
)
1723 /* We can merge the JOIN. */
1724 if (combo_bb
->global_live_at_end
)
1725 COPY_REG_SET (combo_bb
->global_live_at_end
,
1726 join_bb
->global_live_at_end
);
1727 merge_blocks_nomove (combo_bb
, join_bb
);
1728 num_removed_blocks
++;
1732 /* We cannot merge the JOIN. */
1734 /* The outgoing edge for the current COMBO block should already
1735 be correct. Verify this. */
1736 if (combo_bb
->succ
->succ_next
!= NULL_EDGE
1737 || combo_bb
->succ
->dest
!= join_bb
)
1740 /* Remove the jump and cruft from the end of the COMBO block. */
1741 tidy_fallthru_edge (combo_bb
->succ
, combo_bb
, join_bb
);
1744 /* Make sure we update life info properly. */
1745 SET_UPDATE_LIFE (combo_bb
);
1747 num_updated_if_blocks
++;
1750 /* Find a block ending in a simple IF condition. Return TRUE if
1751 we were able to transform it in some way. */
1754 find_if_header (test_bb
)
1755 basic_block test_bb
;
1760 /* The kind of block we're looking for has exactly two successors. */
1761 if ((then_edge
= test_bb
->succ
) == NULL_EDGE
1762 || (else_edge
= then_edge
->succ_next
) == NULL_EDGE
1763 || else_edge
->succ_next
!= NULL_EDGE
)
1766 /* Neither edge should be abnormal. */
1767 if ((then_edge
->flags
& EDGE_COMPLEX
)
1768 || (else_edge
->flags
& EDGE_COMPLEX
))
1771 /* The THEN edge is canonically the one that falls through. */
1772 if (then_edge
->flags
& EDGE_FALLTHRU
)
1774 else if (else_edge
->flags
& EDGE_FALLTHRU
)
1777 else_edge
= then_edge
;
1781 /* Otherwise this must be a multiway branch of some sort. */
1784 if (find_if_block (test_bb
, then_edge
, else_edge
))
1787 && (! HAVE_conditional_execution
|| reload_completed
))
1789 if (find_if_case_1 (test_bb
, then_edge
, else_edge
))
1791 if (find_if_case_2 (test_bb
, then_edge
, else_edge
))
1799 fprintf (rtl_dump_file
, "Conversion succeeded.\n");
1803 /* Determine if a given basic block heads a simple IF-THEN or IF-THEN-ELSE
1804 block. If so, we'll try to convert the insns to not require the branch.
1805 Return TRUE if we were successful at converting the the block. */
1808 find_if_block (test_bb
, then_edge
, else_edge
)
1809 basic_block test_bb
;
1810 edge then_edge
, else_edge
;
1812 basic_block then_bb
= then_edge
->dest
;
1813 basic_block else_bb
= else_edge
->dest
;
1814 basic_block join_bb
= NULL_BLOCK
;
1815 edge then_succ
= then_bb
->succ
;
1816 edge else_succ
= else_bb
->succ
;
1819 /* The THEN block of an IF-THEN combo must have exactly one predecessor. */
1820 if (then_bb
->pred
->pred_next
!= NULL_EDGE
)
1823 /* The THEN block of an IF-THEN combo must have zero or one successors. */
1824 if (then_succ
!= NULL_EDGE
1825 && (then_succ
->succ_next
!= NULL_EDGE
1826 || (then_succ
->flags
& EDGE_COMPLEX
)))
1829 /* If the THEN block has no successors, conditional execution can still
1830 make a conditional call. Don't do this unless the ELSE block has
1831 only one incoming edge -- the CFG manipulation is too ugly otherwise.
1832 Check for the last insn of the THEN block being an indirect jump, which
1833 is listed as not having any successors, but confuses the rest of the CE
1834 code processing. XXX we should fix this in the future. */
1835 if (then_succ
== NULL
)
1837 if (else_bb
->pred
->pred_next
== NULL_EDGE
)
1839 rtx last_insn
= then_bb
->end
;
1842 && GET_CODE (last_insn
) == NOTE
1843 && last_insn
!= then_bb
->head
)
1844 last_insn
= PREV_INSN (last_insn
);
1847 && GET_CODE (last_insn
) == JUMP_INSN
1848 && ! simplejump_p (last_insn
))
1852 else_bb
= NULL_BLOCK
;
1858 /* If the THEN block's successor is the other edge out of the TEST block,
1859 then we have an IF-THEN combo without an ELSE. */
1860 else if (then_succ
->dest
== else_bb
)
1863 else_bb
= NULL_BLOCK
;
1866 /* If the THEN and ELSE block meet in a subsequent block, and the ELSE
1867 has exactly one predecessor and one successor, and the outgoing edge
1868 is not complex, then we have an IF-THEN-ELSE combo. */
1869 else if (else_succ
!= NULL_EDGE
1870 && then_succ
->dest
== else_succ
->dest
1871 && else_bb
->pred
->pred_next
== NULL_EDGE
1872 && else_succ
->succ_next
== NULL_EDGE
1873 && ! (else_succ
->flags
& EDGE_COMPLEX
))
1874 join_bb
= else_succ
->dest
;
1876 /* Otherwise it is not an IF-THEN or IF-THEN-ELSE combination. */
1880 num_possible_if_blocks
++;
1885 fprintf (rtl_dump_file
,
1886 "\nIF-THEN-ELSE block found, start %d, then %d, else %d, join %d\n",
1887 test_bb
->index
, then_bb
->index
, else_bb
->index
,
1890 fprintf (rtl_dump_file
,
1891 "\nIF-THEN block found, start %d, then %d, join %d\n",
1892 test_bb
->index
, then_bb
->index
, join_bb
->index
);
1895 /* Make sure IF, THEN, and ELSE, blocks are adjacent. Actually, we
1896 get the first condition for free, since we've already asserted that
1897 there's a fallthru edge from IF to THEN. */
1898 /* ??? As an enhancement, move the ELSE block. Have to deal with EH and
1899 BLOCK notes, if by no other means than aborting the merge if they
1900 exist. Sticky enough I don't want to think about it now. */
1901 next_index
= then_bb
->index
;
1902 if (else_bb
&& ++next_index
!= else_bb
->index
)
1904 if (++next_index
!= join_bb
->index
)
1912 /* Do the real work. */
1913 return process_if_block (test_bb
, then_bb
, else_bb
, join_bb
);
1916 /* Look for IF-THEN-ELSE cases in which one of THEN or ELSE is
1917 transformable, but not necessarily the other. There need be no
1920 Return TRUE if we were successful at converting the the block.
1922 Cases we'd like to look at:
1925 if (test) goto over; // x not live
1933 if (! test) goto label;
1936 if (test) goto E; // x not live
1950 (3) // This one's really only interesting for targets that can do
1951 // multiway branching, e.g. IA-64 BBB bundles. For other targets
1952 // it results in multiple branches on a cache line, which often
1953 // does not sit well with predictors.
1955 if (test1) goto E; // predicted not taken
1971 (A) Don't do (2) if the branch is predicted against the block we're
1972 eliminating. Do it anyway if we can eliminate a branch; this requires
1973 that the sole successor of the eliminated block postdominate the other
1976 (B) With CE, on (3) we can steal from both sides of the if, creating
1985 Again, this is most useful if J postdominates.
1987 (C) CE substitutes for helpful life information.
1989 (D) These heuristics need a lot of work. */
1991 /* Tests for case 1 above. */
1994 find_if_case_1 (test_bb
, then_edge
, else_edge
)
1995 basic_block test_bb
;
1996 edge then_edge
, else_edge
;
1998 basic_block then_bb
= then_edge
->dest
;
1999 basic_block else_bb
= else_edge
->dest
;
2000 edge then_succ
= then_bb
->succ
;
2003 /* THEN has one successor. */
2004 if (!then_succ
|| then_succ
->succ_next
!= NULL
)
2007 /* THEN does not fall through, but is not strange either. */
2008 if (then_succ
->flags
& (EDGE_COMPLEX
| EDGE_FALLTHRU
))
2011 /* THEN has one predecessor. */
2012 if (then_bb
->pred
->pred_next
!= NULL
)
2015 /* ELSE follows THEN. (??? could be moved) */
2016 if (else_bb
->index
!= then_bb
->index
+ 1)
2019 num_possible_if_blocks
++;
2021 fprintf (rtl_dump_file
,
2022 "\nIF-CASE-1 found, start %d, then %d\n",
2023 test_bb
->index
, then_bb
->index
);
2025 /* THEN is small. */
2026 if (count_bb_insns (then_bb
) > BRANCH_COST
)
2029 /* Find the label for THEN's destination. */
2030 if (then_succ
->dest
== EXIT_BLOCK_PTR
)
2034 new_lab
= JUMP_LABEL (then_bb
->end
);
2039 /* Registers set are dead, or are predicable. */
2040 if (! dead_or_predicable (test_bb
, then_bb
, else_bb
, new_lab
, 1))
2043 /* Conversion went ok, including moving the insns and fixing up the
2044 jump. Adjust the CFG to match. */
2046 SET_UPDATE_LIFE (test_bb
);
2047 bitmap_operation (test_bb
->global_live_at_end
,
2048 else_bb
->global_live_at_start
,
2049 then_bb
->global_live_at_end
, BITMAP_IOR
);
2051 make_edge (NULL
, test_bb
, then_succ
->dest
, 0);
2052 flow_delete_block (then_bb
);
2053 tidy_fallthru_edge (else_edge
, test_bb
, else_bb
);
2055 num_removed_blocks
++;
2056 num_updated_if_blocks
++;
2061 /* Test for case 2 above. */
2064 find_if_case_2 (test_bb
, then_edge
, else_edge
)
2065 basic_block test_bb
;
2066 edge then_edge
, else_edge
;
2068 basic_block then_bb
= then_edge
->dest
;
2069 basic_block else_bb
= else_edge
->dest
;
2070 edge else_succ
= else_bb
->succ
;
2073 /* ELSE has one successor. */
2074 if (!else_succ
|| else_succ
->succ_next
!= NULL
)
2077 /* ELSE outgoing edge is not complex. */
2078 if (else_succ
->flags
& EDGE_COMPLEX
)
2081 /* ELSE has one predecessor. */
2082 if (else_bb
->pred
->pred_next
!= NULL
)
2085 /* THEN is not EXIT. */
2086 if (then_bb
->index
< 0)
2089 /* ELSE is predicted or SUCC(ELSE) postdominates THEN. */
2090 note
= find_reg_note (test_bb
->end
, REG_BR_PROB
, NULL_RTX
);
2091 if (note
&& INTVAL (XEXP (note
, 0)) >= REG_BR_PROB_BASE
/ 2)
2093 else if (else_succ
->dest
->index
< 0
2094 || TEST_BIT (post_dominators
[ORIG_INDEX (then_bb
)],
2095 ORIG_INDEX (else_succ
->dest
)))
2100 num_possible_if_blocks
++;
2102 fprintf (rtl_dump_file
,
2103 "\nIF-CASE-2 found, start %d, else %d\n",
2104 test_bb
->index
, else_bb
->index
);
2106 /* ELSE is small. */
2107 if (count_bb_insns (then_bb
) > BRANCH_COST
)
2110 /* Find the label for ELSE's destination. */
2111 if (else_succ
->dest
== EXIT_BLOCK_PTR
)
2115 if (else_succ
->flags
& EDGE_FALLTHRU
)
2117 new_lab
= else_succ
->dest
->head
;
2118 if (GET_CODE (new_lab
) != CODE_LABEL
)
2123 new_lab
= JUMP_LABEL (else_bb
->end
);
2129 /* Registers set are dead, or are predicable. */
2130 if (! dead_or_predicable (test_bb
, else_bb
, then_bb
, new_lab
, 0))
2133 /* Conversion went ok, including moving the insns and fixing up the
2134 jump. Adjust the CFG to match. */
2136 SET_UPDATE_LIFE (test_bb
);
2137 bitmap_operation (test_bb
->global_live_at_end
,
2138 then_bb
->global_live_at_start
,
2139 else_bb
->global_live_at_end
, BITMAP_IOR
);
2141 remove_edge (else_edge
);
2142 make_edge (NULL
, test_bb
, else_succ
->dest
, 0);
2143 flow_delete_block (else_bb
);
2145 num_removed_blocks
++;
2146 num_updated_if_blocks
++;
2148 /* ??? We may now fallthru from one of THEN's successors into a join
2149 block. Rerun cleanup_cfg? Examine things manually? Wait? */
2154 /* A subroutine of dead_or_predicable called through for_each_rtx.
2155 Return 1 if a memory is found. */
2158 find_memory (px
, data
)
2160 void *data ATTRIBUTE_UNUSED
;
2162 return GET_CODE (*px
) == MEM
;
2165 /* Used by the code above to perform the actual rtl transformations.
2166 Return TRUE if successful.
2168 TEST_BB is the block containing the conditional branch. MERGE_BB
2169 is the block containing the code to manipulate. NEW_DEST is the
2170 label TEST_BB should be branching to after the conversion.
2171 REVERSEP is true if the sense of the branch should be reversed. */
2174 dead_or_predicable (test_bb
, merge_bb
, other_bb
, new_dest
, reversep
)
2175 basic_block test_bb
, merge_bb
, other_bb
;
2179 rtx head
, end
, jump
, earliest
, old_dest
;
2181 /* No code movement can occur if we'd be scrogging EH regions.
2182 Within MERGE_BB, ensure that we've not got stray EH_BEG or EH_END
2183 notes within the block. Between the blocks, checking that the end
2184 region numbers match ensures that we won't disrupt the nesting
2186 if (merge_bb
->eh_beg
!= merge_bb
->eh_end
2187 || merge_bb
->eh_end
!= test_bb
->eh_end
)
2190 jump
= test_bb
->end
;
2192 /* Find the extent of the real code in the merge block. */
2193 head
= merge_bb
->head
;
2194 end
= merge_bb
->end
;
2196 if (GET_CODE (head
) == CODE_LABEL
)
2197 head
= NEXT_INSN (head
);
2198 if (GET_CODE (head
) == NOTE
)
2202 head
= end
= NULL_RTX
;
2205 head
= NEXT_INSN (head
);
2208 if (GET_CODE (end
) == JUMP_INSN
)
2212 head
= end
= NULL_RTX
;
2215 end
= PREV_INSN (end
);
2218 /* Disable handling dead code by conditional execution if the machine needs
2219 to do anything funny with the tests, etc. */
2220 #ifndef IFCVT_MODIFY_TESTS
2221 if (HAVE_conditional_execution
)
2223 /* In the conditional execution case, we have things easy. We know
2224 the condition is reversable. We don't have to check life info,
2225 becase we're going to conditionally execute the code anyway.
2226 All that's left is making sure the insns involved can actually
2231 cond
= cond_exec_get_condition (jump
);
2233 prob_val
= find_reg_note (jump
, REG_BR_PROB
, NULL_RTX
);
2235 prob_val
= XEXP (prob_val
, 0);
2239 cond
= gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond
)),
2240 GET_MODE (cond
), XEXP (cond
, 0),
2243 prob_val
= GEN_INT (REG_BR_PROB_BASE
- INTVAL (prob_val
));
2246 if (! cond_exec_process_insns (head
, end
, cond
, prob_val
, 0))
2254 /* In the non-conditional execution case, we have to verify that there
2255 are no trapping operations, no calls, no references to memory, and
2256 that any registers modified are dead at the branch site. */
2258 rtx insn
, cond
, prev
;
2259 regset_head merge_set_head
, tmp_head
, test_live_head
, test_set_head
;
2260 regset merge_set
, tmp
, test_live
, test_set
;
2261 struct propagate_block_info
*pbi
;
2264 /* Check for no calls or trapping operations. */
2265 for (insn
= head
; ; insn
= NEXT_INSN (insn
))
2267 if (GET_CODE (insn
) == CALL_INSN
)
2271 if (may_trap_p (PATTERN (insn
)))
2274 /* ??? Even non-trapping memories such as stack frame
2275 references must be avoided. For stores, we collect
2276 no lifetime info; for reads, we'd have to assert
2277 true_dependance false against every store in the
2279 if (for_each_rtx (&PATTERN (insn
), find_memory
, NULL
))
2286 if (! any_condjump_p (jump
))
2289 /* Find the extent of the conditional. */
2290 cond
= noce_get_condition (jump
, &earliest
);
2295 MERGE_SET = set of registers set in MERGE_BB
2296 TEST_LIVE = set of registers live at EARLIEST
2297 TEST_SET = set of registers set between EARLIEST and the
2298 end of the block. */
2300 tmp
= INITIALIZE_REG_SET (tmp_head
);
2301 merge_set
= INITIALIZE_REG_SET (merge_set_head
);
2302 test_live
= INITIALIZE_REG_SET (test_live_head
);
2303 test_set
= INITIALIZE_REG_SET (test_set_head
);
2305 /* ??? bb->local_set is only valid during calculate_global_regs_live,
2306 so we must recompute usage for MERGE_BB. Not so bad, I suppose,
2307 since we've already asserted that MERGE_BB is small. */
2308 propagate_block (merge_bb
, tmp
, merge_set
, merge_set
, 0);
2310 /* For small register class machines, don't lengthen lifetimes of
2311 hard registers before reload. */
2312 if (SMALL_REGISTER_CLASSES
&& ! reload_completed
)
2314 EXECUTE_IF_SET_IN_BITMAP
2317 if (i
< FIRST_PSEUDO_REGISTER
2319 && ! global_regs
[i
])
2324 /* For TEST, we're interested in a range of insns, not a whole block.
2325 Moreover, we're interested in the insns live from OTHER_BB. */
2327 COPY_REG_SET (test_live
, other_bb
->global_live_at_start
);
2328 pbi
= init_propagate_block_info (test_bb
, test_live
, test_set
, test_set
,
2331 for (insn
= jump
; ; insn
= prev
)
2333 prev
= propagate_one_insn (pbi
, insn
);
2334 if (insn
== earliest
)
2338 free_propagate_block_info (pbi
);
2340 /* We can perform the transformation if
2341 MERGE_SET & (TEST_SET | TEST_LIVE)
2343 TEST_SET & merge_bb->global_live_at_start
2346 bitmap_operation (tmp
, test_set
, test_live
, BITMAP_IOR
);
2347 bitmap_operation (tmp
, tmp
, merge_set
, BITMAP_AND
);
2348 EXECUTE_IF_SET_IN_BITMAP(tmp
, 0, i
, fail
= 1);
2350 bitmap_operation (tmp
, test_set
, merge_bb
->global_live_at_start
,
2352 EXECUTE_IF_SET_IN_BITMAP(tmp
, 0, i
, fail
= 1);
2355 FREE_REG_SET (merge_set
);
2356 FREE_REG_SET (test_live
);
2357 FREE_REG_SET (test_set
);
2364 /* We don't want to use normal invert_jump or redirect_jump because
2365 we don't want to delete_insn called. Also, we want to do our own
2366 change group management. */
2368 old_dest
= JUMP_LABEL (jump
);
2370 ? ! invert_jump_1 (jump
, new_dest
)
2371 : ! redirect_jump_1 (jump
, new_dest
))
2374 if (! apply_change_group ())
2378 LABEL_NUSES (old_dest
) -= 1;
2380 LABEL_NUSES (new_dest
) += 1;
2381 JUMP_LABEL (jump
) = new_dest
;
2385 rtx note
= find_reg_note (jump
, REG_BR_PROB
, NULL_RTX
);
2387 XEXP (note
, 0) = GEN_INT (REG_BR_PROB_BASE
- INTVAL (XEXP (note
, 0)));
2390 /* Move the insns out of MERGE_BB to before the branch. */
2393 if (end
== merge_bb
->end
)
2394 merge_bb
->end
= PREV_INSN (head
);
2396 head
= squeeze_notes (head
, end
);
2397 if (GET_CODE (end
) == NOTE
2398 && (NOTE_LINE_NUMBER (end
) == NOTE_INSN_BLOCK_END
2399 || NOTE_LINE_NUMBER (end
) == NOTE_INSN_BLOCK_BEG
2400 || NOTE_LINE_NUMBER (end
) == NOTE_INSN_LOOP_BEG
2401 || NOTE_LINE_NUMBER (end
) == NOTE_INSN_LOOP_END
2402 || NOTE_LINE_NUMBER (end
) == NOTE_INSN_LOOP_CONT
2403 || NOTE_LINE_NUMBER (end
) == NOTE_INSN_LOOP_VTOP
))
2407 end
= PREV_INSN (end
);
2410 reorder_insns (head
, end
, PREV_INSN (earliest
));
2419 /* Main entry point for all if-conversion. */
2422 if_convert (life_data_ok
)
2427 num_possible_if_blocks
= 0;
2428 num_updated_if_blocks
= 0;
2429 num_removed_blocks
= 0;
2431 /* Free up basic_block_for_insn so that we don't have to keep it
2432 up to date, either here or in merge_blocks_nomove. */
2433 free_basic_block_vars (1);
2435 /* Compute postdominators if we think we'll use them. */
2436 post_dominators
= NULL
;
2437 if (HAVE_conditional_execution
|| life_data_ok
)
2439 post_dominators
= sbitmap_vector_alloc (n_basic_blocks
, n_basic_blocks
);
2440 calculate_dominance_info (NULL
, post_dominators
, CDI_POST_DOMINATORS
);
2443 /* Record initial block numbers. */
2444 for (block_num
= 0; block_num
< n_basic_blocks
; block_num
++)
2445 SET_ORIG_INDEX (BASIC_BLOCK (block_num
), block_num
);
2447 /* Go through each of the basic blocks looking for things to convert. */
2448 for (block_num
= 0; block_num
< n_basic_blocks
; )
2450 basic_block bb
= BASIC_BLOCK (block_num
);
2451 if (find_if_header (bb
))
2452 block_num
= bb
->index
;
2457 if (post_dominators
)
2458 sbitmap_vector_free (post_dominators
);
2461 fflush (rtl_dump_file
);
2463 /* Rebuild basic_block_for_insn for update_life_info and for gcse. */
2464 compute_bb_for_insn (get_max_uid ());
2466 /* Rebuild life info for basic blocks that require it. */
2467 if (num_removed_blocks
&& life_data_ok
)
2469 sbitmap update_life_blocks
= sbitmap_alloc (n_basic_blocks
);
2470 sbitmap_zero (update_life_blocks
);
2472 /* If we allocated new pseudos, we must resize the array for sched1. */
2473 if (max_regno
< max_reg_num ())
2475 max_regno
= max_reg_num ();
2476 allocate_reg_info (max_regno
, FALSE
, FALSE
);
2479 for (block_num
= 0; block_num
< n_basic_blocks
; block_num
++)
2480 if (UPDATE_LIFE (BASIC_BLOCK (block_num
)))
2481 SET_BIT (update_life_blocks
, block_num
);
2483 count_or_remove_death_notes (update_life_blocks
, 1);
2484 /* ??? See about adding a mode that verifies that the initial
2485 set of blocks don't let registers come live. */
2486 update_life_info (update_life_blocks
, UPDATE_LIFE_GLOBAL
,
2487 PROP_DEATH_NOTES
| PROP_SCAN_DEAD_CODE
2488 | PROP_KILL_DEAD_CODE
);
2490 sbitmap_free (update_life_blocks
);
2493 /* Write the final stats. */
2494 if (rtl_dump_file
&& num_possible_if_blocks
> 0)
2496 fprintf (rtl_dump_file
,
2497 "\n%d possible IF blocks searched.\n",
2498 num_possible_if_blocks
);
2499 fprintf (rtl_dump_file
,
2500 "%d IF blocks converted.\n",
2501 num_updated_if_blocks
);
2502 fprintf (rtl_dump_file
,
2503 "%d basic blocks deleted.\n\n\n",
2504 num_removed_blocks
);
2507 #ifdef ENABLE_CHECKING
2508 verify_flow_info ();