BugFix: when deleting keep-alives of already visited blocks, keep in mind

[libfirm] / ir / ir / irgopt.c

diff --git a/ir/ir/irgopt.c b/ir/ir/irgopt.c
index 5ff0ab1..26dd09c 100644 (file)
--- a/ir/ir/irgopt.c
+++ b/ir/ir/irgopt.c
@@ -184,7 +184,7 @@ void optimize_graph_df(ir_graph *irg) {
        pdeq     *waitq = new_pdeq();
        ir_graph *rem = current_ir_graph;
        ir_node  *end;
-       int      i, state;
+       int      i, state, n_ka;
 
        current_ir_graph = irg;
 
@@ -207,13 +207,22 @@ void optimize_graph_df(ir_graph *irg) {
 
        set_using_irn_link(irg);
 
+       end  = get_irg_end(irg);
+       n_ka = get_End_n_keepalives(end);
+
        /* walk over the graph, but don't touch keep-alives */
        irg_walk(get_irg_end_block(irg), NULL, opt_walker, waitq);
 
-       end = get_irg_end(irg);
-
-       /* optimize keep-alives by removing superfluous ones */
-       for (i = get_End_n_keepalives(end) - 1; i >= 0; --i) {
+       /*
+        * Optimize keep-alives by removing superfluous ones.
+        * Beware: the last transformation might add new keep-alives
+        * that keep blocks that are where visited! So, check only the
+        * "old" keep-alives, not the new ones!
+        *
+        * FIXME: it might be better to completely remove this
+        * optimization here ...
+        */
+       for (i = n_ka - 1; i >= 0; --i) {
                ir_node *ka = get_End_keepalive(end, i);
 
                if (irn_visited(ka) && !is_irn_keep(ka)) {