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[PATCH] Remove backedge handling support in tree-ssa-threadupdate.c

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* tree-ssa-threadupdate.c (register_jump_thraed): Assert that a
	non-FSM path has no edges marked with EDGE_DFS_BACK.
	(ssa_redirect_edges): No longer call mark_loop_for_removal.
	(thread_single_edge, def_split_header_continue_p): Remove.
	(bb_ends_with_multiway_branch): Likewise.
	(thread_through_loop_header): Remove cases of threading from
	latch through the header.  Simplify knowing we won't thread
	the latch.
	(thread_through_all_blocks): Simplify knowing that only the FSM
	threader needs to handle backedges.

From-SVN: r229982
This commit is contained in:
Jeff Law 2015-11-08 20:19:09 -07:00 • committed by Jeff Law
parent a2478e36e0
commit 4f70cb39c0
2 changed files with 59 additions and 246 deletions
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13
gcc/ChangeLog
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@ -1,3 +1,16 @@
2015-11-08 Jeff Law <jeff@redhat.com>
* tree-ssa-threadupdate.c (register_jump_thraed): Assert that a
non-FSM path has no edges marked with EDGE_DFS_BACK.
(ssa_redirect_edges): No longer call mark_loop_for_removal.
(thread_single_edge, def_split_header_continue_p): Remove.
(bb_ends_with_multiway_branch): Likewise.
(thread_through_loop_header): Remove cases of threading from
latch through the header. Simplify knowing we won't thread
the latch.
(thread_through_all_blocks): Simplify knowing that only the FSM
threader needs to handle backedges.
2015-11-08 Eric Botcazou <ebotcazou@adacore.com>
* doc/extend.texi (type attributes): Document scalar_storage_order.

292
gcc/tree-ssa-threadupdate.c
View file

@ -1406,10 +1406,6 @@ ssa_redirect_edges (struct redirection_data **slot,
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
e->src->index, e->dest->index, rd->dup_blocks[0]->index);
/* If we redirect a loop latch edge cancel its loop. */
if (e->src == e->src->loop_father->latch)
mark_loop_for_removal (e->src->loop_father);
/* Redirect the incoming edge (possibly to the joiner block) to the
appropriate duplicate block. */
e2 = redirect_edge_and_branch (e, rd->dup_blocks[0]);
@ -1630,67 +1626,6 @@ thread_block (basic_block bb, bool noloop_only)
return retval;
}
/* Threads edge E through E->dest to the edge THREAD_TARGET (E). Returns the
copy of E->dest created during threading, or E->dest if it was not necessary
to copy it (E is its single predecessor). */
static basic_block
thread_single_edge (edge e)
{
basic_block bb = e->dest;
struct redirection_data rd;
vec<jump_thread_edge *> *path = THREAD_PATH (e);
edge eto = (*path)[1]->e;
delete_jump_thread_path (path);
e->aux = NULL;
thread_stats.num_threaded_edges++;
if (single_pred_p (bb))
{
/* If BB has just a single predecessor, we should only remove the
control statements at its end, and successors except for ETO. */
remove_ctrl_stmt_and_useless_edges (bb, eto->dest);
/* And fixup the flags on the single remaining edge. */
eto->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE | EDGE_ABNORMAL);
eto->flags |= EDGE_FALLTHRU;
return bb;
}
/* Otherwise, we need to create a copy. */
if (e->dest == eto->src)
update_bb_profile_for_threading (bb, EDGE_FREQUENCY (e), e->count, eto);
vec<jump_thread_edge *> *npath = new vec<jump_thread_edge *> ();
jump_thread_edge *x = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
npath->safe_push (x);
x = new jump_thread_edge (eto, EDGE_COPY_SRC_BLOCK);
npath->safe_push (x);
rd.path = npath;
create_block_for_threading (bb, &rd, 0, NULL);
remove_ctrl_stmt_and_useless_edges (rd.dup_blocks[0], NULL);
create_edge_and_update_destination_phis (&rd, rd.dup_blocks[0], 0);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
e->src->index, e->dest->index, rd.dup_blocks[0]->index);
rd.dup_blocks[0]->count = e->count;
rd.dup_blocks[0]->frequency = EDGE_FREQUENCY (e);
single_succ_edge (rd.dup_blocks[0])->count = e->count;
redirect_edge_and_branch (e, rd.dup_blocks[0]);
flush_pending_stmts (e);
delete_jump_thread_path (npath);
return rd.dup_blocks[0];
}
/* Callback for dfs_enumerate_from. Returns true if BB is different
from STOP and DBDS_CE_STOP. */
@ -1769,24 +1704,6 @@ determine_bb_domination_status (struct loop *loop, basic_block bb)
return (bb_reachable ? DOMST_DOMINATING : DOMST_LOOP_BROKEN);
}
/* Return true if BB is part of the new pre-header that is created
when threading the latch to DATA. */
static bool
def_split_header_continue_p (const_basic_block bb, const void *data)
{
const_basic_block new_header = (const_basic_block) data;
const struct loop *l;
if (bb == new_header
|| loop_depth (bb->loop_father) < loop_depth (new_header->loop_father))
return false;
for (l = bb->loop_father; l; l = loop_outer (l))
if (l == new_header->loop_father)
return true;
return false;
}
/* Thread jumps through the header of LOOP. Returns true if cfg changes.
If MAY_PEEL_LOOP_HEADERS is false, we avoid threading from entry edges
to the inside of the loop. */
@ -1869,27 +1786,7 @@ thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
if (single_succ_p (header))
goto fail;
/* If we threaded the latch using a joiner block, we cancel the
threading opportunity out of an abundance of caution. However,
still allow threading from outside to inside the loop. */
if (latch->aux)
{
vec<jump_thread_edge *> *path = THREAD_PATH (latch);
if ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK)
{
delete_jump_thread_path (path);
latch->aux = NULL;
}
}
if (latch->aux)
{
vec<jump_thread_edge *> *path = THREAD_PATH (latch);
tgt_edge = (*path)[1]->e;
tgt_bb = tgt_edge->dest;
}
else if (!may_peel_loop_headers
&& !redirection_block_p (loop->header))
if (!may_peel_loop_headers && !redirection_block_p (loop->header))
goto fail;
else
{
@ -1961,96 +1858,34 @@ thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
tgt_bb = split_edge (tgt_edge);
}
if (latch->aux)
basic_block new_preheader;
/* Now consider the case entry edges are redirected to the new entry
block. Remember one entry edge, so that we can find the new
preheader (its destination after threading). */
FOR_EACH_EDGE (e, ei, header->preds)
{
basic_block *bblocks;
unsigned nblocks, i;
/* First handle the case latch edge is redirected. We are copying
the loop header but not creating a multiple entry loop. Make the
cfg manipulation code aware of that fact. */
set_loop_copy (loop, loop);
loop->latch = thread_single_edge (latch);
set_loop_copy (loop, NULL);
gcc_assert (single_succ (loop->latch) == tgt_bb);
loop->header = tgt_bb;
/* Remove the new pre-header blocks from our loop. */
bblocks = XCNEWVEC (basic_block, loop->num_nodes);
nblocks = dfs_enumerate_from (header, 0, def_split_header_continue_p,
bblocks, loop->num_nodes, tgt_bb);
for (i = 0; i < nblocks; i++)
if (bblocks[i]->loop_father == loop)
{
remove_bb_from_loops (bblocks[i]);
add_bb_to_loop (bblocks[i], loop_outer (loop));
}
free (bblocks);
/* If the new header has multiple latches mark it so. */
FOR_EACH_EDGE (e, ei, loop->header->preds)
if (e->src->loop_father == loop
&& e->src != loop->latch)
{
loop->latch = NULL;
loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
}
/* Cancel remaining threading requests that would make the
loop a multiple entry loop. */
FOR_EACH_EDGE (e, ei, header->preds)
{
edge e2;
if (e->aux == NULL)
continue;
vec<jump_thread_edge *> *path = THREAD_PATH (e);
e2 = path->last ()->e;
if (e->src->loop_father != e2->dest->loop_father
&& e2->dest != loop->header)
{
delete_jump_thread_path (path);
e->aux = NULL;
}
}
/* Thread the remaining edges through the former header. */
thread_block (header, false);
}
else
{
basic_block new_preheader;
/* Now consider the case entry edges are redirected to the new entry
block. Remember one entry edge, so that we can find the new
preheader (its destination after threading). */
FOR_EACH_EDGE (e, ei, header->preds)
{
if (e->aux)
break;
}
/* The duplicate of the header is the new preheader of the loop. Ensure
that it is placed correctly in the loop hierarchy. */
set_loop_copy (loop, loop_outer (loop));
thread_block (header, false);
set_loop_copy (loop, NULL);
new_preheader = e->dest;
/* Create the new latch block. This is always necessary, as the latch
must have only a single successor, but the original header had at
least two successors. */
loop->latch = NULL;
mfb_kj_edge = single_succ_edge (new_preheader);
loop->header = mfb_kj_edge->dest;
latch = make_forwarder_block (tgt_bb, mfb_keep_just, NULL);
loop->header = latch->dest;
loop->latch = latch->src;
if (e->aux)
break;
}
/* The duplicate of the header is the new preheader of the loop. Ensure
that it is placed correctly in the loop hierarchy. */
set_loop_copy (loop, loop_outer (loop));
thread_block (header, false);
set_loop_copy (loop, NULL);
new_preheader = e->dest;
/* Create the new latch block. This is always necessary, as the latch
must have only a single successor, but the original header had at
least two successors. */
loop->latch = NULL;
mfb_kj_edge = single_succ_edge (new_preheader);
loop->header = mfb_kj_edge->dest;
latch = make_forwarder_block (tgt_bb, mfb_keep_just, NULL);
loop->header = latch->dest;
loop->latch = latch->src;
return true;
fail:
@ -2332,20 +2167,6 @@ mark_threaded_blocks (bitmap threaded_blocks)
}
/* Return TRUE if BB ends with a switch statement or a computed goto.
Otherwise return false. */
static bool
bb_ends_with_multiway_branch (basic_block bb ATTRIBUTE_UNUSED)
{
gimple *stmt = last_stmt (bb);
if (stmt && gimple_code (stmt) == GIMPLE_SWITCH)
return true;
if (stmt && gimple_code (stmt) == GIMPLE_GOTO
&& TREE_CODE (gimple_goto_dest (stmt)) == SSA_NAME)
return true;
return false;
}
/* Verify that the REGION is a valid jump thread. A jump thread is a special
case of SEME Single Entry Multiple Exits region in which all nodes in the
REGION have exactly one incoming edge. The only exception is the first block
@ -2788,36 +2609,7 @@ thread_through_all_blocks (bool may_peel_loop_headers)
e->aux = NULL;
ei_next (&ei);
}
else if (bb_ends_with_multiway_branch (path->last ()->e->src))
{
/* The code to thread through loop headers may have
split a block with jump threads attached to it.
We can identify this with a disjoint jump threading
path. If found, just remove it. */
for (unsigned int i = 0; i < path->length () - 1; i++)
if ((*path)[i]->e->dest != (*path)[i + 1]->e->src)
{
delete_jump_thread_path (path);
e->aux = NULL;
ei_next (&ei);
break;
}
/* Our path is still valid, thread it. */
if (e->aux)
{
if (thread_block ((*path)[0]->e->dest, false))
e->aux = NULL;
else
{
delete_jump_thread_path (path);
e->aux = NULL;
ei_next (&ei);
}
}
}
else
else
{
delete_jump_thread_path (path);
e->aux = NULL;
@ -2878,18 +2670,26 @@ register_jump_thread (vec<jump_thread_edge *> *path)
/* First make sure there are no NULL outgoing edges on the jump threading
path. That can happen for jumping to a constant address. */
for (unsigned int i = 0; i < path->length (); i++)
if ((*path)[i]->e == NULL)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file,
"Found NULL edge in jump threading path. Cancelling jump thread:\n");
dump_jump_thread_path (dump_file, *path, false);
}
{
if ((*path)[i]->e == NULL)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file,
"Found NULL edge in jump threading path. Cancelling jump thread:\n");
dump_jump_thread_path (dump_file, *path, false);
}
delete_jump_thread_path (path);
return;
}
delete_jump_thread_path (path);
return;
}
/* Only the FSM threader is allowed to thread across
backedges in the CFG. */
if (flag_checking
&& (*path)[0]->type != EDGE_FSM_THREAD)
gcc_assert (((*path)[i]->e->flags & EDGE_DFS_BACK) == 0);
}
if (dump_file && (dump_flags & TDF_DETAILS))
dump_jump_thread_path (dump_file, *path, true);