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 "basic-block.h"
33 #include "hard-reg-set.h"
37 #ifndef HAVE_conditional_execution
38 #define HAVE_conditional_execution 0
40 #ifndef HAVE_conditional_move
41 #define HAVE_conditional_move 0
50 #ifndef MAX_CONDITIONAL_EXECUTE
51 #define MAX_CONDITIONAL_EXECUTE (BRANCH_COST + 1)
54 #define EDGE_COMPLEX (EDGE_ABNORMAL | EDGE_ABNORMAL_CALL | EDGE_EH)
56 #define NULL_EDGE ((struct edge_def *)NULL)
57 #define NULL_BLOCK ((struct basic_block_def *)NULL)
59 /* # of IF-THEN or IF-THEN-ELSE blocks we looked at */
60 static int num_possible_if_blocks;
62 /* # of IF-THEN or IF-THEN-ELSE blocks were converted to conditional
64 static int num_updated_if_blocks;
66 /* # of basic blocks that were removed. */
67 static int num_removed_blocks;
69 /* The post-dominator relation on the original block numbers. */
70 static sbitmap *post_dominators;
72 /* Forward references. */
73 static int count_bb_insns PARAMS ((basic_block));
74 static rtx first_active_insn PARAMS ((basic_block));
75 static int last_active_insn_p PARAMS ((basic_block, rtx));
77 static int cond_exec_process_insns PARAMS ((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_process_if_block PARAMS ((basic_block, basic_block,
84 basic_block, basic_block));
86 static int process_if_block PARAMS ((basic_block, basic_block,
87 basic_block, basic_block));
88 static void merge_if_block PARAMS ((basic_block, basic_block,
89 basic_block, basic_block));
91 static int find_if_header PARAMS ((basic_block));
92 static int find_if_block PARAMS ((basic_block, edge, edge));
93 static int find_if_case_1 PARAMS ((basic_block, edge, edge));
94 static int find_if_case_2 PARAMS ((basic_block, edge, edge));
95 static int find_memory PARAMS ((rtx *, void *));
96 static int dead_or_predicable PARAMS ((basic_block, basic_block,
97 basic_block, rtx, int));
99 /* Abuse the basic_block AUX field to store the original block index,
100 as well as a flag indicating that the block should be rescaned for
103 #define SET_ORIG_INDEX(BB,I) ((BB)->aux = (void *)((size_t)(I) << 1))
104 #define ORIG_INDEX(BB) ((size_t)(BB)->aux >> 1)
105 #define SET_UPDATE_LIFE(BB) ((BB)->aux = (void *)((size_t)(BB)->aux | 1))
106 #define UPDATE_LIFE(BB) ((size_t)(BB)->aux & 1)
109 /* Count the number of non-jump active insns in BB. */
120 if (GET_CODE (insn) == CALL_INSN || GET_CODE (insn) == INSN)
125 insn = NEXT_INSN (insn);
131 /* Return the first non-jump active insn in the basic block. */
134 first_active_insn (bb)
139 if (GET_CODE (insn) == CODE_LABEL)
143 insn = NEXT_INSN (insn);
146 while (GET_CODE (insn) == NOTE)
150 insn = NEXT_INSN (insn);
153 if (GET_CODE (insn) == JUMP_INSN)
159 /* Return true if INSN is the last active non-jump insn in BB. */
162 last_active_insn_p (bb, insn)
170 insn = NEXT_INSN (insn);
172 while (GET_CODE (insn) == NOTE);
174 return GET_CODE (insn) == JUMP_INSN;
177 /* Go through a bunch of insns, converting them to conditional
178 execution format if possible. Return TRUE if all of the non-note
179 insns were processed. */
182 cond_exec_process_insns (start, end, test, mod_ok)
183 rtx start; /* first insn to look at */
184 rtx end; /* last insn to look at */
185 rtx test; /* conditional execution test */
186 int mod_ok; /* true if modifications ok last insn. */
188 int must_be_last = FALSE;
191 for (insn = start; ; insn = NEXT_INSN (insn))
193 if (GET_CODE (insn) == NOTE)
196 if (GET_CODE (insn) != INSN && GET_CODE (insn) != CALL_INSN)
199 /* Last insn wasn't last? */
203 if (modified_in_p (test, insn))
210 /* Now build the conditional form of the instruction. */
211 validate_change (insn, &PATTERN (insn),
212 gen_rtx_COND_EXEC (VOIDmode, copy_rtx (test),
223 /* Return the condition for a jump. Do not do any special processing. */
226 cond_exec_get_condition (jump)
231 if (condjump_p (jump))
232 test_if = SET_SRC (PATTERN (jump));
233 else if (condjump_in_parallel_p (jump))
234 test_if = SET_SRC (XVECEXP (PATTERN (jump), 0, 0));
237 cond = XEXP (test_if, 0);
239 /* If this branches to JUMP_LABEL when the condition is false,
240 reverse the condition. */
241 if (GET_CODE (XEXP (test_if, 2)) == LABEL_REF
242 && XEXP (XEXP (test_if, 2), 0) == JUMP_LABEL (jump))
243 cond = gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)),
244 GET_MODE (cond), XEXP (cond, 0),
250 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
251 to conditional execution. Return TRUE if we were successful at
252 converting the the block. */
255 cond_exec_process_if_block (test_bb, then_bb, else_bb, join_bb)
256 basic_block test_bb; /* Basic block test is in */
257 basic_block then_bb; /* Basic block for THEN block */
258 basic_block else_bb; /* Basic block for ELSE block */
259 basic_block join_bb; /* Basic block the join label is in */
261 rtx test_expr; /* expression in IF_THEN_ELSE that is tested */
262 rtx then_start; /* first insn in THEN block */
263 rtx then_end; /* last insn + 1 in THEN block */
264 rtx else_start; /* first insn in ELSE block or NULL */
265 rtx else_end; /* last insn + 1 in ELSE block */
266 int max; /* max # of insns to convert. */
267 int then_mod_ok; /* whether conditional mods are ok in THEN */
268 rtx true_expr; /* test for else block insns */
269 rtx false_expr; /* test for then block insns */
272 /* Find the conditional jump to the ELSE or JOIN part, and isolate
274 test_expr = cond_exec_get_condition (test_bb->end);
278 /* Collect the bounds of where we're to search. */
280 then_start = then_bb->head;
281 then_end = then_bb->end;
283 /* Skip a (use (const_int 0)) or branch as the final insn. */
284 if (GET_CODE (then_end) == INSN
285 && GET_CODE (PATTERN (then_end)) == USE
286 && GET_CODE (XEXP (PATTERN (then_end), 0)) == CONST_INT)
287 then_end = PREV_INSN (then_end);
288 else if (GET_CODE (then_end) == JUMP_INSN)
289 then_end = PREV_INSN (then_end);
293 /* Skip the ELSE block's label. */
294 else_start = NEXT_INSN (else_bb->head);
295 else_end = else_bb->end;
297 /* Skip a (use (const_int 0)) or branch as the final insn. */
298 if (GET_CODE (else_end) == INSN
299 && GET_CODE (PATTERN (else_end)) == USE
300 && GET_CODE (XEXP (PATTERN (else_end), 0)) == CONST_INT)
301 else_end = PREV_INSN (else_end);
302 else if (GET_CODE (else_end) == JUMP_INSN)
303 else_end = PREV_INSN (else_end);
306 /* How many instructions should we convert in total? */
310 max = 2 * MAX_CONDITIONAL_EXECUTE;
311 n_insns = count_bb_insns (else_bb);
314 max = MAX_CONDITIONAL_EXECUTE;
315 n_insns += count_bb_insns (then_bb);
319 /* Map test_expr/test_jump into the appropriate MD tests to use on
320 the conditionally executed code. */
322 true_expr = test_expr;
323 false_expr = gen_rtx_fmt_ee (reverse_condition (GET_CODE (true_expr)),
324 GET_MODE (true_expr), XEXP (true_expr, 0),
325 XEXP (true_expr, 1));
327 /* For IF-THEN-ELSE blocks, we don't allow modifications of the test
328 on then THEN block. */
329 then_mod_ok = (else_bb == NULL_BLOCK);
331 /* Go through the THEN and ELSE blocks converting the insns if possible
332 to conditional execution. */
335 && ! cond_exec_process_insns (then_start, then_end,
336 false_expr, then_mod_ok))
340 && ! cond_exec_process_insns (else_start, else_end,
344 if (! apply_change_group ())
347 /* Conversion succeeded. */
349 fprintf (rtl_dump_file, "%d insn%s converted to conditional execution.\n",
350 n_insns, (n_insns == 1) ? " was" : "s were");
352 /* Merge the blocks! */
353 merge_if_block (test_bb, then_bb, else_bb, join_bb);
361 /* Used by noce_process_if_block to communicate with its subroutines.
363 The subroutines know that A and B may be evaluated freely. They
364 know that X is a register. They should insert new instructions
365 before cond_earliest. */
371 rtx jump, cond, cond_earliest;
374 static rtx noce_emit_store_flag PARAMS ((struct noce_if_info *,
376 static int noce_try_store_flag PARAMS ((struct noce_if_info *));
377 static int noce_try_store_flag_inc PARAMS ((struct noce_if_info *));
378 static int noce_try_store_flag_constants PARAMS ((struct noce_if_info *));
379 static int noce_try_store_flag_mask PARAMS ((struct noce_if_info *));
380 static rtx noce_emit_cmove PARAMS ((struct noce_if_info *,
381 rtx, enum rtx_code, rtx,
383 static int noce_try_cmove PARAMS ((struct noce_if_info *));
384 static int noce_try_cmove_arith PARAMS ((struct noce_if_info *));
386 /* Helper function for noce_try_store_flag*. */
389 noce_emit_store_flag (if_info, x, reversep, normalize)
390 struct noce_if_info *if_info;
392 int reversep, normalize;
394 rtx cond = if_info->cond;
398 cond_complex = (! general_operand (XEXP (cond, 0), VOIDmode)
399 || ! general_operand (XEXP (cond, 1), VOIDmode));
401 /* If earliest == jump, or when the condition is complex, try to
402 build the store_flag insn directly. */
405 cond = XEXP (SET_SRC (PATTERN (if_info->jump)), 0);
407 if ((if_info->cond_earliest == if_info->jump || cond_complex)
408 && (normalize == 0 || STORE_FLAG_VALUE == normalize))
412 code = GET_CODE (cond);
414 code = reverse_condition (code);
416 tmp = gen_rtx_fmt_ee (code, GET_MODE (x), XEXP (cond, 0),
418 tmp = gen_rtx_SET (VOIDmode, x, tmp);
421 tmp = emit_insn (tmp);
423 if (recog_memoized (tmp) >= 0)
429 if_info->cond_earliest = if_info->jump;
437 /* Don't even try if the comparison operands are weird. */
441 code = GET_CODE (cond);
443 code = reverse_condition (code);
445 return emit_store_flag (x, code, XEXP (cond, 0),
446 XEXP (cond, 1), VOIDmode,
447 (code == LTU || code == LEU
448 || code == GEU || code == GTU), normalize);
451 /* Convert "if (test) x = 1; else x = 0".
453 Only try 0 and STORE_FLAG_VALUE here. Other combinations will be
454 tried in noce_try_store_flag_constants after noce_try_cmove has had
455 a go at the conversion. */
458 noce_try_store_flag (if_info)
459 struct noce_if_info *if_info;
464 if (GET_CODE (if_info->b) == CONST_INT
465 && INTVAL (if_info->b) == STORE_FLAG_VALUE
466 && if_info->a == const0_rtx)
468 else if (if_info->b == const0_rtx
469 && GET_CODE (if_info->a) == CONST_INT
470 && INTVAL (if_info->a) == STORE_FLAG_VALUE
471 && can_reverse_comparison_p (if_info->cond, if_info->jump))
478 target = noce_emit_store_flag (if_info, if_info->x, reversep, 0);
481 if (target != if_info->x)
482 emit_move_insn (if_info->x, target);
486 emit_insns_before (seq, if_info->cond_earliest);
497 /* Convert "if (test) x = a; else x = b", for A and B constant. */
500 noce_try_store_flag_constants (if_info)
501 struct noce_if_info *if_info;
505 HOST_WIDE_INT itrue, ifalse, diff, tmp;
506 int normalize, can_reverse;
509 && GET_CODE (if_info->a) == CONST_INT
510 && GET_CODE (if_info->b) == CONST_INT)
512 ifalse = INTVAL (if_info->a);
513 itrue = INTVAL (if_info->b);
514 diff = itrue - ifalse;
516 can_reverse = can_reverse_comparison_p (if_info->cond, if_info->jump);
519 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
521 else if (ifalse == 0 && exact_log2 (itrue) >= 0
522 && (STORE_FLAG_VALUE == 1
523 || BRANCH_COST >= 2))
525 else if (itrue == 0 && exact_log2 (ifalse) >= 0 && can_reverse
526 && (STORE_FLAG_VALUE == 1 || BRANCH_COST >= 2))
527 normalize = 1, reversep = 1;
529 && (STORE_FLAG_VALUE == -1
530 || BRANCH_COST >= 2))
532 else if (ifalse == -1 && can_reverse
533 && (STORE_FLAG_VALUE == -1 || BRANCH_COST >= 2))
534 normalize = -1, reversep = 1;
535 else if ((BRANCH_COST >= 2 && STORE_FLAG_VALUE == -1)
543 tmp = itrue; itrue = ifalse; ifalse = tmp;
548 target = noce_emit_store_flag (if_info, if_info->x, reversep, normalize);
555 /* if (test) x = 3; else x = 4;
556 => x = 3 + (test == 0); */
557 if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
559 target = expand_binop (GET_MODE (if_info->x),
560 (diff == STORE_FLAG_VALUE
561 ? add_optab : sub_optab),
562 GEN_INT (ifalse), target, if_info->x, 0,
566 /* if (test) x = 8; else x = 0;
567 => x = (test != 0) << 3; */
568 else if (ifalse == 0 && (tmp = exact_log2 (itrue)) >= 0)
570 target = expand_binop (GET_MODE (if_info->x), ashl_optab,
571 target, GEN_INT (tmp), if_info->x, 0,
575 /* if (test) x = -1; else x = b;
576 => x = -(test != 0) | b; */
577 else if (itrue == -1)
579 target = expand_binop (GET_MODE (if_info->x), ior_optab,
580 target, GEN_INT (ifalse), if_info->x, 0,
584 /* if (test) x = a; else x = b;
585 => x = (-(test != 0) & (b - a)) + a; */
588 target = expand_binop (GET_MODE (if_info->x), and_optab,
589 target, GEN_INT (diff), if_info->x, 0,
592 target = expand_binop (GET_MODE (if_info->x), add_optab,
593 target, GEN_INT (ifalse), if_info->x, 0,
603 if (target != if_info->x)
604 emit_move_insn (if_info->x, target);
608 emit_insns_before (seq, if_info->cond_earliest);
616 /* Convert "if (test) foo++" into "foo += (test != 0)", and
617 similarly for "foo--". */
620 noce_try_store_flag_inc (if_info)
621 struct noce_if_info *if_info;
624 int subtract, normalize;
630 /* Should be no `else' case to worry about. */
631 && if_info->b == if_info->x
632 && GET_CODE (if_info->a) == PLUS
633 && (XEXP (if_info->a, 1) == const1_rtx
634 || XEXP (if_info->a, 1) == constm1_rtx)
635 && rtx_equal_p (XEXP (if_info->a, 0), if_info->x)
636 && can_reverse_comparison_p (if_info->cond, if_info->jump))
638 if (STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
639 subtract = 0, normalize = 0;
640 else if (-STORE_FLAG_VALUE == INTVAL (XEXP (if_info->a, 1)))
641 subtract = 1, normalize = 0;
643 subtract = 0, normalize = INTVAL (XEXP (if_info->a, 1));
647 target = noce_emit_store_flag (if_info,
648 gen_reg_rtx (GET_MODE (if_info->x)),
652 target = expand_binop (GET_MODE (if_info->x),
653 subtract ? sub_optab : add_optab,
654 if_info->x, target, if_info->x, 0, OPTAB_WIDEN);
657 if (target != if_info->x)
658 emit_move_insn (if_info->x, target);
662 emit_insns_before (seq, if_info->cond_earliest);
673 /* Convert "if (test) x = 0;" to "x &= -(test == 0);" */
676 noce_try_store_flag_mask (if_info)
677 struct noce_if_info *if_info;
685 || STORE_FLAG_VALUE == -1)
686 && ((if_info->a == const0_rtx
687 && rtx_equal_p (if_info->b, if_info->x))
688 || ((reversep = can_reverse_comparison_p (if_info->cond,
690 && if_info->b == const0_rtx
691 && rtx_equal_p (if_info->a, if_info->x))))
694 target = noce_emit_store_flag (if_info,
695 gen_reg_rtx (GET_MODE (if_info->x)),
698 target = expand_binop (GET_MODE (if_info->x), and_optab,
699 if_info->x, target, if_info->x, 0,
704 if (target != if_info->x)
705 emit_move_insn (if_info->x, target);
709 emit_insns_before (seq, if_info->cond_earliest);
720 /* Helper function for noce_try_cmove and noce_try_cmove_arith. */
723 noce_emit_cmove (if_info, x, code, cmp_a, cmp_b, vfalse, vtrue)
724 struct noce_if_info *if_info;
725 rtx x, cmp_a, cmp_b, vfalse, vtrue;
728 /* If earliest == jump, try to build the cmove insn directly.
729 This is helpful when combine has created some complex condition
730 (like for alpha's cmovlbs) that we can't hope to regenerate
731 through the normal interface. */
733 if (if_info->cond_earliest == if_info->jump)
737 tmp = gen_rtx_fmt_ee (code, GET_MODE (if_info->cond), cmp_a, cmp_b);
738 tmp = gen_rtx_IF_THEN_ELSE (GET_MODE (x), tmp, vtrue, vfalse);
739 tmp = gen_rtx_SET (VOIDmode, x, tmp);
742 tmp = emit_insn (tmp);
744 if (recog_memoized (tmp) >= 0)
756 /* Don't even try if the comparison operands are weird. */
757 if (! general_operand (cmp_a, GET_MODE (cmp_a))
758 || ! general_operand (cmp_b, GET_MODE (cmp_b)))
761 #if HAVE_conditional_move
762 return emit_conditional_move (x, code, cmp_a, cmp_b, VOIDmode,
763 vtrue, vfalse, GET_MODE (x),
764 (code == LTU || code == GEU
765 || code == LEU || code == GTU));
767 /* We'll never get here, as noce_process_if_block doesn't call the
768 functions involved. Ifdef code, however, should be discouraged
769 because it leads to typos in the code not selected. However,
770 emit_conditional_move won't exist either. */
775 /* Try only simple constants and registers here. More complex cases
776 are handled in noce_try_cmove_arith after noce_try_store_flag_arith
777 has had a go at it. */
780 noce_try_cmove (if_info)
781 struct noce_if_info *if_info;
786 if ((CONSTANT_P (if_info->a) || register_operand (if_info->a, VOIDmode))
787 && (CONSTANT_P (if_info->b) || register_operand (if_info->b, VOIDmode)))
791 code = GET_CODE (if_info->cond);
792 target = noce_emit_cmove (if_info, if_info->x, code,
793 XEXP (if_info->cond, 0),
794 XEXP (if_info->cond, 1),
795 if_info->a, if_info->b);
799 if (target != if_info->x)
800 emit_move_insn (if_info->x, target);
804 emit_insns_before (seq, if_info->cond_earliest);
817 /* Try more complex cases involving conditional_move. */
820 noce_try_cmove_arith (if_info)
821 struct noce_if_info *if_info;
831 /* A conditional move from two memory sources is equivalent to a
832 conditional on their addresses followed by a load. Don't do this
833 early because it'll screw alias analysis. Note that we've
834 already checked for no side effects. */
835 if (! no_new_pseudos && cse_not_expected
836 && GET_CODE (a) == MEM && GET_CODE (b) == MEM
841 x = gen_reg_rtx (Pmode);
845 /* ??? We could handle this if we knew that a load from A or B could
846 not fault. This is also true if we've already loaded
847 from the address along the path from ENTRY. */
848 else if (may_trap_p (a) || may_trap_p (b))
851 /* if (test) x = a + b; else x = c - d;
858 code = GET_CODE (if_info->cond);
859 insn_a = if_info->insn_a;
860 insn_b = if_info->insn_b;
862 /* Possibly rearrange operands to make things come out more natural. */
863 if (can_reverse_comparison_p (if_info->cond, if_info->jump))
866 if (rtx_equal_p (b, x))
868 else if (general_operand (b, GET_MODE (b)))
873 code = reverse_condition (code);
874 tmp = a, a = b, b = tmp;
875 tmp = insn_a, insn_a = insn_b, insn_b = tmp;
881 /* If either operand is complex, load it into a register first.
882 The best way to do this is to copy the original insn. In this
883 way we preserve any clobbers etc that the insn may have had.
884 This is of course not possible in the IS_MEM case. */
885 if (! general_operand (a, GET_MODE (a)))
890 goto end_seq_and_fail;
894 tmp = gen_reg_rtx (GET_MODE (a));
895 tmp = emit_insn (gen_rtx_SET (VOIDmode, tmp, a));
898 goto end_seq_and_fail;
901 a = gen_reg_rtx (GET_MODE (a));
902 tmp = copy_rtx (insn_a);
903 set = single_set (tmp);
905 tmp = emit_insn (PATTERN (tmp));
907 if (recog_memoized (tmp) < 0)
908 goto end_seq_and_fail;
910 if (! general_operand (b, GET_MODE (b)))
915 goto end_seq_and_fail;
919 tmp = gen_reg_rtx (GET_MODE (b));
920 tmp = emit_insn (gen_rtx_SET (VOIDmode, tmp, b));
923 goto end_seq_and_fail;
926 b = gen_reg_rtx (GET_MODE (b));
927 tmp = copy_rtx (insn_b);
928 set = single_set (tmp);
930 tmp = emit_insn (PATTERN (tmp));
932 if (recog_memoized (tmp) < 0)
933 goto end_seq_and_fail;
936 target = noce_emit_cmove (if_info, x, code, XEXP (if_info->cond, 0),
937 XEXP (if_info->cond, 1), a, b);
940 goto end_seq_and_fail;
942 /* If we're handling a memory for above, emit the load now. */
945 tmp = gen_rtx_MEM (GET_MODE (if_info->x), target);
947 /* Copy over flags as appropriate. */
948 if (MEM_VOLATILE_P (if_info->a) || MEM_VOLATILE_P (if_info->b))
949 MEM_VOLATILE_P (tmp) = 1;
950 if (MEM_IN_STRUCT_P (if_info->a) && MEM_IN_STRUCT_P (if_info->b))
951 MEM_IN_STRUCT_P (tmp) = 1;
952 if (MEM_SCALAR_P (if_info->a) && MEM_SCALAR_P (if_info->b))
953 MEM_SCALAR_P (tmp) = 1;
954 if (MEM_ALIAS_SET (if_info->a) == MEM_ALIAS_SET (if_info->b))
955 MEM_ALIAS_SET (tmp) = MEM_ALIAS_SET (if_info->a);
957 emit_move_insn (if_info->x, tmp);
959 else if (target != x)
960 emit_move_insn (x, target);
964 emit_insns_before (tmp, if_info->cond_earliest);
972 /* Look for the condition for the jump first. We'd prefer to avoid
973 get_condition if we can -- it tries to look back for the contents
974 of an original compare. On targets that use normal integers for
975 comparisons, e.g. alpha, this is wasteful. */
978 noce_get_condition (jump, earliest)
984 /* If the condition variable is a register and is MODE_INT, accept it.
985 Otherwise, fall back on get_condition. */
987 if (! condjump_p (jump))
990 cond = XEXP (SET_SRC (PATTERN (jump)), 0);
991 if (GET_CODE (XEXP (cond, 0)) == REG
992 && GET_MODE_CLASS (GET_MODE (XEXP (cond, 0))) == MODE_INT)
996 /* If this branches to JUMP_LABEL when the condition is false,
997 reverse the condition. */
998 if (GET_CODE (XEXP (SET_SRC (PATTERN (jump)), 2)) == LABEL_REF
999 && XEXP (XEXP (SET_SRC (PATTERN (jump)), 2), 0) == JUMP_LABEL (jump))
1000 cond = gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)),
1001 GET_MODE (cond), XEXP (cond, 0),
1005 cond = get_condition (jump, earliest);
1010 /* Given a simple IF-THEN or IF-THEN-ELSE block, attempt to convert it
1011 without using conditional execution. Return TRUE if we were
1012 successful at converting the the block. */
1015 noce_process_if_block (test_bb, then_bb, else_bb, join_bb)
1016 basic_block test_bb; /* Basic block test is in */
1017 basic_block then_bb; /* Basic block for THEN block */
1018 basic_block else_bb; /* Basic block for ELSE block */
1019 basic_block join_bb; /* Basic block the join label is in */
1021 /* We're looking for patterns of the form
1023 (1) if (...) x = a; else x = b;
1024 (2) x = b; if (...) x = a;
1025 (3) if (...) x = a; // as if with an initial x = x.
1027 The later patterns require jumps to be more expensive.
1029 ??? For future expansion, look for multiple X in such patterns. */
1031 struct noce_if_info if_info;
1034 rtx orig_x, x, a, b;
1035 rtx jump, cond, insn;
1037 /* If this is not a standard conditional jump, we can't parse it. */
1038 jump = test_bb->end;
1039 cond = noce_get_condition (jump, &if_info.cond_earliest);
1043 /* We must be comparing objects whose modes imply the size. */
1044 if (GET_MODE (XEXP (cond, 0)) == BLKmode)
1047 /* Look for one of the potential sets. */
1048 insn_a = first_active_insn (then_bb);
1050 || ! last_active_insn_p (then_bb, insn_a)
1051 || (set_a = single_set (insn_a)) == NULL_RTX)
1054 x = SET_DEST (set_a);
1055 a = SET_SRC (set_a);
1057 /* Look for the other potential set. Make sure we've got equivalent
1059 /* ??? This is overconservative. Storing to two different mems is
1060 as easy as conditionally computing the address. Storing to a
1061 single mem merely requires a scratch memory to use as one of the
1062 destination addresses; often the memory immediately below the
1063 stack pointer is available for this. */
1067 insn_b = first_active_insn (else_bb);
1069 || ! last_active_insn_p (else_bb, insn_b)
1070 || (set_b = single_set (insn_b)) == NULL_RTX
1071 || ! rtx_equal_p (x, SET_DEST (set_b)))
1076 insn_b = prev_nonnote_insn (if_info.cond_earliest);
1078 || GET_CODE (insn_b) != INSN
1079 || (set_b = single_set (insn_b)) == NULL_RTX
1080 || ! rtx_equal_p (x, SET_DEST (set_b))
1081 || reg_mentioned_p (x, cond)
1082 || reg_mentioned_p (x, a))
1083 insn_b = set_b = NULL_RTX;
1085 b = (set_b ? SET_SRC (set_b) : x);
1087 /* X may not be mentioned in the range (cond_earliest, jump]. */
1088 for (insn = jump; insn != if_info.cond_earliest; insn = PREV_INSN (insn))
1089 if (INSN_P (insn) && reg_mentioned_p (x, insn))
1092 /* A and B may not be modified in the range [cond_earliest, jump). */
1093 for (insn = if_info.cond_earliest; insn != jump; insn = NEXT_INSN (insn))
1095 && (modified_in_p (a, insn) || modified_in_p (b, insn)))
1098 /* Only operate on register destinations, and even then avoid extending
1099 the lifetime of hard registers on small register class machines. */
1101 if (GET_CODE (x) != REG
1102 || (SMALL_REGISTER_CLASSES
1103 && REGNO (x) < FIRST_PSEUDO_REGISTER))
1107 x = gen_reg_rtx (GET_MODE (x));
1110 /* Don't operate on sources that may trap or are volatile. */
1111 if (side_effects_p (a) || side_effects_p (b)
1112 || (GET_CODE (a) != MEM && may_trap_p (a))
1113 || (GET_CODE (b) != MEM && may_trap_p (b)))
1116 /* Set up the info block for our subroutines. */
1117 if_info.cond = cond;
1118 if_info.jump = jump;
1119 if_info.insn_a = insn_a;
1120 if_info.insn_b = insn_b;
1125 /* Try optimizations in some approximation of a useful order. */
1126 /* ??? Should first look to see if X is live incoming at all. If it
1127 isn't, we don't need anything but an unconditional set. */
1129 /* Look and see if A and B are really the same. Avoid creating silly
1130 cmove constructs that no one will fix up later. */
1131 if (rtx_equal_p (a, b))
1133 /* If we have an INSN_B, we don't have to create any new rtl. Just
1134 move the instruction that we already have. If we don't have an
1135 INSN_B, that means that A == X, and we've got a noop move. In
1136 that case don't do anything and let the code below delete INSN_A. */
1137 if (insn_b && else_bb)
1139 if (else_bb && insn_b == else_bb->end)
1140 else_bb->end = PREV_INSN (insn_b);
1141 reorder_insns (insn_b, insn_b, PREV_INSN (if_info.cond_earliest));
1148 if (noce_try_store_flag (&if_info))
1150 if (HAVE_conditional_move
1151 && noce_try_cmove (&if_info))
1153 if (! HAVE_conditional_execution)
1155 if (noce_try_store_flag_constants (&if_info))
1157 if (noce_try_store_flag_inc (&if_info))
1159 if (noce_try_store_flag_mask (&if_info))
1161 if (HAVE_conditional_move
1162 && noce_try_cmove_arith (&if_info))
1169 /* The original sets may now be killed. */
1170 if (insn_a == then_bb->end)
1171 then_bb->end = PREV_INSN (insn_a);
1172 flow_delete_insn (insn_a);
1174 /* Several special cases here: First, we may have reused insn_b above,
1175 in which case insn_b is now NULL. Second, we want to delete insn_b
1176 if it came from the ELSE block, because follows the now correct
1177 write that appears in the TEST block. However, if we got insn_b from
1178 the TEST block, it may in fact be loading data needed for the comparison.
1179 We'll let life_analysis remove the insn if it's really dead. */
1180 if (insn_b && else_bb)
1182 if (insn_b == else_bb->end)
1183 else_bb->end = PREV_INSN (insn_b);
1184 flow_delete_insn (insn_b);
1187 /* The new insns will have been inserted before cond_earliest. We should
1188 be able to remove the jump with impunity, but the condition itself may
1189 have been modified by gcse to be shared across basic blocks. */
1190 test_bb->end = PREV_INSN (jump);
1191 flow_delete_insn (jump);
1193 /* If we used a temporary, fix it up now. */
1197 emit_move_insn (orig_x, x);
1198 insn_b = gen_sequence ();
1201 test_bb->end = emit_insn_after (insn_b, test_bb->end);
1204 /* Merge the blocks! */
1205 merge_if_block (test_bb, then_bb, else_bb, join_bb);
1210 /* Attempt to convert an IF-THEN or IF-THEN-ELSE block into
1211 straight line code. Return true if successful. */
1214 process_if_block (test_bb, then_bb, else_bb, join_bb)
1215 basic_block test_bb; /* Basic block test is in */
1216 basic_block then_bb; /* Basic block for THEN block */
1217 basic_block else_bb; /* Basic block for ELSE block */
1218 basic_block join_bb; /* Basic block the join label is in */
1220 if (! reload_completed
1221 && noce_process_if_block (test_bb, then_bb, else_bb, join_bb))
1224 if (HAVE_conditional_execution
1226 && cond_exec_process_if_block (test_bb, then_bb, else_bb, join_bb))
1232 /* Merge the blocks and mark for local life update. */
1235 merge_if_block (test_bb, then_bb, else_bb, join_bb)
1236 basic_block test_bb; /* Basic block test is in */
1237 basic_block then_bb; /* Basic block for THEN block */
1238 basic_block else_bb; /* Basic block for ELSE block */
1239 basic_block join_bb; /* Basic block the join label is in */
1241 basic_block combo_bb;
1243 /* All block merging is done into the lower block numbers. */
1247 /* First merge TEST block into THEN block. This is a no-brainer since
1248 the THEN block did not have a code label to begin with. */
1250 if (combo_bb->global_live_at_end)
1251 COPY_REG_SET (combo_bb->global_live_at_end, then_bb->global_live_at_end);
1252 merge_blocks_nomove (combo_bb, then_bb);
1253 num_removed_blocks++;
1255 /* The ELSE block, if it existed, had a label. That label count
1256 will almost always be zero, but odd things can happen when labels
1257 get their addresses taken. */
1260 if (LABEL_NUSES (else_bb->head) == 0
1261 && ! LABEL_PRESERVE_P (else_bb->head)
1262 && ! LABEL_NAME (else_bb->head))
1264 /* We can merge the ELSE. */
1265 merge_blocks_nomove (combo_bb, else_bb);
1266 num_removed_blocks++;
1270 /* We cannot merge the ELSE. */
1272 /* Properly rewire the edge out of the now combined
1273 TEST-THEN block to point here. */
1274 remove_edge (combo_bb->succ);
1275 if (combo_bb->succ || else_bb->pred)
1277 make_edge (NULL, combo_bb, else_bb, EDGE_FALLTHRU);
1279 /* Remove the jump and cruft from the end of the TEST-THEN block. */
1280 tidy_fallthru_edge (combo_bb->succ, combo_bb, else_bb);
1282 /* Make sure we update life info properly. */
1283 SET_UPDATE_LIFE(combo_bb);
1284 if (else_bb->global_live_at_end)
1285 COPY_REG_SET (else_bb->global_live_at_start,
1286 else_bb->global_live_at_end);
1288 /* The ELSE is the new combo block. */
1293 /* If there was no join block reported, that means it was not adjacent
1294 to the others, and so we cannot merge them. */
1298 /* The outgoing edge for the current COMBO block should already
1299 be correct. Verify this. */
1300 if (combo_bb->succ == NULL_EDGE)
1303 /* There should sill be a branch at the end of the THEN or ELSE
1304 blocks taking us to our final destination. */
1305 if (! simplejump_p (combo_bb->end)
1306 && ! returnjump_p (combo_bb->end))
1310 /* The JOIN block had a label. It may have had quite a number
1311 of other predecessors too, but probably not. See if we can
1312 merge this with the others. */
1313 else if (LABEL_NUSES (join_bb->head) == 0
1314 && ! LABEL_PRESERVE_P (join_bb->head)
1315 && ! LABEL_NAME (join_bb->head))
1317 /* We can merge the JOIN. */
1318 if (combo_bb->global_live_at_end)
1319 COPY_REG_SET (combo_bb->global_live_at_end,
1320 join_bb->global_live_at_end);
1321 merge_blocks_nomove (combo_bb, join_bb);
1322 num_removed_blocks++;
1326 /* We cannot merge the JOIN. */
1328 /* The outgoing edge for the current COMBO block should already
1329 be correct. Verify this. */
1330 if (combo_bb->succ->succ_next != NULL_EDGE
1331 || combo_bb->succ->dest != join_bb)
1334 /* Remove the jump and cruft from the end of the COMBO block. */
1335 tidy_fallthru_edge (combo_bb->succ, combo_bb, join_bb);
1338 /* Make sure we update life info properly. */
1339 SET_UPDATE_LIFE (combo_bb);
1341 num_updated_if_blocks++;
1344 /* Find a block ending in a simple IF condition. Return TRUE if
1345 we were able to transform it in some way. */
1348 find_if_header (test_bb)
1349 basic_block test_bb;
1354 /* The kind of block we're looking for has exactly two successors. */
1355 if ((then_edge = test_bb->succ) == NULL_EDGE
1356 || (else_edge = then_edge->succ_next) == NULL_EDGE
1357 || else_edge->succ_next != NULL_EDGE)
1360 /* Neither edge should be abnormal. */
1361 if ((then_edge->flags & EDGE_COMPLEX)
1362 || (else_edge->flags & EDGE_COMPLEX))
1365 /* The THEN edge is canonically the one that falls through. */
1366 if (then_edge->flags & EDGE_FALLTHRU)
1368 else if (else_edge->flags & EDGE_FALLTHRU)
1371 else_edge = then_edge;
1375 /* Otherwise this must be a multiway branch of some sort. */
1378 if (find_if_block (test_bb, then_edge, else_edge))
1381 && (! HAVE_conditional_execution || reload_completed))
1383 if (find_if_case_1 (test_bb, then_edge, else_edge))
1385 if (find_if_case_2 (test_bb, then_edge, else_edge))
1393 fprintf (rtl_dump_file, "Conversion succeeded.\n");
1397 /* Determine if a given basic block heads a simple IF-THEN or IF-THEN-ELSE
1398 block. If so, we'll try to convert the insns to not require the branch.
1399 Return TRUE if we were successful at converting the the block. */
1402 find_if_block (test_bb, then_edge, else_edge)
1403 basic_block test_bb;
1404 edge then_edge, else_edge;
1406 basic_block then_bb = then_edge->dest;
1407 basic_block else_bb = else_edge->dest;
1408 basic_block join_bb = NULL_BLOCK;
1409 edge then_succ = then_bb->succ;
1410 edge else_succ = else_bb->succ;
1413 /* The THEN block of an IF-THEN combo must have exactly one predecessor. */
1414 if (then_bb->pred->pred_next != NULL_EDGE)
1417 /* The THEN block of an IF-THEN combo must have exactly one successor. */
1418 if (then_succ == NULL_EDGE
1419 || then_succ->succ_next != NULL_EDGE
1420 || (then_succ->flags & EDGE_COMPLEX))
1423 /* The THEN block may not start with a label, as might happen with an
1424 unused user label that has had its address taken. */
1425 if (GET_CODE (then_bb->head) == CODE_LABEL)
1428 /* If the THEN block's successor is the other edge out of the TEST block,
1429 then we have an IF-THEN combo without an ELSE. */
1430 if (then_succ->dest == else_bb)
1433 else_bb = NULL_BLOCK;
1436 /* If the THEN and ELSE block meet in a subsequent block, and the ELSE
1437 has exactly one predecessor and one successor, and the outgoing edge
1438 is not complex, then we have an IF-THEN-ELSE combo. */
1439 else if (else_succ != NULL_EDGE
1440 && then_succ->dest == else_succ->dest
1441 && else_bb->pred->pred_next == NULL_EDGE
1442 && else_succ->succ_next == NULL_EDGE
1443 && ! (else_succ->flags & EDGE_COMPLEX))
1444 join_bb = else_succ->dest;
1446 /* Otherwise it is not an IF-THEN or IF-THEN-ELSE combination. */
1450 num_possible_if_blocks++;
1455 fprintf (rtl_dump_file,
1456 "\nIF-THEN-ELSE block found, start %d, then %d, else %d, join %d\n",
1457 test_bb->index, then_bb->index, else_bb->index,
1460 fprintf (rtl_dump_file,
1461 "\nIF-THEN block found, start %d, then %d, join %d\n",
1462 test_bb->index, then_bb->index, join_bb->index);
1465 /* Make sure IF, THEN, and ELSE, blocks are adjacent. Actually, we
1466 get the first condition for free, since we've already asserted that
1467 there's a fallthru edge from IF to THEN. */
1468 /* ??? As an enhancement, move the ELSE block. Have to deal with EH and
1469 BLOCK notes, if by no other means than aborting the merge if they
1470 exist. Sticky enough I don't want to think about it now. */
1471 next_index = then_bb->index;
1472 if (else_bb && ++next_index != else_bb->index)
1474 if (++next_index != join_bb->index)
1482 /* Do the real work. */
1483 return process_if_block (test_bb, then_bb, else_bb, join_bb);
1486 /* Look for IF-THEN-ELSE cases in which one of THEN or ELSE is
1487 transformable, but not necessarily the other. There need be no
1490 Return TRUE if we were successful at converting the the block.
1492 Cases we'd like to look at:
1495 if (test) goto over; // x not live
1503 if (! test) goto label;
1506 if (test) goto E; // x not live
1520 (3) // This one's really only interesting for targets that can do
1521 // multiway branching, e.g. IA-64 BBB bundles. For other targets
1522 // it results in multiple branches on a cache line, which often
1523 // does not sit well with predictors.
1525 if (test1) goto E; // predicted not taken
1541 (A) Don't do (2) if the branch is predicted against the block we're
1542 eliminating. Do it anyway if we can eliminate a branch; this requires
1543 that the sole successor of the eliminated block postdominate the other
1546 (B) With CE, on (3) we can steal from both sides of the if, creating
1555 Again, this is most useful if J postdominates.
1557 (C) CE substitutes for helpful life information.
1559 (D) These heuristics need a lot of work. */
1561 /* Tests for case 1 above. */
1564 find_if_case_1 (test_bb, then_edge, else_edge)
1565 basic_block test_bb;
1566 edge then_edge, else_edge;
1568 basic_block then_bb = then_edge->dest;
1569 basic_block else_bb = else_edge->dest;
1570 edge then_succ = then_bb->succ;
1573 /* THEN has one successor. */
1574 if (!then_succ || then_succ->succ_next != NULL)
1577 /* THEN does not fall through, but is not strange either. */
1578 if (then_succ->flags & (EDGE_COMPLEX | EDGE_FALLTHRU))
1581 /* THEN has one predecessor. */
1582 if (then_bb->pred->pred_next != NULL)
1585 /* THEN has no label. */
1586 if (GET_CODE (then_bb->head) == CODE_LABEL)
1589 /* ELSE follows THEN. (??? could be moved) */
1590 if (else_bb->index != then_bb->index + 1)
1593 num_possible_if_blocks++;
1595 fprintf (rtl_dump_file,
1596 "\nIF-CASE-1 found, start %d, then %d\n",
1597 test_bb->index, then_bb->index);
1599 /* THEN is small. */
1600 if (count_bb_insns (then_bb) > BRANCH_COST)
1603 /* Find the label for THEN's destination. */
1604 if (then_succ->dest == EXIT_BLOCK_PTR)
1608 new_lab = JUMP_LABEL (then_bb->end);
1613 /* Registers set are dead, or are predicable. */
1614 if (! dead_or_predicable (test_bb, then_bb, else_bb, new_lab, 1))
1617 /* Conversion went ok, including moving the insns and fixing up the
1618 jump. Adjust the CFG to match. */
1620 SET_UPDATE_LIFE (test_bb);
1621 bitmap_operation (test_bb->global_live_at_end,
1622 else_bb->global_live_at_start,
1623 then_bb->global_live_at_end, BITMAP_IOR);
1625 make_edge (NULL, test_bb, then_succ->dest, 0);
1626 flow_delete_block (then_bb);
1627 tidy_fallthru_edge (else_edge, test_bb, else_bb);
1629 num_removed_blocks++;
1630 num_updated_if_blocks++;
1635 /* Test for case 2 above. */
1638 find_if_case_2 (test_bb, then_edge, else_edge)
1639 basic_block test_bb;
1640 edge then_edge, else_edge;
1642 basic_block then_bb = then_edge->dest;
1643 basic_block else_bb = else_edge->dest;
1644 edge else_succ = else_bb->succ;
1647 /* ELSE has one successor. */
1648 if (!else_succ || else_succ->succ_next != NULL)
1651 /* ELSE outgoing edge is not complex. */
1652 if (else_succ->flags & EDGE_COMPLEX)
1655 /* ELSE has one predecessor. */
1656 if (else_bb->pred->pred_next != NULL)
1659 /* ELSE has a label we can delete. */
1660 if (LABEL_NUSES (else_bb->head) > 1
1661 || LABEL_PRESERVE_P (else_bb->head)
1662 || LABEL_NAME (else_bb->head))
1665 /* ELSE is predicted or SUCC(ELSE) postdominates THEN. */
1666 note = find_reg_note (test_bb->end, REG_BR_PROB, NULL_RTX);
1667 if (note && INTVAL (XEXP (note, 0)) >= REG_BR_PROB_BASE / 2)
1669 else if (else_succ->dest->index < 0
1670 || (then_bb->index >= 0
1671 && TEST_BIT (post_dominators[ORIG_INDEX (then_bb)],
1672 ORIG_INDEX (else_succ->dest))))
1677 num_possible_if_blocks++;
1679 fprintf (rtl_dump_file,
1680 "\nIF-CASE-2 found, start %d, else %d\n",
1681 test_bb->index, else_bb->index);
1683 /* ELSE is small. */
1684 if (count_bb_insns (then_bb) > BRANCH_COST)
1687 /* Find the label for ELSE's destination. */
1688 if (else_succ->dest == EXIT_BLOCK_PTR)
1692 if (else_succ->flags & EDGE_FALLTHRU)
1694 new_lab = else_succ->dest->head;
1695 if (GET_CODE (new_lab) != CODE_LABEL)
1700 new_lab = JUMP_LABEL (else_bb->end);
1706 /* Registers set are dead, or are predicable. */
1707 if (! dead_or_predicable (test_bb, else_bb, then_bb, new_lab, 0))
1710 /* Conversion went ok, including moving the insns and fixing up the
1711 jump. Adjust the CFG to match. */
1713 SET_UPDATE_LIFE (test_bb);
1714 bitmap_operation (test_bb->global_live_at_end,
1715 then_bb->global_live_at_start,
1716 else_bb->global_live_at_end, BITMAP_IOR);
1718 remove_edge (else_edge);
1719 make_edge (NULL, test_bb, else_succ->dest, 0);
1720 flow_delete_block (else_bb);
1722 num_removed_blocks++;
1723 num_updated_if_blocks++;
1725 /* ??? We may now fallthru from one of THEN's successors into a join
1726 block. Rerun cleanup_cfg? Examine things manually? Wait? */
1731 /* A subroutine of dead_or_predicable called through for_each_rtx.
1732 Return 1 if a memory is found. */
1735 find_memory (px, data)
1737 void *data ATTRIBUTE_UNUSED;
1739 return GET_CODE (*px) == MEM;
1742 /* Used by the code above to perform the actual rtl transformations.
1743 Return TRUE if successful.
1745 TEST_BB is the block containing the conditional branch. MERGE_BB
1746 is the block containing the code to manipulate. NEW_DEST is the
1747 label TEST_BB should be branching to after the conversion.
1748 REVERSEP is true if the sense of the branch should be reversed. */
1751 dead_or_predicable (test_bb, merge_bb, other_bb, new_dest, reversep)
1752 basic_block test_bb, merge_bb, other_bb;
1756 rtx head, end, jump, earliest, old_dest;
1758 jump = test_bb->end;
1760 /* Find the extent of the real code in the merge block. */
1761 head = merge_bb->head;
1762 end = merge_bb->end;
1764 if (GET_CODE (head) == CODE_LABEL)
1765 head = NEXT_INSN (head);
1766 if (GET_CODE (head) == NOTE)
1770 head = end = NULL_RTX;
1773 head = NEXT_INSN (head);
1776 if (GET_CODE (end) == JUMP_INSN)
1780 head = end = NULL_RTX;
1783 end = PREV_INSN (end);
1786 if (HAVE_conditional_execution)
1788 /* In the conditional execution case, we have things easy. We know
1789 the condition is reversable. We don't have to check life info,
1790 becase we're going to conditionally execute the code anyway.
1791 All that's left is making sure the insns involved can actually
1796 cond = cond_exec_get_condition (jump);
1798 cond = gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)),
1799 GET_MODE (cond), XEXP (cond, 0),
1802 if (! cond_exec_process_insns (head, end, cond, 0))
1809 /* In the non-conditional execution case, we have to verify that there
1810 are no trapping operations, no calls, no references to memory, and
1811 that any registers modified are dead at the branch site. */
1813 rtx insn, cond, prev;
1814 regset_head merge_set_head, tmp_head, test_live_head, test_set_head;
1815 regset merge_set, tmp, test_live, test_set;
1816 struct propagate_block_info *pbi;
1819 /* Check for no calls or trapping operations. */
1820 for (insn = head; ; insn = NEXT_INSN (insn))
1822 if (GET_CODE (insn) == CALL_INSN)
1826 if (may_trap_p (PATTERN (insn)))
1829 /* ??? Even non-trapping memories such as stack frame
1830 references must be avoided. For stores, we collect
1831 no lifetime info; for reads, we'd have to assert
1832 true_dependance false against every store in the
1834 if (for_each_rtx (&PATTERN (insn), find_memory, NULL))
1841 if (! condjump_p (jump))
1844 /* Find the extent of the conditional. */
1845 cond = noce_get_condition (jump, &earliest);
1850 MERGE_SET = set of registers set in MERGE_BB
1851 TEST_LIVE = set of registers live at EARLIEST
1852 TEST_SET = set of registers set between EARLIEST and the
1853 end of the block. */
1855 tmp = INITIALIZE_REG_SET (tmp_head);
1856 merge_set = INITIALIZE_REG_SET (merge_set_head);
1857 test_live = INITIALIZE_REG_SET (test_live_head);
1858 test_set = INITIALIZE_REG_SET (test_set_head);
1860 /* ??? bb->local_set is only valid during calculate_global_regs_live,
1861 so we must recompute usage for MERGE_BB. Not so bad, I suppose,
1862 since we've already asserted that MERGE_BB is small. */
1863 propagate_block (merge_bb, tmp, merge_set, 0);
1865 /* For small register class machines, don't lengthen lifetimes of
1866 hard registers before reload. */
1867 if (SMALL_REGISTER_CLASSES && ! reload_completed)
1869 EXECUTE_IF_SET_IN_BITMAP
1872 if (i < FIRST_PSEUDO_REGISTER
1874 && ! global_regs[i])
1879 /* For TEST, we're interested in a range of insns, not a whole block.
1880 Moreover, we're interested in the insns live from OTHER_BB. */
1882 COPY_REG_SET (test_live, other_bb->global_live_at_start);
1883 pbi = init_propagate_block_info (test_bb, test_live, test_set, 0);
1885 for (insn = jump; ; insn = prev)
1887 prev = propagate_one_insn (pbi, insn);
1888 if (insn == earliest)
1892 free_propagate_block_info (pbi);
1894 /* We can perform the transformation if
1895 MERGE_SET & (TEST_SET | TEST_LIVE)
1897 TEST_SET & merge_bb->global_live_at_start
1900 bitmap_operation (tmp, test_set, test_live, BITMAP_IOR);
1901 bitmap_operation (tmp, tmp, merge_set, BITMAP_AND);
1902 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
1904 bitmap_operation (tmp, test_set, merge_bb->global_live_at_start,
1906 EXECUTE_IF_SET_IN_BITMAP(tmp, 0, i, fail = 1);
1909 FREE_REG_SET (merge_set);
1910 FREE_REG_SET (test_live);
1911 FREE_REG_SET (test_set);
1918 /* We don't want to use normal invert_jump or redirect_jump because
1919 we don't want to delete_insn called. Also, we want to do our own
1920 change group management. */
1922 old_dest = JUMP_LABEL (jump);
1924 ? ! invert_jump_1 (jump, new_dest)
1925 : ! redirect_jump_1 (jump, new_dest))
1928 if (! apply_change_group ())
1932 LABEL_NUSES (old_dest) -= 1;
1934 LABEL_NUSES (new_dest) += 1;
1935 JUMP_LABEL (jump) = new_dest;
1939 rtx note = find_reg_note (jump, REG_BR_PROB, NULL_RTX);
1941 XEXP (note, 0) = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (note, 0)));
1944 /* Move the insns out of MERGE_BB to before the branch. */
1947 if (end == merge_bb->end)
1948 merge_bb->end = PREV_INSN (head);
1950 head = squeeze_notes (head, end);
1951 if (GET_CODE (end) == NOTE
1952 && (NOTE_LINE_NUMBER (end) == NOTE_INSN_BLOCK_END
1953 || NOTE_LINE_NUMBER (end) == NOTE_INSN_BLOCK_BEG
1954 || NOTE_LINE_NUMBER (end) == NOTE_INSN_LOOP_BEG
1955 || NOTE_LINE_NUMBER (end) == NOTE_INSN_LOOP_END
1956 || NOTE_LINE_NUMBER (end) == NOTE_INSN_LOOP_CONT
1957 || NOTE_LINE_NUMBER (end) == NOTE_INSN_LOOP_VTOP))
1961 end = PREV_INSN (end);
1964 reorder_insns (head, end, PREV_INSN (earliest));
1973 /* Main entry point for all if-conversion. */
1976 if_convert (life_data_ok)
1981 num_possible_if_blocks = 0;
1982 num_updated_if_blocks = 0;
1983 num_removed_blocks = 0;
1985 /* Free up basic_block_for_insn so that we don't have to keep it
1986 up to date, either here or in merge_blocks_nomove. */
1987 free_basic_block_vars (1);
1989 /* Compute postdominators if we think we'll use them. */
1990 post_dominators = NULL;
1991 if (HAVE_conditional_execution || life_data_ok)
1993 post_dominators = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
1994 compute_flow_dominators (NULL, post_dominators);
1997 /* Record initial block numbers. */
1998 for (block_num = 0; block_num < n_basic_blocks; block_num++)
1999 SET_ORIG_INDEX (BASIC_BLOCK (block_num), block_num);
2001 /* Go through each of the basic blocks looking for things to convert. */
2002 for (block_num = 0; block_num < n_basic_blocks; )
2004 basic_block bb = BASIC_BLOCK (block_num);
2005 if (find_if_header (bb))
2006 block_num = bb->index;
2011 sbitmap_vector_free (post_dominators);
2014 fflush (rtl_dump_file);
2016 /* Rebuild basic_block_for_insn for update_life_info and for gcse. */
2017 compute_bb_for_insn (get_max_uid ());
2019 /* Rebuild life info for basic blocks that require it. */
2020 if (num_removed_blocks && life_data_ok)
2022 sbitmap update_life_blocks = sbitmap_alloc (n_basic_blocks);
2023 sbitmap_zero (update_life_blocks);
2025 /* If we allocated new pseudos, we must resize the array for sched1. */
2026 if (max_regno < max_reg_num ())
2028 max_regno = max_reg_num ();
2029 allocate_reg_info (max_regno, FALSE, FALSE);
2032 for (block_num = 0; block_num < n_basic_blocks; block_num++)
2033 if (UPDATE_LIFE (BASIC_BLOCK (block_num)))
2034 SET_BIT (update_life_blocks, block_num);
2036 count_or_remove_death_notes (update_life_blocks, 1);
2037 update_life_info (update_life_blocks, UPDATE_LIFE_LOCAL,
2040 sbitmap_free (update_life_blocks);
2043 /* Write the final stats. */
2044 if (rtl_dump_file && num_possible_if_blocks > 0)
2046 fprintf (rtl_dump_file,
2047 "\n%d possible IF blocks searched.\n",
2048 num_possible_if_blocks);
2049 fprintf (rtl_dump_file,
2050 "%d IF blocks converted.\n",
2051 num_updated_if_blocks);
2052 fprintf (rtl_dump_file,
2053 "%d basic blocks deleted.\n\n\n",
2054 num_removed_blocks);
2057 #ifdef ENABLE_CHECKING
2058 verify_flow_info ();