1 /* CFG cleanup for trees.
2 Copyright (C) 2001-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC 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 3, or (at your option)
11 GCC 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 GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
22 #include "coretypes.h"
26 #include "basic-block.h"
27 #include "diagnostic-core.h"
30 #include "langhooks.h"
31 #include "tree-ssa-alias.h"
32 #include "internal-fn.h"
34 #include "gimple-expr.h"
38 #include "gimple-iterator.h"
39 #include "gimple-ssa.h"
41 #include "tree-phinodes.h"
42 #include "ssa-iterators.h"
43 #include "stringpool.h"
44 #include "tree-ssanames.h"
45 #include "tree-ssa-loop-manip.h"
49 #include "tree-pass.h"
53 #include "tree-ssa-propagate.h"
54 #include "tree-scalar-evolution.h"
56 /* The set of blocks in that at least one of the following changes happened:
57 -- the statement at the end of the block was changed
58 -- the block was newly created
59 -- the set of the predecessors of the block changed
60 -- the set of the successors of the block changed
61 ??? Maybe we could track these changes separately, since they determine
62 what cleanups it makes sense to try on the block. */
63 bitmap cfgcleanup_altered_bbs
;
65 /* Remove any fallthru edge from EV. Return true if an edge was removed. */
68 remove_fallthru_edge (vec
<edge
, va_gc
> *ev
)
73 FOR_EACH_EDGE (e
, ei
, ev
)
74 if ((e
->flags
& EDGE_FALLTHRU
) != 0)
76 if (e
->flags
& EDGE_COMPLEX
)
77 e
->flags
&= ~EDGE_FALLTHRU
;
79 remove_edge_and_dominated_blocks (e
);
86 /* Disconnect an unreachable block in the control expression starting
90 cleanup_control_expr_graph (basic_block bb
, gimple_stmt_iterator gsi
)
94 gimple stmt
= gsi_stmt (gsi
);
97 if (!single_succ_p (bb
))
104 fold_defer_overflow_warnings ();
105 loc
= gimple_location (stmt
);
106 switch (gimple_code (stmt
))
109 val
= fold_binary_loc (loc
, gimple_cond_code (stmt
),
111 gimple_cond_lhs (stmt
),
112 gimple_cond_rhs (stmt
));
116 val
= gimple_switch_index (stmt
);
122 taken_edge
= find_taken_edge (bb
, val
);
125 fold_undefer_and_ignore_overflow_warnings ();
129 /* Remove all the edges except the one that is always executed. */
131 for (ei
= ei_start (bb
->succs
); (e
= ei_safe_edge (ei
)); )
137 fold_undefer_overflow_warnings
138 (true, stmt
, WARN_STRICT_OVERFLOW_CONDITIONAL
);
142 taken_edge
->probability
+= e
->probability
;
143 taken_edge
->count
+= e
->count
;
144 remove_edge_and_dominated_blocks (e
);
151 fold_undefer_and_ignore_overflow_warnings ();
152 if (taken_edge
->probability
> REG_BR_PROB_BASE
)
153 taken_edge
->probability
= REG_BR_PROB_BASE
;
156 taken_edge
= single_succ_edge (bb
);
158 bitmap_set_bit (cfgcleanup_altered_bbs
, bb
->index
);
159 gsi_remove (&gsi
, true);
160 taken_edge
->flags
= EDGE_FALLTHRU
;
165 /* Try to remove superfluous control structures in basic block BB. Returns
166 true if anything changes. */
169 cleanup_control_flow_bb (basic_block bb
)
171 gimple_stmt_iterator gsi
;
175 /* If the last statement of the block could throw and now cannot,
176 we need to prune cfg. */
177 retval
|= gimple_purge_dead_eh_edges (bb
);
179 gsi
= gsi_last_bb (bb
);
183 stmt
= gsi_stmt (gsi
);
185 if (gimple_code (stmt
) == GIMPLE_COND
186 || gimple_code (stmt
) == GIMPLE_SWITCH
)
187 retval
|= cleanup_control_expr_graph (bb
, gsi
);
188 else if (gimple_code (stmt
) == GIMPLE_GOTO
189 && TREE_CODE (gimple_goto_dest (stmt
)) == ADDR_EXPR
190 && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt
), 0))
193 /* If we had a computed goto which has a compile-time determinable
194 destination, then we can eliminate the goto. */
198 basic_block target_block
;
200 /* First look at all the outgoing edges. Delete any outgoing
201 edges which do not go to the right block. For the one
202 edge which goes to the right block, fix up its flags. */
203 label
= TREE_OPERAND (gimple_goto_dest (stmt
), 0);
204 target_block
= label_to_block (label
);
205 for (ei
= ei_start (bb
->succs
); (e
= ei_safe_edge (ei
)); )
207 if (e
->dest
!= target_block
)
208 remove_edge_and_dominated_blocks (e
);
211 /* Turn off the EDGE_ABNORMAL flag. */
212 e
->flags
&= ~EDGE_ABNORMAL
;
214 /* And set EDGE_FALLTHRU. */
215 e
->flags
|= EDGE_FALLTHRU
;
220 bitmap_set_bit (cfgcleanup_altered_bbs
, bb
->index
);
221 bitmap_set_bit (cfgcleanup_altered_bbs
, target_block
->index
);
223 /* Remove the GOTO_EXPR as it is not needed. The CFG has all the
224 relevant information we need. */
225 gsi_remove (&gsi
, true);
229 /* Check for indirect calls that have been turned into
231 else if (is_gimple_call (stmt
)
232 && gimple_call_noreturn_p (stmt
)
233 && remove_fallthru_edge (bb
->succs
))
239 /* Return true if basic block BB does nothing except pass control
240 flow to another block and that we can safely insert a label at
241 the start of the successor block.
243 As a precondition, we require that BB be not equal to
247 tree_forwarder_block_p (basic_block bb
, bool phi_wanted
)
249 gimple_stmt_iterator gsi
;
252 /* BB must have a single outgoing edge. */
253 if (single_succ_p (bb
) != 1
254 /* If PHI_WANTED is false, BB must not have any PHI nodes.
255 Otherwise, BB must have PHI nodes. */
256 || gimple_seq_empty_p (phi_nodes (bb
)) == phi_wanted
257 /* BB may not be a predecessor of the exit block. */
258 || single_succ (bb
) == EXIT_BLOCK_PTR_FOR_FN (cfun
)
259 /* Nor should this be an infinite loop. */
260 || single_succ (bb
) == bb
261 /* BB may not have an abnormal outgoing edge. */
262 || (single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
265 gcc_checking_assert (bb
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
));
267 locus
= single_succ_edge (bb
)->goto_locus
;
269 /* There should not be an edge coming from entry, or an EH edge. */
274 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
275 if (e
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
) || (e
->flags
& EDGE_EH
))
277 /* If goto_locus of any of the edges differs, prevent removing
278 the forwarder block for -O0. */
279 else if (optimize
== 0 && e
->goto_locus
!= locus
)
283 /* Now walk through the statements backward. We can ignore labels,
284 anything else means this is not a forwarder block. */
285 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
287 gimple stmt
= gsi_stmt (gsi
);
289 switch (gimple_code (stmt
))
292 if (DECL_NONLOCAL (gimple_label_label (stmt
)))
294 if (optimize
== 0 && gimple_location (stmt
) != locus
)
298 /* ??? For now, hope there's a corresponding debug
299 assignment at the destination. */
311 /* Protect loop headers. */
312 if (bb
->loop_father
->header
== bb
)
315 dest
= EDGE_SUCC (bb
, 0)->dest
;
316 /* Protect loop preheaders and latches if requested. */
317 if (dest
->loop_father
->header
== dest
)
319 if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS
)
320 && bb
->loop_father
->header
!= dest
)
323 if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES
)
324 && bb
->loop_father
->header
== dest
)
332 /* If all the PHI nodes in DEST have alternatives for E1 and E2 and
333 those alternatives are equal in each of the PHI nodes, then return
334 true, else return false. */
337 phi_alternatives_equal (basic_block dest
, edge e1
, edge e2
)
339 int n1
= e1
->dest_idx
;
340 int n2
= e2
->dest_idx
;
341 gimple_stmt_iterator gsi
;
343 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
345 gimple phi
= gsi_stmt (gsi
);
346 tree val1
= gimple_phi_arg_def (phi
, n1
);
347 tree val2
= gimple_phi_arg_def (phi
, n2
);
349 gcc_assert (val1
!= NULL_TREE
);
350 gcc_assert (val2
!= NULL_TREE
);
352 if (!operand_equal_for_phi_arg_p (val1
, val2
))
359 /* Removes forwarder block BB. Returns false if this failed. */
362 remove_forwarder_block (basic_block bb
)
364 edge succ
= single_succ_edge (bb
), e
, s
;
365 basic_block dest
= succ
->dest
;
368 gimple_stmt_iterator gsi
, gsi_to
;
369 bool can_move_debug_stmts
;
371 /* We check for infinite loops already in tree_forwarder_block_p.
372 However it may happen that the infinite loop is created
373 afterwards due to removal of forwarders. */
377 /* If the destination block consists of a nonlocal label or is a
378 EH landing pad, do not merge it. */
379 label
= first_stmt (dest
);
381 && gimple_code (label
) == GIMPLE_LABEL
382 && (DECL_NONLOCAL (gimple_label_label (label
))
383 || EH_LANDING_PAD_NR (gimple_label_label (label
)) != 0))
386 /* If there is an abnormal edge to basic block BB, but not into
387 dest, problems might occur during removal of the phi node at out
388 of ssa due to overlapping live ranges of registers.
390 If there is an abnormal edge in DEST, the problems would occur
391 anyway since cleanup_dead_labels would then merge the labels for
392 two different eh regions, and rest of exception handling code
395 So if there is an abnormal edge to BB, proceed only if there is
396 no abnormal edge to DEST and there are no phi nodes in DEST. */
397 if (bb_has_abnormal_pred (bb
)
398 && (bb_has_abnormal_pred (dest
)
399 || !gimple_seq_empty_p (phi_nodes (dest
))))
402 /* If there are phi nodes in DEST, and some of the blocks that are
403 predecessors of BB are also predecessors of DEST, check that the
404 phi node arguments match. */
405 if (!gimple_seq_empty_p (phi_nodes (dest
)))
407 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
409 s
= find_edge (e
->src
, dest
);
413 if (!phi_alternatives_equal (dest
, succ
, s
))
418 can_move_debug_stmts
= MAY_HAVE_DEBUG_STMTS
&& single_pred_p (dest
);
420 /* Redirect the edges. */
421 for (ei
= ei_start (bb
->preds
); (e
= ei_safe_edge (ei
)); )
423 bitmap_set_bit (cfgcleanup_altered_bbs
, e
->src
->index
);
425 if (e
->flags
& EDGE_ABNORMAL
)
427 /* If there is an abnormal edge, redirect it anyway, and
428 move the labels to the new block to make it legal. */
429 s
= redirect_edge_succ_nodup (e
, dest
);
432 s
= redirect_edge_and_branch (e
, dest
);
436 /* Create arguments for the phi nodes, since the edge was not
438 for (gsi
= gsi_start_phis (dest
);
442 gimple phi
= gsi_stmt (gsi
);
443 source_location l
= gimple_phi_arg_location_from_edge (phi
, succ
);
444 tree def
= gimple_phi_arg_def (phi
, succ
->dest_idx
);
445 add_phi_arg (phi
, unshare_expr (def
), s
, l
);
450 /* Move nonlocal labels and computed goto targets as well as user
451 defined labels and labels with an EH landing pad number to the
452 new block, so that the redirection of the abnormal edges works,
453 jump targets end up in a sane place and debug information for
454 labels is retained. */
455 gsi_to
= gsi_start_bb (dest
);
456 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); )
459 label
= gsi_stmt (gsi
);
460 if (is_gimple_debug (label
))
462 decl
= gimple_label_label (label
);
463 if (EH_LANDING_PAD_NR (decl
) != 0
464 || DECL_NONLOCAL (decl
)
465 || FORCED_LABEL (decl
)
466 || !DECL_ARTIFICIAL (decl
))
468 gsi_remove (&gsi
, false);
469 gsi_insert_before (&gsi_to
, label
, GSI_SAME_STMT
);
475 /* Move debug statements if the destination has a single predecessor. */
476 if (can_move_debug_stmts
)
478 gsi_to
= gsi_after_labels (dest
);
479 for (gsi
= gsi_after_labels (bb
); !gsi_end_p (gsi
); )
481 gimple debug
= gsi_stmt (gsi
);
482 if (!is_gimple_debug (debug
))
484 gsi_remove (&gsi
, false);
485 gsi_insert_before (&gsi_to
, debug
, GSI_SAME_STMT
);
489 bitmap_set_bit (cfgcleanup_altered_bbs
, dest
->index
);
491 /* Update the dominators. */
492 if (dom_info_available_p (CDI_DOMINATORS
))
494 basic_block dom
, dombb
, domdest
;
496 dombb
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
497 domdest
= get_immediate_dominator (CDI_DOMINATORS
, dest
);
500 /* Shortcut to avoid calling (relatively expensive)
501 nearest_common_dominator unless necessary. */
505 dom
= nearest_common_dominator (CDI_DOMINATORS
, domdest
, dombb
);
507 set_immediate_dominator (CDI_DOMINATORS
, dest
, dom
);
510 /* Adjust latch infomation of BB's parent loop as otherwise
511 the cfg hook has a hard time not to kill the loop. */
512 if (current_loops
&& bb
->loop_father
->latch
== bb
)
513 bb
->loop_father
->latch
= dest
;
515 /* And kill the forwarder block. */
516 delete_basic_block (bb
);
521 /* STMT is a call that has been discovered noreturn. Fixup the CFG
522 and remove LHS. Return true if something changed. */
525 fixup_noreturn_call (gimple stmt
)
527 basic_block bb
= gimple_bb (stmt
);
528 bool changed
= false;
530 if (gimple_call_builtin_p (stmt
, BUILT_IN_RETURN
))
533 /* First split basic block if stmt is not last. */
534 if (stmt
!= gsi_stmt (gsi_last_bb (bb
)))
535 split_block (bb
, stmt
);
537 changed
|= remove_fallthru_edge (bb
->succs
);
539 /* If there is LHS, remove it. */
540 if (gimple_call_lhs (stmt
))
542 tree op
= gimple_call_lhs (stmt
);
543 gimple_call_set_lhs (stmt
, NULL_TREE
);
545 /* We need to remove SSA name to avoid checking errors.
546 All uses are dominated by the noreturn and thus will
547 be removed afterwards.
548 We proactively remove affected non-PHI statements to avoid
549 fixup_cfg from trying to update them and crashing. */
550 if (TREE_CODE (op
) == SSA_NAME
)
553 imm_use_iterator iter
;
556 unsigned int bb_index
;
558 bitmap blocks
= BITMAP_ALLOC (NULL
);
560 FOR_EACH_IMM_USE_STMT (use_stmt
, iter
, op
)
562 if (gimple_code (use_stmt
) != GIMPLE_PHI
)
563 bitmap_set_bit (blocks
, gimple_bb (use_stmt
)->index
);
565 FOR_EACH_IMM_USE_ON_STMT (use_p
, iter
)
566 SET_USE (use_p
, error_mark_node
);
568 EXECUTE_IF_SET_IN_BITMAP (blocks
, 0, bb_index
, bi
)
569 delete_basic_block (BASIC_BLOCK_FOR_FN (cfun
, bb_index
));
570 BITMAP_FREE (blocks
);
571 release_ssa_name (op
);
576 /* Similarly remove VDEF if there is any. */
577 else if (gimple_vdef (stmt
))
583 /* Split basic blocks on calls in the middle of a basic block that are now
584 known not to return, and remove the unreachable code. */
587 split_bbs_on_noreturn_calls (void)
589 bool changed
= false;
593 /* Detect cases where a mid-block call is now known not to return. */
595 while (vec_safe_length (MODIFIED_NORETURN_CALLS (cfun
)))
597 stmt
= MODIFIED_NORETURN_CALLS (cfun
)->pop ();
598 bb
= gimple_bb (stmt
);
599 /* BB might be deleted at this point, so verify first
600 BB is present in the cfg. */
602 || bb
->index
< NUM_FIXED_BLOCKS
603 || bb
->index
>= last_basic_block_for_fn (cfun
)
604 || BASIC_BLOCK_FOR_FN (cfun
, bb
->index
) != bb
605 || !gimple_call_noreturn_p (stmt
))
608 changed
|= fixup_noreturn_call (stmt
);
614 /* Tries to cleanup cfg in basic block BB. Returns true if anything
618 cleanup_tree_cfg_bb (basic_block bb
)
620 bool retval
= cleanup_control_flow_bb (bb
);
622 if (tree_forwarder_block_p (bb
, false)
623 && remove_forwarder_block (bb
))
626 /* Merging the blocks may create new opportunities for folding
627 conditional branches (due to the elimination of single-valued PHI
629 if (single_succ_p (bb
)
630 && can_merge_blocks_p (bb
, single_succ (bb
)))
632 merge_blocks (bb
, single_succ (bb
));
639 /* Iterate the cfg cleanups, while anything changes. */
642 cleanup_tree_cfg_1 (void)
648 retval
|= split_bbs_on_noreturn_calls ();
650 /* Prepare the worklists of altered blocks. */
651 cfgcleanup_altered_bbs
= BITMAP_ALLOC (NULL
);
653 /* During forwarder block cleanup, we may redirect edges out of
654 SWITCH_EXPRs, which can get expensive. So we want to enable
655 recording of edge to CASE_LABEL_EXPR. */
656 start_recording_case_labels ();
658 /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB_FN,
659 since the basic blocks may get removed. */
660 n
= last_basic_block_for_fn (cfun
);
661 for (i
= NUM_FIXED_BLOCKS
; i
< n
; i
++)
663 bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
665 retval
|= cleanup_tree_cfg_bb (bb
);
668 /* Now process the altered blocks, as long as any are available. */
669 while (!bitmap_empty_p (cfgcleanup_altered_bbs
))
671 i
= bitmap_first_set_bit (cfgcleanup_altered_bbs
);
672 bitmap_clear_bit (cfgcleanup_altered_bbs
, i
);
673 if (i
< NUM_FIXED_BLOCKS
)
676 bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
680 retval
|= cleanup_tree_cfg_bb (bb
);
682 /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn
684 retval
|= split_bbs_on_noreturn_calls ();
687 end_recording_case_labels ();
688 BITMAP_FREE (cfgcleanup_altered_bbs
);
693 /* Remove unreachable blocks and other miscellaneous clean up work.
694 Return true if the flowgraph was modified, false otherwise. */
697 cleanup_tree_cfg_noloop (void)
701 timevar_push (TV_TREE_CLEANUP_CFG
);
703 /* Iterate until there are no more cleanups left to do. If any
704 iteration changed the flowgraph, set CHANGED to true.
706 If dominance information is available, there cannot be any unreachable
708 if (!dom_info_available_p (CDI_DOMINATORS
))
710 changed
= delete_unreachable_blocks ();
711 calculate_dominance_info (CDI_DOMINATORS
);
715 #ifdef ENABLE_CHECKING
716 verify_dominators (CDI_DOMINATORS
);
721 changed
|= cleanup_tree_cfg_1 ();
723 gcc_assert (dom_info_available_p (CDI_DOMINATORS
));
726 #ifdef ENABLE_CHECKING
730 timevar_pop (TV_TREE_CLEANUP_CFG
);
732 if (changed
&& current_loops
)
733 loops_state_set (LOOPS_NEED_FIXUP
);
738 /* Repairs loop structures. */
741 repair_loop_structures (void)
744 unsigned n_new_loops
;
746 calculate_dominance_info (CDI_DOMINATORS
);
748 timevar_push (TV_REPAIR_LOOPS
);
749 changed_bbs
= BITMAP_ALLOC (NULL
);
750 n_new_loops
= fix_loop_structure (changed_bbs
);
752 /* This usually does nothing. But sometimes parts of cfg that originally
753 were inside a loop get out of it due to edge removal (since they
754 become unreachable by back edges from latch). Also a former
755 irreducible loop can become reducible - in this case force a full
756 rewrite into loop-closed SSA form. */
757 if (loops_state_satisfies_p (LOOP_CLOSED_SSA
))
758 rewrite_into_loop_closed_ssa (n_new_loops
? NULL
: changed_bbs
,
761 BITMAP_FREE (changed_bbs
);
763 #ifdef ENABLE_CHECKING
764 verify_loop_structure ();
768 timevar_pop (TV_REPAIR_LOOPS
);
771 /* Cleanup cfg and repair loop structures. */
774 cleanup_tree_cfg (void)
776 bool changed
= cleanup_tree_cfg_noloop ();
778 if (current_loops
!= NULL
779 && loops_state_satisfies_p (LOOPS_NEED_FIXUP
))
780 repair_loop_structures ();
785 /* Tries to merge the PHI nodes at BB into those at BB's sole successor.
786 Returns true if successful. */
789 remove_forwarder_block_with_phi (basic_block bb
)
791 edge succ
= single_succ_edge (bb
);
792 basic_block dest
= succ
->dest
;
794 basic_block dombb
, domdest
, dom
;
796 /* We check for infinite loops already in tree_forwarder_block_p.
797 However it may happen that the infinite loop is created
798 afterwards due to removal of forwarders. */
802 /* If the destination block consists of a nonlocal label, do not
804 label
= first_stmt (dest
);
806 && gimple_code (label
) == GIMPLE_LABEL
807 && DECL_NONLOCAL (gimple_label_label (label
)))
810 /* Redirect each incoming edge to BB to DEST. */
811 while (EDGE_COUNT (bb
->preds
) > 0)
813 edge e
= EDGE_PRED (bb
, 0), s
;
814 gimple_stmt_iterator gsi
;
816 s
= find_edge (e
->src
, dest
);
819 /* We already have an edge S from E->src to DEST. If S and
820 E->dest's sole successor edge have the same PHI arguments
821 at DEST, redirect S to DEST. */
822 if (phi_alternatives_equal (dest
, s
, succ
))
824 e
= redirect_edge_and_branch (e
, dest
);
825 redirect_edge_var_map_clear (e
);
829 /* PHI arguments are different. Create a forwarder block by
830 splitting E so that we can merge PHI arguments on E to
832 e
= single_succ_edge (split_edge (e
));
835 s
= redirect_edge_and_branch (e
, dest
);
837 /* redirect_edge_and_branch must not create a new edge. */
840 /* Add to the PHI nodes at DEST each PHI argument removed at the
842 for (gsi
= gsi_start_phis (dest
);
846 gimple phi
= gsi_stmt (gsi
);
847 tree def
= gimple_phi_arg_def (phi
, succ
->dest_idx
);
848 source_location locus
= gimple_phi_arg_location_from_edge (phi
, succ
);
850 if (TREE_CODE (def
) == SSA_NAME
)
852 edge_var_map_vector
*head
;
856 /* If DEF is one of the results of PHI nodes removed during
857 redirection, replace it with the PHI argument that used
859 head
= redirect_edge_var_map_vector (e
);
860 FOR_EACH_VEC_SAFE_ELT (head
, i
, vm
)
862 tree old_arg
= redirect_edge_var_map_result (vm
);
863 tree new_arg
= redirect_edge_var_map_def (vm
);
868 locus
= redirect_edge_var_map_location (vm
);
874 add_phi_arg (phi
, def
, s
, locus
);
877 redirect_edge_var_map_clear (e
);
880 /* Update the dominators. */
881 dombb
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
882 domdest
= get_immediate_dominator (CDI_DOMINATORS
, dest
);
885 /* Shortcut to avoid calling (relatively expensive)
886 nearest_common_dominator unless necessary. */
890 dom
= nearest_common_dominator (CDI_DOMINATORS
, domdest
, dombb
);
892 set_immediate_dominator (CDI_DOMINATORS
, dest
, dom
);
894 /* Remove BB since all of BB's incoming edges have been redirected
896 delete_basic_block (bb
);
901 /* This pass merges PHI nodes if one feeds into another. For example,
902 suppose we have the following:
909 # tem_6 = PHI <tem_17(8), tem_23(7)>;
912 # tem_3 = PHI <tem_6(9), tem_2(5)>;
915 Then we merge the first PHI node into the second one like so:
922 # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>;
927 merge_phi_nodes (void)
929 basic_block
*worklist
= XNEWVEC (basic_block
, n_basic_blocks_for_fn (cfun
));
930 basic_block
*current
= worklist
;
933 calculate_dominance_info (CDI_DOMINATORS
);
935 /* Find all PHI nodes that we may be able to merge. */
936 FOR_EACH_BB_FN (bb
, cfun
)
940 /* Look for a forwarder block with PHI nodes. */
941 if (!tree_forwarder_block_p (bb
, true))
944 dest
= single_succ (bb
);
946 /* We have to feed into another basic block with PHI
948 if (gimple_seq_empty_p (phi_nodes (dest
))
949 /* We don't want to deal with a basic block with
951 || bb_has_abnormal_pred (bb
))
954 if (!dominated_by_p (CDI_DOMINATORS
, dest
, bb
))
956 /* If BB does not dominate DEST, then the PHI nodes at
957 DEST must be the only users of the results of the PHI
963 gimple_stmt_iterator gsi
;
964 unsigned int dest_idx
= single_succ_edge (bb
)->dest_idx
;
966 /* BB dominates DEST. There may be many users of the PHI
967 nodes in BB. However, there is still a trivial case we
968 can handle. If the result of every PHI in BB is used
969 only by a PHI in DEST, then we can trivially merge the
970 PHI nodes from BB into DEST. */
971 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
);
974 gimple phi
= gsi_stmt (gsi
);
975 tree result
= gimple_phi_result (phi
);
976 use_operand_p imm_use
;
979 /* If the PHI's result is never used, then we can just
981 if (has_zero_uses (result
))
984 /* Get the single use of the result of this PHI node. */
985 if (!single_imm_use (result
, &imm_use
, &use_stmt
)
986 || gimple_code (use_stmt
) != GIMPLE_PHI
987 || gimple_bb (use_stmt
) != dest
988 || gimple_phi_arg_def (use_stmt
, dest_idx
) != result
)
992 /* If the loop above iterated through all the PHI nodes
993 in BB, then we can merge the PHIs from BB into DEST. */
999 /* Now let's drain WORKLIST. */
1000 bool changed
= false;
1001 while (current
!= worklist
)
1004 changed
|= remove_forwarder_block_with_phi (bb
);
1008 /* Removing forwarder blocks can cause formerly irreducible loops
1009 to become reducible if we merged two entry blocks. */
1012 loops_state_set (LOOPS_NEED_FIXUP
);
1018 gate_merge_phi (void)
1025 const pass_data pass_data_merge_phi
=
1027 GIMPLE_PASS
, /* type */
1028 "mergephi", /* name */
1029 OPTGROUP_NONE
, /* optinfo_flags */
1030 true, /* has_gate */
1031 true, /* has_execute */
1032 TV_TREE_MERGE_PHI
, /* tv_id */
1033 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1034 0, /* properties_provided */
1035 0, /* properties_destroyed */
1036 0, /* todo_flags_start */
1037 TODO_verify_ssa
, /* todo_flags_finish */
1040 class pass_merge_phi
: public gimple_opt_pass
1043 pass_merge_phi (gcc::context
*ctxt
)
1044 : gimple_opt_pass (pass_data_merge_phi
, ctxt
)
1047 /* opt_pass methods: */
1048 opt_pass
* clone () { return new pass_merge_phi (m_ctxt
); }
1049 bool gate () { return gate_merge_phi (); }
1050 unsigned int execute () { return merge_phi_nodes (); }
1052 }; // class pass_merge_phi
1057 make_pass_merge_phi (gcc::context
*ctxt
)
1059 return new pass_merge_phi (ctxt
);
1062 /* Pass: cleanup the CFG just before expanding trees to RTL.
1063 This is just a round of label cleanups and case node grouping
1064 because after the tree optimizers have run such cleanups may
1068 execute_cleanup_cfg_post_optimizing (void)
1070 unsigned int todo
= 0;
1071 if (cleanup_tree_cfg ())
1072 todo
|= TODO_update_ssa
;
1073 maybe_remove_unreachable_handlers ();
1074 cleanup_dead_labels ();
1075 group_case_labels ();
1076 if ((flag_compare_debug_opt
|| flag_compare_debug
)
1077 && flag_dump_final_insns
)
1079 FILE *final_output
= fopen (flag_dump_final_insns
, "a");
1083 error ("could not open final insn dump file %qs: %m",
1084 flag_dump_final_insns
);
1085 flag_dump_final_insns
= NULL
;
1089 int save_unnumbered
= flag_dump_unnumbered
;
1090 int save_noaddr
= flag_dump_noaddr
;
1092 flag_dump_noaddr
= flag_dump_unnumbered
= 1;
1093 fprintf (final_output
, "\n");
1094 dump_enumerated_decls (final_output
, dump_flags
| TDF_NOUID
);
1095 flag_dump_noaddr
= save_noaddr
;
1096 flag_dump_unnumbered
= save_unnumbered
;
1097 if (fclose (final_output
))
1099 error ("could not close final insn dump file %qs: %m",
1100 flag_dump_final_insns
);
1101 flag_dump_final_insns
= NULL
;
1110 const pass_data pass_data_cleanup_cfg_post_optimizing
=
1112 GIMPLE_PASS
, /* type */
1113 "optimized", /* name */
1114 OPTGROUP_NONE
, /* optinfo_flags */
1115 false, /* has_gate */
1116 true, /* has_execute */
1117 TV_TREE_CLEANUP_CFG
, /* tv_id */
1118 PROP_cfg
, /* properties_required */
1119 0, /* properties_provided */
1120 0, /* properties_destroyed */
1121 0, /* todo_flags_start */
1122 TODO_remove_unused_locals
, /* todo_flags_finish */
1125 class pass_cleanup_cfg_post_optimizing
: public gimple_opt_pass
1128 pass_cleanup_cfg_post_optimizing (gcc::context
*ctxt
)
1129 : gimple_opt_pass (pass_data_cleanup_cfg_post_optimizing
, ctxt
)
1132 /* opt_pass methods: */
1133 unsigned int execute () {
1134 return execute_cleanup_cfg_post_optimizing ();
1137 }; // class pass_cleanup_cfg_post_optimizing
1142 make_pass_cleanup_cfg_post_optimizing (gcc::context
*ctxt
)
1144 return new pass_cleanup_cfg_post_optimizing (ctxt
);