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Optimise (cons X nil) to (list X)

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* lisp/emacs-lisp/byte-opt.el (byte-optimize-cons): New function.
This commit is contained in:
Mattias Engdegård 2021-06-03 21:15:11 +02:00
parent c3b44858dc
commit a517b77ffe
1 changed files with 8 additions and 0 deletions
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8
lisp/emacs-lisp/byte-opt.el
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@ -1269,6 +1269,14 @@ See Info node `(elisp) Integer Basics'."
form)
form))
(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))
;; Fixme: delete-char -> delete-region (byte-coded)
;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
;; string-make-multibyte for constant args.