Use result of latest possible rematerializations.

When a node is rematerialized because its flag result is needed, rewire
later uses of this node (but not the flags) to use the rematerialized
node's results. This reduces the lifetime of the node's results.

ir/be/beflags.c

@@ -27,6 +27,7 @@
 #include "irtools.h"
 #include "ircons.h"
 #include "iredges_t.h"
+#include "irouts_t.h"
 #include "panic.h"
 
 #include "beflags.h"
@@ -90,6 +91,40 @@ static bool can_move(ir_node *node, ir_node *after)
 	return true;
 }
 
+/**
+ * After node has been rematerialized as copy, this checks all
+ * other uses of node to see if they can use copy instead (this
+ * reduces the lifetime of node's results).
+ */
+static void move_other_uses(ir_node *node, ir_node *copy)
+{
+	/* copy_prev already has its visited flag set, but is still
+	 * scheduled before copy. */
+	ir_node *copy_prev  = get_irn_sched_info(copy)->prev;
+	ir_node *copy_block = get_nodes_block(copy);
+
+	foreach_irn_out(node, i, proj) {
+		if (get_irn_mode(proj) == flag_class->mode) {
+			continue;
+		}
+
+		ir_node *new_proj = NULL;
+		foreach_out_edge_safe(proj, edge) {
+			ir_node *succ = get_edge_src_irn(edge);
+			if (irn_visited(succ) && succ != copy_prev &&
+			    block_dominates(copy_block, get_nodes_block(succ))) {
+				if (new_proj == NULL) {
+					ir_mode *proj_mode = get_irn_mode(proj);
+					int      pn        = get_Proj_proj(proj);
+					new_proj = new_r_Proj(copy, proj_mode, pn);
+				}
+				int n = get_edge_src_pos(edge);
+				set_irn_n(succ, n, new_proj);
+			}
+		}
+	}
+}
+
 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
                                   ir_node *flag_consumers, int pn)
 {
@@ -107,6 +142,7 @@ static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
 	ir_node *copy = remat(flags_needed, node);
 	ir_node *value;
 	if (get_irn_mode(copy) == mode_T) {
+		move_other_uses(flags_needed, copy);
 		ir_mode *mode = flag_class->mode;
 		value = new_r_Proj(copy, mode, pn);
 		be_add_missing_keeps_node(copy);
@@ -155,6 +191,8 @@ static void fix_flags_walker(ir_node *block, void *env)
 	int      pn             = -1;
 	ir_node *place          = block;
 	sched_foreach_reverse(block, node) {
+		mark_irn_visited(node);
+
 		if (is_Phi(node)) {
 			place = node;
 			break;
@@ -244,9 +282,13 @@ void be_sched_fix_flags(ir_graph *irg, const arch_register_class_t *flag_cls,
 	if (check_modify == NULL)
 		check_modify = &default_check_modifies;
 
-	ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
+	assure_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
+	ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK |
+	                          IR_RESOURCE_IRN_VISITED);
+	inc_irg_visited(irg);
 	irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
-	ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
+	ir_free_resources(irg, IR_RESOURCE_IRN_LINK |
+		               IR_RESOURCE_IRN_VISITED);
 
 	if (changed) {
 		be_remove_dead_nodes_from_schedule(irg);