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Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/cfganal.c')
| -rw-r--r-- | gcc-4.2.1-5666.3/gcc/cfganal.c | 1079 |
1 files changed, 1079 insertions, 0 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/cfganal.c b/gcc-4.2.1-5666.3/gcc/cfganal.c new file mode 100644 index 000000000..467c399c8 --- /dev/null +++ b/gcc-4.2.1-5666.3/gcc/cfganal.c @@ -0,0 +1,1079 @@ +/* Control flow graph analysis code for GNU compiler. + Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, + 1999, 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc. + +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, 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301, USA. */ + +/* This file contains various simple utilities to analyze the CFG. */ +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "rtl.h" +#include "obstack.h" +#include "hard-reg-set.h" +#include "basic-block.h" +#include "insn-config.h" +#include "recog.h" +#include "toplev.h" +#include "tm_p.h" +#include "timevar.h" + +/* Store the data structures necessary for depth-first search. */ +struct depth_first_search_dsS { + /* stack for backtracking during the algorithm */ + basic_block *stack; + + /* number of edges in the stack. That is, positions 0, ..., sp-1 + have edges. */ + unsigned int sp; + + /* record of basic blocks already seen by depth-first search */ + sbitmap visited_blocks; +}; +typedef struct depth_first_search_dsS *depth_first_search_ds; + +static void flow_dfs_compute_reverse_init (depth_first_search_ds); +static void flow_dfs_compute_reverse_add_bb (depth_first_search_ds, + basic_block); +static basic_block flow_dfs_compute_reverse_execute (depth_first_search_ds, + basic_block); +static void flow_dfs_compute_reverse_finish (depth_first_search_ds); +static bool flow_active_insn_p (rtx); + +/* Like active_insn_p, except keep the return value clobber around + even after reload. */ + +static bool +flow_active_insn_p (rtx insn) +{ + if (active_insn_p (insn)) + return true; + + /* A clobber of the function return value exists for buggy + programs that fail to return a value. Its effect is to + keep the return value from being live across the entire + function. If we allow it to be skipped, we introduce the + possibility for register lifetime confusion. */ + if (GET_CODE (PATTERN (insn)) == CLOBBER + && REG_P (XEXP (PATTERN (insn), 0)) + && REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0))) + return true; + + return false; +} + +/* Return true if the block has no effect and only forwards control flow to + its single destination. */ + +bool +forwarder_block_p (basic_block bb) +{ + rtx insn; + + if (bb == EXIT_BLOCK_PTR || bb == ENTRY_BLOCK_PTR + || !single_succ_p (bb)) + return false; + + for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn)) + if (INSN_P (insn) && flow_active_insn_p (insn)) + return false; + + return (!INSN_P (insn) + || (JUMP_P (insn) && simplejump_p (insn)) + || !flow_active_insn_p (insn)); +} + +/* Return nonzero if we can reach target from src by falling through. */ + +bool +can_fallthru (basic_block src, basic_block target) +{ + rtx insn = BB_END (src); + rtx insn2; + edge e; + edge_iterator ei; + + if (target == EXIT_BLOCK_PTR) + return true; + if (src->next_bb != target) + return 0; + FOR_EACH_EDGE (e, ei, src->succs) + if (e->dest == EXIT_BLOCK_PTR + && e->flags & EDGE_FALLTHRU) + return 0; + + insn2 = BB_HEAD (target); + if (insn2 && !active_insn_p (insn2)) + insn2 = next_active_insn (insn2); + + /* ??? Later we may add code to move jump tables offline. */ + return next_active_insn (insn) == insn2; +} + +/* Return nonzero if we could reach target from src by falling through, + if the target was made adjacent. If we already have a fall-through + edge to the exit block, we can't do that. */ +bool +could_fall_through (basic_block src, basic_block target) +{ + edge e; + edge_iterator ei; + + if (target == EXIT_BLOCK_PTR) + return true; + FOR_EACH_EDGE (e, ei, src->succs) + if (e->dest == EXIT_BLOCK_PTR + && e->flags & EDGE_FALLTHRU) + return 0; + return true; +} + +/* Mark the back edges in DFS traversal. + Return nonzero if a loop (natural or otherwise) is present. + Inspired by Depth_First_Search_PP described in: + + Advanced Compiler Design and Implementation + Steven Muchnick + Morgan Kaufmann, 1997 + + and heavily borrowed from pre_and_rev_post_order_compute. */ + +bool +mark_dfs_back_edges (void) +{ + edge_iterator *stack; + int *pre; + int *post; + int sp; + int prenum = 1; + int postnum = 1; + sbitmap visited; + bool found = false; + + /* Allocate the preorder and postorder number arrays. */ + pre = XCNEWVEC (int, last_basic_block); + post = XCNEWVEC (int, last_basic_block); + + /* Allocate stack for back-tracking up CFG. */ + stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); + sp = 0; + + /* Allocate bitmap to track nodes that have been visited. */ + visited = sbitmap_alloc (last_basic_block); + + /* None of the nodes in the CFG have been visited yet. */ + sbitmap_zero (visited); + + /* Push the first edge on to the stack. */ + stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs); + + while (sp) + { + edge_iterator ei; + basic_block src; + basic_block dest; + + /* Look at the edge on the top of the stack. */ + ei = stack[sp - 1]; + src = ei_edge (ei)->src; + dest = ei_edge (ei)->dest; + ei_edge (ei)->flags &= ~EDGE_DFS_BACK; + + /* Check if the edge destination has been visited yet. */ + if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index)) + { + /* Mark that we have visited the destination. */ + SET_BIT (visited, dest->index); + + pre[dest->index] = prenum++; + if (EDGE_COUNT (dest->succs) > 0) + { + /* Since the DEST node has been visited for the first + time, check its successors. */ + stack[sp++] = ei_start (dest->succs); + } + else + post[dest->index] = postnum++; + } + else + { + if (dest != EXIT_BLOCK_PTR && src != ENTRY_BLOCK_PTR + && pre[src->index] >= pre[dest->index] + && post[dest->index] == 0) + ei_edge (ei)->flags |= EDGE_DFS_BACK, found = true; + + if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR) + post[src->index] = postnum++; + + if (!ei_one_before_end_p (ei)) + ei_next (&stack[sp - 1]); + else + sp--; + } + } + + free (pre); + free (post); + free (stack); + sbitmap_free (visited); + + return found; +} + +/* Set the flag EDGE_CAN_FALLTHRU for edges that can be fallthru. */ + +void +set_edge_can_fallthru_flag (void) +{ + basic_block bb; + + FOR_EACH_BB (bb) + { + edge e; + edge_iterator ei; + + FOR_EACH_EDGE (e, ei, bb->succs) + { + e->flags &= ~EDGE_CAN_FALLTHRU; + + /* The FALLTHRU edge is also CAN_FALLTHRU edge. */ + if (e->flags & EDGE_FALLTHRU) + e->flags |= EDGE_CAN_FALLTHRU; + } + + /* If the BB ends with an invertible condjump all (2) edges are + CAN_FALLTHRU edges. */ + if (EDGE_COUNT (bb->succs) != 2) + continue; + if (!any_condjump_p (BB_END (bb))) + continue; + if (!invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0)) + continue; + invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0); + EDGE_SUCC (bb, 0)->flags |= EDGE_CAN_FALLTHRU; + EDGE_SUCC (bb, 1)->flags |= EDGE_CAN_FALLTHRU; + } +} + +/* Find unreachable blocks. An unreachable block will have 0 in + the reachable bit in block->flags. A nonzero value indicates the + block is reachable. */ + +void +find_unreachable_blocks (void) +{ + edge e; + edge_iterator ei; + basic_block *tos, *worklist, bb; + + tos = worklist = XNEWVEC (basic_block, n_basic_blocks); + + /* Clear all the reachability flags. */ + + FOR_EACH_BB (bb) + bb->flags &= ~BB_REACHABLE; + + /* Add our starting points to the worklist. Almost always there will + be only one. It isn't inconceivable that we might one day directly + support Fortran alternate entry points. */ + + FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs) + { + *tos++ = e->dest; + + /* Mark the block reachable. */ + e->dest->flags |= BB_REACHABLE; + } + + /* Iterate: find everything reachable from what we've already seen. */ + + while (tos != worklist) + { + basic_block b = *--tos; + + FOR_EACH_EDGE (e, ei, b->succs) + { + basic_block dest = e->dest; + + if (!(dest->flags & BB_REACHABLE)) + { + *tos++ = dest; + dest->flags |= BB_REACHABLE; + } + } + } + + free (worklist); +} + +/* Functions to access an edge list with a vector representation. + Enough data is kept such that given an index number, the + pred and succ that edge represents can be determined, or + given a pred and a succ, its index number can be returned. + This allows algorithms which consume a lot of memory to + represent the normally full matrix of edge (pred,succ) with a + single indexed vector, edge (EDGE_INDEX (pred, succ)), with no + wasted space in the client code due to sparse flow graphs. */ + +/* This functions initializes the edge list. Basically the entire + flowgraph is processed, and all edges are assigned a number, + and the data structure is filled in. */ + +struct edge_list * +create_edge_list (void) +{ + struct edge_list *elist; + edge e; + int num_edges; + int block_count; + basic_block bb; + edge_iterator ei; + + block_count = n_basic_blocks; /* Include the entry and exit blocks. */ + + num_edges = 0; + + /* Determine the number of edges in the flow graph by counting successor + edges on each basic block. */ + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) + { + num_edges += EDGE_COUNT (bb->succs); + } + + elist = XNEW (struct edge_list); + elist->num_blocks = block_count; + elist->num_edges = num_edges; + elist->index_to_edge = XNEWVEC (edge, num_edges); + + num_edges = 0; + + /* Follow successors of blocks, and register these edges. */ + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) + FOR_EACH_EDGE (e, ei, bb->succs) + elist->index_to_edge[num_edges++] = e; + + return elist; +} + +/* This function free's memory associated with an edge list. */ + +void +free_edge_list (struct edge_list *elist) +{ + if (elist) + { + free (elist->index_to_edge); + free (elist); + } +} + +/* This function provides debug output showing an edge list. */ + +void +print_edge_list (FILE *f, struct edge_list *elist) +{ + int x; + + fprintf (f, "Compressed edge list, %d BBs + entry & exit, and %d edges\n", + elist->num_blocks, elist->num_edges); + + for (x = 0; x < elist->num_edges; x++) + { + fprintf (f, " %-4d - edge(", x); + if (INDEX_EDGE_PRED_BB (elist, x) == ENTRY_BLOCK_PTR) + fprintf (f, "entry,"); + else + fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index); + + if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR) + fprintf (f, "exit)\n"); + else + fprintf (f, "%d)\n", INDEX_EDGE_SUCC_BB (elist, x)->index); + } +} + +/* This function provides an internal consistency check of an edge list, + verifying that all edges are present, and that there are no + extra edges. */ + +void +verify_edge_list (FILE *f, struct edge_list *elist) +{ + int pred, succ, index; + edge e; + basic_block bb, p, s; + edge_iterator ei; + + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) + { + FOR_EACH_EDGE (e, ei, bb->succs) + { + pred = e->src->index; + succ = e->dest->index; + index = EDGE_INDEX (elist, e->src, e->dest); + if (index == EDGE_INDEX_NO_EDGE) + { + fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ); + continue; + } + + if (INDEX_EDGE_PRED_BB (elist, index)->index != pred) + fprintf (f, "*p* Pred for index %d should be %d not %d\n", + index, pred, INDEX_EDGE_PRED_BB (elist, index)->index); + if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ) + fprintf (f, "*p* Succ for index %d should be %d not %d\n", + index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index); + } + } + + /* We've verified that all the edges are in the list, now lets make sure + there are no spurious edges in the list. */ + + FOR_BB_BETWEEN (p, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) + FOR_BB_BETWEEN (s, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb) + { + int found_edge = 0; + + FOR_EACH_EDGE (e, ei, p->succs) + if (e->dest == s) + { + found_edge = 1; + break; + } + + FOR_EACH_EDGE (e, ei, s->preds) + if (e->src == p) + { + found_edge = 1; + break; + } + + if (EDGE_INDEX (elist, p, s) + == EDGE_INDEX_NO_EDGE && found_edge != 0) + fprintf (f, "*** Edge (%d, %d) appears to not have an index\n", + p->index, s->index); + if (EDGE_INDEX (elist, p, s) + != EDGE_INDEX_NO_EDGE && found_edge == 0) + fprintf (f, "*** Edge (%d, %d) has index %d, but there is no edge\n", + p->index, s->index, EDGE_INDEX (elist, p, s)); + } +} + +/* Given PRED and SUCC blocks, return the edge which connects the blocks. + If no such edge exists, return NULL. */ + +edge +find_edge (basic_block pred, basic_block succ) +{ + edge e; + edge_iterator ei; + + if (EDGE_COUNT (pred->succs) <= EDGE_COUNT (succ->preds)) + { + FOR_EACH_EDGE (e, ei, pred->succs) + if (e->dest == succ) + return e; + } + else + { + FOR_EACH_EDGE (e, ei, succ->preds) + if (e->src == pred) + return e; + } + + return NULL; +} + +/* This routine will determine what, if any, edge there is between + a specified predecessor and successor. */ + +int +find_edge_index (struct edge_list *edge_list, basic_block pred, basic_block succ) +{ + int x; + + for (x = 0; x < NUM_EDGES (edge_list); x++) + if (INDEX_EDGE_PRED_BB (edge_list, x) == pred + && INDEX_EDGE_SUCC_BB (edge_list, x) == succ) + return x; + + return (EDGE_INDEX_NO_EDGE); +} + +/* Dump the list of basic blocks in the bitmap NODES. */ + +void +flow_nodes_print (const char *str, const sbitmap nodes, FILE *file) +{ + unsigned int node = 0; + sbitmap_iterator sbi; + + if (! nodes) + return; + + fprintf (file, "%s { ", str); + EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, sbi) + fprintf (file, "%d ", node); + fputs ("}\n", file); +} + +/* Dump the list of edges in the array EDGE_LIST. */ + +void +flow_edge_list_print (const char *str, const edge *edge_list, int num_edges, FILE *file) +{ + int i; + + if (! edge_list) + return; + + fprintf (file, "%s { ", str); + for (i = 0; i < num_edges; i++) + fprintf (file, "%d->%d ", edge_list[i]->src->index, + edge_list[i]->dest->index); + + fputs ("}\n", file); +} + + +/* This routine will remove any fake predecessor edges for a basic block. + When the edge is removed, it is also removed from whatever successor + list it is in. */ + +static void +remove_fake_predecessors (basic_block bb) +{ + edge e; + edge_iterator ei; + + for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) + { + if ((e->flags & EDGE_FAKE) == EDGE_FAKE) + remove_edge (e); + else + ei_next (&ei); + } +} + +/* This routine will remove all fake edges from the flow graph. If + we remove all fake successors, it will automatically remove all + fake predecessors. */ + +void +remove_fake_edges (void) +{ + basic_block bb; + + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb) + remove_fake_predecessors (bb); +} + +/* This routine will remove all fake edges to the EXIT_BLOCK. */ + +void +remove_fake_exit_edges (void) +{ + remove_fake_predecessors (EXIT_BLOCK_PTR); +} + + +/* This function will add a fake edge between any block which has no + successors, and the exit block. Some data flow equations require these + edges to exist. */ + +void +add_noreturn_fake_exit_edges (void) +{ + basic_block bb; + + FOR_EACH_BB (bb) + if (EDGE_COUNT (bb->succs) == 0) + make_single_succ_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE); +} + +/* This function adds a fake edge between any infinite loops to the + exit block. Some optimizations require a path from each node to + the exit node. + + See also Morgan, Figure 3.10, pp. 82-83. + + The current implementation is ugly, not attempting to minimize the + number of inserted fake edges. To reduce the number of fake edges + to insert, add fake edges from _innermost_ loops containing only + nodes not reachable from the exit block. */ + +void +connect_infinite_loops_to_exit (void) +{ + basic_block unvisited_block = EXIT_BLOCK_PTR; + struct depth_first_search_dsS dfs_ds; + + /* Perform depth-first search in the reverse graph to find nodes + reachable from the exit block. */ + flow_dfs_compute_reverse_init (&dfs_ds); + flow_dfs_compute_reverse_add_bb (&dfs_ds, EXIT_BLOCK_PTR); + + /* Repeatedly add fake edges, updating the unreachable nodes. */ + while (1) + { + unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds, + unvisited_block); + if (!unvisited_block) + break; + + make_edge (unvisited_block, EXIT_BLOCK_PTR, EDGE_FAKE); + flow_dfs_compute_reverse_add_bb (&dfs_ds, unvisited_block); + } + + flow_dfs_compute_reverse_finish (&dfs_ds); + return; +} + +/* Compute reverse top sort order. + This is computing a post order numbering of the graph. */ + +int +post_order_compute (int *post_order, bool include_entry_exit) +{ + edge_iterator *stack; + int sp; + int post_order_num = 0; + sbitmap visited; + + if (include_entry_exit) + post_order[post_order_num++] = EXIT_BLOCK; + + /* Allocate stack for back-tracking up CFG. */ + stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); + sp = 0; + + /* Allocate bitmap to track nodes that have been visited. */ + visited = sbitmap_alloc (last_basic_block); + + /* None of the nodes in the CFG have been visited yet. */ + sbitmap_zero (visited); + + /* Push the first edge on to the stack. */ + stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs); + + while (sp) + { + edge_iterator ei; + basic_block src; + basic_block dest; + + /* Look at the edge on the top of the stack. */ + ei = stack[sp - 1]; + src = ei_edge (ei)->src; + dest = ei_edge (ei)->dest; + + /* Check if the edge destination has been visited yet. */ + if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index)) + { + /* Mark that we have visited the destination. */ + SET_BIT (visited, dest->index); + + if (EDGE_COUNT (dest->succs) > 0) + /* Since the DEST node has been visited for the first + time, check its successors. */ + stack[sp++] = ei_start (dest->succs); + else + post_order[post_order_num++] = dest->index; + } + else + { + if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR) + post_order[post_order_num++] = src->index; + + if (!ei_one_before_end_p (ei)) + ei_next (&stack[sp - 1]); + else + sp--; + } + } + + if (include_entry_exit) + post_order[post_order_num++] = ENTRY_BLOCK; + + free (stack); + sbitmap_free (visited); + return post_order_num; +} + +/* Compute the depth first search order and store in the array + PRE_ORDER if nonzero, marking the nodes visited in VISITED. If + REV_POST_ORDER is nonzero, return the reverse completion number for each + node. Returns the number of nodes visited. A depth first search + tries to get as far away from the starting point as quickly as + possible. + + pre_order is a really a preorder numbering of the graph. + rev_post_order is really a reverse postorder numbering of the graph. + */ + +int +pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order, + bool include_entry_exit) +{ + edge_iterator *stack; + int sp; + int pre_order_num = 0; + int rev_post_order_num = n_basic_blocks - 1; + sbitmap visited; + + /* Allocate stack for back-tracking up CFG. */ + stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); + sp = 0; + + if (include_entry_exit) + { + if (pre_order) + pre_order[pre_order_num] = ENTRY_BLOCK; + pre_order_num++; + if (rev_post_order) + rev_post_order[rev_post_order_num--] = ENTRY_BLOCK; + } + else + rev_post_order_num -= NUM_FIXED_BLOCKS; + + /* Allocate bitmap to track nodes that have been visited. */ + visited = sbitmap_alloc (last_basic_block); + + /* None of the nodes in the CFG have been visited yet. */ + sbitmap_zero (visited); + + /* Push the first edge on to the stack. */ + stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs); + + while (sp) + { + edge_iterator ei; + basic_block src; + basic_block dest; + + /* Look at the edge on the top of the stack. */ + ei = stack[sp - 1]; + src = ei_edge (ei)->src; + dest = ei_edge (ei)->dest; + + /* Check if the edge destination has been visited yet. */ + if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index)) + { + /* Mark that we have visited the destination. */ + SET_BIT (visited, dest->index); + + if (pre_order) + pre_order[pre_order_num] = dest->index; + + pre_order_num++; + + if (EDGE_COUNT (dest->succs) > 0) + /* Since the DEST node has been visited for the first + time, check its successors. */ + stack[sp++] = ei_start (dest->succs); + else if (rev_post_order) + /* There are no successors for the DEST node so assign + its reverse completion number. */ + rev_post_order[rev_post_order_num--] = dest->index; + } + else + { + if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR + && rev_post_order) + /* There are no more successors for the SRC node + so assign its reverse completion number. */ + rev_post_order[rev_post_order_num--] = src->index; + + if (!ei_one_before_end_p (ei)) + ei_next (&stack[sp - 1]); + else + sp--; + } + } + + free (stack); + sbitmap_free (visited); + + if (include_entry_exit) + { + if (pre_order) + pre_order[pre_order_num] = EXIT_BLOCK; + pre_order_num++; + if (rev_post_order) + rev_post_order[rev_post_order_num--] = EXIT_BLOCK; + /* The number of nodes visited should be the number of blocks. */ + gcc_assert (pre_order_num == n_basic_blocks); + } + else + /* The number of nodes visited should be the number of blocks minus + the entry and exit blocks which are not visited here. */ + gcc_assert (pre_order_num == n_basic_blocks - NUM_FIXED_BLOCKS); + + return pre_order_num; +} + +/* Compute the depth first search order on the _reverse_ graph and + store in the array DFS_ORDER, marking the nodes visited in VISITED. + Returns the number of nodes visited. + + The computation is split into three pieces: + + flow_dfs_compute_reverse_init () creates the necessary data + structures. + + flow_dfs_compute_reverse_add_bb () adds a basic block to the data + structures. The block will start the search. + + flow_dfs_compute_reverse_execute () continues (or starts) the + search using the block on the top of the stack, stopping when the + stack is empty. + + flow_dfs_compute_reverse_finish () destroys the necessary data + structures. + + Thus, the user will probably call ..._init(), call ..._add_bb() to + add a beginning basic block to the stack, call ..._execute(), + possibly add another bb to the stack and again call ..._execute(), + ..., and finally call _finish(). */ + +/* Initialize the data structures used for depth-first search on the + reverse graph. If INITIALIZE_STACK is nonzero, the exit block is + added to the basic block stack. DATA is the current depth-first + search context. If INITIALIZE_STACK is nonzero, there is an + element on the stack. */ + +static void +flow_dfs_compute_reverse_init (depth_first_search_ds data) +{ + /* Allocate stack for back-tracking up CFG. */ + data->stack = XNEWVEC (basic_block, n_basic_blocks); + data->sp = 0; + + /* Allocate bitmap to track nodes that have been visited. */ + data->visited_blocks = sbitmap_alloc (last_basic_block); + + /* None of the nodes in the CFG have been visited yet. */ + sbitmap_zero (data->visited_blocks); + + return; +} + +/* Add the specified basic block to the top of the dfs data + structures. When the search continues, it will start at the + block. */ + +static void +flow_dfs_compute_reverse_add_bb (depth_first_search_ds data, basic_block bb) +{ + data->stack[data->sp++] = bb; + SET_BIT (data->visited_blocks, bb->index); +} + +/* Continue the depth-first search through the reverse graph starting with the + block at the stack's top and ending when the stack is empty. Visited nodes + are marked. Returns an unvisited basic block, or NULL if there is none + available. */ + +static basic_block +flow_dfs_compute_reverse_execute (depth_first_search_ds data, + basic_block last_unvisited) +{ + basic_block bb; + edge e; + edge_iterator ei; + + while (data->sp > 0) + { + bb = data->stack[--data->sp]; + + /* Perform depth-first search on adjacent vertices. */ + FOR_EACH_EDGE (e, ei, bb->preds) + if (!TEST_BIT (data->visited_blocks, e->src->index)) + flow_dfs_compute_reverse_add_bb (data, e->src); + } + + /* Determine if there are unvisited basic blocks. */ + FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb) + if (!TEST_BIT (data->visited_blocks, bb->index)) + return bb; + + return NULL; +} + +/* Destroy the data structures needed for depth-first search on the + reverse graph. */ + +static void +flow_dfs_compute_reverse_finish (depth_first_search_ds data) +{ + free (data->stack); + sbitmap_free (data->visited_blocks); +} + +/* Performs dfs search from BB over vertices satisfying PREDICATE; + if REVERSE, go against direction of edges. Returns number of blocks + found and their list in RSLT. RSLT can contain at most RSLT_MAX items. */ +int +dfs_enumerate_from (basic_block bb, int reverse, + bool (*predicate) (basic_block, void *), + basic_block *rslt, int rslt_max, void *data) +{ + basic_block *st, lbb; + int sp = 0, tv = 0; + unsigned size; + + /* A bitmap to keep track of visited blocks. Allocating it each time + this function is called is not possible, since dfs_enumerate_from + is often used on small (almost) disjoint parts of cfg (bodies of + loops), and allocating a large sbitmap would lead to quadratic + behavior. */ + static sbitmap visited; + static unsigned v_size; + +#define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index)) +#define UNMARK_VISITED(BB) (RESET_BIT (visited, (BB)->index)) +#define VISITED_P(BB) (TEST_BIT (visited, (BB)->index)) + + /* Resize the VISITED sbitmap if necessary. */ + size = last_basic_block; + if (size < 10) + size = 10; + + if (!visited) + { + + visited = sbitmap_alloc (size); + sbitmap_zero (visited); + v_size = size; + } + else if (v_size < size) + { + /* Ensure that we increase the size of the sbitmap exponentially. */ + if (2 * v_size > size) + size = 2 * v_size; + + visited = sbitmap_resize (visited, size, 0); + v_size = size; + } + + st = XCNEWVEC (basic_block, rslt_max); + rslt[tv++] = st[sp++] = bb; + MARK_VISITED (bb); + while (sp) + { + edge e; + edge_iterator ei; + lbb = st[--sp]; + if (reverse) + { + FOR_EACH_EDGE (e, ei, lbb->preds) + if (!VISITED_P (e->src) && predicate (e->src, data)) + { + gcc_assert (tv != rslt_max); + rslt[tv++] = st[sp++] = e->src; + MARK_VISITED (e->src); + } + } + else + { + FOR_EACH_EDGE (e, ei, lbb->succs) + if (!VISITED_P (e->dest) && predicate (e->dest, data)) + { + gcc_assert (tv != rslt_max); + rslt[tv++] = st[sp++] = e->dest; + MARK_VISITED (e->dest); + } + } + } + free (st); + for (sp = 0; sp < tv; sp++) + UNMARK_VISITED (rslt[sp]); + return tv; +#undef MARK_VISITED +#undef UNMARK_VISITED +#undef VISITED_P +} + + +/* Compute dominance frontiers, ala Harvey, Ferrante, et al. + + This algorithm can be found in Timothy Harvey's PhD thesis, at + http://www.cs.rice.edu/~harv/dissertation.pdf in the section on iterative + dominance algorithms. + + First, we identify each join point, j (any node with more than one + incoming edge is a join point). + + We then examine each predecessor, p, of j and walk up the dominator tree + starting at p. + + We stop the walk when we reach j's immediate dominator - j is in the + dominance frontier of each of the nodes in the walk, except for j's + immediate dominator. Intuitively, all of the rest of j's dominators are + shared by j's predecessors as well. + Since they dominate j, they will not have j in their dominance frontiers. + + The number of nodes touched by this algorithm is equal to the size + of the dominance frontiers, no more, no less. +*/ + + +static void +compute_dominance_frontiers_1 (bitmap *frontiers) +{ + edge p; + edge_iterator ei; + basic_block b; + FOR_EACH_BB (b) + { + if (EDGE_COUNT (b->preds) >= 2) + { + FOR_EACH_EDGE (p, ei, b->preds) + { + basic_block runner = p->src; + basic_block domsb; + if (runner == ENTRY_BLOCK_PTR) + continue; + + domsb = get_immediate_dominator (CDI_DOMINATORS, b); + while (runner != domsb) + { + if (bitmap_bit_p (frontiers[runner->index], b->index)) + break; + bitmap_set_bit (frontiers[runner->index], + b->index); + runner = get_immediate_dominator (CDI_DOMINATORS, + runner); + } + } + } + } +} + + +void +compute_dominance_frontiers (bitmap *frontiers) +{ + timevar_push (TV_DOM_FRONTIERS); + + compute_dominance_frontiers_1 (frontiers); + + timevar_pop (TV_DOM_FRONTIERS); +} + |