complete backout of listobject.c v2.171

Misc/ACKS

@@ -62,7 +62,6 @@ Finn Bock
 Paul Boddie
 Matthew Boedicker
 David Bolen
-Duncan Booth
 Jurjen Bos
 Peter Bosch
 Eric Bouck

Misc/NEWS

@@ -118,14 +118,6 @@ Core and builtins
   same as split() except that it scans the string from the end
   working towards the beginning.  See SF feature request 801847.
 
-- in a thread on comp.lang.python, several people noted that list()
-  was much slower than in 2.1 and earlier versions of Python, when used
-  to create new lists from existing lists.  Duncan Booth did some
-  research that uncovered an optimisation that, for lists below
-  about 100 elements, was actually slower than the normal case. The
-  special case criteria have been tightened to rectify the performance
-  regression.
-
 Extension modules
 -----------------
 

Objects/listobject.c

@@ -2242,10 +2242,6 @@ list_fill(PyListObject *result, PyObject *v)
 	int n;		   /* guess for result list size */
 	int i;
 
-	/* if source is destination, we're done. */
-	if (v == (PyObject *)result)
-		return 0;
-
 	n = result->ob_size;
 
 	/* Special-case list(a_list), for speed. */