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* tree-cfg.c (thread_jumps): Speed up by using a worklist.

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From-SVN: r89381
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Kazu Hirata 2004-10-21 16:06:31 +00:00 • committed by Kazu Hirata
parent 072269d857
commit 0844512546
2 changed files with 92 additions and 21 deletions
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4
gcc/ChangeLog
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@ -1,3 +1,7 @@
2004-10-21 Kazu Hirata <kazu@cs.umass.edu>
* tree-cfg.c (thread_jumps): Speed up by using a worklist.
2004-10-21 Kazu Hirata <kazu@cs.umass.edu>
* tree-cfg.c (thread_jumps): Move a part of it to ...

109
gcc/tree-cfg.c
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@ -3942,35 +3942,102 @@ thread_jumps (void)
{
basic_block bb;
bool retval = false;
bool rerun;
int *worklist = xmalloc (sizeof (int) * last_basic_block);
unsigned int size = 0;
FOR_EACH_BB (bb)
bb_ann (bb)->forwardable = tree_forwarder_block_p (bb);
do
{
rerun = false;
FOR_EACH_BB (bb)
bb_ann (bb)->forwardable = tree_forwarder_block_p (bb);
bb->flags &= ~BB_VISITED;
}
/* Initialize WORKLIST by putting the indexes of non-forwarder
blocks that immediately precede forwarder blocks because those
are the ones that we know we can thread jumps from. We use
BB_VISITED to indicate that whether a given basic block is in
WORKLIST or not, thereby avoiding duplicates in WORKLIST. */
FOR_EACH_BB (bb)
{
edge_iterator ei;
edge e;
/* We are not interested in finding non-forwarder blocks
directly. We want to find non-forwarder blocks as
predecessors of a forwarder block. */
if (!bb_ann (bb)->forwardable)
continue;
/* Now we know BB is a forwarder block. Visit each of its
incoming edges and add to WORKLIST all non-forwarder blocks
among BB's predecessors. */
FOR_EACH_EDGE (e, ei, bb->preds)
{
/* Don't waste time on forwarders. */
if (bb_ann (bb)->forwardable)
continue;
if (thread_jumps_from_bb (bb))
/* We are not interested in threading jumps from a forwarder
block. */
if (!bb_ann (e->src)->forwardable
/* We don't want to visit ENTRY_BLOCK_PTR. */
&& e->src->index >= 0
/* We don't want to put a duplicate into WORKLIST. */
&& (e->src->flags & BB_VISITED) == 0)
{
retval = true;
/* If we succeeded in threading a jump at BB, update the
forwardable mark as BB may have become a new
forwarder block. This could happen if we have a
useless "if" statement whose two arms eventually
merge without any intervening statements. */
if (tree_forwarder_block_p (bb))
bb_ann (bb)->forwardable = rerun = true;
e->src->flags |= BB_VISITED;
worklist[size] = e->src->index;
size++;
}
}
}
while (rerun);
/* Now let's drain WORKLIST. */
while (size > 0)
{
size--;
bb = BASIC_BLOCK (worklist[size]);
/* Check if BB is NULL because BB may have been deleted. This
could happen if BB is originally a non-forwarder block, later
becomes a forwarder block, and it is deleted when a jump is
threaded through it. */
if (!bb)
continue;
/* BB->INDEX is not longer in WORKLIST, so clear BB_VISITED. */
bb->flags &= ~BB_VISITED;
if (thread_jumps_from_bb (bb))
{
retval = true;
if (tree_forwarder_block_p (bb))
{
edge_iterator ej;
edge f;
bb_ann (bb)->forwardable = true;
/* Attempts to thread through BB may have been blocked
because BB was not a forwarder block before. Now
that BB is a forwarder block, we should revisit BB's
predecessors. */
FOR_EACH_EDGE (f, ej, bb->preds)
{
/* We are not interested in threading jumps from a
forwarder block. */
if (!bb_ann (f->src)->forwardable
/* We don't want to visit ENTRY_BLOCK_PTR. */
&& f->src->index >= 0
/* We don't want to put a duplicate into WORKLIST. */
&& (f->src->flags & BB_VISITED) == 0)
{
f->src->flags |= BB_VISITED;
worklist[size] = f->src->index;
size++;
}
}
}
}
}
free (worklist);
return retval;
}