diff options
Diffstat (limited to 'lisp/emacs-lisp')
| -rw-r--r-- | lisp/emacs-lisp/byte-opt.el | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el index a9dedae398c..2c9dc8e3314 100644 --- a/lisp/emacs-lisp/byte-opt.el +++ b/lisp/emacs-lisp/byte-opt.el @@ -557,8 +557,20 @@ ;; Otherwise, no args can be considered to be for-effect, ;; even if the called function is for-effect, because we ;; don't know anything about that function. - (cons fn (mapcar 'byte-optimize-form (cdr form))))))) - + (let ((args (mapcar #'byte-optimize-form (cdr form)))) + (if (and (get fn 'pure) + (byte-optimize-all-constp args)) + (list 'quote (apply fn (mapcar #'eval args))) + (cons fn args))))))) + +(defun byte-optimize-all-constp (list) + "Non-nil iff all elements of LIST satisfy `byte-compile-constp'." + (let ((constant t)) + (while (and list constant) + (unless (byte-compile-constp (car list)) + (setq constant nil)) + (setq list (cdr list))) + constant)) (defun byte-optimize-form (form &optional for-effect) "The source-level pass of the optimizer." @@ -1241,6 +1253,18 @@ (setq side-effect-and-error-free-fns (cdr side-effect-and-error-free-fns))) nil) + +;; pure functions are side-effect free functions whose values depend +;; only on their arguments. For these functions, calls with constant +;; arguments can be evaluated at compile time. This may shift run time +;; errors to compile time. + +(let ((pure-fns + '(concat symbol-name regexp-opt regexp-quote string-to-syntax))) + (while pure-fns + (put (car pure-fns) 'pure t) + (setq pure-fns (cdr pure-fns))) + nil) (defun byte-compile-splice-in-already-compiled-code (form) ;; form is (byte-code "..." [...] n) |