X-Git-Url: http://git.sourceforge.jp/view?p=pf3gnuchains%2Fgcc-fork.git;a=blobdiff_plain;f=gcc%2Fcfganal.c;h=22a0503c01336eab9dc43ee324f120a667139b13;hp=c76da55296c545bb3a0fe0163909297b730a5c7b;hb=9232c3b6259f0a56cca9ada3b978ab7d0a0debda;hpb=29cd975191d09486fbbc2de22f78a6e364b48913 diff --git a/gcc/cfganal.c b/gcc/cfganal.c index c76da55296c..22a0503c013 100644 --- a/gcc/cfganal.c +++ b/gcc/cfganal.c @@ -1,12 +1,13 @@ /* Control flow graph analysis code for GNU compiler. Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, - 1999, 2000, 2001, 2003, 2004 Free Software Foundation, Inc. + 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008 + 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 +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 @@ -15,9 +16,8 @@ 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. */ +along with GCC; see the file COPYING3. If not see +. */ /* This file contains various simple utilities to analyze the CFG. */ #include "config.h" @@ -25,12 +25,15 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA #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 "vec.h" +#include "vecprim.h" #include "timevar.h" /* Store the data structures necessary for depth-first search. */ @@ -50,15 +53,16 @@ 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); +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); +static bool flow_active_insn_p (const_rtx); /* Like active_insn_p, except keep the return value clobber around even after reload. */ static bool -flow_active_insn_p (rtx insn) +flow_active_insn_p (const_rtx insn) { if (active_insn_p (insn)) return true; @@ -67,7 +71,7 @@ flow_active_insn_p (rtx insn) 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 livetime aborts. */ + 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))) @@ -80,12 +84,12 @@ flow_active_insn_p (rtx insn) its single destination. */ bool -forwarder_block_p (basic_block bb) +forwarder_block_p (const_basic_block bb) { rtx insn; if (bb == EXIT_BLOCK_PTR || bb == ENTRY_BLOCK_PTR - || EDGE_COUNT (bb->succs) != 1) + || !single_succ_p (bb)) return false; for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn)) @@ -150,7 +154,7 @@ could_fall_through (basic_block src, basic_block target) Steven Muchnick Morgan Kaufmann, 1997 - and heavily borrowed from flow_depth_first_order_compute. */ + and heavily borrowed from pre_and_rev_post_order_compute. */ bool mark_dfs_back_edges (void) @@ -165,11 +169,11 @@ mark_dfs_back_edges (void) bool found = false; /* Allocate the preorder and postorder number arrays. */ - pre = xcalloc (last_basic_block, sizeof (int)); - post = xcalloc (last_basic_block, sizeof (int)); + pre = XCNEWVEC (int, last_basic_block); + post = XCNEWVEC (int, last_basic_block); /* Allocate stack for back-tracking up CFG. */ - stack = xmalloc ((n_basic_blocks + 1) * sizeof (edge_iterator)); + stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); sp = 0; /* Allocate bitmap to track nodes that have been visited. */ @@ -280,7 +284,7 @@ find_unreachable_blocks (void) edge_iterator ei; basic_block *tos, *worklist, bb; - tos = worklist = xmalloc (sizeof (basic_block) * n_basic_blocks); + tos = worklist = XNEWVEC (basic_block, n_basic_blocks); /* Clear all the reachability flags. */ @@ -306,11 +310,15 @@ find_unreachable_blocks (void) basic_block b = *--tos; FOR_EACH_EDGE (e, ei, b->succs) - if (!(e->dest->flags & BB_REACHABLE)) - { - *tos++ = e->dest; - e->dest->flags |= BB_REACHABLE; - } + { + basic_block dest = e->dest; + + if (!(dest->flags & BB_REACHABLE)) + { + *tos++ = dest; + dest->flags |= BB_REACHABLE; + } + } } free (worklist); @@ -339,7 +347,7 @@ create_edge_list (void) basic_block bb; edge_iterator ei; - block_count = n_basic_blocks + 2; /* Include the entry and exit blocks. */ + block_count = n_basic_blocks; /* Include the entry and exit blocks. */ num_edges = 0; @@ -350,10 +358,10 @@ create_edge_list (void) num_edges += EDGE_COUNT (bb->succs); } - elist = xmalloc (sizeof (struct edge_list)); + elist = XNEW (struct edge_list); elist->num_blocks = block_count; elist->num_edges = num_edges; - elist->index_to_edge = xmalloc (sizeof (edge) * num_edges); + elist->index_to_edge = XNEWVEC (edge, num_edges); num_edges = 0; @@ -385,7 +393,7 @@ 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 - 2, elist->num_edges); + elist->num_blocks, elist->num_edges); for (x = 0; x < elist->num_edges; x++) { @@ -478,9 +486,18 @@ find_edge (basic_block pred, basic_block succ) edge e; edge_iterator ei; - FOR_EACH_EDGE (e, ei, pred->succs) - if (e->dest == succ) - return e; + 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; } @@ -504,15 +521,17 @@ find_edge_index (struct edge_list *edge_list, basic_block pred, basic_block succ /* Dump the list of basic blocks in the bitmap NODES. */ void -flow_nodes_print (const char *str, const sbitmap nodes, FILE *file) +flow_nodes_print (const char *str, const_sbitmap nodes, FILE *file) { - int node; + unsigned int node = 0; + sbitmap_iterator sbi; if (! nodes) return; fprintf (file, "%s { ", str); - EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, {fprintf (file, "%d ", node);}); + EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, sbi) + fprintf (file, "%d ", node); fputs ("}\n", file); } @@ -604,7 +623,7 @@ add_noreturn_fake_exit_edges (void) void connect_infinite_loops_to_exit (void) { - basic_block unvisited_block; + 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 @@ -615,7 +634,8 @@ connect_infinite_loops_to_exit (void) /* Repeatedly add fake edges, updating the unreachable nodes. */ while (1) { - unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds); + unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds, + unvisited_block); if (!unvisited_block) break; @@ -627,18 +647,26 @@ connect_infinite_loops_to_exit (void) return; } -/* Compute reverse top sort order. */ +/* Compute reverse top sort order. This is computing a post order + numbering of the graph. If INCLUDE_ENTRY_EXIT is true, then then + ENTRY_BLOCK and EXIT_BLOCK are included. If DELETE_UNREACHABLE is + true, unreachable blocks are deleted. */ -void -flow_reverse_top_sort_order_compute (int *rts_order) +int +post_order_compute (int *post_order, bool include_entry_exit, + bool delete_unreachable) { edge_iterator *stack; int sp; - int postnum = 0; + int post_order_num = 0; sbitmap visited; + int count; + + if (include_entry_exit) + post_order[post_order_num++] = EXIT_BLOCK; /* Allocate stack for back-tracking up CFG. */ - stack = xmalloc ((n_basic_blocks + 1) * sizeof (edge_iterator)); + stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); sp = 0; /* Allocate bitmap to track nodes that have been visited. */ @@ -672,12 +700,12 @@ flow_reverse_top_sort_order_compute (int *rts_order) time, check its successors. */ stack[sp++] = ei_start (dest->succs); else - rts_order[postnum++] = dest->index; + post_order[post_order_num++] = dest->index; } else { if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR) - rts_order[postnum++] = src->index; + post_order[post_order_num++] = src->index; if (!ei_one_before_end_p (ei)) ei_next (&stack[sp - 1]); @@ -686,30 +714,263 @@ flow_reverse_top_sort_order_compute (int *rts_order) } } + if (include_entry_exit) + { + post_order[post_order_num++] = ENTRY_BLOCK; + count = post_order_num; + } + else + count = post_order_num + 2; + + /* Delete the unreachable blocks if some were found and we are + supposed to do it. */ + if (delete_unreachable && (count != n_basic_blocks)) + { + basic_block b; + basic_block next_bb; + for (b = ENTRY_BLOCK_PTR->next_bb; b != EXIT_BLOCK_PTR; b = next_bb) + { + next_bb = b->next_bb; + + if (!(TEST_BIT (visited, b->index))) + delete_basic_block (b); + } + + tidy_fallthru_edges (); + } + free (stack); sbitmap_free (visited); + return post_order_num; +} + + +/* Helper routine for inverted_post_order_compute. + BB has to belong to a region of CFG + unreachable by inverted traversal from the exit. + i.e. there's no control flow path from ENTRY to EXIT + that contains this BB. + This can happen in two cases - if there's an infinite loop + or if there's a block that has no successor + (call to a function with no return). + Some RTL passes deal with this condition by + calling connect_infinite_loops_to_exit () and/or + add_noreturn_fake_exit_edges (). + However, those methods involve modifying the CFG itself + which may not be desirable. + Hence, we deal with the infinite loop/no return cases + by identifying a unique basic block that can reach all blocks + in such a region by inverted traversal. + This function returns a basic block that guarantees + that all blocks in the region are reachable + by starting an inverted traversal from the returned block. */ + +static basic_block +dfs_find_deadend (basic_block bb) +{ + sbitmap visited = sbitmap_alloc (last_basic_block); + sbitmap_zero (visited); + + for (;;) + { + SET_BIT (visited, bb->index); + if (EDGE_COUNT (bb->succs) == 0 + || TEST_BIT (visited, EDGE_SUCC (bb, 0)->dest->index)) + { + sbitmap_free (visited); + return bb; + } + + bb = EDGE_SUCC (bb, 0)->dest; + } + + gcc_unreachable (); +} + + +/* Compute the reverse top sort order of the inverted CFG + i.e. starting from the exit block and following the edges backward + (from successors to predecessors). + This ordering can be used for forward dataflow problems among others. + + This function assumes that all blocks in the CFG are reachable + from the ENTRY (but not necessarily from EXIT). + + If there's an infinite loop, + a simple inverted traversal starting from the blocks + with no successors can't visit all blocks. + To solve this problem, we first do inverted traversal + starting from the blocks with no successor. + And if there's any block left that's not visited by the regular + inverted traversal from EXIT, + those blocks are in such problematic region. + Among those, we find one block that has + any visited predecessor (which is an entry into such a region), + and start looking for a "dead end" from that block + and do another inverted traversal from that block. */ + +int +inverted_post_order_compute (int *post_order) +{ + basic_block bb; + edge_iterator *stack; + int sp; + int post_order_num = 0; + sbitmap visited; + + /* 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); + + /* Put all blocks that have no successor into the initial work list. */ + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) + if (EDGE_COUNT (bb->succs) == 0) + { + /* Push the initial edge on to the stack. */ + if (EDGE_COUNT (bb->preds) > 0) + { + stack[sp++] = ei_start (bb->preds); + SET_BIT (visited, bb->index); + } + } + + do + { + bool has_unvisited_bb = false; + + /* The inverted traversal loop. */ + while (sp) + { + edge_iterator ei; + basic_block pred; + + /* Look at the edge on the top of the stack. */ + ei = stack[sp - 1]; + bb = ei_edge (ei)->dest; + pred = ei_edge (ei)->src; + + /* Check if the predecessor has been visited yet. */ + if (! TEST_BIT (visited, pred->index)) + { + /* Mark that we have visited the destination. */ + SET_BIT (visited, pred->index); + + if (EDGE_COUNT (pred->preds) > 0) + /* Since the predecessor node has been visited for the first + time, check its predecessors. */ + stack[sp++] = ei_start (pred->preds); + else + post_order[post_order_num++] = pred->index; + } + else + { + if (bb != EXIT_BLOCK_PTR && ei_one_before_end_p (ei)) + post_order[post_order_num++] = bb->index; + + if (!ei_one_before_end_p (ei)) + ei_next (&stack[sp - 1]); + else + sp--; + } + } + + /* Detect any infinite loop and activate the kludge. + Note that this doesn't check EXIT_BLOCK itself + since EXIT_BLOCK is always added after the outer do-while loop. */ + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) + if (!TEST_BIT (visited, bb->index)) + { + has_unvisited_bb = true; + + if (EDGE_COUNT (bb->preds) > 0) + { + edge_iterator ei; + edge e; + basic_block visited_pred = NULL; + + /* Find an already visited predecessor. */ + FOR_EACH_EDGE (e, ei, bb->preds) + { + if (TEST_BIT (visited, e->src->index)) + visited_pred = e->src; + } + + if (visited_pred) + { + basic_block be = dfs_find_deadend (bb); + gcc_assert (be != NULL); + SET_BIT (visited, be->index); + stack[sp++] = ei_start (be->preds); + break; + } + } + } + + if (has_unvisited_bb && sp == 0) + { + /* No blocks are reachable from EXIT at all. + Find a dead-end from the ENTRY, and restart the iteration. */ + basic_block be = dfs_find_deadend (ENTRY_BLOCK_PTR); + gcc_assert (be != NULL); + SET_BIT (visited, be->index); + stack[sp++] = ei_start (be->preds); + } + + /* The only case the below while fires is + when there's an infinite loop. */ + } + while (sp); + + /* EXIT_BLOCK is always included. */ + post_order[post_order_num++] = EXIT_BLOCK; + + free (stack); + sbitmap_free (visited); + return post_order_num; } /* Compute the depth first search order and store in the array - DFS_ORDER if nonzero, marking the nodes visited in VISITED. If - RC_ORDER is nonzero, return the reverse completion number for each + 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. */ + 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 -flow_depth_first_order_compute (int *dfs_order, int *rc_order) +pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order, + bool include_entry_exit) { edge_iterator *stack; int sp; - int dfsnum = 0; - int rcnum = n_basic_blocks - 1; + int pre_order_num = 0; + int rev_post_order_num = n_basic_blocks - 1; sbitmap visited; /* Allocate stack for back-tracking up CFG. */ - stack = xmalloc ((n_basic_blocks + 1) * sizeof (edge_iterator)); + 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); @@ -736,27 +997,27 @@ flow_depth_first_order_compute (int *dfs_order, int *rc_order) /* Mark that we have visited the destination. */ SET_BIT (visited, dest->index); - if (dfs_order) - dfs_order[dfsnum] = dest->index; + if (pre_order) + pre_order[pre_order_num] = dest->index; - dfsnum++; + 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 (rc_order) + else if (rev_post_order) /* There are no successors for the DEST node so assign its reverse completion number. */ - rc_order[rcnum--] = dest->index; + rev_post_order[rev_post_order_num--] = dest->index; } else { if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR - && rc_order) + && rev_post_order) /* There are no more successors for the SRC node so assign its reverse completion number. */ - rc_order[rcnum--] = src->index; + rev_post_order[rev_post_order_num--] = src->index; if (!ei_one_before_end_p (ei)) ei_next (&stack[sp - 1]); @@ -768,10 +1029,22 @@ flow_depth_first_order_compute (int *dfs_order, int *rc_order) free (stack); sbitmap_free (visited); - /* The number of nodes visited should be the number of blocks. */ - gcc_assert (dfsnum == n_basic_blocks); + 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 dfsnum; + return pre_order_num; } /* Compute the depth first search order on the _reverse_ graph and @@ -808,12 +1081,11 @@ static void flow_dfs_compute_reverse_init (depth_first_search_ds data) { /* Allocate stack for back-tracking up CFG. */ - data->stack = xmalloc ((n_basic_blocks - (INVALID_BLOCK + 1)) - * sizeof (basic_block)); + 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 - (INVALID_BLOCK + 1)); + data->visited_blocks = sbitmap_alloc (last_basic_block); /* None of the nodes in the CFG have been visited yet. */ sbitmap_zero (data->visited_blocks); @@ -829,7 +1101,7 @@ 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 - (INVALID_BLOCK + 1)); + SET_BIT (data->visited_blocks, bb->index); } /* Continue the depth-first search through the reverse graph starting with the @@ -838,7 +1110,8 @@ flow_dfs_compute_reverse_add_bb (depth_first_search_ds data, basic_block bb) available. */ static basic_block -flow_dfs_compute_reverse_execute (depth_first_search_ds data) +flow_dfs_compute_reverse_execute (depth_first_search_ds data, + basic_block last_unvisited) { basic_block bb; edge e; @@ -850,14 +1123,13 @@ flow_dfs_compute_reverse_execute (depth_first_search_ds data) /* Perform depth-first search on adjacent vertices. */ FOR_EACH_EDGE (e, ei, bb->preds) - if (!TEST_BIT (data->visited_blocks, - e->src->index - (INVALID_BLOCK + 1))) + 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, EXIT_BLOCK_PTR, NULL, prev_bb) - if (!TEST_BIT (data->visited_blocks, bb->index - (INVALID_BLOCK + 1))) + FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb) + if (!TEST_BIT (data->visited_blocks, bb->index)) return bb; return NULL; @@ -878,105 +1150,137 @@ flow_dfs_compute_reverse_finish (depth_first_search_ds data) 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) + bool (*predicate) (const_basic_block, const void *), + basic_block *rslt, int rslt_max, const 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) + { - st = xcalloc (rslt_max, sizeof (basic_block)); + 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; - bb->flags |= BB_VISITED; + MARK_VISITED (bb); while (sp) { edge e; edge_iterator ei; lbb = st[--sp]; if (reverse) - { + { FOR_EACH_EDGE (e, ei, lbb->preds) - if (!(e->src->flags & BB_VISITED) && predicate (e->src, data)) + if (!VISITED_P (e->src) && predicate (e->src, data)) { - gcc_assert (tv != rslt_max); - rslt[tv++] = st[sp++] = e->src; - e->src->flags |= BB_VISITED; + gcc_assert (tv != rslt_max); + rslt[tv++] = st[sp++] = e->src; + MARK_VISITED (e->src); } - } + } else - { + { FOR_EACH_EDGE (e, ei, lbb->succs) - if (!(e->dest->flags & BB_VISITED) && predicate (e->dest, data)) + if (!VISITED_P (e->dest) && predicate (e->dest, data)) { - gcc_assert (tv != rslt_max); - rslt[tv++] = st[sp++] = e->dest; - e->dest->flags |= BB_VISITED; + gcc_assert (tv != rslt_max); + rslt[tv++] = st[sp++] = e->dest; + MARK_VISITED (e->dest); } } } free (st); for (sp = 0; sp < tv; sp++) - rslt[sp]->flags &= ~BB_VISITED; + UNMARK_VISITED (rslt[sp]); return tv; +#undef MARK_VISITED +#undef UNMARK_VISITED +#undef VISITED_P } -/* Computing the Dominance Frontier: +/* Compute dominance frontiers, ala Harvey, Ferrante, et al. - 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: + 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. - (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. + First, we identify each join point, j (any node with more than one + incoming edge is a join point). - (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. */ + We then examine each predecessor, p, of j and walk up the dominator tree + starting at p. -static void -compute_dominance_frontiers_1 (bitmap *frontiers, basic_block bb, sbitmap done) -{ - edge e; - edge_iterator ei; - basic_block c; + 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. - SET_BIT (done, bb->index); + The number of nodes touched by this algorithm is equal to the size + of the dominance frontiers, no more, no less. +*/ - /* 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_EACH_EDGE (e, ei, bb->succs) - { - 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)) +static void +compute_dominance_frontiers_1 (bitmap *frontiers) +{ + edge p; + edge_iterator ei; + basic_block b; + FOR_EACH_BB (b) { - int x; - bitmap_iterator bi; - - EXECUTE_IF_SET_IN_BITMAP (frontiers[c->index], 0, x, bi) + if (EDGE_COUNT (b->preds) >= 2) { - if (get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (x)) != bb) - bitmap_set_bit (frontiers[bb->index], x); + 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); + } + } } } } @@ -985,16 +1289,70 @@ compute_dominance_frontiers_1 (bitmap *frontiers, basic_block bb, sbitmap done) 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); - compute_dominance_frontiers_1 (frontiers, EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest, done); + timevar_pop (TV_DOM_FRONTIERS); +} - sbitmap_free (done); +/* Given a set of blocks with variable definitions (DEF_BLOCKS), + return a bitmap with all the blocks in the iterated dominance + frontier of the blocks in DEF_BLOCKS. DFS contains dominance + frontier information as returned by compute_dominance_frontiers. - timevar_pop (TV_DOM_FRONTIERS); + The resulting set of blocks are the potential sites where PHI nodes + are needed. The caller is responsible for freeing the memory + allocated for the return value. */ + +bitmap +compute_idf (bitmap def_blocks, bitmap *dfs) +{ + bitmap_iterator bi; + unsigned bb_index, i; + VEC(int,heap) *work_stack; + bitmap phi_insertion_points; + + work_stack = VEC_alloc (int, heap, n_basic_blocks); + phi_insertion_points = BITMAP_ALLOC (NULL); + + /* Seed the work list with all the blocks in DEF_BLOCKS. We use + VEC_quick_push here for speed. This is safe because we know that + the number of definition blocks is no greater than the number of + basic blocks, which is the initial capacity of WORK_STACK. */ + EXECUTE_IF_SET_IN_BITMAP (def_blocks, 0, bb_index, bi) + VEC_quick_push (int, work_stack, bb_index); + + /* Pop a block off the worklist, add every block that appears in + the original block's DF that we have not already processed to + the worklist. Iterate until the worklist is empty. Blocks + which are added to the worklist are potential sites for + PHI nodes. */ + while (VEC_length (int, work_stack) > 0) + { + bb_index = VEC_pop (int, work_stack); + + /* Since the registration of NEW -> OLD name mappings is done + separately from the call to update_ssa, when updating the SSA + form, the basic blocks where new and/or old names are defined + may have disappeared by CFG cleanup calls. In this case, + we may pull a non-existing block from the work stack. */ + gcc_assert (bb_index < (unsigned) last_basic_block); + + EXECUTE_IF_AND_COMPL_IN_BITMAP (dfs[bb_index], phi_insertion_points, + 0, i, bi) + { + /* Use a safe push because if there is a definition of VAR + in every basic block, then WORK_STACK may eventually have + more than N_BASIC_BLOCK entries. */ + VEC_safe_push (int, heap, work_stack, i); + bitmap_set_bit (phi_insertion_points, i); + } + } + + VEC_free (int, heap, work_stack); + + return phi_insertion_points; } +