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Commit e4dbb0d4 by Jan Hubicka Committed by Jan Hubicka
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re PR tree-optimization/65337 (LTO bootstrap failure with Ada enabled) 

	PR middle-end/65337
	* tree-ssa-dce.c (bb_postorder): New static var.
	(forward_edge_to_pdom): Remove.
	(remove_dead_stmt): Instead of redirecting edges only keep an edge
	on a path to nearest live BB.
	(eliminate_unnecessary_stmts): Free bb_postorder.
	* cfganal.c (dfs_find_deadend): Add START_POINTES.
	* cfganal.h (inverted_post_order_compute): Update prototype.

From-SVN: r231856
parent e07e03dd
Showing with 77 additions and 86 deletions
gcc/ChangeLog
2015-12-19 Jan Hubicka <hubicka@ucw.cz>
PR middle-end/65337
* tree-ssa-dce.c (bb_postorder): New static var.
(forward_edge_to_pdom): Remove.
(remove_dead_stmt): Instead of redirecting edges only keep an edge
on a path to nearest live BB.
(eliminate_unnecessary_stmts): Free bb_postorder.
* cfganal.c (dfs_find_deadend): Add START_POINTES.
* cfganal.h (inverted_post_order_compute): Update prototype.
2015-12-19 Eric Botcazou <ebotcazou@adacore.com>
PR rtl-optimization/68910
gcc/cfganal.c
......@@ -759,6 +759,9 @@ dfs_find_deadend (basic_block bb)
(from successors to predecessors).
This ordering can be used for forward dataflow problems among others.
Optionally if START_POINTS is specified, start from exit block and all
basic blocks in START_POINTS. This is used by CD-DCE.
This function assumes that all blocks in the CFG are reachable
from the ENTRY (but not necessarily from EXIT).
......@@ -776,7 +779,8 @@ dfs_find_deadend (basic_block bb)
and do another inverted traversal from that block. */
int
inverted_post_order_compute (int *post_order)
inverted_post_order_compute (int *post_order,
sbitmap *start_points)
{
basic_block bb;
edge_iterator *stack;
......@@ -797,6 +801,22 @@ inverted_post_order_compute (int *post_order)
/* None of the nodes in the CFG have been visited yet. */
bitmap_clear (visited);
if (start_points)
{
FOR_ALL_BB_FN (bb, cfun)
if (bitmap_bit_p (*start_points, bb->index)
&& EDGE_COUNT (bb->preds) > 0)
{
stack[sp++] = ei_start (bb->preds);
bitmap_set_bit (visited, bb->index);
}
if (EDGE_COUNT (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds))
{
stack[sp++] = ei_start (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds);
bitmap_set_bit (visited, EXIT_BLOCK_PTR_FOR_FN (cfun)->index);
}
}
else
/* Put all blocks that have no successor into the initial work list. */
FOR_ALL_BB_FN (bb, cfun)
if (EDGE_COUNT (bb->succs) == 0)
......
gcc/cfganal.h
......@@ -62,7 +62,7 @@ extern void add_noreturn_fake_exit_edges (void);
extern void connect_infinite_loops_to_exit (void);
extern int post_order_compute (int *, bool, bool);
extern basic_block dfs_find_deadend (basic_block);
extern int inverted_post_order_compute (int *);
extern int inverted_post_order_compute (int *, sbitmap *start_points = 0);
extern int pre_and_rev_post_order_compute_fn (struct function *,
int *, int *, bool);
extern int pre_and_rev_post_order_compute (int *, int *, bool);
......
gcc/tree-ssa-dce.c
......@@ -112,6 +112,9 @@ static sbitmap visited_control_parents;
to be recomputed. */
static bool cfg_altered;
/* When non-NULL holds map from basic block index into the postorder. */
static int *bb_postorder;
/* If STMT is not already marked necessary, mark it, and add it to the
worklist if ADD_TO_WORKLIST is true. */
......@@ -134,7 +137,7 @@ mark_stmt_necessary (gimple *stmt, bool add_to_worklist)
gimple_set_plf (stmt, STMT_NECESSARY, true);
if (add_to_worklist)
worklist.safe_push (stmt);
if (bb_contains_live_stmts && !is_gimple_debug (stmt))
if (add_to_worklist && bb_contains_live_stmts && !is_gimple_debug (stmt))
bitmap_set_bit (bb_contains_live_stmts, gimple_bb (stmt)->index);
}
......@@ -997,65 +1000,6 @@ remove_dead_phis (basic_block bb)
return something_changed;
}
/* Forward edge E to respective POST_DOM_BB and update PHIs. */
static edge
forward_edge_to_pdom (edge e, basic_block post_dom_bb)
{
gphi_iterator gsi;
edge e2 = NULL;
edge_iterator ei;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Redirecting edge %i->%i to %i\n", e->src->index,
e->dest->index, post_dom_bb->index);
e2 = redirect_edge_and_branch (e, post_dom_bb);
cfg_altered = true;
/* If edge was already around, no updating is necessary. */
if (e2 != e)
return e2;
if (!gimple_seq_empty_p (phi_nodes (post_dom_bb)))
{
/* We are sure that for every live PHI we are seeing control dependent BB.
This means that we can pick any edge to duplicate PHI args from. */
FOR_EACH_EDGE (e2, ei, post_dom_bb->preds)
if (e2 != e)
break;
for (gsi = gsi_start_phis (post_dom_bb); !gsi_end_p (gsi);)
{
gphi *phi = gsi.phi ();
tree op;
source_location locus;
/* PHIs for virtuals have no control dependency relation on them.
We are lost here and must force renaming of the symbol. */
if (virtual_operand_p (gimple_phi_result (phi)))
{
mark_virtual_phi_result_for_renaming (phi);
remove_phi_node (&gsi, true);
continue;
}
/* Dead PHI do not imply control dependency. */
if (!gimple_plf (phi, STMT_NECESSARY))
{
gsi_next (&gsi);
continue;
}
op = gimple_phi_arg_def (phi, e2->dest_idx);
locus = gimple_phi_arg_location (phi, e2->dest_idx);
add_phi_arg (phi, op, e, locus);
/* The resulting PHI if not dead can only be degenerate. */
gcc_assert (degenerate_phi_p (phi));
gsi_next (&gsi);
}
}
return e;
}
/* Remove dead statement pointed to by iterator I. Receives the basic block BB
containing I so that we don't have to look it up. */
......@@ -1075,38 +1019,50 @@ remove_dead_stmt (gimple_stmt_iterator *i, basic_block bb)
stats.removed++;
/* If we have determined that a conditional branch statement contributes
nothing to the program, then we not only remove it, but we also change
the flow graph so that the current block will simply fall-thru to its
immediate post-dominator. The blocks we are circumventing will be
removed by cleanup_tree_cfg if this change in the flow graph makes them
unreachable. */
nothing to the program, then we not only remove it, but we need to update
the CFG. We can chose any of edges out of BB as long as we are sure to not
close infinite loops. This is done by always choosing the edge closer to
exit in inverted_post_order_compute order. */
if (is_ctrl_stmt (stmt))
{
basic_block post_dom_bb;
edge e, e2;
edge_iterator ei;
post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
e = find_edge (bb, post_dom_bb);
/* If edge is already there, try to use it. This avoids need to update
PHI nodes. Also watch for cases where post dominator does not exists
or is exit block. These can happen for infinite loops as we create
fake edges in the dominator tree. */
if (e)
;
else if (! post_dom_bb || post_dom_bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
e = EDGE_SUCC (bb, 0);
else
e = forward_edge_to_pdom (EDGE_SUCC (bb, 0), post_dom_bb);
edge e = NULL, e2;
/* See if there is only one non-abnormal edge. */
if (single_succ_p (bb))
e = single_succ_edge (bb);
/* Otherwise chose one that is closer to bb with live statement in it.
To be able to chose one, we compute inverted post order starting from
all BBs with live statements. */
if (!e)
{
if (!bb_postorder)
{
int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
int postorder_num
= inverted_post_order_compute (postorder,
&bb_contains_live_stmts);
bb_postorder = XNEWVEC (int, last_basic_block_for_fn (cfun));
for (int i = 0; i < postorder_num; ++i)
bb_postorder[postorder[i]] = i;
free (postorder);
}
FOR_EACH_EDGE (e2, ei, bb->succs)
if (!e || e2->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)
|| bb_postorder [e->dest->index]
< bb_postorder [e2->dest->index])
e = e2;
}
gcc_assert (e);
e->probability = REG_BR_PROB_BASE;
e->count = bb->count;
/* The edge is no longer associated with a conditional, so it does
not have TRUE/FALSE flags. */
e->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
not have TRUE/FALSE flags.
We are also safe to drop EH/ABNORMAL flags and turn them into
normal control flow, because we know that all the destinations (including
those odd edges) are equivalent for program execution. */
e->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE | EDGE_EH | EDGE_ABNORMAL);
/* The lone outgoing edge from BB will be a fallthru edge. */
e->flags |= EDGE_FALLTHRU;
......@@ -1516,6 +1472,10 @@ eliminate_unnecessary_stmts (void)
something_changed |= remove_dead_phis (bb);
}
if (bb_postorder)
free (bb_postorder);
bb_postorder = NULL;
return something_changed;
}
......
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