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Improved cons optimisation

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* lisp/emacs-lisp/byte-opt.el (byte-optimize-cons):
Add the transform

 (cons X (list Y...)) -> (list X Y...)
This commit is contained in:
Mattias Engdegård 2022-07-15 23:42:45 +02:00
parent eb0e93478e
commit d1ac1b2108
1 changed files with 8 additions and 5 deletions
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13
lisp/emacs-lisp/byte-opt.el
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@ -1281,11 +1281,14 @@ See Info node `(elisp) Integer Basics'."
(put 'cons 'byte-optimizer #'byte-optimize-cons)
(defun byte-optimize-cons (form)
;; (cons X nil) => (list X)
(if (and (= (safe-length form) 3)
(null (nth 2 form)))
`(list ,(nth 1 form))
form))
(let ((tail (nth 2 form)))
(cond
;; (cons X nil) => (list X)
((null tail) `(list ,(nth 1 form)))
;; (cons X (list YS...)) -> (list X YS...)
((and (consp tail) (eq (car tail) 'list))
`(,(car tail) ,(nth 1 form) . ,(cdr tail)))
(t form))))
(put 'list 'byte-optimizer #'byte-optimize-list)
(defun byte-optimize-list (form)