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

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* lisp/emacs-lisp/byte-opt.el (byte-optimize-nthcdr):
Open-code for any integral N<5.  Always use the byte-op otherwise.
This commit is contained in:
Mattias Engdegård 2024-04-29 20:24:07 +02:00
parent 97a2710554
commit 3000edc617
1 changed files with 9 additions and 7 deletions
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16
lisp/emacs-lisp/byte-opt.el
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@ -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)