2 * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Dead node elimination
23 * @author Michael Beck, Goetz Lindenmaier
25 * Strictly speaking dead node elimination is unnecessary in firm - everthying
26 * which is not used can't be found by any walker.
27 * The only drawback is that the nodes still take up memory. This phase fixes
28 * this by copying all (reachable) nodes to a new obstack and throwing away
33 #include "iroptimize.h"
35 #include "irgraph_t.h"
36 #include "iredges_t.h"
48 * Reroute the inputs of a node from nodes in the old graph to copied nodes in
51 static void rewire_inputs(ir_node *node, void *env)
54 irn_rewire_inputs(node);
57 static void copy_node_dce(ir_node *node, void *env)
59 ir_node *new_node = exact_copy(node);
62 /* preserve the node numbers for easier debugging */
63 new_node->node_nr = node->node_nr;
65 set_irn_link(node, new_node);
69 * Copies the graph reachable from the End node to the obstack
70 * in irg. Then fixes the fields containing nodes of the graph.
72 * @param copy_node_nr If non-zero, the node number will be copied
74 static void copy_graph_env(ir_graph *irg)
76 ir_node *anchor = irg->anchor;
80 irg_walk_in_or_dep(anchor, copy_node_dce, rewire_inputs, NULL);
83 new_anchor = (ir_node*)get_irn_link(anchor);
84 assert(new_anchor != NULL);
85 irg->anchor = new_anchor;
89 * Copies all reachable nodes to a new obstack. Removes bad inputs
90 * from block nodes and the corresponding inputs from Phi nodes.
91 * Merges single exit blocks with single entry blocks and removes
93 * Adds all new nodes to a new hash table for CSE. Does not
94 * perform CSE, so the hash table might contain common subexpressions.
96 void dead_node_elimination(ir_graph *irg)
98 edges_deactivate(irg);
100 /* inform statistics that we started a dead-node elimination run */
101 hook_dead_node_elim(irg, 1);
103 /* Handle graph state */
104 free_callee_info(irg);
107 free_loop_information(irg);
109 clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
111 /* A quiet place, where the old obstack can rest in peace,
112 until it will be cremated. */
113 struct obstack graveyard_obst = irg->obst;
115 /* A new obstack, where the reachable nodes will be copied to. */
116 obstack_init(&irg->obst);
117 irg->last_node_idx = 0;
119 /* We also need a new value table for CSE */
122 /* Copy the graph from the old to the new obstack */
125 /* Free memory from old unoptimized obstack */
126 obstack_free(&graveyard_obst, 0); /* First empty the obstack ... */
128 /* inform statistics that the run is over */
129 hook_dead_node_elim(irg, 0);
132 ir_graph_pass_t *dead_node_elimination_pass(const char *name)
134 return def_graph_pass(name ? name : "dce", dead_node_elimination);