/* 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, 2010
+ 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
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
+<http://www.gnu.org/licenses/>. */
/* This file contains various simple utilities to analyze the CFG. */
#include "config.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 "diagnostic-core.h"
#include "tm_p.h"
+#include "vec.h"
+#include "vecprim.h"
+#include "bitmap.h"
+#include "sbitmap.h"
#include "timevar.h"
/* Store the data structures necessary for depth-first search. */
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);
\f
/* 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;
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)))
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))
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)
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. */
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. */
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);
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;
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;
/* This function provides debug output showing an edge list. */
-void
+DEBUG_FUNCTION 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 - 2, elist->num_edges);
+ elist->num_blocks, elist->num_edges);
for (x = 0; x < elist->num_edges; x++)
{
verifying that all edges are present, and that there are no
extra edges. */
-void
+DEBUG_FUNCTION void
verify_edge_list (FILE *f, struct edge_list *elist)
{
int pred, succ, index;
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;
}
/* 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);
}
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
/* 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;
return;
}
\f
-/* 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
+ 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. */
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]);
}
}
+ 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);
/* 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]);
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
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);
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
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;
/* 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;
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)
+ {
+
+ 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;
- st = xcalloc (rslt_max, sizeof (basic_block));
+ 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_head *frontiers)
+{
+ edge p;
+ edge_iterator ei;
+ basic_block b;
+ FOR_EACH_BB (b)
{
- unsigned 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_set_bit (&frontiers[runner->index],
+ b->index))
+ break;
+ runner = get_immediate_dominator (CDI_DOMINATORS,
+ runner);
+ }
+ }
}
}
}
void
-compute_dominance_frontiers (bitmap *frontiers)
+compute_dominance_frontiers (bitmap_head *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_head *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;
}
+
OSDN Git Service
