1 /* CFG cleanup for trees.
2 Copyright (C) 2001-2015 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"
27 #include "double-int.h"
34 #include "fold-const.h"
37 #include "hard-reg-set.h"
39 #include "dominance.h"
42 #include "cfgcleanup.h"
43 #include "basic-block.h"
44 #include "diagnostic-core.h"
46 #include "langhooks.h"
47 #include "tree-ssa-alias.h"
48 #include "internal-fn.h"
50 #include "gimple-expr.h"
54 #include "gimple-iterator.h"
55 #include "gimple-ssa.h"
57 #include "tree-phinodes.h"
58 #include "ssa-iterators.h"
59 #include "stringpool.h"
60 #include "tree-ssanames.h"
61 #include "tree-ssa-loop-manip.h"
64 #include "statistics.h"
66 #include "fixed-value.h"
67 #include "insn-config.h"
78 #include "tree-pass.h"
81 #include "tree-ssa-propagate.h"
82 #include "tree-scalar-evolution.h"
84 /* The set of blocks in that at least one of the following changes happened:
85 -- the statement at the end of the block was changed
86 -- the block was newly created
87 -- the set of the predecessors of the block changed
88 -- the set of the successors of the block changed
89 ??? Maybe we could track these changes separately, since they determine
90 what cleanups it makes sense to try on the block. */
91 bitmap cfgcleanup_altered_bbs;
93 /* Remove any fallthru edge from EV. Return true if an edge was removed. */
96 remove_fallthru_edge (vec<edge, va_gc> *ev)
101 FOR_EACH_EDGE (e, ei, ev)
102 if ((e->flags & EDGE_FALLTHRU) != 0)
104 if (e->flags & EDGE_COMPLEX)
105 e->flags &= ~EDGE_FALLTHRU;
107 remove_edge_and_dominated_blocks (e);
114 /* Disconnect an unreachable block in the control expression starting
118 cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
122 gimple stmt = gsi_stmt (gsi);
125 if (!single_succ_p (bb))
132 fold_defer_overflow_warnings ();
133 loc = gimple_location (stmt);
134 switch (gimple_code (stmt))
137 val = fold_binary_loc (loc, gimple_cond_code (stmt),
139 gimple_cond_lhs (stmt),
140 gimple_cond_rhs (stmt));
144 val = gimple_switch_index (as_a <gswitch *> (stmt));
150 taken_edge = find_taken_edge (bb, val);
153 fold_undefer_and_ignore_overflow_warnings ();
157 /* Remove all the edges except the one that is always executed. */
159 for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
165 fold_undefer_overflow_warnings
166 (true, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
170 taken_edge->probability += e->probability;
171 taken_edge->count += e->count;
172 remove_edge_and_dominated_blocks (e);
179 fold_undefer_and_ignore_overflow_warnings ();
180 if (taken_edge->probability > REG_BR_PROB_BASE)
181 taken_edge->probability = REG_BR_PROB_BASE;
184 taken_edge = single_succ_edge (bb);
186 bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
187 gsi_remove (&gsi, true);
188 taken_edge->flags = EDGE_FALLTHRU;
193 /* Cleanup the GF_CALL_CTRL_ALTERING flag according to
194 to updated gimple_call_flags. */
197 cleanup_call_ctrl_altering_flag (gimple bb_end)
199 if (!is_gimple_call (bb_end)
200 || !gimple_call_ctrl_altering_p (bb_end))
203 int flags = gimple_call_flags (bb_end);
204 if (((flags & (ECF_CONST | ECF_PURE))
205 && !(flags & ECF_LOOPING_CONST_OR_PURE))
206 || (flags & ECF_LEAF))
207 gimple_call_set_ctrl_altering (bb_end, false);
210 /* Try to remove superfluous control structures in basic block BB. Returns
211 true if anything changes. */
214 cleanup_control_flow_bb (basic_block bb)
216 gimple_stmt_iterator gsi;
220 /* If the last statement of the block could throw and now cannot,
221 we need to prune cfg. */
222 retval |= gimple_purge_dead_eh_edges (bb);
224 gsi = gsi_last_bb (bb);
228 stmt = gsi_stmt (gsi);
230 /* Try to cleanup ctrl altering flag for call which ends bb. */
231 cleanup_call_ctrl_altering_flag (stmt);
233 if (gimple_code (stmt) == GIMPLE_COND
234 || gimple_code (stmt) == GIMPLE_SWITCH)
235 retval |= cleanup_control_expr_graph (bb, gsi);
236 else if (gimple_code (stmt) == GIMPLE_GOTO
237 && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR
238 && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt), 0))
241 /* If we had a computed goto which has a compile-time determinable
242 destination, then we can eliminate the goto. */
246 basic_block target_block;
248 /* First look at all the outgoing edges. Delete any outgoing
249 edges which do not go to the right block. For the one
250 edge which goes to the right block, fix up its flags. */
251 label = TREE_OPERAND (gimple_goto_dest (stmt), 0);
252 target_block = label_to_block (label);
253 for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
255 if (e->dest != target_block)
256 remove_edge_and_dominated_blocks (e);
259 /* Turn off the EDGE_ABNORMAL flag. */
260 e->flags &= ~EDGE_ABNORMAL;
262 /* And set EDGE_FALLTHRU. */
263 e->flags |= EDGE_FALLTHRU;
268 bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
269 bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index);
271 /* Remove the GOTO_EXPR as it is not needed. The CFG has all the
272 relevant information we need. */
273 gsi_remove (&gsi, true);
277 /* Check for indirect calls that have been turned into
279 else if (is_gimple_call (stmt)
280 && gimple_call_noreturn_p (stmt)
281 && remove_fallthru_edge (bb->succs))
287 /* Return true if basic block BB does nothing except pass control
288 flow to another block and that we can safely insert a label at
289 the start of the successor block.
291 As a precondition, we require that BB be not equal to
295 tree_forwarder_block_p (basic_block bb, bool phi_wanted)
297 gimple_stmt_iterator gsi;
300 /* BB must have a single outgoing edge. */
301 if (single_succ_p (bb) != 1
302 /* If PHI_WANTED is false, BB must not have any PHI nodes.
303 Otherwise, BB must have PHI nodes. */
304 || gimple_seq_empty_p (phi_nodes (bb)) == phi_wanted
305 /* BB may not be a predecessor of the exit block. */
306 || single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)
307 /* Nor should this be an infinite loop. */
308 || single_succ (bb) == bb
309 /* BB may not have an abnormal outgoing edge. */
310 || (single_succ_edge (bb)->flags & EDGE_ABNORMAL))
313 gcc_checking_assert (bb != ENTRY_BLOCK_PTR_FOR_FN (cfun));
315 locus = single_succ_edge (bb)->goto_locus;
317 /* There should not be an edge coming from entry, or an EH edge. */
322 FOR_EACH_EDGE (e, ei, bb->preds)
323 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun) || (e->flags & EDGE_EH))
325 /* If goto_locus of any of the edges differs, prevent removing
326 the forwarder block for -O0. */
327 else if (optimize == 0 && e->goto_locus != locus)
331 /* Now walk through the statements backward. We can ignore labels,
332 anything else means this is not a forwarder block. */
333 for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
335 gimple stmt = gsi_stmt (gsi);
337 switch (gimple_code (stmt))
340 if (DECL_NONLOCAL (gimple_label_label (as_a <glabel *> (stmt))))
342 if (optimize == 0 && gimple_location (stmt) != locus)
346 /* ??? For now, hope there's a corresponding debug
347 assignment at the destination. */
359 /* Protect loop headers. */
360 if (bb->loop_father->header == bb)
363 dest = EDGE_SUCC (bb, 0)->dest;
364 /* Protect loop preheaders and latches if requested. */
365 if (dest->loop_father->header == dest)
367 if (bb->loop_father == dest->loop_father)
369 if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
371 /* If bb doesn't have a single predecessor we'd make this
372 loop have multiple latches. Don't do that if that
373 would in turn require disambiguating them. */
374 return (single_pred_p (bb)
375 || loops_state_satisfies_p
376 (LOOPS_MAY_HAVE_MULTIPLE_LATCHES));
378 else if (bb->loop_father == loop_outer (dest->loop_father))
379 return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS);
380 /* Always preserve other edges into loop headers that are
381 not simple latches or preheaders. */
389 /* If all the PHI nodes in DEST have alternatives for E1 and E2 and
390 those alternatives are equal in each of the PHI nodes, then return
391 true, else return false. */
394 phi_alternatives_equal (basic_block dest, edge e1, edge e2)
396 int n1 = e1->dest_idx;
397 int n2 = e2->dest_idx;
400 for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
402 gphi *phi = gsi.phi ();
403 tree val1 = gimple_phi_arg_def (phi, n1);
404 tree val2 = gimple_phi_arg_def (phi, n2);
406 gcc_assert (val1 != NULL_TREE);
407 gcc_assert (val2 != NULL_TREE);
409 if (!operand_equal_for_phi_arg_p (val1, val2))
416 /* Removes forwarder block BB. Returns false if this failed. */
419 remove_forwarder_block (basic_block bb)
421 edge succ = single_succ_edge (bb), e, s;
422 basic_block dest = succ->dest;
425 gimple_stmt_iterator gsi, gsi_to;
426 bool can_move_debug_stmts;
428 /* We check for infinite loops already in tree_forwarder_block_p.
429 However it may happen that the infinite loop is created
430 afterwards due to removal of forwarders. */
434 /* If the destination block consists of a nonlocal label or is a
435 EH landing pad, do not merge it. */
436 label = first_stmt (dest);
438 if (glabel *label_stmt = dyn_cast <glabel *> (label))
439 if (DECL_NONLOCAL (gimple_label_label (label_stmt))
440 || EH_LANDING_PAD_NR (gimple_label_label (label_stmt)) != 0)
443 /* If there is an abnormal edge to basic block BB, but not into
444 dest, problems might occur during removal of the phi node at out
445 of ssa due to overlapping live ranges of registers.
447 If there is an abnormal edge in DEST, the problems would occur
448 anyway since cleanup_dead_labels would then merge the labels for
449 two different eh regions, and rest of exception handling code
452 So if there is an abnormal edge to BB, proceed only if there is
453 no abnormal edge to DEST and there are no phi nodes in DEST. */
454 if (bb_has_abnormal_pred (bb)
455 && (bb_has_abnormal_pred (dest)
456 || !gimple_seq_empty_p (phi_nodes (dest))))
459 /* If there are phi nodes in DEST, and some of the blocks that are
460 predecessors of BB are also predecessors of DEST, check that the
461 phi node arguments match. */
462 if (!gimple_seq_empty_p (phi_nodes (dest)))
464 FOR_EACH_EDGE (e, ei, bb->preds)
466 s = find_edge (e->src, dest);
470 if (!phi_alternatives_equal (dest, succ, s))
475 can_move_debug_stmts = MAY_HAVE_DEBUG_STMTS && single_pred_p (dest);
477 basic_block pred = NULL;
478 if (single_pred_p (bb))
479 pred = single_pred (bb);
481 /* Redirect the edges. */
482 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
484 bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index);
486 if (e->flags & EDGE_ABNORMAL)
488 /* If there is an abnormal edge, redirect it anyway, and
489 move the labels to the new block to make it legal. */
490 s = redirect_edge_succ_nodup (e, dest);
493 s = redirect_edge_and_branch (e, dest);
497 /* Create arguments for the phi nodes, since the edge was not
499 for (gphi_iterator psi = gsi_start_phis (dest);
503 gphi *phi = psi.phi ();
504 source_location l = gimple_phi_arg_location_from_edge (phi, succ);
505 tree def = gimple_phi_arg_def (phi, succ->dest_idx);
506 add_phi_arg (phi, unshare_expr (def), s, l);
511 /* Move nonlocal labels and computed goto targets as well as user
512 defined labels and labels with an EH landing pad number to the
513 new block, so that the redirection of the abnormal edges works,
514 jump targets end up in a sane place and debug information for
515 labels is retained. */
516 gsi_to = gsi_start_bb (dest);
517 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
520 label = gsi_stmt (gsi);
521 if (is_gimple_debug (label))
523 decl = gimple_label_label (as_a <glabel *> (label));
524 if (EH_LANDING_PAD_NR (decl) != 0
525 || DECL_NONLOCAL (decl)
526 || FORCED_LABEL (decl)
527 || !DECL_ARTIFICIAL (decl))
529 gsi_remove (&gsi, false);
530 gsi_insert_before (&gsi_to, label, GSI_SAME_STMT);
536 /* Move debug statements if the destination has a single predecessor. */
537 if (can_move_debug_stmts)
539 gsi_to = gsi_after_labels (dest);
540 for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); )
542 gimple debug = gsi_stmt (gsi);
543 if (!is_gimple_debug (debug))
545 gsi_remove (&gsi, false);
546 gsi_insert_before (&gsi_to, debug, GSI_SAME_STMT);
550 bitmap_set_bit (cfgcleanup_altered_bbs, dest->index);
552 /* Update the dominators. */
553 if (dom_info_available_p (CDI_DOMINATORS))
555 basic_block dom, dombb, domdest;
557 dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
558 domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
561 /* Shortcut to avoid calling (relatively expensive)
562 nearest_common_dominator unless necessary. */
566 dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
568 set_immediate_dominator (CDI_DOMINATORS, dest, dom);
571 /* Adjust latch infomation of BB's parent loop as otherwise
572 the cfg hook has a hard time not to kill the loop. */
573 if (current_loops && bb->loop_father->latch == bb)
574 bb->loop_father->latch = pred;
576 /* And kill the forwarder block. */
577 delete_basic_block (bb);
582 /* STMT is a call that has been discovered noreturn. Fixup the CFG
583 and remove LHS. Return true if something changed. */
586 fixup_noreturn_call (gimple stmt)
588 basic_block bb = gimple_bb (stmt);
590 if (gimple_call_builtin_p (stmt, BUILT_IN_RETURN))
593 /* First split basic block if stmt is not last. */
594 if (stmt != gsi_stmt (gsi_last_bb (bb)))
596 if (stmt == gsi_stmt (gsi_last_nondebug_bb (bb)))
598 /* Don't split if there are only debug stmts
599 after stmt, that can result in -fcompare-debug
600 failures. Remove the debug stmts instead,
601 they should be all unreachable anyway. */
602 gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
603 for (gsi_next (&gsi); !gsi_end_p (gsi); )
604 gsi_remove (&gsi, true);
607 split_block (bb, stmt);
610 /* If there is an LHS, remove it. */
611 tree lhs = gimple_call_lhs (stmt);
614 gimple_call_set_lhs (stmt, NULL_TREE);
616 /* We need to fix up the SSA name to avoid checking errors. */
617 if (TREE_CODE (lhs) == SSA_NAME)
619 tree new_var = create_tmp_reg (TREE_TYPE (lhs));
620 SET_SSA_NAME_VAR_OR_IDENTIFIER (lhs, new_var);
621 SSA_NAME_DEF_STMT (lhs) = gimple_build_nop ();
622 set_ssa_default_def (cfun, new_var, lhs);
628 /* Mark the call as altering control flow. */
629 gimple_call_set_ctrl_altering (stmt, true);
631 return remove_fallthru_edge (bb->succs);
635 /* Tries to cleanup cfg in basic block BB. Returns true if anything
639 cleanup_tree_cfg_bb (basic_block bb)
641 bool retval = cleanup_control_flow_bb (bb);
643 if (tree_forwarder_block_p (bb, false)
644 && remove_forwarder_block (bb))
647 /* Merging the blocks may create new opportunities for folding
648 conditional branches (due to the elimination of single-valued PHI
650 if (single_succ_p (bb)
651 && can_merge_blocks_p (bb, single_succ (bb)))
653 merge_blocks (bb, single_succ (bb));
660 /* Iterate the cfg cleanups, while anything changes. */
663 cleanup_tree_cfg_1 (void)
669 /* Prepare the worklists of altered blocks. */
670 cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL);
672 /* During forwarder block cleanup, we may redirect edges out of
673 SWITCH_EXPRs, which can get expensive. So we want to enable
674 recording of edge to CASE_LABEL_EXPR. */
675 start_recording_case_labels ();
677 /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB_FN,
678 since the basic blocks may get removed. */
679 n = last_basic_block_for_fn (cfun);
680 for (i = NUM_FIXED_BLOCKS; i < n; i++)
682 bb = BASIC_BLOCK_FOR_FN (cfun, i);
684 retval |= cleanup_tree_cfg_bb (bb);
687 /* Now process the altered blocks, as long as any are available. */
688 while (!bitmap_empty_p (cfgcleanup_altered_bbs))
690 i = bitmap_first_set_bit (cfgcleanup_altered_bbs);
691 bitmap_clear_bit (cfgcleanup_altered_bbs, i);
692 if (i < NUM_FIXED_BLOCKS)
695 bb = BASIC_BLOCK_FOR_FN (cfun, i);
699 retval |= cleanup_tree_cfg_bb (bb);
702 end_recording_case_labels ();
703 BITMAP_FREE (cfgcleanup_altered_bbs);
708 /* Remove unreachable blocks and other miscellaneous clean up work.
709 Return true if the flowgraph was modified, false otherwise. */
712 cleanup_tree_cfg_noloop (void)
716 timevar_push (TV_TREE_CLEANUP_CFG);
718 /* Iterate until there are no more cleanups left to do. If any
719 iteration changed the flowgraph, set CHANGED to true.
721 If dominance information is available, there cannot be any unreachable
723 if (!dom_info_available_p (CDI_DOMINATORS))
725 changed = delete_unreachable_blocks ();
726 calculate_dominance_info (CDI_DOMINATORS);
730 #ifdef ENABLE_CHECKING
731 verify_dominators (CDI_DOMINATORS);
736 changed |= cleanup_tree_cfg_1 ();
738 gcc_assert (dom_info_available_p (CDI_DOMINATORS));
741 #ifdef ENABLE_CHECKING
745 timevar_pop (TV_TREE_CLEANUP_CFG);
747 if (changed && current_loops)
748 loops_state_set (LOOPS_NEED_FIXUP);
753 /* Repairs loop structures. */
756 repair_loop_structures (void)
759 unsigned n_new_loops;
761 calculate_dominance_info (CDI_DOMINATORS);
763 timevar_push (TV_REPAIR_LOOPS);
764 changed_bbs = BITMAP_ALLOC (NULL);
765 n_new_loops = fix_loop_structure (changed_bbs);
767 /* This usually does nothing. But sometimes parts of cfg that originally
768 were inside a loop get out of it due to edge removal (since they
769 become unreachable by back edges from latch). Also a former
770 irreducible loop can become reducible - in this case force a full
771 rewrite into loop-closed SSA form. */
772 if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
773 rewrite_into_loop_closed_ssa (n_new_loops ? NULL : changed_bbs,
776 BITMAP_FREE (changed_bbs);
778 #ifdef ENABLE_CHECKING
779 verify_loop_structure ();
783 timevar_pop (TV_REPAIR_LOOPS);
786 /* Cleanup cfg and repair loop structures. */
789 cleanup_tree_cfg (void)
791 bool changed = cleanup_tree_cfg_noloop ();
793 if (current_loops != NULL
794 && loops_state_satisfies_p (LOOPS_NEED_FIXUP))
795 repair_loop_structures ();
800 /* Tries to merge the PHI nodes at BB into those at BB's sole successor.
801 Returns true if successful. */
804 remove_forwarder_block_with_phi (basic_block bb)
806 edge succ = single_succ_edge (bb);
807 basic_block dest = succ->dest;
809 basic_block dombb, domdest, dom;
811 /* We check for infinite loops already in tree_forwarder_block_p.
812 However it may happen that the infinite loop is created
813 afterwards due to removal of forwarders. */
817 /* If the destination block consists of a nonlocal label, do not
819 label = first_stmt (dest);
821 if (glabel *label_stmt = dyn_cast <glabel *> (label))
822 if (DECL_NONLOCAL (gimple_label_label (label_stmt)))
825 /* Record BB's single pred in case we need to update the father
826 loop's latch information later. */
827 basic_block pred = NULL;
828 if (single_pred_p (bb))
829 pred = single_pred (bb);
831 /* Redirect each incoming edge to BB to DEST. */
832 while (EDGE_COUNT (bb->preds) > 0)
834 edge e = EDGE_PRED (bb, 0), s;
837 s = find_edge (e->src, dest);
840 /* We already have an edge S from E->src to DEST. If S and
841 E->dest's sole successor edge have the same PHI arguments
842 at DEST, redirect S to DEST. */
843 if (phi_alternatives_equal (dest, s, succ))
845 e = redirect_edge_and_branch (e, dest);
846 redirect_edge_var_map_clear (e);
850 /* PHI arguments are different. Create a forwarder block by
851 splitting E so that we can merge PHI arguments on E to
853 e = single_succ_edge (split_edge (e));
856 s = redirect_edge_and_branch (e, dest);
858 /* redirect_edge_and_branch must not create a new edge. */
861 /* Add to the PHI nodes at DEST each PHI argument removed at the
863 for (gsi = gsi_start_phis (dest);
867 gphi *phi = gsi.phi ();
868 tree def = gimple_phi_arg_def (phi, succ->dest_idx);
869 source_location locus = gimple_phi_arg_location_from_edge (phi, succ);
871 if (TREE_CODE (def) == SSA_NAME)
873 /* If DEF is one of the results of PHI nodes removed during
874 redirection, replace it with the PHI argument that used
876 vec<edge_var_map> *head = redirect_edge_var_map_vector (e);
877 size_t length = head ? head->length () : 0;
878 for (size_t i = 0; i < length; i++)
880 edge_var_map *vm = &(*head)[i];
881 tree old_arg = redirect_edge_var_map_result (vm);
882 tree new_arg = redirect_edge_var_map_def (vm);
887 locus = redirect_edge_var_map_location (vm);
893 add_phi_arg (phi, def, s, locus);
896 redirect_edge_var_map_clear (e);
899 /* Update the dominators. */
900 dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
901 domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
904 /* Shortcut to avoid calling (relatively expensive)
905 nearest_common_dominator unless necessary. */
909 dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
911 set_immediate_dominator (CDI_DOMINATORS, dest, dom);
913 /* Adjust latch infomation of BB's parent loop as otherwise
914 the cfg hook has a hard time not to kill the loop. */
915 if (current_loops && bb->loop_father->latch == bb)
916 bb->loop_father->latch = pred;
918 /* Remove BB since all of BB's incoming edges have been redirected
920 delete_basic_block (bb);
925 /* This pass merges PHI nodes if one feeds into another. For example,
926 suppose we have the following:
933 # tem_6 = PHI <tem_17(8), tem_23(7)>;
936 # tem_3 = PHI <tem_6(9), tem_2(5)>;
939 Then we merge the first PHI node into the second one like so:
946 # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>;
952 const pass_data pass_data_merge_phi =
954 GIMPLE_PASS, /* type */
955 "mergephi", /* name */
956 OPTGROUP_NONE, /* optinfo_flags */
957 TV_TREE_MERGE_PHI, /* tv_id */
958 ( PROP_cfg | PROP_ssa ), /* properties_required */
959 0, /* properties_provided */
960 0, /* properties_destroyed */
961 0, /* todo_flags_start */
962 0, /* todo_flags_finish */
965 class pass_merge_phi : public gimple_opt_pass
968 pass_merge_phi (gcc::context *ctxt)
969 : gimple_opt_pass (pass_data_merge_phi, ctxt)
972 /* opt_pass methods: */
973 opt_pass * clone () { return new pass_merge_phi (m_ctxt); }
974 virtual unsigned int execute (function *);
976 }; // class pass_merge_phi
979 pass_merge_phi::execute (function *fun)
981 basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks_for_fn (fun));
982 basic_block *current = worklist;
985 calculate_dominance_info (CDI_DOMINATORS);
987 /* Find all PHI nodes that we may be able to merge. */
988 FOR_EACH_BB_FN (bb, fun)
992 /* Look for a forwarder block with PHI nodes. */
993 if (!tree_forwarder_block_p (bb, true))
996 dest = single_succ (bb);
998 /* We have to feed into another basic block with PHI
1000 if (gimple_seq_empty_p (phi_nodes (dest))
1001 /* We don't want to deal with a basic block with
1003 || bb_has_abnormal_pred (bb))
1006 if (!dominated_by_p (CDI_DOMINATORS, dest, bb))
1008 /* If BB does not dominate DEST, then the PHI nodes at
1009 DEST must be the only users of the results of the PHI
1016 unsigned int dest_idx = single_succ_edge (bb)->dest_idx;
1018 /* BB dominates DEST. There may be many users of the PHI
1019 nodes in BB. However, there is still a trivial case we
1020 can handle. If the result of every PHI in BB is used
1021 only by a PHI in DEST, then we can trivially merge the
1022 PHI nodes from BB into DEST. */
1023 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
1026 gphi *phi = gsi.phi ();
1027 tree result = gimple_phi_result (phi);
1028 use_operand_p imm_use;
1031 /* If the PHI's result is never used, then we can just
1033 if (has_zero_uses (result))
1036 /* Get the single use of the result of this PHI node. */
1037 if (!single_imm_use (result, &imm_use, &use_stmt)
1038 || gimple_code (use_stmt) != GIMPLE_PHI
1039 || gimple_bb (use_stmt) != dest
1040 || gimple_phi_arg_def (use_stmt, dest_idx) != result)
1044 /* If the loop above iterated through all the PHI nodes
1045 in BB, then we can merge the PHIs from BB into DEST. */
1046 if (gsi_end_p (gsi))
1051 /* Now let's drain WORKLIST. */
1052 bool changed = false;
1053 while (current != worklist)
1056 changed |= remove_forwarder_block_with_phi (bb);
1060 /* Removing forwarder blocks can cause formerly irreducible loops
1061 to become reducible if we merged two entry blocks. */
1064 loops_state_set (LOOPS_NEED_FIXUP);
1072 make_pass_merge_phi (gcc::context *ctxt)
1074 return new pass_merge_phi (ctxt);
1077 /* Pass: cleanup the CFG just before expanding trees to RTL.
1078 This is just a round of label cleanups and case node grouping
1079 because after the tree optimizers have run such cleanups may
1083 execute_cleanup_cfg_post_optimizing (void)
1085 unsigned int todo = execute_fixup_cfg ();
1086 if (cleanup_tree_cfg ())
1088 todo &= ~TODO_cleanup_cfg;
1089 todo |= TODO_update_ssa;
1091 maybe_remove_unreachable_handlers ();
1092 cleanup_dead_labels ();
1093 group_case_labels ();
1094 if ((flag_compare_debug_opt || flag_compare_debug)
1095 && flag_dump_final_insns)
1097 FILE *final_output = fopen (flag_dump_final_insns, "a");
1101 error ("could not open final insn dump file %qs: %m",
1102 flag_dump_final_insns);
1103 flag_dump_final_insns = NULL;
1107 int save_unnumbered = flag_dump_unnumbered;
1108 int save_noaddr = flag_dump_noaddr;
1110 flag_dump_noaddr = flag_dump_unnumbered = 1;
1111 fprintf (final_output, "\n");
1112 dump_enumerated_decls (final_output, dump_flags | TDF_NOUID);
1113 flag_dump_noaddr = save_noaddr;
1114 flag_dump_unnumbered = save_unnumbered;
1115 if (fclose (final_output))
1117 error ("could not close final insn dump file %qs: %m",
1118 flag_dump_final_insns);
1119 flag_dump_final_insns = NULL;
1128 const pass_data pass_data_cleanup_cfg_post_optimizing =
1130 GIMPLE_PASS, /* type */
1131 "optimized", /* name */
1132 OPTGROUP_NONE, /* optinfo_flags */
1133 TV_TREE_CLEANUP_CFG, /* tv_id */
1134 PROP_cfg, /* properties_required */
1135 0, /* properties_provided */
1136 0, /* properties_destroyed */
1137 0, /* todo_flags_start */
1138 TODO_remove_unused_locals, /* todo_flags_finish */
1141 class pass_cleanup_cfg_post_optimizing : public gimple_opt_pass
1144 pass_cleanup_cfg_post_optimizing (gcc::context *ctxt)
1145 : gimple_opt_pass (pass_data_cleanup_cfg_post_optimizing, ctxt)
1148 /* opt_pass methods: */
1149 virtual unsigned int execute (function *)
1151 return execute_cleanup_cfg_post_optimizing ();
1154 }; // class pass_cleanup_cfg_post_optimizing
1159 make_pass_cleanup_cfg_post_optimizing (gcc::context *ctxt)
1161 return new pass_cleanup_cfg_post_optimizing (ctxt);