1 /* Control flow functions for trees.
2 Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
24 #include "coretypes.h"
29 #include "hard-reg-set.h"
30 #include "basic-block.h"
37 #include "langhooks.h"
38 #include "diagnostic.h"
39 #include "tree-flow.h"
41 #include "tree-dump.h"
42 #include "tree-pass.h"
47 /* This file contains functions for building the Control Flow Graph (CFG)
48 for a function tree. */
50 /* Local declarations. */
52 /* Initial capacity for the basic block array. */
53 static const int initial_cfg_capacity = 20;
55 /* Mapping of labels to their associated blocks. This can greatly speed up
56 building of the CFG in code with lots of gotos. */
57 static GTY(()) varray_type label_to_block_map;
62 long num_merged_labels;
65 static struct cfg_stats_d cfg_stats;
67 /* Nonzero if we found a computed goto while building basic blocks. */
68 static bool found_computed_goto;
70 /* Basic blocks and flowgraphs. */
71 static basic_block create_bb (void *, void *, basic_block);
72 static void create_block_annotation (basic_block);
73 static void free_blocks_annotations (void);
74 static void clear_blocks_annotations (void);
75 static void make_blocks (tree);
76 static void factor_computed_gotos (void);
79 static void make_edges (void);
80 static void make_ctrl_stmt_edges (basic_block);
81 static void make_exit_edges (basic_block);
82 static void make_cond_expr_edges (basic_block);
83 static void make_switch_expr_edges (basic_block);
84 static void make_goto_expr_edges (basic_block);
85 static edge tree_redirect_edge_and_branch (edge, basic_block);
86 static edge tree_try_redirect_by_replacing_jump (edge, basic_block);
87 static void split_critical_edges (void);
89 /* Various helpers. */
90 static inline bool stmt_starts_bb_p (tree, tree);
91 static int tree_verify_flow_info (void);
92 static void tree_make_forwarder_block (edge);
93 static bool thread_jumps (void);
94 static bool tree_forwarder_block_p (basic_block);
95 static void bsi_commit_edge_inserts_1 (edge e);
96 static void tree_cfg2vcg (FILE *);
98 /* Flowgraph optimization and cleanup. */
99 static void tree_merge_blocks (basic_block, basic_block);
100 static bool tree_can_merge_blocks_p (basic_block, basic_block);
101 static void remove_bb (basic_block);
102 static void group_case_labels (void);
103 static void cleanup_dead_labels (void);
104 static bool cleanup_control_flow (void);
105 static bool cleanup_control_expr_graph (basic_block, block_stmt_iterator);
106 static edge find_taken_edge_cond_expr (basic_block, tree);
107 static edge find_taken_edge_switch_expr (basic_block, tree);
108 static tree find_case_label_for_value (tree, tree);
109 static bool phi_alternatives_equal (basic_block, edge, edge);
112 /*---------------------------------------------------------------------------
114 ---------------------------------------------------------------------------*/
116 /* Entry point to the CFG builder for trees. TP points to the list of
117 statements to be added to the flowgraph. */
120 build_tree_cfg (tree *tp)
122 /* Register specific tree functions. */
123 tree_register_cfg_hooks ();
125 /* Initialize rbi_pool. */
128 /* Initialize the basic block array. */
131 last_basic_block = 0;
132 VARRAY_BB_INIT (basic_block_info, initial_cfg_capacity, "basic_block_info");
133 memset ((void *) &cfg_stats, 0, sizeof (cfg_stats));
135 /* Build a mapping of labels to their associated blocks. */
136 VARRAY_BB_INIT (label_to_block_map, initial_cfg_capacity,
137 "label to block map");
139 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
140 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
142 found_computed_goto = 0;
145 /* Computed gotos are hell to deal with, especially if there are
146 lots of them with a large number of destinations. So we factor
147 them to a common computed goto location before we build the
148 edge list. After we convert back to normal form, we will un-factor
149 the computed gotos since factoring introduces an unwanted jump. */
150 if (found_computed_goto)
151 factor_computed_gotos ();
153 /* Make sure there is always at least one block, even if its empty. */
154 if (n_basic_blocks == 0)
155 create_empty_bb (ENTRY_BLOCK_PTR);
157 create_block_annotation (ENTRY_BLOCK_PTR);
158 create_block_annotation (EXIT_BLOCK_PTR);
160 /* Adjust the size of the array. */
161 VARRAY_GROW (basic_block_info, n_basic_blocks);
163 /* To speed up statement iterator walks, we first purge dead labels. */
164 cleanup_dead_labels ();
166 /* Group case nodes to reduce the number of edges.
167 We do this after cleaning up dead labels because otherwise we miss
168 a lot of obvious case merging opportunities. */
169 group_case_labels ();
171 /* Create the edges of the flowgraph. */
174 /* Debugging dumps. */
176 /* Write the flowgraph to a VCG file. */
178 int local_dump_flags;
179 FILE *dump_file = dump_begin (TDI_vcg, &local_dump_flags);
182 tree_cfg2vcg (dump_file);
183 dump_end (TDI_vcg, dump_file);
187 /* Dump a textual representation of the flowgraph. */
189 dump_tree_cfg (dump_file, dump_flags);
193 execute_build_cfg (void)
195 build_tree_cfg (&DECL_SAVED_TREE (current_function_decl));
198 struct tree_opt_pass pass_build_cfg =
202 execute_build_cfg, /* execute */
205 0, /* static_pass_number */
206 TV_TREE_CFG, /* tv_id */
207 PROP_gimple_leh, /* properties_required */
208 PROP_cfg, /* properties_provided */
209 0, /* properties_destroyed */
210 0, /* todo_flags_start */
211 TODO_verify_stmts /* todo_flags_finish */
214 /* Search the CFG for any computed gotos. If found, factor them to a
215 common computed goto site. Also record the location of that site so
216 that we can un-factor the gotos after we have converted back to
220 factor_computed_gotos (void)
223 tree factored_label_decl = NULL;
225 tree factored_computed_goto_label = NULL;
226 tree factored_computed_goto = NULL;
228 /* We know there are one or more computed gotos in this function.
229 Examine the last statement in each basic block to see if the block
230 ends with a computed goto. */
234 block_stmt_iterator bsi = bsi_last (bb);
239 last = bsi_stmt (bsi);
241 /* Ignore the computed goto we create when we factor the original
243 if (last == factored_computed_goto)
246 /* If the last statement is a computed goto, factor it. */
247 if (computed_goto_p (last))
251 /* The first time we find a computed goto we need to create
252 the factored goto block and the variable each original
253 computed goto will use for their goto destination. */
254 if (! factored_computed_goto)
256 basic_block new_bb = create_empty_bb (bb);
257 block_stmt_iterator new_bsi = bsi_start (new_bb);
259 /* Create the destination of the factored goto. Each original
260 computed goto will put its desired destination into this
261 variable and jump to the label we create immediately
263 var = create_tmp_var (ptr_type_node, "gotovar");
265 /* Build a label for the new block which will contain the
266 factored computed goto. */
267 factored_label_decl = create_artificial_label ();
268 factored_computed_goto_label
269 = build1 (LABEL_EXPR, void_type_node, factored_label_decl);
270 bsi_insert_after (&new_bsi, factored_computed_goto_label,
273 /* Build our new computed goto. */
274 factored_computed_goto = build1 (GOTO_EXPR, void_type_node, var);
275 bsi_insert_after (&new_bsi, factored_computed_goto,
279 /* Copy the original computed goto's destination into VAR. */
280 assignment = build (MODIFY_EXPR, ptr_type_node,
281 var, GOTO_DESTINATION (last));
282 bsi_insert_before (&bsi, assignment, BSI_SAME_STMT);
284 /* And re-vector the computed goto to the new destination. */
285 GOTO_DESTINATION (last) = factored_label_decl;
291 /* Create annotations for a single basic block. */
294 create_block_annotation (basic_block bb)
296 /* Verify that the tree_annotations field is clear. */
297 if (bb->tree_annotations)
299 bb->tree_annotations = ggc_alloc_cleared (sizeof (struct bb_ann_d));
303 /* Free the annotations for all the basic blocks. */
305 static void free_blocks_annotations (void)
307 clear_blocks_annotations ();
311 /* Clear the annotations for all the basic blocks. */
314 clear_blocks_annotations (void)
318 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
319 bb->tree_annotations = NULL;
323 /* Build a flowgraph for the statement_list STMT_LIST. */
326 make_blocks (tree stmt_list)
328 tree_stmt_iterator i = tsi_start (stmt_list);
330 bool start_new_block = true;
331 bool first_stmt_of_list = true;
332 basic_block bb = ENTRY_BLOCK_PTR;
334 while (!tsi_end_p (i))
341 /* If the statement starts a new basic block or if we have determined
342 in a previous pass that we need to create a new block for STMT, do
344 if (start_new_block || stmt_starts_bb_p (stmt, prev_stmt))
346 if (!first_stmt_of_list)
347 stmt_list = tsi_split_statement_list_before (&i);
348 bb = create_basic_block (stmt_list, NULL, bb);
349 start_new_block = false;
352 /* Now add STMT to BB and create the subgraphs for special statement
354 set_bb_for_stmt (stmt, bb);
356 if (computed_goto_p (stmt))
357 found_computed_goto = true;
359 /* If STMT is a basic block terminator, set START_NEW_BLOCK for the
361 if (stmt_ends_bb_p (stmt))
362 start_new_block = true;
365 first_stmt_of_list = false;
370 /* Create and return a new empty basic block after bb AFTER. */
373 create_bb (void *h, void *e, basic_block after)
380 /* Create and initialize a new basic block. */
382 memset (bb, 0, sizeof (*bb));
384 bb->index = last_basic_block;
386 bb->stmt_list = h ? h : alloc_stmt_list ();
388 /* Add the new block to the linked list of blocks. */
389 link_block (bb, after);
391 /* Grow the basic block array if needed. */
392 if ((size_t) last_basic_block == VARRAY_SIZE (basic_block_info))
394 size_t new_size = last_basic_block + (last_basic_block + 3) / 4;
395 VARRAY_GROW (basic_block_info, new_size);
398 /* Add the newly created block to the array. */
399 BASIC_BLOCK (last_basic_block) = bb;
401 create_block_annotation (bb);
406 initialize_bb_rbi (bb);
411 /*---------------------------------------------------------------------------
413 ---------------------------------------------------------------------------*/
415 /* Join all the blocks in the flowgraph. */
422 /* Create an edge from entry to the first block with executable
424 make_edge (ENTRY_BLOCK_PTR, BASIC_BLOCK (0), EDGE_FALLTHRU);
426 /* Traverse basic block array placing edges. */
429 tree first = first_stmt (bb);
430 tree last = last_stmt (bb);
434 /* Edges for statements that always alter flow control. */
435 if (is_ctrl_stmt (last))
436 make_ctrl_stmt_edges (bb);
438 /* Edges for statements that sometimes alter flow control. */
439 if (is_ctrl_altering_stmt (last))
440 make_exit_edges (bb);
443 /* Finally, if no edges were created above, this is a regular
444 basic block that only needs a fallthru edge. */
445 if (bb->succ == NULL)
446 make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
449 /* We do not care about fake edges, so remove any that the CFG
450 builder inserted for completeness. */
451 remove_fake_edges ();
453 /* Clean up the graph and warn for unreachable code. */
458 /* Create edges for control statement at basic block BB. */
461 make_ctrl_stmt_edges (basic_block bb)
463 tree last = last_stmt (bb);
464 tree first = first_stmt (bb);
466 #if defined ENABLE_CHECKING
467 if (last == NULL_TREE)
471 if (TREE_CODE (first) == LABEL_EXPR
472 && DECL_NONLOCAL (LABEL_EXPR_LABEL (first)))
473 make_edge (ENTRY_BLOCK_PTR, bb, EDGE_ABNORMAL);
475 switch (TREE_CODE (last))
478 make_goto_expr_edges (bb);
482 make_edge (bb, EXIT_BLOCK_PTR, 0);
486 make_cond_expr_edges (bb);
490 make_switch_expr_edges (bb);
494 make_eh_edges (last);
495 /* Yet another NORETURN hack. */
496 if (bb->succ == NULL)
497 make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
506 /* Create exit edges for statements in block BB that alter the flow of
507 control. Statements that alter the control flow are 'goto', 'return'
508 and calls to non-returning functions. */
511 make_exit_edges (basic_block bb)
513 tree last = last_stmt (bb);
515 if (last == NULL_TREE)
518 switch (TREE_CODE (last))
521 /* If this function receives a nonlocal goto, then we need to
522 make edges from this call site to all the nonlocal goto
524 if (TREE_SIDE_EFFECTS (last)
525 && current_function_has_nonlocal_label)
526 make_goto_expr_edges (bb);
528 /* If this statement has reachable exception handlers, then
529 create abnormal edges to them. */
530 make_eh_edges (last);
532 /* Some calls are known not to return. For such calls we create
535 We really need to revamp how we build edges so that it's not
536 such a bloody pain to avoid creating edges for this case since
537 all we do is remove these edges when we're done building the
539 if (call_expr_flags (last) & (ECF_NORETURN | ECF_LONGJMP))
541 make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
545 /* Don't forget the fall-thru edge. */
546 make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
550 /* A MODIFY_EXPR may have a CALL_EXPR on its RHS and the CALL_EXPR
551 may have an abnormal edge. Search the RHS for this case and
552 create any required edges. */
553 if (TREE_CODE (TREE_OPERAND (last, 1)) == CALL_EXPR
554 && TREE_SIDE_EFFECTS (TREE_OPERAND (last, 1))
555 && current_function_has_nonlocal_label)
556 make_goto_expr_edges (bb);
558 make_eh_edges (last);
559 make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
568 /* Create the edges for a COND_EXPR starting at block BB.
569 At this point, both clauses must contain only simple gotos. */
572 make_cond_expr_edges (basic_block bb)
574 tree entry = last_stmt (bb);
575 basic_block then_bb, else_bb;
576 tree then_label, else_label;
578 #if defined ENABLE_CHECKING
579 if (entry == NULL_TREE || TREE_CODE (entry) != COND_EXPR)
583 /* Entry basic blocks for each component. */
584 then_label = GOTO_DESTINATION (COND_EXPR_THEN (entry));
585 else_label = GOTO_DESTINATION (COND_EXPR_ELSE (entry));
586 then_bb = label_to_block (then_label);
587 else_bb = label_to_block (else_label);
589 make_edge (bb, then_bb, EDGE_TRUE_VALUE);
590 make_edge (bb, else_bb, EDGE_FALSE_VALUE);
594 /* Create the edges for a SWITCH_EXPR starting at block BB.
595 At this point, the switch body has been lowered and the
596 SWITCH_LABELS filled in, so this is in effect a multi-way branch. */
599 make_switch_expr_edges (basic_block bb)
601 tree entry = last_stmt (bb);
605 vec = SWITCH_LABELS (entry);
606 n = TREE_VEC_LENGTH (vec);
608 for (i = 0; i < n; ++i)
610 tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
611 basic_block label_bb = label_to_block (lab);
612 make_edge (bb, label_bb, 0);
617 /* Return the basic block holding label DEST. */
620 label_to_block (tree dest)
622 return VARRAY_BB (label_to_block_map, LABEL_DECL_UID (dest));
626 /* Create edges for a goto statement at block BB. */
629 make_goto_expr_edges (basic_block bb)
632 basic_block target_bb;
634 block_stmt_iterator last = bsi_last (bb);
636 goto_t = bsi_stmt (last);
638 /* If the last statement is not a GOTO (i.e., it is a RETURN_EXPR,
639 CALL_EXPR or MODIFY_EXPR), then the edge is an abnormal edge resulting
640 from a nonlocal goto. */
641 if (TREE_CODE (goto_t) != GOTO_EXPR)
643 dest = error_mark_node;
648 dest = GOTO_DESTINATION (goto_t);
651 /* A GOTO to a local label creates normal edges. */
652 if (simple_goto_p (goto_t))
654 edge e = make_edge (bb, label_to_block (dest), EDGE_FALLTHRU);
655 e->goto_locus = EXPR_LOCUS (goto_t);
660 /* Nothing more to do for nonlocal gotos. */
661 if (TREE_CODE (dest) == LABEL_DECL)
664 /* Computed gotos remain. */
667 /* Look for the block starting with the destination label. In the
668 case of a computed goto, make an edge to any label block we find
670 FOR_EACH_BB (target_bb)
672 block_stmt_iterator bsi;
674 for (bsi = bsi_start (target_bb); !bsi_end_p (bsi); bsi_next (&bsi))
676 tree target = bsi_stmt (bsi);
678 if (TREE_CODE (target) != LABEL_EXPR)
682 /* Computed GOTOs. Make an edge to every label block that has
683 been marked as a potential target for a computed goto. */
684 (FORCED_LABEL (LABEL_EXPR_LABEL (target)) && for_call == 0)
685 /* Nonlocal GOTO target. Make an edge to every label block
686 that has been marked as a potential target for a nonlocal
688 || (DECL_NONLOCAL (LABEL_EXPR_LABEL (target)) && for_call == 1))
690 make_edge (bb, target_bb, EDGE_ABNORMAL);
696 /* Degenerate case of computed goto with no labels. */
697 if (!for_call && !bb->succ)
698 make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
702 /*---------------------------------------------------------------------------
704 ---------------------------------------------------------------------------*/
706 /* Remove unreachable blocks and other miscellaneous clean up work. */
709 cleanup_tree_cfg (void)
711 bool something_changed = true;
713 timevar_push (TV_TREE_CLEANUP_CFG);
715 /* These three transformations can cascade, so we iterate on them until
717 while (something_changed)
719 something_changed = cleanup_control_flow ();
720 something_changed |= thread_jumps ();
721 something_changed |= delete_unreachable_blocks ();
724 /* Merging the blocks creates no new opportunities for the other
725 optimizations, so do it here. */
730 #ifdef ENABLE_CHECKING
733 timevar_pop (TV_TREE_CLEANUP_CFG);
737 /* Cleanup useless labels in basic blocks. This is something we wish
738 to do early because it allows us to group case labels before creating
739 the edges for the CFG, and it speeds up block statement iterators in
741 We only run this pass once, running it more than once is probably not
744 /* A map from basic block index to the leading label of that block. */
745 static tree *label_for_bb;
747 /* Callback for for_each_eh_region. Helper for cleanup_dead_labels. */
749 update_eh_label (struct eh_region *region)
751 tree old_label = get_eh_region_tree_label (region);
754 tree new_label = label_for_bb[label_to_block (old_label)->index];
755 set_eh_region_tree_label (region, new_label);
759 /* Cleanup redundant labels. This is a three-steo process:
760 1) Find the leading label for each block.
761 2) Redirect all references to labels to the leading labels.
762 3) Cleanup all useless labels. */
765 cleanup_dead_labels (void)
768 label_for_bb = xcalloc (last_basic_block, sizeof (tree));
770 /* Find a suitable label for each block. We use the first user-defined
771 label is there is one, or otherwise just the first label we see. */
774 block_stmt_iterator i;
776 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
778 tree label, stmt = bsi_stmt (i);
780 if (TREE_CODE (stmt) != LABEL_EXPR)
783 label = LABEL_EXPR_LABEL (stmt);
785 /* If we have not yet seen a label for the current block,
786 remember this one and see if there are more labels. */
787 if (! label_for_bb[bb->index])
789 label_for_bb[bb->index] = label;
793 /* If we did see a label for the current block already, but it
794 is an artificially created label, replace it if the current
795 label is a user defined label. */
796 if (! DECL_ARTIFICIAL (label)
797 && DECL_ARTIFICIAL (label_for_bb[bb->index]))
799 label_for_bb[bb->index] = label;
805 /* Now redirect all jumps/branches to the selected label.
806 First do so for each block ending in a control statement. */
809 tree stmt = last_stmt (bb);
813 switch (TREE_CODE (stmt))
817 tree true_branch, false_branch;
818 basic_block true_bb, false_bb;
820 true_branch = COND_EXPR_THEN (stmt);
821 false_branch = COND_EXPR_ELSE (stmt);
822 true_bb = label_to_block (GOTO_DESTINATION (true_branch));
823 false_bb = label_to_block (GOTO_DESTINATION (false_branch));
825 GOTO_DESTINATION (true_branch) = label_for_bb[true_bb->index];
826 GOTO_DESTINATION (false_branch) = label_for_bb[false_bb->index];
834 tree vec = SWITCH_LABELS (stmt);
835 size_t n = TREE_VEC_LENGTH (vec);
837 /* Replace all destination labels. */
838 for (i = 0; i < n; ++i)
840 tree label = CASE_LABEL (TREE_VEC_ELT (vec, i));
842 CASE_LABEL (TREE_VEC_ELT (vec, i)) =
843 label_for_bb[label_to_block (label)->index];
849 /* We have to handle GOTO_EXPRs until they're removed, and we don't
850 remove them until after we've created the CFG edges. */
853 tree label = GOTO_DESTINATION (stmt);
854 if (! computed_goto_p (stmt))
855 GOTO_DESTINATION (stmt) =
856 label_for_bb[label_to_block (label)->index];
865 for_each_eh_region (update_eh_label);
867 /* Finally, purge dead labels. All user-defined labels and labels that
868 can be the target of non-local gotos are preserved. */
871 block_stmt_iterator i;
872 tree label_for_this_bb = label_for_bb[bb->index];
874 if (! label_for_this_bb)
877 for (i = bsi_start (bb); !bsi_end_p (i); )
879 tree label, stmt = bsi_stmt (i);
881 if (TREE_CODE (stmt) != LABEL_EXPR)
884 label = LABEL_EXPR_LABEL (stmt);
886 if (label == label_for_this_bb
887 || ! DECL_ARTIFICIAL (label)
888 || DECL_NONLOCAL (label))
898 /* Look for blocks ending in a multiway branch (a SWITCH_EXPR in GIMPLE),
899 and scan the sorted vector of cases. Combine the ones jumping to the
901 Eg. three separate entries 1: 2: 3: become one entry 1..3: */
904 group_case_labels (void)
910 tree stmt = last_stmt (bb);
911 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
913 tree labels = SWITCH_LABELS (stmt);
914 int old_size = TREE_VEC_LENGTH (labels);
915 int i, j, new_size = old_size;
917 /* Look for possible opportunities to merge cases.
918 Ignore the last element of the label vector because it
919 must be the default case. */
921 while (i < old_size - 2)
923 tree base_case, base_label, base_high, type;
924 base_case = TREE_VEC_ELT (labels, i);
929 type = TREE_TYPE (CASE_LOW (base_case));
930 base_label = CASE_LABEL (base_case);
931 base_high = CASE_HIGH (base_case) ?
932 CASE_HIGH (base_case) : CASE_LOW (base_case);
934 /* Try to merge case labels. Break out when we reach the end
935 of the label vector or when we cannot merge the next case
936 label with the current one. */
937 while (i < old_size - 2)
939 tree merge_case = TREE_VEC_ELT (labels, ++i);
940 tree merge_label = CASE_LABEL (merge_case);
941 tree t = int_const_binop (PLUS_EXPR, base_high,
942 integer_one_node, 1);
944 /* Merge the cases if they jump to the same place,
945 and their ranges are consecutive. */
946 if (merge_label == base_label
947 && tree_int_cst_equal (CASE_LOW (merge_case), t))
949 base_high = CASE_HIGH (merge_case) ?
950 CASE_HIGH (merge_case) : CASE_LOW (merge_case);
951 CASE_HIGH (base_case) = base_high;
952 TREE_VEC_ELT (labels, i) = NULL_TREE;
960 /* Compress the case labels in the label vector, and adjust the
961 length of the vector. */
962 for (i = 0, j = 0; i < new_size; i++)
964 while (! TREE_VEC_ELT (labels, j))
966 TREE_VEC_ELT (labels, i) = TREE_VEC_ELT (labels, j++);
968 TREE_VEC_LENGTH (labels) = new_size;
973 /* Checks whether we can merge block B into block A. */
976 tree_can_merge_blocks_p (basic_block a, basic_block b)
979 block_stmt_iterator bsi;
982 || a->succ->succ_next)
985 if (a->succ->flags & EDGE_ABNORMAL)
988 if (a->succ->dest != b)
991 if (b == EXIT_BLOCK_PTR)
994 if (b->pred->pred_next)
997 /* If A ends by a statement causing exceptions or something similar, we
998 cannot merge the blocks. */
999 stmt = last_stmt (a);
1000 if (stmt && stmt_ends_bb_p (stmt))
1003 /* Do not allow a block with only a non-local label to be merged. */
1004 if (stmt && TREE_CODE (stmt) == LABEL_EXPR
1005 && DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt)))
1008 /* There may be no phi nodes at the start of b. Most of these degenerate
1009 phi nodes should be cleaned up by kill_redundant_phi_nodes. */
1013 /* Do not remove user labels. */
1014 for (bsi = bsi_start (b); !bsi_end_p (bsi); bsi_next (&bsi))
1016 stmt = bsi_stmt (bsi);
1017 if (TREE_CODE (stmt) != LABEL_EXPR)
1019 if (!DECL_ARTIFICIAL (LABEL_EXPR_LABEL (stmt)))
1027 /* Merge block B into block A. */
1030 tree_merge_blocks (basic_block a, basic_block b)
1032 block_stmt_iterator bsi;
1033 tree_stmt_iterator last;
1036 fprintf (dump_file, "Merging blocks %d and %d\n", a->index, b->index);
1038 /* Ensure that B follows A. */
1039 move_block_after (b, a);
1041 if (!(a->succ->flags & EDGE_FALLTHRU))
1045 && stmt_ends_bb_p (last_stmt (a)))
1048 /* Remove labels from B and set bb_for_stmt to A for other statements. */
1049 for (bsi = bsi_start (b); !bsi_end_p (bsi);)
1051 if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
1055 set_bb_for_stmt (bsi_stmt (bsi), a);
1060 /* Merge the chains. */
1061 last = tsi_last (a->stmt_list);
1062 tsi_link_after (&last, b->stmt_list, TSI_NEW_STMT);
1063 b->stmt_list = NULL;
1067 /* Walk the function tree removing unnecessary statements.
1069 * Empty statement nodes are removed
1071 * Unnecessary TRY_FINALLY and TRY_CATCH blocks are removed
1073 * Unnecessary COND_EXPRs are removed
1075 * Some unnecessary BIND_EXPRs are removed
1077 Clearly more work could be done. The trick is doing the analysis
1078 and removal fast enough to be a net improvement in compile times.
1080 Note that when we remove a control structure such as a COND_EXPR
1081 BIND_EXPR, or TRY block, we will need to repeat this optimization pass
1082 to ensure we eliminate all the useless code. */
1093 static void remove_useless_stmts_1 (tree *, struct rus_data *);
1096 remove_useless_stmts_warn_notreached (tree stmt)
1098 if (EXPR_LOCUS (stmt))
1100 warning ("%Hwill never be executed", EXPR_LOCUS (stmt));
1104 switch (TREE_CODE (stmt))
1106 case STATEMENT_LIST:
1108 tree_stmt_iterator i;
1109 for (i = tsi_start (stmt); !tsi_end_p (i); tsi_next (&i))
1110 if (remove_useless_stmts_warn_notreached (tsi_stmt (i)))
1116 if (remove_useless_stmts_warn_notreached (COND_EXPR_COND (stmt)))
1118 if (remove_useless_stmts_warn_notreached (COND_EXPR_THEN (stmt)))
1120 if (remove_useless_stmts_warn_notreached (COND_EXPR_ELSE (stmt)))
1124 case TRY_FINALLY_EXPR:
1125 case TRY_CATCH_EXPR:
1126 if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 0)))
1128 if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 1)))
1133 return remove_useless_stmts_warn_notreached (CATCH_BODY (stmt));
1134 case EH_FILTER_EXPR:
1135 return remove_useless_stmts_warn_notreached (EH_FILTER_FAILURE (stmt));
1137 return remove_useless_stmts_warn_notreached (BIND_EXPR_BLOCK (stmt));
1140 /* Not a live container. */
1148 remove_useless_stmts_cond (tree *stmt_p, struct rus_data *data)
1150 tree then_clause, else_clause, cond;
1151 bool save_has_label, then_has_label, else_has_label;
1153 save_has_label = data->has_label;
1154 data->has_label = false;
1155 data->last_goto = NULL;
1157 remove_useless_stmts_1 (&COND_EXPR_THEN (*stmt_p), data);
1159 then_has_label = data->has_label;
1160 data->has_label = false;
1161 data->last_goto = NULL;
1163 remove_useless_stmts_1 (&COND_EXPR_ELSE (*stmt_p), data);
1165 else_has_label = data->has_label;
1166 data->has_label = save_has_label | then_has_label | else_has_label;
1169 then_clause = COND_EXPR_THEN (*stmt_p);
1170 else_clause = COND_EXPR_ELSE (*stmt_p);
1171 cond = COND_EXPR_COND (*stmt_p);
1173 /* If neither arm does anything at all, we can remove the whole IF. */
1174 if (!TREE_SIDE_EFFECTS (then_clause) && !TREE_SIDE_EFFECTS (else_clause))
1176 *stmt_p = build_empty_stmt ();
1177 data->repeat = true;
1180 /* If there are no reachable statements in an arm, then we can
1181 zap the entire conditional. */
1182 else if (integer_nonzerop (cond) && !else_has_label)
1184 if (warn_notreached)
1185 remove_useless_stmts_warn_notreached (else_clause);
1186 *stmt_p = then_clause;
1187 data->repeat = true;
1189 else if (integer_zerop (cond) && !then_has_label)
1191 if (warn_notreached)
1192 remove_useless_stmts_warn_notreached (then_clause);
1193 *stmt_p = else_clause;
1194 data->repeat = true;
1197 /* Check a couple of simple things on then/else with single stmts. */
1200 tree then_stmt = expr_only (then_clause);
1201 tree else_stmt = expr_only (else_clause);
1203 /* Notice branches to a common destination. */
1204 if (then_stmt && else_stmt
1205 && TREE_CODE (then_stmt) == GOTO_EXPR
1206 && TREE_CODE (else_stmt) == GOTO_EXPR
1207 && (GOTO_DESTINATION (then_stmt) == GOTO_DESTINATION (else_stmt)))
1209 *stmt_p = then_stmt;
1210 data->repeat = true;
1213 /* If the THEN/ELSE clause merely assigns a value to a variable or
1214 parameter which is already known to contain that value, then
1215 remove the useless THEN/ELSE clause. */
1216 else if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL)
1219 && TREE_CODE (else_stmt) == MODIFY_EXPR
1220 && TREE_OPERAND (else_stmt, 0) == cond
1221 && integer_zerop (TREE_OPERAND (else_stmt, 1)))
1222 COND_EXPR_ELSE (*stmt_p) = alloc_stmt_list ();
1224 else if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
1225 && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
1226 || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)
1227 && TREE_CONSTANT (TREE_OPERAND (cond, 1)))
1229 tree stmt = (TREE_CODE (cond) == EQ_EXPR
1230 ? then_stmt : else_stmt);
1231 tree *location = (TREE_CODE (cond) == EQ_EXPR
1232 ? &COND_EXPR_THEN (*stmt_p)
1233 : &COND_EXPR_ELSE (*stmt_p));
1236 && TREE_CODE (stmt) == MODIFY_EXPR
1237 && TREE_OPERAND (stmt, 0) == TREE_OPERAND (cond, 0)
1238 && TREE_OPERAND (stmt, 1) == TREE_OPERAND (cond, 1))
1239 *location = alloc_stmt_list ();
1243 /* Protect GOTOs in the arm of COND_EXPRs from being removed. They
1244 would be re-introduced during lowering. */
1245 data->last_goto = NULL;
1250 remove_useless_stmts_tf (tree *stmt_p, struct rus_data *data)
1252 bool save_may_branch, save_may_throw;
1253 bool this_may_branch, this_may_throw;
1255 /* Collect may_branch and may_throw information for the body only. */
1256 save_may_branch = data->may_branch;
1257 save_may_throw = data->may_throw;
1258 data->may_branch = false;
1259 data->may_throw = false;
1260 data->last_goto = NULL;
1262 remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);
1264 this_may_branch = data->may_branch;
1265 this_may_throw = data->may_throw;
1266 data->may_branch |= save_may_branch;
1267 data->may_throw |= save_may_throw;
1268 data->last_goto = NULL;
1270 remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);
1272 /* If the body is empty, then we can emit the FINALLY block without
1273 the enclosing TRY_FINALLY_EXPR. */
1274 if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 0)))
1276 *stmt_p = TREE_OPERAND (*stmt_p, 1);
1277 data->repeat = true;
1280 /* If the handler is empty, then we can emit the TRY block without
1281 the enclosing TRY_FINALLY_EXPR. */
1282 else if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
1284 *stmt_p = TREE_OPERAND (*stmt_p, 0);
1285 data->repeat = true;
1288 /* If the body neither throws, nor branches, then we can safely
1289 string the TRY and FINALLY blocks together. */
1290 else if (!this_may_branch && !this_may_throw)
1292 tree stmt = *stmt_p;
1293 *stmt_p = TREE_OPERAND (stmt, 0);
1294 append_to_statement_list (TREE_OPERAND (stmt, 1), stmt_p);
1295 data->repeat = true;
1301 remove_useless_stmts_tc (tree *stmt_p, struct rus_data *data)
1303 bool save_may_throw, this_may_throw;
1304 tree_stmt_iterator i;
1307 /* Collect may_throw information for the body only. */
1308 save_may_throw = data->may_throw;
1309 data->may_throw = false;
1310 data->last_goto = NULL;
1312 remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);
1314 this_may_throw = data->may_throw;
1315 data->may_throw = save_may_throw;
1317 /* If the body cannot throw, then we can drop the entire TRY_CATCH_EXPR. */
1318 if (!this_may_throw)
1320 if (warn_notreached)
1321 remove_useless_stmts_warn_notreached (TREE_OPERAND (*stmt_p, 1));
1322 *stmt_p = TREE_OPERAND (*stmt_p, 0);
1323 data->repeat = true;
1327 /* Process the catch clause specially. We may be able to tell that
1328 no exceptions propagate past this point. */
1330 this_may_throw = true;
1331 i = tsi_start (TREE_OPERAND (*stmt_p, 1));
1332 stmt = tsi_stmt (i);
1333 data->last_goto = NULL;
1335 switch (TREE_CODE (stmt))
1338 for (; !tsi_end_p (i); tsi_next (&i))
1340 stmt = tsi_stmt (i);
1341 /* If we catch all exceptions, then the body does not
1342 propagate exceptions past this point. */
1343 if (CATCH_TYPES (stmt) == NULL)
1344 this_may_throw = false;
1345 data->last_goto = NULL;
1346 remove_useless_stmts_1 (&CATCH_BODY (stmt), data);
1350 case EH_FILTER_EXPR:
1351 if (EH_FILTER_MUST_NOT_THROW (stmt))
1352 this_may_throw = false;
1353 else if (EH_FILTER_TYPES (stmt) == NULL)
1354 this_may_throw = false;
1355 remove_useless_stmts_1 (&EH_FILTER_FAILURE (stmt), data);
1359 /* Otherwise this is a cleanup. */
1360 remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);
1362 /* If the cleanup is empty, then we can emit the TRY block without
1363 the enclosing TRY_CATCH_EXPR. */
1364 if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
1366 *stmt_p = TREE_OPERAND (*stmt_p, 0);
1367 data->repeat = true;
1371 data->may_throw |= this_may_throw;
1376 remove_useless_stmts_bind (tree *stmt_p, struct rus_data *data)
1380 /* First remove anything underneath the BIND_EXPR. */
1381 remove_useless_stmts_1 (&BIND_EXPR_BODY (*stmt_p), data);
1383 /* If the BIND_EXPR has no variables, then we can pull everything
1384 up one level and remove the BIND_EXPR, unless this is the toplevel
1385 BIND_EXPR for the current function or an inlined function.
1387 When this situation occurs we will want to apply this
1388 optimization again. */
1389 block = BIND_EXPR_BLOCK (*stmt_p);
1390 if (BIND_EXPR_VARS (*stmt_p) == NULL_TREE
1391 && *stmt_p != DECL_SAVED_TREE (current_function_decl)
1393 || ! BLOCK_ABSTRACT_ORIGIN (block)
1394 || (TREE_CODE (BLOCK_ABSTRACT_ORIGIN (block))
1397 *stmt_p = BIND_EXPR_BODY (*stmt_p);
1398 data->repeat = true;
1404 remove_useless_stmts_goto (tree *stmt_p, struct rus_data *data)
1406 tree dest = GOTO_DESTINATION (*stmt_p);
1408 data->may_branch = true;
1409 data->last_goto = NULL;
1411 /* Record the last goto expr, so that we can delete it if unnecessary. */
1412 if (TREE_CODE (dest) == LABEL_DECL)
1413 data->last_goto = stmt_p;
1418 remove_useless_stmts_label (tree *stmt_p, struct rus_data *data)
1420 tree label = LABEL_EXPR_LABEL (*stmt_p);
1422 data->has_label = true;
1424 /* We do want to jump across non-local label receiver code. */
1425 if (DECL_NONLOCAL (label))
1426 data->last_goto = NULL;
1428 else if (data->last_goto && GOTO_DESTINATION (*data->last_goto) == label)
1430 *data->last_goto = build_empty_stmt ();
1431 data->repeat = true;
1434 /* ??? Add something here to delete unused labels. */
1438 /* If the function is "const" or "pure", then clear TREE_SIDE_EFFECTS on its
1439 decl. This allows us to eliminate redundant or useless
1440 calls to "const" functions.
1442 Gimplifier already does the same operation, but we may notice functions
1443 being const and pure once their calls has been gimplified, so we need
1444 to update the flag. */
1447 update_call_expr_flags (tree call)
1449 tree decl = get_callee_fndecl (call);
1452 if (call_expr_flags (call) & (ECF_CONST | ECF_PURE))
1453 TREE_SIDE_EFFECTS (call) = 0;
1454 if (TREE_NOTHROW (decl))
1455 TREE_NOTHROW (call) = 1;
1459 /* T is CALL_EXPR. Set current_function_calls_* flags. */
1462 notice_special_calls (tree t)
1464 int flags = call_expr_flags (t);
1466 if (flags & ECF_MAY_BE_ALLOCA)
1467 current_function_calls_alloca = true;
1468 if (flags & ECF_RETURNS_TWICE)
1469 current_function_calls_setjmp = true;
1473 /* Clear flags set by notice_special_calls. Used by dead code removal
1474 to update the flags. */
1477 clear_special_calls (void)
1479 current_function_calls_alloca = false;
1480 current_function_calls_setjmp = false;
1485 remove_useless_stmts_1 (tree *tp, struct rus_data *data)
1489 switch (TREE_CODE (t))
1492 remove_useless_stmts_cond (tp, data);
1495 case TRY_FINALLY_EXPR:
1496 remove_useless_stmts_tf (tp, data);
1499 case TRY_CATCH_EXPR:
1500 remove_useless_stmts_tc (tp, data);
1504 remove_useless_stmts_bind (tp, data);
1508 remove_useless_stmts_goto (tp, data);
1512 remove_useless_stmts_label (tp, data);
1517 data->last_goto = NULL;
1518 data->may_branch = true;
1523 data->last_goto = NULL;
1524 notice_special_calls (t);
1525 update_call_expr_flags (t);
1526 if (tree_could_throw_p (t))
1527 data->may_throw = true;
1531 data->last_goto = NULL;
1533 if (TREE_CODE (TREE_OPERAND (t, 1)) == CALL_EXPR)
1535 update_call_expr_flags (TREE_OPERAND (t, 1));
1536 notice_special_calls (TREE_OPERAND (t, 1));
1538 if (tree_could_throw_p (t))
1539 data->may_throw = true;
1542 case STATEMENT_LIST:
1544 tree_stmt_iterator i = tsi_start (t);
1545 while (!tsi_end_p (i))
1548 if (IS_EMPTY_STMT (t))
1554 remove_useless_stmts_1 (tsi_stmt_ptr (i), data);
1557 if (TREE_CODE (t) == STATEMENT_LIST)
1559 tsi_link_before (&i, t, TSI_SAME_STMT);
1569 data->last_goto = NULL;
1573 data->last_goto = NULL;
1579 remove_useless_stmts (void)
1581 struct rus_data data;
1583 clear_special_calls ();
1587 memset (&data, 0, sizeof (data));
1588 remove_useless_stmts_1 (&DECL_SAVED_TREE (current_function_decl), &data);
1590 while (data.repeat);
1594 struct tree_opt_pass pass_remove_useless_stmts =
1596 "useless", /* name */
1598 remove_useless_stmts, /* execute */
1601 0, /* static_pass_number */
1603 PROP_gimple_any, /* properties_required */
1604 0, /* properties_provided */
1605 0, /* properties_destroyed */
1606 0, /* todo_flags_start */
1607 TODO_dump_func /* todo_flags_finish */
1611 /* Remove obviously useless statements in basic block BB. */
1614 cfg_remove_useless_stmts_bb (basic_block bb)
1616 block_stmt_iterator bsi;
1617 tree stmt = NULL_TREE;
1618 tree cond, var = NULL_TREE, val = NULL_TREE;
1619 struct var_ann_d *ann;
1621 /* Check whether we come here from a condition, and if so, get the
1624 || bb->pred->pred_next
1625 || !(bb->pred->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
1628 cond = COND_EXPR_COND (last_stmt (bb->pred->src));
1630 if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL)
1633 val = (bb->pred->flags & EDGE_FALSE_VALUE
1634 ? boolean_false_node : boolean_true_node);
1636 else if (TREE_CODE (cond) == TRUTH_NOT_EXPR
1637 && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
1638 || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL))
1640 var = TREE_OPERAND (cond, 0);
1641 val = (bb->pred->flags & EDGE_FALSE_VALUE
1642 ? boolean_true_node : boolean_false_node);
1646 if (bb->pred->flags & EDGE_FALSE_VALUE)
1647 cond = invert_truthvalue (cond);
1648 if (TREE_CODE (cond) == EQ_EXPR
1649 && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
1650 || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)
1651 && (TREE_CODE (TREE_OPERAND (cond, 1)) == VAR_DECL
1652 || TREE_CODE (TREE_OPERAND (cond, 1)) == PARM_DECL
1653 || TREE_CONSTANT (TREE_OPERAND (cond, 1))))
1655 var = TREE_OPERAND (cond, 0);
1656 val = TREE_OPERAND (cond, 1);
1662 /* Only work for normal local variables. */
1663 ann = var_ann (var);
1666 || TREE_ADDRESSABLE (var))
1669 if (! TREE_CONSTANT (val))
1671 ann = var_ann (val);
1674 || TREE_ADDRESSABLE (val))
1678 /* Ignore floating point variables, since comparison behaves weird for
1680 if (FLOAT_TYPE_P (TREE_TYPE (var)))
1683 for (bsi = bsi_start (bb); !bsi_end_p (bsi);)
1685 stmt = bsi_stmt (bsi);
1687 /* If the THEN/ELSE clause merely assigns a value to a variable/parameter
1688 which is already known to contain that value, then remove the useless
1689 THEN/ELSE clause. */
1690 if (TREE_CODE (stmt) == MODIFY_EXPR
1691 && TREE_OPERAND (stmt, 0) == var
1692 && operand_equal_p (val, TREE_OPERAND (stmt, 1), 0))
1698 /* Invalidate the var if we encounter something that could modify it. */
1699 if (TREE_CODE (stmt) == ASM_EXPR
1700 || TREE_CODE (stmt) == VA_ARG_EXPR
1701 || (TREE_CODE (stmt) == MODIFY_EXPR
1702 && (TREE_OPERAND (stmt, 0) == var
1703 || TREE_OPERAND (stmt, 0) == val
1704 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VA_ARG_EXPR)))
1712 /* A CFG-aware version of remove_useless_stmts. */
1715 cfg_remove_useless_stmts (void)
1719 #ifdef ENABLE_CHECKING
1720 verify_flow_info ();
1725 cfg_remove_useless_stmts_bb (bb);
1730 /* Remove PHI nodes associated with basic block BB and all edges out of BB. */
1733 remove_phi_nodes_and_edges_for_unreachable_block (basic_block bb)
1737 /* Since this block is no longer reachable, we can just delete all
1738 of its PHI nodes. */
1739 phi = phi_nodes (bb);
1742 tree next = PHI_CHAIN (phi);
1743 remove_phi_node (phi, NULL_TREE, bb);
1747 /* Remove edges to BB's successors. */
1748 while (bb->succ != NULL)
1749 ssa_remove_edge (bb->succ);
1753 /* Remove statements of basic block BB. */
1756 remove_bb (basic_block bb)
1758 block_stmt_iterator i;
1759 location_t *loc = NULL;
1763 fprintf (dump_file, "Removing basic block %d\n", bb->index);
1764 if (dump_flags & TDF_DETAILS)
1766 dump_bb (bb, dump_file, 0);
1767 fprintf (dump_file, "\n");
1771 /* Remove all the instructions in the block. */
1772 for (i = bsi_start (bb); !bsi_end_p (i); bsi_remove (&i))
1774 tree stmt = bsi_stmt (i);
1776 set_bb_for_stmt (stmt, NULL);
1778 /* Don't warn for removed gotos. Gotos are often removed due to
1779 jump threading, thus resulting in bogus warnings. Not great,
1780 since this way we lose warnings for gotos in the original
1781 program that are indeed unreachable. */
1782 if (TREE_CODE (stmt) != GOTO_EXPR && EXPR_LOCUS (stmt) && !loc)
1783 loc = EXPR_LOCUS (stmt);
1786 /* If requested, give a warning that the first statement in the
1787 block is unreachable. We walk statements backwards in the
1788 loop above, so the last statement we process is the first statement
1790 if (warn_notreached && loc)
1791 warning ("%Hwill never be executed", loc);
1793 remove_phi_nodes_and_edges_for_unreachable_block (bb);
1797 /* Examine BB to determine if it is a forwarding block (a block which only
1798 transfers control to a new destination). If BB is a forwarding block,
1799 then return the edge leading to the ultimate destination. */
1802 tree_block_forwards_to (basic_block bb)
1804 block_stmt_iterator bsi;
1805 bb_ann_t ann = bb_ann (bb);
1808 /* If this block is not forwardable, then avoid useless work. */
1809 if (! ann->forwardable)
1812 /* Set this block to not be forwardable. This prevents infinite loops since
1813 any block currently under examination is considered non-forwardable. */
1814 ann->forwardable = 0;
1816 /* No forwarding is possible if this block is a special block (ENTRY/EXIT),
1817 this block has more than one successor, this block's single successor is
1818 reached via an abnormal edge, this block has phi nodes, or this block's
1819 single successor has phi nodes. */
1820 if (bb == EXIT_BLOCK_PTR
1821 || bb == ENTRY_BLOCK_PTR
1823 || bb->succ->succ_next
1824 || bb->succ->dest == EXIT_BLOCK_PTR
1825 || (bb->succ->flags & EDGE_ABNORMAL) != 0
1827 || phi_nodes (bb->succ->dest))
1830 /* Walk past any labels at the start of this block. */
1831 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
1833 stmt = bsi_stmt (bsi);
1834 if (TREE_CODE (stmt) != LABEL_EXPR)
1838 /* If we reached the end of this block we may be able to optimize this
1840 if (bsi_end_p (bsi))
1844 /* Recursive call to pick up chains of forwarding blocks. */
1845 dest = tree_block_forwards_to (bb->succ->dest);
1847 /* If none found, we forward to bb->succ at minimum. */
1851 ann->forwardable = 1;
1855 /* No forwarding possible. */
1860 /* Try to remove superfluous control structures. */
1863 cleanup_control_flow (void)
1866 block_stmt_iterator bsi;
1867 bool retval = false;
1872 bsi = bsi_last (bb);
1874 if (bsi_end_p (bsi))
1877 stmt = bsi_stmt (bsi);
1878 if (TREE_CODE (stmt) == COND_EXPR
1879 || TREE_CODE (stmt) == SWITCH_EXPR)
1880 retval |= cleanup_control_expr_graph (bb, bsi);
1886 /* Disconnect an unreachable block in the control expression starting
1890 cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi)
1893 bool retval = false;
1894 tree expr = bsi_stmt (bsi), val;
1896 if (bb->succ->succ_next)
1900 switch (TREE_CODE (expr))
1903 val = COND_EXPR_COND (expr);
1907 val = SWITCH_COND (expr);
1908 if (TREE_CODE (val) != INTEGER_CST)
1916 taken_edge = find_taken_edge (bb, val);
1920 /* Remove all the edges except the one that is always executed. */
1921 for (e = bb->succ; e; e = next)
1923 next = e->succ_next;
1924 if (e != taken_edge)
1926 taken_edge->probability += e->probability;
1927 taken_edge->count += e->count;
1928 ssa_remove_edge (e);
1932 if (taken_edge->probability > REG_BR_PROB_BASE)
1933 taken_edge->probability = REG_BR_PROB_BASE;
1936 taken_edge = bb->succ;
1939 taken_edge->flags = EDGE_FALLTHRU;
1941 /* We removed some paths from the cfg. */
1942 if (dom_computed[CDI_DOMINATORS] >= DOM_CONS_OK)
1943 dom_computed[CDI_DOMINATORS] = DOM_CONS_OK;
1949 /* Given a control block BB and a constant value VAL, return the edge that
1950 will be taken out of the block. If VAL does not match a unique edge,
1951 NULL is returned. */
1954 find_taken_edge (basic_block bb, tree val)
1958 stmt = last_stmt (bb);
1960 #if defined ENABLE_CHECKING
1961 if (stmt == NULL_TREE || !is_ctrl_stmt (stmt))
1965 /* If VAL is not a constant, we can't determine which edge might
1967 if (val == NULL || !really_constant_p (val))
1970 if (TREE_CODE (stmt) == COND_EXPR)
1971 return find_taken_edge_cond_expr (bb, val);
1973 if (TREE_CODE (stmt) == SWITCH_EXPR)
1974 return find_taken_edge_switch_expr (bb, val);
1980 /* Given a constant value VAL and the entry block BB to a COND_EXPR
1981 statement, determine which of the two edges will be taken out of the
1982 block. Return NULL if either edge may be taken. */
1985 find_taken_edge_cond_expr (basic_block bb, tree val)
1987 edge true_edge, false_edge;
1989 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
1991 /* If both edges of the branch lead to the same basic block, it doesn't
1992 matter which edge is taken. */
1993 if (true_edge->dest == false_edge->dest)
1996 /* Otherwise, try to determine which branch of the if() will be taken.
1997 If VAL is a constant but it can't be reduced to a 0 or a 1, then
1998 we don't really know which edge will be taken at runtime. This
1999 may happen when comparing addresses (e.g., if (&var1 == 4)). */
2000 if (integer_nonzerop (val))
2002 else if (integer_zerop (val))
2009 /* Given a constant value VAL and the entry block BB to a SWITCH_EXPR
2010 statement, determine which edge will be taken out of the block. Return
2011 NULL if any edge may be taken. */
2014 find_taken_edge_switch_expr (basic_block bb, tree val)
2016 tree switch_expr, taken_case;
2017 basic_block dest_bb;
2020 if (TREE_CODE (val) != INTEGER_CST)
2023 switch_expr = last_stmt (bb);
2024 taken_case = find_case_label_for_value (switch_expr, val);
2025 dest_bb = label_to_block (CASE_LABEL (taken_case));
2027 e = find_edge (bb, dest_bb);
2034 /* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL.
2035 We can make optimal use here of the fact that the case labels are
2036 sorted: We can do a binary search for a case matching VAL. */
2039 find_case_label_for_value (tree switch_expr, tree val)
2041 tree vec = SWITCH_LABELS (switch_expr);
2042 size_t low, high, n = TREE_VEC_LENGTH (vec);
2043 tree default_case = TREE_VEC_ELT (vec, n - 1);
2045 for (low = -1, high = n - 1; high - low > 1; )
2047 size_t i = (high + low) / 2;
2048 tree t = TREE_VEC_ELT (vec, i);
2051 /* Cache the result of comparing CASE_LOW and val. */
2052 cmp = tree_int_cst_compare (CASE_LOW (t), val);
2059 if (CASE_HIGH (t) == NULL)
2061 /* A singe-valued case label. */
2067 /* A case range. We can only handle integer ranges. */
2068 if (cmp <= 0 && tree_int_cst_compare (CASE_HIGH (t), val) >= 0)
2073 return default_case;
2077 /* If all the PHI nodes in DEST have alternatives for E1 and E2 and
2078 those alternatives are equal in each of the PHI nodes, then return
2079 true, else return false. */
2082 phi_alternatives_equal (basic_block dest, edge e1, edge e2)
2084 tree phi, val1, val2;
2087 for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
2089 n1 = phi_arg_from_edge (phi, e1);
2090 n2 = phi_arg_from_edge (phi, e2);
2092 #ifdef ENABLE_CHECKING
2093 if (n1 < 0 || n2 < 0)
2097 val1 = PHI_ARG_DEF (phi, n1);
2098 val2 = PHI_ARG_DEF (phi, n2);
2100 if (!operand_equal_p (val1, val2, 0))
2108 /* Computing the Dominance Frontier:
2110 As described in Morgan, section 3.5, this may be done simply by
2111 walking the dominator tree bottom-up, computing the frontier for
2112 the children before the parent. When considering a block B,
2113 there are two cases:
2115 (1) A flow graph edge leaving B that does not lead to a child
2116 of B in the dominator tree must be a block that is either equal
2117 to B or not dominated by B. Such blocks belong in the frontier
2120 (2) Consider a block X in the frontier of one of the children C
2121 of B. If X is not equal to B and is not dominated by B, it
2122 is in the frontier of B. */
2125 compute_dominance_frontiers_1 (bitmap *frontiers, basic_block bb, sbitmap done)
2130 SET_BIT (done, bb->index);
2132 /* Do the frontier of the children first. Not all children in the
2133 dominator tree (blocks dominated by this one) are children in the
2134 CFG, so check all blocks. */
2135 for (c = first_dom_son (CDI_DOMINATORS, bb);
2137 c = next_dom_son (CDI_DOMINATORS, c))
2139 if (! TEST_BIT (done, c->index))
2140 compute_dominance_frontiers_1 (frontiers, c, done);
2143 /* Find blocks conforming to rule (1) above. */
2144 for (e = bb->succ; e; e = e->succ_next)
2146 if (e->dest == EXIT_BLOCK_PTR)
2148 if (get_immediate_dominator (CDI_DOMINATORS, e->dest) != bb)
2149 bitmap_set_bit (frontiers[bb->index], e->dest->index);
2152 /* Find blocks conforming to rule (2). */
2153 for (c = first_dom_son (CDI_DOMINATORS, bb);
2155 c = next_dom_son (CDI_DOMINATORS, c))
2159 EXECUTE_IF_SET_IN_BITMAP (frontiers[c->index], 0, x,
2161 if (get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (x)) != bb)
2162 bitmap_set_bit (frontiers[bb->index], x);
2169 compute_dominance_frontiers (bitmap *frontiers)
2171 sbitmap done = sbitmap_alloc (last_basic_block);
2173 timevar_push (TV_DOM_FRONTIERS);
2175 sbitmap_zero (done);
2177 compute_dominance_frontiers_1 (frontiers, ENTRY_BLOCK_PTR->succ->dest, done);
2179 sbitmap_free (done);
2181 timevar_pop (TV_DOM_FRONTIERS);
2186 /*---------------------------------------------------------------------------
2188 ---------------------------------------------------------------------------*/
2190 /* Dump tree-specific information of block BB to file OUTF. */
2193 tree_dump_bb (basic_block bb, FILE *outf, int indent)
2195 dump_generic_bb (outf, bb, indent, TDF_VOPS);
2199 /* Dump a basic block on stderr. */
2202 debug_tree_bb (basic_block bb)
2204 dump_bb (bb, stderr, 0);
2208 /* Dump basic block with index N on stderr. */
2211 debug_tree_bb_n (int n)
2213 debug_tree_bb (BASIC_BLOCK (n));
2214 return BASIC_BLOCK (n);
2218 /* Dump the CFG on stderr.
2220 FLAGS are the same used by the tree dumping functions
2221 (see TDF_* in tree.h). */
2224 debug_tree_cfg (int flags)
2226 dump_tree_cfg (stderr, flags);
2230 /* Dump the program showing basic block boundaries on the given FILE.
2232 FLAGS are the same used by the tree dumping functions (see TDF_* in
2236 dump_tree_cfg (FILE *file, int flags)
2238 if (flags & TDF_DETAILS)
2240 const char *funcname
2241 = lang_hooks.decl_printable_name (current_function_decl, 2);
2244 fprintf (file, ";; Function %s\n\n", funcname);
2245 fprintf (file, ";; \n%d basic blocks, %d edges, last basic block %d.\n\n",
2246 n_basic_blocks, n_edges, last_basic_block);
2248 brief_dump_cfg (file);
2249 fprintf (file, "\n");
2252 if (flags & TDF_STATS)
2253 dump_cfg_stats (file);
2255 dump_function_to_file (current_function_decl, file, flags | TDF_BLOCKS);
2259 /* Dump CFG statistics on FILE. */
2262 dump_cfg_stats (FILE *file)
2264 static long max_num_merged_labels = 0;
2265 unsigned long size, total = 0;
2268 const char * const fmt_str = "%-30s%-13s%12s\n";
2269 const char * const fmt_str_1 = "%-30s%13lu%11lu%c\n";
2270 const char * const fmt_str_3 = "%-43s%11lu%c\n";
2271 const char *funcname
2272 = lang_hooks.decl_printable_name (current_function_decl, 2);
2275 fprintf (file, "\nCFG Statistics for %s\n\n", funcname);
2277 fprintf (file, "---------------------------------------------------------\n");
2278 fprintf (file, fmt_str, "", " Number of ", "Memory");
2279 fprintf (file, fmt_str, "", " instances ", "used ");
2280 fprintf (file, "---------------------------------------------------------\n");
2282 size = n_basic_blocks * sizeof (struct basic_block_def);
2284 fprintf (file, fmt_str_1, "Basic blocks", n_basic_blocks, SCALE (size),
2291 for (e = bb->succ; e; e = e->succ_next)
2294 size = n_edges * sizeof (struct edge_def);
2296 fprintf (file, fmt_str_1, "Edges", n_edges, SCALE (size), LABEL (size));
2298 size = n_basic_blocks * sizeof (struct bb_ann_d);
2300 fprintf (file, fmt_str_1, "Basic block annotations", n_basic_blocks,
2301 SCALE (size), LABEL (size));
2303 fprintf (file, "---------------------------------------------------------\n");
2304 fprintf (file, fmt_str_3, "Total memory used by CFG data", SCALE (total),
2306 fprintf (file, "---------------------------------------------------------\n");
2307 fprintf (file, "\n");
2309 if (cfg_stats.num_merged_labels > max_num_merged_labels)
2310 max_num_merged_labels = cfg_stats.num_merged_labels;
2312 fprintf (file, "Coalesced label blocks: %ld (Max so far: %ld)\n",
2313 cfg_stats.num_merged_labels, max_num_merged_labels);
2315 fprintf (file, "\n");
2319 /* Dump CFG statistics on stderr. Keep extern so that it's always
2320 linked in the final executable. */
2323 debug_cfg_stats (void)
2325 dump_cfg_stats (stderr);
2329 /* Dump the flowgraph to a .vcg FILE. */
2332 tree_cfg2vcg (FILE *file)
2336 const char *funcname
2337 = lang_hooks.decl_printable_name (current_function_decl, 2);
2339 /* Write the file header. */
2340 fprintf (file, "graph: { title: \"%s\"\n", funcname);
2341 fprintf (file, "node: { title: \"ENTRY\" label: \"ENTRY\" }\n");
2342 fprintf (file, "node: { title: \"EXIT\" label: \"EXIT\" }\n");
2344 /* Write blocks and edges. */
2345 for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
2347 fprintf (file, "edge: { sourcename: \"ENTRY\" targetname: \"%d\"",
2350 if (e->flags & EDGE_FAKE)
2351 fprintf (file, " linestyle: dotted priority: 10");
2353 fprintf (file, " linestyle: solid priority: 100");
2355 fprintf (file, " }\n");
2361 enum tree_code head_code, end_code;
2362 const char *head_name, *end_name;
2365 tree first = first_stmt (bb);
2366 tree last = last_stmt (bb);
2370 head_code = TREE_CODE (first);
2371 head_name = tree_code_name[head_code];
2372 head_line = get_lineno (first);
2375 head_name = "no-statement";
2379 end_code = TREE_CODE (last);
2380 end_name = tree_code_name[end_code];
2381 end_line = get_lineno (last);
2384 end_name = "no-statement";
2386 fprintf (file, "node: { title: \"%d\" label: \"#%d\\n%s (%d)\\n%s (%d)\"}\n",
2387 bb->index, bb->index, head_name, head_line, end_name,
2390 for (e = bb->succ; e; e = e->succ_next)
2392 if (e->dest == EXIT_BLOCK_PTR)
2393 fprintf (file, "edge: { sourcename: \"%d\" targetname: \"EXIT\"", bb->index);
2395 fprintf (file, "edge: { sourcename: \"%d\" targetname: \"%d\"", bb->index, e->dest->index);
2397 if (e->flags & EDGE_FAKE)
2398 fprintf (file, " priority: 10 linestyle: dotted");
2400 fprintf (file, " priority: 100 linestyle: solid");
2402 fprintf (file, " }\n");
2405 if (bb->next_bb != EXIT_BLOCK_PTR)
2409 fputs ("}\n\n", file);
2414 /*---------------------------------------------------------------------------
2415 Miscellaneous helpers
2416 ---------------------------------------------------------------------------*/
2418 /* Return true if T represents a stmt that always transfers control. */
2421 is_ctrl_stmt (tree t)
2423 return (TREE_CODE (t) == COND_EXPR
2424 || TREE_CODE (t) == SWITCH_EXPR
2425 || TREE_CODE (t) == GOTO_EXPR
2426 || TREE_CODE (t) == RETURN_EXPR
2427 || TREE_CODE (t) == RESX_EXPR);
2431 /* Return true if T is a statement that may alter the flow of control
2432 (e.g., a call to a non-returning function). */
2435 is_ctrl_altering_stmt (tree t)
2439 #if defined ENABLE_CHECKING
2444 switch (TREE_CODE (t))
2447 /* A MODIFY_EXPR with a rhs of a call has the characteristics
2449 call = TREE_OPERAND (t, 1);
2450 if (TREE_CODE (call) != CALL_EXPR)
2455 /* A non-pure/const CALL_EXPR alters flow control if the current
2456 function has nonlocal labels. */
2457 if (TREE_SIDE_EFFECTS (t)
2458 && current_function_has_nonlocal_label)
2461 /* A CALL_EXPR also alters control flow if it does not return. */
2462 if (call_expr_flags (call) & (ECF_NORETURN | ECF_LONGJMP))
2470 /* If a statement can throw, it alters control flow. */
2471 return tree_can_throw_internal (t);
2475 /* Return true if T is a computed goto. */
2478 computed_goto_p (tree t)
2480 return (TREE_CODE (t) == GOTO_EXPR
2481 && TREE_CODE (GOTO_DESTINATION (t)) != LABEL_DECL);
2485 /* Checks whether EXPR is a simple local goto. */
2488 simple_goto_p (tree expr)
2490 return (TREE_CODE (expr) == GOTO_EXPR
2491 && TREE_CODE (GOTO_DESTINATION (expr)) == LABEL_DECL
2492 && (decl_function_context (GOTO_DESTINATION (expr))
2493 == current_function_decl));
2497 /* Return true if T should start a new basic block. PREV_T is the
2498 statement preceding T. It is used when T is a label or a case label.
2499 Labels should only start a new basic block if their previous statement
2500 wasn't a label. Otherwise, sequence of labels would generate
2501 unnecessary basic blocks that only contain a single label. */
2504 stmt_starts_bb_p (tree t, tree prev_t)
2506 enum tree_code code;
2511 /* LABEL_EXPRs start a new basic block only if the preceding
2512 statement wasn't a label of the same type. This prevents the
2513 creation of consecutive blocks that have nothing but a single
2515 code = TREE_CODE (t);
2516 if (code == LABEL_EXPR)
2518 /* Nonlocal and computed GOTO targets always start a new block. */
2519 if (code == LABEL_EXPR
2520 && (DECL_NONLOCAL (LABEL_EXPR_LABEL (t))
2521 || FORCED_LABEL (LABEL_EXPR_LABEL (t))))
2524 if (prev_t && TREE_CODE (prev_t) == code)
2526 if (DECL_NONLOCAL (LABEL_EXPR_LABEL (prev_t)))
2529 cfg_stats.num_merged_labels++;
2540 /* Return true if T should end a basic block. */
2543 stmt_ends_bb_p (tree t)
2545 return is_ctrl_stmt (t) || is_ctrl_altering_stmt (t);
2549 /* Add gotos that used to be represented implicitly in the CFG. */
2552 disband_implicit_edges (void)
2555 block_stmt_iterator last;
2557 tree stmt, label, forward;
2561 last = bsi_last (bb);
2562 stmt = last_stmt (bb);
2564 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2566 /* Remove superfluous gotos from COND_EXPR branches. Moved
2567 from cfg_remove_useless_stmts here since it violates the
2568 invariants for tree--cfg correspondence and thus fits better
2569 here where we do it anyway. */
2570 for (e = bb->succ; e; e = e->succ_next)
2572 if (e->dest != bb->next_bb)
2575 if (e->flags & EDGE_TRUE_VALUE)
2576 COND_EXPR_THEN (stmt) = build_empty_stmt ();
2577 else if (e->flags & EDGE_FALSE_VALUE)
2578 COND_EXPR_ELSE (stmt) = build_empty_stmt ();
2581 e->flags |= EDGE_FALLTHRU;
2587 if (stmt && TREE_CODE (stmt) == RETURN_EXPR)
2589 /* Remove the RETURN_EXPR if we may fall though to the exit
2592 || bb->succ->succ_next
2593 || bb->succ->dest != EXIT_BLOCK_PTR)
2596 if (bb->next_bb == EXIT_BLOCK_PTR
2597 && !TREE_OPERAND (stmt, 0))
2600 bb->succ->flags |= EDGE_FALLTHRU;
2605 /* There can be no fallthru edge if the last statement is a control
2607 if (stmt && is_ctrl_stmt (stmt))
2610 /* Find a fallthru edge and emit the goto if necessary. */
2611 for (e = bb->succ; e; e = e->succ_next)
2612 if (e->flags & EDGE_FALLTHRU)
2615 if (!e || e->dest == bb->next_bb)
2618 if (e->dest == EXIT_BLOCK_PTR)
2621 label = tree_block_label (e->dest);
2623 /* If this is a goto to a goto, jump to the final destination.
2624 Handles unfactoring of the computed jumps.
2625 ??? Why bother putting this back together when rtl is just
2626 about to take it apart again? */
2627 forward = last_and_only_stmt (e->dest);
2629 && TREE_CODE (forward) == GOTO_EXPR)
2630 label = GOTO_DESTINATION (forward);
2632 stmt = build1 (GOTO_EXPR, void_type_node, label);
2633 SET_EXPR_LOCUS (stmt, e->goto_locus);
2634 bsi_insert_after (&last, stmt, BSI_NEW_STMT);
2635 e->flags &= ~EDGE_FALLTHRU;
2640 /* Remove all the blocks and edges that make up the flowgraph. */
2643 delete_tree_cfg (void)
2645 if (n_basic_blocks > 0)
2646 free_blocks_annotations ();
2648 free_basic_block_vars ();
2649 basic_block_info = NULL;
2650 label_to_block_map = NULL;
2655 /* Return the first statement in basic block BB. */
2658 first_stmt (basic_block bb)
2660 block_stmt_iterator i = bsi_start (bb);
2661 return !bsi_end_p (i) ? bsi_stmt (i) : NULL_TREE;
2665 /* Return the last statement in basic block BB. */
2668 last_stmt (basic_block bb)
2670 block_stmt_iterator b = bsi_last (bb);
2671 return !bsi_end_p (b) ? bsi_stmt (b) : NULL_TREE;
2675 /* Return a pointer to the last statement in block BB. */
2678 last_stmt_ptr (basic_block bb)
2680 block_stmt_iterator last = bsi_last (bb);
2681 return !bsi_end_p (last) ? bsi_stmt_ptr (last) : NULL;
2685 /* Return the last statement of an otherwise empty block. Return NULL
2686 if the block is totally empty, or if it contains more than one
2690 last_and_only_stmt (basic_block bb)
2692 block_stmt_iterator i = bsi_last (bb);
2698 last = bsi_stmt (i);
2703 /* Empty statements should no longer appear in the instruction stream.
2704 Everything that might have appeared before should be deleted by
2705 remove_useless_stmts, and the optimizers should just bsi_remove
2706 instead of smashing with build_empty_stmt.
2708 Thus the only thing that should appear here in a block containing
2709 one executable statement is a label. */
2710 prev = bsi_stmt (i);
2711 if (TREE_CODE (prev) == LABEL_EXPR)
2718 /* Mark BB as the basic block holding statement T. */
2721 set_bb_for_stmt (tree t, basic_block bb)
2723 if (TREE_CODE (t) == STATEMENT_LIST)
2725 tree_stmt_iterator i;
2726 for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i))
2727 set_bb_for_stmt (tsi_stmt (i), bb);
2731 stmt_ann_t ann = get_stmt_ann (t);
2734 /* If the statement is a label, add the label to block-to-labels map
2735 so that we can speed up edge creation for GOTO_EXPRs. */
2736 if (TREE_CODE (t) == LABEL_EXPR)
2740 t = LABEL_EXPR_LABEL (t);
2741 uid = LABEL_DECL_UID (t);
2744 LABEL_DECL_UID (t) = uid = cfun->last_label_uid++;
2745 if (VARRAY_SIZE (label_to_block_map) <= (unsigned) uid)
2746 VARRAY_GROW (label_to_block_map, 3 * uid / 2);
2750 #ifdef ENABLE_CHECKING
2751 /* We're moving an existing label. Make sure that we've
2752 removed it from the old block. */
2753 if (bb && VARRAY_BB (label_to_block_map, uid))
2757 VARRAY_BB (label_to_block_map, uid) = bb;
2763 /* Insert statement (or statement list) T before the statement
2764 pointed-to by iterator I. M specifies how to update iterator I
2765 after insertion (see enum bsi_iterator_update). */
2768 bsi_insert_before (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
2770 set_bb_for_stmt (t, i->bb);
2772 tsi_link_before (&i->tsi, t, m);
2776 /* Insert statement (or statement list) T after the statement
2777 pointed-to by iterator I. M specifies how to update iterator I
2778 after insertion (see enum bsi_iterator_update). */
2781 bsi_insert_after (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
2783 set_bb_for_stmt (t, i->bb);
2785 tsi_link_after (&i->tsi, t, m);
2789 /* Remove the statement pointed to by iterator I. The iterator is updated
2790 to the next statement. */
2793 bsi_remove (block_stmt_iterator *i)
2795 tree t = bsi_stmt (*i);
2796 set_bb_for_stmt (t, NULL);
2798 tsi_delink (&i->tsi);
2802 /* Move the statement at FROM so it comes right after the statement at TO. */
2805 bsi_move_after (block_stmt_iterator *from, block_stmt_iterator *to)
2807 tree stmt = bsi_stmt (*from);
2809 bsi_insert_after (to, stmt, BSI_SAME_STMT);
2813 /* Move the statement at FROM so it comes right before the statement at TO. */
2816 bsi_move_before (block_stmt_iterator *from, block_stmt_iterator *to)
2818 tree stmt = bsi_stmt (*from);
2820 bsi_insert_before (to, stmt, BSI_SAME_STMT);
2824 /* Move the statement at FROM to the end of basic block BB. */
2827 bsi_move_to_bb_end (block_stmt_iterator *from, basic_block bb)
2829 block_stmt_iterator last = bsi_last (bb);
2831 /* Have to check bsi_end_p because it could be an empty block. */
2832 if (!bsi_end_p (last) && is_ctrl_stmt (bsi_stmt (last)))
2833 bsi_move_before (from, &last);
2835 bsi_move_after (from, &last);
2839 /* Replace the contents of the statement pointed to by iterator BSI
2840 with STMT. If PRESERVE_EH_INFO is true, the exception handling
2841 information of the original statement is preserved. */
2844 bsi_replace (const block_stmt_iterator *bsi, tree stmt, bool preserve_eh_info)
2847 tree orig_stmt = bsi_stmt (*bsi);
2849 SET_EXPR_LOCUS (stmt, EXPR_LOCUS (orig_stmt));
2850 set_bb_for_stmt (stmt, bsi->bb);
2852 /* Preserve EH region information from the original statement, if
2853 requested by the caller. */
2854 if (preserve_eh_info)
2856 eh_region = lookup_stmt_eh_region (orig_stmt);
2858 add_stmt_to_eh_region (stmt, eh_region);
2861 *bsi_stmt_ptr (*bsi) = stmt;
2866 /* Insert the statement pointed-to by BSI into edge E. Every attempt
2867 is made to place the statement in an existing basic block, but
2868 sometimes that isn't possible. When it isn't possible, the edge is
2869 split and the statement is added to the new block.
2871 In all cases, the returned *BSI points to the correct location. The
2872 return value is true if insertion should be done after the location,
2873 or false if it should be done before the location. */
2876 tree_find_edge_insert_loc (edge e, block_stmt_iterator *bsi)
2878 basic_block dest, src;
2884 /* If the destination has one predecessor which has no PHI nodes,
2885 insert there. Except for the exit block.
2887 The requirement for no PHI nodes could be relaxed. Basically we
2888 would have to examine the PHIs to prove that none of them used
2889 the value set by the statement we want to insert on E. That
2890 hardly seems worth the effort. */
2891 if (dest->pred->pred_next == NULL
2892 && ! phi_nodes (dest)
2893 && dest != EXIT_BLOCK_PTR)
2895 *bsi = bsi_start (dest);
2896 if (bsi_end_p (*bsi))
2899 /* Make sure we insert after any leading labels. */
2900 tmp = bsi_stmt (*bsi);
2901 while (TREE_CODE (tmp) == LABEL_EXPR)
2904 if (bsi_end_p (*bsi))
2906 tmp = bsi_stmt (*bsi);
2909 if (bsi_end_p (*bsi))
2911 *bsi = bsi_last (dest);
2918 /* If the source has one successor, the edge is not abnormal and
2919 the last statement does not end a basic block, insert there.
2920 Except for the entry block. */
2922 if ((e->flags & EDGE_ABNORMAL) == 0
2923 && src->succ->succ_next == NULL
2924 && src != ENTRY_BLOCK_PTR)
2926 *bsi = bsi_last (src);
2927 if (bsi_end_p (*bsi))
2930 tmp = bsi_stmt (*bsi);
2931 if (!stmt_ends_bb_p (tmp))
2934 /* Insert code just before returning the value. We may need to decompose
2935 the return in the case it contains non-trivial operand. */
2936 if (TREE_CODE (tmp) == RETURN_EXPR)
2938 tree op = TREE_OPERAND (tmp, 0);
2939 if (!is_gimple_val (op))
2941 if (TREE_CODE (op) != MODIFY_EXPR)
2943 bsi_insert_before (bsi, op, BSI_NEW_STMT);
2944 TREE_OPERAND (tmp, 0) = TREE_OPERAND (op, 0);
2951 /* Otherwise, create a new basic block, and split this edge. */
2952 dest = split_edge (e);
2958 /* This routine will commit all pending edge insertions, creating any new
2959 basic blocks which are necessary.
2961 If specified, NEW_BLOCKS returns a count of the number of new basic
2962 blocks which were created. */
2965 bsi_commit_edge_inserts (int *new_blocks)
2971 blocks = n_basic_blocks;
2973 bsi_commit_edge_inserts_1 (ENTRY_BLOCK_PTR->succ);
2976 for (e = bb->succ; e; e = e->succ_next)
2977 bsi_commit_edge_inserts_1 (e);
2980 *new_blocks = n_basic_blocks - blocks;
2984 /* Commit insertions pending at edge E. */
2987 bsi_commit_edge_inserts_1 (edge e)
2989 if (PENDING_STMT (e))
2991 block_stmt_iterator bsi;
2992 tree stmt = PENDING_STMT (e);
2994 PENDING_STMT (e) = NULL_TREE;
2996 if (tree_find_edge_insert_loc (e, &bsi))
2997 bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
2999 bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
3004 /* Add STMT to the pending list of edge E. No actual insertion is
3005 made until a call to bsi_commit_edge_inserts () is made. */
3008 bsi_insert_on_edge (edge e, tree stmt)
3010 append_to_statement_list (stmt, &PENDING_STMT (e));
3014 /* Specialized edge insertion for SSA-PRE. FIXME: This should
3015 probably disappear. The only reason it's here is because PRE needs
3016 the call to tree_find_edge_insert_loc(). */
3018 void pre_insert_on_edge (edge e, tree stmt);
3021 pre_insert_on_edge (edge e, tree stmt)
3023 block_stmt_iterator bsi;
3025 if (PENDING_STMT (e))
3028 if (tree_find_edge_insert_loc (e, &bsi))
3029 bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
3031 bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
3035 /*---------------------------------------------------------------------------
3036 Tree specific functions for CFG manipulation
3037 ---------------------------------------------------------------------------*/
3039 /* Split a (typically critical) edge EDGE_IN. Return the new block.
3040 Abort on abnormal edges. */
3043 tree_split_edge (edge edge_in)
3045 basic_block new_bb, after_bb, dest, src;
3050 /* Abnormal edges cannot be split. */
3051 if (edge_in->flags & EDGE_ABNORMAL)
3055 dest = edge_in->dest;
3057 /* Place the new block in the block list. Try to keep the new block
3058 near its "logical" location. This is of most help to humans looking
3059 at debugging dumps. */
3060 for (e = dest->pred; e; e = e->pred_next)
3061 if (e->src->next_bb == dest)
3064 after_bb = dest->prev_bb;
3066 after_bb = edge_in->src;
3068 new_bb = create_empty_bb (after_bb);
3069 new_edge = make_edge (new_bb, dest, EDGE_FALLTHRU);
3071 /* Find all the PHI arguments on the original edge, and change them to
3072 the new edge. Do it before redirection, so that the argument does not
3074 for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
3076 num_elem = PHI_NUM_ARGS (phi);
3077 for (i = 0; i < num_elem; i++)
3078 if (PHI_ARG_EDGE (phi, i) == edge_in)
3080 PHI_ARG_EDGE (phi, i) = new_edge;
3085 if (!redirect_edge_and_branch (edge_in, new_bb))
3088 if (PENDING_STMT (edge_in))
3095 /* Return true when BB has label LABEL in it. */
3098 has_label_p (basic_block bb, tree label)
3100 block_stmt_iterator bsi;
3102 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3104 tree stmt = bsi_stmt (bsi);
3106 if (TREE_CODE (stmt) != LABEL_EXPR)
3108 if (LABEL_EXPR_LABEL (stmt) == label)
3115 /* Callback for walk_tree, check that all elements with address taken are
3116 properly noticed as such. */
3119 verify_expr (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
3120 void *data ATTRIBUTE_UNUSED)
3127 switch (TREE_CODE (t))
3130 if (SSA_NAME_IN_FREE_LIST (t))
3132 error ("SSA name in freelist but still referenced");
3138 x = TREE_OPERAND (t, 0);
3139 if (TREE_CODE (x) == BIT_FIELD_REF
3140 && is_gimple_reg (TREE_OPERAND (x, 0)))
3142 error ("GIMPLE register modified with BIT_FIELD_REF");
3148 x = TREE_OPERAND (t, 0);
3149 while (TREE_CODE (x) == ARRAY_REF
3150 || TREE_CODE (x) == COMPONENT_REF
3151 || TREE_CODE (x) == REALPART_EXPR
3152 || TREE_CODE (x) == IMAGPART_EXPR)
3153 x = TREE_OPERAND (x, 0);
3154 if (TREE_CODE (x) != VAR_DECL && TREE_CODE (x) != PARM_DECL)
3156 if (!TREE_ADDRESSABLE (x))
3158 error ("address taken, but ADDRESSABLE bit not set");
3164 x = TREE_OPERAND (t, 0);
3165 if (TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE)
3167 error ("non-boolean used in condition");
3174 case FIX_TRUNC_EXPR:
3176 case FIX_FLOOR_EXPR:
3177 case FIX_ROUND_EXPR:
3182 case NON_LVALUE_EXPR:
3183 case TRUTH_NOT_EXPR:
3184 x = TREE_OPERAND (t, 0);
3185 /* We check for constants explicitly since they are not considered
3186 gimple invariants if they overflowed. */
3187 if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c'
3188 && !is_gimple_val (x))
3190 error ("Invalid operand to unary operator");
3205 case UNORDERED_EXPR:
3216 case TRUNC_DIV_EXPR:
3218 case FLOOR_DIV_EXPR:
3219 case ROUND_DIV_EXPR:
3220 case TRUNC_MOD_EXPR:
3222 case FLOOR_MOD_EXPR:
3223 case ROUND_MOD_EXPR:
3225 case EXACT_DIV_EXPR:
3235 x = TREE_OPERAND (t, 0);
3236 /* We check for constants explicitly since they are not considered
3237 gimple invariants if they overflowed. */
3238 if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c'
3239 && !is_gimple_val (x))
3241 error ("Invalid operand to binary operator");
3244 x = TREE_OPERAND (t, 1);
3245 /* We check for constants explicitly since they are not considered
3246 gimple invariants if they overflowed. */
3247 if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c'
3248 && !is_gimple_val (x))
3250 error ("Invalid operand to binary operator");
3262 /* Verify STMT, return true if STMT is not in GIMPLE form.
3263 TODO: Implement type checking. */
3266 verify_stmt (tree stmt)
3270 if (!is_gimple_stmt (stmt))
3272 error ("Is not a valid GIMPLE statement.");
3273 debug_generic_stmt (stmt);
3277 addr = walk_tree (&stmt, verify_expr, NULL, NULL);
3280 debug_generic_stmt (addr);
3288 /* Return true when the T can be shared. */
3291 tree_node_can_be_shared (tree t)
3293 if (TYPE_P (t) || DECL_P (t)
3294 /* We check for constants explicitly since they are not considered
3295 gimple invariants if they overflowed. */
3296 || TREE_CODE_CLASS (TREE_CODE (t)) == 'c'
3297 || is_gimple_min_invariant (t)
3298 || TREE_CODE (t) == SSA_NAME)
3301 while ((TREE_CODE (t) == ARRAY_REF
3302 /* We check for constants explicitly since they are not considered
3303 gimple invariants if they overflowed. */
3304 && (TREE_CODE_CLASS (TREE_CODE (TREE_OPERAND (t, 1))) == 'c'
3305 || is_gimple_min_invariant (TREE_OPERAND (t, 1))))
3306 || (TREE_CODE (t) == COMPONENT_REF
3307 || TREE_CODE (t) == REALPART_EXPR
3308 || TREE_CODE (t) == IMAGPART_EXPR))
3309 t = TREE_OPERAND (t, 0);
3318 /* Called via walk_trees. Verify tree sharing. */
3321 verify_node_sharing (tree * tp, int *walk_subtrees, void *data)
3323 htab_t htab = (htab_t) data;
3326 if (tree_node_can_be_shared (*tp))
3328 *walk_subtrees = false;
3332 slot = htab_find_slot (htab, *tp, INSERT);
3341 /* Verify the GIMPLE statement chain. */
3347 block_stmt_iterator bsi;
3352 timevar_push (TV_TREE_STMT_VERIFY);
3353 htab = htab_create (37, htab_hash_pointer, htab_eq_pointer, NULL);
3360 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
3362 int phi_num_args = PHI_NUM_ARGS (phi);
3364 for (i = 0; i < phi_num_args; i++)
3366 tree t = PHI_ARG_DEF (phi, i);
3369 /* Addressable variables do have SSA_NAMEs but they
3370 are not considered gimple values. */
3371 if (TREE_CODE (t) != SSA_NAME
3372 && TREE_CODE (t) != FUNCTION_DECL
3373 && !is_gimple_val (t))
3375 error ("PHI def is not a GIMPLE value");
3376 debug_generic_stmt (phi);
3377 debug_generic_stmt (t);
3381 addr = walk_tree (&t, verify_expr, NULL, NULL);
3384 debug_generic_stmt (addr);
3388 addr = walk_tree (&t, verify_node_sharing, htab, NULL);
3391 error ("Incorrect sharing of tree nodes");
3392 debug_generic_stmt (phi);
3393 debug_generic_stmt (addr);
3399 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3401 tree stmt = bsi_stmt (bsi);
3402 err |= verify_stmt (stmt);
3403 addr = walk_tree (&stmt, verify_node_sharing, htab, NULL);
3406 error ("Incorrect sharing of tree nodes");
3407 debug_generic_stmt (stmt);
3408 debug_generic_stmt (addr);
3415 internal_error ("verify_stmts failed.");
3418 timevar_pop (TV_TREE_STMT_VERIFY);
3422 /* Verifies that the flow information is OK. */
3425 tree_verify_flow_info (void)
3429 block_stmt_iterator bsi;
3433 if (ENTRY_BLOCK_PTR->stmt_list)
3435 error ("ENTRY_BLOCK has a statement list associated with it\n");
3439 if (EXIT_BLOCK_PTR->stmt_list)
3441 error ("EXIT_BLOCK has a statement list associated with it\n");
3445 for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next)
3446 if (e->flags & EDGE_FALLTHRU)
3448 error ("Fallthru to exit from bb %d\n", e->src->index);
3454 bool found_ctrl_stmt = false;
3456 /* Skip labels on the start of basic block. */
3457 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3459 if (TREE_CODE (bsi_stmt (bsi)) != LABEL_EXPR)
3462 if (label_to_block (LABEL_EXPR_LABEL (bsi_stmt (bsi))) != bb)
3464 error ("Label %s to block does not match in bb %d\n",
3465 IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))),
3470 if (decl_function_context (LABEL_EXPR_LABEL (bsi_stmt (bsi)))
3471 != current_function_decl)
3473 error ("Label %s has incorrect context in bb %d\n",
3474 IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))),
3480 /* Verify that body of basic block BB is free of control flow. */
3481 for (; !bsi_end_p (bsi); bsi_next (&bsi))
3483 tree stmt = bsi_stmt (bsi);
3485 if (found_ctrl_stmt)
3487 error ("Control flow in the middle of basic block %d\n",
3492 if (stmt_ends_bb_p (stmt))
3493 found_ctrl_stmt = true;
3495 if (TREE_CODE (stmt) == LABEL_EXPR)
3497 error ("Label %s in the middle of basic block %d\n",
3498 IDENTIFIER_POINTER (DECL_NAME (stmt)),
3503 bsi = bsi_last (bb);
3504 if (bsi_end_p (bsi))
3507 stmt = bsi_stmt (bsi);
3509 if (is_ctrl_stmt (stmt))
3511 for (e = bb->succ; e; e = e->succ_next)
3512 if (e->flags & EDGE_FALLTHRU)
3514 error ("Fallthru edge after a control statement in bb %d \n",
3520 switch (TREE_CODE (stmt))
3526 if (TREE_CODE (COND_EXPR_THEN (stmt)) != GOTO_EXPR
3527 || TREE_CODE (COND_EXPR_ELSE (stmt)) != GOTO_EXPR)
3529 error ("Structured COND_EXPR at the end of bb %d\n", bb->index);
3533 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
3535 if (!true_edge || !false_edge
3536 || !(true_edge->flags & EDGE_TRUE_VALUE)
3537 || !(false_edge->flags & EDGE_FALSE_VALUE)
3538 || (true_edge->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL))
3539 || (false_edge->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL))
3540 || bb->succ->succ_next->succ_next)
3542 error ("Wrong outgoing edge flags at end of bb %d\n",
3547 if (!has_label_p (true_edge->dest,
3548 GOTO_DESTINATION (COND_EXPR_THEN (stmt))))
3550 error ("`then' label does not match edge at end of bb %d\n",
3555 if (!has_label_p (false_edge->dest,
3556 GOTO_DESTINATION (COND_EXPR_ELSE (stmt))))
3558 error ("`else' label does not match edge at end of bb %d\n",
3566 if (simple_goto_p (stmt))
3568 error ("Explicit goto at end of bb %d\n", bb->index);
3573 /* FIXME. We should double check that the labels in the
3574 destination blocks have their address taken. */
3575 for (e = bb->succ; e; e = e->succ_next)
3576 if ((e->flags & (EDGE_FALLTHRU | EDGE_TRUE_VALUE
3577 | EDGE_FALSE_VALUE))
3578 || !(e->flags & EDGE_ABNORMAL))
3580 error ("Wrong outgoing edge flags at end of bb %d\n",
3588 if (!bb->succ || bb->succ->succ_next
3589 || (bb->succ->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL
3590 | EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
3592 error ("Wrong outgoing edge flags at end of bb %d\n", bb->index);
3595 if (bb->succ->dest != EXIT_BLOCK_PTR)
3597 error ("Return edge does not point to exit in bb %d\n",
3610 vec = SWITCH_LABELS (stmt);
3611 n = TREE_VEC_LENGTH (vec);
3613 /* Mark all the destination basic blocks. */
3614 for (i = 0; i < n; ++i)
3616 tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
3617 basic_block label_bb = label_to_block (lab);
3619 if (label_bb->aux && label_bb->aux != (void *)1)
3621 label_bb->aux = (void *)1;
3624 /* Verify that the case labels are sorted. */
3625 prev = TREE_VEC_ELT (vec, 0);
3626 for (i = 1; i < n - 1; ++i)
3628 tree c = TREE_VEC_ELT (vec, i);
3631 error ("Found default case not at end of case vector");
3635 if (! tree_int_cst_lt (CASE_LOW (prev), CASE_LOW (c)))
3637 error ("Case labels not sorted:\n ");
3638 print_generic_expr (stderr, prev, 0);
3639 fprintf (stderr," is greater than ");
3640 print_generic_expr (stderr, c, 0);
3641 fprintf (stderr," but comes before it.\n");
3646 if (CASE_LOW (TREE_VEC_ELT (vec, n - 1)))
3648 error ("No default case found at end of case vector");
3652 for (e = bb->succ; e; e = e->succ_next)
3656 error ("Extra outgoing edge %d->%d\n",
3657 bb->index, e->dest->index);
3660 e->dest->aux = (void *)2;
3661 if ((e->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL
3662 | EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
3664 error ("Wrong outgoing edge flags at end of bb %d\n",
3670 /* Check that we have all of them. */
3671 for (i = 0; i < n; ++i)
3673 tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
3674 basic_block label_bb = label_to_block (lab);
3676 if (label_bb->aux != (void *)2)
3678 error ("Missing edge %i->%i\n",
3679 bb->index, label_bb->index);
3684 for (e = bb->succ; e; e = e->succ_next)
3685 e->dest->aux = (void *)0;
3692 if (dom_computed[CDI_DOMINATORS] >= DOM_NO_FAST_QUERY)
3693 verify_dominators (CDI_DOMINATORS);
3699 /* Updates phi nodes after creating forwarder block joined
3700 by edge FALLTHRU. */
3703 tree_make_forwarder_block (edge fallthru)
3706 basic_block dummy, bb;
3707 tree phi, new_phi, var, prev, next;
3709 dummy = fallthru->src;
3710 bb = fallthru->dest;
3712 if (!bb->pred->pred_next)
3715 /* If we redirected a branch we must create new phi nodes at the
3717 for (phi = phi_nodes (dummy); phi; phi = PHI_CHAIN (phi))
3719 var = PHI_RESULT (phi);
3720 new_phi = create_phi_node (var, bb);
3721 SSA_NAME_DEF_STMT (var) = new_phi;
3722 SET_PHI_RESULT (phi, make_ssa_name (SSA_NAME_VAR (var), phi));
3723 add_phi_arg (&new_phi, PHI_RESULT (phi), fallthru);
3726 /* Ensure that the PHI node chain is in the same order. */
3728 for (phi = phi_nodes (bb); phi; phi = next)
3730 next = PHI_CHAIN (phi);
3731 PHI_CHAIN (phi) = prev;
3734 set_phi_nodes (bb, prev);
3736 /* Add the arguments we have stored on edges. */
3737 for (e = bb->pred; e; e = e->pred_next)
3742 for (phi = phi_nodes (bb), var = PENDING_STMT (e);
3744 phi = PHI_CHAIN (phi), var = TREE_CHAIN (var))
3745 add_phi_arg (&phi, TREE_VALUE (var), e);
3747 PENDING_STMT (e) = NULL;
3752 /* Return true if basic block BB does nothing except pass control
3753 flow to another block and that we can safely insert a label at
3754 the start of the successor block. */
3757 tree_forwarder_block_p (basic_block bb)
3759 block_stmt_iterator bsi;
3762 /* If we have already determined that this block is not forwardable,
3763 then no further checks are necessary. */
3764 if (! bb_ann (bb)->forwardable)
3767 /* BB must have a single outgoing normal edge. Otherwise it can not be
3768 a forwarder block. */
3770 || bb->succ->succ_next
3771 || bb->succ->dest == EXIT_BLOCK_PTR
3772 || (bb->succ->flags & EDGE_ABNORMAL)
3773 || bb == ENTRY_BLOCK_PTR)
3775 bb_ann (bb)->forwardable = 0;
3779 /* Successors of the entry block are not forwarders. */
3780 for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
3783 bb_ann (bb)->forwardable = 0;
3787 /* BB can not have any PHI nodes. This could potentially be relaxed
3788 early in compilation if we re-rewrote the variables appearing in
3789 any PHI nodes in forwarder blocks. */
3792 bb_ann (bb)->forwardable = 0;
3796 /* Now walk through the statements. We can ignore labels, anything else
3797 means this is not a forwarder block. */
3798 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3800 tree stmt = bsi_stmt (bsi);
3802 switch (TREE_CODE (stmt))
3805 if (DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt)))
3810 bb_ann (bb)->forwardable = 0;
3819 /* Thread jumps over empty statements.
3821 This code should _not_ thread over obviously equivalent conditions
3822 as that requires nontrivial updates to the SSA graph. */
3827 edge e, next, last, old;
3828 basic_block bb, dest, tmp;
3831 bool retval = false;
3834 bb_ann (bb)->forwardable = 1;
3836 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
3838 /* Don't waste time on unreachable blocks. */
3842 /* Nor on forwarders. */
3843 if (tree_forwarder_block_p (bb))
3846 /* This block is now part of a forwarding path, mark it as not
3847 forwardable so that we can detect loops. This bit will be
3849 bb_ann (bb)->forwardable = 0;
3851 /* Examine each of our block's successors to see if it is
3853 for (e = bb->succ; e; e = next)
3855 next = e->succ_next;
3857 /* If the edge is abnormal or its destination is not
3858 forwardable, then there's nothing to do. */
3859 if ((e->flags & EDGE_ABNORMAL)
3860 || !tree_forwarder_block_p (e->dest))
3863 /* Now walk through as many forwarder block as possible to
3864 find the ultimate destination we want to thread our jump
3866 last = e->dest->succ;
3867 bb_ann (e->dest)->forwardable = 0;
3868 for (dest = e->dest->succ->dest;
3869 tree_forwarder_block_p (dest);
3871 dest = dest->succ->dest)
3873 /* An infinite loop detected. We redirect the edge anyway, so
3874 that the loop is shrinked into single basic block. */
3875 if (!bb_ann (dest)->forwardable)
3878 if (dest->succ->dest == EXIT_BLOCK_PTR)
3881 bb_ann (dest)->forwardable = 0;
3884 /* Reset the forwardable marks to 1. */
3887 tmp = tmp->succ->dest)
3888 bb_ann (tmp)->forwardable = 1;
3890 if (dest == e->dest)
3893 old = find_edge (bb, dest);
3896 /* If there already is an edge, check whether the values
3897 in phi nodes differ. */
3898 if (!phi_alternatives_equal (dest, last, old))
3900 /* The previous block is forwarder. Redirect our jump
3901 to that target instead since we know it has no PHI
3902 nodes that will need updating. */
3905 /* That might mean that no forwarding at all is possible. */
3906 if (dest == e->dest)
3909 old = find_edge (bb, dest);
3913 /* Perform the redirection. */
3915 e = redirect_edge_and_branch (e, dest);
3917 /* TODO -- updating dominators in this case is simple. */
3918 free_dominance_info (CDI_DOMINATORS);
3922 /* Update PHI nodes. We know that the new argument should
3923 have the same value as the argument associated with LAST.
3924 Otherwise we would have changed our target block above. */
3925 for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
3927 arg = phi_arg_from_edge (phi, last);
3930 add_phi_arg (&phi, PHI_ARG_DEF (phi, arg), e);
3935 /* Reset the forwardable bit on our block since it's no longer in
3936 a forwarding chain path. */
3937 bb_ann (bb)->forwardable = 1;
3944 /* Return a non-special label in the head of basic block BLOCK.
3945 Create one if it doesn't exist. */
3948 tree_block_label (basic_block bb)
3950 block_stmt_iterator i, s = bsi_start (bb);
3954 for (i = s; !bsi_end_p (i); first = false, bsi_next (&i))
3956 stmt = bsi_stmt (i);
3957 if (TREE_CODE (stmt) != LABEL_EXPR)
3959 label = LABEL_EXPR_LABEL (stmt);
3960 if (!DECL_NONLOCAL (label))
3963 bsi_move_before (&i, &s);
3968 label = create_artificial_label ();
3969 stmt = build1 (LABEL_EXPR, void_type_node, label);
3970 bsi_insert_before (&s, stmt, BSI_NEW_STMT);
3975 /* Attempt to perform edge redirection by replacing a possibly complex
3976 jump instruction by a goto or by removing the jump completely.
3977 This can apply only if all edges now point to the same block. The
3978 parameters and return values are equivalent to
3979 redirect_edge_and_branch. */
3982 tree_try_redirect_by_replacing_jump (edge e, basic_block target)
3984 basic_block src = e->src;
3986 block_stmt_iterator b;
3989 /* Verify that all targets will be TARGET. */
3990 for (tmp = src->succ; tmp; tmp = tmp->succ_next)
3991 if (tmp->dest != target && tmp != e)
4000 stmt = bsi_stmt (b);
4002 if (TREE_CODE (stmt) == COND_EXPR
4003 || TREE_CODE (stmt) == SWITCH_EXPR)
4006 e = ssa_redirect_edge (e, target);
4007 e->flags = EDGE_FALLTHRU;
4015 /* Redirect E to DEST. Return NULL on failure. Otherwise, return the
4016 edge representing the redirected branch. */
4019 tree_redirect_edge_and_branch (edge e, basic_block dest)
4021 basic_block bb = e->src;
4022 block_stmt_iterator bsi;
4026 if (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH))
4029 if (e->src != ENTRY_BLOCK_PTR
4030 && (ret = tree_try_redirect_by_replacing_jump (e, dest)))
4033 if (e->dest == dest)
4036 label = tree_block_label (dest);
4038 bsi = bsi_last (bb);
4039 stmt = bsi_end_p (bsi) ? NULL : bsi_stmt (bsi);
4041 switch (stmt ? TREE_CODE (stmt) : ERROR_MARK)
4044 stmt = (e->flags & EDGE_TRUE_VALUE
4045 ? COND_EXPR_THEN (stmt)
4046 : COND_EXPR_ELSE (stmt));
4047 GOTO_DESTINATION (stmt) = label;
4051 /* No non-abnormal edges should lead from a non-simple goto, and
4052 simple ones should be represented implicitly. */
4057 tree vec = SWITCH_LABELS (stmt);
4058 size_t i, n = TREE_VEC_LENGTH (vec);
4060 for (i = 0; i < n; ++i)
4062 tree elt = TREE_VEC_ELT (vec, i);
4063 if (label_to_block (CASE_LABEL (elt)) == e->dest)
4064 CASE_LABEL (elt) = label;
4071 e->flags |= EDGE_FALLTHRU;
4075 /* Otherwise it must be a fallthru edge, and we don't need to
4076 do anything besides redirecting it. */
4077 if (!(e->flags & EDGE_FALLTHRU))
4082 /* Update/insert PHI nodes as necessary. */
4084 /* Now update the edges in the CFG. */
4085 e = ssa_redirect_edge (e, dest);
4091 /* Simple wrapper, as we can always redirect fallthru edges. */
4094 tree_redirect_edge_and_branch_force (edge e, basic_block dest)
4096 e = tree_redirect_edge_and_branch (e, dest);
4104 /* Splits basic block BB after statement STMT (but at least after the
4105 labels). If STMT is NULL, BB is split just after the labels. */
4108 tree_split_block (basic_block bb, void *stmt)
4110 block_stmt_iterator bsi, bsi_tgt;
4115 new_bb = create_empty_bb (bb);
4117 /* Redirect the outgoing edges. */
4118 new_bb->succ = bb->succ;
4120 for (e = new_bb->succ; e; e = e->succ_next)
4123 if (stmt && TREE_CODE ((tree) stmt) == LABEL_EXPR)
4126 /* Move everything from BSI to the new basic block. */
4127 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
4129 act = bsi_stmt (bsi);
4130 if (TREE_CODE (act) == LABEL_EXPR)
4143 bsi_tgt = bsi_start (new_bb);
4144 while (!bsi_end_p (bsi))
4146 act = bsi_stmt (bsi);
4148 bsi_insert_after (&bsi_tgt, act, BSI_NEW_STMT);
4155 /* Moves basic block BB after block AFTER. */
4158 tree_move_block_after (basic_block bb, basic_block after)
4160 if (bb->prev_bb == after)
4164 link_block (bb, after);
4170 /* Return true if basic_block can be duplicated. */
4173 tree_can_duplicate_bb_p (basic_block bb ATTRIBUTE_UNUSED)
4179 /* Create a duplicate of the basic block BB. NOTE: This does not
4180 preserve SSA form. */
4183 tree_duplicate_bb (basic_block bb)
4186 block_stmt_iterator bsi, bsi_tgt;
4188 new_bb = create_empty_bb (EXIT_BLOCK_PTR->prev_bb);
4189 bsi_tgt = bsi_start (new_bb);
4190 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
4192 tree stmt = bsi_stmt (bsi);
4194 if (TREE_CODE (stmt) == LABEL_EXPR)
4197 bsi_insert_after (&bsi_tgt, unshare_expr (stmt), BSI_NEW_STMT);
4204 /* Dump FUNCTION_DECL FN to file FILE using FLAGS (see TDF_* in tree.h) */
4207 dump_function_to_file (tree fn, FILE *file, int flags)
4209 tree arg, vars, var;
4210 bool ignore_topmost_bind = false, any_var = false;
4214 fprintf (file, "%s (", lang_hooks.decl_printable_name (fn, 2));
4216 arg = DECL_ARGUMENTS (fn);
4219 print_generic_expr (file, arg, dump_flags);
4220 if (TREE_CHAIN (arg))
4221 fprintf (file, ", ");
4222 arg = TREE_CHAIN (arg);
4224 fprintf (file, ")\n");
4226 if (flags & TDF_RAW)
4228 dump_node (fn, TDF_SLIM | flags, file);
4232 /* When GIMPLE is lowered, the variables are no longer available in
4233 BIND_EXPRs, so display them separately. */
4234 if (cfun && cfun->unexpanded_var_list)
4236 ignore_topmost_bind = true;
4238 fprintf (file, "{\n");
4239 for (vars = cfun->unexpanded_var_list; vars; vars = TREE_CHAIN (vars))
4241 var = TREE_VALUE (vars);
4243 print_generic_decl (file, var, flags);
4244 fprintf (file, "\n");
4250 if (basic_block_info)
4252 /* Make a CFG based dump. */
4253 if (!ignore_topmost_bind)
4254 fprintf (file, "{\n");
4256 if (any_var && n_basic_blocks)
4257 fprintf (file, "\n");
4260 dump_generic_bb (file, bb, 2, flags);
4262 fprintf (file, "}\n");
4268 /* Make a tree based dump. */
4269 chain = DECL_SAVED_TREE (fn);
4271 if (TREE_CODE (chain) == BIND_EXPR)
4273 if (ignore_topmost_bind)
4275 chain = BIND_EXPR_BODY (chain);
4283 if (!ignore_topmost_bind)
4284 fprintf (file, "{\n");
4289 fprintf (file, "\n");
4291 print_generic_stmt_indented (file, chain, flags, indent);
4292 if (ignore_topmost_bind)
4293 fprintf (file, "}\n");
4296 fprintf (file, "\n\n");
4300 /* Pretty print of the loops intermediate representation. */
4301 static void print_loop (FILE *, struct loop *, int);
4302 static void print_pred_bbs (FILE *, edge);
4303 static void print_succ_bbs (FILE *, edge);
4306 /* Print the predecessors indexes of edge E on FILE. */
4309 print_pred_bbs (FILE *file, edge e)
4314 else if (e->pred_next == NULL)
4315 fprintf (file, "bb_%d", e->src->index);
4319 fprintf (file, "bb_%d, ", e->src->index);
4320 print_pred_bbs (file, e->pred_next);
4325 /* Print the successors indexes of edge E on FILE. */
4328 print_succ_bbs (FILE *file, edge e)
4332 else if (e->succ_next == NULL)
4333 fprintf (file, "bb_%d", e->dest->index);
4336 fprintf (file, "bb_%d, ", e->dest->index);
4337 print_succ_bbs (file, e->succ_next);
4342 /* Pretty print LOOP on FILE, indented INDENT spaces. */
4345 print_loop (FILE *file, struct loop *loop, int indent)
4353 s_indent = (char *) alloca ((size_t) indent + 1);
4354 memset ((void *) s_indent, ' ', (size_t) indent);
4355 s_indent[indent] = '\0';
4357 /* Print the loop's header. */
4358 fprintf (file, "%sloop_%d\n", s_indent, loop->num);
4360 /* Print the loop's body. */
4361 fprintf (file, "%s{\n", s_indent);
4363 if (bb->loop_father == loop)
4365 /* Print the basic_block's header. */
4366 fprintf (file, "%s bb_%d (preds = {", s_indent, bb->index);
4367 print_pred_bbs (file, bb->pred);
4368 fprintf (file, "}, succs = {");
4369 print_succ_bbs (file, bb->succ);
4370 fprintf (file, "})\n");
4372 /* Print the basic_block's body. */
4373 fprintf (file, "%s {\n", s_indent);
4374 tree_dump_bb (bb, file, indent + 4);
4375 fprintf (file, "%s }\n", s_indent);
4378 print_loop (file, loop->inner, indent + 2);
4379 fprintf (file, "%s}\n", s_indent);
4380 print_loop (file, loop->next, indent);
4384 /* Follow a CFG edge from the entry point of the program, and on entry
4385 of a loop, pretty print the loop structure on FILE. */
4388 print_loop_ir (FILE *file)
4392 bb = BASIC_BLOCK (0);
4393 if (bb && bb->loop_father)
4394 print_loop (file, bb->loop_father, 0);
4398 /* Debugging loops structure at tree level. */
4401 debug_loop_ir (void)
4403 print_loop_ir (stderr);
4407 /* Return true if BB ends with a call, possibly followed by some
4408 instructions that must stay with the call. Return false,
4412 tree_block_ends_with_call_p (basic_block bb)
4414 block_stmt_iterator bsi = bsi_last (bb);
4415 tree t = tsi_stmt (bsi.tsi);
4417 if (TREE_CODE (t) == RETURN_EXPR && TREE_OPERAND (t, 0))
4418 t = TREE_OPERAND (t, 0);
4420 if (TREE_CODE (t) == MODIFY_EXPR)
4421 t = TREE_OPERAND (t, 1);
4423 return TREE_CODE (t) == CALL_EXPR;
4427 /* Return true if BB ends with a conditional branch. Return false,
4431 tree_block_ends_with_condjump_p (basic_block bb)
4433 tree stmt = tsi_stmt (bsi_last (bb).tsi);
4434 return (TREE_CODE (stmt) == COND_EXPR);
4438 /* Return true if we need to add fake edge to exit at statement T.
4439 Helper function for tree_flow_call_edges_add. */
4442 need_fake_edge_p (tree t)
4444 if (TREE_CODE (t) == RETURN_EXPR && TREE_OPERAND (t, 0))
4445 t = TREE_OPERAND (t, 0);
4447 if (TREE_CODE (t) == MODIFY_EXPR)
4448 t = TREE_OPERAND (t, 1);
4450 /* NORETURN and LONGJMP calls already have an edge to exit.
4451 CONST, PURE and ALWAYS_RETURN calls do not need one.
4452 We don't currently check for CONST and PURE here, although
4453 it would be a good idea, because those attributes are
4454 figured out from the RTL in mark_constant_function, and
4455 the counter incrementation code from -fprofile-arcs
4456 leads to different results from -fbranch-probabilities. */
4457 if (TREE_CODE (t) == CALL_EXPR
4458 && !(call_expr_flags (t) &
4459 (ECF_NORETURN | ECF_LONGJMP | ECF_ALWAYS_RETURN)))
4462 if (TREE_CODE (t) == ASM_EXPR
4463 && (ASM_VOLATILE_P (t) || ASM_INPUT_P (t)))
4470 /* Add fake edges to the function exit for any non constant and non
4471 noreturn calls, volatile inline assembly in the bitmap of blocks
4472 specified by BLOCKS or to the whole CFG if BLOCKS is zero. Return
4473 the number of blocks that were split.
4475 The goal is to expose cases in which entering a basic block does
4476 not imply that all subsequent instructions must be executed. */
4479 tree_flow_call_edges_add (sbitmap blocks)
4482 int blocks_split = 0;
4483 int last_bb = last_basic_block;
4484 bool check_last_block = false;
4486 if (n_basic_blocks == 0)
4490 check_last_block = true;
4492 check_last_block = TEST_BIT (blocks, EXIT_BLOCK_PTR->prev_bb->index);
4494 /* In the last basic block, before epilogue generation, there will be
4495 a fallthru edge to EXIT. Special care is required if the last insn
4496 of the last basic block is a call because make_edge folds duplicate
4497 edges, which would result in the fallthru edge also being marked
4498 fake, which would result in the fallthru edge being removed by
4499 remove_fake_edges, which would result in an invalid CFG.
4501 Moreover, we can't elide the outgoing fake edge, since the block
4502 profiler needs to take this into account in order to solve the minimal
4503 spanning tree in the case that the call doesn't return.
4505 Handle this by adding a dummy instruction in a new last basic block. */
4506 if (check_last_block)
4508 basic_block bb = EXIT_BLOCK_PTR->prev_bb;
4509 block_stmt_iterator bsi = bsi_last (bb);
4511 if (!bsi_end_p (bsi))
4514 if (need_fake_edge_p (t))
4518 for (e = bb->succ; e; e = e->succ_next)
4519 if (e->dest == EXIT_BLOCK_PTR)
4521 bsi_insert_on_edge (e, build_empty_stmt ());
4522 bsi_commit_edge_inserts ((int *)NULL);
4528 /* Now add fake edges to the function exit for any non constant
4529 calls since there is no way that we can determine if they will
4531 for (i = 0; i < last_bb; i++)
4533 basic_block bb = BASIC_BLOCK (i);
4534 block_stmt_iterator bsi;
4535 tree stmt, last_stmt;
4540 if (blocks && !TEST_BIT (blocks, i))
4543 bsi = bsi_last (bb);
4544 if (!bsi_end_p (bsi))
4546 last_stmt = bsi_stmt (bsi);
4549 stmt = bsi_stmt (bsi);
4550 if (need_fake_edge_p (stmt))
4553 /* The handling above of the final block before the
4554 epilogue should be enough to verify that there is
4555 no edge to the exit block in CFG already.
4556 Calling make_edge in such case would cause us to
4557 mark that edge as fake and remove it later. */
4558 #ifdef ENABLE_CHECKING
4559 if (stmt == last_stmt)
4560 for (e = bb->succ; e; e = e->succ_next)
4561 if (e->dest == EXIT_BLOCK_PTR)
4565 /* Note that the following may create a new basic block
4566 and renumber the existing basic blocks. */
4567 if (stmt != last_stmt)
4569 e = split_block (bb, stmt);
4573 make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
4577 while (!bsi_end_p (bsi));
4582 verify_flow_info ();
4584 return blocks_split;
4588 struct cfg_hooks tree_cfg_hooks = {
4590 tree_verify_flow_info,
4591 tree_dump_bb, /* dump_bb */
4592 create_bb, /* create_basic_block */
4593 tree_redirect_edge_and_branch,/* redirect_edge_and_branch */
4594 tree_redirect_edge_and_branch_force,/* redirect_edge_and_branch_force */
4595 remove_bb, /* delete_basic_block */
4596 tree_split_block, /* split_block */
4597 tree_move_block_after, /* move_block_after */
4598 tree_can_merge_blocks_p, /* can_merge_blocks_p */
4599 tree_merge_blocks, /* merge_blocks */
4600 tree_predict_edge, /* predict_edge */
4601 tree_predicted_by_p, /* predicted_by_p */
4602 tree_can_duplicate_bb_p, /* can_duplicate_block_p */
4603 tree_duplicate_bb, /* duplicate_block */
4604 tree_split_edge, /* split_edge */
4605 tree_make_forwarder_block, /* make_forward_block */
4606 NULL, /* tidy_fallthru_edge */
4607 tree_block_ends_with_call_p, /* block_ends_with_call_p */
4608 tree_block_ends_with_condjump_p, /* block_ends_with_condjump_p */
4609 tree_flow_call_edges_add /* flow_call_edges_add */
4613 /* Split all critical edges. */
4616 split_critical_edges (void)
4623 for (e = bb->succ; e ; e = e->succ_next)
4624 if (EDGE_CRITICAL_P (e) && !(e->flags & EDGE_ABNORMAL))
4631 struct tree_opt_pass pass_split_crit_edges =
4633 "crited", /* name */
4635 split_critical_edges, /* execute */
4638 0, /* static_pass_number */
4639 TV_TREE_SPLIT_EDGES, /* tv_id */
4640 PROP_cfg, /* properties required */
4641 PROP_no_crit_edges, /* properties_provided */
4642 0, /* properties_destroyed */
4643 0, /* todo_flags_start */
4644 TODO_dump_func, /* todo_flags_finish */
4647 /* Emit return warnings. */
4650 execute_warn_function_return (void)
4656 if (warn_missing_noreturn
4657 && !TREE_THIS_VOLATILE (cfun->decl)
4658 && EXIT_BLOCK_PTR->pred == NULL
4659 && !lang_hooks.function.missing_noreturn_ok_p (cfun->decl))
4660 warning ("%Jfunction might be possible candidate for attribute `noreturn'",
4663 /* If we have a path to EXIT, then we do return. */
4664 if (TREE_THIS_VOLATILE (cfun->decl)
4665 && EXIT_BLOCK_PTR->pred != NULL)
4668 for (e = EXIT_BLOCK_PTR->pred; e ; e = e->pred_next)
4670 last = last_stmt (e->src);
4671 if (TREE_CODE (last) == RETURN_EXPR
4672 && (locus = EXPR_LOCUS (last)) != NULL)
4676 locus = &cfun->function_end_locus;
4677 warning ("%H`noreturn' function does return", locus);
4680 /* If we see "return;" in some basic block, then we do reach the end
4681 without returning a value. */
4682 else if (warn_return_type
4683 && EXIT_BLOCK_PTR->pred != NULL
4684 && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl))))
4686 for (e = EXIT_BLOCK_PTR->pred; e ; e = e->pred_next)
4688 tree last = last_stmt (e->src);
4689 if (TREE_CODE (last) == RETURN_EXPR
4690 && TREE_OPERAND (last, 0) == NULL)
4692 locus = EXPR_LOCUS (last);
4694 locus = &cfun->function_end_locus;
4695 warning ("%Hcontrol reaches end of non-void function", locus);
4703 /* Given a basic block B which ends with a conditional and has
4704 precisely two successors, determine which of the edges is taken if
4705 the conditional is true and which is taken if the conditional is
4706 false. Set TRUE_EDGE and FALSE_EDGE appropriately. */
4709 extract_true_false_edges_from_block (basic_block b,
4715 if (e->flags & EDGE_TRUE_VALUE)
4718 *false_edge = e->succ_next;
4723 *true_edge = e->succ_next;
4727 struct tree_opt_pass pass_warn_function_return =
4731 execute_warn_function_return, /* execute */
4734 0, /* static_pass_number */
4736 PROP_ssa, /* properties_required */
4737 0, /* properties_provided */
4738 0, /* properties_destroyed */
4739 0, /* todo_flags_start */
4740 0 /* todo_flags_finish */
4743 #include "gt-tree-cfg.h"