/* Convert a program in SSA form into Normal form. Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc. Contributed by Andrew Macleod 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 3, 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 COPYING3. If not see . */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "ggc.h" #include "basic-block.h" #include "diagnostic.h" #include "bitmap.h" #include "tree-flow.h" #include "timevar.h" #include "tree-dump.h" #include "tree-ssa-live.h" #include "tree-pass.h" #include "toplev.h" DEF_VEC_I(source_location); DEF_VEC_ALLOC_I(source_location,heap); /* Used to hold all the components required to do SSA PHI elimination. The node and pred/succ list is a simple linear list of nodes and edges represented as pairs of nodes. The predecessor and successor list: Nodes are entered in pairs, where [0] ->PRED, [1]->SUCC. All the even indexes in the array represent predecessors, all the odd elements are successors. Rationale: When implemented as bitmaps, very large programs SSA->Normal times were being dominated by clearing the interference graph. Typically this list of edges is extremely small since it only includes PHI results and uses from a single edge which have not coalesced with each other. This means that no virtual PHI nodes are included, and empirical evidence suggests that the number of edges rarely exceed 3, and in a bootstrap of GCC, the maximum size encountered was 7. This also limits the number of possible nodes that are involved to rarely more than 6, and in the bootstrap of gcc, the maximum number of nodes encountered was 12. */ typedef struct _elim_graph { /* Size of the elimination vectors. */ int size; /* List of nodes in the elimination graph. */ VEC(tree,heap) *nodes; /* The predecessor and successor edge list. */ VEC(int,heap) *edge_list; /* Source locus on each edge */ VEC(source_location,heap) *edge_locus; /* Visited vector. */ sbitmap visited; /* Stack for visited nodes. */ VEC(int,heap) *stack; /* The variable partition map. */ var_map map; /* Edge being eliminated by this graph. */ edge e; /* List of constant copies to emit. These are pushed on in pairs. */ VEC(tree,heap) *const_copies; /* Source locations for any constant copies. */ VEC(source_location,heap) *copy_locus; } *elim_graph; /* Create a temporary variable based on the type of variable T. Use T's name as the prefix. */ static tree create_temp (tree t) { tree tmp; const char *name = NULL; tree type; if (TREE_CODE (t) == SSA_NAME) t = SSA_NAME_VAR (t); gcc_assert (TREE_CODE (t) == VAR_DECL || TREE_CODE (t) == PARM_DECL); type = TREE_TYPE (t); tmp = DECL_NAME (t); if (tmp) name = IDENTIFIER_POINTER (tmp); if (name == NULL) name = "temp"; tmp = create_tmp_var (type, name); if (DECL_DEBUG_EXPR_IS_FROM (t) && DECL_DEBUG_EXPR (t)) { SET_DECL_DEBUG_EXPR (tmp, DECL_DEBUG_EXPR (t)); DECL_DEBUG_EXPR_IS_FROM (tmp) = 1; } else if (!DECL_IGNORED_P (t)) { SET_DECL_DEBUG_EXPR (tmp, t); DECL_DEBUG_EXPR_IS_FROM (tmp) = 1; } DECL_ARTIFICIAL (tmp) = DECL_ARTIFICIAL (t); DECL_IGNORED_P (tmp) = DECL_IGNORED_P (t); DECL_GIMPLE_REG_P (tmp) = DECL_GIMPLE_REG_P (t); add_referenced_var (tmp); /* add_referenced_var will create the annotation and set up some of the flags in the annotation. However, some flags we need to inherit from our original variable. */ set_symbol_mem_tag (tmp, symbol_mem_tag (t)); if (is_call_clobbered (t)) mark_call_clobbered (tmp, var_ann (t)->escape_mask); if (bitmap_bit_p (gimple_call_used_vars (cfun), DECL_UID (t))) bitmap_set_bit (gimple_call_used_vars (cfun), DECL_UID (tmp)); return tmp; } /* This helper function fill insert a copy from a constant or variable SRC to variable DEST on edge E. */ static void insert_copy_on_edge (edge e, tree dest, tree src, source_location locus) { gimple copy; copy = gimple_build_assign (dest, src); set_is_used (dest); if (locus != UNKNOWN_LOCATION) gimple_set_location(copy, locus); if (TREE_CODE (src) == ADDR_EXPR) src = TREE_OPERAND (src, 0); if (TREE_CODE (src) == VAR_DECL || TREE_CODE (src) == PARM_DECL) set_is_used (src); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Inserting a copy on edge BB%d->BB%d :", e->src->index, e->dest->index); print_gimple_stmt (dump_file, copy, 0, dump_flags); fprintf (dump_file, "\n"); } gsi_insert_on_edge (e, copy); } /* Create an elimination graph with SIZE nodes and associated data structures. */ static elim_graph new_elim_graph (int size) { elim_graph g = (elim_graph) xmalloc (sizeof (struct _elim_graph)); g->nodes = VEC_alloc (tree, heap, 30); g->const_copies = VEC_alloc (tree, heap, 20); g->copy_locus = VEC_alloc (source_location, heap, 10); g->edge_list = VEC_alloc (int, heap, 20); g->edge_locus = VEC_alloc (source_location, heap, 10); g->stack = VEC_alloc (int, heap, 30); g->visited = sbitmap_alloc (size); return g; } /* Empty elimination graph G. */ static inline void clear_elim_graph (elim_graph g) { VEC_truncate (tree, g->nodes, 0); VEC_truncate (int, g->edge_list, 0); VEC_truncate (source_location, g->edge_locus, 0); } /* Delete elimination graph G. */ static inline void delete_elim_graph (elim_graph g) { sbitmap_free (g->visited); VEC_free (int, heap, g->stack); VEC_free (int, heap, g->edge_list); VEC_free (tree, heap, g->const_copies); VEC_free (tree, heap, g->nodes); VEC_free (source_location, heap, g->copy_locus); VEC_free (source_location, heap, g->edge_locus); free (g); } /* Return the number of nodes in graph G. */ static inline int elim_graph_size (elim_graph g) { return VEC_length (tree, g->nodes); } /* Add NODE to graph G, if it doesn't exist already. */ static inline void elim_graph_add_node (elim_graph g, tree node) { int x; tree t; for (x = 0; VEC_iterate (tree, g->nodes, x, t); x++) if (t == node) return; VEC_safe_push (tree, heap, g->nodes, node); } /* Add the edge PRED->SUCC to graph G. */ static inline void elim_graph_add_edge (elim_graph g, int pred, int succ, source_location locus) { VEC_safe_push (int, heap, g->edge_list, pred); VEC_safe_push (int, heap, g->edge_list, succ); VEC_safe_push (source_location, heap, g->edge_locus, locus); } /* Remove an edge from graph G for which NODE is the predecessor, and return the successor node. -1 is returned if there is no such edge. */ static inline int elim_graph_remove_succ_edge (elim_graph g, int node, source_location *locus) { int y; unsigned x; for (x = 0; x < VEC_length (int, g->edge_list); x += 2) if (VEC_index (int, g->edge_list, x) == node) { VEC_replace (int, g->edge_list, x, -1); y = VEC_index (int, g->edge_list, x + 1); VEC_replace (int, g->edge_list, x + 1, -1); *locus = VEC_index (source_location, g->edge_locus, x / 2); VEC_replace (source_location, g->edge_locus, x / 2, UNKNOWN_LOCATION); return y; } *locus = UNKNOWN_LOCATION; return -1; } /* Find all the nodes in GRAPH which are successors to NODE in the edge list. VAR will hold the partition number found. CODE is the code fragment executed for every node found. */ #define FOR_EACH_ELIM_GRAPH_SUCC(GRAPH, NODE, VAR, LOCUS, CODE) \ do { \ unsigned x_; \ int y_; \ for (x_ = 0; x_ < VEC_length (int, (GRAPH)->edge_list); x_ += 2) \ { \ y_ = VEC_index (int, (GRAPH)->edge_list, x_); \ if (y_ != (NODE)) \ continue; \ (VAR) = VEC_index (int, (GRAPH)->edge_list, x_ + 1); \ (LOCUS) = VEC_index (source_location, (GRAPH)->edge_locus, x_ / 2); \ CODE; \ } \ } while (0) /* Find all the nodes which are predecessors of NODE in the edge list for GRAPH. VAR will hold the partition number found. CODE is the code fragment executed for every node found. */ #define FOR_EACH_ELIM_GRAPH_PRED(GRAPH, NODE, VAR, LOCUS, CODE) \ do { \ unsigned x_; \ int y_; \ for (x_ = 0; x_ < VEC_length (int, (GRAPH)->edge_list); x_ += 2) \ { \ y_ = VEC_index (int, (GRAPH)->edge_list, x_ + 1); \ if (y_ != (NODE)) \ continue; \ (VAR) = VEC_index (int, (GRAPH)->edge_list, x_); \ (LOCUS) = VEC_index (source_location, (GRAPH)->edge_locus, x_ / 2); \ CODE; \ } \ } while (0) /* Add T to elimination graph G. */ static inline void eliminate_name (elim_graph g, tree T) { elim_graph_add_node (g, T); } /* Build elimination graph G for basic block BB on incoming PHI edge G->e. */ static void eliminate_build (elim_graph g, basic_block B) { tree T0, Ti; int p0, pi; gimple_stmt_iterator gsi; clear_elim_graph (g); for (gsi = gsi_start_phis (B); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple phi = gsi_stmt (gsi); source_location locus; T0 = var_to_partition_to_var (g->map, gimple_phi_result (phi)); /* Ignore results which are not in partitions. */ if (T0 == NULL_TREE) continue; Ti = PHI_ARG_DEF (phi, g->e->dest_idx); locus = gimple_phi_arg_location_from_edge (phi, g->e); /* If this argument is a constant, or a SSA_NAME which is being left in SSA form, just queue a copy to be emitted on this edge. */ if (!phi_ssa_name_p (Ti) || (TREE_CODE (Ti) == SSA_NAME && var_to_partition (g->map, Ti) == NO_PARTITION)) { /* Save constant copies until all other copies have been emitted on this edge. */ VEC_safe_push (tree, heap, g->const_copies, T0); VEC_safe_push (tree, heap, g->const_copies, Ti); VEC_safe_push (source_location, heap, g->copy_locus, locus); } else { Ti = var_to_partition_to_var (g->map, Ti); if (T0 != Ti) { eliminate_name (g, T0); eliminate_name (g, Ti); p0 = var_to_partition (g->map, T0); pi = var_to_partition (g->map, Ti); elim_graph_add_edge (g, p0, pi, locus); } } } } /* Push successors of T onto the elimination stack for G. */ static void elim_forward (elim_graph g, int T) { int S; source_location locus; SET_BIT (g->visited, T); FOR_EACH_ELIM_GRAPH_SUCC (g, T, S, locus, { if (!TEST_BIT (g->visited, S)) elim_forward (g, S); }); VEC_safe_push (int, heap, g->stack, T); } /* Return 1 if there unvisited predecessors of T in graph G. */ static int elim_unvisited_predecessor (elim_graph g, int T) { int P; source_location locus; FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, { if (!TEST_BIT (g->visited, P)) return 1; }); return 0; } /* Process predecessors first, and insert a copy. */ static void elim_backward (elim_graph g, int T) { int P; source_location locus; SET_BIT (g->visited, T); FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, { if (!TEST_BIT (g->visited, P)) { elim_backward (g, P); insert_copy_on_edge (g->e, partition_to_var (g->map, P), partition_to_var (g->map, T), locus); } }); } /* Insert required copies for T in graph G. Check for a strongly connected region, and create a temporary to break the cycle if one is found. */ static void elim_create (elim_graph g, int T) { tree U; int P, S; source_location locus; if (elim_unvisited_predecessor (g, T)) { U = create_temp (partition_to_var (g->map, T)); insert_copy_on_edge (g->e, U, partition_to_var (g->map, T), UNKNOWN_LOCATION); FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, { if (!TEST_BIT (g->visited, P)) { elim_backward (g, P); insert_copy_on_edge (g->e, partition_to_var (g->map, P), U, locus); } }); } else { S = elim_graph_remove_succ_edge (g, T, &locus); if (S != -1) { SET_BIT (g->visited, T); insert_copy_on_edge (g->e, partition_to_var (g->map, T), partition_to_var (g->map, S), locus); } } } /* Eliminate all the phi nodes on edge E in graph G. */ static void eliminate_phi (edge e, elim_graph g) { int x; basic_block B = e->dest; gcc_assert (VEC_length (tree, g->const_copies) == 0); gcc_assert (VEC_length (source_location, g->copy_locus) == 0); /* Abnormal edges already have everything coalesced. */ if (e->flags & EDGE_ABNORMAL) return; g->e = e; eliminate_build (g, B); if (elim_graph_size (g) != 0) { tree var; sbitmap_zero (g->visited); VEC_truncate (int, g->stack, 0); for (x = 0; VEC_iterate (tree, g->nodes, x, var); x++) { int p = var_to_partition (g->map, var); if (!TEST_BIT (g->visited, p)) elim_forward (g, p); } sbitmap_zero (g->visited); while (VEC_length (int, g->stack) > 0) { x = VEC_pop (int, g->stack); if (!TEST_BIT (g->visited, x)) elim_create (g, x); } } /* If there are any pending constant copies, issue them now. */ while (VEC_length (tree, g->const_copies) > 0) { tree src, dest; source_location locus; src = VEC_pop (tree, g->const_copies); dest = VEC_pop (tree, g->const_copies); locus = VEC_pop (source_location, g->copy_locus); insert_copy_on_edge (e, dest, src, locus); } } /* Take the ssa-name var_map MAP, and assign real variables to each partition. */ static void assign_vars (var_map map) { int x, num; tree var, root; var_ann_t ann; num = num_var_partitions (map); for (x = 0; x < num; x++) { var = partition_to_var (map, x); if (TREE_CODE (var) != SSA_NAME) { ann = var_ann (var); /* It must already be coalesced. */ gcc_assert (ann->out_of_ssa_tag == 1); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "partition %d already has variable ", x); print_generic_expr (dump_file, var, TDF_SLIM); fprintf (dump_file, " assigned to it.\n"); } } else { root = SSA_NAME_VAR (var); ann = var_ann (root); /* If ROOT is already associated, create a new one. */ if (ann->out_of_ssa_tag) { root = create_temp (root); ann = var_ann (root); } /* ROOT has not been coalesced yet, so use it. */ if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Partition %d is assigned to var ", x); print_generic_stmt (dump_file, root, TDF_SLIM); } change_partition_var (map, root, x); } } } /* Replace use operand P with whatever variable it has been rewritten to based on the partitions in MAP. EXPR is an optional expression vector over SSA versions which is used to replace P with an expression instead of a variable. If the stmt is changed, return true. */ static inline bool replace_use_variable (var_map map, use_operand_p p, gimple *expr) { tree new_var; tree var = USE_FROM_PTR (p); /* Check if we are replacing this variable with an expression. */ if (expr) { int version = SSA_NAME_VERSION (var); if (expr[version]) { SET_USE (p, gimple_assign_rhs_to_tree (expr[version])); return true; } } new_var = var_to_partition_to_var (map, var); if (new_var) { SET_USE (p, new_var); set_is_used (new_var); return true; } return false; } /* Replace def operand DEF_P with whatever variable it has been rewritten to based on the partitions in MAP. EXPR is an optional expression vector over SSA versions which is used to replace DEF_P with an expression instead of a variable. If the stmt is changed, return true. */ static inline bool replace_def_variable (var_map map, def_operand_p def_p, tree *expr) { tree new_var; tree var = DEF_FROM_PTR (def_p); /* Do nothing if we are replacing this variable with an expression. */ if (expr && expr[SSA_NAME_VERSION (var)]) return true; new_var = var_to_partition_to_var (map, var); if (new_var) { SET_DEF (def_p, new_var); set_is_used (new_var); return true; } return false; } /* Remove each argument from PHI. If an arg was the last use of an SSA_NAME, check to see if this allows another PHI node to be removed. */ static void remove_gimple_phi_args (gimple phi) { use_operand_p arg_p; ssa_op_iter iter; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Removing Dead PHI definition: "); print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); } FOR_EACH_PHI_ARG (arg_p, phi, iter, SSA_OP_USE) { tree arg = USE_FROM_PTR (arg_p); if (TREE_CODE (arg) == SSA_NAME) { /* Remove the reference to the existing argument. */ SET_USE (arg_p, NULL_TREE); if (has_zero_uses (arg)) { gimple stmt; gimple_stmt_iterator gsi; stmt = SSA_NAME_DEF_STMT (arg); /* Also remove the def if it is a PHI node. */ if (gimple_code (stmt) == GIMPLE_PHI) { remove_gimple_phi_args (stmt); gsi = gsi_for_stmt (stmt); remove_phi_node (&gsi, true); } } } } } /* Remove any PHI node which is a virtual PHI, or a PHI with no uses. */ static void eliminate_useless_phis (void) { basic_block bb; gimple_stmt_iterator gsi; tree result; FOR_EACH_BB (bb) { for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); ) { gimple phi = gsi_stmt (gsi); result = gimple_phi_result (phi); if (!is_gimple_reg (SSA_NAME_VAR (result))) { #ifdef ENABLE_CHECKING size_t i; /* There should be no arguments which are not virtual, or the results will be incorrect. */ for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = PHI_ARG_DEF (phi, i); if (TREE_CODE (arg) == SSA_NAME && is_gimple_reg (SSA_NAME_VAR (arg))) { fprintf (stderr, "Argument of PHI is not virtual ("); print_generic_expr (stderr, arg, TDF_SLIM); fprintf (stderr, "), but the result is :"); print_gimple_stmt (stderr, phi, 0, TDF_SLIM); internal_error ("SSA corruption"); } } #endif remove_phi_node (&gsi, true); } else { /* Also remove real PHIs with no uses. */ if (has_zero_uses (result)) { remove_gimple_phi_args (phi); remove_phi_node (&gsi, true); } else gsi_next (&gsi); } } } } /* This function will rewrite the current program using the variable mapping found in MAP. If the replacement vector VALUES is provided, any occurrences of partitions with non-null entries in the vector will be replaced with the expression in the vector instead of its mapped variable. */ static void rewrite_trees (var_map map, gimple *values) { elim_graph g; basic_block bb; gimple_stmt_iterator gsi; edge e; gimple_seq phi; bool changed; #ifdef ENABLE_CHECKING /* Search for PHIs where the destination has no partition, but one or more arguments has a partition. This should not happen and can create incorrect code. */ FOR_EACH_BB (bb) { for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple phi = gsi_stmt (gsi); tree T0 = var_to_partition_to_var (map, gimple_phi_result (phi)); if (T0 == NULL_TREE) { size_t i; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = PHI_ARG_DEF (phi, i); if (TREE_CODE (arg) == SSA_NAME && var_to_partition (map, arg) != NO_PARTITION) { fprintf (stderr, "Argument of PHI is in a partition :("); print_generic_expr (stderr, arg, TDF_SLIM); fprintf (stderr, "), but the result is not :"); print_gimple_stmt (stderr, phi, 0, TDF_SLIM); internal_error ("SSA corruption"); } } } } } #endif /* Replace PHI nodes with any required copies. */ g = new_elim_graph (map->num_partitions); g->map = map; FOR_EACH_BB (bb) { for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) { gimple stmt = gsi_stmt (gsi); use_operand_p use_p, copy_use_p; def_operand_p def_p; bool remove = false, is_copy = false; int num_uses = 0; ssa_op_iter iter; changed = false; if (gimple_assign_copy_p (stmt)) is_copy = true; copy_use_p = NULL_USE_OPERAND_P; FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) { if (replace_use_variable (map, use_p, values)) changed = true; copy_use_p = use_p; num_uses++; } if (num_uses != 1) is_copy = false; def_p = SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF); if (def_p != NULL) { /* Mark this stmt for removal if it is the list of replaceable expressions. */ if (values && values[SSA_NAME_VERSION (DEF_FROM_PTR (def_p))]) remove = true; else { if (replace_def_variable (map, def_p, NULL)) changed = true; /* If both SSA_NAMEs coalesce to the same variable, mark the now redundant copy for removal. */ if (is_copy) { gcc_assert (copy_use_p != NULL_USE_OPERAND_P); if (DEF_FROM_PTR (def_p) == USE_FROM_PTR (copy_use_p)) remove = true; } } } else FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF) if (replace_def_variable (map, def_p, NULL)) changed = true; /* Remove any stmts marked for removal. */ if (remove) gsi_remove (&gsi, true); else { if (changed) if (maybe_clean_or_replace_eh_stmt (stmt, stmt)) gimple_purge_dead_eh_edges (bb); gsi_next (&gsi); } } phi = phi_nodes (bb); if (phi) { edge_iterator ei; FOR_EACH_EDGE (e, ei, bb->preds) eliminate_phi (e, g); } } delete_elim_graph (g); } /* These are the local work structures used to determine the best place to insert the copies that were placed on edges by the SSA->normal pass.. */ static VEC(edge,heap) *edge_leader; static VEC(gimple_seq,heap) *stmt_list; static bitmap leader_has_match = NULL; static edge leader_match = NULL; /* Pass this function to make_forwarder_block so that all the edges with matching PENDING_STMT lists to 'curr_stmt_list' get redirected. E is the edge to test for a match. */ static inline bool same_stmt_list_p (edge e) { return (e->aux == (PTR) leader_match) ? true : false; } /* Return TRUE if S1 and S2 are equivalent copies. */ static inline bool identical_copies_p (const_gimple s1, const_gimple s2) { #ifdef ENABLE_CHECKING gcc_assert (is_gimple_assign (s1)); gcc_assert (is_gimple_assign (s2)); gcc_assert (DECL_P (gimple_assign_lhs (s1))); gcc_assert (DECL_P (gimple_assign_lhs (s2))); #endif if (gimple_assign_lhs (s1) != gimple_assign_lhs (s2)) return false; if (gimple_assign_rhs1 (s1) != gimple_assign_rhs1 (s2)) return false; return true; } /* Compare the PENDING_STMT list for edges E1 and E2. Return true if the lists contain the same sequence of copies. */ static inline bool identical_stmt_lists_p (const_edge e1, const_edge e2) { gimple_seq t1 = PENDING_STMT (e1); gimple_seq t2 = PENDING_STMT (e2); gimple_stmt_iterator gsi1, gsi2; for (gsi1 = gsi_start (t1), gsi2 = gsi_start (t2); !gsi_end_p (gsi1) && !gsi_end_p (gsi2); gsi_next (&gsi1), gsi_next (&gsi2)) { if (!identical_copies_p (gsi_stmt (gsi1), gsi_stmt (gsi2))) break; } if (!gsi_end_p (gsi1) || !gsi_end_p (gsi2)) return false; return true; } /* Allocate data structures used in analyze_edges_for_bb. */ static void init_analyze_edges_for_bb (void) { edge_leader = VEC_alloc (edge, heap, 25); stmt_list = VEC_alloc (gimple_seq, heap, 25); leader_has_match = BITMAP_ALLOC (NULL); } /* Free data structures used in analyze_edges_for_bb. */ static void fini_analyze_edges_for_bb (void) { VEC_free (edge, heap, edge_leader); VEC_free (gimple_seq, heap, stmt_list); BITMAP_FREE (leader_has_match); } /* A helper function to be called via walk_tree. Return DATA if it is contained in subtree TP. */ static tree contains_tree_r (tree * tp, int *walk_subtrees, void *data) { if (*tp == data) { *walk_subtrees = 0; return (tree) data; } else return NULL_TREE; } /* A threshold for the number of insns contained in the latch block. It is used to prevent blowing the loop with too many copies from the latch. */ #define MAX_STMTS_IN_LATCH 2 /* Return TRUE if the stmts on SINGLE-EDGE can be moved to the body of the loop. This should be permitted only if SINGLE-EDGE is a single-basic-block latch edge and thus cleaning the latch will help to create a single-basic-block loop. Otherwise return FALSE. */ static bool process_single_block_loop_latch (edge single_edge) { gimple_seq stmts; basic_block b_exit, b_pheader, b_loop = single_edge->src; edge_iterator ei; edge e; gimple_stmt_iterator gsi, gsi_exit; gimple_stmt_iterator tsi; tree expr; gimple stmt; unsigned int count = 0; if (single_edge == NULL || (single_edge->dest != single_edge->src) || (EDGE_COUNT (b_loop->succs) != 2) || (EDGE_COUNT (b_loop->preds) != 2)) return false; /* Get the stmts on the latch edge. */ stmts = PENDING_STMT (single_edge); /* Find the successor edge which is not the latch edge. */ FOR_EACH_EDGE (e, ei, b_loop->succs) if (e->dest != b_loop) break; b_exit = e->dest; /* Check that the exit block has only the loop as a predecessor, and that there are no pending stmts on that edge as well. */ if (EDGE_COUNT (b_exit->preds) != 1 || PENDING_STMT (e)) return false; /* Find the predecessor edge which is not the latch edge. */ FOR_EACH_EDGE (e, ei, b_loop->preds) if (e->src != b_loop) break; b_pheader = e->src; if (b_exit == b_pheader || b_exit == b_loop || b_pheader == b_loop) return false; gsi_exit = gsi_after_labels (b_exit); /* Get the last stmt in the loop body. */ gsi = gsi_last_bb (single_edge->src); stmt = gsi_stmt (gsi); if (gimple_code (stmt) != GIMPLE_COND) return false; expr = build2 (gimple_cond_code (stmt), boolean_type_node, gimple_cond_lhs (stmt), gimple_cond_rhs (stmt)); /* Iterate over the insns on the latch and count them. */ for (tsi = gsi_start (stmts); !gsi_end_p (tsi); gsi_next (&tsi)) { gimple stmt1 = gsi_stmt (tsi); tree var; count++; /* Check that the condition does not contain any new definition created in the latch as the stmts from the latch intended to precede it. */ if (gimple_code (stmt1) != GIMPLE_ASSIGN) return false; var = gimple_assign_lhs (stmt1); if (TREE_THIS_VOLATILE (var) || TYPE_VOLATILE (TREE_TYPE (var)) || walk_tree (&expr, contains_tree_r, var, NULL)) return false; } /* Check that the latch does not contain more than MAX_STMTS_IN_LATCH insns. The purpose of this restriction is to prevent blowing the loop with too many copies from the latch. */ if (count > MAX_STMTS_IN_LATCH) return false; /* Apply the transformation - clean up the latch block: var = something; L1: x1 = expr; if (cond) goto L2 else goto L3; L2: var = x1; goto L1 L3: ... ==> var = something; L1: x1 = expr; tmp_var = var; var = x1; if (cond) goto L1 else goto L2; L2: var = tmp_var; ... */ for (tsi = gsi_start (stmts); !gsi_end_p (tsi); gsi_next (&tsi)) { gimple stmt1 = gsi_stmt (tsi); tree var, tmp_var; gimple copy; /* Create a new variable to load back the value of var in case we exit the loop. */ var = gimple_assign_lhs (stmt1); tmp_var = create_temp (var); copy = gimple_build_assign (tmp_var, var); set_is_used (tmp_var); gsi_insert_before (&gsi, copy, GSI_SAME_STMT); copy = gimple_build_assign (var, tmp_var); gsi_insert_before (&gsi_exit, copy, GSI_SAME_STMT); } PENDING_STMT (single_edge) = 0; /* Insert the new stmts to the loop body. */ gsi_insert_seq_before (&gsi, stmts, GSI_NEW_STMT); if (dump_file) fprintf (dump_file, "\nCleaned-up latch block of loop with single BB: %d\n\n", single_edge->dest->index); return true; } /* Look at all the incoming edges to block BB, and decide where the best place to insert the stmts on each edge are, and perform those insertions. */ static void analyze_edges_for_bb (basic_block bb) { edge e; edge_iterator ei; int count; unsigned int x; bool have_opportunity; gimple_stmt_iterator gsi; gimple stmt; edge single_edge = NULL; bool is_label; edge leader; count = 0; /* Blocks which contain at least one abnormal edge cannot use make_forwarder_block. Look for these blocks, and commit any PENDING_STMTs found on edges in these block. */ have_opportunity = true; FOR_EACH_EDGE (e, ei, bb->preds) if (e->flags & EDGE_ABNORMAL) { have_opportunity = false; break; } if (!have_opportunity) { FOR_EACH_EDGE (e, ei, bb->preds) if (PENDING_STMT (e)) gsi_commit_one_edge_insert (e, NULL); return; } /* Find out how many edges there are with interesting pending stmts on them. Commit the stmts on edges we are not interested in. */ FOR_EACH_EDGE (e, ei, bb->preds) { if (PENDING_STMT (e)) { gcc_assert (!(e->flags & EDGE_ABNORMAL)); if (e->flags & EDGE_FALLTHRU) { gsi = gsi_start_bb (e->src); if (!gsi_end_p (gsi)) { stmt = gsi_stmt (gsi); gsi_next (&gsi); gcc_assert (stmt != NULL); is_label = (gimple_code (stmt) == GIMPLE_LABEL); /* Punt if it has non-label stmts, or isn't local. */ if (!is_label || DECL_NONLOCAL (gimple_label_label (stmt)) || !gsi_end_p (gsi)) { gsi_commit_one_edge_insert (e, NULL); continue; } } } single_edge = e; count++; } } /* If there aren't at least 2 edges, no sharing will happen. */ if (count < 2) { if (single_edge) { /* Add stmts to the edge unless processed specially as a single-block loop latch edge. */ if (!process_single_block_loop_latch (single_edge)) gsi_commit_one_edge_insert (single_edge, NULL); } return; } /* Ensure that we have empty worklists. */ #ifdef ENABLE_CHECKING gcc_assert (VEC_length (edge, edge_leader) == 0); gcc_assert (VEC_length (gimple_seq, stmt_list) == 0); gcc_assert (bitmap_empty_p (leader_has_match)); #endif /* Find the "leader" block for each set of unique stmt lists. Preference is given to FALLTHRU blocks since they would need a GOTO to arrive at another block. The leader edge destination is the block which all the other edges with the same stmt list will be redirected to. */ have_opportunity = false; FOR_EACH_EDGE (e, ei, bb->preds) { if (PENDING_STMT (e)) { bool found = false; /* Look for the same stmt list in edge leaders list. */ for (x = 0; VEC_iterate (edge, edge_leader, x, leader); x++) { if (identical_stmt_lists_p (leader, e)) { /* Give this edge the same stmt list pointer. */ PENDING_STMT (e) = NULL; e->aux = leader; bitmap_set_bit (leader_has_match, x); have_opportunity = found = true; break; } } /* If no similar stmt list, add this edge to the leader list. */ if (!found) { VEC_safe_push (edge, heap, edge_leader, e); VEC_safe_push (gimple_seq, heap, stmt_list, PENDING_STMT (e)); } } } /* If there are no similar lists, just issue the stmts. */ if (!have_opportunity) { for (x = 0; VEC_iterate (edge, edge_leader, x, leader); x++) gsi_commit_one_edge_insert (leader, NULL); VEC_truncate (edge, edge_leader, 0); VEC_truncate (gimple_seq, stmt_list, 0); bitmap_clear (leader_has_match); return; } if (dump_file) fprintf (dump_file, "\nOpportunities in BB %d for stmt/block reduction:\n", bb->index); /* For each common list, create a forwarding block and issue the stmt's in that block. */ for (x = 0; VEC_iterate (edge, edge_leader, x, leader); x++) if (bitmap_bit_p (leader_has_match, x)) { edge new_edge; gimple_stmt_iterator gsi; gimple_seq curr_stmt_list; leader_match = leader; /* The tree_* cfg manipulation routines use the PENDING_EDGE field for various PHI manipulations, so it gets cleared when calls are made to make_forwarder_block(). So make sure the edge is clear, and use the saved stmt list. */ PENDING_STMT (leader) = NULL; leader->aux = leader; curr_stmt_list = VEC_index (gimple_seq, stmt_list, x); new_edge = make_forwarder_block (leader->dest, same_stmt_list_p, NULL); bb = new_edge->dest; if (dump_file) { fprintf (dump_file, "Splitting BB %d for Common stmt list. ", leader->dest->index); fprintf (dump_file, "Original block is now BB%d.\n", bb->index); print_gimple_seq (dump_file, curr_stmt_list, 0, TDF_VOPS); } FOR_EACH_EDGE (e, ei, new_edge->src->preds) { e->aux = NULL; if (dump_file) fprintf (dump_file, " Edge (%d->%d) lands here.\n", e->src->index, e->dest->index); } gsi = gsi_last_bb (leader->dest); gsi_insert_seq_after (&gsi, curr_stmt_list, GSI_NEW_STMT); leader_match = NULL; /* We should never get a new block now. */ } else { PENDING_STMT (leader) = VEC_index (gimple_seq, stmt_list, x); gsi_commit_one_edge_insert (leader, NULL); } /* Clear the working data structures. */ VEC_truncate (edge, edge_leader, 0); VEC_truncate (gimple_seq, stmt_list, 0); bitmap_clear (leader_has_match); } /* This function will analyze the insertions which were performed on edges, and decide whether they should be left on that edge, or whether it is more efficient to emit some subset of them in a single block. All stmts are inserted somewhere. */ static void perform_edge_inserts (void) { basic_block bb; if (dump_file) fprintf(dump_file, "Analyzing Edge Insertions.\n"); /* analyze_edges_for_bb calls make_forwarder_block, which tries to incrementally update the dominator information. Since we don't need dominator information after this pass, go ahead and free the dominator information. */ free_dominance_info (CDI_DOMINATORS); free_dominance_info (CDI_POST_DOMINATORS); /* Allocate data structures used in analyze_edges_for_bb. */ init_analyze_edges_for_bb (); FOR_EACH_BB (bb) analyze_edges_for_bb (bb); analyze_edges_for_bb (EXIT_BLOCK_PTR); /* Free data structures used in analyze_edges_for_bb. */ fini_analyze_edges_for_bb (); #ifdef ENABLE_CHECKING { edge_iterator ei; edge e; FOR_EACH_BB (bb) { FOR_EACH_EDGE (e, ei, bb->preds) { if (PENDING_STMT (e)) error (" Pending stmts not issued on PRED edge (%d, %d)\n", e->src->index, e->dest->index); } FOR_EACH_EDGE (e, ei, bb->succs) { if (PENDING_STMT (e)) error (" Pending stmts not issued on SUCC edge (%d, %d)\n", e->src->index, e->dest->index); } } FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs) { if (PENDING_STMT (e)) error (" Pending stmts not issued on ENTRY edge (%d, %d)\n", e->src->index, e->dest->index); } FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) { if (PENDING_STMT (e)) error (" Pending stmts not issued on EXIT edge (%d, %d)\n", e->src->index, e->dest->index); } } #endif } /* Remove the ssa-names in the current function and translate them into normal compiler variables. PERFORM_TER is true if Temporary Expression Replacement should also be used. */ static void remove_ssa_form (bool perform_ter) { basic_block bb; gimple *values = NULL; var_map map; gimple_stmt_iterator gsi; map = coalesce_ssa_name (); /* Return to viewing the variable list as just all reference variables after coalescing has been performed. */ partition_view_normal (map, false); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "After Coalescing:\n"); dump_var_map (dump_file, map); } if (perform_ter) { values = find_replaceable_exprs (map); if (values && dump_file && (dump_flags & TDF_DETAILS)) dump_replaceable_exprs (dump_file, values); } /* Assign real variables to the partitions now. */ assign_vars (map); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "After Base variable replacement:\n"); dump_var_map (dump_file, map); } rewrite_trees (map, values); if (values) free (values); /* Remove PHI nodes which have been translated back to real variables. */ FOR_EACH_BB (bb) for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi);) remove_phi_node (&gsi, true); /* If any copies were inserted on edges, analyze and insert them now. */ perform_edge_inserts (); delete_var_map (map); } /* Search every PHI node for arguments associated with backedges which we can trivially determine will need a copy (the argument is either not an SSA_NAME or the argument has a different underlying variable than the PHI result). Insert a copy from the PHI argument to a new destination at the end of the block with the backedge to the top of the loop. Update the PHI argument to reference this new destination. */ static void insert_backedge_copies (void) { basic_block bb; gimple_stmt_iterator gsi; FOR_EACH_BB (bb) { for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple phi = gsi_stmt (gsi); tree result = gimple_phi_result (phi); tree result_var; size_t i; if (!is_gimple_reg (result)) continue; result_var = SSA_NAME_VAR (result); for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); edge e = gimple_phi_arg_edge (phi, i); /* If the argument is not an SSA_NAME, then we will need a constant initialization. If the argument is an SSA_NAME with a different underlying variable then a copy statement will be needed. */ if ((e->flags & EDGE_DFS_BACK) && (TREE_CODE (arg) != SSA_NAME || SSA_NAME_VAR (arg) != result_var)) { tree name; gimple stmt, last = NULL; gimple_stmt_iterator gsi2; gsi2 = gsi_last_bb (gimple_phi_arg_edge (phi, i)->src); if (!gsi_end_p (gsi2)) last = gsi_stmt (gsi2); /* In theory the only way we ought to get back to the start of a loop should be with a COND_EXPR or GOTO_EXPR. However, better safe than sorry. If the block ends with a control statement or something that might throw, then we have to insert this assignment before the last statement. Else insert it after the last statement. */ if (last && stmt_ends_bb_p (last)) { /* If the last statement in the block is the definition site of the PHI argument, then we can't insert anything after it. */ if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_DEF_STMT (arg) == last) continue; } /* Create a new instance of the underlying variable of the PHI result. */ stmt = gimple_build_assign (result_var, gimple_phi_arg_def (phi, i)); name = make_ssa_name (result_var, stmt); gimple_assign_set_lhs (stmt, name); /* copy location if present. */ if (gimple_phi_arg_has_location (phi, i)) gimple_set_location (stmt, gimple_phi_arg_location (phi, i)); /* Insert the new statement into the block and update the PHI node. */ if (last && stmt_ends_bb_p (last)) gsi_insert_before (&gsi2, stmt, GSI_NEW_STMT); else gsi_insert_after (&gsi2, stmt, GSI_NEW_STMT); SET_PHI_ARG_DEF (phi, i, name); } } } } } /* Take the current function out of SSA form, translating PHIs as described in R. Morgan, ``Building an Optimizing Compiler'', Butterworth-Heinemann, Boston, MA, 1998. pp 176-186. */ static unsigned int rewrite_out_of_ssa (void) { /* If elimination of a PHI requires inserting a copy on a backedge, then we will have to split the backedge which has numerous undesirable performance effects. A significant number of such cases can be handled here by inserting copies into the loop itself. */ insert_backedge_copies (); /* Eliminate PHIs which are of no use, such as virtual or dead phis. */ eliminate_useless_phis (); if (dump_file && (dump_flags & TDF_DETAILS)) gimple_dump_cfg (dump_file, dump_flags & ~TDF_DETAILS); remove_ssa_form (flag_tree_ter && !flag_mudflap); if (dump_file && (dump_flags & TDF_DETAILS)) gimple_dump_cfg (dump_file, dump_flags & ~TDF_DETAILS); cfun->gimple_df->in_ssa_p = false; return 0; } /* Define the parameters of the out of SSA pass. */ struct gimple_opt_pass pass_del_ssa = { { GIMPLE_PASS, "optimized", /* name */ NULL, /* gate */ rewrite_out_of_ssa, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_TREE_SSA_TO_NORMAL, /* tv_id */ PROP_cfg | PROP_ssa, /* properties_required */ 0, /* properties_provided */ /* ??? If TER is enabled, we also kill gimple. */ PROP_ssa, /* properties_destroyed */ TODO_verify_ssa | TODO_verify_flow | TODO_verify_stmts, /* todo_flags_start */ TODO_dump_func | TODO_ggc_collect | TODO_remove_unused_locals /* todo_flags_finish */ } };