/* Dead code elimination pass for the GNU compiler.
- Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
+ Free Software Foundation, Inc.
Contributed by Ben Elliston <bje@redhat.com>
and Andrew MacLeod <amacleod@redhat.com>
Adapted to use control dependence by Steven Bosscher, SUSE Labs.
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
+Free 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
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/>. */
/* Dead code elimination.
case ASM_EXPR:
case RESX_EXPR:
case RETURN_EXPR:
+ case CHANGE_DYNAMIC_TYPE_EXPR:
mark_stmt_necessary (stmt, true);
return;
/* Remove dead PHI nodes from block BB. */
-static void
+static bool
remove_dead_phis (basic_block bb)
{
tree prev, phi;
+ bool something_changed = false;
prev = NULL_TREE;
phi = phi_nodes (bb);
{
tree next = PHI_CHAIN (phi);
+ something_changed = true;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleting : ");
phi = PHI_CHAIN (phi);
}
}
+ return something_changed;
}
basic_block post_dom_bb;
/* The post dominance info has to be up-to-date. */
- gcc_assert (dom_computed[CDI_POST_DOMINATORS] == DOM_OK);
+ gcc_assert (dom_info_state (CDI_POST_DOMINATORS) == DOM_OK);
/* Get the immediate post dominator of bb. */
post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
3. If the post dominator has PHI nodes we may be able to compute
the right PHI args for them.
-
In each of these cases we must remove the control statement
as it may reference SSA_NAMEs which are going to be removed and
we remove all but one outgoing edge from the block. */
/* Redirect the first edge out of BB to reach POST_DOM_BB. */
redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
+
+ /* It is not sufficient to set cfg_altered below during edge
+ removal, in case BB has two successors and one of them
+ is POST_DOM_BB. */
+ cfg_altered = true;
}
EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
EDGE_SUCC (bb, 0)->count = bb->count;
/* Eliminate unnecessary statements. Any instruction not marked as necessary
contributes nothing to the program, and can be deleted. */
-static void
+static bool
eliminate_unnecessary_stmts (void)
{
+ bool something_changed = false;
basic_block bb;
block_stmt_iterator i;
FOR_EACH_BB (bb)
{
/* Remove dead PHI nodes. */
- remove_dead_phis (bb);
+ something_changed |= remove_dead_phis (bb);
}
FOR_EACH_BB (bb)
/* If `i' is not necessary then remove it. */
if (! NECESSARY (t))
- remove_dead_stmt (&i, bb);
+ {
+ remove_dead_stmt (&i, bb);
+ something_changed = true;
+ }
else
{
tree call = get_call_expr_in (t);
if (call)
- notice_special_calls (call);
+ {
+ tree name;
+
+ /* When LHS of var = call (); is dead, simplify it into
+ call (); saving one operand. */
+ if (TREE_CODE (t) == GIMPLE_MODIFY_STMT
+ && (TREE_CODE ((name = GIMPLE_STMT_OPERAND (t, 0)))
+ == SSA_NAME)
+ && !TEST_BIT (processed, SSA_NAME_VERSION (name)))
+ {
+ tree oldlhs = GIMPLE_STMT_OPERAND (t, 0);
+ something_changed = true;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Deleting LHS of call: ");
+ print_generic_stmt (dump_file, t, TDF_SLIM);
+ fprintf (dump_file, "\n");
+ }
+ push_stmt_changes (bsi_stmt_ptr (i));
+ TREE_BLOCK (call) = TREE_BLOCK (t);
+ bsi_replace (&i, call, false);
+ maybe_clean_or_replace_eh_stmt (t, call);
+ mark_symbols_for_renaming (call);
+ pop_stmt_changes (bsi_stmt_ptr (i));
+ release_ssa_name (oldlhs);
+ }
+ notice_special_calls (call);
+ }
bsi_next (&i);
}
}
}
+
+ return something_changed;
}
as the last tree SSA pass, but keep this in mind when you
start experimenting with pass ordering. */
-static void
+static unsigned int
perform_tree_ssa_dce (bool aggressive)
{
struct edge_list *el = NULL;
+ bool something_changed = 0;
tree_dce_init (aggressive);
propagate_necessity (el);
- eliminate_unnecessary_stmts ();
+ something_changed |= eliminate_unnecessary_stmts ();
+ something_changed |= cfg_altered;
- if (aggressive)
- free_dominance_info (CDI_POST_DOMINATORS);
+ /* We do not update postdominators, so free them unconditionally. */
+ free_dominance_info (CDI_POST_DOMINATORS);
/* If we removed paths in the CFG, then we need to update
dominators as well. I haven't investigated the possibility
tree_dce_done (aggressive);
free_edge_list (el);
+
+ if (something_changed)
+ return (TODO_update_ssa | TODO_cleanup_cfg | TODO_ggc_collect
+ | TODO_remove_unused_locals);
+ else
+ return 0;
}
/* Pass entry points. */
static unsigned int
tree_ssa_dce (void)
{
- perform_tree_ssa_dce (/*aggressive=*/false);
- return 0;
+ return perform_tree_ssa_dce (/*aggressive=*/false);
}
static unsigned int
tree_ssa_dce_loop (void)
{
- perform_tree_ssa_dce (/*aggressive=*/false);
- free_numbers_of_iterations_estimates ();
- scev_reset ();
- return 0;
+ unsigned int todo;
+ todo = perform_tree_ssa_dce (/*aggressive=*/false);
+ if (todo)
+ {
+ free_numbers_of_iterations_estimates ();
+ scev_reset ();
+ }
+ return todo;
}
static unsigned int
tree_ssa_cd_dce (void)
{
- perform_tree_ssa_dce (/*aggressive=*/optimize >= 2);
- return 0;
+ return perform_tree_ssa_dce (/*aggressive=*/optimize >= 2);
}
static bool
NULL, /* next */
0, /* static_pass_number */
TV_TREE_DCE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func
- | TODO_update_ssa
- | TODO_cleanup_cfg
- | TODO_ggc_collect
- | TODO_verify_ssa
- | TODO_remove_unused_locals, /* todo_flags_finish */
+ TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */
0 /* letter */
};
NULL, /* next */
0, /* static_pass_number */
TV_TREE_DCE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func
- | TODO_update_ssa
- | TODO_cleanup_cfg
- | TODO_verify_ssa, /* todo_flags_finish */
+ TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */
0 /* letter */
};
NULL, /* next */
0, /* static_pass_number */
TV_TREE_CD_DCE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func
- | TODO_update_ssa
- | TODO_cleanup_cfg
- | TODO_ggc_collect
- | TODO_verify_ssa
- | TODO_verify_flow, /* todo_flags_finish */
+ TODO_dump_func | TODO_verify_ssa
+ | TODO_verify_flow, /* todo_flags_finish */
0 /* letter */
};
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