- reduce complexity of remove_End_keepalive()

- add a comment that set_End_keepalives() may have high complexity costs in Backend

[r20174]

diff --git a/include/libfirm/irnode.h b/include/libfirm/irnode.h
index 662228a..0ea6a9f 100644 (file)
--- a/include/libfirm/irnode.h
+++ b/include/libfirm/irnode.h
@@ -427,9 +427,15 @@ ir_node *get_End_keepalive(const ir_node *end, int pos);
 void add_End_keepalive(ir_node *end, ir_node *ka);
 /** Set the Keep alive node at position pos. */
 void set_End_keepalive(ir_node *end, int pos, ir_node *ka);
-/** Set new keep-alives. */
+
+/**
+ * Set new keep-alives.
+ * Beware: This might be an expensive operation if dynamic edges are enabled,
+ * so avoid it in the backend.
+ */
 void set_End_keepalives(ir_node *end, int n, ir_node *in[]);
-/** Set new keep-alives from old keep-alives, skipping irn. */
+
+/** Remove irn from the keep-alive set. */
 void remove_End_keepalive(ir_node *end, ir_node *irn);
 
 /** Some parts of the End node are allocated separately -- their memory

diff --git a/ir/ir/irnode.c b/ir/ir/irnode.c
index 6fa35b1..66eb236 100644 (file)
--- a/ir/ir/irnode.c
+++ b/ir/ir/irnode.c
@@ -927,22 +927,35 @@ void set_End_keepalives(ir_node *end, int n, ir_node *in[]) {
 
 /* Set new keep-alives from old keep-alives, skipping irn */
 void remove_End_keepalive(ir_node *end, ir_node *irn) {
-       int     n = get_End_n_keepalives(end);
-       ir_node **in;
-       int     i, idx;
-
-       NEW_ARR_A(ir_node *, in, n);
-
-       for (idx = i = 0; i < n; ++i) {
-               ir_node *old_ka = get_End_keepalive(end, i);
-
-               /* skip irn */
-               if (old_ka != irn)
-                       in[idx++] = old_ka;
+       int      n = get_End_n_keepalives(end);
+       int      i, idx;
+       ir_graph *irg;
+
+       idx = -1;
+       for (i = n -1; i >= 0; --i) {
+               ir_node *old_ka = end->in[1 + END_KEEPALIVE_OFFSET + i];
+
+               /* find irn */
+               if (old_ka == irn) {
+                       idx = i;
+                       goto found;
+               }
        }
-
-       /* set new keep-alives */
-       set_End_keepalives(end, idx, in);
+       return;
+found:
+       irg = get_irn_irg(end);
+
+       /* remove the edge */
+       edges_notify_edge(end, idx, NULL, irn, irg);
+
+       if (idx != n - 1) {
+               /* exchange with the last one */
+               ir_node *old = end->in[1 + END_KEEPALIVE_OFFSET + n - 1];
+               edges_notify_edge(end, n - 1, NULL, old, irg);
+               end->in[1 + END_KEEPALIVE_OFFSET + idx] = old;
+               edges_notify_edge(end, idx, old, NULL, irg);
+       }
+       ARR_RESIZE(ir_node *, end->in, (n - 1) + 1 + END_KEEPALIVE_OFFSET);
 }
 
 void