Optimization guides suggest copying memory in an ascending direction when possible.
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index b2783d2..69d93ae 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -534,13 +534,13 @@
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) {