/* 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.
+ 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, 51 Franklin Street, Fifth Floor, Boston, MA
-02110-1301, 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 "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 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;
its single destination. */
bool
-forwarder_block_p (basic_block bb)
+forwarder_block_p (const_basic_block bb)
{
rtx insn;
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. */
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;
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;
/* 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)
{
unsigned int node = 0;
sbitmap_iterator sbi;
return;
}
\f
-/* Compute reverse top sort order.
- This is computing a post order numbering of the graph. */
+/* 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. */
int
-post_order_compute (int *post_order, bool include_entry_exit)
+post_order_compute (int *post_order, bool include_entry_exit,
+ bool delete_unreachable)
{
edge_iterator *stack;
int sp;
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. */
else
{
if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR)
- post_order[post_order_num++] = 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;
+ {
+ 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);
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
-pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
+pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
bool include_entry_exit)
{
edge_iterator *stack;
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 (rev_post_order)
rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
}
- else
+ else
rev_post_order_num -= NUM_FIXED_BLOCKS;
/* Allocate bitmap to track nodes that have been visited. */
flow_dfs_compute_reverse_init (depth_first_search_ds data)
{
/* Allocate stack for back-tracking up CFG. */
- data->stack = xmalloc (n_basic_blocks * sizeof (basic_block));
+ data->stack = XNEWVEC (basic_block, n_basic_blocks);
data->sp = 0;
/* Allocate bitmap to track nodes that have been visited. */
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;
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))
+#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;
+ size = last_basic_block;
if (size < 10)
size = 10;
v_size = size;
}
- st = xcalloc (rslt_max, sizeof (basic_block));
+ st = XCNEWVEC (basic_block, rslt_max);
rslt[tv++] = st[sp++] = bb;
MARK_VISITED (bb);
while (sp)
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);
+ 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);
+ gcc_assert (tv != rslt_max);
+ rslt[tv++] = st[sp++] = e->dest;
+ MARK_VISITED (e->dest);
}
}
}
/* 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).
+ incoming edge is a join point).
We then examine each predecessor, p, of j and walk up the dominator tree
- starting at p.
-
+ 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
+ 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)
+compute_dominance_frontiers_1 (bitmap_head *frontiers)
{
edge p;
edge_iterator ei;
basic_block domsb;
if (runner == ENTRY_BLOCK_PTR)
continue;
-
+
domsb = get_immediate_dominator (CDI_DOMINATORS, b);
while (runner != domsb)
{
- bitmap_set_bit (frontiers[runner->index],
- b->index);
+ 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)
{
timevar_push (TV_DOM_FRONTIERS);
timevar_pop (TV_DOM_FRONTIERS);
}
+/* 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.
+
+ 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;
+}
+
+
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