/* Control flow functions for trees. Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc. Contributed by Diego Novillo This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "rtl.h" #include "tm_p.h" #include "hard-reg-set.h" #include "basic-block.h" #include "output.h" #include "errors.h" #include "flags.h" #include "function.h" #include "expr.h" #include "ggc.h" #include "langhooks.h" #include "diagnostic.h" #include "tree-flow.h" #include "timevar.h" #include "tree-dump.h" #include "tree-pass.h" #include "toplev.h" #include "except.h" #include "cfgloop.h" /* This file contains functions for building the Control Flow Graph (CFG) for a function tree. */ /* Local declarations. */ /* Initial capacity for the basic block array. */ static const int initial_cfg_capacity = 20; /* Mapping of labels to their associated blocks. This can greatly speed up building of the CFG in code with lots of gotos. */ static GTY(()) varray_type label_to_block_map; /* CFG statistics. */ struct cfg_stats_d { long num_merged_labels; }; static struct cfg_stats_d cfg_stats; /* Nonzero if we found a computed goto while building basic blocks. */ static bool found_computed_goto; /* Basic blocks and flowgraphs. */ static basic_block create_bb (void *, void *, basic_block); static void create_block_annotation (basic_block); static void free_blocks_annotations (void); static void clear_blocks_annotations (void); static void make_blocks (tree); static void factor_computed_gotos (void); static tree tree_block_label (basic_block bb); /* Edges. */ static void make_edges (void); static void make_ctrl_stmt_edges (basic_block); static void make_exit_edges (basic_block); static void make_cond_expr_edges (basic_block); static void make_switch_expr_edges (basic_block); static void make_goto_expr_edges (basic_block); static edge tree_redirect_edge_and_branch (edge, basic_block); static edge tree_try_redirect_by_replacing_jump (edge, basic_block); static void split_critical_edges (void); /* Various helpers. */ static inline bool stmt_starts_bb_p (tree, tree); static int tree_verify_flow_info (void); static void tree_make_forwarder_block (edge); static bool thread_jumps (void); static bool tree_forwarder_block_p (basic_block); static void bsi_commit_edge_inserts_1 (edge e); static void tree_cfg2vcg (FILE *); /* Flowgraph optimization and cleanup. */ static void tree_merge_blocks (basic_block, basic_block); static bool tree_can_merge_blocks_p (basic_block, basic_block); static void remove_bb (basic_block); static void group_case_labels (void); static void cleanup_dead_labels (void); static bool cleanup_control_flow (void); static bool cleanup_control_expr_graph (basic_block, block_stmt_iterator); static edge find_taken_edge_cond_expr (basic_block, tree); static edge find_taken_edge_switch_expr (basic_block, tree); static tree find_case_label_for_value (tree, tree); static bool phi_alternatives_equal (basic_block, edge, edge); /*--------------------------------------------------------------------------- Create basic blocks ---------------------------------------------------------------------------*/ /* Entry point to the CFG builder for trees. TP points to the list of statements to be added to the flowgraph. */ static void build_tree_cfg (tree *tp) { /* Register specific tree functions. */ tree_register_cfg_hooks (); /* Initialize rbi_pool. */ alloc_rbi_pool (); /* Initialize the basic block array. */ init_flow (); n_basic_blocks = 0; last_basic_block = 0; VARRAY_BB_INIT (basic_block_info, initial_cfg_capacity, "basic_block_info"); memset ((void *) &cfg_stats, 0, sizeof (cfg_stats)); /* Build a mapping of labels to their associated blocks. */ VARRAY_BB_INIT (label_to_block_map, initial_cfg_capacity, "label to block map"); ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR; EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR; found_computed_goto = 0; make_blocks (*tp); /* Computed gotos are hell to deal with, especially if there are lots of them with a large number of destinations. So we factor them to a common computed goto location before we build the edge list. After we convert back to normal form, we will un-factor the computed gotos since factoring introduces an unwanted jump. */ if (found_computed_goto) factor_computed_gotos (); /* Make sure there is always at least one block, even if its empty. */ if (n_basic_blocks == 0) create_empty_bb (ENTRY_BLOCK_PTR); create_block_annotation (ENTRY_BLOCK_PTR); create_block_annotation (EXIT_BLOCK_PTR); /* Adjust the size of the array. */ VARRAY_GROW (basic_block_info, n_basic_blocks); /* To speed up statement iterator walks, we first purge dead labels. */ cleanup_dead_labels (); /* Group case nodes to reduce the number of edges. We do this after cleaning up dead labels because otherwise we miss a lot of obvious case merging opportunities. */ group_case_labels (); /* Create the edges of the flowgraph. */ make_edges (); /* Debugging dumps. */ /* Write the flowgraph to a VCG file. */ { int local_dump_flags; FILE *dump_file = dump_begin (TDI_vcg, &local_dump_flags); if (dump_file) { tree_cfg2vcg (dump_file); dump_end (TDI_vcg, dump_file); } } /* Dump a textual representation of the flowgraph. */ if (dump_file) dump_tree_cfg (dump_file, dump_flags); } static void execute_build_cfg (void) { build_tree_cfg (&DECL_SAVED_TREE (current_function_decl)); } struct tree_opt_pass pass_build_cfg = { "cfg", /* name */ NULL, /* gate */ execute_build_cfg, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_TREE_CFG, /* tv_id */ PROP_gimple_leh, /* properties_required */ PROP_cfg, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_verify_stmts /* todo_flags_finish */ }; /* Search the CFG for any computed gotos. If found, factor them to a common computed goto site. Also record the location of that site so that we can un-factor the gotos after we have converted back to normal form. */ static void factor_computed_gotos (void) { basic_block bb; tree factored_label_decl = NULL; tree var = NULL; tree factored_computed_goto_label = NULL; tree factored_computed_goto = NULL; /* We know there are one or more computed gotos in this function. Examine the last statement in each basic block to see if the block ends with a computed goto. */ FOR_EACH_BB (bb) { block_stmt_iterator bsi = bsi_last (bb); tree last; if (bsi_end_p (bsi)) continue; last = bsi_stmt (bsi); /* Ignore the computed goto we create when we factor the original computed gotos. */ if (last == factored_computed_goto) continue; /* If the last statement is a computed goto, factor it. */ if (computed_goto_p (last)) { tree assignment; /* The first time we find a computed goto we need to create the factored goto block and the variable each original computed goto will use for their goto destination. */ if (! factored_computed_goto) { basic_block new_bb = create_empty_bb (bb); block_stmt_iterator new_bsi = bsi_start (new_bb); /* Create the destination of the factored goto. Each original computed goto will put its desired destination into this variable and jump to the label we create immediately below. */ var = create_tmp_var (ptr_type_node, "gotovar"); /* Build a label for the new block which will contain the factored computed goto. */ factored_label_decl = create_artificial_label (); factored_computed_goto_label = build1 (LABEL_EXPR, void_type_node, factored_label_decl); bsi_insert_after (&new_bsi, factored_computed_goto_label, BSI_NEW_STMT); /* Build our new computed goto. */ factored_computed_goto = build1 (GOTO_EXPR, void_type_node, var); bsi_insert_after (&new_bsi, factored_computed_goto, BSI_NEW_STMT); } /* Copy the original computed goto's destination into VAR. */ assignment = build (MODIFY_EXPR, ptr_type_node, var, GOTO_DESTINATION (last)); bsi_insert_before (&bsi, assignment, BSI_SAME_STMT); /* And re-vector the computed goto to the new destination. */ GOTO_DESTINATION (last) = factored_label_decl; } } } /* Create annotations for a single basic block. */ static void create_block_annotation (basic_block bb) { /* Verify that the tree_annotations field is clear. */ if (bb->tree_annotations) abort (); bb->tree_annotations = ggc_alloc_cleared (sizeof (struct bb_ann_d)); } /* Free the annotations for all the basic blocks. */ static void free_blocks_annotations (void) { clear_blocks_annotations (); } /* Clear the annotations for all the basic blocks. */ static void clear_blocks_annotations (void) { basic_block bb; FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) bb->tree_annotations = NULL; } /* Build a flowgraph for the statement_list STMT_LIST. */ static void make_blocks (tree stmt_list) { tree_stmt_iterator i = tsi_start (stmt_list); tree stmt = NULL; bool start_new_block = true; bool first_stmt_of_list = true; basic_block bb = ENTRY_BLOCK_PTR; while (!tsi_end_p (i)) { tree prev_stmt; prev_stmt = stmt; stmt = tsi_stmt (i); /* If the statement starts a new basic block or if we have determined in a previous pass that we need to create a new block for STMT, do so now. */ if (start_new_block || stmt_starts_bb_p (stmt, prev_stmt)) { if (!first_stmt_of_list) stmt_list = tsi_split_statement_list_before (&i); bb = create_basic_block (stmt_list, NULL, bb); start_new_block = false; } /* Now add STMT to BB and create the subgraphs for special statement codes. */ set_bb_for_stmt (stmt, bb); if (computed_goto_p (stmt)) found_computed_goto = true; /* If STMT is a basic block terminator, set START_NEW_BLOCK for the next iteration. */ if (stmt_ends_bb_p (stmt)) start_new_block = true; tsi_next (&i); first_stmt_of_list = false; } } /* Create and return a new empty basic block after bb AFTER. */ static basic_block create_bb (void *h, void *e, basic_block after) { basic_block bb; if (e) abort (); /* Create and initialize a new basic block. */ bb = alloc_block (); memset (bb, 0, sizeof (*bb)); bb->index = last_basic_block; bb->flags = BB_NEW; bb->stmt_list = h ? h : alloc_stmt_list (); /* Add the new block to the linked list of blocks. */ link_block (bb, after); /* Grow the basic block array if needed. */ if ((size_t) last_basic_block == VARRAY_SIZE (basic_block_info)) { size_t new_size = last_basic_block + (last_basic_block + 3) / 4; VARRAY_GROW (basic_block_info, new_size); } /* Add the newly created block to the array. */ BASIC_BLOCK (last_basic_block) = bb; create_block_annotation (bb); n_basic_blocks++; last_basic_block++; initialize_bb_rbi (bb); return bb; } /*--------------------------------------------------------------------------- Edge creation ---------------------------------------------------------------------------*/ /* Join all the blocks in the flowgraph. */ static void make_edges (void) { basic_block bb; edge e; /* Create an edge from entry to the first block with executable statements in it. */ make_edge (ENTRY_BLOCK_PTR, BASIC_BLOCK (0), EDGE_FALLTHRU); /* Traverse basic block array placing edges. */ FOR_EACH_BB (bb) { tree first = first_stmt (bb); tree last = last_stmt (bb); if (first) { /* Edges for statements that always alter flow control. */ if (is_ctrl_stmt (last)) make_ctrl_stmt_edges (bb); /* Edges for statements that sometimes alter flow control. */ if (is_ctrl_altering_stmt (last)) make_exit_edges (bb); } /* Finally, if no edges were created above, this is a regular basic block that only needs a fallthru edge. */ if (bb->succ == NULL) make_edge (bb, bb->next_bb, EDGE_FALLTHRU); } /* If there is a fallthru edge to exit out of the last block, transform it to a return statement. */ for (e = EXIT_BLOCK_PTR->prev_bb->succ; e; e = e->succ_next) if (e->flags & EDGE_FALLTHRU) break; if (e && e->dest == EXIT_BLOCK_PTR) { block_stmt_iterator bsi; basic_block ret_bb = EXIT_BLOCK_PTR->prev_bb; tree x; /* If E->SRC ends with a call that has an abnormal edge (for EH or nonlocal goto), then we will need to split the edge to insert an explicit return statement. */ if (e != ret_bb->succ || e->succ_next) { ret_bb = split_edge (e); e = ret_bb->succ; } e->flags &= ~EDGE_FALLTHRU; x = build (RETURN_EXPR, void_type_node, NULL_TREE); bsi = bsi_last (ret_bb); bsi_insert_after (&bsi, x, BSI_NEW_STMT); } /* We do not care about fake edges, so remove any that the CFG builder inserted for completeness. */ remove_fake_edges (); /* Clean up the graph and warn for unreachable code. */ cleanup_tree_cfg (); } /* Create edges for control statement at basic block BB. */ static void make_ctrl_stmt_edges (basic_block bb) { tree last = last_stmt (bb); tree first = first_stmt (bb); #if defined ENABLE_CHECKING if (last == NULL_TREE) abort(); #endif if (TREE_CODE (first) == LABEL_EXPR && DECL_NONLOCAL (LABEL_EXPR_LABEL (first))) make_edge (ENTRY_BLOCK_PTR, bb, EDGE_ABNORMAL); switch (TREE_CODE (last)) { case GOTO_EXPR: make_goto_expr_edges (bb); break; case RETURN_EXPR: make_edge (bb, EXIT_BLOCK_PTR, 0); break; case COND_EXPR: make_cond_expr_edges (bb); break; case SWITCH_EXPR: make_switch_expr_edges (bb); break; case RESX_EXPR: make_eh_edges (last); /* Yet another NORETURN hack. */ if (bb->succ == NULL) make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE); break; default: abort (); } } /* Create exit edges for statements in block BB that alter the flow of control. Statements that alter the control flow are 'goto', 'return' and calls to non-returning functions. */ static void make_exit_edges (basic_block bb) { tree last = last_stmt (bb); if (last == NULL_TREE) abort (); switch (TREE_CODE (last)) { case CALL_EXPR: /* If this function receives a nonlocal goto, then we need to make edges from this call site to all the nonlocal goto handlers. */ if (TREE_SIDE_EFFECTS (last) && current_function_has_nonlocal_label) make_goto_expr_edges (bb); /* If this statement has reachable exception handlers, then create abnormal edges to them. */ make_eh_edges (last); /* Some calls are known not to return. For such calls we create a fake edge. We really need to revamp how we build edges so that it's not such a bloody pain to avoid creating edges for this case since all we do is remove these edges when we're done building the CFG. */ if (call_expr_flags (last) & (ECF_NORETURN | ECF_LONGJMP)) { make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE); return; } /* Don't forget the fall-thru edge. */ make_edge (bb, bb->next_bb, EDGE_FALLTHRU); break; case MODIFY_EXPR: /* A MODIFY_EXPR may have a CALL_EXPR on its RHS and the CALL_EXPR may have an abnormal edge. Search the RHS for this case and create any required edges. */ if (TREE_CODE (TREE_OPERAND (last, 1)) == CALL_EXPR && TREE_SIDE_EFFECTS (TREE_OPERAND (last, 1)) && current_function_has_nonlocal_label) make_goto_expr_edges (bb); make_eh_edges (last); make_edge (bb, bb->next_bb, EDGE_FALLTHRU); break; default: abort (); } } /* Create the edges for a COND_EXPR starting at block BB. At this point, both clauses must contain only simple gotos. */ static void make_cond_expr_edges (basic_block bb) { tree entry = last_stmt (bb); basic_block then_bb, else_bb; tree then_label, else_label; #if defined ENABLE_CHECKING if (entry == NULL_TREE || TREE_CODE (entry) != COND_EXPR) abort (); #endif /* Entry basic blocks for each component. */ then_label = GOTO_DESTINATION (COND_EXPR_THEN (entry)); else_label = GOTO_DESTINATION (COND_EXPR_ELSE (entry)); then_bb = label_to_block (then_label); else_bb = label_to_block (else_label); make_edge (bb, then_bb, EDGE_TRUE_VALUE); make_edge (bb, else_bb, EDGE_FALSE_VALUE); } /* Create the edges for a SWITCH_EXPR starting at block BB. At this point, the switch body has been lowered and the SWITCH_LABELS filled in, so this is in effect a multi-way branch. */ static void make_switch_expr_edges (basic_block bb) { tree entry = last_stmt (bb); size_t i, n; tree vec; vec = SWITCH_LABELS (entry); n = TREE_VEC_LENGTH (vec); for (i = 0; i < n; ++i) { tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i)); basic_block label_bb = label_to_block (lab); make_edge (bb, label_bb, 0); } } /* Return the basic block holding label DEST. */ basic_block label_to_block (tree dest) { return VARRAY_BB (label_to_block_map, LABEL_DECL_UID (dest)); } /* Create edges for a goto statement at block BB. */ static void make_goto_expr_edges (basic_block bb) { tree goto_t, dest; basic_block target_bb; int for_call; block_stmt_iterator last = bsi_last (bb); goto_t = bsi_stmt (last); /* If the last statement is not a GOTO (i.e., it is a RETURN_EXPR, CALL_EXPR or MODIFY_EXPR), then the edge is an abnormal edge resulting from a nonlocal goto. */ if (TREE_CODE (goto_t) != GOTO_EXPR) { dest = error_mark_node; for_call = 1; } else { dest = GOTO_DESTINATION (goto_t); for_call = 0; /* A GOTO to a local label creates normal edges. */ if (simple_goto_p (goto_t)) { make_edge (bb, label_to_block (dest), EDGE_FALLTHRU); bsi_remove (&last); return; } /* Nothing more to do for nonlocal gotos. */ if (TREE_CODE (dest) == LABEL_DECL) return; /* Computed gotos remain. */ } /* Look for the block starting with the destination label. In the case of a computed goto, make an edge to any label block we find in the CFG. */ FOR_EACH_BB (target_bb) { block_stmt_iterator bsi; for (bsi = bsi_start (target_bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree target = bsi_stmt (bsi); if (TREE_CODE (target) != LABEL_EXPR) break; if ( /* Computed GOTOs. Make an edge to every label block that has been marked as a potential target for a computed goto. */ (FORCED_LABEL (LABEL_EXPR_LABEL (target)) && for_call == 0) /* Nonlocal GOTO target. Make an edge to every label block that has been marked as a potential target for a nonlocal goto. */ || (DECL_NONLOCAL (LABEL_EXPR_LABEL (target)) && for_call == 1)) { make_edge (bb, target_bb, EDGE_ABNORMAL); break; } } } /* Degenerate case of computed goto with no labels. */ if (!for_call && !bb->succ) make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE); } /*--------------------------------------------------------------------------- Flowgraph analysis ---------------------------------------------------------------------------*/ /* Remove unreachable blocks and other miscellaneous clean up work. */ void cleanup_tree_cfg (void) { bool something_changed = true; timevar_push (TV_TREE_CLEANUP_CFG); /* These three transformations can cascade, so we iterate on them until nothing changes. */ while (something_changed) { something_changed = cleanup_control_flow (); something_changed |= thread_jumps (); something_changed |= delete_unreachable_blocks (); } /* Merging the blocks creates no new opportunities for the other optimizations, so do it here. */ merge_seq_blocks (); compact_blocks (); #ifdef ENABLE_CHECKING verify_flow_info (); #endif timevar_pop (TV_TREE_CLEANUP_CFG); } /* Cleanup useless labels in basic blocks. This is something we wish to do early because it allows us to group case labels before creating the edges for the CFG, and it speeds up block statement iterators in all passes later on. We only run this pass once, running it more than once is probably not profitable. */ /* A map from basic block index to the leading label of that block. */ static tree *label_for_bb; /* Callback for for_each_eh_region. Helper for cleanup_dead_labels. */ static void update_eh_label (struct eh_region *region) { tree old_label = get_eh_region_tree_label (region); if (old_label) { tree new_label = label_for_bb[label_to_block (old_label)->index]; set_eh_region_tree_label (region, new_label); } } /* Cleanup redundant labels. This is a three-steo process: 1) Find the leading label for each block. 2) Redirect all references to labels to the leading labels. 3) Cleanup all useless labels. */ static void cleanup_dead_labels (void) { basic_block bb; label_for_bb = xcalloc (last_basic_block, sizeof (tree)); /* Find a suitable label for each block. We use the first user-defined label is there is one, or otherwise just the first label we see. */ FOR_EACH_BB (bb) { block_stmt_iterator i; for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i)) { tree label, stmt = bsi_stmt (i); if (TREE_CODE (stmt) != LABEL_EXPR) break; label = LABEL_EXPR_LABEL (stmt); /* If we have not yet seen a label for the current block, remember this one and see if there are more labels. */ if (! label_for_bb[bb->index]) { label_for_bb[bb->index] = label; continue; } /* If we did see a label for the current block already, but it is an artificially created label, replace it if the current label is a user defined label. */ if (! DECL_ARTIFICIAL (label) && DECL_ARTIFICIAL (label_for_bb[bb->index])) { label_for_bb[bb->index] = label; break; } } } /* Now redirect all jumps/branches to the selected label. First do so for each block ending in a control statement. */ FOR_EACH_BB (bb) { tree stmt = last_stmt (bb); if (!stmt) continue; switch (TREE_CODE (stmt)) { case COND_EXPR: { tree true_branch, false_branch; basic_block true_bb, false_bb; true_branch = COND_EXPR_THEN (stmt); false_branch = COND_EXPR_ELSE (stmt); true_bb = label_to_block (GOTO_DESTINATION (true_branch)); false_bb = label_to_block (GOTO_DESTINATION (false_branch)); GOTO_DESTINATION (true_branch) = label_for_bb[true_bb->index]; GOTO_DESTINATION (false_branch) = label_for_bb[false_bb->index]; break; } case SWITCH_EXPR: { size_t i; tree vec = SWITCH_LABELS (stmt); size_t n = TREE_VEC_LENGTH (vec); /* Replace all destination labels. */ for (i = 0; i < n; ++i) { tree label = CASE_LABEL (TREE_VEC_ELT (vec, i)); CASE_LABEL (TREE_VEC_ELT (vec, i)) = label_for_bb[label_to_block (label)->index]; } break; } /* We have to handle GOTO_EXPRs until they're removed, and we don't remove them until after we've created the CFG edges. */ case GOTO_EXPR: { tree label = GOTO_DESTINATION (stmt); if (! computed_goto_p (stmt)) GOTO_DESTINATION (stmt) = label_for_bb[label_to_block (label)->index]; break; } default: break; } } for_each_eh_region (update_eh_label); /* Finally, purge dead labels. All user-defined labels and labels that can be the target of non-local gotos are preserved. */ FOR_EACH_BB (bb) { block_stmt_iterator i; tree label_for_this_bb = label_for_bb[bb->index]; if (! label_for_this_bb) continue; for (i = bsi_start (bb); !bsi_end_p (i); ) { tree label, stmt = bsi_stmt (i); if (TREE_CODE (stmt) != LABEL_EXPR) break; label = LABEL_EXPR_LABEL (stmt); if (label == label_for_this_bb || ! DECL_ARTIFICIAL (label) || DECL_NONLOCAL (label)) bsi_next (&i); else bsi_remove (&i); } } free (label_for_bb); } /* Look for blocks ending in a multiway branch (a SWITCH_EXPR in GIMPLE), and scan the sorted vector of cases. Combine the ones jumping to the same label. Eg. three separate entries 1: 2: 3: become one entry 1..3: */ static void group_case_labels (void) { basic_block bb; FOR_EACH_BB (bb) { tree stmt = last_stmt (bb); if (stmt && TREE_CODE (stmt) == SWITCH_EXPR) { tree labels = SWITCH_LABELS (stmt); int old_size = TREE_VEC_LENGTH (labels); int i, j, new_size = old_size; /* Look for possible opportunities to merge cases. Ignore the last element of the label vector because it must be the default case. */ i = 0; while (i < old_size - 2) { tree base_case, base_label, base_high, type; base_case = TREE_VEC_ELT (labels, i); if (! base_case) abort (); type = TREE_TYPE (CASE_LOW (base_case)); base_label = CASE_LABEL (base_case); base_high = CASE_HIGH (base_case) ? CASE_HIGH (base_case) : CASE_LOW (base_case); /* Try to merge case labels. Break out when we reach the end of the label vector or when we cannot merge the next case label with the current one. */ while (i < old_size - 2) { tree merge_case = TREE_VEC_ELT (labels, ++i); tree merge_label = CASE_LABEL (merge_case); tree t = int_const_binop (PLUS_EXPR, base_high, integer_one_node, 1); /* Merge the cases if they jump to the same place, and their ranges are consecutive. */ if (merge_label == base_label && tree_int_cst_equal (CASE_LOW (merge_case), t)) { base_high = CASE_HIGH (merge_case) ? CASE_HIGH (merge_case) : CASE_LOW (merge_case); CASE_HIGH (base_case) = base_high; TREE_VEC_ELT (labels, i) = NULL_TREE; new_size--; } else break; } } /* Compress the case labels in the label vector, and adjust the length of the vector. */ for (i = 0, j = 0; i < new_size; i++) { while (! TREE_VEC_ELT (labels, j)) j++; TREE_VEC_ELT (labels, i) = TREE_VEC_ELT (labels, j++); } TREE_VEC_LENGTH (labels) = new_size; } } } /* Checks whether we can merge block B into block A. */ static bool tree_can_merge_blocks_p (basic_block a, basic_block b) { tree stmt; block_stmt_iterator bsi; if (!a->succ || a->succ->succ_next) return false; if (a->succ->flags & EDGE_ABNORMAL) return false; if (a->succ->dest != b) return false; if (b == EXIT_BLOCK_PTR) return false; if (b->pred->pred_next) return false; /* If A ends by a statement causing exceptions or something similar, we cannot merge the blocks. */ stmt = last_stmt (a); if (stmt && stmt_ends_bb_p (stmt)) return false; /* Do not allow a block with only a non-local label to be merged. */ if (stmt && TREE_CODE (stmt) == LABEL_EXPR && DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt))) return false; /* There may be no phi nodes at the start of b. Most of these degenerate phi nodes should be cleaned up by kill_redundant_phi_nodes. */ if (phi_nodes (b)) return false; /* Do not remove user labels. */ for (bsi = bsi_start (b); !bsi_end_p (bsi); bsi_next (&bsi)) { stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) != LABEL_EXPR) break; if (!DECL_ARTIFICIAL (LABEL_EXPR_LABEL (stmt))) return false; } return true; } /* Merge block B into block A. */ static void tree_merge_blocks (basic_block a, basic_block b) { block_stmt_iterator bsi; tree_stmt_iterator last; if (dump_file) fprintf (dump_file, "Merging blocks %d and %d\n", a->index, b->index); /* Ensure that B follows A. */ move_block_after (b, a); if (!(a->succ->flags & EDGE_FALLTHRU)) abort (); if (last_stmt (a) && stmt_ends_bb_p (last_stmt (a))) abort (); /* Remove labels from B and set bb_for_stmt to A for other statements. */ for (bsi = bsi_start (b); !bsi_end_p (bsi);) { if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR) bsi_remove (&bsi); else { set_bb_for_stmt (bsi_stmt (bsi), a); bsi_next (&bsi); } } /* Merge the chains. */ last = tsi_last (a->stmt_list); tsi_link_after (&last, b->stmt_list, TSI_NEW_STMT); b->stmt_list = NULL; } /* Walk the function tree removing unnecessary statements. * Empty statement nodes are removed * Unnecessary TRY_FINALLY and TRY_CATCH blocks are removed * Unnecessary COND_EXPRs are removed * Some unnecessary BIND_EXPRs are removed Clearly more work could be done. The trick is doing the analysis and removal fast enough to be a net improvement in compile times. Note that when we remove a control structure such as a COND_EXPR BIND_EXPR, or TRY block, we will need to repeat this optimization pass to ensure we eliminate all the useless code. */ struct rus_data { tree *last_goto; bool repeat; bool may_throw; bool may_branch; bool has_label; }; static void remove_useless_stmts_1 (tree *, struct rus_data *); static bool remove_useless_stmts_warn_notreached (tree stmt) { if (EXPR_LOCUS (stmt)) { warning ("%Hwill never be executed", EXPR_LOCUS (stmt)); return true; } switch (TREE_CODE (stmt)) { case STATEMENT_LIST: { tree_stmt_iterator i; for (i = tsi_start (stmt); !tsi_end_p (i); tsi_next (&i)) if (remove_useless_stmts_warn_notreached (tsi_stmt (i))) return true; } break; case COND_EXPR: if (remove_useless_stmts_warn_notreached (COND_EXPR_COND (stmt))) return true; if (remove_useless_stmts_warn_notreached (COND_EXPR_THEN (stmt))) return true; if (remove_useless_stmts_warn_notreached (COND_EXPR_ELSE (stmt))) return true; break; case TRY_FINALLY_EXPR: case TRY_CATCH_EXPR: if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 0))) return true; if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 1))) return true; break; case CATCH_EXPR: return remove_useless_stmts_warn_notreached (CATCH_BODY (stmt)); case EH_FILTER_EXPR: return remove_useless_stmts_warn_notreached (EH_FILTER_FAILURE (stmt)); case BIND_EXPR: return remove_useless_stmts_warn_notreached (BIND_EXPR_BLOCK (stmt)); default: /* Not a live container. */ break; } return false; } static void remove_useless_stmts_cond (tree *stmt_p, struct rus_data *data) { tree then_clause, else_clause, cond; bool save_has_label, then_has_label, else_has_label; save_has_label = data->has_label; data->has_label = false; data->last_goto = NULL; remove_useless_stmts_1 (&COND_EXPR_THEN (*stmt_p), data); then_has_label = data->has_label; data->has_label = false; data->last_goto = NULL; remove_useless_stmts_1 (&COND_EXPR_ELSE (*stmt_p), data); else_has_label = data->has_label; data->has_label = save_has_label | then_has_label | else_has_label; fold_stmt (stmt_p); then_clause = COND_EXPR_THEN (*stmt_p); else_clause = COND_EXPR_ELSE (*stmt_p); cond = COND_EXPR_COND (*stmt_p); /* If neither arm does anything at all, we can remove the whole IF. */ if (!TREE_SIDE_EFFECTS (then_clause) && !TREE_SIDE_EFFECTS (else_clause)) { *stmt_p = build_empty_stmt (); data->repeat = true; } /* If there are no reachable statements in an arm, then we can zap the entire conditional. */ else if (integer_nonzerop (cond) && !else_has_label) { if (warn_notreached) remove_useless_stmts_warn_notreached (else_clause); *stmt_p = then_clause; data->repeat = true; } else if (integer_zerop (cond) && !then_has_label) { if (warn_notreached) remove_useless_stmts_warn_notreached (then_clause); *stmt_p = else_clause; data->repeat = true; } /* Check a couple of simple things on then/else with single stmts. */ else { tree then_stmt = expr_only (then_clause); tree else_stmt = expr_only (else_clause); /* Notice branches to a common destination. */ if (then_stmt && else_stmt && TREE_CODE (then_stmt) == GOTO_EXPR && TREE_CODE (else_stmt) == GOTO_EXPR && (GOTO_DESTINATION (then_stmt) == GOTO_DESTINATION (else_stmt))) { *stmt_p = then_stmt; data->repeat = true; } /* If the THEN/ELSE clause merely assigns a value to a variable or parameter which is already known to contain that value, then remove the useless THEN/ELSE clause. */ else if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL) { if (else_stmt && TREE_CODE (else_stmt) == MODIFY_EXPR && TREE_OPERAND (else_stmt, 0) == cond && integer_zerop (TREE_OPERAND (else_stmt, 1))) COND_EXPR_ELSE (*stmt_p) = alloc_stmt_list (); } else if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR) && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL) && TREE_CONSTANT (TREE_OPERAND (cond, 1))) { tree stmt = (TREE_CODE (cond) == EQ_EXPR ? then_stmt : else_stmt); tree *location = (TREE_CODE (cond) == EQ_EXPR ? &COND_EXPR_THEN (*stmt_p) : &COND_EXPR_ELSE (*stmt_p)); if (stmt && TREE_CODE (stmt) == MODIFY_EXPR && TREE_OPERAND (stmt, 0) == TREE_OPERAND (cond, 0) && TREE_OPERAND (stmt, 1) == TREE_OPERAND (cond, 1)) *location = alloc_stmt_list (); } } /* Protect GOTOs in the arm of COND_EXPRs from being removed. They would be re-introduced during lowering. */ data->last_goto = NULL; } static void remove_useless_stmts_tf (tree *stmt_p, struct rus_data *data) { bool save_may_branch, save_may_throw; bool this_may_branch, this_may_throw; /* Collect may_branch and may_throw information for the body only. */ save_may_branch = data->may_branch; save_may_throw = data->may_throw; data->may_branch = false; data->may_throw = false; data->last_goto = NULL; remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data); this_may_branch = data->may_branch; this_may_throw = data->may_throw; data->may_branch |= save_may_branch; data->may_throw |= save_may_throw; data->last_goto = NULL; remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data); /* If the body is empty, then we can emit the FINALLY block without the enclosing TRY_FINALLY_EXPR. */ if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 0))) { *stmt_p = TREE_OPERAND (*stmt_p, 1); data->repeat = true; } /* If the handler is empty, then we can emit the TRY block without the enclosing TRY_FINALLY_EXPR. */ else if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1))) { *stmt_p = TREE_OPERAND (*stmt_p, 0); data->repeat = true; } /* If the body neither throws, nor branches, then we can safely string the TRY and FINALLY blocks together. */ else if (!this_may_branch && !this_may_throw) { tree stmt = *stmt_p; *stmt_p = TREE_OPERAND (stmt, 0); append_to_statement_list (TREE_OPERAND (stmt, 1), stmt_p); data->repeat = true; } } static void remove_useless_stmts_tc (tree *stmt_p, struct rus_data *data) { bool save_may_throw, this_may_throw; tree_stmt_iterator i; tree stmt; /* Collect may_throw information for the body only. */ save_may_throw = data->may_throw; data->may_throw = false; data->last_goto = NULL; remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data); this_may_throw = data->may_throw; data->may_throw = save_may_throw; /* If the body cannot throw, then we can drop the entire TRY_CATCH_EXPR. */ if (!this_may_throw) { if (warn_notreached) remove_useless_stmts_warn_notreached (TREE_OPERAND (*stmt_p, 1)); *stmt_p = TREE_OPERAND (*stmt_p, 0); data->repeat = true; return; } /* Process the catch clause specially. We may be able to tell that no exceptions propagate past this point. */ this_may_throw = true; i = tsi_start (TREE_OPERAND (*stmt_p, 1)); stmt = tsi_stmt (i); data->last_goto = NULL; switch (TREE_CODE (stmt)) { case CATCH_EXPR: for (; !tsi_end_p (i); tsi_next (&i)) { stmt = tsi_stmt (i); /* If we catch all exceptions, then the body does not propagate exceptions past this point. */ if (CATCH_TYPES (stmt) == NULL) this_may_throw = false; data->last_goto = NULL; remove_useless_stmts_1 (&CATCH_BODY (stmt), data); } break; case EH_FILTER_EXPR: if (EH_FILTER_MUST_NOT_THROW (stmt)) this_may_throw = false; else if (EH_FILTER_TYPES (stmt) == NULL) this_may_throw = false; remove_useless_stmts_1 (&EH_FILTER_FAILURE (stmt), data); break; default: /* Otherwise this is a cleanup. */ remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data); /* If the cleanup is empty, then we can emit the TRY block without the enclosing TRY_CATCH_EXPR. */ if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1))) { *stmt_p = TREE_OPERAND (*stmt_p, 0); data->repeat = true; } break; } data->may_throw |= this_may_throw; } static void remove_useless_stmts_bind (tree *stmt_p, struct rus_data *data) { tree block; /* First remove anything underneath the BIND_EXPR. */ remove_useless_stmts_1 (&BIND_EXPR_BODY (*stmt_p), data); /* If the BIND_EXPR has no variables, then we can pull everything up one level and remove the BIND_EXPR, unless this is the toplevel BIND_EXPR for the current function or an inlined function. When this situation occurs we will want to apply this optimization again. */ block = BIND_EXPR_BLOCK (*stmt_p); if (BIND_EXPR_VARS (*stmt_p) == NULL_TREE && *stmt_p != DECL_SAVED_TREE (current_function_decl) && (! block || ! BLOCK_ABSTRACT_ORIGIN (block) || (TREE_CODE (BLOCK_ABSTRACT_ORIGIN (block)) != FUNCTION_DECL))) { *stmt_p = BIND_EXPR_BODY (*stmt_p); data->repeat = true; } } static void remove_useless_stmts_goto (tree *stmt_p, struct rus_data *data) { tree dest = GOTO_DESTINATION (*stmt_p); data->may_branch = true; data->last_goto = NULL; /* Record the last goto expr, so that we can delete it if unnecessary. */ if (TREE_CODE (dest) == LABEL_DECL) data->last_goto = stmt_p; } static void remove_useless_stmts_label (tree *stmt_p, struct rus_data *data) { tree label = LABEL_EXPR_LABEL (*stmt_p); data->has_label = true; /* We do want to jump across non-local label receiver code. */ if (DECL_NONLOCAL (label)) data->last_goto = NULL; else if (data->last_goto && GOTO_DESTINATION (*data->last_goto) == label) { *data->last_goto = build_empty_stmt (); data->repeat = true; } /* ??? Add something here to delete unused labels. */ } /* If the function is "const" or "pure", then clear TREE_SIDE_EFFECTS on its decl. This allows us to eliminate redundant or useless calls to "const" functions. Gimplifier already does the same operation, but we may notice functions being const and pure once their calls has been gimplified, so we need to update the flag. */ static void update_call_expr_flags (tree call) { tree decl = get_callee_fndecl (call); if (!decl) return; if (call_expr_flags (call) & (ECF_CONST | ECF_PURE)) TREE_SIDE_EFFECTS (call) = 0; if (TREE_NOTHROW (decl)) TREE_NOTHROW (call) = 1; } /* T is CALL_EXPR. Set current_function_calls_* flags. */ void notice_special_calls (tree t) { int flags = call_expr_flags (t); if (flags & ECF_MAY_BE_ALLOCA) current_function_calls_alloca = true; if (flags & ECF_RETURNS_TWICE) current_function_calls_setjmp = true; } /* Clear flags set by notice_special_calls. Used by dead code removal to update the flags. */ void clear_special_calls (void) { current_function_calls_alloca = false; current_function_calls_setjmp = false; } static void remove_useless_stmts_1 (tree *tp, struct rus_data *data) { tree t = *tp; switch (TREE_CODE (t)) { case COND_EXPR: remove_useless_stmts_cond (tp, data); break; case TRY_FINALLY_EXPR: remove_useless_stmts_tf (tp, data); break; case TRY_CATCH_EXPR: remove_useless_stmts_tc (tp, data); break; case BIND_EXPR: remove_useless_stmts_bind (tp, data); break; case GOTO_EXPR: remove_useless_stmts_goto (tp, data); break; case LABEL_EXPR: remove_useless_stmts_label (tp, data); break; case RETURN_EXPR: fold_stmt (tp); data->last_goto = NULL; data->may_branch = true; break; case CALL_EXPR: fold_stmt (tp); data->last_goto = NULL; notice_special_calls (t); update_call_expr_flags (t); if (tree_could_throw_p (t)) data->may_throw = true; break; case MODIFY_EXPR: data->last_goto = NULL; fold_stmt (tp); if (TREE_CODE (TREE_OPERAND (t, 1)) == CALL_EXPR) { update_call_expr_flags (TREE_OPERAND (t, 1)); notice_special_calls (TREE_OPERAND (t, 1)); } if (tree_could_throw_p (t)) data->may_throw = true; break; case STATEMENT_LIST: { tree_stmt_iterator i = tsi_start (t); while (!tsi_end_p (i)) { t = tsi_stmt (i); if (IS_EMPTY_STMT (t)) { tsi_delink (&i); continue; } remove_useless_stmts_1 (tsi_stmt_ptr (i), data); t = tsi_stmt (i); if (TREE_CODE (t) == STATEMENT_LIST) { tsi_link_before (&i, t, TSI_SAME_STMT); tsi_delink (&i); } else tsi_next (&i); } } break; case SWITCH_EXPR: fold_stmt (tp); data->last_goto = NULL; break; default: data->last_goto = NULL; break; } } static void remove_useless_stmts (void) { struct rus_data data; clear_special_calls (); do { memset (&data, 0, sizeof (data)); remove_useless_stmts_1 (&DECL_SAVED_TREE (current_function_decl), &data); } while (data.repeat); } struct tree_opt_pass pass_remove_useless_stmts = { "useless", /* name */ NULL, /* gate */ remove_useless_stmts, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ 0, /* tv_id */ PROP_gimple_any, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func /* todo_flags_finish */ }; /* Remove obviously useless statements in basic block BB. */ static void cfg_remove_useless_stmts_bb (basic_block bb) { block_stmt_iterator bsi; tree stmt = NULL_TREE; tree cond, var = NULL_TREE, val = NULL_TREE; struct var_ann_d *ann; /* Check whether we come here from a condition, and if so, get the condition. */ if (!bb->pred || bb->pred->pred_next || !(bb->pred->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE))) return; cond = COND_EXPR_COND (last_stmt (bb->pred->src)); if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL) { var = cond; val = (bb->pred->flags & EDGE_FALSE_VALUE ? boolean_false_node : boolean_true_node); } else if (TREE_CODE (cond) == TRUTH_NOT_EXPR && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)) { var = TREE_OPERAND (cond, 0); val = (bb->pred->flags & EDGE_FALSE_VALUE ? boolean_true_node : boolean_false_node); } else { if (bb->pred->flags & EDGE_FALSE_VALUE) cond = invert_truthvalue (cond); if (TREE_CODE (cond) == EQ_EXPR && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL) && (TREE_CODE (TREE_OPERAND (cond, 1)) == VAR_DECL || TREE_CODE (TREE_OPERAND (cond, 1)) == PARM_DECL || TREE_CONSTANT (TREE_OPERAND (cond, 1)))) { var = TREE_OPERAND (cond, 0); val = TREE_OPERAND (cond, 1); } else return; } /* Only work for normal local variables. */ ann = var_ann (var); if (!ann || ann->may_aliases || TREE_ADDRESSABLE (var)) return; if (! TREE_CONSTANT (val)) { ann = var_ann (val); if (!ann || ann->may_aliases || TREE_ADDRESSABLE (val)) return; } /* Ignore floating point variables, since comparison behaves weird for them. */ if (FLOAT_TYPE_P (TREE_TYPE (var))) return; for (bsi = bsi_start (bb); !bsi_end_p (bsi);) { stmt = bsi_stmt (bsi); /* If the THEN/ELSE clause merely assigns a value to a variable/parameter which is already known to contain that value, then remove the useless THEN/ELSE clause. */ if (TREE_CODE (stmt) == MODIFY_EXPR && TREE_OPERAND (stmt, 0) == var && operand_equal_p (val, TREE_OPERAND (stmt, 1), 0)) { bsi_remove (&bsi); continue; } /* Invalidate the var if we encounter something that could modify it. */ if (TREE_CODE (stmt) == ASM_EXPR || TREE_CODE (stmt) == VA_ARG_EXPR || (TREE_CODE (stmt) == MODIFY_EXPR && (TREE_OPERAND (stmt, 0) == var || TREE_OPERAND (stmt, 0) == val || TREE_CODE (TREE_OPERAND (stmt, 1)) == VA_ARG_EXPR))) return; bsi_next (&bsi); } } /* A CFG-aware version of remove_useless_stmts. */ void cfg_remove_useless_stmts (void) { basic_block bb; #ifdef ENABLE_CHECKING verify_flow_info (); #endif FOR_EACH_BB (bb) { cfg_remove_useless_stmts_bb (bb); } } /* Remove PHI nodes associated with basic block BB and all edges out of BB. */ static void remove_phi_nodes_and_edges_for_unreachable_block (basic_block bb) { tree phi; /* Since this block is no longer reachable, we can just delete all of its PHI nodes. */ phi = phi_nodes (bb); while (phi) { tree next = TREE_CHAIN (phi); remove_phi_node (phi, NULL_TREE, bb); phi = next; } /* Remove edges to BB's successors. */ while (bb->succ != NULL) ssa_remove_edge (bb->succ); } /* Remove statements of basic block BB. */ static void remove_bb (basic_block bb) { block_stmt_iterator i; location_t *loc = NULL; if (dump_file) { fprintf (dump_file, "Removing basic block %d\n", bb->index); if (dump_flags & TDF_DETAILS) { dump_bb (bb, dump_file, 0); fprintf (dump_file, "\n"); } } /* Remove all the instructions in the block. */ for (i = bsi_start (bb); !bsi_end_p (i); bsi_remove (&i)) { tree stmt = bsi_stmt (i); set_bb_for_stmt (stmt, NULL); /* Don't warn for removed gotos. Gotos are often removed due to jump threading, thus resulting in bogus warnings. Not great, since this way we lose warnings for gotos in the original program that are indeed unreachable. */ if (TREE_CODE (stmt) != GOTO_EXPR && EXPR_LOCUS (stmt) && !loc) loc = EXPR_LOCUS (stmt); } /* If requested, give a warning that the first statement in the block is unreachable. We walk statements backwards in the loop above, so the last statement we process is the first statement in the block. */ if (warn_notreached && loc) warning ("%Hwill never be executed", loc); remove_phi_nodes_and_edges_for_unreachable_block (bb); } /* Examine BB to determine if it is a forwarding block (a block which only transfers control to a new destination). If BB is a forwarding block, then return the edge leading to the ultimate destination. */ edge tree_block_forwards_to (basic_block bb) { block_stmt_iterator bsi; bb_ann_t ann = bb_ann (bb); tree stmt; /* If this block is not forwardable, then avoid useless work. */ if (! ann->forwardable) return NULL; /* Set this block to not be forwardable. This prevents infinite loops since any block currently under examination is considered non-forwardable. */ ann->forwardable = 0; /* No forwarding is possible if this block is a special block (ENTRY/EXIT), this block has more than one successor, this block's single successor is reached via an abnormal edge, this block has phi nodes, or this block's single successor has phi nodes. */ if (bb == EXIT_BLOCK_PTR || bb == ENTRY_BLOCK_PTR || !bb->succ || bb->succ->succ_next || bb->succ->dest == EXIT_BLOCK_PTR || (bb->succ->flags & EDGE_ABNORMAL) != 0 || phi_nodes (bb) || phi_nodes (bb->succ->dest)) return NULL; /* Walk past any labels at the start of this block. */ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) != LABEL_EXPR) break; } /* If we reached the end of this block we may be able to optimize this case. */ if (bsi_end_p (bsi)) { edge dest; /* Recursive call to pick up chains of forwarding blocks. */ dest = tree_block_forwards_to (bb->succ->dest); /* If none found, we forward to bb->succ at minimum. */ if (!dest) dest = bb->succ; ann->forwardable = 1; return dest; } /* No forwarding possible. */ return NULL; } /* Try to remove superfluous control structures. */ static bool cleanup_control_flow (void) { basic_block bb; block_stmt_iterator bsi; bool retval = false; tree stmt; FOR_EACH_BB (bb) { bsi = bsi_last (bb); if (bsi_end_p (bsi)) continue; stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR) retval |= cleanup_control_expr_graph (bb, bsi); } return retval; } /* Disconnect an unreachable block in the control expression starting at block BB. */ static bool cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi) { edge taken_edge; bool retval = false; tree expr = bsi_stmt (bsi), val; if (bb->succ->succ_next) { edge e, next; switch (TREE_CODE (expr)) { case COND_EXPR: val = COND_EXPR_COND (expr); break; case SWITCH_EXPR: val = SWITCH_COND (expr); if (TREE_CODE (val) != INTEGER_CST) return false; break; default: abort (); } taken_edge = find_taken_edge (bb, val); if (!taken_edge) return false; /* Remove all the edges except the one that is always executed. */ for (e = bb->succ; e; e = next) { next = e->succ_next; if (e != taken_edge) { taken_edge->probability += e->probability; taken_edge->count += e->count; ssa_remove_edge (e); retval = true; } } if (taken_edge->probability > REG_BR_PROB_BASE) taken_edge->probability = REG_BR_PROB_BASE; } else taken_edge = bb->succ; bsi_remove (&bsi); taken_edge->flags = EDGE_FALLTHRU; /* We removed some paths from the cfg. */ if (dom_computed[CDI_DOMINATORS] >= DOM_CONS_OK) dom_computed[CDI_DOMINATORS] = DOM_CONS_OK; return retval; } /* Given a control block BB and a constant value VAL, return the edge that will be taken out of the block. If VAL does not match a unique edge, NULL is returned. */ edge find_taken_edge (basic_block bb, tree val) { tree stmt; stmt = last_stmt (bb); #if defined ENABLE_CHECKING if (stmt == NULL_TREE || !is_ctrl_stmt (stmt)) abort (); #endif /* If VAL is not a constant, we can't determine which edge might be taken. */ if (val == NULL || !really_constant_p (val)) return NULL; if (TREE_CODE (stmt) == COND_EXPR) return find_taken_edge_cond_expr (bb, val); if (TREE_CODE (stmt) == SWITCH_EXPR) return find_taken_edge_switch_expr (bb, val); return bb->succ; } /* Given a constant value VAL and the entry block BB to a COND_EXPR statement, determine which of the two edges will be taken out of the block. Return NULL if either edge may be taken. */ static edge find_taken_edge_cond_expr (basic_block bb, tree val) { edge true_edge, false_edge; extract_true_false_edges_from_block (bb, &true_edge, &false_edge); /* If both edges of the branch lead to the same basic block, it doesn't matter which edge is taken. */ if (true_edge->dest == false_edge->dest) return true_edge; /* Otherwise, try to determine which branch of the if() will be taken. If VAL is a constant but it can't be reduced to a 0 or a 1, then we don't really know which edge will be taken at runtime. This may happen when comparing addresses (e.g., if (&var1 == 4)). */ if (integer_nonzerop (val)) return true_edge; else if (integer_zerop (val)) return false_edge; else return NULL; } /* Given a constant value VAL and the entry block BB to a SWITCH_EXPR statement, determine which edge will be taken out of the block. Return NULL if any edge may be taken. */ static edge find_taken_edge_switch_expr (basic_block bb, tree val) { tree switch_expr, taken_case; basic_block dest_bb; edge e; if (TREE_CODE (val) != INTEGER_CST) return NULL; switch_expr = last_stmt (bb); taken_case = find_case_label_for_value (switch_expr, val); dest_bb = label_to_block (CASE_LABEL (taken_case)); e = find_edge (bb, dest_bb); if (!e) abort (); return e; } /* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL. We can make optimal use here of the fact that the case labels are sorted: We can do a binary search for a case matching VAL. */ static tree find_case_label_for_value (tree switch_expr, tree val) { tree vec = SWITCH_LABELS (switch_expr); size_t low, high, n = TREE_VEC_LENGTH (vec); tree default_case = TREE_VEC_ELT (vec, n - 1); for (low = -1, high = n - 1; high - low > 1; ) { size_t i = (high + low) / 2; tree t = TREE_VEC_ELT (vec, i); int cmp; /* Cache the result of comparing CASE_LOW and val. */ cmp = tree_int_cst_compare (CASE_LOW (t), val); if (cmp > 0) high = i; else low = i; if (CASE_HIGH (t) == NULL) { /* A singe-valued case label. */ if (cmp == 0) return t; } else { /* A case range. We can only handle integer ranges. */ if (cmp <= 0 && tree_int_cst_compare (CASE_HIGH (t), val) >= 0) return t; } } return default_case; } /* If all the PHI nodes in DEST have alternatives for E1 and E2 and those alternatives are equal in each of the PHI nodes, then return true, else return false. */ static bool phi_alternatives_equal (basic_block dest, edge e1, edge e2) { tree phi, val1, val2; int n1, n2; for (phi = phi_nodes (dest); phi; phi = TREE_CHAIN (phi)) { n1 = phi_arg_from_edge (phi, e1); n2 = phi_arg_from_edge (phi, e2); #ifdef ENABLE_CHECKING if (n1 < 0 || n2 < 0) abort (); #endif val1 = PHI_ARG_DEF (phi, n1); val2 = PHI_ARG_DEF (phi, n2); if (!operand_equal_p (val1, val2, 0)) return false; } return true; } /* Computing the Dominance Frontier: As described in Morgan, section 3.5, this may be done simply by walking the dominator tree bottom-up, computing the frontier for the children before the parent. When considering a block B, there are two cases: (1) A flow graph edge leaving B that does not lead to a child of B in the dominator tree must be a block that is either equal to B or not dominated by B. Such blocks belong in the frontier of B. (2) Consider a block X in the frontier of one of the children C of B. If X is not equal to B and is not dominated by B, it is in the frontier of B. */ static void compute_dominance_frontiers_1 (bitmap *frontiers, basic_block bb, sbitmap done) { edge e; basic_block c; SET_BIT (done, bb->index); /* Do the frontier of the children first. Not all children in the dominator tree (blocks dominated by this one) are children in the CFG, so check all blocks. */ for (c = first_dom_son (CDI_DOMINATORS, bb); c; c = next_dom_son (CDI_DOMINATORS, c)) { if (! TEST_BIT (done, c->index)) compute_dominance_frontiers_1 (frontiers, c, done); } /* Find blocks conforming to rule (1) above. */ for (e = bb->succ; e; e = e->succ_next) { if (e->dest == EXIT_BLOCK_PTR) continue; if (get_immediate_dominator (CDI_DOMINATORS, e->dest) != bb) bitmap_set_bit (frontiers[bb->index], e->dest->index); } /* Find blocks conforming to rule (2). */ for (c = first_dom_son (CDI_DOMINATORS, bb); c; c = next_dom_son (CDI_DOMINATORS, c)) { int x; EXECUTE_IF_SET_IN_BITMAP (frontiers[c->index], 0, x, { if (get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (x)) != bb) bitmap_set_bit (frontiers[bb->index], x); }); } } void compute_dominance_frontiers (bitmap *frontiers) { sbitmap done = sbitmap_alloc (last_basic_block); timevar_push (TV_DOM_FRONTIERS); sbitmap_zero (done); compute_dominance_frontiers_1 (frontiers, ENTRY_BLOCK_PTR->succ->dest, done); sbitmap_free (done); timevar_pop (TV_DOM_FRONTIERS); } /*--------------------------------------------------------------------------- Debugging functions ---------------------------------------------------------------------------*/ /* Dump tree-specific information of block BB to file OUTF. */ void tree_dump_bb (basic_block bb, FILE *outf, int indent) { dump_generic_bb (outf, bb, indent, TDF_VOPS); } /* Dump a basic block on stderr. */ void debug_tree_bb (basic_block bb) { dump_bb (bb, stderr, 0); } /* Dump basic block with index N on stderr. */ basic_block debug_tree_bb_n (int n) { debug_tree_bb (BASIC_BLOCK (n)); return BASIC_BLOCK (n); } /* Dump the CFG on stderr. FLAGS are the same used by the tree dumping functions (see TDF_* in tree.h). */ void debug_tree_cfg (int flags) { dump_tree_cfg (stderr, flags); } /* Dump the program showing basic block boundaries on the given FILE. FLAGS are the same used by the tree dumping functions (see TDF_* in tree.h). */ void dump_tree_cfg (FILE *file, int flags) { if (flags & TDF_DETAILS) { const char *funcname = lang_hooks.decl_printable_name (current_function_decl, 2); fputc ('\n', file); fprintf (file, ";; Function %s\n\n", funcname); fprintf (file, ";; \n%d basic blocks, %d edges, last basic block %d.\n\n", n_basic_blocks, n_edges, last_basic_block); brief_dump_cfg (file); fprintf (file, "\n"); } if (flags & TDF_STATS) dump_cfg_stats (file); dump_function_to_file (current_function_decl, file, flags | TDF_BLOCKS); } /* Dump CFG statistics on FILE. */ void dump_cfg_stats (FILE *file) { static long max_num_merged_labels = 0; unsigned long size, total = 0; long n_edges; basic_block bb; const char * const fmt_str = "%-30s%-13s%12s\n"; const char * const fmt_str_1 = "%-30s%13lu%11lu%c\n"; const char * const fmt_str_3 = "%-43s%11lu%c\n"; const char *funcname = lang_hooks.decl_printable_name (current_function_decl, 2); fprintf (file, "\nCFG Statistics for %s\n\n", funcname); fprintf (file, "---------------------------------------------------------\n"); fprintf (file, fmt_str, "", " Number of ", "Memory"); fprintf (file, fmt_str, "", " instances ", "used "); fprintf (file, "---------------------------------------------------------\n"); size = n_basic_blocks * sizeof (struct basic_block_def); total += size; fprintf (file, fmt_str_1, "Basic blocks", n_basic_blocks, SCALE (size), LABEL (size)); n_edges = 0; FOR_EACH_BB (bb) { edge e; for (e = bb->succ; e; e = e->succ_next) n_edges++; } size = n_edges * sizeof (struct edge_def); total += size; fprintf (file, fmt_str_1, "Edges", n_edges, SCALE (size), LABEL (size)); size = n_basic_blocks * sizeof (struct bb_ann_d); total += size; fprintf (file, fmt_str_1, "Basic block annotations", n_basic_blocks, SCALE (size), LABEL (size)); fprintf (file, "---------------------------------------------------------\n"); fprintf (file, fmt_str_3, "Total memory used by CFG data", SCALE (total), LABEL (total)); fprintf (file, "---------------------------------------------------------\n"); fprintf (file, "\n"); if (cfg_stats.num_merged_labels > max_num_merged_labels) max_num_merged_labels = cfg_stats.num_merged_labels; fprintf (file, "Coalesced label blocks: %ld (Max so far: %ld)\n", cfg_stats.num_merged_labels, max_num_merged_labels); fprintf (file, "\n"); } /* Dump CFG statistics on stderr. Keep extern so that it's always linked in the final executable. */ void debug_cfg_stats (void) { dump_cfg_stats (stderr); } /* Dump the flowgraph to a .vcg FILE. */ static void tree_cfg2vcg (FILE *file) { edge e; basic_block bb; const char *funcname = lang_hooks.decl_printable_name (current_function_decl, 2); /* Write the file header. */ fprintf (file, "graph: { title: \"%s\"\n", funcname); fprintf (file, "node: { title: \"ENTRY\" label: \"ENTRY\" }\n"); fprintf (file, "node: { title: \"EXIT\" label: \"EXIT\" }\n"); /* Write blocks and edges. */ for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next) { fprintf (file, "edge: { sourcename: \"ENTRY\" targetname: \"%d\"", e->dest->index); if (e->flags & EDGE_FAKE) fprintf (file, " linestyle: dotted priority: 10"); else fprintf (file, " linestyle: solid priority: 100"); fprintf (file, " }\n"); } fputc ('\n', file); FOR_EACH_BB (bb) { enum tree_code head_code, end_code; const char *head_name, *end_name; int head_line = 0; int end_line = 0; tree first = first_stmt (bb); tree last = last_stmt (bb); if (first) { head_code = TREE_CODE (first); head_name = tree_code_name[head_code]; head_line = get_lineno (first); } else head_name = "no-statement"; if (last) { end_code = TREE_CODE (last); end_name = tree_code_name[end_code]; end_line = get_lineno (last); } else end_name = "no-statement"; fprintf (file, "node: { title: \"%d\" label: \"#%d\\n%s (%d)\\n%s (%d)\"}\n", bb->index, bb->index, head_name, head_line, end_name, end_line); for (e = bb->succ; e; e = e->succ_next) { if (e->dest == EXIT_BLOCK_PTR) fprintf (file, "edge: { sourcename: \"%d\" targetname: \"EXIT\"", bb->index); else fprintf (file, "edge: { sourcename: \"%d\" targetname: \"%d\"", bb->index, e->dest->index); if (e->flags & EDGE_FAKE) fprintf (file, " priority: 10 linestyle: dotted"); else fprintf (file, " priority: 100 linestyle: solid"); fprintf (file, " }\n"); } if (bb->next_bb != EXIT_BLOCK_PTR) fputc ('\n', file); } fputs ("}\n\n", file); } /*--------------------------------------------------------------------------- Miscellaneous helpers ---------------------------------------------------------------------------*/ /* Return true if T represents a stmt that always transfers control. */ bool is_ctrl_stmt (tree t) { return (TREE_CODE (t) == COND_EXPR || TREE_CODE (t) == SWITCH_EXPR || TREE_CODE (t) == GOTO_EXPR || TREE_CODE (t) == RETURN_EXPR || TREE_CODE (t) == RESX_EXPR); } /* Return true if T is a statement that may alter the flow of control (e.g., a call to a non-returning function). */ bool is_ctrl_altering_stmt (tree t) { tree call = t; #if defined ENABLE_CHECKING if (t == NULL) abort (); #endif switch (TREE_CODE (t)) { case MODIFY_EXPR: /* A MODIFY_EXPR with a rhs of a call has the characteristics of the call. */ call = TREE_OPERAND (t, 1); if (TREE_CODE (call) != CALL_EXPR) break; /* FALLTHRU */ case CALL_EXPR: /* A non-pure/const CALL_EXPR alters flow control if the current function has nonlocal labels. */ if (TREE_SIDE_EFFECTS (t) && current_function_has_nonlocal_label) return true; /* A CALL_EXPR also alters control flow if it does not return. */ if (call_expr_flags (call) & (ECF_NORETURN | ECF_LONGJMP)) return true; break; default: return false; } /* If a statement can throw, it alters control flow. */ return tree_can_throw_internal (t); } /* Return true if T is a computed goto. */ bool computed_goto_p (tree t) { return (TREE_CODE (t) == GOTO_EXPR && TREE_CODE (GOTO_DESTINATION (t)) != LABEL_DECL); } /* Checks whether EXPR is a simple local goto. */ bool simple_goto_p (tree expr) { return (TREE_CODE (expr) == GOTO_EXPR && TREE_CODE (GOTO_DESTINATION (expr)) == LABEL_DECL && (decl_function_context (GOTO_DESTINATION (expr)) == current_function_decl)); } /* Return true if T should start a new basic block. PREV_T is the statement preceding T. It is used when T is a label or a case label. Labels should only start a new basic block if their previous statement wasn't a label. Otherwise, sequence of labels would generate unnecessary basic blocks that only contain a single label. */ static inline bool stmt_starts_bb_p (tree t, tree prev_t) { enum tree_code code; if (t == NULL_TREE) return false; /* LABEL_EXPRs start a new basic block only if the preceding statement wasn't a label of the same type. This prevents the creation of consecutive blocks that have nothing but a single label. */ code = TREE_CODE (t); if (code == LABEL_EXPR) { /* Nonlocal and computed GOTO targets always start a new block. */ if (code == LABEL_EXPR && (DECL_NONLOCAL (LABEL_EXPR_LABEL (t)) || FORCED_LABEL (LABEL_EXPR_LABEL (t)))) return true; if (prev_t && TREE_CODE (prev_t) == code) { if (DECL_NONLOCAL (LABEL_EXPR_LABEL (prev_t))) return true; cfg_stats.num_merged_labels++; return false; } else return true; } return false; } /* Return true if T should end a basic block. */ bool stmt_ends_bb_p (tree t) { return is_ctrl_stmt (t) || is_ctrl_altering_stmt (t); } /* Add gotos that used to be represented implicitly in the CFG. */ void disband_implicit_edges (void) { basic_block bb; block_stmt_iterator last; edge e; tree stmt, label, forward; FOR_EACH_BB (bb) { last = bsi_last (bb); stmt = last_stmt (bb); if (stmt && TREE_CODE (stmt) == COND_EXPR) { /* Remove superfluous gotos from COND_EXPR branches. Moved from cfg_remove_useless_stmts here since it violates the invariants for tree--cfg correspondence and thus fits better here where we do it anyway. */ for (e = bb->succ; e; e = e->succ_next) { if (e->dest != bb->next_bb) continue; if (e->flags & EDGE_TRUE_VALUE) COND_EXPR_THEN (stmt) = build_empty_stmt (); else if (e->flags & EDGE_FALSE_VALUE) COND_EXPR_ELSE (stmt) = build_empty_stmt (); else abort (); e->flags |= EDGE_FALLTHRU; } continue; } if (stmt && TREE_CODE (stmt) == RETURN_EXPR) { /* Remove the RETURN_EXPR if we may fall though to the exit instead. */ if (!bb->succ || bb->succ->succ_next || bb->succ->dest != EXIT_BLOCK_PTR) abort (); if (bb->next_bb == EXIT_BLOCK_PTR && !TREE_OPERAND (stmt, 0)) { bsi_remove (&last); bb->succ->flags |= EDGE_FALLTHRU; } continue; } /* There can be no fallthru edge if the last statement is a control one. */ if (stmt && is_ctrl_stmt (stmt)) continue; /* Find a fallthru edge and emit the goto if necessary. */ for (e = bb->succ; e; e = e->succ_next) if (e->flags & EDGE_FALLTHRU) break; if (!e || e->dest == bb->next_bb) continue; if (e->dest == EXIT_BLOCK_PTR) abort (); label = tree_block_label (e->dest); /* If this is a goto to a goto, jump to the final destination. Handles unfactoring of the computed jumps. ??? Why bother putting this back together when rtl is just about to take it apart again? */ forward = last_and_only_stmt (e->dest); if (forward && TREE_CODE (forward) == GOTO_EXPR) label = GOTO_DESTINATION (forward); bsi_insert_after (&last, build1 (GOTO_EXPR, void_type_node, label), BSI_NEW_STMT); e->flags &= ~EDGE_FALLTHRU; } } /* Remove all the blocks and edges that make up the flowgraph. */ void delete_tree_cfg (void) { if (n_basic_blocks > 0) free_blocks_annotations (); free_basic_block_vars (); basic_block_info = NULL; label_to_block_map = NULL; free_rbi_pool (); } /* Return the first statement in basic block BB. */ tree first_stmt (basic_block bb) { block_stmt_iterator i = bsi_start (bb); return !bsi_end_p (i) ? bsi_stmt (i) : NULL_TREE; } /* Return the last statement in basic block BB. */ tree last_stmt (basic_block bb) { block_stmt_iterator b = bsi_last (bb); return !bsi_end_p (b) ? bsi_stmt (b) : NULL_TREE; } /* Return a pointer to the last statement in block BB. */ tree * last_stmt_ptr (basic_block bb) { block_stmt_iterator last = bsi_last (bb); return !bsi_end_p (last) ? bsi_stmt_ptr (last) : NULL; } /* Return the last statement of an otherwise empty block. Return NULL if the block is totally empty, or if it contains more than one statement. */ tree last_and_only_stmt (basic_block bb) { block_stmt_iterator i = bsi_last (bb); tree last, prev; if (bsi_end_p (i)) return NULL_TREE; last = bsi_stmt (i); bsi_prev (&i); if (bsi_end_p (i)) return last; /* Empty statements should no longer appear in the instruction stream. Everything that might have appeared before should be deleted by remove_useless_stmts, and the optimizers should just bsi_remove instead of smashing with build_empty_stmt. Thus the only thing that should appear here in a block containing one executable statement is a label. */ prev = bsi_stmt (i); if (TREE_CODE (prev) == LABEL_EXPR) return last; else return NULL_TREE; } /* Mark BB as the basic block holding statement T. */ void set_bb_for_stmt (tree t, basic_block bb) { if (TREE_CODE (t) == STATEMENT_LIST) { tree_stmt_iterator i; for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i)) set_bb_for_stmt (tsi_stmt (i), bb); } else { stmt_ann_t ann = get_stmt_ann (t); ann->bb = bb; /* If the statement is a label, add the label to block-to-labels map so that we can speed up edge creation for GOTO_EXPRs. */ if (TREE_CODE (t) == LABEL_EXPR) { int uid; t = LABEL_EXPR_LABEL (t); uid = LABEL_DECL_UID (t); if (uid == -1) { LABEL_DECL_UID (t) = uid = cfun->last_label_uid++; if (VARRAY_SIZE (label_to_block_map) <= (unsigned) uid) VARRAY_GROW (label_to_block_map, 3 * uid / 2); } else { #ifdef ENABLE_CHECKING /* We're moving an existing label. Make sure that we've removed it from the old block. */ if (bb && VARRAY_BB (label_to_block_map, uid)) abort (); #endif } VARRAY_BB (label_to_block_map, uid) = bb; } } } /* Insert statement (or statement list) T before the statement pointed-to by iterator I. M specifies how to update iterator I after insertion (see enum bsi_iterator_update). */ void bsi_insert_before (block_stmt_iterator *i, tree t, enum bsi_iterator_update m) { set_bb_for_stmt (t, i->bb); modify_stmt (t); tsi_link_before (&i->tsi, t, m); } /* Insert statement (or statement list) T after the statement pointed-to by iterator I. M specifies how to update iterator I after insertion (see enum bsi_iterator_update). */ void bsi_insert_after (block_stmt_iterator *i, tree t, enum bsi_iterator_update m) { set_bb_for_stmt (t, i->bb); modify_stmt (t); tsi_link_after (&i->tsi, t, m); } /* Remove the statement pointed to by iterator I. The iterator is updated to the next statement. */ void bsi_remove (block_stmt_iterator *i) { tree t = bsi_stmt (*i); set_bb_for_stmt (t, NULL); modify_stmt (t); tsi_delink (&i->tsi); } /* Move the statement at FROM so it comes right after the statement at TO. */ void bsi_move_after (block_stmt_iterator *from, block_stmt_iterator *to) { tree stmt = bsi_stmt (*from); bsi_remove (from); bsi_insert_after (to, stmt, BSI_SAME_STMT); } /* Move the statement at FROM so it comes right before the statement at TO. */ void bsi_move_before (block_stmt_iterator *from, block_stmt_iterator *to) { tree stmt = bsi_stmt (*from); bsi_remove (from); bsi_insert_before (to, stmt, BSI_SAME_STMT); } /* Move the statement at FROM to the end of basic block BB. */ void bsi_move_to_bb_end (block_stmt_iterator *from, basic_block bb) { block_stmt_iterator last = bsi_last (bb); /* Have to check bsi_end_p because it could be an empty block. */ if (!bsi_end_p (last) && is_ctrl_stmt (bsi_stmt (last))) bsi_move_before (from, &last); else bsi_move_after (from, &last); } /* Replace the contents of the statement pointed to by iterator BSI with STMT. If PRESERVE_EH_INFO is true, the exception handling information of the original statement is preserved. */ void bsi_replace (const block_stmt_iterator *bsi, tree stmt, bool preserve_eh_info) { int eh_region; tree orig_stmt = bsi_stmt (*bsi); SET_EXPR_LOCUS (stmt, EXPR_LOCUS (orig_stmt)); set_bb_for_stmt (stmt, bsi->bb); /* Preserve EH region information from the original statement, if requested by the caller. */ if (preserve_eh_info) { eh_region = lookup_stmt_eh_region (orig_stmt); if (eh_region >= 0) add_stmt_to_eh_region (stmt, eh_region); } *bsi_stmt_ptr (*bsi) = stmt; modify_stmt (stmt); } /* Insert the statement pointed-to by BSI into edge E. Every attempt is made to place the statement in an existing basic block, but sometimes that isn't possible. When it isn't possible, the edge is split and the statement is added to the new block. In all cases, the returned *BSI points to the correct location. The return value is true if insertion should be done after the location, or false if it should be done before the location. */ static bool tree_find_edge_insert_loc (edge e, block_stmt_iterator *bsi) { basic_block dest, src; tree tmp; dest = e->dest; restart: /* If the destination has one predecessor which has no PHI nodes, insert there. Except for the exit block. The requirement for no PHI nodes could be relaxed. Basically we would have to examine the PHIs to prove that none of them used the value set by the statement we want to insert on E. That hardly seems worth the effort. */ if (dest->pred->pred_next == NULL && ! phi_nodes (dest) && dest != EXIT_BLOCK_PTR) { *bsi = bsi_start (dest); if (bsi_end_p (*bsi)) return true; /* Make sure we insert after any leading labels. */ tmp = bsi_stmt (*bsi); while (TREE_CODE (tmp) == LABEL_EXPR) { bsi_next (bsi); if (bsi_end_p (*bsi)) break; tmp = bsi_stmt (*bsi); } if (bsi_end_p (*bsi)) { *bsi = bsi_last (dest); return true; } else return false; } /* If the source has one successor, the edge is not abnormal and the last statement does not end a basic block, insert there. Except for the entry block. */ src = e->src; if ((e->flags & EDGE_ABNORMAL) == 0 && src->succ->succ_next == NULL && src != ENTRY_BLOCK_PTR) { *bsi = bsi_last (src); if (bsi_end_p (*bsi)) return true; tmp = bsi_stmt (*bsi); if (!stmt_ends_bb_p (tmp)) return true; /* Insert code just before returning the value. We may need to decompose the return in the case it contains non-trivial operand. */ if (TREE_CODE (tmp) == RETURN_EXPR) { tree op = TREE_OPERAND (tmp, 0); if (!is_gimple_val (op)) { if (TREE_CODE (op) != MODIFY_EXPR) abort (); bsi_insert_before (bsi, op, BSI_NEW_STMT); TREE_OPERAND (tmp, 0) = TREE_OPERAND (op, 0); } bsi_prev (bsi); return true; } } /* Otherwise, create a new basic block, and split this edge. */ dest = split_edge (e); e = dest->pred; goto restart; } /* This routine will commit all pending edge insertions, creating any new basic blocks which are necessary. If specified, NEW_BLOCKS returns a count of the number of new basic blocks which were created. */ void bsi_commit_edge_inserts (int *new_blocks) { basic_block bb; edge e; int blocks; blocks = n_basic_blocks; bsi_commit_edge_inserts_1 (ENTRY_BLOCK_PTR->succ); FOR_EACH_BB (bb) for (e = bb->succ; e; e = e->succ_next) bsi_commit_edge_inserts_1 (e); if (new_blocks) *new_blocks = n_basic_blocks - blocks; } /* Commit insertions pending at edge E. */ static void bsi_commit_edge_inserts_1 (edge e) { if (PENDING_STMT (e)) { block_stmt_iterator bsi; tree stmt = PENDING_STMT (e); PENDING_STMT (e) = NULL_TREE; if (tree_find_edge_insert_loc (e, &bsi)) bsi_insert_after (&bsi, stmt, BSI_NEW_STMT); else bsi_insert_before (&bsi, stmt, BSI_NEW_STMT); } } /* Add STMT to the pending list of edge E. No actual insertion is made until a call to bsi_commit_edge_inserts () is made. */ void bsi_insert_on_edge (edge e, tree stmt) { append_to_statement_list (stmt, &PENDING_STMT (e)); } /* Specialized edge insertion for SSA-PRE. FIXME: This should probably disappear. The only reason it's here is because PRE needs the call to tree_find_edge_insert_loc(). */ void pre_insert_on_edge (edge e, tree stmt); void pre_insert_on_edge (edge e, tree stmt) { block_stmt_iterator bsi; if (PENDING_STMT (e)) abort (); if (tree_find_edge_insert_loc (e, &bsi)) bsi_insert_after (&bsi, stmt, BSI_NEW_STMT); else bsi_insert_before (&bsi, stmt, BSI_NEW_STMT); } /*--------------------------------------------------------------------------- Tree specific functions for CFG manipulation ---------------------------------------------------------------------------*/ /* Split a (typically critical) edge EDGE_IN. Return the new block. Abort on abnormal edges. */ static basic_block tree_split_edge (edge edge_in) { basic_block new_bb, after_bb, dest, src; edge new_edge, e; tree phi; int i, num_elem; /* Abnormal edges cannot be split. */ if (edge_in->flags & EDGE_ABNORMAL) abort (); src = edge_in->src; dest = edge_in->dest; /* Place the new block in the block list. Try to keep the new block near its "logical" location. This is of most help to humans looking at debugging dumps. */ for (e = dest->pred; e; e = e->pred_next) if (e->src->next_bb == dest) break; if (!e) after_bb = dest->prev_bb; else after_bb = edge_in->src; new_bb = create_empty_bb (after_bb); new_edge = make_edge (new_bb, dest, EDGE_FALLTHRU); /* Find all the PHI arguments on the original edge, and change them to the new edge. Do it before redirection, so that the argument does not get removed. */ for (phi = phi_nodes (dest); phi; phi = TREE_CHAIN (phi)) { num_elem = PHI_NUM_ARGS (phi); for (i = 0; i < num_elem; i++) if (PHI_ARG_EDGE (phi, i) == edge_in) { PHI_ARG_EDGE (phi, i) = new_edge; break; } } if (!redirect_edge_and_branch (edge_in, new_bb)) abort (); if (PENDING_STMT (edge_in)) abort (); return new_bb; } /* Return true when BB has label LABEL in it. */ static bool has_label_p (basic_block bb, tree label) { block_stmt_iterator bsi; for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) != LABEL_EXPR) return false; if (LABEL_EXPR_LABEL (stmt) == label) return true; } return false; } /* Callback for walk_tree, check that all elements with address taken are properly noticed as such. */ static tree verify_expr (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data ATTRIBUTE_UNUSED) { tree t = *tp, x; if (TYPE_P (t)) *walk_subtrees = 0; switch (TREE_CODE (t)) { case SSA_NAME: if (SSA_NAME_IN_FREE_LIST (t)) { error ("SSA name in freelist but still referenced"); return *tp; } break; case MODIFY_EXPR: x = TREE_OPERAND (t, 0); if (TREE_CODE (x) == BIT_FIELD_REF && is_gimple_reg (TREE_OPERAND (x, 0))) { error ("GIMPLE register modified with BIT_FIELD_REF"); return *tp; } break; case ADDR_EXPR: x = TREE_OPERAND (t, 0); while (TREE_CODE (x) == ARRAY_REF || TREE_CODE (x) == COMPONENT_REF || TREE_CODE (x) == REALPART_EXPR || TREE_CODE (x) == IMAGPART_EXPR) x = TREE_OPERAND (x, 0); if (TREE_CODE (x) != VAR_DECL && TREE_CODE (x) != PARM_DECL) return NULL; if (!TREE_ADDRESSABLE (x)) { error ("address taken, but ADDRESSABLE bit not set"); return x; } break; case COND_EXPR: x = TREE_OPERAND (t, 0); if (TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE) { error ("non-boolean used in condition"); return x; } break; case NOP_EXPR: case CONVERT_EXPR: case FIX_TRUNC_EXPR: case FIX_CEIL_EXPR: case FIX_FLOOR_EXPR: case FIX_ROUND_EXPR: case FLOAT_EXPR: case NEGATE_EXPR: case ABS_EXPR: case BIT_NOT_EXPR: case NON_LVALUE_EXPR: case TRUTH_NOT_EXPR: x = TREE_OPERAND (t, 0); /* We check for constants explicitly since they are not considered gimple invariants if they overflowed. */ if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c' && !is_gimple_val (x)) { error ("Invalid operand to unary operator"); return x; } break; case REALPART_EXPR: case IMAGPART_EXPR: break; case LT_EXPR: case LE_EXPR: case GT_EXPR: case GE_EXPR: case EQ_EXPR: case NE_EXPR: case UNORDERED_EXPR: case ORDERED_EXPR: case UNLT_EXPR: case UNLE_EXPR: case UNGT_EXPR: case UNGE_EXPR: case UNEQ_EXPR: case LTGT_EXPR: case PLUS_EXPR: case MINUS_EXPR: case MULT_EXPR: case TRUNC_DIV_EXPR: case CEIL_DIV_EXPR: case FLOOR_DIV_EXPR: case ROUND_DIV_EXPR: case TRUNC_MOD_EXPR: case CEIL_MOD_EXPR: case FLOOR_MOD_EXPR: case ROUND_MOD_EXPR: case RDIV_EXPR: case EXACT_DIV_EXPR: case MIN_EXPR: case MAX_EXPR: case LSHIFT_EXPR: case RSHIFT_EXPR: case LROTATE_EXPR: case RROTATE_EXPR: case BIT_IOR_EXPR: case BIT_XOR_EXPR: case BIT_AND_EXPR: x = TREE_OPERAND (t, 0); /* We check for constants explicitly since they are not considered gimple invariants if they overflowed. */ if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c' && !is_gimple_val (x)) { error ("Invalid operand to binary operator"); return x; } x = TREE_OPERAND (t, 1); /* We check for constants explicitly since they are not considered gimple invariants if they overflowed. */ if (TREE_CODE_CLASS (TREE_CODE (x)) != 'c' && !is_gimple_val (x)) { error ("Invalid operand to binary operator"); return x; } break; default: break; } return NULL; } /* Verify STMT, return true if STMT is not in GIMPLE form. TODO: Implement type checking. */ static bool verify_stmt (tree stmt) { tree addr; if (!is_gimple_stmt (stmt)) { error ("Is not a valid GIMPLE statement."); debug_generic_stmt (stmt); return true; } addr = walk_tree (&stmt, verify_expr, NULL, NULL); if (addr) { debug_generic_stmt (addr); return true; } return false; } /* Return true when the T can be shared. */ static bool tree_node_can_be_shared (tree t) { if (TYPE_P (t) || DECL_P (t) /* We check for constants explicitly since they are not considered gimple invariants if they overflowed. */ || TREE_CODE_CLASS (TREE_CODE (t)) == 'c' || is_gimple_min_invariant (t) || TREE_CODE (t) == SSA_NAME) return true; while ((TREE_CODE (t) == ARRAY_REF /* We check for constants explicitly since they are not considered gimple invariants if they overflowed. */ && (TREE_CODE_CLASS (TREE_CODE (TREE_OPERAND (t, 1))) == 'c' || is_gimple_min_invariant (TREE_OPERAND (t, 1)))) || (TREE_CODE (t) == COMPONENT_REF || TREE_CODE (t) == REALPART_EXPR || TREE_CODE (t) == IMAGPART_EXPR)) t = TREE_OPERAND (t, 0); if (DECL_P (t)) return true; return false; } /* Called via walk_trees. Verify tree sharing. */ static tree verify_node_sharing (tree * tp, int *walk_subtrees, void *data) { htab_t htab = (htab_t) data; void **slot; if (tree_node_can_be_shared (*tp)) { *walk_subtrees = false; return NULL; } slot = htab_find_slot (htab, *tp, INSERT); if (*slot) return *slot; *slot = *tp; return NULL; } /* Verify the GIMPLE statement chain. */ void verify_stmts (void) { basic_block bb; block_stmt_iterator bsi; bool err = false; htab_t htab; tree addr; timevar_push (TV_TREE_STMT_VERIFY); htab = htab_create (37, htab_hash_pointer, htab_eq_pointer, NULL); FOR_EACH_BB (bb) { tree phi; int i; for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) { int phi_num_args = PHI_NUM_ARGS (phi); for (i = 0; i < phi_num_args; i++) { tree t = PHI_ARG_DEF (phi, i); tree addr; /* Addressable variables do have SSA_NAMEs but they are not considered gimple values. */ if (TREE_CODE (t) != SSA_NAME && TREE_CODE (t) != FUNCTION_DECL && !is_gimple_val (t)) { error ("PHI def is not a GIMPLE value"); debug_generic_stmt (phi); debug_generic_stmt (t); err |= true; } addr = walk_tree (&t, verify_expr, NULL, NULL); if (addr) { debug_generic_stmt (addr); err |= true; } addr = walk_tree (&t, verify_node_sharing, htab, NULL); if (addr) { error ("Incorrect sharing of tree nodes"); debug_generic_stmt (phi); debug_generic_stmt (addr); err |= true; } } } for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); err |= verify_stmt (stmt); addr = walk_tree (&stmt, verify_node_sharing, htab, NULL); if (addr) { error ("Incorrect sharing of tree nodes"); debug_generic_stmt (stmt); debug_generic_stmt (addr); err |= true; } } } if (err) internal_error ("verify_stmts failed."); htab_delete (htab); timevar_pop (TV_TREE_STMT_VERIFY); } /* Verifies that the flow information is OK. */ static int tree_verify_flow_info (void) { int err = 0; basic_block bb; block_stmt_iterator bsi; tree stmt; edge e; if (ENTRY_BLOCK_PTR->stmt_list) { error ("ENTRY_BLOCK has a statement list associated with it\n"); err = 1; } if (EXIT_BLOCK_PTR->stmt_list) { error ("EXIT_BLOCK has a statement list associated with it\n"); err = 1; } for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next) if (e->flags & EDGE_FALLTHRU) { error ("Fallthru to exit from bb %d\n", e->src->index); err = 1; } FOR_EACH_BB (bb) { bool found_ctrl_stmt = false; /* Skip labels on the start of basic block. */ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { if (TREE_CODE (bsi_stmt (bsi)) != LABEL_EXPR) break; if (label_to_block (LABEL_EXPR_LABEL (bsi_stmt (bsi))) != bb) { error ("Label %s to block does not match in bb %d\n", IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))), bb->index); err = 1; } if (decl_function_context (LABEL_EXPR_LABEL (bsi_stmt (bsi))) != current_function_decl) { error ("Label %s has incorrect context in bb %d\n", IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))), bb->index); err = 1; } } /* Verify that body of basic block BB is free of control flow. */ for (; !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); if (found_ctrl_stmt) { error ("Control flow in the middle of basic block %d\n", bb->index); err = 1; } if (stmt_ends_bb_p (stmt)) found_ctrl_stmt = true; if (TREE_CODE (stmt) == LABEL_EXPR) { error ("Label %s in the middle of basic block %d\n", IDENTIFIER_POINTER (DECL_NAME (stmt)), bb->index); err = 1; } } bsi = bsi_last (bb); if (bsi_end_p (bsi)) continue; stmt = bsi_stmt (bsi); if (is_ctrl_stmt (stmt)) { for (e = bb->succ; e; e = e->succ_next) if (e->flags & EDGE_FALLTHRU) { error ("Fallthru edge after a control statement in bb %d \n", bb->index); err = 1; } } switch (TREE_CODE (stmt)) { case COND_EXPR: { edge true_edge; edge false_edge; if (TREE_CODE (COND_EXPR_THEN (stmt)) != GOTO_EXPR || TREE_CODE (COND_EXPR_ELSE (stmt)) != GOTO_EXPR) { error ("Structured COND_EXPR at the end of bb %d\n", bb->index); err = 1; } extract_true_false_edges_from_block (bb, &true_edge, &false_edge); if (!true_edge || !false_edge || !(true_edge->flags & EDGE_TRUE_VALUE) || !(false_edge->flags & EDGE_FALSE_VALUE) || (true_edge->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL)) || (false_edge->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL)) || bb->succ->succ_next->succ_next) { error ("Wrong outgoing edge flags at end of bb %d\n", bb->index); err = 1; } if (!has_label_p (true_edge->dest, GOTO_DESTINATION (COND_EXPR_THEN (stmt)))) { error ("`then' label does not match edge at end of bb %d\n", bb->index); err = 1; } if (!has_label_p (false_edge->dest, GOTO_DESTINATION (COND_EXPR_ELSE (stmt)))) { error ("`else' label does not match edge at end of bb %d\n", bb->index); err = 1; } } break; case GOTO_EXPR: if (simple_goto_p (stmt)) { error ("Explicit goto at end of bb %d\n", bb->index); err = 1; } else { /* FIXME. We should double check that the labels in the destination blocks have their address taken. */ for (e = bb->succ; e; e = e->succ_next) if ((e->flags & (EDGE_FALLTHRU | EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)) || !(e->flags & EDGE_ABNORMAL)) { error ("Wrong outgoing edge flags at end of bb %d\n", bb->index); err = 1; } } break; case RETURN_EXPR: if (!bb->succ || bb->succ->succ_next || (bb->succ->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL | EDGE_TRUE_VALUE | EDGE_FALSE_VALUE))) { error ("Wrong outgoing edge flags at end of bb %d\n", bb->index); err = 1; } if (bb->succ->dest != EXIT_BLOCK_PTR) { error ("Return edge does not point to exit in bb %d\n", bb->index); err = 1; } break; case SWITCH_EXPR: { edge e; size_t i, n; tree vec; vec = SWITCH_LABELS (stmt); n = TREE_VEC_LENGTH (vec); /* Mark all the destination basic blocks. */ for (i = 0; i < n; ++i) { tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i)); basic_block label_bb = label_to_block (lab); if (label_bb->aux && label_bb->aux != (void *)1) abort (); label_bb->aux = (void *)1; } for (e = bb->succ; e; e = e->succ_next) { if (!e->dest->aux) { error ("Extra outgoing edge %d->%d\n", bb->index, e->dest->index); err = 1; } e->dest->aux = (void *)2; if ((e->flags & (EDGE_FALLTHRU | EDGE_ABNORMAL | EDGE_TRUE_VALUE | EDGE_FALSE_VALUE))) { error ("Wrong outgoing edge flags at end of bb %d\n", bb->index); err = 1; } } /* Check that we have all of them. */ for (i = 0; i < n; ++i) { tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i)); basic_block label_bb = label_to_block (lab); if (label_bb->aux != (void *)2) { error ("Missing edge %i->%i\n", bb->index, label_bb->index); err = 1; } } for (e = bb->succ; e; e = e->succ_next) e->dest->aux = (void *)0; } default: ; } } if (dom_computed[CDI_DOMINATORS] >= DOM_NO_FAST_QUERY) verify_dominators (CDI_DOMINATORS); return err; } /* Updates phi nodes after creating forwarder block joined by edge FALLTHRU. */ static void tree_make_forwarder_block (edge fallthru) { edge e; basic_block dummy, bb; tree phi, new_phi, var; dummy = fallthru->src; bb = fallthru->dest; if (!bb->pred->pred_next) return; /* If we redirected a branch we must create new phi nodes at the start of BB. */ for (phi = phi_nodes (dummy); phi; phi = TREE_CHAIN (phi)) { var = PHI_RESULT (phi); new_phi = create_phi_node (var, bb); SSA_NAME_DEF_STMT (var) = new_phi; PHI_RESULT (phi) = make_ssa_name (SSA_NAME_VAR (var), phi); add_phi_arg (&new_phi, PHI_RESULT (phi), fallthru); } /* Ensure that the PHI node chains are in the same order. */ set_phi_nodes (bb, nreverse (phi_nodes (bb))); /* Add the arguments we have stored on edges. */ for (e = bb->pred; e; e = e->pred_next) { if (e == fallthru) continue; for (phi = phi_nodes (bb), var = PENDING_STMT (e); phi; phi = TREE_CHAIN (phi), var = TREE_CHAIN (var)) add_phi_arg (&phi, TREE_VALUE (var), e); PENDING_STMT (e) = NULL; } } /* Return true if basic block BB does nothing except pass control flow to another block and that we can safely insert a label at the start of the successor block. */ static bool tree_forwarder_block_p (basic_block bb) { block_stmt_iterator bsi; edge e; /* If we have already determined that this block is not forwardable, then no further checks are necessary. */ if (! bb_ann (bb)->forwardable) return false; /* BB must have a single outgoing normal edge. Otherwise it can not be a forwarder block. */ if (!bb->succ || bb->succ->succ_next || bb->succ->dest == EXIT_BLOCK_PTR || (bb->succ->flags & EDGE_ABNORMAL) || bb == ENTRY_BLOCK_PTR) { bb_ann (bb)->forwardable = 0; return false; } /* Successors of the entry block are not forwarders. */ for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next) if (e->dest == bb) { bb_ann (bb)->forwardable = 0; return false; } /* BB can not have any PHI nodes. This could potentially be relaxed early in compilation if we re-rewrote the variables appearing in any PHI nodes in forwarder blocks. */ if (phi_nodes (bb)) { bb_ann (bb)->forwardable = 0; return false; } /* Now walk through the statements. We can ignore labels, anything else means this is not a forwarder block. */ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); switch (TREE_CODE (stmt)) { case LABEL_EXPR: if (DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt))) return false; break; default: bb_ann (bb)->forwardable = 0; return false; } } return true; } /* Thread jumps over empty statements. This code should _not_ thread over obviously equivalent conditions as that requires nontrivial updates to the SSA graph. */ static bool thread_jumps (void) { edge e, next, last, old; basic_block bb, dest, tmp; tree phi; int arg; bool retval = false; FOR_EACH_BB (bb) bb_ann (bb)->forwardable = 1; FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) { /* Don't waste time on unreachable blocks. */ if (!bb->pred) continue; /* Nor on forwarders. */ if (tree_forwarder_block_p (bb)) continue; /* This block is now part of a forwarding path, mark it as not forwardable so that we can detect loops. This bit will be reset below. */ bb_ann (bb)->forwardable = 0; /* Examine each of our block's successors to see if it is forwardable. */ for (e = bb->succ; e; e = next) { next = e->succ_next; /* If the edge is abnormal or its destination is not forwardable, then there's nothing to do. */ if ((e->flags & EDGE_ABNORMAL) || !tree_forwarder_block_p (e->dest)) continue; /* Now walk through as many forwarder block as possible to find the ultimate destination we want to thread our jump to. */ last = e->dest->succ; bb_ann (e->dest)->forwardable = 0; for (dest = e->dest->succ->dest; tree_forwarder_block_p (dest); last = dest->succ, dest = dest->succ->dest) { /* An infinite loop detected. We redirect the edge anyway, so that the loop is shrinked into single basic block. */ if (!bb_ann (dest)->forwardable) break; if (dest->succ->dest == EXIT_BLOCK_PTR) break; bb_ann (dest)->forwardable = 0; } /* Reset the forwardable marks to 1. */ for (tmp = e->dest; tmp != dest; tmp = tmp->succ->dest) bb_ann (tmp)->forwardable = 1; if (dest == e->dest) continue; old = find_edge (bb, dest); if (old) { /* If there already is an edge, check whether the values in phi nodes differ. */ if (!phi_alternatives_equal (dest, last, old)) { /* The previous block is forwarder. Redirect our jump to that target instead since we know it has no PHI nodes that will need updating. */ dest = last->src; /* That might mean that no forwarding at all is possible. */ if (dest == e->dest) continue; old = find_edge (bb, dest); } } /* Perform the redirection. */ retval = true; e = redirect_edge_and_branch (e, dest); /* TODO -- updating dominators in this case is simple. */ free_dominance_info (CDI_DOMINATORS); if (!old) { /* Update PHI nodes. We know that the new argument should have the same value as the argument associated with LAST. Otherwise we would have changed our target block above. */ for (phi = phi_nodes (dest); phi; phi = TREE_CHAIN (phi)) { arg = phi_arg_from_edge (phi, last); if (arg < 0) abort (); add_phi_arg (&phi, PHI_ARG_DEF (phi, arg), e); } } } /* Reset the forwardable bit on our block since it's no longer in a forwarding chain path. */ bb_ann (bb)->forwardable = 1; } return retval; } /* Return a non-special label in the head of basic block BLOCK. Create one if it doesn't exist. */ static tree tree_block_label (basic_block bb) { block_stmt_iterator i, s = bsi_start (bb); bool first = true; tree label, stmt; for (i = s; !bsi_end_p (i); first = false, bsi_next (&i)) { stmt = bsi_stmt (i); if (TREE_CODE (stmt) != LABEL_EXPR) break; label = LABEL_EXPR_LABEL (stmt); if (!DECL_NONLOCAL (label)) { if (!first) bsi_move_before (&i, &s); return label; } } label = create_artificial_label (); stmt = build1 (LABEL_EXPR, void_type_node, label); bsi_insert_before (&s, stmt, BSI_NEW_STMT); return label; } /* Attempt to perform edge redirection by replacing a possibly complex jump instruction by a goto or by removing the jump completely. This can apply only if all edges now point to the same block. The parameters and return values are equivalent to redirect_edge_and_branch. */ static edge tree_try_redirect_by_replacing_jump (edge e, basic_block target) { basic_block src = e->src; edge tmp; block_stmt_iterator b; tree stmt; /* Verify that all targets will be TARGET. */ for (tmp = src->succ; tmp; tmp = tmp->succ_next) if (tmp->dest != target && tmp != e) break; if (tmp) return NULL; b = bsi_last (src); if (bsi_end_p (b)) return NULL; stmt = bsi_stmt (b); if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR) { bsi_remove (&b); e = ssa_redirect_edge (e, target); e->flags = EDGE_FALLTHRU; return e; } return NULL; } /* Redirect E to DEST. Return NULL on failure. Otherwise, return the edge representing the redirected branch. */ static edge tree_redirect_edge_and_branch (edge e, basic_block dest) { basic_block bb = e->src; block_stmt_iterator bsi; edge ret; tree label, stmt; if (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH)) return NULL; if (e->src != ENTRY_BLOCK_PTR && (ret = tree_try_redirect_by_replacing_jump (e, dest))) return ret; if (e->dest == dest) return NULL; label = tree_block_label (dest); bsi = bsi_last (bb); stmt = bsi_end_p (bsi) ? NULL : bsi_stmt (bsi); switch (stmt ? TREE_CODE (stmt) : ERROR_MARK) { case COND_EXPR: stmt = (e->flags & EDGE_TRUE_VALUE ? COND_EXPR_THEN (stmt) : COND_EXPR_ELSE (stmt)); GOTO_DESTINATION (stmt) = label; break; case GOTO_EXPR: /* No non-abnormal edges should lead from a non-simple goto, and simple ones should be represented implicitly. */ abort (); case SWITCH_EXPR: { tree vec = SWITCH_LABELS (stmt); size_t i, n = TREE_VEC_LENGTH (vec); for (i = 0; i < n; ++i) { tree elt = TREE_VEC_ELT (vec, i); if (label_to_block (CASE_LABEL (elt)) == e->dest) CASE_LABEL (elt) = label; } } break; case RETURN_EXPR: bsi_remove (&bsi); e->flags |= EDGE_FALLTHRU; break; default: /* Otherwise it must be a fallthru edge, and we don't need to do anything besides redirecting it. */ if (!(e->flags & EDGE_FALLTHRU)) abort (); break; } /* Update/insert PHI nodes as necessary. */ /* Now update the edges in the CFG. */ e = ssa_redirect_edge (e, dest); return e; } /* Simple wrapper, as we can always redirect fallthru edges. */ static basic_block tree_redirect_edge_and_branch_force (edge e, basic_block dest) { e = tree_redirect_edge_and_branch (e, dest); if (!e) abort (); return NULL; } /* Splits basic block BB after statement STMT (but at least after the labels). If STMT is NULL, BB is split just after the labels. */ static basic_block tree_split_block (basic_block bb, void *stmt) { block_stmt_iterator bsi, bsi_tgt; tree act; basic_block new_bb; edge e; new_bb = create_empty_bb (bb); /* Redirect the outgoing edges. */ new_bb->succ = bb->succ; bb->succ = NULL; for (e = new_bb->succ; e; e = e->succ_next) e->src = new_bb; if (stmt && TREE_CODE ((tree) stmt) == LABEL_EXPR) stmt = NULL; /* Move everything from BSI to the new basic block. */ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { act = bsi_stmt (bsi); if (TREE_CODE (act) == LABEL_EXPR) continue; if (!stmt) break; if (stmt == act) { bsi_next (&bsi); break; } } bsi_tgt = bsi_start (new_bb); while (!bsi_end_p (bsi)) { act = bsi_stmt (bsi); bsi_remove (&bsi); bsi_insert_after (&bsi_tgt, act, BSI_NEW_STMT); } return new_bb; } /* Moves basic block BB after block AFTER. */ static bool tree_move_block_after (basic_block bb, basic_block after) { if (bb->prev_bb == after) return true; unlink_block (bb); link_block (bb, after); return true; } /* Return true if basic_block can be duplicated. */ static bool tree_can_duplicate_bb_p (basic_block bb ATTRIBUTE_UNUSED) { return true; } /* Create a duplicate of the basic block BB. NOTE: This does not preserve SSA form. */ static basic_block tree_duplicate_bb (basic_block bb) { basic_block new_bb; block_stmt_iterator bsi, bsi_tgt; new_bb = create_empty_bb (EXIT_BLOCK_PTR->prev_bb); bsi_tgt = bsi_start (new_bb); for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) == LABEL_EXPR) continue; bsi_insert_after (&bsi_tgt, unshare_expr (stmt), BSI_NEW_STMT); } return new_bb; } /* Dump FUNCTION_DECL FN to file FILE using FLAGS (see TDF_* in tree.h) */ void dump_function_to_file (tree fn, FILE *file, int flags) { tree arg, vars, var; bool ignore_topmost_bind = false, any_var = false; basic_block bb; tree chain; fprintf (file, "%s (", lang_hooks.decl_printable_name (fn, 2)); arg = DECL_ARGUMENTS (fn); while (arg) { print_generic_expr (file, arg, dump_flags); if (TREE_CHAIN (arg)) fprintf (file, ", "); arg = TREE_CHAIN (arg); } fprintf (file, ")\n"); if (flags & TDF_RAW) { dump_node (fn, TDF_SLIM | flags, file); return; } /* When GIMPLE is lowered, the variables are no longer available in BIND_EXPRs, so display them separately. */ if (cfun && cfun->unexpanded_var_list) { ignore_topmost_bind = true; fprintf (file, "{\n"); for (vars = cfun->unexpanded_var_list; vars; vars = TREE_CHAIN (vars)) { var = TREE_VALUE (vars); print_generic_decl (file, var, flags); fprintf (file, "\n"); any_var = true; } } if (basic_block_info) { /* Make a CFG based dump. */ if (!ignore_topmost_bind) fprintf (file, "{\n"); if (any_var && n_basic_blocks) fprintf (file, "\n"); FOR_EACH_BB (bb) dump_generic_bb (file, bb, 2, flags); fprintf (file, "}\n"); } else { int indent; /* Make a tree based dump. */ chain = DECL_SAVED_TREE (fn); if (TREE_CODE (chain) == BIND_EXPR) { if (ignore_topmost_bind) { chain = BIND_EXPR_BODY (chain); indent = 2; } else indent = 0; } else { if (!ignore_topmost_bind) fprintf (file, "{\n"); indent = 2; } if (any_var) fprintf (file, "\n"); print_generic_stmt_indented (file, chain, flags, indent); if (ignore_topmost_bind) fprintf (file, "}\n"); } fprintf (file, "\n\n"); } /* Pretty print of the loops intermediate representation. */ static void print_loop (FILE *, struct loop *, int); static void print_pred_bbs (FILE *, edge); static void print_succ_bbs (FILE *, edge); /* Print the predecessors indexes of edge E on FILE. */ static void print_pred_bbs (FILE *file, edge e) { if (e == NULL) return; else if (e->pred_next == NULL) fprintf (file, "bb_%d", e->src->index); else { fprintf (file, "bb_%d, ", e->src->index); print_pred_bbs (file, e->pred_next); } } /* Print the successors indexes of edge E on FILE. */ static void print_succ_bbs (FILE *file, edge e) { if (e == NULL) return; else if (e->succ_next == NULL) fprintf (file, "bb_%d", e->dest->index); else { fprintf (file, "bb_%d, ", e->dest->index); print_succ_bbs (file, e->succ_next); } } /* Pretty print LOOP on FILE, indented INDENT spaces. */ static void print_loop (FILE *file, struct loop *loop, int indent) { char *s_indent; basic_block bb; if (loop == NULL) return; s_indent = (char *) alloca ((size_t) indent + 1); memset ((void *) s_indent, ' ', (size_t) indent); s_indent[indent] = '\0'; /* Print the loop's header. */ fprintf (file, "%sloop_%d\n", s_indent, loop->num); /* Print the loop's body. */ fprintf (file, "%s{\n", s_indent); FOR_EACH_BB (bb) if (bb->loop_father == loop) { /* Print the basic_block's header. */ fprintf (file, "%s bb_%d (preds = {", s_indent, bb->index); print_pred_bbs (file, bb->pred); fprintf (file, "}, succs = {"); print_succ_bbs (file, bb->succ); fprintf (file, "})\n"); /* Print the basic_block's body. */ fprintf (file, "%s {\n", s_indent); tree_dump_bb (bb, file, indent + 4); fprintf (file, "%s }\n", s_indent); } print_loop (file, loop->inner, indent + 2); fprintf (file, "%s}\n", s_indent); print_loop (file, loop->next, indent); } /* Follow a CFG edge from the entry point of the program, and on entry of a loop, pretty print the loop structure on FILE. */ void print_loop_ir (FILE *file) { basic_block bb; bb = BASIC_BLOCK (0); if (bb && bb->loop_father) print_loop (file, bb->loop_father, 0); } /* Debugging loops structure at tree level. */ void debug_loop_ir (void) { print_loop_ir (stderr); } /* Return true if BB ends with a call, possibly followed by some instructions that must stay with the call. Return false, otherwise. */ static bool tree_block_ends_with_call_p (basic_block bb) { block_stmt_iterator bsi = bsi_last (bb); tree t = tsi_stmt (bsi.tsi); if (TREE_CODE (t) == RETURN_EXPR && TREE_OPERAND (t, 0)) t = TREE_OPERAND (t, 0); if (TREE_CODE (t) == MODIFY_EXPR) t = TREE_OPERAND (t, 1); return TREE_CODE (t) == CALL_EXPR; } /* Return true if BB ends with a conditional branch. Return false, otherwise. */ static bool tree_block_ends_with_condjump_p (basic_block bb) { tree stmt = tsi_stmt (bsi_last (bb).tsi); return (TREE_CODE (stmt) == COND_EXPR); } /* Return true if we need to add fake edge to exit at statement T. Helper function for tree_flow_call_edges_add. */ static bool need_fake_edge_p (tree t) { if (TREE_CODE (t) == RETURN_EXPR && TREE_OPERAND (t, 0)) t = TREE_OPERAND (t, 0); if (TREE_CODE (t) == MODIFY_EXPR) t = TREE_OPERAND (t, 1); /* NORETURN and LONGJMP calls already have an edge to exit. CONST, PURE and ALWAYS_RETURN calls do not need one. We don't currently check for CONST and PURE here, although it would be a good idea, because those attributes are figured out from the RTL in mark_constant_function, and the counter incrementation code from -fprofile-arcs leads to different results from -fbranch-probabilities. */ if (TREE_CODE (t) == CALL_EXPR && !(call_expr_flags (t) & (ECF_NORETURN | ECF_LONGJMP | ECF_ALWAYS_RETURN))) return true; if (TREE_CODE (t) == ASM_EXPR && (ASM_VOLATILE_P (t) || ASM_INPUT_P (t))) return true; return false; } /* Add fake edges to the function exit for any non constant and non noreturn calls, volatile inline assembly in the bitmap of blocks specified by BLOCKS or to the whole CFG if BLOCKS is zero. Return the number of blocks that were split. The goal is to expose cases in which entering a basic block does not imply that all subsequent instructions must be executed. */ static int tree_flow_call_edges_add (sbitmap blocks) { int i; int blocks_split = 0; int last_bb = last_basic_block; bool check_last_block = false; if (n_basic_blocks == 0) return 0; if (! blocks) check_last_block = true; else check_last_block = TEST_BIT (blocks, EXIT_BLOCK_PTR->prev_bb->index); /* In the last basic block, before epilogue generation, there will be a fallthru edge to EXIT. Special care is required if the last insn of the last basic block is a call because make_edge folds duplicate edges, which would result in the fallthru edge also being marked fake, which would result in the fallthru edge being removed by remove_fake_edges, which would result in an invalid CFG. Moreover, we can't elide the outgoing fake edge, since the block profiler needs to take this into account in order to solve the minimal spanning tree in the case that the call doesn't return. Handle this by adding a dummy instruction in a new last basic block. */ if (check_last_block) { basic_block bb = EXIT_BLOCK_PTR->prev_bb; block_stmt_iterator bsi = bsi_last (bb); tree t = NULL_TREE; if (!bsi_end_p (bsi)) t = bsi_stmt (bsi); if (need_fake_edge_p (t)) { edge e; for (e = bb->succ; e; e = e->succ_next) if (e->dest == EXIT_BLOCK_PTR) { bsi_insert_on_edge (e, build_empty_stmt ()); bsi_commit_edge_inserts ((int *)NULL); break; } } } /* Now add fake edges to the function exit for any non constant calls since there is no way that we can determine if they will return or not... */ for (i = 0; i < last_bb; i++) { basic_block bb = BASIC_BLOCK (i); block_stmt_iterator bsi; tree stmt, last_stmt; if (!bb) continue; if (blocks && !TEST_BIT (blocks, i)) continue; bsi = bsi_last (bb); if (!bsi_end_p (bsi)) { last_stmt = bsi_stmt (bsi); do { stmt = bsi_stmt (bsi); if (need_fake_edge_p (stmt)) { edge e; /* The handling above of the final block before the epilogue should be enough to verify that there is no edge to the exit block in CFG already. Calling make_edge in such case would cause us to mark that edge as fake and remove it later. */ #ifdef ENABLE_CHECKING if (stmt == last_stmt) for (e = bb->succ; e; e = e->succ_next) if (e->dest == EXIT_BLOCK_PTR) abort (); #endif /* Note that the following may create a new basic block and renumber the existing basic blocks. */ if (stmt != last_stmt) { e = split_block (bb, stmt); if (e) blocks_split++; } make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE); } bsi_prev (&bsi); } while (!bsi_end_p (bsi)); } } if (blocks_split) verify_flow_info (); return blocks_split; } struct cfg_hooks tree_cfg_hooks = { "tree", tree_verify_flow_info, tree_dump_bb, /* dump_bb */ create_bb, /* create_basic_block */ tree_redirect_edge_and_branch,/* redirect_edge_and_branch */ tree_redirect_edge_and_branch_force,/* redirect_edge_and_branch_force */ remove_bb, /* delete_basic_block */ tree_split_block, /* split_block */ tree_move_block_after, /* move_block_after */ tree_can_merge_blocks_p, /* can_merge_blocks_p */ tree_merge_blocks, /* merge_blocks */ tree_predict_edge, /* predict_edge */ tree_predicted_by_p, /* predicted_by_p */ tree_can_duplicate_bb_p, /* can_duplicate_block_p */ tree_duplicate_bb, /* duplicate_block */ tree_split_edge, /* split_edge */ tree_make_forwarder_block, /* make_forward_block */ NULL, /* tidy_fallthru_edge */ tree_block_ends_with_call_p, /* block_ends_with_call_p */ tree_block_ends_with_condjump_p, /* block_ends_with_condjump_p */ tree_flow_call_edges_add /* flow_call_edges_add */ }; /* Split all critical edges. */ static void split_critical_edges (void) { basic_block bb; edge e; FOR_ALL_BB (bb) { for (e = bb->succ; e ; e = e->succ_next) if (EDGE_CRITICAL_P (e) && !(e->flags & EDGE_ABNORMAL)) { split_edge (e); } } } struct tree_opt_pass pass_split_crit_edges = { NULL, /* name */ NULL, /* gate */ split_critical_edges, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_TREE_SPLIT_EDGES, /* tv_id */ PROP_cfg, /* properties required */ PROP_no_crit_edges, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0, /* todo_flags_finish */ }; /* Emit return warnings. */ static void execute_warn_function_return (void) { location_t *locus; tree last; edge e; if (warn_missing_noreturn && !TREE_THIS_VOLATILE (cfun->decl) && EXIT_BLOCK_PTR->pred == NULL && !lang_hooks.function.missing_noreturn_ok_p (cfun->decl)) warning ("%Jfunction might be possible candidate for attribute `noreturn'", cfun->decl); /* If we have a path to EXIT, then we do return. */ if (TREE_THIS_VOLATILE (cfun->decl) && EXIT_BLOCK_PTR->pred != NULL) { locus = NULL; for (e = EXIT_BLOCK_PTR->pred; e ; e = e->pred_next) { last = last_stmt (e->src); if (TREE_CODE (last) == RETURN_EXPR && (locus = EXPR_LOCUS (last)) != NULL) break; } if (!locus) locus = &cfun->function_end_locus; warning ("%H`noreturn' function does return", locus); } /* If we see "return;" in some basic block, then we do reach the end without returning a value. */ else if (warn_return_type && EXIT_BLOCK_PTR->pred != NULL && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl)))) { for (e = EXIT_BLOCK_PTR->pred; e ; e = e->pred_next) { tree last = last_stmt (e->src); if (TREE_CODE (last) == RETURN_EXPR && TREE_OPERAND (last, 0) == NULL) { locus = EXPR_LOCUS (last); if (!locus) locus = &cfun->function_end_locus; warning ("%Hcontrol reaches end of non-void function", locus); break; } } } } /* Given a basic block B which ends with a conditional and has precisely two successors, determine which of the edges is taken if the conditional is true and which is taken if the conditional is false. Set TRUE_EDGE and FALSE_EDGE appropriately. */ void extract_true_false_edges_from_block (basic_block b, edge *true_edge, edge *false_edge) { edge e = b->succ; if (e->flags & EDGE_TRUE_VALUE) { *true_edge = e; *false_edge = e->succ_next; } else { *false_edge = e; *true_edge = e->succ_next; } } struct tree_opt_pass pass_warn_function_return = { NULL, /* name */ NULL, /* gate */ execute_warn_function_return, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ 0, /* tv_id */ PROP_ssa, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0 /* todo_flags_finish */ }; #include "gt-tree-cfg.h"