1 /* Control flow optimization code for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2010, 2011
4 Free Software Foundation, Inc.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
22 /* This file contains optimizer of the control flow. The main entry point is
23 cleanup_cfg. Following optimizations are performed:
25 - Unreachable blocks removal
26 - Edge forwarding (edge to the forwarder block is forwarded to its
27 successor. Simplification of the branch instruction is performed by
28 underlying infrastructure so branch can be converted to simplejump or
30 - Cross jumping (tail merging)
31 - Conditional jump-around-simplejump simplification
32 - Basic block merging. */
36 #include "coretypes.h"
39 #include "hard-reg-set.h"
43 #include "insn-config.h"
46 #include "diagnostic-core.h"
51 #include "cfglayout.h"
53 #include "tree-pass.h"
60 #define FORWARDER_BLOCK_P(BB) ((BB)->flags & BB_FORWARDER_BLOCK)
62 /* Set to true when we are running first pass of try_optimize_cfg loop. */
63 static bool first_pass
;
65 /* Set to true if crossjumps occured in the latest run of try_optimize_cfg. */
66 static bool crossjumps_occured
;
68 /* Set to true if we couldn't run an optimization due to stale liveness
69 information; we should run df_analyze to enable more opportunities. */
70 static bool block_was_dirty
;
72 static bool try_crossjump_to_edge (int, edge
, edge
, enum replace_direction
);
73 static bool try_crossjump_bb (int, basic_block
);
74 static bool outgoing_edges_match (int, basic_block
, basic_block
);
75 static enum replace_direction
old_insns_match_p (int, rtx
, rtx
);
77 static void merge_blocks_move_predecessor_nojumps (basic_block
, basic_block
);
78 static void merge_blocks_move_successor_nojumps (basic_block
, basic_block
);
79 static bool try_optimize_cfg (int);
80 static bool try_simplify_condjump (basic_block
);
81 static bool try_forward_edges (int, basic_block
);
82 static edge
thread_jump (edge
, basic_block
);
83 static bool mark_effect (rtx
, bitmap
);
84 static void notice_new_block (basic_block
);
85 static void update_forwarder_flag (basic_block
);
86 static int mentions_nonequal_regs (rtx
*, void *);
87 static void merge_memattrs (rtx
, rtx
);
89 /* Set flags for newly created block. */
92 notice_new_block (basic_block bb
)
97 if (forwarder_block_p (bb
))
98 bb
->flags
|= BB_FORWARDER_BLOCK
;
101 /* Recompute forwarder flag after block has been modified. */
104 update_forwarder_flag (basic_block bb
)
106 if (forwarder_block_p (bb
))
107 bb
->flags
|= BB_FORWARDER_BLOCK
;
109 bb
->flags
&= ~BB_FORWARDER_BLOCK
;
112 /* Simplify a conditional jump around an unconditional jump.
113 Return true if something changed. */
116 try_simplify_condjump (basic_block cbranch_block
)
118 basic_block jump_block
, jump_dest_block
, cbranch_dest_block
;
119 edge cbranch_jump_edge
, cbranch_fallthru_edge
;
122 /* Verify that there are exactly two successors. */
123 if (EDGE_COUNT (cbranch_block
->succs
) != 2)
126 /* Verify that we've got a normal conditional branch at the end
128 cbranch_insn
= BB_END (cbranch_block
);
129 if (!any_condjump_p (cbranch_insn
))
132 cbranch_fallthru_edge
= FALLTHRU_EDGE (cbranch_block
);
133 cbranch_jump_edge
= BRANCH_EDGE (cbranch_block
);
135 /* The next block must not have multiple predecessors, must not
136 be the last block in the function, and must contain just the
137 unconditional jump. */
138 jump_block
= cbranch_fallthru_edge
->dest
;
139 if (!single_pred_p (jump_block
)
140 || jump_block
->next_bb
== EXIT_BLOCK_PTR
141 || !FORWARDER_BLOCK_P (jump_block
))
143 jump_dest_block
= single_succ (jump_block
);
145 /* If we are partitioning hot/cold basic blocks, we don't want to
146 mess up unconditional or indirect jumps that cross between hot
149 Basic block partitioning may result in some jumps that appear to
150 be optimizable (or blocks that appear to be mergeable), but which really
151 must be left untouched (they are required to make it safely across
152 partition boundaries). See the comments at the top of
153 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
155 if (BB_PARTITION (jump_block
) != BB_PARTITION (jump_dest_block
)
156 || (cbranch_jump_edge
->flags
& EDGE_CROSSING
))
159 /* The conditional branch must target the block after the
160 unconditional branch. */
161 cbranch_dest_block
= cbranch_jump_edge
->dest
;
163 if (cbranch_dest_block
== EXIT_BLOCK_PTR
164 || !can_fallthru (jump_block
, cbranch_dest_block
))
167 /* Invert the conditional branch. */
168 if (!invert_jump (cbranch_insn
, block_label (jump_dest_block
), 0))
172 fprintf (dump_file
, "Simplifying condjump %i around jump %i\n",
173 INSN_UID (cbranch_insn
), INSN_UID (BB_END (jump_block
)));
175 /* Success. Update the CFG to match. Note that after this point
176 the edge variable names appear backwards; the redirection is done
177 this way to preserve edge profile data. */
178 cbranch_jump_edge
= redirect_edge_succ_nodup (cbranch_jump_edge
,
180 cbranch_fallthru_edge
= redirect_edge_succ_nodup (cbranch_fallthru_edge
,
182 cbranch_jump_edge
->flags
|= EDGE_FALLTHRU
;
183 cbranch_fallthru_edge
->flags
&= ~EDGE_FALLTHRU
;
184 update_br_prob_note (cbranch_block
);
186 /* Delete the block with the unconditional jump, and clean up the mess. */
187 delete_basic_block (jump_block
);
188 tidy_fallthru_edge (cbranch_jump_edge
);
189 update_forwarder_flag (cbranch_block
);
194 /* Attempt to prove that operation is NOOP using CSElib or mark the effect
195 on register. Used by jump threading. */
198 mark_effect (rtx exp
, regset nonequal
)
202 switch (GET_CODE (exp
))
204 /* In case we do clobber the register, mark it as equal, as we know the
205 value is dead so it don't have to match. */
207 if (REG_P (XEXP (exp
, 0)))
209 dest
= XEXP (exp
, 0);
210 regno
= REGNO (dest
);
211 if (HARD_REGISTER_NUM_P (regno
))
212 bitmap_clear_range (nonequal
, regno
,
213 hard_regno_nregs
[regno
][GET_MODE (dest
)]);
215 bitmap_clear_bit (nonequal
, regno
);
220 if (rtx_equal_for_cselib_p (SET_DEST (exp
), SET_SRC (exp
)))
222 dest
= SET_DEST (exp
);
227 regno
= REGNO (dest
);
228 if (HARD_REGISTER_NUM_P (regno
))
229 bitmap_set_range (nonequal
, regno
,
230 hard_regno_nregs
[regno
][GET_MODE (dest
)]);
232 bitmap_set_bit (nonequal
, regno
);
240 /* Return nonzero if X is a register set in regset DATA.
241 Called via for_each_rtx. */
243 mentions_nonequal_regs (rtx
*x
, void *data
)
245 regset nonequal
= (regset
) data
;
251 if (REGNO_REG_SET_P (nonequal
, regno
))
253 if (regno
< FIRST_PSEUDO_REGISTER
)
255 int n
= hard_regno_nregs
[regno
][GET_MODE (*x
)];
257 if (REGNO_REG_SET_P (nonequal
, regno
+ n
))
263 /* Attempt to prove that the basic block B will have no side effects and
264 always continues in the same edge if reached via E. Return the edge
265 if exist, NULL otherwise. */
268 thread_jump (edge e
, basic_block b
)
270 rtx set1
, set2
, cond1
, cond2
, insn
;
271 enum rtx_code code1
, code2
, reversed_code2
;
272 bool reverse1
= false;
276 reg_set_iterator rsi
;
278 if (b
->flags
& BB_NONTHREADABLE_BLOCK
)
281 /* At the moment, we do handle only conditional jumps, but later we may
282 want to extend this code to tablejumps and others. */
283 if (EDGE_COUNT (e
->src
->succs
) != 2)
285 if (EDGE_COUNT (b
->succs
) != 2)
287 b
->flags
|= BB_NONTHREADABLE_BLOCK
;
291 /* Second branch must end with onlyjump, as we will eliminate the jump. */
292 if (!any_condjump_p (BB_END (e
->src
)))
295 if (!any_condjump_p (BB_END (b
)) || !onlyjump_p (BB_END (b
)))
297 b
->flags
|= BB_NONTHREADABLE_BLOCK
;
301 set1
= pc_set (BB_END (e
->src
));
302 set2
= pc_set (BB_END (b
));
303 if (((e
->flags
& EDGE_FALLTHRU
) != 0)
304 != (XEXP (SET_SRC (set1
), 1) == pc_rtx
))
307 cond1
= XEXP (SET_SRC (set1
), 0);
308 cond2
= XEXP (SET_SRC (set2
), 0);
310 code1
= reversed_comparison_code (cond1
, BB_END (e
->src
));
312 code1
= GET_CODE (cond1
);
314 code2
= GET_CODE (cond2
);
315 reversed_code2
= reversed_comparison_code (cond2
, BB_END (b
));
317 if (!comparison_dominates_p (code1
, code2
)
318 && !comparison_dominates_p (code1
, reversed_code2
))
321 /* Ensure that the comparison operators are equivalent.
322 ??? This is far too pessimistic. We should allow swapped operands,
323 different CCmodes, or for example comparisons for interval, that
324 dominate even when operands are not equivalent. */
325 if (!rtx_equal_p (XEXP (cond1
, 0), XEXP (cond2
, 0))
326 || !rtx_equal_p (XEXP (cond1
, 1), XEXP (cond2
, 1)))
329 /* Short circuit cases where block B contains some side effects, as we can't
331 for (insn
= NEXT_INSN (BB_HEAD (b
)); insn
!= NEXT_INSN (BB_END (b
));
332 insn
= NEXT_INSN (insn
))
333 if (INSN_P (insn
) && side_effects_p (PATTERN (insn
)))
335 b
->flags
|= BB_NONTHREADABLE_BLOCK
;
341 /* First process all values computed in the source basic block. */
342 for (insn
= NEXT_INSN (BB_HEAD (e
->src
));
343 insn
!= NEXT_INSN (BB_END (e
->src
));
344 insn
= NEXT_INSN (insn
))
346 cselib_process_insn (insn
);
348 nonequal
= BITMAP_ALLOC (NULL
);
349 CLEAR_REG_SET (nonequal
);
351 /* Now assume that we've continued by the edge E to B and continue
352 processing as if it were same basic block.
353 Our goal is to prove that whole block is an NOOP. */
355 for (insn
= NEXT_INSN (BB_HEAD (b
));
356 insn
!= NEXT_INSN (BB_END (b
)) && !failed
;
357 insn
= NEXT_INSN (insn
))
361 rtx pat
= PATTERN (insn
);
363 if (GET_CODE (pat
) == PARALLEL
)
365 for (i
= 0; i
< (unsigned)XVECLEN (pat
, 0); i
++)
366 failed
|= mark_effect (XVECEXP (pat
, 0, i
), nonequal
);
369 failed
|= mark_effect (pat
, nonequal
);
372 cselib_process_insn (insn
);
375 /* Later we should clear nonequal of dead registers. So far we don't
376 have life information in cfg_cleanup. */
379 b
->flags
|= BB_NONTHREADABLE_BLOCK
;
383 /* cond2 must not mention any register that is not equal to the
385 if (for_each_rtx (&cond2
, mentions_nonequal_regs
, nonequal
))
388 EXECUTE_IF_SET_IN_REG_SET (nonequal
, 0, i
, rsi
)
391 BITMAP_FREE (nonequal
);
393 if ((comparison_dominates_p (code1
, code2
) != 0)
394 != (XEXP (SET_SRC (set2
), 1) == pc_rtx
))
395 return BRANCH_EDGE (b
);
397 return FALLTHRU_EDGE (b
);
400 BITMAP_FREE (nonequal
);
405 /* Attempt to forward edges leaving basic block B.
406 Return true if successful. */
409 try_forward_edges (int mode
, basic_block b
)
411 bool changed
= false;
413 edge e
, *threaded_edges
= NULL
;
415 /* If we are partitioning hot/cold basic blocks, we don't want to
416 mess up unconditional or indirect jumps that cross between hot
419 Basic block partitioning may result in some jumps that appear to
420 be optimizable (or blocks that appear to be mergeable), but which really
421 must be left untouched (they are required to make it safely across
422 partition boundaries). See the comments at the top of
423 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
425 if (find_reg_note (BB_END (b
), REG_CROSSING_JUMP
, NULL_RTX
))
428 for (ei
= ei_start (b
->succs
); (e
= ei_safe_edge (ei
)); )
430 basic_block target
, first
;
431 int counter
, goto_locus
;
432 bool threaded
= false;
433 int nthreaded_edges
= 0;
434 bool may_thread
= first_pass
|| (b
->flags
& BB_MODIFIED
) != 0;
436 /* Skip complex edges because we don't know how to update them.
438 Still handle fallthru edges, as we can succeed to forward fallthru
439 edge to the same place as the branch edge of conditional branch
440 and turn conditional branch to an unconditional branch. */
441 if (e
->flags
& EDGE_COMPLEX
)
447 target
= first
= e
->dest
;
448 counter
= NUM_FIXED_BLOCKS
;
449 goto_locus
= e
->goto_locus
;
451 /* If we are partitioning hot/cold basic_blocks, we don't want to mess
452 up jumps that cross between hot/cold sections.
454 Basic block partitioning may result in some jumps that appear
455 to be optimizable (or blocks that appear to be mergeable), but which
456 really must be left untouched (they are required to make it safely
457 across partition boundaries). See the comments at the top of
458 bb-reorder.c:partition_hot_cold_basic_blocks for complete
461 if (first
!= EXIT_BLOCK_PTR
462 && find_reg_note (BB_END (first
), REG_CROSSING_JUMP
, NULL_RTX
))
465 while (counter
< n_basic_blocks
)
467 basic_block new_target
= NULL
;
468 bool new_target_threaded
= false;
469 may_thread
|= (target
->flags
& BB_MODIFIED
) != 0;
471 if (FORWARDER_BLOCK_P (target
)
472 && !(single_succ_edge (target
)->flags
& EDGE_CROSSING
)
473 && single_succ (target
) != EXIT_BLOCK_PTR
)
475 /* Bypass trivial infinite loops. */
476 new_target
= single_succ (target
);
477 if (target
== new_target
)
478 counter
= n_basic_blocks
;
481 /* When not optimizing, ensure that edges or forwarder
482 blocks with different locus are not optimized out. */
483 int new_locus
= single_succ_edge (target
)->goto_locus
;
484 int locus
= goto_locus
;
486 if (new_locus
&& locus
&& !locator_eq (new_locus
, locus
))
495 last
= BB_END (target
);
496 if (DEBUG_INSN_P (last
))
497 last
= prev_nondebug_insn (last
);
499 new_locus
= last
&& INSN_P (last
)
500 ? INSN_LOCATOR (last
) : 0;
502 if (new_locus
&& locus
&& !locator_eq (new_locus
, locus
))
515 /* Allow to thread only over one edge at time to simplify updating
517 else if ((mode
& CLEANUP_THREADING
) && may_thread
)
519 edge t
= thread_jump (e
, target
);
523 threaded_edges
= XNEWVEC (edge
, n_basic_blocks
);
528 /* Detect an infinite loop across blocks not
529 including the start block. */
530 for (i
= 0; i
< nthreaded_edges
; ++i
)
531 if (threaded_edges
[i
] == t
)
533 if (i
< nthreaded_edges
)
535 counter
= n_basic_blocks
;
540 /* Detect an infinite loop across the start block. */
544 gcc_assert (nthreaded_edges
< n_basic_blocks
- NUM_FIXED_BLOCKS
);
545 threaded_edges
[nthreaded_edges
++] = t
;
547 new_target
= t
->dest
;
548 new_target_threaded
= true;
557 threaded
|= new_target_threaded
;
560 if (counter
>= n_basic_blocks
)
563 fprintf (dump_file
, "Infinite loop in BB %i.\n",
566 else if (target
== first
)
567 ; /* We didn't do anything. */
570 /* Save the values now, as the edge may get removed. */
571 gcov_type edge_count
= e
->count
;
572 int edge_probability
= e
->probability
;
576 e
->goto_locus
= goto_locus
;
578 /* Don't force if target is exit block. */
579 if (threaded
&& target
!= EXIT_BLOCK_PTR
)
581 notice_new_block (redirect_edge_and_branch_force (e
, target
));
583 fprintf (dump_file
, "Conditionals threaded.\n");
585 else if (!redirect_edge_and_branch (e
, target
))
589 "Forwarding edge %i->%i to %i failed.\n",
590 b
->index
, e
->dest
->index
, target
->index
);
595 /* We successfully forwarded the edge. Now update profile
596 data: for each edge we traversed in the chain, remove
597 the original edge's execution count. */
598 edge_frequency
= ((edge_probability
* b
->frequency
599 + REG_BR_PROB_BASE
/ 2)
602 if (!FORWARDER_BLOCK_P (b
) && forwarder_block_p (b
))
603 b
->flags
|= BB_FORWARDER_BLOCK
;
609 if (!single_succ_p (first
))
611 gcc_assert (n
< nthreaded_edges
);
612 t
= threaded_edges
[n
++];
613 gcc_assert (t
->src
== first
);
614 update_bb_profile_for_threading (first
, edge_frequency
,
616 update_br_prob_note (first
);
620 first
->count
-= edge_count
;
621 if (first
->count
< 0)
623 first
->frequency
-= edge_frequency
;
624 if (first
->frequency
< 0)
625 first
->frequency
= 0;
626 /* It is possible that as the result of
627 threading we've removed edge as it is
628 threaded to the fallthru edge. Avoid
629 getting out of sync. */
630 if (n
< nthreaded_edges
631 && first
== threaded_edges
[n
]->src
)
633 t
= single_succ_edge (first
);
636 t
->count
-= edge_count
;
641 while (first
!= target
);
650 free (threaded_edges
);
655 /* Blocks A and B are to be merged into a single block. A has no incoming
656 fallthru edge, so it can be moved before B without adding or modifying
657 any jumps (aside from the jump from A to B). */
660 merge_blocks_move_predecessor_nojumps (basic_block a
, basic_block b
)
664 /* If we are partitioning hot/cold basic blocks, we don't want to
665 mess up unconditional or indirect jumps that cross between hot
668 Basic block partitioning may result in some jumps that appear to
669 be optimizable (or blocks that appear to be mergeable), but which really
670 must be left untouched (they are required to make it safely across
671 partition boundaries). See the comments at the top of
672 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
674 if (BB_PARTITION (a
) != BB_PARTITION (b
))
677 barrier
= next_nonnote_insn (BB_END (a
));
678 gcc_assert (BARRIER_P (barrier
));
679 delete_insn (barrier
);
681 /* Scramble the insn chain. */
682 if (BB_END (a
) != PREV_INSN (BB_HEAD (b
)))
683 reorder_insns_nobb (BB_HEAD (a
), BB_END (a
), PREV_INSN (BB_HEAD (b
)));
687 fprintf (dump_file
, "Moved block %d before %d and merged.\n",
690 /* Swap the records for the two blocks around. */
693 link_block (a
, b
->prev_bb
);
695 /* Now blocks A and B are contiguous. Merge them. */
699 /* Blocks A and B are to be merged into a single block. B has no outgoing
700 fallthru edge, so it can be moved after A without adding or modifying
701 any jumps (aside from the jump from A to B). */
704 merge_blocks_move_successor_nojumps (basic_block a
, basic_block b
)
706 rtx barrier
, real_b_end
;
709 /* If we are partitioning hot/cold basic blocks, we don't want to
710 mess up unconditional or indirect jumps that cross between hot
713 Basic block partitioning may result in some jumps that appear to
714 be optimizable (or blocks that appear to be mergeable), but which really
715 must be left untouched (they are required to make it safely across
716 partition boundaries). See the comments at the top of
717 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
719 if (BB_PARTITION (a
) != BB_PARTITION (b
))
722 real_b_end
= BB_END (b
);
724 /* If there is a jump table following block B temporarily add the jump table
725 to block B so that it will also be moved to the correct location. */
726 if (tablejump_p (BB_END (b
), &label
, &table
)
727 && prev_active_insn (label
) == BB_END (b
))
732 /* There had better have been a barrier there. Delete it. */
733 barrier
= NEXT_INSN (BB_END (b
));
734 if (barrier
&& BARRIER_P (barrier
))
735 delete_insn (barrier
);
738 /* Scramble the insn chain. */
739 reorder_insns_nobb (BB_HEAD (b
), BB_END (b
), BB_END (a
));
741 /* Restore the real end of b. */
742 BB_END (b
) = real_b_end
;
745 fprintf (dump_file
, "Moved block %d after %d and merged.\n",
748 /* Now blocks A and B are contiguous. Merge them. */
752 /* Attempt to merge basic blocks that are potentially non-adjacent.
753 Return NULL iff the attempt failed, otherwise return basic block
754 where cleanup_cfg should continue. Because the merging commonly
755 moves basic block away or introduces another optimization
756 possibility, return basic block just before B so cleanup_cfg don't
759 It may be good idea to return basic block before C in the case
760 C has been moved after B and originally appeared earlier in the
761 insn sequence, but we have no information available about the
762 relative ordering of these two. Hopefully it is not too common. */
765 merge_blocks_move (edge e
, basic_block b
, basic_block c
, int mode
)
769 /* If we are partitioning hot/cold basic blocks, we don't want to
770 mess up unconditional or indirect jumps that cross between hot
773 Basic block partitioning may result in some jumps that appear to
774 be optimizable (or blocks that appear to be mergeable), but which really
775 must be left untouched (they are required to make it safely across
776 partition boundaries). See the comments at the top of
777 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
779 if (BB_PARTITION (b
) != BB_PARTITION (c
))
782 /* If B has a fallthru edge to C, no need to move anything. */
783 if (e
->flags
& EDGE_FALLTHRU
)
785 int b_index
= b
->index
, c_index
= c
->index
;
787 update_forwarder_flag (b
);
790 fprintf (dump_file
, "Merged %d and %d without moving.\n",
793 return b
->prev_bb
== ENTRY_BLOCK_PTR
? b
: b
->prev_bb
;
796 /* Otherwise we will need to move code around. Do that only if expensive
797 transformations are allowed. */
798 else if (mode
& CLEANUP_EXPENSIVE
)
800 edge tmp_edge
, b_fallthru_edge
;
801 bool c_has_outgoing_fallthru
;
802 bool b_has_incoming_fallthru
;
804 /* Avoid overactive code motion, as the forwarder blocks should be
805 eliminated by edge redirection instead. One exception might have
806 been if B is a forwarder block and C has no fallthru edge, but
807 that should be cleaned up by bb-reorder instead. */
808 if (FORWARDER_BLOCK_P (b
) || FORWARDER_BLOCK_P (c
))
811 /* We must make sure to not munge nesting of lexical blocks,
812 and loop notes. This is done by squeezing out all the notes
813 and leaving them there to lie. Not ideal, but functional. */
815 tmp_edge
= find_fallthru_edge (c
->succs
);
816 c_has_outgoing_fallthru
= (tmp_edge
!= NULL
);
818 tmp_edge
= find_fallthru_edge (b
->preds
);
819 b_has_incoming_fallthru
= (tmp_edge
!= NULL
);
820 b_fallthru_edge
= tmp_edge
;
823 next
= next
->prev_bb
;
825 /* Otherwise, we're going to try to move C after B. If C does
826 not have an outgoing fallthru, then it can be moved
827 immediately after B without introducing or modifying jumps. */
828 if (! c_has_outgoing_fallthru
)
830 merge_blocks_move_successor_nojumps (b
, c
);
831 return next
== ENTRY_BLOCK_PTR
? next
->next_bb
: next
;
834 /* If B does not have an incoming fallthru, then it can be moved
835 immediately before C without introducing or modifying jumps.
836 C cannot be the first block, so we do not have to worry about
837 accessing a non-existent block. */
839 if (b_has_incoming_fallthru
)
843 if (b_fallthru_edge
->src
== ENTRY_BLOCK_PTR
)
845 bb
= force_nonfallthru (b_fallthru_edge
);
847 notice_new_block (bb
);
850 merge_blocks_move_predecessor_nojumps (b
, c
);
851 return next
== ENTRY_BLOCK_PTR
? next
->next_bb
: next
;
858 /* Removes the memory attributes of MEM expression
859 if they are not equal. */
862 merge_memattrs (rtx x
, rtx y
)
871 if (x
== 0 || y
== 0)
876 if (code
!= GET_CODE (y
))
879 if (GET_MODE (x
) != GET_MODE (y
))
882 if (code
== MEM
&& MEM_ATTRS (x
) != MEM_ATTRS (y
))
886 else if (! MEM_ATTRS (y
))
892 if (MEM_ALIAS_SET (x
) != MEM_ALIAS_SET (y
))
894 set_mem_alias_set (x
, 0);
895 set_mem_alias_set (y
, 0);
898 if (! mem_expr_equal_p (MEM_EXPR (x
), MEM_EXPR (y
)))
902 set_mem_offset (x
, 0);
903 set_mem_offset (y
, 0);
905 else if (MEM_OFFSET (x
) != MEM_OFFSET (y
))
907 set_mem_offset (x
, 0);
908 set_mem_offset (y
, 0);
913 else if (!MEM_SIZE (y
))
916 mem_size
= GEN_INT (MAX (INTVAL (MEM_SIZE (x
)),
917 INTVAL (MEM_SIZE (y
))));
918 set_mem_size (x
, mem_size
);
919 set_mem_size (y
, mem_size
);
921 set_mem_align (x
, MIN (MEM_ALIGN (x
), MEM_ALIGN (y
)));
922 set_mem_align (y
, MEM_ALIGN (x
));
926 fmt
= GET_RTX_FORMAT (code
);
927 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
932 /* Two vectors must have the same length. */
933 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
936 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
937 merge_memattrs (XVECEXP (x
, i
, j
), XVECEXP (y
, i
, j
));
942 merge_memattrs (XEXP (x
, i
), XEXP (y
, i
));
949 /* Checks if patterns P1 and P2 are equivalent, apart from the possibly
950 different single sets S1 and S2. */
953 equal_different_set_p (rtx p1
, rtx s1
, rtx p2
, rtx s2
)
958 if (p1
== s1
&& p2
== s2
)
961 if (GET_CODE (p1
) != PARALLEL
|| GET_CODE (p2
) != PARALLEL
)
964 if (XVECLEN (p1
, 0) != XVECLEN (p2
, 0))
967 for (i
= 0; i
< XVECLEN (p1
, 0); i
++)
969 e1
= XVECEXP (p1
, 0, i
);
970 e2
= XVECEXP (p2
, 0, i
);
971 if (e1
== s1
&& e2
== s2
)
974 ? rtx_renumbered_equal_p (e1
, e2
) : rtx_equal_p (e1
, e2
))
983 /* Examine register notes on I1 and I2 and return:
984 - dir_forward if I1 can be replaced by I2, or
985 - dir_backward if I2 can be replaced by I1, or
986 - dir_both if both are the case. */
988 static enum replace_direction
989 can_replace_by (rtx i1
, rtx i2
)
991 rtx s1
, s2
, d1
, d2
, src1
, src2
, note1
, note2
;
994 /* Check for 2 sets. */
995 s1
= single_set (i1
);
996 s2
= single_set (i2
);
997 if (s1
== NULL_RTX
|| s2
== NULL_RTX
)
1000 /* Check that the 2 sets set the same dest. */
1003 if (!(reload_completed
1004 ? rtx_renumbered_equal_p (d1
, d2
) : rtx_equal_p (d1
, d2
)))
1007 /* Find identical req_equiv or reg_equal note, which implies that the 2 sets
1008 set dest to the same value. */
1009 note1
= find_reg_equal_equiv_note (i1
);
1010 note2
= find_reg_equal_equiv_note (i2
);
1011 if (!note1
|| !note2
|| !rtx_equal_p (XEXP (note1
, 0), XEXP (note2
, 0))
1012 || !CONST_INT_P (XEXP (note1
, 0)))
1015 if (!equal_different_set_p (PATTERN (i1
), s1
, PATTERN (i2
), s2
))
1018 /* Although the 2 sets set dest to the same value, we cannot replace
1019 (set (dest) (const_int))
1022 because we don't know if the reg is live and has the same value at the
1023 location of replacement. */
1024 src1
= SET_SRC (s1
);
1025 src2
= SET_SRC (s2
);
1026 c1
= CONST_INT_P (src1
);
1027 c2
= CONST_INT_P (src2
);
1033 return dir_backward
;
1038 /* Merges directions A and B. */
1040 static enum replace_direction
1041 merge_dir (enum replace_direction a
, enum replace_direction b
)
1043 /* Implements the following table:
1062 /* Examine I1 and I2 and return:
1063 - dir_forward if I1 can be replaced by I2, or
1064 - dir_backward if I2 can be replaced by I1, or
1065 - dir_both if both are the case. */
1067 static enum replace_direction
1068 old_insns_match_p (int mode ATTRIBUTE_UNUSED
, rtx i1
, rtx i2
)
1072 /* Verify that I1 and I2 are equivalent. */
1073 if (GET_CODE (i1
) != GET_CODE (i2
))
1076 /* __builtin_unreachable() may lead to empty blocks (ending with
1077 NOTE_INSN_BASIC_BLOCK). They may be crossjumped. */
1078 if (NOTE_INSN_BASIC_BLOCK_P (i1
) && NOTE_INSN_BASIC_BLOCK_P (i2
))
1084 if (GET_CODE (p1
) != GET_CODE (p2
))
1087 /* If this is a CALL_INSN, compare register usage information.
1088 If we don't check this on stack register machines, the two
1089 CALL_INSNs might be merged leaving reg-stack.c with mismatching
1090 numbers of stack registers in the same basic block.
1091 If we don't check this on machines with delay slots, a delay slot may
1092 be filled that clobbers a parameter expected by the subroutine.
1094 ??? We take the simple route for now and assume that if they're
1095 equal, they were constructed identically.
1097 Also check for identical exception regions. */
1101 /* Ensure the same EH region. */
1102 rtx n1
= find_reg_note (i1
, REG_EH_REGION
, 0);
1103 rtx n2
= find_reg_note (i2
, REG_EH_REGION
, 0);
1108 if (n1
&& (!n2
|| XEXP (n1
, 0) != XEXP (n2
, 0)))
1111 if (!rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1
),
1112 CALL_INSN_FUNCTION_USAGE (i2
))
1113 || SIBLING_CALL_P (i1
) != SIBLING_CALL_P (i2
))
1118 /* If cross_jump_death_matters is not 0, the insn's mode
1119 indicates whether or not the insn contains any stack-like
1122 if ((mode
& CLEANUP_POST_REGSTACK
) && stack_regs_mentioned (i1
))
1124 /* If register stack conversion has already been done, then
1125 death notes must also be compared before it is certain that
1126 the two instruction streams match. */
1129 HARD_REG_SET i1_regset
, i2_regset
;
1131 CLEAR_HARD_REG_SET (i1_regset
);
1132 CLEAR_HARD_REG_SET (i2_regset
);
1134 for (note
= REG_NOTES (i1
); note
; note
= XEXP (note
, 1))
1135 if (REG_NOTE_KIND (note
) == REG_DEAD
&& STACK_REG_P (XEXP (note
, 0)))
1136 SET_HARD_REG_BIT (i1_regset
, REGNO (XEXP (note
, 0)));
1138 for (note
= REG_NOTES (i2
); note
; note
= XEXP (note
, 1))
1139 if (REG_NOTE_KIND (note
) == REG_DEAD
&& STACK_REG_P (XEXP (note
, 0)))
1140 SET_HARD_REG_BIT (i2_regset
, REGNO (XEXP (note
, 0)));
1142 if (!hard_reg_set_equal_p (i1_regset
, i2_regset
))
1147 if (reload_completed
1148 ? rtx_renumbered_equal_p (p1
, p2
) : rtx_equal_p (p1
, p2
))
1151 return can_replace_by (i1
, i2
);
1154 /* When comparing insns I1 and I2 in flow_find_cross_jump or
1155 flow_find_head_matching_sequence, ensure the notes match. */
1158 merge_notes (rtx i1
, rtx i2
)
1160 /* If the merged insns have different REG_EQUAL notes, then
1162 rtx equiv1
= find_reg_equal_equiv_note (i1
);
1163 rtx equiv2
= find_reg_equal_equiv_note (i2
);
1165 if (equiv1
&& !equiv2
)
1166 remove_note (i1
, equiv1
);
1167 else if (!equiv1
&& equiv2
)
1168 remove_note (i2
, equiv2
);
1169 else if (equiv1
&& equiv2
1170 && !rtx_equal_p (XEXP (equiv1
, 0), XEXP (equiv2
, 0)))
1172 remove_note (i1
, equiv1
);
1173 remove_note (i2
, equiv2
);
1177 /* Walks from I1 in BB1 backward till the next non-debug insn, and returns the
1178 resulting insn in I1, and the corresponding bb in BB1. At the head of a
1179 bb, if there is a predecessor bb that reaches this bb via fallthru, and
1180 FOLLOW_FALLTHRU, walks further in the predecessor bb and registers this in
1181 DID_FALLTHRU. Otherwise, stops at the head of the bb. */
1184 walk_to_nondebug_insn (rtx
*i1
, basic_block
*bb1
, bool follow_fallthru
,
1189 *did_fallthru
= false;
1192 while (!NONDEBUG_INSN_P (*i1
))
1194 if (*i1
!= BB_HEAD (*bb1
))
1196 *i1
= PREV_INSN (*i1
);
1200 if (!follow_fallthru
)
1203 fallthru
= find_fallthru_edge ((*bb1
)->preds
);
1204 if (!fallthru
|| fallthru
->src
== ENTRY_BLOCK_PTR_FOR_FUNCTION (cfun
)
1205 || !single_succ_p (fallthru
->src
))
1208 *bb1
= fallthru
->src
;
1209 *i1
= BB_END (*bb1
);
1210 *did_fallthru
= true;
1214 /* Look through the insns at the end of BB1 and BB2 and find the longest
1215 sequence that are either equivalent, or allow forward or backward
1216 replacement. Store the first insns for that sequence in *F1 and *F2 and
1217 return the sequence length.
1219 DIR_P indicates the allowed replacement direction on function entry, and
1220 the actual replacement direction on function exit. If NULL, only equivalent
1221 sequences are allowed.
1223 To simplify callers of this function, if the blocks match exactly,
1224 store the head of the blocks in *F1 and *F2. */
1227 flow_find_cross_jump (basic_block bb1
, basic_block bb2
, rtx
*f1
, rtx
*f2
,
1228 enum replace_direction
*dir_p
)
1230 rtx i1
, i2
, last1
, last2
, afterlast1
, afterlast2
;
1233 enum replace_direction dir
, last_dir
, afterlast_dir
;
1234 bool follow_fallthru
, did_fallthru
;
1240 afterlast_dir
= dir
;
1241 last_dir
= afterlast_dir
;
1243 /* Skip simple jumps at the end of the blocks. Complex jumps still
1244 need to be compared for equivalence, which we'll do below. */
1247 last1
= afterlast1
= last2
= afterlast2
= NULL_RTX
;
1249 || (returnjump_p (i1
) && !side_effects_p (PATTERN (i1
))))
1252 i1
= PREV_INSN (i1
);
1257 || (returnjump_p (i2
) && !side_effects_p (PATTERN (i2
))))
1260 /* Count everything except for unconditional jump as insn. */
1261 if (!simplejump_p (i2
) && !returnjump_p (i2
) && last1
)
1263 i2
= PREV_INSN (i2
);
1268 /* In the following example, we can replace all jumps to C by jumps to A.
1270 This removes 4 duplicate insns.
1271 [bb A] insn1 [bb C] insn1
1277 We could also replace all jumps to A by jumps to C, but that leaves B
1278 alive, and removes only 2 duplicate insns. In a subsequent crossjump
1279 step, all jumps to B would be replaced with jumps to the middle of C,
1280 achieving the same result with more effort.
1281 So we allow only the first possibility, which means that we don't allow
1282 fallthru in the block that's being replaced. */
1284 follow_fallthru
= dir_p
&& dir
!= dir_forward
;
1285 walk_to_nondebug_insn (&i1
, &bb1
, follow_fallthru
, &did_fallthru
);
1289 follow_fallthru
= dir_p
&& dir
!= dir_backward
;
1290 walk_to_nondebug_insn (&i2
, &bb2
, follow_fallthru
, &did_fallthru
);
1294 if (i1
== BB_HEAD (bb1
) || i2
== BB_HEAD (bb2
))
1297 dir
= merge_dir (dir
, old_insns_match_p (0, i1
, i2
));
1298 if (dir
== dir_none
|| (!dir_p
&& dir
!= dir_both
))
1301 merge_memattrs (i1
, i2
);
1303 /* Don't begin a cross-jump with a NOTE insn. */
1306 merge_notes (i1
, i2
);
1308 afterlast1
= last1
, afterlast2
= last2
;
1309 last1
= i1
, last2
= i2
;
1310 afterlast_dir
= last_dir
;
1313 if (!(GET_CODE (p1
) == USE
|| GET_CODE (p1
) == CLOBBER
))
1317 i1
= PREV_INSN (i1
);
1318 i2
= PREV_INSN (i2
);
1322 /* Don't allow the insn after a compare to be shared by
1323 cross-jumping unless the compare is also shared. */
1324 if (ninsns
&& reg_mentioned_p (cc0_rtx
, last1
) && ! sets_cc0_p (last1
))
1325 last1
= afterlast1
, last2
= afterlast2
, last_dir
= afterlast_dir
, ninsns
--;
1328 /* Include preceding notes and labels in the cross-jump. One,
1329 this may bring us to the head of the blocks as requested above.
1330 Two, it keeps line number notes as matched as may be. */
1333 bb1
= BLOCK_FOR_INSN (last1
);
1334 while (last1
!= BB_HEAD (bb1
) && !NONDEBUG_INSN_P (PREV_INSN (last1
)))
1335 last1
= PREV_INSN (last1
);
1337 if (last1
!= BB_HEAD (bb1
) && LABEL_P (PREV_INSN (last1
)))
1338 last1
= PREV_INSN (last1
);
1340 bb2
= BLOCK_FOR_INSN (last2
);
1341 while (last2
!= BB_HEAD (bb2
) && !NONDEBUG_INSN_P (PREV_INSN (last2
)))
1342 last2
= PREV_INSN (last2
);
1344 if (last2
!= BB_HEAD (bb2
) && LABEL_P (PREV_INSN (last2
)))
1345 last2
= PREV_INSN (last2
);
1356 /* Like flow_find_cross_jump, except start looking for a matching sequence from
1357 the head of the two blocks. Do not include jumps at the end.
1358 If STOP_AFTER is nonzero, stop after finding that many matching
1362 flow_find_head_matching_sequence (basic_block bb1
, basic_block bb2
, rtx
*f1
,
1363 rtx
*f2
, int stop_after
)
1365 rtx i1
, i2
, last1
, last2
, beforelast1
, beforelast2
;
1369 int nehedges1
= 0, nehedges2
= 0;
1371 FOR_EACH_EDGE (e
, ei
, bb1
->succs
)
1372 if (e
->flags
& EDGE_EH
)
1374 FOR_EACH_EDGE (e
, ei
, bb2
->succs
)
1375 if (e
->flags
& EDGE_EH
)
1380 last1
= beforelast1
= last2
= beforelast2
= NULL_RTX
;
1384 /* Ignore notes, except NOTE_INSN_EPILOGUE_BEG. */
1385 while (!NONDEBUG_INSN_P (i1
) && i1
!= BB_END (bb1
))
1387 if (NOTE_P (i1
) && NOTE_KIND (i1
) == NOTE_INSN_EPILOGUE_BEG
)
1389 i1
= NEXT_INSN (i1
);
1392 while (!NONDEBUG_INSN_P (i2
) && i2
!= BB_END (bb2
))
1394 if (NOTE_P (i2
) && NOTE_KIND (i2
) == NOTE_INSN_EPILOGUE_BEG
)
1396 i2
= NEXT_INSN (i2
);
1399 if ((i1
== BB_END (bb1
) && !NONDEBUG_INSN_P (i1
))
1400 || (i2
== BB_END (bb2
) && !NONDEBUG_INSN_P (i2
)))
1403 if (NOTE_P (i1
) || NOTE_P (i2
)
1404 || JUMP_P (i1
) || JUMP_P (i2
))
1407 /* A sanity check to make sure we're not merging insns with different
1408 effects on EH. If only one of them ends a basic block, it shouldn't
1409 have an EH edge; if both end a basic block, there should be the same
1410 number of EH edges. */
1411 if ((i1
== BB_END (bb1
) && i2
!= BB_END (bb2
)
1413 || (i2
== BB_END (bb2
) && i1
!= BB_END (bb1
)
1415 || (i1
== BB_END (bb1
) && i2
== BB_END (bb2
)
1416 && nehedges1
!= nehedges2
))
1419 if (old_insns_match_p (0, i1
, i2
) != dir_both
)
1422 merge_memattrs (i1
, i2
);
1424 /* Don't begin a cross-jump with a NOTE insn. */
1427 merge_notes (i1
, i2
);
1429 beforelast1
= last1
, beforelast2
= last2
;
1430 last1
= i1
, last2
= i2
;
1434 if (i1
== BB_END (bb1
) || i2
== BB_END (bb2
)
1435 || (stop_after
> 0 && ninsns
== stop_after
))
1438 i1
= NEXT_INSN (i1
);
1439 i2
= NEXT_INSN (i2
);
1443 /* Don't allow a compare to be shared by cross-jumping unless the insn
1444 after the compare is also shared. */
1445 if (ninsns
&& reg_mentioned_p (cc0_rtx
, last1
) && sets_cc0_p (last1
))
1446 last1
= beforelast1
, last2
= beforelast2
, ninsns
--;
1458 /* Return true iff outgoing edges of BB1 and BB2 match, together with
1459 the branch instruction. This means that if we commonize the control
1460 flow before end of the basic block, the semantic remains unchanged.
1462 We may assume that there exists one edge with a common destination. */
1465 outgoing_edges_match (int mode
, basic_block bb1
, basic_block bb2
)
1467 int nehedges1
= 0, nehedges2
= 0;
1468 edge fallthru1
= 0, fallthru2
= 0;
1472 /* If BB1 has only one successor, we may be looking at either an
1473 unconditional jump, or a fake edge to exit. */
1474 if (single_succ_p (bb1
)
1475 && (single_succ_edge (bb1
)->flags
& (EDGE_COMPLEX
| EDGE_FAKE
)) == 0
1476 && (!JUMP_P (BB_END (bb1
)) || simplejump_p (BB_END (bb1
))))
1477 return (single_succ_p (bb2
)
1478 && (single_succ_edge (bb2
)->flags
1479 & (EDGE_COMPLEX
| EDGE_FAKE
)) == 0
1480 && (!JUMP_P (BB_END (bb2
)) || simplejump_p (BB_END (bb2
))));
1482 /* Match conditional jumps - this may get tricky when fallthru and branch
1483 edges are crossed. */
1484 if (EDGE_COUNT (bb1
->succs
) == 2
1485 && any_condjump_p (BB_END (bb1
))
1486 && onlyjump_p (BB_END (bb1
)))
1488 edge b1
, f1
, b2
, f2
;
1489 bool reverse
, match
;
1490 rtx set1
, set2
, cond1
, cond2
;
1491 enum rtx_code code1
, code2
;
1493 if (EDGE_COUNT (bb2
->succs
) != 2
1494 || !any_condjump_p (BB_END (bb2
))
1495 || !onlyjump_p (BB_END (bb2
)))
1498 b1
= BRANCH_EDGE (bb1
);
1499 b2
= BRANCH_EDGE (bb2
);
1500 f1
= FALLTHRU_EDGE (bb1
);
1501 f2
= FALLTHRU_EDGE (bb2
);
1503 /* Get around possible forwarders on fallthru edges. Other cases
1504 should be optimized out already. */
1505 if (FORWARDER_BLOCK_P (f1
->dest
))
1506 f1
= single_succ_edge (f1
->dest
);
1508 if (FORWARDER_BLOCK_P (f2
->dest
))
1509 f2
= single_succ_edge (f2
->dest
);
1511 /* To simplify use of this function, return false if there are
1512 unneeded forwarder blocks. These will get eliminated later
1513 during cleanup_cfg. */
1514 if (FORWARDER_BLOCK_P (f1
->dest
)
1515 || FORWARDER_BLOCK_P (f2
->dest
)
1516 || FORWARDER_BLOCK_P (b1
->dest
)
1517 || FORWARDER_BLOCK_P (b2
->dest
))
1520 if (f1
->dest
== f2
->dest
&& b1
->dest
== b2
->dest
)
1522 else if (f1
->dest
== b2
->dest
&& b1
->dest
== f2
->dest
)
1527 set1
= pc_set (BB_END (bb1
));
1528 set2
= pc_set (BB_END (bb2
));
1529 if ((XEXP (SET_SRC (set1
), 1) == pc_rtx
)
1530 != (XEXP (SET_SRC (set2
), 1) == pc_rtx
))
1533 cond1
= XEXP (SET_SRC (set1
), 0);
1534 cond2
= XEXP (SET_SRC (set2
), 0);
1535 code1
= GET_CODE (cond1
);
1537 code2
= reversed_comparison_code (cond2
, BB_END (bb2
));
1539 code2
= GET_CODE (cond2
);
1541 if (code2
== UNKNOWN
)
1544 /* Verify codes and operands match. */
1545 match
= ((code1
== code2
1546 && rtx_renumbered_equal_p (XEXP (cond1
, 0), XEXP (cond2
, 0))
1547 && rtx_renumbered_equal_p (XEXP (cond1
, 1), XEXP (cond2
, 1)))
1548 || (code1
== swap_condition (code2
)
1549 && rtx_renumbered_equal_p (XEXP (cond1
, 1),
1551 && rtx_renumbered_equal_p (XEXP (cond1
, 0),
1554 /* If we return true, we will join the blocks. Which means that
1555 we will only have one branch prediction bit to work with. Thus
1556 we require the existing branches to have probabilities that are
1559 && optimize_bb_for_speed_p (bb1
)
1560 && optimize_bb_for_speed_p (bb2
))
1564 if (b1
->dest
== b2
->dest
)
1565 prob2
= b2
->probability
;
1567 /* Do not use f2 probability as f2 may be forwarded. */
1568 prob2
= REG_BR_PROB_BASE
- b2
->probability
;
1570 /* Fail if the difference in probabilities is greater than 50%.
1571 This rules out two well-predicted branches with opposite
1573 if (abs (b1
->probability
- prob2
) > REG_BR_PROB_BASE
/ 2)
1577 "Outcomes of branch in bb %i and %i differ too much (%i %i)\n",
1578 bb1
->index
, bb2
->index
, b1
->probability
, prob2
);
1584 if (dump_file
&& match
)
1585 fprintf (dump_file
, "Conditionals in bb %i and %i match.\n",
1586 bb1
->index
, bb2
->index
);
1591 /* Generic case - we are seeing a computed jump, table jump or trapping
1594 /* Check whether there are tablejumps in the end of BB1 and BB2.
1595 Return true if they are identical. */
1600 if (tablejump_p (BB_END (bb1
), &label1
, &table1
)
1601 && tablejump_p (BB_END (bb2
), &label2
, &table2
)
1602 && GET_CODE (PATTERN (table1
)) == GET_CODE (PATTERN (table2
)))
1604 /* The labels should never be the same rtx. If they really are same
1605 the jump tables are same too. So disable crossjumping of blocks BB1
1606 and BB2 because when deleting the common insns in the end of BB1
1607 by delete_basic_block () the jump table would be deleted too. */
1608 /* If LABEL2 is referenced in BB1->END do not do anything
1609 because we would loose information when replacing
1610 LABEL1 by LABEL2 and then LABEL2 by LABEL1 in BB1->END. */
1611 if (label1
!= label2
&& !rtx_referenced_p (label2
, BB_END (bb1
)))
1613 /* Set IDENTICAL to true when the tables are identical. */
1614 bool identical
= false;
1617 p1
= PATTERN (table1
);
1618 p2
= PATTERN (table2
);
1619 if (GET_CODE (p1
) == ADDR_VEC
&& rtx_equal_p (p1
, p2
))
1623 else if (GET_CODE (p1
) == ADDR_DIFF_VEC
1624 && (XVECLEN (p1
, 1) == XVECLEN (p2
, 1))
1625 && rtx_equal_p (XEXP (p1
, 2), XEXP (p2
, 2))
1626 && rtx_equal_p (XEXP (p1
, 3), XEXP (p2
, 3)))
1631 for (i
= XVECLEN (p1
, 1) - 1; i
>= 0 && identical
; i
--)
1632 if (!rtx_equal_p (XVECEXP (p1
, 1, i
), XVECEXP (p2
, 1, i
)))
1638 replace_label_data rr
;
1641 /* Temporarily replace references to LABEL1 with LABEL2
1642 in BB1->END so that we could compare the instructions. */
1645 rr
.update_label_nuses
= false;
1646 for_each_rtx (&BB_END (bb1
), replace_label
, &rr
);
1648 match
= (old_insns_match_p (mode
, BB_END (bb1
), BB_END (bb2
))
1650 if (dump_file
&& match
)
1652 "Tablejumps in bb %i and %i match.\n",
1653 bb1
->index
, bb2
->index
);
1655 /* Set the original label in BB1->END because when deleting
1656 a block whose end is a tablejump, the tablejump referenced
1657 from the instruction is deleted too. */
1660 for_each_rtx (&BB_END (bb1
), replace_label
, &rr
);
1669 /* First ensure that the instructions match. There may be many outgoing
1670 edges so this test is generally cheaper. */
1671 if (old_insns_match_p (mode
, BB_END (bb1
), BB_END (bb2
)) != dir_both
)
1674 /* Search the outgoing edges, ensure that the counts do match, find possible
1675 fallthru and exception handling edges since these needs more
1677 if (EDGE_COUNT (bb1
->succs
) != EDGE_COUNT (bb2
->succs
))
1680 FOR_EACH_EDGE (e1
, ei
, bb1
->succs
)
1682 e2
= EDGE_SUCC (bb2
, ei
.index
);
1684 if (e1
->flags
& EDGE_EH
)
1687 if (e2
->flags
& EDGE_EH
)
1690 if (e1
->flags
& EDGE_FALLTHRU
)
1692 if (e2
->flags
& EDGE_FALLTHRU
)
1696 /* If number of edges of various types does not match, fail. */
1697 if (nehedges1
!= nehedges2
1698 || (fallthru1
!= 0) != (fallthru2
!= 0))
1701 /* fallthru edges must be forwarded to the same destination. */
1704 basic_block d1
= (forwarder_block_p (fallthru1
->dest
)
1705 ? single_succ (fallthru1
->dest
): fallthru1
->dest
);
1706 basic_block d2
= (forwarder_block_p (fallthru2
->dest
)
1707 ? single_succ (fallthru2
->dest
): fallthru2
->dest
);
1713 /* Ensure the same EH region. */
1715 rtx n1
= find_reg_note (BB_END (bb1
), REG_EH_REGION
, 0);
1716 rtx n2
= find_reg_note (BB_END (bb2
), REG_EH_REGION
, 0);
1721 if (n1
&& (!n2
|| XEXP (n1
, 0) != XEXP (n2
, 0)))
1725 /* The same checks as in try_crossjump_to_edge. It is required for RTL
1726 version of sequence abstraction. */
1727 FOR_EACH_EDGE (e1
, ei
, bb2
->succs
)
1731 basic_block d1
= e1
->dest
;
1733 if (FORWARDER_BLOCK_P (d1
))
1734 d1
= EDGE_SUCC (d1
, 0)->dest
;
1736 FOR_EACH_EDGE (e2
, ei
, bb1
->succs
)
1738 basic_block d2
= e2
->dest
;
1739 if (FORWARDER_BLOCK_P (d2
))
1740 d2
= EDGE_SUCC (d2
, 0)->dest
;
1752 /* Returns true if BB basic block has a preserve label. */
1755 block_has_preserve_label (basic_block bb
)
1759 && LABEL_PRESERVE_P (block_label (bb
)));
1762 /* E1 and E2 are edges with the same destination block. Search their
1763 predecessors for common code. If found, redirect control flow from
1764 (maybe the middle of) E1->SRC to (maybe the middle of) E2->SRC (dir_forward),
1765 or the other way around (dir_backward). DIR specifies the allowed
1766 replacement direction. */
1769 try_crossjump_to_edge (int mode
, edge e1
, edge e2
,
1770 enum replace_direction dir
)
1773 basic_block src1
= e1
->src
, src2
= e2
->src
;
1774 basic_block redirect_to
, redirect_from
, to_remove
;
1775 basic_block osrc1
, osrc2
, redirect_edges_to
, tmp
;
1776 rtx newpos1
, newpos2
;
1780 newpos1
= newpos2
= NULL_RTX
;
1782 /* If we have partitioned hot/cold basic blocks, it is a bad idea
1783 to try this optimization.
1785 Basic block partitioning may result in some jumps that appear to
1786 be optimizable (or blocks that appear to be mergeable), but which really
1787 must be left untouched (they are required to make it safely across
1788 partition boundaries). See the comments at the top of
1789 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
1791 if (flag_reorder_blocks_and_partition
&& reload_completed
)
1794 /* Search backward through forwarder blocks. We don't need to worry
1795 about multiple entry or chained forwarders, as they will be optimized
1796 away. We do this to look past the unconditional jump following a
1797 conditional jump that is required due to the current CFG shape. */
1798 if (single_pred_p (src1
)
1799 && FORWARDER_BLOCK_P (src1
))
1800 e1
= single_pred_edge (src1
), src1
= e1
->src
;
1802 if (single_pred_p (src2
)
1803 && FORWARDER_BLOCK_P (src2
))
1804 e2
= single_pred_edge (src2
), src2
= e2
->src
;
1806 /* Nothing to do if we reach ENTRY, or a common source block. */
1807 if (src1
== ENTRY_BLOCK_PTR
|| src2
== ENTRY_BLOCK_PTR
)
1812 /* Seeing more than 1 forwarder blocks would confuse us later... */
1813 if (FORWARDER_BLOCK_P (e1
->dest
)
1814 && FORWARDER_BLOCK_P (single_succ (e1
->dest
)))
1817 if (FORWARDER_BLOCK_P (e2
->dest
)
1818 && FORWARDER_BLOCK_P (single_succ (e2
->dest
)))
1821 /* Likewise with dead code (possibly newly created by the other optimizations
1823 if (EDGE_COUNT (src1
->preds
) == 0 || EDGE_COUNT (src2
->preds
) == 0)
1826 /* Look for the common insn sequence, part the first ... */
1827 if (!outgoing_edges_match (mode
, src1
, src2
))
1830 /* ... and part the second. */
1831 nmatch
= flow_find_cross_jump (src1
, src2
, &newpos1
, &newpos2
, &dir
);
1835 if (newpos1
!= NULL_RTX
)
1836 src1
= BLOCK_FOR_INSN (newpos1
);
1837 if (newpos2
!= NULL_RTX
)
1838 src2
= BLOCK_FOR_INSN (newpos2
);
1840 if (dir
== dir_backward
)
1842 #define SWAP(T, X, Y) do { T tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
1843 SWAP (basic_block
, osrc1
, osrc2
);
1844 SWAP (basic_block
, src1
, src2
);
1845 SWAP (edge
, e1
, e2
);
1846 SWAP (rtx
, newpos1
, newpos2
);
1850 /* Don't proceed with the crossjump unless we found a sufficient number
1851 of matching instructions or the 'from' block was totally matched
1852 (such that its predecessors will hopefully be redirected and the
1854 if ((nmatch
< PARAM_VALUE (PARAM_MIN_CROSSJUMP_INSNS
))
1855 && (newpos1
!= BB_HEAD (src1
)))
1858 /* Avoid deleting preserve label when redirecting ABNORMAL edges. */
1859 if (block_has_preserve_label (e1
->dest
)
1860 && (e1
->flags
& EDGE_ABNORMAL
))
1863 /* Here we know that the insns in the end of SRC1 which are common with SRC2
1865 If we have tablejumps in the end of SRC1 and SRC2
1866 they have been already compared for equivalence in outgoing_edges_match ()
1867 so replace the references to TABLE1 by references to TABLE2. */
1872 if (tablejump_p (BB_END (osrc1
), &label1
, &table1
)
1873 && tablejump_p (BB_END (osrc2
), &label2
, &table2
)
1874 && label1
!= label2
)
1876 replace_label_data rr
;
1879 /* Replace references to LABEL1 with LABEL2. */
1882 rr
.update_label_nuses
= true;
1883 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1885 /* Do not replace the label in SRC1->END because when deleting
1886 a block whose end is a tablejump, the tablejump referenced
1887 from the instruction is deleted too. */
1888 if (insn
!= BB_END (osrc1
))
1889 for_each_rtx (&insn
, replace_label
, &rr
);
1894 /* Avoid splitting if possible. We must always split when SRC2 has
1895 EH predecessor edges, or we may end up with basic blocks with both
1896 normal and EH predecessor edges. */
1897 if (newpos2
== BB_HEAD (src2
)
1898 && !(EDGE_PRED (src2
, 0)->flags
& EDGE_EH
))
1902 if (newpos2
== BB_HEAD (src2
))
1904 /* Skip possible basic block header. */
1905 if (LABEL_P (newpos2
))
1906 newpos2
= NEXT_INSN (newpos2
);
1907 while (DEBUG_INSN_P (newpos2
))
1908 newpos2
= NEXT_INSN (newpos2
);
1909 if (NOTE_P (newpos2
))
1910 newpos2
= NEXT_INSN (newpos2
);
1911 while (DEBUG_INSN_P (newpos2
))
1912 newpos2
= NEXT_INSN (newpos2
);
1916 fprintf (dump_file
, "Splitting bb %i before %i insns\n",
1917 src2
->index
, nmatch
);
1918 redirect_to
= split_block (src2
, PREV_INSN (newpos2
))->dest
;
1923 "Cross jumping from bb %i to bb %i; %i common insns\n",
1924 src1
->index
, src2
->index
, nmatch
);
1926 /* We may have some registers visible through the block. */
1927 df_set_bb_dirty (redirect_to
);
1930 redirect_edges_to
= redirect_to
;
1932 redirect_edges_to
= osrc2
;
1934 /* Recompute the frequencies and counts of outgoing edges. */
1935 FOR_EACH_EDGE (s
, ei
, redirect_edges_to
->succs
)
1939 basic_block d
= s
->dest
;
1941 if (FORWARDER_BLOCK_P (d
))
1942 d
= single_succ (d
);
1944 FOR_EACH_EDGE (s2
, ei
, src1
->succs
)
1946 basic_block d2
= s2
->dest
;
1947 if (FORWARDER_BLOCK_P (d2
))
1948 d2
= single_succ (d2
);
1953 s
->count
+= s2
->count
;
1955 /* Take care to update possible forwarder blocks. We verified
1956 that there is no more than one in the chain, so we can't run
1957 into infinite loop. */
1958 if (FORWARDER_BLOCK_P (s
->dest
))
1960 single_succ_edge (s
->dest
)->count
+= s2
->count
;
1961 s
->dest
->count
+= s2
->count
;
1962 s
->dest
->frequency
+= EDGE_FREQUENCY (s
);
1965 if (FORWARDER_BLOCK_P (s2
->dest
))
1967 single_succ_edge (s2
->dest
)->count
-= s2
->count
;
1968 if (single_succ_edge (s2
->dest
)->count
< 0)
1969 single_succ_edge (s2
->dest
)->count
= 0;
1970 s2
->dest
->count
-= s2
->count
;
1971 s2
->dest
->frequency
-= EDGE_FREQUENCY (s
);
1972 if (s2
->dest
->frequency
< 0)
1973 s2
->dest
->frequency
= 0;
1974 if (s2
->dest
->count
< 0)
1975 s2
->dest
->count
= 0;
1978 if (!redirect_edges_to
->frequency
&& !src1
->frequency
)
1979 s
->probability
= (s
->probability
+ s2
->probability
) / 2;
1982 = ((s
->probability
* redirect_edges_to
->frequency
+
1983 s2
->probability
* src1
->frequency
)
1984 / (redirect_edges_to
->frequency
+ src1
->frequency
));
1987 /* Adjust count and frequency for the block. An earlier jump
1988 threading pass may have left the profile in an inconsistent
1989 state (see update_bb_profile_for_threading) so we must be
1990 prepared for overflows. */
1994 tmp
->count
+= src1
->count
;
1995 tmp
->frequency
+= src1
->frequency
;
1996 if (tmp
->frequency
> BB_FREQ_MAX
)
1997 tmp
->frequency
= BB_FREQ_MAX
;
1998 if (tmp
== redirect_edges_to
)
2000 tmp
= find_fallthru_edge (tmp
->succs
)->dest
;
2003 update_br_prob_note (redirect_edges_to
);
2005 /* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */
2007 /* Skip possible basic block header. */
2008 if (LABEL_P (newpos1
))
2009 newpos1
= NEXT_INSN (newpos1
);
2011 while (DEBUG_INSN_P (newpos1
))
2012 newpos1
= NEXT_INSN (newpos1
);
2014 if (NOTE_INSN_BASIC_BLOCK_P (newpos1
))
2015 newpos1
= NEXT_INSN (newpos1
);
2017 while (DEBUG_INSN_P (newpos1
))
2018 newpos1
= NEXT_INSN (newpos1
);
2020 redirect_from
= split_block (src1
, PREV_INSN (newpos1
))->src
;
2021 to_remove
= single_succ (redirect_from
);
2023 redirect_edge_and_branch_force (single_succ_edge (redirect_from
), redirect_to
);
2024 delete_basic_block (to_remove
);
2026 update_forwarder_flag (redirect_from
);
2027 if (redirect_to
!= src2
)
2028 update_forwarder_flag (src2
);
2033 /* Search the predecessors of BB for common insn sequences. When found,
2034 share code between them by redirecting control flow. Return true if
2035 any changes made. */
2038 try_crossjump_bb (int mode
, basic_block bb
)
2040 edge e
, e2
, fallthru
;
2042 unsigned max
, ix
, ix2
;
2044 /* Nothing to do if there is not at least two incoming edges. */
2045 if (EDGE_COUNT (bb
->preds
) < 2)
2048 /* Don't crossjump if this block ends in a computed jump,
2049 unless we are optimizing for size. */
2050 if (optimize_bb_for_size_p (bb
)
2051 && bb
!= EXIT_BLOCK_PTR
2052 && computed_jump_p (BB_END (bb
)))
2055 /* If we are partitioning hot/cold basic blocks, we don't want to
2056 mess up unconditional or indirect jumps that cross between hot
2059 Basic block partitioning may result in some jumps that appear to
2060 be optimizable (or blocks that appear to be mergeable), but which really
2061 must be left untouched (they are required to make it safely across
2062 partition boundaries). See the comments at the top of
2063 bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
2065 if (BB_PARTITION (EDGE_PRED (bb
, 0)->src
) !=
2066 BB_PARTITION (EDGE_PRED (bb
, 1)->src
)
2067 || (EDGE_PRED (bb
, 0)->flags
& EDGE_CROSSING
))
2070 /* It is always cheapest to redirect a block that ends in a branch to
2071 a block that falls through into BB, as that adds no branches to the
2072 program. We'll try that combination first. */
2074 max
= PARAM_VALUE (PARAM_MAX_CROSSJUMP_EDGES
);
2076 if (EDGE_COUNT (bb
->preds
) > max
)
2079 fallthru
= find_fallthru_edge (bb
->preds
);
2082 for (ix
= 0; ix
< EDGE_COUNT (bb
->preds
);)
2084 e
= EDGE_PRED (bb
, ix
);
2087 /* As noted above, first try with the fallthru predecessor (or, a
2088 fallthru predecessor if we are in cfglayout mode). */
2091 /* Don't combine the fallthru edge into anything else.
2092 If there is a match, we'll do it the other way around. */
2095 /* If nothing changed since the last attempt, there is nothing
2098 && !((e
->src
->flags
& BB_MODIFIED
)
2099 || (fallthru
->src
->flags
& BB_MODIFIED
)))
2102 if (try_crossjump_to_edge (mode
, e
, fallthru
, dir_forward
))
2110 /* Non-obvious work limiting check: Recognize that we're going
2111 to call try_crossjump_bb on every basic block. So if we have
2112 two blocks with lots of outgoing edges (a switch) and they
2113 share lots of common destinations, then we would do the
2114 cross-jump check once for each common destination.
2116 Now, if the blocks actually are cross-jump candidates, then
2117 all of their destinations will be shared. Which means that
2118 we only need check them for cross-jump candidacy once. We
2119 can eliminate redundant checks of crossjump(A,B) by arbitrarily
2120 choosing to do the check from the block for which the edge
2121 in question is the first successor of A. */
2122 if (EDGE_SUCC (e
->src
, 0) != e
)
2125 for (ix2
= 0; ix2
< EDGE_COUNT (bb
->preds
); ix2
++)
2127 e2
= EDGE_PRED (bb
, ix2
);
2132 /* We've already checked the fallthru edge above. */
2136 /* The "first successor" check above only prevents multiple
2137 checks of crossjump(A,B). In order to prevent redundant
2138 checks of crossjump(B,A), require that A be the block
2139 with the lowest index. */
2140 if (e
->src
->index
> e2
->src
->index
)
2143 /* If nothing changed since the last attempt, there is nothing
2146 && !((e
->src
->flags
& BB_MODIFIED
)
2147 || (e2
->src
->flags
& BB_MODIFIED
)))
2150 /* Both e and e2 are not fallthru edges, so we can crossjump in either
2152 if (try_crossjump_to_edge (mode
, e
, e2
, dir_both
))
2162 crossjumps_occured
= true;
2167 /* Search the successors of BB for common insn sequences. When found,
2168 share code between them by moving it across the basic block
2169 boundary. Return true if any changes made. */
2172 try_head_merge_bb (basic_block bb
)
2174 basic_block final_dest_bb
= NULL
;
2175 int max_match
= INT_MAX
;
2177 rtx
*headptr
, *currptr
, *nextptr
;
2178 bool changed
, moveall
;
2180 rtx e0_last_head
, cond
, move_before
;
2181 unsigned nedges
= EDGE_COUNT (bb
->succs
);
2182 rtx jump
= BB_END (bb
);
2183 regset live
, live_union
;
2185 /* Nothing to do if there is not at least two outgoing edges. */
2189 /* Don't crossjump if this block ends in a computed jump,
2190 unless we are optimizing for size. */
2191 if (optimize_bb_for_size_p (bb
)
2192 && bb
!= EXIT_BLOCK_PTR
2193 && computed_jump_p (BB_END (bb
)))
2196 cond
= get_condition (jump
, &move_before
, true, false);
2197 if (cond
== NULL_RTX
)
2200 for (ix
= 0; ix
< nedges
; ix
++)
2201 if (EDGE_SUCC (bb
, ix
)->dest
== EXIT_BLOCK_PTR
)
2204 for (ix
= 0; ix
< nedges
; ix
++)
2206 edge e
= EDGE_SUCC (bb
, ix
);
2207 basic_block other_bb
= e
->dest
;
2209 if (df_get_bb_dirty (other_bb
))
2211 block_was_dirty
= true;
2215 if (e
->flags
& EDGE_ABNORMAL
)
2218 /* Normally, all destination blocks must only be reachable from this
2219 block, i.e. they must have one incoming edge.
2221 There is one special case we can handle, that of multiple consecutive
2222 jumps where the first jumps to one of the targets of the second jump.
2223 This happens frequently in switch statements for default labels.
2224 The structure is as follows:
2230 jump with targets A, B, C, D...
2232 has two incoming edges, from FINAL_DEST_BB and BB
2234 In this case, we can try to move the insns through BB and into
2236 if (EDGE_COUNT (other_bb
->preds
) != 1)
2238 edge incoming_edge
, incoming_bb_other_edge
;
2241 if (final_dest_bb
!= NULL
2242 || EDGE_COUNT (other_bb
->preds
) != 2)
2245 /* We must be able to move the insns across the whole block. */
2246 move_before
= BB_HEAD (bb
);
2247 while (!NONDEBUG_INSN_P (move_before
))
2248 move_before
= NEXT_INSN (move_before
);
2250 if (EDGE_COUNT (bb
->preds
) != 1)
2252 incoming_edge
= EDGE_PRED (bb
, 0);
2253 final_dest_bb
= incoming_edge
->src
;
2254 if (EDGE_COUNT (final_dest_bb
->succs
) != 2)
2256 FOR_EACH_EDGE (incoming_bb_other_edge
, ei
, final_dest_bb
->succs
)
2257 if (incoming_bb_other_edge
!= incoming_edge
)
2259 if (incoming_bb_other_edge
->dest
!= other_bb
)
2264 e0
= EDGE_SUCC (bb
, 0);
2265 e0_last_head
= NULL_RTX
;
2268 for (ix
= 1; ix
< nedges
; ix
++)
2270 edge e
= EDGE_SUCC (bb
, ix
);
2271 rtx e0_last
, e_last
;
2274 nmatch
= flow_find_head_matching_sequence (e0
->dest
, e
->dest
,
2275 &e0_last
, &e_last
, 0);
2279 if (nmatch
< max_match
)
2282 e0_last_head
= e0_last
;
2286 /* If we matched an entire block, we probably have to avoid moving the
2289 && e0_last_head
== BB_END (e0
->dest
)
2290 && (find_reg_note (e0_last_head
, REG_EH_REGION
, 0)
2291 || control_flow_insn_p (e0_last_head
)))
2297 e0_last_head
= prev_real_insn (e0_last_head
);
2298 while (DEBUG_INSN_P (e0_last_head
));
2304 /* We must find a union of the live registers at each of the end points. */
2305 live
= BITMAP_ALLOC (NULL
);
2306 live_union
= BITMAP_ALLOC (NULL
);
2308 currptr
= XNEWVEC (rtx
, nedges
);
2309 headptr
= XNEWVEC (rtx
, nedges
);
2310 nextptr
= XNEWVEC (rtx
, nedges
);
2312 for (ix
= 0; ix
< nedges
; ix
++)
2315 basic_block merge_bb
= EDGE_SUCC (bb
, ix
)->dest
;
2316 rtx head
= BB_HEAD (merge_bb
);
2318 while (!NONDEBUG_INSN_P (head
))
2319 head
= NEXT_INSN (head
);
2323 /* Compute the end point and live information */
2324 for (j
= 1; j
< max_match
; j
++)
2326 head
= NEXT_INSN (head
);
2327 while (!NONDEBUG_INSN_P (head
));
2328 simulate_backwards_to_point (merge_bb
, live
, head
);
2329 IOR_REG_SET (live_union
, live
);
2332 /* If we're moving across two blocks, verify the validity of the
2333 first move, then adjust the target and let the loop below deal
2334 with the final move. */
2335 if (final_dest_bb
!= NULL
)
2339 moveall
= can_move_insns_across (currptr
[0], e0_last_head
, move_before
,
2340 jump
, e0
->dest
, live_union
,
2344 if (move_upto
== NULL_RTX
)
2347 while (e0_last_head
!= move_upto
)
2349 df_simulate_one_insn_backwards (e0
->dest
, e0_last_head
,
2351 e0_last_head
= PREV_INSN (e0_last_head
);
2354 if (e0_last_head
== NULL_RTX
)
2357 jump
= BB_END (final_dest_bb
);
2358 cond
= get_condition (jump
, &move_before
, true, false);
2359 if (cond
== NULL_RTX
)
2366 moveall
= can_move_insns_across (currptr
[0], e0_last_head
,
2367 move_before
, jump
, e0
->dest
, live_union
,
2369 if (!moveall
&& move_upto
== NULL_RTX
)
2371 if (jump
== move_before
)
2374 /* Try again, using a different insertion point. */
2378 /* Don't try moving before a cc0 user, as that may invalidate
2380 if (reg_mentioned_p (cc0_rtx
, jump
))
2387 if (final_dest_bb
&& !moveall
)
2388 /* We haven't checked whether a partial move would be OK for the first
2389 move, so we have to fail this case. */
2395 if (currptr
[0] == move_upto
)
2397 for (ix
= 0; ix
< nedges
; ix
++)
2399 rtx curr
= currptr
[ix
];
2401 curr
= NEXT_INSN (curr
);
2402 while (!NONDEBUG_INSN_P (curr
));
2407 /* If we can't currently move all of the identical insns, remember
2408 each insn after the range that we'll merge. */
2410 for (ix
= 0; ix
< nedges
; ix
++)
2412 rtx curr
= currptr
[ix
];
2414 curr
= NEXT_INSN (curr
);
2415 while (!NONDEBUG_INSN_P (curr
));
2419 reorder_insns (headptr
[0], currptr
[0], PREV_INSN (move_before
));
2420 df_set_bb_dirty (EDGE_SUCC (bb
, 0)->dest
);
2421 if (final_dest_bb
!= NULL
)
2422 df_set_bb_dirty (final_dest_bb
);
2423 df_set_bb_dirty (bb
);
2424 for (ix
= 1; ix
< nedges
; ix
++)
2426 df_set_bb_dirty (EDGE_SUCC (bb
, ix
)->dest
);
2427 delete_insn_chain (headptr
[ix
], currptr
[ix
], false);
2431 if (jump
== move_before
)
2434 /* For the unmerged insns, try a different insertion point. */
2438 /* Don't try moving before a cc0 user, as that may invalidate
2440 if (reg_mentioned_p (cc0_rtx
, jump
))
2444 for (ix
= 0; ix
< nedges
; ix
++)
2445 currptr
[ix
] = headptr
[ix
] = nextptr
[ix
];
2455 crossjumps_occured
|= changed
;
2460 /* Return true if BB contains just bb note, or bb note followed
2461 by only DEBUG_INSNs. */
2464 trivially_empty_bb_p (basic_block bb
)
2466 rtx insn
= BB_END (bb
);
2470 if (insn
== BB_HEAD (bb
))
2472 if (!DEBUG_INSN_P (insn
))
2474 insn
= PREV_INSN (insn
);
2478 /* Do simple CFG optimizations - basic block merging, simplifying of jump
2479 instructions etc. Return nonzero if changes were made. */
2482 try_optimize_cfg (int mode
)
2484 bool changed_overall
= false;
2487 basic_block bb
, b
, next
;
2489 if (mode
& (CLEANUP_CROSSJUMP
| CLEANUP_THREADING
))
2492 crossjumps_occured
= false;
2495 update_forwarder_flag (bb
);
2497 if (! targetm
.cannot_modify_jumps_p ())
2500 /* Attempt to merge blocks as made possible by edge removal. If
2501 a block has only one successor, and the successor has only
2502 one predecessor, they may be combined. */
2505 block_was_dirty
= false;
2511 "\n\ntry_optimize_cfg iteration %i\n\n",
2514 for (b
= ENTRY_BLOCK_PTR
->next_bb
; b
!= EXIT_BLOCK_PTR
;)
2518 bool changed_here
= false;
2520 /* Delete trivially dead basic blocks. This is either
2521 blocks with no predecessors, or empty blocks with no
2522 successors. However if the empty block with no
2523 successors is the successor of the ENTRY_BLOCK, it is
2524 kept. This ensures that the ENTRY_BLOCK will have a
2525 successor which is a precondition for many RTL
2526 passes. Empty blocks may result from expanding
2527 __builtin_unreachable (). */
2528 if (EDGE_COUNT (b
->preds
) == 0
2529 || (EDGE_COUNT (b
->succs
) == 0
2530 && trivially_empty_bb_p (b
)
2531 && single_succ_edge (ENTRY_BLOCK_PTR
)->dest
!= b
))
2534 if (EDGE_COUNT (b
->preds
) > 0)
2539 if (current_ir_type () == IR_RTL_CFGLAYOUT
)
2541 if (b
->il
.rtl
->footer
2542 && BARRIER_P (b
->il
.rtl
->footer
))
2543 FOR_EACH_EDGE (e
, ei
, b
->preds
)
2544 if ((e
->flags
& EDGE_FALLTHRU
)
2545 && e
->src
->il
.rtl
->footer
== NULL
)
2547 if (b
->il
.rtl
->footer
)
2549 e
->src
->il
.rtl
->footer
= b
->il
.rtl
->footer
;
2550 b
->il
.rtl
->footer
= NULL
;
2555 e
->src
->il
.rtl
->footer
= emit_barrier ();
2562 rtx last
= get_last_bb_insn (b
);
2563 if (last
&& BARRIER_P (last
))
2564 FOR_EACH_EDGE (e
, ei
, b
->preds
)
2565 if ((e
->flags
& EDGE_FALLTHRU
))
2566 emit_barrier_after (BB_END (e
->src
));
2569 delete_basic_block (b
);
2571 /* Avoid trying to remove ENTRY_BLOCK_PTR. */
2572 b
= (c
== ENTRY_BLOCK_PTR
? c
->next_bb
: c
);
2576 /* Remove code labels no longer used. */
2577 if (single_pred_p (b
)
2578 && (single_pred_edge (b
)->flags
& EDGE_FALLTHRU
)
2579 && !(single_pred_edge (b
)->flags
& EDGE_COMPLEX
)
2580 && LABEL_P (BB_HEAD (b
))
2581 /* If the previous block ends with a branch to this
2582 block, we can't delete the label. Normally this
2583 is a condjump that is yet to be simplified, but
2584 if CASE_DROPS_THRU, this can be a tablejump with
2585 some element going to the same place as the
2586 default (fallthru). */
2587 && (single_pred (b
) == ENTRY_BLOCK_PTR
2588 || !JUMP_P (BB_END (single_pred (b
)))
2589 || ! label_is_jump_target_p (BB_HEAD (b
),
2590 BB_END (single_pred (b
)))))
2592 rtx label
= BB_HEAD (b
);
2594 delete_insn_chain (label
, label
, false);
2595 /* If the case label is undeletable, move it after the
2596 BASIC_BLOCK note. */
2597 if (NOTE_KIND (BB_HEAD (b
)) == NOTE_INSN_DELETED_LABEL
)
2599 rtx bb_note
= NEXT_INSN (BB_HEAD (b
));
2601 reorder_insns_nobb (label
, label
, bb_note
);
2602 BB_HEAD (b
) = bb_note
;
2603 if (BB_END (b
) == bb_note
)
2607 fprintf (dump_file
, "Deleted label in block %i.\n",
2611 /* If we fall through an empty block, we can remove it. */
2612 if (!(mode
& CLEANUP_CFGLAYOUT
)
2613 && single_pred_p (b
)
2614 && (single_pred_edge (b
)->flags
& EDGE_FALLTHRU
)
2615 && !LABEL_P (BB_HEAD (b
))
2616 && FORWARDER_BLOCK_P (b
)
2617 /* Note that forwarder_block_p true ensures that
2618 there is a successor for this block. */
2619 && (single_succ_edge (b
)->flags
& EDGE_FALLTHRU
)
2620 && n_basic_blocks
> NUM_FIXED_BLOCKS
+ 1)
2624 "Deleting fallthru block %i.\n",
2627 c
= b
->prev_bb
== ENTRY_BLOCK_PTR
? b
->next_bb
: b
->prev_bb
;
2628 redirect_edge_succ_nodup (single_pred_edge (b
),
2630 delete_basic_block (b
);
2636 /* Merge B with its single successor, if any. */
2637 if (single_succ_p (b
)
2638 && (s
= single_succ_edge (b
))
2639 && !(s
->flags
& EDGE_COMPLEX
)
2640 && (c
= s
->dest
) != EXIT_BLOCK_PTR
2641 && single_pred_p (c
)
2644 /* When not in cfg_layout mode use code aware of reordering
2645 INSN. This code possibly creates new basic blocks so it
2646 does not fit merge_blocks interface and is kept here in
2647 hope that it will become useless once more of compiler
2648 is transformed to use cfg_layout mode. */
2650 if ((mode
& CLEANUP_CFGLAYOUT
)
2651 && can_merge_blocks_p (b
, c
))
2653 merge_blocks (b
, c
);
2654 update_forwarder_flag (b
);
2655 changed_here
= true;
2657 else if (!(mode
& CLEANUP_CFGLAYOUT
)
2658 /* If the jump insn has side effects,
2659 we can't kill the edge. */
2660 && (!JUMP_P (BB_END (b
))
2661 || (reload_completed
2662 ? simplejump_p (BB_END (b
))
2663 : (onlyjump_p (BB_END (b
))
2664 && !tablejump_p (BB_END (b
),
2666 && (next
= merge_blocks_move (s
, b
, c
, mode
)))
2669 changed_here
= true;
2673 /* Simplify branch over branch. */
2674 if ((mode
& CLEANUP_EXPENSIVE
)
2675 && !(mode
& CLEANUP_CFGLAYOUT
)
2676 && try_simplify_condjump (b
))
2677 changed_here
= true;
2679 /* If B has a single outgoing edge, but uses a
2680 non-trivial jump instruction without side-effects, we
2681 can either delete the jump entirely, or replace it
2682 with a simple unconditional jump. */
2683 if (single_succ_p (b
)
2684 && single_succ (b
) != EXIT_BLOCK_PTR
2685 && onlyjump_p (BB_END (b
))
2686 && !find_reg_note (BB_END (b
), REG_CROSSING_JUMP
, NULL_RTX
)
2687 && try_redirect_by_replacing_jump (single_succ_edge (b
),
2689 (mode
& CLEANUP_CFGLAYOUT
) != 0))
2691 update_forwarder_flag (b
);
2692 changed_here
= true;
2695 /* Simplify branch to branch. */
2696 if (try_forward_edges (mode
, b
))
2697 changed_here
= true;
2699 /* Look for shared code between blocks. */
2700 if ((mode
& CLEANUP_CROSSJUMP
)
2701 && try_crossjump_bb (mode
, b
))
2702 changed_here
= true;
2704 if ((mode
& CLEANUP_CROSSJUMP
)
2705 /* This can lengthen register lifetimes. Do it only after
2708 && try_head_merge_bb (b
))
2709 changed_here
= true;
2711 /* Don't get confused by the index shift caused by
2719 if ((mode
& CLEANUP_CROSSJUMP
)
2720 && try_crossjump_bb (mode
, EXIT_BLOCK_PTR
))
2723 if (block_was_dirty
)
2725 /* This should only be set by head-merging. */
2726 gcc_assert (mode
& CLEANUP_CROSSJUMP
);
2730 #ifdef ENABLE_CHECKING
2732 verify_flow_info ();
2735 changed_overall
|= changed
;
2742 b
->flags
&= ~(BB_FORWARDER_BLOCK
| BB_NONTHREADABLE_BLOCK
);
2744 return changed_overall
;
2747 /* Delete all unreachable basic blocks. */
2750 delete_unreachable_blocks (void)
2752 bool changed
= false;
2753 basic_block b
, prev_bb
;
2755 find_unreachable_blocks ();
2757 /* When we're in GIMPLE mode and there may be debug insns, we should
2758 delete blocks in reverse dominator order, so as to get a chance
2759 to substitute all released DEFs into debug stmts. If we don't
2760 have dominators information, walking blocks backward gets us a
2761 better chance of retaining most debug information than
2763 if (MAY_HAVE_DEBUG_STMTS
&& current_ir_type () == IR_GIMPLE
2764 && dom_info_available_p (CDI_DOMINATORS
))
2766 for (b
= EXIT_BLOCK_PTR
->prev_bb
; b
!= ENTRY_BLOCK_PTR
; b
= prev_bb
)
2768 prev_bb
= b
->prev_bb
;
2770 if (!(b
->flags
& BB_REACHABLE
))
2772 /* Speed up the removal of blocks that don't dominate
2773 others. Walking backwards, this should be the common
2775 if (!first_dom_son (CDI_DOMINATORS
, b
))
2776 delete_basic_block (b
);
2779 VEC (basic_block
, heap
) *h
2780 = get_all_dominated_blocks (CDI_DOMINATORS
, b
);
2782 while (VEC_length (basic_block
, h
))
2784 b
= VEC_pop (basic_block
, h
);
2786 prev_bb
= b
->prev_bb
;
2788 gcc_assert (!(b
->flags
& BB_REACHABLE
));
2790 delete_basic_block (b
);
2793 VEC_free (basic_block
, heap
, h
);
2802 for (b
= EXIT_BLOCK_PTR
->prev_bb
; b
!= ENTRY_BLOCK_PTR
; b
= prev_bb
)
2804 prev_bb
= b
->prev_bb
;
2806 if (!(b
->flags
& BB_REACHABLE
))
2808 delete_basic_block (b
);
2815 tidy_fallthru_edges ();
2819 /* Delete any jump tables never referenced. We can't delete them at the
2820 time of removing tablejump insn as they are referenced by the preceding
2821 insns computing the destination, so we delay deleting and garbagecollect
2822 them once life information is computed. */
2824 delete_dead_jumptables (void)
2828 /* A dead jump table does not belong to any basic block. Scan insns
2829 between two adjacent basic blocks. */
2834 for (insn
= NEXT_INSN (BB_END (bb
));
2835 insn
&& !NOTE_INSN_BASIC_BLOCK_P (insn
);
2838 next
= NEXT_INSN (insn
);
2840 && LABEL_NUSES (insn
) == LABEL_PRESERVE_P (insn
)
2841 && JUMP_TABLE_DATA_P (next
))
2843 rtx label
= insn
, jump
= next
;
2846 fprintf (dump_file
, "Dead jumptable %i removed\n",
2849 next
= NEXT_INSN (next
);
2851 delete_insn (label
);
2858 /* Tidy the CFG by deleting unreachable code and whatnot. */
2861 cleanup_cfg (int mode
)
2863 bool changed
= false;
2865 /* Set the cfglayout mode flag here. We could update all the callers
2866 but that is just inconvenient, especially given that we eventually
2867 want to have cfglayout mode as the default. */
2868 if (current_ir_type () == IR_RTL_CFGLAYOUT
)
2869 mode
|= CLEANUP_CFGLAYOUT
;
2871 timevar_push (TV_CLEANUP_CFG
);
2872 if (delete_unreachable_blocks ())
2875 /* We've possibly created trivially dead code. Cleanup it right
2876 now to introduce more opportunities for try_optimize_cfg. */
2877 if (!(mode
& (CLEANUP_NO_INSN_DEL
))
2878 && !reload_completed
)
2879 delete_trivially_dead_insns (get_insns (), max_reg_num ());
2884 /* To tail-merge blocks ending in the same noreturn function (e.g.
2885 a call to abort) we have to insert fake edges to exit. Do this
2886 here once. The fake edges do not interfere with any other CFG
2888 if (mode
& CLEANUP_CROSSJUMP
)
2889 add_noreturn_fake_exit_edges ();
2891 if (!dbg_cnt (cfg_cleanup
))
2894 while (try_optimize_cfg (mode
))
2896 delete_unreachable_blocks (), changed
= true;
2897 if (!(mode
& CLEANUP_NO_INSN_DEL
))
2899 /* Try to remove some trivially dead insns when doing an expensive
2900 cleanup. But delete_trivially_dead_insns doesn't work after
2901 reload (it only handles pseudos) and run_fast_dce is too costly
2902 to run in every iteration.
2904 For effective cross jumping, we really want to run a fast DCE to
2905 clean up any dead conditions, or they get in the way of performing
2908 Other transformations in cleanup_cfg are not so sensitive to dead
2909 code, so delete_trivially_dead_insns or even doing nothing at all
2911 if ((mode
& CLEANUP_EXPENSIVE
) && !reload_completed
2912 && !delete_trivially_dead_insns (get_insns (), max_reg_num ()))
2914 if ((mode
& CLEANUP_CROSSJUMP
) && crossjumps_occured
)
2921 if (mode
& CLEANUP_CROSSJUMP
)
2922 remove_fake_exit_edges ();
2924 /* Don't call delete_dead_jumptables in cfglayout mode, because
2925 that function assumes that jump tables are in the insns stream.
2926 But we also don't _have_ to delete dead jumptables in cfglayout
2927 mode because we shouldn't even be looking at things that are
2928 not in a basic block. Dead jumptables are cleaned up when
2929 going out of cfglayout mode. */
2930 if (!(mode
& CLEANUP_CFGLAYOUT
))
2931 delete_dead_jumptables ();
2933 timevar_pop (TV_CLEANUP_CFG
);
2939 rest_of_handle_jump (void)
2941 if (crtl
->tail_call_emit
)
2942 fixup_tail_calls ();
2946 struct rtl_opt_pass pass_jump
=
2950 "sibling", /* name */
2952 rest_of_handle_jump
, /* execute */
2955 0, /* static_pass_number */
2956 TV_JUMP
, /* tv_id */
2957 0, /* properties_required */
2958 0, /* properties_provided */
2959 0, /* properties_destroyed */
2960 TODO_ggc_collect
, /* todo_flags_start */
2961 TODO_verify_flow
, /* todo_flags_finish */
2967 rest_of_handle_jump2 (void)
2969 delete_trivially_dead_insns (get_insns (), max_reg_num ());
2971 dump_flow_info (dump_file
, dump_flags
);
2972 cleanup_cfg ((optimize
? CLEANUP_EXPENSIVE
: 0)
2973 | (flag_thread_jumps
? CLEANUP_THREADING
: 0));
2978 struct rtl_opt_pass pass_jump2
=
2984 rest_of_handle_jump2
, /* execute */
2987 0, /* static_pass_number */
2988 TV_JUMP
, /* tv_id */
2989 0, /* properties_required */
2990 0, /* properties_provided */
2991 0, /* properties_destroyed */
2992 TODO_ggc_collect
, /* todo_flags_start */
2993 TODO_dump_func
| TODO_verify_rtl_sharing
,/* todo_flags_finish */