+/*
+ __ _ __ __
+ (_ __ o _ | \/ |_
+ __)|_| | \_/ | \_/(/_ |_/\__|__
+
+ The following stuff implements a facility that automatically patches
+ registered ir_node pointers to the new node when a dead node elimination occurs.
+*/
+
+struct _survive_dce_t {
+ struct obstack obst;
+ pmap *places;
+ pmap *new_places;
+ hook_entry_t dead_node_elim;
+ hook_entry_t dead_node_elim_subst;
+};
+
+typedef struct _survive_dce_list_t {
+ struct _survive_dce_list_t *next;
+ ir_node **place;
+} survive_dce_list_t;
+
+static void dead_node_hook(void *context, ir_graph *irg, int start)
+{
+ survive_dce_t *sd = context;
+
+ /* Create a new map before the dead node elimination is performed. */
+ if(start) {
+ sd->new_places = pmap_create_ex(pmap_count(sd->places));
+ }
+
+ /* Patch back all nodes if dead node elimination is over and something is to be done. */
+ else {
+ pmap_destroy(sd->places);
+ sd->places = sd->new_places;
+ sd->new_places = NULL;
+ }
+}
+
+static void dead_node_subst_hook(void *context, ir_graph *irg, ir_node *old, ir_node *nw)
+{
+ survive_dce_t *sd = context;
+ survive_dce_list_t *list = pmap_get(sd->places, old);
+
+ /* If the node is to be patched back, write the new address to all registered locations. */
+ if(list) {
+ survive_dce_list_t *p;
+
+ for(p = list; p; p = p->next)
+ *(p->place) = nw;
+
+ pmap_insert(sd->new_places, nw, list);
+ }
+}
+
+/**
+ * Make a new Survive DCE environment.
+ */
+survive_dce_t *new_survive_dce(void)
+{
+ survive_dce_t *res = xmalloc(sizeof(res[0]));
+ obstack_init(&res->obst);
+ res->places = pmap_create();
+ res->new_places = NULL;
+
+ res->dead_node_elim.hook._hook_dead_node_elim = dead_node_hook;
+ res->dead_node_elim.context = res;
+ res->dead_node_elim.next = NULL;
+
+ res->dead_node_elim_subst.hook._hook_dead_node_elim_subst = dead_node_subst_hook;
+ res->dead_node_elim_subst.context = res;
+ res->dead_node_elim_subst.next = NULL;
+
+ register_hook(hook_dead_node_elim, &res->dead_node_elim);
+ register_hook(hook_dead_node_elim_subst, &res->dead_node_elim_subst);
+ return res;
+}
+
+/**
+ * Free a Survive DCE environment.
+ */
+void free_survive_dce(survive_dce_t *sd)
+{
+ obstack_free(&sd->obst, NULL);
+ pmap_destroy(sd->places);
+ unregister_hook(hook_dead_node_elim, &sd->dead_node_elim);
+ unregister_hook(hook_dead_node_elim_subst, &sd->dead_node_elim_subst);
+ free(sd);
+}
+
+/**
+ * Register a node pointer to be patched upon DCE.
+ * When DCE occurs, the node pointer specified by @p place will be
+ * patched to the new address of the node it is pointing to.
+ *
+ * @param sd The Survive DCE environment.
+ * @param place The address of the node pointer.
+ */
+void survive_dce_register_irn(survive_dce_t *sd, ir_node **place)
+{
+ if(*place != NULL) {
+ ir_node *irn = *place;
+ survive_dce_list_t *curr = pmap_get(sd->places, irn);
+ survive_dce_list_t *nw = obstack_alloc(&sd->obst, sizeof(nw));
+
+ nw->next = curr;
+ nw->place = place;
+
+ pmap_insert(sd->places, irn, nw);
+ }
+}
+