(byte-optimize-concat): New function.

1 files changed, 13 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index c75dbe4b696..56dcc9e2427 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -697,7 +697,7 @@
         ((and (null (nthcdr 3 form))
               (or (memq (nth 1 form) '(1 -1))
                   (memq (nth 2 form) '(1 -1))))
-         ;; Optiize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
+         ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
          (let ((integer
                 (if (memq (nth 1 form) '(1 -1))
                     (nth 1 form)
@@ -1076,6 +1076,18 @@
       (while (>= (setq count (1- count)) 0)
         (setq form (list 'cdr form)))
       form)))
+
+(put 'concat 'byte-optimizer 'byte-optimize-concat)
+(defun byte-optimize-concat (form)
+  (let ((args (cdr form))
+        (constant t))
+    (while (and args constant)
+      (or (byte-compile-constp (car args))
+          (setq constant nil))
+      (setq args (cdr args)))
+    (if constant
+        (eval form)
+      form)))
 
 ;;; enumerating those functions which need not be called if the returned 
 ;;; value is not used.  That is, something like