Do NOT ignore Bad Phi predecessors. Otherwise

Phi nodes might be removed in dead cycles (causing normal nodes
pointing to themselfs).

[r19907]

diff --git a/ir/ir/iropt.c b/ir/ir/iropt.c
index fd90fe4..5d040f2 100644 (file)
--- a/ir/ir/iropt.c
+++ b/ir/ir/iropt.c
@@ -1315,7 +1315,15 @@ static ir_node *equivalent_node_Phi(ir_node *n) {
        for (i = 0; i < n_preds; ++i) {
                first_val = get_Phi_pred(n, i);
                if (   (first_val != n)                            /* not self pointer */
-#if 1
+#if 0
+                   /* BEWARE: when the if is changed to 1, Phi's will ignore it's Bad
+                    * predecessors. Then, Phi nodes in dead code might be removed, causing
+                    * nodes pointing to themself (Add's for instance).
+                    * This is really bad and causes endless recursions in several
+                    * code pathes, so we do NOT optimize such a code.
+                    * This is not that bad as it sounds, optimize_cf() removes bad control flow
+                    * (and bad Phi predecessors), so live code is optimized later.
+                    */
                    && (! is_Bad(first_val))
 #endif
                   ) {        /* value not dead */
@@ -1334,7 +1342,8 @@ static ir_node *equivalent_node_Phi(ir_node *n) {
                ir_node *scnd_val = get_Phi_pred(n, i);
                if (   (scnd_val != n)
                    && (scnd_val != first_val)
-#if 1
+#if 0
+                   /* see above */
                    && (! is_Bad(scnd_val))
 #endif
                        ) {