1 /* CFG cleanup for trees.
2 Copyright (C) 2001-2016 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"
28 #include "tree-pass.h"
30 #include "diagnostic-core.h"
31 #include "fold-const.h"
33 #include "cfgcleanup.h"
36 #include "gimple-iterator.h"
38 #include "tree-ssa-loop-manip.h"
42 #include "tree-scalar-evolution.h"
43 #include "gimple-match.h"
44 #include "gimple-fold.h"
45 #include "tree-ssa-loop-niter.h"
48 /* The set of blocks in that at least one of the following changes happened:
49 -- the statement at the end of the block was changed
50 -- the block was newly created
51 -- the set of the predecessors of the block changed
52 -- the set of the successors of the block changed
53 ??? Maybe we could track these changes separately, since they determine
54 what cleanups it makes sense to try on the block. */
55 bitmap cfgcleanup_altered_bbs
;
57 /* Remove any fallthru edge from EV. Return true if an edge was removed. */
60 remove_fallthru_edge (vec
<edge
, va_gc
> *ev
)
65 FOR_EACH_EDGE (e
, ei
, ev
)
66 if ((e
->flags
& EDGE_FALLTHRU
) != 0)
68 if (e
->flags
& EDGE_COMPLEX
)
69 e
->flags
&= ~EDGE_FALLTHRU
;
71 remove_edge_and_dominated_blocks (e
);
78 /* Disconnect an unreachable block in the control expression starting
82 cleanup_control_expr_graph (basic_block bb
, gimple_stmt_iterator gsi
,
87 gimple
*stmt
= gsi_stmt (gsi
);
89 if (!single_succ_p (bb
))
96 fold_defer_overflow_warnings ();
97 switch (gimple_code (stmt
))
100 /* During a first iteration on the CFG only remove trivially
101 dead edges but mark other conditions for re-evaluation. */
104 val
= const_binop (gimple_cond_code (stmt
), boolean_type_node
,
105 gimple_cond_lhs (stmt
),
106 gimple_cond_rhs (stmt
));
108 bitmap_set_bit (cfgcleanup_altered_bbs
, bb
->index
);
114 if (gimple_simplify (stmt
, &rcode
, ops
, NULL
, no_follow_ssa_edges
,
116 && rcode
== INTEGER_CST
)
122 val
= gimple_switch_index (as_a
<gswitch
*> (stmt
));
128 taken_edge
= find_taken_edge (bb
, val
);
131 fold_undefer_and_ignore_overflow_warnings ();
135 /* Remove all the edges except the one that is always executed. */
137 for (ei
= ei_start (bb
->succs
); (e
= ei_safe_edge (ei
)); )
143 fold_undefer_overflow_warnings
144 (true, stmt
, WARN_STRICT_OVERFLOW_CONDITIONAL
);
148 taken_edge
->probability
+= e
->probability
;
149 taken_edge
->count
+= e
->count
;
150 remove_edge_and_dominated_blocks (e
);
157 fold_undefer_and_ignore_overflow_warnings ();
158 if (taken_edge
->probability
> REG_BR_PROB_BASE
)
159 taken_edge
->probability
= REG_BR_PROB_BASE
;
162 taken_edge
= single_succ_edge (bb
);
164 bitmap_set_bit (cfgcleanup_altered_bbs
, bb
->index
);
165 gsi_remove (&gsi
, true);
166 taken_edge
->flags
= EDGE_FALLTHRU
;
171 /* Cleanup the GF_CALL_CTRL_ALTERING flag according to
172 to updated gimple_call_flags. */
175 cleanup_call_ctrl_altering_flag (gimple
*bb_end
)
177 if (!is_gimple_call (bb_end
)
178 || !gimple_call_ctrl_altering_p (bb_end
))
181 int flags
= gimple_call_flags (bb_end
);
182 if (((flags
& (ECF_CONST
| ECF_PURE
))
183 && !(flags
& ECF_LOOPING_CONST_OR_PURE
))
184 || (flags
& ECF_LEAF
))
185 gimple_call_set_ctrl_altering (bb_end
, false);
188 /* Try to remove superfluous control structures in basic block BB. Returns
189 true if anything changes. */
192 cleanup_control_flow_bb (basic_block bb
, bool first_p
)
194 gimple_stmt_iterator gsi
;
198 /* If the last statement of the block could throw and now cannot,
199 we need to prune cfg. */
200 retval
|= gimple_purge_dead_eh_edges (bb
);
202 gsi
= gsi_last_nondebug_bb (bb
);
206 stmt
= gsi_stmt (gsi
);
208 /* Try to cleanup ctrl altering flag for call which ends bb. */
209 cleanup_call_ctrl_altering_flag (stmt
);
211 if (gimple_code (stmt
) == GIMPLE_COND
212 || gimple_code (stmt
) == GIMPLE_SWITCH
)
214 gcc_checking_assert (gsi_stmt (gsi_last_bb (bb
)) == stmt
);
215 retval
|= cleanup_control_expr_graph (bb
, gsi
, first_p
);
217 else if (gimple_code (stmt
) == GIMPLE_GOTO
218 && TREE_CODE (gimple_goto_dest (stmt
)) == ADDR_EXPR
219 && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt
), 0))
222 /* If we had a computed goto which has a compile-time determinable
223 destination, then we can eliminate the goto. */
227 basic_block target_block
;
229 gcc_checking_assert (gsi_stmt (gsi_last_bb (bb
)) == stmt
);
230 /* First look at all the outgoing edges. Delete any outgoing
231 edges which do not go to the right block. For the one
232 edge which goes to the right block, fix up its flags. */
233 label
= TREE_OPERAND (gimple_goto_dest (stmt
), 0);
234 target_block
= label_to_block (label
);
235 for (ei
= ei_start (bb
->succs
); (e
= ei_safe_edge (ei
)); )
237 if (e
->dest
!= target_block
)
238 remove_edge_and_dominated_blocks (e
);
241 /* Turn off the EDGE_ABNORMAL flag. */
242 e
->flags
&= ~EDGE_ABNORMAL
;
244 /* And set EDGE_FALLTHRU. */
245 e
->flags
|= EDGE_FALLTHRU
;
250 bitmap_set_bit (cfgcleanup_altered_bbs
, bb
->index
);
251 bitmap_set_bit (cfgcleanup_altered_bbs
, target_block
->index
);
253 /* Remove the GOTO_EXPR as it is not needed. The CFG has all the
254 relevant information we need. */
255 gsi_remove (&gsi
, true);
259 /* Check for indirect calls that have been turned into
261 else if (is_gimple_call (stmt
)
262 && gimple_call_noreturn_p (stmt
))
264 /* If there are debug stmts after the noreturn call, remove them
265 now, they should be all unreachable anyway. */
266 for (gsi_next (&gsi
); !gsi_end_p (gsi
); )
267 gsi_remove (&gsi
, true);
268 if (remove_fallthru_edge (bb
->succs
))
275 /* Return true if basic block BB does nothing except pass control
276 flow to another block and that we can safely insert a label at
277 the start of the successor block.
279 As a precondition, we require that BB be not equal to
283 tree_forwarder_block_p (basic_block bb
, bool phi_wanted
)
285 gimple_stmt_iterator gsi
;
288 /* BB must have a single outgoing edge. */
289 if (single_succ_p (bb
) != 1
290 /* If PHI_WANTED is false, BB must not have any PHI nodes.
291 Otherwise, BB must have PHI nodes. */
292 || gimple_seq_empty_p (phi_nodes (bb
)) == phi_wanted
293 /* BB may not be a predecessor of the exit block. */
294 || single_succ (bb
) == EXIT_BLOCK_PTR_FOR_FN (cfun
)
295 /* Nor should this be an infinite loop. */
296 || single_succ (bb
) == bb
297 /* BB may not have an abnormal outgoing edge. */
298 || (single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
301 gcc_checking_assert (bb
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
));
303 locus
= single_succ_edge (bb
)->goto_locus
;
305 /* There should not be an edge coming from entry, or an EH edge. */
310 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
311 if (e
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
) || (e
->flags
& EDGE_EH
))
313 /* If goto_locus of any of the edges differs, prevent removing
314 the forwarder block for -O0. */
315 else if (optimize
== 0 && e
->goto_locus
!= locus
)
319 /* Now walk through the statements backward. We can ignore labels,
320 anything else means this is not a forwarder block. */
321 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
323 gimple
*stmt
= gsi_stmt (gsi
);
325 switch (gimple_code (stmt
))
328 if (DECL_NONLOCAL (gimple_label_label (as_a
<glabel
*> (stmt
))))
330 if (optimize
== 0 && gimple_location (stmt
) != locus
)
334 /* ??? For now, hope there's a corresponding debug
335 assignment at the destination. */
347 /* Protect loop headers. */
348 if (bb
->loop_father
->header
== bb
)
351 dest
= EDGE_SUCC (bb
, 0)->dest
;
352 /* Protect loop preheaders and latches if requested. */
353 if (dest
->loop_father
->header
== dest
)
355 if (bb
->loop_father
== dest
->loop_father
)
357 if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES
))
359 /* If bb doesn't have a single predecessor we'd make this
360 loop have multiple latches. Don't do that if that
361 would in turn require disambiguating them. */
362 return (single_pred_p (bb
)
363 || loops_state_satisfies_p
364 (LOOPS_MAY_HAVE_MULTIPLE_LATCHES
));
366 else if (bb
->loop_father
== loop_outer (dest
->loop_father
))
367 return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS
);
368 /* Always preserve other edges into loop headers that are
369 not simple latches or preheaders. */
377 /* If all the PHI nodes in DEST have alternatives for E1 and E2 and
378 those alternatives are equal in each of the PHI nodes, then return
379 true, else return false. */
382 phi_alternatives_equal (basic_block dest
, edge e1
, edge e2
)
384 int n1
= e1
->dest_idx
;
385 int n2
= e2
->dest_idx
;
388 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
390 gphi
*phi
= gsi
.phi ();
391 tree val1
= gimple_phi_arg_def (phi
, n1
);
392 tree val2
= gimple_phi_arg_def (phi
, n2
);
394 gcc_assert (val1
!= NULL_TREE
);
395 gcc_assert (val2
!= NULL_TREE
);
397 if (!operand_equal_for_phi_arg_p (val1
, val2
))
404 /* Removes forwarder block BB. Returns false if this failed. */
407 remove_forwarder_block (basic_block bb
)
409 edge succ
= single_succ_edge (bb
), e
, s
;
410 basic_block dest
= succ
->dest
;
413 gimple_stmt_iterator gsi
, gsi_to
;
414 bool can_move_debug_stmts
;
416 /* We check for infinite loops already in tree_forwarder_block_p.
417 However it may happen that the infinite loop is created
418 afterwards due to removal of forwarders. */
422 /* If the destination block consists of a nonlocal label or is a
423 EH landing pad, do not merge it. */
424 label
= first_stmt (dest
);
426 if (glabel
*label_stmt
= dyn_cast
<glabel
*> (label
))
427 if (DECL_NONLOCAL (gimple_label_label (label_stmt
))
428 || EH_LANDING_PAD_NR (gimple_label_label (label_stmt
)) != 0)
431 /* If there is an abnormal edge to basic block BB, but not into
432 dest, problems might occur during removal of the phi node at out
433 of ssa due to overlapping live ranges of registers.
435 If there is an abnormal edge in DEST, the problems would occur
436 anyway since cleanup_dead_labels would then merge the labels for
437 two different eh regions, and rest of exception handling code
440 So if there is an abnormal edge to BB, proceed only if there is
441 no abnormal edge to DEST and there are no phi nodes in DEST. */
442 if (bb_has_abnormal_pred (bb
)
443 && (bb_has_abnormal_pred (dest
)
444 || !gimple_seq_empty_p (phi_nodes (dest
))))
447 /* If there are phi nodes in DEST, and some of the blocks that are
448 predecessors of BB are also predecessors of DEST, check that the
449 phi node arguments match. */
450 if (!gimple_seq_empty_p (phi_nodes (dest
)))
452 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
454 s
= find_edge (e
->src
, dest
);
458 if (!phi_alternatives_equal (dest
, succ
, s
))
463 can_move_debug_stmts
= MAY_HAVE_DEBUG_STMTS
&& single_pred_p (dest
);
465 basic_block pred
= NULL
;
466 if (single_pred_p (bb
))
467 pred
= single_pred (bb
);
469 /* Redirect the edges. */
470 for (ei
= ei_start (bb
->preds
); (e
= ei_safe_edge (ei
)); )
472 bitmap_set_bit (cfgcleanup_altered_bbs
, e
->src
->index
);
474 if (e
->flags
& EDGE_ABNORMAL
)
476 /* If there is an abnormal edge, redirect it anyway, and
477 move the labels to the new block to make it legal. */
478 s
= redirect_edge_succ_nodup (e
, dest
);
481 s
= redirect_edge_and_branch (e
, dest
);
485 /* Create arguments for the phi nodes, since the edge was not
487 for (gphi_iterator psi
= gsi_start_phis (dest
);
491 gphi
*phi
= psi
.phi ();
492 source_location l
= gimple_phi_arg_location_from_edge (phi
, succ
);
493 tree def
= gimple_phi_arg_def (phi
, succ
->dest_idx
);
494 add_phi_arg (phi
, unshare_expr (def
), s
, l
);
499 /* Move nonlocal labels and computed goto targets as well as user
500 defined labels and labels with an EH landing pad number to the
501 new block, so that the redirection of the abnormal edges works,
502 jump targets end up in a sane place and debug information for
503 labels is retained. */
504 gsi_to
= gsi_start_bb (dest
);
505 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); )
508 label
= gsi_stmt (gsi
);
509 if (is_gimple_debug (label
))
511 decl
= gimple_label_label (as_a
<glabel
*> (label
));
512 if (EH_LANDING_PAD_NR (decl
) != 0
513 || DECL_NONLOCAL (decl
)
514 || FORCED_LABEL (decl
)
515 || !DECL_ARTIFICIAL (decl
))
517 gsi_remove (&gsi
, false);
518 gsi_insert_before (&gsi_to
, label
, GSI_SAME_STMT
);
524 /* Move debug statements if the destination has a single predecessor. */
525 if (can_move_debug_stmts
)
527 gsi_to
= gsi_after_labels (dest
);
528 for (gsi
= gsi_after_labels (bb
); !gsi_end_p (gsi
); )
530 gimple
*debug
= gsi_stmt (gsi
);
531 if (!is_gimple_debug (debug
))
533 gsi_remove (&gsi
, false);
534 gsi_insert_before (&gsi_to
, debug
, GSI_SAME_STMT
);
538 bitmap_set_bit (cfgcleanup_altered_bbs
, dest
->index
);
540 /* Update the dominators. */
541 if (dom_info_available_p (CDI_DOMINATORS
))
543 basic_block dom
, dombb
, domdest
;
545 dombb
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
546 domdest
= get_immediate_dominator (CDI_DOMINATORS
, dest
);
549 /* Shortcut to avoid calling (relatively expensive)
550 nearest_common_dominator unless necessary. */
554 dom
= nearest_common_dominator (CDI_DOMINATORS
, domdest
, dombb
);
556 set_immediate_dominator (CDI_DOMINATORS
, dest
, dom
);
559 /* Adjust latch infomation of BB's parent loop as otherwise
560 the cfg hook has a hard time not to kill the loop. */
561 if (current_loops
&& bb
->loop_father
->latch
== bb
)
562 bb
->loop_father
->latch
= pred
;
564 /* And kill the forwarder block. */
565 delete_basic_block (bb
);
570 /* STMT is a call that has been discovered noreturn. Split the
571 block to prepare fixing up the CFG and remove LHS.
572 Return true if cleanup-cfg needs to run. */
575 fixup_noreturn_call (gimple
*stmt
)
577 basic_block bb
= gimple_bb (stmt
);
578 bool changed
= false;
580 if (gimple_call_builtin_p (stmt
, BUILT_IN_RETURN
))
583 /* First split basic block if stmt is not last. */
584 if (stmt
!= gsi_stmt (gsi_last_bb (bb
)))
586 if (stmt
== gsi_stmt (gsi_last_nondebug_bb (bb
)))
588 /* Don't split if there are only debug stmts
589 after stmt, that can result in -fcompare-debug
590 failures. Remove the debug stmts instead,
591 they should be all unreachable anyway. */
592 gimple_stmt_iterator gsi
= gsi_for_stmt (stmt
);
593 for (gsi_next (&gsi
); !gsi_end_p (gsi
); )
594 gsi_remove (&gsi
, true);
598 split_block (bb
, stmt
);
603 /* If there is an LHS, remove it, but only if its type has fixed size.
604 The LHS will need to be recreated during RTL expansion and creating
605 temporaries of variable-sized types is not supported. Also don't
606 do this with TREE_ADDRESSABLE types, as assign_temp will abort.
607 Drop LHS regardless of TREE_ADDRESSABLE, if the function call
608 has been changed into a call that does not return a value, like
609 __builtin_unreachable or __cxa_pure_virtual. */
610 tree lhs
= gimple_call_lhs (stmt
);
612 && ((TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (lhs
))) == INTEGER_CST
613 && !TREE_ADDRESSABLE (TREE_TYPE (lhs
)))
614 || VOID_TYPE_P (TREE_TYPE (gimple_call_fntype (stmt
)))))
616 gimple_call_set_lhs (stmt
, NULL_TREE
);
618 /* We need to fix up the SSA name to avoid checking errors. */
619 if (TREE_CODE (lhs
) == SSA_NAME
)
621 tree new_var
= create_tmp_reg (TREE_TYPE (lhs
));
622 SET_SSA_NAME_VAR_OR_IDENTIFIER (lhs
, new_var
);
623 SSA_NAME_DEF_STMT (lhs
) = gimple_build_nop ();
624 set_ssa_default_def (cfun
, new_var
, lhs
);
630 /* Mark the call as altering control flow. */
631 if (!gimple_call_ctrl_altering_p (stmt
))
633 gimple_call_set_ctrl_altering (stmt
, true);
641 /* Tries to cleanup cfg in basic block BB. Returns true if anything
645 cleanup_tree_cfg_bb (basic_block bb
)
647 if (tree_forwarder_block_p (bb
, false)
648 && remove_forwarder_block (bb
))
651 /* Merging the blocks may create new opportunities for folding
652 conditional branches (due to the elimination of single-valued PHI
654 if (single_succ_p (bb
)
655 && can_merge_blocks_p (bb
, single_succ (bb
)))
657 /* If there is a merge opportunity with the predecessor
658 do nothing now but wait until we process the predecessor.
659 This happens when we visit BBs in a non-optimal order and
660 avoids quadratic behavior with adjusting stmts BB pointer. */
661 if (single_pred_p (bb
)
662 && can_merge_blocks_p (single_pred (bb
), bb
))
666 merge_blocks (bb
, single_succ (bb
));
674 /* Iterate the cfg cleanups, while anything changes. */
677 cleanup_tree_cfg_1 (void)
683 /* Prepare the worklists of altered blocks. */
684 cfgcleanup_altered_bbs
= BITMAP_ALLOC (NULL
);
686 /* During forwarder block cleanup, we may redirect edges out of
687 SWITCH_EXPRs, which can get expensive. So we want to enable
688 recording of edge to CASE_LABEL_EXPR. */
689 start_recording_case_labels ();
691 /* We cannot use FOR_EACH_BB_FN for the BB iterations below
692 since the basic blocks may get removed. */
694 /* Start by iterating over all basic blocks looking for edge removal
695 opportunities. Do this first because incoming SSA form may be
696 invalid and we want to avoid performing SSA related tasks such
697 as propgating out a PHI node during BB merging in that state. */
698 n
= last_basic_block_for_fn (cfun
);
699 for (i
= NUM_FIXED_BLOCKS
; i
< n
; i
++)
701 bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
703 retval
|= cleanup_control_flow_bb (bb
, true);
706 /* After doing the above SSA form should be valid (or an update SSA
707 should be required). */
709 /* Continue by iterating over all basic blocks looking for BB merging
711 n
= last_basic_block_for_fn (cfun
);
712 for (i
= NUM_FIXED_BLOCKS
; i
< n
; i
++)
714 bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
716 retval
|= cleanup_tree_cfg_bb (bb
);
719 /* Now process the altered blocks, as long as any are available. */
720 while (!bitmap_empty_p (cfgcleanup_altered_bbs
))
722 i
= bitmap_first_set_bit (cfgcleanup_altered_bbs
);
723 bitmap_clear_bit (cfgcleanup_altered_bbs
, i
);
724 if (i
< NUM_FIXED_BLOCKS
)
727 bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
731 retval
|= cleanup_control_flow_bb (bb
, false);
732 retval
|= cleanup_tree_cfg_bb (bb
);
735 end_recording_case_labels ();
736 BITMAP_FREE (cfgcleanup_altered_bbs
);
741 /* Remove unreachable blocks and other miscellaneous clean up work.
742 Return true if the flowgraph was modified, false otherwise. */
745 cleanup_tree_cfg_noloop (void)
749 timevar_push (TV_TREE_CLEANUP_CFG
);
751 /* Iterate until there are no more cleanups left to do. If any
752 iteration changed the flowgraph, set CHANGED to true.
754 If dominance information is available, there cannot be any unreachable
756 if (!dom_info_available_p (CDI_DOMINATORS
))
758 changed
= delete_unreachable_blocks ();
759 calculate_dominance_info (CDI_DOMINATORS
);
763 checking_verify_dominators (CDI_DOMINATORS
);
767 changed
|= cleanup_tree_cfg_1 ();
769 gcc_assert (dom_info_available_p (CDI_DOMINATORS
));
772 checking_verify_flow_info ();
774 timevar_pop (TV_TREE_CLEANUP_CFG
);
776 if (changed
&& current_loops
)
777 loops_state_set (LOOPS_NEED_FIXUP
);
782 /* Repairs loop structures. */
785 repair_loop_structures (void)
788 unsigned n_new_loops
;
790 calculate_dominance_info (CDI_DOMINATORS
);
792 timevar_push (TV_REPAIR_LOOPS
);
793 changed_bbs
= BITMAP_ALLOC (NULL
);
794 n_new_loops
= fix_loop_structure (changed_bbs
);
796 /* This usually does nothing. But sometimes parts of cfg that originally
797 were inside a loop get out of it due to edge removal (since they
798 become unreachable by back edges from latch). Also a former
799 irreducible loop can become reducible - in this case force a full
800 rewrite into loop-closed SSA form. */
801 if (loops_state_satisfies_p (LOOP_CLOSED_SSA
))
802 rewrite_into_loop_closed_ssa (n_new_loops
? NULL
: changed_bbs
,
805 BITMAP_FREE (changed_bbs
);
807 checking_verify_loop_structure ();
810 timevar_pop (TV_REPAIR_LOOPS
);
813 /* Cleanup cfg and repair loop structures. */
816 cleanup_tree_cfg (void)
818 bool changed
= cleanup_tree_cfg_noloop ();
820 if (current_loops
!= NULL
821 && loops_state_satisfies_p (LOOPS_NEED_FIXUP
))
822 repair_loop_structures ();
827 /* Tries to merge the PHI nodes at BB into those at BB's sole successor.
828 Returns true if successful. */
831 remove_forwarder_block_with_phi (basic_block bb
)
833 edge succ
= single_succ_edge (bb
);
834 basic_block dest
= succ
->dest
;
836 basic_block dombb
, domdest
, dom
;
838 /* We check for infinite loops already in tree_forwarder_block_p.
839 However it may happen that the infinite loop is created
840 afterwards due to removal of forwarders. */
844 /* If the destination block consists of a nonlocal label, do not
846 label
= first_stmt (dest
);
848 if (glabel
*label_stmt
= dyn_cast
<glabel
*> (label
))
849 if (DECL_NONLOCAL (gimple_label_label (label_stmt
)))
852 /* Record BB's single pred in case we need to update the father
853 loop's latch information later. */
854 basic_block pred
= NULL
;
855 if (single_pred_p (bb
))
856 pred
= single_pred (bb
);
858 /* Redirect each incoming edge to BB to DEST. */
859 while (EDGE_COUNT (bb
->preds
) > 0)
861 edge e
= EDGE_PRED (bb
, 0), s
;
864 s
= find_edge (e
->src
, dest
);
867 /* We already have an edge S from E->src to DEST. If S and
868 E->dest's sole successor edge have the same PHI arguments
869 at DEST, redirect S to DEST. */
870 if (phi_alternatives_equal (dest
, s
, succ
))
872 e
= redirect_edge_and_branch (e
, dest
);
873 redirect_edge_var_map_clear (e
);
877 /* PHI arguments are different. Create a forwarder block by
878 splitting E so that we can merge PHI arguments on E to
880 e
= single_succ_edge (split_edge (e
));
884 /* If we merge the forwarder into a loop header verify if we
885 are creating another loop latch edge. If so, reset
886 number of iteration information of the loop. */
887 if (dest
->loop_father
->header
== dest
888 && dominated_by_p (CDI_DOMINATORS
, e
->src
, dest
))
890 dest
->loop_father
->any_upper_bound
= false;
891 free_numbers_of_iterations_estimates_loop (dest
->loop_father
);
895 s
= redirect_edge_and_branch (e
, dest
);
897 /* redirect_edge_and_branch must not create a new edge. */
900 /* Add to the PHI nodes at DEST each PHI argument removed at the
902 for (gsi
= gsi_start_phis (dest
);
906 gphi
*phi
= gsi
.phi ();
907 tree def
= gimple_phi_arg_def (phi
, succ
->dest_idx
);
908 source_location locus
= gimple_phi_arg_location_from_edge (phi
, succ
);
910 if (TREE_CODE (def
) == SSA_NAME
)
912 /* If DEF is one of the results of PHI nodes removed during
913 redirection, replace it with the PHI argument that used
915 vec
<edge_var_map
> *head
= redirect_edge_var_map_vector (e
);
916 size_t length
= head
? head
->length () : 0;
917 for (size_t i
= 0; i
< length
; i
++)
919 edge_var_map
*vm
= &(*head
)[i
];
920 tree old_arg
= redirect_edge_var_map_result (vm
);
921 tree new_arg
= redirect_edge_var_map_def (vm
);
926 locus
= redirect_edge_var_map_location (vm
);
932 add_phi_arg (phi
, def
, s
, locus
);
935 redirect_edge_var_map_clear (e
);
938 /* Update the dominators. */
939 dombb
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
940 domdest
= get_immediate_dominator (CDI_DOMINATORS
, dest
);
943 /* Shortcut to avoid calling (relatively expensive)
944 nearest_common_dominator unless necessary. */
948 dom
= nearest_common_dominator (CDI_DOMINATORS
, domdest
, dombb
);
950 set_immediate_dominator (CDI_DOMINATORS
, dest
, dom
);
952 /* Adjust latch infomation of BB's parent loop as otherwise
953 the cfg hook has a hard time not to kill the loop. */
954 if (current_loops
&& bb
->loop_father
->latch
== bb
)
955 bb
->loop_father
->latch
= pred
;
957 /* Remove BB since all of BB's incoming edges have been redirected
959 delete_basic_block (bb
);
964 /* This pass merges PHI nodes if one feeds into another. For example,
965 suppose we have the following:
972 # tem_6 = PHI <tem_17(8), tem_23(7)>;
975 # tem_3 = PHI <tem_6(9), tem_2(5)>;
978 Then we merge the first PHI node into the second one like so:
985 # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>;
991 const pass_data pass_data_merge_phi
=
993 GIMPLE_PASS
, /* type */
994 "mergephi", /* name */
995 OPTGROUP_NONE
, /* optinfo_flags */
996 TV_TREE_MERGE_PHI
, /* tv_id */
997 ( PROP_cfg
| PROP_ssa
), /* properties_required */
998 0, /* properties_provided */
999 0, /* properties_destroyed */
1000 0, /* todo_flags_start */
1001 0, /* todo_flags_finish */
1004 class pass_merge_phi
: public gimple_opt_pass
1007 pass_merge_phi (gcc::context
*ctxt
)
1008 : gimple_opt_pass (pass_data_merge_phi
, ctxt
)
1011 /* opt_pass methods: */
1012 opt_pass
* clone () { return new pass_merge_phi (m_ctxt
); }
1013 virtual unsigned int execute (function
*);
1015 }; // class pass_merge_phi
1018 pass_merge_phi::execute (function
*fun
)
1020 basic_block
*worklist
= XNEWVEC (basic_block
, n_basic_blocks_for_fn (fun
));
1021 basic_block
*current
= worklist
;
1024 calculate_dominance_info (CDI_DOMINATORS
);
1026 /* Find all PHI nodes that we may be able to merge. */
1027 FOR_EACH_BB_FN (bb
, fun
)
1031 /* Look for a forwarder block with PHI nodes. */
1032 if (!tree_forwarder_block_p (bb
, true))
1035 dest
= single_succ (bb
);
1037 /* We have to feed into another basic block with PHI
1039 if (gimple_seq_empty_p (phi_nodes (dest
))
1040 /* We don't want to deal with a basic block with
1042 || bb_has_abnormal_pred (bb
))
1045 if (!dominated_by_p (CDI_DOMINATORS
, dest
, bb
))
1047 /* If BB does not dominate DEST, then the PHI nodes at
1048 DEST must be the only users of the results of the PHI
1055 unsigned int dest_idx
= single_succ_edge (bb
)->dest_idx
;
1057 /* BB dominates DEST. There may be many users of the PHI
1058 nodes in BB. However, there is still a trivial case we
1059 can handle. If the result of every PHI in BB is used
1060 only by a PHI in DEST, then we can trivially merge the
1061 PHI nodes from BB into DEST. */
1062 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
);
1065 gphi
*phi
= gsi
.phi ();
1066 tree result
= gimple_phi_result (phi
);
1067 use_operand_p imm_use
;
1070 /* If the PHI's result is never used, then we can just
1072 if (has_zero_uses (result
))
1075 /* Get the single use of the result of this PHI node. */
1076 if (!single_imm_use (result
, &imm_use
, &use_stmt
)
1077 || gimple_code (use_stmt
) != GIMPLE_PHI
1078 || gimple_bb (use_stmt
) != dest
1079 || gimple_phi_arg_def (use_stmt
, dest_idx
) != result
)
1083 /* If the loop above iterated through all the PHI nodes
1084 in BB, then we can merge the PHIs from BB into DEST. */
1085 if (gsi_end_p (gsi
))
1090 /* Now let's drain WORKLIST. */
1091 bool changed
= false;
1092 while (current
!= worklist
)
1095 changed
|= remove_forwarder_block_with_phi (bb
);
1099 /* Removing forwarder blocks can cause formerly irreducible loops
1100 to become reducible if we merged two entry blocks. */
1103 loops_state_set (LOOPS_NEED_FIXUP
);
1111 make_pass_merge_phi (gcc::context
*ctxt
)
1113 return new pass_merge_phi (ctxt
);
1116 /* Pass: cleanup the CFG just before expanding trees to RTL.
1117 This is just a round of label cleanups and case node grouping
1118 because after the tree optimizers have run such cleanups may
1122 execute_cleanup_cfg_post_optimizing (void)
1124 unsigned int todo
= execute_fixup_cfg ();
1125 if (cleanup_tree_cfg ())
1127 todo
&= ~TODO_cleanup_cfg
;
1128 todo
|= TODO_update_ssa
;
1130 maybe_remove_unreachable_handlers ();
1131 cleanup_dead_labels ();
1132 group_case_labels ();
1133 if ((flag_compare_debug_opt
|| flag_compare_debug
)
1134 && flag_dump_final_insns
)
1136 FILE *final_output
= fopen (flag_dump_final_insns
, "a");
1140 error ("could not open final insn dump file %qs: %m",
1141 flag_dump_final_insns
);
1142 flag_dump_final_insns
= NULL
;
1146 int save_unnumbered
= flag_dump_unnumbered
;
1147 int save_noaddr
= flag_dump_noaddr
;
1149 flag_dump_noaddr
= flag_dump_unnumbered
= 1;
1150 fprintf (final_output
, "\n");
1151 dump_enumerated_decls (final_output
, dump_flags
| TDF_NOUID
);
1152 flag_dump_noaddr
= save_noaddr
;
1153 flag_dump_unnumbered
= save_unnumbered
;
1154 if (fclose (final_output
))
1156 error ("could not close final insn dump file %qs: %m",
1157 flag_dump_final_insns
);
1158 flag_dump_final_insns
= NULL
;
1167 const pass_data pass_data_cleanup_cfg_post_optimizing
=
1169 GIMPLE_PASS
, /* type */
1170 "optimized", /* name */
1171 OPTGROUP_NONE
, /* optinfo_flags */
1172 TV_TREE_CLEANUP_CFG
, /* tv_id */
1173 PROP_cfg
, /* properties_required */
1174 0, /* properties_provided */
1175 0, /* properties_destroyed */
1176 0, /* todo_flags_start */
1177 TODO_remove_unused_locals
, /* todo_flags_finish */
1180 class pass_cleanup_cfg_post_optimizing
: public gimple_opt_pass
1183 pass_cleanup_cfg_post_optimizing (gcc::context
*ctxt
)
1184 : gimple_opt_pass (pass_data_cleanup_cfg_post_optimizing
, ctxt
)
1187 /* opt_pass methods: */
1188 virtual unsigned int execute (function
*)
1190 return execute_cleanup_cfg_post_optimizing ();
1193 }; // class pass_cleanup_cfg_post_optimizing
1198 make_pass_cleanup_cfg_post_optimizing (gcc::context
*ctxt
)
1200 return new pass_cleanup_cfg_post_optimizing (ctxt
);