From: Mattias Engdegård <mattiase@acm.org>
Date: Mon, 29 Apr 2024 18:24:07 +0000 (+0200)
Subject: Use the nthcdr byte-op for drop, and raise open-code limit
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=b266b81884ae6e0a354774d0d722deda90f3521a;p=emacs.git

Use the nthcdr byte-op for drop, and raise open-code limit

* lisp/emacs-lisp/byte-opt.el (byte-optimize-nthcdr):
Open-code for any integral N<5.  Always use the byte-op otherwise.

(cherry picked from commit 3000edc6179dfe0b5f24ae2e472826530809dfd1)
---

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 3d6b35422b8..4095726d276 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -1512,13 +1512,15 @@ See Info node `(elisp) Integer Basics'."
 (put 'nthcdr 'byte-optimizer #'byte-optimize-nthcdr)
 (defun byte-optimize-nthcdr (form)
   (if (= (safe-length form) 3)
-      (if (memq (nth 1 form) '(0 1 2))
-	  (let ((count (nth 1 form)))
-	    (setq form (nth 2 form))
-	    (while (>= (setq count (1- count)) 0)
-	      (setq form (list 'cdr form)))
-	    form)
-	form)
+      (let ((count (nth 1 form)))
+        (cond ((and (integerp count) (<= count 3))
+	       (setq form (nth 2 form))
+	       (while (>= (setq count (1- count)) 0)
+	         (setq form (list 'cdr form)))
+	       form)
+              ((not (eq (car form) 'nthcdr))
+               (cons 'nthcdr (cdr form)))  ; use the nthcdr byte-op
+              (t form)))
     form))
 
 (put 'cons 'byte-optimizer #'byte-optimize-cons)