From 2a0d81fb4d0f7bf97456cb881bc5a3962747721d Mon Sep 17 00:00:00 2001
From: Sebastian Hack <hack@ipd.info.uni-karlsruhe.de>
Date: Mon, 6 Mar 2006 15:16:38 +0000
Subject: [PATCH] Added dead code elimination survival facility

[r7417]
---
 ir/common/survive_dce.c | 76 +++++++++++++++++++++++++++++++++++++++++
 ir/common/survive_dce.h | 29 ++++++++++++++++
 2 files changed, 105 insertions(+)
 create mode 100644 ir/common/survive_dce.c
 create mode 100644 ir/common/survive_dce.h

diff --git a/ir/common/survive_dce.c b/ir/common/survive_dce.c
new file mode 100644
index 000000000..37a83f781
--- /dev/null
+++ b/ir/common/survive_dce.c
@@ -0,0 +1,76 @@
+
+#include "pmap.h"
+
+#include "irnode_t.h"
+#include "irhooks.h"
+#include "irgwalk.h"
+
+#include "survive_dce.h"
+
+struct _survive_dce_t {
+	pmap *places;
+	pmap *new_places;
+	hook_entry_t dead_node_elim;
+	hook_entry_t dead_node_elim_subst;
+};
+
+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;
+	ir_node **place    = (ir_node **) pmap_get(sd->places, old);
+
+	/* If the node is to be patched back, do it. */
+	if(place) {
+		*place = nw;
+		pmap_insert(sd->new_places, nw, (void *) place);
+	}
+}
+
+survive_dce_t *new_survive_dce(void)
+{
+	survive_dce_t *res = xmalloc(sizeof(res[0]));
+	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;
+}
+
+void free_survive_dce(survive_dce_t *sd)
+{
+	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);
+}
+
+void survive_dce_register_irn(survive_dce_t *sd, ir_node **place)
+{
+	pmap_insert(sd->places, *place, (void *) place);
+}
diff --git a/ir/common/survive_dce.h b/ir/common/survive_dce.h
new file mode 100644
index 000000000..3c0c2059b
--- /dev/null
+++ b/ir/common/survive_dce.h
@@ -0,0 +1,29 @@
+/**
+ * A facility for nodes to "survive" the dead code elimination.
+ */
+
+#ifndef _FIRM_SURVIVE_DCE_H
+#define _FIRM_SURVIVE_DCE_H
+
+typedef struct _survive_dce_t survive_dce_t;
+
+/**
+ * Make a new dead code survive instance.
+ */
+survive_dce_t *new_survive_dce(void);
+
+/**
+ * Free a dead node survive instance.
+ */
+void           free_survive_dce(survive_dce_t *sd);
+
+/**
+ * Register a storage place for a node.
+ * @param sd The survive dead code private data.
+ * @param place A pointer to a node pointer which shall be actualized.
+ * The location given by <code>place</code> will be updated with the substitute
+ * of the node it is currently pointing to after dead node elimination.
+ */
+void survive_dce_register_irn(survive_dce_t *sd, ir_node **place);
+
+#endif
-- 
2.20.1