diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2638,52 +2638,20 @@ class _addset(_orderedsetmixin):
         same time, yielding only one value at a time in the given order.
         """
         if not self._iter:
-            def gen():
-                if self._ascending is None:
+            if self._ascending is None:
+                def gen():
                     for r in self._r1:
                         yield r
                     s = self._r1.set()
                     for r in self._r2:
                         if r not in s:
                             yield r
-                else:
-                    iter1 = iter(self._r1)
-                    iter2 = iter(self._r2)
-
-                    val1 = None
-                    val2 = None
-
-                    choice = max
-                    if self._ascending:
-                        choice = min
-                    try:
-                        # Consume both iterators in an ordered way until one is
-                        # empty
-                        while True:
-                            if val1 is None:
-                                val1 = iter1.next()
-                            if val2 is None:
-                                val2 = iter2.next()
-                            next = choice(val1, val2)
-                            yield next
-                            if val1 == next:
-                                val1 = None
-                            if val2 == next:
-                                val2 = None
-                    except StopIteration:
-                        # Flush any remaining values and consume the other one
-                        it = iter2
-                        if val1 is not None:
-                            yield val1
-                            it = iter1
-                        elif val2 is not None:
-                            # might have been equality and both are empty
-                            yield val2
-                        for val in it:
-                            yield val
-
-            self._iter = _generatorset(gen())
-
+                gen = gen()
+            else:
+                iter1 = iter(self._r1)
+                iter2 = iter(self._r2)
+                gen = self._iterordered(self._ascending, iter1, iter2)
+            self._iter = _generatorset(gen)
         return self._iter
 
     def __iter__(self):
@@ -2691,6 +2659,47 @@ class _addset(_orderedsetmixin):
             return iter(self._genlist)
         return iter(self._iterator())
 
+    def _iterordered(self, ascending, iter1, iter2):
+        """produce an ordered iteration from two iterators with the same order
+
+        The ascending is used to indicated the iteration direction.
+        """
+        choice = max
+        if ascending:
+            choice = min
+
+        val1 = None
+        val2 = None
+
+        choice = max
+        if self._ascending:
+            choice = min
+        try:
+            # Consume both iterators in an ordered way until one is
+            # empty
+            while True:
+                if val1 is None:
+                    val1 = iter1.next()
+                if val2 is None:
+                    val2 = iter2.next()
+                next = choice(val1, val2)
+                yield next
+                if val1 == next:
+                    val1 = None
+                if val2 == next:
+                    val2 = None
+        except StopIteration:
+            # Flush any remaining values and consume the other one
+            it = iter2
+            if val1 is not None:
+                yield val1
+                it = iter1
+            elif val2 is not None:
+                # might have been equality and both are empty
+                yield val2
+            for val in it:
+                yield val
+
     def __contains__(self, x):
         return x in self._r1 or x in self._r2