From: Jan Moringen <jmoringe@techfak.uni-bielefeld.de>
Date: Mon, 4 Mar 2013 10:26:35 +0000 (+0100)
Subject: Remove redundant LENGTH calls in NSUBSTITUTE[-IF[-NOT]]
X-Git-Url: http://repo.macrolet.net/gitweb/?a=commitdiff_plain;h=3cd426802c5f093d8d07042b9f180e38b8631c0b;p=sbcl.git

Remove redundant LENGTH calls in NSUBSTITUTE[-IF[-NOT]]

NSUBSTITUTE, NSUBSTITUTE-IF and NSUBSTITUTE-IF used to contain

  (let ((length (length sequence))) ...

in the code path for lists. In the macroexpansion it became clear that
this recomputed and shadowed the LENGTH variables already established
by DEFINE-SEQUENCE-TRAVERSER.

A very brief test with list lengths between 5 and 500 suggests that
the speedup produced by removing the redundant computation can be
around 5 to 20 %.
---

diff --git a/src/code/seq.lisp b/src/code/seq.lisp
index ea6fda7..8725876 100644
--- a/src/code/seq.lisp
+++ b/src/code/seq.lisp
@@ -2082,11 +2082,10 @@ many elements are copied."
   (let ((end (or end length)))
     (seq-dispatch sequence
       (if from-end
-          (let ((length (length sequence)))
-            (nreverse (nlist-substitute*
-                       new old (nreverse (the list sequence))
-                       test test-not (- length end) (- length start)
-                       count key)))
+          (nreverse (nlist-substitute*
+                     new old (nreverse (the list sequence))
+                     test test-not (- length end) (- length start)
+                     count key))
           (nlist-substitute* new old sequence
                              test test-not start end count key))
       (if from-end
@@ -2136,10 +2135,9 @@ many elements are copied."
     (declare (fixnum end))
     (seq-dispatch sequence
       (if from-end
-          (let ((length (length sequence)))
-            (nreverse (nlist-substitute-if*
-                       new predicate (nreverse (the list sequence))
-                       (- length end) (- length start) count key)))
+          (nreverse (nlist-substitute-if*
+                     new predicate (nreverse (the list sequence))
+                     (- length end) (- length start) count key))
           (nlist-substitute-if* new predicate sequence
                                 start end count key))
       (if from-end
@@ -2178,10 +2176,9 @@ many elements are copied."
     (declare (fixnum end))
     (seq-dispatch sequence
       (if from-end
-          (let ((length (length sequence)))
-            (nreverse (nlist-substitute-if-not*
-                       new predicate (nreverse (the list sequence))
-                       (- length end) (- length start) count key)))
+          (nreverse (nlist-substitute-if-not*
+                     new predicate (nreverse (the list sequence))
+                     (- length end) (- length start) count key))
           (nlist-substitute-if-not* new predicate sequence
                                     start end count key))
       (if from-end