From 5bb1b1dd6f94af0e8cb2d4a1686bc4882147ba66 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Wed, 21 Aug 2013 01:34:18 -0700
Subject: [PATCH] Hoist the global dummy lookup out of the inner loop for
 set_merge().

---
 Objects/setobject.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Objects/setobject.c b/Objects/setobject.c
index 9074a76125f..f84c929a47a 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -683,6 +683,7 @@ set_merge(PySetObject *so, PyObject *otherset)
 {
     PySetObject *other;
     PyObject *key;
+    PyObject *dummy_entry;
     Py_hash_t hash;
     Py_ssize_t i;
     setentry *entry;
@@ -702,12 +703,13 @@ set_merge(PySetObject *so, PyObject *otherset)
        if (set_table_resize(so, (so->used + other->used)*2) != 0)
            return -1;
     }
+    dummy_entry = dummy;
     for (i = 0; i <= other->mask; i++) {
         entry = &other->table[i];
         key = entry->key;
         hash = entry->hash;
         if (key != NULL &&
-            key != dummy) {
+            key != dummy_entry) {
             Py_INCREF(key);
             if (set_insert_key(so, key, hash) == -1) {
                 Py_DECREF(key);