From: Raymond Hettinger <python@rcn.com>
Date: Mon, 2 Feb 2015 06:53:41 +0000 (-0800)
Subject: Optimization guides suggest copying memory in an ascending direction when possible.
X-Git-Tag: v3.5.0a1~51
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0e259f18f7ada32dd1a37ac883ea17df9c60bc53;p=python

Optimization guides suggest copying memory in an ascending direction when possible.
---

diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index b2783d2739..69d93ae6a6 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -534,13 +534,13 @@ _deque_rotate(dequeobject *deque, Py_ssize_t n)
             if (m > leftindex)
                 m = leftindex;
             assert (m > 0 && m <= len);
-            src = &rightblock->data[rightindex];
-            dest = &leftblock->data[leftindex - 1];
             rightindex -= m;
             leftindex -= m;
+            src = &rightblock->data[rightindex + 1];
+            dest = &leftblock->data[leftindex];
             n -= m;
             do {
-                *(dest--) = *(src--);
+                *(dest++) = *(src++);
             } while (--m);
         }
         if (rightindex == -1) {