+/**
+ * Compare two opcode representatives.
+ */
+static int cmp_irn_opcode(const ir_node *a, const ir_node *b)
+{
+ int arity;
+
+ if ((get_irn_op(a) != get_irn_op(b)) ||
+ (get_irn_mode(a) != get_irn_mode(b)))
+ return 1;
+
+ /* compare if a's in and b's in are of equal length */
+ arity = get_irn_arity(a);
+ if (arity != get_irn_arity(b))
+ return 1;
+
+ if (is_Block(a)) {
+ /*
+ * Some ugliness here: Two Blocks having the same
+ * IJmp predecessor would be congruent, which of course is wrong.
+ * We fix it by never letting blocks be congruent
+ * which cannot be detected by combo either.
+ */
+ return 1;
+ }
+
+ /*
+ * here, we already know that the nodes are identical except their
+ * attributes
+ */
+ if (a->op->ops.node_cmp_attr)
+ return a->op->ops.node_cmp_attr(a, b);
+
+ return 0;
+} /* cmp_irn_opcode */
+